Cardiovascular Diseases & Diagnosis

Neuregulin1 Improved Cardiac Function in Doxorubicin-Treated Mice with Cardiomyocyte-Specific over expression of a Dominant-Negative PI3Kp110α

Abstract

Yun Bian, Marcy Silver, Jillian Onufrak, Kalon K.L. Ho, Mark A. Marchionni, Peter M Kang, David A Goukassian, Joseph Carrozza, James P Morgan and Xinhua Yan

Neuregulin1s (NRG1s) are effective for protecting the heart from various stresses. Our previous studies show that heterozygous knockout of the NRG1 gene worsens while injections of a recombinant NRG1 improve cardiac function in Chemotherapy Drug Doxorubicin (DOX) - treated mice. In cultured cardiomyocytes, studies show that the Phosphoinositide 3-Kinase (PI3K) pathway is necessary for NRG1 to reduce DOX-induced apoptosis and loss of cardiac troponins. Here, we test whether PI3Kp110α, a Class IA PI3K isoform, is necessary for NRG1’s cardioprotective effects in DOX-treated mice. DOX was administered to mice with cardiomyocyte-specific overexpression of a constitutively active PI3Kp110α (CaPI3K), or a dominant negative PI3Kp110α (dnPI3K). Solvent or NRG1 was administered concurrently with DOX to dnPI3K mice. Our results showed that survival and cardiac function were improved in CaPI3K, but worsened in dnPI3K mice. Concurrent NRG1 injections significantly improved survival and cardiac function in dnPI3K mice, which were associated with increased activation of ERK1/2 and mTORC1 in the heart. These results have demonstrated that PI3Kp110α is important for protecting the heart from DOX. Further, the results suggest that PI3Kp110α is not necessary for NRG1 to protect the heart from DOX. NRG1 may protect the heart by activating alternative survival pathways, such as ERK1/2 and mTORC1, in DOX-treated dnPI3K mouse hearts.