Estradiol differentially regulates lipocalin-type prostaglandin D synthase transcript levels in the rodent brain: Evidence from high-density oligonucleotide arrays and in situ hybridization.

Abstract

Microarrays comprise an efficient approach to discovering large numbers of differentially expressed mRNA transcripts in the CNS resulting from changes in hormonal milieu. We used high-density oligonucleotide microarrays to examine the short- and long-term actions of estradiol (E(2)) on the transcriptomes from the medial basal hypothalamus and other brain regions of E(2)-treated (10 microg) adult female mice. Our results have revealed several unanticipated gene regulations. Most striking is lipocalin prostaglandin D(2) synthase (L-PGDS), which catalyzes the conversion of prostaglandin (PG) H(2) to PGD(2), a neuromodulator involved in a variety of functions, including sleep, pain, and odor responses. In situ hybridization revealed significant increases in L-PGDS expression in the arcuate and ventromedial nucleus of the medial basal hypothalamus compared with vehicle controls. The magnitude of these changes is approximately 2-fold and suggests a modulatory role for PGD(2) in E(2)-controlled neuroendocrine secretions and behaviors. Surprisingly, L-PGDS gene expression is reduced 2-fold after E(2) treatment in the ventrolateral preoptic area (VLPO), the suspected site of action for the sleep-promoting effects of PGD(2). Finally, whereas L-PGDS has been reported to be expressed primarily in oligodendrocytes of the adult rodent brain, we demonstrate, immunocytochemically, that L-PGDS is also expressed in a population of VLPO neurons. Thus, our data suggest the intriguing possibility that E(2) modulation of L-PGDS plays a role in the regulation of sleep-wake states through hitherto unknown mechanisms in VLPO neurons and through hormone-dependent neuronal-glial cooperation.