Stanbouly Seta, Kirshenbaum Lorrie A, Jones Douglas L, Karmazyn Morris
Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
J Pharmacol Exp Ther. 2008 Oct;327(1):105-13. doi: 10.1124/jpet.108.140228. Epub 2008 Jul 23.
Connexin 43, the major connexin isoform in gap junctions of cardiac ventricular myocytes, undergoes changes in distribution and expression in cardiac diseases. The Na(+)-H(+) exchanger (NHE-1), a key mediator of hypertrophy and heart failure, has been shown to be localized in the cardiomyocyte gap junctional regions; however, whether NHE-1 regulates gap junction proteins in the hypertrophied cardiomyocyte is not known. To address this question, neonatal rat ventricular myocytes were treated with phenylephrine (PE) for 24 h to induce hypertrophy. Increased Cx43 expression observed with PE treatment (132.4 +/- 6.3% compared to control; P < 0.05) was further significantly augmented by the specific NHE-1 inhibitor EMD87580 [N-[2-methyl-4,5-bis(methylsulfonyl)-benzoyl]-guanidine hydrochloride] (173.2 +/- 8.7% increase compared to control; P < 0.05 versus PE), an effect that was mimicked by another NHE-1 inhibitor cariporide [4-isopropyl-3-(methylsulfonyl)benzoyl-guanidine methanesulfonate]. PE-induced hypertrophy was associated with mitogen-activated protein kinase c-Jun NH(2)-terminal kinase (JNK) 1/2 activation, whereas inhibition of JNK1/2 with either SP600125 [anthra(1,9-cd)pyrazol-6(2H)-one 1,9-pyrazoloanthrone] or small interfering RNA significantly increased PE-induced up-regulation of Cx43 protein levels. Inhibition of reverse mode Na(+)-Ca(2+) exchange (NCX) with KB-R7943 [2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea mesylate] partially reversed JNK1/2 activation (195.2 +/- 21.4 versus 143.7 +/- 14.4% with KB-R7943; P < 0.05) and augmented up-regulation of Cx43 protein (121.1 +/- 8.3 versus 215.9 +/- 25.6% with KB-R7943; P < 0.05) in the presence of PE. Our results demonstrate that NHE-1 negatively regulates Cx43 protein expression in PE-induced cardiomyocyte hypertrophy via a JNK1/2-dependent pathway, which is probably activated by reverse mode NCX activity.
连接蛋白43是心室肌细胞缝隙连接中的主要连接蛋白亚型，在心脏疾病中其分布和表达会发生变化。钠氢交换体（NHE-1）是肥大和心力衰竭的关键介质，已被证明定位于心肌细胞缝隙连接区域；然而，NHE-1是否调节肥大心肌细胞中的缝隙连接蛋白尚不清楚。为了解决这个问题，用去甲肾上腺素（PE）处理新生大鼠心室肌细胞24小时以诱导肥大。PE处理后观察到连接蛋白43表达增加（与对照组相比为132.4±6.3%；P<0.05），而特异性NHE-1抑制剂EMD87580 [N-[2-甲基-4,5-双（甲磺酰基）-苯甲酰基]-盐酸胍] 进一步显著增强了这种增加（与对照组相比增加了173.2±8.7%；与PE组相比P<0.05），另一种NHE-1抑制剂卡立泊来德 [4-异丙基-3-（甲磺酰基）苯甲酰基-甲烷磺酸胍] 也有类似作用。PE诱导的肥大与丝裂原活化蛋白激酶c-Jun氨基末端激酶（JNK）1/2激活有关，而用SP600125 [蒽（1,9-cd）吡唑-6（2H）-酮1,9-吡唑蒽酮] 或小干扰RNA抑制JNK1/2可显著增加PE诱导的连接蛋白43蛋白水平上调。用KB-R7943 [2-[2-[4-（4-硝基苄氧基）苯基]乙基]异硫脲甲磺酸盐] 抑制反向模式钠钙交换（NCX）可部分逆转JNK1/2激活（有KB-R7943时为195.2±21.4%，无KB-R7943时为143.7±14.4%；P<0.05），并在有PE存在的情况下增强连接蛋白43蛋白的上调（有KB-R7943时为121.1±8.3%，无KB-R7943时为215.9±25.6%；P<0.05）。我们的结果表明，NHE-1通过JNK1/2依赖性途径负调节PE诱导的心肌细胞肥大中的连接蛋白43蛋白表达，这可能是由反向模式NCX活性激活的。
