Attenuation of antigen-induced airway hyperresponsiveness in CGRP-deficient mice

Bronchial hyperresponsiveness and eosinophilia are major characteristics of asthma. Calcitonin gene-related peptide (CGRP) is a neuropeptide that has various biological actions. In the present study, we questioned whether CGRP might have pathophysiological roles in airway hyperresponsiveness and eosinophilia in asthma. To determine the exact roles of endogenous CGRP in vivo, we chose to study antigen-induced airway responses using CGRP gene-disrupted mice. After ovalbumin sensitization and antigen challenge, we assessed airway responsiveness and measured proinflammatory mediators. In the sensitized CGRP gene-disrupted mice, antigen-induced bronchial hyperresponsiveness was significantly attenuated compared with the sensitized wild-type mice. Antigen challenge induced eosinophil infiltration in bronchoalveolar lavage fluid, whereas no differences were observed between the wild-type and CGRP-mutant mice. Antigen-induced increases in cysteinyl leukotriene production in the lung were significantly reduced in the CGRP-disrupted mice. These findings suggest that CGRP could be involved in the antigen-induced airway hyperresponsiveness, but not eosinophil infiltration, in mice. The CGRP-mutant mice may provide appropriate models to study molecular mechanisms underlying CGRP-related diseases.

Source of plasma adrenomedullin in patients with pheochromocytoma

Controversy exists as to the origin of plasma adrenomedullin (AM). To elucidate the source of plasma AM, we measured two molecular forms of AM, an active form of mature AM (AM-m) and an intermediate inactive form of glycine-extended AM (AM-Gly), by immunoradiometric assay using specific kits in two female patients with pheochromocytoma before and 3 weeks after surgery. We also measured plasma AM-m, AM-Gly, and AM-T (AM-m + AM-Gly) levels, in addition to plasma epinephrine (E) and norepinephrine (NE) levels, in bilateral adrenal veins of one patient. Although plasma E and NE levels decreased markedly after surgery in these patients, changes in plasma AM appeared to be confined to the normal range. There were no obvious differences in plasma AM-T, AM-m, or AM-Gly levels in adrenal veins between healthy tissue and tumor sides. Furthermore, plasma AM-T, AM-m, or AM-Gly levels in adrenal veins were comparable with those in the infrarenal inferior vena cavae (IVC) or the suprarenal IVC. In contrast, plasma E and NE levels increased in the adrenal vein of the healthy side and increased further in the adrenal vein of the tumor side compared with those in the infrarenal IVC. These results suggest that the origin of plasma E and NE is the adrenal gland and that elevated plasma levels of E and NE in pheochromocytoma are due to excessive production of E and NE in the adrenal gland of the tumor side. In contrast, it is suggested that neither plasma AM levels in the adrenal vein of the healthy side nor those of the tumor side contribute to the systemic levels of plasma AM. The present results appear to be consistent with the hypothesis that the source of circulating AM is systemic vasculature.

Coordinate regulation of transcription and splicing by steroid receptor coregulators

Recent observations indicating that promoter identity influences alternative RNA-processing decisions have created interest in the regulatory interactions between RNA polymerase II transcription and precursor messenger RNA (pre-mRNA) processing. We examined the impact of steroid receptor-mediated transcription on RNA processing with reporter genes subject to alternative splicing driven by steroid-sensitive promoters. Steroid hormones affected the processing of pre-mRNA synthesized from steroid-sensitive promoters, but not from steroid-unresponsive promoters, in a steroid receptor-dependent and receptor-selective manner. Several nuclear receptor coregulators showed differential splicing effects, suggesting that steroid hormone receptors may simultaneously control gene transcription activity and exon content of the product mRNA by recruiting coregulators involved in both processes.

Virally mediated delivery of enkephalin and other neuropeptide transgenes in experimental pain models

We have constructed recombinant herpes simplex virus type 1 vectors for delivery of genes to sensory neurons in an attempt to modulate nociception. Delivery of recombinant viruses to the skin of mice results in expression of encoded complementary DNA (cDNA) genes in DRG neurons within three to four days. Expression of marker genes persists for at least 10 weeks. Testing of baseline thermal nociceptive latencies at the site of virus application revealed no differences between a control virus and a virus encoding human preproenkephalin (hPPE) when performed at either low stimulus intensities (C-fiber activation) or high stimulus intensities (Adelta neurons). By contrast, sensitization of nociceptors by capsaicin or dimethylsulfoxide was reduced or abolished by infection with the virus encoding hPPE, but not by a control virus. These antihyperalgesic responses are mediated by opioids released at the central terminals of the primary afferents because they are blocked by intrathecal administration of the opioid antagonist naloxone. Similar experiments performed in macaques demonstrated an antihyperalgesic effect of the herpes virus vector encoding hPPE. This hPPE-encoding virus was also tested in a model of neuropathic pain in mice, with similar effect. A virus containing an antisense cDNA for calcitonin gene-related peptide precursor (ACGRP) has also been constructed and found to reverse C-fiber hyperalgesia caused by application of capsaicin to the skin for up to 14 weeks postinfection. These results raise the possibility that herpes-mediated, gene-based approaches to treat chronic pain states may be useful in therapy of chronic pain in humans.

5-HT2A receptor subtype in the peripheral branch of sensory fibers is involved in the potentiation of inflammatory pain in rats

One of the major serotonin (5-HT) receptor subtypes expressed in the rat dorsal root ganglion (DRG) neurons is the 5-HT2A receptor. We have previously shown that 5-HT2A receptors in the peripheral sensory terminals are responsible for 5-HT-induced pain and hyperalgesia. In the present study, we characterized neurons expressing 5-HT2A receptors in the rat DRG neurons by means of in situ hybridization, immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and behavioral tests. In situ hybridization on consecutive sections revealed that 5-HT2A receptor mRNA is colocalized with calcitonin-gene related peptide (CGRP) mRNA (100/104; 96.2%) but not with c-Ret mRNA (1/115; 0.9%). Signals for 5-HT2A receptor mRNA were found in 9.4 +/- 2.2% of normal DRG (L5) neurons, most of which were small to medium in size. Four days of complete Freund's adjuvant-induced inflammation of the hindpaw doubled the incidence of 5-HT2A receptor mRNA-expressing neurons to 19.3 +/- 2.8%. The level of 5-HT2A receptor mRNA in DRGs of normal and various pathological conditions was then determined by RT-PCR. The level was up-regulated by peripheral inflammation, but not by axotomy or chronic constriction of the peripheral nerve. Systemic administration of 5-HT2A receptor antagonist (Sarpogrelate HCI) produced analgesic effects on thermal hyperalgesia caused by peripheral inflammation, but failed to attenuate thermal hyperalgesia in chronic constriction injury model. These findings suggest that 5-HT2A receptors are mainly expressed in CGRP-synthesizing small DRG neurons and may be involved in the potentiation of inflammatory pain in the periphery.

Calcitonin gene-related Peptide and choline acetyltransferase colocalization in the human vestibular periphery

Within the vestibular system, calcitonin gene-related peptide (CGRP) has been localized in the efferent terminals and their brainstem neuronal cell bodies in several animal models. Presently, very few studies have verified these findings in the vestibular system in adult primates or humans. CGRP immunoreactivity (CGRPi) and its colocalization with choline acetyltransferase immunoreactivity (ChATi) in human vestibular end organs and Scarpa's ganglion were studied using polyclonal antibodies against CGRP and ChAT, at the light-microscopic level. The CGRPi axons ramified to produce numerous CGRPi terminals throughout the neurosensory epithelium of the maculae and cristae, primarily in the basal and midbasal areas. Numerous CGRPi efferent terminals made contact with both type II vestibular hair cells and the afferent chalices surrounding type I vestibular hair cells. All CGRP immunoreactive fibers also exhibited ChATi. As in the animal models, no CGRPi was found within Scarpa's ganglion. This study provides evidence for CGRPi in the human vestibular periphery and validates the biomedical relevance of the current animal models.

Production and secretion of calcitonin gene-related peptide from human lymphocytes

Calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide, which is mainly present in primary sensory nerves. Although our previous study has shown that rat lymphocytes can synthesize beta-CGRP, there is no evidence demonstrating whether CGRP can be synthesized by human lymphocytes. In this study, the production of CGRP from human lymphocytes from spleen and blood were investigated by using CGRP-specific radioimmunoassay (RIA), and RNase protection assay (RPA). The results showed that human T lymphocyte mitogen, such as phytohemagglutinin (PHA), could time- and dose-dependently induce hCGRP secretion; rhIL-2 alone did not effect hCGRP secretion, but it could potentiate PHA-evoked hCGRP secretion from human spleen lymphocytes. RPA showed that alpha- and beta-CGRP mRNA were both constitutively expressed in unstimulated human peripheral blood mononuclear cells (PBMC). PHA could cause beta-hCGRP but not alpha-hCGRP mRNA increase in a time-dependent manner. In addition, hCGRP(8-37), a CGRP(1) receptor antagonist, enhanced PHA or human interleukin-2 (rhIL-2), induced the proliferation of splenocytes and PBMC. These results suggest that hCGRP is produced and secreted by human lymphocyte. Lymphocyte mitogen can induce the elevation of beta-CGRP synthesis and secretion. The lymphocyte-derived beta-CGRP may inhibit, at least in part, lymphocytes proliferation, which are then involved in the modulation of human T lymphocyte function in response to immune stimulation.

Calcitonin gene-related peptide (CGRP) and CGRP receptor expression at the human implantation site

Calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide produced by tissue-specific alternative splicing of the primary transcript of the calcitonin gene. The objectives of this study were: 1) to determine the expression of CGRP and its receptor at the human implantation site, and 2) to examine the possible in vitro effect of this neuropeptide on two major partners of implantation, decidual cells and extravillous cytotrophoblasts. Immunohistological analysis of first-trimester placental chorionic villi showed CGRP in decidual cells and glandular cells, but not in extravillous trophoblast cells. CGRP expression was confirmed in cultured decidual cells by Southern blot analysis and immunocytochemistry and by RIA in culture medium. Transcripts of calcitonin receptor-like receptor were detected by Southern blot analysis of RT-PCR amplicons from both decidual and extravillous trophoblast cells, whereas transcripts for the receptor activity-modifying protein 1 were detected in decidual cells only. In vitro, CGRP stimulated cAMP production but not nitric oxide (NO) release by cultured decidual cells; in contrast CGRP increased NO release but not cAMP production in cultured extravillous trophoblasts. The presence of NO synthase (endothelial and inducible) was confirmed by immunodetection in extravillous trophoblasts, both in situ and in vitro. This study points to a paracrine and autocrine effect of CGRP on decidual and extravillous trophoblast cells, two major actors in implantation.

Effect of age on alpha-calcitonin gene-related peptide-mediated delayed cardioprotection induced by intestinal preconditioning in rats

In the present study, we examined whether age-related reduction in cardioprotection of intestinal ischemic preconditioning is related to stimulation of the release and synthesis of calcitonin gene-related peptide (CGRP) in rats. Ischemia-reperfusion injury was induced by a 45-min coronary artery occlusion and 180-min reperfusion, and ischemic preconditioning was induced by six cycles of 4-min ischemia and 4-min reperfusion of the small intestine. The serum concentration of creatine kinase, infarct size, the expression of CGRP isoforms (alpha- and beta-CGRP) mRNA in lumbar dorsal root ganglia and CGRP concentration in plasma were measured. Pretreatment with intestinal ischemic preconditioning for 24 h significantly reduced infarct size and creatine kinase release concomitantly with a significant increase in the expression of alpha-CGRP mRNA, but not beta-CGRP mRNA, and plasma concentrations of CGRP at 6 months of age but not at 24 months of age. These results suggest that the delayed cardioprotective effect of intestinal ischemic preconditioning is decreased in senescent rats, and the age-related change is related to reduction of the synthesis and release of alpha-CGRP.

Neuronal regulation of bone metabolism and anabolism: calcitonin gene-related peptide-, substance P-, and tyrosine hydroxylase-containing nerves and the bone

Bone alters its metabolic and anabolic activities in response to the variety of systemic and local factors such as hormones and growth factors. Classical observations describing abundance of the nerves fibers in bone also predict a paradigm that the nervous system influences bone metabolism and anabolism. Identification of the nerve-derived signaling molecules, capable of modulating cellular activities of the bone cells, facilitates a novel approach to study the biology of skeletal innervation. Many of the signaling molecules that may act as efferent agents on the bone cells fall into the category of neuropeptides. The present article reviews current understanding of the skeletal innervation and their proposed physiological effects on bone metabolism, with a special interest to calcitonin gene-related peptide (CGRP)-containing nerves fibers. CGRP is abundantly distributed in bone via sensory nerves, especially in the epiphyseal trabecular bones. Its in vitro actions to the cultured osteoblasts and osteoclasts, together with its in vivo localization, strongly support the paradigm that the nervous system influences bone metabolism. In addition, CGRP is recently shown to be expressed endogenously by the osteoblasts. Transgenic mice with osteoblasts overexpressing CGRP are characterized by increased bone formation rate and enhanced bone volume, suggesting that CGRP indeed acts on bone metabolism not only via nervous route but also via autocrine loop. The current article also reviews the distribution of nerve fibers containing substance P (SP), another sensory nerve-specific neuropeptide, and tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine. The distinct effects of SP and catecholamines on the bone cells together with their in vivo influences manifested by experimental denervation studies suggest that the sensory and sympathetic nerves play important roles in bone metabolism.

Posttreatment with adenovirus-mediated gene transfer of calcitonin gene-related peptide to reverse cerebral vasospasm in dogs

OBJECT

Gene transfer to cerebral vessels is a promising new therapeutic approach for cerebral vasospasm after subarachnoid hemorrhage (SAH). This study was undertaken to explore whether a delayed treatment with adenovirus encoding the prepro-calcitonin gene-related peptide (CGRP), 2 days after initial blood injection, reduces cerebral vasospasm in a double-hemorrhage model of severe vasospasm in dogs.

METHODS

In 20 dogs, arterial blood was injected into the cisterna magna on Days 0 and 2. Thirty minutes after the second blood injection, the animals received either adenovirus encoding the prepro-CGRP gene (AdCMVCGRP-treated group, eight dogs) or adenovirus encoding the beta-galactosidase gene (AdCMVbeta gal-treated group, six dogs) under the cytomegalovirus (CMV) promoter. One group of dogs did not receive treatment and served as controls (control SAH group, six dogs). Angiography was performed on Days 0 and 7 to assess cerebral vasospasm. On Day 7 following angiography, the animals were killed and their brains were stained with X-gal to detect the distribution of gene expression. Cerebrospinal fluid (CSF) was also tested for CGRP immunoreactivity. Severe vasospasm was observed in control SAH dogs on Day 7, and the mean basilar artery (BA) diameter was 53.4 +/- 5.5% of the value measured on Day 0. Treatment with AdCMVbeta gal did not alter vasospasm (the BA diameter was 55 +/- 3.9% of that measured on Day 0). The leptomeninges and adventitia of the BAs of dogs treated using AdCMVbeta gal demonstrated positive staining with X-gal. High levels of CGRP were measured in CSF from dogs that received AdCMVCGRP. In the group treated with AdCMVCGRP, vasospasm was significantly reduced (the BA diameter was 78.2 +/- 5.3% of that measured on Day 0, p < 0.05 compared with the control SAH group and the AdCMVbeta gal group).

CONCLUSIONS

In a model of severe vasospasm in dogs, gene transfer of CGRP after injection of blood attenuated cerebral vasospasm after SAH.

[Chronic rhinosinusitis in hypogammaglobulinemia. A morphological study]

Primary hypogammaglobulinemia (Bruton's disease) is a rare X-linked infantile immunodeficiency syndrome due to a B-cell defect. The patients suffer from acute and recurrent bacterial infections with chronic rhinosinusitis and chronic lung disorders. Immunoglobulin replacement therapy and antibiotics do not suffice in some cases, making sinus surgery to advance the drainage necessary. A 25-year-old man with hypogammaglobulinemia was treated with functional endoscopic sinus surgery and mucotomy of the turbinates. Tissue samples of the inferior turbinates were taken for histological and electron-microscopic examination. Immuno-electron-microscopic methods were carried out with antibodies against substance P and calcitonin gene-related peptide (CGRP). Morphological investigations to better understand pathophysiological changes in hypogammaglobulinemia are rare. Pathological changes in the glands and venous vessels could be demonstrated. A rich neural supply and participation of neuropeptides such as substance P and CGRP could play a role in the unspecific defense via neurogenetic inflammation in these cases.

Calcitonin gene-related peptide immunoreactive cells and fibers in forebrain vocal and auditory nuclei of the budgerigar (Melopsittacus undulatus)

The distributions of calcitonin gene-related peptide (CGRP) immunoreactive neurons and fibers were mapped within forebrain vocal control and auditory nuclei of a vocal learning psittacine species, the budgerigar (Melopsittacus undulatus). Immunoreactivity was exhibited by telencephalic nuclei previously associated with vocal control pathways on the basis of both tract tracing studies and gene mapping: the central nucleus of the anterior archistriatum (AAc), central nucleus of the lateral neostriatum (NLc), magnocellular nucleus the lobus parolfactorius (LPOm), the oval nucleus of the ventral hyperstiratum (HVo) and the medial division of the oval nucleus of the anterior neostriatum (NAom). The main body of NAo also contained an exceptionally high density of immunoreactive fibers. In contrast to the condition in oscine songbirds, CGRP-positive neuronal somata were not present in any telencephalic vocal control nucleus. CGRP-positive somata were present, however, in diencephalic cell groups that included the shell region of the nucleus ovoidalis (Ov), the nucleus dorsolateralis posterior (DLP) and a region of the ventral thalamus that was retrogradely labeled by tracer deposits into HVo and AAc. CGRP immunoreactive fibers were observed within auditory areas of the telencephalon including Field L and the neostriatum intermedium pars dorsolateralis. The likely sources of these fibers are CGRP-positive neurons within the Ov shell and DLP.

Structure of the mouse calcitonin/calcitonin gene-related peptide alpha and beta genes

We report the cloning, genomic organization and sequence of the mouse alpha-CALC and beta-CALC genes. The two genes share extensive sequence homology. The transcription units of both genes contain 6 exons. Transcripts of the alpha-CALC gene were found to alternatively include exon 4 or exons 5 and 6. For the beta-CALC gene exon 4 was not detected in transcripts derived from this gene. The predicted mouse alpha-CGRP was found to be identical to rat alpha-CGRP, however, beta-CGRP predicted amino acid sequences revealed three amino acid differences suggesting these residues are not critical to CGRP function.

Adrenomedullin promotes formation of xenografted endometrial tumors by stimulation of autocrine growth and angiogenesis

The angiogenic peptide adrenomedullin (ADM) has been implicated as a mediator of the increased risk of endometrial hyperplasia and cancer resulting from the use of tamoxifen for the treatment and prevention of breast cancer. ADM has been shown to be induced by tamoxifen in the endometrium and to be a growth factor for endometrial endothelial cells in vitro. We have now shown ADM to be strongly angiogenic in the mouse subcutaneous sponge angiogenesis assay. To examine the role of ADM in tumor growth, the ADM cDNA was transfected into endometrial carcinoma cells followed by xenografting into athymic mice. Two endometrial cancer cell lines were employed, those in which transfection and expression of ADM resulted in no effect on growthin vitro (Ishikawa cells) and those in which expressionof exogenous ADM stimulated in vitro growth (RL95.2 cells). A clear enhancement of tumor growth was seen with both cell lines but the effect was far greater with the RL95.2 cells. We conclude that ADM is pro-tumorigenic by stimulating either angiogenesis alone or by stimulating angiogenesis and carcinoma cell growth directly. The combined activities lead to a striking increase in tumor growth. These results provide the first direct evidence of tumorigenic activity of ADM and provide further support for ADMs involvement in tamoxifen induced endometrial neoplasia.

Expression of the leptin receptor in rat and human nodose ganglion neurones

There is evidence for interactions between leptin and cholecystokinin in controlling food intake. Since cholecystokinin acts on vagal afferent neurones, we asked whether the leptin receptor was also expressed by these neurones. Primers for different forms of the leptin receptor were used in reverse transcriptase-polymerase chain reaction (RT-PCR) of rat and human nodose ganglia. RT-PCR yielded products corresponding to the long (functional) form as well as short forms of the rat leptin receptor. Moreover, RT-PCR revealed the long form of the leptin receptor in a human nodose ganglion. The identities of RT-PCR products were confirmed by sequencing. Primers corresponding to leptin itself did not give RT-PCR products in nodose ganglia. Immunocytochemical studies revealed leptin-receptor immunoreactivity in neuronal cell bodies. Many neurones co-expressed the leptin and cholecystokinin type A receptors, or leptin receptor and cocaine- and amphetamine-related transcript. We conclude that vagal afferent neurones that express the cholecystokinin type A receptor and cocaine- and amphetamine-related transcript, may also express the long form of the leptin receptor providing a neurochemical basis for observations of interactions between cholecystokinin and leptin.

Rapid increase in cardiac adrenomedullin gene expression caused by acute pressure overload: effect of the renin-angiotensin system on gene expression

To determine whether acute pressure overload (POL) can stimulate adrenomedullin (AM) production, the response of ventricular AM gene expression and plasma AM concentration to aortic banding was investigated in the rat. Furthermore, any link between AM expression and the renin-angiotensin system (RAS) enhanced by acute POL was examined using: a Ca channel blocker (manidipine), an angiotensin II type 1 receptor antagonist (candesartan), and an angiotensin-converting enzyme inhibitor (quinapril). Rats with acute POL produced by suprarenal aortic banding were studied 1, 5 and 14 days after surgery. Plasma AM concentrations in banded rats at day 1 increased 1.49-fold (p<0.01), then gradually declined to near the control level at day 14. Plasma AM concentrations correlated with plasma renin activity (PRA) (p<0.001). Adrenomedullin mRNA expression in the left ventricle (LV) increased 1.35-fold (p<0.05) at day 1. This increase was not significant at either 5 or 14 days after surgery. Adrenomedullin mRNA expression in the right ventricle on days 1 and 5 increased by 1.46-fold (p<0.05) and 1.52-fold (p<0.05), respectively. Candesartan, quinapril and manidipine reduced systolic blood pressure equally and activated PRA at day 1. However, augmented LV AM gene expression was suppressed completely by candesartan and quinapril, but remained unaffected by manidipine. In conclusion, POL induces a rapid increase in cardiac AM gene expression and in plasma AM concentrations. Cardiac AM transcription could therefore be partly regulated by RAS in suprarenal aortic banding rats.

Effect of Brn-3a deficiency on CGRP-immunoreactivity in the dorsal root ganglion

Immunohistochemistry for calcitonin gene-related peptide (CGRP) was performed on the dorsal root ganglion (DRG) and spinal cord in wildtype and knockout mice for Brn-3a. CGRP-immunoreactive (-IR) neurons were abundant in the DRG of wildtype, heterozygous and knockout mice. Cell size analysis revealed that CGRP-IR neurons were of various sizes in wildtype and heterozygous mice. In the knockout mice, however, most of CGRP-IR neurons were small. In the spinal cord of knockout mice, the number of CGRP-IR fibers increased in the dorsal column but decreased in the deep part of the dorsal horn. The loss of Brn-3a may have different effects on CGRP-IR expression in small and large DRG neurons.

Regulation of calcitonin gene-related peptide expression in vitro: possibility of a new role for leukemia inhibitory factor

Calcitonin-gene related peptide is among a group of peptides whose expressions are down-regulated following peripheral nerve damage. It is known that this is probably due to deprivation of some target-derived neurotrophic factors, mainly of nerve growth factor though positive effect of other factors, for example that of leukemia inhibitory factor on galanin has also been demonstrated. In this study, the effects of leukemia inhibitory factor and nerve growth factor on calcitonin gene related peptide expression in cultured dorsal root ganglion explants and in their outgrowing axons were examined. Lumbar dorsal root ganglia with short pieces of peripheral nerves were removed from adult mice and explanted into collagen gels. They were covered with RPMI 1640 culture medium and left in an incubator for 2 days after which they were fixed. These whole mount preparations with outgrowing axons were stained with an antibody against calcitonin gene related peptide. Following microscopic examination and imaging, sections were cut from the cultured ganglia as well as from some freshly taken normal ones and they were also stained to determine calcitonin gene related peptide immunoreactivity in the primary sensory neurons. The results demonstrated that besides the positive effect of nerve growth factor on the expression of this peptide in outgrowing axons, leukemia inhibitory factor also supported the expression of calcitonin gene related peptide in the primary sensory neurons of adult mouse lumbar dorsal root ganglia and in their outgrowing axons in vitro. When the time course of changes in calcitonin gene related peptide expression in dorsal root ganglia and the up-regulation of leukemia inhibitory factor at the site of a peripheral nerve injury in vivo are considered together, this novel finding may lead to new explanations for the changes in neuropeptide expression following axotomy.

Adrenomedullin, calcitonin gene-related peptide and their receptors: evidence for a decreased placental mRNA content in preeclampsia and HELLP syndrome

OBJECTIVE

The human placenta expresses a variety of vasoactive substances and neuropeptides, which play an important role in the regulation of placental blood flow in both the maternal and foetal compartment and are therefore of critical importance for foetal growth and development. Our study was planned to examine placental mRNA amounts of vasodilatory adrenomedullin (AM), calcitonin gene-related peptide (CGRP) and their receptors (AM-R and CGRP-R) in preeclampsia and HELLP syndrome (hemolysis, elevated liver enzymes, low platelets). These are severe maternal conditions leading to an altered uteroplacental and fetoplacental perfusion and a higher risk for foetal growth retardation, premature delivery, infant mortality, and even maternal death.

STUDY DESIGN

We included 17 patients with preeclampsia, four women with HELLP syndrome and 34 controls. After delivery, the mRNA levels of AM, AM-R, CGRP, CGRP-R, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and -actin were measured in placental villi and chorionic plates using quantitative real-time PCR.

RESULTS

AM/-actin and AM/GAPDH mRNA ratios were significantly lower in placental villi in preeclampsia than in controls (P<0.05) as were CGRP/-actin and CGRP/GAPDH mRNA ratios in chorionic plates (P<0.05). Placental AM-R and CGRP-R mRNA amounts were unaffected.

CONCLUSION

Our data show a reduction of AM and CGRP mRNAs in contrast to unchanged mRNA levels of their receptors in placenta specimens of women with preeclampsia or HELLP syndrome.

Involvement of alpha-calcitonin gene-related peptide in monophosphoryl lipid A-induced delayed preconditioning in rat hearts

Recent study has shown that monophosphoryl lipid A-induced delayed preconditioning enhanced preservation with cardioplegia and that the protective effects of monophosphoryl lipid A were related to stimulation of calcitonin gene-related peptide (CGRP) release. The purpose of the present study was to explore whether the elevated release of CGRP induced by monophosphoryl lipid A is secondary to stimulation of CGRP synthesis via the nitric oxide (NO) pathway and to characterize the isoform of CGRP. Sprague-Dawley rats were pretreated with monophosphoryl lipid A 24 h before the experiment, and then the left main coronary artery of rat hearts was subjected to 1 h occlusion followed by 3 h reperfusion. Infarct size, plasma creatine kinase activity, the plasma level of CGRP, and the expression of CGRP isoforms (alpha- and beta-CGRP) mRNA in lumbar dorsal root ganglia were measured. Pretreatment with monophosphoryl lipid A (500 microg/kg, i.p.) significantly reduced infarct size and creatine kinase release. Monophosphoryl lipid A caused a significant increase in the expression of alpha-CGRP mRNA, but not of beta-CGRP mRNA, concomitantly with an increase in plasma concentrations of CGRP, and the increased level of CGRP expression happened before stimulation of CGRP release. The effect of monophosphoryl lipid A was completely abolished by pretreatment with L-nitroarginine methyl ester (L-NAME, 10 mg/kg, i.p.), an inhibitor of NO synthase or capsaicin (50 mg/kg, s.c.), which selectively depletes transmitters in capsaicin-sensitive sensory nerves. The results suggest that the delayed cardioprotection afforded by monophosphoryl lipid A involves the synthesis and release of CGRP via the NO pathway, and that the protection is mainly mediated by the alpha-CGRP isoform.

NGF modulates CGRP synthesis in human B-lymphocytes: a possible anti-inflammatory action of NGF?

We investigated whether the sensory neuropeptide, calcitonin gene-related peptide (CGRP), could be synthesised by human lymphocytes. Our results indicate that in activated B-cells, there is a strong expression of CGRP gene transcripts, which is almost absent in resting cells. Since B-cells autocrinally produce NGF, the neutralisation of endogenous NGF by anti-NGF antibodies resulted in a marked reduction in CGRP expression in both resting and activated B-cells. Thus, NGF appears to directly affect the synthesis of CGRP in B-cells as in sensory neurons. By regulating CGRP synthesis in lymphocytes and neuronal cells, NGF can influence the intensity and duration of the immune response.

Thyroid hormone and retinoids affect motoneuron phenotype and reaction after axotomy in the spinal cord of adult rats

Motoneuron phenotype in the spinal cord is regulated by an intrinsic genetic program, extrinsic environmental signals and target-derived molecules. Axonal lesions trigger a phenotype switch to foster repair phenomena and axonal re-growth. We have investigated the influence of the long-term treatment with thyroid hormone and all trans retinol palmitate (RA) on motoneuron phenotype and spinal cord reaction to axotomy in adult male rats. Neurochemical markers, investigated by in situ hybridization and immunocytochemistry, included choline acetyltransferase (ChAT), calcitonin gene-related peptide (CGRP) and neurotrophin low affinity receptor p75. Treatment was administered for 56 days and then mid-thigh sciatic axotomy was performed on a number of animals from each experimental groups; the rats were examined 9 days after surgery. The results indicate that: (1) Number and size of ChAT-immunoreactive neurons in the lumbar tract of the spinal cord was reduced in hypothyroid compared to control rats, whereas steady-state level of ChAT mRNA in labelled motoneurons failed to be modified by hypo and hyperthyroidism, but was increased by RA administration; (2) none of the administered treatments did alter CGRP mRNA level, whereas all of them influenced the axotomy-induced changes of motoneuron phenotype; (3) in hyperthyroid rats ChAT mRNA level of lumbar motoneurons not reduced homolateral to lesion while the number of ChAT-IR profiles was pronouncedly reduced; (4) up-regulation of p75 induced by peripheral nerve lesion was reduced in RA-treated rats. These data indicate that the motoneuron phenotype is regulated by transcription factors, which also play a role in phenotype switch regulation after axotomy.

The heme oxygenase-1 pathway is involved in calcitonin gene-related peptide-mediated delayed cardioprotection induced by monophosphoryl lipid A in rats

In order to explore whether monophosphoryl lipid A (MLA)-induced delayed cadioprotection is mediated by calcitonin gene-related peptide (CGRP) and the regulatory effect of inducible heme oxygenase isorform (HO-1)/carbon monoxide (CO) on CGRP synthesis and release, the expression of CGRP and HO-1 in dorsal root ganglia (DRG) and CGRP concentration in plasma were determined in rats. Pretreatment with MLA (500 microg/kg, i.p.) significantly reduced infarct size and creatine kinase release after the 45-min coronary artery occlusion and 180-min reperfusion. MLA caused a significant increase in the expression of CGRP and HO-1 and plasma concentrations of CGRP. The cardioprotection as well as the synthesis and release of CGRP induced by MLA were completely abolished by pretreatment with zinc protoporphrin IX (ZnPP-9), an inhibitor of HO-1, or by capsaicin (50 mg/kg, s.c.), which selectively depletes transmitters in capsaicin-sensitive sensory nerves. Pretreatment with Znpp-9 had no effect on HO-1 expression, but capsaicin abrogated the expression of HO-1 induced by MLA in DRG. These results suggest that the delayed cardioprotection afforded by MLA is mediated by CGRP via activation of the HO-1 pathway.

A novel class of peptides with facilitating action on neuronal nicotinic receptors of rat chromaffin cells in vitro: functional and molecular dynamics studies

Peptides related to the N-terminal region of calcitonin gene-related peptide (CGRP) were tested for their ability to modulate neuronal nicotinic acetylcholine receptors (nAChRs) of rat cultured chromaffin cells under whole cell patch-clamp conditions. Although CGRP(1-7) and CGRP(2-7) depressed responses mediated by nAChRs, CGRP(1-6), CGRP(1-5), or CGRP(1-4) rapidly and reversibly potentiated submaximal nicotine currents while sparing maximal currents. CGRP(1-3) was inactive. The threshold concentration for the enhancing effect of CGRP(1-6) was 0.1 microM. CGRP(1-5) or CGRP(1-4) were less effective than CGRP(1-6). Coapplication of CGRP(1-6) and of the allosteric potentiator physostigmine (0.5 microM) gave additive effects on nicotine currents. CGRP(1-6) did not enhance responses generated by muscle-type nicotinic receptors of cultured myoblasts or by gamma-aminobutyric acid(A) receptors expressed by human embryonic kidney cells. Molecular dynamics (MD) simulations suggested that CGRP(1-7) exhibited a relatively rigid ring structure imparted by the disulfide bridge between Cys(2) and Cys(7). The circular dichroism (CD) spectrum recorded from the same peptide was in agreement with this result. Shorter peptides, missing such a bridge, exhibited propensity for alpha-helix configuration. Replacing Cys(7) with Ala yielded CGRP(1-7A), a fragment with partial alpha-helix structure and ability to enhance nicotine currents. CD measurements on CGRP(1-6) were compatible with these MD structural findings. Short terminal fragments of CGRP represent a novel class of substances with selective, rapid, and reversible potentiation of nAChRs.