Western blotting was performed as previously described (21 (link)). Briefly, cells were lysed in Laemmli's buffer. Total proteins were separated using SDS-PAGE and were then transferred to PVDF membranes (Bio-Rad Laboratories, Inc.). After blocking, the membranes were incubated with primary antibodies against rabbit phosphorylated (p)CREB (Ser133; 1:1,000, cat. no. ab32096; Abcam), rabbit PARP-1 (1:1,000 cat. no. 9542; Cell Signaling Technology, Inc.) and mouse α-tubulin (1:1,000, cat. no. 3873; Cell Signaling Technology, Inc.) which was followed by incubation with appropriate horseradish peroxidase-conjugated secondary antibodies against rabbit (1:2,000, cat. no. p0448; Dako Agilent Technologies) and mouse (1:2,000, cat. no. p0260; Dako Agilent Technologies). The expression was visualized using an ECL detection kit (cat. no. RPN2106; Cytiva). Images were acquired using ImageQuant LAS 4000 Mini biomolecular imager (Cytiva). Semi-quantification on the relative expression of proteins was performed using ImageJ 2.1.0 software (National Institutes of Health).