Human mast cells produce matrix metalloproteinase 9

On Connective Tissue Mast Cells as Protectors of Life, Reproduction, and Progeny

The connective tissue mast cell (MC), a sentinel tissue-residing secretory immune cell, has been preserved in all vertebrate classes since approximately 500 million years. No physiological role of the MC has yet been established. Considering the power of natural selection of cells during evolution, it is likely that the MCs exert essential yet unidentified life-promoting actions. All vertebrates feature a circulatory system, and the MCs interact readily with the vasculature. It is notable that embryonic MC progenitors are generated from endothelial cells. The MC hosts many surface receptors, enabling its activation via a vast variety of potentially harmful exogenous and endogenous molecules and via reproductive hormones in the female sex organs. Activated MCs release a unique composition of preformed and newly synthesized bioactive molecules, like heparin, histamine, serotonin, proteolytic enzymes, cytokines, chemokines, and growth factors. MCs play important roles in immune responses, tissue remodeling, cell proliferation, angiogenesis, inflammation, wound healing, tissue homeostasis, health, and reproduction. As recently suggested, MCs enable perpetuation of the vertebrates because of key effects-spanning generations-in ovulation and pregnancy, as in life-preserving activities in inflammation and wound healing from birth till reproductive age, thus creating a permanent life-sustaining loop. Here, we present recent advances that further indicate that the MC is a specific life-supporting and progeny-safeguarding cell.

Molecular profiling of the hippocampus of children with autism spectrum disorder

Several lines of evidence point to a key role of the hippocampus in Autism Spectrum Disorders (ASD). Altered hippocampal volume and deficits in memory for person and emotion related stimuli have been reported, along with enhanced ability for declarative memories. Mouse models have demonstrated a critical role of the hippocampus in social memory dysfunction, associated with ASD, together with decreased synaptic plasticity. Chondroitin sulfate proteoglycans (CSPGs), a family of extracellular matrix molecules, represent a potential key link between neurodevelopment, synaptic plasticity, and immune system signaling. There is a lack of information regarding the molecular pathology of the hippocampus in ASD. We conducted RNAseq profiling on postmortem human brain samples containing the hippocampus from male children with ASD (n = 7) and normal male children (3-14 yrs old), (n = 6) from the NIH NeuroBioBank. Gene expression profiling analysis implicated molecular pathways involved in extracellular matrix organization, neurodevelopment, synaptic regulation, and immune system signaling. qRT-PCR and Western blotting were used to confirm several of the top markers identified. The CSPG protein BCAN was examined with multiplex immunofluorescence to analyze cell-type specific expression of BCAN and astrocyte morphology. We observed decreased expression of synaptic proteins PSD95 (p < 0.02) and SYN1 (p < 0.02), increased expression of the extracellular matrix (ECM) protease MMP9 (p < 0.03), and decreased expression of MEF2C (p < 0.03). We also observed increased BCAN expression with astrocytes in children with ASD, together with altered astrocyte morphology. Our results point to alterations in immune system signaling, glia cell differentiation, and synaptic signaling in the hippocampus of children with ASD, together with alterations in extracellular matrix molecules. Furthermore, our results demonstrate altered expression of genes implicated in genetic studies of ASD including SYN1 and MEF2C.

Peripheral surgery triggers mast cells activation: Focusing on neuroinflammation

Peripheral surgery can lead to a systemic aseptic inflammatory response comprising several mediators aiming at restoring tissue homeostasis. It induces inflammatory mechanisms through neuroimmune interaction between the periphery and to brain which also plays a critical role in causing cognitive impairments. Accumulating scientific evidence revealed that acute neuroinflammation of the brain triggered by peripheral surgery that causes peripheral inflammation leads to transmitting signals into the brain through immune cells. Mast cells (MCs) play an important role in the acute neuroinflammation induced by peripheral surgical trauma. After peripheral surgery, brain-resident MCs can be rapidly activated followed by releasing histamine, tryptase, and other inflammatory mediators. These mediators then interact with other immune cells in the peripheral and amplify the signal into the brain by disrupting BBB and activating principle innate immune cells of brain including microglia, astrocytes, and vascular endothelial cells, which release abundant inflammatory mediators and in turn accelerate the activation of brain MCs, amplify the cascade effect of neuroinflammatory response. Surgical stress may induce HPA axis activation by releasing corticotropin-releasing hormone (CRH) subsequently influence the activation of brain MCs, thus resulting in impaired synaptic plasticity. Herein, we discuss the better understating of MCs mediated neuroinflammation mechanisms after peripheral surgery and potential therapeutic targets for controlling inflammatory cascades.

Targeting active sites of inflammation using inherent properties of tissue-resident mast cells

Mast cells play a pivotal role in initiating and directing host's immune response. They reside in tissues that primarily interface with the external environment. Activated mast cells respond to environmental cues throughout acute and chronic inflammation through releasing immune mediators via rapid degranulation, or long-term de novo expression. Mast cell activation results in the rapid release of a variety of unique enzymes and reactive oxygen species. Furthermore, the increased density of mast cell unique receptors like mas related G protein-coupled receptor X2 also characterizes the inflamed tissues. The presence of these molecules (either released mediators or surface receptors) are particular to the sites of active inflammation, and are a result of mast cell activation. Herein, the molecular design principles for capitalizing on these novel mast cell properties is discussed with the goal of manipulating localized inflammation. STATEMENT OF SIGNIFICANCE: Mast cells are immune regulating cells that play a crucial role in both innate and adaptive immune responses. The activation of mast cells causes the release of multiple unique profiles of biomolecules, which are specific to both tissue and disease. These unique characteristics are tightly regulated and afford a localized stimulus for targeting inflammatory diseases. Herein, these important mast cell attributes are discussed in the frame of highlighting strategies for the design of bioresponsive functional materials to target regions of inflammations.

Acute elevation of interleukin 6 and matrix metalloproteinase 9 during the onset of pituitary apoplexy in Cushing's disease

PURPOSE

Pituitary apoplexy is a rare endocrine emergency. The purpose of this study is to characterize physiological changes involved in pituitary apoplexy, especially during the acute phase.

METHODS

A Cushing's disease patient experienced corticotroph releasing hormone (CRH)-induced pituitary apoplexy during inferior petrosal sinus sampling (IPSS). The IPSS blood samples from the Cushing's disease patient were retrospectively analyzed for cytokine markers. For comparison, we also analyzed cytokine markers in blood samples from two pituitary ACTH-secreting microadenoma patients and one patient with an ectopic ACTH-secreting tumor.

RESULTS

Acute elevation of interleukin 6 (IL-6) and matrix metalloproteinase 9 (MMP9) was observed in the IPSS blood sample on the apoplectic hemorrhagic site of the tumor. In contrast, such a change was not observed in the blood samples from the contralateral side of the apoplexy patient and in other IPSS samples from two non-apoplexy Cushing's disease patient and a patient with ectopic Cushing's syndrome.

CONCLUSION

IL-6 and MMP9 may be involved in the acute process of pituitary apoplexy in Cushing's disease.

Mast cell-derived serotonin enhances methacholine-induced airway hyperresponsiveness in house dust mite-induced experimental asthma

BACKGROUND

Airway hyperresponsiveness (AHR) is a feature of asthma in which airways are hyperreactive to stimuli causing extensive airway narrowing. Methacholine provocations assess AHR in asthma patients mainly by direct stimulation of smooth muscle cells. Using in vivo mouse models, mast cells have been implicated in AHR, but the mechanism behind has remained unknown.

METHODS

Cpa3^{Cre /+} mice, which lack mast cells, were used to assess the role of mast cells in house dust mite (HDM)-induced experimental asthma. Effects of methacholine in presence or absence of ketanserin were assessed on lung function and in lung mast cells in vitro. Airway inflammation, mast cell accumulation and activation, smooth muscle proliferation, and HDM-induced bronchoconstriction were evaluated.

RESULTS

Repeated intranasal HDM sensitization induced allergic airway inflammation associated with accumulation and activation of lung mast cells. Lack of mast cells, absence of activating Fc-receptors, or antagonizing serotonin (5-HT)_2A receptors abolished HDM-induced trachea contractions. HDM-sensitized mice lacking mast cells had diminished lung-associated 5-HT levels, reduced AHR and methacholine-induced airway contraction, while blocking 5-HT_2A receptors in wild types eliminated AHR, implying that mast cells contribute to AHR by releasing 5-HT. Primary mouse and human lung mast cells express muscarinic M3 receptors. Mouse lung mast cells store 5-HT intracellularly, and methacholine induces release of 5-HT from lung-derived mouse mast cells and Ca²⁺ flux in human LAD-2 mast cells.

CONCLUSIONS

Methacholine activates mast cells to release 5-HT, which by acting on 5-HT_2A receptors enhances bronchoconstriction and AHR. Thus, M3-directed asthma treatments like tiotropium may also act by targeting mast cells.

Mechanisms of toxicity mediated by neutrophil and eosinophil granule proteins

Neutrophils and eosinophils are granulocytes which are characterized by the presence of granules in the cytoplasm. Granules provide a safe storage site for granule proteins that play important roles in the immune function of granulocytes. Upon granulocytes activation, diverse proteins are released from the granules into the extracellular space and contribute to the fight against infections. In this article, we describe granule proteins of both neutrophils and eosinophils able to kill pathogens and review their anticipated mechanism of antimicrobial toxicity. It should be noted that an excess of granules protein release can lead to tissue damage of the host resulting in chronic inflammation and organ dysfunction.

Immunological Aspects of Age-Related Macular Degeneration

Increasing evidence over the past two decades points to a pivotal role for immune mechanisms in age-related macular degeneration (AMD) pathobiology. In this chapter, we will explore immunological aspects of AMD, with a specific focus on how immune mechanisms modulate clinical phenotypes of disease and severity and how components of the immune system may serve as triggers for disease progression in both dry and neovascular AMD. We will briefly review the biology of the immune system, defining the role of immune mechanisms in chronic degenerative disease and differentiating from immune responses to acute injury or infection. We will explore current understanding of the roles of innate immunity (especially macrophages), antigen-specific immunity (T cells, B cells, and autoimmunity), immune amplifications systems, especially complement activity and the NLRP3 inflammasome, in the pathogenesis of both dry and neovascular AMD, reviewing data from pathology, experimental animal models, and clinical studies of AMD patients. We will also assess how interactions between the immune system and infectious pathogens could potentially modulate AMD pathobiology via alterations in in immune effector mechanisms. We will conclude by reviewing the paradigm of "response to injury," which provides a means to integrate various immunologic mechanisms along with nonimmune mechanisms of tissue injury and repair as a model to understand the pathobiology of AMD.

Recruitment and maturation of the coronary collateral circulation: Current understanding and perspectives in arteriogenesis

The coronary collateral circulation is a rich anastomotic network of primitive vessels which have the ability to augment in size and function through the process of arteriogenesis. In this review, we evaluate the current understandings of the molecular and cellular mechanisms by which this process occurs, specifically focussing on elevated fluid shear stress (FSS), inflammation, the redox state and gene expression along with the integrative, parallel and simultaneous process by which this occurs. The initiating step of arteriogenesis occurs following occlusion of an epicardial coronary artery, with an increase in FSS detected by mechanoreceptors within the endothelium. This must occur within a 'redox window' where an equilibrium of oxidative and reductive factors are present. These factors initially result in an inflammatory milieu, mediated by neutrophils as well as lymphocytes, with resultant activation of a number of downstream molecular pathways resulting in increased expression of proteins involved in monocyte attraction and adherence; namely vascular cell adhesion molecule 1 (VCAM-1), monocyte chemoattractant protein 1 (MCP-1) and transforming growth factor beta (TGF-β). Once monocytes and other inflammatory cells adhere to the endothelium they enter the extracellular matrix and differentiate into macrophages in an effort to create a favourable environment for vessel growth and development. Activated macrophages secrete inflammatory cytokines such as tumour necrosis factor-α (TNF-α), growth factors such as fibroblast growth factor-2 (FGF-2) and matrix metalloproteinases. Finally, vascular smooth muscle cells proliferate and switch to a contractile phenotype, resulting in an increased diameter and functionality of the collateral vessel, thereby allowing improved perfusion of the distal myocardium subtended by the occluded vessel. This simultaneously reduces FSS within the collateral vessel, inhibiting further vessel growth.

Re-epithelialization and immune cell behaviour in an ex vivo human skin model

A large body of literature is available on wound healing in humans. Nonetheless, a standardized ex vivo wound model without disruption of the dermal compartment has not been put forward with compelling justification. Here, we present a novel wound model based on application of negative pressure and its effects for epidermal regeneration and immune cell behaviour. Importantly, the basement membrane remained intact after blister roof removal and keratinocytes were absent in the wounded area. Upon six days of culture, the wound was covered with one to three-cell thick K14⁺Ki67⁺ keratinocyte layers, indicating that proliferation and migration were involved in wound closure. After eight to twelve days, a multi-layered epidermis was formed expressing epidermal differentiation markers (K10, filaggrin, DSG-1, CDSN). Investigations about immune cell-specific manners revealed more T cells in the blister roof epidermis compared to normal epidermis. We identified several cell populations in blister roof epidermis and suction blister fluid that are absent in normal epidermis which correlated with their decrease in the dermis, indicating a dermal efflux upon negative pressure. Together, our model recapitulates the main features of epithelial wound regeneration, and can be applied for testing wound healing therapies and investigating underlying mechanisms.

IL-33-mediated mast cell activation promotes gastric cancer through macrophage mobilization

The contribution of mast cells in the microenvironment of solid malignancies remains controversial. Here we functionally assess the impact of tumor-adjacent, submucosal mast cell accumulation in murine and human intestinal-type gastric cancer. We find that genetic ablation or therapeutic inactivation of mast cells suppresses accumulation of tumor-associated macrophages, reduces tumor cell proliferation and angiogenesis, and diminishes tumor burden. Mast cells are activated by interleukin (IL)-33, an alarmin produced by the tumor epithelium in response to the inflammatory cytokine IL-11, which is required for the growth of gastric cancers in mice. Accordingly, ablation of the cognate IL-33 receptor St2 limits tumor growth, and reduces mast cell-dependent production and release of the macrophage-attracting factors Csf2, Ccl3, and Il6. Conversely, genetic or therapeutic macrophage depletion reduces tumor burden without affecting mast cell abundance. Therefore, tumor-derived IL-33 sustains a mast cell and macrophage-dependent signaling cascade that is amenable for the treatment of gastric cancer.

Mast cells within the tumor microenvironment have controversial roles. Here, the authors show, using genetic mouse models, that in gastric cancer, mast cells at the periphery of the tumors are activated via cancer cell produced-IL33 and promote tumorigenesis by recruiting macrophages within the tumors.

Trauma-Induced Heterotopic Ossification Regulates the Blood-Nerve Barrier

De novo bone formation can occur in soft tissues as a result of traumatic injury. This process, known as heterotopic ossification (HO), has recently been linked to the peripheral nervous system. Studies suggest that HO may resemble neural crest-derived bone formation and is activated through the release of key bone matrix proteins leading to opening of the blood-nerve barrier (BNB). One of the first steps in this process is the activation of a neuro-inflammatory cascade, which results in migration of chondro-osseous progenitors, and other cells from both the endoneurial and perineurial regions of the peripheral nerves. The perineurial cells undergo brown adipogenesis, to form essential support cells, which regulate expression and activation of matrix metallopeptidase 9 (MMP9) an essential regulatory protein involved in opening the BNB. However, recent studies suggest that, in mice, a key bone matrix protein, bone morphogenetic protein 2 (BMP2) is able to immediately cross the BNB to activate signaling in specific cells within the endoneurial compartment. BMP signaling correlates with bone formation and appears critical for the induction of HO. Surprisingly, several other bone matrix proteins have also been reported to regulate the BNB, leading us to question whether these matrix proteins are important in regulating the BNB. However, this temporary regulation of the BNB does not appear to result in degeneration of the peripheral nerve, but rather may represent one of the first steps in innervation of the newly forming bone.

Activation‑induced upregulation of MMP9 in mast cells is a positive feedback mediator for mast cell activation

Activated mast cells are involved in the pathogenesis of allergic rhinitis (AR). As a member of the matrix metalloproteinase (MMP) family, MMP9 has been previously demonstrated act in a pro‑inflammatory manner. Mast cells regulate the activity of MMP9, and mast cells themselves have been reported to produce MMP9. However, to the best of our knowledge, the involvement of MMP9 in mast cell activation remains to be elucidated. The present study demonstrated an upregulation of MMP9 protein and mRNA expression levels in mast cells activated by phorbol ester and ionomycin. Phosphorylated ERK and AKT protein levels also markedly increased in activated mast cells, and inhibition of the ERK and AKT signaling pathways prevented the increase of MMP9 in activated mast cells. MMP9 was demonstrated to be involved in mast cell activation, since inhibition of MMP9 activity or expression inhibited mast cell activation. Furthermore, IL‑4 treatment reduced MMP9 upregulation in activated mast cells, and interference with IL‑4 signaling with an IL‑4 neutralizing antibody promoted MMP9 upregulation in activated mast cells. These results revealed a novel MMP9‑mediated mechanism underlying mast cell activation, thus providing novel ideas for AR therapy.

Characterization of death receptor 3-dependent aortic changes during inflammatory arthritis

Murine collagen-induced arthritis (mCIA) is characterized by decreased vascular constriction responses and increased MMP-9. Here, we describe additional histological alterations within the aorta and surrounding perivascular adipose tissue (PVAT), study the role of PVAT in constriction response, and investigate the potential involvement of death receptor 3 (DR3). mCIA was induced in wild-type (WT) and DR3-/- mice with nonimmunized, age-matched controls. Vascular function was determined in isolated aortic rings ±PVAT, using isometric tension myography, in response to cumulative serotonin concentrations. Cellular expression of F4/80 (macrophages), Ly6G (neutrophils), DR3, and MMP-9 was determined using immunohistochemistry. In WTs, arthritis-induced vascular dysfunction was associated with increased F4/80+ macrophages and increased DR3 expression in the aorta and PVAT. MMP-9 was also up-regulated in PVAT, but did not correlate with alterations of PVAT intact constriction. DR3-/- mice inherently showed increased leukocyte numbers and MMP-9 expression in the PVAT, but retained the same nonarthritic constriction response as DR3WT mice ±PVAT. Arthritic DR3-/- mice had a worsened constriction response than DR3WT and showed an influx of neutrophils to the aorta and PVAT. Macrophage numbers were also up-regulated in DR3-/- PVAT. Despite this influx, PVAT intact DR3-/- constriction responses were restored to the same level as DR3WT. Impaired vascular constriction in inflammatory arthritis occurs independently of total MMP-9 levels, but correlates with macrophage and neutrophil ingress. Ablating DR3 worsens the associated vasculature dysfunction, however, DR3-/- PVAT is able to protect the aorta against aberrant vasoconstriction caused in this model.

Hataedock Treatment Has Preventive Therapeutic Effects in Atopic Dermatitis-Induced NC/Nga Mice under High-Fat Diet Conditions

This study investigated the preventive therapeutic effects of Hataedock (HTD) treatment on inflammatory regulation and skin protection in AD-induced NC/Nga mice under high-fat diet conditions. Before inducing AD, the extract of Coptidis Rhizoma and Glycyrrhiza uralensis was administered orally to the 3-week-old mice. After that, AD-like skin lesions were induced by applying DNFB. All groups except the control group were fed a high-fat diet freely. We identified the effects of HTD on morphological changes, cytokine release and the induction of apoptosis through histochemistry, immunohistochemistry, and TUNEL assay. HTD downregulated the levels of IL-4 and PKC but increased the levels of LXR. HTD also suppressed the mast cell degranulation and release of MMP-9, Substance P. The levels of TNF-α, p-IκB, iNOS, and COX-2 were also decreased. The upregulation of inflammatory cell's apoptosis is confirmed by our results as increase of apoptotic body and cleaved caspase-3 and decrease of Bcl-2. HTD also reduced edema, angiogenesis, and skin lesion inflammation. Our results indicate HTD suppresses various inflammatory response on AD-induced mice with obesity through the regulation of Th2 differentiation and the protection of lipid barrier. Therefore, HTD could be used as an alternative and preventive therapeutic approach in the management of AD.

Pathways Regulating Spheroid Formation of Human Follicular Thyroid Cancer Cells under Simulated Microgravity Conditions: A Genetic Approach

Microgravity induces three-dimensional (3D) growth in numerous cell types. Despite substantial efforts to clarify the underlying mechanisms for spheroid formation, the precise molecular pathways are still not known. The principal aim of this paper is to compare static 1g-control cells with spheroid forming (MCS) and spheroid non-forming (AD) thyroid cancer cells cultured in the same flask under simulated microgravity conditions. We investigated the morphology and gene expression patterns in human follicular thyroid cancer cells (UCLA RO82-W-1 cell line) after a 24 h-exposure on the Random Positioning Machine (RPM) and focused on 3D growth signaling processes. After 24 h, spheroid formation was observed in RPM-cultures together with alterations in the F-actin cytoskeleton. qPCR indicated more changes in gene expression in MCS than in AD cells. Of the 24 genes analyzed VEGFA, VEGFD, MSN, and MMP3 were upregulated in MCS compared to 1g-controls, whereas ACTB, ACTA2, KRT8, TUBB, EZR, RDX, PRKCA, CAV1, MMP9, PAI1, CTGF, MCP1 were downregulated. A pathway analysis revealed that the upregulated genes code for proteins, which promote 3D growth (angiogenesis) and prevent excessive accumulation of extracellular proteins, while genes coding for structural proteins are downregulated. Pathways regulating the strength/rigidity of cytoskeletal proteins, the amount of extracellular proteins, and 3D growth may be involved in MCS formation.

Mast Cell Targeted Chimeric Toxin Can Be Developed as an Adjunctive Therapy in Colon Cancer Treatment

The association of colitis with colorectal cancer has become increasingly clear with mast cells being identified as important inflammatory cells in the process. In view of the relationship between mast cells and cancer, we studied the effect and mechanisms of mast cells in the development of colon cancer. Functional and mechanistic insights were gained from ex vivo and in vivo studies of cell interactions between mast cells and CT26 cells. Further evidence was reversely obtained in studies of mast cell targeted Fcε-PE40 chimeric toxin. Experiments revealed mast cells could induce colon tumor cell proliferation and invasion. Cancer progression was found to be related to the density of mast cells in colonic submucosa. The activation of MAPK, Rho-GTPase, and STAT pathways in colon cancer cells was triggered by mast cells during cell-to-cell interaction. Lastly, using an Fcε-PE40 chimeric toxin we constructed, we confirmed the promoting effect of mast cells in development of colon cancer. Mast cells are a promoting factor of colon cancer and thus also a potential therapeutic target. The Fcε-PE40 chimeric toxin targeting mast cells could effectively prevent colon cancer in vitro and in vivo. Consequently, these data may demonstrate a novel immunotherapeutic approach for the treatment of tumors.

Inmunohistochemical detection of mastocytes in tissue from patients with actinic prurigo

BACKGROUND

Actinic prurigo (AP) is a type of photodermatosis, the pathophysiology of which has not been determined. AP has been suggested to be a hypersensitivity reaction to the presence of eosinophils and the local production of IgE.

MATERIAL AND METHODS

Descriptive study, using paraffin blocks of tissue that have been diagnosed with AP from the Dermopathology department, Hospital General Dr. Manuel Gea González. In 66 blocks from 63 patients, eosinophils were identified by hematoxylin and eosin staining, and mastocytes were labeled by immunohistochemistry. Three random microphotographs (40x) were used, and cell counts were calculated as the mean count in the 3 microphotographs.

RESULTS

Forty cases (63.5%) were female, and 23 (36.5%) were male. The mean age was 26.49 ±14.09 years; regarding the evolution time of the disease, the average was 11.93 years ±11.39. In 38 of 63 cases (60%), the lip, skin, and conjunctiva were affected clinically. In 22 of 63 cases (34%), AP cheilitis was the sole manifestation, and in 4 of 63 cases (6%), there were lesions in the skin and conjunctiva. The mean eosinophil count was 9 per case, the average number of mastocytes/field was 28.48 (range 0 to 66) Kruskal-Wallis p=0.001.

CONCLUSIONS

There are elements in AP that mediate the reaction of hypersensitivity type IV b, necessitating the identification of triggering factors.

KEY WORDS

Actinic prurigo, eosinophil, hypersensitivity IV b, IgE, mastocytes.

Matrix Metalloproteinase 9 Exerts Antiviral Activity against Respiratory Syncytial Virus

Increased lung levels of matrix metalloproteinase 9 (MMP9) are frequently observed during respiratory syncytial virus (RSV) infection and elevated MMP9 concentrations are associated with severe disease. However little is known of the functional role of MMP9 during lung infection with RSV. To determine whether MMP9 exerted direct antiviral potential, active MMP9 was incubated with RSV, which showed that MMP9 directly prevented RSV infectivity to airway epithelial cells. Using knockout mice the effect of the loss of Mmp9 expression was examined during RSV infection to demonstrate MMP9’s role in viral clearance and disease progression. Seven days following RSV infection, Mmp9^-/- mice displayed substantial weight loss, increased RSV-induced airway hyperresponsiveness (AHR) and reduced clearance of RSV from the lungs compared to wild type mice. Although total bronchoalveolar lavage fluid (BALF) cell counts were similar in both groups, neutrophil recruitment to the lungs during RSV infection was significantly reduced in Mmp9^-/- mice. Reduced neutrophil recruitment coincided with diminished RANTES, IL-1β, SCF, G-CSF expression and p38 phosphorylation. Induction of p38 signaling was required for RANTES and G-CSF expression during RSV infection in airway epithelial cells. Therefore, MMP9 in RSV lung infection significantly enhances neutrophil recruitment, cytokine production and viral clearance while reducing AHR.

Mast cells play an important role in chlamydia pneumoniae lung infection by facilitating immune cell recruitment into the airway

Mast cells are known as central players in allergy and anaphylaxis, and they play a pivotal role in host defense against certain pathogens. Chlamydia pneumoniae is an important human pathogen, but it is unclear what role mast cells play during C. pneumoniae infection. We infected C57BL/6 (wild-type [WT]) and mast cell-deficient mice (Kit(W-sh/W-sh) [Wsh]) with C. pneumoniae. Wsh mice showed improved survival compared with WT mice, with fewer cells in Wsh bronchoalveolar lavage fluid (BALF), despite similar levels of cytokines and chemokines. We also found a more rapid clearance of bacteria from the lungs of Wsh mice compared with WT mice. Cromolyn, a mast cell stabilizer, reduced BALF cells and bacterial burden similar to the levels seen in Wsh mice; conversely, Compound 48/80, a mast cell degranulator, increased the number of BALF cells and bacterial burden. Histology showed that WT lungs had diffuse inflammation, whereas Wsh mice had patchy accumulations of neutrophils and perivascular accumulations of lymphocytes. Infected Wsh mice had reduced amounts of matrix metalloprotease-9 in BALF and were resistant to epithelial integral membrane protein degradation, suggesting that barrier integrity remains intact in Wsh mice. Mast cell reconstitution in Wsh mice led to enhanced bacterial growth and normal epithelial integral membrane protein degradation, highlighting the specific role of mast cells in this model. These data suggest that mast cells play a detrimental role during C. pneumoniae infection by facilitating immune cell infiltration into the airspace and providing a more favorable replicative environment for C. pneumoniae.

IgE-mediated basophil tumour necrosis factor alpha induces matrix metalloproteinase-9 from monocytes

BACKGROUND

IgE-mediated activation of mast cells has been reported to induce the release of tumour necrosis alpha (TNF-α), which may display autocrine effects on these cells by inducing the generation of the tissue remodelling protease matrix metalloproteinase-9 (MMP-9). While mast cells and basophils have been shown to express complementary and partially overlapping roles, it is not clear whether a similar IgE/TNF-α/MMP-9 axis exists in the human basophil. The purpose of this study was thus to investigate whether IgE-mediated activation of human basophils induces TNF-α and MMP-9 release.

METHODS

Human peripheral blood mononuclear cells (PBMC), isolated basophils and monocytes were stimulated up to 21 h with anti-IgE. Mediator releases were assessed by ELISA, and surface expressions of mediators were detected by flow cytometry. Upregulation of cytokine production was detected by Western blot and polymerase chain reaction (PCR).

RESULTS

IgE-mediated activation of basophils induced the synthesis and release of both TNF-α and MMP-9 from PBMC. In contrast, IgE-mediated activation of purified basophils induced the release and cellular expression of TNF-α but not MMP-9. Isolated monocytes did not release MMP-9 upon anti-IgE stimulation, but MMP-9 release was induced by stimulating monocytes with supernatants from activated basophils, and this release was inhibited by anti-TNF-α neutralizing antibodies.

CONCLUSION

Our results strongly indicate that human basophils release TNF-α following IgE-dependent activation and that this cytokine subsequently stimulates MMP-9 release from monocytes. These findings support a direct involvement of basophils in inflammation as well as suggesting a role for the basophil in tissue remodelling.

Tissue remodeling in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a recently recognized, immune-mediated disease characterized clinically by symptoms of esophageal dysfunction and histologically by eosinophil-predominant inflammation. The chronic esophageal eosinophilia of EoE is associated with tissue remodeling that includes epithelial hyperplasia, subepithelial fibrosis, and hypertrophy of esophageal smooth muscle. This remodeling causes the esophageal rings and strictures that frequently complicate EoE and underlies the mucosal fragility that predisposes to painful mucosal tears in the EoE esophagus. The pathogenesis of tissue remodeling in EoE is not completely understood, but emerging studies suggest that secretory products of eosinophils and mast cells, as well as cytokines produced by other inflammatory cells, epithelial cells, and stromal cells in the esophagus, all contribute to the process. Interleukin (IL)-4 and IL-13, Th2 cytokines overproduced in allergic disorders, have direct profibrotic and remodeling effects in EoE. The EoE esophagus exhibits increased expression of transforming growth factor (TGF)-β1, which is a potent activator of fibroblasts and a strong inducer of epithelial-mesenchymal transition. In addition, IL-4, IL-13, and TGF-β all have a role in regulating periostin, an extracellular matrix protein that might influence remodeling by acting as a ligand for integrins, by its effects on eosinophils or by activating fibrogenic genes in the esophagus. Presently, few treatments have been shown to affect the tissue remodeling that causes EoE complications. This report reviews the potential roles of fibroblasts, eosinophils, mast cells, and profibrotic cytokines in esophageal remodeling in EoE and identifies potential targets for future therapies that might prevent EoE complications.

Expression and Roles of MMP-2, MMP-9, MMP-13, TIMP-1, and TIMP-2 in Allergic Nasal Mucosa

Purpose

Allergic rhinitis (AR) and asthma share many characteristics, but structural changes are observed far less often in AR. Matrix metalloproteinases (MMPs) constitute a family of Zn-dependent endopeptidases that can decompose the extracellular matrix and basement membrane, and regulate cell infiltration. We analyzed the expression of MMPs and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), in allergic nasal mucosa after nasal allergen challenge (NAC) and determined their relationship to inflammatory cells.

Methods

Nasal mucosa specimens were obtained at surgery performed for hypertrophied turbinates. We performed NAC with house dust mite (HDM) allergen disks and control disks, and took biopsies at 30 minutes, 6 hours, and 12 hours after NAC. Cells expressing MMP-2, MMP-9, MMP-13, TIMP-1, and TIMP-2, as well as eosinophils and mast cells, were analyzed immunohistochemically. The MMPs and TIMPs in allergic nasal mucosa were quantified using enzyme-linked immunosorbent assays.

Results

At 30 minutes post-NAC, HDM-exposed nasal mucosa exhibited significantly more MMP-2+, MMP-9+, MMP-13+, TIMP-1+, and TIMP-2+ cells compared with control mucosa, and the numbers of MMP-9+ and TIMP-1+ cells correlated strongly with the number of mast cells. At 6 hours post-NAC, the numbers of MMP+ and TIMP+ cells did not differ significantly between HDM-exposed mucosa and control mucosa, but the ratios of MMP+ cells to TIMP+ cells were higher in HDM-exposed mucosa. At 12 hours post-NAC, the number of MMP-13+ cells tended to be higher in HDM-exposed mucosa and was strongly correlated with the number of eosinophils. Quantitatively, the levels of MMP-2 and MMP-13 were significantly higher than the MMP-9 level, and the TIMP-2 level was significantly higher than the TIMP-1 level in allergic nasal mucosa.

Conclusions

We demonstrated increased expression of MMP-2, MMP-9, and MMP-13 in allergic nasal mucosa, high MMPs-to-TIMP-1 ratios, and a strong correlation between MMP-9 and mast cells and between MMP-13 and eosinophils. The imbalance between MMPs and TIMPs may contribute to the migration of inflammatory cells such as eosinophils and mast cells to the nasal mucosa of AR patients, suggesting a possible active role of MMPs in AR.

The dark side of mast cell-targeted therapy in prostate cancer

Tumor development requires accomplices among white blood cells. Other than macrophages, mast cells have been observed to support the outgrowth of certain neoplasias because of their proangiogenic properties. In some tumor settings, however, mast cells may have a protective role, exerted by their proinflammatory mediators. In prostate cancer, no conclusive data on mast cell function were available. Here, we discuss recent work on the role of mast cells in mouse and human prostate cancer, showing that mast cells can behave alternatively as dangerous promoters, innocent bystanders, or essential guardians of tumors, according to the stage and origin of transformed cells. In particular, mast cells are essential for the outgrowth of early-stage tumors due to their matrix metalloproteinase-9 production, become dispensable in advanced-stage, post-epithelial-to-mesenchymal transition, and are protective against neuroendocrine prostate tumor variants. The common expression of c-Kit by mast cells and neuroendocrine clones suggests a possible competition for the ligand Stem cell factor and offers the chance of curing early-stage disease while preventing neuroendocrine tumors using c-Kit-targeted therapy. This review discusses the implications of these findings on the advocated mast cell-targeted cancer therapy and considers future directions in the study of mast cells and their interactions with other c-Kit-expressing cells.

Mast cell targeting hampers prostate adenocarcinoma development but promotes the occurrence of highly malignant neuroendocrine cancers

Mast cells (MC) are c-Kit-expressing cells, best known for their primary involvement in allergic reactions, but recently reappraised as important players in either cancer promotion or inhibition. Here, we assessed the role of MCs in prostate tumor development. In prostate tumors from both tumor-prone transgenic adenocarcinoma of the mouse prostate (TRAMP) mice and human patients, MCs are specifically enriched and degranulated in areas of well-differentiated (WD) adenocarcinoma but not around poorly differentiated (PD) foci that coexist in the same tumors. We derived novel TRAMP tumor cell lines, representative of WD and PD variants, and through pharmacologic stabilization or genetic ablation of MCs in recipients mice, we showed that MCs promote WD adenocarcinoma growth but are dispensable for PD tumors. WD tumors rely on MCs for matrix metalloprotease 9 (MMP-9) provision, as reconstitution of MC-deficient mice with wild-type but not MMP-9(-/-) MCs was sufficient to promote their growth. In contrast, PD tumors are MMP-9 self-competent, consistently with epithelial-to-mesenchymal transition. Such a dual source of MMP-9 was confirmed in human tumors, suggesting that MCs could be a good target for early-stage prostate cancer. Interestingly, in testing whether MC targeting could block or delay tumorigenesis in tumor-prone TRAMP mice, we observed a high incidence of early and aggressive tumors, characterized by a neuroendocrine (NE) signature and c-Kit expression. Taken together, these data underscore the contribution of MCs in tumor progression and uncover a new, opposite role of MCs in protecting against the occurrence of aggressive NE variants in prostate cancer.

Changes in transcriptional output of human peripheral blood mononuclear cells following resistance exercise

Various types of exercise alter the population of circulating peripheral blood mononuclear cells (PBMCs) and change their transcriptional output. This work examines changes in PBMC populations and transcription in response to resistance exercise training (RET), and identify key transcriptional changes in PBMCs that may play a role in altering peripheral tissues in response to RET. Ten resistance-trained men (20-24 years), performed an acute bout of RET for ~30 min following a 12 h fast. Venous blood was sampled at rest, immediately following exercise, and at 2 h post-exercise and analyzed for total and differential leukocytes and global gene expression using Affymetrix Genechips. Results showed elevated leukocytes, monocytes, lymphocytes, and lactate values immediately post-exercise (P < 0.05) over baseline. At 2 h post-exercise, leukocytes, and granulocytes remained elevated (P < 0.05), whereas lymphocytes were lower than (P < 0.05) baseline values. Initial microarray results showed the greatest transcriptional changes in pathways related to immune response, inflammation, and cellular communication. The change in PBMC population (2 h time point) correlated with a dramatic decrease in the expression of CD160, and XCL1, markers of lymphocyte populations. At the 2 h recovery time point upregulation of matrix metalloproteinase 9, orosomucoid 1, dishevelled-associated activator of morphogenesis 2, and arginase 1 suggest an induction in muscle damage and repair during this time frame. These results demonstrate that an acute bout of RET disrupts cellular homeostasis, induces a transient redistribution of certain leukocytes, and results in transcriptional changes in PBMCs translating into systemic changes in response to RET.

MMP-9 gene variants increase the risk for non-atopic asthma in children

Background

Atopic and non-atopic wheezing may be caused by different etiologies: while eosinophils are more important in atopic asthmatic wheezers, neutrophils are predominantly found in BAL samples of young children with wheezing. Both neutrophils as well as eosinophils may secrete matrix metalloproteinase 9 (MMP-9). Considering that MMP-9 plays an important role in airway wall thickening and airway inflammation, it may influence the development of obstructive airway phenotypes in children. In the present study we investigated whether genetic variations in MMP-9 influence the development of different forms of childhood asthma.

Methods

Genotyping of four HapMap derived tagging SNPs in the MMP-9 gene was performed using MALDI-TOF MS in three cross sectional study populations of German children (age 9-11; N = 4,264) phenotyped for asthma and atopic diseases according to ISAAC standard procedures. Effects of single SNPs and haplotypes were studied using SAS 9.1.3 and Haploview.

Results

SNP rs2664538 significantly increased the risk for non-atopic wheezing (OR 2.12, 95%CI 1.40-3.21, p < 0.001) and non-atopic asthma (OR 1.66, 95%CI 1.12-2.46, p = 0.011). Furthermore, the minor allele of rs3918241 may be associated with decreased expiratory flow measurements in non-atopic children. No significant effects on the development of atopy or total serum IgE levels were observed.

Conclusions

Our results have shown that homozygocity for MMP-9 variants increase the risk to develop non-atopic forms of asthma and wheezing, which may be explained by a functional role of MMP-9 in airway remodeling. These results suggest that different wheezing disorders in childhood are affected differently by genetic alterations.

P2 receptor-mediated signaling in mast cell biology

Mast cells are widely recognized as effector cells of allergic inflammatory reactions. They contribute to the pathogenesis of different chronic inflammatory diseases, wound healing, fibrosis, thrombosis/fibrinolysis, and anti-tumor immune responses. In this paper, we summarized the role of P2X and P2Y receptors in mast cell activation and effector functions. Mast cells are an abundant source of ATP which is stored in their granules and secreted upon activation. We discuss the contribution of mast cells to the extracellular ATP release and to the maintenance of extracellular nucleotides pool. Recent publications highlight the importance of purinergic signaling for the pathogenesis of chronic airway inflammation. Therefore, the role of ATP and P2 receptors in allergic inflammation with focus on mast cells was analyzed. Finally, ATP functions as mast cell autocrine/paracrine factor and as messenger in intercellular communication between mast cells, nerves, and glia in the central nervous system.

Mast cell-dependent contraction of human airway smooth muscle cell-containing collagen gels: influence of cytokines, matrix metalloproteases, and serine proteases

In asthma, mast cells infiltrate the airway smooth muscle cell layer and secrete proinflammatory and profibrotic agents that contribute to airway remodeling. To study the effects of mast cell activation on smooth muscle cell-dependent matrix contraction, we developed coculture systems of human airway smooth muscle cells (HASM) with primary human mast cells derived from circulating progenitors or with the HMC-1 human mast cell line. Activation of primary human mast cells by IgE receptor cross-linking or activation of HMC-1 cells with C5a stimulated contraction of HASM-embedded collagen gels. Contractile activity could be transferred with conditioned medium from activated mast cells, implicating involvement of soluble factors. Cytokines and proteases are among the agents released by activated mast cells that may promote a contractile response. Both IL-13 and IL-6 enhanced contraction in this model and the activity of IL-13 was ablated under conditions leading to expression of the inhibitory receptor IL-13Ralpha2 on HASM. In addition to cytokines, matrix metalloproteinases (MMPs), and serine proteases induced matrix contraction. Inhibitor studies suggested that, although IL-13 could contribute to contraction driven by mast cell activation, MMPs were critical mediators of the response. Both MMP-1 and MMP-2 were strongly expressed in this system. Serine proteases also contributed to contraction induced by mast cell-activating agents and IL-13, most likely by mediating the proteolytic activation of MMPs. Hypercontractility is a hallmark of smooth muscle cells in the asthmatic lung. Our findings define novel mechanisms whereby mast cells may modulate HASM-driven contractile responses.

Immunological investigation in the adenoid tissues from children with chronic rhinosinusitis

Objective: Chronic rhinosinusitis (CRS) is characterized by persistent inflammation and tissue remodeling of the nasal mucosa. Adenoidectomy is an effective surgical treatment in pediatric CRS. To evaluate the effect of pediatric CRS on the severity and characteristics of adenoid inflammation, the authors evaluated the expressions of inflammatory cell activation markers and tissue remodeling in adenoid tissues associated with cytokines tissue-remodeling-associated cytokines in adenoid tissues.

Study Design and Setting: A prospective controlled study on 40 pediatric patients admitting for adenotonsillectomy.

Subjects and Methods: Immunoassays were performed on adenoid tissues homogenates from 16 children with CRS and from 24 children without CRS to quantify the levels of inflammatory cell activation markers, such as soluble interleukin (IL)-2 receptor (sIL-2R), soluble CD23 (sCD23), IL-6, eosinophilic cationic protein (ECP), and tryptase, and the levels of cytokines associated with tissue remodeling, such as transforming growth factor (TGF)-β1, matrix metalloproteinase (MMP) 2 and 9, and tissue inhibitor of metalloproteinase (TIMP)-1.

Results: The mean levels (the ratio to albumin level) of sIL-2R, TGF-β1, MMP-2, MMP-9, and TIMP-1 were significantly higher in adenoid tissues of patients with CRS (27.31 ± 30.32, 4894.65 ± 2388.77, 500.13 ± 604.59, and 23.06 ± 10.37, respectively) than those without it (16.27 ± 10.93, 2635.51 ± 1448.63, 120.87 ± 321.50, 16.74 ± 11.10, and 7.39 ± 3.12, respectively; all P < 0.05). Regarding the severity of CRS, ECP level was significantly higher in patients with severe CRS than in those with mild to moderate CRS ( P = 0.033).

Conclusions: Adenoid tissues in pediatric CRS patients had higher levels of tissue-remodeling–associated cytokines, which may explain the relationship between pediatric CRS and adenoid inflammation.

Matrix metalloproteinase-9: a novel biomarker for monitoring disease activity in patients with chronic urticaria patients?

BACKGROUND

Matrix metalloproteinase (MMP)-9, an enzyme that contributes to inflammatory responses and subsequent tissue remodelling, has recently been suggested to be a good biomarker for monitoring disease activity in patients with chronic urticaria (CU). Here, we assessed whether total MMP-9 and/or active MMP-9 plasma levels are increased and correlated to disease activity in patients with CU.

METHODS

Total MMP-9 and active MMP-9 plasma levels were determined by ELISA in 70 CU patients and control subjects (patients with psoriasis and healthy controls). CU activity was measured using weekly and daily composite symptom scores (urticaria activity score) calculated from the number of wheals and the intensity of pruritus.

RESULTS

Significantly increased levels of total and active MMP-9 were detected in patients with CU as compared to healthy controls. Interestingly, patients with psoriasis also had clearly elevated plasma levels of total and active MMP-9, indicating that MMP-9 plasma levels do not specifically reflect CU activity. Most notably, total and active MMP-9 levels were not correlated with disease activity in CU or psoriasis patients.

CONCLUSION

Plasma MMP-9 is not a good CU biomarker and should not be used for assessing the efficacy of treatment in CU patients or their spontaneous changes in disease activity.

Mast cells and angiogenesis in haematological malignancies

Tumor cells are surrounded by an infiltrate of inflammatory cells, namely lymphocytes, neutrophils, macrophages and mast cells (MCs). Increasing evidence indicates that MCs play a role in tumor growth and tumor-related angiogenesis in both solid and haematological tumors. In this review article, we discuss the involvement of MCs in angiogenesis in haematological malignancies and suggest that MCs might act as a new target for the adjuvant treatment of these tumors through the selective inhibition of angiogenesis.

MMP dependence of fibroblast contraction and collagen production induced by human mast cell activation in a three-dimensional collagen lattice

Mast cell-fibroblast interactions may contribute to fibrosis in asthma and other disease states. Fibroblast contraction is known to be stimulated by coculture with the human mast cell line, HMC-1, or by mast cell-derived agents. Matrix metalloproteinases (MMPs) can also mediate contraction, but the MMP-dependence of mast cell-induced fibroblast contractility is not established, and the consequences of mast cell activation within the coculture system have not been fully explored. We demonstrate that activation of primary human mast cells (pHMC) with IgE receptor cross-linking, or activation of HMC-1 with C5a, enhanced contractility of human lung fibroblasts in a three-dimensional collagen lattice system. This enhanced contractility was inhibited by the pan-MMP antagonist, batimastat, and was transferrable in the conditioned medium of activated mast cells. Exogenously added MMPs promoted gel contraction by mediating the proteolytic activation of latent transforming growth factor-beta (TGF-beta). Consistent with this, fibroblast contraction induced by mast cell activation was enhanced by addition of excess latent TGF-beta to the cultures. Batimastat inhibited this response, suggesting that MMPs capable of activating latent TGF-beta were released following mast cell activation in coculture with fibroblasts. Collagen production was also stimulated by activated mast cells in an MMP-dependent manner. MMP-2 and MMP-3 content of the gels increased in the presence of activated mast cells, and inhibition of these enzymes blocked the contractile response. These findings demonstrate the MMP dependence of mast cell-induced fibroblast contraction and collagen production.

Management of atherosclerosis with antiallergic medicine: a lesson from the mouse model

Evaluation of: Sun J, Sukhova GK, Wolters PJ et al.: Mast cells promote atherosclerosis by releasing pro-inflammatory cytokines. Nat. Med. 13, 719-724 (2007). Mast cells are important components in human allergic response and innate immunity. These cells have been implicated in the pathogenesis of atherosclerosis since the 1950s, and a series of studies have proposed their roles in the pathologic events critical to atherogenesis. Despite these studies and hypotheses, there is no evidence to suggest a direct participation of these allergic cells in atherosclerosis. Using mast cell-deficient mice and intravenous mast cell reconstitution technology with a conventional mouse atherosclerosis model, Dr Sun et al. revealed that mast cells contribute to atherogenesis by releasing proinflammatory cytokines, which are utilized to stimulate vascular cell-protease expression and further tissue remodeling. Mice that lack these cells are resistant to diet-induced atherosclerosis. These data suggest that stabilization of mast cells with antiallergic medicine may be utilized in controlling or preventing the initiation and progression of atherosclerosis in humans.

Mast cells are required for angiogenesis and macroscopic expansion of Myc-induced pancreatic islet tumors

An association between inflammation and cancer has long been recognized, but the cause and effect relationship linking the two remains unclear. Myc is a pleiotropic transcription factor that is overexpressed in many human cancers and instructs many extracellular aspects of the tumor tissue phenotype, including remodeling of tumor stroma and angiogenesis. Here we show in a beta-cell tumor model that activation of Myc in vivo triggers rapid recruitment of mast cells to the tumor site-a recruitment that is absolutely required for macroscopic tumor expansion. In addition, treatment of established beta-cell tumors with a mast cell inhibitor rapidly triggers hypoxia and cell death of tumor and endothelial cells. Inhibitors of mast cell function may therefore prove therapeutically useful in restraining expansion and survival of pancreatic and other cancers.

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.

Modulation of keratinocyte-derived MMP-9 by IL-13: a possible role for the pathogenesis of epidermal inflammation

Skin inflammation and remodeling are important pathophysiological features of chronic eczematous skin diseases. Matrix metalloproteinases (MMP) have been described to influence tissue remodeling and to facilitate cell migration through their ability to proteolyse the extracellular matrix. The aim of this study was to investigate the influence of IL-13 on the modulation of MMPs in human primary keratinocytes (KCs). IL-13 stimulation of KCs induced the expression of MMP-9 but not of MMP-3 or MMP-2 at mRNA level. A major substrate of MMP-9 is the type IV collagen of the basement membrane. IL-13 induced the release of active MMP-9 in KCs as detected by an ELISA-based assay. Moreover, migration of lymphocytes cultured with IL-13-activated KC showed increased migration through a basement membrane equivalent. The MMP-9 expression was prominent near the basement membrane of IL-13-treated skin biopsies. Collagen type IV staining pointed to a loss of this major basement membrane constituent in IL-13-treated skin. Finally, we demonstrated the concomitant mRNA expression of MMP-9 and IL-13 in biopsies from lesional, acutely inflamed eczematous skin. Our results suggest that release of active MMP-9 by IL-13-stimulated KCs may play a crucial role in skin inflammation by facilitating migration of leukocytes into the epidermis.

Chymase-positive mast cells play a role in the vascular component of airway remodeling in asthma

BACKGROUND

There is increasing evidence to support a role for total mast cells (MC(TOT)) in the vascular component of airway remodeling in asthma. On the contrary, up to now, no study has addressed the role of chymase-positive mast cells (MC(TC)) in microvasculature changes.

OBJECTIVE

We sought to assess the role of MC(TC) in the vascular component of airway remodeling in asthma.

METHODS

We recruited 8 patients with mild-to-moderate asthma and 8 healthy volunteers as a control group. Fiberoptic bronchoscopy with endobronchial biopsy was successfully performed in all subjects. Immunostaining was performed for quantification of vessels, vascular endothelial growth factor (VEGF)-positive cells, MC(TOT), and MC(TC).

RESULTS

Compared with those from healthy subjects, endobronchial biopsy specimens from asthmatic patients showed increased numbers of MC(TOT) and MC(TC) and VEGF(+) cells (P < .05). In asthmatic patients the number of vessels and the vascular area was also greater than in healthy subjects (P < .05). Additionally, in asthmatic patients the number of MC(TC) was significantly related to the vascular area (r(s) = 0.74, P < .01) and to the number of VEGF(+) cells (r(s) = 0.78, P < .01). Moreover, a colocalization study revealed that MC(TC) were a relevant cellular source of VEGF. Finally, a 6-week treatment with inhaled fluticasone propionate was able to reduce MC(TC) numbers.

CONCLUSION

MC(TC) can play a role in the vascular component of airway remodeling in asthma, possibly through induction of VEGF.

CLINICAL IMPLICATIONS

Specific targeting of MC(TC) might be a tool for treating vascular remodeling in asthma.

Subantimicrobial dose doxycycline in the treatment of recurrent oral aphthous ulceration: a pilot study

BACKGROUND

Recurrent oral aphthous ulceration (ROAU) is a common problem that can result in considerable pain and distress for patients. The aim of this pilot study was to evaluate the role of subantimicrobial dose doxycycline (SDD - 20 mg doxycycline twice daily) in the management of patients with ROAU.

METHODS

50 patients with ROAU were randomly allocated to treatment with SDD or placebo for 90 days. Daily ulcer diaries were completed by the participants to record the number of new ulcers and the pain associated with the ulcers.

RESULTS

There were significantly more days with no new ulcers in the SDD group (80.4 +/- 5.9) than the placebo group (69.8 +/- 18.7; P=0.04). Strong trends were observed towards fewer new ulcers per day, fewer new ulcers over the 90-day period, and more days with no pain in the SDD group compared with the placebo group (P=0.06-0.08).

CONCLUSION

SDD shows promise as potential therapy in the management of ROAU, though this needs to be confirmed in further studies.

Mast cells are required for normal healing of skin wounds in mice

Mast cells (MCs) have recently been reported to play a pivotal role in the elicitation of inflammatory reactions that are beneficial to the host, e.g., during innate immune responses to bacteria. To explore whether MCs also contribute to wound repair, we studied experimentally induced skin wounds in MC-deficient Kit(W)/Kit(W-v) mice, normal Kit+/+ mice, and MC-reconstituted Kit(W)/Kit(W-v) mice. Wound closure was significantly impaired in the absence of MCs during the first 6 days of wound healing and histomorphometric analyses of MC degranulation at the wound edges revealed distance-dependent MC activation, i.e., MC degranulation was most prominent directly adjacent to the wound. In addition, Kit(W)/Kit(W-v) mice showed impaired extravasation and recruitment of neutrophils to the wounded areas. Notably, wound closure, extravasation, and neutrophil recruitment were found to be normal in MC-reconstituted Kit(W)/Kit(W-v) mice. Therefore, we examined whether MCs promote wound healing by releasing histamine or TNF-alpha. Interestingly, wound closure was reduced in mice treated with an H1-receptor antagonist but not after treatment with an H2-receptor antagonist or in the absence of TNF-alpha. Taken together, our findings indicate that MC activation and histamine release are required for normal cutaneous wound healing.

Human Mast Cell-Derived Gelatinase B (Matrix Metalloproteinase-9) Is Regulated by Inflammatory Cytokines: Role in Cell Migration

Mast cells are key effectors in the pathogenesis of inflammatory and tissue destructive diseases such as rheumatoid arthritis (RA). These cells contain specialized secretory granules loaded with bioactive molecules including cytokines, growth factors, and proteases that are released upon activation. This study investigated the regulation of matrix metalloproteinase MMP-9 (gelatinase B) in human mast cells by cytokines that are known to be involved in the pathogenesis of RA. Immunohistochemical staining of synovial tissue showed abundant expression of MMP-9 by synovial tissue mast cells in patients with RA but not in normal controls. The expression, activity, and production of MMP-9 in mast cells was confirmed by RT-PCR, zymography, and Western blotting using cord blood-derived human mast cells (CB-HMC). Treatment of CB-HMC with TNF-alpha significantly increased the expression of MMP-9 mRNA and up-regulated the activity of MMP-9 in a time- and dose-dependent manner. By contrast, IFN-gamma inhibited MMP-9 mRNA and protein expression. The cytokine-mediated regulation of MMP-9 was also apparent in the human mast cell line (HMC-1) and in mouse bone marrow-derived mast cells. Furthermore, TNF-alpha significantly increased the invasiveness of CB-HMC across Matrigel-coated membranes while the addition of IFN-gamma, rTIMP-1, or pharmacological MMP inhibitors significantly reduced this process. These observations suggest that MMP-9 is not a stored product in mast cells but these cells are capable of producing this enzyme under inflammatory conditions that may facilitate the migration of mast cell progenitors to sites of inflammation and may also contribute to local tissue damage.

Production of matrix metalloproteinases in human cultured mast cells: involvement of protein kinase C-mitogen activated protein kinase kinase-extracellular signal-regulated kinase pathway

BACKGROUND

Matrix metalloproteinases (MMPs) have been reported to play crucial roles in the migration of inflammatory cells through basement membrane components. To confirm the role of mast cells as a source of MMPs, we investigated the production of MMP and its pathway in human cultured mast cells (HCMC). We also investigated the production of tissue inhibitors of metalloproteinase (TIMPs).

METHODS

HCMC was stimulated with phorbor 12-miristate 13-acetate (PMA) and/or calcium ionophore A23187 (A23187), and the resulting MMP production was evaluated by gelatin zymography and western blotting. Expression of MMP and TIMP mRNA was also examined. Granulocyte macrophage-colony stimulating factor (GM-CSF) was measured by ELISA and activation of extracellular signal-regulated kinase (ERK) was evaluated by western blotting.

RESULTS

We detected the de novo synthesis of MMP-9 in HCMC after stimulation with PMA and found that the synthesis was mediated through protein kinase C-mitogen activated protein kinase kinase (MEK)-ERK pathway. The MMP-9 production induced by PMA was suppressed by simultaneous treatment with A23187, whereas GM-CSF production was potentiated. We also detected the expression of mRNA for membrane-type 1 (MT1)-MMP, TIMP-1 and TIMP-2 after stimulation with PMA. Glucocorticoids and flavonoids inhibited MMP-9 production, and TIMPs and MMP inhibitors inhibited the gelatinolytic activity of mast cell-derived MMP-9. Furthermore, phenylmethylsulfonyl fluoride, a protease inhibitor, inhibited the conversion from proMMP-9 to active MMP-9.

CONCLUSIONS

These results suggest that the human mast cell is a leading member of MMP production, and the production, activation and activity are controllable by pharmacological agents.

A temporal framework for understanding the effects of stressful life events on inflammation in patients with multiple sclerosis

A growing literature reports that stressful life events are associated with exacerbation and the subsequent development of brain lesions in patients with multiple sclerosis (MS). The evolution an MS exacerbation occurs over a period of many months and involves many different biological processes that change over time. Likewise, the experience of stress also occurs over time, with an onset, a shift from acute to chronic in some cases, and resolution. Each of these phases is associated with unique biological features. Thus, the impact of stress on MS exacerbation may depend on the temporal trajectories of stress and MS exacerbation, and when the intersection between these two trajectories occurs. This paper presents a temporal model, along with three different temporal relationships and associated mechanisms by which stress may impact MS exacerbation. These include the onset of a stressor, which may be mediated by mast cell activation, the point that a stressor begins to become chronic, which may be mediated by glucocorticoid resistance in immune cells, and the resolution of the stressor, which may be mediated by a drop in cortisol. These three hypotheses are not necessarily mutually exclusive. Data on psychosocial mediators and moderators are also briefly reviewed and future research directions are discussed.