BACKGROUND: Methylglyoxal (MG) is a metabolite of glucose. Our previous study demonstrated an elevated cellular level of MG with an increased oxidative stress in vascular smooth cells (VSMCs) from spontaneously hypertensive rats. The purpose of the present study is to investigate which type of free radicals is induced by MG in VSMCs.

METHODS: Cultured rat thoracic aorta SMCs (A-10) were treated with MG. DCF-DA was used as probe to detect H₂O₂ and ONOO^– production. DAF-FM and lucigenin probes were used to detect NO and O₂^.– production.

RESULTS: In A-10 cells treated with MG (3-300 µM) for 45 min to 18 hrs, MG-induced DCF-fluorescence was significantly increased in a concentration- and time-dependent manner. MG-increased DCF-fluorescence was effectively blocked by two MG scavengers, ie, reduced glutathione (GSH, 1 mM) and N-acetyl-L-cysteine (NAC, 600 µM). However, MG-increased DCF-fluorescence was not inhibited by catalase, a scavenger of H₂O₂. MG-induced DCF-fluorescence was, however, significantly inhibited by a NOS inhibitor L-NAME (100 µM). Both superoxide scavenger SOD (400 U/ml) and NAD(P)H oxidase inhibitor DPI (100 µM) significantly decreased MG (100 µM)-induced DCF-fluorescence by 71.6% and 44.7%, respectively. Furthermore, using a NO specific probe DAF-FM, a significant concentration-dependent increase of NO production was detected when A-10 cells were treated with MG (3-300 µM). MG-induced NO generation was significantly inhibited by L-NAME (100 µM). MG significantly and does-dependently increased superoxide generation in A-10 cells, which was significantly inhibited by SOD (400 U/ml) or DPI (100 µM).

CONCLUSION: MG induces a significant generation of NO and superoxide in VSMCs, which in turn causes peroxynitrite formation. An elevated MG level and related peroxynitrite generation may contribute to the development of hypertension.

DNC

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