title: Thyrotropin-releasing hormone and c-fos/c-jun genes are colocalized in rat anterior pituitary cells: stimulation of transcription by glucocorticoids.
abstract: We recently reported that glucocorticoids (GC) enhance the level of TRH peptide and messenger RNA in anterior pituitary cells. However, the regulating mechanism is as yet unclear. The protooncogenes c-fos/c-jun belong to the class of immediate early genes that are activated in neurons by a variety of stimuli, including GC. Fos protein acts as an intracellular third messenger, regulating gene transcription of neurotransmitters. To determine whether c-fos/c-jun are involved in regulating the effect of GC on TRH in rat anterior pituitary cells, the coexpression and nuclear transcription activity of TRH and c-fos/c-jun after dexamethasone (DEX) stimulation (7 days) were investigated. The double labeled in situ hybridization results demonstrated that TRH and c-fos/c-jun are coexpressed in anterior pituitary cells and that DEX (10(-8) M) enhanced the cell intensity for TRH and c-fos/c-jun. The mean cell intensity of treatment vs. control was 2.4-fold for TRH, 1.4-fold for c-fos, and 1.4-fold for c-jun (n = 24; P < 0.01). The Northern blot analysis also showed that DEX increased the messenger RNA level of TRH 5.1-fold (n = 4; P < 0.01), that of c-fos 1.8-fold (n = 5; P < 0.01), and that of c-jun 4.2-fold (n = 4; P < 0.01). The nuclear run-on analysis indicated that DEX increased the nuclear transcription activity of TRH 3.3-fold, that of c-jun 3.2-fold, and that of c-fos 3-fold (n = 3; P < 0.01) vs. the control value. The coexpression of TRH and c-fos/c-jun in anterior pituitary cells as well as the enhancement of transcription after DEX treatment raise the possibility that c-fos/c-jun could mediate the effect of GC on TRH gene transcriptional activity.
authors.affiliation: Division of Endocrinology, Rhode Island Hospital, Brown University School of Medicine, Providence 02903, USA.
authors.forename: L
authors.initials: L
authors.lastname: Luo
authors.forename: I M
authors.initials: IM
authors.lastname: Jackson
mesh_terms: D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D015870:Gene Expression; D016762:Genes, fos; D016758:Genes, jun; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D012333:RNA, Messenger; D013973:Thyrotropin-Releasing Hormone; D003907:Dexamethasone