In Vitro and In Vivo IgE-/Antigen-Mediated Mast Cell Activation

Current utilization trend of immortalized mast cell lines in allergy research: a systematic review

Today, in the modern world, allergic diseases, also described as atopic allergies, are classified as a type of multifactorial disorder due to the complex interplay between genetics, environment, and socioeconomic factors that influence the disease's manifestation, severity, and one's predisposition to allergic diseases. It is undeniable that many reported studies have pointed out that the mast cell is one of the leading key players involved in triggering an allergic reaction. To improve our understanding of the molecular and cellular mechanisms underlying allergy, various mast cell lines have been employed in vitro to study the pathogenesis of allergic diseases for the past decades. However, there is no consensus on many fundamental aspects associated with their use, such as the effects of culture media composition and the type of inducer used for cell degranulation. As the standardization of research protocols and disease models is crucial, we present the outcome of a systematic review of scientific articles using three major immortalized in vitro mast cell lines (HMC-1, LAD2, and RBL-2H3) to study allergy. This systematic review described the cell source, culture conditions, inducers used for degranulation, and mediators released for examination. We hope that the present systematic review may help to standardize the use of immortalized in vitro mast cell lines in allergy research and serve as a user's guide to understand the fundamental aspects of allergy as well to develop an effective allergy therapy in the future for the betterment of human good health and wellbeing.

Mast cell stabilization: new mechanism underlying the therapeutic effect of intense pulsed light on rosacea

BACKGROUND

Rosacea, a chronic inflammatory disorder of the facial skin, is effectively treated by intense pulsed light (IPL).

OBJECTIVE

To explore the potential molecular mechanism underlying the photobiomodulation effect of IPL for rosacea treatment.

METHODS

Skin samples from patients with rosacea were subjected to histological and immunohistological staining. Ten patients were followed up after IPL treatment using the VISIA^® skin analysis system, and the severity was assessed. In vivo, skin changes in mice with rosacea-like inflammation induced by intradermal injection of 320 μM LL-37 with or without IPL treatment were evaluated using L*a*b colorimetry as well as histological and immunological staining. In vitro, LL-37-stimulated mast cells (MCs) with or without IPL treatment were evaluated for protein expression of matrix metalloproteinase (MMP)-9, kallikrein-related peptidase 5 (KLK5), and cathelicidin using western blotting and qRT-PCR.

RESULTS

Profound infiltration of inflammatory cells and evident MC degranulation were found in rosacea skin lesions. The expression of rosacea-related biomarkers and inflammatory cytokines was higher in lesional areas than in non-lesional areas, as demonstrated via immunochemical staining. In all patients, rosacea severity reduced after IPL therapy. In vivo, IPL alleviated inflammation in mice with rosacea-like inflammation, as demonstrated by the significantly decreased MMP-9, KLK5, and cathelicidin expression and reduced percentage of degranulating MCs. In vitro, IPL decreased MMP-9, KLK5, and cathelicidin expression in P815 cells, reducing the release of inflammatory cytokines and inhibiting rosacea-like inflammatory reactions.

CONCLUSION

The photobiomodulation effect of IPL for rosacea treatment may inhibit MC degranulation and alleviate inflammatory reactions.

FAK inhibitor PF-431396 suppresses IgE-mediated mast cell activation and allergic inflammation in mice

Mast cells (MCs) initiate and maintain allergic inflammation. Upon being stimulated with immunoglobulin (Ig)E and antigen (Ag), MCs exhibit FcεRI (high-affinity IgE) receptor-mediated degranulation, cytokine secretion, and increased focal adhesion kinase (FAK) activity. The aims of this study were to examine mechanisms of FAK regulation in IgE-mediated MC activation and the effects of FAK inhibition on MC-mediated allergic responses. FAK activity was manipulated with short hairpin RNA (shRNA) knockdown, FAK overexpression, and the FAK inhibitor PF-431396 (PF). Gene expression and kinase activation were analyzed with quantitative molecular biology assays. PF effects were tested in the passive cutaneous anaphylaxis (PCA), active systemic anaphylaxis (ASA), and allergic conjunctivitis (AC) mouse models. Our results showed that FAK overexpression increased IgE-mediated degranulation and reduced the dexamethasone inhibitory effect on MCs activation. The FAK inhibitor PF diminished MC release of β-hexosaminidase (β-hex), histamine, and inflammatory cytokines, via a mechanism that involves MAPK and NF-κB signaling pathways. CaMKII was identified as a robust FAK-associating protein. Inhibition of CaMKII activation by KN-93 suppressed FAK activity and its downstream pathway. PF attenuated inflammatory responses in our PCA and ASA models, and relieved signs of allergic disease in AC model mice. In conclusions, MC degranulation and production of inflammatory mediators in allergic disease may be consequent to FcεRI crosslinking inducing CaMKII-mediated activation of FAK activity. FAK inhibition may represent a new MC-suppressing treatment strategy for the treatment of allergic diseases.

Aurora kinase inhibitor tozasertib suppresses mast cell activation in vitro and in vivo

BACKGROUND AND PURPOSE

Mast cells are important in allergic reactions. Here, we assessed the anti-allergic effects of the anti-cancer drug tozasertib specifically regarding regulatory effects on mast cell activation.

EXPERIMENTAL APPROACH

Tozasertib effects on mast cell degranulation were determined by measuring β-hexosaminidase and histamine release and by assessing morphological changes in RBL-2H3 and mouse bone marrow-derived mast cells (BMMCs) stimulated with mouse anti-dinitrophenyl (DNP)-IgE/DNP-human serum albumin or human LAD2 cells activated with phorbol-12-myristate 13-acetate plus calcium ionophore (PMACI). Western blots were performed to detect the expression of molecules involved in NF-κB, MAPK, and Aurora kinase signalling. in vivo anti-allergic effects of tozasertib were determined in the murine IgE-mediated passive cutaneous anaphylaxis (PCA) and ovalbumin (OVA)-induced active systemic anaphylaxis (ASA) models.

KEY RESULTS

Tozasertib treatment decreased high-affinity IgE receptor (FcεRI) or PMACI-mediated degranulation in RBL-2H3 cells and in BMMCs or LAD2 cells as shown by β-hexosaminidase or histamine levels. Similarly, tozasertib prevented morphological changes in mast cells, such as particle release and F-actin reorganization. In addition, tozasertib markedly decreased expression of phosphorylated (p)-NF-κB p65, p-Erk1/2, p-p38, and p-Aurora A/B, indicating that tozasertib can inhibit the signalling pathway mediating mast cell activation. Tozasertib attenuated IgE/Ag-induced PCA dose-dependently, as shown by reduced Evans blue staining. Similarly, tozasertib reduced body temperature levels and serum histamine levels in OVA-challenged ASA mice.

CONCLUSION AND IMPLICATIONS

The Aurora kinase inhibitor tozasertib suppressed mast cell activation in vitro and in vivo. Tozasertib may be a potential drug, targeting mast cell activation, to treat allergic diseases or mastocytosis.

The Theranostics Role of Mast Cells in the Pathophysiology of Rosacea

Rosacea is a chronic inflammatory cutaneous disorder that adversely affects patient's health and quality of life due to the complex course and the need for repeated treatment. The exact molecular mechanisms of rosacea are unclear. Mast cells are innate immune cells that can be found in virtually all tissues. Recently, increasing evidence has indicated that mast cells have important effects on the pathogenesis of rosacea. In this review article, we describe recent advances of skin mast cells in the development of rosacea. These studies suggested that mast cells can be an important immune cell that connected innate immunity, nerves, and blood vessels in the development of rosacea. Moreover, we review the inhibition of mast cells for the potential treatment of rosacea.