N-Methyl-D-aspartate (NMDA) and cannabinoid CB2 receptors form functional complexes in cells of the central nervous system: insights into the therapeutic potential of neuronal and microglial NMDA receptors

Abstract

Background The cannabinoid CB2 receptor (CB2R), which is a target to afford neuroprotection, and N-methyl-D-aspartate (NMDA) ionotropic glutamate receptors, which are key in mediating excitatory neurotransmission, are expressed in both neurons and glia. As NMDA receptors are the target of current medication in Alzheimer’s disease patients and with the aim of finding neuromodulators of their actions that could provide benefits in dementia, we hypothesized that cannabinoids could modulate NMDA function. Methods Immunocytochemistry was used to analyze the colocalization between CB2 and NMDA receptors; bioluminescence resonance energy transfer was used to detect CB2-NMDA receptor complexes. Calcium and cAMP determination, mitogen-activated protein kinase (MAPK) pathway activation, and label-free assays were performed to characterize signaling in homologous and heterologous systems. Proximity ligation assays were used to quantify CB2-NMDA heteromer expression in mouse primary cultures and in the brain of APPSw/Ind transgenic mice, an Alzheimer’s disease model expressing the Indiana and Swedish mutated version of the human amyloid precursor protein (APP). Results In a heterologous system, we identified CB2-NMDA complexes with a particular heteromer print consisting of impairment by cannabinoids of NMDA receptor function. The print was detected in activated primary microglia treated with lipopolysaccharide and interferon-γ. CB2R activation blunted NMDA receptor-mediated signaling in primary hippocampal neurons from APPSw/Ind mice. Furthermore, imaging studies showed that in brain slices and in primary cells (microglia or neurons) from APPSw/Ind mice, there was a marked overexpression of macromolecular CB2-NMDA receptor complexes thus becoming a tool to modulate excessive glutamate input by cannabinoids. Conclusions The results indicate a negative cross-talk in CB2-NMDA complexes signaling. The expression of the CB2-NMDA receptor heteromers increases in both microglia and neurons from the APPSw/Ind transgenic mice, compared with levels in samples from age-matched control mice.

Considerations for Cannabinoids in Perioperative Care by Anesthesiologists

“…At least part of this neuroprotection is modulated by activation of peripheral MO via CB2 during ischemia [237]. In addition, modulation of neuroinflammation is frequently suggested as the potential beneficial mechanism of the cannabinoid to alter the natural history of neurodegenerative diseases [238][239][240]. On the other hand, prolonged heavy use of cannabinoids results in hippocampal thinning, neuronal death, and various complications [241][242][243][244].…”

“…However, it may be responsible for increased susceptibility to pulmonary infec-tion in recreational users and patients taking cannabinoid compounds for clinical conditions [90][91][92]325,333]. At the same time, antinociceptive and neuroprotective mechanisms are dependent on the anti-inflammatory action of cannabinoids [74,123,239,[334][335][336].…”

The Binding Mode to Orthosteric Sites and/or Exosites Underlies the Therapeutic Potential of Drugs Targeting Cannabinoid CB2 Receptors

“…Whereas the D 1 is coupled to Gαs and D 2 to Gαi, the macromolecular complex formed when the two receptors are co-expressed in the same neuron couples to Gαq (Rashid et al, 2007; Hasbi et al, 2009;George et al, 2014;Perreault et al, 2015). Notwithstanding, conformational changes that affect the binding and signaling outputs produced by a given agonist have been shown in the interactions with the Gαi-coupled CB 1 R (Callén et al, 2012;Sierra et al, 2015;Angelats et al, 2018), the Gαscoupled adenosine A 2A receptor (Franco et al, 2019a), and the ionotropic NMDA receptor (Rivas-Santisteban et al, 2021). In one of the first studies of biased agonism in GPCR heteromers (CB 1 R/CB 2 R), Navarro and co-workers showed that the allosteric effect of CBD was particularly noteworthy for the endocannabinoid anandamide but also that the effect tested using different agonists was smaller in the heteromer (Navarro et al, 2018a).…”

“…In www.gpcr-hetnet.com and in Figure 2 interactions of CB 2 R with further GPCRs are not yet included (they have not yet been incorporated into the STRING database). Also missing are the recently described interactions of the CB 2 R with glutamate N-Methyl-D-Asp (NMDA) ionotropic receptors ( Rivas-Santisteban et al, 2021 ). From a therapeutic perspective, the fact that CB 2 R may interact with other receptors that are also targeted by cannabinoids, for instance with GPR18 and GPR55, is of high interest ( Balenga et al, 2014 ; Reyes-Resina et al, 2018 ; Martínez-Pinilla et al, 2019 ; Martínez-Pinilla et al, 2020 ; Rivas-Santisteban et al, 2021 ).…”

“…Whereas the D 1 is coupled to Gαs and D 2 to Gαi, the macromolecular complex formed when the two receptors are co-expressed in the same neuron couples to Gαq ( Rashid et al, 2007 ; Hasbi et al, 2009 ; George et al, 2014 ; Perreault et al, 2015 ). Notwithstanding, conformational changes that affect the binding and signaling outputs produced by a given agonist have been shown in the interactions with the Gαi-coupled CB 1 R ( Callén et al, 2012 ; Sierra et al, 2015 ; Angelats et al, 2018 ), the Gαs-coupled adenosine A 2A receptor ( Franco et al, 2019a ), and the ionotropic NMDA receptor ( Rivas-Santisteban et al, 2021 ).…”