Kaempferol alleviates the inflammatory response and stabilizes the pulmonary vascular endothelial barrier in LPS-induced sepsis through regulating the SphK1/S1P signaling pathway

Sepsis, a clinical syndrome causing multi-organ failure, is one of the leading causes of morbidity and mortality. The effective treatment strategies for sepsis are limited. Some studies have demonstrated the benefits of kaempferol in countering sepsis, but its specific mechanism of action is unclear. The study aimed to investigate the anti-sepsis effects and mechanisms of kaempferol via sphingosine kinase 1/sphingosine-1-phosphate (SphK1/S1P) signaling pathway in a lipopolysaccharide (LPS)-induced sepsis model. We elucidated the effect of kaempferol on sepsis in LPS-induced RAW264.7 cells, HUVECs and septic mice. In RAW264.7 cells. We found that kaempferol decreased the levels of inflammatory mediators NO and PGE2. Western blot showed that kaempferol inhibited the expression of SphK1, p-p65 and p-IκB-α. LC-MS/MS analyze showed that kaempferol decreased S1P content in RAW264.7 cells. In HUVECs, we found that kaempferol promoted the expression of SphK1 and S1P, while kaempferol increased the expression levels of VE-Cadherin and β-catenin. In vivo, consistent with the in vitro results, kaempferol alleviated LPS-induced inflammatory responses and endothelial barrier damage. In addition, by immunofluorescence localization of F4/80, CD31 and SphK1, we found that kaempferol inhibited the expression of SphK1 in macrophages and increased the expression of SphK1 in endothelial cells. In summary, our present results not only suggested that kaempferol alleviated the inflammatory response and stabilizes the endothelial barrier in LPS-induced sepsis by regulating the SphK1/S1P signaling pathway, but also showed that kaempferol exhibited cell-specific effects on the regulation of SphK1 expression.