Navegando por Palavras-chave "cyclic AMP"
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- ItemSomente MetadadadosAngiotensin II AT(1) receptor mutants expressed in CHO cells caused morphological change and inhibition of cell growth(Elsevier B.V., 2005-11-15) Corrêa, Silvana Aparecida Alves [UNIFESP]; Pacheco, NAS; Costa-Neto, C. M.; Oliveira, L.; Pesquero, J. B.; Han, S. W.; Paiva, ACM; Shimuta, S. I.; Universidade Federal de São Paulo (UNIFESP); São Paulo State UnivTo assess the importance of the leucine residues in positions 262 and 265 of the angiotensin AT, receptor for signaling pathways and receptor expression and regulation, we compared the properties of CHO cells transfected with the wild type or the L262D or L265D receptor point mutants. It was found that the two mutants significantly increased the basal intracellular cyclic AMP (cAMP) formation in an agonist-independent mode. the morphology transformation of CHO cells was correlated with the increased cAMP formation, since forskolin, a direct activator of adenylate cyclase mimicked this effect on WT-expressing CHO cells. DNA synthesis was found to be inhibited in these cell lines, indicating that cAMP may also have determined the inhibitory effect on cell growth, in addition to the cell transformation from a tumorigenic to a non-tumorigenic phenotype. However a role for an increased Ca2(+) influx induced by the mutants in non-stimulated cells cannot be ruled out since this ion also was shown to cause transformed cells to regain the morphology and growth regulation. (c) 2005 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosDeveloping skeletal muscle cells express functional muscarinic acetylcholine receptors coupled to different intracellular signaling systems(Nature Publishing Group, 2005-10-01) Furlan, Ingrid; Godinho, Rosely Oliveira [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)1 This study analyzed the expression of muscarinic acetylcholine receptors (mAChRs) in the rat cultured skeletal muscle cells and their coupling to G protein, phospholipase C and adenylyl cyclase (AC).2 Our results showed the presence of a homogeneous population of [H-3]methyl-quinuclidinyl benzilate-binding sites in the membrane fraction from the rat cultured muscle (K-D = 0.4 nM, B-max = 8.9 fmol mg protein(-1)). Specific muscarinic binding sites were also detected in denervated diaphragm muscles from adult rats and in myoblasts isolated from newborn rats.3 Activation of mAChRs with carbachol induced specific [S-35]GTP gamma S binding to cultured muscle membranes and potentiated the forskolin-dependent stimulation of AC. These effects were totally inhibited by 0.1-1 mu M atropine.4 in addition, mAChRs were able to stimulate generation of diacylglycerol (DAG) in response to acetylcholine, carbachol or selective mAChR agonist oxotremorine-M.5 the carbachol-dependent increase in DAG was inhibited in a concentration-dependent manner by mAChR antagonists atropine, pirenzepine and 4-DAMP mustard.6 Finally, activation of these receptors was correlated with increased synthesis of acetylcholinesterase, via a PKC-dependent pathway.7 Taken together, these results indicate that expression of mAChRs, coupled to G protein and distinct intracellular signaling systems, is a characteristic of noninnervated skeletal muscle cells and may be responsible for trophic influences of acetylcholine during formation of the neuromuscular synapse.
- ItemSomente MetadadadosDifferential inhibitory mechanism of cyclic AMP on TNF-alpha and IL-12 synthesis by macrophages exposed to microbial stimuli(Stockton Press, 1999-07-01) Procópio, Daniela O. [UNIFESP]; Teixeira, Mauro M.; Camargo, Maristela M.; Travassos, Luiz R.; Ferguson, Michael AJ; Almeida, Igor C.; Gazzinelli, Ricardo T.; Universidade Federal de Minas Gerais (UFMG); FIOCRUZ; Universidade Federal de São Paulo (UNIFESP); Univ Dundee1 Microbial stimuli such as bacterial lipopolysaccharide (LPS) or glycosylphosphatidylinositol-mucins derived from Trypanosoma cruzi trypomastigotes (tGPI-mucins) are effective stimulators of the synthesis of cytokines by macrophages. Here, we evaluated the ability of cyclic AMP mimetic or elevating agents to modulate TNF-alpha and IL-12 synthesis by murine inflammatory macrophages.2 Cholera Toxin (ChTx) inhibited tGPI-mucins (2.5 nM) or LPS (100 ng ml(-1)) induced TNF-alpha and IL-12(p40) synthesis in a concentration-dependent manner. Similarly, the cyclic AMP mimetics, 8-bromo cyclic AMP or dibutyryl cyclic AMP, or prostaglandin (PG) E-2 inhibited the synthesis of both cytokines by macrophages exposed to microbial stimuli.3 the protein kinase A inhibitor H-89 partially reversed the inhibitory effects of dibutyryl cyclic AMP and PGE(2) on both IL-12(p40) and TNF-alpha synthesis.4 Pretreatment of macrophages with dibutyryl cyclic AMP or ChTx augmented the synthesis of IL-10 triggered by microbial products. Elevation of cyclic AMP inhibited the synthesis of TNF-alpha, but not IL-12(p40), by inflammatory macrophages from IL-10 knockout mice.5 Kinetic studies showed that synthesis of both TNF-alpha and IL-10 peaked at 8 h and IL-12 at 24 h after stimulation with microbial stimuli.6 Together, our findings favour the hypothesis that the cyclic AMP inhibitory activity on IL-12(p40) but not on TNF-alpha synthesis is dependent on de novo protein synthesis, most likely involving IL-10, by macrophages stimulated with microbial products. Accordingly, dibutyryl cyclic AMP inhibited IL-12(p40) synthesis only when added before or at the same time of the stimuli. in contrast, the effect of this cyclic AMP analogue on TNF-alpha synthesis was protracted and observed even 2 h after the addition of the stimuli.
- ItemSomente MetadadadosEffect of estrogen on intracellular signaling pathways linked to activation of M-2- and M-3-muscarinic acetylcholine receptors in the rat myometrium(Elsevier B.V., 2000-02-25) Abdalla, Fernando M. F.; Abreu, Lygia C. [UNIFESP]; Porto, Catarina S. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Inst ButantanThe estrogen treatment of adult female rats induces an increase in myometrium sensitivity to cholinergic agonists and in this tissue the presence of M-2- and M-3-muscarinic acetylcholine (mACh) receptor was shown. We now report the effect of estrogen on intracellular signaling pathways linked to activation of M-2- and M-3-mACh receptor subtypes. the intracellular cyclic AMP accumulation and [H-3]-inositol phosphates content were measured in myometrium strips from rats in estrus (control) and estradiol-treated rats (12.5 mu g/100 g body weight, sc, 24 h before experiments) (the plasma estradiol level was 30.9 +/- 3.5 pg/ml and 119.3 +/- 14.1 pg/ml from control and estrogen-treated rats, respectively). Estrogen treatment increased 2.5-fold the intracellular cyclic AMP accumulation induced by 10 mu M forskolin. the effects of muscarinic agonist and antagonists on cyclic AMP accumulation were tested. Carbachol reduced the forskolin-induced intracellular cyclic AMP content, 3.0 and 10.5-fold, in myometrium from control and estradiol-treated rats, respectively. This inhibitory effect failed to occur when carbachol was incubated in the presence of methoctramine. Carbachol also induced increase on total [H-3]-inositol phosphates accumulation in myometrium from estradiol-treated rats when compared with control rats. This effect was reversed by pfHHSiD. These studies suggest the modulation by estrogen of intracellular signaling pathways linked to activation of M-2- and M-3-mACh receptors in the rat myometrium. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.
- ItemAcesso aberto (Open Access)New perspectives in signaling mediated by receptors coupled to stimulatory G protein: the emerging significance of cAMP efflux and extracellular cAMP-adenosine pathway(Frontiers Research Foundation, 2015-03-25) Godinho, Rosely Oliveira [UNIFESP]; Duarte, Thiago [UNIFESP]; Pacini, Enio Setsuo Arakaki [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)G protein coupled receptors (GPCRs) linked to stimulatory G (Gs) proteins (GsPCRs) mediate increases in intracellular cyclic AMP as consequence of activation of nine adenylyl cyclases, which differ considerably in their cellular distribution and activation mechanisms. Once produced, cyclic AMP may act via distinct intracellular signaling effectors such as protein kinase A and the exchange proteins activated by cAMP (Epacs). More recently, attention has been focused on the efflux of cAMP through a specific transport system named multidrug resistance proteins that belongs to the ATP-binding cassette transporter superfamily. Outside the cell, cAMP is metabolized into adenosine, which is able to activate four distinct subtypes of adenosine receptors, members of the GPCR family: A(1), A(2)A, A(2B), and A(3). Taking into account that this phenomenon occurs in numerous cell types, as consequence of GsPCR activation and increment in intracellular cAMP levels, in this review, we will discuss the impact of cAMP efflux and the extracellular cAMP-adenosine pathway on the regulation of GsPCR-induced cell response.
- ItemSomente MetadadadosRegulation of intracellular cyclic AMP in skeletal muscle cells involves the efflux of cyclic nucleotide to the extracellular compartment(Nature Publishing Group, 2003-03-01) Godinho, Rosely Oliveira [UNIFESP]; Costa, Valter Luiz; Universidade Federal de São Paulo (UNIFESP)1 This report analyses the intracellular and extracellular accumulation of cyclic AMP in primary rat skeletal muscle cultures,. after direct and receptor-dependent stimulation of adenylyl cyclase (AC).2 Isoprenaline, calcitonin gene-related peptide (CGRP) and forskolin induced a transient increase in the intracellular cyclic AMP that peaked 5 min after onset stimulation.3 Under stimulation with isoprenaline or CGRP, the intracellular cyclic AMP initial rise was followed by an exponential decline, reaching 46 and 52% of peak levels in 10 min, respectively.4 Conversely, the forskolin-dependent accumulation of intracellular cyclic AMP decreased slowly and linearly, reaching 49% of the peak level in 30 min.5 the loss of intracellular cyclic AMP from peak levels, induced by direct or receptor-induced activation of AC, was followed by an increase in the extracellular cyclic AMP.6 This effect was independent on PDEs, since it was obtained in the presence of 3-isobutyl-1-methylxanthine (IBMX).7 Besides, in isoprenaline treated cells, the beta-adrenoceptor antagonist propranolol reduced both intra- and extracellular accumulation of cyclic AMP, whereas the organic anion transporter inhibitor probenecid reduced exclusively the extracellular accumulation.8 Together our data show that direct or receptor-dependent activation of skeletal muscle AC results in a transient increase in the intracellular cyclic AMP, despite the continuous presence of the stimulus. the temporal declining of intracellular cyclic AMP was not dependent on the cyclic AMP breakdown but associated to the efflux of cyclic nucleotide to the extracellular compartment, by an active transport since it was prevented by probenecid. British Journal of Pharmacology (2003).
- ItemSomente MetadadadosRole of preoptic second messenger systems (cAMP and cGMP) in the febrile response(Elsevier B.V., 2002-07-19) Steiner, A. A.; Antunes-Rodrigues, J.; Branco, LGS; Universidade Federal de São Paulo (UNIFESP); Dent Sch Ribeirao PretoThe present study aimed to test the hypothesis that a decrease in preoptic cAMP mediates fever. To this end, body core temperature (T-c) of unanesthetized, freely moving rats was monitored by biotelemetry before and after pharmacological modulation of the cAMP pathway, and cAMP levels in the anteroventral third ventricular region (AV3V), where the preoptic region (POA) is located, were determined. We observed that intra-POA administration of the cAMP agonist dibutyryl-cAMP (Db-cAMP, 40 mug) reduced T-c. PGE(2) (the proximal mediator of fever, 200 ng) raised T-c with a concomitant decrease in AV3V cAMP levels from 22.7+/-1.8 to 17.0+/-1.0 fmol/mug protein. Moreover, PGE(2)-induced fever was impaired by the phosphodiesterase inhibitor aminophylline. in order to verify the interaction between the cAMP- and cGMP-dependent pathways in the POA, we then co-injected Db-cAMP and 8-Br-cGMP into the POA. As a result, 8-Br-cGMP augmented the drop in 7 evoked by Db-cAMP. Lastly, we observed that intra-POA co-microinjection of the protein kinase A inhibitor (Rp-cAMPS, 1 mug) with the protein kinase G inhibitor (Rp-cGMPS, 1 mug), mimicking the effects of reduced production of cAMP and cGMP, respectively, produced a fever-like response. in summary, the present data support that a decrease in the levels of cAMP and cGMP in the POA is associated with the genesis of fever. (C) 2002 Elsevier Science BY. All rights reserved.