The present study to address one of the mechanisms in preeclampsia, examined whether levels of oxidative stress, human serum albumin, and endothelial function correlate in pregnant women and whether human serum albumin reduces levels of superoxide produced by NADPH oxidase activation in the human vascular smooth muscle cells. Pregnant women with (Preeclampsia group, n = 33) and without preeclampsia (Normal group, n = 37) were recruited to determine levels of reactive oxygen species (serum diacron-reactive oxygen metabolite [d-ROM]), and the flow-mediated dilation (FMD). Human coronary arterial smooth muscle cells or omental arteries were subjected to evaluate isometric force recordings, levels of superoxide, western immunoblotting, and immunohistochemistry. The superoxide scavenging assay was also performed in a cell-free system. Women in the preeclampsia group demonstrated lower FMD and higher serum d-ROM values than those in the normal group. There were the inverse correlations between serum levels of d-ROM and the degree of FMD and between serum levels of albumin and those of d-ROM. D-glucose reduced the levcromakalim-induced dilation of human omental arteries, and it increased levels of superoxide and the recruitment of the NADPH oxidase subunit p47phox in human coronary arterial smooth muscle cells. Human serum albumin (0.05 to 0.5 g/dL) prevented these alterations whereas it exerted no superoxide scavenging effect. Serum albumin relates to oxidative stress inversely, but to the endothelial function positively, in pregnant women. Human serum albumin appears to reduce oxidative stress via NADPH oxidase inhibition in the human vascular smooth muscle, indicating that the serum level may be a critical determinant of vascular oxidative stress in some human diseases.

The present study was designed to examine roles of the phosphatidylinositol 3-kinase-Akt pathway and reduced nicotinamide-adenine dinucleotide phosphate oxidases in the reduced ATP-sensitive K ⁺ channel function via superoxide produced by high glucose in the human artery. We evaluated the activity of the phosphatidylinositol 3-kinase-Akt pathway, as well as reduced nicotinamide-adenine dinucleotide phosphate oxidases, the intracellular levels of superoxide and ATP-sensitive K ⁺ channel function in the human omental artery without endothelium. Levels of the p85-α subunit and reduced nicotinamide-adenine dinucleotide phosphate oxidase subunits, including p47phox, p22phox, and Rac-1, increased in the membrane fraction from arteries treated with d -glucose (20 mmol/L) accompanied by increased intracellular superoxide production. High glucose simultaneously augmented Akt phosphorylation at Ser 473, as well as Thr 308 in the human vascular smooth muscle cells. A phosphatidylinositol 3-kinase inhibitor LY294002, as well as tiron and apocynin, restored vasorelaxation and hyperpolarization in response to an ATP-sensitive K ⁺ channel opener levcromakalim. Therefore, it can be concluded that the activation of the phosphatidylinositol 3-kinase-Akt pathway, in combination with the translocation of p47phox, p22phox, and Rac-1, contributes to the superoxide production induced by high glucose, resulting in the impairment of ATP-sensitive K ⁺ channel function in the human visceral artery.

Objective— The present study was designed to examine in the human omental artery whether high concentrations of D-glucose inhibit the activity of ATP-sensitive K ⁺ channels in the vascular smooth muscle and whether this inhibitory effect is mediated by the production of superoxide. Methods and Results— Human omental arteries without endothelium were suspended for isometric force recording. Changes in membrane potentials were recorded and production of superoxide was evaluated. Glibenclamide abolished vasorelaxation and hyperpolarization in response to levcromakalim. D-glucose (10 to 20 mmol/L) but not l -glucose (20 mmol/L) reduced these vasorelaxation and hyperpolarization. Tiron and diphenyleneiodonium, but not catalase, restored vasorelaxation and hyperpolarization in response to levcromakalim in arteries treated with D-glucose. Calphostin C and Gö6976 simultaneously recovered these vasorelaxation and hyperpolarization in arteries treated with D-glucose. Phorbol 12-myristate 13 acetate (PMA) inhibited the vasorelaxation and hyperpolarization, which are recovered by calphostin C as well as Gö6976. D-glucose and PMA, but not l -glucose, significantly increased superoxide production from the arteries, whereas such increased production was reversed by Tiron. Conclusions— These results suggest that in the human visceral artery, acute hyperglycemia modulates vasodilation mediated by ATP-sensitive K ⁺ channels via the production of superoxide possibly mediated by the activation of protein kinase C.

Background: Vascular dysfunction induced by hyperglycemia has not been studied in cerebral parenchymal circulation. The current study was designed to examine whether high glucose impairs dilation of cerebral parenchymal arterioles via nitric oxide synthase, and whether propofol recovers this vasodilation by reducing superoxide levels in the brain. Methods: Cerebral parenchymal arterioles in the rat brain slices were monitored using computer-assisted videomicroscopy. Vasodilation induced by acetylcholine (10 to 10 m) was obtained after the incubation of brain slices for 60 min with any addition of l-glucose (20 mm), d-glucose (20 mm), or propofol (3 x 10 or 10 m) in combination with d-glucose (20 mm). Superoxide production in the brain slice was determined by dihydroethidium (2 x 10 m) fluorescence. Results: Addition of d-glucose, but not l-glucose, reduced arteriolar dilation by acetylcholine, whereas the dilation was abolished by the neuronal nitric oxide synthase inhibitor S-methyl-l-thiocitrulline (10 m). Both propofol and the superoxide dismutase mimetic Tempol (10 m) restored the arteriolar dilation in response to acetylcholine in the brain slice treated with d-glucose. Addition of d-glucose increased superoxide production in the brain slice, whereas propofol, Tempol, and the nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase inhibitor apocynin (1 mm) similarly inhibited it. Conclusions: Clinically relevant concentrations of propofol ameliorate neuronal nitric oxide synthase-dependent dilation impaired by high glucose in the cerebral parenchymal arterioles via the effect on superoxide levels. Propofol may be protective against cerebral microvascular malfunction resulting from oxidative stress by acute hyperglycemia.

The effects of oxygen free radical scavengers and endothelial cell‐derived nitric oxide (EDNO) on the death of porcine cultured aortic endothelial cells exposed to exogenous superoxide‐ [xanthine (0.4 mM)/xanthine oxidase (0.04 unit ml⁻¹) + diethylenetriaminepentaacetic acid (DTPA, 10 μm)] or hydroxyl radical‐generating system(s) [superoxide generating system + ferric iron (Fe³⁺, 0.1 mM) or peroxynitrite (0–100 μm)] have been evaluated. Spin trapping studies using 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO) with electron paramagnetic resonance spectrometry were also conducted to determine qualitatively the oxidant species generated by the oxidant generating systems. Endothelial cell injury provoked by the exogenous superoxide generating system was inhibited by catalase, DTPA and a hydroxyl radical scavenger (dimethyl sulphoxide, DMSO), but not by superoxide dismutase (SOD). Addition of Fe³⁺ to the superoxide generating system enhanced the cell injury. These suggested that the direct cytotoxicity of exogenous superoxide is limited, and that endogenous transition metal‐dependent hydroxyl radical formation is involved in the cell injury. An inhibitor of the constitutive NO‐pathway, N^G‐monomethyl‐L‐arginine, did not influence cell injury induced by the superoxide generating system, suggesting that basal NO production is not responsible for the cytotoxicity. Stimulation of endothelial cells with bradykinin enhanced cell injury provoked by the exogenous superoxide generating system, but not by the exogenous hydroxyl radical generating system. The enhancement by bradykinin was inhibited by N^G‐monomethyl‐L‐arginine and bradykinin B₂‐receptor antagonist, D‐Arg‐[Hyp³, Thi^{5, 8}, D‐Phe⁷] bradykinin, suggesting that an interaction of NO with superoxide is involved in the enhanced cytotoxicity. A possible intermediate of this reaction, peroxynitrite, also caused endothelial cell injury in a concentration‐dependent manner. The modulatory effects of NO on hydroxyl radical‐like activity (= formaldehyde production) from the superoxide generating system was also evaluated in a cell‐free superoxide/NO generating system, consisting of xanthine/xanthine oxidase, DTPA, DMSO, and various amounts of a spontaneous NO generator, sodium nitroprusside (SNP) and were compared with those of Fe³⁺. At doses up to 10 μm, SNP concentration‐dependently increased the formaldehyde production while the higher concentrations of SNP decreased. The maximum amount of formaldehyde produced by SNP was 5 fold less than that produced by Fe³⁺ (0.1 mM). Peroxynitrite‐induced formaldehyde formation was concentration‐dependently inhibited by SNP. We conclude that agonist‐stimulated but not basal NO production acts as cytotoxic hydroxyl radical donor as well as the endogenous transition metal when endothelial cells are exposed to exogenous superoxide anion, while the modulatory effect of EDNO is limited by a secondary reaction with hydroxyl radicals.