Streptococcus thermophilus, a lactic acid bacterium widely used in the dairy industry, is consumed regularly by a significant proportion of the population. Some strains show in vitro anti-inflammatory activity which is not fully understood. We hypothesized that peptides released from the surface proteins of this bacterium during digestion could be implied in this activity. Consequently, we prepared a peptide hydrolysate by shaving and hydrolysis of surface proteins using trypsin, and the origin of peptides was checked by liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis. Most of the identified peptides originated from bacterial cell surface proteins. The anti-inflammatory activity of peptide hydrolysate was investigated under inflammatory conditions in two cell models. Peptide hydrolysate significantly decreased secretion of pro-inflammatory cytokine IL-8 in lipopolysaccharide (LPS)-stimulated human colon epithelial HT-29 cells. It also reduced the production of pro-inflammatory cytokines IL-8, IL-1? and the protein expression levels of Pro-IL-1? and COX-2 in LPS-stimulated THP-1 macrophages. The results showed that peptides released from bacterial surface proteins by a pancreatic protease could therefore participate in an anti-inflammatory activity of S. thermophilus LMD-9 and could prevent low-grade inflammation

Inflammation provides protection against injury, trauma or infection caused by damaged cells, irritants, or pathogens. This process eliminates injurious agents or intruders and clear components of damaged tissues. Nevertheless, low grade chronic inflammation is often associated with various pathologies. Attention is paid on bioactive peptides released from food proteins that could modulate inflammatory key factors and consequently delay the onset of these chronic diseases. Moreover, LAB, components of fermented dairy products, have also been reported to display anti-inflammatory properties both in in vitro and in vivo studies. Among LAB, Streptococcus thermophilus is widely used as a starter culture in the dairy industry. It is largely and regularly consumed by a significant proportion of the population in fermented milk products. Studies revealed that some strains of S. thermophilus displayed an anti-inflammatory activity in vitro but the mechanism is unknown. Thus, the assumption that peptides generated in the gastro-intestinal tract from hydrolysis of S. thermophilus surface proteins could display an anti-inflammatory activity and contribute to the overall anti-inflammatory effect of the bacterium can be made. After proteolytic “shaving” of S. thermophilus cells with digestive enzymes and subsequent mass spectrometry analysis, it was found that the majority of the identified peptides belongs to the surface-located proteins of this bacterium. The total set of peptides from surface proteins showed an anti-inflammatory activity since secretion of IL-8 and IL-1? cytokines by in macrophage-like THP-1 cells was reduced after LPS-induced inflammation. The results suggest that the peptides from surface proteins of S. thermophilus may contribute to the potential anti-inflammatory action of this bacterium.