Dodiya et al. (2020) also found that rotenone alone reduced the tight junction protein expression, such as zonulae occludens protein 1 (ZO-1), and increased oxidative stress (Nitro-tyrosine) in the colon of mice. Studies have shown that 6-OHDA-induced PD mice have oxidative and/or nitrosation stress, and the expression of inducible nitric oxide synthase (iNOS) is increased and produces peroxynitrite and nitrotyrosine (Lee et al., 2011). Also, rotenone treatment enhanced astrocyte proliferation and α-syn expression in the colonic myenteric plexus of mice (Dodiya et al., 2020). Here, NOS2 is linked to Parkinson disease.