CYTOKINES AND STEROID ENZYME EXPRESSION IN BRAIN

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Cytokines could account for many of the clinical and histopathological findings in the brains of AIDS patients. Our long-term objectives are to elucidate the cellular and molecular mechanisms underlying cytokine actions in the brain. Indirect evidence suggests that some of the cytokine-induced neurological symptoms may be the consequence of activation of the gamma- aminobutyric acid (GABA) receptor complex. Activation of the GABAA receptor results in neurological symptoms that are similar to some of these exhibited by AIDS patients, e.g., anxiety, drowsiness, and motor dysfunction. Moreover, cytokines can act like GABA agonists in that they induce analgesia. Because GABA is the major inhibitory neurotransmitter in the brain and because the GABA receptor is ubiquitously distributed in the brain, abnormal activation of the receptor by cytokines may affect a wide range of brain functions. Our working hypothesis is that cytokine-induced neurological symptoms are due, in part, to activation of the GABA receptor complex and that activation is brought about by increasing the extracellular concentrations of the GABA-receptor ligand 3alpha-hydroxy- 5alpha-dihydroprogesterone (3alphaDHP). We focus our studies on 3alphaDHP, since it is an extremely potent ligand and activator of the GABAA receptor and since it is produced within the brain. We have recently implemented an excellent culture system of dissociated fetal brain cells expressing several steroid metabolizing enzymes including 3alpha-hydroxysteroid oxidoreductase (3alpha-HSOR), the enzyme catalyzing the formation of 3alphaDHP. S.A. 1: to validate that the aggregate culture system can serve as a model to study the regulation of the expression of 3alpha-HSOR. We will establish that the 3alpha-HSOR expressed in intact brain is the enzyme expressed in our cultures; using molecular biology methodology. S.A. 2: to test the hypothesis that interleukin (IL) - 1 induces 3alphaDHP production by the aggregates. We will investigate the effect of IL-1 on steady state levels of 3alpha-HSOR mRNA and protein, and on enzyme activity. We will define the time course and dose dependency of IL-1 action and whether there is a critical time in culture during which IL-1 exerts its effect. These results will serve as the foundation for an extensive, full-scale proposal to elucidate the molecular mechanisms underlying cytokine regulation of 3alpha-HSOR expression in the brain. Hence, the results of these studies will provide new insight into the cellular and molecular mechanisms underlying cytokine actions and their role in the generation of neurological symptoms in HIV-infected people.