Adverse effects of immunosuppressive drugs on long-term graft outcome

Compared Effect of Immunosuppressive Drugs Cyclosporine A and Rapamycin on Cholesterol Homeostasis Key Enzymes CYP27A1 and HMG-CoA Reductase

Hyperlipidaemia, i.e. increase in total cholesterol and triglycerides, is a common side-effect of the immunosuppressive drugs rapamycin (RAPA) and cyclosporine A (CsA), and is probably related to inhibition of the 27-hydroxylation of cholesterol (acid pathway of bile acid biosynthesis). This might be one of the causes for the increase in plasma cholesterol, as 27-hydroxycholesterol is a potent suppressor of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), a key enzyme of cholesterol synthesis. As the sterol 27-hydroxylase (CYP27A1) inhibition by CsA is well known, we evaluated the effect of another immunosuppressive drug, RAPA, on this enzyme in HepG2 mitochondria, which confirmed the dose-dependent inhibition of mitochondrial CYP27A1 by cyclosporine (10-20 microM), while the inhibition by RAPA required a higher dose (50-100 microM). Corresponding K(i) was 10 microM for CsA (non-competitive inhibition) and 110 microM for RAPA (competitive inhibition). Cotreatment with both immunosuppressive drugs showed an additive inhibitory effect on CYP27A1 activity. Later, we analysed the effect of these immunosuppressants on HMGR expression in HepG2 cells, and a dose-dependent up-regulation of HMGR gene expression was observed. The results suggest that RAPA and CsA are both inhibitors of CYP27A1 activity with slightly different mechanisms and that they may accordingly increase HMGR expression.

The Impact of Living Donor Kidney Transplantation on Markers of Cardiovascular Risk in Chronic Kidney Disease Patients

BACKGROUND

Kidney transplant (Tx) patients present a reduced cardiovascular (CV) mortality in comparison to the dialysis population, but in comparison to the general population, it is still several-fold higher.

METHODS

We studied risk factors for CV disease in a group of 38 patients (50% males, median age 36 years) who underwent a living donor Tx at the baseline and after 3 +/- 1 and 9 +/- 2 months.

RESULTS

The prevalence of overweight increased from 26 to 54% after Tx (p < 0.001). The mean systolic blood pressure decreased significantly after the Tx (148 +/- 27.6 vs. 126 +/- 12.7 mm Hg). There was a significant increase in LDL (97 +/- 30 vs. 114 +/- 35) and hematocrit (33.8 +/- 4.4 to 42 +/- 5.7%) levels and a significant reduction in fibrinogen levels (394 +/- 91 vs. 366 +/- 100 mg/dl) after 9 months as compared to the baseline. Obesity and dislipidemia were significantly correlated with inflammation. Significant changes in left ventricle mass index (293 +/- 116 vs. 241 +/- 96) were observed after the Tx. Patients with a low glomerular filtration rate (GFR) in the follow-up evaluation presented higher LDL (128 +/- 7 vs. 99 +/- 7 mg/dl; p < 0.05) and higher fibrinogen levels (399 +/- 21 vs. 332 +/- 22 mg/dl; p < 0.05) compared to patients with a high GFR.

CONCLUSION

Most of the risk factors analyzed (particularly the uremia-related) improved after the renal Tx, which could justify the positive impact of Tx on the development of CV disease. Inflammation and dyslipidemia were related to renal dysfunction after the Tx, suggesting that complete restoration of renal function may have an impact on reducing CV mortality in CKD patients treated with renal Tx.

A New Alloantigen-Independent Control for Chronic Allograft Nephropathy Rat Models

BACKGROUND

Isografts are used as controls in many transplant experiments. Our laboratory and others have noticed histological changes in control isograft groups of rats similar to allograft groups, suggesting alloantigen-independent factors contributing to chronic allograft nephropathy. However, the isograft model as a nonalloantigen control is flawed because of the potential of unrecognized minor antigen differences between rats. We designed a study using autografts to isolate alloantigen-independent factors in the rat renal transplant allograft model.

MATERIALS AND METHODS

Male Lewis rats weighing 150-250 g underwent a procedure designed to mimic the injury of renal transplant, in which the left kidney was perfused with cold University of Wisconsin solution and subjected to similar cold and warm ischemic times as Lewis isograft rats undergoing renal transplanation.

RESULTS

Six autograft rats were compared to five isograft and three single nephrectomy rats. Autograft rats showed normal kidney function according to serum BUN, Cr, and urinary protein. At 360 days, four of six autografts displayed normal renal parenchymal histology, whereas the remaining two autografts displayed histological changes scored as Banff acute rejection 1a and 1b. At sacrifice time, four of five isografts showed histological changes scored as Banff chronic rejection 1 and the single nephrectomy group showed normal histology in the remaining native kidney.

CONCLUSIONS

Our data demonstrate that the chronic nephropathy observed in the isograft cannot be completely freed from suspicion of immunological origin. We propose that the autograft model for rat renal transplant research is a better nonimmunologic control than the isograft model for chronic allograft nephropathy.

Mycophenolate mofetil inhibits intimal hyperplasia and attenuates the expression of genes favouring smooth muscle cell proliferation and migration

AIM

Intimal hyperplasia remains the leading cause of late graft failure following heart transplantation. The immunosuppressive drug mycophenolate mofetil has been shown to inhibit the development of intimal hyperplasia. This study aimed to assess the efficacy of a combination of mycophenolate mofetil, calcineurin inhibition, and sirolimus on the development of intimal hyperplasia.

METHODS

Male Sprague-Dawley rats received mycophenolate mofetil (30 mg/kg per day) and either tacrolimus (0.1 mg/kg per day), cyclosporine (5 mg/kg per day), or sirolimus (0.05 mg/kg per day) and were compared to an untreated control group. All animals underwent left common carotid artery balloon angioplasty. Morphometric analysis was performed on representative transverse sections, and intima medial ratios calculated at 2 weeks. Profibrotic gene expression was assessed with competitive RT-PCR at 2 weeks for metalloproteinase-2, metalloproteinase-9, TIMP-1, collagen III, and TGF-beta. Sections were stained with sirius red, and extracellular matrix deposition was quantified.

RESULTS

Mycophenolate mofetil in combination with rapamycin was associated with the greatest reduction in intimal thickening (intima medial ratio 0.79; range 0.45-0.86), compared to its combination with either cyclosporine (1.41; range 1.06-1.68, P < .02) or tacrolimus (0.93; range 0.81-1.37, P < .05) and controls (1.47; range 1.02-2.04, P < .005). Mycophenolate mofetil and rapamycin significantly inhibited all profibrotic genes studied compared to controls (P < .01) but there were no differences between tacrolimus and cyclosporine. Mycophenolate mofetil and sirolimus significantly attenuated extracellular matrix deposition compared to tacrolimus and cyclosporin (P < .023).

CONCLUSION

The benefits of mycophenolate mofetil in combination with sirolimus are preferential over those with cyclosporine or tacrolimus. Randomised trials are warranted to assess if mycophenolate mofetil should be an alternative agent to calcineurin-inhibitors when used in combination with sirolimus.

Molecular mechanisms of renal allograft fibrosis

BACKGROUND

Chronic graft nephropathy (CGN) remains the leading cause of renal allograft loss after the first year following transplantation. Histologically it is characterized by glomerulosclerosis, intimal hyperplasia and interstitial fibrosis. The pathogenesis is unclear, but is likely to involve both immunological and non-immunological factors. Despite improvements in short-term graft survival rates, new immunosuppressive regimens have made no impact on CGN.

METHODS

A review of the current literature on renal transplantation, novel immunosuppression regimens and advances in the molecular pathogenesis of renal allograft fibrosis was performed.

RESULTS AND CONCLUSION

Recent advances in understanding of the underlying molecular mechanisms involved suggest autocrine secretion of cytokines and growth factors, especially transforming growth factor beta, are associated with a change in fibroblast phenotype leading to the deposition of extracellular matrix. Repeated insults trigger upregulation of the tissue inhibitors of matrix metalloproteinases, favouring accumulation of extracellular matrix. To date, no drug has proved effective in inhibiting or reducing allograft fibrosis. The deleterious consequences of chronic immunosuppression on the development of such fibrosis are now recognized; newer immunosuppressive drugs, including rapamycin and mycophenolate mofetil, reduce profibrotic gene expression in both experimental and clinical settings, and offer potential strategies for prolonging allograft survival.

Tolerability profile of sodium mycophenolate (ERL080) and mycophenolate mofetil with and without cyclosporine (Neoral) in the rat

Mycophenolic acid sodium salt (ERL080) is currently in Phase III clinical trials for the prophylaxis of kidney transplant rejection upon coadministration with Neoral (cyclosporin A microemulsion). To assess the relative side effect profile of ERL080 and MMF as drug substances in Lewis rats, a rat strain commonly used in transplantation experiments, a comparative 4-week tolerability study was performed. Escalating doses of ERL080 and MMF were administered orally at 10-30 mg/kg/d (i.e., doses within or above the immunosuppressive range in rats), either in single compound treatment or in combination with cyclosporine (CsA) at a daily oral dose of 7.5 mg/kg. The compounds were well tolerated as documented by body weight monitoring, hematologic parameters, and weight and histology of organs. Major abnormalities observed were a dose-dependent reduction in thymus weight associated with immunosuppression, in some cases villous atrophy in the jejunum, a reduction in white blood cell counts and lymphocyte counts (mean value in distinct treatment groups not exceeding 40-50%), a decrease in red blood cell counts and hemoglobin concentration (at maximum 25-30%), and an increase in platelet counts (in some groups up to doubling). At a given dose, these adverse effects were slightly more pronounced for MMF than for ERL080, and for groups under CsA coadministration compared to both compounds given alone. No significant potentiation effect of CsA on the changes induced by ERL080 or MMF was observed. Moreover, there were no new toxic entities evident upon CsA microemulsion coadministration.