Cytotoxic effect of chlorpyrifos is associated with activation of Nrf-2/HO-1 system and inflammatory response in tongue of male Wistar rats

Repeated administration of chlorpyrifos (CPF), an organophosphate pesticide, can increase the risk of oral cytotoxicity. The current study was designed to assess the mechanism by which CPF mediates its cytotoxic effect on lingual mucosa of rats. Twenty-four male Wistar rats were used in the present study and divided into three groups: group I: healthy rats (negative control), group II: rats treated with CPF 1/40 LD50 (3.375 mg/kg, orally/daily) for 28 days, group III: rats treated with CPF 1/10 LD50 (13.5 mg/kg, orally/daily) for 28 days. At the end of the experiment, all rats were sacrificed by cervical dislocation under ketamine anesthesia. Tongue samples were dissected out at their base for detection of heme oxygenase-1 (HO-1) and nuclear erythroid 2-related factor 2 (Nrf-2) by western blotting and histopathological and electron microscopic studies. Immunostaining was used to determine cleaved caspase 3 and the nuclear factor kappa B (NF-kappa B) localization. Structural and ultrastructural examination of treated lingual mucosa with CPF demonstrated degenerative changes that involved both the dorsal and ventral surfaces of the tongue as well as the lingual glands. CPF-treated rats demonstrated a significant increase in the levels of pro-inflammatory cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF-alpha) in addition to a significant dose-dependent activation of NF-kappa B and cleaved caspase 3. Furthermore, CPF activated HO-1 and Nrf-2 pathway in a dose-dependent manner. In conclusion, this data suggests that the CPF-induced cytotoxicity may be explained by NF-kappa B activated inflammatory cascade. In addition, CPF triggers an adaptive activation of Nrf-2/HO-1 pathway.