RESUMEN
DPP-4 inhibitors, used for treatment of type 2 diabetes, act by increasing the concentrations of intact glucagon-like peptide-1 (GLP-1), but at the same time, they inhibit secretion of GLP-1, perhaps by a negative feedback mechanism. We hypothesized that GLP-1 secretion is feedback regulated by somatostatin (SS) from neighboring D-cells, and blocking this feedback circuit results in increased GLP-1 secretion. We used a wide range of experimental techniques, including gene expression analysis, immunohistochemical approaches, and the perfused mouse intestine to characterize the paracrine circuit controlling GLP-1 and SS. We show that 1) antagonizing the SS receptor (SSTr) 2 and SSTr5 led to increased GLP-1 and SS secretion in the mouse, 2) SS exhibits strong tonic inhibition of GLP-1 secretion preferentially through SSTr5, and 3) the secretion of S was GLP-1 receptor dependent. We conclude that SS is a tonic inhibitor of GLP-1 secretion, and interventions in the somatostain-GLP-1 paracrine loop lead to increased GLP-1 secretion.
Asunto(s)
Células Enteroendocrinas/metabolismo , Péptido 1 Similar al Glucagón/metabolismo , Receptor del Péptido 1 Similar al Glucagón/metabolismo , Mucosa Intestinal/metabolismo , Comunicación Paracrina , Células Secretoras de Somatostatina/metabolismo , Somatostatina/metabolismo , Animales , Inhibidores de la Dipeptidil-Peptidasa IV/farmacología , Células Enteroendocrinas/efectos de los fármacos , Péptido 1 Similar al Glucagón/efectos de los fármacos , Mucosa Intestinal/citología , Intestino Delgado/citología , Intestino Delgado/metabolismo , Intestinos , Ratones , Receptores de Somatostatina/antagonistas & inhibidores , Receptores de Somatostatina/metabolismo , Somatostatina/farmacología , Somatostatina-28/farmacología , Células Secretoras de Somatostatina/efectos de los fármacosRESUMEN
Somatostatin (SST) is a cyclic peptide that is understood to inhibit the release of hormones and neurotransmitters from a variety of cells by binding to one of five canonical G protein-coupled SST receptors (SSTR1 to SSTR5). Recently, SST was also observed to interact with the amyloid beta (Aß) peptide and affect its aggregation kinetics, raising the possibility that it may bind other brain proteins. Here we report on an SST interactome analysis that made use of human brain extracts as biological source material and incorporated advanced mass spectrometry workflows for the relative quantitation of SST binding proteins. The analysis revealed SST to predominantly bind several members of the P-type family of ATPases. Subsequent validation experiments confirmed an interaction between SST and the sodium-potassium pump (Na+/K+-ATPase) and identified a tryptophan residue within SST as critical for binding. Functional analyses in three different cell lines indicated that SST might negatively modulate the K+ uptake rate of the Na+/K+-ATPase.
Asunto(s)
Encéfalo/metabolismo , ATPasas Tipo P/metabolismo , Somatostatina/metabolismo , Péptidos beta-Amiloides/metabolismo , Animales , Línea Celular , Células HEK293 , Humanos , Cinética , Ratones , Proteínas del Tejido Nervioso/metabolismo , Unión Proteica , Dominios y Motivos de Interacción de Proteínas , Radioisótopos de Rubidio/farmacocinética , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Somatostatina-28/metabolismoRESUMEN
Using an immunocytochemical technique, we have studied the distribution of fibers and cell bodies containing somatostatin-28 (1-12) [SOM-28 (1-12)], calcitonin gene-related peptide (CGRP), and substance P (SP) in the brainstem of Saimiri sciureus. The distribution of the peptidergic cell bodies was very restricted: perikarya containing SOM-28 (1-12) were only observed in the substantia grisea centralis, while no immunoreactive cell bodies containing CGRP or SP were visualized. Fibers containing SOM-28 (1-12), CGRP, or SP were widely distributed in the brainstem: immunoreactive fibers containing SOM-28 (1-12) showed the most widespread distribution and were the most abundant. The distribution of SOM-28 (1-12)-, CGRP- or SP-immunoreactive fibers was very similar. Colocalization of immunoreactive fibers containing SOM-28 (1-12), CGRP or SP was observed in many brainstem nuclei. A neuroanatomical relationship between CGRP- and SP-immunoreactive fibers was observed, although this relationship was less marked for SOM-28 (1-12) and SP and lower still for SOM-28 (1-12) and CGRP. The widespread distribution of the peptidergic fibers suggests that the studied neuropeptides are involved in many physiological actions.
Asunto(s)
Tronco Encefálico/anatomía & histología , Péptido Relacionado con Gen de Calcitonina/análisis , Saimiri/anatomía & histología , Somatostatina-28/análisis , Sustancia P/análisis , Animales , Inmunohistoquímica , Masculino , Fibras NerviosasRESUMEN
Both type 1 and type 2 diabetes involve a complex interplay between genetic, epigenetic, and environmental factors. Our laboratory has been interested in the physical interactions, in nuclei of human pancreatic ß cells, between the insulin (INS) gene and other genes that are involved in insulin metabolism. We have identified, using Circularized Chromosome Conformation Capture (4C), many physical contacts in a human pancreatic ß cell line between the INS promoter on chromosome 11 and sites on most other chromosomes. Many of these contacts are associated with type 1 or type 2 diabetes susceptibility loci. To determine whether physical contact is correlated with an ability of the INS locus to affect expression of these genes, we knock down INS expression by targeting the promoter; 259 genes are either up or down-regulated. Of these, 46 make physical contact with INS We analyze a subset of the contacted genes and show that all are associated with acetylation of histone H3 lysine 27, a marker of actively expressed genes. To demonstrate the usefulness of this approach in revealing regulatory pathways, we identify from among the contacted sites the previously uncharacterized gene SSTR5-AS1 and show that it plays an important role in controlling the effect of somatostatin-28 on insulin secretion. These results are consistent with models in which clustering of genes supports transcriptional activity. This may be a particularly important mechanism in pancreatic ß cells and in other cells where a small subset of genes is expressed at high levels.
Asunto(s)
Diabetes Mellitus/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Células Secretoras de Insulina/metabolismo , Insulina/genética , Oligonucleótidos Antisentido/farmacología , Regiones Promotoras Genéticas , Receptores de Somatostatina/metabolismo , Células Cultivadas , Cromosomas Humanos Par 11/genética , Cromosomas Humanos Par 11/metabolismo , Diabetes Mellitus/genética , Diabetes Mellitus/patología , Susceptibilidad a Enfermedades , Glucosa/metabolismo , Humanos , Insulina/metabolismo , Secreción de Insulina , Células Secretoras de Insulina/efectos de los fármacos , Receptores de Somatostatina/antagonistas & inhibidores , Receptores de Somatostatina/genética , Somatostatina-28/farmacologíaRESUMEN
Adverse life experiences increase the lifetime risk to several stress-related psychopathologies, such as anxiety or depressive-like symptoms following stress in adulthood. However, the neurochemical modulations triggered by stress have not been fully characterized. Neuropeptides play an important role as signaling molecules that contribute to physiological regulation and have been linked to neurological and psychiatric diseases. However, little is known about the influence of stress on neuropeptide regulation in the brain. Here, we have performed an exploratory study of how neuropeptide expression at adulthood is modulated by experiencing a period of multiple stressful experiences. We have targeted hippocampus and prefrontal cortex (PFC) brain areas, which have previously been shown to be modulated by stressors, employing a targeted liquid chromatography-mass spectrometry (LC-MS) based approach that permits broad peptide coverage with high sensitivity. We found that in the hippocampus, Met-enkephalin, Met-enkephalin-Arg-Phe, and Met-enkephalin-Arg-Gly-Leu were upregulated, while Leu-enkephalin and Little SAAS were downregulated after stress. In the PFC area, Met-enkephalin-Arg-Phe, Met-enkephalin-Arg-Gly-Leu, peptide PHI-27, somatostatin-28 (AA1-12), and Little SAAS were all downregulated. This systematic evaluation of neuropeptide alterations in the hippocampus and PFC suggests that stressors impact neuropeptides and that neuropeptide regulation is brain-area specific. These findings suggest several potential peptide candidates, which warrant further investigations in terms of correlation with depression-associated behaviors.
Asunto(s)
Regulación de la Expresión Génica , Hipocampo/metabolismo , Neuropéptidos/genética , Corteza Prefrontal/metabolismo , Estrés Psicológico/metabolismo , Animales , Cromatografía Liquida , Encefalina Metionina/genética , Hipocampo/fisiología , Masculino , Espectrometría de Masas , Corteza Prefrontal/fisiología , Proteómica , Ratas , Somatostatina-28/genética , Estrés Psicológico/genéticaRESUMEN
Using an indirect immunoperoxidase technique, an in depth study has been carried out for the first time on the distribution of fibres and cell bodies containing neurotensin and somatostatin-28 (1-12) (SOM) in the minipig brainstem. The animals used were not treated with colchicine. The distribution of neurotensin- and SOM-immunoreactive fibres was seen to be quite similar and was moderate in the minipig brainstem: a close anatomical relationship between both neuropeptides was observed. The distribution of cell bodies containing neurotensin or SOM was quite different and restricted. Cell bodies containing neurotensin were found in four brainstem nuclei: nucleus centralis raphae, nucleus dorsalis raphae, in the pars centralis of the nucleus tractus spinalis nervi trigemini and in the nucleus ventralis raphae. Cell bodies containing SOM were found in six nuclei/regions of the brainstem: nucleus ambiguus, nucleus dorsalis motorius nervi vagus, formatio reticularis, nucleus parabrachialis medialis, nucleus reticularis lateralis and nucleus ventralis raphae. According to the observed anatomical distribution of the immunoreactive structures containing neurotensin or SOM, the peptides could be involved in sleep-waking, nociceptive, gustatory, motor, respiratory and autonomic mechanisms.
Asunto(s)
Tronco Encefálico/metabolismo , Técnicas para Inmunoenzimas/veterinaria , Neurotensina/metabolismo , Somatostatina-28/metabolismo , Médula Espinal/metabolismo , Porcinos Enanos/anatomía & histología , Porcinos/anatomía & histología , Animales , Tronco Encefálico/anatomía & histología , Femenino , MasculinoRESUMEN
Using an indirect immunoperoxidase technique, we studied the distribution of cell bodies and fibers containing somatostatin-28 (1-12) in the alpaca brainstem. Immunoreactive fibers were widely distributed throughout the whole brainstem: 34 brainstem nuclei/regions showed a high or a moderate density of these fibers. Perikarya containing the peptide were widely distributed throughout the mesencephalon, pons and medulla oblongata. Cell bodies containing somatostatin-28 (1-12) were observed in the lateral and medial divisions of the marginal nucleus of the brachium conjunctivum, reticular formation (mesencephalon, pons and medulla oblongata), inferior colliculus, periaqueductal gray, superior colliculus, pericentral division of the dorsal tegmental nucleus, interpeduncular nucleus, nucleus of the trapezoid body, vestibular nucleus, motor dorsal nucleus of the vagus, nucleus of the solitary tract, nucleus praepositus hypoglossi, and in the substantia nigra. This widespread distribution indicates that somatostatin-28 (1-12) is involved in multiple physiological actions in the alpaca brainstem.
Asunto(s)
Tronco Encefálico/química , Camélidos del Nuevo Mundo/fisiología , Fragmentos de Péptidos/análisis , Somatostatina-28/análisis , Animales , InmunohistoquímicaRESUMEN
Somatostain (SS) is known to inhibit growth hormone (GH) and prolactin (PRL) secretion. Somatolactin (SL) is a member of the GH/PRL family, but its regulation by goldfish brain somatostatin-28 (gbSS-28) has not been examined. To this end, the structural identity of goldfish SLα was established by 5'/3'-rapid amplification of cDNA ends. As revealed by in situ hybridization and immunohistochemical staining, the expression of SL isoforms was detected in pituitary cells located in the neurointermediate lobe (NIL). The transcripts of goldfish SS receptor 5a (Sst5a) but not Sst1b, Sst2, or Sst3a were detected in the goldfish NIL cells by RT-PCR. In goldfish pituitary cells, gbSS-28 not only had an inhibitory effect on basal SLα and SLß mRNA levels but also could abolish insulin-like growth factor-stimulated SL gene expression. In primary cultures of goldfish NIL cells, gbSS-28 reduced forskolin-stimulated total cAMP production. With the use of a pharmacological approach, the adenylate cyclase (AC)/cAMP and phospholipase C (PLC)/inositol trisphosphate (IP3)/protein kinase C (PKC) cascades were shown to be involved in gbSS-28-inhibited SLα mRNA expression. Similar postreceptor signaling cascades were also observed for gbSS-28-reduced SLß mRNA expression, except that PKC coupling to PLC was not involved. These results provide evidence that gbSS-28 can inhibit SLα and SLß gene expression at the goldfish pituitary level via Sst5 through differential coupling of AC/cAMP and PLC/IP3/PKC cascades.
Asunto(s)
Proteínas de Peces/metabolismo , Glicoproteínas/metabolismo , Carpa Dorada/metabolismo , Hipófisis/efectos de los fármacos , Hormonas Hipofisarias/metabolismo , Somatostatina-28/farmacología , Adenilil Ciclasas/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Células Cultivadas , Clonación Molecular , AMP Cíclico/metabolismo , Relación Dosis-Respuesta a Droga , Regulación hacia Abajo , Proteínas de Peces/genética , Glicoproteínas/genética , Carpa Dorada/genética , Inositol 1,4,5-Trifosfato/metabolismo , Datos de Secuencia Molecular , Hipófisis/metabolismo , Hormonas Hipofisarias/genética , Cultivo Primario de Células , Proteína Quinasa C/metabolismo , ARN Mensajero/metabolismo , Receptores de Somatostatina/agonistas , Receptores de Somatostatina/metabolismo , Transducción de Señal/efectos de los fármacos , Factores de Tiempo , Fosfolipasas de Tipo C/metabolismoRESUMEN
Radiolabeled pansomatostatin-like analogues are expected to enhance the diagnostic sensitivity and to expand the clinical indications of currently applied sst2-specific radioligands. In this study, we present the somatostatin mimic [DOTA]LTT-SS28 {[(DOTA)Ser1,Leu8,D-Trp22,Tyr25]SS28} and its 111In radioligand. [DOTA]LTT-SS28 exhibited a pansomatostatin-like profile binding with high affinity to all five hsst1-hsst5 subtypes (IC50 values in the lower nanomolar range). Furthermore, [DOTA]LTT-SS28 behaved as an agonist at hsst2, hsst3, and hsst5, efficiently stimulating internalization of the three receptor subtypes. Radioligand [111In-DOTA]LTT-SS28 showed good stability in the mouse bloodstream. It displayed strong and specific uptake in AR42J tumors 4 h postinjection (9.3±1.6% ID/g vs 0.3±0.0% ID/g during sst2 blockade) in mice. Significant and specific uptake was also observed in HEK293-hsst2-, HEK293-hsst3-, and HEK293-hsst5-expressing tumors (4.43±1.5, 4.88±1.1, and <3% ID/g, respectively, with values of <0.5% ID/g during receptor blockade). In conclusion, the somatostatin mimic [111In-DOTA]LTT-SS28 specifically localizes in sst2-, sst3-, and sst5-expressing xenografts in mice showing promise for multi-sst1-sst5 targeted tumor imaging.
Asunto(s)
Radioisótopos de Indio , Compuestos Organometálicos/química , Fragmentos de Péptidos/química , Radiofármacos/química , Receptores de Somatostatina/metabolismo , Somatostatina-28/análogos & derivados , Animales , Línea Celular Tumoral , Células HEK293 , Xenoinjertos , Humanos , Ligandos , Ratones SCID , Trasplante de Neoplasias , Compuestos Organometálicos/síntesis química , Compuestos Organometálicos/farmacocinética , Fragmentos de Péptidos/síntesis química , Fragmentos de Péptidos/farmacocinética , Ensayo de Unión Radioligante , Radiofármacos/síntesis química , Radiofármacos/farmacocinética , Receptores de Somatostatina/agonistas , Somatostatina-28/síntesis química , Somatostatina-28/química , Somatostatina-28/farmacocinética , Distribución TisularRESUMEN
Somatostatin, a natural inhibitor of growth hormone (GH), and its analogs have been used in clinical settings for the treatment of acromegaly, gigantism, thyrotropinoma, and other carcinoid syndromes. However, natural somatostatin is limited for clinical usage because of its short half-life in vivo. Albumin fusion technology was used to construct long-acting fusion proteins and Pichia pastoris was used as an expression system. Three fusion proteins (SS28)(2)-HSA, (SS28)(3)-HSA, and HSA-(SS28)(2), were constructed with different fusion copies of somatostatin-28 and fusion orientations. The expression level of (SS28)(3)-HSA was much lower than (SS28)(2)-HSA and HSA-(SS28)(2) due to the additional fusion of the somatostatin-28 molecule. MALDI-TOF mass spectrometry revealed that severe degradation occurred in the fermentation process. Similar to the standard, somatostatin-14, all three fusion proteins were able to inhibit GH secretion in blood, with (SS28)(2)-HSA being the most effective one. A pharmacokinetics study showed that (SS28)(2)-HSA had a prolonged half-life of 2 h. These results showed that increasing the number of small protein copies fused to HSA may not be a suitable method for improving protein bioactivity.
Asunto(s)
Pichia/genética , Albúmina Sérica/genética , Somatostatina-28/biosíntesis , Animales , Fermentación , Semivida , Humanos , Ratones , Ratones Endogámicos BALB C , Pichia/metabolismo , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/farmacocinética , Proteínas Recombinantes de Fusión/farmacología , Somatostatina-28/genética , Somatostatina-28/farmacologíaRESUMEN
Somatostatin (SST) 14 and SST 28 activate somatostatin 2A receptors (SSTR2A) on enteric neurons to control gut functions. SST analogs are treatments of neuroendocrine and bleeding disorders, cancer, and diarrhea, with gastrointestinal side effects of constipation, abdominal pain, and nausea. How endogenous agonists and drugs differentially regulate neuronal SSTR2A is unexplored. We evaluated SSTR2A trafficking in murine myenteric neurons and neuroendocrine AtT-20 cells by microscopy and determined whether agonist degradation by endosomal endothelin-converting enzyme 1 (ECE-1) controls SSTR2A trafficking and association with ß-arrestins, key regulators of receptors. SST-14, SST-28, and peptide analogs (octreotide, lanreotide, and vapreotide) stimulated clathrin- and dynamin-mediated internalization of SSTR2A, which colocalized with ECE-1 in endosomes and the Golgi. After incubation with SST-14, SSTR2A recycled to the plasma membrane, which required active ECE-1 and an intact Golgi. SSTR2A activated by SST-28, octreotide, lanreotide, or vapreotide was retained within the Golgi and did not recycle. Although ECE-1 rapidly degraded SST-14, SST-28 was resistant to degradation, and ECE-1 did not degrade SST analogs. SST-14 and SST-28 induced transient interactions between SSTR2A and ß-arrestins that were stabilized by an ECE-1 inhibitor. Octreotide induced sustained SSTR2A/ß-arrestin interactions that were not regulated by ECE-1. Thus, when activated by SST-14, SSTR2A internalizes and recycles via the Golgi, which requires ECE-1 degradation of SST-14 and receptor dissociation from ß-arrestins. After activation by ECE-1-resistant SST-28 and analogs, SSTR2A remains in endosomes because of sustained ß-arrestin interactions. Therapeutic SST analogs are ECE-1-resistant and retain SSTR2A in endosomes, which may explain their long-lasting actions.
Asunto(s)
Sistema Nervioso Entérico/metabolismo , Neuronas/metabolismo , Proteolisis , Receptores de Somatostatina/agonistas , Receptores de Somatostatina/metabolismo , Somatostatina-28/metabolismo , Somatostatina/metabolismo , Animales , Arrestinas/genética , Arrestinas/metabolismo , Ácido Aspártico Endopeptidasas/genética , Ácido Aspártico Endopeptidasas/metabolismo , Línea Celular Tumoral , Endosomas/genética , Endosomas/metabolismo , Enzimas Convertidoras de Endotelina , Femenino , Fármacos Gastrointestinales/farmacología , Aparato de Golgi/genética , Aparato de Golgi/metabolismo , Masculino , Metaloendopeptidasas/genética , Metaloendopeptidasas/metabolismo , Ratones , Octreótido/farmacocinética , Transporte de Proteínas , Ratas , Ratas Sprague-Dawley , Receptores de Somatostatina/genética , Somatostatina/genética , Somatostatina-28/genética , beta-ArrestinasRESUMEN
Based on previous work describing the distribution of somatostatin-28 (1-12) in the male alpaca (Lama pacos) diencephalon, and owing to the well known interactions between this peptide and the catecholaminergic system, the aims of this work are (1) to describe the distribution of putative catecholaminergic cell groups in the alpaca diencephalon and (2) to study the possible morphological basis of the interactions between these substances in the diencephalon of the alpaca by using double immunohistochemistry methods. Thus, the distribution of catecholaminergic cell groups in the alpaca diencephalon agrees with that previously described in the diencephalon of other mammalian species of the same order: the A11, A12, A13, A14 and A15d cell groups have been identified; however, we have observed an additional hitherto undescribed cell group containing tyrosine hydroxylase in the medial habenula. In addition, double-labelling procedures did not reveal neurons containing tyrosine hydroxylase and somatostatin, suggesting that the hypothalamic interactions between catecholamines and somatostatin at intra-cellular level must be carried out by a somatostatin molecule other than fragment (1-12). Otherwise, the overlapping distribution patterns of these substances would suggest some interconnections between groups of chemospecific neurons. These results could be the starting point for future studies on hypothalamic functions in alpacas, for example those concerning reproductive control, since other physiological studies have suggested that this species could have different regulatory mechanisms from other mammalian species. Our results support the Manger hypothesis that the same nuclear complement of neural systems exists in the brain of species of the same order.
Asunto(s)
Camélidos del Nuevo Mundo/metabolismo , Diencéfalo/metabolismo , Neuronas/metabolismo , Fragmentos de Péptidos/análisis , Somatostatina-28/análisis , Tirosina 3-Monooxigenasa/análisis , Animales , Inmunohistoquímica , Masculino , Fragmentos de Péptidos/biosíntesis , Somatostatina-28/biosíntesis , Tirosina 3-Monooxigenasa/biosíntesisRESUMEN
Somatostatin was discovered four decades ago and since then its physiological role has been extensively investigated, first in relation with its inhibitory effect on growth hormone secretion but soon it expanded to extrapituitary actions influencing various stressresponsive systems. Somatostatin is expressed in distinct brain nuclei and binds to five somatostatin receptor subtypes which are also widely expressed in the brain with a distinct distribution pattern. The last few years witnessed the discovery of highly selective peptide somatostatin receptor agonists and antagonists representing valuable tools to delineate the respective pathways of somatostatin signaling. Here we review the centrally mediated actions of somatostatin and related selective somatostatin receptor subtype agonists to influence the endocrine, autonomic, and visceral components of the stress response and basal behavior as well as thermogenesis.
Asunto(s)
Receptores de Somatostatina/metabolismo , Somatostatina-28/metabolismo , Somatostatina/agonistas , Animales , Encéfalo/metabolismo , Humanos , Transducción de Señal/fisiología , Somatostatina/antagonistas & inhibidores , Somatostatina/metabolismo , Estrés Fisiológico/fisiologíaRESUMEN
Excessive activation of the hypothalamic-pituitary-adrenal (HPA) axis has been associated with numerous diseases, including depression, and the tricyclic antidepressant imipramine has been shown to suppress activity of the HPA axis. Central hypothalamic control of the HPA axis is complex and involves a number of neuropeptides released from multiple hypothalamic subnuclei. The present study was therefore designed to determine the effects of imipramine administration on the mouse hypothalamus using a peptidomics approach. Among the factors found to be downregulated after acute (one day) or chronic (21 days) imipramine administration were peptides derived from secretogranin 1 (chromogranin B) as well as peptides derived from cerebellin precursors. In contrast, peptides SRIF-14 and SRIF-28 (1-11) derived from somatostatin (SRIF, somatotropin release inhibiting factor) were significantly upregulated by imipramine in the hypothalamus. Because diminished SRIF levels have long been known to occur in depression, a second part of the study investigated the roles of individual SRIF receptors in mediating potential antidepressant effects. SRA880, an antagonist of the somatostatin-1 autoreceptor (sst1) which positively modulates release of endogenous SRIF, was found to synergize with imipramine in causing antidepressant-like effects in the tail suspension test. Furthermore, chronic co-administration of SRA880 and imipramine synergistically increased BDNF mRNA expression in the cerebral cortex. Application of SRIF or L054264, an sst2 receptor agonist, but not L803807, an sst4 receptor agonist, increased phosphorylation of CaMKII and GluR1 in cerebrocortical slices. Our present experiments thus provide evidence for antidepressant-induced upregulation of SRIF in the brain, and strengthen the notion that augmented SRIF expression and signaling may counter depressive-like symptoms. This article is part of a Special Issue entitled 'Anxiety and Depression'.
Asunto(s)
Antidepresivos Tricíclicos/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Hipotálamo/efectos de los fármacos , Imipramina/farmacología , Neuropéptidos/metabolismo , Análisis de Varianza , Animales , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Cromogranina B/metabolismo , Suspensión Trasera/métodos , Masculino , Espectrometría de Masas , Ratones , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso , Fosforilación/efectos de los fármacos , Piperazinas/farmacología , Precursores de Proteínas/metabolismo , Quinolinas/farmacología , Somatostatina/metabolismo , Somatostatina-28/metabolismo , Factores de TiempoRESUMEN
Using an immunocytochemical technique, we report for the first time the distribution of immunoreactive cell bodies and fibers containing somatostatin-28 (1-12) in the alpaca diencephalon. Somatostatin-28 (1-12)-immunoreactive cell bodies were only observed in the hypothalamus (lateral hypothalamic area, arcuate nucleus and ventromedial hypothalamic nucleus). However, immunoreactive fibers were widely distributed throughout the thalamus and hypothalamus. A high density of such fibers was observed in the central medial thalamic nucleus, laterodorsal thalamic nucleus, lateral habenular nucleus, mediodorsal thalamic nucleus, paraventricular thalamic nucleus, reuniens thalamic nucleus, rhomboid thalamic nucleus, subparafascicular thalamic nucleus, anterior hypothalamic area, arcuate nucleus, dorsal hypothalamic area, around the fornix, lateral hypothalamic area, lateral mammilary nucleus, posterior hypothalamic nucleus, paraventricular hypothalamic nucleus, suprachiasmatic nucleus, supraoptic hypothalamic nucleus, and in the ventromedial hypothalamic nucleus. The widespread distribution of somatostatin-28 (1-12) in the thalamus and hypothalamus of the alpaca suggests that the neuropeptide could be involved in many physiological actions.
Asunto(s)
Camélidos del Nuevo Mundo/metabolismo , Diencéfalo/metabolismo , Fragmentos de Péptidos/metabolismo , Somatostatina-28/metabolismo , Animales , Inmunohistoquímica , Masculino , Fragmentos de Péptidos/análisis , Somatostatina-28/análisisRESUMEN
BACKGROUND: Activation of brain somatostatin receptors (sst(1-5) ) with the stable pan-sst(1-5) somatostatin agonist, ODT8-SST blocks acute stress and central corticotropin-releasing factor (CRF)-mediated activation of endocrine and adrenal sympathetic responses. Brain CRF signaling is involved in delaying gastric emptying (GE) immediately post surgery. We investigated whether activation of brain sst signaling pathways modulates surgical stress-induced inhibition of gastric emptying and food intake. METHODS: Fasted rats were injected intracisternally (i.c.) with somatostatin agonists and underwent laparotomy and 1-min cecal palpation. Gastric emptying of a non-nutrient solution and circulating acyl and desacyl ghrelin levels were assessed 50min post surgery. Food intake was monitored for 24 h. KEY RESULTS: The abdominal surgery-induced inhibition of GE (65%), food intake (73% at 2h) and plasma acyl ghrelin levels (67%) was completely prevented by ODT8-SST (1µg per rat, i.c.). The selective sst(5) agonist, BIM-23052 prevented surgery-induced delayed GE, whereas selective sst(1) , sst(2) , or sst(4) agonists had no effect. However, the selective sst(2) agonist, S-346-011 (1µg per rat, i.c.) counteracted the abdominal surgery-induced inhibition of acyl ghrelin and food intake but not the delayed GE. The ghrelin receptor antagonist, [D-Lys(3) ]-GHRP-6 (0.93mg kg(-1) , intraperitoneal, i.p.) blocked i.p. ghrelin-induced increased GE, while not influencing i.c. ODT8-SST-induced prevention of delayed GE and reduced food intake after surgery. CONCLUSIONS & INFERENCES: ODT8-SST acts in the brain to prevent surgery-induced delayed GE likely via activating sst(5) . ODT8-SST and the sst(2) agonist prevent the abdominal surgery-induced decrease in food intake and plasma acyl ghrelin indicating dissociation between brain somatostatin signaling involved in preventing surgery-induced suppression of GE and feeding response.
Asunto(s)
Abdomen/cirugía , Ingestión de Alimentos/efectos de los fármacos , Vaciamiento Gástrico/efectos de los fármacos , Ghrelina/sangre , Fragmentos de Péptidos/farmacología , Somatostatina/análogos & derivados , Somatostatina/agonistas , Animales , Encéfalo/efectos de los fármacos , Encéfalo/fisiología , Hormona Liberadora de Corticotropina/fisiología , Ingestión de Alimentos/fisiología , Vaciamiento Gástrico/fisiología , Inyecciones Intraventriculares , Masculino , Modelos Animales , Fragmentos de Péptidos/administración & dosificación , Ratas , Ratas Sprague-Dawley , Transducción de Señal/fisiología , Somatostatina/administración & dosificación , Somatostatina/farmacología , Somatostatina-28/administración & dosificación , Somatostatina-28/farmacología , Estrés Psicológico/fisiopatologíaRESUMEN
Dopamine (DA) and pituitary adenylate cyclase-activating polypeptide (PACAP) stimulate goldfish growth hormone (GH) release via cAMP- and Ca(2+)-dependent pathways while DA also utilizes NO. In this study, identified goldfish somatotropes responded to sequential applications of PACAP and the DA D1 agonist SKF38393 with increased intracellular Ca(2+) levels ([Ca(2+)](i)), indicating that PACAP and DA D1 receptors were present on the same cell. A native goldfish brain somatostatin (gbSS-28) reduced SKF38393-stimulated cAMP production and PACAP- and NO donor-elicited GH and [Ca(2+)](i) increases, but not PACAP-induced cAMP production nor the GH and [Ca(2+)](i) responses to forskolin, 8-bromo-cAMP and SKF38393. gbSS-28 might inhibit PACAP-induced GH release by interfering with PACAP's ability to increase [Ca(2+)](i) in a non-cAMP-dependent manner. However, DA D1 receptor activation bypassed gbSS-28 inhibitory effects on cAMP production and NO actions via unknown mechanisms to maintain a normal [Ca(2+)](i) response leading to unhampered GH release.
Asunto(s)
AMP Cíclico/metabolismo , Dopamina/metabolismo , Carpa Dorada/metabolismo , Hormona del Crecimiento/metabolismo , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa/farmacología , Hipófisis/efectos de los fármacos , Sistemas de Mensajero Secundario/efectos de los fármacos , Somatostatina-28/farmacología , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/farmacología , Animales , Calcio/metabolismo , Agonistas de Dopamina/farmacología , Femenino , Masculino , Hipófisis/citología , Hipófisis/metabolismo , Receptores de Dopamina D1/metabolismoRESUMEN
The synthesis, radiolabeling, and initial evaluation of new silicon-fluoride acceptor (SiFA) derivatized octreotate derivatives is reported. So far, the main drawback of the SiFA technology for the synthesis of PET-radiotracers is the high lipophilicity of the resulting radiopharmaceutical. Consequently, we synthesized new SiFA-octreotate analogues derivatized with Fmoc-NH-PEG-COOH, Fmoc-Asn(Ac3AcNH-ß-Glc)-OH, and SiFA-aldehyde (SIFA-A). The substances could be labeled in high yields (38 ± 4%) and specific activities between 29 and 56 GBq/µmol in short synthesis times of less than 30 min (e.o.b.). The in vitro evaluation of the synthesized conjugates displayed a sst2 receptor affinity (IC50 = 3.3 ± 0.3 nM) comparable to that of somatostatin-28. As a measure of lipophilicity of the conjugates, the log P(ow) was determined and found to be 0.96 for SiFA-Asn(AcNH-ß-Glc)-PEG-Tyr³-octreotate and 1.23 for SiFA-Asn(AcNH-ß-Glc)-Tyr³-octreotate, which is considerably lower than for SiFA-Tyr³-octreotate (log P(ow) = 1.59). The initial in vivo evaluation of [¹8F]SiFA-Asn(AcNH-ß-Glc)-PEG-Tyr³-octreotate revealed a significant uptake of radiotracer in the tumor tissue of AR42J tumor-bearing nude mice of 7.7% ID/g tissue weight. These results show that the high lipophilicity of the SiFA moiety can be compensated by applying hydrophilic moieties. Using this approach, a tumor-affine SiFA-containing peptide could successfully be used for receptor imaging for the first time in this proof of concept study.
Asunto(s)
Diagnóstico por Imagen/métodos , Radioisótopos de Flúor/química , Tomografía de Emisión de Positrones/métodos , Radiofármacos/síntesis química , Receptores de Somatostatina/metabolismo , Animales , Carbohidratos/química , Línea Celular Tumoral , Estabilidad de Medicamentos , Fluoruros/química , Radioisótopos de Flúor/metabolismo , Radioisótopos de Flúor/farmacocinética , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Marcaje Isotópico/métodos , Ratones , Ratones Desnudos , Trasplante de Neoplasias , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/metabolismo , Polietilenglicoles/química , Radiofármacos/sangre , Radiofármacos/farmacocinética , Silicio/química , Somatostatina-28/metabolismo , Distribución TisularRESUMEN
Somatostatins have been shown to be involved in the pathophysiology of motor and affective disorders, as well as psychiatric disorders, including schizophrenia. We hypothesized that in addition to motor function, somatostatin may be involved in somatosensory gating and reward processes that have been shown to be dysregulated in schizophrenia. Accordingly, we evaluated the effects of intracerebroventricular administration of somatostatin-28 on spontaneous locomotor and exploratory behavior measured in a behavioral pattern monitor, sensorimotor gating, prepulse inhibition (PPI) of the acoustic startle reflex, and brain reward function (measured in a discrete trial intracranial self-stimulation procedure) in rats. Somatostatin-28 decreased spontaneous locomotor activity during the first 10 min of a 60 min testing session with no apparent changes in the exploratory activity of rats. The highest somatostatin-28 dose (10 microg/5 microl/side) induced PPI deficits with no effect on the acoustic startle response or startle response habituation. The somatostatin-induced PPI deficit was partially reversed by administration of SRA-880, a selective somatostatin 1 (sst(1)) receptor antagonist. Somatostatin-28 also induced elevations in brain reward thresholds, reflecting an anhedonic-like state. The non-peptide sst(1) receptor antagonist SRA-880 had no effect on brain reward function under baseline conditions. Altogether these findings suggest that somatostatin-28 modulates PPI and brain reward function but does not have a robust effect on spontaneous exploratory activity. Thus, increases in somatostatin transmission may represent one of the neurochemical mechanisms underlying anhedonia, one of the negative symptoms of schizophrenia, and sensorimotor gating deficits associated with cognitive impairments in schizophrenia patients.
Asunto(s)
Actividad Motora/fisiología , Reflejo de Sobresalto/fisiología , Recompensa , Filtrado Sensorial/fisiología , Somatostatina-28/metabolismo , Estimulación Acústica , Análisis de Varianza , Animales , Catéteres de Permanencia , Relación Dosis-Respuesta a Droga , Masculino , Actividad Motora/efectos de los fármacos , Ratas , Ratas Wistar , Tiempo de Reacción , Reflejo de Sobresalto/efectos de los fármacos , Filtrado Sensorial/efectos de los fármacos , Somatostatina-28/farmacologíaRESUMEN
Goldfish brain somatostatin-28 (gbSS-28) is present in brain and pituitary tissues of goldfish. We assessed whether gbSS-28 targets Ca(2+) and/or protein kinase C (PKC)-dependent signaling cascades in inhibiting growth hormone (GH) release. gbSS-28 decreased basal GH release from primary cultures of dispersed goldfish pituitary cells and intracellular free calcium levels ([Ca(2+)](i)) in goldfish somatotropes. gbSS-28 partially reduced [Ca(2+)](i) and GH responses induced by two endogeneous gonadotropin-releasing hormones (GnRHs), salmon (s)GnRH and chicken (c)GnRH-II. Furthermore, gbSS-28 reduced GH increases and abolished [Ca(2+)](i) elevations elicited by two PKC activators, tetradecanoyl 4beta-phorbol-13-acetate and dioctanyl glycerol. The PKC inhibitors Gö6976 and Bis II abolished [Ca(2+)](i) responses to PKC activators, but only attenuated GnRH-induced increases in [Ca(2+)](i) and did not alter basal [Ca(2+)](i). In cells pretreated with Bis II, gbSS-28 further reduced basal [Ca(2+)](i). Our results suggest that gbSS-28 inhibits GnRH-induced GH release in part by attenuating PKC-mediated GnRH [Ca(2+)](i) signals. gbSS-28 reduces basal GH release also via reduction in [Ca(2+)](i) but PKC is not involved in this regard.