title: Oxidant-mediated apoptosis in proximal tubular epithelial cells following ATP depletion and recovery.
abstract: Oxidant-mediated apoptosis has been implicated in renal injury due to ischemia reperfusion (IR); however, the apoptotic signaling pathways following IR have been incompletely defined. The purpose of this study was to examine the role of oxidants on cell death in a model of in vitro simulated IR injury in renal proximal tubular epithelial cells by analyzing the effects of a cell-permeable superoxide dismutase mimetic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTmPyP). Renal proximal tubular epithelial cells were ATP depleted for 2, 4, or 6 h, followed by 2 h of recovery. We found that MnTmPyP was effective in attenuating cytotoxicity (P<0.001) and decreasing steady-state oxidant levels (P<0.001) and apoptotic cell death (P<0.001) following ATP depletion-recovery. MnTmPyP treatment prevented the early cytosolic release of cytochrome c and increased Bcl-2 protein levels following short durations of ATP depletion-recovery. After longer periods of ATP depletion-recovery, we observed a significant increase in TNF-alpha protein levels (P<0.001) and caspase-8 activation (P<0.001), both of which were decreased (P<0.001) by treatment with MnTmPyP. Our results suggest that oxidant mediated apoptosis via the mitochondrial pathway during the early phase of ATP depletion and by activation of the receptor-mediated apoptotic pathway following longer durations of injury.
authors.affiliation: Division of Transplant Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Cheryl J
authors.initials: CJ
authors.lastname: Maenpaa
authors.forename: Brian D
authors.initials: BD
authors.lastname: Shames
authors.forename: Scott K
authors.initials: SK
authors.lastname: Van Why
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Johnson
authors.forename: Vani
authors.initials: V
authors.lastname: Nilakantan
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000473:pathology; D007668:Kidney / Q000098:blood supply; D007687:Kidney Tubules, Proximal / Q000473:pathology*; D008665:Metalloporphyrins / Q000494:pharmacology; D016877:Oxidants / Q000633:toxicity*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000473:pathology*; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
chemical_list: D008665:Metalloporphyrins; C502230:Mn(III) 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin; D016877:Oxidants; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D000255:Adenosine Triphosphate