TRANSFECTION OF A MANGANESE-CONTAINING SUPEROXIDE-DISMUTASE GENE INTOHAMSTER TRACHEAL EPITHELIAL-CELLS AMELIORATES ASBESTOS-MEDIATED CYTOTOXICITY

To determine if overexpression of manganese-containing SOD (MnSOD) alt ers cell sensitivity to asbestos, an expression cassette containing mu rine MnSOD cDNA was cotransfected with pSV2neo, a plasmid conferring r esistance to the antibiotic G418, into a diploid cell line of hamster tracheal epithelial (HTE) cells. Pools of G418-resistant transfectants were characterized by Southern and Northern blot analyses and enzyme activity assays. Although increases in MnSOD gene copies in individual cell pools ranged from approximately 7- to 86-fold in comparison to c ells transfected with pSV2neo alone, steady-state levels of MnSOD mRNA were increased only by 1.4-to 2.3-fold. Despite modest increases in M nSOD mRNA, significant elevations in MnSOD enzyme activity were observ ed in pools of G418-resistant cells. MnSOD-transfected cell lines were more resistant to the cytotoxic effects of crocidolite asbestos using a sensitive colony-forming efficiency (CFE) assay. These data show th at MnSOD has a direct role in cell defense against asbestos-induced cy totoxicity, an oxidant-dependent process.