Yu-Wen Wang1, Chin-Tsang Yang2, Chi-Li Gong3, Yi-Hung Chen4, Yu-Wen Chen5, King-Chuen Wu6, Tzu-Hurng Cheng7, Yueh-Hsiung Kuo8, Yuh-Fung Chen9, Yuk-Man Leung10. 1. Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, China Medical University, Taichung, Taiwan. 2. School of Chinese Medicine, China Medical University, Taichung, Taiwan. 3. Department of Physiology, China Medical University, Taichung, Taiwan. 4. Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan. 5. Department of Physical Therapy, China Medical University, Taichung, Taiwan. 6. Department of Anesthesiology, Eda-Hospital, I-Shou University, Kaohsiung, Taiwan. 7. Department of Biochemistry, China Medical University, Taichung, Taiwan. 8. Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, China Medical University, Taichung, Taiwan; Department of Biotechnology, Asia University, Taichung, Taiwan. 9. Department of Pharmacology, China Medical University, Taichung, Taiwan. 10. Department of Physiology, China Medical University, Taichung, Taiwan. Electronic address: ymleung@mail.cmu.edu.tw.
Abstract
BACKGROUND: Hinokiol is a naturally occurring diterpenoid compound isolated from plants such as Taiwania cryptomerioides. Anti-oxidation, anti-cancer, and anti-inflammation effects of this compound have been reported. It is not yet known if hinokiol affects neurons or neuronal ion channel activities. We reported here that hinokiol inhibited voltage-gated Na(+) channels (VGSC) in neuronal cells and we characterized the mechanisms of block. METHODS: The effects of hinokiol on Na(+) channels were examined using the voltage-clamp (whole-cell mode) technique. RESULTS: VGSC was blocked by hinokiol in a concentration-dependent and state-dependent manner in neuroblastoma N2A cells: IC(50) are 11.3 and 37.4μM in holding potentials of -70 and -100 mV, respectively. In the presence of hinokiol there was a 13-mV left shift in steady-state inactivation curves; however, activation gating was not altered. VGSC inhibition by hinokiol did not require channel opening and was thus considered to be closed-channel block. In the presence of hinokiol, since the degree of block did not enhance with stimulation frequency, block by hinokiol thus did not exhibit use-dependence. Recovery from channel inactivation was not significantly affected in the presence of hinokiol. In addition, hinokiol also inhibited VGSC of differentiated neuronal NG108-15 cells and rat hippocampal CA1 neurons. CONCLUSION: Our results therefore suggest hinokiol inhibited VGSC in a closed-channel block manner and such inhibition involved intensification of channel inactivation.
BACKGROUND:Hinokiol is a naturally occurring diterpenoid compound isolated from plants such as Taiwania cryptomerioides. Anti-oxidation, anti-cancer, and anti-inflammation effects of this compound have been reported. It is not yet known if hinokiol affects neurons or neuronal ion channel activities. We reported here that hinokiol inhibited voltage-gated Na(+) channels (VGSC) in neuronal cells and we characterized the mechanisms of block. METHODS: The effects of hinokiol on Na(+) channels were examined using the voltage-clamp (whole-cell mode) technique. RESULTS: VGSC was blocked by hinokiol in a concentration-dependent and state-dependent manner in neuroblastoma N2A cells: IC(50) are 11.3 and 37.4μM in holding potentials of -70 and -100 mV, respectively. In the presence of hinokiol there was a 13-mV left shift in steady-state inactivation curves; however, activation gating was not altered. VGSC inhibition by hinokiol did not require channel opening and was thus considered to be closed-channel block. In the presence of hinokiol, since the degree of block did not enhance with stimulation frequency, block by hinokiol thus did not exhibit use-dependence. Recovery from channel inactivation was not significantly affected in the presence of hinokiol. In addition, hinokiol also inhibited VGSC of differentiated neuronal NG108-15 cells and rat hippocampal CA1 neurons. CONCLUSION: Our results therefore suggest hinokiol inhibited VGSC in a closed-channel block manner and such inhibition involved intensification of channel inactivation.