Diabetes-induced Coronary Vascular Dysfunction Involves Increased Arginase Activity

Abstract

Abstract-Increases in arginase activity have been reported in a variety of disease conditions characterized by vascular dysfunction. Arginase competes with NO synthase for their common substrate arginine, suggesting a cause and effect relationship. We tested this concept by experiments with streptozotocin diabetic rats and high glucose (HG)-treated bovine coronary endothelial cells (BCECs). Our studies showed that diabetes-induced impairment of vasorelaxation to acetylcholine was correlated with increases in reactive oxygen species and arginase activity and arginase I expression in aorta and liver. Treatment of diabetic rats with simvastatin (5 mg/kg per day, subcutaneously) or L-citrulline (50 mg/kg per day, orally) blunted these effects. Acute treatment of diabetic coronary arteries with arginase inhibitors also reversed the impaired vasodilation to acetylcholine. Treatment of BCECs with HG (25 mmol/L, 24 hours) also increased arginase activity. This effect was blocked by treatment with simvastatin (0.1 mol/L), the Rho kinase inhibitor Y-27632 (10 mol/L), or L-citrulline (1 mmol/L). Superoxide and active RhoA levels also were elevated in HG-treated BCECs. Furthermore, HG significantly diminished NO production in BCECs. Transfection of BCECs with arginase I small interfering RNA prevented the rise in arginase activity in HG-treated cells and normalized NO production, suggesting a role for arginase I in reduced NO production with HG. These results indicate that increased arginase activity in diabetes contributes to vascular endothelial dysfunction by decreasing L-arginine availability to NO synthase. (Circ Res. 2008;102:95-102.)Key Words: arginine Ⅲ coronary arteries Ⅲ diabetes Ⅲ endothelial nitric oxide synthase Ⅲ oxidative stress Ⅲ vascular endothelial function Ⅲ vasodilation V ascular dysfunction is a major cause of morbidity and mortality in diabetic patients. 1 The pathological process is characterized by impaired endothelial cell production of the vasodilator and antiplatelet adhesion factor NO and/or decreased NO bioavailability. NO is a major regulator of vascular tone and integrity. In endothelial cells, NO is produced by activity of endothelial NO synthase (eNOS) on its substrate L-arginine. Reduced availability of L-arginine to eNOS has been implicated in vascular dysfunction in diabetes and a variety of other disease conditions. Arginase, which metabolizes L-arginine to urea and ornithine, competes directly with NOS for L-arginine. Hence increases in arginase activity can decrease tissue and cellular arginine levels, reducing its availability to eNOS. 2 This may lead to decreased NO production and increased production of superoxide by eNOS. 3 Enhanced arginase activity has been implicated in a number of conditions characterized by vascular dysfunction, including diabetic erectile dysfunction, pulmonary hypertension, ischemia/reperfusion, atherosclerosis, and agingassociated endothelial dysfunction. 4 -9 During diabetes, impaired vascular function is closely associated with oxidative stress and v...

Endothelial dysfunction in rat adjuvant‐induced arthritis: Up‐regulation of the vascular arginase pathway

“…In contrast, nor-NOHA had no effect on ACh-induced relaxation in control rats. These findings indicate that increased arginase contributes to endothelial dysfunction, probably by limiting the L-arginine availability for NOS, as previously observed in animal models of cardiovascular diseases (19)(20)(21)(22)24). It is noteworthy that beyond its effect on vascular NO production, decreased L-arginine availability secondary to arginase up-regulation might theoretically contribute to the eNOS uncoupling recently identified in vessels of AIA rats (12).…”

“…Arginase uses L-arginine (the substrate of NOS) as substrate and can thereby limit the availability of L-arginine for NO synthesis. Consistent with this theory are the studies demonstrating that arginase inhibition enhanced NOmediated vasodilatory function under pathologic conditions such as aging, hypertension, diabetes, and atherosclerosis (19)(20)(21)(22)(23)(24). Therefore, inhibition of vascular arginase activity might represent a new pharmacologic strategy for increasing availability of arginine for NO synthesis in conditions associated with endothelial dysfunction.…”

“…Because NOS and arginase use L-arginine as a common substrate, arginase may down-regulate NO biosynthesis by competing with NOS for L-arginine degradation. Consistent with this hypothesis, increased vascular arginase activity was reported to contribute to decreased endotheliumdependent NO production in pathologic conditions such as hypertension (19,20), atherosclerosis (21), diabetes (22), and erectile dysfunction (23), or in aging (24). Moreover, even though the regulating factors of arginase expression/activity remain largely unknown, it was demonstrated that various proinflammatory cytokines can act as inducers of arginase expression in cultured endothelial cells (18,25,26).…”

“…See Figure 5 for definitions. ment of reactive oxygen species and NO produced by inducible NOS (iNOS) in arginase up-regulation (22,(45)(46)(47). Since aortas from AIA rats were reported to overproduce O 2 Ϫ (12,13) and to exhibit increased iNOS expression (36), the contribution of these species cannot be excluded.…”

Diabetes-induced peroxynitrite impairs the balance of pro-nerve growth factor and nerve growth factor, and causes neurovascular injury

“…Retinal homogenate was immobilised on to a nitrocellulose membrane that Rho kinase activity Rho kinase activity was assessed by pulldown assay. As previously described, retinas were homogenised in assay buffer [17]. Bound Rho proteins were detected by western blot using anti-RhoA antibody (Millipore).…”