Damage Response in Doxorubicin‐Exposed Cardiac Fibroblasts

Abstract

Pediatric cancers survivors exposed to doxorubicin during treatment are at an increased risk for cardiovascular disease. This study investigates two known responses to doxorubicin injury, the p53‐DNA‐damage pathway and the Parkin‐mitophagy pathway in the cardiac fibroblast. Doxorubicin is known to upregulate p53 expression. However, mitophagy of the mitochondria damaged by doxorubicin may be inhibited by this upregulation. Previous studies in cardiac myocytes have shown that cytosolic p53 can bind to Parkin and prevent it from localizing to damaged mitochondria, an early step of mitophagy. This study investigated if this also occurs in cardiac fibroblasts. Expression levels of p53 and Parkin were measured in primary cardiac fibroblasts exposed to doxorubicin. Immunoblotting and fluorescent microscopy both demonstrated increases in p53 and Parkin after doxorubicin exposure (p<0.05). Furthermore, the pattern of Parkin staining remains diffuse throughout the cytoplasm of the doxorubicin‐treated cells. Fibroblasts treated with a mitochondrial uncoupler had a linear staining pattern that may be due to the localization of Parkin with the mitochondria. As p53 is not upregulated by the uncoupler, Parkin localization would not inhibited. Future studies will determine if doxorubicin‐induced upregulation of p53 inhibits mitophagy and the effect this has on the cardiac fibroblast phenotype. Since cardiac fibroblasts mediate adverse cardiac remodeling, stress‐induced phenotypic changes to the cell will impact this process. Therefore, effects on the cardiac fibroblast are essential to understanding the development of the dilated cardiomyopathy seen in these patients.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.