DOXORUBICIN REMEDY OR HARM? CARDIOTOXICITY AND NOT ONLY...

INTRODUCTION. Doxorubicin (Doxo) is a chemotherapeutic agent whose clinical use is hampered by the serious dose-dependent cardiotoxicity. The accumulation of Reactive Oxygen Species (ROS) is widely accepted as a key factor of cardiotoxic effects. Mitochondrial Connexin 43 (Cx43) conferred cardioprotection by reducing cytosolic and mitochondrial ROS production. Topic of this work was the identification of antioxidant enzymes and molecules involved in Doxo-induced damage, in absence and in presence of Radicicol (Rad), an inhibitor of Cx43 translocation to mitochondria. Due to increasing numbers of young cancer survivors and the raising concerns for their fertility state, elucidating the biological mechanisms of chemotherapy risk is highly relevant. Moreover, it is known that Doxo-induced ovarian toxicity is associated with apoptosis of mouse granulosa cells. MATERIALS AND METHODS. Rat cardiac cells H9c2 were treated with Doxo and Rad. Changes in expression level of SOD, iNOS, CAT and HO were evaluated by FACS and qReal Time-PCR. The expression of molecules involved in apoptosis and NFkB pathway was analysed by FACS and Western blot. Doxo effects were also investigated in Human Granulosa Cells (HGC). RESULTS: In H9c2 cells, FACS analysis showed that cotreatment with Doxo and Rad increased SOD, CAT, HO and the apoptotic response, as shown by hypodiploid nuclei. The induction of apoptosis was confirmed by Western blot analysis that showed how the combined treatment with Doxo and Rad increased caspase-9 expression and reduced procaspase-3 levels. Moreover, after 3h of Doxo treatment a significant increase in IKKα expression was observed, more evident after 6h of co-treatment with Doxo and Rad. These results suggested a rapid activation of pathway involved in inflammatory response mostly in the presence of Cx43 inhibitor. Our preliminary results obtained treating HGC with Doxo showed toxic effects, as determined by MTS assay. CONCLUSIONS: In the model of cardiomyocytes, the understanding of the basic mechanisms underlying the cellular insult induced by Doxo will result in developing new applications for preventing cardiotoxicity. Antioxidant enzymes and molecules involved in inflammatory pathways are mostly increased in presence of Rad. Therefore, our findings help to strengthen the role of Cx43 in cardioprotection mechanisms.