Detection of neuropeptide Y and its mRNA in megakaryocytes: enhanced levels in certain autoimmune mice.

Abstract

Neuropeptide tyrosine (neuropeptide Y, NPY) is a potent vasoconstrictor with a wide distribution in the central and peripheral nervous systems. Here we show that high levels of rat NPY mRNA are also found in peripheral blood cells, bone marrow, lung, and spleen. Furthermore, radioimmunoassay revealed high levels of NPY-like peptide in these tissues. In mice, the levels of splenic NPY mRNA and immunoreactive peptide differed extensively between strains and were greatly elevated in several strains (NZB, NZBxW, and BXSB) that develop a disease resembling human systemic lupus erythematosus. Like the rat, the NZB mouse showed a high content of NPY mRNA in peripheral blood cells and bone marrow. Immunohistochemical staining revealed NPY-like immunoreactivity in large cells morphologically identifiable as megakaryocytes in rat bone marrow and in the spleen of the NZB mouse strain. Expression of NPY mRNA in megakaryocytes in rat bone marrow and NZB mouse spleen was confirmed by in situ hybridization. These results indicate that NPY is synthesized in megakaryocytes, implying that NPY can be released from platelets and function as a vasoconstrictor during blood-vessel damage. In addition, the increase in splenic NPY in certain autoimmune mouse strains adds to the list of abnormalities associated with these strains.Neuropeptide Y (NPY), first isolated from pig brain by Tatemoto et al. (1), is abundant and widespread in the mammalian nervous system (2-7). In addition, NPY-like immunoreactivity has been found in chromaffin cells of the adrenal gland (8). The colocalization of NPY with catecholamines in numerous peripheral and central neurons (2, 9), together with its prejunctional inhibitory effects on transmitter release and its vasoconstrictor actions, suggests a function for NPY as a neurotransmitter and/or neuromodulator (2, 10). The structure of the NPY precursor has been deduced from a human cDNA clone (11) and from the rat gene (12). The rat NPY precursor consists of 98 amino acids including a signal peptide of 29 amino acids (12). At least two proteolytic processing sites are found within the NPY precursor; cleavage at these sites generates the 36 amino acid-long mature NPY peptide and a 30 amino acid-long carboxylterminal peptide (12). The human (13) and rat (12) genes are highly homologous and each consists of four exons, with almost the entire mature peptide encoded in the second exon.In accordance with the widespread distribution of NPYlike immunoreactivity in the brain (3, 4, 6, 7), Larhammar et al. (12) recently showed that NPY mRNA is present throughout the rat brain, with particularly high levels in the cerebral cortex and olfactory bulb. In rat peripheral organs, high levels of NPY mRNA were detected in the adrenal gland, heart, and spleen (12). The high level of NPY mRNA in rat spleen was unexpected, since no neuronal cell bodies are known in this organ, although many NPY-containing nerve terminals exist (2,14). In this paper we show that rat and mouse NPY mRNA and peptide are synthesized in megakar...

Greater Bone Formation of Y2 Knockout Mice Is Associated with Increased Osteoprogenitor Numbers and Altered Y1 Receptor Expression

“…This is supported by a recent study, which used pseudorabies virus-based transneuronal tracing to map transsynaptically connected neurons from rat bone providing direct evidence that nerve fibers within bone tissue are under the control of synaptic transmission from the hypothalamus (5). However, it cannot be excluded that part of the effect on Y1-receptor down-regulation is due to NPY produced by cells such as megakaryocytes within the bone marrow itself (6).…”

Neuropeptide Y Is Expressed by Rat Mononuclear Blood Leukocytes and Strongly Down-Regulated during Inflammation

“…Reports on NPY expression by blood leukocytes are scarce and no peptide data exist (6,7). Platelets secrete NPY (6,8) and NPY mRNA expression can be induced in vitro in human leukocytes by stimulation with T cell mitogens or nerve growth factor (7,9). In this study, we determined whether NPY is expressed by mononuclear blood leukocytes in vivo and, if so, whether its expression is changed during inflammation.…”

Leptin Treatment in Activity-Based Anorexia

“…33 Plabeled anti-sense ribonucleic acid (RNA) probes were made with a 350-base pair (bp) rat POMC complementary deoxyribonucleic acid (cDNA) fragment (Kas et al 2003), a 286-bp rat NPY cDNA fragment (Ericsson et al 1987), and a 396-bp mouse AgRP cDNA fragment (Kas et al 2003). The sections were hybridized overnight at 72°C with 1 ϫ 10 6 cpm probe in buffer containing 50% deionized formamide, 2ϫ standard saline citrate (SSC), 10% dextrane sulphate, 1ϫ Denhardt's solution, 5 mmol/L ethylenediaminetetraacetic acid, and 10 mmol/L phosphate buffer, after 5 min heating at 80°C.…”