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Polysaccharides isolated from Açaí fruit induce innate immune responses.

Holderness J, Schepetkin IA, Freedman B, Kirpotina LN, Quinn MT, Hedges JF, Jutila MA - PLoS ONE (2011)

Bottom Line: Similar polyphenol and polysaccharide fractions are found in Acai fruit.Contrary to previous reports, we did not identify agonist activity in the polyphenol fraction; however, the Acai polysaccharide fraction induced robust γδ T cell stimulatory activity in human, mouse, and bovine PBMC cultures.When delivered in vivo, Acai polysaccharide induced myeloid cell recruitment and IL-12 production.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, United States of America.

ABSTRACT
The Açaí (Acai) fruit is a popular nutritional supplement that purportedly enhances immune system function. These anecdotal claims are supported by limited studies describing immune responses to the Acai polyphenol fraction. Previously, we characterized γδ T cell responses to both polyphenol and polysaccharide fractions from several plant-derived nutritional supplements. Similar polyphenol and polysaccharide fractions are found in Acai fruit. Thus, we hypothesized that one or both of these fractions could activate γδ T cells. Contrary to previous reports, we did not identify agonist activity in the polyphenol fraction; however, the Acai polysaccharide fraction induced robust γδ T cell stimulatory activity in human, mouse, and bovine PBMC cultures. To characterize the immune response to Acai polysaccharides, we fractionated the crude polysaccharide preparation and tested these fractions for activity in human PBMC cultures. The largest Acai polysaccharides were the most active in vitro as indicated by activation of myeloid and γδ T cells. When delivered in vivo, Acai polysaccharide induced myeloid cell recruitment and IL-12 production. These results define innate immune responses induced by the polysaccharide component of Acai and have implications for the treatment of asthma and infectious disease.

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Effect of Acai polysaccharide on TNF-α and IL-6 production in MonoMac-6 and human PBMCs.Human PBMCs or MonoMac-6 macrophages were incubated for 24 h with the indicated concentrations of polysaccharide fractions Acai-1, Acai-1 pretreated with endotoxin-removing gel (Acai-1ER), Acai-2, Acai-3, or 200 ng/mL LPS. Cell-free supernatants were collected, and extracellular TNF-α and IL-6 were quantified by ELISA. Values represent the mean ± SD of triplicate samples from one experiment, which is representative of at least three independent experiments.
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pone-0017301-g005: Effect of Acai polysaccharide on TNF-α and IL-6 production in MonoMac-6 and human PBMCs.Human PBMCs or MonoMac-6 macrophages were incubated for 24 h with the indicated concentrations of polysaccharide fractions Acai-1, Acai-1 pretreated with endotoxin-removing gel (Acai-1ER), Acai-2, Acai-3, or 200 ng/mL LPS. Cell-free supernatants were collected, and extracellular TNF-α and IL-6 were quantified by ELISA. Values represent the mean ± SD of triplicate samples from one experiment, which is representative of at least three independent experiments.

Mentions: The ROS formation and cytokine secretion profile indicated that Acai polysaccharides function similarly to polysaccharide preparations active on monocytes [2], [41]. Therefore, we further analyzed the monocyte response to Acai polysaccharides. Although the amount of endotoxin (LPS) was very low and far larger amounts are required to activate γδ T cells [2], [59], monocytes are exquisitely sensitive to endotoxin. Thus, further steps were taken to ensure that endotoxin was not a component of the Acai preparation. To this end, we prepared a detoxified Acai-1 by elution through a column of endotoxin-removing gel (denoted Acai-1ER). To quantify dose-dependent effects of Acai polysaccharides on monocyte-associated cytokine production, levels of TNF-α and IL-6 were determined in cells treated with the polysaccharide fractions by ELISA. As shown in Figure 5, incubation of PBMCs with the fractions enhanced TNF-α and IL-6 production in a dose-dependent manner. Acai-1 and Acai-1ER induced very similar responses indicating the minor endotoxin contamination had no effect on the activity of Acai-1. Furthermore, as with previous experiments, the Acai-1 fractions were the most active fraction at low concentrations (<1 µg/mL). Although a slight decrease in TNF-α production in Acai-1-treated cultures from 5 to 10 µg/mL was noted, the level of the cytokine was increased when cells were exposed to a higher dose (100 µg/mL) of Acai-1. We hypothesized this was due to the inherent heterogeneous nature of cell populations in PBMC cell preparations and their differing responses to the polysaccharides.


Polysaccharides isolated from Açaí fruit induce innate immune responses.

Holderness J, Schepetkin IA, Freedman B, Kirpotina LN, Quinn MT, Hedges JF, Jutila MA - PLoS ONE (2011)

Effect of Acai polysaccharide on TNF-α and IL-6 production in MonoMac-6 and human PBMCs.Human PBMCs or MonoMac-6 macrophages were incubated for 24 h with the indicated concentrations of polysaccharide fractions Acai-1, Acai-1 pretreated with endotoxin-removing gel (Acai-1ER), Acai-2, Acai-3, or 200 ng/mL LPS. Cell-free supernatants were collected, and extracellular TNF-α and IL-6 were quantified by ELISA. Values represent the mean ± SD of triplicate samples from one experiment, which is representative of at least three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046208&req=5

pone-0017301-g005: Effect of Acai polysaccharide on TNF-α and IL-6 production in MonoMac-6 and human PBMCs.Human PBMCs or MonoMac-6 macrophages were incubated for 24 h with the indicated concentrations of polysaccharide fractions Acai-1, Acai-1 pretreated with endotoxin-removing gel (Acai-1ER), Acai-2, Acai-3, or 200 ng/mL LPS. Cell-free supernatants were collected, and extracellular TNF-α and IL-6 were quantified by ELISA. Values represent the mean ± SD of triplicate samples from one experiment, which is representative of at least three independent experiments.
Mentions: The ROS formation and cytokine secretion profile indicated that Acai polysaccharides function similarly to polysaccharide preparations active on monocytes [2], [41]. Therefore, we further analyzed the monocyte response to Acai polysaccharides. Although the amount of endotoxin (LPS) was very low and far larger amounts are required to activate γδ T cells [2], [59], monocytes are exquisitely sensitive to endotoxin. Thus, further steps were taken to ensure that endotoxin was not a component of the Acai preparation. To this end, we prepared a detoxified Acai-1 by elution through a column of endotoxin-removing gel (denoted Acai-1ER). To quantify dose-dependent effects of Acai polysaccharides on monocyte-associated cytokine production, levels of TNF-α and IL-6 were determined in cells treated with the polysaccharide fractions by ELISA. As shown in Figure 5, incubation of PBMCs with the fractions enhanced TNF-α and IL-6 production in a dose-dependent manner. Acai-1 and Acai-1ER induced very similar responses indicating the minor endotoxin contamination had no effect on the activity of Acai-1. Furthermore, as with previous experiments, the Acai-1 fractions were the most active fraction at low concentrations (<1 µg/mL). Although a slight decrease in TNF-α production in Acai-1-treated cultures from 5 to 10 µg/mL was noted, the level of the cytokine was increased when cells were exposed to a higher dose (100 µg/mL) of Acai-1. We hypothesized this was due to the inherent heterogeneous nature of cell populations in PBMC cell preparations and their differing responses to the polysaccharides.

Bottom Line: Similar polyphenol and polysaccharide fractions are found in Acai fruit.Contrary to previous reports, we did not identify agonist activity in the polyphenol fraction; however, the Acai polysaccharide fraction induced robust γδ T cell stimulatory activity in human, mouse, and bovine PBMC cultures.When delivered in vivo, Acai polysaccharide induced myeloid cell recruitment and IL-12 production.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, United States of America.

ABSTRACT
The Açaí (Acai) fruit is a popular nutritional supplement that purportedly enhances immune system function. These anecdotal claims are supported by limited studies describing immune responses to the Acai polyphenol fraction. Previously, we characterized γδ T cell responses to both polyphenol and polysaccharide fractions from several plant-derived nutritional supplements. Similar polyphenol and polysaccharide fractions are found in Acai fruit. Thus, we hypothesized that one or both of these fractions could activate γδ T cells. Contrary to previous reports, we did not identify agonist activity in the polyphenol fraction; however, the Acai polysaccharide fraction induced robust γδ T cell stimulatory activity in human, mouse, and bovine PBMC cultures. To characterize the immune response to Acai polysaccharides, we fractionated the crude polysaccharide preparation and tested these fractions for activity in human PBMC cultures. The largest Acai polysaccharides were the most active in vitro as indicated by activation of myeloid and γδ T cells. When delivered in vivo, Acai polysaccharide induced myeloid cell recruitment and IL-12 production. These results define innate immune responses induced by the polysaccharide component of Acai and have implications for the treatment of asthma and infectious disease.

Show MeSH
Related in: MedlinePlus