RESUMEN
Thyroid hormone (TH)-regulated gene expression is mainly mediated by TH binding to nuclear thyroid hormone receptors (TRs). Despite extensive studies in mammalian cell lines that show that phosphorylation signaling pathways are important in TH action, little is known about their roles on TH signaling in vivo during development. Anuran metamorphosis is a postembryonic process that is absolutely dependent upon TH and tadpole tail resorption can be precociously induced by exogenous administration of 3,5,3'-triiodothyronine (T(3)). We demonstrate that genistein (a major isoflavone in soy products and tyrosine kinase inhibitor) and the PKC inhibitor (H7) prevent T(3)-induced regression of the Rana catesbeiana tadpole tail. T(3)-induced protein kinase C tyrosine phosphorylation and kinase activity are inhibited by genistein while T(3)-induced up-regulation of TRbeta mRNA, but not TRalpha mRNA, is significantly attenuated, most likely through inhibition of T(3)-dependent phosphorylation of the TRalpha protein. This phosphorylation may be modulated through PKC. These data demonstrate that T(3) signaling in the context of normal cells in vivo includes phosphorylation as an important factor in establishing T(3)-dependent tail regression during development.
Asunto(s)
Proteína Quinasa C/metabolismo , Rana catesbeiana/metabolismo , Cola (estructura animal)/metabolismo , Receptores alfa de Hormona Tiroidea/metabolismo , Hormonas Tiroideas/metabolismo , Animales , Dimetilsulfóxido/farmacología , Electroforesis en Gel Bidimensional , Flavonoides/farmacología , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Genisteína/farmacología , Immunoblotting , Inmunoprecipitación , Larva/efectos de los fármacos , Larva/genética , Larva/crecimiento & desarrollo , Técnicas de Cultivo de Órganos , Fosforilación/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Rana catesbeiana/genética , Rana catesbeiana/crecimiento & desarrollo , Cola (estructura animal)/efectos de los fármacos , Cola (estructura animal)/crecimiento & desarrollo , Receptores alfa de Hormona Tiroidea/genética , Triyodotironina/farmacologíaRESUMEN
Interactions of two fluorescent probes 1-(trimethylammoniumphenyl)-6-phenyl-1,3,5 hexatriene p-toluenesulfonate (TMA-DPH) and 12-(9-anthroyloxy) stearic acid (12-AS) with polyamidoamine (PAMAM) dendrimers were studied. Changes in fluorescence intensity and steady-state fluorescence anisotropy of TMA-DPH and 12-AS were monitored. It was found that 12-AS molecules incorporated into dendrimer cavities whereas TMA-DPH molecules aggregated on the surface of polymer. Dendrimer size had not significant impact on its host properties.
Asunto(s)
Materiales Biocompatibles/química , Difenilhexatrieno/análogos & derivados , Difenilhexatrieno/química , Colorantes Fluorescentes/química , Poliaminas/química , Espectrometría de Fluorescencia/métodos , Ácidos Esteáricos/química , Adsorción , Difenilhexatrieno/análisis , Sustancias Macromoleculares , Conformación Molecular , Polímeros/química , Ácidos Esteáricos/análisisRESUMEN
Polyamidoamine (PAMAM) dendrimers with different concentrations (1 nM-1 mM) (generations 2, 3, and 4) impact on human red blood cell morphology, and membrane integrity is studied. Erythrocyte shape changes from biconcave to echinocytic in dendrimers. Cell aggregation occurs. Polymers cause also concentration- and generation-dependent haemolysis.
Asunto(s)
Tamaño de la Célula/efectos de los fármacos , Eritrocitos/citología , Eritrocitos/efectos de los fármacos , Hemólisis/efectos de los fármacos , Poliaminas/farmacología , Células Cultivadas , Dimerización , Relación Dosis-Respuesta a Droga , Membrana Eritrocítica/efectos de los fármacos , Membrana Eritrocítica/fisiología , Humanos , Poliaminas/clasificación , Polímeros/farmacologíaRESUMEN
BACKGROUND: A protective role for the ultraviolet (UV) A waveband against immunosuppression induced by UVB (280-320 nm) radiation has been identified. The mechanism for UVA immunoprotection was found to involve two apparently unrelated mediators, the T-helper-1-associated proinflammatory cytokine interferon (IFN)-gamma and the UVA-induced redox-regulated stress protein, haem oxygenase (HO). OBJECTIVES: To identify a relationship between these two immune regulators. METHODS: The HO response to UVA radiation in the skin and liver was examined in mice with a targeted disruption of the IFN-gamma gene, known to be unresponsive to UVA photoimmunoprotection. Results IFN-gamma null mice did not respond to UVA irradiation with the normal upregulation of HO activity in either the irradiated skin or the liver. Injection of these mice with recombinant IFN-gamma previously shown to restore the UVA-photoimmunoprotective effect, here partially and dose-responsively restored their ability for induction of HO activity in both skin and liver following UVA irradiation. CONCLUSIONS: IFN-gamma appears to be a prerequisite for the immunoprotective induction of HO, although other mediators may also be involved. The UVA responsiveness of HO in an internal organ such as the liver suggests the existence of a soluble UVA-induced mediator from the skin, which may be IFN-gamma.
Asunto(s)
Hemo Oxigenasa (Desciclizante)/efectos de la radiación , Interferón gamma/farmacología , Rayos Ultravioleta/efectos adversos , Animales , Femenino , Hemo Oxigenasa (Desciclizante)/metabolismo , Tolerancia Inmunológica/efectos de la radiación , Ratones , Ratones Noqueados , Microsomas Hepáticos/enzimologíaRESUMEN
Studies of the photoimmunoprotective properties of sunscreens have produced disparate results. In this study in hairless mice, we compared two UVB absorbers, 2-ethylhexyl-p-methoxycinnamate (2-EHMC) and octyl-N-dimethyl-p-aminobenzoate (o-PABA), individually formulated in a common base lotion with a sunburn protection factor of 6. We measured their capacity to protect against suppression of the contact hypersensitivity (CHS) induced by three daily exposures of the dorsum to 6x the minimal erythemal/edematous dose (MED) of solar-simulated UV radiation (SSUV), in comparison with base lotion-treated mice exposed to 3 x 1 MED of SSUV. All treatments produced a similar minimal erythema. CHS was equally suppressed in mice irradiated through o-PABA and base lotion, but the suppression was significantly reduced in mice irradiated through 2-EHMC. Neither UVB absorber inhibited the epidermal photoisomerization to the immunosuppressive mediator, cis-urocanic acid. However, when mice were treated with exogenous cis-urocanic acid topically on the dorsum, but not when injected subcutaneously on the abdomen, suppression of CHS was observed in o-PABA- and base lotion-treated mice, but not in 2-EHMC-treated mice. Thus, the enhanced immunoprotection in mice irradiated through 2-EHMC apparently resulted from the direct inactivation of epidermal cis-urocanic acid by 2-EHMC. We conclude that comparative assessment of photoimmunoprotection by UV absorbers requires SSUV, erythemally matched exposures and consideration of potential interactions with cutaneous molecules.