When SH-SY5Y cells were coadministered with MPP plus choline or nicotine cell death was inhibited, this protective effect involved activation of the extracellular signal-regulated kinase/p53 (ERK/p53) pathway, and the decreased cleavage of Poly (ADP-ribose) polymerase-1 (PARP-1) and caspase-3; two proteins related to PD and cell apoptosis [104,105]. The gene discussed is TP53; the disease is Parkinson disease.