Nahum Allon

Inhalation exposure to sulfur mustard in the guinea pig model: clinical, biochemical and histopathological characterization of respiratory injuries.

Guinea pigs (GP) were exposed (head only) in individual plethysmographs to various concentrations of sulfur mustard vapor, determined online, using FTIR attached to flow chamber. The LCt(50) and the inhaled LD(50) were calculated at different time points post exposure. Surviving animals were monitored for clinical symptoms, respiratory parameters and body weight changes for up to 30 days. Clinical symptoms were noted at 3 h post exposure, characterized by erythematic and swelling nose with extensive mucous secretion (with or without bleeding). At 6 h post exposure most of the guinea pigs had breathing difficulties, rhonchi and dyspnea and few deaths were noted. These symptoms peaked at 48 h and were noted up to 8 days, associated with few additional deaths. Thereafter, a spontaneous healing was noted, characterized by recovery of respiratory parameters and normal weight gain with almost complete apparent healing within 2 weeks. Histopathological evaluation of lungs and trachea in the surviving GPs at 4 weeks post exposure revealed a dose-dependent residual injury in both lung and trachea expressed by abnormal recovery of the tracheal epithelium concomitant with a dose-dependent increase in cellular volume in the lungs. These abnormal epithelial regeneration and lung remodeling were accompanied with significant changes in protein, LDH, differential cell count and glutathione levels in the bronchoalveolar lavage (BAL). It is suggested that the abnormal epithelial growth and cellular infiltration into the lung as well as the continuous lung inflammation could cause recurrent lung injury similar to that reported for HD exposed human casualties.

Single whole-body exposure to sarin vapor in rats: Long-term neuronal and behavioral deficits

Freely moving rats were exposed to sarin vapor (34.2+/-0.8 microg/l) for 10 min. Mortality at 24 h was 35% and toxic sings in the surviving rats ranged from sever (prolonged convulsions) through moderate to almost no overt signs. Some of the surviving rats developed delayed, intermittent convulsions. All rats were evaluated for long-term functional deficits in comparison to air-exposed control rats. Histological analysis revealed typical cell loss at 1 week post inhalation exposure. Neuronal inflammation was demonstrated by a 20-fold increase in prostaglandin (PGE(2)) levels 24 h following exposure that markedly decreased 6 days later. An additional, delayed increase in PGE(2) was detected at 1 month and continued to increase for up to 6 months post exposure. Glial activation following neural damage was demonstrated by an elevated level of peripheral benzodiazepine receptors (PBR) seen in the brain 4 and 6 months after exposure. At the same time muscarinic receptors were unaffected. Six weeks, four and six months post exposure behavioral evaluations were performed. In the open field, sarin-exposed rats showed a significant increase in overall activity with no habituation over days. In a working memory paradigm in the water maze, these same rats showed impaired working and reference memory processes with no recovery. Our data suggest long lasting impairment of brain functions in surviving rats following a single sarin exposure. Animals that seem to fully recover from the exposure, and even animals that initially show no toxicity signs, developed some adverse neural changes with time.

Sulfur mustard toxicity in macrophages: effect of dexamethasone

Cells from the murine macrophage‐like cell line J774A.1 (J774) and cultures of primary alveolar macrophages (PAM) obtained from guinea pigs were exposed to sulfur mustard (HD, 50‐200 μM) and treated with dexamethasone (2.5 μM) 10 min after HD exposure. Cell cultures were studied at 3 and 24 h after exposure by the cleavage of Thiazolyl blue reaction (MTT) reaction and crystal violet staining (viability assays), by morphological observation and by [3H]thymidine incorporation. Exposure of J774 cells to HD caused a dose‐dependent decrease in viability that was evident at 24 h. Although no significant change in viability was observed at 3–4 h after HD exposure, a dose‐dependent decrease in [3H]thymidine incorporation was observed. Treatment with dexamethasone caused a dose‐dependent decrease in viability. However, the combined exposure to HD and dexamethasone had a synergistic effect on the decrease of cell viability. This synergistic effect is not due to a change in DNA synthesis rate because [3H]thymidine incorporation was not affected by dexamethasone. In PAM cultures, HD caused some ‘activating’ effect on [3H]thymidine incorporation and an increase in cell number at the lower dose (100 μM) but this was less at 200 μM. Both effects were reduced by dexamethasone treatment. We conclude that macrophages derived from different sources exhibit a different responsiveness to immunomodulators (HD and dexamethasone) and that dexamethasone can reduce the ‘inflammatory’ effect of HD in PAM. Published in 2000 by John Wiley & Sons, Ltd.

Protection by extracellular glutathione against sulfur mustard induced toxicity in vitro

1 The present study characterizes the role of extracellularly added glutathione in protection against sulfur mustard (HD) toxicity in a macrophage monocyte cell line J774. 2 Toxic effects of HD depend on dose and duration of exposure with an ED50 of 50 and 75 mM for dividing and confluent cells respectively. 3 Exposure to HD, 100-200 mM caused *15% decrease in the cellular glutathione (GSH) content 2 h after exposure, pretreatment with GSH, 0.2-10 mM, elevated cellular GSH *61.5. 4 GSH pretreatment increased cell viability after HD 2-3-fold. Similar protective effects of GSH treatment were found in a human epidermoid carcinoma cell line (KB). 5 Protection by post treatment with GSH was apparent even 60 min post HD exposure. 6 No protection was afforded when the intracellular GSH concentration was elevated prior to exposure and the extracellular GSH had been washed out. However, GSH depleted cells were more sensitive to HD than normal cells, and were also protected by addition of GSH to the growth medium, although the intracellular GSH content remained low. 7 We conclude that it is essential for the GSH to be present extracellularly in order to protect cells from HD toxicity. 8 Our findings have therapeutic implications in particular for the protection of lungs after inhalation exposure to HD vapor.

Biochemical, pharmacological, and clinical aspects of nitric oxide

Helping rehabilitate Science magazines 1992 Molecule of the Year from its reputation as nothing but an environmental pollutant, the 29 papers give special attention to its characterization in terms of co-factor requirement, substrates, and novel specific inhibitors. They also consider its importanc

Subchronic exposure to low-doses of the nerve agent VX: Physiological, behavioral, histopathological and neurochemical studies

The highly toxic organophosphorous compound VX [O-ethyl-S-(isoporopylaminoethyl) methyl phosphonothiolate] undergoes an incomplete decontamination by conventional chemicals and thus evaporates from urban surfaces, e.g., pavement, long after the initial insult. As a consequence to these characteristics of VX, even the expected low levels should be examined for their potential to induce functional impairments including those associated with neuronal changes. In the present study, we developed an animal model for subchronic, low-dose VX exposure and evaluated its effects in rats. Animals were exposed to VX (2.25 microg/kg/day, 0.05 LD(50)) for three months via implanted mini osmotic pumps. The rapidly attained continuous and marked whole-blood cholinesterase inhibition (approximately 60%), fully recovered 96 h post pump removal. Under these conditions, body weight, blood count and chemistry, water maze acquisition task, sensitivity to the muscarinic agonist oxotremorine, peripheral benzodiazepine receptors density and brain morphology as demonstrated by routine histopathology, remained unchanged. However, animals treated with VX showed abnormal initial response in an Open Field test and a reduction (approximately 30%) in the expression of the exocytotic synaptobrevin/vesicle associate membrane protein (VAMP) in hippocampal neurons. These changes could not be detected one month following termination of exposure. Our findings indicate that following a subchronic, low-level exposure to the chemical warfare agent VX some important processes might be considerably impaired. Further research should be addressed towards better understanding of its potential health ramifications and in search of optimal countermeasures.

Current Capabilities in Extrapolating from Animal to Human the Capacity of Human Butyrylcholinesterase to Detoxify Organophosphates

The concept of using exogenous cholinesterase (ChE) scavenger as a prophylactic measure against the toxicity induced by organophosphorus (OP) inhibitors of ChEs has been examined in the last decade by several investigators who used acetylcholinesterase (AChE) from fetal bovine serum (1–3), and butyrylcholinesterases (BChE) from horse serum (4), or human serum (HuBChE)(2, 5, 6). Preloading of mice, rats, guinea-pigs, marmosets, and rhesus monkeys with one of these enzymes substantially increased survival ratio following exposure to multiple toxic doses of OPs. It also alleviated postexposure toxicity commonly seen after traditional multidrug treatment. Since for most cases reported, no postexposure therapy was required, these bioscavengers were offered as true prophylactic drugs preventing even a single episode of OP intoxication.

Protection of Guinea Pigs against Soman Inhalation by Pretreatment Alone with Human Butyrylcholinesterase

Multi-drug therapy (i. e. pyridostigmine, atropine, oximes, diazepam) is generally considered as effective against organophosphorus (OP) toxicity. However, this treatment raises several problems: 1. It is limited in its protection range. 2. It does not eliminate several post exposure symptoms, and 3. For fast acting OPs self injection of atropine and oximes may not be feasible. Prophylactic antidotes that will scavenge the OP in the blood may afford reasonable solutions for these limitations. Human butyrylcholinesterase (HuBChE) was previously evaluated by us both in vitro and in vivo as a single prophylactic antidote against the lethal effects of nerve agents. Remarkable protection has been demonstrated in Hu-BChE-treated mice (Raveh et al., 1993), rats (Raveh et al., 1993; Brandeis et al., 1993) and monkeys (Ashani et al., 1993) following an iv exposure to lethal doses of sarin, soman, VX and tabun. Since inhalation challenge is the most realistic simulation of exposure to nerve agents, the protection afforded by HuBChE was tested against inhaled soman. Awake animals caged in a whole body plethysmograph designed and built in our laboratory, were exposed for 45 to 75 sec to 417–450 μg/L soman. Five out of 8 animals with 28 to 45 nmol circulating HuBChE/animal were completely protected against 1.3–2.4×LD50 doses of inhaled soman. Two animals displayed slight tremors and ataxia while one guinea pig exposed to 2.6×LD50 died. A linear correlation (r =.946) was established between nmols of inhaled soman and the reduction in the levels of circulating HuBChE with a slope of 0.13. Since the soman to HuBChE ratio required to inhibit in vivo the exogenous enzyme is approximately 1.2, it is suggested that only 16% of inhaled soman reached the circulation.