GSK’872 Improves Prognosis of Traumatic Brain Injury by Switching Receptor-Interacting Serine/Threonine-Protein Kinase 3-dependent Necroptosis to Cysteinyl Aspartate Specific Proteinase-8-Dependent Apoptosis

Abstract

Traumatic brain injury (TBI) is an important health concern in the society. Previous studies have suggested that necroptosis occurs following TBI. However, the underlying mechanisms and roles of necroptosis are not well understood. In this study, we aimed to assess the role of receptor-interacting serine/threonine-protein kinase 3 (RIP3)-mediated necroptosis after TBI both in vitro and in vivo. We established a cell-stretching injury and mouse TBI model by applying a cell injury controller (CIC) and controlled cortical impactor (CCI) to evaluate the relationships among necroptosis, apotosis, inflammation, and TBI both in vitro and in vivo. The results revealed that necroptosis mediated by receptor-interacting serine/threonine-protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain-like protein (MLKL) was involved in secondary TBI. Additionally, protein kinase B (Akt), phosphorylated Akt (p-Akt), mammalian target of rapamycin (mTOR), and phosphorylated mTOR (p-mTOR) potentially contribute to necroptosis. The inhibition of RIP3 by GSK'872 (a specific inhibitor) blocked necroptosis and reduced the activity of Akt/mTOR, leading to the alleviation of inflammation by reducing the levels of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3). Moreover, the inhibition of RIP3 by GSK'872 promoted the activity of cysteinyl aspartate specific proteinase-8(Caspase-8), an enzyme involved in apoptosis and inflammation. These data demonstrate that RIP3 inhibition could improve the prognosis of TBI, based on the attenuation of inflammation by switching RIP3-dependent necroptosis to Caspase-8-dependent apoptosis.