IgE-mediated Mast Cell Degranulation Research Articles

An optimized method for IgE-mediated degranulation of human lung mast cells.

Mast cells are critically involved in IgE-mediated diseases, e.g., allergies and asthma. Human mast cells are heterogeneous, and mast cells from different anatomical sites have been shown to respond differently to certain stimuli and drugs. The origin of the mast cells is therefore of importance when setting up a model system, and human lung mast cells are highly relevant cells to study in the context of asthma. We therefore set out to optimize a protocol of IgE-mediated activation of human lung mast cells. Human lung mast cells were extracted from lung tissue obtained from patients undergoing pulmonary resection by enzyme digestion and mechanical disruption followed by CD117 magnetic-activated cell sorting (MACS) enrichment. Different culturing media and conditions for the IgE-mediated degranulation were tested to obtain an optimized method. IgE crosslinking of human lung mast cells cultured in serum-free media gave a stronger response compared to cells cultured with 10% serum. The addition of stem cell factor (SCF) did not enhance the degranulation. However, when the cells were put in fresh serum-free media 30 minutes prior to the addition of anti-IgE antibodies, the cells responded more vigorously. Maximum degranulation was reached 10 minutes after the addition of anti-IgE. Both CD63 and CD164 were identified as stable markers for the detection of degranulated mast cells over time, while the staining with anti-CD107a and avidin started to decline 10 minutes after activation. The levels of CD203c and CD13 did not change in activated cells and therefore cannot be used as degranulation markers of human lung mast cells. For an optimal degranulation response, human lung mast cells should be cultured and activated in serum-free media. With this method, a very strong and consistent degranulation response with a low donor-to-donor variation is obtained. Therefore, this model is useful for further investigations of IgE-mediated mast cell activation and exploring drugs that target human lung mast cells, for instance, in the context of asthma.

Cannabidiol Inhibits IgE-Mediated Mast Cell Degranulation and Anaphylaxis in Mice.

Cannabidiol (CBD), the most abundant non-psychoactive constituent of the plant Cannabis sativa, is known to possess immune modulatory properties. This study investigates the effects of CBD on mast cell degranulation in human and mouse primary mast cells and passive cutaneous anaphylaxis in mice. Mouse bone marrow-derived mast cells and human cord-blood derived mast cellsare generated. CBD suppressed antigen-stimulated mast cell degranulation in a concentration-dependent manner. Mechanistically, CBD inhibited both the phosphorylation of FcεRI downstream signaling molecules and calcium mobilization in mast cells, while exerting no effect on FcεRI expression and IgE binding to FcεRI. These suppressive effectsare preserved in the mast cells thatare depleted of type 1 (CB1) and type 2 (CB2) cannabinoid receptors, as well as in the presence of CB1 agonist, CB2 agonist, CB1 inverse agonist, and CB2 inverse agonist. CBD also inhibited the development of mast cells in a long-term culture. The intraperitoneal administration of CBD suppressed passive cutaneous anaphylaxis in mice as evidenced by a reduction in ear swelling and decrease in the number of degranulated mast cells. Based on these results, the administration of CBD is a new therapeutic intervention in mast cell-associated anaphylactic diseases.

Evaluation of association of anti-PEG antibodies with anaphylaxis after mRNA COVID-19 vaccination

BackgroundThe mechanism for anaphylaxis following mRNA COVID-19 vaccination has been widely debated; understanding this serious adverse event is important for future vaccines of similar design. A mechanism proposed is type I hypersensitivity (i.e., IgE-mediated mast cell degranulation) to polyethylene glycol (PEG). Using an assay that, uniquely, had been previously assessed in patients with anaphylaxis to PEG, our objective was to compare anti-PEG IgE in serum from mRNA COVID-19 vaccine anaphylaxis case-patients and persons vaccinated without allergic reactions. Secondarily, we compared anti-PEG IgG and IgM to assess alternative mechanisms. MethodsSelected anaphylaxis case-patients reported to U.S. Vaccine Adverse Event Reporting System December 14, 2020–March 25, 2021 were invited to provide a serum sample. mRNA COVID-19 vaccine study participants with residual serum and no allergic reaction post-vaccination (“controls”) were frequency matched to cases 3:1 on vaccine and dose number, sex and 10-year age category. Anti-PEG IgE was measured using a dual cytometric bead assay (DCBA). Anti-PEG IgG and IgM were measured using two different assays: DCBA and a PEGylated-polystyrene bead assay. Laboratorians were blinded to case/control status. ResultsAll 20 case-patients were women; 17 had anaphylaxis after dose 1, 3 after dose 2. Thirteen (65 %) were hospitalized and 7 (35 %) were intubated. Time from vaccination to serum collection was longer for case-patients vs controls (post-dose 1: median 105 vs 21 days). Among Moderna recipients, anti-PEG IgE was detected in 1 of 10 (10 %) case-patients vs 8 of 30 (27 %) controls (p = 0.40); among Pfizer-BioNTech recipients, it was detected in 0 of 10 case-patients (0 %) vs 1 of 30 (3 %) controls (p >n 0.99). Anti-PEG IgE quantitative signals followed this same pattern. Neither anti-PEG IgG nor IgM was associated with case status with both assay formats. ConclusionOur results support that anti-PEG IgE is not a predominant mechanism for anaphylaxis post-mRNA COVID-19 vaccination.

An advanced in vitro human mucosal immune model to predict food sensitizing allergenicity risk: A proof of concept using ovalbumin as model allergen.

The global demand of sustainable food sources leads to introduction of novel foods on the market, which may pose a risk of inducing allergic sensitization. Currently there are no validated in vitro assays mimicking the human mucosal immune system to study sensitizing allergenicity risk of novel food proteins. The aim of this study was to introduce a series of sequential human epithelial and immune cell cocultures mimicking key immune events after exposure to the common food allergen ovalbumin from intestinal epithelial cell (IEC) activation up to mast cell degranulation. This in vitro human mucosal food sensitizing allergenicity model combines crosstalk between IEC and monocyte-derived dendritic cells (moDC), followed by coculture of the primed moDCs with allogenic naïve CD4+ T cells. During subsequent coculture of primed CD4+ T cells with naïve B cells, IgE isotype-switching was monitored and supernatants were added to primary human mast cells to investigate degranulation upon IgE crosslinking. Mediator secretion and surface marker expression of immune cells were determined. Ovalbumin activates IEC and underlying moDCs, both resulting in downstream IgE isotype-switching. However, only direct exposure of moDCs to ovalbumin drives Th2 polarization and a humoral B cell response allowing for IgE mediated mast cell degranulation, IL13 and IL4 release in this sequential DC-T cell-B cell-mast cell model, indicating also an immunomodulatory role for IEC. This in vitro coculture model combines multiple key events involved in allergic sensitization from epithelial cell to mast cell, which can be applied to study the allergic mechanism and sensitizing capacity of proteins.

Drug repositioning of anti-microbial agent nifuratel to treat mast cell-mediated allergic responses.

Objectives: Our objective was to assess the effects and mechanisms of nifuratel on IgE-mediated mast cell (MC) degranulation and anaphylaxis in both in vitro and in vivo settings.Methods: The anti-allergic activity of nifuratel was evaluated in mast cell cultures and the passive cutaneous anaphylaxis (PCA) model. The effects of nifuratel on signaling pathways stimulated by antigen in mast cells were measured by immunoblotting, immunoprecipitation, in vitro protein tyrosine kinase assay, and other molecular biological methods.Results: Nifuratel reversibly inhibited antigen-induced degranulation of MCs (IC50, approximately 0.34μM for RBL-2H3 cells; approximately 0.94μM for BMMCs) and suppressed the secretion of inflammatory cytokines IL-4 (IC50, approximately 0.74μM) and TNF-α (IC50, approximately 0.48μM). Mechanism studies showed that nifuratel inhibited the phosphorylation of Syk by antigen via the inhibition of recruitment of cytosolic Syk to the ɣ subunit of FcεRI, and decreased the activation of Syk downstream signaling proteins LAT, Akt, and MAPKs. Finally, nifuratel dose-dependently suppressed the IgE-mediated passive cutaneous anaphylaxis in mice (ED50, approximately 22mg/kg).Conclusion: Our findings suggest that nifuratel inhibits pathways essential for the activation of mast cells to suppress anaphylaxis, thereby indicating that the anti-microbial drug, nifuratel, could be a potential drug candidate for IgE-mediated allergic disorders.

521 Deciphering Pathomechanisms in Solar Urticaria

Solar Urticaria (SU) is a rare, chronic inducible urticaria characterised by an itching or burning erythemal flare with or without whealing, that can develop within minutes of exposure to ultraviolet radiation (UVR) and/or visible light. It is hypothesised that an unidentified endogenous photo-allergen may be the trigger, leading to IgE-mediated mast cell degranulation. However, the evolution of the response and mechanisms involved are not well understood. We undertook a UVR provocation study with transcriptome analysis to examine early events in SU pathophysiology.

Hereditary alpha-tryptasemia: Brief overview of current knowledge and proposal of indications

Human tryptases are serine proteases, which are synthesized nearly exclusively by mast cells (MCs). Immature pro-tryptases, under the form of α- and β-monomers are constantly released by MCs, can be measured in the serum of normal individuals and constitute the basal serum tryptase (bST) level, usually below 6μg/L. By contrast, tetramers of tryptases, which are the mature forms of the enzyme, are normally retained in the secretory granules of MCs. These mature (α- and β-tetramers of tryptase) are only released when MC are activated by different stimuli, leading to a transient increase in serum tryptase level. Such event occurs for instance after IgE-mediated MC degranulation (immediate hypersensitivity reaction). The mature tryptases, through their various biological activities, account for the pathophysiology of immediate hypersensitivity. Of note, recent studies have reported that around 5% of the general population present with increased bST levels related to a genetic trait called hereditary α-tryptasemia (HαT). While there is still a debate on the fact that HαT+ patients may present more frequently various clinical phenotypes, it is now clearly established that the clinical phenotype of patients with primary (clonal) MC disorders, including mastocytosis, is modified by the presence of the HαT trait. In addition, HαT penetrance seems clearly increased in such patients (up to 18% of the cases), leading to the conclusion that HαT is a disease penetrance and phenotype modifier. In the present manuscript, we will describe briefly the genetic patterns of HαT and the clinical phenotypes encountered in HαT+ patients harboring or not a clonal MC disorder. Finally, we will describe the situations when the search for HαT in human can be considered and the preferred method to be used for such investigation.

Allergen-Specific IgA Antibodies Block IgE-Mediated Activation of Mast Cells and Basophils.

Mast cells and basophils have long been implicated in the pathogenesis of IgE-mediated hypersensitivity reactions. They express the high-affinity IgE receptor, FcϵRI, on their surface. Antigen-induced crosslinking of IgE antibodies bound to that receptor triggers a signaling cascade that results in activation, leading to the release of an array of preformed vasoactive mediators and rapidly synthesized lipids, as well as the de novo production of inflammatory cytokines. In addition to bearing activating receptors like FcεRI, these effector cells of allergy express inhibitory ones including FcγR2b, an IgG Fc receptor with a cytosolic inhibitory motif that activates protein tyrosine phosphatases that suppress IgE-mediated activation. We and others have shown that food allergen-specific IgG antibodies strongly induced during the course of oral immunotherapy (OIT), signal via FcγR2b to suppress IgE-mediated mast cell and basophil activation triggered by food allergen challenge. However, the potential inhibitory effects of IgA antibodies, which are also produced in response to OIT and are present at high levels at mucosal sites, including the intestine where food allergens are encountered, have not been well studied. Here we uncover an inhibitory function for IgA. We observe that IgA binds mouse bone marrow-derived mast cells (BMMCs) and peritoneal mast cells. Binding to BMMCs is dependent on calcium and sialic acid. We also found that IgA antibodies inhibit IgE-mediated mast cell degranulation in an allergen-specific fashion. Antigen-specific IgA inhibits IgE-mediated mast cell activation early in the signaling cascade, suppressing the phosphorylation of Syk, the proximal protein kinase mediating FcεRI signaling, and suppresses mast cell production of cytokines. Furthermore, using basophils from a peanut allergic donor we found that IgA binds to basophils and that activation by exposure to peanuts is effectively suppressed by IgA. We conclude that IgA serves as a regulator of mast cell and basophil degranulation, suggesting a physiologic role for IgA in the maintenance of immune homeostasis at mucosal sites.

Type I hypersensitivity promotes Aedes aegypti blood feeding

Mosquitoes play a major role in human disease by serving as vectors of pathogenic microorganisms. Mosquitoes inject saliva into host skin during the probing process. Mosquito saliva contains a number of proteins that facilitate blood feeding by preventing hemostasis. Mosquito saliva also contains potent allergens that induce type I hypersensitivity reactions in some individuals. Type I hypersensitivity reactions in skin involve IgE-mediated degranulation of mast cells, which leads to vasodilation and an itch sensation. We hypothesized that hypersensitivity to mosquito saliva influences blood feeding. To test this hypothesis, we recruited human subjects who consented to Aedes aegypti bites. We measured their first sensation of itch, the strength of their itch sensation, the number of times mosquitoes attempted to feed, the number of times mosquitoes probed their skin, feeding time, engorgement status, and wheal diameter. Here we show that hypersensitive subjects had a stronger itch sensation, and that the time to first itch sensation was inversely correlated with wheal diameter; however, mosquitoes tended to probe less and engorge more on these subjects. Follow-up experiments testing the impact of oral antihistamine treatment on mosquito feeding parameters failed to reveal a statistically significant result. Histamine also failed to promote blood feeding on an artificial membrane feeder. This study suggests that mosquito saliva-induced type I hypersensitivity promotes blood feeding but that this may be independent from histamine or histamine signaling.

Nanoparticles Displaying Allergen and Siglec-8 Ligands Suppress IgE-FcεRI-Mediated Anaphylaxis and Desensitize Mast Cells to Subsequent Antigen Challenge.

Siglec-8 is an inhibitory receptor expressed on eosinophils and mast cells. In this study, we took advantage of a novel Siglec-8 transgenic mouse model to assess the impact of modulating IgE-dependent mast cell degranulation and anaphylaxis using a liposomal platform to display an allergen with or without a synthetic glycan ligand for Siglec-8 (Sig8L). The hypothesis is that recruitment of Siglec-8 to the IgE-FcεRI receptor complex will inhibit allergen-induced mast cell degranulation. Codisplay of both allergen and Sig8L on liposomes profoundly suppresses IgE-mediated degranulation of mouse bone marrow-derived mast cells or rat basophilic leukemia cells expressing Siglec-8. In contrast, liposomes displaying only Sig8L have no significant suppression of antigenic liposome-induced degranulation, demonstrating that the inhibitory activity by Siglec-8 occurs only when Ag and Sig8L are on the same particle. In mouse models of anaphylaxis, display of Sig8L on antigenic liposomes completely suppresses IgE-mediated anaphylaxis in transgenic mice with mast cells expressing Siglec-8 but has no protection in mice that do not express Siglec-8. Furthermore, mice protected from anaphylaxis remain desensitized to subsequent allergen challenge because of loss of Ag-specific IgE from the cell surface and accelerated clearance of IgE from the blood. Thus, although expression of human Siglec-8 on murine mast cells does not by itself modulate IgE-FcεRI-mediated cell activation, the enforced recruitment of Siglec-8 to the FcεRI receptor by Sig8L-decorated antigenic liposomes results in inhibition of degranulation and desensitization to subsequent Ag exposure.

Resveratrol inhibits MRGPRX2-mediated mast cell activation via Nrf2 pathway

Mast cells (MCs) are crucial effectors in inflammation and allergic reactions. The Mas-related G-protein-coupled receptor X2 (MRGPRX2) was the MC‐specific receptor and play a key role in IgE-independent allergic reactions. The activation of the Nuclear factor erythroid derived 2-related factor 2 (Nrf2) is involved in IgE-mediated MC degranulation. Resveratrol (Res) is a polyphenolic compound in red wine and has been reported to exert a variety of pharmacological effects. In the current study, we investigated the effect of Res in regulating MRGPRX2-mediated MC activation and its underlyingmechanism. We demonstrated that Res reduced compound 48/80 (C48/80)-induced calcium flux in MCs and inhibited MCs degranulation in vitro. Res also suppressed C48/80-induced hind paw extravasation, active systemic anaphylaxis, and MCs degranulation in mouse models of pseudo-allergy in vivo. Furthermore, PCR and immunohistochemistry assay suggest that Res up-regulates Nrf2 expression and Nrf2 inhibitor attenuates the protective effects of Res. In conclusion, Res exerts an inhibitory effect on MRGPRX2-mediated MCs activation by targeting Nrf2 pathway and may present a promising new therapeutic agent for the treatment of MRGPRX2-dependent anaphylactoid reactions.

Isolated Gastrointestinal Alpha-gal Meat Allergy Is a Cause for Gastrointestinal Distress Without Anaphylaxis

Isolated Gastrointestinal Alpha-gal Meat Allergy Is a Cause for Gastrointestinal Distress Without Anaphylaxis

The interaction of host and nematode galectins influences the outcome of gastrointestinal nematode infections.

Galectins are a family of proteins that bind β-galactosides and play key roles in a variety of cellular processes including host defence. They have been well studied in hosts but less so in gastrointestinal nematodes. Both host and parasite galectins are present in the gastrointestinal tract following infection. Parasite galectins can both bind antibody, especially highly glycosylated IgE and be bound by antibody. Parasite galectins may act as molecular sponges that soak up antibody. Host galectins promote mast cell degranulation while parasite galectins inhibit degranulation. Host and parasite galectins can also bind mucins and influence mucus viscosity. As the protective response against gastrointestinal nematode infection is partly dependent on IgE mediated mast cell degranulation and mucus, the interactions between host and parasite galectins play key roles in determining the outcome of infection.

Immunological Mechanisms Explaining the Role of Vaccines, IgE, Mast Cells, Histamine, Elevating Ferritin, IL-6, D-dimer, VEGF Levels in COVID-19 and Dengue, Potential Treatments Such as Mast Cell Stabilizers, Antihistamines: Predictions and Confirmations

A novel coronavirus, SARS-CoV-2 was identified in Wuhan, China. The disease caused by the virus can range in severity from asymptomatic to acute respiratory distress syndrome (ARDS) and death.Primary dengue infection results in IgE mediated sensitization against dengue virus proteins. These IgE bind to receptors on mast cells. Upon subsequent exposure to the antigen recognized by the IgE, mast cell degranulation occurs releasing mediators such as histamine. Therefore secondary dengue infection results in urticaria, increased vascular permeability, hypotension, dengue hemorrhagic fever and dengue shock syndrome. A case of “slow rolling anaphylaxis”.Vaccines contain proteins derived from coronavirus infected animals as well as other proteins with high homology to SARS-CoV-2. So one could develop IgE mediated sensitization to SARS-CoV-2-like proteins. Therefore, receipt of such vaccines acts like a dengue “primary infection”. It results in IgE mediated sensitization. Subsequent SARS-CoV-2 infection becomes a “secondary dengue infection” that has a severe course due to IgE mediated mast cell degranulation and the immune cascade that follows.There are many common observations between COVID-19 and dengue. Elevated levels of ferritin, interleukin-6, vascular endothelial growth factor, D-dimer, coagulopathy, urticaria and ARDS are reported in both diseases. Numerous teams have now confirmed this mechanism that was predicted in Jan 2020, upon analyzing the 2019-nCoV proteome.There are many indicators that mast cell degranulation and histamine release have a major role in COVID-19, dengue and influenza severity. Mast cell stabilizers, antihistamines and anti-parasite treatments may address different aspects of this cascade and thus reduce disease severity.

Two Japanese pepper (Zanthoxylum piperitum) fruit-derived compounds attenuate IgE-mediated allergic response in vitro and in vivo via inhibition of mast cell degranulation

Zanthoxylum piperitum (ZP, ‘Japanese pepper’) is a traditional medicine and pepper used in Asian countries such as Japan. Hydroxy-α-sanshool, a pungent-tasting substance contained within ZP, has been reported to slightly suppress immunoglobulin E (IgE)-mediated mast cell degranulation. The current study aims to newly identify anti-allergic compounds derived from ZP. We examine the inhibitory mechanisms behind IgE-mediated mast cell degranulation. By inhibitory effect-guided isolation, we identified degranulation inhibitory compounds derived from ZP fruit: 1-acetoxy-7-hydroxy-3, 7-dimethylocta-2E, 5E-diene (ZP1) and 8-hydroxygeranyl acetate (ZP2). ZP1 and ZP2 inhibited IgE-mediated degranulation and A23187-mediated degranulation in RBL-2H3 mast cells. Our findings suggest the inhibition of degranulation by ZP1 and ZP2 was by inhibition of Lyn phosphorylation, followed by inhibition of intracellular Ca2+ mobilization, protein kinase C alpha phosphorylation, membrane ruffling, and granule-to-plasma membrane fusion. Oral administration of ZP1 or ZP2 attenuated an IgE-mediated passive cutaneous anaphylactic reaction in mice. Histological observation suggests that this effect occurred via inhibition of mast cell degranulation. These findings indicate that ZP1 and ZP2 attenuate allergic reaction via inhibition of IgE-mediated mast cell degranulation.

The antipsychotic drug pimozide inhibits IgE-mediated mast cell degranulation and migration

BackgroundMast cells (MCs) mediate a key role in allergic diseases. Detailed studies of how the neuroleptic drug pimozide affects MC activity are lacking. The aim of this study was to investigate pimozide inhibition of immunoglobulin E (IgE)-mediated MC activation and MC-mediated allergic responses. MethodMCs were stimulated with anti-dinitrophenyl (DNP) IgE antibodies and DNP-horse serum albumin (HSA) antigen (Ag), and anti-allergic pimozide effects were detected by measuring β-hexosaminidase levels. Morphological changes were observed histologically. In vivo pimozide effects were assessed in passive cutaneous anaphylaxis (PCA) and ovalbumin (OVA)-sensitized active systemic anaphylaxis mouse (ASA) model experiments. Levels of phosphorylated (p-) SYK (spleen tyrosine kinase) and MAPKs (mitogen-activated protein kinases) were detected in western blots. ResultsWe found that pimozide inhibited MC degranulation, reduced MC release of β-hexosaminidase dose-dependently in activated RBL-2H3 (IC50: 13.52 μM) and bone marrow derived MC (BMMC) (IC50: 42.42 μM), and reduced MC morphological changes. The IgE/Ag-induced migration effect was suppressed by pimozide treatment dose-dependently. Pimozide down-regulated IgE/Ag-induced phosphorylation of SYK and MAPKs in activated MCs. Moreover, pimozide attenuated allergic reactions in PCA and ASA model mice, and decreased MC populations among splenic cells. ConclusionsThe antipsychotic drug pimozide can suppress IgE-mediated MC activation in vitro and in vivo and should be considered for repurposing to suppress MC-mediated diseases.

Mouse Models for Food Allergies: Where Do We Stand?

Food allergies are a steadily increasing health and economic problem. Immunologically, food allergic reactions are caused by pathological, allergen-specific Th2 responses resulting in IgE-mediated mast cell degranulation and associated inflammatory reactions. Clinically, food allergies are characterized by local inflammation of the mouth mucosa, the face, the throat, the gastrointestinal tract, are frequently paralleled by skin reactions, and can result in life-threatening anaphylactic reactions. To better understand food allergies and establish novel treatment options, mouse models are indispensable. This review discusses the available mouse food allergy models, dividing them into four categories: (1) adjuvant-free mouse models, (2) mouse models relying on adjuvants to establish allergen-specific Th2 responses, (3) mouse models using genetically-modified mouse strains to allow for easier sensitization, and (4) humanized mouse models in which different immunodeficient mouse strains are reconstituted with human immune or stem cells to investigate humanized immune responses. While most of the available mouse models can reproducibly portray the immunological parameters of food allergy (Th2 immune responses, IgE production and mast cell activation/expansion), so far, the recreation of the clinical parameters has proven more difficult. Therefore, up to now none of the available mouse models can reproduce the complete human pathology.

Autonomous regulation of IgE-mediated mast cell degranulation and immediate hypersensitivity reaction by an inhibitory receptor CD300a

Autonomous regulation of IgE-mediated mast cell degranulation and immediate hypersensitivity reaction by an inhibitory receptor CD300a

Discovery of a natural PI3Kδ inhibitor through virtual screening and biological assay study

Phosphoinositide-3-kinase-δ (PI3Kδ) is a key regulator in the process of IgE mediated mast cell degranulation, which directly induces allergic diseases, such as asthma. This study is aimed at discovery of natural PI3Kδ inhibitors from Chinese medicine and evaluating their anti-mast cell degranulation activity. A combined virtual screening based on 3D pharmacophore model and molecular docking was used to screen for bioactive ingredients directly targeting PI3Kδ. Then, an in vitro kinase inhibition assay was conducted to evaluate the PI3Kδ inhibitory activity of the virtual screening hits. Subsequently, a β-hexosaminidase release assay was performed to verify the anti-mast cell degranulation activity of the active compounds. Finally, ginkgoneolic acid was identified as a PI3Kδ inhibitor (IC50 = 2.49 μM) and exhibited anti-mast cell degranulation activity in vitro (IC50 = 2.40 μM). Docking studies showed that Glu826, Val827 and Val828 were key amino acid residues for PI3Kδ inhibitory activity. Ginkgoneolic acid may be a potential lead compound for developing effective and safe PI3Kδ-inhibiting drugs.

Unique Presentation of Isolated Intestinal Angioedema Without ACE-I Involvement

1651_A Figure 1. Diffuse bowel wall thickening involving stomach, small bowel and colon with suggestion of mucosal enhancement and submucosal edema.1651_B Figure 2 No Caption available.Case reports of intestinal angioedema are well documented in the literature. However, the majority of these cases are due to angiotensin-converting enzyme inhibitor (ACE-I) induced angioedema. We present an unusual case of a patient who had isolated intestinal wall angioedema without taking ACE-I and normal C1 inhibitor levels. The inciting event was ingestion of a food allergen, which is not well described in the literature. The patient is a 63 year old female who presented for 1 day history of severe abdominal pain. The patient was in her usual state of health when she drank her daily smoothie. The only addition to her smoothie was parsley. Upon ingestion, she immediately developed severe cramping pain in her abdomen associated with nausea, vomiting, and watery diarrhea. She denied itching or rash. Upon presentation to the hospital, the patient was noted to be tachycardic and tachypneic. The patient admitted to having a similar reaction years ago to ingestion of kiwi fruit. Her physical exam demonstrated non distended abdomen with diffuse tenderness to palpation and normoactive bowel sounds. Her hospital course entailed a 1 day course of antibiotics and anti-emetics. Her diet was advanced and after a 3 day hospital stay was discharged home. Labs were notable for WBC of 18,000, lactate of 5.9. The remainder of the labs including blood cultures, stool analysis, ESR, C-ANCA, P-ANCA, C1-Inhibitor, complement levels were normal. Angioedema is one of the most common allergic disorders that results in hospitalization. Any hollow viscera are prone to this type of temporary swelling. The severity of presentation of intestinal angioedema can be varied, from mild colicky pain to severe vomiting and diarrhea. Most often the inciting agent is ACE- I. This reaction is well documented but still rare with only 21 cases described in the literature. We present a case of isolated intestinal angioedema following an ingested allergen. What is unique is that this sequela occurred in the absence of ACE-I use. Furthermore, the patient presented with isolated intestinal angioedema which is unreported in literature. No signs of systemic anaphylaxis or oral angioedema were noted which is typical in food allergies. Another unique finding was normal C1 inhibitor levels making hereditary angioedema unlikely. In this instance, the mechanism was most likely due to first time parsley ingestion causing IgE mediated mast cell degranulation releasing histamine leading to intestinal swelling.