Activation of the CD3/T cell receptor (TcR) complex or of protein kinase C potentiate adenylyl cyclase stimulation in a tumoral T cell line: involvement of two distinct intracellular pathways

Inhibition of lymphocyte CD3 expression by Chlamydophila pneumoniae infection

Since lymphocytes are a major immune cell besides macrophages in the development of atherosclerosis, interaction between lymphocytes and Chlamydophila pneumoniae may contribute to the pathogenesis of chronic inflammatory diseases associated with C. pneumoniae. In this regard, we examined a possible alteration of CD3 expression of human lymphocyte Molt-4 cells by C. pneumoniae infection. The expression levels of CD3 molecules of lymphocyte Molt-4 cells were significantly decreased by C. pneumoniae infection. In contrast, heat-killed C. pneumoniae as well as mock (cell lysates) did not cause any alteration of CD3 expression of the cells. Treatment of the infected cells with NS-398 (cyclo-oxyganase-2 inhibitor) or AH-23848 (EP(4) prostanoid receptor antagonist) abolished the inhibition of CD3 expression. The enhanced prostaglandin E(2) (PGE(2)) productions in the culture supernatants of infected cells were confirmed by competitive enzyme-immunosorbent assay (ELISA). C. pneumoniae infection of enriched lymphocytes from human peripheral blood mononuclear cells also induced a decrease of CD3 expression. Thus, C. pneumoniae infection of lymphocytes induces a decrease of CD3 expression mediated by possibly PGE(2) production.

T cell receptor-independent CD4 signalling: CD4-MHC class II interactions regulate intracellular calcium and cyclic AMP

CD4 is a coreceptor on T helper (Th) cells that interacts with MHC class II molecules (MHCII). The mechanisms mediating the effects of CD4 on responses by T helper cells to stimulation of the antigen-specific T cell receptor (TCR) are still poorly understood. Here, we demonstrate T cell costimulation via CD4 signalling independent of T cell receptor-mediated signals. Incubation of T helper cells with peptide mimetics of the CD4-binding region on the MHC class II beta2 domain caused intracellular calcium mobilization in the absence of antigen or other T cell receptor stimuli. Engagement of CD4 by peptide mimetics or wild-type MHC class II, but not by mutant MHC class II molecules incapable of engaging CD4, inhibited the T cell receptor-mediated increase in cyclic AMP (cAMP) concentrations in T helper cells. CD4-mediated signals activated cyclic AMP phosphodiesterases (PDEs) and inhibited adenylyl cyclase. Full activation and clonal expansion of antigen-stimulated T helper cells required the CD4-mediated regulation of cyclic AMP. Our results suggest a costimulatory mechanism of CD4 function that acts on the second messengers, calcium and cyclic AMP.

Modifications of the catalytic and binding subunits of pertussis toxin by formaldehyde: effects on toxicity and immunogenicity

A panel of pertussis toxin (PT) preparations with varying levels of residual toxicity was prepared by treatment of native PT with formaldehyde (0-1.00% (w/v)) with the purpose of investigating the effects of residual toxicity on immunogenicity. The catalytically inactive mutant PT (PT-9K/129G) was used for comparison. Results from in vitro ADP-ribosyl transferase and Chinese hamster ovary (CHO)-cell toxicity assays demonstrated a formaldehyde-dependent reduction in PT toxicity, and implied that both A and B domain functions of PT were modified. The in vivo histamine sensitisation and leukocyte proliferation tests suggested that the formaldehyde-treated native PT preparations were subject to reversion to toxicity. Reversion was confirmed by in vitro toxicity assays, which demonstrated recovery of A and B domain functions. The presence of high molecular weight aggregated and cross-linked species of PT in these preparations did not appear to be detrimental to the production of a neutralising antibody response. IgG responses to native and non-catalytic mutant PT suggested that low levels of residual activity in the native PT enhanced the antibody response, while higher levels of activity inhibited the response. Using the non-catalytic mutant PT showed that formaldehyde-induced changes were not detrimental to the magnitude of the PT-specific antibody response but did reduce the PT-specific neutralising activity. In conclusion, the residual toxicity of PT preparations following formaldehyde treatment may play an important role in the immune response to pertussis vaccine, potentially altering the quality, class and magnitude of the antibodies produced to PT.

Ketoconazole suppresses interleukin-4 plus anti-CD40-induced IgE class switching in surface IgE negative B cells from patients with atopic dermatitis

We previously reported that antimycotic agent ketoconazole suppressed interleukin-4 production in T cells from patients with atopic dermatitis. We herein studied if ketoconazole may suppress B cell IgE class switching. Interleukin-4 plus anti-CD40-induced IgE secretion was enhanced in peripheral blood surface IgE- B cells from atopic dermatitis patients compared to those from normal donors, and the secretion was inhibited by ketoconazole. Ketoconazole suppressed interleukin-4 plus anti-CD40-induced germline and mature epsilon transcripts in surface IgE- B cells. Ketoconazole also inhibited interleukin-4 plus anti-CD40-induced activation of germline epsilon promoter in human Burkitt lymphoma Ramos cells. The regions -171/-155 bp containing CCAAT/enhancer-binding protein element and -155/-109 bp containing Stat6 and nuclear factor kappaB elements were required for the ketoconazole-induced inhibition of the germline epsilon promoter activity. Ketoconazole inhibited interleukin-4 plus anti-CD40-induced enhancer activities of CCAAT/enhancer-binding protein and nuclear factor kappaB, and those of composite elements of CCAAT/enhancer-binding protein/Stat6 or of Stat6/nuclear factor kappaB, but did not alter that of Stat6 in Ramos cells. cAMP analog reversed the inhibitory effects of ketoconazole on interleukin-4 plus anti-CD40-induced IgE secretion, germline and mature epsilon transcripts, and epsilon germline promoter activation. Interleukin-4 plus anti-CD40 increased intracellular cAMP by activating cAMP-synthesizing adenylate cyclase in surface IgE- B cells, and the increase was greater in the cells from atopic dermatitis patients than in those from normal donors. Ketoconazole suppressed interleukin-4 plus anti-CD40-induced activation of adenylate cyclase in surface IgE- B cells. These results suggest that ketoconazole may suppress interleukin-4 plus anti-CD40-induced B cell IgE class switching by inhibiting cAMP signal, and stress its prophylactic effects on allergic diseases.

Anti-mycotics suppress interleukin-4 and interleukin-5 production in anti-CD3 plus anti-CD28-stimulated T cells from patients with atopic dermatitis

It is reported that anti-mycotic agents are effective for the treatment of patients with atopic dermatitis. We studied the in vitro effects of anti-mycotics on T helper-1 and T helper-2 cytokine production in anti-CD3 plus anti-CD28-stimulated T cells from atopic dermatitis patients and normal donors. The amounts of interleukin-4 and interleukin-5 secreted by anti-CD3/CD28-stimulated T cells were higher in atopic dermatitis patients than in normal donors. Azole derivatives, ketoconazole, itraconazole, miconazole, and nonazole terbinafine hydrochloride, and tolnaftate reduced interleukin-4 and interleukin-5 secretion without altering that of interferon-gamma and interleukin-2 in anti-CD3/CD28-stimulated T cells from both atopic dermatitis patients and normal donors. The azole derivatives were more inhibitory than nonazole anti-mycotics. These anti-mycotics reduced the anti-CD3/CD28-induced mRNA expression and promoter activities for interleukin-4 and interleukin-5. The 3',5'-cyclic adenosine monophosphate analog dibutyryl 3',5'-cyclic adenosine monophosphate reversed the inhibitory effects of the anti-mycotics on interleukin-4 and interleukin-5 secretion, mRNA expression, and promoter activities. Anti-CD3/CD28 transiently (< or = 5 min) increased intracellular 3',5'-cyclic adenosine monophosphate in T cells, and the increase was greater in atopic dermatitis patients than in normal donors. The increase of 3',5'-cyclic adenosine monophosphate by anti-CD3/CD28 correlated with interleukin-4 and interleukin-5 secretion by anti-CD3/CD28. The transient 3',5'-cyclic adenosine monophosphate increase was suppressed by anti-mycotics, and azole derivatives were more suppressive than nonazoles. Azole derivatives inhibited the activity of cyclic adenosine monophosphate-synthesizing adenylate cyclase whereas terbinafine hydrochloride and tolnaftate enhanced the activity of 3',5'-cyclic adenosine monophosphate-hydrolyzing cyclic nucleotide phosphodiesterase in atopic dermatitis and normal T cells. These results suggest that the anti-mycotics may suppress interleukin-4 and interleukin-5 production by reducing 3',5'-cyclic adenosine monophosphate signal, and stress their potential use for the suppression of T helper-2-mediated allergic reactions.

Regulatory roles of adenylate cyclase and cyclic nucleotide phosphodiesterases 1 and 4 in interleukin-13 production by activated human T cells

We studied the activities of 3',5'-adenosine-cyclic monophosphate (cAMP)- synthesizing adenylate cyclase (AC) and cAMP-hydrolyzing cyclic nucleotide phosphodiesterase (PDE) in phytohemagglutinin (PHA)- or anti-CD3 plus anti-CD28-stimulated human T cells, and examined their roles in interleukin-13 (IL-13) production. The AC inhibitor MDL 12,330A [cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine hydrochloride] completely blocked PHA- or anti-CD3/CD28-induced IL-13 production. The PDE 1 inhibitor 8-methoxymethyl-3-isobutyl-1-methylxanthine or the PDE4 inhibitor rolipram partially inhibited IL-13 production, and the addition of both resulted in 100 or 85% inhibition in PHA- or anti-CD3/CD28-stimulated T cells, respectively. AC in T cells was transiently activated 5 min after stimuli, followed by the transient activation of PDE4 at 30 min. PDE1 activity, undetectable in resting T cells, was detected 3 hr after stimuli, and then increased gradually. Although PDE1-, 2-, 3-, and 4-independent PDE activity was low (< or = 15% of total), it began to increase 3 hr after anti-CD3/CD28; the increase was blocked by PDE7 antisense oligonucleotide, and such an increase was not induced by PHA. PHA or anti-CD3/CD28 induced PDE1B mRNA expression, undetectable in resting T cells. PDE4 mRNA level in T cells was not altered by either stimulus. PDE7 mRNA expression was detected in resting T cells, and was enhanced by anti-CD3/CD28, but not by PHA. The cAMP level of T cells increased 5 min after stimuli, returned to the basal level at 2 hr, and then continued to decrease. These results suggest that PHA or anti-CD3/CD28 initially (< or = 5 min) increases cAMP in T cells via AC, then reverses the increase via PDE4 (< or = 2 hr), and in the later phase (> 2 hr) further decreases cAMP via PDE1. Both the time-dependent increase and decrease of cAMP may be required for IL-13 production.

Intracellular 3',5'-adenosine cyclic monophosphate level regulates house dust mite-induced interleukin-13 production by T cells from mite-sensitive patients with atopic dermatitis

We studied the relationship between cAMP and house dust mite-induced cytokine production in T cells from mite-sensitive patients with atopic dermatitis. T cells from atopic dermatitis patients secreted high level of interleukin-13 (mean 851.1 pg per ml) when cultured with autologous monocytes pulsed with Dermatophagoides pteronyssinus extract. Dermato- phagoides pteronyssinus-induced interleukin-13 secretion was not detected in normal subjects. Adenylate cyclase inhibitor MDL 12,330A and cyclic nucleotide phosphodiesterase type 4 inhibitor rolipram blocked Dermatophagoides pteronyssinus-induced interleukin-13 secretion in atopic dermatitis T cells. In atopic dermatitis T cells, cAMP level rose at 5 min after Dermatophagoides pteronyssinus stimulus then decreased to the basal level at 1 h. MDL 12,330A blocked the Dermatophagoides pteronyssinus-induced cAMP elevation while rolipram blocked its reversal. In atopic dermatitis T cells, adenylate cyclase activity increased at 5 min after Dermatophagoides pteronyssinus stimulus, followed by the increase of cyclic nucleotide phosphodiesterase activity at 15 min. In atopic dermatitis T cells, phospholipase C inhibitor ET-18-OCH3 blocked Dermatophagoides pteronyssinus-induced activation of adenylate cyclase, while rolipram, protein kinase A inhibitor H-89, and MDL 12,330A blocked the activation of cyclic nucleotide phosphodiesterase. These results suggest that Dermatophagoides pteronyssinus may first increase cAMP in atopic dermatitis T cells by activating adenylate cyclase via phospholipase C, and next decrease cAMP by activating cyclic nucleotide phosphodiesterase 4 via protein kinase A, which may be activated by adenylate cyclase-generated cAMP signal. These events are required for interleukin-13 response Dermatophagoides pteronyssinus.

Gangliosides GD1b, GT1b, and GQ1b enhance IL-2 and IFN-gamma production and suppress IL-4 and IL-5 production in phytohemagglutinin-stimulated human T cells

Gangliosides are sialic acid-containing glycolipids. We studied the in vitro effects of gangliosides on Th1 and Th2 cytokine production in PHA-stimulated human T cells. Gangliosides GD1b, GT1b, and GQ1b (each 100 nM) enhanced PHA-induced IL-2 secretion of peripheral blood T cells approximately 4-fold and enhanced that of IFN-gamma 3- to 4-fold compared with controls. These gangliosides decreased PHA-induced IL-4 secretion by 50-53% and that of IL-5 by 53-63% compared with controls, respectively. The other gangliosides did not alter the secretion of Th1 or Th2 cytokines. RT-PCR showed that GD1b, GT1b, and GQ1b enhanced PHA-induced IL-2 and IFN-gamma transcription and suppressed that of IL-4 and IL-5. Transient transfection assays of Jurkat T cells showed that GD1b, GT1b, and GQ1b enhanced PHA-induced IL-2 and IFN-gamma promoter activities but suppressed those of IL-4 and IL-5. The cAMP analogue dibutyryl cAMP and the cAMP-elevating agents forskolin and 3-isobutyl-1-methylxanthine each reversed GD1b-, GT1b-, and GQ1b-induced stimulation of IL-2 and IFN-gamma production and inhibition of IL-4 and IL-5 production at the levels of proteins, transcription, and promoter activities. GD1b, GT1b, and GQ1b suppressed PHA-induced increase in cAMP level in T cells. These gangliosides suppressed PHA-stimulated adenylate cyclase activity in T cells. These results suggest that GD1b, GT1b, and GQ1b may enhance Th1 cytokine production while suppressing Th2 production by inhibiting adenylate cyclase activity.

PGE(2)-mediated inhibition of T cell p59(fyn) is independent of cAMP

We recently observed that prostaglandin E(2) (PGE(2))-mediated suppression of T cell functions could result from an attenuation of p59(fyn) protein tyrosine kinase activity. The present study evaluated the effects of an adenylate cyclase agonist (forskolin) and antagonist (SQ-22536), as well as those of cAMP analogues (dibutyryl cAMP and 8-bromo- cAMP), on T cell p59(fyn) kinase activity. The study allowed us to assess whether PGE(2)-mediated activation of adenylate cyclase by itself or the elevation in intracellular cAMP levels is an integral event in the modulation of anti-CD3-linked p59(fyn) activation in T cells. The experiments were carried out with splenic T cells from male Sprague-Dawley rats. A 30-50% suppression in the autophosphorylation and the kinase activity of p59(fyn) in T cells incubated with PGE(2) or forskolin was observed. Pretreatment of T cells with SQ-22536 prevented significant PGE(2)-mediated inhibition of T cell p59(fyn) kinase activity. In contrast, no change in p59(fyn) autophosphorylation and kinase activity in T cells treated with cAMP analogues was observed. These data suggest that PGE(2)-mediated suppression of p59(fyn) autophosphorylation and kinase activity in T cells is dependent on the activation of adenylate cyclase and independent of the elevation in cAMP levels.

Regulation of adenylyl cyclase activity in human peripheral blood mononuclear cells: effects of protein kinase inhibitors and of a calcium ionophore

In a previous paper we presented evidence for a negative regulation of adenylyl cyclase activity by tyrosine protein kinase(s) in the human leukemic T cell line Jurkat. In order to examine this point in non malignant cells, we conducted the present study in human peripheral blood mononuclear cells (PBMC). In these cells, staurosporine, a broad spectrum protein kinase inhibitor, enhanced not only the receptor-mediated, induced by prostaglandin E2 (PGE2), but also the direct (forskolin-induced) stimulation of adenylyl cyclase activity. Herbimycin A, a specific protein tyrosine kinase inhibitor, reproduced only in part the effect of staurosporine, whereas bisindolylmaleimide, the most specific protein kinase C (PKC) inhibitor known at present time, was ineffective. All these observations were made both in the absence and presence of isobutylmethylxanthine, a phosphodiesterase inhibitor, indicating that the effects of staurosporine and herbimycin A on cAMP accumulation were not due to phosphodiesterase inhibition. The calcium ionophore A 23187 also enhanced the PGE2-induced cAMP accumulation, and this effect was not additive to that of staurosporine, but additive to that of herbimycin A. These results confirm and extend those obtained in Jurkat cells. Taken together, they indicate that in human PBMC the adenylyl cyclase activity is negatively regulated by tyrosine kinase(s) and not by PKC, and positively regulated by Ca2+. They also suggest that the major enhancement by staurosporine of the PGE2-induced cAMP accumulation, although chiefly mediated by protein tyrosine kinase inhibition, also depends on another, presently undetermined, effect of the drug simulating that of Ca2+.

Staurosporine and herbimycin A augment agonist-induced elevation of cAMP in Jurkat T-lymphoblasts

Cross-talk between signalling pathways appears to play an important role in T-lymphocyte activation. In the present work, we have studied the effects of different inhibitors of protein tyrosine kinases or protein serine/ threonine kinases on the agonist-induced cAMP accumulation in the human T-lymphoblast cell line Jurkat. Staurosporine, a potent but nonspecific inhibitor of protein kinases, produced a ten-fold enhancement of the response to PGE2. No significant effect was obtained with two specific protein kinase C inhibitors (GF 109203X and H7), whereas herbimycin A, a specific protein tyrosine kinase inhibitor, markedly enhanced the PGE2-induced cAMP accumulation: its effect was approximately 60% that of staurosporine. It was confirmed that both staurosporine and herbimycin A inhibited by more than 90% the release of IP3 induced by ligation of the T-cell receptor, a known protein tyrosine kinase-dependent mechanism. To our knowledge, this study provides the first indication of a protein tyrosine kinase-mediated inhibition of agonist-induced cAMP accumulation. The possible targets of this inhibition are discussed.

The phospholipid drug glyceryl-phosphoryl-O-serine modulates pituitary adrenocorticotropin and hypothalamic corticotropin releasing hormone in vitro secretion in the aging rat

We have investigated the effects of the novel phospholipid drug glyceryl-phosphoryl-O-serine (GPS) on pituitary ACTH and hypothalamic corticotropin releasing hormone secretion in vitro in cultures from both 2- and 24 month-old Sprague-Dawley rats. Basal levels of ACTH in primary cultures of pituitary cells from 24 month-old rats were lower than (100 +/- 12 pg/10(5) cells) in 2 month-old rats (207 +/- 18 pg/10(5) cells). Basal medium corticotropin releasing hormone levels in hypothalamic cultures were higher in 24 month-old rats (45 +/- 7 pg/well/20 min.), than in 2 month-old rats (29 +/- 5.5 pg/well/20 min). Treatment of both pituitary cells with corticotropin releasing hormone and hypothalami with serotonin resulted respectively in a significant, concentration-dependent, increase of medium ACTH and corticotropin releasing hormone. However, concentration-response curves for ACTH and corticotropin releasing hormone were shifted to the right in cultures from 24 month-old rats. Incubation with graded concentrations of GPS produced significant increase in medium ACTH and corticotropin releasing hormone in cultures from 24 month-old rats, whereas the drug was ineffective in stimulating secretion of both hormones from 2 month-old rat cells. In addition, the adenylate cyclase stimulator forskolin and the protein kinase C activator oleyl-acyl-glycerol stimulated ACTH secretion in pituicytes from rats of both ages. However, response to oleyl-acyl-glycerol was blunted in pituicytes from 24 month-old rats. Combination of either forskolin or oleyl-acyl-glycerol with GPS resulted in a potentiation of the effect. Our data confirm an impairment of both pituitary ACTH and hypothalamic corticotropin releasing hormone secretion in the aging rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of murine adherent interleukin-2-activated killer cells. Differential effect of prostaglandin E2 and forskolin

We have studied the relationship between cytotoxic activity, size and granularity of murine interleukin-2-activated adherent killer cells issued from spleen cells cultured with high levels of IL-2. The effects of prostaglandin E2 (PGE2) and forskolin upon these cells were assessed. All adherent spleen cells obtained after 5 days of culture were large granular lymphocytes but presented a heterogeneity in size and granularity. After fractionation on a discontinuous-density Percoll gradient, four cellular subpopulations were isolated. Fluorescence-activated cell sorting analysis showed that cells of the lightest fraction (F1) were the largest, while the cells found in the heaviest fraction (F4) were much more granular than the cells collected in the two intermediate fractions (F2 and F3). The serine esterases level was higher in F4 than in unfractionated cells and diminished to about 40% in cells of fractions F2 and F3, which expressed a cytotoxic activity against YAC-1 cells higher than that in unfractionated cells or in F1 or F4, which presented the lowest cytotoxic activity. When AK cells were cultured for 48 h in the presence of either PGE2 or forskolin, which induce an intracellular increase of cAMP, we observed that PGE2 (1 microM) inhibited the cytotoxic activity, but surprisingly forskolin (2 microM) exerted a stimulating effect on the induction of cytotoxic activity. After fractionation on a discontinuous Percoll gradient we observed the same cellular distribution among PGE2 or forskolin-treated or -untreated cells, but PGE2 induced an increase of size and granularity. This effect of PGE2 was more potent on the cells collected in F4. However this variation of granularity was not associated with any variation in the serine esterase level. The cytotoxic activity of PGE2- or forskolin-treated cells did not present any significant variation relative to the control for cells collected in F2 and F3; on the other hand, forskolin-treated cells collected in F4 showed a significantly higher cytotoxicity than did the corresponding untreated or PGE2-treated cells.

T-cell antigen receptor-mediated enhancement of the adenylate cyclase pathway depends on tyrosine protein kinases

We have examined in the human T-cell line Jurkat the interaction between the activation through the T-cell receptor/CD3 complex and the adenylate cyclase pathway. OKT3, an anti-CD3 monoclonal antibody, did not activate by itself adenylate cyclase but produced a 3-7-fold increase of the cAMP accumulation induced by indirect (chloroadenosine, PGE2) or direct (forskolin) agonists of adenylate cyclase. A more detailed study with forskolin showed that OKT3 enhanced the effect of low concentrations of the agonist without affecting the maximal capacity of cAMP synthesis of the cells. The same concentrations of OKT3 produced both the enhancement of the adenylate cyclase pathway and the activation of phospholipase C. The enhancement by OKT3 of the adenylate cyclase pathway was inhibited by 0.5 microM staurosporine, a potent inhibitor of protein kinases, including tyrosine kinases and protein kinase C, whereas it was not inhibited by H7, a specific inhibitor of PKC. Staurosporine, at the same concentration, also inhibited the OKT3-induced activation of phospholipase C, a tyrosine kinase-dependent process. Taken together, these data indicate that activation of T-cell through the T-cell receptor enhances the adenylate cyclase pathway by a tyrosine protein kinase-dependent mechanism.