Effects of Lipofectamine 2000/siRNA complexes on autophagy in hepatoma cells

Lipofectamine 2000 is commonly used for siRNA transfections. However, few studies have examined cellular responses to this delivery system. The purpose of this study is to evaluate the effect of siRNA transfection using Lipofectamine 2000 on cellular autophagy. Huh7.5 cells, stably transfected to express GFP-LC3, were treated with Lipofectamine 2000/negative control siRNA (NC siRNA) complexes. At different time points after treatment, cells were lysed and analyzed by immunoblotting and fluorescence spectroscopy. Cells were also observed using confocal microscopy. An increase of endogenous LC3 lipidation, GFP-LC3 fluorescence, and autophagosomal puncta was observed in cells treated with Lipofectamine 2000/NC siRNA complexes. The kinetics of the increase of GFP-LC3 fluorescence correlated with the concentration of NC siRNA transfected, where 50, 100, and 200 nM NC siRNA caused a significant increase at 72, 48, and 24 h, respectively, after transfection. A similar effect on the GFP-LC3 signal was also observed for cells treated with Lipofectamine 2000 complexed with two other NC siRNAs. The effects were also confirmed in another hepatoma cell line, H4IIE, by immunoblotting. Lipofectamine 2000-mediated transport of NC siRNAs led to an increase of autophagosomes in a dose- and time-dependent manner. Thus, this effect on cells should be taken into consideration when using this approach for intracellular delivery of siRNA.