6'-Sialylactose abolished lipopolysaccharide-induced inflammation and hyper-permeability in endothelial cells

Disruption of the endothelial barrier function and reduction in cell migration leads to endothelial dysfunction. One of the most abundant human milk oligosaccharides, 6'-sialylactose (6'-SL), is reported to exert various biological functions related to inflammatory responses. In this study, we evaluated the effects of 6'-SL on lipopolysaccharide (LPS)-induced inflammation caused by endothelial barrier damage. Our results showed that LPS at 500 ng/mL strongly not only abolished cell migration but also hyperactivated MAPK and NF-κB pathways. 6'-SL suppressed LPS-induced endothelial inflammation via ERK1/2, p38, and JNK MAPK pathways. 6'-SL supported endothelial junctions by upregulating PECAM-1 expression and mRNA levels of tight junctions, such as ZO-1 and occludin, which were downregulated by LPS stimulation. It significantly inhibited the nuclear translocation of NF-κB, along with the downregulation of inflammatory cytokines, including TNF-α, IL-1β, MCP-1, VCAM-1, and ICAM-1. Furthermore, 6'-SL abolished NF-κB-mediated STAT3 in controlling endothelial migration and hyperpermeability via downregulating STAT3 activation and nuclear translocation. Finally, LPS induced over-expression of VCAM-1 and ZO-1 disassembly in both atheroprone and atheroprotective areas of mouse aorta, which were reversed by 6'-SL treatment. Altogether, our findings suggest that 6'-SL is a potent therapeutic agent for modulating inflammatory responses and endothelial hyperpermeability.