Evidence that extracellular HSPB1 contributes to inflammation in alcohol-associated hepatitis

Background: Alcohol-associated hepatitis (AH) is the most life-threatening form of alcohol-associated liver disease (ALD). AH is characterized by severe inflammation attributed to increased levels of ethanol, microbes or microbial components, and damage-associated molecular pattern (DAMP) molecules in the liver. HSPB1 [Heat Shock Protein Family B (Small) Member 1; also known as Hsp25/27] is a DAMP released from stressed cells, including hepatocytes. The goal of this study was to define the role of HSPB1 in AH pathophysiology. Methods: Serum HSPB1 was measured in a retrospective study of 184 healthy controls (HCs), heavy alcohol consumers (HA), patients with alcohol-associated cirrhosis (AC), and patients with AH recruited from major hospital centers.HSPB1 was also evaluated in liver tissue from HC and AH patients, existing RNA-seq data from ALD patient liver and monocytes, and livers from mice fed a Lieber–DeCarli diet. Cellular models of hepatocyte and macrophage interactions were used to evaluate the role of HSPB1 in inflammation during AH. Results: Circulating HSPB1 was significantly increased in AH patients, and levels positively correlated with disease-severity scores. HSPB1 was also increased in the livers of patients with severe AH and ethanol-fed mice. In cellular models, ethanol-stressed hepatocytes released HSPB1, which then triggered TNFα-mediated inflammation in macrophages. Anti-HSPB1 antibody prevented TNFα release from macrophages exposed to media conditioned by ethanol-stressed hepatocytes. Conclusions: Our findings support investigation of HSPB1 as both a biomarker and therapeutic target in ALD. Furthermore, this work demonstrates that anti-HSPB1 antibody is a rational approach to targeting HSPB1 with the potential to block inflammation and protect hepatocytes, without inactivating host defense.