Angiotensin-Converting Enzyme Inhibitor Suppresses Activation of Calcineurin in Renovascular Hypertensive Rats

Curcumin prevents cardiac remodeling secondary to chronic renal failure through deactivation of hypertrophic signaling in rats

The prevalence of left ventricular hypertrophy (LVH) is frequent in patients with end-stage renal disease following chronic renal failure (CRF). We investigated the therapeutic efficacy of curcumin, the principal curcuminoid of the Indian curry spice turmeric, in attenuation of LVH and sought to delineate the associated signaling pathways in blunting the hypertrophic response in nephrectomized rats. Adult Sprague-Dawley rats underwent nephrectomy (Nx) by removal of 5/6 of the kidneys. Four groups were studied for 7 wk: 1) control (sham), 2) Nx, 3) Nx + curcumin (150 mg/kg bid), and 4) Nx + enalapril (15 mg/kg bid) as positive control. Subtotal nephrectomy caused renal dysfunction, as evidenced by a gradual increase in proteinuria and elevation in blood urea nitrogen and plasma creatinine. Nx rats showed a significant hypertrophic response and increased diameter of inferior vena cava at inspiration, which was inhibited by treatment with curcumin or enalapril. Moreover, the Nx rats demonstrated changes in the signaling molecules critically involved in the hypertrophic response. These include increased glycogen synthase kinase-3β phosphorylation, β-catenin expression, calcineurin, phosphorylated (p) nuclear factor of activated T cells, pERK, and p-cAMP-dependent kinase. Both curcumin and enalapril variably but effectively deactivated these pathways. Curcumin attenuates cardiac hypertrophy and remodeling in nephrectomized rats through deactivation of multiple hypertrophic signaling pathways. Considering the safety of curcumin, these studies should facilitate future clinical trials in suppressing hypertrophy in patients with CRF.

Inhibitory effect of antihypertensive drugs on calcineurin in cardiomyocytes

In recent years, a handful of research investigations have shown that some antihypertensive drugs, i.e., angiotensin-converting enzyme inhibitor (ACEI), angiotensin receptor blocker (ARB), and calcium channel blocker (CCB), can inhibit myocardial expression and/or activity of calcineurin. Calcineurin is a Ca(2+)-calmodulin-dependent serine/threonine phosphatase and is a target for some immunosuppressive drugs. It is well known that traditional immunosuppressants, such as cyclosporine A (CsA) and tacrolimus (FK506), are anticalcineurin, and their prohypertensive effects are such that antihypertensive therapy is often required in organ transplant recipients who receive these drugs. Therefore, the idea that ACEI, ARB, and CCBs are both antihypertensive and anticalcineurin seems paradoxical. This invited review tries to summarize these new findings and analyze the scientific and clinical significance of these claims. The review also emphasizes some of the shortcomings in these studies and some questions that need to be addressed in future investigations.

Blockade of calcineurin reverses cardiac hypertrophy and induces the down-regulation of JNK mRNA expression in renovascular hypertensive rats

INTRODUCTION

Recently, calcineurin has been shown to induce cardiac hypertrophy. Mitogen-activated protein kinases (MAPK), including the extracellular-signal regulated kinases (ERK), the c-Jun NH2-terminal kinases (JNK) and the p38 MAPK (p38), have also been shown to be important in the transduction of trophic signals. The objective of this study was to investigate possible cross-talk between calcineurin and MAPK pathways in controlling renovascular hypertension-induced cardiac hypertrophy.

METHODS

Renovascular hypertension was induced by the two kidney-one clip method. The left ventricular weight (LVW) and the ratio of LVW to tibial length were measured to assay the degree of cardiac hypertrophy. Calcineurin activity and MAPK mRNA expression were measured.

RESULTS

In the left ventricle of rats with renovascular hypertension, calcineurin activity and JNK mRNA expression were increased while cardiac hypertrophy developed. Treatment with the calcineurin blocker ciclosporin A induced calcineurin inhibition and regression of cardiac hypertrophy with an improvement of cardiac diastolic function. The treatment also resulted in down-regulation of JNK mRNA expression, but the mRNA expressions of ERK and p38 were unchanged.

CONCLUSIONS

There is cross-talk between the calcineurin and JNK pathway in controlling renovascular hypertension-induced cardiac hypertrophy. Inhibition of the calcineurin and JNK pathways may be the basis of reversal of cardiac hypertrophy by calcineurin blockers.