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IL-18 is likely to contribute to asthma. However, little is known regarding the role of IL-18 binding protein (BP) and IL-18 receptor (R) in asthma. Because the action of IL-18 in the body is regulated by IL-18BP and mast cells and basophils are key cell types involved in asthma, we investigated the expression of IL-18, IL-18BP and IL-18R in basophils and mast cells using flow cytometry and a mouse asthma model. We found that among basophils, approximately 53% and 51% were IL-18 + , 85% and 81% were IL-18BP + basophils, and 19.8% and 8.6% were IL-18R + in healthy control (HC) and asthmatic blood, respectively. The allergens tested had little effect on the expression of IL-18 and related factors. Only 3.5%, 14.3% and 2.4% of dispersed mast cells expressed IL-18, IL-18BP and IL-18R, respectively, in asthmatic sputum. In a mouse asthma model, OVA-sensitized mice exhibited decreased IL-18BP + but increased IL-18R + basophils in their blood. IL-18 increased the number of basophils but eliminated IL-18BP + basophils in mouse blood. IL-18 increased the number of mast cells and IL-18R + mast cells in the lung as well as increased the mast cell numbers and IL-18BP + mast cells in the bronchoalveolar lavage fluid (BALF) of OVA-sensitized mice. Thus, basophils and mast cells may be involved in asthma pathogenesis via an IL-18-associated mechanism., (© 2018 The Foundation for the Scandinavian Journal of Immunology.)

IL-18 has been found to be associated with eczema. However, little is known of the role of IL-18 binding protein (BP) and IL-18 receptor (R) in eczema. We therefore investigated the expression of IL-18, IL-18BP, and IL-18R on mast cells by using flow cytometry analysis and mouse eczema model. The results showed that plasma free IL-18 and free IL-18BP levels in eczema patients were higher than those in healthy controls. IL-18 provoked up to 3.1-fold increase in skin mast cells. IL-18 induced also an increase in IL-18BP+ mast cells, but a reduction of IL-18R+ mast cells in mouse eczema skin. It was found that house dust mite allergen Der p1 and egg allergen OVA induced upregulation of the expression of IL-18, IL-18BP, and IL-18R mRNAs in HMC-1 cells following 2 and 16 h incubation. In conclusion, correlation of IL-18 and IL-18BP in eczema plasma suggests an important balance between IL-18 and IL-18BP in eczema. The decrease in molar concentration ratio of plasma IL-18BP/IL-18 and allergen-induced upregulated expression of IL-18 and IL-18R in skin mast cells of the patients with eczema suggests that anti-IL-18 including IL-18BP therapy may be useful for the treatment of eczema.

Interleukin- (IL-) 18 and tryptase were previously reported to relate to asthma, but the correlation between these two potent proinflammatory molecules in asthma and their roles in mast cell accumulation remain uninvestigated. Using flow cytometric analysis technique and ovalbumin- (OVA-) sensitized mouse model, it was found that IL-18 and tryptase levels in the plasma of moderate and severe asthma were elevated, and they correlated well with each other. Tryptase and agonist peptides of protease activated receptor- (PAR-) 2 induced substantial quantity of IL-18 release. IL-18 and tryptase provoked mast cell accumulation in peritoneum of OVA-sensitized mice. OVA-sensitization increased number of IL-18 receptor (R)(+) mast cells. IL-18 and tryptase induced dramatic increase in IL-18R(+) mast cells and mean fluorescence intensity (MFI) of IL-18R on mast cells. Moreover, while IL-18 induced an increase in PAR-2(+) mast cells in nonsensitized mice, IL-18 and tryptase provoked increases in IL-4 and thymic stromal lymphopoietin (TSLP) in the peritoneum of OVA-sensitized mice. In summary, the correlation between IL-18 and tryptase in plasma of patients with asthma indicates close interactions between them, which should be considered for development of anti-IL-18 and antitryptase therapies. Interactions between IL-18 and tryptase may contribute to mast cell recruitment in asthma.

Poisonous snakebite wound is a popular disease worldwide. However, the pathogenesis remains unclear. In the present study, a novel metalloproteinase atrahagin in Chinese cobra (Naja atra) snake venom was purified, using heparin-sepharose followed by Superdex 75 gel filtration chromatography. Apart from its alpha-fibrinogenase activity, atrahagin potently activated human colon, lung and tonsil mast cells with the net histamine release being 25.9+/-4.4, 17.0+/-1.9, 13.2+/-3.6%, respectively. Time course studies revealed that the peak histamine release induced by atrahagin occurred at 12, 12 and 8 min following incubation of the enzyme with colon, lung and tonsil mast cells, respectively. The response of mast cells to atrahagin was abolished by preincubation of the cells with metabolic inhibitors or pertussis toxin, and by removal of Ca2+ and Mg2+ from the challenge buffer. In conclusion, activation of human mast cells by atrahagin indicated that the enzyme might contribute to the pathogenesis of snakebite wound.

Aim: To examine the influence of protease inhibitors on tryptase release, and as a comparison the influence of the inhibitors on histamine secretion was assessed., Methods: Enzymatically dispersed cells from human tonsil were challenged with anti-IgE or calcium ionophore A23187 (CI) in the absence or presence of the tryptase and chymase inhibitors, and tryptase and histamine release was determined., Results: IgE-dependent tryptase release from dispersed tonsil mast cells was inhibited by a maximum of approximately 35.5% and 35.7% by N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) and N-tosyl-L-phenylalanyl chloromethyl ketone (TPCK), respectively. The similar degree of inhibition of CI-induced tryptase release was observed also with these two inhibitors. Preincubation of TLCK or TPCK with cells at 37 degrees C for 20 min before addition of the stimulus improved slightly their ability to inhibit anti-IgE and CI-induced tryptase release. Protamine showed dual action on tryptase release from tonsil mast cells. The concentration-dependent inhibition of anti-IgE and CI-induced release of histamine from tonsil mast cells was also observed with TLCK, TPCK and protamine. The maximum inhibition of anti-IgE-induced histamine release was approximately 26.6%, 30.8% and 30.1% with TLCK, TPCK and protamine, respectively. At the concentrations tested, TLCK and TPCK by themselves did not stimulate tryptase and histamine release from tonsil mast cells., Conclusion: It was demonstrated that protease inhibitors were able to inhibit IgE-dependent tryptase release from human tonsil mast cells, which suggests strongly that they can be developed to a novel class of anti-inflammatory drugs to treat allergic conditions in man.

Aim: To investigate the effects of the agonists of proteinase activated receptor (PAR)-2, and histamine on degranulation of human mast cells., Methods: Human mast cells were enzymatically dispersed from tonsil and skin tissues. The dispersed cells were then cultured with various stimuli, and tryptase and histamine levels in cell supernatants collected from challenge tubes were measured., Results: PAR-2 agonist peptide SLIGKV provoked a dose-dependent release of histamine from skin mast cells. It also induced tryptase release from tonsil mast cells. tc-LIGRLO appeared less potent than SLIGKV in induction of release of histamine and tryptase. Trypsin was able to induce a bell shape increase in tryptase release from tonsil mast cells. It was also able to induce a dose-dependent release of histamine from both tonsil and skin mast cells. The actions of trypsin on mast cells were inhibited by soy bean trypsin inhibitor (SBTI) or alpha1-antitrypsin (alpha1-AT). Time course study revealed that both stimulated tryptase or histamine release initiated within 10 s and reached their peak release between 4 and 6 min. Pretreatment of cells with metabolic inhibitors or pertussis toxin reduced the ability of mast cells to release tryptase or histamine., Conclusion: It was demonstrated that the in vitro tryptase release properties of human tonsil and skin mast cells suggested a novel type of mast cell heterogeneity. The activation of mast cells by PAR-2 agonists indicated a self-amplification mechanism of mast cell degranulation.

Aim: To examine the ability of calcium ionophore (CI) to induce tryptase and histamine release from human mast cells and its mechanisms., Methods: Enzymatically dispersed cells from human colons were challenged with CI, and the cell supernatants after challenge were collected. Tryptase release was determined with a sandwich ELISA procedure and histamine release was measured using a glass fibre-based fluorometric assay., Results: CI was able to induce a concentration dependent release of histamine and tryptase from human colon mast cells following 15 min incubation. The maximum of induced histamine and tryptase release were approximately 5.3 and 2.8 fold more than the levels of spontaneous release, respectively. CI at the concentrations higher than 1.0 micromol/L was able to induce significantly more histamine than tryptase release from mast cells. The time course revealed that the action of CI on mast cells started from 10 s, peaked at 6 min and lasted at least 15 min following incubation. Pertussis toxin and metabolic inhibitors were able to inhibit mast cell response to CI., Conclusion: Human colon mast cells were able to release tryptase and histamine in response to CI. The process seemed to be associated with the activation of a G-protein coupled receptor on the membrane of mast cells and requires cell energy supply.

Inhibition of IgE dependent histamine release from human mast cells by protease inhibitors has been observed in skin, tonsil and synovial tissues. However, little is known about the actions of protease inhibitors on tryptase release from human lung mast cells. We therefore examined the ability of protease inhibitors to modulate tryptase and histamine release from human lung mast cells. IgE dependent tryptase release from dispersed lung mast cells was inhibited to a maximum of approximately 53.8% and 44.5% by N-a-tosyl-L-lysine chloromethyl ketone (TLCK) and N-p-Tosyl-L-phenylalanine chloromethyl ketone (TPCK), respectively. A similar degree of inhibition of calcium ionophore A23187 (CI) induced tryptase release was also observed with these two inhibitors. Preincubation of TLCK or TPCK with the mast cells at 37 degrees C for 20 minutes before addition of anti-IgE or CI did not improve their ability to inhibit anti-IgE and CI induced tryptase release. At a concentration of 10 microg/ml, protamine inhibited anti-IgE or CI induced tryptase release; but at 100 microg/ml, it increased anti-IgE and CI induced release of tryptase from lung mast cells. A concentration dependent inhibition of anti-IgE and CI induced release of histamine from lung mast cells was also observed with TLCK, TPCK and protamine. The maximum inhibition of anti-IgE induced histamine release was approximately 40.7%, 40.2% and 33.4% with TLCK, TPCK and protamine, respectively. At the concentrations tested, TLCK and TPCK by themselves did not stimulate tryptase and histamine release from lung mast cells. A specific inhibitor of aminopeptidase, amastatin, had no effect on anti-IgE induced tryptase and histamine release and was used as control. In conclusion, it was demonstrated that protease inhibitors are able to inhibit IgE dependent tryptase and histamine release from human lung mast cells, which suggested that they could be developed to a novel class of anti-inflammatory drugs to treat allergic conditions in man.

Aim: To investigate the effect of tryptase inhibitors (TPIs) on histamine release from human colon mast cells., Methods: Human mast cells were prepared by digestion of colon tissue and with collagenase and hyaluronidase, cultured with four kinds of TPIs, leupeptin, protamine, TLCK, and lactoferrin for 15 min at 37 degrees Celsius respectively. A glass fibre-based fluorometry assay was used to detect histamine in mast cell suspension., Results: 200 mmol/L leupeptin and 100 mmol/L protamine were able to stimulate histamine release from colon mast cells, while TLCK and lactoferrin did not. All TPIs inhibited anti-IgE-induced histamine release in a concentration dependent manner, and the inhibitory rates were 48.7%, 36.7%, 40.2% and 34.1%, respectively. However preincubation of TPIs with mast cells for 20 min at 37 degrees Celsius before adding anti-IgE had little effect on anti-IgE induced histamine release. All TPIs were able to inhibit calcium ionophore (CI)-induced histamine release, and the maximum inhibition rate was between 25%-32%. Inhibition on histamine release by leupeptin and TLCK obviously enhanced when colon mast cells were preincubated with them for 20 min before adding CI. However, under the same condition, protamine failed to inhibit histamine release., Conclusion: We prove for the first time that TPIs inhibit anti-IgE-and CI-induced histamine release from human colon mast cells, suggesting that it is possible to treat inflammatory bowel disease or other mast cell-related diseases by using TPIs.

Aim: To investigate the ability of natural chymase inhibitors to modulate histamine release from human mast cells., Methods: Enzymatically dispersed cells from human lung, tonsil, and skin were challenged with anti-IgE or calcium ionophore A23187 in the absence or presence of the natural chymase inhibitors secretory leukocyte protease inhibitor (SLPI) and alpha(1)-antitrypsin, then histamine release was determined., Results: IgE-dependent histamine release from lung, tonsil, and skin mast cells were inhibited by up to 70 %, 61 %, and 62 %, respectively following incubation with alpha(1)-antitrypsin (5000 nmol/L). SLPI 5000 nmol/L was also able to inhibit anti-IgE-dependent histamine released from lung, tonsil and skin mast cells by up to approximately 72 %, 67 %, and 58 %, respectively. While neither alpha(1)-antitrypsin nor SLPI by themselves altered histamine release from lung, tonsil and skin mast cells, they were able to inhibit calcium ionophore-induced histamine release from lung and tonsil mast cells., Conclusion: Both micro(1)-antitrypsin and SLPI could potently inhibit IgE-dependent and calcium ionophore- induced histamine release from dispersed human lung, tonsil, and skin mast cells in a concentration-dependent manner, which suggested that they were likely to play a protective role in mast cell associated diseases including allergy.

Aim: To investigate the ability of protease inhibitors to modulate histamine release from human colon mast cells., Methods: Enzymatically dispersed cells from human colon were challenged with anti-IgE or calcium ionophore A23187 in the absence or presence of tryptase and chymase inhibitors, and histamine release was determined., Results: IgE dependent histamine release from colon mast cells was inhibited by up to approximately 37%, 26% and 36.8% by chymase inhibitors Z-Ile-Glu-Pro-Phe-CO2Me (ZIGPFM), N-Tosyl-L-phenylalanyl-chloromethyl ketone (TPCK), and alpha1-antitrypsin, respectively. Similarly, inhibitors of tryptase leupeptin, N-tosyl-L-lysine chloromethyl ketone (TLCK), lactoferrin and protamine were also able to inhibit anti-IgE induced histamine release by a maximum of some 48%, 37%, 40% and 34%, respectively. Preincubation of these inhibitors with cells for 20 min before challenged with anti-IgE had small effect on the inhibitory actions of these inhibitors on colon mast cells. A specific inhibitor of aminopeptidase amastatin had no effect on anti-IgE induced histamine release. The significant inhibition of calcium ionophore induced histamine release was also observed with the inhibitors of tryptase and chymase examined. Apart from leupeptin and protamine, the inhibitors tested by themselves did not stimulate colon mast cells., Conclusion: It was demonstrated that both tryptase and chymase inhibitors could inhibit IgE dependent and calcium ionophore induced histamine release from dispersed colon mast cells in a concentration dependent of manner, which suggest that they are likely to be developed as a novel class of anti-inflammatory drugs to treat chronic of colitis in man.

Aim: To investigate the ability of protease inhibitors to modulate tryptase release from human colon mast cells., Methods: Enzymatically dispersed cells from human colon were challenged with anti-IgE or calcium ionophore A23187 in the absence or presence of tryptase and chymase inhibitors, and tryptase release was determined., Results: IgE dependent tryptase release from colon mast cells was inhibited by up to approximately 37%, 40% and 36.6% by chymase inhibitors Z-Ile-Glu-Pro-Phe-CO2Me (ZIGPFM), N-tosyl-L-phenylalanyl-chloromethyl ketone (TPCK), and alpha1-antitrypsin, respectively. Similarly, the inhibitors of tryptase leupeptin, N-tosyl-L-lysine chloromethyl ketone (TLCK) and lactoferrin were also able to inhibit anti-IgE induced tryptase release by a maximum of 39.4%, 47.6% and 36.6%, respectively. The inhibitory actions of chymase inhibitors, but not tryptase inhibitors on colon mast cells were enhanced by preincubation of them with cells for 20 min before challenged with anti-IgE. At a concentration of 10 microg/mL, protamine was able to inhibit anti-IgE and calcium ionophore induced tryptase release. However, at 100 microg/mL, protamine elevated tryptase levels in supernatants. A specific inhibitor of aminopeptidase amastatin had no effect on anti-IgE induced tryptase release. The significant inhibition of calcium ionophore induced tryptase release was also observed with the inhibitors of tryptase and chymase examined. The inhibitors tested by themselves did not stimulate tryptase release from colon mast cells., Conclusion: It was demonstrated for the first time that both tryptase and chymase inhibitors could inhibit IgE dependent and calcium ionophore induced tryptase release from dispersed colon mast cells in a concentration dependent of manner, which suggest that they are likely to be developed as a novel class of anti-inflammatory drugs to treat chronic of colitis in man.

Aim: To investigate the ability of agonists of PAR-2 to stimulate release of tryptase and histamine from human colon mast cells and the potential mechanisms., Methods: Enzymatically dispersed cells from human colons were challenged with tc-LIGRLO, tc-OLRGIL, SLIGKV, VKGILS, trypsin, anti-IgE or calcium ionophore A23187, and the cell supernatants after challenge were collected. Tryptase release was determined with a sandwich ELISA procedure and histamine release was measured using a glass fibre-based fluorometric assay., Results: Both PAR-2 agonists tc-LIGRLO-NH2 and SLIGKV-NH2 were able to induce dose dependent release of tryptase and histamine from colon mast cells. More than 2.5 fold increase in both tryptase and histamine release was provoked by 100 micromol/mL tc-LIGRLO-NH2, in comparison with only 2.0 fold increase being stimulated by SLIGKV-NH2. The reverse peptides tc-OLRGIL-NH2 and VKGILS -NH2 at the concentrations tested had no effect on the release of these two mediators. The maximum tryptase release elicited by tc-LIGRLO-NH2 was similar to that induced by anti-IgE (10 microg/mL) or calcium ionophore (1 microg/mL), though the latter was a more potent stimulus for histamine release. Both histamine and tryptase release in response to tc-LIGRLO-NH2 were completed within 3 min. Trypsin at concentrations from 1.0 to 100 microg/mL was capable of provoking a dose dependent release of tryptase as well as histamine with a maximum of 16 ng/mL tryptase and 14 ng/mL histamine release being achieved. An approximately 80% and 70% inhibition of trypsin induced release of tryptase and histamine were observed with SBTI, respectively. Pretreatment of cells with metabolic inhibitors or pertussis toxin abolished the actions of tc-LIGRLO-NH2, SLIGKV-NH2 and trypsin., Conclusion: The agonists of PAR-2 and trypsin are potent secretagogues of human colon mast cells, which are likely to contribute to the development of inflammatory disorders in human gut.

Aim: To investigate the ability of histamine to modulate tryptase release from human colon mast cells and the potential mechanisms., Methods: Enzymatically dispersed cells from human colons were challenged with histamine, anti-IgE or calcium ionophore A23187 (CI), and the cell supernatants after challenge were collected. Tryptase release was determined with a sandwich ELISA procedure., Results: Histamine at concentrations from 1 ng/mL was able to induce a "bell" shape dose related release of tryptase from colon mast cells. The maximum release of tryptase was approximately 3.5 fold more than spontaneous release. As little as 10 ng/mL histamine showed a similar potency to 10 microg/mL anti-IgE in induction of tryptase release. Histamine induced release of tryptase initiated at 10 s when histamine (100 ng/mL) was added to cells, gradually increased thereafter, and completed at 5 min. Both pertussis toxin or metabolic inhibitors were able to inhibit histamine induced tryptase release. When histamine and anti-IgE were added to colon mast cells at the same time, the quantity of tryptase released was similar to that induced by anti-IgE alone. The similar results were observed with CI. However, when various concentrations of histamine were incubated with cells for 20 min before adding anti-IgE or CI, the quantity of tryptase released was similar to that was induced by histamine alone., Conclusion: Histamine is a potent activator of human colon mast cells, which represents a novel and pivotal self-amplification mechanism of mast cell degranulation.

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.

Aim: To investigate the functional properties of mast cells in bronchoalveolar lavage fluid (BALF) of asthma patients., Methods: 29 asthma patients in the recovery phase were enrolled in the study and their bronchoalveolar lavages (BAL) were inspected under fibreoptics bronchoscope. The cells from each BAL fluid(BALF) were added to LP4 tubes containing anti-IgE antibody, adenosine, buffer or anti-IgE antibody + adenosine, and incubated at 37 degrees C for 20 min. The reactions were stopped by placing the tubes on ice and adding 100 microL of cold incomplete Hank's balanced salt solution (HBSS). The histamine chromogenic assay was performed to detect histamine released from mast cells in BALF. Histamine release was expressed in a net release percentage., Results: 100 micromol/L of adenosine failed to induce histamine release from mast cells; while 1,000 micromol/L of adenosine could induce about 17% histamine release from mast cells in BALF; For anti-IgE antibody, as low as 1 x 10(-4) g/L of anti-IgE was able to induce approximately 20% histamine release from the mast cells. When the anti-IgE antibody was combined with adenosine, only 3 x 10(-5) g/L of anti-IgE antibody + adenosine could exert synergistic effectiveness., Conclusion: Mast cells in BALF from asthma patients had a poor reaction to adenosine stimulation,but are much more sensitive to anti-IgE antibody-dependent stimulation; only as low as 3 x 10(-5) g/L of anti-IgE antibody is able to cooperate with adenosine.

The aim of this study is to investigate the histamine-releasing ability of mast cells from asthmatic bronchoalveolar lavage fluid (BALF). Following the measurement of the forced expiratory volume at the first second (FEV1), 29 mild asthmatics were included in the study and were subjected to fibreoptic bronchoscopy. The cells recovered from the BALF were challenged with anti-IgE, calcium ionophore A23187 (CI) or adenosine, and the released histamine was measured with an enzyme-linked chromogenic assay. Enzymatically dispersed mast cells from human lung or colon tissues were employed as control groups. The results showed that mast cells from BALF were at least 100 fold more sensitive to anti-IgE than those from lung or colon tissues. However, there was little difference between mast cells from BALF, lung or colon tissues in response to CI. Adenosine failed to stimulate histamine release from BALF mast cells. In conclusion, asthmatic BALF mast cells are much more sensitive to IgE-dependent stimulation than the non-IgE-dependent ones, indicating that mast cells may play a role in the pathogenesis of asthma.

Aim: To study the ability of bisbenzamidine, a specific inhibitor of tryptase, to stabilize mast cells., Methods: Human tonsil tissues were chopped up finely and digested with collagenase and hyaluronidase. Dispersed cells were separated from undigested tissue by filtration through a nylon gauze. Prior to challenge, the cells were resuspended in complete HBSS and aliquots of 100 mL containing 4 x 10(3)-6 x 10(3) mast cells were added to a 100 microL aliquot of anti-IgE, calcium ionophore, bisbenzamidine or complete HBSS and incubated for 15 min at 37 degrees Celsius. The reaction was terminated by addition of 150 microL ice cold HBSS and the tubes centrifuged immediately. Tryptase was quantified by ELISA., Results: At concentrations of 1 mg/L and 10 mg/L, bisbenzamidine could inhibit spontaneous tryptase release by 47% after 45 min. A 3.2 or 2.6 fold increase in tryptase release was achieved when cells were incubated with 1 g/L anti-IgE antibody or 1 micromol/L calcium ionophore for 15 min at 37 degrees Celsius. A dose dependent inhibition of tryptase release induced by anti-IgE antibody was observed when dispersed tonsil cells were treated with bisbenzamidine., Conclusion: Bisbenzamidine can inhibit IgE-dependent tryptase release from human tonsil mast cells. Therefore, it seems likely that this inhibitor of tryptase is a novel promising mast cell stabilizing drug for treating and preventing allergic inflammation or other mast cell associated diseases.

Proteinase-activated receptor-2 (PAR-2) expression has been observed on numerous cell types. However, little is known about the functional expression of PAR-2 in human mast cells. In the current study, the actions of a PAR-2 agonist trans-cinnamoyl-Leu-Ile-Gly-Arg-Leu-Orn-amide (tc-LIGRLO) on tryptase release from dispersed human colonic mast cells were examined. The results showed that tc-LIGRLO was able to induce a fold increase in tryptase release over the basal level following a 15 min incubation of colonic mast cells, whereas tc-OLRGIL did not have any effect on tryptase release. The potency of tc-LIGRLO appeared greater than that of anti-IgE and calcium ionophore A23187 (CI) in induction of tryptase release. Extending the incubation time to 30 min had no significant effect on the actions of tc-LIGRLO or anti-IgE. In the time course study, it was observed that the tryptase release from mast cells induced by tc-LIGRLO started at 1 min and peaked at 3 min following incubation. The above-mentioned results indicate that tc-LIGRLO is a potent stimulus of tryptase release from human mast cells, which strongly suggests that PAR-2s are expressed in human mast cells.

Background: Increased leucine-rich α2-glycoprotein-1 (LRG1) has been observed in plasma of individuals with various diseases. However, the role of LRG1 in allergic airway disease has not been investigated.Objective: To explore the involvement of LRG1 in allergy and its cell origins.Methods: The expression levels of LRG1 and its receptor transforming growth factor-beta receptor II (TGFBR2) in patients with allergic rhinitis (AR) and asthma (AS) were examined by flow cytometry, and enzyme-linked immunosorbent assay (ELISA).Results: LRG1 and soluble TGFBR2 expression in plasma of patients with AR and AS were markedly lower than that of healthy control (HC) subjects. Large proportions of CD123 + HLA-DR-, CD16+, CD4+, CD8+, CD14+, and CD19+ cells expressed LRG1, although the percentages of LRG1+ cells in these cell populations were lower in AR and AS patients. Up to 89.8 and 15.5 % of dispersed mast cells expressed LRG1 and TGFBR2. Moreover, allergen extract exposure significantly reduced LRG1 and TGFBR2 expression in the plasma and leukocytes of patients with AR and AS.Conclusions: Reduced LRG1 and TGFBR2 levels in patients with allergic airway disorders are likely caused by inhibitory actions of allergens in LRG1 producing cells. Thus, LRG1 may be a key regulatory factor of allergic responses. [ABSTRACT FROM AUTHOR]