Chronic calcineurin inhibitor nephrotoxicity: reflections on an evolving paradigm

Transition from cyclosporine-induced renal dysfunction to nephrotoxicity in an in vivo rat model

Cyclosporin A (CsA), a calcineurin inhibitor, remain the cornerstone of immunosuppressive regimens, regardless of nephrotoxicity, which depends on the duration of drug exposure. The mechanisms and biomarkers underlying the transition from CsA-induced renal dysfunction to nephrotoxicity deserve better elucidation, and would help clinical decisions. This study aimed to clarify these issues, using a rat model of short- and long-term CsA (5 mg/kg bw/day) treatments (3 and 9 weeks, respectively). Renal function was assessed on serum and urine; kidney tissue was used for histopathological characterization and gene and/or protein expression of markers of proliferation, fibrosis and inflammation. In the short-term, creatinine and blood urea nitrogen (BUN) levels increased and clearances decreased, accompanied by glomerular filtration rate (GFR) reduction, but without kidney lesions; at that stage, CsA exposure induced proliferating cell nuclear antigen (PCNA), transforming growth factor beta 1 (TGF-β1), factor nuclear kappa B (NF-κβ) and Tumor Protein P53 (TP53) kidney mRNA up-regulation. In the long-term treatment, renal dysfunction data was accompanied by glomerular and tubulointerstitial lesions, with remarkable kidney mRNA up-regulation of the mammalian target of rapamycin (mTOR) and the antigen identified by monoclonal antibody Ki-67 (Mki67), accompanied by mTOR protein overexpression. Transition from CsA-induced renal dysfunction to nephrotoxicity is accompanied by modification of molecular mechanisms and biomarkers, being mTOR one of the key players for kidney lesion evolution, thus suggesting, by mean of molecular evidences, that early CsA replacement by mTOR inhibitors is indeed the better therapeutic choice to prevent chronic allograft nephropathy.

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

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

JAK3 inhibition: what potential for the future?

JAK3 inhibition with the CP-690,550 compound has an immunosuppressive potency in murine models, nonhuman primates and humans. This drug blocks STAT5 activation in most T-cell subpopulations but less effectively in T-regulator cells. In low to moderate risk human kidney transplant recipients, combined with mycophenolate mofetil, steroids and an induction with basiliximab, CP-690,550 proved as effective as calcineurin inhibitors with regard to prevention of acute rejection but better than calcineurin inhibitors with regard to preservation of kidney function and histology. However, at the same time, an increased incidence of overimmunosuppression consequences (cytomegalovirus, BK virus and lymphoproliferation) was observed and led to discontinuation of this specific drug development in kidney transplantation.

Maintenance immunosuppression in renal transplantation

The need to maintain allograft recipients on immunosuppression is nearly universal. Immunosuppressive agents used in organ transplantation target one or more steps of the host alloimmune response, specifically processes related to CD4-positive T lymphocytes. Calcineurin-inhibitor based steroid-containing regimens have been the mainstay of maintenance immunosuppression over the last two decades. Newer agents have shown efficacy in this role in recent trials with comparable allograft and patient outcomes. These agents have permitted calcineurin-inhibitor minimization and steroid-sparing strategies in selected groups of patients.

Chronic renal allograft damage after transplantation: what are the reasons, what can we do?

PURPOSE OF REVIEW

Chronic renal allograft damage is one of the main problems after kidney transplantation. This review enumerates causes, describes available therapeutic options, and discusses options of the future.

RECENT FINDINGS

Alloantigen-dependent and alloantigen-independent factors are responsible for allograft damage. Prevention of renal allograft damage starts with interventions that occur surrounding the explantation in cadaveric organs. These include the use of dopamine or machine perfusion systems.Followed by the critical phase of ischemia/reperfusion injury, the LCN2/lipocalin-2, HAVCR1, and p38 MAPK pathway are new players involved in that process. Innate immunity plays a part, too. Cold ischemia time is associated with genes of apoptosis. Nondonor-specific antibodies like antihuman leukocyte antibodies-Ia or angiotensin type 1 receptor may also play a role. Recent research indicates that genetic polymorphism like the Ficolin-2 Ala258Ser polymorphism and the mannose-binding lectin-2 polymorphism are involved in that process. New therapeutic options are rare and in the future. However, there is some evidence that drugs interfering with metalloproteinases, sexual hormones like dihydroandrosterone, and mesenchymal stem cell therapy may be of importance.

SUMMARY

Taken together, although the understanding of chronic rejection has improved, the available therapeutic options remain scarce.

The implications of acute rejection for allograft survival in contemporary U.S. kidney transplantation

BACKGROUND

We examined the frequency and clinical impact of acute rejection (AR) in contemporary U.S. kidney transplantation.

METHODS

Data for Medicare-insured kidney transplant recipients in 2000 to 2007 (n=48,179) were drawn from the United States Renal Data System. AR events were ascertained from Organ Procurement and Transplantation Network reports. AR was subclassified as antibody (Ab)-treated AR or other management (non-Ab-treated AR). Associations of AR with subsequent all-cause graft loss were estimated with time-varying Cox regression. Covariates included recipient, donor, and transplant factors in the United Network for Organ Sharing Kidney Allocation Review Committee survival model.

RESULTS

The frequencies of non-Ab-treated AR per 100 graft-years at risk among standard criteria donor recipients over the first 6, 12, 24, and 36 months after transplantation were 9.93, 8.43, 5.71, and 4.70, respectively. Non-Ab-treated AR was consistently more than twice as common as Ab-treated AR by risk period and donor type. Development of Ab-treated AR predicted a greater risk of graft loss than non-Ab-treated AR. The relative risk for graft loss from Ab-treated AR continuously increased with later timing of AR after transplantation, whereas risk associated with non-Ab-treated AR peaked for events reported in months 13 to 24 after kidney transplantation. Regardless of the diagnosis time, the relative risk of graft loss was higher in the first 89 days after a given AR report compared with 90 days and beyond.

CONCLUSIONS

AR events recognized later after transplantation have more serious graft loss implications, especially within the first 89 days after AR reporting. This observation may reflect reduced intensity of monitoring, delays in diagnosis, or clinicopathologic features of late AR.

The accuracy of positron emission tomography in the detection of posttransplant lymphoproliferative disorder

We investigated sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 18F-fluorodeoxyglucose-positron emission tomography in 170 cases with suspected or biopsy-proven posttransplant lymphoproliferative disorder. All solid organ and hematopoietic stem cell transplant recipients who underwent an 18F-fluorodeoxyglucose-positron emission tomography scan between 2003 and 2010 in our center for the indication posttransplant lymphoproliferative disorder, were retrospectively reviewed and results were compared with tissue biopsy whenever possible. One hundred and seventy positron emission tomography scans in 150 patients were eligible for evaluation. In 45 cases, the patient had a biopsy-confirmed posttransplant lymphoproliferative disorder before positron emission tomography scanning and positron emission tomography was performed for staging purposes. In the remaining 125 cases, positron emission tomography was performed to differentiate between posttransplant lymphoproliferative disorder and other diseases. 18F-fluorodeoxyglucose-uptake was quantitatively expressed by calculation of maximum and mean standardized uptake value in the most intense lesion or, in the absence of attenuation corrected positron emission tomography scans, by comparing uptake in target lesion to liver and mediastinal uptake. We found an overall sensitivity of 89%, specificity of 89%, positive predictive value of 91% and negative predictive value of 87% for posttransplant lymphoproliferative disorder detection by 18F-fluorodeoxyglucose-positron emission tomography. In a subanalysis of the 125 scans performed for differentiating posttransplant lymphoproliferative disorder from other diseases, sensitivity, specificity, positive predictive value and negative predictive value were 90%, 89%, 85% and 93%, respectively. 18F-fluorodeoxyglucose-uptake in posttransplant lymphoproliferative disorder was generally high with a median mean and maximum standardized uptake value of 9.0 (range 2.0-18.6) and 17.4 (range 2.6-26.4). Posttransplant lymphoproliferative disorder often had an atypical presentation on positron emission tomography with high incidence of extranodal involvement. In conclusion, from these data, we can conclude that 18F-fluorodeoxyglucose-positron emission tomography is highly sensitive for detecting posttransplant lymphoproliferative disorder and has an excellent ability to differentiate posttransplant lymphoproliferative disorder from non-malignant diseases.

Pathogenesis of calcineurin inhibitor-induced hypertension

This article reviews the current understanding of the mechanisms of calcineurin inhibitor-induced hypertension. Already early after the introduction of cyclosporine in the 1980s, vasoconstriction, sympathetic excitation and sodium retention by the kidney had been shown to play a role in this form of hypertension. The vasoconstrictive effects of calcineurin inhibitors are related to interference with the balance of vasoactive substances, including endothelin and nitric oxide. Until recently, the renal site of the sodium-retaining effect of calcineurin inhibitors was unknown. We and others have shown that calcineurin inhibitors increase the activity of the thiazide-sensitive sodium chloride cotransporter through an effect on the kinases WNK and SPAK. Here, we review the pertinent literature on the hypertensinogenic effects of calcineurin inhibitors, including neural, vascular and renal effects, and we propose an integrated model of calcineurin inhibitor-induced hypertension.

Randomized phase 2b trial of tofacitinib (CP-690,550) in de novo kidney transplant patients: efficacy, renal function and safety at 1 year

In this Phase 2b study, 331 low-to-moderate risk de novo kidney transplant patients (approximately 60% deceased donors) were randomized to a more intensive (MI) or less intensive (LI) regimen of tofacitinib (CP-690, 550), an oral Janus kinase inhibitor or cyclosporine (CsA). All patients received basiliximab induction, mycophenolic acid and corticosteroids. Primary endpoints were: incidence of biopsy-proven acute rejection (BPAR) with a serum creatinine increase of ≥0.3 mg/dL and ≥20% (clinical BPAR) at Month 6 and measured GFR at Month 12. Similar 6-month incidences of clinical BPAR (11%, 7% and 9%) were observed for MI, LI and CsA. Measured GFRs were higher (p < 0.01) at Month 12 for MI and LI versus CsA (65 mL/min, 65 mL/min vs. 54 mL/min). Fewer (p < 0.05) patients in MI or LI developed chronic allograft nephropathy at Month 12 compared with CsA (25%, 24% vs. 48%). Serious infections developed in 45%, 37% and 25% of patients in MI, LI and CsA, respectively. Anemia, neutropenia and posttransplant lymphoproliferative disorder occurred more frequently in MI and LI compared with CsA. Tofacitinib was equivalent to CsA in preventing acute rejection, was associated with improved renal function and less chronic allograft histological injury, but had side-effects at the doses evaluated.

An evaluation of sirolimus in renal transplantation

INTRODUCTION

Sirolimus is a powerful antiproliferative immunosuppressive drug approved for the prevention of kidney allograft rejection. By its unique mechanism of action, sirolimus provides a multitude of clinical potential and has been used effectively in different drug combinations. Extensive experience has been gained regarding the best timing of its application, side effect profile and potential benefits and limitations compared with other immunosuppressive drugs.

AREAS COVERED

The authors evaluate the recent experience with sirolimus in kidney transplantation. Pivotal randomized controlled trials were used to provide an overview with special attention to pharmacokinetic and dynamic aspects of sirolimus, its current clinical use as well as perspectives for its future role.

EXPERT OPINION

Sirolimus enriches the possibilities of immunosuppressive therapies after renal transplantation. Beneficial effects toward kidney function by allowing CNI sparing, lower incidence of malignancies and less viral infections have been suggested. Sirolimus should be used cautiously in de novo patients for reasons of wound healing. An early conversion to a sirolimus-based CNI-free regimen has shown promising results, whereas late conversion is more challenging. Finally, sirolimus-associated side effects are causing tolerability concerns and frequent discontinuations. Future research should aim to better define the therapeutic window and those patients most likely to benefit.

Improvement in renal function in kidney transplant recipients switched from cyclosporine or tacrolimus to belatacept: 2-year results from the long-term extension of a phase II study

Kidney transplant recipients who switched from a calcineurin inhibitor (CNI) to belatacept demonstrated higher calculated glomerular filtration rates (cGFRs) at 1 year in a Phase II study. This report addresses whether improvement was sustained at 2 years in the long-term extension (LTE). Patients receiving cyclosporine or tacrolimus were randomized to switch to belatacept or continue CNI. Of 173 randomized patients, 162 completed the 12-month main study and entered the LTE. Two patients (n = 1 each group) had graft loss between Years 1-2. At Year 2, mean cGFR was 62.0 ml/min (belatacept) vs. 55.4 ml/min (CNI). The mean change in cGFR from baseline was +8.8 ml/min (belatacept) and +0.3 ml/min (CNI). Higher cGFR was observed in patients switched from either cyclosporine (+7.8 ml/min) or tacrolimus (+8.9 ml/min). The frequency of acute rejection in the LTE cohort was comparable between the belatacept and CNI groups by Year 2. All acute rejection episodes occurred during Year 1 in the belatacept patients and during Year 2 in the CNI group. There were more non-serious mucocutaneous fungal infections in the belatacept group. Switching to a belatacept-based regimen from a CNI-based regimen resulted in a continued trend toward improved renal function at 2 years after switching.

Challenges and considerations in diagnosing the kidney disease in deteriorating graft function

Despite significant reductions in acute-rejection rates with the introduction of calcineurin inhibitor (CNI)-based immunosuppressive therapy, improvements in long-term graft survival in renal transplantation have been mixed. Improving long-term graft survival continues to present a major challenge in the management of kidney-transplant patients. CNIs are a key component of immunosuppressive therapy, and chronic CNI toxicity has been widely thought to be a major factor in late graft failure. However, recent studies examining the causes of late graft failure in detail have challenged this view, highlighting the importance of antibody-mediated rejection and other factors. In addition, the diagnosis of CNI nephrotoxicity represents a challenge to clinicians, with the potential for over-diagnosis and an inappropriate reduction in immunosuppressive therapy. When graft function is deteriorating, accurately determining the cause of the kidney disease is essential for effective long-term management of the patient. Diagnosis requires a thorough clinical investigation, and in the majority of cases a specific cause can be identified.

Saquinavir in steroid-dependent and -resistant nephrotic syndrome: a pilot study

BACKGROUND

Some difficult cases of idiopathic nephrotic syndrome (NS) have been treated with a HIV protease inhibitor provided with proteasome-inhibiting activity. The objective of this study was to limit nuclear factor κB (NF-κB) activation which is up-regulated in these patients, aiming at decreasing proteinuria and prednisone need.

METHODS

Ten cases with long-lasting (up to 15 years) history of NS with steroid dependence (six cases, of which three with secondary steroid resistance) or resistance to steroids (four cases) unsuccessfully treated with multiple immunosuppressive drugs, accepted a treatment with the protease inhibitor saquinavir. p50/p65 NF-κB nuclear localization and immunoproteasome/proteasome messenger RNA (mRNA) were monitored in peripheral blood mononuclear cells (PBMCs). The effects of saquinavir on NF-κB nuclear localization in cultured PBMCs and in immortalized human podocytes were assessed.

RESULTS

After a median follow-up of 14.7 months (6-68.7), 1/4 primary steroid-resistant NS (SRNS) and 5/6 steroid-dependent NS or secondary SRNS became infrequent (5) or frequent (1) relapsers, with 63% prednisone reduction (from 25.3 to 8.4 mg/kg/month, P = 0.015). Saquinavir was effective in association with low doses of calcineurin inhibitors (cyclosporine 2 mg/kg/day or tacrolimus 0.01-0.06 mg/kg/day). No side effects were observed apart from transitory mild diarrhoea. In PBMCs, NF-κB was down-regulated, while MECL-1 immunoproteasome/beta2 proteasome mRNA ratio was reversed to normal values. In culture, saquinavir blunted NF-κB activation in human podocytes and in PBMCs.

CONCLUSIONS

In this pilot study, a HIV antiprotease drug reduced proteinuria and had a steroid-sparing effect in some multidrug-resistant/-dependent NS. This observation warrants further investigation.

The impact of donor-specific anti-HLA antibodies on late kidney allograft failure

Despite improvements in outcomes of renal transplantation, kidney allograft loss remains substantial, and is associated with increased morbidity, mortality and costs. Identifying the pathologic pathways responsible for allograft loss, and the attendant development of therapeutic interventions, will be one of the guiding future objectives of transplant medicine. One of the most important advances of the past decade has been the demonstration of the destructive power of anti-HLA alloantibodies and their association with antibody-mediated rejection (ABMR). Compelling evidence exists to show that donor-specific anti-HLA antibodies (DSAs) are largely responsible for the chronic deterioration of allografts, a condition previously attributed to calcineurin inhibitor toxicity and chronic allograft nephropathy. The emergence of sensitive techniques to detect DSAs, together with advances in the assessment of graft pathology, have expanded the spectrum of what constitutes ABMR. Today, subtler forms of rejection--such as indolent ABMR, C4d-negative ABMR, and transplant arteriopathy--are seen in which DSAs exert a marked pathological effect. In addition, arteriosclerosis, previously thought to be a bystander lesion related to the vicissitudes of aging, is accelerated in ABMR. Advances in our understanding of the pathological significance of DSAs and ABMR show their primacy in the mediation of chronic allograft destruction. Therapies aimed at B cells, plasma cells and antibodies will be important therapeutic options to improve the length and quality of kidney allograft survival.

Decreased frequency of peripheral CD4(+) CD161(+) Th(17) -precursor cells in kidney transplant recipients on long-term therapy with Belatacept

Clinical trials have pointed out the promising role of co-stimulation blocker Belatacept for improvement of graft function and avoidance of undesired side-effects associated with calcineurin-inhibitors (CNI). However, due to the worldwide limited availability of appropriate patients, almost no data exist to assess the effects of sustained application of this immunomodulator on the recipient's immune system. The aim of this study was to reveal specific alterations in the composition of immunologic subpopulations potentially involved in development of tolerance or chronic graft rejection following long-term Belatacept therapy. For this, peripheral lymphocyte subsets of kidney recipients treated with Belatacept (n=5; average 7.8years) were determined by flow-cytometry and compared with cells from matched patients on CNI (n=9) and healthy controls (n=10). T cells capable of producing IL-17 and serum levels of soluble CD30 were quantified. Patients on CNI showed a higher frequency of CD4(+) CD161(+) Th(17) -precursors and IL-17-producing CD4(+) T cells than Belatacept patients and controls. Significantly higher serum levels of soluble CD30 were observed in CNI patients, indicating a possible involvement of the CD30/CD30L-system in Th(17) -differentiation. No differences were found concerning CD4(+) CD25(+) CD127(low) FoxP3(+) regulatory T cells. In conclusion, patients on therapy with Belatacept did not show a comparable Th(17) -profile to that seen in individuals with chronic intake of CNI. The distinct effects of Belatacept on Th(17) -immunity might prove beneficial for the long-term outcome following kidney transplantation.

Three-year outcomes from BENEFIT, a randomized, active-controlled, parallel-group study in adult kidney transplant recipients

The clinical profile of belatacept in kidney transplant recipients was evaluated to determine if earlier results in the BENEFIT study were sustained at 3 years. BENEFIT is a randomized 3 year, phase III study in adults receiving a kidney transplant from a living or standard criteria deceased donor. Patients were randomized to a more (MI) or less intensive (LI) regimen of belatacept, or cyclosporine. 471/666 patients completed ≥3 years of therapy. A total of 92% (MI), 92% (LI), and 89% (cyclosporine) of patients survived with a functioning graft. The mean calculated GFR (cGFR) was ∼21 mL/min/1.73 m(2) higher in the belatacept groups versus cyclosporine at year 3. From month 3 to month 36, the mean cGFR increased in the belatacept groups by +1.0 mL/min/1.73 m(2) /year (MI) and +1.2 mL/min/1.73 m(2) /year (LI) versus a decline of -2.0 mL/min/1.73 m(2) /year (cyclosporine). One cyclosporine-treated patient experienced acute rejection between year 2 and year 3. There were no new safety signals and no new posttransplant lymphoproliferative disorder (PTLD) cases after month 18. Belatacept-treated patients maintained a high rate of patient and graft survival that was comparable to cyclosporine-treated patients, despite an early increased occurrence of acute rejection and PTLD.

Mycophenolate mofetil or tacrolimus compared with intravenous cyclophosphamide in the induction treatment for active lupus nephritis

BACKGROUND

Although the use of aggressive immunosuppression has improved both patient and renal survival of patients with lupus nephritis (LN), the optimal treatment of LN remains challenging. The objective of this study is to assess the efficacy and safety of mycophenolate mofetil (MMF) and tacrolimus compared with intravenous cyclophosphamide (IVC) as induction therapies for active lupus nephritis (ALN).

METHODS

In this open-label, 24-week prospective study, 60 patients with biopsy-proven ALN (Classes III, IV, V or combination) were randomly assigned to receive MMF, tacrolimus or IVC in combination with corticosteroids. The remission of proteinuria, systemic lupus erythematosus disease active index and adverse events were compared.

RESULTS

The response rates at 24 weeks were 70% (14/20) in the MMF group, 75% (15/20) in the tacrolimus group and 60% (12/20) in the IVC group (P>0.05). The complete remission rates were also similar in the three groups (40, 45 and 30%, respectively; P>0.05). There were more cases of infection in the IVC group (8/20) and the MMF group (8/20) than the tacrolimus group (3/20) and more hyperglycemia in the tacrolimus group (5/20) than the other two groups (2 or 3/20), but the results were not statistically significant among the three groups. Proteinuria decreased and serum albumin increased more quickly in the patients treated with tacrolimus (P=0.0051 and P=0.048).

CONCLUSIONS

This pilot study suggests that both MMF and tacrolimus are possible alternatives to IVC as induction therapies for ALN in Chinese patients. Tacrolimus possibly results in a faster resolution of proteinuria and hypoalbuminemia. Further studies are necessary to determine the optimal dosage and duration of the therapies.

Targets of new immunosuppressants in renal transplantation

Although current immunosuppression is highly effective in avoiding acute rejection, it is associated with nephrotoxicity, cardiovascular morbidity, infection, and cancer. Thus, new drugs dealing with new mechanisms, as well as minimizing comorbidities, are warranted in renal transplantation. Few novel drugs are currently under investigation in Phase I, II, or III clinical trials. Belatacept is a humanized antibody that inhibits T-cell co-stimulation and has shown encouraging results in Phase II and III trials. Moreover, two new small molecules are under clinical development: AEB071 or sotrastaurin (a protein kinase C inhibitor) and CP-690550 or tasocitinib (a Janus kinase inhibitor). Refinement in selecting the best combinations for the new and current immunosuppressive agents is probably the main challenge for the next few years.

Management of hematological malignancies in patients affected by renal failure

The management of hematological malignancies (HM) in renally impaired patients may be a difficult task. Indeed, the kidney represents a major elimination pathway for many chemotherapeutic agents and their metabolites, whose serum levels are not usually measured in daily clinical practice. In addition, many antineoplastic drugs have a narrow therapeutic index for which they require dose adjustment when administered to patients with renal failure. Only limited data regarding the use of chemotherapy in patients with renal impairment and in those on dialysis are available. Indeed, renal patients with HM are often excluded from most clinical trials. Thus far, in order to provide recommendations, we have reviewed the pertinent literature, gathering information from published guidelines regarding chemotherapy in patients with kidney dysfunction and from articles describing the use of individual agents in renal patients with HM.

Improving long-term renal allograft survival via a road less traveled by

It has become cliché to state that improvements in early renal allograft survival over the past two decades have not led to increased long-term renal allograft survival. However, it is not clear how long-term graft survival can be improved. Here, we present the viewpoint that the road forward does not involve searching for new and more ideal immunosuppressive regimens, but rather detailed patient follow-up to identify specific causes of late renal allograft loss and the development of new therapy designed to address these problems before allograft damage becomes irreversible.

Epithelial-to-mesenchymal transition predicts cyclosporine nephrotoxicity in renal transplant recipients

Maintenance immunosuppression with cyclosporine A (CsA) can cause nephrotoxicity in renal transplant recipients. Identifying patients at increased risk for CsA nephrotoxicity may allow interventions to prolong graft survival. Here, we studied the effect of early CsA withdrawal or maintenance among 96 kidney recipients at risk for interstitial fibrosis and tubular atrophy (IF/TA) on the basis of tubular expression of vimentin and β-catenin in a protocol biopsy performed 3 months after transplant. In this retrospective analysis of biopsies collected during a randomized trial of early withdrawal of CsA or mycophenolate mofetil, the semiquantitative score of early phenotypic changes suggestive of epithelial-to-mesenchymal transition (EMT) progressed with time among those maintained on a CsA-containing regimen. EMT-positive grafts displayed a significantly higher IF/TA score and greater progression of the IF/TA score at 12 months (P=0.001 and 0.008, respectively). EMT-positive grafts exposed to CsA also had a greater decrease in estimated GFR compared with EMT-negative grafts exposed to CsA and EMT-positive grafts withdrawn from CsA exposure. Multivariable analysis revealed that the presence of EMT was an independent risk factor for a 10% decline in graft function up to 4 years posttransplant (odds ratio 4.49; 95% confidence interval 1.02 to 19.9). Collectively, these data demonstrate that changes consistent with EMT are strong prognostic biomarkers in renal transplant recipients exposed to CsA.

Calcineurin (CN) activation promotes apoptosis of glomerular podocytes both in vitro and in vivo

To determine the role of Gq signaling and calcineurin (CN) activation in promoting apoptosis of glomerular podocytes, constitutively active Gq [Gq(+)] or CN [CN(+)] proteins were introduced into cultured podocytes using protein transduction by tagging the proteins with the transactivator of transcription peptide. To investigate the role of CN in promoting podocyte apoptosis in vivo, a genetic model of type 1 diabetes mellitus (Akita mice) was treated with the CN inhibitor FK506. In cultured podocytes, Gq(+) stimulated nuclear translocation of nuclear factor of activated T cells (NFAT) family members, activated an NFAT reporter construct, and enhanced podocyte apoptosis in a CN-dependent fashion. CN(+) similarly promoted podocyte apoptosis, and apoptosis induced by either angiotensin II or endothelin-1 was blocked by FK506. Induction of apoptosis required NFAT-induced gene transcription because apoptosis induced by either Gq(+) or CN(+) was blocked by an inhibitor that prevented CN-dependent NFAT activation without affecting CN phosphatase activity. Podocyte apoptosis was mediated, in part, by the NFAT-responsive gene cyclooxygenase 2 (COX2) and prostaglandin E(2) generation because apoptosis induced by Gq(+) was attenuated by either COX2 inhibition or blockade of the Gq-coupled E-series prostaglandins receptor. The findings appeared relevant to podocyte apoptosis in diabetic nephropathy because apoptosis was significantly reduced in Akita mice by treatment with FK506. These data suggest that Gq stimulates CN and promotes podocyte apoptosis both in vitro and in vivo. Apoptosis requires NFAT-dependent gene transcription and is mediated, in part, by CN-dependent COX2 induction, prostaglandin E(2) generation, and autocrine activation of the Gq-coupled E-series prostaglandins receptor.

Rho kinase inhibition by fasudil attenuates cyclosporine-induced kidney injury

It has been shown that the inhibition of the Rho/Rho kinase (ROCK) pathway prevents tubulointerstitial fibrosis and ameliorates renal function in various progressive renal disorders. The present study was to determine whether fasudil, a ROCK inhibitor, has a protective effect on cyclosporine A (CsA)-induced nephropathy. Male Sprague-Dawley rats were treated with CsA (n = 10, 20 mg · kg(-1) day(-1) s.c.), CsA + fasudil (n = 10, 3 mg · kg(-1) day(-1) i.p.), or vehicle alone (n = 10) for 28 days. Fasudil cotreatment ameliorated CsA-induced changes and restored renal function. CsA decreased the expression of endothelial nitric-oxide synthase and increased inducible nitric-oxide synthase/3-nitrotyrosine in the kidney. Accordingly, there was infiltration of inflammatory cells and up-regulation of inflammatory cytokines. Fasudil also significantly suppressed the expression of transforming growth factor-β1, Smad signaling, and subsequent epithelial-to-mesenchymal processes. In addition, fasudil augmented p27(kip1) expression and decreased the number of proliferating cell nuclear antigen-positive cells. In another series of experiments using HK-2 cells in culture, fasudil also suppressed CsA-induced increases in mitogen-activated protein kinase phosphorylation. CsA induced expression of p53, the degree of which was attenuated by fasudil in association with decreases of proapoptotic markers such as Bad, Bax, and total/cleaved caspase-3. These results suggest that inhibition of the Rho/ROCK pathway attenuates CsA-induced nephropathy through the suppression of the induction of inflammatory, apoptotic, and fibrogenic factors, along with inhibition of Smad, mitogen-activated protein kinases, and nitric oxide signaling pathways.

Renal interstitial fibrosis in children treated with FK506 for nephrotic syndrome

BACKGROUND

Steroid-dependent, steroid-resistant or frequently relapsing nephrotic syndrome carries a poor prognosis, including progression to renal failure. There are a number of studies confirming the efficacy of FK506 in steroid-resistant or steroid-dependent nephrotic syndrome. Although the use of this medication is becoming more common, we know very little about the potential nephrotoxicity when used in nephrotic syndrome.

METHOD

We retrospectively reviewed the characteristics and biopsy findings of 11 children with steroid-dependent or frequently relapsing nephrotic syndrome treated with FK506. Two sequential biopsies were evaluated for the change in interstitial fibrosis, measured by a quantitative stereological method, and the change in arteriolar hyaline thickening, tubular atrophy and interstitial fibrosis, graded according to Banff criteria.

RESULTS

There was an increase in interstitial fibrosis (P = 0.005), with a median absolute change in the per cent volume density between initial and follow-up biopsies of 1.8% [interquartile range (IQR) 3.9%]. Median percentage change in volume density of interstitial fibrosis, relative to volume density of interstitial fibrosis prior to initiating FK506, was 93% (IQR 138%). Banff scores for interstitial fibrosis and tubular atrophy also increased following tacrolimus therapy (P = 0.04 for both). Average FK506 trough level over the treatment period was significantly associated with change in fibrosis (Spearman's rho = 0.67 and P = 0.02).

CONCLUSIONS

This is some of the first histological data concerning tacrolimus nephrotoxicity in childhood nephrotic syndrome. Although the role of the natural progression of the underlying disease in the observed change is not definitively clear, the changes seen are in keeping with the known nephrotoxic effects of FK506 demonstrated in renal transplant. This increase is small when presented as a median change. However, there were a number of children who had a larger change in fibrosis. The factors predictive of interstitial fibrosis while on FK506 are not well defined; the findings from this study suggest that FK506 level may be a factor. Given the observations and limitations of the few published studies, there is an obvious need for further study in a large multicenter prospective trial.

A comparison of short-term exposure of once-daily extended release tacrolimus and twice-daily cyclosporine on renal function in healthy volunteers

BACKGROUND

Calcineurin inhibitor nephrotoxicity remains an issue for recipients of solid organ transplants. After cyclosporine A (CsA) microemulsion administration, effective renal plasma flow (ERPF) and glomerular filtration rate(GFR) are decreased coincident with the maximal concentration (Cmax) of CsA. The pharmacokinetic (PK) profile of the once-daily formulation of tacrolimus extended release (Tac ER) includes an equivalent AUCPK 0-24 hr and a lower Cmax versus twice-daily Tac immediate release.

METHODS

Eighteen healthy subjects were allocated once-daily Tac ER and twice-daily CsA in a prospective, randomized,open-label, two-period, two-sequence single crossover study. CsA was targeted to C2 of 700 to 1400 ng/mL, and Tac ER was targeted to C0 of 5 to 10 ng/mL. Pharmacodynamic (PD) assessments were conducted preexposure, and PD and PK were assessed during a 6-hr postdose period after 10-day exposure.

RESULTS

The achieved mean C(o) Tac and CsA were 6.4 +/- 1.16 and 201 +/- 57 ng/mL, respectively. At Cmax, the change in ERPF was +30 +/- 127 vs. -70 +/- 96 mL/min/1.73 m2 relative to baseline for Tac ER and CsA (P=0.0085). The ERPF and GFR AUC (PD 0-6) hr were 3645 +/- 887 vs. 3210 +/- 582 mL/1.73 m2 (P=0.027) and 604 +/- 98 vs. 543+/- 79 mL/1.73 m2(P=0.023) for Tac ER versus CsA, respectively. Both systolic and diastolic blood pressures were significantly greater with exposure to CsA compared with Tac ER.

CONCLUSIONS

Acute reductions in ERPF and GFR are attenuated with Tac ER compared with CsA and may correlate with the differing PK profiles of these calcineurin inhibitors.

Can the early elimination of calcineurin inhibitors result in clinical benefits?

Ideally, every kidney should serve its owner for his or her remaining life expectancy. Current approaches with immunosuppression have steadily reduced early rejection rates. However, we have not seen a comparable improvement in graft longevity. Reduction of acute rejection rates should improve survival, unless concurrent nephrotoxicity offsets this benefit. An important question is whether selective substitution of other drugs/biologicals for calcineurin inhibitors will permit adequate immunoprophylaxis, yet improve graft longevity.

Evaluation of the novel protein kinase C inhibitor sotrastaurin as immunosuppressive therapy after renal transplantation

IMPORTANCE OF THE FIELD

The prevalence of acute renal allograft rejection has decreased substantially in past decades due to new and more specific immunosuppressive compounds but improvements in long-term graft function have not been achieved. There is a large need for new immunosuppressive agents that lack toxicity of current agents such as calcineurin inhibitors but show high synergistic efficiency in preventing rejection processes.

AREAS COVERED IN THIS REVIEW

This review summarizes data concerning the pharmacokinetics, pharmacodynamics and clinical efficacy of the new PKC inhibitor sotrastaurin with a focus on renal transplantation. The article contains information that has been presented at international transplant meetings and congresses and that has been published between 2006 and 2010. Additionally, current ongoing trials are described in detail.

WHAT THE READER WILL GAIN

Immunosuppressive regimens after kidney transplantation consist of a combination of several agents in order to minimize drug toxicity. Therefore, the reader is presented with the most up-to-date/current developments in sotrastaurin applications in Phase I and II trials with emphasis on data maintained from studies that combined sotrastaurin with established agents such as mycophenolic acid and tacrolimus.

TAKE HOME MESSAGE

Several trials are ongoing and planned to determine the optimal immunosuppressive regimen to benefit from sotrastaurin's distinct mechanism of action.

Cardioprotective effect of calcineurin inhibition in an animal model of renal disease

AIMS

Chronic kidney disease is directly associated with cardiovascular complications. Heart remodelling, including fibrosis, hypertrophy, and decreased vascularization, is frequently present in renal diseases. Our objective was to investigate the impact of calcineurin inhibitors (CNI) on cardiac remodelling and function in a rat model of renal disease.

METHODS AND RESULTS

Male Sprague Dawley rats were divided into six groups: sham-operated rats, 5/6 nephrectomized rats (Nx) treated with vehicle, CNI (cyclosporine A 5.0 or 7.5, or tacrolimus 0.5 mg/kg/day) or hydralazine (20 mg/kg twice a day) for 14 days, starting on the day of surgery. Creatinine clearance was significantly lower and blood pressure significantly higher in Nx rats when compared with controls. Morphological and echocardiographic analyses revealed increased left ventricular hypertrophy and decreased number of capillaries in Nx rats. Treatment with CNI affected neither the renal function nor the blood pressure, but prevented the development of cardiac hypertrophy and improved vascularization. In addition, regional blood volume improved as confirmed by contrast agent-based echocardiography. Hydralazine treatment did not avoid heart remodelling in this model. Gene expression analysis verified a decrease in hypertrophic genes in the heart of CNI-treated rats, while pro-angiogenic and stem cell-related genes were upregulated. Moreover, mobilization of stem/progenitor cells was increased through manipulation of the CD26/SDF-1 system.

CONCLUSION

We conclude from our studies that CNI-treatment significantly prevented cardiac remodelling and improved heart function in Nx rats without affecting renal function and blood pressure. This sheds new light on possible therapeutic strategies for renal patients at high cardiovascular risk.

The pharmacogenetics of calcineurin inhibitor-related nephrotoxicity

Chronic calcineurin inhibitor (CNI)-induced nephrotoxicity is associated with prolonged use of cyclosporine and tacrolimus and has been observed after all types of transplantation, as well as during treatment of autoimmune disease. Extensive alterations in the renal architecture including glomerular sclerosis, tubular atrophy and interstitial fibrosis may lead to end-stage renal failure. Increasing evidence shows that pharmacogenetic factors explain part of the between-patient differences in susceptibility to developing CNI-induced nephrotoxicity. In this paper this evidence is reviewed, with special emphasis on the role of genetic factors influencing metabolism and transportation of CNIs in both acceptor and donor.

[Interstitial fibrosis in renal grafts: On the way to a better detection]

In renal grafts, the progression of interstitial fibrosis and tubular atrophy (IF/TA) is exponential during the first months post-transplant. Consequently, roughly 40% of the cadaveric grafts will function less than ten years. There is, however, no specific strategy to halt fibrogenesis, i.e. the progression of fibrosis with time, in kidney recipients. Epithelial to mesenchymal transition (EMT) is a biological process used to disperse cells during embryogenesis. In the setting of injury, it is also a mechanism to escape cellular death. The last five years, several studies demonstrated that EMT does occur in tubular epithelial cells, which have been shown to loose the expression of epithelial markers, and acquire the expression of mesenchymal proteins, like vimentin. The aim of this review is triple: 1) discuss the connections between EMT and the context of transplantation; 2) explain how EMT markers may be useful in clinical practice, as promising surrogate markers for fibrogenesis; 3) discuss some therapeutic perspectives.