Inhibition of receptor-interacting protein 3 upregulation and nuclear translocation involved in Necrostatin-1 protection against hippocampal neuronal programmed necrosis induced by ischemia/reperfusion injury.

Receptor-interacting protein 3 (RIP3) is a key molecular switch in tumor necrosis factor-induced necroptosis requiring the formation of an RIP3-RIP1 complex. We have recently shown that hippocampal cornu ammonis 1 (CA1) neuronal death induced by 20-min global cerebral ischemia/reperfusion (I/R) injury is a form of programmed necrosis. However, the mechanism behind this process is still unclear and was studied here. Global cerebral ischemia was induced by the four-vessel occlusion method and Necrostatin-1 (Nec-1), a specific inhibitor of necroptosis, was administered by intracerebroventricular injection 1h before ischemia. Normally, in the hippocampal CA1 neurons, RIP1 and RIP3 are located in the cytoplasm. However, after I/R injury, RIP3 was upregulated and translocated to the nucleus while RIP1 was not affected. Nec-1 pretreatment prevented hippocampal CA1 neuronal death and I/R induced changes in RIP3. Decreased level of NAD+ in hippocampus and the release of cathepsin-B from lysosomes after I/R injury were also inhibited by Nec-1. Our data demonstrate that Nec-1 inhibits neuronal death by preventing RIP3 upregulation and nuclear translocation, as well as NAD+ depletion and cathepsin-B release. The nuclear translocation of RIP3 has not been reported previously, so this may be an important role for RIP3 during ischemic injury.