Role of CRH in skin physiology and pathology

University Of Tennessee Health Sci Ctr, Memphis TN

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Abstract

DESCRIPTION (provided by applicant): The skin is both target and source for proopiomelanocortin (POMC)-derived neuropeptides. Corticotropin releasing hormone (CRH) and CRH receptors (CRH-R) are also expressed and fully functional in rodent and human skin, but its significance is not known. CRH and CRH receptors are recognized as main central regulators in the response to systemic stress and CRH peptide has pleiotropic role in regulation of local homeostasis. Therefore, we will investigate whether CRH can regulate local expression of POMC gene, mimicking therefore pituitary physiology, and/or to clarify its specific actions in the skin. Within this context, CRH itself is a potent immunomodulatory factor, acts on vascular function, and is also a local growth factor. These actions suggest that in the skin the role of CRH peptide could be pleiotropic in the regulation of local homeostasis. Our initial objective is the biochemical and functional characterization of the CRH-CRH receptor system in mammalian skin. The specific aims are as follow: 1. To define local mechanisms regulating the expression of CRH in normal melanocytes and keratinocytes; 2. To fully characterize the CRH-R1 receptors in normal melanocytes and keratinocytes by a) defining CRH binding site properties, b) measuring production of second messengers including cAMP, IP3 and Ca, c) testing whether postreceptor CRH signal transduction includes activation transcriptional regulators such as NF-kappa beta, CRE, AP1 and STAT; 3. To test the effect of CRH on the production of the POMC mRNA and POMC-derived peptides in normal melanocytes and keratinocytes; 4. To test the phenotypic effect of CRH on normal epidermal melanocytes and keratinocytes; 5. To test CRH participation in regulation of human hair growth and pigmentation. This will be evaluated in human hair follicle grown ex vivo and in isolated sub-populations of hair follicle-derived follicular melanocytes and keratinocytes and dermal papilla cells. To accomplish these goals we will use standard molecular, biochemical, and cell biology tools, which are currently available in our laboratory. As experimental models we will use epidermal and follicular keratinocytes and melanocytes as well as dermal papilla cells. The realization of the above aims should clarify the role of CRH and CRH receptors in the peripheral (skin) response to stress. The core of the project is the realization of the functional biochemical overlap between the cutaneous and hypothalamic CRH-activating systems. Whereas the central interactions between CRH together with CRH-Rs coordinates the behavioral, autonomic and endocrine responses to systemic stress, the present work will test whether that role extends to peripheral organs. Thus, we will test the effects of common stressors on expression of CRH and CRH-Rs, CRH effect on POMC expression. Moreover, we will characterize these CRH receptors and define their role in the regulation of phenotype in the most important components of the epidermis, e.g., melanocytes and keratinocytes, and test the role of CRH/CRH-R1 axis in the regulation of human hair growth.