In Vitro Analysis of the Effects of Acute and Chronic Phthalate Exposures on Leydig Cell Testosterone Production, and the Molecular Mechanisms Involved

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By interfering with hormone function and action, endocrine-disrupting chemicals (EDCs) such as the plasticizer di-(2-ethylhexyl) phthalate (DEHP) can have negative effects on development and reproduction. With the support of a Research Enhancement (SC2) Award, when he was a faculty member at Elizabeth City State University, Dr. Traore found that in vivo exposure to DEHP during gestation had negative effects on testosterone (T) production in the adult, and that early exposure exacerbated the effects of subsequent exposures. Now at Campbell University School of Medicine, Dr. Traore is proposing to conduct in vitro mechanistic studies of both acute and chronic DEHP effects on T production by Leydig cells. Until recently, Leydig cells isolated and cultured by available methods have been able to produce and maintain high levels of T production for only 3-5 days. Therefore, it has not yet been feasible to use primary cells in vitro to examine the direct, long-term effects of environmentally relevant concentrations of EDCs or to critically evaluate mechanisms involved in their actions on Leydig cells. However, Dr. Zirkin’s lab at the Johns Hopkins Bloomberg School of Public Health (JHSPH) has recently developed a method by which Leydig cells derived from the differentiation of Leydig stem cells are able to produce and sustain high levels of T production for longer periods, several months. Dr. Zirkin, who served in a mentorship position for the SC2 Award, is continuing to collaborate with Dr. Traore and his students. The availability of primary Leydig cells able to sustain high levels of T production will be of great value for our proposed studies of the chronic effects of environmentally relevant phthalate concentrations under highly controlled conditions, and the mechanisms by which they function. With the availability of these cells, we will conduct in vitro studies of the direct effects of MEHP on Leydig cell formation from stem cells, the effects of MEHP exposure on the adult Leydig cells, and the effects of early exposures on the consequences of subsequent exposures. We also will conduct mechanistic studies of acute and long-term effects of phthalate-induced oxidative stress on T production. Campbell University has the equipment and facilities necessary for the proposed studies, as well as outstanding medical students, graduate students and undergraduates who will be involved in this research project. With funds of this REAP grant, Dr. Traore will be able to support and expand ongoing research in his lab at Campbell University, an institution located in a rural, underserved area of North Carolina. The extensive collaboration between the Johns Hopkins School of Public Health and Campbell University will not only help excite Campbell University students but also increase their interest in considering careers in basic science or clinical research. Moreover, the project undoubtedly will attract other Campbell University faculty to seek funding to develop their research, and help strengthen the research environment on campus.