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PubMed2002

The crystal structure of human alpha1-tryptase reveals a blocked substrate-binding region.

Human mast cell tryptases represent a subfamily of trypsin-like serine proteinases implicated in asthma. Unlike beta-tryptases, alpha-tryptases apparently are proteolytically inactive. We have solved the 2.2A crystal structure of mature human alpha1-tryptase. It reveals a frame-like tetrameric architecture that, surprisingly, does not require heparin-binding for stability. In marked contrast to beta2-tryptase, the Ser214-Gly219 segment, which normally provides the template for substrate binding, is kinked in alpha-tryptase, thereby blocking its non-primed subsites. This so far unobserved subsite distortion is incompatible with productive substrate binding and processing. alpha-Tryptase apparently is trapped in this off-conformation by repulsions and attractions of the Asp216 side-chain. However, proteolytic activity could be generated by an induced-fit mechanism.

Amino Acid Sequence↗
PubMed1995

Loratadine reduces allergen-induced mucosal output of alpha 2-macroglobulin and tryptase in allergic rhinitis.

BACKGROUND: Despite the wide use of antihistamines in the treatment of allergic rhinitis, little is known about effects of these drugs on airway mucosal indices, which specifically reflect either mast cell release activity (tryptase) or microvascular-epithelial exudation of bulk plasma (alpha 2-macroglobulin). OBJECTIVE: This study, involving subjects with seasonal allergic rhinitis, examines the effects of loratadine treatment on allergen-induced nasal mucosal output of tryptase and alpha 2-macroglobulin. Effects on nasal symptoms and eosinophils are also examined. METHODS: Placebo and loratadine (20 mg) were given orally once daily for 5 days at 6-week intervals. Nasal diluent and allergen challenges were carried out on day 5. The mucosa was lavaged with saline solution after each challenge, and nasal lavage fluid levels of tryptase and alpha 2-macroglobulin were determined. Nasal symptoms were scored, and nasal peak expiratory flow rates were measured. Superficial cells (eosinophils) were obtained with a brush device before and 24 hours after the allergen challenges. RESULTS: Allergen dose-dependently increased the nasal symptoms and the lavage fluid levels of alpha 2-macroglobulin and tryptase. Allergen also reduced the nasal peak expiratory flow rates. Loratadine inhibited the exudation of alpha 2-macroglobulin and reduced tryptase levels, nasal symptoms, and obstruction, but did not affect the number of eosinophils. CONCLUSION: The inhibitory effects of loratadine on nasal lavage fluid levels of alpha 2-macroglobulin suggest that histamine, through effects on microvascular H1-receptors, mediates allergen challenge-induced exudation of bulk plasma in acute allergic rhinitis. The reduced lavage fluid levels of tryptase suggest either that loratadine directly attenuates mast cell release activity or that loratadine, through inhibition of the exudation process, simply attenuates luminal entry of tissue solutes (in this case, tryptase).

Adolescent↗
PubMed2003

Involvement of proteinase-activated receptor-2 in mast cell tryptase-induced barrier dysfunction in bovine aortic endothelial cells.

We report here a direct modulation by mast cell tryptase of endothelial barrier function through activation of proteinase-activated receptor-2 (PAR-2). In cultured bovine aortic endothelial cells (BAECs), tryptase, trypsin and PAR-2 activating peptide impaired the barrier function as determined by the permeability of protein-conjugated Evans blue. The tryptase-induced barrier dysfunction was completely blocked by U73122, and partially reversed by xestospongin C, calphostin C or Y27632. The intracellular Ca(2+) was elevated by tryptase. It was notable that ioxaglate, a contrast material that degranulates mast cells, markedly increased the permeability when applied to BAECs in combination with mast cells, an action that was blocked by nafamostat, a potent tryptase inhibitor. Immunofluorescence analysis showed that actin stress fibre formation and disruption of VE-cadherin were observed after exposure to tryptase or ioxaglate in combination with mast cells. Therefore, it is suggested that mast cell tryptase impairs endothelial barrier function through activation of endothelial PAR-2 in a manner dependent on the phospholipase C activity.

Actins↗
PubMed2004

Relation of serum levels of mast cell tryptase of left ventricular systolic function, left ventricular volume or congestive heart failure.

BACKGROUND: Activated mast cells (MC) present in the myocardium of patients with cardiomyopathy may contribute to left ventricular dilatation and systolic dysfunction. We sought to determine whether peripheral levels of tryptase, an MC-specific protease, are related to indices of left ventricular size and function, as well as congestive heart failure (CHF) or coronary artery disease (CAD). METHODS AND RESULTS: Serum tryptase was measured in 85 patients undergoing cardiac catheterization with left ventriculography and coronary angiography and examined in relation to left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), congestive heart failure (CHF), and angiographically evident CAD. Systemic tryptase levels were lower in patients with increased (>90 mL) LVEDV (6.2 [5.3-8.0] mcg/L versus 8.3 [6.6-10.3] mcg/L, P=.01) and in patients with CHF (6.2 [3.6-7.3] mcg/L versus 8 [6.2-10] mcg/L, P=.02) and tended to be lower in patients with depressed (<55%) LVEF (6.8 [5.2-9] mcg/L versus 8 [6.3-9.9] mcg/L, P=NS). Linear regression did not show a significant relationship between tryptase levels with either LVEF or LVEDV. Finally, tryptase levels were consistently elevated in relation to the presence of CAD. CONCLUSION: Despite increased numbers of MC in the myocardium of patients with cardiomyopathy, systemic levels of MC tryptase appear to be lower in relation to LV systolic dysfunction, LV dilatation, or clinical CHF. In contrast, the presence of angiographically significant CAD is associated with elevated systemic tryptase levels.

Cardiac Catheterization↗
PubMed2001

Variations of serum eosinophil cationic protein and tryptase, measured in serum and saliva, during the course of immediate allergic reactions to foods.

BACKGROUND: Subjective complaints and reactions after placebo administration during food challenges (FC) may make their outcome difficult to interpret. We determined serum ECP and tryptase as tryptase in saliva during FC, looking for markers to support challenge outcomes. METHODS: Twelve patients with systemic reactions after food intake and nine presenting oral allergy syndrome (OAS) underwent skin tests; total and specific IgE determination; double-blind, placebo-controlled FC (DBPCFC); and open challenges. Blood samples were collected before and 1, 2, and 5 h after challenge and saliva before and 5, 30, and 60 min after challenge. ECP and tryptase were quantified by ImmunoCAP (Pharmacia-Upjohn, Sweden). Serum tryptase of > 10 microg/l was considered positive. RESULTS: After positive DBPCFC (n = 8), ECP rose significantly (P < 0.05) at 1-h - 16.03 (12.8) microg/l (mean [standard deviation]) - and 2-h intervals - 17.56 (10.7) microg/l - compared to basal level of 9 (6.4) microg/l. After negative DBPCFC (n = 6), ECP increased from basal 9.63 (3.9) microg/l to 24.84 (14.17) microg/l at the 2-h time point. There were nonsignificant differences in ECP between patients with positive and negative FC. Two patients with positive challenge showed a tryptase level of >10 microg/l and only one patient with OAS showed 5.6 microg/l of tryptase 5 min after FC. CONCLUSIONS: ECP and tryptase in serum and saliva were not useful markers for FC outcomes.

Adolescent↗
PubMed2000

Human mast cell tryptase stimulates the release of an IL-8-dependent neutrophil chemotactic activity from human umbilical vein endothelial cells (HUVEC).

Tryptase, the major product of human mast cell activation, is a potent stimulus of vascular leakage and neutrophil accumulation in vivo in animal studies, but the mechanisms of action remain unclear. Using HUVEC cultures we have sought to investigate the potential of tryptase to alter monolayer permeability or induce the release of neutrophil chemotactic activity. Tryptase (1-100 mU/ml) failed to alter the permeability of endothelial cell monolayers as assessed by albumin flux over 1 h. However, supernatants from endothelial cells treated with tryptase (1-50 mU/ml) for a 24-h period induced neutrophil migration across Transwell filters, with maximal migration observed at 10 mU/ml tryptase. Pretreatment of tryptase with the protease inhibitor leupeptin abolished the chemotactic activity, indicating a dependence on the catalytic site. Moreover, this effect was abolished by addition of an IL-8 neutralizing antibody, suggesting that IL-8 release makes an important contribution to the chemotactic activity. The interaction of mast cell tryptase with endothelial cells could be important in stimulating the ingress of neutrophils following mast cell activation in inflammatory disease.

Cell Movement↗
PubMed2001

Definition of the extended substrate specificity determinants for beta-tryptases I and II.

Tryptases betaI and betaII were heterologously expressed and purified in yeast to functionally characterize the substrate specificity of each enzyme. Three positional scanning combinatorial tetrapeptide substrate libraries were used to determine the primary and extended substrate specificity of the proteases. Both enzymes have a strict primary preference for cleavage after the basic amino acids, lysine and arginine, with only a slight preference for lysine over arginine. betaI and betaII tryptase share similar extended substrate specificity, with preference for proline at P4, preference for arginine or lysine at P3, and P2 showing a slight preference for asparagine. Measurement of kinetic constants with multiple substrates designed for beta-tryptases reveal that selectivity is highly dependent on ground state substrate binding. Coupled with the functional determinants, structural determinants of tryptase substrate specificity were identified. Molecular docking of the preferred substrate sequence to the three-dimensional tetrameric tryptase structure reveals a novel extended substrate binding mode that involves interactions from two adjacent protomers, including P4 Thr-96', P3 Asp-60B' and Glu-217, and P1 Asp-189. Based on the determined substrate information, a mechanism-based tetrapeptide-chloromethylketone inhibitor was designed and shown to be a potent tryptase inhibitor. Finally, the cleavage sites of several physiologically relevant substrates of beta-tryptases show consistency with the specificity data presented here.

Humans↗
PubMed2002

Serum B12 tryptase level as a marker of allergic airway inflammation in asthma.

Tryptase is a specific marker of mast-cell activation and plays a part in the pathophysiology of various allergic diseases including asthma, but little is known of the spillover of this enzyme into the systemic circulation. Therefore, we measured serum levels of mast-cell-derived tryptase in 21 patients with mild to moderate asthma and 20 healthy, subjects, using a B12 monoclonal antibody-based immunofluoroassay that detects both monomers and tetramers of alpha- and beta-tryptases. There was a good correlation between serum and sputum tryptase levels, and, compared with healthy subjects (1.68 +/- 0.31 ng/ml), asthma patients had higher concentrations of serum tryptase (atopic asthma, 4.18 +/- 0.95 ng/ml, p = 0.022; nonatopic asthma, 3.93 +/- 0.82 ng/ml, p = 0.031). Although serum tryptase levels did not correlate with asthma symptom scores, peak expiratory flow, or forced expiratory volume in 1 s, they positively correlated with mast-cell and eosinophil counts (p = 0.041 and p = 0.025, respectively) and eosinophil cationic protein contents (p = 0.029) in induced sputum. These results suggest that serum tryptase detected with B12 antibody is a marker of allergic airway inflammation in asthma.

Adult↗
PubMed1996

Stem cell factor-dependent human cord blood derived mast cells express alpha- and beta-tryptase, heparin and chondroitin sulphate.

The present study sought to determine the expression of alpha- and beta-tryptase in in vitro differentiated human cord blood derived mast cells. We also analysed the glycosaminoglycan composition and the phenotype of the cells. The major protease in human mast cells is tryptase, and cDNAs for two different human tryptases have been characterized, the so-called alpha- and beta-tryptase. By reverse transcriptase-polymerase chain reaction (RT-PCR) we could show that stem cell factor (SCF)-dependent cord blood derived mast cells express both alpha- and beta-tryptase. Furthermore, the cells were stained with a monoclonal antibody (mAb) against tryptase, and the tryptase was enzymatically active cleaving the substrate Z-Gly-Pro-Arg- methoxy-2- naphthylamide (MNA). The majority of the cord blood derived mast cells could also be stained with mAbs against chymase, cathepsin G and CD68. They also expressed Kit/SCFR (CD117), CD13, CD29 and CD45 on the cell surface. The proteoglycan-derived polysaccharide composition of the cells was estimated to be 25-35% of heparin origin and 65-75% of chondroitin sulphate origin. Hence, the cord blood derived mast cells exhibit a phenotype in common with the so-called MCTC type of human mast cells.

Base Sequence↗
PubMed1993

Tryptase in nasal fluid is a useful marker of allergic rhinitis.

Tryptase is a mast cell-specific marker of degranulation. To investigate the possible diagnostic value of tryptase in allergic rhinitis, we measured the levels in both serum and native nasal fluid with a sandwich RIA-assay (Pharmacia). Twenty-three allergic patients and five patients with chronic ethmoidal sinusitis were included. Eighteen of the 23 allergic patients were tested within the pollen season or had perennial rhinitis; the remainder were tested at least 1 month out of the pollen season. None of the patients had detectable serum tryptase (> 0.1 ng/ml). Also patients with chronic ethmoidal sinusitis showed no tryptase in nasal fluid. One of seven allergic patients tested out of season had slightly increased nasal tryptase of 1.8 ng/ml. In patients with active nasal allergy, the tryptase in nasal fluid ranged from 6.4 ng/ml to 640 ng/ml with a mean of 101 ng/ml and SD 173. These results show a clear distinction between active and non-active nasal allergy and other non-mast-cell-related nasal disease. Further, nasal tryptase release by natural allergen exposure is even higher than that observed in allergen challenge tests.

Biomarkers↗
PubMed1996

T-cell membrane-associated serine protease, tryptase TL2, binds human immunodeficiency virus type 1 gp120 and cleaves the third-variable-domain loop of gp120. Neutralizing antibodies of human immunodeficiency virus type 1 inhibit cleavage of gp120.

It has been suggested that the third variable domain (V3) loop of human immunodeficiency virus type 1 (HIV-1) gp120 has to interact with a cell-surface-associated protease(s) that acts as a cofactor after binding of gp120 to the CD4 receptor during entry of HIV-1 into susceptible cells. We isolated the membrane-associated serine protease, tryptase TL2, from human CD4-positive lymphocytes. This enzyme specifically binds gp120 through interaction with its V3 domain. To investigate the role of tryptase TL2 in HIV infection, we examined the affinity of the interaction and the proteolytic susceptibility of various recombinant gp120 expressed in mammalian cells to the enzyme, and we determined the cleavage sites. Tryptase TL2 bound gp120 with an apparent dissociation constant of 38 nM. The affinity was lower than that of gp120 for CD4 which suggests that gp120 initially binds to CD4, followed by interaction with tryptase TL2 which is localized close to CD4 on the cell surface. After binding, tryptase TL2 cleaved recombinant gp120 expressed in mammalian cells into two protein species of 70 kDa and 50 kDa but did not cleave gp120 expressed in insect cells, which indicates that the structure of the oligosaccharides linked to the polypeptide backbone of gp120 affects the proteolytic susceptibility. Cleavage was specifically inhibited by a neutralizing antibody against the V3 loop. Cleavage-site determination revealed that tryptase TL2 cleaved gp120 at various sites in the V3 in a strain-dependent manner. The amino acid variability at the cleavage site(s) in almost all HIV-1 isolates was restricted to amino acids which are susceptible to the chymotryptic and/or tryptic activities of tryptase TL2.

Amino Acid Sequence↗
PubMed2005

Potential role for mast cell tryptase in recruitment of inflammatory cells to endothelium.

Recent research suggests that activation of protease-activated receptors (PARs) on the surface of endothelial and epithelial cells may play a role in general mechanisms of inflammation. We hypothesized that mast cell tryptase activation of endothelial cell PAR-2 is coupled to increased calcium-independent PLA2 (iPLA2) activity and increased platelet-activating factor (PAF) production that may play a role in inflammatory cell recruitment at sites of vascular injury. Stimulation of human coronary artery endothelial cells (HCAEC) with 20 ng/ml tryptase increased iPLA2 activity, arachidonic acid release, and PAF production. These tryptase-stimulated responses were inhibited by pretreatment with the iPLA2-selective inhibitor bromoenol lactone (BEL; 5 microM, 10 min). Similar patterns of increased iPLA2 activity and PAF production were also seen when HCAEC were treated with SLIGKV, which represents the tethered ligand sequence for the human PAR-2 once the receptor is cleaved by tryptase. Tryptase stimulation also increased cell surface expression of P-selectin, decreased electrical resistance, and increased neutrophil adherence to the endothelial cell monolayer. The tryptase-stimulated increases in both cell surface P-selectin expression and neutrophil adhesion were also inhibited with BEL pretreatment. We conclude that tryptase stimulation of HCAEC contributes importantly to early inflammatory events after vascular injury by activation of iPLA2, leading to arachidonic acid release, PAF production, cell surface P-selectin expression, and increased neutrophil adherence.

Arachidonic Acid↗
PubMed2006

Tryptase as severity marker in drug provocation tests.

BACKGROUND: In the absence of objective symptoms, it is difficult to assess an adverse reaction during drug provocation testing. We evaluated the value of serum tryptase levels to distinguish between positive, negative and, even more important, so-called 'hysterical' reactions (conversion symptoms). The latter are occasionally observed in drug provocation tests when the patient experiences ambiguous subjective symptoms. METHODS: In a prospective single-center study, 303 patients underwent 785 drug provocation tests. Blood was taken for tryptase measurement on each test day before and after drug challenge, and the changes in serum tryptase levels in patients with no reactions were compared with those who experienced immediate reactions to a drug. RESULTS: Thirty-four of 785 drug provocations were clinically judged as being positive. Despite objective symptoms, median serum tryptase values in the afternoon were even lower than baseline levels. However, this decrease was not statistically significant. In the 751 patients suffering no objective reactions, the median values of post-testing tryptase values were statistically significantly decreased as compared with pretesting values. CONCLUSIONS: The measurement of serum tryptase levels does not appear to be helpful to differentiate mild allergic or nonallergic reactions from 'hysterical' ones. The milder decrease in the group with objective drug reactions might indicate slight mast cell activation in some patients. More severe clinical drug reactions led to stronger mast cell degranulation. Mild reactions did not increase the tryptase levels consistently.

Acetaminophen↗
PubMed1997

Mast cell tryptase stimulates the synthesis of type I collagen in human lung fibroblasts.

Mast cell activation is a characteristic feature of chronic inflammation, a condition that may lead to fibrosis as a result of increased collagen synthesis by fibroblasts. We have investigated the potential of tryptase, the major protease of human mast cells, to stimulate collagen synthesis in the human lung fibroblast cell line MRC-5. Tryptase was isolated from human lung tissue by ion-exchange and affinity chromatography. At concentrations of 18 and 36 mU/ml, tryptase stimulated both an increase in cell numbers, and a fivefold increase in DNA synthesis as determined by methyl-[3H]thymidine incorporation. Similar concentrations of tryptase resulted in a 2.5-fold increase in collagen synthesis as determined both by incorporation of [3H]proline into collagen, and by assay of hydroxyproline concentrations in the supernatants. There was also a twofold increase in collagenolytic activity in the culture medium after tryptase treatment, indicating that the increase in collagen synthesis was not a consequence of decreased collagenase production. All of these actions of tryptase were reduced in the presence of the protease inhibitors leupeptin and benzamidine hydrochloride, indicating a requirement for an active catalytic site. SDS-PAGE and autoradiographic analysis of the [3H]collagen produced by the cells revealed it to be predominantly type I collagen. Our findings suggest that the release of tryptase from activated mast cells may provide a signal for abnormal fibrosis in inflammatory disease.

Cell Division↗
PubMed2003

An antibody raised against in vitro-derived human mast cells identifies mature mast cells and a population of cells that are Fc epsilon RI(+), tryptase(-), and chymase(-) in a variety of human tissues.

Selective markers for human mast cells are of paramount importance for understanding their role in physiological and pathological processes. A mouse monoclonal antibody (MAb) designated 2C7, raised against in vitro-derived human mast cells, was used in immunoenzymatic analysis of sections from a variety of human organs. Double immunolabeling with 2C7 and tryptase, chymase, Fc epsilon RIalpha, and c-kit was performed on cryostat tissue sections from skin, colon, uterus, breast, stomach, bladder, and lung. MAb 2C7 stained greater than 93% of the tryptase(+) or chymase(+) mast cells in all tissues examined. In addition, the majority of cells stained with the tryptase or chymase also stained for Fc epsilon RIalpha. However, there were a significant number of Fc epsilon RIalpha(1) cells in all tissues studied that were tryptase(-) and/or chymase(-). In contrast, MAb 2C7 in double immunoenzymatic staining co-localized with 93-96% of the Fc epsilon RIalpha(1) cells in all tissues. Analysis for c-kit expression on the different tissues revealed that the majority of tryptase(+) or chymase(+) cells in skin, uterus, bladder, and lung stained with c-kit. However, only approximately 70-78% of tryptase(+) cells in colon and stomach were c-kit(+). These data suggest that MAb 2C7 appears to identify mature mast cells and a population of Fc epsilon RIalpha(1), chymase(-), and tryptase(-) cells in a variety of human tissues.

Animals↗
PubMed1995

Demonstration of tryptase in bovine cutaneous and tumor mast cells.

We examined three tissue samples from each of four cows with non-lesional skin, tissue samples from a cow with multiple cutaneous mast cell tumors, and samples from another cow in which mast cells were infiltrating multiple lymphosarcomas of the skin, for the presence of tryptase and chymase by enzyme cytochemical and immunohistological methods. The enzyme activities of tryptase and chymase were tested using N-carbobenzoxy-glycilglycil-L-arginine-2-naphthylamide (Z-Gly-Gly-Arg-NA) and naphthol-AS-D-chloroacetate (N-AS-D-CA) as substrates, respectively. Tryptase reactivity could be demonstrated in frozen and Carnoy-fixed paraffin sections. Chymase reactivity was seen in neither frozen nor paraffin sections of formalin- or Carnoy-fixed skin tissues. Antibody linkage with a polyclonal rabbit anti-human skin tryptase antibody was highly specific in bovine normal cutaneous, infiltrating, and tumor mast cells. More than 90% of the tumor mast cells were distinctly tryptase-positive. With alcian blue, only slightly more than 10% of the mast cells stained clearly positive and with methylene blue hardly any staining of mast cell granules could be demonstrated. No antibody labeling of mast cell granules in any of the tissue sections was detected by the use of rabbit anti-dog chymase antiserum. These results indicate that there is a striking antigenic similarity of bovine tryptase to its canine and human equivalents. The demonstration of tryptase is an important tool in confirming the diagnosis of undifferentiated mast cell tumors. In contrast to other species, chymase appears to be completely absent in bovine skin mast cells.

Amino Acid Sequence↗
PubMed2003

Elevated serum tryptase levels identify a subset of patients with a myeloproliferative variant of idiopathic hypereosinophilic syndrome associated with tissue fibrosis, poor prognosis, and imatinib responsiveness.

Since serum tryptase levels are elevated in some patients with myeloproliferative disorders, we examined their utility in identifying a subset of patients with hypereosinophilic syndrome (HES) and an underlying myeloproliferative disorder. Elevated serum tryptase levels (> 11.5 ng/mL) were present in 9 of 15 patients with HES and were associated with other markers of myeloproliferation, including elevated B12 levels and splenomegaly. Although bone marrow biopsies in these patients showed increased numbers of CD25+ mast cells and atypical spindle-shaped mast cells, patients with HES and elevated serum tryptase could be distinguished from patients with systemic mastocytosis and eosinophilia by their clinical manifestations, the absence of mast cell aggregates, the lack of a somatic KIT mutation, and the presence of the recently described fusion of the Fip1-like 1 (FIP1L1) gene to the platelet-derived growth factor receptor alpha gene (PDGFRA). Patients with HES and elevated serum tryptase were more likely to develop fibroproliferative end organ damage, and 3 of 9 died within 5 years of diagnosis in contrast to 0 of 6 patients with normal serum tryptase levels. All 6 patients with HES and elevated tryptase treated with imatinib demonstrated a clinical and hematologic response. In summary, elevated serum tryptase appears to be a sensitive marker of a myeloproliferative variant of HES that is characterized by tissue fibrosis, poor prognosis, and imatinib responsiveness.

Adolescent↗
PubMed2004

Induction of tryptase and histamine release from human colon mast cells by IgE dependent or independent mechanisms.

AIM: To investigate the tryptase and histamine release ability of human colon mast cells upon IgE dependent or independent activation and the potential mechanisms. METHODS: Enzymatically dispersed cells from human colons were challenged with anti-IgE or calcium ionophore A23187, and the cell supernatants after challenge were collected. Both concentration dependent and time course studies with anti-IgE or calcium ionophore A23187 were performed. Tryptase release was determined with a sandwich ELISA procedure and histamine release was measured using a glass fibre-based fluorometric assay. RESULTS: Both anti-IgE and calcium ionophore were able to induce dose dependent release of histamine from colon mast cells with up to approximately 60% and 25% net histamine release being achieved with 1 microg/mL calcium ionophore and 10 microg/mL anti-IgE, respectively. Dose dependent release of tryptase was also observed with up to approximately 19 ng/mL and 21 ng/mL release of tryptase being achieved with 10 microg/mL anti-IgE and 1 microg/mL calcium ionophore, respectively. Time course study revealed that both tryptase and histamine release from colon mast cells stimulated by anti-IgE initiated within 10 sec and reached their maximum release at 6 min following challenge. Pretreatment of cells with metabolic inhibitors abolished the actions of anti-IgE as well as calcium ionophore. Tryptase and histamine release, particularly that induced by calcium ionophore was inhibited by pretreatment of cells with pertussis toxin. CONCLUSION: Both anti-IgE and calcium ionophore are able to induce significant release of tryptase and histamine from colon mast cells, indicating that this cell type is likely to contribute to the pathogenesis of colitis and other mast cell associated intestinal diseases.

Colectomy↗