Background and purpose:The present study evaluated the role of CB2 receptors in the regulation of depressive-like behaviours. Transgenic mice overexpressing the CB2 receptor (CB2xP) were challenged with different types of acute and chronic experimental paradigms to evaluate their response in terms of depressive-like behaviours. Experimental approach: Tail suspension test (TST), novelty-suppressed feeding test (NSFT) and unpredictable chronic mild stress tests (CMS) were carried out in CB2xP mice. Furthermore, acute and chronic antidepressant-like effects of the CB2 receptor-antagonist AM630 were evaluated by means of the forced swimming test (FST) and CMS, respectively, in wild-type (WT) and CB2xP mice. CB2 gene expression, brain-derived neurotrophic factor (BDNF) gene and protein expressions were studied in mice exposed to CMS by real-time PCR and immunohistochemistry, respectively. Key results: Overexpression of CB2 receptors resulted in decreased depressive-like behaviours in the TST and NSFT. CMS failed to alter the TST and sucrose consumption in CB2xP mice. In addition, no changes in BDNF gene and protein expression were observed in stressed CB2xP mice. Interestingly, acute administration of AM630 (1 and 3 mg·kg ; twice daily, i.p.) blocked the effects of CMS on TST, sucrose intake, CB2 receptor gene, BDNF gene and protein expression in WT mice. Conclusion and implications: Taken together, these results suggest that increased CB2 receptor expression significantly reduced depressive-related behaviours and that the CB2 receptor could be a new potential therapeutic target for depressiverelated disorders.

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BACKGROUND AND PURPOSEHeteromerization of GPCRs is key to the integration of extracellular signals and the subsequent cell response via several mechanisms including heteromer-selective ligand binding, trafficking and/or downstream signalling. As the lysophosphatidylinositol GPCR 55 (GPR55) has been shown to affect the function of the cannabinoid receptor subtype 2 (CB2 receptor) in human neutrophils, we investigated the possible heteromerization of CB2 receptors with GPR55. EXPERIMENTAL APPROACHThe direct interaction of human GPR55 and CB2 receptors heterologously expressed in HEK293 cells was assessed by co-immunoprecipitation and bioluminescence resonance energy transfer assays. The effect of cross-talk on signalling was investigated at downstream levels by label-free real-time methods (Epic dynamic mass redistribution and CellKey impedance assays), ERK1/2-MAPK activation and gene reporter assays. KEY RESULTSGPR55 and CB2 receptors co-localized on the surface of HEK293 cells, co-precipitated in membrane extracts and formed heteromers in living HEK293 cells. Whereas heteromerization led to a reduction in GPR55-mediated activation of transcription factors (nuclear factor of activated T-cells, NF-κB and cAMP response element), ERK1/2-MAPK activation was potentiated in the presence of CB2 receptors. CB2 receptor-mediated signalling was also affected by co-expression with GPR55. Label-free assays confirmed cross-talk between the two receptors.

Neurons are highly dependent on astrocyte survival during brain damage. To identify genes involved in astrocyte function during ischemia, we performed mRNA differential display in astrocytes after oxygen and glucose deprivation (OGD). We detected a robust down-regulation of S6 kinase 1 (S6K1) mRNA that was accompanied by a sharp decrease in protein levels and activity. OGD-induced apoptosis was increased by the combined deletion of S6K1 and S6K2 genes, as well as by treatment with rapamycin that inhibits S6K1 activity by acting on the upstream regulator mTOR (mammalian target of rapamycin). Astrocytes lacking S6K1 and S6K2 (S6K1;S6K2 ؊/؊ ) displayed a defect in BAD phosphorylation and in the expression of the antiapoptotic factors Bcl-2 and Bcl-xL. Furthermore reactive oxygen species were increased while translation recovery was impaired in S6K-deficient astrocytes following OGD. Rescue of either S6K1 or S6K2 expression by adenoviral infection revealed that protective functions were specifically mediated by S6K1, because this isoform selectively promoted resistance to OGD and reduction of ROS levels. Finally, "in vivo" effects of S6K suppression were analyzed in the permanent middle cerebral artery occlusion model of ischemia, in which absence of S6K expression increased mortality and infarct volume. In summary, this article uncovers a protective role for astrocyte S6K1 against brain ischemia, indicating a functional pathway that senses nutrient and oxygen levels and may be beneficial for neuronal survival.Astrocytes are the most abundant cells in the central nervous system. Their functions are crucial for central nervous system homeostasis, because they provide trophic, metabolic, and antioxidant support to neurons. In addition, astrocytes show the ability to modulate synaptic activity and are responsible for preserving neuronal integrity in conditions of disease and injury. In this regard, recent evidence indicates that they are protective for neurons during cerebral ischemia (1). As there is a growing consensus that astrocyte dysfunction may compromise the ability of neurons to survive, the need for studies that clarify the molecular mechanisms involved in the astrocytic response to ischemia is plainly justified.Among the intracellular pathways that integrate signals from nutrients and oxygen, the mammalian target of rapamycin (mTOR) 2 kinase plays an evolutionary conserved role in the regulation of cell growth, proliferation, survival, and metabolism (2). mTOR exists in the cell in at least two distinct complexes with different partners, mTORC1 and mTORC2. The activity of mTORC1 is exquisitely sensitive to the energy status of the cell and is blocked by the macrolide antibiotic rapamycin. Glucose and oxygen deprivation inhibits mTORC1 activity, respectively, through the regulation of AMP-activated kinase and REDD1/REDD2 proteins (3-5). These factors favor the action of the tuberous sclerosis proteins TSC1 and TSC2, which suppress mTORC1 by forming a complex with GTPase-activating protein (GAP) activity for t...

BACKGROUND AND PURPOSEThis study evaluated gene expression differences between two mouse strains, characterized by opposite impulsivity-like traits and the involvement of the cannabinoid CB2 receptor in the modulation of impulsivity. EXPERIMENTAL APPROACHBehavioural tests were conducted to compare motor activity, exploration and novelty seeking, attention and cognitive and motor impulsivity (delayed reinforcement task: session duration 30 min; timeout 30 s) between A/J and DBA/2 mice. Expression of genes for dopamine D2 receptors, CB1 and CB2 receptors were measured in the cingulate cortex (CgCtx), caudate-putamen (CPu), accumbens (Acc), amygdala (Amy) and hippocampus (Hipp). Involvement of CB2 receptors in impulsivity was evaluated in DBA/2 mice with a CB2 receptor agonist (JWH133) and an antagonist (AM630). KEY RESULTSDBA/2 mice presented higher motor and exploratory activity, pre-pulse inhibition impairment and higher cognitive and motor impulsivity level than A/J mice. In addition, DBA/2 mice showed lower (CgCtx, Acc, CPu) D2 receptor, lower (Amy) and higher (CgCtx, Acc, CPu, Hipp) CB1 receptor and higher (CgCtx, Acc, Amy) and similar (CPu, Hipp) CB2 receptor gene expressions. Treatment with JWH133 (0.5, 1, 3 mg·kg -1 , i.p.) reduced cognitive and motor impulsivity level, accompanied by CB2 receptor down-regulation (CgCtx, Acc, Amy) but did not modify other behaviours. In contrast, AM630 (1, 2, 3 mg·kg -1 , i.p.) improved pre-pulse inhibition and reduced novelty seeking behaviour in DBA/2 mice. CONCLUSIONS AND IMPLICATIONSCB2 receptors might play an important role in regulating impulsive behaviours and should be considered a promising therapeutic target in the treatment of impulsivity-related disorders.