Dario Cattaneo

Delayed graft function in kidney transplantation

Delayed graft function is a form of acute renal failure resulting in post-transplantation oliguria, increased allograft immunogenicity and risk of acute rejection episodes, and decreased long-term survival. Factors related to the donor and prerenal, renal, or postrenal transplant factors related to the recipient can contribute to this condition. From experimental studies, we have learnt that both ischaemia and reinstitution of blood flow in ischaemically damaged kidneys after hypothermic preservation activate a complex sequence of events that sustain renal injury and play a pivotal part in the development of delayed graft function. Elucidation of the pathophysiology of renal ischaemia and reperfusion injury has contributed to the development of strategies to decrease the rate of delayed graft function, focusing on donor management, organ procurement and preservation techniques, recipient fluid management, and pharmacological agents (vasodilators, antioxidants, anti-inflammatory agents). Several new drugs show promise in animal studies in preventing or ameliorating ischaemia-reperfusion injury and possibly delayed graft function, but definitive clinical trials are lacking. The goal of monotherapy for the prevention or treatment of is perhaps unattainable, and multidrug approaches or single drug targeting multiple signals will be the next step to reduce post-transplantation injury and delayed graft function.

Consensus Report on Therapeutic Drug Monitoring of Mycophenolic Acid in Solid Organ Transplantation

With the increasing use of mycophenolic acid (MPA) in solid organ transplantation, the need for more accurate drug dosing has become evident. Personalized immunosuppressive therapy requires better strategies for avoidance of drug-related toxicity while maintaining efficacy. Few studies have assessed the clinical usefulness of therapeutic drug monitoring (TDM) of MPA in solid organ transplantation in a prospective way, and they have produced opposing results. To provide clinicians with an objective and balanced clinical interpretation of the current scientific evidence on TDM of MPA, a consensus meeting involving 47 experts from around the world was commissioned by The Transplantation Society and held in Rome on November 20 to 21, 2008. The goal of this consensus meeting was to offer information to transplant practitioners on clinically relevant pharmacokinetic characteristics of MPA, to rationalize the basis for currently advised target exposure ranges for MPA in various types of organ transplantation, and to summarize available methods for application of MPA TDM in clinical practice. Although this consensus report does not evaluate the final role of MPA TDM in transplantation, it seeks to examine the current scientific evidence for concentration-controlled dosing of MPA.

How To Fully Protect the Kidney in a Severe Model of Progressive Nephropathy: A Multidrug Approach

The current therapy for chronic proteinuric nephropathies is angiotensin-converting enzyme inhibitors (ACEi), which slow, but may not halt, the progression of disease, and which may be not effective to the same degree in all patients. In accelerated passive Heymann nephritis (PHN), this study assessed the effect of combining ACEi with angiotensin II receptor antagonist (AIIRA) and with statin that, besides lowering cholesterol, influences inflammatory and fibrogenic processes. Uninephrectomized PHN rats were divided into four groups (n = 10 each) and daily given oral doses of the following: vehicle; 40 mg/L lisinopril; 100 mg/L lisinopril plus L-158,809; 0.3 mg/kg lisinopril plus L-158,809 plus cerivastatin. Treatments started at 2 mo when rats had massive proteinuria and signs of renal injury and lasted until 10 mo. Increases in BP were equally lowered by treatments. ACEi kept proteinuria at levels comparable to pretreatment and numerically lower than vehicle. The addition of AIIRA to lisinopril was more effective, being proteinuria reduced below pretreatment values and significantly lower than vehicle. When cerivastatin was added on top of ACE inhibition and AIIR blockade, urinary protein regressed to normal values and renal failure was prevented. Renal ACE activity was increased threefold in PHN, it was inhibited by more than 60% after ACEi, and decreased below control values with triple therapy. Cerivastatin inhibited ACE activity by 30%. Glomerulosclerosis, tubular damage and interstitial inflammation were ameliorated by ACEi alone or combined with AIIRA, and prevented by addition of statin. TGF-beta(1) mRNA upregulation in PHN kidney was partially reduced after ACEi or combined with AIIRA and almost normalized after adding statin. Cerivastatin inhibited TGF-beta(1) gene upregulation by 25%. These data suggest a possible future strategy to induce remission of proteinuria, lessen renal injury, and protect from loss of function in those patients who do not fully respond to ACEi therapy.

Hepatitis C Infection and Chronic Renal Diseases

More than 170 million people worldwide are chronically infected with the hepatitis C virus (HCV), which is responsible for over 1 million deaths resulting from cirrhosis and liver cancers. Extrahepatic manifestations are also relevant and include mixed cryoglobulinemia, lymphoproliferative disorders, and kidney disease. HCV infection is both a cause and a complication of chronic kidney disease, occurring largely in the context of mixed cryoglobulinemia. This infection also represents a major medical and epidemiologic challenge in patients with end-stage renal disease on renal replacement therapy with dialysis or transplantation. In these settings the presence of HCV correlates with higher rates of patient mortality than in HCV-negative subjects on dialysis or undergoing kidney transplant. The major concern is the lack of safe and effective drugs to treat HCV-infected patients with chronic kidney disease. Unfortunately, there are no large-scale clinical trials in this population, especially those receiving renal replacement therapy, so that strong evidence for treatment recommendations is scant. This review article provides the readers with the most recent insights on HCV infection both as cause and complication of chronic kidney disease, discusses pitfalls and limitations of current therapies, and reports on preliminary experience with novel therapeutic agents, as well as directions for future research.

The Aggravating Mechanisms of Aldosterone on Kidney Fibrosis

The renin-angiotensin-aldosterone system (RAS) is a widely known regulator of BP and a determinant of target organ damage. Angiotensin II, the main effector of RAS, is a key mediator of renal injury by increasing intraglomerular capillary pressure and ultrafiltration of plasma proteins and by promoting cell growth and fibroproliferative effects. RAS blockade with inhibitors of RAS is beneficial in slowing progressive loss of renal function in chronic kidney disease. Experimental evidence also indicates that aldosterone, besides being a regulator of extracellular fluid volume and sodium and potassium balance, directly contributes to accelerate renal damage by sustaining cell growth, inflammation, and fibrosis. This occurs through production of growth factors and reactive oxygen species as well as inhibition of extracellular matrix degradation. Attenuation of growth-promoting and fibroproliferative effect of aldosterone may contribute to protection against progressive renal injury. Initial studies that detail the efficacy of aldosterone blockade in animals and humans are encouraging. Nevertheless, further studies in larger populations with longer follow-up are warranted to address more definitely the safety and renoprotective effect of aldosterone antagonism in chronic kidney disease patients.

Atazanavir plus low-dose ritonavir in pregnancy: pharmacokinetics and placental transfer.

Background:Adequate antiretroviral exposure during pregnancy is critical to prevent the vertical transmission of HIV and for maternal health. Pregnancy can alter drug kinetics. We assessed the pharmacokinetics of atazanavir/ritonavir (300/100 mg a day) during pregnancy. Methods:An intensive steady-state 24-h pharmacokinetic profile of atazanavir was performed in the third trimester of pregnancy and postpartum. Maternal and umbilical cord blood samples were obtained at delivery. We measured atazanavir by reverse-phase high-performance liquid chromatography. Results:Seventeen women completed the study. Antepartum, the atazanavir geometric mean area under the plasma concentration-time curve from 0 to 24 h (AUC0–24) was 28 510 ng·h/l, the maximum observed plasma concentration (Cmax) was 2 591 ng/ml and the 24-h postdose concentration (Ctrough) was 486 ng/ml. The same postpartum parameters were 30 465 ng·h/l, 2 878 ng/ml and 514 ng/ml, respectively. The antepartum to postpartum ratio for AUC0–24 was 0.94 and for Ctrough was 0.96, indicating equivalence, whereas Cmax values were slightly although not significantly lower. The ratio of cord blood/maternal atazanavir concentration in 14 paired samples was 0.13. Conclusion:Atazanavir exposure during the third trimester of pregnancy is similar to that observed in the non-pregnant period. Over the whole dosing interval, therapeutic drug concentrations well above the wild-type HIV 90% inhibitory concentration are maintained. Atazanavir crosses the placenta, potentially providing further protection for the newborn. As pregnancy does not appear to alter atazanavir exposure, no dose adjustment is required in pregnant women. Results suggest that atazanavir is a reasonable component of HAART during pregnancy.

Sirolimus versus cyclosporine therapy increases circulating regulatory T cells, but does not protect renal transplant patients given alemtuzumab induction from chronic allograft injury.

Background. In kidney transplant recipients with alemtuzumab induction maintained on mycophenolate mofetil (MMF) immunosuppression, sirolimus (SRL) promotes significant expansion of circulating CD4+CD25high regulatory T cells (Treg). This might translate into more effective protection against chronic graft injury compared to cyclosporin A (CsA), which, in the same clinical setting, does not affect Treg. Methods. To assess this hypothesis, in the extension of a single-center, prospective, randomized, open, blind endpoint study aimed to assess the effect of low-dose SRL or CsA on circulating Treg, we compared the outcomes of renal transplant recipients on SRL (n=11) or CsA (n=10) by per-protocol biopsies and serial measurements of glomerular filtration rate (GFR), renal plasma flow (RPF), and 24-hour proteinuria over 30 months posttransplant. Results. Despite 4-fold higher CD4+CD25high Treg counts (22.1±12.2% vs. 5.7±4.2% of CD3+CD4+ T cells), SRL-treated patients, compared to CsA-treated patients, had a significantly higher tubular C4d staining score (1.1±0.6 vs. 0.2±0.3, P<0.01), with nonsignificant trends to higher chronic allograft damage index score (5.6±2.4 vs. 3.7±3.3), faster GFR (−2.92±0.33 vs. −0.28±0.44 ml/min/1.73m2 per year), and RPF (−10.80±5.45 vs. −1.86±3.09 ml/min/1.73 m2 per year) decline, and more clinical proteinuria (n=6 vs. 4). There was no significant correlation between Treg counts and any considered outcome variable in the study group as a whole and within each cohort. Conclusions. These data suggest that, despite enhanced Treg expression, low-dose SRL combined to alemtuzumab induction and MMF-based steroid-free maintenance therapy, does not appreciably protect renal transplant recipients from chronic allograft injury and dysfunction.

Pharmacokinetics help optimizing mycophenolate mofetil dosing in kidney transplant patients.

Background: Mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), is now routinely used as immunosuppressant in solid organ transplantation in a fixed daily dose regimen (2 g/d) in association with cyclosporine (CsA) and steroids. However, no correlation has been shown between fixed MMF dose and clinical outcome. 
Methods: Here we examined the possibility of optimizing MMF dosing by drug pharmacokinetic monitoring in 46 stable kidney transplant recipients. MPA plasma concentration profiles were measured by a reverse‐phase high‐performance liquid chromatography method 6–9 months after transplantation and related with routine laboratory analysis tests. Since MPA is extensively bound to serum albumin and only the free fraction is pharmacologically active, in a subgroup of 23 patients free plasma MPA was also determined. 
Results: Despite a comparable MMF dose, a large interindividual variability in both MPA area under the curve (AUC) from 0 to 12 h (range 10.1–99.8 μg/mL · h) and in trough levels (range 0.24–7.04 μg/mL) was found. Patients with AUC >40 μg/mL · h showed a better (p<0.05) renal function than patients with lower AUC (creatinine clearance 85.7±23.2 versus 64.5±17.5 mL/min), despite no difference in CsA dose, CsA AUC and blood CsA trough level. The percentage of free plasma MPA but not total MPA correlated with the red blood cell and leukocyte count. 
Conclusions: Therapeutic MMF drug monitoring might contribute to a better management of kidney transplant recipient with the goal of optimizing drug dosing and limiting the risk of MMF‐related toxicity.

C-440T/T-331C polymorphisms in the UGT1A9 gene affect the pharmacokinetics of mycophenolic acid in kidney transplantation

INTRODUCTION The immunosuppressive agent mycophenolic acid (MPA) is metabolized by uridine diphosphate glucuronosyltransferase 1A9 (UGT1A9) to 7-O-glucuronide (MPAG) and excreted by multidrug resistance-associated protein 2 in the bile. By contrast, the production of the acyl MPAG, a minor MPA metabolite, was ascribed to UGT2B7 and UGT1A8. Several polymorphisms in the genes encoding for UGT1A9, UGT2B7 and MRP2 proteins have been described. However, their functional role in vivo on MPA metabolism remains poorly defined. METHODS A total of 40 Caucasian kidney transplant patients, given induction therapies (with Campath-(1)H or the combination basiliximab/rabbit antithymocyte globulin) and on maintenance immunosuppression with cyclosporine in combination with mycophenolate mofetil (MMF) in a steroid-free regimen, were enrolled in the pharmacogenetic study. Patients had clinical and hematochemical evaluations at month 6 after transplantation, as well as complete MPA pharmacokinetic assessment. They were genotyped for SNPs in UGT1A9 C-2152T, T-1887G, C-665T, C-440T, T-331C, T-275A, T98C, for the nonsynonymous C802T SNP in UGT2B7, and for ABCC2 SNPs C-24T and G1249A. The association of these polymorphisms with MPA pharmacokinetic parameters was investigated. RESULTS Differences in the MPA pharmacokinetic profiles confirmed large interpatient variability of MPA exposure, with AUC(0-12) values ranging from 7.9 to 50.1 mg*h/ml. MPA AUC(0-12) was significantly associated with the presence of UGT1A9 -440/-331 genotypes (TT/CC: 61.5 +/- 2.7 mg*h/ml/g MMF; TC/CT: 45.4 +/- 14.0 mg*h/ml/g MMF; CC/TT: 40.8 +/- 10.8 mg*h/ml/g MMF; p = 0.005), whereas MPAG exposure was mainly influenced by renal function. The positive association between MPA AUC and SNPs in position -440/-331 found in kidney transplant patients confirmed previous in vitro findings showing that the abovementioned SNPs had a significant impact on UGT1A9 protein content in the liver. The presence of ABCC2 promoter C-24T and exon 10 G1249A SNPs did not cause any significant variation in MPA and MPAG pharmacokinetic parameters. CONCLUSION The study demonstrated a significant impact of C-440T/T-331C SNPs in the promoter region of the UGT1A9 gene on MPA pharmacokinetics in renal allograft recipients.

Ameliorating Hypertension and Insulin Resistance in Subjects at Increased Cardiovascular Risk. Effects of Acetyl-L-Carnitine Therapy

Insulin resistance, a key component of the metabolic syndrome, is a risk factor for diabetes mellitus and cardiovascular disease. Acetyl-l-carnitine infusion acutely ameliorated insulin sensitivity in type 2 diabetics with insulin resistance. In this sequential off-on-off pilot study, we prospectively evaluated the effects of 24-week oral acetyl-l-carnitine (1 g twice daily) therapy on the glucose disposal rate (GDR), assessed by hyperinsulinemic euglycemic clamps, and components of the metabolic syndrome in nondiabetic subjects at increased cardiovascular risk a priori segregated into 2 groups with GDR ≤7.9 (n=16) or >7.9 (n=16) mg/kg per minute, respectively. Baseline GDR and systolic blood pressure were negatively correlated (n=32; P=0.001; r=−0.545), and patients with GDR ≤7.9 mg/kg per minute had higher systolic/diastolic blood pressure than those with higher GDR. Acetyl-l-carnitine increased GDR from 4.89±1.47 to 6.72±3.12 mg/kg per minute (P=0.003, Bonferroni-adjusted) and improved glucose tolerance in patients with GDR ≤7.9 mg/kg per minute, whereas it had no effects in those with higher GDRs. Changes in GDR were significantly different between groups (P=0.017, ANCOVA). Systolic blood pressure decreased from 144.0±13.6 to 135.1±8.4 mm Hg and from 130.8±12.4 to 123.8±10.8 mm Hg in the lower and higher GDR groups, respectively (P<0.05 for both; P<0.001 overall) and progressively recovered toward baseline over 8 weeks posttreatment. Total and high molecular weight adiponectin levels followed specular trends. Diastolic blood pressure significantly decreased only in those with higher GDRs. Treatment was well tolerated in all of the patients. Acetyl-l-carnitine safely ameliorated arterial hypertension, insulin resistance, impaired glucose tolerance, and hypoadiponectinemia in subjects at increased cardiovascular risk. Whether these effects may translate into long-term cardioprotection is worth investigating.