APP and Parkinson disease: Regarding neurodegenerative disorders involving oxidative stress, decreased plasma H2S levels have been observed in patients with Alzheimer’s disease and dementia [36]; in the brains of APP/PS1 mice, a model of Alzheimer’s disease [55]; in the substantia nigra of a Parkinson’s disease model in rats [11]; and in the blood, cortex, and hippocampus in a traumatic brain injury (TBI) model [56].