Ph.D Researcher CHA medical center Seongnam, Republic of Korea
Abstract: Traumatic optic neuropathy leads to irreversible vision loss due to ischemia and inflammation-induced apoptosis of optic-nerve axons. Models of retinal ganglion cell and optic nerve degeneration involve induction by chemicals (cobalt chloride, LPS, and N-methyl-D-aspartate), mechanical stress (optic nerve compression, light), and ischemia (transient retinal ischemia). Although exposure to severe hypoxia in R28 cells, and retinal precursor cells (RPCs) with retinal phenotypes, such as glial or retinal ganglion cells, can cause cell damage and alter mitochondrial metabolism, the effects and mechanisms of hypoxic conditions on these cells are unclear. Cobalt chloride (CoCl2) is used to mimic hypoxia in the retina and in in vitro models of optic-nerve injury. In this study, CoCl2 was used to cause hypoxic damage to R28 cells, which were subsequently transferred to a hypoxic chamber. The levels of proteins related to hypoxia, mitochondrial homeostasis, neuro-regeneration, and retinal ganglion-like cell markers were investigated by immunoblotting. Additionally, the expression levels of genes associated with ferroptosis were evaluated. Mitochondrial respiration, glycolysis, and ATP synthesis were analyzed using the Seahorse XF. After transfer to a 0.3% hypoxic chamber following CoCl2-induced hypoxic damage, the viability of RPCs was increased compared to the control. Mitochondrial ATP production, which was reduced by CoCl2, was restored in the 0.3% hypoxic chamber. Additionally, the expression levels of ferroptosis-related SUMO specific peptidase 1 (Senp1), glutathione peroxidase 4 (Gpx4), and transferrin receptor (Tfrc) were increased. Furthermore, the reductions in the levels of the neuro-regeneration markers Nf, Gap43, Stx12, and Brn3a were reversed. The 0.3% O2 hypoxic chamber rescued RPC mitochondrial homeostasis from CoCl2-induced hypoxic damage using a hypoxia mimic, thereby reducing ROS production and inhibiting ferroptosis. Thus, hypoxic conditions are implicated in the induction of, and recovery from, apoptosis or ferroptosis through mitochondrial regulation in RPCs. Therefore, we suggested that 0.3% O2 hypoxic chamber has significant neuroprotective potential.
Funding Source: This research was supported by grants from the National Research Foundation of Korea (NRF): 2021R1A2C2010523.
