Andrographolide ameliorates depressive-like behavior by targeting the CyPA–IκBα/NF-κB axis: an APOE-isoform–dependent mechanism in chronic social defeat stress
Description
Hypothesis: We hypothesized that chronic social defeat stress (CSDS) activates the CyPA–IκBα/NF-κB–MMP9 pro-inflammatory axis in the medial prefrontal cortex (mPFC) in an APOE‑isoform‑dependent manner, and that the natural compound andrographolide ameliorates depressive‑like behavior by suppressing this axis and restoring neurotrophic support. Data and methods: CSDS was induced in male C57BL/6J mice. Depressive‑like behavior was quantified by forced swim test (FST) and tail suspension test (TST). mPFC tissue was analyzed by Western blot, MALDI‑TOF mass spectrometry, co‑immunoprecipitation (Co‑IP), and transmission electron microscopy (TEM). In vivo electrophysiology recorded pyramidal neuron firing. Network pharmacology, two‑sample Mendelian randomization (MR), molecular docking, molecular dynamics (MD) simulations (100 ns), and in silico APOE4 knockout (scMAGeCK) were used to predict and validate molecular interactions and pathway enrichment. Key findings: CSDS mice showed increased immobility in FST/TST, mPFC mitochondrial damage, reduced pyramidal neuron firing, elevated CyPA, IL‑6, TNF‑α, MMP9, PD‑1/PD‑L1, and decreased IκBα and BDNF. Co‑IP and MD simulations confirmed CyPA–IκBα interaction. MR indicated causal links of TNF‑α and IL‑6 with MDD risk. Andrographolide (5 mg/kg/day, i.p.) reversed all behavioral, ultrastructural, molecular, and electrophysiological abnormalities. Docking showed andrographolide binds CyPA (−8.2 kcal/mol) and IκBα (−5.8 kcal/mol); MD suggested it may stabilize IκBα via a methylation‑associated conformation. Bortezomib (proteasome inhibitor) produced similar effects; combined andrographolide+bortezomib yielded enhanced improvements. CSDS increased APOE4 and decreased APOE3 protein levels; andrographolide normalized this balance. In silico APOE4 knockout identified NF‑κB as the top pathway, and MD indicated APOE4 binds CyPA less efficiently than APOE3, potentially impairing CyPA clearance. Interpretation: The CyPA–IκBα/NF‑κB–MMP9 axis is a critical driver of CSDS‑induced neuroinflammation and depressive‑like behavior. Andrographolide acts on this axis at multiple nodes—CyPA and IκBα—and modulates APOE isoform expression. The convergence of effects with bortezomib and the enhanced combination outcome support a causal, targetable role for this axis. These data nominate andrographolide as a candidate for neuroinflammation‑associated MDD and provide a mechanistic framework linking APOE4 to exacerbated inflammatory signaling in depression.