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.
Keywords: Kupffer cells; T-cell immunoglobulin domain and mucin domain-4; liver fibrosis; liver transplantation; mitophagy.
© 2019 The Authors. Cell Proliferation published by John Wiley & Sons Ltd.