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Induction of interleukin-1β by activated microglia is a prerequisite for immunologically induced fatigue
Abstract
We previously reported that an intraperitoneal (i.p.) injection of synthetic double-stranded RNA, polyriboinosinic:polyribocytidylic acid (poly-I:C), produced prolonged fatigue in rats, which might serve as a model for chronic fatigue syndrome. The poly-I:C-induced fatigue was associated with serotonin transporter (5-HTT) overexpression in the prefrontal cortex (PFC), a brain region that has been suggested to be critical for fatigue sensation. In the present study, we demonstrated that microglial activation in the PFC was important for poly-I:C-induced fatigue in rats, as pretreatment with minocycline, an inhibitor of microglial activation, prevented the decrease in running wheel activity. Poly-I:C injection increased the microglial interleukin (IL)-1β expression in the PFC. An intracerebroventricular (i.c.v.) injection of IL-1β neutralising antibody limited the poly-I:C-induced decrease in activity, whereas IL-1β (i.c.v.) reduced the activity in a dose-dependent manner. 5-HTT expression was enhanced by IL-1β in primary cultured astrocytes but not in microglia. Poly-I:C injection (i.p.) caused an increase in 5-HTT expression in astrocytes in the PFC of the rat, which was inhibited by pretreatment with minocycline (i.p.) and rat recombinant IL-1 receptor antagonist (i.c.v.). Poly-I:C injection (i.p.) led to a breakdown of the blood–brain barrier and enhanced Toll-like receptor 3 signaling in the brain. Furthermore, direct application of poly-I:C enhanced IL-1β expression in primary microglia. We therefore propose that poly-I:C-induced microglial activation, which may be at least partly caused by a direct action of poly-I:C, enhances IL-1β expression. Then, IL-1β induces 5-HTT expression in astrocytes, resulting in the immunologically induced fatigue.
... 80,81 Previous studies have reported that in infectionrelated CFS, inflammatory cytokines in the brain can lead to reduced behavioral performance, disrupted hypothalamic-pituitary-adrenal axis, and impaired peripheral cellular immunity. 82,83 Therefore, it is speculated that increased cytokine levels and decreased serotonin level can be involved in pathogen-induced CFS. ...
... In a rat model of poly-I:C-induced fatigue, spontaneous wheel running decreased until day 8 after poly-I:C injection. 83,84 In addition, there was increased expression of interleukin 1β messenger RNA (mRNA) in the cerebellum, medial preoptic area, lateral preoptic area, paraventricular hypothalamic nucleus, and lateral hypothalamic, as well as increased expression of interferon-α mRNA. 83,84 As patients with CFS showed impaired cytokine production and immune functions such as an increased level of interferon-α in the cerebrospinal fluid 85 and decreased natural killer cell activity, 86 expression of interferon-α in the brain may be associated with poly-I:C-induced fatigue as well as CFS. ...
... 83,84 In addition, there was increased expression of interleukin 1β messenger RNA (mRNA) in the cerebellum, medial preoptic area, lateral preoptic area, paraventricular hypothalamic nucleus, and lateral hypothalamic, as well as increased expression of interferon-α mRNA. 83,84 As patients with CFS showed impaired cytokine production and immune functions such as an increased level of interferon-α in the cerebrospinal fluid 85 and decreased natural killer cell activity, 86 expression of interferon-α in the brain may be associated with poly-I:C-induced fatigue as well as CFS. Moreover, interferon-α has been shown to upregulate the transcription of serotonin transporter mRNA in cultured cell lines. ...
Central fatigue leads to reduced ability to perform mental tasks, disrupted social life, and impaired brain functions from childhood to old age. Regarding the neurochemical mechanism, neuroactive tryptophan metabolites are thought to play key roles in central fatigue. Previous studies have supported the “tryptophan-serotonin enhancement hypothesis” in which tryptophan uptake into extensive brain regions enhances serotonin production in the rat model of exercise-induced fatigue. However, serotonin was transiently released after 30 minutes of treadmill running to exhaustion, but this did not reflect the duration of fatigue. In addition, as the vast majority of tryptophan is metabolized along the kynurenine pathway, possible involvement of the tryptophan-kynurenine pathway in the mechanism of central fatigue induction has been pointed out. More recently, our study demonstrated that uptake of tryptophan and kynurenine derived from the peripheral circulation into the brain enhances kynurenic acid production in rat brain in sleep deprivation–induced central fatigue, but without change in serotonin activity. In particular, dynamic change in glial-neuronal interactive processes within the hypothalamus-hippocampal circuit causes central fatigue. Furthermore, increased tryptophan-kynurenine pathway activity in this circuit causes reduced memory function. This indicates a major potential role for the endogenous tryptophan-kynurenine pathway in central fatigue, which supports the “tryptophan-kynurenine enhancement hypothesis.” Here, we review research on the basic neuronal mechanism underlying central fatigue induced by neuroactive tryptophan metabolites. Notably, these basic findings could contribute to our understanding of latent mental problems associated with central fatigue.
... Intraperitoneal poly I:C administration induces marked microglial activation and IL-1β in mice prefrontal cortex. This IL-1β up-regulating effect was also observed in microglia cultures exposed to poly I:C [129]. The importance of IL-1β for poly I:C-induced fatigue symptoms was demonstrated recently, once ICV administration of IL-1β neutralizing antibody [129] or of a IL-1 receptor antagonist [130] prevented microglial activation and fatigue-related symptoms. ...
... This IL-1β up-regulating effect was also observed in microglia cultures exposed to poly I:C [129]. The importance of IL-1β for poly I:C-induced fatigue symptoms was demonstrated recently, once ICV administration of IL-1β neutralizing antibody [129] or of a IL-1 receptor antagonist [130] prevented microglial activation and fatigue-related symptoms. Similarly, minocycline treatment prevented IL-1β rise and induction of fatigue. ...
... Similarly, minocycline treatment prevented IL-1β rise and induction of fatigue. These researchers also investigated the participation of other cytokines, such as IFN-, in this effect and concluded that poly I:C-induced fatigue depends on IL-1β synthesis [129]. ...
In 2011, it was reviewed that there is a strong co-occurrence between major depression and chronic fatigue syndrome (CFS), with fatigue and physio-somatic symptoms being key symptoms of depression, and depressive symptoms appearing during the course of CFS. Moreover, the comorbidity between both conditions may in part be explained by activated immune-inflammatory pathways, including increased translocation of Gram-negative bacteria and increased levels of pro-inflammatory cytokines, such as interleukin (IL)-1. Nevertheless, the possible involvement of activated microglia in this comorbidity has remained unclear. This paper aims to review microglial disturbances in major depression, CFS and their comorbidity. A comprehensive literature search was conducted using the PubMed / MEDLINE database to identify studies that are relevant to this current review. Depressed patients present neuroinflammatory alterations, probably related to microglial activation, while animal models show that a microglial response to immune challenges including lipopolysaccharides is accompanied by depressive-like behaviors. Recent evidence from preclinical studies indicate that activated microglia have a key role in the onset of fatigue. In chronic inflammatory conditions, such as infections and senescence, microglia orchestrate an inflammatory microenvironment thereby causing fatigue. In conclusion, based on our review we may posit that shared immune-inflammatory pathways and activated microglia underpin comorbid depression and CFS and that activated microglia are the main orchestrators of this comorbidity. As such, microglial activation and neuro-inflammation may be promising targets to treat the overlapping manifestations of both depression and CFS …………………………………………………………………………………. .Chaves Filho, A.J.M..; Macedo, D.S..; de Lucena, D.F..; Maes, M. Shared Microglial Mechanisms Underpinning Depression and Fatigue and Their Comorbidities. Preprints 2019, 2019020029
... In the case of infection-related CFS, it is well-known that inflammatory cytokines in the brain can affect the sympathetic nervous system, the hypothalamic-pituitary-adrenal (HPA) axis, peripheral cellular immunity, learning and memory, and behavioral activity (46,48,49). It is most likely that cytokines might play a role in the development of CFS initiated/triggered by viral/non-viral pathogens. ...
... To investigate this, systemic injection of poly-I:C, virus-mimicking synthetic double-stranded RNA, is a useful approach. Interestingly, poly-I:C injection causes a sustained decrease in spontaneous running wheel activity that is accompanied by enhanced expression of interferon-α (IFN-α), IL-1β, and 5-HTT in the rat brain (48,50). It must be noted that in this experimental model the reduced activity is not attributable to sickness behavior or depression, as the activity decrease is still observed after the poly-I:C-induced acute-phase responses, such as fever and adrenal responses, were abolished (51). ...
... A question arises whether or not intraperitoneal (i.p.) injection of poly-I:C causes breakdown of BBB. There is evidence that poly-I:C increases BBB permeability in a rat model of CFS (48). The breakdown of the BBB can be assessed by quantification of extravasated Evans Blue in the brain (53)(54)(55)(56). ...
Fatigue is commonly reported in a variety of illnesses and has major impact on quality of life. Chronic fatigue syndrome (CFS) is a debilitating syndrome of unknown etiology. The clinical symptoms include problems in neuroendocrine, autonomic, and immune systems. It is becoming clear that the brain is the central regulator of CFS. For example, neuroinflammation, especially induced by activation of microglia and astrocytes, may play a prominent role in the development of CFS, though little is known about molecular mechanisms. Many possible causes of CFS have been proposed. However, in this mini-review, we summarize evidence for a role for microglia and astrocytes in the onset and the maintenance of immunologically induced CFS. In a model using virus mimicking synthetic double-stranded RNA, infection causes sequential signaling such as increased blood brain barrier (BBB) permeability, microglia/macrophage activation through Toll-like receptor 3 (TLR3) signaling, secretion of IL-1β, upregulation of the serotonin transporter (5-HTT) in astrocytes, reducing extracellular serotonin (5-HT) levels and hence reduced activation of 5-HT1A receptor subtype. Hopefully, drug discovery targeting these pathways may be effective for CFS therapy.
... Several lines of evidence have illustrated increased expression of proinflammatory cytokines, such as interleukin-6 (IL-6), interleukin-1b (IL-1b) and tumor necrosis factor-a (TNF-a), in the serum of CFS patients (Ousman and Kubes, 2012). Further evidence from animal experiments indicated that increased levels of IL-1b were the key stimulus in a poly I:C-induced rodent fatigue model (Ifuku et al., 2014;Vasiadi et al., 2014). Moreover, many studies have reported that high-intensity exercise could result in pro-inflammatory cytokine production and increased oxidative stress, resulting in aggravated feelings of fatigue (Nieman et al., 2005;Spence et al., 2007). ...
... Evidence from several studies has suggested that the proinflammatory cytokine IL-1b in the PFC was involved in the pathogenesis of rodent immunological fatigue (Ifuku et al., 2014). Clinical evidence also identified the PFC as the region of the brain responsible for chronic fatigue sensation using functional magnetic resonance imaging (MRI) (Shortz et al., 2015;Klaassen et al., 2016). ...
... Many prior studies have targeted different stages in the pathway. A study conducted by Ifuku et al. (2014) found that injection of IL-1b could induce mouse fatigue behavior in a dose-dependent manner, whereas IL-1 receptor antibody (IL-1RA) injection could reverse such effects and significantly attenuate the poly I:C-induced decrease in running wheel activity. As we predicted, the NLRP3 À/À / swim mice demonstrated improved performance under the same treatment when compared with WT/swim mice (Fig. 1). ...
Numerous experimental and clinical studies have suggested that the interaction between the immune system and the brain plays an important role in the pathophysiology of chronic fatigue syndrome (CFS). The NLRP3 inflammasome is an important part of the innate immune system. This complex regulates proinflammatory cytokine interleukin-1β (IL-1β) maturation, which triggers different kinds of immune-inflammatory reactions. We employed repeated forced swims to establish a model of CFS in mice. NLRP3 knockout (KO) mice were also used to explore NLRP3 inflammasome activation in the mechanisms of CFS, using the same treatment. After completing repeated swim tests, the mice displayed fatigue-like behaviours, including locomotor activity and reduced fall-off time on the rota-rod test, which was accompanied by significantly higher mature IL-1β level in the prefrontal cortex (PFC) and malondialdehyde (MDA) level in serum. We also found increased NLRP3 protein expression, NLRP3 inflammasome formation and increased mature IL-1β production in the PFC, relative to untreated mice. The NLRP3 KO mice displayed significantly moderated fatigue behaviours along with decreased PFC and serum IL-1β levels under the same treatment. These findings demonstrated the involvement of NLRP3 inflammasome activation in the mechanism of swimming-induced fatigue. Future therapies targeting the NLRP3/IL-1β pathway may have significant potential for fatigue prevention and treatment.
... Studies in animal models suggest an interaction between the immune system and the serotonergic pathway. Upon artificially-induced immune system activation, microglia, an essential immune cell present in the CNS, releases the pro-inflammatory cytokine IL-1β [149,150]. Astrocytes, another CNS cell responsible for regulating the amount of neurotransmitters available for neuronal activity, highly expressed concentrations of IL-1β receptors, and its activation have been proven to increase the expression of the serotonin transporter 5-HTT in specific glial cells [149]. It is hypothesized that increased uptake of serotonin by astrocytes leads to increased deactivation of serotonin by monoamine oxidase A, the enzyme responsible for deamination and scavenge of 5-HT for further re-utilization [151,152]. ...
... Potential therapeutic targets related to serotonin include antidepressants including imipramine (non-selective 5-HT reuptake inhibitor), a medication that has been shown to abolish the inflammatory-induced decrease in extracellular levels of serotonin, and which could potentially impact the pathology [150]. Additionally, specific agonists for the 5-HT1A receptors or inhibitors of 5-HTT may be promising medications for the treatment of CFS [143]. ...
Ovarian hormones play an important role in pain perception, and are responsible, at least in part, for the pain threshold differences between the sexes. Modulation of pain and its perception are mediated by neurochemical changes in several pathways, affecting both the central and peripheral nervous systems. One of the most studied neurotransmitters related to pain disorders is serotonin. Estrogen can modify serotonin synthesis and metabolism, promoting a general increase in its tonic effects. Studies evaluating the relationship between serotonin and disorders such as irritable bowel syndrome, fibromyalgia, migraine, and other types of headache suggest a clear impact of this neurotransmitter, thereby increasing the interest in serotonin as a possible future therapeutic target. This literature review describes the importance of substances such as serotonin and ovarian hormones in pain perception and illustrates the relationship between those two, and their direct influence on the presentation of the aforementioned pain-related conditions. Additionally, we review the pathways and receptors implicated in each disorder. Finally, the objective was to stimulate future pharmacological research to experimentally evaluate the potential of serotonin modulators and ovarian hormones as therapeutic agents to regulate pain in specific subpopulations.
... It has been reported that i.p. injection of poly (I:C) breaks down the blood-brain barrier and enhances toll-like receptors-3 (TLR-3) signaling within the brain ( Ifuku et al. 2014). Furthermore, direct application of poly (I:C) or activation of TLR-3 signaling activates microglial cells in the brain tissue. ...
... Furthermore, direct application of poly (I:C) or activation of TLR-3 signaling activates microglial cells in the brain tissue. Resultant increase in local cytokine levels, i.e., IL-1 and TNF-, and neuromediators, i.e., glutamate and nitric oxide, was reported to cause brain damage ( Ifuku et al. 2014;Jin et al. 2015). On the other hand, it might be speculated that glutamate, as an excitatory neurotransmitter, may possibly activate the development of GnRH neurons as glutamatergic regulation of GnRH neuronal function has been shown ( Yin et al. 2015). ...
This study aimed to investigate the effects of maternal viral infection during a critical time window of fetal hypothalamic development on timing of puberty in the female offspring. For that purpose, a viral mimetic (i.e. synthetic double strand RNA, namely, polyinosinic:polycytidylic acid, Poly (I:C)) or saline was injected (i.p.) to the pregnant rats during the beginning (day 12 of pregnancy, n=5 for each group) or at the end of this time window (day 14 of pregnancy, n=5 for each group). Four study groups were formed from the female pups (n=9 or 10 pups/group). Following weaning of pups, vaginal opening and vaginal smearing was studied daily until two sequential estrous cycles were observed. During the second diestrus phase, blood samples were taken for progesterone, leptin, corticosterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH). Maternal poly (I:C) injection on day 12 of pregnancy increased body weight and reduced the time to puberty in the female offspring. Neither poly (I:C) nor timing of injection affected other parameters studied (p > 0.05). In conclusion, it has been shown for the first time that maternal viral infection during the beginning of fetal hypothalamic development might hasten puberty by increasing body weight in rat offspring.
... Recent investigations have revealed that the interaction between inflammatory pathways and the neuroendocrine system is associated with the manifestation of symptoms such as pain, fatigue, impaired memory and depression, which largely characterize at least some patients suffering from CFS [8]. Induction of interleukin (IL)-1β expression and elevated inflammatory mediators in the brain are prerequisites for decreased locomotor activity and other fatigue-related behaviours [9,10]. Moreover, many CFS patients demonstrate abnormal hypothalamic-pituitaryadrenal (HPA) axis activity [11,12]. ...
... Interestingly, in the biochemical analysis, NLRP3 KO mice had significantly decreased the IL-1β serum levels, whereas the IL-6 levels in these mice were not different from those of the wild-type mice, which suggested that such fatigue model was mainly IL-1β-dependent. These results, together with other reports underlining the importance of IL-1β in CFS [10,40], indicated that LPS-induced fatigue is an IL-1β-dependent disorder and that NLRP3/caspase-1 inhibition therapy may be a promising option for anti-fatigue therapy. To the best of our knowledge, this is the first study to report NLRP3 inflammasome activation in the CNS in a model of fatigue. ...
Background
The NLRP3 inflammasome (NOD-like receptor family, pyrin domain containing 3) is an intracellular protein complex that plays an important role in innate immune sensing. Its activation leads to the maturation of caspase-1 and regulates the cleavage of interleukin (IL)-1β and IL-18. Various studies have shown that activation of the immune system plays a pivotal role in the development of fatigue. However, the mechanisms underlying the association between immune activation and fatigue remained elusive, and few reports have described the involvement of NLRP3 inflammasome activation in fatigue. Methods
We established a mouse fatigue model with lipopolysaccharide (LPS, 3 mg/kg) challenge combined with swim stress. Both behavioural and biochemical parameters were measured to illustrate the characteristics of this model. We also assessed NLRP3 inflammasome activation in the mouse diencephalon, which is the brain region that has been suggested to be responsible for fatigue sensation. To further identify the role of NLRP3 inflammasome activation in the pathogenesis of chronic fatigue syndrome (CFS), NLRP3 KO mice were also subjected to LPS treatment and swim stress, and the same parameters were evaluated. ResultsMice challenged with LPS and subjected to the swim stress test showed decreased locomotor activity, decreased fall-off time in a rota-rod test and increased serum levels of IL-1β and IL-6 compared with untreated mice. Serum levels of lactic acid and malondialdehyde (MDA) were not significantly altered in the treated mice. We demonstrated increased NLRP3 expression, IL-1β production and caspase-1 activation in the diencephalons of the treated mice. In NLRP3 KO mice, we found remarkably increased locomotor activity with longer fall-off times and decreased serum IL-1β levels compared with those of wild-type (WT) mice after LPS challenge and the swim stress test. IL-1β levels in the diencephalon were also significantly decreased in the NLRP3 KO mice. By contrast, IL-6 levels were not significantly altered. Conclusions
These findings suggest that LPS-induced fatigue is an IL-1β-dependent process and that the NLRP3/caspase-1 pathway is involved in the mechanisms of LPS-induced fatigue behaviours. NLRP3/caspase-1 inhibition may be a promising therapy for fatigue treatment.
... We focused on wheel running behavior because it is a voluntary activity that can be intense and thus effortful, and might tap both lethargy as well as altered motivation associated with the symptom of fatigue. In animal studies, immune system activation or treatment with chemotherapy causes a reduction in wheel-running as well as general locomotor activity [8][9][10][11][12]. Some evidence suggests that IL-1β in particular is linked to the reduction of activity. ...
... Disruption of IL-1β signaling in the CNS attenuates LPS effects on locomotor activity [17,18]. Furthermore, central administration of an interleukin-1 receptor antagonist or IL-1β neutralizing antibody attenuates the reduction in wheel-running activity caused by peripheral administration of IL-1β or Poly I:C [12,19,20]. ...
Fatigue is a disabling symptom in patients with multiple sclerosis and Parkinson's Disease, and is also common in patients with traumatic brain injury, cancer, and inflammatory disorders. Little is known about the neurobiology of fatigue, in part due to the lack of an approach to induce fatigue in laboratory animals. Fatigue is a common response to systemic challenge by pathogens, a response in part mediated through action of the pro-inflammatory cytokine interleukin-1 beta (IL-1β). We investigated the behavioral responses of mice to IL-1β. Female C57Bl/6J mice of 3 ages were administered IL-1β at various doses i.p. Interleukin-1β reduced locomotor activity, and sensitivity increased with age. Further experiments were conducted with middle-aged females. Centrally administered IL-1β dose-dependently reduced locomotor activity. Using doses of IL-1β that caused suppression of locomotor activity, we measured minimal signs of sickness, such as hyperthermia, pain or anhedonia (as measured with abdominal temperature probes, pre-treatment with the analgesic buprenorphine and through sucrose preference, respectively), all of which are responses commonly reported with higher doses. We found that middle-aged orexin-/- mice showed equivalent effects of IL-1β on locomotor activity as seen in wild-type controls, suggesting that orexins are not necessary for IL-1β -induced reductions in wheel-running. Given that the availability and success of therapeutic treatments for fatigue is currently limited, we examined the effectiveness of two potential clinical treatments, modafinil and methylphenidate. We found that these treatments were variably successful in restoring locomotor activity after IL-1β administration. This provides one step toward development of a satisfactory animal model of the multidimensional experience of fatigue, a model that could allow us to determine possible pathways through which inflammation induces fatigue, and could lead to novel treatments for reversal of fatigue.
... These TRPM3 ion channels are widely expressed in the cerebellum, dorsal midbrain, amygdala and medulla (Allen Institute, 2022) and are believed to be involved in a range of biological processes including memory formation and consolidation, thermoregulation, pain, inflammation, and coordination (Oberwinkler and Philipp, 2014). Further, the prevalence of TRPM receptors in microglia could result in increased recruitment with neurotoxic potential (Bezzi et al., 2001;Ifuku et al., 2014). Microglial density is 10 times greater in the medulla than in the cortex (Mittelbron et al., 2001) and may account for medulla involvement in both ME/CFS and LCov. ...
Introduction
Debilitating Long-Covid symptoms occur frequently after SARS-COVID-19 infection.
Methods
Functional MRI was acquired in 10 Long Covid (LCov) and 13 healthy controls (HC) with a 7 Tesla scanner during a cognitive (Stroop color-word) task. BOLD time series were computed for 7 salience and 4 default-mode network hubs, 2 hippocampus and 7 brainstem regions (ROIs). Connectivity was characterized by the correlation coefficient between each pair of ROI BOLD time series. We tested for HC versus LCov differences in connectivity between each pair of the 20 regions (ROI-to-ROI) and between each ROI and the rest of the brain (ROI-to-voxel). For LCov, we also performed regressions of ROI-to-ROI connectivity with clinical scores.
Results
Two ROI-to-ROI connectivities differed between HC and LCov. Both involved the brainstem rostral medulla, one connection to the midbrain, another to a DM network hub. Both were stronger in LCov than HC. ROI-to-voxel analysis detected multiple other regions where LCov connectivity differed from HC located in all major lobes. Most, but not all connections, were weaker in LCov than HC. LCov, but not HC connectivity, was correlated with clinical scores for disability and autonomic function and involved brainstem ROI.
Discussion
Multiple connectivity differences and clinical correlations involved brainstem ROIs. Stronger connectivity in LCov between the medulla and midbrain may reflect a compensatory response. This brainstem circuit regulates cortical arousal, autonomic function and the sleep–wake cycle. In contrast, this circuit exhibited weaker connectivity in ME/CFS. LCov connectivity regressions with disability and autonomic scores were consistent with altered brainstem connectivity in LCov.
... There is a negative correlation between fatigue and hippocampus volume in CFS patients (Thapaliya et al., 2022). In addition, the prefrontal cortex has been identified as critical to fatigue (Ifuku et al., 2014). Bilateral prefrontal cortex volume was reduced in CFS patients, and the level of volume reduction in the right prefrontal cortex was correlated with the severity of fatigue (Nakatomi et al., 2014). ...
Background: Chronic fatigue syndrome (CFS) is characterized by significant and persistent fatigue. Ginseng is a traditional anti-fatigue Chinese medicine with a long history in Asia, as demonstrated by clinical and experimental studies. Ginsenoside Rg1 is mainly derived from ginseng, and its anti-fatigue metabolic mechanism has not been thoroughly explored.
Methods: We performed non-targeted metabolomics of rat serum using LC-MS and multivariate data analysis to identify potential biomarkers and metabolic pathways. In addition, we implemented network pharmacological analysis to reveal the potential target of ginsenoside Rg1 in CFS rats. The expression levels of target proteins were measured by PCR and Western blotting.
Results: Metabolomics analysis confirmed metabolic disorders in the serum of CFS rats. Ginsenoside Rg1 can regulate metabolic pathways to reverse metabolic biases in CFS rats. We found a total of 34 biomarkers, including key markers Taurine and Mannose 6-phosphate. AKT1, VEGFA and EGFR were identified as anti-fatigue targets of ginsenoside Rg1 using network pharmacological analysis. Finally, biological analysis showed that ginsenoside Rg1 was able to down-regulate the expression of EGFR.
Conclusion: Our results suggest ginsenoside Rg1 has an anti-fatigue effect, impacting the metabolism of Taurine and Mannose 6-phosphate through EGFR regulation. This demonstrates ginsenoside Rg1 is a promising alternative treatment for patients presenting with chronic fatigue syndrome.
... The interaction between IL-1β released from microglia and astrocytic 5-HTT is well-known, proved by employing IL-1 receptor antagonists. IL-1β can directly induce the upregulation of 5-HTT in primary cultured rat astrocytes [88]. This pro-inflammatory cytokine has also been detected in significantly high concentrations in ME/CFS patients, which is produced by activated microglia [89]. ...
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a serious, complex, and highly debilitating long-term illness. People with ME/CFS are typically unable to carry out their routine activities. Key hallmarks of the disease are neurological and gastrointestinal impairments accompanied by pervasive malaise that is exacerbated after physical and/or mental activity. Currently, there is no validated cure of biomarker signature for this illness. Impaired tryptophan (TRYP) metabolism is thought to play significant role in the pathobiology of ME/CFS. TRYP is an important precursor for serotonin and the essential pyridine nucleotide nicotinamide adenine dinucleotide (NAD+). TRYP has been associated with the development of some parts of the brain responsible for behavioural functions. The main catabolic route for TRYP is the kynurenine pathway (KP). The KP produces NAD+ and several neuroactive metabolites with neuroprotective (i.e., kynurenic acid (KYNA)) and neurotoxic (i.e., quinolinic acid (QUIN)) activities. Hyperactivation of the KP, whether compensatory or a driving mechanism of degeneration can limit the availability of NAD+ and exacerbate the symptoms of ME/CFS. This review discusses the potential association of altered KP metabolism in ME/CFS. The review also evaluates the role of the patient's gut microbiota on TRYP availability and KP activation. We propose that strategies aimed at raising the levels of NAD+ (e.g., using nicotinamide mononucleotide and nicotinamide riboside) may be a promising intervention to overcome symptoms of fatigue and to improve the quality of life in patients with ME/CFS. Future clinical trials should further assess the potential benefits of NAD+ supplements for reducing some of the clinical features of ME/CFS.
... Nevertheless, central inflammation and cytokine secretion appear to be essential steps for the development of fatigue in the context of psychiatric and non-psychiatric disorders. Recent preclinical evidence has shown that microglia could have a key role in the development of fatigue, where induction of fatigue appeared to be dependent on the production of IL-1 beta from activated microglia [38,39]. Similar to chronic fatigue syndrome, patients with fibromyalgia, a condition characterized by widespread pain, cognitive impairment, sleep disturbances and persistent lack of energy, also present with increased levels of inflammatory markers [40]. ...
Long-Coronavirus Disease (Long-COVID) is becoming increasingly recognized due to the persistence of symptoms such as profound fatigue, neurocognitive difficulties, muscle pains and weaknesses and depression, which would last beyond 3–12 weeks following infection with SARS-CoV-2. These particular symptoms have been extensively observed and studied in the context of previous psychoneuroimmunology research. In this short commentary, we discuss how previous neuroimmunology studies could help us to better understand pathways behind the development of these prolonged symptoms. Various mechanisms, including viral neuroinvasion, glial cells activation, neurogenesis, oxidative stress have been shown to explain these symptoms in the context of other disorders. Previous neuroimmunology findings could represent helpful pointers for future research on long-COVID symptoms and suggest potential management strategies for patients suffering with long-COVID.
... The precise causes of fatigue are unknown, but one suggested mechanism is prolonged activation of the immune system, by illness or disease [4][5][6]. Infections are often associated with acute sickness behavior, which in some cases causes prolonged systemic inflammation, resulting in chronic fatigue [7]. High concentrations of circulating pro-inflammatory cytokines such as interleukin-1β (IL-1β), interferon-α (IFN-α) and tumor necrosis factor-α (TNF-α) have been observed in chronic fatigue syndrome (CFS) patients [8,9], and are associated with low-grade fevers that sporadically occur during bouts of chronic fatigue [10]. ...
Central fatigue is a condition associated with impairment of the central nervous system often leading to the manifestation of a range of debilitating symptoms. Fatigue can be a consequence of systemic inflammation following an infection. Administration of lipopolysaccharide (LPS) and polyriboinosinic:polyribocytidlic (poly I:C) to animals can induce systemic inflammation by mimicking a bacterial or viral infection respectively and therefore have been used as models of fatigue. We evaluated a range of phenotypic behaviors exhibited in the LPS and poly I:C animal models to assess whether they adequately replicate fatigue symptomology in humans. In addition to standard observation- and intervention-based behavioral assessments, we used powerful in-cage monitoring technology to quantify rodent behavior without external interference. LPS and poly I:C treated Sprague Dawley rats displayed 'sickness behaviors' of elevated temperature, weight loss and reduced activity in the open field test and with in-cage monitoring within 24 hours post-treatment, but only LPS-treated rats displayed these behaviors beyond these acute timepoints. Once sickness behavior diminished, LPS-treated rats exhibited an increase in reward-seeking and motivation behaviors. Overall, these results suggest that the LPS animal model produces an extensive and sustained fatigue-like phenotype, whereas the poly I:C model only produced acute effects. Our results suggest that the LPS animal model is a more suitable candidate for further studies on central fatigue-like behavior.
... It is well known that inflammatory cytokines, including IL-1β and/or antiviral cytokines including interferons (IFNs), are produced during these infections. In recent studies, peripherally produced cytokines have been shown to affect brain function [92,93]. Cytokine expression in the brain is also thought to be involved in depressive symptoms. ...
Background
Hochuekkito extract (HET) has multiple effects through the digestive and immune systems, including for acute viral infection and chronic inflammation. We review basic pharmacological and clinical researches of HET and discuss the effects of HET against the pandemic COVID‐19.
Methods
We reviewed pharmacological studies from 1996 to 30 April 2020 that used experimental animals orally treated with HET and randomized controlled trials (RCTs) from 2000 to 30 April 2020.
Results
Altogether, 64 pharmacological studies reported immuno‐stimulatory effects against infection and cancer, immuno‐modulative effects against allergy and some inflammatory diseases, and ameliorating effects against exhaustion and frailty. Nine RCTs showed improvement of pulmonary Mycobacterium avium complex disease on chest X‐ray; improved systemic inflammation, nutrition, and quality of life of patients with chronic obstructive pulmonary disease and a decrease in the number getting common cold and exacerbations; reduction of soluble interleukin‐2 receptor and the serum cortisol concentration of postoperative patients; a reduction of the incidence of inflammatory complications and C‐reactive protein elevation after cerebrovascular disease; a reduction of the volume of steroid and tacrolimus during the treatment of atopic dermatitis; a healing effect for intractable chronic wounds; improvement of the physical status of elderly weak patients; and improvement of the fatigue level of cancer patients.
Conclusion
CODIV‐19 is characterized by high risk for the aged and people with other disease complications, cytokine hyperactivity in the severe stage, and sequelae in the recovery stage. Considering the immune‐stimulative/modulative effects of HET on inflammatory conditions and against exhaustion and frailty, it may be useful for prevention, treatment, and recovery from COVID‐19.
... Systemic administration of poly I:C increases the expression of the serotonin transporter (SERT) and reduces extracellular 5-HT in the prefrontal cortex (PFC) of rats, an area associated with essential cognitive and limbic functions (Katafuchi et al., 2006). The increased SERT expression in astrocytes of this brain region is at least partially mediated by TLR3 pathway signaling, microglial activation, and IL-1β production (Ifuku et al., 2014). Furthermore, poly I:C increases tryptophan in the hippocampus and PFC, but this amino acid is directed to the kynurenine pathway which produces several metabolites that may disrupt normal brain function (Gibney et al., 2013). ...
The absence of a specific treatment for SARS-CoV-2 infection led to an intense global effort in order to find new therapeutic interventions and improve patient outcomes. One important feature of COVID-19 pathophysiology is the activation of immune cells, with consequent massive production and release of inflammatory mediators that may cause impairment of several organ functions, including the brain. In addition to its classical role as a neurotransmitter, serotonin (5-hydroxytryptamine, 5-HT) has immunomodulatory properties, downregulating the inflammatory response by central and peripheral mechanisms. In this review, we describe the roles of 5-HT in the regulation of systemic inflammation and the potential benefits of the use of specific serotonin reuptake inhibitors as a coadjutant therapy to attenuate neurological complications of COVID-19.
... We started surgery after animals' breath and pulse were stabilized and the extent of anesthesia was enough, without corneal reflection, touch, and pinch responses. For vermal injection into cerebella, rats were fixed to the stereotaxic apparatus and a small hole (300 mm radius) was drilled in the skull (2.5 mm posterior to lambda), following which a microsyringe was inserted forward to the anterior lobule (3.0-3.3 mm depth at 86 , lobule II-IV) or to the posterior lobule (6.3-6.5 mm depth at 65 , lobule VIII-IX) (Ifuku et al., 2014). To clarify the localized spread of the reagent, we did the post-injection histology, and we confirmed the dextran-conjugated CFâ555 dye (0.30ul, 0.5%; Biotium, CFâ555 Dextran 10,000 MW) was restricted in the targeted anterior lobes through the depth of 3.4 mm to 0.4 mm from the pial surface, in two animals. ...
Cerebellar dysfunction relates to various psychiatric disorders, including autism spectrum and depressive disorders. However, the physiological aspect is less advanced. Here, we investigate the immune-triggered hyperexcitability in the cerebellum on a wider scope. Activated microglia via exposure to bacterial endotoxin lipopolysaccharide or heat-killed Gram-negative bacteria induce a potentiation of the intrinsic excitability in Purkinje neurons, which is suppressed by microglia-activity inhibitor and microglia depletion. An inflammatory cytokine, tumor necrosis factor alpha (TNF-α), released from microglia via toll-like receptor 4, triggers this plasticity. Our two-photon FRET ATP imaging shows an increase in ATP concentration following endotoxin exposure. Both TNF-α and ATP secretion facilitate synaptic transmission. Region-specific inflammation in the cerebellum in vivo shows depression- and autistic-like behaviors. Furthermore, both TNF-α inhibition and microglia depletion revert such behavioral abnormality. Resting-state functional MRI reveals overconnectivity between the inflamed cerebellum and the prefrontal neocortical regions. Thus, immune activity in the cerebellum induces neuronal hyperexcitability and disruption of psychomotor behaviors in animals.
... Die von Rudolf Virchow entdeckten Zellen unterteilen sich unter anderem in Astrozyten, Mikroglia und Oligodendrozyten und nehmen vielfältige Funktionen im zentralen Nervensystem ein, dazu gehören Stütz-, Isolier-, Ernährungs-und Immunfunktionen (Grace et al. 2014). Die Bedeutsamkeit der Aktivierung von proentzündlicher Mikroglia und der damit assoziierten Zytokinaktivierung für die Entstehung einer Hyperalgesie mit Fatigue konnte in Tiermodellen eindrucksvoll nachgewiesen werden (Ifuku et al. 2014;Yasui et al. 2014). Zunehmende Evidenz weist auf die Bedeutsamkeit dieses pathophysiologischen Mechanismus für den Symptomkomplex von Fatigue und Schmerz auch bei den genannten Krankheitsbildern hin (Morris et al. 2015), was insbesondere durch die Wirksamkeit der Anti-TNF-Therapie bei rheumatoider Arthritis unterstrichen wird (Hess et al. 2011 (Bower 2014;Bower et al. 2011;Jager et al. 2008). ...
Pain and fatigue - a systematic review Introduction: Chronic pain and fatigue are symptoms that often occur together and characterize the symptom picture of various diseases. Nevertheless, integrative explanatory approaches have so far received little attention in medical practice.
Methods:
Based on a systematic literature search in the Embase, Medline, PsychInfo, and CENTRAL databases, we searched for high-quality intervention studies for the simultaneous treatment of pain and fatigue.
Results:
From 1,496 total hits, 158 studies were included in the evaluation. The most commonly studied clinical pictures of the symptomcomplex were tumor catabolism, fibromyalgia, chronic fatigue, rheumatoid arthritis, and osteoarthritis.Current explanations of the symptom complex focus on the activation of proinflammatory microglia in centralized pain syndrome with multiple effects on neurotransmission, neuroendocrinology, neuroplasticity, and the autonomic nervous system. In this model, fatigue can be understood as an evolutionary, meaningful symptom protective of the organism.
Conclusions:
A deeper understanding of the relationship between centralized pain syndrome and fatigue allows for new explanatory and treatment approaches.
... Primary microglia cells were isolated from the cerebral cortex of 3-day-old mice according to our previously published report [32]. In brief, whole brains of neonatal mice were taken under sterile condition. ...
Microglial activation is a pathological feature of many neurodegenerative diseases and the role of cellular lipids in these diseases is mostly unknown. It was known that the special ether lipid plasmalogens (Pls) were reduced in the brain and blood samples of Alzheimer’s disease (AD) patients. It has recently been reported that the oral ingestion of scallop-derived Pls (sPls) improved cognition among mild AD patients, which led us to investigate the role of sPls in the microglial activation. We used the lipopolysaccharides (LPS)-induced microglial activation model and found that sPls inhibit the LPS-mediated TLR4 endocytosis and the downstream caspases activation. By using the specific inhibitors, we also confirmed that the TLR4 endocytosis and the caspases activation strictly controlled the pro-inflammatory cytokine expression. In addition, the reduction of cellular Pls by sh-RNA-mediated knockdown of GNPAT (glyceronephosphate O-acyltransferase), a Pls synthesizing enzyme, enhanced the endocytosis of TLR4 and activation of caspase-3 which resulted in the enhanced pro-inflammatory cytokine expression. We also report for the first time that the TLR4 endocytosis was significantly higher in the cortex of aged mice and AD model mice brains, proposing a significant link between the age-related reduction of Pls and microglial activation. Interestingly, the sPls drinking in AD model mice significantly reduced the TLR4 endocytosis. Our cumulative data indicates that the cellular Pls attenuate the microglial activation by maintaining the endocytosis of TLR4, suggesting a possible mechanism of the cognition improvement effect of sPls among mild AD patients.
... Glial cells may also contribute to these changes in neural excitability and therefore psychiatric symptoms. For example, in activated microglia and astrocytes, immunologically induced fatigue was reported (Ifuku, Hossain, Noda, & Katafuchi, 2014). Microglial oxidative reactions in schizophrenia (Kato et al., 2011;Monji et al., 2013) and alteration of astrocytes or oligodendrocyte function in bipolar disorder (Dong & Zhen, 2015) have also been reported. ...
The endocrine system and the central nervous system (CNS) are intimately linked. Among hormones closely related to the nervous system, thyroid hormones (THs) are critical for the regulation of development and differentiation of neurons and neuroglia and hence for development and function of the CNS. T3 (3,3′,5-triiodothyronine), an active form of TH, is important not only for neuronal development but also for differentiation of astrocytes and oligodendrocytes, and for microglial development. In adult brain, T3 affects glial morphology with sex- and age-dependent manner and therefore may affect their function, leading to influence on neuron–glia interaction. T3 is an important signaling factor that affects microglial functions such as migration and phagocytosis via complex mechanisms. Therefore, dysfunction of THs may impair glial function as well as neuronal function and thus disturb the brain, which may cause mental disorders. Investigations on molecular and cellular basis of hyperthyroidism and hypothyroidism will help us to understand changes in neuron–glia interaction and therefore consequent psychiatric symptoms.
... Widespread low-level neuroinflammation has been detected in the brains of ME/CFS patients, with neuropsychological symptom severity associated with the level of neuroinflammation in one study (Nakatomi et al., 2014), and with self-reported chronic pain in another (Ickmans et al., 2015). Furthermore, animal testing appears to indicate that microglial induction of IL-1β may be a prerequisite for immunologically induced fatigue (Ifuku et al., 2014), * * and that gender-specific relationships may exist concerning suppression of T cell contact-mediated glial activation (Brahmachari and Pahan, 2010) and relative prolongation of glial responses following neurotoxin exposure (Ciesielska et al., 2009). These findings accord with numerous human studies highlighting relatively high prevalence of ME/CFS among females (Reyes et al., 2003). ...
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating multi-systemic chronic illness of unknown etiology, classified as a neurological disorder by the World Health Organization (WHO). The symptomatology of the condition appears to emanate from a variety of sources of chronic neurological disturbance and associated distortions, and chronicity, in noxious sensory signaling and neuroimmune activation. This article incorporates a summary review and discussion of biomedical research considered relevant to this essential conception perspective. It is intended to provide stakeholders with a concise, integrated outline disease model in order to help demystify this major public health problem. The primary etiopathological factors presented are: (A) Postural/biomechanical pain signaling, affecting adverse neuroexcitation, in the context of compression, constriction, strain, or damage of vertebral-regional bone and neuromuscular tissues; (B) Immune mediated inflammatory sequelae, in the context of prolonged immunotropic neurotrophic infection—with lymphotropic/gliotropic/glio-toxic varieties implicated in particular; (C) A combination of factors A and B. Sustained glial activation under such conditions is associated with oxidative and nitrosative stress, neuroinflammation, and neural sensitivity. These processes collectively enhance the potential for multi-systemic disarray involving endocrine pathway aberration, immune and mitochondrial dysfunction, and neurodegeneration, and tend toward still more intractable synergistic neuro-glial dysfunction (gliopathy), autoimmunity, and central neuronal sensitization.
... The fifth route, activated by both the humoral and neuronal pathways, is activation of the immunocompetent cells of the brain, being the microglia (5). These cells are able to produce IL-1β locally once they have become activated [25,26]. In chronic fatigue syndrome (CFS), a syndrome characterized by severe fatigue, evidence for microglial activation has already been reported in a small group of patients [27]. ...
Fatigue is commonly reported in a variety of illnesses, and it has major impact on quality of life. Previously, it was thought that fatigue originates in the skeletal muscles, leading to cessation of activity. However, more recently, it has become clear that the brain is the central regulator of fatigue perception. It has been suggested that pro-inflammatory cytokines, especially interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β), play a prominent role in the development of central fatigue, and several studies have been performed to elucidate the connection between inflammation and these central processes.
In this narrative review, mechanisms of action of IL-1 are described, with special attention to its effect on the central nervous system. In addition, we present a summary of studies that (i) investigated the relationship between circulating IL-1α and IL-1β and fatigue severity and/or (ii) evaluated the effect of inhibiting IL-1 on fatigue. We aim to improve the understanding of fatigue in both inflammatory and non-inflammatory illnesses, which could help develop strategies to treat fatigue more effectively.
Reviewing the studies that have been performed, it appears that there is a limited value of measuring circulating IL-1. However, inhibiting IL-1 has a positive effect on severe fatigue in most studies that have been conducted.
... It is now known that neuroinflammation is also an essential pathology in other diseases than neurodegenerative/demyelinating diseases. For example, the chronic fatigue syndrome and its animal models show neuroinflammation causing severe fatigue [3,4]. Furthermore it has been shown that neuroinflammation is also involved in some psychiatric diseases such as schizophrenia, depression and autism, which will be reviewed in this issue. ...
... Studies in this situation showed that this effect was mediated by intracerebral IL-1 receptors, as it was completely blocked by the receptor antagonist IL-1ra. Ifuku et al. [13] took the view that one of the mechanisms of IL-1β-induced decreases in activity in ...
The actions of chronic i.p. administration of the proinflammatory cytokine interleukin-1β (IL-1β) on exploratory behavior and spatial memory were studied in rats. IL-1β was given at the weakly pyrogenic dose of 0.5 μg/kg daily for 14 days (starting seven days before and continuing through seven days of behavioral testing). Behavior was analyzed 23.5 h after sequential injections of cytokine. A battery of tests was used, including the open field test (on three sequential days), exploration of novel objects, and the Morris water maze. Experimental animals showed a significant decrease in motor activity, a minor increase in anxiety, and suppression of exploratory behavior. Impairments to spatial memory were not seen.
... These include directly crossing the blood-brain barrier (BBB) or by circumventing the BBB via several different routes of entry. However, the most critical data relevant to our study comes from publications demonstrating that peripheral injections of poly I:C or peripheral inoculation of West Nile Virus lead to substantial breakdown of the BBB via a TLR3-dependent mechanism, providing ready access of dsRNA (or dsRNA generating viruses) to the brain 41,42 . We hypothesize that the behavioral response to peripheral poly I:C is in part determined by classic TLR3/TRIF pathway-induced attenuation of the BBB, which in turn facilitates viral PAMP signaling via our novel central MyD88-dependent pathway. ...
Sickness behaviors and metabolic responses to invading pathogens are common to nearly all types of infection. These responses evolved to provide short-term benefit to the host to ward off infection, but impact on quality of life, and when prolonged lead to neurodegeneration, depression, and cachexia. Among the major infectious agents, viruses most frequently enter the brain, resulting in profound neuroinflammation. We sought to define the unique features of the inflammatory response in the brain to these infections. We demonstrate that the molecular pathway defining the central response to dsRNA is distinct from that found in the periphery. The behavioral and physical response to the dsRNA mimetic poly I:C is dependent on signaling via MyD88 when it is delivered centrally, whereas this response is mediated via the TRIF pathway when delivered peripherally. We also define the likely cellular candidates for this MyD88-dependent step. These findings suggest that symptom management is possible without ameliorating protective antiviral immune responses.
... [32,33] While the brain is often considered as 'immune privileged', it has been shown that peripheral immune activation can influence the microglia of the brain, with 'sickness behaviour' as a stereotypical example. [34,35] Microglial activation has been implicated in animal models of persistent hyperalgesia, [34] immunologically induced fatigue in animal models [36] and a range of other conditions from major depressive disorder to neurodegenerative diseases. [35] A recent positron emission tomography (PET) study suggests that microglial activation in brainstem and limbic areas may occur in ME/CFS [27]; hopefully replication will follow. ...
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is comparable to multiple sclerosis, diabetes or rheumatoid arthritis in prevalence (∼0.2% to 1%), long-term disability, and quality of life,[1–5] yet the scale of biomedical research and funding has been pitifully limited, as the recent National Institutes of Health (NIH) and Institute of Medicine reports highlight.[6,7] Recently in the USA, NIH Director Francis Collins has stated that the NIH will be ramping up its efforts and levels of funding for ME/CFS,[8] which we hope will greatly increase the interest in, and resources for researching this illness. Despite scant funding to date, researchers in the field have generated promising leads that throw light on this previously baffling illness. We suggest the key elements of a concerted research programme and call on the wider biomedical research community to actively target this condition.
... More than 95% pure primary hippocampal pyramidal neuronal cells (on disk in vitro 21) were used as primary neurons [7]. Primary microglia (>90% pure) and astrocytes (>85% pure) were collected according to our previous report [16] from the hippocampal tissue of the new born mice. ...
The special glycerophospholipids plasmalogens (Pls) are enriched in the brain and reported to prevent neuronal cell death by enhancing phosphorylation of Akt and ERK signaling in neuronal cells. Though the activation of Akt and ERK was found to be necessary for the neuronal cells survival, it was not known how Pls enhanced cellular signaling. To answer this question, we searched for neuronal specific orphan GPCR (G-protein coupled receptor) proteins, since these proteins were believed to play a role in cellular signal transduction through the lipid rafts, where both Pls and some GPCRs were found to be enriched. In the present study, pan GPCR inhibitor significantly reduced Pls-induced ERK signaling in neuronal cells, suggesting that Pls could activate GPCRs to induce signaling. We then checked mRNA expression of 19 orphan GPCRs and 10 of them were found to be highly expressed in neuronal cells. The knockdown of these 10 neuronal specific GPCRs by short hairpin (sh)-RNA lentiviral particles revealed that the Pls-mediated phosphorylation of ERK was inhibited in GPR1, GPR19, GPR21, GPR27 and GPR61 knockdown cells. We further found that the overexpression of these GPCRs enhanced Pls-mediated phosphorylation of ERK and Akt in cells. Most interestingly, the GPCRs-mediated cellular signaling was reduced significantly when the endogenous Pls were reduced. Our cumulative data, for the first time, suggest a possible mechanism for Pls-induced cellular signaling in the nervous system.
... For the selection of detection wavelength, the testing solution was taken for UV scanning at 200-600 nm, the result showed that the maximum absorption of MH was at 348 nm, with the absorption value 0.9825. According to the guidelines for UV-spectrophotometric method in Chinese Pharmacopoeia, 2000 edition, the appropriate UV absorption for testing solution was 0.3-0.7 (Simpson et al, 2014;Ifuku et al, 2014), thus 348 nm was set as the detection wavelength. The detection concentration was set as 15 μg/mL (C23H27N3O7). ...
In present study, a novel minocycline hydrochloride sustained-release capsule was prepared with the new extrusion-spheronization method. The in vitro release studies were performed using marketed sample as a reference and data were analyzed in terms of cumulative release amounts as a function of time. Results demonstrated that the developed analysis method was reliable and convenient for the quantification and dissolution study of minocycline hydrochloride. The release characteristics of different batches of preparations were quite similar with each other, similarity factors f2 of 12 batches were all within 50-100, and our developed sample was similar to reference preparation in release characteristics in vitro. The developed sustained-release preparation may be a promising alternative dosage form for treatment of related diseases.
... ? In a recent microglia study, Fuku, Hossain, Noda, and Katafuchi [110] found 5-HTT astrocyte expression resulted in immunologically induced fatigue in rats. These studies are important as they are addressing the core issues of ME symptomology at the gene level, creating a better understanding of the array of symptoms in this illness. ...
Myalgic Encephalomyelitis (ME) continues to cause significant morbiditiy worldwide with an estimated one million cases in the United States. Hurdles to establishing consensus to achieve accurate evaluation of patients with ME continue, fueled by poor agreement about case definitions, slow progress in development of standardized diagnostic approaches, and issues surrounding research priorities. Because there are other medical problems, such as early MS and Parkinson's Disease, which have some similar clinical presentations, it is critical to accurately diagnose ME to make a differential diagnosis. In this article, we explore and summarize advances in the physiological and neurological approaches to understanding, diagnosing, and treating ME. We identify key areas and approaches to eludicate the core and secondary symptom clusters in ME so as to provide some practical suggestions in evaluation of ME for clinicians and researchers.This review, therefore, represents a synthesis of key discussions in the literature, andhas important implications for a better understanding of ME, its biological markers, and diagnostic criteria. There is a clear need for more longitudinal studies in this area with larger data sets, which correct for multiple testing.
... Neuroglial cells, as well as neurons contribute to psychiatric symptoms. For example, activated microglia and astrocytes in immunologically induced fatigue (Ifuku et al., 2014), microglial oxidative reactions in schizophrenia (Kato et al., 2011;Monji et al., 2013), and alteration of astrocytes or oligodendrocyte function in bipolar disorder (Dong and Zhen, 2015) have been reported. On the other hand, decreased glial density in association with glial hypotrophy in bipolar disorder or major depression (Rajkowska et al., 2001;Bowley et al., 2002) was also reported. ...
It is widely accepted that there is a close relationship between the endocrine system and the central nervous system (CNS). Among hormones closely related to the nervous system, thyroid hormones (THs) are critical for the development and function of the CNS; not only for neuronal cells but also for glial development and differentiation. Any impairment of TH supply to the developing CNS causes severe and irreversible changes in the overall architecture and function of the human brain, leading to various neurological dysfunctions. In the adult brain, impairment of THs, such as hypothyroidism and hyperthyroidism, can cause psychiatric disorders such as schizophrenia, bipolar disorder, anxiety and depression. Although impact of hypothyroidism on synaptic transmission and plasticity is known, its effect on glial cells and related cellular mechanisms remain enigmatic. This mini-review article summarizes how THs are transported into the brain, metabolized in astrocytes and affect microglia and oligodendrocytes, demonstrating an example of glioendocrine system. Neuroglial effects may help to understand physiological and/or pathophysiological functions of THs in the CNS and how hypo- and hyper-thyroidism may cause mental disorders.
... As well as a direct effect of pro-inflammatory cytokines on neurotransmitters, such as serotonin (Anderson et al, 2014;Ifuku et al, 2014) and dopamine (Felger & Miller, 2012;Bower & Lamkin, 2013), IFNc (IFNG) and IL6 may also act indirectly by inducing expression of indoleamine 2,3-dioxygenase (IDO). IDO increases breakdown of the serotonin precursor tryptophan via the kynurenine pathway. ...
Fatigue is an important aspect of health-related quality of life from the patient perspective and can have significant socio-economic consequences. It is a common feature of chronic illnesses and a significant number of both adults and children with immune thrombocytopenia (ITP) suffer from fatigue. Reliable, validated fatigue scales have been developed for use in ITP. These will facilitate future investigation of its pathogenesis and the effectiveness of intervention. Acute inflammation acts on neural and endocrine systems resulting in 'sickness behaviour', an adaptive response to infection and injury. Inflammation is also thought to cause fatigue in chronic disease and immune dysregulation in ITP appears to have a number of pro-inflammatory components. Clinicians should consider fatigue when assessing the burden of disease. Although effective ITP-directed therapy can improve fatigue, a number of fatigue-directed strategies may also need to be considered.
© 2015 John Wiley & Sons Ltd.
Background and purpose: Postoperative fatigue (POF) is a common and distressing post-operative symptom. This study aimed to explore the relationship between neutrophil-to-lymphocyte ratio (NLR) and POF in elderly patients with hip fracture.
Method: Elderly patients (age ≥ 65 years) with acute hip fracture admitted to the Department of Orthopedics of Anqing Hospital affiliated to Anhui Medical University from June 2018 to June 2020 were included. Fatigue was assessed using the Fatigue Severity Scale at the 3-month follow-up postoperatively. Univariate and multivariate analyses were performed to explore the associations between NLR and POF. The diagnostic performance of NLR was analysed using Receiver Operating Characteristic (ROC) curve analysis and the Delong test.
Result: A total of 321 elderly patients with hip fractures were included; 120 (37.4%) of them were diagnosed with POF. Univariate analysis indicated significant differences in NLR, platelet-to-lymphocyte ratio (PLR), education, neutrophil count, lymphocyte count, Hamilton Depression Scale (HAMD) and Insomnia Severity Index (ISI) scores (P<0.05). Multivariate analysis indicated neutrophil count (odds ratio [OR], 1.46; 95% confidence interval [CI] 1.27–1.67), lymphocyte count (OR 0.32, 95% CI 0.19–0.53), NLR (OR1.81, 95% CI 1.50–2.17) and PLR (OR 1.005, 95% CI 1.001–1.009) were significantly associated with POF. The areas under the ROC curves (AUCs) of neutrophil count, lymphocyte count, NLR and PLR were 0.712, 0.667, 0.775 and 0.605, respectively. The Delong test indicated that NLR had the best diagnostic performance (p < 0.05).
Conclusion: NLR independently predicts POF in elderly patients with acute hip fracture.
Ectoenzyme and receptor BST-1/CD157 has been considered as a key molecule involved in the regulation of functional activity of cells in various tissues and organs. It is commonly accepted that CD157 catalyzes NAD+ hydrolysis and acts as a component of integrin adhesion receptor complex. Such properties are important for the regulatory role of CD157 in neuronal and glial cells: in addition to recently discovered role in the regulation of emotions, motor functions, and social behavior, CD157 might serve as an important component of innate immune reactions in the central nervous system. Activation of innate immune system in the brain occurs in response to infectious agents as well as in brain injury and neurodegeneration. As an example, in microglial cells, association of CD157 with CD11b/CD18 complex drives reactive gliosis and neuroinflammation evident in brain ischemia, chronic neurodegeneration, and aging. There are various non-substrate ligands of CD157 belonging to the family of extracellular matrix proteins (fibronectin, collagen I, finbrinogen, and laminin) whose activity is required for controlling cell adhesion and migration. Therefore, CD157 could control structural and functional integrity of the blood-brain barrier and barriergenesis. On the other hand, contribution of CD157 to the regulation of brain development is rather possible since in the embryonic brain, CD157 expression is very high, whereas in the adult brain, CD157 is expressed on neural stem cells and, presumably, is involved in the neurogenesis. Besides, CD157 could mediate astrocytes' action on neural stem and progenitor cells within neurogenic niches. In this review we will summarize how CD157 may affect brain plasticity acting as a molecule at the crossroad of neurogenesis, cerebral angiogenesis, and immune regulation.
In 2011, it was reviewed that a) there is a strong co-occurrence between major depression and chronic fatigue syndrome (CFS), with fatigue and physio-somatic symptoms being key symptoms of depression, and depressive symptoms appearing during the course of CFS; and b) the comorbidity between both disorders may in part be explained by activated immune-inflammatory pathways, including increased translocation of Gram-negative bacteria and increased levels of pro-inflammatory cytokines, such as interleukin (IL)-1. Nevertheless, the possible involvement of activated microglia in this comorbidity has remained unclear. This paper aims to review microglial disturbances in major depression, CFS and their comorbidity. A comprehensive literature search was conducted using the PubMed / MEDLINE database to identify studies, which are relevant to this current review. Depressed patients present neuroinflammatory alterations, probably related to microglial activation, while animal models show that a microglial response to immune challenges including lipopolysaccharides is accompanied by depressive-like behaviors. Recent evidence from preclinical studies indicates that activated microglia have a key role in the onset of fatigue. In chronic inflammatory conditions, such as infections and senescence, microglia orchestrate an inflammatory microenvironment thereby causing fatigue. In conclusion, based on our review we may posit that shared immune-inflammatory pathways and especially activated microglia underpin comorbid depression and CFS. As such, microglial activation and neuro-inflammation may be promising targets to treat the overlapping manifestations of both depression and CFS.
Purpose:
Neuroinflammation is a common feature in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), affecting 85%-90% of all patients, yet the underlying mechanism or mechanisms responsible for the initiation and/or promotion of this process is largely unknown. Multiple reports, however, have suggested a role for Epstein-Barr virus (EBV), in particular, in ME/CFS, but its potential role, if any, in the neuroinflammatory process has not been addressed. In support of this premise, studies by our group have found that the EBV protein deoxyuridine triphosphate nucleotidohydrolase (dUTPase) induces anxiety and sickness behaviors in female mice. We also found that a small subset of patients with ME/CFS exhibited prolonged and significantly elevated neutralizing antibodies against EBV dUTPase protein in serum, which inversely correlated with ME/CFS symptoms. A larger ME/CFS case-control cohort study further confirmed that a significant percentage of patients with ME/CFS (30.91%-52.7%) were simultaneously producing antibodies against multiple human herpesviruses-encoded dUTPases and/or human dUTPase. Altogether, these findings suggest that EBV dUTPase protein may be involved in the neuroinflammatory process observed in ME/CFS. Thus, the aim of the present study was to determine whether the EBV dUTPase protein could contribute to neuroinflammation by altering the expression of genes involved with maintaining blood-brain barrier (BBB) integrity and/or modulating synaptic plasticity.
Methods:
With the use of human immortalized astrocytes, microglia, and cerebral microvascular endothelial cells, we conducted time-course (0-24 h) experiments with EBV dUTPase protein (10 μg/mL) to determine what effect(s) it may have on the expression of genes involved with BBB permeability, astrocytes and microglia cell function, tryptophan metabolism, and synaptic plasticity by quantitative reverse transcription polymerase chain reaction (qRT-PCR). In parallel, in vivo studies were conducted in female C57Bl/6 mice. Mice were injected by the intraperitoneal route with EBV dUTPase protein (10 μg) or vehicle daily for 5 days, and the brains were collected and processed for further qRT-PCR analysis of the in vivo effect of the dUTPase on the dopamine/serotonin and γ-aminobutyric acid/glutamate pathways, which are important for brain function, using RT2 Profiler PCR Arrays.
Findings:
EBV dUTPase protein altered the expression in vitro (12 of 15 genes and 32 of 1000 proteins examined) and in vivo (34 of 84 genes examined) of targets with central roles in BBB integrity/function, fatigue, pain synapse structure, and function, as well as tryptophan, dopamine, and serotonin metabolism.
Implications:
The data suggest that in a subset of patients with ME/CFS, the EBV dUTPase could initiate a neuroinflammatory reaction, which contributes to the fatigue, excessive pain, and cognitive impairments observed in these patients.
Neuroinflammation characterized by activation of glial cells is observed in various neurodegenerative diseases including Alzheimer's disease (AD). Although the reduction of ether-type glycerophospholipids, plasmalogens (Pls), in the brain is reported in AD patients, the mechanism of the reduction and its impact on neuroinflammation remained elusive. In the present study, we found for the first time that various inflammatory stimuli reduced the Pls levels in the murine glial cells via NF-κB activation which then down-regulated a Pls synthesizing enzyme, glycerone phosphate O-acyltransferase (Gnpat) through the increased c-Myc recruitment onto the Gnpat promoter. We also found that systemic injection of lipopolysaccharide, aging and chronic restraint stress reduced brain Pls contents which were associated with the glial NF-κB activation, increase in c-Myc expression and down regulation of Gnpat in the mouse cortex and hippocampus. More interestingly, the reduction of Pls contents in the murine cortex itself could increase the activated phenotype of microglial cells and the expression of proinflammatory cytokines, suggesting further acceleration of neuroinflammation by the reduction of brain Pls. The similar mechanism of Gnpat reduction was also found in the human cell lines, triple transgenic AD mice brain and the postmortem human AD brain tissues. These findings suggest a novel mechanism of neuroinflammation that may explain prolonged progression of AD and help us to explore preventive and therapeutic strategies to treat the neurodegenerative diseases.SIGNIFICANCE STATEMENTEther-type glycerophospholipids, plasmalogens (Pls), are reduced in the brain of Alzheimer disease (AD) patients. We found that inflammatory stimuli reduced Pls contents by downregulation of Pls synthesizing enzyme, glycerone phosphate O-acyltransferase (Gnpat), through the NF-κB-mediated recruitment of c-Myc onto the Gnpat promoter in both murine and human cell lines. Murine brains after systemic lipopolysaccharide, chronic stress and ageing, as well as triple transgenic AD mice and postmortem human AD brain tissues, also showed increased c-Myc and reduced Gnpat expression. Interestingly, the knockdown of Gnpat itself activated NF-κB in glial cell lines and microglia in mouse cortex. Our findings provide a new insight into mechanism of neuroinflammation and may help to explore a novel therapeutic approach to neurodegenerative diseases like AD.
Nutritional conditions in early life can have a lasting impact on health and disease risk, though the underlying mechanisms are incompletely understood. In the healthy individual, physiological and behavioral responses to stress are coordinated in such a way as to mobilize resources necessary to respond to the stressor and to terminate the stress response at the appropriate time. Induction of proinflammatory gene expression within the brain is one such example that is initiated in response to both physiological and psychological stressors, and is the focus of the current study. We tested the hypothesis that early life nutrition would impact the proinflammatory transcriptional response to a stressor. Pregnant and lactating dams were fed one of three diets; a low-protein diet, a high fat diet, or the control diet through pregnancy and lactation. Adult male offspring were then challenged with either a physiological stressor (acute lipopolysaccharide injection, IP) or a psychological stressor (15 min restraint). Expression of 20 proinflammatory and stress-related genes was evaluated in hypothalamus, prefrontal cortex, amygdala and ventral tegmental area. In a second cohort, behavioral responses (food intake, locomotor activity, metabolic rate) were evaluated. Offspring from low protein fed dams showed a generally reduced transcriptional response, particularly to LPS, and resistance to behavioral changes associated with restraint, while HF offspring showed an exacerbated transcriptional response within the PFC, a reduced transcriptional response in hypothalamus and amygdala, and an exacerbation of the LPS-induced reduction of locomotor activity. The present data identify differential proinflammatory transcriptional responses throughout the brain driven by perinatal diet as an important variable that may affect risk or resilience to stressors.
Abstract Neuroinflammation is as an important component of pathogenesis in many types of brain pathology. Immune mechanisms regulate neuroplasticity, memory formation, neurogenesis, behavior, brain development, cognitive functions, and brain metabolism. It is generally believed that essential homeostatic functions of astrocytes - astroglia-neuron metabolic coupling, gliovascular control, regulation of proliferation, and migration of cells in the neurogenic niches - are compromised in neuroinflammation resulting in excitotoxicity, neuronal and glial cell death, and alterations of intercellular communication. Viral neuroinfection, release of non-coding RNAs from the cells at the sites of brain injury or degeneration, and application of siRNA or RNA aptamers as therapeutic agents would require dsRNA-sensing pathways in the cells of neuronal and non-neuronal origin. In this review, we analyze the data regarding the role of astrocytes in dsRNA-initiated innate immune response in neuroinflammation and their contribution to progression of neurodegenerative and neurodevelopmental pathology.
One of the reasons for the insufficient effectiveness of treatment of acute ischemic stroke may be secondary inflammation of the brain tissue, which, according to the results of modern studies, significantly worsens the consequences and outcome of the disease.
The CNS, which consists of the brain and spinal cord, is continuously monitored by resident microglia and blood-borne immune cells such as macrophages, dendritic cells and T cells to detect for damaging agents that would disrupt homeostasis and optimal functioning of these vital organs. Further, the CNS must balance between vigilantly detecting for potentially harmful factors and resolving any immunological responses that in themselves can create damage if left unabated. We discuss the physiological roles of the immune sentinels that patrol the CNS, the molecular markers that underlie their surveillance duties, and the consequences of interrupting their functions following injury and infection by viruses such as JC virus, human immunodeficiency virus, herpes simplex virus and West Nile virus.
Recently it has been shown that mRNA of Iba1 (ionized calcium binding adaptor molecule 1), which was a novel calcium binding protein cDNA-cloned by our group, is specifically expressed in microglia in cultures of rat brain cells [Imai et al. Biophys. Biochem. Res. Commun., 224 (1996) 855–862]. In the present study, immunocytochemical and immunohistochemical examinations demonstrated that Iba1 protein is expressed in microglia alone both in cultured brain cells and in the brain, respectively. In a mixed cell culture of embryonic rat brain, immunocytochemically positive for Iba1 protein were the microglia but it was not detectable in neurons, astroglia, or oligodendroglia. Immunohistochemical staining of adult rat brain sections showed Iba1 protein to be specifically localised in ramified microglia. In addition, immunohistochemical staining and immunoblot analysis of activated microglia in the facial nucleus after facial nerve axotomy shows that expression of Iba1 protein was upregulated and peaked at 7 days. These results indicated that localisation of Iba1 protein is restricted to microglia both in vitro and in vivo, and that Iba1 protein plays a role in regulating the function of microglia, especially in the activated microglia.
Microglial cells are the resident macrophages in the central nervous system. These cells of mesodermal/mesenchymal origin migrate into all regions of the central nervous system, disseminate through the brain parenchyma, and acquire a specific ramified morphological phenotype termed "resting microglia." Recent studies indicate that even in the normal brain, microglia have highly motile processes by which they scan their territorial domains. By a large number of signaling pathways they can communicate with macroglial cells and neurons and with cells of the immune system. Likewise, microglial cells express receptors classically described for brain-specific communication such as neurotransmitter receptors and those first discovered as immune cell-specific such as for cytokines. Microglial cells are considered the most susceptible sensors of brain pathology. Upon any detection of signs for brain lesions or nervous system dysfunction, microglial cells undergo a complex, multistage activation process that converts them into the "activated microglial cell." This cell form has the capacity to release a large number of substances that can act detrimental or beneficial for the surrounding cells. Activated microglial cells can migrate to the site of injury, proliferate, and phagocytose cells and cellular compartments.
Hearing loss (HL) is the most common sensory impairment occurring at birth in developed countries. Epidemiological data show that more than one child in 1000 is born with HL, while more than 50% of prelingual HL cases are found to be hereditary. Approximately 70% of hereditary HL is nonsyndromic and subdivided to autosomal dominant (20%), autosomal recessive (75%), X-linked HL (1%), and maternally-inherited HL associated with the mitochondrial DNA mutation. More than 10 deafness genes have been reported to be responsible for nonsyndromic hereditary HL in Japan. Among them, the most prevalent causative genes, GJB2 and the mitochondrial DNA 12SrRNA are introduced. In addition, this study also refers to the specific genes responsible for the unique audiogram, mainly WFS1. Finally, the genes related to the enlargement of vestibular aqueduct of inner ear abnormality, SLC26A4, EYA1 and SIX1 are discussed. The clinical and genetic findings associated with these disorders including the results of a recent study are reviewed.
Interleukin (IL)-18 is an important regulator of innate and acquired immune responses. Here we show that both the IL-18 and IL-18 receptor (IL-18R), which are induced in spinal dorsal horn, are crucial for tactile allodynia after nerve injury. Nerve injury induced a striking increase in IL-18 and IL-18R expression in the dorsal horn, and IL-18 and IL-18R were upregulated in hyperactive microglia and astrocytes, respectively. The functional inhibition of IL-18 signaling pathways suppressed injury-induced tactile allodynia and decreased the phosphorylation of nuclear factor kappaB in spinal astrocytes and the induction of astroglial markers. Conversely, intrathecal injection of IL-18 induced behavioral, morphological, and biochemical changes similar to those observed after nerve injury. Our results indicate that IL-18-mediated microglia/astrocyte interactions in the spinal cord have a substantial role in the generation of tactile allodynia. Thus, blocking IL-18 signaling in glial cells might provide a fruitful strategy for treating neuropathic pain.
Serotonin (5HT) transporters (SERTs) are responsible for clearance of synaptic and plasma 5HT and are molecular targets for multiple therapeutic and addictive compounds. Recently brain and peripheral SERT cDNAs have been cloned and characterized functionally in transfected cells. Antipeptide (S365) and anti-fusion protein (CT-2) antibodies, directed at epitopes poorly conserved among other Na+/Cl- cotransporters, have been prepared to facilitate the identification and characterization of SERT proteins in native and transfected cells. Immunoprecipitations and immunoblots of rat/human SERT-transfected HeLa cells reveal specific SERT-immunoreactive glycoproteins absent from extracts of vector-transfected cells and absent when incubations were conducted using peptide- or fusion protein-absorbed antibody. In SDS-PAGE of membranes prepared from rat midbrain and cortex, SERTs migrate as single 76 kDa polypeptides with a relative abundance consistent with the known distribution of 5HT neurons and axonal projections. SERT-immunoreactive proteins are also detectable in platelet and pulmonary membranes, sites of peripheral 5HT uptake, but not in liver. Our studies also indicate that brain and platelet SERTs are formed from identical polypeptides differing significantly in their extent of N-linked glycosylation. Immunocytochemistry performed on rat brain sections with CT-2 antibody revealed SERT expression associated with brainstem raphe nuclei in a pattern virtually identical to that obtained by labeling adjacent sections with 5HT antisera. SERT-immunoreactive fibers were found to be widely distributed throughout the rodent brain, with highest density in forebrain regions known to receive a dense serotonergic innervation. In a similar manner, CT-2 antibody also detects endogenous expression of human SERT proteins, providing an opportunity for future studies on the modulation of transporter protein expression in neurologic and psychiatric disorders.
To examine cognitive function in chronic fatigue syndrome.
Twenty patients with chronic fatigue syndrome recruited from primary care and 20 matched normal controls were given CANTAB computerised tests of visuospatial memory, attention, and executive function, and verbal tests of letter and category fluency and word association learning.
Patients with chronic fatigue syndrome were impaired, predominantly in the domain of memory but their pattern of performance was unlike that of patients with amnesic syndrome or dementia. They were normal on tests of spatial pattern recognition memory, simultaneous and delayed matching to sample, and pattern-location association learning. They were impaired on tests of spatial span, spatial working memory, and a selective reminding condition of the pattern-location association learning test. An executive test of planning was normal. In an attentional test, eight subjects with chronic fatigue syndrome were unable to learn a response set; the remainder exhibited no impairment in the executive set shifting phase of the test. Patients with chronic fatigue syndrome were also impaired on verbal tests of unrelated word association learning and letter fluency.
Patients with chronic fatigue syndrome have reduced attentional capacity resulting in impaired performance on effortful tasks requiring planned or self ordered generation of responses from memory.
Ischemic stroke is the most common life-threatening neurological disease and has limited therapeutic options. One component of ischemic neuronal death is inflammation. Here we show that doxycycline and minocycline, which are broad-spectrum antibiotics and have antiinflammatory effects independent of their antimicrobial activity, protect hippocampal neurons against global ischemia in gerbils. Minocycline increased the survival of CA1 pyramidal neurons from 10.5% to 77% when the treatment was started 12 h before ischemia and to 71% when the treatment was started 30 min after ischemia. The survival with corresponding pre- and posttreatment with doxycycline was 57% and 47%, respectively. Minocycline prevented completely the ischemia-induced activation of microglia and the appearance of NADPH-diaphorase reactive cells, but did not affect induction of glial acidic fibrillary protein, a marker of astrogliosis. Minocycline treatment for 4 days resulted in a 70% reduction in mRNA induction of interleukin-1beta-converting enzyme, a caspase that is induced in microglia after ischemia. Likewise, expression of inducible nitric oxide synthase mRNA was attenuated by 30% in minocycline-treated animals. Our results suggest that lipid-soluble tetracyclines, doxycycline and minocycline, inhibit inflammation and are neuroprotective against ischemic stroke, even when administered after the insult. Tetracycline derivatives may have a potential use also as antiischemic compounds in humans.
The only treatment of patients with acute ischemic stroke is thrombolytic therapy, which benefits only a fraction of stroke patients. Both human and experimental studies indicate that ischemic stroke involves secondary inflammation that significantly contributes to the outcome after ischemic insult. Minocycline is a semisynthetic second-generation tetracycline that exerts antiinflammatory effects that are completely separate from its antimicrobial action. Because tetracycline treatment is clinically well tolerated, we investigated whether minocycline protects against focal brain ischemia with a wide therapeutic window. Using a rat model of transient middle cerebral artery occlusion, we show that daily treatment with minocycline reduces cortical infarction volume by 76 +/- 22% when the treatment is started 12 h before ischemia and by 63 +/- 35% when started even 4 h after the onset of ischemia. The treatment inhibits morphological activation of microglia in the area adjacent to the infarction, inhibits induction of IL-1beta-converting enzyme, and reduces cyclooxygenase-2 expression and prostaglandin E(2) production. Minocycline had no effect on astrogliosis or spreading depression, a wave of ionic transients thought to contribute to enlargement of cortical infarction. Treatment with minocycline may act directly on brain cells, because cultured primary neurons were also salvaged from glutamate toxicity. Minocycline may represent a prototype of an antiinflammatory compound that provides protection against ischemic stroke and has a clinically relevant therapeutic window.
The nature of microglia fascinated many prominent researchers in the 19th and early 20th centuries, and in a classic treatise in 1932, Pio del Rio-Hortega formulated a number of concepts regarding the function of these resident macrophages of the brain parenchyma that remain relevant to this day. However, a renaissance of interest in microglia occurred toward the end of the 20th century, fueled by the recognition of their role in neuropathogenesis of infectious agents, such as human immunodeficiency virus type 1, and by what appears to be their participation in other neurodegenerative and neuroinflammatory disorders. During the same period, insights into the physiological and pathological properties of microglia were gained from in vivo and in vitro studies of neurotropic viruses, bacteria, fungi, parasites, and prions, which are reviewed in this article. New concepts that have emerged from these studies include the importance of cytokines and chemokines produced by activated microglia in neurodegenerative and neuroprotective processes and the elegant but astonishingly complex interactions between microglia, astrocytes, lymphocytes, and neurons that underlie these processes. It is proposed that an enhanced understanding of microglia will yield improved therapies of central nervous system infections, since such therapies are, by and large, sorely needed.
West Nile virus (WNV), a mosquito-borne single-stranded (ss)RNA flavivirus, causes human disease of variable severity. We investigated the involvement of Toll-like receptor (Tlr) 3, which recognizes viral double-stranded (ds)RNA, on WNV infection. Tlr3-deficient (Tlr3(-/-)) mice were more resistant to lethal WNV infection and had impaired cytokine production and enhanced viral load in the periphery, whereas in the brain, viral load, inflammatory responses and neuropathology were reduced compared to wild-type mice. Peripheral WNV infection led to a breakdown of the blood-brain barrier and enhanced brain infection in wild-type but not in Tlr3(-/-) mice, although both groups were equally susceptible upon intracerebroventricular administration of the virus. Tumor necrosis factor-alpha receptor 1 signaling is vital for blood-brain barrier compromise upon Tlr3 stimulation by dsRNA or WNV. Collectively, WNV infection leads to a Tlr3-dependent inflammatory response, which is involved in brain penetration of the virus and neuronal injury.
To delineate the risk factors, symptom patterns, and longitudinal course of prolonged illnesses after a variety of acute infections.
Prospective cohort study following patients from the time of acute infection with Epstein-Barr virus (glandular fever), Coxiella burnetii (Q fever), or Ross River virus (epidemic polyarthritis).
The region surrounding the township of Dubbo in rural Australia, encompassing a 200 km geographical radius and 104,400 residents.
253 patients enrolled and followed at regular intervals over 12 months by self report, structured interview, and clinical assessment.
Detailed medical, psychiatric, and laboratory evaluations at six months to apply diagnostic criteria for chronic fatigue syndrome. Premorbid and intercurrent illness characteristics recorded to define risk factors for chronic fatigue syndrome. Self reported illness phenotypes compared between infective groups.
Prolonged illness characterised by disabling fatigue, musculoskeletal pain, neurocognitive difficulties, and mood disturbance was evident in 29 (12%) of 253 participants at six months, of whom 28 (11%) met the diagnostic criteria for chronic fatigue syndrome. This post-infective fatigue syndrome phenotype was stereotyped and occurred at a similar incidence after each infection. The syndrome was predicted largely by the severity of the acute illness rather than by demographic, psychological, or microbiological factors.
A relatively uniform post-infective fatigue syndrome persists in a significant minority of patients for six months or more after clinical infection with several different viral and non-viral micro-organisms. Post-infective fatigue syndrome is a valid illness model for investigating one pathophysiological pathway to chronic fatigue syndrome.
Bradykinin (BK) is produced and acts at the site of injury and inflammation. In the CNS, migration of microglia toward the lesion site plays an important role pathologically. In the present study, we investigated the effect of BK on microglial migration. Increased motility of cultured microglia was mimicked by B1 receptor agonists and markedly inhibited by a B1 antagonist but not by a B2 receptor antagonist. BK induced chemotaxis in microglia isolated from wild-type and B2-knock-out mice but not from B1-knock-out mice. BK-induced motility was not blocked by pertussis toxin but was blocked by chelating intracellular Ca2+ or by low extracellular Ca2+, implying that Ca2+ influx is prerequisite. Blocking the reverse mode of Na+/Ca2+ exchanger (NCX) completely inhibited BK-induced migration. The involvement of NCX was further confirmed by using NCX+/- mice; B1-agonist-induced motility and chemotaxis was decreased compared with that in NCX+/+ mice. Activation of NCX seemed to be dependent on protein kinase C and phosphoinositide 3-kinase, and resultant activation of intermediate-conductance (IK-type) Ca2+-dependent K+ currents (I(K(Ca))) was activated. Despite these effects, BK did not activate microglia, as judged from OX6 staining. Using in vivo lesion models and pharmacological injection to the brain, it was shown that microglial accumulation around the lesion was also dependent on B1 receptors and I(K(Ca)). These observations support the view that BK functions as a chemoattractant by using the distinct signal pathways in the brain and, thus, attracts microglia to the lesion site in vivo.
The tetracycline class of antimicrobials exhibit a broad-spectrum of activity against numerous pathogens, including Gram-positive and Gram-negative bacteria, as well as atypical organisms. These compounds are bacteriostatic, and act by binding to the bacterial 30S ribosomal subunit and inhibiting protein synthesis. The tetracyclines have been used successfully for the treatment of a variety of infectious diseases including community-acquired respiratory tract infections and sexually transmitted diseases, as well in the management of acne. The use of tetracyclines for treating bacterial infections has been limited in recent years because of the emergence of resistant organisms with efflux and ribosomal protection mechanisms of resistance. Research to find tetracycline analogues that circumvented these resistance mechanisms has lead to the development of the glycylcyclines.
The most developed glycylcycline is the 9-tert-butyl-glycylamido derivative of minocycline, otherwise known as tigecycline (GAR-936). The glycylcyclines exhibit antibacterial activities typical of earlier tetracyclines, but with more potent activity against tetracycline-resistant organisms with efflux and ribosomal protection mechanisms of resistance. The glycylcyclines are active against other resistant pathogens including methicillin-resistant staphylococci, penicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant enterococci.
Tigecycline is only available in an injectable formulation for clinical use unlike currently marketed tetracyclines that are available in oral dosage forms. Tigecycline has a significantly larger volume of distribution (>10 L/kg) than the other tetracyclines (range of 0.14 to 1.6 L/kg). Protein binding is approximately 68%. Presently no human data are available describing the tissue penetration of tigecycline, although studies in rats using radiolabelled tigecycline demonstrated good penetration into tissues. Tigecycline has a half-life of 36 hours in humans, less than 15% of tigecycline is excreted unchanged in the urine. On the basis of available data, it does not appear that the pharmacokinetics of tigecycline are markedly influenced by patient gender or age.
The pharmacodynamic parameter that best correlates with bacteriological eradication is time above minimum inhibitory concentration. Several animal studies have been published describing the efficacy of tigecycline. Human phase 1 and 2 clinical trials have been completed for tigecycline. Phase 2 studies have been conducted in patients with complicated skin and skin structure infections, and in patients with complicated intra-abdominal infections have been published as abstracts. Both studies concluded that tigecycline was efficacious and well tolerated. Few human data are available regarding the adverse effects or drug interactions resulting from tigecycline therapy; however, preliminary data report that tigecycline can be safely used, is well tolerated and that the adverse effects experienced were typical of the tetracyclines (i.e. nausea, vomiting and headache).
Tigecycline appears to be a promising new antibacterial based on in vitro and pharmacokinetic/pharmacodynamic activity; however more clinical data are needed to fully evaluate its potential.
We successfully isolated a rat cDNA clone encoding a novel EF hand protein with a molecular weight of about 17 kDa and designated this geneiba1(ionized calcium binding adapter molecule 1). The genomic copy of theiba1gene was located within a segment of the major histocompatibility complex class III region between theBat2andTNFαgenes. Theiba1gene was shown to be highly expressed in testis and spleen, but weakly expressed in brain, lung, and kidney. Among brain cells, theiba1gene was specifically expressed in microglia. A screening of hemopoietic cell lines showed that the Iba1 protein was clearly expressed in monoblastic cell lines but only very weakly expressed in myeloid cell lines. Iba1 protein is therefore suggested to act as an adapter molecule, mediating calcium signals that may function in a monocytic lineage including microglia.
We assessed the role of glial cells in the uptake of serotonin (5-hydroxytryptamine, 5-HT). Primary cultures of rat and mouse cortical astrocytes took up and deaminated 5-HT. The antidepressants citalopram, clomipramine, fluoxetine, fluvoxamine, paroxetine and sertraline inhibited this process. The presence of the mRNAs for the 5-HT transporter and monoamine oxidase-A (MOA-A) was established in cultured astrocytes and in adult rat brain areas with (midbrain and brainstem) and without (frontal cortex) serotonergic cell bodies after reverse transcription-polymerase chain reaction and hybridization with probes complementary to the cloned neuronal 5-HT transporter and MAO-A. To examine in vivo the role of astrocytes in the elimination of 5-HT from the extracellular brain space, 5-HT was perfused through dialysis probes implanted in the frontal cortex of conscious rats and its concentration was measured at the probe outlet. Tissue 5-HT recovery was dose-dependently inhibited by the concurrent perfusion of citalopram, fluoxetine and paroxetine, showing that it essentially measured uptake through the high-affinity 5-HT transporter. Rats lesioned with 5,7-dihydroxytryptamine (5,7-DHT; 88% reduction of tissue 5-HT) displayed tissue 5-HT recovery slightly higher than sham-operated rats (55 ± 2 vs. 46 ± 3%, P < 0.001), a finding perhaps attributable to the astrogliosis induced by 5,7-DHT denervation. Rats lesioned with 6-hydroxydopamine showed tissue 5-HT uptake similar to controls, suggesting negligible reuptake of 5-HT by catecholaminergic terminals. These results are consistent with the presence of a glial component of 5-HT uptake in the rodent brain, sensitive to antidepressants, which takes place through a 5-HT transporter very similar or identical to that present in neurons.
Fatigue is a common and disabling symptom in neurologic disorders including traumatic penetrating brain injury (PBI). Despite fatigue's prevalence and impact on quality of life, its pathophysiology is not understood. Studies on effort perception in healthy subjects, animal behavioral paradigms, and recent evidence in different clinical populations suggest that ventromedial prefrontal cortex could play a significant role in fatigue pathophysiology in neurologic conditions.
We enrolled 97 PBI patients and 37 control subjects drawn from the Vietnam Head Injury Study registry. Fatigue was assessed with a self-report questionnaire and a clinician-rated instrument; lesion location and volume were evaluated on CT scans. PBI patients were divided in 3 groups according to lesion location: a nonfrontal lesion group, a ventromedial prefrontal cortex lesion (vmPFC) group, and a dorso/lateral prefrontal cortex (d/lPFC) group. Fatigue scores were compared among the 3 PBI groups and the healthy controls.
Individuals with vmPFC lesions were significantly more fatigued than individuals with d/lPFC lesions, individuals with nonfrontal lesions, and healthy controls, while these 3 latter groups were equally fatigued. VmPFC volume was correlated with fatigue scores, showing that the larger the lesion volume, the higher the fatigue scores.
We demonstrated that ventromedial prefrontal cortex lesion (vmPFC) plays a critical role in penetrating brain injury-related fatigue, providing a rationale to link fatigue to different vmPFC functions such as effort and reward perception. The identification of the anatomic and cognitive basis of fatigue can contribute to developing pathophysiology-based treatments for this disabling symptom.
Although 17beta-estradiol (E2) is reported to improve the inflammatory response after trauma-hemorrhage (T-H), it remains unknown whether E2 plays any role in the central nervous system after T-H. Microglial cells, resident central macrophages, are thought to play a central role in exacerbating cell-mediated inflammation. We hypothesized that T-H up-regulates microglial cell-mediated inflammatory response in the brain, and E2 produces central anti-inflammatory effects via negative regulation of microglial cells. Male Sprague-Dawley rats were subjected to sham operation (cannulation plus laparotomy) or T-H (midline laparotomy; mean blood pressure, 35 +/- 5 mmHg for 90 min followed by resuscitation) and immediately killed after resuscitation. Rats received vehicle or E2 (1 mg/kg body weight i.v.) at the onset of resuscitation. In other experiments, minocycline (40 mg/kg body weight i.p.), microglia inhibitor, was administered 1 h before T-H to prevent inflammatory response in the microglia after T-H. The plasma and hypothalamic tumor necrosis factor (TNF-alpha) levels were increased, along with the activation of microglial cells in T-H rats compared with shams. Furthermore, T-H increased microglial TNF-alpha productive capacity in vitro. 17beta administration after T-H prevented these inflammatory responses. In rats pretreated with minocycline, decreased microglial TNF-alpha production and hypothalamic TNF-alpha levels were observed, but plasma TNF-alpha levels were not altered after T-H. Thus, T-H induces inflammatory responses even in the hypothalamus, and E2 seems to be a useful adjunct for down-regulating microglial cell-mediated inflammatory response after T-H.
It has been proposed that oxygen-derived radicals, superoxide in particular, are involved in the alteration of blood-brain barrier permeability and the pathogenesis of brain edema following trauma, ischemia, and reperfusion injury. Using transgenic mice that overexpress the human gene for copper-zinc-superoxide dismutase, we studied the role of superoxide radicals in the blood-brain permeability changes, edema development, and delayed infarction resulting from cold-trauma brain injury. At 2 hours after a 30-second cold injury, cerebral water and Evans blue contents were reduced, respectively, from 80 +/- 0.2% and 132.7 +/- 12.9 micrograms/gm of dry weight for nontransgenic mice to 78.5 +/- 0.3% and 87.1 +/- 9.9 micrograms/gm of dry weight for transgenic mice. Infarction, as measured by 2,3,5-triphenyltetrazolium chloride staining, was reduced by 52% in transgenic brains. These data indicate that an increased level of superoxide dismutase activity in the brain reduces the development of vasogenic brain edema and infarction. Superoxide radicals play an important role in the pathogenesis of these lesions in cold-traumatized brain.
The newer tetracyclines are defined as those tetracyclines available in the United States but not approved for veterinary use. These include demeclocycline, methacycline, doxycycline, and minocycline. Of these, doxycycline and minocycline appear to offer advantages that would render them useful in certain situations in veterinary medicine. Their major advantage lies in their greater lipid solubility relative to other tetracyclines. This characteristic probably accounts for their enhanced antimicrobial effectiveness for some organisms, more efficient absorption after oral administration, and enhanced distribution in the body. The principal excretory organ for doxycycline is the intestine, where the drug diffuses through the intestinal mucosa into the intestinal tract. This unique characteristic makes this drug useful in cases of preexisting renal dysfunction and may render this drug superior to other tetracyclines in the treatment of intestinal infections. Doxycycline is used in other countries for respiratory tract and intestinal tract diseases of poultry. The usefulness of doxycycline and minocycline in food-producing animals may be limited because of persistent drug residues. Minocycline has, in large doses, been used with streptomycin in the elimination of the carrier state of canine brucellosis. The superiority of doxycycline and minocycline, relative to other tetracyclines, in their distribution to areas of he body such as the eye, brain, cerebrospinal fluid, and prostate gland suggests that trials of their efficacy in tetracycline-sensitive infections of these areas are indicated. Pharmacokinetic studies designed to determine optimal dosage schedules have not been made for domestic animals. These determinations are necessary to evaluate most effectively the usefulness of the newer tetracyclines in veterinary medicine.
Cytokines exert diverse actions on the PNS and the CNS and have been implicated in neuronally mediated responses to disease and injury. Certain cytokines participate in the central control of host systemic responses to disease, acting as signals to and within the brain. These molecules are also involved in neuronal degeneration and repair in the PNS and CNS, and have been proposed as mediators of various neuropathologies. The actions, mechanisms of action and potential strategies for modifying cytokines in the nervous system will be considered in this review, which continues the discussion of cytokine expression and recognition published in the February issue of TINS.
We assessed the role of glial cells in the uptake of serotonin (5-hydroxytryptamine, 5-HT). Primary cultures of rat and mouse cortical astrocytes took up and deaminated 5-HT. The antidepressants citalopram, clomipramine, fluoxetine, fluvoxamine, paroxetine and sertraline inhibited this process. The presence of the mRNAs for the 5-HT transporter and monoamine oxidase-A (MOA-A) was established in cultured astrocytes and in adult rat brain areas with (midbrain and brainstem) and without (frontal cortex) serotonergic cell bodies after reverse transcription-polymerase chain reaction and hybridization with probes complementary to the cloned neuronal 5-HT transporter and MAO-A. To examine in vivo the role of astrocytes in the elimination of 5-HT from the extracellular brain space, 5-HT was perfused through dialysis probes implanted in the frontal cortex of conscious rats and its concentration was measured at the probe outlet. Tissue 5-HT recovery was dose-dependently inhibited by the concurrent perfusion of citalopram, fluoxetine and paroxetine, showing that it essentially measured uptake through the high-affinity 5-HT transporter. Rats lesioned with 5,7-dihydroxytryptamine (5,7-DHT; 88% reduction of tissue 5-HT) displayed tissue 5-HT recovery slightly higher than sham-operated rats (55 +/- 2 vs. 46 +/- 3%, P < 0.001), a finding perhaps attributable to the astrogliosis induced by 5,7-DHT denervation. Rats lesioned with 6-hydroxydopamine showed tissue 5-HT uptake similar to controls, suggesting negligible reuptake of 5-HT by catecholaminergic terminals. These results are consistent with the presence of a glial component of 5-HT uptake in the rodent brain, sensitive to antidepressants, which takes place through a 5-HT transporter very similar or identical to that present in neurons.
Apoptosis has been known to contribute to neuronal death following a variety of brain insults. However, the role of vasogenic brain edema in neuronal apoptosis is unknown. We studied the temporal pattern of brain edema and neuronal apoptosis following cold injury. Cold injury-induced brain edema, which was detected by the increased water content in the injured hemisphere, reached its maximum level at 24 h and remained there at 72 h, whereas the blood-brain barrier breakdown detected by Evans Blue extravasation returned to the control value by 24 h after injury. Terminal deoxynucleotidyl transferase-mediated uridine-5'-triphosphate-biotin nick end labeling (TUNEL)-positive apoptotic cells were scattered in the center of the lesion at 1 h and were dispersed over the cold lesion at 24 h. The number of these TUNEL-positive cells was maximized in the periphery but decreased in the center at 72 h after cold injury. We postulate that secondary neuronal damage occurred not only through necrotic, but also apoptotic pathways, and that apoptotic neuronal death may result from vasogenic edema development and may contribute to the expansion of the lesion in both the acute and delayed phases after cold injury.
The major classes of glial cells, namely astrocytes, oligodendrocytes, and microglial cells were compared in parallel for their susceptibility to damage after combined hypoxia and hypoglycemia or hypoxia alone. The three glial cell types were isolated from neonatal rat brains, separated, and incubated in N2/CO2-gassed buffer-containing glucose or glucose substitutes, 2-deoxyglucose or mannitol (both nonmetabolizable sugars). The damage to the cells after 6 hours' exposure was determined at 0, 1, 3, 7 days based on release of lactate dehydrogenase and counting of ethidium bromide-stained dead cells, double-stained with cell-type specific markers. When 2-deoxyglucose replaced glucose during 6 hours of hypoxia, both oligodendrocytes and microglia rarely survived (18% and 12%, respectively). Astroglia initially increased the release of lactate dehydrogenase but maintained 98% to 99% viability. When mannitol, a radical scavenger and osmolarity stabilizer, replaced glucose during 6 hours of hypoxia, oligodendrocytes rarely survived (10%), astroglia survival remained at 99%, but microglia survival increased to 50%. After exposure to 6 and 42 hours, respectively, of hypoxic conditions alone, oligodendrocytes exhibited 10% survival whereas microglia and astroglia were only temporarily stressed and subsequently survived. In conclusion, oligodendrocytes, then microglia, are the most vulnerable glial cell types in response to hypoxia or hypoglycemia conditions, whereas astrocytes from the same preparations recover.
Cultured astrocytes derived from neonatal rat brain exhibited high affinity, Na+-dependent, paroxetine and fluoxetine sensitive [3H]5-HT uptake. Reverse transcriptase-PCR demonstrated that astrocytes in culture expressed messenger RNA for the cloned serotonin transporter protein which has been characterised as the neuronal serotonin transporter. Although the serotonin transporter in cultured astrocytes displayed a Km value approximately 10 times greater than found in adult brain synaptosomes, these observations indicated that astrocytes in vitro may express the same serotonin transporter as neurons. Reverse transcriptase-PCR demonstrated the presence of serotonin transporter mRNA in the adult rat cerebral cortex, suggesting that astrocytes in vivo may express low levels of this mRNA. To investigate whether astrocytes in the adult CNS express functional serotonin transporters, glial plasmalemmal vesicles were prepared from cerebral cortex, representing a subcellular fraction composed primarily of vesicles derived from astrocytes. These vesicles were characterised by [3H]-glutamate and [3H]-dopamine uptake and by immunoblot analysis, using glial and synaptic markers: glutamate synthase, SNAP-25 and synaptobrevin. [3H]5-HT was taken up into glial plasmalemmal vesicles in a high affinity (Km approximately 40 nM), Na+ dependent, paroxetine-sensitive manner. The [3H]5-HT uptake capacity (Vmax) in these vesicles was approximately one quarter of that observed in synaptosomes. These data indicate that astrocytes in culture and in vivo are capable of 5-HT uptake via the previously characterised 'neuronal' serotonin transporter.
The frequent association of an active viral infection with the symptoms of CFS led researchers to hypothesize that chronic fatigue syndrome (CFS) is induced by a virus. Results of these studies indicated that despite clinical support for this hypothesis, there were no clear data linking viruses to CFS. In this overview, we will explore the interrelation of the immune, endocrine, and central nervous systems, and the possibility that stress and/or the reactivation/replication of a latent virus (such as Epstein Barr virus) could modulate the immune system to induce CFS. Relevant research conducted in the developing field of psychoneuroimmunology will be reviewed, with a particular focus on cytokine synthesis, natural killer (NK) cell activity, and T-lymphocyte function, as they relate to CFS.
Chronic fatigue syndrome (CFS) is associated with insidious and persistent immunologic abnormalities that have proved difficult to reproduce. The heterogeneity of CFS, the variable quality of immunologic assays and their performance, along with an almost complete absence of longitudinal studies of cellular immune abnormalities in CFS may explain this difficulty. However, in a significant proportion of cases, low levels of natural killer (NK) cell activity have been reported. This article will explore the mechanisms responsible for low NK cell activity, discuss the relation between levels of NK cell activity and health/disease, describe new findings on NK cell-brain interactions, and put forth a specific hypothesis for the role of NK cells in the pathogenesis of CFS.
There is evidence from recent studies that the brain endothelium (of capillaries and/or larger vessels) may serve as a specific target for serotonin [5-hydroxytryptamine (5-HT)]. This neurotransmitter is expected to be involved in the regulation of the blood-brain barrier (BBB) permeability and/or of the cerebral blood flow via receptor-mediated mechanisms. Effective control of these processes depends on a speedy uptake and metabolism of released 5-HT molecules. To realize this, a similar mechanism of 5-HT uptake as in brain may exist at the BBB. In this study, we have demonstrated using RT-PCR that 5-HT transporter mRNA is present in the brain endothelium and that a saturable transport system for 5-HT is functionally expressed in immortalized rat brain endothelial cells (RBE4 cells). These cells take up [3H]5-HT by an active saturable process with a Km value of 397 +/- 64 nmol/L and a transport capacity of 51.7 +/- 3.5 pmol x g(-1) x min(-1). The 5-HT uptake depends on Na+, as indicated by the replacement of NaCl by LiCl. The 5-HT uptake was sensitive to specific 5-HT transport inhibitors such as paroxetine, clomipramine, fluoxetine, and citalopram but not to inhibitors of the vesicular amine transporter such as reserpine or tetrabenazine. Our results demonstrate that cerebral endothelial cells are able to participate actively in the removal and metabolism of the released 5-HT, which supports the concept of direct serotoninergic regulation of the BBB function.
Glial cells regulate some neural functions which depend on the homeostatic maintenance of extracellular calcium within narrow physiological ranges. In this study, the presence of microglia-specific ionized calcium binding adaptor molecule 1 (Iba1) was examined in the mouse olfactory bulb. A heterogenous pattern of Iba1-positive cells expression was observed between the main and accessory olfactory bulbs (MOB and AOB, respectively). While Iba1 was almost uniformly expressed among the laminae of the MOB, its expression showed spatial variations from the anterior to the posterior regions of the AOB. Double immunofluorescence was used to confirm that Iba1 is not expressed in astrocytes which stained for glial fibrillary acidic protein. Since Iba1 may mediate calcium signals in microglia, the observations suggest a potential involvement of Iba1 and hence microglia in olfactory bulb function and/or homeostasis. Together with our previous observation, this provides further support of a bulbar neuron-glia system of potential physiological significance.
Iba1 is a novel calcium-binding protein and is specifically expressed in microglia in the brain. It has been suggested that Iba1 plays an important role in regulation of the function of microglia. In the present study we examined time-dependent Iba1 expression after transient middle cerebral artery occlusion and characterized microglial activation in various brain regions.
Rat middle cerebral artery occlusion was induced by the intraluminal filament technique. After 1.5 hours of transient ischemia, Iba1 expression was examined by immunohistochemical and immunoblot analyses. The microglial activation in association with ischemic severity was characterized by double immunostaining with other specific markers.
In the peri-ischemic area, heavily Iba1 immunoreactive cells rapidly appeared at 3.5 hours after reperfusion. Immunoreactivity was further increased and peaked at 7 days. In the ischemic core, round Iba1-positive cells, which may be blood-borne monocytes, appeared from 24 hours and reached a peak at 4 to 7 days. Double immunostaining revealed that activated microglia in the peri-ischemic area upregulated Iba1 expression but were negative for the macrophage marker ED1. ED1-positive cells were clearly restricted to the ischemic core.
These findings suggest the following: (1) Iba1 expression may be associated with microglial activation in ischemic brain, and Iba1 immunostaining can be useful to evaluate the pathophysiological roles of activated microglia in ischemic injury. (2) Expression of ED1 antigen is strictly restricted to severe ischemic damage, whereas activated microglia in the peri-ischemic area showed Iba1 upregulation without ED1. Therefore, microglia may exhibit difference of antigenicity in the severity of ischemic brain injury.
Microglia are resident monocyte-lineaged cells in the brain. Their characteristic feature is that they react to injury and
diseases of the brain and become morphologically and functionally activated. Although some trigger molecules which activate
microglia are predicted to be released from injured or affected cells, such molecules have not yet been identified. The main
role of activated microglia is believed to be in brain defense, as scavengers of dead cells, and as immune or immunoeffector
cells. Recent biochemical and neurobiological studies have further indicated that they significantly affect the pathological
state and/or regulate the regenerative state and remodeling of the brain by producing a variety of biologically active molecules
including cytotoxic and neuro-trophic molecules.
Microglia are reactively activated by various environmental stimulations caused by brain injury or disease. Activated microglia exhibit morphological transformation, proliferation, migration, phagocytosis, and the production of bioactive molecules. Various molecules are reported and suggested to activate microglia. Among them, macrophage-colony-stimulating factor (M-CSF) is considered one of the most convincing candidates responsible for maintaining activation properties of microglia. Therefore, the focus of the present study is on intracellular molecular events that arise downstream of M-CSF stimulation. M-CSF activates its receptor, Fms tyrosine kinase, and Fms sequentially activates a number of signaling molecules, including PI3K or phospholipase Cgamma (PLCgamma). Stimulation of continuing signaling cascades results in the activation of a small GTPase, Rac, the key molecule in microglia activation. Rac is known to be activated downstream of receptor tyrosine kinases and to regulate reorganization of the actin cytoskeleton, which profoundly underlies the above-mentioned properties of activated microglia. Iba1, a macrophage/microglia-specific calcium-binding protein, was identified by our group and was shown to be involved in the Rac signaling pathway. Further, we introduce a novel signaling pathway in which Rac is activated, dependent on PLCgamma and Iba1. However, to understand the molecular details of microglia activation, future work is required.
Fatigue is an indispensable sense for ordering rest. However, the neuronal and molecular mechanisms of fatigue remain unclear. Chronic fatigue syndrome (CFS) with long-lasting fatigue sensation seems to be a good model for studying these mechanisms underlying fatigue sensation. Recently, we found that most patients with CFS showed a low level of serum acetylcarnitine, which well correlated with the rating score of fatigue, and that a considerable amount of acetyl moiety of serum acetylcarnitine is taken up into the brain. Here we show by metabolite analysis of the mouse brain that an acetyl moiety taken up into the brain through acetylcarnitine is mainly utilized for the biosynthesis of glutamate. When we studied the cerebral uptake of acetylcarnitine by using [2-(11)C]acetyl-L-carnitine in 8 patients with CFS and in 8 normal age- and sex-matched controls, a significant decrease was found in several regions of the brains of the patient group, namely, in the prefrontal (Brodmann's area 9/46d) and temporal (BA21 and 41) cortices, anterior cingulate (BA24 and 33), and cerebellum. These findings suggest that the levels of biosynthesis of neurotransmitters through acetylcarnitine might be reduced in some brain regions of chronic fatigue patients and that this abnormality might be one of the keys to unveiling the mechanisms of the chronic fatigue sensation.
Chronic fatigue syndrome is an illness characterized by disabling fatigue of at least 6 months, accompanied by several other symptoms. This review summarizes the current state of knowledge about chronic fatigue syndrome.
The case definition, prevalence, clinical presentation, evaluation, and prognosis of chronic fatigue syndrome are discussed. Research on the pathophysiology and treatment of chronic fatigue syndrome is reviewed.
Chronic fatigue syndrome is diagnosed on the basis of symptoms. Patients with chronic fatigue syndrome experience significant functional impairment. Pathophysiological abnormalities exist across many domains, suggesting that chronic fatigue syndrome is a heterogeneous condition of complex and multifactorial etiology. Evidence also is beginning to emerge that chronic fatigue syndrome may be familial. Although chronic fatigue syndrome has significant symptom overlap and comorbidity with psychiatric disorders, several lines of research suggest that the illness may be distinct from psychiatric disorders. Patients' perceptions, attributions, and coping skills, however, may help perpetuate the illness. Treatment for chronic fatigue syndrome is symptom-based and includes pharmacological and behavioral strategies. Cognitive behavior therapy and graded exercise can be effective in treating the fatigue and associated symptoms and disability.
Chronic fatigue syndrome is unlikely to be caused or maintained by a single agent. Findings to date suggest that physiological and psychological factors work together to predispose an individual to the illness and to precipitate and perpetuate the illness. The assessment and treatment of chronic fatigue syndrome should be multidimensional and tailored to the needs of the individual patient.
Following 2 weeks acclimation to the running wheel in the home cages, an i.p. injection of a synthetic double-stranded RNA, polyriboinosinic:polyribocytidylic acid (poly I:C, 3 mg/kg), was performed to produce the immunologically induced fatigue in rats. The daily amounts of spontaneous running wheel activity decreased to about 40-60% of the preinjection level until day 9 with normal circadian rhythm, then gradually returned to the baseline level by day 14. Rats given a heat exposure (36 degrees C for 1 h) for the consecutive 3 days showed an increase in activity except for the first day. In the open field test, the total moving distance and the number of rearing of the poly I:C-injected rats decreased on day 1, but they were not different from the saline-injected group on day 7, suggesting that the poly I:C-induced fatigue on day 7 was not due to the peripheral problems such as muscle/joint pain, but involved the CNS. Quantitative analysis of mRNA levels using a real-time capillary reverse transcriptase-polymerase chain reaction (RT-PCR) method revealed that interferon-alpha (IFN-alpha) mRNA contents in the cortex, hippocampus, hypothalamic medial preoptic, paraventricular, and ventromedial nuclei were higher in the poly I:C group than those in the saline and heat-exposed groups on day 7, although the amount of interleukin-1 beta mRNA showed no differences. Serum adrenocorticotropic hormone and catecholamine levels were not significantly different between groups. The present results indicate that the prolonged fatigue induced by poly I:C, which is evaluated by the spontaneous running wheel activity, can be used as an animal model for the immunologically induced fatigue associated with viral infection, and suggest that brain IFN-alpha may play a role in this model.
The tetracycline class of antimicrobials exhibit a broad-spectrum of activity against numerous pathogens, including Gram-positive and Gram-negative bacteria, as well as atypical organisms. These compounds are bacteriostatic, and act by binding to the bacterial 30S ribosomal subunit and inhibiting protein synthesis. The tetracyclines have been used successfully for the treatment of a variety of infectious diseases including community-acquired respiratory tract infections and sexually transmitted diseases, as well in the management of acne. The use of tetracyclines for treating bacterial infections has been limited in recent years because of the emergence of resistant organisms with efflux and ribosomal protection mechanisms of resistance. Research to find tetracycline analogues that circumvented these resistance mechanisms has lead to the development of the glycylcyclines. The most developed glycylcycline is the 9-tert-butyl-glycylamido derivative of minocycline, otherwise known as tigecycline (GAR-936). The glycylcyclines exhibit antibacterial activities typical of earlier tetracyclines, but with more potent activity against tetracycline-resistant organisms with efflux and ribosomal protection mechanisms of resistance. The glycylcyclines are active against other resistant pathogens including methicillin-resistant staphylococci, penicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant enterococci. Tigecycline is only available in an injectable formulation for clinical use unlike currently marketed tetracyclines that are available in oral dosage forms. Tigecycline has a significantly larger volume of distribution (> 10 L/kg) than the other tetracyclines (range of 0.14 to 1.6 L/kg). Protein binding is approximately 68%. Presently no human data are available describing the tissue penetration of tigecycline, although studies in rats using radiolabelled tigecycline demonstrated good penetration into tissues. Tigecycline has a half-life of 36 hours in humans, less than 15% of tigecycline is excreted unchanged in the urine. On the basis of available data, it does not appear that the pharmacokinetics of tigecycline are markedly influenced by patient gender or age. The pharmacodynamic parameter that best correlates with bacteriological eradication is time above minimum inhibitory concentration. Several animal studies have been published describing the efficacy of tigecycline. Human phase 1 and 2 clinical trials have been completed for tigecycline. Phase 2 studies have been conducted in patients with complicated skin and skin structure infections, and in patients with complicated intra-abdominal infections have been published as abstracts. Both studies concluded that tigecycline was efficacious and well tolerated. Few human data are available regarding the adverse effects or drug interactions resulting from tigecycline therapy; however, preliminary data report that tigecycline can be safely used, is well tolerated and that the adverse effects experienced were typical of the tetracyclines (i.e. nausea, vomiting and headache). Tigecycline appears to be a promising new antibacterial based on in vitro and pharmacokinetic/pharmacodynamic activity; however more clinical data are needed to fully evaluate its potential.
Effects of repeated intraperitoneal injections of polyinosine-polycytidylic acid on spinal cord cells were analysed. After each injection, the number of ED-1 microglia significantly increased in rat spinal cords. Expression of endothelial monocyte-activating polypeptide II, however, was not observed. The morphology of microglia indicated an incomplete activation state even after three repeated polyinosine-polycytidylic acid injections. Astrocyte activation was observed after the first injection using glial fibrillary acidic protein staining. Simultaneously with glia activation, hyperalgesia was observed, but the expression of P2X4 receptor, which is considered to be closely associated with hyperalgesia, on microglia was not detected. In sum, our data suggest that repeated peripheral injections of polyinosine-polycytidylic acid might alert the central nervous system through limited activation of microglia and astrocytes.
Immunologically induced fatigue was induced in rats by intraperitoneal injection of a synthetic double-stranded RNA, polyriboinosinic : polyribocytidylic acid (poly I:C). An injection of poly I:C (3 mg/kg) decreased the daily amounts of spontaneous running wheel activity to approximately 60% of the preinjection level until day 8. Quantitative analysis of mRNA levels demonstrated that interferon-alpha (IFN-alpha) and p38 mitogen-activated protein kinase mRNAs increased in the medial preoptic, paraventricular and ventromedial hypothalamic nuclei and in cortex on both days 1 and 8, while interleukin-1beta and an inhibitor of nuclear factor kappaB (IkappaB)-beta mRNAs increased on day 1, but recovered within a week. Serotonin transporter (5-HTT) mRNA also increased on days 1 and 8 after poly I:C injection in the same brain regions where IFN-alpha mRNA increased. The increased 5-HTT had a functional significance, because in vivo brain microdialysis revealed that an i.p. injection of poly I:C induced a decrease in the extracellular concentration of 5-HT in the prefrontal cortex; the decrease was blocked by local perfusion with a nonselective 5-HT reuptake inhibitor, imipramine. Finally, the poly I:C-induced fatigue was attenuated by a 5-HT1A receptor agonist but not by 5-HT2, 5-HT3 or dopamine D3 agonists. These findings, taken together, suggest that disorders in brain IFN-alpha and 5-HTT expression may be involved in the neuronal mechanisms of the poly I:C-induced fatigue.
The noradrenergic system plays an integral role in the stress response and modulates expression of proinflammatory cytokines. Recent work from our laboratory and others has shown that certain stressors increase the expression of the proinflammatory cytokine interleukin-1beta (IL-1beta) in the hypothalamus and spleen. One goal of the following studies was to assess the role of norepinephrine in stress-elicited increases in IL-1beta. To do this, adult male Sprague-Dawley rats were injected with propranolol (20 mg/kg i.p.) or desipramine (20 mg/kg s.c.) and exposed to 80 inescapable footshocks (2.0 mA, 90 s variable ITI, 5 s each). We found that propranolol blocked the IL-1beta response to footshock in both the hypothalamus and the spleen, while the noradrenergic reuptake inhibitor desipramine significantly augmented the footshock-induced IL-1beta response in both of these sites. Our second goal was to determine whether these effects would also be blocked by administration of a putative microglial inhibitor (minocycline). Minocycline (40 mg/kg i.p.) completely reversed the footshock-induced increase in hypothalamic IL-1beta but had no effect on the IL-1beta response in the spleen. Moreover, lack of an effect of minocycline on conditioned fear responding suggests that the effect of this drug cannot be explained by nonspecific sedative properties produced by the drug. Together, these data suggest that NE powerfully modulates the hypothalamic and splenic IL-1beta response to stress, and that microglia may be a primary cellular source of central IL-1beta in response to footshock.
Microglia, the intrinsic macrophages of the central nervous system, have previously been shown to be activated in the spinal cord in several rat mononeuropathy models. Activation of microglia and subsequent release of proinflammatory cytokines are known to play a role in inducing a behavioral hypersensitive state (hyperalgesia and allodynia) in these animals. The present study was undertaken to determine whether minocycline, an inhibitor of microglial activation, could attenuate both the development and existing mechanical allodynia and hyperalgesia in an L5 spinal nerve transection model of neuropathic pain. In a preventive paradigm (to study the effect on the development of hypersensitive behaviors), minocycline (10, 20, or 40 mg/kg intraperitoneally) was administered daily, beginning 1 h before nerve transection. This regimen produced a decrease in mechanical hyperalgesia and allodynia, with a maximum inhibitory effect observed at the dose of 20 and 40 mg/kg. The attenuation of the development of hyperalgesia and allodynia by minocycline was associated with an inhibitory action on microglial activation and suppression of proinflammatory cytokines at the L5 lumbar spinal cord of the nerveinjured animals. The effect of minocycline on existing allodynia was examined after its intraperitoneal administration initiated on day 5 post-L5 nerve transection. Although the postinjury administration of minocycline significantly inhibited microglial activation in neuropathic rats, it failed to attenuate existing hyperalgesia and allodynia. These data demonstrate that inhibition of microglial activation attenuated the development of behavioral hypersensitivity in a rat model of neuropathic pain but had no effect on the treatment of existing mechanical allodynia and hyperalgesia.