Cyclic AMP-mediated alteration of the CD2 activation process in human T lymphocytes. Preferential inhibition of the phosphoinositide cycle-related transduction pathway (original) (raw)
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Immunopharmacology, 1999
The role of the cAMP pathway as an immunomodulatory system has been an area of intensive research. Pharmacological elevation of the cAMP pathway inhibits T lymphocyte proliferation and production of Th1-type cytokines. The effects of Ž. cAMP are thought to be mediated via activation of the intracellular receptor, protein kinase A PKA. We investigated the inhibitory effects of cAMP elevation on human lymphocyte proliferation and function by utilising a range of selective inhibitors of PKA. Elevation of cAMP activity by dbcAMP, Sp-cAMPS and forskolin induced significant decreases of Con A stimulated PBMC proliferation. Co-incubation with the selective PKA inhibitors HA1004, KT5720 and Rp-cAMPS showed these antiproliferative effects to persist, despite measurable PKA activity being inhibited to that of untreated cells or less. IL-2 production was also inhibited by dbcAMP in the presence of HA1004 and Rp-cAMPS. It has been demonstrated that the inhibitory effects of pharmacological elevations in cAMP on human T cell proliferation and IL-2 production do not require PKA activity. These observations indicate that control of lymphocyte proliferation and functional status by cAMP proceeds through PKA-independent events. Identification of the underlying mechanisms behind these effects would increase our understanding of the cAMP cascade and may provide a potentially novel target for immunomodulation.
CD2 is involved in regulating cyclic AMP levels in T cells
European Journal of Immunology, 1988
The human T lymphocyte-specific CD2 (T11) molecule, that regulates T cell activation, is capable of mediating increases of intracellular CAMP. Monoclonal antibodies directed to different epitopes of the CD2 molecule which either induce or inhibit T cell proliferation are capable of triggering an increase of cAMP comparable to that induced by reagents which activate adenylate cyclase. These results indicate that there is a relationship between the CD2 membrane molecule and the adenylate cyclase system. 0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1988 0014-2980/88/0606-0961$02.50/0 We thank Drs. D . Cantrell, E. Rozengurtand M . Crumpton for helpful discussions and critical reading of the manuscript, Drs. F. Shchez-Madrid, A. Bernard and I. De Vries for providing antibodies, and M. A . Vallejo for typing the manuscript.
Scandinavian Journal of Immunology, 1987
Interleukin 2 (IL-2) was shown to induce a small but significant increase in the level of cGMP after 20 min stimulation and a subsequent fall after 1 h in activated T lymphocytes. No change in the level of cAMP was observed. Addition of the cyclic nucleotide analogues dbcAMP or dbcGMP did not stimulate DNA synthesis. On the contrary, IL-2-induced [3H]thymidine incorporation was inhibited by these drugs. Further, the phosphodiesterase inhibitor theophylline inhibited proliferation of activated T lymphocytes. Our results indicate that neither cAMP nor cGMP act as 'second messengers' for IL-2 but support the theory that cAMP is a negative regulator of cell proliferation.
European Journal of Immunology, 1989
cAMP inhibits the OKT3induced increase in cytoplasmic free calcium in the Jurkat T cell line: the degree of inhibition correlates inversely with the amount of CD3 binding ligand used* We have investi ated the effect of cAMP concentration on the CD3-mediated rise in intracellular CaR induced by anti-CD3 monoclonal antibody in the human T cell leukemia line Jurkat. Forskolin, prostaglandin E2 (PGE2) and dibutyryl cAMP (db-CAMP) were used to increase intracellular cAMP concentrations. Treatment of Jurkat cells with forskolin or db-CAMP for 3 h inhibited the subsequent rise in intracellular Ca2+ concentration induced by an optimally mitogenic dose of 100 ng/ml of the anti-CD3 OKT3, whereas PGE2 counteracted the Ca2+ rise only marginally. The inhibitory effect of forskolin and PGE2 on the Ca2+ signal correlated with their abilities to induce increased cAMP levels in Jurkat cells. The suppression of the Ca2+ response was dependent on the concentration of the CAMP-elevating agent and the time of pre-incubation with the drug. The CAMP-mediated inhibition of the Ca2+ response diminished or disappeared when increasing concentrations of OKT3 were used to stimulate the rise in intracellular Ca2+ concentration. The results indicate that cAMP participates in the regulation of T lymphocyte activation at the level of signal transduction. Our findin s, which stress the crucial role of the concentration of the ligand used to trigger C$+ responses, provide an explanation to previous contradictory reports on the impact of cAMP on the signal transduction in T cells. * This study was supported by grants from the Swedish Medical Research Council, Sigrid Juselius Foundation, Finska Lakaresallskapet, the PCrklen Foundation and the Finnish Academy of Sciences.
Cellular Immunology, 1992
Although raising intracellular cyclic adenosine monophosphate (CAMP) levels is generally considered to be inhibitory on the mitogen-induced T cell proliferation, in this study we have shown that the addition of either dbcAMP (50 PM) or cholera toxin (1 rig/ml) resulted in an increase in [3H]thymidine uptake in PBMC cultures stimulated with phorbol ester, 12-tetradecanoylphorbol 13-acetate (TPA), or with a combination of TPA plus anti-CD3 mAb (mAb 235). In contrast, under similar culture conditions, the phytohemagglutininP (PHA-P) response was inhibited by these agents as has been reported. The augmentative effect of dbcAMP in PBMC cultures was due to an increase in IL-2 production and not to increased in IL-2R-a chain expression. The enhancing effect of dbcAMP and CT observed with PBMC was monocyte dependent and not seen with purified T cell preparations. The addition of monocytes reconstituted the ability of intracellular CAMP elevating agents to augment the T cell response to TPA with and without mAb to CD3. The monocytes mediate their action via soluble factor(s) with molecular weight (m.w.) of more than 10 kDa. Neither rIL-1, rIL-6, nor rTNF+ have any augmentative effect as contrast with the supernatant from treated monocytes. Taken together, our results indicate that CAMP can play a positive regulatory role in T cell proliferation due to factor(s) secreted by dbcAMP-treated monocytes resulting in increased IL-2 synthesis in T cells. o
Cyclic AMP-mediated immune regulation — Overview of mechanisms of action in T cells
Cellular Signalling, 2011
The canonical second messenger cAMP is well established as a potent negative regulator of T cell immune function. Through protein kinase A (PKA) it regulates T cell function at the level of transcription factors, members of the mitogen-activated protein kinase pathway, phospholipases (PLs), Ras homolog (Rho)A and proteins involved in the control of cell cycle progression. Type I PKA is the predominant PKA isoform in T cells. Furthermore, whereas type II PKA is located at the centrosome, type I PKA is anchored close to the T cell receptor (TCR) in lipid rafts by the Ezrin-ERM-binding phosphoprotein of 50 kDa (EBP50)-phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG) scaffold complex. The most TCR-proximal target for type I PKA is C-terminal Src kinase (Csk), which upon activation by raft recruitment and phosphorylation inhibits the Src family tyrosine kinases Lck and Fyn and thus functions to maintain T cell homeostasis. Recently, induction of cAMP levels in responder T cells has emerged as one of the mechanisms by which regulatory T (T R) cells execute their suppressive action. Thus, the cAMP-type I PKA-Csk pathway emerges as a putative target for therapeutic intervention in autoimmune disorders as well as in cancer, where T R cell-mediated suppression contributes to suboptimal local immune responses.
Multiple high-affinity cAMP-phosphodiesterases in human T-lymphocytes
Biochemical Pharmacology, 1991
Cyclic nucleotide phosphodiesterases (PDEs) are the only enzymes that inactivate intracellular cyclic AMP (CAMP). Because the functions of T-lymphocytes are modulated by CAMP levels, the isozymes of PDE in these cells are potential targets for new drugs designed to modify the body's immunity through selective alteration of T-lymphocyte PDE activity. Cyclic GMP and 3(2H)-pyridazinone-4,5-dihydro-6-[4-(lfi-imidazol-l-yl)phenyl]-5-methyl-monohydrochloride (CI-930) selectively inhibit the catalytic activity of one of the two high affinity CAMP-PDE isozyme families known to occur in mammals, whereas d,f-1,4-[3-butoxy-4-methoxybenzyl]-Z-imidazolidinone (Ro 20-1724) selectively inhibits the other. The objectives of this investigation were: (1) to determine whether human T-lymphocytes contain one or both of these pharmacologically distinguishable high-affinity CAMP-PDEs, and (2) to determine the effects of selective inhibitors of these PDEs on lymphocyte blastogenesis. High-affinity CAMP-PDE was found in both the soluble and particulate fractions of T-lymphocyte sonicates. Cyclic GMP and CI-930 inhibited PDE in the particulate fraction better than in the soluble fraction, but the converse was found for Ro 20-1724. CI-930 or Ro 20-1724, used alone, attenuated T-lymphocyte blastogenesis, but neither suppressed it completely. In combination, the same PDE inhibitors caused greater suppression of blastogenesis than either produced alone. The results indicate that human T-lymphocytes contain both CI-930-and Ro 20-1724-inhibitable isozymes. Either of the isozymes can modulate human Tlymphocyte blastogenesis, but inhibition of both isozymes produces synergistic antiblastogenic effects, Intracellular cyclic AMP (CAMP) is an essential regulator of lymphocyte blastogenesis [l]. The only enzymes known to catalyze the inactivation of this second messenger are the phosphodiesterases 5 To whom correspondence should be sent at the following address:
British Journal of Pharmacology, 1996
1 The cyclic AMP phosphodiesterases (PDE) expressed by CD4+ and CD8+ T-lymphocytes purified from the peripheral blood of normal adult subjects were identified and characterized, and their role in modulating proliferation and the biosynthesis of interleukin (IL)-2 and interferon (IFN)-y evaluated. 2 In lysates prepared from both subsets, SK&F 95654 (PDE3 inhibitor) and rolipram (PDE4 inhibitor) suppressed cyclic AMP hydrolysis indicating the presence of PDE3 and PDE4 isoenzymes in these cells. Differential centrifugation and subsequent inhibitor and kinetic studies revealed that the particulate fraction contained, predominantly, a PDE3 isoenzyme. In contrast, the soluble fraction contained a PDE4 (-65% of total activity) and, in addition, a novel enzyme that had the kinetic characteristics of the recently identified PDE7. 3 Reverse transcription-polymerase chain reaction (RT-PCR) studies with primer pairs designed to recognise unique sequences in the human PDE4 and PDE7 genes amplified cDNA fragments that corresponded to the predicted sizes of HSPDE4A, HSPDE4B, HSPDE54D and HSPDE7. No message was detected for HSPDE4C after 35 cycles of amplification. 4 Functionally, rolipram inhibited phytohaemagglutinin-(PHA) and anti-CD3-induced proliferation of CD4+ and CD8+ T-lymphocytes, and the elaboration of IL-2, which was associated with a three to four fold increase in cyclic AMP mass. In all experiments, however, rolipram was approximately 60 fold more potent at suppressing IL-2 synthesis than at inhibiting mitogenesis. In contrast, SK&F 95654 failed to suppress proliferation and cytokine generation, and did not elevate the cyclic AMP content in T-cells. Although inactive alone, SK&F 95654 potentiated the ability of rolipram to suppress PHAand anti-CD3-induced T-cell proliferation, and PHA-induced IL-2 release. 5 When a combination of phorbol myristate acetate (PMA) and ionomycin were used as a co-mitogen, rolipram did not affect proliferation but, paradoxically, suppressed IL-2 release indicating that cyclic AMP can inhibit mitogenesis by acting at, or proximal to, the level of inositol phospholipid hydrolysis. 6 Collectively, these data suggest that PDE3 and PDE4 isoenzymes regulate the cyclic AMP content, IL-2 biosynthesis and proliferation in human CD4+ and CD8+ T-lymphocytes. However, the ability of rolipram to suppress markedly mitogen-induced IL-2 generation without affecting T-cell proliferation suggests that growth and division of T-lymphocytes may be governed by mediators in addition to IL-2. Finally, T-cells have the potential to express PDE7, although elucidating the functional role of this enzyme must await the development of selective inhibitors.
Biochemical and Biophysical Research Communications, 1988
The effect of a mito~mic combination of two different anti-CD2 m~noclonal antibodies on the PGE2-stimulated and basal cgMP production in human CD4+ T cell clones was investigated. The anti-[]~2 stimulation strongly potentiates the ~induced ~ pro~ction while beth P~% and A23187 p~mJuced a less potent effect. On the opposite the anti-C~2 treatment is without any effect on the basal cPMP level contrasting with a marked increase of intra~ellular c~%MP concentrations with A23187 or the cQmbination of A23187 and PMA. These results suggest that activation of CD4+ human T cells via the CD2 molecule significantly influences the c~1~-related transduction pathway. Although ~ and A23187 also modulate the activity of this pathway, their effect in this model is more likely mediated through an amplification of basal c~P production. ® 1988 A~d~m±o p ..... zno.