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Background: One adverse side-effect of the immunosuppressive drug cyclosporin A (CsA) is a decrease in glomerular filtration rate (GFR). This effect might be the result of increased glomerular contractions. The present study compared the contractile effects of CsA, cyclosporin G (CsG) and the novel cyclosporin derivative IMM 125 in isolated rat glomeruli and primary cultures of rat mesangial cells., Methods: Interactive image analysis was used to measure glomerular and mesangial cell contraction., Results: CsA, CsG, and IMM 125 at concentrations of 0, 10(-9), 10(-8), 10(-7), 10(-6) and 10(-5) M caused a time-dependent and a concentration-dependent contraction of isolated glomeruli and mesangial cells 30 min after incubation. In glomeruli, CsA was more potent than CsG and IMM 125. In mesangial cells, IMM 125 also exhibited the lowest contractile activity, while CsA and CsG were almost equally myoreactive. The absolute degree of the glomerular contraction was proportional to the number of contracting mesangial cells in one glomeruli. The number of responding cells after incubation with IMM 125 and CsG were lower compared to CsA, which might explain the different response with CsG and CsA in both models., Conclusions: Since the concentrations used in these experiments were close to that reached in rat serum after treatment with CsA, the present results suggest that the contractile effects of IMM 125 and CsG in isolated glomeruli were clearly smaller compared to CsA, which might reflect the cyclosporins induced GFR changes in vivo.

Conventional methods that are used to overcome multidrug resistance (MDR) often involve the coadministration of chemosensitizers and anticancer drugs. The cyclosporin analogue SDZ PSC 833 [(3'-keto-Bmt1)-(Val2)-cyclosporin] (PSC 833) has been shown to possess powerful chemosensitization properties in vitro, in addition to being intrinsically nontoxic. However, coadministration of PSC 833 with anticancer drugs, such as daunorubicin, doxorubicin (DOX), and Taxol, have resulted in the exacerbation of anticancer drug toxicity, which is due to altered anticancer drug pharmacokinetics. Here, we hypothesized that optimization of the anticancer drug delivery, using liposomal carriers, may, by avoiding these adverse interactions, offer a significant advantage over nonencapsulated drugs. Toxicity studies were conducted in normal BDF1 mice, with i.v. DOX (free or liposome encapsulated) administration and p.o. PSC 833 in single and multiple dosage regimens over a 15-day study period. p.o. administration of PSC 833, at a dose of 100 mg/kg, reduced the maximum tolerated dose (MTD) of i.v administered free drug by 2.5-3-fold, in single- and multiple-dose regimens. In contrast, PSC 833 administration resulted in only a 20% reduction of the MTD for DOX encapsulated in 100-nm 1,2 distearoyl-sn-glycero-3-phosphocholine/cholesterol liposomes (55:45 molar lipid ratio) in a single-dose regimen and had no effect on the liposomal DOX MTD for the day 1, 5, and 9 treatment schedule. Modest modulation of P-glycoprotein-mediated MDR was observed in the murine P388/ADR solid tumor model when PSC 833 was administered with free DOX at the MTD. In contrast, liposomal DOX combined with PSC 833 resulted in tumor growth inhibition that was comparable to that observed for drug-sensitive P388/WT tumors. This efficacy of P388/ADR tumors treatment was dependent on PSC 833 because treatment with liposomal DOX alone provided significantly less antitumor activity. Pharmacokinetic and tissue distribution data demonstrated that DOX encapsulated in 1,2 distearoyl-sn-glycero-3-phosphocholine/cholesterol liposomes exhibited comparable plasma elimination and tissue distribution properties in the presence and absence of PSC 833, whereas free DOX displayed reduced plasma elimination rates and altered tissue distribution in the presence of PSC 833. These results provide evidence that PSC 833 can induce P-glycoprotein modulation and chemosensitize MDR tumors in the absence of altered DOX pharmacokinetics when liposomal carriers are used. This suggests that the improved tumor selectivity of anticancer drugs that are administered in liposomal formulations may avoid the complications that are associated with free drug-MDR-reversing agent combinations and enhance the therapy of multidrug-resistant tumors.

In the present study it was investigated whether and by which mechanisms the co-administration of interleukin-3 (IL-3) and the P-glycoprotein blocker PSC 833 can augment mitoxantrone (MX) and daunorubicin (DAU) cytotoxicity in two human growth factor dependent P-glycoprotein (P-gp) positive myeloid leukemic cell lines, Mo-7 and GF-D8. Cytotoxicity was determined in MTT assay. Increased cytotoxicity occurred in Mo-7 cells preincubated with 24h IL-3 followed by 1 h MX (cell survival: 85% +/- 6 vs 68% +/- 2, at 0.05 microM MX, P < 0.005) or DAU (79% +/- 8 vs 62% +/- 9 at 0.8 microg/ml DAU, P < 0.05). Similar results were obtained for the GF-D8 cell line. In this cell line, at 0.5 microM MX the cell survival decreased from 84% +/- 13 to 61% +/- 19 (P < 0.05) and at 5.0 microg/ml DAU from 102% +/- 8 to 69% +/- 5, (P < 0.002). The IL-3 administration did not affect the P-gp and bcl-2 protein expression, cellular MX concentration or MX efflux but coincided with an increased percentage of cells in S-phase and topoisomerase II (topo II)-alpha mRNA and topo II activity especially in the Mo-7 cell line. PSC 833 enhanced DAU cytotoxicity in both cell lines. The administration of IL-3 plus PSC 833 in the Mo-7 cell line resulted in an additive effect on DAU cytotoxicity. At 0.8 microg/ml DAU and 2 microg/ml PSC 833, the percentage surviving cells decreased from 62% +/- 9 in the absence of IL-3 to 37% +/- 3 in the presence of IL-3 (P < 0.01). The additive effect of combined treatment was most pronounced in GF-D8 cells which also had the highest P-gp expression. In contrast, PSC 833 did not modulate the MX effects, irrespective of the presence of IL-3. In summary, the results demonstrate that the combined administration of IL-3 and PSC 833 can enhance the cytotoxic effects of DAU but not MX in these P-gp positive cell lines whereas the effects of MX could be modulated by factors which influence topo II activity.

Cyclosporin G (CsG) is an analogue of cyclosporin A (CsA) with strong immunosuppressive activity. We compared these two drugs in a rat model in which salt depletion promotes irreversible renal interstitial fibrosis with renal dysfunction in animals given CsA for three weeks. When both drugs were given in the same dosage on a weight basis (15 mg/kg/day, subcutaneously), CsA blood levels were higher than CsG (3305 vs. 1824 ng/ml, P < 0.001). This could be explained by a higher CsG clearance (6.4 vs. 4.3 ml/min/kg in CsA, P < 0.0001) resulting in smaller CsG area under the curve. There was also lower renal and hepatic CsG tissue concentrations. CsA induced a dramatic decrease in GFR, 0.14 in CsA versus 0.67 ml/min/100 g in control, P < 0.001, and increased urinary excretion of N-acetyl beta-D-glucosaminidase (NAG), 21 in CsA versus 13 IU/gCr in control rats, P < 0.001. CsG-treated and control rats had similar GFR and urinary NAG. When CsA dosage was decreased to 7.5 mg/kg blood levels were similar to those found with CsG 15 mg/kg. CsA at this dose caused a reduced GFR (0.29 ml/min/100 g) and an increased urinary NAG (20 IU/gCr) (P < 0.01 vs. control for both). Both dosages of CsA induced considerable cortical and medullary injury (interstitial fibrosis and tubular atrophy), more severe than the histological damage found in CsG-treated rats. Neither drug promoted significant changes in liver function or histology.(ABSTRACT TRUNCATED AT 250 WORDS)

The ability to prepare purified islet Beta-cell aggregates was used to examine the survival of this cell type after allotransplantation in diabetic BB rats. The aggregates were intraportally implanted in numbers that were previously found to correct a streptozotocin-induced diabetic state in syngeneic or allogeneic Brown Norway recipients. When the grafts were prepared from RT1u/l donors, which shared the MHC-class I antigen with the BB recipients (RT1u/u), their implant sites became diffusely infiltrated by inflammatory cells and their metabolic function was completely lost within 5 weeks. MHC-class I incompatible islet Beta-cell allografts (RT1n/n) exhibited a longer survival, in particular when combined with other islet endocrine cells and/or when covered by a 5-week cyclosporin treatment. In the latter combination, 10 of 12 BB rat recipients remained normoglycaemic over the 10-week observation period, their liver implants presenting a comparable insulin reserve and similarly discrete mononuclear cell infiltration as streptozotocin-diabetic Brown Norway rats receiving this treatment. However, administration of cyclosporin to diabetic BB rats was associated with a morbidity that was not observed in drug-treated streptozotocin-diabetic Brown Norway animals or in untreated diabetic BB rats. It is concluded that MHC-incompatible islet Beta cells can induce a long-term normalization in diabetic BB rats provided that they are implanted under conditions which allow allograft acceptance. The standardized preparation of purified islet Beta-cell grafts can help assessing the conditions for successful transplantations in diabetes with an autoimmune origin.

Chronic cyclosporine nephrotoxicity is a poorly understood drug side-effect characterized by renal cortical interstitial scarring. To evaluate procollagen mRNA levels as an early factor in the development of this form of renal fibrosis, we measured renal procollagen alpha 1 (I), alpha 1 (III), alpha 1 (IV) and beta-actin mRNA levels in rats treated with cyclosporine (CsA) or the olive oil vehicle (OO) for one or four weeks. Renal morphology was similar without atrophy or fibrosis in one week CsA and OO and four week OO rats. Four week CsA rats had focal cortical interstitial fibrosis and tubular atrophy. Cortical procollagen alpha 1 (I) mRNA levels were increased in CsA versus OO rats at one week (P less than 0.02) and four weeks (P less than 0.02). One week medullary procollagen alpha 1 (I) and all other one week medullary, and one and four week cortical procollagen and beta-actin mRNA levels were no different in CsA versus OO rats. The early increase in renal cortical procollagen alpha 1 (I) mRNA levels precedes renal morphologic abnormalities, and may represent an important step in the pathogenesis of cyclosporine-induced renal cortical fibrosis.

The effect of cyclosporine on the immunopathogenesis of viral myocarditis was studied using a murine viral myocarditis model. Mice in the treated group had a higher mortality rate compared with those of the infected control group before day 15 (47/67 vs. 14/31, p less than 0.05). On day 7, treated mice showed higher titers of anti-heart autoantibody than the control group (12 +/- 7 vs 4 +/- 2, p less than 0.05), but no significant difference was seen on day 14 (28 +/- 15 vs. 39 +/- 34). Histologic lesions, lymphocyte subsets in the peripheral blood and heart in situ, the neutralizing antibody, and virus concentrations in the heart showed no significant differences between these groups. This study suggests that with the use of cyclosporine the production of anti-heart autoantibody was enhanced in the early stages of viral myocarditis in mice, and was associated with higher mortality rate.

In this report we have approached two questions relating to the mechanism of action of cyclosporin A (CsA). First, we address whether the major cytosolic protein for CsA, cyclophilin, is directly involved in mediating the immunosuppressive activity of this drug, and, in particular, whether inhibition of this protein's peptidyl-prolyl cis-trans isomerase (PPIase) activity results in inhibition of murine T cell activation. Second, we ask whether the nephrotoxicity observed with CsA is related to inhibition of PPIase-dependent pathways in cells other than lymphocytes. Using a series of 61 cyclosporin analogues, we generally found a good correlation between cyclophilin binding and immunosuppressive activity for the majority of analogues analyzed. However, a number of compounds of distinct structural classes were found that could interact with cyclophilin but were much less immunosuppressive than expected. The inability of these analogues to inhibit lymphocyte activation could not be explained by their failure to enter the cell and bind to cyclophilin under the conditions used in the cellular assays. Surprisingly, a nonimmunosuppressive analogue, MeAla-6, which bound well to cyclophilin and was active as a PPIase inhibitor, did not induce renal pathology in vivo. Furthermore, another analogue, MeBm2t, which was immunosuppressive in vitro, possessed little or no activity as a PPIase inhibitor. These findings pose serious questions concerning a direct role of cyclosporin in mediating CsA's immunosuppressive and nephrotoxic activities. In addition, they raise doubts about whether PPIase has a direct function in lymphocyte signal transduction.

A patient with Felty's syndrome was treated with cyclosporine, initially 10 mg/kg/day and then 4 mg/kg/day. The neutrophil count increased by 6 weeks and was normal at 3 months. Over the subsequent 27 months the neutrophil count was closely related to the cyclosporine dosage and there was no evidence of cyclosporine toxicity. This case indicates that cyclosporine may have a role in the treatment of Felty's syndrome.

The Ki values of cyclosporins A, G and H for the peptidyl-prolyl cis-trans isomerase (PPIase) of liver and heart mitochondria are about 2, 20 and 500 nM respectively. This parallels their profile as inhibitors of non-specific pore opening of mitochondria induced by supraphysiological Ca2+ concentrations. The novel immunosuppressant FK-506 gave little inhibition of either process at 5 microM. These data support our previous hypothesis [Halestrap & Davidson (1990) Biochem. J. 268, 153-160] that pore opening involves an interaction between matrix PPIase and the adenine nucleotide translocase. It is suggested that this model may help to clarify the mechanism of action of cyclosporin as an immunosuppressant and its toxic effects on the liver and kidney following prolonged therapy.

Since recent studies indicate that cyclosporine (CsA) disrupts endothelial integrity and that injured endothelial cells release excess endothelin, we examined endothelin's role in acute cyclosporine nephrotoxicity. Following CsA (20 mg/kg i.v.), rabbit anti-porcine endothelin (aE) serum was continuously infused into a first order branch of the main renal artery in Munich-Wistar rats whereupon the hemodynamics of glomeruli not infused with aE as well as those infused with aE within the same kidney were simultaneously assessed by micropuncture techniques. In CsA treated kidneys, in glomeruli not infused with aE, single nephron GFR (SNGFR) and glomerular plasma flow rate (QA) fell profoundly (on average by 42 and 48%, respectively) below the baseline values in association with lower glomerular capillary pressure and elevated afferent arteriolar resistance. By contrast, in glomeruli infused with aE within the same CsA treated kidneys, this vasoconstrictive pattern was markedly attenuated: SNGFR was, on average, only 19% lower than baseline and values for QA as well as other parameters determining glomerular filtration were at or near the levels observed before administration of CsA. In another group of rats (N = 6) an identical dose of CsA was given to measure the circulating level of endothelin. In these CsA treated rats, endothelin level (measured by radioimmunoassay) was elevated at 41.7 +/- 14.7 pg/ml, contrasting the value of less than 2 pg/ml uniformly observed in identically instrumented normal rats not given CsA (N = 5). Thus, cyclosporine is a potential inducer for endothelin release and endothelin appears to have a pivotal role in pathophysiology of cyclosporine-induced acute renal vasoconstriction and glomerular dysfunction.

Renal dysfunction, manifested as a dose-dependent reduction in glomerular filtration rate (GFR), is a common complication of cyclosporine A (CyA) administration to laboratory animals and humans. We have recently shown that chronic CyA treatment in normal rats is associated with a selective increase in renal thromboxane A2 (TXA2) synthesis, which may play a role in GFR reduction. The present experiments were designed to investigate whether pharmacological inhibition of TXA2 activity could reduce CyA nephrotoxicity in a rat model of renal transplantation. To discriminate the possible biochemical changes due to rejection episodes from those due to CyA nephrotoxicity, we selected a model of renal isograft free of graft rejection processes. We demonstrated that oral CyA administration for 30 days to rats undergoing renal isograft is associated with the development of renal insufficiency, as indicated by a progressive increase in serum creatinine concentration and reduction in creatinine clearance. In the same animals, a parallel increase in the urinary excretion of TXB2 was found. Combination of the specific thromboxane receptor antagonist GR32191 with CyA treatment partially prevented the deterioration in renal function observed in animals given CyA alone, without modifying the urinary TXB2 excretion. In contrast, renal-isografted rats given GR32191 alone or vehicle alone for 30 days did not show any changes in serum creatinine, creatinine clearance, and urinary TXB2 excretion throughout the experimental period. Mild hypercellularity of the glomerular tuft was observed in isografted kidneys chronically exposed to either CyA or CyA plus GR32191.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was performed to evaluate whether cyclosporine penetrates kidney mitochondria and impairs mitochondrial functions, causing nephrotoxicity. Exposure of rat kidney cortical mitochondria in vitro to cyclosporine had little effect on the oxidation of glutamate plus malate. Oxidation of succinate was markedly inhibited by a toxic level of cyclosporine (25 to 50 nmol/mg protein) under resting (State 4) and ADP-stimulated (State 3) conditions. Under uncoupling conditions, induced by the proton ionophore, CCCP or by the calcium ionophore, A23187 plus calcium, mitochondrial respiration was unchanged by cyclosporine. In mitochondria isolated from rats treated with an immunosuppressive dose of cyclosporine (25 mg/kg/day, p.o.), respiration was not significantly impaired. The respiration stimulated by ADP was only diminished in mitochondria from rats treated with 75 mg/kg. The rate of calcium uptake was unchanged by cyclosporine under in vitro and in vivo conditions. Kidney mitochondria of untreated rats maintained in a medium containing respiratory substrates and phosphate released spontaneously accumulated calcium that was accompanied by large amplitude swelling and enhanced respiration. Cyclosporine in vitro inhibited the process of spontaneous calcium discharge at the concentration range of 0.1 to 0.5 nmol/mg protein. Swelling and respiration induced by accumulated calcium was significantly diminished in kidney mitochondria isolated from cyclosporine-treated rats given doses of 25 or 75 mg/kg. The data obtained indicate that cyclosporine interacts with the membrane of kidney mitochondria in virtually the same way under in vitro and in vivo conditions. Cyclosporine at an immunosuppressive level impairs calcium-induced membrane permeability and at a toxic level, the rate of ADP phosphorylation.

The effects of the immunosuppressant drug cyclosporine were studied in the murine model of Coxsackie B3 myocarditis. Ten BALB/c mice, given daily cyclosporine (15 mg/kg) intraperitoneally but not infected, were normal in all respects after 2 weeks. All 32 BALB/c mice infected, but given no cyclosporine, survived and had moderate myocardial mononuclear infiltrates and minimal necrosis at 7 and 14 days. In contrast, 24 mice concurrently infected and given cyclosporine had a high mortality rate (75%) and a significantly attenuated mononuclear infiltrate in the presence of enhanced necrosis when compared with control infected mice. Sixteen mice started on the drug 1 week after infection had a lower mortality rate (55%), but very similar histologic abnormalities. In contrast to negligible or no virus in the hearts of infected mice that were not given cyclosporine, drug treated, infected groups had easily detectable virus in their hearts 14 days after infection. An identical study in Swiss ICR mice yielded similar results. Cyclosporine, when given early during acute murine Coxsackie B3 myocarditis, causes a significant increase in myocardial necrosis and mortality, possibly secondary to enhanced viral survival.

The pharmacological profiles of two new derivatives of the immunosuppressive drug, cyclosporine, is presented here. (Nva2)-CS has very similar properties to CS, but lacks the nephrotoxic side-effects. This derivative appears to be a potential successor to cyclosporine. (Val2)DH-CS seems to have a different spectrum of activities. It does not suppress humoral immunity and allograft rejection, but suppresses some types of cell-mediated immune responses. This derivative may prove useful in autoimmune situations where T cells are involved in the disease process.

The effects of oral cyclosporin A (25 mg/kg/day) on renal function and structure in groups of normal, laparotomized and unilaterally nephrectomized DA rats was assessed over a 4-week period. In each group, the drug caused impairment of function, although there was evidence of improvement during the course of the study. Cyclosporin A toxicity was most marked in the nephrectomized animals, where histological examination at 4 weeks revealed extensive damage to proximal straight tubular cells. Only minimal structural damage was observed in the two other groups. Cyclosporin A concentrations in whole blood and kidney were estimated by radioimmunoassay at 4 weeks. Similar drug levels were found in normal, laparotomized and nephrectomized animals, except for an unexplained fall in blood levels in the laparotomy group. The significance of these observations is discussed in the context of current knowledge concerning the physiological effects, toxicology and pharmacology of cyclosporin A.

Reports of vascular changes in renal biopsies of transplant patients treated with cyclosporine prompted review of our own renal biopsies and examination of human endothelial cell cultures exposed to cyclosporine in vitro. Endothelial cells were isolated from human umbilical cords by collagenase digestion and cultured in Medium 199 with Earle's salts plus 20% pooled human serum in the absence of antibiotics. Cultures exposed to cyclosporine (0, 0.4, 1.0, 5.0, 10.0 micrograms/ml) for 0, 3, 7, 10, and 14 days were subsequently fixed in 2% glutaraldehyde in 0.1 M cacodylate buffer. Vascular thrombosis was seen in renal biopsies of cyclosporine- and azathioprine-treated patients but the incidence was the same in both groups. No change in the morphology of endothelial cell cultures was observed until 7 days when an increase in size and number of cytoplasmic inclusions became apparent in both control and cyclosporine-treated cultures. By electron microscopy, these inclusions were identified as secondary lysosomes. Their number and size increased with the length of time in culture but did not appear to correlate with the concentration of cyclosporine in the medium. No other morphologic change was identified. It is concluded that the appearance of increased numbers of secondary lysosomes in human endothelial cell cultures is a function of culture age as opposed to cyclosporine exposure. Furthermore, the data indicate that small vessel thrombosis is not specific to treatment with cyclosporine.

Sprague-Dawley rats received cyclosporin A (25 mg/kg) together with either the aminoglycoside gentamicin (50 mg/kg) or one of 3 cephalosporin antibiotics (100 mg/kg) daily for 14 days. Only minor impairment of renal or hepatic function was observed when either cyclosporin A or gentamicin was given on its own and no abnormality was seen in response to cephalosporins. However, concomitant administration of cyclosporin A and gentamicin caused acute renal failure, accompanied by cyclosporin A-induced damage to the proximal straight tubule and gentamicin-induced proximal convoluted tubular cell necrosis. In contrast, the structural abnormalities present in the 3 groups given cephalosporins in addition to cyclosporin A were attributable only to the immune suppressant. Liver functional changes previously found only at higher doses of cyclosporin A were observed in the cyclosporin A/gentamicin group and there was some evidence of possible interactions between cyclosporin A and each cephalosporin affecting liver function. The results indicate that treatment of infection with cephalosporin antibiotics or a less nephrotoxic aminoglycoside is preferable to gentamicin in cyclosporin A-treated patients.

The immunosuppressant agent cyclosporine (Sandimmune) is a calmodulin inhibitor that has potent nephrotoxic properties. Recently, it has been observed that osmoregulation in the proximal tubules of the bony fish Carassius auratus (goldfish) is a calmodulin-regulated cell function. As their mammalian counterparts do, these renal tubule cells swell when exposed to hypotonic solutions. This is followed by a slower volume regulatory decrease phase owing to KCl efflux and osmotically obligated water. The extrusion of potassium and chloride is, in this preparation, a calcium and calmodulin regulated process, respectively. With videometric methods, the effects of both cyclosporine (5, 10, and 50 microM) and Cremophor EL (0.65 mg per ml) on osmoregulation were studied in isolated renal tubules. The tubules were stimulated with hypotonic Ringer's solution in the presence and absence of cyclosporine and Cremophor EL. Cremophor EL did not have toxic effects on cell volume regulation; cyclosporine, however, induced a dose-dependent inhibition of osmoregulation. This is due to a hindrance of ionic efflux rather than a decrease in cellular water permeability. It is concluded that the influence of cyclosporine on cell volume control is due to inhibition of the calmodulin-regulated ionic efflux required for osmoregulation.

Cyclosporin A (CsA) is known to diminish the size of the thymus, especially the thymic medulla. The significance of these changes is not presently understood. This study reveals several immunopathologic changes induced in the thymic medulla by CsA (15 mg/kg/day). The weight and relative size of the thymus dramatically and rapidly involutes, with marked changes observed in 1 week. The medullary thymocytes show segregation of rat T-cell phenotypes as seen in control rats, but the number of such cells is markedly reduced in accordance with the medullary remnant. This is consistent with a maturational arrest of thymocytes. The medullary epithelium was assessed directly by irradiating the control or CsA-treated rats 2 days prior to sacrifice. The epithelium of Hassall's corpuscles was essentially absent in CsA-treated rats but prominent in control rats. The cortical epithelial cells were preserved. Stains for Ia antigen with the anti-OX4 antibody show little change in expression by cortical epithelium, but a marked reduction in the Ia+ medullary cells in the thymocyte purged rats. All of these changes were reversible in the normal rat after cessation of CsA, with near normal recovery in 3 weeks. No morphologic or immunopathologic changes were noted in the cortical thymocytes. These cells did, however, acquire CsA receptors, as detected by the binding of fluorescent dansylated CsA.

Cyclosporin A (50 mg/kg orally for 7 days) produced severe degranulation and hydropic degeneration of islet B cells in rats. These changes were accompanied by hyperglycaemia and hypoinsulinaemia, while the pancreatic insulin content decreased by 75%.

Rats were treated for 3 or 14 days with cyclosporin A (CsA, 50 mg/kg) or indomethacin (2 or 5 mg/kg) either alone or in combination, or with CsA plus 16,16-dimethylprostaglandin E2 (DMPGE2, 0.25 mg/kg). Hepatic and renal function were unaffected by treatment with indomethacin at either dose and only at the higher dose was severe intestinal ulceration observed. CsA caused renal and hepatic toxicity, evidenced by increased urine N-acetyl-beta-D-glucosaminidase activity, serum urea, creatinine and bilirubin and decreased serum albumin and total protein. In rats cotreated with CsA and either dose of indomethacin the increases in serum urea and creatinine and decreases in serum albumin and total protein were accentuated, but serum bilirubin was not further increased. Intestinal lesions were present in rats treated for 14 days with CsA plus the lower dose of indomethacin, but not in rats treated with either drug alone. In rats treated with DMPGE2 plus CsA, serum urea and creatinine were normal and urine N-acetyl-beta-D-glucosaminidase activity was reduced compared to rats treated with CsA alone, but DMPGE2 cotreatment had no effect on the CsA induced hyperbilirubinaemia. Hepatic microsomal cytochrome P-450 concentration and aminopyrine N-demethylase activity were lower in rats treated with CsA plus indomethacin than in untreated rats or those treated with either drug alone. Coadministration of indomethacin or DMPGE2 had no effect on serum trough CsA levels. The results are interpreted as showing an exacerbation by CsA of the intestinal toxicity of indomethacin, an increase by indomethacin in the renal toxicity of CsA and a protection by DMPGE2 against CsA renal toxicity. Possible mechanisms involving drug interactions and either hepatic cytochrome P-450, renal cyclooxygenase or other renal sites are discussed.

Cyclosporine (CSA) is a new immunosuppressant which has selectivity for the immune system and is without systemic side effects at therapeutic doses. In contrast to the cytotoxic class of immunosuppressants, no myelotoxic, teratogenic, mutagenic, or carcinogenic effects were observed. Nevertheless, overdosage may lead to renal dysfunction, which occurs mainly in rats, and often complicates its clinical use. The experimental data also showed that significant nephrotoxicity was only caused under specific conditions at therapeutic doses. These conditions included ischemia, heminephrectomy, concomitant administration of nephrotoxic drugs, and/or genetic predisposition. Thus, concomitant renal damage is a prerequisite in order to obtain overt nephrotoxicity at therapeutic CSA doses. Since these conditions cannot be avoided in patients, nephrotoxicity often occurs at therapeutic doses in man. The rat might be a suitable experimental model of CSA nephropathy displaying similar morphologic and functional changes as observed in man. This model also allows further investigations on the pathogenic mechanisms which are elusive at the present time.

Cyclosporin A (CsA) administration to rats is associated with a selective increase in urinary excretion of immunoreactive thromboxane B2 (i-TxB2), the stable breakdown product of TxA2. The exaggerated synthesis of TxA2 may play a role in the reduction of glomerular filtration rate (GFR) observed both in animals and humans undergoing CsA treatment. The present study was designed to get further insight into the origin of the abnormal i-TxB2 urinary excretion. Rats given orally CsA (50 mg/kg/day) for 30 days had a significant increase in the urinary excretion of both 2,3-dinor-TxB2 and TxB2 measured by technique of capillary column gas chromatography-negative ion chemical ionization mass spectrometry (HRGC-NICIMS). Urinary TxB2 is more likely to reflect the renal synthesis of the parent compound, whereas 2,3-dinor-TxB2 is considered to reflect the amount of TxB2 formed in the circulation. Experiments in isolated perfused kidney (IPK) taken from animals given CsA for 30 days showed a lower percentage increase in urinary TxB2 over vehicle treated animals. Moreover in IPK the ratio 2,3-dinor-TxB2/TxB2 was lower than in vivo. The amount of i-TxB2 detectable in serum of animals given CsA was not different from that of control animals. In contrast, isolated glomeruli taken from rats given CsA had an increase in their TxA2 synthesis measured as i-TxB2 in the supernatants. Ultrastructural studies on kidney specimens from animals given CsA showed a focal glomerular endothelial damage together with a marked infiltration of blood borne cells of monocyte-macrophage type in the glomerular tuft. In contrast, kidney specimens taken from IPK preparations were devoid of inflammatory cells. In vitro CsA did not interfere with platelet arachidonic acid (AA) metabolism as shown by a normal i-TxB2 generation in vitro by rat platelet-rich plasma (PRP) exposed to CsA and then challenged with AA or ADP. Similarly isolated glomeruli and isolated proximal tubules from normal rats when challenged with CsA in vitro converted AA into TxA2 normally. It is suggested that the cause of the increased urinary excretion of 2,3-dinor-TxB2 is the consequence of intrarenal platelet and macrophage activation, probably triggered by the endothelial damage. The parallel increase in the urinary excretion of unmetabolized TxB2 is likely to reflect a concomitant activation of resident renal cell AA metabolism induced by CsA.

Using a recently described rodent model of chronic cyclosporine nephropathy (CCN), the effects of uninephrectomy (UNx) and high protein feeding on the development of CCN were studied. After 28 days of i.p. cyclosporine (Cs; 25 mg/kg/day) in UNx and sham nephrectomized (SNx) rats, the single kidney GFR was higher in UNx animals (0.55 +/- 0.09 vs. 0.29 +/- 0.05 ml/min, P less than 0.04) as was RPF (3.05 +/- 0.46 vs. 1.45 +/- 0.37 ml/min, P less than 0.04). Morphometric evaluation of the chronic tubulointerstitial lesion (TI) demonstrated lower scores and relative protection in the UNx group (16.48 +/- 3.52 vs. 64.76 +/- 18.30, P less than 0.01). In separate groups of rats undergoing UNx or SNx and subsequent treatment with Cs, dry kidney weights confirmed that compensatory renal hypertrophy was present in UNx animals. The modulating effect of dietary protein on the lesion of CCN was studied in UNx rats fed a 5% or 60% protein diet during the period of Cs treatment. At the end of the study period animals fed the high protein diet demonstrated a higher RPF (3.19 +/- 0.58 vs. 1.58 +/- 0.29 ml/min, P less than 0.04), higher GFR (0.55 +/- 0.07 vs. 0.35 +/- 0.04 ml/min, P less than 0.05) and lower TI score (64.45 +/- 17.35 vs. 130.32 +/- 23.48, P less than 0.04) when compared with animals consuming a low protein diet. We conclude that the relative renal vasodilation induced by partial ablation of renal mass and high protein feeding affords some protection against the development of CCN.

This study investigated if and to what extent the acute toxic effect of Cyclosporin A on pancreatic Wistar rat B cells is reversible. After 2 weeks of treatment rats developed marked glucose intolerance accompanied by reduced pancreatic insulin content due to a loss of B cells, diminished islet DNA synthesis and decreased B-cell insulin content. Cyclosporin A had accumulated in the pancreas. Three weeks after withdrawal of Cyclosporin A, pancreatic tissue concentrations of Cyclosporin A were still 100 times larger than in serum. Glucose tolerance, however, had already improved, associated with an increase of B-cell insulin content and apparent islet replication, and the insulin response of isolated islets was reduced. Five weeks after the withdrawal of Cyclosporin A, glucose tolerance was normal, but pancreatic insulin content and relative B-cell volume were still diminished in comparison to vehicle-treated controls. Eight weeks after withdrawal, the morphometric parameters had also been normalized. The results suggest that the loss of pancreatic B cells is caused by a toxic destruction, possibly combined with an apparent decrease of replicatory activity. The acute toxic effects of Cyclosporin A in pancreatic B cells are stepwise reversible.

The effects of cyclosporin A (CsA) on planar surface area of cultured rat mesangial cells (PCSA) and cross-sectional area of isolated rat glomeruli (GCSA) were tested. The same experiments were performed after preincubation with platelet activating factor (PAF) antagonists (BN 52021, alprazolam) or calcium channel blockers (verapamil). Areas of cells or glomeruli were analyzed by a computer-assisted method. CsA reduced PCSA in a time-dependent (significant effects began at 15 min, about 12% of reduction with 10(-6) M CsA) and dose-dependent (no effect at 10(-9) M CsA, maximal reduction of about 30% at 60 min of incubation with 10(-7) M CsA) fashion. BN 52021 (5.10(-5) M) and alprazolam (10(-5) M) completely inhibited the reduction of mesangial cell area induced by CsA. Verapamil (10(-5) M) only partially inhibited this action. Glomerular cross-sectional area decreased after 30 minutes of incubation with 10(-6) M CsA (1.45 +/- 0.02 vs. 1.55 +/- 0.02 m2.10(-8), P less than 0.001), an effect that was inhibited by BN 52021 or verapamil. In addition, 10(-6) M CsA increased PAF production by isolated rat glomeruli (425 +/- 80 pg/mg vs. 198 +/- 13 pg/mg in control glomeruli, P less than 0.01), an effect which was not inhibited by verapamil. These results suggest that CsA could reduce GFR by decreasing the glomerular ultrafiltration coefficient, perhaps as a consequence of the contraction of mesangial cells. PAF seems to play a pivotal role in the genesis of this action.

The immunosuppressant cyclosporine (CSA) has shown usefulness in both animal and human transplantation. The present study investigated the effect of CSA in human to rat skin xenografts. Recipient rats received either a fresh split-thickness (0.020 in.) or full-thickness graft obtained from plastic surgery, or frozen cadaver skin. The graft bed of recipient Lewis rats was prepared by full-thickness excision. Animals were maintained on CSA 25 mg/kg/day X 50 days, followed by 12.5 mg/kg 2 X/week. Control animals received an equivalent volume of vehicle. All animals receiving split-thickness grafts and treated with CSA maintained their grafts significantly longer (up to 255 days) than controls. The 2 CSA-treated full-thickness grafts and the 10 vehicle-treated controls showed clinical and microscopic signs of rejection at a mean of 6.4 days. Histologic examination of successful grafts showed areas of viable epidermis with a negligible inflammatory infiltrate. There was some loss of normal polarity and occasional apoptotic pigmented basal cells. The dermis revealed moderate fibrosis, probably secondary to the surgical procedure. Graft viability was confirmed by autoradiography. Immunohistochemical staining for S-100 protein revealed morphologic alteration of suprabasilar dendritic (Langerhans-indeterminate) cells, as well as their existence in xenografts at 12 weeks posttransplantation. Toxicities reflected by weight loss and blood chemistries were felt to be dose-dependent. This in vivo model may provide a means for testing percutaneous drug penetration and pharmacokinetics in human skin, and for observing the immune component of explanted cutaneous neoplasms and dermatoses.

An athymic rat strain lacking functional T cells was used to assess the role of cell-mediated immunity (CMI) in host defence against renal infection. CMI was ruled out as a relevant host defence component, but when cyclosporin A (CsA) was administered to athymic animals, renal infection was exacerbated. CsA is thought to affect T lymphocyte function and, in the absence of a target cell, cellular defences in the athymic animal were not expected to be compromised by CsA. An effect on non-cellular defence mechanisms was therefore considered but our studies did not support this explanation--rather they indicated a depression of either cellular defences or of a specific cellular component. The present experiments have provided additional information on the relationship between CsA administration and the depression of host defence mechanisms but further studies will be necessary to identify the components affected.

Rabbits given acute serum sickness (ASS) and treated with cyclosporin A (CyA) developed a severe, systemic vascular injury, which was not similar to that normally seen in ASS. Thirty-three NZW rabbits received a single intravenous injection of 250 mg/kg bovine serum albumen (BSA) with or without endotoxin (5 micrograms/kg), on day 0. Groups of rabbits were given intramuscular CyA as follows: 15 mg/kg/day from day -2 to +8, or 25 mg/kg/day from day -2 to +3 or day 0 to 5. Muscular arteries of the heart and splanchnic organs developed an arterial injury in which there was extensive fibrinoid necrosis of the vessel wall but little or none of the mononuclear cell reaction that is normally associated with the arteritis of ASS. A microvascular injury also occurred which led to interstitial haemorrhage in the gastric mucosa and multi-focal necrosis in the heart and liver. These lesions were seen with equal frequency in all groups of rabbits with serum sickness who received CyA, irrespective of whether they also received endotoxin. We suggest that CyA altered the host inflammatory response to the injury initiated by the BSA-anti-BSA immune complexes and this led to enhanced vascular injury. The inhibition by CyA of the perivascular cellular reaction suggests that this reaction may be mediated by T lymphocytes. This model should provide further insight into the pathogenesis of arteritis, as well as the mechanisms of cyclosporin toxicity.

The immunosuppressive agent, cyclosporine, has been found to augment receptor-stimulated calcium fluxes in isolated hepatocytes. After treatment of Quin 2-loaded hepatocytes with cyclosporine, both the amplitude and duration of the vasopressin-induced rise in the cytosolic free Ca2+ are increased. These effects are dependent upon the concentration and time of exposure of the cells to cyclosporine. Cyclosporine increases both 45Ca2+ influx across the plasma membrane and the cellular calcium content. The total cellular magnesium, sodium, and potassium contents are not affected by cyclosporine. However, cyclosporine treatment, per se, has no apparent effect on the cytosolic free Ca2+ concentration as assayed by Quin 2 fluorescence. The increase in total cell calcium is associated with progressive increases in the calcium content of the endoplasmic reticular and mitochondrial calcium pools. The vasopressin-induced net efflux of Ca2+ from hepatocytes was 2-fold greater after treatment with 10 micrograms/ml cyclosporine for 10 min, but the lag time prior to the onset of Ca2+ efflux was not affected. These results are interpreted on the basis of cyclosporine having a primary effect on increasing the permeability of the plasma membrane to Ca2+, thereby leading to an increase of the calcium content of the hormone-sensitive intracellular calcium pool.

Cyclosporin 5, 10, and 20 mg/kg bw was given to rats once daily intragastrically and caused a dose dependent, significant decrease of glucose dependent insulin release from the arterially perfused isolated pancreas, without affecting animal behaviour, weight gain, microscopic appearances of the pancreas, or kidney function. Subcutaneous injection of a new synthetic prostaglandin analogue Rioprostil 7.5 micrograms/kg bw twice daily completely prevented the effect of cyclosporin 5 mg/kg bw and protected significantly against the effects of cyclosporin 10 and 20 mg/kg bw.

Local factors, such as interleukin-1, may mediate the accelerated bone remodeling in the acute estrogen-deficient rat. Cyclosporin A (CsA), which in vitro inhibits some of these local factors, was administered to oophorectomized (OX) rats in an attempt to modify this high turnover state. Three groups of 15 rats were studied. Group A was sham operated, group B was OX, and group C was OX and received CsA (15 mg/kg per day) by gavage commencing 4 days postoophorectomy for 28 days. Estradiol levels were determined to confirm oophorectomy. Blood was sampled on days -7, 0, 7, 14, 21, and 28 for ionized calcium (Ca2+), 1,25-(OH)2-vitamin D, PTH, and bone gla protein (BGP). Rats received tetracycline hydrochloride for bone histomorphometric labeling. All results were compared to group A. Body weight was increased in group B (p less than 0.003) but not in group C. There was no difference in Ca2+ or PTH between the groups. BGP levels were higher in group B by day 28 (p less than 0.005); BGP levels were increased in group C from days 7-28 (p less than 0.002). 1,25-(OH)2-vitamin D was significantly increased in group C (p less than 0.0001) but not in group B. Tibial bone histomorphometry revealed increased measurements of bone formation and osteoclast number without a loss of bone volume (BV/TV) in group B. Group C showed a dramatic increase in bone turnover with significant loss of BV/TV (p less than 0.001). In conclusion, CsA in the OX rat resulted in unexpected enhanced bone remodeling with high BGP levels and severe bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study was undertaken to study the mechanism of cyclosporine-induced nephrotoxicity and hypertension. Cultured rat microvascular endothelial cells were exposed to cyclosporine for up to six days at one of the following concentrations: 10, 50, 250, and 1000 ng/ml of culture medium. Cyclosporine inhibited endothelial cell replication in a dose-dependent manner; at higher concentrations (250 and 1000 ng/ml), cell replication decreased by as much as 70 to 90% of controls at four and six days post-treatment, with no evidence of increased cell death. Drug-treated endothelial cells revealed abnormal morphological changes such as formation of cytoplasmic vesicles and nucleolar changes. Prostacyclin release by endothelial cells was increased by about threefold with the addition of cyclosporine (P less than 0.01). Indomethacin significantly decreased prostacyclin release by endothelial cells in the presence or absence of cyclosporine (P less than 0.01). Our data suggest that cyclosporine-induced nephrotoxicity may be mediated, at least partly, by the inhibitory influence of cyclosporine on the regenerative response of microvascular endothelial cells to injury, and the resultant alterations in prostacyclin production by these cells.

The efficacy of different radiodiagnostic agents for demonstrating the decline in renal function from cyclosporine (CyA) nephrotoxicity was assessed in rats receiving a standard dose of the drug for 2 wk, compared with control rats. The agents included [99mTc]DTPA, [131I]hippuran, [111In]lysozyme, [99mTc]glucoheptonate (GHA), [99mTc]dimercaptosuccinate (DMS) and [111In]aminated dextran (amdex). A small dose of [99mTc]- or [111In]DTPA was administered simultaneously to normalize the results for variations in drug response from one animal to another. There were statistically significant differences in the detectability of the renal functional impairment by plasma clearance, early and 2-hr renal uptake among the different agents. However, none was clearly superior to DTPA. This conclusion is consistent with previous studies which showed a parallel decline in glomerular filtration rate (GFR) and effective renal plasma flow in acute CyA toxicity probably due primarily to vasoconstriction.

Experiments were performed to determine the cause of the reduced glomerular filtration rate (GFR) in cyclosporine nephrotoxicity during compensatory renal growth. Sprague-Dawley rats were uninephrectomized and given daily injections of cyclosporine (30 mg/kg, i.m.) or vehicle (olive oil), and studied 7 or 14 days later. In cyclosporine treated rats GFR was lower seven days (1.34 +/- 0.10 vs. 1.68 +/- 0.07 ml/min) and 14 days (1.19 +/- 0.08 vs. 1.58 +/- 0.04, P less than 0.025) following uninephrectomy. Arterial blood pressure, cardiac output and renal blood flow (RBF) were not different in cyclosporine and control rats. Kidney mass increased to the same extent in cyclosporine and control rats. Micropuncture of the glomerular microcirculation in similarly prepared Munich-Wistar rats demonstrated low whole kidney GFR (1.10 +/- 0.07 vs. 1.55 +/- 0.13 ml/min, P less than 0.01), and single nephron GFR (31.07 +/- 2.27 vs. 42.36 +/- 2.47 nl/min, P less than 0.005) in cyclosporine treated rats as compared to controls. Single nephron plasma flow, afferent and efferent arteriolar resistance, the transglomerular hydrostatic pressure gradient, and arterial blood pressure were the same in both groups. The glomerular capillary ultrafiltration coefficient (Kf) was lower in cyclosporine treated rats compared to controls [0.039 +/- 0.002 vs. 0.075 +/- 0.013 nl/(sec.mm Hg), P less than 0.025]. We conclude that in this model of cyclosporine nephrotoxicity the low GFR is caused solely by a reduction in Kf, and that cyclosporine can reduce GFR without causing renal vasoconstriction.

The authors recently demonstrated that cyclosporine (CsA) enhanced the development of murine thymic lymphomas by its tumor promoter-like action. To clarify the underlying mechanism, they investigated the morphologic alterations in the thymus and other lymphoid tissues and the serum immunoglobulin abnormalities in mice receiving CsA. Feeding male Swiss Webster mice with diets containing 0.015% and 0.027% CsA for 1, 2, 4, and 8 weeks led to a marked reduction of the thymic medulla. Thymocytes remaining after CsA treatment were completely destroyed by a single injection of cortisone acetate (8 mg/mice), and cortisone-resistant cells were markedly decreased. Immunoperoxidase staining using anti-keratin antibodies showed a decrease in the number of keratin-positive cells, presumably epithelial cells, in the thymus of CsA-treated mice. These changes were completely reversible within 4 weeks after withdrawing CsA from the diet. The lymph nodes and the gut-associated lymphoid tissues of CsA-treated mice showed blurring of the germinal centers, diminished Thy-1-positive lymphocytes, and proliferation of lymphocytes carrying IgG, IgM, and IgA on their surface. Similar changes were observed in the spleens of CsA-treated mice. There was a slight increase in serum IgG, a twofold increase in serum IgM, and a six- to tenfold increase in serum IgA. The results suggest that CsA interferes with the functions of both T and B lymphocytes in vivo and that disturbance of T-cell maturation in the thymus may be the mechanism by which CsA promotes the induction of thymic lymphomas in mice.

These studies further delineate the requirements for the establishment and transfer of SGVHD. We show that (a) two mechanisms distinguishable by radiation and drug sensitivities exist, (b) lethal irradiation correlates with a 100% incidence in the induction of SGVHD, whereas (c) both sublethal or lethal irradiation and cytoxan therapy are effective in ablating the host autoregulatory system in order to transfer autoreactivity, (d) unfractionated as well as nylon wool-nonadherent splenocytes effectively inhibit the transfer of autoimmunity, and (e) OX19 depletion of that population, however, destroys the autoregulatory effect present in normal splenocytes. To demonstrate complete inhibition of immune reactivity, twice the number of unfractionated splenocytes from normal animals was required for every splenocyte from autoimmune donors. Last, the infusion of effector splenocytes on 4, 7, and 14 d after transplantation correlates to a decrease from 100%, 70 to 0% incidence of SGVHD, thus emulating the incidence obtained in a pretransplant rat within 2 wk. These findings further clarify the immunobiological complexity of SGVHD and suggest that since autoregulatory cells already exist in normal animals that CsA-induced autoimmunity is a reflection of not an induced reactivity specific to one therapeutic reagent but the uncoupling of normal immunologic mechanisms essential in controlling autoimmunity.

The toxic properties of cyclosporin A and gentamicin give alone and in combination were investigated in groups of Sprague-Dawley rats over a 7-day period. Administration of each drug on its own caused minor impairment of renal and hepatic function: cyclosporin A had additional structural effects on renal tubules and lymphoid tissue. Combined therapy resulted in acute renal failure with two distinct zones of damage in the renal proximal tubules--gentamicin-induced necrosis of the convoluted segment and cyclosporin A-related vacuolation of the straight segment--and the effects on hepatic and haematological parameters were more pronounced. The results indicate the need for caution before cyclosporin A and another potentially nephrotoxic drug and administered together and for specific monitoring or renal function where such combined therapy is considered essential.

Although survival after cardiac transplantation has improved since the introduction of cyclosporine to clinical practice in 1980, the long-term hemodynamic results of transplantation in cyclosporine-treated recipients has not been reported. Annual cardiac catheterization data for 109 cyclosporine-treated recipients were analyzed and compared to those of a nonconcurrent group of 65 recipients treated with azathioprine and corticosteroids. Recipient age, donor age, sex, and human leukocyte antigen mismatch were comparable for the two groups. Satisfactory left ventricular function of the cyclosporine-treated heart was characterized on the first annual study by a normal ejection fraction (60% +/- 10%), cardiac index (3.0 +/- 0.8 L/min/m2) and stroke work index (53 +/- 15 gm-m/m2) associated with moderately increased left ventricular end-diastolic pressures (12 +/- 6 mm Hg) and significantly increased mean aortic pressures (116 +/- 8 mm Hg). With the exception of aortic diastolic pressure, which tended to increase with time, the mean values of each variable analyzed did not change significantly over the period of study. In comparison to the azathioprine group, the cyclosporine cohort displayed higher aortic, left ventricular end-diastolic, and pulmonary artery pressures and produced more stroke work at each annual study. Analysis of the azathioprine group over extended (8 year) follow-up suggested excellent preservation of graft function. In summary, the long-term hemodynamic function of the transplanted heart treated with cyclosporine was satisfactory, demonstrated no deterioration over 5 year follow-up, but manifested substantially greater hypertension than hearts from the pre-cyclosporine era.

During the past decade, treatment with cyclosporine, an immunosuppressive agent, has contributed substantially to enhanced allograft and patient survival after liver transplantation. Currently, the 1-year survival rate after liver transplantation is more than 80% in major liver transplantation centers, in contrast with approximately 60% before the availability of cyclosporine. Its predominant immunologic effect is inhibition of lymphokine production and secretion by helper T cells. The use of cyclosporine, however, is associated with numerous adverse effects, the most important of which are nephrotoxicity, hypertension, neurotoxicity, opportunistic infections, and malignant lesions. Acute nephrotoxicity, hypertension, and neurotoxicity usually can be reversed by decreasing the dose of cyclosporine. Measurement of cyclosporine concentrations in the blood is essential for optimization of immunosuppressive therapy and prevention of toxicity.

Between March 29, 1979, and March 1, 1985, 62 heart transplants were done in 61 patients at the University Medical Center, University of Arizona. There were two treatment groups with nearly equal numbers in each; conventional immunosuppression (1979 to 1982) and cyclosporine (1982 to the present). Comparison of actuarial survival, number of rejection episodes, number of fatal rejection episodes, number of infections, and number of "other complications" failed to reveal any significant difference between the two groups. The cyclosporine-treated patients had a documented increase in blood urea nitrogen and serum creatinine accompanied by an increase in diastolic blood pressure. The length of hospital stay of the cyclosporine group was approximately one half of that of the conventionally treated patients, and they required fewer rehospitalizations. The cost for initial hospitalization was not significantly different between the two groups. Therefore, in 1979 dollars, the cost for cyclosporine-treated patients has decreased. This difference in cost was only minimally diminished by the difference in expenditure for outpatient pharmaceuticals, which was four times higher in the cyclosporine group. We believe that cyclosporine is a potent immunosuppressive agent but that it has toxic, possibly irreversible effects on the kidney. In view of the minimal differences that we were able to demonstrate in survival rejection and infection, it seems prudent to reduce or modify present doses of cyclosporine in an attempt to avoid irreversible renal damage.

Five immunosuppressive and anti-inflammatory agents were tested for their effects on development of experimental autoimmune uveoretinitis (EAU) and immune responses to S-antigen in rats immunized with this retinal antigen. When administered daily from day 0-14 after immunization, cyclosporine at 5-20 mg/Kg was nontoxic and yet effective in inhibiting the development of EAU for at least 30 days. All other tested drugs were found toxic at their immunosuppressive doses. Of these drugs, only cyclophosphamide (at 5-20 mg/Kg) was capable of inhibiting EAU in some of the treated rats for up to 30 days. Other agents, bredinin (40-100 mg/Kg), dexamethasone (0.2-0.4 mg/Kg), or colchicine (0.5 mg/Kg) produced only a delay in the disease onset. Cyclosporine was also unique in its effect on the immune responses of the rats by selectively inhibiting only the specific T-cell-mediated responses to S-antigen (delayed skin response and lymphocyte response in culture), while having no negative effect on antibody production or the lymphocyte response to the polyclonal mitogen, concanavalin A. Other drugs, when effective, inhibited all types of immune response. In addition, cyclosporine was capable of preventing EAU even when given to rats as late as from day 7 after immunization. Only cyclophosphamide (at 20 mg/Kg/day) had a similar effect on 1/3 of the rats, while other drugs only delayed or had no effect on the disease onset when given by this late schedule.

The nephrotoxic property of cyclosporin A (Cy A) was investigated in groups of Sprague-Dawley rats given various dose regimes over a 21-day period. Impairment of glomerular filtration was clearly evidenced by elevated serum urea and creatinine levels and by reduced urea clearance rates. There were also dose-related increases in urinary N-acetyl-beta-D-glucosaminidase activity. These biochemical changes were accompanied by structural evidence of damage to the straight segment of the proximal tubule; this consisted of varying degrees of cytoplasmic vacuolation, due to dilatation of both smooth and rough endoplasmic reticulum, and, at the highest dose tested, occasional individual cell necrosis and desquamation. Ultrastructural examination revealed additional dose-related abnormalities affecting the entire length of the proximal tubule, including increased lysosome production and the formation of cytosegresomes and myeloid bodies.

Arterial hypertension is a common side effect of cyclosporine A therapy; however, the cellular mechanism of cyclosporine A-induced hypertension is still unknown. The present study, therefore, examined the effect of cyclosporine A on Ca2+ kinetics and contraction in primary cultures of vascular smooth muscle cells. Cyclosporine A (10 micrograms/ml) did not affect resting intracellular free Ca2+ ([Ca2+]i) levels (151 +/- 10 vs. 146 +/- 5 nM, NS), but augmented the 10(-8) M arginine vasopressin-induced increase of [Ca2+]i (delta 76 +/- 4 vs. delta 172 +/- 6 nM, p less than 0.001). This effect of cyclosporine A was also observed in Ca2+-free medium. Arginine vasopressin-stimulated [Ca2+]i efflux within 30 seconds compared with baseline efflux rates (1,644 +/- 146 vs. 2,591 +/- 373 cpm/mg prot/30 sec, p less than 0.005), but this transient effect was significantly greater (p less than 0.001) with arginine vasopressin plus cyclosporine A (1,702 +/- 133 vs. 5,605 +/- 1235 cpm/mg prot/30 sec, p less than 0.01). Basal 45Ca2+ efflux rates were not affected by cyclosporine A, and prior incubation of the cells with cyclosporine A was required to elicit the augmentory effect. 45Ca2+ uptake was measured to examine the mechanism by which cyclosporine A may affect [Ca2+]i stores. Cyclosporine A increased Ca2+ uptake when compared with control (6.38 +/- 0.69 vs. 10.99 +/- 0.59 x 10(3) cpm/mg prot/5 min, p less than 0.001). This effect was not blocked by the Ca2+ antagonist verapamil. Arginine vasopressin (10(-8) M) induced contraction of smooth muscle cells with 25.5% of the cells responding.(ABSTRACT TRUNCATED AT 250 WORDS)

In rats given an immunotherapeutic dose (25 mg/kg orally each day for 7 weeks) of cyclosporin A (Cy A) characteristic drug-induced pathological changes were observed, including impaired liver function, renal proximal tubular cell damage, progressive lymphopenia, lymphocyte depletion in lymphoid organs and marrow hypoplasia. Several additional and previously unreported features of Cy A toxicity were also demonstrated. The changes in renal and hepatic function were biphasic with temporary improvement during the course of the study. The most striking liver damage was in the form of a granulomatous hepatitis and a hypochromic microcytic anaemia developed in all experimental animals.