Phosphopeptides (PPPs) from hen egg yolk phosvitin exert anti-inflammatory activity via modulation of cytokine expression

In order to investigate the anti-inflammatory activity of egg yolk-derived phosphopeptides (PPPs), intestinal epithelial (Caco-2 cells, HT-29 cells) and macrophage RAW 264.7 cell lineages were stimulated with either tumor necrosis factor alpha (TNF-α) or Salmonella enterica lipopolysaccharide (LPS). Upon pre-incubation with different doses of PPPs, the secretion of interleukin 8 (IL-8) and TNF-α in cell supernatants was quantified by enzyme-linked immunosorbent assay (ELISA). The gene expression levels of inducible nitric oxide synthase (iNOS) and pro-inflammatory cytokines (i.e., IL-8, IL-12, IL-6, monocyte chemoattractant protein-1 (MCP-1), TNF-α, IL-1β) were determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Results revealed that PPPs significantly inhibit the secretion of IL-8 in TNF-α-stimulated Caco-2 and HT-29 cells in a dose-dependent manner; while no significant difference was observed in LPS-stimulated Caco-2 and HT-29 cells. Interestingly, the expression of IL-8, MCP-1 and IL-12 was inhibited by PPPs in both TNF-α- and LPS-stimulated HT-29 cells, and similarly, the expression of TNF-α, IL-1β, IL-6, and iNOS was downregulated significantly in LPS-stimulated macrophage RAW 264.7 cells pre-incubated with PPPs. We conclude that PPPs possesses anti-inflammatory properties evidenced by the down-regulation of key pro-inflammatory markers. Thus our results suggest that PPPs may serve as nutraceutical compounds with anti-inflammatory properties.