The Role of Gonadotrope in Stress-Induced Reproductive Impairment

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6. Project Summary/Abstract The impact of stress on reproduction in modern society can lead to unwanted cycle disruption and infertility. As an example, functional hypothalamic amenorrhea (FHA) is an anovulatory condition of mixed origin resulting from decreased GnRH drive and reduced pulsatile gonadotropin secretion. FHA has been attributed to stress, especially psychosocial stress, and is associated with hypothalamic-pituitary-adrenal axis activation and enhanced glucocorticoid secretion. Glucocorticoids have long been considered to be potential mediators of stress-induced suppression of ovarian cyclicity; however, the mechanisms involved are not well understood. The overall goal of this proposal is to test the unifying hypothesis that: Elevated circulating glucocorticoids, in response to stress, impair reproductive function in females. This inhibition occurs both by acute non-genomic and by chronic genomic mechanisms. GR is necessary for stress-induced reproductive dysfunction and contributes to suppression via coordinated actions in the pituitary gonadotrope and GnRH neuron. Three specific aims are proposed to: 1) Test the hypothesis that the chronic inhibitory effect of corticosterone is transduced genomically via a reduction in gonadotropin gene transcription, whereas the acute effect of corticosterone involves non-nuclear GR actions that mediate altered intracellular signaling within the gonadotrope. 2: Investigate stress-induced suppression of gonadotropin synthesis and secretion and disruption of ovarian cyclicity in vivo: role of GR action within the gonadotrope cell. 3: Examine the central actions of stress on reproductive neuroendocrine activity in vivo: influence of ovarian steroids and role of GR within the GnRH neuron. Through multidisciplinary training, the Candidate has carefully carved out a scientific niche for herself. Through her graduate and early postdoctoral work, she determined that glucocorticoids were sufficient to act as inhibitory intermediates within the neuroendocrine axis and necessary for reproductive suppression in response to certain types of stress. With the funding of this PATHWAY TO INDEPENDENCE AWARD, the Candidate will specialize her training to dissect the mechanisms of glucocorticoid regulation of gonadotrope function at the molecular and genetic levels. The University of California, San Diego, is located in La Jolla, California, and is a hotbed of research collaboration. The candidate has assembled a team of mentors from two distinguished institutions, University of California, San Diego and the Salk Institute for Biological Study, which will provide expertise in the assimilation of in vivo and in vitro systems for understanding molecular mechanisms. Dr. Pamela Mellon is located at the University of California, San Diego and is a pioneer in the assimilation of in vivo and in vitro systems for understanding molecular mechanisms. At the Salk Institute, Dr. Catherine Rivier will provide expertise in the integration of stress paradigms and stress systems for the study of reproductive neuroendocrine dysfunction. The guidance of these mentors, in conjunction with the candidate's previous work in molecular neuroendocrinology, will provide a solid foundation for the candidate to develop an independent multidisciplinary research program aimed at understanding the molecular basis reproductive neuroendocrine dysfunction. These valuable research experiences will span the study of molecular and cellular mechanisms to whole animal in vivo physiologic function, placing her in a powerful position as a young investigator armed with a host of research skills, techniques and training, all of which would not be possible without transitional K99/R00 funding.