Another study has displayed that aldose reductase (AR) scarcity, a tyrosine hydroxylase (TH) cofactor actively engaged in the generation of DA, may elicit oxidative stress in animal models experiencing PD via elevating NO and nitrite (NO2−), culminating in forfeiture of DArgic nerve cells and aberrations in the autophagy-lysosome system [123]. Here, TH is linked to Parkinson disease.