Efficacy of a combined anti-seizure treatment against cholinergic established status epilepticus following a sarin nerve agent insult in rats

The development of refractory status epilepticus (SE) following sarin intoxication presents a therapeutic challenge. Here, we evaluated the efficacy of delayed combined double or triple treatment in reducing abnormal epileptiform seizure activity (ESA) and the ensuing long-term neuronal insult. SE was induced in rats by exposure to 1.2 LD50 sarin followed by treatment with atropine and TMB4 (TA) 1 min later. Double treatment with ketamine and midazolam or triple treatment with ketamine, midazolam and levetiracetam was administered 30 min post-exposure, and the results were compared to those of single treatment with midazolam alone or triple treatment with ketamine, midazolam, and valproate, which was previously shown to ameliorate this neurological insult. Toxicity and electrocorticogram activity were monitored during the first week, and behavioral evaluations were performed 2 weeks post-exposure, followed by biochemical and immunohistopathological analyses. Both double and triple treatment reduced mortality and enhanced weight recovery compared to TA-only treatment. Triple treatment and, to a lesser extent, double treatment significantly ameliorated the ESA duration. Compared to the TA-only or the TA+ midazolam treatment, both double and triple treatment reduced the sarin-induced increase in the neuroinflammatory marker PGE2 and the brain damage marker TSPO and decreased gliosis, astrocytosis and neuronal damage. Finally, both double and triple treatment prevented a change in behavior, as measured in the open field test. No significant difference was observed between the efficacies of the two triple treatments, and both triple combinations completely prevented brain injury (no differences from the naïve rats). Delayed double and, to a greater extent, triple treatment may serve as an efficacious delayed therapy, preventing brain insult propagation following sarin-induced refractory SE.

Effect of supersaturated oxygen emulsion treatment on chloropicrin-induced chemical injury in ex vivo rabbit cornea

With a possibility for the use of chemical weapons in battlefield or in terrorist activities, effective therapies against the devastating ocular injuries, from their exposure, are needed. Oxygen plays a vital role in ocular tissue preservation and wound repair. We tested the efficacy of supersaturated oxygen emulsion (SSOE) in reducing ex vivo corneal and keratocyte injury from chloropicrin (CP). CP, currently used as a pesticide, is a chemical threat agent like the vesicating mustard agents and causes severe corneal injury. Since our previous study in human corneal epithelial cells showed the treatment potential of SSOE (55 %), we further tested its efficacy in an ex vivo CP-induced rabbit corneal injury model. Corneas were exposed to CP (700 nmol) for 2 h, washed and cultured with or without SSOE for 24 h or 96 h. At 96 h post CP exposure, SSOE treatment presented a healing tendency of the corneal epithelial layer, and abrogated the CP-induced epithelial apoptotic cell death. SSOE treatment also reduced the CP induced DNA damage (H2A.X phosphorylation) and inflammatory markers (e.g. MMP9, IL-21, MIP-1β, TNFα). Further examination of the treatment efficacy of SSOE alone or in combination with other therapies in in vivo cornea injury models for CP and vesicants, is warranted.

Neuroprotection by delayed triple therapy following sarin nerve agent insult in the rat

The development of refractory status epilepticus (SE) induced by sarin intoxication presents a therapeutic challenge. In our current research we evaluate the efficacy of a delayed combined triple treatment in ending the abnormal epileptiform seizure activity (ESA) and the ensuing of long-term neuronal insult. SE was induced in male Sprague-Dawley rats by exposure to 1.2LD50 sarin insufficiently treated by atropine and TMB4 (TA) 1 min later. Triple treatment of ketamine, midazolam and valproic acid was administered 30 min or 1 h post exposure and was compared to a delayed single treatment with midazolam alone. Toxicity and electrocorticogram activity were monitored during the first week and behavioral evaluation performed 3 weeks post exposure followed by brain biochemical and immunohistopathological analyses. The addition of both single and triple treatments reduced mortality and enhanced weight recovery compared to the TA-only treated group. The triple treatment also significantly minimized the duration of the ESA, reduced the sarin-induced increase in the neuroinflammatory marker PGE2, the brain damage marker TSPO, decreased the gliosis, astrocytosis and neuronal damage compared to the TA+ midazolam or only TA treated groups. Finally, the triple treatment eliminated the sarin exposed increased open field activity, as well as impairing recognition memory as seen in the other experimental groups. The delayed triple treatment may serve as an efficient therapy, which prevents brain insult propagation following sarin-induced refractory SE, even if treatment is postponed for up to 1 h.

Broad Spectrum Treatment for Ocular Insult Induced by Organophosphate Chemical Warfare Agents

Warfare organophosphates nerve agents constitute one of the prime threats to mankind on the battlefield and in the scenario of civilian terror. Exposure to organophosphate (OP) nerve agents dose-dependently result in incapacitation. They affect multiple organs, but the eye is one of the first and most frequently affected. Ocular OP insult may result in long-term miosis, impaired visual function, and ocular pain thus inducing functional incapacitation. The currently recommended military medical doctrine of using 1% atropine eye drops is far from being the optimal treatment. Although effective in reducing ocular pain and the miotic response, this treatment induces long-term mydriasis and cycloplegia promoting photophobia and restricted accommodation, which may result in further impairment in visual function. An optimal treatment must ameliorate the long-term ocular insult enabling rapid return of normal visual function, while avoiding the induction of mydriasis and cycloplegia side effects, which could possibly worsen the visual performance. Optimal treatment should also keep effects of misuse to a minimum. Work done in recent years examined treatments with various anticholinergic drugs alone or used in combination with oxime treatments and may offer improved efficacy in ameliorating the ocular insult. This review is a summary of the applied research in animals and will discuss clinical implications and possible alterations in treatment protocols following OP exposure. Taken together the data points toward the use of topical low concentrations of potent anticholinergic ophthalmic drops such as atropine or homatropine, which rapidly ameliorate the long-term OP-induced ocular insult.

Ocular surface histopathological insult following sarin and VX exposure and potential treatments in the rat model

Eye exposure to organophosphate (OP) chemical warfare irreversible acetylcholinesterase inhibitors, results in long-term miosis and impaired visual function. In contrast to the well-documented miotic and ciliary muscle spasm observed following chemical warfare, OP ocular exposure, little is known regarding the ocular surface histopathological insult. The aim of the present study was to determine the degree of the ocular surface insult following sarin or VX ocular exposure and to evaluate potential anti-cholinergic treatments in counteracting this insult. Rats that were whole body exposed to various sarin concentrations (0.049-43 μg/L; 5 min exposure), showed a dose-dependent miotic response and light reflex impairment. Following whole body sarin exposure, a dose dependent ocular surface histopathological insult was developed. A week following exposure to a low concentration of 0.05 μg/L, conjunctival pathology was observed, while corneal insult was noticed only following exposure to a concentration of 0.5 μg/L and above. Both tissues presented poorer outcomes when exposed to higher sarin concentrations. In contrast, eyes topically exposed to 1 μg sarin demonstrated no ocular insult a week following exposure. On the contrary, topical exposure to 1 μg VX resulted in a significant corneal insult. Anticholinergic treatments such as 0.1% atropine or 2% homatropine, given shortly following VX exposure, counteracted this insult. The results of this study show that not only do anti-cholinergic treatments counteract the miotic response, but also prevent the histopathological insult observed when given shortly following OP exposure.