Interaction of Quinolones Carrying New R1 Group with Mycobacterium leprae DNA Gyrase.

Background: Leprosy is a chronic infectious disease caused by Mycobacterium leprae and the treatment of choice is ofloxacin (OFX). Specific amino acid substitutions in DNA gyrase of M. leprae have been reported leading to resistance against the drug. In our previous study, WQ-3810, a fluoroquinolone with a new R1 group (6-amino-3,5-difluoropyridin-2-yl) was shown to have a strong inhibitory activity on OFX-resistant DNA gyrases of M. leprae, and the structural characteristics of its R1 group was predicted to enhance the inhibitory activity. Methodology/Principal Finding: To further understand the contribution of the R1 group, WQ-3334 with the same R1 group as WQ-3810, WQ-4064, and WQ-4065, but with slightly modified R1 group, were assessed on their activities against recombinant DNA gyrase of M. leprae. An in silico study was conducted to understand the molecular interactions between DNA gyrase and WQ compounds. WQ-3334 and WQ-3810 were shown to have greater inhibitory activity against M. leprae DNA gyrase than others. Furthermore, analysis using quinolone-resistant M. leprae DNA gyrases showed that WQ-3334 had greater inhibitory activity than WQ-3810. The R8 group was shown to be a factor for the linkage of the R1 groups with GyrB by an in silico study. Conclusions/Significance: The inhibitory effect of WQ compounds that have a new R1 group against M. leprae DNA gyrase can be enhanced by improving the binding affinity with different R8 group molecules. The information obtained by this work could be applied to design new fluoroquinolones effective for quinolone-resistant M. leprae and other bacterial pathogens.

WQ-3810 inhibits DNA gyrase activity in ofloxacin-resistant Mycobacterium leprae.

BACKGROUND: Mycobacterium leprae causes leprosy and ofloxacin is used to control this bacterium. However, specific amino acid substitutions in DNA gyrases of M. leprae interferes with the effect of ofloxacin. METHODOLOGY/PRINCIPAL FINDINGS: Here we tested the inhibitory effect of WQ-3810 on DNA gyrases in M. leprae, using recombinant gyrases. We theorized that WQ-3810 and DNA gyrases interacted, which was tested in silico. Compared with control drugs like ofloxacin, WQ-3810 showed a better inhibitory effect on ofloxacin-resistant DNA gyrases. The in-silico study showed that, unlike control drugs, a specific linkage between a R1 group in WQ-3810 and aspartic acid at position 464 in the subunit B of DNA gyrases existed, which would enhance the inhibitory effect of WQ-3810. This linkage was confirmed in a further experiment, using recombinant DNA gyrases with amino acid substitutions in subunits B instead. CONCLUSIONS/SIGNIFICANCE: The inhibitory effect of WQ-3810 was likely enhanced by the specific linkage between a R1 group residue in its structure and DNA gyrases. Using interactions like the one found in the present work may help design new fluoroquinolones that contribute to halt the emergence of antibiotic-resistant pathogens.

Quinolone resistance-associated amino acid substitutions affect enzymatic activity of Mycobacterium leprae DNA gyrase.

Quinolones are important antimicrobials for treatment of leprosy, a chronic infectious disease caused by Mycobacterium leprae. Although it is well known that mutations in DNA gyrase are responsible for quinolone resistance, the effect of those mutations on the enzymatic activity is yet to be studied in depth. Hence, we conducted in vitro assays to observe supercoiling reactions of wild type and mutated M. leprae DNA gyrases. DNA gyrase with amino acid substitution Ala91Val possessed the highest activity among the mutants. DNA gyrase with Gly89Cys showed the lowest level of activity despite being found in clinical strains, but it supercoiled DNA like the wild type does if applied at a sufficient concentration. In addition, patterns of time-dependent conversion from relaxed circular DNA into supercoiled DNA by DNA gyrases with clinically unreported Asp95Gly and Asp95Asn were observed to be distinct from those by the other DNA gyrases.

DC-159a Shows Inhibitory Activity against DNA Gyrases of Mycobacterium leprae.

BACKGROUND: Fluoroquinolones are a class of antibacterial agents used for leprosy treatment. Some new fluoroquinolones have been attracting interest due to their remarkable potency that is reportedly better than that of ofloxacin, the fluoroquinolone currently recommended for treatment of leprosy. For example, DC-159a, a recently developed 8-methoxy fluoroquinolone, has been found to be highly potent against various bacterial species. Nonetheless, the efficacy of DC-159a against Mycobacterium leprae is yet to be examined. METHODOLOGY/PRINCIPAL FINDINGS: To gather data that can support highly effective fluoroquinolones as candidates for new remedies for leprosy treatment, we conducted in vitro assays to assess and compare the inhibitory activities of DC-159a and two fluoroquinolones that are already known to be more effective against M. leprae than ofloxacin. The fluoroquinolone-inhibited DNA supercoiling assay using recombinant DNA gyrases of wild type and ofloxacin-resistant M. leprae revealed that inhibitory activities of DC-159a and sitafloxacin were at most 9.8- and 11.9-fold higher than moxifloxacin. Also the fluoroquinolone-mediated cleavage assay showed that potencies of those drugs were at most 13.5- and 9.8-fold higher than moxifloxacin. In addition, these two drugs retained their inhibitory activities even against DNA gyrases of ofloxacin-resistant M. leprae. CONCLUSIONS/SIGNIFICANCE: The results indicated that DC-159a and sitafloxacin are more effective against wild type and mutant M. leprae DNA gyrases than moxifloxacin, suggesting that these antibacterial drugs can be good candidates that may supersede current fluoroquinolone remedies. DC-159a in particular is very promising because it is classified in a subgroup of fluoroquinolones that is known to be less likely to cause adverse effects. Our results implied that DC-159a is well worth further investigation to ascertain its in vivo effectiveness and clinical safety for humans.

[What Hansen's disease research learned from tuberculosis research: from molecular biological aspect].

As for the Mycobacterium leprae which is a causative agent of Hansen's disease, many studies had been done since it was identified in 1873. However, those studies, at the same time, experienced many struggles because of the difficulty of culture of M. leprae on the artificial growth media. Hence, the study of Hansen's disease progressed by taking the knowledge from the study of tuberculosis caused by the bacteria belonging to the same genus, genus Mycobacterium. For instance, the knowledge of mutations in specific genes responsible for rifampicin- and quinolone-resistance in M. tuberculosis led the elucidation of drug-resistant acquisition mechanism of M. leprae. Similarly, it is necessary for the researcher of Hansen's disease to get important information from the latest topic of the tuberculosis study and utilize them to the study of the disease.