The levels of GSH, an antioxidant molecule primarily secreted by astrocytes, are significantly lower in the SNs of PD patients, and the activities of astrocyte-secreted antioxidant enzymes such as SOD, GSH peroxidase (GSH-Px), and catalase (CAT) are markedly decreased in PD patients as compared to healthy controls [58]. The gene discussed is SOD1; the disease is Parkinson disease.