Macrophage ATG16L1 promotes liver regeneration after partial hepatectomy

Abstract

Background & Aims

Autophagy plays an important role in liver regeneration. However, most studies are limited to hepatocytes, and the function and mechanism of macrophage autophagy in liver regeneration remain unclear. This study investigated the role of the essential autophagy gene encoding autophagy-related 16-like 1 (ATG16L1), which regulates the macrophage phenotype in liver regeneration.

Methods

We generated FloxP-Atg16l1 (Atg16l1^FL/FL), Lyz2-Cre Atg16l1 knockout (KO) (Atg16l1^M-KO), and myeloid-specific Atg16l1-overexpression-knock-in (Atg16l1^OE) mice. These mice were subjected to 70% partial hepatectomy to demonstrate the role of ATG16L1 in macrophages during liver regeneration.

Results

ATG16L1 expression was significantly upregulated in macrophages during the early stages of liver regeneration. ATG16L1 deletion in macrophages substantially delayed liver regeneration in mice and caused a marked imbalance in Ly6C^hi and Ly6C^lo macrophage proportions in the liver. RNA-sequencing analysis revealed that, compared with macrophages isolated from Atg16l1^FL/FL mice, those from Atg16l1^M-KO mice exhibited significant downregulation of genes associated with oxidative phosphorylation and upregulation of proinflammatory gene expression. Mechanistically, ATG16L1 loss impaired mitophagy in macrophages, leading to the accumulation of mitochondrial damage and a metabolic shift that promoted proinflammatory macrophage polarization. ATG16L1 deficiency not only promoted macrophage mitochondrial (mt)DNA release and cyclic GMP-AMP synthase–stimulator of interferon genes (STING) activation, but also suppressed STING degradation. Sustained STING hyperactivation and subsequent increased release of downstream interferons further contributed to the inhibition of liver regeneration. Notably, pharmacological activation or genetic overexpression of ATG16L1 significantly enhanced liver regeneration in mice.

Conclusions

ATG16L1 has a pivotal role in liver regeneration by affecting the phenotype and function of macrophages. Thus, targeting ATG16L1 in macrophages could present a novel strategy for promoting liver regeneration.

Impact and implications

The autophagy-related gene ATG16L1 mediates mitophagy, facilitating the clearance of damaged mitochondria in macrophages following partial hepatectomy and maintaining a reparative macrophage phenotype. ATG16L1 deficiency triggers excessive STING activation and inhibits its degradation, thereby suppressing liver regeneration. Thus, targeting ATG16L1 in macrophages could represent a novel strategy to promote liver regeneration.