Oridonin Ameliorates Alzheimer's Disease-Like Pathology in Male Mice Through Inhibition of Receptor-Interacting Protein Kinase 1.

Oridonin (Ori) is a bioactive diterpenoid from Rabdosia rubescens that exhibits potent anti-inflammatory and neuroprotective properties. However, its potential role in Alzheimer's disease (AD), especially in modulating receptor-interacting protein kinase 1 (RIPK1)-mediated neuroinflammation and necroptosis, remains unclear. This study aimed to investigate Ori's therapeutic mechanism in AD by targeting RIPK1. We utilized cellular thermal shift assay (CETSA), drug affinity responsive target stability assay (DARTS), and bio-layer interferometry (BLI) to verify the binding of Ori to RIPK1. In vitro, inflammatory and necroptotic responses were assessed in BV2 microglial cells and HT22 neuronal cells using enzyme-linked immunosorbent assay (ELISA), reverse transcription quantitative polymerase chain reaction (RT-qPCR), Western blotting, immunofluorescence, and flow cytometry assays. In vivo, we evaluated Ori's therapeutic efficacy in 5× FAD transgenic mice, a well-established AD model, through behavioral analysis using the Morris water maze, along with histological and biochemical assessments of brain tissues. Ori demonstrated a robust interaction with RIPK1 (K D = 533 nM) and significantly increased its thermal and proteolytic stability. Treatment with Ori markedly suppressed the secretion of pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFα) in microglia by inhibiting the RIPK1-ERK1/2-NF-κB signaling pathway. In neurons, Ori effectively blocked the activation of the RIPK1-RIPK3-MLKL signaling cascade, prevented necrosome formation, and significantly reduced necroptotic cell death. Importantly, in the 5× FAD mouse model, Ori treatment substantially improved spatial learning and memory performance, decreased amyloid-beta (Aβ) plaque deposition, and attenuated inflammatory and necroptotic markers in both cortical and hippocampal regions. Ori as a natural small-molecule inhibitor of RIPK1, capable of concurrently mitigating neuroinflammation and necroptosis-two critical pathological processes underpinning AD. These findings strongly support Ori's potential as a disease-modifying therapeutic for AD.