Tetramethylpyrazine inhibits activities of glioma cells and glutamate neuro-excitotoxicity: Potential therapeutic application for treatment of gliomas

We tested the herbal extract 2,3,5,6-tetramethylpyra-zine (TMP) for possible therapeutic efficacy against a glioma cell line and against gliomas transplanted into rat brains. In the cultured glioma cells, 50 μM TMP significantly inhibited glutamate-induced increase in intracellular calcium. Significant cell damage (30%) and proliferation suppression (10%), however, occurred only at higher concentrations (200-400 μM). Glioma-neuronal co-culturing resulted in significant neuronal damage and higher proliferation of the glioma cells (140%) compared with single cultures. Low concentrations of TMP (≤200 μM) attenuated the neuronal damage, suppressed glioma migration, and decreased glioma proliferation in the neuronal-glioma co-culture. Gliomas transplanted into the frontal cortical area exhibited high proliferation, with untreated rats dying 10-23 days later. TMP treatment inhibited tumor growth and significantly extended survival time. The results indicate that TMP can suppress glioma activity, including growth, and protect neurons against glioma-induced excitotoxicity, suggesting that TMP may have therapeutic potential in the treatment of malignant gliomas.