Endotoxin-Binding Peptides Derived from Casein Glycomacropeptide Inhibit Lipopolysaccharide-Stimulated Inflammatory Responses via Blockade of NF-κB activation in macrophages.
Systemic low-grade inflammation and increased circulating lipopolysaccharide (LPS) contribute to metabolic dysfunction. The inhibitory effects and underlying molecular mechanisms of casein glycomacropeptide (GMP) hydrolysate on the inflammatory response of LPS-stimulated macrophages were investigated. Results showed that the inhibitory effect of GMP hydrolysates obtained with papain on nitric oxide (NO) production were obviously higher than that of GMP hydrolysates obtained with pepsin, alcalase and trypsin (p < 0.05), and the hydrolysate obtained with papain for 1 h hydrolysis (GHP) exhibited the highest inhibitory effect. Compared with native GMP, GHP markedly inhibited LPS-induced NO production in a dose-dependent manner with decreased mRNA level of inducible nitric oxide synthase (iNOS). GHP blocked toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway activation, accompanied by downregulation of LPS-triggered significant upregulation of tumor necrosis factor (TNF)-α and interleukin (IL)-1β gene expression. Furthermore, GHP could neutralize LPS not only by direct binding to LPS, but also by inhibiting the engagement of LPS with the TLR4/MD2 complex, making it a potential LPS inhibitor. In conclusion, these findings suggest that GHP negatively regulates TLR4-mediated inflammatory response in LPS-stimulated RAW264.7 cells, and therefore may hold potential to ameliorate inflammation-related issues.
Key Laboratory of Functional Dairy, College of Food Science and Nutritional Engineering, China Agriculture University, Beijing 100083, China. xuecheng@163.com.|Key Laboratory of Space Nutrition and Food Engineering, China Astronaut Training Center, Beijing 100094, China. xuecheng@163.com.
Xue
X
Cheng
Key Laboratory of Functional Dairy, College of Food Science and Nutritional Engineering, China Agriculture University, Beijing 100083, China. dongxiao@163.com.
Dongxiao
D
Gao
Synergetic Innovation Center of Food Safety and Nutrition, Northeast Agriculture University, Haerbin 150030, China. chenb12@aliyun.com.
Bin
B
Chen
Key Laboratory of Functional Dairy, College of Food Science and Nutritional Engineering, China Agriculture University, Beijing 100083, China. maoxueying@cau.edu.cn.
Xueying
X
Mao
D000818:Animals; D002364:Caseins / Q000737:chemistry*; D004306:Dose-Response Relationship, Immunologic; D006020:Glycopeptides / Q000737:chemistry*; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism*; D053583:Interleukin-1beta / Q000187:drug effects; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors; D008565:Membrane Proteins / Q000494:pharmacology*; D051379:Mice; D053594:Myeloid Differentiation Factor 88 / Q000187:drug effects; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000187:drug effects; D000067996:RAW 264.7 Cells / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects
D002364:Caseins; D006020:Glycopeptides; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D008565:Membrane Proteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C025357:endotoxin binding proteins; C020251:kappa-casein glycomacropeptide; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase