3′-Sialyllactose protects against LPS-induced endothelial dysfunction by inhibiting superoxide-mediated ERK1/2/STAT1 activation and HMGB1/ RAGE axis

Aim: Endothelial hyperpermeability is an early stage of endothelial dysfunction associated with the progression and development of atherosclerosis. 3 '-Sialyllactose (3 '-SL) is the most abundant compound in human milk oligosaccharides, and it has the potential to regulate endothelial dysfunction. This study investigated the beneficial effects of 3 '-SL on lipopolysaccharide (LPS)-induced endothelial dysfunction in vitro and in vivo. Main methods: We established LPS-induced endothelial dysfunction models in both cultured bovine aortic endothelial cells (BAECs) and mouse models to determine the effects of 3 '-SL. Western blotting, qRT-PCR analysis, immunofluorescence staining, and en face staining were employed to clarify underlying mechanisms. Superoxide production was measured by 2 ',7 '-dichlorofluorescin diacetate, and dihydroethidium staining. Key findings: LPS significantly decreased cell viability, whereas 3 '-SL treatment mitigated these effects via inhibiting ERK1/2 activation. Mechanistically, 3 '-SL ameliorated LPS-induced ROS accumulation leading to ERK1/2 activation-mediated STAT1 phosphorylation and subsequent inhibition of downstream transcriptional target genes, including VCAM-1, TNF-alpha, IL-1 beta, and MCP-1. Interestingly, LPS-induced ERK1/2/STAT1 activation leads to the HMGB1 release from the nucleus into the extracellular space, where it binds to RAGE, while 3 '-SL suppressed EC hyperpermeability by suppressing the HMGB1/RAGE axis. This interaction also led to VE-cadherin endothelial junction disassembly and endothelial cell monolayer disruption through ERK1/2/STAT1 modulation. In mouse endothelium, en face staining revealed that 3 '-SL abolished LPS-stimulated ROS production and VCAM-1 overexpression. Significance: Our findings suggest that 3 '-SL inhibits LPS-induced endothelial hyperpermeability by suppressing superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis. Therefore, 3 '-SL may be a potential therapeutic agent for preventing the progression of atherosclerosis.