Gelatinase B/matrix metalloproteinase-9 contributes to cellular infiltration in a murine model of zymosan peritonitis

Tumor necrosis factor-α and matrix metalloproteinase-9 cooperatively exacerbate neurovascular degeneration in the neonatal rat retina

Matrix metalloproteinases (MMPs) and tumor necrosis factor (TNF)-α contribute to the pathogenesis of several ocular diseases. Previous studies have shown that MMP-9 activation plays an important role in capillary degeneration in injured retinas. In this study, we aimed to determine the roles of TNF-α in capillary degeneration and MMP-9 activation in the injured retina. In rats, retinal injury was induced by intravitreal injection of N-methyl-D-aspartic acid (NMDA, 200 nmol) at postnatal day 7. We examined (1) the effects of blocking MMP-9 and TNF-α signaling pathway on capillary degeneration, (2) changes in protein levels and distribution of MMP-9 and TNF-α, and (3) the interaction between MMP-9 and TNF-α in regulating the expression level of each protein in retinas of NMDA-injected eyes. Intravitreal injection of GM6001, an MMP inhibitor, or TNF-α neutralizing antibody (anti-TNF-α Ab) attenuated capillary degeneration in retinas of NMDA-injected eyes. Protein levels of TNF-α increased 2 h after NMDA injection, whereas those of MMP-9 increased 4 h after the injection. Anti-TNF-α Ab suppressed activation of MMP-9 in retinas of NMDA-injected eyes, whereas GM6001 diminished the TNF-α protein expression. Incubation of recombinant TNF-α with supernatants of homogenized retina increased protein levels and activity of MMP-9. These results suggest that TNF-α and MMP-9 collaboratively increase their expression levels in the retina following neurodegeneration, thus leading to retinal capillary degeneration. The cooperative interaction between MMP-9 and TNF-α could be involved in the exacerbation of retinal neurovascular degeneration.

Synthesis, Characterization, and Biological Activity of Aminated Zymosan

Zymosan (ZM), a naturally occurring insoluble macromolecule obtained from the cell wall of Saccharomyces cerevisiae, is used as a functional food (as dietary fiber), phagocytic stimulus, and immune potentiator. The present study aimed to increase its solubility and evaluate its immunological application. ZM was converted into soluble 6-amino-6-deoxy-β-(1-3)-glucan of a molecular weight of 296 kDa by reduction. Detailed structural characterization of aminated ZM was determined by Fourier transform infrared spectroscopy and two-dimensional NMR analysis (2D, COSY, TOCSY, ROSEY, NOSEY, and HSQC). Aminated ZM was biocompatible with Raw 264.7 macrophage cell lines up to a concentration of 100 μg/mL. Rhodamine tagging revealed that the aminated ZM microparticles were found localized within the nucleus of Raw 264.7 cells. Both native and aminated ZM showed a similar expression pattern of inflammatory genes in Raw 264.7.

Recombinant Protein-Based Nanoparticles: Elucidating their Inflammatory Effects In Vivo and their Potential as a New Therapeutic Format

Bacterial inclusion bodies (IBs) are protein-based nanoparticles of a few hundred nanometers formed during recombinant protein production processes in different bacterial hosts. IBs contain active protein in a mechanically stable nanostructured format that has been broadly characterized, showing promising potential in different fields such as tissue engineering, protein replacement therapies, cancer, and biotechnology. For immunomodulatory purposes, however, the interference of the format immunogenic properties—intrinsic to IBs—with the specific effects of the therapeutic protein is still an uncovered gap. For that, active and inactive forms of the catalytic domain of a matrix metalloproteinase-9 (MMP-9 and mutMMP-9, respectively) have been produced as IBs and compared with the soluble form for dermal inflammatory effects in mmp9 knock-out mice. After protein injections in air-pouches in the mouse model, MMP-9 IBs induce local neutrophil recruitment and increase pro-inflammatory chemokine levels, lasting for at least two days, whereas the effects triggered by the soluble MMP-9 format fade out after 3 h. Interestingly, the IB intrinsic effects (mutMMP-9 IBs) do not last more than 24 h. Therefore, it may be concluded that IBs could be used for the delivery of therapeutic proteins, such as immunomodulating proteins while preserving their stability in the specific tissue and without triggering important unspecific inflammatory responses due to the protein format.

The Biological Potential Hidden in Inclusion Bodies

Inclusion bodies (IBs) are protein nanoclusters obtained during recombinant protein production processes, and several studies have demonstrated their potential as biomaterials for therapeutic protein delivery. Nevertheless, IBs have been, so far, exclusively sifted by their biological activity in vitro to be considered in further protein-based treatments in vivo. Matrix metalloproteinase-9 (MMP-9) protein, which has an important role facilitating the migration of immune cells, was used as model protein. The MMP-9 IBs were compared with their soluble counterpart and with MMP-9 encapsulated in polymeric-based micelles (PM) through ionic and covalent binding. The soluble MMP-9 and the MMP-9-ionic PM showed the highest activity values in vitro. IBs showed the lowest activity values in vitro, but the specific activity evolution in 50% bovine serum at room temperature proved that they were the most stable format. The data obtained with the use of an air-pouch mouse model showed that MMP-9 IBs presented the highest in vivo activity compared to the soluble MMP-9, which was associated only to a low and a transitory peak of activity. These results demonstrated that the in vivo performance is the addition of many parameters that did not always correlate with the in vitro behavior of the protein of interest, becoming especially relevant at evaluating the potential of IBs as a protein-based nanomaterial for therapeutic purposes.

Conservative Mechanisms of Extracellular Trap Formation by Annelida Eisenia andrei: Serine Protease Activity Requirement

Formation of extracellular traps (ETs) capturing and immobilizing pathogens is now a well-established defense mechanism added to the repertoire of vertebrate phagocytes. These ETs are composed of extracellular DNA (extDNA), histones and antimicrobial proteins. Formation of mouse and human ETs depends on enzymes (i) facilitating decondensation of chromatin by citrullination of histones, and (ii) serine proteases degrading histones. In invertebrates, initial reports revealed existence of ETs composed of extDNA and histones, and here we document for the first time that also coelomocytes, immunocompetent cells of an earthworm Eisenia andrei, cast ETs which successfully trap bacteria in a reactive oxygen species (ROS)-dependent and -independent manner. Importantly, the formation of ETs was observed not only when coelomocytes were studied ex vivo, but also in vivo, directly in the earthworm coelom. These ETs were composed of extDNA, heat shock proteins (HSP27) and H3 histones. Furthermore, the formation of E. andrei ETs depended on activity of serine proteases, including elastase-like activity. Moreover, ETs interconnected and hold together aggregating coelomocytes, a processes proceeding encapsulation. In conclusion, the study confirms ET formation by earthworms, and unravels mechanisms leading to ET formation and encapsulation in invertebrates.

Effects of aliphatic polyesters on activation of the immune system: studies on macrophages

There is a constant search for biodegradable polymers with biocompatible characteristics. However, the reported materials are rarely tested for their immunostimulatory properties, which is an important issue as immune cells activated by the polymers might cause their rejection and lead to further injury to the host tissues. Therefore, the aim of the present study was to determine if biodegradable polymers are able to activate RAW 264.7 macrophages. Aliphatic polyesters, poly(L-lactide) (PLLA), poly(L-lactide-co-trimethylene carbonate) (PLTMC), poly(glycolide-co-L-lactide) (PGLA), poly(glycolide-co-L-lactide-co-ε-caprolactone) (PGLCap) and poly(glycolide-co-ε-caprolactone) (PGCap), processed into foils by slip-casting, were characterized in terms of their structure ((1)H-NMR, GPC, DSC) and surface properties (chemical composition, water contact angle, surface free energy, topography and roughness). RAW 264.7 cells were cultured on the materials for 3 or 5 days and their adherence, numbers of apoptotic/necrotic cells, as well as production of several cytokines/chemokines and other inflammation-related molecules (matrix metalloproteinases, nitric oxide) was evaluated. The study demonstrated that PLLA and PGLA did not influence macrophage activation and survival. In contrast, PLTMC, PGLCap and PGCap significantly decreased macrophage adherence, increased ratio of apoptosis and up-regulated synthesis/release of numerous inflammatory mediators. Thus, the latter materials might initiate an undesired inflammatory reaction. The above effects of the polymers were attributed to their high hydrophobicity and low polarity due to the presence of ε-caproyl blocks (PGLCap and PGCap), and/or high flexibility and susceptibility to mechanical deformation due to low glasstransition temperature (PLTMC, PGLCap and PGCap). In conclusion, while PLLA and PGLA do not affect macrophage functioning, the other materials (PLTMC, PGLCap, PGCap) up-regulate macrophage activity.

An iminosugar-based heparanase inhibitor heparastatin (SF4) suppresses infiltration of neutrophils and monocytes into inflamed dorsal air pouches

Local infiltration of inflammatory cells is regulated by a number of biological steps during which the cells likely penetrate through subendothelial basement membranes that contain heparan sulfate proteoglycans. In the present study, we examined whether administration of heparastatin (SF4), an iminosugar-based inhibitor of heparanase, could suppress local inflammation and degradation of heparan sulfate proteoglycans in basement membranes. In a carrageenan- or formyl peptide-induced dorsal air pouch inflammation model, the number of infiltrated neutrophils and monocytes was significantly lower in mice after topical administration of heparastatin (SF4). The concentration of chemokines MIP-2 and KC in pouch exudates of drug-treated mice was similar to control. In a zymosan-induced peritonitis model, the number of infiltrated cells was not altered in drug-treated mice. To further test how heparastatin (SF4) influences transmigration of inflammatory neutrophils, its suppressive effect on migration and matrix degradation was examined in vitro. In the presence of heparastatin (SF4), the number of neutrophils that infiltrated across a Matrigel-coated polycarbonate membrane was significantly lower, while the number of neutrophils passing through an uncoated membrane was not altered. Lysate of bone marrow-derived neutrophils released sulfate-radiolabeled macromolecules from basement membrane-like extracellular matrix, which was suppressed by heparastatin (SF4). Heparan sulfate degradation activity was almost completely abolished after incubation of lysate with protein G-conjugated anti-heparanase monoclonal antibody, strongly suggesting that the activity was due to heparanase-mediated degradation. Taken together, in a dorsal air pouch inflammation model heparastatin (SF4) potentially suppresses extravasation of inflammatory cells by impairing the degradation of basement membrane heparan sulfate.

MMP-7, MMP-8, and MMP-9 in oral and cutaneous squamous cell carcinomas

OBJECTIVES

Oral squamous cell carcinoma (OSCC) and cutaneous squamous cell carcinoma (CSCC) are epithelial neoplasms, of which OSCC has a worse prognosis. Matrix metalloproteinases (MMPs) are involved in the initiation, invasion, metastasis, and defense of cancer. This study aimed to compare differences in MMP expression in these cancers.

STUDY DESIGN

Sixty-one patients with early-stage (T1-T2 N0 M0) cancers, of which 36 were OSCC and 25 CSCC, were enrolled into this study. Immunohistochemical staining was performed with MMP-7, MMP-8, and MMP-9 antibodies.

RESULTS

MMP-7 expression was stronger in OSCC than in CSCC, mainly in the invasive front. MMP-8 was absent and MMP-9 was mildly expressed in OSCC and CSCC cells. However, MMP-8 and MMP-9 were positive in peritumoral inflammatory cells in both cancers. In addition, MMP-7, MMP-8, and MMP-9 were not associated with the overall survival of patients with OSCC and CSCC patients.

CONCLUSIONS

The increased expression of MMP-7 in the invasive front may partly explain the aggressiveness of OSCC.

Cardioprotective potential of annexin-A1 mimetics in myocardial infarction

Myocardial infarction (MI) and its resultant heart failure remains a major cause of death in the world. The current treatments for patients with MI are revascularization with thrombolytic agents or interventional procedures. These treatments have focused on restoring blood flow to the ischemic tissue to prevent tissue necrosis and preserve organ function. The restoration of blood flow after a period of ischemia, however, may elicit further myocardial damage, called reperfusion injury. Pharmacological interventions, such as antioxidant and Ca(2+) channel blockers, have shown premises in experimental settings; however, clinical studies have shown limited success. Thus, there is a need for the development of novel therapies to treat reperfusion injury. The therapeutic potential of glucocorticoid-regulated anti-inflammatory mediator annexin-A1 (ANX-A1) has recently been recognized in a range of systemic inflammatory disorders. ANX-A1 binds to and activates the family of formyl peptide receptors (G protein-coupled receptor family) to inhibit neutrophil activation, migration and infiltration. Until recently, studies on the cardioprotective actions of ANX-A1 and its peptide mimetics (Ac2-26, CGEN-855A) have largely focused on its anti-inflammatory effects as a mechanism of preserving myocardial viability following I-R injury. Our laboratory provided the first evidence of the direct protective action of ANX-A1 on myocardium, independent of inflammatory cells in vitro. We now review the potential for ANX-A1 based therapeutics to be seen as a "triple shield" therapy against myocardial I-R injury, limiting neutrophil infiltration and preserving both cardiomyocyte viability and contractile function. This novel therapy may thus represent a valuable clinical approach to improve outcome after MI.

Contributions of the three CYP1 monooxygenases to pro-inflammatory and inflammation-resolution lipid mediator pathways

All three cytochrome P450 1 (CYP1) monooxygenases are believed to participate in lipid mediator biosynthesis and/or their local inactivation; however, distinct metabolic steps are unknown. We used multiple-reaction monitoring and liquid chromatography-UV coupled with tandem mass spectrometry-based lipid-mediator metabololipidomics to identify and quantify three lipid-mediator metabolomes in basal peritoneal and zymosan-stimulated inflammatory exudates, comparing Cyp1a1/1a2/1b1(⁻/⁻) C57BL/6J-background triple-knockout mice with C57BL/6J wild-type mice. Significant differences between untreated triple-knockout and wild-type mice were not found for peritoneal cell number or type or for basal CYP1 activities involving 11 identified metabolic steps. Following zymosan-initiated inflammation, 18 lipid mediators were identified, including members of the eicosanoids and specialized proresolving mediators (i.e., resolvins and protectins). Compared with wild-type mice, Cyp1 triple-knockout mice exhibited increased neutrophil recruitment in zymosan-treated peritoneal exudates. Zymosan stimulation was associated with eight statistically significantly altered metabolic steps: increased arachidonic acid-derived leukotriene B₄ (LTB₄) and decreased 5S-hydroxyeicosatetraenoic acid; decreased docosahexaenoic acid-derived neuroprotectin D1/protectin D1, 17S-hydroxydocosahexaenoic acid, and 14S-hydroxydocosahexaenoic acid; and decreased eicosapentaenoic acid-derived 18R-hydroxyeicosapentaenoic acid (HEPE), 15S-HEPE, and 12S-HEPE. In neutrophils analyzed ex vivo, elevated LTB₄ levels were shown to parallel increased neutrophil numbers, and 20-hydroxy-LTB₄ formation was found to be deficient in Cyp1 triple-knockout mice. Together, these results demonstrate novel contributions of CYP1 enzymes to the local metabolite profile of lipid mediators that regulate neutrophilic inflammation.

In vivo processing of CXCL5 (LIX) by matrix metalloproteinase (MMP)-2 and MMP-9 promotes early neutrophil recruitment in IL-1β-induced peritonitis

Matrix metalloproteinases (MMPs) have been implicated in the cleavage of several proinflammatory chemokines, thereby modulating their function and having an impact on the inflammatory process. However, in vivo evidence of such a role remains limited. In this study, we use IL-1β-induced peritonitis as a model for an acute immune response, which is initiated by neutrophil influx followed by macrophage infiltration within a few hours of IL-1β injection into the peritoneal cavity. Using single and double knockout mice for MMP-2 and MMP-9, we show that MMP-2 and MMP-9 act synergistically mainly at the initial step of neutrophil recruitment into the peritoneal cavity. The use of bone marrow chimeric mice revealed the cellular sources of MMP-2 and MMP-9 to be distinct, with resident cells being the source of the former and infiltrating leukocytes the source of the latter. We show that the omentum is the main site of neutrophil entry into the peritoneal cavity, where MMP-2 and MMP-9 act synergistically to potentiate the action of CXCL5 (ENA-78/ LIX), thereby, promoting neutrophil migration into the peritoneal cavity. To our knowledge, this is the first in vivo demonstration of MMP-2 and MMP-9 processing of a chemokine that has been directly correlated with an enhanced chemoattracting function.

Modulation of zymosan-induced peritonitis by riboflavin co-injection, pre-injection or post-injection in male Swiss mice

AIMS

We compared the effects of riboflavin pre-injection, co-injection and post-injection on several symptoms of zymosan-induced peritonitis in male Swiss mice. Additionally, the effects of i.p. injection of riboflavin itself were elucidated.

MAIN METHODS

Peritonitis was induced in Swiss mice (50 animals) by i.p. zymosan (Z; 40mg/kg) injection. Riboflavin (R; 0, 20, 50, or 100mg/kg) was applied either alone or in combination with zymosan. In the latter case riboflavin was administered either together with zymosan (R group), or 30min before zymosan (R-Z group), or 1h later (Z-R group). The nociceptive response was evaluated by counting body writhes. The peritoneal exudates retrieved 4h after the R or Z injection were analyzed for the numbers and apoptosis of polymorphonuclear leukocytes (PMNs), and levels of metalloproteinase 9 (MMP-9), nitric oxide, and inflammatory cytokines, IL-12p70, TNFα, MCP-1, IL-6, IL-10, IFNγ.

KEY FINDINGS

Riboflavin itself induced nociceptive-related body writhes and a moderate inflammatory response manifested by PMN influx and the release of some cytokines and MMP-9. In contrast, antinociceptive properties of riboflavin were significant in the ZR group co-injected with the lowest dose of riboflavin (ZR20). At the 4th hour of zymosan-induced peritonitis an intraperitoneal accumulation of PMNs was decreased in the riboflavin-treated groups and cytokine profiles were modified according to riboflavin dose and the time of injection.

SIGNIFICANCE

Riboflavin itself induces low-grade nociception and inflammation while its effects on zymosan-induced inflammation are dependent on the dose and time of its application: either before or during inflammation.

Strain-specific effects of riboflavin supplementation on zymosan-induced peritonitis in C57BL/6J, BALB/c and CBA mice

AIMS

We investigated the effects of riboflavin (vitamin B2) on the kinetics of zymosan-induced peritonitis in three strains of mice.

MAIN METHODS

Peritonitis was induced in males of C57BL/6J, BALB/c and CBA mice by intraperitoneal injection of zymosan (40 mg/kg) or zymosan supplemented with riboflavin (50mg/kg). During the first 45 min of inflammation the pain symptoms were scored. At the selected time points (4, 6, 8, 10, 24, and 30 h) the mice were sacrificed and peritoneal exudates were retrieved. Leukocytes, among them polymorphonuclear cells (PMNs) and macrophages (Mac3(+) cells) were counted. Levels of inducible nitric oxide synthase (iNOS) were measured in cell pellets while supernatants were used for measurements of nitric oxide, cytokine/chemokines (IL-6, IL-10, MCP-1, IFNγ, TNF-α, and IL-12p70), and matrix metalloproteinase-9 (MMP-9).

KEY FINDING

A riboflavin ip injection induced pain symptoms itself, but reduced zymosan-induced pain in C57BL/6J and CBA strains of mice when coinjected with zymosan. In comparison with the mice injected with zymosan only, riboflavin coinjection prolonged inflammation in C57BL/6J mice due to prolonged macrophage accumulation; inhibited peritoneal leukocytes (PTL) accumulation in BALB/c due to inhibited influx of macrophages and PMNs; and inhibited PTL accumulation in CBA mice due to delayed PMN influx. These effects corresponded with the delayed (C57BL/6J) or inhibited (BALB/c and CBA) expression of iNOS in PTL lysates, and with the prolonged (C57BL/6) or inhibited (BALB/c) intraperitoneal accumulation of MMP-9. Moreover, cytokine accumulation was affected in a strain-specific way.

SIGNIFICANCE

Riboflavin is antinociceptive during yeast-induced peritonitis, but its anti-inflammatory effects are strain-specific.

Suppressive effects of azithromycin on zymosan-induced production of proinflammatory mediators by human corneal epithelial cells

PURPOSE

In addition to its antibiotic effects, azithromycin has been noted to have anti-inflammatory activity, particularly in the context of microbial infections. This study was conducted to explore the suppressive effects of azithromycin on the production of proinflammatory mediators by human corneal epithelial cells (HCECs) stimulated by a fungal component, zymosan.

METHODS

Primary HCECs were cultured from donor corneal limbal explants and grown to subconfluence. The cells were treated with toll-like receptor (TLR) 2 agonist zymosan (1-50 μg/mL) for 4 to 48 hours, with or without preincubation with azithromycin (1-50 μg/mL), TLR2 antibody, or NF-κB activation inhibitor quinazoline (NF-κB-I). The cells were subjected to total RNA extraction, reverse transcription (RT), and real-time PCR using gene expression assays. Cells treated for 48 hours were used for immunofluorescence staining and Western blot analysis, and their medium supernatants were collected for protein quantitation by immunobead assays.

RESULTS

The mRNA expression and protein production of proinflammatory cytokines (TNF-α and IL-1β), chemokines (IL-8 and RANTES), and matrix metalloproteinases (MMP-1, -3, and -9) by HCECs were stimulated by zymosan in a concentration-dependent manner, with peak levels noted at 4 hours. These stimulated levels of proinflammatory mediators by zymosan were significantly inhibited by TLR2 antibody, NF-κB-I, or azithromycin, which blocked zymosan-induced NF-κB activation as determined by p65 protein nuclear translocation.

CONCLUSIONS

These findings demonstrated that the fungal component zymosan induces proinflammatory responses through TLR2 and NF-κB signaling pathways, whereas azithromycin suppresses its stimulation by blocking NF-κB activation in HCECs, suggesting the potential efficacy of this antibiotic for treating ocular surface inflammatory disorders.

Staphylococcal superantigen-like protein 5 inhibits matrix metalloproteinase 9 from human neutrophils

Staphylococcal superantigen-like proteins (SSLs) constitute a family of exoproteins exhibiting structural similarities to superantigens and enterotoxins but no superantigenic activity. In this article, we present evidence that SSL5 specifically binds to matrix metalloproteinase 9 (MMP-9) and inhibits its enzymatic activity. When human neutrophil cell lysate was applied to recombinant His-tagged SSL5 conjugated to Sepharose, the bound fraction gave a major band of approximately 100 kDa in SDS-polyacrylamide gel electrophoresis. This protein was identified as the proform of MMP-9 (proMMP-9) by peptide mass fingerprinting analysis. The recombinant SSL5-Sepharose also bound to proMMP-9 secreted by interleukin 8 (IL-8)-stimulated neutrophils and HT1080 fibrosarcoma cells. Surface plasmon resonance analysis revealed that recombinant SSL5 bound to proMMP-9 with rather high affinity (dissociation constant [K(D)] = 1.9 nM). Recombinant SSL5 was found to effectively inhibit MMP-9-catalyzed hydrolysis of gelatin and a synthetic fluorogenic peptide in a noncompetitive manner (K(i) = 0.097 nM), as assessed by zymography and the fluorescence quenching method. Finally, the transmigration of neutrophils across Matrigel basement membranes in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP) was suppressed by the presence of recombinant SSL5. We discuss possible roles that SSL5 may play in immune evasion of staphylococci by inhibiting MMP and interfering with leukocyte trafficking.

Age-dependent stimulatory effect of desipramine and fluoxetine pretreatment on metastasis formation by B16F10 melanoma in male C57BL/6 mice

Although recent data may provide theoretical support for the preventive use of antidepressants in cancer patients, so far no study has demonstrated the clinical benefits of such strategies in the general population of cancer patients [39, 41]. Moreover, an association between antidepressant use and the risk of tumor promotion could neither be excluded nor established. The aim of this study was to compare the effect of desipramine (a tricyclic antidepressant, TCA) and fluoxetine (a selective serotonin reuptake inhibitor, SSRI) on tumor growth of the mouse B16F10 transplanted melanoma in "young" 6-9 month old and "aged" 18-23 month old male C57BL/6 mice. Drugs were administered daily at a dose of 10 mg/kg, ip, for two weeks and tumor cells were inoculated 2 h after the last antidepressant administration. Control animals were treated with saline. Tumor growth was significantly slower in aged than in young saline-treated control animals. Pretreatment with desipramine dramatically promoted metastasis formation and increased mortality rate but inhibited primary tumor growth in young males. On the other hand, both antidepressants increased primary tumor growth in aged animals, whereas metastasis was only moderately promoted. To determine the effect of antidepressant drug pretreatment and tumor progress on some parameters of cell-mediated immunity (proliferative activity and cytokine production by splenocytes) and angiogenesis, vascular endothelial growth factor (VEGF) and metalloproteinase (MMP)-9 plasma levels were established. The prometastatic effect of desipramine in young animals was connected with an increase of VEGF and MMP-9 plasma levels.

Resident peritoneal macrophages and mast cells are important cellular sites of COX-1 and COX-2 activity during acute peritoneal inflammation

INTRODUCTION

Cyclooxygenases (COXs) play important roles during inflammation. While reports on COX-2 function in inflammation preceded those on COX-1, it is now well established that both isoforms participate in this process. During inflammation, COX expression was reported in inflammatory leukocytes, but much less is known about their presence in tissue- resident leukocytes. The aim was thus to verify the expression and activity of the COX isoforms in resident peritoneal mast cells and macrophages during acute peritonitis.

MATERIALS AND METHODS

Zymosan peritoneal inflammation was induced in C57BL/6J mice and COX-1 and COX-2 expression was evaluated by RT-PCR (mRNA level) and immunocytochemistry (protein level). COX activity was assessed by a specific assay and prostaglandin production by ELISA. Furthermore, some mice were selectively depleted of either peritoneal mast cells or macrophages and then COX activity was determined.

RESULTS

The study revealed that both COXs are expressed/active at the peak of inflammation, but COX-2 predominates during resolution. The expressions of the COXs were detectable in both populations of resident peritoneal leukocytes. In peritoneal macrophages both isoforms were active even during the late phases of peritonitis and the cells significantly contributed to PGE(2) and PGD(2) synthesis. The most striking observation was that resident macrophages are critical for PGD(2) production during the resolution of inflammation.

CONCLUSIONS

This study documents that both COX isoforms participate in all stages of acute inflammation and that tissue-resident leukocytes, especially macrophages, are important sites of COX-1/COX-2 expression and prostaglandin synthesis.

Altered apoptosis of inflammatory neutrophils in MMP-9-deficient mice is due to lower expression and activity of caspase-3

Matrix metalloproteinase 9 (MMP-9) is a Zn(2+)-dependent endopeptidase that degrades some of the components of basement membranes and extracellular matrix and thus participates in leukocyte infiltration during inflammation. In a model of zymosan peritonitis, neutrophil infiltration in MMP-deficient (MMP-9(-/-)) mice was significantly weaker at the time of their maximal influx in wild-type mice (6h). However, during the late stages of peritonitis (24h) an extended accumulation of neutrophils was observed in MMP-9(-/-)versus the wild-type mice. Recently, we reported that the ratio of apoptosis of inflammatory leukocytes is impaired in MMP-9(-/-) mice during late peritonitis and the process depends on COX-1-driven PGE(2). Here we scrutinized the alterations in apoptotic mechanisms by comparisons between MMP-9(-/-) and the wild-type mice. Altered apoptosis occurred only during late (24h) peritonitis and concerned only neutrophils, and not macrophages, mast cells or lymphocytes. Furthermore, expression and activity of caspases was altered in MMP-9(-/-) animals, delayed for caspase-8 and -9, and decreased in the case of caspase-3. Also the expression of Bax/Bcl-2 proteins was changed in MMP-9(-/-) mice. These changes, and in particular the impaired neutrophil apoptosis and weaker caspase-3 activity, were restored by the selective COX-1 inhibition. We conclude that in mice lacking MMP-9 the enhanced COX-1-PGE(2) decreases caspase-3 expression and activity leading to impaired apoptosis of inflammatory neutrophils resulting in abnormal accumulation of the cells at the inflammatory focus. The data also reinforce the notion that MMP-9 is a key enzyme in neutrophil biology.

Extracellular matrix turnover and signaling during cardiac remodeling following MI: causes and consequences

The concept that extracellular matrix (ECM) turnover occurs during cardiac remodeling is a well-accepted paradigm. To date, a multitude of studies document that remodeling is accompanied by increases in the synthesis and deposition of ECM components as well as increases in extracellular proteases, especially matrix metalloproteinases (MMPs), which break down ECM components. Further, soluble ECM fragments generated from enzymatic action serve to stimulate cell behavior and have been proposed as candidate plasma biomarkers of cardiac remodeling. This review briefly summarizes our current knowledge base on cardiac ECM turnover following myocardial infarction (MI), but more importantly extends discussion by defining avenues that remain to be explored to drive the ECM remodeling field forward. Specifically, this review will discuss cause and effect roles for the ECM changes observed following MI and the potential role of the ECM changes that may serve as trigger points to regulate remodeling. While the pattern of remodeling following MI is qualitatively similar but quantitatively different from various types of injury, the basic theme in remodeling is repeated. Therefore, while we use the MI model as the prototype injury model, the themes discussed here are also relevant to cardiac remodeling due to other types of injury.

Neutrophil elastase activity compensates for a genetic lack of matrix metalloproteinase-9 (MMP-9) in leukocyte infiltration in a model of experimental peritonitis

Extracellular proteolysis of basement membranes and matrix is required for leukocyte diapedesis and migration to the inflammatory focus. Neutrophil elastase (NE) and matrix metalloproteinases (MMPs) are among the enzymes involved in these processes, as shown in mice genetically deprived of such enzymes. However, studies with MMP-9(-/-) mice revealed that albeit neutrophil influx is impaired initially in these animals versus controls, neutrophilia is subsequently augmented during later stages of zymosan peritonitis. MMP-9 as a MMP and NE as a serine protease belong to different enzyme classes. As MMP-9 and NE are produced by neutrophils and have similar biological effects on matrix remodeling, it was evaluated whether enhanced NE activity might compensate for the lack of MMP-9. In genetically uncompromised mice, two waves of NE expression and activity during zymosan peritonitis were observed in inflammatory neutrophils and macrophages at the time of influx of the respective cell populations into the peritoneum. Additionally, NE expression was associated with the activity of resident peritoneal mast cells and macrophages, as their depletion reduced NE activity. Most importantly, the NE mRNA and protein expression and activity were enhanced significantly in MMP-9(-/-) mice during late stages of zymosan peritonitis. In addition, the application of a selective NE inhibitor restrained enhanced neutrophil accumulation significantly. In conclusion, during acute peritoneal inflammation, NE expression and activity increase gradually, facilitating leukocyte influx. Moreover, increased NE activity might compensate for a genetic lack of MMP-9 (as detected in MMP-9(-/-) mice), resulting in delayed accumulation of neutrophils during late zymosan peritonitis.

Increased cyclooxygenase activity impairs apoptosis of inflammatory neutrophils in mice lacking gelatinase B/matrix metalloproteinase-9

Matrix metalloproteinase-9 (MMP-9)/gelatinase B plays an important role in neutrophil infiltration during inflammation and cyclooxygenases (COX-1 and COX-2) and their products are important regulators of inflammation. Recently, we reported that a genetic lack of MMP-9 impairs neutrophil infiltration during early zymosan-induced peritonitis but at later stages (> 24 hr) neutrophils persist in the peritoneal cavity. Here we show that this is the result of impaired apoptosis of MMP-9(-/-)-derived leucocytes. As enhanced COX-1 expression was reported in MMP-9(-/-) mice, we evaluated the hypothesis that altered COX expression induced the above phenomenon as COX-dependent prostaglandins can act either anti-apoptotically (PGE(2)) or pro-apoptotically (PGD(2)). The current data demonstrate that messenger RNA and protein expression of both COX isoforms and their activities are increased in MMP-9(-/-) mice during late peritonitis. Application of selective COX inhibitors revealed enhanced COX-1-dependent PGE(2) production and impaired COX-2-dependent PGD(2) synthesis in MMP-9(-/-) mice. Most importantly, inhibition of COX-1 abolished prolonged neutrophil accumulation in the peritoneal cavity of MMP-9(-/-) mice and increased apoptosis of inflammatory leucocytes. Similarly, weaker apoptosis of MMP-9(-/-) bone marrow neutrophils treated in vitro with zymosan was reversed by COX-1 inhibition. In conclusion, enhanced COX-1 expression is responsible for persistent neutrophil presence in the peritoneum of MMP-9(-/-) mice because of increased synthesis of anti-apoptotic PGE(2). In non-transgenic mice, however, inflammatory leucocytes die apoptotically in the late stages of peritonitis as a result of COX-2-dependent PGD(2) activity. Overall, we show a dependence of COX expression on the presence of MMP-9.

Strain and model dependent differences in inflammatory cell recruitment in mice

OBJECTIVE AND DESIGN

The objective of this study was to determine genetic differences in inflammation in these distinct inbred mouse strains.

METHODS

Peritoneal leukocyte recruitment, matrix metalloproteinases and cytokines were quantified in A/J, 129/svJ, C57BL/6J, using thioglycollate or biomaterial implants as inflammatory stimuli.

RESULTS

In response to thioglycollate, A/J had significant decreases compared to C57BL/6J in both neutrophil (86 %) and macrophage (62 %) recruitment, and 129/svJ had a significant (43 %) decrease compared to C57BL/6J in macrophage recruitment. The reduced leukocyte recruitment corresponded to reduced matrix metalloproteinase-9. In the bioimplant model, 129/svJ had a 2-fold increase in neutrophil and macrophage recruitment compared to C57BL/6J, and the increased leukocyte recruitment corresponded to elevated cytokines, monocyte inhibitory protein-2 and monocyte chemoattractant protein-1, in the lavage compared to the values for C57BL/6J.

CONCLUSION

Not only was leukocyte recruitment strain dependent, but the three strains had marked differences in metalloproteinases and cytokine response. In addition, there were model specific differences in the metalloproteinase and cytokine response to the two inflammatory stimuli. Thus, inflammatory cell recruitment is genetically determined and stimulus specific and may determine the susceptibility to complex diseases.

Expression profiles of matrix metalloproteinase 9 in teleost fish provide evidence for its active role in initiation and resolution of inflammation

Matrix metalloproteinase 9 (MMP-9) belongs to a family of zinc-dependent endopeptidases. As a consequence of its ability to cleave structural extracellular matrix molecules, mammalian MMP-9 is associated with vital inflammatory processes such as leucocyte migration and tissue remodelling and regeneration. Interestingly, MMP-9 genes have been identified in fish, but functional data are still limited and focus on the involvement of MMP-9 in embryonic development, reproduction and post-mortem tenderization. Here, we describe the involvement of MMP-9 in the innate immunity of carp. In carp, MMP-9 was most notably expressed in classical fish immune organs and in peritoneal and peripheral blood leucocytes, indicating a role of MMP-9 in immune responses. In our well-characterized zymosan-induced peritonitis model for carp, we analysed expression of the MMP-9 gene and the gelatinolytic levels of both pro- and activated forms of MMP-9. The biphasic profile of MMP-9 mRNA expression indicated involvement during the initial phase of inflammation and during the later phase of tissue remodelling. Also, in vitro stimulation of carp phagocytes with lipopolysaccharide or concanavalin A increased MMP-9 gene expression, with a peak at 24 hr. The increase of MMP-9 mRNA correlated with the peak of MMP-9 gelatinolytic level in culture supernatants. These results provide evidence for an evolutionarily conserved and relevant role of MMP-9 in the innate immune response.

C-C chemokine receptor 5 on pulmonary fibrocytes facilitates migration and promotes metastasis via matrix metalloproteinase 9

Previously, our group has used a B16-F10 melanoma model to show that C-C chemokine receptor 5 (CCR5) knockout (CCR5(-/-)) mice form fewer pulmonary metastases than wild-type mice. This advantage can be eliminated by injecting CCR5(-/-) mice with wild-type pulmonary mesenchymal cells before tumor injection. In this article, we present the mechanisms underlying this finding. First, we demonstrate that wild-type mesenchymal cells migrate to CCL4 more efficiently in vitro than CCR5(-/-) cells. Wild-type mesenchymal cells were also 3.6 (1.85 to 5.85) times more efficient than CCR5(-/-) cells at migrating into the lung after intravenous injection (P < 0.01). The injection of wild-type but not CCR5(-/-) mesenchymal cells led to a 7.0 +/- 1.6 (P < 0.05)-fold induction of matrix metalloproteinase 9 (MMP9) in the host lung. Neither wild-type nor CCR5(-/-) cells caused significant increases in MMP2, MMP3, or MMP8. Inhibition of the gelatinase activity of MMP9 decreased the number of metastases and restored the advantage that CCR5(-/-) mice have over wild-type mice. Further analysis showed that the CCR5(+) mesenchymal cells expressed CD45(+) and CD13(+) but did not express alpha-smooth muscle actin. This phenotype is characteristic of a subset of mesenchymal cells called fibrocytes. Together, these data suggest a novel role for CCR5 in the migration of pulmonary fibrocytes and the promotion of metastasis.

Phenotype of the Cyp1a1/1a2/1b1-/- triple-knockout mouse

Crossing the Cyp1a1/1a2(-/-) double-knockout mouse with the Cyp1b1(-/-) single-knockout mouse, we generated the Cyp1a1/1a2/1b1(-/-) triple-knockout mouse. In this triple-knockout mouse, statistically significant phenotypes (with incomplete penetrance) included slower weight gain and greater risk of embryolethality before gestational day 11, hydrocephalus, hermaphroditism, and cystic ovaries. Oral benzo[a]pyrene (BaP) daily for 18 days in the Cyp1a1/1a2(-/-) produced the same degree of marked immunosuppression as seen in the Cyp1a1(-/-) mouse; we believe this reflects the absence of intestinal CYP1A1. Oral BaP-treated Cyp1a1/1a2/1b1(-/-) mice showed the same "rescued" response as that seen in the Cyp1a1/1b1(-/-) mouse; we believe this reflects the absence of CYP1B1 in immune tissues. Urinary metabolite profiles were dramatically different between untreated triple-knockout and wild-type; principal components analysis showed that the shifts in urinary metabolite patterns in oral BaP-treated triple-knockout and wild-type mice were also strikingly different. Liver microarray cDNA differential expression (comparing triple-knockout with wild-type) revealed at least 89 genes up- and 62 genes down-regulated (P-value < or = 0.00086). Gene Ontology "classes of genes" most perturbed in the untreated triple-knockout (compared with wild-type) include lipid, steroid, and cholesterol biosynthesis and metabolism; nucleosome and chromatin assembly; carboxylic and organic acid metabolism; metal-ion binding; and ion homeostasis. In the triple-knockout compared with the wild-type mice, response to zymosan-induced peritonitis was strikingly exaggerated, which may well reflect down-regulation of Socs2 expression. If a single common molecular pathway is responsible for all of these phenotypes, we suggest that functional effects of the loss of all three Cyp1 genes could be explained by perturbations in CYP1-mediated eicosanoid production, catabolism and activities.

Metalloproteinase-9 deficiency protects against hepatic ischemia/reperfusion injury

Leukocyte transmigration across endothelial and extracellular matrix protein barriers is dependent on adhesion and focal matrix degradation events. In the present study we investigated the role of metalloproteinase-9 (MMP-9/gelatinase B) in liver ischemia/reperfusion (I/R) injury using MMP-9-deficient (MMP-9(-/-)) animals and mice treated with a specific anti-MMP-9 neutralizing antibody or with a broad gelatinase inhibitor for both MMP-9 and metalloproteinase-2 (MMP-2/gelatinase A). Compared to wild-type mice, MMP-9(-/-) mice and mice treated with an anti-MMP-9 antibody showed significantly reduced liver damage. In contrast, mice treated with a broad gelatinase inhibitor showed rather inferior protection against I/R injury and were characterized by persistent ongoing liver inflammation, suggesting that MMP-2 and MMP-9 may have distinct roles in this type of injury. MMP-9 was mostly detected in Ly-6G and macrophage antigen-1 leukocytes adherent to the vessel walls and infiltrating the damaged livers of wild-type mice after liver I/R injury. Leukocyte traffic and cytokine expression were markedly impaired in livers of MMP-9(-/-) animals and in livers of mice treated with anti-MMP-9 antibody after I/R injury; however, initiation of the endothelial adhesion cascades was similar in both MMP-9(-/-) and control livers. We also showed that MMP-9-specific inhibition disrupted neutrophil migration across fibronectin in transwell filters and depressed myeloperoxidase (MPO) activation in vitro.

CONCLUSION

These results support critical functions for MMP-9 in leukocyte recruitment and activation leading to liver damage. Moreover, they provide the rationale for identifying inhibitors to specifically target MMP-9 in vivo as a potential therapeutic approach in liver I/R injury.

Gelatinase B/MMP-9 as an inflammatory marker enzyme in mouse zymosan peritonitis: comparison of phase-specific and cell-specific production by mast cells, macrophages and neutrophils

Neutrophil infiltration during zymosan peritonitis depends on matrix metalloproteinase-9 (MMP-9) activity as it is impaired both in MMP-9(-/-) and gelatinase inhibitor-treated animals. The producer cells of MMP-9 and their relative contribution are not known. The aim of this study was to identify and compare the cellular sources, timing and intensity of MMP-9 induction by zymosan in the murine peritoneal cavity. We detected MMP-9 mRNA in unstimulated peritoneal leukocytes and its levels increased after zymosan administration. To detect MMP-9 by flow cytometry, we selected and compared two specific monoclonal antibodies. We show that MMP-9 protein was absent in control peritoneal macrophages, whereas already at 30min of peritonitis almost all macrophages were producing the enzyme. Conversely, MMP-9 was constitutively present in unstimulated mast cells. Macrophages turned out to be prevalent MMP-9 producers in the early phase of peritonitis. During later stages macrophages kept the high expression of MMP-9 for at least 6h of inflammation. In contrast, the early phase expression of MMP-9 by neutrophils was limited albeit the highest percentage of MMP-9(+) neutrophils was observed at 2h but absolute numbers of the MMP-9 carrying neutrophils were low at that time. In contrast, during the late phase of peritonitis neutrophils became major producers of MMP-9 as they numerously infiltrated peritoneum. In conclusion, the study reports detection of MMP-9 at the single-cell level during peritonitis, demonstrates unexpectedly fast MMP-9 expression in macrophages and reveals quantitatively phase-specific contribution of mast cells, macrophages and neutrophils.

Resident peritoneal leukocytes are important sources of MMP-9 during zymosan peritonitis: superior contribution of macrophages over mast cells

Metalloproteinase 9 (MMP-9) is crucial for normal neutrophil infiltration into zymosan-inflamed peritoneum. During the course of zymosan peritonitis MMP-9 is produced in a biphasic-manner as its presence is detectable as early as 30 min post zymosan and then between 2 and 8 h of inflammation. As inflammatory leukocytes were shown to produce MMP-9 we asked if also resident leukocytes, mast cells and macrophages, contribute to its production. And furthermore, if their contribution is limited only to the early phase of inflammation or extends to the later stages. For this purpose some mice were depleted of either resident macrophages or functional mast cells and expression of MMP-9 in peritoneal leukocytes and its release to the exudate were monitored. It turned out that depletion of peritoneal macrophages decreased both MMP-9 content in the leukocytes and its release to the inflammatory exudate at 30 min and 6h of peritonitis. The functional depletion of mast cells also caused a significant decrease in the production/release of MMP-9 that was especially apparent at the early time point (30 min). Moreover, the study shows concomitant kinetics of MMP-9 expression in leukocytes and its release to the exudatory fluid. The findings indicate that resident tissue leukocytes, and among them especially macrophages, constitute an important source of MMP-9 during acute peritoneal inflammation. Overall, the study shows that resident tissue leukocytes, mostly macrophages, constitute an important cellular source(s) of inflammation-related factors and should be regarded as possible targets of anti-inflammatory treatment.

Zymosan-induced inflammation stimulates neo-adipogenesis

OBJECTIVE

To investigate the potential of inflammation to induce new adipose tissue formation in the in vivo environment.

METHODS AND RESULTS

Using an established model of in vivo adipogenesis, a silicone chamber containing a Matrigel and fibroblast growth factor 2 (1 microg/ml) matrix was implanted into each groin of an adult male C57Bl6 mouse and vascularized with the inferior epigastric vessels. Sterile inflammation was induced in one of the two chambers by suspending Zymosan-A (ZA) (200-0.02 microg/ml) in the matrix at implantation. Adipose tissue formation was assessed at 6, 8, 12 and 24 weeks. ZA induced significant adipogenesis in an inverse dose-dependent manner (P<0.001). At 6 weeks adipose tissue formation was greatest with the lowest concentrations of ZA and least with the highest. Adipogenesis occurred both locally in the chamber containing ZA and in the ZA-free chamber in the contralateral groin of the same animal. ZA induced a systemic inflammatory response characterized by elevated serum tumour necrosis factor-alpha levels at early time points. Aminoguanidine (40 microg/ml) inhibited the adipogenic response to ZA-induced inflammation. Adipose tissue formed in response to ZA remained stable for 24 weeks, even when exposed to the normal tissue environment.

CONCLUSIONS

These results demonstrate that inflammation can drive neo-adipogenesis in vivo. This suggests the existence of a positive feedback mechanism in obesity, whereby the state of chronic, low-grade inflammation, characteristic of the condition, may promote further adipogenesis. The mobilization and recruitment of a circulating population of adipose precursor cells is likely to be implicated in this mechanism.

Matrix metalloproteinase inhibitors as therapy for inflammatory and vascular diseases

Matrix metalloproteinases (MMPs) have outgrown the field of extracellular-matrix biology and have progressed towards being important regulatory molecules in cancer and inflammation. This rise in status was accompanied by the development of various classes of inhibitors. Although clinical trials with synthetic inhibitors for the treatment of cancer were disappointing, recent data indicate that the use of selective inhibitors might lead to new therapies for acute and chronic inflammatory and vascular diseases. In this Review, we compare the major classes of MMP inhibitors and advocate that future drug discovery should be based on crucial insights into the differential roles of specific MMPs in pathophysiology obtained with animal models, including knockout studies.

Angiostatin inhibits monocyte/macrophage migration via disruption of actin cytoskeleton

In light of the involvement of tumor-associated macrophages (TAM) in the promotion of tumor growth and metastasis, strategies to prevent TAM recruitment within the tumor microenvironment are currently under investigation. The recent observation that angiostatin reduces macrophage infiltration in an atherosclerosis model prompted our laboratory to further explore the use of human plasminogen angiostatin (hK1-3) protein as a macrophage modulatory agent. We demonstrate that hK1-3 blocks migration of murine peritoneal macrophages (91% decrease, P<0.00005) and human monocytes (85% decrease, P<0.05) in vitro. Cell viability of hK1-3-treated cells is not affected, as determined by fluorochrome-labeled inhibitors of caspase-propidium iodide (FLICA/PI) flow cytometry analysis. Furthermore, confocal microscopy of phalloidin-stained cells reveals that hK1-3 leads to disruption of actin filopodia/lamellipodia in human monocytes and induces distinct podosome accumulation in mature differentiated macrophages. Paradoxically, we observed a 3.5-fold increase in secretion and a 3- to 5.5-fold increase in gelatinolytic activity of macrophage-produced matrix metalloproteinase-9, which we suggest is a cellular response to compensate for the dominant static effect of hK1-3 on actin. We also demonstrate that hK1-3 induces the phosphorylation of extracellular signal-regulated kinase (ERK1/2) in human monocytes. hK1-3-mediated macrophage immobilization has the potential to be exploited therapeutically in pathological conditions associated with cellular hypoxia, such as cancer and atherosclerosis.

Unique and redundant roles of alpha4 and beta2 integrins in kinetics of recruitment of lymphoid vs myeloid cell subsets to the inflamed peritoneum revealed by studies of genetically deficient mice

OBJECTIVE

Leukocyte recruitment to inflammatory sites is a prominent feature of acute and chronic inflammation. Instrumental in this process is the coordinated upregulation of leukocyte integrins (among which alpha4beta1 and beta2 integrins are major players) and their cognate receptors in inflamed tissues. To avoid the ambiguity of previous short-term antibody-based studies and to allow for long-term observation, we used genetically deficient mice to compare roles of alpha4 and beta2 integrins in leukocyte trafficking.

MATERIALS AND METHODS

Aseptic peritonitis was induced in alpha4 or beta2 integrin-deficient (conditional and conventional knockouts, respectively) and control mice, and recruitment of major leukocyte subsets to the inflamed peritoneum was followed for up to 4 days.

RESULTS

Despite normal chemokine levels in the peritoneum and adequate numbers, optimal recruitment of myeloid cells was impaired in both alpha4- and beta2-deficient mice. Furthermore, clearance of recruited neutrophils and macrophages was delayed in these mice. Lymphocyte migration to the peritoneum in the absence of alpha4 integrins was drastically decreased, both at steady state and during inflammation, a finding consistent with impaired lymphocyte in vitro adhesion and signaling. By contrast, in the absence of beta2 integrins, defects in lymphocyte recruitment were only evident when peritonitis was established.

CONCLUSIONS

Our data with concurrent use of genetic models of integrin deficiency reveal nonredundant functions of alpha4 integrins in lymphocyte migration to the peritoneum and further refine specific roles of alpha4 and beta2 integrins concerning trafficking and clearance of other leukocyte subsets at homeostasis and during inflammation.

Fibronectin-alpha4beta1 integrin interactions regulate metalloproteinase-9 expression in steatotic liver ischemia and reperfusion injury

Ischemia/reperfusion injury is a major cause of the highly dysfunctional rate observed in marginal steatotic orthotopic liver transplantation. In this study, we document that the interactions between fibronectin, a key extracellular matrix protein, and its integrin receptor alpha4beta1, expressed on leukocytes, specifically up-regulated the expression and activation of metalloproteinase-9 (MMP-9, gelatinase B) in a well-established steatotic rat liver model of ex vivo ice-cold ischemia followed by isotransplantation. The presence of the active form of MMP-9 was accompanied by massive intragraft leukocyte infiltration, high levels of proinflammatory cytokines, such as interleukin-1beta and tumor necrosis factor-alpha, and impaired liver function. Interestingly, MMP-9 activity in steatotic liver grafts was, to a certain extent, independent of the expression of its natural inhibitor, the tissue inhibitor of metalloproteinases-1. Moreover, the blockade of fibronectin-alpha4beta1-integrin interactions inhibited the expression/activation of MMP-9 in steatotic orthotopic liver transplantations without significantly affecting the expression of metalloproteinase-2 (MMP-2, gelatinase A). Finally, we identified T lymphocytes and monocytes/macrophages as major sources of MMP-9 in steatotic liver grafts. Hence, these findings reveal a novel aspect of the function of fibronectin-alpha4beta1 integrin interactions that holds significance for the successful use of marginal steatotic livers in transplantation.

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.

Recruited leukocytes and local synthesis account for increased matrix metalloproteinase-9 activity in cerebrospinal fluid of dogs with central nervous system neoplasm

Matrix metalloproteinases (MMP) 2 and 9 are enzymes known to degrade several protein components of the extracellular matrix. In humans, increased concentrations of these enzymes have been demonstrated in the cerebrospinal fluid (CSF) of subjects affected by many neurological conditions including brain tumours; nevertheless comparative data in dogs are completely lacking. Aim of this study was to investigate these molecules in CSF of dogs diagnosed with CNS neurological diseases. Higher activity of MMP 2 and 9 was revealed in dogs with space occupying lesions of likely neoplastic origin in comparison to dogs with idiopathic epilepsy. Statistical modelling reveals that increased MMP 9 activity is mainly due to leukocytes recruitment and local synthesis.