Several lines of evidence support the role of proinflammatory cytokines in the pathophysiology of schizophrenia. Patients with first-episode psychosis have been shown to have increased levels of transforming growth factor beta (TGF-b), making this cytokine a potential valuable biomarker for schizophrenia1.
Cytokine imbalances involving dysregulation of interleukin (IL) pathways are under also investigation, reported Dr Milica Borovcanin, Faculty of Medical Sciences, University of Kragujevac, Serbia.
IL-6 appears to have a phase-specific role in the evolution of schizophrenia and a correlation between high IL-6 levels and depressive symptoms, poorer well-being, treatment-resistance and cognitive decline has been found2.
The relationship between psychosis and IL-33
Evidence has demonstrated a relationship between IL-33 and the schizophrenia state. In a study evaluating IL-33 levels in 77 drug-naïve patients with first-episode psychosis (FEP), 27 patients with schizophrenia in remission after a three-month’s stable depot of long-acting injectable (LAI) antipsychotic medication, 45 patients with schizophrenia in relapse, and 18 healthy controls (HCs), patients with FEP had IL-33 concentrations five times higher than the LAI-treated patients in remission and 2.5 times higher than HCs (470, 420, 89, and 188 pg/mL, respectively).3
In a study, IL-33 concentrations were found to be substantially higher in patients with psychosis than patients treated with LAI or healthy controls
There was also a significant correlation between IL-33 levels and positive symptoms in patients in remission, suggesting a potential role for this cytokine in the underlying mechanisms behind psychosis onset.3
The relationship between psychosis and IL-17
Dysregulation of the IL-17 pathway has also been implicated in the pathogenesis of schizophrenia, as patients with FEP have lower sera concentration of IL-17 than HCs (3 pg/mL versus 30 pg/mL, in one study).1,4
In a study, there was no difference in IL-17 levels between healthy controls and patients in remission after LAI medication
In a recent study of 27 patients with schizophrenia in remission after a three-month stable depot of LAI antipsychotic medication period, there was a positive correlation between IL-17 levels and cognitive dysfunction as measured on Montreal-Cognitive Assessment scores, particularly for visuospatial and executive functioning, language functioning and delayed recall.5
There was no significant difference in serum levels of IL-17 between HCs and patients in remission after LAI medication.5
These studies lend weight to the accumulating evidence that schizophrenia could be, at least in part, a disorder bound to immunological alterations.