Sirolimus damages podocytes in rats with protein overload nephropathy.
BACKGROUND
Conversion from calcineurin inhibitors (CNIs) to sirolimus could significantly improve long-term graft survival after kidney transplantation. Proteinuria was found in some recipients after the switch, which could be alleviated by an angiotensin II receptor blocker (ARB). But the mechanisms for this have remained unclear. In this study, we utilized a rat model with protein overload nephropathy to explore the mechanisms of sirolimus-related proteinuria.


METHODS
A rat model with protein overload nephropathy was induced by repeated injections of bovine serum albumin. Model rats also received sirolimus (rapamycin) treatment or ARB agent (losartan) pretreatment. Urinary protein excretion from 24-hour urine specimens was calculated, and the morphological changes of renal tissues were analyzed by hematoxylin and eosin staining and electron microscopy. The expression of desmin, a sensitive marker of podocyte injury, was detected by immunohistochemical staining.


RESULTS
Rapamycin increased urinary protein excretion and intratubular protein cast formation in rats with protein overload nephropathy. The foot process effacement of podocytes was found by electron microscopy after rapamycin treatment. The expression of desmin was up-regulated after rapamycin treatment. However, losartan pretreatment could attenuate proteinuria in spite of rapamycin treatment.


CONCLUSIONS
Sirolimus aggravates proteinuria in rats with protein overload nephropathy by damaging podocytes, a barrier of glomerular filtration. Furthermore, angiotensin II receptor blocker can counteract the effect of sirolimus, not only through hemodynamic changes but also partly by repairing the injury of podocytes. This study might be useful for understanding the mechanism of sirolimus-related proteinuria and guiding clinical treatments.
Department of Renal Transplantation, The First Affiliated Hospital, Wenzhou Medical College, Wenzhou - PR China. yorkcai@126.com
Yong
Y
Cai
Yan
Y
Chen
Shaoling
S
Zheng
Bicheng
B
Chen
Yirong
Y
Yang
Peng
P
Xia
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D003893:Desmin / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D007166:Immunosuppressive Agents / Q000009:adverse effects* / Q000494:pharmacology; D016030:Kidney Transplantation / Q000276:immunology; D019808:Losartan / Q000494:pharmacology / Q000627:therapeutic use; D050199:Podocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D011507:Proteinuria / Q000139:chemically induced* / Q000473:pathology* / Q000517:prevention & control; D051381:Rats; D017208:Rats, Wistar; D020123:Sirolimus / Q000009:adverse effects* / Q000494:pharmacology; D015854:Up-Regulation
D047228:Angiotensin II Type 1 Receptor Blockers; D015415:Biomarkers; D003893:Desmin; D007166:Immunosuppressive Agents; D019808:Losartan; D020123:Sirolimus