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Macrophage-stimulating activities of newly isolated complex polysaccharides from Parachlorella kessleri strain
Mikinori Ueno1, Kichul Cho2, Narumi Hirata1
1Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, Nagasaki 852-8521, Japan.
Abstract:
Our previous studies demonstrated that the microalga Parachlorella kessleri (KNK-A001) has immunostimulatory activities, which were observed as an increase in natural killer (NK) cell activity in mice after intraperitoneal injection or as a protective effect on a virus-infected model shrimp after oral administration. In this study, we attempted to gain insight into the constituent substances of KNK-A001 that are responsible for the immunostimulatory activity. First, we obtained five polysaccharide fractions from KNK-A001 by DEAE anion exchange chromatography. Among the fractions, F5 showed the most potent induction of nitric oxide (NO) secretion in RAW264.7 cells, and both mRNA and protein expression levels of inducible NO synthase (iNOS) were increased in F5-treated RAW264.7 cells. A significant increase in the nuclear translocation of the p65 subunit of nuclear factor-kappa B (NF-κB) was observed in F5-treated RAW264.7 cells. F5 also induced the secretion of tumor necrosis factor (TNF)-α in RAW264.7 cells. Analysis using mitogen-activated protein (MAP) kinase inhibitors suggested that c-Jun N-terminal kinase (JNK) and p38 MAP kinase were mainly involved in F5-induced NO and TNF-α productions. The compositional analysis of F5 identified the main constituents as galactose, glucose, galacturonic acid, and mannose. Gel-filtration analysis suggested that molecular mass of F5 was approximately 400kDa.
Insights
The microalga Parachlorella kessleri (KNK-A001) contains a potent polysaccharide fraction (F5) that enhances immune responses. This fraction stimulates nitric oxide and tumor necrosis factor-alpha secretion, crucial for immune cell activity.
Area of Science:
- Immunology
- Phycology
- Biochemistry
Background:
- Previous research established the immunostimulatory effects of Parachlorella kessleri (KNK-A001).
- Observed effects included increased natural killer (NK) cell activity and protection against viral infections.
Purpose of the Study:
- To identify the specific components of KNK-A001 responsible for its immunostimulatory properties.
- To elucidate the mechanisms underlying the immune-enhancing effects.
Main Methods:
- Isolation of polysaccharide fractions from KNK-A001 using DEAE anion exchange chromatography.
- Assessment of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α) secretion in RAW264.7 cells.
- Analysis of inducible NO synthase (iNOS) expression, NF-κB p65 translocation, and MAP kinase pathway involvement.
Main Results:
- Fraction F5 demonstrated the strongest induction of NO secretion and iNOS expression.
- F5 treatment led to increased nuclear translocation of NF-κB p65.
- F5 induced TNF-α secretion, with involvement of JNK and p38 MAP kinases.
- F5 is composed mainly of galactose, glucose, galacturonic acid, and mannose, with an estimated molecular mass of 400 kDa.
Conclusions:
- A specific polysaccharide fraction (F5) from KNK-A001 is responsible for its immunostimulatory activity.
- F5 activates immune cells via NO and TNF-α production, involving the NF-κB and MAP kinase pathways.
