1.The TLR4/ HIF⁃1α signaling pathway mediates glycated low density lipoprotein induced injury of human umbilical vein endothelial cells
Junhui Qiu ; Meizhi Liu ; Dusang Sun ; Ting Pan ; Weiwei Zhao ; Wenjun Sha ; Jun Lu ; Tao Lei
Acta Universitatis Medicinalis Anhui 2022;57(10):1614-1620
Objective :
To investigate the effects of glycated low density lipoprotein (Gly⁃LDL) on the growth of human umbilical vein endothelial cells (HUVECs) and the expression of toll like receptor 4 (TLR4) and hypoxia inducible factor⁃1α (HIF⁃1α), and to explore its possible mechanism .
Methods :
HUVECs were cultured in vitro and divided into control group, positive control group[50 mg/L normal low density lipoprotein(n⁃LDL)], low concentration, medium concentration and high concentration Gly⁃LDL(50, 75, 100 mg/L) groups . Respectively, the effects of different concentrations of Gly⁃LDL on survival rate of HUVECs were detected by CCK⁃8; The motility of HUVECs under different treatments were detected by wound healing assays; The level of inflammatory cytokine, such as tumor inducing factor⁃α(TNF⁃α), interleukin⁃6(IL⁃6), intercellular adhesion molecule⁃1(ICAM⁃1) and vascular cell adhesion molecule⁃1(VCAM⁃1) were detected by ELISA; The mRNA levels of TLR4, HIF⁃1α, TNF⁃α and IL⁃6 were detected by qRT⁃PCR; Protein expressions of TLR4, HIF⁃1α, TNF⁃α and IL⁃6 were detected by Western blot; Respectively, si⁃RNA of TLR4 and HIF⁃1α was used to intervene the effects of Gly⁃LDL on HUVECs . The experiment was divided into control group, model group (Gly⁃LDL 100 mg/L), si⁃TLR4 group (Gly⁃LDL 100 mg/L + si⁃TLR4), TLR4 unloading group( Gly⁃LDL 100 mg/L + si⁃NC1), si⁃HIF⁃1α group ( Gly⁃LDL 100 mg/L + si⁃HIF⁃1α) and HIF⁃1α unloading group ( Gly⁃LDL 100 mg/L + si⁃NC2) . Protein expressions of TLR4 and HIF⁃1α were detected by Western blot to verify the interaction between TLR4 and HIF⁃1α .
Results:
The survival rate and migration rate of HUVECs were inhibited in Gly⁃LDL(50 mg/L, 75 mg/L, 100 mg/L) group (P < 0. 01), the inflammatory cytokines, such as TNF⁃α, IL⁃6, ICAM⁃1,VCAM⁃1 increased by Gly⁃LDL function on HUVECs(P < 0. 001), and the mRNA and protein levels of TLR4, HIF⁃1α, TNF⁃α and IL⁃6 increased by Gly⁃LDL in a dose dependent manner. After TLR4 was knocked out, the proteins expression of TLR4 and HIF⁃1α were down⁃regulated compared with model group(P < 0. 05),but after HIF⁃1α was knockout, only the protein expression of HIF⁃1α was down⁃regulated compared with model group( P < 0. 01),while the protein expression of TLR4 was up⁃regulated under the influence of Gly⁃LDL.
Conclusion
Gly⁃LDL may inhibit the proliferation and migration of HUVECs by up⁃regulating TLR4/HIF⁃1α inflammatory signaling pathway, and promote the expression of inflamma⁃tory cytokines, leading to vascular endothelial injury .