title: Proteasome inhibitors prevent cisplatin-induced mitochondrial release of apoptosis-inducing factor and markedly ameliorate cisplatin nephrotoxicity.
abstract: We demonstrate the effect of proteasome inhibitors in mitochondrial release of apoptosis-inducing factor (AIF) in cisplatin-exposed renal tubular epithelial cells (LLC-PK(1) cells) and in a model of cisplatin nephrotoxicity. Immunofluorescence and subcellular fractionation studies revealed cisplatin-induced translocation of AIF from the mitochondria to nucleus. Mcl-1, a pro-survival member of the Bcl-2 family, is rapidly eliminated on exposure of renal cells to cisplatin. Proteasome inhibitors PS-341 and MG-132 blocked cisplatin-induced Mcl-1 depletion and markedly prevented mitochondrial release of AIF. PS-341 and MG132 also blocked cisplatin-induced activation of executioner caspases and apoptosis. These studies suggest that proteasome inhibitors prevent cisplatin-induced caspase-dependent and -independent pathways. Overexpression of Mcl-1 was effective in blocking cisplatin-induced cytochrome c and AIF release from the mitochondria. Downregulation of Mcl-1 by small interfering RNA promoted Bax activation and cytochrome c and AIF release, suggesting that cisplatin-induced Mcl-1 depletion and associated Bax activation are involved in the release of AIF. Expression of AIF protein in the mouse was highest in the kidney compared to the heart, brain, intestine, liver, lung, muscle, and spleen. In an in vivo model of cisplatin nephrotoxicity, proteasome inhibitor MG-132 prevented mitochondrial release of AIF and markedly attenuated acute kidney injury as assessed by renal function and histology. These studies provide evidence for the first time that the proteasome inhibitors prevent cisplatin-induced mitochondrial release of AIF, provide cellular protection, and markedly ameliorate cisplatin-induced acute kidney injury. Thus, AIF is an important therapeutic target in cisplatin nephrotoxicity and cisplatin-induced depletion of Mcl-1 is an important pathway involved in AIF release.
authors.affiliation: University of Arkansas for Medical Sciences, Department of Medicine, Little Rock, Arkansas 72205, United States.
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.forename: Christian
authors.initials: C
authors.lastname: Herzog
authors.forename: Rohit
authors.initials: R
authors.lastname: Seth
authors.forename: Gur P
authors.initials: GP
authors.lastname: Kaushal
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000494:pharmacology*; D015153:Blotting, Western; D002945:Cisplatin / Q000009:adverse effects / Q000494:pharmacology*; D047468:Immunoprecipitation; D007668:Kidney / Q000187:drug effects* / Q000473:pathology; D018374:LLC-PK1 Cells; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000187:drug effects*; D011480:Protease Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D013552:Swine
chemical_list: D000970:Antineoplastic Agents; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D002945:Cisplatin