Objective: To investigate the effects of heparin on the secretion of monocyte chemotactic protein-1 (MCP-1) in human umbilical vein endothelial cells (HUVEC) and the adhesion of monocytes to endothelial cells stimulated by lipopolysaccharide (LPS).
Methods: HUVEC were cultured in vitro, and the cells between generation 4 and 5 were used for the experiments. The cells were divided into phosphate buffer saline (PBS) control group, heparin control group, LPS group, and heparin+LPS group. The LPS group was challenged with LPS 10 mg/L; the PBS control group was added with the same amount of PBS; the heparin group was added with 10 kU/L unfractionated heparin; the heparin+LPS group was treated with 10 kU/L unfractionated heparin 15 minutes before LPS stimulation. The cells were harvested at 6 hours and 12 hours after LPS stimulation in each group, and the MCP-1 mRNA expression was determined by real-time fluorescent quantitative reverse transcription-polymerase chain reaction (qRT-PCR). After incubation with each group, the fluorescent dyelabeled human monocyte cell line THP-1 was cultured with each group for 1 hour in the dark, and the adhesion density of THP-1 and HUVEC was observed under fluorescence microscope.
Results: Compared with the PBS control group, the MCP-1 mRNA expression significantly increased at 6 hours and 12 hours after LPS stimulation and peaked at 6 hours, then decreased gradually, but remained significantly higher than the PBS control group at 12 hours [2-ΔΔCt: 16.41 (15.03, 18.00) vs. 1.00 (0.80, 1.26) at 6 hours, 9.27 (8.11, 9.85) vs. 1.00 (0.84, 1.20) at 12 hours, both P < 0.05]. Heparin preconditioning significantly reduced LPS-induced MCP-1 mRNA expression [2-ΔΔCt: 2.06 (1.72, 2.46) vs. 16.41 (15.03, 18.00) at 6 hours, 2.46 (2.19, 4.56) vs. 9.27 (8.11, 9.85) at 12 hours, both P < 0.05]. There was no significant difference in MCP-1 mRNA expression between the heparin control group and the PBS control group [2-ΔΔCt: 1.47 (1.29, 1.65) vs. 1.00 (0.80, 1.26) at 6 hours, 2.69 (2.58, 2.77) vs. 1.00 (0.84, 1.20) at 12 hours, both P > 0.05]. Fluorescence microscopy observation showed that LPS stimulation could promote the adhesion of THP-1 to HUVEC; heparin preconditioning could inhibit the adhesion of THP-1 to HUVEC stimulated by LPS.
Conclusions: Heparin preconditioning could inhibit the MCP-1 mRNA expression , thereby reduce the adhesion of THP-1 to HUVEC, thus play a protective role in sepsis.