Inhibition of calcineurin activity and protection against cyclosporine A induced cytotoxicity by prednisolone sodium succinate in human peripheral mononuclear cells

We have investigated the effects of prednisolone sodium succinate (Pss) and cyclosporin A (CSA), applied alone or concurrently, on the release of arachidonic acid (AA) (cytosolic phospholipase A(2) (cPLA(2)) activity) and on the calcineurin (CN) activity of human peripheral blood mononuclear cells (PBMC). The cytotoxic damage to the cells treated by the drugs was estimated by the release of lactate dehydrogenase (LDH). We found that Pss (10(-5) M) could inhibit the CN activity and higher concentrations (10(-4) M) could decrease the cytotoxic damage caused by CSA (10(-4) M) during their combined application. CSA had no specific effect on the release of AA from the cells. In the combined clinical use of glucocorticosteroids (GCS) and CSA, their additive inhibitory effect on CN activity and the protective membrane influence of GCS against the cytotoxicity of CSA may be beneficial.

Effect of pentoxifylline on cyclosporine-induced nephrotoxicity in rats

Effect of unique hemorrheologic agent pentoxifylline (PTX) was investigated on cyclosporine (CsA) induced nephrotoxicity in rats. Compared to saline control, CsA produced significant increase in blood urea and serum creatinine. Pentoxifylline treatment prevented the CsA-induced rise in blood urea and serum creatinine. Creatinine clearance (Ccr) and lithium clearance (Licr) was decreased with CsA. PTX treatment prevented the CsA-induced decrease in Ccr and Licr. Malondialdehyde (MDA) was increased with CsA compared to saline treated animals. PTX prevented the CsA-induced MDA rise. Kidney form CsA treated rat showed marked vacuolar degeneration of tubular epithelium with excess of microcalcification. Severity of the lesions was markedly reduced in rats treated with PTX plus CsA. The results indicate that PTX reduces CsA-induced renal toxicity in rats.

The novel immunosuppressant SDZ-RAD protects rat brain slices from cyclosporine-induced reduction of high-energy phosphates

1. SDZ-RAD, 40-O-(2-hydroxyethyl)-rapamycin, is a novel macrolide immunosuppressant. Because of its synergistic interaction, SDZ-RAD is under clinical investigation as immunosuppressant in combination with cyclosporine after organ transplantation. Neurotoxicity is a critical side-effect of cyclosporine. 2. We studied the effect of SDZ-RAD and its combination with cyclosporine on high-energy phosphates, phosphocreatine (PCr) and nucleoside triphosphates (NTP), in brain slices using 31P-magnetic resonance spectroscopy (MRS). 3. Cyclosporine significantly reduced high-energy phosphates after 2 h in a dose-dependent manner (100 micrograms l-1: 93 +/- 3% of control (NTP), 91 +/- 3% (PCr); 500 micrograms l-1: 84 +/- 2% (NTP), 73 +/- 2 (PCr); 5000 micrograms l-1: 68 +/- 3% (NTP), 55 +/- 5% (PCr); n = 6; P < 0.02). 4. In contrast, after perfusion for 2 h, SDZ-RAD (500 micrograms l-1 and 5000 micrograms l-1) significantly increased high-energy phosphate concentrations in the brain slices (P < 0.02). Even at the lowest concentration, SDZ-RAD protected brain energy metabolism against cyclosporine toxicity: 100 micrograms l-1 SDZ-RAD + 5000 micrograms l-1 cyclosporine: 86 +/- 3% (NTP), 83 +/- 7% (PCr), n = 3, P < 0.03 compared to cyclosporine alone. 5. As evaluated using an algorithm based on Loewe isobolograms, the effects of SDZ-RAD/cyclosporine combinations on brain energy reduction were antagonistic. Both drugs were found in mitochondria using h.p.l.c-MS analysis. 6. We conclude that cyclosporine inhibits mitochondrial high-energy phosphate metabolism, which can be antagonized by SDZ-RAD.

Glycine: a new anti-inflammatory immunonutrient

The mechanism of the immunosuppressive effects of glycine and its pathophysiological applications are discussed in this review. Glycine has been well characterized in spinal cord as an inhibitory neurotransmitter which activates a glycine-gated chloride channel (GlyR) expressed in postsynaptic membranes. Activation of the channel allows the influx of chloride, preventing depolarization of the plasma membrane and the potentiation of excitatory signals along the axon. Glycine has recently been shown to have similar inhibitory effects on several white blood cells, including hepatic and alveolar macrophages, neutrophils, and lymphocytes. Pharmacological analysis using a GlyR antagonist strychnine, chloride-free buffer, and radiolabeled chloride has provided convincing evidence to support the hypothesis that many white blood cells contain a glycine-gated chloride channel with properties similar to the spinal cord GlyR. Molecular analysis using reverse transcription-polymerase chain reaction and Western blotting has identified the mRNA and protein for the beta subunit of the GlyR in total RNA and purified membrane protein from rat Kupffer cells. Dietary glycine is protective in rat models against endotoxemia, liver ischemia-reperfusion, and liver transplantation, most likely by inactivating the Kupffer cell via this newly identified glycine-gated chloride channel. Glycine also prevents the growth of B 16 melanomas cell in vivo. Moreover, dietary glycine is protective in the kidney against cyclosporin A toxicity and ischemia-reperfusion injury. Glycine may be useful clinically for the treatment of sepsis, adult respiratory distress syndrome, arthritis, and other diseases with an inflammatory component.

Dietary glycine and renal denervation prevents cyclosporin A-induced hydroxyl radical production in rat kidney

Cyclosporin A (CsA) nephrotoxicity is associated with renal hypoxia and increases in free radicals in the urine. This study was designed to elucidate the mechanism of radical production caused by CsA. Pretreatment of rats with CsA (25 mg/kg, i.g.) for 5 days decreased glomerular filtration rates by 65%, an effect largely prevented by both dietary glycine (5%) or renal denervation. CsA dissolved in olive oil produced a 6-line alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (4-POBN)/free radical signal in the urine, which partitioned predominantly into the aqueous phase after chloroform extraction (i.e., it is water soluble). Dimethyl sulfoxide (DMSO) is attacked by the hydroxyl radical to produce a methyl radical; administration of CsA with [(12)C]DMSO produced two radical species in urine, one with hyperfine coupling constants similar to the 4-POBN/methyl radical adduct found in aqueous solution. CsA given with [(13)C]DMSO produced a 12-line spectrum, confirming the formation of hydroxyl radicals. The methyl radical produced by the hydroxyl radical represented 62% of radicals detected in urine but only 15% in bile. Therefore, hydroxyl radicals are produced largely in the kidney. Free radicals in urine were increased about 5-fold by CsA, an effect completely blocked by the inhibitory neurotransmitter, glycine, or by renal denervation. CsA infusion for 30 min increased efferent renal nerve activity 2-fold, and dietary glycine (5%) totally blocked this phenomenon. Taken together, these data are consistent with the hypothesis that CsA increases hydroxyl radical formation by increasing renal nerve activity resulting in vasoconstriction and hypoxia-reoxygenation. Glycine blunts the effect of CsA on the renal nerve, which explains, in part, prevention of nephrotoxicity.

ATP-sensitive K+ channel openers prevent Ca2+ overload in rat cardiac mitochondria

1. Mitochondrial dysfunction, secondary to excessive accumulation of Ca2+, has been implicated in cardiac injury. We here examined the action of potassium channel openers on mitochondrial Ca2+ homeostasis, as these cardioprotective ion channel modulators have recently been shown to target a mitochondrial ATP-sensitive K+ channel. 2. In isolated cardiac mitochondria, diazoxide and pinacidil decreased the rate and magnitude of Ca2+ uptake into the mitochondrial matrix with an IC50 of 65 and 128 microM, respectively. At all stages of Ca2+ uptake, the potassium channel openers depolarized the mitochondrial membrane thereby reducing Ca2+ influx through the potential-dependent mitochondrial uniporter. 3. Diazoxide and pinacidil, in a concentration-dependent manner, also activated release of Ca2+ from mitochondria. This was prevented by cyclosporin A, an inhibitor of Ca2+ release through the mitochondrial permeability transition pore. 4. Replacement of extramitochondrial K+ with mannitol abolished the effects of diazoxide and pinacidil on mitochondrial Ca2+, while the K+ ionophore valinomycin mimicked the effects of the potassium channel openers. 5. ATP and ADP, which block K+ flux through mitochondrial ATP-sensitive K+ channels, inhibited the effects of potassium channel openers, without preventing the action of valinomycin. 6. In intact cardiomyocytes, diazoxide also induced mitochondrial depolarization and decreased mitochondrial Ca2+ content. These effects were inhibited by the mitochondrial ATP-sensitive K+ channel blocker 5-hydroxydecanoic acid. 7. Thus, potassium channel openers prevent mitochondrial Ca2+ overload by reducing the driving force for Ca2+ uptake and by activating cyclosporin-sensitive Ca2+ release. In this regard, modulators of an ATP-sensitive mitochondrial K+ conductance may contribute to the maintenance of mitochondrial Ca2+ homeostasis.

Inhibition of GABA system involved in cyclosporine-induced convulsions

In this study, we attempted to clarify the mechanisms mediating cyclosporine-evoked convulsions. Cyclosporine (50 mg/kg, i.p.) significantly enhanced the intensity of convulsions induced by bicuculline (GABA receptor antagonist), but not those induced by strychnine (glycine receptor antagonist), N-methyl-D-aspartic acid, quisqualic acid or kainic acid (glutamate receptor agonists). Bicuculline plus cyclosporine-induced convulsions were significantly suppressed by an activation of GABAergic transmission with diazepam, phenobarbital and valproate. The GABA turnover estimated by measuring aminooxyacetic acid-induced GABA accumulation in the mouse brain was significantly inhibited by cyclosporine (50 mg/kg, i.p.). When cultured rat cerebellar granule cells were exposed to 1 microM cyclosporine for 24 hr, the specific [3H]muscimol (10 nM) binding to intact granule cells decreased to 53% of vehicle controls. The present study provides the first evidence suggesting that cyclosporine inhibits GABAergic neural activity and binding properties of the GABAA receptor. These events are closely related to the occurrence of adverse central effects including tremors, convulsions, coma and encephalopathy under cyclosporine therapy.

L-propionyl carnitine reduces toxicity correlated to cyclosporine-induced intracellular ATP concentrations

In previous trials we proved how propionyl carnitine, an acyl carnitine characterized by its intense mitochondrial metabolic, and cardio and vasoprotective activity, could prevent the cyclosporine-induced nephrotoxicity. Subsequently we also noted how propionyl carnitine could prevent the increase in renal intracellular calcium, which is the base of many cyclosporine-induced toxic phenomena. In our trials, we used the isolated and perfused rat kidney technique to examine if with the variations of the concentration of intracellular calcium, the adenosine 5'-triphosphate concentrations also varied, and if this decrease could be corrected by administrating propionyl carnitine. The results we obtained in these experiments indicated that when propionyl carnitine was administered preventively, the concentrations of renal intracellular adenosine 5'-triphosphate which were decreased by the cyclosporine returned to their normal values and, at the same time, a decrease in the increased vascular resistance of the kidney was noted. Therefore, propionyl carnitine corrected one of the biochemical alterations which explained the pathogenesis of the renal damage induced by cyclosporine.

S-Adenosylmethionine protects against cyclosporin A-induced alterations in rat liver plasma membrane fluidity and functions

We studied the effect of cyclosporin A (CyA) on liver plasma membrane (LPM) composition, fluidity, and functions and on hepatic glutathione (GS) and oxidative status. We also evaluated the ability of S-adenosylmethionine (SAMe) to antagonize the CyA-induced disturbances in rats. The animals were randomly divided into four groups and treated daily with saline, CyA vehicle, CyA, and SAMe plus CyA, respectively, for 1 week. Bile, blood, and liver samples and LPM vesicles were obtained at the end of the treatments. CyA-induced cholestasis was associated with alterations in LPM composition and fluidity. The contents of total phospholipids, phosphatidylcholine, and proteins were decreased and cholesterol and the cholesterol/phospholipid molar ratio increased. Na(+), K(+)-ATPase activity was decreased, whereas those of 5'-nucleotidase, Mg(2+)-ATPase, and gamma-glutamyltransferase increased. The hepatic contents of proteins and GS and the reduced/oxidized glutathione molar ratio were decreased and hepatic malondialdehyde increased. SAMe cotreatment 1) significantly improved or abolished the CyA-induced changes in LPM fluidity and composition and the changes in the activity of the carrier and enzymes tested, 2) counteracted the hepatic depletion of GS and proteins caused by CyA and normalized the reduced/oxidized glutathione ratio, and, as expected, 3) prevented cholestasis and the inhibitory effect of CyA on hepatobiliary transport of the major bile components. We conclude that CyA-induced cholestasis and hepatotoxicity in the rat is associated with changes in LPM composition and fluidity, liver GS depletion, and oxidative stress. SAMe cotreatment significantly improves or totally protects against these hepatotoxic effects.

Cyclosporine A preparations and their vehicles induce contraction of the guinea pig gallbladder in vitro: the role of cyclooxygenase metabolites

The aim of this study was to establish whether prostanoids play a role in the contraction induced by cyclosporine A (CyA) preparations in the guinea pig isolated gallbladder strips. It was also aimed to study the effects of the preparations and their solvents on the acetylcholine-evoked rhythmic contractions of the guinea pig isolated sphincter of Oddi (SO). Isometric contractions were recorded. CyA parenteral and oral preparations and their vehicles, Cremophor-EL and Labrafil caused concentration-dependent and sustained contractions (74.2 +/- 6.2, 58.4 +/- 6.3, 88.9 +/- 4.9 and 47.5 +/- 6.2% of maximum KCl contraction, respectively) of gallbladder strips, but not of SO. Quinacrine, indometacin and ridogrel inhibited the contraction induced by CyA preparations and their vehicles in gallbladder strips (for CyA parenteral preparation, 34.7 +/- 6.7, 1.4 +/- 0.9, 19.0 +/- 6.4% of maximum KCl contraction, respectively). The drug and its vehicles changed neither the initial contraction nor the amplitude and frequency of the phasic contractions induced by acetylcholine in SO preparations. The results indicate that the drug is able to contract the gallbladder strips and the vehicles contribute to the contracting effect of CyA. Prostanoids may be responsible for the CyA-induced contraction of the gallbladder.

Lacidipine protects against cyclosporine-induced nephrotoxicity in rats

The effect of lacidipine (LA), a new calcium channel blocker with an antioxidant effect, has been studied on cyclosporine (CsA)-induced nephrotoxicity in male Wistar rats. Lacidipine (1 mg/kg BW) was administered orally 3 days before and 14 days concurrently with CsA (50 mg/kg BW orally). Urine volume, Na+, K+, Li+ and creatinine in urine, and blood urea, serum creatinine, lithium, plasma malondialdehyde (MDA) and CsA levels were estimated in blood after 14 days CsA treatment. Kidneys were examined using histological techniques. Blood urea and serum creatinine were increased by 305 and 211%, respectively, with CsA when compared to the saline-treated animals. Creatinine clearance (Ccr) and lithium clearance (Licr) were decreased and proximal tubule fractional reabsorption 1-(Licr/Ccr) was significantly increased with CsA. Lacidipine protected rats from CsA-induced nephrotoxicity. Changes in blood urea, serum creatinine, Ccr, Licr and proximal tubule fractional reabsorption induced by CsA were significantly prevented by LA. There was a 160% rise in MDA levels with CsA, which was significantly reduced equal to control with LA. Histomorphology showed microcalcification with CsA, while it was normal with LA. In rats treated with LA, CsA did not show any microcalcification. Our data suggest that supplementation of LA may be helpful to reduce CsA nephrotoxicity.

Cyclosporin A increases hypoxia and free radical production in rat kidneys: prevention by dietary glycine

The major side effect of cyclosporin A is severe nephrotoxicity. It is likely that cyclosporin A causes vasoconstriction leading to hypoxia-reperfusion injury; therefore, these experiments were designed to attempt to obtain physical evidence for hypoxia and free radical production in kidney following cyclosporin A. Rats were treated daily with cyclosporin A (25 mg/kg ig) for 5 days, and pimonidazole, a hypoxia marker, was injected 2 h after the last dose of cyclosporin A. A dose of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) was injected 3 h after cyclosporin A to trap free radicals. Cyclosporin A doubled serum creatinine and decreased glomerular filtration rates by 65% as expected. Pimonidazole adduct binding in the kidney was increased nearly threefold by cyclosporin A, providing physical evidence for tissue hypoxia. Moreover, cyclosporin A increased 4-POBN/radical adducts nearly sixfold in the urine but did not alter levels in the serum. Glycine, which causes vasodilatation and prevents cyclosporin A toxicity, minimized hypoxia and blocked free radical production; however, it did not alter cyclosporin A blood levels. These results demonstrate for the first time that cyclosporin A causes hypoxia and increases production of a new free radical species exclusively in the kidney. Therefore, it is concluded that cyclosporin A causes renal injury by mechanisms involving hypoxia-reoxygenation, effects which can be prevented effectively by dietary glycine.

Effect of misoprostol on myocardial contractility in rats treated with cyclosporin A

The nephrotoxic side effects of the immunosuppressant cyclosporin A in animals and humans are well known. Misoprostol, a prostaglandin E analog, is used clinically in organ-transplant recipients taking cyclosporin A to protect against these side effects. We reported previously that long-term treatment of rats with cyclosporin A causes a diminution in myocardial peak contractile stress. There is an associated spontaneous sarcomere activity and rest depression of force in the absence of a change in myofilaments sensitivity to intracellular Ca2+. Here we investigated the potential protective effects of misoprostol on the myocardium of cyclosporin A-treated rats. Rats were treated with either cyclosporin A, misoprostol, or their combination. Force-[Ca2+]o and -[Sr2+]o, and force-interval relations as well as the sarcomere length were studied in trabeculae isolated from the right ventricles. At suboptimal [Ca2+]o, cyclosporin A shifted the force-[Ca2+]o relation to the left but reduced peak contractile stress by approximately 35% at the highest (optimal) [Ca2+]o. Co-treatment with misoprostol prevented the leftward shift, and treatment with misoprostol alone did not cause a leftward shift. The diminution of peak stress, however, did not recover with misoprostol treatment, and stress was further reduced. Treatment with only misoprostol also reduced stress generated by the muscles more than that by cyclosporin A alone. Intriguingly, activation of the myofilaments by Sr2+ failed to recover peak stress to control levels in any group treated with misoprostol. Unlike cyclosporin A, however, rest potentiation of force was more pronounced, and spontaneous sarcomere activity was absent with misoprostol. No histopathologic changes were observed with cyclosporin A or misoprostol treatment. Misoprostol modifies the cyclosporin A-induced changes in the Ca2+ handling, but further decreases the stress generated by the muscles.

Heparin suppresses cyclosporine-induced endothelin-1 synthesis in rat endothelial cells

Cyclosporine stimulates vasoconstrictor endothelin-1 (ET-1) synthesis. This study examined the effect of heparin on cyclosporine-induced ET-1 synthesis in Wistar rat aortic endothelial cells in culture. Cyclosporine (0.01-5 mumol/L) stimulated ET-1 mRNA expression in a dose-dependent manner. A nitric oxide synthesis inhibitor, NG-monomethyl-L-arginine (L-NMMA) (10(-5) mol/L), did not affect cyclosporine-induced ET-1 mRNA expression. Heparin (1-20 U/ml) suppressed cyclosporine-induced ET-1 mRNA expression in a dose-dependent manner. The inhibitory effect of heparin was blunted in the presence of either L-NMMA (10(-5) mol/L) or calmodulin inhibitors such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) (5 x 10(-5) mol/L) or calmidazolium (5 x 10(-5) mol/L) in the presence of the phosphodiesterase inhibitor 3-isobutyl 1-methylxanthine (0.1 mmol/L). These results suggest that heparin suppresses cyclosporine-induced ET-1 mRNA expression via both NO- and calmodulin-dependent pathways.

Cyclosporin A-induced hydrogen peroxide synthesis by cultured human mesangial cells is blocked by exogenous antioxidants

Cyclosporin A (CsA) is the immunosupressor most widely used in transplanted patients for preventing organ rejection, but it has some toxic side effects in vascular beds and kidney. The purpose of this work was to study if H2O2, a reactive oxygen species, is involved in the CsA-induced toxic effects on kidney in vitro. Human mesangial cells (HMC) in culture were incubated in presence of CsA (10[-5]-10[-8]M) and H2O2 was measured by flow cytometry. The specificity of the probe used in this method was demonstrated as fluorescence was not detected when superoxide anion generated through a Xanthine-Xanthine oxidase system was present, but fluorescence was noted when H2O2 was present in the incubation medium, both directly and after addition of superoxide dismutase to the medium thus promoting H2O2 synthesis. CsA induced a significant dose and time-response increased H2O2 synthesis by cultured HMC. This increase appeared 5 min after CsA addition, being maximal between 15-45 min at CsA concentration of 10(-7)M. When HMC were preincubated with antioxidants as vitamin E or selenium, the CsA-induced H2O2 production was partially blocked. In addition, selenium also induced an increased activity of glutathion peroxidase in HMC after 24 hours of incubation, suggesting that it exerted its H2O2 scavenging action through the modulation of the activity of this enzyme.

Effect of cyclosporin on liver antioxidants and the protective role of vitamin E in hyperoxaluria in rats

This study aimed to evaluate whether administration of cyclosporin to hyperoxaluric rats affects liver antioxidant status, and whether pretreatment with vitamin E reverses the effect. Male Wistar rats were divided into two major groups of 40. One group was given vitamin E. Both major groups were then divided into four subgroups which received vehicle (olive oil), cyclosporin in olive oil (50 mg kg(-1)), 3% ammonium oxalate or cyclosporin + 3% ammonium oxalate for three days. The activities of liver lactate dehydrogenase, glycolic acid oxidase and xanthine oxidase, and the level of malondialdehyde, an indicator of lipid peroxidation, increased when cyclosporin was administered to hyperoxaluric rats. The levels of antioxidants ascorbic acid, vitamin E and reduced glutathione and the activities of glutathione-metabolizing enzymes were altered significantly when hyperoxaluric rats were treated with cyclosporin. All these enzymes and antioxidants showed highly significant correlation values, r. These changes were restored to near normal by pretreatment with vitamin E. These findings suggest that cyclosporin-induced hepatotoxicity is aggravated in hyperoxaluria. This was almost totally prevented by pretreatment with vitamin E.

FK506 (Tacrolimus) decreases the cytotoxicity of cyclosporin A in rat hepatocytes in primary culture: implication of CYP3A induction

Tacrolimus (FK506) and cyclosporin A (CsA) are two potent immunosuppressants mainly metabolized by hepatic cytochrome P-450 3A (CYP3A) monooxygenase. The aim of this study was to compare the toxic effects of the two drugs on hepatocytes in primary culture as a function of their metabolism and to explore the variations of cytotoxicity when both drugs are associated. The cytotoxicity of FK506 and CsA, as expressed by their IC50 values, was of the same order but with a switch according to whether hepatocytes were induced or uninduced by dexamethasone, CsA being more toxic in its native form and FK506 through its metabolism. Similar results were obtained with the intracellular calcium content. When both drugs were associated at their IC50 values, the expected additive cytotoxic effect was not observed. Moreover, when small quantities of FK506 were added to CsA at its IC50, cell viability improved in the induced cultures. It is hypothesized that the interaction between the two drugs relies on a mechanism involving both competition of FK506 and CsA for CYP3A and of their immunophilin complexes for a common site on the calcineurin-calmodulin complex.

Protective effect of three xanthine derivatives (theophylline, caffeine and pentoxifylline) against the cyclosporin A-induced glomerular contraction in isolated glomeruli and cultured mesangial cells

Cyclosporin A (CyA), an immunosuppressive agent, induces in vivo a severe nephrotoxicity with large decrease in renal hemodynamics correlated with in vitro glomerular contraction. The aim of this study is to show the ability of three xanthine derivatives, caffeine, theophylline and pentoxifylline, to diminish the CyA-induced in vitro glomerular contraction. The use of isolated glomeruli and cultured rat mesangial cells permits us to evaluate by quantitative and qualitative morphometric analysis the contraction elicited either with CyA alone or with previous treatment with nontoxic concentrations of xanthine derivatives. Indirect immunofluorescence of actin filaments makes it possible to appreciate qualitative morphometric changes in mesangial cells. A 10-min pretreatment with caffeine, theophylline or pentoxifylline (10(-4) to 10(-9) M) abolishes the contraction elicited with 10(-6) M CyA. CyA alone induces -13.9% compared to CyA with 10(-6) M pentoxifylline which induces only -3.2% of reduction of planar glomerulus surface area after 30 min. Similar results were provided with cultured rat mesangial cells. As shown by indirect immunofluorescence xanthine derivatives prevent the cytoskeletal reorganization (alpha-actin) of cultured mesangial cells which occurs with CyA. The marked constriction induced by CyA in isolated glomeruli and mesangial cells can be prevented by xanthine derivatives.

Silibinin, a plant extract with antioxidant and membrane stabilizing properties, protects exocrine pancreas from cyclosporin A toxicity

Silymarin can be extracted from the milk thistle, and silibinin is the main component of the plant extract. Possibly due to their antioxidant and membrane-stabilizing properties, the compounds have been shown to protect different organs and cells against a number of insults. Thus liver, kidney, erythrocytes and platelets have been protected from the toxic effects of ethanol, carbon tetrachloride, cold ischemia and drugs, respectively. The effect of silibinin on endocrine and exocrine pancreas, however, has not been studied. We therefore investigated whether silibinin treatment attenuates cyclosporin A (CiA) toxicity on rat endocrine and exocrine pancreas. Groups of 15 male Wistar rats were treated for 8 days with CiA and/or silibinin. On day 9, endocrine and exocrine pancreatic functions were tested in vitro. At the end of the treatment period, blood glucose levels in vivo were significantly higher in rats treated with CiA while silibinin did not affect glucose levels. In vitro, insulin secretion was inhibited after treatment with silibinin, but amylase secretion was not affected. After treatment with CiA both insulin and amylase secretion were reduced. Silibinin and CiA had an additive inhibitory effect on insulin secretion, but silibinin attenuated CiA-induced inhibition of amylase secretion. Despite CiA treatment, amylase secretion was in fact restored to normal with the highest dose of silibinin. Thus silibinin inhibits glucose-stimulated insulin release in vitro, while not affecting blood glucose concentration in vivo. This combination of effects could be useful in the treatment of non-insulin-dependent diabetes mellitus. Furthermore, silibinin protects the exocrine pancreas from CiA toxicity. As this inhibitory effect is probably unspecific, silibinin may also protect the exocrine pancreas against other insult principles, such as alcohol.

Investigation of a possible interaction between ciprofloxacin and cyclosporine in renal transplant patients

BACKGROUND

Bacterial infection is a common complication during the first few months after renal transplantation. Ciprofloxacin, a fluoroquinolone broad-spectrum antibiotic, is used frequently in treating infections in the early posttransplant period. Evidence from in vitro studies has suggested that ciprofloxacin can antagonize the cyclosporine (CsA)-dependent inhibition of interleukin-2 production. Such an effect in renal transplant patients could antagonize the immunosuppressive activity of CsA and lead to rejection of the graft.

METHODS

To investigate the possibility of a pharmacodynamic interaction between ciprofloxacin and CsA, we conducted a case-control study in 42 patients who had received a kidney transplant and who were prescribed ciprofloxacin in the first 1-6 months after transplantation and in their matched controls (two per case) who did not receive ciprofloxacin during the study period.

RESULTS

There was a twofold greater incidence (P=0.008) of ciprofloxacin use at 1-3 months (65%) than was observed at 4-7 months (35%) after transplantation. The proportion of cases experiencing at least one episode of biopsy-proven rejection 1-3 months posttransplant (45%) was significantly greater (P=0.004) than that of controls (19%). Furthermore, there was a marked increase (P<0.001) in the incidence of rejection temporally associated with ciprofloxacin use among cases (29%) compared with that experienced by the controls (2%).

CONCLUSIONS

The possibility that ciprofloxacin increases rejection rates in renal transplant patients may be of clinical importance and therefore warrants further investigation.

Nifedipine protects small intestine from cyclosporine-induced hemodynamic and functional impairment

We have previously shown that cyclosporine (CsA) causes intestinal hemodynamic and functional impairments. In this study, we evaluated whether nifedipine protects the small intestine from such toxic side effects. Isogeneic small intestinal transplantation was performed in rats which then received one of the following two-week treatments: olive oil, 0.15 ml/kg/day i.m. as vehicle controls in group 1; nifedipine, 1 mg/kg/day i.m. in group 2; CsA, 15 mg/kg/day i.m. in group 3; and both nifedipine and CsA in group 4. Vascular resistance, whole tissue blood flow and its mucosal and serosal/muscularis distributions in both graft and recipient residual native intestines, and absorptive function were determined. The data showed that two-week treatment with CsA resulted in a marked elevation of vascular resistance from 51.0 +/- 6.8 to 72.4 +/- 11.1 U/g in the native whole tissue and from 53.7 +/- 7.2 to 78.2 +/- 12.1 U/g in the graft whole tissue, and decreases in blood flow from 1.59 +/- 0.26 to 1.11 +/- 0.17 ml/g/min in the native whole tissue and from 1.50 +/- 0.21 to 1.03 +/- 0.18 ml/g/min in the graft whole tissue and absorption from 227 +/- 36 to 166 +/- 26 mg glucose/dl. Mucosa was preferentially affected, while serosal/muscularis layers remained relatively unchanged. When nifedipine was concomitantly used with CsA, vascular resistance and blood flow values in the mucosal layer and whole intestinal tissue as well as absorptive function showed no significant differences from the baseline data. The changes observed in denervated grafts and recipient native intestines were similar. We conclude that nifedipine is effective in protecting both graft and native small intestines from CsA-induced toxicity in the rat.

L-Arginine and allopurinol protect against cyclosporine nephrotoxicity

The role of nitric oxide (NO) and oxygen free radicals in cyclosporine (CsA) nephrotoxicity was investigated using L-arginine, an NO substrate, and allopurinol, a xanthine oxidase inhibitor (involved in the formation of oxygen radicals) in an experimental model with Wistar rats. CsA, administered at 15 mg/kg/body weight (BW) subcutaneously for 10 days, caused a decrease in glomerular filtration rate, with inulin clearance of 0.33+/-0.04 vs. 1.11+/-0.06 ml/min/100 g BW (P<0.01 vs. control). L-Arginine, 1.5% in drinking water 5 days before and during CsA administration, partially protected the animals against this fall in glomerular filtration rate, with inulin clearance of 0.68+/-0.03 ml/min/100 g BW (P<0.01 vs. CsA). Allopurinol, at 10 mg/kg/BW by gavage, also had a protective action, with inulin clearance of 0.54+/-0.04 ml/min/100 g (P<0.01 vs. CsA). CsA caused an elevation in NO production, as assessed by urinary excretion of its metabolites, nitrite and nitrate (NO2 and NO3; 0.836+/-0.358 vs. 0.107+/-0.019 nmol/microg creatinine). NO production was as much as threefold higher in the L-arginine group (1.853+/-0.206 nmol/g creatinine). This CsA effect is probably related to its vasoconstrictive stimulus. Supplementation with L-arginine, which provides more substrate for NO formation, may enhance vasodilatation and consequently reduce the impairment of renal function. The protection provided by allopurinol may be related to the reduced formation of oxygen radicals, preventing the deleterious effects of lipid peroxidation.

Conformational control of cyclosporin through substitution of the N-5 position. A new class of cyclosporin antagonists

Cyclosporin A (CsA) can be regiospecifically alkylated at the NH of Val-5 with reactive bromides in the presence of phosphazene-base P4-t-Bu to yield derivatives 2-5. These are devoid of immunosuppressive activity in vitro but they have binding affinity for cyclophilin A (CypA) similar to that of CsA and thus represent a new class of cyclosporin antagonists. 1H NMR (DMSO-d6) studies have shown that the compounds exist in a single, all trans conformation. A comparison of this NMR data with X-ray crystallographic analysis of a CypA/CsA derivative complex demonstrates that the solution structure does not correspond to the bioactive conformation.

Reduction of chronic ciclosporin nephrotoxicity by thromboxane synthase inhibition with OKY-046

Ciclosporin A (CsA) is a potent immunosuppressive agent which is extremely effective in controlling allograft rejection and in the treatment of autoimmune disease and nephrotic syndrome. Unfortunately, its use is limited by chronic, irreversible nephrotoxicity. Administration of CsA induces renal vasoconstriction, causing a reduction in renal blood flow. An alteration of the prostaglandin-thromboxane cascade may be involved in the vasoconstriction. We studied the role of thromboxane A2 in CsA nephrotoxicity and the ability of a thromboxane synthase inhibitor, OKY-046, to reduce the CsA nephrotoxicity. Daily administration of CsA 25 mg/kg for 28 days to Sprague-Dawley rats resulted in increased excretion of urinary thomboxane B2 (47.9+/-11.5 vs. 27.2+/-9.7 ng/24 h; p<0.05) and decreased creatinine clearance (0.25+/-0.07 vs. 0.43+/-0.17ml/min/100 g; p<0.01) as compared with administration of vehicle only. Histologically, large numbers of lysosomes in the tubular epithelium were characteristic. Coadministration of OKY-046 prevented both the rise in urinary thromboxane B2 excretion (40.0+/-11.8 ng/24 h) and the reduction in the creatinine clearance (0.44+/-0.11 ml/min/100 g). The severity of the histological changes was significantly diminished. Selective inhibition of thromboxane production with OKY-046 may be valuable in the attenuation of CsA nephrotoxicity.

Formulation of diltiazem affects cyclosporin-sparing activity

OBJECTIVE

To consider the effect of changing from a conventional release formulation of diltiazem to the controlled diffusion diltiazem formulation on the cyclosporin-sparing effect in kidney transplant recipients.

METHODS

Seven stable renal transplant recipients were studied on two separate occasions following at least 2 weeks stabilisation on either formulation. The order of administration of the two formulations was not randomised as all patients were already prescribed lower dosages of diltiazem before entering this phase of a larger study. The doses of diltiazem used were 90 mg (conventional release diltiazem) taken twice daily and 180 mg controlled diffusion diltiazem taken in the morning.

RESULTS

Whilst there were no overall significant differences between the two formulations, the study demonstrated considerable interpatient variability when changing to the controlled diffusion formulation, particularly following the morning cyclosporin dose, with three patients showing a reduced cyclosporin AUC (30-60%) and one an increased cyclosporin AUC of 36%.

CONCLUSION

A change in formulation of the cyclosporin-sparing agent may result in unpredictable alterations in cyclosporin concentrations and resultant clinical sequelae.

Isolated glomeruli and cultured mesangial cells as in vitro models to study immunosuppressive agents

Immunosuppressive agents, such as cyclosporin A (CsA), by their vasoconstrictive properties, induce in vivo in patients and rodents a dramatic fall in renal hemodynamics. The aim of this study is to review the ability of some physiological and/or pharmacological agents which are supposed to be involved in the renal physiopathology of CsA to prevent the contraction induced by CsA in two in vitro glomerular models. Isolated glomeruli are obtained by a sieving method from male Sprague-Dawley rat superficial cortex. Mesangial cells from these isolated glomeruli are cultured in RPM1 1640 medium with 20% FCS in 5% CO2 atmosphere. The area of isolated glomeruli and cultured mesangial cells is assessed by an image analyzer with a video camera. Each glomerulus and cell is its own control and is photographed before incubation with any drug (T0) and then during incubation at 5, 10, 20, and 30 min. Incubations are performed during 30 min with 10(-6) mol/L CsA either with a 10 min pretreatment with the vasoactive agent or without pretreatment. CsA alone induces a time- and dose-dependent decrease in glomerular structure area (-4.7% at 10 min, -10.3% at 20 min, and -12.0% at 30 min for isolated glomeruli); Cremophore excipient or control solute does not induce any significant decrease in surface area. CsA with 10(-6) mol/L verapamil pretreatment induces only a slight decrease: -1.5% at 10 min, -3.0% at 20 min, and -4.8% at 30 min. Calcium blockers nifedipine and felodipine produce similar results. Likewise, with 10(-8) mol/L prostacyclin analog (iloprost), only a slight area decrease in mesangial cells is noted: -1.3% at 5 min, -1.8% at 10 min, and -3.3% at 20 min; with 10(-6) mol/L TXA2 synthesis inhibitor (CGS 12970) the results are -2.0% at 10 min, -3.6% at 20 min, and -4.3% at 30 min. Finally, a similar protective effect can be noted with 10(-5) mol/L theophylline: -0.4; -1.5 and -1.9% at 10, 20, and 30 min. In conclusion, CsA-induced contraction in two in vitro glomerular models can be partially or even totally prevented by pretreatment with various pharmacological agents.

Nitric oxide (NO) donor 3-morpholinosydnonimine antagonizes cyclosporin A-induced contraction in two in vitro glomerular models

Cyclosporin A induces in vivo a severe nephrotoxicity characterized by a large decrease in renal hemodynamics. The aim of this study is to establish the ability of the known NO donor 3-morpholinosydnonimine (SIN-1) to prevent the cyclosporin A-induced contraction by using rat isolated glomeruli and cultured glomerular mesangial cells. Isolated rat glomeruli are obtained from the renal superficial cortex by a sieving method. Mesangial cells are cultured in RPMI 1640 with 15% fetal calf serum. The planar surface area (PSA) of either isolated glomeruli or mesangial cells is assessed using an image analyzer. Each glomerulus or mesangial cell serves as its own control through calculation of the area before any drug incubation and after incubation for 10, 20 and 30 min either in control solution or in control solution with cyclosporin A alone or cyclosporin A and SIN-1. Cyclosporin A (10(-6) mol/L) induces an important time-dependent contraction of either glomerulus or mesangial cell. When pretreated with different concentrations of SIN-1 (10(-4) to 10(-9) mol/L), only a slight size decrease is noted. In conclusion, a direct constrictive effect of cyclosporin A in isolated glomeruli and mesangial cells can be prevented by the NO donor SIN-1, suggesting an important involvement of the nitric oxide pathway in the cyclosporin A-induced nephrotoxicity.

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.

Nephroprotective effect of cilastatin in allogeneic bone marrow transplantation. Results from a retrospective analysis

Cilastatin, an inhibitor of the tubular brush border enzyme dehydropeptidase-I, is added in a fixed combination to imipenem. Cilastatin has been demonstrated in different animal models and in one clinical trial, to reduce the nephrotoxicity associated with cyclosporin A. To evaluate a possible nephroprotective effect of cilastatin following allogeneic BMT we conducted a retrospective analysis of 104 patients transplanted in our BMT Unit from January 1991 to January 1995. Imipenem/cilastatin (I/C) was used in a non-randomized manner in 64 patients during this period. Acute renal failure (ARF) was diagnosed in 32 patients (30%). ARF was not associated with gender, sepsis, conditioning regimen, underlying disease, bilirubin, or age. VOD occurred in 12/32 (37.5%) of patients with ARF whereas it occurred in only 7/72 (9.7%) of patients without ARF (P < 0.0007). ARF was not correlated with use of aminoglycosides, vancomycin, ciprofloxacine, ceftazidime or amphotericin-B. However, 13 patients of 64 exposed to I/C (20.3%) developed ARF vs 19 of 40 patients (47.5%) who were not exposed to I/C (P < 0.003; OR 0.28). Stratified analysis and multiple logistic regression confirmed the I/C nephroprotective action. The mean cyclosporin A levels in the I/C group were significantly decreased (208.6 +/- 64.9) vs the non-I/C group (265 +/- 118). We conclude that these results suggest I/C may counteract acute cyclosporin A nephrotoxicity following BMT and further prospective clinical trials are needed to confirm if routine administration of cilastatine confers benefit in the BMT setting.

Primary porcine endothelial cells express membrane-bound B7-2 (CD86) and a soluble factor that co-stimulate cyclosporin A-resistant and CD28-dependent human T cell proliferation

Increasing evidence suggests that endothelial cells can directly activate syngeneic, allogeneic and xenogeneic T cells. In this study we demonstrate that unstimulated, paraformaldehyde-fixed primary porcine aortic endothelial cells (PAEC) and microvascular endothelial cells (PMVEC) can provide co-stimulation for human T cell IL-2 secretion and proliferation. EC-mediated co-stimulation has both cyclosporin A (CsA)-sensitive and CsA-resistant components. The CsA-resistant component is completely suppressed either by blocking with anti-CD28 F(ab) fragments or CTLA-4-Ig. Northern blot analysis of unstimulated PAEC and PMVEC with porcine-specific probes reveals constitutive expression of B7-2 mRNA while B7-1 message was not detected. hCTLA-4-Ig and anti-B7-2 mAb immunoprecipitates a single 79 kDa PMVEC surface protein. Surprisingly, PMVEC conditioned media also has soluble co-stimulatory activity that is blocked by anti-CD28 F(ab) fragments or anti-B7-2 mAb. These findings demonstrate that primary unstimulated porcine EC can co-stimulate CsA-resistant human T cell proliferation through binding of membrane bound, constitutively expressed EC B7-2 (CD86) to human T cell CD28, providing one of the first demonstrations of functional B7-2 on cells outside the immune system. In addition, PMVEC secrete or shed a soluble factor that mediates CD28-dependent human T cell proliferation, demonstrating the existence of soluble mediators of CD28 activation.

Short-term systemic insulin-like growth factor-1 is unable to prevent cyclosporin A-induced osteopenia in the rat

Immunosuppression with cyclosporin A (CsA) is effective in a number of immune-mediated diseases and in preventing rejection following organ transplantation. We have repeatedly demonstrated that CsA in the rat model produces accelerated bone remodelling with net bone loss, best characterized in trabecular bone. IGF-I holds promise as a treatment for various osteopenic conditions. Although currently a subject of much controversy, various studies have suggested that in vivo it is anabolic to cortical as well as trabecular bone. The purpose of this study was, in part, to further characterize the effects of CsA and IGF-I on trabecular and cortical bone, and to see whether systemic IGF-I is able to modulate CsA's deleterious skeletal effects. Sixty 10 week-old, male, Sprague-Dawley rats were randomized to receive the following daily for 3 weeks: (1) CsA vehicle (veh) per os (po) + recombinant human (rh) IGF-1 veh subcutaneously (sc); (2) CsA 15 mg/kg po + rhIGF-I-veh; (3) CsA-veh + rhIGF-I 200 microg/kg sc; (4) CsA-veh + rhIGF-I 600 microg/kg sc; (5) CsA 15 mg/kg + rhIGF-I 200 microg/kg, and (6) CsA 15 mg/kg + rhIGF-I 600 microg/kg. Rats were weighed and venous blood was sampled serially for determination of glucose, ionized calcium (Ca2+), PTH, vitamin D, and osteocalcin. Following sacrifice on day 20, histomorphometry was performed on double calcein-labeled tibial metaphysis and diaphysis. All rats receiving CsA had elevated levels of blood glucose and osteocalcin by day 9 and vitamin D at day 20. PTH was similar in all groups, and Ca2+ was only raised in the CsA and CsA + IGF-I 200 microg/kg groups. Rats receiving IGF-I 200 microg/kg and IGF-I 600 microg/kg gained more weight than either vehicle- or CsA-treated animals, attesting to IGF-1's anabolic properties. CsA caused severe trabecular bone loss, not prevented by IGF-I; it even further increased the eroded surface. CsA and IGF-I had little effect on cortical bone volume or marrow area. IGF-I increased endocortical matrix synthesis, as evidenced by the increases in the percent endocortical osteoid perimeter, an effect negated by the addition of CsA. This experiment demonstrates that trabecular bone is more susceptible than cortical bone to the deleterious effects of CsA and indicates little role for IGF-1 in the pathophysiology or treatment of CsA-induced bone disease at the given doses and duration of treatment.

Cyclosporine A affects serotonergic mechanisms in uremic rats

The aim of this study was to investigate the mechanism of cyclosporine-induced hypertension in respect to its action on blood serotonergic system. The experiment was carried out on healthy rats and animals with experimental chronic renal failure. Cyclosporine A (CsA) injected into the healthy and uremic rats caused an increase in systolic blood pressure. This effect was completely abolished by ketanserin, an antagonist of 5-HT2 receptors. Concomitantly a rise in blood and platelet serotonin concentration was observed. It is concluded that serotonin may play a role in the development of hypertension caused by CsA. Moreover, ketanserin may serve as a drug for pharmacological protection of CsA-induced rise of blood pressure in uremia.

Cimetidine or ranitidine in renal transplant patients receiving cyclosporine

While H2-receptor antagonists are commonly used in renal transplant patients to prevent peptic ulcer disease, they have been associated with immunostimulation, interference with cyclosporine (CsA) metabolism, and inhibition of tubular secretion of creatinine. In renal transplant patients, cimetidine in high doses has been shown to cause a sustained rise in serum creatinine (SCr) and to reduce creatinine clearance (CrCl) with no change in inulin clearance. In this short-term prospective study, we evaluated the effects of single daily doses of cimetidine or ranitidine on renal function, and CsA serum concentration. Fourteen renal transplant patients with stable renal function were assigned to receive either cimetidine 400 mg daily or ranitidine 150 mg daily for 7 days. In patients who received cimetidine, a slight rise in SCr was observed at days 2 and 5 which was not statistically significant, but no significant change in CsA trough level was noted. No changes in SCr or CsA level were noted in the patients who received ranitidine. No changes in GFR were observed in either cimetidine- or ranitidine-treated patients. We conclude that, in our short-term study, cimetidine or ranitidine in the doses used in this study did not affect the GFR or CsA level, or SCr.

Reversal of cyclosporine A-induced alterations in biliary secretion by S-adenosyl-L-methionine in rats

This study examines the ability of S-adenosyl-L-methionine to prevent or antagonize the cyclosporine A-induced adverse effects on biliary secretion in the rat. S-adenosyl-L-methionine was administered as a single bolus 3, 5 and 8 hr before administering a single dose of cyclosporine A, and also concurrently administered with cyclosporine A for 1 or 2 wk. Acute S-adenosyl-L-methionine preadministration attenuated the cyclosporine-induced cholestasis and inhibition of bile acids, cholesterol and phospholipid biliary secretion. S-adenosyl-L-methionine pretreatment for 1 wk and simultaneous cotreatment with cyclosporine for 1 or 2 wk not only maintained the beneficial effects reported above but further improved them because the adverse effects of the immunosuppressor drug were prevented or antagonized by S-adenosyl-L-methionine. These results provide the first direct evidence of the ability of exogenously administered S-adenosyl-L-methionine to antagonize cyclosporine-induced abnormalities in biliary bile acids, lipids and protein secretion. The beneficial effects of S-adenosyl-L-methionine could be related, at least in part, to the improvement in the hepatobiliary transport of bile acids.

Lipid peroxidation accompanies cyclosporine nephrotoxicity: effects of vitamin E

Cyclosporine A (CsA) has been demonstrated to induce renal microsomal lipid peroxidation in vitro. To examine whether CsA induces lipid peroxidation in vivo, uninephrectomized rats were gavaged with vehicle, CsA 12.5 or 25 mg/kg/day for four weeks. CsA-induced reduction in GFR and RBF was associated with a dose-related increase in renal cortical malondialdehyde (MDA) and conjugated diene, as well as a similar increase in arterial MDA. The latter was apparent within two hours of a single intraperitoneal injection of 25 mg/kg CsA and preceded the acute fall in GFR. To address whether lipid peroxidation contributed to CsA nephrotoxicity, rats were gavaged with vehicles, CsA 25 mg/kg/day or CsA plus vitamin E 25 mg/kg/day for eight weeks. Vitamin E, a lipid radical scavenger, inhibited MDA raise and reduced CsA-induced renal damage. Conversely, CsA administration to vitamin E and selenium deficient rats was accompanied by a greater increase in arterial MDA and fall in GFR. These novel findings, that CsA nephrotoxicity is associated with lipid peroxidation and that a chain-breaking antioxidant ameliorates whereas its deficiency exacerbates, indicate a role for lipid peroxidation, presumably free radical-mediated, in CsA toxicity.

Effects of cyclosporine A on experimental hepatic metastases of mouse colon-26 tumour

Cyclosporine A (CSA), an immunosuppressive agent with apparently selective effects on T lymphocytes and little myelotoxicity, was tested for its effects on hepatic metastases by inoculation of mouse colon-26 tumour cells into the portal vein in male CDF1 mice. CSA, given subcutaneously in daily doses of 10-50 mg/kg/day, for 22 days, significantly increased the incidence of hepatic nodules. This increase was positively correlated with the CSA dose. When 5-fluorouracil was injected at a dose of 15 mg/kg/day every other day after the inoculation of tumour cells a highly significant reduction in the incidence of metastases was seen (compared with the controls). This strong inhibitory effect of 5-fluorouracil on metastasis was almost completely suppressed when mice were treated with CSA concomitantly. The results suggest that CSA affects the host immune system, accelerating the production of hepatic metastases.

Image analyser as a tool for the study of in vitro glomerular vasoreactivity

Many drugs used in clinics can dramatically reduce renal hemodynamics. For some years there have been developed in our laboratory two in vitro glomerular models, isolated glomeruli and mesangial cell cultures, to quantitate, by video image analyzer, the direct glomerular effect of vasoreactive agents. The present study shows the vasoconstrictive effects of angiotensin II and cyclosporin in both models and compares their glomerular vasoconstriction with or without vasodilating agents such as verapamil. This drug-induced glomerular vasoreactivity is time- and dose-dependent; moreover, it can be reversible after perfusion in control conditions. The interest of these in vitro glomerular models is validated by fair correlations between in vivo and in vitro data and between the responses of both. These models can be considered as tools for assessing glomerular vasoreactivity of nephrotoxic agents.

Atrial natriuretic peptide inhibits cyclosporin A-induced endothelin production and calcium accumulation in rat vascular smooth muscle cells

1. As we have previously shown, cyclosporin A enhances the vasoconstrictor-induced rise in intracellular free calcium in vascular smooth muscle cells. This effect may contribute to important side-effects in cyclosporin therapy, such as hypertension and nephrotoxicity. Atrial natriuretic peptide has been shown to inhibit this effect as well as the cyclosporin-stimulated transmembrane calcium influx in smooth muscle cells. 2. The present study, therefore, was designed to examine the effect of cyclosporin and atrial natriuretic peptide on total cellular calcium content in the rat. Furthermore, since cyclosporin was recently shown to induce endothelin production in smooth muscle cells, we investigated the effect of atrial natriuretic peptide on this potentially adverse cellular effect of cyclosporin therapy. 3. Total cell calcium was measured by atomic absorption, and cellular endothelin production was estimated by radioimmunoassay. 4. Preincubation of the cells with cyclosporin (10 micrograms/ml) for 30 min increased total cell calcium from 2.6 +/- 0.5 to 6.9 +/- 0.3 nmol/mg of protein (P < 0.01). Within 24 h endothelin production was significantly enhanced in the presence of cyclosporin (52.2 +/- 2.5 versus 65.9 +/- 2.7 fmol/mg of protein, P < 0.05). Therefore, the cyclosporin-induced rise in total cell calcium in smooth muscle cells is associated with enhanced production of endothelin. Thus, it is tempting to speculate that the cyclosporin-induced changes in calcium kinetics may be mediated by endothelin. 5. In the presence of atrial natriuretic peptide (10(-8) mol/l), the cyclosporin-induced rise in total cell calcium was significantly reduced (6.9 +/- 0.3 versus 5.1 +/- 0.2 nmol/mg of protein, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor necrosis factor alpha is an autocrine growth factor for normal human B cells

Transcription of the human tumor necrosis factor alpha (TNF-alpha) gene is one of the earliest events that occurs after stimulation of B or T cells via their antigen receptors. Antibody directed at surface immunoglobulin (anti-Ig) on B cells has previously been shown to induce a rapid burst of TNF-alpha gene transcription, which can be blocked by the immunosuppressants cyclosporin A (CsA) and FK506. Here, TNF-alpha gene transcription is shown also to be highly and rapidly induced in human B cells after stimulation via the CD40 and interleukin 4 pathways, which similarly is inhibited by CsA and a panel of CsA or FK506 analogues that block calcineurin phosphatase activity. Endogenous TNF-alpha produced after stimulation was involved in B-cell proliferation since anti-TNF-alpha monoclonal antibody inhibited both anti-Ig- and anti-CD40-induced B-cell proliferative responses. Moreover, addition of TNF-alpha during stimulation resulted in augmentation of B-cell proliferation, which was also inhibited by anti-TNF-alpha monoclonal antibody. Although lymphotoxin alpha (LT-alpha) mRNA is induced by both pathways, it is not blocked by CsA, whereas LT-beta mRNA is constitutively expressed in B cells. Thus, TNF-alpha is a necessary autocrine growth factor for human B cells stimulated via two independent CsA-sensitive pathways and plays a role similar to that of interleukin 2 in T-cell proliferation. The autocrine nature of TNF-alpha in activated B cells implies a potential role for this cytokine in infection-related polyclonal B-cell expansion and in B-cell malignancies.

Attenuation of cyclosporine A-induced vascular toxicity by ramipril

We wished to determine whether chronic inhibition of angiotensin-converting enzyme (ACE) prevents the vascular toxicity of cyclosporine A (Cx). In aortas isolated from rats treated with ramipril [10 mg/kg/day orally (p.o.) for 4 weeks], the endothelium-dependent relaxations to acetylcholine (ACh) were potentiated (the area under the curve (AUC) decreased from 154 +/- 35 to 63 +/- 12, p < 0.05), but contractions induced by phenylephrine (PE) and angiotensin II (AII) were not affected. Therefore, we studied three groups of rats in parallel. Group 1 received ramipril 10 mg/kg/day p.o. for 4 weeks and ramipril 10 mg/kg/day p.o. plus Cx 20 mg/kg/day intramuscularly, in fifth week; group 2 received Cx only (20 mg/kg/day i.m. for 1 week), and group 3 served as control. In group 2, ACh-induced relaxations were reduced as compared with those of the control group (AUC increased from 141 +/- 34 to 240 +/- 32, p < 0.05), whereas in group 1, AUC was not significantly different from that of group 3 (195 +/- 28 vs. 141 +/- 34). In group 2, PE- and AII-induced contractions were enhanced; AUC values for PE and AII were 495 +/- 45 versus 348 +/-38 in group 3 and 424 +/- 28 versus 314 +/- 17 in group 3, respectively (p < 0.05). In group 1, AUCs for PE and AII were not significantly different from those of group 3. After mechanical removal of the endothelium, the increased responsiveness to PE and AII persisted in group 2 whereas AUC values in group 1 were not different from those of group 3.(ABSTRACT TRUNCATED AT 250 WORDS)