Direct Endothelial Nitric Oxide Synthase Activation Provides Atheroprotection in Diabetes-Accelerated Atherosclerosis

Abstract

Patients with diabetes have an increased risk of developing atherosclerosis. Endothelial dysfunction, characterized by the lowered bioavailability of endothelial NO synthase (eNOS)-derived NO, is a critical inducer of atherosclerosis. However, the protective aspect of eNOS in diabetes-associated atherosclerosis remains controversial, a likely consequence of its capacity to release both protective NO or deleterious oxygen radicals in normal and disease settings, respectively. Harnessing the atheroprotective activity of eNOS in diabetic settings remains elusive, in part due to the lack of endogenous eNOS-specific NO release activators. We have recently shown in vitro that eNOS-derived NO release can be increased by blocking its binding to Caveolin-1, the main coat protein of caveolae, using a highly specific peptide, CavNOxin. However, whether targeting eNOS using this peptide can attenuate diabetes-associated atherosclerosis is unknown. In this study, we show that CavNOxin can attenuate atherosclerotic burden by ∼84% in vivo. In contrast, mice lacking eNOS show resistance to CavNOxin treatment, indicating eNOS specificity. Mechanistically, CavNOxin lowered oxidative stress markers, inhibited the expression of proatherogenic mediators, and blocked leukocyte-endothelial interactions. These data are the first to show that endogenous eNOS activation can provide atheroprotection in diabetes and suggest that CavNOxin is a viable strategy for the development of antiatherosclerotic compounds.Diabetes is widely regarded as an independent risk factor for the development of cardiovascular diseases, with ;80% of cardiovascular mortality and morbidity being linked to macrovascular complications, such as atherosclerosis (1-3). The increased risk of development of vascular complications in individuals with type 1 (T1D) or type 2 diabetes (T2D) occurs despite intensive glycemic control, stressing the need for novel approaches to lessen the burden of diabetes-mediated macrovascular injury (4).The vascular endothelium plays a crucial role in diabetesassociated atherosclerosis through the regulation of vessel permeability, inflammation, coordination of leukocyte trafficking, and thrombosis (1,5). Indeed, the function of the vascular endothelium is significantly impaired during diabetes, a phenomena termed endothelial dysfunction and characterized by the reduced bioavailability of an important endothelial cell mediator, nitric oxide (NO). Such chronic attenuation of endothelial-derived NO release promotes platelet and leukocyte activation and adhesion, compromises endothelial cell barrier integrity, and causes the upregulation of proinflammatory genes (6-8). Moreover, reduced NO-dependent vasodilation and increased leukocyte adhesion to the endothelium, both of which are hallmarks of endothelial dysfunction, have been observed in patients with diabetes and diabetic animal models (9-12). Similarly, in cultured endothelial cells exposed to high glucose, lowered endothelial NO synthase (eNOS)-derived NO release was observed (13-15). In...

Uncoupling Caveolae From Intracellular Signaling In Vivo

“…These data complement data on the peptide cavnoxin (a cell penetrating caveolin peptide with contains 3 point mutations atT90A, T91A and F92A 20, 35 ) and highlights the significance of F92 for the inhibitory action of Cav-1 on eNOS function. As neither the histological analysis nor the echocardiography showed any signs of cardiac hypertrophy or fibrosis in heart and lung, we surmise that prolonged therapeutic treatment with cavnoxin or similar acting small molecule could lead to a new class of therapeutics to improve endothelial dysfunction.…”

Metformin Suppresses Diabetes-Accelerated Atherosclerosis via the Inhibition of Drp1-Mediated Mitochondrial Fission

“…Genetic deletion and pharmacological inhibition of Nox1 decreases atherosclerotic lesion formation in STZ-injected diabetic ApoE −/− mice (51). In addition, eNOS activation protects against diabetes-accelerated atherosclerosis in STZ-injected diabetic ApoE −/− mice (52). Therefore, whether enhanced mitochondrial fission triggers other ROS sources, such as Nox1, Nox2, Nox4, and eNOS uncoupling, requires further examination.…”

Contemporary Approaches to Modulating the Nitric Oxide–cGMP Pathway in Cardiovascular Disease

“…Cavnoxin increases NO levels reduces vascular tone and lowers the mean blood pressure in wild-type mice, an effect lost in either eNOS-KO or CAV1-KO animals suggestions specificity for the inhibitory clamp of CAV1 60 . Chronic cavnoxin administration reduces atherosclerosis in ApoE-KO mice fed a Western diet as well as in diabetic, atherosclerotic mice 62 and again, the loss of eNOS genetically attenuates the actions of cavnoxin. These two studies imply that cavnoxin can reduce the inhibitory effect of caveolin on eNOS function, allowing for enhancement of endogenous NO biosynthesis.…”