Downregulation of miR­29b­3p promotes α­tubulin deacetylation by targeting the interaction of matrix metalloproteinase­9 with integrin ß1 in nasal polyps.

Matrix metalloproteinase (MMP)­9 is a key enzyme responsible for extracellular matrix degradation and contributes to the progressive histological changes observed in lower respiratory tract infections. Integrin ß1 and α­tubulin are potential MMP­9­interacting proteins, and microRNA (miR)­29b­3p can regulate MMP­9 expression. MMP­9 is highly expressed in chronic rhinosinusitis with nasal polyps (CRSwNPs), regardless of its effects on miR­29b­3p, integrin ß1 and α­tubulin expression. In the present study, samples from 100 patients with CRSwNPs were examined via reverse transcription­quantitative PCR to assess the mRNA expression of miR­29b­3p, and western blotting was performed to assess the protein expression of MMP­2, MMP­9, acetyl­α­tubulin, integrin ß1 and tissue inhibitor of metalloproteinase 1 (TIMP­1). A dual­luciferase reporter assay was used to verify the direct binding of miR­29b­3p and MMP­2/MMP­9. Co­immunoprecipitation (Co­IP) and GST pull­down assays showed that integrin ß1 and α­tubulin were MMP­9­interacting proteins. Cell viability, apoptosis and inflammatory cytokine levels were determined via a Cell Counting Kit­8 assay, flow cytometry and ELISA, respectively. miR­29b­3p expression was found to be positively correlated with MMP­2 and MMP­9 expression. Whereas, TIMP­1 expression was negatively correlated with MMP­2 and MMP­9 expression. The dual­luciferase assay revealed that miR­29b­3p targeted the 3' untranslated region of MMP­2/MMP­9. The Co­IP and GST pull­down assays showed that MMP­9 could directly bind to integrin ß1 and indirectly bind to α­tubulin. Finally, the overexpression of miR­29b­3p decreased the expression of MMP­9 and increased the levels of acetyl­α­tubulin. By contrast, the knockdown of miR­29b­3p increased the expression of MMP­9 and decreased the levels of acetyl­α­tubulin. Additionally, MMP­9 expression was found to be negatively correlated with acetyl­α­tubulin expression. Of note, the expression of integrin ß1 did not change following the overexpression and knockdown of MMP­9. Finally, the overexpression of miR­29b­3p not only decreased MMP­9 expression, but also alleviated lipopolysaccharide­induced inflammation in NP69 cells. The results showed that the downregulation of miR­29b­3p promoted α­tubulin deacetylation by increasing the number of MMP­9­integrin ß1 complexes in CRSwNPs, thus targeting miR­29b­3p/MMP­9 may be a potential novel strategy for the clinical treatment of CRSwNPs.