title: An acute injection of corticosterone increases thyrotrophin-releasing hormone expression in the paraventricular nucleus of the hypothalamus but interferes with the rapid hypothalamus pituitary thyroid axis response to cold in male rats.
abstract: The activity of the hypothalamic-pituitary-thyroid (HPT) axis is rapidly adjusted by energy balance alterations. Glucocorticoids can interfere with this activity, although the timing of this interaction is unknown. In vitro studies indicate that, albeit incubation with either glucocorticoid receptor (GR) agonists or protein kinase A (PKA) activators enhances pro-thyrotrophin-releasing hormone (pro-TRH) transcription, co-incubation with both stimuli reduces this enhancement. In the present study, we used primary cultures of hypothalamic cells to test whether the order of these stimuli alters the cross-talk. We observed that a simultaneous or 1-h prior (but not later) activation of GR is necessary to inhibit the stimulatory effect of PKA activation on pro-TRH expression. We tested these in vitro results in the context of a physiological stimulus on the HPT axis in adult male rats. Cold exposure for 1 h enhanced pro-TRH mRNA expression in neurones of the hypophysiotrophic and rostral subdivisions of the paraventricular nucleus (PVN) of the hypothalamus, thyrotrophin (TSH) serum levels and deiodinase 2 (D2) activity in brown adipose tissue (BAT). An i.p. injection of corticosterone stimulated pro-TRH expression in the PVN of rats kept at ambient temperature, more pronouncedly in hypophysiotrophic neurones that no longer responded to cold exposure. In corticosterone-pretreated rats, the cold-induced increase in pro-TRH expression was detected only in the rostral PVN. Corticosterone blunted the increase in serum TSH levels and D2 activity in BAT produced by cold in vehicle-injected animals. Thus, increased serum corticosterone levels rapidly restrain cold stress-induced activation of TRH hypophysiotrophic neurones, which may contribute to changing energy expenditure. Interestingly, TRH neurones of the rostral PVN responded to both corticosterone and cold exposure with an amplified expression of pro-TRH mRNA, suggesting that these neurones integrate stress and temperature distinctly from the hypophysiotrophic neurones.
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México.
authors.forename: I
authors.initials: I
authors.lastname: Sotelo-Rivera
authors.forename: L
authors.initials: L
authors.lastname: Jaimes-Hoy
authors.forename: A
authors.initials: A
authors.lastname: Cote-Vélez
authors.forename: C
authors.initials: C
authors.lastname: Espinoza-Ayala
authors.forename: J-L
authors.initials: JL
authors.lastname: Charli
authors.forename: P
authors.initials: P
authors.lastname: Joseph-Bravo
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism; D000818:Animals; D003080:Cold Temperature; D003345:Corticosterone / Q000008:administration & dosage / Q000494:pharmacology*; D005786:Gene Expression Regulation; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism*; D007453:Iodide Peroxidase / Q000378:metabolism; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000378:metabolism*; D061251:Primary Cell Culture; D011498:Protein Precursors / Q000096:biosynthesis; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D051381:Rats; D013312:Stress, Physiological / Q000187:drug effects; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000096:biosynthesis*; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D003345:Corticosterone; D007453:Iodide Peroxidase; D011498:Protein Precursors; D011761:Pyrrolidonecarboxylic Acid; D013972:Thyrotropin; D013973:Thyrotropin-Releasing Hormone; D000097564:Iodothyronine Deiodinase Type II; C046418:pro-thyrotropin releasing hormone
keywords: brown adipose tissue; cold exposure; corticosterone; thyroid axis; thyrotrophin-releasing hormone