Doxorubicin-induced phosphorylation of lamin A/C enhances DNMT1 and activates cardiomyocyte death via suppressing GATA-4 and Bcl-xL in rat heart

Abstract

Cardiotoxic effect of Doxorubicin (Dox) limits its clinical application. Previously, we reported that Dox induces phosphorylation of lamin A/C (pS22 lamin A/C), increased nuclear size, damage to the nuclear membrane, and cell death. However, the activation of signalling pathway during this event remains elusive, and it is unclear whether increased phospho-lamin A/C activates the cell death pathway in heart. Here, we demonstrated that Dox-induced lamin A/C phosphorylation causes apoptotic cell death. Increased levels of reactive oxygen species (ROS), DNA methylation and apoptosis markers (Bax, Bid, caspase 3 and caspase 9) were observed in Dox-exposed H9c2 cells. Nuclear membrane damage due to increased pS22 lamin A/C causes increased DNMT1 and DNA methylation followed by reduced expression of GATA-4 and Bcl-xL in Dox-treated H9c2 cells and rat hearts. Further, increased mRNA expression of DNMT1 and reduced expression of GATA-4 and Bcl-xL was observed in H9c2 cells after knocking down of lamin A/C expression. Previously, we reported that N-acetylcysteine improves lamin A/C levels and maintain nuclear membrane integrity. Similarly, in this study Astaxanthin (Ast), a membrane-specific antioxidant, reduces the expression of DNMT1 and phospho-lamin A/C levels; increases mRNA expression of GATA-4 and Bcl-xL; reduces ROS levels and DNA leakage in Dox-treated H9c2 cells and rat hearts. Ast also improves the cardiac structure and function in Dox-treated rats. In conclusion, Dox exposure in cardiomyoblasts and hearts causes cell death by increasing the pS22 lamin A/C, DNA methylation and reducing the expression GATA-4 and Bcl-xL. This study provides a novel pathway for Dox-induced cardiotoxicity and a possible therapeutic approach to reduce it.