The inhibitory effects of a rhamnogalacturonan I (RG-I) domain from ginseng pectin on galectin-3 and its structure-activity relationship

Oligosaccharides from Stellaria dichotoma L. var. lanceolate bind to galectin-3 and ameliorate effects of colitis

Even though Stellaria dichotoma L. var. lanceolate (S. dichotoma) is a well-known medicinal plant in the family Caryophyllaceae, its oligosaccharides remain unexplored in terms of their potential as bioactive agents. Here, we isolated a mixture of oligosaccharides from S. dichotoma (Yield: 12 % w/w), that are primarily non-classical raffinose family oligosaccharides (RFOs). Nine major oligosaccharides were purified and identified from the mixture, including sucrose, raffinose, 1-planteose, lychnose, stellariose, along with four new non-classical RFOs. Two of the four new oligosaccharides are linear hexose pentamers with α-galactosyl extensions on their lychnose moieties, and the other two are branched hexose hexamers with α-galactosyl extensions on their stellariose groups. Their interactions with galectin-3 (Gal-3) revealed significant binding, with the terminal galactose providing enhanced affinity for the lectin. Notably, Gal-3 residues Arg144, His158, Asn160, Arg162, Asn174, Trp181, Glu184 and Arg186 coordinate with the lychnose. In vivo studies using the dextran sulfate sodium (DSS) mouse model for colitis demonstrated the ability of these carbohydrates in mitigating ulcerative colitis (UC). Overall, our study has provided structural information and potential applications of S. dichotoma oligosaccharides, also offers new approaches for the development of medicinal oligosaccharides.

Intestinal lymphatic transport of Smilax china L. pectic polysaccharide via Peyer's patches and its uptake and transport mechanisms in mononuclear phagocytes

Recently, the intestinal lymphatic transport based on Peyer's patches (PPs) is emerging as a promising absorption pathway for natural polysaccharides. Herein, the aim of this study is to investigate the PP-based oral absorption of a pectic polysaccharide from Smilax china L. (SCLP), as well as its uptake and transport mechanisms in related immune cells. Taking advantages of the traceability of fluorescently labeled SCLP, we confirmed that SCLP could be absorbed into PPs and captured by their mononuclear phagocytes (dendritic cells and macrophages) following oral administration. Subsequently, the systematic in vitro study suggested that the endocytic mechanisms of SCLP by model mononuclear phagocytes (BMDCs and RAW264.7 cells) mainly involved caveolae-mediated endocytosis, macropinocytosis and phagocytosis. More importantly, SCLP directly binds and interacts with toll-like receptor 2 (TLR2) and galectin 3 (Gal-3) receptor, and was taken up by mononuclear phagocytes in receptor-mediated manner. After internalization, SCLP was intracellularly transported primarily through endolysosomal pathway and ultimately localized in lysosomes. In summary, this work reveals novel information and perspectives about the in vivo fate of SCLP, which will contribute to further research and utilization of SCLP and other pectic polysaccharides.

Breaking barriers: How modified citrus pectin inhibits galectin-8

Inhibition of galectin-3-mediated interactions by modified citrus pectin (MCP) could affect several rate-limiting steps in cancer metastasis, but the ability of MCP to antagonize galectin-8 function remains unknown. We hypothesized that MCP could bind to galectin-8 in addition to galectin-3. In this study, a combination of gradual ethanol precipitation and DEAE-Sepharose Fast Flow chromatography was used to isolate several fractions from MCP. The ability of these fractions to antagonize galectin-8 function was studied as well as the primary structure and initial structure-function relationship of the major active component MCP-30-3. The results showed that MCP-30-3 (168 kDa) was composed of Gal (13.8%), GalA (63.1%), GlcA (13.0%), and Glc (10.1%). MCP-30-3 could specifically bind to galectin-8, with an MIC value of 0.04 mg mL-1. After MCP-30-3 was hydrolyzed by β-galactosidase or pectinase, its binding activity was significantly reduced. These results provide new insights into the interaction between MCP structure and galectin function, as well as the potential utility in the development of functional foods.

Characterization and emulsifying ability evaluation of whey protein-pectin conjugates formed by glycosylation

Glycosylation is a method that enhances the functional properties of proteins by covalently attaching sugars to them. This study aimed at preparing three conjugates (WP-HG, WP-SBP, and WP-RGI) by dry heating method to research the influence of different pectin structures on the functional properties of WP and characterize properties and structures of these conjugates. The research results manifested that the degree of glycosylation (DG) of HG, SBP and RGI were 13.13 % ± 0.07 %, 23.27 % ± 0.3 % and 36.39 % ± 0.3 % respectively, suggesting that the increase of the number of branch chains promoted the glycosylation reaction. The formation of the conjugate was identified by the FT-IR spectroscopy technique. And SEM showed that WP could covalently bind to pectin, resulting in a smoother and denser surface of the conjugates. The circular dichroism analysis exhibited that the glycosylation reaction altered the secondary structure of WP and decreased the α-Helix content. This structural change in the protein spatial conformation led to a decrease in the hydrophobicity of protein surface. But the addition of pectin further regulated the hydrophilic-hydrophobic ratio on the surface of the protein, thus improving the emulsification properties of WP. In addition, the glycosylation could improve the stability of the emulsion, giving it a smaller droplet size, higher Zeta-potential and more stable properties. In a word, this study pointed out the direction for the application of different pectin structures in the development of functional properties of glycosylation products in food ingredients.

Ginseng-derived type I rhamnogalacturonan polysaccharide binds to galectin-8 and antagonizes its function

Background

Panax ginseng Meyer polysaccharides exhibit various biological functions, like antagonizing galectin-3-mediated cell adhesion and migration. Galectin-8 (Gal-8), with its linker-joined N- and C-terminal carbohydrate recognition domains (CRDs), is also crucial to these biological processes, and thus plays a role in various pathological disorders. Yet the effect of ginseng-derived polysaccharides in modulating Gal-8 function has remained unclear.

Methods

P. ginseng-derived pectin was chromatographically isolated and enzymatically digested to obtain a series of polysaccharides. Biolayer Interferometry (BLI) quantified their binding affinity to Gal-8, and their inhibitory effects on Gal-8 was assessed by hemagglutination, cell migration and T-cell apoptosis.

Results

Our ginseng-derived pectin polysaccharides consist mostly of rhamnogalacturonan-I (RG-I) and homogalacturonan (HG). BLI shows that Gal-8 binding rests primarily in RG-I and its β-1,4-galactan side chains, with sub-micromolar KD values. Both N- and C-terminal Gal-8 CRDs bind RG-I, with binding correlated with Gal-8-mediated function.

Conclusion

P. ginseng RG-I pectin β-1,4-galactan side chains are crucial to binding Gal-8 and antagonizing its function. This study enhances our understanding of galectin-sugar interactions, information that may be used in the development of pharmaceutical agents targeting Gal-8.

Toxicological evaluation of a pumpkin-derived pectin preparation: in vitro genotoxicity studies and a 13-week oral toxicity study in Sprague-Dawley rats

The safety of a rhamnogalacturonan-I-enriched pectin extract (G3P-01) from pumpkin (Cucurbita moschata var. Dickinson) was evaluated for use as an ingredient in food and dietary supplements. G3P-01 was tested in a battery of genetic toxicity studies including reverse mutagenicity and in vitro micronucleus assay. In addition, Sprague-Dawley rats were randomized and orally dosed with G3P-01 incorporated in animal diet at concentrations of 0, 9000, 18,000, and 36,000 ppm daily for 13-weeks (n=10/sex/group) in line with OECD guidelines (TG 408). The results of the in vitro bacterial reverse mutation assay and micronucleus assay in TK6 cells demonstrated a lack of genotoxicity. The 13-week oral toxicity study in Sprague-Dawley rats demonstrated that the test article, G3P-01 was well tolerated; there were no mortalities and no adverse effects on clinical, gross pathology, hematology, blood chemistry, and histological evaluation of the essential organs of the animals. The present study demonstrates that G3P-01 is non-genotoxic and is safe when ingested in diet at concentrations up to 36, 000 ppm. The subchronic no-observed-adverse-effect level (NOAEL) for G3P-01 was concluded to be 36,000 ppm, equivalent to 1,899 and 2,361 mg/kg/day for male and female rats respectively.

Isomerization of proline-46 in the N-terminal tail of galectin-3 enhances T cell apoptosis via the ROS-ERK pathway

Galectin-3 (Gal-3) is unique in the galectin family, due to the presence of a long N-terminal tail (NT) arising from its conserved carbohydrate recognition domain (CRD). Although functional significance of the NT has remained elusive, our previous studies demonstrated the importance of NT prolines to Gal-3 function. Here, we show that during the time Gal-3 stands in solution for three or more days, Gal-3 NT undergoes a slow, intra-molecular, time-dependent conformational/dynamical change associated with proline cis-trans isomerization. From initial dissolution of Gal-3 in buffer to three days in solution, Gal-3-mediated T cell apoptosis is enhanced from 23 % to 37 %. Western blotting and flow cytometry show that the enhancement occurs via the ROS-ERK pathway, and not by the PKC-ERK pathway. To assess which proline(s) is (are) responsible for this effect, we individually mutated all 14 NT prolines within the first 68 residues to alanines, and assessed their effect on ROS production. Our study shows that isomerization of P46 alone is responsible for the upregulation of ROS and T cell apoptosis. NMR studies show that this unique effect is mediated by a change in dynamic interactions between the NT and CRD F-face, which in turn leads to this change in Gal-3 function.

Modified pectin with anticancer activity in breast cancer: A systematic review

Breast cancer is the most commonly diagnosed cancer among women worldwide. The current pharmacological treatments for breast cancer have numerous adverse effects and are not always effective. Recently, the anticancer activity of modified pectins (MPs) against various types of cancers, including breast cancer, has been investigated. This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) model, including scientific articles from the last 22 years that measured the anticancer activity of MPs on breast cancer. The articles were searched in four databases with the terms: "modified pectin" and "breast cancer". Nine articles were included, five in vitro and four mixed (in vitro and in vivo). Different models and methods by which anticancer activity was measured were analyzed. All the studies reported positive results in both cell lines and in vivo murine models of breast cancer. The extracted data suggest a positive effect and provide mechanistic evidence of MPs in the treatment of breast cancer. However, as limited number of studies were included, further in vivo studies are required to obtain more conclusive preclinical evidence.

The Role of Galectin-3 in Heart Failure-The Diagnostic, Prognostic and Therapeutic Potential-Where Do We Stand?

Heart failure (HF) is a clinical syndrome with high morbidity and mortality, and its prevalence is rapidly increasing. Galectin-3 (Gal-3) is an important factor in the pathophysiology of HF, mainly due to its role in cardiac fibrosis, inflammation, and ventricular remodeling. Fibrosis is a hallmark of cardiac remodeling, HF, and atrial fibrillation development. This review aims to explore the involvement of Gal-3 in HF and its role in the pathogenesis and clinical diagnostic and prognostic significance. We report data on Gal-3 structure and molecular mechanisms of biological function crucial for HF development. Over the last decade, numerous studies have shown an association between echocardiographic and CMR biomarkers in HF and Gal-3 serum concentration. We discuss facts and concerns about Gal-3's utility in acute and chronic HF with preserved and reduced ejection fraction for diagnosis, prognosis, and risk stratification. Finally, we present attempts to use Gal-3 as a therapeutic target in HF.

A critical review of RG-I pectin: sources, extraction methods, structure, and applications

In recent years, RG-I pectin isolated by low-temperature alkaline extraction methods has attracted the attention of a large number of researchers due to its huge health benefits. However, studies on other applications of RG-I pectin are still lacking. In this study, we summarized the sources (e.g. potato pulp, sugar beet pulp, okra, apple pomace, citrus peel, pumpkin, grapefruit, ginseng, etc.), extraction methods, fine structure and applications of RG-I pectin in physiological activities (e.g. anti-cancer, anti-inflammatory, anti-obesity, anti-oxidation, immune regulation, prebiotics, etc.), emulsions, gels, etc. These neutral sugar side chains not only endow RG-I pectin with various physiological activities but the entanglement and cross-linking of these side chains also endow RG-I pectin with excellent emulsifying and gelling properties. We believe that this review can not only provide a comprehensive reading for new workers interested in RG-I pectin, but also provide a valuable reference for future research directions of RG-I pectin.

The differences between the water- and alkaline-soluble Poria cocos polysaccharide: A review

Poria cocos (PC) refers to a fungal species which is also known as "Fuling" in China. For >2000 years, PC has demonstrated its therapeutic values as a kind of traditional medicine. It is believed that the various biological benefits created by PCs highly rely on the Poria cocos polysaccharide (PCP). This review recapitulates the recent progress made in PCP in four aspects: i) the methods of extraction, separation, and purification, ii) structural characterization and identification, iii) the related bioactivities and mechanism of action, and iv) structure-activity relationships. Through discussion about the objective as mentioned above, it can be found out that PCP is categorized into water-soluble polysaccharide (WPCP) and alkaline-soluble polysaccharide (APCP), which are totally different in structure and bioactivity. The structures of WPCP are multiplicity whose backbone can be (1,6)-α-galactan and (1,3)-β-mannoglucan etc. to perform various bioactivities including anti-tumor effect, anti-depressant effect, anti-Alzheimer effect, anti-atherosclerosis effect, hepatoprotection etc. The structures of APCP are much more single with backbone of (1,3)-β-D-glucan and the studies of activity concentrate on anti-tumor effect, anti-inflammatory effect and immunomodulation. Besides, the future opportunities of WPCP are primary structure identification. For APCP, scholars can focus on the conformation of polysaccharide and its relationship with activity.

A ginseng-derived rhamnogalacturonan I (RG-I) pectin promotes longevity via TOR signalling in Caenorhabditis elegans

Panax ginseng C. A. Meyer (ginseng), a traditional Chinese herb, is usually used to improve health and increase anti-aging activity for human. Polysaccharides are bioactive components of ginseng. Herein, using Caenorhabditis elegans as a model, we discovered a ginseng-derived rhamnogalacturonan I (RG-I) pectin WGPA-1-RG promoted longevity via TOR signalling pathway with transcription factors FOXO/DAF-16 and Nrf2/SKN-1 accumulated in the nucleus, where they activated target genes. And the WGPA-1-RG-mediated lifespan extension was dependent on endocytosis, rather than a bacterial metabolic process. Glycosidic linkage analyses combined with arabinose- and galactose-releasing enzyme hydrolyses identified the RG-I backbone of WGPA-1-RG was primarily substituted with α-1,5-linked arabinan, β-1,4-linked galactan and arabinogalactan II (AG-II) side chains. Feeding worms with the WGPA-1-RG-derived fractions which lost distinct structural elements by enzymatic digestions, we found the arabinan side chains prominently contributed to the longevity-promoting activity of WGPA-1-RG. These findings provide a novel ginseng-derived nutrient that potentially increases human longevity.

The Preparation and Potential Bioactivities of Modified Pectins: A Review

Pectins are complex polysaccharides that are widely found in plant cells and have a variety of bioactivities. However, the high molecular weights (Mw) and complex structures of natural pectins mean that they are difficult for organisms to absorb and utilize, limiting their beneficial effects. The modification of pectins is considered to be an effective method for improving the structural characteristics and promoting the bioactivities of pectins, and even adding new bioactivities to natural pectins. This article reviews the modification methods, including chemical, physical, and enzymatic methods, for natural pectins from the perspective of their basic information, influencing factors, and product identification. Furthermore, the changes caused by modifications to the bioactivities of pectins are elucidated, including their anti-coagulant, anti-oxidant, anti-tumor, immunomodulatory, anti-inflammatory, hypoglycemic, and anti-bacterial activities and the ability to regulate the intestinal environment. Finally, suggestions and perspectives regarding the development of pectin modification are provided.

Structure-specific antitumor effects and potential gut microbiota-involved mechanisms of ginseng polysaccharides on B16F10 melanoma-bearing mice

Ginseng polysaccharides (GPs) have shown gut microbiota-related antitumor effects. However, the relation between their structures and antitumor functions remains unknown. Here, crude polysaccharide (GP-c) and its fractions neutral polysaccharide (GP-n) and pectin (GP-a) were prepared for structure characterization and anti-B16F10 melanoma effect evaluation, and their influence on gut microbiota diversities and short-chain fatty acids (SCFAs) were also analyzed. Spearman correlations among the altered gut microbiota, SCFAs, and antitumor effects were conducted to elucidate the structure-function relationships. It was shown that the structures of GP-c, GP-n, and GP-a varied in monosaccharide composition and molecular weight distribution. GP-n and GP-c showed anti-melanoma effects, whereas GP-a promoted its growth slightly. GP-n and GP-c restored SCFAs levels such as acetic acid and butyric acid; moreover, it improved the gut microbiota ecosystem by upregulating the abundance of Allobaculum and Bifidobacterium. However, the restoration effect of GP-a was weak, or even worse. In addition, these two bacteria were negatively correlated with the tumor weight and related with the altered SCFAs. In conclusion, GP-n is essential for the anti-melanoma effects of GP, and the potential mechanisms might be related with its specific regulation of Allobaculum and Bifidobacterium abundance, and tumor-associated SCFAs levels. The outcomes highlighted here enable a deeper insight into the structure-function relationship of GP and propose new opinions on its antitumor effect.

Inhibition of galectins in cancer: Biological challenges for their clinical application

Galectins play relevant roles in tumor development, progression and metastasis. Accordingly, galectins are certainly enticing targets for medical intervention in cancer. To date, however, clinical trials based on galectin inhibitors reported inconclusive results. This review summarizes the galectin inhibitors currently being evaluated and discusses some of the biological challenges that need to be addressed to improve these strategies for the benefit of cancer patients.

Fibrin-Rhamnogalacturonan I Composite Gel for Therapeutic Enzyme Delivery to Intestinal Tumors

Therapy of colorectal cancer with protein drugs, including targeted therapy using monoclonal antibodies, requires the preservation of the drug's structure and activity in the gastrointestinal tract or bloodstream. Here, we confirmed experimentally the fundamental possibility of creating composite protein-polysaccharide hydrogels based on non-degrading rhamnogalacturonan I (RG) and fibrin as a delivery vehicle for antitumor RNase binase. The method is based on enzymatic polymerization of fibrin in the presence of RG with the inclusion of liposomes, containing an encapsulated enzyme drug, into the gel network. The proposed method for fabricating a gel matrix does not require the use of cytotoxic chemical cross-linking agents and divalent cations, and contains completely biocompatible and biodegradable components. The process proceeds under physiological conditions, excluding the effect of high temperatures, organic solvents and ultrasound on protein components. Immobilization of therapeutic enzyme binase in the carrier matrix by encapsulating it in liposomes made from uncharged lipid made it possible to achieve its prolonged release with preservation of activity for a long time. The release time of binase from the composite carrier can be regulated by variation of the fibrin and RG concentration.

Pectin-based bioinks for 3D models of neural tissue produced by a pH-controlled kinetics

Introduction: In the view of 3D-bioprinting with cell models representative of neural cells, we produced inks to mimic the basic viscoelastic properties of brain tissue. Moving from the concept that rheology provides useful information to predict ink printability, this study improves and expands the potential of the previously published 3D-reactive printing approach by introducing pH as a key parameter to be controlled, together with printing time. Methods: The viscoelastic properties, printability, and microstructure of pectin gels crosslinked with CaCO3 were investigated and their composition was optimized (i.e., by including cell culture medium, HEPES buffer, and collagen). Different cell models representative of the major brain cell populations (i.e., neurons, astrocytes, microglial cells, and oligodendrocytes) were considered. Results and Discussion: The outcomes of this study propose a highly controllable method to optimize the printability of internally crosslinked polysaccharides, without the need for additives or post-printing treatments. By introducing pH as a further parameter to be controlled, it is possible to have multiple (pH-dependent) crosslinking kinetics, without varying hydrogel composition. In addition, the results indicate that not only cells survive and proliferate following 3D-bioprinting, but they can also interact and reorganize hydrogel microstructure. Taken together, the results suggest that pectin-based hydrogels could be successfully applied for neural cell culture.

Highlights on the Role of Galectin-3 in Colorectal Cancer and the Preventive/Therapeutic Potential of Food-Derived Inhibitors

Colorectal cancer (CRC) is a leading cause of death worldwide. Despite advances in surgical and therapeutic management, tumor metastases and resistance to therapy still represent major hurdles. CRC risk is highly modifiable by lifestyle factors, including diet, which strongly influences both cancer incidence and related mortality. Galectin-3 (Gal-3) is a multifaceted protein involved in multiple pathophysiological pathways underlying chronic inflammation and cancer. Its versatility is given by the ability to participate in a wide range of tumor-promoting processes, including cell-cell/cell-matrix interactions, cell growth regulation and apoptosis, and the immunosuppressive tumor microenvironment. This review provides an updated summary of preclinical and observational human studies investigating the pathogenetic role of Gal-3 in intestinal inflammation and CRC, as well as the potential of Gal-3 activity inhibition by plant-source food-derived bioactive compounds to control CRC onset/growth. These studies highlight both direct and immuno-mediated effects of Gal-3 on tumor growth and invasiveness and its potential role as a CRC prognostic biomarker. Substantial evidence indicates natural food-derived Gal-3 inhibitors as promising candidates for CRC prevention and therapy. However, critical issues, such as their bioavailability and efficacy, in controlled human studies need to be addressed to translate research progress into clinical applications.

Transcriptome reveals insights into biosynthesis of ginseng polysaccharides

BACKGROUND

Ginseng polysaccharides, have been used to treat various diseases as an important active ingredient. Nevertheless, the biosynthesis of ginseng polysaccharides is poorly understood. To elucidate the biosynthesis mechanism of ginseng polysaccharides, combined the transcriptome analysis and polysaccharides content determination were performed on the roots, stems, and leaves collected from four cultivars of ginseng.

RESULTS

The results indicated that the total contents of nine monosaccharides were highest in the roots. Moreover, the total content of nine monosaccharides in the roots of the four cultivars were different but similar in stems and leaves. Glucose (Glc) was the most component of all monosaccharides. In total, 19 potential enzymes synthesizing of ginseng polysaccharides were identified, and 17 enzymes were significantly associated with polysaccharides content. Among these genes, the expression of phosphoglucomutase (PGM), glucose-6-phosphate isomerase (GPI), UTP-glucose-1-phosphate uridylyltransferase (UGP2), fructokinase (scrK), mannose-1-phosphate guanylyltransferase (GMPP), phosphomannomutase (PMM), UDP-glucose 4-epimerase (GALE), beta-fructofuranosidase (sacA), and sucrose synthase (SUS) were correlated with that of MYB, AP2/ERF, bZIP, and NAC transcription factors (TFs). These TFs may regulate the expression of genes involved in ginseng polysaccharides synthesis.

CONCLUSION

Our findings could provide insight into a better understanding of the regulatory mechanism of polysaccharides biosynthesis, and would drive progress in genetic improvement and plantation development of ginseng.

An Overview of Antitumour Activity of Polysaccharides

Cancer incidence and mortality are rapidly increasing worldwide; therefore, effective therapies are required in the current scenario of increasing cancer cases. Polysaccharides are a family of natural polymers that hold unique physicochemical and biological properties, and they have become the focus of current antitumour drug research owing to their significant antitumour effects. In addition to the direct antitumour activity of some natural polysaccharides, their structures offer versatility in synthesizing multifunctional nanocomposites, which could be chemically modified to achieve high stability and bioavailability for delivering therapeutics into tumor tissues. This review aims to highlight recent advances in natural polysaccharides and polysaccharide-based nanomedicines for cancer therapy.

Galactofuranose side chains in galactomannans from Penicillium spp. modulate galectin-8-mediated bioactivity

Polysaccharides from fungi have many bioactivities. Previous studies showed that galactomannans from Penicillium oxalicum antagonize galectin-8-mediated activity. Here, two intracellular and two extracellular galactomannans were purified and their structures were comparatively characterized by NMR, partial acid hydrolysis and methylation. All four of them were identified to be galactomannans with similar mannan backbones having 1,2-/1,6-linkages (~3:1) and various amounts of galactofuranan side chains. The interaction of those polysaccharides with galectin-8 was assessed by hemagglutination and biolayer interferometry. These results show that side chains are important for the interaction, and the more the side chains, the stronger the interaction. But the side chains alone did not show act on galectin-8, which indicated that the cooperation between backbone and side chains is another necessary factor for this interaction. Our findings provide important information about structure-activity relationships and the galactofuranose-containing galactomannans might be as potential therapeutic of galectin-8 related diseases.

Polysaccharide from Spirulina platensis Evokes Antitumor Activity in Gastric Cancer Cells via Modulation of Galectin-3 and Exhibited Cyto/DNA Protection: Structure-Function Study

Polysaccharides play significant role in the management of different cancer types including gastric cancer. Here, we report the effect of spirulina polysaccharide (Sp) on galectin-3 modulatory activity in gastric cancer cells (AGS). The isolated Sp possessed an average molecular weight of 1457 kDa and galactose (42%) as a major sugar consisting of (β1-4d) units with a galactoarabinorhamnoglycan backbone. The Sp inhibited the proliferation of AGS cells by 48% without affecting normal NIH/3T3 cells as compared to doxorubicin, a known anticancer drug. Also, Sp exhibited significant (p < 0.05) galectin-3 mediated hemeagglutination inhibition with MIC of 9.37 μg/mL compared to galactose (6.25 μg/mL), a sugar specific to galectin-3. Galactose showed the highest molecular interaction with galectin-3 in the in silico study. In addition, Sp exhibited the cytoprotection in RBCs, buccal cells, and DNA exposed to oxidants. These findings suggest that Sp offers a promising therapeutic tool in the management of gastric cancer.

Homogalacturonan from squash: Characterization and tau-binding pattern of a sulfated derivative

A pectic polysaccharide (WAP) was isolated from squash and identified as a homogalacturonan with a molecular mass of 83.2 kDa by GPC, monosaccharide composition analysis, FT-IR and NMR spectra. Sulfation modification of WAP was carried out and a sulfated derivative (SWAP) was obtained with a substitution degree of 1.81. The NMR spectrum indicated that the sulfation modification mainly occurred at the C-2 and C-3 positions of galacturonan residues. The binding pattern of SWAP to tau K18 protein was observed in 2D 1H15N HSQC spectra of tau, which resembled the tau-heparin interaction, with R2 domain as the major binding region. These results suggest that SWAP has the potential to act as a heparin mimic to inhibit the transcellular spread of tau; thus natural polysaccharide from squash may be developed into therapies for AD and related tauopathies.

Comparative study of water-soluble polysaccharides isolated from leaves and roots of Isatis indigotica Fort

Water-soluble polysaccharides were isolated from the leaves and roots of Isatis indigotica Fort., and their structural features were studied and compared. One neutral polysaccharide fraction (WFIP-N) and three pectin fractions (WFIP-A-A, WFIP-A-B and WFIP-A-C) were obtained from the leaves, and one neutral polysaccharide fraction (WRIP-N) and two pectin fractions (WRIP-A-A and WRIP-A-B) were obtained from the roots. WFIP-A-B (Mw = 34.6 kDa) and WRIP-A-B (Mw = 29.9 kDa) were the major pectic polysaccharides. Monosaccharide composition, FT-IR, enzymatic hydrolysis, NMR and methylation analysis indicated that both WFIP-A-B and WRIP-A-B are composed of rhamnogalacturonan I (RG-I), rhamnogalacturonan II (RG-II) and homogalacturonan (HG) domains with mass ratios of 1.5:1.0:0.4 and 0.3:1.0:1.7, respectively. WFIP-A-B and WRIP-A-B were found to be rich in RG-I and HG domains, respectively, and mainly contained type II arabinogalactan (AG-II) and α-L-1,5-arabinan side chains, but those in WRIP-A-B were more numerous and longer. Our results provide structural features and differences between these polysaccharides which will help to elucidate their functional differences.

Structural features and anticancer mechanisms of pectic polysaccharides: A review

The anticancer activity of pectic polysaccharides (PPs) was proved by numerous studies, and which also indicated that the bioactivity of PPs was closely related to its complicated structures. Based on the summary and analysis about structure characteristics and corresponding enzymatic process of the reported PPs, the anticancer mechanism and related structural features were systematically clarified. It was found that not only the direct effects on the cancer cells by proliferation inhibition or apoptosis, but also the regulation of immune system, gut microbiota and gut metabolism as indirect effects, jointly played important roles in the anticancer of PPs. Nevertheless, during the study of PPs as promising anticancer components, the exact structure-function relationship, digestion process in vivo, and comprehensive action mechanism are still not well understanding. With the unveiling of the proposed issues, it is believed that PPs are promising to be exploited as effective cancer therapy/adjunctive therapy drugs or functional foods.

Immune-instructive copolymer scaffolds using plant-derived nanoparticles to promote bone regeneration

Background

Age-driven immune signals cause a state of chronic low-grade inflammation and in consequence affect bone healing and cause challenges for clinicians when repairing critical-sized bone defects in elderly patients.

Methods

Poly(l-lactide-co-ɛ-caprolactone) (PLCA) scaffolds are functionalized with plant-derived nanoparticles from potato, rhamnogalacturonan-I (RG-I), to investigate their ability to modulate inflammation in vitro in neutrophils and macrophages at gene and protein levels. The scaffolds’ early and late host response at gene, protein and histological levels is tested in vivo in a subcutaneous rat model and their potential to promote bone regeneration in an aged rodent was tested in a critical-sized calvaria bone defect. Significant differences were tested using one-way ANOVA, followed by a multiple-comparison Tukey’s test with a p value ≤ 0.05 considered significant.

Results

Gene expressions revealed PLCA scaffold functionalized with plant-derived RG-I with a relatively higher amount of galactose than arabinose (potato dearabinated (PA)) to reduce the inflammatory state stimulated by bacterial LPS in neutrophils and macrophages in vitro. LPS-stimulated neutrophils show a significantly decreased intracellular accumulation of galectin-3 in the presence of PA functionalization compared to Control (unmodified PLCA scaffolds). The in vivo gene and protein expressions revealed comparable results to in vitro. The host response is modulated towards anti-inflammatory/ healing at early and late time points at gene and protein levels. A reduced foreign body reaction and fibrous capsule formation is observed when PLCA scaffolds functionalized with PA were implanted in vivo subcutaneously. PLCA scaffolds functionalized with PA modulated the cytokine and chemokine expressions in vivo during early and late inflammatory phases. PLCA scaffolds functionalized with PA implanted in calvaria defects of aged rats downregulating pro-inflammatory gene markers while promoting osteogenic markers after 2 weeks in vivo.

Conclusion

We have shown that PLCA scaffolds functionalized with plant-derived RG-I with a relatively higher amount of galactose play a role in the modulation of inflammatory responses both in vitro and in vivo subcutaneously and promote the initiation of bone formation in a critical-sized bone defect of an aged rodent. Our study addresses the increasing demand in bone tissue engineering for immunomodulatory 3D scaffolds that promote osteogenesis and modulate immune responses.

Galectin-3 in Kidney Diseases: From an Old Protein to a New Therapeutic Target

Galectin-3 (Gal-3) is a 30KDa lectin implicated in multiple pathophysiology pathways including renal damage and fibrosis. Gal-3 binds β-galactoside through its carbohydrate-recognition domain. From intra-cellular to extra-cellular localization, Gal-3 has multiple roles including transduction signal pathway, cell-to-cell adhesion, cell to extracellular matrix adhesion, and immunological chemoattractant protein. Moreover, Gal-3 has also been linked to kidney disease in both preclinical models and clinical studies. Gal-3 inhibition appears to improve renal disease in several pathological conditions, thus justifying the development of multiple drug inhibitors. This review aims to summarize the latest literature regarding Gal-3 in renal pathophysiology, from its role as a biomarker to its potential as a therapeutic agent.

The Complex Biological Effects of Pectin: Galectin-3 Targeting as Potential Human Health Improvement?

Galectin-3 is the only chimeric representative of the galectin family. Although galectin-3 has ubiquitous regulatory and physiological effects, there is a great number of pathological environments where galectin-3 cooperatively participates. Pectin is composed of different chemical structures, such as homogalacturonans, rhamnogalacturonans, and side chains. The study of pectin's major structural aspects is fundamental to predicting the impact of pectin on human health, especially regarding distinct molecular modulation. One of the explored pectin's biological activities is the possible galectin-3 protein regulation. The present review focuses on revealing the structure/function relationship of pectins, their fragments, and their biological effects. The discussion highlighted by this review shows different effects described within in vitro and in vivo experimental models, with interesting and sometimes contradictory results, especially regarding galectin-3 interaction. The review demonstrates that pectins are promissory food-derived molecules for different bioactive functions. However, galectin-3 inhibition by pectin had been stated in literature before, although it is not a fully understood, experimentally convincing, and commonly agreed issue. It is demonstrated that more studies focusing on structural analysis and its relation to the observed beneficial effects, as well as substantial propositions of cause and effect alongside robust data, are needed for different pectin molecules' interactions with galectin-3.

Purification, chemical analysis and inhibitory effects on galectin-3 of enzymatic pH-modified citrus pectin

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EMCP is fractionated by ion-exchange and gel permeation chromatographies.

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EMCP fractions contain glucan backbone and different saccharides as side chains.

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RG-II domain may weaken the binding strength between EMCP fractions and Gal-3.

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EMCP-3p and EMCP-2p exhibit strong cytotoxicity against MCF-7 and A549 cell lines.

Modified citrus pectin (MCP), a commercially available dietary supplement prepared from citrus pectin, contains several different polysaccharide domains, but its primary chemical structure and the binding epitopes that antagonize galectin-3 function remain unclear. In this study, five fractions were isolated from MCP after endo-polygalacturonase degradation (EMCP) and a combination of DEAE-cellulose and Sepharose CL-6B or Sephadex G-75 chromatography. Their primary structures, abilities to inhibit galectin-3-mediated hemagglutination, and antiproliferation activities on MCF-7 and A549 cell lines were studied. Results showed that EMCP-3p, one of the five fractions, was composed of Glc (89.8%), Gal (3.8%), Ara (3.1%), GalA (1.1%), Man (0.9%), and Rha (1.3%) with an average molecular weight of 88.4 KDa, which had the most substantial degree of galectin-3 inhibition with an MIC of 31.25 μg/mL, and it exhibited remarkable cytotoxicity against MCF-7 (36.7%) and A549 (57.4%) cell lines. These results provide new insight into the structure–function relationships of EMCP-derived polysaccharides.

Pectins from various sources inhibit galectin-3-related cardiac fibrosis

PURPOSE OF THE STUDY

A major challenge in cardiology remains in finding a therapy for cardiac fibrosis. Inhibition of galectin-3 with pectins attenuates fibrosis in animal models of heart failure. The purpose of this study is to identify pectins with the strongest galectin-3 inhibitory capacity. We evaluated the in vitro inhibitory capacity, identified potent pectins, and tested if this potency could be validated in a mouse model of myocardial fibrosis.

METHODS

Various pectin fractions were screened in vitro. Modified rhubarb pectin (EMRP) was identified as the most potent inhibitor of galectin-3 and compared to the well-known modified citrus pectin (MCP). Our findings were validated in a mouse model of myocardial fibrosis, which was induced by angiotensin II (Ang II) infusion.

RESULTS

Ang II infusion was associated with a 4-5-fold increase in fibrosis signal in the tissue of the left ventricle, compared to the control group (0•22±0•10 to 1•08±0•53%; P < 0•001). After treatment with rhubarb pectin, fibrosis was reduced by 57% vs. Ang II alone while this reduction was 30% with the well-known MCP (P = NS, P < 0•05). Treatment was associated with a reduced cardiac inflammatory response and preserved cardiac function.

CONCLUSION

The galectin-3 inhibitor natural rhubarb pectin has a superior inhibitory capacity over established pectins, substantially attenuates cardiac fibrosis, and preserves cardiac function in vivo. Bioactive pectins are natural sources of galectin-3 inhibitors and may be helpful in the prevention of heart failure or other diseases characterized by fibrosis.

FUNDING

Dr. Meijers is supported by the Mandema-Stipendium of the Junior Scientific Masterclass 2020-10, University Medical Center Groningen and by the Netherlands Heart Foundation (Dekkerbeurs 2021)Dr. de Boer is supported by the Netherlands Heart Foundation (CVON SHE-PREDICTS-HF, grant 2017-21; CVON RED-CVD, grant 2017-11; CVON PREDICT2, grant 2018-30; and CVON DOUBLE DOSE, grant 2020B005), by a grant from the leDucq Foundation (Cure PhosphoLambaN induced Cardiomyopathy (Cure-PLaN), and by a grant from the European Research Council (ERC CoG 818715, SECRETE-HF).

Fruit Wastes as a Valuable Source of Value-Added Compounds: A Collaborative Perspective

The by-products/wastes from agro-food and in particular the fruit industry represents from one side an issue since they cannot be disposed as such for their impact on the environment but they need to be treated as a waste. However, on the other side, they are a source of bioactive healthy useful compounds which can be recovered and be the starting material for other products in the view of sustainability and a circular economy addressing the global goal of "zero waste" in the environment. An updated view of the state of art of the research on fruit wastes is here given under this perspective. The topic is defined as follows: (i) literature quantitative analysis of fruit waste/by-products, with particular regards to linkage with health; (ii) an updated view of conventional and innovative extraction procedures; (iii) high-value added compounds obtained from fruit waste and associated biological properties; (iv) fruit wastes presence and relevance in updated databases. Nowadays, the investigation of the main components and related bioactivities of fruit wastes is being continuously explored throughout integrated and multidisciplinary approaches towards the exploitation of emerging fields of application which may allow to create economic, environmental, and social value in the design of an eco-friendly approach of the fruit wastes.

Comparisons of Isolation Methods, Structural Features, and Bioactivities of the Polysaccharides from Three Common Panax Species: A Review of Recent Progress

Panax spp. (Araliaceae family) are widely used medicinal plants and they mainly include Panax ginseng C.A. Meyer, Panax quinquefolium L. (American ginseng), and Panax notoginseng (notoginseng). Polysaccharides are the main active ingredients in these plants and have demonstrated diverse pharmacological functions, but comparisons of isolation methods, structural features, and bioactivities of these polysaccharides have not yet been reported. This review summarizes recent advances associated with 112 polysaccharides from ginseng, 25 polysaccharides from American ginseng, and 36 polysaccharides from notoginseng and it compares the differences in extraction, purification, structural features, and bioactivities. Most studies focus on ginseng polysaccharides and comparisons are typically made with the polysaccharides from American ginseng and notoginseng. For the extraction, purification, and structural analysis, the processes are similar for the polysaccharides from the three Panax species. Previous studies determined that 55 polysaccharides from ginseng, 18 polysaccharides from American ginseng, and 9 polysaccharides from notoginseng exhibited anti-tumor activity, immunoregulatory effects, anti-oxidant activity, and other pharmacological functions, which are mediated by multiple signaling pathways, including mitogen-activated protein kinase, nuclear factor kappa B, or redox balance pathways. This review can provide new insights into the similarities and differences among the polysaccharides from the three Panax species, which can facilitate and guide further studies to explore the medicinal properties of the Araliaceae family used in traditional Chinese medicine.

Structural characterization and evaluation the elicitors activity of polysaccharides from Chrysanthemum indicum

This research evaluates the elicitors activity and structure characterization of four Chrysanthemum indicum polysaccharides (CIPs) which were isolated from C. indicum, obtained CIP1, CIP2, CIP3, CIP4. Results demonstrated that there was a distinct difference in inducibility and CIP3 was significantly stronger than other CIPs through bioactivity-tests. Taking CIP3 with total carbohydrate content 91.93 % as a representative, its structure was elucidated as a relative molecular weight of 8. 741 × 10³ g/mol and mainly composed of xylose, galacturonic acid, galactose and glucuronic acid. Through GC, IR and NMR, CIP3 was determined to possess a backbone comprised of T-α-d-GalpA, 1,4-α-d-GlcpA, 1,2-α-d-Xylp, 1,3-α-l-Rhap, 1,2,4-α-l-Rhap and sidechains comprised of 1,3-β-d-Galp, 1,6-α-d-Galp, T-α-Glcp, 1,3-β-d-Glcp, 1,4-α-d-Glcp, 1,3,4-α-d-Manp, T-α-l-Fucp. Further results indicated that CIP3 with active sidechains could significantly increase the expression of defense genes in Atractylodes macrocephala Koidz (AM). It is believed that the sidechains of CIP3 were necessary to its elicitor activity via bioactivity tests.

Oral absorption characteristics and mechanisms of a pectin-type polysaccharide from Smilax china L. across the intestinal epithelium

The elucidation of the oral absorption of natural polysaccharides contributes to their further research and utilization. Herein, to explore the absorption of a pectin-type polysaccharide from Smilax china L. (SCLP), SCLP was respectively fluorescently labeled with fluorescein-5-thioicarbazide (FSCLP) and Cyanine7 amine (Cy7-SCLP) for in vitro and in vivo tracking. The near-infrared imaging demonstrated that Cy7-SCLP was absorbable in the small intestine and distributed in the liver and kidney after oral administration. Subsequently, in vitro intestinal epithelial tissue experiments showed that the jejunum was the dominant site of FSCLP transport. Further transport studies in the Caco-2 cell monolayer illustrated that FSCLP was delivered across the monolayer via transcellular transport by caveolae-mediated endocytosis and macropinocytosis together with paracellular transport by reversibly affecting tight junctions. In summary, this work presents the oral absorption characteristics and mechanisms of SCLP through the intestinal epithelium, which will facilitate the further development of SCLP and pectin polysaccharides.

Impact of Bacterial Metabolites on Gut Barrier Function and Host Immunity: A Focus on Bacterial Metabolism and Its Relevance for Intestinal Inflammation

The diverse and dynamic microbial community of the human gastrointestinal tract plays a vital role in health, with gut microbiota supporting the development and function of the gut immune barrier. Crosstalk between microbiota-gut epithelium and the gut immune system determine the individual health status, and any crosstalk disturbance may lead to chronic intestinal conditions, such as inflammatory bowel diseases (IBD) and celiac disease. Microbiota-derived metabolites are crucial mediators of host-microbial interactions. Some beneficially affect host physiology such as short-chain fatty acids (SCFAs) and secondary bile acids. Also, tryptophan catabolites determine immune responses, such as through binding to the aryl hydrocarbon receptor (AhR). AhR is abundantly present at mucosal surfaces and when activated enhances intestinal epithelial barrier function as well as regulatory immune responses. Exogenous diet-derived indoles (tryptophan) are a major source of endogenous AhR ligand precursors and together with SCFAs and secondary bile acids regulate inflammation by lowering stress in epithelium and gut immunity, and in IBD, AhR expression is downregulated together with tryptophan metabolites. Here, we present an overview of host microbiota-epithelium- gut immunity crosstalk and review how microbial-derived metabolites contribute to host immune homeostasis. Also, we discuss the therapeutic potential of bacterial catabolites for IBD and celiac disease and how essential dietary components such as dietary fibers and bacterial tryptophan catabolites may contribute to intestinal and systemic homeostasis.

Identification of the amino acids residues involved in hemagglutinin-neuraminidase of Newcastle disease virus binding to sulfated Chuanmingshen violaceum polysaccharides

The antiviral mechanism of sulfated polysaccharides is supposed to prevent virus entry, which is mediated by the interactions of anionic charges on sulfated polysaccharides with positively charged domains of viral envelope glycoproteins, leading to shielding of the functional domain involved in virus attachment to cell surface receptors. But, few direct evidences were reported. In the previous study, we found that sulfated Chuanmingshen violaceum polysaccharides (sCVPS) possessed remarkable inhibitory effect against Newcastle disease virus (NDV) through inhibition of NDV attachment to host cells. Whether sCVPS bound to hemagglutinin-neuraminidase (HN) leading to inhibition of NDV attachment needs to be further clarified. The present study conducted site-directed mutagenesis of possible positively charged residues of HN, and found that mutants R197G, H199G, R363G, and R523G could significantly decrease the inhibitory effects of sCVPS on receptor binding ability through hemadsorption assay, especially R363G which suggested that binding to R363 is more effective to shield the sialic acid binding sites. Dual mutants (R363G/R197G, R363G/H199G and R363G/R523G) induced more decreased inhibitory effect of sCVPS than single mutants. The immunofluorescence study using FITC-labeled sCVPS found that the fluorescence intensity of mutants R363G and R363G/H199G were significantly decreased. The binding kinetics of sCVPS to HN measured by surface plasmon resonance indicated that sCVPS had a higher binding affinity for wild-type HN than mutants R363G and R363G/H199G. Plaque reduction study was performed using recombinant NDV with mutant HN_R363G and HN_R363G/H199G, which showed significantly decreased inhibitory effects of sCVPS against mutant NDV adsorption to BHK-21 cells. These results suggested that the residues R197, H199, R363, and R523 were the binding sites for sCVPS, especially R363 act as the main interaction site. The present study provided direct evidence for the theory that antiviral mechanism of sulfated polysaccharides attributed to anionic groups binding to the positively charged residues of viral proteins which led to the shielding of receptor binding sites.

Interaction between Galectin-3 and Integrins Mediates Cell-Matrix Adhesion in Endothelial Cells and Mesenchymal Stem Cells

Galectin-3 (Gal-3) is a β-galactoside-binding protein that influences various cell functions, including cell adhesion. We focused on the role of Gal-3 as an extracellular ligand mediating cell-matrix adhesion. We used human adipose tissue-derived stem cells and human umbilical vein endothelial cells that are promising for vascular tissue engineering. We found that these cells naturally contained Gal-3 on their surface and inside the cells. Moreover, they were able to associate with exogenous Gal-3 added to the culture medium. This association was reduced with a β-galactoside LacdiNAc (GalNAcβ1,4GlcNAc), a selective ligand of Gal-3, which binds to the carbohydrate recognition domain (CRD) in the Gal-3 molecule. This ligand was also able to detach Gal-3 newly associated with cells but not Gal-3 naturally present on cells. In addition, Gal-3 preadsorbed on plastic surfaces acted as an adhesion ligand for both cell types, and the cell adhesion was resistant to blocking with LacdiNAc. This result suggests that the adhesion was mediated by a binding site different from the CRD. The blocking of integrin adhesion receptors on cells with specific antibodies revealed that the cell adhesion to the preadsorbed Gal-3 was mediated, at least partially, by β1 and αV integrins-namely α5β1, αVβ3, and αVβ1 integrins.

Galectin-3 N-terminal tail prolines modulate cell activity and glycan-mediated oligomerization/phase separation

Galectin-3 (Gal-3) has a long, aperiodic, and dynamic proline-rich N-terminal tail (NT). The functional role of the NT with its numerous prolines has remained enigmatic since its discovery. To provide some resolution to this puzzle, we individually mutated all 14 NT prolines over the first 68 residues and assessed their effects on various Gal-3-mediated functions. Our findings show that mutation of any single proline (especially P37A, P55A, P60A, P64A/H, and P67A) dramatically and differentially inhibits Gal-3-mediated cellular activities (i.e., cell migration, activation, endocytosis, and hemagglutination). For mechanistic insight, we investigated the role of prolines in mediating Gal-3 oligomerization, a fundamental process required for these cell activities. We showed that Gal-3 oligomerization triggered by binding to glycoproteins is a dynamic process analogous to liquid-liquid phase separation (LLPS). The composition of these heterooligomers is dependent on the concentration of Gal-3 as well as on the concentration and type of glycoprotein. LLPS-like Gal-3 oligomerization/condensation was also observed on the plasma membrane and disrupted endomembranes. Molecular- and cell-based assays indicate that glycan binding-triggered Gal-3 LLPS (or LLPS-like) is driven mainly by dynamic intermolecular interactions between the Gal-3 NT and the carbohydrate recognition domain (CRD) F-face, although NT-NT interactions appear to contribute to a lesser extent. Mutation of each proline within the NT differentially controls NT-CRD interactions, consequently affecting glycan binding, LLPS, and cellular activities. Our results unveil the role of proline polymorphisms (e.g., at P64) associated with many diseases and suggest that the function of glycosylated cell surface receptors is dynamically regulated by Gal-3.

Comparative study on the structures of intra- and extra-cellular polysaccharides from Penicillium oxalicum and their inhibitory effects on galectins

Here, we compare the content and composition of polysaccharides derived from the mycelium (40.4 kDa intracellular polysaccharide, IPS) and culture (27.2 kDa extracellular polysaccharide, EPS) of Penicillium oxalicum. Their chemical structures investigated by IR, NMR, enzymolysis and methylation analysis indicate that both IPS and EPS are galactomannans composed of α-1,2- mannopyranose (Manp) and α-1,6-Manp in a backbone ratio of ~3:1, respectively, both decorated with β-l,5-galactofuranose (Galf) side chains. A few β-l,6-Galf residues were also detected in the IPS fraction. EPS and IPS have different molecular weights (Mw) and degrees of branching. IPS obtained by alkaline extraction of P. oxalicum have been reported to be galactofuranans, a composition different from our IPS. Up to now, there have been no reports on the fine structure of EPS. Our results of galectin-mediated hemagglutination demonstrate that IPS exhibits greater inhibitory effects on five galectins compared with EPS. In addition, we find that Galf, a five-membered ring form of galactose, can also inhibit galectins. IPS may provide a new source of galectin inhibitors. These results increase our understanding of structure-activity relationships of polysaccharides as galectin inhibitors.

Degraded Arabinogalactans and Their Binding Properties to Cancer-Associated Human Galectins

Galectins represent β-galactoside-binding proteins with numerous functions. Due to their role in tumor progression, human galectins-1, -3 and -7 (Gal-1, -3 and -7) are potential targets for cancer therapy. As plant derived glycans might act as galectin inhibitors, we prepared galactans by partial degradation of plant arabinogalactan-proteins. Besides commercially purchased galectins, we produced Gal-1 and -7 in a cell free system and tested binding capacities of the galectins to the galactans by biolayer-interferometry. Results for commercial and cell-free expressed galectins were comparable confirming functionality of the cell-free produced galectins. Our results revealed that galactans from Echinacea purpurea bind to Gal-1 and -7 with K_D values of 1–2 µM and to Gal-3 slightly stronger with K_D values between 0.36 and 0.70 µM depending on the sensor type. Galactans from the seagrass Zostera marina with higher branching of the galactan and higher content of uronic acids showed stronger binding to Gal-3 (0.08–0.28 µM) compared to galactan from Echinacea. The results contribute to knowledge on interactions between plant polysaccharides and galectins. Arabinogalactan-proteins have been identified as a new source for production of galactans with possible capability to act as galectin inhibitors.

Targeting galectins in T cell-based immunotherapy within tumor microenvironment

Over the past few years, tumor immunotherapy has emerged as an innovative tumor treatment and owned incomparable advantages over other tumor therapy. With unique complexity and uncertainty, immunotherapy still need helper to apply in the clinic. Galectins, modulated in tumor microenvironment, can regulate the disorders of innate and adaptive immune system resisting tumor growth. Considering the role of galectins in tumor immunosuppression, combination therapy of targeted anti-galectins and immunotherapy may be a promising tumor treatment. This brief review summarizes the expression and immune functions of different galectins in tumor microenvironment and discusses the potential value of anti-galectins in combination with checkpoint inhibitors in tumor immunotherapy.

Structural characterization and immunomodulatory activity of a heterogalactan from Panax ginseng flowers

A neutral polysaccharide fraction (WGFPN) was isolated from Panax ginseng flowers. Monosaccharide composition and HPSEC-MALLS-RI (high-performance size exclusion chromatography coupled with multi-angle laser light scattering detector and refractive index detector) analyses showed WGFPN was a heterogalactan with a molecular weight of 11.0 kDa. Methylation, 1D/2D NMR (nuclear magnetic resonance) spectra and enzymatic hydrolysis methods were used to characterize the structure of WGFPN. It possessed a less branched (1 → 4)-β-D-galactan and a significantly branched (1 → 6)-β-D-galactan. The side chains of (1 → 6)-β-D-galactan were branched with α-L-1,5-Araf and t-α-L-Araf residues at O-3. Trace amount of 1,4-linked Glcp, terminal Galp, terminal Glcp and terminal Manp residues might attached to the 1,6-linked galactan through O-3 or 1,4-linked galactan through O-6 as side chains. WGFPN could activate RAW264.7 macrophages through increasing macrophage phagocytosis, releasing NO and secreting TNF-α, IL-6, IFN-γ and IL-1β in vitro. Moreover, WGFPN could enhance the immunity of cyclophosphamide (CTX)-induced immunosuppressed mice in vivo. Hence, WGFPN might be a potential natural immunomodulatory agent.

Dietary pectic substances enhance gut health by its polycomponent: A review

Pectic substances, one of the cell wall polysaccharides, exist widespread in vegetables and fruits. A surge of recent research has revealed that pectic substances can inhibit gut inflammation and relieve inflammatory bowel disease symptoms. However, physiological functions of pectins are strongly structure dependent. Pectic substances are essentially heteropolysaccharides composed of homogalacturonan and rhamnogalacturonan backbones substituted by various neutral sugar sidechains. Subtle changes in the architecture of pectic substances may remarkably influence the nutritional function of gut microbiota and the host homeostasis of immune system. In this context, developing a structure-function understanding of how pectic substances have an impact on an inflammatory bowel is of primary importance for diet therapy and new drugs. Therefore, the present review has summarized the polycomponent nature of pectic substances, the activities of different pectic polymers, the effects of molecular characteristics and the underlying mechanisms of pectic substances. The immunomodulated property of pectic substances depends on not only the chemical composition but also the physical structure characteristics, such as molecular weight (M_w ) and chain conformation. The potential mechanisms by which pectic substances exert their protective effects are mainly reversing the disordered gut microbiota, regulating immune cells, enhancing barrier function, and inhibiting pathogen adhesion. The manipulation of pectic substances on gut health is sophisticated, and the link between structural specificity of pectins and selective regulation needs further exploration.

Structural insights in interactions between RNase from Bacillus Intermedius and rhamnogalacturonan I from potato

Being biocompatible and biodegradable polymers, polysaccharides present a perspective material for drug delivery systems. This study aimed at unraveling the molecular details of interactions between rhamnogalacturonan I, brunched with galactan side chains, and RNase from Bacillus Intermedius, binase. FTIR- and NMR-spectroscopic analyses showed that binase interacts with side chains of the polysaccharide. In complexes with polysaccharide, the protein retains its native structure. The 2D-NMR techniques revealed eight protein residues responsive to polysaccharide binding. Further, computer simulations were carried out to provide the atomistic details of binase-polysaccharide complexes. Both blind and knowledge-based docking procedures elucidate the existence of epitopes on the binase surface with the preferential binding of galactan fragments. The refinement of these complexes by molecular dynamics simulations confirmed stable protein-polysaccharide interactions. The results of this study strengthen the knowledge on non-specific protein-carbohydrate interactions and outline the rhamnogalacturonan I as a possible matrix material for protein delivery systems.

Recent progress in polysaccharides from Panax ginseng C. A. Meyer

Panax ginseng C. A. Meyer (P. ginseng) has a long history of medicinal use and can treat a variety of diseases. P. ginseng contains a variety of active ingredients, such as saponins, polypeptides, volatile oils, and polysaccharides. Among them, saponins have always been considered as the main components responsible for its pharmacological activities. However, more and more studies have shown that polysaccharides play an indispensable role in the medicinal value of ginseng. Modern biological and medical studies have found that ginseng polysaccharides have complex structural characteristics and diverse biological activities, such as immune regulation, anti-tumor, antioxidant, hypoglycemic, and anti-radiation functions, among others. Additionally, the structural characteristics of ginseng polysaccharides are closely related to their activity. In this review, the research background, extraction, purification, structural characteristics, and biological activities of ginseng polysaccharides from different parts of P. ginseng (roots, flowers stems and leaves, and berries) under different growth conditions (artificially cultivated ginseng, mountain ginseng, and wild ginseng) are summarized. The structural characteristics of purified polysaccharides were reviewed. Meanwhile, their biological activities were introduced, and some possible mechanisms were listed. Furthermore, the structure-activity relationship of polysaccharides was discussed. Some research perspectives for the study of ginseng polysaccharides were also provided.

The purification of pectin from commercial fruit flours results in a jaboticaba fraction that inhibits galectin-3 and colon cancer cell growth

Fruits are a prime source of nutrients, bioactive compounds, and dietary fibers. Some products available on the Brazilian market use fruit by-products and claim to have useful effects on human health due to their dietary fiber content. The study aimed to extract and purify the total (28-47 w/w yield) and soluble dietary fiber (4-7 w/w yield) from jaboticaba, papaya, and plum commercial flours sold in Brazil and to study the in vitro biological effects of the fractions. The purified water-soluble fractions consisted mainly of pectin-derived oligosaccharides (5-15 KDa molecular weight) with a negligible content of polyphenols, protein, ashes, and starch. Jaboticaba sample was 95% galacturonic acid while plum and papaya samples were 40% galacturonic acid and 40% galactose (mol%), approximately. The samples were tested for recombinant human galectin-3 inhibition and changes in the cell viability of human colorectal cancer cells. Only the jaboticaba sample inhibited galectin-3 and decreased HCT116 cell viability after 48 h of treatment (p ≤ 0.01) while the plum sample decreased the cell viability after 24 h treatment (p ≤ 0.05). The results obtained in this study demonstrate the relationship between the structure of the soluble fibers extracted from jaboticaba flour and the possible beneficial effects of their consumption.