CHLORPYRIFOS (CPF) is a widely used organophosphate pesticide that has been shown to cause a range of toxic effects, including oxidative stress and endocrine disruption. This review aims to summarize the most recent findings regarding CPF’s toxicological impacts on human health, with a focus on its mechanisms of action, particularly in relation to oxidative stress and endocrine disruption. The review also addresses the environmental persistence of CPF and the potential cumulative effects of chronic exposure. Recent studies (2018–2023) are integrated to present novel insights into CPF-induced cellular damage, as well as its broader implications for public health and the environment. Furthermore, the paper discusses potential strategies for mitigating CPF’s harmful effects, including bioremediation and antioxidant therapies.

Microcerotermes diversus Silvestri, is an important termite in Khuzestan province with a broad range of foraging. In recent years, control of underground termites has been more based on the application of chemicals which has increased pest insecticide resistance. In this study, the resistance of different populations of termites to CHLORPYRIFOS was investigated using estimated LC50 and measuring the activity of two acetylcholinesterase (AChE) and glutathione-s-transferase enzymes. Four populations of M. diversus with different histories of organophosphorus insecticide spraying were studied. Populations A (Am Altamir1), B (Am Altamir2), and C (Mollasani) were collected from date palm groves with 30 and 10-year histories of organophosphorus insecticide spraying, as well as without spraying history, respectively. Population D (Ramin University) was collected from orange trees, three weeks after spraying with CHLORPYRIFOS. The bioassay results showed that the highest and lowest LC50 values were observed in populations A and C, respectively. Moreover, the activity of AChE using acetylthiocholine iodide, propionylthiocholine iodide, and butyrylthiocholine iodide substrates was higher in the populations with CHLORPYRIFOS spraying history, with the highest activity in population A. It was also demonstrated that the AChE activity with acetylthiocholine iodide substrate was higher than the activity of this enzyme with butyrylthiocholine iodide and the propionyl choline substrates in the populations with 30 and 10-year history of spraying. The Michaelis constant (Km) and maximum velocity (Vmax) values of AChE as two important kinetic factors, indicated the highest affinity of this enzyme to the substrate in population A.

Introduction: Paraoxonase 1 (PON1) is a high-density lipoprotein-associated enzyme with both aryl esterase and lactonase activity, and it possesses significant antioxidant and anti-inflammatory properties. PON1 hydrolyzes the active metabolites of several organophosphorus (OP) insecticides, including parathion, diazinon, and CHLORPYRIFOS. This widely studied enzyme is recognized for its protective role against organophosphate poisoning and vascular diseases, as well as its potential as a biomarker for conditions related to oxidative stress, inflammation, and liver disease. However, limited knowledge exists regarding PON1 activity status following acute organophosphate intoxication. The aim of the present study was to investigate changes in serum PON1 activity after acute CHLORPYRIFOS poisoning and its relationship with acetylcholinesterase (AChE) activity. Method: Rats were orally given a single dose of CHLORPYRIFOS (160 mg/kg), and blood samples were collected before treatment, as well as at 6 and 96 hours post-treatment. We measured serum cholinesterase, paraoxonase, and arylesterase activity of PON1. Results: Signs of OP poisoning, including miosis, salivation, tremors, fasciculation, and paralysis, were observed following intoxication, accompanied by a significant inhibition of AChE activity. All symptoms resolved after 48 hours, and AChE activity returned to baseline levels at 96 hours. In contrast, paraoxonase and arylesterase activities progressively increased after 6h and 96h treatment respectively. Conclusion: The results of our study indicated that serum cholinesterase activity and paraoxonase activity negatively associated in OP poisoning. Based on these findings, monitoring paraoxonase activity after OP intoxication may serve as a valuable biomarker for assessing intoxication.