DIFFERENTIATION-INDUCED CHANGES IN ANTIOXIDANT CAPACITY AND ANTIOXIDANT RESPONSE IN SH-SY5Y CELLS: ROLE OF NRF2
Organisms are exposed to reactive oxygen species from internal metabolism and environmental toxicant exposure, which have been linked to the initiation and progression of many neuronal diseases such as Alzheimer’s and Parkinson’s diseases. Exposure to reactive oxygen species are counterbalanced by antioxidant defense systems such as the Nrf2-ARE pathway, the primary regulator of endogenous antioxidant response. Whereas neuronal cells are post-mitotic and are particularly susceptible to oxidative stress because of high oxygen consumption, astrocytes are mitotic and rely more on glycolytic metabolism. In this study, the difference in antioxidant response and capacity in mitotic and post-mitotic cells were investigated using undifferentiated and differentiated SH-SY5Y neuroblastoma cells. The investigations of this study focused on the induction of antioxidant enzymes in SH-SY5Y cells by Nrf2 using tert-Butylhydroquinone (tBHQ). The levels of GSH, Mn-SOD, HO and OGG1 which are all induced by Nrf2 were determined. The results of the experiment showed that differentiated (post-mitotic) and undifferentiated (mitotic) cells responded similarly to Nrf2 induction as was observed in the higher levels of GSH, HO, Mn-SOD and OGG1 compared to the control group. As compared to undifferentiated cells, differentiated cells had relatively lower antioxidant levels except in the case of Mn-SOD. This suggests that post-mitotic and mitotic cells respond to antioxidant induction similarly but differ in their antioxidant capacities. The study also compared DTNB and HPLC methods in determining GSH levels in these cells. The outcome of the experiments showed that HPLC offers a selective method in determining GSH levels.
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