Augmentation of Cytolytic Activity in Murine Natural Killer Cells and Inhibition of Tumor Growth by the Ethanol Fraction of Oyster Extract

Abstract

A reduced number and/or reduced activity of natural killer (NK) cells, which are important for defense against a variety of cancers and viral infections, occur under various stress conditions and in patients with various diseases. In this article, we report that the 30% to 50% ethanol precipitate of oyster extract (EPOE50) dose-dependently enhanced the activity of mouse spleen NK cells in vitro and in vivo. The activity of EPOE50 was eluted with a molecular weight of about 2000 by gel filtration and was inactivated by periodate but not by proteinase K. The activity of highly purified NK cells was also augmented by EPOE50 but not by oligodeoxyribonucleotide 1585, which mimics bacterial DNA. Administration of EPOE50 to mice stimulated splenic NK cell activity without a change in splenic NK cell populations. Although the proliferation of B16 tumor cells in vitro was slightly stimulated by EPOE50, the growth of B16 melanoma in vivo was dose-dependently suppressed by administration of EPOE50. Taken together, our results indicate that EPOE50 augmented NK cell activity and that its administration to mice inhibited tumor growth presumably through the activation of NK cells and also suggest that the active substance is a sugar-containing oligomer or polymer and is not of bacterial origin.

Effect of Natural Compounds on NK Cell Activation

“…The authors discovered that GTLP were able to increase NK cell toxicity against YAC-1 cells and activate macrophages [94]. Finally, one study using polysaccharides extracted from animal origin (oyster) resulted in stimulation of the activity of mouse spleen NK cells in vitro and in vivo [95]. In conclusion, polysaccharides have also a stimulating effect on NK cells and might be an additional source of compounds supporting cancer treatment.…”

Immunomodulatory activity of aqueous extract from Crassostrea sikamea in the splenocytes of Sprague‐Dawley rats

“…Moreover, our results demonstrated that AECs treatment significantly increased the proportion of CD3 ‐ CD161 + NK cells and CD3 + CD161 + NKT cells. Interestingly, Kaito Sakaguchi et al observed that the 30–50% ethanol precipitate of oyster extract (EPOE50) enhanced the activity of mouse spleen NK cells in vitro and in vivo and then inhibited tumor growth in a dose‐dependent manner (Sakaguchi et al., 2018 ). In summary, AECs treatment may regulate the balance of cellular immunity and the body's humoral immunity.…”

“…In addition to their nutritional value, oysters have considerable potential in the functional food industry, exhibiting beneficial health effects. Previous studies have demonstrated that oyster extracts possessed numerous biological properties, such as antitumor (Sakaguchi et al., 2018 ), antimicrobial (Huang et al., 2019 ; Karthikeyan et al., 2014 ), antioxidant (Watanabe et al., 2012 ), and immunomodulatory effects (Cheng et al., 2013 ; Li et al., 2019 ).…”

“…itate of oyster extract (EPOE50) enhanced the activity of mouse spleen NK cells in vitro and in vivo and then inhibited tumor growth in a dose-dependent manner(Sakaguchi et al, 2018). In summary, AECs treatment may regulate the balance of cellular immunity and the body's humoral immunity.…”

Enhanced lactic acid production by Lactobacillus rhamnosus ATCC 7469 through simultaneous saccharification and fermentation from household food waste

“…[29] Total proteins were calculated by multiplying the organic nitrogen content by 6.25 using the Kjeldahl method. [30] 3 RESULTS AND DISCUSSION…”