Acetaminophen alters endogenous lipid signaling and attenuates pathological pain through a mechanism requiring diacylglycerol lipase, monoacylglycerol lipase and cannabinoid CB1 receptors in mice.

Acetaminophen (APAP) produces analgesia through mechanisms that remain poorly understood. Here, we tested the hypothesis that APAP-induced suppression of pathological pain is associated with cannabinoid receptors and activity of enzymes (diacylglycerol lipase, DAGL; monoacylglycerol lipase, MAGL) regulating endogenous lipids, including endocannabinoids. APAP suppressed mechanical hypersensitivity in mouse models of post-surgical and inflammatory pain and the DAGL inhibitors (RHC-80267, DO34) and MAGL inhibitor JZL184 blocked APAP's analgesic effects. Global (rimonabant, AM251) but not peripherally restricted (AM6545) cannabinoid receptor antagonists prevented APAP-induced analgesia. APAP increased corticosterone levels >2-fold and reduced prostaglandins >5-fold across the brain and in the paw skin. In addition, APAP reduced up to 39% of signaling lipids detected in the targeted screen in CFA-treated subjects in a tissue-dependent manner. By contrast, the putative APAP metabolite and endocannabinoid transport inhibitor AM404 was not detected. These observations suggest that APAP plays a wider role in endogenous lipid signaling than previously hypothesized and provides novel insight into mechanisms of action.