The histamine H₄ receptor: targeting inflammatory disorders

Pathophysiological role of histamine signaling and its implications in glioblastoma

Glioblastoma (GBM), an extremely aggressive and prevalent malignant brain tumor, remains a challenge to treat. Despite a multimodality treatment approach, GBM recurrence remains inevitable, particularly with the emergence of temozolomide (TMZ) resistance and limited treatment options. Surprisingly, previous studies show that a history of allergies, atopy, or asthma is inversely associated with GBM risk. Further, the electronic medical record at the University Hospital of Lausanne showed that the GBM patients taking antihistamine during treatment had better survival. Histamine is an essential neurotransmitter in the brain and plays a significant role in regulating sleep, hormonal balance, and cognitive functions. Elevated levels of histamine and increased histamine receptor expression have been found in different tumors and their microenvironments, including GBM. High histamine 1 receptor (HRH1) expression is inversely related to overall and progression-free survival in GBM patients, further emphasizing the role of histamine in disease progression. This review aims to provide insights into the challenges of GBM treatment, the role of histamine in GBM progression, and the rationale for considering antihistamines as targeted therapy. The review concludes by encouraging further investigation into antihistamine mechanisms and their impact on the tumor microenvironment.

Consensus Update for Systemic Treatment of Atopic Dermatitis

Background

In 2015, the Korean Atopic Dermatitis Association (KADA) working group published consensus guidelines for treating atopic dermatitis (AD).

Objective

We aimed to provide updated consensus recommendations for systemic treatment of AD in South Korea based on recent evidence and experience.

Methods

We compiled a database of references from relevant systematic reviews and guidelines on the systemic management of AD. Evidence for each statement was graded and classified based on thestrength of the recommendation. Forty-two council members from the KADA participated in three rounds of voting to establish a consensus on expert recommendations.

Results

We do not recommend long-term treatment with systemic steroids forpatients with moderate-to-severe AD due to the risk of adverse effects. We recommend treatment with cyclosporine or dupilumab and selective treatment with methotrexate or azathioprine for patients with moderate-to-severe AD. We suggest treatment with antihistamines as an option for alleviating clinical symptoms of AD. We recommend selective treatment with narrowband ultraviolet B for patients with chronic moderate-to-severe AD. We do not recommend treatment with oral antibiotics for patients with moderate-to-severe AD but who have no signs of infection. We did not reach a consensus on recommendations for treatment with allergen-specific immunotherapy, probiotics, evening primrose oil, orvitamin D for patients with moderate-to-severe AD. We also recommend educational interventions and counselling for patients with AD and caregivers to improve the treatment success rate.

Conclusion

We look forward to implementing a new and updated consensus of systemic therapy in controlling patients with moderate-to-severe AD.

Emerging Systemic Therapeutic Biologics and Small Molecules for Atopic Dermatitis: How to Decide Which Treatment Is Right for Your Patients

The evolving discoveries in atopic dermatitis (AD) broaden our understanding of the pathogenesis of the disease and, above all, enable better management for patients. Dupilumab was the first biologic for AD, and since its approval, many new treatments have emerged in both late- and early-stage clinical trials. These trials have led to a further understanding of the pathogenesis of AD and to the identification of additional potential therapeutic targets. This review will highlight the emerging therapies and provide approaches on how to choose the right treatment for your patients.

Biological Therapies for Atopic Dermatitis: A Systematic Review

BACKGROUND

Atopic dermatitis (AD) is a widely acquired, relapsing inflammatory skin disease. Biologics are now widely used in patients with moderate-to-severe AD.

OBJECTIVE

This work aims to summarize both label and off-label biologics on AD treatment in phase II and phase III stages, and compile evidence on the efficacy of the most-studied biologics.

METHODS

We conducted a comprehensive literature search through PubMed, EMBASE, and ClinicalTrials.gov to identify all documented biological therapies for AD. The criteria were further refined to focus on those treatments with the highest evidence level for AD with at least one randomized clinical trial supporting their use. Only studies or articles published in English were enrolled in this study.

FINDINGS

Primary searches identified 525 relevant articles and 27 trials. Duplicated articles and papers without a full text were excluded. Only completed trials were enrolled. We included 28 randomized controlled trials, 4 unpublished trials, 2 observational studies, and 1 meta-analysis. Eight kinds of biologics, including IL-4/IL-13 inhibitors, JAK inhibitors, anti-IL-13 antibodies, anti-IL-22 antibodies, anti-IL-33 antibodies, thymic stromal lymphopoietin inhibitor (TSLP), OX40 antibodies, and H4R-antagonists were included in this work. Dupliumab, as the most widely used and investigated biologic, was reported in 1 meta-analysis and 4 trials exploring its long-term use and application in both adults and pediatric patients. Besides dupilumab, four other IL-4/IL-13 inhibitors recruited were all randomized, clinical trials at phase 2-3 stage. Six different kinds of JAK inhibitors were summarized with strong evidence revealing their significant therapeutic effects on AD. There were 3 trials for nemolizumab, an anti-IL-13 antibody, all of which were in the phase 2 clinical trial stage. Results showed nemolizumab could be another alternative therapy for moderate-to-severe AD with long-term efficiency and safety.

CONCLUSION

The biological therapies with the most robust evidence on efficacy and long-term safety for AD treatment include dupilumab, barcitinib, abrocitinib, and delgocitinib. Most of the biologics mentioned in this review were still at the exploratory stage. This review will help practitioners advise patients seeking suitable biological therapies and offer experimental study directions for treatment.

A novel whole blood gene expression signature for asthma, dermatitis, and rhinitis multimorbidity in children and adolescents

BACKGROUND

Allergic diseases often occur in combination (multimorbidity). Human blood transcriptome studies have not addressed multimorbidity. Large-scale gene expression data were combined to retrieve biomarkers and signaling pathways to disentangle allergic multimorbidity phenotypes.

METHODS

Integrated transcriptomic analysis was conducted in 1233 participants with a discovery phase using gene expression data (Human Transcriptome Array 2.0) from whole blood of 786 children from three European birth cohorts (MeDALL), and a replication phase using RNA Sequencing data from an independent cohort (EVA-PR, n = 447). Allergic diseases (asthma, atopic dermatitis, rhinitis) were considered as single disease or multimorbidity (at least two diseases), and compared with no disease.

RESULTS

Fifty genes were differentially expressed in allergic diseases. Thirty-two were not previously described in allergy. Eight genes were consistently overexpressed in all types of multimorbidity for asthma, dermatitis, and rhinitis (CLC, EMR4P, IL5RA, FRRS1, HRH4, SLC29A1, SIGLEC8, IL1RL1). All genes were replicated the in EVA-PR cohort. RT-qPCR validated the overexpression of selected genes. In MeDALL, 27 genes were differentially expressed in rhinitis alone, but none was significant for asthma or dermatitis alone. The multimorbidity signature was enriched in eosinophil-associated immune response and signal transduction. Protein-protein interaction network analysis identified IL5/JAK/STAT and IL33/ST2/IRAK/TRAF as key signaling pathways in multimorbid diseases. Synergistic effect of multimorbidity on gene expression levels was found.

CONCLUSION

A signature of eight genes identifies multimorbidity for asthma, rhinitis, and dermatitis. Our results have clinical and mechanistic implications, and suggest that multimorbidity should be considered differently than allergic diseases occurring alone.

Pharmacological Effects of Novel Peptide Drugs on Allergic Rhinitis at the Small Ribonucleic Acids Level

Using an allergic rhinitis (AR) model, we evaluated the pharmacological effects of novel peptide drugs (P-ONE and P-TWO) at the small RNA (sRNA) level. Using high-throughput sequencing, we assessed the sRNA expression profile of the negative control, AR antagonist (positive control), P-ONE, and P-TWO groups. By functional clustering and Gene Ontology and KEGG pathway analyses, we found that sRNA target genes have a specific enrichment pattern and may contribute to the effects of the novel peptides. Small RNA sequencing confirmed the biological foundations of novel and traditional AR treatments and suggested unique pharmacological effects. Our findings will facilitate evaluation of the pathogenesis of AR and of the pharmacological mechanisms of novel peptide drugs.

Histamine and histidine decarboxylase: Immunomodulatory functions and regulatory mechanisms

Histamine is a bioactive monoamine that is synthesized by the enzymatic activity of histidine decarboxylase (HDC) in basophils, mast cells, gastric enterochromaffin‐like (ECL) cells and histaminergic neuronal cells. Upon a series of cellular stimuli, these cells release stored histamine, which elicits allergies, inflammation, and gastric acid secretion and regulates neuronal activity. Recent studies have shown that certain other types of myeloid lineage cells also produce histamine with HDC induction under various pathogenic stimuli. Histamine has been shown to play a series of pathophysiological roles by modulating immune and inflammatory responses in a number of disease conditions, whereas the mechanistic aspects underlying induced HDC expression remain elusive. In the present review, we summarize the current understanding of the regulatory mechanism of Hdc gene expression and the roles played by histamine in physiological contexts as well as pathogenic processes. We also introduce a newly developed histaminergic cell‐monitoring transgenic mouse line (Hdc‐BAC‐GFP) that serves as a valuable experimental tool to identify the source of histamine and dissect upstream regulatory signals.

TCTP from Loxosceles Intermedia (Brown Spider) Venom Contributes to the Allergic and Inflammatory Response of Cutaneous Loxoscelism

LiTCTP is a toxin from the Translationally Controlled Tumor Protein (TCTP) family identified in Loxosceles brown spider venoms. These proteins are known as histamine-releasing factors (HRF). TCTPs participate in allergic and anaphylactic reactions, which suggest their potential role as therapeutic targets. The histaminergic effect of TCTP is related to its pro-inflammatory functions. An initial characterization of LiTCTP in animal models showed that this toxin can increase the microvascular permeability of skin vessels and induce paw edema in a dose-dependent manner. We evaluated the role of LiTCTP in vitro and in vivo in the inflammatory and allergic aspects that undergo the biological responses observed in Loxoscelism, the clinical condition after an accident with Loxosceles spiders. Our results showed LiTCTP recombinant toxin (LiRecTCTP) as an essential synergistic factor for the dermonecrotic toxin actions (LiRecDT1, known as the main toxin in the pathophysiology of Loxoscelism), revealing its contribution to the exacerbated inflammatory response clinically observed in envenomated patients.

Histamine H4 receptor regulates IL-6 and INF-γ secretion in native monocytes from healthy subjects and patients with allergic rhinitis

Histamine H1 receptor (H1R) and histamine H4 receptor (H4R) are essential in allergic inflammation. The roles of H4R have been characterized in T cell subsets, whereas the functional properties of H4R in monocytes remain unclear. In the current study, the responses of H4R in peripheral monocytes from patients with allergic rhinitis (AR) were investigated. The results confirmed that H4R has the functional effects of mediating cytokine production (i.e., down-regulating IFN-γ and up-regulating IL-6) in cells from a monocyte cell line following challenge with histamine. We demonstrated that when monocytes from AR patients were stimulated with allergen extracts of house dust mite (HDM), IFN-γ secretion was dependent on H4R activity, but IL-6 secretion was based on H1R activity. Furthermore, a combination of H1R and H4R antagonists was more effective at blocking the inflammatory response in monocytes than treatment with either type of antagonist alone.

Histamine H4 receptor mediates chemotaxis of human lung mast cells

The diverse effects of histamine are mediated by discrete histamine receptors. The principal repository of histamine in the body is the mast cell. However, the effects of histamine on mast cells, especially those of human origin, have not been fully elucidated. In this study, the expression of histamine receptors in human lung mast cells was evaluated. Moreover, the effects of histamine receptor engagement on both mediator release and chemotaxis were investigated. Mast cells were isolated and purified from human lung tissue. Histamine receptor expression was determined by RT-PCR and q-PCR. Both methods for the detection of histamine receptors were in accordance and human lung mast cells expressed mRNA for histamine H₄ and histamine H₁ receptors, variably expressed histamine H₂ receptor but did not express histamine H₃ receptor. The effects of selective histamine receptor agonists on the release of both pre-formed (histamine) and newly-synthesised (cysteinyl-leukotriene, prostaglandin D₂) mediators were investigated. None of the agonists tested had any direct effects on mediator release. None of the agonists modulated release stimulated by anti-IgE. Further studies showed that histamine induced migration of mast cells. Chemotaxis appeared to be mediated by the histamine H₄ receptor since JNJ28610244 (H₄ agonist) was chemotactic for mast cells whereas 2-(2-pyridyl) ethylamine (H₁ agonist) was not. Furthermore, the selective histamine H₄ receptor antagonist, JNJ7777120, effectively reversed the chemotaxis of mast cells induced by JNJ28610244. Overall, these experiments identify the histamine H₄ receptor as chemotactic for human lung mast cells. This mechanism might influence mast cell accumulation in the lung.

Effects of a histamine H4 receptor antagonist on cisplatin-induced anorexia in mice

Cancer chemotherapy often induces gastrointestinal symptoms such as anorexia, nausea, and vomiting. Antiemetic agents are effective in inhibiting nausea and vomiting, but patients still experience anorexia. We previously reported that chemotherapeutic agent-induced anorexia is associated with an increase of inflammatory cytokines. Other studies also reported that antagonism of the histamine H₄ receptor is anti-inflammatory. In this study, we investigated the involvement of the H₄ receptor in the development of chemotherapy-induced anorexia in mice. Cisplatin-induced anorexia occurred within 24 h of its administration and continued for 3 days. The early phase (day 1), but not the delayed phase (days 2 and 3), of anorexia was inhibited by the daily injection of a 5-HT₃ receptor antagonist (granisetron). However, a corticosteroid (dexamethasone) or selective H₄ receptor antagonist (JNJ7777120) abolished the delayed phases of anorexia. Cisplatin significantly increased TNF-α mRNA expression in the hypothalamus and spleen, and the period of expression increase paralleled the onset period of anorexia. In addition, pretreatment with JNJ7777120 completely inhibited the increased expression. These results suggest that TNF-α mRNA expression via H₄ receptors may contribute to the development of cisplatin-induced anorexia, and that H₄ receptor antagonists are potentially useful treatments.

Preliminary study of histamine H4 receptor expressed on human CD4+ T cells and its immunomodulatory potency in the IL-17 pathway of psoriasis

BACKGROUND

Previous studies have shown the expression of histamine H₄ receptor (H4R) on CD4⁺ T cells, especially human CD4⁺ T_h2-polarized T cells.

OBJECTIVE

This study aimed to investigate the role of H4R on these effector T cells in psoriasis.

METHODS

We enrolled three patients each with active psoriasis, inactive psoriasis, scalp seborrheic dermatitis, and three normal controls, and compared the basal expression of H4R mRNA in their peripheral blood CD4⁺ T cells. Then, we identified H4R expression in dermal CD4⁺ T cells. Furthermore, we investigated H4R expression after stimulating separated peripheral blood CD4⁺ T cells with several inflammatory cytokines.

RESULTS

The results showed higher H4R expression in the active psoriasis group compared to the inactive psoriasis group. It was interesting that interleukin (IL)-23, which is a representative cytokine contributing to T_h17 cell differentiation, stimulated H4R expression significantly. After adding a selective H4R antagonist (JNJ-7777120) while the CD4⁺ T cells were polarized into T_h17 cells, we observed a tendency toward suppressed IL-17 secretion.

CONCLUSIONS

Histamine stimulation influences the IL-17 pathway in psoriasis via the fourth histamine receptor subtype, H4R, on CD4⁺ T cells. The immunomodulatory roles of H4R suggest its potency as a new therapeutic target for obstinate psoriasis.

Aryl-1,3,5-triazine ligands of histamine H4 receptor attenuate inflammatory and nociceptive response to carrageen, zymosan and lipopolysaccharide

Objective and design

Histamine H₄ receptor (H₄R) offers a great potential for new therapeutic strategies for the treatment of inflammation-based diseases. The aim of this study is to present the pharmacological profile of two recently synthesized ligands of H₄R with particular reference to their anti-inflammatory and analgesic activity.

Materials and subjects

We used mice and rats in the in vivo tests. We also used murine RAW 264.7 cells and isolated guinea-pig ileum in in vitro test.

Treatments

In the in vivo tests, animals were pre-treated with the increasing doses of investigated compounds (12.5, 25 and 50 mg/kg) and reference compounds: JNJ7777120 (25 mg/kg), indomethacin (10 mg/kg). Macrophages were pre-treated with two concentrations of tested compounds 100 and 10 µM.

Methods

We examined anti-inflammatory and analgesic effects of the new H₄R antagonists in the in vivo models of inflammation induced by carrageenan or zymosan. We assessed the level of cAMP and release of cytokines, ROS and NO in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Moreover, we assessed the affinity of the investigated compounds for histamine H₁ receptor in functional studies.

Results

Both investigated compounds reduced paw edema, mechanical and thermal hyperalgesia in the carrageenan-induced acute inflammation. Moreover, administration of the investigated compounds resulted in decreased granulocyte influx and attenuated nociceptive reaction in the zymosan-induced peritonitis model. In the same model of inflammation, the investigated compounds reduced vascular permeability; however, this effect was observed only after the highest applied dose. Furthermore, the test compounds had no impact on cell viability in the experiments on RAW 264.7 macrophages. In these cells, stimulated with LPS, the test compounds decreased reactive oxygen species (ROS) production. They increased the cellular concentration of cAMP and attenuated the production of inflammatory cytokines such as TNFα and IL-1β. All results were comparable to those obtained for the reference compound JNJ7777120 with the exception of the impact on NO production. Nevertheless, this effect was similar to that obtained for the other reference compound rolipram, which is a phosphodiesterase 4 (PDE 4) inhibitor. Further experiments revealed that both of the investigated compounds possessed relatively low affinity for histamine H₁ receptor and do not inhibit the activity of the PDE 4B1 enzyme. In addition, all the effects of the investigated compounds in in vivo experiments were observed at doses that did not cause neurologic deficits in rotarod test and did not reduce spontaneous locomotor activity.

Conclusions

Our results demonstrate the anti-inflammatory and analgesic activity of the new aryl-1,3,5-triazine derivatives, which are primarily H₄R–dependent.

Identification of histamine receptors in the canine gastrointestinal tract

The important role of histamine in chronic gastrointestinal diseases has been increasingly recognized over the last two decades in human medicine. Histamine is released following mast cell activation and exerts its action through binding to four different histamine receptors (H1, H2, H3, and H4). Histamine receptors are dispersed throughout the body, and each different receptor mediates a unique response. Documentation of the presence and type of histamine receptors in the differing sections of the canine gastrointestinal tract will provide additional research opportunities to further explore the role of histamine and its receptors in chronic canine enteropathies, as well as potential therapeutic options. Full thickness gastric, duodenal, jejunal, ileal, and colonic biopsies were obtained from 6 clinically normal adult dogs immediately after humane euthanasia. Commercially available histamine receptor antibodies predicted to react with canine tissues were applied to paraffin-embedded tissue sections using standard immunohistochemistry techniques to identify different histamine receptors. Staining intensity was graded from negative to strong, and the specificity of each antibody was evaluated with western blot. The presence and distribution of histamine receptors varied by anatomic site and histologic level within sections of the canine gastrointestinal tract. All 4 histamine receptors were readily identified, although the distribution of H4 receptors was decreased in comparison to the other histamine receptors. The distribution of the various histamine receptors was similar to that seen in the normal human gastrointestinal tract. H1 receptors were located in the stomach, lymphoid tissue of the ileum and colon, and the smooth muscle and ganglia of all sections. H2 receptors were located in all sections of the gastrointestinal tract, with greatest staining intensity in the gastric mucosa. H3 receptors were located in the stomach and colonic mucosa, smooth muscle and ganglia of all sections, and ileal and colonic lymphoid tissue. H4 receptors were located in the ganglia and smooth muscle of the gastrointestinal tract, as well as the gastric and colonic mucosal and ileal lymphoid tissue. Western blot demonstrated both specific and non-specific staining with the H1 and H3 receptor antibody, but good specificity with the H4 receptor antibody. The H2 receptor antibody was not compatible with western blot techniques, despite excellent immunohistochemical specificity and consistency. Further studies to compare the density and distribution of the various histamine receptors in dogs with gastrointestinal disease are warranted.

Cherry-picked ligands at histamine receptor subtypes

Histamine, a biogenic amine, is considered as a principle mediator of multiple physiological effects through binding to its H1, H2, H3, and H4 receptors (H1-H4Rs). Currently, the HRs have gained attention as important targets for the treatment of several diseases and disorders ranging from allergy to Alzheimer's disease and immune deficiency. Accordingly, medicinal chemistry studies exploring histamine-like molecules and their physicochemical properties by binding and interacting with the four HRs has led to the development of a diversity of agonists and antagonists that display selectivity for each HR subtype. An overview on H1-R4Rs and developed ligands representing some key steps in development is provided here combined with a short description of structure-activity relationships for each class. Main chemical diversities, pharmacophores, and pharmacological profiles of most innovative H1-H4R agonists and antagonists are highlighted. Therefore, this overview should support the rational choice for the optimal ligand selection based on affinity, selectivity and efficacy data in biochemical and pharmacological studies. This article is part of the Special Issue entitled 'Histamine Receptors'.

Mast cells and histamine play an important role in edema and leukocyte recruitment induced by Potamotrygon motoro stingray venom in mice

This work aimed to investigate mechanisms underlying the inflammatory response caused by Potamotrygon motoro stingray venom (PmV) in mouse paws. Pre-treatment of animals with a mast cell degranulation inhibitor (cromolyn) diminished edema (62% of inhibition) and leukocyte influx into the site of PmV injection. Promethazine (histamine type 1 receptor antagonist) or thioperamide (histamine type 3 and 4 receptor antagonist) also decreased edema (up to 30%) and leukocyte numbers, mainly neutrophils (40-50 %). Cimetidine (histamine type 2 receptor antagonist) had no effect on PmV-induced inflammation. In the RBL-2H3 lineage of mast cells, PmV caused proper cell activation, in a dose-dependent manner, with release of PGD2 and PGE2. In addition, the role of COXs products on PmV inflammatory response was evaluated. Indomethacin (COX-1/COX-2 inhibitor) or etoricoxib (COX-2 inhibitor) partially diminished edema (around 20%) in PmV-injected mice. Indomethacin, but not etoricoxib, modulated neutrophil influx into the site of venom injection. In conclusion, mast cell degranulation and histamine, besides COXs products, play an important role in PmV-induced reaction. Since PmV mechanism of action remains unknown, hindering accurate treatment, clinical studies can be performed to validate the prescription of antihistaminic drugs, besides NSAIDs, to patients injured by freshwater stingrays.

Antiallergic effect of piperine on ovalbumin-induced allergic rhinitis in mice

CONTEXT

Allergic rhinitis (AR) is a global health problem that affects a large number of population. Piperine (PIP) has been reported to exhibit anti-inflammatory, anti-histaminic, and immunomodulatory activities; however, its antiallergic profile has not been studied.

OBJECTIVE

The objective of the study was to investigate the antiallergic potential of PIP in ova-albumin (OVA)-induced AR, mast cell degranulation (MSD), and OVA-induced paw edema.

MATERIALS AND METHODS

Mice were sensitized with OVA alternately on 1, 3, 5, 7, 9, 11, and 13th day. They were treated with either vehicle, PIP (10, 20, and 40 mg/kg, p.o.), or montelukast (10 mg/kg, p.o.) from the 14th to 20th day. On the 21st day, intranasal (OVA: 5% µl) challenge was done. Animals were evaluated for physiological parameters, biochemical parameters, spleen weight, expression of interleukins (IL-6 and IL-1β), and immunoglobin-E (IgE). Histopathology of nasal mucosa, lungs, and spleen was carried out. MSD and paw edema studies were made to understand the mechanism of action.

RESULTS

PIP (10, 20, and 40 mg/kg, p.o.) showed a significant dose-dependent protection with respect to nasal rubbing, redness of nose, and sneezing (p < 0.001) following nasal challenge. PIP dose dependently reduced histamine, NO concentration (p < 0.001), as well as reduced expression of IL-6, IL-1β, and IgE (p < 0.001) as compared with the control group. Histopathology showed inhibition of infiltration of eosinophils and hyperplasia. It dose dependently reduced MSD and paw edema (p < 0.001).

DISCUSSION AND CONCLUSION

PIP acts by mast cell-stabilizing activity, exhibits immunomodulatory and anti-inflammatory activity, thereby providing an effective treatment for AR.

Phase 2a, randomized, double-blind, placebo-controlled, multicenter, parallel-group study of a H4 R-antagonist (JNJ-39758979) in Japanese adults with moderate atopic dermatitis

This trial was conducted to evaluate the safety and efficacy of the H4 R-antagonist JNJ-39758979 in adult Japanese patients with moderate atopic dermatitis (AD). Eligible patients were randomly assigned to JNJ-39758979 300 mg, 100 mg or placebo once daily for 6 weeks in this phase 2a, double-blind, multicenter, placebo-controlled study. Primary efficacy was assessed via week-6 Eczema Area and Severity Index (EASI) scores. Secondary efficacy assessments included Investigator's Global Assessment (IGA) and patient-reported outcome (PRO) pruritus assessments (Pruritus Categorical Response Scale [PCRS], Pruritus Numeric Rating Scales [PNRS], Pruritus Interference Numeric Rating Scale [PINRS] and Subject's Global Impressions of Change in Pruritus [SGICP]). Eighty-eight of 105 planned patients were randomized before the study was stopped and unblinded for safety reasons. The study did not meet the primary end-point. However, numerical improvements (i.e. decreases) in median EASI were observed with JNJ-39758979 100 mg (-3.7) and 300 mg (-3.0) versus placebo (-1.3) at week 6. Nominally significant improvements across PRO PCRS, PNRS and SGICP assessments were consistently observed, particularly with JNJ-39758979 300 mg. Safety, including adverse events (AE), was comparable between JNJ-39758979 and placebo with the exception of two patients (both receiving JNJ-39758979 300 mg) with serious AE of neutropenia, leading to premature study discontinuation. No deaths were reported. Except for neutropenia, no clinically relevant changes in laboratory values were observed. Although not conclusive, findings suggest H4 R-antagonism may be beneficial for AD, particularly in controlling pruritus. JNJ-39758979 appears to be associated with drug-induced agranulocytosis, likely an off-target effect.

Increased expression of the histamine H4 receptor following differentiation and mediation of the H4 receptor on interleukin-8 mRNA expression in HaCaT keratinocytes

Recent in vivo studies have demonstrated involvement of the histamine H4 receptor in pruritus and skin inflammation. We previously reported that an H4 receptor antagonist attenuated scratching behaviour and improved skin lesions in an experimental model of atopic dermatitis. We also reported the expression of the H4 receptor in human epidermal tissues. In this study, we investigated the expression of H4 receptor mRNA and the function of the receptor in a culture system that mimics in vivo inflammation on the HaCaT human keratinocyte cell line. Increased expression of the H4 receptor was observed in HaCaT cells following differentiation. Treatment of HaCaT cells with histamine and TNFα enhanced the mRNA expression of interleukin (IL)-8. These increases in expression were significantly inhibited by the H4 receptor antagonist JNJ7777120. Our results indicate that IL-8 mRNA expression might be enhanced by histamine and TNFα via H4 receptor stimulation in keratinocytes.

Procognitive properties of drugs with single and multitargeting H3 receptor antagonist activities

The histamine H3 receptor (H3 R) is an important modulator of numerous central control mechanisms. Novel lead optimizations for H3 R antagonists/inverse agonists involved studies of structure-activity relationships, cross-affinities, and pharmacokinetic properties of promising ligands. Blockade of inhibitory histamine H3 autoreceptors reinforces histaminergic transmission, while antagonism of H3 heteroreceptors accelerates the corticolimbic liberation of acetylcholine, norepinephrine, glutamate, dopamine, serotonin and gamma-aminobutyric acid (GABA). The H3 R positioned at numerous neurotransmission crossroads indicates therapeutic applications of small-molecule H3 R modulators in a number of psychiatric and neurodegenerative diseases with various clinical candidates available. Dual target drugs displaying H3 R antagonism/inverse agonism with inhibition of acetylcholine esterase (AChE), histamine N-methyltransferase (HMT), or serotonin transporter (SERT) are novel class of procognitive agents. Main chemical diversities, pharmacophores, and pharmacological profiles of procognitive agents acting as H3 R antagonists/inverse agonists and dual H3 R antagonists/inverse agonists with inhibiting activity on AChE, HMT, or SERT are highlighted here.

Benzylpiperidine variations on histamine H3 receptor ligands for improved drug-likeness

Several hH3R antagonists/inverse agonists entered clinical phases for a broad spectrum of mainly centrally occurring diseases. Nevertheless, many promising candidates failed due to their pharmacokinetic profile, mostly because of their strong lipophilicity and their dibasic character. Analysis of previously, as potential PET ligands synthesized compounds (ST-889, ST-928) revealed promising results concerning physicochemical properties and drug-likeness. Herein, the synthesis, the evaluation of the binding properties at the hH3R and the estimation of different physicochemical and drug-likeness properties of further novel benzylpiperidine variations on H3R antagonists is described. Due to the introduction of various small hydrophilic moieties in the structure, drug-likeness parameters have been improved. For instance, compound 12 (ST-1032) showed in addition to high affinity at the H3R (pKi (hH3R)=9.3) clogS, clogP, LE, LipE, and LELP values of -2.48, 2.18, 0.44, 7.14, and 4.95, respectively. Also, the keto derivative 5 (ST-1703, pKi (hH3R)=8.6) revealed LipE and LELP values of 5.25 and 6.84, respectively.

The histamine H4 receptor mediates inflammation and Th17 responses in preclinical models of arthritis

Objective

The histamine H₄ receptor (H₄R) has been shown to drive inflammatory responses in models of asthma, colitis and dermatitis, and in these models it appears to affect both innate and adaptive immune responses. In this study, we used both H₄R-deficient mice and a specific H₄R antagonist, JNJ 28307474, to investigate the involvement of the H₄R in mouse arthritis models.

Methods

H₄R-deficient mice and wild-type mice administered the H₄R antagonist were studied in models of collagen antibody-induced arthritis (CAIA) and collagen-induced arthritis (CIA). The impact on Th17 cells was assessed by restimulation of inguinal lymphocytes in the disease or immunisation models and with in vitro stimulation of whole blood.

Results

Both H₄R-deficient mice and mice treated with the H₄R antagonist exhibited reduced arthritis disease severity in both CAIA and CIA models. This was evident from the reduction in disease score and in joint histology. In the CIA model, treatment with the H₄R antagonist reduced the number of interleukin (IL)-17 positive cells in the lymph node and the total production of IL-17. Th17 cell development in vivo was reduced in H₄R-deficient mice or in mice treated with an H₄R antagonist. Finally, treatment of both mouse and human blood with an H₄R antagonist reduced the production of IL-17 when cells were stimulated in vitro.

Conclusions

These results implicate the H₄R in disease progression in arthritis and in the production of IL-17 from Th17 cells. This work supports future clinical exploration of H₄R antagonists for the treatment of rheumatoid arthritis.

An mRNA atlas of G protein-coupled receptor expression during primary human monocyte/macrophage differentiation and lipopolysaccharide-mediated activation identifies targetable candidate regulators of inflammation

G protein-coupled receptors (GPCRs) are among the most important targets in drug discovery. In this study, we used TaqMan Low Density Arrays to profile the full GPCR repertoire of primary human macrophages differentiated from monocytes using either colony stimulating factor-1 (CSF-1/M-CSF) (CSF-1 Mϕ) or granulocyte macrophage colony stimulating factor (GM-CSF) (GM-CSF Mϕ). The overall trend was a downregulation of GPCRs during monocyte to macrophage differentiation, but a core set of 10 genes (e.g. LGR4, MRGPRF and GPR143) encoding seven transmembrane proteins were upregulated, irrespective of the differentiating agent used. Several of these upregulated GPCRs have not previously been studied in the context of macrophage biology and/or inflammation. As expected, CSF-1 Mϕ and GM-CSF Mϕ exhibited differential inflammatory cytokine profiles in response to the Toll-like Receptor (TLR)4 agonist lipopolysaccharide (LPS). Moreover, 15 GPCRs were differentially expressed between these cell populations in the basal state. For example, EDG1 was expressed at elevated levels in CSF-1 Mϕ versus GM-CSF Mϕ, whereas the reverse was true for EDG6. 101 GPCRs showed differential regulation over an LPS time course, with 65 of these profiles being impacted by the basal differentiation state (e.g. GPRC5A, GPRC5B). Only 14 LPS-regulated GPCRs showed asynchronous behavior (divergent LPS regulation) with respect to differentiation status. Thus, the differentiation state primarily affects the magnitude of LPS-regulated expression, rather than causing major reprogramming of GPCR gene expression profiles. Several GPCRs showing differential profiles between CSF-1 Mϕ and GM-CSF Mϕ (e.g. P2RY8, GPR92, EMR3) have not been widely investigated in macrophage biology and inflammation. Strikingly, several closely related GPCRs displayed completely opposing patterns of regulation during differentiation and/or activation (e.g. EDG1 versus EDG6, LGR4 versus LGR7, GPRC5A versus GPRC5B). We propose that selective regulation of GPCR5A and GPCR5B in CSF-1 Mϕ contributes to skewing toward the M2 macrophage phenotype. Our analysis of the GPCR repertoire expressed during primary human monocyte to macrophage differentiation and TLR4-mediated activation provides a valuable new platform for conducting future functional analyses of individual GPCRs in human macrophage inflammatory pathways.

Expression of the histamine H4 receptor in dermal and articular tissues

Histamine H(4) receptor was identified in 2000 and is the most recently identified of the four histamine receptors. It is expressed primarily in immune cells and is involved in physiologic functions related to inflammation and allergy. Recently, the H(4) receptor was highlighted as a promising therapeutic target in atopic dermatitis, asthma, and chronic arthritis. In fact, some H(4) receptor antagonists have reached clinical trials for the treatment of asthma, atopic dermatitis, and allergic rhinitis. Based on an initial assessment of distribution, the H(4) receptor has been referred to as the histamine receptor of the hematopoietic system. However, the H(4) receptor has also been implicated in the regulation of other non-hematopoietic systems. Here, we review the expression and function of the H(4) receptor with a focus on dermal and articular tissues. In skin, the H(4) receptor is expressed in both the epidermis and dermis, with stronger receptor expression in the epidermis. In articular tissue, H(4) receptor expression has been detected in synovial cells. Chondrocytes, a major cell sources for cartilage tissue engineering, also express the H(4) receptor. Further understanding of the functions of H(4) receptors in non-hematopoietic cells might lead to novel treatments for diseases with unmet needs.

A network-based feature selection approach to identify metabolic signatures in disease

The identification and interpretation of metabolic biomarkers is a challenging task. In this context, network-based approaches have become increasingly a key technology in systems biology allowing to capture complex interactions in biological systems. In this work, we introduce a novel network-based method to identify highly predictive biomarker candidates for disease. First, we infer two different types of networks: (i) correlation networks, and (ii) a new type of network called ratio networks. Based on these networks, we introduce scores to prioritize features using topological descriptors of the vertices. To evaluate our method we use an example dataset where quantitative targeted MS/MS analysis was applied to a total of 52 blood samples from 22 persons with obesity (BMI >30) and 30 healthy controls. Using our network-based feature selection approach we identified highly discriminating metabolites for obesity (F-score >0.85, accuracy >85%), some of which could be verified by the literature.

Antiallergic activity of novel isoflavone methyl-glycosides from Cordyceps militaris grown on germinated soybeans in antigen-stimulated mast cells

Isoflavones are known to possess immunomodulating and antiallergic activities. Previously we identified novel isoflavone methyl-glycosides (daidzein 7-O-β-d-glucoside 4″-O-methylate (CDGM), glycitein 7-O-β-D-glucoside 4″-O-methylate (CGLM), genistein 7-O-β-D-glucoside 4″-O-methylate (CGNMI) and genistein 4'-O-β-D-glucoside 4″-O-methylate (CGNMII)) from Cordyceps militaris grown on germinated soybeans (GSC). The biological activity of novel isoflavone methyl-glycosides, however, remains unknown. In this study, CGNMII showed the strongest inhibition of degranulation. Additionally, the release of interleukin (IL)-4 and tumor necrosis factor (TNF)-α was decreased by CGNMII in antigen-stimulated RBL-2H3 cells. To elucidate the antiallergic mechanism of CGNMII, we examined whether it affected levels of signaling molecules responsible for degranulation. The levels of activated Lyn, Syk, PLCγ1 and LAT proteins were reduced in CGNMII treated RBL-2H3 cells. CGNMII also inhibited the activation of AKT and ERK1/2 proteins. These results suggest that CGNMII might be used as a therapeutic agent for allergic diseases.

Histamine H4 receptor ligands and their potential therapeutic applications: an update

INTRODUCTION

Several studies underlined the critical role of histamine H4 receptor (H4R) in inflammation, thus H4 modulators have been suggested as promising drug candidates in inflammatory diseases. First H4 ligands typically have indole or amino-pyrimidine scaffolds. During the last few years, however, serious efforts have been made to identify novel H4 chemotypes with improved pharmacodynamic and pharmacokinetic properties.

AREAS COVERED

Areas covered in this review include an overview on H4 ligands published in scientific papers, as well as in patent applications between 2009 and 2011. Recently discovered scaffolds possessing significant H4 activity were analyzed and their therapeutic potential was reviewed.

EXPERT OPINION

Recent results from the scientific literature and novel patent applications reinforce the major role of H4R in inflammatory diseases such as pruritus, asthma, inflammatory pain and allergic rhinitis. Novel studies suggest further indications of H4 modulators in cancer, neuropathic pain, vestibular disorders and type 2 diabetes. The number of active H4 chemotypes was increased significantly. The first H4 antagonist entered to clinics and the results from a proof-of-concept Phase II clinical study is expected to be disclosed soon.