Mast cells in the promotion and limitation of chronic inflammation

The localisation of inflammatory cells and expression of associated proteoglycans in response to implanted chitosan

Implantation of a foreign material almost certainly results in the formation of a fibrous capsule around the implant however, mechanistic events leading to its formation are largely unexplored. Mast cells are an inflammatory cell type known to play a role in the response to material implants, through the release of pro-inflammatory proteases and cytokines from their α-granules following activation. This study examined the in vivo and in vitro response of mast cells to chitosan, through detection of markers known to be produced by mast cells or involved with the inflammatory response. Mast cells, identified as Leder stained positive cells, were shown to be present in response to material implants. Additionally, the mast cell receptor, c-kit, along with collagen, serglycin, perlecan and chondroitin sulphate were detected within the fibrous capsules, where distribution varied between material implants. In conjunction, rat mast cells (RBL-2H3) were shown to be activated following exposure to chitosan as indicated by the release of β-hexosaminidase. Proteoglycan and glycosaminoglycans produced by the cells showed similar expression and localisation when in contact with chitosan to when chemically activated. These data support the role that mast cells play in the inflammatory host response to chitosan implants, where mediators released from their α-granules impact on the formation of a fibrous capsule by supporting the production and organisation of collagen fibres.

TRPA1-dependent pruritus in IL-13-induced chronic atopic dermatitis

Chronic debilitating pruritus is a cardinal feature of atopic dermatitis (AD). Little is known about the underlying mechanisms. Antihistamines lack efficacy in treating itch in AD, suggesting the existence of histamine-independent itch pathways in AD. Transient receptor potential ankyrin 1 (TRPA1) is essential in the signaling pathways that promote histamine-independent itch. In this study, we tested the hypothesis that TRPA1-dependent neural pathways play a key role in chronic itch in AD using an IL-13-transgenic mouse model of AD. In these mice, IL-13 causes chronic AD characterized by intensive chronic itch associated with markedly enhanced growth of dermal neuropeptide-secreting afferent nerve fibers and enhanced expression of TRPA1 in dermal sensory nerve fibers, their dorsal root ganglia, and mast cells. Inhibition of TRPA1 with a specific antagonist in these mice selectively attenuated itch-evoked scratching. Genetic deletion of mast cells in these mice led to significantly diminished itch-scratching behaviors and reduced TRPA1 expression in dermal neuropeptide containing afferents in the AD skin. Interestingly, IL-13 strongly stimulates TRPA1 expression, which is functional in calcium mobilization in mast cells. In accordance with these observations in the AD mice, TRPA1 expression was highly enhanced in the dermal afferent nerves, mast cells, and the epidermis in the lesional skin biopsies from patients with AD, but not in the skin from healthy subjects. These studies demonstrate a novel neural mechanism underlying chronic itch in AD and highlight the complex interactions among TRPA1(+) dermal afferent nerves and TRPA1(+) mast cells in a Th2-dominated inflammatory environment.

The scaffold protein prohibitin is required for antigen-stimulated signaling in mast cells

The protein prohibitin (PHB) is implicated in diverse cellular processes, including cell signaling, transcriptional control, and mitochondrial function. We found that PHB was abundant in the intracellular granules of mast cells, which are critical for allergic responses to antigens. Thus, we investigated whether PHB played a role in signaling mediated by the high-affinity receptor for antigen-bound immunoglobulin E (IgE), FcεRI. PHB-specific small interfering RNAs (siRNAs) inhibited antigen-mediated signaling, degranulation, and cytokine secretion by mast cells in vitro. Knockdown of PHB inhibited the antigen-dependent association of the tyrosine kinase Syk with FcεRI and inhibited the activation of Syk. Fractionation studies revealed that PHB translocated from intracellular granules to plasma membrane lipid rafts in response to antigen, and knockdown of PHB suppressed the movement of FcεRIγ and Syk into lipid rafts. Tyrosine phosphorylation of PHB by Lyn was observed early after exposure to antigen, and point mutations in PHB indicated that Tyr(114) and Tyr(259) were required for the recruitment of Syk to FcεRIγ and mast cell activation. In mice, PHB-specific siRNAs inhibited antigen-initiated mast cell degranulation, passive cutaneous anaphylaxis, and passive systemic anaphylaxis. Together, these results suggest that PHB is essential for FcεRI-mediated mast cell activation and allergic responses in vivo, raising the possibility that PHB might serve as a therapeutic target for the treatment of allergic diseases.

Study to determine the criterion validity of the SenseWear Armband as a measure of physical activity in people with rheumatoid arthritis

OBJECTIVE

Measuring physical activity in people with rheumatoid arthritis (RA) is of great importance in light of the increased mortality in this population due to cardiovascular disease. Validation of activity monitors in specific populations is recommended to ensure the accuracy of physical activity measurement. Thus, the purpose of this study was to determine the validity of the SenseWear Pro3 Armband (SWA) as a measure of physical activity during activities of daily living (ADL) in people with RA.

METHODS

Fourteen subjects (8 men and 6 women) with a diagnosis of RA were recruited from rheumatology clinics at the Mid-Western Regional Hospitals, Limerick, Ireland. Participants undertook a series of ADL of varying intensities. The SWA was compared to the criterion measures of the Oxycon Mobile indirect calorimetry system (energy expenditure in kJ) and of manual video observation (step count). Bland and Altman, intraclass correlation coefficient (ICC), and correlation analyses were done using SPSS, version 19.0.

RESULTS

The SWA showed substantial agreement (ICC 0.717, P < 0.001) and a strong relationship (Pearson's correlation coefficient = 0.852) compared with the criterion measure when estimating energy expenditure during ADL. However, it was found that the SWA overestimated energy expenditure, particularly at higher intensity levels. The ability of the SWA to estimate step counts during ADL was poor (ICC 0.304, P = 0.038).

CONCLUSION

The SWA can be considered a valid tool to estimate energy expenditure during ADL in the RA population; however, attention should be paid to its tendency to overestimate energy expenditure.

Prevention of F-actin assembly switches the response to SCF from chemotaxis to degranulation in human mast cells

Following antigen/IgE-mediated aggregation of high affinity IgE-receptors (FcεRI), mast cells (MCs) degranulate and release inflammatory mediators leading to the induction of allergic reactions including anaphylaxis. Migration of MCs to resident tissues and sites of inflammation is regulated by tissue chemotactic factors such as stem cell factor (SCF (KIT ligand)). Despite inducing similar early signaling events to antigen, chemotactic factors, including SCF, produce minimal degranulation in the absence of other stimuli. We therefore investigated whether processes regulating MC chemotaxis are rate limiting for MC mediator release. To investigate this issue, we disrupted actin polymerization, a requirement for MC chemotaxis, with latrunculin B and cytochalasin B, then examined chemotaxis and mediator release in human (hu)MCs induced by antigen or SCF. As expected, such disruption minimally affected early signaling pathways, but attenuated SCF-induced human mast cell chemotaxis. In contrast, SCF, in the absence of other stimuli, induced substantial degranulation in a concentration-dependent manner following actin disassembly. It also moderately enhanced antigen-mediated human mast cell degranulation which was further enhanced in the presence of SCF. These observations suggest that processes regulating cell migration limit MC degranulation as a consequence of cytoskeletal reorganization.

The role of mast cells in neuroinflammation

Mast cells (MCs) are densely granulated perivascular resident cells of hematopoietic origin and well known for their pathogenetic role in allergic and anaphylactic reactions. In addition, they are also involved in processes of innate and adaptive immunity. MCs can be activated in response to a wide range of stimuli, resulting in the release of not only pro-inflammatory, but also anti-inflammatory mediators. The patterns of secreted mediators depend upon the given stimuli and microenvironmental conditions, accordingly MCs have the ability to promote or attenuate inflammatory processes. Their presence in the central nervous system (CNS) has been recognized for more than a century. Since then a participation of MCs in various pathological processes in the CNS has been well documented. They can aggravate CNS damage in models of brain ischemia and hemorrhage, namely through increased blood-brain barrier damage, brain edema and hemorrhage formation and promotion of inflammatory responses to such events. In contrast, recent evidence suggests that MCs may have a protective role following traumatic brain injury by degrading pro-inflammatory cytokines via specific proteases. In neuroinflammatory diseases such as multiple sclerosis, the role of MCs seems to be ambiguous. MCs have been shown to be damaging, neuroprotective, or even dispensable, depending on the experimental protocols used. The role of MCs in the formation and progression of CNS tumors such as gliomas is complex and both positive and negative relationships between MC activity and tumor progression have been reported. In summary, MCs and their secreted mediators modulate inflammatory processes in multiple CNS pathologies and can thereby either contribute to neurological damage or confer neuroprotection. This review intends to give a concise overview of the regulatory roles of MCs in brain disease.

Arthritis augments breast cancer metastasis: role of mast cells and SCF/c-Kit signaling

Introduction

Breast cancer remains the second leading cause of cancer-related deaths for women in the United States. Metastasis is regulated not only by intrinsic genetic changes in malignant cells, but also by the microenvironment, especially those associated with chronic inflammation. We recently reported that mice with autoimmune arthritis have significantly increased incidence of bone and lung metastasis and decreased survival associated with breast cancer. In this study, we evaluated the mechanism underlying the increased metastasis.

Methods

We used two mouse models; one that develops spontaneous autoimmune arthritis (SKG mice) injected with metastatic breast cancer cells (4T1), and another that develops spontaneous breast cancer (MMTV-PyV MT mice) injected with type II collagen to induce autoimmune arthritis. Mast cell levels and metastasis were monitored.

Results

First, we confirmed that breast tumor-bearing arthritic mice have a significantly higher incidence of bone and lung metastasis than do their nonarthritic counterparts. Next, we showed increased recruitment of mast cells within the primary tumor of arthritic mice, which facilitates metastasis. Next, we report that arthritic mice without any tumors have higher numbers of mast cells in the bones and lungs, which may be the underlying cause for the enhanced lung and bone metastases observed in the arthritic mice. Next, we showed that once the tumor cells populate the metastatic niches (bones and lungs), they further increase the mast cell population within the niche and assist in enhancing metastasis. This may primarily be due to the interaction of c-Kit receptor present on mast cells and stem cell factor (SCF, the ligand for ckit) expressed on tumor cells. Finally, we showed that targeting the SCF/cKit interaction with an anti-ckit antibody reduces the differentiation of mast cells and consequently reduces metastasis.

Conclusion

This is the first report to show that mast cells may play a critical role in remodeling not only the tumor microenvironment but also the metastatic niche to facilitate efficient metastasis through SCF/cKit interaction in breast cancer with arthritis.

Mast Cells in Adjacent Normal Colon Mucosa rather than Those in Invasive Margin are Related to Progression of Colon Cancer

OBJECTIVE

Mast cells (MC) reside in the mucosa of the digestive tract as the first line against bacteria and toxins. Clinical evidence has implied that the infiltration of mast cells in colorectal cancers is related to malignant phenotypes and a poor prognosis. This study compared the role of mast cells in adjacent normal colon mucosa and in the invasive margin during the progression of colon cancer.

METHODS

Specimens were obtained from 39 patients with colon adenomas and 155 patients with colon cancers treated at the Sun Yat-sen University Cancer Center between January 1999 and July 2004. The density of mast cells was scored by an immunohistochemical assay. The pattern of mast cell distribution and its relationship with clinicopathologic parameters and 5-year survival were analyzed.

RESULTS

The majority of mast cells were located in the adjacent normal colon mucosa, followed by the invasive margin and least in the cancer stroma. Mast cell count in adjacent normal colon mucosa (MCC(adjacent)) was associated with pathologic classification, distant metastases and hepatic metastases, although it was not a prognostic factor. In contrast, mast cell count in the invasive margin (MCC(invasive)) was associated with neither the clinicopathlogic parameters nor overall survival.

CONCLUSION

Mast cells in the adjacent normal colon mucosa were related to the progression of colon cancer, suggesting that mast cells might modulate tumor progression via a long-distance mechanism.

Tryptase serum levels in patients suffering from hepatocellular carcinoma undergoing intra-arterial chemoembolization: Possible predictive role of response to treatment

Tryptase is a serin protease stored in mast cell granules that has recently been found to be involved in tumor angiogenesis. Data from experimental tumor models have suggested that prior to the onset of angiogenesis mast cells were accumulated near tumor cells and were required for the macroscopic expansion and metastatic spread of primary tumor cells. Hepatocellular cancer (HCC) is a well-established, highly angiogenesis-dependent hypervascular tumor. The aim of this preliminary study was to assess tryptase serum levels in 30 HCC patients prior and subsequent to hepatic transarterial chemoembolization (TACE). In this study, patients with intermediate stage (B) HCC, according to the Barcelona Clinic Liver Cancer (BCLC) staging classification, were enrolled. Additional patient features were adequate liver functional reserve and A or B status, according to the Child-Pugh classification. Tryptase levels were measured using the UniCAP-Tryptase fluoroimmunoassay. TACE was performed by loading doxorubicin on microspheres. The mean ± standard deviation (SD) tryptase level pre-TACE was 7.74±3.62 μg/l, and post-TACE 4.67±2.79 μg/l. A statistically significant difference (P<0.001) was detected, using the Student's t-test, between pre- and post-TACE tryptase level concentrations. No correlations were found between tryptase levels and other important clinicopathological features of patients. This is the first preliminary study analyzing the potential significance of serum tryptase levels in HCC patients. The results demonstrated higher serum tryptase levels in HCC patients, suggesting tryptase release from HCC tissue. As expected, after TACE, serum tryptase levels were decreased. Therefore, we suggested that tryptase was a potential biomarker of response to TACE treatment in HCC patients.

Effects of probiotic Lactobacillus rhamnosus GG and Propionibacterium freudenreichii ssp. shermanii JS supplementation on intestinal and systemic markers of inflammation in ApoE*3Leiden mice consuming a high-fat diet

A high-fat diet disturbs the composition and function of the gut microbiota and generates local gut-associated and also systemic responses. Intestinal mast cells, for their part, secrete mediators which play a role in the orchestration of physiological and immunological functions of the intestine. Probiotic bacteria, again, help to maintain the homeostasis of the gut microbiota by protecting the gut epithelium and regulating the local immune system. In the present study, we explored the effects of two probiotic bacteria, Lactobacillus rhamnosus GG (GG) and Propionibacterium freudenreichii spp. shermanii JS (PJS), on high fat-fed ApoE*3Leiden mice by estimating the mast cell numbers and the immunoreactivity of TNF-α and IL-10 in the intestine, as well as plasma levels of several markers of inflammation and parameters of lipid metabolism. We found that mice that received GG and PJS exhibited significantly lower numbers of intestinal mast cells compared with control mice. PJS lowered intestinal immunoreactivity of TNF-α, while GG increased intestinal IL-10. PJS was also observed to lower the plasma levels of markers of inflammation including vascular cell adhesion molecule 1, and also the amount of gonadal adipose tissue. GG lowered alanine aminotransferase, a marker of hepatocellular activation. Collectively, these data demonstrate that probiotic GG and PJS tend to down-regulate both intestinal and systemic pro-inflammatory changes induced by a high-fat diet in this humanised mouse model.

Neurotensin and CRH interactions augment human mast cell activation

Stress affects immunity, but the mechanism is not known. Neurotensin (NT) and corticotropin-releasing hormone (CRH) are secreted under stress in various tissues, and have immunomodulatory actions. We had previously shown that NT augments the ability of CRH to increase mast cell-dependent skin vascular permeability in rodents. Here we show that NT triggered human mast cell degranulation and significantly augmented CRH-induced vascular endothelial growth factor (VEGF) release. Investigation of various signaling molecules indicated that only NF-κB activation was involved. These effects were blocked by pretreatment with the NTR antagonist SR48692. NT induced expression of CRH receptor-1 (CRHR-1), as shown by Western blot and FACS analysis. Interestingly, CRH also induced NTR gene and protein expression. These results indicate unique interactions among NT, CRH, and mast cells that may contribute to auto-immune and inflammatory diseases that worsen with stress.

The chymase mouse mast cell protease 4 degrades TNF, limits inflammation, and promotes survival in a model of sepsis

Mouse mast cell protease 4 (mMCP-4), the mouse counterpart of human mast cell chymase, is thought to have proinflammatory effects in innate or adaptive immune responses associated with mast cell activation. However, human chymase can degrade the proinflammatory cytokine TNF, a mediator that can be produced by mast cells and many other cell types. We found that mMCP-4 can reduce levels of mouse mast cell-derived TNF in vitro through degradation of transmembrane and soluble TNF. We assessed the effects of interactions between mMCP-4 and TNF in vivo by analyzing the features of a classic model of polymicrobial sepsis, cecal ligation and puncture (CLP), in C57BL/6J-mMCP-4-deficient mice versus C57BL/6J wild-type mice, and in C57BL/6J-Kit(W-sh/W-sh) mice containing adoptively transferred mast cells that were either wild type or lacked mMCP-4, TNF, or both mediators. The mMCP-4-deficient mice exhibited increased levels of intraperitoneal TNF, higher numbers of peritoneal neutrophils, and increased acute kidney injury after CLP, and also had significantly higher mortality after this procedure. Our findings support the conclusion that mMCP-4 can enhance survival after CLP at least in part by limiting detrimental effects of TNF, and suggest that mast cell chymase may represent an important negative regulator of TNF in vivo.

Targeting c-kit in the therapy of mast cell disorders: current update

Classically, mast cells have been widely associated with allergic reactions and parasite infections, but recent studies have elucidated the important role of these cells in innate and acquired immunity, wound healing, fibrosis, and chronic inflammatory diseases. Mast cells release an impressive array of proinflammatory and immunoregulatory mediators after activation induced by either immunoglobulin-E (IgE)-dependent or IgE-independent mechanisms. Proliferation, differentiation, survival and activation of mast cells are regulated by stem cell factor (SCF), the ligand for the c-kit tyrosine kinase receptor which is expressed on the mast cell surface. Inappropriate c-kit activation causes accumulation of mast cells in tissues resulting in mastocytosis. A number of activating mutations in c-kit have recently been identified and these mutations results in aberrant mast cell growth. Thus, c-kit inhibitors may have potential application in multiple conditions associated with mast cell disorders including systemic mastocytosis, anaphylaxis, and asthma. The present perspective aims to summarize recent findings in mast cell biology and the role of c-kit tyrosine kinase inhibitors in the treatment of different mast cell associated disorders.

Mast Cells are Important Modifiers of Autoimmune Disease: With so Much Evidence, Why is There Still Controversy?

There is abundant evidence that mast cells are active participants in events that mediate tissue damage in autoimmune disease. Disease-associated increases in mast cell numbers accompanied by mast cell degranulation and elaboration of numerous mast cell mediators at sites of inflammation are commonly observed in many human autoimmune diseases including multiple sclerosis, rheumatoid arthritis, and bullous pemphigoid. In animal models, treatment with mast cell stabilizing drugs or mast cell ablation can result in diminished disease. A variety of receptors including those engaged by antibody, complement, pathogens, and intrinsic danger signals are implicated in mast cell activation in disease. Similar to their role as first responders in infection settings, mast cells likely orchestrate early recruitment of immune cells, including neutrophils, to the sites of autoimmune destruction. This co-localization promotes cellular crosstalk and activation and results in the amplification of the local inflammatory response thereby promoting and sustaining tissue damage. Despite the evidence, there is still a debate regarding the relative role of mast cells in these processes. However, by definition, mast cells can only act as accessory cells to the self-reactive T and/or antibody driven autoimmune responses. Thus, when evaluating mast cell involvement using existing and somewhat imperfect animal models of disease, their importance is sometimes obscured. However, these potent immune cells are undoubtedly major contributors to autoimmunity and should be considered as important targets for therapeutic disease intervention.

VEGF is involved in the increase of dermal microvascular permeability induced by tryptase

Tryptases are predominantly mast cell-specific serine proteases with pleiotropic biological activities and play a critical role in skin allergic reactions, which are manifested with rapid edema and increases of vascular permeability. The exact mechanisms of mast cell tryptase promoting vascular permeability, however, are unclear and, therefore, we investigated the effect and mechanism of tryptase or human mast cells (HMC-1) supernatant on the permeability of human dermal microvascular endothelial cells (HDMECs). Both tryptase and HMC-1 supernatant increased permeability of HDMECs significantly, which was resisted by tryptase inhibitor APC366 and partially reversed by anti-VEGF antibody and SU5614 (catalytic inhibitor of VEGFR). Furthermore, addition of tryptase to HDMECs caused a significant increase of mRNA and protein levels of VEGF and its receptors (Flt-1 and Flk-1) by Real-time RT-PCR and Western blot, respectively. These results strongly suggest an important role of VEGF on the permeability enhancement induced by tryptase, which may lead to novel means of controlling allergic reaction in skin.

Mast cell: an emerging partner in immune interaction

Mast cells (MCs) are currently recognized as effector cells in many settings of the immune response, including host defense, immune regulation, allergy, chronic inflammation, and autoimmune diseases. MC pleiotropic functions reflect their ability to secrete a wide spectrum of preformed or newly synthesized biologically active products with pro-inflammatory, anti-inflammatory and/or immunosuppressive properties, in response to multiple signals. Moreover, the modulation of MC effector phenotypes relies on the interaction of a wide variety of membrane molecules involved in cell–cell or cell-extracellular-matrix interaction. The delivery of co-stimulatory signals allows MC to specifically communicate with immune cells belonging to both innate and acquired immunity, as well as with non-immune tissue-specific cell types. This article reviews and discusses the evidence that MC membrane-expressed molecules play a central role in regulating MC priming and activation and in the modulation of innate and adaptive immune response not only against host injury, but also in peripheral tolerance and tumor-surveillance or -escape. The complex expression of MC surface molecules may be regarded as a measure of connectivity, with altered patterns of cell–cell interaction representing functionally distinct MC states. We will focalize our attention on roles and functions of recently discovered molecules involved in the cross-talk of MCs with other immune partners.

Fine-Tuning of Mast Cell Activation by FcεRIβ Chain

Mast cells play a key role in allergic reaction and disorders through the high affinity receptor for IgE (Fc_εRI) which is primarily activated by IgE and antigen complex. In humans, mast cells express two types of Fc_εRI on the cell surface, tetrameric αβγ₂ and trimeric αγ₂, whereas in mice, the tetrameric αβγ₂ type is exclusively expressed. In human allergic inflammation lesions, mast cells increase in number and preferentially express the αβγ₂ type Fc_εRI. By contrast, in the lesion of non-allergic inflammation, mast cells mainly express the αγ₂type. Since the β chain amplifies the expression and signaling of FcεRI, mast cell effector functions and allergic reaction in vivo are enhanced in the presence of the β chain. In contrast, a truncated β chain-isoform (βT) inhibits FcεRI surface expression. The human Fc_εRIβ gene contains seven exons and a repressor element located in the forth intron, through which Fc_εRIβ transcription is repressed in the presence of GM-CSF. Regarding the additional signal regulatory function of the β chain, the β chain ITAM has dual (positive and negative) functions in the regulation of the mast cell activation. Namely, the Fc_εRIβ chain ITAM enhances the mast cell activation signal triggered by a low-intensity (weak) stimulation whereas it suppresses the signal triggered by high-intensity (strong) stimulation. In an oxazolone-induced mouse CHS model, IgE-mediated mast cell activation is required and the β chain ITAM is crucially involved. Adenosine receptor, one of the GPCRs, triggers a synergistic degranulation response with FcεRI in mast cells, for which the β chain ITAM critically plays positive role, possibly reflecting the in vivo allergic response. These regulatory functions of the FcεRIβ ITAM finely tune FcεRI-induced mast cell activation depending on the stimulation strength, enabling the Fc_εRIβ chain to become a potential molecular target for the development of new strategies for therapeutic interventions for allergies.

Roles for ca(2+) mobilization and its regulation in mast cell functions

Mobilization of Ca²⁺ in response to IgE receptor-mediated signaling is a key process in many aspects of mast cell function. Here we summarize our current understanding of the molecular bases for this process and the roles that it plays in physiologically relevant mast cell biology. Activation of IgE receptor signaling by antigen that crosslinks these complexes initiates Ca²⁺ mobilization as a fast wave that is frequently followed by a series of Ca²⁺ oscillations which are dependent on Ca²⁺ influx-mediated by coupling of the endoplasmic reticulum luminal Ca²⁺ sensor STIM1 to the calcium release activated calcium channel protein Orai1. Granule exocytosis depends on this process, together with the activation of protein kinase C isoforms, and specific roles for these signaling steps are beginning to be understood. Ca²⁺ mobilization also plays important roles in stimulated exocytosis of recycling endosomes and newly synthesized cytokines, as well as in antigen-mediated chemotaxis of rat mucosal mast cells. Phosphoinositide metabolism plays key roles in all of these processes, and we highlight these roles in several cases.

Antiallergic effects of Scutellaria baicalensis on inflammation in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Scutellaria baicalensis (SB) is one of the most widely used medicinal herbs for the treatment of inflammation. In this study, we investigated the antiallergic effect of SB in vivo and in vitro.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats received intradermal injections of anti-DNP IgE at each of three dorsal skin sites. Forty-eight hours later, each rat received an injection of DNP-HSA in saline containing 4% Evans blue through the dorsal vein of the penis. One hour before injection, SB extract was administered orally. The dorsal skin of the rats was removed and the pigment area measured. In addition, rat peritoneal mast cells (RPMCs) were cultured and purified to investigate histamine release. In vitro, human mast cells (HMC-1) were pretreated with SB extract for 30min before stimulation with phorbol 12-myristate 13-acetate (PMA) plus A23187. The effects on pro-inflammatory cytokine expression and mitogen activated protein (MAP) kinase expression were investigated using TNF-α and IL-8 assays, and Western blotting analysis of HMC-1 cells.

RESULTS AND CONCLUSIONS

SB treatment inhibited the passive cutaneous anaphylaxis reaction compared to the control group, and histamine release decreased significantly following treatment of RPMCs with SB. In HMC-1 cells, SB restored IL-8 and TNF-α expression and inhibited MAP kinase expression in compound 48/80-induced HMC-1 cells. These data suggest that SB may prove to be a useful anti-inflammatory agent through its downregulation of the expression of various inflammatory mediators.

Do Adventitial Mast Cells Contribute to the Pathogenesis of Ascending Thoracic Aorta Aneurysm?

The precise pathogenesis of the ascending aortic aneurysm (AscAA) remains to be determined. Mast cells in the adventitia of human AscAA lesions may play a role in this pathogenesis. Adventitial mast cell density per 10 high-power fields (0.25 mm2) was assessed in multiple biopsy samples, from aneurysmal aortic sections (n = 41) and control (nondilated) aortic specimens (n = 50), stained by orcein-Giemsa method, an inexpensive (<$1) method. In a multivariable adjusted logistic regression model, using AscAA as the dependent variable, mast cell density was found to be an independent predictor of AscAA occurrence (odds ratio = 2.21; 95% confidence interval = 1.58-3.08; P < .001). Receiver operating characteristic curve analysis showed that the proposed cutoff value of ≥3 mast cells per 10 high-power fields was very sensitive to detect AscAA occurrence, yielding a sensitivity of 90% with a specificity of 80%. In conclusion, a significant increase in the number of mast cells in the adventitia of human ascending aortic lesions proposes a role for these cells in the pathogenesis of AscAA.

The role of SHIP in the development and activation of mouse mucosal and connective tissue mast cells

Although SHIP is a well-established suppressor of IgE plus Ag-induced degranulation and cytokine production in bone marrow-derived mast cells (BMMCs), little is known about its role in connective tissue (CTMCs) or mucosal (MMCs) mast cells. In this study, we compared SHIP's role in the development as well as the IgE plus Ag and TLR-induced activation of CTMCs, MMCs, and BMMCs and found that SHIP delays the maturation of all three mast cell subsets and, surprisingly, that it is a positive regulator of IgE-induced BMMC survival. We also found that SHIP represses IgE plus Ag-induced degranulation of all three mast cell subsets and that TLR agonists do not trigger their degranulation, whether SHIP is present or not, nor do they enhance IgE plus Ag-induced degranulation. In terms of cytokine production, we found that in MMCs and BMMCs, which are poor producers of TLR-induced cytokines, SHIP is a potent negative regulator of IgE plus Ag-induced IL-6 and TNF-α production. Surprisingly, however, in splenic or peritoneal derived CTMCs, which are poor producers of IgE plus Ag-induced cytokines, SHIP is a potent positive regulator of TLR-induced cytokine production. Lastly, cell signaling and cytokine production studies with and without LY294002, wortmannin, and PI3Kα inhibitor-2, as well as with PI3K p85α(-/-) BMMCs and CTMCs, are consistent with SHIP positively regulating TLR-induced cytokine production via an adaptor-mediated pathway while negatively regulating IgE plus Ag-induced cytokine production by repressing the PI3K pathway.

Pathogenic role of mast cells in the development of diabetic nephropathy: a study of patients at different stages of the disease

AIMS/HYPOTHESIS

Increased renal mast cells have been detected in diabetic nephropathy. However, only a few patients have been examined. Evidence of the involvement of mast cells in diabetic nephropathy is still scarce, and no observation of mast cells during the development of diabetic nephropathy has yet been reported in humans. Here, we examined changes in renal mast cells in patients at different stages of diabetic nephropathy and related these to the development of the disease.

METHODS

Eighty patients at different clinical stages of diabetic nephropathy and 16 normal kidney donors were recruited. Immunohistochemical staining for tryptase, chymase, TGF-β1, renin and TNF-α was done on renal sections from patients and control participants. Changes in mast cell number, degranulation, subtype and phenotype were examined. Correlation between mast cells and patients' clinical and pathological indices was analysed.

RESULTS

With progression of diabetic nephropathy, the number and degranulation level of mast cells increased. Increase in mast cell number and degranulation level correlated significantly with tubular interstitial injury. Almost all renal mast cells in patients with diabetic nephropathy were found to produce chymase, renin, TGF-β1 and TNF-α. The level of TNF-α in mast cells increased with progression of diabetic nephropathy.

CONCLUSIONS/INTERPRETATION

This study suggests that mast cells are involved in development of diabetic nephropathy. Through release of bioactive substances, such as tryptase, chymase, TGF-β1, renin and TNF-α, into the tubular interstitium by degranulation, mast cells could promote renal inflammation and fibrosis, and thus contribute to diabetic nephropathy.

Enhanced effects of cigarette smoke extract on inflammatory cytokine expression in IL-1β-activated human mast cells were inhibited by Baicalein via regulation of the NF-κB pathway

Background

Human mast cells are capable of a wide variety of inflammatory responses and play a vital role in the pathogenesis of inflammatory diseases such as allergy, asthma, and atherosclerosis. We have reported that cigarette smoke extract (CSE) significantly increased IL-6 and IL-8 production in IL-1β-activated human mast cell line (HMC-1). Baicalein (BAI) has anti-inflammatory properties and inhibits IL-1β- and TNF-α-induced inflammatory cytokine production from HMC-1. The goal of the present study was to examine the effect of BAI on IL-6 and IL-8 production from CSE-treated and IL-1β-activated HMC-1.

Methods

Main-stream (Ms) and Side-stream (Ss) cigarette smoke were collected onto fiber filters and extracted in RPMI-1640 medium. Two ml of HMC-1 at 1 × 10⁶ cells/mL were cultured with CSE in the presence or absence of IL-1β (10 ng/mL) for 24 hrs. A group of HMC-1 cells stimulated with both IL-1β (10 ng/ml) and CSE was also treated with BAI. The expression of IL-6 and IL-8 was assessed by ELISA and RT-PCR. NF-κB activation was measured by electrophoretic mobility shift assay (EMSA) and IκBα degradation by Western blot.

Results

Both Ms and Ss CSE significantly increased IL-6 and IL-8 production (p < 0.001) in IL-1β-activated HMC-1. CSE increased NF-κB activation and decreased cytoplasmic IκBα proteins in IL-1β-activated HMC-1. BAI (1.8 to 30 μM) significantly inhibited production of IL-6 and IL-8 in a dose-dependent manner in IL-1β-activated HMC-1 with the optimal inhibition concentration at 30 μM, which also significantly inhibited the enhancing effect of CSE on IL-6 and IL-8 production in IL-1β-activated HMC-1. BAI inhibited NF-κB activation and increased cytoplasmic IκBα proteins in CSE-treated and IL-1β-activated HMC-1.

Conclusions

Our results showed that CSE significantly increased inflammatory cytokines IL-6 and IL-8 production in IL-1β-activated HMC-1. It may partially explain why cigarette smoke contributes to lung and cardiovascular diseases. BAI inhibited the production of inflammatory cytokines through inhibition of NF-κB activation and IκBα phosphorylation and degradation. This inhibitory effect of BAI on the expression of inflammatory cytokines induced by CSE suggests its usefulness in the development of novel anti-inflammatory therapies.

Mast Cells and Wound Healing

BACKGROUND

Mast cells (MC) are ubiquitous resident cells, traditionally viewed as effector cells of allergic reactions that can store and synthesize de novo many mediators upon activation by a variety of stimuli. Exciting new insights are unveiling MC involvement in the pathogenesis of connective tissue disorders including wound healing and fibrosis.

THE PROBLEM

Abnormal wound repair is associated with an increased number of MC strategically located around blood vessels. Therapeutic local manipulation of MC population and reactivity may help improve and even prevent impaired repair processes for which there is no cure.

BASIC/CLINICAL SCIENCE ADVANCES

Chymase, a MC-restricted protease, is pre-stored in MC cytoplasmic granules with other mediators. The development of a highly specific inhibitor targeting chymase established its pivotal effect on fibrosis pathogenesis in a mouse model of silica-induced fibrosis. This novel finding evokes the potential therapeutic relevance of chymase inhibition to prevent aberrant wound healing.

CLINICAL CARE RELEVANCE

MC are increased in number in a variety of fibrotic diseases, compared to normal scars. Chymase has become a rising target prompting the development of chymase-specific inhibitors to be used as prophylactic or therapeutic agents. Another emerging strategy may consist in evaluating the efficacy of mast cell stabilizing drugs such as cromolyn in abnormal wound healing-drugs which are already approved for human use in other MC-driven disorders.

CONCLUSION

Limited treatment success of dysregulated wound healing underscores the need for novel targets be considered such as MC and/or MC-derived mediators and the necessity to design new therapeutic strategies for wounds that remain difficult to treat.

Extracellular matrix alterations in the atria: insights into the mechanisms and perpetuation of atrial fibrillation

Atrial fibrillation is the most common arrhythmia in clinical practice and is associated with increased cardiovascular morbidity and mortality. Atrial fibrosis, a detrimental process that causes imbalance in extracellular matrix deposition and degradation, has been implicated as a substrate for atrial fibrillation, but the precise mechanisms of structural remodelling and the relationship between atrial fibrosis and atrial fibrillation are not completely understood. A large number of experimental and clinical studies have shed light on the mechanisms of atrial fibrosis at the molecular and cellular level, including interactions between matrix metalloproteinases and their endogenous tissue inhibitors, and profibrotic signals through specific molecules and mediators such as angiotensin II, transforming growth factor-β1, connective tissue growth factor, and platelet-derived growth factor. This review focuses on the mechanisms of atrial fibrosis and highlights the relationship between atrial fibrosis and atrial fibrillation.

IL-10-induced gp130 expression in mouse mast cells permits IL-6 trans-signaling

It is reported that human and mouse mast cells express the IL-27R, which consists of WSX-1 (the IL-27Rα subunit) and the signal-transducing subunit gp130. Although it has been proposed that IL-27 may negatively regulate mast cell-dependent, immediate hypersensitivity responses directly, this has yet to be examined specifically. We found that mouse BMMC and primary peritoneal mast cells are unresponsive to IL-27. Consistent with this, gp130 protein in resting BMMC was not on the cell surface to a measurable degree but was found intracellularly, and data are consistent with incompletely processed N-linked glycosylation. Furthermore, BMMC constitutively expressed SOCS3, a major negative regulator of gp130 signaling. However, BMMC stimulation with IL-10 and consequential STAT3 activation increased gp130 expression, which resulted in a functional gp130 receptor on the BMMC cell surface. IL-10 has not been previously shown to regulate gp130 expression, which on the BMMC surface, permitted IL-6 trans-signaling, found to increase survival under limiting conditions and enhance IL-13 and TNF-α secretion. This study identifies factors that regulate mouse mast cell gp130 expression and signaling and makes conspicuous the limitations of using cultured mouse mast cells to study the effects of the IL-6/IL-12 cytokine family on mast cell biology.

Histamine-releasing factor has a proinflammatory role in mouse models of asthma and allergy

IgE-mediated activation of mast cells and basophils underlies allergic diseases such as asthma. Histamine-releasing factor (HRF; also known as translationally controlled tumor protein [TCTP] and fortilin) has been implicated in late-phase allergic reactions (LPRs) and chronic allergic inflammation, but its functions during asthma are not well understood. Here, we identified a subset of IgE and IgG antibodies as HRF-interacting molecules in vitro. HRF was able to dimerize and bind to Igs via interactions of its N-terminal and internal regions with the Fab region of Igs. Therefore, HRF together with HRF-reactive IgE was able to activate mast cells in vitro. In mouse models of asthma and allergy, Ig-interacting HRF peptides that were shown to block HRF/Ig interactions in vitro inhibited IgE/HRF-induced mast cell activation and in vivo cutaneous anaphylaxis and airway inflammation. Intranasally administered HRF recruited inflammatory immune cells to the lung in naive mice in a mast cell- and Fc receptor-dependent manner. These results indicate that HRF has a proinflammatory role in asthma and skin immediate hypersensitivity, leading us to suggest HRF as a potential therapeutic target.

mTORC1 and mTORC2 differentially regulate homeostasis of neoplastic and non-neoplastic human mast cells

Increased mast cell burden is observed in the inflamed tissues and affected organs and tissues of patients with mast cell proliferative disorders. However, normal mast cells participate in host defense, so approaches to preferentially target clonally expanding mast cells are needed. We found that mammalian target of rapamycin complex 1 (mTORC1) and 2 (mTORC2) are up-regulated in neoplastic and developing immature mast cells compared with their terminally differentiated counterparts. Elevated mTOR mRNA was also observed in bone marrow mononuclear cells of patients exhibiting mast-cell hyperplasia. Selective inhibition of mTORC1 and mTORC2 through genetic and pharmacologic manipulation revealed that, whereas mTORC1 may contribute to mast-cell survival, mTORC2 was only critical for homeostasis of neoplastic and dividing immature mast cells. The cytostatic effect of mTORC2 down-regulation in proliferating mast cells was determined to be via inhibition of cell-cycle progression. Because mTORC2 was observed to play little role in the homeostasis of differentiated, nonproliferating, mature mast cells, these data provide a rationale for adopting a targeted approaching selectively inhibiting mTORC2 to effectively reduce the proliferation of mast cells associated with inflammation and disorders of mast cell proliferation while leaving normal differentiated mast cells largely unaffected.

The development of myocardial fibrosis in transgenic mice with targeted overexpression of tumor necrosis factor requires mast cell-fibroblast interactions

BACKGROUND

Transgenic mice with cardiac-restricted overexpression of tumor necrosis factor (MHCsTNF mice) develop progressive myocardial fibrosis, diastolic dysfunction, and adverse cardiac remodeling. Insofar as tumor necrosis factor (TNF) does not directly stimulate fibroblast collagen synthesis, we asked whether TNF-induced fibrosis was mediated indirectly through interactions between mast cells and cardiac fibroblasts.

METHODS AND RESULTS

Cardiac mast cell number increased 2 to 3 fold (P<0.001) in MHCsTNF mice compared with littermate controls. Outcrossing MHCsTNF mice with mast cell-deficient (c-kit(-/-)) mice showed that the 11-fold increase (P<0.001) in collagen volume fraction in MHCsTNF/c-kit(+/-) mice was abrogated in MHCsTNF/c-kit(-/-) mice, and that the leftward shifted left ventricular pressure-volume curve in the MHCsTNF/c-kit(+/-) mice was normalized in the MHCsTNF/c-kit(-/-) hearts. Furthermore, the increase in transforming growth factor β1 and type I transforming growth factor β receptor messenger RNA levels was significantly (P=0.03, P=0.01, respectively) attenuated in MHCsTNF/c-kit(-/-) when compared with MHCsTNF/c-kit(+/-) mice. Coculture of fibroblasts with mast cells resulted in enhanced α-smooth muscle actin expression, increased proliferation and collagen messenger RNA expression, and increased contraction of 3-dimensional collagen gels in MHCsTNF fibroblasts compared with littermate fibroblasts. The effects of mast cells were abrogated by type I transforming growth factor β receptor antagonist NP-40208.

CONCLUSIONS

These results suggest that increased mast cell density with resultant mast cell-cardiac fibroblast cross-talk is required for the development of myocardial fibrosis in inflammatory cardiomyopathy. Cardiac fibroblasts exposed to sustained inflammatory signaling exhibit an increased repertoire of profibrotic phenotypic responses in response to mast cell mediators.

Mast cell tryptase stimulates myoblast proliferation; a mechanism relying on protease-activated receptor-2 and cyclooxygenase-2

BACKGROUND

Mast cells contribute to tissue repair in fibrous tissues by stimulating proliferation of fibroblasts through the release of tryptase which activates protease-activated receptor-2 (PAR-2). The possibility that a tryptase/PAR-2 signaling pathway exists in skeletal muscle cell has never been investigated. The aim of this study was to evaluate whether tryptase can stimulate myoblast proliferation and determine the downstream cascade.

METHODS

Proliferation of L6 rat skeletal myoblasts stimulated with PAR-2 agonists (tryptase, trypsin and SLIGKV) was assessed. The specificity of the tryptase effect was evaluated with a specific inhibitor, APC-366. Western blot analyses were used to evaluate the expression and functionality of PAR-2 receptor and to assess the expression of COX-2. COX-2 activity was evaluated with a commercial activity assay kit and by measurement of PGF2α production. Proliferation assays were also performed in presence of different prostaglandins (PGs).

RESULTS

Tryptase increased L6 myoblast proliferation by 35% above control group and this effect was completely inhibited by APC-366. We confirmed the expression of PAR-2 receptor in vivo in skeletal muscle cells and in satellite cells and in vitro in L6 cells, where PAR-2 was found to be functional. Trypsin and SLIGKV increased L6 cells proliferation by 76% and 26% above control, respectively. COX-2 activity was increased following stimulation with PAR-2 agonist but its expression remained unchanged. Inhibition of COX-2 activity by NS-398 abolished the stimulation of cell proliferation induced by tryptase and trypsin. Finally, 15-deoxy-Δ-12,14-prostaglandin J2 (15Δ-PGJ2), a product of COX-2-derived prostaglandin D2, stimulated myoblast proliferation, but not PGE2 and PGF2α.

CONCLUSIONS

Taken together, our data show that tryptase can stimulate myoblast proliferation and this effect is part of a signaling cascade dependent on PAR-2 activation and on the downstream activation of COX-2.

Lipopolysaccharide-induced lung injury: role of P2X7 receptor

RATIONALE

P2X7 receptors have been involved in inflammatory and immunological responses, and their activation modulates pro-inflammatory cytokines production by LPS-challenged macrophages.

OBJECTIVES

To determine the role of P2X7R in LPS-induced acute lung injury in mice.

METHODS

Wild-type (C57BL/6) and P2X7 knockout mice received intratracheal injection of saline or Escherichia coli LPS (60 μg). After 24h, changes in lung mechanics were determined by the end-inflation occlusion method. Bronchoalveolar lavage was performed, and lungs were harvested for measurement of morphometry, fibers content, inflammatory cells and cytokine expression by histochemistry and immunohistochemistry.

RESULTS

Compared with saline, LPS increased lung mechanical parameters, mast cell, collagen and fibronectin deposition in lung parenchyma, as well as nitric oxide and lactate dehydrogenase release into bronchoalveolar fluid in wild-type, but not in P2X7R knockout mice. Alveolar collapse, lung influx of polymorphonuclear and CD14(+) cells, as well as TGF-β, MMP-2, and IL-1β release were higher in wild-type than knockout LPS-challenged mice, while MMP-9 release where similar between the two genotypes. LPS increased macrophage immunoreactivity in lung tissue in both genotypes, but macrophages were not activated in the P2X7R knockout mice. Furthermore, LPS administration increased P2X7R immunoexpression in lung parenchyma in wild-type mice, and TLR4 in both wild-type and P2X7R knockout mice.

CONCLUSION

P2X7 receptors are implicated in the pathophysiology of LPS-induced lung injury, modulating lung inflammatory and functional changes.

Mountain cedar pollen induces IgE-independent mast cell degranulation, IL-4 production, and intracellular reactive oxygen species generation

Cedar pollens cause severe allergic disease throughout the world. We have previously characterized allergenic pollen glycoproteins from mountain cedar (Juniperus ashei) that bind to allergen-specific immunoglobulin E (IgE). In the present report, we investigated an alternative pathway of mast cell activation by mountain cedar pollen extract through IgE-independent mechanisms. We show that mountain cedar pollen directly induces mast cell serotonin and IL-4 release and enhances release induced by IgE cross-linking. Concomitant with mediator release, high levels of intracellular reactive oxygen species (ROS) were generated, and both ROS and serotonin release were inhibited by anti-oxidants. These findings suggest that alternative mechanisms exist whereby pollen exposure enhances allergic inflammatory mediator release through mechanisms that involve ROS. These mechanisms have the potential for enhancing the allergenic potency of pollens.

Gut-brain chemokine changes in portal hypertensive rats

BACKGROUND

Hepatic encephalopathy is a syndrome whose physiopathology is poorly understood; therefore, current diagnostic tests are imperfect and modern therapy is nonspecific. Particularly, it has been suggested that inflammation plays an important role in the pathogenesis of portal hypertensive encephalopathy in the rat.

AIM

We have studied an experimental model of portal hypertension based on a triple partial portal vein ligation in the rat to verify this hypothesis.

METHODS

One month after portal hypertension we assayed in the splanchnic area (liver, small bowel and mesenteric lymph nodes) and in the central nervous system (hippocampus and cerebellum) fractalkine (CX3CL1) and stromal cell-derived factor alpha (SDF1-α) as well as their respective receptors (CX3CR1 and CXCR4) because of their key role in inflammatory processes.

RESULTS

The significant increase of fractalkine in mesenteric lymph nodes (P<0.05) and its receptor (CX3CR1) in the small bowel (P<0.05) and hippocampus (P<0.01), associated with the increased expression of SDF1-α in the hippocampus (P<0.01) and the cerebellum (P<0.01) suggest that prehepatic portal hypertension in the rat induces important alterations in the expression of chemokines in the gut-brain axis.

CONCLUSION

The present study revealed that portal hypertension is associated with splanchnic-brain inflammatory alterations mediated by chemokines.

Roles of mast cells in gastric carcinogenesis

There is a growing acceptance that mast cells play an active role in tumor growth. However, little is known about the role of mast cells in gastric carcinogenesis. Accumulated evidence suggests that mast cells play critical roles in gastric carcinogenesis in terms of promoting angiogenesis, modulating immune responses and participating in tissue remodeling. All these roles are closely related to tumor growth and metastasis. In this paper, we review recent advances in research on the roles of mast cells in gastric carcinogenesis. We also discuss the clinical application of drugs regulating mast cell function in tumors.

The two faces of mast cells in food allergy and allergic asthma: the possible concept of Yin Yang

The purpose of this review is to discuss the role of mast cells in allergic inflammation. We have focused on inflammation associated with allergic asthma and food allergy. Mast cells are 'first line of defense' innate/adaptive immune cells and are widely distributed in tissues in surfaces exposed to the environment. Especially in allergic settings mast cells are extensively studied, as they can be activated to release a wide range of mediators by allergen-IgE specific triggers. In addition, in allergic inflammation mast cells can also be activated non-allergic triggers. Recent studies revealed that mast cells, besides the classical role of pro-inflammatory effector cell, have also emerged as modulators of allergic sensitization and down-regulators of allergic inflammation. Therefore, mast cells can be regarded as 'Ying Yan' modulators in allergic responses in intestinal tract and airways. This article is part of a Special Issue entitled: Mast Cells in Inflammation.

Surface TLR2 and TLR4 expression on mature rat mast cells can be affected by some bacterial components and proinflammatory cytokines

The aim of our study was to determine whether some bacterial components as well as some proinflammatory cytokines can affect surface mast cell levels. By the use of flow cytometry technique, we documented that freshly isolated mature rat peritoneal mast cells do express surface TLR2 and TLR4 protein, but not CD14 molecules, and respond to stimulation with TLR2 and TLR4 ligands by cysteinyl leukotriene generation. The level of TLR2 protein is modulated by PGN and CCL5 treatment, but not by LPS, LAM, TNF, or IL-6. Surface mast cell TLR4 expression is affected by LPS, LAM, IL-6, and CCL5. Considering that TLR-mediated activation conditions not only engaged these cells in antibacterial defense and development of inflammation but also might influence allergic processes, our observations that surface TLR2 and TLR4 expression can be regulated both bacterial components and proinflammatory cytokines seem to be very intriguing and importance.

Probiotic Lactobacillus rhamnosus downregulates FCER1 and HRH4 expression in human mast cells

AIM: To investigate the effects of four probiotic bacteria and their combination on human mast cell gene expression using microarray analysis.

METHODS: Human peripheral-blood-derived mast cells were stimulated with Lactobacillus rhamnosus (L. rhamnosus) GG (LGG^®), L. rhamnosus Lc705 (Lc705), Propionibacterium freudenreichii ssp. shermanii JS (PJS) and Bifidobacterium animalis ssp. lactis Bb12 (Bb12) and their combination for 3 or 24 h, and were subjected to global microarray analysis using an Affymetrix GeneChip^® Human Genome U133 Plus 2.0 Array. The gene expression differences between unstimulated and bacteria-stimulated samples were further analyzed with GOrilla Gene Enrichment Analysis and Visualization Tool and MeV Multiexperiment Viewer-tool.

RESULTS: LGG and Lc705 were observed to suppress genes that encoded allergy-related high-affinity IgE receptor subunits α and γ (FCER1A and FCER1G, respectively) and histamine H4 receptor. LGG, Lc705 and the combination of four probiotics had the strongest effect on the expression of genes involved in mast cell immune system regulation, and on several genes that encoded proteins with a pro-inflammatory impact, such as interleukin (IL)-8 and tumour necrosis factor alpha. Also genes that encoded proteins with anti-inflammatory functions, such as IL-10, were upregulated.

CONCLUSION: Certain probiotic bacteria might diminish mast cell allergy-related activation by downregulation of the expression of high-affinity IgE and histamine receptor genes, and by inducing a pro-inflammatory response.

Antiinflammatory and immunosuppressive functions of mast cells

Through the release of biologically active products, mast cells function as important effector and immunoregulatory cells in diverse immunological reactions and other biological responses; for example, mast cells promote inflammation and other tissue changes in immunoglobulin E (IgE)-associated allergic disorders, as well as in certain innate and adaptive immune responses that are thought to be independent of IgE. Despite the mast cell's well-deserved reputation as a promoter of inflammation, others and we have used bone marrow-derived cultured mast cell (BMCMC) engrafted mast cell-deficient c-kit-mutant mice (so-called "mast cell knock-in" mice) to show that mast cells can also have important antiinflammatory and immunosuppressive functions in vivo. An early study showed that mast cells can contribute to susceptibility to ultraviolet B (UVB)-induced immunosuppression in one model of contact hypersensitivity (CHS), through effects mediated at least in part by histamine. Subsequently, it was reported that mast cells can mediate negative immunomodulatory effects following Anopheles mosquito bites, and in peripheral tolerance to skin allografts; however, the mechanism(s) by which mast cells mediate immunosuppressive functions in these two studies remains to be elucidated. Finally, we showed that mast cells and mast cell-derived IL-10 can limit the magnitude of and promote the resolution of certain CHS responses, and suppress the inflammation and skin injury associated with innate cutaneous responses to chronic low-dose UVB irradiation. This chapter outlines the generation of BMCMCs, a powerful model system commonly used to: (1) identify potential mast cell mediators in vitro; (2) study the mechanisms of mast cell activation and mediator release in response to specific stimuli in vitro; and (3) engraft mast cell-deficient mice to study the effector and immunoregulatory roles of mast cells or specific mast cell mediators in diverse immunological responses in vivo.