RIP1K Contributes to Neuronal and Astrocytic Cell Death in Ischemic Stroke via Activating Autophagic-lysosomal Pathway

Yong Ni, Wei-Wei Gu, Zhi-He Liu, Yong-Ming Zhu, Jia-Guo Rong, Thomas A. Kent, Min Li, Shi-Gang Qiao, Jian-Zhong An, Hui-Ling Zhang

Although the receptor-interacting protein 1 kinase (RIP1K)-regulated necroptosis can be evoked by cerebral ischemia, the effects of RIP1K in mediating neuronal and astrocytic cell death and the underlying mechanisms remain poorly understood. This study evaluates the contribution of RIP1K to ischemic stroke-induced neuronal and astrocytic cell death, and the activation of autophagic-lysosomal pathway. Using an in vitro oxygen and glucose deprivation (OGD) in primary cultured neurons or astrocytes and a permanent middle cerebral artery occlusion (pMCAO) model in rats or mice, we observed the role of RIP1K in the ischemic neuronal and astrocytic cell death and the underlying mechanisms by pharmacological or genetic inhibition of RIP1K. pMCAO or OGD condition led to an increase in RIP1K, RIP3K and RIP1K-RIP3K complex. RIP1K knockdown or necrostatin-1 (Nec-1, a specific inhibitor of RIP1K) treatment reduced infarct volume, improved neurological deficits, increased microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP) levels, and attenuated neuronal or astrocytic necrotic cell death in the ischemic cortex. RIP1K knockdown decreased RIP1K-RIP3K complex formation, light chain 3 II (LC3II) and active cathepsin B levels and lysosomal membrane permeability (LMP). Furthermore, a combination of Nec-1 and an inhibitor of autophagy or cathepsin B produced an enhancement of protective effect on neuronal or astrocytic cell death. RIP1K-mediated necroptosis may play important roles in ischemia-induced neuronal and astrocytic cell death through the activation of autophagic-lysosomal pathway.