Myocardial protective effect of tezosentan, an endothelin receptor antagonist, for ischemia-reperfusion injury in experimental heart failure models

Abstract

The myocardial protective effects of endothelin antagonist in ischemic cardiomyopathy (ICMP), doxorubicin-induced cardiomyopathy (DOX) and pressure-overload hypertrophy by transverse aortic constriction (TAC) models have been predicted to be different. The objective of this experiment, therefore, is to evaluate the myocardial protective effect of tezosentan, an endothelin receptor antagonist, in various experimental heart failure models. Sprague-Dawley rats (6-8 weeks old, 200-300 g) were randomized to three experimental groups (n=30 each): ICMP; DOX; and TAC group. Each of these groups was randomly assigned further to the following subgroups (n=10 each): sham-operated ischemia-reperfusion subgroup (SHAM); tezosentan treated ischemia-reperfusion subgroup (Tezo); and tezosentan non-treated ischemia-reperfusion subgroup (N-Tezo). Total circulatory arrest was induced for 1 hr, followed by 2 hr of reperfusion. The left ventricular developed pressure, peak positive and negative first derivatives, and coronary blood flow were significantly different (P<0.05) among the SHAM, Tezo, and N-Tezo subgroups of the ICMP group at 30 min of reperfusion, but there were no statistically significant differences among the subgroups of the DOX and TAC groups. In conclusion, tezosentan, an endothelin receptor antagonist, showed myocardial protection effects only on the ischemic cardiomyopathy rat model, but not in the non-ischemic heart failure rat models.

Keywords: Cardiomyopathies; Myocardial Ischemia; Myocardial Reperfusion Injury; Receptors, Endothelin.

Fig. 1

(A) Experimental designs: there are three cardiomyopathy rat groups needed and each group was divided into three sub-groups. As mentioned previously, three groups, including ischemic dilated cardiomyopathy group (ICMP, n=30), doxorubicin-induced non-ischemic dilated cardiomyopathy group (DOX, n=30) and hypertrophic cardiomyopathy group by Transverse Aortic Constriction method (TAC, n=30) are prepared. After 1 month following constructions of cardiomyopathic rat groups, each group was then randomly assigned to a SHAM operation (SHAM; control group, n=10) subgroup or tezosentan treatment ischemia-reperfusion subgroup (Tezo, n=10) or tezosentan non-treatment ischemia-reperfusion subgroup (N-Tezo, n=10). (B) Ischemia-reperfusion injury experimental protocol (isolated heart perfusion via Langendorff technique): after the stabilization period of 20-30 min, total circulatory arrest for ischemia about 1 hr was performed. After then, reperfusion was performed during 2 hr. In Tezo subgroup, the tezosentan, each 10^-5 M/L concentrations, is added to the cardioplegic solution and the perfusate.

Fig. 2

The results of cardiac performance. (A) LV developed pressure (LVDP) during ischemia-reperfusion injury. (B) dP/dT^max during ischemia-reperfusion injury. (C) dP/dT^min during ischemia-reperfusion injury. (D) Coronary blood flow (CBF) during ischemia-reperfusion injury. ^*P<0.05 at 30 min of reperfusion among SHAM, Tezo and N-Tezo subgroups. NS, there is no statistical significance among subgroups; ICMP, ischemic cardiomyopathy rat group; DOX, doxorubicin treated non-ischemic dilated cardiomyopathy rat group; TAC, hypertrophic cardiomyopathy rat group by transverse aortic constriction; SHAM, Sham operated ischemia-reperfusion subgroup; Tezo, tezosentan treated ischemia-reperfusion subgroup; N-Tezo, tezosentan non-treatment ischemia-reperfusion subgroup.

Fig. 3

(A) In the ICMP models, staining of triphenyltetrazolium chloride with evans blue was used for visualizing ischemia-infarct area of myocardium (black dash). (B) In the DOX models, dilated myocardium was confirmed with pathologic specimens (white arrow-enlarged left ventricle). (C) In the TAC models, hypertrophied myocardium was confirmed with pathologic specimens (white arrow). ^*The scale of the ruler in the photo is millimeter (mm). ICMP, ischemic cardiomyopathy rat group; DOX, doxorubicin treated non-ischemic dilated cardiomyopathy rat group; TAC, hypertrophic cardiomyopathy rat group by transverse aortic constriction.