Search

Tetrabromobisphenol A (TBBPA) is widely used in materials like plastics and textiles as a fire retardant. In a previous study, we reported TBBPA might disrupt hippocampal neurogenesis and neurocognitive function in mice. However, the mechanism responsible for these effects has not been established. The present study was undertaken to investigate the potential involvement of oxidative stress and mitochondrial dysfunction in TBBPA-mediated neurotoxicity in neural stem cells. We confirmed TBBPA was more cytotoxic to neural stem cells than to neurons, astrocytes, or fibroblasts, and found that TBBPA-induced neural stem cell apoptosis was accompanied by increased reactive oxygen species generation and mitochondrial dysfunction. At a molecular level, TBBPA-induced apoptosis was determined to be mediated by c-Jun N-terminal kinase-p53 pathway activation. Taken together, these findings suggest that the adverse effects of TBBPA on hippocampal neurogenesis are due to the inhibition of neural stem cell expansion.

Abstract: The mitochondrial adenine nucleotide translocators (Ant) are bi-functional proteins that transport ADP and ATP across the mitochondrial inner membrane, and regulate the mitochondrial permeability transition pore (mtPTP) which initiates apoptosis. The mouse has three Ant isoforms: Ant1 expressed in heart, muscle, and brain; Ant2 expressed in all tissues but muscle; and Ant4 expressed primarily in testis. Ant1-deficient mice manifest muscle and heart but not brain pathology. Brain Ant1 is induced by stress, while Ant2 is not. Ant1-deficient mice are resistant to death induced by systemic exposure to the brain excitotoxin, kainic acid (KA), and their hippocampal and cortical neurons are significantly more resistant to neuronal death induced by glutamate, KA, and etoposide. The mitochondrial membrane potential of Ant1-deficient brain mitochondria is increased and the mtPTP is more resistance to Ca++ induced permeability transition. Hence, Ant1-deficiency may protect the brain from excitotoxicity by desensitizing the mtPTP and by blocking the pro-apoptotic induction of Ant1 by stress. [Copyright &y& Elsevier]

Abstract: Mitochondria produce ATP, regulate apoptosis, and maintain calcium homeostasis, and thus, mitochondrial dysfunction critically impairs nervous system development. Furthermore, the disruption of oxidative phosphorylation (OXPHOS) in mitochondria could lead to energy depletion and elevate oxidative stress. In the present study, the authors investigated how perturbation of the respiratory chain and bioenergetics affects neural progenitor cells (NPCs). Mitochondrial OXPHOS was impaired by inhibiting electron transfer using the antimycin A and ATP synthase inhibitor oligomycin. It was found that oligomycin impaired NPCs proliferation and was toxic at high concentrations, whereas antimycin A-treated cells showed no changes in NPCs proliferation. Although ROS production was elevated concentration-dependently by both inhibitors, oligomycin-treated C17.2 NPCs, but not antimycin A-treated NPCs, showed a significantly higher cell death rate and lower levels of intracellular ATP. These findings suggest that bioenergetic considerations are critically important for cell viability regulation in NPCs. Taken together, the present study shows that OXPHOS disruption can have a neurotoxic effect on NPCs, and thus, adversely influence the developing brain and the neurogenic capacity of the adult brain. [Copyright &y& Elsevier]