Heart rate reduction with ivabradine improves erectile dysfunction in parallel to decrease in atherosclerotic plaque load in ApoE-knockout mice.

OBJECTIVE: To determine the effect of heart rate reduction with ivabradine on atherosclerotic lesions and erectile dysfunction. METHODS: Two different treatment regimes with ivabradine were applied in wild-type (C57/B6) and ApoE(-/-)-mice to study effects of ivabradine on erectile function and atherosclerosis in animals with and without present endothelial dysfunction. Preventive effects of ivabradine were evaluated in animals fed a high-cholesterol diet in parallel to treatment with ivabradine (orally via chow, 10 mg/kg per day). The other treatment regime started treatment with a high-cholesterol diet for 4 weeks to induce endothelial dysfunction. Thereafter, treatment with ivabradine (orally via chow, 15 mg/kg per day) was started in ApoE(-/-) mice for 3 months. Vital parameters were measured using the tail-cuff method. Erectile function was assessed by pharmacological stimulation of corpora cavernosa in organ bath chambers. Atherosclerotic plaque formation, oxidative stress, eNOS and collagen content were determined. RESULTS: Treatment with ivabradine significantly reduced heart rate (p<0.01), with no effect on blood pressure. Aortic atherosclerotic lesion size decreased with ivabradine in both treatment regimes (p<0.05). Endothelium-dependent relaxation of corpora cavernosa significantly decreased in ApoE(-/-)-mice with a restoration by ivabradine in prevention and reversal. Dihydroethidium-stained penile sections (p<0.05) and lipid peroxidase assay (p<0.05) revealed a reduction in superoxide production in ivabradine-treated animals. Penile eNOS-expression increased and collagen content significantly decreased (p<0.01) in ivabradine-treated animals. CONCLUSION: Ivabradine improves penile endothelial function by reduction of oxidative stress and penile fibrosis. Beneficial effects were achieved in prevention and manifest endothelial dysfunction.

[Erectile dysfunction: indicator of end-organ damage in cardiovascular patients]. / Erektile Dysfunktion: Indikator für Endorganschädigung beim kardiovaskulären Patienten.

Prevalence of erectile dysfunction (ED) amounts to 20-30% in a general population and increases to 50-70% in cardiovascular high-risk patients. Association of ED with known cardiovascular risk factors is causal with endothelial function of penile vessels and corpora cavernosa playing a crucial role in physiology of erection. Moreover, severity of ED correlates with cardiovascular risk of patients and represents an early symptom of generalized atherosclerosis. Hence, cardiovascular risk factors and diseases are sooner diagnosed in patients with ED with the opportunity of risk-adjusted prevention. Furthermore, different trials suggest erectile function as a strong predictor of cardiovascular events like myocardial infarction or stroke.

Improvement of endothelial function of the corpus cavernosum in apolipoprotein E knockout mice treated with irbesartan.

Angiotensin receptor blockers enhance endothelial function and are suggested to improve erectile function. The effects and underlying mechanisms of treatment with the angiotensin receptor blocker irbesartan on penile endothelial function in apolipoprotein E (ApoE)(-/-) mice were determined. Wild-type (C57/B6) and ApoE(-/-) mice were fed with a high-fat, cholesterol-rich diet for 7 weeks and treated with irbesartan (50 mg/kg . day) or hydralazine (250 mg/l). Vital parameters were measured with the tail-cuff method. Endothelial (aortic rings) and erectile function (corpora cavernosa) were assessed by pharmacological stimulation in an organ bath chamber. Oxidative stress and angiotensin receptor expression were determined. Blood pressure was significantly decreased in irbesartan- and hydralazine-treated ApoE(-/-) mice (p < 0.05) compared with controls and wild-type mice. Endothelial function of the aorta and corpus cavernosum was significantly impaired in ApoE(-/-) mice (p < 0.05) and could be restored by treatment with irbesartan (p < 0.05). Consistently, nitric oxide production of corpora cavernosa was impaired in ApoE(-/-) mice (p < 0.01), with a restoration in irbesartan- but not hydralazine-treated mice. Dihydroethidium-stained sections and lipid peroxidase assay revealed a reduction of superoxide production in irbesartan (p < 0.05) compared with hydralazine-treated and control ApoE(-/-) mice. In summary, irbesartan improves penile endothelial function in ApoE(-/-) mice by reduction of vascular and cavernosal oxidative stress. This result emphasizes the beneficial effect of inhibition of the renin-angiotensin system even in terms of erectile function.

Heart rate reduction by ivabradine reduces oxidative stress, improves endothelial function, and prevents atherosclerosis in apolipoprotein E-deficient mice.

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.

Nebivolol, but not metoprolol, improves endothelial function of the corpus cavernosum in apolipoprotein e-knockout mice.

To determine the effects and underlying mechanisms of treatment with the beta-receptor blockers nebivolol and metoprolol on penile endothelial function in apolipoprotein E (ApoE)-/- mice, wild-type (WT) and ApoE-/- mice were fed with a cholesterol-rich diet for 7 weeks. ApoE-/- mice were treated with nebivolol (10 mg/kg/day) or metoprolol (90 mg/kg/day). Endothelial function of aortic and corpora cavernosal tissue was assessed by pharmacological stimulation with carbachol (endothelium dependent) or glycerol trinitrate (endothelium independent) in organ bath experiments. Atherosclerotic lesion formation was evaluated with oil-red staining, and modulation of reactive oxygen species (ROS) production was determined with lipid peroxidation. Heart rate, but not blood pressure, was decreased in nebivolol- and metoprolol-treated ApoE-/- mice (p < 0.01) compared with controls and WT mice without significant intergroup differences. Atherosclerotic lesion formation in the aortic root was increased in ApoE-/- mice (p < 0.01) with a more significant improvement in nebivolol- (p < 0.01) compared with metoprolol-treated mice (p < 0.05). Endothelium-dependent relaxation of the corpora cavernosa was significantly impaired in ApoE-/- mice (p < 0.05), which improved in nebivolol- versus metoprolol-treated mice. Efficacy of endothelium-dependent relaxation was comparable in aortic and penile tissue. Quantification of ROS production via lipid peroxidation revealed a significant reduction of superoxide anion production in nebivolol-treated (p < 0.05) but not metoprolol-treated mice compared with ApoE-/- controls. Nebivolol improves penile endothelial function as a surrogate of erectile function in ApoE-/- mice. These effects may be related to a reduction of ROS production, which is independent of heart rate reduction, because metoprolol did not increase endothelial function.