Enoxacin Up‐Regulates MicroRNA Biogenesis and Down‐Regulates Cytotoxic CD8 T‐Cell Function in Autoimmune Cholangitis

Background and Aims Primary biliary cholangitis (PBC) is a prototypical organ‐specific autoimmune disease that is mediated by autoreactive T‐cell attack and destruction of cholangiocytes. Despite the clear role of autoimmunity in PBC, immune‐directed therapies have failed to halt PBC, including biologic therapies effective in other autoimmune diseases. MicroRNA (miRNA) dysregulation is implicated in the pathogenesis (PBC). In the dominant‐negative TGF‐β receptor type II (dnTGFβRII) mouse model of PBC, autoreactive CD8 T cells play a major pathogenic role and demonstrate a striking pattern of miRNA down‐regulation. Enoxacin is a small molecule fluoroquinolone that enhances miRNA biogenesis, partly by stabilizing the interaction of transactivation response RNA‐binding protein with Argonaute (Ago) 2. Approach and Results We hypothesized that correcting aberrant T‐cell miRNA expression with enoxacin in dnTGFβRII mice could modulate autoreactive T‐cell function and prevent PBC. Here, we show that liver‐infiltrating dnTGFβRII CD8 T cells have significantly decreased levels of the miRNA biogenesis molecules prolyl 4‐hydroxylase subunit alpha 1 (P4HA1) and Ago2 along with significantly increased levels of granzyme B and perforin. Enoxacin treatment significantly up‐regulated miRNAs in dnTGFβRII CD8 T cells and effectively treated autoimmune cholangitis in dnTGFβRII mice. Enoxacin treatment directly altered T cells both ex vivo and in vitro , resulting in altered memory subset numbers, decreased proliferation, and decreased interferon‐γ production. Enoxacin significantly decreased CD8 T‐cell expression of the transcription factor, Runx3 , and significantly decreased perforin expression at both the mRNA and protein levels. Conclusions Enoxacin increases miRNA expression in dnTGFβRII CD8 T cells, reduces CD8 T‐cell pathogenicity, and effectively halted progression of autoimmune biliary disease. Targeting the miRNA pathway is a therapeutic approach to autoimmunity that corrects pathological miRNA abnormalities in autoreactive T cells.