Protective Effect of N-Arachidonoyl Glycine-GPR18 Signaling after Excitotoxical Lesion in Murine Organotypic Hippocampal Slice Cultures.

Urszula Grabiec,Alexandra Antonietti,Candy Rothgänger,Ken Mackie,Daniel Wong,Tim Hohmann,Faramarz Dehghani,Thomas Groth,Chalid Ghadban

doi:10.3390/ijms20061266

Abstract

N-arachidonoyl glycine (NAGly) is an endocannabinoid involved in the regulation of different immune cells. It was shown to activate the GPR18 receptor, which was postulated to switch macrophages from cytotoxic to reparative. To study GPR18 expression and neuroprotection after NAGly treatment we used excitotoxically lesioned organotypic hippocampal slice cultures (OHSC). The effect of NAGly was also tested in isolated microglia and astrocytes as these cells play a crucial role during neuronal injury. In the present study, the GPR18 receptor was found in OHSC at mRNA level and was downregulated after N-Methyl-D-aspartate (NMDA) treatment at a single time point. Furthermore, treatment with NAGly reduced neuronal damage and this effect was abolished by GPR18 and cannabinoid receptor (CB)2 receptor antagonists. The activation but not motility of primary microglia and astrocytes was influenced when incubated with NAGly. However, NAGly alone reduced the phosphorylation of Akt but no changes in activation of the p44/42 and p38 MAPK and CREB pathways in BV2 cells could be observed. Given NAGly mediated actions we speculate that GPR18 and its ligand NAGly are modulators of glial and neuronal cells during neuronal damage.

Highlights

Neuroprotective effects have been reported for several cannabinoids in different models
GPR18 mRNA and Protein are Expressed in Primary Astrocytes, Microglia and Neurons
GPR18 was found on astrocytes (GFAP), neurons (NeuN) and microglia (IB4) (Figure 1)

Summary

Introduction

Neuroprotective effects have been reported for several cannabinoids in different models. About effects of NAGly on CB2, which is expressed in the central nervous system and on the immune cells, little is known [4]. GPR18 has been found in peripheral blood cells, lymphoid tissues, macrophages with different expression levels for cytotoxic and reparative cells [5]. It is present in the brain [6,7] and in some glioblastoma multiforme cells [8]. Since GPR18 was highly expressed on the cellular components of the immune system, different effects of NAGly on immune cells were examined. As a putative GPR18 ligand is controversially discussed in the literature [8,13,14]

Methods

Results

Conclusion