Summary
Mast cells and basophils play a pathogenetic role in allergic, inflammatory, and autoimmune disorders. These cells have different development, anatomical location and life span but share many ...similarities in mechanisms of activation and type of mediators. Mediators secreted by mast cells and basophils correlate with clinical severity in asthma, chronic urticaria, anaphylaxis, and other diseases. Therefore, effective biomarkers to measure mast cell and basophil activation in vivo could potentially have high diagnostic and prognostic values. An ideal biomarker should be specific for mast cells or basophils, easily and reproducibly detectable in blood or biological fluids and should be metabolically stable. Markers of mast cell and basophil include molecules secreted by stimulated cells and surface molecules expressed upon activation. Some markers, such as histamine and lipid mediators are common to mast cells and basophils whereas others, such as tryptase and other proteases, are relatively specific for mast cells. The best surface markers of activation expressed on mast cells and basophils are CD63 and CD203. While these mediators and surface molecules have been associated to a variety of diseases, none of them fulfills requirements for an optimal biomarker and search for better indicators of mast cell/basophil activation in vivo is ongoing.
Highlights • Mast cells are strategically located at major body surfaces and along blood vessels. • They play a key role as first line defense against bacterial, viral and parasitic infections. • ...Mast cells display a wide set of receptors which recognize and internalize pathogens. • Activation of mast cell receptors induces release of mediators that promote inflammation and recruitment of cells of innate immunity. • Mast cells shape adaptive immunity through soluble mediators and cognate interactions with T, B and Treg cells.
Mast cells (MCs) are immune cells distributed in many organs and tissues and involved in the pathogenesis of allergic and inflammatory diseases as a major source of pro-inflammatory and vasoactive ...mediators. MC-related disorders are heterogeneous conditions characterized by the proliferation of MC within tissues and/or MC hyper-reactivity that leads to the uncontrolled release of mediators. MC disorders include mastocytosis, a clonal disease characterized by tissue MC proliferation, and MC activation syndromes that can be primary (clonal), secondary (related to allergic disorders), or idiopathic. Diagnosis of MC disorders is difficult because symptoms are transient, unpredictable, and unspecific, and because these conditions mimic many other diseases. Validation of markers of MC activation in vivo will be useful to allow faster diagnosis and better management of MC disorders. Tryptase, being the most specific MC product, is a widely used biomarker of proliferation and activation. Other mediators, such as histamine, cysteinyl leukotrienes, and prostaglandin D2, are unstable molecules and have limitations in their assays. Surface MC markers, detected by flow cytometry, are useful for the identification of neoplastic MC in mastocytosis but, so far, none of them has been validated as a biomarker of MC activation. Further studies are needed to identify useful biomarkers of MC activation in vivo.
Background. Mastocytosis is a condition characterized by the expansion and accumulation of mast cells (MCs) in various organs. The symptoms are related to the increased release of MC-derived ...mediators that exert local and distant effects. MCs are a source and target of phospholipase enzymes (PLs), which catalyze the cleavage of membrane phospholipids releasing lipid mediators (e.g., diacylglycerols (DAGs) and the endocannabinoid (EC) 2-arachidonoylglycerol (2-AG)). To date, there are no data on the role of these lipid mediators in mastocytosis. Here, we analyzed plasma levels of PLA2, PLC, DAG, ECs, and EC-related N-acylethanolamines in patients with mastocytosis. Methods. In 23 patients with mastocytosis and 23 healthy individuals, we measured plasma PLA2 and PLC activities, DAG, 2-AG, anandamide (AEA), palmitoylethanolamide (PEA), and oleoylethanolamide (OEA). Results. Plasma PLA2 and PLC activities were increased in mastocytosis patients compared to controls. Concentrations of DAG (18:1 20:4 and 18:0 20:4), two second messengers produced by PLC, were higher in mastocytosis compared to controls, whereas the concentrations of their metabolite, 2-AG, were not altered. AEA was decreased in mastocytosis patients compared to controls; by contrast, AEA congener, PEA, was increased. PLA2 and PLC activities were increased only in patients with mediator-related symptoms. Moreover, PLC activity was positively correlated with disease severity and tryptase concentrations. By contrast, AEA was negatively correlated with tryptase concentrations. Conclusions. PLs and some lipid mediators are altered in patients with mastocytosis. Our results may pave the way for investigating the functions of these mediators in the pathophysiology of mastocytosis and provide new potential biomarkers and therapeutic targets.
Angioedema due to C1 inhibitor deficiency (AE-C1-INH) is a rare disease characterized by recurrent and unpredictable attacks of angioedema. Multiple trigger factors, including trauma, emotional ...stress, infectious diseases, and drugs, could elicit angioedema attacks. The aim of this study was to collect data on the safety and tolerability of COVID-19 vaccines in a population of patients affected by AE-C1-INH. Adult patients with AE-C1-INH, followed by Reference Centers belonging to the Italian Network for Hereditary and Acquired Angioedema (ITACA), were enrolled in this study. Patients received nucleoside-modified mRNA vaccines and vaccines with adenovirus vectors. Data on acute attacks developed in the 72 h following COVID-19 vaccinations were collected. The frequency of attacks in the 6 months after the COVID-19 vaccination was compared with the rate of attacks registered in the 6 months before the first vaccination. Between December 2020 and June 2022, 208 patients (118 females) with AE-C1-INH received COVID-19 vaccines. A total of 529 doses of the COVID-19 vaccine were administered, and the majority of patients received mRNA vaccines. Forty-eight attacks of angioedema (9%) occurred within 72 h following COVID-19 vaccinations. About half of the attacks were abdominal. Attacks were successfully treated with on-demand therapy. No hospitalizations were registered. There was no increase in the monthly attack rate following the vaccination. The most common adverse reactions were pain at the site of injection and fever. Our results show that adult patients with angioedema due to C1 inhibitor deficiency can be safely vaccinated against SARS-CoV-2 in a controlled medical setting and should always have available on-demand therapies.
A kinetic model for pore-mediated and perturbation-mediated flip-flop is presented and used to characterize the mechanism of peptide-induced phospholipid flip-flop in bilayers. The model assumes that ...certain peptides can bind to and aggregate within the membrane. When the aggregate attains a critical size (M peptides), a channel is created that results in a fast flip-flop of phospholipids. In addition, certain peptides induce flip-flop through perturbation of the membrane without forming a pore. Donor phospholipid vesicles with an asymmetrical distribution of the fluorescent phospholipid 1-oleoyl-2-12-(7-nitro-1,2,3-benzoxadiazol-4- yl)aminododecanoylphosphatidylcholine (NBD-PC) were used to measure the extent of flip-flop by quantitating the decrease in fluorescence as the NBD-PC exchanged from the donor vesicles to acceptor vesicles that contained a quencher of the NBD fluorescence. Flip-flop curves generated at lipid/peptide ratios ranging from 30/1 to 300000/1 could be well-simulated by the model. Pore-forming peptides, such as melittin or the synthetic peptide GALA (WEAALAEALAEALAEHLAEALAEALEALAA), induce rapid phospholipid flip-flop with half-times for flip-flop of seconds at low peptide/vesicle ratios. The deduced pore sizes are M = 10 +/- 2 for GALA and M = 2 - 4 for melittin. The synthetic peptide LAGA (WEAALAEAEALALAEHEALALAEAELALAA) can catalyze flip-flop via bilayer perturbation. In contrast, hydrophobic peptides such as gramicidin A and valinomycin intercalate into the membrane, but induce little flip-flop. Modeling of the kinetics of phospholipid translocation supports pore formation as the key factor in accelerating phospholipid flip-flop. Thus, amphipathic segments from membrane proteins may account for non-energy-dependent phospholipid flip-flop in biological membranes.
Mastocytosis is a rare disease characterized by clonal proliferation of mast cells (MCs) in different organs. Clinical manifestations of mastocytosis are mostly due to release of mediators from MCs ...and, in many cases, such as urticaria, flushing, angioedema, and anaphylaxis, are an expression of the biological effects of mediators on endothelial cells. Chronic secretion of mediators in patients with mastocytosis can lead to alteration of endothelial function.
We sought to investigate endothelial function in patients with mastocytosis using a noninvasive technique of flow-mediated dilation (FMD).
Twenty-five adult patients with indolent and advanced forms of mastocytosis and 20 healthy control subjects were enrolled in the study. Ultrasound assessment of FMD was performed by measuring changes in the diameter of the brachial artery after 5 minutes of arterial occlusion. Changes in FMD were correlated with clinical parameters and serum tryptase levels.
Patients with mastocytosis had lower FMD compared with healthy control subjects (P < .001). Advanced and smoldering forms showed a lower FMD compared with indolent forms (P < .001). FMD inversely correlated with age and serum tryptase levels and directly with median arterial pressure and recurrent flushing episodes. No correlation was found between FMD and osteoporosis, recurrent anaphylaxis, presence of skin lesions, and long-term antihistamine treatment.
Endothelial dysfunction, as demonstrated by FMD reduction, is detectable in patients with mastocytosis and is more severe in patients with high tryptase levels and advanced disease. Endothelial function appears to be negatively influenced by MC proliferation rather than by the severity of mediator-related symptoms.
Patients with primary antiphospholipid syndrome (PAPS) may suffer from venous and/or arterial thrombosis, but studies addressing eventual clinical and laboratory features that may discriminate ...between arterial thromboembolism (ATE) from venous thromboembolism (VTE) have been poorly addressed.
Cross sectional comparison of baseline characteristics of 100 patients enrolled in the multi center ATHERO-APS cohort study; patients with previous ATE and VTE were compared with regards to clinical and biochemical variables as well as to echocardiographic features and ankle-brachial index (ABI) measured at enrolment.
Mean age of patients was 51 years, 72 were women. 60 patients suffered VTE and 40 ATE. Compared to VTE, ATE patients displayed a higher prevalence of hypertension (43.3% vs. 65%, p = 0.034) and diabetes (3.3% vs. 17.5%, p = 0.015). Mean concentration of inflammation and complement activation markers were similar between the two groups as well as autoantibodies titres; mean D-dimer concentration was greater in VTE patients (184 ng/ml vs. 347 ng/ml; p = 0.024) whereas mean platelet count was greater in ATE patients (263 × 109/L vs 216 × 109/L, p = 0.044). By multivariable logistic regression analysis, adjusted for age, sex, hypertension and diabetes, ABI ≤ 0.9 (OR: 3.4; p = 0.041) and left atrial enlargement (OR: 3.5; p = 0.035) were associated with a history of ATE. ATE patients had a higher prevalence of ABI <0.9 (32.5% vs 10% p = 0.005) than VTE patients. At logistic regression analysis, IgG aCL >120 GPL U/ml was associated with an ABI ≤0.9 (OR: 5; p = 0.023) after adjustment for age and sex.
Clinical, laboratory and cardiovascular variables distinguish arterial from venous APS patients, amongst which the ABI and left atrial enlargement. Implications for these two distinct clinical phenotypes of APS patients need further investigation.
•Cardiovascular risk factors are frequent in PAPS patients with previous arterial thromboembolic events (ATE).•Low ankle brachial index (ABI) and left atrium enlargement are frequent in PAPS and associated with ATE.•Impaired right ventricular function correlates with previous venous thromboembolism in PAPS patients.•Vascular doppler and echocardiography may identify distinct phenotypes of PAPS requiring tailored anti-thrombotic strategies
The synthetic, amphipathic peptide GALA undergoes a pH-dependent conformational change and induces leakage of contents from large unilamellar phosphatidylcholine vesicles when in a helical ...conformation. The kinetics of this process have been investigated over a wide range of pH and lipid and peptide concentrations. Leakage from lipid vesicles is rapidly initiated (within 2 s) when the pH is lowered below 6 and is rapidly terminated when the pH is raised to 7.5. The leakage shows a selectivity to the size of the entrapped molecules and occurs by an all or none mechanism; vesicles either leak or retain all of their contents. Using this experimental data, we have developed a mathematical description of the kinetics of leakage induced by GALA. This model assumes that GALA becomes incorporated into the vesicle bilayer and aggregates to form a pore. Leakage occurs when a critical number of peptides assemble into a supramolecular aggregate in the bilayer. Leakage curves generated at lipid/peptide ratios ranging from 500/1 to 30000/1 can be well described by this formalism. On the basis of the results and the model, we suggest that GALA forms a transbilayer channel composed of 8-12 monomers. The channel diameter ranges from 5 to 10 A. To the best of our knowledge, this is the first model that can predict the leakage kinetics of solutes entrapped in lipid vesicles induced by a pore-forming peptide. The analysis may be of general use in defining the kinetics and state of aggregation of similarly acting peptides and proteins which form multimeric assemblies in membranes.
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