Tissue factor regulation and cytokine expression in monocyte-endothelial cell co-cultures: effects of a statin, an ACE-inhibitor and a low-molecular-weight heparin.

INTRODUCTION

Mounting evidence implies beneficial properties of statins and angiotensin converting enzyme (ACE)-inhibitors beyond those of their original indications in the treatment of coronary artery disease (CAD). Less is known of the mechanisms by which low-molecular-weight (LMW) heparin, also used in unstable CAD, affects the cellular micro-environment. The effects of these drugs in monocyte-endothelial cell co-culture systems have so far been sparsely investigated.

MATERIALS AND METHODS

We studied the expression of tissue factor (TF) and the cytokines tumour necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-10 in a co-culture model with monocytic, vitamin D(3)(vitD(3))-differentiated U-937 cells and human coronary artery endothelial cells (HCAEC), and the effects of the above-mentioned drugs in this system. Cells were co-cultured for 18 h, with or without pre-stimulation of the HCAEC with interferon (IFN)-gamma, and in the presence or absence of simvastatin, enalapril or dalteparin. Analyses of surface tissue factor and intracellular cytokines were done by flow cytometry.

RESULTS

Co-culture with activated HCAEC induced tissue factor expression in U-937 cells but not in the endothelial cells. All three drugs significantly reduced tissue factor up-regulation (p<0.001 for each). Co-culture also induced IL-6 expression in U-937 cells and an increase in IL-10 production by HCAEC, none of which was affected by drugs. When cultured separately, both cell types expressed TNF-alpha. This was attenuated in U-937 cells by all three drugs (p<0.001 for each), whereas only enalapril reduced the TNF-alpha content of activated HCAEC (p=0.02). Enalapril also down-regulated the basal expression of IL-6 (p=0.01) and IL-10 (p<0.01) in HCAEC, which simvastatin and dalteparin failed to do.

CONCLUSIONS

In this study, we demonstrated for the first time that a statin, an ACE-inhibitor and an LMW-heparin all suppress tissue factor up-regulation in monocyte-endothelial cell co-cultures, thus adding new information regarding the cellular effects of these drugs that may be of importance in the treatment of CAD.