The overall goal of my laboratory is to evaluate the regulation and cell-specific expression of glutathione S-transferases (GSTs) in neural cells and the potential role of GSTs in prevention of neurotoxicity. Recently, I have demonstrated that the concentration of a specific Mu-class GST isoenzyme was greatest in the lateral regions and lowest in the central region in rat cerebellar cortex. This pattern of expression coincides inversely with the known regional susceptibility of this structure to degeneration after insults such as hyperbilirubinemic. In the hyperbilirubinemic Gunn rat, cerebellar Purkinje cells are severely affected in central regions of the cerebellum, while neurons present in the lateral hemispheres and flocculus are less affected. HPLC analysis of GSTs in jaundiced (jj) rats revealed that hyperbilirubinemia increased the concentration of Mu- class GST subunit 4 (yb2) preferentially in the flocculus and lateral hemispheres of the cerebellar cortex, but not the vennis. Interestingly, this effect was present in 2O day old, but not lO day old jj rats. Furthermore, displacement of bilirubin from its albumin binding site by injection of sulfadimethoxine potentiates both the subunit- and region- specific induction of GSTs in jaundiced Gunn rats. Preliminary immunohistochemical analysis of adult cerebellar cortex indicated that Mu- class GST subunit 4 (yb2) immunofluorescence in Bergmann radial glial cells and ependymal cells was more intense in jj rats. In addition, microsomal GST immunofluorescence in Purkinje cells was also more intense in jj rats. These data support the hypothesis that the changes in GST subunit protein concentrations are due to induction in specific cell types. The effect of hyperbilirubinemia on the developmental expression of GSTs in brain , and the potential mechanism(s) mediating the cell-specific induction of GSTs in cerebellum remain to be determined. Thus, the specific aims of this proposal are: 11 To determine the effect of hyperbilirubinemia on the cell-specific pattern of GST expression in nonjaundiced (Jj) and jaundiced (jj) Gunn rat cerebellum during development by immunohistochemistry and in situ hybridiza- tion; 2] To characterize the expression of GSTs in cultured cerebellar slices, primary glial cells and Purkinje cells; 3] To characterize the possible mechanism(s) which regulate GST expression in cerebellar cultures; 4] To determine the potential role of the antioxidant responsive element (ARE) in the induction of neural GSTs by transient transfection of cerebellar cultures with reporter gene constructs regulated by the ARE. The data generated from these studies will significantly increase our understanding of how GSTs are regulated in brain and further our knowledge of the role of these enzymes in modulating neurotoxicity.
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