Neuroimmune Mechanisms of Glucocorticoid Resistance

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DESCRIPTION (provided by applicant): A number of illnesses including autoimmune, infectious and inflammatory disorders as well as certain neuropsychiatric disorders such as major depression have been associated with decreased responsiveness to glucocorticoids. Impaired responsiveness to glucocorticpids in turn is believed to contribute to excessive inflammation as well as hyperactivity of corticotropin releasing hormone (CRH) and sympathetic nervous system pathways, which may contribute to behavioral alterations. The primary hypothesis of this proposal is that chronic exposure to proinflammatory cytokines as may occur in the context of chronic medical illness and/or chronic stress leads to impaired glucocorticoid responsiveness through direct effects on the glucocorticoid receptor (GR). The long-term objectives of the proposed work are to determine the molecular mechanisms by which cytokines influence GR signaling and to identify specific signaling molecules/pathways that may be targeted to reverse cytokine-induced GR changes. In this project, the following specific aims are proposed: 1) to determine the signal transduction pathways that mediate the effects of proinflammatory cytokines and other immunoregulatory cytokines on GR function, 2) to determine the interaction of PKA and proinflammatory signaling pathways in the regulation of GR, and 3) to investigate the relationship between intracellular p38, JNK, STAT, and NF-kB signaling pathways and PKA signaling pathways as they relate to GR signaling, neuroendocrine function and mood in patients treated with IFN-a for hepatitis C. To accomplish these aims, a series of in vitro studies (Aims 1 and 2) will be conducted on cell lines and primary cells, examining the impact of IL-1-and IFN-alpha-induced signal transduction events (including activation of p38, JNK, and STAT as well as NF-kB and COX signaling pathways) on GR function. In Aim 2, these studies will be expanded to examine the interaction of PKA signaling pathways with IL-1-and IFN-alpha-induced signaling pathways using PKA deficient cell lines and primary cells (fibroblasts) from depressed patients with reduced PKA activity. Finally, in Aim 3, 30 patients with hepatitis C will be assessed before and during IFN-alpha treatment and compared to 15 hepatitis C patients awaiting IFN therapy. IFN-alpha is a potent activator of proinflammatory cytokines and is notorious for inducing mood alterations. Peripheral blood mononuclear cells will be obtained from IFN-alpha-treated patients for the assessment of p38, JNK, and STAT as well as NF-kB, STAT, COX-2 and PKA signaling. Results will be correlated with data being collected in a companion study examining mood and in vivo measures of glucocorticoid responsiveness (Dex-CRH test). Taken together, these studies will help identify novel targets for the treatment of mood disorders in both medically ill and medically healthy patients.