Reduction of cyclosporine-induced nephrotoxicity by cilastatin following clinical heart transplantation

The objective of this prospective, randomized, placebo-controlled, single-blinded study in 28 heart-transplanted patients was to investigate whether the dehydropeptidase inhibitor cilastatin reduces cyclosporine-induced nephrotoxicity. Cilastatin is available only in combination with imipenem, a beta-lactam antibiotic to which it is added for reduction of nephrotoxic side-effects of the antimicrobial agent. Patients received either 100 ml placebo (n = 12) or 100 ml (500 mg) imipenem/cilastatin (n = 16) twice perioperatively, and 4 times daily for the first 7 postoperative days. Serum creatinine and urea, as well as urine concentrations of N-acetyl-beta-D-glucosaminidase, which is directly correlated with tubular cell damage, were used as markers for renal function. Thromboxane B2 and 6-keto-prostaglandin F1-alpha serum concentrations were determined to investigate whether there is an imbalance in synthesis of thromboxane A2 and prostacyclin as a possible mechanism for cyclosporine-induced nephrotoxicity. Two placebo patients and 6 patients receiving imipenem/cilastatin had to be excluded from further analysis. Three of 10 placebo patients required hemofiltration, and 2 of them even required hemodialysis, as compared with none in the imipenem/cilastatin group. Creatinine concentrations increased significantly from the second to the fourth postoperative day in the placebo group, but remained nearly normal in cilastatin patients (P < 0.05 for intergroup comparison on postoperative days 2-4). The same trend was observed in urea and N-acetyl-beta-D-glucosaminidase concentrations, without the difference reaching statistical significance. For thromboxane B2 and 6-keto-prostaglandin F1-alpha no differences between the groups could be found. These results suggest that imipenem/cilastatin can counteract acute cyclosporine-induced nephrotoxicity, which appears to be associated with alterations of tubular cell function. The combined use of cyclosporine and imipenem/cilastatin appears to be advantageous in patients following heart transplantation during the initial postoperative period.

The immunomodulator LS-2616 (linomide) more effectively than sensitization of the donor enhances graft-versus-host reaction after small bowel transplantation

The effects of the immunomodulating substance LS-2616 (linomide) on graft-versus-host reaction (GVHR) were investigated in a semi-syngeneic small bowel transplantation model. The entire bowel of Lewis donors were transplanted heterotopically into (Lewis x BN) F1 hybrids. Both untreated animals and animals treated with LS-2616, in a daily dose of 160 mg/kg, developed a lethal GVHR. The median survival time in untreated animals was 14.5 days while in LS-2616 treated animals it was just eight days (p < 0.01). LS-2616 in combination with cyclosporin A (CyA), 15 mg/kg given orally on days 0-20, did not seem to alter the survival times compared with CyA treatment alone; 56% of the animals treated with CyA survived for more than 100 days and after combined treatment with CyA/LS-2616 there were 50% permanent survivors. Also the effect of earlier sensitization of the donor on the course of GVHR was investigated. Hearts from BN rats were transplanted heterotopically to the neck vessels of Lewis rats. The hearts were rejected on about day six; five days later the bowels were harvested and transplanted into (Lewis x BN) F1 hybrids. The median survival time in this group was 12.5 days. Taken together our results, in combination with earlier findings, suggest that, at the level of effector mechanisms, GVHR is not an exact mirror image of rejection. Also, LS-2616 appears to be a useful tool for further studies of the mechanisms of action of GVHR.

Direct vascular smooth muscle contractile effect of cyclosporin A and its vehicle in rabbit isolated arteries

cyclosporin A is a widely used immunosuppressant agent which has direct vascular effects such as contraction of the arterial smooth muscle and potentiation of other vasoconstrictor agents. In rabbit isolated arterial segments, the contractile effects of a cyclosporin A preparation (Sandimmun; 10(-6) M) and its solvent (Cremophor-EL) were investigated. Both caused an increase in the basal tension of arterial segments after an incubation period of 1 hour. Several substances were tested to antagonize the contractile activity of the cyclosporin A preparation and its solvent. Prednisolone and quinacrine (phospholipase A2 inhibitors), indomethacin (cyclooxygenase inhibitor), verapamil (calcium antagonist), phentolamine (alpha-adrenoceptor blocker), captopril (angiotensin-converting enzyme inhibitor) and prazosin (alpha 1-adrenoceptor-blocking agent) decreased the contractile responses to the cyclosporin A preparation and its solvent in a comparable manner. These findings indicate that the solvent of the cyclosporin A preparation is responsible for the contractile effect of this latter preparation and that this contractile activity cannot be explained by a single mechanism.

Evidence that the antibiotic ciprofloxacin counteracts cyclosporine-dependent suppression of cytokine production

The fluoroquinolone antibiotic ciprofloxacin (cipro) has been reported to upregulate interleukin 2 and interferon-gamma production in lectin-stimulated lymphocytes. The aim of this study was to elucidate whether cipro and the immunosuppressive agent CsA have antagonistic action on cytokine synthesis. Accumulation of IL-2 and IFN-gamma protein and mRNA were analyzed in polyclonally (PHA or Con A) or alloantigen-stimulated human peripheral blood lymphocytes. CsA added simultaneously with PHA partially blocked cytokine synthesis. The present study also shows that cipro supplemented with CsA and PHA resulted in significant higher concentrations of IL-2 (up to 60 times) and IFN-gamma (4.3 times) as compared with PHA and CsA alone. Similar results were obtained with primary mixed lymphocyte reactions. In parallel, a greater amount of IL-2 and IFN-gamma mRNA was observed in lymphocytes incubated with both cipro and CsA as compared with CsA alone. Our results reveal that CsA-dependent inhibition of both IL-2 and IFN-gamma expression is counteracted by high concentrations of cipro. These findings may be of importance in clinical transplantation.

Alteration of cyclosporine (CsA)-induced nephrotoxicity by gamma linolenic acid (GLA) and eicosapentaenoic acid (EPA) in Wistar rats

Administration of cyclosporine (CsA), 37.4 microM (45 mg)/Kg, per day for 7 days, to Wistar rats, induced decreased creatinine clearance (Ccr) and body weight loss (BWL), but it did not induce proteinuria. These changes were associated with enhanced urinary thromboxane B2 (TXB2) and diminished 6-keto-PGF1 alpha (6kPGF1 alpha) and prostaglandin E2 (PGE2) excretions. The augmentation in TXB2 and the decrease in PGs highly diminished the ratios of 6kPGF1 alpha/TXB2 and PGE2/TXB2. In microscopic sections all of the kidneys were affected to variable degrees. When CsA was administered to animals fed for 70 days, prior to the experiment, on standard chow (SC) containing evening primrose oil (EPO) or fish oil (FO), 1% and 10% respectively (EPO contained 9% gamma-linolenic acid (GLA) and FO 5.6% eicosapentaenoic acid (EPA)), the nephrotoxic effect of CsA was partially prevented. These changes were accompanied by increased ratios of urinary 6kPGF1 alpha/TXB2 and PGE2/TXB2 excretions. Light microscopic (LM) studies showed that rats' kidneys fed on SC containing EPO or FO were not always affected and the lesions were of minor importance. In conclusion, these results suggest that EPO (GLA) and FO (EPA) could play a beneficial role in the development or the modulation of the renal syndrome induced by CsA.

Prevention of experimental cyclosporine nephrotoxicity by dietary supplementation with LSL 90202, a lysine salt of eicosapentaenoic acid. Role of thromboxane and prostacyclin in renal tissue

Cyclosporine (CsA) nephrotoxicity is partially mediated by renal vasoconstriction due to an imbalance between vasodilator and vasoconstrictor eicosanoids. LSL 90202 is a purified lysine salt of eicosapentaenoic acid which is a known inhibitor of renal eicosanoid synthesis. The aim of the present work was to determine if chronic dietary supplementation with LSL 90202 prevented CsA nephrotoxicity and to establish the role of thromboxane and prostacyclin in renal tissue. Thirty-three male Sprague-Dawley rats were divided into 4 groups: group 1, CsA in olive oil (n = 10); group 2, isovolumetric olive oil (n = 7); group 3, CsA in olive oil plus LSL 90202 (n = 8); group 4, isovolumetric olive oil plus LSL 90202 (n = 8). CsA and LSL 90202 were given at 20 mg/kg/day. Weight and creatinine clearance (CrCl) were determined before and on days 14 and 30. On day 30 whole-blood CsA was determined and renal tissue processed for renal malondialdehyde, thromboxane B2 and 6-keto-PGF1 alpha measurement and for conventional histology. CrCl was severely reduced in the CsA in olive oil group compared to olive oil and LSL 90202 control groups. On day 30, CrCl in the CsA in olive oil plus LSL 90202 group showed a slight decrease, but the mean CrCl was significantly higher than in the CsA in olive oil group. Trough whole blood CsA levels were not significantly different in both groups given the drug. No morphological differences were found between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of acute cyclosporin nephrotoxicity by verapamil and atrial natriuretic factor in the rat

Nephrotoxicity is the most common and important side-effect of cyclosporin (CsA) therapy. CsA alters renal haemodynamics with a reduction in renal blood flow (RBF) and glomerular filtration rate (GFR) and a significant increase in renal vascular resistances (RVR). The present experimental study investigates whether verapamil or atrial natriuretic factor (ANF) are able to prevent the nephrotoxicity of CsA. All studies were conducted in an in-situ autoperfused rat kidney model which allows continuous measurement of renal blood flow without dissection of the renal artery. CsA as a 40 mg/kg bolus dose significantly decreased RBF (from 2.15 +/- 0.1 and 2.19 +/- 0.1 before CsA, to 1.29 +/- 0.16 ml/min/100 g BW, 60 min after CsA administration) (P < 0.05), and GFR (from 0.14 +/- 0.1 and 0.13 +/- 0.01 before CsA, to 0.08 +/- 0.01 ml/min/100 g BW, 60 min after CsA administration) (P < 0.05). CsA significantly increased RVR (from 9.5 +/- 0.73 and 9.8 +/- 0.78 before CsA, to 16.7 +/- 2.9 mmHg x min/ml 60 min after CsA administration) (P < 0.05). Verapamil pretreatment (as continuous intrarenal infusion at the rate of 1.25 micrograms/kg/min) attenuated the fall in GFR (from 0.16 +/- 0.01 and 0.19 +/- 0.03 ml/min/100 g before CsA to 0.20 +/- 0.05 ml/min/100 g BW, 60 min after CsA administration) (NS) and in RBF (from 2.42 +/- 0.2 and 2.6 +/- 0.22 ml/min/100 g before CsA to 1.79 +/- 0.17 ml/min/100 g BW, 60 min after CsA administration (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Lipophilic dihydropyridines provide renal protection from cyclosporin toxicity

AIM

To review cyclosporin nephrotoxicity and its prevention by calcium antagonists.

METHOD

Review of published and unpublished studies.

RESULTS

Cyclosporin A nephrotoxicity is the most important side effect of this potent immunosuppressive drug. Several mechanisms have been implicated in the production of this adverse effect but elevated endothelin release is perhaps the most frequently cited cause. Calcium antagonists have demonstrated a beneficial effect in preventing cyclosporin A nephrotoxicity in renal cadaveric transplants, during both short- and long-term follow-up. Lacidipine, a lipophilic dihydropyridine calcium antagonist, prevents the reductions in the glomerular filtration rate and renal plasma flow that are often seen after cyclosporin A administration. This effect is not related to endothelin suppression.

CONCLUSIONS

Calcium antagonists can provide renal protection in patients who undergo renal cadaveric transplantation and are treated with cyclosporin.

Calcium channel blockade in rats with cyclosporine-induced vasoconstriction

Calcium channel blockade has been found to attenuate nephrotoxicity of cyclosporine. However, it is not known whether intrarenal vasoconstriction caused by cyclosporine is totally mediated by vascular smooth muscle calcium influx. To study the protective effects of two calcium blockers on cyclosporine-induced intrarenal vasoconstriction and renal microvascular blood flow, hydronephrotic rat kidneys were suspended in an environmentally controlled tissue bath. Renal microvessel diameters and microvascular blood flow were determined by in vivo videomicroscopy and Doppler velocimetry. Calcium channel blockade was achieved by adding verapamil hydrochloride (5.6 x 10(-5) M) or diltiazem hydrochloride (2.8 x 10(-5) M) to the tissue bath, which respectively resulted in a 15 +/- 2% and 16 +/- 3% interlobular arteriolar dilation, a 13 +/- 3% and 12 +/- 2% afferent arteriolar dilation, and a 60 +/- 8% and 46 +/- 14% increase in interlobular blood flow. When cyclosporine (1.7 x 10(-3) M) was added to the tissue bath, there was a constriction of the interlobular arterioles to 4 +/- 3% below baseline in rats receiving verapamil and 9 +/- 3% below baseline in rats receiving diltiazem. Microvascular blood flow was reduced by the addition of cyclosporine to 3 +/- 4% above original baseline values in the verapamil group and 22 +/- 6% below baseline in the diltiazem group. Afferent arterioles were similarly constricted by cyclosporine. The results indicate that calcium blockade causes preglomerular vasodilation and protects the microvascular blood flow induced by cyclosporine. Since verapamil or diltiazem did not prevent arteriolar constriction as observed when cyclosporine was added, it was concluded that the mechanism of acute cyclosporine-induced vasoconstriction is not solely mediated by vascular smooth muscle calcium influx through potential dependent channels.

Blockade of cyclosporine-induced vasoconstriction by the calcium channel blocker diltiazem in dogs

The calcium channel blocker diltiazem has been shown to reduce cyclosporine toxicity both in clinical and in experimental studies. To determine the effect of diltiazem administration on cyclosporine vasoconstriction and on renal release of endothelin, we administered cyclosporine in models of renal and hind limb autoperfusion in the dog. Infusion of cyclosporine in the hind limb (20 mg) during diltiazem perfusion caused an average increase of 6 +/- 2 mm Hg in hind limb perfusion pressure compared with 17 +/- 2 mm Hg before diltiazem, a significant difference (p < 0.05). Similarly, injections of cyclosporine (10 mg) in the kidney during diltiazem infusion caused an average increase of 26 +/- 4 mm Hg in renal perfusion pressure compared with 83 +/- 13 mm Hg before diltiazem infusion, a significant decrease in the renal vascular response (p < 0.05). On the other hand, sodium nitroprusside did not change the renal vasoconstriction to cyclosporine, which suggests a specific effect of diltiazem. Serum levels of endothelin in renal venous blood increased from 0.5 +/- 0.4 pg/ml to 3.8 +/- 0.6 pg/ml with cyclosporine, despite diltiazem infusion. Therefore, although the calcium channel blocker diltiazem effectively decreases cyclosporine-induced renal and hind limb vasoconstriction, it does not act by preventing endothelin release induced by cyclosporine stimulation.

Diminution of an acute cyclosporin-induced cholestasis by tauroursodeoxycholate in the rat

CsA is a commonly used immunosuppressive drug known to possibly induce cholestatic side effects. Ursodeoxycholic acid (UDC), a nonhepatotoxic bile acid, has proved to be efficient for several types of cholestasis. The aim of this experiment was to evaluate the ability of tauroursodeoxycholate (TUDC) in preventing CsA-induced cholestasis on bile duct-cannulated rats. After bile flow stabilization, a bolus of 30 mg/kg CsA was given i.v. to one group (n = 7) and was associated with a 2 mumol/kg/min TUDC infusion in another group (n = 7). The control group was injected with CsA-solvent. CsA, as used here, had a rapid and marked cholestatic effect. However, both bile flow and bile salt secretion were significantly enhanced in the TUDC group when compared to the CsA alone-treated group and showed no difference with the solvent control group. In addition, TUDC significantly increased elimination of CsA and its metabolites in bile. In contrast to what was found for endogenous bile salts, TUDC uptake was not affected by CsA. The anticholestatic effect of TUDC probably resulted from preventing CsA-induced hepatocyte membrane damage and from easing biliary excretion of CsA. Such properties could be helpful for CsA-treated liver recipients who are especially exposed to cholestatic problems, and thus, to toxic CsA accumulation in the liver. Moreover, regulation of CsA elimination might prevent, in part, its general toxicity.

Synergism between the CD3 antigen- and CD2 antigen-derived signals. Exploration at the level of induction of DNA-binding proteins and characterization of the inhibitory activity of cyclosporine

We have demonstrated earlier that the crosslinkage of the CD3/TCR complex with the CD2 antigen results in the proliferation of normal human T cells. The effect of this synergism was perceptible at the level of induction of the IL-2 gene, a process critical for T cell growth. To further understand the molecular and nuclear basis for this synergism, we have explored the induction of DNA-binding proteins in highly purified normal human T cells signaled via the CD3 and/or CD2 proteins. The effect of transmembrane signaling of T cells with ionomycin, and/or sn-1,2 dioctanoyl glycerol, was also determined. The emergence of nuclear binding proteins was investigated using interleukin-2 sequence specific oligonucleotide probes in the electrophoretic mobility shift assay. Our studies demonstrate for the first time that CD3 antigen-derived signals and CD2 antigen-derived signals are synergistic in inducing the emergence of transcription factors that bind to the NF-AT1, AP-1, and NF-kB sites located in the promoter/enhancer region of the IL-2 gene. Moreover, cyclosporine, at concentrations readily accomplished in clinical practice, was found to inhibit the emergence of these DNA-binding proteins in normal human T cells signaled via cell surface proteins implicated in antigen-dependent T cell activation and in T cells stimulated by mobilization of cellular calcium and activation of protein kinase C.

The reversal of experimental cyclosporin A nephrotoxicity by thromboxane synthetase inhibition

The ability of thromboxane synthetase inhibition to reverse acute cyclosporin A (CsA)-induced nephrotoxicity in the rat was investigated. CsA administration (50 mg/kg/day p.o. for 14 days) to male Sprague-Dawley rats caused a significant 50% decline in creatinine clearance rates, an increase in N-acetyl-beta-D-glucosaminidase (NAG) enzymuria and renal tubulointerstitial damage by day 14. These changes were associated with a 5-6-fold increase in urinary thromboxane B2 excretion (from pretreatment values of 28.1 +/- 7.9 to 122.6 +/- 38.9 and 165.8 +/- 39.0 eta g/24 hr body weight on days 7 and 14, respectively). Excretion rates of 6-keto-prostaglandin F1 alpha and prostaglandin E2 were, however, unaffected by CsA administration. Co-treatment with a thromboxane synthetase inhibitor (CGS 12970; 8-[3-methyl-2-(3-pyridyl)-1-indolyl]-octanoic acid) from day 7 (10 mg/kg/day) normalized thromboxane B2 excretion, resulted in creatine clearance rates which were similar to pretreatment values on days 10 and 14, reduced NAG enzymuria on day 10 and prevented acute proximal tubular vacuolation. However, the severity of chronic CsA nephrotoxicity, namely chronic tubular damage and microcalcification at the corticomedullary junction, was not diminished by the thromboxane synthetase inhibition. These results demonstrate that (i) elevated thromboxane synthesis plays an important role in the development of acute CsA nephrotoxicity and (ii) that different and/or additional mechanisms are involved in the pathogenesis of chronic nephrotoxicity.

Calcium channel blockers protect transplant patients from cyclosporine-induced daily renal hypoperfusion

Renal toxicity, possibly due to vasoconstriction and vascular injury, is the most relevant side-effect of chronic cyclosporine (CsA) therapy given to prevent graft rejection. In kidney transplant recipients each oral dose of CsA is invariably followed by a transient reduction in renal plasma flow (RPF) and glomerular filtration rate (GFR) that results from a form of acute reversible hypoperfusion. We sought to determine whether the Ca2+ channel blocker, lacidipine, prevented CsA-associated renal hypoperfusion in these patients. Parallel studies on CsA pharmacokinetics, renal function parameters (GFR and RPF), as inulin and p-aminohippurate (PAH) clearances, respectively, and urinary excretion of the vasoconstrictor endothelin in 10 consecutive renal transplant patients given CsA as a part of their immunosuppressive therapy were performed. Patients were studied at different time intervals after CsA alone, CsA and lacidipine (4 mg/day), and again seven days after lacidipine withdrawal. In all patients basal RPF and GFR declined on average 51% (139.3 +/- 20.7 ml/min/1.73 m2) and 50% (32.5 +/- 5.8 ml/min/1.73 m2), respectively, two to four hours after maximum blood CsA concentration was reached. As blood levels of CsA returned to trough, both parameters progressively increased to baseline. Lacidipine administration completely prevented the fall in RPF (pre-CsA: 277.1 +/- 23.6; 6 hr post-CsA: 304.5 +/- 31.1 ml/min/1.73 m2) and GFR (pre-CsA: 66.6 +/- 8.1; 6 hr post-CsA: 70.1 +/- 9.8 ml/min/1.73 m2). When lacidipine treatment was discontinued the abnormal RPF and GFR response to CsA administration was again observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular signaling by cyclosporine A in contractile cells: interactions with atrial natriuretic peptide

Immunosuppressive therapy with cyclosporine A (CyA) may be associated with severe side effects such as nephrotoxicity and arterial hypertension. The partial reversibility of these effects suggests that they are at least in part functional. The present study examined the effects of CyA on cellular signaling in vascular smooth muscle cells and in glomerular mesangial cells and the interactions with the endogenous vasodilator atrial natriuretic peptide (ANP). Intracellular free calcium concentrations ([Ca2+]i) were measured using Fura-2. 45Ca2+ was used to measure Ca2+ efflux and cellular Ca2+ influx. In the presence of cyclosporine (10 micrograms/ml), the Ca(2+)-mobilizing effects of angiotensin II (10(-8)M) in smooth muscle cells and of arginine vasopressin (AVP) in mesangial cells were significantly enhanced. CyA significantly stimulated cellular Ca2+ uptake in both cell types. ANP blocked the Ca2+ mobilization by angiotensin II and AVP and also completely inhibited the potentiating effect of CyA on angiotensin II- and AVP-induced Ca2+ mobilization. ANP also completely blocked the CyA-stimulated Ca2+ uptake. These findings suggest that CyA stimulates transmembrane Ca2+ influx, thereby increasing vasopressor-sensitive intracellular Ca2+ stores and augmenting vasopressor-induced Ca2+ mobilization. This cellular effect of CyA in vitro was markedly diminished by ANP. The effects of CyA on intracellular signaling may directly enhance the contractile response of smooth muscle and the glomerular mesangium to vasopressor stimuli and may also contribute to other disturbances of cell metabolism associated with CyA.

Atrial natriuretic peptide blunts the cellular effects of cyclosporine in smooth muscle

The effect of cyclosporine A to enhance vasoconstrictor-induced calcium (Ca2+) mobilization in vascular smooth muscle cells may contribute to important side effects in cyclosporine therapy such as hypertension and nephrotoxicity. On the other hand, atrial natriuretic peptide (ANP) is known to diminish vasoconstrictor-stimulated Ca2+ mobilization. The present study, therefore, examined the interaction of cyclosporine and ANP on Ca2+ kinetics in cultured rat vascular smooth muscle cells. Intracellular free calcium concentrations ([Ca2+]i) were measured using fura-2. 45Ca2+ was used to estimate Ca2+ efflux and cellular Ca2+ influx. Preincubation of the cells with cyclosporine (10 micrograms/ml) for 12 minutes lowered basal [Ca2+]i from 48 +/- 4 to 28 +/- 3 nM (p < 0.01). However, in the presence of cyclosporine, the angiotensin II (10(-8) M)-stimulated rise of [Ca2+]i was increased from 296 +/- 22 to 460 +/- 47 nM (p < 0.001). ANP (5 x 10(-9) M) blocked the Ca2+ mobilization by angiotensin II (71 +/- 7 versus 69 +/- 7 nM, NS) and also completely inhibited the effect of angiotensin II in the presence of cyclosporine (77 +/- 5 versus 78 +/- 5 nM, NS). Basal efflux as well as angiotensin II-stimulated 45Ca2+ efflux were not altered by preincubation with cyclosporine, indicating that the effect of cyclosporine on [Ca2+]i was not due to an inhibition of 45Ca2+ efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-thymectomy organ-specific autoimmunity: enhancement by cyclosporine A and inhibition by IL-2

It has previously been shown that the administration of cyclosporine A to newborn mice results in the development of autoimmunity later in life. It has been proposed that the neonatal administration of cyclosporine A results in altered thymic selection or inhibition of the development of suppressor cells. In the present study, treatment of day 3 thymectomized C3H/HeN mice with cyclosporine A (20 mg/kg/day) for 9 d post surgery increased the prevalence of antigastric autoantibodies. In contrast, the administration of IL-2 (300-600 Units/g/day) for 7 days after thymectomy inhibited the development of antigastric antibodies. We hypothesize that CsA may act by causing transient lymphokine abnormalities in the extrathymic environment during the first few weeks of life which lead to the development of antigastric antibodies. In contrast to the inhibition of development of antigastric antibodies, the administration of a similar course of IL-2 produced only a transient suppression of diabetes in NOD mice. These results and other data suggest that diabetes in NOD mice is probably due to a different immunologic defect.

Protection by cyclosporin A of cultured hepatocytes from the toxic consequences of the loss of mitochondrial energization produced by 1-methyl-4-phenylpyridinium

Cyclosporin A prevented the killing of cultured rat hepatocytes by 1-methyl-4-phenylpyridinium (MPP+). However, in the presence of both cyclosporin and atractyloside, there was no protection. Cyclosporin had no effect on the depletion of ATP or the loss of mitochondrial energization by MPP+. Cyclosporin, however, did prevent the increase in the molecular order of hepatocyte membranes produced by MPP+. These data suggest that mitochondrial de-energization produced by MPP+ is accompanied by a "permeability transition" analogous to that which occurs in vitro in the presence of calcium. By preventing this transition, cyclosporin protects the cells. By antagonizing this action of cyclosporin, atractyloside restores the cell killing. The mitochondrial transition is causally linked to cell killing by a mechanism that increases the molecular order of the hepatocyte plasma membrane.

Urodilatin: a new peptide with beneficial effects in the postoperative therapy of cardiac transplant recipients

Renal failure after heart transplantation (HTx) still remains a serious problem, especially when cyclosporin A is used for immunosuppression in the early postoperative therapy. To preserve good renal function without reducing immunosuppressive cyclosporin A treatment, we administered urodilatin (CDD/ANP-95-126) in a long-term, low-dose infusion in addition to the usual medication after heart transplantation. From November 1990 to June 1991, 51 patients (46 male and 5 female; mean age 48 years) were treated with a 6-20 ng/kg bw.min infusion for 96 h after HTx. The renal function and hemodynamic parameters of these urodilatin-treated patients were compared in this sequential study with 40 patients (33 male and 7 female; mean age 49 years) who had undergone HTx previously from May to November, 1990, as controls. In this phase IIa study, both groups did not differ significantly with respect to age, sex, indication for HTx, and preoperative renal function. In comparison with controls patients treated with urodilatin had a significantly better renal function: a reduction in the peak plasma creatinine (PC values day 4: 1.5 +/- 0.11 vs. 2.19 +/- 0.19 mg/dl; P = 0.002), a lower peak serum urea (SU values day 4: 109 +/- 8 vs. 154.7 +/- 8.94 mg/dl; P = 0.0036), and a lower incidence of hemodialysis (6% vs. 10%) were observed. Adequate diuresis was maintained in spite of the reduction of furosemide by more than 60% (P = 0.005) on each day of urodilatin infusion in comparison with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Fenoldopam Reverses Cyclosporine-Induced Renal Vasoconstriction in Kidney Transplant Recipients

Cyclosporine causes renal vasoconstriction and reduced renal blood flow that may contribute to chronic nephrotoxicity. This effect has not been consistently reversed by available pharmacologic agents. The efficacy of orally administered fenoldopam, a dopamine-1 (DA-1) agonist with renal vasodilator properties, was evaluated in six patients whose condition was stable 3 to 6 months following renal transplantation. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by inulin and p-aminohippurate (PAH) clearances, respectively, at baseline, after the acute oral administration of 100 mg of fenoldopam, and following 3 weeks of chronic oral fenoldopam therapy (100 mg thrice daily). Mean ERPF increased from 3.15 +/- 0.17 mL/s/1.73 m2 (189 +/- 10 mL/min/1.73 m2) at baseline to 3.48 +/- 0.17 mL/s/1.73 m2 (209 +/- 10 mL/min/1.73 m2) 4 hours after acute administration of fenoldopam (P = 0.04). Urine flow rate and fractional excretion of sodium also increased after acute administration, but not significantly. Mean systolic (SBP) and diastolic blood pressure (DBP) decreased maximally by 18 and 6 mm Hg, respectively, and mean pulse rate increased maximally by 8 bpm between 75 and 90 minutes after both acute and chronic administration. GFR was unchanged following both acute and chronic administration. The increase in ERPF was not maintained to the end of the dosing interval during chronic administration, probably due to the short half-life of fenoldopam. However, the renal vasodilatory response was still observed 3 to 4 hours after readministration of the drug following 3 weeks of oral dosing. Thus, fenoldopam significantly reverses the renal vasoconstriction caused by cyclosporine in renal transplant recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of calcium antagonists in human renal transplantation

To test the hypothesis that calcium antagonists decrease the incidence and severity of delayed graft function, we conducted three separate, prospective, randomized trials. In these trials, we investigated the effects of diltiazem and those of the prostacyclin analogue iloprost. In the first study, 22 control patients and 20 diltiazem patients received grafts perfused with either vehicle or diltiazem 20 mg/liter in the Euro-Collins solution. Subsequently, the diltiazem subjects were given the drug as a bolus of 0.28 mg/kg, followed by a continuous infusion of 0.002 mg/min/kg for the following two days. Thereafter, diltiazem 60 mg was given to the treated subjects orally for up to four years. In the second study, 11 control subjects and 10 diltiazem subjects received the same postoperative regimen, but all grafts were harvested without addition of diltiazem to the perfusion solution. In the third protocol, four groups were studied as follows: 19 control subjects who received no specific treatment, 16 subjects who received diltiazem, 16 subjects who were given iloprost, and 14 subjects who received both iloprost and diltiazem. The donor kidney of treated patients was perfused with either diltiazem, iloprost, or both drugs. Primary graft function occurred more commonly in the groups receiving diltiazem. Further, in the first study the number of hemodialyses per patient was reduced in those patients with delayed graft function. Fewer rejection episodes occurred in patients receiving diltiazem. Plasma levels of soluble interleukin-2 receptors decreased significantly during diltiazem treatment. Moreover, renal biopsies showed less severe signs of Cyclosporin A (CsA) nephrotoxicity in diltiazem-treated patients compared to controls, even though these patients also exhibited higher CsA trough levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium antagonists and the kidney: implications for renal protection

During the past decade, attention has focused on the effects of calcium antagonists on renal function. When administered in vitro to the isolated perfused kidney, calcium antagonists exhibit consistent actions permitting characterization of their renal effects. Calcium antagonists do not affect the vasodilated isolated perfused kidney, but they do dramatically alter the response of this preparation to vasoconstrictor agents. Our recent studies using the isolated perfused hydronephrotic rat kidney model, which permits direct visualization of afferent and efferent arterioles, have demonstrated that the preferential augmentation of glomerular filtration rate observed in the isolated perfused kidney is attributable to preferential vasodilatation of preglomerular vessels. Although the clinical implications of such observations have not been fully delineated, the results of recent studies indicate that calcium antagonists exert salutary effects on renal function in patients with impaired renal hemodynamics. Such disorders include radiocontrast-induced nephrotoxicity and transplant-associated acute renal insufficiency. It is apparent, however, that the effects of calcium antagonists on renal blood flow commend their use in the management of essential hypertension.

Thromboxane receptor blockade attenuates chronic cyclosporine nephrotoxicity and improves survival in rats with renal isograft

The question of whether pharmacological inhibition of the thromboxane A2 activity prevents cyclosporine-induced chronic renal dysfunction in a Lewis rat model of renal isograft was addressed. Transplanted animals were given a daily oral dose of cyclosporine (20 mg/kg; N = 15), cyclosporine (20 mg/kg) and the thromboxane A2 receptor antagonist GR32191 (3 mg/kg twice daily, by gavage; N = 15), or the vehicle alone (N = 12). Treatments were started the day of kidney transplant, and animals were monitored for 1 year. Cyclosporine-treated animals developed renal insufficiency, as documented by serum creatinine levels of 0.49 +/- 0.09, 0.95 +/- 0.12, and 1.38 +/- 0.15 mg/dL before and after 6 and 12 months of observation, respectively. Cyclosporine and GR32191 used in combination partially but significantly prevented the deterioration of renal function (serum creatinine, basal, 0.52 +/- 0.06; month 6, 0.68 +/- 0.04; month 12, 0.93 +/- 0.10 mg/dL). At the end of the study, GFR, as insulin clearance, was significantly lower in rats given cyclosporine (0.28 +/- 0.09 mL/min/100 g) than in rats given cyclosporine plus GR32191 (0.45 +/- 0.05 mL/min/100 g) or than in vehicle-treated animals (0.56 +/- 0.07 mL/min/100 g). Similar results were obtained for the effective RPF, measured as p-aminohippurate clearance. At the same time points, comparable to whole-blood cyclosporine levels were found in rats receiving cyclosporine alone and in those given cyclosporine plus GR32191. More than 50% of the animals on cyclosporine alone died from uremia before the end of the observation period. By contrast, rats receiving cyclosporine in combination with GR32191 had a prolonged survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of thromboxane synthase inhibition with CGS 13080 in human cyclosporine nephrotoxicity

Cyclosporine is a potent immunosuppressive agent, however, its use is limited by nephrotoxicity. Increased production of the potent vasoconstrictor thromboxane A2 contributes to cyclosporine nephrotoxicity in animal models, but the role of thromboxane in human cyclosporine nephrotoxicity has not been established. We therefore studied cyclosporine-treated renal allograft recipients who had evidence of toxicity manifested by decreased renal function. We measured GFR and PAH clearance (CPAH) before, during, and one week after a 48-hour intravenous infusion of the thromboxane synthase inhibitor CGS 13080. At baseline, the urinary excretion of TXB2 and 2,3-dinor-TXB2 was elevated in the study patients compared to healthy subjects. CGS 13080 infusion caused selective and nearly complete inhibition of thromboxane metabolite excretion in all patients. Mean CPAH improved 33% from 223 +/- 45 to 298 +/- 59 ml/min/m2 (P = 0.055) during infusion, while mean GFR improved 9% from 50.1 +/- 3.9 at baseline to 54.6 +/- 4.5 ml/min/1.73 m2 (P = 0.111). The effect on GFR occurred primarily in those patients taking calcium channel blockers. The mean increase in GFR in these 5 patients was 10.0 +/- 2.8 versus -1.0 +/- 2.8 ml/min/m2 in the remainder. We conclude that thromboxane synthase inhibitors may be useful in attenuating the nephrotoxic effects of cyclosporine following renal transplantation.

Acute cytotoxic effect of cyclosporin A on pancreatic acinar cells in rats. Protective effect of the synthetic protease inhibitor E3123

This study was designed to evaluate the acute toxic effects of cyclosporin A on the exocrine pancreas and the protective effects of a new potent protease inhibitor, 4-(2-succinimidoethylthio) phenyl 4-guanidinobenzoate methanesulfonate, E3123. Cyclosporin A in a dose of 5 mg/kg.h caused a significant increase in serum amylase levels, pancreatic amylase content, and interstitial edema, suggesting that it induces exocrine pancreatic injury. Cyclosporin A also caused redistribution of cathepsin B from the lysosomal fraction to the zymogen fraction, indicating colocalization of lysosomal enzymes with pancreatic digestive enzymes. E3123 in a dose of 2 mg/kg.h prevented almost completely these changes caused by cyclosporin A. These results indicate that exocrine pancreatic injury is induced by cyclosporin A and that lysosomal enzymes play important roles in the pathogenesis of this injury and also suggest that E3123 might protect the exocrine pancreas of patients receiving cyclosporin A after organ transplantation.

Iloprost preserves endothelial function against cyclosporin A and sensitises microvessels towards endothelium-dependent and -independent vasodilatation

The effects of iloprost have been investigated on the endothelial damage produced by cyclosporin-A (Cy-A) and on the microvascular reactivity to sodium nitroprusside (SNP), acetylcholine (ACh) and isoprenaline (ISO) following iloprost treatment i.e. in the absence of effective plasma levels, using the hamster cheek pouch. It has been shown that iloprost protects the microvascular arteriolar endothelium from functional damage by Cy-A and that iloprost infusion for 12-14 hr sensitizes the arterioles to ACh, SNP and ISO, an effect which is evident 5 hr but not 24 hr following treatment and in the case of ACh is abolished by indomethacin.

The nonspecific inner membrane pore of liver mitochondria: modulation of cyclosporin sensitivity by ADP at carboxyatractyloside-sensitive and insensitive sites

Cyclosporin A prevents the opening of a nonspecific pore in the inner membrane of liver mitochondria when added prior to Ca2+. In the presence of 10 microM Ca2+ cyclosporin is unable to close the pore and restore the original permeability unless ADP is also added. ADP acts at a high-affinity site (Km 5 microM), corresponding to the adenine nucleotide transporter. This effect of ADP is prevented and reversed by carboxyatractyloside. In the presence of carboxyatractyloside, cyclosporin added with higher concentrations of ADP (Km 70 microM) also can close the pore. This suggests that a lower-affinity ADP-binding component as well as cyclophilin and the adenine nucleotide transporter can modulate the sensitivity of the pore to cyclosporin.

Cytoprotective and dose-dependent inhibitory effects of prostaglandin E1 on rat pancreas treated with ciclosporin A

The prostaglandin E1 analogue rioprostil protects the pancreas from the noxious effect of ciclosporin A (CsA). To determine whether this cytoprotective action of rioprostil is dependent on or independent of inhibitory effects on pancreatic exocrine and endocrine secretion we studied the effect of different doses of rioprostil on pancreatic exocrine and endocrine secretions in the presence or absence of CsA. Rats received either CsA at a dose of 10 mg/kg body weight by tube feeding once in the morning, rioprostil at linearly increasing doses from 1.8 to 120 micrograms/kg body weight subcutaneously twice daily, a combination of both substances or NaCl. After 8 treatment days, the animals were operated on, and the pancreas isolated and arterially perfused. Insulin secretion was determined after stimulation with glucose, and amylase secretion after stimulation with CCK-8. Insulin and amylase secretion were significantly impaired by CsA. Rioprostil at doses of 1.8, 3.6 and 7.5 micrograms/kg body weight had no significant effect on insulin secretion in the absence of CsA but significantly improved insulin secretion in the presence of CsA. Higher doses of rioprostil significantly inhibited insulin secretion both in the presence or absence of CsA. Amylase secretion was not influenced by rioprostil at doses up to 15 micrograms/kg body weight but improved significantly amylase secretion in the presence of CsA. CsA blood and pancreatic tissue levels were not influenced by rioprostil at doses up to 120 micrograms/kb body weight. We conclude that the cytoprotective effect of the prostaglandin E1 analogue rioprostil against the noxious effect of CsA is dose dependent and is not related to its inhibitory action on endocrine and exocrine pancreatic secretion.

Critical ketoconazole dosage range for ciclosporin clearance inhibition in the dog

Ciclosporin (CsA) is metabolized exclusively by the hepatic cytochrome P-450 mixed function oxidase system. Ketoconazole (KC) is a potent inhibitor of this enzyme system. CsA was administered alone and in combination with five different doses of KC (1.25, 2.5, 5.0, 10.0, 20.0 mg/kg/day) under steady-state conditions to 7 adult mongrel dogs. KC produced a highly significant (p = 0.0001), dose-dependent decrease in CsA total body clearance [Cl(T)]. The critical KC dosage range for this to occur was found to be between 2.5 and 10 mg/kg/day. The reduction of CsA CL(T) was insignificant (p greater than 0.05) at a KC dose of less than 2.5 mg/kg/day, and the 92% reduction observed using 20 mg/kg/day KC was not significantly greater than the 85% reduction occurring after only 10 mg/kg/day KC (p greater than 0.05). The dose of concomitant KC was also highly correlated with a reduction in the whole blood CsA parent/parent + metabolite ratio as determined using high-performance liquid chromatography and polyclonal fluorescent polarization immunoassay for CsA measurement (r = 0.998, p less than 0.0001). The absolute oral bioavailability of CsA as well as the time required to reach its maximum concentration in the blood following oral administration did not change significantly over the course of the study (p greater than 0.05). We conclude from these new observations that the KC-induced decrease in CsA Cl(T) in the dog in vivo is dose-dependent and maximized within the KC dosage range of 2.5-10 mg/kg/day. The effect does not appear to involve a decrease in the rate of CsA oral absorption, and may be compensated for by an appropriate reduction in the concomitantly administered dose of CsA.

Effects of defibrotide on renal function and urinary prostanoid excretion in ciclosporin-treated rats

Defibrotide (DF) has been proposed as a new antithrombotic agent in renal transplantation. Because it was also found to increase prostacyclin synthesis, a reduction in ciclosporin (CS) nephrotoxicity could be supposed. To ascertain this hypothesis, renal function and urinary prostanoids were evaluated in four groups of rats after 10 days of oral treatment (doses in mg/kg/day): CS 50 (group A), CS 50 + DF 400 (group B), DF 400 (group C) and controls (group D). Compared to controls, creatinine clearance (CCR) was significantly lower in groups A and B (In CCr: A = 6.62 +/- 0.28, B = 6.83 +/- 0.24 vs. 8.17 +/- 0.13 microliters/min, p less than 0.01), whereas it did not change in group C (8.03 +/- 0.24 microliters/min). The urinary excretion of prostaglandin E2 (PGE2) was significantly (p less than 0.05) higher in group A (In PGE2: 3.98 +/- 0.98 nmol/mol Cr) and more evidently in groups B and C (6.89 +/- 0.38 and 6.01 +/- 0.32 nmol/mol Cr, respectively) compared to controls (1.43 +/- 0.45 nmol/mol Cr). The urinary excretion of 6-keto-PGF1 alpha and of thromboxane B2 (TxB2) were higher only in groups A and B (ln 6-keto-PGF1 alpha and ln TxB2: A = 6.45 +/- 0.22 and 4.97 +/- 0.20, B = 7.06 +/- 0.31 and 5.43 +/- 0.41 vs. group D = 5.53 +/- 0.22 and 3.79 +/- 0.42 nmol/mol Cr; p less than 0.05). The 6-keto-PGF1 alpha/Tx molar ratio was not significantly affected, although a trend for a reduction in the ratio was found in the treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)