Sea Squirt (Halocynthia roretzi) Hydrolysates Induce Apoptosis in Human Colon Cancer HT-29 Cells through Activation of Reactive Oxygen Species

Abstract

Recent evidence provides that seafood has a lot of health benefits due to its unique bioactive compounds. Sea squirt is widely cultured and consumed as a foodstuff in Korea; however, seldom reports with reference to bioactivities are available until now. In this study, edible part of sea squirt was hydrolyzed by pepsin and its hydrolysates was evaluated for anticancer effect on human colon cancer HT-29 cells. Sea squirt hydrolysates (SSQ) reduced HT-29 cell viability. Treatment with SSQ resulted in the increase in reactive oxygen species (ROS) generation followed by disruption of mitochondrial membrane potential (MMP). Flow cytometry analysis revealed that SSQ induced G2/M phase arrest and apoptosis evidenced by Hoechst 33342 staining. Levels of mRNA expression by real-time polymerase chain reaction (PCR) showed that treatment with SSQ in HT-29 cells upregulated expression of p53, bax, and caspase-3 genes and downregulated expression of bcl-2 gene. Protein level of cytochrome c into cytosol and caspase-3 by Western blotting were also increased by treatment with SSQ in HT-29 cells. These results suggest that SSQ may be useful for functional food ingredients and/or nutraceuticals.

Acknowledgment

This study was supported by a grant from the Ascidian Hanging Culture Fisheries Cooperatives, Republic of Korea.