Characterization of endozepine-related peptides in the central nervous system and in peripheral tissues of the rat

doi:10.1016/0196-9781(92)90032-X

Peptides

Volume 13, Issue 6, November–December 1992, Pages 1219-1225

https://doi.org/10.1016/0196-9781(92)90032-X Get rights and content

Abstract

Endozepines represent a novel family of regulatory peptides that have been isolated by their ability to displace benzodiazepines from their binding sites. All endozepines derive from an 86 amino acid precursor polypeptide called diazepam binding inhibitor (DBI), which generates, through proteolytic cleavage, several biologically active endozepines. The aim of the present study was to compare the molecular forms of endozepines present in different regions of the rat brain and in various peripheral organs using an antiserum raised against the central (biologically active) region of DBI. Combination of HPLC analysis and RIA detection revealed the existence of two major forms (peaks I and II) of endozepine-immunoreactive peptides. The retention times of the two peaks (36 and 39 min, respectively) were identical in all tissues or organs tested. Western blotting analysis of cerebral cortex extracts confirmed the existence of two immunoreactive species with apparent molecular weights 4000 and 6000 Da, which respectively correspond to peaks I and II. Tryptic digestion of peaks I and II generated a single immunoreactive peptide that coeluted with the synthetic octadecaneuropeptide ODN [DBI(33–50)]. These results show that, in different parts of the brain and in various peripheral organs, DBI is rapidly processed to generate two peptides of apparent molecular weight of 4000 and 6000 Da, which both possess the biologically active determinant of endozepines.

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Cited by (29)

Endozepines and their receptors: Structure, functions and pathophysiological significance
2020, Pharmacology and Therapeutics
Citation Excerpt :
In the brain, the DBI gene is primarily expressed in astrocytes, and DBI-derived peptides are particularly abundant in the olfactory bulb (OB), hypothalamus and hippocampus (Tonon, Désy, Nicolas, Vaudry, & Pelletier, 1990). TTN/ODN-related peptides are also present in several peripheral organs (Rouet-Smih, Tonon, Pelletier, & Vaudry, 1992). Consistent with the widespread distribution of DBI and its processing products, these peptides appear to exert a large array of biological effects notably on anxiety-related behaviors (de Mateos-Verchere, Leprince, Tonon, Vaudry, & Costentin, 1998), food consumption (Guillebaud et al., 2017; de Mateos-Verchere, Leprince, Tonon, Vaudry, & Costentin, 2001), neuroprotection (Ghouili et al., 2018; Masmoudi-Kouki et al., 2018) and hormonal secretions (Yoshida, Tsunoda, & Owyang, 1999).
The existence of specific binding sites for benzodiazepines (BZs) in the brain has prompted the search for endogenous BZ receptor ligands designated by the generic term « endozepines ». This has led to the identification of an 86-amino acid polypeptide capable of displacing [³H]diazepam binding to brain membranes, thus called diazepam-binding inhibitor (DBI). It was subsequently found that the sequence of DBI is identical to that of a lipid carrier protein termed acyl-CoA-binding protein (ACBP). The primary structure of DBI/ACBP has been well preserved, suggesting that endozepines exert vital functions. The DBI/ACBP gene is expressed by astroglial cells in the central nervous system, and by various cell types in peripheral organs. Endoproteolytic cleavage of DBI/ACBP generates several bioactive peptides including a triakontatetraneuropeptide that acts as a selective ligand of peripheral BZ receptors/translocator protein, and an octadecaneuropeptide that activates a G protein-coupled receptor and behaves as an allosteric modulator of the GABA_AR. Although DBI/ACBP is devoid of a signal peptide, endozepines are released by astrocytes in a regulated manner. Consistent with the diversity and wide distribution of BZ-binding sites, endozepines appear to exert a large array of biological functions and pharmacological effects. Thus, intracerebroventricular administration of DBI or derived peptides induces proconflict and anxiety-like behaviors, and reduces food intake. Reciprocally, the expression of DBI/ACBP mRNA is regulated by stress and metabolic signals. In vitro, endozepines stimulate astrocyte proliferation and protect neurons and astrocytes from apoptotic cell death. Endozepines also regulate neurosteroid biosynthesis and neuropeptide expression, and promote neurogenesis. In peripheral organs, endozepines activate steroid hormone production, stimulate acyl chain ceramide synthesis and trigger pro-inflammatory cytokine secretion. The expression of the DBI/ACBP gene is enhanced in addiction/withdrawal animal models, in patients with neurodegenerative disorders and in various types of tumors. We review herein the current knowledge concerning the various actions of endozepines and discuss the physiopathological implications of these regulatory gliopeptides.
Liver fatty acid-binding protein and obesity
2010, Journal of Nutritional Biochemistry
While low levels of unesterified long chain fatty acids (LCFAs) are normal metabolic intermediates of dietary and endogenous fat, LCFAs are also potent regulators of key receptors/enzymes and at high levels become toxic detergents within the cell. Elevated levels of LCFAs are associated with diabetes, obesity and metabolic syndrome. Consequently, mammals evolved fatty acid-binding proteins (FABPs) that bind/sequester these potentially toxic free fatty acids in the cytosol and present them for rapid removal in oxidative (mitochondria, peroxisomes) or storage (endoplasmic reticulum, lipid droplets) organelles. Mammals have a large (15-member) family of FABPs with multiple members occurring within a single cell type. The first described FABP, liver-FABP (L-FABP or FABP1), is expressed in very high levels (2–5% of cytosolic protein) in liver as well as in intestine and kidney. Since L-FABP facilitates uptake and metabolism of LCFAs in vitro and in cultured cells, it was expected that abnormal function or loss of L-FABP would reduce hepatic LCFA uptake/oxidation and thereby increase LCFAs available for oxidation in muscle and/or storage in adipose. This prediction was confirmed in vitro with isolated liver slices and cultured primary hepatocytes from L-FABP gene-ablated mice. Despite unaltered food consumption when fed a control diet ad libitum, the L-FABP null mice exhibited age- and sex-dependent weight gain and increased fat tissue mass. The obese phenotype was exacerbated in L-FABP null mice pair fed a high-fat diet. Taken together with other findings, these data suggest that L-FABP could have an important role in preventing age- or diet-induced obesity.
Endozepines
2006, Handbook of Biologically Active Peptides
The existence of specific binding sites for benzodiazepines has led to the discovery of endogenous ligands for benzodiazepine receptors that are collectively designated by the term endozepines. In the brain and in peripheral nervous tissues, endozepines are exclusively expressed by glial cells. The release of endozepines from cultured astrocytes is finely regulated by neurotransmitters and neuropeptides. Endozepines exert their effects either through classical central- and peripheral-type benzodiazepine receptors or through G-protein-coupled receptors. Intracerebroventricular injection of endozepines causes marked effects on anxiety, sleep, and food consumption. The concentration of endozepines in the brain and cerebrospinal fluid is affected in various diseases, including depression and hepatic encephalopathy.
Biosynthesis of Neurosteroids and regulation of their synthesis
2001, International Review of Neurobiology
The brain, like the gonads, adrenal glands, and placenta, is a steroidogenic organ. The steroids synthesized by the brain and by the nervous system, given the name neurosteroids, have a wide variety of diverse functions. In general, they mediate their actions not through classic steroid hormone nuclear receptors but through ion-gated neurotransmitter receptors. This chapter summarizes the biochemistry of the enzymes involved in the biosynthesis of neurosteroids, their localization during development and in adulthood, and the regulation of their expression, highlighting both similarities and differences between expression in the brain and in classic steroldogenlc tissues.
Regulation of the expression of peripheral benzodiazepine receptors and their endogenous ligands during rat sciatic nerve degeneration and regeneration: A role for PBR in neurosteroidogenesis
1999, Brain Research
Peripheral benzodiazepine receptors (PBR) and their endogenous ligands, the diazepam-binding inhibitor derived-peptides, are present in Schwann cells in the peripheral nervous system. The aim of this study was to determine the influence of reversible (freeze-injury) and permanent (transection and ligature) nerve lesion on PBR density and on the levels of their endogenous ligands, by autoradiography (using [ $^{3} H$ ]PK11195) and radioimmunoassay (using antisera directed against the octadecaneuropeptide (ODN), a diazepam-binding inhibitor fragment). The potential role of PBR on peripheral nerve steroidogenesis, was studied by investigating the effect of specific PBR agonists and antagonists on pregnenolone levels in the sciatic nerve. Sixteen to 30 days after nerve lesion, PBR density and ODN–LI level were highly increased. Their expression returned to normal level when regeneration was completed 60 days after freeze-injury, but remained elevated when regeneration did not occur in transected distal stumps. Reverse-phase HPLC analysis of ODN–LI showed that in control nerve extracts, the major immunoreactive peak co-elutes with triakontatetraneuropeptide (TTN). After freeze-injury, intermediate molecular forms eluting between ODN and TTN were predominant and remained elevated at day 60. The greater accumulation of intermediate forms when regeneration is allowed to occur may indicate a particular role of these forms in axonal elongation and myelination. Ro5–4864, a high affinity PBR agonist increased pregnenolone concentration in the sciatic nerve. This effect was antagonised by PK11195, a high affinity PBR antagonist, which had no effect on pregnenolone basal level, indicating a specific action of PBR in neurosteroid production. These results suggest a role for PBR and their endogenous ligands in peripheral nerve regeneration. A trophic effect could be exerted via stimulation of steroid synthesis.
The octadecaneuropeptide ODN inhibits apomorphine-induced yawning in rats
1998, European Journal of Pharmacology
High concentrations of diazepam-binding inhibitor (DBI) have been detected in brain areas containing dopaminergic cell bodies and nerve terminals. In the present study, we have investigated the effect of a proteolytic fragment of DBI, the octadecaneuropeptide ODN, on apomorphine-induced yawning in Sprague–Dawley rats. Injection of graded doses of ODN (12.5 to 100 ng i.c.v.) caused a dose-dependent inhibition of apomorphine-induced yawning and penile erections. At a dose of 100 ng, intracerebroventricularly administered ODN was able to inhibit, during more than 3 h, the apomorphine-evoked yawning. ODN also inhibited pilocarpine-induced yawning. Apomorphine induces a bell-shaped dose-dependent effect on yawning with a maximum response at the dose of 100 μg/kg and a much lower effect at a dose of 200 μg/kg. Injection (i.c.v.) of 100 ng ODN markedly attenuated the number of yawns induced by 100 μg/kg apomorphine but partially restored the yawning behavior in rats treated with a 200 μg/kg dose of apomorphine. At doses of 0.5 or 5 mg/kg s.c., diazepam did not modify the inhibitory effect of ODN on the apomorphine-induced yawning. Taken together, the present data suggest that ODN inhibits yawning downstream dopaminergic as well as cholinergic synapses involved in yawning. In addition, the effect of ODN cannot be ascribed to an inverse agonistic activity on central-type benzodiazepine receptors.

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Peptides

Abstract

References (31)

Octadecaneuropeptide, benzodiazepine ligand, -like immunoreactivity in rat central nervous system, plasma and peripheral tissues

Neurosci. Lett.

Octadecaneuropeptide (ODN; anxiety peptide) displaces diazepam more potently for astrocytic than from neuronal binding sites

Eur. J. Pharmacol.

Distribution and characterization of diazepam binding inhibitor (DBI) in peripheral tissues of rat

Regul. Pept.

Increased brain content of the endogenous benzodiazepine receptor ligand, octadecaneuropeptide (ODN), following portacaval anastomosis in the rat

Peptides

An octadecaneuropeptide (ODN) derived from diazepam binding inhibitor increases aggressive interactions in mice

Brain Res.

Distribution and characterization of endozepine-like immunoreactivity in the central nervous system of the frog Rana ridibunda

Peptides

Localization and characterization of endozepine-like peptides in the brain of the trout (Salmo gairdneri)

Brain Res.

The benzodiazepine receptor

Complete amino acid sequences of bovine and human endozepines. Homology with rat diazepam binding inhibitor

J. Biol. Chem.

Effects of porcine diazepam-binding inhibitor on insulin and glucagon secretion in vitro from the rat endocrine pancreas

Regul. Pept.

Sequence and expression of the murine diazepam binding inhibitor

Mol. Brain Res.

Localization of diazepam-binding inhibitor (DBI) mRNA in the rat brain by high resolution in situ hybridization

Neuropeptides

Immunocytochemical localization of the endogenous benzodiazepine ligand octadecaneuropeptide (ODN) in the rat brain

Neuropeptides

Diazepam-binding inhibitor: A neuropeptide located in selected neuronal populations of rat brain

Science

Neuropeptide modulation of GABA receptor Cl⁻ channels

Regul. Pept.

Cited by (29)

Endozepines and their receptors: Structure, functions and pathophysiological significance

Liver fatty acid-binding protein and obesity

Endozepines

Biosynthesis of Neurosteroids and regulation of their synthesis

Regulation of the expression of peripheral benzodiazepine receptors and their endogenous ligands during rat sciatic nerve degeneration and regeneration: A role for PBR in neurosteroidogenesis

The octadecaneuropeptide ODN inhibits apomorphine-induced yawning in rats

ArticleCharacterization of endozepine-related peptides in the central nervous system and in peripheral tissues of the rat

Abstract

Neurosci. Lett.

Eur. J. Pharmacol.

Regul. Pept.

Peptides

Brain Res.

Peptides

Brain Res.

J. Biol. Chem.

Regul. Pept.

Mol. Brain Res.

Neuropeptides

Neuropeptides

Diazepam-binding inhibitor: A neuropeptide located in selected neuronal populations of rat brain

Science

Neuropeptide modulation of GABA receptor Cl− channels

Regul. Pept.

Article
Characterization of endozepine-related peptides in the central nervous system and in peripheral tissues of the rat

Neuropeptide modulation of GABA receptor Cl⁻ channels