ABSTRACT
Although adriamycin is a potent chemotherapeutic agent, it elicits serious adverse effects, including cardiac toxicity. Evidence suggests that congestive heart failure induced by adriamycin is mediated by oxidative stress. We investigated whether regulators of adenosine A1 receptor and KATP channel, which have been demonstrated to mediate protective effects of ischemic -preconditioning in myocardium, are able to modulate adriamicin -induced impairment of cardiomyocyte. To study the effect of antioxidant, adenosine A1 receptor agonist & antagonist and KATP channel agonist & antagonist, ICR mice were pretreated with Cu,Zn -SOD, dimethyl thiourea, RPIA (R (-)N6 -(2 -Phenylisopropropyl)- adenosine, adenosine A1 receptor agonist), 8 -CPDPX (8 -Cyclopentyl -1, 3 -dipropylxanthine, adenosine A1 receptor antagonist), Pinacidil (KATP channel opener) and glibenclamide (KATP channel closer), followed by i.p injection with adriamycin. Mice were sacrificed day 1 or day 4 after adriamycin injection and cardiac toxicity was accessed by measurement of creatine phosphokinase (CK) levels in serum, immunohistochemistry using anti -Bcl -2 antibody and TUNEL histochemical assay. As expected, pretreatment of mice with Cu, Zn -SOD and DMTU reduced the frequency of TUNEL positive cells, indicating antioxidants protected cardiocytes from adriamycin -induced apoptosis. Interestingly, pretreatment with RPIA and pinacidil induced a significant decrease in adriamycin -induced cytotoxicity, whereas 8 -CPDPX and glibenclamide generated the opposite results. In Bcl -2 immunohistochemistry, an increased expression of Bcl -2 was found in all ADR treated groups, especially in glibenclamide pretreated group, and 8 -CPDPX pretreated groups, but Bcl -2 failed to protect myocytes from apoptosis. All ADR treated groups exhibited elevated levels of serum CK, compared with nomal controls, especially mice sacrificed at day 4 than those at day 1, and showed similar patterns of TUNNEL assay, reflecting heart tissue damages. This observation implicated cytoprotective roles of RPIA and pinacidil against adriamycin -induced cardiac toxicity. In conclusion, these results demonstrated that adriamycin -induced cardiotoxicity was associated with the generation of reactive oxygen species and that regulators including SOD, DMTU, RPIA and pinacidil elicited protective effects on this toxicity. In particular, pinacidil, the KATP channel opener, was more effective than RPIA, the adenosine A, receptor agonist, to attenate the adriamycin -induced cardiac toxicity.