Buspirone is an anxiolytic drug with robust serotonin receptor 1A (Htr1a) agonist activities. However, evidence has demonstrated that this drug also targets the dopamine D3 receptor (Drd3), where it acts as a potent antagonist. In vivo, Drd3 blockade is neuroprotective and reduces inflammation in models of Parkinson's disease. To test if buspirone also elicited anti-inflammatory activities in vitro, we generated stable Drd3-/- and Htr1a-/- BV2 microglial cell lines using CRISPR-Cas9 technology and then tested the effects of buspirone after lipopolysaccharide (LPS) challenge. We found that LPS exposure had no effect on cell viability, except in Htr1a-/- cells, where viability was reduced (p < 0.001). Drug treatment reduced viability in Drd3-/- cells, but not in WT or Htr1a-/- cells. Buspirone counteracted LPS-induced NO release, NOS2, IL-1β and TNF-α gene expression in WT cells, whereas it exerted limited effects in Drd3-/- or Htr1a-/- microglia. In summary, our findings indicate that buspirone attenuates microglial polarization after LPS challenge. These results also highlight some major effects of Drd3 or Htr1a genetic ablation on microglial biology, raising important questions on the complex role of neurotransmitters in regulating microglia functions.
Keywords: 5-hydroxytryptamine 1a receptor; Parkinson’s disease; dopamine D3 receptor; microglia; neuroinflammation.