TLR4-antagonizing bioactive components from Blaps rynchopetera polysaccharide-glycoprotein complex: Biolayer interferometry-mass spectrometry identification and NF-κB-mediated anti-inflammation.

ETHNOPHARMACOLOGICAL RELEVANCE: Blaps rynchopetera Fairmaire (Coleoptera: Tenebrionidae), a traditional medicinal insect employed by the Yi and Dai ethnic communities in Yunnan, China, has long been utilized for treating inflammatory conditions such as fever, mumps, and gastritis. Its potential application in managing symptoms akin to neuroinflammatory disorders provides an ethnopharmacological basis for this investigation. However, the bioactive components underpinning its anti-inflammatory properties, particularly its polysaccharides, remain poorly investigated.

AIM OF THE STUDY: This study aimed to isolate the polysaccharide fraction from Blaps rynchopetera Fairmaire (BRPs), characterize its structure, and evaluate its anti-neuroinflammatory activity in cellular and animal models, with a focus on the TLR4/NF-κB pathway.

MATERIALS AND METHODS: BRPs were extracted from whole insects using hot water and purified by ethanol precipitation. Structural characterization was performed via HPAEC-PAD, GPC-RI-MALS, SEM, and FT-IR. The anti-neuroinflammatory effects and TLR4/NF-κB or MAPK signaling pathway were investigated in LPS-stimulated primary microglia and a TLR4-overexpressing (TLR4-OE) HEK293 cell model for target validation. TLR4-binding components within BRPs were identified using the affinity-based technique of biolayer interferometry-mass spectrometry (BLI-MS). The in vivo efficacy of the TLR4-affinity enriched fraction (BRPs-AEF) was further assessed in a mouse model of transient middle cerebral artery occlusion/reperfusion (MCAO/R).

RESULTS: BRPs was a polysaccharide-glycoprotein complex containing 77.88% carbohydrates (dominant glucose and galactose) and 8.51% protein, with a porous microstructure and α-glycosidic linkages. In primary microglia, BRPs dose-dependently suppressed LPS-induced production of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), and inhibited the activation of TLR4/NF-κB activation and MAPK signaling pathways. Using a BLI-MS strategy, 10 unique TLR4-binding proteins (e.g., WH2 domain proteins and calreticulin) and 21 interaction peptides were identified within BRPs. This TLR4-mediated mechanism was functionally validated in TLR4-OE cells. In MCAO/R mice, BRPs-AEF significantly reduced cerebral infarction, improved neurological deficits, attenuated neuroinflammation, and preserved neuronal integrity in a murine stroke model.

CONCLUSIONS: These results demonstrate that BRPs from B. rynchopetera alleviate neuroinflammation through multi-target mechanisms, with the TLR4/NF-κB pathway being a major and directly validated target. This work provides pharmacological insights supporting the traditional use of this insect and illustrates a targeted approach for identifying bioactive constituents from complex mixtures.