Takeaki Honda

Critical role of Rho-kinase pathway for cardiac performance and remodeling in failing rat hearts

OBJECTIVES Rho and Rho-kinase play a critical role in the regulation of cellular functions such as proliferation and migration. To elucidate the molecular mechanisms that regulate cardiac function and cardiovascular remodeling, we determined whether the signaling pathway through Rho is involved in Dahl salt-sensitive hypertensive rats with congestive heart failure (CHF) using a specific Rho-kinase inhibitor, Y-27632. METHODS Y-27632 was administered from the left ventricular hypertrophy stage (11 weeks) to the CHF stage (18 weeks) for 7 weeks. The left ventricular end-systolic pressure-volume relationship (contractility: E(es)) was evaluated using a conductance catheter. RESULTS Downregulated E(es) in the CHF stage was significantly ameliorated by Y-27632 treatment. Increased RhoA protein, Rho-kinase gene expression and myosin light chain phosphorylations in CHF rats were suppressed by Y-27632. Upregulated proto-oncogene c-fos gene expression in CHF rats was decreased by inhibiting Rho-kinase. In contrast, Y-27632 showed no effect on upregulated extracellular signal-regulated kinases (ERK) and p70S6 kinase phosphorylations, which were reported to be involved in protein synthesis. In the CHF stage, Y-27632 effectively inhibited vascular lesion formation such as medial thickness and perivascular fibrosis. CONCLUSIONS These results suggest that differential activation of the Rho-Rho-kinase and the ERK-p70S6 kinase pathways may play a critical role in CHF, and the Rho-Rho-kinase pathway is involved in the pathogenesis of cardiac dysfunction and cardiovascular remodeling. Thus, inhibition of the Rho-kinase pathway may be at least a potential therapeutic strategy for CHF.

Cardioprotective Mechanisms of Eplerenone on Cardiac Performance and Remodeling in Failing Rat Hearts

Aldosterone may play a pivotal role in the pathophysiology of heart failure. To elucidate the beneficial cardioprotective mechanism of eplerenone, a novel selective aldosterone blocker, we hypothesized that eplerenone stimulates endothelial NO synthase (eNOS) through Akt and inhibits inducible NO synthase (iNOS) via nuclear factor &kgr;B (NF-&kgr;B) after the development of oxidative stress and activation of the lectin-like, oxidized, low-density lipoprotein receptor 1 (LOX-1) pathway in Dahl salt-sensitive rats with heart failure. Eplerenone (10, 30, and 100 mg/kg per day) was given from the age of the left ventricular hypertrophy stage (11 weeks) to the failing stage (18 weeks) for 7 weeks. The left ventricular end-systolic pressure-volume relationship was evaluated using a conductance catheter. Decreased percentage of fractional shortening by echocardiography and end-systolic pressure-volume relationship in failing rats was significantly ameliorated by eplerenone. Downregulated eNOS expression, eNOS and Akt phosphorylation, and NOS activity in failing rats were increased by eplerenone. Upregulated expression of the mineralocorticoid receptor aldosterone synthase (CYP11B2); NAD(P)H oxidase p22phox, p47phox, gp91phox, iNOS, and LOX-1; and activated p65 NF-&kgr;B, protein kinase C&bgr;II, c-Src, p44/p42 extracellular signal-regulated kinase, and p70S6 kinase phosphorylation were inhibited by eplerenone. Eplerenone administration resulted in significant improvement of cardiac function and remodeling and upregulation of sarcoplasmic reticulum Ca2+-ATPase expression. These findings suggest that eplerenone may have significant therapeutic potential for heart failure, and these cardioprotective mechanisms of eplerenone may be mediated in part by stimulating eNOS through Akt and inhibiting iNOS via NF-&kgr;B after activation of the oxidative stress-LOX-1 pathway and signal transduction pathway.

Eplerenone Shows Renoprotective Effect by Reducing LOX-1–Mediated Adhesion Molecule, PKCε-MAPK-p90RSK, and Rho-Kinase Pathway

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) may play an important role in atherosclerosis by inducing leukocyte adhesion molecules, such as intercellular and vascular cell adhesion molecule-1 (intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1]). We hypothesized that eplerenone, a novel selective aldosterone blocker, produces inhibition of LOX-1–mediated adhesion molecules, suppresses mitogen-activated protein (MAP) kinase and its downstream effector p90 ribosomal S6 kinase (p90RSK) through the protein kinase C&egr; (PKC&egr;) pathway, and improves endothelial function by inhibition of Rho-kinase in the renal cortex of Dahl salt-sensitive hypertensive (DS) and salt-resistant (DR) rats. Eplerenone (10, 30, and 100 mg/kg per day) was given from the age of 6 weeks to the left ventricular hypertrophy stage (11 weeks) for 5 weeks. At 11 weeks, expression levels of LOX-1, ICAM-1, VCAM-1, and Rho-kinase were higher in DS rats than in DR rats and were decreased by eplerenone. Similarly, upregulated phosphorylation of PKC&egr;, MAP kinase, and p90RSK in DS rats was also inhibited by eplerenone. In contrast, downregulated endothelial nitric oxide synthase mRNA was increased by eplerenone to a similar degree as after treatment with Y-27632, a selective Rho-kinase inhibitor. Eplerenone administration resulted in significant improvement in glomerulosclerosis (eplerenone 10 mg, −61%; 30 mg, −78%; and 100 mg, −84% versus DS; P<0.01, respectively) and urinary protein (10 mg, −78%; 30 mg, −87%; and 100 mg, −88% versus DS; P<0.01, respectively). These results suggest that the renoprotective effects of eplerenone may be partly caused by inhibition of LOX-1–mediated adhesion molecules and PKC&egr;–MAP kinase–p90RSK pathway, and improvement in endothelial function.

Celiprolol Activates eNOS Through the PI3K-Akt Pathway and Inhibits VCAM-1 Via NF-κB Induced by Oxidative Stress

Abstract—Vascular cell adhesion molecule-1 (VCAM-1) and reactive oxygen species play critical roles in early atherogenesis, and nitric oxide (NO) is an important regulator of the cardiovascular system. Although celiprolol, a specific &bgr;1-antagonist with weak &bgr;2-agonistic action, stimulates endothelial nitric oxide synthase (eNOS) production, the mechanisms remain to be determined. Because it was recently reported that phosphatidylinositol 3-kinase (PI3K) and its downstream effector Akt are implicated in the activation of eNOS and that regulation of VCAM-1 expression is mediated via nuclear factor-&kgr;B (NF-&kgr;B), we hypothesized that celiprolol activates phosphorylation of eNOS through the PI3K-Akt signaling pathway; that celiprolol modulates VCAM-1 expression, which is associated with inhibiting NF-&kgr;B phosphorylation; and that celiprolol suppresses NAD(P)H oxidase p22phox, p47phox, gp91phox, and nox1 expression in the left ventricle of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. eNOS and Akt phosphorylation upregulated by celiprolol alone were suppressed by treatment with celiprolol plus wortmannin. Increased expression of VCAM-1, p22phox, p47phox, gp91phox, nox1, activated p65 NF-&kgr;B, c-Src, p44/p42 extracellular signal-regulated kinases, and their downstream effector p90 ribosomal S6 kinase phosphorylation in DOCA rats was inhibited by celiprolol. Celiprolol administration resulted in a significant improvement in cardiovascular remodeling and suppression of transforming growth factor-&bgr;1 gene expression. In conclusion, celiprolol suppresses VCAM-1 expression because of inhibition of oxidative stress, NF-&kgr;B, and signal transduction, while increasing eNOS via stimulation of the PI3K-Akt signaling pathway and improving cardiovascular remodeling.

Protective effects of an angiotensin II receptor blocker and a long-acting calcium channel blocker against cardiovascular organ injuries in hypertensive patients.

The purpose of this study is to compare the long-term effects of an angiotensin II receptor blocker (ARB) and a long-acting calcium channel blocker (CCB) on left ventricular geometry, hypertensive renal injury and a circulating marker of collagen synthesis in hypertensive patients. Patients with essential hypertension (24 men and 19 women; age, 37–79 years) were treated with a long-acting CCB, amlodipine (AML; 2.5–7.5 mg once daily) for 6 months. Then, AML was switched to an ARB, candesartan (CS; 4–12 mg once daily), in 22 patients (CS group), while AML was continued in the remaining 21 patients for another 6 months (AML group). At the end of each treatment period, ambulatory blood pressure monitoring (ABPM), echocardiography and sampling of blood and urine were performed. The average office blood pressure during the latter period was comparably controlled in the AML and the CS groups (AML: 130±8/87±7 mmHg; CS: 133±11/88±7 mmHg), while the average systolic blood pressure of 24-h ABPM was significantly lower in the AML than in the CS group (127±9 vs. 133 ±14 mmHg, p<0.05). Consequently, the left ventricular mass index was significantly decreased in the AML group (102±18 to 92±12 g/m2, p<0.05), while the change was insignificant in the CS group (103±25 to 98±21 g/m2). On the other hand, plasma procollagen I C-terminal peptide (PICP), a marker of collagen synthesis, was lowered by CS (86±21 to 70±21 ng/ml, p<0.01), but was not significantly affected by AML (80±127 to 74±91 ng/ml). CS reduced urinary albumin excretion (57±123 to 26±33 mg/g creatinine, p<0.05), but AML did not bring about significant changes (85±27 to 73±19 mg/g creatinine). The results suggested that long-acting CCBs are effective in improving left ventricular hypertrophy by controlling 24-h blood pressure, while ARBs possess protective effects against cardiovascular fibrosis and renal injury beyond their antihypertensive effects.