Oxidative stress is a cellular imbalance between production and elimination of reactive oxygen species (ROS). ROS associated apoptosis has been implicated as an important feature in stroke and neurodegenerative diseases. However, the mechanisms underlying ROS-induced apoptosis are still not clearly understood yet. The major objective of this research is to study the signaling pathways involved in oxidative stress-related apoptosis in neuronal cells. This study involves three parts. First, we established a model system of ROS-induced apoptosis in neuronal cells by using SK-N-SH human neuroblastoma cell line and hydrogen peroxide (H₂O₂) as the ROS inducer. Second, we investigated the functional roles of calcium (Ca²⁺) signaling and poly(ADP-ribose) polymerase (PARP) signaling in regulatin...[ Read more ]

Oxidative stress is a cellular imbalance between production and elimination of reactive oxygen species (ROS). ROS associated apoptosis has been implicated as an important feature in stroke and neurodegenerative diseases. However, the mechanisms underlying ROS-induced apoptosis are still not clearly understood yet. The major objective of this research is to study the signaling pathways involved in oxidative stress-related apoptosis in neuronal cells. This study involves three parts. First, we established a model system of ROS-induced apoptosis in neuronal cells by using SK-N-SH human neuroblastoma cell line and hydrogen peroxide (H₂O₂) as the ROS inducer. Second, we investigated the functional roles of calcium (Ca²⁺) signaling and poly(ADP-ribose) polymerase (PARP) signaling in regulating the progression of ROS-induced apoptosis. We observed a biphasic Ca²⁺ elevation in the cytosol and a transient PARP activation following H₂O₂ treatment. The Ca²⁺ signal appears to mediate the ROS-induced mitochondria damage, including mitochondrial membrane potential (ΔΨm) decrease, mitochondria fission and cytochrome c release, since pretreatment of cells with BAPTA/AM, an intracellular Ca²⁺ chelator, inhibited the response induced by H₂O₂ on mitochondrial damage and prevented cells to undergo apoptosis. Pretreatment of cells with PARP inhibitor DPQ, on the other hand, only slightly prevented ΔΨm decrease and failed to block mitochondria fission or cytochrome c release, although the apoptotic cell death was still suppressed. Results of this study thus suggest that both Ca²⁺ mediated mitochondria-dependent signaling pathway and PARP mediated mitochondria-independent signaling pathway are involved in oxidative stress-induced neuronal cell death. Third, we also examined the signaling pathway downstream of mitochondria in H₂O₂-induced apoptosis. We found evidence suggesting that both the caspase-dependent and caspase-independent pathways are involved in our model system. Finally, we used our model system to evaluate whether one can prevent ROS-induced neuronal cell death by using a combination of drugs that block the ROS, Ca²⁺ elevation and PARP signaling. We have examined the effects of different combination treatments on oxidative stress-related cell death. Our results suggest that certain treatments can significantly reduce the damage caused by ROS-induced neuronal cell death. These treatments may be developed into novel anti-stroke therapy in the future.