Anti-atherogenic effects of the combination therapy with olmesartan and azelnidipine in diabetic apolipoprotein E-deficient mice.

Many studies have aimed to identify anti-atherogenic agents in cardiovascular medicine. We have recently demonstrated that the combination therapy with olmesartan (OLM), an angiotensin II receptor blocker, and azelnidipine (AZL), a dihydroprydine calcium-channel blocker, improves endothelial function in diabetic Apolipoprotein-deficient (ApoE(-/-)) mice. In the present study, we examined whether this combination therapy also inhibits atherosclerosis in mice. We used male control and streptozocin-induced diabetic ApoE(-/-) mice. Diabetic ApoE(-/-) mice were orally treated for 5 weeks with vehicle (Untreated), OLM (30 mg/kg/day), AZL (10 mg/kg/day), their combination (OLM+AZL), or hydralazine (HYD, 5 mg/kg/day) as an antihypertensive control. At 5 weeks, systolic blood pressure was significantly elevated in Untreated but was normalized in OLM+AZL and HYD. The atherosclerosis area in the thoracic aorta, perivascular fibrosis and medial thickness of the coronary arteries were increased in Untreated and were ameliorated in OLM+AZL but not in HYD. Staining with a fluorescent probe dihydroethidium showed that production of reactive oxygen species was increased in Untreated, and ameliorated in OLM+AZL. Consistent with these findings, macrophage infiltration in the kidney and the expression of receptor for advanced glycation end-products in the heart, kidney and liver were increased in Untreated and were all ameliorated in OLM+AZL, associated with up-regulation of endothelial NO syntheses (eNOS). In conclusion, the combination therapy with OLM and AZL exerts anti-atherogenic effect in diabetic ApoE(-/-) mice through suppression of oxidative stress and activation of eNOS, independent of its blood pressure-lowering effects. Clinically, this combination therapy may be useful for patients with hypertension, hyperlipidemia and diabetes.

Combination therapy with olmesartan and azelnidipine improves EDHF-mediated responses in diabetic apolipoprotein E-deficient mice.

BACKGROUND: The endothelium modulates vascular tone by synthesizing and releasing several vasodilating factors, including vasodilator prostaglandins, nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). In the present study, we examined whether an angiotensin-receptor blocker, a calcium-channel blocker or their combination improved EDHF-mediated responses in diabetic apolipoprotein E-deficient (ApoE(-/-)) mice. METHODS AND RESULTS: We used male C57BL/6N (control) and streptozocin-induced diabetic ApoE(-/-) mice. The diabetic ApoE(-/-) mice were administered oral vehicle (untreated), olmesartan (OLM, 30 mgxkg(-1)xday(-1)), azelnidipine (AZL, 10 mgxkg(-1)xday(-1)), their combination (OLM + AZL), or hydralazine (HYD 5 mgxkg(-1)xday(-1)) for 5 weeks. In the untreated group, systolic blood pressure was significantly higher and both EDHF-mediated relaxation and endothelium-dependent hyperpolarization were markedly reduced as compared with the control group. Although EDHF-mediated relaxation was not significantly improved in the HYD, OLM and AZL groups, it was significantly improved in the OLM + AZL group, as was also the case with phosphorylation of Akt and endothelial NO synthase (eNOS). In contrast, the endothelium-independent relaxation response to sodium nitroprusside or NS-1619 (a direct opener of K(Ca) channels) was unaltered in any group. CONCLUSIONS: OLM + AZL may improve the severely impaired EDHF-mediated responses in diabetic ApoE(-/-) mice, in which activation of the endothelial Akt - eNOS pathway may be involved.

Roles of endothelial oxidases in endothelium-derived hyperpolarizing factor responses in mice.

The endothelium synthesizes and releases several vasodilator substances, including prostacyclin, nitric oxide (NO), and endothelium-derived hyperpolarizing factor (EDHF). We have demonstrated that endothelium-derived hydrogen peroxide (H2O2) is an EDHF in animals and humans and that superoxide anions derived from endothelial nitric oxide synthases (NOSs) system are an important precursor for EDHF/H2O2 in mice. There are several intracellular sources of superoxide anions other than NOSs, including NAD(P)H oxidase, xanthine oxidase, lipoxygenase, and mitochondrial electron transport chain. In this study, we examined the possible role of endothelial oxidases other than NOSs in the EDHF-mediated responses. In angiotensin II-infused mice, both EDHF-mediated relaxations and hyperpolarizations to acetylcholine were significantly reduced, nitric oxide-mediated relaxations were rather enhanced, and vascular smooth muscle responses were preserved. Antihypertensive treatment normalized blood pressure but failed to improve EDHF-mediated responses in those mice. Acute inhibition of endothelial oxidases other than NOSs, including NAD(P)H oxidase, xanthine oxidase, lipoxygenase, or mitochondrial electron transport chain, had no inhibitory effects on EDHF-mediated responses. Furthermore, in p47phox-knockout mice, EDHF-mediated responses were unaltered. These results suggest that endothelial oxidases other than NOSs are not involved in EDHF/H2O2 responses in mice, suggesting a specific link between endothelial NOSs system and EDHF responses under physiological conditions.