Activation of human STING by a molecular glue-like compound

Stimulator of interferon genes (STING) is a dimeric transmembrane adapter protein that plays a key role in the human innate immune response to infection and has been therapeutically exploited for its antitumor activity. The activation of STING requires its high-order oligomerization, which could be induced by binding of the endogenous ligand, cGAMP, to the cytosolic ligand-binding domain. Here we report the discovery through functional screens of a class of compounds, named NVS-STGs, that activate human STING. Our cryo-EM structures show that NVS-STG2 induces the high-order oligomerization of human STING by binding to a pocket between the transmembrane domains of the neighboring STING dimers, effectively acting as a molecular glue. Our functional assays showed that NVS-STG2 could elicit potent STING-mediated immune responses in cells and antitumor activities in animal models.

CYP27A1-dependent anti-melanoma activity of limonoid natural products targets mitochondrial metabolism

Three limonoid natural products with selective anti-proliferative activity against BRAF(V600E) and NRAS(Q61K)-mutation-dependent melanoma cell lines were identified. Differential transcriptome analysis revealed dependency of compound activity on expression of the mitochondrial cytochrome P450 oxidase CYP27A1, a transcriptional target of melanogenesis-associated transcription factor (MITF). We determined that CYP27A1 activity is necessary for the generation of a reactive metabolite that proceeds to inhibit cellular proliferation. A genome-wide small interfering RNA screen in combination with chemical proteomics experiments revealed gene-drug functional epistasis, suggesting that these compounds target mitochondrial biogenesis and inhibit tumor bioenergetics through a covalent mechanism. Our work suggests a strategy for melanoma-specific targeting by exploiting the expression of MITF target gene CYP27A1 and inhibiting mitochondrial oxidative phosphorylation in BRAF mutant melanomas.

Author Correction: CPSF3-dependent pre-mRNA processing as a druggable node in AML and Ewing's sarcoma

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

CPSF3-dependent pre-mRNA processing as a druggable node in AML and Ewing's sarcoma

The post-genomic era has seen many advances in our understanding of cancer pathways, yet resistance and tumor heterogeneity necessitate multiple approaches to target even monogenic tumors. Here, we combine phenotypic screening with chemical genetics to identify pre-messenger RNA endonuclease cleavage and polyadenylation specificity factor 3 (CPSF3) as the target of JTE-607, a small molecule with previously unknown target. We show that CPSF3 represents a synthetic lethal node in a subset of acute myeloid leukemia (AML) and Ewing's sarcoma cancer cell lines. Inhibition of CPSF3 by JTE-607 alters expression of known downstream effectors in AML and Ewing's sarcoma lines, upregulates apoptosis and causes tumor-selective stasis in mouse xenografts. Mechanistically, it prevents the release of newly synthesized pre-mRNAs, resulting in read-through transcription and the formation of DNA-RNA hybrid R-loop structures. This study implicates pre-mRNA processing, and specifically CPSF3, as a druggable target providing an avenue to therapeutic intervention in cancer.

A High Content Screen in Macrophages Identifies Small Molecule Modulators of STING-IRF3 and NFkB Signaling

We screened a library of bioactive small molecules for activators and inhibitors of innate immune signaling through IRF3 and NFkB pathways with the goals of advancing pathway understanding and discovering probes for immunology research. We used high content screening to measure the translocation from the cytoplasm to nucleus of IRF3 and NFkB in primary human macrophages; these transcription factors play a critical role in the activation of STING and other pro-inflammatory pathways. Our pathway activator screen yielded a diverse set of hits that promoted nuclear translocation of IRF3 and/or NFkB, but the majority of these compounds did not cause activation of downstream pathways. Screening for antagonists of the STING pathway yielded multiple kinase inhibitors, some of which inhibit kinases not previously known to regulate the activity of this pathway. Structure-activity relationships (SARs) and subsequent chemical proteomics experiments suggested that MAPKAPK5 (PRAK) is a kinase that regulates IRF3 translocation in human macrophages. Our work establishes a high content screening approach for measuring pro-inflammatory pathways in human macrophages and identifies novel ways to inhibit such pathways; among the targets of the screen are several molecules that may merit further development as anti-inflammatory drugs.

Ternatin and improved synthetic variants kill cancer cells by targeting the elongation factor-1A ternary complex

Cyclic peptide natural products have evolved to exploit diverse protein targets, many of which control essential cellular processes. Inspired by a series of cyclic peptides with partially elucidated structures, we designed synthetic variants of ternatin, a cytotoxic and anti-adipogenic natural product whose molecular mode of action was unknown. The new ternatin variants are cytotoxic toward cancer cells, with up to 500-fold greater potency than ternatin itself. Using a ternatin photo-affinity probe, we identify the translation elongation factor-1A ternary complex (eEF1A·GTP·aminoacyl-tRNA) as a specific target and demonstrate competitive binding by the unrelated natural products, didemnin and cytotrienin. Mutations in domain III of eEF1A prevent ternatin binding and confer resistance to its cytotoxic effects, implicating the adjacent hydrophobic surface as a functional hot spot for eEF1A modulation. We conclude that the eukaryotic elongation factor-1A and its ternary complex with GTP and aminoacyl-tRNA are common targets for the evolution of cytotoxic natural products.

DOI:http://dx.doi.org/10.7554/eLife.10222.001

Many plants, fungi, and bacteria have evolved to produce small molecules that have powerful effects on the cells of other living organisms, and can even kill them. These naturally produced compounds are often used as starting points for developing new drugs. One such class of compounds are the cyclic peptides, which can be relatively easily produced in the laboratory and are able to penetrate cells. Some cyclic peptides have also proved to be useful for treating cancer and immune diseases, so researchers are keen to identify others that have similar effects. One promising prospect, called ternatin, is produced by several species of fungi. In high doses, ternatin can kill mammalian cells, but it was not clear how it does so.

To learn more, Carelli et al. searched a chemical database for cyclic peptides related to ternatin and identified several similar compounds that were reported to kill cancer cells. Inspired by the structures of these cyclic peptides, Carelli et al. synthesized modified versions of ternatin. One of these was 500 times more potent than ternatin, which means a much lower dose of the compound is still able to kill cancer cells.

Further experiments showed that ternatin blocks the production of new proteins in cells. Specifically, ternatin binds to a complex that includes a protein called elongation factor-1A (eEF1A). Mutations in a particular region of eEF1A prevent ternatin from killing cells, suggesting a potential binding site for ternatin.

The next challenge is to dissect the mechanism by which compounds binding to this site on eEF1A block protein synthesis and kill cells. A related challenge is to understand why certain cancer cells are hypersensitive to ternatin and other eEF1A inhibitors, while other cancer cells are relatively resistant. These questions are relevant to the development of eEF1A inhibitors as cancer treatments.

DOI:http://dx.doi.org/10.7554/eLife.10222.002

Local lung responses following local lung challenge with recombinant lungworm antigen in systemically sensitized sheep

BACKGROUND

Chronic mast cell-mediated inflammation may contribute significantly towards the extensive tissue remodelling that is a feature of lungworm infection in ruminants. Understanding the factors that control tissue remodelling is a necessary step toward effective management and treatment of conditions that feature such pathology.

OBJECTIVE

We sought to define in a novel ovine model system, the cellular, immune and mast cell phenotypic events that occur following local lung challenge with a recombinant protein antigen, DvA-1, derived from the ruminant lungworm nematode, Dictyocaulus viviparus.

METHODS

Two spatially disparate lung segments in systemically sensitized sheep were challenged on three occasions with DvA-1 (3xDVA) and two further segments were challenged with saline (3xSAL). Two months after the third challenge, one of the two segments previously repeatedly challenged with DvA-1 was challenged again with DvA-1 (3xDVA:DVA) whilst the other was challenged with saline (3xDVA:SAL). A similar protocol was followed with the saline challenged segments (3xSAL:SAL and 3xSAL:DVA). Bronchoalveolar lavage fluid (BALF) (n = 16) and tissue (n = 3) were collected after the last challenge.

RESULTS

Cellular changes 24 h after the fourth challenge were characterized by an increase in the absolute numbers of neutrophils and eosinophils in BALF from 3xDVA:DVA and 3xSAL:DVA segments. Local antibody production was implied through increased levels of antibody in both 3xDVA:DVA and 3xDVA:SAL segments, with the latter being unaffected by inflammation. Levels of active transforming growth factor beta-1 (TGF-beta(1)) were significantly increased in 3xDVA:SAL segments and a trend towards an increase was apparent in 3xDVA:DVA segments. Total TGF-beta1 levels were significantly correlated with eosinophil counts in all except the 3xDVA:SAL segments. Such changes in the bronchoalveolar space were complemented by increased ratios of sheep mast cell proteinase-1 expressing cells and tryptase expressing cells, to toluidine blue positive cells in airways from 3xDVA:DVA segments.

CONCLUSION

Mast cell phenotypic events occurring as a consequence of antigen challenge were limited to segments in which changes in BALF were characterized by neutrophil influx and increased local antibody production.

Approaches to vaccines for Psoroptes ovis (sheep scab)

A brief outline of the history of sheep scab in the UK is presented together with the current chemical methods used for its control and problems associated with these. Possible alternative approaches to control are discussed, as are selected aspects of the physiology of Psoroptes ovis and the pathogenesis of the scab lesion from the perspective of control through immunisation. Evidence is provided that immunity to the disease can indeed be acquired, both naturally after a previous infection and following inoculation of mite proteins in adjuvant. These results support the view that control by vaccination may be possible, although little is known to date about the antigens involved or the mechanism of protection.

Delayed expulsion of the nematode Trichinella spiralis in mice lacking the mucosal mast cell-specific granule chymase, mouse mast cell protease-1

Expulsion of gastrointestinal nematodes is associated with pronounced mucosal mast cell (MMC) hyperplasia, differentiation, and activation, accompanied by the systemic release of MMC granule chymases (chymotrypsin-like serine proteases). The beta-chymase mouse mast cell protease-1 (mMCP-1) is expressed predominantly by intraepithelial MMCs, and levels in the bloodstream and intestinal lumen are maximal at the time of worm expulsion in parasitized mice. To address the in vivo functions of MMC-specific beta-chymases, we have generated transgenic mice that lack the mMCP-1 gene. They were backcrossed onto a congenic BALB/c background to investigate the response to nematode infection. The deletion of the mMCP-1 gene is associated with significantly delayed expulsion of Trichinella spiralis and increased deposition of muscle larvae in BALB/c mice despite the presence of normal and sometimes increased numbers of MMCs. Neither worm fecundity nor worm burdens were altered in Nippostrongylus-infected mMCP-1(-/)- BALB/c mice. These data demonstrate, for the first time, that the ablation of an MMC-derived effector molecule compromises the expulsion process.

Cutaneous and systemic responses during primary and challenge infestations of sheep with the sheep scab mite, Psoroptes ovis

Lesional area was estimated and lesional mast cells and eosinophils were counted during primary and challenge infestations of sheep with Psoroptes ovis. In addition, circulating basophils and eosinophils and serum P. ovis-specific immunoglobulin IgE antibody were quantified. Expansion of lesional area was significantly less and serum IgE titres significantly greater in challenge than primary infestations. Lesional mast cell hyperplasia and massive eosinophil infiltration accompanied by raised titres of P. ovis antigen-specific IgE antibody were compatible with an IgE-mediated Type-1 allergic reaction, while detection of lesional basophils was suggestive of cutaneous basophil hypersensitivity. The temporal pattern of lesional mastocytosis and eosinophil infiltration and the role of these cells and serum IgE in the immune response is discussed.

cDNA sequence of two sheep mast cell tryptases and the differential expression of tryptase and sheep mast cell proteinase-1 in lung, dermis and gastrointestinal tract

BACKGROUND

Mast cell tryptases are a family of serine proteinases which are implicated in the proliferation of smooth muscle cells and fibroblasts, upregulation of interleukin-8 synthesis by endothelial cells, and recruitment of neutrophils and eosinophils. Trials in sheep showed that administration of a specific tryptase inhibitor reduced the late-phase response to inhaled allergen.

OBJECTIVES

The aim of this study was to characterize the sequence and distribution of sheep tryptase(s), to validate the sheep model of allergic lung disease.

METHODS

Reverse transcriptase PCR cloning was used to obtain cDNA sequences for two sheep tryptases. Lung and gut extracts were used as a source of tryptase for partial purification and characterization of the protein. The distribution of tryptase in skin, lung and gut was determined by immunohistochemistry, and compared with the distribution of sheep mast cell proteinase-1 (sMCP-1).

RESULTS

Two highly similar cDNA sequences encoding sheep tryptase were found, indicating the presence of a 28 amino acid leader sequence, and a mature peptide of 245 amino acids. Partial purification of a putative sheep tryptase from lung and gut extracts was achieved using heparin-Sepharose affinity chromatography. Rabbit antihuman skin tryptase antiserum recognized the putative sheep tryptase on Western blot (approximate Mr 32-34 000) and paraformaldehyde-fixed tissue sections. Tryptase was detected in all lung, skin and gut mast cells by this antibody, and transcripts for tryptase were detected in all three tissues by RT PCR. Sheep mast cell proteinase-1, detected by a specific monoclonal antibody, was present in all intestinal and gastric mucosal mast cells, but was not found in mast cells of the muscularis, thus defining at least two mast cell phenotypes in the gut. Whereas all dermal and pulmonary mast cells were tryptase positive, only a low proportion in the lung, and almost none in the dermis, were positive for sMCP-1.

CONCLUSION

In view of the structural and functional similarities of sheep and human tryptases, and their similarity in tissue distribution in normal sheep, the sheep lung appears to be a good model for in vivo studies relating to human tryptase.

Thyroid function in cord blood

OBJECTIVE

To determine the biochemical parameters of thyroid function in the cord blood of Saudi infants.

METHODS

Cord blood samples sent to the Pathology Department for screening for congenital hypothyroidism were used to determine the reference ranges for thyrotropin, free thyroxine, free triiodothyronine, thyroxine-binding globulin and thyroglobulin. All the measurements were carried out by immunoassay (Elisa, microparticle enzyme immunoassay or chemiluminescence immunoassay). Reference ranges were calculated after exclusion of outliers.

RESULTS

Reference ranges for thyrotropin, free thyroxine and thyroxine-binding globulin were similar to published values, whereas those for free triiodothyronine and thyroglobulin were different.

CONCLUSION

For correct interpretation of the parameters of thyroid function in cord blood it is essential to have reference ranges based on the laboratory's current methods and derived from the local population.

Kinetics of equine neutrophil elastase release and superoxide anion generation following secretagogue activation: a potential mechanism for antiproteinase inactivation

Man and horses both suffer from neutrophil mediated pulmonary diseases however there are striking species differences in the underlying pathology. In particular while pulmonary emphysema is a common pathological sequel to human respiratory disease it is not a major feature of the common equine neutrophil mediated condition, chronic obstructive pulmonary disease (COPD). The proposed reason for this difference is that equine neutrophils contain less elastase than equivalent human cells and therefore there is a reduced risk of excess and/or uninhibited elastase activity, which is considered the major cause of pulmonary emphysema in man, in the horse lung. In previous studies equine neutrophil elastase (ENE) has been assayed by measuring elastinolytic activity whereas human neutrophil elastase content has been determined using immunological techniques. Neutrophils contain several intracellular protease inhibitors therefore measurement of elastase activity may underestimate the total NE content. The aim of the current study was to develop immunological techniques to allow investigation of the cellular content, distribution and release of ENE from purified equine neutrophils. Equine neutrophil elastase 2A (ENE 2A), the most abundant elastase in equine neutrophils, and equine alpha-1-proteinase inhibitor (API), the main inhibitor of elastase were found to be present at 0.813 pg +/- 0.179 and 0.021 pg +/- 0.003 (mean +/- SEM, n = 11 individual horses) per neutrophil, respectively. This represents twice as much elastase as previously found in the equine neutrophil and a comparable amount to that reported in human neutrophils. Immunolocalisation demonstrated that ENE 2A has a granular distribution within the cytosol of neutrophils, whereas API exhibits a uniform non-granular cytoplasmic appearance. In addition the kinetics of simultaneous generation and release of superoxide anions (SOA) and release of ENE 2A from equine neutrophils, stimulated in vitro by zymosan-activated serum (ZAS) in the presence and absence of the cation chelator ethylene glycol-N,N,N',N'-tetraacetic acid (EGTA), showed a close relationship between total SOA generation and total ENE 2A release during the initial 90 min post-ZAS stimulation and the dependence of both events on extracellular cations. In conclusion these studies have shown that horse and human neutrophil elastase content and mediator release functions are more closely matched than was previously thought. This suggests that the species differences in pathology resulting from neutrophil-mediated respiratory disease are determined by other factors such as differences in the abundance and function of intra- and extra-cellular protease inhibitors.

A novel function for transforming growth factor-beta1: upregulation of the expression and the IgE-independent extracellular release of a mucosal mast cell granule-specific beta-chymase, mouse mast cell protease-1

Intestinal mucosal mast cells (IMMC) express granule neutral proteases that are regulated by T-cell-derived cytokines, including interleukin-3 (IL-3) and IL-9, and by stem cell factor (SCF). The IMMC-specific chymase, mouse mast cell protease-1 (mMCP-1), is released in substantial quantities into the blood stream during gastrointestinal allergic responses. We used cultured bone marrow-derived mast cells (mBMMC) to identify cytokines that regulate the expression and extracellular release of mMCP-1. When grown in IL-3-rich WEHI (15% vol/vol) and 50 ng/mL recombinant rat SCF (rrSCF) bone marrow cells supplemented with IL-9 (5 ng/mL) differentiated into mBMMC that expressed a maximum of less than 250 ng mMCP-1/10(6) cells and 189 ng mMCP-1/mL of culture supernatant. Supplementation of the same three cytokines with transforming growth factor-beta1 (TGF-beta1; 1 ng/mL) resulted in substantially enhanced expression (6 micrograms/10(6) mBMMC) and extracellular release (2 micrograms/mL of culture supernatant) of mMCP-1. The response to TGF-beta1 was dose-dependent, with maximal effect at 1 ng/mL, and was associated with immunohistochemical and ultrastructural changes in the secretory granules. IL-9-induced expression of mMCP-1 may be due to endogenously expressed TGF-beta1, because it was blocked by anti-TGF-beta antibodies. In conclusion, the expression and extracellular release of the IMMC-specific chymase, mMCP-1, is strictly regulated by TGF-beta1.

Synthesis of a series of stromelysin-selective thiadiazole urea matrix metalloproteinase inhibitors

The synthesis and enzyme inhibition data for a series of thiadiazole urea matrix metalloproteinase (MMP) inhibitors are described. A broad screening effort was utilized to identify several thiadiazoles which were weak inhibitors of stromelysin. Optimization of the thiadiazole leads to include an alpha-amino acid side chain with variable terminal amide substituents provided a series of ureas which were moderately effective stromelysin inhibitors, with Ki's between 0.3 and 1.0 microM. The most effective analogues utilized an L-phenylalanine as the amino acid component. In particular, unsubstituted 46 had a Ki of 710 nM, while the p-fluoro analogue 52 displayed increased potency (100 nM). Stromelysin inhibition was further improved using a pentafluorophenylalanine substituent which resulted in 70, a 14 nM inhibitor. While gelatinase inhibition was generally poor, the use of 1-(2-pyridyl)piperazine as the amide component usually provided for enhanced activity, with 71 inhibiting gelatinase with a Ki of 770 nM. The combination of this heterocycle with a p-fluorophenylalanine substituent provided the only analogue, 69, with collagenase activity (13 microM). The SAR for analogues described within this series can be rationalized through consideration of the X-ray structure recently attained for70 complexed to stromelysin. Uniquely, this structure showed the inhibitor to be completely orientated on the left side of the enzyme cleft. These results suggest that thiadiazole urea heterocycles which incorporate a substituted phenylalanine can provide selective inhibitors of stromelysin. Careful selection of the amide substituent can also provide for analogues with modest gelatinase inhibition.

Studies on pulmonary and systemic Aspergillus fumigatus-specific IgE and IgG antibodies in horses affected with chronic obstructive pulmonary disease (COPD)

Inhalant exposure to Aspergillus fumigatus (Asp. f.) antigens induces marked inflammatory and immunological alterations in the lungs of horses affected with chronic obstructive pulmonary disease (COPD). In this study we investigated the role of specific allergen(s) present in Asp. f. on systemic and pulmonary IgE and IgG responses in control and COPD-affected horses, using an enzyme-linked immunosorbent assay (ELISA) and immunoblotting techniques. Compared with controls, horses affected with COPD had significantly higher levels of BALF IgE and IgG to somatic Asp. f. antigens as well as to the allergen 1/a (Asp. f. 1/a). Serum levels of IgE and IgG against these antigens did not differ between control and COPD-affected horses. Antigen specific IgE and IgG levels did not correlate between BALF and serum. Scanning of Asp. f. and IgE and IgG blots revealed bands that are recognised by both IgE- and IgG-specific antibodies. Additionally, all horses responded with BALF IgE- and IgG-specific for 93, 35, 31 and 23 kDa allergens, suggesting that these antigens are involved in the induction of airway IgE and IgG responses. These allergens may have the potential to be used as biomarkers for the diagnosis of Asp. f. related exacerbations of equine COPD.

Improved hepatic and pancreatic localisation of the equine alpha-1-proteinase inhibitor family of serpins using an antigen enhancement technique and a monoclonal antibody

Equine alpha-1-proteinase inhibitor (API) consists of three, occasionally four, serum glycoproteins. This study investigated the immunohistochemical localisation of equine API in paraformaldehyde fixed, paraffin embedded equine tissue samples of liver, lung, stomach, pancreas, jejunum and colon in five horses using affinity purified sheep polyclonal and protein A purified mouse monoclonal antibodies, whose specificities were verified by Western blotting. Exposing tissue sections to boiling citrate buffer greatly enhanced antigen recovery and improved immunostaining with both antibodies, resulting in discovery of novel tissue distribution patterns for the horse. In the horses studied, all hepatocytes showed some degree of cytoplasmic staining, many having perinuclear intense granular inclusions. This finding is contrary to findings in human studies where hepatocytes of Pi MM phenotype have proven difficult to stain for human API, despite evidence at the molecular level suggesting hepatocytes as the major source of serum API. This discrepancy may be due to the use of different tissue fixation and antigen recovery techniques. In all other tissues examined, the distribution of equine API was similar to human studies.

Histochemical and ultrastructural modification of mucosal mast cell granules in parasitized mice lacking the beta-chymase, mouse mast cell protease-1

The soluble beta-chymases mouse mast cell protease-1 (mMCP-1) and rat mast cell protease-II are predominantly expressed by intestinal mucosal mast cells (IMMCs) and may promote mucosal epithelial permeability when released during intestinal allergic hypersensitivity responses. To study the function of these chymases, we generated mice with a homozygous null mutation of the mMCP-1 gene and investigated their response to infection with the intestinal nematode Nippostrongylus brasiliensis. Whereas mMCP-2, -4, and -5 were transcribed normally, there was no transcription of the mMCP-1 gene in null (-/-) mice, nor was mature mMCP-1 protein detected in (-/-) jejunal mucosa. In contrast, levels of mMCP-1 in wild-type (+/+) jejunal mucosa increased 200- to 350-fold from 0.66 microg mMCP-1/g wet weight in uninfected mice to 129 and 229 microg/g wet weight on days 8 and 10 of infection, respectively. The kinetics of IMMC recruitment differed in -/- mice compared with +/+ controls on days 8 (P < 0.05) and 10 (P < 0.03) of infection. The IMMCs in infected -/- mice stained poorly, if at all, for esterase with naphthol AS-D chloroacetate compared with the intense staining observed in +/+ controls. Ultrastructurally, the prominent crystal intragranular structures that are found in intraepithelial +/+ IMMCs were absent from -/- IMMCs. These data show that disruption of the mMCP-1 gene leads to profound histochemical and ultrastructural changes in IMMC granules.

Sheep mast-cell proteinases-1 and -3: cDNA cloning, primary structure and molecular modelling of the enzymes and further studies on substrate specificity

Sheep mast-cell proteinase-1 (sMCP-1) is a serine proteinase expressed predominantly by mucosal mast cells, with specificity for cleavage C-terminal to basic and hydrophobic amino acid residues. A cDNA encoding sMCP-1 has been cloned using reverse transcriptase (RT)-PCR. It appears to be translated as a pre-proenzyme with a 17-amino-acid signal peptide, a basic 2-amino-acid propeptide and a 226-amino-acid catalytic domain. A second cDNA, encoding a serine proteinase 90% identical with sMCP-1, was also cloned and named sMCP-3. Molecular models were constructed for both enzymes using coordinates for the refined X-ray structures of human cathepsin G, chymase and rat mast-cell proteinase-2. The model for sMCP-1 suggests that the acidic Asp-226 side chain extends into the substrate-binding pocket, hydrogen-bonding with Ser-190 on the opposite side and bisecting the pocket. The location of an acidic moiety in this position would favour interaction with basic substrate residues and binding of aromatic residues is rationalized by interaction of the positively charged equatorial plane with Asp-226. The balance between chymotryptic and tryptic activities of sMCP-1 was found to be sensitive to salt concentration, with increasing univalent cation concentration favouring chymotryptic activity relative to the tryptic. Using a peptide substrate representing residues 36-59 of the human thrombin receptor, increasing salt concentration favoured cleavage at Phe-43 rather than at Arg-41.

The rat mucosal mast cell chymase, RMCP-II, alters epithelial cell monolayer permeability in association with altered distribution of the tight junction proteins ZO-1 and occludin

Mucosal mast cells undergo hyperplasia in a variety of inflammatory bowel diseases including nematode infection in man and animals. The intra-epithelial localization of these cells make their soluble mediators prime candidates for modulators of epithelial function. In particular previous in vivo and ex vivo studies have established a link between the release of the highly soluble mast cell granule chymases and increased mucosal permeability. The hypothesis that the rat mast cell protease, RMCP-II, directly increases permeability to macromolecules via the paracellular route is tested in this study. Monolayers of epithelial cells (Madin-Darby canine kidney cell line) were exposed to varying concentrations of RMCP-II in vitro, in the absence of other cell types or mediators, and the effect on permeability and tight junction associated proteins was investigated. Basolateral, but not apical, exposure of polarized MDCK monolayers on porous supports to RMCP-II led to concentration- (> 100 microg/ml) and time-dependent increases in electrical conductance and permeability to mannitol (MW182) and inulin (MW5000), which was accompanied by decreases in the immunostaining of the tight junction-associated proteins occludin and ZO-1. Furthermore, prolonged exposure to RMCP-II (> 12 hours) resulted in the formation of identifiable gaps separating adjacent epithelial cells, in the absence of evidence of cytotoxicity. Inhibition of RMCP-II with Soya bean trypsin inhibitor completely abrogated the response, demonstrating that proteolysis was required. These data provide direct evidence that the rat mast cell chymase RMCP-II can, in the absence of other inflammatory mediators, increase epithelial permeability via an effect on the paracellular route.

Differential inhibition of mast cell chymases by secretory leukocyte protease inhibitor

The major physiological role of human secretory leukocyte protease inhibitor (SLPI), a low molecular weight inhibitor present in mucus, is the rapid formation of a tight-binding inhibitory complex with neutrophil elastase. It is also the most effective known inhibitor of human mast cell chymase. The inhibitory efficacy of recombinant SLPI towards three other mast cell chymases was therefore investigated. Rat mast cell proteinases-1 and -2 (rMCP-1 and -2, respectively) and sheep mast cell proteinase-1 (sMCP-1), a chymase with additional tryptase-like properties, were treated with the inhibitor. SLPI inhibited rMCP-1 very efficiently in the absence of heparin, with a low dissociation constant, Ki = 3 x 10(-10) M and high second order association constant, kass = 8.0 x 10(6) M(-1) s(-1), and inhibition was enhanced when heparin was present. rMCP-2 was not inhibited by SLPI in the presence or absence of heparin, and did not degrade SLPI on prolonged incubation. SLPI inhibited sMCP-1 very poorly in the absence of heparin (Ki = 9 X 10(-6) M). However, in the presence of heparin, the Ki for inhibition of sMCP-1 by SLPI was reduced to the nanomolar range. sMCP-1 was observed to cleave SLPI with chymase-like specificity at Leu72-Met73 on prolonged incubation in the absence of heparin, but increasing concentrations of heparin reduced the extent of cleavage.

Mast cell specific proteases in rat brain: changes in rats with experimental allergic encephalomyelitis

Mast cell populations were identified within brain parenchyma by their specific proteases, using antibodies for immunohistochemistry and ELISAs, and riboprobes were developed for in situ hybridisation. Connective tissue mast cells expressing rat mast cell protease I (RMCPI) mRNA and immunoreactivity were observed in thalamus and showed no degranulation at 3, 8 and 13 days after induction of experimental allergic encephalomyelitis (EAE). Mucosal-like mast cells were clearly demonstrated in control rats by measuring RMCPII and by visualising cells expressing RMCPII mRNA and immunoreactivity. At day 13, but not 3 and 8 post immunisation, the number of RMCPII-expressing cells markedly increased in the EAE-induced group, mainly within brainstem and spinal cord close to inflammed blood vessels. The markers of histaminergic neurons were marginally affected 13 days after immunisation and the increase of [3H] histamine synthesis elicited by the H3-receptor antagonist, thioperamide, was not modified in any region of the brain. It is concluded that the cerebral RMCPII-expressing mast cells could play a role during EAE.

Mast cell heterogeneity in the gastrointestinal tract: variable expression of mouse mast cell protease-1 (mMCP-1) in intraepithelial mucosal mast cells in nematode-infected and normal BALB/c mice

Soluble granule chymases in rodent intestinal mucosal mast cells (IMMCs) may play an important role in altering epithelial permeability during immediate hypersensitivity reactions. Using a monoclonal antibody against the chymase mouse mast cell protease-1 (mMCP-1), we have shown that it is constitutively expressed in < or = 20% of esterase-positive (esterase+) IMMCs but not in esterase+ gastric mucosal mast cells (GMMCs) in normal BALB/c mice. Intestinal infection with mouse- or rat-adapted strains of Nippostrongylus brasiliensis resulted in IMMC hyperplasia with 100% of esterase+ IMMCs expressing mMCP-1. In contrast, there was a variable response in terms of numbers of GMMCs and of the proportion expressing mMCP-1. Esterase+ mast cells in the gastric submucosa, muscularis, ear pinna, lung parenchyma, major airway submucosa, and peritoneal cavity did not express mMCP-1. The few airway esterase+ mast cells expressing mMCP-1 were, like the great majority of IMMCs and GMMCs, located intraepithelially. In conclusion, mMCP-1 is predominantly expressed by intraepithelial mucosal mast cells but not in all sites; the immunological stimulus associated with intestinal nematodiasis substantially up-regulates mMCP-1 expression by mast cells in the jejunum but not in the stomach; IMMCs and GMMCs in BALB/c mice are phenotypically and possibly functionally distinct.

Sheep mast cell proteinase-1, a serine proteinase with both tryptase- and chymase-like properties, is inhibited by plasma proteinase inhibitors and is mitogenic for bovine pulmonary artery fibroblasts

Sheep mast cell proteinase-1 (sMCP-1), a serine proteinase with dual chymase/tryptase activity, is expressed in gastrointestinal mast cells, and released systemically and on to the mucosal surface during gastrointestinal nematode infection. The potential for native plasma proteinase inhibitors to control sMCP-1 activity was investigated. Sheep alpha1-proteinase inhibitor (alpha1PI) inhibited sMCP-1 slowly, with second-order association rate constant (kass) 1. 1x10(3) M-1.s-1, whereas sheep contrapsin inhibited trypsin (kass 2.2x10(6) M-1.s-1) but not sMCP-1. Western-blot analysis and gel filtration showed that when added to serum or plasma, sMCP-1 was partitioned between alpha1PI and alpha2-macroglobulin. The possibility that significant cleavage of plasma proteins could occur before sMCP-1 was inhibited was investigated using gel filtration and SDS/PAGE after adding sMCP-1 to plasma. Cleavage of ovine fibrinogen occurred in the presence of excess alpha1PI and alpha2-macroglobulin, the alpha-chain being cleaved C-terminally and the beta-chain at the putative Lys-27. In addition, sMCP-1 was found to be mitogenic for bovine pulmonary artery fibroblasts, but was not mitogenic in the presence of soya-bean trypsin inhibitor. In terms of fibrinogen cleavage and fibroblast stimulation, sMCP-1 shows functional similarities to mast cell tryptase.

Functional relationships between sensory nerve fibers and mast cells of dura mater in normal and inflammatory conditions

In this study, we have characterized the phenotype of mast cells in rat dura mater and their topological and functional relationships with C-fibers in normal and inflammatory conditions. Three mast cell populations with different size, morphology and localization were characterized by their content of specific neutral serine proteases. They showed immunoreactivity corresponding to rat mast cell protease I, rat mast cell protease II, or both proteases. Using confocal microscopy, all three mast cell types were observed in close apposition (distance less than 100 nm) to calcitonin gene-related peptide- and substance P-immunoreactive nerve fibers in both controls and rats infected with the nematode Nippostrongylus brasiliensis. After nematode infection or neonatal treatment with capsaicin, a large increase in the number of rat mast cell protease II-immunoreactive mast cells was found within dura mater segments (+1478% and +596%, respectively), without concomitant changes of rat mast cell protease I- or rat mast cell protease I/II-immunoreactive mast cells. Under both these conditions, the increase in mast cell number was accompanied by a significant increase in rat mast cell protease II level within tissue extracts (+281% after nematode infection and +36% after capsaicin treatment). The functional interaction of mast cells with sensory nerve fibers in the dura mater was assessed by evaluating [3H]histamine synthesis after administration of L-[3H]histidine, an index of mast cell activity. The H3 receptor agonist (R)-alpha-methylhistamine (15 mg/kg, i.p.) had no effect, but administration of the H3 receptor antagonist, thioperamide (10 mg/kg, i.p.), resulted in a significant increase of [3H]histamine synthesis (+62%). This effect was reduced in neonatal capsaicin-treated rats, but not completely suppressed (+35%), very likely because of partial denervation, as assessed by monitoring calcitonin gene-related peptide immunoreactivity. It is concluded that, in the dura mater, as in peripheral tissues, sensory nerve fibers and mast cells actively synthesizing and releasing histamine form a short inhibitory feedback loop involving prejunctional H3 receptors that could regulate the release of pro-inflammatory mediators, thus limiting the extent of inflammatory reactions.

Constitutive expression of mouse mast cell protease-1 in normal BALB/c mice and its up-regulation during intestinal nematode infection

Rodent intestinal mucosal mast cells (IMMC) store and secrete soluble granule serine proteases, the beta-chymases, which may promote epithelial permeability during intestinal hypersensitivity reactions. The beta-chymase mouse mast cell protease-1 (mMCP-1) is generally considered to be expressed late in the in vitro differentiation of mast cells. The purpose of this study was to determine the kinetics of mMCP-1 transcription and expression in vivo during nematode-induced IMMC hyperplasia. Concentrations of mMCP-1 in blood and jejunum of BALB/c mice were quantified by enzyme-linked immunosorbent assay before and at various stages after infection with the intestinal nematode Nippostronglyus brasilliensis. Mature mMCP-1 enzyme was detected in jejunal homogenate (194 ng/mg soluble protein) and in blood (8.3 ng/ml serum) from normal uninfected BALB/c mice. Maximal IMMC hyperplasia occurred 7-14 days post infection and was significantly correlated with increased levels of mMCP-1 in jejunum (r = 0.58, P < 0.001) and with raised concentrations of mMCP-1 in serum (r = 0.66, P < 0.001). Transcription of the mMCP-1 gene was detected by RNA blotting in normal, uninfected jejunum, but transcription was up-regulated after infection with maximal transcription occurring on days 7 and 14. In conclusion, mMCP-1 transcription, storage and secretion occur constitutively in normal BALB/c jejunum but this basal secretion is up-regulated during nematode infection, suggesting both a physiological and pathological function for this protease.

Sheep mast cell proteinase-1: characterization as a member of a new class of dual-specific ruminant chymases

Sheep mast cell proteinase 1 (SMCP-1), which is abundantly expressed in gastrointestinal but not skin mast cells, was isolated and its substrate specificity was investigated. Peptide substrates, including angiotensin I, substance P, bradykinin and oxidized insulin B chain were hydrolysed at P1 Phe, Leu or Tyr residues, conforming to the known chymotrypsin-like properties of the enzyme. However, SMCP-1 was found to hydrolyse some chromogenic substrates with P1 Lys and Arg residues. The enzyme also demonstrated trypsin-like activity against protein substrates, cleaving BSA at Lys114-Leu115, Lys238-Val239, Lys260-Tyr261 and Lys376-His377. Bovine fibrinogen beta-chain was cleaved at Lys28-Lys29. To ensure homogeneity of the enzyme, the ratio of chymotrypsin-like to trypsin-like activity was observed; it was found to be constant during purification and between different preparations of SMCP-1. Treatment of SMCP-1 with a range of inhibitors decreased chymotrypsin-like and trypsin-like activities by similar extents, supporting the assertion that both activities are the property of a single enzyme. In terms of activity, and by N-terminal amino acid sequencing, SMCP-1 strongly resembles the similarly dual-specific bovine duodenal proteinase, duodenase. It is proposed that SMCP-1 and duodenase represent a new class of ruminant chymases with unusual dual specificities.

Trypsin stimulates proteinase-activated receptor-2-dependent and -independent activation of mitogen-activated protein kinases

We have examined protease-mediated activation of the mitogen-activated protein (MAP) kinase cascade in rat aortic smooth-muscle cells and bovine pulmonary arterial fibroblasts. Exposure of smooth-muscle cells to trypsin evoked rapid and transient activation of c-Raf-1, MAP kinase kinase 1 and 2 and MAP kinase that was sensitive to inhibition by soybean trypsin inhibitor. The actions of trypsin were closely mimicked by the proteinase-activated receptor 2 (PAR-2)-activating peptide sequence SLIGRL but not LSIGRL. Peak MAP kinase activation in response to both trypsin and SLIGRL was also dependent on concentration, with EC50 values of 12.1 +/- 3.4 nM and 62.5 +/- 4.5 microM respectively. Under conditions where MAP kinase activation by SLIGRL was completely desensitized by prior exposure of smooth-muscle cells to the peptide, trypsin-stimulated MAP kinase activity was markedly attenuated (78.9 +/- 15.1% desensitization), whereas the response to thrombin was only marginally affected (16.6 +/- 12.1% desensitization). Trypsin and SLIGRL also weakly stimulated the activation of the MAP kinase homologue p38 in smooth-muscle cells without any detectable activation of c-Jun N-terminal kinase. Strong activation of the MAP kinase cascade and modest activation of p38 by trypsin were also observed in fibroblasts, although in this cell type these effects were not mimicked by SLIGRL nor by the thrombin receptor-activating peptide SFLLRNPNDKYEPF. Reverse transcriptase-PCR analysis confirmed the presence of PAR-2 mRNA in smooth-muscle cells but not fibroblasts. Our results suggest that in vascular smooth-muscle cells, trypsin stimulates the activation of the MAP kinase cascade relatively selectively, in a manner consistent with an interaction with the recently described PAR-2. Activation of MAP kinase by trypsin in vascular fibroblasts, however, seems to be independent of PAR-2 and occurs by an undefined mechanism possibly involving novel receptor species.

Early pulmonary cell response during experimental maedi-visna virus infection

A model of experimental infection with EV1, a British isolate of maedi-visna virus (MVV), has been developed. Twelve male Texel sheep were allocated to three groups and inoculated by the respiratory route with different inocula. Six of the animals received 10(7.2) tissue culture infective dose (TCID50) of MVV EV1 strain. Two sheep were inoculated with the same dose of heat inactivated MVV EV1 strain. An additional group of four sheep was sham-inoculated with identically prepared virus-free culture media. Experimental infection was followed for 16 weeks. Prior to inoculation, routine haematology, bronchoalveolar lavage (BAL) and flow cytometric analysis of bronchoalveolar lavage fluid (BALF) lymphocytes were performed in all animals to provide baseline parameters. Flow cytometric analysis of BALF lymphocytes and differential BALF cell counts were performed. Precipitating antibodies to MVV developed in all MVV-inoculated animals during the first 4 weeks post-inoculation, while the rest remained seronegative to MVV. MVV-infected animals had significantly decreased (P < 0.05) percentages of macrophages and significantly increased (P < 0.05) percentages of lymphocytes in BALF 4 weeks post-inoculation. Phenotypic changes in BALF T lymphocytes from MVV-inoculated animals, compared with the other two groups, showed significantly decreased (P < 0.05) percentages of CD4+ and gamma delta + T lymphocytes, significantly increased (P < 0.05) percentages of CD8+ lymphocytes and significant inversion (P < 0.05) of the CD4+/CD8+ ratio at different sampling times, but between 2 and 12 weeks post-inoculation. These findings indicate that during experimental MVV-infection an early, short-term cellular reaction occurs in the lung, that is characterised by T lymphocyte phenotypic changes that are very similar, if not identical, to those observed in natural MVV infection.

Rat cerebral mast cells undergo phenotypic changes during development

The evolution of rat cerebral mast cell phenotype during development was studied using antibodies against the granule chymases, rat mast cell protease I (RMCP-I) and rat mast cell protease II (RMCP-II) and their gene transcripts, as markers for serosal and mucosal mast cells, respectively. In situ hybridization using specific oligoprobes for RMCP-II permitted visualization of RMCP-II mRNA-containing cells as early as day 15 of embryonic development (E15). From E19 to day 4 postpartum (D4) their number increased whilst they migrated from the pia mater to the choroid fissure; at D8 cells expressing RMCP-II gene transcripts were no longer observed. The 3'-end untranslated nucleotide sequence of the RMCP-I cDNA was established in order to design selective cDNA probes for Northern blot analysis of both enzymes. Northern blot analysis revealed a strong expression of RMCP-I and RMCP-II mRNAs at D2. At D4, RMCP-I mRNA expression was still high, whereas that of RMCP-II was decreased. In adult brain, mRNA expression for both proteases was low, but detectable. Quantification of both proteases by ELISA showed that, from E19 to D4, levels of RMCP-II were maximal at E19 and remained constant until D4, whereas RMCP-I increased as a function of age. Thereafter, levels of both proteases decreased progressively, but were still present in the adult brain, with RMCP-II being uniformly distributed and RMCP-I concentrated in the thalamus. Immunohistochemical staining showed RMCP-II-immunoreactive cells within the pia mater at E19; on D2 and D4, cells with both RMCP-I and RMCP-II immunoreactivities were found within the choroid fissure and from D8, only RMCP-I-immunoreactive mast cells were observed. In the thalamus of adult rats, the latter had a perivascular localization. This study shows that in the adult, both types of mast cells are present, although in small numbers, except for RMCP-I-immunoreactive mast cells which are abundant in the thalamus. The changes in the number and phenotype of cerebral mast cells may result from the influence of a number of growth factors during development.

Mucosal mast cells and the allergic response against nematode parasites

IgE-mediated Type-I allergic reactions at nematode-infected mucosal surfaces are considered to have a direct protective function. The contribution of mucosal mast cells (MMC) to these mucosal allergic responses is reviewed. In addition to the T helper 2 cell-mediated regulation of MMC hyperplasia during nematode infection the kit ligand, stem cell factor (SCF), plays a key role in the early development of the MMC response. Studies in the mouse suggest that MMC protect against certain nematodes which enter the mucosa but not against lumen dwelling nematodes. The protective roles of MMC in other species, including sheep, are less certain and there is some evidence that MMC might enhance parasite fecundity. The measurement of MMC-specific granule chymases released systemically, and into the gut lumen, permits precise monitoring of mast cell activation and suggests that the secreted chymases may target epithelial junctional complex proteins, thereby causing increased mucosal permeability. The abundant intraepithelial MMC found in parasitised mucosa may, therefore, serve as epithelial gatekeepers permitting the translocation of plasma proteins onto the mucosal surface.

Characterization of whole-cell currents in mucosal and connective tissue rat mast cells using amphotericin-B-perforated patches and temperature control

Rat mucosal type mast cells are thought to possess only a K+-selective inwardly rectifying (IRK) current in the resting state. We used rat-bone-marrow-derived mast cells (BMMCs) as a model of mucosal mast cells and recorded whole-cell membrane currents from cells perforated with amphotericin B. Under these conditions, both inwardly rectifying (IR) and outwardly rectifying (OR) currents were observed. The reversal potential and conductance of the IR current depended on the extracellular K+ concentration, indicating that the channel was K+ selective. The OR current was not affected by changes in extracellular K+ concentration, but lowering extracellular Cl- concentration reduced the conductance and shifted the reversal potential in a positive direction. The OR current was not affected by K+ channel blockers, but was reversibly blocked by the chloride channel blocker 4,4'-diisothiocyanato-2,2'-stilbenedisulphonate (DIDS), again indicating a Cl- conductance. The IRK current was also detected in the majority of cells using the conventional whole-cell recording configuration at room temperature. In contrast, the ORCl current was only observed in 7% of recordings made at room temperature with the conventional whole-cell voltage-clamp mode, but was detected in 66% of cells if the bath temperature was increased and the integrity of the cell's cytoplasm was preserved by using the perforated-patch technique. Under similar conditions, the ORCl current was also present in rat peritoneal mast cells, a connective tissue phenotype previously thought to have no whole-cell currents in the resting state. The role of this current and factors affecting its activation are discussed.

Canine leucocyte histamine release: response to antigen and to anti-IgE

Histamine release from canine leucocyte-enriched peripheral blood preparations was measured in atopic, non-atopic and artificially sensitised dogs after immunological challenge with D. farinae antigen and anti-IgE. Total cell histamine and spontaneous histamine release was also measured. The total cell histamine content of equal leucocyte preparations was not statistically significant between the atopic and non-atopic groups. At all dilutions of antigen a higher amount of histamine was released from the leucocytes of atopic dogs than was seen in the non-atopic group. No histamine release in response to D. farinae was seen in the sensitised dogs although a statistically significant increase in serum D. farinae-specific IgE could be demonstrated after sensitisation (P < 0.03). Histamine release in response to anti-IgE was significantly greater in the atopic dogs than the non-atopic dogs (P < 0.004) and the sensitised dogs (P < 0.003). There was no statistically significant difference in total serum IgE between the groups. The authors conclude that the leucocytes of atopic dogs have a greater tendency to release histamine than those of normal and artificially sensitised dogs and that this is independent of the concentration of total serum IgE or antigen-specific IgE. They suggest that there may be immunoregulatory abnormalities in atopic dogs intrinsic to the atopic state as is described in man.

Prospects for the immunological control of ruminant gastrointestinal nematodes: natural immunity, can it be harnessed?

Current understanding of the mucosal immune response to nematode parasites is briefly reviewed with emphasis on the role of the cytokines interleukins-4 and -12 and gamma interferon (IFN gamma) in the development of T-helper responses in rodents. Data from laboratory animals and ruminants indicate that the events associated with a T-helper 2 (Th2) cell response, notably IgE synthesis, eosinophilia and mucosal mastocytosis are protective. Evidence that effector mechanisms may vary for different parasite species is considered. Current gaps in understanding such as the location in the gut and mechanism of antigen processing and presentation as well as the relative contribution of non-immunological effector responses, such as gut motility and mucus secretion, to worm expulsion are discussed.

Rat bone marrow-derived mast cells co-cultured with 3T3 fibroblasts in the absence of T-cell derived cytokines require stem cell factor for their survival and maintain their mucosal mast cell-like phenotype

When cultured without fibroblasts, rat bone marrow-derived mast cells (BMMC) contain abundant rat mast cell proteinase type II (RMCP-II), and exhibit survival and proliferation when maintained in mesenteric lymph node conditioned medium (CM). When BMMC were co-cultured with 3T3 fibroblasts in the absence of CM, BMMC numbers increased for 7 days and the BMMC survived for up to 23 days. There was a gradual loss of stored RMCP-II in BMMC that were co-cultured with 3T3 cells, but the fibroblast microenvironment did not induce a detectable increase in the low levels of the connective tissue mast cell (CTMC)-associated proteinase, RMCP-I, in the BMMC. Nor did 3T3 cell co-culture induce significant heparin synthesis in BMMC as judged by the cells' reactivity with the fluorescent heparin-binding dye, berberine sulphate. These results suggest that rat BMMC, unlike murine BMMC, do not have the potential to develop multiple CTMC-like characteristics upon co-culture with 3T3 cells. However, when BMMC and fibroblast co-cultures were treated with an antibody to recombinant rat stem cell factor (rrSCF), mast cell survival was completely abrogated. This result suggests that endogenous, fibroblast-derived SCF is essential for the maintenance of rat BMMC viability in the absence of CM. On the other hand, prior treatment of the fibroblasts with the anti-rrSCF antibody did not affect the adherence of BMMC to the monolayer, implying that (an) other molecule(s) is(are) involved in the attachment process. The demonstration that rat BMMC survival on fibroblasts in vitro is dependent upon SCF may indicate an important mechanism by which tissue mucosal cells can be maintained in vivo in the absence of T-cell derived factors.

Stem cell factor enhances immunoglobulin E-dependent mediator release from cultured rat bone marrow-derived mast cells: activation of previously unresponsive cells demonstrated by a novel ELISPOT assay

Mucosal mast cells (MMC) are important effector cells in the immune response against gastrointestinal nematodes. We used cultured rat bone marrow-derived mast cells (BMMC) as an in vitro model of MMC to study the effects of the multifunctional cytokine stem cell factor (SCF) on immunoglobulin E (IgE)-dependent secretion of granule mediators. SCF (< or = 1000 ng/ml) was not a direct secretagogue for these cells, but it significantly enhanced IgE-mediated secretion of the granule constituents rat mast cell protease-II (RMCP-II) and beta-hexosaminidase from mature BMMC in a dose-dependent manner (> 10 ng/ml). Maximum up-regulation of secretion occurred after cells were pretreated with SCF (50 ng/ml) for 5 minutes before challenge with anti-IgE, but the effect then declined and was absent in cells incubated with the cytokine for 3 to 24 h. In a novel ELISPOT assay developed to identify individual BMMC secreting RMCP-II, the proportion of mature BMMC responding to anti-IgE was significantly increased by treatment with SCF. To investigate this effect further, the percentage release of RMCP-II and beta-hexosaminidase from populations of mature BMMC was directly compared to the proportion of individual cells releasing RMCP-II as detected by ELISPOT. The release of both mediators was enhanced by SCF, and the increased percentage release reflected both an increased proportion of secreting cells, and enhanced mediator release from individual cells. These results suggest that SCF can enhance IgE-dependent mediator release from BMMC not only by augmenting the secretory response from individual cells, but also by activating previously unresponsive cells.

Release of the mucosal mast cell granule chymase, rat mast cell protease-II, during anaphylaxis is associated with the rapid development of paracellular permeability to macromolecules in rat jejunum

The soluble granule chymase, rat mast cell protease-II (RMCP-II), is abundantly expressed in intestinal mucosal mast cells (MMC) but its function is not known. One hypothesis is that RMCP-II degrades the epithelial basement membrane and promotes the loss of enterocytes typically associated with type I hypersensitivity reactions in the rat. To test this hypothesis more directly, ex vivo perfusion of the cranial mesenteric artery and jejunal lumen was used to monitor the anaphylactic release of RMCP-II and its effects on mucosal permeability and epithelial integrity. Within 2 min of intravascular challenge with soluble adult Nippostrongylus brasiliensis worm antigen there was a 1,000-fold (P < 0.02) increase in the concentration of RMCP-II in the vascular perfusate from the jejunum of Nippostrongylus-sensitized rats but not the controls. Similarly, translocation of RMCP-II into the gut lumen increased 10-fold (P < 0.02) after 2 min only in worm antigen-challenged immune rats. Using an identical protocol, but incorporating Evans blue-labeled human serum albumin (EB-HSA) in the vascular perfusate, the timing of the release of RMCP-II into the two compartments was very similar to the first experiment and furthermore the translocation of EB-HSA increased 18-fold (P < 0.05) after 4 min in sensitized rats challenged with worm antigen. To examine the effects of RMCP-II more directly 1 mg of the highly purified chymase was introduced into the cranial mesenteric artery in ex vivo perfused normal rats. A significant (P < 0.05) 70-fold increase in concentration of RMCP-II in jejunal perfusate occurred after 6 min. In a repeat dose-response experiment, infusion of 0.375, 0.75, or 1.5 mg of RMCP-II, together with EB-HSA, established that the cumulative amounts of RMCP-II and EB-HSA translocated from the vasculature to the gut lumen in each perfusion (during the 10-min period of RMCP-II infusion) were significantly correlated. Analysis of intestinal perfusates by SDS-PAGE and by Western blotting using monoclonal anti-RMCP-II antibody confirmed that there was a concomitant translocation of both the protease and EB-HSA into the gut lumen. Histological evaluation of the mucosa failed to reveal any significant morphological change in any of the experiments. The rapid development of macromolecular leak, its association with the translocation of RMCP-II, and the absence of gross epithelial lesions, suggest for the first time that a mast cell granule chymase increases epithelial permeability via a paracellular route and implies that the substrate may be a protein, or proteins, in the epithelial junctional complex.

In vitro response of lymphocytes from bronchoalveolar lavage fluid and peripheral blood to mitogen stimulation during natural maedi-visna virus infection

To investigate the effects of maedi-visna virus (MVV) infection on cell-mediated immunity, the in vitro response of bronchoalveolar lavage fluid (BALF) and peripheral blood (BP) lymphocytes (PBL) to exogenous mitogen was analysed. BALF and PBL from control (n = 9) and MVV-infected (n = 7) animals were cultured fro 3 days in the presence and absence of concanavalin A (Con A). Lymphocyte expression of the interleukin-2 receptor (IL-2R) antigen, a parameter of lymphocyte activation, was quantified by dual-colour flow cytometry using the bovine anti-IL-2R monoclonal antibody IL-A111. IL-2R expression by lymphocytes in BALF and PB from control and MVV-infected animals, with and without Con A stimulation, were compared. In the absence of Con A stimulation, the proportion of cultured BALF CD8+ and gamma delta T cells expressing IL-2R was significantly (P < 0.05) lower for MVV-infected animals than for controls. After Con A stimulation the proportion of BALF CD4+ lymphocytes from MVV-infected animals that expressed IL-2R remained significantly (P < 0.05) lower than for controls. Comparisons within group showed that, after Con A stimulation, the proportion of all the T cell subsets in the control group expressing IL-2R, namely CD4+ (P < 0.001), CD8+ (P < 0.001) and gamma delta T cells (P < 0.05), was significantly increased. In the MVV-infected group, this increase was significant (P < 0.05) for CD4+ and CD8+ T cells, but not for gamma delta T cells. In vitro mitogen stimulation of PB T lymphocytes from both control and MVV-infected animals induced a significant elevation in the proportion of all T cell subsets expressing IL-2R when compared to cultured unstimulated control cells. However, there was considerable heterogeneity in the response to Con A of PB T cells from both groups of animals. The expression of IL-2R followed a different pattern to that of BALF lymphocytes, the proportion of unstimulated gamma delta / IL-2R+ T cells from MVV-infected animals being significantly (P < 0.05) higher than that of controls, and the proportion of cultured unstimulated CD8+ / IL-2R+ T cells from MVV-infected animals being significantly (P < 0.05) lower than that from controls. From these studies it can be concluded that the BALF T lymphocyte immune dysfunction observed during natural MVV infection, characterized by impaired IL-2R expression, is maintained under in vitro conditions.

Ovine mast cell heterogeneity is defined by the distribution of sheep mast cell proteinase

The presence or absence of the granule chymase, sheep mast cell proteinase (SMCP), was determined in trachea, bronchus, bronchial lymph node, lung, thymus, spleen, liver, flank skin, abomasum, duodenum, jejunum, ileum, colon and mesenteric lymph node by immunohistochemistry and by enzyme-linked immunosorbent assay using a polyclonal, affinity purified anti-SMCP antibody. Additionally, the presence of putative ovine mast cell subsets was investigated by comparing the number of mast cells identified histochemically (toluidine blue pH 0.5) with the number detected by immunostaining. The thymus had the greatest density of mast cells (225.7 +/- 23.4 cells mm-2, histochemically) and the highest concentration of SMCP (19.7 +/- 9.3 micrograms SMCP g-1 wet tissue). There was a high degree of correlation between toluidine blue and anti-SMCP cell counts for all tissues (r2 = 0.96, P < 0.001) with the exception of skin and liver. On the basis of reactivity to the anti-SMCP antibody, two populations of mast cells were defined, notably those in gastrointestinal tissues (analogs to the mucosal mast cell subset) and those present in skin (the putative ovine connective tissue mast cell subset). Ovine mast cell heterogeneity, resulting from differential expression of SMCP, was thus confirmed.

Quantitation of transforming growth factor-beta in plasma and pulmonary epithelial lining fluid of sheep experimentally infected with maedi-visna virus

A model of experimental infection with EV1, a lytic British isolate of maedi-visna virus (MVV), was developed. Ten Texel sheep were allocated to two groups and inoculated by the respiratory route with different inocula. Six of the animals received 10(7.2) TCID50 (tissue culture infective dose) of EV1 strain, while four sheep were sham-inoculated with identically prepared virus-free buffer solution. Experimental infection was followed for 8 weeks post-inoculation (PI), with development of precipitating antibodies to MVV developed in the MVV-inoculated animals during the first 4 weeks PI. Transforming growth factor-beta (TGF-beta) levels, in both bronchoalveolar lavage fluid supernatant and plasma samples, were measured. Concentrations of pulmonary epithelial lining fluid (PELF) TGF-beta were calculated. TGF-beta concentrations in PELF were approximately 165-fold higher than in plasma. No significant differences in the concentrations of plasma or PELF TGF-beta, either within or between groups, were observed.

Stem cell factor contributes to intestinal mucosal mast cell hyperplasia in rats infected with Nippostrongylus brasiliensis or Trichinella spiralis, but anti-stem cell factor treatment decreases parasite egg production during N brasiliensis infection

We assessed the effects of the c-kit ligand, stem cell factor (SCF), in the jejunal mucosal mast cell hyperplasia that occurs during infection with the intestinal nematodes, Nippostrongylus brasiliensis or Trichinella spiralis in rats. Compared with vehicle-treated rats, rats treated with SCF (25 micrograms/kg/d, intravenous [i.v.] for 14 days) during N brasiliensis infection exhibited significantly higher levels of the rat mucosal mast cell (MMC)-associated protease, rat mast cell protease II (RMCP II) in the jejunum and serum on day 8 of infection, but not on days 10 or 15 of infection. By contrast, in comparison to rats treated with normal sheep IgG, rats treated with a polyclonal sheep antirat SCF antibody exhibited markedly decreased numbers of jejunal MMCs, levels of jejunal RMCP II, and serum concentrations of RMCP II during infection with either nematode, particularly at the earlier intervals of infection (< or = day 10). Taken together, these findings indicate that SCF importantly contributes to MMC hyperplasia and/or survival during N brasiliensis or T spiralis infection in rats, but that levels of endogenous SCF are adequate to sustain near maximal MMC hyperplasia during infection with these nematodes. Notably, treatment of rats with SCF somewhat increased, and treatment with anti-SCF significantly decreased, parasite egg production during N brasiliensis infection. This finding raises the interesting possibility that certain activities of intestinal MMCs may contribute to parasite fecundity during infection with this nematode.

What's in a name? The MMPI-2 PTSD scales

The MMPI-2 post-traumatic stress disorder scales (PK and PS) were examined with a sample of 96 outpatient anxiety disorder and 97 outpatient traffic accident subjects. PK and PS correlated .96 and showed highly similar correlations with MMPI-2 validity, clinical, content and supplementary scales for both groups, which indicated that these scales are indices of MMPI first-factor variance. This was supported by separate principal components analyses for each group, in which PK and PS contributed the most variance to the first component. Although the groups showed different MMPI-2 mean profiles, neither PK nor PS contributed to discriminant function classification of group members. It is suggested that PK and PS are indices of general emotional distress and maladjustment; implications for their use in diagnosing post-traumatic stress disorder were discussed.

Basal secretion and anaphylactic release of rat mast cell protease-II (RMCP-II) from ex vivo perfused rat jejunum: translocation of RMCP-II into the gut lumen and its relation to mucosal histology

The kinetics of the release of rat mast cell protease-II (RMCP-II) from mucosal mast cells in the jejunum of Nippostrongylus brasiliensis primed (immune) rats was investigated using ex vivo perfusion of a segment of jejunum through the cranial mesenteric artery. The aim of the study was to assess the role of the protease in anaphylaxis and in particular to ascertain whether it is responsible for the histological changes, which include widespread epithelial shedding, seen in the mucosa in in vivo models of anaphylaxis. Perfusion of the jejunal vasculature with a Krebs-Ringer buffer showed that there was basal secretion of RMCP-II by jejunal mast cells in all rats studied. The baseline concentration of RMCP-II was significantly greater (p < 0.05) in immune rats (> 7 ng/ml) previously exposed to nippostrongylus infection than in control, naive animals (< 2 ng/ml). Challenge of immune rats with 100 or 400 worm equivalents of whole worm antigen resulted in an immediate (within 40 seconds) and significant (p < 0.02) increase in the concentration of RMCP-II (to > 3 micrograms/ml) in the vascular perfusate, which was not seen in naive rats or immune rats challenged with an irrelevant antigen. Greater amounts of RMCP-II were also recovered from the jejunal lumen of immune rats compared with naive rats after challenge of both groups with worm antigen. Despite the release of microgram quantities of RMCP-II into the gut lumen and vascular perfusate, however, there were no significant changes seen in the mucosal histology. These results suggest that RMCP-II alone is not responsible fore the loss of gut epithelium seen during anaphylaxis in the rat.

Mast cell tryptase levels in normal canine tissues

Levels of canine tryptase from various tissues were quantified using a competition enzyme-linked immunosorbent assay (ELISA). The assay utilises an affinity-purified rabbit anti-tryptase antibody in the solid phase and alkaline-phosphatase conjugated tryptase together with unlabelled tryptase in the fluid phase. The assay will rapidly quantify 40-5000 ng ml-1 of tryptase in tissue extracts. Tissues from the skin, gut, liver and lung were studied, of which canine gut appeared to contain the highest levels of tryptase per milligram wet weight, which may suggest an important role for this enzyme at this site. This assay may prove valuable in assessing the role of mast cells in various disease states in the dog.

Development of a three-scale MMPI: the MMPI-TRI

A 60-item short form of the MMPI with very high content validity and items that appear on both the MMPI and MMPI-2 was developed and named the MMPI-TRI. It contains three 20-item scales--the Subjective Distress, Acting-Out, and Psychosis scales. These three scales have excellent internal consistency and sufficient independence from each other. An anxiety and depression group of patients, prison inmate group, and a schizophrenic and other psychotic group had the highest mean scores on Subjective Distress, Acting-Out, and Psychosis, respectively. Correlations with the 13 regular scales of the MMPI and MMPI-2, their content and supplementary scales, and four other psychometric instruments provided very strong evidence for validity. Norms are provided.