Effects of cyclosporin on kidney glutathione metabolism and cytochrome P-450 in the rabbit: possible implication of eicosanoid metabolism

In vitro and in vivo characterization on amorphous solid dispersion of cyclosporine A for inhalation therapy

Cyclosporine A (CsA) has been clinically used as immunosuppressant, and new application for airway inflammation was also proposed. However, the clinical use of CsA was limited due to severe adverse effects after systemic exposure and the poor solubility. In the present investigation, novel respirable powder (RP) of CsA was developed for pulmonary administration with use of solid dispersion of wet-milled CsA (WM/CsA), and the physicochemical and pharmacological properties of the WM/CsA and its RP formulation were characterized. CsA in the solid dispersion was found to be amorphous by X-ray powder diffraction and differential scanning calorimetry. It exhibited the improved dissolution behavior as compared to active pharmaceutical ingredients. Laser diffraction and cascade impactor analysis of newly developed WM/CsA-RP, consisting of jet-milled WM/CsA and lactose carriers, suggested high dispersion and deposition in the respiratory organs with the emitted dose and the fine particle fraction of 96 and 54%, respectively. Intratracheal administration of WM/CsA-RP (100 microg CsA) in experimental inflammatory rats led to 71 and 85% reduction of granulocyte recruitment in bronchoalveolar lavage fluids and lung tissues, respectively, with showing ca 10(2)-fold reduced AUC and C(max) values of plasma CsA as compared to the oral dosage form of CsA at toxic concentration (10 mg/kg). Upon these findings, WM/CsA-RP would be efficacious dosage form for clinical treatment of airway inflammations with minimal systemic side effects.

Effect of cyclosporin A treatment on renal calcium oxalate binding in experimental hyperoxaluria

This study was aimed to investigate the effect ofCyclosporin A administration on renal calcium oxalate binding under hyperoxaluric condition. Cyclosporin A administration or ammonium oxalate treatment increased calcium oxalate binding, which was further increased in kidney treated with cyclosporin A and ammonium oxalate together. The increase of calcium oxalate binding was associated with lipid peroxidation as well as with a concomitant decrease in total thiol in both rat and human kdiney homogenate. Cyclosporin A administration to hyperoxaluric rats resulted with increased calcium oxalate binding protein. However there was no change with specific activity of the protein. In conclusion, Cyclosporin A administration either to normal or hyperoxaluric rats is resulted with increased concentration of calcium oxalate binding protein as well as enhanced activity due to membrane lipid peroxidation.

Glutathione metabolism in cyclosporine A-treated rats: dose- and time-related changes in liver and kidney

1. We investigated the simultaneous effects of cyclosporine A (CsA) treatment in rats on glutathione metabolism, oxidative status and their interorgan relationship in the liver and kidney. 2. Reduced and oxidized glutathione (GSH and GSSG, respectively), lipid peroxidation and the activity of several enzymes of the glutathione cycle were evaluated in adult Wistar rats treated daily (i.p.) with saline, CsA vehicle (olive oil) or CsA (10 and 20mg/kg per day) for either 1 or 4 weeks (short- and long-term treatments, respectively). 3. Cyclosporine A treatment elicited a significant depletion in liver GSH content and a decrease in the GSH/GSSG ratio that was unrelated to either the time of treatment or the dose used; these effects were already evident after 1 week of treatment. Renal GSH levels remained unaffected or increased, while those of GSSG increased markedly in all CsA-treated rats, leading to decreases in the GSH/GSSG ratio, except in rats treated in the short term with the lower dose of CsA. These changes in the GSH/GSSG ratio were time and dose dependent. Short-term CsA treatment using the higher dose and long-term treatment with both doses of CsA progressively enhanced lipid peroxidation, which was reflected by increased levels of thiobarbituric acid-reactive substances in both hepatic and renal homogenates. Hepatic gamma-glutamylcysteine synthetase activity was increased after long-term treatment with both doses of CsA, whereas the activity of GSH hepatic peroxidase and GSH transferase was not significantly modified in any of the experimental groups. In contrast, renal gamma-glutamyl transpeptidase activity decreased in a progressive fashion, with the magnitude of this decrease being dose and time dependent. The plasma levels of total glutathione increased only in rats treated in the long term, regardless of the dose of CsA used, and remained unaltered in animals treated in the short term. 4. In summary, the data collected indicate that CsA treatment alters the interorgan homeostasis of glutathione and the oxidative status of the rat liver and kidney, which is associated with increases in lipid peroxidation in both organs, and also induces modifications in the activity of some enzyme related to the glutathione cycle.

The effect of immunosuppressive agents (FK-506, rapamycin) on renal P450 systems in rat models

It is well known that cyclosporin, rapamycin and FK-506 (tacrolimus) are metabolized by the liver microsomal cytochrome P450 enzyme system. Although there have been reports of interaction between these drugs and the renal P450 enzyme system, differences among these immunosuppressants has not been comprehensively demonstrated. We have studied the individual capacities of these immunosuppressants to induce renal microsomal P450 enzymes similar to CYP2B4 and CYP4A2 by examining renal function in treated rats, and have correlated the results by means of biochemical, immunological and immunohistochemical assays of renal P450 enzymes. Cyclosporin caused impairment of renal function with an increase in renal-specific P450 content, but FK-506 and rapamycin did not. Laurate omega- and (omega-1)-hydroxylase activity increased in rats treated with rapamycin but decreased in those treated with FK-506. Prostaglandin A1 (PGA1) omega-hydroxylase activity increased in rats treated with FK-506 but was reduced by treatment with cyclosporin. Aminopyrine N-demethylase activity increased in rats treated with cyclosporin or FK-506, but not in those treated with rapamycin. Western-blot analysis revealed significant induction of P450, (similar to CYP2B4 of the rabbit P450 isozyme) in kidneys from rats treated with cyclosporin but not in those from rats receiving FK-506 or rapamycin. Histochemical studies clearly demonstrated a form of P450 such as CYP4A2 in the proximal tubules of rats treated with cyclosporin, but not in those of rats treated with FK-506 or rapamycin. These results show that although cyclosporin has a strong effect on renal P450 systems and induces such a system in kidney cortex (microsomal P450), FK-506 and rapamycin have no substantial effect on the induction of renal P450. These findings might clarify the nephrotoxicity induced by these immunosuppressive drugs.

Cyclosporine increases local glomerular synthesis of reactive oxygen species in rats: effect of vitamin E on cyclosporine nephrotoxicity

BACKGROUND

We report an investigation of the effects of cyclosporine (CsA) on kidney function, the glomerular synthesis of reactive oxygen species, the peroxidation of lipids, and the levels of thromboxane B2 (TXB2). The effect of the simultaneous administration of the antioxidant vitamin E (Vit E) and CsA in rats was also evaluated.

METHODS

Adult male Wistar rats were treated for 30 days with CsA (30 mg/kg/day), with Vit E (0.05 mg/ml), with CsA plus Vit E, or with the vehicle used for administration of CsA, namely 12.6% ethanol.

RESULTS

CsA induced kidney failure and increased the glomerular synthesis of superoxide anion, H2O2, malonyldialdehyde, and TXB2. Vit E minimized the adverse effects of CsA on kidney function and the glomerular synthesis of these compounds.

CONCLUSIONS

Our results suggest that the acute decrease in glomerular filtration rate induced by CsA might be mediated by the synthesis of reactive oxygen species and subsequent peroxidation of lipids, which increases the levels of TXB2. Treatment with Vit E prevented these effects, suggesting a possible role for antioxidants in the prevention of CsA nephrotoxicity.

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

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

Reevaluation of cyclosporine induced hepatotoxicity in the isolated perfused rat liver

Livers of male rats were perfused for 120 min in a recirculating hemoglobin-free system with different concentrations of cyclosporine (CS 2, 10, 50, 150 and 200 mg/l). CS produced damage to the livers in a dose dependent manner. The first sign of hepatotoxicity was a reduction of bile flow amounting to 50% already at 50 mg/l CS. At concentrations of 150 mg/l and 200 mg/l, CS lead to a nearly complete suppression of bile flow, furthermore to a release of cytosolic (GPT, glutamate-pyruvate transaminase, LDH, lactate dehydrogenase) and mitochondrial (GLDH, glutamate dehydrogenase) enzymes into the perfusate and to a decrease in hepatic oxygen consumption (30% at 200 mg/l CS). As a consequence of the reduced aerobic energy supply, hepatic ATP concentration declined (70% at 200 mg/l CS). The hepatic concentrations of reduced glutathione (GSH) were not changed but those of oxidized glutathione (GSSG) increased up to 5-fold by CS. Malondialdehyde (MDA) concentrations in the liver and in the perfusate were not affected consistently by CS. The toxic actions of CS in the isolated rat liver were not influenced (a) by the feeding status of the rats (fed or fasted before surgery) or (b) by addition of superoxide dismutase (SOD, 20 mg/l) and catalase (20 mg/l) to the perfusate 30 min before CS. On the other hand, CS-induced hepatic injury could be attenuated or inhibited completely by addition to the perfusate of (1) 2 mmol/l GSH; (2) 12 mmol/l serine; (3) 12 mmol/l glycine; (4) 0.09 mmol/l deferoxamine (DFO).

CONCLUSIONS

CS induces cholestasis at lower concentrations, probably by another mechanism(s) than the other signs of hepatotoxicity (enzyme release, ATP depletion). Several lines of evidence indicate a probable participation of reactive oxygen species in CS-induced hepatotoxicity. GSH, DFO, glycine and serine could provide therapeutic opportunities to prevent CS-induced hepatotoxicity in patients treated with high doses of CS.

Preventive effects of two PAF-antagonists, PMS 536 and PMS 549, on cyclosporin-induced LLC-PK1 oxidative injury

The present study was undertaken to evaluate the effects of platelet activating factor (PAF) antagonists, PMS 536 and PMS 549, on LLC-PK1 toxicity induced by Cyclosporin A (CsA). The LLC-PK1 cell line was used as an in vitro model. CsA cytotoxicity was determined in relation with ATP content. Alkaline phosphatase and N-acetyl-beta-glucosaminidase activities, which are directly correlated with tubular cell damage, were used as markers for renal injury. CsA alone provoked in the LLC-PK1 cell line a marked decrease in cell viability (55%) and membrane integrity (56%), and a significant increase in AP and NAG activities and in oxidized glutathione level. The ATP decrease and the ADP increase, resulting in a decline of the ATP/ADP ratio, is indicative of an anoxic energy charge. Co-treatment with CsA plus PMS 536 or PMS 549 resulted in a minor decrease in cell viability and in significant membrane integrity recovery. Moreover, the ATP depletion and the increase in ATP metabolites, hypoxanthine and uric acid induced by CsA were strongly prevented by PAF antagonists. In contrast, GSSG level remained high as in CsA-treated cells, but GSH level was in the range of controls. Our results suggest that both PAF antagonists attenuate CsA oxidative injury and prevent energy metabolism disturbances probably by maintaining cell integrity. The lipophilicity of both molecules may be responsible for membrane stabilization and may confer the protective effects observed in energy metabolism. The results obtained with PMS 536 and PMS 549 are indicative of interactions between PAF and CsA in renal injury and suggest the therapeutic potential of these PAF-antagonists against CsA-induced nephrotoxicity.