Arabinogalactan in the side chain of pectin from persimmon is involved in the interaction with small intestinal epithelial cells.

Pectin in Diospyros kaki (persimmon) is a complex polysaccharide and is classified as a dietary fiber. Pectin is characterized by the presence of side chains of neutral sugars, such as galactose residues; however, the structure and properties of these sugars vary greatly depending on the plant species from which it is derived. Here, we report the structural features of pectin extracted from persimmon. The polysaccharide was low-methoxy pectin with a degree of methyl esterification <50% and ratio of side chain galactan to arabinan in the rhamnogalacturonan-I region of pectin of 3-20. To investigate the physiological function of pectin from persimmon, we performed a coculture assay using Caco-2 cells. As a result, it was shown that the proliferation of undifferentiated Caco-2 cells was promoted, and further, the importance of arabinogalactan among the pectin structures was shown.

Diospyros kaki extract protects myoblasts from oxidative stress-induced cytotoxicity via secretions derived from intestinal epithelium.

Under oxidative stress, reactive oxygen species (ROS) alter signal transduction and induce macromolecular damage in cells. Such oxidative damage can lead to sarcopenia, an age-related syndrome characterized by a progressive loss of mass and strength of skeletal muscles. Because food components do not directly come in contact with muscle cells, we focused on the effects of secretions produced by stimulated intestinal epithelial cells on oxidative stress in myoblast cells. An extract of Diospyros kaki was fractionated using different concentrations of ethanol. Each fraction showed different levels of antioxidant and phenolic compounds. The biological activity was evaluated using a Caco-2 cell coculture system. Secretions from Caco-2 cells exposed to 0.5 mg/mL D. kaki extract attenuated the oxidative stress-induced reduction of C2C12 cell viability, suggesting that the D. kaki extract could stimulate intestinal epithelial cells to produce secretions that reduce oxidative stress in myoblasts in vitro.

The effects of denatured major bovine whey proteins on the digestive tract, assessed by Caco-2 cell differentiation and on viability of suckling mice.

Alpha-lactalbumin (α-LA) and ß-lactoglobulin (ß-LG) are contained in bovine milk whey. Chemical and physical treatments are known to alter the conformation of these proteins and we have previously reported that α-LA denatured with trifluoroethanol (TFE) and isolated from sterilized market milk inhibited the growth of rat crypt IEC-6 cells. In the present study, we aimed to evaluate the effects of TFE-treated α-LA and ß-LG on cell growth using cultured intestinal cells and on their safety using a suckling mouse model. First, we investigated the effect of the TFE-treated whey proteins on human colonic Caco-2 cells at various differentiation stages. In the undifferentiated stage, we assessed cell growth by a water-soluble tetrazolium-1 method. The native whey proteins enhanced cell proliferation, whereas the TFE-treated whey proteins strongly inhibited cell growth. We investigated cell barrier function in the post-differentiated stage by measuring transepithelial electrical resistance (TER). Not only native but also the TFE-treated whey proteins increased TER. Next, we evaluated whether the TFE-treated α-LA and ß-LG have adverse effects on healthy suckling mice. No mice given by the TFE-treated samples showed any adverse symptoms. We also performed a safety test using a human rotavirus infected gastrointestinal disease suckling mice model. Even the TFE-treated whey proteins appeared to prevent the development of diarrheal symptoms without any adverse effects. Although we cannot know the effect of long-term ingestion of denatured whey proteins, these results suggest that they have no adverse effects on differentiated intestinal cells and digestive tract, at least in short-term ingestion.

Characterization and comparison of recombinant honeybee chymotrypsin-like protease (HCLPase) expressed in Escherichia coli and insect cells.

We previously found a novel chymotrypsin-like protease in honeybee, designated as HCLPase. The recombinant enzyme expressed in insect cells was produced and compared to that in Escherichia coli. Both enzymes showed equivalent molecular size and specificity. However, HCLPase produced in insect cells showed higher specific activity. The C-terminal cleavage sites of HCLPase were phenylalanine, leucine, and tyrosine residues.

Development of a photoreactive probe-based system for detecting heparin.

We previously identified a peptide heparin-associated peptide Y (HappY) that binds specifically to heparin. In this article, we report a novel heparin detection system using chemically modified HappY as a probe. The photoreactive HappY probe was serially diluted and dispensed into a 96-well plate coated with biotinylated heparin. After ultraviolet irradiation, the HappY probe crosslinked to the heparin on the plate was detected with fluorescein isothiocyanate-conjugated streptavidin. Furthermore, the photoreactive HappY probe was used to stain cutaneous tissue sections obtained from dermatitis-affected or mastocytoma-affected cats and dogs. The photoreactive HappY probe stained limited resident mast cells in the connective tissue of skin compared with the anti-heparan sulfate monoclonal antibody 10E4, suggesting that the probe can be used to distinguish the structure of heparin in tissues. The interactions between glycosaminoglycans and proteins in vivo tend to be weak. Therefore, our method for enhancing such weak interactions may be a promising tool for intermolecular interaction studies in glycobiology research.

Pectin from Prunus domestica L. induces proliferation of IEC-6 cells through the alteration of cell-surface heparan sulfate on differentiated Caco-2 cells in co-culture.

Dietary fiber intake provides various physiological and metabolic effects for human health. Pectin, a water-soluble dietary fiber, induces morphological changes of the small intestine in vivo. However, the molecular mechanisms underlying pectin-derived morphological alterations have not been elucidated. Previously, we found that pectin purified from Prunus domestica L. altered the sulfated structure of cell-surface heparan sulfate (HS) on differentiated Caco-2 cells via fibronectin and α5ß1 integrin. In this study, we investigated the biological significance of the effect of pectin on HS in differentiated Caco-2 cells. An in vitro intestinal epithelium model was constructed by co-culture of differentiated Caco-2 cells and rat IEC-6 cells, which were used as models of intestinal epithelium and intestinal crypt cells, respectively. We found that pectin-treated differentiated Caco-2 cells promoted growth of IEC-6 cells. Real-time RT-PCR analysis and western blotting showed that relative mRNA and protein expression levels of Wnt3a were upregulated by pectin treatment in differentiated Caco-2 cells. Analysis by surface plasmon resonance spectroscopy demonstrated that pectin-induced structural alteration of HS markedly decreased the interaction with Wnt3a. However, depression in the secretion of Wnt3a from Caco-2 cells by anti-Wnt3a antibody did not affect the proliferation of IEC-6 cells in co-culture system. These observations indicated that pectin altered the sulfated structure of cell-surface HS to promote secretion of Wnt3a from differentiated Caco-2 cells and Wnt3a indirectly stimulated the proliferation of IEC-6 cells.

Structure-Activity Relationship Study of the Neuritogenic Potential of the Glycan of Starfish Ganglioside LLG-3 (‡).

LLG-3 is a ganglioside isolated from the starfish Linchia laevigata. To clarify the structure-activity relationship of the glycan of LLG-3 toward rat pheochromocytoma PC12 cells in the presence of nerve growth factor, a series of mono- to tetrasaccharide glycan derivatives were chemically synthesized and evaluated in vitro. The methyl group at C8 of the terminal sialic acid residue was crucial for neuritogenic activity, and the terminal trisaccharide moiety was the minimum active motif. Furthermore, the trisaccharide also stimulated neuritogenesis in human neuroblastoma SH-SY5Y cells via mitogen-activated protein kinase (MAPK) signaling. Phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 was rapidly induced by adding 1 or 10 nM of the trisaccharide. The ratio of phosphorylated ERK to ERK reached a maximum 5 min after stimulation, and then decreased gradually. However, the trisaccharide did not induce significant Akt phosphorylation. These effects were abolished by pretreatment with the MAPK inhibitor U0126, which inhibits enzymes MEK1 and MEK2. In addition, U0126 inhibited the phosphorylation of ERK 1/2 in response to the trisaccharide dose-dependently. Therefore, we concluded that the trisaccharide promotes neurite extension in SH-SY5Y cells via MAPK/ERK signaling, not Akt signaling.

Pectin of Prunus domestica L. alters sulfated structure of cell-surface heparan sulfate in differentiated Caco-2 cells through stimulation of heparan sulfate 6-O-endosulfatase-2.

Although previous reports have suggested that pectin induces morphological changes of the small intestine in vivo, the molecular mechanisms have not been elucidated. As heparan sulfate plays important roles in development of the small intestine, to verify the involvement of heparan sulfate (HS) in the pectin-induced morphological changes of the small intestine, the effects of pectin from Prunus domestica L. on cell-surface HS were investigated using differentiated Caco-2 cells. Disaccharide compositional analysis revealed that sulfated structures of HS were markedly changed by pectin administration. Real-time RT-PCR showed that pectin upregulated human HS 6-O-endosulfatase-2 (HSulf-2) expression and markedly inhibited HSulf-1 expression. Furthermore, inhibition analysis suggested that pretreatment with fibronectin III1C fragment, RGD peptide, and ERK1/2 inhibitor suppressed pectin-induced HSulf-2 expression. These observations indicate that pectin induced the expression of HSulf-2 through the interaction with fibronectin, α5ß1 integrin, and ERK1/2, thereby regulating the sulfated structure of HS on differentiated Caco-2 cells.

Structural alteration of cell surface heparan sulfate through the stimulation of the signaling pathway for heparan sulfate 6-O-sulfotransferase-1 in mouse fibroblast cells.

Heparan sulfate (HS) is a randomly sulfated polysaccharide that is present on the cell surface and in the extracellular matrix. The sulfated structures of HS were synthesized by multiple HS sulfotransferases, thereby regulating various activities such as growth factor signaling, cell differentiation, and tumor metastasis. Therefore, if the sulfated structures of HS could be artificially controlled, those manipulations would help to understand the various functions depending on HS. However, little knowledge is currently available to realize the mechanisms controlling the expression of such enzymes. In this study, we found that the ratio of 6-O-sulfated disaccharides increased at 3 h after adrenaline stimulation in mouse fibroblast cells. Furthermore, adrenaline-induced up-regulation of HS 6-O-sulfotransferase-1 (6-OST-1) was controlled by Src-ERK1/2 signaling pathway. Finally, inhibiting the signaling pathways for 6-OST-1 intentionally suppressed the adrenaline-induced structural alteration of HS. These observations provide fundamental insights into the understanding of structural alterations in HS by extracellular cues.

Novel role of homogalacturonan region of pectin in disrupting the interaction between fibronectin and integrin ß1.

Pectin interacts with fibronectin (FN), a modular protein in the extracellular matrix. This interaction is significant as FN plays a pivotal role by binding to the receptor integrin α5ß1. However, the molecular mechanism underlying the pectin-FN interaction and its impact on integrin binding remains unknown. In this study, water-soluble pectins (WSPs) were extracted from three different pectin sources and subsequently characterized. These included Citrus WSP, which primarily comprises the homogalacturonan region, and Kaki and Yuzu WSPs, both of which are rich in rhamnogalacturonan regions. We investigated the molecular interactions between these WSPs and two FN fragments, Anastellin and RetroNectin, using surface plasmon resonance analysis. Citrus WSP exhibited a notable binding affinity to FN, with a dissociation constant (KD) of approximately 10-7 M. In contrast, Kaki and Yuzu WSPs displayed comparatively weaker or negligible binding affinities. The binding reactivity of Citrus WSP with FN was notably diminished following the enzymatic removal of its methyl-ester groups. Additionally, Citrus WSP disrupted the binding of integrin ß1 to RetroNectin without altering the affinity, despite its minimal direct binding to integrin itself. This study furthers our understanding of the intricate pectin-FN interaction and sheds light on their potential physiological relevance and impact on cellular responses.

Simple method for refining arabinan polysaccharides by alcohol extraction of the prune, Prunus domestica L.

L-Arabinose is a useful sugar in the food industry. We demonstrate here simple methods for refining arabinan polysaccharides by alcohol extraction from prune, Prunus domestica L., as a source of L-arabinose. Alcohol-soluble polysaccharides were purified from a solution of prune extracted by 80% ethanol. After fractionating the polysaccharides by ion-exchange chromatography, arabinans were identified as mainly constituted by (1→5)-linked arabinofuranosyl units.

A preparation of cow's late colostrum fraction containing αs1-casein promoted the proliferation of cultured rat intestinal IEC-6 epithelial cells.

Colostrum is a complex mixture of bioactives that promotes neonate growth. Recently, we have found by in vivo study that skimmed, sterilized, and concentrated bovine late colostrum (SCBLC), obtained from a Holstein herd on days 6-7 after parturition, had an ability to maintain intestinal integrity. In the present study we investigated effects of SCBLC on rat intestinal IEC-6 cell proliferation in vitro. A fraction containing αs1-casein was found to have a robust stimulation effect as compared to other protein fractions from SCBLC and even the αs1-casein fraction from milk from other Holstein herds. Furthermore, the SCBLC αs1-casein molecule demonstrated not only slightly slower mobility on both SDS- and native-PAGE than other bovine milk αs1-caseins, but also a peculiar conformation reminiscent of moltenglobule in the circular dichroism spectrum. These findings may be of relevant to the competence of SCBLC to preserve intestinal integrity.

Pectin Modulates Calcium Absorption in Polarized Caco-2 Cells via a Pathway Distinct from Vitamin D Stimulation.

Pectin, a type of soluble fiber, promotes morphological changes in the small intestinal villi. Although its physiological significance is unknown, we hypothesized that changes in villus morphology enhance the efficiency of nutrient absorption in the small intestine and investigated the effect of pectin derived from persimmon on calcium absorption using polarized Caco-2 cells. In polarized Caco-2 cells, pectin altered the mRNA expression levels of substances involved in calcium absorption and the regulation of intracellular calcium concentration and significantly reduced calcium absorption. Although this was comparable to the results of absorption and permeability associated with the addition of active vitamin D, the simultaneous action of pectin and active vitamin D did not show any additive effects. Furthermore, as active vitamin D significantly increases the activity of intestinal alkaline phosphatase (ALP), which is known to be involved in the regulation of intestinal absorption of calcium and lipids, we also investigated the effect of pectin on intestinal ALP activity. As a result, it was found that, unlike the effect of active vitamin D, pectin significantly reduced intestinal ALP activity. These results suggest that pectin stimulates polarized Caco-2 cells through a mechanism distinct from the regulation of calcium absorption by vitamin D, modulating total calcium absorption from the elongated villi through morphological changes in the small intestine by suppressing it at the cellular level.

The effect of edible bird's nests on the expression of MHC-II and costimulatory molecules of C57BL/6 mouse splenocytes.

The glutinous nest that builds by the saliva secretion of swiftlet is recognizable as an edible bird's nest (EBN). It enriched a medicinal value and was regarded as supplementary food that exerts various beneficial health effects, especially immune boosters. This study's objective was to determine the impact of EBN on the expression of MHC-II and costimulatory molecules (CD86 and CD80) related to the initiation of T-cell activation. Both rEBN and pEBN samples were prepared with simulated gastrointestinal digestion for enhancing the bioaccessibility of bioactive compounds. Our result showed that digested EBN samples slightly influence the upregulation of MHC-II, CD86, and CD80 in gene expression of LPS-stimulated Raw 264.7 cells. The concern of endotoxin contamination in EBN samples, which may cause a false-positive result, was measured by quantitative PCR. We found that the inflammatory genes (IL-1ß and TNF-α) were not induced by EBN treatments. Moreover, cell surface protein expression in splenocytes treated with EBN was assessed using flow cytometric analysis. Digested EBN samples demonstrated their capacity to promote the elevation of MHC-II, CD86, and CD80 cell surface protein expression. Finally, the digested-EBN-treated splenocytes only exhibited a specific response in the T-cells population. Thus, EBN is a source of the bioactive compound that has been proposed to exert a role in the stimulation of both MHC-II and costimulatory molecules for TCR/pMHC-II interaction leading to T-cell activation.

A peptide found by phage display discriminates a specific structure of a trisaccharide in heparin.

A number of recent studies have shown that heparan sulfate can control several important biological events on the cell surface through changes in sulfation pattern. The in vivo modification of sugar chains with sulfates, however, is complicated, and the discrimination of different sulfation patterns is difficult. Heparin, which is primarily produced by mast cells, is closely approximated by the structural analog heparan sulfate. Screening of heparin-associating peptides using phage display and antithrombin-bound affinity chromatography identified a peptide, heparin-associating peptide Y (HappY), that acts as a target of immobilized heparin. The peptide consists of 12 amino acid residues with characteristic three arginines and exclusively binds to heparin and heparan sulfate but does not associate with other glycosaminoglycans. HappY recognizes three consecutive monosaccharide residues in heparin through its three arginine residues. HappY should be a useful probe to detect heparin and heparan sulfate in studies of glycobiology.

Comparison of the efficacy of alpha-lactalbumin from equine, bovine, and human milk in the growth of intestinal IEC-6 cells.

Native alpha-lactalbumins (α-LA) from equine, bovine, and human milk were not cytotoxic. However, after treatment with trifluoroethanol (TFE), all three α-LAs exhibited cytotoxicity. Toxic potencies were distinctly different among them. Equine α-LA was the most robust, bovine α-LA was moderate, and human α-LA was weak. There were no significant structural changes as between the native and the TFE-treated α-LAs.

Histochemical Analysis of Heparan Sulfate 3-O-sulfotransferase Expression in Mouse Brain.

In situ hybridization provides information for understanding the localization of gene expression in various tissues. The relative expression levels of mRNAs in a single cell can be sensitively visualized by this technique. Furthermore, since in situ hybridization is a histological technique, tissue structure is maintained after fixation, and it is possible to accurately identify the cell types. We have examined the expression of heparan sulfate sulfotransferases by in situ hybridization to better understand the functions of heparan sulfate in the development of mouse nervous system. This chapter describes methods of in situ hybridization analyses using cRNA probes labeled with non-radioactive nucleotides.

An assay for detecting neutralization of rotavirus infection by quantitative determination of VP6 protein fluorescence intensity.

Previous rotavirus infection studies used the focus reduction assay extensively to evaluate cellular responses to viral infection, but this technique has a number of limitations. In this study, we developed a simplified, accurate rotavirus infection assay to evaluate the effects of inhibitory substances on rotavirus infection in vitro by measurement of the fluorescence intensities of stained cells.

Non-reducing terminal fucose within N-linked glycan plays a significant role in the recognition of human milk lactoferrin by the 1CF11 monoclonal antibody.

We have recently demonstrated that the 1CF11 monoclonal antibody bound human milk lactoferrin (hLf) through the recognition of two distinct portions of the molecule, namely the N-glycan-relevant and -irrelevant structural elements. In this present study, we prepared four immunoreactive peptide fractions containing N-linked glycan from tryptic digests of reduced and alkylated hLf by using a concanavalin A lectin column and reverse-phase HPLC. Deglycosylation of these fractions and a competitive binding assay using fucosylated oligosaccharides revealed that the non-reducing terminal fucose residue in N-linked glycan(s) played a significant role in recognizing the N-glycan-relevant element in hLf by 1CF11.

Involvement of both the N-glycan-relevant and N-glycan-irrelevant structural elements in the recognition of human milk lactoferrin by the 1CF11 monoclonal antibody.

Monoclonal antibody 1CF11 has been suggested to specifically recognize a certain carbohydrate epitope shared by glycoproteins in human external secretions. We examined the effect of cleaving the polypeptide backbone and removing N-linked oligosaccharides on the reactivity with 1CF11 of human milk lactoferrin (hLf) to elucidate the structural features of the 1CF11 epitope. We reveal by treating hLF with trypsin and/or N-glycosidase that both the N-glycan-relevant and N-glycan-irrelevant structural elements were involved in the recognition of hLf by 1CF11.