Intracellular delivery of lipopolysaccharide during DNA transfection activates a lipid A-dependent cell death response that can be prevented by polymyxin B

The presence of lipopolysaccharide (LPS) as a contaminant in plasmid DNA prepared from Escherichia coli is well documented, and we have previously demonstrated that LPS internalization during adenovirus-mediated gene transfer can generate a toxicity in some primary cell types. We demonstrate here that in addition to adenoviral systems, several commonly used nonviral methods of gene transfer also activate this cell death response in the presence of LPS. Subcomponents of LPS were analyzed and the toxicity was found to be due to the lipid A component of LPS. The LPS-chelating antibiotic polymyxin B, when present at concentration of 10-30 mu g/ml, can block this toxicity.