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

Background and aimsAlcohol-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 that is rapidly increased in and released from cells experiencing stress, including hepatocytes. The goal of this study was to define the role of HSPB1 in AH pathophysiology. MethodsSerum HSPB1 was measured in a retrospective study of 184 heathy controls (HC), heavy alcohol consumers (HA), patients with alcohol-associated cirrhosis (AC), and patients with AH recruited from major hospital centers. HSPB1 was also retrospectively evaluated in liver tissue from 10 HC and AH patients and an existing liver RNA-seq dataset. Finally, HSPB1 was investigated in a murine Lieber-DeCarli diet model of early ALD as well as cellular models of ethanol stress in hepatocytes and hepatocyte-macrophage communication during ethanol stress. ResultsCirculating HSPB1 was significantly increased in AH patients and levels positively correlated with disease-severity scores. Likewise, HSPB1 was increased in the liver of patients with severe AH and in the liver of ethanol-fed mice. In vitro, ethanol-stressed hepatocytes released HSPB1, which then triggered TNF-mediated inflammation in macrophages. Anti-HSPB1 antibody prevented TNF release from macrophages exposed to media conditioned by ethanol-stressed hepatocytes. ConclusionsOur 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. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=188 SRC="FIGDIR/small/24313193v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@141816eorg.highwire.dtl.DTLVardef@1985d66org.highwire.dtl.DTLVardef@1c0ed4org.highwire.dtl.DTLVardef@118ca9_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIHSPB1 is significantly increased in serum and liver of patients with alcohol-associated hepatitis. C_LIO_LIEthanol consumption leads to early increases in HSPB1 in the mouse liver. C_LIO_LIHepatocytes subjected to ethanol stress release HSPB1 into the extracellular environment where it activates TNF-mediated inflammation in macrophages. C_LIO_LIAnti-HSPB1 antibody blocks hepatocyte-triggered TNF in a model of hepatocyte-macrophage communication during ethanol stress. C_LI