Protective effects of glutamine on human melanocyte oxidative stress model.

BACKGROUND: Vitiligo is a disorder caused by the loss of the melanocyte activity on melanin pigment generation. Studies show that oxidative-stress induced apoptosis in melanocytes is closely related to the pathogenesis of vitiligo. Glutamine is a well known antioxidant with anti-apoptotic effects, and is used in a variety of diseases. However, it is unclear whether glutamine has an antioxidant or anti-apoptotic effect on melanocytes. AIMS: The aim of this study was to investigate the protective effects of glutamine on a human melanocyte oxidative stress model. METHODS: The oxidative stress model was established on human melanocytes using hydrogen peroxide. The morphology and viability of melanocytes, levels of oxidants [reactive oxygen species and malondialdehyde], levels of antioxidants [superoxide dismutase and glutathione-S-transferase], and apoptosis-related indicators (caspase-3, bax and bcl-2) were examined after glutamine exposure at various concentrations. Expressions of nuclear factor-E2-related factor 2, heme oxygenase-1, and heat shock protein 70 were detected using western blot technique after glutamine exposure at various concentrations. RESULTS: Our results demonstrate that pre-treatment and post-treatment with glutamine promoted melanocyte viability, increased levels of superoxide dismutase, glutathione-S-transferase and bcl-2, decreased levels of reactive oxygen species, malondialdehyde, bax and caspase-3, and enhanced nuclear factor-E2-related factor 2, heme oxygenase-1, and heat shock protein 70 expression in a dose dependent manner. The effect of pre-treatment was more significant than post-treatment, at the same concentration. LIMITATIONS: The mechanisms of glutamine activated nuclear factor-E2-related factor 2 antioxidant responsive element signaling pathway need further investigation. CONCLUSIONS: Glutamine enhances the antioxidant and anti-apoptotic capabilities of melanocytes and protects them against oxidative stress.

Further investigations on M. leprae. Growth promotion and inhibition by organic substances and observations on antagonistic and syntergistic effects.

The multiplication of 2 strains of M. leprae on a medium containing a sonic extract (SE), prepared from M. smegmatis, was promoted by cysteine, tryptophane and dimethylasulfoxide (DMSO), while glutamic acid, glutamine and histidine exerted variable effects. The final effects of glutamic acid and glutamine were determined by the total concentration of both compounds together. The presence of cysteine and glutamic acid alone or together with DMSO abolished all inhibitory effects. Desferal did not enable the multiplication of M. leprae on media devoid of SE prepared from M. smegmatis. However with SE and 0.005 per cent and 0.002 per cent concentrations of Desferal its initial growth was accelerated. Its final counts, noted after an 8-month incubation, did not exceed those observed without Desferal. Puring and pyrimidine compounds promoted markekly the multiplication of M. leprae (counts greater than 3 times 10-7/ml). The highest counts were observed with pyrimidines (thymine, thymidine, cytosine) applied single or combined.