Cannabinoids Rescue Cocaine-Induced Seizures by Restoring Brain Glycine Receptor Dysfunction
Guichang Zou, Xin Zuo, Kai Chen, …, Guangming Huang, Dan Liu, Wei Xiong
Cell Reports, 2020, 30, 4209–4219
Doi : 10.1016/j.celrep.2020.02.106
Zou et al. identify the glycine receptor as a potential therapeutic target for cannabinoids in treating cocaine-induced seizures. The function of extra-synaptic glycine receptors in the prefrontal cortex
and hippocampus is impaired by cocaine and rescued by cannabinoids, therefore leading to the therapeutic effects of cannabinoids in treating cocaine-induced seizures.
- Cannabinoids alleviate cocaine-induced seizures (CISs) by glycine receptors (GlyRs)
- Cannabinoid docking reduces hydrogen-bonding interaction between cocaine and GlyRs
- The prefrontal cortex and hippocampus mediate the effect of cannabinoids on CISs
- Cannabinoids suppress neuronal hyperexcitability by potentiating extra-synaptic GlyRs
Cannabinoids are reported to rescue cocaineinduced seizures (CISs), a severe complication in cocaine users. However, the molecular targets for cannabinoid therapy of CISs remain unclear. Here, we report that the systemic administration of cannabinoids alleviates CISs in a CB1/CB2-receptor-independent manner. In HEK293 cells and cortical neurons, cocaine-induced dysfunction of the glycine receptor (GlyR) is restored by cannabinoids. Such restoration is blocked by GlyRa1S296A mutation. Consistently,
the therapeutic effects of cannabinoids on CISs are also eliminated in GlyRa1S296A mutant mice. Based on molecular dynamic simulation, the hydrogenbonding interaction between cocaine and the GlyR is weakened by cannabinoid docking. Without altering cocaine distribution across the brain, cannabinoids
significantly suppress cocaine-exaggerated neuronal excitability in the prefrontal cortex (PFC) and hippocampus by rehabilitating extra-synaptic GlyR function. Microinjection of cannabinoids into
the PFC and hippocampus restores cocaine-puzzled neural activity and alleviates CISs. These findings suggest that using GlyR-hypersensitive cannabinoids may represent a potential therapeutic strategy for treating CISs.
Cocaine-induced seizures (CISs), characterized by abnormal brain activity and repeated or rhythmic jerking muscle movements, have always been considered one of the major effects of cocaine poisoning, in addition to psychosis and cardiovascular effects (Jonsson et al., 1983; Spivey and Euerle, 1990; Tseng et al., 1992; Williams, 1990; Pascual-Leone et al., 1990; Heard et al., 2008). Although CISs have become an insidious and global public health problem for years, little is known about the underlying mechanism of CISs. Emerging evidence has revealed effects of cocaine on voltage-gated sodium, potassium, and calcium ion channels and ligand-gated ion channels including the glycine receptor (GlyR), g-aminobutyric acid type A receptor (GABAAR), and 5-HT3AR (Crumb and Clarkson, 1990; Premkumar, 1999, 2005; Carta et al., 2003; Ren et al., 1999; Ye et al., 1997). This suggests a probable involvement of these ion channels in CISs. However, medications specifically targeting these ion channels are limited. The most effective medication used for treating seizures in clinics is benzodiazepine, which targets
GABAAR, accompanied by the nonnegligible psychoactive or sedative side effects (Chen et al., 2016). New side-effect-free drugs are urgently needed.
Cannabis has increasingly been used as an antiepileptic medication in clinics (Friedman and Devinsky, 2015; Perucca, 2017; Rubin, 2018). The primary active ingredients of cannabis are D-9-tetrahydro-cannabinol (THC) and cannabidiol (CBD) (Devinsky et al., 2016). Compared withTHC,CBDhas been considered safer and more effective in treating seizures (Zaheer et al., 2018; Perucca, 2017; Rubin, 2018). For instance, three clinical trials of a purified CBD product have been completed, and it proved to be effective in treating patients with Dravet syndrome and Lennox- Gastaut syndrome (Perucca, 2017). The Epidiolex (CBD) oral solution has recently been approved by the U.S. Food and Drug Administration (FDA) for treating seizures related to both rare diseases (Rubin, 2018). Furthermore, cannabinoids are often incorporated with other anti-seizure medications in clinical trials (Zaheer et al., 2018; Gaston et al., 2017). There is also evidence indicating the therapeutic effects of CBD on CISs in a few animal studies, although the cellular and molecular mechanisms remain unsolved (Gobira et al., 2015; Vilela et al., 2015).
The success of CBD, but not THC, in treating seizures suggests that the antiepileptic effects of cannabinoids may not be achieved through cannabinoid receptors (CBRs) because CBD is a cannabis non-psychoactive ingredient, which does not activate cannabinoid receptors type 1/2 (CB1/2Rs) (Zlebnik and Cheer, 2016). With the exception of CBRs, cannabinoids also act on many other membrane targets in the central nervous system, such as the GlyR, vanilloid receptor, 5-HT3A receptor, GABAAR, and sodium channel. Phytocannabinoids such as THC and CBD can target the GlyR, 5-HT3A receptor, and sodium
channel (Xiong et al., 2011; Barann et al., 2002; Watkins, 2019).
The endocannabinoid 2-arachidonoyl glycerol (2-AG) is a positive modulator of GABAAR (Sigel et al., 2011). WIN 55,212-2, a synthetic cannabinoid, inhibits transient receptor potential vanilloid 1 (TRPV1) (Patwardhan et al., 2006), while another synthetic cannabinoid, dehydroxylcannabidiol (DH-CBD), potentiates the function of the GlyR (Xiong et al., 2014, 2012a, 2012b; Zou et al., 2019). However, there is no direct evidence linking the action of a cannabinoid on these membrane receptors to its antiepileptic
effects. The molecular targets and specific brain regions of cannabinoid action also remain uninvestigated. To answer these questions, we conducted experiments using various approaches, including electrophysiological recording in vitro and in vivo, behavioral tests, molecular dynamic simulation, c-Fos immunostaining, and mass spectrometry (MS) imaging, to explore the characteristics of cannabinoids in treating CISs.