A STUDY OF ZINC-DEPENDENT METALLOENDOPEPTIDASE INHIBITORS AS PHARMACOLOGICAL ANTAGONISTS IN BOTULINUM NEUROTOXIN POISONING

Zinc-dependent metalloprotease inhibitors phosphoramidon, captopril an d a peptide hydroxamate were studied as potential pretreatment Compoun ds by examining their ability to delay the onset or to prolong the tim e to 50% block of nerve-elicited muscle twitch tension in the mouse ph renic-nerve diaphragm (in vitro at 36 degrees C) after botulinum neuro toxin serotypes A and B (BoNT-A, BoNT-B). Addition of BoNT-A or BoNT-B (1 x 10(-10) M) produced 50% block of the twitch response at 56 +/- 9 min and 76 +/- 4 min, respectively. Preincubation (45 min) of muscles with phosphoramidon (0.2 mM) prolonged the time to 50% block by 15 mi n in BoNT-B-poisoned muscles with no effect on the time-course of para lysis in BoNT-A exposed muscles, When the same quantities of BoNT-A or BoNT-B (equivalent to 1 x 10(-10) M bath concentration) were preincub ated for 2 hr with phosphoramidon (equivalent to 0.2 mM final bath con centration), and the incubation mixture was added to the muscle chambe r, the times to 50% block were prolonged by 38 min and 18 min for BoNT -B and BoNT-A, respectively. Preincubation of diaphragms with captopri l (up to 10 mM) or peptide hydroxamate (75 mu M) failed to antagonize BoNT-A or BoNT-B-induced neuromuscular block, Among the three metallop rotease inhibitors examined here, only phosphoramidon showed a signifi cant protection against both serotypes of BoNT. A search for better in hibitor compounds specifically tailored to match the active site on Bo NT molecule deserves attention.