Histamine and serotonin

Metabolite signatures associated with microRNA miR-143-3p serve as drivers of poor lung function trajectories in childhood asthma

BACKGROUND

Lung function trajectories (LFTs) have been shown to be an important measure of long-term health in asthma. While there is a growing body of metabolomic studies on asthma status and other phenotypes, there are no prospective studies of the relationship between metabolomics and LFTs or their genomic determinants.

METHODS

We utilized ordinal logistic regression to identify plasma metabolite principal components associated with four previously-published LFTs in children from the Childhood Asthma Management Program (CAMP) (n = 660). The top significant metabolite principal component (PCLF) was evaluated in an independent cross-sectional child cohort, the Genetic Epidemiology of Asthma in Costa Rica Study (GACRS) (n = 1151) and evaluated for association with spirometric measures. Using meta-analysis of CAMP and GACRS, we identified associations between PCLF and microRNA, and SNPs in their target genes. Statistical significance was determined using an false discovery rate-adjusted Q-value.

FINDINGS

The top metabolite principal component, PCLF, was significantly associated with better LFTs after multiple-testing correction (Q-value = 0.03). PCLF is composed of the urea cycle, caffeine, corticosteroid, carnitine, and potential microbial (secondary bile acid, tryptophan, linoleate, histidine metabolism) metabolites. Higher levels of PCLF were also associated with increases in lung function measures and decreased circulating neutrophil percentage in both CAMP and GACRS. PCLF was also significantly associated with microRNA miR-143-3p, and SNPs in three miR-143-3p target genes; CCZ1 (P-value = 2.6 × 10-5), SLC8A1 (P-value = 3.9 × 10-5); and TENM4 (P-value = 4.9 × 10-5).

INTERPRETATION

This study reveals associations between metabolites, miR-143-3p and LFTs in children with asthma, offering insights into asthma physiology and possible interventions to enhance lung function and long-term health.

FUNDING

Molecular data for CAMP and GACRS via the Trans-Omics in Precision Medicine (TOPMed) program was supported by the National Heart, Lung, and Blood Institute (NHLBI).

Expression of airway smooth muscle contractile proteins in children with acute interstitial pneumonia

The purpose of the present study was to investigate the expression of α-SMA and SM22α in airway smooth muscle (ASM) of bronchioles from children younger than 14 years who died of acute interstitial pneumonia (AIP). This is based upon the hypothesis that as contractile marker proteins α-SMA and SM22α can serve as an index of the overcontractile phenotype of ASM that is seen in AIP. Lung tissue samples of children were obtained from autopsies and divided into the AIP group (55.9% male and 44.1% female, between 0.4 and 132 months old, n = 34) and the control group (60% male and 40% female, between 2 and 156 months old, n = 10). We recorded the post-mortem interval (PMI), height, clinical symptoms and abdominal fat thickness (AFT) of each case. Haematoxylin-and-eosin-stained sections were used to examine the luminal area and observe the morphological changes in the bronchioles. Immunohistochemistry and Masson's trichrome staining were used to detect the expression of contractile marker proteins and the degree of pulmonary fibrosis respectively. Compared with the control group, the luminal areas of bronchioles in the AIP group were smaller (p < .001). The expression differences in α-SMA and SM22α between the two groups were statistically significant (p = .01 and p = .02 respectively). Also, there was no significant correlation of the contractile marker proteins expression with PMI, height, clinical symptoms and AFT. The collagen deposition difference in lung between the two groups was not statistically significant (p = .224). These findings suggest that enhancement of ASM contractile function appears to be involved in the death mechanism of children with AIP, which affords more insights into the understanding of AIP.

Feline Asthma: Diagnostic and Treatment Update

Asthma is an important allergic lower-airway disease in cats affecting approximately 1% to 5% of the pet cat population. New diagnostics are being developed to help better differentiate asthma from other lower-airway diseases and improve monitoring. In addition, new treatments are being developed to help in refractory cases or in those cases in which traditional therapeutics are contraindicated. This article discusses potential pitfalls in the diagnosis of asthma. In addition, current literature investigating new diagnostic tests and therapies for feline asthma is reviewed.

Inonotus obliquus attenuates histamine-induced microvascular inflammation

Cell-to-cell communication is a key element of microvascular blood flow control, including rapidly carrying signals through the vascular endothelium in response to local stimuli. This cell-to-cell communication is negatively impacted during inflammation through the disruption of junctional integrity. Such disruption is associated with promoting the onset of cardiovascular diseases as a result of altered microvascular blood flow regulation. Therefore, understanding the mechanisms how inflammation drives microvascular dysfunction and compounds that mitigate such inflammation and dysfunction are of great interest for development. As such we aimed to investigate extracts of mushrooms as potential novel compounds. Using intravital microscopy, the medicinal mushroom, Inonotus obliquus was observed, to attenuate histamine-induced inflammation conducted vasodilation in second-order arterioles in the gluteus maximus muscle of C57BL/6 mice. Mast cell activation by C48/80 similarly disrupted endothelial junctions and conducted vasodilation but only histamine was blocked by the histamine antagonist, pyrilamine not C48/80 suggesting the importance of mast cell activation. Data presented here supports that histamine induced inflammation is a major disruptor of junctional integrity, and highlights the important anti-inflammatory properties of Inonotus obliquus focusing future assessment of mast cells as putative target for Inonotus obliquus.

pH-induced conformational changes in histamine in the solid state

Histamine is one of the most basic biogenic amino-compounds, which is composed of imidazole and a flexible ethylamine side chain moiety. Histamine is known to take the form of various types of cations, free base, monocation and dication form, where its conformational change is highly sensitively to the pH conditions. The details of these changes are still controversial due to a lack of detailed information on its crystal structures. Thus, in this study, the molecular packing structures of histidine at various pH were analyzed via X-ray diffraction in combination with vibrational spectroscopy and energy calculations. A variety of molecular conformations including the tautomeric phenomenon was found to be intimately related with intra- and intermolecular hydrogen bonds. The role of the hydrogen bonds was studied also to check the possibility of high proton conductivity of histamine, as predicted by computer simulation. Consequently, the thus-predicted proton conductivity was confirmed for the first time experimentally. During the heating process, the conductivity showed the relatively high maximum value of 10⁻⁴ S cm⁻¹ at around 60 °C, which is related to the effective proton transfer between the amino NH group of one histamine unit and the imidazole ring of another.

The tautomeric and conformational preferences of histamine related to proton transfer were investigated from both theoretical and experimental points of view.

Inflammatory mediators mediate airway smooth muscle contraction through a G protein-coupled receptor-transmembrane protein 16A-voltage-dependent Ca2+ channel axis and contribute to bronchial hyperresponsiveness in asthma

BACKGROUND

Allergic inflammation has long been implicated in asthmatic hyperresponsiveness of airway smooth muscle (ASM), but its underlying mechanism remains incompletely understood. Serving as G protein-coupled receptor agonists, several inflammatory mediators can induce membrane depolarization, contract ASM, and augment cholinergic contractile response. We hypothesized that the signal cascade integrating on membrane depolarization by the mediators might involve asthmatic hyperresponsiveness.

OBJECTIVE

We sought to investigate the signaling transduction of inflammatory mediators in ASM contraction and assess its contribution in the genesis of hyperresponsiveness.

METHODS

We assessed the capacity of inflammatory mediators to induce depolarization currents by electrophysiological analysis. We analyzed the phenotypes of transmembrane protein 16A (TMEM16A) knockout mice, applied pharmacological reagents, and measured the Ca²⁺ signal during ASM contraction. To study the role of the depolarization signaling in asthmatic hyperresponsiveness, we measured the synergistic contraction by methacholine and inflammatory mediators both ex vivo and in an ovalbumin-induced mouse model.

RESULTS

Inflammatory mediators, such as 5-hydroxytryptamin, histamine, U46619, and leukotriene D₄, are capable of inducing Ca²⁺-activated Cl^- currents in ASM cells, and these currents are mediated by TMEM16A. A combination of multiple analysis revealed that a G protein-coupled receptor-TMEM16A-voltage-dependent Ca²⁺ channel signaling axis was required for ASM contraction induced by inflammatory mediators. Block of TMEM16A activity may significantly inhibit the synergistic contraction of acetylcholine and the mediators and hence reduces hypersensitivity.

CONCLUSIONS

A G protein-coupled receptor-TMEM16A-voltage-dependent Ca²⁺ channel axis contributes to inflammatory mediator-induced ASM contraction and synergistically activated TMEM16A by allergic inflammatory mediators with cholinergic stimuli.

Crystal structure of 2-(1H-imidazol-3-ium-4-yl)ethanaminium dichloride, a re-determination

The crystal structure of the title mol-ecular salt, C5H11N3 (+)·2Cl(-), was redetermined. In comparison with the previous study [Bonnet et al. (1975 ▸). Bull. Soc. Fr. Mineral. Crist. 98, 208-213.], the positions of some H atoms were corrected, allowing a more accurate description of the hydrogen-bonding scheme. In addition, the absolute structure was also determined. The maximum differences in terms of bond lengths and angles between the two determinations are 0.022 Å and 1.43°, respectively. The organic cation display a anti conformation of the protonated amine function and the imidazolium ring. The dihedral angle between the imidazolium plane and the plane through the C-C-N side chain is 29.58 (3)°. In the crystal, the organic cations and Cl(-) anions are stacked alternatively into layers parallel to (100). N-H⋯Cl hydrogen bonds between all H atoms of the ammonium group and both N-H groups of the imidazolium ring and the Cl(-) acceptor anions lead to the linkage of organic and inorganic layers into a three-dimensional network.

Histamine H(1)- and H(4)-receptor signaling cooperatively regulate MAPK activation

The histamine (HA) receptor subtype 1 (H1R) and H4R are expressed on immune cells and contribute to an inflammatory reaction. Both receptor subtypes individually enhance the intracellular concentrations of calcium and regulate the accumulation of cAMP, increase MAPK activity, and regulate expression of e.g., inflammatory genes. In a previous study we characterized and compared signaling pathways of the murine orthologs of the H1R and the H4R recombinantly expressed at comparable levels in HEK 293 cells. In the present study, we aimed at analyzing possible interactions of the signaling pathways emerging at the mH1R and the mH4R. Therefore, we co-expressed both receptor subtypes at comparable levels in HEK 293 cells and investigated HA-induced signaling parameters such as the concentrations of intracellular calcium and cAMP, phosphorylation of the MAPKs p38, ERK 1, and ERK 2, and of the transcription factor CREB, and expression of the immediate early gene EGR-1. We demonstrate that the intracellular concentrations of calcium and cAMP as well as the EGR-1 expression are regulated exclusively via the mH1R. In contrast, both receptor subtypes H1R and H4R synergize in HA-induced MAPK activation. This synergism most probably relies on signaling pathways independent of the second messenger calcium and cAMP. In summary, we provide evidence that the mH1R inhibits or dampens the function of the co-expressed mH4R regarding specific parameters, while other signaling events are regulated cooperatively by the mH1R and the mH4R.

Crystal structure of 2-(1H-imidazol-4-yl)ethanaminium chloride

The title mol­ecular salt, C₅H₁₀N₃⁺·Cl⁻, was obtained as by-product in the attempted synthesis of a histamine derivative. The terminal amino group of the starting material is protonated. The C_imidazole—C—C—N(H₃)⁺ group in the cation is in an anti conformation with a torsion angle of 176.22 (10)°. In the crystal, cations and anions are linked via N—H⋯N and N—H—Cl hydrogen bonds, forming a two-dimensional network parallel to (10-1). A single weak C—H⋯Cl hydrogen bond completes a three-dimensional network.

Distinct signalling pathways of murine histamine H1- and H4-receptors expressed at comparable levels in HEK293 cells

Histamine (HA) is recognized by its target cells via four G-protein-coupled receptors, referred to as histamine H₁-receptor (H₁R), H₂R, H₃R, and H₄R. Both H₁R and H₄R exert pro-inflammatory functions. However, their signal transduction pathways have never been analyzed in a directly comparable manner side by side. Moreover, the analysis of pharmacological properties of the murine orthologs, representing the main targets of pre-clinical research, is very important. Therefore, we engineered recombinant HEK293 cells expressing either mouse (m)H₁R or mH₄R at similar levels and analyzed HA-induced signalling in these cells. HA induced intracellular calcium mobilization via both mH₁R and mH₄R, with the mH₁R being much more effective. Whereas cAMP accumulation was potentiated via the mH₁R, it was reduced via the mH₄R. The regulation of both second messengers via the H₄R, but not the H₁R, was sensitive to pertussis toxin (PTX). The mitogen-activated protein kinases (MAPKs) ERK 1/2 were massively activated downstream of both receptors and demonstrated a functional involvement in HA-induced EGR-1 gene expression. The p38 MAPK was moderately activated via both receptors as well, but was functionally involved in HA-induced EGR-1 gene expression only in H₄R-expressing cells. Surprisingly, in this system p38 MAPK activity reduced the HA-induced gene expression. In summary, using this system which allows a direct comparison of mH₁R- and mH₄R-induced signalling, qualitative and quantitative differences on the levels of second messenger generation and also in terms of p38 MAPK function became evident.

Transcriptional down-regulation of suppressor of cytokine signaling (SOCS)-3 in chronic obstructive pulmonary disease

BACKGROUND

Tobacco is a leading environmental factor in the initiation of respiratory diseases and causes chronic obstructive pulmonary disease (COPD). Suppressor of cytokine signaling (SOCS) family members are involved in the pathogenesis of many inflammatory diseases and SOCS-3 has been shown to play an important role in the regulation, onset and maintenance of airway allergic inflammation indicating that SOCS-3 displays a potential therapeutic target for anti-inflammatory respiratory drugs development. Since chronic obstructive pulmonary disease (COPD) is also characterized by inflammatory changes and airflow limitation, the present study assessed the transcriptional expression of SOCS-3 in COPD.

METHODS

Real-time PCR was performed to assess quantitative changes in bronchial biopsies of COPD patients in comparison to unaffected controls.

RESULTS

SOCS-3 was significantly down-regulated in COPD at the transcriptional level while SOCS-4 and SOCS-5 displayed no change.

CONCLUSIONS

It can be concluded that the presently observed inhibition of SOCS-3 mRNA expression may be related to the dysbalance of cytokine signaling observed in COPD.

Update on feline asthma

This article provides an overview of recent advances in the diagnosis and treatment of feline asthma. The authors discuss the potential pitfalls in the diagnosis of feline asthma. In addition, current literature investigating new therapies for the treatment of feline asthma is reviewed.

Localization and upregulation of the nasal histamine H1 receptor in perennial allergic rhinitis

In the present study, we have investigated the expression of histamine H1 receptor in human turbinates by RT-PCR, western blotting, and immunohistochemistry. Human turbinates were obtained by turbinectomy from 12 patients with nasal obstruction refractory to medical therapy. RT-PCR analysis of total RNA extracted from human nasal turbinate, primary cultured human nasal epithelial cells, and nasal vascular endothelial cells demonstrated the expression of histamine H1 receptor mRNA. About 56 kDa band was detected in human turbinates by western blot analysis using anti-H1 receptor antibody. The expression level of H1 receptor protein was marked in patients with nasal allergy than in patients with nonallergic rhinitis. The immunohistochemical study revealed that epithelial cells and vascular endothelial cells showed intense immunoreactivity for histamine H1 receptor. In addition, the blood vessels in superficial area expressed higher level of H1 receptor immunoreactivity than that in deeper area in the nasal mucosa. These results may have an important clinical implication for understanding the role of histamine H1 receptor on upper airway diseases such as allergic rhinitis and nonallergic rhinitis.

Smooth muscle in tissue remodeling and hyper-reactivity: airways and arteries

Smooth muscle comprises a key functional component of both the airways and their supporting vasculature. Dysfunction of smooth muscle contributes to and exacerbates a host of breathing-associated pathologies such as asthma, chronic obstructive pulmonary disease and pulmonary hypertension. These diseases may be marked by airway and/or vascular smooth muscle hypertrophy, proliferation and hyper-reactivity, and related conditions such as fibrosis and extracellular matrix remodeling. This review will focus on the contribution of airway or vascular smooth dysfunction to common airway diseases.

Association of serotonin transporter gene variation with smoking, chronic obstructive pulmonary disease, and its depressive symptoms

A serotonin transporter gene, SLC6A4, is thought to be related to nicotine dependence and depression, one of the comorbidities of chronic obstructive pulmonary disease (COPD). To investigate the association between SLC6A4 variation and tobacco consumption, susceptibility to COPD, and depression status. In all, 247 patients with COPD and 119 control subjects were genotyped for 5 tag single-nucleotide polymorphisms (SNPs) of SLC6A4. We analyzed the correlation between these genotypes and COPD, using the results of a pulmonary function test or chest computed tomography; data on tobacco consumption (pack-years); and the depression score based on the hospital anxiety and depression scale (HADS) after adjusting for age, gender, and smoking status (and pack-years, when appropriate). The rare allele rs2020936 was significantly associated with COPD incidence in the trend model (P = 0.003; odds ratio, 2.20; 95% confidence interval, 1.31-3.74). This allele was also associated with the number of pack-years (P = 0.026). The major allele of another SNP of SLC6A4, namely rs3794808, correlated with the HADS depression score (P = 0.016). We conclude that SLC6A4 variation affects COPD pathogenesis, and this effect depends partly on tobacco consumption. SLC6A4 variation also affects depressive symptoms. SLC6A4 could be modified to prevent COPD and treat the depressive symptoms of COPD.

Clinical correlates of blood serotonin levels in patients with mastocytosis

BACKGROUND

Mastocytosis is a clonal disorder associated with an increased mast cell burden. We have recently demonstrated the ability of human mast cells to express and be activated through multiple serotonin receptors; to synthesize and release serotonin; and that mastocytosis patients may have abnormal serotonin levels. As serotonin has been implicated in the genesis of clinical symptoms found in association with some chronic diseases, we have now determined the whole blood serotonin levels in 29 patients diagnosed with mastocytosis, and correlated these levels with multiple clinical and laboratory parameters.

MATERIALS AND METHODS

Patients with mastocytosis were categorized according to disease variant. Blood serotonin values were determined and correlated with values reported for normal subjects; and clinical and laboratory features of the disease.

RESULTS

Total blood serotonin levels followed a bimodal distribution in line with our earlier report, unlike the normal distribution reported for normal individuals. Serotonin levels did not correlate with platelet numbers, liver function tests or serum tryptase levels. Patients with lower serotonin values had greater rates of fatigue (P = 0.0001), migraine headaches (P = 0.0028), psychiatric symptoms (P = 0.0001), diarrhoea (P = 0.0407), flushing (0.0085), and abdominal and bone pain (P = 0.0001).

CONCLUSIONS

Our study suggests that low blood serotonin levels help define a sub-group of patients with mastocytosis that are more likely to present with neurological and gastrointestinal complaints, and suggests that the use of pharmacologic agents that alter blood serotonin levels could be explored in selected patients.

PAF, rather than histamine, participates in mouse anaphylactic hypotension

We determined the roles of platelet-activating factor (PAF) and histamine in anaphylactic hypotension in ovalbumin-sensitized anesthetized BALB/c mice. The effects of PAF and histamine on hemodynamic variables were studied by measuring the systemic arterial (Psa), portal venous (Ppv) and central venous (Pcv) pressures. Intravenous PAF evoked a biphasic Psa response, an initial rapid and transient drop followed by marked hypotension, accompanied by a decrease in Pcv. Histamine caused only mild systemic hypotension. Both agents similarly increased Ppv by approximately 4 cm H(2)O at high doses. After an injection of antigen, Psa initially increased slightly and then decreased from the baseline of 94 +/- 1 mm Hg to 46 +/- 1 mm Hg at 10 min after antigen administration, with Pcv decreasing by 2.5 cm H(2)O. Ppv increased by 3.5 cm H(2)O at 5 min after antigen injection. Pretreatment with either CV-6209 (PAF receptor antagonist, 1 mg/kg) or diphenhydramine (histamine H(1) receptor antagonist, 20 mg/kg) significantly attenuated an antigen-induced decrease in Psa. The inhibitory action of CV-6209 was greater than that of diphenhydramine, and the combination of these 2 antagonists almost completely inhibited the anaphylactic hypotension. In contrast, the antigen-induced increase in Ppv was attenuated by CV-6209 alone but augmented by diphenhydramine. It is concluded that anaphylactic hypotension is mainly mediated by PAF and, to a lesser extent, by histamine in anesthetized BALB/c mice.

Effects of cyproheptadine and cetirizine on eosinophilic airway inflammation in cats with experimentally induced asthma

OBJECTIVE

To determine whether oral administration of cyproheptadine or cetirizine blocks the action of serotonin and histamine, respectively, and results in diminished eosinophilic airway inflammation in cats with experimentally induced asthma.

ANIMALS

9 cats in which asthma was experimentally induced through exposure to Bermuda grass allergen (BGA) during a 3-month period.

PROCEDURES

Cats were randomized to receive monotherapy with each of 3 treatments for 1 week: placebo (flour in a gelatin capsule, PO, q 12 h), cyproheptadine (8 mg, PO, q 12 h), or cetirizine (5 mg, PO, q 12 h). A 1-week washout period was allowed to elapse between treatments. Prior to and following each 1-week treatment period, blood and bronchoalveolar lavage fluid (BALF) samples were collected. The percentage of eosinophils in BALF was evaluated to determine treatment efficacy. Serum and BALF BGA-specific immunoglobulin contents and plasma and BALF histamine concentrations were determined via ELISAs. Plasma and BALF serotonin concentrations were measured by use of a fluorometric method.

RESULTS

The mean +/- SD percentage of eosinophils in BALF did not differ significantly among treatment groups (placebo, 40 +/- 22%; cyproheptadine, 27 +/- 16%; and cetirizine, 31 +/- 20%). Among the treatment groups, BGA-specific immunoglobulin content and histamine and serotonin concentrations were not significantly different.

CONCLUSIONS AND CLINICAL RELEVANCE

In cats with experimentally induced asthma, cyproheptadine and cetirizine were not effective in decreasing airway eosinophilic inflammation or in altering several other measured immunologic variables. Neither cyproheptadine nor cetirizine can be advocated as monotherapy for cats with allergen-induced asthma.

Sputum indoleamine-2, 3-dioxygenase activity is increased in asthmatic airways by using inhaled corticosteroids

BACKGROUND

Indoleamine-2, 3-dioxygenase (IDO), a tryptophan-degrading enzyme, plays a key role in the regulation of T-lymphocyte function. IDO inhibits eosinophilic inflammation in a murine asthma model, but little is known about its role in asthmatic patients or the effects of corticosteroids on this key regulatory enzyme.

OBJECTIVE

We studied IDO activity and the effect of inhaled corticosteroids (ICSs) in patients with asthma and how this correlated with eosinophilic inflammation.

METHODS

After a 1-week run-in period on no therapy, 34 asthmatic patients were treated with only short-acting beta(2)-agonists as required or an ICS or an ICS in combination with a long-acting beta(2)-agonist, which were required for asthma control, and the treatment was continued for a further 4 weeks. Each patient underwent sputum induction at the end of the run-in and treatment periods. Sputum supernatant specimens were analyzed for IDO activity and kynurenine concentrations by using HPLC.

RESULTS

All patients with mild intermittent and mild-to-moderate persistent asthma had low baseline IDO activity in induced sputum compared with that seen in age-matched nonasthmatic subjects. The IDO activity was markedly enhanced by either ICS (P = .03) or ICS/long-acting beta(2)-agonist (P < .0001) treatment, and this increase negatively correlated with sputum eosinophils but was positively associated with an increase in IL-10-positive macrophages.

CONCLUSION

ICSs might exert their anti-inflammatory activity in asthmatic airways, at least in part, through the upregulation of IDO activity associated with increased IL-10 secretion from macrophages.

Serotonin activates human monocytes and prevents apoptosis

Monocytes play a critical role in chronic atopic dermatitis (AD) and are the primary leukocytes that interact with activated platelets. Although activated platelets release a variety of mediators, the role of platelets in cutaneous allergic inflammation remains unclear. Serotonin (5-hydroxytryptamine, 5-HT) is one of the prototypic mediators produced by activated platelets. We examined the effect of 5-HT on the function and lifespan of human monocytes. Normal human monocytes treated with 5-HT exhibited upregulated expression of costimulatory molecules, enhanced capacity to produce cytokines following lipopolysaccharide treatment, and to stimulate allogeneic CD4+ T cells. 5-HT also attenuated the apoptosis in normal human monocytes in a dose-dependent manner. The plasma levels of 5-HT were increased in patients with AD compared with controls and correlated with the SCORAD index. 5-HT also inhibited monocyte apoptosis in these patients. 5-HT upregulated Bcl-2 and Mcl-1, and inhibited the activation of caspase-3. The effects of 5-HT on monocyte apoptosis were mediated by the 5-HT1 and/or 5-HT7 receptors. 5-HT and a 5-HT(1/6/7)-receptor agonist induced phosphorylation of extracellular signal-regulated kinase1/2 and activation of nuclear transcription factor-kappaB. These findings support that 5-HT activates monocytes and inhibits apoptosis, allowing them to remain in the tissue and contribute to chronic inflammation.

IL-1beta induces murine airway 5-HT2A receptor hyperresponsiveness via a non-transcriptional MAPK-dependent mechanism

BACKGROUND

Interleukin 1 beta (IL-1beta) is found in bronchoalveolar lavage fluids from asthmatic patients and plays an important role in normal immunoregulatory processes but also in pathophysiological inflammatory responses. The present study was designed to investigate if IL-1beta could be involved in the development of airway hyperresponsiveness and if transcriptional mechanisms, epithelium contractile factors and mitogen-activated protein kinase (MAPK) pathways are involved in IL-1beta effect.

METHODS

The effect of IL-1beta on 5-hydroxytryptamine (5-HT) induced bronchoconstriction was evaluated in an in-vitro model for assessment of long-term effects of inflammatory mediators on the airway smooth muscle. Murine tracheal segments were cultured up to 8 days in the absence or presence of IL-1beta with subsequent evaluation in a myograph system, along with mRNA quantification, focusing on the role of the epithelium, acetylcholine release, transcriptional mechanisms and MAPK activity.

RESULTS

During control conditions, 5-HT induced a relatively weak contraction. Presence of IL-1beta increased this response in a time- and concentration-dependent way. The increased concentration-effect curves could be shifted rightwards in a parallel manner by ketanserin, a selective 5-HT2A receptor antagonist, indicating that the responses are mediated by 5-HT2A receptors. The mRNA levels of 5-HT2A receptors were not changed as a consequence of the IL-1beta treatment and actinomycin D, a general transcriptional inhibitor, failed to affect the contractile response, suggesting a non-transcriptional mechanism behind this phenomenon. Neither the removal of the epithelium nor the addition of atropine affected the IL-1beta induced enhancement of 5-HT2A receptor-mediated contractile response. Application of inhibitors for c-Jun N-terminal kinase (JNK), p38 and extracellular signal-regulated kinase 1 and 2 (ERK1/2) showed that the signaling pathways for JNK and ERK1/2 dominated only in cultured segments (control) whereas JNK and p38 dominated in segments treated with IL-1beta.

CONCLUSION

IL-1beta induces murine airway hyperresponsiveness, via a non-transcriptional up-regulation of 5-HT2A receptor-mediated contractile response. The increase of 5-HT contraction is unrelated to epithelial and cholinergic factors, but is dependent on IL-1beta-induced changes of MAPK pathways. The fact that IL-1beta can alter airway responses to contractile agents such as 5-HT, via alteration of the intracellular MAPK signal transduction pathways, might provide a new concept for future treatment of asthma.

Histamine reverses IL-5-afforded human eosinophil survival by inducing apoptosis: pharmacological evidence for a novel mechanism of action of histamine

Eosinophils are essential inflammatory cells in the pathogenesis of asthma and atopic conditions. Histamine, released from mast cells and basophils in response to allergen exposure, is a critical mediator in the allergic response. Histamine exerts its effects via four unequivocally characterized histamine receptors, H(1-4). Several functions of eosinophils have previously been shown to be stimulated by histamine. However, its effects on eosinophil apoptosis are unknown. The aim of the present study was to resolve the effects of histamine on constitutive apoptosis of human eosinophils and on the survival-enhancing action of interleukin (IL)-5. Additional experiments were conducted to elucidate the histamine receptor(s) involved in any response seen and the associated signal transduction cascade. Human isolated peripheral blood eosinophils were cultured in the absence or presence of histamine, IL-5 and receptor antagonists/agonists or mediator inhibitors/analogues. Apoptosis was assessed by measuring the relative DNA content of propidium iodide (PI)-stained cells and the effects were confirmed by morphological analysis with bright field microscopy. Caspase activities were assessed by using commercial Caspase-Glo 3/7, 8 and 9 luminescence assays. Histamine (10-100 microM) partially reversed IL-5-induced human eosinophil survival by enhancing apoptosis as assessed by measuring the relative DNA content of PI-stained cells. This effect was not mediated through any of the known histamine receptors or through non-specific activation of 5-hydroxytryptamine receptors or alpha-adrenoceptors. Moreover, the reversal of IL-5-inhibited eosinophil apoptosis by histamine seemed not to utilize the conventional intracellular second-messenger pathways including cyclic AMP, protein kinase A or phospholipase C. Inhibition of caspase 6 and caspases 1, 10 or 12 reversed the effects of histamine but also inhibited apoptosis in general. In conclusion, the data presented herein indicate that histamine induces human eosinophil apoptosis in the presence of a survival-prolonging cytokine by a mechanism that does not apparently involve the activation of any of the currently known histamine receptor subtypes. The possibility exists that another, as yet unidentified, histamine receptor may exist in human eosinophils that regulates survival, although the participation of histamine receptor-independent mechanisms cannot be excluded.

Effect of serotonin on the differentiation of human monocytes into dendritic cells

The local cytokine environment and presence of stimulatory signals determine whether monocytes acquire dendritic cell (DC) or macrophage characteristics and functions. Because enhanced platelet activation is reported in patients with many allergic disorders, such as atopic dermatitis, platelet-derived factors may influence monocytic differentiation into DC. In this study we examined the effect of serotonin, a prototypic mediator of allergic inflammation released mainly by activated platelets at the inflammatory site, on the granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4-driven differentiation of monocytes into monocyte-derived DC. Monocytes from healthy adult donors were cultured with GM-CSF and IL-4 in the presence or absence of serotonin, and the phenotypes and function of these cells were analysed. In the presence of serotonin, monocytes differentiated into DC with reduced expression of co-stimulatory molecules and CD1a, whereas expression of CD14 was increased. These serotonin-treated DC exhibited significantly reduced stimulatory activity toward allogeneic T cells. However, these cells showed enhanced cytokine-producing capacity, including IL-10 but not IL-12. There was no significant difference between both types of DC in phagocytic activity. Experiments using agonists and antagonists indicated that serotonin 5-hydroxytryptamine (5-HT) induced the alteration of their phenotype and reduction in antigen-presenting capacity were mediated via 5-HTR(1/7). It is therefore suggested that serotonin-driven DC may have a regulatory function in the inflammatory process.

Analysis of airway secretions in a model of sulfur dioxide induced chronic obstructive pulmonary disease (COPD)

Hypersecretion and chronic phlegm are major symptoms of chronic obstructive pulmonary disease (COPD) but animal models of COPD with a defined functional hypersecretion have not been established so far. To identify an animal model of combined morphological signs of airway inflammation and functional hypersecretion, rats were continuously exposed to different levels of sulfur dioxide (SO2, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm) for 3 (short-term) or 20–25 (long-term) days. Histology revealed a dose-dependent increase in edema formation and inflammatory cell infiltration in short-term-exposed animals. The submucosal edema was replaced by fibrosis after long-term-exposure. The basal secretory activity was only significantly increased in the 20 ppm group. Also, stimulated secretion was significantly increased only after exposure to 20 ppm. BrdU-assays and AgNOR-analysis demonstrated cellular metaplasia and glandular hypertrophy rather than hyperplasia as the underlying morphological correlate of the hypersecretion.

In summary, SO2-exposure can lead to characteristic airway remodeling and changes in mucus secretion in rats. As only long-term exposure to 20 ppm leads to a combination of hypersecretion and airway inflammation, only this mode of exposure should be used to mimic human COPD. Concentrations less or higher than 20 ppm or short term exposure do not induce the respiratory symptom of hypersecretion. The present model may be used to characterize the effects of new compounds on mucus secretion in the background of experimental COPD.

Transcriptional up-regulation of histamine receptor-1 in epithelial, mucus and inflammatory cells in perennial allergic rhinitis

BACKGROUND

Histamine receptors play an important role in the pathogenesis of nasal allergy. Activation of histamine receptor 1 (H1R) and 2 (H2R) can cause allergic symptoms which can be blocked effectively by antihistamines. H1R and H2R transcript levels have been found to be up-regulated in perennial - but not in seasonal - allergic rhinitis (AR). The present study aimed to explore H1R and H2R expression in complex tissues of the nasal mucosa of perennial allergic rhinitis (PAR).

METHODS

Ten patients with PAR and 13 non-AR subjects were recruited for the study by medical history, physical examination and laboratory screening tests. In this study, we have analysed single cells dissected from the nasal mucosa biopsies by laser-assisted microdissection. H1R mRNA expression was analysed in different cell types such as epithelial, endothelial, mucus and inflammatory cells isolated from the nasal mucosa of PAR in comparison with non-AR subjects.

RESULTS

H1R mRNA gene expression level was significantly increased in the nasal mucosa of PAR in comparison with non-AR (P<0.0001). H1R mRNA was significantly elevated in epithelial (P<0.001) and mucus cells (P<0.05) of PAR in comparison with non-AR whereas H1R gene expression levels in endothelial cells between both groups were not changed (P=0.23). Interestingly, inflammatory cells in the nasal mucosa of PAR patients were also strongly expressed H1R mRNA (P<0.001).

CONCLUSION

The present study indicates that PAR alters the expression of H1R mRNA in epithelial, mucus and inflammatory cells of the nasal mucosa and but not in endothelial cells. Therefore, epithelial, mucus and inflammatory cells may play an important role in histamine-mediated allergic airway inflammation in PAR.

Alternative promoter use and splice variation in the human histamine H1 receptor gene

Upstream gene structure and mRNA expression of the human histamine H1 receptor gene was investigated in cells relevant to the pathogenesis of asthma, (primary cultured human airway smooth muscle (HASM) cells, primary cultured human bronchial epithelial cells and bronchial epithelial cell line [BEAS2B]), and other tissues known to express histamine H1 receptors (placenta and brain). Splice variation of the 5' terminal exons gave three separate locations for novel promoters upstream of the detected transcription start sites. Further splice variants in the 5' untranslated region were also observed. Transient transfections of promoter/luciferase constructs showed these regions directed expression in HASM cells and BEAS2B cells. Polymorphism screening of the major regulatory regions identified a number of novel single-nucleotide polymorphisms. Expression of splice variants was confirmed by real-time PCR assays. Results showed one 5' terminal exon splice variant, comprising exons B/K, expressed preferentially in all tissues. Interestingly, the other 5' terminal exon splice variants showed tissue-specific patterns of expression, with variant F/K expressed negligibly (0.1%) in HASM cells, but accounting for 19.3% and 8.3% of total expression in BEAS2B cells and differentiated human bronchial epithelial cells, respectively. Splice variant A/K was second most highly expressed in differentiated human bronchial epithelial cells (23%), whereas its expression in BEAS2B and HASM cells was 1.7% and 4.4%, respectively. These data suggest the use of alternative promoters directing human H1 receptor gene expression, both within and between cell types.

Oedematogenic activity induced by Kunitz-type inhibitors from Dimorphandra mollis seeds

Proteinase inhibitors from plants represent a form of storage protein or may be involved in plant defense mechanisms against pests and diseases. In this study, we have investigated the oedematogenic activity of DMTI (20 kDa) and DMTI-II (23 kDa), two serine proteinases inhibitors isolated from Dimorphandra mollis (Leguminosae-Mimosoideae) seeds, belonging to the Kunitz family. Paw oedema was induced in male Wistar rats, and measured before and selected times after injection of the proteinase inhibitors. Injection of DMTI-II (3-100 microg/paw) induced a dose-dependent rat paw oedema of rapid onset and short duration, whereas DMTI (3-100 microg/paw) caused a discrete response. The histamine/5-HT receptor antagonist cyproheptadine (2 mg/kg) markedly reduced the DMTI-II-induced oedema. The bradykinin B2 receptor antagonist JE 049 (0.6 mg/kg), the tachykinin NK1 receptor antagonist SR140333 (100 microg/kg) or the NK2 receptor antagonist SR48968 (1 mg/kg) all significantly reduced the DMTI-II-induced oedema. Depletion of sensory neuropeptides by capsaicin also resulted in a significant reduction of oedema formation. In rat isolated peritoneal mast cells, DMTI-II failed to directly release histamine. In conclusion, the proteinase inhibitor DMTI-II induces rat paw oedema by triggering the formation of different inflammatory mediators and pathways, where mast cells and sensory fibers seem to play a pivotal role.

Signal transduction pathways involved in particulate matter induced relaxation in rat aorta--spontaneous hypertensive versus Wistar Kyoto rats

Previously we reported that in vivo exposure to ambient particulate matter (PM) induces vasodilatation in rat aorta. The purpose of the current study was to investigate the intracellular messengers involved in PM-elicited vasodilatation in aortas from spontaneous hypertensive (SHR) and normotensive (WKY) rats.

METHODS

The contribution of three different intracellular pathways, i.e. (1) the NO-cGMP pathway, (2) prostanoids signaling and (3) endothelial hyperpolarisation factors were evaluated by using specific inhibitors (NS2028, Diclofenac and high K-concentration/17-ODYA, respectively). Using antagonists of capsaicin- or histamine receptors we tested potential interactions of PM with these receptors. Particle suspensions (EHC-93), particle filtrates (particle-free) and Cu(2+)- or Zn(2+)-containing solutions were used to obtain cumulative dose-response curves of relaxation in normal and endothelium-denuded rings.

RESULTS

Our present data confirm that PM and its soluble components elicit an endothelium-independent vasodilatation in rat aorta rings. The response is mainly linked to the activation of soluble guanylate cyclase (sGC), since its inhibition by NS2028 almost abolished relaxation. Indeed PM suspensions stimulated cGMP production in purified isolated sGC. Neither the receptor nor their signaling pathways played a significant role in the direct relaxation by PM or metals. Vasodilatation responses were significantly higher in SHR than WKY control rats.

CONCLUSION

Our data demonstrate that PM elicits a dose-dependent vasodilatation via activation of sGC in vascular smooth muscles. PM components, including soluble transition metals play a major role in this response. The stronger effect in SHR rats is in accordance with the observation that acute effects of PM are mainly seen in patients with underlying cardiovascular diseases.

Transcriptional down-regulation of neurotrophin-3 in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) leads to progressive development of airflow limitation and is characterised by cough, mucus hypersecretion and inflammatory changes. These characteristic features of the disease may be modulated by neural mediators such as neurotrophins (NT). Here we examined the expression and transcriptional regulation of neurotrophins in bronchial biopsies of COPD patients and compared the data to control biopsies. Histology revealed characteristic changes in the COPD tissues, including remodelling of the epithelial lining. RT-PCR demonstrated the mRNA expression of neurotrophins in all biopsies. Immunohistochemistry confirmed the expression of different proteins. To assess changes in the transcriptional expression level, quantitative real-time PCR was carried out and revealed differential mRNA expression of neurotrophins, with marked down-regulation of NT-3 mRNA expression and constant levels of nerve growth factor (NGF), brain-derived nerve factor (BDNF), and NT-4/5 mRNA expression. The present data on neurotrophin-specific transcriptional down-regulation of NT-3 in human COPD indicate a pathophysiological role for neurotrophins in COPD.

The rise of the phoenix: the expanding role of the eosinophil in health and disease

We have entered a new phase in the evolution of our understanding of the role of the eosinophil with a greater appreciation of novel potential functions that may be ascribed to this enigmatic cell type. This review not only provides an update to our current understanding of the various immunobiological roles for the eosinophil, but also attracts attention to some novel observations predicting functions beyond its putative effector role. These observations include the intriguing possibility that the eosinophil may possess the capacity to regulate the immune and inflammatory responses in diseases such as asthma.

Neuropeptide Y (NPY)

Neuropeptides such as neuropeptide Y (NPY) have long been proposed to play a role in the pathogenesis of inflammatory diseases. NPY is a 36 amino acid neuropeptide which participates in the regulation of a large number of physiological and pathophysiological processes in the cardiorespiratory system, immune system, nervous system and endocrine system. Serum levels of NPY are increased during exacerbations of asthma, whereas the number of NPY-immunoreactive nerves in the airways remains constant in the airways of patients with inflammatory airway diseases such asthma or rhinitis. Next to a role in the regulation of glandular activity, NPY exerts a major influence on humoral and cellular immune functions. In this respect, NPY is known to modulate potent immunological effects such as immune cell distribution, T helper cell differentiation, mediator release, or natural killer cell activation. In addition to these direct effects, NPY also acts as an immunomodulator by influencing the effects of a variety of other neurotransmitters. Whereas the peptide has been focused for therapeutic options in the central nervous system, a potential use in the treatment of pulmonary inflammatory disorders has not been revealed so far due to the complex pulmonary effects of NPY. However, since selective antagonists and agonists and gene-depleted animals for the different receptors are now available, NPY may be of value for future strategies in airway nerve modulation.

Models of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major global health problem and is predicted to become the third most common cause of death by 2020. Apart from the important preventive steps of smoking cessation, there are no other specific treatments for COPD that are as effective in reversing the condition, and therefore there is a need to understand the pathophysiological mechanisms that could lead to new therapeutic strategies. The development of experimental models will help to dissect these mechanisms at the cellular and molecular level. COPD is a disease characterized by progressive airflow obstruction of the peripheral airways, associated with lung inflammation, emphysema and mucus hypersecretion. Different approaches to mimic COPD have been developed but are limited in comparison to models of allergic asthma. COPD models usually do not mimic the major features of human COPD and are commonly based on the induction of COPD-like lesions in the lungs and airways using noxious inhalants such as tobacco smoke, nitrogen dioxide, or sulfur dioxide. Depending on the duration and intensity of exposure, these noxious stimuli induce signs of chronic inflammation and airway remodelling. Emphysema can be achieved by combining such exposure with instillation of tissue-degrading enzymes. Other approaches are based on genetically-targeted mice which develop COPD-like lesions with emphysema, and such mice provide deep insights into pathophysiological mechanisms. Future approaches should aim to mimic irreversible airflow obstruction, associated with cough and sputum production, with the possibility of inducing exacerbations.

Inhibition of experimental asthma by indoleamine 2,3-dioxygenase

Epidemiological evidence points to the inverse relationship between microbial exposure and the prevalence of allergic asthma and autoimmune diseases in Westernized countries. The molecular basis for this observation has not yet been completely delineated. Here we report that the administration of certain toll-like receptor (TLR) ligands, via the activation of innate immunity, induces high levels of indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme of tryptophan catabolism in various organs. TLR9 ligand-induced pulmonary IDO activity inhibits Th2-driven experimental asthma. IDO activity expressed by resident lung cells rather than by pulmonary DCs suppressed lung inflammation and airway hyperreactivity. Our results provide a mechanistic insight into the various formulations of the hygiene hypothesis and underscore the notion that activation of innate immunity can inhibit adaptive Th cell responses.

Smads as intracellular mediators of airway inflammation

Transforming growth factor-beta (TGF-beta) plays an important role in the pathogenesis of allergic asthma and other airway diseases. Signals from the activated TGF-beta receptor complex are transduced to the nucleus of airway cells by Smad proteins, which represent a family of transcription factors that have recently been implicated to play a major role as intracellular mediators of inflammation. The Smad family consists of the receptor-regulated Smads, a common pathway Smad, and inhibitory Smads. Receptor-regulated Smads (R-Smads) are phosphorylated by the TGF-beta type Ireceptor. They include Smad2 and Smad3, which are recognized by TGF-beta and activin receptors, and Smads 1, 5, 8, and 9, which are recognized by bone morphogenetic protein (BMP) receptors. Smad4 is a common pathway Smad, which is also defined as cooperating Smad (co-Smad) and is not phosphorylated by the TGF-beta type I receptor. Inhibitory Smads(anti-Smads) include Smad6 and Smad7, which down-regulate TGF-beta signaling. To date, the Smads are the only TGF-beta receptor substrates with a demonstrated ability to propagate signals and with regard to the growing number of investigations of Smad-mediated effects in the airways, Smads may prove to be an important target for future development of new therapeutic strategies for asthma and chronic obstructive pulmonary disease.

Raman and IR study on copper binding of histamine

A comparative Raman and FTIR study of histamine (Hm), a small hormone present in a wide selection of living organisms, and its complexes with copper(II) at different pH values was carried out. Both the Raman and IR spectra present some marker bands useful for the identification of the structure of the species predominating in the Cu(II) aqueous and alcoholic systems. In particular, Raman spectroscopy appears to be a useful tool for analyzing the tautomeric equilibrium of the imidazole ring of Hm, because some bands (i.e., nuC(4)dbond;C(5)) appear at different wavenumbers, depending on whether the imidazole moiety is in the N(tau)-H (tautomer I) or N(pi)-H (tautomer II) protonated form. In aqueous solutions the manner in which Hm binds to Cu(II) depends on the pH. At basic pH the most relevant species formed are a dimer, [Cu(2)L(2)H(-2)](2+), and a monomeric complex, [CuL](2-) or [CuL(2)](+). On the contrary, by decreasing the pH, Hm acts as a mono- or bidentate ligand, giving rise to two types of monomeric complexes, [CuLH](2-) and [CuL](2-) or [CuL(2)](+). With respect to the Cu(II)-Hm alcoholic system, both the aminic group and the imidazole ring (tautomer I) take part in the Cu(II) coordination, leading to the formation of the [CuL](2-) or [CuL(2)](+) monomeric complex.

Pulmonary inflammation and thrombogenicity caused by diesel particles in hamsters: role of histamine

Short-term increases in particulate air pollution are associated with increased incidence of cardiovascular events. Previously, we showed that intratracheally instilled diesel exhaust particles (DEPs) are prothrombotic. Here, we investigated the time course and the mechanisms. At 1, 6, and 24 hours after instillation of 50 microg DEPs per hamster, the mean size of in vivo-induced and quantified venous thrombosis was increased by 480%, 770%, and 460%, respectively. Platelets activation in blood was confirmed by a shortened closure time in the platelet function analyzer (PFA-100). In bronchoalveolar lavage, neutrophils and histamine levels were increased at all time points. In plasma, histamine was increased at 6 and 24 hours but not at 1 and 3 hours. Pretreatment with a histamine H1-receptor antagonist (diphenhydramine, 30 mg/kg intraperitoneally) abolished the DEP-induced neutrophil influx in bronchoalveolar lavage at all time points. However, diphenhydramine pretreatment did not affect DEP-induced thrombosis or platelet activation at 1 hour, whereas both were markedly reduced at 6 and 24 hours. In conclusion, pulmonary inflammation and peripheral thrombosis are correlated at 6 and 24 hours, but at 1 hour, the prothrombotic effects do not appear to result from pulmonary inflammation but possibly from the blood penetration of DEP-associated components or by DEP particles themselves.

Animal models of allergic and inflammatory conjunctivitis

Allergic eye diseases are complex inflammatory conditions of the conjunctiva with an increasing prevalence and incidence. The diseases are often concomitant with other allergic diseases such as allergic rhinitis, atopic dermatitis and allergic asthma. Despite the disabling and prominent symptoms of ocular allergies, they are less well studied and further insights into the molecular basics are still required. To establish new therapeutic approaches and assess immunological mechanisms, animal models of ocular allergies have been developed in the past years. The major forms of allergic ocular diseases, seasonal and perennial allergic conjunctivitis, vernal and atopic keratoconjunctivitis and giant papillary conjunctivitis, each have different pathophysiological and immunological components. In contrast to these distinct entities, the current animal models are based on the sensitization against a small number of allergens such as ovalbumin, ragweed pollen or major cat allergens and consecutive challenge. Different animal species have been used so far. Starting with guinea-pig models of allergic conjunctivitis to assess pharmacological aspects, new models including rats and mice have been developed which mimic major features of ocular allergy. The presently preferred species for the investigation of the immunological basis of the disease is represented by murine models of allergic conjunctivitis. In the future, combined ocular, nasal and aerosolic challenges with allergens may provide a model of allergy that encompasses simultaneously the target organs eye, nose and airways with conjunctivitis, rhinitis and asthma.

Abolition of arteriolar dilation but not constriction to histamine in cremaster muscle of eNOS-/- mice

Histamine increases the permeability of capillaries and venules but little is known of its precapillary actions on the control of tissue perfusion. Using gene ablation and pharmacological interventions, we tested whether histamine could increase muscle blood flow through stimulating nitric oxide (NO) release from microvascular endothelium. Vasomotor responses to topical histamine were investigated in second-order arterioles in the superfused cremaster muscle of anesthetized C57BL6 mice and null platelet endothelial cell adhesion molecule-1 (PECAM-1-/-) and null endothelial NO synthase (eNOS-/-) mice aged 8-12 wk. Neither resting (17 +/- 1 microm) nor maximum diameters (36 +/- 2 microm) were different between groups, nor was the constrictor response (approximately 5 +/- 1 microm) to elevating superfusate oxygen from 0 to 21%. For arterioles of C57BL6 and PECAM-1-/- mice, cumulative addition of histamine to the superfusate produced vasodilation (1 nM-1 microM; peak response, 9 +/- 1 microm) and then vasoconstriction (10-100 microM; peak response, 12 +/- 2 microm). In eNOS-/- mice, histamine produced only vasoconstriction. In C57BL6 and PECAM-1-/- mice, vasodilation was abolished with Nomega-nitro-l-arginine (30 microM); in all mice, vasoconstriction was abolished with nifedipine (1 microM). Vasomotor responses were eliminated with pyrilamine (1 microM; H1 receptor antagonist) yet remained intact with cimetidine (1 microM; H2 receptor antagonist). These findings illustrate that the biphasic vasomotor response of mouse cremaster arterioles to histamine is mediated through H1 receptors on endothelium (NO-dependent vasodilation) as well as smooth muscle (Ca2+ entry and constriction). Thus histamine can increase as well as decrease muscle blood flow, according to local concentration. However, when NO production is compromised, only vasoconstriction and flow reduction occur.

ATP stimulates Ca2+ oscillations and contraction in airway smooth muscle cells of mouse lung slices

In airway smooth muscle cells (SMCs) from mouse lung slices, > or =10 microM ATP induced Ca2+ oscillations that were accompanied by airway contraction. After approximately 1 min, the Ca2+ oscillations subsided and the airway relaxed. By contrast, > or =0.5 microM adenosine 5'-O-(3-thiotriphosphate) (nonhydrolyzable) induced Ca2+ oscillations in the SMCs and an associated airway contraction that persisted for >2 min. Adenosine 5'-O-(3-thiotriphosphate)-induced Ca2+ oscillations occurred in the absence of external Ca2+ but were abolished by the phospholipase C inhibitor U-73122 and the inositol 1,4,5-trisphosphate receptor inhibitor xestospongin. Adenosine, AMP, and alpha,beta-methylene ATP had no effect on airway caliber, and the magnitude of the contractile response induced by a variety of nucleotides could be ranked in the following order: ATP = UTP > ADP. These results suggest that the SMC response to ATP is impaired by ATP hydrolysis and mediated via P2Y(2) or P2Y(4) receptors, activating phospholipase C to release Ca2+ via the inositol 1,4,5-trisphosphate receptor. We conclude that ATP can serve as a spasmogen of airway SMCs and that Ca2+ oscillations in SMCs are required to sustain airway contraction.