Background and purpose: Interleukin-36 is induced by proinflammatory cytokines and promotes inflammatory responses, creating an IL-36-based inflammation loop. Although hepatocytes, produce IL-36 responses to drug-induced liver injury, little is known about the mechanistic role of IL-36 signalling during the progression of alcoholic steatohepatitis (ASH). Regarding IL-36/IL-36R and P2X7R coregulating the inflammatory response, we elucidated that modulation of IL-36R-P2X7R-TLR axis affected hepatocyte steatosis as well as the IL-36-based inflammatory feedback loop that accompanies the onset of ASH.
Experimental approach: C57BL/6J mice were subjected to either chronic-plus-binge ethanol feeding or acute gavage with multiple doses of ethanol to establish ASH, followed by pharmacological inhibition or genetic silencing of IL-36R and P2X7R. AML12 cells or mouse primary hepatocytes were stimulated with alcohol, LPS plus ATP or Poly(I:C) plus ATP, followed by silencing of IL-36γ, IL-36R or P2X7R.
Key results: P2X7R and IL-36R deficiency blocked the inflammatory loop, specifically initiated by IL-36 cytokines, in hepatocytes of mice suffering from ASH. Pharmacological inhibition to P2X7R or IL-36R alleviated lipid accumulation and inflammatory response in ASH. IL-36R was indispensable for P2X7R modulated NLRP3 inflammasome activation in ASH, and IL-36 led to a vicious cycle of P2X7R-driven inflammation in alcohol-treated hepatocytes. TLR ligands promoted IL-36γ production in hepatocytes, based on synergism with P2X7R.
Conclusions and implications: Blockade of IL-36 based inflammatory feedback loop, via IL-36R-P2X7R-TLRs-modulated NLRP3 inflammasome activation, circumvented steatosis and inflammation that accompanies the onset of ASH, suggesting that targeting IL-36 can serve as a novel therapeutic approach to combat ASH.
Keywords: HMGB1; IL-36R; P2X7R; TLR; alcoholic steatohepatitis; hepatocyte.
© 2022 British Pharmacological Society.