Elevated TNF-α levels due to systemic inflammation are associated with the decline of DA neurons in PD (Sriram et al., 2006; Allegra Mascaro et al., 2013), and TNF-α level was found to be elevated in the midbrain of a PD mouse model; in fact, the initial oxidative insult in the induction of PD caused a loss of ventral midbrain DA neurons that triggered an inflammatory response (Srivastava et al., 2012). Here, TNF is linked to Parkinson disease.