RESUMO
Cellular senescence is a stable proliferative arrest state. Pituitary adenomas are frequent and mostly benign, but the mechanism for this remains unknown. IL-6 is involved in pituitary tumor progression and is produced by the tumoral cells. In a cell autonomous fashion, IL-6 participates in oncogene-induced senescence in transduced human melanocytes. Here we prove that autocrine IL-6 participates in pituitary tumor senescence. Endogenous IL-6 inhibition in somatotroph MtT/S shRNA stable clones results in decreased SA-ß-gal activity and p16INK4a but increased pRb, proliferation and invasion. Nude mice injected with IL-6 silenced clones develop tumors contrary to MtT/S wild type that do not, demonstrating that clones that escape senescence are capable of becoming tumorigenic. When endogenous IL-6 is silenced, cell cultures derived from positive SA-ß-gal human tumor samples decrease the expression of the senescence marker. Our results establish that IL-6 contributes to maintain senescence by its autocrine action, providing a natural model of IL-6 mediated benign adenoma senescence.
Assuntos
Comunicação Autócrina , Interleucina-6/genética , Interleucina-6/metabolismo , Neoplasias Hipofisárias/metabolismo , Animais , Linhagem Celular Tumoral , Proliferação de Células , Senescência Celular , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Humanos , Camundongos , Camundongos Nus , Invasividade Neoplásica , Transplante de Neoplasias , Fosforilação , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/patologia , Proteína do Retinoblastoma/metabolismo , beta-Galactosidase/metabolismoRESUMO
Background: Measuring circulating cardiac troponin using novel sensitive assays has revealed that even minute elevations are associated with increased mortality in patients with coronary artery disease or even in the general population. Less well defined, however, is the incremental value of measuring circulating cardiac troponin I (cTnI) by a sensitive assay for risk assessment in primary prevention. Methods: We measured circulating concentrations of cTnI, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and high-sensitivity C-reactive protein (hsCRP) in 5388 individuals free of known cardiovascular disease recruited into the DETECT study, a prospective longitudinal population-based cohort study. We determined the prognostic implications for incident major adverse cardiovascular events (MACE) during 5 years of follow-up. Results: Circulating cTnI was detectable in 19% of the subjects. Increased cTnI concentrations were associated with established risk factors for atherosclerosis and demonstrated a graded relationship with all-cause mortality and incident MACE during 5-year follow-up. A single measurement of cTnI significantly improved risk prediction over established risk factors, and also added prognostic information, when adjusted for serum concentrations of NT-proBNP and hsCRP. Conclusions: Minute increases in cTnI are associated with increased mortality and incident MACE in a large primary prevention cohort and, thus, identify contributors to cardiovascular risk not fully captured by traditional risk factor assessment.
Antecedentes: La medición de troponina cardíaca en circulación mediante nuevos ensayos sensibles ha revelado que incluso mínimas elevaciones se asocian con mayor mortalidad en pacientes con enfermedad arterial coronaria, o incluso en la población general. Sin embargo, menos conocido es el valor incremental o agregado de la medición de la troponina I cardiaca (cTnI) circulante mediante un ensayo sensible para la evaluación del riesgo en prevención primaria. Métodos: Se midieron las concentraciones circulantes de cTnI, de pro- péptido natriurético tipo B N-terminal (NT-proBNP), y de proteína C reactiva de alta sensibilidad (PCRus), en 5388 personas sin enfermedad cardiovascular conocida reclutadas en el estudio DETECT, un estudio prospectivo longitudinal de cohorte de base poblacional. Se determinaron las implicancias pronósticas en la incidencia de eventos adversos cardiovasculares mayores (MACE) durante 5 años de seguimiento. Resultados: La cTnI se detectó en el 19% de los sujetos. El aumento de las concentraciones de cTnI se asoció con factores de riesgo establecidos para la aterosclerosis y demostró una relación gradual con la mortalidad por todas las causas y la incidencia de MACE durante los 5 años de seguimiento. Una sola medición de cTnI mejoró significativamente la predicción del riesgo por encima de los factores de riesgo establecidos, y también agregó información pronóstica cuando se ajustó por la concentración sérica de NT-proBNP y PCRus. Conclusiones: Mínimos incrementos de cTnI se asociaron con mayor mortalidad e incidencia de MACE en una gran cohorte de prevención primaria y, por tanto, la identificación de sujetos con riesgo cardiovascular no siempre son detectados completamente por la evaluación de factores de riesgo tradicionales.
Assuntos
Humanos , Doenças Cardiovasculares/prevenção & controle , Troponina I/sangue , Biomarcadores , Doenças Cardiovasculares/diagnóstico , Prevenção Primária , Fatores de RiscoRESUMO
The anterior pituitary gland has the ability to respond to complex signals derived from central and peripheral systems. Perception of these signals and their integration are mediated by cell interactions and cross-talk of multiple signaling transduction pathways and transcriptional regulatory networks that cooperate for hormone secretion, cell plasticity, and ultimately specific pituitary responses that are essential for an appropriate physiological response. We discuss the physiopathological and molecular mechanisms related to this integrative regulatory system of the anterior pituitary gland and how it contributes to modulate the gland functions and impacts on body homeostasis.
Assuntos
Comunicação Celular/fisiologia , Hipófise/citologia , Hipófise/fisiologia , Transdução de Sinais/fisiologia , Animais , Sistema Endócrino/fisiologia , Homeostase/fisiologia , Hormônios/metabolismo , Humanos , Sistemas Neurossecretores/fisiologiaRESUMO
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
Research performed on the pituitary has proven that cytokines play an important role in maintaining pituitary physiology, affecting not only cell proliferation but also hormone secretion. The effects of cytokines can be autocrine or paracrine. This review gives an overview on the effects of the most studied cytokines in the pituitary. Special interest is focused on interleukin-6 (IL-6) because it has the distinctive characteristic of stimulating pituitary tumor cell growth, but has the opposite effect on normal pituitary cells. On the other hand, IL-6 is a cytokine of interest in the pituitary because recent work has shown that it promotes and maintains senescence in certain types of tumors. Given that the majority of pituitary adenomas are microadenomas and the fact that clinically inapparent pituitary tumors are quite common, senescence, perhaps mediated by IL-6, is an attractive mechanism for explaining the benign nature of pituitary tumors.
Assuntos
Citocinas/fisiologia , Hipófise/fisiologia , Adenoma/etiologia , Animais , Senescência Celular/fisiologia , Citocinas/metabolismo , Humanos , Interleucina-6/fisiologia , Modelos Biológicos , Hipófise/crescimento & desenvolvimento , Hipófise/metabolismo , Hipófise/patologia , Neoplasias Hipofisárias/etiologiaRESUMO
Although several genes and signalling pathways have been identified as important effectors in the development of pituitary tumours, our understanding of pituitary tumorigenesis remains incomplete and is the focus of much current research. Use of the mRNA differential display technique in prolactinomas from D2-receptor knockout mice and in stable GH3 cell line clones with enhanced tumorigenicity in vivo has led to the identification of two genes that are involved in the pathogenic process--BMP-4 and RSUME. Bone morphogenetic protein-4 (BMP-4) has been found to have a crucial role in prolactinoma development and also in signalling crosstalk with oestrogens. In contrast, BMP-4 has an inhibitory role in corticotrophinomas. RSUME (RWD-containing sumoylation enhancer) was identified from a transformed lactosomatotrophic cell line that had increased tumorigenic and angiogenic potential. Expression of RSUME was induced under hypoxic conditions and it has a potential role during vascularization. The differential expression and action of BMP-4 in prolactinomas and corticotrophinomas highlights the importance of studying a gene with contrasting actions in two cell lineages of the same organ in order to understand the pituitary transformation process. Both BMP-4 and RSUME may be interesting targets for inhibiting steps involved in pituitary tumorigenesis.
Assuntos
Proteína Morfogenética Óssea 4/biossíntese , Regulação Neoplásica da Expressão Gênica , Modelos Biológicos , Proteínas de Neoplasias/biossíntese , Prolactinoma/metabolismo , Fatores de Transcrição/biossíntese , Animais , Proteína Morfogenética Óssea 4/genética , Hipóxia Celular/genética , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Perfilação da Expressão Gênica , Humanos , Camundongos , Camundongos Knockout , Proteínas de Neoplasias/genética , Prolactinoma/genética , Prolactinoma/terapia , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Transdução de Sinais/genética , Fatores de Transcrição/genéticaRESUMO
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
SUMO conjugation to proteins is involved in the regulation of diverse cellular functions. We have identified a protein, RWD-containing sumoylation enhancer (RSUME), that enhances overall SUMO-1, -2, and -3 conjugation by interacting with the SUMO conjugase Ubc9. RSUME increases noncovalent binding of SUMO-1 to Ubc9 and enhances Ubc9 thioester formation and SUMO polymerization. RSUME enhances the sumoylation of IkB in vitro and in cultured cells, leading to an inhibition of NF-kB transcriptional activity. RSUME is induced by hypoxia and enhances the sumoylation of HIF-1alpha, promoting its stabilization and transcriptional activity during hypoxia. Disruption of the RWD domain structure of RSUME demonstrates that this domain is critical for RSUME action. Together, these findings point to a central role of RSUME in the regulation of sumoylation and, hence, several critical regulatory pathways in mammalian cells.
Assuntos
Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Proteína SUMO-1/metabolismo , Fatores de Transcrição/fisiologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Hipóxia Celular , Linhagem Celular Tumoral , Chlorocebus aethiops , Humanos , Quinase I-kappa B/metabolismo , Dados de Sequência Molecular , NF-kappa B/metabolismo , Especificidade de Órgãos , Ligação Proteica , Proteínas Modificadoras Pequenas Relacionadas à Ubiquitina/metabolismo , Fatores de Transcrição/genética , Enzimas de Conjugação de Ubiquitina/metabolismo , Ubiquitinas/metabolismoRESUMO
Highly sophisticated mechanisms confer on the immune system the capacity to respond with a certain degree of autonomy. However, the final outcome of an immune response depends on the interaction of the immune system with other systems. The immune and neuroendocrine systems have an intimate cross-communication that makes possible a satisfactory response to environmental changes. Part of this interaction occurs through cytokines and steroid hormones. The last step of this cross-talk is the molecular level. As a model of interaction, this review focuses on the gp130 cytokine family. These cytokines, as well as their receptors, are expressed in pituitary cells. They regulate hormone production as well as growth of pituitary cells. During acute or chronic inflammation or infection, systemic, hypothalamic and hypophyseal gp130 cytokines act on anterior pituitary cells, integrating the neuroendocrine-immune response. Disruptions of these pathways may lead not only to abnormal growth of pituitary cells but also to immune disorders, for which, based on recent findings, targeting these cytokines might be a novel therapeutic approach.
Assuntos
Receptor gp130 de Citocina/fisiologia , Citocinas/fisiologia , Hormônios/fisiologia , Neuroimunomodulação/fisiologia , Transdução de Sinais/imunologia , Animais , Humanos , Sistemas Neurossecretores/fisiologiaRESUMO
The anterior pituitary can develop benign tumors of different sizes, classified as micro- and macroadenomas, frequently associated with high levels of hormone production, leading to different associated syndromes like Cushing's disease, acromegaly or prolactinomas. Much work has been done in order to understand the signaling pathways and the factors and hormones involved in the pituitary tumorigenic process. In recent years, much evidence has been collected and it is now well documented that cytokines of the gp130 family, such as interleukin-6, that use gp130 as a common signaling protein stimulate not only the proliferation but also the hormone secretion of pituitary cells. Experiments in vivo have shown that the overexpression of the gp130 receptor resulted in pituitary abnormal growth. Moreover, it has been recently described that bone morphogenetic protein-4 (BMP-4), a member of the TGF-beta family, has a stimulatory role on lactosomatotropic cells promoting the development of prolactinomas but it has an inhibitory action on the corticotropic lineage. This inhibitory action prevents Cushing's disease progression. Furthermore, BMP-4 mediates the antiproliferative action of retinoic acid in these cells. The present review highlights the most recent work about gp130 and TGF-beta cytokine families and their role in pituitary tumorigenesis.