Hepatic microtubule destabilization facilitates liver fibrosis in the mouse model of Wilson disease.

Abstract

Wilson disease (WD) is a potentially fatal metabolic disorder caused by the inactivation of the copper (Cu) transporter ATP7B, resulting in systemic Cu overload and fibroinflammatory liver disease. The molecular mechanism and effects of elevated Cu on cytoskeletal dynamics in liver fibrogenesis are not clear. Here, we tested the regulation of hepatic cytoskeleton and fibrogenesis with respect to Cu overload in WD. Atp7b^-/- (knockout) mice with established liver disease, hepatocyte-specific Atp7b△^Hep knockout mice without fibroinflammatory disease, and the age-and sex-matched controls were compared using Western blotting, real-time quantitative reverse transcription PCR (qRT-PCR), immunohistochemical (IHC) staining and transcriptomics (RNA-sequencing) analysis. In Atp7b^-/- mice with developed liver disease, there is a significant increase in cytoskeletal protein expression with a reduction in α-tubulin acetylation. In these mice before the onset of liver pathology, no significant changes in cytoskeletal nor hepatic stellate cell activation are observed. As hepatic copper levels rise, an increase in cytoskeletal proteins with a decrease in acetylated-α-tubulin/α-tubulin ratio occurs. RNA-sequencing, qRT-PCR, and immunostaining confirm that the tubulin is upregulated at the transcriptional level and hepatocytes are the primary source of early tubulin increases before fibrosis. An increase in α-tubulin with a decrease in α-tubulin acetylation via Hdac6 and Sirt2 induction facilitates fibrosis as reflected by concomitant increases in desmin and α-SMA immunostaining in Atp7b^-/- mice at 20 weeks. Moreover, strongly positive correlations between α-tubulin and α-tubulin deacetylase with the expression of liver fibrosis markers are observed in animal and human WD. Hepatocyte-specific Atp7b△^Hep mice lack significant changes in tubulin as well as fibrosis despite hepatic steatosis. This study provides evidence that microtubule destabilization causes cytoskeletal rearrangement and facilitates hepatic stellate cell (HSC) activation and fibrosis in the murine model of WD. KEY MESSAGES: Hepatic cytoskeleton system is induced in Wilson disease. Hepatic microtubules acetylation is dysregulated in murine Wilson disease. Microtubules destabilization is positively associated with liver fibrosis in Wilson disease. Microtubules destabilization concomitant with fibrogenesis exacerbates WD progression.