Pituitary adenylate cyclase-activating polypeptide regulates neuroendocrine markers and transcription factors in differentiating pheochromocytoma cells.
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Animals↗
Biomedical subjects
H Vaudry
Publications and source records attributed to H Vaudry.
Pituitary adenylate cyclase--activating polypeptide stimulates secretoneurin release and secretogranin II gene transcription in bovine adrenochromaffin cells.
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Animals↗
Immunohistochemical localization of 3 beta-hydroxysteroid dehydrogenase and 5 alpha-reductase in the brain of the African lungfish Protopterus annectens.
The localization of the enzymes responsible for the biosynthesis of neurosteroids in the brain of dipnoans has not yet been determined. In the present study, we investigated the immunohistochemical distribution of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and 5 alpha-reductase (5 alpha-R) in the brain and pituitary of the African lungfish Protopterus annectens by using antibodies raised against type I human 3 beta-HSD and type I human 5 alpha-R. The 3 beta-HSD and 5 alpha-R immunoreactivities were detected in cell bodies and fibers located in the same areas of the lungfish brain, namely, in the pallium, thalamus, hypothalamus, tectum, and periaqueductal gray. Identification of astrocytes, oligodendrocytes, and neurons with antisera against glial fibrillary acidic protein, galactocerebroside and neurofilaments revealed that, in the lungfish brain, 3 beta-HSD immunolabeling is expressed exclusively by neurons, whereas the 5 alpha-R-immunoreactive material is contained in both neurons and glial cells. In the pituitary gland, 3 beta-HSD- and 5 alpha-R-like immunoreactivity was localized in both the pars distalis and the pars intermedia. The present study provides the first immunocytochemical mapping of two key steroidogenic enzymes in the brain and pituitary of a lungfish. These data strongly suggest that neurosteroid biosynthesis occurs in the brain of fishes, as previously shown for amphibians, birds, and mammals.
3-Hydroxysteroid Dehydrogenases↗
Immunohistochemical localization of atrial natriuretic factor and autoradiographic distribution of atrial natriuretic factor-binding sites in the brain of the cave salamander Hydromantes genei (Amphibia, Plethodontidae).
The distribution of atrial natriuretic factor (ANF)-like immunoreactivity in the central nervous system of the cave salamander Hydromantes genei (Amphibia, Plethodontidae) was investigated by using antisera raised against rat and human ANF(1-28). Concurrently, the location of ANF-binding sites was determined by autoradiography, using radioiodinated human ANF(1-28) as a tracer. In several regions of the brain, including the olfactory bulb, the preoptic area, the ventral thalamus, the tectum of the mesencephalon, and the choroid plexuses inside the ventricles, a good correlation was observed between the distribution of ANF-immunoreactive elements and the location of ANF-binding sites. Mismatching was found in the habenular nucleus, the commissura habenularis, the fasciculum retroflexus, and the interpeduncular nucleus, which contained high levels of binding sites but were devoid of ANF-immunoreactive structures. In contrast, a few other regions, such as the pineal gland and the subcommissural organ, showed a high concentration of ANF-like immunoreactivity but did not contain ANF-binding sites. This study provides the first localization of ANF-like immunoreactivity and ANF-binding sites in the brain of an urodele amphibian. The results show that the ANF peptidergic system in the cave salamander has an organization more simple than the organizations described for the brain of frog or other vertebrates. This feature is probably related to the expression of highly pedomorphic characters in plethodontids. The anatomical distribution of ANF-immunoreactive elements and ANF-binding sites suggests that ANF-related peptides may act as hypophysiotropic hormones as well as neurotransmitters and/or neuromodulators in the salamander brain.
Animals↗
Pituitary adenylate cyclase-activating polypeptide and its receptors in amphibians.
Pituitary adenylate cyclase-activating polypeptide (PACAP), a novel peptide of the secretin/glucagon/vasoactive intestinal polypeptide superfamily, has been initially characterized in mammals in 1989 and, only 2 years later, its counterpart has been isolated in amphibians. A number of studies conducted in the frog Rana ridibunda have demonstrated that PACAP is widely distributed in the central nervous system (particularly in the hypothalamus and the median eminence) and in peripheral organs including the adrenal gland. The cDNAs encoding the PACAP precursor and 3 types of PACAP receptors have been cloned in amphibians and their distribution has been determined by in situ hybridization histochemistry. Ontogenetic studies have revealed that PACAP is expressed early in the brain of tadpoles, soon after hatching. In the frog Rana ridibunda, PACAP exerts a large array of biological effects in the brain, pituitary, adrenal gland, and ovary, suggesting that, in amphibians as in mammals, PACAP may act as neurotrophic factor, a neurotransmitter and a neurohormone.
Adrenal Glands↗
The octadecaneuropeptide [diazepam-binding inhibitor (33-50)] exerts potent anorexigenic effects in rodents.
The effects of intracerebroventricular administration of the octadecaneuropeptide ODN on food intake have been investigated in rat and mouse. In rats deprived of food from 9:00 a.m. to 7:00 p.m., i.c.v. injection of ODN (30 to 100 ng) provoked a dose-dependent reduction of food consumption during the following 12-h nocturnal period. At a dose of 100 ng, ODN almost completely suppressed food intake. Treatment of rats with diazepam (2 mg/kg s.c.; 15 min before ODN administration) did not affect the anorexigenic response evoked by 100 ng ODN. Continuous i.c.v. infusion of ODN (10 ng/h during 15 days) using osmotic minipumps, significantly reduced food intake during the 2nd, 3rd and 4th days of treatment. The decrease in food consumption was associated with a significant reduction in body weight, which persisted during the 15-day duration of the experiment. In mice deprived of food for 18 h, i.c.v. administration of a low dose of ODN (5 ng) significantly reduced food intake. Treatment of mice with diazepam (1 mg/kg s.c.; 10 min before ODN administration) did not prevent the inhibitory effect of ODN (100 ng) on food intake. The C-terminal octapeptide fragment of ODN mimicked the anorexigenic effect of the intact peptide. Taken together, the present data demonstrate that i.c.v. injection of ODN causes, in both rat and mouse, a long-lasting anorexigenic effect that is not mediated through central-type benzodiazepine receptors. The biologically active region of ODN appears to be located in the C-terminal domain of the peptide.
Animals↗
Ontogeny of pituitary adenylate cyclase-activating polypeptide (PACAP) in the frog (Rana ridibunda) tadpole brain: immunohistochemical localization and biochemical characterization.
The anatomic distribution and biochemical characteristics of the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) were investigated in the central nervous system of the frog, Rana ridibunda, during development. Three to four days after hatching, at stages IV-VII, PACAP-immunoreactive perikarya were detected in the dorsal thalamus within the anterior ventral area, and a few fibers were found in the medial pallium. Positive cell bodies were first observed in the hypothalamus at stages VIII-IX, at the level of the dorsal and ventral infundibular nuclei. In these regions, the number of positive perikarya increased during ontogeny. In tadpoles, during the mid- and late premetamorphosis, a more complex organization of the PACAP-immunoreactive system was found in the thalamus with the appearance, at stages IX-XII, of two additional groups of positive neurons in the ventrolateral area and posterocentral nucleus. At stages XIII-XVIII of larval development and subsequent larval stages, PACAP-immunoreactive fibers were found in the median eminence. In newly metamorphosed animals, several additional groups of positive perikarya appeared in the medial pallium, the preoptic nucleus, the torus semicircularis, the tegmentum of the mesencephalon, and the cerebellum. The immunoreactive peptide contained in the tadpole brain was characterized by high performance liquid chromatography analysis combined with radioimmunoassay quantification. At all stages investigated, the predominant form of PACAP-immunoreactive material coeluted with synthetic frog PACAP38. The occurrence of PACAP soon after hatching indicates that the peptide may exert neurotrophic activities. The existence of immunoreactive elements in several thalamic regions at mid- and late premetamorphic stages suggests that PACAP may act as a neurotransmitter, neuromodulator, or both, during ontogenesis. Finally, the presence of PACAP-immunoreactive perikarya in hypothalamic nuclei and nerve fibers in the median eminence supports the view that PACAP may play a role in the control of pituitary hormone secretion during larval development.
Age Factors↗
Immunohistochemical localization and biochemical characterization of hypocretin/orexin-related peptides in the central nervous system of the frog Rana ridibunda.
In the present study, we have investigated the distribution and biochemical characteristics of hypocretin (hcrt) -like immunoreactivity in the central nervous system (CNS) of the frog Rana ridibunda by using an antiserum directed against rat hcrt2. Immunoreactive cell bodies were only detected in four diencephalic nuclei, including the anterior preoptic area and the suprachiasmatic, magnocellular, and ventral hypothalamic nuclei. In contrast, hcrt2-immunoreactive fibers were widely distributed throughout the frog CNS. In particular, a high density of hcrt-positive fibers was detected in several areas of the telencephalon, including the olfactory bulb, the nucleus of the diagonal band of Broca, and the amygdala. A dense network of hcrt-containing fibers was observed in all thalamic and hypothalamic nuclei. A low to moderate density of immunoreactive fibers was also found in the mesencephalon, rhombencephalon, and spinal cord. Reversed-phase high performance liquid chromatography analysis of frog brain extracts revealed that hcrt2-immunoreactive material eluted as two peaks, the major one exhibiting the same retention time as synthetic rat hcrt2. The present data provide the first detailed mapping of the hcrt neuronal system in the CNS of a nonmammalian vertebrate. The occurrence of hcrt-containing cell bodies in the hypothalamus and the widespread distribution of hcrt-immunoreactive fibers throughout the brain and spinal cord suggest that, in amphibians, hcrts may exert neuroendocrine, neurotransmitter, and/or neuromodulator activities.
Animals↗
The triakontatetraneuropeptide TTN increases [CA2+]i in rat astrocytes through activation of peripheral-type benzodiazepine receptors.
Astrocytes synthesize a series of regulatory peptides called endozepines, which act as endogenous ligands of benzodiazepine receptors. We have recently shown that one of these endozepines, the triakontatetraneuropeptide TTN, stimulates DNA synthesis in astroglial cells. The purpose of the present study was to determine the mechanism of action of TTN on cultured rat astrocytes. Binding of the peripheral-type benzodiazepine receptor ligand [3H]Ro5-4864 to intact astrocytes was displaced by TTN, whereas its C-terminal fragment (TTN[17-34], the octadecaneuropeptide ODN) did not compete for [3H]Ro5-4864 binding. Microfluorimetric measurement of cytosolic calcium concentrations ([Ca2+]i) with the fluorescent probe indo-1 showed that TTN (10(-10) to 10(-6) M) provokes a concentration-dependent increase in [Ca2+]i in cultured astrocytes. Simultaneous administration of TTN (10(-8) M) and Ro5-4864 (10(-5) M) induced an increase in [Ca2+]i similar to that obtained with Ro5-4864 alone. In contrast, the effects of TTN (10(-8) M) and ODN (10(-8) M) on [Ca2+]i were strictly additive. Chelation of extracellular Ca2+ by EGTA (6 mM) or blockage of Ca2+ channels with Ni2+ (2 mM) abrogated the stimulatory effect of TTN. The calcium influx evoked by TTN (10(-7) M) or by Ro5-4864 (10(-5) M) was not affected by the N- and T-type calcium channel blockers omega-conotoxin (10(-6) M) and mibefradil (10(-6) M), but was significantly reduced by the L-type calcium channel blocker nifedipine (10(-7) M). Patch-clamp studies showed that, at negative potentials, TTN (10(-7) M) induced a sustained depolarization. Reduction of the chloride concentration in the extracellular solution shifted the reversal potential from 0 mV to a positive potential. These data show that TTN, acting through peripheral-type benzodiazepine receptors, provokes chloride efflux, which in turn induces calcium influx via L-type calcium channels in rat astrocytes.
Animals↗
Regulation of neurosteroid biosynthesis in the frog diencephalon by GABA and endozepines.
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3-Hydroxysteroid Dehydrogenases↗
Biosynthesis of neurosteroids and regulation of their synthesis.
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 steroidogenic tissues.
Animals↗
Anatomical and biochemical evidence for the synthesis of unconjugated and sulfated neurosteroids in amphibians.
Various studies have shown that, in mammals, neurons and glial cells are capable of synthesizing bioactive steroids, or neurosteroids, which regulate the activity of the central nervous system (CNS). However, although steroid hormones are involved in the regulation of behavioral and neuroendocrine processes in amphibians, neurosteroid biosynthesis has never been studied in the CNS of non-mammalian vertebrates. Reviewed here are several data sets concerning the production of unconjugated and sulfated neurosteroids in amphibians. These data were obtained by investigating the immunohistochemical localization and activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and hydroxysteroid sulfotransferase (HST), in the frog brain. Numerous 3beta-HSD-immunoreactive neurons were detected in the anterior preoptic area, nucleus of the periventricular organ, posterior tuberculum, ventral and dorsal hypothalamic nuclei. 17beta-HSD-like immunoreactivity was found in ependymal gliocytes bordering the lateral ventricles of the telencephalon. Two populations of HST-immunoreactive neurons were localized in the anterior preoptic area and the dorsal magnocellular nucleus of the hypothalamus. High amounts of progesterone (PROG), 17-hydroxyprogesterone (17OH-PROG), testosterone (T) and dehydroepiandrosterone sulfate (DHEAS) were measured in the frog brain by combining HPLC analysis of tissue extracts with radioimmunoassay detection. Incubation of telencephalic or hypothalamic explants with tritiated pregnenolone ([3H]PREG) yielded the synthesis of various metabolites including PROG, 17OH-PROG, DHEA and T. Incorporation of [35S]3'-phosphoadenosine 5'-phosphosulfate ([35S]PAPS) and [3H]PREG or [3H]DHEA into frog brain homogenates led to the formation of [3H,35S]pregnenolone sulfate ([3H,35S]PREGS) or [3H,35S]DHEAS, respectively. Altogether, these results demonstrate that the process of neurosteroid biosynthesis occurs in amphibians as previously seen in mammals.
17-Hydroxysteroid Dehydrogenases↗
Characterization of a novel Sepia officinalis neuropeptide using MALDI-TOF MS and post-source decay analysis.
A novel neuropeptide acting as a myosuppressor on esophagus, funnel and mantle muscular fibers has been isolated from the stellar ganglia of the mollusk cephalopod Sepia officinalis by means of HPLC analysis. Fractions were monitored using a myotropic bioassay. After three separation steps, MALDI-TOF spectrum revealed one main peak at m/z 756.6. The partial N-terminal and C-terminal digestions by exopeptidases followed by MALDI-TOF analysis allowed the determination of the nature of the two C-terminal and N-terminal amino acids. Post Source Decay fragmentation of the molecular ion accurately determined the following primary sequence: Val-Tyr-Ser-Ala-Pro-Tyr-Gly-OH. The mapping of this heptapeptide performed in ESI-MS revealed that its distribution is restricted to the stellar ganglia, the giant fibers III, and the nervous bundle containing the giant fibers II and the palleal nerve. The neuropeptide was not detected in the hemolymph suggesting a release by nerve endings next to the targets.
Amino Acid Sequence↗
Specific expression of the urotensin II gene in sacral motoneurons of developing rat spinal cord.
The neuropeptide urotensin II (UII) is expressed in motoneurons of the brainstem and spinal cord in adults. Here, the expression pattern of the UII gene was studied in the developing rat spinal cord. UII mRNA was detected by reverse-transcription-polymerase chain reaction (RT-PCR) as early as E10. From E14 to E21, in situ hybridization revealed intense expression of the UII gene specifically in sacral motoneurons, while only faint expression was detected at cervical and thoracic levels. After birth (P0, P4), the expression of UII mRNA increased in motoneurons at all rostrocaudal levels. Thus, UII is the first gene reported to show expression limited to the sacral pool of motoneurons, which are known to have particular properties in terms of targets and programmed cell death.
Animals↗
Evidence for the involvement of nitric oxide in the control of steroid secretion by the frog adrenal gland.
Nitric oxide (NO) has been found to modulate the response of rat, bovine and human adrenocortical cells to corticotropic factors. The aim of the present study was to investigate the possible involvement of NO in the control of corticosteroid secretion in the frog Rana ridibunda. Histochemical studies using the NADPH-diaphorase reaction and immunohistochemical labeling with antibodies against NO synthase (NOS) revealed that NOS is exclusively expressed in chromaffin cells. The NO donor sodium nitroprusside (SNP) and the NO synthase inhibitor Nw-nitro-L-arginine (L-NO(2)Arg) did not modify the spontaneous production of corticosterone and aldosterone by perifused adrenal slices. Similarly, L-NO(2)Arg had no effect on the secretory responses induced by ACTH, angiotensin II (AII) and endothelin-1 (ET-1). In contrast, SNP significantly inhibited the stimulatory effects of ACTH, AII and ET-1 on corticosterone and aldosterone secretion. These data provide the first evidence for a modulatory role of NO on adrenocortical cell activity in amphibians.
Adrenal Glands↗
Role of neurotransmitters and neuropeptides in the regulation of the adrenal cortex.
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Acetylcholine↗
Synthesis, conformational analysis and biological activity of cyclic analogs of the octadecaneuropeptide ODN. Design of a potent endozepine antagonist.
The octadecaneuropeptide (ODN; QATVGDVNTDRPGLLDLK) and its C-terminal octapeptide (OP; RPGLLDLK), which exert anxiogenic activity, have been previously shown to increase intracellular calcium concentration ([Ca2+]i) in cultured rat astrocytes through activation of a metabotropic receptor positively coupled to phospholipase C. It has also been found that the [d-Leu5]OP analog possesses a weak antagonistic activity. The aim of the present study was to synthesize and characterize cyclic analogs of OP and [d-Leu5]OP. On-resin homodetic backbone cyclization of OP yielded an analog, cyclo1-8 OP, which was three times more potent and 1.4-times more efficacious than OP to increase [Ca2+]i in cultured rat astrocytes. Cyclo1-8 OP also mimicked the effect of both OP and ODN on polyphosphoinositide turnover. Conversely, the cyclo1-8 [d-Leu5]OP analog was totally devoid of agonistic activity but suppressed the effect of OP and ODN on [Ca2+]i and phosphoinositide metabolism in astrocytes. The structure of these cyclic analogs has been determined by two-dimensional 1H-NMR and molecular dynamics. Cyclo1-8 OP exhibited a single conformation characterized by a gamma turn comprising residues Pro2-Leu4 and a type III beta turn encompassing residues Leu5-Lys8. Cyclo1-8 [d-Leu5]OP was present as two equimolar conformers resulting from cis/trans isomerization of the Arg-Pro peptide bond. These pharmacological and structural data should prove useful for the rational design of non peptidic ODN analogs.
Amino Acid Sequence↗
Nitric oxide directly activates GABA(A) receptor function through a cGMP/protein kinase-independent pathway in frog pituitary melanotrophs.
The direct effects of nitric oxide (NO) donors and sulfhydryl-modifying agents on the GABA(A) receptor function were examined by perforated patch, whole-cell and single channel recordings in cultured frog melanotrophs. In amphotericin B-perforated cells incubated with the soluble guanylyl cyclase inhibitors LY 83583 and ODQ (10-4 M each), the NO donor sodium nitroprusside (SNP) (10(-3) M) reversibly increased the current evoked by GABA (5 x 10(-6) M). In the whole-cell configuration, internal application of the oxidizing agent H2O2 (0.05%) potentiated the GABA-evoked current while the reducing agent 2-mercaptoethanol (5 x 10(-3) M) slightly decreased the current amplitude. In inside-out patches, GABA (2 x 10(-7) M) triggered single channel bursts of openings. Incubation with the NO donors SNP or DEA/NO (10(-4) M each) enhanced the open probability of the GABA(A) receptor channel but did not modify the chloride reversal potential and did not affect the conductance states. The oxidizing agents H2O2 (0.05%) or DTNB (10-4 M) mimicked the stimulatory effect of the NO donors on the open probability while the reducing compounds 2-mercaptoethanol (5 x 10(-3) M) or DTT (10(-4) M) markedly attenuated the channel activity. Potentiation of the GABA-induced single channel activity by SNP or H2O2 was blocked by 2-mercaptoethanol. Similarly, the potentiating effect produced by DEA/NO or DTNB on the open probability was reversed by DTT. In outside-out patches, incubation with SNP also significantly enhanced the open probability of single channels activated by GABA (10(-6) M). These data indicate that, in frog pituitary melanotrophs, NO potentiates the GABA-evoked current independently of the cGMP/protein kinase pathway. The effect of NO can be accounted for by S-nitrosylation/oxidation of thiol groups either directly on the GABA(A) receptor subunits or on a regulatory protein tightly associated with the GABA(A) receptor.
Aminoquinolines↗