HDAC6 deficiency aggravates ductular reactions through aggresome-mediated hepatocyte apoptosis

Ductular reactions (DRs) contribute significantly to the occurrence and development of liver disease. While histone deacetylase 6 (HDAC6) is known to regulate injury repair in multiple tissues, its exact role in DRs remains unclear. This study examined the role and underlying mechanism of HDAC6 in DRs using an HDAC6 knockout (HDAC6^-/y) male mouse model. Wild type and HDAC6-deficient male mice were administered 3,5 diethoxicarbonyl-1,4 dihydrocollidine (DDC) to induce DRs. The impact of HDAC6 inhibition on aggresome formation was assessed in vitro using AML-12 hepatocytes exposed to H₂O₂ and treated with tubastatin A (TSA), a selective HDAC6 inhibitor. Fluorescence immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR) were employed to quantify protein and gene expression levels, respectively. Immunohistochemical and qRT-PCR analyses revealed that HDAC6 deficiency exacerbated DRs and fibrosis, accompanied by increased expression of transforming growth factor β (TGF-β) and activation of the Notch signaling pathway. Additionally, genetic knockout or pharmacological inhibition of HDAC6 promoted hepatocyte apoptosis in vivo and in vitro, as evidenced by elevated caspase3, caspase9, and p53 expression. Furthermore, TSA treatment induced the formation of aggresomes in H₂O₂-exposed AML-12 hepatocytes, which were encased by vimentin filaments. These findings demonstrate that HDAC6 deficiency promotes DRs and liver fibrosis through the formation of intracellular aggregates, ultimately leading to hepatocyte apoptosis.