Maternal immune activation by poly(I:C) induces expression of cytokines IL-1β and IL-13, chemokine MCP-1 and colony stimulating factor VEGF in fetal mouse brain

Background: Maternal viral infection during pregnancy is associated with an increase in the incidence of psychiatric disorders with presumed neurodevelopmental origin, including autism spectrum disorders and schizophrenia. The enhanced risk for developing mental illness appears to be caused by deleterious effects of innate immune response-associated factors on the development of the central nervous system, which predispose the offspring to pathological behaviors in adolescence and adulthood. To identify the immune response-associated soluble factors that may affect central nervous system development, we examined the effect of innate immune response activation by polyriboinosinic-polyribocytidylic acid (poly(I:C)), a synthetic analogue of viral double-stranded RNA, on the expression levels of pro- and anti-inflammatory cytokines, chemokines and colony stimulating factors in fetal and postnatal mouse brain 6 h and 24 h after treatment. Methods: C57BL/6J pregnant mice (gestational day 16) or newborn mice (postnatal day 4) received a single intraperitoneal injection of the synthetic analogue of viral double-stranded RNA poly(I:C) (20 mg/kg). Thirty-two immune response-associated soluble factors, including pro- and anti-inflammatory cytokines, chemokines and colony stimulating factors, were assayed 6 h and 24 h after poly(I:C) injection using multiplexed bead-based immunoassay (Milliplex Map) and processed in a Luminex 100 IS instrument. Results: Maternal exposure to poly(I:C) at gestational day 16 induced a significant increase in cytokines interleukin (IL)-1 beta, IL-7 and IL-13; chemokines monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein (MIP)-1 alpha, interferon gamma-induced protein (IP)-10 and monokine induced by IFN-gamma (MIG); and in the colony stimulating factor vascular endothelial growth factor (VEGF) in the fetal brain. IL-1 beta showed the highest concentration levels in fetal brains and was the only cytokine significantly up-regulated 24 h after maternal poly(I:C) injection, suggesting that IL-1 beta may have a deleterious impact on central nervous system development. In contrast, poly(I:C) treatment of postnatal day 4 pups induced a pronounced rise in chemokines and colony stimulating factors in their brains instead of the pro-inflammatory cytokine IL-1 beta. Conclusions: This study identified a significant increase in the concentration levels of the cytokines IL-1 beta and IL-13, the chemokine MCP-1 and the colony stimulating factor VEGF in the developing central nervous system during activation of an innate immune response, suggesting that these factors are mediators of the noxious effects of maternal immune activation on central nervous system development, with potential long-lasting effects on animal behavior.