Reactive oxygen species (ROS)-induced oxidative stress in cells is an important pathophysiological process during myocardial ischemia/reperfusion (I/R) injury, and the transcription factor Egr-1 is a master switch for various damage pathways during reperfusion injury. An in vitro model of myocardial I/R injury and H9c2 cardiomyoblast cells hypoxia/reoxygenation (H/R) was used to assess whether there is abnormal intracellular ROS/JNK/Egr-1 signaling. We also assessed whether N-n-butyl haloperidol (F2), which exerts protective effects during myocardial I/R injury, can modulate this pathway. H/R induced ROS generation, JNK activation, and increased the expression of Egr-1 protein in H9c2 cells. The ROS scavengers edaravone (EDA) and N-acetyl-L-cysteine (NAC) reduced ROS level, downregulated JNK activation, and Egr-1 expression in H9c2 cells after H/R. The JNK inhibitor SP600125 inhibited Egr-1 overexpression in H9c2 cells caused by H/R. F2 could downregulate H/R-induced ROS level, JNK activation, and Egr-1 expression in H9c2 cells in a dose-dependent manner. The ROS donor hypoxanthine-xanthine oxidase (XO/HX) and the JNK activator ANISO antagonized the effects of F2. Therefore, H/R activates ROS/Egr-1 signaling pathway in H9c2 cells, and JNK activation plays an important role in this pathway. F2 regulates H/R-induced ROS/JNK/Egr-1 signaling, which might be an important mechanism by which it antagonizes myocardial I/R injury.

Aims: In this study, we tested whether Egr-1 is a potential target of calcium channel blockers in cardioprotection with I/R injury. Methods: We treated rats in vivo I/R and rat cultured cardiomyocytes in vitro hypoxia/reoxygenation (H/R) models with three types of classical calcium channel blockers (verapamil, diltiazem and nifedipine). Activity of creatine kinase (CK), lactate dehydrogenase (LDH), myeloperoxidase (MPO) superoxide dismutase (SOD) and level of malondialdehyde (MDA) in plasma and culture medium were measured to assess the degree of injury and inflammation of myocardial tissues and cells. Egr-1 mRNA and protein expressions were examined by RT-PCR and Western-blot analyses. Results: Calcium channel blockers (verapamil, diltiazem and nifedipine) significantly attenuated myocardial injury, as shown by reduced release of CK and LDH, preserved SOD activity and decreased MDA production and MPO activity. Concomitant with cardioprotection by calcium channel blockers, the mRNA and protein expression of Egr-1 increased with I/R and H/R injury was significantly reduced in myocardial tissue and cultured cardiomyocytes. Conclusions: These results suggested that the cardioprotective effects of calcium channel blockers with I/R or H/R injury might be mediated by downregulating Egr-1 expression. Egr-1 might be the potential target of calcium channel blockers in cardioprotection with ischemia/reperfusion injury.

Aims: Our previous studies have shown that myocardial ischemia-reperfusion (I/R) injury is related closely with early growth response (Egr)-1 overexpression. The present study is to confirm thoroughly the effects of Egr-1 on the occurrance and development of myocardial I/R injury. Methods: The Sprague-Dawley rat myocardial I/R model and cultured cardiomyocyte hypoxia-reoxygenation (H/R) model were established. The synthesized Egr-1 antisense oligodeoxyribonucleotide (AS-ODN) was transfected into myocardial tissues and cells. Hemodynamic parameters, myeloperoxidase (MPO), cardiac troponin I (cTnI), tumor necrosis factor-α (TNF-α), morphology, spontaneous beat and cell viability were measured to assess the degree of injury and inflammation of myocardial tissues and cells. Results: In vivo, Egr-1 AS-ODN significantly attenuated injury and inflammation of myocardial tissues caused by I/R evidenced by the amelioration of hemodynamics and the reduction in MPO activity. In vitro, Egr-1 AS-ODN significantly relieved injury and inflammation of cultured cardiomyocyte caused by H/R evidenced by the improvement in morphology, structure and beat as well as the decrease in leakage of cTnI and release of TNF-α from cultured cardiomyocyte. Conclusions: These data suggest that Egr-1 plays a vital role in the pathogenesis of myocardial I/R injury and Egr-1 AS-ODN could protect the myocardium from I/R injury.

Aims: N-n-butyl haloperidol (F₂), a novel compound of quaternary ammonium salt derivatives of haloperidol, was reported to antagonize myocardial ischemia/reperfusion injuries. The antiarrhythmic potential and electrophysiological effects of F₂ on rat cardiac tissues were investigated. Methods and Results: In Langendorff-perfused rat hearts, the ventricular arrhythmias were induced by left anterior descending coronary artery of rat heart ligated for 20 min before the release of the ligature. F₂ provided some inhibitive effects against ischemia- and reperfusion-induced ventricular arrhythmias. In His bundle electrogram and epicardial ECG recordings, the drug produced bradycardia, delayed the conduction through the atrioventricular node and prolonged the Wenckebach cycle length and atrioventricular nodal effective refractory period. In whole-cell patch-clamp study, F₂ primarily inhibited the L-type Ca²⁺ current (I_Ca,L) (IC₅₀ = 0.17 µM) with tonic blocking properties and little use-dependence. And the drug also decreased the Na⁺ current (IC₅₀ = 77.5 µM), the transient outward K⁺ current (IC₅₀ = 20.4 µM), the steady-state outward K⁺ current (IC₅₀ = 56.2 µM) and the inward rectifier K⁺ current (IC₅₀ = 127.3 µM). Conclusion: F₂ may be a promising drug for the treatment of ischemic heart disease with cardiac arrhythmia.

The ability of N-n-butyl haloperidol iodide (F2) to cause vasodilation, and thereby produce a cardioprotective effect, has been well documented. The aim of this study was to investigate whether F2 might act as a Ca2+ antagonist. Myocytes were obtained from rat heart, and the whole-cell patch-clamp technique was used to record Ca2+ current. Laser scanning confocal microscopy was used to measure intracellular free calcium ([Ca2+]i). The results obtained from this study demonstrate that F2 reduced calcium current (ICa) in a concentration-dependent manner with an IC50 of 1.19 micromol/L, upshifted the current-voltage curve of ICa, shifted the inactivation kinetics of ICa leftward, and slowed down the recovery of ICa from inactivation. F2 decreased the fluorescent intensity of [Ca2+]i elevation induced by KCl with an IC50 of 1.61 micromol/L, and had no effects on the intracellular calcium release induced by caffeine and inositol-1,4,5-trisphosphate. These findings indicate that F2 may act as a calcium antagonist, which could account for its cardiovascular benefits.