TIM‐4 interference in Kupffer cells against CCL4‐induced liver fibrosis by mediating Akt1/Mitophagy signalling pathway

OBJECTIVES: T‐cell immunoglobulin domain and mucin domain‐4 (TIM‐4) is selectively expressed on antigen‐presenting cells (APCs) and modulates various immune responses. However, the role of TIM‐4 expressed by Kupffer cells (KCs) in liver fibrosis remains unclear. The present study aimed to explore whether and how TIM‐4 expressed by KCs is involved in liver fibrosis. MATERIALS AND METHODS: Mice chronic liver fibrosis models were established and divided into the olive‐induced control group, CCL4‐induced control group, olive‐induced TIM‐4 interference group and CCL4‐induced TIM‐4 interference group. Different techniques were used to monitor the fibrotic effects of TIM‐4, including histopathological assays, Western blotting, ELISA and transmission electron microscopy. Additionally, mice liver transplant models were established to determine the fibrotic effects of TIM‐4 on fibrosis after liver transplantation (LT). RESULTS: We found that the induction of liver fibrosis by CCL4 was associated with TIM‐4 expression in KCs. TIM‐4 interference essentially contributed to liver fibrosis resolution. KCs from the TIM‐4 interference group had decreased levels of pro‐fibrotic markers, reduced TGF‐β1 secretion and inhibited hepatic stellate cell (HSC) differentiation into myofibroblast‐like cells. In addition, we used GdCl3 to verify that KCs are the primary source of TGF‐β1 during fibrosis progression. Moreover, KCs from CCL4‐induced mice showed increased ROS production, mitophagy activation and TGF‐β1 secretion. However, TIM‐4 interference in the KCs inhibited Akt1‐mediated ROS production, resulting in the suppression of PINK1, Parkin and LC3‐II/I activation and the reduction of TGF‐β1 secretion during liver fibrosis. Additionally, TIM‐4 interference potentially attenuated development of fibrosis after LT. CONCLUSIONS: Our findings revealed the underlying mechanisms of TIM‐4 interference in KCs to mitigate liver fibrosis.