Histamine,part of the metabolome

Histamine, a decarboxylated amino acid with a molecular mass of 112 daltons reveals multicoloured functional activities. Its role in allergy and inflammation is abundantly characterized. Moreover histamine is one of the neuotransmitters, has a role in gastric acid production and in maintenance of blood-brain barrier. In the last decade, many data were collected suggesting an important function of histamine in events of immune response and also in both benign and malignant cell proliferation. Our group collected data on the relevance of histamine as an autocrine factor in human melanoma. The outcome of the action seems to be closely related to the local and actual balance of histamine receptors (H1R, H2R, H3R and H4R) on tumor cells. Recently, using a gene targeted mouse strain (lacking an enzyme, histidine decarboxylase, the only one responsible for histamine production) many phenotype of the histamine-free mice were demonstrated. Our data suggest, that histamine, as part of the poorly characterized metabolome of the mammalian cells plays significant role in many physiological and pathological processes.     

Different h2 receptor antihistamines dissimilarly retard the growth of xenografted human melanoma cells in immunodeficient mice

Melanoma cells and tissues contain considerable amounts of histamine and express histamine receptors, suggesting the existence of autocrine and paracrine regulation by histamine. Our previous in vitro results suggested that histamine elevates melanoma cell growth through the H2 receptor. In this work we show that in vivo tumour proliferation in immunodeficient mice xenotransplanted with a human melanoma cell line is diminished by cimetidine, an H2 receptor antagonist, if combined with a tamoxifen derivate acting on cytochrome p450 molecules (DPPE). Ranitidine, another H2 receptor antagonist, has a weaker inhibitory effect, the kinetics and mechanism of which is probably dissimilar to that of the cimetidine/DPPE mixture.     

Histamine as a growth factor and chemoattractant for human carcinoma and melanoma cells: action through Ca2(+)-mobilizing H1 receptors

Histamine receptors are present on the surface of various normal and tumor-derived cell types, where their biological function is incompletely understood. Here we report that histamine not only stimulates cell proliferation under serum-free conditions, but also is chemotactic for human carcinoma (Hela and A431) and melanoma (A875) cells expressing H1 type receptors. Histamine was found to be a potent activator of phospholipase C, leading to polyphosphoinositide hydrolysis and subsequent intracellular Ca2+ mobilization. In addition, histamine also causes the protein kinase C-mediated activation of Na+/H+ exchange, as evidenced by an amiloride-sensitive rise in cytoplasmic pH. All histamine-induced responses, including chemotaxis and DNA synthesis, are completely inhibited by the H1 receptor antagonist pyrilamine, but not by cimetidine, an inhibitor of histamine H2 type receptors. Our results suggest that histamine may have a previously unrecognized role in the migration and proliferation of cells expressing H1 receptors.     

Histamine acting on H1 receptor promotes inhibition of proliferation via PLC, RAC, and JNK-dependent pathways

It is well established that histamine modulates cell proliferation through the activation of the histamine H1 receptor (H1R), a G protein-coupled receptor (GPCR) that is known to couple to phospholipase C (PLC) activation via Gq. In the present study, we aimed to determine whether H1R activation modulates Rho GTPases, well-known effectors of Gq/G₁₁-coupled receptors, and whether such modulation influences cell proliferation. Experiments were carried out in CHO cells stably expressing H1R (CHO-H1R). By using pull-down assays, we found that both histamine and a selective H1R agonist activated Rac and RhoA in a time- and dose-dependent manner without significant changes in the activation of Cdc42. Histamine response was abolished by the H1R antagonist mepyramine, RGS2 and the PLC inhibitor U73122, suggesting that Rac and RhoA activation is mediated by H1R via Gq coupling to PLC stimulation. Histamine caused a marked activation of serum response factor activity via the H1R, as determined with a serum-responsive element (SRE) luciferase reporter, and this response was inhibited by RhoA inactivation with C3 toxin. Histamine also caused a significant activation of JNK which was inhibited by expression of the Rac-GAP β2-chimaerin. On the other hand, H1R-induced ERK1/2 activation was inhibited by U73122 but not affected by C3 or β2-chimaerin, suggesting that ERK1/2 activation was dependent on PLC and independent of RhoA or Rac. [³H]-Thymidine incorporation assays showed that both histamine and the H1R agonist inhibited cell proliferation in a dose-dependent manner and that the effect was independent of RhoA but partially dependent on JNK and Rac. Our results reveal that functional coupling of the H1R to Gq-PLC leads to the activation of RhoA and Rac small GTPases and suggest distinct roles for Rho GTPases in the control of cell proliferation by histamine.     

Identification and Characterization of ZEL-H16 as a Novel Agonist of the Histamine H(3) Receptor

The histamine H3 receptor (H3R) has been recognized as a promising target for the treatment of various central and peripheral nervous system diseases. In this study, a non-imidazole compound, ZEL-H16, was identified as a novel histamine H3 receptor agonist. ZEL-H16 was found to bind to human H3R with a Ki value of approximately 2.07 nM and 4.36 nM to rat H3R. Further characterization indicated that ZEL-H16 behaved as a partial agonist on the inhibition of forskolin-stimulated cAMP accumulation (the efficacy was 60% of that of histamine) and activation of ERK1/2 signaling (the efficacy was 50% of that of histamine) at H3 receptors, but acted as a full agonist just like histamin in the guinea-pig ileum contraction assay. These effects were blocked by pertussis toxin and H3 receptor specific antagonist thioperamide. ZEL-H16 showed no agonist or antagonist activities at the cloned human histamine H1, H2, and H4 receptors and other biogenic amine GPCRs in the CRE-driven reporter assay. Furthermore, our present data demonstrated that treatment of ZEL-H16 resulted in intensive H3 receptor internalization and delayed recycling to the cell surface as compared to that of control with treatment of histamine. Thus, ZEL-H16 is a novel and potent nonimidazole agonist of H3R, which might serve as a pharmacological tool for future investigations or as possible therapeutic agent of H3R.     

Demonstration of histamine H2 receptors on human melanoma cells

Histamine induced a concentration-dependent increase in intracellular cyclic-AMP of the two human melanoma cell lines SK23 and DX3.LT5.1; maximal stimulation was obtained with 17.8 microM histamine which consistently produced greater than 50-fold increases in the cyclic AMP content of both cell lines. The dose-response curve for histamine in each culture was progressively displaced to the right with increasing concentrations of the histamine H2 receptor antagonist cimetidine. Ranitidine, another H2 receptor antagonist also prevented the histamine-induced cyclic AMP elevation, but the H1 receptor antagonists mepyramine and tripelennamine had no significant effect. These findings indicate that human melanoma cells express histamine H2 receptors, stimulation of which activates adenylate cyclase with a subsequent rise in intracellular cyclic AMP. Mast cell:melanoma interactions mediated by histamine in vivo might therefore be expected to modify some aspects of melanoma cell behaviour.     

Disruption of the protein interaction between FAK and IGF-1R inhibits melanoma tumor growth

FAK (focal adhesion kinase) and IGF-1R (insulin-like growth factor receptor-1) directly interact with each other and thereby activate crucial signaling pathways that benefit cancer cells. Inhibition of FAK and IGF-1R function has been shown to significantly decrease cancer cell proliferation and increase sensitivity to chemotherapy and radiation treatment. As a novel approach in human melanoma, we evaluated the effect of a small-molecule compound that disrupts the protein interaction of FAK and IGF-1R.

Previously, using virtual screening and functional testing, we identified a lead compound (INT2–31) that targets the known FAK-IGF-1R protein interaction site. We studied the ability of this compound to disrupt FAK-IGF-1R protein interactions, inhibit downstream signaling, decrease human melanoma cell proliferation, alter cell cycle progression, induce apoptosis and decrease tumor growth in vivo.

INT2–31 blocked the interaction of FAK and IGF-1R in vitro and in vivo in melanoma cells and tumor xenografts through precluding the activation of IRS-1, leading to reduced phosphorylation of AKT upon IGF-1 stimulation. As a result, INT2–31 significantly inhibited cell proliferation and viability (range 0.05–10 μM). More importantly, 15 mg/kg of INT2–31 given for 21 d via intraperitoneal injection disrupted the interaction of FAK and IGF-1R and effectively decreased phosphorylation of tumor AKT, resulting in significant melanoma tumor regression in vivo.

Our data suggest that the FAK-IGF-1R protein interaction is an important target, and disruption of this interaction with a novel small molecule (INT2–31) has potential anti-neoplastic therapeutic effects in human melanoma.     

Disruption of the protein interaction between FAK and IGF-1R inhibits melanoma tumor growth

FAK (focal adhesion kinase) and IGF-1R (insulin-like growth factor receptor-1) directly interact with each other and thereby activate crucial signaling pathways that benefit cancer cells. Inhibition of FAK and IGF-1R function has been shown to significantly decrease cancer cell proliferation and increase sensitivity to chemotherapy and radiation treatment. As a novel approach in human melanoma, we evaluated the effect of a small-molecule compound that disrupts the protein interaction of FAK and IGF-1R. Previously, using virtual screening and functional testing, we identified a lead compound (INT2–31) that targets the known FAK-IGF-1R protein interaction site. We studied the ability of this compound to disrupt FAK-IGF-1R protein interactions, inhibit downstream signaling, decrease human melanoma cell proliferation, alter cell cycle progression, induce apoptosis and decrease tumor growth in vivo. INT2–31 blocked the interaction of FAK and IGF-1R in vitro and in vivo in melanoma cells and tumor xenografts through precluding the activation of IRS-1, leading to reduced phosphorylation of AKT upon IGF-1 stimulation. As a result, INT2–31 significantly inhibited cell proliferation and viability (range 0.05–10 μM). More importantly, 15 mg/kg of INT2–31 given for 21 d via intraperitoneal injection disrupted the interaction of FAK and IGF-1R and effectively decreased phosphorylation of tumor AKT, resulting in significant melanoma tumor regression in vivo. Our data suggest that the FAK-IGF-1R protein interaction is an important target, and disruption of this interaction with a novel small molecule (INT2–31) has potential anti-neoplastic therapeutic effects in human melanoma.     

Role of histamine in natural killer cell-mediated resistance against tumor cells

The formation of lung metastases by i.v.-injected B16 melanoma (F1 and F10 strain) cells in Swiss albino, C57BL/6, and BALB/c mice was reduced by a single dose of histamine given 24 h before tumor cell inoculation. The antimetastatic effect of histamine was specifically mediated by histamine H2-receptors (H2R): it was blocked by the H2R antagonist ranitidine and mimicked by dimaprit, a specific H2R agonist but not by an H2R-inactive structural analog of this compound, nor-dimaprit, or the H1R agonist 2-thiazolyl-ethylamide. A single dose of any of the H2R antagonists ranitidine, tiotidine, famotidine, or cimetidine drastically augmented metastasis. Effects of H2R-interactive compounds on B16 metastasis required intact NK cells, as judged by the inability of histamine or ranitidine to affect B16 metastasis after NK cell depletion in vivo using antibodies to asialo-GM1. NK-cell-mediated lysis of YAC-1 lymphoma cells in vivo was enhanced by histamine and reduced by ranitidine within 4 h after inoculation of tumor cells. The antimetastatic effect of IL-2 was potentiated by histamine; in some experiments, combined treatment with a low dose of IL-2 (6000 U/kg) and histamine completely eliminated metastasis, whereas concomitant treatment with ranitidine abrogated antimetastatic effects of IL-2; animals treated with ranitidine and IL-2 displayed the same level of enhanced metastasis as those treated with ranitidine alone. The presented data are suggestive of an earlier unrecognized role for histamine in NK cell-mediated resistance against metastatic tumor cells.     

Regulatory effects of mast cells on lymphoid cells: the role of histamine type 1 receptors in the interaction between mast cells, helper T cells and natural suppressor cells

We have investigated the role of mast cells as modulators of lymphocyte function because the mast cells are concentrated in the areas of lymphoid storage; they are dependent upon T-cell growth factor for their proliferation; and they appear to be the principle if not sole storage site for histamine. We have tested the influence of mast cells on the proliferation of alloreactive cloned helper T cells, mixed leukocyte reactions, and the suppressive capacity of natural suppressor cells. We used an IL-3-dependent mast cell line that at high numbers (greater than 10(5)) suppressed and at low numbers (10(3) to 6 X 10(4)) augmented the proliferation of TH cells. Addition of histamine to cocultures enhanced the mast cell mediated proliferation of TH cells without directly affecting the helper cells. The action of histamine appeared to be mediated with H1 type receptors on these mast cells. Pretreatment of natural suppressor cells with supernatants from mast cell enhanced their suppressive capability. Here too, histamines enhanced suppression by the NS cell via histamine type 1 receptors on the natural suppressor cells. Our data suggest that mast cells may be a major modulator of the lymphoid cell immune function and demonstrate a role of histamine type 1 receptors in the interaction between mast cells, helper T cells, and natural suppressor cells.     

Histamine H2 receptor activity during the differentiation of the human monocytic-like cell line U-937. Comparison with prostaglandins and isoproterenol

Histamine H2 receptor activity (cAMP generation) has been characterized in U-937 cells before and after retinoic acid-induced differentiation into monocyte-/macrophage-like cells. The differentiation is associated with a decreased capacity of U-937 monocytes to generate cAMP under basal conditions or after cell surface receptor stimulation by histamine, isoproterenol and PGE1. In contrast, the potencies of the hormones are unchanged during monocytic maturation (EC50 values = 3.2-4.6 X 10(-6) M histamine, 4.6-7 X 10(-9) M isoproterenol, 2-4.6 X 10(-6) M PGE1). The data support the view that histamine and cAMP-inducing agents may control the proliferation and differentiation of normal and leukemic cells committed to monocytic maturation in man. They also raise the possibility that normal human monocytes also possess functional H2 receptors and that histamine may be implicated in the regulation of monocyte/macrophage functions.     

Failure to detect IL-3-binding sites on human mast cells

IL-3, a pleiotropic lymphokine, has been termed mast cell growth factor because it promotes growth and differentiation of murine mast cells. Murine mast cells, in turn, express cell surface receptors for IL-3. Human rIL-3 has been shown to induce proliferation and differentiation of human basophils and to activate basophils via high affinity binding sites. To investigate whether human mast cells express IL-3R, binding studies with 125I-radiolabeled human rIL-3 were performed on HMC-1, a novel human mast cell line, and on pure populations (i.e., 93 to 99% purity) of human tissue mast cells obtained with mAb and C from dispersed lung (n = 2). Unexpectedly, neither enriched human lung mast cells nor HMC-1 cells bound radiolabeled human rIL-3 specifically. Moreover, human rIL-3 failed to promote uptake of [3H]thymidine, synthesis of histamine, histamine releasability, or changes in expression of mast cell differentiation Ag (YB5B8, CD54/ICAM-1, CD9/p24, CD33/gp67) on either human lung mast cells or HMC-1 cells. It is hypothesized that the fundamental difference in the biologic response to IL-3 between human and murine mast cells is due to a loss during evolution of mast cell high affinity IL-3 binding sites.     

The proteins DLK1 and DLK2 modulate NOTCH1-dependent proliferation and oncogenic potential of human SK-MEL-2 melanoma cells

NOTCH receptors regulate cell proliferation and survival in several types of cancer cells. Depending on the cellular context, NOTCH1 can function as an oncogene or as a tumor suppressor gene. DLK1 is also involved in the regulation of cell growth and cancer, but nothing is known about the role of DLK2 in these processes. Recently, the proteins DLK1 and DLK2 have been reported to interact with NOTCH1 and to inhibit NOTCH1 activation and signaling in different cell lines. In this work, we focused on the role of DLK proteins in the control of melanoma cell growth, where NOTCH1 is known to exert an oncogenic effect. We found that human DLK proteins inhibit NOTCH signaling in SK-MEL-2 metastatic melanoma cells. Moreover, the proliferation rate of these cells was dependent upon the level of NOTCH activation and signaling as regulated by DLK proteins. In particular, high levels of NOTCH inhibition resulted in a decrease, whereas lower levels of NOTCH inhibition led to an increase in melanoma cell proliferation rates, both in vitro and in vivo. Finally, our data revealed additive NOTCH-mediated effects of DLK proteins and the γ-secretase inhibitor DAPT on cell proliferation. The data presented in this work suggest that a fine regulation of NOTCH signaling plays an important role in the control of metastatic melanoma cell proliferation. Our results open the way to new research on the role of DLK proteins as potential therapeutic tools for the treatment of human melanoma.     

Histamine and the heart

Histamine has been known as a cardiac stimulant for over 70 years. Work in our laboratory over the past decade has established that histamine receptors exist in the hearts of various species. The type of histamine receptor varies not only between species but also in the various regions of the heart. In the guinea pig heart H1 receptors are found in left atria and ventricles while H2 receptors are found in right atria and are the predominant histamine receptor in the ventricles. Rabbit atria contain both H1 and H2 receptors while the ventricles appear to possess only H1. Rat and cat heart do not seem to have histamine receptors and the positive inotropic and chronotropic effects elicited by histamine in cardiac preparations of these species are due to the release of noradrenaline. Dog heart contains H1 receptors while human heart has H2 receptors. In all cases H2 receptors are associated with adenylate cyclase and stimulation of such receptors results in an increase in cyclic AMP levels. H1 receptors are not associated with cyclic nucleotides in the heart. There are certain similarities between beta-adrenergic and H2-histaminergic receptors as well as between alpha-adrenergic and H1-histaminergic receptors. Stimulation of either histamine receptor must result in an increase in the free calcium ion concentration in the cardiac cell but the mechanisms involved are obviously different.     

Involvement of hydrogen peroxide in histamine-induced modulation of WM35 human malignant melanoma cell proliferation

Histamine is a recognized growth factor in melanoma, and exogenous histamine produces a dual effect on proliferation. We have previously reported that histamine at micromolar concentrations reduces the proliferation of melanoma cell lines. To investigate the mechanism by which histamine inhibits proliferation of WM35 human melanoma cells, we have studied the involvement of histamine in reactive oxygen species production and antioxidant enzyme regulation in these cells. Results indicate that histamine treatment (10 μM) significantly increased hydrogen peroxide levels, whereas it slightly decreased superoxide levels associated with an enhancement of superoxide dismutase and a reduction in catalase activity. Additionally, catalase treatment reversed the inhibitory effect of histamine on proliferation, and various treatments that reduce hydrogen peroxide formation increased proliferation of these cells. Furthermore, we demonstrate that the inhibition of proliferation produced by histamine was mediated at least in part by an induction of cell senescence. We conclude that hydrogen peroxide is involved in histamine-mediated modulation of proliferation in malignant melanoma cells.     

Molecular and cellular analysis of histamine H1 receptors on cultured smooth muscle cells

Histamine is an important mediator of immediate hypersensitivity for both animals and humans. The action of histamine on target tissues is believed to be mediated by specific cell surface receptors, especially H1 and H2 receptors for hypersensitivity and inflammatory reactions, which involve stimulation of smooth muscle contractility, alterations in vascular permeability, and modifications in the activities of macrophages and lymphocytes. Although the nature of histamine receptors in the brain and peripheral tissues has been studied extensively by many laboratories, the molecular mechanism of histamine receptor-mediated reactions is not fully understood, mainly because histamine receptors are incompletely characterized from the biochemical point of view. In previous studies, we have found that the cultured smooth muscle cell line DDT1MF-2, derived from hamster vas deferens, expresses low-affinity histamine H1 receptors and responds biochemically and functionally to H1-specific stimulation (Mitsuhashi and Payan, J Cell Physiol 134:367, 1988). This cell line provides a model for analyzing the biochemical responses of H1 receptor-mediated reactions in peripheral tissues. In this review, we summarized our recent progress in the study of low-affinity H1 receptors on DDT1MF-2 cells.     

Cutting edge: histamine is required for IL-4-driven eosinophilic allergic responses

Histamine is an important allergic mediator, and studies have defined roles for both histamine 1 and 4 receptors in allergic airway inflammation. In this study, we show that histamine is necessary to generate IL-4-driven eosinophilic inflammation, as histamine-deficient mice cannot generate eosinophilic lung inflammation in response to intratracheal IL-4 and exogenous histamine restores responsiveness. This is histamine 2 receptor (H2R) dependent because H2R knockout mice fail to respond to IL-4, and a H2R agonist restores inflammation in histidine decarboxylase knockout. Furthermore, alveolar epithelial cells require H2R to produce CCL24, an eosinophil recruitment factor, whereas H2R blockade reduces CCL24 production from wild-type cells. In an allergic inflammation model, H2R knockout mice show significantly reduced eosinophilic inflammation and CCL24 expression. These data demonstrate a previously unidentified role for H2R in allergic inflammation and establishes a synergy between endogenous histamine and IL-4 that supports eosinophilic recruitment to the lung.     

Mouse mammary epithelial histamine system.

Histamine is suggested to play a role in mammary gland growth regulation, differentiation and functioning during pregnancy and lactation. Two pools of histamine are thought to be involved in these processes: mastocyte- and epithelial cell related histamine. In the present study we focused on epithelial cells. Immunohistochemistry has shown that the epithelial cells positive for histamine and L-histidine decarboxylase (HDC), the primary enzyme regulating histamine biosynthesis, were mainly found in cells forming alveolar structures in the mammary gland. Cultured primary mouse mammary epithelial cells (MMEC) expressed strong HDC immunoreactivity, especially dividing cells and non-differentiated ones. Histidine decarboxylase activity undergoes significant changes during pregnancy and lactation. Pregnancy associated intensive growth of the mammary gland coincided with an increase and the first days of lactation with a decrease of HDC protein expression. Binding studies with mammary tissue membranes and epithelial cell membranes revealed the presence of H1 and H3 but not H2 receptors. Summarizing, our data have shown that mammary epithelial cells are capable of synthesizing and excreting histamine and they bear histamine receptors. These findings further substantiate the role of histamine in mammary gland physiology.     

New role for histamine in interleukin-3-induced proliferation of hematopoietic stem cells

This study investigated the effect of histamine generated by murine bone marrow cells in response to IL-3 on one particular biological activity of this growth factor, i.e., triggering of cells forming colonies in spleen (CFU-S) into S phase. Evidence is provided that i) IL-3-induced day-8 CFU-S cell cycling, evaluated by hydroxy-urea suicide, is completely abrogated when the binding of histamine to its H2 receptors is blocked by the specific antagonist oxmetidine, whereas cetirizine, a H1 receptor antagonist, is ineffective; and ii) the entry of day-8 CFU-S into S phase in response to IL-3 is likewise abolished when the histamine synthesis promoted by the growth factor is prevented by alpha-fluoromethylhistidine, a specific inhibitor of the histamine-forming enzyme, histidine decarboxylase. Similar results are obtained with both drugs, when a progenitor-enriched bone marrow population is used instead of total cells. Furthermore, i.v. injection of recombinant (r)IL-3 results within 2 hr in a substantial increase in bone marrow cell histamine synthesis together with triggering of day-8 CFU-S into cycle, the latter being completely abolished by a simultaneous injection of the H2 histamine receptor antagonist oxmetidine. Thus, our findings support the notion that both in vitro and in vivo the proliferation of early CFU-S in response to IL-3 is modulated by histamine via its H2 receptors. This conclusion is also consistent with the observation that dimaprit, a specific agonist of these receptors not only enhances the sensitivity of day-8 CFU-S to HU after a 2 hr incubation with bone marrow cells but also increases, to the same extent as IL-3, the number of colonies formed in irradiated spleens after a 5 hr pretreatment.