Effect of eplerenone on endothelial progenitor cells and oxidative stress in ischemic hindlimb.

BACKGROUND: We have demonstrated that angiotensin II receptor blocker (ARB) improved endothelial progenitor cells (EPCs) dysfunction through the antioxidative mechanism. Therefore, we investigate whether the selective mineralocorticoid receptor (MR) antagonist eplerenone improves EPCs function in rat hindlimb ischemia. METHODS: Unilateral hindlimb ischemia was surgically induced in Wistar rats. After induced ischemia, rats received eplerenone (30 mg/kg/day), valsartan (3 mg/kg/day), or vehicle for 3 weeks. Peripheral blood mononuclear cells were isolated, subjected to flow cytometric analysis to determine the number of circulating EPCs, cultured to assay EPC colony formation, and subjected to a migration chamber assay to evaluate EPCs migration. RESULTS: Blood perfusion by laser Doppler image was significantly higher in eplerenone than in vehicle. Capillary density by isolectin B4 stained of ischemic muscle was significantly increased in eplerenone compared with vehicle. Eplerenone significantly increased the number, colony formation, and migration of EPCs. Levels of endothelial nitric oxide synthase (eNOS) and angiogenic factor such as vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), and angiopoietin-2 (Ang-2) protein expression by western blot were significantly higher in eplerenone than in vehicle. Eplerenone significantly decreased the NAD(P)H oxidase p22(phox), p47(phox), gp91(phox) and MR expression and expression of aldosterone effector kinase serum and glucocorticoid-induced protein kinase 1 (Sgk1). These effects of eplerenone are similar extent as valsartan. CONCLUSIONS: This study showed that eplerenone improves the proliferation and function of EPCs in rat hindlimb ischemia, suggesting that eplerenone may provide a novel and effective therapeutic strategy for the repair of cardiovascular diseases.

Cardioprotective effects of pitavastatin on cardiac performance and remodeling in failing rat hearts.

BACKGROUND: Activation of phosphatidylinositol 3-kinase (PI3K)-Akt signaling by statins increases the activity of endothelial nitric oxide synthase (eNOS). We investigate whether statins (pitavastatin) improve cardiac function and remodeling via eNOS production associated with the PI3K-Akt signaling pathway, Rho-kinase (ROCK) pathway, and the development of oxidative stress in Dahl salt-sensitive (DS) hypertensive rats with heart failure (DSHF). METHODS: Pitavastatin (3 mg/kg per day), or pitavastatin plus specific PI3K inhibitor, wortmannin (1 mg/kg per day), or wortmannin alone were administered from the age of 11-18 weeks. Age-matched male Dahl salt-resistant (DR) rats served as a control group. RESULTS: Decreased end-systolic elastance (Ees) and percent fractional shortening (%FS) in failing rats was significantly ameliorated by pitavastatin, but not pitavastatin plus wortmannin or wortmannin alone. Upregulation of eNOS and Akt phosphorylation by pitavastatin was suppressed by pitavastatin plus wortmannin or wortmannin alone. Pitavastatin effectively inhibited the vascular lesion formation such as medial thickness and perivascular fibrosis, but not pitavastatin plus wortmannin or wortmannin alone. Activated RhoA and myosin light chain phosphorylation and RhoA, ROCK expression was inhibited by pitavastatin or a specific ROCK inhibitor, Y-27632, and downregulated eNOS expression and Akt phosphorylation was ameliorated by Y-27632. Increased expression of NAD(P)H oxidase subunits and activated p65 nuclear factor (NF)-kappaB, p44/p42 extracellular signal-regulated kinases and its downstream effector p90 ribosomal S6 kinase phosphorylation in failing rat hearts was inhibited by pitavastatin. CONCLUSIONS: These findings suggest that pitavastatin may improve cardiac function and remodeling via eNOS production associated with the PI3K-Akt signaling pathway, the ROCK pathway and oxidative stress.

Cardioprotective mechanism of telmisartan via PPAR-gamma-eNOS pathway in dahl salt-sensitive hypertensive rats.

BACKGROUND: Recently, some investigators have shown that telmisartan, an angiotensin II (Ang II)-receptor blocker (ARB), is a partial agonist of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). We investigate whether telmisartan improves cardiovascular remodeling associated with the production of endothelial nitric oxide synthase (eNOS) through PPAR-gamma, inhibits the Rho-kinase pathway, and suppresses oxidative stress in Dahl salt-sensitive (DS) hypertensive rats. METHODS: Telmisartan (1 mg/kg per day) or telmisartan plus PPAR-gamma inhibitor, GW9662 (1 mg/kg per day) was administered from the age of 6-11 weeks. Age-matched male Dahl salt-resistant (DR) rats served as a control group. RESULTS: The levels of eNOS and PPAR-gamma expression, and eNOS phosphorylation were significantly lower in DS rats than in DR rats. Chronic telmisartan treatment in DS rats significantly increased these parameters, but not telmisartan plus GW9662. Telmisartan effectively inhibited the vascular lesion formation such as medial thickness and perivascular fibrosis, but not telmisartan plus GW9662. Moreover, upregulated RhoA protein, Rho-kinase mRNA, and myosin light-chain phosphorylation in DS rats was decreased by telmisartan to a similar degree as observed after treatment with Y-27632, a selective Rho-kinase inhibitor. In addition, NAD(P)H oxidase p22phox, p47phox, gp91phox expression, and mitogen-activated protein kinase and its downstream effector p70 S6 kinase phosphorylation in DS rats was also inhibited by telmisartan. CONCLUSIONS: These results suggest that the cardioprotective mechanism of telmisartan may be partly due to improvement of endothelial function associated with PPAR-gamma-eNOS, oxidative stress, and Rho-kinase pathway.

Effects of olmesartan medoxomil as an angiotensin II-receptor blocker in chronic hypoxic rats.

We established a rat chronic alveolar hypoxia in vivo model to evaluate the efficacy against hypoxic pulmonary hypertension of a new angiotensin II-receptor I blocker, olmesartan medoxomil. Three groups of rats were established: rats exposed for 2-6 weeks to 10% oxygen atmosphere in a normobaric chamber; hypoxic rats treated with olmesartan medoxomil oral administration (5 mg/day) every day; and control rats fed in a normoxic condition. After hypoxia treatment, the presence, etiology and severity of pulmonary hypertension, was echocardiographically evaluated, and expressions of brain natriuretic peptide (BNP), transforming growth factor (TGF-beta) and endothelin-1 genes measured by both immunohistochemical assay and real-time polymerase chain reaction. Olmesartan medoxomil significantly reduced the induction of hypoxic cor pulmonale not only on echocardiographical observations but also in BNP, TGF-beta and endothelin gene expressions in molecular studies. However, systolic blood pressure was independent of olmesartan medoxomil. The present study clearly indicates that the angiotensin II-type I-receptor blocker olmesartan medoxomil has significant efficacy for hypoxic cor pulmonale.