Modulation of inflammatory markers by miR-146a during replicative senescence in trabecular meshwork cells.
PURPOSE: To investigate the alterations in microRNA (miRNA) expression during replicative senescence (RS) in human trabecular meshwork (HTM) cells. METHODS: Two HTM cell lines were serially passaged until they reached RS. Changes in expression of 30 miRNAs were assessed by real-time quantitative (q)-PCR. The effects of miR-146a on gene expression were analyzed with gene arrays and the results confirmed by real-time q-PCR. Protein levels of IRAK1 and PAI-1 were analyzed by Western blot and those of IL6 and IL8 by ELISA. Senescence-associated markers were monitored by flow cytometry and cell proliferation by BrdU incorporation. RESULTS: RS of HTM cells was associated with significant changes in expression of 18 miRNAs, including the upregulation of miR-146a. miR-146a downregulated multiple genes associated with inflammation, including IRAK1, IL6, IL8, and PAI-1, inhibited senescence-associated beta-galactosidase (SA-beta-gal) activity and production of intracellular reactive species (iROS), and increased cell proliferation. Overexpression of either IRAK1 or PAI-1 inhibited the effects of miR-146a on cell proliferation and iROS production in senescent cells. CONCLUSIONS: RS in HTM cells was associated with changes in miRNA expression that could influence the senescent phenotype. Upregulation of the anti-inflammatory miR-146a may serve to restrain excessive production of inflammatory mediators in senescent cells and limit their deleterious effects on the surrounding tissue. Among the different proteins repressed by miR-146a, the inhibition of PAI-1 may act to minimize the effects of senescence on the generation of iROS and growth arrest and prevent alterations of the extracellular proteolytic activity of the TM.
Li, G; Luna, C; Qiu, J; Epstein, DL; Gonzalez, P
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