The natural product honokiol inhibits calcineurin inhibitor-induced and Ras-mediated tumor promoting pathways

Although calcineurin inhibitors (CNIs) are very useful in preventing allograft rejection, they can mediate a rapid progression of post-transplantation malignancies. The CNI cyclosporine A (CsA) can promote renal tumor growth through activation of the proto-oncogene ras and over-expression of the angiogenic cytokine VEGF; the ras activation also induces over-expression of the cytoprotective enzyme HO-1, which promotes survival of renal cancer cells. Here, we show that the natural product honokiol significantly inhibited CsA-induced and Ras-mediated survival of renal cancer cells through the down-regulations of VEGF and HO-1. Thus, honokiol treatment may help to prevent tumor-promoting effects of CsA in transplant patients.

Melatonin suppresses cyclosporine A-induced autophagy in rat pituitary GH3 cells

Cyclosporine A (CsA) is a powerful immunosuppressive drug with side effects including the induction of chronic nephrotoxicity including endoplasmic reticulum (ER) stress in tubular cells. Recently, it was reported that autophagy is induced by ER stress and serves to alleviate the associated deleterious effects. In the current study, CsA treatment (0-100 microm) decreased cell survival of rat pituitary GH3 cells in a dose-dependent manner. At concentrations ranging from 1.0 to 10 microm, CsA induced a dose-dependent increase in the expression of microtubule-associated protein 1 light chain 3 (LC3)-I and LC3-II. Cells treated with 2.5 microm CsA exhibited cytoplasmic vacuolation, indicating that CsA induces autophagy in rat pituitary GH3 cells. In the presence of 1.0-10 microm CsA, the expression of catalase decreased while that of the ER stress markers, ER luminal binding protein (BiP) and inositol-requiring enzyme 1 alpha (IRE1alpha), increased as compared those levels in untreated cells. These results suggested that CsA-induced autophagy is dependent on ER stress. To determine whether melatonin would protect cells against CsA-induced autophagy, we treated rat pituitary GH3 cells with melatonin in the presence of CsA. Melatonin treatment (100 and 200 microm) suppressed autophagy induced by 2.5 and 5 microm CsA. Furthermore, co-treatment with 100 microm melatonin inhibited LC3-II expression, and increased catalase and phosphorylated p-ERK levels in the presence of 2.5 and 5 microm CsA. BiP and IRE1alpha expression in melatonin-co-treated cells was superior to that in cells treated with 2.5 and 5 microm CsA alone. Thus, melatonin suppresses CsA-mediated autophagy in rat pituitary GH3 cells.

Role of sulphated polysaccharides from Sargassum Wightii in Cyclosporine A-induced oxidative liver injury in rats

BACKGROUND

Seaweeds or marine algae have long been made up a key part of the Asian diet, and as an antioxidant, sulphated polysaccharides have piqued the interest of many researchers as one of the ocean's greatest treasures. The present investigation suggests the therapeutic potential of sulphated polysaccharides from marine brown algae "Sargassum wightii" in Cyclosporine A (CsA)- induced liver injury. CsA is a potent immunosuppressive agent used in the field of organ transplantations and various autoimmune disorders. However, hepatotoxicity due to CsA remains to be one of the major clinical challenges.

METHODS

The effect of sulphated polysaccharides on CsA-induced hepatotoxicity was studied in adult male albino rats of Wistar strain, and the animals were randomized into four groups with six rats in each. Group I served as vehicle control. Group II rats were given CsA at a dosage of 25 mg/kg body weight, orally for 21 days. Group III rats were given sulphated polysaccharides at a dosage of 5 mg/kg body weight, subcutaneously for 21 days. Group IV rats were given sulphated polysaccharides simultaneously along with CsA, as mentioned in Group II for 21 days.

RESULTS

CsA provoked hepatotoxicity was evident from the decreased activities of hepatic marker enzymes. A significant rise in the level of oxidants, along with a striking decline in both the enzymic and non-enzymic antioxidants, marks the severity of oxidative stress in CsA-induced rats. This in turn led to enhanced levels of lipid peroxidation, 8-hydroxy-2-deoxy guanosine and protein carbonyls, along with a decrease in ATPase activities and alterations in lipid profile. Histopathological changes also strongly support the above aberrations. However, concomitant treatment with sulphated polysaccharides restored the above deformities to near control and prevented the morphological alterations significantly.

CONCLUSION

Thus, the present study highlights that sulphated polysaccharides can act therapeutically against CsA-induced hepatotoxicity.

Dyslipidemia can reduce the immunosuppressive effects of cyclosporine

AIMS

Dyslipidemia is a significant risk factor for the development of atherosclerotic disease and of chronic allograft rejection. Few data are available on the effects of dyslipidemia on the immunosuppressive action of immunosuppressive agents. We investigate the in vitro effects of lipids solution on the immunosuppressive action of cyclosporine (CsA).

METHODS

Peripheral blood mononuclear cells (PBMC) were PHA or OKT3 activated in vitro with/without different concentrations of Intralipid solution (INT, range 0.5% to 15%). CsA inhibition of activation was measured after a 3 day incubation, by adding H3-thimidine. The intracellular concentration of CsA was measured by radioimmunoassay and related to the CsA inhibitory effects.

RESULTS

Increasing INT concentration in the medium, CsA inhibition of PBMC activation by PHA or OKT3 was reduced from 72+/-13% to 8+/-2% and from 80+/-10% to 18+/-3%, respectively. A significant reduction of the intracellular CsA concentration was also evident with increasing INT concentrations and was related to the inhibitory activity of CsA.

CONCLUSIONS

These results suggest that dyslipidemia may reduce the availability of intracellular CsA concentration to inhibit the immune activation process and may explain the relationship between dyslipidemia and chronic allograft loss.

Conversion of immunosuppressive monotherapy from cyclosporin a to tacrolimus reverses bone loss in rats

Tacrolimus is used for transplant patients with refractory graft rejection and those with intolerance to cyclosporin (CsA), without the disfiguring adverse effects frequently attributed to CsA therapy. Since we have shown that CsA-associated bone loss can also affect alveolar bone, the purpose of this study was to evaluate the effects of conversion of monotherapy from CsA to tacrolimus on alveolar bone loss in rats. Groups of rats were treated with either CsA (10 mg/kg/day, s.c.), tacrolimus (1 mg/kg/day, s.c.), or drug vehicle for 60 and 120 days, and an additional group received CsA for 60 days followed by conversion to tacrolimus for a further 60-day period. Bone-specific alkaline phosphatase (BALP), tartrate-resistent acid phosphatase (TRAP-5b), calcium (Ca(2+)), interleukin (IL)-1beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) concentrations were evaluated in the serum. Analyses of bone volume, bone surface, number of osteblasts, and osteoclasts were performed. Treatment with CsA for either 60 or 120 days was associated with bone resorption, represented by lower bone volume and increased number of osteoclasts; serum BALP, TRAP-5b, IL-1beta, IL-6, and TNF-alpha were also higher in these animals. After conversion from CsA to tacrolimus, all the altered serum markers returned to control values in addition to a significant increase of bone volume and a lower number of osteoclasts. This study shows that conversion from CsA to tacrolimus therapy leads to a reversal of the CsA-induced bone loss, which can probably be mediated by downregulation of IL-1beta, IL-6, and TNF-alpha production.

Decision support tool to individualize cyclosporine dose in stable, long-term heart transplant recipients receiving metabolic inhibitors: overcoming limitations of cyclosporine C2 monitoring

BACKGROUND

Monitoring of the 2-hour post-dose sample (C(2)) for cyclosporine (CsA) has gained favor; however, choosing a single-point surrogate marker of therapeutic effect for a drug with extensive pharmacokinetic variability is problematic and has limitations.

METHODS

A Bayesian decision support tool was developed using published pharmacokinetic information implemented using ABBOTTBASE pharmacokinetic software. The model was evaluated in 47 stable heart transplant recipients who received concomitant administration of drugs known to inhibit CsA metabolism: diltiazem; ketoconazole; and a combination of diltiazem and ketoconazole.

RESULTS

A 3-point feedback strategy with samples collected at 0, 1 and 2 hours after an oral CsA dose was used to predict area under the concentration-time curve in the first 12 hours post-dose (AUC(0-12)). In Group A, patients who received CsA alone showed a good correlation between observed and model-predicted CsA AUC(0-12) (r(2) = 0.871, p < 0.001, precision of 12%, accuracy of 13%). Furthermore, the Bayesian model provided acceptable predictions in patients who received CsA with metabolic inhibitors: Group B (diltiazem), r(2) = 0.791, p < 0.001, precision of 19%, accuracy of 22%; Group C (ketoconazole), r(2) = 0.761, p < 0.001, precision of 4%, accuracy of 12%; and Group D (diltiazem plus ketoconazole), r(2) = 0.818, p < 0.001, precision of 14%, accuracy of 17%.

CONCLUSIONS

A Bayesian decision support tool is described that can predict CsA AUC(0-12) in a cohort of patients with variable CsA absorption who received metabolic inhibitors. Bayesian modeling offers a number of advantages over single point metrics that are used to adjust CsA dose and may provide another refinement to optimize CsA therapy.

Possible therapeutic effect of lipid supplementation on neurological complications in liver transplant recipients

Neurological complications (NCs) represent a serious problem following liver transplantation and may develop either because of various peri-operative factors or the toxicity of immunosuppression. Although the causality assessment of NCs can be particularly difficult in the setting of organ transplantation, calcineurin inhibitors (CNIs) might influence NCs to a certain extent, regardless of the etiology. Therefore, minimizing the influence of CNIs could be a reasonable strategy for alleviating NCs. Based on our hypothesis that lipid supplementation prevents lipophilic CNIs from crossing the blood-brain barrier, soybean oil was administered to five liver transplant patients with NCs. In all of these patients, the neurological symptoms improved without discontinuing or reducing the dose of CNIs. Thus, lipid supplementation might be able to reduce the adverse neurological effects of CNIs.

Discovery and synthesis of new immunosuppressive alkaloids from the stem of Fissistigma oldhamii (Hemsl.) Merr

Three new alkaloids (1-3) and twenty-one known compounds were isolated from the stem of Fissistigma oldhamii (Hemsl.) Merr. which was the ruler herb in an approved Traditional Chinese herbal formula used for treatment of rheumatoid arthritis in China and synthesis of one new immunosuppressive alkaloid was achieved. These compounds, including the crude extracts of this herb, exhibited strong activities in the inhibition of T and B cell proliferation.

Involvement of oxidative stress induction in Na+ toxicity and its relation to the inhibition of a Ca2+ -dependent but calcineurin-independent mechanism in Saccharomyces cerevisiae

Uridine 5'-hexadecylphosphate (UMPC16) inhibited the growth of Saccharomyces cerevisiae under a hypersaline stress condition with Na+ more strongly than the calcineurin inhibitor cyclosporine A (CsA). Additional Ca2+ supplementation similarly suppressed the inhibitory activities of UMPC16 and CsA on yeast cell growth in a medium with Na+. UMPC16, but not CsA, accelerated mitochondrial reactive oxygen species (ROS) generation in combination with Na+, suggesting its inhibition of a Ca2+ -dependent but calcineurin-independent mechanism for protection against Na+ toxicity.

TAURINE ATTENUATES HYPERTENSION AND RENAL DYSFUNCTION INDUCED BY CYCLOSPORINE A IN RATS

Cyclosporine A (CsA) is the first-line immunosuppressant used for the management of solid organ transplantation and autoimmune diseases. Nephrotoxicity is the major limitation of CsA use. Recent evidence suggests that reactive oxygen species (ROS) play an important role in mediating CsA-induced hypertension and nephrotoxicity. Taurine, the major intracellular free beta-amino acid, is known to be an endogenous anti-oxidant and membrane-stabilizing agent. The present study was designed to investigate the effects of taurine on CsA-induced oxidative stress, hypertension and renal dysfunction. 2. Animals were assigned into four groups of seven rats each as follows: (i) control group, receiving vehicle (olive oil; 1 mL/kg, s.c.); (ii) CsA group, given CsA (25 mg/kg per day, s.c.) for 21 days; (iii) taurine group, supplemented with taurine (1% in the drinking water); and (iv) taurine + CsA group, treated with taurine 3 days before and concurrently during CsA injections for 21 days. 3. Cyclosporine A administration elevated blood pressure, reduced serum nitric oxide (NO) levels and deteriorated renal function, as assessed by increased serum creatinine levels and proteinuria and reduced urine flow rate and creatinine clearance compared with vehicle-treated rats. Cyclosporine A induced oxidative stress, as indicated by increased renal tissue concentrations of thiobarbituric acid-reactive substances and reduced concentrations of renal glutathione, glutathione peroxidase and superoxide dismutase. Conversely, no change was noted in renal catalase activity. Moreover, the kidneys of CsA-treated rats showed interstitial inflammation and renal tubular atrophy. 4. Taurine markedly reduced elevated blood pressure, attenuated renal dysfunction and the reduction in serum NO levels and counteracted the deleterious effects of CsA on oxidative stress markers. Furthermore, taurine ameliorated CsA-induced morphological changes. 5. These data clearly indicate the protective potential of taurine against CsA-induced hypertension and nephrotoxicity and suggest a significant contribution of its anti-oxidant property to this beneficial effect.

Antioxidant supplementation enhances erythrocyte antioxidant status and attenuates cyclosporine-induced vascular dysfunction

The aim of this study was to determine the effects of dietary antioxidant supplementation with alpha-tocopherol and alpha-lipoic acid on cyclosporine-induced alterations to erythrocyte and plasma redox balance, and cyclosporine-induced endothelial and smooth muscle dysfunction. Rats were randomly assigned to either control, antioxidant, cyclosporine or cyclosporine + antioxidant treatments. Cyclosporine A was administered for 10 days after an 8-week feeding period. Plasma was analyzed for alpha-tocopherol, total antioxidant capacity, malondialdehyde and creatinine. Erythrocytes were analyzed for glutathione, methemoglobin, superoxide dismutase, catalase, glutathione peroxidase, glucose-6-phosphate dehydrogenase, alpha-tocopherol and malondialdehye. Vascular endothelial and smooth muscle function was determined in vitro. Antioxidant supplementation resulted in significant increases in erythrocyte alpha-tocopherol concentration and glutathione peroxidase activity in both of the antioxidant-supplemented groups. Cyclosporine administration caused significant decreases in glutathione concentration, methemoglobin concentration and superoxide dismutase activity. Antioxidant supplementation attenuated the cyclosporine-induced decrease in superoxide dismutase activity. Cyclosporine therapy impaired both endothelium-independent and -dependent relaxation of the thoracic aorta, and this was attenuated by antioxidant supplementation. In summary, dietary supplementation with alpha-tocopherol and alpha-lipoic acid attenuated the cyclosporine-induced decrease in erythrocyte superoxide dismutase activity and attenuated cyclosporine-induced vascular dysfunction.

Protective effect of L-propionylcarnitine in chronic cyclosporine-a induced nephrotoxicity

Cyclosporine (CyA) is an immunosuppressive agent used after solid organ transplantation, but its clinical use is limited by side effects, the most important of which is nephrotoxicity. In a previous work we demonstrated that L-propionylcarnitine (L-PC), a propionyl ester of L-carnitine, is able to prevent CyA-induced acute nephrotoxicity reducing lipid peroxidation in the isolated and perfused rat kidney. CyA administration was associated with a dose dependent increase in renovascular resistance prevented by a pretreatment with L-PC. The aim of the present study was to confirm L-PC protective effect, previously described in vitro, in an in vivo rat model. Chronic nephrotoxicity study was carried out for 28 days. L-PC was administered (i.p. 25 mg/kg b.w.) since the first day, while CyA treatment was performed for the last 21 days (by oral administration 25 mg/kg b.w.). We demonstrate that L-PC was able to significantly lower blood pressure in CyA treated animals and to prevent CyA induced decrease in creatinine clearance. Moreover renal tissue analysis revealed that L-PC was able to reduce lipid hydroperoxide content and morphological abnormalities associated to chronic CyA administration. In conclusion our study demonstrated for the first time in vivo that L-PC protects against functional and tissue damage associated to chronic CyA administration.

Curcumin, a diferuloylmethane, attenuates cyclosporine-induced renal dysfunction and oxidative stress in rat kidneys

Background

In India, Curcumin (CMN) is popularly known as "Haldi", and has been well studied due to its economic importance. Traditional Indian medicine claims the use of its powder against biliary disorders, anorexia, coryza, cough, diabetic wounds, hepatic disorder, rheumatism and sinusitis. This study was designed to examine the possible beneficial effect of CMN in preventing the acute renal failure and related oxidative stress caused by chronic administration of cyclosporine (CsA) in rats. CMN was administered concurrently with CsA (20 mg/kg/day s.c) for 21 days. Oxidative stress in kidney tissue homogenates was estimated using thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) content, superoxide dismutase (SOD), and Catalase (CAT). Nitrite levels were estimated in serum and tissue homogenates.

Results

CsA administration for 21 days produced elevated levels of TBARS and marked depletion of renal endogenous antioxidant enzymes and deteriorated the renal function as assessed by increased serum creatinine, Blood Urea Nitrogen (BUN) and decreased creatinine and urea clearance as compared to vehicle treated rats. CMN markedly reduced elevated levels of TBARS, significantly attenuated renal dysfunction increased the levels of antioxidant enzymes in CsA treated rats and normalized the altered renal morphology.

Conclusion

In conclusion our study showed that CMN through its antioxidant activity effectively salvaged CsA nephrotoxicity.

Pharmacokinetic and pharmacodynamic interactions of morin and cyclosporin

Morin is a flavonoid present in mulberry and herbs. We have reported that morin exerted anti-inflammatory activity on the activated macrophages. Cyclosporin (CsA) is a potent immunosuppressive agent with narrow therapeutic range, which is widely used for the treatments of autoimmune diseases and transplantation rejection. This study aimed to measure the effects of morin on the disposition of CsA in lymphoid and non-lymphoid tissues, and on the functions of immune cells in mice. CsA (Neoral, 10 mg/kg) was orally administered with and without a concomitant dose of morin (0, 50, 100, 200 mg/kg) to mice once daily for 2 weeks. CsA concentrations in blood, liver, kidney, and spleen were determined by a specific monoclonal fluorescence polarization immunoassay. The decreased levels of CsA in tissues were found well correlated to increased doses of morin. The coadministration of 200 mg/kg morin significantly decreased CsA in blood, liver, kidney, and spleen by 33%, 17%, 38%, and 45%, respectively. On the other hand, coadministration of morin decreased dramatically the nitric oxide production by the activated macrophages when compared to CsA treatment alone. Moreover, morin maintained the level of CsA-suppressed T helper 1 (Th1) type cytokine, although the CsA concentration in spleen was markedly reduced. In conclusion, morin coadministration profoundly reduced CsA concentration but did not significantly alter the CsA-suppressed Th1 immune response in mice.

Tetrahydrobiopterin prevents cyclosporine-induced vasomotor dysfunction

BACKGROUND

Cyclosporine A (CsA) is associated with negative side effects such as endothelial injury, which may lead to transplant vasculopathy. CsA can impair nitric oxide (NO) homeostasis. Therefore, tetrahydrobiopterin (BH4), a NO synthase cofactor, may limit endothelial injury by improving NO production. Our study examines the effect of CsA and BH4 exposure on endothelial function.

METHODS

Lewis rats were injected with CsA, BH4, CsA+BH4, or saline intraperitoneally daily for 2 weeks. With use of a small vessel myograph, thoracic aortic segments were assessed for endothelial-dependent (Edep) and independent relaxation after exposure to acetylcholine and sodium nitroprusside. Sensitivity to vasospasm was evaluated after exposure to endothelin (ET)-1.

RESULTS

CsA exposure resulted in impaired Edep vasorelaxation compared with control (P=0.01). BH4 attenuated the deleterious effects of CsA. Compared with control, all treatment groups demonstrated significantly increased sensitivity to ET-1. Furthermore, endothelial nitric oxide synthase expression in the thoracic aorta was reduced after CsA treatment, and this reduction was attenuated by BH4 therapy (P<0.01). ETA receptor expression in the aorta was increased after CsA treatment, but BH4 treatment prevented CsA-induced ETA over-expression (P=0.004). However, ETB receptor expression was increased by BH4 treatment compared with CsA and control (P=0.02).

CONCLUSION

Our findings suggest that CsA-induced vasomotor dysfunction is a result of alterations in both NO and ET-1 regulation and that BH4 may prevent the deleterious effects of CsA. However, the beneficial effects of BH4 are associated with increased sensitivity to ET-1. Therefore, a combination of BH4 and ET-1 blockade may prove to be an ideal combination for preservation of endothelial function.

Effect of colchicine on cyclosporine nephrotoxicity, reduction of TGF-beta overexpression, apoptosis, and oxidative damage: an experimental animal study

BACKGROUND

Proinflamatory and profibrotic cytokines may be responsible for the cyclosporine A nephrotoxicity. Increased levels of apoptosis, free oxygen redicals, and transforming growth factor beta (TGF-beta), may play an important roles in the pathogenesis of nephrotoxicity. In this experimental animal study, we sought to investigate the effects of colchicine on the cyclosporine nephrotoxicity.

METHOD

Twenty-four Wistar albino rats were divided into three groups: cyclosporine 15 mg/kg subcutaneously (SC); cyclosporine 15 mg/kg SC plus colchicine 30 mcg/kg orally; and a control group; equal doses of olive oil orally were administered to groups 1, 2, and 3. Renal function, cyclosporine levels, and serum malonyldialdehyde (MDA) levels were measured at the end of 4 weeks. Apoptosis, TGF-beta, and other findings were detected in renal tissue with the TUNEL method, with a immunohistochemical method, and with routine staining procedures, respectively.

RESULTS

There were significant differences in the values of mean creatinine clearance between group 1 and group 3 and between group 2 and group 3 (P < .05 for each comparison), but not between group 1 and group 2 (P > .05). MDA levels in group 1 were high compared with the control group (P < .05) with a trend toward elevation relative to group 2 but the results were not statistically significant (P > .05). Renal tubular vacuolization in group 1 and group 2 animal were greater than in the control group, but no significant difference were observed between any of the groups (P > .05). Mononuclear cell infiltration in group 1 and group 2 hosts were higher than the control group, but there was no significant differences between the groups (P > .05). Afferent arteriolar hyalinization was observed group 1 and 2 but not group 3. There was a statistically significant difference between group 1 and group 3 and between group 2 and group 3 (P < .05 for each comparison). The expression level of TGF-beta was higher in group 1 than group 2 or group 3 (P <.05 for each comparison) but group 2 and group 3 were similar (P > .05). Apoptotic cell death count of group 1 was higher than that in group 2 or group 3 (P < .05, for each comparison); moreover, group 2 also showed greater numbers of apoptotic cells than group 3 (P < .001). At the end of the 4 weeks, there was no intersititial fibrosis in any of the hosts.

CONCLUSION

While cyclosporine caused increased TGF-beta expression and apoptotic cell death in the renal tissue of rats colchicine prevented the increase in MDA serum levels, TGF-beta expression, and apoptosis in renal tissue. Our study suggests that colchicine may diminish the cyclosporine nephrotoxicity by its suppressing the expression of TGF-beta, apoptotic cell death, and MDA production.

Green tea extract attenuates cyclosporine A-induced oxidative stress in rats

Cyclosporine A (CsA) nephrotoxicity underweighs the therapeutic benefits of such a powerful immunosuppressant. Whether oxidative stress plays a role in such toxicity is not well delineated. We investigated the potential of green tea extract (GTE) to attenuate CsA-induced renal dysfunction in rats. Three main groups of Sprague-Dawley rats were used: CsA, GTE, and GTE plus CsA-receiving animals. Corresponding control groups were also used. CsA was administered in a dose of 20mg kg(-1) day(-1), i.p., for 21 days. In the GTE/CsA groups, the rats received different concentrations of GTE (0.5, 1.0 and 1.5%), as their sole source of drinking water, 4 days before and 21 days concurrently with CsA. The GTE group was treated with 1.5% concentration of GTE only for 25 days. A concomitant administration of GTE, to CsA receiving rats, markedly prevented the generation of thiobarbituric acid-reacting substances (TBARS) and significantly attenuated CsA-induced renal dysfunction as assessed by estimating serum creatinine, blood urea nitrogen, uric acid and urinary excretion of glucose. A considerable improvement in terms of reduced glutathione content and activity of antioxidant enzymes in the kidney homogenate of the GTE/CsA-receiving rats was observed. The activity of lysosomal enzymes, N-acetyl-beta-glucosaminidase, beta-glucuronidase and acid phosphatase was significantly inhibited following GTE co-administration. Our data prove the role of oxidative stress in the pathogenesis of CsA-induced kidney dysfunction. Supplementation of GTE could be useful in reducing CsA nephrotoxicity in rats. However, clinical studies are warranted to investigate such an effect in human subjects.

Long-term Levothyroxine Treatment Decreases the Oral Bioavailability of Cyclosporin A by Inducing P-glycoprotein in Small Intestine

We have noticed that the trough level of blood concentration of cyclosporin A (CyA) tends to be lower in patients receiving long-term oral levothyroxine (LTX) than in patients not receiving LTX. We confirmed this clinical observation in experiments using Wistar rats orally given LTX (8 microg/kg) or saline (control) for 3 weeks, followed by CyA (10 mg/kg). The LTX treatment had little effect on the blood concentrations of CyA after i.v. administration, whereas they were decreased significantly after p.o. administration. After p.o. administration, the value of the area under the blood concentration-time curve from 0 to 24 hr and the bioavailability of CyA in the LTX group were decreased to only about one-fifth and a quarter of those in the control group, respectively. After treatment with LTX, the expression levels of mdr1a, mdr1b and CYP3A2 mRNAs in the duodenum were markedly increased to about twice the control, but in jejunum, ileum and liver the expression levels were little changed. These findings suggest that the absorption of CyA, which occurs mainly from the upper intestine, is reduced as a result of efflux transport via P-glycoprotein induced by LTX. In conclusion, careful monitoring of CyA levels is required in the event of LTX administration to patients receiving immunotherapy with CyA.

EphrinB1 Is Essential in T-cell-T-cell Co-operation during T-cell Activation

Eph kinases are the largest family of receptor tyrosine kinases, and their ligands are ephrins (EFNs), which are also cell surface molecules. We have very limited knowledge about the expression and function of these kinases and their ligands in the immune system. In this study we investigated the effect of EFNB1 on mouse T-cells. EFNB1 and the Eph kinases it interacts with (collectively called EFNB1 receptors (EFNB1R)) were expressed on T-cells, B cells, and monocytes/macrophages. Some T-cells were double positive for EFNB1 and EFBB1R. Solid phase EFNB1 in the presence of suboptimal TCR ligation augmented T-cell responses in terms interferon-gamma secretion, proliferation, and cytotoxic T lymphocyte activity but not interleukin-2 production. After T-cell receptor (TCR) ligation, EFNB1R congregated to TCR caps, and then both of them translocated to raft caps. This provides a morphological basis for EFNB1R to enhance TCR signaling. Further downstream of the signaling pathway, EFNB1R stimulation led to increased LAT (linker for activation of T-cells) phosphorylation and p44/42 and p38 MAPK activation. Similar to CD28 costimulation, EFNB1R costimulation was insensitive to cyclosporin A inhibition. On the other hand, unlike the former, EFNB1R costimulation failed to activate Akt, which is essential in triggering interleukin-2 production. Our study suggests that EFNB1 is pivotal in T-cell-T-cell costimulation and in reducing T-cell response threshold to antigen stimulation.

Diffusion MR findings in cyclosporin-A induced encephalopathy

Cyclosporin encephalopathy is a well-known entity, which is clinically characterized by altered mental status, vision problems, focal neurological deficits and seizures. The exact pathophysiology of the cyclosporin encephalopathy has not yet been defined. We report the diffusion-weighted MR imaging and proton MR spectroscopy findings in a case of cyclosporin encephalopathy. The white-matter lesions with reversible restricted diffusion supported the hypothesis of reversible vasospasm induced by the cyclosporin.

S-Adenosylmethionine protects against intrabiliary glutathione degradation induced by long-term administration of cyclosporin A in the rat

We investigate the ability of S-adenosylmethionine (SAMe) to antagonize the cyclosporine A (CyA)-induced inhibition of biliary glutathione efflux induced by long-term administration of CyA (10 mg/kg per day-CyA10 or 20 mg/kg per day-CyA20 for 4 weeks) in rats. CyA treatment reduced the liver content of total glutathione and caused a significant increase in the oxidized-to-reduced glutathione ratio and the thiobarbituric acid-reactive substances (TBARS) concentration. When the rats were concurrently treated with SAMe (10 mg/kg twice daily) and CyA, all these parameters did not significantly differ from control values. Treatment with CyA induced a significant increase in liver GGT activity that was attenuated by coadministration of SAMe. Biliary efflux of total glutathione was significantly reduced in animals treated with CyA. These changes were abolished by SAMe administration. Following inhibition of the intrabiliary catabolism of the tripeptide by acivicin, glutathione efflux rates increased to a lesser extent in animals cotreated with SAMe when compared to those receiving only CyA. The significant decrease in biliary efflux of oxidized glutathione induced by CyA was totally (S + CyA10) or partially (S + CyA20) prevented by coadministration of SAMe. Our observations confirm that SAMe cotreatment in rats antagonizes CyA-induced inhibition in the biliary efflux of glutathione and suggest that protection against intrabiliary glutathione degradation plays a major role in this protective effect.

Phosphodiesterase type 5 inhibition ameliorates nephrotoxicity induced by cyclosporin A in spontaneous hypertensive rats

Our recent study suggests that there is a reciprocal mechanism to maintain cGMP content, via both a decrease in cGMP degradation (decrease in cGMP-phosphodiesterase activity) and an increase in synthesis of cGMP (increase in guanylate cyclase activity) in the kidney of cyclosporin A-treated rats. We undertook this study to clarify the role of cGMP-phosphodiesterase in cyclosporin A nephrotoxicity by evaluating N-(3,4-dimethoxybenzyl)-2-[[(1R)-2-hydroxy-1-methylethyl]amino]-5-nitrobenzamide (FR226807), a phosphodiesterase type 5 inhibitor, in an animal model. Male spontaneous hypertensive rats (SHR) were treated with cyclosporin A (50 mg/kg) for 2 weeks or with cyclosporin A and FR226807 (3.2 mg/kg or 10 mg/kg) for 2 weeks. Cyclosporin A-treated rats showed renal dysfunction and histological change compared with vehicle-treated rats. Administration of FR226807 improved the renal dysfunction (increase in serum creatinine and fractional excretion of sodium, and decrease in creatinine clearance) as well as the pathological changes (tubular vacuolization) induced by cyclosporin A in SHR. At the molecular level, administration of FR226807 resulted in a further increase in cGMP content in the kidney, aorta and platelets from cyclosporin A-treated rats. Our present study demonstrates that cGMP-phosphodiesterase plays an important role in the cyclosporin A nephrotoxicity and also suggests that further inhibition of cGMP-phosphodiesterase is a potential pharmacological target for preventing cyclosporin A nephrotoxicity.

The protective effect of taurine against cyclosporine A-induced oxidative stress and hepatotoxicity in rats

Cyclosporine A (CsA) is the immunosuppressor which is most frequently used in transplant surgery and in the treatment of autoimmune diseases. Oxidative stress has been implicated as one of the possible mechanisms of CsA-induced hepatotoxicity. The present investigation examined the ability of taurine as an antioxidant to protect against CsA-induced oxidative stress and hepatotoxicity. CsA hepatotoxicity was induced by subcutaneous injection of CsA at a dose of 20mg/kg body weight daily for 21 days. Hepatotoxicity was assessed by reduced serum total protein level and increased serum levels of gamma glutamyl transferase (GGT), alanine aminotransferase (ALT), and aspartate aminotransaminase (AST). CsA treatment increased lipid peroxidation measured as thiobarbituric acid reactive substances (TBARS) concentration and decreased reduced glutathione (GSH) content and activities of catalase and glutathione peroxidase (GSH-Px) in the rat liver. Taurine administration (1% in the drinking water) for 3 days before and concurrently during CsA injections improved liver functions, as indicated by decline of serum transaminases and GGT levels and elevation of serum total protein. Moreover, taurine significantly reduced hepatic TBARS and increased GSH content and catalase and GSH-Px activities in the hepatic tissue. These results indicate that taurine has a protective action against CsA hepatotoxicity and suggest that taurine may find clinical application against a variety of toxins where cellular damage is a consequence of reactive oxygen species.

Inhibition of brush border dipeptidase with cilastatin reduces toxic accumulation of cyclosporin A in kidney proximal tubule epithelial cells

BACKGROUND

Cilastatin reduces nephrotoxicity associated with cyclosporin A (CyA) in solid organ and bone marrow transplantation. This appears to be unrelated to changes in renal haemodynamics or CyA metabolism. How cilastatin induces this protection is unclear, but it could result from changes on accumulation of CyA proximal cells.

METHODS

We investigated the effects of cilastatin on primary cultures of pig kidney proximal tubule epithelial cells (PTECs) treated with CyA and FK506. Cell membrane fluidity and membrane-bound cholesterol-rich raft (MBCR) distribution were evaluated by fluorescence microscopy, and CyA transport by radioimmunoassay. Changes in CyA- and FK506-induced apoptosis were also evaluated by electron and light microscopy, flow cytometry, and detection of cytoplasmic nucleosones by enzyme-linked immuosorbent assay.

RESULTS

CyA caused a dose-dependent reduction of cell membrane fluidity, which was prevented by pre-treating PTECs with cilastatin. Cilastatin also inhibited CyA transport across membranes and reduced recovery of CyA in mitochondria and membrane-bound fractions from cilastatin-treated PTECs. This effect was not related to an altered distribution of MBCRs, which are essential for CyA transport. Cilastatin protected against CyA- and FK506-induced apoptosis.

CONCLUSIONS

Prevention of CyA-induced reduction of cell membrane fluidity and inhibition of CyA transport are features of cilastatin's direct effects on PTECs. Unaltered distribution of MBCRs in the presence of cilastatin suggests that cilastatin binding to raft-bound dipeptidases, rather than MBCR modifications, causes interference with CyA transport. These results provide additional insight into the mechanisms and scope of cilastatin nephroprotection.

Effects of S-adenosylmethionine on intrabiliary glutathione degradation induced by long-term administration of cyclosporin A in the rat

We investigate the ability of S-adenosylmethionine (SAMe) to antagonize the cyclosporine A (CyA)-induced inhibition of biliary glutathione efflux induced by long-term administration of CyA (10 mg/kg per day-CyA(10) or 20 mg/kg per day-CyA(20) for 4 weeks) in rats. CyA treatment reduced the liver content of total glutathione and caused a significant increase in the oxidized-to-reduced glutathione ratio and the thiobarbituric acid-reactive substances (TBARS) concentration. When the rats were concurrently treated with SAMe (10 mg/kg twice daily) and CyA, all these parameters did not significantly differ from control values. Treatment with CyA induced a significant increase in liver GGT activity that was attenuated by coadministration of SAMe. Biliary efflux of total glutathione was significantly reduced in animals treated with CyA. These changes were abolished by SAMe administration. Following inhibition of the intrabiliary catabolism of the tripeptide by acivicin, glutathione efflux rates increased to a lesser extent in animals cotreated with SAMe when compared to those receiving only CyA. The significant decrease in biliary efflux of oxidized glutathione induced by CyA was totally (S + CyA(10)) or partially (S + CyA(20)) prevented by coadministration of SAMe. Our observations confirm that SAMe cotreatment in rats antagonizes CyA-induced inhibition in the biliary efflux of glutathione and suggest that protection against intrabiliary glutathione degradation plays a major role in this protective effect.

Effect of probucol on the oral bioavailability of cyclosporine A

We have previously reported the reduction in oral bioavailability of cyclosporine A (CsA) by probucol, a lipid-lowering drug. To evaluate the mechanism, we examined the effect of probucol on the transport of CsA across Caco-2 cell monolayers, on the influence of CsA pharmacokinetics in rats, and on the change of ultraviolet-absorption spectrum of the drug. Pretreatment with probucol (50 microM) inhibited (P < 0.001) both the apical-to-basal (-73.1%) and basal-to-apical (-77.8%) fluxes of [3H]-CsA. In rats, probucol orally given 6 h after, but not simultaneous with CsA did not decrease peak CsA concentration or area under the blood CsA concentration-time curve following a single oral dosing of CsA after the pretreatment with probucol for 7 days. These data indicate that P-glycoprotein-mediated active transport from intracellular to apical is not involved in the mechanism of probucol-CsA interaction, and absorption of CsA decreases in the presence of probucol in the gastrointestinal tract. In difference spectral analysis, probucol reduced the absorption peak of CsA in a concentration-dependent manner, indicating that probucol could form a complex with CsA. These results suggest that probucol interferes with CsA absorption probably by physicochemical mechanism such as complex formation, but not the enhancement of P-glycoprotein function.

Calcineurin inhibitor-associated early renal insufficiency in cardiac transplant recipients: risk factors and strategies for prevention and treatment

Cardiac transplantation is the definitive treatment for eligible patients with end-stage cardiac failure. Techniques have evolved to reduce surgical mortality to under 5%. Immediate and subsequent long-term survival is more dependent on acute and chronic rejection and the complications of immunosuppressive therapy. Ten-year survival is greater than 50%.The success of transplantation over the last 20 years has been largely due to the advances in immunosuppression. The most notable and dramatic milestone was the introduction of cyclosporine in the early 1980s, which resulted in a significant improvement in allograft and patient survival. Cyclosporine is a peptide that inhibits the immune system by suppressing T-helper cell activation via inhibition of calcineurin, a critical intracellular enzyme. Tacrolimus has a similar (but not identical) mechanism of action, and was introduced in the 1990s. Drugs such as cyclosporine and tacrolimus, generically referred to as calcineurin inhibitors, have become the cornerstones of immunosuppressive protocols. As a group, calcineurin inhibitors have adverse effects, including neurotoxicity, hypertension, and nephrotoxicity, which complicate their use. Early renal insufficiency manifests as postoperative oliguria (<50 mL/h urine output) or rising serum creatinine levels. There are a variety of postulated causes for calcineurin inhibitor-associated early renal insufficiency including direct calcineurin inhibitor-mediated renal arteriolar vasoconstriction, increased levels of endothelin-1 (a potent vasoconstrictor), as well as decreased nitric oxide production and alterations in the kidney's ability to adjust to changes in serum tonicity. Once early renal insufficiency occurs, no single treatment has been shown to be effective. Approaches discussed in this paper include reduction in calcineurin inhibitor dosages, as well as various drugs to promote increased renal perfusion such as misoprostol and dopamine. In addition, the paper emphasizes the importance of ruling out other causes of renal insufficiency in the early postoperative period, including volume depletion, depressed cardiac output, and mechanical obstruction to urine flow. Given that there is no highly efficacious treatment for this syndrome, ways to avoid its occurrence are desirable. One paper is referenced that suggests that avoidance of rapid changes in tacrolimus level during the first three days of therapy is associated with a low occurrence of early renal insufficiency.

[Clinical use of the interaction between cyclosporine A and its inhibitors]

This article concerns cyclosporine A and cyclosporine--sparing agents. The drugs are evaluated due to their clinical usefulness in elevating cyclosporine blood level and their safety in long-term administration. We analyzed imidazole antifungal agents, calcium channel blockers and, additionally, pharmacological properties of cyclosporine A.

Calcineurin-independent inhibition of mitochondrial Ca2+ uptake by cyclosporin A

1. Cyclosporin A (CsA) is a widely used compound because of its potent immunosupressive properties, derived mainly from the inhibition of calcineurin, and also because of its ability to block the mitochondrial permeability transition pore (PTP). This second effect has been involved in the protection against apoptosis mediated by release of mitochondrial factors. We show here that CsA (1-10 microm) has an additional effect on Ca(2+) homeostasis in mitochondria that cannot be attributed to inhibition of PTP. 2. By measuring specifically mitochondrial [Ca(2+)] with targeted aequorin, we show that CsA inhibited Ca(2+) entry into mitochondria both in intact and in permeabilized cells, and this effect was stronger when Ca(2+) entry was triggered by low cytosolic [Ca(2+)], below 5 microm. 3. Inhibition of mitochondrial Ca(2+) uptake required micromolar concentrations of CsA and was not mimicked by other inhibitors of calcineurin such as FK-506 or cypermethrin, nor by a different inhibitor of the PTP, bongkrekic acid. 4. CsA blocked the increase in mitochondrial Ca(2+) uptake rate induced by the mitochondrial Ca(2+) uniporter activator SB202190. 5. Our results suggest that CsA inhibits Ca(2+) entry through the Ca(2+) uniporter by a mechanism independent of the inhibition of PTP or calcineurin. This effect may contribute to reduce depolarization and Ca(2+) overloading in mitochondria after cell stimulation, and thus cooperate with the direct inhibition of PTP to prevent apoptosis.

Effect of cyclophosphamide on serum cyclosporine levels at the conditioning of hematopoietic stem cell transplantation

We retrospectively analyzed the factors that affect serum cyclosporine (CsA) concentrations up to day 14 after allogeneic hematopoietic stem cell transplantation (HSCT). In all, 103 transplant recipients who received MTX and CsA for acute GVHD prophylaxis were analyzed. No significant relationships between serum CsA concentrations and gender, age, serum creatinine levels, AST/ALT levels, or antibiotic/fluconazole administration were found by comparing median CsA concentrations or by using longitudinal or regression multivariate analyses. However, the mean of the median serum CsA concentration in patients (n=54) receiving the regimen containing cyclophosphamide (CY) (149.7 ng/ml; 95% confidence interval (CI): 132.1-167.4) was significantly (P<0.0001) lower than that in patients (n=49) receiving the non-CY regimen (217.3 ng/ml; 95% CI: 198.9-235.6). Longitudinal analysis and regression multivariate analysis showed that only administration of CY had a significant effect on the serum CsA concentration. Our results suggest that administration of CY during conditioning can reduce the effects on serum CsA concentrations during the 2 weeks following HSCT. The mechanism of this effect is not clear, but it may be due to the autoinduction of CY.

Rapamycin antagonizes cyclosporin A- and tacrolimus (FK506)-mediated augmentation of linker for activation of T cell expression in T cells

The discovery of new immunosuppressive drugs such as rapamycin, cyclosporin A (CsA) and tacrolimus (FK506) has been very useful for preventing graft rejection and autoimmune disease. However, these drugs are not specific, and are associated with side-effects and toxicities. Therefore, understanding the molecular mechanisms of these drugs is important for designing specific immunosuppressants. Here, we show that in contrast to CsA and FK506, rapamycin blocks activation-induced expression of the linker for activation of T cells (LAT), a signaling molecule critical for initiating TCR signaling. Thus, whereas CsA and FK506 strongly enhanced TCR- and phorbol myristate acetate-induced LAT expression in T cells, rapamycin effectively inhibited activation-induced LAT expression. Importantly, these opposite effects were mutually antagonistic, as rapamycin acted as a potent antagonist for both CsA and FK506. Because CsA, unlike FK506 and rapamycin, does not bind to the intracellular immunophilin FK-binding protein (FKBP), the antagonism between these drugs is not simply due to competition for intracellular FKBP. Accordingly, RNA and protein stability analyses suggest inhibition by rapamycin at the translational level. Given the important role of LAT in initiating T cell activation, our data suggests that the effects of rapamycin, CsA and FK506 on T cell activation involve regulating early T cell signaling. These findings refine our understanding of the manifold effects of these immunosuppressants, thus providing insight into the drastic physiological contrasts observed between these drugs.

Amelioration of cyclosporin A effect on microvasculature by endothelin inhibitor

BACKGROUND

We have previously shown that endothelial injury by cyclosporin A (CyA) is associated with an increased endothelin-1 (ET-1) release. We now sought to determine, in an animal model of angiogenesis, if inhibiting the effect of ET-1 on endothelial cells (ECs) would reverse the CyA-mediated endothelial injury in an animal model of angiogenesis.

METHODS

An angiogenic mixture of Matrigel (0.5 ml), fibroblast growth factor (1 ng/ml), vascular endothelial growth factor (100 ng/ml), and heparin (64 unit/ml) was injected as a subcutaneous plug in the flank of C3H mice (n = 5). In experimental groups CyA (20 mg/ml), CyA, and BQ 123 (ET-A receptor antagonist), CyA and PD 142893 (ET-A and ET-B receptor antagonist), or CyA and ET-1 antibody were added to the angiogenic mixture. Angiogenesis in the mixture was quantified by modified planimetric point counting method in skin/Matrigel cross-sections stained with factor VIII to highlight endothelial neocapillaries. Mean +/- SD of angiogenic area was analyzed with analysis of variance and Bonferroni test. The survival curves obtained by Kaplan-Meier analysis were compared between the groups, and the statistical significance of survival and mortality rates was computed by log rank's and Fisher's exact test, respectively.

RESULTS

The mean +/- SD of angiogenic area in control animals (without CyA in the angiogenic mixture) was 56.76 +/- 4.2. CyA inhibited angiogenesis in the subcutaneous angiogenic plug. Adding CyA to the angiogenic mixture significantly reduced angiogenic area (5.33 +/- 1.4, P <.001) while vehicle for CyA had no such effect (56.33 +/- 3.8, P =.10). Polyclonal ET-1 antibody or PD 142893 ameliorated the effect of CyA, whereas BQ 123 did not. The mean angiogenic areas in animals with ET-1 antibody, PD 142893, or BQ 123 in the angiogenic mixture were 57.20 +/- 7.5 (P =.06), 46.00 +/- 11.5 (P = 1.0), 8.60 +/- 2.9 (P <.001), respectively.

CONCLUSIONS

Our data show that blocking ET-B receptors specifically ameliorates the microvascular injury to the neocapillaries in angiogenesis caused by CyA. Antiendothelin-1 antibody and ETR antagonist (PD 142893) could, therefore, reduce the ill effects of CyA on microvascular endothelium.

Antioxidant nutrients protect against cyclosporine A nephrotoxicity

The immunosuppressive drug cyclosporine A (CsA) has been successfully used in several diseases with immunological basis and in transplant patients. Nephrotoxicity is the main secondary effect of CsA treatment. Although the mechanisms of nephrotoxitity are not completely defined, there is evidence that suggests the role of reactive oxygen species (ROS) in its pathogenesis. It has been demonstrated in numerous in vivo and in vitro experiments that CsA induced renal failure and increased the synthesis of ROS, thromboxane (TX) and lipid peroxidation products in the kidney. Furthermore, CsA modified the expression and activity of several renal enzymes (ciclooxygenase, superoxide-dismutase, catalase and glutathione-peroxidase). Antioxidant nutrients (e.g. Vitamins E and C) can neutralize some of the effects that CsA produced in the kidney. Thus, Vit E inhibited the synthesis of ROS and TX and the lipid peroxidation process induced by CsA in kidney structures. Antioxidants can also improve renal function and histological damage produced by CsA administration. Although there are few data in humans treated with CsA, the possibility exists that antioxidants can also neutralize CsA nephrotoxicity and LDL oxidation. Thus, antioxidant nutrients could have a therapeutic role in transplant patients treated with CsA.

Isosorbide-5-mononitrate treatment prevents cyclosporin A-induced platelet hyperactivation and the underlying nitric oxide-cyclic guanosine-3',5'-monophosphate disturbances

INTRODUCTION

The clinical use of cyclosporin A (CsA) is commonly associated with the development of hypertension and increased risk of thromboembolic events. Decreased endothelium-dependent relaxation and increased platelet activation seems to be involved on those side effects, but the underlying mechanisms are not yet elucidated. The present study aimed to evaluate the CsA effect on the platelet NO-cyclic guanosine-3',5'-monophosphate (cGMP) pathway and the putative benefits of concomitant isosorbide-5-mononitrate (IS-5-MN) administration on CsA-induced hypertension and on platelet hyperactivation.

MATERIALS AND METHODS

Blood pressures, platelet NO synthase activity and cGMP content, intracellular free calcium concentration ([Ca2+]i) and whole blood platelet aggregation were assessed in three rat groups orally treated, during 7 weeks, with the following diets: orange juice (control group), 5 mg/kg/day of CsA (CsA group) and 150 mg/kg/day, b.i.d., of IS-5-MN for 2 weeks and IS-5-MN plus 5 mg/kg/day of CsA for 7 weeks (IS-5-MN+CsA group).

RESULTS

IS-5-MN treatment has prevented hypertension development obtained in the solely CsA-treated rats. CsA treatment has inhibited NOS activity, which was reverted by the concomitant IS-5-MN and CsA administration. On the contrary, platelets from CsA-treated rats had cGMP content increased when compared with the control rats. The variation obtained when ISMN was present was less predominant. Therefore, the organic nitrate treatment has prevented platelet hyperactivation, namely, by decreasing thrombin-evoked [Ca2+]i and collagen-evoked platelet aggregation, when compared with the solely CsA-treated group. The preventive effect of IS-5-MN was reinforced by electron microscopy studies of platelet activation.

CONCLUSIONS

By increasing [Ca2+]i and aggregation, CsA induces platelet hyperactivation and simultaneously increases cGMP content, which might represent a compensatory inhibitory mechanism. The concomitant IS-5-MN treatment prevents the above-mentioned platelet hyperreactivity and tends to normalize the NO-cGMP pathway as well as the development of hypertension.

Hydrocortisone has a protective effect on CyclosporinA-induced cardiotoxicity

CyclosporinA (CsA) is an immunosuppressive drug which induces severe adverse effects such as cardiotoxicity and nephrotoxicity. In several therapeutic protocols CsA is used in association with corticosteroids to obtain better therapeutic results. Recently, our studies showed that CsA increases blood pressure while inhibit Nitric Oxide (NO) production in vivo. In this study we evaluated in rat cardiomyocytes the effects of CsA, used alone or in association with Hydrocortisone (HY), on intracellular calcium concentration, NO production and lipid peroxidation (MDA level). Our results demonstrated that CsA increased intracellular calcium and such effect was dose-dependent. HY used alone, slightly decreased intracellular calcium, while dramatically reduced CsA-induced calcium fluxes. CsA (3.2 microM) increased lipid peroxidation and this effect was blunted by HY. Both CsA and HY inhibited NO production in rat cardiomyocytes acting on this pathway synergically. Our results demonstrated that in rat cardiomyocytes, CsA toxicity is due to a calcium overload, which in turn induce lipid peroxidation and determines oxidative stress-induced cell injury. Treatment with HY effectively inhibits CsA-induced toxicity, decreasing lipid peroxidation as well as calcium intracellular concentration. Our findings seem to suggest that glucocorticoids may be effective in reducing CsA-induced cardiotoxicity at concentrations which are consistent with current therapeutic doses.

Comparison of the effects of polysaccharides from wood-cultured and bag-cultured Ganoderma lucidum on murine spleen lymphocyte proliferation in vitro

AIM

To compare the influences of wood-cultured Ganoderma lucidum polysaccharides (Gl-PS-WC) and bag-cultured Ganoderma lucidum polysaccharides (Gl-PS-BC) on the proliferation activities of murine spleen lymphocytes in vitro, and investigate whether Gl-PS-BC can be substituted for Gl-PS-WC.

METHODS

Mixed lymphocyte culture (MLC) reaction, lymphocyte proliferation induced by concanavalin A (Con A, 1 mg.L-1) or lipopolysaccharide (LPS, 5 mg.L-1), MLC reactions inhibited by immunosuppressive drugs, cyclosporine A (CsA, 0.1 mg.L-1), mitomycin (Mit C, 0.1 mg.L-1), or antitumor drug, etoposide (VP-16, 0.1 mg.L-1), were detected in the presence or absence of Gl-PS-WC and Gl-PS-BC in the concentration range of 0.2-12.8 mg.L-1.

RESULTS

Two kinds of polysaccharides were shown to promote MLC in the range of 0.2-12.8 mg.L-1, increase lymphocyte proliferation induced by Con A or LPS and antagonize the inhibitory effects of CsA, Mit C or VP-16 on MLC. No significant difference was observed between these two kinds of polysaccharides in selected concentrations.

CONCLUSION

Gl-PS-WC and Gl-PS-BC showed similar effects on the proliferation activities of murine spleen lymphocytes in vitro.

Cyclosporin-A differentially affects apoptosis during in vivo rat thymocyte maturation

Maturation arrest and interference with selection are two well-documented effects of cyclosporin-A (CsA) on the thymus. We recently hypothesized that these effects are related and owing to the reduced T-cell receptor (TCR)-CD3 complex-mediated signal transduction in thymocytes upon CsA treatment. In this hypothesis, the maturation arrest is the result of the additional depletion of thymocytes that normally survive by positive selection, whereas the impaired self-tolerance induction is caused by an increased survival of thymocytes that normally undergo negative selection. In this view, it is anticipated that CsA differentially affects thymocyte apoptosis during in vivo thymocyte maturation. Indeed, we report in this study a strong increase in apoptotic cells in the thymic cortex on in situ analysis. Simultaneously, the number of apoptotic cells had decreased at the cortico-medullary zone which is held to be the site for negative selection. Rapamycin (Rapa) also interferes with thymocyte maturation by inhibiting cytokine-driven proliferation. Hence, Rapa preferentially affects the early maturational stages of thymocyte development and is considered not to alter thymocyte selection and subsequent apoptotic events. Indeed, the number of apoptotic events appears not to be altered. However, possibly owing to the decrease in cortical macrophages, the apoptotic cells revealed an atypical enumeration around blood vessels. Taken together, our results favour the hypothesis that the dominant effect of CsA on the thymus is the reduction of the TCR-CD3 complex-mediated signal transduction in thymocytes upon interaction with stromal cells. Furthermore, the preferential localization of apoptotic cells next to blood vessels upon Rapa administration may indicate that endothelial cells are a back-up system for the removal of apoptotic cells.

Effects of thyroxine on hyperkalemia and renal cortical Na+, K+ - ATPase activity induced by cyclosporin A

Cyclosporin A (CsA)-induced hyperkalemia is caused by alterations in transepithelial K+ secretion resulting from the inhibition of renal tubular Na+, K+ -ATPase activity. Thyroxine enhances renal cortical Na+, K+ -ATPase activity. This study investigated the effect of thyroxine on CsA-induced hyperkalemia. Sprague-Dawley rats were treated with either CsA, thyroxine, CsA and thyroxine, or olive-oil vehicle. CsA resulted in an increase in BUN and serum K+, along with a decrease in creatinine clearance, fractional excretion of potassium, and renal cortical Na+, K+ -ATPase activity, as compared with oil vehicle administration. Histochemical study showed reduced Na+, K+ -ATPase activity in the proximal tubular epithelial cells of the CsA-treated compared with the oil-treated rats. Histologically, isometric intracytoplasmic vacuolation, disruption of the arrangement and swelling of the mitochondria, and a large number of lysosomes in the tubular epithelium were characteristic of the CsA-treated rats. Co-administration of thyroxine prevented CsA-induced hyperkalemia and reduced creatinine clearance, Na+, K+ -ATPase activity, and severity of the histologic changes in the renal tubular cells when compared with the CsA-treated rats. Thyroxine increased the fractional excretion of potassium via the preservation of Na+, K+ -ATPase activity in the renal tubular cells. Thus, the beneficial effects of thyroxine may be suited to treatment modalities for CsA-induced hyperkalemia.

Selective angiotensin II type 1 receptor blockade ameliorates cyclosporine nephrotoxicity

Nephrotoxicity associated with cyclosporine A (CsA) administration is characterized by marked renal vasoconstriction, interstitial fibrosis and arteriolar hypertrophy. The molecular mechanisms of CsA nephrotoxicity are not well characterized, but previous studies have demonstrated that angiotensin II (Ang II), the primary mediator of renin-angiotensin system (RAS) cascade plays a role in its pathogenesis. Recent studies also suggest an involvement of reactive oxygen species (ROS) in CsA nephrotoxicity. There is emerging evidence that Ang II induces oxidative stress in vitro and in vivo. The aims of this study were to investigate the role of Ang II-induced oxidative stress in CsA nephrotoxicity, and to examine the effects of the insurmountable Ang II type 1 (AT (1)) receptor antagonist, candesartan on CsA-induced nephrotoxicity in rats. Candesartan cilexetil (1.0 mg kg (-1), perorally (p.o.), once a day) was administered 24 h before and 21 days concurrently with CsA (20 mg kg(-1), subcutaneously (s.c.)). Tissue lipid peroxidation was measured as thiobarbituric acid reacting substances (TBARS). Renal function was assessed by estimating serum creatinine, blood urea nitrogen (BUN), creatinine and urea clearance. Renal morphological alterations were assessed by histopathological examination of Haematoxylin-Eosin, PAS and Mason's trichome stained sections of the kidneys. CsA (20 mg kg (-1), s.c.) administration for 21 days produced elevated levels of TBARS and deteriorated the renal function as assessed by increased serum creatinine, BUN and decreased creatinine and urea clearance as compared to vehicle treated rats. The kidneys of CsA-treated rats showed severe striped interstitial fibrosis, arteriolopathy, glomerular basement thickening, tubular vacuolisation and hyaline casts. Candesartan cilexetil (1.0 mg kg (-1)) markedly reduced elevated levels of TBARS, significantly attenuated renal dysfunction and morphological changes in CsA-treated rats. These results clearly demonstrate the pivotal role of Ang II-induced oxidative stress and the therapeutic potential of AT (1)receptor antagonists in ameliorating CsA-induced nephrotoxicity.

Does methylene blue protect the kidney tissues from damage induced by ciclosporin A treatment?

Ciclosporin A (CsA) is the first-choice immunosuppressant universally used in allotransplantation and autoimmune diseases. However, it has been demonstrated that this drug produces negative side effects in several organs and in particular in the lymphoid organs and in the kidney. It has been suggested that the CsA causes deleterious effects because it increases the oxygen free radical production. Here we wanted to test whether antioxidants protect the kidney parenchyma from the toxicity induced by CsA. We used methylene blue (MB), because it inhibits the formation of oxygen free radicals. The study was carried out in four groups of Wistar rats. Group I animals were intraperitoneally injected with MB (1 mg/kg/day) for 21 days; group II animals were subcutaneously injected with CsA (15 mg/kg/day) for 21 days; group III animals were treated with CsA combined with MB at the same doses and for the same periods as groups I and II, and group IV animals were injected subcutaneously with olive oil for 21 days as controls. The kidneys and the thymuses were subsequently removed and examined by conventional morphological staining (hematoxylin-eosin and Masson's trichrome) and enzymatic (NADPH-diaphorase, cytochrome, c oxidase, and superoxide anion production) and immunoenzymatic (inducible nitric oxide synthase--iNOS, endothelial nitric oxide synthase--eNOS) techniques. The thymuses were used to check the persistence of CsA-immunosuppressive effects during MB administration. Group I, III, and IV animals showed a normal kidney architecture and low levels of NADPH-diaphorase and of superoxide anion in all structures studied (proximal and distal tubules, glomeruli and the Henle loops). The cytochrome c oxidase showed a strong activity in proximal tubules, a moderate activity in distal tubules, and a weak activity in glomeruli and in the Henle loops. The expression of iNOS was weak in the proximal tubular epithelial cells and negative in the glomeruli, while eNOS was found to be moderately positive in the glomeruli and in the interstitial arteries, but not in the tubules and in the Henle loops. Degenerative changes with tubulointerstitial injury in the cortex of CsA-treated kidneys (group II) and increases of NADPH-diaphorase levels, iNOS activity, and superoxide staining were found in all structures. The expression of eNOS did not change in group I, III and IV animals. MB combined with CsA prevented the degenerative changes caused by CsA, preserving the structural, enzymatic, and immunoenzymatic integrity of the renal parenchyma. The mechanism by which MB exerts its protective action is not yet clear, but it seems to be due to its ability to inhibit xanthine oxidase and to quench nitric oxide production. Moreover, these data have been also supported by the following: (1) the superoxide anion levels were very high after CsA treatment and reduced after CsA-MB treatment, and (2) the iNOS levels increased in CsA-treated rats and showed normal levels after CsA-MB treatment. Moreover we demonstrated that MB administration did no compromise the CsA immunosuppressive effects, since the thymus showed a cytoarchitecture like that observed in CsA-treated rats.

Melatonin antagonises the cyclosporine A immunosuppressive effects in rat thymuses

Cyclosporine A (CsA) is a powerful immunosuppressant inducing marked involution of the thymus with disappearance of interdigitating cells (IDCs) and reducing the number of macrophages (Mphi). Melatonin (Mel) is a potent antioxidant agent that could be useful in attempting to reduce CsA toxicity. Moreover, Mel has been found to exert positive influence on lymphocytes, spleen and thymus. In this study, we evaluated the effects of Mel on the thymic involution induced by CsA. CsA caused profound changes in thymic cytoarchitecture, i.e. the complete disappearance of thymic medulla and reduced the number of acid phosphatase positive macrophages. There was no difference between thymic morphology of Mel-treated rats and the control animals injected only with olive oil. The simultaneous Mel-CsA administration prevented the involution of the thymic medulla and the reduction of the number of macrophages. These findings suggested that Mel probably antagonized the immunosuppressive CsA effects.

Detection of drug-induced, superoxide-mediated cell damage and its prevention by antioxidants

The mode of the cytotoxic activity of three benzo(c)fluorene derivatives was characterized. The observed morphological changes of lysosomes or variations of mitochondrial activity are assumed to be the consequence of cell protection against oxidative damage and/or the part of the damage process. To establish the relationship between the quantity of superoxide (O2*-) generated and the degree of damage resulting from O2*-, a simple system based on measurement of 3-(4-iodophenyl)-2-(4-nitrophenyl)-5-phenyltetrazolium chloride (INT) reductase activity in the presence of superoxide dismutase (SOD) was used. The functionality of the chosen battery of in vitro tests was proved using several known superoxide inducers: cyclosporin A (CsA) and benzo(a)pyrene (BP), as well as noninducers: citrinin (CT) and cycloheximide (CH). From the results followed that the cell growth tests are much better indices of toxicity than the other tests. The model system for the evaluation of the protective capacity of antioxidants against superoxide-induced cytotoxicity included simultaneous exposure of HeLa cells to cytotoxic drugs and to quercetin (Qe), an antioxidant of plant origin. The complete abolishment of the inhibition of cell proliferation and clonogenic survival was concluded to be due to the protective effect of the antioxidant. These observations correlated with the decrease of superoxide content as estimated by the INT-reductase assay in the presence of SOD using the same model system, as well as with the increase of intracellular SOD content and its activity.

A reexamination of PSC 833 (Valspodar) as a cytotoxic agent and in combination with anticancer agents

BACKGROUND

The cyclosporins have been thought as being mainly immunosuppressive agents which interfere with the function of the MDR pump and thus play a role in resistance to drug anticancer effects. We reexamined their cytotoxicity in defined cell lines both as single agents and in combination with agents which may be of value in human malignant disease.

METHODS

Cells were grown to confluence following inoculation at 5,000-8,000 cells/well in 96-well dishes, and growth patterns and death were determined by an MTT assay. Median effect analysis was used to look for synergy, additive effects, or antagonism between the cyclosporins and drugs with antitumor effects in humans.

RESULTS

Cyclosporin A and PSC 833 were found to have cytotoxic activity at clinically achievable concentrations in breast, leukemia, and prostate cell lines. Synergistic or additive effects were demonstrated in all three prostate cell lines when PSC 833 was combined with estramustine, etoposide, ketoconazole, suramin, or vinorelbine in the prostate cancer cell lines. Cell line-selective additive effects or synergism were also identified with bicalutamide, carboplatin, cisplatinum, cis-retinoic acid, dexamethasone, 5-fluorouracil, liarozole, and trans-retinoic acid.

CONLCLUSIONS

PSC 833 or cyclosporin alone or in combination with other agents may have an anticancer effect independently of their modulatory action on MDR. Several of the synergistic combinations which are not mediated by the MDR pump need to be tested in vivo for efficacy.

Sulfinpyrazone reduces cyclosporine levels: a new drug interaction in heart transplant recipients

BACKGROUND

Management of cyclosporine (CsA)-associated hyperuricemia in heart transplantation (HT) is difficult. Because of the myelotoxicity of combined allopurinol and azathioprine, we tested sulfinpyrazone.

METHODS

We studied 120 HT recipients (109 men; mean age at HT, 52+/-10 years). All had received allopurinol for at least 6 months, which was stopped for 1 month before initiation of sulfinpyrazone. Mean follow-up from HT to onset of sulfinpyrazone (200 mg/day) was 59+/-41 months. We stopped the drug after 6+/-2 months. We compared CsA level and daily dose, serum creatinine, blood urea, and uric acid at onset and before interruption of sulfinpyrazone and, as control, in the last 6 months of allopurinol.

RESULTS

Mean uricemia decreased with allopurinol (0.58+/-0.12 vs. 0.41+/-0.07 mmol/liter, p = 0.0001) as well as with sulfinpyrazone (0.51+/-0.13 vs. 0.40+/-0.12 mmol/liter, p = 0.0001). Mean creatinine increased (171+/-42 and 164+/-35 micromol/liter, p = 0.01) with allopurinol, whereas it tended to decrease with sulfinpyrazone (160+/-35 and 154+/-48 micromol/liter, p = NS). Mean urea did not change with allopurinol (14+/-5 vs. 15+/-7 mmol/liter, p = NS), but fell with sulfinpyrazone (14.01+/-5 vs. 12.60 +/-5 mmol/liter, p = 0.0004). Mean CsA levels were constant with allopurinol (193+/-73 vs. 188+/-65 ng/ml, p = NS), although CsA dose was slightly reduced (2.7+/-0.8 vs. 2.6+/-0.8 mg/kg/day, p = 0.007). Conversely, CsA levels dropped with sulfinpyrazone (183+/-89 vs. 121 +/-63 ng/ml, p = 0.0001) despite an increase in CsA daily dose (2.6 +/-0.9 vs. 2.8+/-0.9 mg/kg/day, p = 0.0001). Two subjects were treated for acute rejection. We observed no other side effects. In HT recipients sulfinpyrazone, as an alternative to allopurinol, is effective in achieving metabolic control of hyperuricemia. However, this drug reduced CsA levels, thus the risk of rejection is present.

Enalaprilat directly ameliorates in vitro cyclosporin nephrotoxicity in human tubulo-interstitial cells

BACKGROUND/AIMS

Several recent studies have suggested that angiotensin-converting enzyme (ACE) inhibitors ameliorate chronic cyclosporin A (CyA) tubulo-interstitial disease by mechanisms independent of their antihypertensive effects. The aim of the present study was to determine whether ACE inhibition exerts a direct beneficial effect on the tubulo-interstitium in an in vitro model of chronic CyA nephropathy.

METHODS

Primary cultures of human proximal tubular cells (PTC) and renal cortical fibroblasts (CF) were exposed for 24 h to CyA in the presence or absence of enalaprilat. Parameters of tubulo-interstitial nephrotoxicity were then measured including collagen synthesis (proline incorporation), tubular viability and function (thymidine incorporation, lactate dehydrogenase release, and apical sodium-hydrogen exchange), and secretion of insulin-like growth factor I, transforming growth factor beta 1 (TGFbeta1), and platelet-derived growth factor.

RESULTS

CyA promoted CF collagen synthesis, PTC cytotoxicity (suppressed viability, growth and sodium transport), and tubulo-interstitial fibrogenic cytokine release (CF secretion of insulin-like growth factor I and PTC secretion of TGFbeta1 and platelet-derived growth factor). Enalaprilat completely reversed the stimulatory effects of CyA on CF collagen synthesis (CyA + enalaprilat 6.40 +/- 0.50% vs. CyA alone 8.33 +/- 0.56% vs. control 6.57 +/- 0.62% vs. enalaprilat alone 5.55 +/- 0.93%, p < 0.05) and PTC secretion of TGFbeta1 (0.71 +/- 0.11, 1.13 +/- 0.09, 0.89 +/- 0.07, and 0.67 +/- 0.09 ng/mg protein/day, respectively, p < 0.05). However, the other manifestations of CyA toxicity were not significantly reversed by concomitant enalaprilat administration.

CONCLUSIONS

ACE inhibition directly prevents CyA-induced interstitial fibrosis, but not proximal tubule cytotoxicity, independently of haemodynamic and systemic renin-angiotensin system effects. Renoprotection may be partially afforded by directly preventing the tubular secretion of TGFbeta1.

Dinitrophenol, cyclosporin A, and trimetazidine modulate preconditioning in the isolated rat heart: support for a mitochondrial role in cardioprotection

BACKGROUND

Recent studies have postulated that mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel activation may modulate mitochondrial function with the resultant induction of a preconditioning phenotype in the heart. We hypothesized that the modulation of mitochondrial homeostasis might confer preconditioning-like cardioprotection.

METHODS

We used a model of regional ischemia in Langendorff-perfused isolated rat hearts. Short-term administration of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation and cyclosporin A (CSA), an inhibitor of mitochondrial respiration, was used in an attempt to elicit preconditioning-like cardioprotection. The anti-ischemic drug trimetazidine, known to attenuate CSA-induced disruption in mitochondrial function, and the mitoK(ATP) channel blocker 5-hydroxydecanoic acid (5-HD) were used to inhibit the effects of DNP and CSA. Finally, we studied the effect of trimetazidine on adenosine-induced and ischemic preconditioning. Risk zone and infarct size were measured and expressed as a percentage of the risk zone (I/R ratio).

RESULTS

DNP, CSA and adenosine pretreatment reduced infarct size (I/R ratio: DNP 9.0+/-2.4%, CSA 12.5+/-1.4%, adenosine 11.9+/-3.6%, all P<0.001 vs. control, 30.2+/-1.3%) similarly to ischemic preconditioning (9.5+/-0.6%, P<0.001 vs. control). Trimetazidine limited the effect of ischemic preconditioning (22.2+/-2.0%, P<0.001 vs. ischemic preconditioning) and completely reversed the DNP, CSA, and the adenosine-mediated reduction in infarct size. 5-HD abolished the effect of ischemic preconditioning and CSA.

CONCLUSION

DNP and CSA trigger preconditioning-like cardioprotection in the isolated rat heart. Trimetazidine, a known mitochondrial 'protector', attenuated both drug-induced and ischemic preconditioning. These data support the hypothesis that modulation of mitochondrial homeostasis may be a common downstream cellular event linking different triggers of preconditioning.

Strategies to antagonise the cyclosporine A-induced proliferation of human pulmonary artery smooth muscle cells: anti-endothelin-1 antibodies, verapamil, and octreotide

The present study investigated the mechanisms mediating the actions of the immunosuppressive drug cyclosporine A (CsA) on human pulmonary artery smooth muscle cell (PASMC) proliferation. The new hydroxyethyl derivative of D-serine(8)-cyclosporine, SDZ IMM 125, was used for comparison. CsA-induced proliferation was determined by incorporation of [(3)H]thymidine ([(3)H]Thy). CsA in the concentration range between 0.1 nM and 0.1 microM induced a concentration-dependent increase in proliferation after 24, 48, and 72 hr of incubation. Higher CsA concentrations were cytotoxic. When proliferation experiments were performed in the presence of a monoclonal antibody against endothelin-1 (ET-1), CsA-induced proliferation was totally inhibited. No inhibition occurred in the presence of the same antibody when heat-inactivated or a non-specific monoclonal antibody. In parallel, CsA increased the production of ET-1, as determined by radioimmunoassay. Incubation of PASMCs with ET-1 at the concentration range at which the latter was released by CsA induced cell proliferation. The somatostatin derivative Sandostatin (SDT; octreotide), which is an inhibitor of the growth of smooth muscle cells as well as a potent inhibitor of ET-1 secretion, inhibited both the CsA-induced ET-1 release and the increase in [3H]Thy incorporation by PASMCs. A similar effect was observed for the calcium channel blocker verapamil (VP). SDZ IMM 125 induced weaker effects than CsA in terms of PASMC proliferation and ET-1 secretion. In conclusion, CsA increased the rate of proliferation of PASMCs, while SDZ IMM 125 induced a weaker effect. Anti-ET-1 antibody, VP, and SDT significantly inhibited CsA-induced PASMC proliferation.