The paradox of matrix metalloproteinases in infectious disease

Matrix metalloproteinase inhibitor, CTS-1027, attenuates liver injury and fibrosis in the bile duct-ligated mouse

AIM

Excessive matrix metalloproteinase (MMP) activity has been implicated in the pathogenesis of acute and chronic liver injury. CTS-1027 is an MMP inhibitor, which has previously been studied in humans as an anti-arthritic agent. Thus, our aim was to assess if CTS-1027 is hepato-protective and anti-fibrogenic during cholestatic liver injury.

METHODS

C57/BL6 mice were subjected to bile duct ligation (BDL) for 14 days. Either CTS-1027 or vehicle was administered by gavage.

RESULTS

BDL mice treated with CTS-1027 demonstrated a threefold reduction in hepatocyte apoptosis as assessed by the TUNEL assay or immunohistochemistry for caspase 3/7-positive cells as compared to vehicle-treated BDL animals (P < 0.01). A 70% reduction in bile infarcts, a histological indicator of liver injury, was also observed in CTS-1027-treated BDL animals. These differences could not be ascribed to differences in cholestasis as serum total bilirubin concentrations were nearly identical in the BDL groups of animals. Markers for stellate cell activation (alpha-smooth muscle actin) and hepatic fibrogenesis (collagen 1) were reduced in CTS-1027 versus vehicle-treated BDL animals (P < 0.05). Overall animal survival following 14 days of BDL was also improved in the group receiving the active drug (P < 0.05).

CONCLUSION

The BDL mouse, liver injury and hepatic fibrosis are attenuated by treatment with the MMP inhibitor CTS-1027. This drug warrants further evaluation as an anti-fibrogenic drug in hepatic injury.

Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy

In the cystic fibrosis (CF) airway, chronic infection by Pseudomonas aeruginosa results from biofilm formation in a neutrophil-rich environment. We tested the capacity of human neutrophils to modify early biofilm formation of P. aeruginosa strain PAO1, and an isogenic CF strain isolated early and years later in infection. In a static reactor, P. aeruginosa biofilm density of all strains was enhanced at 24 h in the presence of neutrophils, with the greatest relative increase associated with the lowest inoculum of P. aeruginosa tested. Previously, neutrophil-induced biofilm enhancement was shown to largely result from the incorporation of F-actin and DNA polymers into the bacterial biofilm. This finding was advanced by the comparison of biofilm enhancement from intact unstimulated neutrophils and from lysed or apoptotic neutrophils. Apoptotic neutrophils, with an intact cell membrane, were unable to contribute to biofilm enhancement, while lysed neutrophils evoked a similar response to that of intact cells. Using F-actin and DNA as targets, the capacity of negatively charged poly(amino acids) to disrupt, or prevent, early biofilm formation was tested. Anionic poly(aspartic acid) effectively prevented or disrupted biofilm formation. Combination of poly(aspartic acid) with DNase resulted in a synergistic increase in biofilm disruption. These results demonstrate that the presence of dying neutrophils can facilitate the initial stages of biofilm development by low inocula of P. aeruginosa. Neutrophil F-actin represents a potential new therapeutic target for disruption of pathogenic biofilms.

Analysis of matrix metalloproteinase secretion by macrophages

Matrix metalloproteinases (MMPs) are zinc-dependent proteases whose physiological roles include control of leukocyte migration. They are implicated in tissue destruction in inflammatory and infectious diseases. MMPs are not only capable of degrading all components of the extracellular matrix, but they also can modulate the immune response by cleaving cytokines and chemokines to alter their activity. Macrophages secrete a broad range of MMPs and represent a key source of MMPs in inflammatory lesions such as granulomas. Zymography is substrate-based gel electrophoresis that allows direct visualization of MMP activity. Here we describe measurement of MMP secretion from macrophages focusing on quantitative zymography. We also discuss complementary methods that should be used in parallel with zymography. The ability to analyze and quantify MMP secretion by macrophages offers an additional window through which to understand the contributions of macrophages to a wide variety of infectious, inflammatory, and immunologic disorders.

Nitric oxide participation in granulomatous response induced by Paracoccidioides brasiliensis infection in mice

The role of nitric oxide (NO) in granulomas of Paracoccidioides brasiliensis-infected inducible NO synthase-deficient C57BL/6 mice (iNOS KO) and their wild-type counterparts and its association with osteopontin (OPN) and matrix metalloproteinases (MMPs) was studied. At 15 days after infection (DAI), iNOS KO mice showed compact and necrotic granulomas with OPN+ macrophages and multinucleated giant cells, whereas wild-type mice developed loose granulomas with many fungi and OPN+ cells distributed throughout the tissue. In addition, high OPN levels and fungal load were observed in iNOS KO mice. Both experimental groups had MMP-9 activity. At 120 DAI, iNOS KO had smaller granulomas with OPN+ cells, lower OPN levels, lower fungal load and decreased MMP-9 activity compared with wild-type mice. These findings suggest that NO has an important role in granuloma modulation, by controlling OPN and MMP production, as well as by inducing loose granulomas formation and fungal dissemination, resulting, at later phases, in progression of paracoccidioidomycosis.

Enhanced systemic matrix metalloproteinase response in Helicobacter pylori gastritis

BACKGROUND

Helicobacter pylori causes chronic gastritis, peptic ulcer disease, and is the most important risk factor for non-cardia gastric cancer, and has been shown to upregulate matrix metalloproteinases (MMPs) in infected gastric mucosa. MMPs are proteolytic enzymes regulated by tissue inhibitors of metalloproteinases (TIMPs).

AIMS

We set up this study to find out whether H. pylori gastritis induces systemic MMP response.

METHODS

Serum samples were collected from patients undergoing gastroscopy; 26 patients had H. pylori gastritis and 18 were H. pylori-negative controls with normal gastric mucosa. Serum MMP levels were analysed by enzyme-linked immunosorbent assay.

RESULTS

Significantly elevated serum levels of collagenase-2 (MMP-8), gelatinase B (MMP-9), neutrophil elastase (NE), and myeloperoxidase (MPO), and reduced serum levels of gelatinase A (MMP-2) and TIMP-1 were demonstrated in patients with H. pylori gastritis as compared to H. pylori-negative controls. No significant differences were shown in serum matrilysin-1 (MMP-7) levels.

CONCLUSIONS

For the first time, we show enhanced MMP-8 response in H. pylori infection together with other neutrophil degranulation products (MMP-9, MPO, NE). Elevated circulating neutrophil degranulation product levels in serum of H. pylori-positive patients reflect accelerated proteolysis and oxidative stress, and may contribute to extraintestinal sequelae, such as cardiovascular diseases.

1alpha,25-dihydroxyvitamin D3 inhibits matrix metalloproteinases induced by Mycobacterium tuberculosis infection

Matrix metalloproteinases (MMP) can degrade all components of pulmonary extracellular matrix. Mycobacterium tuberculosis induces production of a number of these enzymes by human macrophages, and these are implicated in the pathogenesis of pulmonary cavitation in tuberculosis. The active metabolite of vitamin D, 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)], has previously been reported to inhibit secretion of MMP-9 in human monocytes (MN), but its influence on the secretion and gene expression of MMP and tissue inhibitors of MMP (TIMP) in M. tuberculosis-infected cells has not previously been investigated. We therefore determined the effects of 1alpha,25(OH)(2)D(3) on expression, secretion and activity of a number of MMP and TIMP in M. tuberculosis-infected human leucocytes; we also investigated the effect of 1alpha,25(OH)(2)D(3) on the secretion of interleukin-10 (IL-10) and prostaglandin E(2) (PGE(2)), both transcriptional regulators of MMP expression. We found that M. tuberculosis induced expression of MMP-1, MMP-7 and MMP-10 in MN and MMP-1 and MMP-10 in peripheral blood mononuclear cells (PBMC). 1alpha,25(OH)(2)D(3) significantly attenuated M. tuberculosis-induced increases in expression of MMP-7 and MMP-10, and suppressed secretion of MMP-7 by M. tuberculosis-infected PBMC. MMP-9 gene expression, secretion and activity were significantly inhibited by 1alpha,25(OH)(2)D(3) irrespective of infection. In contrast, the effects of 1alpha,25(OH)(2)D(3) on the expression of TIMP-1, TIMP-2 and TIMP-3 and secretion of TIMP-1 and TIMP-2 were small and variable. 1alpha,25(OH)(2)D(3) also induced secretion of IL-10 and PGE(2) from M. tuberculosis-infected PBMC. These findings represent a novel immunomodulatory role for 1alpha,25(OH)(2)D(3) in M. tuberculosis infection.

Leishmania surface protein gp63 binds directly to human natural killer cells and inhibits proliferation

Natural killer (NK) cells contribute to immunity as the first line of defence in numerous infections by early cytokine secretion and cytotoxicity. In Leishmania infection, NK cells contribute with interferon-gamma and may assist in directing the immune response towards T helper type 1, which is essential for successful control of the parasites. Thus, NK cells may play an important role in both resistance and control of the infection. However, during Leishmania infection NK cells show signs of suppression. To explore the reason for this suppression, we exposed naive and interleukin (IL)-2 activated NK cells directly to promastigotes of Leishmania major in vitro. As a rapid consequence of contact between naive NK cells and promastigotes, expression of NK cell receptors show significant changes. We identify one of the major surface molecules of promastigotes, glycoprotein (gp) 63, as an important agent for these suppressive effects by using promastigotes of a gp63ko strain of L. major. Furthermore, proliferation of IL-2-activated purified NK cells is suppressed after exposure to the wild-type but not to gp63ko promastigotes. However, gp63ko L. major induced no NK cell proliferation when NK cells were co-cultured with peripheral blood mononuclear cells populations such as CD14(+) monocytes or T cells.

Gelatinase matrix metalloproteinase (MMP)-2 and MMP-9 of the umbilical cord blood in preeclampsia

BACKGROUND

Preeclampsia is associated with accumulation of collagen and proteoglycans in the umbilical cord tissues as a result of increased biosynthesis and decreased degradation of these components. Matrix metalloproteinases (MMPs) are enzymes engaged in the degradation of collagen and the protein core structures of proteoglycans, including those which bind peptide growth factors.

METHODS

We used Western immunoblots, immunoenzymatic assay (ELISA) and zymography techniques for the detection of gelatinases and their inhibitors.

RESULTS

We found that both umbilical cord blood plasma and serum of controls and preeclamptic newborns contained MMP-2 and MMP-9, as well tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2. The umbilical cord plasma of preeclamptic subjects contained large amounts of MMP-9 in a form of complexes with other plasma components, and zymographic analysis demonstrated increased gelatinolytic activity at a position corresponding to MMP-9, compared to control samples. By contrast, MMP-2, TIMP-1 and TIMP-2 data showed no significant differences between preeclamptic and control samples.

CONCLUSIONS

The high activity of MMP-9 in preeclamptic plasma suggests its participation in the proteolytic release of peptide growth factors from their complexes with other matrix components, with subsequent stimulation of cell division and matrix biosynthesis. We suggest this might represent one of the mechanisms for matrix remodeling in the umbilical cord of preeclamptic newborns.

l-Glutamate in Middlebrook 7H9 culture medium upregulates matrix metalloproteinase-2 secretion from human astrocytoma cells

Matrix metalloproteinases (MMPs) are implicated in the pathology of CNS tuberculosis. Whilst investigating the secretion of MMP-2 from human U373-MG astrocytoma cells, we observed elevated MMP-2 secretion in response to Middlebrook 7H9 media but not to Mycobacterium tuberculosis itself. Middlebrook 7H9 media did not stimulate MMP-1 or MMP-9 secretion from astrocytoma cells. The excitatory neurotransmitter l-glutamate, at concentrations found in Middlebrook 7H9 media, induced significant astrocytoma MMP-2 secretion (p<0.05). l-Glutamate-induced MMP-2 activity may contribute to neuropathology in various CNS diseases and may generate misleading data in pathogen studies where Middlebrook 7H9 is the culture medium.

Zinc metalloproteins as medicinal targets

Zinc bioinorganic chemistry has emphasized the role of the metal ion on the structure and function of the protein. There is, more recently, an increasing appreciation of the role of zinc proteins in a variety of human diseases. This critical review, aimed at both bioinorganic and medicinal chemists, shows how apparently widely-diverging diseases share the common mechanistic approaches of targeting the essential function of the metal ion to inhibit activity. Protein structure and function is briefly summarized in the context of its clinical relevance. The status of current and potential inhibitors is discussed along with the prospects for future developments (162 references).

In vitro evidence for metallopeptidase participation in hepatocyte damage induced by Leishmania chagasi-infected macrophages

Leishmania (Leishmania) chagasi infection activates macrophages, which release several microbicidal agents, including peptidases, to eliminate the parasite. Leishmanicidal mediators released in large amounts may cause morphological and/or functional injuries to the liver. In order to investigate the involvement of peptidases in this phenomenon, an in vitro co-culture model of peritoneal macrophages infected with L. chagasi and hepatocytes was used. High levels of released hepatic transaminases were found in supernatants from infected co-cultures at the same time point in which alterations in hepatocyte morphology and maximum proteolytic activity were observed. The largest proteolytic activity being at pH 10 as well as the greatest efficiency of treatment with 1,10-phenantroline observed in supernatants from the infected co-cultures suggests the presence of metallopeptidases during the leishmanicidal activity by infected macrophages. Furthermore, TNF-alpha levels and high levels of TGF-beta were increased at this time point, and this can be related to the synthesis of metallopeptidases and the conversion of the latent form to the active form. Metallopeptidase activities were detected by gelatin SDS-PAGE in higher amounts in infected macrophages and co-culture supernatant; moreover, one metallopeptidase migrating at 85 kDa produced in excess (41% more) by infected macrophages was identified as MMP-9. This metallopeptidase may be participating in this phenomenon together with other leishmanicidal factors released by these host cells.

Multiple expression of matrix metalloproteinases in murine neurocysticercosis: Implications for leukocyte migration through multiple central nervous system barriers

During the course of murine neurocysticercosis (NCC), disruption of the unique protective barriers in the central nervous system (CNS) is evidenced by extravasation of leukocytes. This process varies according to the anatomical sites and diverse vascular beds analyzed. To examine mechanisms involved in the observed differences, the expression and activity of eight matrix metalloproteinases (MMPs) were analyzed in a murine model of NCC. The mRNA expression of the MMPs studied was upregulated as a result of infection, and active MMPs were mainly detected in leukocytes migrating into the brain. Polarized expression and gelatinolytic activity of several MMPs were identified in immune cells extravasating pial vessels as early as 1 day post infection. In contrast, leukocytes expressing active MMPs and extravasating parenchymal vessels were not observed until 5 weeks post infection. In ventricular areas, most of the MMP activity was detected in leukocytes traversing the ependyma from leptomeningeal infiltrates. In addition, immune cells continued to express active MMPs after exiting vessels suggesting that enzymatic activity of MMPs is not just required for diapedesis. These results correlate with our previous studies showing differential kinetics in the disruption of the CNS barriers upon infection and help document the important role of MMPs during leukocyte infiltration and inflammation.

Identification of a lepidopteran matrix metalloproteinase with dual roles in metamorphosis and innate immunity

Matrix metalloproteinases (MMPs) are key enzymes in mammalian tissue remodeling and inflammation. Recently, we postulated that an endogenous MMP expressed in the lepidopteran model Galleria mellonella during metamorphosis causes degradation of collagen-IV, which in turn results in activation of innate immunity. Here, we report that degradation of collagen-IV by hemocytes is enhanced upon injection of bacterial lipopolysaccharide (LPS), and that this activity is sensitive to the MMP-inhibitor GM6001. Therefore, we screened for enzymes behind this activity and identified the first MMP from Lepidoptera (Gm1-MMP), and the third from insects. Gm1-MMP shares homology with the first MMP from Drosophila (Dm1-MMP) known to be essential for tissue remodeling during metamorphosis. Using quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis, we confirmed up-regulation of Gm1-MMP expression after pupation, when extracellular matrix breakdown of larval tissues occurs. In addition, we determined that LPS challenge induces Gm1-MMP expression in hemocytes, implicating its participation in collagen-IV degradation upon septic injury. These results suggest dual roles of Gm1-MMP in innate immunity and metamorphosis. Interestingly, our phylogenetic analysis elucidates that Gm1-MMP share highest similarity with human MMP-19 and MMP-28, whose functions in mammalian wounding and inflammatory response have recently been demonstrated; hence, the present findings may provide insights into the evolutionarily conserved features of MMPs.

Human neutrophils uniquely release TIMP-free MMP-9 to provide a potent catalytic stimulator of angiogenesis

Several lines of evidence have implicated matrix metalloproteinase 9 (MMP-9) as a protease inducing an angiogenic switch critical for tumor progression. Among MMP-9-expressing cell types, including cancer cells and tumor-associated leukocytes, inflammatory neutrophils appear to provide an important source of MMP-9 for tumor angiogenesis. However, delivery of MMP-9 by neutrophils has not been mechanistically linked to its catalytic activity at the angiogenic site. By using a modified angiogenic model, allowing for a direct analysis of exogenously added cells and their products in collagen onplants grafted on the chorioallantoic membrane of the chicken embryo, we demonstrate that intact human neutrophils and their granule contents are highly angiogenic. Furthermore, purified neutrophil MMP-9, isolated from the released granules as a zymogen (proMMP-9), constitutes a distinctly potent proangiogenic moiety inducing angiogenesis at subnanogram levels. The angiogenic response induced by neutrophil proMMP-9 required activation of the tissue inhibitor of metalloproteinases (TIMP)-free zymogen and the catalytic activity of the activated enzyme. That the high angiogenic potency of neutrophil proMMP-9 is associated with its unique TIMP-free status was confirmed when a generated and purified stoichiometric complex of neutrophil proMMP-9 with TIMP-1 failed to induce angiogenesis. Recombinant human proMMP-9, operationally free of TIMP-1, also induced angiogenesis at subnanomolar levels, but lost its proangiogenic potential when stoichiometrically complexed with TIMP-1. Similar proMMP-9/TIMP-1 complexes, but naturally produced by human monocytic U937 cells and HT-1080 fibrosarcoma cells, did not stimulate angiogenesis. These findings provide biochemical evidence that infiltrating neutrophils, in contrast to other cell types, deliver a potent proangiogenic moiety, i.e., the unencumbered TIMP-free MMP-9.

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.

Matrix metalloproteinase dysregulation in HIV infection: implications for therapeutic strategies

The emerging role of immune activation and inflammation in the pathogenesis of human immunodeficiency virus (HIV) disease has stimulated the search for new approaches for managing HIV infection. Recent evidence suggests that an imbalance between matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs) might contribute to HIV-associated pathology by inducing remodelling of the extracellular matrix. Here, we discuss the evidence and the potential mechanisms for altered MMP or TIMP function in HIV infection and disease. Furthermore, we outline the possible medical implications for the use of compounds that target MMP activity, and we propose that antiretroviral drugs, particularly HIV protease inhibitors (PIs), and compounds with anti-inflammatory properties, such as statins, natural omega-3 fatty acids and tetracyclines, which inhibit MMP function, might represent useful therapeutic approaches to mitigate potential MMP-related damage during HIV infection.

CD16+ monocytes produce IL-6, CCL2, and matrix metalloproteinase-9 upon interaction with CX3CL1-expressing endothelial cells

The CD16+ subset of peripheral blood monocytes (Mo) is expanded dramatically during inflammatory conditions including sepsis, HIV-1 infection, and cancer. CD16+ express high levels of CX3CR1, which mediates arrest onto CX3CL1-expressing endothelial cells (EC) under flow conditions. In contrast, attachment of CD16- Mo onto cytokine-activated EC is independent of CX3CL1. Here, we investigate the ability of CD16+ and CD16- Mo to produce proinflammatory cytokines upon interaction with CX3CL1-expressing HUVEC. We demonstrate that CD16+ but not CD16- Mo produce high levels of IL-6, CCL2, and matrix metalloproteinase (MMP)-9 when cocultured with TNF/IFN-gamma-activated HUVEC or nonactivated HUVEC expressing CX3CL1. Furthermore, supernatants from Mo cocultured with cytokine-activated HUVEC induce neuronal death in vitro. These results suggest that membrane-bound CX3CL1 stimulates production of IL-6, CCL2, and MMP-9 by CD16+ Mo, likely via engagement of CX3CR1. Thus, expansion of CD16+ Mo and their accumulation onto CX3CL1-expressing EC may result in recruitment of Mo and T cell subsets at sites of inflammation in response to CCL2, IL-6-induced cell activation and/or differentiation, and MMP-9-mediated vascular and tissue injury.

Individual matrix metalloproteinases control distinct transcriptional responses in airway epithelial cells infected with Pseudomonas aeruginosa

Airway epithelium is the initial point of host-pathogen interaction in Pseudomonas aeruginosa infection, an important pathogen in cystic fibrosis and nosocomial pneumonia. We used global gene expression analysis to determine airway epithelial transcriptional responses dependent on matrilysin (matrix metalloproteinase 7 [MMP-7]) and stromelysin-2 (MMP-10), two MMPs induced by acute P. aeruginosa pulmonary infection. Extraction of differential gene expression (EDGE) analysis of gene expression changes in P. aeruginosa-infected organotypic tracheal epithelial cell cultures from wild-type, Mmp7-/-, and Mmp10-/- mice identified 2,091 matrilysin-dependent and 1,628 stromelysin-2-dependent genes that were differentially expressed. Key node network analysis showed that these MMPs controlled distinct gene expression programs involved in proliferation, cell death, immune responses, and signal transduction, among other host defense processes. Our results demonstrate discrete roles for these MMPs in regulating epithelial responses to Pseudomonas infection and show that a global genomics strategy can be used to assess MMP function.

Achillea millefolium L. s.l. -- is the anti-inflammatory activity mediated by protease inhibition?

Achillea millefolium L. s.l. is traditionally used not only in the treatment of gastro-intestinal and hepato-biliary disorders, but also as an antiphlogistic drug. As various proteases, for instance human neutrophil elastase (HNE) and matrix metalloproteinases (MMP-2 and -9), are associated with the inflammatory process, the aim of this study was to test a crude plant extract in in vitro-protease inhibition assays for understanding the mechanisms of anti-inflammatory action. Furthermore, two fractions enriched in flavonoids and dicaffeoylquinic acids (DCQAs), respectively, were also tested in order to evaluate their contribution to the antiphlogistic activity of the plant. The extract and the flavonoid fraction inhibited HNE showing IC(50) values of approximately 20 microg/ml, whereas the DCQA fraction was less active (IC(50)=72 microg/ml). The inhibitory activity on MMP-2 and -9 was observed at IC(50) values from 600 to 800 microg/ml, whereas the DCQA fraction showed stronger effects than the flavonoid fraction and the extract. In conclusion, the in vitro-antiphlogistic activity of Achillea is at least partly mediated by inhibition of HNE and MMP-2 and -9. After the recently described spasmolytic and choleretic effects the obtained results give further insights into the pharmacological activity of Achillea and confirm the traditional application as antiphlogistic drug.

Matrix metalloproteinases as modulators of inflammation

An increased expression of members of the matrix metalloproteinase (MMP) family of enzymes is seen in almost every human tissue in which inflammation is present. Through the use of models of human disease in mice with targeted deletions of individual MMPs, it has become clear that MMPs act broadly in inflammation to regulate barrier function, inflammatory cytokine and chemokine activity, and the generation of chemokine gradients. Individual MMPs regulate both normal and pathological inflammatory processes, and therefore, developing rational therapies requires further identification of specific MMP substrates and characterization of the downstream consequences of MMP proteolytic activity.

Topical p38 MAPK inhibition reduces bacterial growth in an in vivo burn wound model

BACKGROUND

Although the inflammatory response is a prerequisite for wound healing, excessive activation of the innate immune system can induce epithelial cell damage and apoptosis, which may further compromise dermal integrity. In a noninfectious burn wound model, we previously demonstrated that topical inhibition of p38 MAPK, an important inflammatory signaling pathway, attenuated epithelial cell damage and apoptosis. We now question whether attenuating local inflammation would weaken bacterial wound resistance and compromise host defense.

METHODS

Rats received 30% total body surface area burn, and the wound was treated with topical application of a p38 MAPK inhibitor or vehicle. At 24 hours after injury, burn wounds were inoculated with Pseudomonas aeruginosa. At 48 hours postinjury, animals were sacrificed, and the burn wound was analyzed.

RESULTS

Inoculating burn wounds induced significant bacterial growth. Dermal inflammatory changes were markedly accentuated in the inoculated animals. Topical p38 MAPK inhibition reduced the proinflammatory cytokine expression in the burn wounds and neutrophil sequestration with or without bacterial inoculation. Interestingly, the bacterial wound growth was significantly attenuated in animals treated with topical p38 MAPK inhibitor.

CONCLUSIONS

Topical p38 MAPK inhibition attenuated wound inflammation without interfering with bacterial host defense. Attenuation of excessive burn wound inflammatory signaling may prevent secondary damage of the dermal barrier and reduce the growth of opportunistic pathogens.

Brucella requires a functional Type IV secretion system to elicit innate immune responses in mice

The virB operon, encoding a Type IV secretion system (T4SS), is essential for intracellular survival and persistent infection by Brucella spp. To better understand the role of the T4SS in evading host defence mechanisms and establishing chronic infection, we compared transcriptional profiles of the host response to infection with wild-type and virB mutant Brucella strains. Analysis of gene expression profiles in murine splenocytes 3 days after inoculation with wild-type Brucella strains revealed an inflammatory response, with a prominent upregulation of genes induced by both type I and type II interferons. Real-time RT-PCR showed that a group of genes from these pathways were induced by day 3 post infection and declined to baseline levels by day 7. In contrast, neither of the two virB mutant strains elicited a proinflammatory gene expression profile, demonstrating that the T4SS was required to trigger this response. Infection studies using type I interferon receptor knockout mice showed that a lack of type I interferon signalling did not affect Brucella replication during the first 4 weeks of infection. Thus, induction of type I interferons does not appear to be an essential mechanism by which the T4SS promotes persistent infection by Brucella.

Collagenase 2/matrix metalloproteinase 8 in critically ill patients with secondary peritonitis

Secondary peritonitis is an important indication for surgical intensive care admissions, and it is associated with high morbidity and mortality. Collagenase 2/matrix metalloproteinase (MMP) 8 is a tissue matrix-degrading enzyme that is released from leukocytes upon inflammatory stimuli and may thus contribute to peritonitis-associated organ damage. We studied the levels and activity of MMP-8 in the peritoneal fluid of 15 critically ill patients with secondary peritonitis. The MMP-8 levels were measured from the patients' peritoneal fluid, serum, and urine, and from the serum and urine of 10 healthy controls by immunofluorometric assay. Median MMP-8 level in peritoneal fluid supernatant was 1,317 microg/L (interquartile range [IQR]) (1,254-1,359 microg/L) being significantly higher than in the sera of the patients (P=0.008). Molecular forms and isoform distribution of MMP-8, MMP-1, and MMP-13 in peritoneal fluid, assessed by Western immunoblotting, revealed that the neutrophil-type MMP-8 was the major collagenase species in peritoneal fluid, and it was partially in an activated form. Catalytically competent, active MMP-8 produced the characteristic cleavage products from intact human type I collagen. The serum levels of MMP-8 were higher in the patients, 49 microg/L (IQR, 23-214 microg/L), than in the controls, 11 microg/L (IQR, 8-24 microg/L) (P<0.01). The MMP-8 levels in the urine were higher in the patients, 0.27 microg/L (IQR, 0.04-1.89 microg/L), than in the controls, 0.03 microg/L (IQR, 0.0-0.05 microg/L) (P=0.013). Our data demonstrate for the first time that MMP-8 levels are remarkably elevated and in an active and catalytically competent form in the peritoneal fluid samples of patients with secondary peritonitis.

Antiretroviral therapy inhibits matrix metalloproteinase-9 from blood mononuclear cells of HIV-infected patients

OBJECTIVE

To investigate whether antiretroviral therapy (ART) influences the release of matrix metalloproteinase (MMP)-9 from peripheral blood mononuclear cells (PBMC) of HIV-infected individuals.

DESIGN

Culture supernatants were collected from PBMC isolated from 46 HIV-infected subjects and 19 healthy donors (HD). Among the HIV-infected subjects, 30 were receiving ART therapy, while 16 were naive for any ART treatment.

METHODS

Zymography of culture supernatants was followed by determination of MMP-9 using computered scanning densitometry. MMP-9 net enzymatic activity was determined by the sensitive fluorescent-activated substrate conversion assay (FASC) to complement the zymography data.

RESULTS

MMP-9 was significantly elevated in culture supernatants from PBMC of ART-naive subjects in comparison with HD. In the supernatants from 30 HIV-infected subjects receiving ART therapy, MMP-9 was significantly lower than that in those from ART-naive subjects. Analysis by the reverse transcriptase polymerase chain reaction indicated that MMP-9 expression was increased in ART-naive subjects in comparison with HD but ART induced a decrease of MMP-9 expression to levels comparable with those of HD. FASC used as a functional assay showed conversion of fluorescent gelatine in ART-naive subjects, indicating the presence of active MMP-9. By contrast, in both HD and ART-treated subjects, there was no MMP-9 activity, indicating that MMP-9 was completely blocked by binding to its natural tissue inhibitor TIMP-1.

CONCLUSIONS

The present findings show for the first time that ART can reduce the capacity of PBMC from HIV-infected patients to secrete increased amounts of MMP-9.

Induction of multiple matrix metalloproteinases in human dermal and synovial fibroblasts by Staphylococcus aureus: implications in the pathogenesis of septic arthritis and other soft tissue infections

Infections of body tissue by Staphylococcus aureus are quickly followed by degradation of connective tissue. Patients with rheumatoid arthritis are more prone to S. aureus-mediated septic arthritis. Various types of collagen form the major structural matrix of different connective tissues of the body. These different collagens are degraded by specific matrix metalloproteinases (MMPs) produced by fibroblasts, other connective tissue cells, and inflammatory cells that are induced by interleukin-1 (IL-1) and tumor necrosis factor (TNF). To determine the host's contribution in the joint destruction of S. aureus-mediated septic arthritis, we analyzed the MMP expression profile in human dermal and synovial fibroblasts upon exposure to culture supernatant and whole cell lysates of S. aureus. Human dermal and synovial fibroblasts treated with cell lysate and filtered culture supernatants had significantly enhanced expression of MMP-1, MMP-2, MMP-3, MMP-7, MMP-10, and MMP-11 compared with the untreated controls (p < 0.05). In the S. aureus culture supernatant, the MMP induction activity was identified to be within the molecular-weight range of 30 to >50 kDa. The MMP expression profile was similar in fibroblasts exposed to a combination of IL-1/TNF. mRNA levels of several genes of the mitogen-activated protein kinase (MAPK) signal transduction pathway were significantly elevated in fibroblasts treated with S. aureus cell lysate and culture supernatant. Also, tyrosine phosphorylation was significantly higher in fibroblasts treated with S. aureus components. Tyrosine phosphorylation and MAPK gene expression patterns were similar in fibroblasts treated with a combination of IL-1/TNF and S. aureus. Mutants lacking staphylococcal accessory regulator (Sar) and accessory gene regulator (Agr), which cause significantly less severe septic arthritis in murine models, were able to induce expression of several MMP mRNA comparable with that of their isogenic parent strain but induced notably higher levels of tissue inhibitors of metalloproteinases (TIMPs). To our knowledge, this is the first report of induction of multiple MMP/TIMP expression from human dermal and synovial fibroblasts upon S. aureus treatment. We propose that host-derived MMPs contribute to the progressive joint destruction observed in S. aureus-mediated septic arthritis.

Matrix metalloproteinase 9 activity enhances host susceptibility to pulmonary infection with type A and B strains of Francisella tularensis

A striking feature of pulmonary infection with the Gram-negative intracellular bacterium Francisella tularensis, a category A biological threat agent, is an intense accumulation of inflammatory cells, particularly neutrophils and macrophages, at sites of bacterial replication. Given the essential role played by host matrix metalloproteinases (MMPs) in modulating leukocyte recruitment and the potentially indiscriminate destructive capacity of these cells, we investigated whether MMP-9, an important member of this protease family released by neutrophils and activated macrophages, plays a role in the pathogenesis of respiratory tularemia. We found that F. tularensis induced expression of MMP-9 in FVB/NJ mice and that the action of this protease is associated with higher bacterial burdens in pulmonary and extrapulmonary tissues, development of more extensive histopathology predominated by neutrophils, and increased morbidity and mortality compared with mice lacking MMP-9 (MMP-9(-/-)). Moreover, MMP-9(-/-) mice were able to resolve infection with either the virulence-attenuated type B (live vaccine strain) or the highly virulent type A (SchuS4) strain of F. tularensis. Disease resolution was accompanied by diminished leukocyte recruitment and reductions in both bacterial burden and proinflammatory cytokine production. Notably, neutrophilic infiltrates were significantly reduced in MMP-9(-/-) mice, owing perhaps to limited release of Pro-Gly-Pro, a potent neutrophil chemotactic tripeptide released from extracellular matrix through the action of MMP-9. Collectively, these results suggest that MMP-9 activity plays a central role in modulating the clinical course and severity of respiratory tularemia and identifies MMPs as novel targets for therapeutic intervention as a means of modulating neutrophil recruitment.

Matrix metalloproteinase-7, -8, -9, -25, and -26 and CD43, -45, and -68 cell-markers in HIV-infected patients' saliva and gingival tissue

BACKGROUND

Matrix metalloproteinases (MMPs) process the extracellular matrix and act in tissue remodelling in many physiological and pathological conditions. Certain MMPs can also exert protective anti-inflammatory properties. The levels and expression of MMPs and tissue inhibitors of MMPs (TIMPs) in saliva and gingival tissues of human immunodeficiency virus-seropositive (HIV+) patients are unclear.

METHODS

Enzyme-linked immunosorbent assay methods and Western blots were used to study levels and molecular forms of MMP-7, -8, -9, -25, and -26 and TIMP-1 from salivary samples of HIV+ patients (n = 55) and healthy controls (n = 10). The expression of MMPs was also studied by immunohistochemical means in gingival tissue specimens (n = 11, HIV+ patients; n = 10, healthy controls).

RESULTS

The HIV+ patients' MMP-8 levels in saliva were statistically significantly higher only in the acquired immunodeficiency syndrome (AIDS)-phase. MMP-9 levels in ASX- and AIDS-phases showed increased expression. TIMP-1 levels were significantly decreased in lymphadenopathy syndrome (LAS)- and AIDS-related complex (ARC)-phases, while MMP-8/TIMP-1 and MMP-9/TIMP-1 molar ratios were increased in all phases in comparison with controls. The molecular forms of MMP-7, -25, and -26 were different between patients and controls as assessed by Western blot. Immunohistochemical studies showed slightly enhanced MMP-7, -8, -9, -25, and -26 staining in HIV+ gingival tissue samples in comparison with controls.

CONCLUSIONS

This study confirmed and further demonstrated differences in salivary amounts and molecular forms of MMPs and TIMP-1 in HIV+ patients. The results may reflect alterations in host defence reactions associated with HIV infection.

Life and death in the granuloma: immunopathology of tuberculosis

During tuberculosis (TB) infection, the granuloma provides the microenvironment in which antigen-specific T cells colocate with and activate infected macrophages to inhibit the growth of Mycobacterium tuberculosis. Although the granuloma is the site for mycobacterial killing, virulent mycobacteria have developed a variety of mechanisms to resist this macrophage-mediated killing. These surviving mycobacteria become dormant, however, if host cellular immunity or the signals maintaining granuloma structure wane, or if mycobacteria resume replication, leading to reactivation of TB. This balance of life and death applies not only to the mycobacterium but also to the host macrophages that may undergo apoptosis or necrosis, leading to the characteristic caseous necrosis within the granuloma, and the potential spread of TB infection. The immunological factors controlling the development and maintenance of the granuloma will be reviewed.

Monocyte-Astrocyte Networks Regulate Matrix Metalloproteinase Gene Expression and Secretion in Central Nervous System Tuberculosis In Vitro and In Vivo

CNS tuberculosis (CNS-TB) is the most deadly form of tuberculous disease accounting for 10% of clinical cases. CNS-TB is characterized by extensive tissue destruction, in which matrix metalloproteinases (MMPs) may play a critical role. We investigated the hypothesis that Mycobacterium tuberculosis activates monocyte-astrocyte networks increasing the activity of key MMPs. We examined the expression of all human MMPs and the tissue inhibitors of metalloproteinases (TIMPs) in human astrocytes stimulated by conditioned medium from M. tuberculosis-infected monocytes (CoMTB). Real-time RT-PCR showed that gene expression of MMP-1, -2, -3, -7, and -9 was increased (p < 0.05). MMP-9 secretion was significantly up-regulated at 24 h and increased over 120 h (p < 0.01). MMP-1, -3, and -7 secretion was not detected. Secretion of MMP-2 was constitutive and unaffected by CoMTB. Astrocyte gene expression and secretion of TIMP-1 was not affected by CoMTB although TIMP-2 secretion increased 3-fold at 120 h. Immunohistochemical analysis of human brain biopsies confirmed that astrocyte MMP-9 secretion is a predominant feature in CNS-TB in vivo. Dexamethasone inhibited astrocyte MMP-9, but not TIMP-1/2 secretion in response to CoMTB. CoMTB stimulated the nuclear translocation of NF-kappaB, inducing a 6-fold increase in nuclear p65 and a 2-fold increase in nuclear p50. This was associated with degradation of IkappaBalpha and beta within 30 min, persisting for 24 h. In summary, networks active between monocytes and astrocytes regulate MMP-9 activity in tuberculosis and astrocytes are a major source of MMP-9 in CNS-TB. Astrocytes may contribute to a matrix degrading environment within the CNS and subsequent morbidity and mortality.

Abdominal Aortic Aneurysm as a Complex Multifactorial Disease: Interactions of Polymorphisms of Inflammatory Genes, Features of Autoimmunity, and Current Status of MMPs

The role of matrix metalloproteinases (MMPs) in the pathogenesis of abdominal aortic aneurysm (AAA) has focused on the degradation of the extracellular matrix (ECM). The new frontier of MMP biology involves the role of MMPs in releasing cryptic fragments and neoepitopes from the ECM and the impact of MMPs on the regulation of the inflammatory response. The ECM is a complex structure, much more important than an inert scaffold. Both MMP-2 and MMP-9 expose a cryptic epitope that controls angiogenesis. MMPs inhibit angiogenesis through the release of endostatin, endorepellin, arresten, canstatin, and tumstatin. Other breakdown products of the ECM include fragments of fragmin and elastin degradation products (EDPs). In addition, the ECM contains embedded vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-beta). Inflammation is a complex, highly regulated system that involves the identification of injury or infection, response to the injury or infection, repair and healing, and return to normal homeostasis. In some instances, the inflammatory process leads to a pathologic process that is damaging to the host. MMPs play an important role in the control of the inflammatory response through the modification of proinflammatory cytokines, chemokines, and shedding of membrane receptors. Genetic association studies have been performed to help determine the genetic risk associated with certain single nucleotide polymorphisms (SNPs) However, because of the variability in the patient populations and the size of the population, it is difficult to draw any conclusions from these studies. While the etiology of AAA remains unknown, understanding of the inflammatory process and its regulatory points will develop new strategies for the treatment of AAA. Perhaps one difficulty with understanding the pathogenesis of AAA is the lack of precise definition of the phenotype.

Matrix metalloproteinases, their production by monocytes and macrophages and their potential role in HIV-related diseases

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that are a subfamily of metzincins. Matrix metalloproteinases are responsible for much of the turnover of extra-cellular matrix components and are key to a wide range of processes including tissue remodeling and release of biological factors. Imbalance between the MMPs and endogenous tissue inhibitors of metalloproteinases (TIMPs) can result in dysregulation of many biologic processes and lead to the development of malignancy, cardiovascular disease, and autoimmune and inflammatory disorders. MMP production by monocyte/macrophages is dependent on the cell type, state of differentiation, and/or level of activation and whether they are infected, e.g., by HIV-1. MMP expression by HIV-1 infected monocytes and macrophages may alter cellular trafficking and contribute to HIV-associated pathology such as HIV-associated dementia (HAD). This review will provide a classification of the MMP super-family with particular reference to those produced by monocyte/macrophages, describe their regulation and function within the immune system, and indicate their possible roles in the pathogenesis of disease, including HIV-associated dementia.

Electrochemical Proteolytic Beacon for Detection of Matrix Metalloproteinase Activities

This communication describes a novel method for detecting matrix metalloproteinase-7 activity using a peptide substrate labeled with a ferrocene reporter. The substrate serves as a selective "electrochemical proteolytic beacon" (EPB) for this metalloproteinase. The EPB is immobilized on a gold electrode surface to enable "on-off" electrochemical signaling capability for uncleaved and cleaved events. The EPB is efficiently and selectively cleaved by MMP-7 as measured by the rate of decrease in redox current of ferrocene. Direct transduction of a signal corresponding to peptide cleavage events into an electronic signal thus provides a simple, sensitive route for detecting the MMP activity. The new method allows for identification of the activity of MMP-7 in concentrations as low as 3.4 pM. The concept can be extended to design a multiple peptide substrate labeled with different electroactive reporters for assaying multiple MMPs activities.

Matrix metalloproteinases and tumor metastasis

Functions of individual matrix metalloproteinases (MMPs) differentially expressed by tumor cells and stromal cells, are finely regulated by their spatial as well as temporal interactions with distinct cellular and extracellular components of the tumor microenvironment and also distant pre-metastatic sites. Certain aspects of MMP involvement in tumor metastasis such as tumor-induced angiogenesis, tumor invasion, and establishment of metastatic foci at the secondary site, have received extensive attention that resulted in an overwhelming amount of experimental and observational data in favor of critical roles of MMPs in these processes. In particular, dependency of tumor angiogenesis on the activity of MMPs, especially that of MMP-9, renders this step possibly the most effective target of synthetic MMP inhibitors. MMP functioning in other stages of metastasis, including the escape of individual tumor cells from the primary tumor, their intravasation, survival in circulation, and extravasation at the secondary site, have not yet received enough consideration, resulting in insufficient or controversial data. The major pieces of evidence that are most compelling and clearly determine the role and involvement of MMPs in the metastatic cascade are provided by molecular genetic studies employing knock-out or transgenic animals and tumor cell lines, modified to overexpress or downregulate a specific MMP. Findings from all of these studies implicate different functional mechanisms for both tumor and stromal MMPs during distinct steps of the metastatic cascade and indicate that MMPs can exhibit pro-metastatic as well as anti-metastatic roles depending on their nature and the experimental setting. This dual function of individual MMPs in metastasis has become a major focus of this review.

Matrix metalloproteinase-9 in laminae of black walnut extract treated horses correlates with neutrophil abundance

We sought to determine whether a correlation exists between neutrophil infiltration and tissue matrix metalloproteinase-9 (MMP-9) content in digital laminae collected during the prodromal and acute phases of laminitis in horses treated with an aqueous black walnut heartwood extract (BWE). Hoof laminar tissue was obtained at the onset of leukopenia and at the onset of clinical signs of lameness from BWE-treated horses and at equivalent times from control horses. Thin sections of laminae were screened for neutrophils by immunohistochemistry with an anti-CD13 monoclonal antibody and extracts of the same tissues were screened for SDS-renaturable and native MMP-9 activities by denaturing and non-denaturing gelatin zymography. Samples were also screened for MMP-2 and MMP-9 gene expression by RT-qPCR. Control laminae were devoid of both MMP-9 and neutrophils, whereas neutrophils and SDS-renaturable MMP-9 activity were detected in laminae from BWE-treated horses and were strongly correlated at the acute stage of the disease at which time laminar MMP-9 gene expression was significantly (15-fold) elevated. In contrast, BWE-treatment did not significantly elevate MMP-2 gene or protein expression in the laminae. Interestingly, MMP-9 that was present in extracts of laminae from BWE-treated horses at both the prodromal and acute stages of the disease was mainly in the zymogen form, suggesting that the accumulation of the MMP did not contribute to pathology during these stages. However, elevated presence of the MMP-9 zymogen in the tissue would predispose it to catastrophic damage should conditions arise that cleave the regulatory propeptide domain.

MODULATION OF LIPOPOLYSACCHARIDE-INDUCED ACUTE LUNG INFLAMMATION

The present study was undertaken to investigate the influence of insulin on lipopolysaccharide (LPS)-induced acute lung injury. Diabetic male Wistar rats (alloxan, 42 mg/kg, i.v., 30 days) and controls were instilled with saline containing LPS (750 microg/0.4 mL) or saline alone. The following analyses were performed 6 h there after: (a) total and differential cell counts in bronchoalveolar lavage (BAL) fluid, (b) quantification of tumor necrosis factor alpha, interleukin (IL) 1beta, IL-10, and cytokine-induced neutrophil chemoattractant 1 in the BAL (enzyme-linked immunosorbent assay), (c)immunohistochemistry for intercellular adhesion molecule 1 and E-selectin on lung vessels, and (d) quantification of metalloproteinases (MMP) 2 and 9 in the BAL (zymography). Relative to controls, diabetic rats exhibited a reduction in the number of neutrophils (80%) and reduced concentrations of tumor necrosis factor alpha (56%), IL-1beta (66%), and IL-10 (35%) after LPS instillation. Cytokine-induced neutrophil chemoattractant 1 levels did not differ between groups. Increased levels of MMP-2 (90%) and MMP-9 (500%) were observed in diabetic rats compared with controls. Treatment of diabetic rats with neutral protamine Hagedorn insulin (4 IU, s.c.), 2 h before LPS instillation, completely restored the number of neutrophils and concentrations of cytokines in the BAL fluid. Despite no significant differences between diabetic and control groups, there was a remarkable increase in intercellular adhesion molecule 1 and E-selectin expression on lung vessels after insulin treatment. Levels of MMP-2 and MMP-9 did not change after treatment with insulin. Levels of corticosterone were equivalent among groups. Data presented suggest that insulin modulates the production/release of cytokines and the expression of adhesion molecules controlling, therefore, neutrophil migration during the course of LPS-induced acute lung inflammation.

Matrix metalloproteinases: contribution to pathogenesis, diagnosis and treatment of periodontal inflammation

Matrix metalloproteinases (MMPs) form a family of enzymes that mediate multiple functions both in the tissue destruction and immune responses related to periodontal inflammation. The expression and activity of MMPs in non-inflamed periodontium is low but is drastically enhanced to pathologically elevated levels due to the dental plaque and infection-induced periodontal inflammation. Soft and hard tissue destruction during periodontitis and peri-implantitis are thought to reflect a cascade of events involving bacterial virulence factors/enzymes, pro-inflammatory cytokines, reactive oxygen species and MMPs. However, recent studies suggest that MMPs can also exert anti-inflammatory effects in defence of the host by processing anti-inflammatory cytokines and chemokines, as well as by regulating apoptotic and immune responses. MMP-inhibitor (MMPI)-drugs, such as doxycycline, can be used as adjunctive medication to augment both the scaling and root planing-treatment of periodontitis locally and to reduce inflammation systematically. Furthermore, MMPs present in oral fluids (gingival crevicular fluid (GCF), peri-implant sulcular fluid (PISF), mouth-rinses and saliva) can be utilized to develop new non-invasive, chair/bed-side, point-of-care diagnostics for periodontitis and dental peri-implantitis.