Histamine H(1)-receptor activation of nuclear factor-kappa B: roles for G beta gamma- and G alpha(q/11)-subunits in constitutive and agonist-mediated signaling

The role of histamine and its receptors in breast cancer: from pathology to therapeutic targets

Breast cancer is the most common malignancy in women, and despite the development of new treatment methods and the decreasing mortality rate in recent years, one of the clinical problems in breast cancer treatment is chronic inflammation in the tumor microenvironment. Histamine, an inflammatory mediator, is produced by tumor cells and can induce chronic inflammation and the growth of some tumors by recruiting inflammatory cells. It can also affect tumor physiopathology, antitumor treatment efficiency, and patient survival. Antihistamines, as histamine receptor antagonists, play a role in modulating the effects of these receptors in tumor cells and can affect some treatment methods for breast cancer therapy; in this review, we investigate the role of histamine, its receptors, and antihistamines in breast cancer pathology and treatment methods.

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.

Pharmacological Characterization of the Zebrafish (Danio Rerio) Histamine H1 Receptor Reveals the Involvement of the Second Extracellular Loop in the Binding of Histamine

The zebrafish (Danio rerio) histamine H1 receptor gene (zfH1R) was cloned in 2007 and reported to be involved in fish locomotion. Yet, no detailed characterization of its pharmacology and signaling properties have so far been reported. In this study, we pharmacologically characterized the zfH1R expressed in HEK-293T cells by means of [3H]-mepyramine binding and G protein-signaling assays. The zfH1R [dissociation constant (KD), 0.7 nM] displayed similar affinity for the antagonist [3H]-mepyramine as the human histamine H1 receptor (hH1R) (KD, 1.5 nM), whereas the affinity for histamine is 100-fold higher than for the human H1R. The zfH1R couples to Gαq/11 proteins and activates several reporter genes, i.e., NFAT, NFϰB, CRE, VEGF, COX-2, SRE, and AP-1, and zfH1R-mediated signaling is prevented by the Gαq/11 inhibitor YM-254890 and the antagonist mepyramine. Molecular modeling of the zfH1R and human H1R shows that the binding pockets are identical, implying that variations along the ligand binding pathway could underly the differences in histamine affinity instead. Targeting differentially charged residues in extracellular loop 2 (ECL2) using site-directed mutagenesis revealed that Arg21045x55 is most likely involved in the binding process of histamine in zfH1R. This study aids the understanding of the pharmacological differences between H1R orthologs and the role of ECL2 in histamine binding and provides fundamental information for the understanding of the histaminergic system in the zebrafish. SIGNIFICANCE STATEMENT: The use of the zebrafish as in vivo models in neuroscience is growing exponentially, which asks for detailed characterization of the aminergic neurotransmitter systems in this model. This study is the first to pharmacologically characterize the zebrafish histamine H1 receptor after expression in HEK-293T cells. The results show a high pharmacological and functional resemblance with the human ortholog but also reveal interesting structural differences and unveils an important role of the second extracellular loop in histamine binding.

Reshaping the yeast galactose regulon via GPCR signaling cascade

Dynamically regulated systems are preferable to control metabolic pathways for an improved strain performance with better productivity. Here, we harnessed to the G protein-coupled receptor (GPCR) signaling pathway to reshape the yeast galactose regulon. The galactose-regulated (GAL) system was coupled with the GPCR signaling pathway for mating pheromone via a synthetic transcription factor. In this study, we refabricated the dynamic range, sensitivity, and response time of the GAL system to α factor by modulating the key components of the GPCR signaling cascade. A series of engineered yeasts with self-secretion of α factor were constructed to achieve quorum-sensing behaviors. In addition, we also repurposed the GAL system to make it responsive to heat shock. Taken together, our work showcases the great potential of synthetic biology in creating user-defined metabolic controls. We envision that the plasticity of our genetic design would be of significant interest for the future fabrication of novel gene expression systems.

Histamine-producing bacteria and their role in gastrointestinal disorders

INTRODUCTION

Gut microbiota produces thousands of metabolites, which have a huge impact on the host health. Specific microbial strains are able to synthesize histamine, a molecule with a crucial role in many physiologic and pathologic mechanisms of the host. This function is mediated by the histidine decarboxylase enzyme (HDC) that converts the amino acid histidine to histamine.

AREAS COVERED

This review summarizes the emerging data on histamine production by gut microbiota, and the effect of bacterial-derived histamine in different clinical contexts, including cancer, irritable bowel syndrome, and other gastrointestinal and extraintestinal pathologies. This review will also outline the impact of histamine on the immune system and the effect of probiotics that can secrete histamine. Search methodology: we searched the literature on PubMed up to February 2023.

EXPERT OPINION

The potential of modulating gut microbiota to influence histamine production is a promising area of research, and although our knowledge of histamine-secreting bacteria is still limited, recent advances are exploring their diagnostic and therapeutical potential. Diet, probiotics, and pharmacological treatments directed to the modulation of histamine-secreting bacteria may in the future potentially be employed in the prevention and management of several gastrointestinal and extraintestinal disorders.

Role of Histamine and Related Signaling in Kaposi's Sarcoma-Associated Herpesvirus Pathogenesis and Oncogenesis

Although Kaposi's sarcoma-associated herpesvirus (KSHV) has been reported to cause several human cancers including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), the mechanisms of KSHV-induced tumorigenesis, especially virus-host interaction network, are still not completely understood, which therefore hinders the development of effective therapies. Histamine, together with its receptors, plays an important role in various allergic diseases by regulating different inflammation and immune responses. Our previous data showed that antagonists targeting histamine receptors effectively repressed KSHV lytic replication. In the current study, we determined that histamine treatment increased cell proliferation and anchorage-independent growth abilities of KSHV-infected cells. Furthermore, histamine treatment affected the expression of some inflammatory factors from KSHV-infected cells. For clinical relevance, several histamine receptors were highly expressed in AIDS-KS tissues when compared to normal skin tissues. We determined that histamine treatment promoted KSHV-infected lymphoma progression in immunocompromised mice models. Therefore, besides viral replication, our data indicate that the histamine and related signaling are also involved in other functions of KSHV pathogenesis and oncogenesis.

Ameliorative effect of desloratadine against cisplatin-induced renal and testicular toxicity in rats: Attention to TLR4/NLRP3 inflammasome signaling pathway

Cisplatin (CIS) is a potent anticancer drug that is used in the treatment of different types of cancer. Owing to its serious side effects, its clinical use is considerably limited.

AIMS

This study was mapped to investigate the potential effects of desloratadine (DES) against CIS-induced nephrotoxicity and testicular injury.

MAIN METHODS

DES (5 and 10 mg/kg) was orally administered for 10 days, and CIS was injected once (10 mg/kg, i.p.) in adult male rats on day 9 to induce both renal and testicular toxicity.

KEY FINDINGS

DES significantly attenuated CIS-induced alterations in histopathology and biomarkers. DES resulted in a significant reduction in serum levels of creatinine (Cr), urea, and blood urea nitrogen (BUN), in addition to a marked decrease in urinary levels of albumin and total protein. Additionally, DES efficiently reinstated the oxidative balance by preventing the elevation of malondialdehyde (MDA) and enhancing superoxide dismutase (SOD) activity, and increasing glutathione (GSH) levels. Moreover, DES produced a profound decrease in renal and testicular levels of nucleotide-binding domain-(NOD) like receptor 3 (NLRP3), interleukin (IL)-1β, and caspase-1 when compared to the CIS group. Furthermore, DES significantly decreased CIS-induced elevation in toll-like receptor 4 (TLR4), tumor necrosis factor-alpha (TNF-α), and nuclear factor-kappa B (NF-κB) levels in both renal and testicular tissues.

SIGNIFICANCE

DES can be used as adjuvant therapy with CIS in cancerous cases, pending further clinical studies.

Therapeutic potential of bromhexine for acute itch in mice: Involvement of TMPRSS2 and kynurenine pathway

Itching is an unpleasant sensation on the skin that could negatively impact the quality of life. Over the years, many non-pharmacological and pharmacological approaches have been introduced to mitigate this burdensome condition; However, the effectiveness of these methods remains questioned. Bromhexine, derived from the Adhatoda vasica plant, is a safe drug with minimal side effects. It has been widely used in managing respiratory symptoms over the years. The results of our study revealed that bromhexine has the potential to alleviate acute itch induced by Compound 48/80, a known mast cell destabilizer. According to our findings, bromhexine exerts its antipruritic effects primarily by inhibiting the Transmembrane Protein Serine Protease 2 (TMPRSS2) and, to a lesser extent, by decreasing the activation of the Kynurenine Pathway (KP). We further investigated the KP involvement by administrating 1-Methyl Tryptophan (1-MT), a known indoleamine-2,3-dioxygenase (IDO) inhibitor. 1-MT was found to be effective in reducing the itch itself. Moreover, co-administration of bromhexine and 1-MT resulted in synergistic antipruritic effects, suggesting that KP plays a role in acute itch. To conclude, we have presented for the first time a repositioning of bromhexine as a treatment for acute itch. In addition, we addressed the involvement of TMPRSS2 and KP in this process.

Pharmacogenomics for the efficacy and side effects of antihistamines

Antihistamines, especially H1 antihistamines, are widely used in the treatment of allergic diseases such as urticaria and allergic rhinitis, mainly for reversing elevated histamine and anti-allergic effects. Antihistamines are generally safe, but some patients experience adverse reactions, such as cardiotoxicity, central inhibition, and anticholinergic effects. There are also individual differences in antihistamine efficacy in clinical practice. The concept of individualized medicine has been deeply rooted in people's minds since it was put forward. Pharmacogenomics is the study of the role of inheritance in individual variations in drug response. In recent decades, pharmacogenomics has been developing rapidly, which provides new ideas for individualized medicine. Polymorphisms in the genes encoding metabolic enzymes, transporters, and target receptors have been shown to affect the efficacy of antihistamines. In addition, recent evidence suggests that gene polymorphisms influence urticaria susceptibility and antihistamine therapy. Here, we summarize current reports in this area, aiming to contribute to future research in antihistamines and clinical guidance for antihistamines use in individualized medicine.

Polysorbate 80-Induced Anaphylactoid Reaction and the Effects on Cardiovascular Function: Dose Threshold and Species Comparison

Polysorbate 80 (PS80) is commonly used in pre-clinical formulations. The dose threshold for cardiovascular (CV) changes and hypersensitivity reaction in the dog was assessed and compared to other species. PS80 was administered by intravenous (IV) bolus (.5, 1 mg/kg), IV infusion (.3, .5, 1, 3 mg/kg), subcutaneous (SC) injection (5, 10, 15 mg/kg) and oral gavage (10 mg/kg) to dogs with CV monitoring. Monkeys and minipigs received PS80 by IV infusion at 3 mg/kg. Plasma histamine concentration was measured following PS80 IV infusion and with diphenhydramine pre-treatment in dogs only. In dogs, PS80 was not associated with CV changes at doses up to 15 mg/kg SC and 10 mg/kg oral, but decreased blood pressure and increased heart rate with IV bolus at ≥ .5 mg/kg and IV infusion at ≥ 1.0 mg/kg and decreased body temperature with IV infusion at 3 mg/kg was observed. Transient edema and erythema were noted with all administration routes, in all three species including doses that were devoid of CV effects. In monkeys and minipigs, PS80 did not induce CV, cutaneous or histamine concentration changes. These results suggest that mild, transient skin changes occur following PS80 administration at doses that are not associated with CV effects in the dogs. In dogs, the cardiovascular effect threshold was <.5 mg/kg for IV bolus, .3 mg/kg for IV infusion, 15 mg/kg for SC injection, and 10 mg/kg for oral administration. Monkey and minipig were refractory to PS80-induced histamine release at 3 mg/kg by IV infusion over 15 minutes.

The Skeletal Muscle Relaxer Cyclobenzaprine Is a Potent Non-Competitive Antagonist of Histamine H1 Receptors

Cyclobenzaprine is a tricyclic dimethylpropanamine skeletal muscle relaxant, which is used clinically to decrease muscle spasm and hypercontractility, as well as acute musculoskeletal pain. Although the absolute mechanism of action of cyclobenzaprine remains elusive, it is known to mediate its effects centrally via inhibition of tonic somatic motor function, likely through modulation of noradrenergic and serotonergic systems. While cyclobenzaprine is effective as a muscle relaxant, greater than 30% of patients experience drowsiness and sedative-hypnotic effects, yet the mechanisms that cause this adverse effect are also undescribed. Based on this common adverse effect profile and the structural similarity of cyclobenzaprine to tricyclic antidepressants, as well as ethanolamine first-generation antihistamines, we hypothesized that cyclobenzaprine facilitates sedative effects via off-target antagonism of central histamine H1 receptors (H1Rs). Here, for the first time, we present data that demonstrate that cyclobenzaprine exhibits low nanomolar affinity for the cloned human H1R, as well as that expressed in both rat and mouse brain. Using saturation radioligand binding, we also demonstrate that cyclobenzaprine binds to the H1R in a noncompetitive manner. Similarly, functional assays measuring both Ca+2 influx and novel TRUPATH G-protein subunit bioluminescence resonance energy transfer biosensors reveal that cyclobenzaprine also blocks histamine-mediated H1R functional activity in a noncompetitive manner, whereas the classical H1R antagonist diphenhydramine does so competitively. Given that cyclobenzaprine readily crosses the blood-brain barrier and its muscle relaxant effects occur centrally, our data suggest that off-target central antagonism of H1R by cyclobenzaprine facilitates the significant sedative effect of this agent seen in patients. SIGNIFICANCE STATEMENT: Cyclobenzaprine, a clinically used muscle relaxant that is strongly linked to sedation, demonstrates high-affinity noncompetitive antagonism at the histamine H1 receptor. This effect likely modulates the high degree of sedation that patients experience.

Effects of Osthole on Inflammatory Gene Expression and Cytokine Secretion in Histamine-Induced Inflammation in the Caco-2 Cell Line

Hyperactivity of the immune system in the gastrointestinal tract leads to the development of chronic, inflammation-associated disorders. Such diseases, including inflammatory bowel disease, are not completely curable, but the specific line of treatment may reduce its symptoms. However, the response to treatment varies among patients, creating a necessity to uncover the pathophysiological basis of immune-mediated diseases and apply novel therapeutic strategies. The present study describes the anti-inflammatory properties of osthole during histamine-induced inflammation in the intestinal Caco-2 cell line. Osthole reduced the secretion of cytokines (CKs) and the expression level of inflammation-associated genes, which were increased after a histamine treatment. We have shown that the secretion of pro-inflammatory CKs (IL-1β, IL-6, IL-8, and TNF-α) during inflammation may be mediated by NFκB, and, after osthole treatment, this signaling pathway was disrupted. Our results suggest a possible role for osthole in the protection against inflammation in the gastrointestinal tract; thus, osthole may be considered as an anti-inflammatory modulator.

Antihistamines Potentiate Dexamethasone Anti-Inflammatory Effects. Impact on Glucocorticoid Receptor-Mediated Expression of Inflammation-Related Genes

Antihistamines and glucocorticoids (GCs) are often used together in the clinic to treat several inflammation-related situations. Although there is no rationale for this association, clinical practice has assumed that, due to their concomitant anti-inflammatory effects, there should be an intrinsic benefit to their co-administration. In this work, we evaluated the effects of the co-treatment of several antihistamines on dexamethasone-induced glucocorticoid receptor transcriptional activity on the expression of various inflammation-related genes in A549 and U937 cell lines. Our results show that all antihistamines potentiate GCs' anti-inflammatory effects, presenting ligand-, cell- and gene-dependent effects. Given that treatment with GCs has strong adverse effects, particularly on bone metabolism, we also examined the impact of antihistamine co-treatment on the expression of bone metabolism markers. Using MC3T3-E1 pre-osteoblastic cells, we observed that, though the antihistamine azelastine reduces the expression of dexamethasone-induced bone loss molecular markers, it potentiates osteoblast apoptosis. Our results suggest that the synergistic effect could contribute to reducing GC clinical doses, ineffective by itself but effective in combination with an antihistamine. This could result in a therapeutic advantage, as the addition of an antihistamine may reinforce the wanted effects of GCs, while related adverse effects could be diminished or at least mitigated. By modulating the patterns of gene activation/repression mediated by GR, antihistamines could enhance only the desired effects of GCs, allowing their effective dose to be reduced. Further research is needed to correctly determine the clinical scope, benefits, and potential risks of this therapeutic strategy.

Clemastine improves electrophysiologic and histomorphometric changes through promoting myelin repair in a murine model of compression neuropathy

Compression neuropathies are common and debilitating conditions that result in variable functional recovery after surgical decompression. Recent drug repurposing studies have verified that clemastine promotes functional recovery through enhancement of myelin repair in demyelinating disease. We investigated the utility of clemastine as a treatment for compression neuropathy using a validated murine model of compression neuropathy encircling the compression tube around the sciatic nerve. Mice received PBS or clemastine solution for 6 weeks of compression phase. Mice taken surgical decompression received PBS or clemastine solution for 2 weeks of decompression phase. Electrodiagnostic, histomorphometric, and Western immunoblotting analyses were performed to verify the effects of clemastine. During the compression phase, mice treated with clemastine had significantly decreased latency and increased amplitude compared to untreated mice that received PBS. Histomorphometric analyses revealed that mice treated with clemastine had significantly higher proportions of myelinated axons, thicker myelin, and a lower G-ratio. The expression levels of myelin proteins, including myelin protein zero and myelin associated glycoprotein, were higher in mice treated with clemastine. However, the electrophysiologic and histomorphometric improvements were observed regardless of clemastine treatment in mice taken surgical decompression. Mice treated with clemastine during compression of the sciatic nerve demonstrated that clemastine treatment attenuated electrophysiologic and histomorphometric changes caused by compression through promoting myelin repair.

Lipid Cubic Systems for Sustained and Controlled Delivery of Antihistamine Drugs

Antihistamines are capable of blocking mediator responses in allergic reactions including allergic rhinitis and dermatological reactions. By incorporating various H1 receptor antagonists into a lipid cubic phase network, these active ingredients can be delivered locally over an extended period of time owing to the mucoadhesive nature of the system. Local delivery can avoid inducing unwanted side effects, often observed after systematic delivery. Lipid-based antihistamine delivery systems are shown here to exhibit prolonged release capabilities. In vitro drug dissolution studies investigated the extent and release rate of two model first-generation and two model second-generation H1 antagonist antihistamine drugs from two monoacyglycerol-derived lipid models. To optimize the formulation approach, the systems were characterized macroscopically and microscopically by small-angle X-ray scattering and polarized light to ascertain the mesophase accessed upon an incorporation of antihistamines of varying solubilities and size. The impact of encapsulating the antihistamine molecules on the degree of mucoadhesivity of the lipid cubic systems was investigated using multiparametric surface plasmon resonance. With the ultimate goal of developing therapies for the treatment of allergic reactions, the ability of the formulations to inhibit mediator release utilizing RBL-2H3 mast cells with the propensity to release histamine upon induction was explored, demonstrating no interference from the lipid excipient on the effectiveness of the antihistamine molecules.

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.

Analysis of Missense Variants in the Human Histamine Receptor Family Reveals Increased Constitutive Activity of E4106.30×30K Variant in the Histamine H1 Receptor

The Exome Aggregation Consortium has collected the protein-encoding DNA sequences of almost 61,000 unrelated humans. Analysis of this dataset for G protein-coupled receptor (GPCR) proteins (available at GPCRdb) revealed a total of 463 naturally occurring genetic missense variations in the histamine receptor family. In this research, we have analyzed the distribution of these missense variations in the four histamine receptor subtypes concerning structural segments and sites important for GPCR function. Four missense variants R127^3.52×52H, R139^34.57×57H, R409^6.29×29H, and E410^6.30×30K, were selected for the histamine H₁ receptor (H₁R) that were hypothesized to affect receptor activity by interfering with the interaction pattern of the highly conserved D(E)RY motif, the so-called ionic lock. The E410^6.30×30K missense variant displays higher constitutive activity in G protein signaling as compared to wild-type H₁R, whereas the opposite was observed for R127^3.52×52H, R139^34.57×57H, and R409^6.29×29H. The E410^6.30×30K missense variant displays a higher affinity for the endogenous agonist histamine than wild-type H₁R, whereas antagonist affinity was not affected. These data support the hypothesis that the E410^6.30×30K mutation shifts the equilibrium towards active conformations. The study of these selected missense variants gives additional insight into the structural basis of H₁R activation and, moreover, highlights that missense variants can result in pharmacologically different behavior as compared to wild-type receptors and should consequently be considered in the drug discovery process.

Biased agonism at histamine H1 receptor: Desensitization, internalization and MAPK activation triggered by antihistamines

Histamine H₁ receptor ligands used clinically as antiallergics rank among the most widely prescribed and over-the-counter drugs in the world. They exert the therapeutic actions by blocking the effects of histamine, due to null or negative efficacy towards Gα_q-phospholipase C (PLC)-inositol triphosphates (IP₃)-Ca²⁺ and nuclear factor-kappa B cascades. However, there is no information regarding their ability to modulate other receptor responses. The aim of the present study was to investigate whether histamine H₁ receptor ligands could display positive efficacy concerning receptor desensitization, internalization, signaling through Gα_q independent pathways or even transcriptional regulation of proinflammatory genes. While diphenhydramine, triprolidine and chlorpheniramine activate ERK1/2 (extracellular signal-regulated kinase 1/2) pathway in A549 cells, pre-treatment with chlorpheniramine or triprolidine completely desensitize histamine H₁ receptor mediated Ca²⁺ response, and both diphenhydramine and triprolidine lead to receptor internalization. Unlike histamine, histamine H₁ receptor desensitization and internalization induced by antihistamines prove to be independent of G protein-coupled receptor kinase 2 (GRK2) phosphorylation. Also, unlike the reference agonist, the recovery of the number of cell-surface histamine H₁ receptors is a consequence of de novo synthesis. On the other hand, all of the ligands lack efficacy regarding cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) mRNA regulation. However, a prolonged exposure with each of the antihistamines impaires the increase in COX-2 and IL-8 mRNA levels induced by histamine, even after ligand removal. Altogether, these findings demonstrate the biased nature of histamine H₁ receptor ligands contributing to a more accurate classification, and providing evidence for a more rational and safe use of them.

Diphenhydramine may be a preventive medicine against cisplatin-induced kidney toxicity

Cisplatin is widely used as an anti-tumor drug for the treatment of solid tumors. Unfortunately, it causes kidney toxicity as a critical side effect, limiting its use, given that no preventive drug against cisplatin-induced kidney toxicity is currently available. Here, based on a repositioning analysis of the Food and Drug Administration Adverse Events Reporting System, we found that a previously developed drug, diphenhydramine, may provide a novel treatment for cisplatin-induced kidney toxicity. To confirm this, the actual efficacy of diphenhydramine was evaluated in in vitro and in vivo experiments. Diphenhydramine inhibited cisplatin-induced cell death in kidney proximal tubular cells. Mice administered cisplatin developed kidney injury with significant dysfunction (mean plasma creatinine: 0.43 vs 0.15 mg/dl) and showed augmented oxidative stress, increased apoptosis, elevated inflammatory cytokines, and MAPKs activation. However, most of these symptoms were suppressed by treatment with diphenhydramine. Furthermore, the concentration of cisplatin in the kidney was significantly attenuated in diphenhydramine-treated mice (mean platinum content: 70.0 vs 53.4 μg/g dry kidney weight). Importantly, diphenhydramine did not influence or interfere with the anti-tumor effect of cisplatin in any of the in vitro or in vivo experiments. In a selected cohort of 98 1:1 matched patients from a retrospective database of 1467 patients showed that patients with malignant cancer who had used diphenhydramine before cisplatin treatment exhibited significantly less acute kidney injury compared to ones who did not (6.1 % vs 22.4 %, respectively). Thus, diphenhydramine demonstrated efficacy as a novel preventive medicine against cisplatin-induced kidney toxicity.

A Dynamic, Split-Luciferase-Based Mini-G Protein Sensor to Functionally Characterize Ligands at All Four Histamine Receptor Subtypes

In drug discovery, assays with proximal readout are of great importance to study target-specific effects of potential drug candidates. In the field of G protein-coupled receptors (GPCRs), the determination of GPCR-G protein interactions and G protein activation by means of radiolabeled GTP analogs ([³⁵S]GTPγS, [γ-³²P]GTP) has widely been used for this purpose. Since we were repeatedly faced with insufficient quality of radiolabeled nucleotides, there was a requirement to implement a novel proximal functional assay for the routine characterization of putative histamine receptor ligands. We applied the split-NanoLuc to the four histamine receptor subtypes (H₁R, H₂R, H₃R, H₄R) and recently engineered minimal G (mini-G) proteins. Using this method, the functional response upon receptor activation was monitored in real-time and the four mini-G sensors were evaluated by investigating selected standard (inverse) agonists and antagonists. All potencies and efficacies of the studied ligands were in concordance with literature data. Further, we demonstrated a significant positive correlation of the signal amplitude and the mini-G protein expression level in the case of the H₂R, but not for the H₁R or the H₃R. The pEC₅₀ values of histamine obtained under different mini-G expression levels were consistent. Moreover, we obtained excellent dynamic ranges (Z’ factor) and the signal spans were improved for all receptor subtypes in comparison to the previously performed [³⁵S]GTPγS binding assay.

Antihistamines in children and adolescents: A practical update

Histamine is a chemical mediator, released predominantly by tissue mast cells, circulating basophils, and neurons, which are activated in response to various immunological and non-immunological stimuli. Histamine has to bind to specific receptors to exert its physiological and pathophysiological functions. Endogenous histamine is the main mediator of the immediate allergic response, which moreover, performs other multiple functions, including regulation of gastric secretion, neurotransmission in the central nervous system, and immunomodulatory activity. The involvement of histamine in various disorders and the importance of receptors in the clinical features have relevant implications in clinical practice. Anti-H1 antihistamines contrast the histamine-dependent effects, mainly concerning nasal symptoms and cutaneous itching and wheal. Antihistamines are among the most prescribed drugs in pediatric care. This review updates the practical use of antihistamines in children and adolescents.

Effects of histamine on human periodontal ligament fibroblasts under simulated orthodontic pressure

As type-I-allergies show an increasing prevalence in the general populace, orthodontic patients may also be affected by histamine release during treatment. Human periodontal ligament fibroblasts (PDLF) are regulators of orthodontic tooth movement. However, the impact of histamine on PDLF in this regard is unknown. Therefore PDLF were incubated without or with an orthodontic compressive force of 2g/cm² with and without additional histamine. To assess the role of histamine-1-receptor (H1R) H1R-antagonist cetirizine was used. Expression of histamine receptors and important mediators of orthodontic tooth movement were investigated. PDLF expressed histamine receptors H1R, H2R and H4R, but not H3R. Histamine increased the expression of H1R, H2R and H4R as well as of interleukin-6, cyclooxygenase-2, and prostaglandin-E2 secretion even without pressure application and induced receptor activator of NF-kB ligand (RANKL) protein expression with unchanged osteoprotegerin secretion. These effects were not observed in presence of H1R antagonist cetirizine. By expressing histamine receptors, PDLF seem to be able to respond to fluctuating histamine levels in the periodontal tissue. Increased histamine concentration was associated with enhanced expression of proinflammatory mediators and RANKL, suggesting an inductive effect of histamine on PDLF-mediated osteoclastogenesis and orthodontic tooth movement. Since cetirizine inhibited these effects, they seem to be mainly mediated via histamine receptor H1R.

Asymmetric Catalysis upon Helically Chiral Loratadine Analogues Unveils Enantiomer-Dependent Antihistamine Activity

Analogues of the conformationally dynamic Claritin (loratadine) and Clarinex (desloratadine) scaffolds have been enantio- and chemoselectively N-oxidized using an aspartic acid containing peptide catalyst to afford stable, helically chiral products in up to >99:1 er. The conformational dynamics and enantiomeric stability of the N-oxide products have been investigated experimentally and computationally with the aid of crystallographic data. Furthermore, biological assays show that rigidifying the core structure of loratadine and related analogues through N-oxidation affects antihistamine activity in an enantiomer-dependent fashion. Computational docking studies illustrate the observed activity differences.

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.

Antimicrobial Properties on Non-Antibiotic Drugs in the Era of Increased Bacterial Resistance

In recent years, due to the dramatic increase in and global spread of bacterial resistance to a number of commonly used antibacterial agents, many studies have been directed at investigating drugs whose primary therapeutic purpose is not antimicrobial action. In an era where it is becoming increasingly difficult to find new antimicrobial drugs, it is important to understand these antimicrobial effects and their potential clinical implications. Numerous studies report the antibacterial activity of non-steroidal anti-inflammatory drugs, local anaesthetics, phenothiazines such as chlorpromazine, levomepromazine, promethazine, trifluoperazine, methdilazine and thioridazine, antidepressants, antiplatelets and statins. Several studies have explored a possible protective effect of statins inreducing the morbidity and mortality of many infectious diseases. Various non-antibiotic agents exhibit antimicrobial activity via multiple and different mechanisms of action. Further studies are required in the field to further investigate these antimicrobial properties in different populations. This is of paramount importance in the antimicrobial resistance era, where clinicians have limited therapeutic options to combat problematic infections.

Histamine-mediated autocrine signaling in mesenteric perilymphatic mast cells

Lymphatic vessels play a critical role in mounting a proper immune response by trafficking peripheral immune cells to draining lymph nodes. Mast cells (MCs) are well known for their roles in type I hypersensitivity reactions, but little is known about their secretory regulation in the lymphatic niche. MCs, as innate sensor and effector cells, reside close to mesenteric lymphatic vessels (MLVs), and their activation and ability to release histamine influences the lymphatic microenvironment in a histamine-NF-κB-dependent manner. Using an established experimental protocol involving surgical isolation of rat mesenteric tissue segments, including MLVs and surrounding perilymphatic tissues, we tested the hypothesis that perilymphatic mesenteric MCs possess histamine receptors (HRs) that bind and respond to the histamine released from these same MCs. Under various experimental conditions, including inflammatory stimulation by LPS, we measured histamine in mesenteric perilymphatic tissues, evaluated expression of histidine decarboxylase in MCs along with the degree of MC degranulation, assessed the functional status of HRs in MCs, and evaluated the ability of histamine itself to induce MC activation. Finally, we evaluated the importance of MCs and HR1 and -2 for MLV-directed trafficking of CD11b/c-positive cells during acute tissue inflammation. Our data indicate the existence of a functionally potent MC-histamine autocrine regulatory loop, the elements of which are crucially important for acute inflammation-induced trafficking of the CD11b/c-positive cells toward MLVs. This MC-histamine loop serves as a first-line cellular servo control system, playing a key role in the innate and adaptive immune response as well as NF-κB-mediated maintenance of body homeostasis.

Ethno-medicinal study of Artemisia ordosica Krasch. (traditional Chinese/Mongolian medicine) extracts for the treatment of allergic rhinitis and nasosinusitis

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia ordosica Krasch. (AOK) has been used for rheumatic arthritis, cold headache, sore throat, etc. in traditional Chinese/Mongolian medicine and is used for nasosinusitis by local Mongolian "barefoot" doctors. Up to now, their mechanisms are still unclear.

AIM

To evaluate the in vivo anti-inflammatory and allergic rhinitis (AR) alleviating effect as well as in vitro antimicrobial activities of AOK extracts to verify its ethno-medicinal claims.

MATERIALS AND METHODS

Crude extracts (methanol/95%-ethanol/ethyl acetate) of AOK root/stem/leaf and fractions (petroleum ether/ethyl acetate/n-butanol/aqueous) of AOK root extract were prepared. Xylene-induced ear swelling model in mouse and ovalbumin (OVA)-induced AR model in guinea pig were established. Ear swelling degrees of mice were measured. The numbers of rubbing movement and sneezes of guinea pigs were counted to evaluate the symptoms of AR. The serum levels of histamine, INF-γ, IL-2/4/10, and VCAM-1 were measured by ELISA assay. The histological changes of nasal mucosa were investigated by light microscope after H&E staining. Antimicrobial activities of AOK extracts were also tested. LC-MS/MS analysis was performed to characterize the constituents of active extract and molecular docking was conducted to predict the biological mechanism.

RESULTS

In ear-swelling model, extract (100.00 mg/kg) from the ethyl acetate layer of 95% ethanol (100.00 mg/kg) showed better swelling inhibition in mice than positive control (dexamethasone, 191.91 mg/kg). In AR model, extract from the ethyl acetate layer of 95% ethanol significantly alleviated the AR symptoms in guinea pigs, decreased the serum levels of histamine, INF-γ, IL-2/4/10, and VCAM-1, and reduced the infiltration of eosinophil in nasal mucosa. For Staphylococcus aureus, the ethyl acetate extract of AOK stem showed the highest inhibition (MIC=1.25 mg/mL), for Escherichia coli, n-butanol layer of 95% ethanol extract of AOK root showed the highest inhibition (MIC=15.00 mg/mL), for Candida glabrata, 95%-ethyl acetate extract of AOK leaf showed the best inhibition (MIC=0.064 mg/mL), while ethyl acetate and n-butanol layers showed similar inhibition on MRSA (MIC=7.50 mg/mL). LC-MS/MS characterization showed that dicaffeoylquinic acids account for more than 30% of ethyl acetate layer of AOK extract. Dicaffeoylquinic acids bind with histamine-1 receptor with high affinities and interesting modes.

CONCLUSIONS

Extracts from AOK had interesting anti-inflammatory activity in mice, alleviating effect against OVA-induced AR in guinea pigs, and antimicrobial activities in vitro, which support the ethno-medicinal use of it. The main constituents in ethyl acetate layer of AOK root extract are dicaffeoylquinic acids and could bind with histamine-1 receptor well. These findings highlighted the importance of natural product chemistry study of AOK.

Effect of H4R Antagonist N-(2-Aminoethyl)-5-Chloro-1H-Indole-2-Carboxamide (Compound A) in a Mouse Model of Allergic Asthma

Context: Allergic asthma is a multifactorial airway disease characterised by chronic lung inflammation and airway remodelling. The histamine H4 receptor involved in the chemotaxis of leukocytes and mast cells to the site of inflammation is suggested to be a potential drug target for allergy and asthma. In this study we examined the effect of Compound A, N-(2-Aminoethyl)-5-chloro-1H-indol-2-carboxamide a H4 receptor antagonist in allergic asthma mice model. Objective: To investigate the anti-asthmatic effect of compound A in in vivo, airway inflammation in ovalbumin (OVA) induced allergic asthma mouse model was used. Methodology: Allergic asthma was induced in Balb/c mice using ovalbumin. BAL fluid was examined for the level of IgE, IL-4, IL-5, IL-13 and IL-17 using ELISA. Furthermore, infiltration of leucocytes by histopathology and effect of compound A on signalling molecules were examined in lung tissue. Results: In mice pre-treatment with compound A (10 mg/kg, 20 mg/kg, 30 mg/kg) at different concentrations markedly reduced the levels of IgE, Th2 cytokine IL-4, IL-5, IL-13 and Th17 cytokine IL-17 in BAL fluid. Histopathological examination of lung tissue showed that compound A was able to reduce the level of inflammatory infiltrates. Furthermore, lung tissue from Compound A treated group shown to down-regulate the levels of signalling molecules such as ERK1/2, Akt, SAPK/JNK and NF-κB compared to OVA treated group. Discussion and conclusion: Taken together our data demonstrates that compound A has shown to block the H4R-mediated allergic inflammation in this allergic asthma mice model and may be used as a molecule to study the function of H4R. Abbreviations: Compound A, N-(2-Aminoethyl)-5-chloro-1H-indol-2-carboxamide; JNJ7777120, 1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine; H₄R: Histamine 4 Receptor; AHR: Airway hyper responsiveness.

Identification of new antiviral agents against Kaposi's sarcoma-associated herpesvirus (KSHV) by high-throughput drug screening reveals the role of histamine-related signaling in promoting viral lytic reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several human cancers, such as Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). Current treatment options for KSHV infection and virus associated diseases are sometimes ineffective, therefore, more effectively antiviral agents are urgently needed. As a herpesvirus, lytic replication is critical for KSHV pathogenesis and oncogenesis. In this study, we have established a high-throughput screening assay by using an inducible KSHV+ cell-line, iSLK.219. After screening a compound library that consisted of 1280 Food and Drug Administration (FDA)-approved drugs, 15 hit compounds that effectively inhibited KSHV virion production were identified, most of which have never been reported with anti-KSHV activities. Interestingly, 3 of these drugs target histamine receptors or signaling. Our data further confirmed that antagonists targeting different histamine receptors (HxRs) displayed excellent inhibitory effects on KSHV lytic replication from induced iSLK.219 or BCBL-1 cells. In contrast, histamine and specific agonists of HxRs promoted viral lytic replication from induced iSLK.219 or KSHV-infected primary cells. Mechanistic studies indicated that downstream MAPK and PI3K/Akt signaling pathways were required for histamine/receptors mediated promotion of KSHV lytic replication. Direct knockdown of HxRs in iSLK.219 cells effectively blocked viral lytic gene expression during induction. Using samples from a cohort of HIV+ patients, we found that the KSHV+ group has much higher levels of histamine in their plasma and saliva than the KSHV- group. Taken together, our data have identified new anti-KSHV agents and provided novel insights into the molecular bases of host factors that contribute to lytic replication and reactivation of this oncogenic herpesvirus.

Therapeutic utility of glucocorticoids and antihistamines cotreatment. Rationale and perspectives

Antihistamines and glucocorticoids (GCs) are often used together in the clinic, in several inflammatory-related situations. Even though there is no clear rationale for this drug association, the clinical practice is based on the assumption that due to their concomitant antiinflammatory effects, there should be an intrinsic benefit in their coadministration. Our group has studied the molecular interaction between the histamine H1 receptor and the glucocorticoid receptor (GR) signaling pathways, showing an enhancing effect on GC-induced GR transcriptional activity induced by antihistamines. We hypothesize that the existence of this synergistic effect could contribute in reducing the GCs clinical doses, ineffective by itself but effective in combination with an antihistamine. This could result in a therapeutic advantage as the GC-desired effects may be reinforced by the addition of an antihistamine and, as a consequence of the dose reduction, GC-related adverse effects could be reduced or at least mitigated. Here we discuss the potential therapeutic applications of this cotreatment seeking to evaluate its usefulness, especially in inflammatory-related conditions.

Engineering a Model Cell for Rational Tuning of GPCR Signaling

G protein-coupled receptor (GPCR) signaling is the primary method eukaryotes use to respond to specific cues in their environment. However, the relationship between stimulus and response for each GPCR is difficult to predict due to diversity in natural signal transduction architecture and expression. Using genome engineering in yeast, we constructed an insulated, modular GPCR signal transduction system to study how the response to stimuli can be predictably tuned using synthetic tools. We delineated the contributions of a minimal set of key components via computational and experimental refactoring, identifying simple design principles for rationally tuning the dose response. Using five different GPCRs, we demonstrate how this enables cells and consortia to be engineered to respond to desired concentrations of peptides, metabolites, and hormones relevant to human health. This work enables rational tuning of cell sensing while providing a framework to guide reprogramming of GPCR-based signaling in other systems.

Persistent activation of histamine H1 receptors in the hippocampal CA1 region enhances NMDA receptor-mediated synaptic excitation and long-term potentiation in astrocyte- and D-serine-dependent manner

Behavioral studies using pharmacological tools have implicated histamine H₁ receptors in cognitive function via their interactions with N-methyl-D-aspartate receptors (NMDARs) in the hippocampus. However, little is known about the neurophysiological mechanism that underlies the interaction between H₁ receptors and NMDARs. To explore how H₁ receptor activation affects hippocampal excitatory neurotransmission and synaptic plasticity, this study aimed to examine the effect of H₁ receptor ligands on both NMDAR-mediated synaptic currents and long-term potentiation (LTP) at synapses between Schaffer collaterals and CA1 pyramidal neurons using acute mouse hippocampal slices. We found that the H₁ receptor antagonist/inverse agonists, pyrilamine (0.1 μM) and cetirizine (10 μM), decreased the NMDAR-mediated component of stimulation-induced excitatory postsynaptic currents (EPSCs) recorded from CA1 pyramidal neurons without affecting the AMPA receptor-mediated component of EPSCs and its paired pulse ratio. Pretreatment of slices with either the glial metabolism inhibitor, fluoroacetate (5 mM), or D-serine (100 μM) diminished the pyrilamine- or cetirizine-induced attenuation of the NMDAR-mediated EPSCs. Furthermore, the LTP of field excitatory postsynaptic potentials induced following high frequency stimulation of Schaffer collaterals was attenuated with application of pyrilamine or cetirizine. Pretreatment with D-serine again attenuated the pyrilamine-induced suppression of LTP. Our data suggest that H₁ receptors in the CA1 can undergo persistent activation induced by their constitutive receptor activity and/or tonic release of endogenous histamine, resulting in facilitation of the NMDAR activity in a manner dependent of astrocytes and the release of D-serine. This led to the enhancement of NMDA-component EPSC and LTP at the Schaffer collateral-CA1 pyramidal neuron synapses.

Quantum chemical calculation and binding modes of H1R; a combined study of molecular docking and DFT for suggesting therapeutically potent H1R antagonist

Histamine-1 receptor (H1R) belongs to the family of rhodopsin-like G-protein-coupled receptors expressed in cells that mediates allergies and other pathophysiological diseases. For alleviation of allergic symptoms, H1R antagonists are therapeutic drugs; of which the most frequently prescribed are second generation drugs, such as; Cetirizine, Loratadine, Hydroxyzine, Desloratadine, Bepotastine, Acrivastine and Rupatadine. To understand their potency, binding affinity and interaction; we have employed molecular docking and quantum chemical study such as; Induced-fit docking and calculation of quantum chemical descriptors. This study also introduces the binding site characterization of H1R, with its known antagonists and Curcumin (our proposed alternative H1R antagonist); useful for future drug target site. The interactive binding site residues of H1R are found to be; Lys-191, Tyr-108, Asp-107, Tyr-100, Lys-179, Lys-191, Thr-194, Trp-428, Phe-432, Tyr-458, Hie-450, with most of these shown to be inhibited by naturally-occurring compound curcumin. Amongst the FDA approved drugs, Hydroxyzine showed best ligand binding affinity, calculated as - 141.491 kcal/mol and naturally occurring compound, Curcumin showed binding affinity of - 87.046 kcal/mol. The known antagonists of H1R has been used for hypothesizing curcumin as naturally occurring lead compound for the target using accurate molecular docking simulation study. Though the pharmacological action of known inhibitor is already established, they could differ from their reactivity, which we have also focused in our study for predicting drug reactivity.

Histamine and diabetic nephropathy: an up-to-date overview

The classification of diabetic nephropathy (DN) as a vascular complication of diabetes makes the possible involvement of histamine, an endogenous amine that is well known for its vasoactive properties, an interesting topic for study. The aim of the present review is to provide an extensive overview of the possible involvement of histamine in the onset and progression of DN. The evidence collected on the role of histamine in kidney function together with its well-known pleiotropic action suggest that this amine may act simultaneously on glomerular hyperfiltration, tubular inflammation, fibrosis development and tubular hypertrophy.

Cerebrospinal inflammatory response following scorpion envenomation: role of histamine H1 and H3 receptors

BACKGROUND

The mechanism of the inflammatory process induced by scorpion venom in the cerebrospinal tissues has not yet been completely elucidated. Therefore, we aimed to investigate the role of histamine through its H1 and H3 receptors in this process.

METHODS

Histamine H1 and H3 receptor antagonists, Hydroxyzine (10 mg/kg) and Betaserc (20 mg/kg), respectively, were administered by intraperitoneal route to mice 1 h before subcutaneous envenomation with a subletal dose (0.5 mg/kg) of Androctonus australis hector venom. Cerebrospinal inflammation response was assessed 24 h after envenomation by evaluating the vascular permeability changes, inflammatory cell infiltration, oxidative/nitrosative stress marker levels (hydrogen peroxide, nitric oxide, malondialdehyde, glutathione and catalase) and by histological examination of cerebrospinal tissue.

RESULTS

Envenomed mice displayed an installation of an inflammatory response marked by increased vascular permeability (76% and 68% in brain and spinal cord, respectively, in comparison to controls), inflammatory cell infiltration, increased pro-oxidant levels and decreased anti-oxidant markers (p  < 0.05 to p  < 0.001). Scorpion venom also induced structural changes in brain and spinal cord tissues. Hydroxyzine seemed to be more efficient than Betaserc in the prevention of the induced cerebrospinal inflammation response, as evidenced by the decreased vascular permeability, inflammatory cell infiltration, pro-oxidant levels, increased anti-oxidant defense (p  < 0.05 to p  < 0.001) and a reduction of the anatomo-pathological alterations.

CONCLUSION

The results showed that the histamine H1 receptor is more involved in the induced central nervous system inflammatory response during scorpion envenomation.

Effect of the H1-antihistamine clemastine on PACAP38 induced migraine

Objective

To investigate the effect of the H1-antihistamine clemastine on the migraine-inducing abilities of pituitary adenylate cyclase activating peptide-38.

Methods

We conducted a double-blind, randomized, placebo controlled two-way cross-over study. Twenty migraine without aura patients were randomly allocated to receive bolus clemastine 2 mg (1 mg/ml) or bolus saline 2 ml intravenously over 2 min on two study days. Following each bolus injection, 10 pmol/kg/min of pituitary adenylate cyclase activating peptide-38 was administered intravenously over 20 min. We recorded migraine/headache characteristics every 10 min until 90 min after the start of infusion, and collected blood to investigate mast cell degranulation and the inflammation markers tryptase and tumor necrosis factor-alpha before and after infusion of pituitary adenylate cyclase activating peptide-38.

Results

After clemastine pretreatment, five out of 20 participants developed a migraine-like attack in response to a pituitary adenylate cyclase activating peptide-38 infusion compared to nine out of 20 after placebo pretreatment ( p = 0.288). Following clemastine pretreatment, 15 out of 20 participants reported headache in response to a pituitary adenylate cyclase activating peptide-38 infusion, whereas 19 out of 20 participants did so following placebo pretreatment ( p = 0.221). We found no difference in area under the curve 12 h for headache intensity between the two experimental days ( p = 0.481). We found no difference in area under the curve 180 min for tryptase ( p = 0.525) or tumor necrosis factor-alpha ( p = 0.487) between clemastine and placebo pretreatment days.

Conclusion

H1-antihistamine, clemastine, failed to prevent migraine or headache after pituitary adenylate cyclase activating peptide-38 infusion, thus making a role for histamine release or mast cell degranulation in pituitary adenylate cyclase activating peptide-38-induced migraine less likely.

Levocetirizine Pretreatment Mitigates Lipopolysaccharide-Induced Lung Inflammation in Rats

This research was conducted to investigate possible protective influences of levocetirizine, a nonsedating H₁ antihistamine, against lipopolysaccharide (LPS)-induced lung injury in rats. Male Sprague Dawley rats received either levocetirizine (1 mg/kg/day, orally) or the vehicle of the drug (2 ml/kg/day, orally) for 1 week before a single IP injection of LPS (7.5 mg/kg). A group of normal rats served as control. The experiments were terminated 18 h after the LPS challenge. Serum C-reactive protein levels were determined. Moreover, total cell count, lactate dehydrogenase (LDH) activity, protein levels, and total NOx were evaluated in bronchoalveolar lavage fluid (BALF). Pulmonary edema was evaluated as the wet/dry lung weight ratio. Lung tissue homogenate was assessed for antioxidant/pro-oxidant status. BALF and lung tissue levels of tumor necrosis factor-α (TNF-α) were assessed. Lungs were examined for histological alterations. LPS-mediated lung injury was manifested by pulmonary edema, leukocyte infiltration, oxidative stress, and inflammation. Levocetirizine attenuated lung edema and mitigated the increases in BALF protein levels, LDH activity, and lung leukocyte recruitment in LPS-challenged rats. Additionally, TNF-α protein levels in BALF and lung tissue were diminished by levocetirizine administration. Levocetirizine also exhibited a potent antioxidant activity as indicated by a decrease in lung tissue levels of malondialdehyde and an enhancement of superoxide dismutase activity. Histological examination of lung tissues confirmed the beneficial effect of levocetirizine against LPS-induced histopathological alterations. In conclusion, levocetirizine may offer protection against lung tissue damage and inflammation in LPS-challenged rats.

The Role of Histamine and Histamine Receptors in Mast Cell-Mediated Allergy and Inflammation: The Hunt for New Therapeutic Targets

Histamine and its receptors (H1R–H4R) play a crucial and significant role in the development of various allergic diseases. Mast cells are multifunctional bone marrow-derived tissue-dwelling cells that are the major producer of histamine in the body. H1R are expressed in many cells, including mast cells, and are involved in Type 1 hypersensitivity reactions. H2R are involved in Th1 lymphocyte cytokine production. H3R are mainly involved in blood–brain barrier function. H4R are highly expressed on mast cells where their stimulation exacerbates histamine and cytokine generation. Both H1R and H4R have important roles in the progression and modulation of histamine-mediated allergic diseases. Antihistamines that target H1R alone are not entirely effective in the treatment of acute pruritus, atopic dermatitis, allergic asthma, and other allergic diseases. However, antagonists that target H4R have shown promising effects in preclinical and clinical studies in the treatment of several allergic diseases. In the present review, we examine the accumulating evidence suggesting novel therapeutic approaches that explore both H1R and H4R as therapeutic targets for histamine-mediated allergic diseases.

Cancer; an induced disease of twentieth century! Induction of tolerance, increased entropy and 'Dark Energy': loss of biorhythms (Anabolism v. Catabolism)

Maintenance of health involves a synchronized network of catabolic and anabolic signals among organs/tissues/cells that requires differential bioenergetics from mitochondria and glycolysis (biological laws or biorhythms). We defined biological circadian rhythms as Yin (tumoricidal) and Yang (tumorigenic) arms of acute inflammation (effective immunity) involving immune and non-immune systems. Role of pathogens in altering immunity and inducing diseases and cancer has been documented for over a century. However, in 1955s decision makers in cancer/medical establishment allowed public (current baby boomers) to consume million doses of virus-contaminated polio vaccines. The risk of cancer incidence and mortality sharply rose from 5% (rate of hereditary/genetic or innate disease) in 1900s, to its current scary status of 33% or 50% among women and men, respectively. Despite better hygiene, modern detection technologies and discovery of antibiotics, baby boomers and subsequent 2–3 generations are sicker than previous generations at same age. American health status ranks last among other developed nations while America invests highest amount of resources for healthcare. In this perspective we present evidence that cancer is an induced disease of twentieth century, facilitated by a great deception of cancer/medical establishment for huge corporate profits. Unlike popularized opinions that cancer is 100, 200 or 1000 diseases, we demonstrate that cancer is only one disease; the severe disturbances in biorhythms (differential bioenergetics) or loss of balance in Yin and Yang of effective immunity. Cancer projects that are promoted and funded by decision makers are reductionist approaches, wrong and unethical and resulted in loss of millions of precious lives and financial toxicity to society. Public vaccination with pathogen-specific vaccines (e.g., flu, hepatitis, HPV, meningitis, measles) weakens, not promotes, immunity. Results of irresponsible projects on cancer sciences or vaccines are increased population of drug-dependent sick society. Outcome failure rates of claimed ‘targeted’ drugs, ‘precision’ or ‘personalized’ medicine are 90% (± 5) for solid tumors. We demonstrate that aging, frequent exposures to environmental hazards, infections and pathogen-specific vaccines and ingredients are ‘antigen overload’ for immune system, skewing the Yin and Yang response profiles and leading to induction of ‘mild’, ‘moderate’ or ‘severe’ immune disorders. Induction of decoy or pattern recognition receptors (e.g., PRRs), such as IRAK-M or IL-1dRs (‘designer’ molecules) and associated genomic instability and over-expression of growth promoting factors (e.g., pyruvate kinases, mTOR and PI3Ks, histamine, PGE2, VEGF) could lead to immune tolerance, facilitating cancer cells to hijack anabolic machinery of immunity (Yang) for their increased growth requirements. Expression of constituent embryonic factors would negatively regulate differentiation of tumor cells through epithelial–mesenchymal-transition and create “dual negative feedback loop” that influence tissue metabolism under hypoxic conditions. It is further hypothesized that induction of tolerance creates ‘dark energy’ and increased entropy and temperature in cancer microenvironment allowing disorderly cancer proliferation and mitosis along with increased glucose metabolism via Crabtree and Pasteur Effects, under mitophagy and ribophagy, conditions that are toxic to host survival. Effective translational medicine into treatment requires systematic and logical studies of complex interactions of tumor cells with host environment that dictate clinical outcomes. Promoting effective immunity (biological circadian rhythms) are fundamental steps in correcting host differential bioenergetics and controlling cancer growth, preventing or delaying onset of diseases and maintaining public health. The author urges independent professionals and policy makers to take a closer look at cancer dilemma and stop the ‘scientific/medical ponzi schemes’ of a powerful group that control a drug-dependent sick society before all hopes for promoting public health evaporate.

A Combined In Vitro/In Silico Approach to Identifying Off-Target Receptor Toxicity

Many xenobiotics can bind to off-target receptors and cause toxicity via the dysregulation of downstream transcription factors. Identification of subsequent off-target toxicity in these chemicals has often required extensive chemical testing in animal models. An alternative, integrated in vitro/in silico approach for predicting toxic off-target functional responses is presented to refine in vitro receptor identification and reduce the burden on in vivo testing. As part of the methodology, mathematical modeling is used to mechanistically describe processes that regulate transcriptional activity following receptor-ligand binding informed by transcription factor signaling assays. Critical reactions in the signaling cascade are identified to highlight potential perturbation points in the biochemical network that can guide and optimize additional in vitro testing. A physiologically based pharmacokinetic model provides information on the timing and localization of different levels of receptor activation informing whole-body toxic potential resulting from off-target binding.

Inhibition of hepatic apolipoprotein A-I gene expression by histamine

In a recent high throughput analysis to identify drugs that alter hepatic apolipoprotein A-I (apo A-I) expression, histamine receptor one (H₁) antagonists emerged as potential apo A-1 inducing drugs. Thus the present study was undertaken to identify some of the underlying molecular mechanisms of the effect of antihistaminic drugs on apo AI production. Apo A-I levels were measured by enzyme immunoassay and Western blots. Apo A-I mRNA levels were measured by reverse transcription real-time PCR using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA as the internal control. The effects of histamine and antihistamines on apo A-I gene were determined by transient transfection of plasmids containing the apo A-I gene promoter. Histamine repressed while (H₁) receptor antagonist azelastine increased apo A-I protein and mRNA levels within 48 h in a dose-dependent manner. Azelastine and histamine increased and suppressed, respectively, apo A-I gene promoter activity through a peroxisome proliferator activated receptor α response element. Treatment of HepG2 cells with other H₁ receptor antagonists including fexofenadine, cetirizine, and diphenhydramine increased apo A-I levels in a dose-dependent manner while treatment with H₂ receptor antagonists including cimetidine, famotidine, and ranitidine had no effect. We conclude that H₁ receptor signaling is a novel pathway of apo A1 gene expression and therefore could be an important therapeutic target for enhancing de-novo apo A-1 synthesis.

Evaluating the dose-dependent mechanism of action of trazodone by estimation of occupancies for different brain neurotransmitter targets

Trazodone is a drug that was introduced in the clinic almost 40 years ago. It is licensed to treat depression, but it is also commonly used off-label to treat insomnia. A recent study shows that it could be promising in preventing neurodegeneration in mice, and clinical trials to assess its possible beneficial effects on dementia and Alzheimer's disease are expected to start soon in humans. In this study, we describe the dose-dependent pharmacology of trazodone by carrying out pharmacokinetic simulations aiming to predict the brain concentrations of trazodone for different drug-dosing regimens and calculating occupancy for 28 different targets for which published trazodone-binding data are available. Our study indicates that low doses of trazodone (typically 50 mg daily) should suffice to block specific receptors responsible for the hypnotic effect, and to provide the protective effect against neuroinflammation and neurodegeneration that could be beneficial in dementia. Higher doses are required for an antidepressant effect. The occupancy of specific receptors at therapeutic doses also explains peculiar side effects reported by patients treated with trazodone (e.g. dry-mouth, hypotension and priapism).

The Histamine H1 Receptor Participates in the Increased Dorsal Telencephalic Neurogenesis in Embryos from Diabetic Rats

Increased neuron telencephalic differentiation during deep cortical layer formation has been reported in embryos from diabetic mice. Transitory histaminergic neurons within the mesencephalon/rhombencephalon are responsible for fetal histamine synthesis during development, fibers from this system arrives to the frontal and parietal cortex at embryo day (E) 15. Histamine is a neurogenic factor for cortical neural stem cells in vitro through H₁ receptor (H₁R) which is highly expressed during corticogenesis in rats and mice. Furthermore, in utero administration of an H₁R antagonist, chlorpheniramine, decreases the neuron markers microtubuline associated protein 2 (MAP2) and forkhead box protein 2. Interestingly, in the diabetic mouse model of diabetes induced with streptozotocin, an increase in fetal neurogenesis in terms of MAP2 expression in the telencephalon is reported at E11.5. Because of the reported effects on cortical neuron differentiation of maternal diabetes in one hand and of histamine in the other, here the participation of histamine and H₁R on the increased dorsal telencephalic neurogenesis was explored. First, the increased neurogenesis in the dorsal telencephalon at E14 in diabetic rats was corroborated by immunohistochemistry and Western blot. Then, changes during corticogenesis in the level of histamine was analyzed by ELISA and in H₁R expression by qRT-PCR and Western blot and, finally, we tested H₁R participation in the increased dorsal telencephalic neurogenesis by the systemic administration of chlorpheniramine. Our results showed a significant increase of histamine at E14 and in the expression of the receptor at E12. The administration of chlorpheniramine to diabetic rats at E12 prevented the increased expression of βIII-tubulin and MAP2 mRNAs (neuron markers) and partially reverted the increased level of MAP2 protein at E14, concluding that H₁R have an important role in the increased neurogenesis within the dorsal telencephalon of embryos from diabetic rats. This study opens new perspective on the participation of HA and H₁R receptor in early corticogenesis in health and disease.

ALDH enzyme activity is regulated by Nodal and histamine in the A549 cell line

The present study aimed to examine whether the enzyme activity of aldehyde dehydrogenase (ALDH) was regulated by Nodal and histamine in the human alveolar adenocarcinoma A549 cell line. The regulated enzyme activity of ALDH was analyzed by flow cytometry in the A549 cell line. ALDH1 and Nodal expression was investigated by immunohistochemistry in28 cases of lung mixed adenocarcinoma. The enzyme activity of ALDH was upregulated by histamine and agonists of histamine H1 receptor (H1R) and histamine H2 receptor (H2R). ALDH activity was also downregulated by recombinant human Nodal and antagonists of H1R and H2R in the A549 cell line. In addition, expression of Nodal and ALDH1 were inversely correlated in lung mixed adenocarcinoma. ALDH enzyme activity was regulated by Nodal and histamine in lung adenocarcinoma.

Practical and Sustainable Synthesis of Optically Pure Levocabastine, a H₁ Receptor Antagonist

A practical and sustainable method for the synthesis of levocabastine hydrochloride (1), a H₁ receptor antagonist for the treatment of allergic conjunctivitis, that can be applied to the industrial production of the compound has been developed. Substantial improvements over the previously reported procedure are achieved via efficient preparation of an optically active key intermediate (5) without chiral resolution and with a more effective detosylation, which complements the previous procedure. Notably, our process requires no chromatographic purification and provides levocabastine hydrochloride in greater than 99.5% purity in a 14.2% overall yield.

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.

Proteomic Response of Human Umbilical Vein Endothelial Cells to Histamine Stimulation

The histamine receptors (HRs) represent a subclass of G protein-coupled receptors (GPCRs) and comprise four subtypes. Due to their numerous physiological and pathological effects, HRs are popular drug targets for the treatment of allergic reactions or the regulation of gastric acid secretion. Hence, an understanding of the functional selectivity of HR ligands has gained importance. These ligands can bind to specific GPCRs and selectively activate defined pathways. Supporting the activation of a therapeutically necessary pathway without the activation of other signaling cascades can result in drugs with more specific activity and fewer side effects. To evaluate the cellular consequences resulting from receptor binding, comprehensive analyses of cellular protein alterations upon incubation with ligands are required. For this purpose, endothelial cells are treated with histamine, as the endogenous ligand of HRs, to obtain a global overview of its cellular effects. Quantitative proteomics and pathway analyses of histamine-treated and untreated cells reveal enrichment of the nuclear factor-κB and tumor necrosis factor signaling pathways, cytokine-cytokine receptor interactions, complement and coagulation cascades, and acute inflammatory processes upon histamine treatment. This strategy offers the opportunity to monitor HR-mediated signaling in a multidimensional manner.