P4475Vasodilation- and blood pressure normalization-independent cardioprotective effects of endogenous, physical activity-induced alpha calcitonin gene-related peptide in chronic hypertension

Background

Alpha calcitonin gene-related peptide (αCGRP) is one of the strongest vasodilators and, as such, is cardioprotective in chronic hypertension when reducing the associated elevated blood pressure. However, we hypothesize that endogenous, physical activity-induced αCGRP has blood pressure independent cardioprotective effects in chronic hypertension.

Methods

Chronic hypertension was induced in WT and αCGRP−/− mice by one-kidney one-clip surgery. Chronic hypertensive WT and αCGRP−/− mice lived sedentarily or performed voluntary wheel running and were treated simultaneously with either vehicle, αCGRP or αCGRP receptor antagonist CGRP8–37. Cardiac function and tissue phenotype were evaluated echocardiographically and by ddPCR, Western blotting and histology, respectively.

Results

Blood pressure was similar among all hypertensive experimental groups. Endogenous αCGRP limited pathological cardiac remodeling and symptomatic heart failure already in sedentary, chronic hypertensive WT mice. In these mice, voluntary wheel running significantly improved cardiac tissue phenotype and function, that was abolished by CGRP8–37 treatment. In αCGRP−/− mice, αCGRP treatment, in contrast to voluntary wheel running, improved cardiac tissue phenotype and function. Specific inhibition of proliferation and myofibroblast differentiation of primary murine cardiac fibroblasts by αCGRP suggests involvement of these cells in αCGRP-mediated blunting of pathological cardiac remodeling.

Conclusion

Endogenous, physical activity-induced αCGRP has blood pressure independent cardioprotective effects and is crucial for maintaining cardiac function in chronic hypertension. Consequently, permanently inhibiting endogenous αCGRP signaling, as currently approved for migraine prophylaxis, could endanger hypertensive patients.

Acknowledgement/Funding

Swiss National Science Foundation, Novartis Foundation for Medical-biological Research

Primary tumour growth in an orthotopic osteosarcoma mouse model is not influenced by analgesic treatment with buprenorphine and meloxicam

Little is known about the treatment of bone pain in animal models of bone cancer. In the present study, the orthotopic 143-B human osteosarcoma xenotransplantation model was used to address the following questions: (1) Can repetitive analgesic treatment extend the experimental period by prolonging the time to reach humane endpoints and (2) Does repetitive analgesic treatment affect bone tumour development and metastasis? The analgesics, buprenorphine and meloxicam, were either applied individually or in combination at 12 h intervals as soon as the animals began to avoid using the tumour cell injected leg. While control mice treated with NaCl showed continuous body weight loss, the major criterion previously for terminating the experiments, animals treated with analgesic substances did not. The control mice had to be sacrificed 26 days after tumour cell injection, whereas the groups of animals with the different pain treatments were euthanized after an additional eight days. Importantly, primary intratibial tumour growth was not affected in any of the experimental groups by any of the pain treatment procedures. Between days 26 and 34 after tumour cell injection an increase of about 100% of the number of lung metastases was found for the groups treated with buprenorphine alone or together with meloxicam, but not for the group treated with meloxicam alone. In summary, the results indicated that both buprenorphine and meloxicam are suitable analgesics for prolonging the experimental periods in an experimental intratibial osteosarcoma mouse model.

Endogenous α-calcitonin-gene-related peptide promotes exercise-induced, physiological heart hypertrophy in mice

AIM

It is unknown how the heart distinguishes various overloads, such as exercise or hypertension, causing either physiological or pathological hypertrophy. We hypothesize that alpha-calcitonin-gene-related peptide (αCGRP), known to be released from contracting skeletal muscles, is key at this remodelling.

METHODS

The hypertrophic effect of αCGRP was measured in vitro (cultured cardiac myocytes) and in vivo (magnetic resonance imaging) in mice. Exercise performance was assessed by determination of maximum oxygen consumption and time to exhaustion. Cardiac phenotype was defined by transcriptional analysis, cardiac histology and morphometry. Finally, we measured spontaneous activity, body fat content, blood volume, haemoglobin mass and skeletal muscle capillarization and fibre composition.

RESULTS

While αCGRP exposure yielded larger cultured cardiac myocytes, exercise-induced heart hypertrophy was completely abrogated by treatment with the peptide antagonist CGRP(8-37). Exercise performance was attenuated in αCGRP(-/-) mice or CGRP(8-37) treated wild-type mice but improved in animals with higher density of cardiac CGRP receptors (CLR-tg). Spontaneous activity, body fat content, blood volume, haemoglobin mass, muscle capillarization and fibre composition were unaffected, whereas heart index and ventricular myocyte volume were reduced in αCGRP(-/-) mice and elevated in CLR-tg. Transcriptional changes seen in αCGRP(-/-) (but not CLR-tg) hearts resembled maladaptive cardiac phenotype.

CONCLUSIONS

Alpha-calcitonin-gene-related peptide released by skeletal muscles during exercise is a hitherto unrecognized effector directing the strained heart into physiological instead of pathological adaptation. Thus, αCGRP agonists might be beneficial in heart failure patients.

Biochemical composition of the superficial layer of articular cartilage

To gain more information on the mechanism of lubrication in articular joints, the superficial layer of bovine articular cartilage was mechanically removed in a sheet of ice that formed on freezing the cartilage. Freeze-dried samples contained low concentrations of chondroitin sulphate and protein. Analysis of the protein by SDS PAGE showed that the composition of the sample was comparable to that of synovial fluid (SF). Attenuated total reflection infrared (ATR-IR) spectroscopy of the dried residue indicated that the sample contained mostly hyaluronan. Moreover, ATR-IR spectroscopy of the upper layer of the superficial layer, adsorbed onto silicon, showed the presence of phospholipids. A gel could be formed by mixing hyaluronan and phosphatidylcholine in water with mechanical properties similar to those of the superficial layer on cartilage. Much like the superficial layer of natural cartilage, the surface of this gel became hydrophobic on drying out. Thus, it is proposed that the superficial layer forms from hyaluronan and phospholipids, which associate by hydrophobic interactions between the alkyl chains of the phospholipids and the hydrophobic faces of the disaccharide units in hyaluronan. This layer is permeable to material from the SF and the cartilage, as shown by the presence of SF proteins and chondroitin sulphate. As the cartilage dries out after removal from the joint, the phospholipids migrate towards the surface of the superficial layer to reduce the surface tension. It is also proposed that the highly efficient lubrication in articular joints can, at least in part, be attributed to the ability of the superficial layer to adsorb and hold water on the cartilage surface, thus creating a highly viscous boundary protection.

Enhanced Vascular Responses to Adrenomedullin in Mice Overexpressing Receptor-Activity–Modifying Protein 2

Adrenomedullin (AM) levels are elevated in cardiovascular disease, but little is known of the role of specific receptor components. AM acts via the calcitonin receptor-like receptor (CLR) interacting with a receptor-activity–modifying protein (RAMP). The AM 1 receptor is composed of CLR and RAMP2, and the calcitonin gene–related peptide (CGRP) receptor of CLR and RAMP1, as determined by molecular and cell-based analysis. This study examines the relevance of RAMP2 in vivo. Transgenic (TG) mice that overexpress RAMP2 in smooth muscle were generated. The role of RAMP2 in the regulation of blood pressure and in vascular function was investigated. Basal blood pressure, acute angiotensin II–raised blood pressure, and cardiovascular properties were similar in wild-type (WT) and TG mice. However, the hypotensive effect of IV AM, unlike CGRP, was enhanced in TG mice ( P <0.05), whereas a negative inotropic action was excluded by left-ventricular pressure–volume analysis. In aorta relaxation studies, TG vessels responded in a more sensitive manner to AM (EC 50 , 8.0±1.5 nmol/L) than WT (EC 50 , 17.9±3.6 nmol/L). These responses were attenuated by the AM receptor antagonist, AM 22-52 , such that residual responses were identical in all mice. Remaining relaxations were further inhibited by CGRP receptor antagonists, although neither affected AM responses when given alone. Mesenteric and cutaneous resistance vessels were also more sensitive to AM in TG than WT mice. Thus RAMP2 plays a key role in the sensitivity and potency of AM-induced hypotensive responses via the AM 1 receptor, providing evidence that this receptor is a selective target for novel therapeutic approaches.

Receptors for calcitonin gene-related peptide, adrenomedullin, and amylin: the contributions of novel receptor-activity-modifying proteins

The discovery of receptor-activity-modifying proteins (RAMP) revealed a new principle for the function of G protein-coupled receptors. The initially orphan calcitonin receptor-like receptor (CRLR) was identified as a CGRP receptor when coexpressed with RAMP1. The same receptor is specific for adrenomedullin (ADM) in the presence of RAMP2. Calcitonin receptors (CTR) with 60% homology to the CRLR predominantly recognize calcitonin in the absence of RAMP. An amylin/CGRP receptor was recognized when a calcitonin receptor (CTR) was coexpressed with RAMP1. In the presence of RAMP3, the CTR only interacts with amylin. Noncovalent association of the RAMP with the CRLR or the CTR reveals heterodimeric RAMP/receptor complexes at the cell surface. Thus, two Class II G protein-coupled receptors, the CRLR and CTR, associate with three RAMP to form high affinity receptors for CGRP, ADM, or amylin. Here, the molecular composition and the functional properties of these receptors is reviewed.

Circulating procalcitonin and cleavage products in septicaemia compared with medullary thyroid carcinoma

OBJECTIVE

Raised plasma levels of procalcitonin (proCT) represent an early marker for septicaemia. They are related to disease severity and inversely to outcome and response to treatment. ProCT is presumably synthesised in tIssues other than the thyroid C-cells which are the source of calcitonin (CT) in normal physiology. This study compares proCT and its cleavage products in the serum of patients with septicaemia with those in medullary thyroid carcinoma (MTC).

METHODS

Immunoreactive proCT and its cleavage products were extracted from the serum of patients with septicaemia or MTC using octadecylsilyl silica columns and characterised by reversed phase HPLC and Western blot analysis. ProCT, CT(1-32) and the flanking peptides PAS-57 and PDN-21 were recognised with antibodies specific for the individual peptides.

RESULTS

ProCT and a 10 kDa polypeptide were recognised with antibodies to PAS-57, CT(1-32) and PDN-21. An 8 kDa proCT fragment was detected with antibodies to CT and PDN-21. However, intact CT(1-32), PAS-57 and PDN-21, found in the serum of MTC patients, were undetectable. The results indicate partial cleavage of proCT in septicaemia different from that in MTC patients.

CONCLUSIONS

ProCT and 10 and 8 kDa proCT fragments were recognised in the circulation of septic patients. They were different from the known proCT-processing products PAS-57, CT(1-32) and PDN-21 identified in the serum of normal subjects and of MTC patients. Distinct cleavage of proCT may contribute to the symptoms of septicaemia.

Extensive and preferential Fas/Fas ligand-dependent death of gammadelta T cells following infection with Listeria monocytogenes

In the spleens of mice infected intraperitoneally with the bacterium Listeria monocytogenes, both alphabeta and gammadelta T cells became rapidly activated, followed by a massive apoptotic death response predominantly within the gammadelta population. The death response involved two major splenic gammadelta T-cell subsets and was Fas/Fas ligand (Fas-L)-dependent. Among T cells isolated from the Listeria-infected spleen, Fas-L was almost exclusively expressed in gammadelta T cells. gammadelta T cells coexpressed Fas and Fas-L, suggesting activation-induced suicide as a mechanism of their death. In vivo treatment with an antibody specific for CD3epsilon induced activation, preferential Fas-L expression and apoptosis of gammadelta T cells, resembling the response pattern in listeriosis, whereas antibodies specific for T-cell receptor-beta (TCR-beta) or TCR-delta did not, suggesting that the complete response seen in listeriosis requires both gammadelta TCR engagement and additional stimuli. L. monocytogenes causes early nonspecific, Fas-independent lymphocyte death in heavily infected tissues. In contrast, the death response described here is selective, Fas-dependent and triggered at low local levels of bacteria, suggesting that it is controlled by interactions with other infection-activated host cells, and perhaps part of a regulatory circuit specifically curtailing gammadelta T cells.

Functional relevance of G-protein-coupled-receptor-associated proteins, exemplified by receptor-activity-modifying proteins (RAMPs)

The calcitonin (CT) receptor (CTR) and the CTR-like receptor (CRLR) are close relatives within the type II family of G-protein-coupled receptors, demonstrating sequence identity of 50%. Unlike the interaction between CT and CTR, receptors for the related hormones and neuropeptides amylin, CT-gene-related peptide (CGRP) and adrenomedullin (AM) require one of three accessory receptor-activity-modifying proteins (RAMPs) for ligand recognition. An amylin/CGRP receptor is revealed when CTR is co-expressed with RAMP1. When complexed with RAMP3, CTR interacts with amylin alone. CRLR, initially classed as an orphan receptor, is a CGRP receptor when co-expressed with RAMP1. The same receptor is specific for AM in the presence of RAMP2. Together with human RAMP3, CRLR defines an AM receptor, and with mouse RAMP3 it is a low-affinity CGRP/AM receptor. CTR-RAMP1, antagonized preferentially by salmon CT-(8-32) and not by CGRP-(8-37), and CRLR-RAMP1, antagonized by CGRP-(8-37), are two CGRP receptor isotypes. Thus amylin and CGRP interact specifically with heterodimeric complexes between CTR and RAMP1 or RAMP3, and CGRP and AM interact with complexes between CRLR and RAMP1, RAMP2 or RAMP3.

Tumor necrosis factor-alpha negatively regulates airway hyperresponsiveness through gamma-delta T cells

Tumor necrosis factor (TNF)-alpha is a potent cytokine with immunomodulatory, proinflammatory, and pathobiologic activities. Although TNF-alpha is thought to play a role in mediating airway inflammation and airway hyperresponsiveness (AHR), its function is not well defined. TNF-alpha-deficient mice and mice expressing TNF-alpha in their lungs because of a TNF-alpha transgene placed under the control of the surfactant protein (SP)-C promoter (SP-C/TNF-alpha-transgenic mice) were sensitized to ovalbumin (OVA) and subsequently challenged with OVA via the airways; airway function in response to inhaled methacholine was monitored. In the TNF-alpha-deficient mice, AHR was significantly increased over that in controls. In contrast, the transgenic mice failed to develop AHR. In addition, sensitized/ challenged TNF-alpha-deficient mice had significantly increased numbers of eosinophils and higher levels of interleukin (IL)-5 and IL-10 in their bronchoalveolar lavage fluid than were found for control mice. However, in SP-C/TNF-alpha-transgenic mice, both the numbers of eosinophils and levels of IL-5 and IL-10 were significantly lower than in sensitized/challenged transgene-negative mice. gammadelta T cells have been shown to be activated by TNF-alpha and to negatively regulate AHR. Depletion of gammadelta T cells in the TNF-alpha-transgenic mice in the present study increased AHR, whereas depletion of these cells had no significant effect in TNF-alpha-deficient mice. These data indicate that TNF-alpha can negatively modulate airway responsiveness, controlling airway function in allergen-induced AHR through the activation of gammadelta T cells.

Adrenomedullin and related peptides: receptors and accessory proteins

Adrenomedullin (AM), alpha- and beta-calcitonin gene-related peptide (CGRP), amylin and calcitonin (CT) are structurally and functionally related peptides. The structure of a receptor for CT (CTR) was elucidated in 1991 through molecular cloning, but the structures of the receptors for the other three peptides had yet to be elucidated. The discovery of receptor-activity-modifying proteins (RAMP) 1 and -2 and their co-expression with an orphan receptor, calcitonin receptor-like receptor (CRLR) has led to the elucidation of functional CGRP and AM receptors, respectively. RAMP1 and -3 which are co-expressed with CTR revealed two amylin receptor isotypes. Molecular interactions between CRLR and RAMPs are involved in their transport to the cell surface. Heterodimeric complexes between CRLR or CTR and RAMPs are required for ligand recognition.

Mutations of the asparagine117 residue of a receptor activity-modifying protein 1-dependent human calcitonin gene-related peptide receptor result in selective loss of function

The initially orphan human calcitonin (CT) receptor-like receptor (hCRLR) interacts with novel accessory receptor activity-modifying protein 1 (RAMP1) to reveal a functional CT gene-related peptide (CGRP) receptor. In mammalian cells, RAMP1 is required for mature N-glycosylation of the hCRLR predicted to occur at Asn(60), Asn(112), and/or Asn(117) in the amino-terminal extracellular domain. Here we have shown that the substitution of Asn(117) with Ala, Gln, Thr, or Pro abolished CGRP-evoked cAMP formation which was left unchanged when the Asn(117) was replaced with Asp. Moreover, the hCRLR and the Asn(117) mutants exhibited comparable N-glycosylation and cell surface expression, and the association with RAMP1 was only slightly impaired. In contrast, the hCRLR Asn(60,112) to Thr double mutant exhibited defective RAMP1-dependent N-glycosylation, and impaired cell surface expression and CGRP receptor function. Unlike Asn(60) and Asn(112), Asn(117) is normally not N-glycosylated, but essential for CGRP binding to the hCRLR-RAMP1 complex.

Calcitonin Gene-Related Peptide (Cgrp), Adrenomedullin (Am), Amylin, And Calcitonin (Ct) Receptors And Overlapping Biological Actions

CGRP, AM, amylin, and CT have in common N-terminal 6-7 amino acid ring structures linked by disulfide bridges and amidated C-termini required for biological activity. For the related bioactive peptides, receptor-binding sites linked to cAMP stimulation and to a lesser extent to the phospholipase C signaling pathway have been identified in tissue specific manner. The highest density of CGRP receptors has been recognized in the cerebellum and the spinal cord. There photoaffinity-labeled N-glycosylated 60,000 and 54,000 Mr proteins are converted to 46,000 and 41,000 Mr components following endoglycosidase F/N-glycosidase F treatment. The same proteins were specifically labeled with [125I]-hCGRP-I(1-37) and -(8-37). Some cross-reaction between the CGRP receptor and AM was evident whereas amylin and CT were only recognized at over 10-7 M. A different AM receptor localized predominantly in the lung recognized CGRP at low, and amylin and calcitonin at equally high concentrations. CT receptor binding sites have been identified in osteoclasts and in the periventricular region of the brain. They cross-reacted with amylin at low concentrations and with CGRP and AM at over 10-7 M. Amylin receptor binding sites cross-reacting with salmon CT and CGRP but not with hCT and adrenomedullin to any great extent were originally described by Sexton in the nucleus accumbens and may represent a second CGRP receptor. The structure of a CT receptor was elucidated by the group of Goldring in 1991 through molecular cloning, and of a 60% homologous human CT receptor-like receptor (CRLR) shortly thereafter here. The latter was an orphan receptor until the discovery of the receptor-activity-modifying proteins (RAMP) by Foord which upon coexpression yield a CGRP receptor with RAMP1 and an AM receptor with RAMP2. Coexpression of the hCT receptor isotype 2 revealed a CGRP/amylin receptor with RAMP1 and an amylin receptor isotype with RAMP3. The CRLR/RAMP1 receptor antagonized by CGRP(8-37) corresponds to the CGRP1 receptor defined by Quirion, whereas his CGRP2 receptor remains to be identified. Another CGRP receptor isotype remains to be discovered in the cerebellum with no detectable CRLR encoding mRNA. Overlapping biological actions include inhibition of bone resorption obtained predominantly with CT, but also at high concentrations with CGRP, AM, and amylin. CGRP and AM are potent vasodilators, an effect shared with CT at pharmacological concentrations. Biological actions of amylin include suppression of insulin secretion, stimulation of glycogenolysis and inhibition of glycogen synthesis. In conclusion, the hCT2 receptor or the CRLR are associated with one of three RAMPs to bind to CGRP, AM, or amylin.

Structural Determinants in the Calcitonin Receptor-Like Receptor (Crlr) Important for Cgrp and Adrenomedullin (Am) Receptor Function of Crlr/Receptor-Activity-Modifying Protein (Ramp) 1 and Crlr/Ramp2 Heterodimers

Cell surface protein cross-linking, coimmmunoprecipitation, and confocal microscopy identified CRLR/RAMP1-, CRLR/RAMP2-, and calcitonin receptor isotype 2 (CTR2)/RAMP1 heterodimers as CGRP-, AM-, and CGRP/amylin receptors, linked to cAMP production. Along these lines, effects of structural alterations in the N-terminal extracellular domain of the human CRLR on cell surface expression as well as the association with RAMP and CGRP or AM have been investigated.

Glycosylation of the calcitonin receptor-like receptor at Asn(60) or Asn(112) is important for cell surface expression

The human calcitonin (CT) receptor-like receptor (hCRLR) of the B family of G protein-coupled receptors is N-glycosylated and associates with receptor-activity-modifying proteins for functional interaction with CT gene-related peptide (CGRP) or adrenomedullin (ADM), respectively. Three putative N-glycosylation sites Asn(60), Asn(112) and Asn(117) are present in the amino-terminal extracellular domain of the hCRLR. Tunicamycin dose-dependently inhibited the glycosylation of a myc-tagged hCRLR and in parallel specific [(125)I]CGRP and -ADM binding. Similarly, the double mutant myc-hCRLR(N60,112T) exhibited minimal N-glycosidase F sensitive glycosylation, presumably at the third Asn(117), and the cell surface expression and specific radioligand binding were impaired. Substitution of the Asn(117) by Thr abolished CGRP and ADM binding in the face of intact N-glycosylation and cell surface expression.

Receptor-activity-modifying protein 1 forms heterodimers with two G-protein-coupled receptors to define ligand recognition

Receptor-activity-modifying proteins (RAMPs) with single transmembrane domains define the function of two G-protein-coupled receptors of the B family. Cell-surface complexes of human RAMP1 (hRAMP1) and human calcitonin (CT) receptor isotype 2 (hCTR2) or rat CT-receptor-like receptor (rCRLR) have now been identified through protein cross-linking, co-immunoprecipitation and confocal microscopy. They are two distinct CT-gene-related peptide (CGRP) receptors coupled to cAMP production and pharmacologically distinguished by the CT and CGRP antagonists salmon CT(8-32) and human or rat CGRP(8-37). Thus direct molecular interactions of hRAMP1 with hCTR2 or rCRLR are required for CGRP recognition. hCTR2, moreover, adopts non-traditional functions through its association with hRAMP1.

Mouse receptor-activity-modifying proteins 1, -2 and -3: amino acid sequence, expression and function

The calcitonin receptor-like receptor (CRLR) requires novel receptor-activity-modifying proteins (RAMPs) for its function as an adrenomedullin (ADM) or a calcitonin (CT) gene-related peptide (CGRP) receptor. Here, mouse cDNA clones representing expressed sequence tags (ESTs) in the GenEMBL database have been identified. They encode for proteins with 70, 68 and 84% amino acid sequence identity with respect to human RAMP1, -2 and -3. On Northern blot analysis of polyA(+) RNA mouse RAMP1 (mRAMP1) encoding mRNA with an apparent size of 0.8 kb was predominantly observed in embryonic and adult brain and lung and in adult skeletal muscle. Mouse RAMP2 encoding 0.8 and 1.2 kb mRNA were recognized in all tissues analyzed with the highest levels in embryonic brain, lung and gut and in adult heart, lung, skeletal muscle and brain. A single 1.2 kb mRAMP3 encoding transcript was mainly expressed in embryonic and adult brain. In COS-7 cells co-expressing rat CRLR (rCRLR) and mRAMP1, [125I]halphaCGRP binding was inhibited by ralphaCGRP(8-37), ralphaCGRP and rbetaCGRP with IC(50) of 1.4+/-0.5, 4.5+/-0.6 and 7+/-0.3 nM, respectively. CyclicAMP accumulation was maximally stimulated tenfold by rbetaCGRP and ralphaCGRP with EC(50) of 0. 65+/-0.67 and 0.86+/-0.6 nM. In the same cells co-expressing rCRLR and mRAMP2, binding of [125I]rADM was displaced by rADM and rADM(20-50) with IC(50) of 1.9+/-0.5 and 3.4+/-1.4 nM, respectively, and a maximal sevenfold stimulation of cAMP accumulation was observed with rADM with an EC(50) of 0.82+/-0.85 nM. In the cells co-expressing rCRLR and mRAMP3, [125I]halphaCGRP binding was inhibited by ralphaCGRP(8-37), rbetaCGRP, ralphaCGRP, rADM and rADM(20-50) with IC(50) between 4 and 22 nM. cAMP accumulation was stimulated by rADM with an EC(50) of 5.1+/-2.7 nM that was 12-fold and 11-fold lower than that of ralphaCGRP and rbetaCGRP. In conclusion, mouse RAMP1, -2 and -3 exhibit high amino acid sequence homology to the corresponding human RAMPs. Co-expression of rCRLR with mRAMP1, -2 or -3 in COS-7 cells revealed distinct CGRP-, ADM- or ADM/CGRP receptors.

Mammalian calcitonin receptor-like receptor/receptor activity modifying protein complexes define calcitonin gene-related peptide and adrenomedullin receptors in Drosophila Schneider 2 cells

Differential glycosylation of human and rat (r) calcitonin (CT) receptor-like receptors (CRLR) as a result of interactions with accessory receptor activity-modifying proteins (RAMP)1 or -2 was considered to define CT gene-related peptide (CGRP) or adrenomedullin (ADM) receptors in mammalian cells. Here, Drosophila Schneider (S2) cells stably co-expressed rCRLR and RAMP1 or -2 as functional CGRP or ADM receptors. Different from mammalian cells, rCRLR expressed in S2 cells are uniformly glycosylated proteins independent of RAMP1 or RAMP2. Bis(sulfosuccinimidyl)suberate cross-linking revealed receptor components with the size of rCRLR, increased by the molecular weights of the corresponding RAMPs and [(125)I]CGRP or [(125)I]ADM. In conclusion, [(125)I]CGRP/rCRLR/RAMP1 and [(125)I]ADM/rCRLR/RAMP2 complexes have been recognized in Drosophila S2 cells.

Negative regulation of airway responsiveness that is dependent on gammadelta T cells and independent of alphabeta T cells

The mechanisms regulating airway function are complex and still poorly understood. In diseases such as asthma, involvement of immune-dependent mechanisms has been suggested in causing changes in airway responsiveness to bronchoconstrictors. We now demonstrate that gammadelta T cells can regulate airway function in an alphabeta T cell-independent manner, identifying them as important cells in pulmonary homeostasis. This function of gammadelta T cells differs from previously described immune-dependent mechanisms and may reflect their interaction with innate systems of host defense.

A receptor activity modifying protein (RAMP)2-dependent adrenomedullin receptor is a calcitonin gene-related peptide receptor when coexpressed with human RAMP1

Adrenomedullin (ADM) and alpha- and beta-calcitonin (CT) gene-related peptide (alpha-, betaCGRP) are structurally related vasodilatory peptides with homology to CT and amylin. An originally orphan human CT receptor-like receptor (hCRLR) is a Gs protein-coupled CGRP or ADM receptor when coexpressed with recently identified human single transmembrane domain receptor activity modifying proteins 1 (hRAMP1) or -2 (hRAMP2), respectively. Here, the function of the rat CRLR homologue (rCRLR) has been investigated in rat osteoblast-like UMR-106 cells and in COS-7 cells, in the absence and presence of hRAMP1 and -2 and combinations thereof. Transient expression of rCRLR in UMR-106 cells revealed an ADM receptor, and [125I]rat (r) ADM binding was enhanced with hRAMP2 and inhibited by 50% when hRAMP1 was coexpressed. Detectable [125I]h alphaCGRP binding required the presence of hRAMP1, and the expression of CGRP binding sites was unaffected by coexpressed hRAMP2. Specificity of ADM binding sites in [125I]rADM binding inhibition experiments was reflected by an over 1000-fold higher potency of rADM [half-maximal effective concentration = 0.19 +/- 0.05 nM (mean +/- SEM, n = 4)], compared with r alphaCGRP and r betaGRP, to induce a cAMP-responsive luciferase reporting gene (CRE-luc). In rCRLR and hRAMP1 cotransfected cells, expressing predominantly CGRP binding sites, r betaCGRP, r alphaCGRP, and rADM induced CRE-luc with half-maximal effective concentration of 0.27 +/- 0.17 nM, 0.37 +/- 0.27 nM, and 1.4 +/- 0.9 nM, respectively. In COS-7 cells, the results were comparable, but rCRLR required coexpressed hRAMP2 for ADM receptor function. This is consistent with higher levels of endogenous RAMP2 encoding messenger RNA in UMR-106, compared with COS-7 cells. In conclusion, the recognition of RAMP1 and -2 as mediators of CRLR expression as a CGRP or ADM receptor has been extended, with evidence that endogenous RAMP2 is sufficient to reveal an ADM receptor in UMR-106 cells. Inhibition of RAMP2-evoked ADM receptor expression by RAMP1 and generation of a CGRP receptor is consistent with competitive interactions of the different RAMPs with rCRLR.

An amylin receptor is revealed following co-transfection of a calcitonin receptor with receptor activity modifying proteins-1 or -3

Human receptor activity modifying proteins (RAMP) regulate the ligand specificity of the calcitonin-receptor-like-receptor (McLatchie et al., Nature 393:333-339 (1998)). Here we have investigated binding of [125I]-labeled human (h) calcitonin ([125I]hCT) and rat amylin ([125I]amylin) to rabbit aortic endothelial cells (RAEC) co-transfected with the hCT receptor isotype 2 (hCTR2) and RAMP1, -2 or -3. Specific binding of 125 pM [125I]hCT to cells transfected with hCTR2 alone was 6.7 +/- 0.7 fmol/50,000 cells (n=5), and was reduced by 45 +/- 2% and 86 +/- 3% (P < 0.001) in the presence of RAMP1 and -3, but remained unchanged with RAMP2. In the absence and presence of individual RAMPs [125I]hCT binding inhibition occured with similar IC50 of between 6 nM and 11 nM hCT, and human amylin was 24- to 54-fold less potent. Specific binding of 125 pM [125I]amylin to cells transfected with hCTR2 alone was 0.9 +/- 0.2 fmol/50,000 cells (n=6), and was increased by 262 +/- 48% (P < 0.005), 73 +/- 26% (P < 0.05) and 338 +/- 57% (P < 0.005) with RAMP1, -2 or -3, respectively. [125I]amylin binding was inhibited with IC50 of 3.1 +/- 0.5 nM and 4.0 +/- 0.8 nM human amylin in cells co-transfected with RAMP1 or -3, respectively, and hCT was 45 +/- 2- and 126 +/- 3-fold less potent. In conclusion, RAMP1 and -3 decrease calcitonin receptor expression in RAEC transfected with hCTR2 encoding cDNA and simultanously reveal an amylin receptor.

Maxadilan interacts with receptors for pituitary adenylyl cyclase activating peptide in human SH-SY5Y and SK-N-MC neuroblastoma cells

Receptors for pituitary adenylyl cyclase activating peptide (PACAP) have been identified in human SH-SY5Y neuroblastoma cells with PACAP being 1000-fold more potent than vasoactive intestinal peptide (VIP) in [(125)I]PACAP binding inhibition and stimulation of cAMP accumulation. Maxadilan, a vasodilator peptide from the salivary gland of the sand fly Lutzomyia longipalpis also specifically bound to SH-SY5Y cells, and was equipotent to PACAP in [(125)I]PACAP and [(125)I]maxadilan binding inhibition, and stimulation of cAMP accumulation. Maxadilan and PACAP also increased the cytosolic free calcium concentration. In human SK-N-MC neuroblastoma cells PACAP, VIP and maxadilan equipotently stimulated cAMP accumulation. The maximal effects of VIP and maxadilan were additive and reached those of PACAP alone. In human T47D breast carcinoma cells PACAP and VIP were also equipotent in the stimulation of cAMP accumulation, but maxadilan was inactive. The results are consistent with the interaction of maxadilan with PACAP specific PAC(1)receptors in SH-SY5Y cells, but not with VPAC receptors, not differentiating between VIP and PACAP in T47D cells. Moreover, maxadilan is a PAC(1)receptor specific agonist which allows discrimination of co-expressed PAC(1)and VPAC receptors in SK-N-MC cells.

Islet amyloid polypeptide/amylin messenger RNA and protein expression in human insulinomas in relation to amyloid formation

OBJECTIVE

Islet amyloid polypeptide (IAPP), also named amylin, is the predominant protein component of amyloid deposits in human islet beta cell tumours of the pancreas (insulinomas). IAPP is co-produced with insulin by islet beta cells. We investigated IAPP expression in relation to insulin expression and to amyloid formation in eleven insulinomas.

DESIGN AND METHODS

RNA and protein extracts were prepared from the same pieces of tumour tissue, and from specimens of two normal human pancreata. IAPP and insulin mRNA and peptide content were quantified using Northern blot analysis and radioimmunoassay (RIA) respectively. Molecular forms of IAPP immunoreactivity were analysed by reversed-phase high-performance liquid chromatography (HPLC). The presence of islet hormones and of amyloid was assessed by (immuno)histochemical staining of paraffin sections. Plasma levels of IAPP and insulin prior to tumour resection were determined by RIA.

RESULTS

IAPP and insulin mRNA and peptide content varied widely between the tumour specimens, and there was considerable intratumour heterogeneity of peptide content. HPLC analysis indicated correct proteolytic processing of the IAPP precursor protein. Amyloid deposits were detected only in the three tumours with the highest IAPP content. In contrast to insulin, plasma levels of IAPP were not elevated in the insulinoma patients.

CONCLUSIONS

The spectrum of hormone production by insulinomas cannot be inferred from only a few tissue sections due to intratumour heterogeneity. Expression of the IAPP and insulin genes is not coupled in insulinomas, which produce properly processed mature IAPP. In addition to IAPP overproduction, additional factors such as intracellular accumulation of IAPP are involved in amyloidogenesis in insulinomas.

Receptor activity modifying proteins regulate the activity of a calcitonin gene-related peptide receptor in rabbit aortic endothelial cells

In Xenopus oocytes with an endogenous calcitonin gene-related peptide (CGRP) receptor, a receptor activity modifying protein (RAMP1) enhancing CGRP stimulated chloride currents of the cystic fibrosis transmembrane regulator was recently cloned [McLatchie, L.M. et al. (1998) Nature 393, 333-339]. Here, transient expression of RAMP1 in rabbit aortic endothelial cells (RAEC) brought about stimulation of cAMP accumulation by human (h) alphaCGRP with an EC50 of 0.41 nM. This was antagonized by a CGRP receptor antagonist alphaCGRP(8-37). Co-expression of RAMP3 together with RAMP1 reduced the maximal cAMP response to h alphaCGRP by 47% (P < 0.05). The cells also express RAMP2 encoding mRNA and an adrenomedullin (ADM) receptor coupled to stimulation of cAMP formation by hADM (EC50 0.18 nM). The latter was antagonized by an ADM receptor antagonist hADM(22-52). In conclusion, expression of a CGRP receptor in RAEC requires RAMP1. The same receptor presumably recognizes ADM making use of endogenous RAMP2. The results reveal competition between the different RAMPs in the regulation of CGRP/ADM receptor activity.

Early preferential stimulation of gamma delta T cells by TNF-alpha

Although recent findings indicate that gamma delta T cells influence both early innate and Ag-specific adaptive host responses, it has remained unclear what triggers gamma delta T cell reactivity. Investigating very early T cell activation in mouse and human models of bacterial infection, we measured CD69 expression as an indicator of early cellular activation. Both murine alpha beta and gamma delta T cells responded polyclonally to systemic bacterial infections, and to LPS. However, gamma delta T cells responded more strongly to the bacteria and to LPS. In vitro LPS-stimulated human T cells showed a similar differential response pattern. We identified TNF-alpha as mediator of the early differential T cell activation, and of differential proliferative responses. The stronger response of gamma delta T cells to TNF-alpha was correlated with higher inducible expression levels of TNF-Rp75. Among unstimulated splenocytes, more gamma delta T cells than alpha beta T cells expressed CD44 at high levels. The data suggest that TNF-Rp75 determines the differential T cell reactivity, and that most gamma delta T cells in the normal spleen are present in a presensitized state. As TNF-alpha stimulates activated T cells, it may early preferentially connect gamma delta T cell functions with those of cells that produce this cytokine, including activated innate effector cells and Ag-stimulated T lymphocytes.

Parathyroid hormone responses of cyclic AMP-, serum- and phorbol ester-responsive reporter genes in osteoblast-like UMR-106 cells

Parathyroid hormone (PTH) and PTH-related protein interact with a G protein-coupled receptor linked to the activation of adenylyl cyclase and phospholipase C signaling pathways. Regulation by PTH of the expression of three distinct, stably transfected luciferase reporter genes responsive to cAMP (CRE-luc), serum (SRE-luc) and phorbol ester (TRE-luc) has been studied in rat osteoblast-like UMR-106 cells. Maximal 43-fold induction of CRE-luc expression occurred in response to 100 nM rat (r)PTH(1-34) (EC50=0.44 nM), but SRE-luc and TRE-luc remained unaffected. Maximal 2.8- and 3.4-fold inductions of SRE-luc by 10 ng/ml EGF and 100 nM phorbol ester (PMA) were suppressed with 100 nM rPTH(1-34) (IC50=0.04 and 0.15 nM, respectively). Similarly, 7.3-fold induction of TRE-luc by 100 nM PMA was inhibited to 50% with 100 nM rPTH(1-34) (IC50=0.5 nM). Activation of mitogen-activated protein kinase by EGF and PMA was also suppressed by rPTH(1-34). 1 mM 8-Br-cAMP and 0.1 mM forskolin mimicked all the effects of rPTH(1-34). In conclusion, the regulation of target genes by PTH in osteoblast-like UMR-106 cells is mediated by the activation of the cAMP/protein kinase A signaling pathway.

An inherited mutation associated with functional deficiency of the alpha-subunit of the guanine nucleotide-binding protein Gs in pseudo- and pseudopseudohypoparathyroidism

Pseudohypoparathyroidism type Ia (PSP) is a disorder characterized by Albright's osteodystrophy, secondary hyperparathyroidism, lowered Gs activity, and resistance of the urinary cAMP excretion to exogenous PTH. The patients had raised basal serum levels of TSH and/or excessive TSH response to TRH. Here we have described a 38-bp deletion at the exon 1/intron 1 boundary of one Gs alpha allele in two mothers with pseudo-PSP and in six offsprings with PSP of a kindred with Albright's osteodystrophy. The deletion eliminates the splice donor site of exon 1. The pseudo-PSP patients presented decreased Gs activity, but normal urinary cAMP responses to PTH and normal TSH levels and responses to TRH. As monitored during 22 yr, they had normal serum levels of calcium and PTH. The findings demonstrate the same inherited functional defect of Gs alpha in two female patients with pseudo-PSP and in six of their offspring with PSP. The pathogenesis of clinical hypoparathyroidism remains to be clarified.

Evidence that the same gamma delta T cells respond during infection-induced and autoimmune inflammation

Inflammatory responses are induced in both testes of a mouse following injection of Listeria monocytogenes into one testis. Although the uninjected testis contains no detectable bacteria, it undergoes an autoimmune attack. Normally, the testis lacks lymphocytes, but in the infected and autoimmune state, both gamma delta and alpha beta T cells are found as infiltrates. Here, we have examined the repertoire of the infiltrating gamma delta T cells, using two different methods, and found a high frequency of V gamma 6/V delta 1 gamma delta T cells in both infected and autoimmune testes. All of these expressed the invariant V gamma 6/V delta 1 TCR previously reported. However, secondary gamma and delta transcripts present within V gamma 6/V delta 1 hybridomas indicated nonclonality. Interestingly, some of these secondary transcripts were derived from gamma gene rearrangements not previously found in this gamma delta T cell subset, implying a difference in its origin. The increase in V gamma 6/V delta 1 cells observed here in both infected and autoimmune testes, together with our previous finding of a preferential response by the same subset in Listeria-infected liver, indicates that their response is triggered by the inflammation rather than by the infectious agent or because they are already resident in the tissue. We and others have previously reported that the presence of gamma delta T cells during certain inflammatory conditions correlates with less host tissue damage. This result, together with the evidence presented here, further implies that a response by the V gamma 6/V delta 1 subset in some way exerts a controlling influence on the host inflammatory response.

Evidence that the same gamma delta T cells respond during infection-induced and autoimmune inflammation

Inflammatory responses are induced in both testes of a mouse following injection of Listeria monocytogenes into one testis. Although the uninjected testis contains no detectable bacteria, it undergoes an autoimmune attack. Normally, the testis lacks lymphocytes, but in the infected and autoimmune state, both gamma delta and alpha beta T cells are found as infiltrates. Here, we have examined the repertoire of the infiltrating gamma delta T cells, using two different methods, and found a high frequency of V gamma 6/V delta 1 gamma delta T cells in both infected and autoimmune testes. All of these expressed the invariant V gamma 6/V delta 1 TCR previously reported. However, secondary gamma and delta transcripts present within V gamma 6/V delta 1 hybridomas indicated nonclonality. Interestingly, some of these secondary transcripts were derived from gamma gene rearrangements not previously found in this gamma delta T cell subset, implying a difference in its origin. The increase in V gamma 6/V delta 1 cells observed here in both infected and autoimmune testes, together with our previous finding of a preferential response by the same subset in Listeria-infected liver, indicates that their response is triggered by the inflammation rather than by the infectious agent or because they are already resident in the tissue. We and others have previously reported that the presence of gamma delta T cells during certain inflammatory conditions correlates with less host tissue damage. This result, together with the evidence presented here, further implies that a response by the V gamma 6/V delta 1 subset in some way exerts a controlling influence on the host inflammatory response.

Coexistence of novel amylin-binding sites with calcitonin receptors in human breast carcinoma MCF-7 cells

Amylin, calcitonin (CT) and calcitonin gene-related peptide (CGRP) share limited structural homology including amino-terminal ring structures linked by a disulfide bridge and amidated carboxy-termini. Here, we have compared [125I]Bolton-Hunter-[Lys1] rat amylin ([125I]amylin) binding and the stimulation of cyclic AMP accumulation by human (h) amylin, hCT and hCGRP-I in the human breast carcinoma cell lines MCF-7 and T47D, which predominantly express hCT1a and hCT1b receptor isoforms (hCTR1a, hCTR1b) at a similar total number of hCT-binding sites. In MCF-7 cells, half-maximal inhibition (IC50) of [125I]amylin binding by human amylin was observed at 3.6 +/- 0.8 nM (n = 6). hCT and hCGRP-I displaced [125I]amylin binding with 22 and 66 times higher IC50. [125I]hCT binding was inhibited by hCT with an IC50 of 8.1 +/- 1.9 nM (n = 5), and human amylin and hCGRP-I were over 100 times less potent. In T47D cells, on the other hand, specific binding of [125I]amylin was not observed, but hCT inhibited [125I]hCT binding with an IC50 of 3.2 +/- 0.4 nM (n = 3), and human amylin and hCGRP-I had over 200 times higher IC50. In MCF-7 cells, half-maximal stimulation (EC50) of cyclic AMP accumulation by human amylin, hCT and hCGRP-I occurred at 1.4 +/- 0.2, 1.7 +/- 0.4 and 6.3 +/- 1.3 nM respectively. In T47D cells, the EC50 of hCT was 0.32 +/- 0.02 nM (n = 3), and 30- and 1900-fold higher with human amylin and hCGRP-I. In conclusion, the expression of hCTR1a and hCTR1b and [125I]hCT binding were indistinguishable in MCF-7 and T47D cells. Yet, [125I]amylin binding was only recognized in MCF-7 cells, consistent with a distinct amylin receptor.

Parathyroid hormone-related protein (PTHrP) inhibits proliferation of Chinese hamster ovary cells stably transfected with a PTH/PTHrP receptor cDNA

The effect of parathyroid hormone-related protein (PTHrP) on proliferation was examined in Chinese hamster ovary (CHO) cells transfected with a PTH/PTHrP receptor encoding cDNA. Treatment with chicken PTHrP(1-36) (chPTHrP) lowered the cell number to 49 +/- 2% of untreated controls after 6 days with a half-maximal effect at 1 nM. The effect was mimicked by human (h) PTH(1-34), Br-cAMP and forskolin, but not by the receptor antagonist hPTH(3-34). Reduction of cell number was accompanied by increased PTH/PTHrP receptor expression and persistently activated adenylyl cyclase, together with altered cell morphology from epithelial to spindle-like forms, clustered growth and increased phosphate uptake. chPTHrP increased [Ca2+]i, but failed to activate membrane bound protein kinase C (PKC). Pretreatment with chPTHrP did not affect phorbol ester stimulated PKC activity, and chPTHrP or serum evoked increases in [Ca2+]i. In conclusion, PTHrP induced inhibition of proliferation and altered cell morphology is mediated by increased adenylyl cyclase rather than by PKC-dependent mechanisms in CHO cells.

Tissue-specific mRNA expression of a calcitonin receptor-like receptor during fetal and postnatal development

The distribution of calcitonin receptor-like receptor (CRLR) mRNA in developing rats was investigated by in situ hybridization. Signals were found in the piriform cortex, the central and basolateral amygdala and the amygdalostriatal transition area. Among peripheral organs, the CRLR was predominantly expressed in the lung. mRNA expression in blood vessels, liver, midgut, rectum and urethra was restricted to gestational days 16 and/or 20. The CRLR was thought to be a calcitonin gene-related peptide (CGRP) type 1 receptor (Aiyar et al., J. Biol. Chem., 271 (1996) 11325-11329). This contrasts with previously reported evidence that the CRLR is an orphan receptor with no identifiable interactions with CGRP and other related ligands (Flühmann et al., Biochem. Biophys. Res. Commun., 206 (1995) 341-347). In situ hybridization signals have not been detected in the cerebellum and the spleen known to present a high density of CGRP binding sites. The different regional distribution of CGRP receptor binding sites and CRLR mRNA implies the latter encoding a different CGRP receptor subtype.

Reconstitution of SCID mice with haemopoietic precursors: a detailed analysis of gamma delta T-cell reconstitution

A well-known characteristic of gamma delta T cells is that they are produced in waves during ontogeny, with cells expressing T-cell receptor V gamma 5 appearing early in fetal thymic ontogeny, followed by V gamma 6, then by other gamma delta T-cell types. In addition, evidence exists to suggest that the potential of haemopoietic precursors to generate different types of gamma delta T cells changes in ontogeny. We have used these observations as the basis for an extensive study of the potential for haemopoietic precursors isolated from fetal liver, neonatal spleen and adult bone marrow to reconstitute severe combined immunodeficient (SCID) mice. Mice that were reconstituted as newborns with fetal liver cells most closely resembled normal C.B-17 mice with respect to both lymphocyte numbers and subsets, while mice reconstituted with adult bone marrow had fewer cells than normal mice. This deficit spanned both T and B cells in all organs examined. Among the gamma delta T-cell subsets examined, the ability to reconstitute V gamma 4+ cells was particularly dependent on the ontogenic age of the reconstituting presursors, with fetal liver cells having the greatest capacity to generate V gamma 4+ cells, and adult bone marrow cells the least. The vast majority of the T cells produced in the reconstituted mice were of donor origin, and the level of reconstitution was found to be dependent upon some factor other than the presursor frequency.

Biologically active human islet amyloid polypeptide/amylin in transgenic mice

OBJECTIVE

Human islet amyloid polypeptide (hIAPP), also named amylin, is a pancreatic beta cell protein implicated in the pathogenesis of pancreatic islet amyloid formation and type 2 diabetes mellitus. To study the (patho)physiological roles of hIAPP, we have generated transgenic mice that overexpress hIAPP mRNA, in relation to endogenous mouse IAPP (mIAPP) mRNA, in pancreatic beta cells. The biological activity of human and mouse IAPP derived from pancreatic extracts was determined.

METHODS

Pancreatic and plasma extracts of transgenic and control mice were analyzed by reversed-phase high-performance liquid chromatography (HPLC) and radioimmunoassay, yielding a separation of hIAPP from mIAPP. Biological activity of immunoreactive human and mouse IAPP components derived from pancreatic extracts was assessed by calcitonin receptor-mediated stimulation of cyclic AMP accumulation in T47D human breast carcinoma cells.

RESULTS

The predominant immunoreactive human and mouse IAPP gene products had the retention times on HPLC analysis of the corresponding synthetic peptides. The ratio of bioactive over immunoreactive hIAPP and mIAPP was 0.93 +/- 0.18 and 1.19 +/- 0.56 respectively. In extracts of two plasma pools from 4 transgenic animals, hIAPP was 4.6- to 7-fold more abundant than mIAPP.

CONCLUSION

This study has shown that correctly processed hIAPP produced in transgenic mouse pancreatic beta cells exhibits full biological activity. The results validate these transgenic mice for the study of (patho)physiological roles of hIAPP in vivo.

Bias in the gamma delta T cell response to Listeria monocytogenes. V delta 6.3+ cells are a major component of the gamma delta T cell response to Listeria monocytogenes

Despite extensive research, the role that gamma delta T cells play in the immune response to infectious disease has yet to be established. Here we report the generation of a mAb specific for the V delta 6.3 TCR and investigate the gamma delta+ and V delta 6.3+ T cell responses to the intracellular bacterium Listeria monocytogenes in BALB/c mice. By infecting animals with various doses of Listeria and analyzing the components of the cellular immune response at the two primary sites of infection, the liver and spleen, we have shown that the kinetics, composition, and magnitude of the gamma delta and V delta 6.3 T cell responses are dependent upon the injected dose of bacteria and the organ in which the infection is established. At low doses of infection, the gamma delta T cell response occurs late in the disease course, while at high doses, the response is earlier and of greater magnitude, particularly in the liver. At all infectious doses and in both tissues, the V delta 6.3+ population predominates and together with V delta 4+ cells composes the bulk of the gamma delta T cell response. Changes in the morphology of gamma delta+ and V delta 6.3+ cells at the site of infection are consistent with cellular activation and suggest that these cells are active participants in the Listeria-induced immune response. The results of our study suggest that many features of the gamma delta T cell response to Listeria are dose and tissue related.

Bias in the gamma delta T cell response to Listeria monocytogenes. V delta 6.3+ cells are a major component of the gamma delta T cell response to Listeria monocytogenes

Despite extensive research, the role that gamma delta T cells play in the immune response to infectious disease has yet to be established. Here we report the generation of a mAb specific for the V delta 6.3 TCR and investigate the gamma delta+ and V delta 6.3+ T cell responses to the intracellular bacterium Listeria monocytogenes in BALB/c mice. By infecting animals with various doses of Listeria and analyzing the components of the cellular immune response at the two primary sites of infection, the liver and spleen, we have shown that the kinetics, composition, and magnitude of the gamma delta and V delta 6.3 T cell responses are dependent upon the injected dose of bacteria and the organ in which the infection is established. At low doses of infection, the gamma delta T cell response occurs late in the disease course, while at high doses, the response is earlier and of greater magnitude, particularly in the liver. At all infectious doses and in both tissues, the V delta 6.3+ population predominates and together with V delta 4+ cells composes the bulk of the gamma delta T cell response. Changes in the morphology of gamma delta+ and V delta 6.3+ cells at the site of infection are consistent with cellular activation and suggest that these cells are active participants in the Listeria-induced immune response. The results of our study suggest that many features of the gamma delta T cell response to Listeria are dose and tissue related.

Cutaneous exposure to the superantigen staphylococcal enterotoxin B elicits a T-cell-dependent inflammatory response

We analyzed the impact of superantigens secreted by skin-colonizing Staphylococci on the skin and the associated lymphoid tissue following epicutaneous application and intracutaneous injection of small amounts of staphylococcal enterotoxin B (SEB). A single intracutaneous injection of 50 ng of SEB elicited a strong inflammatory response in the skin of BALB/c mice. Three to 6 h later, we observed langerhans cell activation, mast cell degranulation, vasodilation, upregulation of ICAM-1, and induction of VCAM-1 on dermal blood vessels, with vascular adhesion of granulocytes. by 12 to 24 h, cell infiltration of the dermis increased, reaching the epidermis. Among the infiltrating leukocytes, a substantial number of eosinophils was found. After 48 h, the infiltrate was dominated by mononuclear cells. The response to SEB was dose-dependent, and signs of inflammation slowly disappeared over 5 to 7 days. Although the induction of VCAM-1 on dermal blood vessels suggested a role for interleukin-1/tumor necrosis factor-alpha in this reaction, the activation of monocytes/macrophages was not able to substitute for lymphocytes, as severe combined immunodeficiency (SCID) mice (which are lymphocyte-deficient) did not mount an inflammatory skin response to intradermal injection of SEB. The fact that nude mice (T-cell-deficient) also did not mount an inflammatory response to SEB indicated the T-cell dependency of the response. The V beta specificity of the SEB effect was demonstrated by the fact that SJL/J mice, which lack V beta 8+ T cells (the major SEB-reactive T cell population in mice), exhibited much weaker responses. Deletion or tolerization of SEB-reactive V beta T cells was not observed after a single intradermal injection of such minute amounts of SEB.

Structure of a parathyroid hormone/parathyroid hormone-related peptide receptor of the human cerebellum and functional expression in human neuroblastoma SK-N-MC cells

Cloning and functional expression of a cDNA from the human cerebellum revealed a parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) receptor protein of 593 amino acids, identical in sequence to the PTH/PTHrP receptor of the human kidney and an osteoblast-like cell line (Schipani et al., Endocrinology, 132 (1993) 2157-2165). Expression of mRNA hybridizing with the cloned cDNA, indistinguishable in size on Northern blots from a 2.3 kb transcript in kidney and liver, was detected in eight brain areas. In situ hybridization histochemistry in rat brain tissue sections revealed predominant signals in the Purkinje cell layer of the cerebellum and in the mesencephalic nucleus of the trigeminal nerve. In human neuroblastoma (SK-N-MC) cells, stably transfected with the cloned cDNA, hPTH(1-84) and hPTH(1-34) displaced binding of 125 pM [125I][Tyr36]chPTHrP(1-36) to the PTH/PTHrP receptor with IC50 values of 4.0 +/- 0.6 nM and 2.00 +/- 0.08 nM, and stimulated cyclic AMP accumulation with EC50 values of 0.19 +/- 0.06 nM and 0.09 +/- 0.01 nM, respectively. 16 out of 48 cells responded to 100 nM hPTH(1-34) with a 2-10-fold transient increase of cytosolic free calcium concentrations. In conclusion, a PTH/PTHrP receptor, identified in the human cerebellum, has the primary structure of the corresponding receptors of kidney and bone. Expression in human neuroblastoma SK-N-MC cells revealed functional properties indistinguishable from those of non-neuronal tissues. The widespread distribution of PTHrP and its receptor in brain implies biological functions remaining to be elucidated.

Bacterial infection of the testis leading to autoaggressive immunity triggers apparently opposed responses of alpha beta and gamma delta T cells

The mechanisms that lead to the breakdown of self-tolerance and testis-specific immune reactivity in the murine orchitis model are understood only in part. We investigated the histopathologic and immunologic consequences of a unilateral bacterial (Listeria monocytogenes) infection of the testis. Both infected and contralateral sides of this bilateral organ suffered severe inflammatory responses despite a conspicuous absence of bacteria in the contralateral tissue. Also, in both testicles, T cell populations increased, involving both alpha beta and gamma delta T cell subsets. Concomitant with the bilateral orchitis, testis-specific delayed type hypersensitivity and Ab responses developed. Ab depletion experiments indicated that in this orchitis model, as in others, alpha beta T cells are initiators of the autoaggressive reactivity. In contrast, Ab depletion of gamma delta T cells accelerated the inflammatory response in both testicles, suggesting a regulatory role for this type of T cells in both infection-induced and autoimmune orchitis.

Bacterial infection of the testis leading to autoaggressive immunity triggers apparently opposed responses of alpha beta and gamma delta T cells

The mechanisms that lead to the breakdown of self-tolerance and testis-specific immune reactivity in the murine orchitis model are understood only in part. We investigated the histopathologic and immunologic consequences of a unilateral bacterial (Listeria monocytogenes) infection of the testis. Both infected and contralateral sides of this bilateral organ suffered severe inflammatory responses despite a conspicuous absence of bacteria in the contralateral tissue. Also, in both testicles, T cell populations increased, involving both alpha beta and gamma delta T cell subsets. Concomitant with the bilateral orchitis, testis-specific delayed type hypersensitivity and Ab responses developed. Ab depletion experiments indicated that in this orchitis model, as in others, alpha beta T cells are initiators of the autoaggressive reactivity. In contrast, Ab depletion of gamma delta T cells accelerated the inflammatory response in both testicles, suggesting a regulatory role for this type of T cells in both infection-induced and autoimmune orchitis.

Receptors for calcitonin, calcitonin gene related peptide, amylin, and adrenomedullin

Calcitonin, calcitonin gene related peptide, amylin, and adrenomedullin are structurally related polypeptides characterized by a six or seven amino acid ring structure linked by a disulfide bridge and an amidated C-terminus. They exhibit overlapping biological actions as a result of cross-reactivity between the different receptors. In this article, the respective receptors and G-protein-coupled postreceptor events are reviewed in relation to some of the biological actions of the peptides.

Calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin: homologous peptides, separate receptors and overlapping biological actions

Calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin are structurally related peptides with N-terminal 6-7 amino acid ring structures linked by a disulfide bridge and with amidated C-termini. Among the related bioactive peptides, the structures of the calcitonin receptor and subtypes thereof have been identified so far through molecular cloning. Cross-reaction between receptors of calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin, as well as overlapping biological actions, anticipate that the respective receptors belong to a family of G-protein-coupled receptors that include those of parathyroid hormone, secretin and vasointestinal peptide.

A human orphan calcitonin receptor-like structure

A novel calcitonin receptor-like protein of 461 amino acids with seven putative transmembrane domains has been identified through molecular cloning in a cDNA library of the human cerebellum. 91% and 56% of the amino acids are identical in a rat orphan calcitonin receptor-like sequence and the human calcitonin receptor, respectively. 5.2 kb mRNA is predominantly expressed in the lung, heart and kidney. Specific binding of 125I-labeled salmon calcitonin and human calcitonin gene-related peptide-I to COS-7 cells transiently transfected with the receptor cDNA was less then 0.5%. Cellular cAMP accumulation was indistinguishable in cDNA transfected and non-transfected control COS-7 and renal tubular cells from the American opossum stimulated with human and salmon calcitonin, human calcitonin gene-related peptide-I and -II, human amylin, human adrenomedullin, lizard helodermin, salmon stanniocalcin and chicken parathyroid hormone-related protein. The receptor-like protein whose ligand remains to be discovered belongs to the family of receptors of calcitonin, parathyroid hormone, secretin, vasointestinal peptide and pituitary adenylate cyclase-activating polypeptide.

Recognition of trophoblasts by gamma delta T cells

The juxtaposition of maternal and fetal tissues in the hemochorial placenta has led to speculation that maternal recognition of fetal Ags present on trophoblasts might play an important role in reproductive biology. We report here for the first time such recognition of trophoblasts by T lymphocyte hybridomas representative of certain cells present in the maternal decidua. Trophoblast recognition is TCR dependent and is mediated by members of the V gamma 1+ subset of gamma delta T lymphocytes, a population that we previously have shown to be associated with heat shock protein-60 reactivity. Recognition occurred in experiments in which trophoblast clones or freshly prepared trophoblasts were used and requires cell-cell interaction. Although the maternal-fetal immune relationship typically has been cast in terms of an allograft, the T cell recognition of trophoblasts as described herein is not MHC-restricted, inasmuch as freshly prepared trophoblasts from beta 2-microglobulin-deficient mice were found to be stimulatory. Furthermore, the trophoblast ligand that mediates this recognition is probably a conserved mammalian molecule, because a human trophoblast cell line is also stimulatory. Our findings suggest a novel form of T cell recognition, and may provide an enhanced understanding of the maternal-fetal immune relationship.

Immune protection and control of inflammatory tissue necrosis by gamma delta T cells

Host defenses against experimental listeriosis in mice involve neutrophils, macrophages, NK cells, and alpha beta T cells. Recently gamma delta T cells have also been implicated in antilisterial resistance. However, their specific role has remained unclear. Here we show that efficient resistance to infection by this bacterium depends on the functions of both alpha beta and gamma delta T cells in both primary and secondary responses. We also present evidence that these functions are complementary. In the livers of alpha beta T cell-depleted mice, bacteria grow to large numbers within hepatocytes but are infrequently found extracellularly. Granulomatous lesions are more frequent and somewhat larger than in normal controls, but remain focal. Neutrophils are absent from liver lesions in these mice. In contrast, the livers of gamma delta T cell-depleted mice contain many extracellular bacteria, but do not show hepatocytes containing large numbers of Listeria. Liver lesions in gamma delta T cell-depleted mice are far more extensive than in normal controls or in alpha beta T cell-depleted mice, and contain large numbers of neutrophils. Particularly in secondary listeriosis, gamma delta T cell-depleted mice show vast coalescent areas of necrotic liver parenchyma within 48 h after infection. Because the bacterial numbers in gamma delta T cell-depleted mice remain lower than in alpha beta T cell-depleted mice, increased mortality in the former may be in part caused by liver failure. We conclude that gamma delta T cells are required to control inflammatory reactivity and to prevent excessive liver damage during the immune response to Listeria monocytogenes.