Serum concentrations of mast cell tryptase are reduced in heavy drinkers

BACKGROUND

Baseline serum tryptase concentrations are commonly used in clinical practice as a marker of the body's mast cell burden. This study aimed to investigate serum tryptase concentrations in heavy drinkers.

METHODS

Serum tryptase concentrations were determined in 126 heavy drinkers (75% males, median age 47 years) who were admitted to the hospital because of alcohol withdrawal syndrome (n = 60), general symptoms with abnormalities on biochemical tests that indicated acute liver disease (n = 19), complications of advanced liver disease (n = 33), and miscellaneous reasons (n = 14). Results were compared with those of 70 healthy controls (66% males, median age 40 years).

RESULTS

Serum tryptase concentrations were lower in heavy drinkers than in healthy controls (median 2.23 μg/l vs. median 3.25 μg/l, p < 0.001). Ten heavy drinkers (7.9%) had undetectable (<1 μg/l) serum tryptase levels versus none of the healthy controls (p = 0.01). The association of low tryptase levels with heavy drinking was independent of age, gender, and smoking status. Among heavy drinkers, the lowest tryptase concentrations were observed in patients with alcohol withdrawal syndrome and patients with general symptoms with abnormalities on biochemical tests that indicated acute liver disease. Furthermore, serum tryptase concentrations were negatively correlated with markers of acute liver damage or alcohol consumption (serum aspartate aminotransferase and gamma-glutamyl transferase). Atopy (skin prick test positivity) was not associated with serum tryptase concentrations in heavy drinkers.

CONCLUSIONS

Serum concentrations of mast cell tryptase are lower in heavy drinkers than in healthy controls.

Anaphylaxis to chemotherapy and monoclonal antibodies

Hypersensitivity reactions are increasingly prevalent, although underrecognized and underreported. Platins induce immunoglobulin E-mediated sensitization; taxenes and some monoclonal antibodies can induce reactions at first exposure. Severe hypersensitivity can preclude first-line therapy. Tryptase level at the time of a reaction is a useful diagnostic tool. Skin testing provides a specific diagnosis. Newer tests are promising diagnostic tools to help identify patients at risk before first exposure. Safe management includes rapid drug desensitization. This review provides information regarding the scope of hypersensitivity and anaphylactic reactions induced by chemotherapy and biological drugs, as well as diagnosis, management, and treatment options.

Mast cell activation syndromes presenting as anaphylaxis

Anaphylaxis results from severe systemic mast cell activation. In addition to IgE-mediated and physical triggers, it may occur with a clonal mast cell disease and in an idiopathic fashion without clear provoking factors. Disorders of mast cell activation are classified into primary (clonal), secondary, and idiopathic. Mast cell activation syndrome (MCAS) is a multisystem disorder characterized by objective documentation of elevated mast cell mediators during attacks and a favorable response to antimediator therapy. It should be considered in the differential diagnosis of patients presenting with recurrent anaphylaxis without a clear cause. This article discusses the diagnosis of MCAS.

Response of patients with indolent systemic mastocytosis to tamoxifen citrate

We examined whether tamoxifen citrate at 20mg/day for 1 year had a beneficial effect on laboratory findings, bone marrow mastocytosis, common clinical symptoms, or quality-of-life assessment for 5 women and 2 men with indolent systemic mastocytosis. Tamoxifen was well tolerated. We found significant reductions in the platelet count, serum alkaline phosphatase, and 24-h urinary excretion of N-methylhistamine and significant increases in serum lactate dehydrogenase and (excluding 2 patients taking aspirin) in 24-h urinary excretion of 11β-prostaglandin F2α. Overall, no change occurred in percent involvement of bone marrow by mastocytosis. Symptom scores were mild and did not change during the treatment. The 36-Item Short Form Health Survey scores for quality of life physical and mental components showed no marked changes. Tamoxifen, an older, nonhematotoxic medication, has limited activity in systemic mastocytosis at the dosage used in this study.

Urinary 11β-PGF2α and N-methyl histamine correlate with bone marrow biopsy findings in mast cell disorders

BACKGROUND

The utility of measuring histamine and prostaglandin metabolites in the urine of patients with mastocytosis has not been critically examined in a large series of patients. This study examined the relationship between the extent of increase in urinary excretion of 11β-prostaglandinF2α and N-methyl histamine, with serum tryptase, whole blood serotonin, and bone marrow findings including morphology, percentage involvement, and abnormal mast cell phenotype.

METHODS

This was a retrospective analysis of 90 patients who were continuously enrolled in the study for a period of 6 years (2008-2014). We recorded serum tryptase, whole blood serotonin, levels of urinary mast cell metabolites 11β-prostaglandinF2α and N-methyl histamine (NMH), and bone marrow findings.

RESULTS

Urinary mast cell metabolites 11β-prostaglandinF2α and N-methyl histamine correlated with levels of serum tryptase, mast cell burden in the bone marrow, the presence of mast cell aggregates, and atypical mast cells on bone marrow biopsy. Whole blood serotonin did not have a significant correlation with the serum tryptase or mast cell burden in the bone marrow. Urinary NMH was significantly different between c-kit D816V-positive and c-kit D816V-negative patients, while 11β-prostaglandinF2α was not. Urinary 11β-prostaglandinF2α 24-h excretion >3500 ng and NMH levels >400 μg/gm Cr corresponded with the high degree of bone marrow biopsies positive for atypical mast cells, the presence of aggregates, and c-kit mutation.

CONCLUSIONS

Easily obtained and quantified urinary metabolites of histamine (greater than twice the upper limit of normal) and prostaglandin D2 (>3.4 times the upper limit of normal) correlate well with bone marrow findings of mastocytosis.

Pharmacological Activities and Hydrolysis by Peptidases of [Phospho-Ser(6)]-Bradykinin (pS(6)-BK)

Phosphorylated kininogen and some of its fragments containing serine phosphorylated bradykinin ([pS(6)]-Bk) were identified in human serum and plasma by a phosphoproteomic approach. We report the kininogenase ability of human tissue and plasma kallikreins and tryptase to generate [pS(6)]-Bk or Lys-[pS(6)]-Bk having as substrate the synthetic human kininogen fluorescent fragment Abz-MISLMKRPPGF[pS(386)]PFRSSRI-NH2. The pharmacological assays of [pS(6)]-Bk showed it as a full B2 bradykinin receptor agonist in smooth muscle, it produces a portal liver hypertensive response in rat and mouse paw edema that lasts longer than Bk. The rat hypotensive response to infusions of Bk is greater than that of [pS(6)]Bk, both if injected through femoral vein or aorta. [pS(6)]-Bk was more resistant than Bk to kininase digestion performed with angiotensin converting enzyme, neprilysin, thimet oligopeptidase, aminopeptidase P and carboxypeptidase M. (1)H-NMR experiments indicated that [pS(6)]-Bk has lower flexibility, with the pS(6)-P(7) bond restricted to the trans conformation, and can explain [pS(6)]-Bk resistance to hydrolysis. In conclusion, [pS(6)]-Bk presenting lower activity than Bk, with longer lasting effects and being slowly released by kininogenases from synthetic Abz-MISLMKRPPGF[pS(386)]PFRSSRI-NH2, suggests that phosphorylation of the kininogens can be an efficient kallikrein-kinin system regulator.

Serum tryptase detected during acute coronary syndrome is significantly related to the development of major adverse cardiovascular events after 2 years

BACKGROUND

One of the greatest challenges in cardiovascular medicine is to define the best tools for performing an accurate risk stratification for the recurrence of ischemic events in acute coronary syndrome (ACS) patients.

METHODS

We followed 65 ACS patients enrolled in a previous pilot study for 2 years after being discharged, focusing on the occurrence of major adverse cardiovascular events (MACE). The relationship between serum tryptase levels on admission, SYNergy between percutaneous coronary intervention with the TAXUS drug-eluting stent and the cardiac surgery score (SX-score), cardiovascular complexity and MACE at 2 years follow-up were analyzed.

RESULTS

The ACS population was divided in two groups: patients with MACE (n = 23) and patients without MACE (n = 42). The tryptase measurement at admission (T0) and at discharge (T3) and SX-score were higher in patients who experienced MACE than in those without (p = 0.0001, p < 0.0001 and p = 0.006, respectively). Conversely, we found no significant association between MACE and C-reactive protein (CRP), and between MACE and maximum level of high-sensitivity troponin (hs-Tn) values. Among all patients with MACE, 96% belonged to the group that presented with cardiovascular complexity at the beginning of ACS index admission (p < 0.0001). The predictive accuracy of serum tryptase for MACE at follow up set at the cut-off point of 4.95 ng/ml at T0 and of 5.2 ng/ml at T3. Interestingly, patients with both the above cut-off tryptase values at T0 and at T3 presented a 1320% increase in the odds of developing MACE (p < 0.0001).

CONCLUSION

In ACS patients, serum tryptase measured during index admission is significantly correlated to the development of MACE up to 2 years, demonstrating a possible long-term prognostic role of this biomarker.

[Vulvar oedema revealing systemic mastocytosis]

BACKGROUND

Systemic mastocytosis is characterised by abnormal proliferation of mast cells in various organs. We report an original case of systemic mastocytosis revealed by vulvar oedema.

PATIENTS AND METHODS

A 24-year-old patient was examined in the dermatology department for vulvar oedema appearing during sexual intercourse. She presented vasomotor dysfunction of the lower limbs, urticaria on the trunk on exertion, diarrhoea and bone pains. Laboratory tests showed serum tryptase of 29.7μg and plasma histamine at twice the normal value. Myelogram results showed infiltration by dysmorphic mast cells. Screening for c-kit D816V mutation was positive. Duodenal biopsies revealed mast-cell clusters with aggregation involving over 15 mast cells. CD2 staining was inconclusive and CD25 staining could not be done. Trabecular osteopenia was found, and we thus made a diagnosis of indolent systemic mastocytosis (ISM variant Ia) as per the WHO 2008 criteria. Symptomatic treatment was initiated (antiH1, H2, antileukotrienes) and clinical and laboratory follow-up was instituted.

DISCUSSION

The cutaneous signs leading to diagnosis in this patient of systemic mastocytosis involving several organs were seemingly minimal signs associated with mastocyte degranulation. This is the third recorded case of mastocytosis revealed by vulvar oedema and the first case revealing systemic involvement. The two previously reported cases of vulvar oedema revealed cutaneous mastocytosis alone. Mastocytosis, whether systemic or cutaneous, must be included among the differential diagnoses considered in the presence of vulvar oedema.

Vascular endothelial growth factor and tryptase changes after chemoembolization in hepatocarcinoma patients

AIM: To evaluate vascular endothelial growth factor (VEGF) and tryptase in hepatocellular cancer (HCC) before and after trans-arterial chemoembolization (TACE).

METHODS: VEGF and tryptase serum concentrations were assessed from 71 unresectable HCC patients before and after hepatic TACE performed by binding DC-Beads^® to doxorubicin. VEGF levels were examined for each serum sample using the Quantikine Human VEGF-enzyme-linked immuno-absorbent assay (ELISA), whereas tryptase serum concentrations were assessed for each serum sample by means of fluoro-enzyme immunoassay (FEIA) using the Uni-CAP100 tool. Differences between serum VEGF and tryptase values before and after TACE were evaluated using Student t test. Person's correlation was used to assess the degree of association between the two variables.

RESULTS: VEGF levels and serum tryptase in HCC patients before TACE had a mean value and standard deviation (SD) of 114.31 ± 79.58 pg/mL and 8.13 ± 3.61 μg/L, respectively. The mean levels and SD of VEGF levels and serum tryptase in HCC patients after TACE were 238.14 ± 109.41 pg/mL and 4.02 ± 3.03 μg/L. The changes between the mean values of concentration of VEGF and tryptase before treatment and after treatment was statistically significant (P < 0.000231 and P < 0.00124, by Wilcoxon-Mann-Whitney respectively). A significant correlation between VEGF levels before and after TACE and between tryptase levels before and after TACE was demonstrated (r = 0.68, P = 0.003; r = 0.84, P = 0.000 respectively).

CONCLUSION: Our pilot results suggest that the higher serum VEGF levels and the lower tryptase levels following TACE may be potential biomarkers changing in response to therapy.

Mast cell proteases as pharmacological targets

Mast cells are rich in proteases, which are the major proteins of intracellular granules and are released with histamine and heparin by activated cells. Most of these proteases are active in the granule as well as outside of the mast cell when secreted, and can cleave targets near degranulating mast cells and in adjoining tissue compartments. Some proteases released from mast cells reach the bloodstream and may have far-reaching actions. In terms of relative amounts, the major mast cell proteases include the tryptases, chymases, cathepsin G, carboxypeptidase A3, dipeptidylpeptidase I/cathepsin C, and cathepsins L and S. Some mast cells also produce granzyme B, plasminogen activators, and matrix metalloproteinases. Tryptases and chymases are almost entirely mast cell-specific, whereas other proteases, such as cathepsins G, C, and L are expressed by a variety of inflammatory cells. Carboxypeptidase A3 expression is a property shared by basophils and mast cells. Other proteases, such as mastins, are largely basophil-specific, although human basophils are protease-deficient compared with their murine counterparts. The major classes of mast cell proteases have been targeted for development of therapeutic inhibitors. Also, a human β-tryptase has been proposed as a potential drug itself, to inactivate of snake venins. Diseases linked to mast cell proteases include allergic diseases, such as asthma, eczema, and anaphylaxis, but also include non-allergic diseases such as inflammatory bowel disease, autoimmune arthritis, atherosclerosis, aortic aneurysms, hypertension, myocardial infarction, heart failure, pulmonary hypertension and scarring diseases of lungs and other organs. In some cases, studies performed in mouse models suggest protective or homeostatic roles for specific proteases (or groups of proteases) in infections by bacteria, worms and other parasites, and even in allergic inflammation. At the same time, a clearer picture has emerged of differences in the properties and patterns of expression of proteases expressed in human mast cell subsets, and in humans versus other mammals. These considerations are influencing prioritization of specific protease targets for therapeutic inhibition, as well as options of pre-clinical models, disease indications, and choice of topical versus systemic routes of inhibitor administration.

Perioperative anaphylactic reactions: Review and procedure protocol in paediatrics

Perioperative anaphylactic reactions are immediate, hypersensitive reactions that are potentially life-threatening resulting from a sudden release of mediators from mast cells and basophiles, due to either immune (IgE or non-IgE mediated) or non-immune mechanisms. The most frequent causing agents are neuromuscular blocking agents (NMBAs), latex and antibiotics, with latex being the first cause in paediatrics. With regard to perioperative anaphylactic reactions, the usual early signs and symptoms of an anaphylactic reaction could be overlooked or erroneously interpreted and non-severe anaphylaxis could go undetected, with a risk of more severe reactions in the future. Using the data registered on the anaesthesia sheet, it is essential to establish a chronological relationship between drugs and/or substances administered and the reaction observed. An elevated level of tryptase confirms an anaphylactic reaction, but this does not usually increase in the absence of compromised circulation. An allergy study should be carried out preferably between 4 and 6 weeks after the reaction, using a combination of specific IgE, skin and controlled exposure tests (if indicated). Test sensitivity is good for NMBAs, latex, antibiotics, chlorhexidine, gelatine and povidone, and poor for barbiturates, opiates (these can give false positives since they are histamine releasers) and benzodiazepines. Special preventive measures should be taken, especially in the case of latex. We present the maximum concentrations recommended for skin tests, the recommended dosage to treat anaphylactic reactions in paediatrics and a procedure algorithm for the allergological study of these reactions.

Immunohistochemical Expression of Mast Cell in Oral Reactive Lesions

STATEMENT OF THE PROBLEM

Soft tissue reactive lesions are the most common lesions of the oral cavity. Although many studies have shown the interaction of mast cells with fibroblasts and their participation in fibrosis, the role of mast cells in these lesions is not well understood.

PURPOSE

The aim of this study was to evaluate the mast cells (MCs) count in oral soft-tissue reactive lesions including peripheral giant cell granuloma (PGCG), peripheral ossifying fibroma (POF), irritation fibroma (IF) and normal oral mucosa.

MATERIALS AND METHOD

In this cross-sectional study, 50 samples including IF, PGCG, POF (14 cases for each group) and 8 cases of normal oral mucosa were stained with tryptase antibody through immunohistochemistry. The number of mast cells was counted in 5HPF containing maximum counts for each section stained with tryptase. Statistical analysis including Chi-square test and Tukey test with a significance level of 0.05 were considered.

RESULTS

The number of MCs was found to have increased in reactive lesions compared with normal oral mucosa. MCs count in the POF group was higher than the others.

CONCLUSION

These findings suggest a possible role of mast cells in the pathogenesis of reactive oral lesions and induction of fibrous tissues. Chemical mediators released from mast cells might influence other cells, especially fibroblasts, to induce fibrosis.

Perioperative anaphylaxis: diagnosis, evaluation, and management

Perioperative anaphylaxis can occur during or after surgery and can have life-threatening consequences. As anesthesia protocols become more complex and incorporate multiple agents to regulate physiologic processes intraoperatively, perioperative anaphylaxis is becoming increasingly recognized. The allergist should obtain detailed records from the anesthesiologist in order to perform appropriate testing to identify the likely causative agents. Testing should ideally be performed 4 to 6 weeks after the reaction to account for a refractory period after mast cell activation. This article includes 2 cases of perioperative anaphylaxis and reviews the historical elements that must be considered after a reaction has occurred.

Refractory intraoperative hypotension with elevated serum tryptase

Severe intraoperative hypotension has been reported in patients on angiotensin-converting enzyme inhibitors and angiotensin II receptor subtype 1 antagonists. We describe a patient on lisinopril who developed refractory intraoperative hypotension associated with increased serum tryptase level suggesting mast cell activation (allergic reaction). However, allergology workup ruled out an allergic etiology as well as mastocytosis, and hypotension recalcitrant to treatment was attributed to uninterrupted lisinopril therapy. Elevated serum tryptase was attributed to our patient's chronic renal insufficiency.

Mastocytosis: immunophenotypical features of the transformed mast cells are unique among hematopoietic cells

Mastocytosis is a disease of bone marrow origin histologically characterized by compact tissue infiltrates of atypical mast cells never seen in reactive states. Most patients with mastocytosis have transformed mast cells carrying an activating point mutation at codon 816 of KIT and also show an elevated serum tryptase level. In this article immunophenotypical features of mast cells are described. Based on these features, mast cells are not closely related to other myeloid cells. Using the knowledge on aberrantly expressed antigens by mast cells, the hematopathologist should be able to recognize the disease even in the presence of unusual morphologic findings or an associated hematologic non-mast cell lineage disease.

Tryptase, a novel angiogenic factor stored in mast cell granules

Human mast cells (MCs) are a rich reservoir of neutral proteases, packed in large amounts in their granules and comprising a high fraction of all cellular proteins. Among these proteases, tryptase is involved in angiogenesis after its release from activated MC granules, as it has been demonstrated in different in vitro and in vivo assays. Moreover, tryptase-positive MCs increase in number and vascularization increases in a linear fashion in different solid and hematological tumors. This complex interplay between MCs and tumor angiogenesis have led to consider the therapeutic use of angiogenesis inhibitors, which specifically target the angiogenic activity of tryptase, such as gabexate mesilate and nafamostat mesilate, two inhibitors of trypsin-like serine proteases.

Clinical implications of correlation between peripheral eosinophil count and serum levels of IL-5 and tryptase in acute eosinophilic pneumonia

BACKGROUND

The peripheral eosinophil count (PEC) tends to increase during the course of acute eosinophilic pneumonia (AEP), and an initially elevated PEC is associated with milder disease. However, there is a lack of data regarding these phenomena and inflammatory process of AEP.

METHODS

We prospectively evaluated serial changes in serum interleukin (IL)-5 levels and the correlation between the initial level of IL-5 and the PEC to investigate whether the initial PEC indicates a resolving state of inflammation. We also evaluated serum tryptase levels to investigate the possibility of involvement of mast cell activity in AEP.

RESULTS

Twenty-one AEP patients were included, and all patients improved within 10 days after corticosteroid treatment. The median initial serum IL-5 level among all patients was 561.0 pg/mL, which decreased to zero at 10 days of follow-up (n = 15, P < 0.001). The median initial serum tryptase level (detectable in 20 of 21 patients) was 3.7 ng/mL and decreased to a median of 1.1 ng/mL at 10 days of follow-up (n = 15, P < 0.001). The initial serum IL-5 and C-reactive protein levels were positively correlated (P = 0.009, r = 0.556), and the initial serum IL-5 level was inversely correlated with the initial PEC (P = 0.004, r = -0.603).

CONCLUSIONS

Our data suggest that IL-5 is an important cytokine involved in the recruitment of eosinophils from peripheral blood into the lungs, that an initially elevated PEC is associated with a resolving state of inflammation, and that mast cells are potentially involved in the inflammatory process of AEP.

Studies on distribution of α1-antitrypsin, lysozyme, lactoferrin, and mast cell enzymes in diseased middle ear mucosa

CONCLUSION

Antimicrobial agents (AMAs) and mast cells in chronic otitis media (COM) may play a protective role in the pathogenesis of COM. Among them, our results indicated that lysozyme may be the most important parameter of the mucosa infectivity in COM.

OBJECTIVES

AMAs include alpha 1-antitrypsin (α1-AT), lysozyme, and lactoferrin and exhibit innate immune activity that is known to play a critical role in mucosal defenses. In addition, proteases expressed in mast cells contribute to mucosal defenses. The aim of this study was to identify AMAs responsible for COM as well as their association with middle ear mucosal diseases.

METHODS

Middle ear mucosa (MEM) was intraoperatively collected by biopsy from patients, diagnosed as COM without or with cholesteatoma, and immediately processed for immunohistochemical study to evaluate expression of AMAs and mast cell proteases (chymase and tryptase).

RESULTS

The AMAs and mast cell enzymes were observed prominently in the chronic middle ear diseases whereas immunoreactivity of α1-AT and lysozyme was not significantly increased in the COM with cholesteatoma compared with that in COM without cholesteatoma. Lactoferrin was not detected in the diseased MEMs.

Possible biological and translational significance of mast cells density in colorectal cancer

Mast cells (MCs), located ubiquitously near blood vessels, are descended from CD34⁺ hematopoietic stem cells. Initially, although their role has been well defined in hypersensitivity reactions, the discovery of their sharing in both innate and adaptive immunity has allowed to redefine their crucial interplay on the regulatory function between inflammatory and tumor cells through the release of mediators granule-associated (mainly tryptase and vascular endothelial growth factor). In particular, in several animal and human malignancies it has been well demonstrated that activated c-Kit receptor (c-KitR) and tryptase (an agonist of the proteinase-activated receptor-2) take pivotal part in tumor angiogenesis after the MCs activation, contributing to tumor cells invasion and metastasis. In this review, we focused on crucial MCs density (MCD) role in colorectal cancer (CRC) development and progression angiogenesis-mediated; then, we will analyze the principal studies that have focused on MCD as possible prognostic factor. Finally, we will consider a possible role of MCD as novel therapeutic target mainly by c-KitR tyrosine kinase inhibitors (imatinib, masitinib) and tryptase inhibitors (gabexate and nafamostat mesylate) with the aim to prevent CRC progression.

Perioperative allergic reactions: experience in a Flemish referral centre

BACKGROUND

The incidence of perioperative anaphylactic reactions is overall estimated to be 1 per 10,000-20,000 anaesthetic procedures. We performed a retrospective analysis of patients referred to a University Allergy Centre in Belgium with the suspicion of an allergic reaction during or shortly after general anaesthesia.

OBJECTIVES

Our aim was to assess the causes of perioperative allergic reactions, to evaluate cross-reactivity among neuromuscular blocking agents (NMBA) and to analyze the diagnostic relevance of tryptase levels in the discrimination between IgE and non-IgE-mediated reactions.

METHODS

A total of 119 patients, referred from 2007 to 2011 were included. The diagnostic protocol consisted in case history, serum tryptase measurements, immunoassays and skin tests.

RESULTS

A diagnosis of IgE-mediated reaction was established in 76 cases (63.9%). The most common agents were NMBA (61.8%), antibiotics (14.5%), latex (9.2%) and chlorhexidine (5.2%). Rocuronium was the most frequently causative NMBA (48.9%). Vecuronium cross-reactivity was established by skin testing in 47.6% of cases. Cisatracurium was the NMBA most frequently tolerated (cross-reaction in 13.9%). In 23.4% of NMBA allergic patients, the reaction occurred on the first exposure. Most IgE-mediated reactions occurred during the induction phase (72.4%). Latex-induced reactions occurred mainly during maintenance and recovery phases (71.4%; p<0.02). Mean tryptase values were significantly higher in patients with IgE-mediated reactions (p=0.0001), than in those with no identified cause.

CONCLUSIONS

NMBA, antibiotics, latex and chlorhexidine were the main culprits of IgE-mediated perioperative reactions. Uncertainties remain concerning the specificity and sensitivity of skin testing. Tryptase assays can be useful in the discrimination of IgE and non-IgE-mediated reactions.

Tryptase inhibitor APC 366 prevents hepatic fibrosis by inhibiting collagen synthesis induced by tryptase/protease-activated receptor 2 interactions in hepatic stellate cells

Protease-activated receptor (PAR) 2 is a G-protein-coupled receptor that is activated by mast cell tryptase. PAR-2 activation augments profibrotic pathways through the induction of extracellular matrix proteins. PAR-2 is widely expressed in hepatic stellate cells (HSCs), but the role of tryptase/PAR-2 interaction in liver fibrosis is unclear. We studied the development of bile duct ligation (BDL)-induced hepatic fibrosis in rats treated with mast cell tryptase inhibitor APC 366, and showed that APC 366 reduced hepatic fibrosis scores, collagen content and serum biochemical parameters. Reduced fibrosis was associated with decreased expression of PAR-2 and α-smooth muscle actin (α-SMA). Our findings demonstrate that mast cell tryptase induces PAR-2 activation to augment HSC proliferation and promote hepatic fibrosis in rats. Treatment with tryptase antagonists may be a novel therapeutic approach to prevent fibrosis in patients with chronic liver disease.

Eosinophilia in mast cell disease

Eosinophils and mast cells coexist in clonal and nonclonal disorders. The interplay between these cells is complex and not fully understood. Discussed are both allergic/nonclonal disorders in which both cell types are increased in number are likely to play a role in pathogenesis and clonal disorders in which both cell types are affected and play key roles in pathogenesis. Finally, some treatment options, keeping both disorders in mind, are discussed. Future directions in thinking about these disorders are also briefly explored.

A concise, practical guide to diagnostic assessment for mast cell activation disease

As recognition of mast cell (MC) involvement in a range of chronic inflammatory disorders has increased, diagnosticians’ suspicions of MC activation disease (MCAD) in their chronically mysteriously inflamed patients have similarly increased. It is now understood that the various forms of systemic mastocytosis - diseases of inappropriate activation and proliferation of MCs seemingly driven by a small set of rare, usually constitutively activating mutations in assorted MC regulatory elements - comprise merely the tip of the MCAD iceberg, whereas the far larger and far more clinically heterogeneous (and thus more difficult to recognize) bulk of the iceberg consists of assorted forms of MC activation syndrome (MCAS) which manifest little to no abnormal MC proliferation and may originate from a far more heterogeneous set of MC mutations. It is reasonable to suspect MCAD when symptoms and signs of MC activation are present and no other diagnosis better accounting for the full range of findings is present. Initial laboratory assessment should include not only routine blood counts and serum chemistries but also a serum total tryptase level, which helps direct further evaluation for mastocytosis vs MCAS. Appropriate tissue examinations are needed to diagnose mastocytosis, while elevated levels of relatively specific mast cell mediators are sought to support diagnosis of MCAS. Whether assessing for mastocytosis or MCAS, testing is fraught with potential pitfalls which can easily yield false negatives leading to erroneous rejection of diagnostic consideration of MCAD in spite of a clinical history highly consistent with MCAD. Efforts at accurate diagnosis of MCAD are worthwhile, as many patients then respond well to appropriately directed therapeutic efforts.

A concise, practical guide to diagnostic assessment for mast cell activation disease

As recognition of mast cell (MC) involvement in a range of chronic inflammatory disorders has increased, diagnosticians’ suspicions of MC activation disease (MCAD) in their chronically mysteriously inflamed patients have similarly increased. It is now understood that the various forms of systemic mastocytosis - diseases of inappropriate activation and proliferation of MCs seemingly driven by a small set of rare, usually constitutively activating mutations in assorted MC regulatory elements - comprise merely the tip of the MCAD iceberg, whereas the far larger and far more clinically heterogeneous (and thus more difficult to recognize) bulk of the iceberg consists of assorted forms of MC activation syndrome (MCAS) which manifest little to no abnormal MC proliferation and may originate from a far more heterogeneous set of MC mutations. It is reasonable to suspect MCAD when symptoms and signs of MC activation are present and no other diagnosis better accounting for the full range of findings is present. Initial laboratory assessment should include not only routine blood counts and serum chemistries but also a serum total tryptase level, which helps direct further evaluation for mastocytosis vs MCAS. Appropriate tissue examinations are needed to diagnose mastocytosis, while elevated levels of relatively specific mast cell mediators are sought to support diagnosis of MCAS. Whether assessing for mastocytosis or MCAS, testing is fraught with potential pitfalls which can easily yield false negatives leading to erroneous rejection of diagnostic consideration of MCAD in spite of a clinical history highly consistent with MCAD. Efforts at accurate diagnosis of MCAD are worthwhile, as many patients then respond well to appropriately directed therapeutic efforts.

Proteolytic histone modification by mast cell tryptase, a serglycin proteoglycan-dependent secretory granule protease

A hallmark feature of mast cells is their high content of cytoplasmic secretory granules filled with various preformed compounds, including proteases of tryptase-, chymase-, and carboxypeptidase A3 type that are electrostatically bound to serglycin proteoglycan. Apart from participating in extracellular processes, serglycin proteoglycan and one of its associated proteases, tryptase, are known to regulate cell death by promoting apoptosis over necrosis. Here we sought to outline the underlying mechanism and identify core histones as primary proteolytic targets for the serglycin-tryptase axis. During the cell death process, tryptase was found to relocalize from granules into the cytosol and nucleus, and it was found that the absence of tryptase was associated with a pronounced accumulation of core histones both in the cytosol and in the nucleus. Intriguingly, tryptase deficiency resulted in defective proteolytic modification of core histones even at baseline conditions, i.e. in the absence of cytotoxic agent, suggesting that tryptase has a homeostatic impact on nuclear events. Indeed, tryptase was found in the nucleus of viable cells and was shown to cleave core histones in their N-terminal tail. Moreover, it was shown that the absence of the serglycin-tryptase axis resulted in altered chromatin composition. Together, these findings implicate histone proteolysis through a secretory granule-derived serglycin-tryptase axis as a novel principle for histone modification, during both cell homeostasis and cell death.