Toxicodynamic Therapeutic Drug Monitoring of Immunosuppressants: Promises, Reality, and Challenges

The IMBG Test for Evaluating the Pharmacodynamic Response to Immunosuppressive Therapy in Kidney Transplant Patients: Current Evidence and Future Applications

Immunosuppressive drugs are widely used to prevent rejection after kidney transplantation. However, the pharmacological response to a given immunosuppressant can vary markedly between individuals, with some showing poor treatment responses and/or experiencing serious side effects. There is an unmet need for diagnostic tools that allow clinicians to individually tailor immunosuppressive therapy to a patient’s immunological profile. The Immunobiogram (IMBG) is a novel blood-based in vitro diagnostic test that provides a pharmacodynamic readout of the immune response of individual patients to a range of immunosuppressants commonly used in kidney transplant recipients. Here, we discuss the current approaches used to measure the pharmacodynamic responses of individual patients to specific immunosuppressive drugs in vitro, which can then be correlated with patient’s clinical outcomes. We also describe the procedure of the IMBG assay, and summarize the results obtained using the IMBG in different kidney transplant populations. Finally, we outline future directions and other novel applications of the IMBG, both in kidney transplant patients and other autoimmune diseases.

Immunosuppressive Drug-Associated Adverse Event Profiles in De Novo Kidney Transplant Recipients Receiving Everolimus and Reduced Tacrolimus Doses

BACKGROUND

The safety of immunosuppressive regimens is influenced by the induction agent, maintenance drug combination, and prophylactic strategy for cytomegalovirus (CMV) infection. Herein, this safety analysis compares rabbit antithymocyte globulin (r-ATG) or basiliximab (BAS) combined with everolimus (EVR) versus BAS combined with mycophenolate sodium (MPS) in kidney transplant recipients receiving tacrolimus, prednisone, and preemptive CMV therapy.

METHODS

In this single-center, prospective, randomized study, adverse events (AEs), serious AEs (SAEs), viral infections, laboratory abnormalities, dose reductions, and temporary or permanent discontinuation of the immunosuppressant were compared among patients receiving r-ATG/EVR (n = 85), BAS/EVR (n = 102), and BAS/MPS (n = 101).

RESULTS

A total of 2741 AEs and 344 SAEs were observed. There were no differences in the proportion of patients with at least one AE (96% versus 98% versus 96%, respectively; P > 0.05). The proportion of patients with at least one SAE was highest in the BAS/MPS group (33% versus 48% versus 69%, respectively; P < 0.05). This difference was due primarily to a high incidence of CMV infection in the BAS/MPS group (4.7% versus 10.8% versus 37.6%, respectively). The incidence of mild/moderate abnormalities in creatinine, cholesterol, and triglyceride levels was higher in both EVR groups. The cumulative freedom from dose reduction or treatment discontinuation due to an AE was higher in both EVR groups than in the BAS/MPS group (89.2% versus 92.8% versus 76.3%, respectively, P = 0.003). There was no difference in the incidence of biopsy-confirmed acute rejection (9.4% versus 18.6 versus 15.8%, respectively; P = 0.403).

CONCLUSIONS

This analysis suggests that r-ATG induction combined with EVR is associated with a comparable incidence of acute rejection, lower incidence of CMV infection, and fewer changes in initial immunosuppressive regimen due to AEs in kidney transplant recipients receiving tacrolimus, prednisone, and preemptive CMV therapy.

The interleukin-17 G-197A polymorphism is associated with cyclosporine metabolism and transplant rejection in liver transplant recipients

Aim: This study aimed to investigate the effect of and mechanism involved in the IL-17 SNP on cyclosporine metabolism and outcomes of liver transplantation (LT). Materials & methods: The IL-17 genotype, IL-17 expression, postoperative outcome and cyclosporine concentration were reviewed in 106 LT recipients. The functional relevance of rs2275913 was evaluated by luciferase assay. Furthermore, L02 cells were treated with IL-17 recombinant protein or/and pregnane X receptor (PXR) knockdown lentiviruses, then the expression of PXR, CYP3A4, CYP3A5 and IL-17R were detected by PCR and western blotting. Result: The significant distribution difference at IL-17 locus G-197A was confirmed between patients with and without rejection (p = 0.035). Patients with acute rejection showed higher IL-17 level than those without rejection. Cyclosporine concentration was associated with the different IL-17 genotype (p < 0.05). Luciferase assay revealed that 197G genotype had higher luciferase activity than that in 197A genotype (p = 0.009). Furthermore, IL-17 recombinant protein remarkably promoted the expressions of PXR, CYP3A4 and CYP3A5 (p < 0.01), but not IL-17R. PXR knockdown significantly inhibited the mRNA levels of CYP3A4 and CYP3A5 but not IL-17R (p < 0.01), while IL-17 recombinant protein had no influence on the expressions of CYP3A4 and CYP3A5 when PXR was downregulated. Conclusion: This study revealed the possible association of IL-17 G-197A with cyclosporine metabolism and transplant rejection after LT, which might be partly related to the upregulations of CYP3A4/5 dependent on PXR.

How scientific literature analysis yields innovative therapeutic hypothesis through integrative iterations

It is becoming generally accepted that the current diagnostic system often guarantees, rather than diminishes, disease heterogeneity. In effects, syndrome-dominated conceptual thinking has become a barrier to understanding the biological causes of complex, multifactorial diseases characterized by clinical and therapeutic heterogeneity. Furthermore, not only is the flood of currently available medical and biological information highly heterogeneous, it is also often conflicting. Together with the entire absence of functional models of pathogenesis and pathological evolution of complex diseases, this leads to a situation where illness activity cannot be coherently approached and where therapeutic developments become highly problematic. Acquisition of the necessary knowledge can be obtained, in parts, using in silico models produced through analytical approaches and processes collectively known as `Systems Biology'. However, without analytical approaches that specifically incorporate the facts that all that is called `information' is not necessarily useful nor utilisable and that all information should be considered as a priori suspect, modelling attempts will fail because of the much too numerous conflicting and, although correct in molecular terms, physiologically invalid reports. In the present essay, we suggest means whereby this body of problems could be functionally attacked and describe new analytical approaches that have demonstrated their efficacy in alleviating these difficulties.

Ensemble of rankers for efficient gene signature extraction in smoke exposure classification

Background

System toxicology aims at understanding the mechanisms used by biological systems to respond to toxicants. Such understanding can be leveraged to assess the risk of chemicals, drugs, and consumer products in living organisms. In system toxicology, machine learning techniques and methodologies are applied to develop prediction models for classification of toxicant exposure of biological systems. Gene expression data (RNA/DNA microarray) are often used to develop such prediction models.

Results

The outcome of the present work is an experimental methodology to develop prediction models, based on robust gene signatures, for the classification of cigarette smoke exposure and cessation in humans. It is a result of the participation in the recent sbv IMPROVER SysTox Computational Challenge. By merging different gene selection techniques, we obtain robust gene signatures and we investigate prediction capabilities of different off-the-shelf machine learning techniques, such as artificial neural networks, linear models and support vector machines. We also predict six novel genes in our signature, and firmly believe these genes have to be further investigated as biomarkers for tobacco smoking exposure.

Conclusions

The proposed methodology provides gene signatures with top-ranked performances in the prediction of the investigated classification methods, as well as new discoveries in genetic signatures for bio-markers of the smoke exposure of humans.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2035-3) contains supplementary material, which is available to authorized users.

The Immunosuppressant Mycophenolic Acid Alters Nucleotide and Lipid Metabolism in an Intestinal Cell Model

The study objective was to elucidate the molecular mechanisms underlying the negative effects of mycophenolic acid (MPA) on human intestinal cells. Effects of MPA exposure and guanosine supplementation on nucleotide concentrations in LS180 cells were assessed using liquid chromatography-mass spectrometry. Proteomics analysis was carried out using stable isotope labeling by amino acids in cell culture combined with gel-based liquid chromatography-mass spectrometry and lipidome analysis using ¹H nuclear magnetic resonance spectroscopy. Despite supplementation, depletion of guanosine nucleotides (p < 0.001 at 24 and 72 h; 5, 100, and 250 μM MPA) and upregulation of uridine and cytidine nucleotides (p < 0.001 at 24 h; 5 μM MPA) occurred after exposure to MPA. MPA significantly altered 35 proteins mainly related to nucleotide-dependent processes and lipid metabolism. Cross-reference with previous studies of MPA-associated protein changes widely corroborated these results, but showed differences that may be model- and/or method-dependent. MPA exposure increased intracellular concentrations of fatty acids, cholesterol, and phosphatidylcholine (p < 0.01 at 72 h; 100 μM MPA) which corresponded to the changes in lipid-metabolizing proteins. MPA affected intracellular nucleotide levels, nucleotide-dependent processes, expression of structural proteins, fatty acid and lipid metabolism in LS180 cells. These changes may compromise intestinal membrane integrity and contribute to gastrointestinal toxicity.

Tacrolimus Modulates TGF-β Signaling to Induce Epithelial-Mesenchymal Transition in Human Renal Proximal Tubule Epithelial Cells

Epithelial-mesenchymal transition (EMT), a process which describes the trans-differentiation of epithelial cells into motile mesenchymal cells, is pivotal in stem cell behavior, development and wound healing, as well as contributing to disease processes including fibrosis and cancer progression. Maintenance immunosuppression with calcineurin inhibitors (CNIs) has become routine management for renal transplant patient, but unfortunately the nephrotoxicity of these drugs has been well documented. HK-2 cells were exposed to Tacrolimus (FK506) and EMT markers were assessed by RT PCR and western blot. FK506 effects on TGF-β mRNA were assessed by RT PCR and TGF-β secretion was measured by ELISA. The impact of increased TGF-β secretion on Smad signaling pathways was investigated. The impact of inhibition of TGF-β signaling on EMT processes was assessed by scratch-wound assay. The results presented in this study suggest that FK506 initiates EMT processes in the HK-2 cell line, with altered expression of epithelial and myofibroblast markers evident. Additionally, the study demonstrates that FK506 activation of the TGF-β/ SMAD pathways is an essential step in the EMT process. Overall the results demonstrate that EMT is heavily involved in renal fibrosis associated with CNI nephrotoxicity.

Renal Cell Carcinoma: A Study through NMR-Based Metabolomics Combined with Transcriptomics

Renal cell carcinoma (RCC) is a heterogeneous cancer often showing late symptoms. Until now, some candidate protein markers have been proposed for its diagnosis. Metabolomics approaches have been applied, predominantly using Mass Spectrometry (MS), while Nuclear Magnetic Resonance (NMR)-based studies remain limited. There is no study about RCC integrating NMR-based metabolomics with transcriptomics. In this work, ¹H-NMR spectroscopy combined with multivariate statistics was applied on urine samples, collected from 40 patients with clear cell RCC (ccRCC) before nephrectomy and 29 healthy controls; nine out of 40 patients also provided samples one-month after nephrectomy. We observed increases of creatine, alanine, lactate and pyruvate, and decreases of hippurate, citrate, and betaine in all ccRCC patients. A network analysis connected most of these metabolites with glomerular injury, renal inflammation and renal necrosis/cell death. Interestingly, intersecting metabolites with transcriptomic data from CD133+/CD24+ tumoral renal stem cells isolated from ccRCC patients, we found that both genes and metabolites differentially regulated in ccRCC patients belonged to HIF-α signaling, methionine and choline degradation, and acetyl-CoA biosynthesis. Moreover, when comparing urinary metabolome of ccRCC patients after nephrectomy, some processes, such as the glomerular injury, renal hypertrophy, renal necrosis/cell death and renal proliferation, were no more represented.

A high-performance liquid chromatography-tandem mass spectrometry-based targeted metabolomics kidney dysfunction marker panel in human urine

BACKGROUND

Previous studies have examined and documented fluctuations in urine metabolites in response to disease processes and drug toxicity affecting glomerular filtration, tubule cell metabolism, reabsorption, oxidative stress, purine degradation, active secretion and kidney amino acylase activity representative of diminished renal function. However, a high-throughput assay that incorporates metabolites that are surrogate markers for such changes into a kidney dysfunction panel has yet to be described.

METHODS

A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay for the quantification of ten metabolites associated with the Krebs cycle, purine degradation, and oxidative stress in human urine was developed and validated. Normal values were assessed in healthy adult (n=120) and pediatric (n=36) individuals. In addition, 9 pediatric renal transplant recipients patients were evaluated before and after initial dosing of the immunosuppressant tacrolimus in a proof-of-concept study.

RESULTS

The assay met all predefined acceptance criteria. The lower limit of quantification ranged from 0.1 to 1000 μmol/l. Inter-day trueness and imprecisions ranged from 91.4-112.9% and 1.5-12.4%, respectively. The total assay run time was 5.5 minutes. Concentrations of glucose, sorbitol, and trimethylamine oxide (TMAO) were elevated in pediatric renal transplant patients (n=9) prior to transplantation as well as before and immediately after initial dosing of tacrolimus. One month post-transplant urine metabolite patterns matched those of healthy children (n=36).

CONCLUSIONS

The LC-MS/MS assay will provide the basis for further large-scale clinical studies to explore these analytes as molecular markers for the patients with renal insufficiency.

Mycophenolate mofetil enhances the negative effects of sirolimus and tacrolimus on rat kidney cell metabolism

Background and Purpose

Mycophenolate mofetil (MMF) per se is not known to have negative effects on the kidney. MMF alone or in combination with sirolimus, can be the basis of calcineurin inhibitor (CNI)-free, kidney sparing drug protocols. However, long-term outcomes in patients on MMF/SRL seem to be inferior to those treated with regimens that include the CNI tacrolimus (TAC) due to an increased risk of allo-immune reactions. Interestingly, potential enhancement of the negative effects of SRL and TAC on the kidney by MMF has never been considered.

Experimental Approach

It was our aim to study the effects of TAC, SRL and MMF alone and evaluate their interactions when combined on the rat kidney. For this purpose we used a comprehensive molecular marker approach including measurements of urinary 8-isoprostane concentrations (oxidative stress marker) and changes of urinary metabolite patterns (¹H-NMR spectroscopy) and comparing these markers to renal function (glomerular filtration rate (GFR)) and morphologic alterations (histology).

Key Results

While MMF alone did not impact GFR, its interaction with SRL and TAC led to a significant decrease of rats’ renal function. The decline went in parallel with a significant increase in urinary isoprostane concentrations and an enhancement of negative effects on urinary metabolite patterns.

Conclusions

In broad summary, the present study showed that MMF may enhance the negative effects of TAC on kidney function and may even display nephrotoxic properties when combined with SRL.

The applied basic research of systemic lupus erythematosus based on the biological omics

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the production of autoantibodies directed against nuclear self-antigens and circulating immune complexes. This results in damages to various organs or systems, including skin, joints, kidneys and the central nervous system. Clinical manifestations of SLE could be diverse, including glomerulonephritis, dermatitis, thrombosis, vasculitis, seizures and arthritis. The complicated pathogenesis and varied clinical symptoms of SLE pose great challenges in the diagnosis and monitoring of this disease. Unfortunately, the etiological factors and pathogenesis of SLE are still not completely understood. It is noteworthy that recent advances in our understanding of the biological omics and emerging technologies have been providing new tools in the analyses of SLE, such as genomics, epigenomics, transcriptomics, proteomics, metabolomics and so on. In this article, we summarize our current knowledge in this field for a better understanding of the pathogenesis, diagnosis and treatment for SLE.

Metabolomics of human intestinal transplant rejection

Surveillance endoscopy with biopsy is the standard method to monitor intestinal transplant recipients but it is invasive, costly and prone to sampling error. Early noninvasive biomarkers of intestinal rejection are needed. In this pilot study we applied metabolomics to characterize the metabolomic profile of intestinal allograft rejection. Fifty-six samples of ileostomy fluid or stool from 11 rejection and 45 nonrejection episodes were analyzed by ultraperformance liquid chromatography in conjunction with Quadrupole time-of-flight mass spectrometry (UPLC-QTOFMS). The data were acquired in duplicate for each sample in positive ionization mode and preprocessed using XCMS (Scripps) followed by multivariate data analysis. We detected a total of 2541 metabolites in the positive ionization mode (mass 50-850 Daltons). A significant interclass separation was found between rejection and nonrejection. The proinflammatory mediator leukotriene E4 was the metabolite with the highest fold change in the rejection group compared to nonrejection. Water-soluble vitamins B2, B5, B6, and taurocholate were also detected with high fold change in rejection. The metabolomic profile of rejection was more heterogeneous than nonrejection. Although larger studies are needed, metabolomics appears to be a promising tool to characterize the pathophysiologic mechanisms involved in intestinal allograft rejection and potentially to identify noninvasive biomarkers.

Urinary metabolomics in newborns and infants

Metabolomics is a new approach based on the systematic study of the full complement of metabolites in a biological sample. This technology consists of two sequential steps: (1) an experimental technique, based on nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry, designed to profile low-molecular-weight compounds, and (2) multivariate data analysis. The metabolomic analysis of biofluids or tissues has been successfully used in the fields of physiology, diagnostics, functional genomics, pharmacology, toxicology, and nutrition. Recent studies have evaluated how physiological variables or pathological conditions can affect metabolomic profiles of different biofluids in pediatric populations. The overall metabolic status of the neonate is little known. If more information on perinatal/neonatal maturational processes and their metabolic background were available, the management of sick or preterm newborns might be improved. Currently, the use of metabolomics in neonatology is still in the pioneering phase. Meaningful diagnostic information and simple, noninvasive collection techniques make urine a particularly suitable biofluid for metabolomic approach in neonatal medicine, although blood has also been investigated. Different fields of neonatology such as postnatal maturation, asphyxia/hypoxia, inborn errors of metabolism, nutrition, nephrouropathies, nephrotoxicity, cardiovascular diseases, and other conditions have been investigated using a metabolomic approach. Together with genomics and proteomics, metabolomics appears to be a promising tool in neonatology for the monitoring of postnatal metabolic maturation, the identification of biomarkers as early predictors of outcome, the diagnosis and monitoring of various diseases, and the "tailored" management of neonatal disorders.

Identification of urinary metabolites that distinguish membranous lupus nephritis from proliferative lupus nephritis and focal segmental glomerulosclerosis

Introduction

Systemic lupus erythematosus (SLE or lupus) is a chronic autoimmune disease, and kidney involvement with SLE, a.k.a. lupus nephritis (LN), is a frequent and severe complication of SLE that increases patient morbidity and mortality. About 50% of patients with SLE encounter renal abnormalities which, if left untreated, can lead to end-stage renal disease. Kidney biopsy is considered the criterion standard for diagnosis and staging of LN using the International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification, which was developed to help predict renal outcomes and assist with medical decision-making. However, kidney biopsy-based classification of LN is highly invasive and impractical for real-time monitoring of LN status. Here, nuclear magnetic resonance (NMR) spectroscopy-based metabolic profiling was used to identify urinary metabolites that discriminated between proliferative and pure membranous LN as defined by the ISN/RPS classification, and between LN and primary focal segmental glomerulosclerosis (FSGS).

Methods

Metabolic profiling was conducted using urine samples of patients with proliferative LN without membranous features (Class III/IV; n = 7) or pure membranous LN (Class V; n = 7). Patients with primary FSGS and proteinuria (n = 10) served as disease controls. For each patient, demographic information and clinical data was obtained and a random urine sample collected to measure NMR spectra. Data and sample collection for patients with LN occurred around the time of kidney biopsy. Metabolic profiling analysis was done by visual inspection and principal component analysis.

Results

Urinary citrate levels were 8-fold lower in Class V LN compared to Class III/IV patients, who had normal levels of urinary citrate (P < 0.05). Class III/IV LN patients had > 10-fold lower levels of urinary taurine compared to Class V patients, who had mostly normal levels (P < 0.01). Class V LN patients had normal urinary hippurate levels compared to FSGS patients, who completely lacked urinary hippurate (P < 0.001).

Conclusions

This pilot study indicated differences in urinary metabolites between proliferative LN and pure membranous LN patients, and between LN and FSGS patients. If confirmed in larger studies, these urine metabolites may serve as biomarkers to help discriminate between different classes of LN, and between LN and FSGS.

Biomarkers of acute kidney injury

Acute kidney injury (AKI) is a common problem in both the inpatient and outpatient setting and often results from drug toxicities. Traditional methods of identifying AKI, through measurement of blood urea nitrogen and serum creatinine, are problematic in that they are slow to detect decreases in glomerular filtration rate (GFR) and are influenced by a variety of factors that are not related to GFR changes. The problems inherent in a creatinine-based diagnosis of AKI have impeded the development of proper therapeutics in AKI and posed problems in evaluating nephrotoxicity of drugs and other chemical exposures. In recent years, a number of new biomarkers of AKI with more favorable test characteristics than creatinine have been identified and studied in a variety of experimental and clinical settings. This review will consider the most well-established biomarkers and appraise the literature, with particular attention given to the use of biomarkers in identifying toxin-mediated AKI.

A high-throughput U-HPLC-MS/MS assay for the quantification of mycophenolic acid and its major metabolites mycophenolic acid glucuronide and mycophenolic acid acyl-glucuronide in human plasma and urine

Mycophenolic acid (MPA) is used as an immunosuppressant after organ transplantation and for the treatment of immune diseases. There is increasing evidence that therapeutic drug monitoring and plasma concentration-guided dose adjustments are beneficial for patients to maintain immunosuppressive efficacy and to avoid toxicity. The major MPA metabolite that can be found in high concentrations in plasma is MPA glucuronide (MPAG). A metabolite usually present at lower concentrations, MPA acyl-glucuronide (AcMPAG), has been implicated in some of the adverse effects of MPA. We developed and validated an automated high-throughput ultra-high performance chromatography-tandem mass spectrometry (U-HPLC-MS/MS) assay using liquid-handling robotic extraction for the quantification of MPA, MPAG, and AcMPAG in human EDTA plasma and urine. The ranges of reliable response were 0.097 (lower limit of quantitation) to 200 μg/mL for MPA and MPAG and 0.156-10 μg/mL for AcMPAG in human urine and plasma. The inter-day accuracies were 94.3-104.4%, 93.8-105.0% and 94.4-104.7% for MPA, MPAG and AcMPAG, respectively. Inter-day precisions were 0.7-7.8%, 0.9-6.9% and 1.6-8.6% for MPA, MPAG and AcMPAG. No matrix interferences, ion suppression/enhancement and carry-over were detected. The total assay run time was 2.3 min. The assay met all predefined acceptance criteria and the quantification of MPA was successfully cross-validated with an LC-MS/MS assay routinely used for clinical therapeutic drug monitoring. The assay has proven to be robust and reliable during the measurement of samples from several pharmacokinetics trials.

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.

Pharmacokinetics and pharmacodynamics of A77 1726 and leflunomide in domestic cats

The pharmacokinetics and pharmacodynamics of A77 1726 and leflunomide after intravenous (i.v.) and oral (p.o.) administration were evaluated in adult cats. Three treatments were administered: a single i.v. dose of A77 1726 (4 mg/kg), a single oral dose of leflunomide (4 mg/kg), and multiple oral doses of leflunomide (2 mg/kg). Mean pharmacokinetic parameter values after a single i.v. dose of A77 1726 were distribution (A) and elimination (B) intercepts (15.2 μg/mL and 34.5 μg/mL, respectively), distribution and elimination half-lives (1.5 and 71.8 h, respectively), area under the curve (AUC(0 → ∞); 3723 μg*h/mL), mean residence time (MRT; 93 h), clearance (Cl(obs); 1.1 mL/kg/h), and volume of distribution at steady state (Vd(ss); 97 mL/kg). Mean pharmacokinetic parameter values after a single oral dose of leflunomide were absorption and elimination rate constants (0.3 1/h and 0.01 1/h, respectively), absorption and elimination half-lives (2.3 and 59.1 h, respectively), AUC(0 → ∞) (3966 μg*h/mL), and maximum observed plasma concentration (C(max); 38 μg/mL). The bioavailability after a single oral dose of leflunomide was 100%. The mean ± SD A77 1726 concentration that inhibited 50% lymphocytes (EC(50) ) was 16 ± 13.5 μg/mL. The mean ± SD maximum A77 1726 concentration (EC(max)) was 61.0 ± 23.9 μg/mL.

Toxicodynamic effects of ciclosporin are reflected by metabolite profiles in the urine of healthy individuals after a single dose

WHAT IS ALREADY KNOWN ABOUT THE SUBJECT * Ciclosporin's nephrotoxicity initially targets the proximal tubule and is, at least in part, driven by increased formation of oxygen radicals. * (1)H-nuclear magnetic resonance spectroscopy (NMR)- and mass spectrometry (MS)-based biochemical profiling (metabolomics) allows for the sensitive detection of metabolite pattern changes in urine. * In systematic studies in rats we showed that ciclosporin caused urine metabolite pattern changes typical for proximal tubule damage and that these pattern changes seemed to be more sensitive than established clinical kidney function markers such as serum creatinine concentrations. WHAT THIS PAPER ADDS * This study showed that urine metabolite pattern changes as assessed by (1)H-NMR and HPLC-MS are sensitive enough to detect the effect of ciclosporin as early as 4 h after a single oral dose. * In our previous rat studies, changes in urine metabolite pattern in response to ciclosporin translated into healthy humans, indicating the involvement of the same toxicodynamic mechanisms. * The results provide proof of concept for further development of this combination molecular marker strategy into diagnostic tools for the detection and monitoring of drug nephrotoxicity. AIMS The immunosuppressant ciclosporin is an efficient prophylaxis against transplant organ rejection but its clinical use is limited by its nephrotoxicity. Our previous systematic studies in the rat indicated urine metabolite pattern changes to be sensitive indicators of the negative effects of ciclosporin on the kidney. To translate these results, we conducted an open label, placebo-controlled, crossover study assessing the time-dependent toxicodynamic effects of a single oral ciclosporin dose (5 mg kg(-1)) on the kidney in 13 healthy individuals. METHODS In plasma and urine samples, ciclosporin and 15-F(2t)-isoprostane concentrations were assessed using HPLC-MS and metabolite profiles using (1)H-NMR spectroscopy. RESULTS The maximum ciclosporin concentrations were 1489 +/- 425 ng ml(-1) (blood) and 2629 +/- 1308 ng ml(-1) (urine). The increase in urinary 15-F(2t)-isoprostane observed 4 h after administration of ciclosporin indicated an increase in oxidative stress. 15-F(2t)-isoprostane concentrations were on average 2.9-fold higher after ciclosporin than after placebo (59.8 +/- 31.2 vs. 20.9 +/- 19.9 pg mg(-1) creatinine, P < 0.02). While there were no conclusive changes in plasma 15-F(2t)-isoprostane concentrations or metabolite patterns, non-targeted metabolome analysis using principal components analysis and partial least square fit analysis revealed significant changes in urine metabolites typically associated with negative effects on proximal tubule cells. The major metabolites that differed between the 4 h urine samples after ciclosporin and placebo were citrate, hippurate, lactate, TMAO, creatinine and phenylalanine. CONCLUSION Changes in urine metabolite patterns as a molecular marker are sufficiently sensitive for the detection of the negative effects of ciclosporin on the kidney after a single oral dose.

Molecular diagnostics in transplantation

The past few decades are characterized by an explosive evolution of genetics and molecular cell biology. Advances in chemistry and engineering have enabled increased data throughput, permitting the study of complete sets of molecules with increasing speed and accuracy using techniques such as genomics, transcriptomics, proteomics, and metabolomics. Prediction of long-term outcomes in transplantation is hampered by the absence of sufficiently robust biomarkers and a lack of adequate insight into the mechanisms of acute and chronic alloimmune injury and the adaptive mechanisms of immunological quiescence that may support transplantation tolerance. Here, we discuss some of the great opportunities that molecular diagnostic tools have to offer both basic scientists and translational researchers for bench-to-bedside clinical application in transplantation medicine, with special focus on genomics and genome-wide association studies, epigenetics (DNA methylation and histone modifications), gene expression studies and transcriptomics (including microRNA and small interfering RNA studies), proteomics and peptidomics, antibodyomics, metabolomics, chemical genomics and functional imaging with nanoparticles. We address the challenges and opportunities associated with the newer high-throughput sequencing technologies, especially in the field of bioinformatics and biostatistics, and demonstrate the importance of integrative approaches. Although this Review focuses on transplantation research and clinical transplantation, the concepts addressed are valid for all translational research.

Differential proteome and phosphoproteome signatures in human T-lymphoblast cells induced by sirolimus

OBJECTIVES

The present study was designed to investigate early proteome and phosphoproteome changes during inhibition of lymphocyte proliferation induced by sirolimus (SRL).

MATERIALS AND METHODS

Proliferation assays were conducted using human CCRF-CEM T lymphoblasts under different SRL concentrations. Total protein lysates after SRL treatment were used to identify significantly regulated proteins and phosphorylated proteins by 2-DE and Q-TOF Ultima Global mass spectrometer.

RESULTS AND CONCLUSIONS

Incubation with 2.5 micromol/l SRL resulted in a approximately 70% inhibition of cell proliferation. Cells incubated with 2.5 micromol/l for 30 min showed a differential phosphorylation pattern with one higher (TCPQ) and six lower phosphorylation signals (TBA1B, VIME, HNRPD, ENPL, SEPT9, PLSL). On investigating the differential protein expression, five proteins were found to be up-regulated (ECHB, PSB3, MTDC, LDHB and NDKA) and four were down-regulated (EHD1, AATC, LMNB1 and MDHC). Nine of these differentially regulated proteins/phosphoproteins (TCPQ, TBA1B, VIME, HNRPD, ENPL, ECHB, PSB3, LDHB and LMNB1) showed significant interaction potential, through binding protein YWHAZ using MINT software.

CONCLUSIONS

We report for the first time the simultaneous early influence of SRL on phosphorylation status and on protein expression in the total proteome of CCRF-CEM T lymphoblasts and predict that 56% of the proteins interact with each other, highlighting significance of these results.

Chronic treatment with cyclosporine affects systemic purinergic parameters, homocysteine levels and vascular disturbances in rats

Vascular disease is a major cause of morbidity and mortality among transplanted recipients and cyclosporine (CsA) treatment has been consistently implicated in this event. In this study we assessed total blood homocysteine levels (tHcy), ecto-nucleotidase activities and adenine nucleotide/nucleoside levels searching for parameters related to the mechanisms of vascular damage induced by chronic CsA treatment in non-transplanted rats. Thirty male Wistar rats were divided in three groups: control group treated with corn oil, CsA 5mg/kg and CsA 15 mg/kg, administered by daily gastric gavage during 8 weeks. CsA 15 mg/kg treatment increased blood levels of tHcy. Both CsA treatments (5mg/kg and 15 mg/kg) decreased adenine nucleotides hydrolysis by ecto-nucleotidases in serum, which negatively correlated with tHcy levels (r: -0.74, r: -0.63 and r: -0.63, p<0.004, for ATP, ADP and AMP, respectively). CsA 15mg/kg induced a statistically significant increase in ADP and decrease in adenosine (ADO) plasma levels compared to control group. THcy levels were positively correlated with plasma ADP levels and negatively correlated with ADO levels (r: 0.84, p<0.0001 and r: -0.68, p<0.0001, respectively). Rats under CsA 15 mg/kg treatment presented cell injury and inflammatory responses in the endothelium and intima layer of the aorta artery. In conclusion, blood ecto-nucleotidases activity, tHcy, and ADP and ADO levels may be implicated in vascular injury induced by CsA treatment.

Association of immunosuppressant-induced protein changes in the rat kidney with changes in urine metabolite patterns: a proteo-metabonomic study

The basic mechanisms underlying calcineurin inhibitor (CI) nephrotoxicity and its enhancement by sirolimus are still largely unknown. We investigated the effects of CIs alone and in combination with sirolimus on the renal proteome and correlated these effects with urine metabolite pattern changes. Thirty-six male Wistar rats were assigned to six treatment groups (n = 4/group for proteome analysis and n = 6/group for urine (1)H NMR metabolite pattern analysis): vehicle controls, sirolimus 1 mg/kg/day, cyclosporine 10 mg/kg/day, cyclosporine 10 mg/kg/day + sirolimus 1 mg/kg/day, tacrolimus 1 mg/kg/day, tacrolimus 1 mg/kg/day + sirolimus 1 mg/kg/day. After 28 days, 24 h-urine was collected for (1)H NMR-based metabolic analysis and kidneys were harvested for 2D-gel electrophoresis and histology. Cyclosporine affected the following groups of proteins: calcium homeostasis (regucalcin, calbindin), cytoskeleton (vimentin, caldesmon), response to hypoxia and mitochondrial function (prolyl 4-hydroxylase, proteasome, NADH dehydrogenase), and cell metabolism (kidney aminoacylase, pyruvate dehydrogenase, fructose-1,6-bis phosphate). Several of the changes in protein expression, confirmed by Western blot, were associated with and explained changes in metabolite concentrations in urine. Representative examples are an increase in kidney aminoacylase expression (decrease of hippurate concentrations in urine), up regulation of pyruvate dehydrogenase and fructose-1,6-bisphosphatase, (increased glucose metabolism), and down regulation of arginine/glycine-amidino transferase (most likely due to an increase in creatinine concentrations). Protein changes explained and qualified immunosuppressant-induced metabolite pattern changes in urine.

Molecular pathways involved in loss of graft function in kidney transplant recipients

Interstitial fibrosis (IF) and tubular atrophy (TA) are integral parts of chronic allograft dysfunction and represent in the new classification a separate entity with or without the identification of a specific etiology. Loss of kidney graft function with IF/TA is one of the causes of most kidney allograft losses. Despite progress in immunosuppression, chronic allograft dysfunction remains the main clinical challenge for improving long-term graft survival. The sustained damage to the allograft does not represent a single entity but the summated effects of tissue injury from several pathogenic insults, as well as the kidney's healing response, modified by alloimmunity and immunosuppression. A major challenge in the future of kidney transplantation includes the study of chronic allograft dysfunction pathogenesis to identify early markers of disease progression, as well as potential therapeutics pathways.

Immunotherapy in elderly transplant recipients: a guide to clinically significant drug interactions

Currently, >50% of candidates for solid organ transplantation in Europe and the US are aged >50 years while approximately 15% of potential recipients are aged >or=65 years. Elderly transplant candidates are characterized by specific co-morbidity profiles that compromise graft and patient outcome after transplantation. The presence of coronary artery or peripheral vascular disease, cerebrovascular disease, history of malignancy, chronic obstructive lung disease or diabetes mellitus further increases the early post-transplant mortality risk in elderly recipients, with infections and cardiovascular complications as the leading causes of death. Not only are elderly patients more prone to developing drug-related adverse effects, but they are also more susceptible to pharmacokinetic and pharmacodynamic drug interactions because of polypharmacy. The majority of currently used immunosuppressant drugs in organ transplantation are metabolized by cytochrome P450 (CYP) or uridine diphosphate-glucuronosyltransferases and are substrates of the multidrug resistance (MDR)-1 transporter P-glycoprotein, the MDR-associated protein 2 or the canalicular multispecific organic anion transporter, which predisposes these immunosuppressant compounds to specific interactions with commonly prescribed drugs. In addition, important drug interactions between immunosuppressant drugs have been identified and require attention when choosing an appropriate immunosuppressant drug regimen for the frail elderly organ recipient. An age-related 34% decrease in total body clearance of the calcineurin inhibitor ciclosporin was observed in elderly renal recipients (aged >65 years) compared with younger patients, while older recipients also had 44% higher intracellular lymphocyte ciclosporin concentrations. Similarly, using a Bayesian approach, an inverse relationship was noted between sirolimus clearance and age in stable kidney recipients. Ciclosporin and tacrolimus have distinct pharmacokinetics, but both are metabolized by intestinal and hepatic CYP3A4/3A5 and transported across the cell membrane by P-glycoprotein. The most common drug interactions with ciclosporin are therefore also observed with tacrolimus, but the two drugs do not interact identically when administered with CYP3A inhibitors or inducers. The strongest effects on calcineurin-inhibitor disposition are observed with azole antifungals, macrolide antibacterials, rifampicin, calcium channel antagonists, grapefruit juice, St John's wort and protease inhibitors. Drug interactions with mycophenolic acids occur mainly through inhibition of their enterohepatic recirculation, either by interference with the intestinal flora (antibacterials) or by limiting drug absorption (resins and binders). Rifampicin causes a reduction in mycophenolic acid exposure probably through induction of uridine diphosphate-glucuronosyltransferases. Proliferation signal inhibitors (PSIs) such as sirolimus and everolimus are substrates of CYP3A4 and P-glycoprotein and have a macrolide structure very similar to tacrolimus, which explains why common drug interactions with PSIs are comparable to those with calcineurin inhibitors. Ciclosporin, in contrast to tacrolimus, inhibits the enterohepatic recirculation of mycophenolic acids, resulting in significantly lower concentrations and hence risk of underexposure. Therefore, when switching from tacrolimus to ciclosporin and vice versa or when reducing or withdrawing ciclosporin, this interaction needs to be taken into account. The combination of ciclosporin with PSIs requires dose reductions of both drugs because of a synergistic interaction that causes nephrotoxicity when left uncorrected. Conversely, when switching between calcineurin inhibitors, intensified monitoring of PSI concentrations is mandatory. Increasing age is associated with structural and functional changes in body compartments and tissues that alter absorptive capacity, volume of distribution, hepatic metabolic function and renal function and ultimately drug disposition. While these age-related changes are well-known, few specific effects of the latter on immunosuppressant drug metabolism have been reported. Therefore, more clinical data from elderly organ recipients are urgently required.

Calcineurin inhibitor minimization in pediatric liver allograft recipients

The use of CNI in pediatric LTx has dramatically improved the outcome for children with end-stage liver disease by significantly reducing the rate of acute and chronic rejection. Long-term concerns about CNI-induced nephrotoxicity and other adverse effects remain an issue, particularly as the emphasis moves from short-term survival to long-term quality of life. This review summarizes lessons learnt from pediatric and adult solid organ transplantation in minimizing CNI use in immunosuppression protocols in children following LTx. There are three models for CNI minimization: dose reduction, withdrawal or avoidance, supplemented by the use of IL-2 receptor blocking antibodies in the peri-transplant period, and early transition to alternate drugs such as MMF or SRL. Prospective studies evaluating reduction or withdrawal protocols in adult and pediatric LTx indicate that rejection rates are comparable with traditional CNI-based immunosuppression and that two and five yr patient and graft survival are similar, with recovery in renal function. There are few studies evaluating complete avoidance of CNI, apart from that in renal transplantation, although the benefits of long-term reduction in cardiovascular, metabolic, and possibly neoplastic side effects may justify this approach. It is not clear yet how CNI minimization will affect the development of tolerance but experimental and preliminary clinical studies indicate that CNI and steroid avoidance or minimization in the peri-operative period may favor the development of long-term graft tolerance. In summary, CNI minimization may be safe and effective in the short term but large-scale pediatric randomized studies are required to evaluate the long-term efficacy of these regimes in the development of chronic rejection, PTLD, and graft tolerance.

Calcineurin inhibitor minimization protocols in liver transplantation

Liver transplant recipients are at increasingly high risk for suffering from impaired renal function and probable need of renal replacement therapy. Extended criteria organs and transplantation of patients with higher model for end-stage liver disease scores further increase this problem. Acute and chronic nephrotoxicity are the trade-off in immunosuppression with potent calcineurin inhibitors (CNIs). As a good renal function is associated with better graft and patient survival, CNI minimization protocols have been developed. Current strategies to overcome CNI toxicity include reduction or withdrawal of CNIs concurrently with switching over to mammalian target of rapamycin inhibitor or mycophenolate mofetil (MMF)-based regimens. This strategy caused an improvement in renal function in a significant number of liver transplantation patients according to several studies. However, total CNI avoidance seems to result in higher rejection rates. To prevent chronic renal dysfunction in patients prone to or with acute renal failure, CNI delay - with induction therapy for bridging - followed by low-dose CNI in combination with MMF are proven strategies without risking higher rejection rates. An individualized, tailor-made immunosuppressive regime, with a special focus on renal function is recommended. This review gave an overview on CNI minimization protocols in liver transplantation also focusing on recently analyzed studies.

Systems biology and functional genomics approaches for the identification of cellular responses to drug toxicity

Extensive growth in the field of molecular biology in recent decades has led to the development of new and powerful experimental and computational tools that enable the analysis of complex biological responses to chemical exposure on both a functional and structural genetic level. The ability to profile global responses on a transcriptional level has become a valuable resource in the science of toxicology and attempts are now being made to further understand toxicity mechanisms by incorporating metabolomics and proteomics approaches. In addition, recent progress in understanding the extent of the genetic diversity within and between species allows us to take a fresh look at research on genetic polymorphisms that may influence an individual's susceptibility to toxicity. Whereas new technologies have the potential to make a sizeable impact on our understanding of the mechanisms of toxicity, considerable challenges remain to be addressed, especially with regard to the regulatory acceptance and successful integration of omics data. This review highlights recent advancements in the application of functional and structural genomics techniques to chemical hazard identification and characterization, and to the understanding of the interindividual differences in susceptibility to adverse drug reactions.

Urine metabolites reflect time-dependent effects of cyclosporine and sirolimus on rat kidney function

The clinical use of the immunosuppressant calcineurin inhibitor cyclosporine is limited by its nephrotoxicity. This is enhanced when combined with the immunosuppressive mTOR inhibitor sirolimus. Nephrotoxicity of both drugs is not yet fully understood. The goal was to gain more detailed mechanistic insights into the time-dependent effects of cyclosporine and sirolimus on the rat kidney by using a comprehensive approach including metabolic profiling in urine ((1)H NMR spectroscopy), kidney histology, kidney function parameters in plasma, measurement of glomerular filtration rates, the oxidative stress marker 15-F(2t)-isoprostane in urine, and immunosuppressant concentrations in blood and kidney. Male Wistar rats were treated with vehicle (controls), cyclosporine (10/25 mg/kg/day), and/or sirolimus (1 mg/kg/day) by oral gavage once daily for 6 and 28 days. Twenty-eight day treatment led to a decrease of glomerular filtration rates (cyclosporine, -59%; sirolimus, -25%). These were further decreased when both drugs were combined (-86%). Histology revealed tubular damage after treatment with cyclosporine, which was enhanced when sirolimus was added. No other part of the kidney was affected. (1)H NMR spectroscopy analysis of urine (day 6) revealed time-dependent changes of 2-oxoglutarate, citrate, and succinate concentrations. In combination with increased urine isoprostane concentrations, these changes indicated oxidative stress. After 28 days of cyclosporine treatment, urine metabonomics shifted to patterns typical for proximal tubular damage with reduction of Krebs cycle intermediates and trimethylamine-N-oxide concentrations, whereas acetate, lactate, trimethylamine, and glucose concentrations increased. Again, sirolimus enhanced these negative effects. Our results indicate that cyclosporine and/or sirolimus induce damage of the renal tubular system. This is reflected by urine metabolite patterns, which seem to be more sensitive than currently used clinical kidney function markers such as creatinine concentrations in serum. Metabolic profiling in urine may provide the basis for the development of toxicodynamic monitoring strategies for immunosuppressant nephrotoxicity.