Protective efficacy of catalytic bioscavenger, paraoxonase 1 against sarin and soman exposure in guinea pigs

Human paraoxonase 1 (PON1) has been portrayed as a catalytic bioscavenger which can hydrolyze large amounts of chemical warfare nerve agents (CWNAs) and organophosphate (OP) pesticides compared to the stoichiometric bioscavengers such as butyrylcholinesterase. We evaluated the protective efficacy of purified human and rabbit serum PON1 against nerve agents sarin and soman in guinea pigs. Catalytically active PON1 purified from human and rabbit serum was intravenously injected to guinea pigs, which were 30 min later exposed to 1.2 × LCt50 sarin or soman using a microinstillation inhalation exposure technology. Pre-treatment with 5 units of purified human and rabbit serum PON1 showed mild to moderate increase in the activity of blood PON1, but significantly increased the survival rate with reduced symptoms of CWNA exposure. Although PON1 is expected to be catalytic, sarin and soman exposure resulted in a significant reduction in blood PON1 activity. However, the blood levels of PON1 in pre-treated animals after exposure to nerve agent were higher than that of untreated control animals. The activity of blood acetylcholinesterase and butyrylcholinesterase and brain acetylcholinesterase was significantly higher in PON1 pre-treated animals and were highly correlated with the survival rate. Blood O2 saturation, pulse rate and respiratory dynamics were normalized in animals treated with PON1 compared to controls. These results demonstrate that purified human and rabbit serum PON1 significantly protect against sarin and soman exposure in guinea pigs and support the development of PON1 as a catalytic bioscavenger for protection against lethal exposure to CWNAs

Recombinant paraoxonase 1 protects against sarin and soman toxicity following microinstillation inhalation exposure in guinea pigs

To explore the efficacy of paraoxonase 1 (PON1) as a catalytic bioscavenger, we evaluated human recombinant PON1 (rePON1) expressed in Trichoplusia ni larvae against sarin and soman toxicity using microinstillation inhalation exposure in guinea pigs. Animals were pretreated intravenously with catalytically active rePON1, followed by exposure to 1.2 X LCt50 sarin or soman. Administration of 5 units of rePON1 showed mild increase in the blood activity of the enzyme after 30 min, but protected the animals with a significant increase in survival rate along with minimal signs of nerve agent toxicity. Recombinant PON1 pretreated animals exposed to sarin or soman prevented the reduction of blood O2 saturation and pulse rate observed after nerve agent exposure. In addition, rePON1 pretreated animals showed significantly higher blood PON1, acetylcholinesterase (AChE), and butyrylcholinesterase activity after nerve agent exposure compared to the respective controls without treatments. AChE activity in different brain regions of rePON1 pretreated animals exposed to sarin or soman were also significantly higher than respective controls. The remaining activity of blood PON1, cholinesterases and brain AChE in PON1 pretreated animals after nerve agent exposure correlated with the survival rate. In summary, these data suggest that human rePON1 protects against sarin and soman exposure in guinea pigs

Acute Gene Expression Profile of Lung Tissue Following Sulfur Mustard Inhalation Exposure in Large Anesthetized Swine

Sulfur mustard (HD) is a vesicating and alkylating agent widely used on the battlefield during World War I and more recently in the Iran-Iraq War. It targets the eyes, skin, and lungs, producing skin burns, conjunctivitis, and compromised respiratory function; early acute effects lead to long-term consequences. However, it is the effects on the lungs that drive morbidity and eventual mortality. The temporal postexposure response to HD within lung tissue raises the question of whether toxicity is driven by the alkylating properties of HD on critical homeostatic pathways. We have established an anesthetized swine model of inhaled HD vapor exposure to investigate the toxic effects of HD 12 h postexposure. Large white female swine were anesthetized and instrumented prior to exposure to air, 60 (sublethal) or 100 μg·kg^–1 (∼LD₄₀) doses of HD (10 min). Physiological parameters were continuously assessed. Data indicate that exposure to 100 μg·kg^–1 HD lowered arterial blood oxygenation and increased shunt fraction and lavage protein compared with those of air-exposed controls and the 60 μg·kg^–1 dose of HD. Histopathology showed an increased total pathology score between the 100 μg·kg^–1 HD group and air-exposed controls. Principal component analysis of differentially expressed genes demonstrated a distinct and separable response of inhaled HD between air-exposed controls and the 60 and 100 μg·kg^–1 doses of HD. Canonical pathway analysis demonstrated changes in acute phase response signaling, aryl hydrocarbon receptor signaling, NRF-2 mediated oxidative stress, and zymosterol biosynthesis in the 60 and 100 μg·kg^–1 HD dose group. Transcriptional changes also indicated alterations in immune response, cancer, and cell signaling and metabolism canonical pathways. The 100 μg·kg^–1 dose group also showed significant changes in cholesterol biosynthesis. Taken together, exposure to inhaled HD had a significant effect on physiological responses coinciding with acute changes in gene expression and lung histopathology. In addition, transcriptomics support the observed beneficial effects of <i>N</i>-acetyl-l-cysteine for treatment of acute inhalation HD exposure

The physiology and toxicology of acute inhalation phosphine poisoning in conscious male rats

<p>Phosphine (PH₃) is a toxidrome-spanning chemical that is widely used as an insecticide and rodenticide. Exposure to PH₃ causes a host of target organ and systemic effects, including oxidative stress, cardiopulmonary toxicity, seizure-like activity and overall metabolic disturbance. A custom dynamic inhalation gas exposure system was designed for the whole-body exposure of conscious male Sprague-Dawley rats (250–350 g) to PH₃. An integrated plethysmography system was used to collect respiratory parameters in real-time before, during and after PH₃ exposure. At several time points post-exposure, rats were euthanized, and various organs were removed and analyzed to assess organ and systemic effects. The 24 h post-exposure LCt₅₀, determined by probit analysis, was 23,270 ppm × min (32,345 mg × min/m³). PH₃ exposure affects both pulmonary and cardiac function. Unlike typical pulmonary toxicants, PH₃ induced net increases in respiration during exposure. Gross observations of the heart and lungs of exposed rats suggested pulmonary and cardiac tissue damage, but histopathological examination showed little to no observable pathologic changes in those organs. Gene expression studies indicated alterations in inflammatory processes, metabolic function and cell signaling, with particular focus in cardiac tissue. Transmission electron microscopy examination of cardiac tissue revealed ultrastructural damage to both tissue and mitochondria. Altogether, these data reveal that in untreated, un-anesthetized rats, PH₃ inhalation induces acute cardiorespiratory toxicity and injury, leading to death and that it is characterized by a steep dose-response curve. Continued use of our interdisciplinary approach will permit more effective identification of therapeutic windows and development of rational medical countermeasures and countermeasure strategies.</p