Vitamin D3 attenuates hepatic inflammation in primary biliary cholangitis by inhibiting TLR4/NF-κB mediated M1 macrophage polarization

Primary biliary cholangitis (PBC) is an autoimmune liver disease in which macrophages play a critical role in disease progression. Vitamin D₃ (VitD₃) exerts immunomodulatory effects and can regulate the phenotype and function of macrophages. However, the role of VitD₃ in modulating macrophage polarization during PBC progression remains unclear. In this study, the relationship between VitD₃ levels and macrophage polarization in PBC patients was evaluated by bioinformatics as well as clinical validation, and the underlying mechanisms were investigated using a mouse model of PBC and an in vitro cellular model. Bioinformatics analysis of vitamin D-related genes involved in PBC disease. The number of M1-type macrophages is increased in the liver of PBC patients. After calcitriol treatment, the serum 25(OH)D₃ level of PBC patients was increased, liver injury was alleviated, and the number of M1 macrophages in the liver was decreased. In the liver of PBC mice, VitD₃ treatment significantly reduced the infiltration of inflammatory cells, especially M1 macrophages, and reduced the release of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), thereby alleviating liver injury. In vitro and in vivo experiments showed that VitD₃ inhibited the expression of TLR4/NF-κB signaling pathway-related proteins TLR4 and MyD88 and the phosphorylation of p65 and IκB. In conclusion, VitD₃ may attenuate M1 macrophage polarization through the TLR4/NF-κB signaling pathway, thereby ameliorating the liver inflammatory injury in PBC. This study provides novel insights into the immunomodulatory effects of VitD₃ in PBC and highlights its potential therapeutic implications.