Evaluation of adenosine A1 receptor agonists as neuroprotective countermeasures against Soman intoxication in rats

Soman, an organophosphorus (OP) compound, disrupts nervous system function through inactivation of acetylcholinesterase (AChE), the enzyme that breaks down acetylcholine at synapses. Left untreated, a state of prolonged seizure activity (status epilepticus, SE) is induced, causing widespread neuronal damage and associated cognitive and behavioral impairments. Previous research demonstrated that therapeutic stimulation of A1 adenosine receptors (A1ARs) can prevent or terminate soman-induced seizure. This study examined the ability of three potent A1AR agonists to provide neuroprotection and, ultimately, prevent observable cognitive and behavioral deficits following exposure to soman. Sprague Dawley rats were challenged with a seizure-inducing dose of soman (1.2 x LD50) and treated 1 min later with one of the following A1AR agonists: (6)-Cyclopentyladenosine (CPA), 2-Chloro-N6-cyclopentyladenosine (CCPA) or N-bicyclo(2.2.1)hept-2-yl-5'-chloro-5'-deoxyadenosine (cdENBA). An active avoidance shuttle box task was used to evaluate locomotor responses to aversive stimuli at 3, 7 and 14 days post-exposure. Animals treated with CPA, CCPA or cdENBA demonstrated a higher number of avoidance responses and a faster reaction to the aversive stimulus than the soman/saline control group across all three sessions. Findings suggest that A1AR agonism is a promising neuroprotective countermeasure, capable of preventing the long-term deficits in learning and memory that are characteristic of soman intoxication.

Organophosphorus compounds and oximes: a critical review

Organophosphorus (OP) pesticides and nerve agents still pose a threat to the population. Treatment of OP poisoning is an ongoing challenge and burden for medical services. Standard drug treatment consists of atropine and an oxime as reactivator of OP-inhibited acetylcholinesterase and is virtually unchanged since more than six decades. Established oximes, i.e. pralidoxime, obidoxime, TMB-4, HI-6 and MMB-4, are of insufficient effectiveness in some poisonings and often cover only a limited spectrum of the different nerve agents and pesticides. Moreover, the value of oximes in human OP pesticide poisoning is still disputed. Long-lasting research efforts resulted in the preparation of countless experimental oximes, and more recently non-oxime reactivators, intended to replace or supplement the established and licensed oximes. The progress of this development is slow and none of the novel compounds appears to be suitable for transfer into advanced development or into clinical use. This situation calls for a critical analysis of the value of oximes as mainstay of treatment as well as the potential and limitations of established and novel reactivators. Requirements for a straightforward identification of superior reactivators and their development to licensed drugs need to be addressed as well as options for interim solutions as a chance to improve the therapy of OP poisoning in a foreseeable time frame.

Prevalence of Intermediate Syndrome among Admitted Patients with Organophosphorous Poisoning in a Tertiary Care Hospital

Introduction:

Organophosphorous poisoning is a common problem prevalent in Nepal. Intermediate syndrome is a common clinical feature seen among the patients those have ingested poison. There is a scarcity of data related to intermediate syndrome and other general complications in patients with organophosphorous poisoning in context of Nepal. This study was carried out to observe the prevalence of intermediate syndrome and the general complications of oraganophosphorus poisoning among admitted patients in a tertiary care hospital.

Methods:

This was a descriptive cross-sectional study conducted at a tertiary care hospital from April 2008 to June 2009 after ethical approval was from Institiutional Review Board of tertiary care hospital. Forty four patients with history of ingestion of organophosphorus poisoning within 24 hours were included in our study through convenience sampling. Clinical examinations were done to look for Intermediate syndrome. Data was entered in Statistical Package for Social Sciences and point estimate at 95% of CI was calculated along with frequency and proportion for binary data.

Results:

Out of 44 patients, features of intermediate syndrome were seen in 40 (90.9%) at 95% of CI (84.2-97.6) patients in the study. The frequency of intermediate syndrome signs like weakness of neck flexion, inability to sit up and swallowing difficulty were seen among the patients. Complications like pneumonia 4 (9.09%), hyponatremia 3 (6.8%), hypokalemia 1 (2.27%) and bradycardia 1 (2.27%) were seen in the study. Mortality seen in the study was 2 (4.5%) among the admitted patients.

Conclusions:

Prevalence of intermediate syndrome was higher compared to other studies done in similar settings. Complications like pneumonia, hyponatremia, hypokalemia and bradycardia were seen among the patients.

Prevalence of Intermediate Syndrome among Admitted Patients with Organophosphorous Poisoning in a Tertiary Care Hospital

INTRODUCTION

Organophosphorous poisoning is a common problem prevalent in Nepal. Intermediate syndrome is a common clinical feature seen among the patients those have ingested poison. There is a scarcity of data related to intermediate syndrome and other general complications in patients with organophosphorous poisoning in context of Nepal. This study was carried out to observe the prevalence of intermediate syndrome and the general complications of oraganophosphorus poisoning among admitted patients in a tertiary care hospital.

METHODS

This was a descriptive cross-sectional study conducted at a tertiary care hospital from April 2008 to June 2009 after ethical approval was from Institiutional Review Board of tertiary care hospital. Forty four patients with history of ingestion of organophosphorus poisoning within 24 hours were included in our study through convenience sampling. Clinical examinations were done to look for Intermediate syndrome. Data was entered in Statistical Package for Social Sciences and point estimate at 95% of CI was calculated along with frequency and proportion for binary data.

RESULTS

Out of 44 patients, features of intermediate syndrome were seen in 40 (90.9%) at 95% of CI (84.2-97.6) patients in the study. The frequency of intermediate syndrome signs like weakness of neck flexion, inability to sit up and swallowing difficulty were seen among the patients. Complications like pneumonia 4 (9.09%), hyponatremia 3 (6.8%), hypokalemia 1 (2.27%) and bradycardia 1 (2.27%) were seen in the study. Mortality seen in the study was 2 (4.5%) among the admitted patients.

CONCLUSIONS

Prevalence of intermediate syndrome was higher compared to other studies done in similar settings. Complications like pneumonia, hyponatremia, hypokalemia and bradycardia were seen among the patients.

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.

Modeling of Heart Rate Variability and Respiratory Muscle Activity in Organophosphate Poisoned Patients

We propose an extended model of cardiovascular regulation to assess heart rate variability in patients poisoned with organophosphate during their treatment with mechanical ventilation. The model was modified to fit a population of 21 patients poisoned with organophosphorus compounds and undergoing mechanical ventilation. The extended model incorporated the respiratory muscle activity measured by surface electromyography for quantifying the vagal-sympathetic engagement during spontaneous breathing test. The order and structure of the parasympathetic and the sympathetic transfer function with respect to the original model were modified to a second-order system. In this extended model, the parameters related to the vagal-sympathetic response (corner frequency and constant gain) were correlated with respiratory muscle activity. When the diaphragm's contractions were stronger, the sympathetic corner frequency increased while the parasympathetic corner frequency and gain decreased. Thus, the proposed model could be useful to improve the ventilatory support and pharmacological treatment for patients poisoned with organophosphorus compounds considering the vagal-sympathetic response inferred from the respiratory muscle activity.

MicroRNA expression profiling in human acute organophosphorus poisoning and functional analysis of dysregulated miRNAs

OBJECTIVE

Acute organophosphorus(OP) pesticide poisoning is associated with dysfunctions in multiple organs, especially skeletal muscles, the nervous system and the heart. However, little is known about the specific microRNA (miRNA) changes that control the pathophysiological processes of acute OP poisoning damage. We aimed to explore miRNA expression profiles and gain insight into molecular mechanisms of OP toxic effects.

METHODS

MicroRNA expression was analyzed by TaqMan Human MicroRNA Array analysis and subsequent validated with quantitive PCR. The targets of the significantly different miRNAs were predicted with miRNA prediction databases, and pathway analysis of the predicted target genes was performed using bioinformatics resources.

RESULTS

37 miRNAs were significantly different in the sera of poisoned patients compared to the healthy controls, including 29 miRNAs that were up-regulated and 8 miRNAs that were down-regulated. Functional analysis indicated that many pathways potentially regulated by these miRNAs are involved in skeletal muscle, nervous system and heart disorders.

CONCLUSION

This study mapped changes in the serum miRNA expression profiles of poisoning patients and predicted functional links between miRNAs and their target genes in the regulation of acute OP poisoning. Our findings are an important resource for further understanding the role of these miRNAs in the regulation of OP-induced injury.

Subchronic exposure to kalach 360 SL-induced endocrine disruption and ovary damage in female rats

Kalach 360 SL (KL), glyphosate (G) surfactant-based herbicides, is a systemic herbicide effective against weeds. It was applied in agriculture in Tunisia and throughout the world, which can represent a risk to non-target organisms. The aim of this study was to investigate the morphological and biochemical aspects of ovary injury after exposure to KL. Female Wistar rats were divided into three groups: group 1 was used as a control; group 2 orally received 0.07 ml of KL, (126 mg of G/kg) and group 3 orally received 0.175 ml of KL (315 mg of G/kg) each day for 60 days. The subchronic exposure of KL induces impaired folliculogenesis, ovary development, decreased oestrogen secretion, promoted oxidative stress and impairments of ovary histological aspects. Histological finding shows necrosis cell, vacuolisation of follicles, dissociated oocytes and granulosa cell, associated with several atretic follicles. We conclude that KL induces endocrine disruption and ovary damage in female rats.

Increased risk for hypothyroidism after anticholinesterase pesticide poisoning: a nationwide population-based study

PURPOSE

Previous animal studies have reported that acute anticholinesterase pesticide (organophosphate and carbamate) poisoning may affect thyroid hormones. However, there is no human study investigating the association between hypothyroidism and anticholinesterase pesticide poisoning, and therefore, we conducted a retrospective nationwide population-based cohort study to delineate this issue.

METHODS

We identified 10,372 anticholinesterase pesticide poisoning subjects and matched 31,116 non-anticholinesterase pesticide poisoning subjects between 2003 and 2012 from the Nationwide Poisoning Database and the Longitudinal Health Insurance Database 2000, respectively, in a 1:3 ratio by index date, age, and sex for this study. We compared the cumulative incidence of hypothyroidism between the two cohorts by following up until 2013. Independent predictors for hypothyroidism were also investigated.

RESULTS

In total, 75 (0.72%) anticholinesterase pesticide poisoning subjects and 184 (0.59%) non-anticholinesterase pesticide poisoning subjects were diagnosed with hypothyroidism during the follow-up. Cox proportional hazard regression analysis showed that anticholinesterase pesticide poisoning subjects had higher risk for hypothyroidism than did non-anticholinesterase pesticide poisoning subjects (adjusted hazard ratio: 1.47, 95% confidence interval: 1.11-1.95) after adjusting for age, sex, hypertension, malignancy, liver disease, renal disease, atrial fibrillation or flutter, thyroiditis, goiter, other endocrine disorders, and mental disorder. Stratified analysis showed that anticholinesterase pesticide poisoning subjects had higher risk for hypothyroidism than did non-anticholinesterase pesticide poisoning subjects in terms of the age subgroup of 40-64 years, female sex, past history of goiter, follow-up of <1 month, and anticholinesterase pesticide poisoning subjects without atropine treatment (incidence rate ratio [IRR]: 1.66, 95% confidence interval: 1.20-2.30). Female sex, malignancy, renal disease, thyroiditis, goiter, mental disorder, and anticholinesterase pesticide poisoning without atropine treatment were independent predictors for hypothyroidism.

CONCLUSIONS

Anticholinesterase pesticide poisoning is associated with increased risk for hypothyroidism. Early evaluation of thyroid function in anticholinesterase pesticide poisoning subjects is suggested, especially in subjects without atropine treatment, aged 40-64 years, female sex, and past history of goiter.

Translation of in vitro to in vivo pyridinium oxime potential in tabun poisoning

Even if organophosphorus (OP) nerve agents were banned entirely, their presence would remain a problem as weapons of terror (like in Syria). Oxime antidotes currently used in medical practice still fall short of their therapeutic purpose, as they fail to fully restore the activity of cholinesterases, the main target for OPs. As orphan drugs, these antidotes are tested too seldom for anybody's benefit. Over the last few decades, search for improved reactivators has reached new levels, but the translation of data obtained in vitro to in vivo application is still a problem that hinders efficient therapy. In this study, we tested the strengths and weaknesses of extrapolating pyridinium oxime antidotes reactivation efficiency from in vitro to in vivo application. Our results show that this extrapolation is possible with well-determined kinetic constants, but that it also largely depends on oxime circulation time and its tissue-specific distribution. This suggests that pharmacokinetic studies should be planned at the early stages of antidote development. Special attention should also be given to improving oxime distribution throughout the organism to overcome this major constraint in improving overall OP therapy.

Delayed Polyneuropathy Induced by Organophosphate Poisoning

An 89-year-old man attempted suicide by ingesting a pesticide (trichlorfon). After surviving the initial critical period in the intensive care unit, he developed rapidly progressive distal weakness and sensory disturbance. Electrophysiological examinations revealed sensory motor axonal polyneuropathy. Delayed polyneuropathy is a rare manifestation of organophosphate poisoning. Nerve conduction studies play an important role in the diagnosis of this rare clinical condition.

[Acute organophosphorus intoxications in pregnant women]

Acute organophosphorus pesticides (OPs) poisoning during pregnancy are rare events, not well documented in the literature. We conducted a retrospective analysis of outcomes in seven cases of suicidal ingestion of OP in pregnant women. This intoxication was most often serious. Indeed, five of seven parturients had an initial Glasgow score < 9 and the POP score was ≥ 3 in all parturients. Five patients required mechanical ventilation for a mean duration of 3,4 days. All patients reported favorable outcomes but in more than half of the cases fetuses had unfavorable outcomes (fetal death in utero). Two mechanisms can explain these fetal complications. The first mechanism is fetal hypoxia, associated or not with a state of shock, which can be reflected in the Fetal Heart Rate (FHR) by tachycardia or decelerations and result in intrauterine fetal death. The second mechanism is the passage of these pesticides through the placental barrier representing a potential risk to the fetus due to the alteration of the microsomal enzyme systems.

Mechanism-specific injury biomarkers predict nephrotoxicity early following glyphosate surfactant herbicide (GPSH) poisoning

Acute kidney injury (AKI) is common following glyphosate surfactant herbicide (GPSH) self-poisoning. Serum creatinine (sCr) is the most widely used renal biomarker for diagnosis of AKI although a recent study in rats suggested that urinary kidney injury molecule-1 predicted AKI earlier and better after GPSH-induced nephrotoxicity. We explored the utility of a panel of biomarkers to diagnose GPSH-induced nephrotoxicity in humans. In a prospective multi-centre observational study, serial urine and blood samples were collected until discharge and at follow-up. The diagnostic performance of each biomarker at various time points was assessed. AKI was diagnosed using the Acute Kidney Injury Network (AKIN) definitions. The added value of each biomarker to sCr to diagnose AKI was assessed by the integrated discrimination improvement (IDI) metric. Of 90 symptomatic patients, 51% developed AKI and 5 patients who developed AKIN≥2 died. Increased sCr at 8 and 16h predicted moderate to severe AKI and death. None of the 10 urinary biomarkers tested increased above normal range in patients who did not develop AKI or had mild AKI (AKIN1); most of these patients also had only minor clinical toxicity. Absolute concentrations of serum and urinary cystatin C, urinary interleukin-18 (IL-18), Cytochrome C (CytoC) and NGAL increased many fold within 8h in patients who developed AKIN≥2. Maximum 8 and 16h concentrations of these biomarkers showed an excellent diagnostic performance (AUC-ROC ≥0.8) to diagnose AKIN≥2. However, of these biomarkers only uCytoC added value to sCr to diagnose AKI when assessed by IDI metrics. GPSH-induced nephrotoxicity can be diagnosed within 24h by sCr. Increases in uCytoC and uIL-18 confirm GPSH-induces apoptosis and causes mitochondrial toxicity. Use of these biomarkers may help to identify mechanism specific targeted therapies for GPSH nephrotoxicity in clinical trials.

Management of Organophosphorus Poisoning

Organophosphorus (OP) compounds are widely used for agriculture, domestic pest-control and chemical warfare. Pesticide self-poisoning accounts for one-sixth to one-eighth of the world's suicides and a third of suicide deaths in rural Asia each year. OP pesticides inhibit cholinesterase enzymes leading to overstimulation of cholinergic receptors. Clinical features depend on the types of receptors stimulated at various sites of the body. The diagnosis of OP poisoning is made on the basis of history of poisoning, smell of pesticides, the characteristic clinical signs and reduced cholinesterase activity. Measurement of plasma cholinesterase is useful for diagnosis of OP poisoning although it may not directly correlate with severity of the poisoning. Atropine remains the main stay of treatment of OP poisoning with clear evidence of benefit if administered effectively. Atropine therapy should be monitored to maintain systolic blood pressure > 80 mmHg, pulse > 80 beats/min and clear chest on auscultation. Oximes reactivate cholinesterase enzymes and help to overcome even the nicotinic effects of OP poisoning. However, evidence for its effectiveness after self-poisoning is weak. Although several newer adjuvant therapies are tried to achieve better outcome, their potential benefits are not yet established.

Effects of acute organophosphorus poisoning on function of peripheral nerves: a cohort study

BACKGROUND

Following acute organophosphorus (OP) poisoning patients complain of numbness without objective sensory abnormalities or other features of OP induced delayed polyneuropathy. The aim of this study was to measure peripheral nerve function after acute exposure to OP.

METHODS

A cohort study was conducted with age, gender and occupation matched controls. Motor nerve conduction velocity (MNCV), amplitude and area of compound muscle action potential (CMAP), sensory nerve conduction velocity (SNCV), F- waves and electromyography (EMG) on the deltoid and the first dorsal interosseous muscles on the dominant side were performed, following acute OP poisoning. All neurophysiological assessments except EMG were performed on the controls. Assessments were performed on the day of discharge from the hospital (the first assessment) and six weeks (the second assessment) after the exposure. The controls were assessed only once.

RESULTS

There were 70 patients (50 males) and 70 controls. Fifty-three patients attended for the second assessment. In the first assessment MNCV of all the motor nerves examined, CMAP amplitude and SNCV of ulnar nerve, median and ulnar F-wave occurrence in the patients were significantly reduced compared to the controls. In the second assessment significant reduction was found in SNCV of both sensory nerves examined, MNCV of ulnar nerve, CMAP amplitude of common peroneal nerve, F-wave occurrence of median and ulnar nerves. No abnormalities were detected in the patients when compared to the standard cut-off values of nerve conduction studies except F-wave occurrence. EMG studies did not show any abnormality.

CONCLUSION

There was no strong evidence of irreversible peripheral nerve damage following acute OP poisoning, however further studies are required.