Histamine is a potent inducer of IL-18 and IFN-gamma in human peripheral blood mononuclear cells

Mast cell-mediated immune regulation in health and disease

Mast cells are important components of the immune system, and they perform pro-inflammatory as well as anti-inflammatory roles in the complex process of immune regulation in health and disease. Because of their strategic perivascular localization, sensitivity and adaptability to the microenvironment, and ability to release a variety of preformed and newly synthesized effector molecules, mast cells perform unique functions in almost all organs. Additionally, Mast cells express a wide range of surface and cytoplasmic receptors which enable them to respond to a variety of cytokines, chemicals, and pathogens. The mast cell's role as a cellular interface between external and internal environments as well as between vasculature and tissues is critical for protection and repair. Mast cell interactions with different immune and nonimmune cells through secreted inflammatory mediators may also turn in favor of disease promoting agents. First and forefront, mast cells are well recognized for their multifaceted functions in allergic diseases. Reciprocal communication between mast cells and endothelial cells in the presence of bacterial toxins in chronic/sub-clinical infections induce persistent vascular inflammation. We have shown that mast cell proteases and histamine induce endothelial inflammatory responses that are synergistically amplified by bacterial toxins. Mast cells have been shown to exacerbate vascular changes in normal states as well as in chronic or subclinical infections, particularly among cigarette smokers. Furthermore, a potential role of mast cells in SARS-CoV-2-induced dysfunction of the capillary-alveolar interface adds to the growing understanding of mast cells in viral infections. The interaction between mast cells and microglial cells in the brain further highlights their significance in neuroinflammation. This review highlights the significant role of mast cells as the interface that acts as sensor and early responder through interactions with cells in systemic organs and the nervous system.

Histamine Activates Human Eosinophils via H2R and H4R Predominantly in Atopic Dermatitis Patients

Atopic dermatitis (AD) is maintained by a variety of cells and inflammatory mediators, including eosinophils and histamine. We recently reported that eosinophils from AD patients highly express the H₄R. However, its immunomodulatory function in eosinophils is still largely unexplored. In this study, transcriptome analysis of blood eosinophils from AD patients stimulated with histamine and the H₄R agonist ST-1006 revealed several regulated genes (e.g., IL-18R, IL-1RL1, PDE4B, CXCR4) involved in inflammation. Subsequently, the impact of histamine on one of the strongly regulated genes, the IL-18 receptor (IL-18Rα), was investigated in detail. Stimulation with histamine induced the upregulation of IL-18Rα at mRNA and at the protein level in human eosinophils, which was more pronounced in cells from AD patients than in cells from healthy controls. IL-18 was upregulated via histamine as well. After pre-incubation with histamine and IFN-γ, subsequent stimulation with IL-18 resulted in an increased ECP mRNA expression. The activation of eosinophils by histamine, in combination with IFN-γ and IL-5, was also accompanied by an upregulation of CD69. Thus, our results indicate a crucial role of histamine in the upregulation of the IL-18/IL-18R axis and in the activation of human eosinophils from AD patients.

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.

Induced histamine regulates Ni elution from an implanted Ni wire in mice by downregulating neutrophil migration

Histamine regulates various inflammatory reactions. We have reported that the expression of histidine decarboxylase (HDC) was induced by subcutaneous implantation of nickel (Ni) wire. However, the source and functions of histamine in Ni elution and Ni wire-induced inflammation have not been completely studied. We aimed to elucidate the effects of de novo synthesized histamine on leucocyte infiltration and Ni elution. Implantation of Ni wire induced an increase in the Ni ion content of the surrounding tissues and serum and in the mRNA levels of HDC, a histamine-producing enzyme, macrophage inflammatory protein-2 (MIP-2), a chemoattractant for neutrophils, and monocyte chemoattractant protein-1 (MCP-1), a chemoattractant for monocytes. The Ni wire induced HDC expression even in mast cell-deficient WBB6F1-W/W^V mice. In HDC knockout (HDC KO) mice, the Ni wire-induced increase in MIP-2 mRNA expression was significantly higher than that in wild-type mice but not MCP-1. MIP-2 expression was enhanced in histamine H2 receptor knockout (H2R KO) mice but not in WBB6F1-W/W^V mice. Histamine inhibited NiCl₂ -induced MIP-2 mRNA expression in mouse bone marrow-derived macrophages (BMDMs) obtained from wild-type mice; this inhibition was not observed in BMDMs from H2R KO mice. Ni elution increased in HDC KO mice, in which leucocyte infiltration also increased, and was suppressed in mice treated with neutrophil-specific antibody. These results suggest that the Ni wire induced HDC expression in non-mast cells and that, in the chronic phase of inflammation, endogenous histamine reduced Ni elution, probably through regulation of MIP-2 expression and neutrophil migration.

Histamine 4 receptor promotes expression of costimulatory B7.1/B7.2 molecules, CD28 signaling and cytokine production in stress-induced immune responses

Recently, the expression of histamine 4 receptor (H4R) on neurons was reported, however its function in cells within the central nervous system (CNS) remains poorly understood. To this end, we used the H4R agonist, 4-methylhistamine (4-MeH), and the H4R antagonist, JNJ77777120 (JNJ), to investigate the function of H4R signaling in immune cells in a murine model of chronic stress. Treatment of stressed mice with 4-MeH resulted in an increase in the proportion of lymphocyte subsets (CD3(+), CD8(+), CD28(+), and CD4(+)CD28(+)) and cells expressing the co-stimulatory molecules CD80(+) (B7.1) and CD86(+) (B7.2) in heparinized blood as compared to normal control (NC) and stressed control (SC) groups. We also observed that as compared to NC and SC mice, 4-MeH-treated mice showed greater production of IL-2(+), IL-6(+), IL-9(+), IL-21(+), and IL-27(+) cytokines in the spleen and by splenic CD4(+) T cells. Furthermore, 4-MeH treatment of stressed mice led to an increase in the levels of serum Th1/Th17 cytokines and corticosterone, and a decrease in Th2 cytokines. Treatment of chronically-stressed mice with 4-MeH also augmented expression of IL-6, IL-21, NF-κB p65, and STAT3 mRNA. Moreover, Western blot analyses confirmed increased protein expression of NF-κB, iNOS, and STAT3 expression following 4-MeH treatment of chronically-stressed mice as compared to controls. These proteins provide a novel relevant targets for the manipulation of chronic stress induced immune regulation. In striking contrast, treatment of stressed mice with the H4R antagonist, JNJ, resulted in a substantial reduction in all of the aforementioned effects upon immune cell percentages and cytokine production.

Histamine inhibits high mobility group box 1-induced adhesion molecule expression on human monocytes

Cell-cell interaction through binding of adhesion molecules on monocytes to their ligands on T-cells plays roles in cytokine production and lymphocyte proliferation. High mobility group box 1 (HMGB1), an abundant and conserved nuclear protein, acts in the extracellular environment as a primary pro-inflammatory signal. HMGB1 induces expression of intercellular adhesion molecule (ICAM), B7.1, B7.2 and CD40 on monocytes, resulting in production of interferon (IFN)-γ and tumor necrosis factor (TNF)-α production and lymphocyte proliferation in human peripheral blood mononuclear cells (PBMCs). Histamine inhibits pro-inflammatory cytokine production via histamine H2-receptors; however, it is not known whether histamine inhibits HMGB1 activity. This study was designed to study the inhibitory effect of histamine on HMGB1 activity. We examined the effect of histamine on HMGB1-induced expression of ICAM-1, B7.1, B7.2 and CD40 on monocytes, production of IFN-γ and TNF-α and lymphocyte proliferation in PBMCs. Histamine inhibited HMGB1 activity in a concentration-dependent manner. The effects of histamine were partially ablated by the H2-receptor antagonist, famotidine, and mimicked by the H2/H4-receptor agonists, dimaprit and 4-methylhistamine. Histamine induced cyclic adenosine monophosphate (cAMP) production in the presence and absence of HMGB1. The effects of histamine were reversed by the protein kinase A (PKA) inhibitor, H89, and mimicked by the membrane-permeable cAMP analog, dibutyryl cAMP (dbcAMP), and the adenylate cyclase activator, forskolin. These results together indicated that histamine inhibited HMGB1 activity.

Protective effect of 3,4-methylenedioxyphenol (sesamol) on stress-related mucosal disease in rats

Stress-related mucosal disease (SRMD) causes considerable morbidity and mortality in critically ill patients. 3,4-Methylenedioxyphenol (sesamol) has been reported to have potent antioxidative and anti-inflammatory properties. The aim of this study was to investigate the effect of sesamol on water immersion restraint- (WIR-) induced SRMD in rats. Rat gastric ulcer and hemorrhage were induced by WIR. Rats were pretreated orally with various doses of sesamol (0.1, 0.3, and 1 mg/kg, resp.) 30 min before WIR. Gastric mucosal ulceration, hemoglobin, lipid peroxidation, mucus secretion, proinflammatory cytokines, and nuclear factor (NF)-κB levels were determined 4 h after WIR. In addition, the infiltration of neutrophil and macrophage into gastric mucosa was also determined after WIR. Water immersion restraint increased gastric mucosal ulcer and hemorrhage, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels but failed to affect mucosal lipid peroxidation and mucus secretion compared with non-WIR. Sesamol significantly decreased gastric ulceration and hemorrhage and inhibited mucosal TNF-α, IL-1β, and IL-6 production and NF-κB activity in WIR-treated rats. In addition, increased myeloperoxidase and CD68 levels in gastric mucosa were found in WIR-treated rats compared to non-WIR rats. Sesamol did not affect myeloperoxidase but decreased CD68 levels in mucosa in WIR-treated rats. Sesamol may protect against SRMD by inhibiting gastric mucosal proinflammatory cytokines in rats.

Molecular and cellular analysis of human histamine receptor subtypes

The human histamine receptors hH(1)R and hH(2)R constitute important drug targets, and hH(3)R and hH(4)R have substantial potential in this area. Considering the species-specificity of pharmacology of H(x)R orthologs, it is important to analyze hH(x)Rs. Here, we summarize current knowledge of hH(x)Rs endogenously expressed in human cells and hH(x)Rs recombinantly expressed in mammalian and insect cells. We present the advantages and disadvantages of the various systems. We also discuss problems associated with the use of hH(x)R antibodies, an issue of general relevance for G-protein-coupled receptors (GPCRs). There is much greater overlap in activity of 'selective' ligands for other hH(x)Rs than the cognate receptor subtype than generally appreciated. Studies with native and recombinant systems support the concept of ligand-specific receptor conformations, encompassing agonists and antagonists. It is emerging that for characterization of hH(x)R ligands, one cannot rely on a single test system and a single parameter. Rather, multiple systems and parameters have to be studied. Although such studies are time-consuming and expensive, ultimately, they will increase drug safety and efficacy.

Lipopolysaccharide induces H1 receptor expression and enhances histamine responsiveness in human coronary artery endothelial cells

Summary Histamine is a well-recognized modulator of vascular inflammation. We have shown that histamine, acting via H1 receptors (H1R), synergizes lipopolysaccharide (LPS)-induced production of prostaglandin I(2) (PGI(2)), PGE(2) and interleukin-6 (IL-6) by endothelial cells. The synergy between histamine and LPS was partly attributed to histamine -induced expression of Toll-like receptor 4 (TLR4). In this study, we examined whether LPS stimulates the H1R expression in human coronary artery endothelial cells (HCAEC) with resultant enhancement of histamine responsiveness. Incubation of HCAEC with LPS (10-1000 ng/ml) resulted in two-fold to fourfold increases in H1R mRNA expression in a time-dependent and concentration-dependent fashion. In contrast, LPS treatment did not affect H2R mRNA expression. The LPS-induced H1R mRNA expression peaked by 4 hr after LPS treatment and remained elevated above the basal level for 20-24 hr. Flow cytometric and Western blot analyses revealed increased expression of H1R protein in LPS-treated cells. The specific binding of [(3)H]pyrilamine to H1R in membrane proteins from LPS-treated HCAEC was threefold higher than the untreated cells. The LPS-induced H1R expression was mediated through TLR4 as gene silencing by TLR4-siRNA and treatment with a TLR4 antagonist inhibited the LPS effect. When HCAEC were pre-treated with LPS for 24 hr, washed and challenged with histamine, 17-, 10- and 15-fold increases in PGI(2), PGE(2) and IL-6 production, respectively, were noted. Histamine-induced enhancement of the synthesis of PGI(2), PGE(2) and IL-6 by LPS-primed HCAEC was completely blocked by an H1R antagonist. The results demonstrate that LPS, through TLR4 activation, up-regulates the expression and function of H1R and amplifies histamine-induced inflammatory responses in HCAEC.

Histamine inhibits advanced glycation end products-induced adhesion molecule expression on human monocytes

Advanced glycation end products (AGEs) are modifications of proteins/lipids that become nonenzymatically glycated after contact with aldose sugars. Among various subtypes of AGEs, glyceraldehyde-derived AGE (AGE-2) and glycolaldehyde-derived AGE (AGE-3) are suggested to play roles in inflammation in diabetic patients. Because the engagement of intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, and CD40 on monocytes with their ligands on T cells plays roles in cytokine production, we examined the effects of AGE-2 and AGE-3 on the expression of adhesion molecules and cytokine production in human peripheral blood mononuclear cells (PBMC) and their modulation by histamine in the present study. AGE-2 and AGE-3 induced the expressions of ICAM-1, B7.1, B7.2, and CD40 on monocytes and the production of interferon-gamma in PBMC. Histamine concentration-dependently inhibited the action of AGE-2 and AGE-3. The effects of histamine were antagonized by an H2 receptor antagonist, famotidine, and mimicked by H2/H4 receptor agonists dimaprit and 4-methylhistamine. Histamine induced cAMP production in the presence and absence of AGE-2 and AGE-3. The effects of histamine were reversed by a protein kinase A (PKA) inhibitor, N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89), and mimicked by a dibutyryl cAMP and an adenylate cyclase activator, forskolin. These results as a whole indicated that histamine inhibited the AGE-2- and AGE-3-induced adhesion molecule expression and cytokine production via H2 receptors and the cAMP/PKA pathway.

Histamine induces MUC5AC expression via a hCLCA1 pathway

BACKGROUND

Histamine is an important inflammatory mediator and associated with early phase allergic response. However, the involvement of histamine in mucin gene expression or production has not been elucidated.

OBJECTIVE

The aim of this study is to investigate whether histamine induces MUC5AC production in NCI-H292 cells, and to evaluate which pathway is involved in this mucin production.

METHODS

MUC5AC production in NCI-H292 cells was analyzed by RT-PCR, immunoassay and immunocytochemical analysis. The effect of histamine on MUC5AC production in these cells at different time courses and concentrations was assessed, and the relationship between hCLCA1 expression and histamine concentration was also evaluated. In addition, cells were pretreated with antihistamine or an hCLCA1 blocker (niflumic acid, NFA) to evaluate the mechanism underlying histamine-induced MUC5AC production.

RESULTS

Histamine upregulated MUC5AC gene expression and mucin protein production in a dose-dependent and time-related fashion. Histamine also dose-dependently increased hCLCA1 mRNA expression. Moreover, pretreatment of cells with chlorpheniramine or NFA reduced histamine-induced MUC5AC mRNA expression and protein production in these cells. The histamine-treated cells showed increased cytoplasmic staining for MUC5AC compared to cells treated with media alone, and cells pretreated with chlorpheniramine or NFA before histamine treatment.

CONCLUSION

Our results suggest that histamine-induced MUC5AC production occurs via the upregulation of hCLCA1. It is assumed that antihistamines or hCLCA1 channel blockers can partially suppress histamine-induced MUC5AC production in allergic diseases, e.g. allergic rhinitis.

The effect of ranitidine on antibody responses to polysaccharide vaccines in patients with B-cell chronic lymphocytic leukaemia

OBJECTIVES

To analyse the effects of ranitidine treatment on vaccination induced antibody responses in patients with chronic lymphocytic leukaemia (CLL).

METHODS

Fifty CLL patients were vaccinated with tetanus conjugated Hib vaccine and a 23-valent pneumococcal polysaccharide vaccine with (n = 25) or without (n = 25) ranitidine treatment in a matched case--control setting. Anti tetanus toxoid (TT), anti-Hib and anti-pneumococcal antibody levels were determined before and after vaccination. Additionally, cytokine levels were assessed in patients treated with ranitidine.

RESULTS

Vaccination-induced increases in anti-Hib and anti-TT antibody levels were higher in the ranitidine group compared with the control group. Anti-pneumococcal antibody responses were not improved by administration of ranitidine. Higher levels of IL-18 were found in patients treated with ranitidine compared with healthy controls. Levels of IL-6, IL-8, IL-18, RANTES, IP-10, sVCAM-1 and sICAM-1 were within normal ranges and did not change during ranitidine treatment.

CONCLUSION

Ranitidine treatment improves vaccination-induced T-cell dependent antibody responses in patients with CLL but has no beneficial effect on the response to vaccination with unconjugated polysaccharide antigens.

An essential role for IL-18 in CD8 T cell-mediated suppression of IgE responses

The ability of CD8 T cells to suppress IgE responses is well established. Previously, we demonstrated that CD8 T cells inhibit IgE responses via the induction of IL-12, which promotes Th1 and suppresses Th2 responses. In this study, we show that IL-18 also plays an essential role in IgE suppression. In vitro, IL-18 synergized with IL-12 to promote Th1/T cytotoxic 1 and inhibit Th2/T cytotoxic 2 differentiation. OVA-specific TCR transgenic (OT-I) CD8 cells induced both IL-12 and IL-18 when cultured with OVA(257-264) peptide-pulsed dendritic cells. In vivo, IL-18(-/-) mice exhibited higher IgE and IgG1 levels compared with wild-type mice after immunization with OVA/alum. Furthermore, adoptive transfer of CD8 T cells from OVA-primed mice suppressed IgE responses in OVA/alum-immunized mice, but not in IL-18(-/-) mice. IgE suppression in IL-18(-/-) mice was restored if CD8 T cells were coadoptively transferred with IL-18-competent wild-type bone marrow dendritic cell progenitors, demonstrating an essential role of IL-18 in CD8 T cell-mediated suppression of IgE responses. The data suggest that CD8 T cells induce IL-18 production during a cognate interaction with APCs that synergizes with IL-12 to promote immune deviation away from the allergic phenotype. Our data identify IL-18 induction as a potentially useful target in immunotherapy of allergic disease.

Cimetidine Induces Interleukin-18 Production through H2-Agonist Activity in Monocytes

The present study demonstrates a possible mechanism for the improvement of gastrointestinal cancer patients' prognosis by the histamine receptor type 2 (H2R) antagonist cimetidine. This agent, but not the H2R antagonists ranitidine and famotidine, induced the production of an antitumor cytokine, interleukin (IL)-18, by human monocytes and dendritic cells (DC). In fact, ranitidine and famotidine antagonized cimetidine-induced IL-18 production. Cimetidine induced the activation of caspase-1, which is reported to modify immature IL-18 to mature/active IL-18, and the elevation of intracellular cAMP, leading to the activation of protein kinase A (PKA). The PKA inhibitor H89 abolished the IL-18 production induced by cimetidine. Moreover, the effects of cimetidine on IL-18 production were reproduced in peripheral blood mononuclear cells from wild-type mice, but not in those from H2R knockout mice. In conclusion, cimetidine, a partial agonist for H2R, has a pharmacological profile different from ranitidine and famotidine, possibly contributing to its antitumor activity on gastrointestinal cancers.

The role of histamine H1 receptor and H2 receptor in LPS-induced liver injury

To examine the role of histamine H1 and H2 receptors in the regulation of lipopolysaccharide (LPS)-induced liver injury, a combination of D-galactosamine and LPS (GalN/LPS) was administered to histamine H1 receptor knockout (H1-R KO) and H2 receptor knockout (H2-R KO) mice. The numbers of necrotic and apoptotic hepatocytes in the liver, as well as the levels of serum aspartate transaminase (AST) and alanine transaminase (ALT), were increased significantly by GalN/LPS treatment compared to the appropriate controls. Pretreatment with histamine ameliorated the GalN/LPS-induced necrotic and apoptotic changes in the hepatocytes and inhibited the elevation of serum AST and ALT levels. Histamine attenuated the GalN/LPS-induced increases in the levels of TNF-alpha, but augmented those of IL-10 both in the liver and serum. Histamine inhibited the GalN/LPS-induced caspase-3 activity in the liver. Furthermore, these effects of histamine were completely or partially attenuated in H2-R KO mice, but not in H1-R KO mice. Peritoneal macrophages from H2-R KO mice exhibited blunted changes in the effects of histamine on LPS-induced TNF-alpha and IL-10 production in vitro compared to the wild-type (WT) controls. In summary, the present findings suggest that the histamine H2-R-TNF-alpha and -IL-10 pathways play protective roles in endotoxin-induced hepatic injury.

The role of histamine in the intracellular survival of Mycobacterium bovis BCG

The course and outcome of infection with mycobacteria are determined by a complex interplay between the immune system of the host and the survival mechanisms developed by the bacilli. Histamine plays an important role in various processes, including cell division, metabolism, and apoptosis, and it modulates innate and adaptive immune responses. In the present study we investigated the intracellular survival of Mycobacterium bovis BCG in murine bone-marrow macrophages isolated from wild-type (WT) and histidine-decarboxylase knock-out [HDC (-/-)] mice. Mycobacterial titers were significantly higher in the HDC (-/-) macrophages as compared with the WT cells. M. bovis BCG growth in WT macrophages could be enhanced by pyrilamine and cimetidine. Exogenously added histamine decreased the intracellular counts of M. bovis BCG in HDC (-/-) macrophages. Infection of activated macrophages with M. bovis BCG elicited apoptosis, but there was no significant difference between the WT and the HDC (-/-) cells. These bacilli induced comparable levels of tumor necrosis factor-alpha production in the WT and the HDC (-/-) macrophages. M. bovis BCG stimulated interleukin-18 (IL-18) production in the macrophages from WT mice, but not in the HDC (-/-) cells. Exogenously added IL-18 decreased the titers of intracellular mycobacteria in HDC (-/-) cells. In conclusion, these data implicate histamine in the intracellular survival of M. bovis BCG. The cellular control mechanisms restricting the growth of M. bovis BCG are complex and involve H1 and H2 receptor-mediated events. Histamine might be an important mediator of M. bovis BCG-induced IL-18 production, which in turn contributes to immune protection.

Histamine production via mast cell-independent induction of histidine decarboxylase in response to lipopolysaccharide and interleukin-1

Histamine modulates immune responses. There are at least two ways histamine might be supplied: one is its release from cells that pool pre-formed histamine and the other is its de novo formation via induction of histidine decarboxylase (HDC). Lipopolysaccharide (LPS) and the proinflammatory cytokine interleukin (IL)-1 induce a marked elevation of HDC activity in various tissues or organs. To examine the contribution of mast cells to HDC induction in mice given LPS or IL-1, we examined the effects of LPS and IL-1 on HDC activity and/or histamine content in various organs (liver, lung, spleen or bone marrow) in mast cell-deficient mice (W/Wv), their normal littermates (+/+) and BALB/c mice deficient in IL-1alpha, IL-1beta and tumor necrosis factor (TNF)-alpha (IL-1alpha beta/TNFalphaKO mice). In non-stimulated mice, the histamine in the lung and spleen was contained largely within mast cells. The LPS-stimulated increase in HDC activity in a given organ was similar between +/+ and W/W(v) mice, and between IL-1alpha beta/TNFalphaKO BALB/c and control BALB/c mice, and led to increases in histamine. In W/Wv and +/+ mice, IL-1alpha also elevated HDC activity. These results suggest that (i) in liver, lung and spleen, either the major cells supplying histamine via HDC induction in response to LPS and IL-1 are not mast cells, or mast cells are not a prerequisite for the induction of HDC; (ii) the cells in which HDC is induced by LPS and IL-1 are similar or identical in a given organ; and (iii) neither IL-1 nor TNF-alpha is a prerequisite for the induction of HDC by LPS.

??1-Adrenergic Receptor Antagonists Induce Production of IL-18 and Expression of ICAM-1 and CD40 in Human Monocytes

The activation of T cells plays a role in antitumor response. Monocytes activate T cells by inducing the cell-to-cell interaction that involves the engagement of adhesion molecules with their ligands, and the production of IL-18. The authors examined the effect of the quinazoline-based alpha1-adrenergic receptor antagonists bunazosin, doxazosin, prazosin, and terazosin on the expression of adhesion molecules such as ICAM-1, B7.1, B7.2, CD40, and CD40L on monocytes isolated from human peripheral blood mononuclear cells. Doxazosin, prazosin, and terazosin induced the expression of ICAM-1 and CD40 but had no effect on the expression of B7.1, B7.2, and CD40L. Moreover, IL-18 was detected in the medium of incubated monocytes treated with doxazosin, prazosin, and terazosin. Bunazosin did not affect adhesion molecule expression and IL-18 production, suggesting that the chemical structure of quinazoline might not be related to the effect of doxazosin, prazosin, and terazosin. Although caspase-1 inhibitor completely abolished the production of IL-18, anti-IL-18 mAb and caspase-1 inhibitor partially inhibited the increase in ICAM-1 and CD40 expression induced by doxazosin, prazosin, and terazosin. Doxazosin, prazosin, and terazosin can induce monocyte activation with a specific pattern of expression of adhesion molecules and IL-18 production, and this may lead to T-cell activation through the cell-to-cell interaction. The activation of T cells induced by the increase of the expression of ICAM-1 and CD40 and the production of IL-18 may be involved in the anti-cancer effects of doxazosin, prazosin, and terazosin.

Differential effect of LFA703, pravastatin, and fluvastatin on production of IL-18 and expression of ICAM-1 and CD40 in human monocytes

A novel, proinflammatory cytokine, interleukin (IL)-18 production was detected in the medium of human monocytes treated with 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase inhibitors, pravastatin, and fluvastatin (0.1 and 1 muM) but not with the statin-derived lymphocyte function-associated antigen-1 (LFA-1) inhibitor LFA703, which did not inhibit HMG-CoA reductase. Pravastatin and fluvastatin also induced the production of IL-18, tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in human peripheral blood mononuclear cells (PBMC) in contrast to LFA703. IL-18 production by PBMC is located upstream of the cytokine cascade activated by these statins. The IL-18-induced cytokine production was demonstrated to be dependent on adhesion molecule expression on monocytes. In the absence and presence of lower concentrations (0.1 and 1 ng/ml) of IL-18, pravastatin and fluvastatin inhibited the expression of intercellular adhesion molecule (ICAM)-1 and induced the expression of CD40, whereas LFA703 had no effect. In the presence of higher concentrations (5, 10, and 100 ng/ml) of IL-18, pravastatin, fluvastatin, and LFA703 similarly inhibited the expression of ICAM-1 and CD40 as well as the production of IL-12, TNF-alpha, and IFN-gamma in PBMC. The effects of pravastatin and fluvastatin but not LFA703 were abolished by the addition of mevalonate, indicating the involvement of HMG-CoA reductase in the action of pravastatin and fluvastatin. Thus, the effects of LFA703 were distinct from those of pravastatin and fluvastatin in the presence of lower concentrations of IL-18. It was concluded that LFA703 has the inhibitory effect on an IL-18-initiated immune response without any activation on monocytes.

Histamine induces Toll-like receptor 2 and 4 expression in endothelial cells and enhances sensitivity to Gram-positive and Gram-negative bacterial cell wall components

Histamine is a major inflammatory molecule released from the mast cell, and is known to activate endothelial cells. However, its ability to modulate endothelial responses to bacterial products has not been evaluated. In this study we determined the ability of histamine to modulate inflammatory responses of endothelial cells to Gram-negative and Gram-positive bacterial cell wall components and assessed the role of Toll-like receptors (TLR) 2 and 4 in the co-operation between histamine and bacterial pathogens. Human umbilical vein endothelial cells (HUVEC) were incubated with lipopolysaccharide (LPS), lipoteichoic acid (LTA), or peptidoglycan (PGN) in the presence or absence of histamine, and the expression and release of interleukin-6 (IL-6), and NF-kappaB translocation were determined. The effect of histamine on the expression of mRNA and proteins for TLR2 and TLR4 was also evaluated. Incubation of HUVEC with LPS, LTA and PGN resulted in marked enhancement of IL-6 mRNA expression and IL-6 secretion. Histamine alone markedly enhanced IL-6 mRNA expression in HUVEC, but it did not stimulate proportional IL-6 release. When HUVEC were incubated with LPS, LTA, or PGN in the presence of histamine marked amplification of both IL-6 production and mRNA expression was noted. HUVEC constitutively expressed TLR2 and TLR4 mRNA and proteins, and these were further enhanced by histamine. The expression of mRNAs encoding MD-2 and MyD88, the accessory molecules associated with TLR signalling, were unchanged by histamine treatment. These results demonstrate that histamine up-regulates the expression of TLR2 and TLR4 and amplifies endothelial cell inflammatory responses to Gram-negative and Gram-positive bacterial components.

Stress-related mucosal disease: risk factors and prophylactic therapy

BACKGROUND

The term stress-related mucosal disease (SRMD) represents a continuum of conditions ranging from stress-related injury (superficial mucosal damage) to stress ulcers (focal deep mucosal damage). Caused by mucosal ischemia, SRMD is most commonly seen in critically ill patients in the intensive care unit (ICU). Prophylaxis of stress ulcers may reduce major bleeding but has not yet been shown to improve survival.

OBJECTIVES

This article reviews currently available agents for the prophylaxis of SRMD and discusses their uses and potential adverse effects.

METHODS

Relevant articles in the English-language literature were identified through a MEDLINE search (1968-2003) using the key words stress-related mucosal disease, stress-related injury, ulcer, prophylaxis, intensive care unit, and upper gastrointestinal bleeding.

RESULTS

The most widely used drugs for stress-related injury are the intravenous histamine(2)-receptor antagonists. These drugs raise gastric pH but are associated with the development of tolerance and possible drug interactions and neurologic manifestations. Sucralfate, which can be administered by the nasogastric route, can protect the gastric mucosa without raising pH, but may decrease the absorption of concomitantly administered oral medications. The prostaglandin misoprostol has not been shown to be of benefit in the prophylaxis of SRMD. Antacids lower the risk of gastrointestinal bleeding, but large volumes of antacids are required and treatment is labor intensive. Proton pump inhibitors (PPIs) are the most potent acid-suppressive pharmacologic agents available. Esomeprazole, lansoprazole, omeprazole, pantoprazole, and rabeprazole substantially raise gastric pH for up to 24 hours after a single dose. The availability of an intravenous formulation of pantoprazole may help improve the treatment of SRMD in ICU patients, particularly those receiving mechanical ventilation. Tolerance does not develop, and few adverse effects have been reported.

CONCLUSIONS

Recent studies of PPIs have shown promising results in high-risk patients, making this class of drugs an option for the prophylaxis of SRMD.

E-prostanoid (EP)2/EP4 receptor-dependent maturation of human monocyte-derived dendritic cells and induction of helper T2 polarization

Prostaglandin (PG) E(2) induces dendritic cell maturation in cooperation with proinflammatory cytokines [such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta]. To clarify the involvement of E-prostanoid (EP) receptors in the effect of prostaglandin E(2) on human monocyte-derived dendritic cell (MoDC) maturation, we examined the effect of four types of EP receptor-selective agonists on MoDC maturation. PGE(2) as well as 11,15-O-dimethyl prostaglandin (E(2)ONO-AE1-259-01) (EP2 receptor agonist) and ONO-AE1-329 (EP4 receptor agonist) concentration dependently enhanced the expression of CD80, CD86, CD83, and HLA-DR on MoDCs during maturation, especially in the presence of TNF-alpha, whereas 17S-2,5-ethano-6-oxo-17,20-dimethyl prostaglandin E(1) (EP1 receptor agonist) and 16S-9-deoxy-9beta-chloro-15-deoxy-16-hyfroxy-17,17-trimethylene-19,20-didehydro prostaglandin F(2) (EP3 receptor agonist) showed no effect. The maximal effect of ONO-AE1-259-01 was higher than that of ONO-AE1-329; however, the stimulation with ONO-AE1-259-01 was less effective than that with PGE(2). Simultaneous stimulation with both EP receptor agonists produced additive effects and 11-deoxy-PGE(1) (EP2/EP4 receptor mixed agonist) mimicked the effects of PGE(2). Dibutyryl cAMP mimicked the effects of PGE(2), indicating the mediation of PGE(2) action by cAMP. Matured MoDCs induced by PGE(2) or EP2 and/or EP4 receptor agonists showed a decrease in lipopolysaccharide (LPS)-stimulated IL-12p70, IL-6, and IL-10 production. The coculture of naive T cells with matured MoDCs induced under different conditions showed that EP2/EP4-stimulated MoDCs preferentially induced alloresponsive helper T (Th)2 cells. Together, it was concluded that the cooperative stimulation of EP2 and EP4 receptor subtypes by PGE(2) promoted MoDC maturation and inhibited LPS-induced cytokine production in MoDCs. The matured MoDCs under such conditions preferably induced Th2 polarization, indicating the importance of EP2 and EP4 receptors in the determination of Th1/Th2 development of naive T cells.

β2-Adrenergic receptor agonist induces IL-18 production without IL-12 production

Endogenous catecholamine, epinephrine and norepinephrine, and isoproterenol concentration-dependently induced the production of interleukin (IL)-18, tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma, and inhibited that of IL-10 in human peripheral blood mononuclear cells (PBMC). All responses by these stimulations were antagonized by the selective beta 2-adrenergic receptor (AR) antagonist, butoxamine, but not by alpha 1-, alpha 2- and beta 1-AR antagonists. The selective beta 2-AR agonists, salbutamol and terbutaline, induced a similar pattern of cytokine production, indicating that the effect of these AR agonists on cytokine production was through beta 2-AR stimulation. Anti-IL-18 Ab or caspase-1 inhibitor prevented all increase/decrease effects, suggesting that IL-18 might affect the production of all other cytokines. While endogenous IL-18 produced by salbutamol and terbutaline reached a sufficient concentration to induce IL-12 production, these beta 2-AR agonists did not induce the production of IL-12 at all. Epinephrine/norepinephrine/isoproterenol/beta 2-AR agonists increased the production of IL-18 in monocytes, but had no effect on IL-12, TNF-alpha, IFN-gamma and IL-10 production. The lack of beta 2-AR-induced effect on IL-12 production was due to a beta 2-AR-induced inhibition of an IL-18-elicited upregulation of both CD40 and CD40 ligand (CD40L/CD154) expressions on monocytes. The sympathetic innervating lymphoid organs may be under the control of beta2-AR stimulation, maintaining the basal cytokine environment in the tissues.

Bystander suppression of allergic airway inflammation by lung resident memory CD8+ T cells

CD8+ memory T cells have recently been recognized as playing a key role in natural immunity against unrelated viral infections, a phenomenon referred to as "heterologous antiviral immunity." We now provide data that the cellular immunological interactions that underlie such heterologous immunity can play an equally important role in regulating T helper 2 immune responses and protecting mucosal surfaces from allergen-induced inflammation. Our data show that CD8+ T cells, either retained in the lung after infection with influenza virus, or adoptively transferred via the intranasal route can suppress allergic airway inflammation. The suppression is mediated by IFN-gamma, which acts to reduce the activation level, T helper 2 cytokine production, airways hyperresponsiveness, and migration of allergen-specific CD4+ T cells into the lung, whereas the systemic and draining lymph node responses remain unchanged. Of note, adoptive transfer of previously activated transgenic CD8+ T cells conferred protection against allergic airway inflammation, even in the absence of specific-antigen. Airway resident CD8+ T cells produced IFN-gamma when directly exposed to conditioned media from activated dendritic cells or the proinflammatory cytokines IL-12 and IL-18. Taken together these data indicate that effector/memory CD8+ T cells present in the airways produce IFN-gamma after inflammatory stimuli, independent of specific-antigen, and as a consequence play a key role in modifying the degree and frequency of allergic responses in the lung.

Behavioural endocrine immune-conditioned response is induced by taste and superantigen pairing

Administration of bacterial superantigen, such as staphylococcal enterotoxin B (SEB), induces in vivo stimulation of T cell proliferation and cytokine production such as interleukin-2 (IL-2). It has been previously reported that SEB administration induces fever, c-Fos expression in the brain, and hypothalamus-pituitary-adrenal axis activation, demonstrating that the brain is able to sense and respond to SEB. Previously it had been shown that immune functions can be behaviourally conditioned pairing a novel gustatory stimulus together with an immunomodulatory drug or an antigen. We designed an experimental protocol using Dark Agouti rats in which saccharin taste, as conditioned stimulus, was paired with an i.p. injection of SEB (2 mg/kg), as unconditioned stimulus. Six days later, when conditioned animals were re-exposed to the conditioned stimulus they displayed strong conditioned taste avoidance to the saccharin. More importantly, re-exposure to the conditioned stimulus significantly increased IL-2, interferon-gamma and corticosterone plasma levels, in comparison with conditioned animals which had not been re-exposed to saccharin taste. These results demonstrate a behavioural-immune-endocrine conditioned response using a superantigen as unconditioned stimulus. In addition, they illustrate the brain abilities to mimic the unconditioned effects of a superantigen by yet unknown mechanisms.

CD8+ T cells and immunoregulatory networks in asthma

It is well established that infection with respiratory viruses can cause acute local inflammation in humans and is a leading cause in the hospitalization of asthmatics. Less well recognized is the potential for viral infections to actually protect against the development of asthma, as are the cellular mechanisms which might underlie such protection. This review outlines the basic immunological pathways involved in atopic asthma and details the currently recognized cellular mechanisms induced by respiratory viral infections which can protect against the development of asthma. Specifically, it appears that virus infection induced memory T cells that remain in tissues, e.g. the lung and airways, can under certain circumstances create a local cytokine milieu which inhibits the development of ensuing allergic immune responses at that site. One key aspect of this immune modulation is the cytokine-dependent communication which occurs between the innate and the adaptive immune systems. The mechanistic principles underlying this form of immunomodulation should be taken into consideration when developing future forms of therapy and rational vaccine design.

The histamine-cytokine network in allergic inflammation

Histamine is synthesized and released by human basophils, mast cells, and neurons. Its pleiotropic effects are mediated by the activation of 4 receptors: H(1), H(2), H(3), and H(4). With the advent of selective antagonists (the antihistamines widely used to treat allergic disorders), the H(1)-receptor was the first member of the receptor family to be pharmacologically defined. Increasing evidence indicates that, in addition to exerting immediate vascular and bronchial responses, histamine might modulate the immune reaction by interacting with T cells, macrophages, basophils, eosinophils, and monocytes. We have shown that, in vitro, histamine induces a concentration-dependent release of IL-6 and beta-glucuronidase from macrophages isolated from the human lung parenchyma. These effects are inhibited by fexofenadine, an H(1)-receptor antagonist, but not by ranitidine, an H(2)-receptor antagonist. This observation raises the possibility that long-term treatment with fexofenadine might have beneficial effects on immune dysregulation and tissue damage/remodeling associated with histamine-mediated macrophage activation.

Exacerbated and prolonged allergic and non-allergic inflammatory cutaneous reaction in mice with targeted interleukin-18 expression in the skin

Interleukin 18 induces both T helper 1 and T helper 2 cytokines, proinflammatory cytokines, chemokines, and IgE and IgG1 production. A role of interleukin 18 in inflammatory cutaneous reactions is still unclear, however. Here we generated keratin 5/interleukin 18 transgenic mice overexpressing mature murine interleukin 18 in the skin using a human keratin 5 promoter. In the contact hypersensitivity model, trinitrochlorobenzene elicited a stronger ear swelling in keratin 5/interleukin 18 transgenic mice compared with control littermate wild-type or immunoglobulin/interleukin 18 transgenic mice in which mature interleukin 18 was expressed by B and T cells under the control of the immunoglobulin promoter. Application of an irritant, croton oil, induced stronger and more sustained ear swelling in keratin 5/interleukin 18 transgenic mice than in immunoglobulin/interleukin 18 transgenic or wild-type mice. Repetitive topical application (weekly for six consecutive weeks) of trinitrochlorobenzene to their ears also elicited a stronger cutaneous inflammation in keratin 5/interleukin 18 transgenic mice than seen in immunoglobulin/interleukin 18 transgenic or wild-type mice. After these six trinitrochlorobenzene applications, the expression of interferon-gamma, interleukin-4, and CCL20 mRNA in the ear tissue was increased and dermal changes, such as acanthosis and eosinophilic, neutrophilic, and mast cell infiltration, were greater in keratin 5/interleukin 18 transgenic mice than in wild-type mice. Furthermore, the repetitive application elicited a significant increase in serum IgE levels and the number of B cells in the draining lymph node in keratin 5/interleukin 18 transgenic mice. These results suggest that overexpression of interleukin 18 in the skin aggravates allergic and nonallergic cutaneous inflammation, which is accompanied by high expression of T helper 1 and T helper 2 cytokines and chemokines in the skin.

Impaired reproduction of histamine deficient (histidine-decarboxylase knockout) mice is caused predominantly by a decreased male mating behavior

PROBLEM

Histamine induces a Th2 shift. As successful allopregnancy is characterized by a peripheral Th2 dominance, we investigated the role of histamine in reproduction.

METHOD OF STUDY

HDC knockout (HDC-/-) or wild-type (HDC+/+) mice kept on histamine-deficient or normal diet were mated. Appearance of vaginal plugs indicated day 0.5 of pregnancy. On day 10.5 uteri were inspected. Splenic IFN-gamma production and cytotoxic activity were determined.

RESULTS

In HDC+/+ or HDC-/- females on normal diet, plugs appeared between 3 and 6 days. In 80% of the (HDC-/-)/(HDC-/-) matings on histamine-deficient diet, no vaginal plugs were observed for more than 1 month. After replacing males with the wild type, plugs appeared within 3 days. In HDC-/- mice, litter size was lower than in HDC+/+ animals. Cytotoxicity and IFN-gamma production were significantly increased in non-pregnant histamine-deficient mice, but not in pregnant mice.

CONCLUSION

Histamine affects male mating behavior, but is not indispensable for successful pregnancy.

The regulation of ICAM-1 and LFA-1 interaction by autacoids and statins: a novel strategy for controlling inflammation and immune responses

Histamine, prostaglandin E(2), and catecholamines have been demonstrated to regulate the innate and acquired immune responses. In this review, we describe one of the mechanisms common to the action of these agonists; the regulation of the expression of costimulatory adhesion molecules such as ICAM-1 and B7 antigens on monocytes/macrophages. The specific receptor subtypes involved in the action of each agonist were H(2) for histamine, EP(2)/EP(4) for prostaglandin E(2), and beta(2) for catecholamines, all of which are coupled with adenylate cyclase via Gs protein. The regulation of the expression of adhesion molecules by these agonists in turn leads to the modulation of subsequent cytokine production mediated by cell-cell interaction under different stimuli. Histamine is synthesized in monocytes and T cells by the induction of histidine decarboxylase. The inducible histamine has different dynamics from that in storage granules of mast cells and basophils. Also, noradrenaline appears to be synthesized in lymphocytes. Thus, immune cells can produce histamine, prostaglandins, and noradrenaline by themselves and modulate the cell-cell interaction between monocytes and other cells. Some of the inhibitors of HMG-CoA reductase were shown to bind to the ICAM-1-binding domain of LFA-1, reducing the interaction mediated by ICAM-1/LFA-1. The regulation of interaction mediated by adhesion molecules may provide a new target for controlling inflammatory and immune responses.

A role for histamine in cytokine modulation by the adenosine A(3) receptor agonist, 2-Cl-IB-MECA

The effects of adenosine receptor agonists on cytokine production in vivo were investigated in mouse models of endotoxemia. Selective adenosine A(3) (2-chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methyluronamide) (2-Cl-IB-MECA) and A(2A) (2-p-(2-carboxyethyl) phenethylamino-5'-N-ethylcarboxamido adenosine hydrochloride) (CGS 21860) receptor agonists were found to modulate endotoxin-induced cytokine responses in mice sensitized to D-galactosamine or primed with Corynebacterium parvum. The adenosine receptor agonists had similar effects in these models of endotoxemia, suppressing the production of tumor necrosis factor alpha (TNF-alpha) and interleukin-12 while enhancing that of interleukin-10. However, 2-Cl-IB-MECA also caused a dramatic increase in circulating histamine levels shortly after its injection into mice. The cytokine modulatory activities of 2-Cl-IB-MECA were mimicked by the mast cell depleting compound 48/80 and both drugs only produced such effects at doses that caused an elevation in circulating histamine levels. Furthermore, the capacity of 2-Cl-IB-MECA to modulate cytokine responses was greatly diminished when the drug was administered to mast cell deficient (WBB6F-W/W(V)) mice. Together, these results strongly suggest a role for histamine in cytokine modulation by 2-Cl-IB-MECA. Cimetidine, a histamine H(2) receptor antagonist, did not reverse cytokine modulation by 2-Cl-IB-MECA and pyrilamine, a histamine H(1) receptor antagonist, prevented the increase in serum histamine that was induced by 2-Cl-IB-MECA. This effect of pyrilamine and other histamine H(1) receptor antagonists confounded attempts to determine a role for the histamine H(1) receptor in cytokine modulation by 2-Cl-IB-MECA. However, under some experimental conditions, pyrilamine appeared to antagonize the modulatory effects of the adenosine A(3) receptor agonist on cytokine responses. The apparent antagonism of pyrilamine was unrelated to its suppressive effects on histamine release and appeared to reflect activity at the level of the histamine H(1) receptor.

Histamine H(2) receptor-mediated modulation of local cytokine expression in a mouse experimental tumor model

Accumulating evidence indicates that histamine is involved in the modulation of cytokine expression patterns. We previously reported that daily treatment with the H(2) receptor antagonist, cimetidine, suppressed tumor growth through alteration of the local cytokine expression pattern. In this study, we used a mouse strain genetically lacking histidine decarboxylase (HDC), to evaluate the role of endogenous histamine synthesis on cytokine expression and tumor development. In the mutant mice, cimetidine had no effect on tumor growth, whereas an H(2) agonist, dimaprit, significantly enhanced tumor growth. When the HDC-deficient mice were implanted with mutant CT-26 cells stably expressing HDC, drastic suppression of tumor growth by cimetidine was observed, which was accompanied by augmentation of mRNA expression of LT-beta, TNF-alpha, and IFN-gamma in the tumor tissues. These results suggest that endogenous histamine synthesis in tumor tissues suppresses local tumor immunity via the H(2) receptors, resulting in tumor growth promotion.

Histamine h(4) and h(2) receptors control histamine-induced interleukin-16 release from human CD8(+) T cells

Histamine is known to trigger the release of interleukin (IL)-16 from human CD8(+) cells. However, the individual roles of the presently known histamine receptor subtypes (H(1)-H(4)) in this inflammatory response have not been fully characterized. Histamine stimulation of human CD8(+) T lymphocytes purified from peripheral blood led to a 5- to 8-fold increase in the basal release of IL-16 within 24 h, and this increase was significantly blocked by the H(2)-selective antagonist, cimetidine, or by thioperamide, an antagonist of H(3) and H(4) receptors, respectively. The H(1) antagonist pyrilamine showed limited effects. Agonists selective for H(2) (dimaprit), H(3/4) (R-(-)-alpha-methylhistamine), and H(4) (clobenpropit) were capable of inducing the release of bioactive IL-16 because CD8(+) cell supernatants induced CD4(+) cell migration, which was abrogated by an anti-IL-16 antibody. Furthermore, preincubation of lymphocytes with pertussis toxin abolished IL-16 release triggered by activation of the G(i/o)-coupled H(4) receptor but not by the H(2) receptor. Messenger RNA expression studies confirmed H(4), H(2), and H(1) expression in human CD8(+) lymphocytes, whereas H(3) mRNA was completely absent. All leukocyte populations investigated expressed mRNA for H(4), with highest levels found in eosinophils, dendritic cells, and tonsil B cells. H(4) expression was also detected in human lung, trachea, and various cells of human lung origin, such as fibroblasts, bronchial smooth muscle cells, epithelial, and endothelial cells. Since many of those are known sources of IL-16, immune cell- and lung cell-expressed H(4) receptors may have a general role in the control of this mediator of inflammatory disorders such as asthma.

Effect of histamine on intercellular adhesion molecule-1 expression and production of interferon-gamma and interleukin-12 in mixed lymphocyte reaction stimulated with interleukin-18

BACKGROUND

Interleukin (IL)-18 was identified as an interferon (IFN)-gamma-inducing factor and was demonstrated to up-regulate the expression of intercellular adhesion molecule (ICAM)-1 on human monocytes. In organ transplantation, elevation of plasma IL-18 levels has been reported during acute rejection. In the present study, we examined the effect of IL-18 on human mixed lymphocyte reaction (MLR), an in vitro model of acute rejection after organ transplantation. We also investigated the modulatory effects of histamine on IL-18 action because histamine has been demonstrated to be a modulator of IL-18 effect and a mediator of inflammation.

METHODS

We measured the expression of ICAM-1 on human monocytes in MLR in the presence or absence of IL-18 by flow cytometer and determined the associated production of IFN-gamma and IL-12 by ELISA. The modulatory effects of histamine and the relevant histamine receptor subtypes were characterized pharmacologically.

RESULTS

The expression of ICAM-1 on monocytes in MLR was markedly enhanced by the addition of IL-18 in a concentration- and time-dependent manner. In parallel to ICAM-1 up-regulation, IL-18 significantly enhanced the production of IFN-gamma and IL-12 in MLR. Histamine concentration-dependently inhibited ICAM-1 expression and cytokine production in MLR stimulated with IL-18, whereas histamine alone did not show any effects on these responses in the absence of IL-18. The effects of histamine on both ICAM-1 expression and cytokine production were mimicked by the selective H2-receptor agonists 4-methylhistamine and dimaprit and were antagonized by the H2-receptor antagonist famotidine but not by H1- and H3-receptor antagonists.

CONCLUSION

IL-18 strongly enhanced human MLR with respect to ICAM-1 expression and cytokine production. The fact that histamine could inhibit the IL-18-stimulated MLR implies that immunomodulation by histamine and selective H2-receptor agonists may have an important role in future immunosuppressive strategies.

Fexofenadine modulates T-cell function, preventing allergen-induced airway inflammation and hyperresponsiveness

BACKGROUND

Antihistamines have been evaluated for usefulness in the treatment of asthma for more than 50 years. Interest was limited until the introduction of newer compounds that were free of much of the dose-limiting sedation associated with the earlier drugs.

OBJECTIVE

In a murine model of allergen-induced airway inflammation and hyperresponsiveness, the efficacy of an H1 receptor antagonist to prevent allergic inflammation and altered airway function was evaluated.

METHODS

Mice were sensitized and challenged to an allergen, ovalbumin, which elicited marked airway and tissue eosino-philia and airway hyperresponsiveness. Fexofenadine was administered before challenge, and airway responsiveness to inhaled methacholine, airway and tissue eosinophilia, bronchoalveolar lavage fluid cytokine levels, and serum IgE levels were assayed. In a second group of experiments, sensitized and challenged mice were treated or not treated with fexofenadine before challenge. T cells were isolated from the lungs and adoptively transferred into naive recipients before exposure to limited airway allergen challenge, and lung function and inflammation were evaluated.

RESULTS

Fexofenadine treatment of sensitized mice prevented the development of airway hyperresponsiveness in both the primary sensitization and challenge, as well as in the adoptive transfer experiments. These changes were accompanied by decreases in bronchoalveolar lavage and tissue eosinophilia, lymphocyte numbers, and T(H)2 cytokine production.

CONCLUSION

The results demonstrate the efficacy of an H1 receptor antagonist in preventing allergen-induced alterations in pulmonary inflammation and airway function. The data support the evaluation of drugs such as fexofenadine in the treatment of allergic asthma.

Effect of interleukin-18 on mouse core body temperature

We have studied, using a telemetry system, the pyrogenic properties of recombinant murine interleukin-18 (rmIL-18) injected into the peritoneum of C57BL/6 mice. The effect of IL-18 was compared with the febrile response induced by human IL-1beta, lipopolysaccharide (LPS), and recombinant murine interferon-gamma (rmIFN-gamma). Both IL-1beta and LPS induced a febrile response within the first hour after the intraperitoneal injection, whereas rmIL-18 (10-200 microg/kg) and rmIFN-gamma (10-150 microg/kg) did not cause significant changes in the core body temperature of mice. Surprisingly, increasing doses of IL-18, injected intraperitoneally 30 min before IL-1beta, significantly reduced the IL-1beta-induced fever response. In contrast, the same pretreatment with IL-18 did not modify the febrile response induced by LPS. IFN-gamma does not seem to play a role in the IL-18-mediated attenuation of IL-1beta-induced fever. In fact, there was no elevation of IFN-gamma in the serum of mice treated with IL-18, and a pretreatment with IFN-gamma did not modify the fever response induced by IL-1beta. We conclude that IL-18 is not pyrogenic when injected intraperitoneally in C57BL/6 mice. Furthermore, a pretreatment with IL-18, 30 min before IL-1beta, attenuates the febrile response induced by IL-1beta.

Effect of steroids on lipopolysaccharide/interleukin 2-induced interleukin 18 production in peripheral blood mononuclear cells

Interleukin (IL) 18, a powerful inducer of the immunoregulatory cytokine interferon-gamma (IFN-gamma), presents upstream of the cytokine activation cascade in the inflammatory response. The anti-inflammatory properties of steroids permit their use in various conditions, although effects are transient and pathological states are not fully relieved by short-term steroidal use. We examined the effect of lipopolysaccharide (LPS)/IL-2 on the cytokine cascade in human peripheral blood mononuclear cells (PBMCs). We also examined the effect of steroids on LPS/IL-2-induced cytokine production in human PBMCs taken from healthy volunteers. Cell-free supernatant fractions were assayed for IL-18, IL-12, IL-2, IFN-gamma and IL-10 protein, using enzyme-linked immunosorbent assays, and synergy between LPS and IL-2 in enhanced production of IL-18 was observed. Steroids suppressed the production of IL-18 and other secondary cytokines in LPS/IL-2-stimulated PBMCs, in a concentration- and time-dependent manner, although inhibition was incomplete even at high concentrations. Effects of steroid treatment on expression of membrane-bound LPS receptor antigen (mCD14) and intercellular adhesion molecule-1 (ICAM-1) in PBMCs were studied by flow cytometric analysis. Steroid treatment up-regulated mCD14 expression in a concentration-dependent manner, with no effect on ICAM-1 expression. These results suggest that the incomplete counteraction of steroids in the LPS/IL-2-initiating cytokine cascade is due, at least partly, to the up-regulation of mCD14 by steroid preparations, which increases susceptibility to bacterial endotoxins.

Expression and function of histamine receptors 1 and 2 on human monocyte-derived dendritic cells

BACKGROUND

Histamine is a well-known mediator of inflammatory and allergic reactions and has immunomodulatory capacities. There is increasing evidence that dendritic cells as professional antigen-presenting cells play a major role in the development of allergic reactions. However, a possible link between histamine and dendritic cells has not been investigated thus far.

OBJECTIVE

We investigated the effect of histamine on human monocyte-derived dendritic cells (MoDCs).

METHODS

Expression of histamine H1 and H2 receptors (H1R and H2R) on MoDCs was assessed by means of RT-PCR and flow cytometry. Functional exploration of these receptors was performed by monitoring the increase of intracellular calcium levels (H1R), cyclic adenosine monophosphate formation (H2R), F-actin polymerization, and IL-12p70 production.

RESULTS

MoDCs express both H1R and H2R. Stimulation of dendritic cells with histamine resulted in F-actin polymerization and cyclic adenosine monophosphate production through H2R. Influx of calcium could not be detected after stimulation of dendritic cells with histamine under conditions in which histamine induced calcium influx in monocytes. Histamine and H1R and H2R agonists downregulated IL-12p70 production of prestimulated MoDCs.

CONCLUSION

MoDCs express histamine H1 and H2 receptors. Our results indicate chemotactic (F-actin polymerization) and immunomodulatory (inhibition of IL-12p70 production) effects of histamine on MoDCs. Therefore histamine might represent a link between immediate-type hypersensitivity reactions and cellular inflammation in allergic disease (eg, in atopic dermatitis).

Troglitazone suppresses cell growth of KU812 cells independently of PPARgamma

We examined the effects of troglitazone, one of thiazolidinedione derivatives on human basophilic leukemia cell line KU812. Troglitazone caused the suppression of cell growth, which was suggested to result from the decrease in cyclin E and the hyperphosphorylated form of retinoblastoma tumor suppressor gene product (pRb). In addition, troglitazone caused a decrease in histamine secretion due to the reduced expression of histidine decarboxylase mRNA. Peroxisome proliferator-activated receptor (PPAR)-gamma mRNA was undetectable by reverse transcription-polymerase chain reaction (RT-PCR) in KU812 cells. These findings suggested that troglitazone suppressed cell growth and histamine synthesis independently of PPARgamma.

Histamine regulation of interleukin-18-initiating cytokine cascade is associated with down-regulation of intercellular adhesion molecule-1 expression in human peripheral blood mononuclear cells

In the previous study, we demonstrated that interleukin (IL)-18 up-regulated intercellular adhesion molecule-1 (ICAM-1) expression on monocytes in human peripheral blood mononuclear cells (PBMC) and that heterotypic interaction between monocytes/T or NK cells through ICAM-1/LFA-1 intensified the production of IL-12, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) in PBMC. In the present study, we demonstrate that histamine inhibited the ICAM-1 expression in monocytes induced by IL-18 using flow cytometry and that the responses of IL-12, IFN-gamma, and TNF-alpha induced by IL-18 were concentration dependently inhibited by coexisting histamine, whereas IL-18-inhibited IL-10 production was reversed by the same concentrations of histamine. The modulatory effects of histamine on ICAM-1 expression and cytokine production were all concentration dependently antagonized by famotidine but not by d-chlorpheniramine and thioperamide, and were mimicked by selective H(2)-receptor agonists but not by H(1)- and H(3)-receptor agonists, indicating the involvement of H(2)-receptors in histamine action. The inhibition of IL-18-induced IFN-gamma by histamine was ascribed to the strong inhibition of IL-12 production by histamine. Histamine thus operates the negative feedback mechanism against IL-18-activated cytokine cascade through the strong inhibitory effect on ICAM-1 expression and IL-12 production in monocytes, contributing to the formation of diverse pattern of cytokine activation from Th1 to Th2, depending on the monocyte/macrophage activation and cytokine environment.

Expression of IL-18 mRNA and secretion of IL-18 are reduced in monocytes from patients with atopic dermatitis

BACKGROUND

IL-18 has been found to be an IFN-gamma-inducing factor that plays an important role in T(H)1 cell activation. Recently, IL-18 has also been found to enhance a T(H)2 cellular response in a specific setting.

OBJECTIVE

The aim of this study was to elucidate the role of monocytes and soluble factors, with special focus on IL-18, in the pathogenesis of atopic dermatitis (AD).

METHODS

The release of cytokines from PBMCs and purified monocytes was measured through use of ELISA; mRNA expression was evaluated by RT-PCR. The results from patients with AD were compared with those from healthy controls.

RESULTS

IL-18 secretion was reduced in both unstimulated and lipopolysaccharide-stimulated monocytes from patients with AD. The mRNA expression of IL-18 and IL-1 beta-converting enzyme was significantly reduced in unstimulated monocytes from patients with AD (P <.03 and P <.01, respectively). Patients with AD had an elevated secretion of prostaglandin E(2) (PGE(2)) from unstimulated PBMCs (P <.001). The anti-PGE(2) antibody reversed the suppressive effect of PGE(2) on IL-18 secretion in unstimulated PBMCs from patients with AD.

CONCLUSIONS

Decreased IL-18 production, together with a significantly reduced IL-18 and ICE mRNA expression in unstimulated monocytes and elevated PGE(2) secretion from PBMCs, was associated with the pathogenesis of AD.

Histamine polarizes human dendritic cells into Th2 cell-promoting effector dendritic cells

Allergic disorders are characterized by allergen-specific Th2-biased responses. Signals controlling Th2 cell polarization, especially those acting by polarizing dendritic cells (DC) into Th2-promoting DC (DC2), are not well known. Histamine, a mediator released by allergen-stimulated mast cells from allergic subjects, has been reported to activate human immature DC. We have therefore tested whether histamine affects DC polarization. We report here that histamine inhibits LPS-induced IL-12 production and polarizes uncommitted maturing DC into effector DC2. DC matured in the presence of histamine fail to produce IL-12 upon subsequent stimulation and prime Th2 responses, even in presence of IFN-gamma, a potent DC1-driving factor. All these effects are mediated through both H1 and H2 receptors. These data show that histamine is a potent DC2-polarizing factor and provide evidence for a novel mechanism that explains the initiation and maintenance of a predominant Th2 response in allergic disorders.

Interleukin-18 regulates both Th1 and Th2 responses

Although interleukin-18 is structurally homologous to IL-1 and its receptor belongs to the IL-1R/Toll-like receptor (TLR) superfamily, its function is quite different from that of IL-1. IL-18 is produced not only by types of immune cells but also by non-immune cells. In collaboration with IL-12, IL-18 stimulates Th1-mediated immune responses, which play a critical role in the host defense against infection with intracellular microbes through the induction of IFN-gamma. However, the overproduction of IL-12 and IL-18 induces severe inflammatory disorders, suggesting that IL-18 is a potent proinflammatory cytokine that has pathophysiological roles in several inflammatory conditions. IL-18 mRNA is expressed in a wide range of cells including Kupffer cells, macrophages, T cells, B cells, dendritic cells, osteoblasts, keratinocytes, astrocytes, and microglia. Thus, the pathophysiological role of IL-18 has been extensively tested in the organs that contain these cells. Somewhat surprisingly, IL-18 alone can stimulate Th2 cytokine production as well as allergic inflammation. Therefore, the functions of IL-18 in vivo are very heterogeneous and complicated. In principle, IL-18 enhances the IL-12-driven Th1 immune responses, but it can also stimulate Th2 immune responses in the absence of IL-12.

[Regulation of cytokine production by histamine through H2-receptor stimulation]

Histamine is a well known mediator of inflammation including the allergic reaction. Histamine has been suggested to be a immunomodulator. Recent studies revealed that induction of histidine decarboxylase occurs by the stimulation of several cytokines and LPS, suggesting an immunomodulatory role of the inducible histamine. Using human PBMC culture, it was demonstrated that histamine was a potent inducer of IL-18, IFN-gamma in human PBMC. Histamine did not induce the production of IL-12. The effects of histamine on cytokine production were mimicked by H2-selective agonists and inhibited by H2- but not by H1- and H3-antagonists, indicating the involvement of H2-receptors in histamine action. All effects of histamine were abolished by the presence of anti-IL-18 antibody or IL-1b-converting enzyme/caspase-1 inhibitor, indicating that histamine action is dependent on mature IL-18 secretion and that IL-18 production was present most upstream of the cytokine cascade triggered by histamine. Histamine is a very important modulator of Th1 cytokine production in PBMC and is quite unique in triggering the cytokine cascade without inducing IL-12 production.

IL-18-induced expression of intercellular adhesion molecule-1 in human monocytes: involvement in IL-12 and IFN-gamma production in PBMC

IL-18 time- and concentration-dependently upregulated the expression of intercellular adhesion molecule-1 (ICAM-1) in a monocyte population in human PBMC as determined by FACS analysis while the expression of CD11a, CD18, CD29, CD44, and CD62L in monocytes and that of ICAM-1, CD11a, CD18, CD29, CD44, and CD62L in T cells was not influenced by IL-18. IL-18 in the same concentration range stimulated the production of IL-12, TNF-alpha, and IFN-gamma in culture of PBMC; however, IL-18-induced expression of ICAM-1 in monocytes was not inhibited by anti-IL-12, anti-TNF-alpha, or anti-IFN-gamma Ab, suggesting the independence of the upregulating effect of IL-18 on endogenous IL-12, TNF-alpha, and IFN-gamma production. IL-18 also induced the aggregation of PBMC, which was prevented by anti-ICAM-1 and anti-LFA-1 Abs. On the other hand, anti-ICAM-1 and anti-LFA-1 Abs inhibited IL-18-induced production of three cytokines, IL-12, IFN-gamma, and TNF-alpha, by 60 and 40%, respectively. These results strongly suggested that the IL-18-induced upregulation of ICAM-1 and the subsequent adhesive interaction through ICAM-1 on monocytes and LFA-1 on T/NK cells generate an additional stimulatory signaling as well as an efficient paracrine environment for the IL-18-initiated cytokine cascade.