Variations to plasma H2O2 levels and TAC in chronical medicated and treatment-resistant male schizophrenia patients: Correlations with psychopathology

Accumulating evidence suggests that imbalanced oxidative stress (OS) may contribute to the mechanism of schizophrenia. The aim of the present study was to evaluate the associations of OS parameters with psychopathological symptoms in male chronically medicated schizophrenia (CMS) and treatment-resistant schizophrenia (TRS) patients. Levels of hydrogen peroxide (H₂O₂), hydroxyl radical (·OH), peroxidase (POD), α-tocopherol (α-toc), total antioxidant capacity (TAC), matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinases-1 (TIMP-1) were assayed in males with CMS and TRS, and matched healthy controls. Schizophrenia symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). The results demonstrated significant differences in the variables H₂O₂ (F = 5.068, p = 0.008), ·OH (F = 31.856, p < 0.001), POD (F = 14.043, p < 0.001), α-toc (F = 3.711, p = 0.027), TAC (F = 24.098, p < 0.001), and MMP-9 (F = 3.219, p = 0.043) between TRS and CMS patients and healthy controls. For TRS patients, H₂O₂ levels were correlated to the PANSS positive subscale (r = 0.386, p = 0.032) and smoking (r = −0,412, p = 0.021), while TAC was significantly negatively correlated to the PANSS total score (r = −0.578, p = 0.001) and POD and TAC levels were positively correlated to body mass index (r = 0.412 and 0.357, p = 0.021 and 0.049, respectively). For patients with CMS, ·OH levels and TAC were positively correlated to the PANSS general subscale (r = 0.308, p = 0.031) and negatively correlated to the PANSS total score (r = −0.543, p < 0.001). Furthermore, H₂O₂, α-toc, and ·OH may be protective factors against TRS, and POD was a risk factor. Patients with CMS and TRS exhibit an imbalance in OS, thus warranting future investigations.