Inhibitory effects of cannabinoids on calcium mobilisation in microglial cells

Khalil Eldeeb1,3, Stephen PH Alexander1,2, David Pritchard1, David A Kendall1. 1School of Biomedical SciencesUniversity of Nottingham, Nottingham, United Kingdom, 2School of Pharmacy, Nottingham, United Kingdom, 3Pharmacology department, Faculty of Medicine, Al-Azhar University, Damietta, Egypt.

Microglial cell activation is a key element in a variety of neuroinflammatory CNS disorders such as multiple sclerosis and stroke. Cannabinoid compounds have well known immunomodulatory properties, via their actions on CB2 receptors and, potentially GPR55, a cannabinoid-related receptor (Kreitzer & Stella, 2009). In the present study, we assessed the effects of cannabinoid receptor ligands against lysophosphatidylinositol (LPI, the putative endogenous ligand for GPR55) Oka et al. (2009) and ATP on Ca2+ levels in BV2 mouse microglial cells.

Intracellular calcium levels ([Ca2+]i) in BV2 cells were monitored using Fluo-4 using a FlexStation-96 (Kasorn et al., 2006).

Taqman qRT-PCR analysis indicated expression of GPR55 mRNA in BV2 cells. The endocannabinoids, anandamide and 2AG, as well as synthetic cannabinoid ligands, HU210, CP55940, WIN55212-2 and rimonabant did not alter [Ca2+]i (9±1, 8.3±3, 10±1, 9.8±1.3, 8.8±1.3 and 8.4±1.9 % ATP response respectively n = 5). The phytocannabinoids cannabidiol and THC produced modest increases in [Ca2+]i (15 ±2 and 16 ±1.9%, respectively n = 5). Pre-treatment with CP55940, rimonabant, cannabidiol or THC (10 μM) produced significant attenuations of LPI- (23±9, 33±13, 9±1 and 2±0.5 % respectively n = 3) and ATP-evoked (1.4±1.6, 26±4, 2±1.5 and 5±3% respectively n = 3) [Ca2+]i responses.

These results are consistent with a non-selective inhibition of evoked Ca2+ release by cannabinoid ligands in BV2 microglial cells. The functional importance of these effects on microglial calcium mobilization remains to be determined

Kasorn A et al. (2006). pA2 online 3: 24P.
Kreitzer FR, Stella N (2009). Pharmacol Ther 122: 83-96.
Oka, S., Toshida, T., Maruyama, K., Nakajima, K., Yamashita, A. & Sugiura, T. (2009).Biochem, 145, 13-20.

This work was made possible by a scholarship to Khalil Eldeeb from the Egyptian government.