Byline: Bao-You. Fan, Yi-Lin. Pang, Wen-Xiang. Li, Chen-Xi. Zhao, Yan. Zhang, Xu. Wang, Guang-Zhi. Ning, Xiao-Hong. Kong, Chang. Liu, Xue. Yao, Shi-Qing. Feng
Our previous studies showed that ferroptosis plays an important role in the acute and subacute stages of spinal cord injury. High intracellular iron levels and low glutathione levels make oligodendrocytes vulnerable to cell death after central nervous system trauma. In this study, we established an oligodendrocyte (OLN-93 cell line) model of ferroptosis induced by RSL-3, an inhibitor of glutathione peroxidase 4 (GPX4). RSL-3 significantly increased intracellular concentrations of reactive oxygen species and malondialdehyde. RSL-3 also inhibited the main anti-ferroptosis pathway, i.e., SLC7A11/glutathione/glutathione peroxidase 4 (xCT/GSH/GPX4), and downregulated acyl-coenzyme A synthetase long chain family member 4. Furthermore, we evaluated the ability of several compounds to rescue oligodendrocytes from ferroptosis. Liproxstatin-1 was more potent than edaravone or deferoxamine. Liproxstatin-1 not only inhibited mitochondrial lipid peroxidation, but also restored the expression of GSH, GPX4 and ferroptosis suppressor protein 1. These findings suggest that GPX4 inhibition induces ferroptosis in oligodendrocytes, and that liproxstatin-1 is a potent inhibitor of ferroptosis. Therefore, liproxstatin-1 may be a promising drug for the treatment of central nervous system diseases.
After traumatic central nervous system (CNS) injury, significant oligodendrocyte loss occurs as a result of secondary injury (Lytle and Wrathall, 2007; Oyinbo, 2011; Scheller et al., 2017). Death of oligodendrocytes leads to demyelination, which accounts for poor functional recovery. Because of low levels of glutathione (GSH) and high levels of iron, oligodendrocytes are highly susceptible to oxidative damage (Thorburne and Juurlink, 1996; Juurlink et al., 1998). Low glutathione and high iron are also key inducers of ferroptosis, a recently-discovered form of regulated cell death (Dixon et al., 2012). However, ferroptosis in oligodendrocytes has not been well-studied.
Glutathione peroxidase 4 (GPX4) is a central regulator of ferroptosis (Yang et al., 2014). In the spinal cord, GPX4 is mainly expressed in neurons and oligodendrocytes, but not in astrocytes (Hu et al., 2019). Numerous studies have investigated the mechanisms of ferroptosis in neurons (Chen et al., 2015; Zhang et al., 2018, 2020; Kenny et al., 2019; Chu et al., 2020). GPX4 plays a pivotal role in neuronal ferroptosis. Knockout of GPX4 in neurons results in ferroptosis (Chen et al., 2015). After spinal cord injury, GPX4 is downregulated, and the ferroptosis inhibitor SRS 16-86 and deferoxamine (DFO) can prevent this reduction in GPX4 and improve the survival of neurons in the injured spinal cord (Yao et al., 2019; Zhang et al., 2019). GPX4 is localized to the nucleus in oligodendrocytes in vivo , in contrast to the neuronal cytoplasmic localization (Hu et al., 2019). However, whether GPX4 also plays a key role in oligodendrocyte survival has not been investigated.
RSL-3 was discovered before ferroptosis, and it increases lethality in the presence of oncogenic Ras. RSL-3 was demonstrated to induce ferroptosis (Yang and Stockwell, 2008). Further research demonstrated that RSL-3 binds to and inhibits GPX4 (Yang et al., 2014). GPX4 is decreased during ferroptosis in intracerebral hemorrhage and spinal cord injury...