Kaempferol inhibits multiple pathways involved in the secretion of inflammatory mediators from LPS-induced rat intestinal microvascular endothelial cells

Abstract

Inflammatory bowel disease (IBD) is a chronic, idiopathic inflammatory disease of the small and/or large intestine. Endothelial expression of inflammatory mediators, including cytokines and adhesion molecules, serves a critical role in the initiation and progression of IBD. The dietary flavonoid, kaempferol, has been reported to inhibit expression of inflammatory mediators; however, the underlying mechanisms require further investigation. In the present study, a novel molecular mechanism of kaempferol against IBD was identified. The potential anti-inflammatory effect of kaempferol in a cellular model of intestinal inflammation was assessed using lipopolysaccharide (LPS)-induced rat intestinal microvascular endothelial cells (RIMVECs), and an underlying key molecular mechanism was identified. RIMVECs were pretreated with kaempferol of various concentrations (12.5, 25 and 50 µM) followed by LPS (10 µg/ml) stimulation. ELISA was used to examine the protein levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the supernatant. Protein expression levels of Toll-like receptor 4 (TLR4), nuclear factor-κB (NF-κB) p65, inhibitor of NF-κB, mitogen-activated protein kinase p38 and signal transducer and activator of transcription (STAT) in cells were measured by western blotting. Kaempferol significantly reduced the overproduction of TNF-α, IL-1β, interleukin-6, ICAM-1 and VCAM-1 induced by LPS, indicating the negative regulation of kaempferol in TLR4, NF-κB and STAT signaling underlying intestinal inflammation. The present results provide support for the potential use of kaempferol as an effective therapeutic agent for IBD treatment.