RESUMO
MAIDS (murine AIDS) is caused by infection with the murine leukaemia retrovirus RadLV-Rs and is characterized by a severe immunodeficiency and T-cell anergy combined with a lymphoproliferative disease affecting both B- and T-cells. Hyperactivation of the cAMP-protein kinase A pathway is involved in the T-cell dysfunction of MAIDS and HIV by inhibiting T-cell activation through the T-cell receptor. In the present study, we show that MAIDS involves a strong and selective up-regulation of cyclo-oxygenase type 2 in the CD11b+ subpopulation of T- and B-cells of the lymph nodes, leading to increased levels of PGE2 (prostaglandin E2). PGE2 activates the cAMP pathway through G-protein-coupled receptors. Treatment with cyclo-oxygenase type 2 inhibitors reduces the level of PGE2 and thereby reverses the T-cell anergy, restores the T-cell immune function and ameliorates the lymphoproliferative disease.
Assuntos
Dinoprostona/metabolismo , Prostaglandina-Endoperóxido Sintases/metabolismo , Vírus da Leucemia Induzida por Radiação/fisiologia , Linfócitos T/patologia , Linfócitos T/virologia , Animais , Linfócitos B/metabolismo , Linfócitos B/virologia , Antígeno CD11b/análise , Antígeno CD11b/metabolismo , Anergia Clonal , AMP Cíclico/metabolismo , Ciclo-Oxigenase 1 , Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase/farmacologia , Dinoprostona/antagonistas & inibidores , Dinoprostona/biossíntese , Indução Enzimática , HIV/imunologia , HIV/patogenicidade , Linfonodos/citologia , Linfonodos/enzimologia , Linfonodos/imunologia , Linfonodos/virologia , Ativação Linfocitária , Masculino , Proteínas de Membrana , Camundongos , Camundongos Endogâmicos C57BL , Síndrome de Imunodeficiência Adquirida Murina/imunologia , Síndrome de Imunodeficiência Adquirida Murina/metabolismo , Síndrome de Imunodeficiência Adquirida Murina/patologia , Síndrome de Imunodeficiência Adquirida Murina/virologia , Vírus da Leucemia Induzida por Radiação/patogenicidade , Receptores Acoplados a Proteínas G/metabolismo , Transdução de Sinais , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
Thiamine triphosphate (ThTP) is found in most organisms, but its biological role remains unclear. In mammalian tissues, cellular ThTP concentrations remain low, probably because of hydrolysis by a specific 25 kDa thiamine triphosphatase (ThTPase). The aim of the present study was to use quantitative PCR, for comparing the 25 kDa ThTPase mRNA expression in various mouse tissues with its enzyme activities. ThTPase mRNA was expressed at only a few copies per cell. The highest amount of mRNA was found in testis, followed by lung and muscle, while the highest enzyme activities were found in liver and kidney. The poor correlation between mRNA levels and enzyme activities might result either from tissue-specific post-transcriptional regulation of mRNA processing and/or translation or from the regulation of enzyme activities by post-translational mechanisms. Purified recombinant human ThTPase was phosphorylated by casein kinase II, but this phosphorylation did not modify the enzyme activity. However, the characterization of the 3'-untranslated mRNA region revealed a unique, highly conserved, 200-nucleotide sequence that might be involved in translational control. In situ hybridization studies in testis suggest a predominant localization of ThTPase mRNA in poorly differentiated spermatogenic cells. This is the first study demonstrating a cell-specific 25 kDa ThTPase mRNA expression, suggesting that this enzyme might be related to the degree of differentiation or the metabolic state of the cell.
Assuntos
Perfilação da Expressão Gênica , RNA Mensageiro/metabolismo , Tiamina Trifosfatase/genética , Tiamina Trifosfatase/metabolismo , Regiões 3' não Traduzidas/genética , Animais , Sequência de Bases , Caseína Quinase II/metabolismo , Bovinos , Sequência Conservada/genética , Humanos , Macaca/genética , Masculino , Camundongos , Dados de Sequência Molecular , Fosforilação , Reação em Cadeia da Polimerase , RNA Mensageiro/genética , Ratos , Alinhamento de Sequência , Suínos/genética , Testículo/metabolismo , Tiamina Trifosfatase/biossínteseRESUMO
Melanin-concentrating hormone (MCH) is highly expressed in the brain and modulates feeding behavior. It is also expressed in some peripheral tissues where its role remains unknown. We have investigated MCH function in human and mouse immune cells. RT-PCR analysis revealed a low expression of prepro-MCH and MCH receptor 1 (MCHR1) but not of MCHR2 transcript in tissular and peripheral blood immune cells. FACS and in vitro assay studies demonstrated that MCHR1 receptor expression on most cell types can trigger, in the presence of MCH, cAMP synthesis and calcium mobilization in peripheral blood mononuclear cells (PBMCs). Moreover, MCH treatment decreases the CD3-stimulated PBMC proliferation in vitro. Accordingly, our data indicate for the first time that MCH and MCHR1 may exert immunomodulatory functions.
Assuntos
Hormônios Hipotalâmicos/genética , Linfócitos/imunologia , Precursores de Proteínas/genética , Receptores do Hormônio Hipofisário/metabolismo , Animais , Complexo CD3/farmacologia , Células CHO , Cálcio/metabolismo , Divisão Celular/efeitos dos fármacos , Criança , Pré-Escolar , Colforsina/farmacologia , Cricetinae , AMP Cíclico/metabolismo , Humanos , Hormônios Hipotalâmicos/metabolismo , Hormônios Hipotalâmicos/farmacologia , Imunidade Celular/fisiologia , Lactente , Linfócitos/citologia , Linfócitos/efeitos dos fármacos , Melaninas/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Tonsila Palatina/citologia , Tonsila Palatina/imunologia , Tonsila Palatina/metabolismo , Hormônios Hipofisários/farmacologia , Precursores de Proteínas/metabolismo , RNA Mensageiro/análise , Receptores do Hormônio Hipofisário/efeitos dos fármacos , Receptores do Hormônio Hipofisário/genética , Baço/citologia , Baço/imunologia , Baço/metabolismo , Timo/imunologia , Timo/metabolismoRESUMO
The evolution of mitochondrial oxidative phosphorylation was studied during cancer induction in a model of thymic radiolymphomagenesis in C57BL/Ka mice. During the preneoplastic period, thymuses displayed an increase of the cytochrome c oxidase activity and oxygen consumption together with oxidative DNA damage assessed by the presence of the 8-hydroxydeoxyguanine DNA base modification. These transient changes in mitochondrial functional activity were not observed in thymuses of mice rescued from lymphoma development by a bone marrow graft, suggesting an important role of mitochondria for neoplastic transformation in this model, which might therefore be of interest to test the utilization of antioxidants for the prevention of radiation-induced malignancies.