Histamine H1 receptor cell membrane chromatography online high-performance liquid chromatography with mass spectrometry method reveals houttuyfonate as an activator of the histamine H1 receptor.

Allergy is an abnormal reaction of the body to an allergen. Histamine is responsible for many of the acute symptoms of allergic diseases. Many of the allergic and inflammatory actions of histamine are mediated by the histamine H1 receptor. In the present study, we established a two-dimensional histamine H1 receptor/cell membrane chromatography with online high-performance liquid chromatography and mass spectrometry method for screening potential histamine-activating components in a traditional Chinese medicine injection. The specification of the method was validated by screening, separating, and identifying a mixed standard solution of diphenhydramine hydrochloride, gefitinib, tamsulosin, and nitrendipine. The Yujin injection, an example of traditional Chinese medicine injection, was screened and potential allergic components acting on the histamine H1 receptor were identified. A Ca(2+) flux assay showed that houttuyfonate and Yujin injection induced calcium release in a dose-dependent manner. This suggests that houttuyfonate is an activator of the histamine H1 receptor. The mechanism of houttuyfonate activation involves phosphorylation of the inositol-1,4,5-trisphosphate receptor. In conclusion, this two-dimensional method can rapidly detect and enrich target components isolated from the Yujin injection. This indicates that individuals with an overexpression of the histamine H1 receptor should be aware of possible allergic reactions when receiving the Yujin injection.

The histamine H1-receptor mediates the motivational effects of novelty.

Novelty-induced arousal has motivational effects and can reinforce behavior. The mechanisms by which novelty acts as a reinforcer are unknown. Novelty-induced arousal can be either rewarding or aversive dependent on its intensity and the preceding state of arousal. The brain's histamine system has been implicated in both arousal and reinforcement. Histamine and histamine-1-receptor (H1R) agonists induced arousal and wakefulness in humans and rodents, e.g. by stimulating cortical acetylcholine (ACh) release. The H1R has also been implicated in processes of brain reward via interactions with the nigrostriatal- and mesolimbic dopamine (DA) systems. We asked whether the motivational effects of novelty-induced arousal are compromised in H1R knockout (KO) mice. The H1R-KO mice failed to develop a conditioned place-preference induced by novel objects. Even though they still explore novel objects, their reinforcing value is diminished. Furthermore, they showed impaired novelty-induced alternation in the Y-maze. Rearing activity and emotional behavior in a novel environment was also altered in H1R-KO mice, whereas object-place recognition was unaffected. The H1R-KO mice had higher ACh concentrations in the frontal cortex and amygdala (AMY). In the latter, the H1R-KO mice had also increased levels of DA, but a lower dihydrophenylacetic acid/DA ratio. Furthermore, the H1R-KO mice had also increased tyrosine hydroxylase immunoreactivity in the basolateral anterior, basolateral ventral and cortical AMY nuclei. We conclude that the motivational effects of novelty are diminished in H1R-KO mice, possibly due to reduced novelty-induced arousal and/or a dysfunctional brain reward system.

Differentiation of monocytes into macrophages induces the upregulation of histamine H1 receptor.

BACKGROUND: Histamine modulates several functions in human monocytes, macrophages, and dendritic cells. However, responses elicited by histamine differ depending on cell type, suggesting variable expression of histamine receptors in the monocyte/macrophage lineage. OBJECTIVE: We sought to examine whether the expression of H(1) receptors was regulated by cell differentiation of human monocytes into macrophages or dendritic cells. METHODS: Expression of H(1) receptor was evaluated by RT-PCR and western blot in monocytes, monocyte-derived macrophages (MDMs), monocyte-derived dendritic cells (DCs) and human lung macrophages (HLMs). RESULTS: Expression of H(1) receptor mRNA and protein was higher in HLMs and DCs than in monocytes. H(1) expression was approximately 15-fold and 4-fold higher in MDMs and HLMs, respectively, as compared with that seen in monocytes. H(1) receptor protein was undetectable in monocytes, whereas it was conspicuous in MDMs. Simultaneous analysis of H(2) and H(1) mRNA expression indicated that the H(2)/H(1) ratio decreased from 202.7 +/- 14.8 in monocytes to 2.2 +/- 0.4 in MDM and 39.5 +/- 5.0 in DCs. Incubation of monocytes with histamine neither affected intracellular Ca(2+) concentrations nor influenced IL-8 production. In contrast, histamine rapidly induced a Ca(2+) signal and stimulated IL-8 production in MDMs. Both effects were inhibited by H(1) blockade with levocetirizine, but not by H(2) blockade with ranitidine. CONCLUSIONS: Differentiation of monocytes into macrophages or dendritic cells is associated with profound changes of histamine receptor expression. Upregulation of H(1) receptors confers on macrophages the capacity of being activated by histamine. CLINICAL IMPLICATIONS: Regulation of H(1) and H(2) receptor expression in the monocyte/macrophage lineage can be relevant to the pathogenesis of allergic inflammation.

Histamine-induced ion secretion across rat distal colon: involvement of histamine H1 and H2 receptors.

The aim of the present study was to investigate the effect of histamine, a product of e.g. mast cells, on short-circuit current (I(sc)) across rat distal colon. Histamine concentration-dependently stimulated an increase in I(sc), which often was preceded by a transient negative current. Neither a release of neurotransmitters nor a release of prostaglandins contributed to the histamine response. The histamine-induced increase in I(sc) was blocked by the histamine H(1) antagonist, pyrilamine, but was resistant against the histamine H(2) antagonist, cimetidine. Conversely, the histamine H(1) agonist, TMPH (2-(3-trifluoromethylphenyl)histamine), exclusively evoked an increase in I(sc), whereas the histamine H(2) agonist, amthamine, evoked only a decrease in I(sc) suggesting that stimulation of different types of histamine receptors is responsible for the two phases of the response evoked by native histamine. Histamine induces the opening of glibenclamide-sensitive Cl(-) channels and of charybdotoxin-sensitive K(+) channels in the apical membrane as demonstrated by experiments at basolaterally depolarized epithelia. A further action site is the basolateral membrane, because histamine stimulates a charybdotoxin- and tetrapentylammonium-sensitive K(+) conductance in this membrane as observed in tissues, in which the apical membrane was permeabilized with an ionophore, nystatin. The increase in I(sc) evoked by histamine was blocked after depletion of intracellular Ca(2+) stores with cyclopiazonic acid and after blockade of inositol 1,4,5-trisphosphate (IP(3)) receptors, suggesting a release of stored Ca(2+). This was confirmed by the observation that the histamine H(1) agonist TMPH induced an increase in the fura-2 ratio signal of epithelial cells within isolated colonic crypts. Consequently, the mediator histamine seems to stimulate both histamine H(1) and H(2) receptors, from which the former seems to be prominently involved in the induction of epithelial chloride secretion.

Selective expression of histamine receptors H1R, H2R, and H4R, but not H3R, in the human intestinal tract.

BACKGROUND AND AIMS: Histamine is known as a regulator of gastrointestinal functions, such as gastric acid production, intestinal motility, and mucosal ion secretion. Most of this knowledge has been obtained from animal studies. In contrast, in humans, expression and distribution of histamine receptors (HR) within the human gastrointestinal tract are unclear. METHODS: We analysed HR expression in human gastrointestinal tissue specimens by quantitative reverse transcription-polymerase chain reaction and immunostaining. RESULTS: We found that H1R, H2R, and H4R mRNA were expressed throughout the gastrointestinal tract, while H3R mRNA was absent. No significant differences in the distribution of HR were found between different anatomical sites (duodenum, ileum, colon, sigma, and rectum). Immunostaining of neurones and nerve fibres revealed that H3R was absent in the human enteric nervous system; however, H1R and H2R were found on ganglion cells of the myenteric plexus. Epithelial cells also expressed H1R, H2R and, to some extent, H4R. Intestinal fibroblasts exclusively expressed H1R while the muscular layers of human intestine stained positive for both H1R and H2R. Immune cells expressed mRNA and protein for H1R, H2R, and low levels of H4R. Analysis of endoscopic biopsies from patients with food allergy and irritable bowel syndrome revealed significantly elevated H1R and H2R mRNA levels compared with controls. CONCLUSIONS: We have demonstrated that H1R, H2R and, to some extent, H4R, are expressed in the human gastrointestinal tract, while H3R is absent, and we found that HR expression was altered in patients with gastrointestinal diseases.

Histamine H1 receptor antagonist blocks histamine-induced proinflammatory cytokine production through inhibition of Ca2+-dependent protein kinase C, Raf/MEK/ERK and IKK/I kappa B/NF-kappa B signal cascades.

Histamine H1 receptor (H1R), a therapeutic target for alleviation of acute allergic reaction, may be also involved in mediating inflammatory responses via effects on cytokine production. However, the mechanisms whereby histamine induces cytokine production are poorly defined. In this study, we comprehensively investigated the signaling pathway involved in cytokine expression caused by histamine, using native human epidermal keratinocytes. We confirmed the expression of functional H1R by reverse transcription-polymerase chain reaction (RT-PCR), Western blotting and histamine-induced Ca(2+) elevation. Histamine induced concentration- and time-dependent production of granulocyte-macrophage-colony stimulating factor (GM-CSF), interleukin (IL)-8 and IL-6, which was completely blocked by olopatadine, an H1 antagonist. Histamine activated the phosphorylation of protein kinase C (PKC), c-Raf, mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK), extracellular signal-regulated kinase (ERK), I kappa B kinase (IKK), inhibitory kappa B (I kappa B)-alpha and nuclear factor-KB (NF-kappa B) p65, which was inhibited by Ro-31-8220, a PKC inhibitor. Also, Ro-31-8220 significantly suppressed the expression of these cytokines. BAPTA-AM, an intracellular Ca(2+) chelator, also reduced PKC phosphorylation and cytokine expression. PD98059, a MEK inhibitor, and BAY 11-8702, an I kappa B-alpha inhibitor, reduced ERK and NF-kappa B cascade activation, respectively, with little effect on PKC phosphorylation. PD98059 preferentially inhibited GM-CSF production whereas BAY 11-8702 prevented IL-8 and IL-6 production. Furthermore, in addition to the above cytokines, histamine stimulated the biosynthesis and/or release of numerous keratinocyte-derived mediators, which are probably regulated by the ERK or NF-kappa B cascades. Our study suggests that histamine activates Ca(2+)-dependent PKC isoforms that play crucial roles in the activation of Raf/MEK/ERK and IKK/I kappa B/NF-kappa B cascades, leading to up-regulation of cytokine expression. Thus, the anti-inflammatory benefit of H1 antagonists may be in part due to prevention of cytokine production.

Homologous and heterologous phosphorylations of human histamine H1 receptor in intact cells.

Homologous and heterologous phosphorylations of histamine H1 receptor (H1R) in intact cells were investigated using Chinese hamster ovary cells stably co-expressing c-myc-tagged human histamine H1 and muscarinic M3 receptors. Increase in histamine-induced homologous phosphorylation of H1R was induced in a dose- and time-dependent manner. Maximum phosphorylation of H1R by 8-fold over the basal level was induced 1 min after the stimulation, and the increased phosphorylation level was maintained over 40 min. M3 receptor-mediated heterologous phosphorylation of H1R reached maximum by 2-fold over the basal level at 5 min after the stimulation and then rapidly returned to the basal level by 40 min after the stimulation. Histamine-induced phosphorylation of H1R was partially inhibited by three protein kinase inhibitors including Ro-31-8220 for protein kinase C (PKC), KN-93 for calcium/calmodulin-dependent kinase II (CaMKII), and KT5823 for protein kinase G (PKG), while, M3-receptor-mediated phosphorylation of H1R was completely inhibited by Ro 31-8220. Protein kinase activators including phorbol 12-myristate 13-acetate (PMA), 8-bromo-cyclic GMP (8-Br-cGMP), and 8-bromo-cyclic AMP (8-Br-cAMP) induced increases in H1R phosphorylation. Increased phosphorylation of H1R, by 5-fold over the basal level, induced with a combination of PMA, 8-Br-cGMP, and 8-Br-cAMP was still lower than that with histamine. It was suggested that H1R-mediated H1R phosphorylation involves the activation of PKC, CaMKII, PKG, and other unidentified kinases including G-protein coupled receptor kinases (GRKs) and that PKC is solely involved in M3 receptor-mediated H1R phosphorylation.

Immunohistochemical localization of histamine receptors in rat cochlea.

OBJECTIVE: Histamine may have physiologic functions in the inner ear. The locations of histamine receptors, however, have not yet been identified in the mammalian cochlea. The aim of this study was to investigate the localization of histamine receptor subtypes (H1, H2, and H3 receptors) in rat cochlea. METHODS: Immunohistochemistry was performed with antibodies specific for each of the histamine receptors (H1, H2, and H3). To identify the type I and II spiral ganglion cells in the cochlea, some cryostat sections were double stained with antibodies to both a histamine receptor and neurofilament 200 kD, which predominantly stains type II spiral ganglion cells in the cochlea. RESULTS: All H1, H2, and H3 receptor immunoreactive staining was limited to the spiral ganglion cells of the cochlea. Spiral ganglion cells with positive immunoreactivity to the neurofilament 200 kD antibody were stained only slightly by histamine H1, H2, and H3 receptor antibodies, indicating that histamine receptor immunoreactivity is specific to type I ganglion cells. CONCLUSIONS: These findings indicate that histamine receptors are present in the cochlea and support the hypothesis that histamine plays a physiologic role in the cochlea.

Domain swapping in the human histamine H1 receptor.

G-protein-coupled receptors (GPCRs) represent the largest family of receptors involved in transmembrane signaling. Although these receptors were generally believed to be monomeric entities, accumulating evidence supports the presence of GPCRs in multimeric forms. Here, using immunoprecipitation as well as time-resolved fluorescence resonance energy transfer to assess protein-protein interactions in living cells, we unambiguously demonstrate the occurrence of dimerization of the human histamine H(1) receptor. We also show the presence of domain-swapped H(1) receptor dimers in which there is the reciprocal exchange of transmembrane domain TM domains 6 and 7 between the receptors present in the dimer. Mutation of aspartate(107) in transmembrane (TM) 3 or phenylalanine(432) in TM6 to alanine results in two radioligand-binding-deficient mutant H(1) receptors. Coexpression of H(1)D(107) A and H(1)F(432)A, however, results in a reconstituted radioligand binding site that exhibits a pharmacological profile that corresponds to the wild-type H(1) receptor. Interestingly, the H(1) receptor radioligands [(3)H]mepyramine and [(3)H]-(-)-trans-1-phenyl-3-N,N-dimethylamino-1,2,3,4-tetrahydronaphthalene show differential saturation binding values (B(max)) for wild-type H(1) receptors but not for the radioligand binding site that is formed upon coexpression of H(1) D(107)A and H(1) F(432)A receptors, suggesting the presence of different H(1) receptor populations.

New concepts of histamine receptors and actions.

Histamine and antihistamines are so deeply woven into the fabric of allergic diseases that it is sometimes difficult to see how this field could advance beyond our current, potent histamine H1-receptor drugs. Investigations of other actions of histamine and the identification of H2, H3, and now H4 receptors have suddenly reignited the search for new mono- and multi-receptor-specific agonists and antagonists. There is great excitement due to preliminary findings that H3 receptors act as neural inhibitory autoreceptors, and H4 receptors might modulate immune cell functions.

H1 and H2 histamine receptors are absent on Langerhans cells and present on dermal dendritic cells.

Human monocyte-derived dendritic cells (MoDC) have both histamine H1 and H2 receptors and can induce CD86 expression by histamine. Nevertheless, it has not been reported whether human epidermal Langerhans cells (LC) have histamine receptors or not. In this study, using RT-PCR, we investigated the expression of H1 and H2 receptor mRNA on DC with the features of LC (LC-like DC) that were generated in vitro from peripheral blood monocytes, LC derived from CD34+ hematopoietic progenitor cells, and LC obtained from human epidermis. We compared the histamine-induced CD86 expression among these cells. In contrast to MoDC, LC and LC-like DC did not express H1 or H2 receptors. In addition, they could not augment the CD86 expression by histamine. Interestingly, when transforming growth factor-beta1 (TGF-beta1) was added to the culture of MoDC, the expression of H1 and H2 receptors and the histamine-induced CD86 expression were abrogated in a concentration-dependent fashion. Finally, in the assessment of the cell surface expression of histamine receptors using fluorescence-labeled histamine, histamine could bind to MoDC and dermal dendritic cells obtained from the skin, whereas there was no specific binding of histamine to LC-like DC or LC obtained from the skin. These data suggest that LC do not express either H1 or H2 receptors, mainly because of the effect of TGF-beta1. This made a striking contrast with the expression of the functional H1 and H2 receptors on MoDC and dermal dendritic cells.

[The role of positron emission tomography in neuropharmacology in the living human brain and drug development].

Neuroimaging is a powerful and innovative tool for studying the pathology of psychiatric and neurological diseases and, more recently, for studying the drugs used in their treatment. Technological advances in imaging have made it possible to noninvasively extract information from the human brain regarding a drug's mechanism and site of action. Until now, our understanding of human brain pharmacology has depended primarily on indirect assessments or models derived from animal studies. However, the advent of multiple techniques for human brain imaging allows researchers to focus directly on human pharmacology and brain function. In this review article, our PET studies on histaminergic neuron system were presented as an example. We have developed and used the PET techniques for 10 years in order to examine the functions of histaminergic neurons in the living human brain. This review outlines available PET techniques and examines how these various methods have already been applied to the drug development process and neuropharmacology in the living human brain.

Histamine H(1) receptors in patients with Alzheimer's disease assessed by positron emission tomography.

Cerebral histamine H(1) receptor binding was measured in vivo in 11 normal subjects (six young and five old) and 10 patients with Alzheimer's disease by positron emission tomography and [11C]doxepin, a radioligand for H(1) receptors. The parametric images describing the tracer kinetics were generated by either compartmental or graphical analysis, and were examined statistically on region-of-interest and voxel-by-voxel bases. The binding potential of H(1) receptors showed a significant decrease particularly in the frontal and temporal areas of the Alzheimer's disease brain compared to the old, normal subjects. In addition, the receptor binding correlated closely to the severity of Alzheimer's disease assessed by the Mini-Mental State Examination score within several brain areas. The ratio of K1 values between the brain areas and the cerebellum was used as a relative measure of regional cerebral blood flow which decreased in the frontal and temporal areas of the Alzheimer's disease brain. However, the difference in the binding potential (total concentration of receptor/equilibrium dissociation constant) between the Alzheimer's disease patients and the old, normal subjects was greater than that in the cerebral blood flow, and the rate of decrease in the binding potential with the progression of Alzheimer's disease was greater than the rate of decrease in the cerebral blood flow. This study reveals the predominant disruption of the histaminergic neurotransmission in the neurodegenerative processes of Alzheimer's disease. This study suggests that the decline of the histamine receptor binding might play a substantial role in the cognitive deficits of Alzheimer's disease patients.

Expression of histamine H1 and H2 receptors in human nasal mucosa.

mRNA encoding histamine H1 and H2 receptors were detected in the human nasal mucosa using reverse transcriptase-polymerase chain reaction. The possibility of local release in connection with specific target receptors suggests a role for histamine in the regulation of vascular tone, glandular secretion and epithelial functions.

[Can one adjust the distribution of a drug in an organism to its target sites? The example of antihistaminics (anti-H1) and cetirizine]. / Peut-on adapter la distribution d'un médicament dans l'organisme aux localisations de ses cibles? L'exemple des antihistaminiques (anti H1) et de la cétirizine.

When comparing the fate of a drug in the body with the location of its receptors, it appears that a large amount of the administered dosage will never reach these receptors. Thus this large amount is useless in terms of drug efficacy whereas it may generate side of toxic effects in other tissues. An attempt to optimize drug distribution is to limit or even to suppress its useless localisations. This is possible with H1 antagonists as these drugs develop benefic effects in organs which are distinct from those where toxic effects may occur. Cetirizine is an example of choice of this strategy. It is poorly distributed into tissues, especially in heart and liver which favors preferential binding at its target H1 selected receptors.

Positron emission tomographic study of central histamine H1-receptor occupancy in human subjects treated with epinastine, a second-generation antihistamine.

Histamine H1-receptor occupancy in the human brain was measured in healthy young volunteers by positron emission tomography (PET) using [11C]doxepin. d-Chlorpheniramine, a selective and classical antihistamine, occupied 76.8 +/- 4.2% of the averaged values of available histamine H1 receptors in the frontal cortex after its administration in a single oral dose of 2 mg. Epinastine, a non-sedative antihistamine, occupied 13.2 +/- 18.5% of the available H1 receptors in the human frontal cortex after its administration in a single oral dose of 20 mg. There was significant correlation between H1 receptor occupancy by epinastine and its plasma concentration in each subject. PET data on the human brain were essentially compatible with those on H1-receptor occupancy in the guinea pig brain as determined by an in vivo binding technique, although for the same H1-receptor occupancy, the dose was less in humans than in guinea pigs. Our PET studies demonstrated that receptor occupancy by a second-generation H1 antagonist, epinastine, was less than 20% of the total H1 receptors, and that the low receptor occupancy was closely related to the low incidence of central side effects.