In vitro examination of microglia-neuron crosstalk with BV2 cells, and primary cultures of glia and hypothalamic neurons

Microglia respond to environmental changes by releasing cytokines that beneficially or detrimentally affect surrounding cells in addition to functioning as the resident CNS macrophages. Interactions between glia and neurons participate in many critical brain functions and diseases. We previous demonstrated that activation of microglia facilitates hypothalamic CRF neuronal activity and pain precipitation in rats. The intricate CNS environment complicates studying crosstalk between microglia and hypothalamic neurons in vivo. BV2 cells derived from raf/myc-immortalised murine neonatal microglia are the most frequently used substitute for primary cultures of microglia. In this study, we used BV2 cells and primary cultures of glia from neonatal rats to explore the interaction between microglia and hypothalamic neurons in vitro. Lipopolysaccharide (LPS) stimulated BV2 cells to adopt a microglia-like phenotype including an amoebae-like shape, Iba-1 positive staining and IL-1β secretion. Primary cultures of hypothalamic neurons treated with culture medium from LPS-treated BV2 cells increased CRF, CRFR, pCREB and cAMP levels compared to untreated neurons. Primary cultures of hypothalamic neurons incubated with culture medium from LPS-treated primary cultures of glia or exogenous IL-1β also increased CRF levels. Importantly, this increase in protein expression appeared to be IL-1β mediated and treatment with an anti-IL-1β antibody blocked the increased expression. Our data provide direct evidence that microglia can modulate hypothalamic neuronal activity and IL-1β may play a critical role in bridging the communication between microglia and neurons.