Botulinum neurotoxins are class I tier bioterrorism agent, accountable for causing rare but fatal illness ‘botulism’. Out of seven serotypes, A, B, E, and F are responsible for intoxicating humans. Despite knowing harmful effects on human health for centuries, there is no commercial antidote for post-neuronal intoxication is available. In the present study, we report efficacy of regioisomers of (8-hydroxyquinolin-7-yl)(phenyl) methylaminobenzoic acid against zinc-dependent light chain activities of BoNT/A, /B, /E & /F by combining molecular modeling with in vitro and in vivo studies. Based on structure similarity search, multiple regioisomers of 8-hydroxyquinoline were mined and screened by performing molecular docking. The best-scored compounds were analyzed for inhibitory and binding potential against these serotypes via endopeptidase and surface plasmon resonance assays. The best two compounds (NSC1011 and NSC1012) with potential inhibition and binding kinetics across serotypes were evaluated for therapeutic potential in mouse model. NSC1011 and NSC1012 (regioisomers) docking data revealed their binding energies with active domains of BoNT/A, /B, /E, and /F light chains ranging between − 9.70 to − 4.27, and − 9.84 to − 7.23 kcal/mol, respectively. The endopeptidase assay displayed ˃ 90% inhibition of catalytic activities, with the IC 50 values varying among serotypes from 20 to 40 µM concentrations. SPR interaction of both compounds with the targeted proteins was observed in the range of 3.83E-05 to 4.95E-04 M. These molecules have shown complete protection at one MLD (mouse lethal dose), whereas median extension of animal survival was recorded up to 24 h when exposed to 5X MLD. The in silico, in vitro, and in vivo data reveal that NSC1011 and NSC1012 exhibited good binding affinity, stability, inhibition with promising therapeutic potential against human botulism-causing toxinotypes.
Agnihotri et al. (Sat,) studied this question.