Rapidly changing perspectives about mast cells at mucosal surfaces

Summary: Mast cells (MCs) are major effector cells of immunoglobulin E (IgE)‐mediated allergic inflammation. However, it has become increasingly clear that they also play important roles in diverse physiological and pathological processes. Recent advances have focused on the importance of MCs in both innate and adaptive immune responses and have fostered studies of MCs beyond the myopic focus on allergic reactions. MCs possess a variety of surface receptors and may be activated by inflammatory mediators, IgE, IgG, light chains, complement fragments, proteases, hormones, neuropeptides, and microbial products. Following activation, they produce a plethora of pro‐inflammatory mediators and participate in inflammatory reactions in many organs. This review focuses on the role of MCs in inflammatory reactions in mucosal surfaces with particular emphasis on their role in respiratory and gastrointestinal inflammatory conditions.     

Anti-inflammatory effect of β2-agonists: Inhibition of TNF-α release from human mast cells

β₂-Agonists inhibit the release of preformed mediators such as histamine and newly synthesized mediators such as prostaglandin D₂ from mast cells. However, although mast cells have been identified as an important source of several cytokines including tumor necrosis factor-α (TNF-α), there is no information about their regulation by β₂-agonists. Thus given the importance of TNF-α in inflammation and the widespread use of β₂-agonists, we investigated the effect of long-acting (salmeterol) and short-acting (salbutamol) β₂-agonists on the secretion of TNF-α from human skin mast cells. Treatment of mast cells with salmeterol or salbutamol (100 nmol/L) inhibited the IgE-dependent release of TNF-α (82% and 74%, respectively). Moreover, 2-hour treatment with salmeterol, isoproterenol, or salbutamol inhibited mast cell cytotoxicity against a TNF-α–sensitive cell line, WEHI-164, with an IC₅₀ of 71, 50, and 29 nmol/L, respectively. Specificity for β-adrenergic receptors was shown with propranolol. The inhibitory effect of β₂-agonists was observed after only 20 minutes of treatment but was lost by 24 hours after removal of salbutamol and isoproterenol (7% and 11% inhibition remaining, respectively). In contrast, the inhibition of TNF-α release was increased 1 hour after removal of salmeterol and remained significant 24 hours later. Furthermore, β₂-agonists did not show tachyphylaxis for the inhibition of TNF-α release. Thus selective β₂-agonists demonstrate anti-inflammatory activity by inhibiting the release of TNF-α from mast cells stimulated through their IgE receptor or by a tumor target cell. This inhibitory effect of β-agonists may be important in their mode of action in the treatment of allergic diseases. (J Allergy Clin Immunol 1997;100:825-31.)     

The supraepitrochlear process of the humerus

On the basis of five cases of supraepitrochlear process of the humerus the authors recall the most significant anatomical and clinical aspects of the disease. The presence of clinical symptoms, going under the name of Struthers syndrome, indicates surgical removal.     

A myofibroblast–mast cell–neuropeptide axis of fibrosis in post‐traumatic joint contractures: An in vitro analysis of mechanistic components

Previous studies have implicated a myofibroblast–mast cell–neuropeptide axis of fibrosis in pathologic joint capsules from post‐traumatic contractures. The hypothesis to be tested is that joint capsule cells (JC) from human elbows with post‐traumatic contractures and their interactions with mast cells (MC) and neuropeptides in the microenvironment underlie the pathogenesis of contractures. The hypothesis was tested using an in vitro collagen gel contraction model. The JC were isolated from human elbow capsules and mixed with neutralized PureCol collagen I. The gels were treated in various ways, including addition of MC (HMC‐1), the neuropeptide substance P (SP), an NK₁ receptor (SP receptor) antagonist RP67580 and the mast cell stabilizer ketotifen fumarate (KF). The collagen gels were released from the wells and gel size (contraction) was measured optically at multiple time points. The JC contracted collagen gels in a dose‐dependent manner. This was enhanced in the presence of MC and increased further with SP. Increasing concentrations of the SP receptor antagonist, RP67580 or the mast cell stabilizer, KF decreased the magnitude of contraction. These observations identify putative mechanistic components of a myofibroblast–mast cell–neuropeptide axis of fibrosis in the joint capsules in post‐traumatic contractures and potential prophylactic or therapeutic interventions. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1290–1296, 2014.     

Epidemiology of all-complaint injuries in youth basketball

This study evaluated the incidence and characteristics of all-complaint injuries, including acute and overuse injuries, in female and male youth basketball players. A total of 518 players (16 ± 1.4 years; 38.6% females), from 63 teams, participated in this prospective cohort study. Players were observed through one competitive high school or club basketball season to record exposure and all-complaint injuries, defined as any complaint resulting from participating in basketball-related activities, including but irrespective of the need for medical attention or time loss. Injury incidence rates and rate ratios were derived from Poisson's regression with 99.4% CI (Bonferroni's correction for multiple comparisons). The overall injury incidence rate was 14.4 (99.4% CI: 12.2-17.0) injuries/1000 h; 13.8 (99.4% CI: 11.2-16.8) in females and 14.8 (99.4% CI: 11.7-18.8) in males. While the incidence of injury was similar across injury classifications for female and male players, a potential lower overuse knee injury rate was noted for females vs males [IRR = 0.61 (99.4% CI: 0.34-1.07)]. The most commonly injured body location was the ankle (45%) in females and the knee (51%) in males. Overuse (vs acute) injuries were about 2x more common in the knee while acute (vs overuse) injuries were about 3x more common in the ankle, overall, and for female and male players. Based on an all-complaint injury definition, injury rates in competitive female and male youth basketball players are much higher than previously reported. This study provides an evidence base to inform more tailored interventions to reduce injuries in youth basketball.     

Serotonergic fiber sprouting to external anal sphincter motoneurons after spinal cord contusion

The present study analyzed the anatomical plasticity of serotonergic immunoreactive projections to external anal sphincter (EAS) motoneurons, and the behavioral plasticity of EAS reflexes, penile erection, and locomotion in rats with spinal contusion injury (SCI) or complete spinal cord transection (TX). Electromyographic activity of the EAS, penile erection latency, and BBB locomotor score exhibited parallel recovery over the 6-week recovery period after contusion SCI. This pattern of recovery was not observed in TX animals. While locomotor scores demonstrated a small increase after TX, erectile and anorectal function remained at abnormal levels established immediately after injury. Serotonergic immunofluorescent (5-HT-IF) staining at the lesion site identified a small number of fibers spared after SCI that may provide a substrate for functional recovery. Pixel density measurements of 5-HT-IF in the vicinity of retrogradely labeled EAS and unlabeled pudendal motoneurons necessary for penile erection provide indirect evidence of serotonergic sprouting that parallels the observed functional recovery in animals with SCI. No 5-HT-IF was detected caudal to the injury site in TX animals. These studies indicate: (1) lumbosacral eliminative and reproductive reflexes provide a valid means of studying the mechanisms of post-SCI plasticity; (2) the similar recovery curves suggest similar return of descending control, perhaps through sprouting of descending serotonergic fibers; (3) the observed deficits after TX likely represent the permanent removal of descending inhibition and reflect reorganization of segmental circuitry.     

Frontline: Inhibition of allergen-induced pulmonary inflammation by the tripeptide feG: a mimetic of a neuro-endocrine pathway

Interactions between the neuro-endocrine system and immune system help maintain health. One interaction involves the superior cervical ganglia (SCG), which regulate the prohormone submandibular rat 1 (SMR1) produced by the submandibular gland (SMG). A peptide derived from SMR1, feG, has anti-inflammatory activity, and modification to D-isomer feG enhances bioactivity. We tested feG as a therapeutic agent for airways inflammation, using rats sensitized by OVA or Nippostrongylus brasiliensis (Nb). Treatment with feG but not fdG down-regulated OVA-challenge-induced increases in bronchoalveolar lavage (BAL)-derived macrophages, eosinophils and PMN (neutrophils) by 44%, 69% and 67%, respectively, at 24 h. We found that feG also reduced ICAM-1 on BAL-derived macrophages and eosinophils by 27% and 65%, and L-selectin on PMN by 55% following OVA challenge. Furthermore, feG but not fdG reduced the OVA-induced TNF increase in BAL fluid. We showed that feG also down-regulated both hyper-responsiveness to methacholine (by 27%) and microgranulomata formation in the lung parenchyma. In Nb-challenged rats, feG treatment inhibited ex vivo allergen-induced contraction of tracheal smooth muscle by up to 73%. In conclusion, feG, which is a mimetic of a peptide derived from a rat salivary gland prohormone, has anti-inflammatory properties in allergic airways inflammation in Brown-Norway rats. The role of the SCG-SMG neuro-endocrine pathway in allergic asthma and other inflammatory diseases requires additional study.     

Mast cell heterogeneity: two-dimensional gel electrophoretic analyses of rat peritoneal and intestinal mucosal mast cells

Peritoneal mast cells (PMC) and intestinal mucosal mast cells (IMMC) were purified from rats infected with the nematode Nippostrongylus brasiliensis. Overall protein constituents of both mast cell subtypes were analyzed by two-dimensional gel electrophoresis using either nonequilibrium pH gradient electrophoresis (NEPHGE) or isoelectric focusing (IEF) in the first dimension and SDS-PAGE (10%) in the second dimension followed by silver staining. PMC had seven dominant basic proteins (PB2-8; pI 9-9.5) with estimated molecular masses of 26 to 37 kDa, as well as 80 to 90 neutral or acidic proteins, most of which had pI 6 to 7.5 and estimated molecular masses of 20 to 100 kDa. All the basic proteins were granule-associated. Three basic proteins, PB6 (29 kDa), PB7 (28 kDa) and PB8 (RMCP I, 26 kDa), bound [3H]diisopropyl fluorophosphate (DFP), suggesting that they are serine proteases. However, only PB8 was reactive with antibodies to RMCP I. Another basic component (less than 14 kDa), perhaps a degradation product of PB6, PB7 or PB8, also bound [3H]DFP. By comparison, IMMC possessed nine basic proteins (IB1-9) and, in general, they were more acidic (pI about 8.5-9) than those of PMC. Four major basic proteins (IB6-9) were all 24 kDa but were slightly different in isoelectric points. These and another 46-kDa basic component (IB2) were reactive with antibodies to RMCP II and bound [3H]DFP. There were no other DFP-binding proteins in IMMC. In spite of remarkable differences between basic granule-associated proteins in PMC and basic proteins in IMMC, spots in the neutral-acidic range were for the most part similar in the two mast cell subsets, although quantitative differences were evident for some spots. Thus, rat mast cell populations from the peritoneal cavity and intestinal mucosa exhibit marked heterogeneity in their protein constituents with basic pI, including in their granule-associated proteins with serine protease activity.     

Interferon-γ regulates the interaction of RBL-2H3 cells with fibronectin through production of nitric oxide

Interferon-gamma (IFN-gamma) is an important regulatory cytokine in cell proliferation, differentiation, adhesion, mediator release, and gene induction. This diversity of effector roles is achieved by a variety of incompletely understood mechanisms. In the mast cell (MC), IFN-gamma downregulates mediator synthesis and secretion. The present study demonstrates and characterizes for the first time IFN-gamma inhibition of adhesion of the MC analogue RBL-2H3 to the extracellular matrix protein fibronectin (FN). Inhibition requires preincubation of the cells with IFN-gamma for 20 hr, and is statistically significant at 100 U/ml IFN-gamma. Flow cytometry indicates that cell surface expression of very late antigen-4 (VLA-4), VLA-5, and the vitronectin receptor (VNR) remain constant following IFN-gamma treatment, indicating the inhibitory effect of IFN-gamma on adhesion to FN is not achieved through a reduction in integrin receptors for FN. Fluorescent labelling with Texas red phalloidin demonstrated rearrangement of the actin cytoskeleton in response to IFN-gamma was not significant. The tyrosine phosphatase inhibitor vanadate, and the nitric oxide (NO) synthase inhibitor L-NAME, reduced the IFN-gamma effect on adhesion to FN by 62 and 70%, respectively, demonstrating that the IFN-gamma effect is dependent upon the production of NO, potentially though a tyrosine phosphatase dependent mechanism. The NO donors sodium nitroprusside and S-nitrosoglutathione mimicked the effect of IFN-gamma. Thus, following stimulation with IFN-gamma, NO plays an autocrine role in the MC, and is able to modulate integrin function. This adds to the pathways NO is able to inhibit in the mast cell, shows that endogenous NO is able to inhibit these pathways, and suggests NO is impinging upon an element common to many signalling mechanisms in the MC.     

Platelet-activating factor synthesis by peritoneal mast cells and its inhibition by two quinoline-based compounds.

1. Peritoneal mast cells from rat were co-incubated in vitro in a platelet aggregometer cuvette with washed rabbit platelets. In response to stimulation with calcium ionophore (A23187; 1-5 microM), the mast cells released a substance which stimulated the platelets to aggregate. These concentrations of ionophore did not stimulate platelet aggregation in the absence of mast cells, nor affect the responsiveness of the platelets to aggregation induced by thrombin or PAF. Release of a PAF-like substance was also observed in response to stimulation of the mast cells with antigen. 2. This pro-aggregatory activity is attributable to the release of PAF by the mast cells, since the activity could be abolished by preincubating the platelets with a specific PAF receptor antagonist (WEB 2086; 10 microM). Furthermore, the platelet-aggregating factor co-migrated with PAF on thin-layer chromatographs and could be abolished by incubation with phospholipase A2 (20 micrograms ml-1) or a specific antibody directed against PAF. 3. The release of PAF by peritoneal mast cells could be inhibited, in a concentration-dependent manner, by PF-5901 (IC50 of 3.9 microM) or Wy-50,295 (IC50 of 1.2 microM), two structurally similar compounds with inhibitory effects on leukotriene synthesis, as well as leukotriene D4 (LTD4) receptor antagonist properties. 4. Inhibition of PAF synthesis was not observed when the mast cells were incubated with a structurally unrelated 5-lipoxygenase inhibitor (A-64077), a structurally dissimilar inhibitor of 5-lipoxygenase activating protein (MK-886) or with a structurally related LTD4 receptor antagonist (MK-571) which lacks inhibitory effects on leukotriene synthesis, each at concentrations of up to 100 microM.(ABSTRACT TRUNCATED AT 250 WORDS)