Pharmacological inhibition of endocannabinoid degradation modulates the expression of inflammatory mediators in the rat hypothalamus following an immunological stressor

The endocannabinoid system is an important regulator of the nervous, neuroendocrine and immune systems, thus representing a novel therapeutic target for stress-related neuroinflammatory and psychiatric disorders. However, there is a paucity of data relating to the effects of endocannabinoids on neuroinflammatory mediators following an immune stress/challenge in vivo. This study investigated the effects of URB597, a selective inhibitor of fatty acid amine hydrolyase (FAAH), the enzyme that preferentially metabolises anandamide, on lipopolysaccharide (LPS)-induced increases in the expression of immune mediators in the hypothalamus. Systemic administration of URB597 increased the levels of anandamide and the related N-acylethanolamines, N-palmitoyl ethanolamide and N-oleoyl ethanolamide, but not 2-arachidonoyl glycerol, in the hypothalamus and spleen. URB597 attenuated the LPS-induced increase in interleukin (IL)-1Beta expression while concurrently augmenting the LPS-induced increase in suppressor of cytokine signalling (SOCS)-3 expression. In addition, URB597 tended to enhance and reduce the LPS-induced increase in IL-6 and IL-10 mRNA expression respectively. LPS-induced increases in peripheral cytokine levels or plasma corticosterone were not altered by URB597. The present study provides evidence for a role for FAAH in the regulation of LPS-induced expression of inflammatory mediators in the hypothalamus. Improved understanding of endocannabinoidmediated regulation of neuroimmune function has fundamental physiological and potential therapeutic significance in the context of stress-related disorders

The endocannabinoid system in the rat dorsolateral periaqueductal grey mediates fear-conditioned analgesia and controls fear expression in the presence of nociceptive tone

BACKGROUND AND PURPOSE Endocannabinoids in the midbrain periaqueductal grey (PAG) modulate nociception and unconditioned stress-induced analgesia; however, their role in fear-conditioned analgesia (FCA) has not been examined. The present study examined the role of the endocannabinoid system in the dorsolateral (dl) PAG in formalin-evoked nociceptive behaviour, conditioned fear and FCA in rats. EXPERIMENTAL APPROACH Rats received intra-dlPAG administration of the CB1 receptor antagonist/inverse agonist rimonabant, or vehicle, before re-exposure to a context paired 24 h previously with foot shock. Formalin-evoked nociceptive behaviour and fear-related behaviours (freezing and 22 kHz ultrasonic vocalization) were assessed. In a separate cohort, levels of endocannabinoids [2-arachidonoyl glycerol (2-AG) and N-arachidonoyl ethanolamide (anandamide; AEA)] and the related N-acylethanolamines (NAEs) [N-palmitoyl ethanolamide (PEA) and N-oleoyl ethanolamide (OEA)] were measured in dlPAG tissue following re-exposure to conditioned context in the presence or absence of formalin-evoked nociceptive tone. KEY RESULTS Re-exposure of rats to the context previously associated with foot shock resulted in FCA. Intra-dlPAG administration of rimonabant significantly attenuated FCA and fear-related behaviours expressed in the presence of nociceptive tone. Conditioned fear without formalin-evoked nociceptive tone was associated with increased levels of 2-AG, AEA, PEA and OEA in the dlPAG. FCA was specifically associated with an increase in AEA levels in the dlPAG. CONCLUSIONS AND IMPLICATIONS Conditioned fear to context mobilises endocannabinoids and NAEs in the dlPAG. These data support a role for endocannabinoids in the dlPAG in mediating the potent suppression of pain responding which occurs during exposure to conditioned aversive contexts

The monoacylglycerol lipase inhibitor jzl184 attenuates lps-induced increases in cytokine expression in the rat frontal cortex and plasma: differential mechanisms of action

Background and purpose JZL184 is a selective inhibitor of monoacylglycerol lipase (MAGL), the enzyme that preferentially catabolizes the endocannabinoid 2-arachidonoyl glycerol (2-AG). Here, we have studied the effects of JZL184 on inflammatory cytokines in the brain and plasma following an acute immune challenge and the underlying receptor and molecular mechanisms involved. Experimental approach JZL184 and/or the CB1 receptor antagonist, AM251 or the CB2receptor antagonist, AM630 were administered to rats 30min before lipopolysaccharide (LPS). 2h later cytokine expression and levels, MAGL activity, 2-AG, arachidonic acid and prostaglandin levels were measured in the frontal cortex, plasma and spleen. Key results JZL184 attenuated LPS-induced increases in IL-1, IL-6, TNF- and IL-10 but not the expression of the inhibitor of NFkB (IB) in rat frontal cortex. AM251 attenuated JZL184-induced decreases in frontal cortical IL-1 expression. Although arachidonic acid levels in the frontal cortex were reduced in JZL184-treated rats, MAGL activity, 2-AG, PGE2 and PGD2 were unchanged. In comparison, MAGL activity was inhibited and 2-AG levels enhanced in the spleen following JZL184. In plasma, LPS-induced increases in TNF- and IL-10 levels were attenuated by JZL184, an effect partially blocked by AM251. In addition, AM630 blocked LPS-induced increases in plasma IL-1 in the presence, but not absence, of JZL184. Conclusion and implications Inhibition of peripheral MAGL in rats by JZL184 suppressed LPS-induced circulating cytokines that in turn may modulate central cytokine expression. The data provide further evidence for the endocannabinoid system as a therapeutic target in treatment of central and peripheral inflammatory disorders. Linked Articles This article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-4 & http://dx.doi.org/10.1111/bph.2012.167.issue-

The endocannabinoid system in the rat dorsolateral periaqueductal grey mediates fear-conditioned analgesia and controls fear expression in the presence of nociceptive tone

BACKGROUND AND PURPOSE Endocannabinoids in the midbrain periaqueductal grey (PAG) modulate nociception and unconditioned stress-induced analgesia; however, their role in fear-conditioned analgesia (FCA) has not been examined. The present study examined the role of the endocannabinoid system in the dorsolateral (dl) PAG in formalin-evoked nociceptive behaviour, conditioned fear and FCA in rats. EXPERIMENTAL APPROACH Rats received intra-dlPAG administration of the CB1 receptor antagonist/inverse agonist rimonabant, or vehicle, before re-exposure to a context paired 24 h previously with foot shock. Formalin-evoked nociceptive behaviour and fear-related behaviours (freezing and 22 kHz ultrasonic vocalization) were assessed. In a separate cohort, levels of endocannabinoids [2-arachidonoyl glycerol (2-AG) and N-arachidonoyl ethanolamide (anandamide; AEA)] and the related N-acylethanolamines (NAEs) [N-palmitoyl ethanolamide (PEA) and N-oleoyl ethanolamide (OEA)] were measured in dlPAG tissue following re-exposure to conditioned context in the presence or absence of formalin-evoked nociceptive tone. KEY RESULTS Re-exposure of rats to the context previously associated with foot shock resulted in FCA. Intra-dlPAG administration of rimonabant significantly attenuated FCA and fear-related behaviours expressed in the presence of nociceptive tone. Conditioned fear without formalin-evoked nociceptive tone was associated with increased levels of 2-AG, AEA, PEA and OEA in the dlPAG. FCA was specifically associated with an increase in AEA levels in the dlPAG. CONCLUSIONS AND IMPLICATIONS Conditioned fear to context mobilises endocannabinoids and NAEs in the dlPAG. These data support a role for endocannabinoids in the dlPAG in mediating the potent suppression of pain responding which occurs during exposure to conditioned aversive contexts

The monoacylglycerol lipase inhibitor jzl184 attenuates lps-induced increases in cytokine expression in the rat frontal cortex and plasma: differential mechanisms of action

Background and purpose JZL184 is a selective inhibitor of monoacylglycerol lipase (MAGL), the enzyme that preferentially catabolizes the endocannabinoid 2-arachidonoyl glycerol (2-AG). Here, we have studied the effects of JZL184 on inflammatory cytokines in the brain and plasma following an acute immune challenge and the underlying receptor and molecular mechanisms involved. Experimental approach JZL184 and/or the CB1 receptor antagonist, AM251 or the CB2receptor antagonist, AM630 were administered to rats 30min before lipopolysaccharide (LPS). 2h later cytokine expression and levels, MAGL activity, 2-AG, arachidonic acid and prostaglandin levels were measured in the frontal cortex, plasma and spleen. Key results JZL184 attenuated LPS-induced increases in IL-1, IL-6, TNF- and IL-10 but not the expression of the inhibitor of NFkB (IB) in rat frontal cortex. AM251 attenuated JZL184-induced decreases in frontal cortical IL-1 expression. Although arachidonic acid levels in the frontal cortex were reduced in JZL184-treated rats, MAGL activity, 2-AG, PGE2 and PGD2 were unchanged. In comparison, MAGL activity was inhibited and 2-AG levels enhanced in the spleen following JZL184. In plasma, LPS-induced increases in TNF- and IL-10 levels were attenuated by JZL184, an effect partially blocked by AM251. In addition, AM630 blocked LPS-induced increases in plasma IL-1 in the presence, but not absence, of JZL184. Conclusion and implications Inhibition of peripheral MAGL in rats by JZL184 suppressed LPS-induced circulating cytokines that in turn may modulate central cytokine expression. The data provide further evidence for the endocannabinoid system as a therapeutic target in treatment of central and peripheral inflammatory disorders. Linked Articles This article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-4 & http://dx.doi.org/10.1111/bph.2012.167.issue-

Pharmacological inhibition of endocannabinoid degradation modulates the expression of inflammatory mediators in the hypothalamus following an immunological stressor

The endocannabinoid system is an important regulator of the nervous, neuroendocrine, and immune systems, thus representing a novel therapeutic target for stress-related neuroinflammatory and psychiatric disorders. However, there is a paucity of data relating to the effects of endocannabinoids on neuroinflammatory mediators following an immune stress/challenge in vivo. This study investigated the effects of URB597, a selective inhibitor of fatty acid amide hydrolyase (FAAH), the enzyme that preferentially metabolizes anandamide, on lipopolysaccharide (LPS)-induced increases in the expression of immune mediators in the hypothalamus. Systemic administration of URB597 increased the levels of anandamide and the related N-acylethanolamines, N-palmitoylethanolamide, and N-oleoylethanolamide, but not 2-arachidonoyl glycerol, in the hypothalamus and spleen. URB597 attenuated the LPS-induced increase in interleukin (IL)-1 expression while concurrently augmenting the LPS-induced increase in suppressor of cytokine signalling (SOCS)-3 expression. In addition, URB597 tended to enhance and reduce the LPS-induced increase in IL-6 and IL-10 mRNA expression, respectively. LPS-induced increases in peripheral cytokine levels or plasma corticosterone were not altered by URB597. The present study provides evidence for a role for FAAH in the regulation of LPS-induced expression of inflammatory mediators in the hypothalamus. Improved understanding of endocannabinoid-mediated regulation of neuroimmune function has fundamental physiological and potential therapeutic significance in the context of stress-related disorders