Fetal cocaine exposure causes epigenetic changes in the rat heart

Cocaine abuse continues to be prevalent in the United States and other industrialized nations. In addition to the negative health effects that cocaine abuse has on the user, a mother who uses cocaine while pregnant also exposes the developing fetus to cocaine. Although there have been many studies of the effects of cocaine on the adult heart, studies of cocaine on the fetal heart and its potential delayed pathophysiological effects on cardiac function in adult offspring are extremely limited. The studies of the present project sought to enhance the understanding of the effect of cocaine exposure on the fetal heart using a rat model. When pregnant dams were treated with cocaine during late gestation there were no gross cardiac defectives observed and the offspring appeared to be healthy. The hearts of adult offspring exposed to cocaine in utero were compared with hearts from control animals. Baseline cardiac function was unperturbed. However, protection from ischemia induced by ischemic preconditioning was absent in the hearts of cocaine treated male animals. Our studies demonstrated that this absence was due to impaired function of protein kinase C epsilon (PKCepsilon) in cocaine treated male offspring. The rest of the project focused on assessing the direct effect of cocaine on the fetal rat heart. This was accomplished by using an ex vivo intact fetal heart model. The heart was removed from the fetal rat at gestational day 17 and kept in M199 cell culture media. By adding cocaine to the media the direct effect of cocaine on the heart has been determined. We found that direct expose to cocaine reduced cardiac PKCepsilon protein and mRNA levels. There was also an increase in DNA methylation at the SP-1 binding sites in the PKCepsilon promoter region after cocaine exposure and a decrease in SP-1 binding to those sites. Studies with DNA methylation inhibitors have demonstrated a cause and effect relation between cocaine-mediated increase in DNA methylation and PKCepsilon gene repression in the heart. This project has demonstrated that cocaine has direct effects on the fetal heart and causes an epigenetic modification of PKCepsilon gene repression, which is likely to have long term cardiac consequences in the adult offspring.