Aims/hypothesis: Increased oxidative stress in vascular smooth muscle cells (VSMCs) has been implicated in the pathogenesis of accelerated atherosclerosis in patients with diabetes mellitus. Uncoupling protein 2 (UCP-2) is an important regulator of intracellular reactive oxygen species (ROS) production. We hypothesised that UCP-2 functions as an inhibitor of the atherosclerotic process in VSMCs. Methods: Overexpression of human UCP-2 was performed in primary cultured human VSMCs (HVSMCs) via adenovirus-mediated gene transfer. Its effects on ROS production, AP-1 activity, plasminogen activator inhibitor 1 (PAI-1) gene expression, and cellular proliferation and migration were measured in response to high glucose and angiotensin II (Ang II) concentrations, two major factors in the pathogenesis of atherosclerosis in patients with diabetes and hypertension. Mitochondrial membrane potential and NAD(P)H oxidase activity were also measured. Results: High glucose and Ang II caused transient mitochondrial membrane hyperpolarisation. They also significantly stimulated ROS production, NAD(P)H oxidase activity, mitochondrial membrane potential, AP-1 activity, PAI-1 mRNA expression, and proliferation and migration of HVSMCs. Adenovirus-mediated transfer of the UCP-2 gene reversed all of these effects. Conclusions/interpretation: The present study demonstrates that UCP-2 can modify atherosclerotic processes in HVSMCs in response to high glucose and Ang II. Our data suggest that agents increasing UCP-2 expression in vascular cells may help prevent the development and progression of atherosclerosis in patients with diabetes and hypertension.
Vascular complications of diabetes represent the leading cause of morbidity and mortality in affected patients. Production of reactive oxygen species is increased in diabetic patients, especially in those with poor glycemic control. Reactive oxygen species affect vascular smooth muscle cell growth and migration, endothelial function, including abnormal endothelium-dependent relaxation and expression of a proinflammatory phenotype, and modification of the extracellular matrix. All of these events contribute to the development of diabetic microvascular and macrovascular complications, suggesting that the sources of reactive oxygen species and the signaling pathways that they modify may represent important therapeutic targets.
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