Anti-inflammatory action of high molecular weight Mytilus edulis hydrolysates fraction in LPS-induced RAW264.7 macrophage via NF-κB and MAPK pathways

Anti-inflammatory Mytilus edulis hydrolysates (MEHs) were prepared by peptic hydrolysis and MEH was further fractionated into three fractions based on molecular weight, namely >5 kDa, 1-5 kDa, and <1 kDa. The >5 kDa peptide fraction exerted the highest nitric oxide (NO) inhibitory activity and inhibited prostaglandin E2 (PGE2) secretion in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Pretreatment with the >5 kDa peptide fraction markedly inhibited LPS-stimulated inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein and gene expressions. Stimulation by LPS induced the production of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and -1β (IL-1β), whereas co-treatment with the >5 kDa peptide fraction suppressed pro-inflammatory cytokine production. The >5 kDa peptide fraction inhibited the translocation of NF-κB (nuclear factor-kappa B) through the prevention of IκBα (inhibitory factor kappa B alpha) phosphorylation and degradation and also inhibited the MAPK signaling pathway in LPS-stimulated RAW264.7 macrophages.