Stimulation of histamine H1 receptor up-regulates histamine H1 receptor itself through activation of receptor gene transcription

Structure-activity relationship studies of pyrogallol as a calcineurin/NFAT signaling suppressor

Previously, we have shown that pyrogallol alleviated nasal symptoms and suppressed IL-9 gene up-regulation in allergy model rats by inhibiting calcineurin/NFAT signaling. As pyrogallol has antioxidative activity, it may be responsible for inhibiting calcineurin/NFAT signaling-mediated IL-9 gene expression. However, the relationship between antioxidative activity and suppression of IL-9 gene expression has not been elucidated yet. Here, we conducted the structure-activity relationship studies of pyrogallol and its structurally related compounds to understand the mechanism of IL-9 gene suppression by pyrogallol. 2, 2-Diphenyl-1-picrylhydrazyl radical scavenging assay showed that the antioxidative activity of catechol, resorcinol, phloroglucinol, and gallic acid is 60.1%, 10.4%, 18.8%, and 113.5% of pyrogallol, respectively. Catechol, resorcinol, and phloroglucinol did not suppress NFAT dephosphorylation. Gallic acid suppressed dephosphorylation of NFAT. Gallic acid also suppressed ionomycin-induced up-regulation of IL-9 gene expression with the IC50 value of 82.6 μM. However, catechol, resorcinol and phloroglucinol showed no suppressive activity. In addition, using gallic acid-immobilized beads, we isolated and identified Poly(U)-binding-splicing factor 60 (PUF60) as a pyrogallol binding protein. These results suggest that the antioxidative activity of pyrogallol is not likely to be the mechanism of IL-9 gene suppression. Data also suggest that PUF60 is one of its target molecules responsible for the suppression of calcineurin/NFAT signaling by pyrogallol.

Histamine and receptors in neuroinflammation: Their roles on neurodegenerative diseases

Histamine, an auto-reactive substance and mediator of inflammation, is synthesized from histidine through the action of histidine decarboxylase (HDC). It primarily acts on histamine receptors in the central nervous system (CNS). Increasing evidence suggests that histamine and its receptors play a crucial role in neuroinflammation, thereby modulating the pathology of neurodegenerative diseases. Recent studies have demonstrated that histamine regulates the phenotypic switching of microglia and astrocytes, inhibits the production of pro-inflammatory cytokines, and alleviates inflammatory responses. In the CNS, our research group has also found that histamine and its receptors are involved in regulating inflammatory responses and play a central role in ameliorating chronic neuroinflammation in neurodegenerative diseases. In this review, we will discuss the role of histamine and its receptors in neuroinflammation associated with neurodegenerative diseases, potentially providing a novel therapeutic target for the treatment of chronic neuroinflammation-related neurodegenerative diseases in clinical settings.

Function and Role of Histamine H1 Receptor in the Mammalian Heart

Histamine can change the force of cardiac contraction and alter the beating rate in mammals, including humans. However, striking species and regional differences have been observed. Depending on the species and the cardiac region (atrium versus ventricle) studied, the contractile, chronotropic, dromotropic, and bathmotropic effects of histamine vary. Histamine is present and is produced in the mammalian heart. Thus, histamine may exert autocrine or paracrine effects in the mammalian heart. Histamine uses at least four heptahelical receptors: H₁, H₂, H₃ and H₄. Depending on the species and region studied, cardiomyocytes express only histamine H₁ or only histamine H₂ receptors or both. These receptors are not necessarily functional concerning contractility. We have considerable knowledge of the cardiac expression and function of histamine H₂ receptors. In contrast, we have a poor understanding of the cardiac role of the histamine H₁ receptor. Therefore, we address the structure, signal transduction, and expressional regulation of the histamine H₁ receptor with an eye on its cardiac role. We point out signal transduction and the role of the histamine H₁ receptor in various animal species. This review aims to identify gaps in our knowledge of cardiac histamine H₁ receptors. We highlight where the published research shows disagreements and requires a new approach. Moreover, we show that diseases alter the expression and functional effects of histamine H₁ receptors in the heart. We found that antidepressive drugs and neuroleptic drugs might act as antagonists of cardiac histamine H₁ receptors, and believe that histamine H₁ receptors in the heart might be attractive targets for drug therapy. The authors believe that a better understanding of the role of histamine H₁ receptors in the human heart might be clinically relevant for improving drug therapy.

Cancer cell autophagy, reprogrammed macrophages, and remodeled vasculature in glioblastoma triggers tumor immunity

Glioblastoma (GBM) is poorly responsive to therapy and invariably lethal. One conceivable strategy to circumvent this intractability is to co-target distinctive mechanistic components of the disease, aiming to concomitantly disrupt multiple capabilities required for tumor progression and therapeutic resistance. We assessed this concept by combining vascular endothelial growth factor (VEGF) pathway inhibitors that remodel the tumor vasculature with the tricyclic antidepressant imipramine, which enhances autophagy in GBM cancer cells and unexpectedly reprograms immunosuppressive tumor-associated macrophages via inhibition of histamine receptor signaling to become immunostimulatory. While neither drug is efficacious as monotherapy, the combination of imipramine with VEGF pathway inhibitors orchestrates the infiltration and activation of CD8 and CD4 T cells, producing significant therapeutic benefit in several GBM mouse models. Inclusion up front of immune-checkpoint blockade with anti-programmed death-ligand 1 (PD-L1) in eventually relapsing tumors markedly extends survival benefit. The results illustrate the potential of mechanism-guided therapeutic co-targeting of disparate biological vulnerabilities in the tumor microenvironment.

Targeting spinal microglia with fexofenadine-loaded nanoparticles prolongs pain relief in a rat model of neuropathic pain

Targeting microglial activation is emerging as a clinically promising drug target for neuropathic pain treatment. Fexofenadine, a histamine receptor 1 antagonist, is a clinical drug for the management of allergic reactions as well as pain and inflammation. However, the effect of fexofenadine on microglial activation and pain behaviors remains elucidated. Here, we investigated nanomedicinal approach that targets more preferentially microglia and long-term analgesics. Fexofenadine significantly abolished histamine-induced microglial activation. The fexofenadine-encapsulated poly(lactic-co-glycolic acid) nanoparticles (Fexo NPs) injection reduced the pain sensitivity of spinal nerve ligation rats in a dose-dependent manner. This alleviation was sustained for 4 days, whereas the effective period by direct fexofenadine injection was 3 h. Moreover, Fexo NPs inhibited microglial activation, inflammatory signaling, cytokine release, and a macrophage phenotype shift towards the alternative activated state in the spinal cord. These results show that Fexo NPs exhibit drug repositioning promise as a long-term treatment modality for neuropathic pain.

Long-Term Functional and Cytoarchitectonic Effects of the Systemic Administration of the Histamine H1 Receptor Antagonist/Inverse Agonist Chlorpheniramine During Gestation in the Rat Offspring Primary Motor Cortex

The transient histaminergic system is among the first neurotransmitter systems to appear during brain development in the rat mesencephalon/rhombencephalon. Histamine increases FOXP2-positive deep-layer neuron differentiation of cortical neural stem cells through H₁ receptor activation in vitro. The in utero or systemic administration of chlorpheniramine (H₁ receptor antagonist/inverse agonist) during deep-layer cortical neurogenesis decreases FOXP2 neurons in the developing cortex, and H₁R- or histidine decarboxylase-knockout mice show impairment in learning and memory, wakefulness and nociception, functions modulated by the cerebral cortex. Due to the role of H₁R in cortical neural stem cell neurogenesis, the purpose of this study was to evaluate the postnatal impact of the systemic administration of chlorpheniramine during deep-layer cortical neuron differentiation (E12–14) in the primary motor cortex (M1) of neonates (P0) and 21-day-old pups (P21). Chlorpheniramine or vehicle were systemically administered (5 mg/kg, i.p.) to pregnant Wistar rats at gestational days 12–14, and the expression and distribution of deep- (FOXP2 and TBR1) and superficial-layer (SATB2) neuronal cortical markers were analyzed in neonates from both groups. The qRT-PCR analysis revealed a reduction in the expression of Satb2 and FoxP2. However, Western blot and immunofluorescence showed increased protein levels in the chlorpheniramine-treated group. In P21 pups, the three markers showed impaired distribution and increased immunofluorescence in the experimental group. The Sholl analysis evidenced altered dendritic arborization of deep-layer neurons, with lower excitability in response to histamine, as evaluated by whole-cell patch-clamp recording, as well as diminished depolarization-evoked [³H]-glutamate release from striatal slices. Overall, these results suggest long-lasting effects of blocking H₁Rs during early neurogenesis that may impact the pathways involved in voluntary motor activity and cognition.

Patho-Pharmacological Research of Anti-allergic Natural Products Targeting Antihistamine-Sensitive and -Insensitive Allergic Mechanisms

Histamine H₁ receptor (H1R) has a special up-regulation mechanism by the stimulation of H1R, mediated by protein kinase C-delta (PKCδ) signaling and H1R gene expression, resulting increase in H1R signaling. Increase in H1R mRNA in nasal mucosa was induced after the provocation of nasal hypersensitivity model rats and suppressed by the pre-treatment of antihistamines. Improvement of nasal symptoms and suppression of H1R mRNA expression in nasal mucosa were also observed by the pre-treatment of antihistamines in pollinosis patients. Elucidation of a correlation between symptoms and H1R mRNA level suggests that H1R gene is an allergic disease (AD)-susceptibility gene, targeted by antihistamines. Similar to antihistamines, pre-treatment of Kujin extract, an anti-allergic Kampo medicine improved nasal symptoms and suppressed H1R mRNA expression in nasal hypersensitivity model rats. (-)-Maackiain targeting heat shock protein 90 (Hsp90) was isolated as an inhibitor of PKCδ signaling-mediated H1R gene expression from Kujin extract. In addition to H1R-mediated activation of H1R gene expression as the first mechanism, nuclear factor of activated T-cells (NFAT)-mediated IL-9 gene expression is suggested to participate to allergic symptoms as the second mechanism insensitive to antihistamines. Pyrogallol and proanthocyanidin suppressing IL-9 gene expression were discovered from Awa-tea and lotus root knots, respectively. Combination therapy using medicines suppressing both H1R gene expression and IL-9 gene expression is promising for outstanding alleviation of AD. Multifactorial diseases involving H1R gene expression may be treated by the combination therapy with antihistamine and complementary drugs, and diseases involving PKCδ signaling may be treated by drugs targeting Hsp90.

Molecular Signaling and Transcriptional Regulation of Histamine H1 Receptor Gene

Histamine-activated histamine H₁ receptor (H1R) signaling regulates many gene expressions, mainly through the protein kinase C (PKC)/extracellular signal-regulated kinases (ERK) signaling. Involvement of other signaling, including NF-κB, Wnt, RUNX-2, and Rho A signaling was also demonstrated. In addition, cAMP production through the activation of H1R signaling was reported. H1R gene itself is also up-regulated by the activation of H1R signaling with histamine. Here, we review our recent findings in the molecular signaling and transcriptional regulation of the H1R gene. Stimulation with histamine up-regulates H1R gene expression through the activation of H1R in HeLa cells. The PKCδ/ERK/poly(ADP)ribosyl transferase-1 (PARP-1) signaling was involved in this up-regulation. Heat shock protein 90 also plays an important role in regulating PKCδ translocation. Promoter analyses revealed the existence of two promoters in the human H1R gene in HeLa cells. H1R-activated H1R gene up-regulation in response to histamine was also observed in U373 astroglioma cells. However, this up-regulation was mediated not through the PKCδ signaling but possibly through the PKCα signaling. In addition, the promoter region responsible for histamine-induced H1R gene transcription in U373 cells was different from that of HeLa cells. These findings suggest that the molecular signaling and transcriptional regulation of the H1R gene are different between neuronal cells and non-neuronal cells.

Signaling Pathway of Histamine H1 Receptor-Mediated Histamine H1 Receptor Gene Upregulation Induced by Histamine in U-373 MG Cells

Histamine H₁ receptor (H1R) is one of the targets of histamine in the nervous system and the peripheral tissues. Protein kinase Cδ (PKCδ) signaling is involved in histamine-induced upregulation of H1R gene expression in HeLa cells. Histamine also upregulates H1R gene expression in U-373 MG cells. However, the molecular signaling of this upregulation is still unclear. Here, we investigated the molecular mechanism of histamine-induced H1R gene upregulation in U-373 MG cells. Histamine-induced H1R gene upregulation was inhibited by H1R antagonist d-chlorpheniramine, but not by ranitidine, ciproxifan, or JNJ77777120, and H2R, H3R, or H4R antagonists, respectively. Ro-31-8220 and Go6976 also suppressed this upregulation, however, the PKCδ selective inhibitor rottlerin and the PKCβ selective inhibitor Ly333531 did not. Time-course studies showed distinct kinetics of H1R gene upregulation in U-373 MG cells from that in HeLa cells. A promoter assay revealed that the promoter region responsible for H1R gene upregulation in U-373 MG cells was different from that of HeLa cells. These data suggest that the H1R-activated H1R gene expression signaling pathway in U-373 MG cells is different from that in HeLa cells, possibly by using different promoters. The involvement of PKCα also suggests that compounds that target PKCδ could work as peripheral type H1R-selective inhibitors without a sedative effect.

Effects of Syo-seiryu-to and Its Constituent Crude Drugs on Phorbol Ester-Induced Up-Regulation of IL-33 and Histamine H1 Receptor mRNAs in Swiss 3T3 and HeLa Cells

Syo-seiryu-to (SST) is a traditional herbal medicine that has been used clinically to treat allergic rhinitis (AR) in Japan. SST improves acute symptoms, such as sneezing and rhinorrhea, as well as chronic symptoms, such as nasal obstruction, in patients with AR. However, its therapeutic mechanisms remain unknown. We examined the effects of SST and eight constituent crude drugs on phorbol 12-myristate-13-acetate (PMA)-induced gene up-regulation of IL-33 and histamine H1 receptor (H1R), which are responsible for the pathogenesis of AR. We found that SST and its crude drugs, except for Pinellia tuber, significantly and dose-dependently suppressed PMA-induced both IL-33 and H1R mRNA up-regulation in vitro. The half-maximal inhibitory concentration values of the seven crude drugs to inhibit PMA-induced IL-33 mRNA up-regulation were correlated with those related to H1R mRNA up-regulation, suggesting that they act on a common signal molecule. These results suggest that SST improves nasal congestion that is induced by IL-33-related eosinophil infiltration and inhibits sneezing and rhinorrhea that are induced by H1R-mediated histamine signaling in the nasal mucosa of AR patients through its inhibition of a common molecule in the gene expression pathways of IL-33 and H1R. The results could explain the advantages of traditional herbal medicine, in which mixing various crude drugs not only acts on a common target to enhance its pharmacological action, similar to the effect of a high concentration of a single crude extract but also has the benefit of reducing the side effects of each crude drug.

Anti-Allergic Rhinitis Effects of Medicinal Plants and Their Bioactive Metabolites via Suppression of the Immune System: A Mechanistic Review

Allergic rhinitis (AR) is a common inflammatory condition of the nasal mucosa and it is an immunoglobulin E-mediated disease. The incidence and prevalence of AR globally have been escalating over recent years. Antihistamines, intranasal corticosteroids, decongestants, intranasal anticholinergics, intranasal cromolyn, leukotriene receptor antagonists and immunotherapy have been used in the treatment of AR. However, there is a need to search for more effective and safer remedies as many of the current treatments have reported side effects. Medicinal plants have been used traditionally to relief symptoms of AR but their efficacy and safety have not been scientifically proven. In this review, up-to-date reports of studies on the anti-allergic rhinitis of several medicinal plants and their bioactive metabolites through suppression of the immune system are compiled and critically analyzed. The plant samples were reported to suppress the productions of immunoglobulin E, cytokines and eosinophils and inhibit histamine release. The suppression of cytokines production was found to be the main mechanistic effect of the plants to give symptomatic relief. The prospect of these medicinal plants as sources of lead molecules for development of therapeutic agents to treat AR is highlighted. Several bioactive metabolites of the plants including shikonin, okicamelliaside, warifteine, methylwarifteine, luteolin-7-O-rutinoside, tussilagone, petasin, and mangiferin have been identified as potential candidates for development into anti-allergic rhinitis agents. The data collection was mainly from English language articles published in journals, or studies from EBSCOHOST, Medline and Ovid, Scopus, Springer, and Google Scholar databases from the year 1985-2020. The terms or keywords used to find relevant studies were allergic rhinitis OR pollinosis OR hay fever, AND medicinal plant OR single plant OR single herb OR phytotherapy. This comprehensive review serves as a useful resource for medicinal plants with anti-allergic rhinitis potential, understanding the underlying mechanisms of action and for future exploration to find natural product candidates in the development of novel anti-allergic rhinitis agents.

Effects of corticosteroid on mRNA levels of histamine H1 receptor in nasal mucosa of healthy participants and HeLa cells

The purpose of this study is to examine the effect of intranasal corticosteroid (INCS) administration on histamine H1 receptor (H1R) gene expression in the nasal mucosa of healthy participants and the effects of dexamethasone on basal and histamine-induced H1R mRNA expression, and histamine-induced phosphorylation of extracellular signal-regulated kinase (ERK) in HeLa cells. Sixteen healthy participants were given INCS once daily for a week. After pretreatment of dexamethasone, HeLa cells were treated with histamine. Levels of H1R mRNA and phosphorylation of ERK were measured using real time PCR and immunoblot analysis, respectively. Levels of H1R mRNA in the nasal mucosa of healthy participants receiving INCS was significantly decreased. Dexamethasone suppressed basal levels of H1R mRNA, and histamine-induced up-regulation of H1R mRNA and ERK phosphorylation in HeLa cells. These data suggested that corticosteroid inhibited both basal transcription and histamine-induced transcriptional activation of H1R through its suppression of ERK phosphorylation in the signaling pathway involved in H1R gene transcription. It is further suggested that pre-seasonal prophylactic administration of INCS suppresses both basal and pollen-induced upregulation of H1R gene expression in the nasal mucosa of patients with pollinosis, leading to prevention of the exacerbation of nasal symptoms during peak pollen season. J. Med. Invest. 67 : 311-314, August, 2020.

Elucidation of Inverse Agonist Activity of Bilastine

H₁-antihistamines antagonize histamine and prevent it from binding to the histamine H₁ receptor (H1R). Some of them also act as inverse agonists, which are more potent than pure antagonists because they suppress the constitutive H1R activity. Bilastine is a non-sedative antihistamine which is one of the most satisfy the requirements for oral antihistamines. However, there is no information to show the inverse agonist activity of bilastine including inositol phosphates accumulation, and its inverse agonist activity is yet to be elucidated. Here we evaluated whether bilastine has inverse agonist activity or not. Intracellular calcium concentration was measured using Fluo-8. Inositol phosphates accumulation was assayed using [³H]myo-inositol. The H1R mRNA level was measured using real-time RT-PCR. At rest, Ca²⁺ oscillation was observed, indicating that H1R has intrinsic activity. Bilastine attenuated this fluorescence oscillation. Bilastine suppressed the increase in IPs formation in a dose-dependent manner and it was about 80% of the control level at the dose of 3 μM. Bilastine also suppressed histamine-induced increase in IPs formation to the control level. Furthermore, bilastine suppressed basal H1R gene expression in a dose-dependent manner. Data suggest that bilastine is an inverse agonist. Preseasonal prophylactic administration with bilastine could down-regulate basal H1R gene expression in the nasal mucosa and ameliorate the nasal symptoms during the peak pollen period.

Identification of pyrogallol from Awa-tea as an anti-allergic compound that suppresses nasal symptoms and IL-9 gene expression

As the expression level of allergic disease sensitive genes are correlated with the severity of allergic symptoms, suppression of these gene expressions could be promising therapeutics. We demonstrated that protein kinase Cδ / heat shock protein 90-mediated H1R gene expression signaling and nuclear factor of activated T-cells (NFAT)-mediated IL-9 gene expression signaling are responsible for the pathogenesis of pollinosis. Treatment with Awa-tea combined with wild grape hot water extract suppressed these signaling and alleviated nasal symptoms in toluene-2,4-diisocyanate (TDI)-sensitized rats. However, the underlying mechanism of its anti-allergic activity is not elucidated yet. Here, we sought to identify an anti-allergic compound from Awa-tea and pyrogallol was identified as an active compound. Pyrogallol strongly suppressed ionomycin-induced up-regulation of IL-9 gene expression in RBL-2H3 cells. Treatment with pyrogallol in combination with epinastine alleviated nasal symptoms and suppressed up-regulation of IL-9 gene expression in TDI-sensitized rats. Pyrogallol itself did not inhibit calcineurin phosphatase activity. However, pyrogallol suppressed ionomycin-induced dephosphorylation and nuclear translocation of NFAT. These data suggest pyrogallol is an anti-allergic compound in Awa-tea and it suppressed NFAT-mediated IL-9 gene expression through the inhibition of dephosphorylation of NFAT. This might be the underlying mechanism of the therapeutic effects of combined therapy of pyrogallol with antihistamine. J. Med. Invest. 67 : 289-297, August, 2020.

Upregulation of histamine receptor H1 promotes tumor progression and contributes to poor prognosis in hepatocellular carcinoma

H1 histamine receptor (H1HR) belongs to the family of rhodopsin-like G-protein-coupled receptors. Recent studies have shown that H1HR expression is increased in several types of cancer. However, its functional roles in tumor progression remain largely unknown, especially in hepatocellular carcinoma (HCC). We found that H1HR is frequently unregulated in HCC, which is significantly associated with both recurrence-free survival and overall survival in HCC patients. Functional experiments revealed that H1HR promoted both the growth and metastasis of HCC cells by inducing cell cycle progression, formation of lamellipodia, production of matrix metalloproteinase 2, and suppression of cell apoptosis. Activation of cyclic adenosine monophosphate-dependent protein kinase A was found to be involved in H1HR-mediated HCC cell growth and metastasis. In addition, we found that overexpression of H1HR was mainly due to the downregulation of miR-940 in HCC cells. Moreover, the H1HR inhibitor terfenadine significantly suppressed tumor growth and metastasis in an HCC xenograft nude mice model. Our findings demonstrate that H1HR plays a critical role in the growth and metastasis of HCC cells, which provides experimental evidence supporting H1HR as a potential drug target for the treatment of HCC.

Effect of wild grape on the signaling of histamine H1 receptor gene expression responsible for the pathogenesis of allergic rhinitis

As expression level of allergic disease-sensitive genes are correlated with allergic symptom severity, suppression of these gene expressions could be good therapeutics. We have demonstrated that PKCδ signaling and NFAT signaling, involve in histamine H₁ receptor (H1R) and IL-9 gene expressions, respectively, are responsible for the pathogenesis of allergic rhinitis. We explore anti-allergic compounds that suppress these signaling pathways and found that wild grape (WG) contains such compounds. Here, we investigated the effect of WG hot water extract (WGE) on the signaling pathways for PKCδ-mediated H1R and NFAT-mediated IL-9 gene expressions. WGE suppressed histamine/PMA-induced H1R gene up-regulation in HeLa cells. Toluene-2,4-diisocyanate (TDI)-induced H1R mRNA elevation in TDI-sensitized rats was also suppressed by WGE treatment. Treatment with WGE in combination with Awa-tea, suppresses NFAT signaling-mediated IL-9 gene, markedly alleviated nasal symptoms. Furthermore, WGE suppressed PMA-induced IL-33 gene up-regulation in Swiss 3T3 cells. Data suggest that combination of WGE, suppresses PKCδ signaling with Awa-tea, suppresses NFAT signaling would have distinct clinical and therapeutic advantages as a substitute for anti-allergic drugs. In addition, as the expression level of IL-33 mRNA was correlated with the blood eosinophils number in patients with pollinosis, WG could alleviate eosinophilic inflammation through the suppression of IL-33 gene expression. J. Med. Invest. 65:242-250, August, 2018.

Effect of Royal Jelly and Brazilian Green Propolis on the Signaling for Histamine H1 Receptor and Interleukin-9 Gene Expressions Responsible for the Pathogenesis of the Allergic Rhinitis

The significant correlation between nasal symptom scores and level of histamine H₁ receptor (H1R) mRNA in nasal mucosa was observed in patients with pollinosis, suggesting that H1R gene is an allergic disease sensitive gene. We demonstrated that H1R and interleukin (IL)-9 gene are the allergic rhinitis (AR)-sensitive genes and protein kinase Cδ (PKCδ) signaling and nuclear factor of activated T-cells (NFAT) signaling are involved in their expressions, respectively. Honey bee products have been used to treat allergic diseases. However, their pathological mechanism remains to be elucidated. In the present study, we investigated the mechanism of the anti-allergic effect of royal jelly (RJ) and Brazilian green propolis (BGPP). Treatment with RJ and BGPP decreased in the number of sneezing on toluene 2,4-diissocyanate (TDI)-stimulated rats. The remarkable suppression of H1R mRNA in nasal mucosa was observed. RJ and BGPP also suppressed the expression of IL-9 gene. RJ and BGPP suppressed phorbol-12-myristate-13-acetate-induced Tyr³¹¹ phosphorylation of PKCδ in HeLa cells. In RBL-2H3 cells, RJ and BGPP also suppressed NFAT-mediated IL-9 gene expression. These results suggest that RJ and BGPP improve allergic symptoms by suppressing PKCδ and NFAT signaling pathways, two important signal pathways for the AR pathogenesis, and suggest that RJ and BGPP could be good therapeutics against AR.

Effects of irradiation with narrowband-ultraviolet B on up-regulation of histamine H1 receptor mRNA and induction of apoptosis in HeLa cells and nasal mucosa of rats

Narrowband-ultraviolet B (NB-UVB) phototherapy is used for the treatment of atopic dermatitis. Previously, we reported that irradiation with 200 mJ/cm² of 310 nm NB-UVB suppressed phorbol-12-myristate-13-acetate (PMA)-induced up-regulation of histamine H₁ receptor (H1R) gene expression without induction of apoptosis in HeLa cells. However, the effect of NB-UVB irradiation on nasal symptoms is still unclear. Here, we show that low dose irradiation with 310 nm NB-UVB alleviates nasal symptoms in toluene 2,4-diisocyanate (TDI)-sensitized allergy model rats. Irradiation with 310 nm NB-UVB suppressed PMA-induced H1R mRNA up-regulation in HeLa cells dose-dependently at doses of 75-200 mJ/cm² and reversibly at a dose of 150 mJ/cm² without induction of apoptosis. While, at doses of more than 200 mJ/cm², irradiation with 310 nm NB-UVB induced apoptosis. Western blot analysis showed that the suppressive effect of NB-UVB irradiation on H1R gene expression was through the inhibition of ERK phosphorylation. In TDI-sensitized rat, intranasal irradiation with 310 nm NB-UVB at an estimated dose of 100 mJ/cm² once a day for three days suppressed TDI-induced sneezes and up-regulation of H1R mRNA in nasal mucosa without induction of apoptosis. These findings suggest that repeated intranasal irradiation with low dose of NB-UVB could be clinically used as phototherapy of AR.

Curcumin derivative, 2,6-bis(2-fluorobenzylidene)cyclohexanone (MS65) inhibits interleukin-6 production through suppression of NF-κB and MAPK pathways in histamine-induced human keratinocytes cell (HaCaT)

Background

Histamine is a well-known mediator involved in skin allergic responses through up-regulation of pro-inflammatory cytokines. Antihistamines remain the mainstay of allergy treatment, but they were found limited in efficacy and associated with several common side effects. Therefore, alternative therapeutic preferences are derived from natural products in an effort to provide safe yet reliable anti-inflammatory agents. Curcumin and their derivatives are among compounds of interest in natural product research due to numerous pharmacological benefits including anti-inflammatory activities. Here, we investigate the effects of chemically synthesized curcumin derivative, 2,6-bis(2-fluorobenzylidene)cyclohexanone (MS65), in reducing cytokine production in histamine-induced HaCaT cells.

Methods

Interleukin (IL)-6 cytokine production in histamine-induced HaCaT cells were measured using enzyme-linked immunosorbent assay (ELISA) and cytotoxicity effects were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Real-time polymerase chain reaction (RT-qPCR) was carried out to determine the inhibitory effects of MS65 on nuclear factor-kappa B (NF-κB) and mitogen activated protein kinase (MAPK) pathways.

Results

Histamine enhanced IL-6 production in HaCaT cells, with the highest production of IL-6 at 97.41 ± 2.33 pg/mL after 24 h of exposure. MS65 demonstrated a promising anti-inflammatory activity by inhibiting IL-6 production with half maximal inhibitory concentration (IC₅₀) value of 4.91 ± 2.50 μM and median lethal concentration (LC₅₀) value of 28.82 ± 7.56 μM. In gene expression level, we found that MS65 inhibits NF-κB and MAPK pathways through suppression of IKK/IκB/NFκB and c-Raf/MEK/ERK inflammatory cascades.

Conclusion

Taken together, our results suggest that MS65 could be used as a lead compound on developing new medicinal agent for the treatment of allergic skin diseases.

Histamine H1 Receptor Gene Expression and Drug Action of Antihistamines

The upregulation mechanism of histamine H₁ receptor through the activation of protein kinase C-δ (PKCδ) and the receptor gene expression was discovered. Levels of histamine H₁ receptor mRNA and IL-4 mRNA in nasal mucosa were elevated by the provocation of nasal hypersensitivity model rats. Pretreatment with antihistamines suppressed the elevation of mRNA levels. Scores of nasal symptoms were correlatively alleviated to the suppression level of mRNAs above. A correlation between scores of nasal symptoms and levels of histamine H₁ receptor mRNA in the nasal mucosa was observed in patients with pollinosis. Both scores of nasal symptoms and the level of histamine H₁ receptor mRNA were improved by prophylactic treatment of antihistamines. Similar to the antihistamines, pretreatment with antiallergic natural medicines showed alleviation of nasal symptoms with correlative suppression of gene expression in nasal hypersensitivity model rats through the suppression of PKCδ. Similar effects of antihistamines and antiallergic natural medicines support that histamine H₁ receptor-mediated activation of histamine H₁ receptor gene expression is an important signaling pathway for the symptoms of allergic diseases. Antihistamines with inverse agonist activity showed the suppression of constitutive histamine H₁ receptor gene expression, suggesting the advantage of therapeutic effect.

Efficacy of 0.05% epinastine and 0.1% olopatadine for allergic conjunctivitis as seasonal and preseasonal treatment

Purpose

To evaluate the efficacy and safety of 0.05% epinastine and 0.1% olopatadine eye drop preparations as seasonal and preseasonal treatments in patients with seasonal allergic conjunctivitis (SAC).

Subjects and methods

This was a prospective, randomized, case-control study involving two institutions. The subjects were patients diagnosed with SAC at two institutions between February and March in 2014. To examine the clinical effects of seasonal treatment, 0.05% epinastine and 0.1% olopatadine were administered, and their effects were investigated every 2 weeks (Stage 1). To evaluate the clinical effects of preseasonal therapy, in January 2015, the same eye drop preparations as adopted in Stage 1 were administered to patients who had participated in Stage 1 and provided consent to participate in this study, and their effects were investigated every month (Stage 2).

Results

In Stage 1, the 0.05% epinastine group consisted of 43 patients, and the 0.1% olopatadine group consisted of 42 patients. There were significant improvements in the total symptom and objective finding scores at each time point after administration in comparison with those before its baseline, but there were no significant differences between the two groups. In Stage 2, the 0.05% epinastine group consisted of 15 patients, and the 0.1% olopatadine group consisted of 14 patients. The rate of change in the total symptom score in comparison with that at the baseline of preseasonal treatment was significantly higher in the 0.1% olopatadine group 1 month after the start of treatment, suggesting symptom deterioration (P=0.025). There was no significant difference in the rate of change in the total objective finding score between the two groups.

Conclusion

Seasonal treatment with 0.05% epinastine or 0.1% olopatadine was equally effective for patients with allergic conjunctivitis. However, for preseasonal therapy, 0.05% epinastine was more effective than 0.1% olopatadine.

The Target Residence Time of Antihistamines Determines Their Antagonism of the G Protein-Coupled Histamine H1 Receptor

The pharmacodynamics of drug-candidates is often optimized by metrics that describe target binding (K_d or K_i value) or target modulation (IC₅₀). However, these metrics are determined at equilibrium conditions, and consequently information regarding the onset and offset of target engagement and modulation is lost. Drug-target residence time is a measure for the lifetime of the drug-target complex, which has recently been receiving considerable interest, as target residence time is shown to have prognostic value for the in vivo efficacy of several drugs. In this study, we have investigated the relation between the increased residence time of antihistamines at the histamine H₁ receptor (H₁R) and the duration of effective target-inhibition by these antagonists. Hela cells, endogenously expressing low levels of the H₁R, were incubated with a series of antihistamines and dissociation was initiated by washing away the unbound antihistamines. Using a calcium-sensitive fluorescent dye and a label free, dynamic mass redistribution based assay, functional recovery of the H₁R responsiveness was measured by stimulating the cells with histamine over time, and the recovery was quantified as the receptor recovery time. Using these assays, we determined that the receptor recovery time for a set of antihistamines differed more than 40-fold and was highly correlated to their H₁R residence times, as determined with competitive radioligand binding experiments to the H₁R in a cell homogenate. Thus, the receptor recovery time is proposed as a cell-based and physiologically relevant metric for the lead optimization of G protein-coupled receptor antagonists, like the H₁R antagonists. Both, label-free or real-time, classical signaling assays allow an efficient and physiologically relevant determination of kinetic properties of drug molecules.

Effect of budesonide and azelastine on histamine signaling regulation in human nasal epithelial cells

Both glucocorticoids and H1-antihistamines are widely used on patients with airway diseases. However, their direct effects on airway epithelial cells are not fully explored. Therefore, we use the primary culture of human nasal epithelial cells (HNEpC) to delineate in vitro mucosal responses to above two drugs. HNEpC cells were cultured with/without budesonide and azelastine. The growth rate at each group was recorded and measured as population double time (PDT). The histamine1-receptor (H1R), muscarinic1-receptor (M1R) and M3R were measured using immunocytochemistry and western blotting after 7-days treatment. Then, we used histamine and methacholine to stimulate the mucus secretion from HNEpC and observed the MUC5AC expression in culture supernatants. Concentration-dependent treatment-induced inhibition of HNEpC growth rate was observed. Cells incubated with azelastine proliferated significantly slower than that with budesonide and the combined use of those drugs led to significant PDT prolong. The immunocytochemistry showed the H1R, M1R and M3R were obviously located in the cell membrane without apparent difference after treatment. However, western blotting showed that budesonide can significantly up-regulate the H1R, M1R and M3R level while azelastine had opposite effects. Histamine and methacholine stimulated MUC5AC secretion was greater in cells treated with budesonide but was lesser in those treated with azelastine, as compared to controls. Our data suggest that both budesonide and azelastine can significantly inhibit HNEpC proliferation, and therefore, be helpful in against airway remodeling. Long-term use of budesonide might amplify histamine signaling and result in airway hyperreactivity to stimulants by enhancing H1R, M1R and M3R expression while azelastine can oppose this effect. Therefore, combined use of those two drugs in patients with chronic inflammatory airway diseases may be an ideal option.

Antihistamines suppress upregulation of histidine decarboxylase gene expression with potencies different from their binding affinities for histamine H1 receptor in toluene 2,4-diisocyanate-sensitized rats

Antihistamines inhibit histamine signaling by blocking histamine H1 receptor (H1R) or suppressing H1R signaling as inverse agonists. The H1R gene is upregulated in patients with pollinosis, and its expression level is correlated with the severity of nasal symptoms. Here, we show that antihistamine suppressed upregulation of histidine decarboxylase (HDC) mRNA expression in patients with pollinosis, and its expression level was correlated with that of H1R mRNA. Certain antihistamines, including mepyramine and diphenhydramine, suppress toluene-2,4-diisocyanate (TDI)-induced upregulation of HDC gene expression and increase HDC activity in TDI-sensitized rats. However, d-chlorpheniramine did not demonstrate any effect. The potencies of antihistamine suppressive effects on HDC mRNA elevation were different from their H1R receptor binding affinities. In TDI-sensitized rats, the potencies of antihistamine inhibitory effects on sneezing in the early phase were related to H1R binding. In contrast, the potencies of their inhibitory effects on sneezing in the late phase were correlated with those of suppressive effects on HDC mRNA elevation. Data suggest that in addition to the antihistaminic and inverse agonistic activities, certain antihistamines possess additional properties unrelated to receptor binding and alleviate nasal symptoms in the late phase by inhibiting synthesis and release of histamine by suppressing HDC gene transcription.

Irradiation with narrowband-ultraviolet B suppresses phorbol ester-induced up-regulation of H1 receptor mRNA in HeLa cells

Conclusion These findings suggest that low dose irradiation with 310 nm NB-UVB specifically suppressed the up-regulation of H1R gene expression without inducing apoptosis and that UVB of shorter or longer wavelength than 310 nm NB-UVB had no such effects. Objective To develop a narrowband-ultraviolet B(NB-UVB) phototherapy for allergic rhinitis, this study investigated the effects of irradiation with NB-UVB at wavelength of 310 nm on phorbol-12-myristate-13-acetate (PMA)-induced up-regulation of histamine H1 receptor (H1R) mRNA in HeLa cells. Methods The mRNA levels of H1R in HeLa cells were measured using real-time RT-PCR. Apoptosis were evaluated with DNA fragmentation assay. Results PMA induced a significant increase in H1R mRNA expression in HeLa cells. Irradiation with 305 nm UVB and 310 nm NB-UVB, but not with 315 nm UVB at doses of 200 and 300 mJ/cm(2) significantly suppressed PMA-induced up-regulation of H1R mRNA. At a dose of 200 mJ/cm(2), irradiation with 305 nm UVB, but not with 310 nm NB-UVB, induced apoptosis, although exposure of the cells to both 305 and 310 nm UVB induced apoptosis at a dose of 300 mJ/cm(2) after PMA treatment in HeLa cells. Conversely, irradiation with 315 nm UVB at doses of 200 and 300 mJ/cm(2) did not induce apoptosis.

Suplatast tosilate alleviates nasal symptoms through the suppression of nuclear factor of activated T-cells-mediated IL-9 gene expression in toluene-2,4-diisocyanate-sensitized rats

Histamine H1 receptor (H1R) gene is upregulated in patients with pollinosis; its expression level is highly correlated with the nasal symptom severity. Antihistamines are widely used as allergy treatments because they inhibit histamine signaling by blocking H1R or suppressing H1R signaling as inverse agonists. However, long-term treatment with antihistamines does not completely resolve toluene-2,4-diisocyanate (TDI)-induced nasal symptoms, although it can decrease H1R gene expression to the basal level, suggesting additional signaling is responsible for the pathogenesis of the allergic symptoms. Here, we show that treatment with suplatast tosilate in combination with antihistamines markedly alleviates nasal symptoms in TDI-sensitized rats. Suplatast suppressed TDI-induced upregulation of IL-9 gene expression. Suplatast also suppressed ionomycin/phorbol-12-myristate-13-acetate-induced upregulation of IL-2 gene expression in Jurkat cells, in which calcineurin (CN)/nuclear factor of activated T-cells (NFAT) signaling is known to be involved. Immunoblot analysis demonstrated that suplatast inhibited binding of NFAT to DNA. Furthermore, suplatast suppressed ionomycin-induced IL-9 mRNA upregulation in RBL-2H3 cells, in which CN/NFAT signaling is also involved. These data suggest that suplatast suppressed NFAT-mediated IL-9 gene expression in TDI-sensitized rats and this might be the underlying mechanism of the therapeutic effects of combined therapy of suplatast with antihistamine.

Disruption of Heat Shock Protein 90 (Hsp90)-Protein Kinase Cδ (PKCδ) Interaction by (-)-Maackiain Suppresses Histamine H1 Receptor Gene Transcription in HeLa Cells

The histamine H1 receptor (H1R) gene is an allergic disease sensitive gene, and its expression level is strongly correlated with the severity of allergic symptoms. (-)-Maackiain was identified as a Kujin-derived anti-allergic compound that suppresses the up-regulation of the H1R gene. However, the underlying mechanism of H1R gene suppression remains unknown. Here, we sought to identify a target protein of (-)-maackiain and investigate its mechanism of action. A fluorescence quenching assay and immunoblot analysis identified heat shock protein 90 (Hsp90) as a target protein of (-)-maackiain. A pull-down assay revealed that (-)-maackiain disrupted the interaction of Hsp90 with PKCδ, resulting in the suppression of phorbol 12-myristate 13-acetate (PMA)-induced up-regulation of H1R gene expression in HeLa cells. Additional Hsp90 inhibitors, including 17-(allylamino)-17-demethoxygeldanamycin, celastrol, and novobiocin also suppressed PMA-induced H1R gene up-regulation. 17-(Allylamino)-17-demethoxygeldanamycin inhibited PKCδ translocation to the Golgi and phosphorylation of Tyr(311) on PKCδ. These data suggest that (-)-maackiain is a novel Hsp90 pathway inhibitor. The underlying mechanism of the suppression of PMA-induced up-regulation of H1R gene expression by (-)-maackiain and Hsp90 inhibitors is the inhibition of PKCδ activation through the disruption of Hsp90-PKCδ interaction. Involvement of Hsp90 in H1R gene up-regulation suggests that suppression of the Hsp90 pathway could be a novel therapeutic strategy for allergic rhinitis.

Effects of antihistamine on up-regulation of histamine H1 receptor mRNA in the nasal mucosa of patients with pollinosis induced by controlled cedar pollen challenge in an environmental exposure unit

In the present study, we examined the effects of antihistamine on the up-regulation of H1R mRNA in the nasal mucosa of patients with pollinosis induced by controlled exposure to pollen using an environmental exposure unit. Out of 20 patients, we designated 14 responders, whose levels of H1R mRNA in the nasal mucosa were increased after the first pollen exposure and excluded 6 non-responders. Accordingly, the first exposure to pollen without treatment significantly induced both nasal symptoms and the up-regulation of H1R mRNA in the nasal mucosa of the responders. Subsequently, prophylactic administration of antihistamine prior to the second pollen exposure significantly inhibited both of the above effects in the responders. Moreover, the nasal expression of H1R mRNA before the second pollen exposure in the responders pretreated with antihistamine was significantly decreased, as compared with that before the first pollen exposure without treatment. These findings suggest that antihistamines suppressed histamine-induced transcriptional activation of H1R gene in the nasal mucosa, in addition to their blocking effect against histamine on H1R, resulting in a decrease of nasal symptoms. These findings further suggest that by their inverse agonistic activity, antihistamines suppress the basal transcription of nasal H1R in the absence of histamine in responders.

Maackiain is a novel antiallergic compound that suppresses transcriptional upregulation of the histamine H1 receptor and interleukin-4 genes

Kujin contains antiallergic compounds that inhibit upregulation of histamine H1 receptor (H1R) and interleukin (IL)-4 gene expression. However, the underlying mechanism remains unknown. We sought to identify a Kujin-derived antiallergic compound and investigate its mechanism of action. The H1R and IL-4 mRNA levels were determined by real-time quantitative RT-PCR. To investigate the effects of maackiain in vivo, toluene-2,4-diisocyanate (TDI)-sensitized rats were used as a nasal hypersensitivity animal model. We identified (-)-maackiain as the responsible component. Synthetic maackiain showed stereoselectivity for the suppression of IL-4 gene expression but not for H1R gene expression, suggesting distinct target proteins for transcriptional signaling. (-)-Maackiain inhibited of PKCδ translocation to the Golgi and phosphorylation of Tyr(311) on PKCδ, which led to the suppression of H1R gene transcription. However, (-)-maackiain did not show any antioxidant activity or inhibition of PKCδ enzymatic activity per se. Pretreatment with maackiain alleviated nasal symptoms and suppressed TDI-induced upregulations of H1R and IL-4 gene expressions in TDI-sensitized rats. These data suggest that (-)-maackiain is a novel antiallergic compound that alleviates nasal symptoms in TDI-sensitized allergy model rats through the inhibition of H1R and IL-4 gene expression. The molecular mechanism underlying its suppressive effect for H1R gene expression is mediated by the inhibition of PKCδ activation.

Dexmedetomidine Modulates Histamine-induced Ca(2+) Signaling and Pro-inflammatory Cytokine Expression

Dexmedetomidine is a sedative and analgesic agent that exerts its effects by selectively agonizing α2 adrenoceptor. Histamine is a pathophysiological amine that activates G protein-coupled receptors, to induce Ca(2+) release and subsequent mediate or progress inflammation. Dexmedetomidine has been reported to exert inhibitory effect on inflammation both in vitro and in vivo studies. However, it is unclear that dexmedetomidine modulates histamine-induced signaling and pro-inflammatory cytokine expression. This study was carried out to assess how dexmedetomidine modulates histamine-induced Ca(2+) signaling and regulates the expression of pro-inflammatory cytokine genes encoding interleukin (IL)-6 and -8. To elucidate the regulatory role of dexmedetomidine on histamine signaling, HeLa cells and human salivary gland cells which are endogenously expressed histamine 1 receptor were used. Dexmedetomidine itself did not trigger Ca(2+) peak or increase in the presence or absence of external Ca(2+). When cells were stimulated with histamine after pretreatment with various concentrations of dexmedetomidine, we observed inhibited histamine-induced [Ca(2+)]i signal in both cell types. Histamine stimulated IL-6 mRNA expression not IL-8 mRNA within 2 hrs, however this effect was attenuated by dexmedetomidine. Collectively, these findings suggest that dexmedetomidine modulates histamine-induced Ca(2+) signaling and IL-6 expression and will be useful for understanding the antagonistic properties of dexmedetomidine on histamine-induced signaling beyond its sedative effect.

Rupatadine effectively prevents the histamine-induced up regulation of histamine H1R and bradykinin B2R receptor gene expression in the rat paw

BACKGROUND

Activation of histamine H1 receptor (H1R) is a well-known hallmark of allergic and inflammatory pathology. Both types of bradykinin receptors (B1R and B2R) are also known to contribute significantly to the latter and some sort of functional interaction between them and H1R has been alluded to in the past. Here we use an experimental model of rat paw oedema formation to examine the effect of exogenously added histamine on the gene expression of H1R and bradykinin receptors B1R and B2R, alone or in combination to rupatadine, a second generation antihistamine agent.

METHODS

Histamine-induced oedema formation was monitored with a plethysmometer. The gene expression of H1R, B1R and B2R was analyzed with both conventional and real-time PCR. Rupatadine fumarate was used in pure form and administered intraperitoneally, prior to histamine injection into the paw. Microscopy of haematoxylin and eosin-stained sections of paw tissue was used to examine effects on tissue architecture.

RESULTS

Histamine injection into the paw resulted in significant up regulation of H1R and B2R without inducing significant cellular infiltration, but appears to affect less the expression of B1R. Rupatadine was, under the conditions used in this study, very effective in preventing this effect and in suppressing oedema formation through its antihistamine action.

CONCLUSION

Rupatadine has a suppressing effect on H1R and B2R gene expression which could add to its efficacy towards allergy and allergy-like conditions.

Combination of leukotoriene receptor antagonist with antihistamine has an additive suppressive effect on the up-regulation of H1-receptor mRNA in the nasal mucosa of toluene 2,4-diisocyanate-sensitized rat

An attempt was made to clarify the additive suppressive effects of pranlukast, a cysteinyl leukotriene-receptor (LTR) antagonist, in combination with chlorpheniramine, an antihistamine, on the up-regulation of histamine H1-receptor (H1R) mRNA in toluene 2,4-diisocyanate (TDI)-sensitized rats. Although pre-treatment with pranlukast partially, but significantly, suppressed TDI-induced up-regulation of H1R mRNA and nasal symptoms, pre-treatment with the combination of pranlukast and chlorpheniramine significantly suppressed them in a manner greater than either drug alone. These findings suggest that the additive therapeutic effect of the combination of LTR antagonist and antihistamine is due to their additive suppression of H1R up-regulation.

Usefulness of HeLa cells to evaluate inverse agonistic activity of antihistamines

Antihistamines are thought to antagonize histamine and prevent it from binding to the histamine H1 receptor (H1R). However, recent studies indicate that antihistamines are classified into two groups, i.e., inverse agonists and neutral antagonists on the basis of their ability to down-regulate the constitutive activity of H1R. As H1R is an allergy-sensitive gene whose expression influences the severity of allergic symptoms, inverse agonists should more potently alleviate allergic symptoms than neutral antagonists by inhibiting H1R constitutive activity. Therefore, it is important to assess inverse agonistic activity of antihistamines. Here we report a novel assay method using HeLa cells expressing H1R endogenously for evaluation of inverse agonistic activity of antihistamines. Pretreatment with inverse agonists down-regulated H1R gene expression below to its basal level. On the other hand, basal H1R mRNA expression was unchanged by neutral antagonist pretreatment. Both inverse agonists and neutral antagonists suppressed histamine-induced H1R mRNA elevation. Classification of antihistamines on the basis of their suppressive activity of basal H1R gene expression was consistent with that of inositol phosphate accumulation in H1R-overexpressed cells. Our data suggest that the assay method using HeLa cells is more convenient and useful than the existing methods and may contribute to develop new antihistamines with inverse agonistic activity.

Quercetin inhibits transcriptional up-regulation of histamine H1 receptor via suppressing protein kinase C-δ/extracellular signal-regulated kinase/poly(ADP-ribose) polymerase-1 signaling pathway in HeLa cells

It has been reported that the histamine H1 receptor (H1R) gene is up-regulated in patients with allergic rhinitis and H1R expression level strongly correlates with the severity of allergy symptoms. Accordingly compounds that suppress the H1R gene expression are promising as useful anti-allergic medications. Recently, we demonstrated that histamine or phorbol-12-myristate-13-acetate (PMA) stimulation induced the up-regulation of H1R gene expression through the protein kinase Cδ (PKCδ)/extracellular signal-regulated kinase/poly(ADP-ribose) polymerase-1 signaling pathway in HeLa cells expressing H1R endogenously. Quercetin is one of the well-characterized flavonoids and it possesses many biological activities including anti-allergic activity. However, effect of quercetin on H1R signaling is remained unknown. In the present study, we examined the effect of quercetin on histamine- and PMA-induced up-regulation of H1R gene expression in HeLa cells. We also investigated its in vivo effects on the toluene-2,4-diisocyanate (TDI)-sensitized allergy model rats. Quercetin suppressed histamine- and PMA-induced up-regulation of H1R gene expression. Quercetin also inhibited histamine- or PMA-induced phosphorylation of Tyr(311) of PKCδ and translocation of PKCδ to the Golgi. Pre-treatment with quercetin for 3weeks suppressed TDI-induced nasal allergy-like symptoms and elevation of H1R mRNA in the nasal mucosa of TDI-sensitized rats. These data suggest that quercetin suppresses H1R gene expression by the suppression of PKCδ activation through the inhibition of its translocation to the Golgi.

Molecular and cellular analysis of human histamine receptor subtypes

The human histamine receptors hH(1)R and hH(2)R constitute important drug targets, and hH(3)R and hH(4)R have substantial potential in this area. Considering the species-specificity of pharmacology of H(x)R orthologs, it is important to analyze hH(x)Rs. Here, we summarize current knowledge of hH(x)Rs endogenously expressed in human cells and hH(x)Rs recombinantly expressed in mammalian and insect cells. We present the advantages and disadvantages of the various systems. We also discuss problems associated with the use of hH(x)R antibodies, an issue of general relevance for G-protein-coupled receptors (GPCRs). There is much greater overlap in activity of 'selective' ligands for other hH(x)Rs than the cognate receptor subtype than generally appreciated. Studies with native and recombinant systems support the concept of ligand-specific receptor conformations, encompassing agonists and antagonists. It is emerging that for characterization of hH(x)R ligands, one cannot rely on a single test system and a single parameter. Rather, multiple systems and parameters have to be studied. Although such studies are time-consuming and expensive, ultimately, they will increase drug safety and efficacy.

PMA-induced dissociation of Ku86 from the promoter causes transcriptional up-regulation of histamine H(1) receptor

Histamine H₁ receptor (H1R) gene is up-regulated in patients with allergic rhinitis, and its expression level strongly correlates with the severity of symptoms. However, the mechanism underlying this remains unknown. Here we report the mechanism of H1R gene up-regulation. The luciferase assay revealed the existence of two promoter regions, A and B1. Two AP-1 and one Ets-1 bound to region A, while Ku86, Ku70, and PARP-1 bound to region B1. Ku86 was responsible for DNA binding and poly(ADP-ribosyl)ated in response to phorbol-12-myristate-13-acetate stimulation, inducing its dissociation from region B1 that is crucial for promoter activity. Knockdown of Ku86 gene enhanced up-regulation of H1R gene expression. Experiments using inhibitors for MEK and PARP-1 indicate that regions A and B1 are downstream regulatory elements of the PKCδ/ERK/PARP-1 signaling pathway. Data suggest a novel mechanism for the up-regulation of H1R gene expression.

A novel fluorescent histamine H(1) receptor antagonist demonstrates the advantage of using fluorescence correlation spectroscopy to study the binding of lipophilic ligands

BACKGROUND AND PURPOSE

Fluorescent ligands facilitate the study of ligand-receptor interactions at the level of single cells and individual receptors. Here, we describe a novel fluorescent histamine H(1) receptor antagonist (mepyramine-BODIPY630-650) and use it to monitor the membrane diffusion of the histamine H(1) receptor.

EXPERIMENTAL APPROACH

The human histamine H(1) receptor fused to yellow fluorescent protein (YFP) was transiently expressed in CHO-K1 cells. The time course of binding of mepyramine-BODIPY630-650 to the H(1) receptor was determined by confocal microscopy. Additionally, fluorescence correlation spectroscopy (FCS) was used to characterize the diffusion coefficient of the H(1) receptor in cell membranes both directly (YFP fluorescence) and in its antagonist-bound state (with mepyramine-BODIPY630-650).

KEY RESULTS

Mepyramine-BODIPY630-650 was a high-affinity antagonist at the histamine H(1) receptor. Specific membrane binding, in addition to significant intracellular uptake of the fluorescent ligand, was detected by confocal microscopy. However, FCS was able to quantify the receptor-specific binding in the membrane, as well as the diffusion coefficient of the antagonist-H(1) receptor-YFP complexes, which was significantly slower than when determined directly using YFP. FCS also detected specific binding of mepyramine-BODIPY630-650 to the endogenous H(1) receptor in HeLa cells.

CONCLUSIONS AND IMPLICATIONS

Mepyramine-BODIPY630-650 is a useful tool for localizing the H(1) receptor using confocal microscopy. However, its use in conjunction with FCS allows quantification of ligand binding at the membrane, as well as determining receptor diffusion in the absence of significant bleaching effects. Finally, these methods can be successfully extended to endogenously expressed untagged receptors in HeLa cells.

Preseasonal prophylactic treatment with antihistamines suppresses IL-5 but not IL-33 mRNA expression in the nasal mucosa of patients with seasonal allergic rhinitis caused by Japanese cedar pollen

CONCLUSIONS

These findings suggest that the down-regulation of interleukin (IL)-5 gene expression in collaboration with the suppression of histamine H(1) receptor (H1R) gene expression in the nasal mucosa provides the basis for better therapeutic effects of preseasonal prophylactic treatment with antihistamines in patients with seasonal allergic rhinitis caused by Japanese cedar pollen.

OBJECTIVES

The effects of prophylactic administration of antihistamines on the expression of IL-5 and IL-33 mRNA in the nasal mucosa of the patients with pollinosis were investigated.

METHODS

Eight patients had already visited the hospital before the peak pollen period and started preseasonal prophylactic treatment with antihistamines. Seventeen patients who first visited the hospital during the peak pollen period were designated as the no treatment group. After local anesthesia, nasal mucosa was obtained by scraping the inferior concha with a small spatula during the peak pollen period.

RESULTS

During the peak pollen period, the expression of IL-5 mRNA, but not that of IL-33 mRNA, in the nasal mucosa of patients receiving preseasonal prophylactic treatment with antihistamines was significantly lower in comparison with that of patients without treatment. Moreover, there was a significant correlation between the expression of IL-5 mRNA and the nasal symptoms or the expression of H1R mRNA.

Inverse agonistic activity of antihistamines and suppression of histamine H1 receptor gene expression

Histamine H(1) receptor (H1R) expression influences the severity of allergy symptoms. We examined the effect of inverse agonists on H1R gene expression. Two inverse agonists (carebastine and mepyramine), but not the neutral antagonist oxatomide, decreased inositol phosphate accumulation. The inverse agonists also decreased H1R gene expression and down-regulated H1R mRNA below basal expression, while basal H1R mRNA expression was maintained after oxatomide treatment. These results suggest that inverse agonists more potently alleviate allergy symptoms by not only inhibiting stimulus-induced up-regulation of H1R gene expression but also by suppressing basal histamine signaling through their inverse agonistic activity.

Histamine H4 receptors in normal conjunctiva and in vernal keratoconjunctivitis

BACKGROUND

While it is known that histamine is the primary mediator of ocular allergy, the presence and distribution of histamine receptors are not well documented in the human eye. Our aim was to evaluate histamine receptor expression in normal and vernal keratoconjunctivitis conjunctiva.

METHODS

Mucosal biopsies were obtained from conjunctiva of healthy donors and from tarsal conjunctiva of vernal patients. Immunostaining and semi-quantitative reverse-transcriptase polymerase chain reaction for H(1), H(2), H(3), and H(4) receptors were performed. Histamine receptor expression was also evaluated in conjunctival cell cultures exposed to histamine, interleukin-4, interleukin-5, interferon-γ and tumor necrosis factor-α.

RESULTS

Immunostaining for H(1) and H(2) receptors was slightly positive in normal and over-expressed in vernal tissues. H(3) receptors were rarely present in normal and inflamed conjunctiva. In striking contrast to control tissues, H(4) receptors were highly expressed in all inflamed tissues, particularly by stromal inflammatory cells. Semi-quantitative reverse-transcriptase polymerase chain reaction demonstrated an over-expression of H(1), H(2), and H(4) receptors in vernal vs control tissues. Notably, H(4) receptors were five times more expressed in vernal vs control tissues. In cell cultures, H(2) receptor expression was stimulated eight times the normal levels by interleukin-4 and three times by histamine, but the H(4) receptor was only slightly affected by stimulation with these mediators.

CONCLUSIONS

Increased expression of H1, and particularly of H(2) and H(4) receptors in vernal keratoconjunctival tissues indicate their important role in the pathogenesis of this disease. H(4) receptors may be a target in the treatment of allergic inflammation.

Albizia lebbeck suppresses histamine signaling by the inhibition of histamine H1 receptor and histidine decarboxylase gene transcriptions

Histamine plays major roles in allergic diseases and its action is mediated mainly by histamine H(1) receptor (H1R). We have demonstrated that histamine signaling-related H1R and histidine decarboxylase (HDC) genes are allergic diseases sensitive genes and their expression level affects severity of the allergic symptoms. Therefore, compounds that suppress histamine signaling should be promising candidates as anti-allergic drugs. Here, we investigated the effect of the extract from the bark of Albizia lebbeck (AL), one of the ingredients of Ayruvedic medicines, on H1R and HDC gene expression using toluene-2,4-diisocyanate (TDI) sensitized allergy model rats and HeLa cells expressing endogenous H1R. Administration of the AL extract significantly decreased the numbers of sneezing and nasal rubbing. Pretreatment with the AL extract suppressed TDI-induced H1R and HDC mRNA elevations as well as [(3)H]mepyramine binding, HDC activity, and histamine content in the nasal mucosa. AL extract also suppressed TDI-induced up-regulation of IL-4, IL-5, and IL-13 mRNA. In HeLa cells, AL extract suppressed phorbol-12-myristate-13-acetate- or histamine-induced up-regulation of H1R mRNA. Our data suggest that AL alleviated nasal symptoms by inhibiting histamine signaling in TDI-sensitized rats through suppression of H1R and HDC gene transcriptions. Suppression of Th2-cytokine signaling by AL also suggests that it could affect the histamine-cytokine network.

Involvement of protein kinase Cdelta/extracellular signal-regulated kinase/poly(ADP-ribose) polymerase-1 (PARP-1) signaling pathway in histamine-induced up-regulation of histamine H1 receptor gene expression in HeLa cells

The histamine H(1) receptor (H1R) gene is up-regulated in patients with allergic rhinitis. However, the mechanism and reason underlying this up-regulation are still unknown. Recently, we reported that the H1R expression level is strongly correlated with the severity of allergic symptoms. Therefore, understanding the mechanism of this up-regulation will help to develop new anti-allergic drugs targeted for H1R gene expression. Here we studied the molecular mechanism of H1R up-regulation in HeLa cells that express H1R endogenously in response to histamine and phorbol 12-myristate 13-acetate (PMA). In HeLa cells, histamine stimulation caused up-regulation of H1R gene expression. Rottlerin, a PKCδ-selective inhibitor, inhibited up-regulation of H1R gene expression, but Go6976, an inhibitor of Ca(2+)-dependent PKCs, did not. Histamine or PMA stimulation resulted in PKCδ phosphorylation at Tyr(311) and Thr(505). Activation of PKCδ by H(2)O(2) resulted in H1R mRNA up-regulation. Overexpression of PKCδ enhanced up-regulation of H1R gene expression, and knockdown of the PKCδ gene suppressed this up-regulation. Histamine or PMA caused translocation PKCδ from the cytosol to the Golgi. U0126, an MEK inhibitor, and DPQ, a poly(ADP-ribose) polymerase-1 inhibitor, suppressed PMA-induced up-regulation of H1R gene expression. These results were confirmed by a luciferase assay using the H1R promoter. Phosphorylation of ERK and Raf-1 in response to PMA was also observed. However, real-time PCR analysis showed no inhibition of H1R mRNA up-regulation by a Raf-1 inhibitor. These results suggest the involvement of the PKCδ/ERK/poly(ADP-ribose) polymerase-1 signaling pathway in histamine- or PMA-induced up-regulation of H1R gene expression in HeLa cells.

Antihistaminic, anti-inflammatory, and antiallergic properties of the nonsedating second-generation antihistamine desloratadine: a review of the evidence

The allergy cascade presents widespread inflammatory and proinflammatory activation, robust cytokine and chemokine signaling, and heterogeneous immune and endothelial responses that lead ultimately to the manifestations of allergic reaction. Histamine, a small peptide with inherent vasoactive properties, is released from granules contained within mast cells, basophils, lymphocytes, and other reservoirs and interacts with histamine receptors to regulate numerous cellular functions involved in allergic inflammation and immune modulation. Of the known histamine receptors, the H(1)-receptor is most clearly associated with potentiation of proinflammatory immune cell activity and enhanced effector function and is the prime focus of suppressive therapy. Second-generation oral H(1)-antihistamines, such as cetirizine, desloratadine, fexofenadine, levocetirizine, and loratadine, are mainstays of allergy treatment, acting as highly specific, long-acting H(1)-receptor agonists at its unique receptor. The ongoing identification of immune effector cells and mediators involved in the allergic cascade indicates that further research is necessary to define the role of antihistamines such as desloratadine in anti-inflammatory therapy.