Unfractionated heparin inhibits lipopolysaccharide-induced expression of granulocyte colony-stimulating factor in human endothelial cells through Toll-like receptor 4 signaling pathway / 中华危重病急救医学

ABSTRACT

ObjectiveTo determine the effect of unfractionated heparin (UFH) on lipopolysaccharide (LPS)-induced expression of granulocyte colony-stimulating factor (G-CSF), and the role of Toll-like receptor 4 (TLR4) signaling pathway in this process.Methods Human pulmonary microvascular endothelial cells (HPMECs) were cultured in vitro, and the cells between passages 3 and 5 were used in the experiments. ExperimentⅠ the cells were divided into four groups as follows control group, LPS stimulation group (LPS 10μg/mL), LPS+ 0.1 U/mL UFH group, and LPS+ 1 U/mL UFH group. HPMECs in UFH groups were treated with 0.1 U/mL or 1 U/mL UFH 15 minutes before LPS stimulation, and HPMECs in control group were treated with an equal volume of phosphate-buffered saline (PBS) instead. The concentrations of interleukin-6 (IL-6) and G-CSF in cell culture supernatants were determined by enzyme linked immunosorbent assay (ELISA) 24 hours after LPS challenge to detect the effect of UFH on HPMECs. ExperimentⅡ HPMECs were treated with 5μg/mL of rhodobacter sphaeroides LPS (LPS-RS, antagonist for TLR4) 4 hours before the addition of PBS or LPS. The concentrations of IL-6 and G-CSF in cell culture supernatants were determined 24 hours after LPS stimulation to detect the effect of TLR4 on LPS-induced HPMEC injury. ExperimentⅢ HPMECs were divided into four groups as before control group, LPS stimulation group, LPS+ 0.1 U/mL UFH group, LPS+ 1 U/mL UFH group. Treatments to cells were the same as experimentⅠ. The protein expression of TLR4 in HPMECs was determined by Western Blot 1 hour after LPS stimulation to detect the effect of UFH on TLR4.Results① Compared with control group, the levels of IL-6 and G-CSF in LPS stimulation group were increased [IL-6 (ng/L) 655.9±58.3 vs. 75.5±18.2, G-CSF (ng/L) 388.7±36.2 vs. 35.3±12.6, both P 0.05].③ Compared with control group, the protein expression of TLR4 (grey value) in LPS stimulation group was significantly upregulated after 1 hour (0.87±0.23 vs. 0.36±0.12,P< 0.05). UFH with 0.1 U/mL and 1 U/mL lowered TLR-4 protein expression induced by LPS (0.68±0.18, 0.62±0.26 vs. 0.87±0.23, bothP< 0.05).ConclusionsThe expressions of IL-6 and G-CSF were increased obviously in LPS treated HPMECs. UFH might take its therapeutic effect through TLR4-dependent pathway.