Attenuation of Ischemia/Reperfusion-Induced Renal Injury in Mice Deficient in Na+/Ca2+ Exchanger

Abstract

Using Naϩ /Ca 2ϩ exchanger (NCX1)-deficient mice, the pathophysiological role of Ca 2ϩ overload via the reverse mode of NCX1 in ischemia/reperfusion-induced renal injury was investigated. Because NCX1 Ϫ/Ϫ homozygous mice die of heart failure before birth, we used NCX1 ϩ/Ϫ heterozygous mice. NCX1 protein in the kidney of heterozygous mice decreased to about half of that of wild-type mice. Expression of NCX1 protein in the tubular epithelial cells and Ca 2ϩ influx via NCX1 in renal tubules were markedly attenuated in the heterozygous mice. Ischemia/ reperfusion-induced renal dysfunction in heterozygous mice was significantly attenuated compared with cases in wild-type mice. Histological renal damage such as tubular necrosis and proteinaceous casts in tubuli in heterozygous mice were much less than that in wild-type mice. Ca 2ϩ deposition in necrotic tubular epithelium was observed more markedly in wild-type than in heterozygous mice. Increases in renal endothelin-1 content were greater in wild-type than in heterozygous mice, and this reflected the difference in immunohistochemical endothelin-1 localization in necrotic tubular epithelium. When the preischemic treatment with KB-R7943 was performed, the renal functional parameters of both NCX1 ϩ/ϩ and NCX1 ϩ/Ϫ acute renal failure mice were improved to the same level. These findings strongly support the view that Ca 2ϩ overload via the reverse mode of Na ϩ /Ca 2ϩ exchange, followed by renal endothelin-1 overproduction, plays an important role in the pathogenesis of ischemia/reperfusion-induced renal injury.Renal ischemia is characterized by the depletion of ATP and the development of intracellular acidosis, which alter cellular ionic homeostasis. In particular, elevated intracellular Ca 2ϩ concentration causes cellular injury during ischemia and leads to irreversible renal damage during reperfusion (Schrier et al., 1987). An increase in the intracellular Na ϩ concentration has been shown to correlate with Ca 2ϩ

YM-244769, a Novel Na+/Ca2+ Exchange Inhibitor That Preferentially Inhibits NCX3, Efficiently Protects against Hypoxia/Reoxygenation-Induced SH-SY5Y Neuronal Cell Damage

“…Under pathological conditions, such as ischemia/reperfusion injury in various organs, the NCX is believed to cause Ca 2ϩ overload as a result of elevated [Na ϩ ] i , leading to cell damage (Blaustein and Lederer, 1999;Annunziato et al, 2004). Indeed, KB-R7943, SN-6, and SEA0400 have been shown to efficiently guard against ischemia/reperfusion injury in the heart Elias et al, 2001;Takahashi et al, 2003), kidney Yamashita et al, 2003), and brain (Schröder et al, 1999;Matsuda et al, 2001). On the other hand, it has been reported that during permanent cerebral ischemia, the inhibition of NCX1 and NCX3 aggravates brain injury , suggesting that the roles of NCX should be differentiated in the phases of ischemia and reperfusion.…”

Visualization of Calcium Dynamics in Kidney Proximal Tubules

“…Because data in the literature indicate that reperfusion in renal PTE cells may cause a large calcium influx as a result of the reverse operation of the NCX, 20,21 we explored the effect of an efficient inhibitor of this transporter, KB-R7943, 22 on in vivo calcium signals evoked by ischemia-reperfusion. This agent, at a dose of 8.0 mg/kg (final blood concentration, approximately 300 nM) did not significantly affect the baseline PT calcium levels ( Figure 5B).…”

“…Because data in the literature indicate that reperfusion may cause a large calcium influx in renal PTE cells because of the reverse operation of the Na-Ca exchanger (NCX), 20,21 we tested the effect of a powerful inhibitor of the NCX, KB-R7943, 22 on this process. As shown in Figure 2E, addition of KB-R7943 in CoCl 2 -pretreated PTE cells slightly increased the basal calcium levels while eliminating the rise in calcium due to reoxygenation.…”

MicroRNA-214 Antagonism Protects against Renal Fibrosis

“…19 NCX-1 is expressed on renal tubular epithelial cells, 22 and mice heterozygous for NCX-1 (NCX-1 knockout is embryonic lethal 23,24 ) are protected against renal ischemia reperfusion injury. 22 However, neither protein nor mRNA expression levels of NCX-1 were derepressed in miR-214 2/2 animals ( Figure 6A and Supplemental Figure 6). Similarly, NCX-1 mRNA was not increased in those animals treated with anti-miR-214 ( Figure 6B).…”