Intramuscular cobinamide as an antidote to methyl mercaptan poisoning.

BACKGROUND: Methyl mercaptan occurs naturally in the environment and is found in a variety of occupational settings, including the oil, paper, plastics, and pesticides industries. It is a toxic gas and deaths from methyl mercaptan exposure have occurred. The Department of Homeland Security considers it a high threat chemical agent that could be used by terrorists. Unfortunately, no specific treatment exists for methyl mercaptan poisoning. METHODS: We conducted a randomized trial in 12 swine comparing no treatment to intramuscular injection of the vitamin B12 analog cobinamide (2.0 mL, 12.5 mg/kg) following acute inhalation of methyl mercaptan gas. Physiological and laboratory parameters were similar in the control and cobinamide-treated groups at baseline and at the time of treatment. RESULTS: All six cobinamide-treated animals survived, whereas only one of six control animals lived (17% survival) (p = 0.0043). The cobinamide-treated animals returned to a normal breathing pattern by 3.8 ± 1.1 min after treatment (mean ± SD), while all but one animal in the control group had intermittent gasping, never regaining a normal breathing pattern. Blood pressure and arterial oxygen saturation returned to baseline values within 15 minutes of cobinamide-treatment. Plasma lactate concentration increased progressively until death (10.93 ± 6.02 mmol [mean ± SD]) in control animals, and decreased toward baseline (3.79 ± 2.93 mmol [mean ± SD]) by the end of the experiment in cobinamide-treated animals. CONCLUSION: We conclude that intramuscular administration of cobinamide improves survival and clinical outcomes in a large animal model of acute, high dose methyl mercaptan poisoning.

Flavanone silibinin treatment attenuates nitrogen mustard-induced toxic effects in mouse skin.

Currently, there is no effective antidote to prevent skin injuries by sulfur mustard (SM) and nitrogen mustard (NM), which are vesicating agents with potential relevance to chemical warfare, terrorist attacks, or industrial/laboratory accidents. Our earlier report has demonstrated the therapeutic efficacy of silibinin, a natural flavanone, in reversing monofunctional alkylating SM analog 2-chloroethyl ethyl sulfide-induced toxic effects in mouse skin. To translate this effect to a bifunctional alkylating vesicant, herein, efficacy studies were carried out with NM. Topical application of silibinin (1 or 2mg) 30 min after NM exposure on the dorsal skin of male SKH-1 hairless mice significantly decreased NM-induced toxic lesions at 24, 72 or 120 h post-exposure. Specifically, silibinin treatment resulted in dose-dependent reduction of NM-induced increase in epidermal thickness, dead and denuded epidermis, parakeratosis and microvesication. Higher silibinin dose also caused a 79% and 51%reversal in NM-induced increases in myeloperoxidase activity and COX-2 levels, respectively. Furthermore, silibinin completely prevented NM-induced H2A.X phosphorylation, indicating reversal of DNA damage which could be an oxidative DNA damage as evidenced by high levels of 8-oxodG in NM-exposed mouse skin that was significantly reversed by silibinin. Together, these findings suggest that attenuation of NM-induced skin injury by silibinin is due to its effects on the pathways associated with DNA damage, inflammation, vesication and oxidative stress. In conclusion, results presented here support the optimization of silibinin as an effective treatment of skin injury by vesicants.

Alpha-lipoic acid induces elevated S-adenosylhomocysteine and depletes S-adenosylmethionine.

Lipoic acid is a disulfhydryl-containing compound used in clinical medicine and in experimental models as an antioxidant. We developed a stable isotope dilution capillary gas chromatography/mass spectrometry assay for lipoic acid. We assayed a panel of the metabolites of transmethylation and transsulfuration 30 min after injecting 100 mg/kg lipoic acid in a rat model. Lipoic acid values rose 1000-fold in serum and 10-fold in liver. A methylated metabolite of lipoic acid was also detected but not quantitated. Lipoic acid injection caused a massive increase in serum S-adenosylhomocysteine and marked depletion of liver S-adenosylmethionine. Serum total cysteine was depleted but liver cysteine and glutathione were maintained. Serum total homocysteine doubled, with increases also in cystathionine, N,N-dimethylglycine, and alpha-aminobutyric acid. In contrast, after injection of 2-mercaptoethane sulfonic acid, serum total cysteine and homocysteine were markedly depleted and there were no effects on serum S-adenosylmethionine or S-adenosylhomocysteine. We conclude that large doses of lipoic acid displace sulfhydryls from binding sites, resulting in depletion of serum cysteine, but also pose a methylation burden with severe depletion of liver S-adenosylmethionine and massive release of S-adenosylhomocysteine. These changes may have previously unrecognized deleterious effects that should be investigated in both human disease and experimental models.

Lung epithelial cells release ATP during ozone exposure: signaling for cell survival.

The common air pollutant ozone causes acute toxicity to human airways. In primary and transformed epithelial cells from all levels of human or rat airways, ozone levels relevant to air pollution (50-200 ppb) increased extracellular [ATP] within 7-30 min. A human bronchial epithelial cell line (16HBE14o(-)) that forms electrically resistant polarized monolayers had up to 10-fold greater apical than basolateral surface extracellular [ATP] within 7 min of ozone exposure. Increased extracellular [ATP] appeared due to ATP secretion or release because (1) inhibition of ectonucleotidase (cell surface enzyme(s) which degrade ATP) by ozone did not occur until >120 min of ozone exposure and (2) brefeldin A, a secretory inhibitor, eliminated elevation of extracellular [ATP] without affecting intracellular ATP. Extracellular ATP protected against ozone toxicity in a P2Y receptor-dependent manner as (1) removal of ATP and adenosine by apyrase and adenosine deaminase, respectively, potentiated ozone toxicity, (2) extracellular supplementation with ATP, a poorly hydrolyzable ATP analog ATPgammaS, or UTP inhibited apoptotic and necrotic ozone-mediated cell death, and (3) ATP-mediated protection was eliminated by P2 and P2Y receptor inhibitors suramin and Cibacron blue (reactive blue 2), respectively. The decline in glucose uptake caused by prolonged ozone exposure was prevented by supplemental extracellular ATP, an effect blocked by suramin. Further, Akt and ERK phosphorylation resulted from exposure to supplemental extracellular ATP. Thus, extracellularly released ATP signals to prevent ozone-induced death and supplementation with ATP or its analogs can augment protection, at least in part via Akt and /or ERK signaling pathways and their metabolic effects.