Functional suppression of Ripk1 blocks the NF-κB signaling pathway and induces neuron autophagy after traumatic brain injury

Traumatic brain injury (TBI), known as intracranial injury, has been a serious threat to human health. Evidence exists indicating that autophagy and inflammatory responses contribute to secondary brain injury after TBI. Notably, receptor-interacting protein kinase 1 (Ripk1) exerts an important role in cell autophagy. Therefore, this study aims to explore the effect of Ripk1 on neuron autophagy and apoptosis in TBI. Initially, blood samples of patients with TBI and healthy persons were collected to detect the expression of Ripk1, nuclear factor-kappa B (NF-kappa B), and NF-kappa B inhibitor alpha (IKB alpha). Then rat models with TBI were successfully established and, respectively, treated with shRNA targeting Ripk1 (sh-Ripk1), Ripk1 overexpression plasmid (oe-Ripk1), or IKK alpha inhibitor (BAY 11-7082). Subsequently, reverse transcription quantitative polymerase chain reaction and Western blot analysis were conducted to detect the expression of Ripk1, IKB alpha, NF-kappa B signaling pathway-, and apoptosis-related factors. Enzyme-linked immunosorbent assay was used to detect the expression of inflammatory cytokines. Compared with healthy persons, the expression of Ripk1, NF-kappa B and IKB alpha in blood of TBI patients was significantly upregulated. After silencing of Ripk1 or inhibition of the NF-kappa B signaling pathway, the expression of IL-1 beta, IL-6, TNF-alpha Bax, and cleaved-caspase-3 was downregulated, and the expression of Bcl-2, ATG5, and LC3II/LC3I was upregulated. Furthermore, neuron injury and apoptosis were notably reduced and neuron autophagy increased significantly by Ripk1 downregulation or IKK alpha inhibitor. Ripk1 overexpression contributed to activation of NF-kappa B signaling pathway, whereby aggravating TBI-induced damage. Silencing Ripk1 suppresses TBI by inhibiting inflammation and promoting autophagy of neurons via inhibition of NF-kappa B signaling pathway.