Glutamic-Alanine Rich Glycoprotein from Undaria pinnatifida: A Promising Natural Anti-Inflammatory Agent

Abstract

This study aimed to assess the anti-inflammatory properties of a bioactive glutamic-alanine rich glycoprotein (GP) derived from Undaria pinnatifida. This research explored the effects of GP on both LPS-stimulated RAW264.7 cells, peritoneal macrophages, and mouse models of carrageenan- and xylene-induced inflammation, investigating the underlying molecular mechanisms. In both in-vitro and in-vivo settings, GP was found to reduce the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) while also inhibiting the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in response to lipopolysaccharide (LPS) stimulation. GP treatment significantly impeded the nuclear translocation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway by blocking the phosphorylation of IKKα and IκBα, leading to a reduction in proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Additionally, GP effectively inhibited the activation of mitogen-activated protein kinases (MAPKs), with specific inhibitors of p38 and ERK enhancing GP’s anti-inflammatory efficacy. Notably, GP administration at 10 mg/kg/day (p.o.) markedly reduced carrageenan-induced paw inflammation and xylene-induced ear edema by preventing the infiltration of inflammatory cells into targeted tissues. GP treatment also downregulated key inflammatory markers, including iNOS, COX-2, IκBα, and NF-κB, by suppressing the phosphorylation of p38 and extra-cellular signal regulated kinase (ERK), thereby improving the inflammatory index in both carrageenan- and xylene-induced mouse models. These findings suggest that marine resources, particularly seaweeds like U. pinnatifida, could serve as valuable sources of natural anti-inflammatory proteins for the effective treatment of inflammation and related conditions.