Effect of cyclosporin A (CyA) on the immune response. CyA competitively inhibits the function of monocyte/macrophage-derived T-lymphocyte-activating factor(s)

Effects of cyclosporin A on contractile activity and cytoskeleton in chick embryo cardiomyocytes

The effects of cyclosporin A (CsA), a clinically used immunosupressive drug, on contractile activity of chick cardiomyocytes grown as small aggregates or explants suspended on a network of elastic glass fibres or cultured in a monolayer were analysed in vitro with computer-aided image cytometry methods. At therapeutic concentrations (200-1500 ng/mL), CsA induced changes in the frequency and amplitude of the beating activity of cardiomyocytes 15 min after application. Longer treatment of cardiomyocytes, for 20-24 h, additionally induced changes in their shape and cytoskeleton organization (F-actin and alpha-actinin distribution). These results indicate that CsA is able to affect directly the contractile activity, morphology, and cytoskeleton architecture of heart cells.Key words: heart, cardiomyocytes, contractibility, cyclosporin A, cytoskeleton, image analysis.

Cyclic thrombocytopenia in a patient treated with cyclosporine for refractory idiopathic thrombocytopenic purpura

Cyclic thrombocytopenia (CT) is a rare disorder with cyclic changes of the platelet counts. Though the pathogenesis of this disorder has not been clarified, recent reports suggest that periodic destruction and/or ineffective production of platelets may be important causes of the disease. We report a case of a patient with refractory idiopathic thrombocytopenic purpura (ITP) in whom CT developed after cyclosporine A (CyA) therapy. There was an inverse relation between platelet counts and the serum levels of platelet-associated immunoglobulin G (PAIgG). The ploidy of bone marrow megakaryocytes also had an inverse relation with platelet counts. When the platelet count was low, the ploidy of megakaryocytes increased (P < 0.01). The number and area of bone marrow megakaryocytes were unrelated to platelet counts. These results indicate the possibility of platelet destruction caused by immunological mechanisms in CT. Cyclosporine A could have certain but fluctuating regulatory effects against antibody production for circulating platelets, which could lead to cyclic changes of the platelet counts. This case also suggests that CyA can be effective in severe refractory ITP. Regulatory mechanisms of platelet production and destruction and appropriate doses of CyA should be further studied in autoimmune-mediated thrombocytopenias.

Pharmacological inhibition of interleukin-1 activity on T cells by hydrocortisone, cyclosporine, prostaglandins, and cyclic nucleotides

The effects of a panel of hormones and pharmacological agents on the activation of T cells by a combination of interleukin-1 and phytohemagglutinin (IL-1/PHA) was studied. Pharmacological effects on various stages of IL-1/PHA-induced interleukin-2 (IL-2) production by the cloned murine thymoma cell line LBRM-33-1A5.7 were dissected using a multi-step assay procedure. A 4-h lag phase in the kinetics of IL-2 production allowed the operational definition of an early, IL-1-dependent programming stage, followed by an IL-2-production stage of the assay. A cell-washing procedure between these stages was introduced in order to distinguish IL-1 receptor antagonists from functional IL-1/PHA antagonists. Hydrocortisone and cyclosporine were potent inhibitors (active in the nM range) of both stages of IL-2 production, suggesting that neither is an IL-1 receptor antagonist. The cyclic adenosine monophosphate (cAMP)-elevating agents prostaglandin E2, dibutyryl cAMP, and theophylline inhibited IL-2 production during the early, IL-1-dependent programming stage. By contrast, prostaglandin F2 alpha and dibutyryl cyclic guanosine monophosphate did not appreciably inhibit IL-1/PHA activity. These results are discussed in relationship to the effects of these test agents in thymocyte IL-1 assays or mitogenesis assays and the implications toward understanding the mechanisms underlying IL-1/PHA activation of T cells.

Effects of cyclic GMP-agonists on cyclosporin-induced suppression of human lymphokine production

Cyclosporin (Cs) inhibits the elaboration of the lymphokine leukocyte migration inhibitory factor (LIF) from human blood mononuclear cells (MNC) stimulated with recall antigen. This inhibition was counteracted by 3 X 10(-5) M dibutyryl-cyclic GMP and 8-bromo-cyclic GMP and by the cyclic GMP-agonists, sodium nitroprusside (NaNPr), ascorbic acid (As A), sodium azide (NaN3) and carbacholine. Using 5 X 10(-5) M NaNPr, 1 X 10(-3) M NaN3, or 3 X 10(-3) M As A, 25-50-, 4-8- and 2-3-fold elevations of MNC and T-lymphocyte cyclic GMP-levels were obtained independently of the presence of Cs. NaNPr was the most potent of these three cyclic GMP-agonists in counteracting the effect of Cs. The results indicate that intracellular cyclic GMP is a major factor involved in the reversal of Cs-induced inhibition of LIF-production. None of the cyclic GMP-analogues or -agonists by themselves possessed Interleukin 1-like activity, measured by their ability to induce LIF-production by macrophage-depleted T-lymphocytes challenged by recall antigen.

Effect of cyclosporin A on human neutrophil and monocyte function

The effect of various concentrations of cyclosporin A (CyA), ranging from below peak blood levels to 20 times higher than blood levels of human peripheral blood polymorphonuclear and mononuclear leukocytes, was examined. CyA was found to bind to neutrophils with Kd values in the range of 20-50 nM. CyA at clinically obtainable blood level concentrations had no effect on neutrophil and monocyte chemotaxis, neutrophil oxidative burst, monocyte phagocytosis, or neutrophil bactericidal activity. The data on the release of lactoferrin, a secondary granule substance, from activated neutrophils showed that the calcium ionophore A 23187-induced lactoferrin release was inhibited by treatment of cells with 4 microM CyA, whereas release of lactoferrin from zymosan- or phorbol myristate acetate-activated neutrophils was not affected by the same concentration of CyA. This effect could either be due to differences in the degree of cell membrane perturbation by the various activators or to calcium dependence of neutrophil activation. A third possibility may be that CyA acts at some subsequent steps in the release process of neutrophils. It is concluded that CyA does not interfere with important functions of human phagocytes, the cells that play a major role in the defence against invading microorganisms.

Disappearance and reappearance of islet cell cytoplasmic antibodies in cyclosporin-treated insulin-dependent diabetics

In 68 newly diagnosed patients with insulin-dependent diabetes mellitus (IDDM) whose treatment included cyclosporin (CyA) the prevalence and mean titre of islet cell cytoplasmic antibodies (ICA) fell faster than they did in the 56 who received only insulin. However, in the CyA-treated patients the prevalence or titre of ICA at diagnosis did not correlate with beta-cell function as measured by glucagon-stimulated C-peptide levels; improvement and recovery of beta-cell function after 30 days of CyA therapy occurred despite the continued presence of ICA; and CyA-induced remission of IDDM (ie, glucagon stimulated plasma C-peptide levels greater than 0.6 pmol/ml) was not predicted by nor coincident with disappearance of ICA. Therefore, although CyA therapy was associated with a higher than expected frequency of remission and faster disappearance of ICA, the two observations were not temporally and may not be causally related. ICA should not be used to identify the target population for or to predict response to immunosuppressive therapy. The contribution of ICA to the pathogenesis of beta-cell destruction in IDDM needs serious re-examination.

Different susceptibilities to cyclosporin A of the mitogenic and potentiating activities of interleukins

A dissociation was observed between the mitogenic and potentiating activities of interleukins (ILs)-1 or -2 in murine thymocyte cultures treated with drugs. The direct mitogenic effects of the ILs were unaffected by cyclosporin A (CsA) at concentrations which abolished the potentiating activities of these mediators, i.e. their synergy with lectins. Conversely to CsA, dexamethasone was more inhibitory to the mitogenic activity of the ILs than to their synergistic reactions with the lectins. The resistance to CsA of the mitogenic activity of IL-1 was unexpected since this response is assumed to be mediated by newly formed IL-2 and CsA inhibits IL-2 production. This resistance was further tested by coculturing thymocytes with the IL-2-dependent CT6 cells; net gains of thymidine uptake by the cocultures were attributed to IL-2 release. Such net gains were observed in cocultures stimulated with IL-1 alone and were relatively resistant to CsA. On the other hand, net gains stimulated by mitogenic lectins, alone or with IL-1, were eliminated by CsA. These results support the notion that IL-1 direct activity on thymocytes is mediated by newly released IL-2 and show that this IL-1 activity is unusual in being resistant to CsA. Low levels of protection against CsA were also observed in cultures potentiated by IL-1: lymphocytes stimulated by lectins or antigens and IL-1 were inhibited by CsA less than lymphocytes stimulated without IL-1. Yet, this partial protection by IL-1 was achieved only at CsA concentrations about 100 fold lower than those resisted by thymocytes directly stimulated by IL-1.

Mechanism of action of cyclosporin A. Effect on T-cell-binding of interleukin 1 and antagonizing effect of insulin

Previous studies have shown that cyclosporin A (CyA) prevents the elaboration of the lymphokine leucocyte migration inhibitory factor (LIF). Since LIF production is interleukin 1 (IL-1)-dependent, we carried out experiments using partially and highly purified IL-1 preparations to study the effect of CyA. We found that (a) IL-1 was consistently depleted during a 1-h incubation with human blood T lymphocytes but not with B lymphocytes or erythrocytes; (b) the depletion could not be ascribed to pinocytosis, cell functions requiring active metabolism, or enzyme-mediated destruction of IL-1; (c) CyA, but not biologically inactive cyclosporin, antagonized the apparent absorption of IL-1; (d) T cells pre-exposed to CyA were rendered incapable of removing the monokine; and (e) CyA was capable of displacing IL-1 once absorbed by T cells. Because the putative binding of IL-1 showed saturability, reversibility (with CyA as a probe), and tissue specificity consistent with a known target for the monokine, we propose that IL-1 interacts with a receptor-like structure on T cells. Finally, we found that insulin interfered with the function of CyA at the very early macrophage-T-cell co-operative stage, even at physiological concentrations.