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.

Long-Term Pulmonary Damage in Surviving Antitoxin-Treated Mice following a Lethal Ricin Intoxication

Ricin, a highly potent plant-derived toxin, is considered a potential bioterrorism weapon due to its pronounced toxicity, high availability, and ease of preparation. Acute damage following pulmonary ricinosis is characterized by local cytokine storm, massive neutrophil infiltration, and edema formation, resulting in respiratory insufficiency and death. A designated equine polyclonal antibody-based (antitoxin) treatment was developed in our laboratory and proved efficacious in alleviating lung injury and increasing survival rates. Although short-term pathogenesis was thoroughly characterized in antitoxin-treated mice, the long-term damage in surviving mice was never determined. In this study, long-term consequences of ricin intoxication were evaluated 30 days post-exposure in mice that survived antitoxin treatment. Significant pulmonary sequelae were demonstrated in surviving antitoxin-treated mice, as reflected by prominent histopathological changes, moderate fibrosis, increased lung hyperpermeability, and decreased lung compliance. The presented data highlight, for the first time to our knowledge, the possibility of long-term damage development in mice that survived lethal-dose pulmonary exposure to ricin due to antitoxin treatment.

Monitoring Exposure to Five Chemical Warfare Agents Using the Dried Urine Spot Technique and Liquid Chromatography-Mass Spectrometry/Mass Spectrometry-In Vivo Determination of Sarin Metabolite in Mice

Dried urine spot (DUS) is a micro-sample collection technique, known for its advantages in handling, storage and shipping. It also uses only a small volume of urine, an essential consideration in working with small animals, or in acute medical situations. Alkyl-phosphonic acids are the direct and indicative metabolites of organophosphorus chemical warfare agents (OP-CWAs) and are present in blood and urine shortly after exposure. They are therefore crucially important for monitoring casualties in war and terror scenarios. We report here a new approach for the determination of the metabolites of five CWAs in urine using DUS. The method is based on a simple and rapid sample preparation, using only 50 µL of urine, spotted and dried on DBS paper, extracted using 300 µL methanol/water and analyzed via targeted LC-MS/MS. The detection limits for the five CWAs, sarin (GB), soman (GD), cyclosarin (GF), VX and RVX in human urine were from 0.5 to 5 ng/mL. Recoveries of (40-80%) were obtained in the range of 10-300 ng/mL, with a linear response (R2 > 0.964, R > 0.982). The method is highly stable, even with DUS samples stored up to 5 months at room temperature before analysis. It was implemented in a sarin in vivo exposure experiment on mice, applied for the time course determination of isopropyl methylphosphonic acid (IMPA, sarin hydrolysis product) in mice urine. IMPA was detectable even with samples drawn 60 h after the mice's (IN) exposure to 1 LD50 sarin. This method was also evaluated in a non-targeted screening for multiple potential CWA analogs (LC-Orbitrap HRMS analysis followed by automatic peak detection and library searches). The method developed here is applicable for rapid CWA casualty monitoring.

Predicting clinical outcome of sulfur mustard induced ocular injury using machine learning model

The sight-threatening sulfur mustard (SM) induced ocular injury presents specific symptoms in each clinical stage. The acute injury develops in all exposed eyes and may heal or deteriorate into chronic late pathology. Early detection of eyes at risk of developing late pathology may assist in providing unique monitoring and specific treatments only to relevant cases. In this study, we evaluated a machine-learning (ML) model for predicting the development of SM-induced late pathology based on clinical data of the acute phase in the rabbit model. Clinical data from 166 rabbit eyes exposed to SM vapor was used retrospectively. The data included a comprehensive clinical evaluation of the cornea, eyelids and conjunctiva using a semi-quantitative clinical score. A random forest classifier ML model, was trained to predict the development of corneal neovascularization four weeks post-ocular exposure to SM vapor using clinical scores recorded three weeks earlier. The overall accuracy in predicting the clinical outcome of SM-induced ocular injury was 73%. The accuracy in identifying eyes at risk of developing corneal neovascularization and future healed eyes was 75% and 59%, respectively. The most important parameters for accurate prediction were conjunctival secretion and corneal opacity at 1w and corneal erosions at 72 h post-exposure. Predicting the clinical outcome of SM-induced ocular injury based on the acute injury parameters using ML is demonstrated for the first time. Although the prediction accuracy was limited, probably due to the small dataset, it pointed out towards various parameters during the acute injury that are important for predicting SM-induced late pathology and revealing possible pathological mechanisms.

The use of aflibercept (VEGF trap) in mitigating sulfur mustard-induced corneal neovascularization in a rabbit model

Sulfur mustard (SM)-induced ocular injury is characterized by an acute inflammatory response that may become chronic or enter a latent phase with delayed pathology. This study aimed to evaluate the efficacy of ziv-aflibercept and aflibercept in preventing and ameliorating corneal neovascularization (NV), respectively, following chemical eye exposure to SM vapor in a rabbit model. Chemical SM ocular insult was induced in the right eye of rabbits. A single application of ziv-aflibercept was administered 2 h or 9 days post-exposure. A single subconjunctival aflibercept treatment in an ocular formulation was administered 4 weeks after SM vapor exposure and subsequent to an initial 1-week treatment with 0.1 % dexamethasone. Clinical monitoring was performed 5-12 weeks post-exposure, and digital corneal pictures were taken to assess the extent of NV. The rabbits were euthanized and the corneas were processed for histological assessment. Treatment with ziv-aflibercept 2 h and 9 days post-exposure moderately reduced insult severity and partially delayed or prevented corneal NV. Aflibercept application 4 weeks post-exposure significantly reduced the extent of NV for 8 weeks. The substantial decrease in existing corneal NV in this group was confirmed by histology. These results reveal the powerful anti-angiogenic efficacy of the VEGF-trap for ameliorating existing NV as opposed to preventing NV development, revealing the ability of this treatment to mitigate corneal NV.

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.

Efficacy of retigabine in ameliorating the brain insult following sarin exposure in the rat

BACKGROUND

Sarin is an irreversible organophosphate cholinesterase inhibitor. Following toxic signs, an extensive long-term brain damage is often reported. Thus, we evaluated the efficacy of a novel anticonvulsant drug retigabine, a modulator of neuronal voltage gated K⁺ channels, as a neuroprotective agent following sarin exposure.

METHODS

Rats were exposed to 1 LD₅₀ or 1.2 LD₅₀ sarin and treated at onset of convulsions with retigabine (5 mg/kg, i.p.) alone or in combination with 5 mg/kg atropine and 7.5 mg/kg TMB-4 (TA) respectively. Brain biochemical and immunohistopathological analyses were processed 24 h and 1 week following 1 LD₅₀ sarin exposure and at 4 weeks following exposure to 1.2 LD₅₀ sarin. EEG activity in freely moving rats was also monitored by telemetry during the first week following exposure to 1.2 LD₅₀ and behavior in the Open Field was evaluated 3 weeks post exposure.

RESULTS

Treatment with retigabine following 1 LD₅₀ sarin exposure or in combination with TA following 1.2 LD₅₀ exposure significantly reduced mortality rate compared to the non-treated groups. In both experiments, the retigabine treatment significantly reduced gliosis, astrocytosis and brain damage as measured by translocator protein (TSPO). Following sarin exposure the combined treatment (retigabine+ TA) significantly minimized epileptiform seizure activity. Finally, in the Open Field behavioral test the non-treated sarin group showed an increased mobility which was reversed by the combined treatment.

CONCLUSIONS

The M current modulator retigabine has been shown to be an effective adjunct therapy following OP induced convulsion, minimizing epileptiform seizure activity and attenuating the ensuing brain damage.

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.

Lung damage following whole body, but not intramuscular, exposure to median lethality dose of sarin: findings in rats and guinea pigs

Objective: Sarin is an irreversible organophosphate cholinesterase inhibitor and a highly toxic, volatile warfare agent. Rats and guinea pigs exposed to sarin display cholinergic excitotoxicity which includes hyper-salivation, respiratory distress, tremors, seizures, and death. Here we focused on the characterization of the airways injury induced by direct exposure of the lungs to sarin vapor and compared it to that induced by the intramuscularly route. Materials and methods: Rats were exposed to sarin either in vapor (∼1LCT50, 34.2 ± 0.8 µg/l/min, 10 min) or by i.m. (∼1LD50, 80 µg/kg), and lung injury was evaluated by broncho-alveolar lavage (BAL). Results and discussion: BAL analysis revealed route-dependent effects in rats: vapor exposed animals showed elevation of inflammatory cytokines, protein, and neutrophil cells. These elevations were seen at 24 h and were still significantly higher compared to control values at 1 week following vapor exposure. These elevations were not detected in rats exposed to sarin i.m. Histological evaluation of the brains revealed typical changes following sarin poisoning independent of the route of administration. The airways damage following vapor exposure in rats was also compared to that induced in guinea pigs. The latter showed increased eosinophilia and histamine levels that constitutes an anaphylactic response not seen in rats. Conclusions: These data clearly point out the importance of using the appropriate route of administration in studying the deleterious effects of volatile nerve agents, as well as the selection of the appropriate animal species. Since airways form major target organs for the development of injury following inhalation toxicity, they should be included in any comprehensive evaluation of countermeasures efficacy.

Successful single treatment with ziv-aflibercept for existing corneal neovascularization following ocular chemical insult in the rabbit model

PURPOSE

To evaluate the efficacy of ziv-aflibercept as a treatment for established corneal neovascularization (NV) and to compare its efficacy to that of bevacizumab following ocular chemical insult of sulfur mustard (SM) in the rabbit model.

METHODS

Chemical SM burn was induced in the right eye of NZW rabbits by vapor exposure. Ziv-aflibercept (2 mg) was applied once to neovascularized eyes by subconjunctival injection while subconjunctival bevacizumab (5 mg) was administered twice a week, for 3 weeks. Non-treated exposed eyes served as a control. A clinical follow-up employed by slit-lamp microscope, was performed up to 12 weeks following exposure and digital photographs of the cornea were taken for measurement of blood vessels length using the image analysis software. Eyes were taken for histological evaluation 2, 4 and 8 weeks following treatment for general morphology and for visualization of NV, using H&E and Masson Trichrome stainings, while conjunctival goblet cell density was determined by PAS staining.

RESULTS

Corneal NV developed, starting as early as two weeks after exposure. A single subconjunctival treatment of ziv-aflibercept at 4 weeks post exposure, significantly reduced the extent of existing NV already one week following injection, an effect which lasted for at least 8 weeks following treatment, while NV in the non-treated exposed eyes continued to advance. The extensive reduction in corneal NV in the ziv-aflibercept treated group was confirmed by histological evaluation. Bevacizumab multiple treatment showed a benefit in NV reduction, but to a lesser extent compared to the ziv-aflibercept treatment. Finally, ziv-aflibercept increased the density of conjunctival goblet cells as compared to the exposed non-treated group.

CONCLUSIONS

Subconjunctival ziv-aflibercept single treatment presented a highly efficient long-term therapeutic benefit in reducing existing corneal NV, following ocular sulfur mustard exposure. These findings show the robust anti-angiogenic efficacy of ziv-aflibercept and demonstrate the advantage of this treatment over the other anti-angiogenic therapies in ameliorating corneal NV and protecting the ocular surface.

Characterization of acute and long-term pathologies of superficial and deep dermal sulfur mustard skin lesions in the hairless guinea pig model

Sulfur mustard induces severe acute and prolonged damage to the skin and only partially effective treatments are available. We have previously validated the use of hairless guinea pigs as an experimental model for skin lesions. The present study aimed to characterize a model of a deep dermal lesion and to compare it with the previously described superficial lesion. Clinical evaluation of the lesions was conducted using reflectance colorimetry, trans-epidermal water loss and wound area measurements. Prostaglandin E(2) content, matrix metalloproteinase-2 and 9 activity, and histopathology were conducted up to 4 weeks post-exposure. Sulfur mustard skin injury, including erythema and edema, impairment of skin barrier and wounds developed in a dose-dependent manner. Prostaglandin E(2) content and matrix metalloproteinase-2 and 9 activities were elevated during the wound development and the healing process. Histological evaluation revealed severe damage to the epidermis and deep dermis and vesications. At 4 weeks postexposure, healing was not completed: significantly impaired stratum corneum, absence of hair follicles, and epidermal hyperplasia were observed. These results confirm the use of the superficial and deep dermal skin injuries in the hairless guinea pigs as suitable models that can be utilized for the investigation of the pathological processes of acute as well as long-term injuries. These models will be further used to develop treatments to improve the healing process and prevent skin damage and long-term effects.