Circulating levels of sTNFR1 as a marker of severe clinical course in schizophrenia

Background: Schizophrenia (SZ) has been associated with an imbalance in the inflammatory cytokine TNF-α. The objectives of this study were to compare TNF-α and its soluble receptors' serum levels in individuals with SZ with the levels found in a group of healthy volunteers and to investigate the possible association between these biomarkers and the dimensions and severity of symptoms, clinical outcomes and response to treatment in patients with SZ. Methods: Fifty-four chronically medicated SZ outpatients and 118 healthy controls were included in the study. TNF-α levels were measured by Cytometric Bead Assay (CBA), and serum levels of soluble tumor necrosis factor receptor 1 (sTNFR1) and soluble tumor necrosis factor receptor 2 (sTNFR2) were measured by ELISA. Results: sTNFR1 and sTNFR2 were significantly elevated in patients with SZ as compared to the healthy control group. In the group of individuals with SZ, the levels of both types of soluble TNF receptors showed a negative correlation with global functioning. sTNFR1 levels were higher in the treatment-resistant patients as compared to the non-treatment-resistant patients and the controls. sTNFR1 levels were also heightened in patients with SZ and concomitant depression. Conclusion: Our findings reinforce that SZ is associated with an inflammatory profile and suggest that sTNFR1 is a marker of a treatment-resistance and severe clinical course in SZ.