Neuroprotective effects of Yi-Gan San against beta amyloid-induced cytotoxicity on rat cortical neurons

IntroductionRecent clinical studies have demonstrated that Yi-Gan San (YGS, Yokukan-San in Japanese), a Chinese herbal medicine, alleviates various dementia-related symptoms. However, Chinese herbal medicines have rarely been investigated scientifically and the underlying mechanism of YGS remains uncertain. In this study, we investigated the effect of YGS on beta amyloid protein (Aβ)-induced cytotoxicity in a primary culture of rat cortical neurons.MethodsCortical neurons prepared from rat embryos were exposed to Aβ in the presence or absence of YGS. The protective effect of YGS was measured as the % of control (unexposed neurons) by using MTT assay and LDH assay.ResultsAβ significantly decreased the number of surviving cortical neurons at a dose of 20 μM and higher. In the presence of 20 μM Aβ, YGS concentrations of 10− 5 g/L (W/V) and higher significantly increased the number of viable neurons.ConclusionOur study demonstrated a neuroprotective effect of Yi-Gan San against Aβ-induced cytotoxicity. Since according to traditional herbal medicine beliefs, YGS most likely exerts its clinical effects not through a single constituent but as a mixture of several herbal ingredients, the true mechanism of this neuroprotective action remains unclear. However, our results suggest that this Chinese herbal medicine might be a valuable treatment for clinical symptoms associated with dementia having fewer side effects and possible additional neuroprotective effects in the elderly.