Modulatory effect of IL-1 inhibition following lipopolysaccharide-induced neuroinflammation in neonatal microglia and astrocytes.

Abstract

Inflammation-induced white matter injury (WMI) in preterm infants is characterized by microglia activation, astrogliosis, oxidative stress and neurodevelopmental impairments. Microglia and astrocytes activation can be described under a broad spectrum of activation profile with extremes described as pro-inflammatory/neurotoxic (M1 microglia or A1 astrocyte) or anti-inflammatory/neuroprotective (M2 microglia or A2 astrocyte) in response to stimuli including lipopolysaccharide (LPS) and interleukin 1 (IL-1). As IL-1 signalling pathway has been posited as a major driver of inflammation-induced perinatal WMI, our aim was to evaluate the contribution of IL-1 modulation in LPS-induced microglia and astrocyte activation. Primary neonatal cell co-cultures of astrocytes and microglia were treated with LPS (100 ng/ml) for 8h or 24 h. Two distinct IL-1 receptor antagonists, Rytvela or Kineret (1μg/ml), were added simultaneously with LPS to respectively modulate or block IL-1 receptor. Medium was collected to measure levels of IL-1β. Expression of markers related to pro- and anti-inflammatory microglia and astrocyte activation profiles and antioxidant genes were assessed. At 8h, LPS exposure induced pro- (M1/A1) and anti-inflammatory (M2/A2) marker expression and inhibited antioxidant gene expression in microglia and astrocytes. By 24 h, continuous LPS exposure increased pro-inflammatory and neurotoxic microglial and astrocytic markers (M1/A1), as well as antioxidant genes. Administration of IL-1 antagonists Rytvela and Kineret with continuous LPS exposure had no significant effect on modulation of specific microglia and astrocyte activation pathways. We show that LPS effects on in vitro neonatal microglia and astrocytes co-cultures are time dependent eliciting a number of pro- and anti-inflammatory responses during the acute phase of inflammation (8h), which shift towards pro-inflammatory and neurotoxic factors by 24 h. Although LPS-induced inflammation led to abundant IL-1 expression, IL-1 inhibition had no significant impact on in vitro modulation of microglia and astrocyte activation pathways towards M2 and A2 activation profile.