Effects of hydroxamate metalloendoprotease inhibitors on botulinum neurotoxin A poisoned mouse neuromuscular junctions.
Currently the only therapy for botulinum neurotoxin A (BoNT/A) poisoning is antitoxin. Antidotes that are effective after BoNT/A has entered the motor nerve terminals would dramatically benefit BoNT/A therapy. Inhibition of proteolytic activity of BoNT/A light chain by metalloendoprotease inhibitors (MEIs) is under development. We tested the effects of MEIs on in vitro as well as in vivo BoNT/A poisoned mouse nerve-muscle preparations (NMPs). The K(i) for inhibition of BoNT/A metalloendoprotease was 0.40 and 0.36 muM, respectively, for 2,4-dichlorocinnamic acid hydroxamate (DCH) and its methyl derivative, ABS 130. Acute treatment of nerve-muscle preparations with 10 pM BoNT/A inhibited nerve-evoked muscle twitches, reduced mean quantal content, and induced failures of endplate currents (EPCs). Bath application of 10 muM DCH or 5 muM ABS 130 reduced failures, increased the quantal content of EPCs, and partially restored muscle twitches after a delay of 40-90 min. The restorative effects of DCH and ABS 130, as well as 3,4 diaminopyridine (DAP) on twitch tension were greater at 22 degrees C compared to 37 degrees C. Unlike DAP, neither DCH nor ABS 130 increased Ca(2+) levels in cholinergic Neuro 2a cells. Injection of MEIs into mouse hind limbs before or after BoNT/A injection neither prevented the toe spread reflex inhibition nor improved muscle functions. We suggest that hydroxamate MEIs partially restore neurotransmission of acutely BoNT/A poisoned nerve-muscle preparations in vitro in a temperature dependent manner without increasing the Ca(2+) levels within motor nerve endings.
Thyagarajan
Baskaran
B
Department of Pharmacology and Physiology, UMDNJ - New Jersey Medical School, Newark, NJ 07103, USA.
Potian
Joseph G
JG
Garcia
Carmen C
CC
Hognason
Kormakur
K
Capková
Katerina
K
Moe
Scott T
ST
Jacobson
Alan R
AR
Janda
Kim D
KD
McArdle
Joseph J
JJ
D015761:4-Aminopyridine / Q000031:analogs & derivatives / Q000494:pharmacology; D000109:Acetylcholine / Q000378:metabolism; D000077770:Amifampridine; D000818:Animals; D000931:Antidotes / Q000494:pharmacology*; D019274:Botulinum Toxins, Type A / Q000506:poisoning*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002934:Cinnamates / Q000494:pharmacology*; D006877:Hydroxamic Acids / Q000494:pharmacology*; D066298:In Vitro Techniques; D045727:Metalloexopeptidases / Q000037:antagonists & inhibitors*; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D012018:Reflex / Q000187:drug effects
C550771:2,4-dichlorocinnamic acid hydroxamate; C550772:ABS 130; D000931:Antidotes; D002934:Cinnamates; D006877:Hydroxamic Acids; D015761:4-Aminopyridine; D045727:Metalloexopeptidases; D019274:Botulinum Toxins, Type A; D000109:Acetylcholine; D000077770:Amifampridine; D002118:Calcium