Human urokinase-type plasminogen activator stimulates chemotaxis of human neutrophils

100

Basophils circulate in the blood and are able to migrate into tissues at sites of inflammation. Urokinase plasminogen activator (uPA) binds a specific high affinity surface receptor (uPAR). The uPA-uPAR system is crucial for cell adhesion and migration, and tissue repair. We have investigated the presence and function of the uPA-uPAR system in human basophils. The expression of uPAR was found at both mRNA and protein levels. The receptor was expressed on the cell surface of basophils, in the intact and cleaved forms. Basophils did not express uPA at either the protein or mRNA level. uPA (10−12–10−9 M) and its uPAR-binding N-terminal fragment (ATF) were potent chemoattractants for basophils, but did not induce histamine or cytokine release. Inactivation of uPA enzymatic activity by di-isopropyl fluorophosphate did not affect its chemotactic activity. A polyclonal Ab against uPAR inhibited uPA-dependent basophil chemotaxis. The uPAR-derived peptide 84–95 (uPAR84–95) induced basophil chemotaxis. Basophils expressed mRNA for the formyl peptide receptors formyl peptide receptor (FPR), FPR-like 1 (FPRL1), and FPRL2. The FPR antagonist cyclosporin H prevented chemotaxis induced by FMLP, but not that induced by uPA and uPAR84–95. Incubation of basophils with low and high concentrations of FMLP, which desensitize FPR and FPRL1, respectively, but not FPRL2, slightly reduced the chemotactic response to uPA and uPAR84–95. In contrast, desensitization with WKYMVm, which also binds FPRL2, markedly inhibited the response to both molecules. Thus, uPA is a potent chemoattractant for basophils that seems to act through exposure of the chemotactic uPAR epitope uPAR84–95, which is an endogenous ligand for FPRL2 and FPRL1.

Section: Discussionmentioning

confidence: 99%

Urokinase Induces Basophil Chemotaxis through a Urokinase Receptor Epitope That Is an Endogenous Ligand for Formyl Peptide Receptor-Like 1 and -Like 2

Paulis

Montuori

Prevete

et al. 2004

100

“…Conversely, there is substantial, but fragmented, evidence suggesting that uPA is a modulator of immune and inflammatory responses. For example, early reports showed that plasminogen activator could act as a lymphocyte mitogen (45), that uPA was a neutrophil chemotaxin (46), and that IL-2 synthesis by Jurkat T cells requires a membrane-associated serine protease (47). Many of these early studies were limited by an inability to characterize the involved proteases completely.…”

Section: Discussionmentioning

confidence: 99%

Urokinase-Type Plasminogen Activator Is Required for the Generation of a Type 1 Immune Response to PulmonaryCryptococcus neoformansInfection

Gyetko¹,

Sud²,

Chen³

et al. 2002

Urokinase-type plasminogen activator (uPA)−/− mice cannot mount protective host defenses during infection with the opportunistic yeast Cryptococcus neoformans (52D). Because effective host defense against C. neoformans requires specific immune responses and the generation of type 1 (T1) cytokines, we determined how the absence of uPA impacts these processes. Wild-type (WT) and uPA−/− mice were inoculated with C. neoformans. Macrophage antifungal activity was assessed histologically, T lymphocyte responses in vivo and proliferation in vitro were quantified, and cytokine concentrations were determined by ELISA. uPA−/− macrophages have impaired antimicrobial activity. Regional lymph nodes of infected uPA−/− mice contained fewer cells than WT, suggesting impaired T cell proliferation in response to the pathogen in vivo. In vitro, uPA−/− T lymphocytes had impaired proliferative responses to C. neoformans rechallenge compared with WT. Infected WT mice generated T1 cytokines in the lung, characterized by high levels of IFN-γ and IL-12. uPA−/− mice had decreased levels of IFN-γ and IL-12, and increased IL-5, a type 2 cytokine. In the absence of uPA, the cytokine profile of regional lymph nodes shifted from a T1 pattern characterized by IFN-γ and IL-2 to a weak, nonpolarized response. We conclude that in the absence of uPA, lymphocyte proliferative responses are diminished, and mice fail to generate protective T1 cytokines, resulting in impaired antimicrobial activity. This study provides novel evidence that uPA is a critical modulator of immune responses and of immune cell effector functions in vivo.

“…Interaction of prouPA with the uPA receptor (uPAR) facilitates cleavage of pro-uPA to the active two-chain form, at least in part through enhancing interaction with membrane-associated plasmin (1, 2, 9 -11). In addition, association of uPA with uPAR and other membrane receptors via the kringle or growth factor domains induces cellular migration and activation of intracellular signaling pathways through mechanisms that are not dependent on proteolysis (2,(11)(12)(13)(14)(15)(16)(17)(18)(19).…”

Section: U Rokinase Plasminogen Activator (Upa)mentioning

confidence: 99%

Urokinase-Type Plasminogen Activator Potentiates Lipopolysaccharide-Induced Neutrophil Activation

Abraham

Gyetko

Kuhn

et al. 2003

101

Urokinase plasminogen activator (uPA) is a serine protease that catalyzes the conversion of plasminogen to plasmin. Although increased circulating levels of uPA are present in endotoxemia and sepsis, conditions in which activated neutrophils contribute to the development of acute organ dysfunction, the ability of uPA to participate directly in LPS-induced neutrophil activation has not been examined. In the present experiments, we show that uPA can enhance activation of neutrophils exposed to submaximal stimulatory doses of LPS. In particular, uPA increased LPS-induced activation of intracellular signaling pathways, including Akt and c-Jun N-terminal kinase, nuclear translocation of the transcriptional regulatory factor NF-κB, and expression of proinflammatory cytokines, including IL-1β, macrophage-inflammatory protein-2, and TNF-α. There was no effect of uPA on LPS-induced activation of p38 mitogen-activated protein kinase in neutrophils. Transgenic mice unable to produce uPA (uPA−/−) were protected from endotoxemia-induced lung injury, as determined by development of lung edema, pulmonary neutrophil accumulation, lung IL-1β, macrophage-inflammatory protein-2, and TNF-α cytokine levels. These results demonstrate that uPA can potentiate LPS-induced neutrophil responses and also suggest that such effects are sufficiently important in vivo to play a major contributory role in neutrophil-mediated inflammatory responses, such as the development of acute lung injury.