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Effects of intraperitoneally administered dietary fibers on superoxide generation from peritoneal exudate macrophages
K Hishinuma1, A Hosono, H Inaba
1Biophoton Project, Research Development Corporation of Japan, Miyagi.
Abstract:
To clarify whether edible polysaccharides (dietary fibers) have a host defense stimulating activity, the effects of intraperitoneally administered dietary fiber on the generation of microbicidal superoxide anion (O2-) in mouse peritoneal exudate macrophages (MP) were investigated. MP obtained from mice injected cellulose or pectin generated larger amount of O2- when stimulated by 12-o-tetradecanoylphorbol-13-acetate (TPA) or during phagocytosis of opsonized zymosan than those from mice injected proteose peptone, a widely used elicitor for MP. Especially, generated O2- from cellulose-elicited MP was as strikingly large as that from MP elicited by lentinan, a strong antitumor polysaccharide, when stimulated by TPA. Yeast mannan had no effect on O2(-)-generation. These results suggest the possibility that cellulose and pectin may act as host defense stimulators. The augmentation by cellulose or pectin of O2(-)-generation during phagocytosis was not inhibited by the calmodulin (CaM) antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7). However, the augmentation was completely disappeared when the protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) was added. These results strongly suggest that the augmentation of O2(-)-generation in phagocytosing MP by cellulose or pectin might be due to the increased activity of PKC in the MP, and that CaM may not be involved in the augmentation.
Insights
Edible polysaccharides like cellulose and pectin stimulate host defense by enhancing microbicidal superoxide anion generation in macrophages. This effect is mediated by protein kinase C, not calmodulin.
Area of Science:
- Immunology
- Nutrition Science
- Biochemistry
Background:
- Dietary fibers, or edible polysaccharides, are known for their roles in digestion and metabolism.
- Their potential to modulate host immune responses remains an area of active investigation.
- Understanding how dietary components interact with immune cells is crucial for developing novel therapeutic strategies.
Purpose of the Study:
- To investigate the host defense stimulating activity of edible polysaccharides.
- To determine the effects of dietary fibers on superoxide anion (O2-) generation in mouse peritoneal exudate macrophages (MP).
- To elucidate the signaling pathways involved in the immune-modulating effects of these fibers.
Main Methods:
- Mice were intraperitoneally injected with various dietary fibers (cellulose, pectin, yeast mannan) or a control (proteose peptone).
- Peritoneal exudate macrophages (MP) were isolated and stimulated with 12-o-tetradecanoylphorbol-13-acetate (TPA) or opsonized zymosan.
- Superoxide anion (O2-) generation was measured, and the involvement of calmodulin (CaM) and protein kinase C (PKC) was assessed using specific inhibitors (W-7 and H-7, respectively).
Main Results:
- Cellulose and pectin administration significantly increased O2- generation in MP upon stimulation compared to proteose peptone.
- The O2- generation induced by cellulose was comparable to that induced by lentinan, a known potent polysaccharide.
- The augmentation of O2- generation by cellulose and pectin was dependent on protein kinase C (PKC) activity and independent of calmodulin (CaM).
Conclusions:
- Cellulose and pectin exhibit host defense stimulating activity by enhancing microbicidal O2- generation in macrophages.
- The observed immune-modulatory effect is primarily mediated through the activation of PKC signaling pathway.
- These findings suggest a potential role for specific dietary fibers in bolstering innate immune responses.