MiR-185/AKT and miR-29a/Collagen 1a pathways are activated in IPF BAL cells

Abstract

MicroRNA signatures of BAL cells and alveolar macrophages are currently lacking in IPF. Here we sought to investigate the expression of fibrosis-related microRNAs in the cellular component of the BAL in IPF. We thus focused on microRNAs previously associated with fibrosis (miR-29a, miR-29b, miR-29c, let-7d, and miR-21) and rapid IPF progression (miR-185, miR-210, miR-302c-3p miR-376c and miR-423-5p). Among the tested microRNAs miR-29a and miR-185 were found significantly downregulated in IPF while miR-302c-3p and miR-376c were not expressed by BAL cells. Importantly, the downregulation of miR-29a inversely correlated with the significantly increased levels of COL1A1 mRNA in IPF BAL cells. Collagen 1 a was found mainly overexpressed in alveolar macrophages and not other cell types of the BAL by immunofluorescence. In view of the downregulation of miR-185, we tested the response of THP-1 macrophages to profibrotic cytokine TGFb and observed the downregulation of miR-185. Conversely, proinflammatory stimulation lead to miR-185 upregulation. Upon examination of the mRNA levels of known miR-185 targets AKT1, DNMT1 and HMGA2, no significant correlations were observed in the BAL cells. However, increased levels of total AKT and AKTser473 phosphorylation were observed in the IPF BAL cells. Furthermore, miR-185 inhibition in THP-1 macrophages resulted in significant increase of AKTser473 phosphorylation. Our study highlights the importance of BAL microRNA signatures in IPF and identifies significant differences in miR-185/AKT and miR-29a/collagen axes in the BAL cells of IPF patients.

miR-185 and miR-29a are similarly expressed in the bronchoalveolar lavage cells in IPF and lung cancer but common targets DNMT1 and COL1A1 show disease specific patterns

“…BAL was obtained from all the patients, as previously described ( 25 ). Cells (1–1.5 million) were homogenised in TriReagent™ (MBL) for total RNA analysis, followed by storage at −80°C.…”

“…Cells (1–1.5 million) were homogenised in TriReagent™ (MBL) for total RNA analysis, followed by storage at −80°C. Differential cell population count was analysed following May-Grünwald Giemsa staining of cell cytospins, as previously described ( 25 ).…”

“…Additionally, miR-185 is increasingly recognized as an oncomir commonly deregulated in IPF and LC ( 25 ). Downregulation of miR-185 has been demonstrated in IPF lung tissue ( 26 ) and in several malignancies including LC, glioma, hepatocellular and breast cancer ( 27 ).…”

“…Interestingly, the expression of miR-29 and miR-185 is downregulated by TGFb ( 18 , 25 , 30 ). Furthermore, there are emerging data suggesting an overlap of miR-29a and miR-185 targets; miR-185 appears to regulate collagens ( 26 , 30 , 31 ), while miR-29a seems to regulate AKT1 ( 32 ) and AKT2 ( 33 ).…”

“…Furthermore, there are emerging data suggesting an overlap of miR-29a and miR-185 targets; miR-185 appears to regulate collagens ( 26 , 30 , 31 ), while miR-29a seems to regulate AKT1 ( 32 ) and AKT2 ( 33 ). Recently, both miR-185 and miR-29a were downregulated in IPF bronchoalveolar lavage (BAL) cells compared to controls ( 25 ).…”