Neuroprotective effects of yokukansan, a traditional Japanese medicine, on glutamate-mediated excitotoxicity in cultured cells.
To clarify the mechanism of yokukansan (TJ-54), a traditional Japanese medicine, against glutamate-mediated excitotoxicity, the effects of TJ-54 on glutamate uptake function were first examined using cultured rat cortical astrocytes. Under thiamine-deficient conditions, the uptake of glutamate into astrocytes, and the levels of proteins and mRNA expressions of glutamate aspartate transporter of astrocytes significantly decreased. These decreases were ameliorated in a dose-dependent manner by treatment with TJ-54 (100-700 microg/ml). The improvement of glutamate uptake with TJ-54 was completely blocked by the glutamate transporter inhibitor DL-threo-beta-hydroxyaspartic acid. Effects of TJ-54 on glutamate-induced neuronal death were next examined by using cultured PC12 cells as a model for neurons. Addition of 17.5 mM glutamate to the culture medium induced an approximately 50% cell death, as evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. TJ-54 (1-1000 microg/ml) inhibited the cell death in a dose-dependent manner. Furthermore, competitive binding assays to glutamate receptors showed that TJ-54 bound potently to N-methyl-D-aspartate receptors, in particular, to its glutamate and glycine recognition sites. These results suggest that TJ-54 may exert a neuroprotective effect against glutamate-induced excitotoxicity not only by amelioration of dysfunction of astrocytes but also by direct protection of neuronal cells.
Kawakami
Z
Z
Tsumura Research Laboratories, Tsumura & Co, Inashiki-gun, Ibaraki, Japan. kawakami_zenji@mail.tsumura.co.jp
Kanno
H
H
Ueki
T
T
Terawaki
K
K
Tabuchi
M
M
Ikarashi
Y
Y
Kase
Y
Y
D027322:Amino Acid Transport System X-AG / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives; D001253:Astrocytes / Q000187:drug effects* / Q000502:physiology; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D003164:Competitive Bidding; D004305:Dose-Response Relationship, Drug; D004365:Drugs, Chinese Herbal / Q000008:administration & dosage*; D027341:Excitatory Amino Acid Transporter 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D027342:Excitatory Amino Acid Transporter 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D016716:PC12 Cells; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate; D013778:Tetrazolium Salts; D013832:Thiamine Deficiency / Q000188:drug therapy / Q000503:physiopathology; D013844:Thiazoles
D027322:Amino Acid Transport System X-AG; D004365:Drugs, Chinese Herbal; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D018696:Neuroprotective Agents; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; C493392:Slc1a3 protein, rat; D013778:Tetrazolium Salts; D013844:Thiazoles; C524644:Yi-Gan San; C011274:3-hydroxyaspartic acid; D001224:Aspartic Acid; D018698:Glutamic Acid; C022616:thiazolyl blue