RESUMEN
The activin receptor-like kinase 1 (ALK1) is a type I receptor for transforming growth factor-beta (TGF-beta) family proteins. Expression of ALK1 in blood vessels and mutations of the ALK1 gene in human type II hereditary hemorrhagic telangiectasia patients suggest that ALK1 may have an important role during vascular development. To define the function of ALK1 during development, we inactivated the ALK1 gene in mice by gene targeting. The ALK1 homozygous embryos die at midgestation, exhibiting severe vascular abnormalities characterized by excessive fusion of capillary plexes into cavernous vessels and hyperdilation of large vessels. These vascular defects are associated with enhanced expression of angiogenic factors and proteases and are characterized by deficient differentiation and recruitment of vascular smooth muscle cells. The blood vessel defects in ALK1-deficient mice are reminiscent of mice lacking TGF-beta1, TGF-beta type II receptor (TbetaR-II), or endoglin, suggesting that ALK1 may mediate TGF-beta1 signal in endothelial cells. Consistent with this hypothesis, we demonstrate that ALK1 in endothelial cells binds to TGF-beta1 and TbetaR-II. Furthermore, the ALK1 signaling pathway can inhibit TGF-beta1-dependent transcriptional activation mediated by the known TGF-beta1 type I receptor, ALK5. Taken together, our results suggest that the balance between the ALK1 and ALK5 signaling pathways in endothelial cells plays a crucial role in determining vascular endothelial properties during angiogenesis.
Asunto(s)
Receptores de Activinas Tipo I , Neovascularización Fisiológica , Proteínas Serina-Treonina Quinasas/fisiología , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Receptores de Activinas , Animales , Capilares/fisiología , Diferenciación Celular , Proteínas de Unión al ADN/metabolismo , Endotelio Vascular/enzimología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Músculo Liso Vascular/citología , Mutación , Fosfoproteínas/metabolismo , Plasminógeno/metabolismo , Inhibidor 1 de Activador Plasminogénico/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Receptor Tipo I de Factor de Crecimiento Transformador beta , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Proteínas Smad , Proteína Smad5 , Transactivadores/metabolismo , Transfección , Regulación hacia ArribaRESUMEN
Fatty acid ethyl esters (FAEE), nonoxidative ethanol metabolites present in human organs commonly damaged by ethanol abuse, have been implicated as mediators of organ damage. FAEE are additives in various foods and beverages to provide flavor or fragrance, and therefore are common dietary lipid constituents. We hypothesized that FAEE could be generated during alcoholic beverage production because fatty acids are present within microorganisms and ethanol is generated during the fermentation process. In this report, we demonstrate that FAEE are present in commercially available scotch beverages, and that in the preparation of scotch, FAEE can be produced during the fermentation reaction as a result of FAEE synthase activity in the yeast. Following ingestion of scotch, preformed FAEE are delivered to GI tract. The consequences of ingestion of FAEE in scotch, if any, remain to be determined.
Asunto(s)
Bebidas Alcohólicas/análisis , Ésteres/metabolismo , Ácidos Grasos/análisis , Ácidos Grasos/metabolismo , Aciltransferasas/metabolismo , Esterificación , Etanol/metabolismo , Fermentación , Cromatografía de Gases y Espectrometría de Masas , Humanos , Levaduras/enzimologíaRESUMEN
It has been a controversial issue as to how many DNA cytosine methyltransferase mammalian cells have and whether de novo methylation and maintenance methylation activities are encoded by a single gene or two different genes. To address these questions, we have generated a null mutation of the only known mammalian DNA methyltransferase gene through homologous recombination in mouse embryonic stem cells and found that the development of the homozygous embryos is arrested prior to the 8-somite stage. Surprisingly, the null mutant embryonic stem cells are viable and contain low but stable levels of methyl cytosine and methyltransferase activity, suggesting the existence of a second DNA methyltransferase in mammalian cells. Further studies indicate that de novo methylation activity is not impaired by the mutation as integrated provirus DNA in MoMuLV-infected homozygous embryonic stem cells become methylated at a similar rate as in wild-type cells. Differentiation of mutant cells results in further reduction of methyl cytosine levels, consistent with the de novo methylation activity being down regulated in differentiated cells. These results provide the first evidence that an independently encoded DNA methyltransferase is present in mammalian cells which is capable of de novo methylating cellular and viral DNA in vivo.
Asunto(s)
ADN-Citosina Metilasas/metabolismo , Animales , Diferenciación Celular , Línea Celular , Supervivencia Celular , Metilación de ADN , ADN Viral/metabolismo , ADN-Citosina Metilasas/genética , Desarrollo Embrionario , Femenino , Eliminación de Gen , Ratones , Virus de la Leucemia Murina de Moloney/genética , Embarazo , Provirus/genéticaRESUMEN
The aim of the study was to determine whether fatty acid ethyl esters, nonoxidative products of ethanol metabolism selectively present in organs damaged by ethanol abuse, are detectable in the serum after ethanol ingestion. Serum samples of hospital emergency room patients with positive (n = 32) and negative (n = 5) blood ethanol levels were assayed for fatty acid ethyl esters. In a separate study, five healthy subjects received an ethanol dose based on body weight mixed with fruit juice in a 1:2 ratio and administered by measured ingestion. Fatty acid ethyl esters were found in the serum of hospital emergency room patients with positive blood ethanol levels. The concentration of fatty acid ethyl esters in these patients correlated with the concentration of blood ethanol (r = 0.57; 95% confidence interval 0.28 to 0.77; P = 0.0002). In the controlled ethanol ingestion study with five healthy subjects, it was also determined that the serum fatty acid ethyl ester concentration began to decrease within 2 h of the time ethanol ingestion had been stopped. The fatty acid ethyl esters in the serum were bound to lipoprotein and albumin, and there was a higher percentage of saturated fatty acids in the FAEE pool than in the serum free fatty acid and triglyceride pools. These studies indicate that fatty acid ethyl esters, which have been implicated as mediators of ethanol-induced organ toxicity, are present in serum after ethanol ingestion.