Toll like receptor 4 activation upregulates miR-181b attenuating pulmonary fibrosis via targeting TGFBR1

Introduction: Recent studies have indicated that Toll like receptor 4 (TLR4) activity is required in the resolution of pulmonary fibrosis. However, whether miRNAs are involved in anti-fibrotic effect of TLR4 activation is still undefined. Aims and Objectives: To test the hypothesis that miRNAs play a pivotal role in the anti-fibrotic ability of TLR4 activation, focusing on miR-181b and its target TGFBR1. Methods: miRNA array and qRT-PCR was preformed to determine the TLR4 activation induced miRNAs profling in human epithelial cell line A549 cells. Regulation of miR-181b on TGF-β receptor Ι (TGFBR1) expression was confirmed using Western blot and qRT-PCR. Effects of miR-181b on TGF-β 1 induced epithelial-mesenchymal transition (EMT) in A549 cells were evaluated using Western blot, qRT-PCR and immunofluorescence (IF). In bleomycin induced pulmonary fibrosis murine, miR-181b was overexpressed by intravenous administration of recombinant adeno-associated viral vector encoding miR-181b gene, and its effects were determined by immunohistochemistry, IF, qRT-PCR, and morphometry Results: miR-181b was significantly upregulated in A549 cells after treated with LPS. miR-181b could suppress the TGFBR1 gene expression by targeting the 39UTR without affecting its mRNA level in A549 cells. Overexpression of miR-181b could mitigate TGF-β1 induced EMT in vitro. miR-181b overexpression in vivo alleviated alveolar septal thickening and caused decreases in collagen and MMPs expression. Conclusions: Our results indicate a key role for TLR4/miR-181b/TGFBR1 axis in IPF. Targeting this axis may provide novelty therapeutic strategies and facilitate drug discovery against pulmonary fibrosis.