RESUMO
Cysteine is the limiting precursor for glutathione synthesis. Because of its low bioavailability, cysteine is generally produced from cystine, which may be taken up through two different transporters. The cystine/glutamate antiporter (x system) transports extracellular cystine in exchange for intracellular glutamate. The X(AG) transport system takes up extracellular cystine, glutamate, and aspartate. Both are sensitive to competition between cystine and glutamate, and excess extracellular glutamate thus inhibits glutathione synthesis, a nonexcitotoxic mechanism for glutamate toxicity. We demonstrated previously that human macrophages express the glutamate transporters excitatory amino acid transporter (EAAT)1 and EAAT2 (which do not transport cystine, X system) and overcome competition for the use of cystine transporters. We now show that macrophages take up cystine through the x and not the X(AG) system. We also found that glutamate, although competing with cystine uptake, dose-dependently increases glutathione synthesis. We used inhibitors to demonstrate that this increase is mediated by EAATs. EAAT expression in macrophages thus leads to glutamate-dependent enhancement of glutathione synthesis by providing intracellular glutamate for direct insertion in glutathione and also for fueling the intracellular pool of glutamate and trans-stimulating the cystine/glutamate antiporter.
Assuntos
Sistema y+ de Transporte de Aminoácidos , Proteínas de Transporte/metabolismo , Transportador 1 de Aminoácido Excitatório/metabolismo , Transportador 2 de Aminoácido Excitatório/metabolismo , Ácido Glutâmico/metabolismo , Glutationa/metabolismo , Macrófagos/metabolismo , Células Cultivadas , Cistina/metabolismo , Cistina/farmacologia , Transportador 1 de Aminoácido Excitatório/antagonistas & inibidores , Transportador 2 de Aminoácido Excitatório/antagonistas & inibidores , Ácido Glutâmico/farmacologia , Humanos , Modelos BiológicosRESUMO
Oxidative stress and glutathione deficiency seem to play a major role in the pathogenesis of HIV infection, as suggested by the increased survival of HIV-infected patients treated with N-acetylcysteine, a prodrug of glutathione. However, beneficial effects of GSH-replenishing drugs are restricted in vivo by the high concentrations needed to obtain biological effects and their low bioavailability. In this study, we evaluated the antiretroviral and antioxidant activities of new more lipophilic GSH-replenishing molecules, in macrophages infected in vitro with HIV-1. In these experimental conditions, a prodrug of N-acetylcystéine and beta-mercaptoethylamine, I-152 demonstrated a potent anti-HIV activity, increased intracellular GSH level, and decreased TNF-alpha production. Altogether, these results suggest that I-152 could be beneficial as adjuvant therapy of antiretrovirals in HIV-infected patients, especially in those with damages to the central nervous system or with mitochondrial damages associated with highly active antiretroviral therapy.
Assuntos
Acetilcisteína/análogos & derivados , Acetilcisteína/farmacologia , Fármacos Anti-HIV/farmacologia , Antioxidantes/farmacologia , Cisteamina/análogos & derivados , Cisteamina/farmacologia , Glutationa/fisiologia , HIV-1/efeitos dos fármacos , Macrófagos/virologia , Pró-Fármacos/farmacologia , Acetilcisteína/toxicidade , Butionina Sulfoximina/farmacologia , Células Cultivadas , Cisteamina/toxicidade , Avaliação Pré-Clínica de Medicamentos , HIV-1/fisiologia , Humanos , Macrófagos/metabolismo , Estresse Oxidativo , Fator de Necrose Tumoral alfa/biossíntese , Replicação Viral/efeitos dos fármacosRESUMO
I-152 is a prodrug of NAC and MEA with potent pro-GSH effects in human macrophages, astrocytes and lymphocytes. This molecule could be of interest in HIV infection in respect to its antioxidant and anti-HIV activities, but also in other diseases to counteract oxidative stress, that is, inflammation, cardiovascular diseases, and neurodegenerative diseases.
Assuntos
Acetilcisteína/síntese química , Acetilcisteína/farmacologia , Antioxidantes/síntese química , Antioxidantes/farmacologia , Cisteamina/síntese química , Cisteamina/farmacologia , Glutationa/metabolismo , Pró-Fármacos/síntese química , Pró-Fármacos/farmacologia , Acetilcisteína/análogos & derivados , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Linfócitos T CD4-Positivos/efeitos dos fármacos , Linfócitos T CD4-Positivos/metabolismo , Linhagem Celular , Cisteamina/análogos & derivados , Infecções por HIV/metabolismo , Humanos , Indicadores e Reagentes , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Monócitos/efeitos dos fármacos , Monócitos/metabolismoRESUMO
Oxidative stress and glutathione (GSH) deficit may play an important role in HIV infection pathogenesis, and oral administration of GSH-replenishing drugs such as N-acetylcysteine (NAC) and 2-oxothiazolidine-4(R)-carboxylic acid (OTC) may be associated with an increased survival rate of HIV-infected patients. Nevertheless, beneficial effects of these molecules are restricted in vivo by the high concentrations that are necessary to obtain biological effects, rapid extracellular metabolization, and low availability and plasma concentrations. We synthesized OTC derivatives that are more lipophilic than OTC and theoretically able to overcome these limitations and to generate, in addition to cysteine, other substrates of the gamma-glutamyl cycle. Their antiviral effects were investigated in human HIV-1/Ba-L-infected monocyte-derived macrophages. In our experimental conditions, OTC exhibited anti-HIV-1 effects and little cytotoxicity at high doses. None of the nine tested derivatives showed higher cytotoxicity than OTC, nor anti-HIV-1/Ba-L activity.