Proteinase 3 enhances endothelial monocyte chemoattractant protein-1 production and induces increased adhesion of neutrophils to endothelial cells byupregulating intercellular cell adhesion molecule-1

Wegener's granulomatosis is an autoimmune disease that is characterized by systemic vasculitis and granuloma formation. Early influx of polymorphonucl ear neutrophils (PMN), followed at a later stage by mononuclear cells, cont ributes to the granulomatous inflammation. Previous studies have shown that proteinase 3 (PR3), the major autoantigen in Wegener's granulomatosis, spe cifically binds to endothelial cells and plays a possible role in activatio n of these cells by enhancing interleukin-8 production, thus providing a ch emotactic and activating stimulus for PMN. The present study demonstrated t hat PR3 enhances the production of monocyte chemoattractant protein-1 (MCP- 1) by human umbilical vein endothelial cells (HUVEC) in a dose- and time-de pendent manner. The PR3-induced increase in MCP-1 production was demonstrat ed at both the protein and the mRNA levels and was chemotactic for monocyte s. In addition, it was demonstrated that PR3 induces a dose- and time-depen dent increase in the expression of intercellular adhesion molecule-1 (ICAM- 1) as determined by fluorescence-activated cell sorter analysis. The PR3-in duced increase in expression of ICAM-1 was also demonstrated at the mRNA le vel. PR3 induced a slight increase in vascular cell adhesion molecule-1 exp ression and had no effect on the expression of both P- and E-selectin. Incu bation of HUVEC for 24 h in the presence of PR3 resulted in a significant i ncrease in adhesion of PMN, which was reduced to baseline levels in the pre sence of blocking monoclonal antibody anti-ICAM-1 or anti-CD18 or a combina tion of both. Monocytes showed a slight but statistically not significant i ncrease in adhesion. Incubation of HUVEC with PR3 for 4 h did not result in enhanced adhesion of either PMN or monocytes. It was hypothesized that PR3 , which may be released locally at inflammatory sites after activation of c ytokine-primed PMN, plays a role in endothelial cell activation by enhancin g both interleukin-8 and MCP-1 production, thus providing a chemotactic and activating stimulus for both PMN and monocytes. In addition, PR3 may contr ibute to the ongoing inflammation by enhancing the adhesion of PMN to endot helial cells by upregulating ICAM-1 expression.