Enhanced leucocyte adhesion to interleukin-1 beta stimulated vascular smooth muscle cells is mainly through intercellular adhesion molecule-1.

OBJECTIVE

The aim was to investigate whether interleukin-1 beta (IL-1 beta) plays a role in modulating the adhesion of monocytes and neutrophils to vascular smooth muscle cells, and to identify what molecules on these cells may be involved in the adhesion.

METHODS

Rat aortic smooth muscle cells were challenged with IL-1 beta and tested for adhesion of prelabelled monocytes and neutrophils. Northern analysis, reverse transcription/polymerase chain reaction (RT/PCR), and immunocytochemical staining were used to measure the changes of intercellular adhesion molecule-1 (ICAM-1) and other adhesion molecules in response to IL-1 beta stimulation. Neutralising antibody against ICAM-1 was used to demonstrate a role of ICAM-1 in this IL-1 beta induced adhesion.

RESULTS

IL-1 beta induced the adhesion of monocytes and neutrophils to aortic smooth muscle cells in a concentration and time dependent manner. IL-1 beta-induced adhesion was inhibited by preincubation of the cells with an IL-1 receptor antagonist (IL-1ra). Northern analysis and RT/PCR showed that ICAM-1 mRNA represents a predominant adhesion molecule induced by IL-1 beta, and that the expression of ICAM-1 mRNA precedes and parallels the induced adhesion profiles of aortic smooth muscle cells for leucocytes. Immunocytochemical staining confirmed the IL-1 beta induced ICAM-1 expression on the smooth muscle cells. Moreover, a monoclonal anti-rat ICAM-1 antibody produced a concentration dependent inhibition of the IL-1 beta induced adhesion of monocytes and neutrophils to the smooth muscle cells.

CONCLUSIONS

IL-1 beta actively regulates functional ICAM-1 expression in vascular smooth muscle cells. The IL-1 beta-induced expression of ICAM-1 on the smooth muscle cells may be an important contributor to the increased adhesion by monocytes and neutrophils to these cells and suggests that IL-1 beta might play a role in the proinflammatory and immune functions of the modified smooth muscle cells during atherosclerosis and restenosis.