Estradiol regulation of lipocalin-type prostaglandin D synthase promoter activity: Evidence for direct and indirect mechanisms

In the CNS, lipocalin-type prostaglandin D synthase (L-PGDS) is predominantly a non-neuronal enzyme responsible for the production of PGD2, an endogenous sleep promoting substance. We have previously demonstrated that estradiol differentially regulates L-PGDS transcript levels in the rodent brain. In hypothalamic nuclei, estradiol increases L-PGDS transcript expression, whereas in the ventrolateral preoptic area L-PGDS gene expression is reduced after estradiol treatment. In the present study, we have used an immortalized glioma cell line transfected with a L-PGDS reporter construct and estrogen receptor (ER) α and ERβ expression plasmids to further elucidate the mechanisms underlying estradiol regulation of L-PGDS gene expression. We found that physiologically relevant concentrations of estradiol evoked an inverted U response in cells expressing ERα. The most effective concentration of estradiol (10−11 M) increased the promoter activity 3-fold over baseline. Expression of ERβ did not increase activity over control and when ERβ was co-expressed with ERα there was a significant attenuation of the promoter activity. While ERα significantly increased L-PGDS promoter activity, our previous in vivo studies demonstrate a greater magnitude of change in L-PGDS gene expression in the presences of estradiol. This led us to ask whether estradiol is signaling via a paracrine factor released by the neighboring neurons. Conditioned media from estradiol treated neurons applied to the glioma cell line resulted in a significant 7-fold increase in L-PGDS promoter activity supporting the possibility that neuronal–glial interactions are involved in estradiol regulation of L-PGDS.