Long-term methylglyoxal treatment impairs smooth muscle contractility in organ-cultured rat mesenteric artery

Methylglyoxal (MGO), a metabolite of glucose accumulates in vascular tissues of hypertensive rats. We recently showed that short-term (30 min) treatment with MGO inhibits noradrenaline (NA)-induced smooth muscle contraction in rat aorta and mesenteric artery. In the present study, long-term effect of MGO was examined using organ culture method. The contractility, morphology, and protein expression of rat mesenteric artery after organ culture with MGO for 3 days were examined. MGO (4 and 42 μM) inhibited NA (0.1 nM to 3 μM) or KCl (72.7 mM)-induced contraction. The inhibitory effect was higher in endothelium-denuded than endothelium-intact artery. An anti-oxidant drug, N-acetyl- l-cysteine (NAC; 1 mM) or an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), gp91ds-tat (0.1 μM) prevented the inhibitory effect of MGO. MGO increased superoxide production as detected by lucigenin assay. In the medial layer of the arteries cultured with MGO, apoptotic morphological change was observed, and NAC or gp91ds-tat prevented it. MGO significantly increased expression of a homolog of gp91 phox, NOX1 but not gp91 phox as determined by Western blotting. An NF-κB inhibitor, pyrrolidine dithiocarbamate prevented the MGO-induced NOX1 expression. MGO had no effect on protein expression of p22 phox, p67 phox, p47 phox, as well as superoxide dismutase (SOD)-1, SOD-2 and SOD-3. Present results indicate that long-term MGO treatment has an inhibitory effect on contractility of isolated blood vessel, which is likely mediated via increased NOX1-derived superoxide production and subsequent apoptosis.