Several studies have suggested a higher oxidative stress in schizophrenia. However, the implications of oxidative stress on clinical symptoms remain unclear. This study aimed to investigate the platelet oxidative stress in different stages of schizophrenia (i.e., chronic stable and acute relapse) in order to clarify the clinical implications of oxidative stress and the treatment effects. We recruited 43 chronic stable patients with schizophrenia and 48 non-psychiatric controls. Platelets were collected for measuring the levels of nitric oxide (NO), lipid peroxidation (LPO), and glutathione (GSH) and the activity of GSH peroxidase (GPx) and superoxide dismutase (SOD). The levels and activity were compared between patients and controls and were examined for their relationship with clinical severity. Further, we evaluated the changes of levels and activity before and after treatment in an independent sample with acute relapse (N = 19). Patients with chronic stable schizophrenia had lower SOD activity compared to non-psychiatric controls. In chronic stable patients, NO level was positively correlated with positive and disorganized symptoms, while the GPx activity were negatively correlated with excitement. In patients with acute relapse, the levels and activity were not different before and after four weeks of antipsychotic treatment, but LPO level was negatively correlated with pretreatment disorganized symptoms. The change of LPO can also predict the change of disorganized symptoms and negative symptoms. Our findings suggest that platelet SOD was lower in chronic stable schizophrenia. Platelet LPO may be associated with less disorganized symptoms in acute relapse patients and better treatment response.
