Bile acid retention in efferocytic macrophages shapes their inflammatory status during cholangitis.

The clearance of apoptotic cells by phagocytes is crucial for restoring tissue balance after injury. In autoimmune liver diseases like primary sclerosing cholangitis, cell death is thought to result from accumulation of toxic bile acids within parenchymal cells. Whether, in this context, bile acid-loaded dying cells impact the efficiency of phagocytic macrophages in restoring tissue balance remains unknown. Here, we demonstrate that in a murine model of cholangitis, bile acids accumulate in a subpopulation of efferocytic macrophages with pro-inflammatory features. Our in vitro results indicate that, upon their engulfment, apoptotic hepatocytes laden with bile acids can serve as Trojan horses, delivering bile acids into efferocytic macrophages and thereby shaping macrophage function. This contrasts with the characteristics of macrophages that engulf apoptotic parenchymal cells lacking bile acids. Together, our findings delineate a system in which the content of the phagocytosed dying cells, specifically bile acid-laden hepatocytes, drives a pro-inflammatory program in the corresponding efferocytic macrophages, potentially contributing to chronic hepatic inflammation.