RESUMO
Claudin-5 is a protein component of many endothelial tight junctions, including those at the blood-brain barrier, a barrier that limits molecular exchanges between the central nervous system and the circulatory system. To test the contribution of claudin-5 to this barrier function of tight junctions, we expressed murine claudin-5 in Madin-Darby canine kidney II cells. The result was a fivefold increase in transepithelial resistance in claudin-5 transductants and a reduction in conductance of monovalent cations. However, the paracellular flux of neither neutral nor charged monosaccharides was significantly changed in claudin-5 transductants compared to controls. Therefore, expression of claudin-5 selectively decreased the permeability to ions. Additionally, site-directed mutations of particular amino acid residues in the first extracellular domain of claudin-5 altered the properties of the tight junctions formed in response to claudin-5 expression. In particular, the conserved cysteines were crucial: mutation of either cysteine abolishted the ability of claudin-5 to increase transepithelial resistance, and mutation of Cys(64) strikingly increased the paracellular flux of monosaccharides. These new insights into the functions of claudin-5 at the molecular level in tight junctions may account for some aspects of the blood-brain barrier's selective permeability.
Assuntos
Proteínas de Membrana/metabolismo , Junções Íntimas/metabolismo , Sequência de Aminoácidos , Animais , Cisteína/genética , Cisteína/metabolismo , Manitol/metabolismo , Proteínas de Membrana/genética , Camundongos , Microscopia Confocal , Dados de Sequência Molecular , MutaçãoRESUMO
The human immunodeficiency virus type 1-associated cognitive-motor disorder, including the AIDS dementia complex, is characterized by brain functional abnormalities that are associated with injury initiated by viral infection of the brain. Indoleamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme in tryptophan catabolism in extrahepatic tissues, can lead to neurotoxicity through the generation of quinolinic acid and immunosuppression and can alter brain chemistry via depletion of tryptophan. Using the simian immunodeficiency virus (SIV)-infected rhesus macaque model of AIDS, we demonstrate that cells of the macrophage lineage are the main source for expression of IDO in the SIV-infected monkey brain. Animals with SIV encephalitis have the highest levels of IDO mRNA, and the level of IDO correlates with gamma interferon (IFN-gamma) and viral load levels. In vitro studies on mouse microglia reveal that IFN-gamma is the primary inducer of IDO expression. These findings demonstrate the link between IDO expression, IFN-gamma levels, and brain pathology signs observed in neuro-AIDS.
Assuntos
Encéfalo/enzimologia , Síndrome de Imunodeficiência Adquirida dos Símios/enzimologia , Síndrome de Imunodeficiência Adquirida dos Símios/genética , Triptofano Oxigenase/genética , Complexo AIDS Demência/etiologia , Animais , Sequência de Bases , Encéfalo/imunologia , Encéfalo/patologia , Modelos Animais de Doenças , Regulação Enzimológica da Expressão Gênica , Humanos , Técnicas In Vitro , Indolamina-Pirrol 2,3,-Dioxigenase , Interferon gama/genética , Interferon gama/metabolismo , Interferon gama/farmacologia , Macaca mulatta , Camundongos , Microglia/efeitos dos fármacos , Microglia/enzimologia , Dados de Sequência Molecular , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Fator de Necrose Tumoral alfa/metabolismoRESUMO
The duration and severity of the symptomatology present during the early phase of human immunodeficiency virus (HIV) infection (known as the acute retroviral syndrome) is associated with alterations in the clinical profile of infection, such as a shortening of duration between infection with HIV and the onset of neurocognitive impairment and acquired immunodeficiency syndrome (AIDS). Viral-specific CD8+ cytotoxic T lymphocytes (CTLs) and CD8+ natural killer (NK) cells play a key role in antiviral immunity. Loss of CD8+ cells or their functional impairment during the early period of infection is associated with a rapid progression to AIDS in nonhuman primate studies. However, no studies have determined whether CD8+ cell loss or impairment is associated with symptoms of acute retroviral illness such as fever. In this study, the authors compared the early phase of simian immunodeficiency virus (SIV) infection in animals that were treated with the anti-CD8 monoclonal antibody cM-T807 to deplete CD8+ cells during the early period of infection (SIV+ CD8- group) to those with intact CD8+ cells (SIV+ CD8+ group). The SIV+ CD8- group had an enhanced acute retroviral syndrome when compared to the SIV+ CD8+ group. The SIV+ CD8- group also had prolonged high viral loads and distinct alterations in the proinflammatory cytokines interleukin (IL)-6 and interferon (IFN)-alpha, as well as in monocyte chemoattractant protein (MCP)-1. CD8+ cell depletion, therefore, appears to enhance symptoms of the acute retroviral syndrome and alters several of the immunological factors associated with the early phase of infection.