| Objective: c-Jun NH2-terminal kinase(JNK) is a key regulator of cardiac hypertrophy and apoptosis during pathological stress, but its role in regulating ion channels remodeling in the diseased heart is unclear. Thus, this study compared the kinase profile and electrophysiological phenotype of the rat ventricle 6–8 weeks after myocardial infarction(MI).Methods: All animal procedures were carried out in accordance with guidelines approved by the University of He Bei Medical Institutional Animal Care.Male Sprague–Dawley rats(180–200g) were established model of myocardial infarction. Six to eight weeks after MI or sham operation, rats were given an overdose of pentobarbital sodium(100mg/kg, i.p.). Hearts were excised and perfused via the coronary vasculature by the Langendorff method. Single Myocytes were dissociated from perfused hearts by a collagenase digestion procedure described previously, and were incubated in 95%?C and5% O2 for 4h, then were patched for recording Ito current. Samples of myocardial cell were dissected and rapidly frozen for subsequent molecular and biochemical analyses.Results:1 Molecular analyses shown that JNK activities were markedly increased 1 times in post-MI hearts than that in sham, while parallel voltage-clamp studies in ventricular myocytes revealed a characteristic downregulation of transient outward K+ current(Ito) density(Sham: 28.9±3.1 p A/p F, n=20; MI: 15.2±2.7 p A/p F, n=15; P<0.05).2 When post-MI myocytes were treated with JNK inhibitors SP600125 10 μM for 4h, Ito density increased to control levels(MI+SP600125: 31.6±3.5 p A/p F, n=11; Sham: 28.9±3.1 p A/p F, n=20 P<0.05). Treatment of myocytes from sham hearts with SP600125 had no significant effect on maximum Ito density(27.9±3.6 p A/p F; n=9) relative to untreated sham controls. A similar upregulation of Ito in MI myocytes was observed with a membrane-permeable peptide inhibitor, JNKI-1(10 μM), whereas a negative control peptide(JNKI-Neg) had no effect.3 These changes of Upregulation of Ito were also elicited by JNK inhibitor SP600125 was blocked by the thioredoxin(Trx) reductase inhibitor auranofin(AF, 1μM)(MI+AF+SP600125: 15.6±1.7 p A/p F, n=15), while AF did not change the Ito density of Sham heart.4 MI hearts perfused with SP600125 showed a marked increase in Kv4.2 protein expression, although not to the level of sham hearts. These findings agreewith the upregulation of Ito density observed in isolated MI myocytes, which also in agreement with Ito electrophysiological alternation.Conclusions: Kv channel remodeling in post-MI heats is redox regulated, and the Ito remodeling possible be correlated with the persistent activation of c-JNK signaling pathway. Our data showed that persistent activation of c-JNK kinase will down expression of Kv channel in post-MI rat heart, while Ito channel is normalized by inhibiting JNK signaling pathway. It suggests that Kv channel remodeling may be involved in the regulation of Trx system. |
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