Pro-2-PAM therapy for central and peripheral cholinesterases.
Novel therapeutics to overcome the toxic effects of organophosphorus (OP) chemical agents are needed due to the documented use of OPs in warfare (e.g. 1980-1988 Iran/Iraq war) and terrorism (e.g. 1995 Tokyo subway attacks). Standard OP exposure therapy in the United States consists of atropine sulfate (to block muscarinic receptors), the acetylcholinesterase (AChE) reactivator (oxime) pralidoxime chloride (2-PAM), and a benzodiazepine anticonvulsant to ameliorate seizures. A major disadvantage is that quaternary nitrogen charged oximes, including 2-PAM, do not cross the blood brain barrier (BBB) to treat brain AChE. Therefore, we have synthesized and evaluated pro-2-PAM (a lipid permeable 2-PAM derivative) that can enter the brain and reactivate CNS AChE, preventing seizures in guinea pigs after exposure to OPs. The protective effects of the pro-2-PAM after OP exposure were shown using (a) surgically implanted radiotelemetry probes for electroencephalogram (EEG), (b) neurohistopathology of brain, (c) cholinesterase activities in the PNS and CNS, and (d) survivability. The PNS oxime 2-PAM was ineffective at reducing seizures/status epilepticus (SE) in diisopropylfluorophosphate (DFP)-exposed animals. In contrast, pro-2-PAM significantly suppressed and then eliminated seizure activity. In OP-exposed guinea pigs, there was a significant reduction in neurological damage with pro-2-PAM but not 2-PAM. Distinct regional areas of the brains showed significantly higher AChE activity 1.5h after OP exposure in pro-2-PAM treated animals compared to the 2-PAM treated ones. However, blood and diaphragm showed similar AChE activities in animals treated with either oxime, as both 2-PAM and pro-2-PAM are PNS active oximes. In conclusion, pro-2-PAM can cross the BBB, is rapidly metabolized inside the brain to 2-PAM, and protects against OP-induced SE through restoration of brain AChE activity. Pro-2-PAM represents the first non-invasive means of administering a CNS therapeutic for the deleterious effects of OP poisoning by reactivating CNS AChE.
Walter Reed Army Institute of Research, Division of Regulated Activities, Department of Regulated Laboratories, Silver Spring, MD 20910-7500, United States.
James C
JC
Demar
Edward D
ED
Clarkson
Ruthie H
RH
Ratcliffe
Amy J
AJ
Campbell
Sonia G
SG
Thangavelu
Christine A
CA
Herdman
Haim
H
Leader
Susan M
SM
Schulz
Elizabeth
E
Marek
Marie A
MA
Medynets
Therese C
TC
Ku
Sarah A
SA
Evans
Farhat A
FA
Khan
Roberta R
RR
Owens
Madhusoodana P
MP
Nambiar
Richard K
RK
Gordon
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology; D002490:Central Nervous System / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D002801:Cholinesterase Reactivators / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography; D004789:Enzyme Activation / Q000187:drug effects; D006168:Guinea Pigs; D006624:Hippocampus / Q000473:pathology; D007531:Isoflurophate / Q000506:poisoning; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D017933:Peripheral Nervous System / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D011220:Pralidoxime Compounds / Q000494:pharmacology*; D011355:Prodrugs / Q000494:pharmacology*; D012867:Skin; D012999:Soman / Q000506:poisoning; D013226:Status Epilepticus / Q000139:chemically induced / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology; D016019:Survival Analysis
D002801:Cholinesterase Reactivators; D011220:Pralidoxime Compounds; D011355:Prodrugs; D007531:Isoflurophate; D012999:Soman; D000110:Acetylcholinesterase