Cationic amphiphilic antihistamines inhibit STAT3 via Ca2+-dependent lysosomal H+ efflux.

Commonly used antihistamines and other cationic amphiphilic drugs (CADs) are emerging as putative cancer drugs. Their unique chemical structure enables CADs to accumulate rapidly inside lysosomes, where they increase lysosomal pH, alter lysosomal lipid metabolism, and eventually cause lysosomal membrane permeabilization. Here, we show that CAD-induced rapid elevation in lysosomal pH is caused by a lysosomal H+ efflux that requires P2RX4-mediated lysosomal Ca2+ release and precedes the lysosomal membrane permeabilization. The subsequent cytosolic acidification triggers the dephosphorylation, lysosomal translocation, and inactivation of the oncogenic signal transducer and activator of transcription 3 (STAT3) transcription factor. Moreover, CAD-induced lysosomal H+ efflux sensitizes cancer cells to apoptosis induced by STAT3 inhibition and acts synergistically with STAT3 inhibition in restricting the tumor growth of A549 non-small cell lung carcinoma xenografts. These findings identify lysosomal H+ efflux and STAT3 inhibition as anticancer mechanisms of CADs and reinforce the repurposing of safe and inexpensive CADs as cancer drugs with a drug combination strategy.

Disruption of histamine/H1R-STAT3-SLC7A11 axis exacerbates doxorubicin-induced cardiac ferroptosis.

Doxorubicin (DOX) is widely used in the treatment of various cancers, increasing the great risk of adverse cardiovascular events, while the clinical intervention effect is not ideal. Histamine has been documented to participate in pathophysiological processes of cardiovascular diseases and inflammation-associated carcinogenesis. However, the potential roles of histamine in antitumor-related cardiotoxicity have not been fully elucidated. In this study, cardiomyocytes (hiPSC-CMs, HL-1 cells) and mice were treated with DOX to establish DOX-induced cardiotoxicity (DIC) models. Histidine decarboxylase knockout mice (HDC-/-) mice and histamine 1 receptor (H1R) antagonist were used to explore the effect of histamine/H1R signaling on DIC. Our results demonstrated that histamine deficiency or pharmaceutical inhibition of H1R accelerated myocardial ferroptosis, which is responsible for the aggravated DIC both in vivo and in vitro, while the supplementation of exogenous histamine reversed these changes. Our data revealed that the dysfunction of histamine/H1R signaling repressed the activation of transducer and activator of transcription 3 (STAT3), accompanying with decreased expression of solute carrier family7member11 (SLC7A11), a major modulator of ferroptosis. Conclusively, the disruption of histamine/H1R axis triggered ferroptosis and exacerbated DIC possibly by modulating STAT3-SLC7A11 pathway. Our findings point to a potential therapeutic target for DIC and provide more consideration on the usage of antihistamine drugs.

Heparin-binding motif mutations of human diamine oxidase allow the development of a first-in-class histamine-degrading biopharmaceutical.

Background: Excessive plasma histamine concentrations cause symptoms in mast cell activation syndrome, mastocytosis, or anaphylaxis. Anti-histamines are often insufficiently efficacious. Human diamine oxidase (hDAO) can rapidly degrade histamine and therefore represents a promising new treatment strategy for conditions with pathological histamine concentrations. Methods: Positively charged amino acids of the heparin-binding motif of hDAO were replaced with polar serine or threonine residues. Binding to heparin and heparan sulfate, cellular internalization and clearance in rodents were examined. Results: Recombinant hDAO is rapidly cleared from the circulation in rats and mice. After mutation of the heparin-binding motif, binding to heparin and heparan sulfate was strongly reduced. The double mutant rhDAO-R568S/R571T showed minimal cellular uptake. The short α-distribution half-life of the wildtype protein was eliminated, and the clearance was significantly reduced in rodents. Conclusions: The successful decrease in plasma clearance of rhDAO by mutations of the heparin-binding motif with unchanged histamine-degrading activity represents the first step towards the development of rhDAO as a first-in-class biopharmaceutical to effectively treat diseases characterized by excessive histamine concentrations in plasma and tissues. Funding: Austrian Science Fund (FWF) Hertha Firnberg program grant T1135 (EG); Sigrid Juselius Foundation, Medicinska Understödsförening Liv och Hälsa rft (TAS and SeV).

Development of a buccal doxepin platform for pain in oral mucositis derived from head and neck cancer treatment.

This study describes the development of semisolid formulations containing doxepin (DOX) for pain relief in oral mucositis, frequently related to chemotherapy and/or radiotherapy treatments in patients with head and neck cancer. Chemical permeation enhancers were evaluated and selected according to the results obtained from rheological studies, drug release, and drug permeation and retention through buccal mucosa. Finally, the selected formulation was compared in vivo, with a reference DOX mouthwash, whose clinical efficacy had been previously reported. The obtained findings showed that an orabase® platform loading transcutol® (10%) and menthol (5%) for the buccal vehiculization of DOX exhibited a decreased elastic and viscous behavior improving its application. The main drug release mechanism could be considered as diffusion according to Higuchi model. Obtained DOX permeation rates were considered optimal for an analgesic effect and far below to an antidepressant activity. Similar in vivo plasma concentrations were found for the semisolid formulation and the reference mouthwash. However, DOX amounts retained in the mucosa of animals for the semisolid formulation were higher than the reference, which let us hypostatize even stronger potential local therapeutic effect with additional advantages such as, mucoadhesive properties, absence of alcohol, some degree of freshness, as well as, drug palatability improvement.

Vasopeptidase-activated latent ligands of the histamine receptor-1.

Whether peptidases present in vascular cells can activate prodrugs active on vascular cells has been tested with 2 potential latent ligands of the histamine H1 receptor (H1R). First, a peptide consisting of the antihistamine cetirizine (CTZ) condensed at the N-terminus of ε-aminocaproyl-bradykinin (εACA-BK) was evaluated for an antihistamine activity that could be revealed by degradation of the peptide part of the molecule. CTZ-εACA-BK had a submicromolar affinity for the BK B2 receptor (B2R; IC50 of 590 nM, [(3)H]BK binding competition), but a non-negligible affinity for the human H1 receptor (H1R; IC50 of 11 µM for [(3)H]pyrilamine binding). In the human isolated umbilical vein, a system where both endogenous B2R and H1R mediate strong contractions, CTZ-εACA-BK exerted mild antagonist effects on histamine-induced contraction that were not modified by omapatrilat or by a B2R antagonist that prevents endocytosis of the BK conjugate. Cells expressing recombinant ACE or B2R incubated with CTZ-εACA-BK did not release a competitor of [(3)H]pyrilamine binding to H1Rs. Thus, there is no evidence that CTZ-εACA-BK can release free cetirizine in biological environments. The second prodrug was a blocked agonist, L-alanyl-histamine, potentially activated by aminopeptidase N (APN). This compound did not compete for [(3)H]pyrilamine binding to H1Rs. The human umbilical vein contractility assay responded to L-alanyl-histamine (EC50 54.7 µM), but the APN inhibitor amastatin massively (17-fold) reduced its apparent potency. Amastatin did not influence the potency of histamine as a contractile agent. One of the 2 tested latent H1R ligands, L-alanyl-histamine, supported the feasibility of pro-drug activation by vascular ectopeptidases.

Development of a novel model for comparative evaluation of intranasal pharmacokinetics and effects of anti-allergic nasal sprays.

For locally acting drugs, an extended residence time in the nasal cavity is desirable and related to a prolonged effect. We sought to develop a model for comparative determination of intranasal pharmacokinetics. We embedded human respiratory tissue into a solid matrix and coated the surface with artificial nasal fluid. Nasal spray suspensions of fluticasone propionate (FP) and budesonide (Bud) as well as a solution of azelastine hydrochloride (AZ) were applied onto the surface and removed after 30 min to simulate mucociliary clearance. As exemplary anti-inflammatory measure, we evaluated the inhibition of IL-8 release from epithelial cells. FP and Bud were initially bound to the same extent to the tissue gel while AZ displayed a more 4-fold higher binding than FP or Bud. After equilibrium with plasma, approximately 5-fold higher tissue concentrations of AZ compared to FP and 77-fold higher levels in relation to Bud were determined. This tissue retention revealed an excellent correlation with the volume of distribution of the respective drugs (r=0.9999, p ≤ 0.05). The inhibitory effect of FP on IL-8 release was approximately 5-fold more pronounced compared to AZ. The present model realistically mirrors conditions in vivo where solubility and tissue absorption of intranasally applied drugs compete with mucociliary clearance mechanisms.

Rational quantitative structure-activity relationship (RQSAR) screen for PXR and CAR isoform-specific nuclear receptor ligands.

Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are closely related orphan nuclear receptor proteins that share several ligands and target overlapping sets of genes involved in homeostasis and all phases of drug metabolism. CAR and PXR are involved in the development of certain diseases, including diabetes, metabolic syndrome and obesity. Ligand screens for these receptors so far have typically focused on steroid hormone analogs with pharmacophore-based approaches, only to find relatively few new hits. Multiple CAR isoforms have been detected in human liver, with the most abundant being the constitutively active reference, CAR1, and the ligand-dependent isoform CAR3. It has been assumed that any compound that binds CAR1 should also activate CAR3, and so CAR3 can be used as a ligand-activated surrogate for CAR1 studies. The possibility of CAR3-specific ligands has not, so far, been addressed. To investigate the differences between CAR1, CAR3 and PXR, and to look for more CAR ligands that may be of use in quantitative structure-activity relationship (QSAR) studies, we performed a luciferase transactivation assay screen of 60 mostly non-steroid compounds. Known active compounds with different core chemistries were chosen as starting points and structural variants were rationally selected for screening. Distinct differences in agonist versus inverse agonist/antagonist effects were seen in 49 compounds that had some ligand effect on at least one receptor and 18 that had effects on all three receptors; eight were CAR1 ligands only, three were CAR3 only ligands and four affected PXR only. This work provides evidence for new CAR ligands, some of which have CAR3-specific effects, and provides observational data on CAR and PXR ligands with which to inform in silico strategies. Compounds that demonstrated unique activity on any one receptor are potentially valuable diagnostic tools for the investigation of in vivo molecular targets.

Bioconversion of the antihistaminc drug loratadine by tobacco cell suspension cultures expressing human cytochrome P450 3A4.

In this study we have expanded the metabolic potential of plant cell suspension cultures by introducing active human cytochrome P450 monooxygenase 3A4 into tobacco cells. Exogenously supplied loratadine was metabolized in a 3A4-specific manner, showing the capacity of this system for the generation of metabolites.

The new biology of histamine receptors.

The physiologic functions of histamine have been recognized for more than 100 years, yet new roles are still being uncovered. Most importantly, a newly discovered receptor of the amine has helped refine our understanding of histamine. This new receptor, the histamine H4 receptor (H4R), has a higher affinity for histamine compared with the histamine H1 receptor and appears to be more selectively expressed, found mainly on hematopoietic cells. H4R is involved in chemotaxis and inflammatory mediator release by eosinophils, mast cells, monocytes, dendritic cells, and T cells. Studies in animal models using selective antagonists or H4R-deficient mice have shown a role for the receptor in inflammation in vivo. In particular, H4R antagonists have shown promise in experimental models of asthma and pruritus, two conditions where currently marketed antihistamines targeting the histamine H1 receptor are not optimally effective in humans. Thus, a new class of H4R-specific antihistamines may be distinctively effective in treating allergic diseases associated with chronic pruritus and asthma.

Development of a homogeneous binding assay for histamine receptors.

Histamine is critically involved in a wide range of physiological and pathological processes through its actions at different receptors. Thus, histamine receptors have been actively pursued as therapeutic targets in the pharmaceutical industry for the treatment of a variety of diseases. There are currently four histamine receptors that have been cloned, all of which are G protein-coupled receptors. Studies from both academia and pharmaceutical companies have identified compounds that modulate the function of specific histamine receptors. These efforts led to the successful introduction of histamine H(1) and H(2) receptor antagonists for the treatment of allergy and excess gastric acid secretion, respectively. Histamine H(3) receptor ligands are currently under investigation for the treatment of obesity and neurological disorders. The recently identified histamine H(4) receptor is preferentially expressed in the immune tissues, suggesting a potential role in normal immune functions and possibly in the pathogenesis of inflammatory diseases. Even with the long history of histamine research and the important applications of histamine receptor ligands, assays to measure the affinity of compounds binding to histamine receptors are still routinely analyzed using a filtration assay, a very low-throughput assay involving washing and filtration steps. This article describes a simple, robust, and homogeneous binding assay based on the scintillation proximity assay (SPA) technology that provides results equivalent to those obtained using the more complex filtration assay. The SPA format is easily adapted to high-throughput screening because it is amenable to automation. In summary, this technique allows high-throughput screening of compounds against multiple histamine receptors and, thus, facilitates drug discovery efforts.

A new class of diamine-based human histamine H3 receptor antagonists: 4-(aminoalkoxy)benzylamines.

4-(Aminoalkoxy)benzylamines were prepared and screened for in vitro activity at the human histamine H(3) receptor. Some members of this series exhibited subnanomolar binding affinities. Analogues in which one nitrogen atom was replaced with a methine group showed greatly reduced binding affinities. Six members of this series were found to be antagonists in a cell-based model of human histamine H(3) receptor activation. One member of this series, 1-[4-(3-piperidin-1-ylpropoxy)benzyl]piperidine (7b), was found to be a selective and potent human H(3) receptor antagonist.

Butyric acid sensitizes Vero cells to ricin-induced apoptosis via accelerated activation of multiple signal transduction pathways.

We found that the treatment with 1 mM butyric acid for 2 days renders Vero cells highly sensitive to ricin-induced apoptosis reflected by cytolysis concomitant with apoptotic cellular and nuclear morphological changes, DNA fragmentation, and increase in caspase-3 like activity, whereas butyric acid alone had no cytotoxic effect on Vero cells. During the treatment with butyric acid, gradual increase in alkaline phosphatase activity, an indicator for butyric acid-induced differentiation, was observed in Vero cells. Although the potency of ricin-mediated protein synthesis was increased in butyric acid-treated Vero cells as compared to untreated cells, the binding and internalization of ricin to the cells were not much affected. Furthermore, DNA fragmentation caused by other protein synthesis inhibitors such as diphtheria toxin and anisomysin were also highly potentiated in butyric acid-treated Vero cells, whereas the potencies of these toxins to inhibit the protein synthesis were not affected by butyric acid treatment. These results suggest that the apoptosis signaling pathway, which may be triggered by cytotoxic stress response caused by toxins, is sensitized in butyric acid-treated cells, while the pathways leading to the protein synthesis inhibition by these toxins are relatively unchanged. No significant differences in the expression levels of p21, p53, and Bcl-2 proteins were observed between butyric acid-treated and untreated Vero cells. The treatment with ricin resulted in the activation of p38 MAP kinase, and this activation occurred on an accelerated time schedule in butyric acid-treated Vero cells than in untreated cells. The specific inhibitor of p38 MAP kinase SB203580 showed a partial inhibitory effect on ricin-induced apoptosis in control Vero cells, but it was less effective in butyric acid-treated Vero cells. Taken together, our results suggest that butyric acid-treatment may result in sensitization of multiple intracellular signal transduction pathways including apoptotic signaling pathways and p38 MAP kinase pathway.

Inhibition of antigen-induced mediator release from IgE-sensitized cells by a monoclonal anti-Fc epsilon RI alpha-chain receptor antibody: implications for the involvement of the membrane-proximal alpha-chain region in Fc epsilon RI-mediated cell activation.

The interaction between human IgE and its high affinity receptor, FcepsilonRI, is a critical event in mediating the allergic response. Aggregation of the alpha-chain of FcepsilonRI (FcepsilonRIalpha) occurs via cross-linking of receptor-bound IgE by Ag, resulting in cell activation and the release of mediators of hypersensitivity. Recently, we mapped the epitopes of two anti-FcepsilonRIalpha mAbs, 15/1 and 5H5F8. In contrast to 15/1, mAb 5H5F8 does not inhibit IgE binding to FcepsilonRIalpha. Here we demonstrate both 5H5F8 binding to FcepsilonRI(+) cells as well as a high level of IgE binding to 5H5F8-saturated cells. At the same time 5H5F8 strongly inhibits hexosaminidase release and Ca(2+) flux after Ag triggering from human IgE-sensitized RBL-2H3 cells stably transfected with human FcepsilonRIalpha. Further, 5H5F8 and its Fab inhibit sulfidoleukotriene and histamine release from primary human peripheral blood leukocytes, including cells bearing endogenous IGE: Furthermore, we confirm that 5H5F8 maps to a linear peptide sequence in close proximity to the cell membrane. Two chemically synthesized peptides containing the 5H5F8 epitope sequence PREKY were selected for detailed analysis of 5H5F8 and 5H5F8 Fab binding and were found to produce K(d) values of similar magnitude to that observed for binding to recombinant FcepsilonRIalpha. These peptides may prove useful as targets for the identification of antagonists of FcepsilonRIalpha-mediated biological activity. Moreover, our data indicate that FcepsilonRIalpha-mediated activation may involve a novel alpha-chain epitope in an early step of the cell-triggering pathway leading to cellular activation.

Synthesis and in vitro pharmacology of a series of new chiral histamine H3-receptor ligands: 2-(R and S)-Amino-3-(1H-imidazol-4(5)-yl)propyl ether derivatives.

To investigate stereospecificity and the mechanism of activation of the histamine H3-receptor, a series of 2-(R and S)-amino-3-(1H-imidazol-4(5)-yl)propyl ether derivatives were synthesized. In these compounds, the structures of the well-known antagonist iodoproxyfan and the full agonists R- or S-(alpha)-methylhistamine were combined in one molecule. The obtained "hybrid" molecules were tested for H3-receptor affinity on rat cerebral cortex. Some selected compounds were further screened for H3-receptor functional activity with GTPgamma[35S] autoradiography studies using rat brain tissue sections. The affinity of all the synthesized compounds (-log Ki = 5.9-7.9) was lower than that found for iodoproxyfan or two of its analogues; however, the compounds showed stereospecificity. The S-configuration of the series of 2-amino-3-(1H-imidazol-4(5)-yl)propyl ether derivatives, which resembles the stereochemistry of R-(alpha)-methylhistamine, was more favorable. Incorporation of an amino group in the propyl chain of iodoproxyfan and analogues did not alter the antagonistic behavior for compounds with an aromatic side chain. However, when also the aromatic moiety was replaced by a cyclohexyl group, the compounds behaved as agonists. This indicates that an interaction between the side chain amino group and the H3-receptor protein is involved in H3-receptor activation. The 2-(S)-amino-3-(1H-imidazol-4(5)-yl)propyl cyclohexylmethyl ether (23) has H3-receptor agonistic properties with high affinity for the histamine H3-receptor (-log Ki = 7.9 +/- 0.2) and might serve as a useful tool for further studies concerning drug design and receptor-ligand interactions.

Synergy between tamoxifen and cisplatin in human melanoma cells is dependent on the presence of antiestrogen-binding sites.

We have demonstrated previously that cisplatin (DDP) and tamoxifen (TAM) act synergistically to kill human melanoma T-289 cells, and that the observed synergy is lost in the 3-fold TAM-resistant subline, 289/TAM6. We have identified the intracellular antiestrogen-binding sites (AEBSs), defined by their ability to bind antiestrogens while having no affinity for estrogen, as a possible mediator of this synergy. We report here that [3H]TAM binds to AEBSs, as defined by the ability of N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine-HCl, an AEBS-specific ligand, to compete with [3H]TAM binding. Furthermore, we have characterized the number of binding sites and their affinity for [3H]TAM by Scatchard analysis in whole-cell lysates, microsomal fractions, and nuclear fractions of both cell lines by competing [3H]TAM binding with increasing concentrations of unlabeled TAM. These data demonstrate that the loss of a high-affinity AEBS from the nuclear fraction of the 289/TAM6 cell line correlates with the loss of synergy between DDP and TAM in these cells. This implicates AEBSs as a critical component of the mechanism that mediates the synergistic interaction of DDP and TAM in human melanoma cells.

Binding of histamine H3-receptor antagonists to hematopoietic progenitor cells. Evidence for a histamine transporter unrelated to histamine H3 receptors.

Hematopoietic progenitor cells can take up histamine or release IL-3-induced histamine through a bi-directional transport system that is blocked by H3-receptor antagonists. In the present study we demonstrate a correlation between the affinity of various H3-receptor antagonists and their potency as inhibitors of histamine uptake. All compounds that blocked histamine uptake also inhibited IL-3-induced histamine release. Yet, classical H3 receptors are not involved in this biological activity, since highly specific histamine H3-receptor agonists neither alter histamine uptake nor affect the release of endogenous histamine synthesized in response to IL-3. Furthermore, the inhibitory effect of H3-receptor antagonists on histamine uptake was not reversed by the agonists. Unlike H3-receptor antagonists, the agonists did not displace the binding of the labeled antagonist iodoproxyfan.

Differences in ketanserin binding in the ventromedial hypothalamus of ewes responsive or refractory to short days.

Participation of central 5HT receptors in the inhibition of LH pulsatility during refractoriness to short days (SD) in ewes has been suggested by previous in vivo studies using various 5HT-antagonist such as ketanserin. In the present study, binding of [3H]ketanserin in ewe brain sections was similar to that described in the brain of other species and could correspond with an interaction at 5HT2 receptors sites. Rosenthal analysis from the caudate nucleus was linear (Kd = 3 nM). The displacement studies from the cortex slices showed that the 5HT antagonists such as methysergide, ketanserin, cyproheptadine and spiperone competed with the labelled ligand at nanomolar concentrations whereas serotonin was less active. However, the first 3 drugs recognized different populations of binding sites. Prazosin, an alpha 1-adrenergic antagonist was inactive, but a slight inhibition of [3H]ketanserin binding was induced by pyrilamine, an H1 histaminic antagonist, within a nanomolar range. Methysergide (10(-6) M), which does not bind to H1 receptors, was therefore used to determine the nonspecific binding. Quantitative analysis of the binding of 3 nM [3H]ketanserin on sections of the ewe brain at the preopticohypothalamic level was then carried out by autoradiography. The highest binding densities were observed in the caudate nuclei (64.0 fmol/mg tissue Eq) and the mammillary bodies (52.7 fmol/mg tissue Eq) whereas intermediate or low densities were found in the other structures. The anatomical distribution of the labelling was similar to that described in other species for 5HT2 receptors. Ketanserin binding in these areas was compared between two groups of ovariectomized estradiol-treated Ile-de-France ewes, submitted to artificial short days (SD: 8L:16D), one group with a high LH pulsatility (responsive to SD) and the other one with a low LH pulsatility (photorefractory to SD). Binding densities were similar for each one of the studied regions between the two groups, except in the ventrolateral part of the mediobasal hypothalamus, where ewes exhibiting high LH pulsatility had a more than 2-fold higher binding density than those with a low LH pulsatility (mean +/- SEM, 14.6 +/- 1.4 vs. 5.7 +/- 1.0 fmol/mg tissue Eq, respectively; p < 0.0016). These results suggest that [3H]ketanserin binding sites in the ventromedial part of the mediobasal hypothalamus could be associated to the regulation of the photoperiodic inhibition of LH at the time of establishment of refractoriness to short days in the Ile-de-France ewe.