title: Cannabidiol enhances microglial phagocytosis via transient receptor potential (TRP) channel activation.
abstract: OBJECTIVE
  Microglial cells are important mediators of the immune response in the CNS. The phytocannabinoid, cannabidiol (CBD), has been shown to have central anti-inflammatory properties, and the purpose of the present study was to investigate the effects of CBD and other phytocannabinoids on microglial phagocytosis.
  
  
  METHODS
  Phagocytosis was assessed by measuring ingestion of fluorescently labelled latex beads by cultured microglial cells. Drug effects were probed using single-cell Ca²⁺ imaging and expression of mediator proteins by immunoblotting and immunocytochemistry.
  
  
  RESULTS
  CBD (10 μM) enhanced bead phagocytosis to 175 ± 7% control. Other phytocannabinoids, synthetic and endogenous cannabinoids were without effect. The enhancement was dependent upon Ca²⁺ influx and was abolished in the presence of EGTA, the Ca²⁺ channel inhibitor SKF96365, the transient receptor potential (TRP) channel blocker ruthenium red, and the TRPV1 antagonists capsazepine and AMG9810. CBD produced a sustained increase in intracellular Ca²⁺ concentration in BV-2 microglia and this was abolished by ruthenium red. CBD rapidly increased the expression of TRPV2 and TRPV1 proteins and caused a translocation of TRPV2 to the cell membrane. Wortmannin blocked CBD enhancement of BV-2 cell phagocytosis, suggesting that it is mediated by PI3K signalling downstream of the Ca²⁺ influx.
  
  
  CONCLUSIONS
  The TRPV-dependent phagocytosis-enhancing effect of CBD suggests that pharmacological modification of TRPV channel activity could be a rational approach to treating neuroinflammatory disorders involving changes in microglial function and that CBD is a potential starting point for future development of novel therapeutics acting on the TRPV receptor family.
authors.affiliation: School of Life Sciences, University of Nottingham, Nottingham, UK.
authors.forename: Samia
authors.initials: S
authors.lastname: Hassan
authors.forename: Khalil
authors.initials: K
authors.lastname: Eldeeb
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Millns
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Bennett
authors.forename: Stephen P H
authors.initials: SP
authors.lastname: Alexander
authors.forename: David A
authors.initials: DA
authors.lastname: Kendall
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002185:Cannabidiol / Q000494:pharmacology*; D002478:Cells, Cultured; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C485717:Trpv2 protein, mouse; D002185:Cannabidiol
keywords: calcium influx; cannabidiol; cannabinoid; microglia; phagocytosis