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BackgroundSeveral 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.MethodsYoung 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.ResultsThe 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.

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 ␤-amyloid (A␤) is thus important for the development of therapeutic strategies that can thwart A␤ toxicity and preserve cell viability. We have previously reported that lysosomal membrane permeabilization plays a distinct role in the apoptotic pathway initiated by A␤. In the present study, we provide evidence that the endocannabinoid system can stabilize lysosomes against A␤-induced permeabilization and in turn sustain cell survival. We report that endocannabinoids stabilize lysosomes by preventing the A␤-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 A␤ 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. Alzheimer disease (AD)2 is a debilitating illness of the brain defined by the progressive deterioration of cognition and memory as a result of selective neuronal loss in the hippocampus and surrounding areas of the cerebral cortex (1). There is substantial evidence to suggest that at least a subset of neurons in the AD brain die by apoptosis (2). The principal neuropathological hallmark of the disease, ␤-amyloid peptide (A␤), has been shown to induce apoptosis in neuronal cells in vivo and in vitro (3, 4) through a variety of enzymatic pathways that include activation of caspase-3 (5), calpain (6, 7), and lysosomal cathepsins (8, 9).Recently, the lysosomal system has been implicated in AD pathogenesis (9, 10). Neurons of AD patients demonstrate alterations in the lysosomal system, including the cellular pathways that converge on it, namely endocytosis and autophagy (10, 11). Such alterations include an increase in the size and number of endosomes (10, 12), autophagosomes (13) and lysosomes (10) and an increase in the gene expression and synthesis of all classes of lysosomal hydrolases, including cathepsins (14). In addition to their role in the digestion of cellular waste, it has become clear that partial and selective lysosomal membrane permeabilization (LMP), followed by the release of lysosomal enzymes into the cytosol, can induce apoptotic cell death (15). Cathepsins D and L are among the lysosomal proteases that have been implicated in apoptosis by virtue of their ability to activate apoptotic effectors, such as mitochondrial uncoupling and caspases (16).Among the agents that are ca...

The long-acting, highly lipophilic, β2-adrenoceptor agonist clenbuterol may represent a suitable therapeutic agent for the treatment of neuroinflammation as it drives an anti-inflammatory response within the CNS. However, clenbuterol is also known to increase the expression of IL-1β in the brain, a potent neuromodulator that plays a role in provoking sickness related symptoms including anxiety and depression-related behaviours. Here we demonstrate that, compared to the immunological stimulus lipopolysaccharide (LPS, 250μg/kg), clenbuterol (0.5mg/kg) selectively up-regulates expression of the central IL-1 system resulting in a mild stress-like response which is accompanied by a reduction in locomotor activity and food consumption in rats. We provide further evidence that clenbuterol-induced activation of the central IL-1 system occurs in a controlled and selective manner in tandem with its negative regulators IL-1ra and IL-1RII. Furthermore, we demonstrate that peripheral β2-adrenoceptors mediate the suppression of locomotor activity and food consumption induced by clenbuterol and that these effects are not linked to the central induction of IL-1β. Moreover, despite increasing central IL-1β expression, chronic administration of clenbuterol (0.03mg/kg; twice daily for 21days) fails to induce anxiety or depressive-like behaviour in rats in contrast to reports of the ability of exogenously administered IL-1 to induce these symptoms in rodents. Overall, our findings suggest that clenbuterol or other selective β2-adrenoceptor agonists could have the potential to combat neuroinflammatory or neurodegenerative disorders without inducing unwanted symptoms of depression and anxiety.

Neurodegenerative disorders carry a significant social and economic burden, and the effective treatment of such illnesses remains a challenge for neuroscientists and neurologists. Although significant advances have been made on our understanding of the molecular mechanisms underlying neurodegenerative diseases, the translation of this knowledge into effective therapeutic treatments has been limited. There is still a dearth of curative treatments for most neurodegenerative disorders, with symptomatic relief being the principal target for drug action. Endocannabinoids belong to an evolutionary conserved neuro‐signaling system and certain endogenous and exogenous components of this system are emerging as clinically promising neuroprotective agents due to their anti‐oxidative, anti‐excitotoxic, and anti‐inflammatory properties. The cannabinoid system is, therefore, a potential target for several neurodegenerative conditions, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Research on the therapeutic potential of drugs that modulate endogenous cannabinoid tone is intense. Recent evidence implicates the endocannabinoid system as a potential pharmacological target to circumvent neurodegenerative disease pathology. WIREs Membr Transp Signal 2012, 1:633–639. doi: 10.1002/wmts.64 For further resources related to this article, please visit the http://wires.wiley.com/remdoi.cgi?doi=10.1002/wmts.64.