MAOB and Parkinson disease: MPTP, as a common agent for generating PD animal models (Jiang et al., 2017), is first metabolized by monoamine oxidase-B (MAO-B) to 1-methyl-4-phenyl-2,3-dihydropyridinium (MPDP+), and then deprotonates to generate MPP+, which can enter cells through the dopamine reuptake system and inhibit complex I of the mitochondrial respiratory chain to induce oxidative stress (Desai et al., 1996; Cassarino et al., 1999; Smeyne and Jackson-Lewis, 2005; Shen et al., 2017).