A hypothesis concerning the role of PPAR family on cardiac energetics in Adriamycin-induced cardiomyopathy.

Adriamycin is an effective anti-neoplastic drug against a variety of cancer types. However, the drug causes adverse side effects in a number of organ systems. Cardiomyopathy is one of the life-threatening side effects of Adriamycin. In the current work, we have derived a hypothesis with possible involvement of PPAR family members in the development of Adriamycin-induced cardiomyopathy. Dysregulation of PPAR family by Adriamycin causes impairment in the transport and ß-oxidation of fatty acids, the key substrate for ATP synthesis in heart. Evidences suggest that dysregulation of PPAR family alters the recruitment of glucose transporters. Furthermore, heme oxygenase-1 is a crucial enzyme regulating the iron homeostasis in the heart whose expression is regulated by PPAR family. Inverse relationship exists between the expression levels of PPARγ and heme oxygenase-1. Adriamycin upregulates the expression of heme oxygenase-1 which in turn disrupts the iron homeostasis in cardiomyocytes. Our molecular docking results show that Adriamycin has a high affinity for iron-binding sites of heme oxygenase-1, thereby hindering formation of iron-sulfur complex. The lack of iron-sulfur complex impairs the electron transport chain. In addition, succinate dehydrogenase subunit A is downregulated by Adriamycin. The lack of this subunit uncouples Krebs cycle from ETC. Further, lack of this subunit increases the concentration of succinate, which further alters the mitochondrial membrane potential. Overall, in the present work, we hypothesize that alteration in the expression of PPAR family members is one of the major causes of metabolic chaos and oxidative stress caused by Adriamycin during the development of cardiomyopathy.