Caffeic acid phenethyl ester attenuates inflammatory pain through promoting spinal microglial M1-to-M2 polarization by suppressing the PI3K/Akt/NF-κB pathway and attenuating peripheral inflammation

Inflammatory pain is a major global health challenge, significantly affecting quality of life and emotional well-being. Current treatment options are limited and often accompanied by adverse effects. Caffeic acid phenethyl ester (CAPE), a natural compound with notable anti-inflammatory properties, has not yet been fully elucidated for its efficacy in inflammatory pain. This work examined the role of CAPE in modulating inflammatory pain. Inflammatory pain was induced in mice by administration of Complete Freund's Adjuvant (CFA), and pain relief was assessed through mechanical and thermal sensitivity tests. Combined with network pharmacology and molecular docking analysis, the PI3K/Akt/NF-κB pathway was identified as a potential therapeutic target. Further validation was performed using Western blot, immunofluorescence, qRT-PCR, toe thickness measurement, and H&E staining of the plantar skin sections. CAPE administration produced significant reductions in CFA-induced pain and anxiety-like behaviors. Intraperitoneal administration of CAPE significantly suppressed the phosphorylation of PI3K, Akt, and NF-κB in microglia, reduced the expression of M1 microglial marker CD86 and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), and increased the expression of M2 marker CD206 and anti-inflammatory cytokines (IL-4, IL-10). Additionally, CAPE reduced paw edema and inflammatory factor levels in toe tissue. In vitro experiments further confirmed that CAPE induced the polarization of microglia from the M1 to M2 phenotype. Our results demonstrate that CAPE facilitates the transition of microglia to the M2 phenotype mediated by the PI3K/Akt/NF-κB pathway, which attenuates peripheral inflammation and subsequently diminishes inflammation-induced hypersensitivity. These results offer novel perspectives on the possible therapeutic applications of CAPE in the management of inflammatory pain.