The Effects Of Antioxidant Transcription Factor NRF2 Overexpression On Cell Fate In Different Environments

Cell death and survivor are important parts of Cell fate, which are affected by many factors. ROS generated as a toxic by-product of oxidative energy production by OXPHO; which damage the mitochondrial and cellular DNA, proteins, lipids, and other molecules causing oxidative stress. An increase in oxidative stress has independently been implicated in cellular senescence. Senescence can be observed in normal human fibroblasts and Mouse Embryonic Fibroblast (MEF) in culture, which have a finite replicative life span and then become permanently arrested. The expression of proto-oncogene c-myc, loss or mutations of tumor suppressor gene p53, as well as some overexpression of glycolysis metabolism genes can achieve the reprogramming of cells, shift metabolism and destiny of MEF, inhibit the increase in ROS and cell toxicity caused by aging, so as to make the cells occur immortality.The main function of the transcription factor NRF2 is to activate the cellular antioxidant response by inducing the transcription of several genes to protect cells from the effects of exogenous and endogenous insults such as xenobiotics and oxidative stress. NRF2 also affects multiple aspects of intermediary metabolism and mitochondrial function, and so influences the synthesis of carbohydrates, nucleic acids, lipids, and amino acids. In view of the implication of oxidative stress in MEF senescence and the capacity of NRF2 to reduce oxidative stress levels, affect metabolism, protect cells from various stresses, we studied the involvement of NRF2 in oxidative stress-induced senescence and how conditions of NRF2 expression may modulate oxidative stress balance to achieve different cell fate outcomes.We over express mutant oxidation resistance transcription factor NRF2 by lentivirus in MEF cells, activate expression of NRF2 downstream genes, and then detect the cell growth and cell immortalized situation. Our experimental results show that, the overexpression of NRF2 is not conducive to the proliferation of cell growth in the early stage of the MEF. We find that the cells have significantly suppressed intracellular ROS level, decreased cell proliferation and increased senescence. However, as the oxidative stress and toxic substances of inner and outer cell increased within the cultured cells in vitro, strengthening NRF2 regulating the antioxidant capacity is beneficial to the growth and survival of cell. Therefore, the cells have different fates by expressing NRF2 to inhibit oxidative stress level in the different periods of MEFs.On the other hand, the mitochondrial membrane potential and ATP production also decrease in the early stage of the MEF with NRF2 overexpression, which reflect that the NRF2 take part in the regulation of cell metabolism and mitochondrial function. Surprisingly, the expression of another important oxidation resistance gene FOXO3 can extend the limited life span of cells to some extent, and rescue NRF2 effects on cells, which suggest the effects of the two factors on cell fate are different and may have some relationships. These clues will help us to further reveal more content about the NRF2 effects on cells.