HMOX1 and Parkinson disease: Although CP’s ferroxidase activity may efficiently oxidize Fe2+ into Fe3+, enabling iron efflux from cells, almost 80% of this activity was reduced in the SN of PD patients, suggesting that decreased CP expression and consequent iron buildup play a role in neuronal mortality in PD.118–121 Iron buildup in the brain that is neurotoxic will also be aided by microglia and astrocytes overexpressing heme oxygenase-1.122,123 To remove ROS from DA neurons, reactive astrocytes may also produce different antioxidant molecules like GSH and metallothioneins.