Milligan Carol J, Anderson Lyndsey L, McGregor Iain S, Arnold Jonathon C, Petrou Steven
Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia.
Brain and Mind Centre, The University of Sydney, Sydney, NSW, Australia.
Front Physiol. 2023 Feb 20;14:1081186. doi: 10.3389/fphys.2023.1081186. eCollection 2023.
Cannabis contains cannabidiol (CBD), the main non-psychoactive phytocannabinoid, but also many other phytocannabinoids that have therapeutic potential in the treatment of epilepsy. Indeed, the phytocannabinoids cannabigerolic acid (CBGA), cannabidivarinic acid (CBDVA), cannabichromenic acid (CBCA) and cannabichromene (CBC) have recently been shown to have anti-convulsant effects in a mouse model of Dravet syndrome (DS), an intractable form of epilepsy. Recent studies demonstrate that CBD inhibits voltage-gated sodium channel function, however, whether these other anti-convulsant phytocannabinoids affect these classic epilepsy drug-targets is unknown. Voltage-gated sodium (Na) channels play a pivotal role in initiation and propagation of the neuronal action potential and Na1.1, Na1.2, Na1.6 and Na1.7 are associated with the intractable epilepsies and pain conditions. In this study, using automated-planar patch-clamp technology, we assessed the profile of the phytocannabinoids CBGA, CBDVA, cannabigerol (CBG), CBCA and CBC against these human voltage-gated sodium channels subtypes expressed in mammalian cells and compared the effects to CBD. CBD and CBGA inhibited peak current amplitude in the low micromolar range in a concentration-dependent manner, while CBG, CBCA and CBC revealed only modest inhibition for this subset of sodium channels. CBDVA inhibited Na1.6 peak currents in the low micromolar range in a concentration-dependent fashion, while only exhibiting modest inhibitory effects on Na1.1, Na1.2, and Na1.7 channels. CBD and CBGA non-selectively inhibited all channel subtypes examined, whereas CBDVA was selective for Na1.6. In addition, to better understand the mechanism of this inhibition, we examined the biophysical properties of these channels in the presence of each cannabinoid. CBD reduced Na1.1 and Na1.7 channel availability by modulating the voltage-dependence of steady-state fast inactivation (SSFI, V inact), and for Na1.7 channel conductance was reduced. CBGA also reduced Na1.1 and Na1.7 channel availability by shifting the voltage-dependence of activation (V act) to a more depolarized potential, and for Na1.7 SSFI was shifted to a more hyperpolarized potential. CBDVA reduced channel availability by modifying conductance, SSFI and recovery from SSFI for all four channels, except for Na1.2, where V inact was unaffected. Collectively, these data advance our understanding of the molecular actions of lesser studied phytocannabinoids on voltage-gated sodium channel proteins.
大麻含有大麻二酚（CBD），这是主要的非精神活性植物大麻素，但也含有许多其他在癫痫治疗中具有治疗潜力的植物大麻素。事实上，植物大麻素大麻萜酚酸（CBGA）、大麻二戊酸（CBDVA）、大麻色烯酸（CBCA）和大麻色烯（CBC）最近已被证明在难治性癫痫——德雷维特综合征（DS）的小鼠模型中具有抗惊厥作用。最近的研究表明，CBD会抑制电压门控钠通道功能，然而，这些其他抗惊厥植物大麻素是否会影响这些经典的癫痫药物靶点尚不清楚。电压门控钠（Na）通道在神经元动作电位的起始和传播中起关键作用，并且Na1.1、Na1.2、Na1.6和Na1.7与难治性癫痫和疼痛状况有关。在本研究中，我们使用自动平面膜片钳技术，评估了植物大麻素CBGA、CBDVA、大麻萜酚（CBG）、CBCA和CBC对在哺乳动物细胞中表达的这些人类电压门控钠通道亚型的作用概况，并将其与CBD的作用进行了比较。CBD和CBGA在低微摩尔范围内以浓度依赖性方式抑制峰值电流幅度，而CBG、CBCA和CBC对该钠通道亚群仅显示出适度的抑制作用。CBDVA在低微摩尔范围内以浓度依赖性方式抑制Na1.6峰值电流，而对Na1.1、Na1.2和Na1.7通道仅表现出适度的抑制作用。CBD和CBGA非选择性地抑制所有检测的通道亚型，而CBDVA对Na1.6具有选择性。此外，为了更好地理解这种抑制的机制，我们在每种大麻素存在的情况下研究了这些通道的生物物理特性。CBD通过调节稳态快速失活（SSFI，V inact）的电压依赖性来降低Na1.1和Na1.7通道的可用性，并且对于Na1.7通道，电导降低。CBGA还通过将激活电压依赖性（V act）转移到更去极化的电位来降低Na1.1和Na1.7通道的可用性，并且对于Na1.7，SSFI转移到更超极化的电位。CBDVA通过改变所有四个通道的电导、SSFI和从SSFI恢复来降低通道可用性，但Na1.2除外，其V inact不受影响。总的来说，这些数据推进了我们对研究较少的植物大麻素对电压门控钠通道蛋白分子作用的理解。
