Circular RNA RORβ regulates TGFBR1 by decoying miR-140 in alcohol-exposed lungs and fibroblasts

Alcohol ingestion exaggerates transforming growth factor-beta 1 (TGFβ1) expression and signaling leading to fibroproliferation. Inhibition of TGFβ receptor type 1 (TGFβR1) mitigates the effect of TGFβ1 signaling. We showed that alcohol can modulate microRNA (miRNA) expressions. The mechanism by which alcohol modulates microRNA and how it ties to TGFβ1 signaling has not been well elucidated. Circular RNA (circRNAs or circ) emerges as a potential therapeutic target based on its stability, tissue specificity, and its ability to modify miRNAs. In this study, we showed that alcohol upregulates TGFβR1 and circRNA form of retinoic acid receptor-related orphan receptor beta (circ-RORβ) in lung fibroblasts (LF) and the lung. We identified miR-140 to have binding sites for both TGFβR1 3’ UTR and circ-RORβ and alcohol attenuated miR-140 expression in LF and the lung. We demonstrated that inhibition of circ-RORβ upregulated miR-140 and completely abrogated alcohol-induced miR-140 suppression. We further showed that inhibition of circ-RORβ attenuated alcohol-induced TGFβR1, fibronectin (FN1), and α-smooth muscle actin (αSMA) expressions and myofibroblast development as seen by an attenuation of αSMA stress fiber formation in LF. Taken together, these findings identify circ-RORβ-miR-140-TGFβR1 axis as a novel mechanism by which alcohol induces TGFβ1 signaling and promotes FMD. Highlights Alcohol induces circ-RORβ expression in lung fibroblasts Circ-RORβ regulates TGFβR1 by decoying miR-140 in lung fibroblasts Inhibition of Circ-RORβ restores miR-140 expression Inhibition of Circ-RORβ mitigates alcohol-mediated myofibroblast differentiation This is the first description of circ-RORβ functional significance in lung fibroblast