Insulin-Stimulated Hydrogen Peroxide Increases Guanylate Cyclase Activity in Vascular Smooth Muscle

Abstract

Abstract-Insulin resistance is associated with vascular disease. Physiological concentrations of insulin inhibit cultured vascular smooth muscle cell (VSMC) contraction and migration by increasing nitric oxide (NO)-stimulated cGMP accumulation. The failure to do so in insulin-resistant states may aggravate vascular disease. We sought to determine the mechanism of insulin's increase in cGMP accumulation. Isobutylmethylxanthine, an inhibitor of phosphodiesterase activity, inhibited the decline in cGMP levels measured by immunoassay in cGMP-loaded cultured rat aortic VSMCs, but 1 nmol insulin did not. Thus, insulin's increase in cGMP accumulation is due to stimulated production, not inhibited hydrolysis and/or efflux. Insulin, which increases the NADH/NAD ϩ ratio in these cells, stimulated superoxide anion (O 2 -) accumulation measured by lucigenin luminescence to 256Ϯ25% (PϽ0.05) by a process that was blocked by the NADH oxidase inhibitor diphenyliodonium (DPI) and enhanced by the superoxide dismutase inhibitor diethyldithiocarbonate (DETCA). Insulin also stimulated hydrogen peroxide (H 2 O 2 ) accumulation measured by horseradish peroxidase/luminol luminescence to 221Ϯ22% (PϽ0.05) by a DETCA-sensitive mechanism. H 2 O 2 (100 mol/L) in the absence of insulin increased NO-stimulated cGMP accumulation to 151Ϯ11% (PϽ0.05). Insulin alone increased NO-stimulated cGMP accumulation to 183Ϯ17% (PϽ0.05), and this was blocked by either DPI or DETCA. We conclude that insulin increases NADH oxidase-derived O 2 -production in cultured rat VSMCs. This did not cause the expected scavenging of NO resulting in the reduction of NO-stimulated guanylate cyclase activity, but enough O 2 -was metabolized to H 2 O 2 to increase overall NO-stimulated cGMP production. Key Words: muscle, smooth, vascular Ⅲ insulin Ⅲ cyclic GMP Ⅲ nitric oxide A therosclerosis and restenosis after balloon catheter angioplasty are increased in insulin-resistant states. [1][2][3] Some studies support the view that hyperinsulinemia, which is present in these conditions, stimulates vascular smooth muscle cell (VSMC) migration and proliferation, thereby accelerating the pathological process. 4,5 Other data show that insulin can stimulate cGMP accumulation in normal cultured VSMCs 6,7 and that cGMP inhibits migration and proliferation of those cells. 8 -10 The latter data are consistent with the notion that insulin normally inhibits atherosclerosis and restenosis in vivo and that the functional lack of insulin in insulin-resistant states contributes to vascular disease.We have shown that insulin alone does not affect cGMP accumulation in cultured VSMCs, but when cGMP production is stimulated by a permissive amount of nitric oxide (NO), physiological concentrations of insulin increase the accumulation of cGMP. 6 We found that insulin stimulates glucose uptake and aerobic glycolysis in these cells and that the resultant increase in lactate is responsible for insulin's increase in NO-stimulated cGMP accumulation. 6,11,12 Increased lactate in VSMCs has been reported ...

High-dose insulin inhibits gap junction intercellular communication in vascular smooth muscle cells

“…H 2 O 2 is a stable component of reactive oxygen species in VSMCs and is also a second messenger for various stimulators in smooth muscle cells (44). The current study demonstrated that high-dose insulin could induce a release of H 2 O 2 , which is consistent with the conclusions drawn from previous studies (45). In addition, the inhibition of GJIC function by H 2 O 2 through the induction of Cx43 phosphorylation has been verified in various types of cells (46,47).…”

Mechanisms of vascular dysfunction in mice with endothelium-specific deletion of the PPAR-δ gene

“…Consistent with this interpretation, H 2 O 2 was not able to increase cGMP levels in endothelium-denuded arteries. In agreement with our observations, previous studies have reported that in vascular smooth muscle cells(54) or in endothelium-denuded arteries (23), H 2 O 2 did not affect the production of cGMP, again suggesting that the presence of an intact endothelium is required for H 2 O 2 to increase cGMP.…”

A Nitric Oxide Producing Pin-to-Hole Spark Discharge Plasma Enhances Endothelial Cell Proliferation and Migration

“…In previous studies, ROS (specifically hydrogen peroxide, H 2 O 2 ) increased NO-induced cGMP activity. 54 We demonstrated that PHD plasma-produced NO enhanced endothelial cell proliferation and migration but not tube formation. However, these studies are not without limitations.…”