Abstract
High molecular weight kininogen (HK) is known to bind specifically and saturably to Mac-1 with a Kd = 9–18 nM for neutrophils and to uPAR with a Kd =30 nM for endothelial cells. However, the functional results of HK interaction with Mac-1 or uPAR on leukocytes is not fully understood. Kallikrein cleavage of single chain HK to a two chain form (HKa) with release of bradykinin (BK) occurs in sepsis, arthritis, and inflammatory bowel disease. We hypothesized that HKa stimulates secretion of inflammatory cytokines. Mononuclear cells were isolated from normal subjects by a Histopaque density gradient. We have expressed kininogen domain 3 (D3) and a fragment of domain 3, coded for by exon 7, E7P (aaG235-Q292), in E. Coli as glutathione S-transferase (GST) fusion proteins. HK and HKa were purified proteins. GST was recombinant. All proteins contained <0.01 EU/ml endotoxin. For all experiments, 2 X 106/ml mononuclear cells/ml were preincubated with monoclonal antibodies, murine IgG (both at 1.8 mM) or HANKS buffer containing 0.15 M NaCl, pH 7.4 for 30 minutes at 37°C. HK, HKa, GST-D3, GST-E7P, GST-D5 or GST all at 600 nM were added. Centrifugation allowed separation of the mononuclear cell suspension into cells and supernatant. The latter was used for assay of interleukin-1β (IL-1β) by ELISA. HK and all fragments tested stimulated secretion of IL-1β of 84.8 to 306.3 pg/ml when incubated with mononuclear cells for 30 minutes at 37°C. Anti-Mac-1 antibody inhibited IL-1β secretion by HK 100%, by HKa 89%, by GST-D3 78%, by GST-E7P 94% and by GST-D5 98%. Anti-uPAR antibody inhibited IL-1β release by HK 88%, by HKa 77%, by GST-D3 95%, by GST-E7P 85%, and by GST-D5 76%. Inhibition by both receptor antibodies is consistent with their known complex formation. A monoclonal antibody (mAb) to HK D5 (C11C1) and a mAb to HK D3 (2B5) both inhibited IL-1β release by HK, HKa, GST-D5 and GST-D3 indicate that both D3 and D5 are important in cytokine release. Murine IgG gave 0% inhibition in all studies. These results indicate that kininogen may contribute to the pathogenesis of inflammatory diseases by releasing IL-1β from human blood mononuclear cells.
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