P46: Low sodium nitrite (but not nitrate) concentrations attenuate MMP-9 production by endothelial cells

Abstract

Reduced nitric oxide (NO) bioavailability and imbalanced matrix metalloproteinase (MMP) activity have important roles in the pathogenesis of cardiovascular diseases, and some NO donors were shown to downregulate MMP expression in some cell types. However, while nitrite and nitrate can be recycled back to NO by non enzymatic and enzymatic mechanisms as an alternative to NO formation from l -arginine, no previous study has examined whether sodium nitrite can downregulate stimulated MMP release by endothelial cells. We examined the effect of sodium nitrite and sodium nitrate on MMP-9 production by endothelial cells. Human umbilical vein endothelial cells were cultured in a modified DMEM (iron(III) nitrate is replaced by iron(III) sulfate) and treated for 24 h with 10 nM phorbol myristate acetate (PMA; a MMP-9 inducer) and sodium nitrite or sodium nitrate, or their vehicles. Conditioned medium were analyzed by gelatin zimography to assess MMP-9 activity. PMA increased MMP-9 activity from 0.02 ± 0.01 arbitrary units (AU) to 1.14 ± 0.34 AU ( P < 0.05). While low nitrite concentrations (0.2 or 2 μM) attenuated the increases in MMP-9 activity induced by PMA (0.77 ± 0.12 AU or 0.71 ± 0.14 AU, respectively; both P < 0.05 vs. PMA), high nitrite concentrations (10 or 20 μM) had no effects on PMA-induced increases in MMP-9 activity (0.88 ± 0.14 AU or 1.18 ± 0.36 AU, respectively; both P > 0.05 vs. PMA). Both low (10 or 100 μM) or high (200 or 400 μM) nitrate concentrations had no effects on PMA-induced increases in MMP-9 activity PMA ( P > 0.05 vs. PMA). Our results suggest that low nitrite (but not nitrate) concentrations attenuate MMP-9 production by endothelial cells. FAPESP, CNPq, FAEPA. Nothing to disclose.