[Clinical, biochemical and epidemiological features of macro-AST preceding inflammatory bowel disease diagnosis by several years]

INTRODUCTION

An isolated elevation of aspartate aminotransferase (AST) is a diagnostic issue. Macro-aspartate aminotransferase (macro-AST) corresponds to the formation of complexes between AST and immunoglobulins.

CASE REPORT

We report the case of a patient with macro-AST identified several years before the onset of inflammatory bowel disease (IBD). A 6-year retrospective analysis in our laboratory identified only one case out of 42 540 adult patients.

CONCLUSION

The objective of this work is to increase awareness of this benign disorder among clinicians and biologists, as well as to aid in prescribing only the required tests.

Development and validation of a UPLC-UV method for the quantification of thiopurine methyltransferase enzyme activity in human erythrocytes

Thiopurines are drugs widely used for the treatment of autoimmune conditions, inflammatory bowel disease or acute lymphoblastic leukemia. Determination of thiopurine methyltransferase activity (TPMT), a major determinant of thiopurines toxicity, has been suggested before implementing thiopurine treatment. An ultraperformance liquid chromatography (UPLC) method was developed and validated for the quantification of TPMT enzyme activity based on the conversion of 6-mercaptopurine (6-MP) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-L-methionine (SAM) as methyl donor in red blood cell lysates (RBC). This method was improved from a previous laborious high performance liquid chromatography (HPLC) method, using a lower volume of injection and with a shorter runtime. After incubation and protein precipitation 6-MMP was separated on a HSS-T3 (2.1 × 50 mm, 1.8 μm) column and monitored by UV detection (290 nm). A change on the organic solvent used to dissolve 6-MP resulted in a reduction of interference by endogenous or non-enzymatic methylated 6-MMP. A full validation of the 6-MMP assay was performed according to the FDA and EMA guidelines. The method was linear from 0.125 to 2 nmol/mL, with acceptable values of accuracy and precision. The method was applied in 106 patients treated with thiopurines whose TPMT activity was previously quantified by HPLC. Evaluation through Bland-Altman plot showed that TPMT activities were in agreement between both methods.

Predictive Modeling of Tacrolimus Dose Requirement Based on High-Throughput Genetic Screening

Any biochemical reaction underlying drug metabolism depends on individual gene-drug interactions and on groups of genes interacting together. Based on a high-throughput genetic approach, we sought to identify a set of covariant single-nucleotide polymorphisms predictive of interindividual tacrolimus (Tac) dose requirement variability. Tac blood concentrations (Tac C₀ ) of 229 kidney transplant recipients were repeatedly monitored after transplantation over 3 mo. Given the high dimension of the genomic data in comparison to the low number of observations and the high multicolinearity among the variables (gene variants), we developed an original predictive approach that integrates an ensemble variable-selection strategy to reinforce the stability of the variable-selection process and multivariate modeling. Our predictive models explained up to 70% of total variability in Tac C₀ per dose with a maximum of 44 gene variants (p-value <0.001 with a permutation test). These models included molecular networks of drug metabolism with oxidoreductase activities and the multidrug-resistant ABCC8 transporter, which was found in the most stringent model. Finally, we identified an intronic variant of the gene encoding SLC28A3, a drug transporter, as a key gene involved in Tac metabolism, and we confirmed it in an independent validation cohort.

Long-Term Clinical Impact of Adaptation of Initial Tacrolimus Dosing to CYP3A5 Genotype

Pretransplantation adaptation of the daily dose of tacrolimus to CYP3A5 genotype is associated with improved achievement of target trough concentration (C0 ), but whether this improvement affects clinical outcomes is unknown. In the present study, we have evaluated the long-term clinical impact of the adaptation of initial tacrolimus dosing according to CYP3A5 genotype: The transplantation outcomes of the 236 kidney transplant recipients included in the Tactique study were retrospectively investigated over a period of more than 5 years. In the Tactique study, patients were randomly assigned to receive tacrolimus at either a fixed dosage or a dosage determined by their genotype, and the primary efficacy end point was the proportion of patients for whom tacrolimus C0 was within target range (10-15 ng/mL) at day 10. Our results indicate that the incidence of biopsy-proven acute rejection and graft survival were similar between the control and the adapted tacrolimus dose groups, as well as between the patients who achieve the tacrolimus C0 target ranges earlier. Patients' death, cancer, cardiovascular events, and infections were also similar, and renal function did not change. We conclude that optimization of initial tacrolimus dose using pharmacogenetic testing does not improve clinical outcomes.

Angiogenic response following renal ischemia reperfusion injury: new players

Ischemia-reperfusion (IR) injury can negatively influence the short- and long-term outcomes of kidney transplantation because it promotes acute tubular necrosis and tissue scarring and activates innate alloimmunity. The adaptive responses to IR are centrally involved in reducing tissue damage but can also be deleterious when they activate programmed cell death and inflammation. The HIF-1α-mediated angiogenic responses following IR at early and late stages are complex and poorly understood. The early stages of IR seem to be associated with an antiangiogenic response, whereas the hypoxia that follows IR at later stages may activate angiogenic factors such as vascular endothelial growth factor (VEGF) and may be beneficial by stabilizing the microvasculature and favoring local blood supply. In addition to HIF-1α, new players in angiogenesis, including mTOR and the unfolded protein response, may lead to innovative therapeutic strategies for treating patients with ischemia- and reperfusion-associated tissue inflammation and organ dysfunction.

Kidney transplant recipients carrying the CYP3A4*22 allelic variant have reduced tacrolimus clearance and often reach supratherapeutic tacrolimus concentrations

CYP3A4*22 is an allelic variant of the cytochrome P450 3A4 associated with a decreased activity. Carriers of this polymorphism may require reduced tacrolimus (Tac) doses to reach the target residual concentrations (Co). We tested this hypothesis in a population of kidney transplant recipients extracted from a multicenter, prospective and randomized study. Among the 186 kidney transplant recipients included, 9.3% (18 patients) were heterozygous for the CYP3A4*22 genotype and none were homozygous (allele frequency of 4.8%). Ten days after transplantation (3 days after starting treatment with Tac), 11% of the CYP3A4*22 carriers were within the target range of Tac Co (10-15 ng/mL), whereas among the CYP3A4*1/*1 carriers, 40% were within the target range (p = 0.02, OR = 0.19 [0.03; 0.69]). The mean Tac Co at day 10 in the CYP3A4*1/*22 group was 23.5 ng/mL (16.6-30.9) compared with 15.1 ng/mL (14-16.3) in the CYP3A4*1/*1 group, p < 0.001. The Tac Co/dose significantly depended on the CYP3A4 genotype during the follow-up (random effects model, p < 0.001) with the corresponding equivalent dose for patients heterozygous for CYP3A4*22 being 0.67 [0.54; 0.84] times the dose for CYP3A4*1/*1 carriers. In conclusion, the CYP3A4*22 allelic variant is associated with a significantly altered Tac metabolism and carriers of this polymorphism often reach supratherapeutic concentrations.

Emerging functions of autophagy in kidney transplantation

In response to ischemic, toxic or immunological insults, the more frequent injuries encountered by the kidney, cells must adapt to maintain vital metabolic functions and avoid cell death. Among the adaptive responses activated, autophagy emerges as an important integrator of various extracellular and intracellular triggers (often related to nutrients availability or immunological stimuli), which, as a consequence,may regulate cell viability, and also immune functions,both innate or adaptive. The aim of this review is to make the synthesis of the recent literature on the implications of autophagy in the kidney transplantation field and to discuss the future directions for research.

The nephroprotective properties of recombinant human erythropoietin in kidney transplantation: experimental facts and clinical proofs

Adaptive responses to hypoxia, including hypoxia-inducible factor signaling, allow the cell to satisfy its basal metabolic demand and avoid death, but these responses can also be deleterious by promoting inflammation, cell dedifferentiation and fibrogenesis. Therefore, targeting hypoxia constitutes a promising therapeutic avenue. Recombinant human erythropoietin (rhEPO) appeared as a good candidate therapy because its hematopoietic properties could reverse anemia, and its tissue-protective properties could reduce cell death and limit maladaptive cellular responses to hypoxia. Despite experimental evidence on the nephroprotecive properties of rhEPO, recent clinical trials provided evidence that rhEPO was ineffective in preventing delayed graft function after ischemic acute injury but that the normalization of hemoglobin values preserved kidney function deterioration and reduced graft loss. Our aim here is to provide a survey of the rationale for evaluating the administration of rhEPO in the setting of kidney transplantation. We will discuss the intriguing findings that emerged from the clinical trials and the discrepancies between promising experimental results and negative clinical studies, as well as the differences in terms of the benefits and safety profiles of the normalization of hemoglobin values in chronic kidney disease patients and kidney transplant patients.

The molecular legacy of apoptosis in transplantation

Transplanted organs have to cope with diverse immunologic and metabolic stressors that augment the percentage of stressed and dying cells. Cell death, whether apoptotic or necrotic, is crucial in various transplantation-associated conditions. Necrosis, a proinflammatory type of cell death classically considered as accidental, is increasingly recognized as a highly controlled death program. Apoptosis, the classical programmed cell death mode program, is tightly orchestrated and culminates in the activation of caspases. Apoptosis was classically regarded as a silent form of cell death, but mounting evidence indicates that apoptotic cells "don't go silently" and leave a heritage to the local microenvironment. This apoptotic legacy, embedded within the effector phase of apoptosis, is aimed, at least in part, at controlling leukocyte trafficking and fostering tissue remodeling at sites of apoptotic cell deletion and can promote maladaptive remodeling pathways of importance for obliterative vascular remodeling. Moreover, apoptotic cells can transfer bioactive molecules by the release of apoptotic membrane vesicles that, in turn, shapes the phenotype and functions of immune cells. In this review, we summarize recent data highlighting the importance of apoptosis-associated intercellular communication networks in the regulation of allograft remodeling and immune responses in transplantation.

Metabolic stress promotes renal tubular inflammation by triggering the unfolded protein response

The renal epithelium contributes to the development of inflammation during ischemic injury. Ischemia induces endoplasmic reticulum (ER) stress and activates the unfolded protein response (UPR). Ischemic tissues generate distress signals and inflammation that activates fibrogenesis and may promote adaptive immunity. Interestingly, the UPR may activate inflammation pathways. Our aim was to test whether the UPR is activated during metabolic stress and mediates a tubular inflammatory response. Glucose deprivation, not hypoxia and amino acids deprivation, activated the UPR in human renal cortical tubular cells in culture. This stress activated NF-κB and promoted the transcription of proinflammatory cytokines and chemokines, including IL-6, IL-8, TNF-α, RANTES and MCP-1. The protein kinase RNA (PKR)-like ER kinase signaling pathway was not required for the induction of inflammation but amplified cytokine. Inositol-requiring enzyme 1 activated NF-κB signaling and was required for the transcription of proinflammatory cytokines and chemokines following metabolic stress. Moreover, acute ischemia activated ER stress and inflammation in rat kidneys. Finally, the ER stress marker GRP78 and NF-κB p65/RelA were coexpressed in human kidney transplants biopsies performed before implantation, suggesting that ER stress activates tubular inflammation in human renal allografts. In conclusion, this study establishes a link between ischemic stress, the activation of the UPR and the generation of a tubular inflammatory response.

Therapeutic mTOR inhibition in autosomal dominant polycystic kidney disease: What is the appropriate serum level?

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disease, and sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been shown to significantly retard cyst expansion in animal models. The optimal therapeutic dose of sirolimus is not yet defined. Here, we report the history of a previously unknown ADPKD deceased donor whose kidneys were engrafted in two different recipients. One of the two received an immunosuppressive regimen based on sirolimus for 5 years while the other did not. After transplantation, both patients developed severe transplant cystic disease. Donor DNA sequence identified a new hypomorphic mutation in PKD1. The rate of cyst growth was identical in the two patients regardless of the treatment. While sirolimus treatment reduced the activation of mTOR in peripheral blood mononuclear cells, it failed to prevent mTOR activation in kidney tubular cells, this could account for the inefficiency of treatment on cyst growth. Together, our results suggest that the dose of sirolimus required to inhibit mTOR varies according to the tissue.

High dose epoetin beta in the first weeks following renal transplantation and delayed graft function: Results of the Neo-PDGF Study

Erythropoietin promotes nephroprotection in animal models of ischemia-reperfusion injury. Neorecormon and Prevention of Delayed Graft Function (Neo-PDGF) is a French open-label multicenter randomized study to evaluate the effect of high doses of epoetin beta (EPO-beta) during the first 2 weeks of renal transplantation on renal function in patients at risk for delayed graft function (DGF). One hundred and four patients were included in the study. Patients randomized in treatment group (A) received four injections of EPO-beta (30.000 UI each), given before surgery and at 12 h, 7 days and 14 days posttransplantation. Patients randomized in control group (B) did not receive EPO-beta. Immunosuppression included induction with basiliximab and maintenance therapy with steroids, mycophenolate mofetil and tacrolimus. At 1 month posttransplant, the estimated glomerular filtration rate (MDRD formula) was 42.5 +/- 19.0 mL/min in the EPO-beta group and 44.0 +/- 16.3 mL/min in the control group (p = ns). The frequency of DGF was similar in both groups (32% vs. 38.8%; p = ns). No difference in the incidence of serious adverse events was observed. (ClinicalTrials.gov number, NCT00815867.).

Bortezomib as the sole post-renal transplantation desensitization agent does not decrease donor-specific anti-HLA antibodies

Persistence of donor-specific anti-HLA antibodies (DSA) associated with antibody-mediated graft injuries following kidney transplantation predicts evolution toward chronic humoral rejection and reduced graft survival. Targeting plasma cells, the main antibody-producing cells, with the proteasome inhibitor bortezomib may be a promising desensitization strategy. We evaluated the in vivo efficacy of one cycle of bortezomib (1.3 mg/m(2)x 4 doses), used as the sole desensitization therapy, in four renal transplant recipients experiencing subacute antibody-mediated rejection with persisting DSA (>2000 [Mean Fluorescence Intensity] MFI). Bortezomib treatment did not significantly decrease DSA MFI within the 150-day posttreatment period in any patient. In addition, antivirus (HBV, VZV and HSV) antibody levels remained stable following treatment suggesting a lack of efficacy on long-lived plasma cells. In conclusion, one cycle of bortezomib alone does not decrease DSA levels in sensitized kidney transplant recipients in the time period studied. These results underscore the need to evaluate this new desensitization agent properly in prospective, randomized and well-controlled studies.

Kidney transplantation at Necker Hospital: the most recent 5-year period (2004-2009)

The results of our last 5 years activity in kidney transplantation clearly show that it is possible to perform high-risk transplantations with very acceptable results: ECD kidneys, dual transplantation, recipients with DSAs. In depth statistical analysis of these data should allow a clearer definition of the best strategies to use in these situations.

Cyclosporine-induced endoplasmic reticulum stress triggers tubular phenotypic changes and death

The molecular mechanisms by which cyclosporine induces chronic nephrotoxicity remain poorly understood. A previous transcriptomic study suggested that cyclosporine might induce endoplasmic reticulum (ER) stress in human tubular cells. The aim of the present study was to characterize the features of tubular ER stress induced by cyclosporine and to investigate its effects on cell differentiation and viability. Using primary cultures of human tubular cells, we confirmed that cyclosporine is responsible for ER stress in vitro. This was also confirmed in vivo in the rat. In vitro, cyclosporine and other ER stress inducers were responsible for epithelial phenotypic changes leading to the generation of protomyofibroblasts, independent of transforming growth factor-beta signaling. RNA interference directed against cyclophilin A supported the role of its inhibition in triggering ER stress as well as epithelial phenotypic changes induced by cyclosporine. Salubrinal, which is known to protect cells from ER stress, significantly reduced epithelial phenotypic changes and cytotoxicity induced by cyclosporine in vitro. Salubrinal also reduced cyclosporine nephrotoxicity in rat kidneys. Thus, we describe a novel mechanism that initiates dedifferentiation and tubular cell death upon cyclosporine treatment. These results provide an interesting framework for further nephroprotective therapies by targeting ER stress.

Role of P-glycoprotein in cyclosporine cytotoxicity in the cyclosporine-sirolimus interaction

Cyclosporine nephrotoxicity remains a major side effect in solid organ transplantation, and can be exacerbated by concomitant administration of sirolimus. Cyclosporine and sirolimus are P-glycoprotein (Pgp) substrates. We hypothesized that the Pgp activity level may affect cyclosporine cytotoxicity by interfering with the ability of Pgp to remove cyclosporine from within tubular cells, and that an interaction between cyclosporine and sirolimus on Pgp function may explain the enhancement of cyclosporine nephrotoxicity by sirolimus. Cyclosporine cytotoxicity was evaluated in primary cultures of normal human renal epithelial cells (HRECs) by cell viability and cytotoxicity assays. Verapamil, quinine, PSC833, and PGP-4008 were used as Pgp inhibitors. Rhodamine-123 (R-123), a fluorescent substrate of Pgp, was used to assess Pgp-mediated transport. Cellular cyclosporine concentration was measured by high-performance liquid chromatography coupled to tandem mass spectrometry. Pgp expression and function were confirmed in HRECs and cyclosporine and sirolimus were shown to be Pgp inhibitors in this model. Verapamil-induced inhibition of Pgp led to a significant increase in cellular concentration of cyclosporine (P<0.05). Cyclosporine exerted a concentration-dependent cytotoxic effect on HRECs that was significantly increased by inhibition of Pgp activity. Sirolimus exerted an inhibitory effect on R-123 efflux in HRECs and increased cellular cyclosporine concentrations in a dose-dependent manner. These data demonstrate that Pgp plays a critical role in protecting renal epithelial cells from cyclosporine toxicity. The inhibitory effect of sirolimus on Pgp-mediated efflux and the cellular concentration of cyclosporine could explain the exacerbation of cyclosporine nephrotoxicity observed clinically.

[Rapamycine and mTOR inhibitors: from bench to bedside]

Rapamycin is a macrocyclic lactone with antifungal and antibiotic properties isolated from Streptomyces hygroscopicus during the 70's. Studies of rapamycin properties in yeast led to the discovery of TOR (Target Of Rapamycin) and its mammalian analogue, mTOR. mTOR is a central regulator of cell growth and proliferation in response to environmental stimuli such as growth factors or nutrients. There are two proteins that have been shown to be regulated by mTOR in response to a broad range of mitogenic stimuli. The translation regulation induced by mTOR is mediated by the p70 S6 kinase activation and the 4E-BP1 inhibition. Both proteins participate in the regulation of translation process and growth in cells stimulated by either mitogens or hormones. Antiproliferative effects of rapamycin and analogues have been demonstrated on numerous cell types, explaining the development of these drugs in clinical practice: as immunosuppressive drugs in solid organ transplantation, in oncology for the treatment of various types of cancer, and for the prevention of restenosis after coronary angioplasty. Rapamycin is a potent immunosuppressive drug used in solid organ transplantation for the prevention of acute rejection. In oncology these antiproliferative effects are evaluated in several types of cancers. Rapamycin is now widely used for coating stents to reduce post-stenting restenosis phenomenon after coronary angioplasty. Finally, rapamycin is now evaluated in various diseases characterized by proliferative disorders.

Kikuchi-Fujimoto disease associated with mixed connective tissue disease

Kikuchi-Fujimoto disease is characterized by painful cervical lymphadenopathy and constitutional symptoms. Microscopical study of lymph nodes shows focal areas of non-suppurative necrosis with histiocytic and plasmacytoid cell infiltrates. The course is usually benign. Often primitive, necrotising histiocytic lymphadenopathy may be associated with autoimmune disorders. We describe the case of a 30-year-old female patient with two 15-day courses of Kikuchi-Fujimoto disease flares within a period of 3 months, occurring in association with mixed connective tissue disease.