ABHD6 suppression attenuates pro-inflammatory responses in mice and promotes anti-inflammatory polarization of macrophages during endotoxin stress.

α/β-hydrolase domain-containing-6 (ABHD6) hydrolyzes various lipids, including monoacylglycerols (MAGs). Pharmacological inhibition of ABHD6 with WWL70 is anti-inflammatory in animal models. However, because of the multiple substrates of ABHD6 and the off-target effects of WWL70, the precise role of ABHD6 in inflammation remains to be clarified. Here, we investigated the role of ABHD6 in lipopolysaccharide (LPS)-mediated inflammatory response, employing a more specific ABHD6 inhibitor, KT203, and ABHD6-KO mice. ABHD6-KO mice showed lower susceptibility to LPS-mediated systemic endotoxemia. Inhibition by KT203 or deletion of ABHD6 in LPS-stressed macrophages reduced the pro-inflammatory and elevated the anti-inflammatory markers. In RAW 264.7 macrophages, KT203 reduced LPS-induced morphological changes, migration and cytokine release. In vivo, KT203 treatment of LPS-exposed wild-type mice markedly curtailed circulating TNF-α levels. Analysis of cellular and secreted bioactive lipids in the LPS-treated RAW 264.7 macrophages revealed that KT203 markedly elevated the levels of various lipid species, in particular secreted docosahexaenoic acid (DHA)-derived MAG (1/2-docosahexaenoylglycerol (DHG)) and DHA-containing N-acylethanolamines and oxylipins. We further observed that 1-DHG, 2-arachidonoylglycerol, docosahexaenoylethanolamide and 17-hydroxydocosahexaenoic acid showed anti-inflammatory effects and PPARα agonism in LPS-treated RAW 264.7 macrophages. The data suggest that ABHD6 suppression results in the accumulation of various bioactive lipids, in particular DHA-containing MAG, N-acylethanolamines and oxylipins, which activate PPARα signaling pathway to curtail the inflammatory response of macrophages to LPS. Overall, the findings provide evidence for a mechanism involving MAG and possibly other lipid species/PPARα signaling, for the anti-inflammatory effects of ABHD6 suppression during endotoxemia. Thus, the inhibition of ABHD6 is a promising approach to mitigate inflammation.