Histamine receptors in immune regulation and allergen-specific immunotherapy

Mast Cells and Basophils in IgE-Independent Anaphylaxis

Anaphylaxis is a life-threatening or even fatal systemic hypersensitivity reaction. The incidence of anaphylaxis has risen at an alarming rate in the past decades in the majority of countries. Generally, the most common causes of severe or fatal anaphylaxis are medication, foods and Hymenoptera venoms. Anaphylactic reactions are characterized by the activation of mast cells and basophils and the release of mediators. These cells express a variety of receptors that enable them to respond to a wide range of stimulants. Most studies of anaphylaxis focus on IgE-dependent reactions. The mast cell has long been regarded as the main effector cell involved in IgE-mediated anaphylaxis. This paper reviews IgE-independent anaphylaxis, with special emphasis on mast cells, basophils, anaphylactic mediators, risk factors, triggers, and management.

Differential expression of histamine receptors in the bladder wall tissues of patients with bladder pain syndrome/interstitial cystitis - significance in the responsiveness to antihistamine treatment and disease symptoms

Background

Activation of mast cells plays an important role in the pathogenesis of bladder pain syndrome/interstitial cystitis (BPS/IC). Histamine, a mast cell-derived mediators, induced inflammation and hypersensitivity of the bladder. The present study investigated the expressions of histamine receptors in the bladder wall tissues of patients with BPS/IC, and its association with the effectiveness of antihistamine therapy and disease symptoms.

Methods

Bladder tissues were collected from 69 BPS/IC patients and 10 control female patients. The expression of H3R in BPS/IC was further examined in an independent cohort of 10 female patients with BPS/IC and another 10 age-matched female patients. Immunohistochemistry, Western blotting, and quantitative RT-PCR were performed to quantify the expressions of histamine receptors. Statistical analyses of the correlation of histamine receptor expression with antihistamine therapy outcome and severity of disease symptoms were also performed.

Results

The expression of four histamine receptors was significantly elevated in BPS/IC (H1R, P < 0.001; H2R, P = 0.031; H3R, P = 0.008; H4R, P = 0.048). Western blotting revealed that H3R were significantly reduced in the patients, whereas the mRNA levels of H3R were significantly increased. The patients were further divided into antihistamine responders (n = 38) and nonresponders (n = 22). No significant correlation was found in the expression of histamine receptors between responder and nonresponder groups. However, significant correlations between OLS and H1R (P = 0.003) and H3R (P = 0.045) were found.

Conclusion

The present study showed that expression of all the 4 histamine receptors were elevated in BPS/IC. There were no statistical significant correlations between the expression levels of the four different histamine receptors and the treatment outcome of antihistamine therapy (amtitriptyline or cimetidine).

Ranitidine Inhibition of Breast Tumor Growth Is B Cell Dependent and Associated With an Enhanced Antitumor Antibody Response

Background

The histamine receptor 2 antagonist ranitidine is a commonly used, non-prescription, medication. It limits the development, growth, and metastasis of breast cancers in mouse models of disease. In this study, we examined the role of B cells in this response, the impact of ranitidine on the development of antitumor antibodies and subpopulations of natural killer cells using murine breast cancer models.

Methods

Peripheral blood granulocyte populations were assessed in both E0771-GFP and 4T1 orthotopic tumor-bearing mice by evaluation of stained blood smears. Antibody responses were assessed both in terms of the levels of anti-GFP antibodies detected by enzyme-linked immunosorbent assay and also by antibody binding to the surface of tumor cells evaluated by flow cytometry. B cell and NK cell populations were examined in the draining lymph nodes and spleens of tumor-bearing animals, by flow cytometry with and without ranitidine treatment.

Results

Oral ranitidine treatment was not associated with changes in peripheral blood granulocyte populations in tumor-bearing mice. However, ranitidine treatment was associated with the development of enhanced antitumor antibody responses. This was not limited to the tumor setting since ranitidine-treated mice immunized with ovalbumin also demonstrated increased IgG antibody responses. Analysis of B cell populations indicated that while B1 cell populations remained unchanged there was a significant decrease in B2 cells in the tumor-draining inguinal lymph nodes. Notably, ranitidine did not significantly inhibit primary tumor growth in B cell-deficient animals. Examination of NK cell populations revealed a significant decrease in the proportion of intermediately functionally mature NK cells populations (CD27⁺CD11b⁻) in ranitidine-treated tumor-bearing mice compared with untreated tumor-bearing controls.

Conclusion

These data demonstrate an important role for B cells in the enhanced antitumor immune response that occurs in response to ranitidine treatment. Our findings are consistent with a model, whereby ranitidine reduces tumor-associated immune suppression allowing for the development of more effective antitumor responses mediated by B cells which may include the participation of NK cells. These data underline the importance of considering widely used histamine receptor antagonists as modulators of antitumor immunity to breast cancer.

A randomized, double-blind, placebo-controlled clinical trial evaluating the role of systemic antihistamine therapy for the reduction of adverse effects associated with topical 5-aminolevulinic acid photodynamic therapy

BACKGROUND AND OBJECTIVE

Following photodynamic therapy with 5-aminolevulinic acid (ALA-PDT), patients experience inflammation that may be partially attributable to H1 histamine receptor activation. The objective of this study was to evaluate the impact of antihistamines upon adverse effects following ALA-PDT.

STUDY DESIGN/MATERIALS AND METHODS

This was a randomized, placebo-controlled clinical trial conducted at a single study site. Twenty subjects with facial actinic keratoses were randomized to ALA-PDT plus cetirizine 10 mg (n = 10) versus placebo daily (n = 10) from 3 days pre-treatment to 3 days post-treatment for a total of 7 days. Signs of inflammation including erythema, edema, crusting, exudation, vesiculation, and erosion were evaluated on post-treatment days 1, 2, 3, 7, 30, 90, and 180. Actinic keratosis counts, investigator-rated Global Assessment Improvement Score (GAIS), healing, tolerability, and subject satisfaction were also assessed.

RESULTS

Erythema, edema, crusting, exudation, vesiculation, and erosion were not different between treatment groups. Actinic keratoses were significantly reduced by day 30 in both the antihistamine and placebo groups (P = 0.01 and 0.0009, respectively), with results sustained to day 60 in the antihistamine group and day 180 for the placebo group. However, counts were not different between groups at any time point. Investigator-rated GAIS, subject satisfaction, healing, and tolerability were similar between treatment groups.

CONCLUSION

This study suggests that while H1 antihistamines do not impair the efficacy of ALA-PDT, they also do not relieve post-treatment inflammation and discomfort. Lasers Surg. Med. 49:738-742, 2017. © 2017 Wiley Periodicals, Inc.

Role of histamine in the regulation of intestinal immunity in fish

In mammals, during the acute inflammatory response, the complex interrelationship and cross-talk among histamine and the immune system has been fairly well characterized. There is a substantial body of information on its structure, metabolism, receptors, signal transduction, physiologic and pathologic effects. However, for early vertebrates, there is little such knowledge. In the case of teleost fish, this lack of knowledge has been due to the widely held belief that histamine is not present in this phylogenetic group. However, it has been recently demonstrated, that granules of mast cells in perciforms contain biologically active histamine. More importantly, the inflammatory response was clearly demonstrated to be regulated by the direct action of histamine on professional phagocytes. Nevertheless, the molecular basis and exact role of this biogenic amine in perciforms is still a matter of speculation. Therefore, this review intends to summarize recent experimental evidence regarding fish mast cells and correlate the same with their mammalian counterparts to establish the possible role of histamine in the fish intestinal inflammatory response.

Identification of potential crucial gene network related to seasonal allergic rhinitis using microarray data

The aim of this study was to reveal a potential key gene network associated with seasonal allergic rhinitis (SAR). The microarray data GSE50101 downloaded from Gene Expression Omnibus were used to screen differentially expressed genes (DEGs) between SAR patients and healthy controls. Then, functional enrichment analysis was conducted using Database for Annotation, Visualization, and Integrated Discovery. Afterwards, the protein-protein interactions (PPIs) of DEGs were obtained from STRING, and the PPI network was constructed. In addition, the PPI network module was analyzed. In total, 98 up-regulated and 63 down-regulated DEGs were identified from the SAR samples, comparing the healthy controls. The up-regulated DEGs were mainly enriched in the Gene Ontology terms about cell death (e.g., DUSP1 and JUN) and pathways related to immune (e.g., FOS and JUN). The down-regulated DEGs were mainly enriched in regulation of transcription (e.g., CEBPD and SCML1). In the PPI network, a set of genes was predicted to interact with each other, such as FOS, JUN, and CEBPD. Furthermore, genes in the network module (e.g., FOS, JUN and CEBPD) was mainly enriched in regulation of transcription, and pathways about immune, such as mitogen-activated protein kinase signaling pathway, B cell receptor signaling pathway, and toll-like receptor signaling pathway. Several genes related to immunity and regulation of transcription, such as FOS, JUN, and CEBPD, may play crucial roles during the process of SAR through the interactions with each other.

Ranitidine modifies myeloid cell populations and inhibits breast tumor development and spread in mice

Histamine receptor 2 (H2) antagonists are widely used clinically for the control of gastrointestinal symptoms, but also impact immune function. They have been reported to reduce tumor growth in established colon and lung cancer models. Histamine has also been reported to modify populations of myeloid-derived suppressor cells (MDSCs). We have examined the impact of the widely used H2 antagonist ranitidine, on both myeloid cell populations and tumor development and spread, in three distinct models of breast cancer that highlight different stages of cancer progression. Oral ranitidine treatment significantly decreased the monocytic MDSC population in the spleen and bone marrow both alone and in the context of an orthotopic breast tumor model. H2 antagonists ranitidine and famotidine, but not H1 or H4 antagonists, significantly inhibited lung metastasis in the 4T1 model. In the E0771 model, ranitidine decreased primary tumor growth while omeprazole treatment had no impact on tumor development. Gemcitabine treatment prevented the tumor growth inhibition associated with ranitidine treatment. In keeping with ranitidine-induced changes in myeloid cell populations in non-tumor-bearing mice, ranitidine also delayed the onset of spontaneous tumor development, and decreased the number of tumors that developed in LKB1^−/−/NIC mice. These results indicate that ranitidine alters monocyte populations associated with MDSC activity, and subsequently impacts breast tumor development and outcome. Ranitidine has potential as an adjuvant therapy or preventative agent in breast cancer and provides a novel and safe approach to the long-term reduction of tumor-associated immune suppression.

Impact of allergic rhinitis and specific subcutaneous immunotherapy on peripheral blood basophils of patients sensitized to Dermatophagoides pteronyssinus

Background

Basophils are important effectors cells in allergic rhinitis (AR) since they are involved in immunoglobulin (Ig) E – mediated inflammation and in the release of pro-inflammatory mediators. Specific subcutaneous immunotherapy (SCIT) provides clear immunologic modulation in some immune cells, however its systemic effects on basophils are not well known.

Methods

Peripheral blood (PB) samples from 43 patients with allergic rhinitis mono-sensitized to Dermatophagoides pteronyssinus (Dpt) [33 of them under SCIT with allergoid Dpt extract, in maintenance dose (SCIT), with evaluation just before SCIT injection (SCIT-T0) and 4 hours later (SCIT-T4) and the other 10 Dpt allergic patients never having, in the past, undergone specific immunotherapy treatment (NSIT)], and 15 healthy age- and gender-matched controls (HG), were analyzed. For each sample, the total (t-IgE) and specific IgE (s-IgE) was performed, as well as, the relative frequency and absolute number of PB basophils and receptor-bound IgE and IgG expression were evaluated by flow cytometry and the Histamine N-methyltransferase (HNMT) and tryptase α/β1 (TPSAB1) gene expression was assessed by real-time PCR.

Results

Higher levels of receptor-bound IgE were observed in SCIT patients, which are correlated with the levels of serum t-IgE and s-IgE, whereas no significant differences were observed for receptor-bound IgG. Regarding HNMT mRNA expression, significantly lower expression levels were detected in AR patients compared to HG, independently of type of therapy. Moreover a negative correlation was found between HNMT gene expression and time under SCIT. Conversely, tryptase gene expression was significantly up-regulated in NSIT when compared to HG; however in SCIT patients, tryptase gene expression was significantly decreased than in NSIT patients. No differences were found for any parameter between SCIT-T0 and SCIT-T4 with exception of a transient increased expression of tryptase in SCIT-T4.

Conclusion

PB basophils from patients with AR show altered functional features, which seems to be influenced by SCIT, suggesting that these cells could be useful to clarify the SCIT triggered mechanisms at a systemic level.

Proteome map of the neural complex of the tunicate Ciona intestinalis, the closest living relative to vertebrates

Ciona intestinalis (the common sea squirt) is the closest living chordate relative to vertebrates with cosmopolitan presence worldwide. It has a relatively simple nervous system and development, making it a widely studied alternative model system in neuroscience and developmental biology. The use of Ciona as a model organism has increased significantly after the draft genome was published. In this study, we describe the first proteome map of the neural complex of C. intestinalis. A total of 544 proteins were identified based on 1DE and 2DE FTMS/ITMSMS analyses. Proteins were annotated against the Ciona database and analyzed to predict their molecular functions, roles in biological processes, and position in constructed network pathways. The identified Ciona neural complex proteome was found to map onto vertebrate nervous system pathways, including cytoskeleton remodeling neurofilaments, cell adhesion through the histamine receptor signaling pathway, γ-aminobutyric acid-A receptor life cycle neurophysiological process, glycolysis, and amino acid metabolism. The proteome map of the Ciona neural complex is the first step toward a better understanding of several important processes, including the evolution and regeneration capacity of the Ciona nervous system.

Cutting edge: histamine is required for IL-4-driven eosinophilic allergic responses

Histamine is an important allergic mediator, and studies have defined roles for both histamine 1 and 4 receptors in allergic airway inflammation. In this study, we show that histamine is necessary to generate IL-4-driven eosinophilic inflammation, as histamine-deficient mice cannot generate eosinophilic lung inflammation in response to intratracheal IL-4 and exogenous histamine restores responsiveness. This is histamine 2 receptor (H2R) dependent because H2R knockout mice fail to respond to IL-4, and a H2R agonist restores inflammation in histidine decarboxylase knockout. Furthermore, alveolar epithelial cells require H2R to produce CCL24, an eosinophil recruitment factor, whereas H2R blockade reduces CCL24 production from wild-type cells. In an allergic inflammation model, H2R knockout mice show significantly reduced eosinophilic inflammation and CCL24 expression. These data demonstrate a previously unidentified role for H2R in allergic inflammation and establishes a synergy between endogenous histamine and IL-4 that supports eosinophilic recruitment to the lung.

Histamine H4 receptor optimizes T regulatory cell frequency and facilitates anti-inflammatory responses within the central nervous system

Histamine is a biogenic amine that mediates multiple physiological processes, including immunomodulatory effects in allergic and inflammatory reactions, and also plays a key regulatory role in experimental allergic encephalomyelitis, the autoimmune model of multiple sclerosis. The pleiotropic effects of histamine are mediated by four G protein-coupled receptors, as follows: Hrh1/H(1)R, Hrh2/H(2)R, Hrh3/H(3)R, and Hrh4/H(4)R. H(4)R expression is primarily restricted to hematopoietic cells, and its role in autoimmune inflammatory demyelinating disease of the CNS has not been studied. In this study, we show that, compared with wild-type mice, animals with a disrupted Hrh4 (H(4)RKO) develop more severe myelin oligodendrocyte glycoprotein (MOG)(35\x{2013}55)-induced experimental allergic encephalomyelitis. Mechanistically, we also show that H(4)R plays a role in determining the frequency of T regulatory (T(R)) cells in secondary lymphoid tissues, and regulates T(R) cell chemotaxis and suppressor activity. Moreover, the lack of H(4)R leads to an impairment of an anti-inflammatory response due to fewer T(R) cells in the CNS during the acute phase of the disease and an increase in the proportion of Th17 cells.

Antihistamine therapy in allergic rhinitis

Antihistamines have long been a mainstay in the therapy for allergic rhinitis. Many different oral antihistamines are available for use, and they are classified as first generation or second generation based on their pharmacologic properties and side-effect profiles. The recent introduction of intranasal antihistamines has further expanded the role of antihistamines in the treatment of allergic rhinitis. Certain patient populations, such as children and pregnant or lactating women, require special consideration regarding antihistamine choice and dosing as part of rhinitis therapy.

NAADP links histamine H1 receptors to secretion of von Willebrand factor in human endothelial cells

A variety of endothelial agonist-induced responses are mediated by rises in intracellular Ca(2+), suggesting that different Ca(2+) signatures could fine-tune specific inflammatory and thrombotic activities. In search of new intracellular mechanisms modulating endothelial effector functions, we identified nicotinic acid adenine dinucleotide phosphate (NAADP) as a crucial second messenger in histamine-induced Ca(2+) release via H1 receptors (H1R). NAADP is a potent intracellular messenger mobilizing Ca(2+) from lysosome-like acidic compartments, functionally coupled to the endoplasmic reticulum. Using the human EA.hy926 endothelial cell line and primary human umbilical vein endothelial cells, we show that selective H1R activation increases intracellular NAADP levels and that H1R-induced calcium release involves both acidic organelles and the endoplasmic reticulum. To assess that NAADP links H1R to Ca(2+)-signaling we used both microinjection of self-inactivating concentrations of NAADP and the specific NAADP receptor antagonist, Ned-19, both of which completely abolished H1R-induced but not thrombin-induced Ca(2+) mobilization. Interestingly, H1R-mediated von Willebrand factor (VWF) secretion was completely inhibited by treatment with Ned-19 and by siRNA knockdown of 2-pore channel NAADP receptors, whereas thrombin-induced VWF secretion failed to be affected. These findings demonstrate a novel and specific Ca(2+)-signaling mechanism activated through H1R in human endothelial cells, which reveals an obligatory role of NAADP in the control of VWF secretion.

Prophylactic and Therapeutic Potential of Asp f1 Epitopes in Naïve and Sensitized BALB/c Mice

BACKGROUND

The present study examines a hypothesis that short allergen-derived peptides may shift an Aspergillus fumigatus (Afu-) specific TH2 response towards a protective TH1. Five overlapping peptides (P1-P5) derived from Asp f1, a major allergen/antigen of Afu, were evaluated for prophylactic or therapeutic efficacy in BALB/c mice.

METHODS

To evaluate the prophylactic efficacy, peptides were intranasally administered to naïve mice and challenged with Afu-allergens/antigens. For evaluation of therapeutic efficacy, the mice were sensitized with Afu-allergens/antigens followed by intranasal administration of peptides. The groups were compared for the levels of Afu-specific antibodies in sera and splenic cytokines evaluated by ELISA. Eosinophil peroxidase activity was examined in the lung cell suspensions and lung inflammation was assessed by histopathogy.

RESULTS

Peptides P1-, P2- and P3 decreased Afu-specific IgE (84.5~98.9%) and IgG antibodies (45.7~71.6%) in comparison with Afu-sensitized mice prophylactically. P1- and P2-treated ABPA mice showed decline in Afu-specific IgE (76.4~88%) and IgG antibodies (15~54%). Increased IgG2a/IgG1 and IFN-gamma/IL-4 ratios were observed. P1-P3 prophylactically and P1 therapeutically decreased IL-5 levels and eosinophil peroxidase activity. P1 decreased inflammatory cells' infiltration in lung tissue comparable to non-challenged control.

CONCLUSION

Asp f1-derived peptide P1, prophylactically and therapeutically administered to Balb/c mice, is effective in regulating allergic response to allergens/antigens of Afu, and may be explored for immunotherapy of allergic aspergillosis in humans.

Endogenous signaling pathways and chemical communication between sperm and egg

Red abalone (Haliotis rufescens) sperm detect a waterborne chemical cue released by conspecific eggs, and change their swimming behavior to increase the likelihood of fertilization success. Previously, we isolated the natural sperm attractant by bioassay-guided fractionation and high-performance liquid chromatography, and chemically identified it as the free-amino acid l-tryptophan (l-Trp). In the present study, levels of this ecologically meaningful compound were quantified in various abalone tissues, and in freshly spawned eggs. Tryptophan was the least abundant of 19 dissolved free amino acids (DFAAs) in ovary, testis, foot muscle, gill, stomach and hemolymph. As a proportion of the DFAA pool, however, Trp concentrations were significantly elevated in eggs (three- to seven-times higher) relative to all other sampled tissues. Natural rates of Trp release from eggs also were measured and correlated with fertility. Fertilization success peaked during an initial 30 min period (post-spawn), but decreased to nil over the next 50 min. Closely paralleling these events, Trp accumulated in seawater around freshly spawned eggs for the first 45 min (post-spawn) before decaying rapidly from solution. Older eggs stopped releasing Trp approximately when they became infertile, revealing a critical link between gamete physiology and chemical signaling. This apparent negative feedback loop did not arise from tryptophan oxidation, uptake by bacteria in seawater, or a degrading enzyme released by eggs. As a metabolic precursor critical to development of the larval nervous system, Trp could be an honest indicator of egg fitness for prospective sperm suitors. Our results suggest that endogenous signaling pathways have been co-opted for external communication between gametes, as an adaptation to increase reproductive success by promoting sperm navigation towards fertile eggs.

Practice of venom immunotherapy in the United Kingdom: a national audit and review of literature

BACKGROUND

Venom immunotherapy (VIT) is the only effective treatment for prevention of serious allergic reactions to bee and wasp stings in sensitized individuals. However, controversies exist relating to diagnosis, indications for treatment and treatment schedules. We audited current practice of VIT in the United Kingdom to evaluate adherence to international guidelines.

METHODS

An online questionnaire was sent to all clinicians practising immunotherapy identified on the British Society of Allergy and Clinical Immunology website. Eighty-six questionnaires were sent and 53 responses (61.6%) were received. Of these, 48 (85%) carried out VIT at their centre.

RESULTS

Skin prick tests (SPT) and serum venom-specific IgE (SSIgE) were equally preferred as first-line investigation. Fifty percent of the respondents perform intradermal tests if both SPT and SSIgE are negative. While 8% of respondents commence VIT in patients with negative SSIgE and a history of severe reaction, 57% prefer to repeat the tests in 6-12 months if serum tryptase is elevated. If the insect responsible is uncertain and SSIgE is detected against bee and wasp venoms, 22% of the respondents will desensitize to both while 32% initiate treatment against the venom with the higher SSIgE. A protocol of weekly up-dosing for 12 weeks is preferred for induction and only 25% of respondents have ever used rush or ultra-rush protocols. Three years is thought to be optimum duration of VIT by most (56%). Eleven percent perform sting challenges at the end of treatment. Although 47% measure SSIgE at the end of treatment, only 3% use these results as a basis for discontinuing VIT.

CONCLUSION

Currently there is considerable variation in the diagnosis and management of hymenoptera venom allergy in the United Kingdom. This audit has demonstrated that the current international guidelines for the diagnosis and management of hymenoptera venom allergy are not being followed by UK allergy practitioners.

Allergy vaccines: dreams and reality

Allergy, extrinsic asthma and atopic eczema derive from deregulated immune responses against innocuous antigens. The incidence of atopic diseases is actually affecting approximately 30% of the population in industrialized countries. Although much progress has been achieved in the development of efficient symptomatic treatments for allergic diseases, the only curative treatment remains allergen-specific immunotherapy. In contrast to classical vaccines, which elicit strong host immune responses after one or a few injections, allergen-specific immunotherapy might require a long treatment time of 3-5 years with up to 80 injections to confer some protection. The reality is that 'allergy vaccines' achieve beneficial effects through immunomodulation, which takes a long time to establish. The dream would be to develop highly efficient allergy vaccines able to cure the disease with a few injections.