Oscillating flow promotes inflammation through the TLR2-TAK1-IKK2 signalling pathway in human umbilical vein endothelial cell (HUVECs)

Background: Oscillatory shear stress (OSS) occurs in areas where atherosclerosis is prevalent. Toll-like Receptor 2 (TLR2) has been associated with mechanical-stress-mediated activation of signalling pathways that may lead to inflammation, Apoptosis, and atherosclerosis. Nonetheless, the mechanism underlying the connection between TLR2 and OSS is not fully understood. The purpose of this study was to investigate the link between OSS and TLR2 in human umbilical vein endothelial cell (HUVECs).

Methods: Monolayer endothelial cells were stimulated or not stimulated by OSS. Protein expression was determined by western blotting and immunofluorescent staining. Endothelial function was assessed by using dihydroethidium assay, RT-PCR, immunofluorescent staining and western blotting. The carotid artery of rats was ligated for 1 week, and a section exposed to OSS was excised and analysed.

Results: In vitro, the expression of TLR2 in HUVECs was activated by OSS. Additionally, OSS increased Apoptosis, inflammatory changes, and oxidative stress in HUVECs, and these effects were reversed by down-regulation the expression of TLR2. We proved that OSS regulates the inflammatory response of endothelial cells through the TLR2-TAK1-IKK2 pathway. In the rats with carotid artery ligation, TLR2, TAK1 and phospho-IKK2 amounts increased at the site of OSS.

Significance: According to our results, the OSS-mediated HUVECs injury may be associated with an increase in TLR2 expression. Accordingly, strategies designed to reduce TLR2 expression or inhibit TLR2 activation may be an effective approach to reduce the incidence of atherosclerosis.