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Zheng J, Chen J, Zou X, Zhao F, Guo M, Wang H, Zhang T, Zhang C, Feng W, Pessah IN, Cao Z. Saikosaponin d causes apoptotic death of cultured neocortical neurons by increasing membrane permeability and elevating intracellular Ca 2+ concentration. Neurotoxicology 2019; 70:112-121. [PMID: 30458186 PMCID: PMC6342622 DOI: 10.1016/j.neuro.2018.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 11/01/2018] [Accepted: 11/14/2018] [Indexed: 01/28/2023]
Abstract
Saikosaponins (SSs) are a class of naturally occurring oleanane-type triterpenoid saponins found in Radix bupleuri that has been widely used in traditional Chinese medicine. As the main active principals of Radix bupleuri, SSs have been shown to suppress mouse motor activity, impair learning and memory, and decrease hippocampal neurogenesis. In the present study, we investigated the effect of five SSs (SSa, SSb1, SSb2, SSc, and SSd) on neuronal viability and the underlying mechanisms in cultured murine neocortical neurons. We demonstrate that SSa, SSb1 and SSd produce concentration-dependent apoptotic neuronal death and induce robust increase in intracellular Ca2+ concentration ([Ca2+]i) at low micromolar concentrations with a rank order of SSd > SSa > SSb1, whereas SSb2 and SSc have no detectable effect on both neuronal survival and [Ca2+]i. Mechanistically, SSd-induced elevation in [Ca2+]i is the primary result of enhanced extracellular Ca2+ influx, which likely triggers Ca2+-induced Ca2+ release through ryanodine receptor activation, but not SERCA inhibition. SSd-induced Ca2+ entry occurs through a non-selective mechanism since blockers of major neuronal Ca2+ entry pathways, including L-type Ca2+ channel, NMDA receptor, AMPA receptor, Na+-Ca2+ exchanger, and TRPV1, all failed to attenuate the Ca2+ response to SSd. Further studies demonstrate that SSd increases calcein efflux and induces an inward current in neocortical neurons. Together, these data demonstrate that SSd elevates [Ca2+]i due to its ability to increase membrane permeability, likely by forming pores in the surface of membrane, which leads to massive Ca2+ influx and apoptotic neuronal death in neocortical neurons.
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Affiliation(s)
- Jing Zheng
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Juan Chen
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Xiaohan Zou
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Fang Zhao
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Mengqi Guo
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Yantai University, Yantai, China, 2640050
| | - Hongbo Wang
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Yantai University, Yantai, China, 2640050
| | - Tian Zhang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China, 100875
| | - Chunlei Zhang
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Wei Feng
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA, 95616
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA, 95616
| | - Zhengyu Cao
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
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