A1AT dysregulation of metabolically stressed hepatocytes by Kupffer cells drives MASH and fibrosis

Metabolic dysfunction-associated steatohepatitis (MASH) is associated with the activation of Kupffer cells (KCs) and hepatic stellate cells, at which point a metabolically stressed hepatocyte becomes integral to the progression of the disease. We observed a significant reduction in the level of alpha-1-antitrypsin (A1AT), a hepatocyte-derived secreted factor, in both patients with MASH and mice fed a fast-food diet (FFD). KC-mediated hepatic inflammation, most notably IL-1β, led to the transcriptional inhibition of A1AT by HNF4α. In quintuple Serpina1a–e knockout mice, ablation of A1AT worsened MASH through increased activity of proteinase 3 (PR3), a proinflammatory protease produced by F4/80hi/CD11blow/TIM4−/CCR2+ monocyte-derived KCs (MoKCs). Conversely, A1AT restoration or PR3 inhibition mitigated MASH progression. A PR3-bound cytokine array identified IL-32 as a key factor associated with MASH. Combining IL-32 with SERPINA1, the gene encoding A1AT, synergistically predicted patients at risk of MASH through univariate logistic regression analysis. Furthermore, in vivo overexpression of IL-32γ alleviated MASH induced by FFD. However, additional knockout of A1AT increased PR3 activity, consequently abolishing the anti-MASH effects of IL-32γ. Blocking PR3-mediated IL-32γ cleavage via the V104A mutation sustained its protective actions, while the PR3-cleaved C-terminal fragment activated KCs. Additionally, after cleavage, the antifibrogenic effect of IL-32γ is lost, resulting in a failure to prevent the activation of hepatic stellate cells. This study highlights the critical role of hepatocyte-derived A1AT in the PR3/IL-32γ axis during MASH development. Strategies to correct A1AT dysregulation, such as A1AT supplementation or PR3 inhibition with sivelestat, may offer protection against the development and progression of MASH and fibrosis. Metabolic dysfunction-associated steatotic liver disease (MASLD) is a major cause of liver failure worldwide. Researchers are trying to understand how it progresses to more severe conditions such as metabolic dysfunction-associated steatohepatitis (MASH). This study focuses on a protein called alpha-1-antitrypsin, which is important for liver health. The researchers used mice and human samples to study the role of A1AT in liver disease. They found that A1AT levels are lower in people and mice with MASLD, which leads to increased inflammation and liver damage. They also discovered that a protein called proteinase 3 becomes more active when A1AT is low, worsening the condition. By experimenting with mice, they showed that increasing A1AT or blocking PR3 can reduce liver damage. This suggests new treatment possibilities for MASH. The study concludes that targeting the A1AT/PR3 pathway could help manage liver disease progression. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.