Alcohol-induced disruption of hepatic m6A modification exacerbates alcohol-associated steatohepatitis by impairing liver immune microenvironment homeostasis.

BACKGROUND AND AIMS Alcohol-associated steatohepatitis (ASH), a severe form of alcohol-associated liver disease (ALD), is characterized by pronounced steatosis and immune cells infiltration. As an inflammatory disease, ASH still lacks effective immunotherapies, and the mechanisms underlying alcohol-induced immune imbalance in the liver microenvironment remain elusive. RNA modifications are known to maintain hepatic homeostasis during physiological and pathological processes. This study aimed to investigate the alteration of RNA modification in ASH and its specific roles in regulating immune homeostasis. APPROACH AND RESULTS In this study, we found that the levels of RNA N6-methyladenosine (m6A) modification and its key writer, METTL3, are markedly reduced in mice livers during ASH. Notably, hepatocyte-specific Mettl3 knockout exacerbated ASH by enhancing steatosis and neutrophil infiltration, whereas hepatocyte-specific Mettl3 overexpression alleviated these effects. Mechanistically, ethanol promotes METTL3 degradation via E3-ubiquitin-ligase STUB1-mediated ubiquitination and disrupts the protective interaction between HSP70 and METTL3, impairing hepatic m6A modification. Furthermore, the expression of ATF3 was upregulated via m6A-dependent mechanism. Importantly, hepatocyte-specific Atf3 overexpression abolished METTL3-mediated amelioration of ASH, whereas hepatocyte-specific Atf3 knockdown attenuated Metl3 knockout-induced exacerbation of ASH in vivo. Consistently, high hepatic ATF3 expression is associated with an inflammatory liver microenvironment in ALD patients. CONCLUSIONS Collectively, our results demonstrate that alcohol consumption disrupts the homeostasis of hepatic immune microenvironment in ASH through impairment of METTL3-dependent m6A RNA modification. Targeting METTL3 to preserve its enzymatic activity and stability could represent a novel therapeutic avenue for ASH intervention.