Tetrachlorobenzoquinone triggers the cleavage of Bid and promotes the cross-talk of extrinsic and intrinsic apoptotic signalings in pheochromocytoma (PC) 12 cells

• TCBQ induces apoptosis in PC12 cells.
• TCBQ-induced apoptosis involved in both extrinsic and intrinsic signals.
• TCBQ activates caspase 8 and triggers the cleavage of Bid.
• TCBQ-induced tBid promotes the caspase family amplification loop.
• TCBQ-induced apoptotic signals are ROS dependent.

Although there are few studies suggested PCP exposure induced developmental and behavioral disorders, however, the occurrence of neurotoxicity and PCP has not been firmly established. Tetrachlorobenzoquinone (TCBQ) is a reactive metabolite of environmental pollutant pentachlorophenol (PCP). To the best of our knowledge, there has no information regarding to the neurological toxic effect of TCBQ available. Here, we demonstrated that TCBQ induces cytotoxicity in pheochromocytoma PC12 cell line, and the mode-of-action analysis indicated the involvement of apoptotic signalings, such as the activation of caspase family proteins, the increased expressions of Fas and Fas-associated death domain (FADD), the loss of mitochondrial membrane potential (MMP), the release of cytochrome c (Cyt c) and the cleavage of the caspase substrates poly(ADP-ribose) polymerase (PARP). BI-6C9, a specific BH3-interacting domain death agonist (Bid) inhibitor, repressed TCBQ-induced Bid truncation, along with the activation of caspase 3 and the release of Cyt c, suggested the cross-talk of extrinsic and intrinsic apoptotic signalings. Furthermore, the inhibition of caspase 8 impaired TCBQ-induced the activation of caspase 3, as well as the release of Cyt c and the cleavage of Bid, suggesting caspase 8 acting as the upstream molecule of Bid, and TCBQ-induced apoptosis is initiated via caspase 8, leads to the activation of caspase 9/3 through Bid-mediated amplification loop. Finally, the pretreatment of antioxidant NAC ameliorated Fas, FADD and caspase 8/3 expressions, which illustrated that TCBQ-induced apoptotic signaling is ROS dependent. Taken together, these results indicated that the cleavage of Bid may play an important role in TCBQ-induced neurotoxicity which promotes the cross-talk of extrinsic and intrinsic apoptotic signalings in PC12 cells.