Elsevier

Peptides

Volume 21, Issue 4, April 2000, Pages 565-570
Peptides

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

https://doi.org/10.1016/S0196-9781(00)00184-4Get rights and content

Abstract

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.

Introduction

Orexins (hypocretins) are neuropeptides that have recently been discovered from rat brain and have a strong stimulatory effect on food consumption [8], [21]. The orexins consist of two peptides; orexin-A, a 33 amino acid peptide and orexin-B, a 28-amino acid peptide, which are derived from the same precursor by proteolytic processing [8], [21]. Orexin-A and -B share 46% identity. Studies by immunocytochemistry and in situ hybridization in the rat and human brain showed that orexin-A and -B positive cell bodies were restricted to the lateral and posterior hypothalamus, which is well known to be a feeding center in the hypothalamus [4], [7], [8], [9], [13], [21]. Both orexin-A and -B nerve fibers projected from the hypothalamus widely to various brain regions, such as the olfactory bulb, cerebral cortex, thalamus, and brain stem.

Intracerebroventricular administration of orexin-A or -B stimulated food consumption in rat [21] and gastric acid secretion [30]. Expression levels of orexin mRNA were up regulated by fasting [21] and down regulated in genetically obese mice [32]. The orexins modulated luteinizing hormone secretion in an ovarian steroid-dependent manner [18]. Canine narcolepsy is caused by a mutation in the orexin (hypocretin) receptor 2 gene [15], and orexin knockout mice exhibit a phenotype strikingly similar to human narcolepsy patients [5], indicating that orexin regulates sleep/wakefulness states. Consistent with these reports, orexin-A activated locus coeruleus cell firing and increased arousal and locomoter activity in rats [12]. Thus, the orexins are involved in regulating various brain and endocrine functions, such as feeding and arousal.

On the other hand, regional distribution of the orexins in the human brain and pituitary has not been studied. We therefore studied regional distribution of orexin-A-like immunoreactivity (orexin-A-LI) in human brain and pituitary by radioimmunoassay and expression of orexin mRNA by reverse transcriptase-PCR (RT-PCR).

It is known that adrenal medulla and neural crest-derived tumors, such as pheochromocytomas and neuroblastomas, produce various kinds of neuropeptides, e.g. neuropeptide Y (NPY) [2], calcitonin-gene-related peptide (CGRP) [17], pituitary adenylate cyclase activating polypeptide (PACAP) [27] and adrenomedullin [22]. However, there has been no report on the production of the orexins by tumors. We therefore examined tissue concentrations of orexin-A-LI in human adrenal glands and tumor tissues of pheochromocytomas, adrenocortical tumors, ganglioneuroblastomas, and neuroblastomas.

Section snippets

Tissues

This study has been approved by the Ethics Committee of Tohoku University School of Medicine. Human brain tissues were obtained at autopsy performed at the Department of Pathology, Tohoku University Hospital within 4-h postmortem from 13 patients (nine male and four female, 20–75 years old). These patients had no neurologic or endocrinological diseases. Tumor tissues of pheochromocytomas (n = 15), ganglioneuroblastomas (n = 4), neuroblastomas (n = 6), aldosterone-producing adrenocortical

Results

A standard curve of orexin-A and dilution curves of human brain extracts are shown in Fig. 1. The dilution curves were parallel with a standard curve of orexin-A. Orexin-A-LI was detected in every region of human brain, but not in the pituitary (<0.220 pmol/g wet weight) (Fig. 2). The highest concentration of orexin-A-LI in the human brain was found in hypothalamus (17.8 ± 4.4 pmol/g wet weight, mean ± SEM, n = 7), followed by thalamus (12.1 ± 2.3 pmol/g wet weight, n = 7), medulla oblongata

Discussion

The present study has shown the wide distribution of orexin-A-LI in various human brain regions and the expression of orexin mRNA in the hypothalamus. Furthermore, the present study has shown the production of orexin-A in ganglioneuroblastomas and neuroblastomas. This is the first report on the production of orexin-A by tumors.

The findings in the human brain are consistent with previous studies by others using immunocytochemistry and in situ hybridization showing that orexin is produced only in

Acknowledgements

The authors are grateful to Ms Kikuchi for her technical assistance. This study has been supported in part by a Research Grant from the Takeda Science Foundation (to K. To.), by a Research Grant for the Renal Anemia Research (to K. To.), by the Mochida Memorial Foundation for Medical and Pharmaceutical Research (to K. Ta.), and a Grant-in-Aid for Scientific Research on Priority Areas (A) (to K. Ta.) from the Ministry of Education, Science, Sports, and Culture, Japan.

References (33)

  • K. Takahashi et al.

    Human brain natriuretic peptide-like immunoreactivity in human brain

    Peptides

    (1992)
  • N. Takahashi et al.

    Stimulation of gastric acid secretion by centrally administered orexin-A in conscious rats

    Biochem Biophys Res Commun

    (1999)
  • K. Totsune et al.

    C-type natriuretic peptide in the human central nervous systemdistribution and molecular form

    Peptides

    (1994)
  • Y. Yamamoto et al.

    Down regulation of the prepro-orexin gene expression in genetically obese mice

    Mol Brain Res

    (1999)
  • T.E. Adrian et al.

    Neuropeptide Y in human brain

    Nature

    (1983)
  • Adrian TE, Allen JM, Terenghi G, et al. Neuropeptide Y in phaeochromocytomas and ganglioneuroblastomas. Lancet...
  • Cited by (0)

    View full text