Histamine release and surface CD200R1 staining as sensitive methods for assessing murine mast cell activation

Gut bacteria interact directly with colonic mast cells in a humanized mouse model of IBS

Both mast cells and microbiota play important roles in the pathogenesis of Irritable Bowel Syndrome (IBS), however the precise mechanisms are unknown. Using microbiota-humanized IBS mouse model, we show that colonic mast cells and mast cells co-localized with neurons were higher in mice colonized with IBS microbiota compared with those with healthy control (HC) microbiota. In situ hybridization showed presence of IBS, but not control microbiota, in the lamina propria and RNAscope demonstrated frequent co-localization of IBS bacteria and mast cells. TLR4 and H₄ receptor expression was higher in mice with IBS microbiota, and in peritoneal-derived and bone marrow-derived mast cells (BMMCs) stimulated with IBS bacterial supernatant, which also increased BMMCs degranulation, chemotaxis, adherence and histamine release. While both TLR4 and H₄ receptor inhibitors prevented BMMCs degranulation, only the latter attenuated their chemotaxis. We provide novel insights into the mechanisms, which contribute to gut dysfunction and visceral hypersensitivity in IBS.

Mast cell activation markers for in vitro study

Mast cells (MCs) are well known for their role in allergic conditions. This cell can be activated by various types of secretagogues, ranging from a small chemical to a huge protein. Mast cell activation by secretagogues triggers the increase in intracellular calcium (iCa²⁺) concentration, granule trafficking, and exocytosis. Activated mast cells release their intra-granular pre-stored mediator or the newly synthesized mediator in the exocytosis process, in the form of degranulation or secretion. There are at least three types of exocytosis in mast cells, which are suggested to contribute to the release of different mediators, i.e.,, piecemeal, kiss-and-run, and compound exocytosis. The status of mast cells, i.e., activated or resting, is often determined by measuring the concentration of the released mediator such as histamine or β-hexosaminidase. This review summarizes several mast cell components that have been and are generally used as mast cell activation indicator, from the classical histamine and β-hexosaminidase measurement, to eicosanoid and granule trafficking observation. Basic principle of the component determination is also explained with their specified research application and purpose. The information will help to predict the experiment results with a certain study design.

PDE3 Inhibition Reduces Epithelial Mast Cell Numbers in Allergic Airway Inflammation and Attenuates Degranulation of Basophils and Mast Cells

Epithelial mast cells are generally present in the airways of patients with allergic asthma that are inadequately controlled. Airway mast cells (MCs) are critically involved in allergic airway inflammation and contribute directly to the main symptoms of allergic patients. Phosphodiesterase 3 (PDE3) tailors signaling of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are critical intracellular second messenger molecules in various signaling pathways. This paper investigates the pathophysiological role and disease-modifying effects of PDE3 in mouse bone marrow-derived MCs (bmMCs), human LAD2- and HMC1 mast cell lines, human blood basophils, and peripheral blood-derived primary human MCs (HuMCs). In a chronic house dust mite (HDM)-driven allergic airway inflammation mouse model, we observed that PDE3 deficiency or PDE3 inhibition (PDE3i) therapy reduced the numbers of epithelial MCs, when compared to control mice. Mouse bone marrow-derived MCs (bmMCs) and the human HMC1 and LAD2 cell lines predominantly expressed PDE3B and PDE4A. BmMCs from Pde3^−/− mice showed reduced loss of the degranulation marker CD107b compared with wild-type BmMCs, when stimulated in an immunoglobulin E (IgE)-dependent manner. Following both IgE-mediated and substance P-mediated activation, PDE3i-pretreated basophils, LAD2 cells, and HuMCs, showed less degranulation than diluent controls, as measured by surface CD63 expression. MCs lacking PDE3 or treated with the PDE3i enoximone exhibited a lower calcium flux upon stimulation with ionomycine. In conclusion PDE3 plays a critical role in basophil and mast cell degranulation and therefore its inhibition may be a treatment option in allergic disease.

Anti-allergic effect of inotodiol, a lanostane triterpenoid from Chaga mushroom, via selective inhibition of mast cell function

Inotodiol is a lanostane triterpenoid found only in Chaga mushroom. In the previous study investigating anti-allergic effects of fractionated Chaga mushroom extracts, we have found evidence that purified inotodiol holds an activity to suppress the mast cell function in vivo. To address the therapeutic relevance of the finding, in this study, we investigated whether inotodiol could also alleviate allergy symptoms observed in a chicken ovalbumin (cOVA)-induced mouse model of food allergy. Like the crude 70% ethanol extract of Chaga mushroom (320 mg/kg), oral administration of inotodiol (20 mg/kg), regardless of whether that was for preventive or treatment purpose, resulted in a significant improvement in allergic symptoms and inflammatory lesions in the small intestine appearing after repeated oral challenge with cOVA. Despite the results that inotodiol (20 mg/kg) and the Chaga mushroom extract (320 mg/kg) took effect to a similar extent, immunological mechanisms underlying those effects were found to be distinct from each other. That is, the results obtained from several in vivo assays, including mast cell-mediated passive systemic anaphylaxis, activation/proliferation of adoptively transferred antigen-specific T cells and immunoglobulin (IgG1, IgE, IgA) production by antigen-specific B cells, illustrated that inotodiol selectively inhibited the mast cell function without having any noticeable effect on other immune responses while the crude Chaga mushroom extract indiscriminately suppressed diverse immune responses. The strong anti-allergic activity of inotodiol, along with its remarkable selectivity to mast cell, makes it an excellent therapeutic candidate for food allergy with both high efficacy and outstanding safety.

Chronic infection with a tissue-invasive helminth attenuates sublethal anaphylaxis and reduces granularity and number of mast cells

BACKGROUND

Immunoglobulin E (IgE)-mediated anaphylaxis is a potentially fatal condition in which allergy effector cells rapidly discharge pre-formed inflammatory mediators. Treatments that address the immune component of allergic anaphylaxis are inadequate. Helminths have been previously shown to suppress effector cell function; however, their ability to treat pre-existing allergy remains unclear.

OBJECTIVE

To evaluate the ability of chronic helminth infection to protect against anaphylaxis in previously sensitized mice.

METHODS

A sublethal model of anaphylaxis was used, in which BALB/c mice were sensitized by three intraperitoneal (i.p.) injections of OVA/alum. Temperature drop was then monitored after systemic OVA challenge in uninfected mice and in mice infected chronically with Litomosoides sigmodontis, a tissue-invasive filarial nematode.

RESULTS

Litomosoides sigmodontis-infected mice exhibited significantly lower serum levels of mMCP-1 and were less hypothermic at 30-minute post-challenge compared to uninfected OVA-challenged controls. Characterization of anaphylaxis revealed that FcԑR1 and mast cells were required for hypothermia and elevated serum mMCP-1. OVA-IgE and OVA-IgG1 serum levels were not significantly altered by L sigmodontis infection, and experiments with IL-10^-/- mice demonstrated that IL-10 was not required for protection against anaphylaxis. However, peritoneal mast cell numbers were significantly lower in infected mice, and those that were present exhibited decreased granularity by flow cytometry and marked depletion of intracytoplasmic granules by light microscopy. Mast cells from infected mice had lower expression of the activation markers CD200R and CD63 and contained significantly lower basal stores of histamine.

CONCLUSIONS

Chronic L sigmodontis infection protects against anaphylaxis, likely due to reduction in mast cell numbers and depletion of pre-formed inflammatory mediators in remaining mast cells.

Sini San ameliorates duodenal mucosal barrier injury and low‑grade inflammation via the CRF pathway in a rat model of functional dyspepsia

The gut-brain interaction is associated with impaired duodenal mucosal integrity and low-grade inflammation, which have been proven to be important pathological mechanisms of functional dyspepsia (FD). Sini San (SNS) is a classical Chinese medicine used to treat FD, but its underlying mechanisms are poorly understood. The aim of the present study was to evaluate the effects of SNS on duodenal mucosal barrier injury and low-grade inflammation with FD, and to assess its potential molecular mechanisms on the brain-gut axis. FD rats were established using the iodoacetamide and tail-squeezed methods. The expression of corticotropin-releasing factor (CRF), CRF receptor 1 (CRF-R1) and CRF-R2, were determined by western blot analysis and/or immunohistochemistry (IHC). In addition, mast cell (MC) migration was assessed by IHC with an anti-tryptase antibody, and histamine concentration was quantified using ELISA. The mRNA expression levels of tryptase and protease-activated receptor 2 (PAR-2) were quantified using reverse transcription-quantitative PCR, and the protein expression levels of zona occludens protein 1 (ZO-1), junctional adhesion molecule 1 (JAM-1), β-catenin and E-cadherin were determined via western blot analysis. It was demonstrated that the expression level of CRF was downregulated in the central nervous system and duodenum following SNS treatment, and that SNS modulated the expression of both CRF-R1 and CRF-R2. In addition, SNS suppressed MC infiltration and the activity of the tryptase/PAR-2 pathway in the duodenum. Furthermore, treatment with SNS restored the normal expression levels of ZO-1, JAM-1 and β-catenin in FD rats. These findings suggested that the therapeutic effects of SNS on FD were achieved by restoring mucosal barrier integrity and suppressing low-grade inflammation in the duodenum, which was at least partially mediated via the CRF signaling pathway.

Effects of 8-Hydroxyisocapnolactone-2-3-diol and friedelin on mast cell degranulation

OBJECTIVE

To investigate the effects of friedelin (terpenoid) and 8-hydroxyisocapnolactone-2-3-diol (coumarin) with concentration 10 μM, 30 μM, and 100 μM on inhibiting mast cells (MCs) degranulation.

METHODS

The investigation was performed in vitro by administering each compound into rat peritoneal MCs and rat basophilic leukemia-2H3 cells followed by activation with 50 μg/mL of compound 48/80 or 1 μM of ionomycin. The concentration of histamine released from each group was measured by a high-performance liquid chromatography-fluorometry system with post-column derivatization using o-phthalaldehyde.

RESULTS

8-Hydroxyisocapnolactone-2-3-diol inhibited degranulation of compound 48/80 activated-rat peritoneal MCs with the histamine release percentages of 74.57%, 72.21% and 51.79% when the 10 μM, 30 μM and 100 μM concentrations were used, respectively. Where as about 81% histamine was released by the control group. Degranulation inhibition ability was also observed in ionomycin-activated rat basophilic leukemia-2H3 cells. In contrast, friedelin failed to inhibit degranulation in either cell type. The inhibition of 8-hydroxyisocapnolactone-2-3-diol was not related to the depletion of histamine synthesis as implied by the total histamine measurement.

CONCLUSIONS

These results exhibit the promising of 8-hydroxyisocapnolactone-2-3-diol is a potential parent structure for developing a MCs stabilizer.

Investigating palygorskite's role in the development of mesothelioma in southern Nevada: Insights into fiber-induced carcinogenicity

Similar to asbestos fibers, nonregulated mineral fibers can cause malignant mesothelioma (MM). Recently, increased proportions of women and young individuals with MM were identified in southern Nevada, suggesting that environmental exposure to carcinogenic fibers was causing the development of MM. Palygorskite, a fibrous silicate mineral with a history of possible carcinogenicity, is abundant in southern Nevada. In this study, our aim was to determine whether palygorskite was contributing to the development of MM in southern Nevada. While palygorskite, in vitro, displayed some cytotoxicity toward primary human mesothelial (HM) cells and reduced their viability, the effects were roughly half of those observed when using similar amounts of crocidolite asbestos. No Balb/c (0/19) or MexTAg (0/18) mice injected with palygorskite developed MM, while 3/16 Balb/c and 13/14 MexTAg mice injected with crocidolite did. Lack of MM development was associated with a decreased acute inflammatory response, as injection of palygorskite resulted in lower percentages of macrophages (p = .006) and neutrophils (p = .02) in the peritoneal cavity 3 d after exposure compared to injection of crocidolite. Additionally, compared to mice injected with crocidolite, palygorskite-injected mice had lower percentages of M2 (tumor-promoting) macrophages (p = .008) in their peritoneal cavities when exposed to fiber for several weeks. Our study indicates that palygorskite found in the environment in southern Nevada does not cause MM in mice, seemingly because palygorskite, in vivo, fails to elicit inflammation that is associated with MM development. Therefore, palygorskite is not a likely contributor to the MM cases observed in southern Nevada.

The immunophenotype of mast cells and its utility in the diagnostic work-up of systemic mastocytosis

SM comprises a heterogeneous group of disorders, characterized by an abnormal accumulation of clonal MCs in 1 or more tissues, frequently involving the skin and BM. Despite the fact that most adult patients (>90%) carry the same genetic lesion (D816V KIT mutation), the disease presents with multiple variants with very distinct clinical and biologic features, a diverse prognosis, and different therapeutic requirements. Recent advances in the standardization of the study of BM MC by MFC allowed reproducible identification and characterization of normal/reactive MCs and their precursors, as well as the establishment of the normal MC maturational profiles. Analysis of large groups of patients versus normal/reactive samples has highlighted the existence of aberrant MC phenotypes in SM, which are essential for the diagnosis of the disease. In turn, 3 clearly distinct and altered maturation-associated immunophenotypic profiles have been reported recently in SM, which provide criteria for the distinction between ISM patients with MC-restricted and multilineage KIT mutation; thus, immunphenotyping also contributes to prognostic stratification of ISM, particularly when analysis of the KIT mutation on highly purified BM cells is not routinely available in the diagnostic work-up of the disease.