Localization of cannabinoid and cannabinoid related receptors in the cat gastrointestinal tract

A growing body of literature indicates that activation of cannabinoid receptors may exert beneficial effects on gastrointestinal inflammation and visceral hypersensitivity. The present study aimed to immunohistochemically investigate the distribution of the canonical cannabinoid receptors CB₁ (CB1R) and CB₂ (CB2R) and the putative cannabinoid receptors G protein-coupled receptor 55 (GPR55), nuclear peroxisome proliferator-activated receptor alpha (PPARα), transient receptor potential ankyrin 1 (TRPA1), and serotonin receptor 5-HT1a 5-HT1aR) in tissue samples of the gastrointestinal tract of the cat. CB1R-immunoreactivity (CB1R-IR) was observed in gastric epithelial cells, intestinal enteroendocrine cells (EECs) and goblet cells, lamina propria mast cells (MCs), and enteric neurons. CB2R-IR was expressed by EECs, enterocytes, and macrophages. GPR55-IR was expressed by EECs, macrophages, immunocytes, and MP neurons. PPARα-IR was expressed by immunocytes, smooth muscle cells, and enteroglial cells. TRPA1-IR was expressed by enteric neurons and intestinal goblet cells. 5-HT1a receptor-IR was expressed by gastrointestinal epithelial cells and gastric smooth muscle cells. Cannabinoid receptors showed a wide distribution in the feline gastrointestinal tract layers. Although not yet confirmed/supported by functional evidences, the present research might represent an anatomical substrate potentially useful to support, in feline species, the therapeutic use of cannabinoids during gastrointestinal inflammatory diseases.

Altered expression of IL-18 binding protein and IL-18 receptor in basophils and mast cells of asthma patients

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.

Inhibitory effects of 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate on allergic inflammatory responses in rat basophilic leukemia cells

Mast cells play crucial roles in the initiation of allergic inflammatory responses by releasing various mediators such as histamines, cytokines, and leukotrienes. In addition, signaling cascade pathways, such as the mitogen-activated protein kinase (MAPK) pathway, contribute to the regulation of mast cell degranulation. Accordingly, different research strategies have been pursued to develop anti-inflammatory and anti-allergic drugs by regulating these signaling pathways. The development of new drugs that inhibit mast cell degranulation may help in the treatment of allergies. In this study, we investigated the effects of coumarin derivatives on mast cell degranulation. The effect of coumarin derivatives on degranulation in rat basophilic leukemia (RBL)-2H3 cells was determined by a β-hexosaminidase assay and histamine assay. A coumarin derivative 1 (C1), 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate, inhibited degranulation in a dose-dependent manner and demonstrated maximum therapeutic effect when used at 25μM. Additionally, these compounds inhibited the phosphorylation of the extracellular signal-regulated kinase (ERK) pathway. Taken together, these results indicate that 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate inhibits mast cell degranulation by suppressing the activation of the ERK pathway and this inhibitory effect suggests potential therapeutic strategies towards the prevention of allergic disorders.

Comparative Study of Apo-Cetirizine Single Therapy and Intermittent Sequential Therapy with Cetirizine, Loratadine and Chlorpheniramine in Allergic Rhinitis

There are limited numbers of articles, studying combined use of antihistamines. In this study, we compare single therapy of Apo-Cetirizine with a new regimen of intermittent sequential therapy with cetirizine, loratadine and chlorpheniramine in treatment of seasonal allergic rhinitis. This randomized clinical trial was performed between April and September at the peak prevalence of seasonal allergic rhinitis. Fifty-four eligible patients diagnosed clinically to have seasonal allergic rhinitis were randomized in two groups: 24 cases in single therapy arm, received Apo-Cetirizine 10 mg tablet daily and in other arm, 30 patients received sequential regimen of cetirizine 10 mg tablet, loratadine 10 mg tablet and chlorpheniramine 4 mg tablet, one tablet each day. Major Symptom Complex Score (MSCS) and Total Symptom Complex Score (TSCS) of patients were recorded before treatment and after 30 days of treatment in two groups. The average post-treatment MSCS and TSCS in combination therapy group showed better improvement than single therapy group but difference was not statistically significant (p value = 0.053 and p value = 0.104 respectively). Combination therapy regimen was better in improvement of nasal congestion (p value = 0.006). There were no significant difference between two groups in efficacy, side effects and patient's satisfaction. Combination therapy would be effective on a wide spectrum of symptoms with lower price and theoretically offers lower chance of tolerance and re-appearance of complaints.

The chemistry and biological potential of azetidin-2-ones

Azetidin-2-ones, commonly referred as β-lactams, represent a unique ring system, with interesting chemistry and great biological potential. Besides its well known antibiotic activity, this ring system exhibits a wide range of activities, attracting the attention of researchers. The biological and pharmacological profile of azetidin-2-ones is reviewed here comprehensively with several examples under fourteen different activity heads. The chemistry and methods of synthesis have also been discussed.

Perinatal bisphenol A exposures increase production of pro-inflammatory mediators in bone marrow-derived mast cells of adult mice

Bisphenol A (BPA) is a widely used monomer of polycarbonate plastics and epoxide resin that has been implicated in asthma pathogenesis when exposure occurs to the developing fetus. However, few studies have examined the relationship between perinatal BPA exposure and asthma pathogenesis in adulthood. This study used an isogenic mouse model to examine the influence of perinatal BPA exposure via maternal diet on inflammatory mediators associated with asthma in 6-month-old adult offspring by measuring bone marrow-derived mast cell (BMMC) production of lipid mediators (cysteinyl leukotrienes and prostaglandin D2), cytokines (interleukin [IL]-4, IL-5, IL-6, IL-13, and tumor necrosis factor [TNF]-α), and histamine. Global DNA methylation levels in BMMCs from adult offspring were determined to elucidate a potential regulatory mechanism linking perinatal exposure to mast cell phenotype later in life. Four BPA exposure doses were tested: low (50 ng BPA/kg diet, n = 5), medium (50 μg BPA/kg diet, n = 4), high (50 mg BPA/kg diet, n = 4), and control (n = 3). Following BMMC activation, increases in cysteinyl leukotriene (p < 0.01) and TNFα (p < 0.05) production were observed in all BPA-exposure groups, and increases in prostaglandin D2 (p < 0.01) and IL-13 (p < 0.01) production were observed in the high exposure group. Additionally, BMMCs from adult mice in all exposure groups displayed a decrease in global DNA methylation compared to control animals. Thus, perinatal BPA exposure displayed a long-term influence on mast cell-mediated production of pro-inflammatory mediators associated with asthma and global DNA methylation levels, suggesting a potential for mast cell dysregulation, which could affect pulmonary inflammation associated with allergic airway disease into adulthood.

Anti-inflammatory activity of ethanol extract from Geranium sibiricum Linne

ETHNOPHARMACOLOGICAL RELEVANCE

Geranium sibiricum (Geraniaceae) Linne (GSL) is used to heal various disorders of the diarrhea and the intestinal inflammation as an herbal agent in East Asia.

AIMS OF THE STUDY

The purpose of the present study is to determine whether the ethanol (EtOH) extract of GSL regulates the inflammatory reaction stimulated by phorbol-12-myristate 13-acetate plus calcium ionophore A23187 (PMACI) in human mast cells (HMC-1).

MATERIALS AND METHODS

Western blot was used for activation of mitogen activated protein kinase (MAPK), transcription factors, induced nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2 proteins. EMSA was for DNA binding activity. RT-PCR was used for gene expression.

RESULTS

EtOH extract of GSL (EGS) inhibits the expression of extracellular signal-regulated kinase (ERK), one of a MAPK, nuclear transcription factors involving nuclear factor (NF)-kappaB and Activator protein (AP)-1, COX-2 and iNOS. The results indicated that EGS decreased gene expression of interleukin (IL)-1beta and COX-2 in PMACI stimulated HMC-1 cells.

CONCLUSION

Hence, we speculate that EGS can use as a potent anti-inflammatory agent for inflammatory allergic diseases.

Inhibitory effect of glycoprotein isolated from Cudrania tricuspidata bureau on expression of inflammation-related cytokine in bisphenol A-treated HMC-1 cells

Cudrania tricuspidata is one of the most omnipresent traditional herbal drugs for anti-inflammation and anti-tumor. The purpose of the present study was to determine whether the CTB glycoprotein regulates the inflammatory reaction stimulated by bisphenol A (BPA) in human mast cells (HMC-1). Thus, we investigated that CTB glycoprotein inhibits the degranulation of histamine, expression of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), as a mitogen activated protein (MAP) kinase, nuclear transcription factors involving nuclear factor (NF)-kappaB and Activator protein (AP)-1, cyclooxygenase (COX)-2. The results indicated that CTB glycoprotein decreased gene expression of cytokines of IL-4, IFN-gamma, interleukin (IL)-1beta and cyclooxygenase (COX)-2 in BPA-stimulated HMC-1 cells. Hence, we speculate that CTB glycoprotein can use as a potent anti-inflammatory agent for inflammatory allergic diseases.

Activation of human tonsil and skin mast cells by agonists of proteinase activated receptor-2

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.

Polymorphism of the mast cell chymase gene (CMA1) promoter region: lack of association with asthma but association with serum total immunoglobulin E levels in adult atopic dermatitis

BACKGROUND

Mast cell chymase has the potential to be an important mediator of inflammation and remodelling in the asthmatic lung. Previous studies have examined association between promoter polymorphism of the chymase gene (CMA1) and allergic phenotypes but the significance of this polymorphism is unclear. We have examined association of a CMA1 variant in relation to asthma in a large UK Caucasian family cohort.

METHODS

A polymorphism of the CMA1 gene promoter (-1903G/A) was genotyped in 341 asthmatic families and in 184 non-asthmatic adults recruited from the UK PCR-RFLP based genotyping. Association with asthma diagnosis, atopy, specific and total IgE, and atopy and asthma severity was examined.

RESULTS

Case-control studies did not reveal a significant difference in allele frequency between asthmatics and controls. A significant association was found between CMA1 genotypes and total IgE levels in subjects with self-reported eczema that remained significant after correction for multiple testing (median total serum IgE GG 297 kU/L, GA 144 kU/L, AA 48.4 kU/L, Pc=0.0032).

CONCLUSION

These data suggest that CMA1 promoter polymorphism does not contribute to asthma susceptibility or severity but may be involved in regulating IgE levels in patients with eczema.

Key role of mast cells and their major secretory products in inflammatory bowel disease

Historically, mast cells were known as a key cell type involved in type I hypersensitivity. Until last two decades, this cell type was recognized to be widely involved in a number of non-allergic diseases including inflammatory bowel disease (IBD). Markedly increased numbers of mast cells were observed in the mucosa of the ileum and colon of patients with IBD, which was accompanied by great changes of the content in mast cells such as dramatically increased expression of TNF-α, IL-16 and substance P. The evidence of mast cell degranulation was found in the wall of intestine from patients with IBD with immunohistochemistry technique. The highly elevated histamine and tryptase levels were detected in mucosa of patients with IBD, strongly suggesting that mast cell degranulation is involved in the pathogenesis of IBD. However, little is known of the actions of histamine, tryptase, chymase and carboxypeptidase in IBD. Over the last decade, heparin has been used to treat IBD in clinical practice. The low molecular weight heparin (LMWH) was effective as adjuvant therapy, and the patients showed good clinical and laboratory response with no serious adverse effects. The roles of PGD2, LTC4, PAF and mast cell cytokines in IBD were also discussed. Recently, a series of experiments with dispersed colon mast cells suggested there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. The hypothesis is that mast cell secretogogues induce mast cell degranulation, release histamine, then stimulate the adjacent mast cells or positively feedback to further stimulate its host mast cells through H₁ receptor. Whereas released tryptase acts similarly to histamine, but activates mast cells through its receptor PAR-2. The connections between current anti-IBD therapies or potential therapies for IBD with mast cells were discussed, implicating further that mast cell is a key cell type that is involved in the pathogenesis of IBD. In conclusion, while pathogenesis of IBD remains unclear, the key role of mast cells in this group of diseases demonstrated in the current review implicates strongly that IBD is a mast cell associated disease. Therefore, close attentions should be paid to the role of mast cells in IBD.

Modulation of tryptase secretion from human colon mast cells by histamine

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 μg/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.

Modulation of tryptase secretion from human colon mast cells by histamine

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 μg/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.

Modulation of histamine release from human colon mast cells by protease inhibitors

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 α₁-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.

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 μg/mL calcium ionophore and 10 μg/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 μg/mL anti-IgE and 1 μg/ 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.

Inhibition of tryptase release from human colon mast cells by protease inhibitors

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 α₁-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 μg/mL, protamine was able to inhibit anti-IgE and calcium ionophore induced tryptase release. However, at 100 μg/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.

The release of basogranulin in response to IgE-dependent and IgE-independent stimuli: validity of basogranulin measurement as an indicator of basophil activation

BACKGROUND

Basogranulin, the novel basophil granule protein recognized by the monoclonal antibody BB1, can be released by stimulation with anti-IgE antibody or calcium ionophore. However, the kinetics and regulation of its secretion are unknown.

OBJECTIVE

We quantified basogranulin and histamine release in response to a range of stimuli to assess whether basogranulin secretion is a reliable marker of basophil activation.

METHODS

Isolated peripheral blood basophils were stimulated with anti-IgE antibody, calcium ionophore, N -formyl-Met-Leu-Phe, and complement C5a. The released basogranulin and histamine were quantified by dot blotting with BB1 and a fluorometric method, respectively. Basogranulin localization was confirmed by flow cytometry.

RESULTS

Both basogranulin and histamine displayed a bell-shaped response curve when basophils were challenged with anti-IgE. Half-maximal release occurred within 30 seconds. Basogranulin levels were maximal by 15 minutes, whereas those for histamine continued increasing to 30 minutes. Wortmannin, a PI3-K inhibitor, suppressed the release of both mediators. Basophils from donors with the "nonreleaser" phenotype secreted neither mediator in response to anti-IgE. Non-IgE-dependent stimuli released both mediators in parallel in a concentration-dependent manner. The correlation between the relative amounts of each mediator released was highly significant (r =.901, P <.0001, n = 87). Flow cytometry revealed that some of the secreted basogranulin adhered to the cell surface.

CONCLUSIONS

Basogranulin is secreted along with histamine in response to both FcepsilonR I-related and unrelated stimuli. It is therefore a valid marker of basophil activation and could provide the basis for an immunoassay that distinguishes between basophil and mast cell activation.

The inhibition of mast cell activation by neutrophil lactoferrin: uptake by mast cells and interaction with tryptase, chymase and cathepsin G

Inhibitors of mast cell tryptase and chymase can be effective as mast cell stabilising compounds. Lactoferrin has been reported to inhibit tryptase activity, but its actions on other serine proteases of mast cells and its potential to alter mast cell function are not known. We have examined the ability of lactoferrin to inhibit mast cell tryptase, chymase and cathepsin G, and investigated its potential to modulate the activation of human mast cells. Enzymatically dispersed cells from human skin, lung and tonsil were challenged with anti-IgE or calcium ionophore A23187, following incubation with recombinant human lactoferrin, and histamine release determined. IgE-dependent histamine release from skin mast cells was inhibited by up to 50% following incubation with lactoferrin (50 or 500 nM). Tonsil mast cells were also stabilised by lactoferrin, but not those from lung. Calcium ionophore A23187-induced histamine release was not altered by lactoferrin. A double-labelling immunocytochemical procedure revealed the presence of lactoferrin in 4-6% of mast cells, and this proportion increased to 40% following incubation with lactoferrin. Lactoferrin did not inhibit cleavage of synthetic substrates by tryptase and chymase directly, though it was able to diminish the ability of heparin to stabilise tryptase. Cathepsin G activity was inhibited by lactoferrin. The ability of lactoferrin to inhibit IgE-dependent activation of human mast cells and modulate protease activity suggests that the release of this neutrophil product may have a role in the downregulation of allergic inflammation.