Plasma levels of matrix metalloproteinase-9 (MMP-9) are associated with cognitive performance in patients with schizophrenia

Aim Matrix metalloproteinase-9 (MMP-9) has been shown to modulate synaptic plasticity and may contribute to the pathophysiology of schizophrenia. This study investigated the peripheral levels of MMP-9 and its association with cognitive functions in patients with schizophrenia to see the possible involvement of MMP-9 in pathophysiology of schizophrenia, especially in cognitive decline. Methods We measured the plasma levels of MMP-9 in 257 healthy controls and 249 patients with schizophrenia, including antipsychotic drug-free patients. We also explored the possible association between plasma MMP-9 levels and cognitive performance in healthy controls and patients with schizophrenia using the Wechsler Adult Intelligence Scale, Third Edition (WAIS- III), the Wechsler Memory Scale-Revised (WMS-R), and the Rey Auditory Verbal Learning Test (AVLT). Results We found that the plasma levels of MMP-9 were significantly higher in patients with schizophrenia, including antipsychotic drug-free patients, than in healthy controls. We found a significant negative association between plasma MMP-9 levels and cognitive performance in controls and patients with schizophrenia. Conclusion Together, these convergent data suggest a possible biological mechanism for schizophrenia, whereby increased MMP-9 levels are associated with cognitive impairment.