Western blotting analysis

The protein expressions were performed by Western blotting as previously described³⁷. Briefly, the protein samples (50 μg) of each cell lysate were subjected to electrophoresis on 10% SDS-polyacrylamide gels. The protein samples were electroblotted on polyvinylidene difluoride membranes and then blocking. The blots were incubated with antibodies for cleaved poly (ADP-ribose) polymerase (PARP) (Cell Signaling Technology, Danvers, MA, USA), phosphorylated extracellular signal-regulated kinase (ERK)1/2, ERK1/2, phosphorylated Jun N-terminal kinase (JNK), JNK, phosphorylated p38 mitogen-activated protein kinase (MAPK), p38, and α-tubulin (Santa Cruz Biotechnology, Santa Cruz, CA, USA). The membranes were then incubated with horseradish peroxidase-conjugated secondary antibodies. An enhanced chemiluminescence reagent (BioRad Laboratories, Redmond, WA, USA) was used to depict the protein bands on membranes. The gel band quantitative densitometric analysis was determined by the image J 1.48 software (National Institutes of Health, Bethesda, MD, USA).