Assuntos
Aspartato Carbamoiltransferase/deficiência , Encefalopatias Metabólicas Congênitas , Carbamoil Fosfato Sintase (Glutamina-Hidrolizante)/deficiência , Di-Hidro-Orotase/deficiência , Epilepsia Resistente a Medicamentos , Anticonvulsivantes/administração & dosagem , Encefalopatias Metabólicas Congênitas/complicações , Encefalopatias Metabólicas Congênitas/diagnóstico , Encefalopatias Metabólicas Congênitas/tratamento farmacológico , Encefalopatias Metabólicas Congênitas/enzimologia , Consanguinidade , Epilepsia Resistente a Medicamentos/diagnóstico , Epilepsia Resistente a Medicamentos/tratamento farmacológico , Epilepsia Resistente a Medicamentos/enzimologia , Epilepsia Resistente a Medicamentos/etiologia , Humanos , Lactente , Fenitoína/administração & dosagem , Uridina/administração & dosagemRESUMO
Regardless of proximal cause, photoreceptor injury or disease almost invariably leads to the activation of Muller cells, the principal glial cells in the retina. This observation implies the existence of signaling systems that inform Muller cells of the health status of photoreceptors. It further suggests that diverse types of photoreceptor damage elicit a limited range of biochemical responses. Using the mouse retina, we show by microarray, RNA blot, and in situ hybridization that the genomic responses to both light damage and inherited photoreceptor degeneration involve a relatively small number of genes and that the genes activated by these two insults overlap substantially with one another and with the genes activated by retinal detachment. Among the induced transcripts, those coding for endothelin2 (Edn2) are unusual in that they are localized to photoreceptors and are also highly induced in all of the tested models of photoreceptor disease or injury. Acute light damage also leads to a >10-fold increase in endothelin receptor B (Ednrb) in Muller cells 24 h after injury. These observations suggest that photoreceptor-derived EDN2 functions as a general stress signal, that EDN2 signals to Muller cells by binding to EDNRB, and that Muller cells can increase their sensitivity to EDN2 as part of the injury response.
Assuntos
Endotelinas/metabolismo , Genômica , Neuroglia/metabolismo , Células Fotorreceptoras/fisiopatologia , Doenças Retinianas/genética , Transdução de Sinais/fisiologia , Animais , Anexina A2/genética , Anexina A2/metabolismo , Aspartato Carbamoiltransferase/deficiência , Northern Blotting/métodos , Western Blotting/métodos , Carbamoil Fosfato Sintase (Glutamina-Hidrolizante)/deficiência , Ceruloplasmina/genética , Ceruloplasmina/metabolismo , Di-Hidro-Orotase/deficiência , Modelos Animais de Doenças , Antagonistas dos Receptores de Endotelina , Endotelina-2/genética , Endotelina-2/metabolismo , Imunofluorescência/métodos , Regulação da Expressão Gênica/genética , Regulação da Expressão Gênica/fisiologia , Proteína Glial Fibrilar Ácida/metabolismo , Imuno-Histoquímica/métodos , Hibridização In Situ/métodos , Proteínas de Filamentos Intermediários/deficiência , Luz/efeitos adversos , Glicoproteínas de Membrana/deficiência , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Dados de Sequência Molecular , Proteínas do Tecido Nervoso/deficiência , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Peptídeos Cíclicos/farmacologia , Periferinas , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Receptores de Endotelina/genética , Receptores de Endotelina/metabolismo , Doenças Retinianas/etiologia , Doenças Retinianas/metabolismo , Transdução de Sinais/genética , Fatores de TempoRESUMO
A77 1726 (LEF) is the active metabolite of leflunomide, a recently approved immunosuppressive agent. We examined the ability of LEF to induce differentiation of a human erythroleukemia (K562) cell line and show that LEF induces a dose- and time-dependent differentiation of these cells as characterized by growth inhibition, hemoglobin production, and erythroid membrane protein glycophorin A expression. This effect was dependent on depletion of the intracellular pyrimidine ribonucleotides (UTP and CTP), and preceded by a specific S-phase arrest of the cell cycle. Supplementation of the cultures with exogenous uridine restored intracellular UTP and CTP to normal levels and prevented the LEF-induced cell cycle block and differentiation of K562 cells. Interestingly, addition of cytidine alone blocked the LEF-induced differentiation of K562 cells but only restored the CTP pool. By contrast, neither deoxycytidine nor thymidine prevented the effects of LEF on these cells. Similarly, pyrimidine starvation of a cell line lacking the de novo pyrimidine pathway (G9c) resulted in an S-phase arrest that was reversed by the addition of cytidine. Thus these studies demonstrate an important role for CTP in regulating cell cycle progression and show that LEF is an effective inducer of tumor cell differentiation through depletion of this ribonucleotide.