Transcriptomic profiling of the acute mucosal response to local food injections in adults with eosinophilic esophagitis.

BACKGROUND: Exposure of the esophageal mucosa to food allergens can cause acute mucosal responses in patients with eosinophilic esophagitis (EoE), but the underlying local immune mechanisms driving these acute responses are not well understood. OBJECTIVE: We sought to gain insight into the early transcriptomic changes that occur during an acute mucosal response to food allergens in EoE. METHODS: Bulk RNA sequencing was performed on esophageal biopsy specimens from adult patients with EoE (n = 5) collected before and 20 minutes after intramucosal injection of various food extracts in the esophagus. Baseline biopsy specimens from control subjects without EoE (n = 5) were also included. RESULTS: At baseline, the transcriptome of the patients with EoE showed increased expression of genes related to an EoE signature. After local food injection, we identified 40 genes with a potential role in the early immune response to food allergens (most notably CEBPB, IL1B, TNFSF18, PHLDA2, and SLC15A3). These 40 genes were enriched in processes related to immune activation, such as the acute-phase response, cellular responses to external stimuli, and cell population proliferation. TNFSF18 (also called GITRL), a member of the TNF superfamily that is best studied for its costimulatory effect on T cells, was the most dysregulated early EoE gene, showing a 12-fold increase compared with baseline and an 18-fold increase compared with a negative visual response. Further experiments showed that the esophageal epithelium may be an important source of TNFSF18 in EoE, which was rapidly induced by costimulating esophageal epithelial cells with the EoE-relevant cytokines IL-13 and TNF-α. CONCLUSIONS: Our data provide unprecedented insight into the transcriptomic changes that mediate the acute mucosal immune response to food allergens in EoE and suggest that TNFSF18 may be an important effector molecule in this response.

Mast cells disrupt the function of the esophageal epithelial barrier.

Mast cells (MCs) accumulate in the epithelium of patients with eosinophilic esophagitis (EoE), an inflammatory disorder characterized by extensive esophageal eosinophilic infiltration. Esophageal barrier dysfunction plays an important role in the pathophysiology of EoE. We hypothesized that MCs contribute to the observed impaired esophageal epithelial barrier. Herein, we demonstrate that coculture of differentiated esophageal epithelial cells with immunoglobulin E-activated MCs significanly decreased epithelial resistance by 30% and increased permeability by 22% compared with non-activated MCs. These changes were associated with decreased messenger RNA expression of barrier proteins filaggrin, desmoglein-1 and involucrin, and antiprotease serine peptidase inhibitor kazal type 7. Using targeted proteomics, we detected various cytokines in coculture supernatants, most notably granulocyte-macrophage colony-stimulating factor and oncostatin M (OSM). OSM expression was increased by 12-fold in active EoE and associated with MC marker genes. Furthermore, OSM receptor-expressing esophageal epithelial cells were found in the esophageal tissue of patients with EoE, suggesting that the epithelial cells may respond to OSM. Stimulation of esophageal epithelial cells with OSM resulted in a dose-dependent decrease in barrier function and expression of filaggrin and desmoglein-1 and an increase in protease calpain-14. Taken together, these data suggest a role for MCs in decreasing esophageal epithelial barrier function in EoE, which may in part be mediated by OSM.

Mast cells-fetal mast cells crosstalk with maternal interfaces during pregnancy: Friend or foe?

Mast cells (MC) are hematopoietic immune cells that play a major role during allergic reactions in adults by releasing a myriad of vasoactive and inflammatory mediators. MC seed all vascularized tissues and are most prominent in organs with a barrier function such as skin, lungs, and intestines. These secreted molecules cause mild symptoms such as localized itchiness and sneezing to life-threatening symptoms (i.e., anaphylactic shock). Presently, despite the extensive research on Th2-mediated immune responses in allergic diseases in adults, we are still unable to determine the mechanisms of the role of MC in developing pediatric allergic (PA) disorders. In this review, we will summarize the most recent findings on the origin of MC and discuss the underappreciated contribution of MC in the sensitization phase to maternal antibodies during pregnancy in allergic reactions and other diseases such as infectious diseases. Then, we will lay out potential MC-dependent therapeutic strategies to be considered in future investigations to understand the remaining gaps in MC research for a better quality of life for these young patients.

A human IgE bispecific antibody shows potent cytotoxic capacity mediated by monocytes.

The generation of bispecific antibodies (bsAbs) targeting two different antigens opens a new level of specificity and, compared to mAbs, improved clinical efficacy in cancer therapy. Currently, the different strategies for development of bsAbs primarily focus on IgG isotypes. Nevertheless, in comparison to IgG isotypes, IgE has been shown to offer superior tumor control in preclinical models. Therefore, in order to combine the promising potential of IgE molecules with increased target selectivity of bsAbs, we developed dual tumor-associated antigen-targeting bispecific human IgE antibodies. As proof of principle, we used two different pairing approaches - knobs-into-holes and leucine zipper-mediated pairing. Our data show that both strategies were highly efficient in driving bispecific IgE formation, with no undesired pairings observed. Bispecific IgE antibodies also showed a dose-dependent binding to their target antigens, and cell bridging experiments demonstrated simultaneous binding of two different antigens. As antibodies mediate a major part of their effector functions through interaction with Fc receptors (FcRs) expressed on immune cells, we confirmed FcεR binding by inducing in vitro mast cell degranulation and demonstrating in vitro and in vivo monocyte-mediated cytotoxicity against target antigen-expressing Chinese hamster ovary cells. Moreover, we demonstrated that the IgE bsAb construct was significantly more efficient in mediating antibody-dependent cell toxicity than its IgG1 counterpart. In conclusion, we describe the successful development of first bispecific IgE antibodies with superior antibody-dependent cell toxicity-mediated cell killing in comparison to IgG bispecific antibodies. These findings highlight the relevance of IgE-based bispecific antibodies for clinical application.

Esterified derivatives of DHA and EPA increase bortezomib cytotoxicity in human multiple myeloma cells.

BACKGROUND & AIMS: Although the proteasome inhibitor bortezomib has greatly improved the clinical outcome of patients with multiple myeloma (MM), acquired drug resistance remains the greatest obstacle on the road of treating MM. We previously showed that omega-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) with the chemotherapeutic agent bortezomib can overcome its chemoresistance in MM cells. However, most DHA/EPA are esterified shortly after oral administration, which may affect their bioactivity. This study was to evaluate the cytotoxicity of ethyl ester-DHA/EPA in human MM cells. The mechanisms relevant for the cytotoxicity of these esterified-fatty acids were further investigated. METHODS: Human MM cell lines L363, OPM2, U266 were treated with ethyl ester-DHA/EPA with or without bortezomib. The percentage of dead cells and intracellular reactive oxygen species (ROS) levels were analyzed by flow cytometry. RESULTS: Ethyl ester-DHA and -EPA were much more potent than DHA/EPA to induce cytotoxicity in MM cells, even in DHA/EPA-resistant MM cells. Pretreating MM cells with esterified-DHA/EPA before bortezomib potently increased its cytotoxicity. Additionally, intracellular ROS levels were upregulated in MM cells after treatment with ethyl ester-DHA/EPA, which reflected the enhanced oxidative stress in treated cells. CONCLUSIONS: This study provides evidence that ethyl ester-DHA/EPA in combination with bortezomib may improve the overall efficacy in MM cells, similar to DHA/EPA, relieving the concern that esterification of DHA/EPA may affect its bioactivity and further supporting the potential clinical use of fatty acids DHA/EPA for combating drug resistance during MM therapy.

Binding to Iron Quercetin Complexes Increases the Antioxidant Capacity of the Major Birch Pollen Allergen Bet v 1 and Reduces Its Allergenicity.

Bet v 1 is the major allergen in birch pollen to which up to 95% of patients sensitized to birch respond. As a member of the pathogenesis-related PR 10 family, its natural function is implicated in plant defense, with a member of the PR10 family being reported to be upregulated under iron deficiency. As such, we assessed the function of Bet v 1 to sequester iron and its immunomodulatory properties on human immune cells. Binding of Bet v 1 to iron quercetin complexes FeQ2 was determined in docking calculations and by spectroscopy. Serum IgE-binding to Bet v 1 with (holoBet v1) and without ligands (apoBet v 1) were assessed by ELISA, blocking experiments and Western Blot. Crosslinking-capacity of apo/holoBet v 1 were assessed on human mast cells and Arylhydrocarbon receptor (AhR) activation with the human reporter cellline AZ-AHR. Human PBMCs were stimulated and assessed for labile iron and phenotypic changes by flow cytometry. Bet v 1 bound to FeQ2 strongly with calculated Kd values of 1 nm surpassing affinities to quercetin alone nearly by a factor of 1000. Binding to FeQ2 masked IgE epitopes and decreased IgE binding up to 80% and impaired degranulation of sensitized human mast cells. Bet v 1 facilitated the shuttling of quercetin, which activated the anti-inflammatory AhR pathway and increased the labile iron pool of human monocytic cells. The increase of labile iron was associated with an anti-inflammatory phenotype in CD14+monocytes and downregulation of HLADR. To summarize, we reveal for the first time that FeQ2 binding reduces the allergenicity of Bet v 1 due to ligand masking, but also actively contributes anti-inflammatory stimuli to human monocytes, thereby fostering tolerance. Nourishing immune cells with complex iron may thus represent a promising antigen-independent immunotherapeutic approach to improve efficacy in allergen immunotherapy.

Micronutritional supplementation with a holoBLG-based FSMP (food for special medical purposes)-lozenge alleviates allergic symptoms in BALB/c mice: Imitating the protective farm effect.

BACKGROUND: Previously, the protective farm effect was imitated using the whey protein beta-lactoglobulin (BLG) that is spiked with iron-flavonoid complexes. Here, we formulated for clinical translation a lozenge as food for special medical purposes (FSMP) using catechin-iron complexes as ligands for BLG. The lozenge was tested in vitro and in a therapeutical BALB/c mice model. METHODS: Binding of iron-catechin into BLG was confirmed by spectroscopy and docking calculations. Serum IgE binding of children allergic or tolerating milk was assessed to loaded (holo-) versus empty (apo-) BLG and for human mast cell degranulation. BLG and Bet v 1 double-sensitized mice were orally treated with the holoBLG or placebo lozenge, and immunologically analysed after systemic allergen challenge. Human PBMCs of pollen allergic subjects were flow cytometrically assessed after stimulation with apoBLG or holoBLG using catechin-iron complexes as ligands. RESULTS: One major IgE and T cell epitope were masked by catechin-iron complexes, which impaired IgE binding of milk-allergic children and degranulation of mast cells. In mice, only supplementation with the holoBLG lozenge reduced clinical reactivity to BLG and Bet v 1, promoted Tregs, and suppressed antigen presentation. In allergic subjects, stimulation of PBMCs with holoBLG led to a significant increase of intracellular iron in circulating CD14+ cells with significantly lower expression of HLADR and CD86 compared to their stimulation with apoBLG. CONCLUSION: The FSMP lozenge targeted antigen presenting cells and dampened immune activation in human immune cells and allergic mice in an antigen-non-specific manner, thereby conferring immune resilience against allergic symptoms.

Butyrate and propionate restore interleukin 13-compromised esophageal epithelial barrier function.

BACKGROUND: Eosinophilic esophagitis (EoE) is a food allergen driven disease that is accompanied by interleukin (IL) 13 overexpression and esophageal barrier dysfunction allowing transepithelial food allergen permeation. Nutraceuticals, such as short-chain fatty acids (SCFAs) that restore barrier function and increase immune fitness may be a promising tool in the management of EoE. Here, we investigated the effects of the SCFAs acetate, propionate, and butyrate on an IL-13-compromised human esophageal epithelial barrier, including the mechanisms involved. METHODS: An air-liquid interface culture model of differentiated human EPC2-hTERT (EPC2) was used to study whether SCFAs could restore barrier function after IL-13-induced impairment. Esophageal epithelial barrier function was monitored by transepithelial electrical resistance (TEER) and FITC-dextran paracellular flux, and was further examined by qPCR and immunohistochemical analysis. G protein-coupled receptor (GPR) GPR41, GPR43, GPR109a, or histone deacetylase (HDAC) (ant)agonists were used to assess mechanisms of action of SCFAs. RESULTS: IL-13 stimulation decreased TEER and increased FITC flux, which was counteracted by butyrate and propionate, but not acetate treatment. Barrier proteins FLG and DSG1 mRNA expression was upregulated following butyrate and propionate treatment, whereas expression of eosinophil chemoattractant CCL26 and protease CAPN14 was downregulated. Similarly, butyrate and propionate restored FLG and DSG1 protein expression. Similar effects were observed with an HDAC antagonist but not with GPR agonists. CONCLUSION: Nutraceuticals butyrate and propionate restore the barrier function of esophageal epithelial cells after an inflammatory insult and may be of therapeutic benefit in the management of EoE.

Omega-3 Fatty Acids DHA and EPA Reduce Bortezomib Resistance in Multiple Myeloma Cells by Promoting Glutathione Degradation.

Multiple myeloma (MM) is a hematological malignancy that exhibits aberrantly high levels of proteasome activity. While treatment with the proteasome inhibitor bortezomib substantially increases overall survival of MM patients, acquired drug resistance remains the main challenge for MM treatment. Using a combination treatment of docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) and bortezomib, it was demonstrated previously that pretreatment with DHA/EPA significantly increased bortezomib chemosensitivity in MM cells. In the current study, both transcriptome and metabolome analysis were performed to comprehensively evaluate the underlying mechanism. It was demonstrated that pretreating MM cells with DHA/EPA before bortezomib potently decreased the cellular glutathione (GSH) level and altered the expression of the related metabolites and key enzymes in GSH metabolism, whereas simultaneous treatment only showed minor effects on these factors, thereby suggesting the critical role of GSH degradation in overcoming bortezomib resistance in MM cells. Moreover, RNA-seq results revealed that the nuclear factor erythroid 2-related factor 2 (NRF2)-activating transcription factor 3/4 (ATF3/4)-ChaC glutathione specific gamma-glutamylcyclotransferase 1 (CHAC1) signaling pathway may be implicated as the central player in the GSH degradation. Pathways of necroptosis, ferroptosis, p53, NRF2, ATF4, WNT, MAPK, NF-κB, EGFR, and ERK may be connected to the tumor suppressive effect caused by pretreatment of DHA/EPA prior to bortezomib. Collectively, this work implicates GSH degradation as a potential therapeutic target in MM and provides novel mechanistic insights into its significant role in combating bortezomib resistance.

Human milk extracellular vesicles target nodes in interconnected signalling pathways that enhance oral epithelial barrier function and dampen immune responses.

Maternal milk is nature's first functional food. It plays a crucial role in the development of the infant's gastrointestinal (GI) tract and the immune system. Extracellular vesicles (EVs) are a heterogeneous population of lipid bilayer enclosed vesicles released by cells for intercellular communication and are a component of milk. Recently, we discovered that human milk EVs contain a unique proteome compared to other milk components. Here, we show that physiological concentrations of milk EVs support epithelial barrier function by increasing cell migration via the p38 MAPK pathway. Additionally, milk EVs inhibit agonist-induced activation of endosomal Toll like receptors TLR3 and TLR9. Furthermore, milk EVs directly inhibit activation of CD4+ T cells by temporarily suppressing T cell activation without inducing tolerance. We show that milk EV proteins target key hotspots of signalling networks that can modulate cellular processes in various cell types of the GI tract.

Local immune response to food antigens drives meal-induced abdominal pain.

Up to 20% of people worldwide develop gastrointestinal symptoms following a meal1, leading to decreased quality of life, substantial morbidity and high medical costs. Although the interest of both the scientific and lay communities in this issue has increased markedly in recent years, with the worldwide introduction of gluten-free and other diets, the underlying mechanisms of food-induced abdominal complaints remain largely unknown. Here we show that a bacterial infection and bacterial toxins can trigger an immune response that leads to the production of dietary-antigen-specific IgE antibodies in mice, which are limited to the intestine. Following subsequent oral ingestion of the respective dietary antigen, an IgE- and mast-cell-dependent mechanism induced increased visceral pain. This aberrant pain signalling resulted from histamine receptor H1-mediated sensitization of visceral afferents. Moreover, injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid mucosa of patients with irritable bowel syndrome induced local oedema and mast cell activation. Our results identify and characterize a peripheral mechanism that underlies food-induced abdominal pain, thereby creating new possibilities for the treatment of irritable bowel syndrome and related abdominal pain disorders.

Direct Inhibition of the Allergic Effector Response by Raw Cow's Milk-An Extensive In Vitro Assessment.

The mechanisms underlying the allergy-protective effects of raw cow's milk are poorly understood. The current focus is mainly on the modulation of T cell responses. In the present study, we investigated whether raw cow's milk can also directly inhibit mast cells, the key effector cells in IgE-mediated allergic responses. Primary murine bone marrow-derived mast cells (BMMC) and peritoneal mast cells (PMC), were incubated with raw milk, heated raw milk, or shop milk, prior to IgE-mediated activation. The effects on mast cell activation and underlying signaling events were assessed. Raw milk was furthermore fractionated based on molecular size and obtained fractions were tested for their capacity to reduce IgE-mediated mast cell activation. Coincubation of BMMC and PMC with raw milk prior to activation reduced ß-hexosaminidase release and IL-6 and IL-13 production, while heated raw milk or shop milk had no effect. The reduced mast cell activation coincided with a reduced intracellular calcium influx. In addition, SYK and ERK phosphorylation levels, both downstream signaling events of the FcεRI, were lower in raw milk-treated BMMC compared to control BMMC, although differences did not reach full significance. Raw milk-treated BMMC furthermore retained membrane-bound IgE expression after allergen stimulation. Raw milk fractionation showed that the heat-sensitive raw milk components responsible for the reduced mast cell activation are likely to have a molecular weight of > 37 kDa. The present study demonstrates that raw cow's milk can also directly affect mast cell activation. These results extend the current knowledge on mechanisms via which raw cow's milk prevents allergic diseases, which is crucial for the development of new, microbiologically safe, nutritional strategies to reduce allergic diseases.

Defining biomarkers to predict symptoms in subjects with and without allergy under natural pollen exposure.

BACKGROUND: Pollen exposure induces local and systemic allergic immune responses in sensitized individuals, but nonsensitized individuals also are exposed to pollen. The kinetics of symptom expression under natural pollen exposure have never been systematically studied, especially in subjects without allergy. OBJECTIVE: We monitored the humoral immune response under natural pollen exposure to potentially uncover nasal biomarkers for in-season symptom severity and identify protective factors. METHODS: We compared humoral immune response kinetics in a panel study of subjects with seasonal allergic rhinitis (SAR) and subjects without allergy and tested for cross-sectional and interseasonal differences in levels of serum and nasal, total, and Betula verrucosa 1-specific immunoglobulin isotypes; immunoglobulin free light chains; cytokines; and chemokines. Nonsupervised principal component analysis was performed for all nasal immune variables, and single immune variables were correlated with in-season symptom severity by Spearman test. RESULTS: Symptoms followed airborne pollen concentrations in subjects with SAR, with a time lag between 0 and 13 days depending on the pollen type. Of the 7 subjects with nonallergy, 4 also exhibited in-season symptoms whereas 3 did not. Cumulative symptoms in those without allergy were lower than in those with SAR but followed the pollen exposure with similar kinetics. Nasal eotaxin-2, CCL22/MDC, and monocyte chemoattactant protein-1 (MCP-1) levels were higher in subjects with SAR, whereas IL-8 levels were higher in subjects without allergy. Principal component analysis and Spearman correlations identified nasal levels of IL-8, IL-33, and Betula verrucosa 1-specific IgG4 (sIgG4) and Betula verrucosa 1-specific IgE (sIgE) antibodies as predictive for seasonal symptom severity. CONCLUSIONS: Nasal pollen-specific IgA and IgG isotypes are potentially protective within the humoral compartment. Nasal levels of IL-8, IL-33, sIgG4 and sIgE could be predictive biomarkers for pollen-specific symptom expression, irrespective of atopy.

Role of Mast Cells in Shaping the Tumor Microenvironment.

Early mast cell (MC) infiltration has been reported in a wide range of human and animal tumors particularly malignant melanoma and breast and colorectal cancer. The consequences of their presence in the tumor microenvironment (TME) or at their margins still remain unclear as it is associated with a good or poor prognosis based on the type and anatomical site of the tumor. Within the tumor, MC interactions occur with infiltrated immune cells, tumor cells, and extracellular matrix (ECM) through direct cell-to-cell interactions or release of a broad range of mediators capable of remodeling the TME. MCs actively contribute to angiogenesis and induce neovascularization by releasing the classical proangiogenic factors including VEGF, FGF-2, PDGF, and IL-6, and nonclassical proangiogenic factors mainly proteases including tryptase and chymase. MCs support tumor invasiveness by releasing a broad range of matrix metalloproteinases (MMPs). MC presence within the tumor gained additional significance when it was assumed that controlling its activation by tyrosine kinase inhibitors (imatinib and masitinib) and tryptase inhibitors (gabexate and nafamostat mesylate) or controlling their interactions with other cell types may have therapeutic benefit.

EPA and DHA have selective toxicity for PBMCs from multiple myeloma patients in a partly caspase-dependent manner.

Poly-unsaturated fatty acids (PUFAs) have been shown to have cytotoxic effects in both solid and non-solid tumors. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are among the most studied PUFAs. The aim of the present study was to evaluate the cytotoxic effects of these two fatty acids (FAs) in the peripheral blood mononuclear cells (PBMCs) obtained from untreated patients (new cases) with confirmed symptomatic multiple myeloma (MM). Our results showed that EPA at the concentration of 100 µM and DHA at 50 and 100 µM induce potent apoptotic effects in the PBMCs of MM patients (P < 0.05) as evidenced by Annexin V and propidium iodide (PI) staining, while they have little or no effects on the PBMCs isolated from healthy donors (P > 0.05). The observed effects were concentration- and time-dependent and 72 h treatment with DHA at a concentration of 100 µM had the strongest effect (P < 0.01). CD138 + cells isolated from MM patients showed great sensitivity to EPA/DHA. EPA- and DHA-induced apoptosis was significantly inhibited by the pan-caspase inhibitor (Z-VAD-FMK), indicating that cell death was at least partly dependent on caspase activation. The results of the present study showed that EPA and DHA have selective toxicities for malignant human plasma cells from MM patients, but not for mononuclear cells of healthy donors. These results warrant further studies with larger study populations to investigate the usefulness of PUFAs as a promising adjunctive therapy in the treatment of MM.

A Transcriptomic Insight into the Impact of Colon Cancer Cells on Mast Cells.

Mast cells (MCs) are one of the first immune cells recruited to a tumor. It is well recognized that MCs accumulate in colon cancer lesion and their density is associated with the clinical outcomes. However, the molecular mechanism of how colon cancer cells may modify MC function is still unclear. In this study, primary human MCs were generated from CD34⁺ progenitor cells and a 3D coculture model was developed to study the interplay between colon cancer cells and MCs. By comparing the transcriptomic profile of colon cancer-cocultured MCs versus control MCs, we identified a number of deregulated genes, such as MMP-2, VEGF-A, PDGF-A, COX2, NOTCH1 and ISG15, which contribute to the enrichment of cancer-related pathways. Intriguingly, pre-stimulation with a TLR2 agonist prior to colon cancer coculture induced upregulation of multiple interferon-inducible genes as well as MHC molecules in MCs. Our study provides an alternative approach to study the influence of colon cancer on MCs. The transcriptome signature of colon cancer-cocultured MCs may potentially reflect the mechanism of how colon cancer cells educate MCs to become pro-tumorigenic in the initial phase and how a subsequent inflammatory signal-e.g., TLR2 ligands-may modify their responses in the cancer milieu.