title: Mammalian Target of Rapamycin Inhibitors and Nephrotoxicity: Fact or Fiction.
abstract: Mammalian target of rapamycin inhibitors, such as rapamycin and more recently everolimus, have substituted calcineurin inhibitors in many minimization strategies. Despite their acclaimed renal safety profile, several lines of evidence are emerging on their potential nephrotoxic effect. Predisposing conditions for nephrotoxicity involve a complex interplay between several environmental and genetic factors in the donor-recipient pair. Renal injury may be enhanced by pharmacodynamic interactions when combined with other drugs such as calcineurin inhibitors or nutrients that are predominantly related to an increase in local tissue exposure. These toxic interactions may occur within adequate doses and therapeutic blood levels. This explains the occurrence of nephrotoxicity in some but not all cases. Here, we postulated that activity of a low permeability glycoprotein efflux pump related to low protein expression and/or inhibition enhanced immunosuppressive drug entry in different cells. A rise in intracellular drug concentration increases bioactivity, leading to greater immunosuppression and more immune-related, nonrenal adverse events in the recipient and increased nephrotoxicity in the kidney graft. Under specific isolated or combined environmental and/or genetic conditions in both the recipient and donor affecting the glycoprotein efflux pump and/or the mammalian target of rapamycin pathway, these renal injuries may be aggravated by heightened drug tissue concentrations despite adherence to therapeutic drug and blood levels. Mammalian target of rapamycin inhibitors may induce predominantly a dose-dependent renal epithelial cell injury affecting either the glomerular or the renal tubular epithelial cells, leading to cell death and apoptosis. Epithelial mesenchymal transition mediated interstitial fibrosis and tubular atrophy observed with these drugs may be the result of a cumulative toxic renal tubular injury induced by the direct insult of the drug itself and/or podocytopathy-associated proteinuria. The resulting glomerular tubular damage will ultimately lead to graft failure and loss, if exposure persists.
authors.affiliation: Rafik Hariri University Hospital, Beirut, Lebanon.
authors.forename: Antoine
authors.initials: A
authors.lastname: Barbari
authors.forename: Maria
authors.initials: M
authors.lastname: Maawad
authors.forename: Hala
authors.initials: H
authors.lastname: Kfoury Kassouf
authors.forename: Gaby
authors.initials: G
authors.lastname: Kamel
mesh_terms: D000368:Aged; D001706:Biopsy; D005260:Female; D006084:Graft Rejection / Q000201:enzymology / Q000276:immunology / Q000517:prevention & control*; D006085:Graft Survival / Q000187:drug effects*; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects* / Q000493:pharmacokinetics; D007668:Kidney / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D007674:Kidney Diseases / Q000139:chemically induced* / Q000201:enzymology / Q000473:pathology; D016030:Kidney Transplantation / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D047428:Protein Kinase Inhibitors / Q000009:adverse effects* / Q000493:pharmacokinetics; D012307:Risk Factors; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016896:Treatment Outcome
chemical_list: D007166:Immunosuppressive Agents; D047428:Protein Kinase Inhibitors; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases