Hypothalamic Median Eminence Thyrotropin-Releasing Hormone-Degrading Ectoenzyme Activity Is Dispensable for Basal Thyroid Axis Activity in Lean Rodents
Por:
Rodríguez-Rodríguez, A, Uribe, RM, Cote-Vélez, A, Joseph-Bravo, P, Charli, JL
Publicada:
15 may 2025
Resumen:
The amplitude of the phasic output of thyrotropin-releasing hormone (TRH) into the hypothalamus-pituitary portal capillaries is likely controlled by the TRH-degrading ectoenzyme (TRH-DE) expressed on the surface of median eminence (ME) beta 2-tanycytes. To extend this hypothesis, we performed experiments on adult rodents reared in standard conditions. TRH-DE was close to the putative sites of TRH release in the male rat external layer of the ME. In global Trhde knockout mice, basal hypothalamus-pituitary-thyroid (HPT) axis parameters were not altered but we detected an increased vimentin (a tanycyte marker) positive coverage of the portal vessels. We then overexpressed TRH-DE or a dominant negative isoform by microinjection of adeno-associated virus 1 (AAV1) vectors into the third ventricle of adult male rats. Two weeks after microinjection, cold-stress-induced serum TSH concentration was decreased if ME TRH-DE activity had been enhanced. However, the long-term modification of TRH-DE activity in the ME had only a small impact on basal serum TSH concentration but increased Trhr expression in the anterior pituitary of animals transduced with AAV1-TRH-DE. Thus, long-term modifications of ME TRH-DE activity lead to limited changes in serum TSH concentration in adult rodents reared in standard conditions, possibly because of adaptations of TRH communication in the ME and/or anterior pituitary.
Filiaciones:
Rodríguez-Rodríguez, A:
Univ Nacl Autonoma Mexico, Dept Genet Desarrollo & Fisiol Mol, Inst Biotecnol, Ave Univ 2001, Cuernavaca 62210, Mexico
Uribe, RM:
Univ Nacl Autonoma Mexico, Dept Genet Desarrollo & Fisiol Mol, Inst Biotecnol, Ave Univ 2001, Cuernavaca 62210, Mexico
Cote-Vélez, A:
Univ Nacl Autonoma Mexico, Dept Genet Desarrollo & Fisiol Mol, Inst Biotecnol, Ave Univ 2001, Cuernavaca 62210, Mexico
Joseph-Bravo, P:
Univ Nacl Autonoma Mexico, Dept Genet Desarrollo & Fisiol Mol, Inst Biotecnol, Ave Univ 2001, Cuernavaca 62210, Mexico
Charli, JL:
Univ Nacl Autonoma Mexico, Dept Genet Desarrollo & Fisiol Mol, Inst Biotecnol, Ave Univ 2001, Cuernavaca 62210, Mexico
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