Sub-chronic administration of benzo[a]pyrene disrupts hippocampal long-term potentiation via inhibiting CaMK II/PKC/PKA-ERK-CREB signaling in rats.

Benzo[a]pyrene (B[a]P) is recognized as a neurotoxic pollutant to mammals, which could impair learning and memory function. Although there is some evidence to suggest that N-methyl-d-aspartate receptor (NMDAR), a glutamate receptor and ion channel protein in nerve cells, is involved into the B[a]P induced neurotoxicity, the exact molecular mechanisms remain to be elucidated, particularly the effects of B[a]P on the NMDAR downstream signaling transduction pathways. In the present study, we examined the neurotoxicity of sub-chronic administrated B[a]P on male Sprague-Dawley rats. Our data suggested that B[a]P exposure caused significant deficits in learning and memory function and the impairment of hippocampal LTP in rats. Further mechanistic studies indicate that B[a]P-induced learning and memory deficits are associated with the inhibition of NMDAR NR1 subunit transcription and protein phosphorylation. More importantly, the inactivation of CaMK II/PKC/PKA-ERK-CREB signaling pathways in hippocampus was detected at both the 2.5 and 6.25 mg/kg B[a]P-treated groups, indicating that multiple targets in NMDAR and downstream signaling pathways are involved in the B[a]P-induced neurotoxicity.

Benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide induces ferroptosis in neuroblastoma cells through redox imbalance.

As a widespread environmental pollutant, benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE)-induced neurotoxicity has received increasing attention. Studies have shown that BPDE-induced neurodegeneration is due partly to neuronal apoptosis. Unlike apoptosis, ferroptosis is a non-apoptotic form of programmed cell death, but its specific role in the neurotoxicity of BPDE remains unclear. In this work, we investigated the ferroptosis in BPDE-induced cell death in human neuroblastoma cell line SH-SY5Y using a specific pharmacological inhibitor. Lipid peroxides, malondialdehyde production, glutathione / glutathione peroxidase activity, superoxide dismutase activity, and iron content were evaluated. Consistent with previous studies, our data showed that 0.5 µM BPDE poisoning for 24 hr could induce cell apoptosis and that cell survival could be improved by using apoptosis inhibitors. But with prolonged exposure time (72 hr) or increased exposure dose (1.0 µM), we have elucidated and validated that BPDE triggered ferroptosis in human SH-SY5Y cells. We also revealed that suppression of ferroptosis by specific inhibitors, ferrostatin-1 and deferoxamine, significantly rescued the phenotypes of ferroptosis induced by BPDE. BPDE downregulated Nrf2 and its target genes related to redox regulation, GPX4 and SLC7A11, but upregulated HO-1. Our results first demonstrated that BPDE caused cytotoxic effects on cell death via apoptosis and ferroptosis. Most notably, long-term environmental exposure to BPDE becomes a concern due to ferroptosis. Redox imbalance is controlled by the Nrf2, SLC7A11, and HO-1, through which lipid peroxides and ferrous ion accumulation cause ferroptosis after BPDE treatment. These findings highlight that targeting ferroptosis could serve as an effective protective strategy for neurotoxicity of BPDE.