Pathogenesis and Novel Therapeutic Targets of Steatotic Liver Disease and Cancer

National Institute On Alcohol Abuse And Alcoholism

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Abstract

Our laboratory has been actively studying alcohol metabolism and the pathogenesis of alcohol-associated liver disease, focusing on characterization of inflammatory cells in alcohol-associated hepatitis and liver cancer. We have demonstrated that multiple organ ALDH2 has a redundant role in metabolizing acetaldehyde and controlling drinking behavior. Gut-liver crosstalk plays an important role in alcohol-associated liver disease (ALD) pathogenesis; but underlying mechanisms remain obscure. We examined the regulation of intestinal and intrahepatic CD8+ T lymphocytes and their contribution to ALD. ALD patients were recruited for evaluation of intestinal and liver T cells. Single-cell RNA sequencing (scRNA seq) was performed to analyze intrahepatic and peripheral T cells in ALD. Wildtype, CD8-specific Bcl2 transgenic (Cd8 Bcl-2), and Cd8 -/- mice were subjected to chronic-plus-binge ethanol feeding. In ALD patients, duodenal CD8+ T cells were selectively reduced and negatively correlated with liver injury and bacterial translocation markers, while intrahepatic CD8+ T cells were markedly increased. ScRNA seq analysis of ALD patient livers revealed several populations of CD8+ T cells expressing activation and survival genes (e.g., Bcl2). Transcriptomics and functional studies revealed a key role of prosurvival BCL2 in this opposite regulation of CD8+ T cells. Mechanistically, chronic-plus-binge ethanol feeding reduced CD8+ T cells specifically in the duodenum where ethanol levels are high. Inducing BCL2 in CD8+ T cells reversed ethanol-induced loss of duodenal CD8+ T cells, improved gut barrier function and ameliorated ALD, while CD8 deficiency was linked to enhanced neutrophil and macrophage infiltration in the liver, exacerbating ALD in mice. In conclusion: ALD is associated with loss of duodenal CD8+ T cells but elevation of intrahepatic CD8+ T cells, which aggravates and ameliorates ALD, respectively. Restoration of survival and functions of intestinal and intrahepatic CD8+ T cells may represent a novel therapeutic strategy for ALD patients. Patients with alcohol-associated cirrhosis (AC) may develop severe alcohol-associated hepatitis (sAH), a disease with high short-term mortality. Our previous studies have demonstrated that sAH, but not AC livers, are infiltrated with high numbers of self-sustaining IL-8+ neutrophils that likely drive the transition from AC to sAH. Monocyte-derived macrophages (MoMFs) also infiltrate the liver in sAH, but their roles remain largely obscure. In the current study, we characterized liver macrophages in human liver explants from sAH and AC patients. Our data revealed a marked reduction of Kupffer cells, while MoMFs were increased in sAH and AC. Single-cell RNA Seq analyses identified several populations in both AC and sAH including C1Q+, S100A8+, APOE+, TNF+ and VSIG4+ macrophages, with sAH containing unique C1Q+ macrophages potentially playing a role in removing apoptotic neutrophils in sAH. C1Q+ macrophages also express a large number of genes involved in phagocytosis, pro-inflammatory, and anti-inflammatory functions, suggesting that C1Q+ macrophages have diverse functions in sAH. The roles of C1Q, S100A8, and APOE were further examined in experimental models of alcohol-induced liver injury. Our data revealed that C1q KO mice and macrophage-specific S100a8 KO mice had similar alcohol-induced liver injury and hepatic neutrophil infiltration, while Apoe KO mice developed much more severe liver injury than WT mice following chronic-plus-binge ethanol challenge. Taken together, sAH and AC are infiltrated with multiple populations of macrophages playing diverse functions to drive chronic disease progression. Unique C1Q+ macrophages in sAH play a compensatory role in removing dead cells but may also promote inflammation in sAH.