Elevated plasma matrix metalloproteinase 9 in schizophrenia patients associated with poor antipsychotic treatment response and white matter density deficits.

Oxidative stress and neuroinflammation contribute to schizophrenia (SCZ) pathology and may influence treatment efficacy. Matrix metalloproteinase 9 (MMP9) is a critical molecular node mediating the interaction between oxidative stress and inflammation, and so may influence treatment efficacy. Here we examined the associations of plasma MMP9 concentration with antipsychotic drug responses, clinical symptoms, and brain structure. A total of 129 healthy controls and 124 patients with SCZ were included in this study. Patients were monitored clinically during 8 weeks of antipsychotic treatment and classified as poor responders (n = 49) or good responders (n = 75). We then compared plasma MMP9 concentrations in healthy controls at baseline and both SCZ responder groups at baseline and after the 8-week antipsychotic treatment regimen. Cognitive function was also examined using the MATRICS Consensus Cognitive Battery. In addition, we extracted regional white matter density from magnetic resonance images of patients. Compared to healthy controls, plasma MMP9 levels were significantly elevated in poor responders at baseline and negatively correlated with both white matter density in the right superior temporal gyrus and the change in cognitive symptoms after treatment. Conversely, there was no significant difference in plasma MMP9 between good responders and healthy controls, and no associations of plasma MMP9 with cognitive symptoms or regional white matter density among good responders. Elevated plasma MMP9 is associated with poor antipsychotic drug efficacy and white matter deficits in SCZ patients, and so may be a useful biomarker to guide personalized treatment.