Histamine Receptor Research Articles

IN VITRO ANTI-EMETIC EFFECT OF METHANOL ROOT EXTRACT OF TERMINALIA AVICENNIOIDES GUILL. & PERR. ON ISOLATED RABBIT ILEUM

Abstract Background: Terminalia avicennioides is a medicinal plant used traditionally in Nigeria to treat numerous ailments and disorders which include coughs, purgative and emetic. Objective: This study scientifically evaluated the probable mechanism of the anti-emetic activity of methanol root extract of Terminalia avicennioides Guill. & Perr. on histaminergic and serotonergic receptors of isolated rabbit ileum. Methodology: Fresh root bark was extracted using methanol and the antiemetic effect was evaluated by experimenting on a small segment (3 cm) of isolated rabbit ileum, using the data capsule (Ugo Basile) and single chamber isolated tissue apparatus. Varying concentrations of histamine and serotonin (0.05, 0.1, 0.2, and 0.4 mg/ml) were used to obtain contractions as they act on histamine and serotonergic receptors respectively. Results: META (0.05 mg/ml, 0.1 mg/ml, 0.2 mg/ml, and 0.4 mg/ml) exhibited a significant concentration-dependent decrease at p<0.05 in histamine-induced and serotonin-induced contractions on isolated rabbit ileum from the data capsule reading with percentage inhibition of 43.22, 53.96, 75.35, 85.58 % and 21.62, 49.50, 78.67 and 86.96 % respectively for the different concentrations. Conclusion: The study showed that methanol root extract of Terminalia avicennioides acts on cholinergic (muscarinic), histaminergic, and serotonergic receptors of isolated rabbit ileum by inhibitory spasmolytic action against smooth muscle contractility, hence its ability to possess anti-emetic effect to relieve vomiting.

Characteristics of histamine H4 receptor agonist-induced allergic conjunctivitis model in Guinea pigs

Histamine is strongly associated with the onset of allergic conjunctivitis. The most recent cloned histamine H4 receptor antagonist is highly expected as a new therapeutic drug candidate. As a model for a therapeutic drug targeting the histamine H4 receptor, a mouse model in which conjunctivitis symptoms are induced by instilling 4-methylhistamine, a histamine H4 receptor agonist, has been reported. However, the affinity of the H4 receptor for histamine varies in species, and it is known that the histamine binding affinity for the guinea pig H4 receptor is closer to that for human receptor than mice receptor. In this paper, we investigated a possibility that a guinea pig model would become a drug efficacy evaluation model with higher evaluation accuracy than the mouse model.As a result, hyperemia was observed in the conjunctivae and iris of guinea pigs after instillation of 4-methylhistamine and specifically suppressed by the histamine H4 receptor antagonist. Unlikely to the previously reported mouse model, however, none of edema, increased vascular permeability or scratching behavior was observed, suggesting that there may be differences between mice and guinea pigs not only in the binding affinity of histamine to the H4 receptor but also in the biological reaction to 4-methylhistamine. Although the symptoms of allergic conjunctivitis do not appear comprehensively in the guinea pig model, results of this study indicated a possibility that this model can be used as a simple screening model in the early stages of drug development.

Bicalutamide, an androgen receptor antagonist, effectively alleviate allergic rhinitis via suppression of PI3K–PKB activity

ObjectivesTo investigate the therapeutic effect of Bicalutamide, an androgen receptor antagonist on the onset and development of allergic rhinitis in an animal model.Methods40 male BALB/c mice were randomly divided into five groups (eight mice per group). Aluminum hydroxide powder was used as an adjuvant, combined with Ovalbumin (OVA) to establish the mouse model of allergic rhinitis via ultrasonic nebulization of OVA to stimulate the nasal cavity. Mice in Bica#1 group were intraperitoneally injected with 0.02 mg Bicalutamide/0.5 ml of normal saline daily for 7 consecutive days; mice in Bica#2 group were administered 0.02 mg Bicalutamide/0.5 ml of normal saline via intraperitoneal injection for 5 consecutive days, and then the same amount of normal saline was injected intraperitoneally for 2 consecutive days. Enzyme-linked immunosorbent assay was adopted to detect the serological levels of IgE, IL-4, and IL-6 production. Eosinophil infiltration was observed under microscope after hematoxylin and eosin staining of nasal mucosa. Quantitative PCR and Western blot were employed for determination of histamine receptors mRNA expression and PI3K/PKB associated protein levels, respectively.ResultsHistological analysis shown that allergic lesion was induced after OVA sensitization. Intraperitoneal injection with 0.02 mg Bicalutamide daily for 7 consecutive days significantly reduced the allergic lesion; however, mice injected with the same amount of normal saline at the same time demonstrated no allergic rhinitis symptoms. In addition, there was a significant reduction in eosinophils number in Bicalutamide treated mice (n = 8) compared to the OVA group (n = 8) (OVA: 19.6 ± 5.3 vs. Bica#1: 7.7 ± 0.8 vs. Bica#2: 9.4 ± 1.2, both p < 0.01). Furthermore, ELISA results revealed that the serological levels of IgE (OVA: 17.3 ± 1.7 µg/ml vs. Bica#1: 9.2 ± 0.6 vs. Bica#2: 10.4 ± 2.3, both p < 0.05), IL-4 (OVA: 164.3 ± 5.1 pg/ml vs. Bica#1: 110.2 ± 3.1 vs. Bica#2: 115.3 ± 4.1, both p < 0.05) and IL-6 (OVA: 167.3 ± 3.7 pg/ml vs. Bica#1: 117.5 ± 6.5 vs. Bica#2: 114.8 ± 2.4, both p < 0.05) were significantly decreased after two different dosage of Bicalutamide treatment. Similarly, histamine receptors in mast cells were significantly reduced after two different dosage of Bicalutamide treatment. More importantly, p-PKB protein was notably reduced after two different dosage of Bicalutamide treatment compared to the OVA group, mTOR protein levels were also down regulated after two different dosage of Bicalutamide treatment.ConclusionsOur data demonstrated that androgen receptor antagonist Bicalutamide can significantly alleviate allergic rhinitis lesion in the animal model. PI3K/PKB activity in mast cells was suppressed after Bicalutamide injection. Our results provide important implication in allergic rhinitis prevention and treatment.

Histamine via histamine H1 receptor enhances the muscarinic receptor-induced calcium response to acetylcholine in an enterochromaffin cell model.

As a prerequisite for serotonin secretion, the P‐STS ileal enterochromaffin cell line responds to acetylcholine (ACh) stimulation with an increase in intracellular calcium mediated by the muscarinic ACh receptor M3 (M3R). Histamine increases intracellular calcium via histamine H1 receptor (H1R) in P‐STS cells and pre‐incubation with histamine specifically augments the response to ACh but not to epinephrine or nicotine. We aimed to elucidate whether histamine receptors are involved in this synergism. Astonishingly, HEK‐293 T cells—known to express M3R, but only a very low amount of histamine receptor messenger RNA—showed a similar enhancement of the calcium response to ACh by pre‐incubation with histamine. Despite the much lower level of H1R protein detected in HEK‐293 T cells as compared to P‐STS cells, in both cell lines pre‐treatment with H1R antagonists inhibited the synergism between histamine and ACh. No indication for an involvement of histamine H2 or H4 receptors in the synergism was found. Furthermore, pre‐incubation with the cAMP‐inducing compound forskolin had no influence on the intracellular calcium response to ACh. Serotonin secretion from P‐STS cells was increased after challenge with ACh and histamine added simultaneously compared to ACh alone, suggesting that histamine increases ACh‐induced serotonin secretion from enterochromaffin cells. In conclusion, our data suggest that histamine enhances the M3R‐mediated intracellular calcium response to ACh via activation of H1R. This probably increases serotonin secretion from enterochromaffin cells and thereby affects intestinal motility in histamine intolerance, food allergies and irritable bowel syndrome.

VIRTUAL TARGET CONSTRUCTION FOR DISCOVERY OF HUMAN HISTAMINE H4 RECEPTOR LIGANDS EMPLOYING A STRUCTURE-BASED VIRTUAL SCREENING APPROACH

Objective: This study aimed to construct a virtual target to be used in structure-based virtual screening (SBVS) campaigns to discover ligands for human histamine receptor H4 (hHRH4). Methods: The virtual targets construction was initiated by hHRH4 homology modeling, followed by molecular docking of seliforant to the homolog model, and the virtual target candidate was constructed. The hHRH4 complexed to seliforant was subjected to molecular dynamics (MD) simulations in 100 ns. Finally, the pose with the least free energy of binding from the MD simulations was selected for further validation through re-docking simulations. All simulations were conducted by using the YASARA-Structure program package. Results: This study resulted in one validated target for SBVS protocols development. All RMSD values in the internal validation in snapshot 519 molecular dynamics simulation results were less than 2 Å, and this hHRH4 homology model is valid as a virtual target in an SBVS protocol. Moreover, using the clusterization module on MD simulations analysis, ten different virtual targets were available for further utilization. Conclusion: Virtual targets resulted from this study offer more possibilities to construct SBVS protocols to identify hHRH4 ligands. The validated virtual target and the ten different virtual targets resulted from clusterization can be accessed in the following GitHub repository: https://github.com/nugrahagerry/hHRH4.

Mast cells selectively target large cholangiocytes during biliary injury via H2HR-mediated cAMP/pERK1/2 signaling.

Bile ducts are heterogenous in structure and function, and primary sclerosing cholangitis (PSC) damages specific bile ducts leading to ductular reaction (DR), mast cell (MC) infiltration, increased histamine release, inflammation, and fibrosis. Bile duct ligation (BDL) induces large duct damage via cyclic adenosine monophosphate (cAMP)/extracellular signal‐related protein kinase (ERK) signaling, and large cholangiocytes express H2 histamine receptor (H2HR). We evaluated how MCs interact with large cholangiocytes during cholestasis. Male wild‐type (WT) and MC‐deficient (Kit W‐sh ) mice 10–12 weeks of age were subjected to BDL for 7 days. Select Kit W‐sh mice were injected with MCs pretreated with control or H2HR antagonist (ranitidine, 25 μm, 48 h) via tail vein injection. In vitro, MC migration toward small mouse cholangiocytes (SMCCs) and large mouse cholangiocytes (LMCCs) treated with lipopolysaccharide or histamine (±ranitidine) was measured. LMCCs were stimulated with MC supernatants pretreated with control, α‐methyl‐dl‐histidine (to block histamine release), or ranitidine. Liver damage, large duct DR/senescence, inflammation, fibrosis, and cAMP/ERK immunoreactivity increased in BDL WT and Kit W‐sh +MC mice but decreased in BDL Kit W‐sh and Kit W‐sh +MC‐H2HR mice. In vitro, MCs migrate toward damaged LMCCs (but not SMCCs) blocked by inhibition of H2HR. Loss of MC histamine or MC‐H2HR decreases LMCC proliferation, senescence, H2HR, and cAMP/ERK levels. Human PSC livers have increased MC number found near DR, senescent ducts, and H2HR‐positive ducts. Conclusion: Infiltrating MCs preferentially interact with large ducts via H2HR signaling promoting biliary and liver damage. Mediation of MCs may be a therapeutic strategy for PSC.

Anti-histamine effects of dipotassium glycyrrhizinate on lung fibroblasts, implicating its therapeutic mechanism for pulmonary fibrosis.

To examine the possible anti-histamine effects of dipotassium glycyrrhizinate (DG), a dipotassium salt of glycyrrhizic acid, on histamine-mediated lung fibroblast activation, differentiation and proliferation; to investigate the potential and underlying mechanisms for pulmonary fibrosis (PF) treatment. Rat primary lung fibroblasts were extracted to establish cell models; histamine, DG and loratadine (LTD, a histamine receptor antagonist) were applied. Cell proliferation, migration and cell cycle were explored; intracellular signal proteins were detected; mitochondrial membrane potential was examined. The anti-histamine effects of DG were found in a similar pattern of LTD on lung fibroblasts. DG inhibited histamine-induced cell activation, proliferation and migration; DG altered histamine-mediated mitochondrial membrane potentials. DG reduced the histamine-induced PAR-2 (a tryptase receptor) expression to impair mast cell tryptase co-working. Histamine-induced expressions of MMP-2, FAK, TNF-α, P38, iNOS were decreased by DG, while Bax and caspase-3, P53 were increased by DG against histamine effects. Histamine drove cells from G0/G1 to S phases, whereas DG rested cells by inhibiting G0/G1 and G2/M phases. This study provided the evidences that DG can inhibit histamine-induced effects on lung fibroblasts and promote apoptosis of abnormally activated lung fibroblasts, implicating its potential therapeutic mechanisms against PF development, also for those histamine-related diseases.

Omalizumab for the management of refractory chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a heterogeneous, systemic, primarily mast cell-driven disease with sudden appearance of wheals with or without angioedema with pruritus for more than 6 weeks. It affects 0.3%–0.6% of the general population. CSU is a complex immune-mediated disease due to induction of basophil and mast cell degranulation with more than one mechanism of auto-allergy Type I (mediated by specific immunoglobulin E (IgE) targeting auto-allergens as thyroperoxidase, etc.) and auto-immunity Type II (mediated by IgG auto-antibodies binding to alpha-subunit of high affinity IgE receptor [FcERI]) with increased expression of Type II cytokines and activation of coagulation cascade. Pruritus is due to sensory nerve activation by histaminergic pathway (Histamine receptors- H1R and H4R) and histamine-independent pathway (Substance P, Capsacin, and Reactive oxygen species, etc.). The international guidelines on CSU recommend to treat CSU until it is gone. The use of second-generation anti-histamine in effective dose as the first-line treatment and up-dosing of second generation (SgAH) up to four-fold is recommended in treatment-resistant patients. The humanized anti-IgE monoclonal antibody Omalizumab has been shown to have both excellent safety profiles as the only third-line treatment option in anti-histamine-resistant urticaria (approved by United States Food and Drug Administration in August, 2014). However, there are several questions to be answered with reference to the optimal dose, duration, and the rates of long-term remission with omalizumab. Other biologics as Ligelizumab are less well studied but have an important role in the specific type of omalizumab-resistant CSU. In this review, we will summarize the role of omalizumab in anti-histamine resistant CSU.

First person – Sarit Pal

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Sarit Pal is first author on ‘ Nuclear localization of histamine receptor 2 in primary human lymphatic endothelial cells’, published in BiO. Sarit conducted the research described in this article while a graduate research assistant in Dr Anatoliy Gashev's lab at Texas A&M University, Bryan, TX, USA. He is now a senior field application scientist at BICO LLC, Waltham, MA, USA, investigating histamine signalling in the regulation of lymphatic immunophysiology.

Nuclear localization of histamine receptor 2 in primary human lymphatic endothelial cells.

ABSTRACTHistamine exerts its physiological functions through its four receptor subtypes. In this work, we report the subcellular localization of histamine receptor 2 (H2R), a G protein-coupled receptor (GPCR), which is expressed in a wide variety of cell and tissue types. A growing number of GPCRs have been shown to be localized in the nucleus and contribute toward transcriptional regulation. In this study, for the first time, we demonstrate the nuclear localization of H2R in lymphatic endothelial cells. In the presence of its ligand, we show significant upregulation of H2R nuclear translocation kinetics. Using fluorescently tagged histamine, we explored H2R-histamine binding interaction, which exhibits a critical role in this translocation event. Altogether, our results highlight the previously unrecognized nuclear localization pattern of H2R. At the same time, H2R as a GPCR imparts many unresolved questions, such as the functional relevance of this localization, and whether H2R can contribute directly to transcriptional regulation and can affect lymphatic specific gene expression. H2R blockers are commonly used medications that recently have shown significant side effects. Therefore, it is imperative to understand the precise molecular mechanism of H2R biology. In this aspect, our present data shed new light on the unexplored H2R signaling mechanisms. This article has an associated First Person interview with the first author of the paper.

Meclizine and Metabotropic Glutamate Receptor Agonists Attenuate Severe Pain and Ca2+ Activity of Primary Sensory Neurons in Chemotherapy-Induced Peripheral Neuropathy.

Chemotherapy-induced peripheral neuropathy (CIPN) affects ∼68% of patients undergoing chemotherapy, causing debilitating neuropathic pain and reducing quality of life. Cisplatin is a commonly used platinum-based chemotherapeutic drug known to cause CIPN, possibly by causing oxidative stress damage to primary sensory neurons. Metabotropic glutamate receptors (mGluRs) are widely hypothesized to be involved in pain processing and pain mitigation. Meclizine is an H1 histamine receptor antagonist known to have neuroprotective effects, including an anti-oxidative effect. Here, we used a mouse model of cisplatin-induced CIPN using male and female mice to test agonists of mGluR8 and Group II mGluR as well as meclizine as interventions to reduce cisplatin-induced pain. We performed behavioral pain tests, and we imaged Ca2+ activity of the large population of dorsal root ganglia (DRG) neurons in vivo For the latter, we used a genetically-encoded Ca2+ indicator, Pirt-GCaMP3, which enabled us to monitor different drug interventions at the level of the intact DRG neuronal ensemble. We found that CIPN increased spontaneous Ca2+ activity in DRG neurons, increased number of Ca2+ transients, and increased hyper-responses to mechanical, thermal, and chemical stimuli. We found that mechanical and thermal pain caused by CIPN was significantly attenuated by the mGluR8 agonist, (S)-3,4-DCPG, the Group II mGluR agonist, LY379268, and the H1 histamine receptor antagonist, meclizine. DRG neuronal Ca2+ activity elevated by CIPN was attenuated by LY379268 and meclizine, but not by (S)-3,4-DCPG. Furthermore, meclizine and LY379268 attenuated cisplatin-induced weight loss. These results suggest that Group II mGluR agonist, mGluR8 agonist, and meclizine are promising candidates as new treatment options for CIPN, and studies of their mechanisms are warranted.SIGNIFICANCE STATEMENT Chemotherapy-induced peripheral neuropathy (CIPN) is a painful condition that affects most chemotherapy patients and persists several months or longer after treatment ends. Research on CIPN mechanism is extensive but has produced only few clinically useful treatments. Using in vivo GCaMP Ca2+ imaging in live animals over 1800 neurons/dorsal root ganglia (DRG) at once, we have characterized the effects of the chemotherapeutic drug, cisplatin and three treatments that decrease CIPN pain. Cisplatin increases sensory neuronal Ca2+ activity and develops various sensitization. Metabotropic glutamate receptor (mGluR) agonist, LY379268 or the H1 histamine receptor antagonist, meclizine decreases cisplatin's effects on neuronal Ca2+ activity and reduces pain hypersensitivity. Our results and experiments provide insights into cellular effects of cisplatin and drugs preventing CIPN pain.

Effectiveness of bilastine and fexofenadine among allergic Rhinitis patients in Ranchi, Jharkhand, India.

Allergic rhinitis is a worldwide health problem which impairs quality of life and interferes with daily activities. Untreated allergic rhinitis also carries a significant financial burden for the society. Bilastine, a novel second-generation antihistaminic drug that is highly selective for the H1 histamine receptor, has a rapid onset and prolonged duration of action. Thus, the aim of our study was to compare the effectiveness of bilastine and fexofenadine in treatment of allergic Rhinitis patients. 104 patients were enrolled who have fulfilled the inclusion criteria for the study from the OPD of Ear, Nose and Throat Department. Patients were divided randomly in two groups A and B. Patients of group A were allowed to take tab Bilastine 20 mg OD whereas, patients of group B were allowed to take tab. Fexofenadine Hydrochloride 120 mg OD orally for two weeks. The baseline Total Nasal Symptom Score (TNSS) were compared between two groups. The study findings showed that the mean TNSS was significantly reduced in our study group. Baseline TNSS was 13.55 and 13.45 in Group A and Group B respectively. Reduction in this parameter first become apparent in the 24 hours and maintained till 2nd week. Bilastine showed significant improvement in quality of life of Allergic rhinitis patients and proved to be more effective than fexofenadine in reducing the TNSS score, when used alone in allergic rhinitis patient.

Expression pattern and prognostic potential of histamine receptors in epithelial ovarian cancer

PurposeDespite recent advances in the treatment of ovarian cancer (OC), long-term remissions remain scarce. For a targeted approach, prognostic markers are indispensable for predicting survival and treatment response. Given their association with multiple hallmarks of cancer, histamine receptors (HR) are emerging as promising candidates. Here, we investigate their expression pattern and prognostic value in OC.MethodsSpecimens of 156 epithelial OC patients were collected during cytoreductive surgery at the Department of Obstetrics and Gynecology, LMU, between 1990 and 2002 and combined in a tissue microarray. Immunohistochemical staining of the HR H1, H2, H3 and H4 was quantified by an immunoreactive score and linked with clinico-pathological data by Spearman’s correlation. Via ROC curve analysis, optimal cut-off values for potential prognostic markers were defined. Overall survival (OS) was visualized in Kaplan–Maier curves and significances determined by log-rank testing. A Cox regression model was applied for multivariate analysis.ResultsHR H3 and H4 expression was restricted to the cytosol of OC cells, while H1 was also present in the nucleus. A significant association between HR H1, H3 and H4 expression with several clinico-pathological parameters was revealed. In addition, HR H1 and H3 expression correlated positively, HR H4 expression negatively with OS. In addition, HR H3 was identified as independent prognostic marker for OS. HR H2 expression had no prognostic value.ConclusionsHR H1, H3 and H4 could serve as potential predictors for OS of OC patients. Further research is warranted to elucidate their pathophysiologic role and their predictive and therapeutic potential in OC.

High throughput screen of small molecules as potential countermeasures to galactic cosmic radiation induced cellular dysfunction

Space travel increases galactic cosmic ray exposure to flight crews and this is significantly elevated once travel moves beyond low Earth orbit. This includes combinations of high energy protons and heavy ions such as 56Fe or 16O. There are distinct differences in the biological response to low-energy transfer (x-rays) or high-energy transfer (High-LET). However, given the relatively low fluence rate of exposure during flight operations, it might be possible to manage these deleterious effects using small molecules currently available. Virtually all reports to date examining small molecule management of radiation exposure are based on low-LET challenges. To that end an FDA approved drug library (725 drugs) was used to perform a high throughput screen of cultured cells following exposure to galactic cosmic radiation. The H9c2 myoblasts, ES-D3 pluripotent cells, and Hy926 endothelial cell lines were exposed to a single exposure (75 cGy) using the 5-ion GCRsim protocol developed at the NASA Space Radiation Laboratory (NSRL). Following GCR exposure cells were maintained for up to two weeks. For each drug (@10µM), a hierarchical cumulative score was developed incorporating measures of mitochondrial and cellular function, oxidant stress and cell senescence. The top 160 scores were retested following a similar protocol using 1µM of each drug. Within the 160 drugs, 33 are considered to have an anti-inflammatory capacity, while others also indirectly suppressed pro-inflammatory pathways or had noted antioxidant capacity. Lead candidates came from different drug classes that included angiotensin converting enzyme inhibitors or AT1 antagonists, COX2 inhibitors, as well as drugs mediated by histamine receptors. Surprisingly, different classes of anti-diabetic medications were observed to be useful including sulfonylureas and metformin. Using a hierarchical decision structure, we have identified several lead candidates. That no one drug or even drug class was completely successful across all parameters tested suggests the complexity of managing the consequences of galactic cosmic radiation exposure.

Effect of thallium on phototactic behaviour in Daphnia magna.

Thallium (Tl) is a trace metal enriched in wastewaters associated with mining and smelting of base metals. The toxicity of Tl to aquatic biota is poorly understood, particularly with respect to its sublethal effects. In this study, phototactic behavioural responses of naïve (i.e. no previous exposure to Tl) Daphnia magna, a key regulatory freshwater crustacean species, were examined in waters containing Tl. Fed and fasted neonate daphnids (< 24h old) and fed adults (10-15days old) showed no significant response at any tested water Tl concentration. However, in fasted adults, an increase in the positive phototactic response (measured as a greater number of daphnids closer to the light source after a 5-min exposure) was seen at Tl concentrations of 917 and 2099µg L-1, values representative of extreme environmental Tl concentrations. The presence of Tl also decreased the swimming speed of adult Daphnia towards a light source. In the presence of cimetidine, a histamine receptor blocker, the increase in positive phototaxis induced by Tl disappeared, suggesting that Tl acts to perturb the phototaxis response through sensory inhibition. Conversely, although there was a trend towards enhanced activity, Tl had no significant effect on acetylcholinesterase, a marker of locomotor capacity.

OLHA (Nα-oleoylhistamine) modulates activity of mouse brain histaminergic neurons

Histaminergic (HA) neurons are located in the tuberomamillary nucleus (TMN) of the posterior hypothalamus, from where they project throughout the whole brain to control wakefulness. We examined the effects of Nα-oleoylhistamine (OLHA), a non-enzymatic condensation product of oleic acid (OLA) and histamine, on activity of mouse HA neurons in brain slices. OLHA bidirectionally modulated the firing of HA neurons. At 10 nM OLHA inhibited or had no action, whereas at 1 μM it evoked excitatory and inhibitory responses. Inhibition was not seen in presence of the histamine receptor H3 (H3R) antagonist clobenpropit and in calcium-free medium. Pre-incubation with a histamine-reuptake blocker prevented the decrease in firing by OLHA. OLHA-evoked increase in firing (EC50 ∼44 nM) was insensitive to blockers of cannabinoid 1 and 2 receptors and of the capsaicin receptor, but was significantly impaired by the peroxisome proliferator-activated receptor-alpha (PPAR-alpha) antagonist MK886, which suppressed also the rise in intracellular calcium level caused by OLHA. The OLHA-evoked excitation was mimicked by synthetic PPAR-alpha agonists (gemfibrozil and GW7647) and was abolished by the PKA inhibitor H-89. The H3R affinity (Ki) for histamine, measured in HEK293 cells with stable expression of human H3R, was higher than for OLHA (Ki: 42 vs 310 nM, respectively). Expression of PPAR-alpha was not different between TMN regions of males and females, responses to OLHA did not differ. Molecular modelling of PPAR-alpha bound to either OLHA or OEA showed similar binding energies. These findings shed light on a novel biotransformation product of histamine which may play a role in health and disease.

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.

Abstract 6156: High-fat diet-induced gut dysbiosis promotes prostate cancer growth through mast cells and histamine 1 receptor

Abstract Introduction and Objective High-fat diet (HFD) induce prostate inflammation and promote cancer growth. However, the mechanism of this inflammation has not been entirely clear. We provide the evidence of new histamine-mediated mechanism and the crucial role of the gut microbiota on HFD-induced prostate cancer (PCa) growth. Methods We compared between HFD-fed and control diet (CD)-fed prostate-specific Pten KO mice at 22 weeks of age as PCa models. HFD-fed mice were given histamine receptor antagonist. Tumor growth was evaluated by prostate weight and Ki67 staining. Gut microbiota compositions were analyzed by 16S rRNA gene sequencing. Histamine signaling in PCa was assessed at gene and protein level. Results HFD significantly increased prostate weight (0.25 vs. 0.46g, P = 0.01) and Ki67-positive cancer cell ratio (0.15 vs. 0.36, P = 0.01). cDNA microarray of PCa showed that expression of Hdc encoding histidine decarboxylase (HDC), which is responsible for histamine production, was upregulated in HFD-fed mice (Fold change = 2.71). The elevated expression of Hdc was also confirmed by quantitative PCR (P &amp;lt; 0.01). Infiltrating mast cells highly produced HDC protein, and mast cell counts around cancer foci were significantly increased in HFD-fed mice. Fexofenadine (Fexo), an H1 blocker, inhibited HFD-induced PCa growth, while ranitidine, an H2 blocker, had no inhibitory effect. Fexo reduced MDSC counts and suppressed IL6-STAT3 signaling in PCa of HFD-fed mice. In vitro, both histamine and Fexo did not affect the proliferation of DU145. HFD altered the composition of gut microbiota, and Shannon index suggesting diversity of gut microbiota was reduced in HFD-fed mice. Serum lipopolysaccharide (LPS) levels were elevated in 11-week-old HFD-fed mice, and LPS injection resulted in upregulation of Hdc in PCa. Conclusions We found that HFD caused gut microbiota dysbiosis and elevated systemic LPS level, which could promote inflammatory PCa progression through mast cells and histamine H1 receptor signaling. These results suggest the existence of “Gut-Prostate Axis.” Citation Format: Kazutoshi Fujita, Makoto Matsushita, Daisuke Motooka, Takuaki Hase, Eri Banno, Marco De Velasco, Taigo Kato, Atsunari Kawashima, Motohide Uemura, Shota Nakamura, Kazutake Tsujikawa, Eiichi Morii, Kazuhiro Yoshimura, Hirotsugu Uemura. High-fat diet-induced gut dysbiosis promotes prostate cancer growth through mast cells and histamine 1 receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6156.

Pharmacotherapy of Itch-Antihistamines and Histamine Receptors as G Protein-Coupled Receptors.

Itching can decrease quality of life and exacerbate skin symptoms due to scratching. Itching not only contributes to disease progression but also triggers complications such as skin infections and eye symptoms. Therefore, controlling itching is very important in therapeutic management. In addition to the well-known histamine, IL-31, IL-4 and IL-13 have recently been reported as factors that induce itching. Itching may also be caused by factors other than these histamines. However, we do not know the extent to which these factors are involved in each disease. In addition, the degree of involvement is likely to vary among individuals. To date, antihistamines have been widely used to treat itching and are often effective, suggesting that histamine is more or less involved in itchy diseases. This review discusses the ligand-receptor perspective and describes the dynamics of G protein-coupled receptors, their role as biased agonists, their role as inverse agonists, proactive antihistamine therapy, and drug selection with consideration of impaired performance and anti-PAF effects.

Green Liquid Chromatography Method for the Determination of Related Substances Present in Olopatadine HCl Nasal Spray Formulation, Robustness by Design Expert.

Dual therapeutic nature drug mast cell stabilizer and histamine receptor antagonist olopatadine hydrochloride (OPT) nasal spray does not have an official monograph, and no literature is available. Eye drops formulation had the official monograph for impurities, but the determination was done in two methods. A simple and effective green liquid chromatography method to develop and validate for the related substances of OPT nasal spray formulation. A 25 min gradient method was employed to separate impurities and OPT with a 1.0 mL/min flow rate using a Boston green C8 (150 mm × 4.6 mm, 5 µm) HPLC column. The set wavelength and column oven temperatures were 299 nm and 30°C, respectively. pH 3.5 phosphate buffer-acetonitrile in the ratio of (70:30, v/v) as mobile phase A and (50:50, v/v) ratio as mobile phase B. A Quality by Design (QbD) based Design of Experiments (DoE) was employed to evaluate the robustness characteristics of the analytical method validation. The obtained RSD from the precision and intermediate precision was 0.4 to 4.1%. The % recovery of the impurities from LOQ to 150% of specification level was 87.5 to 110.3%. The linear regression curves for the impurities with a correlation coefficient of >0.999 indicate that all peak responses are linear with the concentration. The sample and standard solutions were stable for 24 h at benchtop and refrigerator conditions. All the critical peaks were well separated from the forced degradation studies' diluent, placebo, and generated degradation peaks. The method validation data and QbD based robustness study results indicate that the developed impurities method fits the routine quality control laboratory use. National Environmental Index (NMEI), Green Analytical Procedure Index (GAPI), Analytical Eco-scale and Analytical Greenness (AGREE) tools expressed the method's greenness. The proposed method is QbD utilized and green chemistry assessed impurities determination method for OPT in nasal spray formulation.