An NADPH oxidase superoxide-generating system in the rabbit aorta

Abstract

Superoxide anion can modulate vascular smooth muscle tone and potentially affect the growth response in vascular disease. The present studies were undertaken to characterize the source of superoxide in rabbit aorta. Rings of aorta (5 mm) were incubated in physiological salt solution (PSS) for 30 min at 37 degrees C in the presence of 10 mM diethyldithiocarbamate (DDC) with or without inhibitors of superoxide-generating systems. Rings were then placed in PSS containing 250 microM lucigenin at 37 degrees C in the presence or absence of inhibitors, and changes in amounts of superoxide were determined by measuring chemiluminescence (units). The inhibitors of xanthine oxidase, oxypurinol (300 microM), and of mitochondrial NADH dehydrogenase, rotenone (50 microM), had no significant effect on superoxide levels. An inhibitor of NADPH oxidase, iodonium thiophen, caused a concentration-dependent inhibition of superoxide anion (12.49 +/- 1.48 vs 5.27 +/- 1.81 and 2.30 +/- 0.36 units, control vs 7 microM and 70 microM iodonium thiopen, respectively). A structurally related iodonium compound, diphenyleneiodonium (20 microM), caused a 78% reduction in basal and DDC-evoked superoxide levels. In the presence or absence of DDC, exogenous administration of NADPH (10 microM-1 mM), but not NADP (1 mM), elicited a concentration-dependent rise in superoxide levels that was inhibited by iodonium thiophen. Particulate fractions of whole aortic tissue exhibited NADPH-dependent superoxide production that was inhibited by 1 microM diphenyleneiodonium.(ABSTRACT TRUNCATED AT 250 WORDS)

Intercellular signalling within vascular cells under high D-glucose involves free radical-triggered tyrosine kinase activation

“…Moreover, D-glucose-dependent · O 2 -release from porcine aortic SMC is in line with our previous report that the release of · O 2 -is enhanced in uterine arteries of diabetic patients [6]. The source of SMC · O 2 -and the mechanisms of its release under elevated D-glucose conditions are still a matter of debate, but NAD(P)H oxidase [29,30,31,32,33] and mitochondria [34,35] have been discussed frequently to contribute to increased · O 2 -production in diabetes [7]. Overall, recent literature and our present data suggest that under hyperglycaemic conditions · O 2 -release from SMC is augmented and affects EC function.…”

Angiotensin AT 1 receptor antagonism normalizes retinal blood flow and acetylcholine-induced vasodiliation in normotensive diabetic rats

“…The mechanisms that mediate these chronic effects of the AT 1 pathway on RBF likely involve the local production of factors that cause microvascular vasoconstriction. The AngII/AT 1 pathway has been shown to up-regulate a number of pathways that induced vasoconstriction, including endothelin-1 expression, superoxide ion production, and the DAG/PKC activation in a number of vascular tissues in diabetes [33,34,35,36,37]. Retinal DAG levels are increased in STZ-induced diabetic rats and elevation of DAG levels by treatment of NDM rats with a DAG kinase inhibitor reduces RBF in a manner similar to that observed in diabetes [28].…”

Association of the p22phox Component of NAD(P)H Oxidase With Susceptibility to Diabetic Nephropathy in Patients With Type 1 Diabetes

“…Consequently, it might be predicted that less NADPH was available as cofactor for NAD(P)H oxidase, but this might be counterbalanced by the increased abundance of NADH. The latter has been suggested as the preferred substrate for NAD(P)H oxidase, although there have been studies that suggest otherwise (10,11,(21)(22)(23). The flux through the entire polyol pathway and the build-up of NADH may be important rather than the single enzyme reactions.…”