Background— Elevated heart rate is associated with increased cardiovascular morbidity. We hypothesized that selective heart rate reduction may influence endothelial function and atherogenesis and tested the effects of the I (f) current inhibitor ivabradine in apolipoprotein E–deficient mice. Methods and Results— Male apolipoprotein E–deficient mice fed a high-cholesterol diet were treated with ivabradine (10 mg · kg −1 · d −1 ) or vehicle for 6 weeks (n=10 per group). Ivabradine reduced heart rate by 13.4% (472±9 versus 545±11 bpm; P <0.01) but did not alter blood pressure or lipid levels. Endothelium-dependent relaxation of aortic rings was significantly improved in ivabradine-fed animals ( P <0.01). Ivabradine decreased atherosclerotic plaque size in the aortic root by >40% and in the ascending aorta by >70% ( P <0.05). Heart rate reduction by ivabradine had no effect on the number of endothelial progenitor cells and did not alter aortic endothelial nitric oxide synthase, phosphorylated Akt, vascular cell adhesion molecule-1, or intercellular adhesion molecule-1 expression but decreased monocyte chemotactic protein-1 mRNA and exerted potent antioxidative effects. Ivabradine reduced vascular NADPH oxidase activity to 48±6% and decreased markers of superoxide production and lipid peroxidation in the aortic wall ( P <0.05). The in vivo effects of ivabradine were absent at a dose that did not lower heart rate, in aortic rings treated ex vivo, and in cultured vascular cells. In contrast to ivabradine, treatment with hydralazine (25 mg · kg −1 · d −1 for 6 weeks) reduced blood pressure (−15%) but increased heart rate (37%) and did not improve endothelial function, atherosclerosis, or oxidative stress. Conclusions— Selective heart rate reduction with ivabradine decreases markers of vascular oxidative stress, improves endothelial function, and reduces atherosclerotic plaque formation in apolipoprotein E–deficient mice.

The Rho/Rho-associated coiled-coil forming kinases (ROCKs) are important regulators of the actin cytoskeleton. Because changes in the actin cytoskeleton underlie vascular contractility and remodeling, inflammatory cell recruitment, and cellular proliferation, it is likely that the Rho/ ROCK pathway will play a central role in mediating vascular function. Indeed, increased ROCK activity is observed in cerebral and coronary vasospasm, hypertension, vascular inflammation, arteriosclerosis, and atherosclerosis. Recent experimental and clinical studies suggest that inhibition of ROCK could be a promising target for the treatment of cardiovascular disease. For example, inhibition of ROCK might be the underlying mechanism by which statins or HMG-CoA reductase inhibitors exert their therapeutic benefits beyond cholesterol reduction. In this review, we provide a current understanding of the critical role of RhoA/ROCK pathway in the regulation of vascular function and discuss its therapeutic potential in the treatment of atherosclerosis and vascular disease.

OBJECTIVE-Peroxisome proliferator-activated receptor-␥ (PPAR␥) agonists (thiazolidinediones [TZDs]) are used for the treatment of diabetes. Bone marrow-derived endothelial progenitor cells (EPCs) improve vascular function and predict cardiovascular risk. The effect of pioglitazone therapy on EPCs was examined. RESEARCH DESIGN AND METHODS AND RESULTS-Weperformed a prospective, randomized, double-blind study on patients with documented stable coronary artery disease and normal glucose tolerance. Of 54 patients with normal fasting glucose levels, 18 showed impaired glucose tolerance and 36 patients with normal glucose tolerance were randomized to 30-day treatment with pioglitazone (45 mg) or placebo in addition to optimal medical therapy. All patients in the TZD group showed an increase of adiponectin levels as an indicator of compliance (11.4 Ϯ 1.1 to 36.8 Ϯ 2.1 g/ml; P Ͻ 0.001). TZD, but not placebo, decreased mean high-sensitivity C-reactive protein to 43 Ϯ 19% (P Ͻ 0.05). Pioglitazone increased CD34 ϩ /kinase insert domain receptor ϩ EPCs to 142 Ϯ 9% and cultured 1,1Ј-dioctadecyl-3,3,3Ј,3Ј-tetramethylindocarbocyanine-labeled acetylated LDL ϩ / lectin ϩ EPCs to 180 Ϯ 3% (P Ͻ 0.05). EPC numbers were not changed in the placebo group. TZD increased the SDF-1-induced migratory capacity to 146 Ϯ 9% per EPC number (P Ͻ 0.05) and upregulated the clonogenic potential of EPCs, increasing the colony-forming units to 172 Ϯ 12% (P Ͻ 0.001). In cultured human EPCs, TZD increased EPC numbers and migration and reduced NADPH-oxidase activity. The TZD effect was reversed by the PPAR␥ antagonist GW9662 and mimicked by treatment with adiponectin.CONCLUSIONS-The PPAR␥ agonist pioglitazone increases the number and function of EPCs in patients with coronary artery disease. The effect represents a potential regenerative mechanism in atherosclerosis and is observed in normoglycemic individuals with stable coronary artery disease.

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