Proximal tubular cells are most vulnerable to ischemia reperfusion injury (IRI) in renal transplantation. Caspase-3 can be up-regulated by IRI due to a variety of pathogenic processes such as oxidative damage. This study utilized synthetic small interfering RNA (siRNA) to posttranscriptionally silence target gene, caspase-3, may represent a feasible approach to produce transient effects, but avoid side actions caused by viral vectors. The porcine proximal tubular cells (LLC-PK1), with or without the stimulation of hydrogen peroxide (H(2) O(2) , an oxidizer), were transfected with synthetic caspase-3 siRNA using a cationic lipid-based transfection regent. The expression of caspase-3 at mRNA and protein level was assessed at different times posttransfection and its downstream biological events were also monitored. The caspase-3 mRNA was posttranscriptionally silenced by its siRNA up to 50% after 24 h. The active caspase-3 protein was increased by transfection reagent alone and H(2) O(2) in a dose- and time-dependent manner. Both the precursor and active protein of caspase-3 were decreased by siRNA after 48 h and maintained up to 96 h at least, with a consistent change in its activity. Consequently, apoptotic cells and active IL-1β protein expression was reduced by caspase-3 siRNA; cell viability, especially with H(2) O(2) treatment, was also improved. Taken together, caspase-3 and apoptosis are sensitive markers for cellular injury; using synthetic siRNA silencing caspase-3 may provide not only a valid approach for underlying mechanisms of diseases, but also a potential therapeutic intervention for a wide range of acute clinical disorders including IRI in renal transplantation.