Transcriptional impact of organophosphate pesticides chlorpyrifos and malathion and their mixture on the juvenile coho salmon olfactory system.. Oncorhynchus kisutch

Exposure to environmental concentrations of organophosphate pesticides in Pacific salmon can cause neurobehavioral injuries leading to loss of survival. However, the molecular mechanisms underlying olfactory impairment remain poorly understood. In the current study, we exposed juvenile salmon to three environmentally-relevant doses of chlorpyrifos (CPF) and malathion (MAL) individually and to three concentrations of binary mixtures of both compounds. Brain acetylcholinesterase (AChE) activity was significantly reduced only in the highest dosage of binary mixture group (47% inhibition). Microarray analysis on RNA from coho olfactory rosettes revealed a number of differentially expressed genes in all exposure groups. Overall, there were little overlapping of affected canonical pathways between CPF groups and MAL groups, suggesting the different biofunctions targeted by these two OP pesticides. Several metabolic and signaling pathways also represented the significant toxicological impact of OP pesticides on olfactory system, such as Aryl Hydrocarbon Receptor Signaling, Xenobiotic Metabolism Signaling, Mitochondrial Dysfunction, Pro-Apoptosis, and Oxidative Stress. Overall design: To determine the effects of chlorpyrifos and malathion separately and as a mixture we performed microarray analysis on juvenile coho salmon olfactory rosettes after exposure.