cyclic-gmp and sorbinil

Pretreatment of porcine aortic endothelial cells with high D-glucose results in enhanced endothelium-derived relaxing factor (EDRF) formation (39%) due to increased endothelial Ca2+ release (57%) and Ca2+ entry (97%) to bradykinin. This study was designed to investigate the intracellular mechanisms by which high D-glucose affects endothelial Ca2+/EDRF response. The aldose-reductase inhibitors, sorbinil and zopolrestat, failed to diminish high D-glucose-mediated alterations in Ca2+/EDRF response, suggesting that aldose-reductase does not contribute to high D-glucose-initiated changes in Ca2+/EDRF signaling. Pretreatment of cells with the nonmetabolizing D-glucose analog, 3-O-methylglucopyranose (3-OMG), mimicked the effect of high D-glucose on Ca2+ release (41%) and Ca2+ entry (114%) to bradykinin, associated with elevated EDRF formation (26%). High D-glucose and 3-OMG increased superoxide anion (O2-) formation (133 and 293%, respectively), which was insensitive to inhibitors of cyclooxygenase (5,8,11,14-eicosatetraynoic acid [ETYA], indomethacin), lipoxygenase (ETYA, gossypol, nordihydroguaiaretic acid [NDGA]), cytochrome P450 (NDGA, econazole, miconazole), and nitric oxide (NO) synthase (L-omega N-nitroarginine), while it was diminished by desferal, a metal chelator. The gamma-glutamyl-cysteine-synthase inhibitor, buthioninesulfoximine (BSO), also increased formation of O2- by 365% and mimicked the effect of high D-glucose on Ca2+/EDRF signaling. The effects of high D-glucose, 3-OMG, and BSO were abolished by co-incubation with superoxide dismutase. Like high D-glucose, pretreatment with the O2(-)-generating system, xanthine oxidase/hypoxanthine, elevated bradykinin-stimulated Ca2+ release (+10%), Ca2+ entry (+75%), and EDRF (+73%). We suggest that prolonged exposure to pathologically high D-glucose concentration results in enhanced formation of O2-, possibly due to metal-mediated oxidation of D-glucose within the cells. This overshoot of O2- enhances agonist-stimulated Ca2+/EDRF signaling via a yet unknown mechanism.

Topics: 5,8,11,14-Eicosatetraynoic Acid; Animals; Aorta; Bradykinin; Calcium; Cells, Cultured; Cyclic GMP; Cytochalasin B; Deferoxamine; Econazole; Endothelium, Vascular; Enzyme Inhibitors; Glucose; Gossypol; Imidazoles; Imidazolidines; Indomethacin; Kinetics; Masoprocol; Miconazole; Nitric Oxide; Nitric Oxide Synthase; Signal Transduction; Superoxides; Swine; Time Factors

A possible relationship between increased aldose reductase activity and abnormal endothelium-dependent relaxation was examined in aorta from alloxan-induced diabetic rabbits. Isolated aorta of diabetic rabbits, contracted submaximally with phenylephrine, showed significantly decreased endothelium-dependent relaxations induced by acetylcholine or adenosine diphosphate compared to those from normal rabbits. Basal and acetylcholine-stimulated levels of cyclic GMP and the relaxations in response to an endothelium-independent vasodilator, sodium nitroprusside, were not significantly different between diabetic and normal rabbits, indicating that nitric oxide release and action on the vascular smooth muscle were unchanged. The release of thromboxane A2 from diabetic vessels was increased, as previously demonstrated. Treatment with an aldose reductase inhibitor, zopolrestat, normalized the elevated red blood cell sorbitol levels in diabetic rabbits. Zopolrestat also restored the abnormal acetylcholine- and adenosine diphosphate-induced relaxations of the aorta. The aldose reductase inhibitor had no effect on the levels of cyclic GMP or on the increased release of thromboxane A2 in diabetic aorta. These findings suggest that increased activity of the aldose reductase pathway in hyperglycemia is responsible for the abnormal endothelium-dependent relaxation in diabetic blood vessels. Significant alterations in endothelial production of neither nitric oxide nor vasoconstrictor prostanoids could be directly implicated in the improvement caused by the drug, suggesting another mechanism of action.

Topics: Acetylcholine; Adenosine Diphosphate; Aldehyde Reductase; Animals; Aorta; Blood Glucose; Body Weight; Cyclic GMP; Diabetes Mellitus, Experimental; Endothelium, Vascular; Imidazoles; Imidazolidines; In Vitro Techniques; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Phenylephrine; Prostaglandins; Rabbits; Sorbitol