Alpha-Lipoic Acid and Its Enantiomers Prevent Methemoglobin Formation and DNA Damage Induced by Dapsone Hydroxylamine: Molecular Mechanism and Antioxidant Action.

Dapsone (DDS) therapy can frequently lead to hematological side effects, such as methemoglobinemia and DNA damage. In this study, we aim to evaluate the protective effect of racemic alpha lipoic acid (ALA) and its enantiomers on methemoglobin induction. The pre- and post-treatment of erythrocytes with ALA, ALA isomers, or MB (methylene blue), and treatment with DDS-NOH (apsone hydroxylamine) was performed to assess the protective and inhibiting effect on methemoglobin (MetHb) formation. Methemoglobin percentage and DNA damage caused by dapsone and its metabolites were also determined by the comet assay. We also evaluated oxidative parameters such as SOD, GSH, TEAC (Trolox equivalent antioxidant capacity) and MDA (malondialdehyde). In pretreatment, ALA showed the best protector effect in 2.5 µg/mL of DDS-NOH. ALA (1000 µM) was able to inhibit the induced MetHb formation even at the highest concentrations of DDS-NOH. All ALA tested concentrations (100 and 1000 µM) were able to inhibit ROS and CAT activity, and induced increases in GSH production. ALA also showed an effect on DNA damage induced by DDS-NOH (2.5 µg/mL). Both isomers were able to inhibit MetHb formation and the S-ALA was able to elevate GSH levels by stimulating the production of this antioxidant. In post-treatment with the R-ALA, this enantiomer inhibited MetHb formation and increased GSH levels. The pretreatment with R-ALA or S-ALA prevented the increase in SOD and decrease in TEAC, while R-ALA decreased the levels of MDA; and this pretreatment with R-ALA or S-ALA showed the effect of ALA enantiomers on DNA damage. These data show that ALA can be used in future therapies in patients who use dapsone chronically, including leprosy patients.

Theoretical and practical study of the cefoxitin-Escherichia coli PBP5 complex interaction by molecular dynamics to obtain computational prototype of antimicrobial susceptibility to Gram negative bacteria.

The penicillin-binding proteins (PBPs) are important biological target for new antibacterial drugs development. This study focused on molecular interaction between cefoxitin and the Escherichia coli PBP5 by molecular dynamics (MD) using hybrid quantum mechanics/molecular mechanics (QM/MM) simulations approach, searching to develop a computational simulations prototype method on antimicrobial susceptibility of gram-negative bacteria against antibiotics. Escherichia coliATCC 8739 strain susceptibility for the drugs used in the antimicrobial susceptibility testing and selection of bioactive molecules against resistant strain. The protonation revealed a deprotonate state for His146, His151, His216, and His320 residues. The complex was stabilized after 0.6 ns of MD simulation. The global interaction means for inhibition zone diameters of E. coliATCC8739 strain and cefoxitin were 24.33 mm no showing significant difference between computational and experimental methods. Our computational simulation method can reliably be performed as a molecular modeling prototype for gram-negative antimicrobial susceptibility testing bacteria.