The Protective Role Of Mitochondrial Ferritin On Hypoxia Induced SH-SY5Y Cell Damage

Iron is an essential element in all living organisms and is required as a cofactor for oxygen-binding proteins. In iron metabolism, oxygen homeostasis and erythropoiesis are consequently strongly interconnected. Iron metabolism needs to be tightly regulated, and its disruption would cause serious disease. For example, iron-deficiency induces a hypoferric anemia in humans, coupled to hypoxia in tissues, whereas iron overload is toxic, and causes severe oxidative damage. Therefore, the links between hypoxia and iron metabolism are important in studies. Previous studies show that hypoxia increases the intake of ferric iron (Fe3+), so that cells exposed to oxidative stress.Mitochondrial ferritin (MtFt) and H-ferritin have a high homology and many similarities on the function. Mature MtFt is localized in mitochondria and it has a very restricted Tissue-specific. MtFt was found highly expressed in spermatozoa in testis, neurons of brain cortex and spinal cord, where require high mitochondria metabolic activity and oxygen consumption. MtFt could store iron, to reduce the production of Fenton reaction, so it could protect mitochondria from oxidative stress damage. In addition, studies on the physiological function of MtFt may be useful for revealing mitochondria iron metabolism and finding possible therapeutic applications in involving increased iron deposition. Previous studies suggested that overexpression of MtFt caused a redistribution of iron from cytosol to mitochondria, thus high levels of MtFt resulted in an iron deficient phenotype in cytosol, and inhibited in vivo tumor growth due to cytosolic iron deprivation. To examine the role of MtFt in hypoxia induced neuroblastoma cell damage, we chose MtFt overexpressed SH-SY5Y as model, P10-3-SY5Y(blank vector) and SH-SY5Y as control, hypoxia as oxidative stress induced cell damage treating, using MTT, flow cytometry, and western blot to investigate the feature of MtFt-SY5Y cell, the results were as follows:1. Hypoxia increased the level of labile iron pool (LIP) and reactive oxygen species (ROS) in SH-SY5Y cells.2. Overexpression of MtFt inhibited HIF-1αprotein levels in SH-SY5Y cells caused by hypoxia. 3. Overexpression of MtFt inhibited labile iron pool levels in SH-SY5Y cells caused by hypoxia.4. Overexpression of MtFt inhibited ROS levels in SH-SY5Y cells caused by hypoxia.5. Overexpression of MtFt inhibited the reduce of mitochondrial membrane potential level in SH-SY5Y cells caused by hypoxia.6. Overexpression of MtFt inhibited cell apoptosis in SH-SY5Y cells caused by hypoxia.7. Overexpression of MtFt prevented the disorder of iron metabolism caused by hypoxia and maintained cellular iron homeostasis.Conclusion:In this study,we transfected MtFt gene into neurons SH-SY5Y and establish the hypoxia-induced oxidative stress model to investigate the function of MtFt and the relationship between iron metabolism and neuron oxidative stress.1. Our results firstly showed that MtFt played an impotant role in mitochondrial oxidative damage induced by hypoxia. It has two mechanisms.(1)MtFt inhibited HIF-1αprotein levels in SH-SY5Y cells caused by hypoxia and maintain the stability of Bcl-2 protein expression, thereby reducing apoptosis. (2)It reduces the generation of ROS,then prevented the reduction of mitochondrial membrane potential, inhibited cell apoptosis, thereby protected cells from oxidative stress damage.2. The expression of MtFt can effectively prevent the death of nerve cells caused by oxidative stress. Understanding the function and regulation mechanism of MtFt would become the focus of future studies, our work may provide a new effective strategy to treat the brain damage caused by cerebral hypoxia.