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Pharmacological augmentation of endocannabinoid signaling reduces the neuroendocrine response to stress
Abstract
Activation of the hypothalamic-pituitary-adrenal axis (HPA) is critical for survival when the organism is exposed to a stressful stimulus. The endocannabinoid system (ECS) is currently considered an important neuromodulator involved in numerous pathophysiological processes and whose primary function is to maintain homeostasis. In the tissues constituting the HPA axis, all the components of the ECS are present and the activation of this system acts in parallel with changes in the activity of numerous neurotransmitters, including nitric oxide (NO). NO is widely distributed in the brain and adrenal glands and recent studies have shown that free radicals, and in particular NO, may play a crucial role in the regulation of stress response. Our objective was to determine the participation of the endocannabinoid and NOergic systems as probable mediators of the neuroendocrine HPA axis response to a psychophysical acute stress model in the adult male rat. Animals were pre-treated with cannabinoid receptors agonists and antagonists at central and systemic level prior to acute restraint exposure. We also performed in vitro studies incubating adrenal glands in the presence of ACTH and pharmacological compounds that modifies ECS components. Our results showed that the increase in corticosterone observed after acute restraint stress is blocked by anandamide administered at both central and peripheral level. At hypothalamic level both cannabinoid receptors (CB1 and CB2) are involved, while in the adrenal gland, anandamide has a very potent effect in suppressing ACTH-induced corticosterone release that is mainly mediated by vanilloid TRPV1 receptors. We also observed that stress significantly increased hypothalamic mRNA levels of CB1 as well as adrenal mRNA levels of TRPV1 receptor. In addition, anandamide reduced the activity of the nitric oxide synthase enzyme during stress, indicating that the anti-stress action of endocannabinoids may involve a reduction in NO production at hypothalamic and adrenal levels. In conclusion, an endogenous cannabinoid tone maintains the HPA axis in a stable basal state, which is lost with a noxious stimulus. In this case, the ECS dampens the response to stress allowing the recovery of homeostasis. Moreover, our work further contributes to in vitro evidence for a participation of the endocannabinoid system by inhibiting corticosterone release directly at the adrenal gland level.
... A HHM aktiválása stressz esetén a túléléshez szükséges és szabályozásában részt vesz az ECR is [35]. Így, a CB1 receptor kifejeződik a PVN-ben, az agyalapi mirigyben és a mellékvesekéregben is, míg a CB2 csak a hipotalamuszban, a TRPV1 csatorna pedig csak a mellékvesekéregben [36,37,38]. E három receptortípus közül a CB1 szerepe ismert leginkább: bazális körülmények között az ECR részt veszt a HHM tengely normális működésében, míg stresszhelyzetben mérsékli a stresszválaszt, és lehetővé teszi a homeosztázis visszaállását [36]. ...
... Így, a CB1 receptor kifejeződik a PVN-ben, az agyalapi mirigyben és a mellékvesekéregben is, míg a CB2 csak a hipotalamuszban, a TRPV1 csatorna pedig csak a mellékvesekéregben [36,37,38]. E három receptortípus közül a CB1 szerepe ismert leginkább: bazális körülmények között az ECR részt veszt a HHM tengely normális működésében, míg stresszhelyzetben mérsékli a stresszválaszt, és lehetővé teszi a homeosztázis visszaállását [36]. Ennek megfelelően, a CB1 receptor szintetikus kannabinoidokkal való aktivációja a perifériás szteroidogenézist és a glükokortikoid (GK) felszabadulást gátolja [38]. ...
... A centrális, in vivo idegszöveti EC szintekről egyelőre nincs irodalmi adat, azonban egyre nyilvánvalóbb, hogy a mediátorszint-változás fontos a patogenézis szempontjából. A már említett CB1 receptorsűrűség-változás a szigetlebeny szintjén tovább hangsúlyozza az ECR jelentőségét, így felvetődik a FAAH és a MAGL gátlók használata [36]. Ezek potenciális előnye az lenne, hogy az EC-k szintjét emelik, elhanyagolható pszichotrop hatás mellett. ...
The endocannabinoid system (ECS) received a lot of attention ever since its discovery. Advancements of the last three decades have shown that there are numerous mechanisms by which the ECS regulates the energy metabolism. These can either be central (regulating appetite and calorie expenditure) or peripheral (adipocyte-specific and other) mechanisms. The current review highlights some of the most important observations leading to the discovery of the ECS first, followed by a part detailing the synthesis and transport of these mediators, the receptor types and second messenger systems involved. The next part is dedicated to the mechanisms by which this system regulates the energy metabolism. Lastly, the drugs that reached the clinical phase and the main targets and strategies for future drug development will be reviewed.
... In light of the potential antioxidant and anti-inflammatory profile of CMI, we hypothesized that this organoselenium compound should be able to counteract stress-induced depression-like behavior in mice. We used for this purpose a model of acute restraint stress in mice that had already been validated (Pesarico et al. 2015;Thakare et al. 2016;Surkin et al. 2018). We show here that CMI has antidepressant properties in this model that are associated with downregulation of stressinduced inflammation and oxidative stress. ...
... The ARS is a widely used animal model to induce depressive-like behavior (Thakare et al. 2016;Surkin et al. 2018) akin to major depressive disorder symptoms, partially by targeting the brain antioxidant and inflammatory systems (Buynitsky and Mostofsky 2009;Spiers et al. 2016;Jope et al. 2017;Surkin et al. 2018). Indeed, the establishment of brain oxidative stress as a result of increased activity of nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase (NOX) (Schiavone et al. 2009) and/or mitochondrial impairment (Jevtić et al. 2016) has been linked to neuropathogenetic alterations induced by different types of stress in rodents. ...
... The ARS is a widely used animal model to induce depressive-like behavior (Thakare et al. 2016;Surkin et al. 2018) akin to major depressive disorder symptoms, partially by targeting the brain antioxidant and inflammatory systems (Buynitsky and Mostofsky 2009;Spiers et al. 2016;Jope et al. 2017;Surkin et al. 2018). Indeed, the establishment of brain oxidative stress as a result of increased activity of nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase (NOX) (Schiavone et al. 2009) and/or mitochondrial impairment (Jevtić et al. 2016) has been linked to neuropathogenetic alterations induced by different types of stress in rodents. ...
Rationale and objectives
Stress-induced alterations in oxidative and inflammatory parameters have been implicated in the pathophysiology of mood disorders. Based on the antioxidant and anti-inflammatory properties of the selenium-containing compound 3-((4-chlorophenyl)selanyl)-1-methyl-1H-indole (CMI), we assessed its ability to reverse depression-like behavioral alterations, neuroinflammation, and oxidative imbalance induced by acute restraint stress.
Methods
Mice submitted to restraint for 240 min received CMI (1 or 10 mg/kg, orally) 10 min after the end of the stress induction. Behavioral and biochemical tests were carried out after further 30 min.
Results
Restraint-induced depression-like behavior in the tail suspension test (TST), splash test, and new object exploration test was reversed by CMI. None of the treatments evoked locomotor alteration. In addition, CMI abrogated restraint-induced increases in plasma levels of corticosterone and in markers of oxidative stress and impaired superoxide dismutase and catalase activity in the prefrontal cortex (PFC) and hippocampus (HC). CMI also blocked stress-induced downregulation of mRNA levels of glucocorticoid receptor and brain-derived neurotrophic factor and upregulation of nuclear factor kappa B, inducible nitric oxide synthase, tumor necrosis alpha, indoelamine-2,3-dioxygenase, and glycogen synthase kinase 3 beta in PFC and HC.
Conclusions
These preclinical results indicate that administration of selenium-containing compounds might help to treat depression associated with inflammation and oxidative stress.
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Graphical abstract ᅟ
... In this regard, there clearly exist site-specific roles of the ECS within the HPA, and divergent functions of AEA and 2-AG in the HPA were observed [343]. While a few studies report on acute activation of the HPA triggered by cannabis consumption or by the use of CB1 agonists, numerous studies revealed that the ECS is involved in stabilization of the HPA axis under physiological, basal conditions, while upon stressful mediators, the ECS is thought to dampen the stress response finally allowing for the recovery of homeostasis [344]. ...
... Further studies demonstrated that inhibition of the ECS results in an increase of circulating corticosterone concentrations in animal models of stress, like forced swimming and tail suspension [348,349]. Injection of CB1 and CB2 inverse agonists into the third ventricle acutely increased serum corticosterone levels in stressed rats [344]. In accordance to these results, previous studies demonstrated that i.p. ...
... AM251 treatment raised both, the basal control and stress-induced levels of HPA-axis activity [350][351][352]. In line with this, elevation of eCBs, as induced by treatment with FAAH inhibitor, decreased the stress-induced corticosterone serum levels [344]. However, another study showed that acute central application of AEA induced secretion of adrenocorticotropin (ACTH) hormone [353]. ...
Maintenance of body weight is fundamental to maintain one’s health and to promote longevity. Nevertheless, it appears that the global obesity epidemic is still constantly increasing. Endocannabinoids (eCBs) are lipid messengers that are involved in overall body weight control by interfering with manifold central and peripheral regulatory circuits that orchestrate energy homeostasis. Initially, blocking of eCB signaling by first generation cannabinoid type 1 receptor (CB1) inverse agonists such as rimonabant revealed body weight-reducing effects in laboratory animals and men. Unfortunately, rimonabant also induced severe psychiatric side effects. At this point, it became clear that future cannabinoid research has to decipher more precisely the underlying central and peripheral mechanisms behind eCB-driven control of feeding behavior and whole body energy metabolism. Here, we will summarize the most recent advances in understanding how central eCBs interfere with circuits in the brain that control food intake and energy expenditure. Next, we will focus on how peripheral eCBs affect food digestion, nutrient transformation and energy expenditure by interfering with signaling cascades in the gastrointestinal tract, liver, pancreas, fat depots and endocrine glands. To finally outline the safe future potential of cannabinoids as medicines, our overall goal is to address the molecular, cellular and pharmacological logic behind central and peripheral eCB-mediated body weight control, and to figure out how these precise mechanistic insights are currently transferred into the development of next generation cannabinoid medicines displaying clearly improved safety profiles, such as significantly reduced side effects.
... The transient-receptor potential cation channel, subfamily vanilloid member 1 (TRPV1), is a transmembrane channel called capsaicin receptor because capsaicin, the pungent compound of the red chili pepper, activates it (Caterina et al., 1997). The sensory nerve fibers highly express TRPV1, but many tissues, including the liver and adrenal glands, also express this channel (Caterina et al., 1997;Rosenfeld et al., 2020;Sugiura et al., 2007;Surkin et al., 2018). TRPV1 participates in several functions, such as maintaining energy homeostasis and spontaneous locomotor activity (SLA) (Wanner et al., 2011). ...
... This result goes along with increased serum corticosterone levels induced by heat activation of TRPV1 (Rosenfeld et al., 2020). However, it diverges from an in vitro study showing J o u r n a l P r e -p r o o f that TRPV1 antagonist capsazepine stimulates the corticosterone release from adrenal gland cells (Surkin et al., 2018). Also, it diverges from TRPV1 desensitization induced by RTX treatment, which did not alter basal corticosterone levels (observed here at ZT0 and ZT18). ...
Purpose:
TRPV1 desensitization or blockade promotes hyperthermia in rodents. Daily changes in core body temperature (Tc), spontaneous locomotor activity (SLA), and glucocorticoids are temporal cues for peripheral clocks. Thus, this study aimed to evaluate the effects of both desensitization and blockade of TRPV1 on Tc, SLA, blood corticosterone, and the clock genes Per1 and Bmal1 in the liver and adrenal.
Methods and results:
Resiniferatoxin (RTX, 20 μg kg-1) known to desensitize the intra-abdominal TRPV1 channels was i. p. administered in adult male rats. One day after, RTX rats displayed higher Tc than vehicle rats (control) in the light and dark phases. RTX rats showed higher corticosterone at zeitgeber time (ZT) 6 and ZT12 compared to ZT0. Control rats showed a rise in corticosterone at ZT12. RTX abolished the Per1 peak in both the liver and adrenal glands, whereas it enhanced the peak of Bmal1 expression in the liver and decreased it in adrenal glands. Circadian variation in Tc and SLA was unaffected despite higher Tc being found along the light phase up to 5 days after RTX injection. Acute blockade of TRPV1 with the antagonist AMG-517 injected at ZT0 increased Tc and reduced corticosterone without affecting SLA. In the liver, while AMG-517 did not affect Per1, it increased Bmal1 mRNA. In adrenal glands, AMG-517 increased Per1 and did not affect Bmal1 expression. Although rats exposed to a 60-min 34 °C environment showed similar hyperthermia to that observed in AMG-517 rats, neither corticosterone nor liver nor adrenal clock genes changed.
Conclusions:
Inactivation of TRPV1 by abdominal desensitization or by antagonism alters the time-of-day changes of clock genes expression in the liver and adrenal, as well as corticosterone. TRPV1 may be necessary for signaling cyclical temporal cues for clock genes in the periphery but less critical for the circadian profile of Tc and SLA.
... Therefore, considering the above activities, preliminary pharmacological studies were performed to investigate the effect of polar extract from I. tinctoria leaves (IT) on stress-associated behaviors, as well as for the reduction of anxiety-like or depression-like behaviors. For this purpose, we used a validated model of acute restraint stress in mice [36,[41][42][43]. The latter is a widely used animal model to induce stress-related behaviors [36,42], which are at least in part attributable to aberrations in the brain antioxidant and inflammatory systems [36,44,45]. ...
... The most significant changes were observed after a dose of 500 mg/kg body weight and 50 mg/kg b.w., which correlates with the results of behavioral studies, because, as described above, it was the use of these doses that had a significant effect in reducing the symptoms of stress. It should be emphasized that the reduced CAT activity in the brain of stressed mice observed in the present study is in agreement with data previously reported by others [41,43,53]. Reduced CAT activity is an indicator of a prooxidative state since SOD converts superoxide anion to hydrogen peroxide (H 2 O 2 ), but CAT does not metabolize H 2 O 2 to water [54]. ...
Stress that can occur at different levels of a person’s life can cause and exacerbate various diseases. Oxidative stress and inflammation underlie this process at the cellular level. There is an urgent need to identify new and more effective therapeutic targets for the treatment of stress-induced behavioral disorders and specific drugs that affect these targets. Isatis tinctoria L. is a herbaceous species in the Brassicaceae family. Due to its potential antioxidant, nitric oxide- (NO-) inhibiting, anti-inflammatory, and neuroprotective properties, I. tinctoria could be used to treat depression, anxiety, and stress resistance. Hence, the present study is aimed at delineating whether administration of I. tinctoria leaf extract may improve stress-induced disorders in mice. A set of four behavioral tests was selected that together are suitable for phenotyping acute restraint stress-associated behaviors in mice, namely locomotor activity, social integration, dark/light box, and splash tests. The plasma and brains were collected. A brain-derived neurotrophic factor, tumor necrosis factor-alpha, C-reactive protein, corticosterone, NO, reactive oxygen species levels, superoxide dismutase and catalase activity, and ferric-reducing antioxidant power were measured. In mice stressed by immobilization, decreased locomotor activity, anxiety-like behavior, and contact with other individuals were observed, as well as increased oxidative stress and increased levels of nitric oxide in the brain and plasma C-reactive protein. A single administration of I. tinctoria leaf extract was able to reverse the behavioral response to restraint by a mechanism partially dependent on the modulation of oxidative stress, neuroinflammation, and NO reduction. In conclusion, Isatis tinctoria hydroalcoholic leaf extract can reduce stress-induced behavioral disturbances by regulating neurooxidative, neuronitrosative, and neuroimmune pathways. Therefore, it could be recommended for further research on clinical efficacy in depression and anxiety disorder treatment.
... The information presented in this section supports the proposal of Surkin et al. (2018), namely, the ECS could be part of a negative feedback system that limits the acute neuroendocrine stress response [132]. Additionally, the ECS has been associated with neuroendocrine modulation in several stages of life, particularly in adolescence, when the ECS is highly sensitive to pharmacological manipulation. ...
... The information presented in this section supports the proposal of Surkin et al. (2018), namely, the ECS could be part of a negative feedback system that limits the acute neuroendocrine stress response [132]. Additionally, the ECS has been associated with neuroendocrine modulation in several stages of life, particularly in adolescence, when the ECS is highly sensitive to pharmacological manipulation. ...
The endocannabinoid system (ECS) is a crucial modulatory system in which interest has been increasing, particularly regarding the regulation of behavior and neuroplasticity. The adolescent-young adulthood phase of development comprises a critical period in the maturation of the nervous system and the ECS. Neurogenesis occurs in discrete regions of the adult brain, and this process is linked to the modulation of some behaviors. Since marijuana (cannabis) is the most consumed illegal drug globally and the highest consumption rate is observed during adolescence, it is of particular importance to understand the effects of ECS modulation in these early stages of adulthood. Thus, in this article, we sought to summarize recent evidence demonstrating the role of the ECS and exogenous cannabinoid consumption in the adolescent-young adulthood period; elucidate the effects of exogenous cannabinoid consumption on adult neurogenesis; and describe some essential and adaptive behaviors, such as stress, anxiety, learning, and memory. The data summarized in this work highlight the relevance of maintaining balance in the endocannabinoid modulatory system in the early and adult stages of life. Any ECS disturbance may induce significant modifications in the genesis of new neurons and may consequently modify behavioral outcomes.
... In addition, by binding to CRHR1 in the PFC, CRH leads to increased 2-AG levels, an effect that is abolished by CRHR1 antagonist administration [136]. Alternatively, the AEA's modulatory role in the stress response was demonstrated to involve the activation of transient receptor potential cation channel subfamily V member 1 (TRPV1) on adrenal glands and subsequent suppression of cortisol release in rats [137]. Consistently, it was shown that stress significantly increases the hypothalamic mRNA levels of CB1 receptors and the adrenal mRNA levels of TRPV1 [137]. ...
... Alternatively, the AEA's modulatory role in the stress response was demonstrated to involve the activation of transient receptor potential cation channel subfamily V member 1 (TRPV1) on adrenal glands and subsequent suppression of cortisol release in rats [137]. Consistently, it was shown that stress significantly increases the hypothalamic mRNA levels of CB1 receptors and the adrenal mRNA levels of TRPV1 [137]. In conclusion, under stressful conditions, CRH acts on CRH1R in the amygdala, increasing FAAH activity. ...
Cannabis is the most widely trafficked and abused illicit drug due to its calming psychoactive properties. It has been increasingly recognized as having potential health benefits and relatively less adverse health effects as compared to other illicit drugs; however, growing evidence clearly indicates that cannabis is associated with considerable adverse cardiovascular events. Recent studies have linked cannabis use to myocardial infarction (MI); yet, very little is known about the underlying mechanisms. A MI is a cardiovascular disease characterized by a mismatch in the oxygen supply and demand of the heart, resulting in ischemia and subsequent necrosis of the myocardium. Since cannabis is increasingly being considered a risk factor for MI, there is a growing need for better appreciating its potential health benefits and consequences. Here, we discuss the cellular mechanisms of cannabis that lead to an increased risk of MI. We provide a thorough and critical analysis of cannabinoids’ actions, which include modulation of adipocyte biology, regional fat distribution, and atherosclerosis, as well as precipitation of hemodynamic stressors relevant in the setting of a MI. By critically dissecting the modulation of signaling pathways in multiple cell types, this paper highlights the mechanisms through which cannabis may trigger life-threatening cardiovascular events. This then provides a framework for future pharmacological studies which can identify targets or develop drugs that modulate cannabis’ effects on the cardiovascular system as well as other organ systems. Cannabis’ impact on the autonomic outflow, vascular smooth muscle cells, myocardium, cortisol levels and other hemodynamic changes are also mechanistically reviewed.
... In this situation, the upregulation of CRH produced a sustained increase in the activity of FAAH [156]. Interestingly, it was revealed that the presence of AEA or the inhibition of FAAH completely reversed the adrenocorticotropic hormone (ACTH) stimulated release of corticosterone [157]. When the transient potential vanilloid type-1 channel (TRPV1) was blocked by the antagonist capsazepine, the inhibitory effect of AEA was reverted and this suggests that the endovanilloid system could also play a role [157]. ...
... Interestingly, it was revealed that the presence of AEA or the inhibition of FAAH completely reversed the adrenocorticotropic hormone (ACTH) stimulated release of corticosterone [157]. When the transient potential vanilloid type-1 channel (TRPV1) was blocked by the antagonist capsazepine, the inhibitory effect of AEA was reverted and this suggests that the endovanilloid system could also play a role [157]. ...
Major depressive disorder (MDD) is considered a serious public health issue that adversely impacts an individual’s quality of life and contributes significantly to the global burden of disease. The clinical heterogeneity that exists among patients limits the ability of MDD to be accurately diagnosed and currently, a symptom-based approach is utilized in many cases. Due to the complex nature of this disorder, and lack of precise knowledge regarding the pathophysiology, effective management is challenging. The aetiology and pathophysiology of MDD remain largely unknown given the complex genetic and environmental interactions that are involved. Nonetheless, the aetiology and pathophysiology of MDD have been the subject of extensive research, and there is a vast body of literature that exists. Here we overview the key hypotheses that have been proposed for the neurobiology of MDD and highlight the need for a unified model, as many of these pathways are integrated. Key pathways discussed include neurotransmission, neuroinflammation, clock gene machinery pathways, oxidative stress, role of neurotrophins, stress response pathways, the endocannabinoid and endovanilloid systems, and the endogenous opioid system. We also describe the current management of MDD, and emerging novel therapies, with particular focus on patients with treatment-resistant depression (TRD).
... No significant effect has been found on cannabinoid CB1, CB2 receptor expression and/or activity in the mPFC or amygdala of rats following restraint stress exposure (Hill et al., 2009;MacDowell et al., 2017). However, these studies are not consistent with those described by Surkin et al. (2018) showing an increased CB1 mRNA expression in hypothalamus of stressed rats, suggesting that the effects of acute stress exposure on CB1 receptors could be related to distinct anatomical regions. Restraint stress seems to affect TRPV1 and FAAH expression in specific brain regions, as well. ...
... Restraint stress seems to affect TRPV1 and FAAH expression in specific brain regions, as well. Consistently, an increased mRNA and protein expression of TRPV1 has been detected in hippocampus (Navarria et al., 2014), but not in hypothalamus (Surkin et al., 2018) or mPFC (Navarria et al., 2014) of stressed rats as well as FAAH activity seems to be affected in the basolater amygdala (Hill et al., 2009), but not in mPFC (Navarria et al., 2014). These discrepant findings are usually attributed to difference in strain and species, restraint stress procedure, experimental conditions. ...
The endocannabinoid system (ECS), which is composed of the cannabinoid receptors types 1 and 2 (CB1 and CB2) for marijuana's psychoactive ingredient ∆9-tetrahydrocannabinol (∆9-THC), the endogenous ligands (AEA and 2-AG) and the enzymatic systems involved in their biosynthesis and degradation, recently emerged as important modulator of emotional and non-emotional behaviors. In addition to its recreational actions, some of the earliest reports regarding the effects of Cannabis use on humans were related to endocrine system changes. Accordingly, the ∆9-THC and later on, the ECS signaling have long been known to regulate the hypothalamic-pituitary-adrenocortical (HPA) axis, which is the major neuroendocrine stress response system of mammals. However, how the ECS could modify the stress hormone secretion is not fully understood. Thus, the present article reviews current available knowledge on the role of the ECS signaling as important mediator of interaction between HPA axis activity and stressful conditions, which, in turn could be involved in the development of psychiatric disorders.
... Pharmacological agents modulating the ECS have demonstrated efficacy in alleviating depressive and anxiety disorders as well as conditions such as post-traumatic stress disorder (PTSD, attention deficit-hyperactivity disorder (ADHD), Tourette syndrome, and psychosis [35]. Existing evidence indicates that the ECS acts as a homeostatic mechanism preventing unnecessary activation of the HPA axis and restoring its activity to baseline following stress [36]. The eCBs and their target receptors CB 1 play a critical role in the brain's adaptation to repeated stress. ...
Stress-related mental disorders have become increasingly prevalent, thus endangering mental health worldwide. Exploring stress-associated brain alterations is vital for understanding the possible neurobiological mechanisms underlying these changes. Based on existing evidence, the brain endogenous cannabinoid system (ECS) plays a significant role in the stress response, and disruptions in its function are associated with the neurobiology of various stress-related disorders. This study primarily focuses on investigating the impact of chronic unpredictable stress (CUS) on the expression of hippocampal cannabinoid type 1 (CB1) receptors, part of the ECS, in adult male and female Wistar rats. Additionally, it explores whether environmental enrichment (EE) initiated during adolescence could mitigate the CUS-associated alterations in CB1 expression. Wistar rats, shortly after weaning, were placed in either standard housing (SH) or EE conditions for a duration of 10 weeks. On postnatal day 66, specific subgroups of SH or EE animals underwent a 4-week CUS protocol. Western blot (WB) analysis was conducted in the whole hippocampus of the left brain hemisphere to assess total CB1 protein expression, while immunohistochemistry (IHC) was performed on the right hemisphere to estimate the expression of CB1 receptors in certain hippocampal areas (i.e., CA1, CA3 and dentate gyrus-DG). The WB analysis revealed no statistically significant differences in total CB1 protein levels among the groups; however, reduced CB1 expression was found in specific hippocampal sub-regions using IHC. Specifically, CUS significantly decreased CB1 receptor expression in the CA1 and DG of both sexes, whereas in CA3 the CUS-associated decrease was limited to SH males. Interestingly, EE housing proved protective against these reductions. These findings suggest a region and sex-specific endocannabinoid response to chronic stress, emphasizing the role of positive early experiences in the protection of the adolescent brain against adverse conditions later in life.
... Pharmacological agents modulating the ECS have demonstrated efficacy in alleviating depressive and anxiety disorders as well as conditions such as post-traumatic stress disorder (PTSD, attention deficit-hyperactivity disorder (ADHD), Tourette syndrome, and psychosis [35]. Existing evidence indicates that the ECS acts as a homeostatic mechanism preventing unnecessary activation of the HPA axis and restoring its activity to baseline following stress [36]. The eCBs and their target receptors CB 1 play a critical role in the brain's adaptation to repeated stress. ...
... In this sense, mental states characterized by stress induce ROS by altering the balance of excitatory neurotransmitters (adrenaline, glutamate), serotonin, and GABA, which also modulate the immune response and maintain the body's homeostasis and the functionality of the hypothalamic-pituitary-adrenal axis (HPA) [166]. For this purpose, in post-traumatic stress syndrome (PTSD), CBD finds applicability by blocking FAAH and increasing available AEA [167][168][169]; in depression, CBD alleviates symptoms by stimulating serotoninergic neurotransmission, mediated by 5-HT 1A , and by activating the BDNF-TrkB complex [170][171][172], whereas in anxiety and fear, these beneficial effects are mediated by the same 5-HT 1A receptor, but also by GABA A receptors, respectively, by inhibiting the enzymatic activity of iNOS and FAAH [173]. ...
The literature provides scientific evidence for the beneficial effects of cannabidiol (CBD), and these effects extend beyond epilepsy treatment (e.g., Lennox–Gastaut and Dravet syndromes), notably the influence on oxidative status, neurodegeneration, cellular protection, cognitive function, and physical performance. However, products containing CBD are not allowed to be marketed everywhere in the world, which may ultimately have a negative effect on health as a result of the uncontrolled CBD market. After the isolation of CBD follows the discovery of CB1 and CB2 receptors and the main enzymatic components (diacylglycerol lipase (DAG lipase), monoacyl glycerol lipase (MAGL), fatty acid amino hydrolase (FAAH)). At the same time, the antioxidant potential of CBD is due not only to the molecular structure but also to the fact that this compound increases the expression of the main endogenous antioxidant systems, superoxide dismutase (SOD), and glutathione peroxidase (GPx), through the nuclear complex erythroid 2-related factor (Nrf2)/Keep1. Regarding the role in the control of inflammation, this function is exercised by inhibiting (nuclear factor kappa B) NF-κB, and also the genes that encode the expression of molecules with a pro-inflammatory role (cytokines and metalloproteinases). The other effects of CBD on cognitive function and physical performance should not be excluded. In conclusion, the CBD market needs to be regulated more thoroughly, given the previously listed properties, with the mention that the safety profile is a very good one.
... Moreover, enhancing hypothalamic endocannabinoid signaling by brain administration of a FAAH inhibitor (URB597) potentiated LPS-induced increases in circulating OXT and TNF-α levels. The amplification of endocannabinoid signaling at the hypothalamic level thus seems to facilitate the response of neuropeptides and cytokines after an acute immune challenge [57,89,90,104]. These results suggest that endocannabinoids may signal through hypothalamic cannabinoid receptors to facilitate LPS-induced neuroendocrine response during infection. ...
The endocannabinoid system plays a key role in the intersection of the nervous, endocrine, and immune system, regulating not only their functions but also how they interplay with each other. Endogenous ligands, named endocannabinoids, are produced “on demand” to finely regulate the synthesis and secretion of hormones and neurotransmitters, as well as to regulate the production of cytokines and other proinflammatory mediators.
It is well known that immune challenges, such as exposure to lipopolysaccharide (LPS), the main component of the Gram-negative bacteria cell wall, disrupts not only the hypothalamic-pituitary-adrenal axis but also affects other endocrine systems such as the hypothalamic-pituitary-gonadal axis and the release of oxytocin from the neurohypophysis. Here we explore which actors and molecular mechanisms are involved in these processes.
... For instance, the mechanism of endocannabinoids seems to be dependent on stress and trauma history and can be affected by epigenetic modulation that may be transmitted through trans-generational epigenetic inheritance [270]. Individuals with a trauma history may then in fact self-medicate with cannabis [271,272] in order to treat an endocannabinoid-deficient state that impacts stress susceptibility and may be especially amenable to treatment enhancing endocannabinoid tone [127]. Populations with significant trauma history may also be uniquely impacted by modulation of the endocannabinoid system. ...
Social behaviour is an essential component of human life and deficits in social function are seen across multiple psychiatric conditions with high morbidity. However, there are currently no FDA-approved treatments for social dysfunction. Since social cognition and behaviour rely on multiple signalling processes acting in concert across various neural networks, treatments aimed at social function may inherently require a combinatorial approach. Here, we describe the social neurobiology of the oxytocin and endocannabinoid signalling systems as well as translational evidence for their use in treating symptoms in the social domain. We leverage this systems neurobiology to propose a network-based framework that involves pharmacology, psychotherapy, non-invasive brain stimulation and social skills training to combinatorially target trans-diagnostic social impairment. Lastly, we discuss the combined use of oxytocin and endocannabinoids within our proposed framework as an illustrative strategy to treat specific aspects of social function. Using this framework provides a roadmap for actionable treatment strategies for neuropsychiatric social impairment.
This article is part of the theme issue ‘Interplays between oxytocin and other neuromodulators in shaping complex social behaviours’.
... Interestingly, 2-AG levels increase in the AMY and forebrain, but only after a few days of restraining stress [181,182]. Thus, changes in 2-AG concentrations and CB1r content and activity could contribute to repeated and chronic stress [183,184]. Similar results were found in another study developed by Rademacher et al. Both stressful situations (acute and chronic) reduced AEA and PEA protein levels in the AMY and PFC and increased them in the VS, as observed with OEA levels (only after 10 day-daily exposure). ...
The therapeutic benefits of the current medications for patients with psychiatric disorders contrast with a great variety of adverse effects. The endocannabinoid system (ECS) components have gained high interest as potential new targets for treating psychiatry diseases because of their neuromodulator role, which is essential to understanding the regulation of many brain functions. This article reviewed the molecular alterations in ECS occurring in different psychiatric conditions. The methods used to identify alterations in the ECS were also described. We used a translational approach. The animal models reproducing some behavioral and/or neurochemical aspects of psychiatric disorders and the molecular alterations in clinical studies in post-mortem brain tissue or peripheral tissues were analyzed. This article reviewed the most relevant ECS changes in prevalent psychiatric diseases such as mood disorders, schizophrenia, autism, attentional deficit, eating disorders (ED), and addiction. The review concludes that clinical research studies are urgently needed for two different purposes: (1) To identify alterations of the ECS components potentially useful as new biomarkers relating to a specific disease or condition, and (2) to design new therapeutic targets based on the specific alterations found to improve the pharmacological treatment in psychiatry.
... Frontiers in Molecular Biosciences | www.frontiersin.org April 2022 | Volume 9 | Article 895814 8 significantly increased the mRNA levels of TRPV1 channels in adrenal cells (Surkin et al., 2018). TRPV1 is a ligand-gated, nonselective cation channel with high permeability to Ca 2+ and therefore Ca 2+ influx in adrenocortical cells when TRPV1 is activated (Moran and Szallasi, 2018). ...
Transient receptor potential (TRP) channels are polymodal channels capable of sensing environmental stimuli, which are widely expressed on the plasma membrane of cells and play an essential role in the physiological or pathological processes of cells as sensors. TRPs often form functional homo- or heterotetramers that act as cation channels to flow Na+ and Ca2+, change membrane potential and [Ca2+]i (cytosolic [Ca2+]), and change protein expression levels, channel attributes, and regulatory factors. Under normal circumstances, various TRP channels respond to intracellular and extracellular stimuli such as temperature, pH, osmotic pressure, chemicals, cytokines, and cell damage and depletion of Ca2+ reserves. As cation transport channels and physical and chemical stimulation receptors, TRPs play an important role in regulating secretion, interfering with cell proliferation, and affecting neural activity in these glands and their adenocarcinoma cells. Many studies have proved that TRPs are widely distributed in the pancreas, adrenal gland, and other glands. This article reviews the specific regulatory mechanisms of various TRP channels in some common glands (pancreas, salivary gland, lacrimal gland, adrenal gland, mammary gland, gallbladder, and sweat gland).
... Restraint stress has been demonstrated to decrease the AEA, but increase the 2-AG content in the amygdala of rats 22,23 . Moreover, pharmacological enhancement of EC signaling has been shown to attenuate the response to restraint stress in rodents by reducing corticosterone release 24,25 . Furthermore, EC support anabolic metabolism by promoting fat storage and decreasing energy expenditure 26 . ...
Endocannabinoids, particularly anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are instrumental in regulating energy homeostasis and stress response. However, little is known about the endocannabinoid system (ECS) in ruminants, although EC could improve dairy health and productivity, at least by increasing feed intake. In this study, we report if intraperitoneal (i.p.) AEA and 2-AG administration affects feed intake, whole-body macronutrient metabolism, isolation and restraint stress, and whether diet composition modulates circulating endocannabinoid concentrations in cows. Twenty Simmental cows in late lactation were fed a grass silage and a corn silage based diet. On each diet, cows received daily i.p. injections with either AEA (5 µg/kg; n = 7), 2-AG (2.5 µg/kg; n = 6) or saline ( n = 7) for 8 days. Endocannabinoid administration for 5 days under free-ranging (non-stressed) conditions had no effect on feed intake or energy balance, but attenuated the stress-induced suppression of feed intake when housing changed to individual tie-stalls without social or tactile interaction. Endocannabinoids increased whole-body carbohydrate oxidation, reduced fat oxidation, and affected plasma non-esterified fatty acid concentrations and fatty acid contents of total lipids. There was no effect of endocannabinoids on plasma triglyceride concentrations or hepatic lipogenesis. Plasma AEA concentrations were not affected by diet, however, plasma 2-AG concentrations tended to be lower on the corn silage based diet. In conclusion, endocannabinoids attenuate stress-induced hypophagia, increase short-term feed intake and whole-body carbohydrate oxidation and decrease whole-body fat oxidation in cows.
... TRPV1 knock out had reduced expression of glucocorticoid receptor-mediated histone deacetylase 2, and it is more resilient to chronic unpredictable stress (Wang et al., 2017). Moreover, acute stress increased mRNA levels of TRPV1 in the adrenal gland, and TRPV1 mediates anandamide regulation of HPA axis (Surkin et al., 2018). ...
The transient receptor potential vanilloid-1 channel (TRPV1) is responsible for decoding physical and chemical stimuli. TRPV1 is activated by capsaicin (a compound from chili peppers), heat (above 43°C) and acid environment, playing a major role in pain, inflammation and body temperature. Molecular and histological studies have suggested TRPV1 expression in specific brain regions, where it can be activated primarily by the endocannabinoid anandamide, fostering studies on its potential role in psychiatric disorders. TRPV1 blockers are effective in various animal models predictive of anxiolytic and antipanic activities, in addition to reducing conditioned fear. In models of antidepressant activity, these compounds reduce behavioral despair and promote active stress-coping behavior. TRPV1 blockers also reduce the effects of certain drugs of abuse and revert behavioral changes in animal models of neurodevelopmental disorders. The main limiting factor in developing TRPV1 blockers as therapeutic agents concerns their effects on body temperature, particularly hyperthermia. New compounds, which block specific states of the channel, could represent an alternative. Moreover, compounds blocking both TRPV1 and the anandamide-hydrolyzing enzyme, fatty acid amide hydrolase (FAAH), termed dual TRPV1/FAAH blockers, have been investigated with promising results. Overall, preclinical studies yield favorable results with TRPV1 blockers in animal models of psychiatric disorders.
... In hypothalamus, both CB1 and CB2 were involved. In adrenal gland, AEA's effects were caused by activation of TRPV1 [118]. Though CB1 antagonism usually leads to anxiety-like symptoms, it has been shown that CB1 antagonism in a specific region may have the opposite effect. ...
The endocannabinoid system (ECS) is one of the most crucial systems in the human organism, exhibiting multi-purpose regulatory character. It is engaged in a vast array of physiological processes, including nociception, mood regulation, cognitive functions, neurogenesis and neuroprotection, appetite, lipid metabolism, as well as cell growth and proliferation. Thus, ECS proteins, including cannabinoid receptors and their endogenous ligands’ synthesizing and degrading enzymes, are promising therapeutic targets. Their modulation has been employed in or extensively studied as a treatment of multiple diseases. However, due to a complex nature of ECS and its crosstalk with other biological systems, the development of novel drugs turned out to be a challenging task. In this review, we summarize potential therapeutic applications for ECS-targeting drugs, especially focusing on promising synthetic compounds and preclinical studies. We put emphasis on modulation of specific proteins of ECS in different pathophysiological areas. In addition, we stress possible difficulties and risks and highlight proposed solutions. By presenting this review, we point out information pivotal in the spotlight of ECS-targeting drug design, as well as provide an overview of the current state of knowledge on ECS-related pharmacodynamics and show possible directions for needed research.
... These hormones are produced by the adrenal medulla (16) and cortical zona fasciculata (ZF) (17), respectively, and their secretion is dependent on intracellular calcium (Ca 2+ ) concentration ( Fig. 1A) (16,18,19). Notably, mRNA profiling studies demonstrate robust expression of TRPV1 in the adrenal glands of rabbits and rats (15,20). Therefore, we reasoned that remotely delivered magnetothermal stimuli may trigger Ca 2+ -permeable TRPV1 channels in the cells of adrenal medulla and ZF allowing for temporally precise control of adrenal hormones (Fig. 1B). ...
The field of bioelectronic medicines seeks to modulate electrical signaling within peripheral organs, providing temporally precise control of physiological functions. This is usually accomplished with implantable devices, which are often unsuitable for interfacing with soft and highly vascularized organs. Here, we demonstrate an alternative strategy for modulating peripheral organ function, which relies on the endogenous expression of a heat-sensitive cation channel, transient receptor potential vanilloid family member 1 (TRPV1), and heat dissipation by magnetic nanoparticles (MNPs) in remotely applied alternating magnetic fields. We use this approach to wirelessly control adrenal hormone secretion in genetically intact rats. TRPV1-dependent calcium influx into the cells of adrenal cortex and medulla is sufficient to drive rapid release of corticosterone and (nor)epinephrine. As altered levels of these hormones have been correlated with mental conditions such as posttraumatic stress disorder and major depression, our approach may facilitate the investigation of physiological and psychological impacts of stress.
... The actual analysis of the female EC and NAE data at Neumayer III revealed the same reaction pattern as stated in their male colleagues which strengthens the assertion of a potential environmental influence. However, in regard to the simultaneously high cortisol concentrations in females, the negative feedback control between the HPA axis and the EC system [47,48] seems to be blunted in women in this experimental set-up. Sex differences in the HPA axis response to stress have been identified on each level of the regulatory pathway although mostly in animal models [49,50]. ...
Background
Antarctica challenges human explorers by its extreme environment. The effects of these unique conditions on the human physiology need to be understood to best mitigate health problems in Antarctic expedition crews. Moreover, Antarctica is an adequate Earth-bound analogue for long-term space missions. To date, its effects on human physiology have been studied mainly in male cohorts though more female expeditioners and applicants in astronaut training programs are selected. Therefore, the identification of sex differences in stress and immune reactions are becoming an even more essential aim to provide a more individualized risk management.
Methods
Ten female and 16 male subjects participated in three 1-year expeditions to the German Antarctic Research Station Neumayer III. Blood, saliva, and urine samples were taken 1–2 months prior to departure, subsequently every month during their expedition, and 3–4 months after return from Antarctica. Analyses included cortisol, catecholamine and endocannabinoid measurements; psychological evaluation; differential blood count; and recall antigen- and mitogen-stimulated cytokine profiles.
Results
Cortisol showed significantly higher concentrations in females than males during winter whereas no enhanced psychological stress was detected in both sexes. Catecholamine excretion was higher in males than females but never showed significant increases compared to baseline. Endocannabinoids and N-acylethanolamides increased significantly in both sexes and stayed consistently elevated during the confinement. Cytokine profiles after in vitro stimulation revealed no sex differences but resulted in significant time-dependent changes. Hemoglobin and hematocrit were significantly higher in males than females, and hemoglobin increased significantly in both sexes compared to baseline. Platelet counts were significantly higher in females than males. Leukocytes and granulocyte concentrations increased during confinement with a dip for both sexes in winter whereas lymphocytes were significantly elevated in both sexes during the confinement.
Conclusions
The extreme environment of Antarctica seems to trigger some distinct stress and immune responses but—with the exception of cortisol and blood cell counts—without any major relevant sex-specific differences. Stated sex differences were shown to be independent of enhanced psychological stress and seem to be related to the environmental conditions. However, sources and consequences of these sex differences have to be further elucidated.
... Photographs were taken with a digital camera (Olympus C-5060) and analyzed with the ImageJ software package. The relative mRNA level was normalized to βactin, and results were expressed as arbitrary units (AU) of relative optical density [28]. ...
The exposition to hypoxia is a stressful stimulus, and the organism develops acclimation mechanisms to ensure homeostasis, but if this fails, it leads to the development of pathological processes. Considering the large number of people under hypoxic conditions, it is of utmost importance to study the mechanisms implicated in hypoxic acclimation in oral tissues and the possible alteration of some important inflammatory markers that regulate salivary and periodontal function. It is the aim of the present study to analyze submandibular (SMG) and periodontal status of animals chronically exposed to continuous (CCH) or intermittent (CIH) hypoxia in order to elucidate the underlying molecular mechanisms that may lead to hypoxic acclimation. Adult Wistar rats were exposed to CCH or CIH simulating 4200 meters of altitude during 90 days. Salivary secretion was decreased in animals exposed to hypoxia, being lower in CIH, together with increased prostaglandin E 2 (PGE 2 ) content, TBARS concentration, and the presence of apoptotic nuclei and irregular secretion granules in SMG. AQP-5 mRNA levels decreased in both hypoxic groups. Only the CCH group showed higher HIF-1 α staining, while CIH alone exhibited interradicular bone loss and increased concentration of the bone resorption marker CTX-I. In summary, animals exposed to CIH show a worse salivary secretion rate, which related with higher levels of PGE 2 , suggesting a negative role of this inflammatory mediator during hypoxia acclimation. We link the weak immunorreactivity of HIF-1 α in CIH with improper hypoxia acclimation, which is necessary to sustaining SMG physiology under this environmental condition. The alveolar bone loss observed in CIH rats could be due mainly to a direct effect of PGE 2 , as suggested by its higher content in gingival tissue, but also to the indirect effect of hyposalivation. This study may eventually contribute to finding therapeutics to treat the decreased salivary flow, improving in that way oral health.
... The chronic stressor of confinement resulted here in an interaction of these systems that is in contrast to our findings albeit it also displays its apparent inverse character. Moreover, the hypothesis of an inverse interaction is also supported by Ishac et al. (1996) who stated an inhibitory effect of presynaptic cannabinoid CB 1 receptors on noradrenaline release in peripheral sympathetic nerves and Surkin et al. (2018) who evidenced that pharmacological augmentation of EC signaling reduces the neuroendocrine response to stress. Niederhoffer and others also found this inhibitory effect of ECs on noradrenaline to be the cause of cardiovascular depression (Wagner et al., 1998;Niederhoffer et al., 2003;Pfitzer et al., 2005). ...
The Antarctic continent is an environment of extreme conditions. Only few research stations exist that are occupied throughout the year. The German station Neumayer III and the French-Italian Concordia station are such research platforms and human outposts. The seasonal shifts of complete daylight (summer) to complete darkness (winter) as well as massive changes in outside temperatures (down to -80°C at Concordia) during winter result in complete confinement of the crews from the outside world. In addition, the crew at Concordia is subjected to hypobaric hypoxia of ∼650 hPa as the station is situated at high altitude (3,233 m). We studied three expedition crews at Neumayer III (sea level) (n = 16) and two at Concordia (high altitude) (n = 15) to determine the effects of hypobaric hypoxia on hormonal/metabolic stress parameters [endocannabinoids (ECs), catecholamines, and glucocorticoids] and evaluated the psychological stress over a period of 11 months including winter confinement. In the Neumayer III (sea level) crew, EC and n-acylethanolamide (NAE) concentrations increased significantly already at the beginning of the deployment (p < 0.001) whereas catecholamines and cortisol remained unaffected. Over the year, ECs and NAEs stayed elevated and fluctuated before slowly decreasing till the end of the deployment. The classical stress hormones showed small increases in the last third of deployment. By contrast, at Concordia (high altitude), norepinephrine concentrations increased significantly at the beginning (p < 0.001) which was paralleled by low EC levels. Prior to the second half of deployment, norepinephrine declined constantly to end on a low plateau level, whereas then the EC concentrations increased significantly in this second period during the overwintering (p < 0.001). Psychometric data showed no significant changes in the crews at either station. These findings demonstrate that exposition of healthy humans to the physically challenging extreme environment of Antarctica (i) has a distinct modulating effect on stress responses. Additionally, (ii) acute high altitude/hypobaric hypoxia at the beginning seem to trigger catecholamine release that downregulates the EC response. These results (iii) are not associated with psychological stress.
... Previous studies suggested that endocannabinoids inhibited the release of glutamate, a type of excitatory neurotransmitter, to parvicellular neurons in PVN, which caused the downregulation of CRH (Davies et al. 2002;Freund et al. 2003;Trettel and Levine 2003). An endogenous cannabinoid tone maintains the HPA axis in a stable state, which is lost with a noxious stimulus (Surkin et al. 2017). Therefore, we hypothesized that hyperglycaemia break this stable state. ...
Hypothalamus-pituitary-adrenal (HPA) axis, as the key moderator in energy metabolism, plays an important role in diabetes. The endogenous cannabinoid system (eCBs) involves in neuronal functions, and simultaneously cannabinoid receptors are almost expressed in all regions of the hypothalamus according to a spate of reports. However, few data investigate the changes of eCBs and HPA axis in type 2 diabetes. In this study, five diabetes mellitus rhesus monkeys, five prediabetes rhesus monkeys and five healthy rhesus monkeys were observed. In the present study, we detected cell swelling and necrosis extensively in the paraventricular nucleus (PVN) and neurohypophysis in prediabetes and overt diabetes monkeys. The adrenocorticotropic hormone in the pituitary gland, adrenocorticotropic hormone receptor, and 11β-hydroxysteroid dehydrogenase in the adrenal gland were all hyper-secreted and expressed from healthy to overt diabetes. Meanwhile, the cortisol concentration in the adrenal gland was increased along with the progress of diabetes. It could be concluded that hyperfunction of the HPA axis exists in the type 2 Diabetes pathogenesis. However, we also found a weakened expression and secretion of corticotrophin releasing hormone and glucocorticoids receptor in PVN. The expression of corticotropin releasing hormone receptor 1 in pituitary gland decreased in prediabetes monkeys, but increased in overt diabetes monkeys. The downregulation of cannabinoid receptor 1 and upregulation of monoglycerol lipase and fatty acid amide hydrolase in PVN was involved in the pathogenesis of type 2 diabetes. Collectively, we can conclude that changes in endocannabinoid hydrolase and cannabinoid receptor might indicate the effect of downregulation of eCBs. It can be assumed that hyper-function of the HPA axis from healthy to overt diabetes is due to the undermining inhibition of eCBs. However, the regulatory mechanism of eCBs targets on the HPA axis need to be further explored.
... The endocannabinoid system has been implicated in anti-stress mechanisms during adulthood [47]. Considering the influence of the endocannabinoid system in early development, it was demonstrated in a mouse CB1 knockout model that this receptor modulates the stress response during early life stages, since the lack of CB1 increased vulnerability to acute (swimming) and chronic (repeated bell) stress, inducing greater and prolonged freezing behaviour and decreased ultrasonic vocalizations [48]. ...
Although stress is an adaptive physiological response to deal with adverse conditions, its occurrence during early stages of life such as infancy or adolescence can induce adaptations in multiple physiological systems, including the reproductive axis (HPG), the hypothalamic‐pituitary‐adrenal (HPA) axis, the limbic cortex and the immune system. These early changes have consequences in adult life, as seen in the physiological and behavioral responses to stress. This review highlights the impact of several stress challenges incurred at various stages of development (peri‐natal, juvenile, adolescent periods) and how developmental timing of early life stress confers unique physiological adaptations that may persist across the lifespan. In doing so, we will emphasize how intrinsic sex differences in the stress response might contribute to sex‐specific vulnerabilities, the molecular processes underlying stress in the adult, and potential therapeutic interventions to mitigate the effects of early stage stress, including the novel molecular mechanism of SUMOylation as a possible key target of HPA regulation during early life stress.
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Objective
The objective of the study was to evaluate the expression of oxytocin receptors in normal and inflamed gingiva, as well as the effects of systemic administration of oxytocin in bone loss and gum inflammatory mediators in a rat model of experimental periodontitis.
Background Data
Current evidence supports the hypothesis of a disbalance between the oral microbiota and the host's immune response in the pathogenesis of periodontitis. Increased complexity of the microbial biofilm present in the periodontal pocket leads to local production of nitrogen and oxygen‐reactive species, cytokines, chemokines, and other proinflammatory mediators which contribute to periodontal tissue destruction and bone loss. Oxytocin has been suggested to participate in the modulation of immune and inflammatory processes. We have previously shown that oxytocin, nitric oxide, and endocannabinoid system interact providing a mechanism of regulation for systemic inflammation. Here, we aimed at investigating not only the presence and levels of expression of oxytocin receptors on healthy and inflamed gingiva, but also the effects of oxytocin treatment on alveolar bone loss, and systemic and gum expression of inflammatory mediators involved in periodontal tissue damage using ligature‐induced periodontitis. Therefore, anti‐inflammatory strategies oriented at modulating the host's immune response could be valuable adjuvants to the main treatment of periodontal disease.
Methods
We used an animal model of ligature‐induced periodontitis involving the placement of a linen thread (Barbour flax 100% linen suture, No. 50; size 2/0) ligature around the neck of first lower molars of adult male rats. The ligature was left in place during the entire experiment (7 days) until euthanasia. Animals with periodontitis received daily treatment with oxytocin (OXT, 1000 μg/kg, sc.) or vehicle and/or atosiban (3 mg/kg, sc.), an antagonist of oxytocin receptors. The distance between the cement–enamel junction and the alveolar bone crest was measured in stained hemimandibles in the long axis of both buccal and lingual surfaces of both inferior first molars using a caliper. TNF‐α levels in plasma were determined using specific rat enzyme‐linked immunosorbent assays (ELISA). OXT receptors, IL‐6, IL‐1β, and TNF‐α expression were determined in gingival tissues by semiquantitative or real‐time PCR.
Results
We show that oxytocin receptors are expressed in normal and inflamed gingival tissues in male rats. We also show that the systemic administration of oxytocin prevents the experimental periodontitis‐induced increased gum expression of oxytocin receptors, TNF‐α, IL‐6, and IL‐1β ( p < .05). Furthermore, we observed a reduction in bone loss in rats treated with oxytocin in our model.
Conclusions
Our results demonstrate that oxytocin is a novel and potent modulator of the gingival inflammatory process together with bone loss preventing effects in an experimental model of ligature‐induced periodontitis.
Early nicotine exposure compromises offspring's phenotype at long-term in both sexes. We hypothesize that offspring exposed to nicotine during breastfeeding show deregulated central and peripheral endocannabinoid system (ECS), compromising several aspects of their metabolism. Lactating rats received nicotine (NIC, 6 mg/Kg/day) or saline from postnatal day (PND) 2 to 16 through implanted osmotic minipumps. Offspring were analyzed at PND180. We evaluated protein expression of N-acylphosphatidylethanolamide-phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), diacylglycerol lipase (DAGL), monoacylglycerol lipase (MAGL) and cannabinoid receptors (CB1 and/or CB2) in lateral hypothalamus, paraventricular nucleus of the hypothalamus, liver, visceral adipose tissue (VAT), adrenal and thyroid. NIC offspring from both sexes did not show differences in hypothalamic ECS markers. Peripheral ECS markers showed no alterations in NIC males. In contrast, NIC females had lower liver DAGL and CB1, higher VAT DAGL, higher adrenal NAPE-PLD and higher thyroid FAAH. Endocannabinoids biosynthesis was affected by nicotine exposure during breastfeeding only in females; alterations in peripheral tissues suggest lower action in liver and higher action in VAT, adrenal and thyroid. Effects of nicotine exposure during lactation on ECS markers are sex- and tissue-dependent. This characterization helps understanding the phenotype of the adult offspring in this model and may contribute to the development of new pharmacological targets for the treatment of several metabolic diseases that originate during development.
Analysis of hair samples provides unique advantages, including non-invasive sampling, sample stability, and the possibility of additional optimization of high sensitivity detection methods. Hair sample analysis is often used in psychiatric disease research to evaluate previous periods of stress encountered by patients. Glucocorticoid analysis is the most frequently tested indicator of stress. Furthermore, the hypothalamus-pituitary-gonad axis and endocannabinoid system also are involved in the occurrence and development of mental disorders. The endocannabinoid and sex hormone levels in patients experiencing mental illness are considerably different from levels observed in healthy individuals. Nevertheless, due to the different methods used to assess the degree of disease and the range of analytical methods involved in clinical research, the trends in changes for these biomarkers are not uniform. The correlations between changes in biomarker concentrations and illness severity also are not clear. The observed alterations suggest these biochemical substances in hair have potential as biomarkers for diagnosis or predictive treatment. However, the variable results obtained thus far could hamper further development of hair samples for clinical assessment in psychiatric disorders. This article summarizes the published reports documenting the changes in the content of relevant substances in hair in individuals experiencing mental illness and the degree of correlation. In the discussion section, we proposed several issues that should be considered in future studies of hair samples obtained from patients with mental disorders to promote the use of hair sample assessment as an aid in diagnosis or predictive treatment.
The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic “M1” microglial phenotype to a more neuroprotective “M2” phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.
Aim: The present study was designed to investigate the role of nitric oxide (NO) in the non-development of stress adaptation in high-intensity foot-shock stress (HIFS) subjected mice.
Methods: Mice were subjected to low-intensity shocks (LIFS i.e. 0.5 mA) or HIFS (1.5 mA) for 5 days. Stress-induced behavioral changes were assessed by actophotometer, hole board, open field and social interaction tests. Biochemically, the serum corticosterone levels were measured as a marker of stress. L-arginine (100 mg/kg and 300 mg/kg), as NO donor, and L-NAME (10 mg/kg and 30 mg/kg), as nitric oxide synthase (NOS) inhibitor, were employed as pharmacological agents.
Results: A single exposure of LIFS and HIFS produced behavioral and biochemical alterations. However, there was the restoration of behavioral and biochemical alterations on 5th day in response to repeated LIFS exposure suggesting the development of stress adaptation. However, no stress adaptation was observed in HIFS subjected mice. Administration of L-arginine (300 mg/kg) abolished the stress adaptive response in LIFS-subjected mice, while L-NAME (30 mg/kg) induced the development of stress adaptation in HIFS subjected mice.
Conclusion: It is concluded that an increase in the NO release may possibly impede the process of stress adaptation in HIFS-subjected mice.
Endogenous cannabinoids (endocannabinoids, eCB) are expressed throughout the body and contribute to regulation of the hypothalamo-pituitary-adrenal (HPA) axis and general stress reactivity. This study assessed the contributions of CB1 receptors (CB1R) in the modulation of basal and stress-induced neural and HPA axis activities. Catheterized adult male rats were placed in chambers to acclimate overnight, with their catheters connected and exteriorized from the chambers for relatively stress-free remote injections. The next morning, the CB1R antagonist AM251 (1 or 2 mg/kg) or vehicle was administered, and 30 min later, rats were exposed to loud noise stress (30 min) or no noise (basal condition). Blood, brains, pituitary and adrenal glands were collected immediately after the procedures for analysis of c-fos and CB1R mRNAs, corticosterone (CORT) and adrenocorticotropin hormone (ACTH) plasma levels. Basally, CB1R antagonism induced c-fos mRNA in the basolateral amygdala (BLA) and auditory cortex (AUD) and elevated plasma CORT, indicating disruption of eCB-mediated constitutive inhibition of activity. CB1R blockade also potentiated stress-induced hormone levels and c-fos mRNA in several regions such as the bed nucleus of the stria terminalis (BST), lateral septum (LS), and basolateral amygdala (BLA) and the paraventricular nucleus of the hypothalamus (PVN). CB1R mRNA was detected in all central tissues investigated, and the adrenal cortex, but at very low levels in the anterior pituitary gland. Interestingly, CB1R mRNA was rapidly and bidirectionally regulated in response to stress and/or antagonist treatment in some regions. eCBs therefore modulate the HPA axis by regulating both constitutive and activity-dependent inhibition at multiple levels.
Introduction
Glucocorticoid release by adrenals has been described as significant to survive sepsis. The activation of transient receptor potential vanilloid type 1 (TRPV1) inhibited ACTH-induced glucocorticoid release by adrenal glands in vitro.
Objective
The aim of this study was to investigate if capsaicin, an activator of TRPV1, would prevent LPS-induced glucocorticoid production by adrenals.
Methods
Male Swiss-Webster mice were treated with capsaicin intraperitoneally (0.2 or 2 mg/kg) 30 min before LPS injection. All analyses were performed 2 h after the LPS stimulation, including plasma corticosterone and peritoneal IL-1β and TNF-α levels. Furthermore, murine adrenocortical Y1 cells were used to assess the effects of capsaicin on LPS-induced corticosterone production in vitro.
Results
Capsaicin (2 mg/kg, i.p.) significantly reduced plasma corticosterone levels and adrenal hypertrophy induced by LPS without alter the levels of pro-steroidogenic cytokines IL-1β and TNF-α in peritoneal cavity of mice, while the dose of 0.2 mg/kg of capsaicin did not interfere with adrenal steroidogenesis, attested by RIA and ELISA, respectively. Y1 cells express TRPV1, measured by immunofluorescence and western blot, and capsaicin decreased LPS-induced corticosterone production by these cells in vitro. Capsaicin also induces calcium mobilization in Y1 cells in vitro.
Conclusions
These findings suggest that capsaicin inhibits corticosterone production induced by LPS by acting directly on adrenal cells producing glucocorticoids, in a mechanism probably associated with induction of a cytoplasmic calcium increase in these cells.
Stress is a major risk factor for the development of mood and anxiety disorders; elucidation of novel approaches to mitigate the deleterious effects of stress could have broad clinical applications. Pharmacological augmentation of central endogenous cannabinoid (eCB) signaling may be an effective therapeutic strategy to mitigate the adverse behavioral and physiological consequences of stress. Here we show that acute foot-shock stress induces a transient anxiety state measured 24 h later using the light-dark box assay and novelty-induced hypophagia test. Acute pharmacological inhibition of the anandamide-degrading enzyme, fatty acid amide hydrolase (FAAH), reverses the stress-induced anxiety state in a cannabinoid receptor-dependent manner. FAAH inhibition does not significantly affect anxiety-like behaviors in non-stressed mice. Moreover, whole brain anandamide levels are reduced 24 h after acute foot-shock stress and are negatively correlated with anxiety-like behavioral measures in the light-dark box test. These data indicate that central anandamide levels predict acute stress-induced anxiety, and that reversal of stress-induced anandamide deficiency is a key mechanism subserving the therapeutic effects of FAAH inhibition. These studies provide further support that eCB-augmentation is a viable pharmacological strategy for the treatment of stress-related neuropsychiatric disorders.
The physiological and behavioral effects of stress are well characterized. Endocannabinoids are produced on demand and function to attenuate many of the physiological effects of the stress response. The endocannabinoid system is made up of cannabinoid receptors, the fatty acid signaling molecules that bind to and activate these receptors, and the enzymes that synthesize and catabolize these endocannabinoid signaling molecules. Cannabinoid research has recently grown substantially, due in no small part to the development of genetic research models as well as highly selective pharmaceutical tools. The purpose of this minireview is to discuss a subset of the many parallels between cannabinoid and behavioral neuroimmunology research, with specific discussion of interactions between the endocannabinoid system and psychological stress, emotionality, and inflammation.
The psychoactive constituent in cannabis, Δ(9)-tetrahydrocannabinol (THC), was isolated in the mid-1960s, but the cannabinoid receptors, CB1 and CB2, and the major endogenous cannabinoids (anandamide and 2-arachidonoyl glycerol) were identified only 20 to 25 years later. The cannabinoid system affects both central nervous system (CNS) and peripheral processes. In this review, we have tried to summarize research-with an emphasis on recent publications-on the actions of the endocannabinoid system on anxiety, depression, neurogenesis, reward, cognition, learning, and memory. The effects are at times biphasic-lower doses causing effects opposite to those seen at high doses. Recently, numerous endocannabinoid-like compounds have been identified in the brain. Only a few have been investigated for their CNS activity, and future investigations on their action may throw light on a wide spectrum of brain functions. Expected final online publication date for the Annual Review of Psychology Volume 64 is November 30, 2012. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
Stress can be defined as a brain-body reaction towards stimuli arising from the environment or from internal cues that are interpreted as a disruption of homeostasis. The organization of the response to a stressful situation involves not only the activity of different types of neurotransmitter systems in several areas of the limbic system, but also the response of neurons in these areas to several other chemicals and hormones, chiefly glucocorticoids, released from peripheral organs and glands. Thus, stress is probably the process through which body-brain integration plays a major role. Here we review first the responses to an acute stress in terms of neurotransmitters such as dopamine, acetylcholine, glutamate and GABA in areas of the brain involved in the regulation of stress responses. These areas include the prefrontal cortex, amygdala, hippocampus and nucleus accumbens and the interaction among those areas. Then, we consider the role of glucocorticoids and review some recent data about the interaction of these steroids with several neurotransmitters in those same areas of the brain. Also the actions of other substances (neuromodulators) released from peripheral organs such as the pancreas, liver or gonads (insulin, IGF-1, estrogens) are reviewed. The role of an environmental enrichment on these same responses is also discussed. Finally a section is devoted to put into perspective all these environmental-brain-body-brain interactions during stress and their consequences on aging. It is concluded that the integrative perspective framed in this review is relevant for better understanding of how the organism responds to stressful challenges and how this can be modified through different environmental conditions during the process of aging. This article is part of a Special Issue entitled: Brain Integration.
The mechanisms subserving the ability of glucocorticoid signaling within the medial prefrontal cortex (mPFC) to terminate stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis are not well understood. We report that antagonism of the cannabinoid CB(1) receptor locally within the mPFC prolonged corticosterone secretion following cessation of stress in rats. Mice lacking the CB(1) receptor exhibited a similar prolonged response to stress. Exposure of rats to stress produced an elevation in the endocannabinoid 2-arachidonoylglycerol within the mPFC that was reversed by pretreatment with the glucocorticoid receptor antagonist RU-486 (20 mg/kg). Electron microscopic and electrophysiological data demonstrated the presence of CB(1) receptors in inhibitory-type terminals impinging upon principal neurons within layer V of the prelimbic region of the mPFC. Bath application of corticosterone (100 nm) to prefrontal cortical slices suppressed GABA release onto principal neurons in layer V of the prelimbic region, when examined 1 h later, which was prevented by application of a CB(1) receptor antagonist. Collectively, these data demonstrate that the ability of stress-induced glucocorticoid signaling within mPFC to terminate HPA axis activity is mediated by a local recruitment of endocannabinoid signaling. Endocannabinoid activation of CB(1) receptors decreases GABA release within the mPFC, likely increasing the outflow of the principal neurons of the prelimbic region to contribute to termination of the stress response. These data support a model in which endocannabinoid signaling links glucocorticoid receptor engagement to activation of corticolimbic relays that inhibit corticosterone secretion.
There are two well characterized cannabinoid receptors (CBRs), CB1-Rs and CB2-Rs, with other candidates, such as GPR55, PPARs and vanilloid TRPV1 (VR1) receptors, which are either activated by cannabinoids and/or endocannabinoids (eCBs). The neuronal and functional expression of CB2-Rs in the brain has been much less well characterized in comparison with the expression of the ubiquitous CB1-Rs. CB2-Rs were previously thought to be predominantly expressed in immune cells in the periphery and were traditionally referred to as peripheral CB2-Rs. We and others have now demonstrated the expression of CB2-Rs in neuronal, glial and endothelial cells in the brain, and this warrants a re-evaluation of the CNS effects of CB2-Rs. In the present review we summarize our current understanding of CNR2 genomic structure, its polymorphic nature, subtype specificity, from mice to human subjects, and its variants that confer vulnerabilities to neuropsychiatric disorders beyond neuro-immuno-cannabinoid activity.
All forms of stress, including restraint stress (RS) and lipopolysaccharide (LPS) administration, activate the hypothalamic-pituitary-adrenal (HPA) axis. LPS binds to a recognition protein (CD14) and toll-like receptor 2/4 in different cells and tissues, including the adrenal gland, to induce the production of cytokines and cause upregulation of cyclooxygenase and nitric oxide synthase (NOS) enzymes. Acute ethanol exposure activates the HPA axis, but in some conditions prolonged administration can dampen this activation as well as decrease the inflammatory responses to LPS. Therefore, this study was designed to evaluate the adrenal response to a challenge dose of LPS (50 μg/kg) injected i.p., after submitting male rats to RS, twice a day (2 h each time) for 5 days and/or ethanol administration (3 g/kg) by gavage also for 5 days, twice daily. At the end of the experiment, plasma corticosterone concentrations and adrenal gland content of prostaglandin E (PGE) and NOS activity were measured as stress mediators. The results showed that repetitive ethanol administration attenuated the adrenal stress response to LPS challenge alone and after RS, by preventing the increase in plasma corticosterone concentrations and by decreasing the PGE content and NOS activity in the adrenal gland. Therefore, we conclude that moderate alcohol consumption could attenuate the effects of psychophysical stress and impair an inflammatory response.
Glucocorticoid hormones are secreted in response to stimuli that activate the hypothalamo-pituitary-adrenocortical (HPA) axis and self-regulate through negative feedback. Negative feedback that occurs on a rapid time scale is thought to act through nongenomic mechanisms. In these studies, we investigated fast feedback inhibition of HPA axis stress responses by direct glucocorticoid action at the paraventricular nucleus of the hypothalamus (PVN). Local infusion of dexamethasone or a membrane-impermeant dexamethasone-BSA conjugate into the PVN rapidly inhibits restraint-induced ACTH and corticosterone release in a manner consistent with feedback actions at the cell membrane. The dexamethasone fast feedback response is blocked by the cannabinoid CB1 receptor antagonist AM-251, suggesting that fast feedback requires local release of endocannabinoids. Hypothalamic tissue content of the endocannabinoid 2-arachidonoyl glycerol is elevated by restraint stress, consistent with endocannabinoid action on feedback processes. These data support the hypothesis that glucocorticoid-induced fast feedback inhibition of the HPA axis is mediated by a nongenomic signaling mechanism that involves endocannabinoid signaling at the level of the PVN.
Secretion of glucocorticoid hormones during stress produces an array of physiological changes that are adaptive and beneficial in the short term. In the face of repeated stress exposure, however, habituation of the glucocorticoid response is essential as prolonged glucocorticoid secretion can produce deleterious effects on metabolic, immune, cardiovascular, and neurobiological function. Endocannabinoid signaling responds to and regulates the activity of the hypothalamic-pituitary-adrenal (HPA) axis that governs the secretion of glucocorticoids; however, the role this system plays in adaptation of the neuroendocrine response to repeated stress is not well characterized. Herein, we demonstrate a divergent regulation of the two endocannabinoid ligands, N-arachidonylethanolamine (anandamide; AEA) and 2-arachidonoylglycerol (2-AG), following repeated stress such that AEA content is persistently decreased throughout the corticolimbic stress circuit, whereas 2-AG is exclusively elevated within the amygdala in a stress-dependent manner. Pharmacological studies demonstrate that this divergent regulation of AEA and 2-AG contribute to distinct forms of HPA axis habituation. Inhibition of AEA hydrolysis prevented the development of basal hypersecretion of corticosterone following repeated stress. In contrast, systemic or intra-amygdalar administration of a CB(1) receptor antagonist before the final stress exposure prevented the repeated stress-induced decline in corticosterone responses. The present findings demonstrate an important role for endocannabinoid signaling in the process of stress HPA habituation, and suggest that AEA and 2-AG modulate different components of the adrenocortical response to repeated stressor exposure.
Endogenous cannabinoids are important signaling molecules in neuroendocrine control of homeostatic and reproductive functions including stress response and energy metabolism. The hypothalamic paraventricular and supraoptic nuclei have been shown to release endocannabinoids, which act as retrograde messengers to modulate the synaptic release of glutamate during stress response. This study endeavors to elucidate possible interaction of the endocannabinoid system with the regulation of adrenocortical function at the adrenal level. Human adrenocortical NCI-H295R cells and normal human adrenal glands were used to study the possible effects of anandamide and cannabinoid receptor 1 (CB1) antagonist SR141716A on aldosterone and cortisol secretion. Our data indicate the expression of CB1 in human adrenal cortex and adrenocortical NCI-H295R cells; CB2 was not expressed. Furthermore, anandamide inhibited basal release and stimulated release of adrenocortical steroids (corticosterone and aldosterone); this effect was reversed by CB1 antagonist (SR141716A). Therefore, the endocannabinoid system at the level of the adrenal, can directly influence adrenocortical steroidogenesis.
Our objective was to determine the effect of arachidonylethanolamide (anandamide, AEA) injected intracerebroventricularly (icv) into the lateral ventricle of the rat brain on submandibular gland (SMG) salivary secretion. Parasympathetic decentralization (PSD) produced by cutting the chorda tympani nerve strongly inhibited methacholine (MC)-induced salivary secretion while sympathetic denervation (SD) produced by removing the superior cervical ganglia reduced it slightly. Also, AEA (50 ng/5 microL, icv) significantly decreased MC-induced salivary secretion in intact rats (MC 1 microg/kg: control (C), 5.3 +/- 0.6 vs AEA, 2.7 +/- 0.6 mg; MC 3 microg/kg: C, 17.6 +/- 1.0 vs AEA, 8.7 +/- 0.9 mg; MC 10 microg/kg: C, 37.4 +/- 1.2 vs AEA, 22.9 +/- 2.6 mg). However, AEA did not alter the significantly reduced salivary secretion in rats with PSD, but decreased the slightly reduced salivary secretion in rats with SD (MC 1 microg/kg: C, 3.8 +/- 0.8 vs AEA, 1.4 +/- 0.6 mg; MC 3 microg/kg: C, 14.7 +/- 2.4 vs AEA, 6.9 +/- 1.2 mg; P < 0.05; MC 10 microg/kg: C, 39.5 +/- 1.0 vs AEA, 22.3 +/- 0.5 mg; P < 0.001). We showed that the inhibitory effect of AEA is mediated by cannabinoid type 1 CB1 receptors and involves GABAergic neurotransmission, since it was blocked by previous injection of the CB1 receptor antagonist AM251 (500 ng/5 microL, icv) or of the GABA A receptor antagonist, bicuculline (25 ng/5 microL, icv). Our results suggest that parasympathetic neurotransmission from the central nervous system to the SMG can be inhibited by endocannabinoid and GABAergic systems.
Nitric oxide (NO) was initially described as a mediator of endothelial relaxation, and now its participation is recognized in numerous physiological and pathological processes. It was demonstrated that lipopolysaccharide-stimulated corticotropin-releasing factor release involves NO production. Furthermore, it has been shown that interleukin (IL)-1, tumor necrosis factor (TNF)-alpha, IL-6, and IL-2 can stimulate adrenocorticotropic hormone release from anterior pituitary via NO. Also, we found that NO released from hypothalamic NOergic neurons in response to norepinephrine diffuses to luteinizing hormone-releasing hormone (LHRH) neurons that activate cyclooxygenase and guanylate cyclase. This activation results in an increase in prostaglandin E2 and cyclic guanosine monophosphate, respectively, which leads to the exocytosis of LHRH granules. During pathological conditions, such as manganese intoxication, NO production is increased, leading to an increase in LHRH secretion that can advance puberty. In another study we demonstrated that NO reduces oxytocin as well as vasopressin secretion from the posterior pituitary, suggesting it has a modulatory role during dehydration. An increase in NO synthase (NOS) activity and protein in the hippocampus and cerebellum was found in offspring of rats that were subjected to prenatal stress, and this was correlated with behavioral changes in adults. Also NO participates in signal transduction pathways in peripheral tissue in physiological processes, such as in corticosterone release from the adrenal gland. Pathological conditions, such as tumors of the head and neck, that are treated with radiation are followed by xerostomy. In a rat model, radiation diminished NOS activity in the submandibulary gland, and this was followed by inhibition in salivary secretion. In summary, this review describes the wide participation of NO in the cross-talk between neuroendocrine and neuroimmune systems in physiological and pathological processes.
The release of cytokines during infection, inflammation and stress induces brain-mediated responses, including alterations of neuroendocrine functions. We examined the effect of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) on release of gamma-aminobutyric acid (GABA) from mediobasal hypothalamic (MBH) explants and posterior pituitaries (PP) of male rats. IL-6 (10 ng/ml) did not modify basal GABA release from MBH and PP, but significantly increased GABA release under depolarizing conditions (40 mM K(+)). This effect was abolished by incubation of the tissue with indomethacin, an inhibitor of cyclooxygenase activity, indicating that prostaglandins could mediate the stimulation of GABA release induced by IL-6. On the contrary, TNF-alpha (50 ng/ml) significantly decreased K(+)-evoked GABA release from both MBH and PP. This inhibitory effect was not modified by indomethacin. Neither IL-6 nor TNF-alpha affected nitric oxide synthesis, as measured by [(14)C]citrulline production. The current results indicate that IL-6 stimulates GABA release from both hypothalamus and posterior pituitary by a mechanism mediated by prostaglandins. On the contrary, TNF-alpha inhibits GABA release from both tissues. These results suggest the possibility that GABAergic activity in the hypothalamic-pituitary axis could be involved in neuroendocrine responses to cytokines.
Little is known about the expression and function of cannabinoid receptor type 1 (CB1) in the human pituitary gland. The aim of this study was to investigate CB1 expression in human normal and tumoral pituitaries by in situ hybridization and immunohistochemistry using an antibody against CB1. CB1 was found in corticotrophs, mammotrophs, somatotrophs, and folliculostellate cells in the anterior lobe of normal pituitary. After examination of 42 pituitary adenomas, CB1 was detected in acromegaly-associated pituitary adenomas, Cushing's adenomas, and prolactinomas, whereas faint or no expression was found in nonfunctioning pituitary adenomas. Experiments with cultured pituitary adenoma cells showed that the CB1 agonist WIN 55,212--2 inhibited GH secretion in most of acromegaly-associated pituitary adenomas tested and that the CB1 antagonist SR 141716A was generally able to reverse this effect. Moreover, WIN 55,212--2 was able to suppress GHRH-stimulated GH release, and this effect was not blocked by coincubation with SR 141716A, possibly indicating a non-CB1-mediated effect. In contrast, WIN 55,212--2 was ineffective on GH-releasing peptide-stimulated GH release. In four Cushing's adenomas tested, WIN 55,212--2 was not able to modify basal ACTH secretion. However, simultaneous application of CRF and WIN 55,212--2 resulted in a synergistic effect on ACTH secretion, and this effect could be abolished by SR 141716A, demonstrating a CB1-mediated effect. In the single case of prolactinomas tested, WIN 55,212--2 was able to inhibit basal secretion of PRL. Finally, the presence of endocannabinoids (anandamide and 2-arachidonoylglycerol) was investigated in normal and tumoral pituitaries. All tumoral samples had higher contents of anandamide and 2-arachidonoylglycerol compared with the normal hypophysis. Moreover, endocannabinoid content in the different pituitary adenomas correlated with the presence of CB1, being elevated in the tumoral samples positive for CB1 and lower in the samples in which no or low levels of CB1 were found. The results of this study point to a direct role of cannabinoids in the regulation of human pituitary hormone secretion.
Two types of cannabinoid receptor have been discovered so far, CB(1) (2.1: CBD:1:CB1:), cloned in 1990, and CB(2) (2.1:CBD:2:CB2:), cloned in 1993. Distinction between these receptors is based on differences in their predicted amino acid sequence, signaling mechanisms, tissue distribution, and sensitivity to certain potent agonists and antagonists that show marked selectivity for one or the other receptor type. Cannabinoid receptors CB(1) and CB(2) exhibit 48% amino acid sequence identity. Both receptor types are coupled through G proteins to adenylyl cyclase and mitogen-activated protein kinase. CB(1) receptors are also coupled through G proteins to several types of calcium and potassium channels. These receptors exist primarily on central and peripheral neurons, one of their functions being to inhibit neurotransmitter release. Indeed, endogenous CB(1) agonists probably serve as retrograde synaptic messengers. CB(2) receptors are present mainly on immune cells. Such cells also express CB(1) receptors, albeit to a lesser extent, with both receptor types exerting a broad spectrum of immune effects that includes modulation of cytokine release. Of several endogenous agonists for cannabinoid receptors identified thus far, the most notable are arachidonoylethanolamide, 2-arachidonoylglycerol, and 2-arachidonylglyceryl ether. It is unclear whether these eicosanoid molecules are the only, or primary, endogenous agonists. Hence, we consider it premature to rename cannabinoid receptors after an endogenous agonist as is recommended by the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. Although pharmacological evidence for the existence of additional types of cannabinoid receptor is emerging, other kinds of supporting evidence are still lacking.
Unlabelled:
Nitric oxide (NO) is involved in stress physiology and stress-related disease processes. Like stress, NO seems to be capable of principally exerting either beneficial or deleterious effects. The actual distinction depends on a multitude of factors. Moreover, NO counteracts norepinephrine (NE) activity and sympathetic responsivity. Thus, NO and the stress (patho)physiology are closely connected and molecular mechanisms or pathways may be shared under certain conditions. NO is involved in immunological, cardiovascular, and neurodegenerative diseases/ mental disorders. It represents a 'double-edged sword', since small quantities produced by constitutive enzymes may predominantly mediate physiological effects, whereas the expression of inducible NO synthases may lead to larger quantities of NO, a situation that may be associated with cytotoxic and detrimental effects of NO. The key step for normally useful physiological mechanisms becoming pathophysiological may be represented by the loss of balance, the loss of control over the different pathways induced. A failure to terminate or shift originally protective mechanisms may lead to a vicious cycle of disease-supporting pathophysiological pathways.
Conclusions:
Profound connections between stress and various disease processes exist. Thereby, common pathophysiological pathways in stress-related diseases have been described, and they involve stress hormone (cortisol, NE) and, in particular, NO activity. Thus, NO has detrimental capacities. However, NO not only exerts deleterious but also strongly ameliorating effects. The balance between both properties is crucial. Yet, nitric oxide involvement in stress-related diseases represents a common pathway, with various pathophysiological analogies, that may be accessible for strategies using stress management and relaxation response techniques.
Hypoxia results in decreased arterial PO2, arterial chemoreflex activation, and compensatory increases in breathing, sympathetic outflow, and neuroendocrine secretions, including increased secretion of vasopressin (AVP), corticotropin releasing hormone (CRH), adrenocorticotropin hormone (ACTH), and corticosterone. In addition to a brainstem pathway including the nucleus tractus solitarius (nTS) and the rostral ventrolateral medulla (RVLM), medullary pathways to the paraventricular nucleus of the hypothalamus (PVN) contribute to chemoreflex responses. Experiments evaluated activation of specific cell phenotypes within the PVN following an acute hypoxic stimulus (AH, 2 hr, 10% O2) in conscious rats. Retrograde tracers (from spinal cord and RVLM) labeled pre-sympathetic (PreS) neurons; immunohistochemistry (IHC) identified AVP- and CRH-IR cells; Fos- IR was an index of neuronal activation. Hypoxia activated AVP-IR (~ 6%) and CRH-IR (~15%) cells, but not PreS cells in the PVN, suggesting that sympathoexcitation during moderate AH is mediated mainly by a pathway that does not include PreS neurons in the PVN. Approximately 14 to 17% of all PVN cell phenotypes examined expressed nNOS-IR. AH activated only nNOS-negative AVP-IR neurons. In contrast ~ 23% of activated CRH-IR neurons in the PVN contained nNOS. In the median eminence, CRH-IR terminals were closely opposed to tanycyte processes and endfeet (vimentin-IR) in the external zone, where vascular NO participates in tanycyte retraction to facilitate neuropeptide secretion into the pituitary portal circulation. Results are consistent with an inhibitory role of NO on AVP and PreS neurons in the PVN, and an excitatory role of NO on CRH secretion in the PVN and median eminence.
Background:
The aim of this study was to compare the expression of interleukin-1β (IL-1β), neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in the prefrontal cortex (PFC), hippocampus (HIP) and hypothalamus (HT) during chronic crowding (CS) (psychosocial) and restraint (RS) (physico-psychological) stress. Adaptational changes of these stress mediators to a subsequent acute RS, in two models of chronic stress were investigated.
Methods:
Rats were crowded (24 in one cage) or restrained in metal tubes for 10min twice a day for 3, 7, and 14 consecutive days and decapitated. For determination of adaptational changes the chronically crowded and restrained rats 24h after the last stress session were subjected to a single 10min RS. The IL-1β, nNOS and iNOS protein levels in brain structures samples were analyzed by Western blot procedure.
Results:
Chronic CS for 3days did not markedly change the subsequent acute stress induced expression of nNOS, iNOS and IL-1β protein level in PFC and iNOS protein level in HT. CS markedly decreased the expression of nNOS, iNOS and IL-1β in HIP. By contrast, parallel chronic RS, significantly increased the subsequent acute stress-induced expression of iNOS and IL-1β in PFC and considerably increased iNOS level in HT.
Conclusion:
Chronic psychosocial stress, may protect against possible harmful action of hyperproduction of iNOS and iNOS derived nitric oxide (NO) mainly in PFC and HIP. By contrast, chronic physico-psychosocial stress may strongly potentiate additional stress-induced harmful effects of NOS and IL-1β hyperproduction.
There is currently considerable interest in the development of medicines that would enhance endocannabinoid-induced "autoprotection", for example through inhibition of endocannabinoid metabolizing enzymes or cellular uptake processes or that would oppose endocannabinoid-induced "autoimpairment". This volume describes the physiology, pathophysiology and pharmacology of the endocannabinoid system and potential strategies for targeting this system in the clinic. © Springer International Publishing Switzerland 2015. All rights reserved.
The endocannabinoid system (ECS) is a widespread neuromodulatory system that plays important roles in central nervous system development, synaptic plasticity, and the response to endogenous and environmental insults. The ECS comprises cannabinoid receptors, endogenous cannabinoids (endocannabinoids), and the enzymes responsible for the synthesis and degradation of the endocannabinoids. The most abundant cannabinoid receptors are the CB1 cannabinoid receptors; however, CB2 cannabinoid receptors, transient receptor potential channels, and peroxisome proliferator activated receptors are also engaged by some cannabinoids. Exogenous cannabinoids, such as tetrahydrocannabinol, produce their biological effects through their interactions with cannabinoid receptors. The best-studied endogenous cannabinoids are 2-arachidonoyl glycerol and arachidonoyl ethanolamide (anandamide). Despite similarities in chemical structure, 2-arachidonoyl glycerol and anandamide are synthesized and degraded by distinct enzymatic pathways, which impart fundamentally different physiologic and pathophysiologic roles to these two endocannabinoids. As a result of the pervasive social use of cannabis and the involvement of endocannabinoids in a multitude of biological processes, much has been learned about the physiologic and pathophysiologic roles of the ECS. This review provides an introduction to the ECS with an emphasis on its role in synaptic plasticity and how the ECS is perturbed in schizophrenia.
Some of the earliest reports of the effects of cannabis consumption on humans were related to endocrine system changes. In this review, the effects of cannabinoids and the role of the CB1 cannabinoid receptor in the regulation of the following endocrine systems are discussed: the hypothalamic-pituitary- gonadal axis, prolactin and oxytocin, thyroid hormone and growth hormone, and the hypothalamic-pituitary-adrenal axis. Preclinical and human study results are presented. © Springer International Publishing Switzerland 2015. All rights reserved.
Stress and stress related disorders are a major cause of morbidity and mortality and understanding stress mechanisms is of great importance for devising appropriate therapeutic measures in such situations. The brain and its complex neurotransmitter systems regulate physiological and behavioral responses to a variety of stressors. Several other factors like age, gender and emotionality of the organism, as well as type, intensity and duration of the stressor may decide the nature and extent of stress effects. Nitric oxide (NO) is widely distributed in the brain and its role in Central nervous system (CNS) pathophysiology has been suggested. Recent studies have shown that free radicals and in particular NO may play a crucial role in the regulation of stress effects. All the various factors, mentioned above, that might influence stress responsiveness have been discussed with reference to regulatory role of NO during stress and it appears that NO may act as a therapeutic target for development of novel strategies against stress related disorders.
Copyright © 2015. Published by Elsevier B.V.
There is evidence that endogenous cannabinoids (eCBs) play a role in the control of the hypothalamic-pituitary-adrenal (HPA) axis, although they appear to have dual, stimulatory and inhibitory, effects. Recent data in rats suggest that eCBs, acting through CB1 receptors (CB1R), may be involved in adaptation of the HPA axis to daily repeated stress. In the present study we analyze this issue in male mice and rats. Using a knock-out mice for the CB1 receptor (CB1-/-) we showed that mutant mice presented similar adrenocorticotropic hormone (ACTH) response to the first IMO as wild-type mice. Daily repeated exposure to 1h of immobilization reduced the ACTH response to the stressor, regardless of the genotype, demonstrating that adaptation occurred to the same extent in absence of CB1R. Prototypical changes observed after repeated stress such as enhanced corticotropin releasing factor (CRH) gene expression in the paraventricular nucleus of the hypothalamus, impaired body weight gain and reduced thymus weight were similarly observed in both genotypes. The lack of effect of CB1R in the expression of HPA adaptation to another similar stressor (restraint) was confirmed in wild-type CD1 mice by the lack of effect of the CB1R antagonist AM251 just before the last exposure to stress. Finally, the latter drug did not blunt the HPA, glucose and behavioral adaptation to daily repeated forced swim in rats. Thus, the present results indicate that CB1R is not critical for overall effects of daily repeated stress or proper adaptation of the HPA axis in mice and rats.
Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.
Nitric oxide (NO) synthase (NOS) expression was analyzed in rat adrenal zona fasciculata. Both neuronal NOS and endothelial NOS mRNAs were detected by RT-PCR, immunohistochemistry, and immunoblot analysis. The biochemical characterization of adrenal zona fasciculata NOS enzymatic activity confirmed the presence of a constitutive isoform. In a cell line derived from mouse adrenal cortex, only endothelial NOS expression was detected by both RT-PCR and immunoblot analysis. Nitrate plus nitrite levels in Y1 cell incubation medium were increased in the presence of l-arginine and the calcium ionophore A23187, but not d-arginine, indicating enzymatic activity. Moreover, a low, but significant, conversion of larginine to l-citrulline, abolished by the NOS inhibitor, NG-nitro-l-arginine, was detected in Y1 cells. The effect of l-arginine on pregnenolone production was examined. l-Arginine decreased both basal and ACTH-stimulated pregnenolone production in Y1 cells. The inhibitory effect of l-arginine could be attributed to endogenously generated NO, because it was blocked by NG-nitro-l-arginine, and it was mimicked by the addition of a NO donor, diethylenetriamine-NO. An inhibitory effect of NO on pregnenolone production from 22Rhydroxycholesterol and on steroidogenic acute regulatory protein expression was also determined. Taken together, these results suggest that at least part of the adrenal NO could derive from steroidogenic cells and modulate their function.
The CB1 cannabinoid receptor is a G protein coupled receptor that is widely expressed throughout the brain. The endogenous ligands for the CB1 receptor (endocannabinoids) are N-arachidonylethanolamine and 2-arachidonoylglycerol; together the endocannabinoids and CB1R subserve activity dependent, retrograde inhibition of neurotransmitter release in the brain. Deficiency of CB1 receptor signaling is associated with anhedonia, anxiety, and persistence of negative memories. CB1 receptor-endocannabinoid signaling is activated by stress and functions to buffer or dampen the behavioral and endocrine effects of acute stress. Its role in regulation of neuronal responses is more complex. Chronic variable stress exposure reduces endocannabinoid-CB1 receptor signaling and it is hypothesized that the resultant deficiency in endocannabinoid signaling contributes to the negative consequences of chronic stress. On the other hand, repeated exposure to the same stress can sensitize CB1 receptor signaling, resulting in dampening of the stress response. Data are reviewed that support the hypothesis that CB1 receptor signaling is stress responsive and that maintaining robust endocannabinoid/CB1 receptor signaling provides resilience against the development of stress-related pathologies.
Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis is accepted as one of the fundamental biological mechanisms that underlie major depression. This hyperactivity is caused by diminished feedback inhibition of glucocorticoid (GC)-induced reduction of HPA axis signaling and increased corticotrophin-releasing hormone (CRH) secretion from the hypothalamic paraventricular nucleus (PVN) and extra-hypothalamic neurons. During chronic stress-induced inhibition of systemic feedback, cytosolic glucocorticoid receptor (GR) levels were significantly changed in the prefrontal cortex (PFC) and hippocampus, both structures known to be deeply involved in the pathogenesis of depression.
Stress-exposure produces excitoxicity and neuroinflammation, contributing to the cellular damage observed in stress-related neuropathologies. The endocannabinoid system is present in stress-responsive neural circuits and it is emerging as a homeostatic system. The aim of this study was to elucidate the possible regulatory role of cannabinoid-2 receptor in stress-induced excitotoxicity and neuroinflammation.
Different genetic and pharmacological approaches were used: 1) Wild type (WT), transgenic over-expressing CB2 receptor (CB2xP) and CB2 receptor knockout (CB2-KO) mice were exposed to immobilization/acoustic stress (2h/day for 4 days), and 2) the CB2 receptor agonist JWH-133 was administered daily (2 mg kg(-1) , i.p.) to WT and CB2 receptor-KO animals.
Stress-induced HPA axis activation was not modified by CB2 receptor manipulations. JWH-133 treatment or overexpression of CB2 resulted in an increase of control levels of glutamate uptake, which is then reduced by stress exposure back to control levels. JWH-133 prevented the stress-induced increase in the cytokines TNF-α and MCP-1, the nuclear factor kappa B, the enzymes inducible nitric oxide synthase 2 and cyclooxygenase-2 and the cellular oxidative/nitrosative damage (lipid peroxidation) in brain frontal cortex. CB2xP mice displayed anti-inflammatory/neuroprotective actions similar to those observed in JWH-133 pre-treated animals. Conversely, CB2-KO mice experiments indicated that the lack of CB2 receptor exacerbated stress-induced neuroinflammatory responses and validated the CB2 receptor-dependent effects of JWH-133.
These results suggest that pharmacological manipulation of CB2 receptor is a potential therapeutic strategy for the treatment of stress-related pathologies with a neuroinflammatory component, such as depression.
The neurohypophyseal hormones oxytocin (OT) and vasopressin (VP) are involved in behavioral, autonomic and neuroendocrine functions. Both peptides are synthesized in magnocellular neurons of paraventricular and supraoptic nuclei at hypothalamic level whose axons terminate in the neurohypophysis (NH), from where OT and VP are released into the systemic circulation. NH contains abundant nitric oxide (NO) synthase suggesting that NO plays a role in the release of these neuropeptides. The endocannabinoid system is present in magnocellular neurons of the hypothalamic neurohypophyseal system, and we have previously demonstrated that endocannabinoids modulate OT secretion at hypothalamic level. In the present work, we investigated the in vitro effect of the endocannabinoid anandamide (AEA) on OT and VP release from NH of untreated adult male rats and the involvement of NO in this action. Our results showed that AEA decreased OT and VP secretion from NH. AEA action was mediated by NO, since the inhibition of NO synthesis completely blocked this inhibitory effect. We found that cannabinoid receptor type 2 (CB2) and transient receptor potential cation channel subfamily V member 1 (TRPV1) are involved in the inhibitory effect of AEA because AM630 and capsazepine, CB2 and TRPV1 antagonists respectively, but not AM251, a CB1 antagonist, blocked AEA effect at neurohypophyseal level. These findings revealed an interaction between endocannabinoid, nitric oxide and oxytocin/vasopressin systems that could be involved in the modulation of homeostatic, behavioral and reproductive processes.
Studies in male rodents have shown that stress-induced increases in circulating corticosterone are increased by both CB1 receptor (CB1R) antagonist treatment and genetic deletion. The purposes of the current study were to determine whether female mice respond in the same manner as males, and whether indirect CB1R agonists accelerate the return of corticosterone to baseline. In agreement with earlier studies, CB1R null and rimonabant-treated male mice had significantly increased circulating corticosterone 30minutes following the end of a restraint episode compared to wild type and vehicle-treated, respectively. Females treated with rimonabant had significantly higher circulating corticosterone compared to vehicle. However, corticosterone concentrations were not different between CB1R null and wild type females at 30minutes recovery, although CB1R null mice had higher corticosterone concentrations at 90minutes of recovery. Female CB1R null mice exhibited greater serum binding capacity for corticosterone than wild type. The monoacylglycerol lipase inhibitor, JZL184, attenuated corticosterone concentrations at restraint offset in male, and at 30minutes recovery in female mice compared to vehicle. Male mice treated with JZL184 exhibited greater concentrations of circulating corticosterone at 120minutes recovery, even in the absence of restraint. JZL184 had no effect on corticosterone concentrations in CB1R null mice. The fatty acid amide hydrolase inhibitor, URB597, did not affect corticosterone responses to restraint in male or female, wild type or CB1R null mice. These data suggest that 2-arachidonoylglycerol is the primary endocannabinoid involved in CB1R regulation of the recovery of the HPA axis from restraint stress. These data support a role for endocannabinoid-CB1R signaling in the regulation of the corticosterone response to restraint stress and suggest that female mice with life-long loss of the CB1R undergo compensatory changes that minimize the impact of loss of endocannabinoid signaling on circulating corticosterone.
Hyperactivation of the amygdala following chronic stress is believed to be one of the primary mechanisms underlying the increased propensity for anxiety-like behaviors and pathological states; however, the mechanisms by which chronic stress modulates amygdalar function are not well characterized. The aim of the current study was to determine the extent to which the endocannabinoid (eCB) system, which is known to regulate emotional behavior and neuroplasticity, contributes to changes in amygdalar structure and function following chronic stress. To examine the hypothesis, we have exposed C57/Bl6 mice to chronic restraint stress, which results in an increase in fatty acid amide hydrolase (FAAH) activity and a reduction in the concentration of the eCB N-arachidonylethanolamine (AEA) within the amygdala. Chronic restraint stress also increased dendritic arborization, complexity and spine density of pyramidal neurons in the basolateral nucleus of the amygdala (BLA) and increased anxiety-like behavior in wild-type mice. All of the stress-induced changes in amygdalar structure and function were absent in mice deficient in FAAH. Further, the anti-anxiety effect of FAAH deletion was recapitulated in rats treated orally with a novel pharmacological inhibitor of FAAH, JNJ5003 (50 mg per kg per day), during exposure to chronic stress. These studies suggest that FAAH is required for chronic stress to induce hyperactivity and structural remodeling of the amygdala. Collectively, these studies indicate that FAAH-mediated decreases in AEA occur following chronic stress and that this loss of AEA signaling is functionally relevant to the effects of chronic stress. These data support the hypothesis that inhibition of FAAH has therapeutic potential in the treatment of anxiety disorders, possibly by maintaining normal amygdalar function in the face of chronic stress.
Background:
Interleukin-1β (IL-1β), the major cytokine involved in activation of hypothalamic-pituitary-adrenal (HPA) axis modulates both central and peripheral components regulating HPA activity. The role of nitric oxide (NO) generated by neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in brain structures involved in HPA axis regulation has not been elucidated. The aim of the study was to assess the receptor selectivity of IL-1β stimulatory action on HPA axis and to determine the involvement of nNOS and iNOS in this stimulation.
Methods:
Experiments were performed on male Wistar rats which were injected intraperitoneally (ip) with IL-1β (5 μg/kg) or IL-1 receptor antagonist (IL-1ra) (50 μg/kg or 100 μg/kg) 15 min before IL-1β. Rats were sacrificed by rapid decapitation 1, 2 or 3 h after IL-1β administration. Trunk blood for ACTH, corticosterone and IL-1β determinations was collected and prefrontal cortex, hippocampus and hypothalamus were excised and snap frozen. Western blot analyses were performed and IL-1β, nNOS and iNOS protein were determined in brain structures samples.
Results:
IL-1β significantly increased plasma ACTH, corticosterone and IL-1β levels during 2 h after ip administration. IL-1 receptor antagonist was able to abolish the stimulatory effect of IL-1β on plasma ACTH and corticosterone levels and significantly, but not totally, reduced plasma IL-1β level. The role of NO in prefrontal cortex, hippocampus and hypothalamus in the IL-1β-induced HPA axis activity alterations was determined by measuring the changes in nNOS and iNOS levels. The highest level of both izoenzymes 1 h following IL-1β administration decreased in a regular, parallel manner 2 and 3 h later, approaching control values. These changes were almost totally prevented by pretreatment with IL-1 receptor antagonist. In the hypothalamus the IL-1β-induced initial significant increase of nNOS regularly decreased in a modest rate and remained at significant higher level compared to control values. By contrast, iNOS level gradually increased 2 and 3 h after IL-1β administration in a significant time-dependent manner. The changes in both NOS izoenzyme levels in hypothalamus were suppressed by pretreatment with IL-1 receptor antagonist. Results also show that a regular and parallel decrease of nNOS in the hypothalamus and prefrontal cortex are parallel in time and magnitude to respective fall in plasma IL-1β and ACTH levels.
Conclusion:
The present study suggests that the IL-1β-induced transient stimulation of HPA axis activity is parallel in time and magnitude to the respective changes of nNOS in hypothalamus and prefrontal cortex, the brain structures involved in regulation of HPA axis activity.
We have tested our prediction that AM630 is a CB2 cannabinoid receptor ligand and also investigated whether L759633 and L759656, are CB2 receptor agonists.
Binding assays with membranes from CHO cells stably transfected with human CB1 or CB2 receptors using [3H]-CP55940, confirmed the CB2-selectivity of L759633 and L759656 (CB2/CB1 affinity ratios=163 and 414 respectively) and showed AM630 to have a Ki at CB2 receptors of 31.2 nM and a CB2/CB1 affinity ratio of 165.
In CB2-transfected cells, L759633 and L759656 were potent inhibitors of forskolin-stimulated cyclic AMP production, with EC50 values of 8.1 and 3.1 nM respectively and CB1/CB2 EC50 ratios of >1000 and >3000 respectively.
AM630 inhibited [35S]-GTPγS binding to CB2 receptor membranes (EC50=76.6 nM), enhanced forskolin-stimulated cyclic AMP production in CB2-transfected cells (5.2 fold by 1 μM), and antagonized the inhibition of forskolin-stimulated cyclic AMP production in this cell line induced by CP55940.
In CB1-transfected cells, forskolin-stimulated cyclic AMP production was significantly inhibited by AM630 (22.6% at 1 μM and 45.9% at 10 μM) and by L759633 at 10 μM (48%) but not 1 μM. L759656 (10 μM) was not inhibitory. AM630 also produced a slight decrease in the mean inhibitory effect of CP55940 on cyclic AMP production which was not statistically significant.
We conclude that AM630 is a CB2-selective ligand that behaves as an inverse agonist at CB2 receptors and as a weak partial agonist at CB1 receptors. L759633 and L759656 are both potent CB2-selective agonists.
British Journal of Pharmacology (1999) 126, 665–672; doi:10.1038/sj.bjp.0702351
The endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol are removed from the extracellular space by a process of cellular uptake followed by metabolism. Although the enzymes responsible for endocannabinoid metabolism have been well characterised, the processes involved in uptake have been the subject of much controversy. Recent studies, however, have identified intracellular transport proteins (fatty acid binding proteins 5 and 7, heat shock protein 70, albumin, and fatty acid amide hydrolase-like AEA transporter protein) that shuttle AEA from the plasma membrane to its metabolic enzymes. Proteins such as the fatty acid amide hydrolase-like anandamide transporter protein may be useful targets for novel therapeutic strategies aimed at potentiating AEA signalling. In this article I review the current state of the art of endocannabinoid uptake.
Altered regulation of the hypothalamic-pituitary-adrenal (HPA) axis is associated with stress-induced changes in cognitive, emotional, and physical health. Recent evidence indicates that the endogenous cannabinoid (eCB) system may modulate HPA-axis function both directly and more centrally, via regulation of limbic brain systems that control HPA-axis activity. The current study examines the contribution of cannabinoid type 1 (CB1) receptor modulation throughout the neuraxis on control and stress-induced HPA-axis activity. Adult male Sprague-Dawley rats were given intraperitoneal injections of either CB1 receptor antagonist (AM251, 2 mg/kg) or vehicle 30 min prior to a session of loud white noise stress (95 dBA for 30 min) or placement in a familiar sound-proof chamber. Immediately following stress and control treatments, rats were killed, the brains and pituitary glands were excised for subsequent immediate early gene (c-fos mRNA) measurement, and trunk blood was collected for subsequent determination of corticosterone (CORT) and adrenocorticotropic (ACTH) hormone levels. AM251 treatment resulted in a potentiated plasma ACTH response to loud noise stress. AM251 treatment also increased stress-induced plasma CORT levels, but that increase may be due to an increase in basal plasma CORT levels, as was evident in control rats. AM251 treatment produced three distinctive c-fos mRNA response patterns across the various brain regions examined. In cortical (prelimbic, infralimbic, somatosensory, and auditory) and some subcortical structures (basolateral amygdala and paraventricular nucleus of the hypothalamus), AM251 treatment produced a substantial increase in c-fos mRNA that was comparable with the elevated c-fos mRNA levels present in those brain regions of both vehicle and AM251-treated stressed rats. In some other subcortical structures (bed nucleus of the stria terminalis and medial preoptic area) and the anterior pituitary, AM251 treatment produced a c-fos mRNA response pattern that was similar to the response pattern of ACTH hormone levels, that is, no effect on no noise control levels, but an augmentation of stress-induced levels. Conversely, in the medial geniculate and ventral posterior thalamus, AM251 treatment inhibited stress-induced c-fos mRNA induction. These data indicate that disruption of eCB signaling through CB1 receptors results in potentiated neural and endocrine responses to loud noise stress, but also substantial increases in activity in various brain regions and the adrenal gland.
The endocannabinoid system has been recognized as a major neuromodulatory system, which functions to maintain brain homoeostasis. Endocannabinoids are synthesized and released from the postsynapse and act as retrograde neuronal messengers, which bind to cannabinoid type 1 receptors at the presynapse. Here, they inhibit the release of neurotransmitters, including glutamate and GABA. By these means, endocannabinoids control the activation of various neuronal circuits including those involved in neuroendocrine stress processing. Accordingly, exogenous cannabinoids such as the major active component of marijuana, Delta(9)-tetrahydrocannabinol, have long been known to activate the major neuroendocrine stress response system of mammals, the hypothalamic-pituitary-adrenocortical (HPA) axis. However, the function of the endocannabinoid system in the regulation of stress hormone secretion has only recently begun to be understood. It is the focus of the present review to provide the reader with an overview of our current knowledge of the role of endocannabinoid signalling in HPA axis regulation under basal as well as under stressful conditions. This includes the specific sites of action, potential underlying neuronal pathways and interactions between behavioural and neuroendocrine stress coping. Furthermore, the potential role of HPA axis activity dysregulations, caused by deficits in the endocannabinoid system, for the pathophysiology of psychiatric diseases is discussed.
The involvement of nitric oxide (NO) in the effects of dehydroepiandrosterone sulphate (DHEAS) on restraint stress induced neurobehavioral and brain oxidative/nitrosative stress markers was investigated in rats. Exposure of rats to restraint stress suppressed behavioral activity in the elevated plus maze and this was associated with increases in malondialdehyde (MDA) and decrease in reduced glutathione (GSH) and brain NO metabolite (NOx) levels in brain homogenates. Pretreatment with DHEAS (5-40mg/s.c.) reversed the stress induced changes in behavioral and oxidative stress markers and also brain NOx levels. The beneficial effect of DHEAS (40mg/kgs.c.) was blocked by pretreatment with nitric oxide synthase inhibitor, L-NAME (50mg/kgi.p.) while pretreatment of rats with NO-precursor l-Arginine (100mg/kg i.p.) produced potentiation of action of sub effective dose of DHEAS (5mg/kgs.c.). The DHEAS effects were stress specific as these behavioral and biochemical parameters were not much influenced in non-stressed rats. These observations suggest that pretreatment with DHEAS has a protective effect on restraint stress induced alteration of neurobehavioral changes and brain oxidative injury in rats and NO-dependent mechanisms may be involved in this effect.
CB 2 was first considered to be the ‘peripheral cannabinoid receptor’. This title was bestowed based on its abundant expression in the immune system and presumed absence from the central nervous system. However, multiple recent reports question the absence of CB 2 from the central nervous system. For example, it is now well accepted that CB 2 is expressed in brain microglia during neuroinflammation. However, the extent of CB 2 expression in neurons has remained controversial. There have been studies claiming either extreme‐its complete absence to its widespread expression‐as well as everything in between. This review will discuss the reported tissue distribution of CB 2 with a focus on CB 2 in neurons, particularly those in the central nervous system as well as the implications of that presence. As CB 2 is an attractive therapeutic target for pain management and immune system modulation without overt psychoactivity, defining the extent of its presence in neurons will have a significant impact on drug discovery. Our recommendation is to encourage cautious interpretation of data that have been presented for and against CB 2 's presence in neurons and to encourage continued rigorous study.
This article is part of a themed issue on Cannabinoids. To view the editorial for this themed issue visit http://dx.doi.org/10.1111/j.1476‐5381.2010.00831.x
This study investigated the participation of the hypothalamic endocannabinoid system in the response to lipopolysaccharide (LPS) challenge evaluating oxytocin (OXT) and tumor necrosis factor-alpha (TNF-alpha) plasma levels in vivo and their release from hypothalamic fragments in vitro. LPS increased OXT and TNF-alpha release through anandamide-activation of hypothalamic cannabinoid receptor CB(1,) since the antagonist AM251 blocked this effect. Anandamide, through its receptors, also increased hypothalamic nitric oxide (NO) which inhibited OXT release, ending the stimulatory effect of the endocannabinoid. Our findings reveal a hypothalamic interaction between oxytocin, endocannabinoid and NO-ergic systems providing a regulation of the hypothalamic-neurohypophyseal axis under basal and stress conditions.
Arachidonylethanolamide (anandamide) was identified some 15 years ago as a brain constituent that binds to the cannabinoid receptor. After this seminal discovery, multiple new receptors for anandamide have been identified, including the vanilloid receptor (TRPV1), and anandamide is now frequently referred as an "endovanilloid." Characterization of the action of anandamide on TRPV1 revealed that (1) the potency and efficacy of anandamide on TRPV1 very much depend on the species and tissue, (2) anandamide responsiveness in vivo is significantly controlled by its local metabolism, (3) anandamide activation of cannabinoid receptors regulates TRPV1 responsiveness, (4) TRPV1 activation regulates anandamide synthesis, (5) anandamide metabolites affect TRPV1 responses, (6) the often observed convergent physiological actions of anandamide and TRPV1 agonists in neither case necessarily represent direct effects on TRPV1, and (7) coactivation of the cannabinoid receptors and TRPV1 often complicates the distinction between these pathways. These issues are reviewed here together with the potential implications for the pathophysiological and pharmacological regulation of inflammatory, respiratory, and cardiovascular disorders, as well as of appetite and fat metabolism.
The stress response is associated with a broad spectrum of physiological and behavioural effects including hypothalamo-pituitary-adrenal (HPA) axis activation, altered central nervous system activity, neuroimmune alterations, anxiety- and depressive-like behaviour and analgesia. While the acute stress response has essential survival value, chronic stress and dysfunction of the stress response can be maladaptive, contributing to the development and severity of psychiatric and pain disorders. The endogenous cannabinoid (endocannabinoid) system has emerged as an important lipid signalling system playing a key role in mediating and/or modulating behavioural, neurochemical, neuroendocrine, neuroimmune and molecular responses to stress. The weight of evidence, reviewed here, points largely to a system which serves to constrain HPA axis activity, facilitate adaptation or habituation of HPA axis and behavioural responses to stress, reduce anxiety- and depressive-like behaviour and mediate analgesic responses to unconditioned or conditioned stress. Possible involvement of the immune system and associated signalling molecules (e.g. cytokines) in endocannabinoid-mediated modulation of neuroendocrine and behavioural responses to stress is considered. The goal now should be to exploit our understanding of the role of the endocannabinoid system in fundamental stress physiology and pathophysiological processes to better understand and treat a range of stress-related disorders including anxiety, depression and pain.
In the 15 years since the publication of two previous reviews on restraint stress much advancement has been made in the field. However, while previous reviews have focused mainly on drug effects, recent research has focused on broader implications in the health fields. This research has placed an increased emphasis on stress effects in physiological, immunological, endocrine and developmental processes as well as the impact of stress on numerous disorders. A major problem with our review was the inability to identify a large number of articles focusing on restraint and immobilization, since those keywords were often omitted from the title or not referred to within the body of the article. It seems likely that additional reviews with extended literature research of this field are required.
The present study evaluated the effects of acute and chronic restraint stress (RS 1 h or 6 h), and their modulation by nitrergic agents on neurobehavioral and oxidative stress markers in rats. Acute RS (1 h or 6 h) reduced open arm entries (OAE) and open arm time (OAT) in the elevated plus maze test - which were attenuated by the NO precursor, L-arginine but not influenced appreciably by the NO synthase inhibitor, L-NAME. These behavioral changes were associated with differential changes in brain NO metabolites (NOx) but consistently reduced GSH and raised MDA levels in comparison to the control group. Following RS 1 h x 10 the neurobehavioral suppression and changes in brain oxidative stress markers were less pronounced as compared to the acute RS (1 h) group indicating adaptation. L-arginine pretreatment facilitated this adaptation to chronic RS (1 h). Interestingly RS 6 h x 10, induced severe behavioral suppression and aggravation of MDA and NOx levels and L-NAME pretreatment tended to protect against these chronic RS induced aggravations. These results suggest that acute and chronic RS induces duration/intensity dependent neurobehavioral and oxidative injury which are under the differential regulatory control of NO.
Stimulation of corticotropin-releasing factor (CRF) release from the hypothalamus by interleukin 2 (IL-2) was recently demonstrated. Cytokines induce nitric oxide synthase (NOS), an enzyme that converts L-arginine into L-citrulline and nitric oxide (NO). NO is believed to be responsible for the cytotoxic action of these agents. The constitutive form of NOS occurs in neurons in the central nervous system and NO appears to play a neurotransmitter role in cerebellar and hippocampal function. We explored the probability that IL-2 and synaptic transmitters might release CRF via NO. The effects of L-arginine, the substrate for NOS, and NG-monomethyl-L-arginine (NMMA), a competitive inhibitor of NOS, on IL-2-induced CRF release were studied using mediobasal hypothalami (MBHs) incubated in vitro in Krebs-Ringer bicarbonate buffer. L-Arginine did not alter basal and IL-2-induced CRF release after 30 min of incubation but significantly elevated both basal and IL-2-induced CRF release when MBHs were incubated 30 min longer, presumably because the endogenous substrate had been depleted after the initial 30-min incubation period. In 30-min incubations, both carbachol, an acetylcholineomimetic drug, and norepinephrine stimulated CRF release. There was an additive effect of incubation of the MBHs in the presence of carbachol (10(-7) M) and IL-2 (10(-13) M). On the other hand, coincubation of MBHs with norepinephrine (10(-6) M) and IL-2 (10(-13) M) did not produce any additive effect. Addition of NMMA, an inhibitor of NOS, at 1 or 3 x 10(-4) M completely suppressed IL-2-induced release of CRF as well as that caused by IL-2 plus carbachol. In contrast, the release of CRF induced by norepinephrine was not blocked by 3 x 10(-4) M NMMA. The data indicate that IL-2 can activate constitutive NOS leading to increased NO release, which activates CRF release. It appears that NO is also involved in the release of CRF induced by carbachol but not by norepinephrine.
High densities of nerve cells containing corticotropin-releasing hormone (CRH) are located in the central nucleus of the amygdala (CeA) and paraventricular nucleus (PVN) of the hypothalamus. These brain regions play an important role in activating autonomic, behavioral, and endocrine responses to stress. This study was conducted to provide needed information concerning the acute effects of stress on CeA and PVN CRH mRNA expression. Rats were exposed to restraint stress for 1 h and brains collected after a 1-h post-stress interval. CRH mRNA expression occurring in the CeA and PVN was examined using in situ hybridization techniques. Densitometric analysis revealed that acute restraint stress produced significant increases in CRH mRNA levels in the PVN and in the rostral CeA region. In addition, the area in the rostral CeA encompassing high CRH mRNA signals increased significantly after stress. Results provide clear evidence that CRH neurons in the CeA and PVN exhibit rapid increases in CRH mRNA expression after exposure to stress.
The endogenous cannabinoid anandamide was identified as an agonist for the recombinant human VR1 (hVR1) by screening a large array of bioactive substances using a FLIPR-based calcium assay. Further electrophysiological studies showed that anandamide (10 or 100 μM) and capsaicin (1 μM) produced similar inward currents in hVR1 transfected, but not in parental, HEK293 cells. These currents were abolished by capsazepine (1 μM). In the FLIPR anandamide and capsaicin were full agonists at hVR1, with pEC50 values of 5.94±0.06 (n=5) and 7.13±0.11 (n=8) respectively. The response to anandamide was inhibited by capsazepine (pKB of 7.40±0.02, n=6), but not by the cannabinoid receptor antagonists AM630 or AM281. Furthermore, pretreatment with capsaicin desensitized the anandamide-induced calcium response and vice versa. In conclusion, this study has demonstrated for the first time that anandamide acts as a full agonist at the human VR1.
British Journal of Pharmacology (2000) 129, 227–230; doi:10.1038/sj.bjp.0703050