Doxorubicin (Dox) is an Anthracycline commonly used to treat many types of cancer; unfortunately this chemotherapeutic agent often induces side effects such as cardiotoxicity leading to cardiomyocyte death and dilated cardiomyopathy (DCM). This cardiotoxicity has been related to reactive oxygen species generation, DNA intercalation, topoisomerase II inhibition and bioenergetics alterations resulting in DNA damages leading to cardiomyocyte death.

There is a need for new therapeutic agents and strategies aiming at reducing Dox side effects in the heart. Among these mechanisms, the role of Epac (exchange protein directly activated by cAMP) could be worth investigating.

Therefore we have investigated the time/dose-dependent Dox effect on Epac signaling in both in vivo mice model (C57BL/6 vs. Epac1 KO mice, iv injections, 12mg/kg) and in vitro (primary culture of neonatal rat cardiomyocytes (NRVM), Dox 1μM).

In vivo, Dox-treated mice developed a DCM associated with Ca²⁺ homeostasis dysfunction. In vitro, as measured by flow cytometry and western blot, Dox induced DNA damage and cell death. This cell death is associated with apoptotic features including mitochondrial membrane permeabilization, caspase activation, cell size reduction and relative plasma membrane integrity. We also observed that Dox led to a modification of the protein level of Epac1 and Epac2 isoforms. The inhibition of Epac1 (ESI09, CE3F4), but not of Epac2 (ESI05), prevented DNA/TopIIβ complexes, decreased Dox-induced DNA damage, loss of mitochondrial membrane potential, apoptosis and finally cardiomyocyte death. These results were confirmed in vivo since Dox-induced cardiotoxicity was prevented in Epac1 KO mice as evidenced by unaltered cardiac function (no DCM) 15 weeks post-treatment.

Inhibition of Epac1 could be a valuable therapeutic strategy to limit Dox-induced cardiomyopathy during cancer chemotherapy.