Gelatinase B/matrix metalloproteinase-9 and other neutrophil proteases switch off interleukin-2 activity.

Interleukin 2 (IL-2) is critical for T cell development and homeostasis, being a key regulator of adaptive immune responses in autoimmunity, hypersensitivity reactions and cancer. Therefore, its abundance in serum and peripheral tissues needs tight control. Here, we described a new mechanism contributing to the immunobiology of IL-2. We demonstrated, both in biochemical and cell-based assays, that IL-2 is subject to proteolytic processing by neutrophil matrix metalloproteinase-9 (MMP-9). IL-2 fragments produced after cleavage by MMP-9 remained linked by a disulfide bond and displayed a reduced affinity for all IL-2 receptor subunits and a distinct pattern and timing of signal transduction. Stimulation of IL-2-dependent cells, including murine CTLL-2 and primary human regulatory T cells, with cleaved IL-2 resulted in significantly decreased proliferation. The concerted action of neutrophil proteases destroyed IL-2. Our data suggest that in neutrophil-rich inflammatory conditions in vivo, neutrophil MMP-9 may reduce the abundance of signaling-competent IL-2 and generate a fragment that competes with IL-2 for receptor binding, whereas the combined activity of granulocyte proteases has the potential to degrade and thus eliminate bioavailable IL-2.

Immunopathology and dexamethasone therapy in a new model for malaria-associated acute respiratory distress syndrome.

RATIONALE: Malaria infection is often complicated by malaria-associated acute respiratory distress syndrome (MA-ARDS), characterized by pulmonary edema and hemorrhages. No efficient treatments are available for MA-ARDS and its pathogenesis remains poorly understood. OBJECTIVES: Development of a new animal model for MA-ARDS to explore the pathogenesis and possible treatments. METHODS: C57BL/6 mice were infected with Plasmodium berghei NK65, and the development of MA-ARDS was evaluated by the analysis of lung weight, histopathology, and bronchoalveolar lavages. Cytokine and chemokine expression in the lungs was analyzed by reverse transcription-polymerase chain reaction, and the accumulation of leukocyte subclasses was determined by flow cytometric analysis. MEASUREMENTS AND MAIN RESULTS: In this model, the pulmonary expression of several cytokines and chemokines was increased to a higher level than in mice infected with Plasmodium chabaudi AS, which does not cause MA-ARDS. By depletion experiments, CD8(+) T lymphocytes were shown to be pathogenic. High doses of dexamethasone blocked MA-ARDS, even when administered after appearance of the complication, and reduced pulmonary leukocyte accumulation and the expression of a monocyte/macrophage-attracting chemokine. CONCLUSIONS: We developed a novel model of MA-ARDS with many similarities to human MA-ARDS and without cerebral complications. This contrasts with the more classical model with P. berghei ANKA, characterized by fulminant cerebral malaria. Hence, infection with P. berghei NK65 generates a broader time window to study the pathogenesis and to evaluate candidate treatments. The finding that high doses of dexamethasone cured MA-ARDS suggests that it might be more effective against MA-ARDS than it was in the clinical trials for cerebral malaria.

Increased gelatinase B/matrix metalloproteinase 9 (MMP-9) activity in a murine model of acute coxsackievirus B4-induced pancreatitis.

Infection of mice with coxsackievirus B4 results within days in a severe acute necrotizing pancreatitis, which resolves completely within weeks. Gelatinase B or matrix metalloproteinase 9 (MMP-9) has previously been shown to be involved in several models of pancreatitis, but its role in virus-induced pancreatitis has never been investigated. We here report that MMP-9 levels are markedly increased in the pancreas of mice that developed acute pancreatitis following infection with coxsackievirus B4. Moreover, using in situ zymography, we demonstrated that MMP-9 is active in vivo. Double immunohistochemical analysis revealed that macrophages and neutrophils were the cellular source of MMP-9. Extensive tissue rearrangements involving collagen turnover were observed, and these were associated with extensive pathology and resolution of the disease. In summary, this report demonstrates that acute coxsackievirus B4-induced pancreatitis involves the action of MMP-9, which is mainly originating from macrophages and neutrophils.

Adenylyl cyclase-associated protein-1/CAP1 as a biological target substrate of gelatinase B/MMP-9.

Matrix metalloproteinases (MMPs) are classically associated with the turnover of secreted structural and functional proteins. Although MMPs have been shown to process also a kaleidoscope of membrane-associated substrates, little is known about the processing of intracellular proteins by MMPs. Physiological and pathological cell apoptosis, necrosis and tumor lysis by chemotherapy, radiotherapy or immunological cytotoxicity, are examples of conditions in which an overload of intracellular proteins becomes accessible to the action of MMPs. We used a model system of dying human myelomonocytic cells to study the processing of intracellular protein substrates by gelatinase B/MMP-9 in vitro. Adenylyl cyclase-associated protein-1 or CAP1 was identified as a novel and most efficient substrate of gelatinase B/MMP-9. The presence of CAP1 in the extracellular milieu in vivo was documented by analysis of urine of patients with systemic autoimmune diseases. Whereas no active MMP-9 could be detected in urines of healthy controls, all urine samples of patients with clinical parameters of renal failure contained activated MMP-9 and/or MMP-2. In addition, in some of these patients indications of CAP1 cleavage are observed, implying CAP1 degradation in vivo. The high turnover rate of CAP1 by MMP-9, comparable to that of gelatin as the natural extracellular substrate of this enzyme, may be critical to prevent pathological conditions associated with considerable cytolysis.

CXCR3 determines strain susceptibility to murine cerebral malaria by mediating T lymphocyte migration toward IFN-gamma-induced chemokines.

Cerebral malaria (CM) results from the binding of infected erythrocytes and leukocytes to brain endothelia. The precise mechanisms underlying lymphocyte recruitment and activation in CM remain unclear. Therefore, the expression of various chemokines was quantified in brains of mice infected with Plasmodium berghei ANKA (PbA). Several chemokines attracting monocytes and activated T-lymphocytes were expressed at high levels. Their expression was almost completely abrogated in IFN-gamma ligand and receptor KO mice, indicating that IFN-gamma is an essential chemokine inducer in vivo. Surprisingly, the expression levels of chemokines, IFN-gamma and also adhesion molecules in the brain were not lower in CM-resistant Balb/c and DBA/2 mice compared to CM-sensitive C57BL/6 and DBA/1 mice, although T lymphocyte sequestration in the brain was significantly less in CM-resistant than in CM-sensitive mice. This difference correlated with a higher up-regulation of the CXC chemokine receptor (CXCR)-3 on splenic T cells and a higher chemotactic response to IFN-gamma-inducible protein-10 (IP-10) in C57BL/6 compared to Balb/c mice. In conclusion, parasite-induced IFN-gamma in the brain results in high local expression levels of specific chemokines for monocytes and lymphocytes. The strain-dependent susceptibility to develop CM is more related to the expression of CXCR3 in circulating leukocytes than to the chemokine expression levels in the brain.

Gastric gelatinase B/matrix metalloproteinase-9 is rapidly increased in Helicobacter felis-induced gastritis.

It has previously been shown that matrix metalloproteinase-9 (MMP-9) levels, originating from macrophages, are considerably increased in human Helicobacter pylori-associated gastritis. Here, the early kinetics of the MMP-9 response resulting from Helicobacter infection in C57BL/6 and MMP-9 knock-out mice using the murine Helicobacter felis model were examined. H. felis infection induced severe gastritis in the murine stomach at just 2 weeks after infection. Before gastritis, an increase was observed in MMP-9-positive cells detected by immunohistochemistry in the basal lamina propria. This finding was corroborated by gelatin zymography of stomach samples. As the gastritis increased so did the concentration of MMP-9 and the incidence of gastric MMP-9-positive cells, their location corresponding to that of macrophages. In contrast, systemic levels of MMP-9 remained unchanged. When MMP-9-deficient mice were infected with H. felis, no significant difference in gastritis development was detected compared with disease development in wild-type animals. We conclude that MMP-9 production is an early event in the response to gastric Helicobacter infection, a feature that may favor the recruitment of immune cells early during infection. At later stages, however, the increased levels of MMP-9 may damage the integrity of the stomach mucosa.

A monoclonal antibody inhibits gelatinase B/MMP-9 by selective binding to part of the catalytic domain and not to the fibronectin or zinc binding domains.

Gelatinase B/matrix metalloproteinase-9 (MMP-9) is a multidomain enzyme functioning in acute and chronic inflammatory and neoplastic diseases. It belongs to a family of more than 20 related zinc proteinases. Therefore, the discovery and the definition of the action mechanism of selective MMP inhibitors form the basis for future therapeutics. The monoclonal antibody REGA-3G12 is a most selective inhibitor of human gelatinase B. REGA-3G12 was found to recognize the aminoterminal part and not the carboxyterminal O-glycosylated and hemopexin protein domains. A variant of gelatinase B, lacking the two carboxyterminal domains, was expressed in insect cells and fragmented with purified proteinases. The fragments were probed by one- and two-dimensional Western blot and immunoprecipitation experiments with REGA-3G12 to map the interactions between the antibody and the enzyme. The interaction unit was identified by Edman degradation analysis as the glycosylated segment from Trp(116) to Lys(214) of gelatinase B. The sequence of this segment was analysed by hydrophobicity/hydrophilicity, accessibility and flexibility profiling. Four hydrophilic peptides were chemically synthesized and used in binding and competition assays. The peptide Gly(171)-Leu(187) in molar excess inhibited partially the binding of MMP-9 to REGA-3G12 and thus refines the structure of the conformational binding site. These results define part of the catalytic domain of gelatinase B/MMP-9, and not the zinc-binding or fibronectin domains, as target for the development of selective inhibitors.

Matrix metalloproteinases, tissue inhibitors of MMPs and TACE in experimental cerebral malaria.

Cerebral malaria (CM) is a life-threatening disorder and a major medical problem in developing countries. It is caused by the sequestration of malaria-infected erythrocytes onto brain endothelia, followed by blood-brain barrier (BBB) damage and neurological deficit. In the present study, matrix metalloproteinases (MMPs) were analysed in a mouse model of CM with Plasmodium berghei ANKA. Increased numbers of gelatinase B (MMP-9)-positive cells, which were also CD11b(+), were detected in the brain. In addition, activation of gelatinase B occurred in CM brains, and not in brains of mice with non-CM. However, selective genetic knockout of gelatinase B did not alter the clinical evolution of experimental CM. To study other protease balances, the mRNA expression levels of nine matrix metalloproteinases (MMPs), five membrane-type MMPs, TNF-alpha converting enzyme (TACE) and the four tissue inhibitors of metalloproteinases (TIMPs) were analysed during CM in different organs. Significant alterations in expression were observed, including increases of the mRNAs of MMP-3, -8, -13 and -14 in the spleen, MMP-8, -12, -13 and -14 in the liver and MMP-8 and -13 in the brain. Net gelatinolytic activity, independent of gelatinase B and inhibitable with EDTA, was detected in situ in the endothelia of blood vessels in CM brains, but not in brains of mice with non-CM, suggesting that metalloproteases, different from gelatinase B, are active in the BBB environment in CM. The increase in MMP expression in the brain was significantly less pronounced after infection of C57Bl/6 mice with the noncerebral strain P. berghei NK65, but it was similar in CM-susceptible C57Bl/6 and CM-resistant Balb/C mice upon infection with P. berghei ANKA. Furthermore, in comparison with C57Bl/6 mice, a larger increase in TIMP-1 and a marked, >30-fold induction in MMP-3 were found in the brains of Balb/C mice, suggesting possible protective roles for TIMP-1 and MMP-3.