Search

We evaluated the efficacy of aerosolized acetylcholinesterase (AChE) reactivator oxime MMB-4 in combination with the anticholinergic atropine sulfate for protection against respiratory toxicity and lung injury following microinstillation inhalation exposure to nerve agent soman (GD) in guinea pigs. Anesthetized animals were exposed to GD (841 mg/m3, 1.2 LCt50) and treated with endotracheally aerosolized MMB-4 (50 µmol/kg) plus atropine sulfate (0.25 mg/kg) at 30 sec post-exposure. Treatment with MMB-4 plus atropine increased survival to 100% compared to 38% in animals exposed to GD. Decreases in the pulse rate and blood O2 saturation following exposure to GD returned to normal levels in the treatment group. The body-weight loss and lung edema was significantly reduced in the treatment group. Similarly, bronchoalveolar cell death was significantly reduced in the treatment group while GD-induced increase in total cell count was decreased consistently but was not significant. GD-induced increase in bronchoalveolar protein was diminished after treatment with MMB-4 plus atropine. Bronchoalveolar lavage AChE and BChE activity were significantly increased in animals treated with MMB-4 plus atropine at 24 h. Lung and diaphragm tissue also showed a significant increase in AChE activity in the treatment group. Treatment with MMB-4 plus atropine sulfate normalized various respiratory dynamics parameters including respiratory frequency, tidal volume, peak inspiratory and expiratory flow, time of inspiration and expiration, enhanced pause and pause post-exposure to GD. Collectively, these results suggest that aerosolization of MMB-4 plus atropine increased survival, decreased respiratory toxicity and lung injury following GD inhalation exposure. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in the blood and tissues of animals that are treated with a number of endotracheally aerosolized therapeutics for protection against inhalation toxicity to sarin. Therapeutics included, aerosolized atropine methyl bromide (AMB), scopolamine or combination of AMB with salbutamol, sphingosine 1-phosphate, keratinocyte growth factor, adenosine A1 receptor antisense oligonucleotide (EPI2010), 2,3-diacetyloxybenzoic acid (2,3 DABA), oxycyte, and survanta. Guinea pigs exposed to 677.4 mg/m3 or 846.5 mg/m3 (1.2 LCt50) sarin for 4 min using a microinstillation inhalation exposure technique and treated 1 min later with the aerosolized therapeutics. Treatment with all therapeutics significantly increased the survival rate with no convulsions throughout the 24 h study period. Blood AChE activity determined using acetylthiocholine as substrate showed 20% activity remaining in sarin-exposed animals compare to controls. In aerosolized AMB and scopolamine-treated animals the remaining AChE activity was significantly higher (45-60%) compared to sarin-exposed animals ( p < 0.05). Similarly, treatment with all the combination therapeutics resulted in significant increase in blood AChE activity in comparison to sarin-exposed animals although the increases varied between treatments ( p < 0.05). BChE activity was increased after treatment with aerosolized therapeutics but was lesser in magnitude compared to AChE activity changes. Various tissues showed elevated AChE activity after therapeutic treatment of sarin-exposed animals. Increased AChE and BChE activities in animals treated with nasal therapeutics suggest that enhanced breathing and reduced respiratory toxicity/lung injury possibly contribute to rapid normalization of chemical warfare nerve agent inhibited cholinesterases. [ABSTRACT FROM AUTHOR]

The protective efficacy of the antimuscarinic agent scopolamine was evaluated against soman (o-pinacolyl methylphosphonofluoridate [GD])-induced respiratory toxicity in guinea pigs. Anesthetized animals were exposed to GD (841 mg/m3) by microinstillation inhalation exposure and treated 30 seconds later with endotracheally aerosolized scopolamine (0.25 mg/kg) and allowed to recover for 24 hours. Treatment with scopolamine significantly increased survival and reduced clinical signs of toxicity and body weight loss in GD-exposed animals. Analysis of bronchoalveolar lavage (BAL) fluid showed normalization of GD-induced increased cell death, total cell count, and protein following scopolamine treatment. The BAL fluid acetylcholinesterase and butyrylcholinesterase levels were also increased by scopolamine treatment. Respiratory dynamics parameters were normalized at 4 and 24 hours post–GD exposure in scopolamine-treated animals. Lung histology showed that scopolamine treatment reduced bronchial epithelial and subepithelial inflammation and multifocal alveolar septal edema. These results suggest that aerosolized scopolamine considerably protects against GD-induced respiratory toxicity. [ABSTRACT FROM PUBLISHER]

Sarin is a volatile nerve agent that has been used in the Tokyo subway attack. Inhalation is predicted to be the major route of exposure if sarin is used in war or terrorism. Currently available treatments are limited for effective postexposure protection against sarin under mass casualty scenario. Nasal drug delivery is a potential treatment option for mass casualty under field conditions. We evaluated the efficacy of endotracheal administration of muscarinic antagonist scopolamine, a secretion blocker which effectively crosses the blood-brain barrier for protection against sarin inhalation toxicity. Age and weight matched male Hartley guinea pigs were exposed to 677.4 mg/m3 or 846.5 mg/ m3 (1.2 ×× LCt50) sarin by microinstillation inhalation exposure for 4 min. One minute later, the animals exposed to 846.5 mg/ m3 sarin were treated with endotracheally aerosolized scopolamine (0.25 mg/kg) and allowed to recover for 24 h for efficacy evaluation. The results showed that treatment with scopolamine increased the survival rate from 20% to 100% observed in untreated sarin-exposed animals. Behavioral symptoms of nerve agent toxicity including, convulsions and muscular tremors were reduced in sarin-exposed animals treated with scopolamine. Sarin-induced body weight loss, decreased blood O2 saturation and pulse rate were returned to basal levels in scopolamine-treated animals. Increased bronchoalveolar lavage (BAL) cell death due to sarin exposure was returned to normal levels after treatment with scopolamine. Taken together, these data indicate that postexposure treatment with aerosolized scopolamine prevents respiratory toxicity and protects against lethal inhalation exposure to sarin in guinea pigs. [ABSTRACT FROM AUTHOR]

Barometric whole-body plethysmography (WBP) was used to examine pulmonary functions at 4 and 24 hours postexposure to soman (GD) in guinea pigs without therapeutics to improve survival. Endotracheal aerosolization by microinstillation was used to administer GD (280, 561, and 841 mg/m3) or saline to anesthetized guinea pigs. Significant increases in respiratory frequency (RF), tidal volume (TV), and minute volume (MV) were observed with 841 mg/m3 GD at 4 hours and that were reduced at 24 hours postexposure. A dose-dependent increase in peak inspiration flow and peak expiration flow was present at 4-hour post-GD exposure that was reduced at 24 hours. Time of inspiration and expiration were decreased in all doses of GD exposure at 4 and 24 hours, with significant inhibition at 841 mg/m3. End-expiratory pause (EEP) increased at 280 and 561 mg/m3, but decreased in animals exposed 841 mg/m3 at 24 hours postexposure. Pseudo-lung resistance (Penh) and pause followed similar patterns and increased at 4 hours, but decreased at 24 hours postexposure to 841 mg/m3 of GD compared to control. These studies indicate GD exposure induces dose-dependent changes in pulmonary function that are significant at 841 mg/m3 at 4 hours and remains 24 hours postexposure. Furthermore, at 4 hours, GD induces bronchoconstriction possibly due to copious airway secretion and ongoing lung injury in addition to cholinergic effects, while at 24 hours GD induces bronchodilation a possible consequence of initial compensatory mechanisms. [ABSTRACT FROM PUBLISHER]

The efficacy of endotracheal aerosolization of atropine sulfate for protection against soman (GD)-induced respiratory toxicity was investigated using microinstillation technique in guinea pigs. GD (841 mg/m3, 1.3 LCt50 or 1121 mg/m3, 1.7 LCt50) was aerosolized endotracheally to anesthetized male guinea pigs that were treated with atropine sulfate (5.0 mg/kg) 30 s postexposure by endotracheal microinstillation. Animals exposed to 841 mg/m3 and 1121 mg/m3GD resulted in 31 and 13% while treatment with atropine sulfate resulted in 100 and 50% survival, respectively. Cholinergic symptoms and increased body weight loss were reduced in atropine-treated animals compared to GD controls. Diminished pulse rate and blood O2 saturation in GD-exposed animals returned to normal levels after atropine treatment. Increased cell death, total cell count and protein in the bronchoalveolar fluid (BALF) in GD-exposed animals returned to normal levels following atropine treatment. GD exposure increased glutathione and superoxide dismutase levels in BALF and that were reduced in animals treated with atropine. Respiratory parameters measured by whole-body barometric plethysmography revealed that treatment with atropine sulfate resulted in normalization of respiratory frequency, tidal volume, time of expiration, time of inspiration, end expiratory pause, pseudo lung resistance (Penh) and pause at 4 and 24 h post 841 mg/m3 GD exposure. Lung histopathology showed that atropine treatment reduced bronchial epithelial subepithelial inflammation and multifocal alveolar septal edema. These results suggest that endotracheal aerosolization of atropine sulfate protects against respiratory toxicity and lung injury induced by microinstillation inhalation exposure to lethal doses of GD. [ABSTRACT FROM AUTHOR]

Abstract: Respiratory toxicity and lung injury following inhalation exposure to chemical warfare nerve agent soman was examined in guinea pigs without therapeutics to improve survival. A microinstillation inhalation exposure technique that aerosolizes the agent in the trachea was used to administer soman to anesthetized age and weight matched male guinea pigs. Animals were exposed to 280, 561, 841, and 1121mg/m3 concentrations of soman for 4min. Survival data showed that all saline controls and animals exposed to 280 and 561mg/m3 soman survived, while animals exposed to 841, and 1121mg/m3 resulted in 38% and 13% survival, respectively. The microinstillation inhalation exposure LCt50 for soman determined by probit analysis was 827.2mg/m3. A majority of the animals that died at 1121mg/m3 developed seizures and died within 15–30min post-exposure. There was a dose-dependent decrease in pulse rate and blood oxygen saturation of animals exposed to soman at 5–6.5min post-exposure. Body weight loss increased with the dose of soman exposure. Bronchoalveolar lavage (BAL) fluid and blood acetylcholinesterase and butyrylcholinesterase activity was inhibited dose-dependently in soman treated groups at 24h. BAL cells showed a dose-dependent increase in cell death and total cell counts following soman exposure. Edema by wet/dry weight ratio of the accessory lung lobe and trachea was increased slightly in soman exposed animals. An increase in total bronchoalveolar lavage fluid protein was observed in soman exposed animals at all doses. Differential cell counts of BAL and blood showed an increase in total lymphocyte counts and percentage of neutrophils. These results indicate that microinstillation inhalation exposure to soman causes respiratory toxicity and acute lung injury in guinea pigs. [Copyright &y& Elsevier]

Abstract: 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 30min, 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. [Copyright &y& Elsevier]

Abstract: 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 30min 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. [Copyright &y& Elsevier]