Forkhead box protein M1 network induction and crosstalk drives the development of alcohol-associated liver disease

Forkhead Box Protein M1 (FOXM1) is an oncoprotein that plays an important role in liver inflammation and fibrosis. It is phosphorylated by multiple kinases at specific sites, leading to interaction with peptidyl-prolyl isomerase NIMA-interacting 1 (PIN1) for further activation. The role of FOXM1 in alcohol-associated liver disease (ALD) is unknown and investigated here.

We used the NIAAA ALD protocol in wild-type, flox, and albumin-Cre Foxm1 knockout ( Foxm1Hep-/- ) mice, ethanol (EtOH)-treated human and mouse hepatocytes, and human ALD specimens, and examined the effect of FDI-6, a small molecule inhibitor of FOXM1. We found FOXM1 was upregulated in murine and human ALD, particularly in hepatocytes. FOXM1-PIN1 interaction increased in both cytosol and nuclei, along with increased total and nuclear levels of FOXM1, FOXM1-pT600 (marker of activation), cyclin D1, pERK, and pPKC. Total PIN1 level was unchanged, but nuclear PIN1 content increased. Silencing PIN1, cyclin D1, or inhibiting MEK alone blunted the EtOH-mediated increase in nuclear FOXM1 expression/activity, but the combination inhibited completely. FDI-6-treated and Foxm1Hep-/- mice were protected from EtOH-induced liver injury, the increase in triglyceride and proinflammatory cytokines. RNA-Seq analysis, validated in Foxm1Hep-/- livers and human ALD, revealed multiple novel Foxm1 targets, including granulin (GRN), cathepsins L/E, and importin-α5, which enhanced the nuclear translocation of PIN1.

Taken together, FOXM1 is activated in hepatocytes in response to EtOH through a mechanism that involves PKCε, MEK/ERK, cyclin D1-CDK4/6, PIN1, and GRN. Targeting this pathway may represent a novel therapeutic strategy for ALD.