Phenotype modulation in cultures of vascular smooth muscle cells from diabetic rats: Association with increased nitric oxide synthase expression and superoxide anion generation

Abstract

Proliferative modification of vascular smooth muscle cell (vSMC) and impaired bioavailability of nitric oxide (NO) have both been proposed among the mechanisms linking diabetes and atherosclerosis. However, diabetes induced modifications in phenotype and nitric oxide synthase(s) (NOS) expression and activity in vSMC have not been fully characterized. In this study, cell morphology, proliferative response to serum, alpha-SMactin levels, eNOS expression and activity, cGMP intracellular content, and superoxide anion release were measured in cultures of vSMC obtained from aorta medial layer of ten diabetic (90% pancreatectomy, DR) and ten control (sham surgery, CR) rats. Vascular SMC from DR showed a less evident "hill and valley" culture morphology, increased growth response to serum, greater saturation density, and lower levels of alpha-SMactin. In the same cells, as compared to CR cells, eNOS mRNA levels and NOS activity were increased, while intracellular cGMP level was lower and superoxide anion production was significantly greater. These data indicate that chronic hyperglycemia might induce, in the vascular wall, an increased number of vSMC proliferative clones which persist in culture and are associated with increased eNOS expression and activity. However, upregulation of eNOS and increased NO synthesis occur in the presence of a marked concomitant increase of O(2-) production. Since NO bioavailability, as reflected by cGMP levels, was not increased in DR cells, it is tempting to hypothesize that the proliferative phenotype observed in DR cells is associated with a redox imbalance responsible quenching and/or trapping of NO, with the consequent loss of its biological activity.

Oxygen‐derived free radicals mediate endothelium‐dependent contractions in femoral arteries of rats with streptozotocin‐induced diabetes

“…This interpretation is consistent with the augmented DCF fluorescence observed. Taken together, the present findings thus confirm an increased generation of reactive oxygen species, in particular hydrogen peroxide, in diabetes (Karasu, 1999;Pandolfi et al, 2003).…”

Altered PDGF-BB–Induced p38 MAP Kinase Activation in Diabetic Vascular Smooth Muscle Cells

“…25 Pandolfi et al reported that the proliferative characteristics is observed in diabetic VSMCs between 4 and 8 passages and the properties are associated with a redox imbalance responsible quenching and/or trapping of nitric oxide by glucose and its related metabolites. 26 These findings may support the possibility that diabetes can bring about some phenotypic change in VSMCs. As one consequence of the phenotypic change in diabetic VSMCs, as shown in another report, 27 the level of the PDGF ␤-receptor was remarkably enhanced compared with that in normal rat cells.…”

The intermediate-conductance calcium-activated potassium channel KCa3.1 contributes to atherogenesis in mice and humans

“…The therapy significantly reduced superoxide production compared with vehicle treatment ( Figure 9K), consistent with its inhibition of superoxide production in activated VSMCs ( Figure 5D). Because ECs contribute only 10% of total superoxide generated in whole vascular walls in aortas of Apoe -/-mice (32), the inhibitory effect is most likely due to suppression of superoxide production by VSMCs and macrophages (8,28,31). Thus, TRAM-34 and clotrimazole may decrease atherosclerosis and the necrotic area by inhibiting VSMCs, macrophages, and T cells.…”