RIP1 and RIP3 mediate hemin-induced cell death in HT22 hippocampal neuronal cells

Xingfen Su,1 Handong Wang,2 Yuanxiang Lin,1 Fuxiang Chen1 1Department of Neurosurgery, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, People’s Republic of China; 2Department of Neurosurgery, Jinling Hospital, School of Medicine, Nanjing University, Nanjing 210002, Jiangsu, People’s Republic of China Background: Intracerebral hemorrhage (ICH) is a devastating neurological injury associated with significant mortality. Necroptosis is a newly identified type of programmed necrosis initiated by the activation of tumor necrosis factor alpha. Evidences had demonstrated the importance of necroptosis in neuronal cell death. Necrostatin-1 is a specific inhibitor of necroptosis. The present study was carried out to explore whether RIP1/RIP3 pathways participate in hemin induced cell death in HT-22 hippocampal neuronal cells and investigate the potential neuroprotection of necrostatin-1 in hemin induced cell death in HT-22. Methods: First, different concentrations of hemin (0, 25, 50, 100 µmol/L) were added to HT-22 cells. Propidium iodide (PI) positive cells and cell viability were measured at 24 hours after hemin treatment. Then, necrostatin-1, pan-caspase inhibitor Benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (z-VAD-fmk) and reactive oxygen species (ROS) scavenger butylated hydroxyanisole (BHA) were applied to hemin-treated HT-22 cells. PI positive cells and cell viability were measured at 24 hours after hemin treatment. MitoSox Red was used to indicate ROS level. Last, the effect of RIP3 in hemin induced HT-22 cell death was explored through RIP3 knockdown using siRNA. PI positive cells, cell viability and ROS lever were measured at 24 h after hemin treatment. Results: Hemin could induce a dose dependent cell death in HT22 neural cells. RIP1 specific inhibitor necrostatin-1 significantly inhibited cell death induced by hemin in HT-22 cells, greatly reducing PI positive cells, dramatically improving cell viability and decreasing ROS accumulation. BHA could significantly inhibit PI positive cells induced by hemin in HT-22 cells. Furthermore, silencing of RIP3 using siRNA attenuated hemin induced cell death in HT-22 cells, greatly reducing PI positive cells, dramatically improving cell viability and decreasing ROS accumulation. Conclusion: These data revealed that RIP1/RIP3 might mediate hemin induced cell death in HT-22 cells, and necrostatin-1 played a neuroprotection role in hemin induced cell death in HT-22. RIP1 and RIP3 might represent novel therapeutic targets for ICH. Keywords: intracerebral hemorrhage, necroptosis, HT22, RIP1, RIP3, necrostatin-1