RESUMO
SOM230 (pasireotide) is a multiligand somatostatin (SRIF) analog able to bind to somatostatin receptor (SSTR) subtypes 1, 2, 3 and 5, and trigger antisecretory and antiproliferative signaling cascades. Canines have become in vivo models to test the pharmacological treatment of corticotropinomas because they frequently develop Cushing's disease in a spontaneous manner, due to adrenocorticotropic hormone (ACTH)-producing pituitary adenomas. Different levels of expression of SSTR2 and SSTR5 have been shown in both mouse AtT20 cells and canine tumoral corticotropinoma cells. The objective of this study was to evaluate whether SOM230 controls both tumor cell growth and hormone synthesis, therefore controlling the disease. SOM230 was tested in dogs suffering from Cushing's disease (10 animals were treated continuously during 6 months, and another 10 were treated with 3 cycles consisting of 2 months of treatment followed by a 2-month rest period). A significant decrease in ACTH, urinary cortisol creatinine ratio, adenoma size (magnetic nuclear resonance) and improvement of clinical signs were obtained, without side effects. AtT20 cells treated with SOM230 suppressed pro-opiomelanocortin (POMC) promoter activity through SSTR2, via the G(i) α-subunit, and reduced Nur77/Nurr1 transcriptional activity. We conclude that SOM230, in addition to its well-described antisecretory effects, inhibits, as shown in AtT20 cells, ACTH synthesis at the POMC transcriptional level, an effect mediated mainly through SSTR2, and limits tumor growth. The controlled Cushing's disease in the dogs that received the treatment indicates that SOM230 has a potential therapeutic use in humans suffering from Cushing's disease.
Assuntos
Hormônio Adrenocorticotrópico/biossíntese , Corticotrofos/efeitos dos fármacos , Corticotrofos/metabolismo , Hipersecreção Hipofisária de ACTH/metabolismo , Somatostatina/análogos & derivados , Hormônio Adrenocorticotrópico/sangue , Alanina Transaminase/sangue , Fosfatase Alcalina/sangue , Animais , Aspartato Aminotransferases/sangue , Glicemia/metabolismo , Linhagem Celular Tumoral , Colesterol/sangue , Creatinina/urina , Cães , Feminino , Hidrocortisona/urina , Testes de Função Hepática , Imageamento por Ressonância Magnética , Masculino , Hipersecreção Hipofisária de ACTH/patologia , Somatostatina/farmacologia , Triglicerídeos/sangue , alfa-MSH/sangueRESUMO
The regulatory role of estrogen, bone morphogenetic protein-4 (BMP-4), and TGF-beta has a strong impact on hormone secretion, gene transcription, and cellular growth of prolactin (PRL)-producing cells. In contrast to TGF-beta, BMP-4 induces the secretion of PRL in GH3 cells. Therefore, we studied the mechanism of their transcriptional regulation. Both BMP-4 and TGF-beta inhibited the transcriptional activity of the estrogen receptor (ER). Estrogens had no effect on TGF-beta-specific Smad protein transcriptional activity but presented a stimulatory action on the transcriptional activity of the BMP-4-specific Smads. BMP-4/estrogen cross talk was observed both on PRL hormone secretion and on the PRL promoter. This cross talk was abolished by the expression of a dominant-negative form for Smad-1 and treatment with ICI 182780 but not by point mutagenesis of the estrogen response element site within the promoter, suggesting that Smad/ER interaction might be dependent on the ER and a Smad binding element. By serial deletions of the PRL promoter, we observed that indeed a region responsive to BMP-4 is located between -2000 and -1500 bp upstream of the transcriptional start site. Chromatin immunoprecipitation confirmed Smad-4 binding to this region, and by specific mutation and gel shift assay, a Smad binding element responsible site was characterized. These results demonstrate that the different transcriptional factors involved in the Smad/ER complexes regulate their transcriptional activity in differential ways and may account for the different regulatory roles of BMP-4, TGF-beta, and estrogens in PRL-producing cells.
Assuntos
Proteína Morfogenética Óssea 4/metabolismo , Estrogênios/farmacologia , Lactotrofos/metabolismo , Prolactina/genética , Regiões Promotoras Genéticas , Fator de Crescimento Transformador beta/metabolismo , Animais , Sítios de Ligação , Proteína Morfogenética Óssea 4/fisiologia , Células Cultivadas , Estrogênios/metabolismo , Lactotrofos/efeitos dos fármacos , Prolactina/metabolismo , Regiões Promotoras Genéticas/efeitos dos fármacos , Regiões Promotoras Genéticas/fisiologia , Ligação Proteica/fisiologia , Ratos , Receptor Cross-Talk/efeitos dos fármacos , Receptor Cross-Talk/fisiologia , Receptores de Estrogênio/metabolismo , Receptores de Estrogênio/fisiologia , Proteínas Smad/metabolismo , Proteínas Smad/fisiologia , Ativação Transcricional/fisiologia , Fator de Crescimento Transformador beta/fisiologiaRESUMO
OBJECTIVE: In a previous study, we reported an imbalance in the hypothalamus-pituitary-adrenal axis of mice acutely infected with the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. METHODS: Possible effects of this parasitic infection on the endocrine function of other pituitary cell types were studied, in particular regarding the production of prolactin (PRL) and growth hormone (GH). RESULTS: In the mammosomatotrophic cell line GH3, both GH and PRL secretion were decreased, reflecting the diminished PRL concentrations in the pituitary glands of infected mice. Additionally, expression of extracellular matrix proteins, e.g. laminin, was increased in T. cruzi-infected GH3 cells, which may be related to the diminished secretory function of these cells. Lastly, the expression of Pit-1, a major transcription factor for the PRL and GH genes, is also decreased in T. cruzi-infected cultures. CONCLUSION: T. cruzi infection downregulates PRL and GH production. Combined with our previous data showing increased glucocorticoid levels following T. cruzi infection, the immunosuppression induced by T. cruzi infection may be partially related to multiple endocrine changes involving the hypothalamus-pituitary axis and corresponding target endocrine glands.
Assuntos
Hormônio do Crescimento/metabolismo , Tolerância Imunológica/imunologia , Hipófise/metabolismo , Hipófise/parasitologia , Prolactina/metabolismo , Trypanosoma cruzi/imunologia , Animais , Células Cultivadas , Doença de Chagas/imunologia , Doença de Chagas/fisiopatologia , Regulação para Baixo/fisiologia , Sistema Endócrino/metabolismo , Sistema Endócrino/fisiopatologia , Matriz Extracelular/metabolismo , Hormônio do Crescimento/genética , Sistema Hipotálamo-Hipofisário/metabolismo , Sistema Hipotálamo-Hipofisário/parasitologia , Sistema Hipotálamo-Hipofisário/fisiopatologia , Laminina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Hipófise/fisiopatologia , Prolactina/genética , Fator de Transcrição Pit-1/metabolismoRESUMO
Cushing's disease is almost always caused by an ACTH-secreting pituitary tumor, but effective medical therapy is currently limited. Because retinoic acid has been shown to be potentially useful in decreasing corticotroph secretion and proliferation in rodent models, we have studied its action in dogs with Cushing's disease. A randomized treatment with retinoic acid (n = 22) vs. ketoconazole (n = 20) in dogs with Cushing's disease was assigned for a period of 180 d. Clinical signs, plasma ACTH and alpha-MSH, the cortisol/creatinine urine ratio, and pituitary magnetic resonance imaging were assessed and compared at different time points. We recorded a significant reduction in plasma ACTH and alpha-MSH, and also in the cortisol/creatinine urine ratio, of the dogs treated with retinoic acid. Pituitary adenoma size was also significantly reduced at the end of retinoic acid treatment. Survival time and all the clinical signs evaluated showed an improvement in the retinoic-acid-treated dogs. No adverse events or signs of hepatotoxicity were observed, suggesting that the drug is not only effective but also safe. Retinoic acid treatment controls ACTH and cortisol hyperactivity and tumor size in dogs with ACTH-secreting tumors, leading to resolution of the clinical phenotype. This study highlights the possibility of using retinoic acid as a novel therapy in the treatment of ACTH-secreting tumors in humans with Cushing's disease.
Assuntos
Doenças do Cão/tratamento farmacológico , Hipersecreção Hipofisária de ACTH/veterinária , Tretinoína/uso terapêutico , Adenoma/patologia , Hormônio Adrenocorticotrópico/sangue , Animais , Peso Corporal , Creatinina/urina , Cães , Feminino , Hidrocortisona/urina , Cetoconazol/uso terapêutico , Imageamento por Ressonância Magnética/veterinária , Masculino , Hipersecreção Hipofisária de ACTH/tratamento farmacológico , Hipersecreção Hipofisária de ACTH/patologia , Hipófise/patologia , Neoplasias Hipofisárias/patologia , Taxa de Sobrevida , alfa-MSH/sangueRESUMO
Functional interactions between neuroendocrine and immune systems are mediated by similar ligands and receptors, which establish a bi-directional communication that is relevant for homeostasis. We investigated herein the hypothalamus-pituitary-adrenal (HPA) axis in mice acutely infected by Trypanosoma cruzi, the causative agent of Chagas' disease. Parasites were seen in the adrenal gland, whereas T. cruzi specific PCR gene amplification product was found in both adrenal and pituitary glands of infected mice. Histological and immunohistochemical analyses of pituitary and adrenal glands of infected animals revealed several alterations including vascular stasis, upregulation of the extracellular matrix proteins fibronectin and laminin, as well as T cell and macrophage infiltration. Functionally, we detected a decrease in CRH and an increase in corticosterone contents, in hypothalamus and serum respectively. In contrast, we did not find significant changes in the amounts of ACTH in sera of infected animals, whereas the serum levels of the glucocorticoid-stimulating cytokine, IL-6 (interleukin-6), were increased as compared to controls. When we analyzed the effects of T. cruzi in ACTH-producing AtT-20 cell line, infected cultures presented lower levels of ACTH and pro-opiomelanocortin production when compared to controls. In these cells we observed a strong phosphorylation of STAT-3, together with an increased synthesis of IL-6, suppressor of cytokine signaling 3 (SOCS-3) and inhibitor of activated STAT-3 (PIAS-3), which could explain the partial blockage of ACTH production. In conclusion, our data reveal that the HPA axis is altered during acute T. cruzi infection, suggesting direct and indirect influences of the parasite in the endocrine homeostasis.