Neuroprotective Effects of Kaempferol, Quercetin, and Its Glycosides by Regulation of Apoptosis

Kaempferol, quercetin 및 그 배당체들의 apoptosis 조절을 통한 신경세포 보호 효과

Abstract

Alzheimer's disease (AD) is a neurodegenerative disease caused by accumulation of amyloid beta ($A{\beta}$) in the brain. In the present study, we investigated the neuroprotective effects of four flavonoids such as kaempferol, kaempferol-3-O-glucoside, quercetin, and quercetin-3-${\beta}$-D-glucoside against neuronal apoptosis induced by $A{\beta}$ in SH-SY5Y neuronal cells. Treatment with $A{\beta}$ decreased cell viability compared to the non-treated normal group. However, treatment with the four flavonoids increased cell viability in SH-SY5Y cells treated with $A{\beta}$. In addition, we measured the expression of apoptosis-related proteins such as Bcl-2-associated X protein (Bax) and cleaved caspase-9. Treatment with the four flavonoids down-regulated Bax and cleaved caspase-9 in $A{\beta}$-treated SH-SY5Y neuronal cells. Overall, the results of the present study demonstrated the neuroprotective effect of flavonoids by anti-apoptotic activity in $A{\beta}$-induced SH-SY5Y neuronal cells. These results suggest that these four flavonoids would be useful therapeutic and prevention agents for AD.

알츠하이머 질환은 대표적인 신경퇴행성 질환으로, 뇌 내에서 $A{\beta}$ 단백질 축적은 알츠하이머 질환의 원인으로 알려져 있다. 본 연구에서는 amyloid beta ($A{\beta}$)로 손상을 유도한 SH-SY5Y 신경세포에서 kaempferol, kaempferol-3-O-glucoside, quercetin, quercetin-3-${\beta}$-D-glucoside의 신경세포 보호 효과에 대해 검토하였다. SH-SY5Y 신경세포에 $A{\beta}_{25-35}$ ($25{\mu}M$)를 처리하였을 때, 처리하지 않은 normal군에 비해 세포생존율이 유의적으로 감소하였다. 반면, kaempferol, quercetin 및 그 배당체들을 각각 처리하였을 때 $A{\beta}_{25-35}$만을 처리한 control군에 비해 유의적으로 세포생존율의 증가를 나타내었다. 또한, apoptosis에 관여하는 cleaved caspase9, Bcl-2-associated X protein (Bax) 단백질 발현을 측정한 결과, normal군에 비해 control군에서 유의적으로 cleaved caspase9 및 Bax 단백질 발현의 증가를 나타내어 $A{\beta}$ 유도 신경세포 손상으로 인한 apoptosis가 유발됨을 확인 하였으며, kaempferol, quercetin 및 그 배당체들의 처리 시 apoptosis 관련 단백질 발현이 감소함으로써 신경세포 보호 효능이 나타냄을 확인하였다. 이러한 결과는 kaempferol, quercetin 및 그 배당체들이 apoptosis 조절을 통해 신경세포 보호 효과를 나타내며, 신경세포 손상으로 인한 알츠하이머 질환을 예방하는 유용한 소재로써 사용 가능성이 있음을 보여준다.

Fig. 1. Chemical structure of kaempferol (A), kaempferol -3-O-glucoside (B), quercetin (C), quercetin-3-β -D-glucoside (D)

Fig. 2. Effect of kaempferol (K), kaempferol-3-O-glucoside (KG), quercetin (Q), and quercetin-3-β-D-glucoside(QG) on apoptosis-related protein expression in SH-SY5Y cells treated with Aβ_25-35. Values are mean ± SD. ^a~dMeans with the different letters are significantly different (P<0.05) by Duncan’s multiple range test. N:normal group; C:control group; K:kaempferol; KG:kaempferol-3-O-glucoside

Table 1. Effect of kaempferol, quercetin and its glycosides on cell viability of SH-SY5Y cells treated with Aβ_25-35