Objective: To explore whether lipoxin A(4) (LXA(4))could prevent lipopolysaccharide (LPS)-induced human umbilical vein endothelial cells (HUVEC) monolayer hyperpermeability and its possible mechanism.
Methods: Human umbilical cords were obtained from women with normal pregnancy immediately after delivery from Tongji Hospital Affiliated of Tongji Medical College. Primary HUVEC were isolated from umbilical veins and subcultured, then, HUVEC were divided into four groups:control group; LPS group (10 mg/L of LPS); LPS + LXA(4) group(10 mg/L of LPS and 100 nmol/L of LXA(4)); LPS + LXA(4) + BOC-2 group [10 µmol/L of BOC-2, an effective antagonist of formyl peptide receptor like 1 (FPRL-1)]. All expriments were performed after cells were treated for 24 hours. Endothelial permeability was measured by fluorescein isothiocyan-ate labelled bovine serum albumin (FITC-BSA) clearance across the monolayer; tumor necrosis factor α (TNF-α) mRNA and secretion were detected by reverse transcriplase (RT)-PCR and ELISA assay respectively, and nuclear factor κB (NF-κB) protein change was determined by western blot.
Results: (1) LPS induced a significant increase in the permeability [Pa value of LPS group was (183.1 ± 1.7)%], while co-administrating with LXA(4) obviously attenuated this LPS-induced hyperpermeability, Pa value of LPS + LXA(4) group was (103.1 ± 2.2)%, LPS + LXA(4) + BOC-2 group was (162.2 ± 2.8)%, control group was 100%, the permeability of HUVEC monolayer was significantly increased by LPS which was (83.1 ± 1.7)% of control (P < 0.01), however, it was notably inhibited by LXA(4) (P < 0.05); the blockade of FPRL-1 could attenuate the effect of LXA(4), that is, there was no difference between the LPS + LXA(4) + BOC-2 group and the LPS group. (2) After treatment with different concentration of LPS(0, 0.1, 1, 10 mg/L), the mRNA expressions of TNF-α were increased (1.11 ± 0.11, 1.27 ± 0.03, 1.60 ± 0.06, 1.82 ± 0.04, respectively), compared with the control group, at the concentration of 1, 10 mg/L LPS, the difference was statistically significant (P < 0.05). (3) The increased levels of NF-κB and inflammatory mediator TNF-α in the LPS group were both inhibited by LXA(4). Levels of NF-κB protein and TNF-α mRNA secretion in LPS treated group (0.53 ± 0.06 and 0.81 ± 0.09, respectively) were both inhibited by LXA(4)(0.19 ± 0.05 and 0.41 ± 0.07, respectively, and both had significant difference, P < 0.05). (4) Levels of TNF-α in HUVEC culture medium of LPS group [(31.94 ± 0.01) ng/L] was significantly higher than the control group [(18.17 ± 0.03) ng/L, P < 0.05], LPS + LXA(4) group [(15.72 ± 0.07) ng/L] was significantly lower than the LPS group (P < 0.05).
Conclusion: Our findings demonstrated that LXA(4) could prevent the endothelial cell hyperpermeability induced by LPS in HUVEC under which the possible mechanism was through inhibiting the expression of NF-κB and its related cytokines through receptor-dependent.