LIPOSOME-MEDIATED TRANSFECTION OF FETAL LUNG EPITHELIAL-CELLS - DNA-DEGRADATION AND ENHANCED SUPEROXIDE TOXICITY

Cationic Liposomes, 1:1 (mol/mol) 1,2-dioleoyldimethylammonium ide-1,2 -dioleoyl-sn-glycero-3-phosphoethanolamine, were used to transfect pri mary cultures of distal rat fetal lung epithelial cells with pCMV4-bas ed plasmids. A DNA-to-lipid ratio of 1:10 to 1:15 (wt/wt) optimized DN A uptake over a 24-h exposure. At a fixed DNA-to-lipid ratio of 1:15, chloramphenicol acetyltransferase (CAT) reporter gene expression decli ned at lipid concentrations > 2.5 nmol/cm(2) cell surface area, wherea s DNA uptake remained concentration dependent. CAT expression peaked 4 8 h after removal of the liposome-DNA complex, declining thereafter. R eporter gene expression was increased, and supercoiled cDNA degradatio n was reduced by the addition of 0.2 mM nicotinamide and 10 mu M chlor oquine. Rat fetal lung epithelial cells transfected with two different expression cassettes had an increased susceptibility to superoxide-me diated cytotoxicity. This could be attributed to a nonspecific deliver y of exogenous DNA or some other copurified factor. The DNA-dependent increase in superoxide-mediated cytotoxicity, but not basal levels of cytotoxicity, was inhibited by the addition of 0.2 mM nicotinamide and 10 mu M chloroquine.