RESUMO
Chemoprevention and risk-stratification studies in Barrett's esophagus (BE) rely on biomarkers but the variability in their temporal and spatial expression is unknown. If such variability exists, it will impact sampling techniques and sample size calculations. Specimens from three levels of biopsies over two serial endoscopies in nondysplastic BE patients were analyzed for aneuploidy, proliferation markers (Ki67, Mcm2), and cell cycle markers (cyclin A and cyclin D1). A modification of the image cytometry technique, where cytokeratin staining automatically distinguished epithelial and stromal cells, measured aneuploidy on whole tissue sections. Other biomarkers were studied by immunohistochemistry. Coefficient of variability (SD/mean) was calculated; a value <10% indicated low variability. A total of 120 specimens (20 subjects each with three biopsy levels at two time points) from nondysplastic BE patients (71 ± 8.8 years, all Caucasian, 90% males, C5.1M7.5 ± 3.4 cm) were analyzed. The mean interval between endoscopies was 32.8 ± 8.4 months. Aneuploidy had a spatial variability of 6.8% at visit 1 (mean diploid index: 1.1 ± 0.09) and 7.9% at visit 2 (mean diploid index: 1.1 ± 0.06) and a temporal variability of 7.0-8.1% for the three levels. For other biomarkers, the spatial variability ranged from â¼5 to 30% at visit 1 and 11-92% at visit 2 and the temporal variability ranged from 0 to 77%. To conclude, of all the biomarkers, only aneuploidy had both spatial and temporal variability of <10%. Spatial and temporal variability were biomarker dependent and could be as high as 90% even without progression. These data will be useful to design chemoprevention and risk-stratification studies in BE.
Assuntos
Aneuploidia , Esôfago de Barrett/genética , Esôfago de Barrett/metabolismo , Esôfago/metabolismo , Idoso , Esôfago de Barrett/patologia , Biomarcadores/metabolismo , Biópsia , Proliferação de Células , Ciclina A/metabolismo , Ciclina D1/metabolismo , Esofagoscopia , Esôfago/patologia , Feminino , Humanos , Antígeno Ki-67/metabolismo , Masculino , Pessoa de Meia-Idade , Componente 2 do Complexo de Manutenção de Minicromossomo/metabolismo , Análise Espaço-Temporal , Fatores de TempoRESUMO
Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (< 1 week after 15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3-18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C:N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N x ha(-1) x yr(-1) above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.
Assuntos
Ecossistema , Ciclo do Nitrogênio , Nitrogênio/química , Altitude , Amônia/química , Vazamento de Resíduos Químicos , Nitratos/química , Isótopos de Nitrogênio , Chuva , TemperaturaRESUMO
OBJECTIVES: Risk stratification of Barrett's esophagus (BE) using biomarkers remains an important goal. We evaluated feasibility and clinical accuracy of novel microRNA (miRNA) biomarkers for prediction of BE dysplasia. METHODS: Paired fresh-frozen and hematoxylin/eosin specimens from a prospective tissue repository where only biopsies with the lesion of interest (i.e., intestinal metaplasia (IM) or high-grade dysplasia (HGD)/esophageal adenocarcinoma (EAC)) occupying >50% of biopsy area were included. Tissue miRNA expression was determined by microarrays and validated by quantitative reverse transcription-PCR (qRT-PCR). Three groups were compared-group A, IM tissues from BE patients without dysplasia; group B, IM tissues from group C patients; and group C, dysplastic tissues from BE patients with HGD/EAC. RESULTS: Overall, 22 BE patients, 11 with and without dysplasia (mean age 64 ± 8.2 and 63 ± 11.6 years, respectively, all Caucasian males) were evaluated. Nine miRNAs were identified by high-throughout analysis (miR-15b, -21, -192, -205, 486-5p, -584, -1246, let-7a, and -7d) and qRT-PCR confirmed expression of miR-15b, -21, 486-5p, and let-7a. Two of 4 miRNAs (miR-145 and -203, but not -196a and -375) previously described in BE patients also exhibited differential expression. Sensitivity and specificity of miRNAs for HGD/EAC were miR-15b: 87 and 80%, miR-21: 93 and 70%, miR-203: 87 and 90%, miR-486-5p: 82 and 55%, and miR-let-7a: 88 and 70%. MiRNA-15b, -21, and -203 exhibited field effects (i.e., groups A and B tissues while histologically similar yet exhibited different miRNA expression). CONCLUSIONS: This pilot study demonstrates feasibility of miRNAs to discriminate BE patients with and without dysplasia with reasonable clinical accuracy. However, the specific miRNAs need to be evaluated further in future prospective trials.
Assuntos
Esôfago de Barrett/genética , Esôfago de Barrett/patologia , MicroRNAs/análise , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/patologia , Adenocarcinoma/genética , Adenocarcinoma/patologia , Idoso , Biomarcadores/análise , Biópsia por Agulha , Estudos Cross-Over , Progressão da Doença , Estudos de Viabilidade , Feminino , Regulação da Expressão Gênica , Marcadores Genéticos , Humanos , Imuno-Histoquímica , Modelos Lineares , Masculino , Análise em Microsséries , Pessoa de Meia-Idade , Projetos Piloto , Valor Preditivo dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Medição de RiscoRESUMO
This manuscript outlines estimated risk and clinical course of pretransplant MM, donor-transmitted MM and de novo MM posttransplantation and includes an analysis of risk factors for metastasis, data from clinical studies and current and proposed management. MM in situ and thin melanoma (<1 mm) in the transplant population has similar recurrence and survival estimates to those in the general population. A minimum wait time of 2 years prior to transplantation is suggested for MM with a Breslow depth <1 mm and no clinical evidence of metastasis. More advanced MM may adopt a more aggressive course in transplant recipients. Sentinel lymph node biopsy may be of additional prognostic benefit. Revision of immunosuppression in the management of de novo melanoma in collaboration with the transplant team should be considered. Larger studies utilizing uniform staging criteria or at minimum Breslow depth, are required to assess true risk and outcome of MM in the immunosuppressed transplant population. Emphasis remains on patient education and regular screening to provide early detection of MM.
Assuntos
Melanoma , Humanos , Terapia de Imunossupressão , Masculino , Melanoma/patologia , Melanoma/secundário , Melanoma/cirurgia , Prognóstico , Procedimentos de Cirurgia Plástica , Fatores de Risco , Biópsia de Linfonodo SentinelaRESUMO
Post-transcriptional gene regulation, a regulatory mechanism classically involved in female and male germ cell function has recently been implicated in control of somatic cells of the ovary and testis. Recent advancements in this field may be attributed primarily to the discovery and study of microRNAs (miRNA), small RNA transcripts that can influence mRNA expression via post-transcriptional gene regulatory mechanisms. In the ovary, targeted deletion of Dicer 1, a key enzyme in miRNA biogenesis, provided the first empirical evidence that miRNA/siRNA were critically involved in multiple aspects of ovarian function (folliculogenesis, oocyte maturation, ovulation, and luteal function). Functional studies of miRNA in the ovary have mostly focused on granulosa cells during the critical period of the ovarian cycle surrounding the ovulatory surge of luteinizing hormone (LH). Specific miRNA have been implicated in ovarian responses, due to their transcriptional induction by the LH surge (i.e., miR-21, -132 and -212) or through bioinformatic approaches (miR-224, -17-5p and let-7b). Numerous other miRNA are highly abundant in ovarian somatic tissues, suggesting that we have much to discover with respect to the role of miRNA and regulation of ovarian function. This review will recap the key observations of these early studies and provide insight into future experiments that might further our understanding of ovarian function.
RESUMO
Posttranscriptional gene regulation plays a vital role in male and female germ cell function, but our understanding of this regulatory process in somatic cells and its effect on reproductive tissue development and function is not understood. In mammalian cells, microRNA (miRNA) are key posttranscriptional regulators and function by modulating translation or degradation of their target mRNA. Mature miRNA are synthesized through a multi-step process that concludes with the cleavage of stem-loop pre-miRNA by the RNase III enzyme, Dicer1. To determine the extent of miRNA regulation and establish a baseline, miRNA profiling has indicated the presence of large numbers of miRNA within reproductive tissues and cells. Moreover, several studies have indicated that miRNA expression in reproductive tissues varies in response to pituitary and gonadal hormones. To understand the role that miRNA-mediated posttranscriptional gene regulation plays in female reproduction, a global Dicer1 hypomorph mouse and several tissue-specific Dicer1 knockout mice have been studied. Interestingly, when Dicer1 expression is decreased in reproductive tissues or cells, the females are infertile. This review discusses all the work regarding miRNA regulation within the mammalian female reproductive system published to date.
Assuntos
Doenças dos Genitais Femininos/veterinária , Genitália Feminina/metabolismo , MicroRNAs , Animais , Feminino , Doenças dos Genitais Femininos/metabolismo , MicroRNAs/biossíntese , MicroRNAs/metabolismo , Zigoto/metabolismoRESUMO
Trophoblast expression of immunomodulatory proteins in the human placenta is among the mechanisms that are critical for ensuring lymphocyte tolerance to the semi-allogeneic fetus. High levels of B7-H1 on trophoblast cells together with the known role of this protein in establishment of peripheral tolerance suggest that B7-H1 mediates immunological protection of the placenta during gestation. In this study, we investigated the molecular mechanisms of regulation of B7-H1 in trophoblast cells by epidermal growth factor (EGF), a key regulator of trophoblast cell differentiation. EGF increased B7-H1 protein levels within 24 h and mRNA levels within 4h of the initiation of treatment; by 24 h B7-H1 mRNA levels were similar between control and EGF-treated cells. Analysis of two different potential promoter regions revealed strong promoter activity in response to IFN-gamma. In contrast, no promoter activity could be induced by EGF, suggesting that this cytokine regulates B7-H1 expression post-transcriptionally in trophoblast cells. EGF-induced B7-H1 protein expression was completely blocked in the presence of inhibitors of the PI3Kinase/Akt/mTOR pathway, a pathway known to regulate gene expression at the translational level. Finally, analysis of monosomal and polysomal mRNA fractions of untreated and EGF-treated term trophoblast cells revealed that EGF induces a shift towards the translatable fractions and away from the untranslated fractions. These results highlight a novel mechanism for regulation of B7 family proteins in the placenta.
Assuntos
Antígenos CD/metabolismo , Diferenciação Celular/fisiologia , Processamento de Proteína Pós-Traducional/fisiologia , Trofoblastos/citologia , Adulto , Antígenos CD/genética , Antígenos CD/imunologia , Antígeno B7-H1 , Fusão Celular , Separação Celular , Células Cultivadas , Vilosidades Coriônicas , Inibidores Enzimáticos/farmacologia , Fator de Crescimento Epidérmico/farmacologia , Feminino , Expressão Gênica , Humanos , Interferon gama/farmacologia , Gravidez , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , RNA Mensageiro/metabolismo , Trofoblastos/metabolismo , Adulto JovemRESUMO
BACKGROUND: Reduction of immunosuppression is considered a reasonable adjuvant therapeutic strategy in solid-organ transplant recipients experiencing multiple or high-risk skin cancers. However, the literature provides no guidance about what threshold of cancer development would warrant initiation of reduction of immunosuppression. OBJECTIVES: To develop expert consensus guidelines for initiation of reduction of transplant-associated immunosuppression for solid-organ transplant recipients with severe skin cancer. METHODS: An expert consensus panel was convened by the International Transplant Skin Cancer Collaborative and Skin Care for Organ Transplant Patients Europe Reduction of Immunosuppression Task Force. Thirteen hypothetical patient scenarios with graduated morbidity and mortality risks were presented and mean and mode expert opinions about appropriate level of reduction of systemic immunosuppression (mild, moderate, severe) were generated. RESULTS: Mild reduction of transplant-associated immunosuppression was considered warranted once multiple skin cancers per year developed or with individual high-risk skin cancers. Moderate reduction was considered appropriate when patients experienced > 25 skin cancers per year or for skin cancers with a 10% 3-year risk of mortality. Severe reduction was considered warranted only for life-threatening skin cancers. CONCLUSIONS: Reduction of immunosuppression is considered a reasonable adjuvant management strategy for transplant recipients with numerous or life-threatening skin cancers. Proposed guidelines are presented for the graduated reduction of immunosuppression coincident with the increasing skin cancer risks.
Assuntos
Terapia de Imunossupressão/efeitos adversos , Transplante de Órgãos , Neoplasias Cutâneas/prevenção & controle , Esquema de Medicação , Humanos , Hospedeiro Imunocomprometido , Terapia de Imunossupressão/métodos , Imunossupressores/administração & dosagem , Neoplasias Cutâneas/etiologia , Neoplasias Cutâneas/imunologiaRESUMO
Estrogen sulfotransferase (EST) is a cytosolic enzyme that catalyzes the sulfoconjugation and inactivation of estrogens. It is expressed abundantly in the mammalian testes in which it may modulate the activity of locally produced estrogen. We demonstrate here that testicular Leydig cells from mice rendered deficient in EST expression by targeted gene deletion acquire a phenotype of increased cholesterol ester accumulation and impaired steroidogenesis with natural aging or in response to estrogen challenge. Abnormal accumulation of cholesterol ester in the mutant Leydig cells correlated with induced expression of the scavenger receptor type B class I, and cultured EST-deficient but not wild-type Leydig cells avidly uptook high-density lipoprotein cholesterol ester ex vivo. EST-deficient Leydig cells in culture produced 50-70% less testosterone than wild-type cells. This deficiency was reversed by androstenedione but not progesterone supplementation, indicating that reduced activities of 17-alpha-hydroxylase-17, 20-lyase were responsible. This conclusion was corroborated by decreased expression levels of 17-alpha-hydroxylase-17, 20-lyase but not of other key steroidogenic enzymes in the mutant cells. These results suggest that EST plays a physiologic role in protecting Leydig cells from estrogen-induced biochemical lesions and provide an example of critical regulation of tissue estrogen sensitivity by a ligand-transformation enzyme rather than through estrogen receptors.
Assuntos
Colesterol/metabolismo , Células Intersticiais do Testículo/enzimologia , Esteroides/biossíntese , Sulfotransferases/deficiência , Animais , Transporte Biológico , Células Cultivadas , Ésteres do Colesterol/metabolismo , Gonadotropina Coriônica/farmacologia , AMP Cíclico/farmacologia , Células Intersticiais do Testículo/metabolismo , Hormônio Luteinizante/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosfoproteínas/análise , Fosfoproteínas/genética , RNA Mensageiro/análise , Receptores Imunológicos/análise , Receptores Imunológicos/genética , Receptores Depuradores , Receptores Depuradores Classe B , Esteroide 17-alfa-Hidroxilase/análise , Esteroide 17-alfa-Hidroxilase/genética , Sulfotransferases/metabolismo , Testosterona/biossínteseRESUMO
Steroidogenic acute regulatory (StAR) protein controls the rate-limiting step in steroidogenesis: the transport of cholesterol from the outer to the inner mitochondrial membrane. Early studies indicated that rate of transcription of the StAR gene is a primary determinant of steroidogenesis. The transcription factors that govern basal and cAMP-dependent StAR expression are reviewed, as are new findings regarding chromatin modifications associated with activation of the StAR promoter. Molecular genetic studies of congenital lipoid adrenal hyperplasia, a rare disease caused by mutations in the StAR gene, and structure-function studies defined two major domains within the StAR protein, the N-terminal mitochondrial targeting sequence and the C-terminal StAR-related lipid transfer (START) domain, which promotes the translocation of cholesterol between the two mitochondrial membranes. Several models of StAR's mechanism of action have been proposed based on a combination of structure/function studies or on the crystal structure of a related START domain. The models-intermembrane shuttle hypothesis, and cholesterol desorption hypothesis-are discussed with respect to the known biochemical and biophysical events associated with steroidogenesis and the structure of StAR.
Assuntos
Proteínas de Transporte , Colesterol/metabolismo , Fosfoproteínas/fisiologia , Esteroides/biossíntese , Acetilação , Hiperplasia Suprarrenal Congênita/classificação , Hiperplasia Suprarrenal Congênita/genética , Animais , Sequência de Bases , Transporte Biológico , Feminino , Regulação da Expressão Gênica , Histonas/metabolismo , Humanos , Membranas Intracelulares/metabolismo , Metabolismo dos Lipídeos , Masculino , Lipídeos de Membrana/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/fisiologia , Camundongos , Camundongos Knockout , Mitocôndrias/metabolismo , Modelos Biológicos , Dados de Sequência Molecular , Fenótipo , Fosfoproteínas/química , Fosfoproteínas/deficiência , Fosfoproteínas/genética , Fosforilação , Regiões Promotoras Genéticas , Processamento de Proteína Pós-Traducional , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/fisiologia , Alinhamento de Sequência , Deleção de Sequência , Homologia de Sequência do Ácido Nucleico , Relação Estrutura-Atividade , Transcrição GênicaRESUMO
The expression of the steroidogenic acute regulatory protein (StAR) in the human corpus luteum (CL) was examined throughout the luteal phase. The primary 1.6-kb StAR transcript was in greater abundance in early (3.1-fold) and mid (2.2-fold) luteal phase CL compared with late luteal phase CL. The larger StAR transcript (4.4 kb) was found in early and midluteal phase CL, but was not detected in late luteal phase specimens. Mature StAR protein (30 kDa) was present in lower amounts within late CL compared with early and midluteal phase CL. The StAR preprotein (37 kDa) was also detected in greater abundance in early and midluteal CL. Immunohistochemistry revealed that StAR staining was most prominent in thecal-lutein cells throughout the luteal phase. The intensity of the signal for StAR exhibited significant changes throughout the luteal phase, being most intense during the midluteal phase and least during the late luteal phase. Plasma progesterone concentrations were highly correlated (r = 0.73 and r = 0.79) with luteal expression of the preprotein and mature StAR isoforms, respectively, throughout the luteal phase. To examine the LH dependency of StAR expression, the GnRH antagonist, Cetrorelix, was administered during the midluteal phase. Cetrorelix caused a decline in serum LH levels within 2 h, which, in turn, caused a pronounced decline in plasma progesterone within 6 h. The StAR 4.4-kb transcript was not detectable, and the 1.6-kb transcript was reduced by approximately 50% within 24 h of Cetrorelix treatment. The mature 30-kDa StAR protein level declined approximately 30% after Cetrorelix treatment. We conclude that 1) StAR mRNA and protein are highly expressed in early and midluteal phase CL; 2) StAR protein is present in both thecal-lutein and granulosa-lutein cells throughout the luteal phase; 3) StAR protein levels in the CL are highly correlated with plasma progesterone levels; 4) declining StAR mRNA and protein levels are characteristic of late luteal phase CL; and 5) suppression of LH levels during the midluteal phase results in a marked decline in plasma progesterone and a diminished abundance of StAR transcripts in the CL without a corresponding significant decline in StAR protein. Collectively, these data are consistent with the idea that StAR gene expression is a key determinant of luteal progesterone during the normal menstrual cycle. However, the pharmacologically induced withdrawal in the midluteal phase of LH support diminishes luteal progesterone output by mechanisms others than reduced StAR protein levels.
Assuntos
Corpo Lúteo/metabolismo , Fase Luteal/metabolismo , Fosfoproteínas/biossíntese , Adulto , Northern Blotting , Western Blotting , Feminino , Humanos , Imuno-Histoquímica , RNA Mensageiro/biossíntese , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Reported here is a 15-year-old with lesions demonstrating histologic features of targetoid hemosiderotic hemangioma (THH) developing after trauma to inflammatory lesions. These lesions pose as simulators of THH. Targetoid hemosiderotic hemangioma is a benign vascular lesion first described by Santa Cruz and Aaronburg. It classically presents as a single, small, red/brown, targetoid lesion on the trunk or extremities of a young or middle-aged individual. Histologically, it is characterized by ectatic vascular lumina in the papillary dermis lined by a single layer of endothelial cells with an epithelioid or "hobnail" appearance. In the deeper dermis, vascular spaces become slit-like and angulated, appearing to dissect through collagen bundles. A commonly proposed etiology of THH is trauma to a preexisting hemangioma. This case is remarkable for its unusual clinical presentation, histologic simulation of THH, and for its support for the theory that trauma can induce the histologic changes seen in THH.
Assuntos
Hemangioma/patologia , Hemossiderina/análise , Neoplasias Pós-Traumáticas/patologia , Neoplasias Cutâneas/patologia , Adolescente , Vasos Sanguíneos/patologia , Feminino , Hemangioma/química , Humanos , Pele/irrigação sanguínea , Pele/patologia , Neoplasias Cutâneas/químicaRESUMO
Transcriptional regulation of steroidogenic acute regulatory protein (StAR) determines adrenal and gonadal cell steroidogenesis. Chromatin immunoprecipitation assays were combined with quantitative real-time polymerase chain reaction to assess histone acetylation associated with the StAR promoter. MA-10 cells treated with 8-bromo-cAMP had increased acetylated histone H3 associated with the proximal (but not distal) StAR promoter, nascent StAR transcripts, and progesterone production within 15 min, whereas StAR mRNA increased at 30 min. At 360 min, steroidogenesis remained elevated, but mRNA, nascent RNA, and StAR promoter-associated H3 acetylation all declined. StAR promoter-associated H4 acetylation was unchanged by 8-bromo-cAMP treatment of MA-10 cells. In vivo analysis of macaque and human granulosa cells showed that luteinization was associated with increased StAR promoter-associated H3 acetylation. We conclude that acetylation of H3 (but not H4) associated with the proximal promoter is associated with StAR gene transcription, that chromatin modification occurs in discrete regions of the promoter, that the initial steroidogenic response to 8-bromo-cAMP occurs prior to increased StAR mRNA accumulation, and that MA-10 cell StAR gene transcription and promoter-associated H3 acetylation are biphasic during a 6-h treatment period. The union of the chromatin immunoprecipitation assay with quantitative real-time polymerase chain reaction described and validated here should enhance the analysis of gene expression.
Assuntos
Histonas/metabolismo , Fosfoproteínas/genética , Regiões Promotoras Genéticas , Acetilação , Animais , Sequência de Bases , DNA , Humanos , Camundongos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , RNA Mensageiro/genética , Homologia de Sequência do Ácido Nucleico , Transcrição Gênica , Células Tumorais CultivadasRESUMO
The steroidogenic acute regulatory protein (StAR) gene controls the rate-limiting step in the biogenesis of steroid hormones, delivery of cholesterol to the cholesterol side-chain cleavage enzyme on the inner mitochondrial membrane. We determined whether the human StAR promoter is responsive to sterol regulatory element-binding proteins (SREBPs). Expression of SREBP-1a stimulated StAR promoter activity in the context of COS-1 cells and human granulosa-lutein cells. In contrast, expression of SREBP-2 produced only a modest stimulation of StAR promoter activity. One of the SREBP-1a response elements in the StAR promoter was mapped in deletion constructs and by site-directed mutagenesis between nucleotides -81 to -70 from the transcription start site. This motif bound recombinant SREBPs in electrophoretic mobility shift assays, but with lesser affinity than a low density lipoprotein receptor SREBP-binding site. An additional binding site for the transcriptional modulator, yin yang 1 (YY1), was observed within the SREBP-binding site (nucleotides -73 to -70). Mutation of the YY1-binding site increased the responsiveness of the StAR promoter to exogenous SREBP-1a, but did not alter the affinity for SREBP-1a binding in electrophoretic mobility gel shift assays. Manipulations that altered endogenous mature SREBP-1a levels (e.g. culture in lipoprotein-deficient medium and addition of 27-hydroxycholesterol) did not affect StAR promoter function, but influenced low density lipoprotein receptor promoter activity. We conclude that 1) the human StAR promoter is conditionally responsive to SREBP-1a such that promoter activity is up-regulated in the presence of high levels of SREBP-1a, but is unaffected when mature SREBP levels are suppressed; and 2) the human StAR promoter is selectively responsive to SREBP-1a.
Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica , Fosfoproteínas/genética , Regiões Promotoras Genéticas , Animais , Sequência de Bases , Proteínas Estimuladoras de Ligação a CCAAT/genética , Células COS , Bovinos , Chlorocebus aethiops , Proteínas de Ligação a DNA/genética , Feminino , Genes Reporter , Células da Granulosa/metabolismo , Humanos , Proteínas de Membrana/genética , Camundongos , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Ratos , Receptores de LDL/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Deleção de Sequência , Homologia de Sequência do Ácido Nucleico , Proteína de Ligação a Elemento Regulador de Esterol 1 , Fatores de Transcrição/metabolismo , TransfecçãoRESUMO
The steroidogenic acute regulatory (StAR) protein regulates the rate limiting step in steroidogenesis, the transport of cholesterol from the outer to the inner mitochondrial membrane. Insight into the structure and function of StAR was attained through molecular genetic studies of congenital lipoid adrenal hyperplasia, a rare disease caused by mutations in the StAR gene. Subsequent functional analysis defined two major domains within the StAR protein, the N-terminal mitochondrial targeting sequence and the C-terminus, which promotes the translocation of cholesterol between the two mitochondrial membranes. Two models of StAR's mechanism of action, (1) stimulation of cholesterol desorption from the outer mitochondrial membrane and (2) an intermembrane shuttle hypothesis, are discussed with respect to the known biochemical and biophysical events associated with the process of steroidogenesis and the structure of StAR. StAR gene expression is regulated primarily at the transcriptional level, and the roles of transcription factors that govern basal and cAMP-dependent StAR expression including SF-1, C/EBP beta, Sp1 and GATA-4 are reviewed.
Assuntos
Proteínas de Transporte , Colesterol/metabolismo , Membranas Intracelulares/metabolismo , Mitocôndrias/metabolismo , Fosfoproteínas/metabolismo , Hiperplasia Suprarrenal Congênita/genética , Sequência de Aminoácidos , Sequência de Bases , Células Cultivadas , Regulação da Expressão Gênica , Humanos , Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Modelos Químicos , Dados de Sequência Molecular , Fosfoproteínas/deficiência , Fosfoproteínas/genética , Fosforilação , Pregnenolona/metabolismo , Homologia de Sequência , Relação Estrutura-Atividade , Transcrição GênicaRESUMO
To determine the temporal expression of vascular growth factors during the lifespan of the primate corpus luteum, experiments were designed to detect mRNA for vascular endothelial growth factor (VEGF), angiopoietin (Ang)-1 and Ang-2 and to localize protein expression for VEGF in macaque luteal tissue during the menstrual cycle. Corpora lutea (n = 3-5/stage) were collected during the early (3-5 days post-luteinizing hormone surge), mid- (6-8 days), mid-late (10-12 days), and late (14-16 days) luteal phase and at menstruation (17-18 days). Reverse transcription-polymerase chain reaction products equated to cDNA for VEGF, Ang-1 and Ang-2 in all corpora lutea. VEGF mRNA levels increased (P: < 0.05) from early to mid-luteal phase and declined in the late luteal phase and at menstruation. Immunostaining for VEGF was detected in the cytoplasm of steroidogenic luteal cells, with the most intense staining in the early luteal phase. Ang-1 and Ang-2 mRNA expression was low in the early to mid-luteal phase but increased (P: < 0.05) at late luteal phase before declining at menstruation. These data suggest transcriptional control of VEGF, Ang-1 and Ang-2, as well as post-transcriptional control of VEGF, in macaque corpus luteum. Dynamic expression of angiogenic/angiostatic factors appears critical for development, maintenance and regression of the luteal microvasculature during the menstrual cycle.
Assuntos
Corpo Lúteo/fisiologia , Fatores de Crescimento Endotelial/metabolismo , Linfocinas/metabolismo , Glicoproteínas de Membrana/metabolismo , Ciclo Menstrual/fisiologia , Proteínas/metabolismo , Angiopoietina-1 , Angiopoietina-2 , Animais , Fatores de Crescimento Endotelial/genética , Feminino , Regulação da Expressão Gênica , Imuno-Histoquímica , Linfocinas/genética , Macaca mulatta , Glicoproteínas de Membrana/genética , Proteínas/genética , RNA Mensageiro/metabolismo , Fator A de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio VascularRESUMO
Progesterone, which is required to support human gestation, is derived initially from the corpus luteum and subsequently from the placenta. The rate-limiting step in progesterone synthesis is the delivery of cholesterol to the mitochondrial cholesterol side-chain cleavage system. The steroidogenic acute regulatory protein (StAR) mediates this process in the corpus luteum, whereas in the placenta, which does not express StAR, a StAR homologue, MLN64, may accomplish this function. StAR expression is regulated in the ovary at the transcriptional level by a cAMP-activated signal transduction system and StAR activity is also increased acutely by protein kinase A-mediated phosphorylation. These long-term (transcriptional) and short-term (post-translational, that is, phosphorylation) mechanisms govern luteal steroidogenic activity. The StAR protein has two key functional domains. The StAR C-terminal domain increases cholesterol movement to cytochrome P450scc by promoting sterol desorption from the sterol-rich outer mitochondrial membrane, driving it to the relatively sterol-poor inner membrane. The N-terminal domain mitochondrial targeting sequence directs the StAR protein to the mitochondria.
Assuntos
Proteínas de Transporte , Enzima de Clivagem da Cadeia Lateral do Colesterol/metabolismo , Colesterol/metabolismo , Corpo Lúteo/metabolismo , Fosfoproteínas/metabolismo , Progesterona/biossíntese , Feminino , Humanos , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Fosfoproteínas/química , Fosforilação , Placenta/metabolismo , Gravidez , Relação Estrutura-AtividadeRESUMO
Human corpora lutea undergo an extremely rapid period of growth, development and regression during the course of non-fertile cycles. The tissue consists of steroidogenic (parenchymal) and non-steroidogenic (stromal) cells. In women and other primates, steroid hormone production by corpora lutea depends on the presence of pituitary-derived LH. Nevertheless, there is also intra-luteal regulation of steroid synthesis. Steroidogenic luteal cells and non-steroidogenic cells interact via endocrine and paracrine pathways, and by contact-dependent pathways (gap junctions). Thus, hormones and locally produced factors including steroids, growth factors, cytokines, reactive oxygen species and nitric oxide may modulate luteal lifespan. The factors regulating regression and rescue of the corpus luteum are not understood completely. This review describes the expression of two representative intragonadal peptides that may influence luteal regression (interleukin 1 beta) and luteal rescue (steroidogenic acute regulatory protein).
Assuntos
Corpo Lúteo/metabolismo , Interleucina-1/metabolismo , Fase Luteal/metabolismo , Fosfoproteínas/metabolismo , Animais , Comunicação Celular/fisiologia , Gonadotropina Coriônica/metabolismo , Feminino , Humanos , Fator de Crescimento Insulin-Like I/metabolismo , Hormônio Luteinizante/metabolismoRESUMO
BACKGROUND: Cutaneous leiomyomas are benign tumors that can be exquisitely painful. Symptomatic lesions often necessitate treatment, but many options are inadequate or create substantial morbidity. Without a definitive therapy of first choice, the search continues for alternative methods to alleviate discomfort in affected patients. OBJECTIVE: To describe the use of CO2 laser ablation for the symptomatic treatment of a 73-year-old woman with multiple cutaneous leiomyomas in whom pharmacologic therapy was contraindicated and surgical excision was impractical. METHODS: CO2 laser ablation of six symptomatic cutaneous leiomyomas was performed under local anesthesia. After initial success, all remaining symptomatic lesions were treated. RESULTS: There was complete pain relief in the originally treated lesions 9 months postoperatively, and in all remaining treated lesions 3 months postoperatively. CONCLUSION: CO2 laser ablation may be an effective alternative treatment for symptomatic cutaneous leiomyomas.