The purpose of this F32 application is to support Dr. Zachary Clayton, a promising first-year postdoctoral fellow in the laboratory of Dr. Douglas Seals, to conduct original research and scientific training that will prepare him to become an independent, extramurally-funded investigator in the field of translational cardiovascular physiology aimed at the prevention of cardiovascular diseases (CVD). Dr. Clayton will learn a variety of new technical, conceptual and professional skills, including focused training in translational preclinical vascular physiology research in mice. His proposed research project seeks to (Aim 1) investigate the mechanism(s) by which doxorubicin (DOXO), the most commonly used anthracycline-chemotherapy drug, mediates vascular endothelial dysfunction, a key pathophysiological step in the development of CVD. He also will determine (Aim 2) if a translational mitochondrial-targeted antioxidant therapy, Mitoquinol Mesylate (MitoQ), can restore vascular endothelial dysfunction caused by DOXO in: a) young adult mice soon after treatment; and b) middle-aged mice (treated with DOXO in adolescence) to ?model? effects on middle-aged DOXO-treated childhood cancer survivors. Endothelial dysfunction is typically mediated by reduced bioavailability of the endothelium-derived dilator molecule, nitric oxide (NO), as a result of excessive production of superoxide, which reacts with NO. Dysfunctional mitochondria are a major source of overall superoxide production, due in part to inadequate compensatory increases in antioxidant defenses. DOXO has been reported to decrease vascular endothelial function, but the underlying mechanisms and potential therapeutic strategies are currently unknown. Guided by strong preliminary data, Dr. Clayton will investigate the mechanism(s) by which DOXO mediates endothelial dysfunction, using ex vivo ?pharmaco-dissection? techniques, specifically focusing on the role of mitochondrial superoxide in decreasing NO bioavailability (Aim 1). Furthermore, Dr. Clayton will seek to establish initial (preclinical) proof-in-concept evidence that oral supplementation of a mitochondrial-specific antioxidant, MitoQ, can mitigate DOXO-induced endothelial dysfunction (Aim 2). Overall the proposed research has the potential to address 2 important strategic research priorities of NHLBI: 1) determine the best strategy for reducing vascular morbidity and mortality in childhood cancer survivors who are at enhanced risk of vascular events; 2) identifying therapeutic targets, establishing proof of concept, and developing data for investigational new drug applications to enable early translation of research findings to clinical applications. The sponsor, Dr. Seals, is an internationally recognized and NIH funded scientist with a strong history of successful mentoring in translational biomedical research. With his guidance, and the guidance of consulting mentors Drs. Anthony Donato, Michael Murphy and Judith Campisi, Dr. Clayton will be able to successfully complete the proposed research and training plan, preparing him to succeed as an extramurally-funded independent investigator in translational cardiovascular physiology.
In the proposed project, I will investigate the mechanisms by which the highly effective anti-cancer, anthracycline-chemotherapy drug, doxorubicin (DOXO), mediates vascular endothelial dysfunction in preclinical mouse models, and whether these impairments occur through excess mitochondrial oxidative stress and an impaired compensatory increase in mitochondrial antioxidant defenses. Furthermore, I will determine whether the mitochondria-targeted antioxidant, Mitoquinol Mesylate (MitoQ), can partially or fully restore initial impairments in vascular endothelial function or during middle-age in mice treated with DOXO during adolescence. Overall, this research will be the first to investigate the mechanisms by which DOXO induces endothelial dysfunction with the aim of identifying potential therapeutic targets for counteracting DOXO?s toxic effects on artery health, while also providing initial insight into a promising, novel treatment (MitoQ therapy), thereby reducing risk of cardiovascular diseases.
