Cannabidiol Attenuates Seizures and Social Deficits in a Mouse Model of Dravet Syndrome
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Cannabidiol attenuates seizures and social deficits in a mouse model of Dravet syndrome Joshua S. Kaplana, Nephi Stellaa,b,1, William A. Catteralla,1,2, and Ruth E. Westenbroeka,1 aDepartment of Pharmacology, University of Washington, Seattle, WA 98195; and bDepartment of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA 98195 Contributed by William A. Catterall, September 7, 2017 (sent for review July 3, 2017; reviewed by Lori L. Isom, Daniele Piomelli, and Peter C. Ruben) Worldwide medicinal use of cannabis is rapidly escalating, despite 17). Previous work showed that DS symptoms result from the loss- limited evidence of its efficacy from preclinical and clinical studies. of-function of Nav1.1 channels, which selectively reduces sodium Here we show that cannabidiol (CBD) effectively reduced seizures current and excitatory drive in many types of GABAergic inter- and autistic-like social deficits in a well-validated mouse genetic neurons (13, 14, 18–20). Accordingly, targeting the Scn1a mutation model of Dravet syndrome (DS), a severe childhood epilepsy disorder to Nav1.1 channels in forebrain GABAergic interneurons re- caused by loss-of-function mutations in the brain voltage-gated capitulated the DS phenotype and established that hypoexcitability sodium channel NaV1.1. The duration and severity of thermally in- of these interneurons is sufficient to cause the epileptic phenotype duced seizures and the frequency of spontaneous seizures were sub- (21) and autistic-like behaviors (16) observed in DS mice. In con- stantially decreased. Treatment with lower doses of CBD also trast, targeting the Scn1a mutation to excitatory neurons ameliorates improved autistic-like social interaction deficits in DS mice. Pheno- DS in mice, which is opposite to the effects of gene disruption in typic rescue was associated with restoration of the excitability of inhibitory neurons (22). Additional effects of compensatory changes inhibitory interneurons in the hippocampal dentate gyrus, an impor- in gene expression, electrical excitability, and genetic background tant area for seizure propagation. Reduced excitability of dentate also have a strong influence on epileptic phenotypes of DS mice granule neurons in response to strong depolarizing stimuli was also (SI Discussion). These results suggest that effective treatment of observed. The beneficial effects of CBD on inhibitory neurotransmis- DS could potentially be achieved through enhancing GABAergic sion were mimicked and occluded by an antagonist of GPR55, sug- signaling by inhibitory neurons (16, 23) or selectively decreasing gesting that therapeutic effects of CBD are mediated through this electrical excitability in excitatory neurons (24). lipid-activated G protein-coupled receptor. Our results provide critical Given the promising results for CBD in treating seizures in preclinical evidence supporting treatment of epilepsy and autistic- DS, coupled with its low side-effect profile, we have analyzed its like behaviors linked to DS with CBD. We also introduce antagonism of GPR55 as a potential therapeutic approach by illustrating its ben- effects on epilepsy and autistic-like behaviors in DS mice. Here eficial effects in DS mice. Our study provides essential preclinical we report that CBD substantially reduces the frequency, dura- evidence needed to build a sound scientific basis for increased me- tion, and severity of seizures and ameliorates the impaired social dicinal use of CBD. interaction behaviors of DS mice. These beneficial effects are cor- related with enhanced GABAergic neurotransmission, decreased cannabidiol | Dravet syndrome | epilepsy | autism | Scn1a excitation/inhibition ratio, and decreased action potential firing of excitatory neurons in response to strong stimuli. These changes in GABAergic neurotransmission are mimicked and lobal use of medicinal cannabis is rapidly escalating (www. Gunodc.org/wdr2017/) (1). In particular, extracts rich in can- occluded by inhibition of the lipid-activated G protein-coupled nabidiol (CBD), an abundant bioactive but nonpsychotomimetic constituent of Cannabis sativa, are increasingly used to treat Significance refractory epilepsy (2). However, there is only limited evidence for its efficacy in preclinical models (3, 4) and human studies (5–7). Medicinal cannabis use is booming despite limited preclinical Recent clinical trials found that CBD reduced seizure frequency in evidence and mechanistic insight. Recent clinical trials of can- patients with DS and other treatment-refractory epilepsies (6, 7). nabidiol (CBD) in Dravet syndrome (DS) support its clinical ef- However, preclinical studies of CBD in validated animal models ficacy for reduction of seizure frequency and invite study of its can provide quantitative measures of CBD’s efficacy in controlling benefits for additional DS symptoms. We demonstrate here seizure duration and severity in addition to frequency. Studies in that treatment with CBD is beneficial for seizure frequency, animal models can also assess potential beneficial effects of CBD duration, and severity and for autistic-like social deficits in a on the behavioral comorbidities of Dravet syndrome (DS) and mouse model of DS. CBD rescue of DS symptoms is associated probe the underlying physiological and molecular mechanisms with increased inhibitory neurotransmission, potentially me- mediating these therapeutic effects. diated by antagonism of the lipid-activated G protein-coupled Heterozygous loss-of-function mutations in SCN1A cause receptor GPR55. These studies lend critical support for treat- DS, a severe childhood neuropsychiatric disorder characterized by ment of seizures in DS with CBD, extend the scope of CBD treatment-refractory epilepsy, autism, other comorbidities, and treatment to autistic-like behaviors, and provide initial mech- ’ frequent premature death (8–10). The uncertainty of seizure on- anistic insights into CBD s therapeutic actions. set; the increasing frequency, duration, and intensity of seizures; Author contributions: J.S.K., N.S., W.A.C., and R.E.W. designed research; J.S.K. and R.E.W. and the risk of injury is an immense source of anxiety for parents performed research; J.S.K., N.S., W.A.C., and R.E.W. analyzed data; and J.S.K., N.S., W.A.C., (11, 12). Moreover, the ensuing social impairment associated with and R.E.W. wrote the paper. DS adds an additional burden of care and increases risk for ac- Reviewers: L.L.I., University of Michigan Medical School; D.P., University of California, cidents and premature death (9, 10). Thus, pharmacological res- Irvine; and P.C.R., Simon Fraser University. cue of both epilepsy and autism-related behaviors would greatly The authors declare no conflict of interest. increase the quality of life for DS patients and their caregivers. 1N.S., W.A.C., and R.E.W. contributed equally to this work. +/− Scn1a mice (DS mice) are a well-defined phenocopy of 2To whom correspondence should be addressed. Email: [email protected]. human DS (13, 14), as they exhibit both thermally induced and This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. NEUROSCIENCE spontaneous seizures (13, 15) and autism-like social deficits (16, 1073/pnas.1711351114/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1711351114 PNAS | October 17, 2017 | vol. 114 | no. 42 | 11229–11234 Downloaded by guest on September 24, 2021 receptor GPR55, suggesting that CBD’s effects are mediated, at center of the open field (Fig. S1B). DS mice performed better on least in part, by this signal transduction pathway. Our results the rotorod than WT mice, and their performance was reduced to strengthen basic science support for clinical use of CBD in DS the WT level in the presence of 100 mg/kg CBD (Fig. S1C). One and give initial clues to its physiological and molecular mecha- interpretation of these results is that the hyperactivity of DS mice nisms of action. improves their performance on the rotorod compared with WT due to their more frenetic efforts to stay on the rotatrod, and this Results advantage is lost upon CBD treatment because it reverses their CBD Protects Against Seizure in DS Mice. The initial symptoms as- hyperactivity. Together, these results suggest that 100 mg/kg CBD sociated with DS are observed as early as 6–9 mo of age with the has a therapeutic effect to reverse hyperactivity of DS mice but onset of febrile seizures, followed by spontaneous epileptic sei- does not have a significant adverse effect to impair motor function zures with increasing severity and frequency (8, 9). We modeled and coordination compared with untreated WT mice. febrile seizures by thermal induction in DS mice, in which core body temperature was slowly raised to 38 °C and held there for CBD Rescues Autistic-Like Social Interaction Deficits in DS Mice. In 30 min (15). Acute treatment with CBD (100 mg/kg or 200 mg/kg, both humans diagnosed with DS and in our mouse genetic model i.p.) 1 h before thermal induction reduced the duration (Fig. 1A) of DS, the frequency and severity of seizures abate following and severity (Fig. 1B) of seizures. Such reduction in seizure se- sexual maturity, while severe social deficits that are characteristic – verity to a Racine score of 3.5 or less is known to greatly reduce of autism persist (8 10, 16). Social/behavioral outcomes have not risk of sudden unexpected death in epilepsy in DS mice (21, 25). been measured in previous studies of CBD in DS (6, 7). To test ’ Because the half-life of CBD in rodents is much shorter than in CBD s efficacy in treating autistic-like behaviors in DS mice, we humans [∼4.5 h in mice (26); ∼24 h in human (27)], it is difficult to used the Three-Chamber Test of social interaction (29) in which precisely compare the 100–200 mg/kg effective i.p. dose range that DS mice show profound deficits compared with WT littermates we observed here with the 20–50 mg/kg oral dose range used in (16). We found that low doses of CBD (10 mg/kg or 20 mg/kg) recent clinical trials (6, 7).