M. leprae HSP18 suppresses copper (II) mediated ROS generation: Effect of redox stress on its structure and function.

Mycobacterium leprae, causative organism of leprosy, is known to counter redox stress generated by reactive oxygen species (ROS) during its survival inside host macrophages. But, the involvement of any antigenic protein(s) for countering such redox stress is still unknown. Interestingly, M. leprae HSP18, an important antigenic protein that helps in the growth and survival of M. leprae pathogen inside host macrophages, is induced under redox stress. Moreover, HSP18 also interacts with Cu2+. Copper (II) can induce redox stress via Fenton reaction. But, whether HSP18 suppresses Cu2+ mediated ROS generation, is still far from clear. Also, the effect of redox stress on its structure and function is not known. In this study, we show that HSP18 efficiently suppresses Cu2+ mediated generation of ROS and also prevents the redox mediated aggregation of a client protein (γD-crystallin). Upon exposure to substantial redox stress, irreversible perturbation in the secondary and tertiary structure of HSP18 and the tryptophan and tyrosine oxidation are evidenced. Interestingly, HSP18 retains a considerable amount of functionality even after being exposed to substantial redox stress. Perhaps, the redox scavenging ability as well as the chaperone function of HSP18 may possibly help M. leprae pathogen to counter redox stress inside host macrophages.

Antioxidant factors, nitric oxide levels, and cellular damage in leprosy patients.

INTRODUCTION: The immune response caused by Mycobacterium leprae is a risk factor for the development of oxidative stress (OS) in leprosy patients. This study aimed to assess OS in leprosy patients before the use of a multidrug therapy. METHODS: We evaluated the nitric oxide (NO) concentration; antioxidant capacity; levels of malondialdehyde, methemoglobin and reduced glutathione; and the activity of catalase and superoxide dismutase (SOD) in leprosy patients. RESULTS: We observed lower SOD activity in these leprosy patients; however, the NO levels and antioxidant capacity were increased. CONCLUSIONS: The infectious process in response to M. leprae could primarily be responsible for the OS observed in these patients.

Antioxidant factors, nitric oxide levels, and cellular damage in leprosy patients

Introduction The immune response caused by Mycobacterium leprae is a risk factor for the development of oxidative stress (OS) in leprosy patients. This study aimed to assess OS in leprosy patients before the use of a multidrug therapy. Methods We evaluated the nitric oxide (NO) concentration; antioxidant capacity; levels of malondialdehyde, methemoglobin and reduced glutathione; and the activity of catalase and superoxide dismutase (SOD) in leprosy patients. Results We observed lower SOD activity in these leprosy patients; however, the NO levels and antioxidant capacity were increased. Conclusions The infectious process in response to M. leprae could primarily be responsible for the OS observed in these patients. .

Reduction of clofazimine by mycobacterial type 2 NADH:quinone oxidoreductase: a pathway for the generation of bactericidal levels of reactive oxygen species.

The mechanism of action of clofazimine (CFZ), an antimycobacterial drug with a long history, is not well understood. The present study describes a redox cycling pathway that involves the enzymatic reduction of CFZ by NDH-2, the primary respiratory chain NADH:quinone oxidoreductase of mycobacteria and nonenzymatic oxidation of reduced CFZ by O(2) yielding CFZ and reactive oxygen species (ROS). This pathway was demonstrated using isolated membranes and purified recombinant NDH-2. The reduction and oxidation of CFZ was measured spectrally, and the production of ROS was measured using a coupled assay system with Amplex Red. Supporting the ROS-based killing mechanism, bacteria grown in the presence of antioxidants are more resistant to CFZ. CFZ-mediated increase in NADH oxidation and ROS production were not observed in membranes from three different Gram-negative bacteria but was observed in Staphylococcus aureus and Saccharomyces cerevisiae, which is consistent with the known antimicrobial specificity of CFZ. A more soluble analog of CFZ, KS6, was synthesized and was shown to have the same activities as CFZ. These studies describe a pathway for a continuous and high rate of reactive oxygen species production in Mycobacterium smegmatis treated with CFZ and a CFZ analog as well as evidence that cell death produced by these agents are related to the production of these radical species.

[Functional characteristics of the antioxidative system in mycobacteria grown on perfluorodecalin-modified media]. / Osobennosti funktsionirovaniia antiokislitel'noi sistemy mikobakterii, vyrashchennykh na sredakh, modifitsirovannykh perftordekalinom.

The growth of mycobacteria on perfluorodecalin-modified media was shown to be accompanied by distinct alterations in the activity of the antioxidant enzyme system in M. bovis BCG and M. lufu. In M. bovis BCG the levels of glutathione transferase and glutathione peroxidase-hydrogen peroxidase activity are decreased by 45.47% and 100.88%, respectively. In M. lufu, on the contrary, the level of superoxide dismutase is increased by 42.23%, with no changes observed in the levels of glutathione transferase and glutathione peroxidases. The data obtained suggest physiological heterogeneity of mycobacteria and, thus, open prospects for the differential approaches to the problem of increasing the efficacy of in vitro cultivation of various mycobacterial species, including M. leprae.

Vitamin E and dapsone-induced hemolysis.

Sixteen patients, each receiving 100 mg of dapsone per day, were studied for evidence of hemolysis. Vitamin E (dl-alpha tocopherol acetate), 800 mg/day, was then administered for up to three months, and dapsone therapy was continued at the same dose. Hemolysis factors were reexamined immediately prior to cessation of vitamin E therapy. No substantial change was demonstrable for levels of hemoglobin, reticulocyte count, and haptoglobin at the end of vitamin E therapy, despite a significant rise in serum vitamin E levels. Erythrocyte survival measured in four patients before and at the end of vitamin E therapy also showed no substantial change. Erythrocyte Heinz body count, however, fell in nine of 15 patients studied, and none showed an increase in this measurement while receiving vitamin E. We conclude that in patients receiving dapsone at 100 mg/day, vitamin E therapy at 800 mg/day does not substantially ameliorate the hemolytic effect of this drug.

[Mechanism of action of the inhibition of pyridine-nucleotide-dependent flavine enzymes using the systemic fungicide Dexon]. / Zum Wirkungsmechanismus der Hemmung von pyridinnukleotidabhängigen Flavinenzymen durch das Systemfungizid Dexon.

The actions of Dexon on the NADH-ferricyanide oxidoreductase and the NADPH oxidase system of electron transfer particles (ETP) from beef heart as well as on the NADPH-cytochrome c oxidoreductase from brewer's yeast (Saccharomyces carlsbergensis Hansen) were investigated. The inhibition of the NADH dehydrogenase activity of ETP and that of the yeast enzyme correspond with respect to the following characteristics: 1) increase in the inhibition, 2) enhancement of the Dexon sensitivity by one order of magnitude after preincubation in the presence of NAD(P)H, 3) irreversibility of the inhibition, 4) no detectable changes in the spectral properties and in coenzyme activity of FMN after acid extraction from Dexon-treated enzyme. The inhibition of the NADH dehydrogenase activity of ETP is diminished by both NAD+ and FMN. However, no interaction of Dexon with NAD(P)H or FMN could be detected in the absence of enzyme or apoenzyme. The concentration of half-inhibition by Dexon for the yeast enzyme corresponds with its FMN concentration. It is proposed that both apoenzyme, NAD(P)H and FMN are involved in the interaction with Dexon. Possible mechanisms of binding are both complanar complexations of the ring systems and a triazene formation between FMNH2 and Dexon. The NADPH oxidase activity of the ETP is partly inhibited; the share inhibited by Dexon may represent the pathway via the transhydrogenase reaction.