Toxicogenomic Characterization of Molecular Mechanisms Contributing to Chlorpyrifos Neurotoxicity in Adult Male Rats [microarray]

Chlorpyrifos (CPF) is an organophosphorus pesticide (OP), and one of the most widely used pesticides in the world. Metabolites of CPF and other OPs continue to be identified in the majority of human samples, even in countries such as the United States where OP use is declining (Arcury et al., 2010). The effects of repeated occupational and environmental exposures to OPs are poorly understood, although human and animal studies consistently identify neurotoxicity as the primary endpoint of concern. Thus, occupational exposures to sublethal doses of CPF are consistently associated with problems in cognitive abilities, such as learning and memory but the biological mechanism(s) underlying this association remain speculative. To identify potential mechanisms of CPF neurotoxicity, we employed a rat model that simulated documented CPF exposures in Egyptian agricultural workers. We quantified mRNA expression profiles in the CA1 region of the hippocampus of adult male Long Evans (LE) rats administered CPF at 3 or 10 mg/kg/d (s.c.) for 21 days. Despite significant inhibition of cholinesterase activity by the end of the 21 d exposure period, the CPF-exposed rats displayed minimal signs of cholinergic toxicity. Distinct hippocampal mRNA and miRNA signatures were associated with CPF exposure. Toxicogenomics-based evidence identified increased expression of neuropeptide genes in the hippocampi of CPF-exposed rats, which have been shown to activate receptor-mediated signaling pathways involved in cell survival. The analysis of small non-coding RNA profiles suggested the possibility that miR132/212-mediated homeostatic regulatory pathways may also be activated by repeated exposures to CPF. These findings identify potential molecular effects that may contribute to neurobehavioral deficits.

60