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

Abstract

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.

Fig. 1.

Experimental protocol. Arrows indicate time points for treatment, performance of surgical procedures, and measurement of various parameters. CMC, carboxymethylcellulose; Nx, nephrectomized; BUN, blood urea nitrogen; SBP, systolic blood pressure.

Fig. 2.

Doppler echocardiography showing left ventricular (LV) function in rats. A: representative M-mode images of LV from sham-operated and 5/6 Nx rats at 8 wk. Note that there is more LV dilatation and wall thickening in Nx rats compared with sham control. B: average data showing left ventricular end-diastolic diameter (LVEED, m). C: LV mass. Note that there is a significant increase in LVEDD and LV mass in Nx rats compared with sham control. Curcumin- and enalapril-treated rats had significantly lower LV mass.

Fig. 3.

Changes of diameter of the inferior vena cava (IVC) at end-inspiration, as measured by echocardiography using a subcostal approach. A: representative images of sham control and Nx rats. B: average IVC diameter data. Note that end-inspiration IVC diameter is significantly higher in Nx rats compared with the sham control. Treatment with curcumin or enalapril significantly attenuated the increase in end-inspiration IVC diameter, reflective of lower right atrial pressure. NS, not significant.

Fig. 4.

Western blot showing glycogen synthase kinase-3β (GSK-3β) expression in LV from the experimental groups. Note the enhancement in GSK-3β phosphorylation with 5/6 Nx and its attenuation by treatment with curcumin and enalapril. The summary results are shown as the ratio of total GSK-3β/glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphorylated (p) GSK-3β/GAPDH, and pGSK-3β/GSK-3β.

Fig. 5.

The effect of curcumin and enalapril on changes in β-catenin in LV from sham and 5/6 Nx rats. mRNA (A), cytosolic (B), and nuclear (C) levels, normalized with lamin. Note that 5/6 Nx caused significant increase in mRNA and cytosolic as well as nuclear levels of β-catenin. Curcumin significantly reduced β-catenin in the cytosol and nuclear fraction without having any effect on the mRNA. Enalapril had no effect on β-catenin. The nuclear fraction was devoid of GAPDH signal, suggesting that the nuclear extracts were free from cytosolic contamination.

Fig. 6.

The effect of curcumin and enalapril on changes in calcineurin in LV from sham and 5/6 Nx rats. mRNA (A), cytosolic (B), and nuclear (C) levels, normalized with lamin. Note that 5/6 Nx caused significant increase in mRNA and cytosolic levels of calcineurin that were significantly reduced by enalapril but not curcumin.

Fig. 7.

The effect of curcumin and enalapril on changes in p-nuclear factor of activated T cells (NFAT) and nuclear NFAT in the cytosolic and nuclear fractions of LV from sham and 5/6 Nx rats. Cytosolic (A) and nuclear (B) levels, normalized with lamin. C: DNA binding of NFAT determined by TransAm Assay. Note that 5/6 Nx caused significantly reduced cytosolic levels of pNFAT and increased nuclear NFAT translocation and activity determined by Western blots and DNA-binding assay, respectively. Both curcumin and enalapril reversed this trend.

Fig. 8.

The effect of curcumin and enalapril on changes in pERK (A) and p-cAMP-dependent kinase (Akt) (B) from LV of sham and 5/6 Nx rats. The summary results are shown as the ratio of pERK/ERK and pAkt/Akt. Compared with controls, the phosphorylation of both ERK and Akt were significantly higher in Nx animals. Curcumin and enalapril treatment blunted the increase in phosphorylation.

Fig. 9.

Summary of signaling pathways by which curcumin and enalapril attenuate LV hypertrophy 5/6 Nx rats.