RESUMO
The antioxidant properties of the phenothiazine nucleus (PHT) associated with mitochondrial membranes and liposomes were investigated. PHT exhibited hydrophobic interaction with lipid bilayers, as shown by the quenching of excited states of 1-palmitoyl-2[10-pyran-1-yl)]-decanoyl-sn-glycero-3-phophocholine (PPDPC) incorporated in phosphatidylcholine/phosphatidylethanolamine/cardiolipin liposomes, observed even in high ionic strength; and by the spectral changes of PHT following the addition of mitochondrial membranes. Inserted into bilayers, 5 microM PHT was able to protect lipids and cytochrome c against pro-oxidant agents and exhibited spectral changes suggestive of oxidative modifications promoted by the trapping of the reactive species. In this regard, PHT exhibited the ability to scavenge DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical. PHT was also able to protect rat liver mitochondria against peroxide- and iron-induced oxidative damage and consequent swelling. At the concentration range in which the antioxidant properties were observed, PHT did not cause alterations in the membrane structure and function. This study contributes to the comprehension of the correlation structure and function of phenothiazines and antioxidant properties.
Assuntos
Antioxidantes/farmacologia , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Membranas Mitocondriais/efeitos dos fármacos , Fenotiazinas/farmacologia , Animais , DNA/farmacologia , Relação Dose-Resposta a Droga , Interações Hidrofóbicas e Hidrofílicas/efeitos dos fármacos , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , Lipossomos/química , Lipossomos/metabolismo , Fluidez de Membrana/efeitos dos fármacos , Fluidez de Membrana/fisiologia , Lipídeos de Membrana/metabolismo , Lipídeos de Membrana/farmacologia , Membranas Mitocondriais/química , Membranas Mitocondriais/metabolismo , Modelos Biológicos , Fenotiazinas/química , Fosfatidilcolinas/química , Fosfatidilcolinas/farmacologia , Proteínas/efeitos dos fármacos , Proteínas/metabolismo , RatosRESUMO
A study was undertaken to evaluate the physical, chemical and immunological aspects of a receptor for Pixuna virus present on 1-day-old chicken erythrocytes. The proteases trypsin and chymotrypsin were able to expose more binding sites on the erythrocytes, increasing the hemagglutinating titer (p < 0.001). Membrane components from red blood cell membranes (ROG) were extracted with the nonionic detergent octyl glucoside. ROG could bind to Pixuna virus and prevent hemagglutination. When ROG was filtered through a 0.22 mu filter, the activity was lost, but the filtrate inhibited plaque formation in Vero cells. The membrane components did not lose activity when kept at temperatures from -5 degrees C to -134 degrees C for months. After heating at 37 degrees C for 1 h and/or at 75 degrees C for 15 min the activity remained constant. A rabbit policlonal antiserum against the membranes gave precipitin lines in ID and in CIEF that disappeared after the enzymatic treatment, but the proteases did not affect the activity to produce hemagglutination-inhibition. Similar results were obtained when a mouse antiserum against ROG was used. The present study showed that the receptor for Pixuna virus present on 1-day-old chicken erythrocytes is not proteic in nature. The membrane components, ROG, with the property of inhibiting hemagglutination, contain proteins but they were not essential for the activity. It appears that the active compound was not able to produce antibodies in these experimental conditions. ROG had two different kinds of receptors: one that was able to produce hemagglutination-inhibition and another one with the property to inhibit plaque formation in Vero cells. Apparently, lipids would be involved in the hemagglutination-inhibition activity.
Assuntos
Galinhas/metabolismo , Vírus da Encefalite Equina Venezuelana/metabolismo , Membrana Eritrocítica/química , Receptores Virais/sangue , Animais , Galinhas/crescimento & desenvolvimento , Chlorocebus aethiops , Armazenamento de Medicamentos , Endopeptidases/farmacologia , Membrana Eritrocítica/efeitos dos fármacos , Glucosídeos , Testes de Hemaglutinação , Soros Imunes , Lipídeos de Membrana/isolamento & purificação , Lipídeos de Membrana/farmacologia , Lipídeos de Membrana/fisiologia , Camundongos , Coelhos , Solventes , Células Vero , Ensaio de Placa ViralRESUMO
The nicotinic acetylcholine receptor (AChR) is still the paradigm of rapid ligand-gated ion channels. Since the early finding of a motionally restricted shell of lipids ("annulus") in the immediate perimeter of the membrane-bound AChR, experimental evidence has supported the notion that the interface between the protein moiety and the adjacent lipid molecules is the site of action of a variety of pharmacologically relevant substances, including non-competitive inhibitors of the cholinergic system like some local anesthetics, short-chain alcohols, and steroids. Patch-clamp data on cells expressing the AChR protein add another dimension to this knowledge, enabling correlations to be established between the chemical composition of lipid-modified cells and the functional properties (ligand binding, channel gating) of the receptor protein in situ.
Assuntos
Ativação do Canal Iônico , Lipídeos de Membrana/metabolismo , Receptores Nicotínicos/metabolismo , Anestésicos/farmacologia , Animais , Colesterol/metabolismo , Colesterol/farmacologia , Dexametasona/farmacologia , Espectroscopia de Ressonância de Spin Eletrônica , Ácidos Graxos não Esterificados/metabolismo , Ácidos Graxos não Esterificados/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Cinética , Lipídeos de Membrana/farmacologia , Receptores Nicotínicos/efeitos dos fármacos , Relação Estrutura-Atividade , TorpedoRESUMO
The nicotinic acetylcholine receptor (AChR) is still the paradigm of rapid ligand-gated ion channels. Since the early finding of a motionally restricted shell of lipids ( annulus ) in the immediate perimeter of the membrane-bound AChR, experimental evidence has supported the notion that the interface between the protein moiety and the adjacent lipid molecules is the site of action of a variety of pharmacologically relevant substances, including non-competitive inhibitors of the cholinergic system like some local anesthetics, short-chain alcohols, and steroids. Patch-clamp data on cells expressing the AChR protein add another dimension to this knowledge, enabling correlations to be established between the chemical composition of lipid-modified cells and the functional properties (ligand binding, channel gating) of the receptor protein in situ
Assuntos
Animais , Ativação do Canal Iônico , Lipídeos de Membrana/metabolismo , Receptores Nicotínicos/metabolismo , Anestésicos/farmacologia , Colesterol/metabolismo , Colesterol/farmacologia , Dexametasona/farmacologia , Espectroscopia de Ressonância de Spin Eletrônica , Ácidos Graxos não Esterificados/metabolismo , Ácidos Graxos não Esterificados/farmacologia , Ativação do Canal Iônico , Cinética , Lipídeos de Membrana/farmacologia , Receptores NicotínicosRESUMO
1. A short review is given of the chemical, physical, and pharmacological development of the idea that target cell lipid membranes may catalyze the interaction between regulatory peptides (or other pharmacologic agents) and their cell surface receptors. 2. The message-address and the membrane compartments concepts explain the observed correlations between the three-dimensional structures of peptides induced by a membrane surface and their preference for a certain receptor subtype. 3. Examples are given for opioid peptides (enkephalin, dynorphin, etc.), tachykinin peptides (substance P, neurokinin A, etc.), and melanocortin peptides (ACTH, alpha-MSH, etc.). 4. Relationships between the conformation of substance P induced by membrane association and that of a non-peptide substance P mimetic are discussed. Possible reasons for the difference between agonistic and antagonistic properties in the peptide field are revealed by this case.
Assuntos
Lipídeos de Membrana/farmacologia , Peptídeos/farmacologia , Animais , Interações Medicamentosas , Humanos , Ligantes , Lipídeos de Membrana/química , Peptídeos/química , Conformação Proteica , Receptores de Peptídeos/química , Receptores de Peptídeos/efeitos dos fármacos , Relação Estrutura-AtividadeRESUMO
1. A short review is given of the chemical, physical, and pharmacological development of the idea that target cell lipid membranes may catalyze the interaction between regulatory peptides (or other pharmacologic agents) and their cell surface receptors. 2. The message-address and the membrane compartments concepts explain the observed correlations between the three-dimensional structures of peptides induced by a membrane surface and their preference for a certain receptor subtype. 3. Examples are given for opioid peptides (enkephalin, dynorphin, etc.), tachykinin peptides (substance P, neurokinin A, etc.), and melanocortin peptides (ACTH, alpha-MSH, etc.). 4. Relationships between the conformation of substance P induced by membrane association and that of a non-peptide substance P mimetic are discussed. Possible reasons for the difference between agonistic and antagonistic properties in the peptide field are revealed by this case