PARP1 and Parkinson disease: Similar to previous reports that have implicated apoptosis in the loss of DA neurons in patients with PD6,8, western blot analyses revealed significant increases in the levels of caspase-3, cleaved caspase-3, and cleaved PARP-1 were observed in the SN of patients with PD compared to age-matched controls (Fig. 3a; &p = 0.014, &&p = 0.019, and &&&p = 0.009 vs. CON, respectively).