Adenosine A3 receptor-mediated cardioprotection against doxorubicin-induced mitochondrial damage

Abstract Cardiotoxicity associated with doxorubicin (DOX) treatment limits the therapeutic efficiency of this drug against cancer. 2-Chloro-N(6)-(3-iodobenzyl)adenosine-5′-N-methyluronamide (Cl-IB-MECA), a selective agonist of A 3 adenosine receptor (A 3 R), reduces DOX toxicity in newborn rat cultured cardiomyocytes. The study's aim was to determine whether the protection demonstrated by Cl-IB-MECA attenuates cardiac depression in vivo . In addition, we wished to examine whether this protective pathway affects the sarcoplasmic reticulum (SR) calcium uptake and release, as well as intramitochondrial Ca 2+ accumulation induced by DOX. Rats were injected every alternate day (6 times) with (1) saline, (2) 2.5 mg/kg i.p. DOX, (3) 33 μg/kg i.v. Cl-IB-MECA, (4) DOX + Cl-IB-MECA. Left ventricular functions were assessed by invasive (pressure) and non-invasive (echocardiography) techniques at the end of the injection period and 4 weeks later. Cytosolic and intramitochondrial calcium levels were measured with indo-1 and rhod-2 probes. SR Ca 2+ content was determined by exposing cultured rat cardiomyocytes to caffeine. Echocardiography data demonstrate left ventricular wall thinning (23%), an increase in the end systolic dimension (170%) and decreased fractional shortening (35 ± 5% vs. 54 ± 5%, p 2+ levels in the cytosol and in mitochondria by diminishing the SR Ca 2+ uptake. Pretreatment with Cl-IB-MECA attenuated left ventricular dysfunction, improved SR calcium storage capacity and prevented mitochondrial Ca 2+ overload. We conclude that the adenosine A 3 receptor agonist is effective in vivo against DOX cardiotoxicity via the restoration of Ca 2+ homeostasis and prevention of mitochondrial damage that occurs as a result of Ca 2+ overload.