Baricitinib alleviates interstitial lung disease in CIA mice by inhibiting macrophage polarization and increase exosomal miR-126a-3p with anti-fibrotic activity in vitro

Background Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a severe condition with an unclear pathogenesis. Here, we investigated the effects of baricitinib on lung fibrosis progression. Methods A collagen-induced arthritis (CIA) mouse model was established. Lung tissues were analyzed using Western blotting, immunofluorescence staining, immunohistochemical staining, Masson’s trichrome and hematoxylin and eosin staining. Protein expression was assessed in vitro using Western blotting and immunofluorescence staining. The cytokine levels in supernatants were measured using ELISA, and macrophage-derived exosomes were identified using transmission electron microscopy and Western blotting, followed by microRNA sequencing analyses. miR-126a-3p-regulated genes were identified using dual-luciferase reporter assays. Results In vivo , baricitinib reduced iNOS, CD206 and MerTK levels and collagen deposition in the lungs of CIA mice through the JAK/STAT pathway. In vitro , baricitinib downregulated the expression of arginase-1, CD206 and MerTK in macrophages and TGF-β and IL-10 in supernatants. Baricitinib also increased miR-126a-3p expression in macrophage-derived exosomes. miR-126a-3p exerted antifibrotic effects by regulating apoptosis and autophagy via the PI3K/AKT1/mTOR pathway. Silencing JAK1 reduced JAK1 and JAK2 expression. Conclusion Baricitinib targets the JAK/STAT signaling pathway in macrophages, thereby exerting dual anti-inflammatory and anti-fibrotic inhibitory effects on CIA-ILD mice. Meanwhile, it increases miR-126a-3p secretion by suppressing M2 polarization, further contributing to its anti-fibrotic activity in vitro using NIH3T3 cell.