Prolonged inflammatory gene response following soman-induced seizures in mice

Following exposure to the organophosphorus nerve agent soman, the development of long-lasting seizures and build-up of irreversible seizure-related brain damage (SRBD) still represent a therapeutic challenge. A neuro-inflammatory reaction takes place in the brain after poisoning but its characteristics and potential role in SRBD and post-status epilepticus epileptogenesis is not well understood. In the present study we have analyzed by quantitative RT-PCR the time course of changes in mRNA levels of IL-1beta, TNFalpha, IL-6, ICAM-1 and SOCS3 in hippocampus, whole cortex and cerebellum in a mouse model of severe seizures and neuropathy up to 7 days after poisoning. Mice received an injection of the oxime HI-6 (50mg/kg) 5 min prior to the administration of a convulsive dose of soman (172 microg/kg). An important and highly significant increase of the five mRNA levels was recorded in cortex and hippocampus. In the cortex, the activation was generally detected as early as 1h post-intoxication with a peak response recorded between 6 and 24h. In the hippocampus, the gene up-regulation was delayed to 6h post-soman and the peak response observed between 24 and 48 h. After peaking, the response declined (except for ICAM in the hippocampus) but remained elevated, some of them significantly, at day 7. Interestingly, in the cerebellum, some changes were also observed but were several fold smaller. In conclusion, the present study indicates a quick neuro-inflammatory gene response that does not subside over 7 days suggesting a potential role in the neurological consequences of soman-induced status epilepticus.