Tryptase as an inflammatory marker in allergic disease and asthma

The Rise of Boron-Containing Compounds: Advancements in Synthesis, Medicinal Chemistry, and Emerging Pharmacology

Boron-containing compounds (BCC) have emerged as important pharmacophores. To date, five BCC drugs (including boronic acids and boroles) have been approved by the FDA for the treatment of cancer, infections, and atopic dermatitis, while some natural BCC are included in dietary supplements. Boron's Lewis acidity facilitates a mechanism of action via formation of reversible covalent bonds within the active site of target proteins. Boron has also been employed in the development of fluorophores, such as BODIPY for imaging, and in carboranes that are potential neutron capture therapy agents as well as novel agents in diagnostics and therapy. The utility of natural and synthetic BCC has become multifaceted, and the breadth of their applications continues to expand. This review covers the many uses and targets of boron in medicinal chemistry.

A novel mast cell-dependent allergic peritonitis model

Typical murine models of allergic inflammation are induced by the combination of ovalbumin and aluminum hydroxide. However, accumulating evidence indicates that, in models of asthma and atopic dermatitis, allergic inflammation can be generated in the absence of aluminum hydroxide. Moreover, co-administration of Staphylococcus aureus enterotoxin B with ovalbumin can enhance inflammation. The objective of this study was to establish a rapid and mast cell-dependent murine model of allergic inflammation by inducing allergic peritonitis using ovalbumin and S. aureus enterotoxin B. Allergic peritonitis was induced in C57BL/6 mice by subcutaneous sensitization and intraperitoneal challenge with ovalbumin and S. aureus enterotoxin B. Disease characteristics were assessed by flow cytometry, enzyme-linked immunosorbent assay (ELISA), trypan blue exclusion and colorimetric assays. The time-course of the allergic peritonitis revealed a peak of peritoneal inflammation 48 h after challenge, as assessed by total cells and eosinophil counts. The decrease of cell numbers started 96 h post-challenge, with complete clearance within 168 h. Moreover, significantly higher levels of tryptase and increased vascular permeability were found 30 min following challenge. Allergic inflammation induction by ovalbumin and S. aureus enterotoxin B was impaired in mast cell-deficient mice and partially restored by mice reconstitution with bone marrow-derived mast cells, indicating the mast cell role in this model. We present a novel model of allergic peritonitis that is mast cell-dependent, simple and robust. Moreover, the use of S. aureus enterotoxin B better resembles human allergic inflammation, which is known to be characterized by the colonization of S. aureus.

Post mortem tryptase: A review of literature on its use, sampling and interpretation in the investigation of fatal anaphylaxis

Post mortem tryptase is a commonly-used ancillary test in the investigation of possible anaphylactic deaths. Ante mortem tryptase interpretation differs from post mortem interpretation due to differing priorities, biochemical behaviours and capacity for follow-up. Additionally, post mortem tryptase sampling site, method and even cut-off levels are not standardised between facilities. This review of the literature investigates the existing research and recommendations on the use of post mortem tryptase in suspected anaphylactic deaths. Currently, autopsy recommendations suggest early sampling, standardised sampling technique with clamping of and aspiration from the femoral vein, and for the results to be interpreted within the wider autopsy and clinical context. Areas in need of further research include the effects of cytolysis on tryptase levels and studies to stratify differing tryptase levels based on type of death and anaphylactic trigger.

Novel, Self-Assembling Dimeric Inhibitors of Human β Tryptase

β-Tryptase, a homotetrameric serine protease, has four identical active sites facing a central pore, presenting an optimized setting for the rational design of bivalent inhibitors that bridge two adjacent sites. Using diol, hydroxymethyl phenols or benzoyl methyl hydroxamates, and boronic acid chemistries to reversibly join two [3-(1-acylpiperidin-4-yl)phenyl]methanamine core ligands, we have successfully produced a series of self-assembling heterodimeric inhibitors. These heterodimeric tryptase inhibitors demonstrate superior activity compared to monomeric modes of inhibition. X-ray crystallography validated the dimeric mechanism of inhibition, and compounds demonstrated high selectivity against related proteases, good target engagement, and tryptase inhibition in HMC1 xenograft models. Screening 3872 possible combinations from 44 boronic acid and 88 diol derivatives revealed several combinations that produced nanomolar inhibition, and seven unique pairs produced greater than 100-fold improvement in potency over monomeric inhibition. These heterodimeric tryptase inhibitors demonstrate the power of target-driven combinatorial chemistry to deliver bivalent drugs in a small molecule form.

Postmortem serum levels of IgE and mast cell tryptase in fatal asthma

The aim of this study was to characterize the concentrations of total and specific IgE as well as mast cell-derived tryptase in postmortem serum from femoral blood and evaluate the usefulness of their determination for diagnostic purposes in cases of fatal asthma attacks. 36 autopsy cases were retrospectively selected including cases of witnessed death in asthmatic subjects, deaths in asthmatics and atopic subjects with causes of death unrelated to asthma or allergic anaphylaxis as well as deaths in non-atopic, non-allergic individuals with causes of death unrelated to asthma or allergic anaphylaxis. Initial results indicated increased postmortem serum total IgE in atopic and asthmatic individuals, irrespective of the cause of death. Conversely, increased mast cell tryptase levels were noted exclusively in fatal asthma attacks. This suggests that mast cell tryptase measurement in cases of death potentially caused by severe acute bronchial asthma may be useful for diagnostic purposes.

Epoxyeicosatrienoic acids are involved in the C(70) fullerene derivative-induced control of allergic asthma

BACKGROUND

Fullerenes are molecules being investigated for a wide range of therapeutic applications. We have shown previously that certain fullerene derivatives (FDs) inhibit mast cell (MC) function in vitro, and here we examine their in vivo therapeutic effect on asthma, a disease in which MCs play a predominant role.

OBJECTIVE

We sought to determine whether an efficient MC-stabilizing FD (C(70)-tetraglycolate [TGA]) can inhibit asthma pathogenesis in vivo and to examine its in vivo mechanism of action.

METHODS

Asthma was induced in mice, and animals were treated intranasally with TGA either simultaneously with treatment or after induction of pathogenesis. The efficacy of TGA was determined through the measurement of airway inflammation, bronchoconstriction, serum IgE levels, and bronchoalveolar lavage fluid cytokine and eicosanoid levels.

RESULTS

We found that TGA-treated mice have significantly reduced airway inflammation, eosinophilia, and bronchoconstriction. The TGA treatments are effective, even when given after disease is established. Moreover, we report a novel inhibitory mechanism because TGA stimulates the production of an anti-inflammatory P-450 eicosanoid metabolites (cis-epoxyeicosatrienoic acids [EETs]) in the lung. Inhibitors of these anti-inflammatory EETs reversed TGA inhibition. In human lung MCs incubated with TGA, there was a significant upregulation of CYP1B gene expression, and TGA also reduced IgE production from B cells. Lastly, MCs incubated with EET and challenged through FcεRI had a significant blunting of mediator release compared with nontreated cells.

CONCLUSION

The inhibitory capabilities of TGA reported here suggest that FDs might be used a platform for developing treatments for asthma.

Protease inhibitors in respiratory disease: focus on asthma and chronic obstructive pulmonary disease

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are a major health burden on society and current treatment modalities for these diseases have not significantly changed over the past 40 years. The only major pharmacological advancement for the treatment of these diseases has been to increase the duration of action of bronchodilators (asthma: salmeterol; COPD: tiotropium bromide) and glucocorticosteroids (asthma: fluticasone propionate) and, increasingly, to formulate these agents in the same delivery device. Despite our increasing understanding of the cell and molecular biology of these diseases, the development of novel treatments remains beyond the reach of the scientific community. Proteases are a family of proteins with diverse biological activity, which are found in abundance within the airways of asthma and COPD, and have been implicated in the pathogenesis of these diseases. The targeting of proteases, including mast cell tryptase, neutrophil elastase and matrix metalloprotease with low-molecular-weight inhibitors, has highlighted the potential role of these enzymes in mediating certain aspects of the disease process in preclinical studies. Several challenges remain regarding the development of protease inhibitors, including the synthesis of highly potent and specific inhibitors, and target validation in man.

Extracellular proteases as targets for drug development

Proteases constitute one of the primary targets in drug discovery. In the present review, we focus on extracellular proteases (ECPs) because of their differential expression in many pathophysiological processes, including cancer, cardiovascular conditions, and inflammatory, pulmonary, and periodontal diseases. Many new ECP inhibitors are currently under clinical investigation and a significant increase in new therapies based on protease inhibition can be expected in the coming years. In addition to directly blocking the activity of a targeted protease, one can take advantage of differential expression in disease states to selectively deliver therapeutic or imaging agents. Recent studies in targeted drug development for the metalloproteases (matrix metalloproteinases, adamalysins, pappalysins, neprilysin, angiotensin-converting enzyme, metallocarboxypeptidases, and glutamate carboxypeptidase II), serine proteases (elastase, coagulation factors, tissue/urokinase plasminogen activator system, kallikreins, tryptase, dipeptidyl peptidase IV) and cysteine proteases (cathepsin B) are discussed herein.