Effects of Aged Black Garlic Extracts on the Tight Junction Permeability and Cell Invasion in Human Gastric Cancer Cells

Abstract

Garlic (Allium sativum) has been well-known as a folk remedy for a variety of ailments since ancient times, and it is well documented that enhanced garlic consumption leads to a decrease in incidences of cancer. Tight junctions (TJs) are critical structures for the maintenance of cellular polarity, acting as paracellular permeability barriers and playing an essential role in regulating the diffusion of fluid, electrolytes and macromolecules through the paracellular pathway. Matrix metalloproteinases (MMPs) have been implicated as possible mediators of invasiveness and metastasis in some cancers. In this study, we investigated the potential effects of water extract of aged black garlic (ABG) on the correlation between tightening of TJs and anti-invasive activity in human gastric carcinoma AGS cells. The inhibitory effects of ABG on cell motility and invasiveness were found to be associated with increased tightness of TJs, which was demonstrated by an increase in transepithelial electrical resistance. Additionally, the activities of MMP-2 and-9 in AGS cells were inhibited by treatment with ABG, and this was also correlated with a decrease in the expression of their mRNA and proteins. Furthermore, RT-PCR and immunoblotting results indicated that ABG repressed the levels of the claudin proteins, major components of TJs that play a key role in the control and selectivity of paracellular transport. In conclusion, these results suggest that ABG treatment may inhibit tumor metastasis and invasion, and therefore may act as a dietary source to decrease the risk of developing cancer. 서 론 세포사이의 몇 가지 junction 중 tight junction (TJ)은 다이 나믹한 구조를 가지고 있으며, 상처회복과 염증, 특히 암의 발생과 진행 동안 구조적 변화를 유발한다. Epithelial sheet 안쪽에 존재하는 TJ은 선단(apical)에 위치하는 몇 가지 단백 질 복합체(multi-protein complex)로 paracellular pathway를 통한 병원성 물질과 거대분자의 차단하고 이온 물질과 미량분 자의 통과 조절을 위해 intercellular strand를 형성 한다 [14,19,21]. 그리고 TJ 사이의 연결 단백질인 ZO-1과 claudin family 단백질은 액틴과 연결되어 세포극성의 유지에도 중요 하다[10,12,14,16,18]. 1970년대 초 상피세포 유래 종양에서 TJ 구조의 다양한 변화가 보고[11]된 이후, 투과성상피세포의 전 기적 저항성(transepithelial electrical resistance, TER)이 암세 포에서 정상 조직보다 높게 형성되어 있음이 보고된 바 있다 [16,24]. 최근 TJ 구성 단백질로서 관심을 모으고 있는 claudin family 단백질은 막단백질로 인접세포의 claudin 단백질군의 세포 외 영역과 서로 인접되어있다고 알려져 있다[13,21]. 현재 21 종류의 transmembrane 단백질을 포함하는 claudin family는 TJ strand의 중요한 구성요소로 큰 범위에서 TJ의 투과도 특성 (permeability characteristics)을 결정하는 것으로 알려져 있다 [24,25]. 또한 TJ는 세포막의 apical과 bassolateral 사이에 지방 과 단백질의 이동을 막는 연속적인 circumferential "fence"를 형성하므로 세포의 극성의 형…