Transition from oxidative stress to nitrosative stress in rostral ventrolateral medulla underlies fatal intoxication induced by organophosphate mevinphos

Chlorpyrifos intermittent exposure enhances cardiovascular but not behavioural responses to contextual fear conditioning in adult rats: Possible involvement of brain oxidative-nitrosative stress

Exposure to organophosphorus compounds (OPs) may cause psychiatric, neurologic, biochemical, and cardiovascular abnormalities. Neurotoxicity of OP compounds is primarily due to irreversibly inhibition of the acetylcholinesterase (AChE) enzyme both centrally and peripherally. Chlorpyrifos (CPF) is a widely used OP classified as moderately toxic. Previously, it has been shown that CPF administration, given every other day to adult rats, impairs spatial memory and prepulse inhibition associated with brain AChE inhibition. Our group also found that intermittent treatment with CPF, simulating occupational exposure, impairs the cardiorespiratory reflexes and causes cardiac hypertrophy. Thereby, we aimed to examine whether subchronic and intermittent administration of CPF would affect the behavioural (freezing) and cardiovascular (mean arterial pressure, MAP; heart rate, HR) responses elicited during contextual fear conditioning (CFC) and extinction. Wistar adult male rats were injected with sublethal and intermittent CPF doses (4 and 7 mg/kg) three times a week for one month. Two days after the last injection, a range of tests were performed to assess depression (sucrose preference), anxiety (elevated plus-maze, EPM), locomotion (open field, OF), and conditioned fear expression and extinction. Separate cohorts of animals were euthanized to measure plasma butyrylcholinesterase (BChE), erythrocyte AChE, brain AChE activity, and markers of oxidative-nitrosative stress. Intermittent CPF treatment did not affect sucrose preference. CPF (4 and 7 mg/kg) reduced open-arms exploration in the EPM, suggesting an anxiogenic effect. The higher dose of CPF decreased the total distance travelled in the OFT, suggesting motor impairment. After a seven-day CPF-free washout period, CPF (7 mg/kg) increased the tachycardic response without affecting freezing behaviour in the CFC extinction session. CPF 7 mg/kg decreased AChE activity in the hippocampus, pre-frontal cortex and brainstem 72 after the last administration whilst transiently increasing oxidative-nitrosative stress specifically in the brainstem. Overall, our results outlined the behavioural, autonomic and biochemical abnormalities caused by an intermittent dosing regimen of CPF that elicits brain AChE inhibition and brain oxidative-nitrosative stress. This paradigm might be valuable in further exploring long-term consequences and mechanisms of OP neurotoxicity as well as comprehensive therapeutic approaches.

Acute poisoning by chlorpyrifos differentially impacts survival and cardiorespiratory function in normotensive and hypertensive rats

Hypertension is the most important and well-known risk factor for cardiovascular disease (CVD). Recently, acute organophosphate (OP) poisoning has also been pointed as a CVD risk factor. Despite this evidence, no studies have contrasted the acute toxicosis and cardiovascular (CV) effects of OP poisoning under conditions of normotension and hypertension. In this work, adult male normotensive Wistar and Spontaneously Hypertensive rats (SHR) were intraperitoneally injected with saline or chlorpyrifos (CPF), an OP compound, monitored for acute toxicosis signs and 24-h survival. After poisoning, blood pressure, heart rate and ventilation were recorded, the Bezold-Jarisch Reflex (BJR), the Chemoreflex (CR) were chemically activated, as well as the cardiac autonomic tone (AUT) was assessed. Erythrocyte and brainstem acetylcholinesterase and plasmatic butyrylcholinesterase (BuChE) activities were measured as well as lipid peroxidation, advanced oxidation protein products (AOPP), nitrite/nitrate levels, expression of catalase, TNFα and angiotensin-I converting enzyme (ACE-1) within the brainstem. CPF induced a much more pronounced acute toxicosis and 33 % lethality in SHR. CPF poisoning impaired ventilation in SHR, the BJR reflex responses in Wistar rats, and the chemoreflex tachypneic response in both strains. CPF inhibited activity of cholinesterases in both strains, increased AOPP and nitrite/nitrate levels and expression of TNFα and ACE-1 in the brainstem of Wistar rats. Interestingly, SHR presented a reduced intrinsic BuChE activity, an important bioscavenger. Our findings show that, CPF at sublethal doses in normotensive rats lead to lethality and much more pronounced acute toxicity signs in the SHR. We also showed that cardiorespiratory reflexes were differentially impacted after CPF poisoning in both strains and that the cardiorespiratory disfunction seems to be associated with interference in cholinergic transmission, oxidative stress and inflammation. These results points to an increased susceptibility to acute toxicosis in hypertension, which may impose a significant risk to vulnerable populations.

Synergistic action of organophosphates and COVID-19 on inflammation, oxidative stress, and renin-angiotensin system can amplify the risk of cardiovascular maladies

Organophosphates (OPs) are ubiquitous environmental contaminants, widely used as pesticides in agricultural fields. In addition, they serve as flame-retardants, plasticizers, antifoaming or antiwear agents in lacquers, hydraulic fluids, and floor polishing agents. Therefore, world-wide and massive application of these compounds have increased the risk of unintentional exposure to non-targets including the human beings. OPs are neurotoxic agents as they inhibit the activity of acetylcholinesterase at synaptic cleft. Moreover, they can fuel cardiovascular issues in the form of myocardities, cardiac oedema, arrhythmia, systolic malfunction, infarction, and altered electrophysiology. Such pathological outcomes might increase the severity of cardiovascular diseases which are the leading cause of mortality in the developing world. Coronavirus disease-19 (COVID-19) is the ongoing global health emergency caused by SARS-CoV-2 infection. Similar to OPs, SARS-CoV-2 disrupts cytokine homeostasis, redox-balance, and angiotensin-II/AT₁R axis to promote cardiovascular injuries. Therefore, during the current pandemic milieu, unintentional exposure to OPs through several environmental sources could escalate cardiac maladies in patients with COVID-19.

Clinical correlates of hypotension in patients with acute organophosphorus poisoning

BACKGROUND

The aim of the present study is to describe the clinical correlates of hypotension and its associated outcomes in patients with acute organophosphorus poisoning (AOPP).

METHODS

In this retrospective cohort study, we analyzed data pertaining to 871 patients with AOPP who were treated at two hospitals. Data from hypotensive and non-hypotensive patients were compared to identify clinical correlates of hypotension. We also evaluated the association between clinical parameters (including hypotension) and in-hospital mortality.

RESULTS

The incidence of hypotension in AOPP patients was 16.4%. Hypotensive patients showed significantly higher in-hospital mortality (1.1% vs. 39.9%, P<0.001). Advanced age (odds ratio [OR] 1.25, 95% confidence interval [CI] 1.08-1.44), history of diabetes (OR 2.65, 95% CI 1.14-5.96), and increased white blood cell count (OR 1.06, 95% CI 1.03-1.09), plasma cholinesterase (OR 0.91, 95% CI 0.84-0.94), plasma albumin (OR 0.88, 95% CI 0.85-0.92), serum amylase (OR 1.01, 95% CI 1.01-1.02), and blood pH (OR 0.64, 95% CI 0.54-0.75) were significantly associated with hypotension. After adjusting for potential confounders, hypotension was associated with increased in-hospital mortality (hazard ratio 8.77-37.06, depending on the controlled variables).

CONCLUSIONS

Hypotension is a common complication of AOPP and is associated with increased in-hospital mortality. Advanced age, history of diabetes, and changes in laboratory parameters were associated with hypotension in AOPP patients.