Early detection of heart transplant patients with increased risk of ciclosporin nephrotoxicity

A high level of urinary retinol-binding protein is associated with cytomegalovirus infection in kidney transplantation

The indirect effects of cytomegalovirus (CMV) viremia can be related to chronic changes in renal allograft structure, but its real impact in early and late graft function remains speculative. A total of 159 patients undergoing renal transplantation using a preemptive therapeutic strategy to prevent CMV disease were included in the present study. The patients were prospectively followed, with serial measurements of urinary retinol-binding protein (uRBP), a marker of proximal tubule injury. uRBP levels and their dynamic performance were compared according to CMV viremia and the 5-year estimated glomerular filtration rate (eGFR), as measured with the modification of diet in renal disease (MDRD) equation. CMV viremia was detected in 79.9% of the patients, with high uRBP levels being detected in 76.0% of these patients (compared with 40.7% in CMV-, P=0.005). High uRBP was associated with male recipients (P=0.02), the number of mismatches (P=0.02) and CMV infection (P=0.001). Five-year eGFR was worse in patients with high uRBP levels (50.3 ± 25.8 compared with 59.8 ± 26.4 ml/min, P=0.04). In a multivariate model, eGFR <60 ml/min was associated with donor age (P<0.001), the number of mismatches (P=0.04), thymoglobulin dose (P=0.02), the presence of and time with delayed graft function (DGF) (P=0.005 and P=0.04), 1-month tacrolimus levels (P=0.03), and uRBP levels after CMV treatment (P=0.01). Patients with CMV viremia in whom uRBP levels were normalized up to 3 months after treatment showed significantly better 5-year eGFR than those in whom uRBP remained high: 61.0 ± 24.2 compared with 42.3 ± 23.9 ml/min, P<0.001. CMV viremia was associated with high uRBP levels, which represent a profile of proximal tubule injury, and the dynamic performance of uRBP after treatment was associated with long-term kidney graft function.

Biomarkers of immunosuppressant organ toxicity after transplantation: status, concepts and misconceptions

INTRODUCTION

A major challenge in transplantation is improving long-term organ transplant and patient survival. Immunosuppressants protect the transplant organ from alloimmune reactions, but sometimes also exhibit limiting side effects. The key to improving long-term outcome following transplantation is the selection of the correct immunosuppressive regimen for an individual patient for minimizing toxicity while maintaining immunosuppressive efficacy.

AREAS COVERED

Proteomics and metabolomics have the potential to develop sensitive and specific diagnostic tools for monitoring early changes in cell signal transduction, regulation and biochemical pathways. Here, we review the steps required for the development of molecular markers from discovery, mechanistic and clinical qualification to regulatory approval, and present a critical discussion of the current status of molecular marker development as relevant for the management and individualization of immunosuppressive drug regimens.

EXPERT OPINION

Although metabolomics and proteomics-based studies have yielded several candidate molecular markers, most published studies are poorly designed, statistically underpowered and/or often have not gone beyond the discovery stage. Most molecular marker candidates are still at an early stage. Due to the high complexity of and the resources required for diagnostic marker development, initiatives and consortia organized and supported by funding agencies and regulatory agencies will be critical.

Functional and morphologic evaluation of kidney proximal tubuli and correlation with renal allograft prognosis

Renal transplant patients with stable graft function and proximal tubular dysfunction (PTD) have an increased risk for chronic allograft nephropathy (CAN). In this study, we investigated the histologic pattern associated with PTD and its correlation with graft outcome. Forty-nine transplant patients with stable graft function were submitted to a biopsy. Simultaneously, urinary retinol-binding protein (uRBP) was measured and creatinine clearance was also determined. Banff's score and semi-quantitative histologic analyses were performed to assess tubulointerstitial alterations. Patients were followed for 24.0 + or - 7.8 months. At biopsy time, mean serum creatinine was 1.43 + or - 0.33 mg/dl. Twelve patients (24.5%) had uRBP > or = 1 mg/l, indicating PTD and 67% of biopsies had some degree of tubulointerstitial injury. At the end of the study period, 18 (36.7%) patients had lost renal function. uRBP levels were not associated with morphologic findings of interstitial fibrosis and tubular atrophy (IF/TA), interstitial fibrosis measured by Sirius red or tubulointerstitial damage. However, in multivariate analysis, the only variable associated with the loss of renal function was uRBP level > or = 1 mg/l, determining a risk of 5.290 of loss of renal function (P = 0.003). Renal transplant patients who present PTD have functional alteration, which is not associated with morphologic alteration. This functional alteration is associated to progressive decrease in renal function.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

The challenge of renal function in heart transplant children

Renal dysfunction may occur after pediatric heart transplantation and impacts on long-term prognosis. This study aims to review the incidence and mechanisms of chronic nephropathy following heart transplantation, and suggest therapeutic directions. The proportion of pediatric heart-transplant recipients with impaired renal function varies from 22 to 57%, and end-stage renal failure from 3 to 10%, depending on the method used for estimating the glomerular filtration rate. The pathophysiology of renal dysfunction is in part due to calcineurin inhibitor-induced renal vasoconstriction, through activation of the intrarenal renin-angiotensin system, TGF-beta1 upregulation and TGF-beta1 gene polymorphisms. Overproduction of angiotensin II, associated with angiotensin-converting-enzyme genotype, might be associated with poor prognosis and pharmacological factor gene polymorphisms, and may contribute to variation of calcineurine inhibitor exposure in the kidney. Strategies to prevent renal dysfunction include reducing calcineurine inhibitor exposure or delaying calcineurine inhibitor administration from the early post-transplant period. Calcium channel blockers and angiotensin-converting-enzyme inhibitors, blockade of angiotensin II, or anti-TGF-beta1 antibodies might limit nephrotoxicity. No accurate marker can predict the potential of renal lesions to develop. Lowering calcineurine inhibitors levels with immunosuppressive agents that are either less nephrotoxic or non-nephrotoxic should be formally studied. Of high interest is the impact of genetic polymorphism on the development of renal dysfunction.

Determination of renal function in long-term heart transplant patients by measurement of urinary retinol-binding protein levels

Significant improvements have been noted in heart transplantation with the advent of cyclosporine. However, cyclosporine use is associated with significant side effects, such as chronic renal failure. We were interested in evaluating the incidence of long-term renal dysfunction in heart transplant recipients. Fifty-three heart transplant recipients were enrolled in the study. Forty-three patients completed the entire evaluation and follow-up. Glomerular (serum creatinine, creatinine clearance measured, and creatinine clearance calculated) and tubular functions (urinary retinol-binding protein, uRBP) were re-analyzed after 18 months. At the enrollment time, the prevalence of renal failure ranged from 37.7 to 54% according to criteria used to define it (serum creatinine > or = 1.5 mg/dL and creatinine clearance <60 mL/min). Mean serum creatinine was 1.61 +/- 1.31 mg/dL (range 0.7 to 9.8 mg/dL) and calculated and measured creatinine clearances were 67.7 +/- 25.9 and 61.18 +/- 25.04 mL min-1 (1.73 m(2))-1, respectively. Sixteen of the 43 patients who completed the follow-up (37.2%) had tubular dysfunction detected by increased levels of uRBP (median 1.06, 0.412-6.396 mg/dL). Eleven of the 16 patients (68.7%) with elevated uRBP had poorer renal function after 18 months of follow-up, compared with only eight of the 27 patients (29.6%) with normal uRBP (RR = 3.47, P = 0.0095). Interestingly, cyclosporine trough levels were not different between patients with or without tubular and glomerular dysfunction. Renal function impairment is common after heart transplantation. Tubular dysfunction, assessed by uRBP, correlates with a worsening of glomerular filtration and can be a useful tool for early detection of renal dysfunction.

ACE Gene D/D Genotype as a Risk Factor for Chronic Nephrotoxicity from Calcineurin Inhibitors in Liver Transplant Recipients

BACKGROUND

Chronic renal failure (CRF) is a major cause of morbidity and mortality after orthotopic liver transplantation (OLTX) and is predominantly caused by calcineurin inhibitors (CI)-induced nephrotoxicity. The activation of the renin angiotensin system (RAS) has been implicated in the pathogenesis of chronic nephrotoxicity from CI.

METHODS

We retrospectively investigated the genes coding for components of the RAS (ACE gene, Angiotensin II receptor 1 gene, Angiotensinogen gene) in 233 liver transplant recipients receiving Cyclosporine (CsA) or Tacrolimus (Tac) as maintenance immunosuppressant. All patients with serum creatinine (sCr) <1.0 mg/dL (n=143) before orthotopic liver transplantation (OLTX) were included in the final analysis. Patients were than categorized into two groups based upon their most recent postliver transplant sCr level: Group 1 (n=83) with sCr <1.5 mg/dL (mean 1.1+/-0.2) and group 2 (n=60) with sCr > or =1.5 mg/dL (mean 2.5+/-1.3)

RESULTS

ACE D/D genotype was found in 57% of patients with sCr > or =1.5 mg/dL compared to 20% of patients with sCr <1.5 mg/dL (P<0.0001)

CONCLUSIONS

Our analysis strongly suggests that liver transplant patients with ACE gene D/D genotype are at a significant higher risk of developing CI-induced chronic nephrotoxicity.

Improvement of Renal Function in Pediatric Heart Transplant Recipients Treated with Low-Dose Calcineurin Inhibitor and Mycophenolate Mofetil

BACKGROUND

Renal dysfunction is a major complication in heart transplant recipients treated with calcineurin inhibitors. The goal of the study was to investigate the effect of a reduction of calcineurin inhibitor dosage with the concomitant introduction of mycophenolate mofetil on both renal function and cardiac allograft function.

METHODS

Fourteen of 52 consecutive pediatric cardiac allograft recipients experienced a progressive decrease of renal function. A renal biopsy was performed before the dose of calcineurin inhibitors was reduced by 50% and azathioprine was replaced by mycophenolate mofetil. Renal function was evaluated by inulin clearance and maximal urinary osmolality before and yearly after the therapeutic changes. Acute rejection was monitored clinically, by echocardiography and endomyocardial biopsies.

RESULTS

Inulin clearance in the fourteen children decreased from 84.2 mL/min/1.73 m at one year posttransplantation to 46.5+/-9.6 mL/min/1.73 m at the time of the change in immunosuppressive therapy. Significant renal lesions were observed in the renal biopsies performed before the change. At 1 year, inulin clearance had increased by 67%. In six patients who had a second determination 2 years after the switch, inulin clearance was not significantly different from the value at 1 year. There were three reversible acute rejection episodes in three patients. The incidence of rejection episodes was not different from a control group of patients whose treatment was not changed.

CONCLUSION

The reduction of calcineurin inhibitor dosage and replacement of azathioprine by mycophenolate mofetil is a safe way to improve renal function in children with heart transplants and calcineurin inhibitor induced nephrotoxicity.

Proximal Tubular Dysfunction is Associated with Chronic Allograft Nephropathy and Decreased Long-Term Renal-Graft Survival

BACKGROUND

Chronic allograft nephropathy is the major cause of graft loss after the first year of transplantation. Although many conditions are associated with its development, there is no method that can anticipate its risk in patients with good renal function.

METHODS

We prospectively studied 92 renal-transplant recipients with good and stable allograft function and correlated the development of chronic allograft nephropathy and graft loss with their levels of urinary retinol binding protein (uRBP). Patients were divided in two groups regarding the level of their tubular protein: high, above 0.400 mg/L, and normal levels, 0.400 mg/L or less.

RESULTS

Forty-eight (52%) patients had high levels of uRBP. At the enrollment time, patients with high and normal uRBP had comparable serum creatinine and cyclosporine trough levels. During a 5-year follow-up period, chronic allograft nephropathy was detected in 23 (25%) patients, 19 (82.6%) of whom had high levels of uRBP. Five-year chronic allograft nephropathy-free and graft survivals were significantly worse in patients with higher levels of uRBP than in patients with normal levels (57.5% vs. 89.9% P=0.0004; 70.7% vs. 100%, respectively, P=0.0002). High levels of uRBP were the strongest factor associated with the development of chronic allograft nephropathy (RR=5.3, 95% confidence interval 1.45-19.58, P=0.012).

CONCLUSIONS

Among renal-transplant patients with good and stable graft function, high levels of uRBP identify those having a high risk of developing chronic allograft nephropathy.

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.

Predictive value of urinary retinol binding protein for graft dysfunction after kidney transplantation

High concentrations of retinol binding protein (RBP) are found in the urine of patients with tubulointerstitial injury. We evaluated the predictive value of urinary RBP (RBPu) for development graft dysfunction after kidney transplantation.

METHODS

Serum creatinine and RBPu were prospectively measured at months 3, 6, and 12 in 221 kidney transplant patients. Baseline graft function was defined as the lowest serum creatinine value during the first 3 months after transplantation. Graft dysfunction was assessed at 1 year as a >-20% or >-30% change in the inverse creatinine ((Delta)1/Cr) compared to baseline value at month 3.

RESULTS

Among 183 patients with normal graft function (Cr </= 1.6 mg/dL) the mean (Delta)1/Cr from month 3 to 12 was -17 +/- 22% (-80% to + 44%). Using a receiver operating characteristic (ROC) analysis, concentrations higher than 0.6 mg/L showed the best predictive value for diagnosis of graft dysfunction at 1 year. Mean (Delta)1/Cr from month 3 to 12 was -13 +/- 20% for those with RBP < 0.6 mg/L vs -20 +/- 23% in those with RBPu > 0.6 mg/L (95% CI = -13% to -1.3%, P =.018). The percentage of patients with >-20% or >-30% (Delta)1/Cr was higher among patients with RBPu > 0.6 mg/L (34% vs 47%, P =.042; 21% vs 34%, P =.035). RBPu > 0.6 mg/L was the only variable independently associated with >-30% (Delta)1/Cr at 1 year, with an odds ratio (OR) of 1.95 (95% CI 0.99 to 3.80, P =.05).

CONCLUSIONS

RBPu may serve as a surrogate marker for graft dysfunction early after transplantation for patients with normal graft function, allowing early institution of intervention therapies to prolong allograft survival.

The incidence of end-stage renal failure in 17 years of heart transplantation: a single center experience

BACKGROUND

Predictions of the incidence of renal failure within a heart transplant population are based on the early experiences of cyclosporine (CsA)-based immunosuppression. We report a single-center experience of end-stage renal failure (ESRF) during a 17-year period encompassing current lower dose CsA regimens.

METHOD

Prospectively collected data were analyzed on all patients who underwent first heart transplants between April 1982 and February 1999 (n = 697). We further categorized patients by the date of transplantation into a higher and lower dosage maintenance CsA group.

RESULTS

End-stage renal failure developed in 44 patients. The median time to dialysis was 87 months after transplantation and was independent of the initial CsA regimens used (p = 0.798). In the ESRF group, 14 underwent hemodialysis, 28 underwent peritoneal dialysis, and 9 underwent renal transplantation. One- and 5-year survival rates after dialysis were 82% and 62% respectively. The incidence of ESRF at our institution was 5.8%. It increased with post-operative survival and was independent of the initial CsA regimen used. We found no difference in pre-transplant age, sex, diagnosis, immediate post-operative creatinine, or the development of diabetes between the ESRF group and controls. The ESRF group received higher dosages of CsA within the first post-transplant year, although this did not reach significance (CsA dosage, 5.9 microg/kg/day vs 5.1 microg/kg/day, respectively p = 0.075).

CONCLUSIONS

Lower dosage CsA regimes have not altered the incidence of ESRF at our institution, suggesting an individual predisposition to nephropathy. Therefore, reduction in the future incidence of ESRF may rely on extremely low-dose or calcineurin-free immunosuppression regimes.