Highly Soluble Mussel Foot Protein and Its Derivatives Inhibit Inflammation by Targeting NF-κB/PI3K-Akt Signaling and Promoting M2 Macrophage Polarization

Chronic inflammation is closely associated with various diseases, underscoring the need for natural, biocompatible anti-inflammatory candidates. For this purpose, mussel foot protein could be an excellent candidate due to its diverse biological activities. Hence, this study systematically evaluates the anti-inflammatory effects of a highly soluble mussel foot protein (HMFP) and HMFP-PEG using LPS-stimulated RAW264.7 cells as an in vitro inflammation model. The results reveal that both HMFP and HMFP-PEG markedly reduced intracellular reactive oxygen species (ROS) levels and suppressed the secretion of pro-inflammatory mediators, including IL-1β, TNF-α, and NO, while promoting the production of anti-inflammatory cytokines such as IL-10 and TGF-β. Mechanistically, both agents markedly inhibited the LPS-induced phosphorylation of PI3K, Akt, NF-κB, and IκB, indicating that their anti-inflammatory effects are mediated via suppression of the PI3K/Akt and NF-κB signaling pathways. Furthermore, HMFP and HMFP-PEG downregulated the expression of the inflammatory marker iNOS and markedly upregulated the M2 macrophage marker CD206, suggesting a role in promoting macrophage polarization toward an anti-inflammatory M2 phenotype. Notably, NF-κB signaling was identified as a key mediator in the anti-inflammatory mechanisms of both HMFP and its PEG-modified form. Collectively, these findings demonstrate that HMFP and HMFP-PEG exert significant anti-inflammatory effects through dual inhibition of NF-κB and PI3K/Akt signaling and by promoting M2 macrophage polarization, indicating their potential as promising candidates for the treatment of inflammation-related diseases.