The well-known toxicity of chlorpyrifos (CPF) occurs via inhibition of cholinesterase (ChE), but in recent years the detrimental effects of low-dose CPF exposure have been attributed to an unknown non-cholinergic mechanism of action. We previously showed that CPF can alter gene expression of transient receptor potential canonical (TRPC) channels in vitro. In this study, we analyzed the gene expression of TRPCs at various time points after CPF treatment in vivo. The results showed that TRPC1 mRNA expression in mouse brain was significantly reduced 2-8 h after CPF treatment, but the TRPC4 mRNA expression was not significantly changed. To investigate the possible involvement of Transforming Growth Factor-beta1 (TGF-beta1) in contributing to TRPCs gene alteration by CPF, we used TGF-beta receptor inhibitor (LY2109761) as a pretreatment prior to CPF treatment. The serum TGF-beta1 concentration was significantly increased 24 h after CPF treatment. After pretreatment with LY2109761, both TRPC1 and TRPC5 mRNAs were significantly downregulated 1 and 2 h after CPF treatment, but were significantly upregulated 3 and 24 h after CPF treatment. TRPC4 mRNA was also significantly downregulated at 1 h. These results suggest that interference with ion channels, a non-cholinergic mechanism of CPF, may contribute to the cellular neurotoxicity of CPF.
