Degraded polysaccharides from Porphyra haitanensis: purification, physico-chemical properties, antioxidant and immunomodulatory activities.

To explore effect of the structural properties of porphyra haitanensis polysaccharide on its biological activity, degraded porphyra polysaccharides were separated and purified by Cellulose DEAE-52 and Sephadex G-100 chromatography, obtaining three purified components (P1, P2 and P3). All the three components were sulfate polysaccharides containing the repeating units of → 3) ß-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →, and → 3) ß-D-galactose (1 → 4) α-L-galactose-6-S (1 →, and → 3) 6-O-methyl-ß-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →. The molecular weight of the three fractions was measured to be 300.3, 130.4 and 115.1 kDa, respectively. Their antioxidant activity was investigated by the determination of the free radical scavenging effect and ferric reducing power. It was found that P1, P2 and P3 possessed marked antioxidant activity. It was also found that they appreciably enhanced the proliferation, phagocytic ability and nitric oxide secretion in RAW264.7 cells. Lower molecular weight and higher sulfate content were beneficial to bioactivities of P. haitanensis polysaccharides. Overall, P2 and P3 possess superior immuno-modulatory activity to that of P1 and PHP. Thus, the current work will provide the basis for the better utilization of P. haitanensis to develop the related functional foods.

Improved antioxidant and immunomodulatory activities of enzymatically degraded Porphyra haitanensis polysaccharides.

Porphyra haitanensis polysaccharide (CPH) was degraded by pectinase to improve its biological activities. Box-Behnken response surface design was used to optimize the hydrolysis conditions. The molecular weight of CPH and the degraded P. haitanensis polysaccharide (DCPH) were measured to be 524 and 217 kDa, respectively. GC-MS spectrometry results showed that CPH and DCPH were mainly composed of galactose. In vitro antioxidant assays indicated that DCPH possessed improved radical scavenging activity and ferric iron reducing power when compared to those of CPH. In H2 O2 -treated RAW264.7 cells, DCPH was also found to be more effective in reducing the generation of malondialdehyde and reactive oxygen species than CPH. The immunomodulatory assays demonstrated that DCPH possessed superior activities in enhancing the proliferation, phagocytosis, and NO secretion in a RAW264.7 macrophage cell model to those of CPH. PRACTICAL APPLICATIONS: Polysaccharide is the most abundant bioactive component of an edible red algae Porphyra haitanensis. However, the use of CPH is limited due to its relatively low biological activities. Thus, in order to fully utilize P. haitanensis, it is necessary to enhance the biological activities of CPH for its practical use. An efficient and practical method to enhance the bioactivities of P. haitanensis polysaccharide has been developed in the present work. The DCPH prepared in this work could have potential applications in food and medicinal areas.

Intestinal inflammation modulates expression of the iron-regulating hormone hepcidin depending on erythropoietic activity and the commensal microbiota.

States of chronic inflammation such as inflammatory bowel disease are often associated with dysregulated iron metabolism and the consequent development of an anemia that is caused by maldistribution of iron. Abnormally elevated expression of the hormone hepcidin, the central regulator of systemic iron homeostasis, has been implicated in these abnormalities. However, the mechanisms that regulate hepcidin expression in conditions such as inflammatory bowel disease are not completely understood. To clarify this issue, we studied hepcidin expression in mouse models of colitis. We found that dextran sulfate sodium-induced colitis inhibited hepcidin expression in wild-type mice but upregulated it in IL-10-deficient animals. We identified two mechanisms contributing to this difference. Firstly, erythropoietic activity, as indicated by serum erythropoietin concentrations and splenic erythropoiesis, was higher in the wild-type mice, and pharmacologic inhibition of erythropoiesis prevented colitis-associated hepcidin downregulation in these animals. Secondly, the IL-10 knockout mice had higher expression of multiple inflammatory genes in the liver, including several controlled by STAT3, a key regulator of hepcidin. The results of cohousing and fecal transplantation experiments indicated that the microbiota was involved in modulating the expression of hepcidin and other STAT3-dependent hepatic genes in the context of intestinal inflammation. Our observations thus demonstrate the importance of erythropoietic activity and the microbiota in influencing hepcidin expression during colitis and provide insight into the dysregulated iron homeostasis seen in inflammatory diseases.

Tea polyphenols inhibit Pseudomonas aeruginosa through damage to the cell membrane.

This paper aims to delineate the inhibition mechanism of tea polyphenols (TP) toward Pseudomonas aeruginosa by cell membrane damage. Morphological changes in bacteria treated with TP were investigated by transmission electron microscopy, with results indicating that the primary inhibitory action of TP is to damage bacterial cell membranes. TP also increased the permeability of the outer and inner membranes of P. aeruginosa and disrupted the cell membrane with the release of small cellular molecules. A proteomics approach based on two-dimensional gel electrophoresis and MALDI-TOF/TOF MS analysis was used to study the differences in the membrane proteins of TP-treated P. aeruginosa and those of control samples. Twenty-seven differentially expressed proteins were observed in the treated and the control groups. Most of the proteins identified by MALDI-TOF/TOF MS were enzymes (dihdrollpoamide dehydrogenase 50s ribosomal protein, and so on), which may have induced the metabolic disorder of the bacteria and resulted in their death.