RESUMO
Normal anterior pituitary function is essential for fertility. Release from the gland of the reproductive hormones luteinising hormone and follicle-stimulating hormone is regulated primarily by hypothalamically-derived gonadotrophin-releasing hormone (GnRH), although other releasing factors (RF) have been postulated to exist. Using a bioinformatic approach, we have identified a novel peptide, phoenixin, that regulates pituitary gonadotrophin secretion by modulating the expression of the GnRH receptor, an action with physiologically relevant consequences. Compromise of phoenixin in vivo using small interfering RNA resulted in the delayed appearance of oestrus and a reduction in GnRH receptor expression in the pituitary. Phoenixin may represent a new class of hypothalamically-derived pituitary priming factors that sensitise the pituitary to the action of other RFs, rather than directly stimulating the fusion of secretary vesicles to pituitary membranes.
Assuntos
Hormônios Hipotalâmicos/metabolismo , Hormônios Peptídicos/metabolismo , Hormônios Hipofisários/isolamento & purificação , Reprodução/genética , Sequência de Aminoácidos , Animais , Células Cultivadas , Clonagem Molecular , Relação Dose-Resposta a Droga , Feminino , Fármacos para a Fertilidade/química , Fármacos para a Fertilidade/isolamento & purificação , Fármacos para a Fertilidade/metabolismo , Fármacos para a Fertilidade/farmacologia , Hormônio Liberador de Gonadotropina/genética , Hormônio Liberador de Gonadotropina/metabolismo , Hormônios Hipotalâmicos/genética , Hormônios Hipotalâmicos/isolamento & purificação , Hormônios Hipotalâmicos/farmacologia , Hormônio Luteinizante/sangue , Masculino , Dados de Sequência Molecular , Hormônios Peptídicos/genética , Hormônios Peptídicos/isolamento & purificação , Hormônios Peptídicos/farmacologia , Hormônios Hipofisários/genética , Hormônios Hipofisários/metabolismo , Hormônios Hipofisários/farmacologia , Ratos , Ratos Sprague-Dawley , Reprodução/efeitos dos fármacos , Reprodução/fisiologia , Homologia de Sequência de AminoácidosRESUMO
Recent advances in comparative genomics allow a new paradigm for hormonal research. At the centennial of the first use of the term hormone by Ernest Starling, we reflected on the changing approaches in elucidating hormonal signaling mechanisms and highlighted the inadequacy of the term endocrinology, implying remote activation, to describe the diverse modes of hormone actions. Several examples were presented to underscore the power of comparative genomics in the identification of new polypeptide hormones, receptors, and signaling pathways. We propose the use of the term hormonology to more accurately reflect the expanding boundaries of the discipline.
Assuntos
Genômica , Hormônios/fisiologia , Proteína Morfogenética Óssea 15 , Proteína Morfogenética Óssea 2 , Proteínas Morfogenéticas Ósseas/genética , Proteínas Morfogenéticas Ósseas/fisiologia , Comunicação Celular/genética , Comunicação Celular/fisiologia , Genoma Humano , Fator 9 de Diferenciação de Crescimento , Hormônios/sangue , Hormônios/genética , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/genética , Peptídeos e Proteínas de Sinalização Intercelular/fisiologia , Ligantes , Hormônios Peptídicos/genética , Hormônios Peptídicos/fisiologia , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/fisiologia , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Fator de Crescimento Transformador beta/genética , Fator de Crescimento Transformador beta/fisiologiaRESUMO
Urocortin (UCN), a member of the Corticotropin-Releasing Factor (CRF) family of peptides is a well described cardioprotective agent. UCN is able to bind to two types of G-protein coupled receptors: CRF receptor type 1 (CRFR1) and CRF receptor type 2 (CRFR2), whereas, two homologues of UCN, stresscopin (SCP) or also known as urocortin III (UCNIII) and stresscopin related peptide (SRP), or urocortin II (UCNII), bind exclusively and with high affinity to CRFR2, we hypothesised that they will exhibit more pronounced cardioprotective effects than UCN. We show for the first time that SCP is expressed in rat cardiomyocytes and that the levels of SRP and SCP are increased by hypoxic stress. All three peptides have potent cardioprotective effects in cells exposed to hypoxia/reoxygenation. When used at 10(-8) M they increased the amount of live cells by 25% when added prior to hypoxia, and by 20% when UCN and SCP were added at the onset of reoxygenation. In addition, the peptides are equally are more potent antiapoptotic factors than UCN. The antiapoptotic effects of SCP were more pronounced than SRP and UCN at a concentration of 10(-10) M. Furthermore, SCP and SRP protect cardiomyocytes better than UCN at concentrations up to and including 10(-10) M and reduced the amount of TUNEL positive cells almost by half at concentrations of 10(-12) to 10(-10) M. More importantly, we demonstrate that SCP and SRP are able to protect cardiomyocytes even if they are administered after the hypoxic insult and prior to reoxygenation. In this case SCP was more potent than UCN and SRP at 10(-12) M and both SCP and SRP exhibited higher protection at 10(-8) M compared to UCN. Cardioprotection of cardiomyocytes by 10(-8) M of peptides was abolished when treated with 50 microM LY294002 or 100 microM PD98059, but not by 10 microM SB203580 prior to the hypoxic insult. Transfection of dominant negative Akt and MEK1 also blocked protection by the peptides, whereas dominant negative MEKK6 had no effects, demonstrating that SCP and SRP, like UCN, require activation of p42/44 Mitogen activated protein kinase and Akt/Protein Kinase B in order to produce their cardioprotective effects. In addition, we showed that SCP and UCN are potent activators of the p42/44 MAPK pathway, with SRP able to induce phosphorylation of p42/44 MAPK as well, albeit not as pronounced.