Oxidizability of low-density lipoproteins from Neoral and tacrolimus-treated renal transplant patients

Chronic kidney disease after nonrenal solid-organ transplantation

Chronic kidney disease (CKD) is a common complication after nonrenal solid-organ transplantation. The risk for CKD is influenced by many factors, some of which have a direct impact on how such patients are treated in the pre-, peri-, and posttransplantation settings. This review describes hazards for acute and chronic kidney injury, with particular emphasis on calcineurin inhibitor-mediated nephrotoxicity. Rather than a detailed description of management issues that are common to the general CKD population, highlighted are aspects that are more specific to nonrenal solid-organ transplant recipients with a focus on liver, heart, and lung recipients. Strategies to minimize nephrotoxic insults and retard progressive renal injury are discussed, as are issues that are pertinent to dialysis and transplantation. Finally, future approaches to prevent and treat CKD without compromising function of the transplanted organ are addressed.

Cyclosporine A induced changes to plasma and erythrocyte antioxidant defences

Organ transplant recipients develop pronounced cardiovascular disease, and decreased antioxidant capacity in plasma and erythrocytes is associated with the pathogenesis of this disease. These experiments tested the hypothesis that the immunosuppressant cyclosporine A (CsA) alters erythrocyte redox balance and reduces plasma antioxidant capacity. Female Sprague-Dawley rats were randomly assigned to a control or CsA treated group. Treatment animals received 25 mg/kg/day of CsA via intraperitoneal injection for 18 days. Control rats were injected with the same volume of the vehicle. Three hours after the final CsA injection, rats were exsanguinated and plasma analysed for total antioxidant status (TAS), alpha-tocopherol, malondialdehyde (MDA), and creatinine. Erythrocytes were analysed for superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and glucose-6-phosphate dehydrogenase (G6PD) activities, alpha-tocopherol, and MDA. CsA administration resulted in a significant (P < 0.05) decrease in plasma TAS and significant increases (P < 0.05) in plasma creatinine and MDA. Erythrocyte CAT was significantly (P < 0.05) increased in CsA treated rats compared to controls. There were no significant differences (P > 0.05) in erythrocyte SOD, GPX, G6PD, alpha-tocopherol or MDA between groups. In summary, CsA alters erythrocyte antioxidant defence and decreases plasma total antioxidant capacity.

Effect of Calcineurin Inhibitors on Low-Density Lipoprotein Oxidation

INTRODUCTION

Low-density lipoprotein (LDL) oxidation is considered a key factor in the biological processes that trigger and accelerate atherosclerosis. Reported data suggest that tacrolimus improves the lipid profile in renal transplant recipients.

OBJECTIVE

The objective of this study was to analyze the effect of converting from cyclosporine to tacrolimus on lipoprotein oxidation in renal transplant recipients.

METHODS

We studied a group of 12 recipients (6 men and 6 women of mean age 55 +/- 11 years) treated with a cyclosporine-mycophenolate mofetil (MMF)-prednisone combination that was converted to tacrolimus-MMF-prednisone because of gingival hyperplasia. The LDL fraction was isolated by density-gradient ultracentrifugation. Oxidative stress was studied before converting (baseline) and at 6 and 12 weeks, thereafter by in vivo oxidation analysis of LDL, a direct assay of oxidized LDL (oxLDL) and oxLDL autoantibodies (Ab-oxLDL) using enzyme-immunoassay techniques. We measured total cholesterol (TC), triglyceride, LDL-cholesterol, high-density lipoprotein (HDL)-cholesterol, ApoA1, ApoB, and Lp(a) levels.

RESULTS

The change to tacrolimus resulted in significant decreases in TC levels, 213 +/- 30 (B) versus 185 +/- 27 (12s) (P < .01); LDL, 129 +/- 24 (B) versus 104 +/- 14 (12s) (P = .002); and ApoB 98 +/- 15 (B) versus 85 +/- 10 (12s) (P < .01). HDL levels significantly increased (45 +/- 10 vs 48 +/- 10 [12s]; P = .018), whereas oxLDL concentrations decreased significantly after conversion (B) (55.42 +/- 10.61 vs 12s 45.76 +/- 10.21; P < .01). Converting to tacrolimus produced a nonsignificant decrease in Ab-oxLDL (baseline 204.88 +/- 134.49 vs 12s 179.51 +/- 143.54). A correlation was observed between LDL and oxLDL (r = 65, P = .02 [B] and r = 0.7, P = .01 [12s]) but not between oxLDL levels and Ab-oxLDL concentration (r = -0.05, P = .87 [3] and r = -0.1, P = .77 [12s]).

CONCLUSIONS

In renal transplantation, tacrolimus therapy was associated with a better lipid profile and lower in vivo LDL oxidation when compared with cyclosporine treatment.

Assessment of oxidative stress in the early posttransplant period: comparison of cyclosporine A and tacrolimus-based regimens

BACKGROUND

Oxidative stress is one of the leading causes of cardiovascular morbidity and mortality in chronic kidney disease. Although it is clear that many metabolic abnormalities improve, the effects of kidney transplantation on oxidative state are obscure.

METHODS

Twenty-three kidney transplant patients were included in the study. Eleven patients (mean age 27.9+/- 9.1 years) were treated with cyclosporine A (CsA) whereas 12 patients (mean age 22.4 +/- 3.4 years) were treated with tacrolimus. Twenty-three healthy subjects served as controls. None of the patients or controls suffered from diabetes mellitus or an acute infection at the time of the study. Plasma malondialdehyde (MDA), plasma selenium (Se), erythrocyte glutathione peroxidase (GSH-Px), erythrocyte superoxide dismutase (SOD), erythrocyte Zn (EZn), and erythrocyte Cu (ECu) levels were studied before and in the 1st, 3rd, 7th, 14th and 28th days after the transplantation.

RESULTS

The GSH-Px, SOD, ECu, EZn and selenium levels were lower and MDA levels were higher in patients than controls before transplantation (p < 0.001 for all). MDA levels decreased and SOD, GSH-Px, ECu, EZn levels increased in parallel to the decrement of serum creatinine levels following the renal transplantation. No difference was found among the patients regarding the treatment regime.

CONCLUSION

The study data suggest that the improvement in oxidative state parameters begins at the first day of renal transplantation and continues at the 28th posttransplant day in living donor transplantations.

Effect of immunosuppressive agents on long-term survival of renal transplant recipients: focus on the cardiovascular risk

In the control of acute rejection, attention is being focused more and more on the long-term adverse effects of the immunosuppressive agents used. Since cardiovascular disease is the main cause of death in renal transplant recipients, optimal control of cardiovascular risk factors is essential in the long-term management of these patients. Unfortunately, several commonly used immunosuppressive drugs interfere with the cardiovascular system. In this review, the cardiovascular adverse effects of the immunosuppressive agents currently used for maintenance immunosuppression are thoroughly discussed. Optimising immunosuppression means finding a balance between efficacy and safety. Corticosteroids induce endothelial dysfunction, hypertension, hyperlipidaemia and diabetes mellitus, and impair fibrinolysis. The use of corticosteroids in transplant recipients is undesirable, not only because of their cardiovascular effects, but also because they induce such adverse effects as osteoporosis, obesity, and atrophy of the skin and vessel wall. Calcineurin inhibitors are the most powerful agents for maintenance immunosuppression. The calcineurin inhibitor ciclosporin (cyclosporine) not only induces these same adverse effects as corticosteroids but is also nephrotoxic. Tacrolimus has a more favourable cardiovascular risk profile than ciclosporin and is also less nephrotoxic. It has little or no effect on blood pressure and serum lipids; however, its diabetogenic effect is more prominent in the period immediately following transplantation, although at maintenance dosages, the diabetogenic effect appears to be comparable to that of ciclosporin. The diabetogenic effect of tacrolimus can be managed by reducing the dose of tacrolimus and early corticosteroid withdrawal. The effect of tacrolimus on endothelial function has not been completely elucidated. The proliferation inhibitors azathioprine and mycophenolate mofetil (MMF) have little effect on the cardiovascular system. Yet, indirectly, by inducing anaemia, they may lead to left ventricular hypertrophy. MMF is an attractive alternative to azathioprine because of its higher potency and possibly lower risk of malignancies. Sirolimus also induces anaemia, but may be promising because of its antiproliferative features. Whether the hyperlipidaemia induced by sirolimus counteracts its beneficial effects is, as yet, unknown. It may be combined with MMF, however, initial attempts resulted in severe mouth ulcers.

Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation

The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immunosuppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.

Insights into cyclosporine A-induced atherosclerotic risk in transplant recipients: macrophage scavenger receptor regulation

Clinical monitoring of organ-transplant recipients suggests that administration of cyclosporine (CsA) may increase the risk of atherosclerosis when compared with the general population. The purpose of this work is to demonstrate the utility of the in vitro Tamm-Horsfall protein (THP)-1 human monocyte cell culture model for determining drug-related atherosclerotic potential in macrophages. The effect of CsA on the mRNA expression of macrophage scavenger receptor genes including CD36, CD68, scavenger receptor (SR)-A, SR-BII, and lectin-like oxidized low-density lipoprotein receptor (LOX-1); the nuclear hormone receptors, including peroxisome-proliferator activated receptor (PPAR)gamma and liver-X-receptor (LXR)alpha; and the cholesterol efflux pump ABCA1 were investigated as markers of atherosclerotic progression. The THP-1 cells were cultured and differentiated into macrophages. The macrophages were then treated with CsA to assess gene expression. Time- (1, 2, 4, 8, and 24 hours) and dose- (concentrations [mg/L] corresponding to the trough [0.5], peak [1.25] and 4x peak [5]) dependency of CsA was assessed. The treated macrophage mRNA gene expression of CD36, CD68, and PPARgamma were up-regulated in the presence of CsA. Interestingly, SR-A, SR-BII, LOX-1, and LXRalpha expression appeared to be slightly down-regulated, and ABCA1 was relatively unchanged. Immunoblotting studies demonstrated that the protein expression of CD36 was unchanged or increased, PPARgamma was unchanged, and ABCA1 was unchanged or decreased at 4 and 8 hours. The results document CsA-induced mRNA and protein changes in receptors relevant to lipid-laden foam cell formation and demonstrate the utility of THP-1 macrophages for screening of atherosclerotic risk potential.

Oxidative stress and antioxidant defense systems in patients after heart transplantation

Heart transplantation ranks among those surgical interventions associated with ischemia-reperfusion injury to the donor heart as well as to the recipient. These events are connected with increased production of reactive oxygen species which evoke metabolic, structural and functional disturbances. Twenty-four transplant patients were investigated for oxidative stress (plasma levels of thiobarbituric acid reactive substances, TBARS) and antioxidant capacity (plasma total antioxidant status, TAS), and for activities of erythrocyte superoxide dismutase (SOD) and glutathione peroxidase (GPx) during the first year after heart transplantation. The post-transplant period was characterized by progressive decrease of plasma TAS, indicating a significant long-term drop of antioxidant reserves in patients after successful heart transplantation. The decrease in plasma TAS is accompanied by long-lasting increase of TBARS levels, which may represent oxidative stress of the organism. We conclude that additional therapy with antioxidant substances should be an important component of the complex therapeutic programme of patients after heart transplantation.

Improved cardiovascular risk profile and renal function in renal transplant patients after randomized conversion from cyclosporine to tacrolimus

Cyclosporine is considered to contribute to the high cardiovascular morbidity and mortality in patients after renal transplantation. Tacrolimus may be more favorable in this respect, but controlled data are scarce. In this prospective randomized study in 124 stable renal transplant patients, the effects of conversion from cyclosporine to tacrolimus on cardiovascular risk factors and renal function were investigated. Follow-up was 6 mo. Statistical analysis was performed by ANOVA for repeated measurements. The serum creatinine level decreased from 137 +/- 30 micromol/L to 131 +/- 29 micromol/L (P < 0.01). Three months after conversion from cyclosporine to tacrolimus, mean BP significantly decreased from 104 +/- 13 to 99 +/- 12 mmHg (P < 0.001). Serum LDL cholesterol decreased from 3.48 +/- 0.80 to 3.11 +/- 0.74 mmol/L (P < 0.001,) and serum apolipoprotein B decreased from 1018 +/- 189 to 935 +/- 174 mg/L (P < 0.001). Serum triglycerides decreased from 2.11 +/- 1.12 to 1.72 +/- 0.94 mmol/L (P < 0.001). In addition, both rate and extent of LDL oxidation were reduced. The fibrinogen level decreased from 3638 +/- 857 to 3417 +/- 751 mg/L (P < 0.05). Plasma homocysteine concentration did not change. Three months after conversion, plasma fasting glucose level temporarily increased from 5.4 +/- 1.3 mmol/L to 5.8 +/- 1.9 mmol/L (P < 0.05). Conversion to tacrolimus resulted in a significant reduction of the Framingham risk score. In conclusion, conversion from cyclosporine to tacrolimus in stable renal transplant patients has a beneficial effect on renal function, BP, serum concentration and atherogenic properties of serum lipids, and fibrinogen.

Effects of sirolimus on lipids in renal allograft recipients: an analysis using the Framingham risk model

This report describes the effects of sirolimus on plasma lipids, and uses the Framingham risk model to assess the clinical importance of these effects. Lipid data from two large controlled studies of 1295 renal transplant patients were analyzed retrospectively. Sirolimus 2 mg/day and 5 mg/day were compared with placebo or azathioprine, and administered concomitantly with steroids and cyclosporine over 12 months. Hypercholesterolemia and hypertriglyceridemia occurred in all treatment groups and were maximal at 2-3 months. The sirolimus groups evidenced higher lipid levels than the controls, but the elevations diminished over time. At 1 year, the patients given sirolimus 2 mg/day had a mean cholesterol level 17 mg/dL greater and a mean triglyceride level 59 mg/dL greater than the controls. Among the patients given sirolimus 5 mg/day, mean cholesterol was 30 mg/dL greater and mean triglycerides were 103 mg/dL greater than the controls. Treatment with statins and fibrates was effective in reducing cholesterol and triglyceride levels, respectively, in the sirolimus-treated patients. The Framingham risk model predicted that the 17 mg/dL elevation in cholesterol would increase the incidence of coronary heart disease (CHD) by 1.5 new cases per 1000 persons per year and CHD death by 0.7 events per 1000 persons per year. Lipid elevations observed in the sirolimus-treated patients were manageable, improved over time, and responded to lipid-lowering therapy. Based on the Framingham risk model, the CHD risks associated with these cholesterol elevations are small compared with the baseline risks of the transplant population.

Markers of oxidative stress in cyclosporine-treated and tacrolimus-treated children after liver transplantation

Oxidative stress is presumed to have a major role in cyclosporine A (CsA)- and tacrolimus-induced tissue toxicity. The present study was performed to elucidate the degree of oxidative stress after liver transplantation in CsA- and tacrolimus-treated patients. Twenty-three patients (14 patients, CsA; 9 patients, tacrolimus) aged 2.5 to 18 years (mean, 9.8 years) who had undergone liver transplantation 1.5 to 12 years (mean, 5.4 years) before were studied. Eighteen healthy children aged 2 to 16.5 years (mean, 9.4 years) served as a control group. The following parameters were assessed: plasma lipoprotein levels; plasma carbonyl levels, as markers of oxidative damage to proteins; total plasma oxidizability, which evaluates plasma antioxidant capacity (lag phase) and lipoprotein susceptibility to oxidation; and plasma antioxidant capacity by cyclic voltammetry (CV), which measures antioxidant capacity stemming from hydrophilic low-molecular-weight antioxidant components. Carbonyl levels and rates of plasma oxidation did not differ between groups. The lag phase of plasma oxidation was significantly longer in CsA-treated children compared with tacrolimus-treated children or controls (mean, 54.4 +/- 4.8 [SE] v 40.2 +/- 2.2 v 46.5 +/- 2.8 minutes, respectively; P < 0.05). Antioxidant capacity, assessed by CV, did not differ among CsA-treated patients, tacrolimus-treated patients, and healthy controls. Plasma alpha-tocopherol and beta-carotene levels did not differ between CsA-treated and tacrolimus-treated patients. In children post-liver transplantation, oxidative damage assessed by markers of lipid and protein oxidation is not increased, and plasma antioxidant capacity is not diminished.

Tacrolimus, cyclosporine and plasma lipoproteins in renal transplant recipients

To compare the effect of tacrolimus (FK506) and cyclosporine (CsA) on plasma lipoproteins in renal transplant recipients receiving maintainance therapy, the following prospective study was undertaken. Blood from nineteen recipients on tacrolimus (FK group) and from twenty-one on CsA (CsA group) was collected at baseline, 3-, 6-, and 10-month intervals. Plasma lipids, lipoproteins and oxidation properties of lipoproteins were determined. Plasma total cholesterol, low density lipoprotein (LDL) cholesterol, and apolipoprotein B (apoB) were substantially increased in both groups, although only the CsA group showed significant differences at all time intervals and at the baseline. High density lipoprotein cholesterol, triglycerides, and apolipoprotein A varied in both groups at time intervals from the baseline, but not significantly. The susceptibility to oxidation of LDL isolated from the FK group at all times was uninfluenced by the tacrolimus treatment, and values were comparable to those obtained from LDL isolated from healthy individuals. A significantly higher susceptibility to oxidation as indicated by the shorter time required to start the formation of conjugated dienes was observed in LDL isolated from the CsA group at 3 and at 6 months of therapy. Tacrolimus-treated patients appear to have less hyperlipidemic and have LDL less susceptible to oxidation than patients treated with CsA.

Tacrolimus: a further update of its pharmacology and therapeutic use in the management of organ transplantation

Tacrolimus (FK-506) is an immunosuppressant agent that acts by a variety of different mechanisms which include inhibition of calcineurin. It is used as a therapeutic alternative to cyclosporin, and therefore represents a cornerstone of immunosuppressive therapy in organ transplant recipients. Tacrolimus is now well established for primary immunosuppression in liver and kidney transplantation, and experience with its use in other types of solid organ transplantation, including heart, lung, pancreas and intestinal, as well as its use for the prevention of graft-versus-host disease in allogeneic bone marrow transplantation (BMT), is rapidly accumulating. Large randomised nonblind multicentre studies conducted in the US and Europe in both liver and kidney transplantation showed similar patient and graft survival rates between treatment groups (although rates were numerically higher with tacrolimus- versus cyclosporin-based immunosuppression in adults with liver transplants), and a consistent statistically significant advantage for tacrolimus with respect to acute rejection rate. Chronic rejection rates were also significantly lower with tacrolimus in a large randomised liver transplantation trial, and a trend towards a lower rate of chronic rejection was noted with tacrolimus in a large multicentre renal transplantation study. In general, a similar trend in overall efficacy has been demonstrated in a number of additional clinical trials comparing tacrolimus- with cyclosporin-based immunosuppression in various types of transplantation. One notable exception is in BMT, where a large randomised trial showed significantly better 2-year patient survival with cyclosporin over tacrolimus, which was primarily attributed to patients with advanced haematological malignancies at the time of (matched sibling donor) BMT. These survival results in BMT require further elucidation. Tacrolimus has also demonstrated efficacy in various types of transplantation as rescue therapy in patients who experience persistent acute rejection (or significant adverse effect's) with cyclosporin-based therapy, whereas cyclosporin has not demonstrated a similar capacity to reverse refractory acute rejection. A corticosteroid-sparing effect has been demonstrated in several studies with tacrolimus, which may be a particularly useful consideration in children receiving transplants. The differences in the tolerability profiles of tacrolimus and cyclosporin may well be an influential factor in selecting the optimal treatment for patients undergoing organ transplantation. Although both drugs have a similar degree of nephrotoxicity, cyclosporin has a higher incidence of significant hypertension, hypercholesterolaemia, hirsutism and gingival hyperplasia, while tacrolimus has a higher incidence of diabetes mellitus, some types of neurotoxicity (e.g. tremor, paraesthesia), diarrhoea and alopecia.

CONCLUSION

Tacrolimus is an important therapeutic option for the optimal individualisation of immunosuppressive therapy in transplant recipients.

Calcineurin inhibitors enhance low-density lipoprotein oxidation in transplant patients

BACKGROUND

Our objective was to assess the pro-oxidant status of neoral and tacrolimus in renal transplant patients and monitor the protection provided by vitamin C and vitamin E in normalizing low density lipoprotein (LDL) oxidation lag time of tacrolimus-treated patients.

METHODS

Plasma LDL was isolated by density gradient ultracentrifugation from renal transplant patients receiving neoral, tacrolimus and tacrolimus with vitamin C and vitamin E. Oxidation was initiated by the addition of CuCl2 at 37 degrees C and monitored at 234 nm over 480 minutes and oxidation lag time was computed. Total antioxidant capacity of serum was measured using the enhanced chemiluminescent method.

RESULTS

LDL from tacrolimus-treated patients had significantly lower oxidation lag time and serum antioxidant activity in comparison with neoral-treated patients, and this was particularly significant during the first four months after transplantation. Vitamin C and E supplementation in tacrolimus treated patients provided protection against oxidation and normalized their oxidation lag time.

CONCLUSION

Calcineurin-inhibiting drugs, CsA and tacrolimus, have pro-oxidant activity and they increase the susceptibility of LDL to oxidation. Neoral formulation is fortified with DL-alpha tocopherol and therefore provides protection against oxidation. The present study clearly demonstrates the benefit of giving vitamin C and E supplements to patients taking tacrolimus and this seems to be particularly important during the early period after transplantation.