RESUMO
Proenkephalin peptides produced by endocrine and nervous tissues are involved in stress-induced immunosuppression. However, the role of peptides produced by immune cells remains unknown. The present study examines the effect of acute and chronic foot-shock stress on proenkephalin peptide content in bone marrow (BMMC), thymus (TMC), and spleen (SMC) rat mononuclear cells. Proenkephalin was not processed to met-enkephalin in BMMC, while in TMC and SMC met-enkephalin represented 10% and 26% of total met-enkephalin-containing peptides, respectively. Naive rats receiving a stress stimulus showed a significant decrease of proenkephalin derived peptides in BMMC, TMC and SMC. However, in chronically stressed rats that already showed basal low peptide levels, a new stress stimulus produced a differential response in each immune tissue. That is, in BMMC peptide levels reached control rats values; in TMC remained unmodified; and in SMC, although precursors content increased, met-enkephalin levels were even lower than those observed in acutely stressed rats. Free synenkephalin content paralleled met-enkephalin changes in SMC of acutely and chronically stressed rats. The in vitro release of met-enkephalin and free synenkephalin increased in SMC of stressed rats. Met-enkephalin produced in SMC and partially processed proenkephalin peptides detected in BMMC, were only found in macrophages. However, met-enkephalin only appeared in bone marrow macrophages after at least 4 h of cell culture. Altogether, these results suggest that a stress stimulus induced proenkephalin peptide release from immune tissue macrophages. The differential response observed in chronically stressed rats suggest an alternative activation of heterogeneous proenkephalin-storing macrophage subpopulations.
Assuntos
Células da Medula Óssea/metabolismo , Encefalinas/metabolismo , Leucócitos Mononucleares/metabolismo , Precursores de Proteínas/metabolismo , Baço/metabolismo , Estresse Fisiológico/metabolismo , Timo/metabolismo , Animais , Eletrochoque , Encefalina Metionina/metabolismo , Macrófagos/metabolismo , Masculino , Ratos , Ratos Wistar , Baço/citologia , Timo/citologiaRESUMO
Synenkephalin (proenkephalin 1-70) is produced and secreted as an intact molecule or as a part of precursors in the adult brain and adrenal medulla, respectively. However, it is cleaved to low molecular weight peptides in proliferating immune cells. Considering that the pre-proenkephalin gene is expressed in the embryonic rat brain during the cell proliferation stage, we studied the processing of synenkephalin in embryonic rat brains (E18) and compared it with the processing in adult rat brains. IR-synenkephalin was measured by RIA using a C-terminally directed antiserum. Adult rat brains contained higher concentrations of immunoreactive (IR)-synenkephalin (2,612 + 264) than embryonic rat brain (1,361 + 100) (results in fmol/mg proteins, n = 5). Gel filtration chromatography (Sephadex G-50) showed that in the extracts of adult rat brain, 50% of the IR-synenkephalin eluted in the position of the authentic peptide (8 kDa) and the rest of the immunoreactivity corresponded to partially processed peptides of 4.0 and 2.5 kDa. In embryonic rat brains synenkephalin was processed to intermediate peptides of 2.5, 1.7 and mainly to a low molecular weight peptide of 1.0 kDa. The concentration of this last peptide, which was further characterized by affinity column and HPLC, represented 45% of the total immunoreactivity. IR-met-enkephalin in embryonic rat brains (analyzed before and after enzymatic digestion with trypsin and carboxypeptidase B) corresponded principally to non-processed or partially processed products. However, these were cleaved to free met-enkephalin in adult rat brains.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Química Encefálica/fisiologia , Encéfalo/embriologia , Encefalinas/metabolismo , Precursores de Proteínas/metabolismo , Envelhecimento/metabolismo , Animais , Anticorpos Monoclonais/imunologia , Encéfalo/citologia , Divisão Celular , Cromatografia de Afinidade , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Encefalinas/imunologia , Feminino , Neostriado/metabolismo , Gravidez , Precursores de Proteínas/imunologia , Radioimunoensaio , Ratos , Ratos WistarRESUMO
Proenkephalin (PENK) messenger RNA was reported to be present in bone marrow mononuclear cells (BMMC) and spleen mononuclear cells (SMC). Nevertheless, the pattern of PENK products in normal cells of the rat immune system, which is important for defining the physiological role of PENK gene expression, has not been well established. In this work we have characterized the processing of the opioid portion (met-enkephalin-containing peptides) and nonopioid portion (synenkephalin-derived peptides) of PENK in rat BMMC and SMC. Met-enkephalin-containing peptides were detected in mononuclear cells of both hematopoietic tissues. In BMMC, free immunoreactive (IR)-met-enkephalin corresponded only to the 15% of total met-enkephalin-IR, whereas in SMC it represented the 66.5%. Gel filtration chromatography showed that BMMC contained partially processed PENK-derived peptides of high and intermediate molecular weight, whereas SMC displayed fully processed products containing met-enkephalin and/or the carboxyterminal portion of synenkephalin. HPLC purification of low molecular weight products showed that free IR-met-enkephalin in SMC mainly corresponded to met-enkephalin and oxidized met-enkephalin. In addition we have characterized in SMC three peptides lower than 3.0 kilodalton containing the C-terminal sequence of synenkephalin. These peptides were purified by gel filtration, affinity chromatography, ion exchange chromatography, and HPLC. These results show that PENK was processed in mononuclear cells of the primary (bone marrow) and secondary (spleen) organs of the rat hematopoietic system, as occurs in neural and endocrine tissues. Nevertheless, the precursor was cleaved only in the latter tissue to low molecular weight peptides. Furthermore we demonstrated that synenkephalin (proenkephalin 1-70) in SMC was processed to low molecular weight peptides containing the C-terminus free. This last result suggests that a dibasic Lys-Lys and monobasic (Lys) sites were cleaved.
Assuntos
Medula Óssea/metabolismo , Encefalinas/metabolismo , Monócitos/metabolismo , Precursores de Proteínas/metabolismo , Processamento de Proteína Pós-Traducional , Baço/metabolismo , Animais , Células da Medula Óssea , Cromatografia/métodos , Encefalinas/química , Peso Molecular , Precursores de Proteínas/química , Ratos , Baço/citologiaRESUMO
Proenkephalin-derived peptides, in common with other prohormones, are associated with membranes of microsomes and secretory granules in the bovine adrenal medulla. Post-translational processing of the precursor molecule varies depending upon the tissue. The relationship between post-translational events in different tissues was examined by studying the membrane association of endogenous proenkephalin-derived peptides in the crude microsomal fraction of rat adrenal medulla, brain striatum and heart ventricle. [Met]-Enkephalin and synenkephalin (proenkephalin(1-70)) immunoreactivities were quantified by radioimmunoassay after sequential enzymatic digestion with trypsin and carboxypeptidase B. Between 60 and 75% of total immunoreactive peptides present in intact microsomes of the three tissues were associated with membranes and specifically released with 2 M KSCN (pH 7.4). Analysis of the chromatographic profile of materials present in the soluble and associated fractions produced the following results. In the three tissues the materials associated with microsomal membranes corresponded to peptides larger than 3-5 kDa and displayed synenkephalin and [Met]-enkephalin immunoreactivity. Adrenal and heart microsomes showed a continuous pattern of membrane-associated proenkephalin-derived peptides of high, intermediate and low molecular weights containing the synenkephalin and [Met]-enkephalin sequences. These tissues, however, presented quantitative differences, as the highest concentrations belonged to materials larger and smaller than 12.5 kDa in adrenal and heart microsomes respectively. On the other hand, brain striatal microsomes displayed a discontinuous pattern of associated materials, with the absence of some products of high and intermediate molecular weight. Only in the soluble fraction of striatal microsomes were peptides detected of high and intermediate molecular weight containing the [Met]-enkephalin but not the synenkephalin sequence.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Medula Suprarrenal/metabolismo , Corpo Estriado/metabolismo , Encefalina Metionina/metabolismo , Encefalinas/metabolismo , Ventrículos do Coração/metabolismo , Microssomos/metabolismo , Precursores de Proteínas/metabolismo , Sequência de Aminoácidos , Animais , Membranas Intracelulares/metabolismo , Dados de Sequência Molecular , Especificidade de Órgãos , Processamento de Proteína Pós-Traducional , Ratos , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie , Vertebrados/genética , Xenopus/genéticaRESUMO
In the hematopoietic system a pluripotent stem cell generates precursors for lymphoid and myeloid lineages. Proenkephalin-derived peptides were previously detected in differentiated lymphoid cells. We have studied whether the proenkephalin system is expressed in a typical differentiated cell of the myeloid lineage, the neutrophil. Human peripheral polymorphonuclear cells contain and release proenkephalin-derived peptides. The opioid portion of proenkephalin (met-enkephalin-containing peptides) was incompletely processed, resulting in the absence of low molecular weight products. The nonopioid synenkephalin (proenkephalin 1-70) molecule was completely processed to a 1.0-kD peptide derived from the COOH-terminal. This molecule was characterized in neutrophils by biochemical and immunocytochemical methods. The chemotactic peptide FMLP and the calcium ionophore A23187 induced the release of the proenkephalin-derived peptides, and this effect was potentiated by cytochalasin B. The materials secreted were similar to those present in the cell, although in the supernatant a higher proportion corresponded to more processed products. The 1.0-kD peptide was detected in human, bovine, and rat neutrophils, but the chromatographic pattern of synenkephalin-derived peptides suggests a differential posttranslational processing among species. These findings demonstrate the existence of the proenkephalin system in human neutrophils and the production and release of a novel 1.0-kD peptide derived from the synenkephalin molecule. The presence of opioid peptides in neutrophils suggests their participation in the inflammatory process, including a local analgesic effect.
Assuntos
Encefalinas/metabolismo , Neutrófilos/metabolismo , Precursores de Proteínas/metabolismo , Animais , Calcimicina/farmacologia , Bovinos , Cromatografia em Gel , Humanos , Técnicas Imunoenzimáticas , Técnicas In Vitro , Peso Molecular , N-Formilmetionina Leucil-Fenilalanina/farmacologia , RatosRESUMO
The association of endogenous synenkephalin and met-enkephalin containing peptides with the membrane of bovine chromaffin granules and physicochemical characteristics of this association were studied. The associated materials were only released at a non physiological pH range and this effect was enhanced with growing salt concentrations (0.5, 1.0 and 2.0 M KSCN). A higher peptide dissociation occurred with membrane solubilizing agents (SDS greater than Triton X-100 greater than digitonin). In microsomes the materials dissociated with 2 M KSCN (pH 7.4) corresponded to peptides larger than 12.0 kDa, while in granules corresponded to molecules smaller than 8.5 kDa, displaying synenkephalin and met-enkephalin immunoreactivities. These data suggest that some sequence of the C-terminal portion of synenkephalin may be responsible for the association of proenkephalin derived peptides with microsome and granule membranes.
Assuntos
Medula Suprarrenal/ultraestrutura , Encefalina Metionina/metabolismo , Encefalinas/metabolismo , Membranas Intracelulares/metabolismo , Precursores de Proteínas/metabolismo , Animais , Bovinos , Fenômenos Químicos , Físico-Química , Grânulos Cromafim/ultraestrutura , Cromatografia em Gel , Digitonina/farmacologia , Concentração de Íons de Hidrogênio , Membranas Intracelulares/efeitos dos fármacos , Microssomos/ultraestrutura , Peso Molecular , Octoxinol , Concentração Osmolar , Polietilenoglicóis/farmacologia , Dodecilsulfato de Sódio/farmacologia , Tiocianatos/farmacologiaRESUMO
Adrenal enkephalin and enkephalin-containing peptides were studied during postnatal development in normotensive (WKY) and spontaneously hypertensive rats (SHR). The effect of chronic treatment with the ganglionic blocker chlorisondamine (5 mg/kg) was also assessed. Free enkephalin immunoreactivity and total enkephalin immunoreactivity, as determined by enzymatic digestion of large enkephalin containing fragments, were quantitated in the adrenal glands at 11 days and 7, 16, and 24 weeks of age. Both total and free metenkephalin were significantly diminished in the adrenal of SHR when compared to WKY at all ages tested. The analysis of the chromatographic profile showed that SHR displayed reduced levels of high and low molecular weight materials at 11 days and 16 weeks of age; however intermediate compounds were high in the glands of these animals. Similar increased values for free met-enkephalin were found in adrenals of WKY and SHR after ganglionic blocker treatment, which means that the relative increase was larger in SHR than WKY; while for total enkephalin the relative increase and the concentration reached in SHR was about half of those presented in WKY. These and other results presented suggest that the basic alteration of the adrenal proenkephalin system of SHR may be due to a genetic reduction of proenkephalin levels. Otherwise, the free enkephalin decrease could be related to changes in nervous input to the adrenal gland.
Assuntos
Glândulas Suprarrenais/metabolismo , Envelhecimento/metabolismo , Encefalinas/metabolismo , Hipertensão/metabolismo , Precursores de Proteínas/metabolismo , Glândulas Suprarrenais/efeitos dos fármacos , Animais , Clorisondamina/farmacologia , Cromatografia em Gel , Encefalina Leucina/metabolismo , Encefalina Metionina/metabolismo , Masculino , Peso Molecular , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
We have compared the enkephalin-like material derived from proenkephalin released from perfused cat adrenal glands stimulated with pilocarpine (5 X 10(-4)M) and nicotine (5 X 10(-6) M). In addition, two doses of acetylcholine (10(-5) and 10(-4) M) and 50 mM K+ were tested. Free Met-enkephalin immunoreactivity and total Met-enkephalin immunoreactivity, as determined by enzymatic digestion of large enkephalin-containing fragments, were coreleased with catecholamines. Free Met-enkephalin immunoreactivity represented 13% of total immunoreactivity for nicotinic stimulation, 46% for pilocarpine, 33% for 10(-5) M acetylcholine, 22% for 10(-4) M acetylcholine, and 16% for 50 mM K+. Analysis of the perfusate by gel filtration showed that 80% of the total Met-enkephalin immunoreactivity whose release was induced by pilocarpine was eluted in fractions corresponding to fragments of low molecular weight, whereas these fractions accounted only for 10% of the total Met-enkephalin immunoreactivity whose release was induced by nicotine. HPLC analysis of low-molecular-weight peptide fractions revealed that Met-enkephalin, Met-enkephalin-Arg-Gly-Leu, and Met-enkephalin-Arg-Phe represented 69% of total Met-enkephalin immunoreactivity whose release was induced by pilocarpine. These results indicate that selective activation of muscarinic receptors is followed by release of low-molecular-weight material, whereas nicotine application also yielded high-molecular-weight peptides. Furthermore, increasing the acetylcholine concentration from 10(-5) to 10(-4) M and using 50 mM K+ increased proportionally the high-molecular-weight peptide secretion. Results are discussed in relation to the existence of a heterogeneous population of granules either in the same cell or in different cells, containing proenkephalin-derived peptides. (ABSTRACT TRUNCATED AT 250 WORDS)