Acute and Long-Lasting Cardiac Changes Following a Single Whole-Body Exposure to Sarin Vapor in Rats

The Associations between Organophosphate Pesticides (OPs) and Respiratory Disease, Diabetes Mellitus, and Cardiovascular Disease: A Review and Meta-Analysis of Observational Studies

Although some epidemiological studies have identified the associations between exposure to organophosphate pesticides (Ops) and respiratory diseases, diabetes mellitus (DM), and cardiovascular diseases (CVDs), controversial results still exist. In this review and meta-analysis, we aimed to investigate the overall pooled effect estimates and the possible mechanisms of the relationship between OP exposure and adverse health outcomes. In this study, Web of Science, PubMed, Embase, OVID, and the Cochrane Library were systematically searched until September 2022. Nineteen observational studies that focused on the general population or occupational populations examined the associations between OP exposure and respiratory diseases, DM, and CVD were included. Based on the overall pooled results, a significantly positive association was observed between OP exposure and respiratory diseases (OR: 1.12, 95% CI: 1.06-1.19). A significant link was also observed between various individual species of OP exposure and respiratory diseases, with an OR value of 1.11 (95% CI: 1.05-1.18). In particular, there was a significant association of OPs with wheezing and asthma, with OR values of 1.19 (95% CI: 1.08-1.31) and 1.13 (95% CI: 1.05-1.22), respectively. In addition, a significant association was also observed between OP exposure and DM (OR: 1.18, 95% CI: 1.07-1.29). However, no significant association was observed between OP exposure and CVD (OR: 1.00, 95% CI: 0.94-1.05). Exposure to OPs was associated with a significantly increased risk of respiratory diseases and DM, but there was no evidence of a significant association between OP exposure and CVD. Considering the moderate strength of the results, further evidence is needed to confirm these associations.

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.

QT Prolongation as an Isolated Long-Term Cardiac Manifestation of Dichlorvos Organophosphate Poisoning in Rats

Organophosphates (OP) are used extensively as pesticides and as chemical weapons. Cardiotoxicity is a major concern in survivors of the acute poisoning. To characterize the delayed cardiac effects of OP, rats were poisoned by intraperitoneal administration of dichlorvos. In group I, poisoning (0.25-, 0.75-, 1.4-LD₅₀) was followed by application of atropine and obidoxime. In group II, poisoning (0.35-, 0.5-LD₅₀) was done without antidotes. Cardiac evaluation included electrocardiography and echocardiography 2- and 6-week post-exposure, arrhythmia susceptibility following administration of Isoproterenol (150 mcg/kg), and histological evaluation. All poisoned animals displayed cholinergic symptoms. In group I, all animals exposed to 1.4-LD₅₀ (n = 3) had profound convulsions and died despite antidote treatment. However, in the lower doses, all animals survived and no cardiac abnormalities were noted during follow-up. In group II, six animals had convulsions and died. Surviving animals had mild but significant prolongation of corrected QT at both 2 and 6 weeks, compared to shams. There were no notable echocardiographic, gravimetric, or histological differences between poisoned and sham animals. Our data indicate that dichlorvos poisoning is associated with QT prolongation without anatomical or histopathological abnormalities. This new model can be used to elaborate the molecular mechanism\s of QT prolongation following OP poisoning.

Early changes in M2 muscarinic acetylcholine receptors (mAChRs) induced by sarin intoxication may be linked to long lasting neurological effects

The effect of sarin on the binding parameters (KD & Bmax) of M2 muscarinic acetylcholine receptor (mAChR) was studied 24h and 1 week post exposure. Male & female Sprague-Daweley rats were poisoned with 1XLD50 sarin (80μg/kg, im) followed by treatment of trimedoxime bromide and atropine (7.5:5mg/kg, im) 1min later. Brains were removed and analyzed for M2 mAChR binding, using [³H]AFDX384, an M2 selective antagonist. A significant increase in KD of M2 mAChR was found in the cortex 24h post poisoning, displaying elevation from 4.65±1.16 to 8.45±1.06nM and 5.24±0.93 to 9.29±1.56nM in male and female rats, respectively. A rise in KD was also noted 1 week following exposure from 5.04±1.20 to 11.75±2.78 and from 5.37±1.02 to 11.66±1.73nM, presenting an added increase of 51 and 40% (compared to 24h) in males and females, respectively. Analysis of M2 receptor density (Bmax) revealed a significant reduction of 68% in males and insignificant reduction of 22% in females, 24h after sarin exposure which was followed by 37% recovery in males and 100% recovery in females, 1 week later. These results indicate that sarin induces a long-term decreased affinity in M2 mAChR (elevated KDs) and a transient effect on the number of this receptor subtype (Bmax). We hypothesize that the reduced affinity of the M2 receptors (negative auto-regulatory receptors) may cause long-term brain deficits by impairing the normal regulation release of ACh into the synaptic cleft.

Methamidophos, an Organophosphorus Insecticide, Induces Pro-aggressive Behaviour in Mice

Although evidence indicates that exposure to organophosphorus (OP) pesticides induces neurobehavioral disorders, little is known about the effects of OP on aggressive behaviour. Our study investigated the effects of repeated exposure to an OP pesticide, methamidophos, on the isolation-induced aggressive behaviour in mice. Forty seven male mice were individually housed for a month. Socially isolated animals were then confronted with a standard non-isolated opponent for 15 min (pre-treatment trial), and the latency and frequency of aggressive and general exploratory behaviours were recorded. Based on the presence of attack behaviour in the pre-treatment trial, mice were classified as isolation-induced aggressive and non-aggressive. All mice were then treated for 7 days with methamidophos (3.5 mg/kg/day, n = 22, intraperitoneal (i.p.)) or saline (1 mL/kg/day, control group, n = 25, i.p.), and a second trial was performed. Repeated exposure to methamidophos induced attack behaviour in non-aggressive mice. The treatment with methamidophos also decreased plasma butyrylcholinesterase and brain acetylcholinesterase activity. These results suggest that methamidophos has a pro-aggressive effect on socially isolated mice.

The role of multifunctional drug therapy as an antidote to combat experimental subacute neurotoxicity induced by organophosphate pesticides

Organophosphate pesticides are used in agriculture where they are associated with numerous cases of intentional and accidental misuse. These toxicants are potent inhibitors of cholinesterases leading to a massive build-up of acetylcholine which induces an array of deleterious effects, including convulsions, oxidative damage and neurobehavioral deficits. Antidotal therapies with atropine and oxime yield a remarkable survival rate, but fail to prevent neuronal damage and behavioral problems. It has been indicated that multifunction drug therapy with potassium channel openers, calcium channel antagonists and antioxidants (either single-agent therapy or combination therapy) may have the potential to prevent cell death and/or slow down the processes of secondary neuronal damage. The aim of the present study, therefore, was to make a relative assessment of the potential effects of nicorandil (2 mg/kg), clinidipine (10 mg/kg), and grape seed proanthocyanidin (GSPE) extract (200 mg/kg) individually against subacute chlorpyrifos induced toxicity. The test drugs were administered to Wistar rats 2 h after exposure to Chlorpyrifos (CPF). Different behavioral studies and biochemical estimation has been carried in the study. The results showed that chronic administration of CPF significantly impaired learning and memory, along with motor coordination, and produced a marked increase in oxidative stress along with significantly reduced acetylcholine esterase (AChE) activity. Treatment with nicorandil, clinidipine and GSPE was shown to significantly improve memory performance, attenuate oxidative damage and enhance AChE activity in rats. The present study also suggests that a combination of nicorandil, clinidipine, and GSPE has a better neuroprotective effect against subacute CPF induced neurotoxicity than if applied individually. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1017-1026, 2016.

Possible role for anisodamine in organophosphate poisoning

In cases of organophosphate poisoning, patients are treated with a combination of antidotes. In addition to these poison-directed antidotes, patients may require extra oxygen and artificial ventilation; other modalities may also be needed due to the wide range of toxic effects. Anisodamine is a belladonna alkaloid, and like other drugs from this family is non subtype-selective muscarinic, and a nicotinic cholinoceptor antagonist, which has been employed in traditional Chinese medicine. As a muscarinic antagonist, it displays similar pharmacological effects to atropine and scopolamine. However, anisodamine is not only less potent than atropine and scopolamine but also less toxic. Current in vitro and animal model studies have demonstrated that anisodamine has protective effects in a variety of diseases. Organophosphate poisoning involves not only the central and peripheral nervous systems, but also the cardiac and respiratory systems, as well as activation of inflammatory processes and oxidative stress. Therefore, the anticholinergic and additional activities of anisodamine appear to be relevant and justify its consideration as an addition to the existing remedies. However, more research is needed, as at present data on the role of anisodamine in the management of organophosphate poisoning are limited. Here, we review the beneficial effects of anisodamine on processes relevant to organophosphate poisoning.

Exposure to Agrochemicals and Cardiovascular Disease: A Review

INTRODUCTION

In the agricultural world there is a continuous loss of food, fiber and other commodities due to pests, disease and weeds before harvesting time. These losses had create lots of financial burden to the farm owners that might lead to shutting down of their daily business. Worldwide, there is an overall very high loss of agricultural products due to weeds growth alone. To counteract this problem most farmers resort to the use of agrochemicals to increase their production but compromising the health of their farmworkers. The purpose of the study will be to assess the relationship between the agrochemical particles and cardiovascular diseases among farmworkers.

METHOD

Non-systematic review was used to collect data. The following database were use: Medline, EBSCO, and Science Direct to search for the existing journal articles.

RESULTS

This study addresses the relationship between agrochemicals particles and cardiovascular diseases in the farming industries using literature review.

DISCUSSION

Other researchers had already done an extensive research on the pathway of potential mechanisms linking the ultrafine particulate matter to cardiovascular diseases. The outcomes of those investigations were the clinical results of events that might lead to the development of myocardial infarction, congestive heart failure (CHF), stroke, arrhythmia and sudden death. Xenobiotic compounds that maybe implicated in the pathophysiology of human cardiovascular diseases, will be examined and included in this study. There is compelling evidence suggesting that toxic free radicals of pesticides play an important role in human health.

CONCLUSION

There is a close relationship between agrochemicals particle and cardiovascular diseases.

The possible role of intravenous lipid emulsion in the treatment of chemical warfare agent poisoning

Organophosphates (OPs) are cholinesterase inhibitors that lead to a characteristic toxidrome of hypersecretion, miosis, dyspnea, respiratory insufficiency, convulsions and, without proper and early antidotal treatment, death. Most of these compounds are highly lipophilic. Sulfur mustard is a toxic lipophilic alkylating agent, exerting its damage through alkylation of cellular macromolecules (e.g., DNA, proteins) and intense activation of pro-inflammatory pathways. Currently approved antidotes against OPs include the peripheral anticholinergic drug atropine and an oxime that reactivates the inhibited cholinesterase. Benzodiazepines are used to stop organophosphate-induced seizures. Despite these approved drugs, efforts have been made to introduce other medical countermeasures in order to attenuate both the short-term and long-term clinical effects following exposure. Currently, there is no antidote against sulfur mustard poisoning. Intravenous lipid emulsions are used as a source of calories in parenteral nutrition. In recent years, efficacy of lipid emulsions has been shown in the treatment of poisoning by fat-soluble compounds in animal models as well as clinically in humans. In this review we discuss the usefulness of intravenous lipid emulsions as an adjunct to the in-hospital treatment of chemical warfare agent poisoning.

The Long-Term Effects of Organophosphates Poisoning as a Risk Factor of CVDs: A Nationwide Population-Based Cohort Study

BACKGROUND

Organophosphorus pesticides are widely used throughout the world. Because of their ease of availability, organophosphorus compounds are commonly used for self-poisoning in developing countries. The acute effects of exposure to organophosphorus pesticides are well known, but the chronic effects are unclear. Recent studies suggest that abnormalities of the central and peripheral nervous systems persisted for up to 5 years after acute poisoning due to a single large dose of organophosphates (OPs). However, the long-term effects on cardiovascular diseases are poorly understood.

METHODOLOGY/PRINCIPAL FINDINGS

An OPs-exposed cohort (N = 7,561) and an age- and gender-matched control cohort (N = 30,244), both identified from the National Health Insurance Research Database, were compared. We utilized the multivariable Cox proportional model to estimate the risks of developing arrhythmia, coronary artery disease (CAD) and congestive heart failure (CHF). The patients with acute poisoning from OPs had higher incidence rates of arrhythmia (5.89 vs. 3.61 per 1,000 person-years), CAD (9.10 vs. 6.88 per 1,000 person-years), and CHF (3.89 vs. 2.98 per 1,000 person-years) compared with that of the non-OPs poisoning cohort, with a crude subhazard ratio (SHR) of 1.40, 1.13, and 1.12, respectively. Additionally, a significantly higher risk of arrhythmia was observed in the OPs poisoning cohort (adjusted SHR = 1.25) compared with the non-OPs poisoning cohort, particularly in male patients (adjusted SHR = 1.33) and those under 49 years of age (adjusted SHR = 3.16). After accounting for the competing risks of death, there was a higher risk of arrhythmia and CAD during a three year follow-up period (adjusted SHR = 1.50 for arrhythmia; adjusted SHR = 1.10 for CAD). We also found an adjusted SHR of 1.36 associated with developing CHF after 6 years of follow-up for OPs poisoning cohort.

CONCLUSIONS

Acute OPs poisoning may continuously impact human health through mechanisms that are unclear. Any supportive measurements that could contribute to a reduction in the risk of heart disease may be beneficial in cases of OPs poisoning survivors.

Prophylaxis with human serum butyrylcholinesterase protects Göttingen minipigs exposed to a lethal high-dose of sarin vapor

Serum-derived human butyrylcholinesterase (Hu BChE) is a stoichiometric bioscavenger that is being developed as a potential prophylactic nerve agent countermeasure. Previously, we reported the prophylactic efficacy of Hu BChE in Göttingen minipigs against a whole-body exposure to 4.1mg/m(3) of sarin (GB) vapor, which produced lethality over 60min. Since the toxicity of nerve agent is concentration-dependent, in the present study, we investigated the toxic effects of an almost 3-fold higher rate of GB vapor exposure and the ability of Hu BChE to protect minipigs against this exposure. Male minipigs were subjected to: (1) air exposure; (2) GB vapor exposure; or (3) pretreatment with 7.5mg/kg of Hu BChE by i.m. injection, 24h prior to whole-body exposure to 11.4mg/m(3) of GB vapor for 10min. Electrocardiogram, electroencephalogram, and pupil size were monitored throughout exposure. Blood drawn before and throughout exposure was analyzed for blood gases, electrolytes, metabolites, acetylcholinesterase and BChE activities, and amount of GB bound to red blood cells and plasma. A novel finding was that saline-treated animals exposed to GB vapor did not develop any seizures, but manifested a variety of cardiac and whole blood toxic signs and rapidly died due to respiratory failure. Strikingly, pre-treatment with 7.5mg/kg of Hu BChE not only prevented lethality, but also avoided all cardiac toxic signs manifested in the non-treated cohort. Thus, Hu BChE alone can serve as an effective prophylactic countermeasure versus a lethal high-dose exposure to GB vapor.

The M2 muscarinic receptors are essential for signaling in the heart left ventricle during restraint stress in mice

We hypothesized that muscarinic receptors (MRs) in the heart have a role in stress responses and thus investigated changes in MR signaling (gene expression, number of receptors, adenylyl cyclase (AC), phospholipase C (PLC), protein kinase A and C (PKA and PKC) and nitric oxide synthase [NOS]) in the left ventricle, together with telemetric measurement of heart rate (HR) in mice (wild type [WT] and M2 knockout [KO]) during and after one (1R) or seven sessions (7R) of restraint stress (seven mice per group). Stress decreased M2 MR mRNA and cell surface MR in the left ventricle in WT mice. In KO mice, 1R, but not 7R, decreased surface MR. Similarly, AC activity was decreased in WT mice after 1R and 7R, whereas in KO mice, there was no change. PLC activity was also decreased after 1R in WT and KO mice. This is in accord with the concept that cAMP is a key player in HR regulation. No change was found with stress in NOS activity. Amount of AC and PKA protein was not changed, but was altered for PKC isoenzymes (PKCα, β, γ, η and ϵ (increased) in KO mice, and PKCι (increased) in WT mice). KO mice were more susceptible to stress as shown by inability to compensate HR during 120 min following repeated stress. The results imply that not only M2 but also M3 are involved in stress signaling and in allostasis. We conclude that for a normal stress response, the expression of M2 MR to mediate vagal responses is essential.

Caramiphen edisylate: an optimal antidote against organophosphate poisoning

Potent cholinesterase inhibitors such as sarin, induce an array of harmful effects including hypersecretion, convulsions and ultimately death. Surviving subjects demonstrate damage in specific brain regions that lead to cognitive and neurological dysfunctions. An early accumulation of acetylcholine in the synaptic clefts was suggested as the trigger of a sequence of neurochemical events such as an excessive outpour of glutamate and activation of its receptors. Indeed, alterations in NMDA and AMPA central receptors' densities were detected in brains of poisoned animals. Attempts to improve the current cholinergic-based treatment by adding potent anticonvulsants or antiglutamatergic drugs produced unsatisfactory results. In light of recent events in Syria and the probability of various scenarios of military or terrorist attacks involving organophosphate (OP) nerve agent, research should focus on finding markedly improved countermeasures. Caramiphen, an antimuscarinic drug with antiglutamatergic and GABAergic facilitating properties, was evaluated in a wide range of animals and experimental protocols against OP poisoning. Its remarkable efficacy against OP exposure was established both in prophylactic and post-exposure therapies in both small and large animals. The present review will highlight the outstanding neuroprotective effect of caramiphen as the optimal candidate for the treatment of OP-exposed subjects.

Sarin causes autonomic imbalance and cardiomyopathy: an important issue for military and civilian health

Sarin, a lethal chemical nerve agent, may be a causative factor in multifactorial syndrome implicated in the Gulf War and Tokyo terrorist attacks. Although a high dose results in seizure and death, low-dose exposure may lead to autonomic imbalance and chronic cardiac pathologies. In this study, echocardiography and electrocardiography were used to examine the late-onset effects of a low-dose sarin on cardiac structure and function in mice. Adrenal corticosterone and tyrosine hydroxylase mRNA levels were measured. Stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis was also tested. Findings demonstrate changes consistent with a dilated cardiomyopathy, including left ventricular dilatation, reduced contractility, and altered electrophysiological and inotropic responses to β-adrenergic stimulation. Results also indicate reduced adrenal tyrosine hydroxylase mRNA, corticosterone and altered stress responsiveness of HPA indicating autonomic imbalance. The role of low-dose sarin/organophosphate exposure needs to be considered in the military and civilian populations that suffer from autonomic imbalance and/or cardiomyopathies of indeterminate origin.

Deterioration in brain and heart functions following a single sub-lethal (0.8 LCt50) inhalation exposure of rats to sarin vapor: a putative mechanism of the long term toxicity

The main injuries among victims of the terrorist act in the Tokyo subway resulted from sub-lethal inhalation and whole body exposure to sarin vapor. In order to study the long term effects of such exposure and to simulate these conditions, freely moving rats were exposed to sarin vapor (27.2±1.7 μg/l) for 10 min. About 50% of the rats showed no overt symptoms and the rest had mild to moderate clinical symptoms that subsided within 4h following exposure. A reduction of weight was noted during the first 3 days with full recovery on the 4th day. Rat's heart was challenged with epinephrine 1 and 6 months post exposure. A significant reduction in the threshold for epinephrine-induced arrhythmia (EPIA) was noted in rats exposed to sarin. A time dependent increase in the kD and Bmax values of muscarinic auto receptors (M2) was recorded in the rat's cortex and striatum. No changes were recorded in the rats' brain trans locator protein (TSPO) levels, concomitant with no observed changes in the animals' performance in A Morris water maze test. A significant increase in open field activity was noted 6 months following exposure to sarin vapor as well as a significant decrease in prostaglandin E₂ (PGE₂) production in the brain. It is speculated that down regulation of the M2 auto receptor function, caused hyper reactivity of the cholinergic system which leads to the changes described above. The continuous reduction in M2 auto-receptor system through an unknown mechanism may be the cause for long lasting decline in sarin-exposed casualties' health.

Pesticides and myocardial infarction incidence and mortality among male pesticide applicators in the Agricultural Health Study

Acute organophosphate and carbamate pesticide poisonings result in adverse cardiac outcomes. The cardiac effects of chronic low-level pesticide exposure have not been studied. The authors analyzed self-reported lifetime use of pesticides reported at enrollment (1993-1997) and myocardial infarction mortality through 2006 and self-reported nonfatal myocardial infarction through 2003 among male pesticide applicators in the Agricultural Health Study. Using proportional hazard models, the authors estimated the association between lifetime use of 49 pesticides and fatal and nonfatal myocardial infarction. There were 476 deaths from myocardial infarction among 54,069 men enrolled in the study and 839 nonfatal myocardial infarctions among the 32,024 participants who completed the follow-up interview. Fatal and nonfatal myocardial infarctions were associated with commonly reported risk factors, including age and smoking. There was little evidence of an association between having used pesticides, individually or by class, and myocardial infarction mortality (e.g., insecticide hazard ratio (HR) = 0.91, 95% confidence interval (CI): 0.67, 1.24; herbicide HR = 0.74, 95% CI: 0.49, 1.10) or nonfatal myocardial infarction incidence (e.g., insecticide HR = 0.85, 95% CI: 0.66, 1.09; herbicide HR = 0.91, 95% CI: 0.61, 1.36). There was no evidence of a dose response with any pesticide measure. In a population with low risk for myocardial infarction, the authors observed little evidence of increased risk of myocardial infarction mortality or nonfatal myocardial infarction associated with the occupational use of pesticides.

Blood and bronchoalveolar lavage fluid acetylcholinesterase levels following microinstillation inhalation exposure to sarin in Guinea pigs

We determined acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition in the bronchoalveolar lavage fluid (BALF) following inhalation exposure to chemical threat nerve agent (CTNA) sarin. Age- and weight-matched male guinea pigs were exposed to five different doses of sarin (169.3, 338.7, 508, 677.4, and 846.5 mg/m(3)) using a microinstillation inhalation exposure technique for 4 min. The technique involves aerosolization of the agent in the trachea using a microcatheter with a center hole that delivers the agent and multiple peripheral holes that pumps air to aerosolize the agent at the tip. Animals exposed to higher doses of sarin occasionally developed seizures and succumbed to death within 15 min after exposure. The LCt(50) for sarin using the microinstillation technique was determined to be close to 677.4 mg/m(3). Ear blood AChE activity showed a dose-dependent inhibition at 15 min postexposure. The inhibition of blood AChE remained constant over 35 and 55 min after sarin exposure indicating that there was no lung depot effect. Cardiac blood AChE and butyrylcholinesterase (BChE) activity in surviving animals euthanized at 24 h postexposure showed a dose-dependent inhibition with an inhibition of 60% at 677.4 and 846.5 mg/m(3) sarin exposure. AChE and BChE activity in bronchoalveolar lavage fluid (BALF) showed a slight increase at 338.7 to 677.4 mg/m(3) sarin exposure but a marginal inhibition at 169.3 mg/m(3). In contrast, the AChE protein levels determined by immunoblotting showed an increase at 169.3 mg/m(3) in the BALF. The BALF protein level, a biomarker of lung injury, was increased maximally at 338.7 mg/m(3) and that increase was dropped with an increase in the dose of sarin. The BALF protein levels correlated with the AChE and BChE activity. These data suggest that sarin microinstillation inhalation exposure results in respiratory toxicity and lung injury characterized by changes in lavage AChE, BChE, and protein levels.

Guidelines for treating cardiac manifestations of organophosphates poisoning with special emphasis on long QT and Torsades De Pointes

Organophosphate poisoning may precipitate complex ventricular arrhythmias, a frequently overlooked and potentially lethal aspect of this condition. Acute effects consist of electrocardiographic ST-T segment changes and AV conduction disturbances of varying degrees, while long-lasting cardiac changes include QT prolongation, polymorphic tachycardia ("Torsades de Pointes"), and sudden cardiac death. Cardiac monitoring of organophosphate intoxicated patients for relatively long periods after the poisoning and early aggressive treatment of arrhythmias may be the clue to better survival. We present here a review of the literature with a focus on late cardiac arrhythmias (mainly "Torsades de pointes"), possible mechanisms, and treatment modalities, with special emphasis on postpoisoning monitoring for development of arrhythmias.

Adaptive changes in acetylcholinesterase gene expression as mediators of recovery from chemical and biological insults

Both organophosphate (OP) exposure and bacterial infection notably induce short- and long-term cholinergic responses. These span the central and peripheral nervous system, neuromuscular pathway and hematopoietic cells and involve over-expression of the "readthrough" variant of acetylcholinesterase, AChE-R, and its naturally cleavable C-terminal peptide ARP. However, the causal involvement of these changes with post-exposure recovery as opposed to apoptotic events remained to be demonstrated. Here, we report the establishment of stably transfected cell lines expressing catalytically active human "synaptic" AChE-S or AChE-R which are fully viable and non-apoptotic. In addition, intraperitoneally injected synthetic mouse ARP (mARP) elevated serum AChE levels post-paraoxon exposure. Moreover, mARP treatment ameliorated post-exposure increases in corticosterone and decreases in AChE gene expression and facilitated earlier retrieval of motor activity following both paraoxon and lipopolysaccharide (LPS) exposures. Our findings suggest a potential physiological role for overproduction of AChE-R and the ARP peptide following exposure to both chemical warfare agents and bacterial LPS.

Sarin produces delayed cardiac and central autonomic changes

The aim was to evaluate the acute and delayed effects of low dose sarin exposure on cardiac autonomic and brainstem catecholaminergic function in mice. The rationale was to expand our knowledge of the cardiovascular effects of this neurotoxic, acetylcholinesterase (AChE) inhibitor. C57BL/6 male mice with telemetric arterial catheters were injected with saline or sarin (8 microg/kg, 0.05x LD(50); sc, two injections) with blood pressure (BP) measurements made at 1 and 10 weeks after sarin exposure. BP and pulse interval variability (PI) and low and high frequency spectral oscillations were measured using autoregressive spectral analysis. In situ hybridization (ISH) was used to quantify tyrosine hydroxylase (TH) mRNA expression in brainstem cardiovascular centers. Sarin had no effect on blood AChE activity, heart rate (HR) or BP. There was a biphasic response in PI variance, an early increase (+140%) and a delayed decrease (-62%) at more than 2 months after sarin exposure. There were no changes in BP variance. Assuming that increased PI variance is a positive outcome, the short-term response to sarin should be protective. This is opposite for the delayed decrease in PI variance which is associated with adverse cardiovascular effects. There was an increase in TH mRNA in both locus coeruleus (0.18+/-0.05 vs. 1.4+/-0.2 microCi/g; control vs. sarin) and dorsal vagal complex (0.09+/-0.06 vs. 1.17+/-0.03 microCi/g; control vs. sarin). Results show that a dose of sarin which had no peripheral cholinergic effects caused changes in autonomic modulation, a short-term enhancement followed by a delayed impairment in heart rate variability. Sarin-induced cardiac effects suggest a controversial aspect to the use of pharmacological agents which target AChE for management of cardiovascular risk.