Endogenous PARP1 in Raw 264.7 cells was silenced using siRNA targeting a distinguished sequence of PARP1, and human WT PARP1, Y829F PARP1 and Y907F PARP1 expressional plasmids were transfected and then the cells were stimulated with LPS or not for 1 h. Immunoblotting was performed to detect the interference of endogenous PARP1, as well as the ectopic expression of Flag-tagged WT, Y829F and Y907F PARP1 (a). Raw 264.7 cells as describe above were used, pro-inflammatory genes mRNA levels were detected by RT-PCR and electrophoresis (upper), or real-time PCR (lower) (b). Data were expressed as mean ± SD. Difference significance was analyzed by one-way ANOVA. **P < 0.01.