Chronic NHE-1 blockade induces an antiapoptotic effect in the hypertrophied heart

Abstract

Na(+)/H(+) exchanger (NHE-1) inhibition was demonstrated to induce the regression of cardiac hypertrophy (CH) in several experimental models and to inhibit mitochondrial death pathway in "in-vitro" experiments. Since recent reports show that NHE-1 inhibition delays the transition from CH to failure, and apoptosis plays a key role in this process, we investigated the effect of chronic treatment with the NHE-1 blocker cariporide on CH and apoptosis in the SHR. One month of cariporide treatment (30 mg x kg(-1) x day(-1)) induced the regression of CH (cardiomyocyte cross-sectional area: 468 +/- 20 vs. 285 +/- 9 microm(2) in untreated and cariporide-treated spontaneously hypertensive rats; P < 0.05). Apoptosis was assessed by TUNEL staining, the expression of Bcl-2, Bax, and activation of caspase-3 and PARP-1 by immunoblot. Cariporide treatment decreased the TUNEL-positive cells, the Bax-to-Bcl-2 ratio (3.16 +/- 0.32 vs. 1.70 +/- 0.17, untreated and cariporide-treated, respectively; P < 0.05); caspase-3 and PARP-1 activation (465 +/- 62 vs. 260 +/- 22 and 2,239 +/- 62 vs. 1,683 +/- 85 AU, untreated and cariporide-treated, respectively; P < 0.05). Angiotensin II, a growth factor and apoptotic stimulus, was used to induce O(2)(-) production that activated the ERK1/2-p90(RSK) pathway, increasing NHE-1 phosphorylation. These effects were prevented by losartan, N-(2-mercaptopropionyl)-glycine, and cariporide. In conclusion, we present data demonstrating that chronic NHE-1 inhibition with cariporide decreases both hypertrophy and apoptosis susceptibility in the spontaneously hypertensive rat heart. The antiapoptotic effect would be the consequence of two different actions of cariporide: the prevention of cytosolic Na(+) and Ca(2+) overload due to the inhibition of the sarcolemmal NHE-1 and a direct mitochondrial effect preventing mitochondrial permeability transition pore opening.

Effect of Bacterial Lipopolysaccharide on Na⁺/H⁺ Exchanger Activity in Dendritic Cells

“…Notably, addition of cariporide in the absence of LPS did not significantly modify the survival of DCs. In other cell types the Na + /H + exchanger activity has been shown to foster [60][61][62][63] or inhibit [64][65][66] apoptosis. The inhibitory effect of Na + /H + exchanger activity on apoptosis was explained by the prevention of acidosis [64,65] or of cell shrinkage [66].…”

Amiloride attenuates lipopolysaccharide-accelerated atherosclerosis via inhibition of NHE1-dependent endothelial cell apoptosis

“…Increased intracellular Ca 2+ activates calpains, which are Ca 2+ -dependent proteases [9] that have been shown to regulate anti-apoptotic proteins including Bcl-2 [10] . Previous studies have shown that LPSinduced apoptosis is dependent on changes in Bcl-2 levels [11,12] . Based on these results, we hypothesized that LPS-induced atherosclerosis is mediated by calpain-induced endothelial cell apoptosis.…”

Effect of Azathioprine on Na+/H+Exchanger Activity in Dendritic Cells

“…LPS treatment has previously been shown to decrease apoptosis of DCs, an effect abrogated by inhibition of the Na + /H + exchanger [50]. As shown in other cell types, activation of Na + /H + exchanger activity may enhance [87][88][89][90] or inhibit [91][92][93] apoptosis. The inhibitory effect of Na + /H + exchanger activity on apoptosis may result from cytosolic alkalinization [91,92] or from prevention of cell shrinkage [93].…”