BACKGROUND: Patients with schizophrenia (SCZ) run a lifelong risk of suicide. Alterations in glia activities in the prefrontal cortex (PFC) have been reported in relation to suicide in patients with SCZ. While immune processes in the CNS have been related to the susceptibility and course of SCZ, there are hardly any direct comparisons between individuals with SCZ, both those who died of natural causes and those that committed suicide, and healthy controls.
MATERIALS AND METHODS: We compared mRNA expression using real time qPCR of 16 glia-related genes in the dorsal lateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC) between 35 patients with SCZ (7 suicide completers and 28 patients who died of natural causes) and 34 well-matched controls without psychiatric or neurological diseases.
RESULTS: We found an increased expression of the astrocytic gene aldehyde dehydrogenase-1 family member L1 (ALDH1L1) mRNA, a marker involved in dopaminergic activity, in SCZ versus controls. Excluding individuals with SCZ that committed suicide resulted in an elevated expression in the DLPFC of both ALDH1L1 and glutamine synthetase (GS) genes in patients with SCZ, compared to suicide completers and non-psychiatric controls. Regarding microglia genes: in the ACC, homeostatic markers such as chemokine (C-X3-C motif) ligand 1 (CX3CR1) mRNA expression was increased in SCZ without suicide as compared to suicide completers, while no change was found when compared to controls. Another, purinergic receptor 12 (P2RY12) mRNA was exclusively elevated in the ACC of suicide completers, compared to either other group. Triggering receptor expressed on myeloid cells 2 (TREM2) expression, which maintains microglial metabolism, was reduced in non-suicide patients with SCZ, compared to suicide victims and control subjects.
CONCLUSIONS: Differential changes are found in astrocyte and microglia genes in the PFC subregions in relation to SCZ and suicide, indicating possible disturbances of glia homeostasis in these conditions.