Histamine Response Research Articles

The importance of mast cell histamine secretion in IgG-mediated systemic anaphylaxis.

IgG can mediate murine and human systemic anaphylaxis (SA). The roles of mast cells (MCs) and histamine in IgG-mediated anaphylaxis are controversial for mice and have not been studied invivo for humans. We are now investigating these issues. Actively or passively sensitized wild-type and immune-deficient mice were induced to develop anaphylaxis by intravenous antigen challenge. Anaphylaxis was characterized by evaluating hypothermia, hypomobility, histamine, and MC protease responses. In contrast to our previous results with protein-immunized mice from a conventional colony, IgG-mediated passive SA in our specific pathogen-free colony mice depended considerably on histamine produced by connective tissue MCs (CTMCs) in response to FcγRIII crosslinking. This was found for C57BL/6 and young male and female BALB/c mice, including BALB/c mice newly arrived from 3 vendors. IgG-mediated anaphylaxis was less histamine dependent in old than young mice. Although both mucosal MC (MMC) and CTMC responses were severely depleted in c-kit-deficient mice, MMC responses depended considerably more than CTMC responses on c-kit for maintenance. In immunologically naive mice, FcγRIII crosslinking strongly activated a subset of CTMCs but had little ability to activate MMCs. Invivo LPS+ poly I:C treatment decreased histamine dependence of IgG-mediated anaphylaxis, while a strong TH2 immune response increased FcγRIII crosslinking-induced MMC activation. IgG-mediated activation of human MCs in reconstituted immunodeficient mice induced histamine-dependent anaphylaxis. IgG-dependent SA can be mediated largely by histamine released by mouse CTMCs and human MCs; histamine dependence is influenced by mouse age, sex, and immune and infectious history, as well as the anaphylaxis model studied.

Novel Use of 1-methylhistamine as a Biomarker of the Histamine Response to Exercise

Histamine is released within skeletal muscle during exercise, promoting a sustained post-exercise vasodilation and contributing to adaptive responses to exercise training. Tracking this response is complicated by the short half-life and localization of histamine, requiring invasive methods such as intramuscular microdialysis or arteriovenous catheterization. Surrogates based on regional blood flow to assess post-exercise vasodilation require skilled use of expensive equipment, such as ultrasonography. These approaches may not be available in many research or athletic settings. Therefore, we explored the use of 1-methylhistamine (1-MH), a primary metabolite of histamine, as a novel biomarker of histamine’s release in response to aerobic and resistance exercise. We hypothesized that urinary 1-MH production would increase following exercise and that it would be positively correlated with post-exercise femoral artery blood flow and vascular conductance. Six healthy (1F, 5M; 22±4y; 24.3±1.9 kg·m2) trained participants (VO2peak: 51.8±7.7 ml·kg−1·min−1; back squat 1-repetition maximum, 1-RM: 1.66±0.27 kg·bodyweight−1) completed two exercise sessions separated by 1-wk: Aerobic, 30-min of cycling exercise at 70% VO2peak; Resistance, 6 sets of 10 repetitions of back squat exercise at 70% 1-RM. Femoral artery blood flow and vascular conductance were measured and venous blood samples were obtained before, immediately after, and throughout 2-h of post-exercise recovery. Urine was collected during the 24-h before and 2-, and 24-h post-exercise. Histamine and 1-MH concentrations were measured via high-performance liquid chromatography. Results are presented as mean ± SD and were compared by repeated-measures ANOVA and Pearson’s correlations. Blood flow increased immediately after exercise vs before (Aerobic: 442±60 vs 184±58 mL·min−1, p<0.05; Resistance: 626±190 vs 194±54 mL·min−1, p<0.05) and remained elevated 30-min into recovery (Aerobic: 273±63, p<0.05; Resistance: 396±99 mL·min−1, p<0.05). The area under the curve for blood flow after exercise tended to be greater following resistance (16117±5504 mL) vs aerobic (8732±5360 mL, p=0.06) exercise. When averaged across exercise modes, urine 1-MH production was elevated 2-h post-exercise vs before (23.6±15.9 vs 9.2±5.9 μg/h, p<0.05). Urine 1-MH production tended to correlate with percent elevation in femoral artery blood flow (r=0.59, p=0.09) and correlated with the percent elevation in vascular conductance following exercise (r=0.53, p<0.05). These results demonstrate that both aerobic and resistance exercise elicit a histamine response and support the utility of urinary 1-MH production as a biomarker of histamine’s release in response to exercise. Supported by NIH grant R01 AG072805. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mechanical stimulation of human hair follicle outer root sheath cultures activates adjacent sensory neurons.

Mechanical stimuli, such as stroking or pressing on the skin, activate mechanoreceptors transmitting information to the sensory nervous system and brain. It is well accepted that deflection of the hair fiber that occurs with a light breeze or touch directly activates the sensory neurons surrounding the hair follicle, facilitating transmission of mechanical information. Here, we hypothesized that hair follicle outer root sheath cells act as transducers of mechanical stimuli to sensory neurons surrounding the hair follicle. Using electrochemical analysis on human hair follicle preparations in vitro, we were able to show that outer root sheath cells release ATP and the neurotransmitters serotonin and histamine in response to mechanical stimulation. Using calcium imaging combined with pharmacology in a coculture of outer root sheath cells with sensory neurons, we found that the release of these three molecules from hair follicle cells leads to activation of sensory neurons.

Naphthalene-2,3-dicarboxaldehyde as a pulsed-post column derivatization reagent; comparison with two alternative o-phthalaldehyde based chemistries for the determination of histamine.

In the present study, naphthalene-2,3-dicarboxaldehyde (NDA) was used in on-line post column derivatization (PCD) coupled to liquid chromatography under the new concept of Pulsed-PCD. In Pulsed-PCD, the reagents are introduced into the flowing stream of the mobile phase under precise timing overlapping the eluted analyte. The consumption of the reagents is minimized to a few microliters, resulting in a significant advantage, that is the use of expensive reagents in PCD. For this reason, NDA-CN chemistry was used for the determination of histamine in food samples, such as eggplant and spinach. Two additional methods were developed based on the reaction of histamine with o-phthalaldehyde (OPA), namely the classic OPA - nucleophilic compound reaction and the specific OPA - histamine reaction in alkaline medium. The chromatographic conditions and the Pulsed-PCD conditions were investigated, while the analytical figures of merit were satisfactory. In all three methods, a pulse of 50μL was used (OPA/NDA+Buffer), reducing dramatically the consumption of PCD reagents.

Influence of a single oral dose of trazodone on intradermal histamine reactivity in clinically healthy dogs.

Drug interactions are significant considerations for intradermal testing (IDT). Trazodone (TRZ) is an anxiolytic and selective histaminergic (H1 ) antagonist with no interaction in human prick tests; however, interaction in canine IDT is unknown. Trazodone will not adversely affect intradermal histamine reactions in dogs. Fourteen nonanxious, nonatopic, healthy client-owned dogs were enrolled in this randomised, blinded, cross-over study. Dogs were randomised to receive low-dose TRZ (4 mg/kg) (Teva Pharmaceuticals), high-dose TRZ (8 mg/kg) or no TRZ per os two hours before intravenous sedation with dexmedetomidine (5 mcg/kg) (Dexdomitor; Zoetis). Intradermal testing was performed with five quadrupling dilutions of histamine (1:100,000 to 1:25,600,000 w/v; Greer) and 0.9% saline (Hospira), observing a minimum two weeks washout period between treatments. Two observers, who were blinded to treatment and the identity of the injections, evaluated each test using previously established subjective and objective methods. The mean wheal diameter of histamine 1:1,600,000 w/v was significantly smaller with low-dose TRZ (4 mg/kg) compared to the control group (p = 0.048; repeated measures ANOVA with post hoc Tukey's test). For all other histamine dilutions and saline, mean wheal diameter was not significantly different among groups. There were no significant differences in the subjective scores of all histamine dilutions and saline (p > 0.05; Friedman test). A single oral dose of TRZ does not adversely affect intradermal histamine reactions in dogs.

Comparative evaluation of the potential anti-spasmodic activity of Piper longum, Piper nigrum, Terminalia bellerica, Terminalia chebula, and Zingiber officinale in experimental animals

BackgroundSpasm of muscle is one of the frequent complaints seen by most of the population worldwide. The present study evaluated the efficacy of some of the commonly used herbal extracts against known spasmogens, such as histamine and 5-hydroxytryptamine (5-HT). Material and methodsThe study was conducted on isolated guinea pig ileum and rat uterus preparations using histamine and 5-HT, respectively. Five herbal extracts such as Piper longum (P.L), Piper nigrum (P.N), Terminalia bellerica (T.B), Terminalia chebula (T.C), and Zingiber officinale (Z.O) were tested. Herbal extracts at doses 50, 150, 500, 1500, and 5000 mcg/ml were pretreated to the isolated tissue preparation, and the contractile response of histamine and 5-HT was recorded. The efficacy and the inhibitory concentration (IC50) were calculated and statistically analyzed by one-way ANOVA. ResultsThe study indicated that all five herbal extracts produced a concentration-dependent suppression of histamine and 5-HT-induced responses. A significant (p < 0.05) non-competitive antagonism was observed against the known spasmogen induced smooth muscle contraction for P.L, P.N, T.B, and Z.O in both guinea pigs and rat uterus preparation. Moreover, P.L and P.N completely abolished (100%) the contractile response induced by histamine and 5-HT. Although, T.C produced a concentration-dependent reduction in known spasmogen-induced contraction but the response was found to be statistically non-significant (p greater than 0.05). ConclusionThe finding suggested that P.L. and P.N. have better activity in terms of reducing the spasmogenic contractions compared to other extracts. Additionally, T.B. and Z.O. can lessen the uterine and intestinal contractions brought on by spasmogens. Although P.L and P.N demonstrated better efficacy against the spasmogenic activity of histamine and 5-HT, more research, particularly on isolated phytochemicals of the extracts and involving different experimental models, is required before establishing the precise safety and efficacy against spasmogenic-induced disorders.

(084) A Case Report of Alcohol-Induced Vestibule Pain, Resolved in the Setting of Vestibular Anesthesia Test

Abstract Introduction Vestibulodynia is a term to denote pain in the vestibule, which encompasses the vulvar tissue beginning within the labia minora at Hart’s line to the hymen, extending anteriorly just inferior to the clitoris and to the posterior fourchette. Three subtypes of vestibulodynia exist including neuroproliferative, hormonally-mediated and inflammatory. All three subtypes can cause a constellation of symptoms including dyspareunia, dysuria, and discomfort with wearing tight clothes or wiping. Objective Described here are two patients who note pain in the vestibule within seconds of drinking alcohol. Notably, in the setting of a vestibular anesthesia test, in which the entire vestibule was completely numbed, they noticed resolution of their typical symptoms and were able to drink alcohol without vestibular pain. Methods This first patient is a 40 year old female with endometriosis, adenomyosis, PMDD, POTS, pelvic pain and 19 year history of unprovoked vestibulodynia with multiple failed treatment modalities. Upon consumption of alcohol, notices immediate pain in the vestibule. The second patient is a 27 year old female with provoked neuroproliferative vestibulodynia s/p vestibulectomy. Notes that four minutes after drinking any type of alcohol has worsening stinging and burning of the vestibule. A vestibular anesthesia test was performed, coating the vestibule in 30% Benzocaine, 8% Lidocaine and 6% Tetracaine, allowing it to sit for 10 minutes. Results Both patients drank alcohol after the 10 minutes and noted no symptoms at the tissue level whatsoever. They both still had hypertonic pelvic floors. The second patient went on to vestibulectomy and still had symptoms present, though they had decreased. Conclusions These cases indicate that alcohol may play a role in inciting vestibulodynia symptoms, and numbing of the vestibule can negate those symptoms. Possible pathophysiology may be due to the vasodilation effects of alcohol on the vestibular tissue, or a histamine response, but further research is needed to determine any potential link. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Sprout

Rapid determination of histamine levels in canned tuna by a novel spectrophotometric method

Histamine is the most common biogenic amine and is responsible for Scombroid fish poisoning. The presence of histamine at high concentrations in foodstuff indicates a public health issue Therefore, to the assurance of safety and quality, the monitoring of histamine concentration in fish and fishery products is urgent. To this aim, histamine content in 30 samples of canned tuna was measured by the UV-Vis spectrophotometry method. Linear regression was gained (R2 = 0.9905). The range of histamine levels was calculated between 85.04-125.08 mg kg-1 with an overall mean of 98.104 ± 5.18 mg kg-1. 40% of the samples were contained more than 100 mg kg-1, the allowable limit declared by Iranian National Standard (INS). However, The histamine amount of all samples were below the limit set by Codex Alimentarius (200 mg kg-1). There was no significant difference between the mean values of histamine in various brands of canned tuna. This spectrophotometric method used in this study can be introduced as a simple, applicable method for rapid monitoring of fish products, which is based on histamine reaction with copper and Alizarin Red S.

Specific Engineered G Protein Coupling to Histamine Receptors Revealed from Cellular Assay Experiments and Accelerated Molecular Dynamics Simulations.

G protein-coupled receptors (GPCRs) are targets of extracellular stimuli and hence occupy a key position in drug discovery. By specific and not yet fully elucidated coupling profiles with α subunits of distinct G protein families, they regulate cellular responses. The histamine H2 and H4 receptors (H2R and H4R) are prominent members of Gs- and Gi-coupled GPCRs. Nevertheless, promiscuous G protein and selective Gi signaling have been reported for the H2R and H4R, respectively, the molecular mechanism of which remained unclear. Using a combination of cellular experimental assays and Gaussian accelerated molecular dynamics (GaMD) simulations, we investigated the coupling profiles of the H2R and H4R to engineered mini-G proteins (mG). We obtained coupling profiles of the mGs, mGsi, or mGsq proteins to the H2R and H4R from the mini-G protein recruitment assays using HEK293T cells. Compared to H2R–mGs expressing cells, histamine responses were weaker (pEC50, Emax) for H2R–mGsi and –mGsq. By contrast, the H4R selectively bound to mGsi. Similarly, in all-atom GaMD simulations, we observed a preferential binding of H2R to mGs and H4R to mGsi revealed by the structural flexibility and free energy landscapes of the complexes. Although the mG α5 helices were consistently located within the HR binding cavity, alternative binding orientations were detected in the complexes. Due to the specific residue interactions, all mG α5 helices of the H2R complexes adopted the Gs-like orientation toward the receptor transmembrane (TM) 6 domain, whereas in H4R complexes, only mGsi was in the Gi-like orientation toward TM2, which was in agreement with Gs- and Gi-coupled GPCRs structures resolved by X-ray/cryo-EM. These cellular and molecular insights support (patho)physiological profiles of the histamine receptors, especially the hitherto little studied H2R function in the brain, as well as of the pharmacological potential of H4R selective drugs.

Is Body Mass Index Related to Skin Reactivity to Histamine but not to Specific Allergens? A 2-Year Follow-up Study on Korean Children.

Skin prick tests are widely used to diagnose allergic sensitization. The influence of obesity on the skin prick test result has not been clearly established, even though the association between allergic disease and obesity is relatively well known. To determine whether a change in body mass index (BMI) contributes to skin reactivity to histamine and allergens in a skin prick test, we performed a 2-year follow-up study on Korean children. Skin prick tests for common aeroallergens were performed on elementary school students from Jeju Island, Korea. BMI was calculated using weight and height after measuring both, and demographic characteristics were surveyed. The same tests were repeated after 2 years. The sensitization rate increased during the 2 years between tests and the children's mean BMI also increased, along with their age. The wheal sizes induced by Dermatophagoides pteronyssinus, Dermatophagoides farinae, Japanese cedar, and histamine were significantly increased during 2 years; however, only the histamine reaction associated with increased BMI had statistical significance. Furthermore, other variables-including the number of sensitized allergens-were not related to histamine skin reactivity. Histamine skin reactivity increased in children over time and some allergens showed increased specific reactions; however, BMI gain is a specific predictor of histamine reactivity. Further studies are needed to elucidate the clinical significance of these changes.

Anti-asthmatic effect of laurotetanine extracted from Litsea cubeba (Lour.) Pers. root on ovalbumin-induced allergic asthma rats, and elucidation of its mechanism of action

Purpose: To investigate the anti-asthmatic effect of laurotetanine on allergic asthma rat model.&#x0D; Methods: Laurotetanine was extracted from the roots of Litsea cubeba (Lour.) Pers. Asthma was induced in rats by ovalbumin injection. Laurotetanine (20, 40, or 60 mg/kg) was administered orally to the rats for 21 days. Inflammatory cells and cytokines released by T-cell subsets Th1 and Th2 in the bronchoalveolar lavage fluid were determined. Serum immunoglobulin E (IgE) and histamine, in addition to expression of mucin 5AC (MUC-5AC), nuclear factor-kappa B (NF-κB), and an inhibitor of NF-κB (IκB) in lung tissues were also evaluated.&#x0D; Results: Laurotetanine treatment (20, 40, 60 mg/kg) significantly reduced inflammatory cells, including eosinophils, neutrophils, lymphocytes, and macrophages in treated rats compared with control animals (p &lt; 0.01). Inflammatory cytokines, viz, interleukin (IL) -4, IL-6, IL-13 were also significantly (p &lt; 0.01) decreased by laurotetanine treatment (20, 40, 60 mg/kg), whereas interferon gamma (IFN-γ) was increased (p &lt; 0.01). Serum IgE and histamine were significantly reduced (p &lt; 0.01) by laurotetanine (20, 40, 60 mg/kg). Furthermore, MUC5AC expression in lung tissues was significantly (p &lt; 0.01) downregulated by laurotetanine (20, 40, and 60 mg/kg, but NF-κB and IκB were significantly (p &lt; 0.01) upregulated by laurotetanine (20, 40, and 60 mg/kg).&#x0D; Conclusion: Laurotetanine exerts an anti-asthmatic effect in rats by inhibition of IgE, histamine, and inflammatory reactions via down-regulating MUC5AC and NF-κB signaling pathways. This finding justifies the need for further development of laurotetanine as a potential anti-asthmatic drug.

Think Twice before Interpreting the Skin Prick Test as Age, Body Mass Index, and Atopy Affect Reaction Time and Size

Introduction: The skin prick test (SPT) is a reliable method to confirm sensitization in IgE-mediated allergic diseases; however, it has been reported to be affected by several personal and environmental factors. Our objective was to determine the factors affecting the skin reactivity to histamine and allergens and investigate whether it differs according to age in terms of reading time. Methods: A total of 500 patients, aged 4 months–18 years, were enrolled in the study. Wheal and flare reaction sizes were documented as the mean of the longest and the midpoint perpendicular diameter in the 5th, 10th, 15th, and 20th min. Skin reactivity was compared between children >24 and ≤24 months of age. Results: We found larger histamine and allergen wheal sizes in children >24 months than the ones ≤24 months of age (p < 0.001 and p = 0.007, respectively). The duration of maximum histamine reactivity was 15 min for children >24 months whereas 10 min for children ≤24 months of age. The number of children losing their histamine reactivity after 15 and 20 min was significantly higher in the smaller age-group. Multiple regression analysis revealed a larger histamine reactivity in children >24 months of age, having obesity, and having allergen sensitization (p = 0.002, p = 0.003, and p = 0.018, respectively). Conclusion: It seems more accurate to evaluate SPT after 10 min in children ≤24 months of age. Cutoff values and ideal measurement time according to individual factors such as age, body mass index, or atopy are needed.

Targeted inhibition of allergen-induced histamine production by neutrophils.

Histamine is a critical inflammatory mediator in allergic diseases. We showed in a previous work that neutrophils from allergic patients produce histamine in response to allergens to which the patients were sensitized. Here, we investigate the molecular mechanisms involved in this process using peripheral blood neutrophils. We challenged these cells in vitro with allergens and analyzed histamine release in the culture supernatants. We also explored the effect of common therapeutic drugs that ameliorate allergic symptoms, as well as allergen-specific immunotherapy. Additionally, we examined the expression of histidine decarboxylase and diamine oxidase, critical enzymes in the metabolism of histamine, under allergen challenge. We show that allergen-induced histamine release is dependent on the activation of the phosphoinositide 3-kinase, mitogen-activated protein kinase p38, and extracellular signal-regulated kinase 1/2 signaling pathways. We also found a contribution of the phosphatase calcineurin to lesser extent. Anti-histamines, glucocorticoids, anti-M3-muscarinic receptor antagonists, and mainly β2 -receptor agonists abolished the allergen-dependent histamine release. Interestingly, allergen-specific immunotherapy canceled the histamine release through the downregulation of histidine decarboxylase expression. Our observations describe novel molecular mechanisms involved in the allergen-dependent histamine release by human neutrophils and provide new targets to inhibit histamine production.

Transcriptome analysis provides insights into a molecular mechanism of histamine response in the cyprid larvae of Amphibalanus amphitrite

Barnacles are notorious marine fouling creatures; their planktonic cyprid larvae attach to material substrates and metamorphose. Histamine has shown great importance in regulating cyprid settlement and metamorphosis. This study aimed to investigate the mechanisms of histamine-induced larval settlement. Cyprids were exposed to histamine or loratadine, an anti-histamine compound. The percent larval settlements of the histamine- and anti-histamine-treated cyprids were significantly higher and lower, respectively, than the control group. Transcriptomic analyses showed that histamine-treated cyprids had 18498 differentially expressed genes (DEGs, 14531 up-regulated, 3967 down-regulated) and the anti-histamine group had 18055 DEGs (17237 up-regulated, 818 down-regulated) in comparison to untreated controls. In both treatment groups, significant enrichment of DEGs involved in the mitogen-activated protein kinase signaling pathway was observed. Based on the results of larval settlement bioassays, we set 4 filter conditions to perform DEG analyses, and 19 DEGs were selected as functional genes related to cyprid settlement. The functional categories of these genes included structural proteins, spider silk proteins, energy metabolism proteins, cement proteins, glycosyl proteins, and multifunctional proteins. The energy metabolism protein AdipoR was significantly up-regulated in the histamine-treated cyprids but significantly down-regulated in the anti-histamine group. The activity of adenosine monophosphate-activated protein kinase, a downstream signaling protein of AdipoR, increased in the histamine-treated group and decreased in the anti-histamine-treated group. Our results provide new insights into the molecular mechanisms underlying the histamine-induced settlement of barnacle cyprids and identify AdipoR as an important gene that can affect the settlement of cyprids, likely through regulating cyprid energy metabolism.

Improved FcεRI-Mediated CD203c Basophil Responsiveness Reflects Rapid Responses to Omalizumab in Chronic Spontaneous Urticaria

Omalizumab is effective in patients with chronic spontaneous urticaria (CSU) although its mechanism of action is poorly understood. Several studies reported that decreased high-affinity IgE receptor (FcεRI)-mediated histamine release and/or responsiveness was characteristic of basophils in patients with CSU. However, few studies have focused on the relationship between changes in basophil responsiveness via FcεRI after omalizumab treatment and the therapeutic effect in patients with CSU. To assess basophil responsiveness via FcεRI stimulation, as well as FcεRI expression and IgE binding on blood basophils from patients with CSU before and after omalizumab treatment and its possible association with the clinical response. We analyzed 34 patients with CSU treated with omalizumab who were categorized as fast responders (FRs) (n=20) and non or slow responders (N/SRs) (n= 14). CD203c expression induced by FcεRI stimulation, and IgE and FcεRI expressions on blood basophils from patients with CSU before and after omalizumab treatment were analyzed. Basophil responsiveness via FcεRI stimulation was observed invitro using basophils pretreated with omalizumab. FRs had increased CD203c responsiveness after treatment with omalizumab compared with N/SRs. This improvement of basophil responsiveness via FcεRI stimulation in FRs was not observed in peripheral blood basophils preincubated with omalizumab invitro, suggesting that omalizumab does not directly affect circulating pre-existing abnormal basophils. Increased basophil responsiveness via FcεRI after omalizumab treatment is associated with the therapeutic effect and mechanism of action of omalizumab.

Calcium signaling mediated by aminergic GPCRs is impaired by the PI3K inhibitor LY294002 and its analog LY303511 in a PI3K-independent manner

The phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (LY294) and its much less active analog LY303511 (LY303) constitute the paired probe that is commonly used to demonstrate the involvement of PI3K in intracellular signaling. We studied effects of LY294 and LY303 on Ca2+ signaling initiated by certain GPCR agonists in cells of several lines, including CHO cells expressing the recombinant serotonin receptor 5-HT2C and mesenchymal stromal cells derived from the human adipose tissue (AD-MSCs) and umbilical cord (UD-MSCs). The LY294/LY303 pair exerted apparently specific effects on responsiveness of AD-MSCs to ATP, suggesting the involvement of PI3K in ATP transduction. Surprisingly, LY303 inhibited Ca2+ transients elicited by histamine in the same cells, while LY294 was ineffective. This observation and other findings implicated a PI3K-unrelated mechanism in mediating effects of the LY compound on AD-MSC responsiveness to histamine. With LY303 in the bath, the dose dependence of histamine responses was shifted positively at the invariable number of responsive cells, as would be the case with a competitive antagonist of histamine receptors. Moreover, LY303 and LY294 inhibited Ca2+ transients elicited by acetylcholine and serotonin in UD-MSCs and CHO/5-HT2C cells, respectively. Our overall results argued for the possibility that LY294 and LY303 could directly affect activity of aminergic GPCRs. Thus, LY303511 and LY294002 should be used cautiously in studies of PI3K as a factor of GPCR signaling.

Perinatal androgen exposure impacts mast cell development and sex differences in mast cell-mediated pathophysiology

Abstract Mast cell (MC)-associated diseases exhibit a sex bias with females often exhibiting more severe symptoms. Further, these sex biases exist in both prepubertal children and adults indicating that mechanisms other than adult sex hormones are involved. In previous studies, we showed that, compared with female MCs, male MCs store and release less histamine which coincided with reduced severity of MC-mediated anaphylaxis, and that these sex differences emerge prior to puberty. The early life mechanisms responsible for the emergence of sex differences in MC-associated disease remain poorly understood. Here we tested the hypothesis that perinatal androgen exposure, a major sexual organization event in males, drives sex differences in MC-mediated pathophysiology. Adult female mice that were previously exposed to high levels of androgens in the perinatal period (E16-PN7) via perinatal testosterone propionate administration had reduced IgE-mediated serum histamine levels and hypothermic responses compared with control females. In contrast, perinatal exposure of males to the endocrine disruptor DEHP, with known anti-androgenic effects, exacerbated IgE-mediated histamine levels and hypothermia. MC-deficient sash mice engrafted with BMMCs from adult perinatally androgenized females, exhibited reduced serum histamine and hypothermia responses compared with WT BMMC engrafted sash controls. Together, these data demonstrate that androgen exposure during the perinatal period shapes MC phenotype and MC-mediated anaphylaxis and thus could be an important determinant of differences in later life MC disease risk between the sexes.

Omeprazole inhibits IgE-mediated mast cell activation and allergic inflammation induced by ingested allergen in mice

Patients with eosinophilic esophagitis have increased numbers of mucosal mast cells. Administration of the proton pump inhibitor omeprazole can reduce both esophageal mast cell and eosinophil numbers and attenuate type 2 inflammation in these subjects. Given that maintenance of an acidic environment within granules is important for mast cell homeostasis, we sought to evaluate the effects of omeprazole on mast cell functions including development, IgE:FcεRI-mediated activation, and responses to food allergen. Mast cell degranulation, cytokine secretion, and early signaling events in the FcεRI pathway, including protein kinase phosphorylation and Ca2+ flux, were measured after IgE crosslinking in murine bone marrow-derived mast cells and human cord blood-derived mast cells. The effects of omeprazole on these responses were investigated as was its impact on mast cell-dependent anaphylaxis and food allergy phenotypes invivo. Murine and human mast cells treated with omeprazole exhibited diminished degranulation and release of cytokines and histamine in response to allergen. In murine mast cells, phosphorylation of protein kinases, ERK and SYK, was decreased. Differentiation of mast cells from bone marrow progenitors was also inhibited. IgE-mediated passive anaphylaxis was blunted in mice treated with omeprazole as was allergen-induced mast cell expansion and mast cell activation in the intestine in a model of food allergy. Our findings suggest that omeprazole targets pathways important for the differentiation and activation of murine mast cells and for the manifestations of food allergy and anaphylaxis.

The Reliability of Histamine Pharmacodynamic Response Phenotype Classification in Children With Allergic Disease.

We have identified distinct histamine pharmacodynamic response phenotypes in children with allergic disease utilizing histamine iontophoresis with laser Doppler (HILD). These response phenotypes may be relevant in guiding therapeutic decision making for agents targeting the allergic response pathways. However, the reliability of these response phenotypes has not been assessed. Therefore, we performed HILD in children with allergic rhinitis and/or asthma on two to three separate occasions. HILD response-time data were analyzed in NONMEM using a linked effect PKPD model. Examination of observed vs. classified response phenotypes predicted response plots and the sum of residuals. The intraclass correlation coefficient (ICC) was used to determine the reliability of phenotype classification. Eighty-two percent of children exhibited a reliable histamine response phenotype [intraclass correlation coefficient 0.77 (95% CI 0.44–0.93]. These preliminary results suggest moderate reliability of HILD response phenotype in children. Further exploration is needed to determine contributions to phenotype variability.

Alterations in histamine responses between juvenile and adult urinary bladder urothelium, lamina propria and detrusor tissues

Inflammatory mediators may have a role in various lower urinary tract disorders. Histamine is known to induce significant increases in both the tension and frequency of spontaneous phasic contractions in both urothelium with lamina propria (U&LP) and detrusor muscle via the activation of H1 receptor in juvenile animal models. However, it is unclear whether age affects these contractile responses to histamine. This study assessed the histamine receptor subtypes mediating contraction in juvenile and adult porcine bladders and compared the urothelium with lamina propria and detrusor responses to histamine. Isolated tissue bath studies were conducted using strips of porcine U&LP and detrusor obtained from juvenile (6 months) and adult (3 years) animals exposed to histamine receptor agonists and antagonists. Treatment with histamine (100 µM) in U&LP of juvenile animals caused increases in baseline tension by 47.84 ± 6.52 mN/g (p < 0.001, n = 51) and by 50.76 ± 4.10 mN/g (p < 0.001, n = 55) in adult animals. Furthermore, the frequency of spontaneous phasic contractions was significantly enhanced in response to histamine in U&LP of both juvenile and adult tissues (p < 0.001 for both age groups). Treatment with an H2 agonist in U&LP of juvenile animals decreased baseline tension by 13.97 ± 3.45 mN/g (n = 12, p < 0.05), but had no effect in adult animals. Inhibition of H1 receptors resulted in significantly reduced contractile responses of U&LP and detrusor to histamine in both juvenile and adult animals (p < 0.05). Treatment with an H2 receptor antagonist significantly enhanced contractions in juvenile preparations (n = 10, p < 0.05) but had no effect in adult preparations (n = 8). In detrusor, treatment with histamine (100 µM) in juvenile tissues showed a significantly higher increase in baseline tension of 19.10 ± 4.92 mN/g (n = 51) when compared to adult tissues exhibiting increases of 8.21 ± 0.89 mN/g (n = 56, p < 0.05). The increases in the baseline tension were significantly inhibited by the presence of H1 receptor antagonists in both juvenile and adult detrusor preparations. Treatment with either the H2 receptor antagonist or agonist in detrusor had no effect on both juvenile and adult tissues. Therefore, the histamine receptor system may play an essential role in the maintenance of bladder function or in bladder dysfunction observed in some lower urinary tract disorders.