Emerging indications for the use of cyclosporin in organ transplantation and autoimmunity

The design, synthesis and in vitro immunosuppressive evaluation of novel isobenzofuran derivatives

The synthesis and biological evaluation of a series of novel isobenzofuran-based compounds are described. The compounds were evaluated for their immunosuppressive effects of T-cell proliferation and IMPDH type II inhibitor activity in vitro, as well as their structure-activity relationships were assessed. Several compounds demonstrated highly efficacious immunosuppressive properties, especially compounds 2d, 2e, 2h and 2j, which were superior to MPA, while compounds 2k, 2m, 2n, 4c and 5d exhibited an equipotent inhibitory activity compared to MPA. Generally, it was obviously demonstrated that α,β-unsaturated amides proved more potent than the diamide and urea series. The present study provides a guide for further research on development of safe and effective immunosuppressive agents.

Modifications in lipoprotein surface charge alter cyclosporine A association with low-density lipoproteins

PURPOSE

The purpose of this study was to examine the influence of lipoprotein surface charge on the plasma distribution of cyclosporine A (CSA).

METHODS

Phosphatidylinositol (PI; 40 micromol) was administered intravenously to rabbits. Blood was removed 10 min after injection and plasma was retrieved. Radiolabeled CSA ([3H] CSA) at a concentration of 1000 ng/mL was incubated for 60 min at 37 degrees C in control and PI-treated rabbit plasma. After incubation, plasma was separated into its lipoprotein and lipoprotein-deficient plasma (LPDP) fractions by density gradient ultracentrifugation, and the percentage of [3H]CSA recovered in each fraction was determined by radioactivity. To determine lipoprotein surface charge within control and PI-treated plasma, the zeta potential of each lipoprotein fraction was measured. The effect of PI on lipoprotein surface charge was further confirmed by gel electrophoresis.

RESULTS

PI treatment caused low-density lipoprotein (LDL) fraction to migrate further on the agarose gel, indicative of an increased negative surface charge. Zeta potential analysis further showed that LDL particles had a surface potential of -11.4 +/- 1.9 mV and -17.4 +/- 3 mV in control and PI-treated groups, respectively. A greater percentage of [3H]CSA was recovered within the LDL (16.4 +/-1.1% vs. 7.7 +/- 2.1%; n = 3; p < 0.05) fraction after incubation in PI treated than in control plasma, respectively.

CONCLUSION

These findings suggest that modifications in lipoprotein surface charge alter CSA distribution within the LDL plasma fraction.

Cholesteryl ester transfer protein facilitates the movement of water-insoluble drugs between lipoproteins: a novel biological function for a well-characterized lipid transfer protein

This review article addresses the recently discovered finding that cholesteryl ester transfer protein (CETP) can facilitate the transfer of water-insoluble drugs between different lipoprotein subclasses. This protein, which is often referred to as lipid transfer protein I (LTP I), is involved in the lipid regulation of lipoproteins. It is responsible for the facilitated transfer of core lipoprotein lipids, cholesteryl ester and triglycerides, and approximately one-third of the coat lipoprotein lipid, phosphatidylcholine, between different plasma lipoproteins. The human body appears to recognize exogenous water-insoluble drugs as lipid-like particles, which suggests that these compounds may interact with lipoproteins just like endogenous plasma lipids, and thus their transfer between lipoproteins may be facilitated by plasma CETP. Patients with a variety of diseases (i.e. diabetes, cancer, AIDS) often exhibit hypo- and/or hypercholesterolemia and triglyceridemia, commonly referred to as dyslipidemias, which result in changes in their plasma lipoprotein-lipid composition and concentration. The interaction of water-insoluble drugs with these dyslipidemic lipoproteins may be responsible for the differences seen in the pharmacokinetics and pharmacodynamics of the drug within different diseased patient populations. It is possible that these differences may be linked to the ability of CETP to transfer these compounds from one lipoprotein to another. This review examines the current understanding of the relationship between CETP activity and the lipoprotein distribution of a number of compounds (e.g. amphotericin B and cyclosporine A). It further suggests that additional research will expand our understanding of the role of CETP to explain other functions in lipophilic drug distribution and metabolism.

Effect of cyclosporine A on the binding affinity and internalization of low-density lipoproteins in human skin fibroblasts

The aim of this study was to elucidate the possible causes of elevated low-density lipoprotein (LDL)-cholesterol levels in patients with transplants who were treated with the immunosuppressant drug cyclosporine A (CSA). The binding and internalization of (125)I-LDL in the presence or absence of CSA at varying concentrations (5-15 microg/mL) within human skin fibroblasts were determined. In addition, the effect of LDL-associated CSA on the binding of LDL to its receptor was determined. CSA decreases LDL internalization without altering the extent and affinity of its binding to the LDL receptor. CSA did not alter the number of available LDL binding sites. Furthermore, the association of CSA with LDL did not affect the binding affinity of LDL to its receptor, suggesting that this binding may not be a mechanism by which CSA affects the subsequent clearance of LDL from the bloodstream. These findings suggest that CSA may cause an increase in plasma LDL-cholesterol in patients with transplants, thereby inhibiting LDL particle internalization without altering LDL receptor binding.

Effects of lipoproteins on cyclosporine A toxicity and uptake in LLC-PK1 pig kidney cells

Cyclosporine A (CSA) is an effective immunosuppressant, but side effects such as renal toxicity can limit its therapeutic use. The current studies investigate the effects of lipoproteins on CSA-induced renal toxicity in the pig epithelial cell line LLC-PK(1). Protein synthesis and tritiated CSA were used as measures of toxicity and uptake of CSA, respectively, in the LLC-PK(1) cell line. The three main classes of lipoproteins, very low (VLDL), low (LDL), and high density lipoproteins (HDL) at hypo-, normo-, and hyperlipidemic levels were tested for their ability to affect CSA-induced toxicity and uptake. The major component of each lipoprotein was also tested to determine its effects on CSA-induced toxicity and uptake. ApoA-I, the major protein component of HDL, and intact LDL particles showed the most significant effects of CSA uptake and toxicity. The uptake and toxicity of CSA was effectively reduced with elevated LDL concentrations but showed a significant increase (p < 0.05) when incubated with elevated concentrations of apoA-I. Increasing VLDL and HDL concentrations slightly reduced CSA toxicity and uptake, but showed little effect with increased incubation time. Triglyceride and cholesterol, the respective major components of VLDL and LDL, did not alter CSA uptake or toxicity under the conditions tested. LDL and apoA-I are identified as the major effectors of CSA toxicity and uptake in LLC-PK(1) cells. These effects may be mediated through receptors such as the LDL receptor or those involved in protein reabsorption. The data presented here clearly demonstrate a relationship between CSA-induced toxicity and the nature of the associated lipoprotein.

Autoimmune-mediated vasculopathy

The use of the immunosuppressive drug cyclosporine A (CsA) in solid organ transplantation can be associated with the development of vasculopathy as part of the complex immune response involved in chronic rejection, including autoimmune recognition. Although CsA can directly affect endothelial cells, this drug alters the T cell repertoire promoting autoimmune recognition. The present studies evaluated the ability of CsA-induced autoreactive T cells to mediate vascular lesions in syngeneic heart grafts. Graft vasculopathy developed in syngeneic heart grafts following either the primary induction of autoimmunity with CsA or the adoptive transfer of CsA-induced autoreactive T cells. Initially, an inflammatory response occurred in the medial wall of the small arterial vessels, accompanied by a perivascular lymphocytic infiltrate (including a lymphocytic infiltrate into the myocardium), followed by progression of vascular disease with endothelial cell proliferation. The development and progression of vascular disease correlated with the cytokine profile of the infiltrating lymphocytes with type 1 cytokines detected early and type 2 cytokines detected as the disease progressed. Initiation of this response correlated with upregulation of the target antigen recognized by the CsA-induced autoreactive T cells, the MHC class II-invariant chain peptide complex. This antigen complex, when upregulated on endothelial cells by interferon, allowed effective targeting by the autoreactive T lymphocytes. Strategies to inhibit the upregulation of MHC class II antigens by treatment of the recipients with chloroquine truncated the disease process. The results of these studies suggest that CsA-induced autoreactive mechanisms can contribute to the development of graft vasculopathy.

Renal function of children exposed to cyclosporin in utero

BACKGROUND

The use of cyclosporin (CsA) has improved graft survival in transplant (Tx) patients despite its potential nephrotoxicity. Children born to transplanted women may present with intrauterine growth retardation (IUGR). On the basis of potential reduced nephron mass both in IUGR and in newborn experimental animals exposed to CsA in utero, we investigated the renal function of children >1 year of age born to women under maintenance immunosuppression, including CsA.

METHODS

Fourteen children born to 12 Tx women (nine kidney, one pancreas-kidney, one heart, one liver) were investigated using inulin clearance (C(in)), para-aminohippuric acid clearance (C(PAH)), microalbuminuria, and electrolyte reabsorption rate.

RESULTS

Gestational age of the 14 infants was 34+/-3 weeks and birth weight 2018+/-620 g. During pregnancy, CsA trough blood level was 234+/-115 microg/l and plasma creatinine range was 96-136 micromol/l. Two children were excluded from the study because renal investigation led to a diagnosis of hereditary nephritis (one Alport syndrome, one familial dominant focal segmental glomerulosclerosis) that was retrospectively completed in the mother. Renal function tests were finally performed in 12 children at 2.6+/-1.8 years of age: BP 94+/-7/55+/-5 mmHg, C(in) 117+/-28 ml/min/1.73 m(2), C(PAH) 545+/-124 ml/min/1.73 m(2), filtration fraction 0.23+/-0.03, microalbuminuria 4.2+/-3.5 mg/mmol. Electrolyte tubular reabsorption rates and urine concentrating capacity were normal.

CONCLUSION

These results suggest that in children born to transplanted women taking CsA, renal function develops normally despite prolonged exposure in utero.

Effect of cyclosporine on human sperm motility in vitro

Cyclosporine affects motility and viability of human sperm when incubated together in vitro. Sperm motility was almost reduced to nil following 10 min of incubation with cyclosporine at a concentration of 1 mg/mL. However, 200 micrograms/mL of the drug has no effect on motility and viability when tested for up to 60 min under standard laboratory conditions. Cyclosporine effect on sperm was both dose and time dependent. Sperm sensitivity and susceptibility to cyclosporine even to lower doses increased significantly following withdrawal of bovine serum albumin from the incubating medium. Compared to untreated controls, lactate dehydrogenase was estimated higher by more than 2 to 4 times in the sperm-free incubating media, suggesting an altered membrane porosity in the affected spermatozoa.

Preparation and immunosuppressive activity of 32-(O)-acylated and 32-(O)-thioacylated analogues of ascomycin

A series of 32-(O)-acylated and 32-(O)-thioacylated derivatives of the antibiotic ascomycin (1) have been synthesized. These readily accessible analogues exhibit potent immunosuppressive activity in vitro, as measured by an interleukin-2 reporter gene assay and the mixed lymphocyte reaction. Such molecules are expected to have a therapeutic potential in chronic inflammatory diseases of the airways such as asthma.

Cyclosporine induces neuronal apoptosis and selective oligodendrocyte death in cortical cultures

Cyclosporine is used clinically as an immunosuppressant, but carries a risk of central nervous system toxicity due to undefined mechanisms. We examined the ability of cyclosporine exposure to kill cultured mouse cortical neurons and glia. Mixed neuron/glial cultures exposed to 1 to 20 microM cyclosporine for 24 to 48 hours developed concentration-dependent neuronal death, with most neurons destroyed by 20 microM cyclosporine. This neuronal death was characterized by cell body shrinkage and blebbing, chromatin condensation, and internucleosomal DNA fragmentation, consistent with apoptosis. Neuronal death was reduced by addition of cycloheximide, brain-derived neurotrophic factor, or insulin-like growth factor I but not N-methyl-D-aspartate- or AMPA-type glutamate receptor antagonists. Oligodendrocytes were more sensitive to cyclosporine-induced damage than were neurons, but astrocytes were relatively resistant. Oligodendrocyte death was accompanied by positive TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling) staining and was attenuated by application of ciliary neurotrophic factor or insulin-like growth factor I but not glutamate receptor antagonists. Present observations raise the possibility that the central nervous system toxicity syndrome associated with cyclosporine may be caused by the drug-induced death of oligodendrocytes and neurons.

Effect of cyclosporin A on platelet aggregation and thromboxane/prostacyclin balance in a model of extrahepatic cholestasis in the rat

Cyclosporin A (CsA), a potent immunosuppressor used in organ transplants and autoimmune diseases, is associated with adverse effects in the kidney, liver, and nervous system. This drug was recently shown to stimulate platelet aggregation, to increase thromboxane synthesis, and to decrease vascular prostacyclin synthesis. In experimental cholestasis, thrombocyte function is altered. The present study was designed to assess the effects of CsA on platelet function in extrahepatic biliary obstruction (EBO) in rats. Cyclosporin or its excipient (Cremaphore El, polyethoxylated castor oil) did not modify collagen-induced platelet aggregation. In animals with EBO, platelet aggregation decreased by 50%. The administration of CsA (5 or 10 mg/kg) or Cremaphore El increased aggregation by 163%, 253% and 123% respectively. Thromboxane production increased by 119% after Cremaphore El was administered, but was not significantly modified by CsA. Cholestasis increased thromboxane synthesis by 48.4%, whereas CsA showed a direct dose-dependent effect, and excipient had no significant effect. Excipient inhibited the vascular synthesis of 6-keto-PFG1 alpha by 67.2%, as did 5 mg/kg (56.8%) and 10 mg/kg CsA (27.6%). EBO led to a nonsignificant increase in the vascular synthesis of 6-keto-PFG1 alpha. Cremaphore EI inhibited prostacyclin synthesis by 79%; inhibition by CsA was dose-dependent (31% at 5 mg/kg, 60% at 10 mg/kg). Our findings show that cholestasis enhances the effects of CsA on platelet aggregation and thromboxane/prostacyclin balance. These results may reflect the vascular effects of CsA, which in turn may be enhanced by cholestasis.

In vitro and ex vivo effects of cyclosporin A on phagocytic host defenses against Aspergillus fumigatus

Because cyclosporin A (CsA) is extensively used as an immunosuppressive agent, its effects on phagocytic defenses against Aspergillus fumigatus were studied in vitro and ex vivo. After incubation with 10 to 250 ng of CsA per ml at 37 degrees C for 60 min, polymorphonuclear leukocytes (PMNs) exhibited unaltered superoxide anion (O2-) production in response to phorbol myristate acetate and N-formylmethionyl leucyl phenylalanine, whereas > or = 500 ng/ml significantly suppressed it (P < 0.01). Moreover, at < 250 ng of CsA per ml, PMNs exhibited no change in their capacity to damage unopsonized hyphae of A. fumigatus compared with controls, whereas at > or = 250 ng/ml, CsA suppressed the function (P < 0.01). Although neither CsA (250 ng/ml) nor hydrocortisone (10 micrograms/ml) suppressed PMN O2- production in response to phorbol myristate acetate and N-formylmethionyl leucyl phenylalanine, combination of the two agents reduced the function compared with that at the baseline (P < 0.05). Incubation of monocytes with 100 ng of CsA per ml for 1 or 2 days suppressed their antihyphal activity. No essential change in phagocytic activity of monocyte-derived macrophages (MDMs) against A. fumigatus conidia, tested as the percentage of phagocytosing MDMs and average number of MDM-associated conidia, was detected after 2 or 4 days of incubation with 10 to 1,000 ng of CsA per ml. Furthermore, in rabbits treated with CsA (up to 20 mg/kg of body weight per day intravenously for 7 days), neither O2- production and hyphal damage caused by PMNs or monocytes against hyphae nor phagocytosis of conidia by pulmonary alveolar macrophages was significantly suppressed. Thus, these results demonstrated that CsA within therapeutically relevant concentrations does not suppress antifungal activity of phagocytes except that of circulating monocytes. However, it may induce significant immunosuppression of phagocytes' antifungal function at relatively high concentrations in vitro, especially when combined with corticosteroids.

Sensitivity of baboon lymphocytes to cyclosporin A and FK 506: relative resistance of alloactivated cells to CyA

The interspecies differences in CyA pharmacokinetics necessitate the establishment of optimal immunosuppressive doses in the baboon, especially as its use as host for preclinical xenografts is anticipated. We assessed the immunosuppressive effects of CyA and FK 506 on lymphocytes from chacma baboons, using human cells for comparison. At concentrations up to 100 mumol/l, neither drug was toxic to lymphocytes. FK 506 inhibited baboon and human lymphocyte proliferation and IL-2 synthesis equally. In contrast, approximately four times higher doses of CyA were needed to inhibit baboon lymphocytes responding to alloantigens. This may explain the inadequate immunosuppression of baboon graft recipients treated with clinically acceptable doses of CyA. We propose that CyA whole blood target levels of +/- 1500 ng/ml should be used in this species and we provide evidence that chacma baboons are able to tolerate such doses without nephrotoxicity.

Short-term effect of various doses of cyclosporin A on plasma lipoproteins and its distribution in blood: an experimental study

Hyperlipidaemia commonly develops in both transplant recipients and experimental animals receiving cyclosporin A (CsA). However, the threshold of CsA induced-changes on lipoproteins and the role of parenteral vehicle (cremophor) has not been defined. Male Wistar rats were classified into five groups of six animals each and received CsA in cremophor vehicle at doses of 5, 10 or 20 mg kg-1 d-1, s.c., vehicle alone or saline for 7 d. Blood was obtained 24 h after the last dose and plasma was analysed. Plasma very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein subfractions (HDL-2, HDL-3) were isolated by sequential ultracentrifugation and their content of cholesterol, triglyceride and phospholipid was determined. Whole blood and trough plasma CsA levels were measured by monoclonal radioimmunoassay. Plasma lipids did not differ significantly among the five groups. At a dose of 20 mg kg-1 d-1 of CsA VLDL cholesterol rose significantly (P < 0.05). Administration of either CsA or cremophor vehicle increased HDL-2 phospholipids (P < 0.05) and decreased HDL-3 cholesterol. There was not a linear relationship between whole blood and plasma CsA levels and increasing CsA doses. Short-term treatment with low doses of CsA have little influence on lipid profile in the rat. Changes on lipoprotein composition can be attributed mainly to cremophor vehicle, conceivably due to its ethanol content.