Neuropeptide Y in phaeochromocytomas and ganglioneuroblastomas

Neuropeptide Y Peptide Family and Cancer: Antitumor Therapeutic Strategies

Currently available data on the involvement of neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) and their receptors (YRs) in cancer are updated. The structure and dynamics of YRs and their intracellular signaling pathways are also studied. The roles played by these peptides in 22 different cancer types are reviewed (e.g., breast cancer, colorectal cancer, Ewing sarcoma, liver cancer, melanoma, neuroblastoma, pancreatic cancer, pheochromocytoma, and prostate cancer). YRs could be used as cancer diagnostic markers and therapeutic targets. A high Y1R expression has been correlated with lymph node metastasis, advanced stages, and perineural invasion; an increased Y5R expression with survival and tumor growth; and a high serum NPY level with relapse, metastasis, and poor survival. YRs mediate tumor cell proliferation, migration, invasion, metastasis, and angiogenesis; YR antagonists block the previous actions and promote the death of cancer cells. NPY favors tumor cell growth, migration, and metastasis and promotes angiogenesis in some tumors (e.g., breast cancer, colorectal cancer, neuroblastoma, pancreatic cancer), whereas in others it exerts an antitumor effect (e.g., cholangiocarcinoma, Ewing sarcoma, liver cancer). PYY or its fragments block tumor cell growth, migration, and invasion in breast, colorectal, esophageal, liver, pancreatic, and prostate cancer. Current data show the peptidergic system's high potential for cancer diagnosis, treatment, and support using Y2R/Y5R antagonists and NPY or PYY agonists as promising antitumor therapeutic strategies. Some important research lines to be developed in the future will also be suggested.

Proneuropeptide Y and neuropeptide Y metabolites in healthy volunteers and patients with a pheochromocytoma or paraganglioma

Neuropeptide Y (NPY1-36) is a vasoconstrictor peptide co-secreted with catecholamines by sympathetic nerves, the adrenal medulla, and neoplasms such as pheochromocytomas and paragangliomas (PPGLs). It is produced by the intracellular cleavage of proNPY and metabolized into multiple fragments with distinct biological activities. NPY immunoassays for PPGL have a diagnostic sensitivity ranging from 33 to 100%, depending on the antibody used. We have validated a multiplex micro-UHPLC-MS/MS assay for the specific and sensitive quantification of proNPY, NPY1-39, NPY1-37, NPY1-36, NPY2-36, NPY3-36, NPY1-35, NPY3-35, and the C-flanking peptide of NPY (CPON) (collectively termed NPYs), and determined the NPYs reference intervals and concentrations in 32 PPGL patients before, during, and after surgery. Depending on the peptide measured, NPYs were above the upper reference limit (URL) in 20% to 67% of patients, whereas plasma free metanephrine and normetanephrine, the gold standard for PPGL, were above the URL in 40% and 87% of patients, respectively. Age, sex, tachycardia, and tumor localization were not correlated with NPYs. Plasma free metanephrines performed better than NPYs in the detection of PPGL, but NPYs may be a substitute for an early diagnosis of PPGL for patients that suffer from severe kidney impairment or receiving treatments that interfere with catecholamine reuptake.

Targeted Orexin and Hypothalamic Neuropeptides for Migraine

The hypothalamus is involved in the regulation of homeostatic mechanisms and migraine-related trigeminal nociception and as such has been hypothesized to play a central role in the migraine syndrome from the earliest stages of the attack. The hypothalamus hosts many key neuropeptide systems that have been postulated to play a role in this pathophysiology. Such neuropeptides include but are not exclusive too orexins, oxytocin, neuropeptide Y, and pituitary adenylate cyclase activating protein, which will be the focus of this review. Each of these peptides has its own unique physiological role and as such many preclinical studies have been conducted targeting these peptide systems with evidence supporting their role in migraine pathophysiology. Preclinical studies have also begun to explore potential therapeutic compounds targeting these systems with some success in all cases. Clinical efficacy of dual orexin receptor antagonists and intranasal oxytocin have been tested; however, both have yet to demonstrate clinical effect. Despite this, there were limitations in these cases and strong arguments can be made for the further development of intranasal oxytocin for migraine prophylaxis. Regarding neuropeptide Y, work has yet to begun in a clinical setting, and clinical trials for pituitary adenylate cyclase activating protein are just beginning to be established with much optimism. Regardless, it is becoming increasingly clear the prominent role that the hypothalamus and its peptide systems have in migraine pathophysiology. Much work is required to better understand this system and the early stages of the attack to develop more targeted and effective therapies aimed at reducing attack susceptibility with the potential to prevent the attack all together.

Therapeutic potential of neuropeptide Y (NPY) receptor ligands

Neuropeptide Y (NPY) is widely distributed in the human body and contributes to a vast number of physiological processes. Since its discovery, NPY has been implicated in metabolic regulation and, although interest in its role in central mechanisms related to food intake and obesity has somewhat diminished, the topic remains a strong focus of research concerning NPY signalling. In addition, a number of other uses for modulators of NPY receptors have been implied in a range of diseases, although the development of NPY receptor ligands has been slow, with no clinically approved receptor therapeutics currently available. Nevertheless, several interesting small molecule compounds, notably Y2 receptor antagonists, have been published recently, fueling optimism in the field. Herein we review the role of NPY in the pathophysiology of a number of diseases and highlight instances where NPY receptor signalling systems are attractive therapeutic targets.

Expression of peptide YY in human brain and pituitary tissues

Expression of peptide YY (PYY) in the human brain and pituitary tissues was studied by radioimmunoassay, immunocytochemistry, and reverse transcription polymerase chain reaction. The polyclonal antibody raised against human PYY(1-36) in a rabbit was used in the assay, which showed 100% cross-reactivity with PYY(3-36) and no significant cross-reactivity with other peptides including neuropeptide Y and pancreatic polypeptide. The highest concentration of immunoreactive PYY was found in the hypothalamus (0.44+/-0.060 pmol/g of wet weight, mean +/- SEM, n=8), followed by the pituitary (0.41+/-0.16 pmol/g of wet weight, n=3). Reverse-phase high performance liquid chromatography of tissue extracts of human rectum and cortical brain showed a peak eluted in the position of authentic PYY(1-36) and PYY(3-36). Immunocytochemistry showed positive immunostaining for PYY in neurons of the paraventricular, arcuate, and supraoptic nuclei of the human hypothalamus. Moreover, reverse transcription polymerase chain reaction analysis showed expression of mRNA for PYY in human brain and pituitary tissues. The present study has shown for the first time expression of PYY in the human brain and pituitary tissues, suggesting a role for PYY as a neurotransmitter, in the neuroendocrine physiology, such as regulation of appetite and energy expenditure and modulation of pituitary hormone secretion.

Immunolocalization of urotensin II and its receptor in human adrenal tumors and attached non-neoplastic adrenal tissues

Urotensin II (UII), first identified from goby urophysis, is a potent vasoactive peptide hormone and an endogenous ligand for an orphan G protein-coupled receptor GPR14, now named urotensin II receptor (UT-R). In addition to its vascular actions, UII has been shown to have mitogenic effects on tumor growth and some regulatory effects on adrenal steroidogenesis. In the present study, we examined expression of UII and UT-R in human adrenal tumors and attached non-neoplastic adrenal tissues by immunohistochemistry. Both UII and UT-R were immunolocalized in tumor cells of all adrenal tumors examined: 8 cases of cortisol-producing adenomas, 8 cases of aldosterone-producing adenomas, 2 cases of non-functioning adenomas, 17 cases of adrenocortical carcinomas, and 8 cases of pheochromocytomas. In attached adrenals, immunoreactivity for UII was detected in medulla, but much weaker in the cortex than in cortical tumors, suggesting that expression of UII was up-regulated in neoplastic adrenocortical tissues. No significant differences were found in the degree of immunoreactivity for UT-R between the tumors and the attached adrenal tissues. The present study showed that both UII and UT-R were expressed in the adrenal tumors and attached non-neoplastic adrenal tissues, and suggests possible roles of UII and UT-R in tumor growth and/or secretory activities of these tumors.

Neuropeptide Y expression in phaeochromocytomas: relative absence in tumours from patients with von Hippel-Lindau syndrome

Phaeochromocytomas are rare neuroendocrine tumours that produce catecholamines and numerous secretory proteins and peptides, including neuropeptide Y (NPY), a vasoactive peptide with influences on blood pressure. The production of catecholamines and NPY by phaeochromocytomas is highly variable. This study examined influences of hereditary factors and differences in catecholamine production on tumour expression of NPY, as assessed by quantitative PCR, enzyme immunoassay and immunohistochemistry. Phaeochromocytomas included hereditary adrenaline-producing tumours (adrenergic phenotype) in multiple endocrine neoplasia type 2 (MEN 2), predominantly noradrenaline-producing tumours (noradrenergic phenotype) in von Hippel-Lindau (VHL) syndrome, and other adrenergic and noradrenergic tumours where there was no clear hereditary syndrome. NPY levels in phaeochromocytomas from VHL patients were lower (P<0.0001) than in those from MEN 2 patients for both mRNA (84-fold difference) and the peptide (99-fold difference). These findings were supported by immunohistochemistry. NPY levels were also lower in VHL tumours than in those where there was no hereditary syndrome. Relative absence of expression of NPY in phaeochromocytomas from VHL patients when compared with other groups appears to be largely independent of differences in catecholamine production and is consistent with a unique phenotype in VHL syndrome.

Role of NPY for vasoregulation in the splanchnic circulation during portal hypertension

Vascular dysfunction in the splanchnic circulation during portal hypertension is characterized by enhanced NO-mediated vasorelaxation and vascular hyporeactivity to norepinephrine that lead to arterial vasodilation. NPY most likely counteracts both of these key features. Firstly, NPY appears to inhibit Ach- and PNS-induced vasorelaxation in mesenteric arteries. This effect is more pronounced in portal hypertensive rats as compared to control, and most likely reflects the inhibition of increased e- and nNOS-derived NO-synthesis during portal hypertensive conditions. Secondly, NPY sensitizes the mesenteric vasculature to alpha(1)-adrenergic vasoconstriction. Most importantly, in portal hypertensive rats but not in sham rats NPY markedly augments vascular contractility and thereby corrects vascular hyporeactivity. Both actions of NPY increase vascular tone and may well act synergistically in the splanchnic circulation during portal hypertension. Moreover, the vasoconstrictive effects of NPY are most pronounced at particularly high levels of alpha(1)-adrenergic activity. Therefore, it appears that NPY becomes increasingly important for optimizing adrenergic vasoconstriction at particularly high adrenergic drive and also for playing a predominant role for vascular homeostasis. Cirrhotic patients present with elevated circulating plasma levels of NPY, which appears to be independent from the severity of liver dysfunction and to correlate with portal pressure. This finding indicates enhanced NPY release during portal hypertension that may represent a compensatory mechanism aimed at counterbalancing arterial vasodilation by restoring the efficacy of endogenous catecholamines and inhibiting vasodilative drive in the splanchnic circulation.

Expression of urocortin 3/stresscopin in human adrenal glands and adrenal tumors

Urocortin 3 (Ucn 3)/stresscopin (SCP) is a novel peptide of the corticotropin-releasing factor (CRF) family and is a specific ligand for the CRF type 2 receptor. In the present study, we studied expression of Ucn3/SCP in the normal adrenal and adrenal tumors by radioimmunoassay and reverse transcriptase-polymerase chain reaction (RT-PCR). High concentrations of immunoreactive (IR)-Ucn3 were present in the normal portions of adrenal glands (4.2+/-0.51 pmol/g wet weight, mean+/-S.E.M., n = 14), and the levels were higher than those in the brain. IR-Ucn3 was also detected in the tumor tissues of aldosterone-secreting adenomas (6.2+/-0.6 pmol/g wet weight, n = 10), cortisol-secreting adenomas (5.0+/-1.2 pmol/g wet weight, n = 4), and pheochromocytomas (1.9+/-0.4 pmol/g wet weight, n = 7). Reverse phase high performance liquid chromatography showed that IR-Ucn3 in normal portions of adrenal glands and aldosterone-secreting adenomas was eluted mainly in the positions of Ucn3 and SCP with several minor peaks eluting earlier. The RT-PCR showed expression of Ucn3 mRNA in normal portions of adrenal gland (positive ratio; 4/4), aldosterone-secreting adenomas (3/4), cortisol-secreting adenomas (1/3) and pheochromocytomas (6/7). These findings indicate that Ucn3 is produced in normal adrenal and adrenal tumors (both adrenocortical tumors and pheochromocytomas), and suggest that Ucn3 acts as an autocrine or paracrine regulator in normal adrenal and adrenal tumors.

Modulator role of neuropeptide Y in human vascular sympathetic neuroeffector junctions

Reverse transcription polymerase chain reaction (RT-PCR) studies identified the mRNA coding for the Y1 and Y2 receptors in human mammary artery/vein and saphenous vein biopsies. Y1 receptors are expressed in vascular smooth muscles and potentiate the contractile action of sympathetic co-transmitters, adenosine triphosphate (ATP) and noradrenaline (NA); BIBP 3226, a competitive Y1 receptor antagonist, blocked the neuropeptide Y (NPY)-induced modulation. The Y2 receptor is expressed in sympathetic nerves terminals and modulates the pool of sympathetic co-transmitters released at the neuroeffector junction. NPY plays a dual role as a modulator of sympathetic co-transmission; it facilitates vascular smooth muscle reactivity and modulates the presynaptic release of ATP and NA. Sympathetic reflexes regulate human vascular resistance, where NPY plays a modulator role of paramount importance following increased sympathetic discharges, such as stress and vascular disease.

Functional expression of neuropeptide Y receptors in human neuroblastoma cells

Expression of neuropeptide Y (NPY) receptors in human SK-N-MC neuroblastoma cells was investigated. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that Y1, Y4, and Y5 receptors were expressed in these cells. Expression was confirmed by Western blot and immunocytochemistry demonstrated abundant presence of all three receptors on cell membranes. NPY peptide was also expressed in these cells, but other members of the larger peptide family (peptide YY and pancreatic polypeptide) were not expressed. Incubation with U0126, a specific mitogen-activated protein kinase (MAPK) inhibitor, decreased cell number in serum-free medium culture. Since NPY activates MAPK via different subtypes of NPY receptors, results suggest that endogenously expressed NPY may control proliferation of these cells through a paracrine/autocrine mechanism.

Urocortins as cardiovascular peptides

Urocortins (Ucn) 1, 2 and 3, human homologues of fish urotensin I, form the corticotropin-releasing factor (CRF) family, together with CRF, urotensin I and sauvagine. Ucn 3 is a novel member of this family and is a specific ligand for CRF type 2 receptor. CRF type 2 receptor is thought to mediate the stress-coping responses, such as anxiolysis, anorexia, vasodilatation, a positive inotropic action on myocardium and dearousal. Endogenous ligands for the CRF type 2 receptor expressed in the cardiovascular tissues, such as the myocardium, have long been unknown. We have shown expression of Ucn 3 as well as Ucn 1 in the human heart. Ucn 3 is also expressed in the kidney, particularly distal tubules. Studies in various rat tissues showed that high concentrations of immunoreactive Ucn 3 were found in the pituitary gland, adrenal gland, gastrointestinal tract, ovary and spleen in addition to the brain, heart and kidney. These observations suggest that Ucn 3 is expressed in various tissues including heart and kidney, and may regulate the circulation in certain aspects of stress and diseases, such as inflammation. Ucn 1 and 3 appear to have important pathophysiological roles in some cardiovascular diseases.

Expression of urotensin II and its receptor in adrenal tumors and stimulation of proliferation of cultured tumor cells by urotensin II

Urotensin II is a potent vasoactive peptide, which was originally isolated from fish urophysis. We studied expression of urotensin II and its receptor mRNAs in the tumor tissues of adrenocortical tumors, pheochromocytomas and neuroblastomas. Effects of exogenously added urotensin II on cell proliferation were studied in a human adrenocortical carcinoma cell line, SW-13 and a human renal cell carcinoma cell line, VMRC-RCW. The reverse transcriptase polymerase chain reaction (RT-PCR) showed expression of urotensin II and its receptor mRNAs in all the samples examined; seven pheochromocytomas, nine adrenocortical adenomas (four with primary aldosteronism, four with Cushing syndrome and one with non-functioning adenoma), four adrenocortical carcinomas, one ganglioneuroblastoma and five neuroblastomas, as well as four normal portions of adrenal glands (cortex and medulla). Urotensin II-like immunoreactivity was detected in one of eight adrenocortical adenomas, two of four adrenocortical carcinomas, one of six pheochromocytomas, and one of five neuroblastomas by radioimmunoassay, but not in normal portions of adrenal glands (detection limit; 0.2pmol/g wet weight). Treatment with urotensin II for 24h significantly increased number of SW-13 cells (at 10(-8) and 10(-7)mol/l) and VMRC-RCW cells (at 10(-8)mol/l). These findings raise the possibility that urotensin II may act as an autocrine/paracrine growth stimulating factor in adrenal tumors.

Pheochromocytoma: an approach to antihypertensive management

Pheochromocytoma and paragangliomas are rare tumors of chromaffin tissue that secrete catecholamines either intermittently or continuously, producing hypertension with a constellation of symptoms and signs that can be frightening to the patient and that continue to provide perplexing problems for clinicians. With surgical treatment, symptoms will be relieved and hypertension normalized or ameliorated for patients who do not have malignant tumors. Appropriate antihypertensive drugs are used to manage hypertension, to control associated cardiovascular symptoms, and to prepare patients for operation. The question debated most often regarding medical therapy of pheochromocytoma is whether antihypertensive treatment regimens other than nonspecific alpha-blockade are just as effective and safe. Understanding the pathophysiologic mechanisms that sustain the hypertension and the pharmacology of antihypertensive agents allows better selection of antihypertensive therapy.

Expression of prolactin-releasing peptide and its receptor in the human adrenal glands and tumor tissues of adrenocortical tumors, pheochromocytomas and neuroblastomas

Adrenal tumors, such as pheochromocytomas, are known to express various peptides and their receptors. Prolactin-releasing peptide (PrRP) is a novel neuropeptide isolated from bovine hypothalamic tissues. In the present study, expression of PrRP receptor was studied in the human brain, pituitaries, adrenal glands and tumor tissues of adrenocortical tumors, pheochromocytomas, a ganglioneuroblastoma and neuroblastomas by reverse transcriptase polymerase chain reaction (RT-PCR) and Northern blot analysis. The presence of immunoreactive-PrRP in the adrenal glands and in these tumor tissues was studied by radioimmunoassay. Human brain tissues and pituitaries were obtained at autopsy. Normal portions of adrenal glands and tumor tissues were obtained at surgery. RT-PCR analysis showed expression of PrRP receptor in the human brain, pituitaries, normal portions of adrenal glands and various tumor tissues. Northern blot analysis showed high expression of PrRP receptor only in tumor tissues of pheochromocytomas, indicating that PrRP receptor expression is high in pheochromocytomas. Immunoreactive-PrRP was detected in normal portions of adrenal glands (0.162+/-0.024 pmol/g wet weight, n=4, mean+/-S.E.M.), four out of six cases of pheochromocytomas (0.050-7.9 pmol/g wet weight), one neuroblastoma and some adrenocortical tumors. The present study has shown that PrRP receptor mRNA was widely expressed in the brain tissues, pituitaries, adrenal glands and various tumors. The high expression of PrRP receptor in pheochromocytomas suggests potential pathophysiological roles of PrRP in these tumors.

Regulation of olfactory neurogenesis by amidated neuropeptides

The existence of stem cells in the CNS raises issues concerning the ability of nervous tissues to regenerate in the adult mammal and provides new perspectives on the treatment of degenerative disease and traumatic injury of the nervous system. These cells have a relatively limited range of locations within the nervous system and include cells of the rostral migratory stream, hippocampus, retina, and olfactory epithelium. The olfactory epithelium has been studied as a model of adult neuronal regeneration, with neuronal precursor/basal cells serving as the olfactory "stem cells." The identification of factors that promote neuronal proliferation or regeneration within the olfactory epithelium can provide clues to the process of adult mammalian nervous system repair and treatment. Multiple factors have been examined that appear to influence the proliferation and subsequent maturation of basal cells. These factors include nerve growth factor, fibroblast growth factor-2, epidermal growth factor, and insulin/insulin-like growth factor-1. Recently, two amidated neuropeptides, neuropeptide Y (NPY) and pituitary adenylate cyclase-activating polypeptide (PACAP38), identified in the olfactory epithelium have been shown to promote dramatically neuronal proliferation. The effects of NPY and PACAP suggest that amidated neuropeptides may serve a broad developmental and regenerative role in the mammalian olfactory epithelium.

Neuropeptide Y functions as a neuroproliferative factor

Neuropeptide Y (NPY) has a number of functions in mammalian physiology. Here we identify a role for NPY in promoting proliferation of postnatal neuronal precursor cells. NPY is synthesized in the postnatal olfactory epithelium by sustentacular cells, previously proposed to function only in structural support. Mice with a targeted deletion of NPY contain half as many dividing olfactory neuronal precursor cells as do controls. Furthermore, NPY-deficient mice develop significantly fewer olfactory neurons by adulthood. NPY acts on multipotent neuronal precursor or basal cells to activate rapidly and transiently the extracellular signal-regulated kinase (ERK)1/2 subgroup of mitogen-activated protein kinases. The NPY Y1 receptor subtype appears to mediate this effect. The ability of NPY to induce neuronal precursor proliferation is mediated by protein kinase C (PKC), indicating an upstream PKC-dependent activation of ERK1/2. These results indicate that NPY may regulate neuronal precursor proliferation in the adult mammal.

Levels of vasodilators (SP, CGRP) and vasoconstrictor (NPY) peptides in early human burns

An intact nociceptor system of primary afferent sensory nerves is important for the initiation of the inflammatory process and successful tissue repair. Dysfunction of this system could be a contributing factor for delayed wound healing in humans. We examined the levels of vasodilators [substance P (SP), calcitonin gene-related peptide (CGRP)] and a vasoconstrictor peptide [neuropeptide Y (NPY)] in the peripheral blood samples of patients with burns covering from 20 to 75% of body surface area. Thirteen patient samples were obtained immediately on admission (OA), which was within 12 h of the thermal injury, and 24 h post-admission (PA). Enzyme immunoassay techniques were used for the measurement of the neuropeptides. In addition, an inflammatory marker, tumour necrosis factor-alpha (TNF-alpha), and a myofibrillar protein, creatine kinase (CK), were examined and compared with levels in 13 control subjects. CGRP was high OA and the levels were maintained PA (P < 0.05). SP was also significantly high at both sampling times (P < 0.05). Although TNF-alpha and NPY were somewhat higher in the patients' samples than in the control samples, these levels were not statistically significant (P = NS). CK was higher OA (P < 0.01) than PA (P < 0.04), compared to controls. Plasma levels of SP and CGRP increased significantly in patients with thermal injuries. These peptides may yet be another group of neuromodulators playing a significant role in immune, pain, inflammatory and wound healing in burns.

Limited neuropeptide Y precursor processing in unfavourable metastatic neuroblastoma tumours

Neuropeptide Y (NPY) is found at high concentrations in neural crest-derived tumours and has been implicated as a regulatory peptide in tumour growth and differentiation. Neuroblastomas, ganglioneuromas and phaeochromocytomas with significant concentrations of NPY-like immunoreactivity were investigated for different molecular forms of NPY and for significance of proNPY processing. Gel-permeation chromatography identified intact NPY (1-36) in all tumours, whereas proNPY (69 amino acids) was detected only in control adrenal tissue and malignant neuroblastomas. Purification of NPY-like immunoreactivity in tumour extracts and structural characterization revealed that both NPY (1-36) and the truncated form NPY (3-36) was present. The degree of processing of proNPY to NPY in tumour tissue was lower in advanced neuroblastomas with regional or metastatic spread (stage 3 and 4) (n = 6), (41%, 12-100%, median, range), compared to the less aggressive stage 1, 2 and 4S tumours (n = 12), (93%; 69-100%), (P= 0.012). ProNPY processing of less than 50% was correlated with poor clinical outcome (P = 0.004). MYCN oncogene amplification was also correlated to a low degree of proNPY processing (P = 0.025). In summary, a low degree of proNPY processing was correlated to clinical advanced stage and poor outcome in neuroblastomas. ProNPY/NPY processing generated molecular forms of NPY with known differences in NPY-receptor selectivity, implicating a potential for in vivo modulation of NPY-like effects in tumour tissue.

Orexin-A in the human brain and tumor tissues of ganglioneuroblastoma and neuroblastoma

Regional distribution of orexin-A-like immunoreactivity in the human brain and pituitary, and the presence of orexin-A-like immunoreactivity in the tumor tissues of pheochromocytomas, ganglioneuroblastomas and neuroblastomas were studied by radioimmunoassay. Expression of orexin mRNA was studied by reverse transcriptase polymerase chain reaction (PCR) method. Orexin-A-like immunoreactivity was detected in every region of human brain, but not in the pituitary. The highest concentration of orexin-A-like immunoreactivity in the human brain was found in hypothalamus (17.8 +/- 4.3 pmol/g wet weight, mean +/- SEM, n = 7), followed by thalamus, medulla oblongata, and pons. Orexin-A-like immunoreactivity was detected in the tumor tissues of ganglioneuroblastoma and neuroblastoma, but not in the tumor tissues of pheochromocytoma. Reverse phase high performance liquid chromatographic analyses of the orexin-A-like immunoreactivity in the human brain extracts and neuroblastoma extracts showed a single immunoreactive peak, which was eluted in an identical position to synthetic human orexin-A. Orexin mRNA was expressed in the hypothalamus and in the tumor tissues of ganglioneuroblastoma and neuroblastoma. These findings suggest that orexin-A is produced in the hypothalamus and transported to various brain regions via axons. In addition, this study has shown for the first time the production of orexin-A by ganglioneuroblastomas and neuroblastomas.

Production and secretion of two vasoactive peptides, adrenomedullin and endothelin-1, by cultured human adrenocortical carcinoma cells

The production and secretion of peptides by adrenocortical tumors have not been well studied. We therefore studied the production and secretion of two vasoactive peptides, adrenomedullin and endothelin-1 in SW-13 human adrenocortical carcinoma cells by radioimmunoassay and Northern blot analysis. Both immunoreactive-adrenomedullin and immunoreactive-endothelin were detected in the culture medium of SW-13 cells (27.7 +/- 1.6 fmol/10 (5) cells/24 h and 11.0 +/- 0.8 fmol/10 (5) cells/24 h, respectively, mean +/- SEM, n = 6). Northern blot analysis showed the expression of adrenomedullin mRNA and endothelin-1 mRNA in SW-13 cells. On the other hand, no significant amount of calcitonin gene-related peptide, corticotropin-releasing hormone, neuropeptide Y, or urocortin was secreted by SW-13 cells. Treatment with ACTH (10(-9)-10(-7) mol/l), angiotensin II (10(-9)-10(-7) mol/l), or dexamethasone (10(-8)-10(-6) mol/l) for 24 h had no significant effects on immunoreactive-adrenomedullin levels and immunoreactive-endothelin levels in the culture medium of SW-13. Treatment with tumor necrosis factor (TNF)-alpha (20 ng/ml) increased significantly both immunoreactive-adrenomedullin levels and immunoreactive-endothelin levels in the culture medium. Interferon-gamma (100 U/ml) increased the immunoreactive-endothelin levels, but not immunoreactive-adrenomedullin levels, whereas interleukin-1 (IL-1)beta (10 ng/ml) increased immunoreactive-adrenomedullin levels, but not immunoreactive-endothelin levels. These findings indicate that SW-13 human adrenocortical carcinoma cells produce and secrete two vasoactive peptides, adrenomedullin, and endothelin-1 and that the secretion of these two peptides is modulated differently by cytokines.

Release of neuropeptide Y and hemodynamic changes during surgical removal of human pheochromocytomas

This study investigates the release of Neuropeptide Y from eight human pheochromocytomas. Profil immunoreactive Neuropeptide Y (Ir-NPY) levels during the management of surgery were compared with these of norepinephrine (NE) while hemodynamics were monitored. Plasma IrNPY and NE levels increased during tumor manipulation and returned to near normal one hour after operation. However, Ir-NPY levels remained high just after tumor resection while NE levels were significantly decreased. At tumor manipulation and just after tumor resection, plasma Ir-NPY levels were correlated with the systemic vascular resistances (SVR) (r = 0.74; P<0.04 and r = 0.86; P<0.006 respectively). No correlation was found either between plasma Ir-NPY and NE levels or between plasma NE levels and SVR. The release of Ir-NPY from tumor tissue, studied by a superfusion method, exhibited a significant correlation with the plasma Ir-NPY concentrations at the time of corresponding tumor resection (r = 0.95; P<0.007). Chromatographic analysis showed that Ir-NPY in plasma and outflow migrate as human NPY (1-36). These results confirmed that in pheochromocytoma, plasma NPY mainly originates from the tumor and argue for an important role of NPY in pheochromocytoma hypertension as indicated by the correlation between the Ir-NPY levels and the SVR.

Calcitonin gene-related peptide and other neuropeptides in the plasma of patients with soft tissue injury

Calcitonin gene-related peptide [CGRP]--a powerful vasodilator, is a 37 amino acid peptide that is find primarily in the central and peripheral nervous system. It affects the regulation of local blood flow, smooth muscle tone and glandular secretion. It is an endocrine regulator and in the lungs it also exerts a bronchoconstricting effect. CGRP has a proliferative effect on human endothelial cells. Therefore, it is important for the formation of new vessels, example, in ischemia, inflammations, and in the healing of wounds. Plasma levels of CGRP are increase in patients with chronic cardiac failure and sepsis, indicating that CGRP may be another important peptide in chronic illness. We have therefore measured the release of this peptide and another sensory peptide [Substance P (SP)]; a vasoconstrictor peptide [Endothelin (ET)]; and a perivascular peptide [Neuropeptide Y (NPY)], within 24 hours of injury, in the plasma of patients with soft tissue injury. Neuropeptides were measure by enzyme immunoassay technique. Median: (lower quartile-upper quartile) in pmol/L CGRP level was elevated in patients [50.37: (12.4-110.9)] compared to controls [13.9: (10.9-36.96)] p<0.05; Endothelin and NPY did not vary much between groups p=NS; ET: patients [8.7: (1.7-87.1), controls 8.8: (1.7-32.9)]; NPY: Patients [11.7: (10.5-14.99), controls 11: (10.3-12.8)]. SP was increase in patients [302.3: (79.9-707.3)], than controls [5.6: (3.2-36.6)] p<0.05. Furthermore, Elastase (a decisive marker for inflammation and infectious complications), was measure (ng/L), and found to be slightly higher in patients (102: 25.5-223), than controls (91.8: 45.9-127). In summary, plasma levels of sensory peptides increased significantly, in patients with soft tissue injury, in contrast to vasocostrictor peptides that remained unchanged. These sensory peptides may yet be another group of neuromodulators playing a significant role in immune, pain, inflammatory and wound healing in soft tissue injury patients.

Plasma neuropeptide Y of children with neuroblastoma in relation to stage, age and prognosis, and tissue neuropeptide Y

The objective of this study was to relate plasma neuropeptide Y (NPY) concentrations of patients with neuroblastoma with the stage of the disease, the patients' age, the prognosis, the tumor mRNA expression and with the effect on tumor cell proliferation. Plasma NPY of 85 patients with neuroblastoma was measured by radioimmunoassay. The patients' median age was 18 months (range, three weeks-12 years). Ten children with childhood tumors that did not affect neurological or neuroendocrine structures and ten healthy children served as control groups. NPY mRNA expression in neuroblastoma tissue was assessed by Northern blot analysis. Proliferation of neuroblastoma cells (SK-N-MC and CHP 234) was evaluated by 5-bromo-2'-deoxyuridine incorporation during DNA synthesis in vitro. Plasma NPY levels were significantly higher in stage 3 (p < 0.05), 4 (p < 0.001) and 4S (p < 0.05) patients than in both control groups. Plasma levels above 8 pmol/l were only seen in stages 2 (17%), 3 (32%), 4 (45%) and 4S (44%). Seven of the 12 patients (58%) who died had NPY levels above 8 pmol/l (vs. 29% in survivors; p = 0.05). In patients with longer follow-up monitoring, relapse coincided with increasing NPY levels. There was no relationship between the patients' age and their plasma NPY concentrations (r = 0.08; p = 0.49). No relation was found between NPY mRNA expression in tumor tissue and NPY plasma concentrations of the ten patients (r = 0.08; p = 0.81). NPY in the supernatant of neuroblastoma cells did not alter the 5-bromo-2'-deoxyuridine incorporation during DNA synthesis. In summary, NPY plasma concentrations in patients with neuroblastoma relate to the stage of the disease. The relation to the prognosis is at the threshold of significance. No relation between tissue and plasma NPY, nor any effect of NPY on proliferation of tumor cells was found.

Human neuropeptide Y potentiates alpha1-adrenergic blood pressure responses in vivo

Human neuropeptide Y (hNPY) potentiates the postjunctional vasoconstrictor effects of alpha1-adrenoceptor agonists in animals and in human hand veins in vivo. We therefore hypothesized that such an interaction might also occur in the human arterial bed. With the present single-blind cross-over study in 12 healthy volunteers, the effect of subpressor doses of hNPY on the blood pressure response to alpha1-adrenoceptor stimulation was evaluated. Dose-response curves were constructed to intravenously infuse phenylephrine with and without coinfusion with two different doses of hNPY (1.4 and 14.3 pmol . kg-1 . min-1). Blood pressure, heart rate, and forearm blood flow were recorded, and plasma hNPY was determined. During infusion of the higher hNPY dose, which increased hNPY from 24.0 +/- 12.0 to 495.1 +/- 12.6 pmol/l, blood pressure curves were 2.4-fold shifted toward lower phenylephrine dose rates (P < 0.001). Forearm vascular resistance showed a similar trend, whereas the counterregulatory decrease of heart rate was similar in both groups. In contrast, the lower hNPY dose rate producing a fourfold increase in hNPY concentrations did not modify the response to phenylephrine. This in vivo study in humans demonstrates that hNPY induced potentiating effects on alpha1-adrenergic constriction also in the systemic arterial circulation and suggests that circulating hNPY may participate in the control of vascular tone.

Neuropeptide Y Y1 receptors in vascular pharmacology

The existence of neurogenic mediator candidates apart from noradrenaline and acetylcholine involved in the control of vascular tone has attracted enormous attention during the past few decades. One such mediator is neuropeptide Y (NPY), which is co-localized with noradrenaline in sympathetic perivascular nerves. Stimulation of sympathetic nerves in vitro and in vivo causes non-adrenergic vasoconstriction which can be blocked by experimental manipulations that inhibit NPY mechanisms. Thus, the vasopressor response to stimulation of sympathetic nerves can be attenuated by chemical or surgical sympathectomy, treatment with reserpine or other pharmacological agents, and tachyphylaxis to NPY or by NPY antagonists. The NPY field was long plagued by a lack of specific antagonists, but with the recently developed, selective, non-peptide and stable NPY antagonists it has now become possible to study subtypes of this receptor family. For instance, it has become clear that the NPY Y1 receptor mediates most of the direct peripheral effects of NPY on vascular tone. These antagonists promise to stimulate NPY research and will likely unravel the true significance of NPY in cardiovascular control under physiological conditions as well as in pathophysiological states.

Elevated plasma concentrations of neuropeptide Y in children and adults with chronic and terminal renal failure

Neuropeptide Y (NPY) is a peptide hormone that is expressed, stored, and released in sympathetic neurones together with noradrenaline. Elevated plasma concentrations of NPY have been reported in patients with neural crest tumors (neuroblastoma, pheochromocytoma) and following exercise. We studied plasma concentrations of NPY in children and adults with chronic and terminal renal failure and compared them with those in healthy controls. Neuropeptide Y was significantly higher in children and adolescents receiving peritoneal dialysis (5.3 +/- 2.8 pmol/L; n = 11 [mean +/- SD]) or hemodialysis (5.4 +/- 2.1 pmol/L; n = 14) than in healthy children (2.3 +/- 0.9 pmol/L; n = 19) or pediatric patients with impaired renal function who are not receiving dialysis (2.7 +/- 0.6 pmol/L; n = 8; mean glomerular filtration rate, 41 mL/min x 1.73 m2). There was a small but insignificant negative correlation between glomerular filtration rate and NPY concentrations in children with impaired renal function (r = 0.49; P = 0.25). In healthy adults, NPY concentration was similar to that in healthy children (1.8 +/- 1.0 pmol/L; n = 13), and it was significantly elevated in adults receiving hemodialysis (5.9 +/- 1.7 pmol/L; n = 16). No significant changes in NPY concentrations were found before and after hemodialysis in pediatric or adult patients. We conclude that plasma concentrations of NPY are elevated in patients with chronic renal failure who are receiving either peritoneal or hemodialysis, but not in patients with moderately impaired renal function. Whether elevated NPY concentration indicates increased sympathetic activity or is caused by reduced NPY clearance remains to be shown.

Production and secretion of adrenomedullin from glial cell tumors and its effects on cAMP production

The expression of adrenomedullin (ADM) and its mRNA was studied in human glial cell tumors and cultured glioblastoma cell lines, T98G and A172. Northern blot analysis showed that ADM mRNA was expressed in all brain tumors examined (three anaplastic astrocytomas and two glioblastomas multiforme) and in the glioblastoma cell lines. Immunoreactive (IR-) ADM was detectable in these brain tumors by radioimmunoassay (0.31-2.0 pmol/g wet weight), except for one anaplastic astrocytoma. Reverse phase high performance liquid chromatography of the tumor extracts showed a single peak eluting in the position of ADM-(1-52). IR-ADM concentrations in the cultured media of T98G cells were 205.5 +/- 8.4 fmol/10(5) cells/24 h (mean +/- SEM, n = 5). Treatment of T98G cells with interferon gamma or interleukin 1 beta increased the expression levels of ADM mRNA and the IR-ADM concentrations in the cultured media, whereas tumor necrosis factor alpha decreased them in a dose-dependent manner. Treatment with synthetic ADM-(1-52) (10(-8) or 10(-7) mol/l) increased the cAMP concentrations in the cultured media of T98G cells. These findings suggest that ADM is secreted from glial cell tumors and is related to the pathophysiology of these tumors.

Neuropeptide Y in human hand veins: pharmacologic characterization and interaction with cyclic guanosine monophosphate-dependent venodilators in vivo

The dorsal hand vein compliance technique was used to study direct vascular effects of human neuropeptide Y in vivo. Human neuropeptide Y is an endogenous vasoconstrictor peptide that is costored with norepinephrine in sympathetic nerve endings and coreleased with the catecholamine under various physiologic and pathologic conditions. Compared with the alpha 1-adrenergic agonist phenylephrine (geometric mean dose-rate that produces the half-maximal response [ED50]: 1.05 nmol/min; maximum venoconstriction [Emax] +/- SEM, expressed as a percentage of baseline compliance: 91% +/- 3%), human neuropeptide Y was nine times more potent (geometric mean ED50: 0.122 nmol/min; p < 0.001) but markedly less efficacious (Emax: 58% +/- 4%; n = 12; p < 0.001). Venoconstrictor effects of human neuropeptide Y lasted several hours and were unchanged by simultaneous administration of alpha-adrenergic antagonists but were readily reversed by nitroglycerin or bradykinin. The high responsiveness of subcutaneous veins to human neuropeptide Y indicates that human neuropeptide Y may regulate venous compliance and filling of the venous subcutaneous capacitance bed in vivo.

Production, characterization, and expression of neuropeptide Y by human pheochromocytoma

Neuropeptide Y (NPY) levels are increased in plasma and tumors of patients with pheochromocytoma. The present study was designed to evaluate plasma and tissue NPY levels simultaneously as well as to study its release and expression in patients with either adrenal or extraadrenal pheochromocytomas. Plasma NPY levels were higher (P < 0.01) in patients with adrenal tumors than in matched normal subjects and patients with extraadrenal tumors. NPY levels were also higher (P < 0.05) in adrenal than in extraadrenal tumors. Bioactive NPY (1-36) was the predominant form in plasma and tumors of patients with adrenal pheochromocytomas. In contrast, patients with extraadrenal pheochromocytomas had an abundance of NPY fragments. NPY mRNA was abundant in 11 of 13 adrenal tumors but in only 1 of 6 extraadrenal tumors. Moreover, NPY was coreleased with NE with manipulation of adrenal but not extraadrenal tumors. These findings indicate that increased NPY gene expression in adrenal pheochromocytomas accounts for the greater biosynthesis and storage of NPY in these tumors and that increased release of NPY results in elevated plasma NPY. Factors regulating NPY gene expression in pheochromocytoma and the role of NPY in the clinical manifestations of the disease remain to be elucidated.

Phaeochromocytoma--a laboratory experience

Thirteen phaeochromocytomas were found over five and a half years from 2,834 patient requests for tumour screens. HMMA (VMA) was the usual screening test requested. Free catecholamines were reported when specifically requested by clinicians and where the HMMA level was > 40 mumol/24 hr. HMMA and urinary free catecholamines were estimated using HPLC with electrochemical detection in acidified 24 hr collections. Noradrenaline was elevated in all thirteen, nine had raised adrenaline and two had raised levels of all three catecholamines. Urinary free catecholamines are the most appropriate analyte package in our circumstances for the diagnosis of phaeochromocytoma. HMMA if used alone could lead to false negative diagnoses but it has a role in minimising false negatives where urinary catecholamine results are normal.

Neuropeptide Y analog with selective antagonism of effects mediated by postjunctional Y1 receptors

Neuropeptide, a 36 amino acid peptide, is one of the most ubiquitous neuropeptides in the nervous system. It is released during stimulation of sympathetic nerves and is implicated as an important neurotransmitter regulating cardiovascular activity. Administration of neuropeptide Y results in vasoconstriction and inhibition of neurotransmitter release. However, the absence of any effective inhibitors of neuropeptide Y action have precluded the examination of its possible role in hypertension. Here we describe a synthetic hexapeptide (BRC 672), corresponding to residues 22-27 of neuropeptide Y. Following the administration of BRC 672 (6.7 mumol/kg), neuropeptide Y-induced pressor responses were reduced by 32-48% in a dose-dependent fashion. The inhibition was specific for neuropeptide Y, as the pressor response to phenylephrine, an alpha-adrenoceptor agonist, was unchanged. It was selective for the postsynaptic (neuropeptide Y Y1 receptor-mediated) vasoconstrictor activity, because the presynaptic (neuropeptide Y Y2 receptor-mediated) cardiac vagal inhibition evoked by injection of neuropeptide Y to rats was not affected. The hexapeptide inhibited the neuropeptide Y-induced increase in cytosolic free Ca2+ in mammalian cells expressing the cloned human neuropeptide Y Y1 receptor. Injections of BRC 672 significantly reduced blood pressure in anaesthetised rats and in conscious spontaneously hypertensive rats. Resting arterial blood pressure decreased from 136 +/- 4 mm Hg to 122 +/- 3 mm Hg and remained depressed 2 h after the administration of the hexapeptide in anaesthetised rats. In spontaneously hypertensive rats blood pressure was decreased for up to 4 h.

High levels of expression of neuropeptide Y mRNA in human phaeochromocytomas

1. Neuropeptide Y (NPY) gene expression in human phaeochromocytomas was investigated by measuring the levels of NPY mRNA and NPY-immunoreactivity (NPY-IR) in human phaeochromocytoma tissues in comparison with those in normal human adrenal tissues. 2. The amounts of NPY mRNA and NPY-IR in human phaeochromocytomas were 18 and 93 times higher, respectively, than those in normal adrenal glands. In contrast, beta-actin gene expression was similar in human phaeochromocytomas to that in normal adrenal glands. 3. The amount of NPY mRNA relative to total cellular RNA was 6-fold higher in phaeochromocytoma tissues than in normal human adrenal medulla, suggesting increased NPY gene expression in the tumour cells. 4. Induction of differentiation of PC12 rat phaeochromocytoma cells by compounds, such as dexamethasone and nerve growth factor, resulted in a marked increase in the NPY mRNA level. 5. These findings suggest that NPY gene expression is increased in well-differentiated human phaeochromocytoma cells. Its high level of expression could be responsible for the marked overproduction of NPY by this tumour.

Plasma neuropeptide Y in healthy children: influence of age, anaesthesia and the establishment of an age-adjusted reference interval

Plasma concentrations of neuropeptide Y, analysed in 112 healthy children, decreased significantly with age, while sex, discomfort induced by the sampling procedure or induction of general anaesthesia did not have a significant influence. An age-adjusted upper reference limit was established and proved to be useful when tested prospectively in 56 children with tumours. Two of 18 children with preliminary diagnosis of rhabdomyosarcoma had elevated plasma neuropeptide Y; both showed malignant ectomesenchymoma (p < 0.01), a mixed tumour with neural crest features. Among 38 children with neural crest derived tumours, all 7 with benign ganglioneuromas had plasma neuropeptide Y concentrations below the reference limit, while 13 of 31 with neuroblastoma had elevated concentrations (p < 0.05). Only neuroblastoma patients with elevated plasma neuropeptide Y had a poor outcome; 10 of 13 died, whereas all with normal concentrations are alive after 3-74 months of follow-up (p < 0.001).

Immunoreactive C-type natriuretic peptide in human adrenal glands and adrenal tumors

C-type natriuretic peptide (CNP) in human adrenal glands and adrenal tumors was measured with a specific radioimmunoassay for CNP. Tissue immunoreactive (IR-) CNP concentrations were 0.54 +/- 0.40 pmol/g wet tissue (gwt) (mean +/- SD) in 14 pheochromocytomas, 0.69 +/- 0.19 pmol/gwt in six adrenocortical tumors, and 0.49 +/- 0.22 pmol/gwt in seven normal adrenal glands (cortex and medulla mixed). These concentrations were comparable to those found in tissues from human brains. Sephadex G-50 superfine column chromatography and reverse-phase high performance liquid chromatography revealed that IR-CNP in normal adrenal glands and pheochromocytoma consisted of at least two components: a component in low molecular weight form chromatographically identical to CNP-22 and the other, a high molecular weight form very similar to human CNP-53. This study has shown that IR-CNP is present in human adrenal glands and adrenal tumors with similar molecular forms and comparable concentrations to those in the human brain.

Serial measurements of neuropeptide Y in plasma for monitoring neuroblastoma in children

Neuropeptide Y (NPY) was studied as a marker for neuroblastoma in 12 children. All but one patient with neuroblastoma had elevated plasma NPY concentrations at diagnosis. During treatment NPY values returned to normal in 9 of 12 children. All three children without normalization of plasma NPY values died; two of them had a relapse and the third died of toxic effects. Plasma NPY appears to be a sensitive marker of neuroblastoma.

Pituitary adenylate cyclase activating polypeptide (PACAP)-like immunoreactivity in pheochromocytomas

Pituitary adenylate cyclase activating polypeptide (PACAP) is a novel hypothalamic peptide consisting of 38 amino acids [PACAP(1-38)] with a potent stimulatory action on adenylate cyclase in rat pituitary. The presence of immunoreactive (IR-) PACAP in the tumor tissue of pheochromocytomas was studied by radioimmunoassay and immunocytochemistry. The antibody to PACAP was raised in a rabbit injected with a peptide containing amino acids 28-38 of PACAP. This antibody showed no significant cross-reactivity with either PACAP(1-27) or vasoactive intestinal polypeptide. The tumor tissue concentrations of IR-PACAP(1-38) were 0.5-57.5 pmol/g wet weight (n = 13) (24.5 +/- 22.4 pmol/g wet weight, mean +/- SD), while those in the normal adrenal glands were 3.58 +/- 2.02 pmol/g wet weight (n = 7) and those in the adrenal cortical tumors were 5.58 +/- 2.02 pmol/g wet weight (n = 6). The IR-PACAP(1-38) concentrations in 7 out of 13 pheochromocytomas exceeded 18 pmol/g wet weight. Sephadex G-50 column chromatography revealed that the IR-PACAP(1-38) in extracts of pheochromocytomas eluted in both the positions of PACAP(1-38) and a larger molecular weight. Reverse-phase high performance liquid chromatography of the tumor extracts revealed a peak in the position of PACAP(1-38) and at least four other peaks. Immunocytochemistry of pheochromocytomas showed numerous immunoreactive cells. The immunostaining was abolished by absorption of the antiserum with synthetic PACAP(1-38). These findings indicate that multiple forms of IR-PACAP(1-38) are present in pheochromocytomas.

Neuropeptide Y in neuroblastoma: increased concentration in metastasis, release during surgery, and characterization of plasma and tumor extracts

Five children with neural crest tumors (two ganglioneuromas, one ganglioneuroblastoma, and two neuroblastomas) were investigated regarding neuropeptide Y-like immunoreactivity (NPY-LI) in tumor tissue and plasma at diagnosis and during surgery. Radioimmunoassay of extracted plasma revealed higher NPY-LI at diagnosis of neuroblastoma (640 and 230 pmol/L resp) than ganglioneuroblastoma or ganglioneuroma (74, 45, and 26 pmol/L resp). During surgery of neuroblastoma plasma NPY-LI increased two- to four-fold while no peroperative increase was seen in the other children. NPY-LI was considerably higher in neuroblastoma tissue (220 pmol/g and 144 pmol/g) than in ganglioneuroblastoma (40.2 pmol/g), ganglioneuroma (0.6 and 4.4 pmol/g), or healthy adrenal tissue (5.5 pmol/g). The highest NPY-LI concentration was found in neuroblastoma metastasis, 3,091 pmol/g. Gel-permeation chromatography of a neuroblastoma tumor showed that a majority of NPY-LI was representing intact NPY (NPY 1-36) while metastasis and plasma from the same child mainly contained smaller immunoreactive fragments. High concentrations of systemic NPY in neuroblastoma patients are of tumoral origin. Plasma levels of NPY and its fragments can be useful in diagnosing and monitoring neuroblastoma, and for early detection of relapse or metastatic disease. A possible involvement of NPY in neuroblastoma tumor growth and spread deserves further investigation.

A sensitive and specific two-site, sandwich-amplified enzyme immunoassay for neuropeptide Y

The development of a new enzyme immunoassay for neuropeptide Y (NPY) is reported. Two monoclonal antibodies directed against distinct epitopes of NPY are used, one as a capture antibody (NPY02) and the other one as an indicator antibody (NPY05), this latter antibody being labeled with alkaline phosphatase. The assay calibration curve was performed over concentrations of 1 to 250 pM in a NPY-free plasma. The intra-assay coefficient of variation (CV) ranged from 0.025 to 11.9%, whereas the interassay CV was comprised between 5 and 12%. The limit of detection of this assay was 1 pM (100 amol/well). Neuropeptide Y levels are related to sampling conditions; basal concentrations of NPY with low SEM are found when less than 1.2 ml of blood is taken in EDTA tubes, the sample is centrifuged at 4 degrees C, and immediately frozen. Unanesthetized spontaneously hypertensive rats exhibited higher NPY plasma concentrations than normotensive Wistar-Kyoto controls (53 +/- 7 pM and 25 +/- 2 pM, respectively, mean +/- SEM, p < 0.01). Plasma NPY levels are similar in 16- and 36-week-old animals. In conclusion, this technique makes it possible to assay a large number of samples within 24 h without requiring radioactivity.

Neuropeptide Y secretion from a malignant extraadrenal retroperitoneal paraganglioma

A patient with a malignant extraadrenal retroperitoneal paraganglioma had elevated levels of immunoreactive neuropeptide Y (NPY) in the peripheral blood (5988 pg/ml; normal, 123 +/- 30 pg/ml [mean +/- standard error of the mean]). A 6-month course of chemotherapy allowed surgical removal of the previously unresectable primary tumor. Postoperatively, the plasma NPY level initially fell to 1089 pg/ml; continued chemotherapy caused an additional decrease to 440 pg/ml. Four months after surgery, the plasma NPY level increased to 940 mg/ml, coincident with hepatic metastases. This case is the first report of a NPY-secreting clinically nonfunctional malignant extraadrenal paraganglioma. Determination of circulating NPY levels may be useful in the diagnosis and follow-up of patients with neuroendocrine tumors.

Circulating neuropeptide Y in dog plasma consists of multiple peptide fragments

Neuropeptide Y-like immunoreactivity (NPY-LI) in dog plasma was characterized and quantified using three extraction methods (Sep-Pak:acetonitrile, HCl:ethanol, and ethanol). Sep-Pak extraction yields the best recovery and preserves the integrity of the peptide. Oxidized NPY is not generated during blood collection. Using two antisera of different specificities, at least three peptide forms in normal dog arterial and venous plasma were detected. A peptide with retention times similar to oxidized NPY or peptide YY is the major component of plasma NPY-LI under basal conditions, but NPY(1-36) predominates during sympathetic stimulation. The mature peptide in dog plasma is similar to human NPY. The antiserum ABII provides a more accurate measure of circulating NPY(1-36) and its oxidized form. The antiserum ABI is useful for detecting NPY-like fragments.

Neuropeptide Y in the primate model of subarachnoid hemorrhage

The cause of cerebral vasospasm after subarachnoid hemorrhage (SAH) remains unknown. Recently, an association between the potent vasoconstricting peptide, neuropeptide Y, and delayed cerebral vasospasm after SAH has been postulated. This was based on the findings of increased neuropeptide Y levels in the cerebrospinal fluid (CSF) and plasma after SAH in animals and humans. For this study, the primate model of SAH was used to assess the possible role of neuropeptide Y in delayed vasospasm after SAH. Fifteen cynomolgus monkeys underwent placement of a clot of either whole blood or red blood cells in the subarachnoid space around the middle cerebral artery (MCA). Sequential arteriography for assessment of MCA diameter and sampling of blood and CSF for neuropeptide Y were performed: before SAH (Day 0); 7 days after SAH, when signs of delayed cerebral vasospasm peak in this model and in humans; 12 days after SAH; and 28 days after SAH. Subarachnoid hemorrhage did not evoke changes in CSF or plasma levels of neuropeptide Y. Nine monkeys had arteriographic evidence of vasospasm on Day 7, but no change in neuropeptide Y levels occurred in plasma or CSF. In addition, neuropeptide Y levels did not change, even after resolution of vasospasm on Day 12 or Day 28. Neuropeptide Y levels were substantially higher in CSF than in arterial plasma (p less than 0.003 at each interval). No correlation was found between neuropeptide Y levels in CSF and in plasma. These results do not confirm a relationship between neuropeptide Y levels in the CSF or peripheral plasma and delayed cerebral vasospasm in SAH.

Roux-en-Y jejunal bypass abolishes postprandial neuropeptide Y release

Numerous physiologic aberrations occur after Roux-en-Y bypass procedures. Neuropeptide Y (NPY), a 36 amino acid polypeptide, has been shown to have many effects on gastrointestinal physiology, including alterations in blood flow, motility, and secretion and absorption. Recent work demonstrating a postprandial increase in circulating NPY prompted this investigation into its potential roles after Roux-en-Y bypass. Three groups of rats underwent Roux-en-Y cholangiojejunostomy, jejunojejunostomy, or proximal jejunal transection with reanastomosis. After a 3-month recovery, the animals were tested with both mixed and fat meals. Control animals had rapid increases in circulating NPY after the mixed meal. This response was not seen in either of the Roux-en-Y groups (P less than 0.05). No animals had circulating changes in NPY after the fat meal. Additionally, small intestinal NPY receptor analysis revealed high NPY affinity to the epithelial cells of the proximal small intestine. Our results demonstrate a dependence of postprandial NPY release on proximal small intestinal continuity that is abolished by Roux-en-Y bypass of a jejunal segment. The absence of postprandial elevation in plasma NPY after proximal jejunal bypass and the abundance of NPY receptors in the proximal small intestine merits further investigation into the physiologic roles of NPY in the foregut.