Modulation of IL-36-based inflammatory feedback loop through hepatocytes-derived IL-36R-P2X7R axis improves steatosis in alcoholic steatohepatitis

BACKGROUND AND PURPOSE

IL-36 is induced by proinflammatory cytokines and itself promotes inflammatory responses, shaping an IL-36-based inflammation loop. Although, hepatocytes, as "epithelial cell-like" hepatic parenchymal cells, produce IL-36 responses to drug-induced liver injury, little is known about the mechanistic role of the IL-36 signalling during the progression of alcoholic steatohepatitis (ASH). Regarding IL-36/IL-36R and P2X7R coregulates the inflammatory response, we elucidated the modulation of IL-36R-P2X7R-TLRs axis affected hepatocytes steatosis and IL-36-based inflammatory feedback loop that accompanies the onset of ASH.

EXPERIMENTAL APPROACH

C57BL/6J mice were subjected to 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, especially made 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-exposed hepatocytes. TLR ligands promoted IL-36γ production in hepatocytes based on the synergism of P2X7R.

CONCLUSIONS AND IMPLICATIONS

Blockade of IL-36-based inflammatory feedback loop via IL-36R-P2X7R-TLRs-modulated NLRP3 inflammasome activation circumvented the steatosis and inflammation that accompanies the onset of ASH, suggesting that targeting IL-36 might serve as a novel therapeutic approach to combat ASH.

Inhibition of HMGB1/TLR4 Signaling Pathway by Digitoflavone: A Potential Therapeutic Role in Alcohol-Associated Liver Disease

Digitoflavone (DG) is a natural flavonoid abundant in many fruits, vegetables, and medicinal plants. We investigated whether DG inhibits lipid accumulation and inflammatory responses in alcoholic liver disease (ALD) in vivo and in vitro. The mouse ALD model was established by chronically feeding male C57BL/6 mice an ethanol-containing Lieber-DeCarli liquid diet. In vitro, mouse peritoneal macrophages (MPMs) and mouse bone marrow-derived macrophages (BMDMs) were stimulated with LPS/ATP, whereas HepG2 cells and mouse primary hepatocytes were treated with ethanol. DG reduced the serum levels of transaminase and serum and hepatic levels of triglycerides and malondialdehyde in ALD mice. DG downregulated SREBP1 and its target genes and upregulated PPARα and its target genes in the liver of mice with ALD. DG inhibited TLR4-mediated NLRP3 inflammasome activation, consequently reversing the inflammatory response, including the production of HMGB1, IL-1β, and IL-36γ, as well as the infiltration of macrophages and neutrophils. DG blocked NLRP3/ASC/caspase-1 inflammasome activation and HMGB1 release in LPS/ATP-stimulated MPMs. When Tlr4 was knocked in LPS/ATP-stimulated BMDMs, HMGB1 production and release were blocked, and NLRP3-mediated cleavage and release of IL-1β was suppressed in Hmgb1-silenced BMDMs. DG amplified these inhibitory effects in Tlr4 or Hmgb1 knockdown BMDMs. In ethanol-exposed hepatocytes, DG reduced lipogenesis and promoted lipid oxidation by inhibiting the HMGB1-TLR4 signaling pathway while suppressing the inflammatory response induced by ethanol exposure. Our data demonstrated that DG inhibited the occurrence of lipid accumulation and the inflammatory response via the HMGB1-TLR4 axis, underscoring a promising approach and utility of DG for the treatment of ALD.

Comparison of high-speed counter-current chromatography instruments for the separation of the extracts of the seeds of Oroxylum indicum

Analytical Milli high-speed counter-current chromatography (HSCCC) was used for the selection and optimization of the two-phase solvent system to separate flavonoids from the extracts of the seeds of Oroxylum indicum. The optimum solvent system obtained from Milli-CCC was also the best solvent system for preparative HSCCC and led to the successful separation of two crude flavonoids from the seeds of O. indicum by Lab/Prep (laboratory preparative) HSCCC using different sized coils. Four flavonoids were isolated by preparative HSCCC: baicalein-7-O-diglucoside (25.0 mg, 92% purity), baicalein-7-o-glucoside (50.4 mg; 95% purity), baicalein (75 mg; purity 98%) and chrysin (100 mg; purity 98%).