Role of mitochondria in neuronal cell death induced by oxidative stress; neuroprotection by Coenzyme Q10

Neuronal cells depend on mitochondrial oxidative phosphorylation for most of their energy needs and therefore are at a particular risk for oxidative stress. Mitochondria play an important role in energy production and oxidative stress-induced apoptosis. In the present study, we have demonstrated that external oxidative stress induces mitochondrial dysfunction leading to increased ROS generation and ultimately apoptotic cell death in neuronal cells. Furthermore, we have investigated the role of Coenzyme Q10 as a neuroprotective agent. Coenzyme Q10 is a component of the mitochondrial respiratory chain and a potent anti-oxidant. Our results indicate that total cellular ROS generation was inhibited by Coenzyme Q10. Further, pre-treatment with Coenzyme Q10 maintained mitochondrial membrane potential during oxidative stress and reduced the amount of mitochondrial ROS generation. Our study suggests that water-soluble Coenzyme Q10 acts by stabilizing the mitochondrial membrane when neuronal cells are subjected to oxidative stress. Therefore, Coenzyme Q10 has the potential to be used as a therapeutic intervention for neurodegenerative diseases.

Paraquat induces oxidative stress and neuronal cell death; neuroprotection by water-soluble Coenzyme Q10

Neuronal cell death induced by oxidative stress is correlated with numerous neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and stroke. The causes of sporadic forms of age-related neurodegenerative diseases are still unknown. Recently, a correlation between paraquat exposure and neurodegenerative diseases has been observed. Paraquat, a nonselective herbicide, was once widely used in North America and is still routinely used in Taiwan. We have used differentiated Human Neuroblastoma (SHSY-5Y) cells as an in vitro model to study the mechanism of cell death induced by paraquat. We observed that paraquat-induced oxidative stress in differentiated SHSY-5Y cells as indicated by an increase in the production of cellular reactive oxygen species (ROS). Furthermore, apoptosis was evident as indicated by cellular and nuclear morphology and DNA fragmentation. Interestingly, pretreatment of SHSY-5Y cells with water-soluble Coenzyme Q10 (CoQ10) before paraquat exposure inhibited ROS generation. Pretreatment with CoQ10 also significantly reduced the number of apoptotic cells and DNA fragmentation. We also analyzed the effect of paraquat and CoQ10 on isolated mitochondria. Our results indicated that treatment with paraquat induced the generation of ROS from isolated mitochondria and depolarization of the inner mitochondrial membrane. Pretreatment with CoQ10 was able to inhibit ROS generation from isolated mitochondria as well as the collapse of mitochondrial membrane potential. Our results indicate that water-soluble CoQ10 can prevent oxidative stress and neuronal damage induced by paraquat and therefore, can be used for the prevention and therapy of neurodegenerative diseases caused by environmental toxins.