Yuchuan Liu

High-Molecular-Weight Kininogen Fragments Stimulate the Secretion of Cytokines and Chemokines Through uPAR, Mac-1, and gC1qR in Monocytes

Objective—Plasma high-molecular-weight kininogen (HK) is cleaved in inflammatory diseases by kallikrein to HKa with release of bradykinin (BK). We postulated a direct link between HKa and cytokine/chemokine release. Methods and Results—HKa, but not BK, releases cytokines tumor necrosis factor (TNF)-&agr;, interleukin (IL)-1&bgr;, IL-6, and chemokines IL-8 and MCP-1 from isolated human mononuclear cells. At a concentration of 600 nM, glutathione-S-transferase (GST) fusion proteins of kininogen domain 3 (D3), a fragment of domain 3, E7P (aaG255-Q292), HK domain 5 (D5), the D5 recombinant peptides HG (aa K420-D474) and HGK (aa H475-S626) stimulated secretion of IL-1&bgr; from mononuclear cells. Monoclonal antibodies (MAbs) specific for D5 or specific for D3 blocked release of IL-1&bgr; by HKa, supporting the importance of both domains. Antibodies to HK receptors on leukocytes including Mac-1, LFA-1, uPAR, and C1qR inhibited IL-1&bgr; secretion induced by tKa 98%, 89%, 85%, and 62%, respectively. Fractionation of mononuclear cells identified the responsible cell, a blood monocyte. Inhibitors of signaling pathways NFkB, JNK, and p38 but not extracellular signal-regulated kinase (ERK) decreased cytokine release from mononuclear cells. HKa increased the synthesis of IL-1&bgr; as deduced by an increase of IL-1&bgr; mRNA at 1 to 2 hours. Conclusions—HKa domains 3 and 5 may contribute to the pathogenesis of inflammatory diseases by releasing IL-1&bgr; from human monocytes using intracellular signaling pathways initiated by uPAR, &bgr;2 integrins and gC1qR.

Cleaved high-molecular-weight kininogen and its domain 5 inhibit migration and invasion of human prostate cancer cells through the epidermal growth factor receptor pathway

Upregulation and activation of epidermal growth factor receptor and/or urokinase-type plasminogen activator receptor in a variety of cancers have been shown to be associated with poor prognosis. High-molecular-weight kininogen can be hydrolysed by plasma kallikrein to bradykinin and cleaved high-molecular-weight kininogen (HKa). HKa and its domain 5 (D5) both have been shown to have potent anti-angiogenic activity. We now show that HKa blocks human prostate cancer cell (DU145) migration by 76.0±2.4% at 300 nM and invasion by 78.0±12.9% at 11.1 nM. D5 inhibits tumor migration and invasion in a concentration-dependent manner. Stimulation by basic fibroblast growth factor (bFGF) or vascular endothelial growth factor results in clustering of urokinase-type plasminogen activator receptor (uPAR) and epidermal growth factor receptor (EGFR) on the surface of DU145 cells. The co-localization of uPAR and EGFR is prevented by HKa. Immunoprecipitation suggests that uPAR, EGFR and α5β1 integrin formed a ternary complex. Immunoblotting shows that HKa significantly decreases the bFGF-transactivated phosphorylation of EGFR at Tyr 1173 between 30 min and 4 h. The phosphorylation of extracellular signal-regulated kinase (ERK) and AKT, which are downstream effectors of EGFR, is also inhibited by HKa. These novel data indicate that HKa and D5 inhibit migration and invasion of human prostate cancer cells through an EGFR/uPAR pathway, suggesting the therapeutic potential of HKa and D5 to decrease metastasis of human prostate cancer.

The inhibitory effect of HKa in endothelial cell tube formation is mediated by disrupting the uPA-uPAR complex and inhibiting its signaling and internalization

In two-dimensional (2-D) culture systems, we have previously shown that cleaved two-chain high-molecular-weight kininogen (HKa) or its domain 5 induced apoptosis by disrupting urokinase plasminogen activator (uPA) receptor (uPAR)-integrin signal complex formation. In the present study, we used a three-dimensional (3-D) collagen-fibrinogen culture system to monitor the effects of HKa on tube formation. In a 3-D system, HKa significantly inhibited tube and vacuole formation as low as 10 nM, which represents 1.5% of the physiological concentration of high-molecular-weigh kininogen (660 nM), without apparent apoptosis. However, HKa (300 nM) completely inhibited tube formation and increased apoptotic cells about 2-fold by 20-24 h of incubation. uPA-dependent ERK activation and uPAR internalization regulate cell survival and migration. In a 2-D system, we found that exogenous uPA-induced ERK phosphorylation and uPAR internalization were blocked by HKa. In a 3-D system, we found that not only uPA-uPAR association but also the activation of ERK were inhibited by HKa. HKa disrupts the uPA-uPAR complex, inhibiting the signaling pathways, and also inhibits uPAR internalization and regeneration to the cell surface, thereby interfering with uPAR-mediated cell migration, proliferation, and survival. Thus, our data suggest that the suppression of ERK activation and uPAR internalization by HKa contributes to the inhibition of tube formation. We conclude that in this 3-D collagen-fibrinogen gel, HKa modulates the multiple functions of uPAR in endothelial cell tube formation, a process that is closely related to in vivo angiogenesis.

Kininostatin Associates With Membrane Rafts and Inhibits αvβ3 Integrin Activation in Human Umbilical Vein Endothelial Cells

Objective—The cleaved form of high molecular weight kininogen (HKa) is a potent inhibitor of angiogenesis and tumor growth in vivo; the functional domain has been identified as domain 5 (D5, named as kininostatin). We now identify the subcellular targeting site for D5 on endothelial cells (ECs), and investigate D5 inhibition of integrin functions. Methods and Results—Endothelial membrane rafts were isolated using sucrose density gradient centrifugation. D5, bound to ECs, was predominantly associated with membrane rafts, in which uPAR, a HKa receptor, was also localized. In contrast, other HKa receptors, cytokeratin-1 and gC1q receptor, were not detected in membrane rafts. Colocalization of D5 with caveolin-1 was demonstrated on ECs by confocal microscopy. Disruption of membrane rafts by cholesterol removal decreased D5 binding to ECs. On stimulation with vascular endothelial growth factor, αvβ3 integrin formed a complex with uPAR and caveolin-1, which was accompanied by an increase in ligand binding affinity of αvβ3 integrin. These events were inhibited by D5. Consistently, D5 suppressed specific αvβ3 integrin-mediated EC adhesion and spreading as well as small guanosine triphosphatase Rac1 activation. Conclusions—D5 binds to ECs via membrane rafts and downregulates αvβ3 integrin bidirectional signaling and the downstream Rac1 activation pathway.

Mechanisms by which cleaved kininogen inhibits endothelial cell differentiation and signalling

We have shown that cleaved high-molecular-weight kininogen inhibits endothelial cell tube and vacuole formation in a concentration-dependent manner and this correlates with its recognised anti-angiogenic activity. The antibody against the urokinase plasminogen activator receptor (uPAR) mimicked the inhibitory effect of cleaved kininogen (HKa) on apoptosis (HKa: 30% and uPAR antibody: 26%) and tube formation. In tumour angiogenesis, cancer cells release angiogenic stimulators, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), thus stimulating the transformation of endogenous pro-uPA to uPA. The proteolytic enzyme urokinase plasminogen activator (uPA) then binds to its receptor in a complex with its inhibitor PAI-1, which results in the internalisation of this complex, and activates extracellular signal-regulated kinase (ERK). Recycling of the uPAR regulates the migration of endothelial cells (ECs). ERK activation stimulates migration and proliferation and suppresses apoptosis of ECs. HKa disrupted the uPA-uPAR complex, inhibited ERK activation, and blocked the internalization of uPAR, eventually resulting in cell death and cell motility arrest. Both are critical steps in angiogenesis.

Upregulation of tissue factor in monocytes by cleaved high molecular weight kininogen is dependent on TNF-α and IL-1β

Inflammatory bowel disease and arthritis are associated with contact activation that results in cleavage of kininogen to form high molecular weight kininogen (HKa) and bradykinin. We have previously demonstrated that HKa can stimulate inflammatory cytokine and chemokine secretion from human monocytes. We now show that HKa can upregulate tissue factor antigen and procoagulant activity on human monocytes as a function of time (1-4 h) and HKa concentration (75-900 nM). The amino acid sequence responsible to block HKa effects is G440-H455. The HKa receptor macrophage-1 (Mac-1; CD11b18) is the binding site as shown by inhibition by a monoclonal antibody to CD11b/18. Chemical inhibitors of JNK, ERK, and p38 signaling pathways block cell signaling, as does an inhibitor to the transcription factor NF-kappaB. A combination of monoclonal antibodies to TNF-alpha and IL-1beta but neither alone inhibited the HKa induction of tissue factor. These results suggest that HKa mimics LPS by triggering a paracrine pathway in monocytes that depends on TNF-alpha and IL-1beta. Antibodies to kininogen or peptidomimetics might be a useful and safe therapy in inflammatory diseases or sepsis involving cytokines.