Introduction: 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.
Methods: Primary neonatal cell co-cultures of astrocytes and microglia were treated with LPS (100 ng/ml) for 8 h or 24 h. Two distinct IL-1 receptor antagonists, Rytvela or Kineret (1 μg/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.
Results: At 8 h, 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.
Discussion/conclusion: 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 (8 h), 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.
Keywords: astrocyte activation; glial cell activation; interleukin 1; interleukin 1 receptor antagonist; lipopolysaccharide; microglia activation.
© 2022 International Society for Developmental Neuroscience.