[Show abstract][Hide abstract] ABSTRACT: Significant loss of bone due to trauma, underlying metabolic disease, or lack of repair due to old age surpasses the body's endogenous bone repair mechanisms. Mesenchymal stem cells (MSCs) are adult stem cells which may represent an ideal cell type for use in cell-based tissue engineered bone regeneration strategies. The body's endocannabinoid system has been identified as a central regulator of bone metabolism. The aim of the study was to elucidate the role of the cannabinoid receptor type 1 in the differentiation and survival of MSCs. We show that the cannabinoid receptor type 1 has a prosurvival function during acute cell stress. Additionally, we show that the phytocannabinoid, Δ(9)-Tetrahydrocannabinol, has a negative impact on MSC survival and osteogenesis. Overall, these results show the potential for the modulation of the cannabinoid system in cell-based tissue engineered bone regeneration strategies whilst highlighting cannabis use as a potential cause for concern in the management of orthopaedic patients.
[Show abstract][Hide abstract] ABSTRACT: Aberrant Notch signaling has recently emerged as a possible mechanism for the altered neurogenesis, cognitive impairment, and learning and memory deficits associated with Alzheimer disease (AD). Recently, targeting the endocannabinoid system in models of AD has emerged as a potential approach to slow the progression of the disease process. Although studies have identified neuroprotective roles for endocannabinoids, there is a paucity of information on modulation of the pro-survival Notch pathway by endocannabinoids. In this study the influence of the endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol, on the Notch-1 pathway and on its endogenous regulators were investigated in an in vitro model of AD. We report that AEA up-regulates Notch-1 signaling in cultured neurons. We also provide evidence that although Aβ(1-42) increases expression of the endogenous inhibitor of Notch-1, numb (Nb), this can be prevented by AEA and 2-arachidonoylglycerol. Interestingly, AEA up-regulated Nct expression, a component of γ-secretase, and this was found to play a crucial role in the enhanced Notch-1 signaling mediated by AEA. The stimulatory effects of AEA on Notch-1 signaling persisted in the presence of Aβ(1-42). AEA was found to induce a preferential processing of Notch-1 over amyloid precursor protein to generate Aβ(1-40). Aging, a natural process of neurodegeneration, was associated with a reduction in Notch-1 signaling in rat cortex and hippocampus, and this was restored with chronic treatment with URB 597. In summary, AEA has the proclivity to enhance Notch-1 signaling in an in vitro model of AD, which may have relevance for restoring neurogenesis and cognition in AD.
Journal of Biological Chemistry 08/2012; 287(41):34709-21. · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Several factors contribute to the deterioration in synaptic plasticity which accompanies age and one of these is neuroinflammation. This is characterized by increased microglial activation associated with increased production of proinflammatory cytokines like interleukin-1β (IL-1β). In aged rats these neuroinflammatory changes are associated with a decreased ability of animals to sustain long-term potentiation (LTP) in the dentate gyrus. Importantly, treatment of aged rats with agents which possess anti-inflammatory properties to decrease microglial activation, improves LTP. It is known that endocannabinoids, such as anandamide (AEA), have anti-inflammatory properties and therefore have the potential to decrease the age-related microglial activation. However, endocannabinoids are extremely labile and are hydrolyzed quickly after production. Here we investigated the possibility that inhibiting the degradation of endocannabinoids with the fatty acid amide hydrolase (FAAH) inhibitor, URB597, could ameliorate age-related increases in microglial activation and the associated decrease in LTP.
Young and aged rats received subcutaneous injections of the FAAH inhibitor URB597 every second day and controls which received subcutaneous injections of 30% DMSO-saline every second day for 28 days. Long-term potentiation was recorded on day 28 and the animals were sacrificed. Brain tissue was analyzed for markers of microglial activation by PCR and for levels of endocannabinoids by liquid chromatography coupled to tandem mass spectrometry.
The data indicate that expression of markers of microglial activation, MHCII, and CD68 mRNA, were increased in the hippocampus of aged, compared with young, rats and that these changes were associated with increased expression of the proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor-α (TNFα) which were attenuated by treatment with URB597. Coupled with these changes, we observed an age-related decrease in LTP in the dentate gyrus which was partially restored in URB597-treated aged rats. The data suggest that enhancement of levels of endocannabinoids in the brain by URB597 has beneficial effects on synaptic function, perhaps by modulating microglial activation.
Journal of Neuroinflammation 04/2012; 9:79. · 4.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The cannabinoid (CB) system is widespread in the central nervous system and is crucial for controlling a range of neurophysiological processes such as pain, appetite, and cognition. The endogenous CB molecules, anandamide, and 2-arachidonoyl glycerol, interact with the G-protein coupled CB receptors, CB(1) and CB(2). These receptors are also targets for the phytocannabinoids isolated from the cannabis plant and synthetic CB receptor ligands. The CB system is emerging as a key regulator of neuronal cell fate and is capable of conferring neuroprotection by the direct engagement of prosurvival pathways and the control of neurogenesis. Many neurological conditions feature a neurodegenerative component that is associated with excitotoxicity, oxidative stress, and neuroinflammation, and certain CB molecules have been demonstrated to inhibit these events to halt the progression of neurodegeneration. Such properties are attractive in the development of new strategies to treat neurodegenerative conditions of diverse etiology, such as Alzheimer's disease, multiple sclerosis, and cerebral ischemia. This article will discuss the experimental and clinical evidence supporting a potential role for CB-based therapies in the treatment of certain neurological diseases that feature a neurodegenerative component.
[Show abstract][Hide abstract] ABSTRACT: Neuronal cell loss underlies the pathological decline in cognition and memory associated with Alzheimer disease (AD). Recently, targeting the endocannabinoid system in AD has emerged as a promising new approach to treatment. Studies have identified neuroprotective roles for endocannabinoids against key pathological events in the AD brain, including cell death by apoptosis. Elucidation of the apoptotic pathway evoked by β-amyloid (Aβ) is thus important for the development of therapeutic strategies that can thwart Aβ toxicity and preserve cell viability. We have previously reported that lysosomal membrane permeabilization plays a distinct role in the apoptotic pathway initiated by Aβ. In the present study, we provide evidence that the endocannabinoid system can stabilize lysosomes against Aβ-induced permeabilization and in turn sustain cell survival. We report that endocannabinoids stabilize lysosomes by preventing the Aβ-induced up-regulation of the tumor suppressor protein, p53, and its interaction with the lysosomal membrane. We also provide evidence that intracellular cannabinoid type 1 receptors play a role in stabilizing lysosomes against Aβ toxicity and thus highlight the functionality of these receptors. Given the deleterious effect of lysosomal membrane permeabilization on cell viability, stabilization of lysosomes with endocannabinoids may represent a novel mechanism by which these lipid modulators confer neuroprotection.
Journal of Biological Chemistry 10/2010; 285(49):38543-54. · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The phytocannabinoid Delta(9)-Tetrahydrocannabinol (Delta(9)-THC), the main psychoactive cannabinoid in cannabis, activates a number of signalling cascades including p53. This study examines the role of Delta(9)-THC in regulating the p53 post-translational modifier proteins, Murine double minute (Mdm2) and Small Ubquitin-like MOdifier protein 1 (SUMO-1) in cortical neurons. Delta(9)-THC increased both Mdm2 and SUMO-1 protein expression and induced the deSUMOylation of p53 in a cannabinoid receptor type 1 (CB(1))-receptor dependent manner. We demonstrate that Delta(9)-THC decreased the SUMOylation of the CB(1) receptor. The data reveal a novel role for cannabinoid receptor activation in modulating the SUMO regulatory system.
[Show abstract][Hide abstract] ABSTRACT: Beta-amyloid accumulates around neurons in Alzheimer's disease and is thought to contribute to the neurodegenerative process. This study examined the role of the tumour suppressor protein, p53, in the neurodegenerative pathway, with focus on the interaction of p53 with the lysosomal system. beta-Amyloid increased expression of p53 and its transcription target, Bax, in cultured cortical neurons. In addition, A beta increased the association of phospho-p53(ser15) with the lysosomal compartment and this correlated with destabilization of the lysosomal membrane and a concomitant increase in cytosolic cathepsin-L activity. These effects of beta-amyloid were abolished by the p53 inhibitor, pifithrin-alpha, and siRNA-mediated knockdown of p53, demonstrating that p53 is a critical regulator of lysosomal integrity and the induction of cathepsin-L protease activity. In addition, activation of the apoptotic cascade was abolished by pifithrin-alpha. We conclude that p53 associates with the lysosome to regulate a lysosomal branch of the apoptotic cascade which contributes to beta-amyloid-mediated neurodegeneration.
Neurobiology of aging 01/2009; 31(10):1774-86. · 5.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The psychoactive ingredient of marijuana, Delta9-tetrahydrocannabinol (Delta9-THC), can evoke apoptosis in cultured cortical neurones. Whilst the intracellular mechanisms responsible for this apoptotic pathway remain to be fully elucidated, we have recently identified a role for the CB1 type of cannabinoid (CB) receptor and the tumour suppressor protein, p53. In the current study, we demonstrate the Delta9-THC promotes a significant increase in lysosomal permeability in a dose- and time-dependent manner. The increase in lysosomal permeability was blocked by the CB1 receptor antagonist, AM251. Delta9-THC increased the localization of phospho-p53Ser15 at the lysosome and stimulated the release of the lysosomal cathepsin enzyme, cathepsin-D, into the cytosol. The p53 inhibitor, pifithrin-alpha and small interfering RNA-mediated knockdown of p53 prevented the Delta9-THC-mediated increase in lysosomal permeability. Furthermore, the Delta9-THC -mediated induction of apoptosis was abrogated by a cell-permeable cathepsin-D inhibitor (10 microM). Thus, the study demonstrates that Delta9-THC impacts on the lysosomal system, via p53, to evoke lysosomal instability as an early event in the apoptotic cascade. This provides evidence for a novel link between the CB1 receptor and the lysosomal branch of the apoptotic pathway which is crucial in regulating neuronal viability following exposure to Delta9-THC.
Journal of Neurochemistry 06/2008; 105(4):1513-24. · 3.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alzheimer's disease is an age-related neurodegenerative condition associated with cognitive decline. The pathological hallmarks of the disease are the deposition of beta-amyloid protein and hyperphosphorylation of tau, which evoke neuronal cell death and impair inter-neuronal communication. The disease is also associated with neuroinflammation, excitotoxicity and oxidative stress. In recent years the proclivity of cannabinoids to exert a neuroprotective influence has received substantial interest as a means to mitigate the symptoms of neurodegenerative conditions. In brains obtained from Alzheimer's patients alterations in components of the cannabinoid system have been reported, suggesting that the cannabinoid system either contributes to, or is altered by, the pathophysiology of the disease. Certain cannabinoids can protect neurons from the deleterious effects of beta-amyloid and are capable of reducing tau phosphorylation. The propensity of cannabinoids to reduce beta-amyloid-evoked oxidative stress and neurodegeneration, whilst stimulating neurotrophin expression neurogenesis, are interesting properties that may be beneficial in the treatment of Alzheimer's disease. Delta 9-tetrahydrocannabinol can also inhibit acetylcholinesterase activity and limit amyloidogenesis which may improve cholinergic transmission and delay disease progression. Targeting cannabinoid receptors on microglia may reduce the neuroinflammation that is a feature of Alzheimer's disease, without causing psychoactive effects. Thus, cannabinoids offer a multi-faceted approach for the treatment of Alzheimer's disease by providing neuroprotection and reducing neuroinflammation, whilst simultaneously supporting the brain's intrinsic repair mechanisms by augmenting neurotrophin expression and enhancing neurogenesis. The evidence supporting a potential role for the cannabinoid system as a therapeutic target for the treatment of Alzheimer's disease will be reviewed herewith.
British Journal of Pharmacology 12/2007; 152(5):655-62. · 5.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The maternal use of cannabis during pregnancy results in a number of cognitive deficits in the offspring that persist into adulthood. The endocannabinoid system has a role to play in neurodevelopmental processes such as neurogenesis, migration and synaptogenesis. However, exposure to phytocannabinoids, such as Delta(9)-tetrahydrocannabinol, during gestation may interfere with these events to cause abnormal patterns of neuronal wiring and subsequent cognitive impairments. Aberrant cell death evoked by Delta(9)-tetrahydrocannabinol may also contribute to cognitive deficits and in cultured neurones Delta(9)-tetrahydrocannabinol induces apoptosis via the CB(1) cannabinoid receptor. In this study we report that Delta(9)-tetrahydrocannabinol (5-50 microM) activates the stress-activated protein kinase, c-jun N-terminal kinase, and the pro-apoptotic protease, caspase-3, in in vitro cerebral cortical slices obtained from the neonatal rat brain. The proclivity of Delta(9)-tetrahydrocannabinol to impact on these pro-apoptotic signalling molecules was not observed in in vitro cortical slices obtained from the adult rat brain. In vivo, subcutaneous administration of Delta(9)-tetrahydrocannabinol (1-30 mg/kg) activated c-jun N-terminal kinase, caspase-3 and cathepsin-D, and induced DNA fragmentation in the cerebral cortex of neonatal rats. In contrast, in vivo administration of Delta(9)-tetrahydrocannabinol to adult rats was not associated with the apoptotic pathway in the cerebral cortex. The data provide evidence which supports the hypothesis that the neonatal rat brain is more vulnerable to the neurotoxic influence of Delta(9)-tetrahydrocannabinol, suggesting that the cognitive deficits that are observed in humans exposed to marijuana during gestation may be due, in part, to abnormal engagement of the apoptotic cascade during brain development.
Brain Research 11/2007; 1175:39-47. · 2.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cannabis is the most commonly used illegal drug of abuse in Western society. Delta(9)-tetrahydrocannabinol, the psychoactive ingredient of marijuana, regulates a variety of neuronal processes including neurotransmitter release and synaptic transmission. An increasing body of evidence suggests that cannabinoids play a key role in the regulation of neuronal viability. In cortical neurons tetrahydrocannabinol has a neurodegenerative effect, the mechanisms of which are poorly understood, but involve the cannabinoid receptor subtype, CB(1). In this study we report that tetrahydrocannabinol (5 muM) evokes a rapid phosphorylation, and thus activation, of the tumour suppressor protein, p53, in a manner involving the cannabinoid CB(1) receptor, and the stress-activated protein kinase, c-jun N-terminal kinase, in cultured cortical neurons. Tetrahydrocannabinol increased expression of the p53-transcriptional target, Bax and promoted Bcl phosphorylation. These events were abolished by the p53 inhibitor, pifithrin-alpha (100 nM). The tetrahydrocannabinol-induced activation of the pro-apoptotic cysteine protease, caspase-3, and DNA fragmentation was also blocked by pifithrin-alpha. A siRNA knockdown of p53 further verified the role of p53 in tetrahydrocannabinol-induced apoptosis. This study demonstrates a novel cannabinoid signalling pathway involving p53 that culminates in neuronal apoptosis.
European Journal of Pharmacology 07/2007; 564(1-3):57-65. · 2.59 Impact Factor