Cyclooxygenase-2 (COX-2) catalyzes the oxygenation of arachidonic acid and the endocannabinoids, 2-arachidonoylglycerol and arachidonoylethanolamide. Evaluation of a series of COX-2 inhibitors revealed that many weak, competitive inhibitors of arachidonic acid oxygenation are potent inhibitors of endocannabinoid oxygenation. (R)-Enantiomers of ibuprofen, naproxen, and flurbiprofen, which are considered to be inactive as COX-2 inhibitors, are potent “substrate-selective inhibitors” of endocannabinoid oxygenation. Crystal structures of the COX-2-(R)-naproxen and COX-2-(R)-flurbiprofen complexes verified this unexpected binding and defined the orientation of the (R)-enantiomers relative to (S)-enantiomers. (R)-Profens selectively inhibited endocannabinoid oxygenation by lipopolysaccharide-stimulated dorsal root ganglion cells. Substrate-selective inhibition provides novel tools for investigating the role of COX-2 in endocannabinoid oxygenation and a possible explanation for the ability of (R)-profens to maintain endocannabinoid tone in models of neuropathic pain.

Corticotropin-releasing hormone (CRH) is a central integrator in the brain of endocrine and behavioral stress responses, whereas activation of the endocannabinoid CB1 receptor suppresses these responses. Although these systems regulate overlapping functions, few studies have investigated whether these systems interact. Here we demonstrate a novel mechanism of CRH-induced anxiety that relies on modulation of endocannabinoids. Specifically, we found that CRH, through activation of the CRH receptor type 1 (CRHR1), evokes a rapid induction of the enzyme fatty acid amide hydrolase (FAAH), which causes a reduction in the endocannabinoid anandamide (AEA), within the amygdala. Similarly, the ability of acute stress to modulate amygdala FAAH and AEA in both rats and mice is also mediated through CRHR1 activation. This interaction occurs specifically in amygdala pyramidal neurons and represents a novel mechanism of endocannabinoid-CRH interactions in regulating amygdala output. Functionally, we found that CRH signaling in the amygdala promotes an anxious phenotype that is prevented by FAAH inhibition. Together, this work suggests that rapid reductions in amygdala AEA signaling following stress may prime the amygdala and facilitate the generation of downstream stress-linked behaviors. Given that endocannabinoid signaling is thought to exert "tonic" regulation on stress and anxiety responses, these data suggest that CRH signaling coordinates a disruption of tonic AEA activity to promote a state of anxiety, which in turn may represent an endogenous mechanism by which stress enhances anxiety. These data suggest that FAAH inhibitors may represent a novel class of anxiolytics that specifically target stressinduced anxiety.

SUMMARY Endocannabinoid (eCB) signaling has been heavily implicated in the modulation of anxiety, depressive behaviors and emotional learning. However, the role of the most abundant endocannabinoid 2-arachidonoylglycerol (2-AG) in the physiological regulation of affective behaviors is not well understood. Here we show that genetic deletion of the 2-AG synthetic enzyme diacylglycerol lipase α (DAGLα) in mice reduces brain, but not circulating, 2-AG levels. DAGLα deletion also results in anxiety-like and sex-specific anhedonic phenotypes associated with impaired activity-dependent eCB retrograde signaling at amygdala glutamatergic synapses. Importantly, acute pharmacological normalization of 2-AG levels reverses both phenotypes of DAGLα deficient mice. These data suggest 2-AG deficiency could contribute to the pathogenesis of affective disorders and that pharmacological normalization of 2-AG signaling could represent a novel approach for the treatment of mood and anxiety disorders.

Background:The oxicams are anti-inflammatory drugs targeting the cyclooxygenase enzymes. Results: Crystal complexes of mCOX-2⅐isoxicam, mCOX-2⅐meloxicam, and oCOX-1⅐meloxicam are solved. Conclusion: Oxicams bind to the cyclooxygenase active sites in a novel mode. Significance: The first structural description of cyclooxygenase-oxicam complexes reveal a new binding pocket of inhibitors to cyclooxygenases.

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Augmentation of endogenous cannabinoid (eCB) signaling represents an emerging approach to the treatment of affective disorders. Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid to form prostaglandins, but also inactivates eCBs in vitro. However, the viability of COX-2 as a therapeutic target for in vivo eCB augmentation has not been explored. Here we utilized medicinal chemistry and in vivo analytical and behavioral pharmacological approaches to demonstrate a key role for COX-2 in the regulation of endocannabinoid (eCB) levels in vivo. A novel pharmacological strategy involving “substrate-selective” inhibition of COX-2 was used to augment eCB signaling without affecting related non-eCB lipids or prostaglandin synthesis. Behaviorally, substrate-selective inhibition of COX-2reducedanxiety-like behaviors in mice via increasede CB signaling. These data elucidate a key role for COX-2 in the regulation of eCB signaling and suggest substrate-selective pharmacology represents a viable approach for eCB augmentation with broad therapeutic potential.

Summary Phospholipids are important determinants of membrane biophysical properties, but the impact of membrane acyl chain composition on dietary lipid absorption is unknown. Here we demonstrate that the LXR-responsive phospholipid-remodeling enzyme Lpcat3 modulates intestinal fatty acid and cholesterol absorption and is required for survival on a high-fat diet. Mice lacking Lpcat3 in the intestine thrive on carbohydrate-based chow, but lose body weight rapidly and become moribund on a triglyceride-rich diet. Lpcat3-dependent incorporation of polyunsaturated fatty acids into phospholipids is required for the efficient transport of dietary lipids into enterocytes. Furthermore, loss of Lpcat3 amplifies the production of gut hormones including GLP-1 and oleoylethanolamide in response to high-fat feeding, contributing to the paradoxical cessation of food intake in the setting of starvation. These results reveal that membrane phospholipid composition is a gating factor in passive lipid absorption, and implicate LXR-Lpcat3 signaling in a gut-brain feedback loop that couples absorption to food intake.

Stress is a major risk factor for the development of mood and anxiety disorders; elucidation of novel approaches to mitigate the deleterious effects of stress could have broad clinical applications. Pharmacological augmentation of central endogenous cannabinoid (eCB) signaling may be an effective therapeutic strategy to mitigate the adverse behavioral and physiological consequences of stress. Here we show that acute foot-shock stress induces a transient anxiety state measured 24 h later using the light–dark box assay and novelty-induced hypophagia test. Acute pharmacological inhibition of the anandamide-degrading enzyme, fatty acid amide hydrolase (FAAH), reverses the stress-induced anxiety state in a cannabinoid receptor-dependent manner. FAAH inhibition does not significantly affect anxiety-like behaviors in non-stressed mice. Moreover, whole brain anandamide levels are reduced 24 h after acute foot-shock stress and are negatively correlated with anxiety-like behavioral measures in the light–dark box test. These data indicate that central anandamide levels predict acute stress-induced anxiety, and that reversal of stress-induced anandamide deficiency is a key mechanism subserving the therapeutic effects of FAAH inhibition. These studies provide further support that eCB-augmentation is a viable pharmacological strategy for the treatment of stress-related neuropsychiatric disorders.