Rat Peritoneal Mast Cells Research Articles

Lemon Juice and Peel Constituents Potently Stabilize Rat Peritoneal Mast Cells.

Lemons (Citrus limon ) contain various nutrients and are among the most popular citrus fruit. Besides their antioxidant, anticancer, antibacterial, and anti-inflammatory properties, clinical studies have indicated their anti-allergic properties. Using the differential-interference contrast (DIC) microscopy, we examined the effects of lemon juice and peel constituents, such as citric acid, ascorbic acid, hesperetin and eriodictyol, on the degranulation from rat peritoneal mast cells. Using fluorescence imaging with a water-soluble dye, Lucifer Yellow, we also examined their effects on the deformation of the plasma membrane. Lemon juice dose-dependently decreased the number of degranulated mast cells. At concentrations equal to or higher than 0.25 mM, citric acid, hesperetin, and eriodictyol significantly reduced the number of degranulating mast cells in a dose-dependent manner, while ascorbic acid required much higher doses to exert significant effects. At 1 mM, citric acid, hesperetin, and eriodictyol almost completely inhibited exocytosis and washed out the Lucifer Yellow trapped on the mast cell surface, while ascorbic acid did not. This study provides in vitro evidence for the first time that lemon constituents, such as citric acid, hesperetin, and eriodictyol, potently exert mast cell-stabilizing properties. These properties are attributable to their inhibitory effects on plasma membrane deformation in degranulating mast cells.

Adipokine receptor expression in mast cells is altered by specific ligands and proinflammatory cytokines.

Adipokines play essential roles in regulating a range of biological processes, but growing evidence indicates that they are also fundamental in immunological mechanisms and, primarily, inflammatory responses. Adipokines mediate their actions through specific receptors. However, although adipokine receptors are widely distributed in many cell and tissue types, limited data are available on their expression in mast cells (MCs) and, consequently, adipokine's significance in the modulation of MC activity within the tissues. In this study, we demonstrate that rat peritoneal MCs constitutively express the leptin receptor (i.e. LEPR), adiponectin receptors (i.e. ADIPOR1 and ADIPOR2) and the chemerin receptor (i.e. CMKLR1). We also found that LEPR, ADIPOR1, ADIPOR2 and CMKLR1 expression in MCs changes in response to stimulation by their specific ligands and some cytokines with potent proinflammatory properties. Furthermore, the involvement of intracellular signaling molecules in leptin-, adiponectin- and chemerin-induced MC response was analyzed. Overall, our findings suggest that adipokines leptin, adiponectin and chemerin can significantly affect the activity of MCs in various processes, especially during inflammation. These observations may contribute significantly to understanding the relationship between adipokines, immune mechanisms and diseases or conditions with an inflammatory component.

Prazosin Potentiates Mast Cell-Stabilizing Property of Adrenaline

Background/Aims: Adrenaline quickly inhibits the release of histamine from mast cells. Besides β2-adrenergic receptors, several in vitro studies also indicate the involvement of α-adrenergic receptors in the process of exocytosis. Since exocytosis in mast cells can be detected electrophysiologically by the changes in the membrane capacitance (Cm), its continuous monitoring in the presence of drugs would determine their mast cell-stabilizing properties. Methods: Employing the whole-cell patch-clamp technique in rat peritoneal mast cells, we examined the effects of adrenaline on the degranulation of mast cells and the increase in the Cm during exocytosis. We also examined the degranulation of mast cells in the presence or absence of α-adrenergic receptor agonists or antagonists. Results: Adrenaline dose-dependently suppressed the GTP-γ-S-induced increase in the Cm and inhibited the degranulation from mast cells, which was almost completely erased in the presence of butoxamine, a β2-adrenergic receptor antagonist. Among α-adrenergic receptor agonists or antagonists, high dose prazosin, a selective α1-adrenergic receptor antagonist, significantly reduced the ratio of degranulating mast cells and suppressed the increase in the Cm. Conclusion: This study provided electrophysiological evidence for the first time that adrenaline dose-dependently inhibited the process of exocytosis, confirming its usefulness as a potent mast cell-stabilizer. The pharmacological blockade of α1-adrenergic receptor by prazosin synergistically potentiated such mast cell-stabilizing property of adrenaline, which is primarily mediated by β2-adrenergic receptors.

Retracted: α1-Adrenergic Receptor Blockade by Prazosin Synergistically Stabilizes Rat Peritoneal Mast Cells.

[This retracts the article DOI: 10.1155/2020/3214186.].

Dehydroleucodine and xanthatin, two natural anti-inflammatory lactones, inhibit mast cell degranulation by affecting the actin cytoskeleton.

Actin remodeling is a critical regulator of mast cell secretion. In previous work, we have shown that dehydroleucodine and xanthatin, two natural α,β-unsaturated lactones, exhibit anti-inflammatory and mast cell stabilizing properties. Based on this background, this study aimed to determine whether the mast cell stabilizing action of these lactones is associated with changes in the actin cytoskeleton. Rat peritoneal mast cells were preincubated in the presence of dehydroleucodine or xanthatin before incubation with compound 48/80. Comparative studies with sodium cromoglycate and latrunculin B were also made. After treatments, different assays were performed on mast cell samples: β-hexosaminidase release, cell viability studies, quantification of mast cells and their state of degranulation by light microscopy, transmission electron microscopy, and actin staining for microscopy observation. Results showed that dehydroleucodine and xanthatin inhibited mast cell degranulation, evidenced by the inhibition of β-hexosaminidase release and decreased degranulated mast cell percentage. At the same time, both lactones altered the F-actin cytoskeleton in mast cells resulting, similarly to Latrunculin B, in a higher concentration of nuclear F-actin when activated by compound 48/80. For the first time, this study describes the biological properties of dehydroleucodine and xanthatin concerning to the rearrangement of actin filaments during stimulated exocytosis in mast cells. These data have important implications for developing new anti-inflammatory and mast cell stabilizing drugs and for designing new small molecules that may interact with the actin cytoskeleton.

Determination of the Toxicity and Sensitizing effect of a Therapeutic Probiotic agent against Intestinal and Concomitant human infections

Studies were conducted on the toxicity and possible sensitizing effect of the lyophilizate of a therapeutic probiotic agent from the most active strains of lactic acid and propionic acid bacteria isolated from healthy people: L. plantarum 2v/A-6+L. brevis B-3/A-26+L. acidophilus 27w/60+P. shermanii 8. Based on the studies conducted to evaluate acute toxicity with an oral single administration of probiotic agent solutions (lyophilizate of lactic acid and propionic acid bacteria) at doses of 300, 2,000, 4,000, and 5,001mg/kg of weight, the toxicity class of the preparation under study has been defined as a non-toxic substance. In the study on laboratory mice of subchronic (subacute) toxicity of probiotic agent (lyophilizate of lactic acid and propionic acid bacteria)) in doses of 5.0×106, 10.0×106, and 15.0×106 CFU, it has been found that the preparation does not have a toxic effect on the body in case of 28-day use. Studies of the chronic toxicity of the probiotic agent (lyophilizate of lactic acid and propionic acid bacteria) in doses of 5.0×106, 10.0×106, and 15.0×106 CFU, in laboratory mice have shown that this preparation does not have a toxic effect on the body in case of prolonged 60-day use and does not cause structural changes in internal organs. It has been established that the therapeutic probiotic agent (lyophilizate of lactic acid and propionic acid bacteria) does not have a potential sensitizing (allergenic) effect on rat peritoneal mast cells.

Propolis inhibits IgE-mediated mast cell activation by suppressing SYK/MAPK signaling pathway

Abstract Mast cells play a critical role in the effector phase of immediate hypersensitivity and allergic reactions. Propolis exerts multiple biological effects and exhibits immunomodulatory and antioxidant properties. However, its role in antidinitrophenyl (DNP) immunoglobulin E (IgE)-activated mast cells has not been investigated. In this study, we examined the mechanism underlying the inhibitory effect of propolis (Unibee powder propolis, Uniquebiotech, Co., Ltd., Iksan) on DNP-IgE-mediated mast cell degranulation, with a specific focus on histamine and cytokines release, using rat peritoneal mast cells. Propolis protected mast cell degranulation and inhibited histamine release triggered by anti-DNP IgE in rat peritoneal mast cells (RPMC) in vitro. Interestingly, propolis also decreased the level of TNF-a, IL-4, and IL-13 released from anti-DNP IgE-activated RPMC. Moreover, the SYK and its downstream-MAPK signaling pathway also were suppressed in the anti-DNP IgE-activated RPMC by the incubation with propolis. Together, these results suggest that propolis extract effectively inhibits IgE-mediated mast cell anaphylaxis-like reactions. This research was supported by the 2022 Collaborative R&BD Program of The Food Industry Promotional Agency of Korea. This research was supported by the 2022 Collaborative R&BD Program of The Food Industry Promotional Agency of Korea.

An extract from the culture of a thermophilic <i>Staphylococcus aureus</i> strain suppresses allergic inflammation in the airways <i>in vivo</i> and degranulation of mast cells and basophils <i>in vitro</i>

Aim. To study the anti-allergic effects of ruzam, an extract from the culture of a thermophilic Staphylococcus aureus strain, in an in vivo model of asthma and its influence on degranulation of mast cells and basophils in vitro.Materials and methods. Allergic asthma in guinea pigs was reproduced by two intraperitoneal injections of ovalbumin followed by a series of inhalations of this antigen for 1.5 months. Ruzam (6 μg / kg) or a reference drug (sodium cromoglycate, 3 mg / kg) was administered daily via a nebulizer during the last 6 days of immunization. One day after completion of inhalations with ovalbumin and compared drugs, changes in the airways were assessed using cytological, morphometric, and histologic methods. Rabbit blood basophils and rat peritoneal mast cells were used to determine the effect of ruzam on IgE-independent degranulation induced by the compound 48 / 80 in vitro. The effect of ruzam was compared with that of hydrocortisone hemisuccinate. Basophils from the blood of ovalbumin-sensitized guinea pigs were used to evaluate the effect of the drug on IgE-dependent degranulation induced by ovalbumin. Granules of mast cells and basophils were detected by alcian blue staining to calculate the degranulation index.Results. In the asthma model, ruzam reduced the degree of airway obstruction by increasing the bronchoalveolar lavage volume returned and suppressed neutrophilic and eosinophilic inflammation, while mobilizing other effector cells of the anti-pathogen immunity (lymphocytes and macrophages). Ruzam has proven to have a stronger anti-allergic effect than sodium cromoglycate by several parameters. At concentrations of 8.4–840 μg / ml, ruzam inhibited degranulation of mast cells and basophils, induced by the compound 48 / 80, equally to hydrocortisone hemisuccinate (10–3 M). At concentrations of 280 and 420 μg / ml, ruzam dose-dependently inhibited ovalbumin-induced degranulation of basophils in sensitized guinea pigs.Conclusion. The anti-allergic effect of ruzam was confirmed in test systems in vivo and in vitro. We speculate here that the TLR2 signaling pathway may be involved in biological and pharmacological effects of this drug.

Oleanolic Acid Acetate Inhibits Mast Cell Activation in Ovalbumin-Induced Allergic Airway Inflammation.

Asthma is a complex, heterogeneous chronic inflammatory airway disease with multiple phenotypes. There has been a great progress in managing asthma, but there are still unmet needs for developing uncontrolled asthma treatments. The present study aimed to determine the effectiveness of oleanolic acid acetate (OAA) from Vigna angularis against allergic airway inflammation and the underlying mechanism of action with a focus on mast cells. To investigate the effect of OAA in allergic airway inflammation, we used the ovalbumin (OVA)-sensitized and challenged mice. To examine allergic airway inflammation associated with immune responses of mast cell activation in vitro, various types of mast cells were used. Systemic and cutaneous anaphylaxis models were used for mast cell-mediated hyper-responsiveness in vivo. OAA reduced OVA-induced airway inflammatory responses such as bronchospasm, increase of immune cell infiltration and serum immunoglobulin E and G1 levels. Especially, OAA decreased the mast cell infiltration, and β-hexosaminidase release as a mast cell activation marker in the bronchoalveolar lavage fluid. OAA inhibited mast cell degranulation in mast cell line (RBL-2H3) and primary cells (rat peritoneal mast cell and mouse bone marrow-derived mast cell). Mechanistically, OAA suppressed intracellular signaling pathways including the phosphorylation of phospholipase Cγ and nuclear factor-κB, resulting from the suppression of intracellular calcium influx and pro-inflammatory cytokine expression. Further, oral administration of OAA attenuated mast cell-mediated systemic and cutaneous anaphylaxis. Our study showed that OAA can inhibit mast cell-mediated allergic reaction. Consequently, the application of OAA to mast cells for the allergic airway inflammation facilitate a new direction of treating allergic asthma.

RANKL down-regulates the mast cell proliferation through inducing senescence.

An increase in the number of mast cells could contribute to inflammatory diseases and pathologic conditions. A receptor activator of NF-κB ligand (RANKL)/RANK system is one of the key signaling pathways accelerating mast cell-mediated allergic inflammatory reactions. However, the biological functions of RANKL in mast cell proliferation remains to be clarified. The aim of the present study is to clarify the role of RANKL in mast cell proliferation. Surprisingly, RANKL remarkably reduced the proliferation of human mast cell line, HMC-1 cells through the inhibition of murine double minute 2 (MDM2) and Ki-67 mRNA expressions in a dose-dependent manner. RANKL significantly reduced cell viability, whereas it increased cellular senescence via increasing levels of p53, phosphorylated(p)-p53, p21, and p16 and decreasing levels of retinoblastoma protein (pRb) and p-pRb in HMC-1 cells. Even in rat peritoneal mast cells, RANKL induced cellular senescence by increasing filamentous-actin polymerization. In addition, RANKL remarkably reduced thymic stromal lymphopoietin (TSLP)-induced mast cell proliferation via the downregulation of MDM2 and Ki-67. RANKL decreased levels of p-signal transducer and activator of transcription 6 in TSLP-stimulated HMC-1 cells. The mast cell growth factor, interleukin-13 was remarkably down-regulated by treatment with RANKL in TSLP-stimulated HMC-1 cells. Furthermore, RANKL increased the number of senescence-associated β-galactosidase-stained cells and protein levels of p53, p-p53, and p21 in TSLP-stimulated HMC-1 cells. These data suggest that RANKL down-regulates mast cell proliferation by inducing senescence.

Cetirizine more potently exerts mast cell-stabilizing property than diphenhydramine.

Cetirizine, a second-generation antihistamine, and diphenhydramine, a first-generation antihistamine, are among the most widely used anti-allergic drugs. In addition to longer duration of action and less incidence of sedative side effects, recent clinical studies also indicate a higher potency of cetirizine than diphenhydramine in the treatment or prevention of allergic disorders. In the present study, using the differential-interference contrast (DIC) microscopy, we examined the effects of cetirizine and diphenhydramine (1 μM to 1 mM) on the degranulation from rat peritoneal mast cells. Using fluorescence imaging of a water-soluble dye, lucifer yellow, we also examined their effects on the deformation of the plasma membrane. At relatively higher concentrations (100 μM, 1 mM), both cetirizine and diphenhydramine significantly reduced the numbers of degranulating mast cells. Of note, at 1 mM, cetirizine more markedly reduced the number than diphenhydramine, almost entirely suppressing the degranulation of mast cells. Additionally, 1 mM cetirizine and levocetirizine, another second-generation antihistamine, almost totally inhibited the process of exocytosis in mast cells and washed out the trapping of the lucifer yellow on the cell surface, while diphenhydramine and chlorpheniramine, another first-generation antihistamine, did not. This study provided in vitro evidence for the first time that cetirizine more potently inhibited the process of exocytosis in mast cells than diphenhydramine, indicating its higher potency as a mast cell-stabilizer. Such mast cell-stabilizing property of cetirizine could be ascribed to its counteracting effect on the plasma membrane deformation in degranulating mast cells.

Pyridoxine Synergistically Potentiates Mast Cell-Stabilizing Property of Ascorbic Acid.

Besides their physiological properties, vitamins, such as vitamin C (ascorbic acid) and B6 (pyridoxine), ameliorate the symptoms of allergic disorders. Because exocytosis in mast cells can be detected electrophysiologically by the changes in the membrane capacitance (Cm), its continuous monitoring in the presence of these vitamins would determine their mast cell-stabilizing, anti-allergic properties. Employing the whole-cell patch-clamp technique in rat peritoneal mast cells, we examined the effects of ascorbic acid and pyridoxine on the degranulation of mast cells and the increase in the Cm during exocytosis. Both ascorbic acid and pyridoxine dose-dependently suppressed the GTP-γ-S-induced increase in the Cm and inhibited the degranulation from mast cells. Surprisingly enough, relatively low concentrations of pyridoxine (1, 2 mM) synergistically enhanced the suppressive effect of 2 mM ascorbic acid on mast cell degranulation. These results provided electrophysiological evidence for the first time that ascorbic acid and pyridoxine inhibited the process of exocytosis in a dose-dependent manner. At relatively lower concentrations, these vitamins were not enough to stabilize mast cells. However, such concentrations of pyridoxine synergistically potentiated the mast cell-stabilizing property of ascorbic acid.

Different effectiveness of fungal pathogen-associated molecular patterns (PAMPs) in activating rat peritoneal mast cells

Mast cells (MCs) are the first immune cell type that can contact with the external environment, where they may rapidly sense the presence of pathogens. These cells are directly involved in innate defense through their ability to pathogen destruction by several mechanisms and the pattern recognition receptors (PRRs) they express. Several studies have focused on the aspects of MC responses to bacterial and viral pathogens or their specific components and the role of those cells in antibacterial or antiviral defense mechanisms. However, to date, the knowledge of the influence of various fungi-derived molecules on MC activity is primarily based on limited data. Thus, this study aims to compare the effect of the major fungi cell wall-associated antigens, i.e., two β-(1,3)-glucans: zymosan - β-(1,3)-glucan containing mannan and chitin, and curdlan - purified linear model β-(1,3)-glucan as well as mannan on peritoneal MC activity. In particular, the potency of various fungal cell wall components to induce MC migration, degranulation, and generation and/or release of de novo-synthesized mediators/cytokines/chemokines was analyzed. The most striking result to emerge from the data is that MC activation differs depending on the fungal stimuli. Our study outlines that components of the inner layer of the fungi cell wall - β-glucans, i.e., zymosan and curdlan, are more potent stimulators of MC activity compared to mannan. On this note, the data described here may provide a foundation for further studying the role of MC in antifungal immunity and be helpful for a better understanding of host-pathogenic fungi interactions.

In Vitro Antioxidant and Mast Cell Stabilizing Activity of Different Extracts of Vanda Spathulata Flowers

Objective: The objective of the present work is to evaluate the petroleum ether, ethyl acetate and methanolic extracts of vanda spathulata on experimental models for in vitro antioxidant activity and mast cell stabilizing activity. Methods: Mast cell stabilization effect was assessed using compound 48/80 induced mast cell degranulation in rat peritoneal mast cell. The antioxidant activity was evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Results and Discussion: Vanda spathulata methanolic extract (VSME) at doses of 200 and 400mg/kg exhibited significant protection (p<0.01) and petroleum ether (VSPE) and ethylacetate (VSEA) extracts at the dose of 400mg/kg showed significant protection (p<0.05) against mast cell degranulation. VSME revealed better DPPH radical scavenging activity (IC50 value 38.39 µg/ml) which was closely resembled to standard ascorbic acid (IC50 value 33.98 µg/ml) when compared to other extracts. Phytochemical study revealed the presence of alkaloids, saponins, flavonoids, tannins, steroids and glycosides. Conclusion: From the results Vanda spathulata shows mast cell stabilizing activity mainly due to phytochemical constituents and strong antioxidant property of plant extracts.

Mast Cell Stabilizing, Antianaphylactic and Bronchodilatory activity of Methanolic extract of Averrhoa carambola Fruit

This work was mainly aimed to study the mast cell stabilizing, anti-anaphylactic and bronchodilatory activities of methanolic extract of Averrhoa carambola (ACME). Mast cell stabilization activity was investigated by Compound 48/80 induced mast cell degranulation in rats and antianaphylactic activity was performed by determining the mortality rate of mice upon exposure to compound 48/80. The bronchodilatory effect of ACME was studied on histamine aerosol-induced bronchospasm using guinea pigs, in which occurrence of preconvulsive dyspnea (PCD) was noted as end point. Treatment with ACME (100, 200 and 400mg/kg) showed significant (p<0.05) protection of rat peritoneal mast cells and significantly (p<0.05) reduced the mortality of mice in a dose dependent manner. ACME significantly (p<0.05) increased the time of preconvulsive dyspnea (PCD) in a dose dependent manner that suggestive of bronchodilating activity. Phytochemical studies observed presence of saponins, tannins, steroids, alkaloids, flavonoids and glycosides. From these finding, we concluded that ACME possesses mast cell stabilizing; anti anaphylactic and bronchodilatory activity which might be used in treatment of asthma.

Crosstalk between AdipoR1/AdipoR2 and Nrf2/HO-1 signal pathways activated by β-caryophyllene suppressed the compound 48/80 induced pseudo-allergic reactions.

Mast cell activation is initiated by two signalling pathways: immunoglobulin E (IgE)-dependent and IgE-independent pathway. It is reported that the IgE-independent type or pseudo-allergy pathway gets activated by G-protein-dependent activation of the mast cell. Recently, adiponectin (APN) receptors, AdipoR1, and AdipoR2 have been identified as G-protein-coupled receptors(GPCRs). Interestingly, APN replenishment is reported to activate the Nrf2/HO-1signalling axis. However, no study has been performed interlinking the role of APN and the Nrf2/HO-1signalling axis in pseudo-allergic reaction. In the present study, we evaluated the anti-pseudo-allergic effects of β-caryophyllene, an FDA-approved food additive, in activating AdipoR1/AdipoR2 and Nrf2/HO-1 axis signalling pathway. Compound 48/80 (C48/80)-induced systemic and cutaneous anaphylaxis-like shock in BALB/c mice was performed to assess the efficacy of β-caryophyllene (BCP). To assess the effect of BCP in anaphylactic hypotension, mean arterial pressure was measured in Wistar rats. Inhibitory properties of BCP in mast cell degranulation were estimated in rat peritoneal mast cells (RPMCs). ELISA was performed to estimate interleukin (IL)-6, tumour necrosis factor (TNF), IL-1β, IgE, ovalbumin (OVA)-IgE and APN and western blotting for protein expression of Nrf2/HO-1 and AdipoR1-AdipoR2. BCP dose-dependently inhibited systemic and cutaneous anaphylaxis-like shock induced by C48/80. BCP dose-dependently inhibited the mast cell degranulation followed by inhibition of histamine release. Also BCP dose-dependently activated the Nrf2/HO-1 and AdipoR1-AdipoR2signalling axis pathway. Moreover, BCP reversed the drop in blood pressure when the haemodynamic parameters were accessed. Our findings suggest that BCP is a potent AdipoR1/AdipoR2-Nrf2/HO-1 axis pathway agonist that may suppress the IgE-independent pathway towards allergic response to secretagogues.

Mast cell and heparin promote adipogenesis in superficial fascia of rats

Fascial adipocytes are recently identified as a unique population of adipose cells, which have different developmental origins, anatomical locations, cytological and functional characteristics compared with subcutaneous or visceral adipocytes. Superficial fascia in rats (also in pigs but not obviously in mice) contains numbers of lineage committed preadipocytes which possess adipogenic potential in vivo. The present study aimed to investigate the physiological factors that contribute to fascial adipogenesis in rats. We detected that mast cells, adipose progenitor cells, and mature adipocytes distributed in certain fascia areas were closely associated with each other, and numerous heparin-loaded granules released from mast cells were distributed around fascial preadipocytes. The culture supernatants of rat peritoneal mast cells and RBL-2H3 mast cells contained 20–30 μg/ml of heparin, effectively activated PPAR-responsive luciferase activity, promoted mRNA and protein expressions of key adipogenic genes, and hence increased adipogenic differentiation of fascia- or epididymal adipose-derived stromal cells. Adipogenic effects of mast cell supernatants were mimicked by heparin but not by histamine or 5-hydroxytryptamine, and were antagonized by protamine sulfate. In rats, local administration of heparin-loaded microspheres for 30 days induced adipogenesis in local areas of superficial fascia. This adipogenic effects of heparin might be related by chain length of glucosamine units, because heparin stimulated stronger adipogenesis than dalteparin and enoxaparin with relatively short chains. Our findings suggested that mast cell and its granule heparin could serve as the endogenous physiological factors to initiate and accelerate local adipogenesis in superficial fascia, or in adipose tissue with the fascia naturally embedded inside.

Light‐driven Activation of NADP(H) Oxidase 5

Ultraviolet band A (UVA) light irradiation has been shown to induce cytosolic calcium oscillations in the isolated rat peritoneal mast cells via activation of NADPH oxidase (NOX). It has been clarified that UVA-triggered calcium oscillations in mast cells (isolated rat peritoneal mast cells, rat mast cell line RBL-2H3, mouse bone marrow-derived mast cells) was due to NOX2 activation. To elucidate whether UVA light irradiation would also activate NOX5, a monomeric isoform of the NOX family of oxidases not requiring transmembrane p22 or cytosolic subunits for activity and not endogenously expressed in rodents, NOX5 was expressed ectopically in CHO-K1 cells, and the effect of UVA irradiation or photodynamic action on cytosolic calcium concentration was monitored with Fura-2 fluorescent calcium imaging. It was found that NOX5 expressed ectopically in CHO-K1 cells was activated by UVA (LED 380 nm) light irradiation to induce persistent cytosolic calcium oscillations. Blue LED (450 nm) light irradiation of CHO-K1 cells expressing protein photosensitizer miniSOG-NOX5 fusion protein triggered also persistent cytosolic calcium oscillations which were completely blocked by NOX inhibitor diphenyleneiodonium (DPI), and inhibited by singlet oxygen quencher Trolox C. Sulphonated aluminium phthalocyanine (SALPC) photodynamically activated the heterologously expressed NOX5 in CHO-K1 cells to trigger similarly cytosolic calcium oscillations, which were completely inhibited by DPI. These data suggest that both UVA light irradiation and 1O2 generation with photodynamic action could activate NOX5, to ultimately trigger calcium oscillations. It is therefore possible now to realize light-driven NOX5 activation for cell-type or subcellular organelle specific generation of superoxide anion.

Native and IgE-primed rat peritoneal mast cells exert pro-inflammatory activity and migrate in response to yeast zymosan upon Dectin-1 engagement

Mast cells (MCs) play an essential role in host defense, primarily because of their location, their ability to pathogen destruction via several mechanisms, and the pattern recognition receptors they express. Even though most data is available regarding MC activation by various bacteria- or virus-derived molecules, those cells’ activity in response to constituents associated with fungi is not recognized enough. Our research aimed to address whether Saccharomyces cerevisiae-derived zymosan, i.e., β-(1,3)-glucan containing mannan particles, impacts MC activity aspects. Overall, the obtained results indicate that zymosan has the potential to elicit a pro-inflammatory response of rat peritoneal MCs. For the first time ever, we provided evidence that zymosan induces fully mature MC migration, even in the absence of extracellular matrix (ECM) proteins. Moreover, the zymosan-induced migratory response of MCs is almost entirely a result of directional migration, i.e., chemotaxis. We found that zymosan stimulates MCs to degranulate and generate lipid mediators (cysLTs), cytokines (IFN-α, IFN-β, IFN-γ, GM-CSF, TNF), and chemokine (CCL2). Zymosan also upregulated mRNA transcripts for several cytokines/chemokines with pro-inflammatory/immunoregulatory activity. Moreover, we documented that zymosan activates MCs to produce reactive oxygen species (ROS). Lastly, we established that the zymosan-induced MC response is mediated through activation of the Dectin-1 receptor. In general, our results strongly support the notion that MCs contribute to innate antifungal immunity and bring us closer to elucidate their role in host-pathogenic fungi interactions. Besides, provided findings on IgE-sensitized MCs appear to indicate that exposure to fungal zymosan could affect the severity of IgE-dependent disorders, including allergic ones.

The impact of TLR7 agonist R848 treatment on mast cell phenotype and activity

Bearing in mind that mast cell contribution to viral clearance is still not fully understood, in this study, we evaluated the effect of Toll-like receptor (TLR)7 viral single-stranded ribonucleic acid (ssRNA) mimic ligand, namely resiquimod (R)848, on mast cell phenotype and activity. We demonstrated that rat peritoneal mast cells exhibit surface and intracellular expression of ssRNA-specific TLR7 molecule, and that mimic ligand switches the self-expression of this receptor. We also detected other proteins associated with the cellular antiviral response: interferon-alpha receptor 1 (IFNAR1), interferon-gamma receptor 1 (IFNGR1), and major histocompatibility complex I (MHC I). Moreover, we showed that R848 caused the decrease of all molecule’s expression after prolonged incubation. Interestingly, we found that R848 induced the increase of high-affinity IgE receptor (FcεRI) expression. Finally, we documented that TLR7 ligand-stimulated mast cells synthesize/release interferon (IFN)-α and -β, tumor necrosis factor (TNF), and chemokines CCL3, CXCL8, as well as pro-inflammatory lipid mediators. Our findings confirm that mast cells may respond to TLR7 ligand by altering their phenotype and synthesizing mediators and could serve as active participants in the antiviral immune response.