Chronic cyclosporin nephropathy: long-term effects of cyclosporin on renal allografts

[The pathology of renal transplants]

In order to make an objective assessment of the histopathology of a renal biopsy during a kidney transplant, all the various elements involved in the process must be understood. It is important to know the characteristics of the donor organ, especially if the donor is older than 65. The histopathological features of the donor biopsy, especially its vascular status, are often related to an initial poor function of the transplanted kidney. The T lymphocyte inflammatory response is characteristic in acute cellular rejection; the degree of tubulitis, together with the amount of affected parenchyme, are important factors. The proportion of cellular sub-populations, such as plasma cells and macrophages, is also important, as they can be related to antibody-mediated humoral rejection. Immunofluorescent or immunohistochemical studies are necessary to rule out C4d deposits or immunogloblulins. The presence of abundant deposits of C4d in tubular basement membranes supports a diagnosis of humoral rejection, as does the presence of capillaritis, glomerulitis which, together with vasculitis, are typical diagnostic findings in C4d negative cases. Interstitial fibrosis, tubular atrophy and glomerular sclerosis, although non-specific, imply a chronic phase. Transplant glomerulopathy and multilamination in more than 6 layers of the tubular and glomerular basement membranes are quasi-specific characteristics of chronic humoral rejection. Electron microscopy is essential to identify of these pathologies as well as to demonstrate the presence of other glomerular renal diseases.

Pathology of Calcineurin and Mammalian Target of Rapamycin Inhibitors in Kidney Transplantation

The recent evolution in immunosuppression therapy has led to significant improvement in short-term kidney allograft outcomes; however, this progress did not translate into similar improvement in long-term graft survival. The latter, at least in part, is likely to be attributed to immunosuppressant side effects. In this review, we focus on the histologic manifestations of calcineurin inhibitor and mammalian target of rapamycin inhibitor toxicity. We discuss the pathologic features attributed to such toxicity and allude to the lack of highly specific pathognomonic lesions. Finally, we highlight the importance of clinicopathologic correlation to achieve a meaningful pathologic interpretation.

TMBIM6 (transmembrane BAX inhibitor motif containing 6) enhances autophagy and reduces renal dysfunction in a cyclosporine A-induced nephrotoxicity model

Cyclosporine A (CsA) is widely used as an immunosuppressor in transplantation. Previous studies reported that CsA induces autophagy and that chronic treatment with CsA results in accumulation of autophagosomes and reduced autophagic clearance. Autophagy is a prosurvival process that promotes recovery from acute kidney injury by degrading misfolded proteins produced in the kidney. In the present study, we used TMBIM6-expressing HK-2, human kidney tubular cells (TMBIM6 cells) and Tmbim6 knockout (tmbim6(-/-)) mice. When exposed to CsA, the TMBIM6 cells maintained autophagy activity by preventing autophagosome accumulation. With regard to signaling, PRKKA/AMPK phosphorylation and mechanistic target of rapamycin (serine/threonine kinase) complex 1 (MTORC1) expression and its downstream target TFEB (transcription factor EB), a lysosome biogenesis factor, were regulated in the TMBIM6 cells. Lysosomal activity was highly increased or stably maintained in the presence of TMBIM6. In addition, treatment of tmbim6(-/-) mice with CsA resulted in increased autophagosome formation and decreased lysosome formation and activity. We also found that tmbim6(-/-) mice were susceptible to CsA-induced kidney injury. Taken together, these results indicate that TMBIM6 protects against CsA-induced nephrotoxicity both in vitro and in vivo by inducing autophagy and activating lysosomes.

Mechanisms of cyclosporine-induced renal cell apoptosis: a systematic review

BACKGROUND/AIMS

Chronic cyclosporine A (CsA) nephrotoxicity (CCN) is an important cause of chronic renal dysfunction with no effective clinical intervention. To further elucidate the mechanisms of renal cell apoptosis in CCN, all relevant in vivo studies on this subject were analyzed.

METHODS

We searched for in vivo studies on the mechanisms of CsA-induced renal cell apoptosis in Medline (1966-July 2010), Embase (1980-July 2010) and ISI (1986-July 2010). The studies were evaluated for their quality according to a set of in vivo standards, data extracted according to PICOS, and then synthesized.

RESULTS

Renal cell apoptosis was an important feature of CCN and an important factor of renal dysfunction. First, CsA could upregulate Fas/Fas ligand, downregulate Bcl-2/Bcl-XL, and increase caspase-1 and caspase-3. Second, it could induce oxidative stress and damage the antioxidant defense system. Third, it could increase endoplasmic reticulum stress protein in a dose- and time-dependent manner. Fourth, CsA could impair the urine concentration and decrease the expression of hypertonicity-induced genes. Fifth, CsA-induced renal cell apoptosis was significantly decreased by blocking the angiotensin II type 1 receptor using losartan.

CONCLUSIONS

The in vivo mechanisms for CCN are more complex than those found in vitro. CsA can induce renal cell apoptosis using five pathways in vivo and activated caspases might be the ultimate intersection of these pathways and the common intracellular pathway mediating apoptosis. These data provide new potential points for intervention and need to be confirmed by further studies.

The protective effects of omega 3 fatty acids and sesame oil against cyclosporine A-induced nephrotoxicity

Cyclosporine A (CsA) is a drug used in autoimmune disorders and organ transplantations. Omega 3 fatty acids (O-3) and sesame oil (SO) have antioxidant properties. We aimed to investigate and compare the protective effects of O-3 and SO against CsA-induced nephrotoxicity. Seven groups of male Wistar albino rats were included in the study. In group 1 (control), saline was administered, and in group 2, CsA (subcutaneously) was administered. In group 3, CsA+SO (orally; p.o.) was given; in group 4, CsA+O-3 (p.o.) was given; and in group 5, CsA+SO+O-3 was given. In group 6, SO was administered, and in group 7, O-3 was administered. After 15 days of treatment, kidneys were excised. Histopathological evaluation, apoptotic cell count, and renal/hepatic function tests were performed. In group 2, vacuolar degeneration and necrosis of tubular cells as well as hemorrhagic foci were observed; the apoptotic cell number was higher than in the control (P < 0.001). In groups 3, 4, and 5, tubular scores and apoptotic cell count were lower than in group 2 (P < 0.01 and P < 0.001, respectively). In groups 6 and 7, healthy renal histology and a few apoptotic cells were determined. In groups 2, 3, 4, and 5, blood urea nitrogen was higher and albumin was lower than in the control (P < 0.001). Liver enzymes were unchanged. O-3/SO showed similar protective effects against CsA-induced nephrotoxicity, as revealed by a remarkable decrease in histopathological changes and apoptotic cell count. However, impaired renal function tests were not improved with O-3/SO treatment. SO and O-3 can be used as chemoprotectants against CsA.

Endothelial cell transforming growth factor-β receptor activation causes tacrolimus-induced renal arteriolar hyalinosis

Arteriolar hyalinosis is a common histological finding in renal transplant recipients treated with the calcineurin inhibitor tacrolimus; however, the pathophysiologic mechanisms remain unknown. In addition to increasing transforming growth factor (TGF)-β levels, tacrolimus inhibits calcineurin by binding to FK506 binding protein 12 (FKBP12). FKBP12 alone also inhibits TGF-β receptor activation. Here we tested whether tacrolimus binding to FKBP12 removes an inhibition of the TGF-β receptor, allowing ligand binding, ultimately leading to receptor activation and arteriolar hyalinosis. We found that specific deletion of FKBP12 from endothelial cells was sufficient to activate endothelial TGF-β receptors and induce renal arteriolar hyalinosis in these knockout mice, similar to that induced by tacrolimus. Tacrolimus-treated and knockout mice exhibited significantly increased levels of aortic TGF-β receptor activation as evidenced by SMAD2/3 phosphorylation, along with increased collagen and fibronectin expression compared to controls. Treatment of isolated mouse aortas with tacrolimus increased TGF-β receptor activation, collagen and fibronectin expression. These effects were independent of calcineurin, absent in endothelial denuded aortic rings, and could be prevented by the small molecule TGF-β receptor inhibitor SB-505124. Thus endothelial cell TGF-β receptor activation is sufficient to cause vascular remodeling and renal arteriolar hyalinosis.

Mechanisms of renal cell apoptosis induced by cyclosporine A: a systematic review of in vitro studies

BACKGROUND

Chronic cyclosporine A (CsA) nephrotoxicity (CCN) is a major cause of chronic renal dysfunction and has no effective clinical interventions yet.

OBJECTIVE

To reveal the mechanisms of renal cell apoptosis in CCN, we analyzed all in vitro studies of such mechanisms.

METHODS

We collected all in vitro studies about the mechanisms of renal cell apoptosis induced by CsA in Medline (1966 to July 2010), Embase (1980 to July 2010) and ISI (1986 to July 2010), evaluated their quality according to in vitro standards and extracted data following the PICOS principles and synthesized the data.

RESULTS

First,CsA could upregulate Fas and Fas-L expression, increase FADD and apoptosis enzymes (caspase-2, -3, -4, -7, -8, -9 and -10) and downregulate the Bcl-2 and Bcl-xL. Second, CsA could induce oxidative stress and damage the antioxidant defense system. Third, CsA could increase the expression of HERP, GRP78 and CHOP. Fourth, CsA could induce renal cell apoptosis and increase their iNOS and p53 expression in cultured cells.

CONCLUSIONS

At least four pathways are involved in renal cell apoptosis induced by CsA in different cell species. Caspases might be their final common pathway in vitro. They might all provide potential points for interventions, but these need to be confirmed in vivo.

mToR inhibitors-induced proteinuria: mechanisms, significance, and management

Massive urinary protein excretion has been observed after conversion from calcineurin inhibitors to mammalian target of rapamycin (mToR) inhibitors, especially sirolimus, in renal transplant recipients with chronic allograft nephropathy. Because proteinuria is a major predictive factor of poor transplantation outcome, many studies focused on this adverse event during the past years. Whether proteinuria was due to sirolimus or only a consequence of calcineurin inhibitors withdrawal remained unsolved until high range proteinuria has been observed during sirolimus therapy in islet transplantation and in patients who received sirolimus de novo. Podocyte injury and focal segmental glomerulosclerosis have been related to mToR inhibition in some patients, but the pathways underlying these lesions remain hypothetic. We discuss herein the possible mechanisms and the significance of mToR blockade-induced proteinuria.

Benefits of cyclosporine absorption profiling in nephrotic syndrome: preprandial once-daily administration of cyclosporine microemulsion improves slow absorption and can standardize the absorption profile

AIM

Cyclosporine is known to improve proteinuria in nephrotic syndrome (NS), but is also associated with drug-related renal impairment. In this case series, therapeutic drug monitoring using the absorption profile was applied to adults with NS to investigate the efficacy and safety of once-daily administration of cyclosporine microemulsion (CSAME).

METHODS

Twenty patients received CSAME starting at 100-175 mg/day (1.4-3.1 mg/kg per day) once daily after breakfast. The area under the concentration-time curve up to 4 h after administration of cyclosporine (AUC(0-4 h)) was determined in each patient within 1 week after the start of CSAME treatment. Thereafter, the dose of CSAME was adjusted according to the absorption profile.

RESULTS

After 6 months, treatment with CSAME improved efficacy test values compared with those prior to treatment, and the severe nephrotic state was eliminated in all patients. No changes in serum creatinine or blood urea nitrogen levels were observed. The dose of CSAME was adjusted so that AUC(0-4 h) and the peak level fell within the range of target values, resulting in a significant decrease in the mean dose of cyclosporine (P = 0.0001). Time of peak level was variable among patients, but when CSAME was administered before breakfast, good absorption was achieved in all patients.

CONCLUSION

By monitoring the absorption profile in patients with NS, a once-daily administration of CSAME was used to achieve both efficacy and a reduction in total exposure to the drug. Preprandial administration provided a more stable absorption profile of cyclosporine. The authors hope this method will become standard procedure during cyclosporine treatment in these patients.

Recurrence of proteinuria 10 years post-transplant in NPHS2-associated focal segmental glomerulosclerosis after conversion from cyclosporin A to sirolimus

Mutations in the NPHS2 gene, which encodes podocin, are associated with steroid-resistant nephrotic syndrome in childhood. Renal histology frequently presents focal segmental glomerulosclerosis (FSGS). Post-transplant recurrence of proteinuria in patients affected by homozygous or compound heterozygous NPHS2 mutation is encountered rarely (1-2%) compared to 30% recurrence in nonhereditary FSGS. We report on a pediatric kidney transplant recipient with NPHS2-associated nephrotic syndrome and FSGS, who developed biopsy-proven recurrence of FSGS 10 years post-transplant in temporal association with conversion from cyclosporin A (CsA)- to sirolimus (SRL)-based immunosuppression, due to histological evidence of severe CsA-induced nephrotoxicity. Reswitch of the immunosuppressive regimen from SRL to CsA led to a noticeable decrease of proteinuria and to stabilization of graft function. We conclude that patients with hereditary FSGS are not entirely protected from post-transplant recurrence of proteinuria, even in the long term. The close temporal relationship of FSGS recurrence with CsA withdrawal and conversion to SRL suggests that caution should be exercised in the use of CsA-free immunosuppression also in patients with NPHS2-associated FSGS.

Proteinuria Following a Switch from Calcineurin Inhibitors to Sirolimus

BACKGROUND

Sirolimus is an alternative option for kidney transplant patients treated with calcineurin inhibitors (CNI) when renal function is deteriorating. However, the incidence of proteinuria following a switch from CNI to sirolimus has caused concern, and was therefore investigated here.

METHODS

In a retrospective study, 68 renal transplant recipients were switched from CNI to sirolimus. Proteinuria was measured using 24-hour urine collection before the switch and collections 3, 6, 12, and 24 months thereafter. In addition, proteinuria was measured in patients who had to be switched back to CNI due to side effects. Survival analyses were performed.

RESULTS

Baseline proteinuria was 0.39+/-0.69 g/day in all 68 patients. It increased to a mean 1.44+/-1.90 g/day at 3 months (P<0.001) and remained elevated at 6, 12 and 24 months. When sirolimus was withdrawn after the CNI-sirolimus switch for 19 patients, proteinuria decreased from 1.95+/-2.06 g/day to 0.9+/-1.4 g/day (P<0.05). Proteinuria above 0.3 g/day before the CNI-sirolimus switch correlated significantly with the decrease of renal function thereafter.

CONCLUSION

CNI-treated kidney transplant recipients may develop reversible proteinuria when switched to sirolimus.