The influence of interleukin-4 on transendothelial transport of low-density lipoproteins

BACKGROUND: Cytokines are important participants in the atherosclerotic process. The product of T-helpers and mast cells, interleukin-4, causes activation of endothelial cells and induces polarization of macrophages into anti-inflammatory M2 phenotype.

AIM: The aim was to study the influence of interleukin-4 on the activation of transendothelial transport of low-density lipoproteins.

MATERIALS AND METHODS: Low-density lipoproteins transendothelial transport was evaluated in a two-chamber model on a monolayer of human endothelial cell line EA.hy926. For that, 200 mkg/ml of low-density lipoproteins, and 1, or 10, or 100 ng/ml of interleukin-4, or 10, or 50 ng/ml of interleukin-6, or 50 ng/ml of tumor necrosis factor, or 10 ng/ml of interleukin-4 and 50 ng/ml of tumor necrosis factor, or a phosphate buffer saline were added to the cells on 24 h. The integrity of endothelial monolayer was controlled by the passage through 1 mkg/ml of fluorescein Na. The levels of mRNA and proteins in the cells were determined by reverse transcription polymerase chain reaction and Western blotting, the activity of matrix metalloproteinases-1, -2 and -9 in the culture medium — by zymography, interleukin-6 and -8 concentrations — by enzyme-linked immunosorbent assay.

RESULTS: Interleukin-4 had no effect on the passage of low-density lipoproteins through the monolayer of endothelial cells in basal and tumor necrosis factor stimulation conditions. At the same time, interleukin-4 suppressed interleukin-8 secretion by cells and increased their production of interleukin-6. The latter also did not cause the changes in the permeability of endothelial monolayer. In addition, interleukin-4 did not affect the expression of CAV, SCARB1, ACVRL1 genes, encoding proteins involved in low-density lipoproteins transendothelial transport. An addition of interleukin-4 or -6 to the cells did not change the activity of the matrix metalloproteinases.

CONCLUSIONS: Interleukin-4 does not affect the transendothelial transport of low-density lipoproteins, while modulating the production of other cytokines by endothelial cells. In the future, it is necessary to establish the effect of a wider range of cytokines produced by intimal cells on low-density lipoproteins transendothelial transport, as well as to clarify the molecular mechanisms of influence of tumor necrosis factor on this process in order to identify new targets for atherosclerosis therapy.