A proof-of-concept study of maternal immune activation mediated induction of Toll-like receptor (TLR) and inflammasome pathways leading to neuroprogressive changes and schizophrenia-like behaviours in offspring

Infection, particularly prenatal infection, leads to an enhanced risk of schizophrenia in the offspring. Interestingly, few data exist on the pathway(s) such as TLR and inflammasome, primarily involved in sensing the microorganisms and inducing downstream inflammatory responses, apoptosis and neuroprogressive changes that drive prenatal infection-induced risk of schizophrenia. Herein, we aimed to discern whether prenatal infection-induced maternal immune activation (MIA) causes schizophrenia-like behaviours through activation of TLR and inflammasome pathways in the brain of offspring. Sprague Dawley rats (n=15/group) were injected either with poly (I:C) or LPS or saline at gestational day (GD)-12. Significantly elevated plasma levels of IL-6, TNF-α and IL-17A assessed after 24 hours were observed in both the poly (I:C) and LPS-treated rats, while IL-1β was only elevated in LPS-treated rats, indicating MIA. The offspring of poly (I:C)-and LPS-treated dams displayed increased anxiety-like behaviours, deficits in social behaviours and prepulse inhibition. The hippocampus of offspring rats showed increased expression of Tlr3, Tlr4, Nlrp3, Il1b, and Il18 of poly (I:C) and Tlr4, Nlrp3, Cas1, Il1b, and Il18 of LPS-treated dams. Furthermore, Tlr and inflammasome genes were associated with social deficits and impaired prepulse inhibition in offspring rats. The results suggest that MIA due to prenatal infection can trigger TLR and inflammasome pathways and enhances the risk of schizophrenia-like behaviours in the later stages of life of the offspring.