Tight junction, mucin, and inflammasome-related molecules are differentially expressed in eosinophilic, mixed, and neutrophilic experimental asthma in mice

BACKGROUND

Asthma is a chronic respiratory disease with marked clinical and pathophysiological heterogeneity. Specific pathways are thought to be involved in the pathomechanisms of different inflammatory phenotypes of asthma; however, direct in vivo comparison has not been performed.

METHODS

We developed mouse models representing three different phenotypes of allergic airway inflammation-eosinophilic, mixed, and neutrophilic asthma via different methods of house dust mite sensitization and challenge. Transcriptomic analysis of the lungs, followed by the RT-PCR, western blot, and confocal microscopy, was performed. Primary human bronchial epithelial cells cultured in air-liquid interface were used to study the mechanisms revealed in the in vivo models.

RESULTS

By whole-genome transcriptome profiling of the lung, we found that airway tight junction (TJ), mucin, and inflammasome-related genes are differentially expressed in these distinct phenotypes. Further analysis of proteins from these families revealed that Zo-1 and Cldn18 were downregulated in all phenotypes, while increased Cldn4 expression was characteristic for neutrophilic airway inflammation. Mucins Clca1 (Gob5) and Muc5ac were upregulated in eosinophilic and even more in neutrophilic phenotype. Increased expression of inflammasome-related molecules such as Nlrp3, Nlrc4, Casp-1, and IL-1β was characteristic for neutrophilic asthma. In addition, we showed that inflammasome/Th17/neutrophilic axis cytokine-IL-1β-may transiently impair epithelial barrier function, while IL-1β and IL-17 increase mucin expressions in primary human bronchial epithelial cells.

CONCLUSION

Our findings suggest that differential expression of TJ, mucin, and inflammasome-related molecules in distinct inflammatory phenotypes of asthma may be linked to pathophysiology and might reflect the differences observed in the clinic.

IL-17 and TNF-α Are Key Mediators of Moraxella catarrhalis Triggered Exacerbation of Allergic Airway Inflammation

Alterations of the airway microbiome are often associated with pulmonary diseases. For example, detection of the bacterial pathogen Moraxella catarrhalis in the upper airways is linked with an increased risk to develop or exacerbate asthma. However, the mechanisms by which M. catarrhalis augments allergic airway inflammation (AAI) remain unclear. We here characterized the cellular and soluble mediators of M. catarrhalis triggered excacerbation of AAI in wt and IL-17 deficient as well as in animals treated with TNF-α and IL-6 neutralizing antibodies. We compared the type of inflammatory response in M. catarrhalis infected, house dust mite (HDM)-allergic and animals infected with M. catarrhalis at different time points of HDM sensitization. We found that airway infection of mice with M. catarrhalis triggers a strong inflammatory response with massive neutrophilic infiltrates, high amounts of IL-6 and TNF-α and moderate levels of CD4⁺ T-cell-derived IFN-γ and IL-17. If bacterial infection occurred during HDM allergen sensitization, the allergic airway response was exacerbated, particularly by the expansion of Th17 cells and increased TNF-α levels. Neutralization of IL-17 or TNF-α but not IL-6 resulted in accelerated clearance of M. catarrhalis and effectively prevented infection-induced exacerbation of AAI. Taken together, our data demonstrate an essential role for TNF-α and IL-17 in infection-triggered exacerbation of AAI.

Influenza-derived peptides cross-react with allergens and provide asthma protection

BACKGROUND

The hygiene hypothesis is the leading concept to explain the current asthma epidemic, which is built on the observation that a lack of bacterial contact early in life induces allergic T_H2 immune responses.

OBJECTIVE

Because little is known about the contribution of respiratory tract viruses in this context, we evaluated the effect of prior influenza infection on the development of allergic asthma.

METHODS

Mice were infected with influenza and, once recovered, subjected to an ovalbumin- or house dust mite-induced experimental asthma protocol. Influenza-polarized effector memory T (Tem) cells were transferred adoptively to allergen-sensitized animals before allergen challenge. A comprehensive in silico analysis assessed homologies between virus- and allergen-derived proteins. Influenza-polarized Tem cells were stimulated ex vivo with candidate peptides. Mice were immunized with a pool of virus-derived T-cell epitopes.

RESULTS

In 2 murine models we found a long-lasting preventive effect against experimental asthma features. Protection could be attributed about equally to CD4⁺ and CD8⁺ Tem cells from influenza-infected mice. An in silico bioinformatic analysis identified 4 influenza- and 3 allergen-derived MHC class I and MHC class II candidate T-cell epitopes with potential antigen-specific cross-reactivity between influenza and allergens. Lymphocytes from influenza-infected mice produced IFN-γ and IL-2 but not IL-5 on stimulation with the aforementioned peptides. Immunization with a mixture of the influenza peptides conferred asthma protection, and peptide-immunized mice transferred protection through CD4⁺ and CD8⁺ Tem cells.

CONCLUSION

For the first time, our results illustrate heterologous immunity of virus-infected animals toward allergens. This finding extends the original hygiene hypothesis.

House Dust Mite-Specific Sublingual Immunotherapy Prevents the Development of Allergic Inflammation in a Mouse Model of Experimental Asthma

BACKGROUND

Evidence regarding sublingual immunotherapy (SLIT) efficacy and its good safety profile has been demonstrated with pollen and house dust mite (HDM) allergens in the treatment of airway allergies. In addition, the use of grass pollen presents a SLIT disease-modifying treatment for respiratory allergies.

OBJECTIVES

The aim of this study was to demonstrate the efficacy of HDM-based SLIT in mouse models of allergic airway inflammation and to gain insights into the involved local immunological mechanisms.

METHODS

Balb/c mice were sensitized/challenged with Dermatophagoides farinae (Der f) extract and underwent Der f-SLIT in prophylactic and therapeutic settings. The SLIT efficacy was assessed using lung function measurements, analysis of local inflammatory responses by bronchoalveolar lavage cell differentiation and lung histology. Humoral and cellular responses were monitored by ELISA, cytokine bead array and flow cytometry analyses.

RESULTS

In a prophylactic setting, Der f-SLIT with 12 development units per dose reduced the eosinophil-dominated inflammatory response in the lung paralleled by a marked reduction in airway hyperresponsiveness. Local Th2 responses were prevented as demonstrated by significantly lower levels of IL-5 and IL-13. Additionally, SLIT-treated mice revealed a lower proportion of CD4-CD8- x03B3;δ cells and a higher frequency of CD8+CD25+IFNx03B3;+ T cells in the lungs compared to sham-treated mice. In a therapeutic setting, Der f-SLIT also resulted in reduced inflammatory responses in the lung.

CONCLUSION

The efficacy of Der f-SLIT was demonstrated in prophylactic and therapeutic conditions using experimental mouse models of HDM-induced airway inflammation. A potential role of a so far underestimated lymphocyte subpopulation was also indicated.

Functional relevance of NLRP3 inflammasome-mediated interleukin (IL)-1β during acute allergic airway inflammation

Overall asthmatic symptoms can be controlled with diverse therapeutic agents. However, certain symptomatic individuals remain at risk for serious morbidity and mortality, which prompts the identification of novel therapeutic targets and treatment strategies. Thus, using an adjuvant-free T helper type 2 (Th2) murine model, we have deciphered the role of interleukin (IL)-1 signalling during allergic airway inflammation (AAI). Because functional IL-1β depends on inflammasome activation we first studied asthmatic manifestations in specific inflammasome-deficient [NACHT, LRR and PYD domains-containing protein 3 (NLRP3(-/-) ) and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC(-/-) )] and IL-1 receptor type 1(-/-) (IL-1R1(-/-) ) mice on the BALB/c background. To verify the onset of disease we assessed cellular infiltration in the bronchial regions, lung pathology, airway hyperresponsiveness and ovalbumin (OVA)-specific immune responses. In the absence of NLRP3 inflammasome-mediated IL-1β release all symptoms of AAI were reduced, except OVA-specific immunoglobulin levels. To address whether manipulating IL-1 signalling reduced asthmatic development, we administered the IL-1R antagonist anakinra (Kineret®) during critical immunological time-points: sensitization or challenge. Amelioration of asthmatic symptoms was only observed when anakinra was administered during OVA challenge. Our findings indicate that blocking IL-1 signalling could be a potential complementary therapy for allergic airway inflammation.

Lipid Analysis of Airway Epithelial Cells for Studying Respiratory Diseases

Airway epithelial cells play an important role in the pathogenesis of inflammatory lung diseases such as asthma, cystic fibrosis and COPD. Studies concerning the function of the lipid metabolism of the airway epithelium are so far based only on the detection of lipids by immunohistochemistry but quantitative analyses have not been performed. Although recent advances in mass spectrometry have allowed to identify a variety of lipid classes simultaneously in isolated tissue samples, up until now, these methods were not suitable to analyze lipids in the airway epithelium. To determine all major lipid classes in airway epithelial cells, we used an LC-MS-based approach that can easily be combined with the specific isolation procedure to obtain epithelial cells. We tested the suitability of this method with a mouse model of experimental asthma. In response to allergen challenge, perturbations in the sphingolipids were detected, which led to increased levels of ceramides. We expanded the scope of this approach analysing human bronchus samples without pathological findings of adenocarcinoma patients. For the human lung epithelium an unusual lipid class distribution was found in which ceramide was the predominant sphingolipid. In summary, we show that disease progression and lipid metabolism perturbation can be monitored in animal models and that the method can be used for the analysis of clinical samples.

β5i subunit deficiency of the immunoproteasome leads to reduced Th2 response in OVA induced acute asthma

The immunoproteasome subunit β5i has been shown to play an important role in Th1/Th17 driven models of colitis and arthritis. However, the function of β5i in Th2 dependent diseases remains enigmatic. To study the role of β5i in Th2-driven pathology, β5i knockout (KO) and control mice were tested in different models of experimental allergic asthma. β5i-deficient mice showed reduced OVA/Alum- and subcutaneous/OVA-induced acute asthma with decreased eosinophilia in the bronchoalveolar lavage (BAL), low OVA-specific IgG1 and reduced local and systemic Th2 cytokines. While Th2 cells in the lungs were reduced, Tregs and Th1 cells were not affected. Attenuated asthma in β5i KO mice could not be attributed to defects in OVA uptake or maturation of dendritic cells in the lung. Surprisingly, β5i deficient mice developed HDM asthma which was comparable to control mice. Here, we present novel evidence for the requirement of the β5i immunosubunit to generate a strong Th2 response during OVA- but not HDM-induced acute asthma. The unexpected role of β5i in OVA asthma remains to be clarified.

Farm-derived Gram-positive bacterium Staphylococcus sciuri W620 prevents asthma phenotype in HDM- and OVA-exposed mice

BACKGROUND

Farm-derived dust samples have been screened for bacteria with potential allergo-protective properties. Among those was Staphylococcus sciuri W620 (S. sciuri W620), which we tested with regard to its protective capacities in murine models of allergic airway inflammation.

METHODS

We employed two protocols of acute airway inflammation in mice administering either ovalbumin (OVA) or house dust mite extract (HDM) for sensitization. Mechanistic studies on the activation of innate immune responses to S. sciuri W620 were carried out using human primary monocytic dendritic cells (moDC) and co-culture with autologous T cells.

RESULTS

The allergo-protective properties of S. sciuri W620 were proven in a T(H)2-driven OVA model as well as in a mixed T(H)1/T(H)2 phenotype HDM model as demonstrated by abrogation of eosinophils and neutrophils in the airways after intranasal treatment. In the HDM model, lymph node cell T(H)1/T(H)2 signature cytokines were decreased in parallel. Studies on human moDC revealed an activation of TLR2 and NOD2 receptors and initiation of DC maturation following incubation with S. sciuri W620. Cytokine expression analyses after exposure to S. sciuri W620 showed a lack of IL-12 production in moDC due to missing transcription of the IL-12p35 mRNA. However, such DC selectively supported T(H)1 cytokine release by co-cultured T cells.

CONCLUSION AND CLINICAL RELEVANCE

Our proof-of-concept experiments verify the screening system of farm-derived dust samples as suitable to elucidate new candidates for allergo-protection. S. sciuri W620 was shown to possess preventive properties on airway inflammation providing the basis for further mechanistic studies and potential clinical implication.

Tc9 cells, a new subset of CD8(+) T cells, support Th2-mediated airway inflammation

Similar to T-helper (Th) cells, CD8(+) T cells also differentiate into distinct subpopulations. However, the existence of IL-9-producing CD8(+) T (Tc9) cells has not been elucidated so far. We show that murine CD8(+) T cells activated in the presence of IL-4 plus TGF-β develop into transient IL-9 producers characterized by specific IFN-γ and IL-10 expression patterns as well as by low cytotoxic function along with diminished expression of the CTL-associated transcription factors T-bet and Eomesodermin. Similarly to the CD4(+) counterpart, Tc9 cells required for their differentiation STAT6 and IRF4. Tc9 cells deficient for these master regulators displayed increased levels of Foxp3 that in turn suppressed IL-9 production. In an allergic airway disease model, Tc9 cells promoted the onset of airway inflammation, mediated by subpathogenic numbers of Th2 cells. This support was specific for Tc9 cells because CTLs failed to exert this function. We detected increased Tc9 frequency in the periphery in mice and humans with atopic dermatitis, a Th2-associated skin disease that often precedes asthma. Thus, our data point to the existence of Tc9 cells and to their supportive function in Th2-dependent airway inflammation, suggesting that these cells might be a therapeutic target in allergic disorders.

Suppression of adrenomedullin contributes to vascular leakage and altered epithelial repair during asthma

BACKGROUND

The anti-inflammatory peptide, adrenomedullin (AM), and its cognate receptor are expressed in lung tissue, but its pathophysiological significance in airway inflammation is unknown.

OBJECTIVES

This study investigated whether allergen-induced airway inflammation involves an impaired local AM response.

METHODS

Airway AM expression was measured in acute and chronically sensitized mice following allergen inhalation and in airway epithelial cells of asthmatic and nonasthmatic patients. The effects of AM on experimental allergen-induced airway inflammation and of AM on lung epithelial repair in vitro were investigated.

RESULTS

Adrenomedullin mRNA levels were significantly (P < 0.05) reduced in acute ovalbumin (OVA)-sensitized mice after OVA challenge, by over 60% at 24 h and for up to 6 days. Similarly, reduced AM expression was observed in two models of chronic allergen-induced inflammation, OVA- and house dust mite-sensitized mice. The reduced AM expression was restricted to airway epithelial and endothelial cells, while AM expression in alveolar macrophages was unaltered. Intranasal AM completely attenuated the OVA-induced airway hyperresponsiveness and mucosal plasma leakage but had no effect on inflammatory cells or cytokines. The effects of inhaled AM were reversed by pre-inhalation of the putative AM receptor antagonist, AM ((22-52)) . AM mRNA levels were significantly (P < 0.05) lower in human asthmatic airway epithelial samples than in nonasthmatic controls. In vitro, AM dose-dependently (10(-11) -10(-7) M) accelerated experimental wound healing in human and mouse lung epithelial cell monolayers and stimulated epithelial cell migration.

CONCLUSION

Adrenomedullin suppression in T(H) 2-related inflammation is of pathophysiological significance and represents loss of a factor that maintains tissue integrity during inflammation.

Expression of calcitonin receptor-like receptor in human vascular tumours

BACKGROUND

Vascular tumours such as Kaposi's sarcoma and capillary haemangioma are characterised by abnormal vascularisation and proliferation of endothelial cells or neoplastic cells. Adrenomedullin, a potent vasodilative peptide, and its receptor, calcitonin receptor-like receptor (CRLR), play an important part in angiogenesis.

AIM

To establish whether this system also plays a part in vascular diseases, showing abnormal proliferation such as vascular tumours.

METHODS

CRLR expression was investigated in several specimens of Kaposi's sarcoma and other vascular tumours, using immunohistochemical analysis with a previously described CRLR-specific polyclonal antibody and reverse transcriptase-polymerase chain reaction.

RESULTS

Intense and specific CRLR-immunoreactive staining of neoplastic cells was observed in all specimens, which was of greater intensity than similar staining of adjacent normal endothelium.

CONCLUSIONS

CRLR is expressed in vascular tumours and, with adrenomedullin, may have a role in neoplastic vascular growth.

Two novel cell specific receptor proteins, CRLR and CD 117 in human glial tumors

OBJECTIVE

CRLR (calcitonin receptor-like receptor) and CD 117, the gene product of c-kit have been shown to be expressed in cells of glial tumors, especially in those with higher malignancy. Here we report the distribution of these peptides in various cellular compartments within those tumors.

MATERIAL

Both receptor proteins have been investigated in 95 glial tumor biopsies of different grades.

METHODS

Both proteins were visualized by immunohistochemistry with antibodies either commercially available or raised for this purpose.

RESULTS

Both receptor peptides can be identified in or around tumor blood vessels. CRLR occurs in some endothelial cells, especially in the microvascular proliferations of glioblastoma multiforme, whereas CD 117 preferentially occurs in cells of the thickened vascular wall within cells of pericyte or fibroblast morphology. Both antigens are found in addition in few neoplastic cells of overt astrocyte morphology.

CONCLUSIONS

The occurrence of identical antigens in glial tumor blood vessels and in neighboring tumor cells underlines the common origin of "mesenchymal" and "neuroepithelial" components of such (malignant) glial neoplasms.

Post-transcriptional regulation of CRLR expression during hypoxia

Adrenomedullin and CGRP are two potent vasodilator peptides, and their receptors are formed by heterodimerization of the CRLR and a RAMP molecule. Hypoxia is associated with many diseases of the cardiovascular system. It was recently shown that the human CRLR gene promoter contains an HIF-1alpha regulatory element, and that CRLR mRNA was increased by hypoxia in human endothelial cells. In the present work, we have assessed the effect of hypoxia on CRLR expression both in vivo and in vitro using two different experimental models. We have also investigated the effect of hypoxia on RAMP expression. (1) We analyzed the effects of a chronic hypobaric hypoxia on rat ventricle expression of RAMPs and CRLR. (2) Acute hypoxia was studied in human vascular smooth cells from coronary artery (CASMC) exposed for 6h to 2% O(2). RT-PCR was used to analyze the mRNA expression, and protein levels were determined by Western blotting. A sharp increase in HIF-1alpha protein levels was induced by hypoxia in CASMC, and 3.5-fold rise of the CRLR protein occurred after 1h of hypoxia in face of unchanged mRNA levels. The CRLR mRNA levels were only elevated later. A clear decrease of the CRLR protein level occurred after 3 and 6h of hypoxia. Thus, acute hypoxia in CASMC induced a rapid change of the CRLR protein amount independently of changes in the CRLR mRNA. This finding suggested a major post-transcriptional effect of hypoxia on CRLR expression in CASMC. RAMP2 and adrenomedullin mRNAs were increased after 4h, but no change was observed for RAMP1. Chronic hypoxia in rats enhanced both mRNA and protein levels of the three RAMPs and CRLR in right and left ventricles. Together, our in vivo and in vitro data suggested that hypoxia up-regulates both adrenomedullin and its receptor (CRLR/RAMP2) to enhance the signaling at the target cell.

The immunohistochemical expression of calcitonin receptor-like receptor (CRLR) in human gliomas

BACKGROUND

Gliomas are the most common primary tumours of the central nervous system and exhibit rapid growth that is associated with neovascularisation. Adrenomedullin is an important tumour survival factor in human carcinogenesis. It has growth promoting effects on gliomas, and blockade of its actions has been experimentally shown to reduce the growth of glioma tissues and cell lines. There is some evidence that the calcitonin receptor-like receptor (CRLR) mediates the tumorigenic actions of adrenomedullin.

AIM

To determine whether CRLR is expressed in human gliomas and the probable cellular targets of adrenomedullin.

METHODS

Biopsies from 95 human gliomas of varying grade were processed for immunohistochemical analysis using a previously developed and characterised antibody to CRLR.

RESULTS

All tumour specimens were positive for CRLR. As previously found in normal peripheral tissues, CRLR immunostaining was particularly intense in the endothelial cells. This was evident in all the various vascular conformations that were observed, and which are typical of gliomas. In addition, clear immunostaining of tumour cells with astrocyte morphology was observed. These were preferentially localised around vessels.

CONCLUSIONS

This study has shown for the first time that the CRLR protein is present in human glioma tissue. The expression of the receptor in endothelial cells and in astrocytic tumour cells is consistent with the evidence that its endogenous ligand, adrenomedullin, may influence glioma growth by means of both direct mitogenic and indirect angiogenic effects. CRLR may be a valuable target for effective therapeutic intervention in these malignant tumours.

Expression and distribution of the calcitonin receptor-like receptor in the developing rat heart

During ontogenesis the 52 amino acid peptide adrenomedullin is first expressed in the heart and it is essential for normal cardiovascular development. Recent work suggests that most adrenomedullin effects are conveyed via the calcitonin receptor-like receptor (CRLR) in combination with appropriate receptor activity-modifying proteins (RAMPs). Here, we investigated the expression of these components during the development of the rat heart, focusing on the period of coronary vascular development. Using RT-PCR, transcripts for CRLR, RAMP1 and RAMP2 were detected at all stages from E 14 to adulthood. The distribution of CRLR was investigated by immunohistochemistry, and endothelial cells and their precursors identified with monoclonal antibodies against RECA-1 and flk-1. On E 14, intense CRLR immunoreactivity was observed in endothelial cells of the large vessels and the endocardial cushions at the AV-junction. Small CRLR immunoreactive cell clusters were located in the wall of the outflow tract and subepicardially in the ventricular wall. On E 16, tubes of CRLR immunoreactive cells formed a subepicardial plexus, from which they penetrated radially towards the trabecular network and entered at E 18. Smooth muscle cells of coronary arteries gained a moderate CRLR immunoreactivity at E 20 which persisted at this intensity up to P 8 and then decreased. At the same time, CRLR immunoreactivity of endothelial cells in coronary arteries vanished while those of coronary veins still exhibited intense CRLR immunoreactivity. These data suggest multiple functions of the adrenomedullin/CRLR signaling pathway in cardiac development, among which the most prominent appears to be the early outgrowth and proliferation of the immature endothelial cells of the coronary vasculature.

Immunohistochemical detection of the calcitonin receptor-like receptor protein in the microvasculature of rat endothelium

Calcitonin-gene-related peptide and adrenomedullin have similar and potent vascular effects, which appear to be mediated by the G protein-coupled calcitonin receptor-like (CRL) receptor. Using immunohistochemical and Western blot analyses, we have obtained novel evidence that CRL receptor is expressed in the rat vascular endothelium using an antibody to rat CRL receptor that we have raised and fully characterised. These results are an important basis for further studies aimed at determining the so far ill-defined functional significance of the extensive distribution of CRL receptor in the vascular endothelium.

Calcitonin receptor-like receptor is expressed on gastrointestinal immune cells

BACKGROUND/AIMS

Pharmacological and morphological studies suggest that the gut mucosal immune system and local neuropeptide-containing neurones interact. We aimed to determine whether gut immune cells are targets for calcitonin gene-related peptide (CGRP), which has potent immune regulatory properties.

METHODS

Using density gradient centrifugation, rat lamina propria mononuclear cells (LP-MNCs) and intra-epithelial lymphocytes (IELs) were isolated. RT-PCR was employed for the detection of mRNA of rat calcitonin receptor-like receptor (CRLR), which is considered to represent the pharmacologically defined CGRP receptor-1 subtype, as well as mRNA of the receptor activity-modifying proteins, which are essential for CRLR function and determine ligand specificity. A radioreceptor assay was employed for the detection of specific CGRP binding sites.

RESULTS

RT-PCR and DNA sequencing showed that LP-MNCs and IELs express CRLR. Incubation of isolated LP-MNCs with radiolabelled alphaCGRP revealed the existence of specific binding sites for CGRP.

CONCLUSION

These novel data indicate that mucosal immune cells of the rat gut are a target for CGRP and provide significant evidence that CGRP functions as an immune regulator in the gut mucosa.

Calcitonin receptor-like receptor: identification and distribution in human peripheral tissues

We report here on the characterization and immunohistochemical localization in human tissues of calcitonin receptor-like receptor (CRLR) which was recently found to mediate the effects of both calcitonin gene-related peptide (CGRP) and adrenomedullin (ADM). Western blot analysis using antibodies raised against the first extracellular loop and the carboxy-terminal part of hCRLR, respectively, detected two major bands corresponding to about 70 and 60 kDa in membrane preparations of cultured endothelial cells and numerous organs including lung, heart ventricle and kidney. Immunohistochemical analysis of the cardiovascular system revealed CRLR-like immunoreactivity (CRLR-LI) in the endothelium of all blood vessels including large and small arteries, veins and capillaries, and in heart muscle cells and endocardium. The lung showed intense staining over the alveolar capillaries. Within the digestive tract, staining was observed over the cells lining the excretory ducts of the parotid gland, over the epithelium of the fundic glands of stomach, endocrine cells of the duodenum and ileum and some myenteric ganglia. The kidney presented staining of the juxtaglomerular arteries, the glomerular capillaries and chief cells of the collecting duct. Within the endocrine organs, a strong CRLR-LI signal was observed over the Langerhans islets, and weak immunoreactivity in the Leydig cells of testis. Spleen showed intense staining in trabecular veins and sinuses. Macrophages displayed a variable immunoreactivity. Our data demonstrate a wide distribution of CRLR throughout the human body and suggest CRLR to be involved in the mediation of a variety of actions in addition to vascular control.

Comparison of the expression of calcitonin receptor-like receptor (CRLR) and receptor activity modifying proteins (RAMPs) with CGRP and adrenomedullin binding in cell lines

1. The calcitonin receptor-like receptor (CRLR) and specific receptor activity modifying proteins (RAMPs) together form receptors for calcitonin gene-related peptide (CGRP) and/or adrenomedullin in transfected cells. 2. There is less evidence that innate CGRP and adrenomedullin receptors are formed by CRLR/RAMP combinations. We therefore examined whether CGRP and/or adrenomedullin binding correlated with CRLR and RAMP mRNA expression in human and rat cell lines known to express these receptors. Specific human or rat CRLR antibodies were used to examine the presence of CRLR in these cells. 3. We confirmed CGRP subtype 1 receptor (CGRP(1)) pharmacology in SK-N-MC neuroblastoma cells. L6 myoblast cells expressed both CGRP(1) and adrenomedullin receptors whereas Rat-2 fibroblasts expressed only adrenomedullin receptors. In contrast we could not confirm CGRP(2) receptor pharmacology for Col-29 colonic epithelial cells, which, instead were CGRP(1)-like in this study. 4. L6, SK-N-MC and Col-29 cells expressed mRNA for RAMP1 and RAMP2 but Rat-2 fibroblasts had only RAMP2. No cell line had detectable RAMP3 mRNA. 5. SK-N-MC, Col-29 and Rat-2 fibroblast cells expressed CRLR mRNA. By contrast, CRLR mRNA was undetectable by Northern analysis in one source of L6 cells. Conversely, a different source of L6 cells had mRNA for CRLR. All of the cell lines expressed CRLR protein. Thus, circumstances where CRLR mRNA is apparently absent by Northern analysis do not exclude the presence of this receptor. 6. These data strongly support CRLR, together with appropriate RAMPs as binding sites for CGRP and adrenomedullin in cultured cells.

Expression and distribution of calcitonin receptor-like receptor in human hairy skin

Calcitonin gene-related peptide and adrenomedullin exert potent effects in skin but their cellular targets are unknown. This study aimed to identify the cellular location of calcitonin receptor-like receptor (CRLR) which is pharmacologically identical to CGRP receptor-1, a putative molecular target of CGRP and adrenomedullin. RT-PCR analysis of human hairy skin revealed the presence of CRLR mRNA and immunohistochemical analysis, employing a previously characterized polyclonal antibody raised to CRLR, provided novel evidence of the cellular distribution of CRLR. Extensive and specific CRLR-immunostaining was detected in arteriolar smooth muscle and venular endothelium and is consistent with CGRP's putative role in neurogenic inflammation. Novel targets for CGRP and/or adrenomedullin were identified, including capillary endothelium, hair follicles and sweat glands.

Immunohistochemical detection of calcitonin gene-related peptide receptor (CGRPR)-1 in the endothelium of human coronary artery and bronchial blood vessels

The potent vasodilatory peptide, calcitonin gene-related peptide (CGRP) is present in the innervation of vascular tissue. The actions of CGRP occur via a receptor, CGRP receptor(R)-1, which is also a target for the cardioprotective peptide adrenomedullin. The human version of the pharmacologically-defined CGRPR-1 has been cloned but its distribution and cellular location is unknown. A rabbit antibody was generated to a synthetic peptide that corresponds to the C-terminus of human CGRPR-1 Immunochemical analysis of the human cell-line, SK-N-MC, which exhibits functional expression of the CGRPR-1 confirmed the antibody's specificity. The antiserum revealed specific staining in the endothelium of human coronary arteries. The vascular smooth muscle and ventricular myocardium were not immunoreactive. In bronchial blood vessels CGRPR-1-immunoreactivity was detected in the endothelium of the venules and not in the arterioles, which is particularly relevant for elucidating the putative role of CGRP in inflammation in this tissue.

Stroke prevention trial in sickle cell anemia

Stroke occurs in 7-8% of children with Sickle Cell Disease (Hb SS) and is a major cause of morbidity. Rates of recurrence have been reduced from 46-90% to less than 10% through chronic blood transfusions. Prevention of first stroke, however, would be preferable because even one stroke can cause irreversible brain injury. Transcranial Doppler (TCD) ultrasound can detect arterial blood flow rates associated with subsequent stroke risk. By combining TCD screening and a potentially effective treatment, first stroke may be prevented. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) is the first stroke prevention trial in Hb SS and the first randomized, controlled use of transfusion in Hb SS. This multi-center trial is designed to test whether reducing sickle hemoglobin to 30% or less with periodic blood transfusions will reduce first-time stroke by at least 70% compared to standard care. Primary endpoints will be clinically evident symptoms of cerebral infarction with consistent findings on Magnetic Resonance Imaging and Angiography (MRI/MRA) or symptomatic intracranial hemorrhage. Secondary endpoints will be asymptomatic brain lesions detected by MRI in brain areas not involved in primary endpoints. The design calls for a 6-month start-up interval, 18 months of TCD screening and randomization, and observation for stroke from entry through month 54. Key features of the trial are standardized TCD and MRI/MRA protocols interpreted blindly, and blinded adjudication of endpoints. The sample size (60 per treatment group) is based on prospective data relating TCD velocity to risk of stroke. A time-averaged mean velocity of > or = 200 cm/sec is associated with a 46% risk of cerebral infarction over 39 months. The sample size is sufficient to detect 70% reduction in the primary endpoint at 90% power. This trial will determine if transfusion is effective in the primary prevention of stroke. Secondary aims may further the understanding of the effects of transfusion on the brain and guide future research into cerebrovascular disease in Hb SS.

Enhanced cAMP accumulation by the human thyrotropin receptor variant with the Pro52Thr substitution in the extracellular domain

Recently, a naturally occurring variant of the human thyrotropin receptor with a Pro52Thr substitution in the N-terminal extracellular domain of the receptor has been identified. To determine the functional significance of this substitution, cDNAs of wild-type and variant thyrotropin receptors were stably expressed in Chinese hamster ovary cells. The Pro52Thr substitution did not affect synthesis and membrane localization of the receptor, as evidenced by 125I-thyrotropin binding analysis to intact cells. The variant receptor and the wild-type receptor were expressed in equivalent numbers and displayed identical binding affinity for thyrotropin. Strikingly, thyrotropin increased cAMP accumulation to a much greater extent in cells expressing the variant receptor as compared to the wild-type receptor-expressing cells. Basal and cholera toxin-stimulated or forskolin-stimulated cAMP levels were not different. It is concluded that the Pro52Thr substitution in the N-terminal region of the human thyrotropin receptor produces a receptor protein with enhanced coupling to cAMP production. This naturally occurring hyperactive thyrotropin receptor may participate in hyperthyroidism of patients with Graves' disease.