RESUMO
BACKGROUND: Mycobacterium tuberculosis infection is thought to induce oxidative stress. N-acetyl-cysteine (NAC) is widely used in patients with chronic pulmonary diseases including tuberculosis due to its mucolytic and anti-oxidant activities. Here, we tested whether NAC exerts a direct antibiotic activity against mycobacteria. METHODS: Oxidative stress status in plasma was compared between pulmonary TB (PTB) patients and those with latent M. tuberculosis infection (LTBI) or healthy uninfected individuals. Lipid peroxidation, DNA oxidation and cell death, as well as accumulation of reactive oxygen species (ROS) were measured in cultures of primary human monocyte-derived macrophages infected with M. tuberculosis and treated or not with NAC. M. tuberculosis, M. avium and M. bovis BCG cultures were also exposed to different doses of NAC with or without medium pH adjustment to control for acidity. The anti-mycobacterial effect of NAC was assessed in M. tuberculosis infected human THP-1 cells and bone marrow-derived macrophages from mice lacking a fully functional NADPH oxidase system. The capacity of NAC to control M. tuberculosis infection was further tested in vivo in a mouse (C57BL/6) model. RESULTS: PTB patients exhibited elevated levels of oxidation products and a reduction of anti-oxidants compared with LTBI cases or uninfected controls. NAC treatment in M. tuberculosis-infected human macrophages resulted in a decrease of oxidative stress and cell death evoked by mycobacteria. Importantly, we observed a dose-dependent reduction in metabolic activity and in vitro growth of NAC treated M. tuberculosis, M. avium and M. bovis BCG. Furthermore, anti-mycobacterial activity in infected macrophages was shown to be independent of the effects of NAC on the host NADPH oxidase system in vitro. Short-term NAC treatment of M. tuberculosis infected mice in vivo resulted in a significant reduction of mycobacterial loads in the lungs. CONCLUSIONS: NAC exhibits potent anti-mycobacterial effects and may limit M. tuberculosis infection and disease both through suppression of the host oxidative response and through direct antimicrobial activity.
Assuntos
Acetilcisteína/farmacologia , Antibacterianos/farmacologia , Antioxidantes/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Adolescente , Adulto , Animais , Estudos de Casos e Controles , Morte Celular/efeitos dos fármacos , Linhagem Celular , Modelos Animais de Doenças , Humanos , Tuberculose Latente/sangue , Tuberculose Latente/tratamento farmacológico , Tuberculose Latente/microbiologia , Peroxidação de Lipídeos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Macrófagos/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Mycobacterium avium/efeitos dos fármacos , Mycobacterium avium/crescimento & desenvolvimento , Mycobacterium avium/metabolismo , Mycobacterium bovis/efeitos dos fármacos , Mycobacterium bovis/crescimento & desenvolvimento , Mycobacterium bovis/metabolismo , NADPH Oxidases/deficiência , NADPH Oxidases/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Tuberculose Pulmonar/sangue , Tuberculose Pulmonar/tratamento farmacológico , Tuberculose Pulmonar/microbiologia , Adulto JovemRESUMO
In trials evaluating the immune responses to Bacille of Calmette-Guérin (BCG), the genetic background and the nutritional status are host-related factors that could affect the heterogeneity in these parameters. The IFNG+874 A/T (rs 62559044) polymorphism has been reported to influence the IFN-γ production by BCG-vaccinated individuals challenged in vitro with mycobacterial antigens. The body mass index (BMI) is a proxy for the nutritional status and has been associated both with the susceptibility to tuberculosis and with the IFN-γ response. We show that although the IFNG+874 A/T polymorphism was not associated with the heterogeneity of IFN-γ production in a randomized controlled trial that evaluated long-term immune responses to BCG revaccination previously conducted in Salvador, Bahia, Brazil, the effect of this polymorphism on the observed increase in IFN-γ production among revaccinated subjects was adjusted in individuals with a low BMI.
Assuntos
Vacina BCG/administração & dosagem , Índice de Massa Corporal , Imunização Secundária , Interferon gama/biossíntese , Polimorfismo Genético , Brasil , Voluntários Saudáveis , Humanos , Interferon gama/genética , Análise MultivariadaRESUMO
The Bacille Calmette-Guérin (BCG) vaccine is the only vaccine currently available for tuberculosis, and it demonstrates variable efficacy against the disease. The assessment of new vaccine strategies is hindered by the small annual probability that an infected individual will develop tuberculosis, and the lack of simple and reliable surrogate markers of protection. The frequency of cytokine-producing T cells as well as the production of IFN-γ have been disputed as surrogate markers of protection. We evaluated the evolution of these immune parameters in a population from a high burden city where BCG revaccination has been shown to result in mild protection. We found that individuals whose in vitro IFN-γ responses to mycobacterial antigens had increased by more than 3.3-fold were more likely to maintain higher responses after 1 year and to show increased expansion of IFN-γ-producing T lymphocytes than those with lower or null increase of IFN-γ.