Calcineurin inhibitor nephrotoxicity: a review and perspective of the evidence

Plasma neutrophil gelatinase-associated lipocalin and worsening renal function during everolimus therapy after heart transplantation

Recently, the mammalian target of rapamycin inhibitor everolimus (EVL) has been introduced as a novel immunosuppressant for heart transplant (HTx) recipients, and is expected to preserve renal function compared to conventional calcineurin inhibitors (CNIs). However, a considerable number of recipients treated with EVL were not free from worsening renal function regardless of CNI reduction. Data were collected retrospectively from 27 HTx recipients who had received EVL (trough concentration, 3.1-9.2 ng/mL) along with reduced CNIs (%decreases in trough concentration, 27.3 ± 13.0%) because of switching from mycophenolate mophetil due to digestive symptoms or neutropenia, progressive coronary artery vasculopathy, or persistent renal dysfunction, and had been followed over 1 year between August 2008 and January 2013. Estimated glomerular filtration rate (eGFR) decreased in 5 recipients (18.5%) during the study period. Univariate logistic regression analysis demonstrated that a higher plasma neutrophil gelatinase-associated lipocalin (P-NGAL) level was the only significant predictor for a decrease in eGFR over a 1-year EVL treatment period among all baseline parameters (P = 0.008). eGFR and proteinuria worsened almost exclusively in patients with baseline P-NGAL ≥ 85 ng/mL, which was the cutoff value calculated by an ROC analysis (area under the curve, 0.955; sensitivity, 1.000; specificity, 0.955). In conclusion, higher P-NGAL may be a novel predictor for the worsening of renal function after EVL treatment that is resistant to CNI reduction in HTx recipients.

Now or never? The case for cell-based immunosuppression in kidney transplantation

By exploiting mechanisms of immunological regulation against donor alloantigen, it may be possible to reduce the dependence of kidney transplant recipients upon calcineurin inhibitor-based maintenance immunosuppression. One means to strengthen regulatory responses is treating recipients with preparations of regulatory cells obtained by ex vivo manipulation. This strategy, which is a well-established experimental method, has been developed to the point that early-phase clinical trials in kidney transplantation are now feasible. Cell-based therapies represent a radical departure from conventional treatment, so what grounds are there for this new approach? This article offers a three-part justification for trialing cell-based therapies in kidney transplantation: first, a clinical need for alternatives to standard immunosuppression is identified, based on the inadequacies of calcineurin inhibitor-based regimens in preventing late allograft loss; second, a mechanistic explanation of how cell-based therapies might address this clinical need is given; and third, the possible benefit to patients is weighed against the potential risks of cell-based immunosuppressive therapy. It is concluded that the safety of cell-based immunosuppressive therapy will not be greatly improved by further basic scientific and preclinical development. Only trials in humans can now tell us whether cell-based therapy is likely to benefit kidney transplant recipients, but these should be conservative in design to minimize any potential harm to patients.

Use of pharmacogenomics in pediatric renal transplant recipients

Transplant recipients receive potent immunosuppressive drugs in order to prevent graft rejection. Therapeutic drug monitoring is the current approach to guide the dosing of calcineurin inhibitors, mammalian target of rapamycin inhibitors (mTORi) and mofetil mycophenolate. Target concentrations used in pediatric patients are extrapolated from adult studies. Gene polymorphisms in metabolizing enzymes and drug transporters such as cytochromes CYP3A4 and CYP3A5, UDP-glucuronosyl transferase, and P-glycoprotein are known to influence the pharmacokinetics and dose requirements of immunosuppressants. The implications of pharmacogenomics in this patient population is discussed. Genetic information can help with achieving target concentrations in the early post-transplant period, avoiding adverse drug reactions and drug-drug interactions. Evidence about genetic studies and transplant outcomes is revised.

Biomarkers of calcineurin inhibitor nephrotoxicity in transplantation

Over 35 years of use has demonstrated the revolutionary therapeutic benefits of calcineurin inhibitors (CNI) in not only preventing transplant rejection, but also the renal and nonrenal toxicity of CNI. Acute reversible and insidious irreversible forms of CNI nephrotoxicity have been identified, with ischemia from an imbalance between vasoconstrictors and vasodilators playing an important role. The ongoing search to define toxicity pathways has been enriched by ‘Omics’ studies. Changes in proteins including those involved in activation of pro-inflammatory responses, oxidative stress, ER stress and the unfolded protein response have been identified, and these may serve as biomarkers of toxicity. However, the current standard of CNI toxicity, histology, lacks specificity, which creates challenges for biomarker validation. This review focuses on progress in nephrotoxic pathway identification of CNI and biomarker validation.

The Basics of Renal Allograft Pathology

Renal allograft biopsy provides critical information in the management of renal transplant patients, and must be analyzed in close collaboration with the clinical team. The histologic correlates of acute T-cell mediated rejection are interstitial inflammation, tubulitis, and endothelialitis; polyomavirus nephropathy is a potential mimic. Evidence of antibody-mediated rejection includes C4d deposition; morphologic acute tissue injury; and donor specific antibodies. Acute tubular injury/necrosis is a reversible cause of impaired graft function, especially in the immediate post-transplant period. Drug toxicity, recurrent disease, chronic injury, and other entities affecting both native and transplant kidneys must also be evaluated.

Renal teratogens

In utero exposure to certain drugs early in pregnancy may adversely affect nephrogenesis. Exposure to drugs later in pregnancy may affect the renin-angiotensin system, which could have an impact on fetal or neonatal renal function. Reduction in nephron number and renal function could have adverse consequences for the child several years later. Data are limited on the information needed to guide decisions for patients and providers regarding the use of certain drugs in pregnancy. The study of drug nephroteratogenicity has not been systematized, a large, standardized, global approach is needed to evaluate the renal risks of in utero drug exposures.

Calcineurin/NFAT signaling and innate host defence: a role for NOD1-mediated phagocytic functions

The calcineurin/nuclear factor of activated T cells (NFATs) signaling pathway plays a central role in T cell mediated adaptive immune responses, but a number of recent studies demonstrated that calcineurin/NFAT signaling also plays a key role in the control of the innate immune response by myeloid cells. Calcineurin inhibitors, such as cyclosporine A (CsA) and tacrolimus (FK506), are commonly used in organ transplantation to prevent graft rejection and in a variety of immune diseases. These immunosuppressive drugs have adverse effects and significantly increase host's susceptibility towards bacterial or fungal infections. Recent studies highlighted the role of NFAT signaling in fungal infection and in the control of the pattern recognition receptor nucleotide-binding oligomerization domain-containing protein 1 (NOD1), which predominantly senses invasive Gram-negative bacteria and mediates neutrophil phagocytic functions. This review summarises some of the current knowledge concerning the role of NFAT signaling in the innate immune response and the recent advances on NFAT-dependent inhibition of NOD1-mediated innate immune response caused by CsA, which may contribute to sensitizing transplant recipients to bacterial infection.

Comparative efficacy and safety of mizoribine with mycophenolate mofetil for Asian renal transplantation--a meta-analysis

OBJECTIVES

Mizoribine (MZR) with its high safety and low cost has been widely used in Asia. It has been questioned whether high or low dose of MZR could obtain the efficacy and safety similar to mycophenolate mofetil (MMF) following renal transplantation. This meta-analysis was done to compare the efficacy and safety of high- or low-dose MZR with MMF for immunosuppressive therapy in renal transplantation.

DESIGN AND METHODS

Available data comparing MZR with MMF in renal transplant recipients were searched. Subgroup analysis was conducted according to the administration dosage of MZR. Trials were pooled using Meta-analysis software and confidence intervals were set at 95%.

RESULTS

Altogether 1149 Asian patients from 7 RCTs and 9 cohort studies were included. The efficacy of different MZR doses put on par with MMF, but the safety was better than MMF. Specifically, recipients taking MZR favor significantly fewer episodes of leucocytopenia [RR 0.40 (0.26, 0.60)], gastrointestinal disorder [RR 0.54 (0.40, 0.73)], CMV infection [RR 0.47 (0.34, 0.64)] and more favorable outcome of hepatic dysfunction, although the difference failed to reach a statistical significance [RR 0.67 (0.44, 1.00)]. Unfortunately, hyperuricemia was significantly obvious in MZR group [RR 1.96 (1.47, 2.61)].

CONCLUSIONS

MZR is an effective and safe immunosuppressive agent and high-dose MZR can be recommended as an alternative to MMF following adult renal transplantation in Asia, but hyperuricemia and liver damage should be closely monitored during the medication period.