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

Wegener's granulomatosis is an autoimmune disease that is characterized by systemic vasculitis and granuloma formation. Early influx of polymorphonuclear neutrophils (PMN), followed at a later stage by mononuclear cells, contributes to the granulomatous inflammation. Previous studies have shown that proteinase 3 (PR3), the major autoantigen in Wegener's granulomatosis, specifically binds to endothelial cells and plays a possible role in activation of these cells by enhancing interleukin-8 production, thus providing a chemotactic and activating stimulus for PMN. The present study demonstrated that PR3 enhances the production of monocyte chemoattractant protein-1 (MCP-1) by human umbilical vein endothelial cells (HUVEC) in a dose- and time-dependent manner. The PR3-induced increase in MCP-1 production was demonstrated at both the protein and the mRNA levels and was chemotactic for monocytes. In addition, it was demonstrated that PR3 induces a dose- and time-dependent increase in the expression of intercellular adhesion molecule-1 (ICAM-1) as determined by fluorescence-activated cell sorter analysis. The PR3-induced increase in expression of ICAM-1 was also demonstrated at the mRNA level. PR3 induced a slight increase in vascular cell adhesion molecule-1 expression and had no effect on the expression of both P- and E-selectin. Incubation of HUVEC for 24 h in the presence of PR3 resulted in a significant increase in adhesion of PMN, which was reduced to baseline levels in the presence of blocking monoclonal antibody anti-ICAM-1 or anti-CD18 or a combination of both. Monocytes showed a slight but statistically not significant increase 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 cytokine-primed PMN, plays a role in endothelial cell activation by enhancing both interleukin-8 and MCP-1 production, thus providing a chemotactic and activating stimulus for both PMN and monocytes. In addition, PR3 may contribute to the ongoing inflammation by enhancing the adhesion of PMN to endothelial cells by upregulating ICAM-1 expression.