title: Cell density and antioxidant vitamins determine the effects of hyperoxia on proliferation and death of MDCK epithelial cells.
abstract: Epithelial cells are prone to oxidant injury, which could change epithelial cell homeostasis and lead to degenerative diseases. We examined the effects of hyperoxia on death and proliferation off Madin-Darby canine kidney (MDCK) epithelial cells and antioxidant vitamin protection. Subconfluent and near-confluent MDCK cells were cultured under normoxia or hyperoxia for two days. We measured cell number and viability, mitochondria enzymatic activity, thymidine incorporation, necrosis [lactate dehydrogenase (LDH) release], and apoptosis (DNA fragmentation and morphological changes). When the cells were subconfluent, hyperoxia decreased the number of adherent cells, mitochondrial enzymatic activity, and thymidine incorporation, but neither LDH release nor apoptotic changes increased compared with normoxic controls. In normoxia, near-confluent cells had lower nonadherent cell numbers, mitochondrial enzymatic activity, and thymidine incorporation than subconfluent cells; hyperoxia further decreased the latter two parameters and increased apoptotic changes and LDH release in near-confluent cells. Vitamin E protected mitochondrial enzymatic activity, apoptotic changes, and LDH release against hyperoxic injury but did not affect changes in thymidine incorporation with hyperoxia. Vitamin C partially protected the mitochondrial enzymatic activity and thymidine incorporation in subconfluence, but not in near confluence. These results indicate that cell density is a major determinant of the effects of hyperoxic injury and the profile of antioxidant vitamin protection.
authors.affiliation: Department of Pediatrics, University of Minnesota, Minneapolis 55455, USA. jyono001@maroon.tc.umm.edu
authors.forename: H
authors.initials: H
authors.lastname: Jyonouchi
authors.forename: S
authors.initials: S
authors.lastname: Sun
authors.forename: M
authors.initials: M
authors.lastname: Mizokami
authors.forename: D H
authors.initials: DH
authors.lastname: Ingbar
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D001205:Ascorbic Acid / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002452:Cell Count / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects / Q000235:genetics; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D018496:Hyperoxia / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D007770:L-Lactate Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D014810:Vitamin E / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D014810:Vitamin E; D007770:L-Lactate Dehydrogenase; D001205:Ascorbic Acid