title: Endogenous natural killer enhancing factor-B increases cellular resistance to oxidative stresses.
abstract: Natural killer-enhancing factor (NKEF) was identified and cloned on the basis of its ability to increase NK cytotoxicity. Two genes, NKEF-A and -B, encode NKEF proteins and sequence analysis presented suggests that each belongs to a highly conserved family of antioxidants. To examine the antioxidant potential of NKEF, we transfected the coding region of NKEF-B cDNA into the human endothelial cell line ECV304. The stable transfectant, B/1, was found to overexpress NKEF-B gene transcript and protein. We subjected B/1 to oxidative stress by either culturing them with glucose oxidase (GO), which continuously generates hydrogen peroxide, or by direct addition of hydrogen peroxide. We found that B/1 cells were more resistant than control cell lines. Resistance to hydrogen peroxide was originally thought to be mediated mainly by catalase and the glutathione cycle. Therefore, we used inhibitors to block the two pathways and found that B/1 cells were more resistant to oxidative stress than control cells when we used inhibitors to preblock either pathway. We also examined the cellular inflammatory responses to oxidized low-density lipoprotein (LDL) and bacterial lipopolysaccharide (LPS) by measuring monocyte adhesion to endothelial cells in vitro and found that B/1 cells were resistant to such responses. Lastly, we found that B/1 cells were more resistant to a novel chemotherapeutic agent CT-2584, which appears to kill tumor cells by stimulating production of reactive oxygen intermediates in mitochondria. These results demonstrate that the NKEF-B is an antioxidant that protects cells from oxidative stress, chemotherapy agents, and inflammation-induced monocyte adhesion. Furthermore, its expression may mediate cellular responses to proinflammatory molecules.
authors.affiliation: Division of Surgical Oncology, UCLA Medical Center 90095, USA.
authors.forename: H
authors.initials: H
authors.lastname: Shau
authors.forename: A T
authors.initials: AT
authors.lastname: Kim
authors.forename: C C
authors.initials: CC
authors.lastname: Hedrick
authors.forename: A J
authors.initials: AJ
authors.lastname: Lusis
authors.forename: C
authors.initials: C
authors.lastname: Tompkins
authors.forename: R
authors.initials: R
authors.lastname: Finney
authors.forename: D W
authors.initials: DW
authors.lastname: Leung
authors.forename: D E
authors.initials: DE
authors.lastname: Paglia
mesh_terms: D000975:Antioxidants; D001798:Blood Proteins / Q000235:genetics / Q000502:physiology*; D002374:Catalase / Q000378:metabolism; D002448:Cell Adhesion; D002460:Cell Line; D004351:Drug Resistance; D004730:Endothelium, Vascular / Q000502:physiology; D005949:Glucose Oxidase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006360:Heat-Shock Proteins; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology; D009000:Monocytes / Q000502:physiology; D018384:Oxidative Stress; D010544:Peroxidases; D054464:Peroxiredoxins; D014162:Transfection; D014970:Xanthines / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D001798:Blood Proteins; D006360:Heat-Shock Proteins; D008070:Lipopolysaccharides; D008077:Lipoproteins, LDL; D014970:Xanthines; C099252:oxidized low density lipoprotein; C106011:CT 2584; D006861:Hydrogen Peroxide; D005949:Glucose Oxidase; D010544:Peroxidases; C086065:PRDX2 protein, human; D054464:Peroxiredoxins; D002374:Catalase; D005978:Glutathione