Autophagy deficiency promotes M1 macrophage polarization to exacerbate acute liver injury via ATG5 repression during aging

Abstract Aging disrupts the maintenance of liver homeostasis, which impairs hepatocyte regeneration and aggravates acute liver injury (ALI), ultimately leading to the development of acute liver failure (ALF), a systemic inflammatory response, and even death. Macrophages influence the progression and outcome of ALI through the innate immune system. However, it is still unclear how macrophages regulate ALI during aging. The variation in macrophage autophagy with aging and the influence on macrophage polarization and cytokine release were assessed in BMDMs in vitro. Then, after BMDMs subjected to several treatments were intravenously or intraperitoneally injected into mice, thioacetamide (TAA)-induced ALI (TAA-ALI) was established, and its effects on inflammation, injury, and mortality were assessed. We found that aging aggravated the liver injury, along with increases in the levels of proinflammatory mediators, presenting a senescence-associated secretory phenotype (SASP), which promoted macrophage polarization to the M1 phenotype. In addition, autophagy levels decreased significantly in aged mice, which was ascribed to ATG5 repression during aging. Notably, enhancing autophagy levels in aged BMDMs restored macrophage polarization to that observed under young conditions. Finally, autophagy restoration in aged BMDMs enhanced the protective effect against TAA-ALI, similar to M2 macrophages induced by IL-4. Overall, we demonstrated that the influence of aging on macrophage polarization is an important aggravating factor in TAA-ALI, and the autophagy in macrophages is associated with the aging phenotype.