The Antineoplastic Effect Of Trans-EPA And DHA From Antarctic Krill

Antarctic krill(Eupausia superba)has attracted more and more attention for its immense biomass and high nutritional value(e.g.lipids and proteins).As a kind of health food,Antarctic krill oil has already been used to treat hypertension and hyperlipidemia,protect the vessel and prevent atherosclerosis for its high content of poly-unsaturated fatty acids,phospholipids and astaxanthin.The earlier research in our group has indicated that Antarctic krill oil could inhibit the growth of several tumor cell lines in vitro,but as a kind of complicated mixture,it is still unclear which kind of the compound(s)played the antineoplastic effect,as well as the molecular mechanism.In order to solve the mentioned problems,the main work of the thesis was listed as follows:(1)Solvent extraction,silica chromatography and high performance liquid chromatography were used to separate the antineoplastic compounds in Antarctic krill oil.Then LC-MS,FTIR,HRESIMS,1H-NMR and 13C-NMR were used to confirm the structure.The results indicated that two compounds,i.e.eicosapentaenoic acid(EPA)and docosahexaenoic acid(DHA),could inhibit the growth of tumor cells in vitro.Raman spectra showed that Antarctic krill EPA and DHA were trans-EPA and DHA.(2)The antineoplastic effect of Antarctic krill EPA and DHA was evaluated.According to the results,the antineoplastic effect of Antarctic krill trans-EPA and DHA were 3-7 times higher than cis-EPAs and DHAs from other three resources.Taking MCF-7 as example,the IC50 value of Antarctic krill EPA was 14.01?M,while the other three ones were 81.45,82.11 and 80.51?M,respectively.The IC50 value of Antarctic krill DHA was 19.94?M,while the other three ones were 73.13,75.31 and 70.13?M,respectively.Additionally,Antarctic krill EPA and DHA could not inhibit the growth of human normal liver cell line HL7702.(3)The apoptotic mechanism induced by Antarctic krill EPA and DHA in MCF-7 cells was checked.The results showed that after treating at different concentrations of Antarctic krill EPA and DH A,the ROS level was concentration-dependent.Meanwhile,the ROS level increased at first and then decreased with the increase of treatment time.Compared with all-cis EPA and DHA standards,Antarctic krill EPA and DHA could induce much more ROS,and also significantly down-regulate the level ofT-AOC,GSH and T-SOD.Furthermore,Antarctic krill EPA and DHA could not induce ROS in human normal liver cell line HL7702.(4)The effect of Antarctic krill trans-EPA and DHA on the ability of migration and invasion of MCF-7 cells was evaluated.According to the results,Antarctic krill EPA could not down-regulate the ability of migration and invasion of MCF-7 cells,while Antarctic krill DHA could significantly down-regulate the ability.In MCF-7/CD95i,down-regulation of migrating and invasive ability was also observed,whereas the down-regulation effect in MCF-7 was much stronger than that in MCF-7/CD95i.Meanwhile,an accumulated interaction between CD95 and Caveolin-1 was demonstrated with the increasing Antarctic krill DHA concentration in MCF-7.The accumulated interaction could inhibit FAK/Src/PI3K/Akt signaling pathway and result in downregulation of MMP2,and then inhibit the migration and invasion of MCF-7 cells.All these results indicated that low concentration of Antarctic krill DHA could down-regulate the ability migration and invasion in MCF-7,and CD95 might be one of the targets.In conclusion,the thesis confirmed that natural trans-EPA and DHA extracted from Antarctic krill could significantly inhibit tumor cell growth.Furthermore,the mechanism of apoptosis,migration and invasion induced by these trans-EPA and DHA were studied,which will help to understand the healthy and medical value of Antrctic krill oil.