Little is known about the roles of AQP9 in human brain as most studies of AQP9 in humans have focused on the reproductive system and placenta [59–61] If applicable to humans, the present data suggest that pharmacologic inhibition of AQP9 could be considered a viable approach to curb the progression of Parkinson’s disease in cases where exposure to exogenous toxins is documented or suspected as a cause of morbidity. This evidence concerns the gene AQP9 and Parkinson disease.