Targeting neutrophil collagenase/matrix metalloproteinase-8 and gelatinase B/matrix metalloproteinase-9 with a peptidomimetic inhibitor protects against endotoxin shock

Sappanone A ameliorated imiquimod-induced psoriasis-like dermatitis in BALB/c mice via suppressing Mmp8 expression and IL-17 signaling pathway

Psoriasis is a prevalent immune-mediated inflammatory skin disease characterized by excessive abnormal proliferation of keratinocytes and infiltration of immune cells, which have significant impact on the life quality of individuals. Although biological agents and small molecule targeted drugs have brought significant clinical benefits to psoriasis patients, adverse reactions and high prices remains key issues in clinical medication of psoriasis, while natural product monomers possess high efficiency, low toxicity, anti-inflammatory and immunomodulatory properties, and bring new hope for the clinical treatment of psoriasis. Sappanone A (SA), a small molecule compound isolated from Caesalpinia sappan L, exhibits significant anti-inflammatory properties in various models, such as kidney inflammation and LPS-induced mice inflammation. Among these effects, the anti-inflammatory property of SA has received significant attention. In our study, we found that SA exhibited anti-proliferation and anti-inflammatory effects in HaCaT cells, and significantly alleviated imiquimod-induced psoriasis-like skin lesions via the inhibition of the excessive proliferation of keratinocytes and the infiltration of lymphocytes. Furthermore, the combinational analysis of network pharmacology and transcriptome sequencing revealed that SA exerted anti-psoriasis effects by inhibiting the matrix metalloproteinase 8 (Mmp8) expression and IL-17 pathway activation. In summary, we have first demonstrated that SA can be used as a novel anti-psoriasis drug, which may provide a novel strategy for the clinical treatment of psoriasis.

DLK1 overexpression improves sepsis-induced cardiac dysfunction and fibrosis in mice through the TGF-β1/Smad3 signaling pathway and MMPs

Sepsis is a serious inflammatory disease caused by bacterial infection. Cardiovascular dysfunction and remodeling are serious complications of sepsis, which can significantly affect sepsis patients' mortality. Delta-like homologue 1 (DLK1) has been reported could inhibit cardiac myofibroblast differentiation. However, the function of DLK1 in sepsis is unknown. In the present study, the DLK1 expression was first identified based on the online dataset GSE79962 analysis and cecal ligation and puncture (CLP)-induced sepsis mouse model. DLK1 expression was significantly reduced in septic heart tissues. In septic mouse heart, CLP operation decreased the fractional shortening (EF) (%) and ejection fraction (FS) (%) and caused significant edema, disordered myofilament arrangement, and degradation and necrosis in myocardial cells; CLP operation also increased collagen deposition and elevated the protein levels of fibrotic markers (α-SMA and F-actin). DLK1 overexpression in septic mice could effectively increase EF (%) and FS (%), attenuate CLP-caused ECM degradation and deposition and partially inhibit the CLP-induced TGF-β1/Smad signaling activation. In conclusion, DLK1 expression was poorly expressed in the CLP-induced septic mouse heart. DLK1 overexpression partially alleviated sepsis-induced cardiac dysfunction and fibrosis, with the involvement of the TGF-β1/Smad3 signaling pathway and MMPs.

Matrix metalloproteinases in arthritis: towards precision medicine

Proteolysis of structural molecules of the extracellular matrix (ECM) is an irreversible post-translational modification in all arthropathies. Common joint disorders, including osteoarthritis and rheumatoid arthritis, have been associated with increased levels of matrix remodelling enzymes, including matrix metalloproteinases (MMPs). MMPs, in concert with other host proteinases and glycanases, destroy proteoglycans, collagens and other ECM molecules. MMPs may also control joint remodelling indirectly by signalling through cell-surface receptors or by proteolysis of cytokines and receptor molecules. After synthesis as pro-forms, MMPs can be activated by various types of post-translational modifications, including proteolysis. Once activated, MMPs are controlled by general and specific tissue inhibitors of metalloproteinases (TIMPs). In rheumatoid arthritis, proteolysis of the ECM results in so-called remnant epitopes that enhance and perpetuate autoimmune processes in susceptible hosts. In osteoarthritis, the considerable production of MMP-13 by chondrocytes, often concurrent with mechanical overload, is a key event. Hence, information about the regulation, timing, localization and activities of MMPs in specific disease phases and arthritic entities will help to develop better diagnostics. Insights into beneficial and detrimental effects of MMPs on joint tissue inflammation are also necessary to plan and execute (pre)clinical studies for better therapy and precision medicine with MMP inhibitors. With the advances in proteomics and single-cell transcriptomics, two critical points need attention: neglected neutrophil MMP biology, and the analysis of net proteolytic activities as the result of balances between MMPs and their inhibitors.

How to place the duality of specific MMP-9 inhibition for treatment of inflammatory bowel diseases into clinical opportunities?

Crohn’s disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) with the involvement of immune cells and molecules, including cytokines, chemokines and proteases. A previous extensive review about the molecular biology of matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs), related to intestinal barrier destruction and restoration functions in IBD, is here complemented with the literature from the last five years. We also compare IBD as a prototypic mucosal inflammation of an epithelial barrier against microorganisms with inflammatory retinopathy as a disease with a barrier dysfunction at the level of blood vessels. Multiple reasons are at the basis of halting clinical trials with monoclonal antibodies against MMP-9 for IBD treatment. These include (i) the absence of a causative role of MMP-9 in the pathology in animal models of IBD, (ii) the fact that endotoxins, crossing the intestinal barrier, induce massive local release of both neutrophil collagenase (MMP-8) and gelatinase B (MMP-9), (iii) insufficient recognition that MMPs modify the activities of cytokines, chemokines and their receptors, (iv) ignorance that MMPs exist as mixtures of proteoforms with different posttranslational modifications and with different specific activities and (v) the fact that MMPs and TIMPs act in an interactive network, possibly having also beneficial effects on IBD evolution. Nevertheless, inhibition of MMPs may be a useful therapeutic approach during specific IBD disease phases or in specific sub-phenotypes. This temporary “window of opportunity” for MMP-9 inhibition may be complemented by a locoregional one, provided that the pharmacological agents are targeted in time to affected tissues, as is achieved in ophthalmological inflammation. Thus, in order to discover spatial and temporal windows of opportunity for MMP inhibition as treatment of IBD, more preclinical work including well controlled animal studies will be further needed. In this respect, MMP-9/NGAL complex analysis in various body compartments is helpful for better stratification of IBD patients who may benefit from anti-MMP-9.

Peptide-Based Inhibitors of ADAM and ADAMTS Metalloproteinases

ADAM and ADAMTS are two large metalloproteinase families involved in numerous physiological processes, such as shedding of cell-surface protein ectodomains and extra-cellular matrix remodelling. Aberrant expression or dysregulation of ADAMs and ADAMTSs activity has been linked to several pathologies including cancer, inflammatory, neurodegenerative and cardiovascular diseases. Inhibition of ADAM and ADAMTS metalloproteinases have been attempted using various small molecules and protein-based therapeutics, each with their advantages and disadvantages. While most of these molecular formats have already been described in detail elsewhere, this mini review focuses solely on peptide-based inhibitors, an emerging class of therapeutic molecules recently applied against some ADAM and ADAMTS members. We describe both linear and cyclic peptide-based inhibitors which have been developed using different approaches ranging from traditional medicinal chemistry and rational design strategies to novel combinatorial peptide-display technologies.

Peptides and Peptidomimetics as Inhibitors of Enzymes Involved in Fibrillar Collagen Degradation

Collagen fibres degradation is a complex process involving a variety of enzymes. Fibrillar collagens, namely type I, II, and III, are the most widely spread collagens in human body, e.g., they are responsible for tissue fibrillar structure and skin elasticity. Nevertheless, the hyperactivity of fibrotic process and collagen accumulation results with joints, bone, heart, lungs, kidneys or liver fibroses. Per contra, dysfunctional collagen turnover and its increased degradation leads to wound healing disruption, skin photoaging, and loss of firmness and elasticity. In this review we described the main enzymes participating in collagen degradation pathway, paying particular attention to enzymes degrading fibrillar collagen. Therefore, collagenases (MMP-1, -8, and -13), elastases, and cathepsins, together with their peptide and peptidomimetic inhibitors, are reviewed. This information, related to the design and synthesis of new inhibitors based on peptide structure, can be relevant for future research in the fields of chemistry, biology, medicine, and cosmeceuticals.

Bivalent Inhibitor with Selectivity for Trimeric MMP-9 Amplifies Neutrophil Chemotaxis and Enables Functional Studies on MMP-9 Proteoforms

A fundamental part of the immune response to infection or injury is leukocyte migration. Matrix metalloproteinases (MMPs) are a class of secreted or cell-bound endopeptidases, implicated in every step of the process of inflammatory cell migration. Hence, specific inhibition of MMPs is an interesting approach to control inflammation. We evaluated the potential of a bivalent carboxylate inhibitor to selectively inhibit the trimeric proteoform of MMP-9 and compared this with a corresponding monovalent inhibitor. The bivalent inhibitor efficiently inhibited trimeric MMP-9 (IC₅₀ = 0.1 nM), with at least 500-fold selectivity for MMP-9 trimers over monomers. Surprisingly, in a mouse model for chemotaxis, the bivalent inhibitor amplified leukocyte influxes towards lipopolysaccharide-induced inflammation. We verified by microscopic and flow cytometry analysis increased amounts of neutrophils. In a mouse model for endotoxin shock, mice treated with the bivalent inhibitor had significantly increased levels of MMP-9 in plasma and lungs, indicative for increased inflammation. In conclusion, we propose a new role for MMP-9 trimers in tempering excessive neutrophil migration. In addition, we have identified a small molecule inhibitor with a high selectivity for the trimeric proteoform of MMP-9, which will allow further research on the functions of MMP-9 proteoforms.

Sirtuin 1 and endothelial glycocalyx

Sirtuin1 deficiency or reduced activity comprises one of the hallmarks of diseases as diverse as chronic cardiovascular, renal, and metabolic, some malignancies, and infections, as well as aging-associated diseases. In a mouse model of endothelium-limited defect in sirtuin 1 deacetylase activity, we found a dramatic reduction in the volume of endothelial glycocalyx. This was associated with the surge in the levels of one of key scaffolding heparan sulfate proteoglycans of endothelial glycocalyx, syndecan-4, and specifically, its extracellular domain (ectodomain). We found that the defect in endothelial sirtuin 1 deacetylase activity is associated with (a) elevated basal and stimulated levels of superoxide generation (via the FoxO1 over-acetylation mechanism) and (b) increased nuclear translocation of NF-kB (via p65 over-acetylation mechanism). These findings laid the foundation for the proposed novel function of sirtuin 1, namely, the maintenance of endothelial glycocalyx, particularly manifest in conditions associated with sirtuin 1 depletion. In the forthcoming review, we summarize the emerging conceptual framework of the enhanced glycocalyx degradation in the states of defective endothelial sirtuin 1 function, thus explaining a broad footprint of the syndrome of endothelial dysfunction, from impaired flow-induced nitric oxide production, deterrent leukocytes infiltration, increased endothelial permeability, coagulation, and pro-inflammatory changes to development of microvascular rarefaction and progression of an underlying disease.

Protease propeptide structures, mechanisms of activation, and functions

Proteases are a diverse group of hydrolytic enzymes, ranging from single-domain catalytic molecules to sophisticated multi-functional macromolecules. Human proteases are divided into five mechanistic classes: aspartate, cysteine, metallo, serine and threonine proteases, based on the catalytic mechanism of hydrolysis. As a protective mechanism against uncontrolled proteolysis, proteases are often produced and secreted as inactive precursors, called zymogens, containing inhibitory N-terminal propeptides. Protease propeptide structures vary considerably in length, ranging from dipeptides and propeptides of about 10 amino acids to complex multifunctional prodomains with hundreds of residues. Interestingly, sequence analysis of the different protease domains has demonstrated that propeptide sequences present higher heterogeneity compared with their catalytic domains. Therefore, we suggest that protease inhibition targeting propeptides might be more specific and have less off-target effects than classical inhibitors. The roles of propeptides, besides keeping protease latency, include correct folding of proteases, compartmentalization, liganding, and functional modulation. Changes in the propeptide sequence, thus, have a tremendous impact on the cognate enzymes. Small modifications of the propeptide sequences modulate the activity of the enzymes, which may be useful as a therapeutic strategy. This review provides an overview of known human proteases, with a focus on the role of their propeptides. We review propeptide functions, activation mechanisms, and possible therapeutic applications.

Hirsutanol A Attenuates Lipopolysaccharide-Mediated Matrix Metalloproteinase 9 Expression and Cytokines Production and Improves Endotoxemia-Induced Acute Sickness Behavior and Acute Lung Injury

Activated human monocytes/macrophages, which increase the levels of matrix metalloproteinases (MMPs) and pro-inflammatory cytokines, are the essential mechanisms for the progression of sepsis. In the present study, we determined the functions and mechanisms of hirsutanolA (HA), which is isolated from the red alga-derived marine fungus Chondrostereum sp. NTOU4196, on the production of pro-inflammatory mediators produced from lipopolysaccharide (LPS)-treated THP-1 cells. Our results showed that HA suppressed LPS-triggered MMP-9-mediated gelatinolysis and expression of protein and mRNA in a concentration-dependent manner without effects on TIMP-1 activity. Also, HA significantly attenuated the levels of TNF-α, IL-6, and IL-1β from LPS-treated THP-1 cells. Moreover, HA significantly inhibited LPS-mediated STAT3 (Tyr705) phosphorylation, IκBα degradation and ERK1/2 activation in THP-1 cells. In an LPS-induced endotoxemia mouse model, studies indicated that HA pretreatment improved endotoxemia-induced acute sickness behavior, including acute motor deficits and anxiety-like behavior. HA also attenuated LPS-induced phospho-STAT3 and pro-MMP-9 activity in the hippocampus. Notably, HA reduced pathologic lung injury features, including interstitial tissue edema, infiltration of inflammatory cells and alveolar collapse. Likewise, HA suppressed the induction of phospho-STAT3 and pro-MMP-9 in lung tissues. In conclusion, our results provide pharmacological evidence that HA could be a useful agent for treating inflammatory diseases, including sepsis.

Simultaneous Inhibition of Tumor Necrosis Factor Receptor 1 and Matrix Metalloproteinase 8 Completely Protects Against Acute Inflammation and Sepsis

OBJECTIVES

Sepsis causes very high mortality and morbidity rates and remains one of the biggest medical challenges. This study investigates whether plasma levels of both matrix metalloproteinase 8 and tumor necrosis factor receptor 1 are associated with sepsis severity and also investigates the therapeutic applicability of simultaneous inhibition of the two molecules in sepsis.

DESIGN

Observational human pilot study-prospective controlled animal study.

SETTING

University hospital and research laboratory.

SUBJECTS

Sepsis patients and C57BL/6 mice deficient for matrix metalloproteinase 8 and/or tumor necrosis factor receptor 1.

INTERVENTION

Plasma and whole blood RNA were collected from 13 sepsis patients for 7 consecutive days and within 24 hours of admission to ICU. Matrix metalloproteinase 8 and tumor necrosis factor receptor 1 plasma and expression levels were determined in these patients. Mice deficient for both matrix metalloproteinase 8 and tumor necrosis factor receptor 1 were generated and subjected to endotoxemia and cecal ligation and puncture. Additionally, a bispecific Nanobody that simultaneously blocks matrix metalloproteinase 8 and tumor necrosis factor receptor 1 was created.

MEASUREMENTS AND MAIN RESULTS

Plasma levels of matrix metalloproteinase 8 and tumor necrosis factor receptor 1 were positively correlated with the Sequential Organ Failure Assessment score (r, 0.51 and 0.58) and interleukin 6 levels (r, 0.59 and 0.52) in 13 sepsis patients. Combined elimination of tumor necrosis factor receptor 1 and matrix metalloproteinase 8 in double knockout mice resulted in superior survival in endotoxemia and CLP compared with single knockouts and wild-type mice. Cotreatment with our bispecific Nanobody in CLP resulted in improved survival rates (28% vs 19%) compared with untreated mice.

CONCLUSIONS

Inhibition of matrix metalloproteinase 8 and tumor necrosis factor receptor 1 might have therapeutic potential to treat sepsis and proof-of-principle was provided as therapeutics that inhibit both tumor necrosis factor receptor 1 and matrix metalloproteinase 8 are effective in CLP.

Endotoxemia shifts neutrophils with TIMP-free gelatinase B/MMP-9 from bone marrow to the periphery and induces systematic upregulation of TIMP-1

Lipopolysaccharides or endotoxins elicit an excessive host inflammatory response and lead to life-threatening conditions such as endotoxemia and septic shock. Lipopolysaccharides trigger mobilization and stimulation of leukocytes and exaggerated production of pro-inflammatory molecules including cytokines and proteolytic enzymes. Matrix metalloproteinase-9 (MMP-9) or gelatinase B, a protease stored in the tertiary granules of polymorphonuclear leukocytes, has been implicated in such inflammatory reactions. Moreover, several studies even pinpointed MMP-9 as a potential target molecule to counter excessive inflammation in endotoxemia. Whereas the early effect of lipopolysaccharide-induced inflammation in vivo on the expression of MMP-9 in various peripheral organs has been described, the effects on the bone marrow and during late stage endotoxemia remain elusive. We demonstrate that TIMP-free MMP-9 is a major factor in bone marrow physiology and pathology. By using a mouse model for late-stage endotoxemia, we show that lipopolysaccharides elicited a depletion of neutrophil MMP-9 in the bone marrow and a shift of MMP-9 and MMP-9-containing cells towards peripheral organs, a pattern which was primarily associated with a relocation of CD11b^highGr-1^high cells. In contrast, analysis of the tissue inhibitors of metalloproteinases was in line with a natural, systematic upregulation of TIMP-1, the main tissue inhibitor of TIMP-free MMP-9, and a general shift toward control of matrix metalloproteinase activity by tissue inhibitors of metalloproteinases.

Second Generation Triple-Helical Peptide Inhibitors of Matrix Metalloproteinases

The design of selective matrix metalloproteinase (MMP) inhibitors that also possess favorable solubility properties has proved to be especially challenging. A prior approach using collagen-model templates combined with transition state analogs produced a first generation of triple-helical peptide inhibitors (THPIs) that were effective in vitro against discrete members of the MMP family. These THPI constructs were also highly water-soluble. The present study sought improvements in the first generation THPIs by enhancing thermal stability and selectivity. A THPI selective for MMP-2 and MMP-9 was redesigned to incorporate non-native amino acids (Flp and mep), resulting in an increase of 18 °C in thermal stability. This THPI was effective in vivo in a mouse model of multiple sclerosis, reducing clinical severity and weight loss. Two other THPIs were developed to be more selective within the collagenolytic members of the MMP family. One of these THPIs was serendipitously more effective against MMP-8 than MT1-MMP and was utilized successfully in a mouse model of sepsis. The THPI targeting MMP-8 minimized lung damage, increased production of the anti-inflammatory cytokine IL-10, and vastly improved mouse survival.

Differential inhibition of activity, activation and gene expression of MMP-9 in THP-1 cells by azithromycin and minocycline versus bortezomib: A comparative study

Gelatinase B or matrix metalloproteinase-9 (MMP-9) (EC 3.4.24.35) is increased in inflammatory processes and cancer, and is associated with disease progression. In part, this is due to MMP-9-mediated degradation of extracellular matrix, facilitating influx of leukocytes into inflamed tissues and invasion or metastasis of cancer cells. MMP-9 is produced as proMMP-9 and its propeptide is subsequently removed by other proteases to generate proteolytically active MMP-9. The significance of MMP-9 in pathologies triggered the development of specific inhibitors of this protease. However, clinical trials with synthetic inhibitors of MMPs in the fight against cancer were disappointing. Reports on active compounds which inhibit MMP-9 should be carefully examined in this regard. In a considerable set of recent publications, two antibiotics (minocycline and azythromycin) and the proteasome inhibitor bortezomib, used in cancers, were reported to inhibit MMP-9 at different stages of its expression, activation or activity. The current study was undertaken to compare and to verify the impact of these compounds on MMP-9. With exception of minocycline at high concentrations (>100 μM), the compounds did not affect processing of proMMP-9 into MMP-9, nor did they affect direct MMP-9 gelatinolytic activity. In contrast, azithromycin specifically reduced MMP-9 mRNA and protein levels without affecting NF-κB in endotoxin-challenged monocytic THP-1 cells. Bortezomib, although being highly toxic, had no MMP-9-specific effects but significantly upregulated cyclooxygenase-2 (COX-2) activity and PGE₂ levels. Overall, our study clarified that azithromycin decreased the levels of MMP-9 by reduction of gene and protein expression while minocycline inhibits proteolytic activity at high concentrations.

Autodigestion: Proteolytic Degradation and Multiple Organ Failure in Shock

There is currently no effective treatment for multiorgan failure following shock other than supportive care. A better understanding of the pathogenesis of these sequelae to shock is required. The intestine plays a central role in multiorgan failure. It was previously suggested that bacteria and their toxins are responsible for the organ failure seen in circulatory shock, but clinical trials in septic patients have not confirmed this hypothesis. Instead, we review here evidence that the digestive enzymes, synthesized in the pancreas and discharged into the small intestine as requirement for normal digestion, may play a role in multiorgan failure. These powerful enzymes are nonspecific, highly concentrated, and fully activated in the lumen of the intestine. During normal digestion they are compartmentalized in the lumen of the intestine by the mucosal epithelial barrier. However, if this barrier becomes permeable, e.g. in an ischemic state, the digestive enzymes escape into the wall of the intestine. They digest tissues in the mucosa and generate small molecular weight cytotoxic fragments such as unbound free fatty acids. Digestive enzymes may also escape into the systemic circulation and activate other degrading proteases. These proteases have the ability to clip the ectodomain of surface receptors and compromise their function, for example cleaving the insulin receptor causing insulin resistance. The combination of digestive enzymes and cytotoxic fragments leaking into the central circulation causes cell and organ dysfunction, and ultimately may lead to complete organ failure and death. We summarize current evidence suggesting that enteral blockade of digestive enzymes inside the lumen of the intestine may serve to reduce acute cell and organ damage and improve survival in experimental shock.

Endothelial Response to Glucocorticoids in Inflammatory Diseases

The endothelium plays a crucial role in inflammation. A balanced control of inflammation requires the action of glucocorticoids (GCs), steroidal hormones with potent cell-specific anti-inflammatory properties. Besides the classic anti-inflammatory effects of GCs on leukocytes, recent studies confirm that endothelial cells also represent an important target for GCs. GCs regulate different aspects of endothelial physiology including expression of adhesion molecules, production of pro-inflammatory cytokines and chemokines, and maintenance of endothelial barrier integrity. However, the regulation of endothelial GC sensitivity remains incompletely understood. In this review, we specifically examine the endothelial response to GCs in various inflammatory diseases ranging from multiple sclerosis, stroke, sepsis, and vasculitis to atherosclerosis. Shedding more light on the cross talk between GCs and endothelium will help to improve existing therapeutic strategies and develop new therapies better tailored to the needs of patients.

Fusion Peptides CPU1 and CPU2 Inhibit Matrix Metalloproteinases and Protect Mice from Endotoxin Shock Within a Strict Time Window

Endotoxin shock induction in mice is a commonly used animal model to evaluate the protective effect of biologically active reagents. After an lipopolysaccharides (LPS) stimulus, matrix metalloproteinase-8 (MMP-8) and matrix metalloproteinase-9 (MMP-9) are rapidly degranulated and released by neutrophils, aside other enzymes and effector molecules. MMPs cleave extracellular matrix components and cytokines, and such processes contribute to shock syndrome development. CPU1 and CPU2 are two peptide MMP inhibitors with different in vitro IC50 values to several key enzymes, including MMP-8 and MMP-9. In vivo work confirmed that CPU1 and CPU2 protected mice from endotoxin shock after intravenous and intraperitoneal injections. Furthermore, their minimal effective dose after an intravenous injection and the maximum time interval between intraperitoneal peptide injection (150 mg/kg) and intravenous LPS injection were determined. With the use of an indirect competitive ELISA, plasma CPU1 and CPU2 concentrations in different experimental settings were measured. In addition, the acuteness of MMP-9 release in the mouse circulation after an intravenous LPS injection was confirmed with the zymography technique. Our findings reinforce previous work with other inhibitors about a strict time window within which effective MMP inhibition is needed to obtain significant survival rate improvements and also show that, with strict pharmacokinetic monitoring, potent protease inhibitors may in the future become life-savers in shock conditions.

Matrix metalloproteinase inhibitors prevent sepsis-induced refractoriness to vasoconstrictors in the cecal ligation and puncture model in rats

Previous studies have shown that the loss of contractility in aortas from lipopolysaccharide (LPS)-treated rats is related to intracellular activation of matrix metalloproteinase (MMPs). However, the role of MMPs in the vascular refractoriness to vasoconstrictors has not been investigated in a model of polymicrobial sepsis. We evaluated the effects of the oral administration of the MMP inhibitors doxycycline or ONO-4817 in the in vitro vascular reactivity of aortic rings from rats subjected to the cecal ligation and puncture (CLP) model of sepsis. Both doxycycline and ONO-4817 did not change vascular responses in sham-operated rats, but fully prevented hyporeactivity to KCl, phenylephrine and angiotensin II in vessels from CLP rats. This protective effect was not associated with changes in hematological parameters or blood nitrate and nitrite. The refractoriness to contractile agents was accompanied by enhanced activity of MMP-2 in aorta from CLP rats, which was abrogated by MMP inhibitors. CLP-induced sepsis did not impair the levels of MMP-2 in aorta, but significantly reduced calponin-1, a regulatory protein of vascular contraction. In addition, augmented levels of TIMP-1 were found in vessels from CLP rats. All these differences were prevented by either doxycycline or ONO-4817. Our study shows, for the first time in the CLP rat model of sepsis, that the vascular refractoriness to different contractile agents induced by polymicrobial sepsis is associated with increased activity of MMP-2 and reduced amounts of calponin-1 in the aorta. These findings reinforce the importance of the enhanced activity of MMPs for vascular failure in septic shock.

A biosensor for the activity of the "sheddase" TACE (ADAM17) reveals novel and cell type-specific mechanisms of TACE activation

Diverse environmental conditions stimulate protein "shedding" from the cell surface through proteolytic cleavage. The protease TACE [tumor necrosis factor-α (TNFα)--converting enzyme, encoded by ADAM17] mediates protein shedding, thereby regulating the maturation and release of various extracellular substrates, such as growth factors and cytokines, that induce diverse cellular responses. We developed a FRET (fluorescence resonance energy transfer)-based biosensor called TSen that quantitatively reports the kinetics of TACE activity in live cells. In combination with chemical biology approaches, we used TSen to probe the dependence of TACE activation on the induction of the kinases p38 and ERK (extracellular signal-regulated kinase) in various epithelial cell lines. Using TSen, we found that disruption of the actin cytoskeleton in keratinocytes induced rapid and robust TSen cleavage and the accumulation of TACE at the plasma membrane. Cytoskeletal disruption also increased the cleavage of endogenous TACE substrates, including transforming growth factor-α. Thus, TSen is a useful tool for unraveling the mechanisms underlying the spatiotemporal activation of TACE in live cells.

Inhibition of neutrophil collagenase/MMP-8 and gelatinase B/MMP-9 and protection against endotoxin shock

Endotoxin shock is a life-threatening disorder, associated with the rapid release of neutrophil enzymes, including neutrophil collagenase/matrix metalloproteinase-8 (MMP-8) and gelatinase B/matrix metalloproteinase-9 (MMP-9). After activation, these enzymes cleave extracellular matrix components and cytokines and thus may contribute to shock syndrome development. MMP inhibitors have been suggested as immunotherapy of endotoxin shock. However, little is known about the therapeutic time window of MMP inhibition. Here, a sublethal endotoxin shock mouse model was used to evaluate the effect of an MMP inhibiting peptide (P2) after intravenous or intraperitoneal injection and to study the time window between LPS and inhibitor injections. With the use of a specific ELISA the plasma P2 concentrations were monitored. Whereas we corroborated the treatment strategy of MMP targeting in endotoxin shock with a new inhibitor, we also demonstrated that the time window, within which effective MMP inhibition increased the survival rates, is rather limited.

Recognition of Streptococcus pneumoniae and muramyl dipeptide by NOD2 results in potent induction of MMP-9, which can be controlled by lipopolysaccharide stimulation

Matrix metallopeptidase 9 (MMP-9) is a protease involved in the degradation of extracellular matrix collagen. Evidence suggests that MMP-9 is involved in pathogenesis during Streptococcus pneumoniae infection. However, not much is known about the induction of MMP-9 and the regulatory processes involved. We show here that the Gram-positive bacteria used in this study induced large amounts of MMP-9, in contrast to the Gram-negative bacteria that were used. An important pathogen-associated molecular pattern (PAMP) for Gram-positive bacteria is muramyl dipeptide (MDP). MDP is a very potent inducer of MMP-9 and showed a dose-dependent MMP-9 induction. Experiments using peripheral blood mononuclear cells (PBMCs) from Crohn's disease patients with nonfunctional NOD2 showed that MMP-9 induction by Streptococcus pneumoniae and MDP is NOD2 dependent. Increasing amounts of lipopolysaccharide (LPS), an important PAMP for Gram-negative bacteria, resulted in decreasing amounts of MMP-9. Moreover, the induction of MMP-9 by MDP could be counteracted by simultaneously adding LPS. The inhibition of MMP-9 expression by LPS was found to be regulated posttranscriptionally, independently of tissue inhibitor of metalloproteinase 1 (TIMP-1), an endogenous inhibitor of MMP-9. Collectively, these data show that Streptococcus pneumoniae is able to induce large amounts of MMP-9. These high MMP-9 levels are potentially involved in Streptococcus pneumoniae pathogenesis.

Transmural intestinal wall permeability in severe ischemia after enteral protease inhibition

In intestinal ischemia, inflammatory mediators in the small intestine's lumen such as food byproducts, bacteria, and digestive enzymes leak into the peritoneal space, lymph, and circulation, but the mechanisms by which the intestinal wall permeability initially increases are not well defined. We hypothesize that wall protease activity (independent of luminal proteases) and apoptosis contribute to the increased transmural permeability of the intestine's wall in an acutely ischemic small intestine. To model intestinal ischemia, the proximal jejunum to the distal ileum in the rat was excised, the lumen was rapidly flushed with saline to remove luminal contents, sectioned into equal length segments, and filled with a tracer (fluorescein) in saline, glucose, or protease inhibitors. The transmural fluorescein transport was determined over 2 hours. Villi structure and epithelial junctional proteins were analyzed. After ischemia, there was increased transmural permeability, loss of villi structure, and destruction of epithelial proteins. Supplementation with luminal glucose preserved the epithelium and significantly attenuated permeability and villi damage. Matrix metalloproteinase (MMP) inhibitors (doxycycline, GM 6001), and serine protease inhibitor (tranexamic acid) in the lumen, significantly reduced the fluorescein transport compared to saline for 90 min of ischemia. Based on these results, we tested in an in-vivo model of hemorrhagic shock (90 min 30 mmHg, 3 hours observation) for intestinal lesion formation. Single enteral interventions (saline, glucose, tranexamic acid) did not prevent intestinal lesions, while the combination of enteral glucose and tranexamic acid prevented lesion formation after hemorrhagic shock. The results suggest that apoptotic and protease mediated breakdown cause increased permeability and damage to the intestinal wall. Metabolic support in the lumen of an ischemic intestine with glucose reduces the transport from the lumen across the wall and enteral proteolytic inhibition attenuates tissue breakdown. These combined interventions ameliorate lesion formation in the small intestine after hemorrhagic shock.

Removal of luminal content protects the small intestine during hemorrhagic shock but is not sufficient to prevent lung injury

The small intestine plays a key role in the pathogenesis of multiple organ failure following circulatory shock. Current results show that reduced perfusion of the small intestine compromises the mucosal epithelial barrier, and the intestinal contents (including pancreatic digestive enzymes and partially digested food) can enter the intestinal wall and transport through the circulation or mesenteric lymph to other organs such as the lung. The extent to which the luminal contents of the small intestine mediate tissue damage in the intestine and lung is poorly understood in shock. Therefore, rats were assigned to three groups: No-hemorrhagic shock (HS) control and HS with or without a flushed intestine. HS was induced by reducing the mean arterial pressure (30 mmHg; 90 min) followed by return of shed blood and observation (3 h). The small intestine and lung were analyzed for hemorrhage, neutrophil accumulation, and cellular membrane protein degradation. After HS, animals with luminal contents had increased neutrophil accumulation, bleeding, and destruction of E-cadherin in the intestine. Serine protease activity was elevated in mesenteric lymph fluid collected from a separate group of animals subjected to intestinal ischemia/reperfusion. Serine protease activity was elevated in the plasma after HS but was detected in lungs only in animals with nonflushed lumens. Despite removal of the luminal contents, lung injury occurred in both groups as determined by elevated neutrophil accumulation, permeability, and lung protein destruction. In conclusion, luminal contents significantly increase intestinal damage during experimental HS, suggesting transport of luminal contents across the intestinal wall should be minimized.

Peptide-based selective inhibitors of matrix metalloproteinase-mediated activities

The matrix metalloproteinases (MMPs) exhibit a broad array of activities, some catalytic and some non-catalytic in nature. An overall lack of selectivity has rendered small molecule, active site targeted MMP inhibitors problematic in execution. Inhibitors that favor few or individual members of the MMP family often take advantage of interactions outside the enzyme active site. We presently focus on peptide-based MMP inhibitors and probes that do not incorporate conventional Zn²⁺ binding groups. In some cases, these inhibitors and probes function by binding only secondary binding sites (exosites), while others bind both exosites and the active site. A myriad of MMP mediated-activities beyond selective catalysis can be inhibited by peptides, particularly cell adhesion, proliferation, motility, and invasion. Selective MMP binding peptides comprise highly customizable, unique imaging agents. Areas of needed improvement for MMP targeting peptides include binding affinity and stability.

A novel role for matrix metalloproteinase-8 in sepsis

OBJECTIVES

Matrix metalloproteinase-8 messenger RNA expression was previously found to be increased in whole blood of children with septic shock. The impact of this finding on the severity and inflammatory response to sepsis is unknown. Here, we investigate the relationship between matrix metalloproteinase-8 and disease severity in children with septic shock. We further corroborate the role of matrix metalloproteinase-8 in sepsis in a murine model.

DESIGN

Retrospective observational clinical study and randomized controlled laboratory experiments.

SETTING

Pediatric intensive care units and an animal research facility at an academic children's hospital.

PATIENTS AND SUBJECTS

Patients age ≤10 yrs admitted to the intensive care unit with a diagnosis of septic shock. For laboratory studies, we utilized male mice deficient for matrix metalloproteinase-8 and male wild-type C57BL/6J mice.

INTERVENTIONS

Blood from children with septic shock was analyzed for matrix metalloproteinase-8 messenger RNA expression and matrix metalloproteinase-8 activity, and correlated with disease severity based on mortality and degree of organ failure. A murine model of sepsis was used to explore the effect of genetic and pharmacologic inhibition of matrix metalloproteinase-8 on the inflammatory response to sepsis. Finally, activation of nuclear factor-κB was assessed both in vitro and in vivo.

MEASUREMENTS AND MAIN RESULTS

Increased matrix metalloproteinase-8 mRNA expression and activity in septic shock correlates with decreased survival and increased organ failure in pediatric patients. Genetic and pharmacologic inhibition of matrix metalloproteinase-8 leads to improved survival and a blunted inflammatory profile in a murine model of sepsis. We also identify matrix metalloproteinase-8 as a direct in vitro activator of the proinflammatory transcription factor, nuclear factor-κB.

CONCLUSIONS

Matrix metalloproteinase-8 is a novel modulator of inflammation during sepsis and a potential therapeutic target.

Matrix metalloproteinase-8/collagenase-2 in childhood otitis media with effusion

BACKGROUND

Matrix metalloproteinases (MMPs), gelatinases, have been associated with otitis media with effusion (OME), but the role of collagenase-2/matrix metalloproteinase-8 (MMP-8) in OME has not been studied previously. We studied the levels, isoenzyme distribution, and activation of MMP-8 in childhood OME, and also the levels of pro- and active forms of MMP-2 and -9 as well as 120 kDa gelatinase complexes were assessed.

METHODS

Seventy middle ear fluid (MEF) samples were collected from 54 children with OME and classified to mucoid (n = 39) or serous (n = 31). MMPs were studied from MEF samples by time-resolved immunofluorometric assay, Western immunoblotting, and gelatin-zymography.

RESULTS

MMP-8 was found in its active form in MEF of children with OME. MMP-8 levels were significantly higher in mucous relative to serous OME. The pro- or active MMP-2 and -9 were found in MEF, but no MEF type-specific differences were found.

CONCLUSION

Our results suggest that MMP-8 may play a role in the pathogenesis of childhood OME. New therapeutic strategies with MMP inhibitors targeting MMP-8, but allowing MMP-8 to carry out the protective action, may play a role in the future treatment of otitis media and OME. However, further studies of this topic are needed.

Matrix metalloproteinases as therapeutic targets in protozoan parasitic infections

Matrix metalloproteinases (MMPs) are associated with processes of tissue remodeling and are expressed in all infections with protozoan parasites. We here report the status of MMP research in malaria, trypanosomiasis, leishmaniasis and toxoplasmosis. In all these infections, the balances between MMPs and endogenous MMP inhibitors are disturbed, mostly in favor of active proteolysis. When the infection is associated with leukocyte influx into specific organs, immunopathology and collateral tissue damage may occur. These pathologies include cerebral malaria, sleeping sickness (human African trypanosomiasis), Chagas disease (human American trypanosomiasis), leishmaniasis and toxoplasmic encephalitis in immunocompromised hosts. Destruction of the integrity of the blood-brain barrier (BBB) is a common denominator that may be executed by leukocytic MMPs under the control of host cytokines and chemokines as well as influenced by parasite products. Mechanisms by which parasite-derived products alter host expression of MMP and endogenous MMP inhibitors, have only been described for hemozoin (Hz) in malaria. Hence, understanding these interactions in other parasitic infections remains an important challenge. Furthermore, the involved parasites are also known to produce their own metalloproteinases, and this forms an extra stimulus to investigate MMP inhibitory drugs as therapeutics. MMP inhibitors (MMPIs) may dampen collateral tissue damage, as is anecdotically reported for tetracyclines as MMP regulators in parasite infections.

Identification of candidate serum biomarkers for severe septic shock-associated kidney injury via microarray

Introduction

Septic-shock-associated acute kidney injury (SSAKI) carries high morbidity in the pediatric population. Effective treatment strategies are lacking, in part due to poor detection and prediction. There is a need to identify novel candidate biomarkers of SSAKI. The objective of our study was to determine whether microarray data from children with septic shock could be used to derive a panel of candidate biomarkers for predicting SSAKI.

Methods

A retrospective cohort study compared microarray data representing the first 24 hours of admission for 179 children with septic shock with those of 53 age-matched normal controls. SSAKI was defined as a >200% increase of baseline serum creatinine, persistent to 7 days after admission.

Results

Patients with SSAKI (n = 31) and patients without SSAKI (n = 148) were clinically similar, but SSAKI carried a higher mortality (45% vs. 10%). Twenty-one unique gene probes were upregulated in SSAKI patients versus patients without SSAKI. Using leave-one-out cross-validation and class prediction modeling, these probes predicted SSAKI with a sensitivity of 98% (95% confidence interval (CI) = 81 to 100) and a specificity of 80% (95% CI = 72 to 86). Serum protein levels of two specific genes showed high sensitivity for predicting SSAKI: matrix metalloproteinase-8 (89%, 95% CI = 64 to 98) and elastase-2 (83%, 95% CI = 58 to 96). Both biomarkers carried a negative predictive value of 95%. When applied to a validation cohort, although both biomarkers carried low specificity (matrix metalloproteinase-8: 41%, 95% CI = 28 to 50; and elastase-2: 49%, 95% CI = 36 to 62), they carried high sensitivity (100%, 95% CI = 68 to 100 for both).

Conclusions

Gene probes upregulated in critically ill pediatric patients with septic shock may allow for the identification of novel candidate serum biomarkers for SSAKI prediction.

Matrix metalloproteinase-9 as new biomarkers of severity in multiple organ dysfunction syndrome caused by trauma and infection

Multiple organ dysfunction syndrome (MODS) is an important cause of morbidity and mortality in intensive care unit. A severe insult in the form of infection or trauma primes the host immune system so that a subsequent, relatively trivial insult produces systemic inflammation response syndrome, which can lead to MODS and death. Matrix metalloproteinase-9 (MMP-9) is stored in the tertiary granules of polymorphonuclear leukocytes. These cells are key effectors in acute inflammatory diseases, such as sepsis and MODS. Endotoxin leads to rapid release of MMP-9 from these granules in vitro and in vivo. However, the role of this enzyme in MODS, and whether it is associated with organ injury at the early stage of MODS remains unclear. This present work may study role of MMP-9 with the MODS rats that caused by trauma and infection and investigate the mechanism of organ injury at the early stage of MODS. Here, we developed a rat model for MODS caused by trauma and infection and analyzed the dynamic level of MMP-9 and determined the relationship between MMP-9 level and early phase of organ injury in MODS rat. The histological changes in pulmonary, renal, and hepatic tissue were observed by light microscope. The expressions of plasma MMP-9 proteins were detected by an enzyme linked immunosorbent assay and its levels in the pulmonary, renal, and hepatic tissue were detected by using immunohistochemistry, respectively. The results indicated that there were no significant improvements in histopathology of rats in control group. However, the pulmonary, renal, and hepatic damage were serious in MODS groups. The concentration of MMP-9 in plasma and tissues of MODS rats increased markedly at the early stage and were higher than that of the control group. Moreover, the MMP-9 level in plasma positively correlated with the levels of pulmonary, renal, and hepatic tissue. This study clearly shows that MMP-9 is good biomarker to predict the severity of injury organ at the early phase of MODS.

Serum MMP-8, -9 and TIMP-1 in sepsis: high serum levels of MMP-8 and TIMP-1 are associated with fatal outcome in a multicentre, prospective cohort study. Hypothetical impact of tetracyclines

Recent evidence suggests that matrix metalloproteinases (MMPs) and their endogenous inhibitors are involved in the pathogenesis of sepsis. We studied serum levels of MMP-8, MMP-9 and TIMP-1 (tissue inhibitor of matrix metalloproteinase-1) in a multicentre, prospective cohort study of patients with sepsis treated in Intensive Care Units (ICUs). We analyzed serum samples taken on ICU admission from 248 critically ill sepsis patients. MMP-8, -9 and TIMP-1 serum levels were analyzed by enzyme-linked immunosorbent assays. Serum MMP-8, MMP-9 and TIMP-1 levels were significantly higher in patients with severe sepsis than in healthy controls. Serum MMP-8 levels among non-survivors (n=33) were significantly (p=0.006) higher than among survivors (n=215). Serum TIMP-1 but not MMP-9 levels were significantly higher among non-survivors than survivors (p<0.0001, p=0.079, respectively). Systemic MMP-8 is upregulated in sepsis suggesting that MMP-8 may contribute to the host response during sepsis. High serum MMP-8 and TIMP-1 levels at ICU admission were seen among patients with fatal outcome. With this background, clinical studies examining the ability of MMP-inhibitors (such as the non-antimicrobial properties of tetracyclines) to diminish the MMP-mediated inflammatory response are needed to develop novel therapies in order to improve the outcome of sepsis.

Matrix metalloproteinase inhibitor properties of tetracyclines: therapeutic potential in cardiovascular diseases

Matrix metalloproteinases (MMPs) are a family of proteases best known for their capacity to proteolyse several proteins of the extracellular matrix. Their increased activity contributes to the pathogenesis of several cardiovascular diseases. MMP-2 in particular is now considered to be also an important intracellular protease which has the ability to proteolyse specific intracellular proteins in cardiac muscle cells and thus reduce contractile function. Accordingly, inhibition of MMPs is a growing therapeutic aim in the treatment or prevention of various cardiovascular diseases. Tetracyclines, especially doxycycline, have been frequently used as important MMP inhibitors since they inhibit MMP activity independently of their antimicrobial properties. In this review we will focus on the intracellular actions of MMPs in some cardiovascular diseases including ischemia and reperfusion (I/R) injury, inflammatory heart diseases and septic shock; and explain how tetracyclines, as MMP inhibitors, have therapeutic actions to treat such diseases. We will also briefly discuss how MMPs can be intracellularly regulated and activated by oxidative stress, thus cleaving several important proteins inside cells. In addition to their potential therapeutic effects, MMP inhibitors may also be useful tools to understand the biological consequences of MMP activity and its respective extra- and intracellular effects.

Matrix metalloproteinase8 has a central role in inflammatory disorders and cancer progression

The predominant role of matrix metalloproteinase 8 in extracellular matrix turnover, modulation of inflammatory responses and other physiological processes is well documented. Several recent studies highlight the involvement of MMP8 in a wide range of pathologies. This review will shed light on the putative role of MMP8 as a drug target or disease marker in some inflammatory disorders and in cancer progression.

Emerging principles in protease-based drug discovery

Proteases have an important role in many signalling pathways, and represent potential drug targets for diseases ranging from cardiovascular disorders to cancer, as well as for combating many parasites and viruses. Although inhibitors of well-established protease targets such as angiotensin-converting enzyme and HIV protease have shown substantial therapeutic success, developing drugs for new protease targets has proved challenging in recent years. This in part could be due to issues such as the difficulty of achieving selectivity when targeting protease active sites. This Perspective discusses the general principles in protease-based drug discovery, highlighting the lessons learned and the emerging strategies, such as targeting allosteric sites, which could help harness the therapeutic potential of new protease targets.

"Reverse degradomics", monitoring of proteolytic trimming by multi-CE and confocal detection of fluorescent substrates and reaction products

A platform for profiling of multiple proteolytic activities acting on one specific substrate, based on the use of a 96-channel capillary DNA sequencer with CE-LIF of labeled substrate peptides and reaction products is introduced. The approach consists of synthesis of a substrate peptide of interest, fluorescent labeling of the substrate, either aminoterminally by chemical coupling, or carboxyterminally by transglutaminase reaction, proteolysis by a biological mixture of proteases in the absence or presence of protease inhibitors, multi-channel analysis of substrate and reaction products, and data collection and processing. Intact substrate and reaction products, even when varying by only one amino acid, can be relatively semi-quantified in a high-throughput manner, yielding information on proteases acting in complex biological mixtures and without prepurification. Monitoring, classification and inhibition of multiple proteolytic activities are demonstrated on a model substrate, the aminoterminus of the mouse granulocyte chemotactic protein-2. In view of extensive processing of chemokines into various natural forms with different specific biological activities, and of the fragmentary knowledge of processing proteases, examples of processing by neutrophil degranulate, tumor cell culture fluids and plasma are provided. An example of selection and comparison of inhibitory mAbs illustrates that the platform is suitable for inhibitor screening. Whereas classical degradomics technologies analyze the substrate repertoire of one specific protease, here the complementary concept, namely the study of all proteases acting, in a biological context, on one specific substrate, is developed and tuned to identify key proteases and protease inhibitors for the processing of any biological substrate of interest.

CD14 inhibition efficiently attenuates early inflammatory and hemostatic responses in Escherichia coli sepsis in pigs

Sepsis is a severe infection-induced systemic inflammatory syndrome. Inhibition of downstream inflammatory mediators of sepsis, e.g., TNF-alpha, has failed in clinical trials. The aim of this study was to investigate the effects of inhibiting CD14, a key upstream innate immunity molecule, on the early inflammatory and hemostatic responses in a pig model of gram-negative sepsis. The study comprised two arms, whole live Escherichia coli bacteria and E. coli lipopolysaccharide (LPS) (n=25 and n=9 animals, respectively). The animals were allocated into treatment (anti-CD14) and control (IgG isotype or saline) groups. Inflammatory, hemostatic, physiological, and microbiological parameters were measured. The proinflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-8, but not the anti-inflammatory cytokine IL-10, were efficiently inhibited by anti-CD14. Furthermore, anti-CD14 preserved the leukocyte count and significantly reduced granulocyte enzyme matrix metalloproteinase-9 release and expression of the granulocyte membrane activation molecule wCD11R3 (pig CD11b). The hemostatic markers thrombin-antithrombin III complexes and plasminogen activator inhibitor-1 were significantly attenuated. Anti-CD14 did not affect LPS or E. coli DNA levels. This study documents that CD14 inhibition efficiently attenuates the proinflammatory cytokine response and granulocyte activation and reverses the procoagulant state but does not interfere with LPS levels or bacterial counts in E. coli-induced sepsis.-Thorgersen, E. B., Hellerud, B. C., Nielsen, E. W., Barratt-Due, A., Fure, H., Lindstad, J. K., Pharo, A., Fosse, E., Tønnessen, T. I., Johansen, H. T., Castellheim, A., Mollnes, T. E. CD14 inhibition efficiently attenuates early inflammatory and hemostatic responses in Escherichia coli sepsis in pigs.

Matrix metalloproteinases as drug targets in infections caused by gram-negative bacteria and in septic shock

The mammalian immune system is optimized to cope effectively with the constant threat of pathogens. However, when the immune system overreacts, sepsis, severe sepsis, or septic shock can develop. Despite extensive research, these conditions remain the leading cause of death in intensive care units. The matrix metalloproteinases (MMPs) constitute a family of proteases that are expressed in developmental, physiological, and pathological processes and also in response to infections. Studies using MMP inhibitors and MMP knockout mice indicate that MMPs play essential roles in infection and in the host defense against infection. This review provides a brief introduction to some basic concepts of infections caused by gram-negative bacteria and reviews reports describing MMP expression and inhibition, as well as studies with MMP-deficient mice in models of infection caused by gram-negative bacteria and of septic shock. We discuss whether MMPs should be considered novel drug targets in infection and septic shock.

Short term effects of doxycycline on matrix metalloproteinases 2 and 9

PURPOSE

To investigate the short term effects of Doxycycline on MMP-2 and MMP-9.

METHODS

Short term effects of Doxycycline (100 mg B.I.D.) on plasma levels of MMP-2 and MMP-9 were investigated in 20 healthy subjects; the effects of Doxy, Acetylsalicylic acid, Nitrates, and Enalapril on MMP-9 release from were assessed in isolated polymorphonuclear cells.

RESULTS

In plasma, MMP-9 activity was reduced (-22%, 95% CI -32/-11; P = 0.002) starting at 12 h after doxy; in vitro, MMP-9 released from stimulated neutrophils was reduced by Doxy (-28%, 95% CI -43/-14; P = 0.001), inhibiting degranulation, and by nitrates (-52%, 95% CI -76/-28 P = 0.005), increasing three times both pro- and active-MMP-9 bound to neutrophils (P = 0.007 and 0.040, respectively).

CONCLUSIONS

Doxy decreases MMP-9 plasma levels by around 20%, within the first 12 h. The mechanism leading to such reduction seems due to the inhibition of PMN degranulation.

The Kazal motifs of RECK protein inhibit MMP-9 secretion and activity and reduce metastasis of lung cancer cells in vitro and in vivo

RECK is a membrane-anchored glycoprotein which may negatively regulate matrix metalloproteinase (MMP) activity to suppress tumor invasion and metastasis. In this study, recombinant proteins corresponding to the residues 285–368 (named as CKM which contained cysteine knot motif), 605–799 (named as K123 which contained three Kazal motifs), 676–799 (named as K23 which contained the last two Kazal motifs) and full-length RECK were produced and their anti-cancer effects were tested. Full-length RECK and K23 but not K123 and CKM inhibited MMP9 secretion and activity. In addition, RECK and K23 inhibited invasion but not migration of metastatic lung cancer cells in vitro. Protein binding and kinetic study indicated that K23 physically interacted with MMP-9 and inhibited its activity by a non-competitive manner. Moreover, K23 reduced metastatic tumor growth in lungs of nude mice. Taken together, our results suggest that the K23 motifs of RECK protein can inhibit MMP-9 secretion and activity and attenuate metastasis of lung cancer cells.

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.

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.

Matrix metalloproteinases contribute to endotoxin and interleukin-1beta induced vascular dysfunction

BACKGROUND AND PURPOSE

The acute vascular inflammatory dysfunction associated with endotoxaemia may reflect an imbalance between matrix metalloproteinases (MMPs) and their natural inhibitors (TIMPs), induced by the endotoxin. This possibility was tested in rat aortic tissue.

EXPERIMENTAL APPROACHES

Tone induced by phenylephrine in aortic rings was measured after exposure in vitro to ambient lipopolysaccharide (LPS) or the proinflammatory cytokine interleukin-1beta (IL-1beta) for 6h, with or without MMP inhibitors (doxycycline or GM6001). Gelatinase and MMP activities, TIMP proteins and contractility were measured in aortae taken from rats 6h after receiving LPS in vivo.

KEY RESULTS

Inhibition of MMP prevented the loss of phenylephrine-induced tone in aortic rings after LPS or IL-1beta. IL-1beta also increased release of MMP-2 activity from aortic tissue. In aortae exposed in vivo to LPS, net gelatinase, MMP-9 activities and TIMP-1 protein levels were increased, whereas TIMP-4 was reduced. These aortae were hypocontractile to both phenylephrine and KCl. Hypocontractility was partially reversed by doxycycline ex vivo.

CONCLUSIONS AND IMPLICATIONS

MMP inhibitors ameliorate vascular hyporeactivity induced by either LPS or IL-1beta in vitro. LPS in vivo alters the balance between MMPs and TIMPs, contributing to vascular dysfunction which is partially reversed by MMP inhibitors. Vascular MMPs are activated as a result of LPS or IL-1beta-induced stress and contribute to the hyporeactivity of blood vessels to vasoconstrictors.

Inflammation dampened by gelatinase A cleavage of monocyte chemoattractant protein-3

Tissue degradation by the matrix metalloproteinase gelatinase A is pivotal to inflammation and metastases. Recognizing the catalytic importance of substrate-binding exosites outside the catalytic domain, we screened for extracellular substrates using the gelatinase A hemopexin domain as bait in the yeast two-hybrid system. Monocyte chemoattractant protein-3 (MCP-3) was identified as a physiological substrate of gelatinase A. Cleaved MCP-3 binds to CC-chemokine receptors-1, -2, and -3, but no longer induces calcium fluxes or promotes chemotaxis, and instead acts as a general chemokine antagonist that dampens inflammation. This suggests that matrix metalloproteinases are both effectors and regulators of the inflammatory response.