The mast cells

Mast Cell Proteases Tryptase and Chymase Induce Migratory and Morphological Alterations in Bronchial Epithelial Cells

Chronic respiratory diseases are often characterized by impaired epithelial function and remodeling. Mast cells (MCs) are known to home into the epithelium in respiratory diseases, but the MC-epithelial interactions remain less understood. Therefore, this study aimed to investigate the effect of MC proteases on bronchial epithelial morphology and function. Bronchial epithelial cells were stimulated with MC tryptase and/or chymase. Morphology and epithelial function were performed using cell tracking analysis and holographic live-cell imaging. Samples were also analyzed for motility-associated gene expression. Immunocytochemistry was performed to compare cytoskeletal arrangement. Stimulated cells showed strong alterations on gene, protein and functional levels in several parameters important for maintaining epithelial function. The most significant increases were found in cell motility, cellular speed and cell elongation compared to non-stimulated cells. Also, cell morphology was significantly altered in chymase treated compared to non-stimulated cells. In the current study, we show that MC proteases can induce cell migration and morphological and proliferative alterations in epithelial cells. Thus, our data imply that MC release of proteases may play a critical role in airway epithelial remodeling and disruption of epithelial function.

Mast cell-mediated splanchnic cholestatic inflammation

INTRODUCTION

Splanchnic mast cells increase in chronic liver and in acute-on-chronic liver diseases. We administered Ketotifen, a mast cell stabilizer, and measured the mast cells in the splanchnic organs of cholestatic rats.

MATERIAL AND METHODS

These groups were studied: sham-operated rats (S; n = 15), untreated microsurgical cholestasic rats (C; n = 20) and rats treated with Ketotifen: early (SK-e; n = 20 and CKe; n = 18), and late (SK-l; n = 15 and CK-l; n = 14).

RESULTS

The cholestatic rats showed systemic and splanchnic impairments, such as ascites, portal hypertension, and biliary proliferation and fibrosis. The rats also showed a splanchnic increase of TNF-α, IL-1β and MCP-1, and a reduction of IL-4, IL-10 and antioxidants. An increase of VEGF in the ileum and mesenteric lymphatic complex was associated with a liver reduction of TGF-β1. Ketotifen reduces the degree of hepatic insufficiency and the splanchnic inflammatory mediators, as well as VEGF and TGF-ß1 levels. Ketotifen also reduces the connective tissue mast cells in the mesenteric lymphatic complex of cholestatic rats, while increases the hepatic mucosal mast cells.

CONCLUSIONS

In cholestatic rats, Ketotifen improves liver function and ascites, and also reduces pro-inflammatory mediators in the splanchnic area. The decrease in connective tissue mast cells in the mesenteric lymphatic complex due to the administration of Ketotifen would lead to the improvement of the inflammatory splanchnic response, and consequently the abovementioned complications.

Regulation of mast cell responses in health and disease

Mast cells are multifunctional cells that initiate not only IgE-dependent allergic diseases but also play a fundamental role in innate and adaptive immune responses to microbial infection. They are also thought to play a role in angiogenesis, tissue remodeling, wound healing, and tumor repression or growth. The broad scope of these physiologic and pathologic roles illustrates the flexible nature of mast cells, which is enabled in part by their phenotypic adaptability to different tissue microenvironments and their ability to generate and release a diverse array of bioactive mediators in response to multiple types of cell-surface and cytosolic receptors. There is increasing evidence from studies in cell cultures that release of these mediators can be selectively modulated depending on the types or groups of receptors activated. The intent of this review is to foster interest in the interplay among mast cell receptors to help understand the underlying mechanisms for each of the immunological and non-immunological functions attributed to mast cells. The second intent of this review is to assess the pathophysiologic roles of mast cells and their products in health and disease. Although mast cells have a sufficient repertoire of bioactive mediators to mount effective innate and adaptive defense mechanisms against invading microorganisms, these same mediators can adversely affect surrounding tissues in the host, resulting in autoimmune disease as well as allergic disorders.

The mast cell: an evolutionary perspective

This review article is an attempt to trace the evolution of mast cells (MCs). These immune cells have been identified in all vertebrate classes as single-lobed cells containing variable amounts of membrane-bound secretory granules which store a large series of mediators, namely histamine, proteases, cytokines and growth factors. Other MC features, at least in mammals, are the c-kit receptor for the stem cell factor and the high-affinity receptor, FcepsilonRI, for immunoglobulin E (IgE). The c-kit receptor also has been identified in fish MCs. The FcepsilonRI receptor seems to be a more recent acquisition in MC phylogenesis given that IgE originated in mammalian species. Tryptase and histamine have also been recognized in MCs of teleost fish. Thus, a cell population with the overall characteristics of higher vertebrate MCs is identifiable in the most evolutionarily advanced fish species. Two potential MC progenitors have been identified in ascidians (urochordates which appeared approximately 500 million years ago): the basophil/MC-like granular haemocyte and the test cell. Both contain histamine and heparin, and provide defensive functions. Some granular haemocytes in Arthropoda also closely approximate the ultrastructure of modern MCs. The origin of MCs is probably to be found in a leukocyte ancestor operating in the context of a primitive local innate immunity and involved in phagocytic and killing activity against pathogens. From this type of defensive cell, the MC phylogenetic progenitor evolved into a tissue regulatory and remodelling cell, which was incorporated into the networks of recombinase activating genes (RAG)-mediated adaptive immunity in the Cambrian era, some 550 million years ago. Early MCs probably appeared in the last common ancestor we shared with hagfish, lamprey and sharks about 450-500 million years ago.

Increased Chymase in Livers with Autoimmune Disease: Colocalization with Fibrosis

Chymase, one of the proteases contained in human mast cells, promotes myocardial and renal interstitial fibrosis by converting angiotensin I to II (AII). We previously established a method for measuring chymase in liver tissue and examined the relationship between chymase and fibrosis in chronic hepatitis. In the present study, chymase was determined in liver specimens affected by autoimmune hepatitis (AIH, n=10) or primary biliary cirrhosis (PBC, n=12). To investigate spatial relationships between hepatic fibrosis and human chymase, mast cell distribution in the specimens was determined immunohistochemically using anti-chymase antibody. The mean amounts of chymase in livers with AIH and PBC were 11.56+/-10.64 and 11.67+/-9.96 ng/mg respectively. Hepatic chymase in AIH and PBC was significantly more abundant than in acute hepatitis (AH, 2.72+/-2.23 ng/mg, n=10; p<0.05). When sections from patients with AIH and PBC were immunostained for chymase, immunoreactive mast cells were detected in portal areas and sinusoidal walls, coinciding with zones of fibrosis. Thus chymase appears to be involved in hepatic fibrosis in AIH and PBC.

Increased mast cell infiltration in varicose veins of the lower limbs: a possible role in the development of varices

BACKGROUND

This study shows increased infiltration of mast cells in the walls of varicose veins in the lower limbs as an explanation of the pathogenesis of varix formation.

METHODS

Great saphenous veins exhibiting varicosity were histologically examined after vein stripping surgery, and the numbers of mast cells in the varicose lesions were estimated in 20 high-power fields (x400). Normal-looking regions of the veins were referred to as controls, and normal saphenous veins were prepared during coronary artery bypass grafting and designated baseline controls.

RESULTS

The varicose lesions showed a greater extent of mast cell infiltration (15.0 +/- 8.4 cells; mean +/- standard deviation), whereas control veins (5.9 +/- 4.0) and baseline control veins (4.4 +/-2.9) had a smaller number of mast cells.

CONCLUSIONS

The study suggests that increased mast cell infiltration contributes to the development of varicose veins.

Virus-induced increases in airway mast cells in brown Norway rats are associated with enhanced pulmonary viral replication and persisting lymphocytic infiltration

Brown Norway (BN) rats are more susceptible than Fischer 344 (F344) rats to parainfluenza virus-induced lung injury and to bronchiolar mast cell increases that are associated with persistent airway hyperresponsiveness. In this study, pulmonary viral replication as well as immune, inflammatory, and airway mast cell responses to Sendai virus infection were compared between neonatal BN and F344 rats. BN rats supported prolonged viral replication, and viral titers in BN rats were 5-fold higher (p < .05) than in F344 rats at 7 days after inoculation. F344 rats had 18-fold higher (p < .06) numbers of lymphocytes in bronchoalveolar lavage fluid at 7 days after inoculation than did BN rats. Persisting bronchiolar aggregates of lymphocytes, plasma cells, and macrophages were more common, and increases in bronchiolar mast cells were greater in BN rats than in F344 rats. No strain differences were detected in bronchiolar intramural infiltrates of CD4 + or CD8 + cells. The greater susceptibility of BN rats to virus-induced increases in bronchiolar mast cells and airway responsiveness may be the result of their less efficient viral clearance mechanisms and more persistent bronchiole-centered inflammatory response.

Angiogenesis: models and modulators

Angiogenesis in vivo is distinguished by four stages: subsequent to the transduction of signals to differentiate, stage 1 is defined as an altered proteolytic balance of the cell allowing it to digest through the surrounding matrix. These committed cells then proliferate (stage 2), and migrate (stage 3) to form aligned cords of cells. The final stage is the development of vessel patency (stage 4), generated by a coalescing of intracellular vacuoles. Subsequently, these structures anastamose and the initial flow of blood through the new vessel completes the process. We present and discuss how the available models most closely represent phases of in vivo angiogenesis. The enhancement of angiogenesis by hyaluronic acid fragments, transforming growth factor beta, tumor necrosis factor alpha, angiogenin, okadaic acid, fibroblast growth factor, interleukin 8, vascular endothelial growth factor, haptoglobin, and gangliosides, and the inhibition of the process by hyaluronic acid, estrogen metabolites, genestein, heparin, cyclosporin A, placental RNase inhibitor, steroids, collagen synthesis inhibitors, thrombospondin, fumagellin, and protamine are also discussed.

PU.1 and GATA: components of a mast cell-specific interleukin 4 intronic enhancer

Interleukin 4 (IL-4), a critical immunoregulatory cytokine, is produced by a subset of T lymphocytes and cells of the mast cell/basophil lineage. There are cell-specific differences in the regulatory elements that control IL-4 transcription in these two cell types. A 683-bp Bgl II fragment, located within the second intron of the murine IL-4 gene, was previously shown to exhibit mast cell-specific enhancer activity. To define critical cis-acting elements that regulate this enhancer, a series of deletions from the 5' and 3' ends of the Bgl II fragment were generated. Their effect on enhancer activity was assessed in IL-4-producing mast cell lines in transient transfection assays. Two functionally independent subregions, E1 and E2, were defined in this analysis. Both are required for full enhancer activity. Sequences identical to previously defined DNA-binding sites for SP1 and GATA are present within E1, and an ets binding site is located within E2. Although mutation of the SP1 sites had no effect on enhancer function, alteration of either the GATA or ets site reduced enhancer activity by 50-60%. Proteins that associate with the IL-4 intronic GATA and ets sites were detected in mast cell nuclear extracts by mobility-shift assays. Specific antibodies identified these factors as GATA-1 and GATA-2 and the ets family member PU.1. GATA-1, GATA-2, and PU.1 exhibit cell-specific expression, suggesting that these proteins play a critical role in the lineage-restricted activity of the IL-4 intronic enhancer in mast cells.

Middle ear diseases in relation to atopy and nasal metachromatic cells in infancy

The relation between middle ear morbidity and atopy was prospectively studied in 44 infants with and 20 without a confirmed family history of atopy. Signs of atopy were recorded at 3, 6, 9 and 18 months of age and signs of middle ear disease were recorded and controlled as needed. Twenty-seven children developed definite signs of atopy, while 12 showed probable signs and 25 remained free from allergic symptoms. The number of episodes of acute otitis media was higher and the duration of episodes of otitis media with effusion were longer in 13 infants with respiratory tract allergy, as compared with 14 allergic children with only skin manifestations and with 25 non-atopic children. Middle ear diseases were more commonly encountered in infants in whom nasal metachromatic cells were detected. Children exposed to tobacco smoke suffered more often from respiratory tract infections but not from increased middle ear morbidity in comparison with non-exposed children. In conclusion, middle ear morbidity during the first 18 months of life is more common in atopic children with asthma than in non-atopic infants and early appearance of nasal metachromatic cells is associated with middle ear infections.

Mast cells and eosinophils in the allergic mucosal response to allergen challenge: changes in distribution and signs of activation in relation to symptoms

An allergen challenge was performed in 10 asymptomatic patients with strictly seasonal allergic rhinitis. For comparison; seven nonallergic subjects were challenged with allergen, and seven allergic patients were challenged with diluent. Cell samples, obtained with use of a brush technique to recover cells from within the epithelium and nasal lavage to collect cells from the epithelial surface, and symptom scores were taken before challenge and at 2-hour intervals during 12 hours. The cell suspensions were cytocentrifuged onto object slides for light microscopy. Histamine was determined in the cell pellets. In brush samples from the allergic patients challenged with allergen, eosinophils, expressed as a percentage of the total granulocytes, increased from 4.3% +/- 2.7% (mean +/- SEM) to 10.3% +/- 3.8% (p < 0.05) 4 hours after challenge. This level was maintained for up to 12 hours. A similar increase was noted in the lavage specimens 2, 6, and 8 hours after the challenge. In the brush samples the proportion of eosinophils containing two or more cytoplasmic vacuoles, taken as a sign of activation, increased from 20% to 72% (p < 0.05) 8 hours after provocation. In brush samples from the allergic patients challenged with allergen, the numbers of metachromatic cells increased to a maximum of eightfold at 10 hours. In the lavage specimens, no metachromatic cells were observed before provocation, but they progressively increased in number 2 to 12 hours after provocation. Cell pellet histamine content decreased temporarily 2 to 4 hours after challenge (p < 0.05) in brush samples from allergen-challenged allergic patients. The local metachromatic cell density before challenge, as reflected in the brush specimens, correlated with nasal congestion, sneezing, and the degree of eosinophilia.

An immunohistochemical study of mononuclear cells in meningiomas

A consecutive series of 34 meningiomas were re-examined as to subtype and presence of nuclear atypia, mitotic figures, areas of high cellularity and necrosis. Meningioma cells were epithelial membrane antigen (EMA) positive in 31 out of the 34 tumours. The presence of mononuclear cells and macrophages was assessed by immunohistochemistry using the monoclonal antibodies L26 (CD20, B cell marker), DF-T1 (CD43, T cell marker), KP1 (CD68, macrophage marker) and MAC387 (monocytes). L26 positive B cells were observed infrequently. CD43 positive mononuclear cells were infiltrating the parenchyma as individual cells and as groups of cells in 29 (87% of the tumours). CD68 positive macrophages were seen in 19 (59% of the tumours), as scattered single cells or groups of cells. There was a statistically significant association between the number of CD68 positive cells (necrotic areas excluded) and microscopic features of aggressiveness, i.e. high cellularity as well as the combination of nuclear atypia and frequent mitotic figures. MAC387 stained only a few cells; the immunopositive cells were present mainly within and around vessels. Meningioma cells displayed a diffuse immunopositivity for L26 (CD20) in 29 out of 34 meningiomas, but did not stain with macrophage markers. Mast cells were found in 9 out of 32 tumours; when present they were significantly more prevalent in the syncytial subtype. Thus, mononuclear cell infiltrates in meningiomas are mainly composed of T cells and macrophages, indicating an immune system surveillance and response to the tumour cells. The functional and prognostic significance of the presence of CD68 positive cells, macrophages, deserve further study in the search for more reliable histological criteria to predict recurrence and biological aggressiveness in meningiomas.

Brown Norway rats are high responders to bronchiolitis, pneumonia, and bronchiolar mastocytosis induced by parainfluenza virus

The pathogenesis of parainfluenza 1 (Sendai) virus infection was compared among 25-day-old BN, F344, and LEW rats to identify a sensitive as well as a resistant inbred rat strain to Sendai virus-induced lung injury during early life. At 7 days after inoculation, BN rats had 65-fold higher (P less than .001) pulmonary viral titers and threefold higher (P less than .002) numbers of neutrophils in bronchoalveolar lavage fluid than did F344 rats. At 14 days after inoculation, when most virus-induced inflammation had been resolved, BN rats had a threefold greater (P less than .01) incidence of bronchioles with aggregates of lymphocytes and macrophages than did F344 rats. Control BN rats had higher numbers of bronchiolar eosinophils than did F344 or LEW rats. Although viral inoculation resulted in increased numbers of bronchiolar mast cells in all three strains at 14 days, bronchiolar mast cell density was greater (P less than .005) in virus-inoculated BN and LEW rats than in F344 rats. We conclude that BN rats are high responders and F344 rats are low responders to Sendai virus-induced bronchiolitis, pneumonia, and airway mastocytosis. These strain differences may be useful in elucidating important pathogenetic mechanisms in virus-induced airway injury and mastocytosis.

Mast cells in brains during experimental allergic encephalomyelitis in Lewis rats

We studied the number of mast cells and their extent of degranulation in brains of Lewis rats with acute experimental allergic encephalomyelitis (EAE), activity induced with guinea pig spinal cord and Freund's complete adjuvant. Non-immunized controls and EAE rats were killed on days 10, 11, 12, and 16 post-immunization (p.i.). The percentage of degranulated mast cells was significantly increased in EAE brains. Signs of degranulation were observed as early as day 10 p.i. Clinical EAE signs appeared from day 10 p.i. A significant change in mast cell number was not observed. The percentage of degranulated cells was largest at day 16 p.i., at a time when the inflammation had reached the thalamus. This indicates that mast cell degranulation may occur as a result of the inflammation. Collectively, the data suggest that mast cells may play a role in the pathogenesis of EAE.

Mast cells and tissue reaction to intraperitoneally implanted polymer capsules

The inflammatory reaction to implanted biomaterials often compromises the clinical usefulness of implantable devices. Dexamethasone, an anti-inflammatory agent, acts on macrophages to decrease production of inflammatory mediators, and on mast cells to prevent degranulation. Systemic administration of dexamethasone (dms) in rats decreases the tissue reaction to intraperitoneally implanted vinyl chloride-acrylic copolymer capsules. Local release of even smaller amounts of dms from a polymeric substrate placed inside an acrylic copolymer capsule may control the tissue reaction while avoiding the undesirable side effects of systemic treatment. Such a system also allows investigation of the local effect of soluble molecules on tissue-material interactions without altering the surface properties of the implant or adding the effect of a releasing material. In the present study, we investigated the effect of dms released from ethylene vinyl acetate (EVAc) rods placed in acrylic copolymer capsules and implanted in the peritoneal cavity of rats. In vitro the release of dms from EVAc rods was quasilinear for 5 weeks. When implanted intraperitoneally into rats, polymer capsules containing EVAc/dms rods generated a tissue reaction that was significantly thinner and featured fewer fibroblast and collagen layers than that around capsules containing pure EVAc rods at all time points studied. The tissue reaction layer was also thinner than that previously described in rats treated systemically with dms. The trabeculae of implants with dms-loaded EVAc rods contained significantly more intact mast cells than implants with EVAc alone, suggesting that degranulation of mast cells is involved in the tissue reaction to intraperitoneal polymer implants.

Mast-cell secretion and angiogenesis, a quantitative study in rats and mice

The activation of the autogenous mast cells (MCs) in situ in intact mesenterial windows was elicited by the intraperitoneal injection of the MC secretagogue Compound 48/80 over a period of 1, 3 and 5 days in Sprague-Dawley rats and in C57 BL/6 and CBA/Ca mice. As a probe of MC secretion, the release of histamine was quantified fluorometrically at predetermined intervals during the treatment. Fourteen days after the start of the treatment, the angiogenic response was quantified histologically as the number of vessel profiles per unit length of mesenteric window. Both the MC-activating and the angiogenic effect of the 48/80-treatment was greater in the rats than in the mice. The occurrence of MC-mediated angiogenesis in the mouse is demonstrated here for the first time. In the rat, 48/80-induced MC mediated angiogenesis increased in a distinctly dose-dependent manner. Two daily doses of 48/80 was the most efficient angiogenic protocol tested; a single day's treatment increased the number of vessels almost fivefold. The remarkable potency of the angiogenic reaction following MC secretion supports our previous notion that MC-mediated angiogenesis may have therapeutic implications in poorly vascularized tissues.