Three acidic polysaccharides derived from sour jujube seeds protect intestinal epithelial barrier function in LPS induced Caco-2 cell inflammation model

Epithelial and/or endothelial barriers play a critical role in animal, including human, life forms. The tight junction (TJ) is an essential component of these barriers. Occludin is a major component of the TJ. The structure of occludin, including its gene splice variants and protein essential components have been elucidated. Phosphorylation/dephosphorylation plays a major role in regulation of occludin and TJ. Disruption of occludin regulation is an important aspect of a number of diseases. Strategies to prevent and/or reverse occludin downregulation may be an important therapeutic target.

Water-soluble acidic polysaccharides from the cell walls of Ulva rigida are mainly composed of disaccharides that contain glucuronic acid and sulphated rhamnose. The structure of disaccharides resembles that of glycosaminoglycans (GAGs) as they both contain glucuronic acid and sulphated sugars. Glycosaminoglycans occur in the extracellular matrix of animal connective tissues but can also be produced by leucocytes at inflammatory sites. Certain types of GAGs can even activate macrophages and therefore the acidic polysaccharides from U. rigida probably modulate macrophage activity. In the present study, we evaluated the effects of U. rigida polysaccharides on several RAW264.7 murine macrophage activities, including expression of inflammatory cytokines and receptors, nitric oxide and prostaglandin E2 (PGE(2)) production, and nitric oxide synthase 2 (NOS-2) and cyclooxygenase-2 (COX-2) gene expression. U. rigida acidic polysaccharides induced a more than two-fold increase in the expression of several chemokines (chemokine (C motif) ligand 1, chemokine (C-X-C motif) ligand 12, chemokine (C-C motif) ligand 22 and chemokine (C-X-C motif) ligand 14 (Cxcl14)) and in the expression of IL6 signal transducer and IL12 receptor beta 1. Incubation of macrophages with U. rigida polysaccharides also induced an increase in nitrite production, although this effect decreased considerably after desulphation of polysaccharides, suggesting that the sulphate group is important for the stimulatory capacity of these molecules. U. rigida polysaccharides also stimulated macrophage secretion of PGE(2) and induced an increase in COX-2 and NOS-2 expression. The results indicate that U. rigida acid polysaccharide can be used as an experimental immunostimulant for analysing inflammatory responses related to macrophage functions. In addition, these polysaccharides may also be of clinical interest for modifying certain macrophage activities in diseases where macrophage function is impaired or needs to be boosted.

Background Jujube ( Ziziphus jujuba Mill.) fruit is one of the largest productions in China and its increasing production has drawn considerable attention from researchers. Polysaccharide is one of the most abundant components of jujube, and it represents a major group of biolotegically active constituents. This study intended to investigate the special structure of a homogeneous acidic polysaccharide (PZMP4) produced from Ziziphus Jujuba cv. Muzao fruit using novel methods, including DEAE-Sepharose Fast Flow and Sephacryl S-300 column chromatography. Results The structure of PZMP4 was determined via high-performance gel permeation chromatography (HPGPC), gas chromatography (GC), Fourier transform infrared spectroscopy (FT-IR), methylation analysis, nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results reveal that PZMP4 with a molecular weight of 27.90 kDa was composed of rhamnose, arabinose, mannose, glucose, galactose, and galacturonic acid at a ratio of 2.32:2.21:0.22:0.88:2.08:8.83. Advanced structural analysis revealed a netted structure with molecular aggregates of PZMP4. Structural features demonstrated that the basic backbone of PZMP4 appeared to mainly consist of (1→4)-linked Gal p A with three branches bonded to O -3 of (1→3)-linked Ara f , (1→2)-linked Rha p , and terminated with Gal p A. Conclusions PZMP4’s unique structure could imply distinct bioactivities and have considerable utilization in functional food. Graphic abstract