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Objective: To investigate the efficacy and safety profile of different doses of magnesium isoglycyrrhizinate in the treatment of chronic liver disease with elevated alanine aminotransferase (ALT). Methods: Computer retrieval of literature was conducted in the CNKI, Wanfang, and PubMed databases from the establishment of the databases until February 2023. The Cochrane risk of bias assessment tool was used to evaluate the quality of the included literature after screening the literature and extracting the data. RevMan 5.4 and Stata 15.0 software were used to analyze the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBil), total effective rate, and incidence of adverse events. Results: Finally, 10 articles were selected, including a total of 1 522 cases. All the included studies were of good quality and at low risk of bias. Meta-analysis results showed that compared with 100 mg/d magnesium isoglycyrrhizinate injection, 200 mg/d magnesium isoglycyrrhizinate injection had significantly reduced patients' ALT [MD = -30.73, 95% confidence interval (CI): -52.52 ~ -8.94, Z = 2.76, P = 0.006; I (2) = 98%, P < 0.001], AST (MD = -34.30, 95% CI: -57.78 ~ -10.82, Z = 2.86, P = 0.004; I (2) = 99%, P < 0.001) and TBil (MD = -15.37, 95% CI: -27.66 ~ -3.09), Z = 2.45, P = 0.01; I (2) = 98%, P < 0.001) levels. The total effective rate reported in seven articles showed no heterogeneity among the studies (I (2) = 0.0%, P = 0.98). The total effective rate was higher in 200 mg/d magnesium isoglycyrrhizinate injection than that of 100 mg/d magnesium isoglycyrrhizinate injection (OR = 3.49, 95% CI: 2.05 ~ 5.95, Z = 4.59, P < 0.001), and there was no statistically significant difference in adverse reactions. Conclusion: 200 mg/d magnesium isoglycyrrhizinate injection can more rapidly and effectively improve the levels of ALT, AST, and TBil in patients with chronic liver disease, with an increased total effective rate and a good safety profile.
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Hepatopatías , Saponinas , Triterpenos , Humanos , Alanina Transaminasa , Bilirrubina , Saponinas/efectos adversos , Triterpenos/efectos adversosRESUMEN
Spinal metastases (SM) is the commonest form of solid tumors osseous metastasis, for which surgical dissection is often performed when combined with spinal cord compression. Leptomeningeal metastasis (LM) results from dissemination of cancer cells to both the leptomeninges (pia and arachnoid) and cerebrospinal fluid (CSF) compartment. The spread of LM may occur via multiple routes, such as hematogenous, direct infiltration from metastatic brain lesions, or via iatrogenic seeding of CSF. Signs and symptoms associated with LM are generalized and various while early diagnosis of LM is challenging. Cytological evaluation of the CSF and gadolinium enhanced MRI brain and spine is the gold standard for diagnosing LM and CSF can help assess treatment response. While a number of other potential CSF biomarkers have been investigated both for the diagnosis as well as monitoring of LM, none have been established as a component of the standard evaluation of all LM or suspected LM patients. Management goals of LM include improving patient's neurologic function, quality of life, preventing further neurologic deterioration and prolonging survival. In many cases, it may be reasonable to pursue a palliative and comfort focused course, even from the initial LM diagnosis. Surgery is not recommended considering the risk of seeding with cerebrospinal fluid. A diagnosis of LM carries a poor prognosis with an estimated median survival of only 2-4 months despite therapy. Spinal metastases combined with leptomeningeal metastasis (SM+LM) is not uncommon and its treatment is similar to LM. LM can appear at the same time as SM or directly invaded by SM, which is thought regarding the pathophysiology of LM remains speculative and not systematically studied. The present article reports a 58-year-old woman who was first diagnosed with SM, but worsened after surgery repeated MRI examinations confirmed coexisting LM. Relevant literature was reviewed to summarize the epidemiology, clinical manifestations, imaging characteristics, diagnosis and treatment of SM+LM, so as to improve the understanding of the disease and promote early diagnosis. It should be vigilant to merge LM for the patient with SM when atypical clinical manifestations, rapid disease progression or inconsistent with imaging occurred. Repeated examinations of cerebrospinal fluid cytology and enhanced MRI should be considered when SM+LM is suspected to achieve timely adjustment of diagnosis and treatment strategy for better prognosis.
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Neoplasias Meníngeas , Neoplasias de la Columna Vertebral , Femenino , Humanos , Persona de Mediana Edad , Neoplasias de la Columna Vertebral/cirugía , Calidad de Vida , Pronóstico , Imagen por Resonancia MagnéticaRESUMEN
OBJECTIVE: To analyze the effect of short-segment circumferential decompression and the nerve function improvement in 30 cases of multilevel thoracic OPLL assisted by intraoperative ultrasound. METHODS: A total of 30 patients with multilevel thoracic OPLL from January 2016 to January 2021 were enrolled, all of whom were located by intraoperative ultrasound and underwent circumferential decompression. There were 14 males and 16 females, with an average age of (49.3±11.4) years. The initial symptoms were mainly numbness and weakness of lower limbs (83.3%), and the mean duration of symptoms was (33.9±42.9) months (1-168 months). Neurological function was assessed by the Modified Japanese Orthopedic Association (mJOA) score (0-11) preoperative and at the last follow-up, in which the rate of neurological improvement was calculated by the Harabayashi method. The patients were divided into excellent improved group and poor improved group according to the improvement of neurological function. The age, body mass index (BMI), duration of symptoms, operation time, blood loss, mJOA score, surgical level, and cerebrospinal fluid leakage of the two groups were collected and analyzed for statistical differences. The factors influencing the improvement of neurological function were analyzed by univariate and multivariate Logisitic regression analysis. RESULTS: The mean operation time was 137.4±33.8 (56-190) min, and the mean blood loss was (653.7±534.2) mL (200ï¼3 000 mL). The preoperative mJOA score was 6.0±2.1 (2ï¼9), and the last follow-up mJOA score was 7.6±1.9 (4ï¼11), which was significantly improved in all the patients (P < 0.001). The average improvement rate of neurological function was 38.1%±24.4% (14.3%ï¼100%), including 75%ï¼100% in 4 cases, 50%ï¼74% in 3 cases, 25%ï¼49% improved in 14 cases, and 0%ï¼24% in 9 cases. There was significant difference in intraoperative blood loss between the excellent improved group and the poor improved group (P=0.047). Intraoperative blood loss was also an independent risk factor in regression analysis of neurological improvement. CONCLUSION: Thoracic circumferential decompression assisted with intraoperative ultrasound can significantly improve the neurological function of patients with multilevel OPLL and achieve good efficacy. The improvement rate of nerve function can be improved effectively by controlling intraoperative blood loss.
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Osificación del Ligamento Longitudinal Posterior , Fusión Vertebral , Adulto , Pérdida de Sangre Quirúrgica , Descompresión Quirúrgica/métodos , Femenino , Humanos , Ligamentos Longitudinales/cirugía , Masculino , Persona de Mediana Edad , Osificación del Ligamento Longitudinal Posterior/cirugía , Osteogénesis , Estudios Retrospectivos , Fusión Vertebral/métodos , Vértebras Torácicas/cirugía , Resultado del TratamientoRESUMEN
Objective: To analyze the changes of patellar tendon elasticity quantitatively of amateur marathon runners by shear wave elastography (SWE) in a half marathon. Methods: A total of 47 amateur marathon runners (31 males and 16 females, aged from 20 to 44 years) were enrolled as the marathon group, and divided into dominant side (47 patellar tendons) and non-dominant side (47 patellar tendons). Grey-scale ultrasound and SWE were performed on the bilateral patellar tendons before and after the half marathon within 2 h and after a period of 1 week. Thirty healthy volunteers (18 males and 12 females, aged from 22 to 39 years) were enrolled as the control group, the SWE-values derived from the patellar tendon were collected and analyzed. Multivariate logistic regression was performed to analyze the relationship between the changes of SWE-values and running age as well as weekly amount of running. Results: None of any runners showed knee pain and sports injury during the test. The dominant side had a higher SWE-values than non-dominant side in marathon group before running [(55.1±15.7) kPa vs (43.8±15.9) kPa, P<0.05]. The marathon group had higher SWE-values than the control group both in dominant side [(55.1±15.7) kPa vs (18.5±3.7) kPa] and non-dominant side [(43.8±15.9) kPa vs (17.4±3.2) kPa], respectively, before running (P<0.05). The SWE-values increased significantly both in dominant side [(80.2±23.2) kPa vs (55.1±15.7) kPa] and non-dominant side [(76.5±26.6) kPa vs (43.8±15.9) kPa] 2 h after running in marathon group. After a week, the SWE-values were not statistically different from those before running (P>0.05). Multivariate logistic regression showed that running age and weekly amount of running were related factors leading to the increase of SWE-values after running. Conclusions: The patellar tendon of amateur marathon runners has higher SWE-values. SWE can dynamically evaluate the changes of patellar tendon during exercise and is helpful for runners in scientific training and avoiding sports injury.
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Diagnóstico por Imagen de Elasticidad , Ligamento Rotuliano , Adulto , Elasticidad , Femenino , Humanos , Masculino , Carrera de Maratón , Ligamento Rotuliano/diagnóstico por imagen , Ultrasonografía , Adulto JovenRESUMEN
Low HDL is an independent risk factor for myocardial infarction. This paper reviews our current understanding of HDL, HDL structure and function, HDL subclasses, the relationship of low HDL with myocardial infarction, HDL targeted therapy, and clinical trials and studies. Furthermore potential new agents, such as alirocumab (praluent) and evolocumab (repatha) are discussed.
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OBJECTIVE: To explore the relationship between spino-pelvic sagittal and coronal parameters in Lenke 1 group of adolescent idiopathic scoliosis (AIS). METHODS: The subjects were retrospectively collected from 2005 to 2013. On the posteroanterior and lateral radiographs, apical vertebra (AV), Cobb angle of main thoracic curve (MT), pelvic incidence (PI), C7 translation ratio (C7TR) and other sagittal parameters were measured and recorded. Comparison and correlation studies were conducted between these parameters using specific softwares. RESULTS: In the study, 51 subjects, including 18 males and 33 females, were recruited, aged (14.9±2.0) years averagely. The apical vertebra ranged from T7 to T11,with mean MT being 49.6°±16.7°, and mean PI 44.7°±6.7°. Significant correlation existed between PI and PT, SS, LL, as well as between LL and SS, TK (P <0.05). Significant differences were found in TK, LL and SS among the different LM groups, but no difference in the other sagittal parameters. AV had no significant correlation with any sagittal parameter. MT was significantly correlated with TK, LL and SS, but its correlation with PI was not significant. CONCLUSION: Most of sagittal parameters were significantly correlated in Lenke 1 adolescent idiopathic scoliosis, forming a regulation chain of spine-pelvic sagittal balance on the basis of PI. Significant correlation exists between some sagittal and coronal parameters.
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Cifosis , Escoliosis , Adolescente , Femenino , Humanos , Incidencia , Masculino , Pelvis/patología , Estudios Retrospectivos , Columna Vertebral/patologíaRESUMEN
To examine signaling pathways underlying transforming growth factor-beta (TGF-beta)-mediated changes in cell morphology, we used a microarray system to identify downstream target genes that may play a role in this process. Through this approach, we found that the NET1 gene was induced upon TGF-beta treatment in several cell types. NET1 is a guanine nucleotide exchange factor for RhoA whose activity has been implicated in stress fiber formation. In the Swiss 3T3 cell line, TGF-beta induces NET1 expression, and this correlated with an increase in stress fiber formation. Overexpression of the wild type NET1 gene increases stress fiber formation, and overexpression of a dominant negative NET1 mutant (L392E) prevented TGF-beta dependent increase in stress fiber formation. Furthermore, treatment of the cells with a RhoA kinase inhibitor Y-27632 blocks TGF-beta-induced stress fiber formation. By using a stable cell line expressing dominant negative Smad3, we found that the Smad signaling pathway is essential for the induction of NET1, which in turn leads to the increase of Rho activity. Taken together, those data suggest that induction of NET1 is important for the increase of Rho activity upon TGF-beta treatment, which may represent the critical trigger for a variety of downstream events in different cells. Our results support the presence of a novel signaling pathway by which TGF-beta may regulate the formation of stress fibers and reorganization of cytoskeletal structures.
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Actinas/biosíntesis , Factores de Intercambio de Guanina Nucleótido/metabolismo , Factor de Crecimiento Transformador beta/fisiología , Células 3T3 , Animales , Línea Celular , Factores de Intercambio de Guanina Nucleótido/genética , Humanos , Ratones , Transducción de Señal , Transactivadores/metabolismoRESUMEN
Transforming growth factor-beta (TGF-beta)can induce the cyclin-dependent kinase inhibitors p21 and p15 in a variety of cell types. We have shown previously that Smad3 is required for the growth inhibitory activity of TGF-beta, whereas overexpression of Smads is not sufficient to activate the expression of p21 in HaCaT cells. These data suggest that an additional signaling pathway may be involved in stimulating p21 in HaCaT cells. Given the recent finding that the mitogen-activated protein kinase (MAPK) pathway can cause p21 induction and arrest cells, we examined the involvement of this pathway for p21 and p15 induction by TGF-beta. We found that TGF-beta can regulate the MAPK pathway, leading to the increased transactivation ability of transcription factor Elk. Constitutively active components in the MAPK pathway activate p21 expression, and inhibitors or dominant negative constructs for the MAPK pathway significantly decrease p21 induction by TGF-beta. Both constitutively active MEK and inhibitors for MEK have no effect on Smad activity, including DNA binding, localization, and interaction with coactivator p300/CBP. These findings suggest that the MAPK pathway may be an independent pathway that is involved in p21 and p15 induction by TGF-beta.
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Ciclinas/metabolismo , Inhibidores Enzimáticos/farmacología , MAP Quinasa Quinasa 4 , Quinasa 1 de Quinasa de Quinasa MAP , Quinasas Quinasa Quinasa PAM/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Proteínas Serina-Treonina Quinasas , Factor de Crecimiento Transformador beta/farmacología , Benzoquinonas , Inhibidor p21 de las Quinasas Dependientes de la Ciclina , Ciclinas/genética , Inhibidores Enzimáticos/metabolismo , Humanos , Cinética , Lactamas Macrocíclicas , Luciferasas/genética , Luciferasas/metabolismo , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-raf/metabolismo , Quinonas/farmacología , Proteínas Recombinantes de Fusión/metabolismo , Rifabutina/análogos & derivados , Transducción de Señal/efectos de los fármacos , Transfección , Proteínas ras/metabolismoRESUMEN
Transforming growth factor-beta (TGFbeta) enhances transcription from reporter genes regulated by a single consensus cAMP-response element (CRE) upon transfection into the immortalized human keratinocyte cell line, HaCaT. Whereas both CRE-binding protein (CREB) and c-Jun present in extracts of unstimulated cells can complex with a CRE in gel-shift experiments, TGFbeta treatment increases the amount of c-Jun found in the complex. Overexpression of c-Jun is sufficient to increase CRE and GAL4-CREB-dependent transcription and mimics the stimulatory effects of TGFbeta on transcription from either reporter gene. Surprisingly, although a portion of CREB in unstimulated cells is phosphorylated on the activating serine residue, Ser-133, this level of phospho-CREB is not altered by TGFbeta treatment. In fact, the CREB-dependent transcriptional effects of TGFbeta or c-Jun do not require phosphorylation of Ser-133, although CREB-binding protein (CBP) is required as evidenced by the observation that the adenoviral oncoprotein E1A can block the effects of both agents. c-Jun enhancement of CRE or GAL4-CREB-dependent transcription neither requires the DNA-binding nor N-terminal domains of c-Jun. Collectively, these results are consistent with a model in which signaling pathways initiated by TGFbeta can stimulate CREB-dependent transcription by increasing the cellular concentration of c-Jun, which participates in activation of the CBP-containing transcription complex.
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Proteína de Unión a Elemento de Respuesta al AMP Cíclico/fisiología , ADN/metabolismo , Proteínas Proto-Oncogénicas c-jun/fisiología , Transcripción Genética , Factor de Crecimiento Transformador beta/farmacología , Proteínas E1A de Adenovirus/farmacología , Línea Celular Transformada , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/farmacología , Sinergismo Farmacológico , Expresión Génica , Humanos , Queratinocitos/metabolismo , Proteínas Proto-Oncogénicas c-jun/genética , Proteínas Proto-Oncogénicas c-jun/farmacología , TransfecciónRESUMEN
Smads are intermediate effector proteins that transduce the TGF-beta signal from the plasma membrane to the nucleus, where they participate in transactivation of downstream target genes. We have shown previously that coactivators p300/CREB-binding protein are involved in TGF-beta-mediated transactivation of two Cdk inhibitor genes, p21 and p15. Here we examined the possibility that Smads function to regulate transcription by directly interacting with p300/CREB-binding protein. We show that Smad3 can interact with a C-terminal fragment of p300 in a temporal and phosphorylation-dependent manner. TGF-beta-mediated phosphorylation of Smad3 potentiates the association between Smad3 and p300, likely because of an induced conformational change that removes the autoinhibitory interaction between the N- and C-terminal domains of Smad3. Consistent with a role for p300 in the transcription regulation of multiple genes, overexpression of a Smad3 C-terminal fragment causes a general squelching effect on multiple TGF-beta-responsive reporter constructs. The adenoviral oncoprotein E1A can partially block Smad-dependent transcriptional activation by directly competing for binding to p300. Taken together, these findings define a new role for phosphorylation of Smad3: in addition to facilitating complex formation with Smad4 and promoting nuclear translocation, the phosphorylation-induced conformational change of Smad3 modulates its interaction with coactivators, leading to transcriptional regulation.
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Proteínas de Unión al ADN/metabolismo , Proteínas Nucleares/metabolismo , Transactivadores/metabolismo , Factor de Crecimiento Transformador beta/farmacología , Proteínas E1A de Adenovirus/metabolismo , Sitios de Unión , Unión Competitiva , Línea Celular , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Expresión Génica , Humanos , Modelos Biológicos , Proteínas Nucleares/química , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/metabolismo , Fosforilación , Regiones Promotoras Genéticas , Unión Proteica , Conformación Proteica , Transducción de Señal , Proteína smad3 , Transactivadores/química , Transactivadores/genética , Activación TranscripcionalRESUMEN
Transforming growth factor beta (TGF-beta) causes growth arrest at the G1 phase of the cell cycle in most cell types. Both the cyclin dependent kinase inhibitor p15(INK4B) and p21(Cip1/WAF1) genes have been found to be induced by TGF-beta in human keratinocyte HaCaT cells. Analyses of the human p15 and p21 promoters have led to the identification of GC-rich sequences capable of binding to Sp1 transcription factors as necessary elements for the TGF-beta induction of both promoters. We report here that canonical Sp1 binding sites derived from the SV40 21 bp repeat could also support promoter induction by TGF-beta when placed upstream of a minimal luciferase reporter construct containing only the TATA and Inr elements. Gel retardation assays identified Sp1, Sp3 and DeltaSp3 as major factors binding to the canonical Sp1 sites in HaCaT cells and that TGF-beta treatment did not change their binding activities over a 24 h period. More importantly, GAL4-Sp1, but not GAL4-Sp3, chimeric protein supported TGF-beta mediated gene induction from a luciferase reporter construct driven by five GAL4 DNA binding sites. Our results suggest that Sp1 binding site can function as a distinct TGF-beta responsive element for TGF-beta mediated promoter expression and Sp1 per se can mediate this response.
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Proteínas de Unión al ADN/fisiología , Factor de Transcripción Sp1/fisiología , Factores de Transcripción/fisiología , Activación Transcripcional/genética , Factor de Crecimiento Transformador beta/farmacología , Proteínas E1A de Adenovirus/genética , Proteínas E1A de Adenovirus/fisiología , Sitios de Unión , Línea Celular , Proteínas de Unión al ADN/genética , Humanos , Queratinocitos , Receptores de Factores de Crecimiento Transformadores beta/genética , Receptores de Factores de Crecimiento Transformadores beta/fisiología , Proteínas Recombinantes de Fusión , Secuencias Repetitivas de Ácidos Nucleicos/fisiología , Eliminación de Secuencia , Virus 40 de los Simios/genética , Factor de Transcripción Sp1/genética , Factor de Transcripción Sp3 , Factores de Transcripción/genéticaRESUMEN
Transforming growth factor beta (TGF-beta) is the prototype of a large superfamily of signaling molecules involved in the regulation of cell growth and differentiation. In certain patients infected with human immunodeficiency virus type 1 (HIV-1), increased levels of TGF-beta promoted the production of virus and also impaired the host immune system. In an effort to understand the signaling events linking TGF-beta action and HIV production, we show here that TGF-beta can stimulate transcription from the HIV-1 long terminal repeat (LTR) promoter through NF-kappaB binding sites in both HaCaT and 300.19 pre-B cells. When introduced into a minimal promoter, NF-kappaB binding sites supported nearly 30-fold activation from the luciferase reporter upon TGF-beta treatment. Electrophoretic mobility shift assay indicated that a major factor binding to the NF-kappaB site is the p50-p65 heterodimeric NF-kappaB in HaCaT cells. Coexpression of Gal4-p65 chimeric proteins supported TGF-beta ligand-dependent gene expression from a luciferase reporter gene driven by Gal4 DNA binding sites. NF-kappaB activity present in HaCaT cells was not affected by TGF-beta treatment as judged by the unchanged DNA binding activity and concentrations of p50 and p65 proteins. Consistently, steady-state levels of IkappaB alpha and IkappaB beta proteins were not changed by TGF-beta treatment. Our results demonstrate that TGF-beta is able to stimulate transcription from the HIV-1 LTR promoter by activating NF-kappaB through a mechanism distinct from the classic NF-kappaB activation mechanism involving the degradation of IkappaB proteins.
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Infecciones por VIH/genética , Duplicado del Terminal Largo de VIH/genética , VIH-1/genética , FN-kappa B/genética , Activación Transcripcional/efectos de los fármacos , Factor de Crecimiento Transformador beta/farmacología , Linfocitos B/metabolismo , Linfocitos B/virología , Línea Celular , Elementos de Facilitación Genéticos/genética , Infecciones por VIH/metabolismo , Humanos , FN-kappa B/metabolismoRESUMEN
The traditional Chinese medicine Nao Li Shen (containing ginseng, gastrodia tuber, chuanxiong rhizome and red sage root) is used in craniocerebral injury, cervical spondylosis and cerebrovascular diseases. The preparation, as an orally administered liquid, was tested in Mongolian gerbils and shown to increase tolerance to ischaemia and anoxia. Clinical use of the preparation resulted in improvement in 96% of 202 patients, as judged by right cerebral blood flow, TCD and CT examination. We conclude that Nao Li Shen has a positive curative effect upon craniocerebral injury and sequelae of cerebrovascular diseases.
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Encefalopatías/tratamiento farmacológico , Medicamentos Herbarios Chinos/uso terapéutico , Adulto , Anciano , Animales , Lesiones Encefálicas/tratamiento farmacológico , Isquemia Encefálica/tratamiento farmacológico , Trastornos Cerebrovasculares/tratamiento farmacológico , Femenino , Gerbillinae , Humanos , MasculinoRESUMEN
Transforming growth factor beta (TGF-beta) causes growth arrest in most cell types. TGF-beta induces hypophosphorylation of retinoblastoma susceptibility gene 1 product (RB), which sequesters E2F factors needed for progression into S phase of the cell cycle, thereby leading to cell cycle arrest at G1. It is possible, however, that the E2F-RB complex induced by TGF-beta may bind to E2F sites and suppress expression of specific genes whose promoters contain E2F binding sites. We show here that TGF-beta treatment of HaCaT cells induced the formation of E2F4-RB and E2F4-p107 complexes, which are capable of binding to E2F sites. Disruption of their binding to DNA with mutation in the E2F sites did not change the expression from promoters of E2F1, B-myb, or HsORC1 genes in cycling HaCaT cells. However, the same mutation stimulated 5- to 6-fold higher expression from all three promoters in cells treated with TGF-beta. These results suggest that E2F binding sites play an essential role in the transcription repression of these genes under TGF-beta treatment. Consistent with their repression of TGF-beta-induced gene expression, introduction of E2F sites into the promoter of cyclin-dependent kinase inhibitor p15(INK4B) gene effectively inhibited its induction by TGF-beta. Experiments utilizing Gal4-RB and Gal4-p107 chimeric constructs demonstrated that either RB or p107 could directly repress TGF-beta induction of p15(INK4B) gene when tethered to p15(INK4B) promoter through Gal4 DNA binding sites. Therefore, E2F functions to bring RB and p107 to E2F sites and represses gene expression by TGF-beta. These results define a specific function for E2F4-RB and E2F4-p107 complexes in gene repression under TGF-beta treatment, which may constitute an integral part of the TGF-beta-induced growth arrest program.
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Inhibidor p16 de la Quinasa Dependiente de Ciclina , Proteínas de Unión al ADN/metabolismo , Proteínas Nucleares/metabolismo , Proteína de Retinoblastoma/metabolismo , Factores de Transcripción/metabolismo , Transcripción Genética/fisiología , Factor de Crecimiento Transformador beta/farmacología , Proteínas Supresoras de Tumor , Secuencia de Bases , Sitios de Unión , Proteínas Portadoras/biosíntesis , Ciclo Celular , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Inhibidor p15 de las Quinasas Dependientes de la Ciclina , Proteínas de Unión al ADN/aislamiento & purificación , Factores de Transcripción E2F , Factor de Transcripción E2F1 , Factor de Transcripción E2F4 , Humanos , Queratinocitos , Proteínas Nucleares/aislamiento & purificación , Oligodesoxirribonucleótidos , Regiones Promotoras Genéticas , Unión Proteica , Proteínas Recombinantes de Fusión/aislamiento & purificación , Proteínas Recombinantes de Fusión/metabolismo , Proteína de Retinoblastoma/aislamiento & purificación , Proteína 1 de Unión a Retinoblastoma , Proteína p107 Similar a la del Retinoblastoma , Factor de Transcripción DP1 , Factores de Transcripción/aislamiento & purificación , Transcripción Genética/efectos de los fármacosRESUMEN
The adenovirus early gene product E1A is a potent stimulator of cellular proliferation, which when overexpressed can overcome the growth-inhibitory effects of the polypeptide hormone transforming growth factor beta (TGF-beta). The ability of TGF-beta to arrest cell growth in G1 correlates with the transcriptional induction of the cyclin-dependent kinase inhibitors, p15/INK4B and p21/WAF1/Cip1; an inhibition of the G1 cyclin-Cdk complexes; and a maintenance of the retinoblastoma susceptibility gene product, Rb, in a hypophosphorylated state. The ability of E1A to overcome TGF-beta-mediated growth inhibition derives, in part, from its ability to sequester Rb and Rb family members. We report here that E1A also acts upstream of Rb by blocking the TGF-beta-mediated induction of p15 and p21. Consistent with these findings, E1A expression also blocks the ability of TGF-beta to inhibit Cdk2 kinase activity, as well as its ability to hold Rb in a hypophosphorylated state. The effect of E1A on the induction of p15 and p21 is independent of E1A's Rb binding activity. The E1A-mediated decrease in p15 levels is primarily the result of a block at the level of transcriptional activation by TGF-beta. This effect is dependent on E1A's ability to bind p300, one of E1A's target proteins. Thus, the ability of E1A to affect p15 and p21 expression represents an additional possible mechanism by which E1A can circumvent the negative regulation of cell cycle progression.