Sulfated polysaccharides: Immunomodulation and signaling mechanisms

Bioactive Carbohydrate Polymers-Between Myth and Reality

Polysaccharides are complex macromolecules long regarded as energetic storage resources or as components of plant and fungal cell walls. They have also been described as plant mucilages or microbial exopolysaccharides. The development of glycosciences has led to a partial and difficult deciphering of their other biological functions in living organisms. The objectives of glycobiochemistry and glycobiology are currently to correlate some structural features of polysaccharides with some biological responses in the producing organisms or in another one. In this context, the literature focusing on bioactive polysaccharides has increased exponentially during the last two decades, being sometimes very optimistic for some new applications of bioactive polysaccharides, notably in the medical field. Therefore, this review aims to examine bioactive polysaccharide, taking a critical look of the different biological activities reported by authors and the reality of the market. It focuses also on the chemical, biochemical, enzymatic, and physical modifications of these biopolymers to optimize their potential as bioactive agents.

Recent advances in antiviral activities and potential mechanisms of sulfated polysaccharides

Natural polysaccharides derived from plants, fungi and animals are well known as ideal functional products with multiple biological activities and few side effects. Among them, natural occurring sulfated polysaccharides and those from synthetic origin are increasingly causing more attention worldwide, as they have been proved to possess broad-spectrum antiviral activities. The focus of this review is on analyzing the current state of knowledge about the origin of sulfated polysaccharides, more importantly, the potential connection between the structure and their antiviral mechanisms. Sulfated polysaccharide may interfere with a few steps in the virus life cycle (i.e. adsorption, invasion, transcription and replication) and/or improve the host antiviral immune response. Moreover, their antiviral activity was affected by degree of substitution, substitution position, molecular weight, and spatial conformation. This review may provide approach for the development of novel and potent therapeutic agents.

In Vitro Immunomodulation of the Polysaccharides from Yam (Dioscorea opposita Thunb.) in Response to a Selenylation of Lower Extent

The immunomodulation of chemically selenylated polysaccharides has been attracting more attention recently, but the corresponding performance of the yam polysaccharides (YPS) with lower selenylation extent remains, thus far, unsolved. In this study, the YPS was selenylated with Na₂SeO₃ under acidic conditions generated by HNO₃ to reach two lower selenylation extents, yielding two selenylated YPSs, namely SeYPS-1 and SeYPS-2 with selenium contents of 715 and 1545 mg/kg, respectively. The results indicated that YPS, SeYPS-1, and SeYPS-2 all had in vitro immuno-modulation when using RAW 264.7 macrophages and murine splenocytes as cell models. In detail, the three polysaccharide samples at dose levels of 5–160 μg/mL showed insignificant cytotoxicity to the macrophages and splenocytes with cell exposure times of 12–24 h, because of the measured values of cell viability larger than 100%. However, Na₂SeO₃ at dose levels of 1.3–3.25 μg/mL mostly caused obvious cytotoxic effects on the cells, resulting in reduced cell viability values or cell death, efficiently. The results demonstrated that, compared with YPS, both SeYPS-1 and SeYPS-2 at a lower dose level (5 μg/mL) were more active at promoting phagocytosis activity, increasing the CD4⁺/CD8⁺ ratio of the T-lymphocyte sub-population in the murine splenocyte, improving cytokine secretion, including interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α in the macrophages, or increasing interferon-γ secretion, but suppressing IL-4 production in the splenocytes. Consistently, SeYPS-2 has more potential than SeYPS-1 at exerting these assessed bioactivities in the cells. Thus, we conclude that a chemical modification of YPS using trace element Se at a lower selenylation extent could bring about higher immunomodulatory activity towards macrophages and splenocytes, while selenylation extent of YPS is a critical factor used to govern the assessed activity changes of YPS.

Interaction between polysaccharides and toll-like receptor 4: Primary structural role, immune balance perspective, and 3D interaction model hypothesis

Various structural types of polysaccharides are recognized by toll-like receptor 4 (TLR4). However, the mechanism of interaction between the polysaccharides with different structures and TLR4 is unclarified. This review summarized the primary structure of polysaccharides related to TLR4, mainly including molecular weight, monosaccharide composition, glycosidic bonds, functional groups, and branched-chain structure. The optimal primary structure for interacting with TLR4 was obtained by the statistical analysis. Besides, the dual-directional regulation of TLR4 signaling cascade by polysaccharides was also elucidated from an immune balance perspective. Finally, the 3D interaction model of polysaccharides to TLR4-myeloid differentiation factor 2 (MD2) complex was hypothesized according to the LPS-TLR4-MD2 dimerization model and the polysaccharides solution conformation. The essence of polysaccharides binding to TLR4-MD2 complex is a multivalent non-covalent bond interaction. All the arguments summarized in this review are intended to provide some new insights into the interaction between polysaccharides and TLR4.

Polysaccharides From the Roots of Millettia Speciosa Champ Modulate Gut Health and Ameliorate Cyclophosphamide-Induced Intestinal Injury and Immunosuppression

Cyclophosphamide (CTX), a common anticancer drug, can cause a variety of side effects such as immunosuppression and intestinal mucosal injury. Polysaccharides are the major bioactive components of the roots of Millettia Speciosa Champ and have gained attention for their immunomodulatory activity. This study was designed to evaluate the immunomodulatory effect of Millettia Speciosa Champ polysaccharide (MSCP) on CTX-induced mice and the possible mechanism. The results showed that MSCP attenuated the CTX-induced decrease in body weight and immune organ indices in mice and promoted the secretion of immune-related cytokines (IL-2, IL-4, IL-10, TNF-α, and IgG). Meanwhile, MSCP restored intestinal morphology, increased the ratio of villus height/crypt depth (V/C), and improved the number of goblet cells and mucins expression. At the mRNA level, MSCP activated the TLRs/MyD88/NF-κB p65 pathway and enhanced the expression of genes related to intestinal mucosal integrity (Occludin1, Claudin1, and MUC-2). In addition, MSCP as a prebiotic improved microbial community diversity, regulated the relative abundance of dominant microbiota from the phylum level to the genus level, restored CTX-induced gut microbial dysbiosis, and promoted short-chain fatty acid production in mice. Based on the present findings, MSCP may modulate the immune response depending on enhancing intestinal health, suggesting that MSCP holds promise as a promising immunostimulant in functional foods and drugs.

Enteromorpha prolifera polysaccharide-zinc complex modulates the immune response and alleviates LPS-induced intestinal inflammation via inhibiting the TLR4/NF-κB signaling pathway

Enteromorpha prolifera polysaccharide-zinc (EP-Zn), a kind of polysaccharide-zinc complex, has been shown to improve the immune response and reduce the inflammatory factors in weaned piglets. Yet, the molecular mechanism remains unclear. The present study was conducted to investigate the immunomodulating activity and anti-inflammatory mechanism of EP-Zn in mice. Different doses (350 mg kg^-1, 700 mg kg^-1, 1050 mg kg^-1 and 1400 mg kg^-1) of EP-Zn were administered to C57BL/6J mice for 28 days. The results showed that under physiological conditions, 350 mg kg^-1 EP-Zn stimulated cytokine (TNF-α, IL-1β, IL-6 and IL-10) secrection, regulated the intestinal microbiota, and reduced the levels of short-chain fatty acids (SCFAs) (acetic acid and propionic acid). In addition, in the LPS-induced inflammation model, EP-Zn pretreatment effectively alleviated LPS-induced shortening of colonic length and increased MPO and DAO contents, improved intestinal physical barrier function by modulating mucosal structure, and attenuated intestinal inflammation via inhibiting the TLR4/NF-κB signaling pathway. These findings suggested that EP-Zn exerted immunomodulatory and anti-inflammatory activities under physiological and inflammatory conditions, respectively.

Sulphation and Hydrolysis Improvements of Bioactivities, and Immuno-Modulatory Properties of Edible Amanita hemibapha Subspecies javanica (Corner and Bas) Mucilage Polysaccharide as a Potential in Personalized Functional Foods

In this study, the mucilage polysaccharide (MP) from Amanita hemibapha subspecies javanica was prepared by hot water extraction and ethanol precipitation and then fractionated using anion-exchange chromatography equipped with a DEAE Sepharose fast flow column. The most immune-enhancing polysaccharide fraction 2 (MPF2) was subjected to a structural modification such as hydrolysis or over-sulphation. The sulphate and molecular weight (Mw) of over-sulphated (OS1-3) and hydrolysed (HS1-3) derivatives of MPF2 differed between 9.85% and 14.2% and 32.8 and 88.1 × 103 g/mol, respectively. Further, the immune-enhancing properties of MPF2 and its derivatives were tested on RAW264.7 and NK cells through various in vitro assays. Interestingly, a low molecular weight of HS1-3 significantly increased the nitric oxide (NO) production (p < 0.05) more than MPF2, indicating that Mw is a major factor in RAW264.7 cell stimulation. In addition, RAW264.7 cells produced various cytokines by up-regulating mRNA expression levels and the activation of nuclear factor kappa-B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. On the other hand, OS1-3-treated natural killer (NK) cells induced cytotoxicity in HepG2 cells through the expression of IFN-γ, Grandzyme-B, perforin, NKp30, and FasL. These results demonstrated that sulphate derivatives play an important role in NK cell activation. Further, this study also explores how polysaccharide binds to RAW264.7 and NK cells. MPF2 and HS3 may activate RAW264.7 cells via binding to TLR4 receptors, and OS2 could be activated through the CR3 signalling pathways.

Modifications of polysaccharide-based biomaterials under structure-property relationship for biomedical applications

Polysaccharides are well accepted biomaterials that have attracted considerable attention. Compared with other materials under research, polysaccharides show unique advantages: they are available in nature and are normally easily acquired, those acquired from nature show favorable immunogenicity, and are biodegradable and bioavailable. The bioactivity and possible applications are based on their chemical structure; however, naturally acquired polysaccharides sometimes have unwanted flaws that limit further applications. For this reason, carefully summarizing the possible modifications of polysaccharides to improve them is crucial. Structural modifications can not only provide polysaccharides with additional functional groups but also change their physicochemical properties. This review based on the structure-property relation summarizes the common chemical modifications of polysaccharides, the related bioactivity changes, possible functionalization methods, and major possible biomedical applications based on modified polysaccharides.

Chemically Sulfated Polysaccharides from Agaricus blazei Murill: Synthesis, Characterization and Anti-HIV Activity

AIDS, caused by HIV-1, is one of the most dangerous infectious diseases in the world. Therefore, it is necessary to develop new drugs with more potent bioactivities, less toxicity and higher tolerability for controlling the viral load, particularly by using the raw materials that are widely available. Agaricus blazei Murill (AbM), known in China as jisongrong, is of great importance as a food source and as a health-promoting supplement for immunomodulation. The polysaccharides of AbM exhibit various biological activities, such as regulating cellular immunity and providing anti-oxidative, anti-infective, and anti-inflammatory effects. At present, to our knowledge, no report has explored the chemically sulfated and anti-HIV-1 activity of AbM polysaccharides. Herein, the sulfated AbM polysaccharides with different sulfur contents were prepared by the chlorosulfonic acid-pyridine method. The characteristics of sulfated derivatives were established by the determination of the sulfur content, the relative molecular weight, and the Fourier-transform infrared spectroscopy. The anti-HIV activities of the sulfated AbM polysaccharides were evaluated by CCK-8 and the single-cycle pseudovirus infection (TZM-bl) assay. The sulfated AbM polysaccharides had strong antiviral properties, and the half-maximal inhibitory concentrations approached that of the positive control, azidothymidine. Sulfated modification of AbM polysaccharides can increase their anti-HIV pharmacological activity, which makes them promising alternative candidates as bioactive macromolecules for biomedical applications in HIV/AIDS.

Marine sulfated polysaccharides as potential antiviral drug candidates to treat Corona Virus disease (COVID-19)

The viral infection caused by SARS-CoV-2 has increased the mortality rate and engaged several adverse effects on the affected individuals. Currently available antiviral drugs have found to be unsuccessful in the treatment of COVID-19 patients. The demand for efficient antiviral drugs has created a huge burden on physicians and health workers. Plasma therapy seems to be less accomplishable due to insufficient donors to donate plasma and low recovery rate from viral infection. Repurposing of antivirals has been evolved as a suitable strategy in the current treatment and preventive measures. The concept of drug repurposing represents new experimental approaches for effective therapeutic benefits. Besides, SARS-CoV-2 exhibits several complications such as lung damage, blood clot formation, respiratory illness and organ failures in most of the patients. Based on the accumulation of data, sulfated marine polysaccharides have exerted successful inhibition of virus entry, attachment and replication with known or unknown possible mechanisms against deadly animal and human viruses so far. Since the virus entry into the host cells is the key process, the prevention of such entry mechanism makes any antiviral strategy effective. Enveloped viruses are more sensitive to polyanions than non-enveloped viruses. Besides, the viral infection caused by RNA virus types embarks severe oxidative stress in the human body that leads to malfunction of tissues and organs. In this context, polysaccharides play a very significant role in providing shielding effect against the virus due to their polyanionic rich features and a molecular weight that hinders their reactive surface glycoproteins. Significantly the functional groups especially sulfate, sulfate pattern and addition, uronic acids, monosaccharides, glycosidic linkage and high molecular weight have greater influence in the antiviral activity. Moreover, they are very good antioxidants that can reduce the free radical generation and provokes intracellular antioxidant enzymes. Additionally, polysaccharides enable a host-virus immune response, activate phagocytosis and stimulate interferon systems. Therefore, polysaccharides can be used as candidate drugs, adjuvants in vaccines or combination with other antivirals, antioxidants and immune-activating nutritional supplements and antiviral materials in healthcare products to prevent SARS-CoV-2 infection.

The activation effects of fucoidan from sea cucumber Stichopus chloronotus on RAW264.7 cells via TLR2/4-NF-κB pathway and its structure-activity relationship

Sea cucumber Stichopus chloronotus is a traditional tonic food with high nutritive value in Southern China. Fucoidan from sea cucumber Stichopus chloronotus (Fuc-Sc) is its main bio-active polysaccharide, the immune-activation effects of which have been fully investigated on RAW264.7 cells in the present study. The results indicated that Fuc-Sc could stimulate the RAW264.7 cells by promoting the production of NO, TNF-α, IL-6 and IL-10. Western blot and RT-PCR analysis revealed that TLR4 and TLR2 were involved in the recognition of Fuc-Sc and activation of downstream NF-κB signal pathway. Moreover, the chemical structure parameter molecular weight showed obvious impact on the stimulation effects of Fuc-Sc on NO production. Degraded product of Fuc-Sc with weight average molecular weight of 113.1 × 10⁴ Da exhibited higher activities than that of intact Fuc-Sc, suggesting the existent of optimum chain length to exert its highest activities. Taken together, Fuc-Sc exerted its immunostimulating activity via TLR2/4 activation of NF-κB pathway and showed potentials to be a good immunoadjuvant.

Current trends in the anti-photoaging activities and mechanisms of dietary non-starch polysaccharides from natural resources

Photoaging is a complex and multistage process triggered mainly by ultraviolet (UV) radiation due to exposure to sunlight. Photoaging induces DNA damage and oxidative stress that initiate an inflammatory response and an increase of matrix metalloproteinases (MMPs) expression, which results in cumulative changes in skin appearance, structure, and functions, and eventually causes skin carcinogenesis. Dietary polysaccharides from bio-resources have been utilized as functional ingredients in healthy food, cosmetics, and drug due to their good bioactivities. However, a systematic introduction to their effects and underlying mechanisms in anti-photoaging is limited. This review discusses the damage and pathogenesis of UV-induced photoaging and summarizes the up-to-date advances in research on the anti-photoaging activity of non-starch polysaccharides from natural edible resources considering the influence of oxidative stress, DNA damage, MMPs regulation, inflammation, and melanogenesis, primarily focusing on the cellular and molecular mechanisms. This paper will help to understand the anti-photoaging functions of dietary non-starch polysaccharides from natural resources and further application in drug and functional food.

Structural characterization, anticancer, hypoglycemia and immune activities of polysaccharides from Russula virescens

Russula virescens is an edible wild mushroom that is widely distributed in south of China. This research aimed to analyze the structure characterization and evaluate the hypoglycemic, anticancer and immunological activities of two water soluble polysaccharides RVP-1 and RVP-2 from R. virescens. The results showed RVP-1 and RVP-2 were non-triple helix structured hetero-polysaccharides with different weight-average molecular weight 14,883 and 13,301 Da, respectively. Both RVP-1 and RVP-2 were composed of galactose, glucose, mannose and fructose, and the sugar residues were mainly linked by 1,6→, 1,2→, 1→ and 1,3,6→ glycosidic bonds. Moreover, the antidiabetic, anticancer and immune activities of RVP-1 and RVP-2 were explored in vitro methods. The two polysaccharides have potential for inhibiting α-glucosidase and α-amylase activities, suppressing HepG-2, A549 and MCF-7 cancer cells proliferation, and activating macrophage RAW 264.7 cells to secret immune cytokines for mediating cellular immune response. These findings provided a scientific basis for further utilization of polysaccharide from R. virescens.

Natural Food Polysaccharides Ameliorate Inflammatory Bowel Disease and Its Mechanisms

Natural polysaccharides and their metabolites’ short chain fatty acids (SCFAs) have attracted much attention. Recently, they have shown great potential in attenuating systemic inflammation activities, especially in inflammatory bowel disease (IBD). IBD is a complex pathological process and is related to epithelial damage and microbiota imbalance in the gut. Recent studies have indicated that natural polysaccharides could improve IBD recovery by different mechanisms. They could not only influence the ratio of intestine microbiota, but also regulate the secretion levels of immunity cytokines through multiple pathways, the latter including modulation of the TLR/MAPK/NF-κB signaling pathways and stimulation of G-protein-coupled receptors. Moreover, they could increase intestinal integrity and modulate oxidative stress. In this review, recent research about how natural polysaccharides impact the pathogenesis of IBD are summarized to prove the association between polysaccharides and disease recovery, which might contribute to the secretion of inflammatory cytokines, improve intestine epithelial damage, reduce oxidative stress, sustain the balanced microenvironment of the intestines, and finally lower the risk of IBD.

Antihypertensive and Immunomodulatory Effects of Defatted Corn Germ Hydrolysates: An in vivo Study

This study investigated the antihypertensive and immunomodulatory effects of defatted corn germ hydrolysates (DCGHs) in vivo and their potential regulatory mechanisms. The systolic blood pressure (SBP) of spontaneously hypertensive rats (SHRs) was significantly reduced (10.30%) by the long-term intragastric administration of DCGHs (high doses). Also, there was drastic inhibition of angiotensin-I-converting enzyme (ACE) activity in the lung, kidney, and heart tissues by 24.53, 22.28, and 12.93%, respectively. It could regulate the blood pressure by adjusting the balance between endothelium-derived vasoconstrictor factors and endothelium-derived relaxing factors. Meanwhile, DCGHs enhanced the phagocytosis of mononuclear macrophages, cellular immunity, and humoral immunity of ICR mice by increasing the phagocytic index of mononuclear macrophages (23.71%), ear swelling degree (44.82%), and antibody levels (52.32%). Moreover, it stimulated the release of immunoactive substances (e.g., lysozyme, interferon-γ, immunoglobulin G, and complement 3). Consequently, DCGHs could suitably be used in the formulation of novel functional foods with antihypertensive and immunomodulatory properties.

Biological activities of Pleurotus spp. polysaccharides: A review

Mushrooms are consumed for their nutrients and therapeutic bioactive compounds and are used medicinally in Chinese and Japanese medicine traditions since time immemorial. Members of the genus Pleurotus form a heterogeneous group of edible species with outstanding nutritional profiles rich in fiber, vitamins (thiamine, riboflavin, ascorbic acid, ergosterine, and niacin), micro and macro-elements (phosphorus and iron), and carbohydrates. Pleurotus is one of the most diversified medicinal and edible mushrooms related to the composition of chemical structures such as polysaccharides, glycoproteins, and secondary metabolites such as alkaloids and betalains. The cultivation of Pleurotus spp. on lignocellulosic wastes represents one of the most economically and cost-effective organic recycling processes, especially for the utilization of different feasible and cheap recyclable residues. Also, several Pleurotus spp. have the ability to remove phenolic compounds from wastewater with the action of phenoloxidase activity. Here, we have reviewed the chemistry of such polysaccharides and their reported biological activities, namely, anti-inflammatory, immunomodulatory, anti-diabetic, anti-tumor, antioxidant, etc. The mechanism of action and effects of novel polysaccharides extracted from various species of Pleurotus have been studied. The current study will be beneficial for guiding future research projects on the above concept and investigating more deeply the health of human beings. PRACTICAL APPLICATIONS: Mushrooms are one of the most delicious foods around the globe and have many medicinal properties for decades. Various Pleurotus species have been in focus in recent years because of their palatability and medicinal importance too. It contains many bioactive compounds among which polysaccharides are valued to a great extent. Many biological activities are exerted by polysaccharides derived from the Pleurotus spp., namely, anti-tumor, antioxidant, and many more. They are responsible for significant physiological responses in animals, animal-alternative in vitro models, and humans. Their important physicochemical characteristics benefit their use in the food industry as well. So, the biological activities of these Pleurotus spp. polysaccharides will provide an insight to develop Pleurotus spp. as functional foods, because of their nutritional value and presence of bioactive components.

Digestion & fermentation characteristics of sulfated polysaccharides from Gracilaria chouae using two extraction methods in vitro and in vivo

The sulfated polysaccharides extracted from Gracilaria chouae using critic acid extraction and water extraction, respectively, and their digestion and fermentation characteristics were compared in vitro and in vivo. The molecular weight of water extracted polysaccharide of G. chouae (WGCP) was 1.73 × 10³ kDa while critic acid extracted polysaccharide (CGCP) was 31.5 kDa. During stimulated gastrointestinal digestion in vitro, WGCP and CGCP were lightly degraded. However, the glycemic index (GI) of WGCP and CGCP were 17.7 and 36.12, respectively. After 24 h of fermentation in vitro, the pH values of CGLP in the fecal culture decreased from 6.89 to 4.82, similar to the inulin but significantly (p < 0.05) lower than those of the WGCP and normal control. In addition, CGCP and inulin showed similar microbial fermentation characteristics according to the microbiome compositions and contents of short-chain fatty acids (SCFAs). Nevertheless, CGCP gavage for four weeks could also promote the growth of microbes producing the SCFAs such as Peptococcus, Roseburia and Butyricicoccus in the cecum of KM mice. The present study suggests that polysaccharides prepared by acid-extraction method could potentially be used as a good source of prebiotics.

The Influence of Polysaccharides-Based Material on Macrophage Phenotypes

Macrophage polarization is a key factor in determining the success of implanted tissue engineering scaffolds. Polysaccharides (derived from plants, animals, and microorganisms) are known to modulate macrophage phenotypes by recognizing cell membrane receptors. Numerous studies have developed polysaccharide-based materials into functional biomaterial substrates for tissue regeneration and pharmaceutical application due to their immunostimulatory activities and anti-inflammatory response. They are used as hydrogel substrates, surface coatings, and drug delivery carriers. In addition to their innate immunological functions, the newly endowed physical and chemical properties, including substrate modulus, pore size/porosity, surface binding chemistry, and the mole ratio of polysaccharides in hybrid materials may regulate macrophage phenotypes more precisely. Growing evidence indicates that the sulfation pattern of glycosaminoglycans and proteoglycans expressed on polarized macrophages leads to the changes in protein binding, which may alter macrophage phenotype and influence the immune response. A comprehensive understanding of how different types of polysaccharide-based materials alter macrophage phenotypic changes can be beneficial to predict transplantation/implantation outcomes. This review focuses on recent advances in promoting wound healing and balancing macrophage phenotypes using polysaccharide-based substrates/coatings and new directions to address the limitations in the current understanding of macrophage responses to polysaccharides.

Role of food nutrients and supplementation in fighting against viral infections and boosting immunity: A review

BACKGROUND

The viral infections can be highly contagious and easily transmissible, which even can lead to a pandemic, like the recent COVID-19 outbreak, causing massive deaths worldwide. While, still the best practical way to prevent the transmission of viruses is to practice self-sanitation and follow social distancing principles, enhancing the individual's immunity through the consumption of proper foods containing balanced nutrients can have significant result against viral infections. Foods containing nutrients such as vitamins, minerals, fatty acids, few polysaccharides, and some non-nutrients (i.e. polyphenols) have shown therapeutic potential against the function of viruses and can increase the immunity of people.

SCOPE AND APPROACH

The results of conducted works aiming for studying the potential antiviral characteristics of diverse groups of foods and food's nutrients (in terms of polysaccharides, proteins, lipids, vitamins, and minerals) are critically discussed.

KEY FINDINGS AND CONCLUSION

Nutrients, besides playing an important role in maintaining normal physiology of human's body and healthiness, are also required for enhancing the immunity of the body and can be effective against viral infections. They can present antiviral capacity either by entering into the defensive mechanism directly through interfering with the target viruses, or indirectly through activating the cells associated with the adaptive immune system. During the current situation of COVID-19 pandemic (the lack of proper curative viral drug), enhancing the immunity of individual's body through proposing the appropriate diet (rich in both macro and micro-nutrients) is one of few practical preventive measures available in fighting against Coronaviruses, this significant health-threatening virus, as well as other viruses in general.

Potential applications of hydrophobically modified inulin as an active ingredient in functional foods and drugs - A review

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Inulin is a substance found in a wide variety of fruits, vegetables, and herbs.

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Inulin was modified by physical and chemical means to improve functionality.

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HMI has been used in the stability of emulsions and suspensions.

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SCFAs inulin esters have transformed the gut microbiota and improved the bioavailability of SCFAs.

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HMI based bioconjugates, hydrogel, and nanomicelles were used as a controlled release of drugs and vaccines.

Over the past few years, hydrophobically modified inulin (HMI) has gained considerable attention due to its multitudinous features. The targeted release of drugs remains a subject of research interest. Moreover, it is important to explore the properties of short-chain fatty acids (SCFAs) inulin esters because they are less studied. Additionally, HMI has been used to stabilize various dispersion formulations, which have been observed to be safe because inulin is generally recognized as safe (GRAS). However, the results regarding HMI-based dispersion products are dispersed throughout the literature. This comprehensive review is discussed the possible limitations regarding SCFAs inulin esters, real food dispersion formulations, and HMI drugs. The results revealed that SCFAs inulin esters can regulate the human gut microbiota and increase the biological half-life of SCFAs in the human body. This comprehensive review discusses the versatility of HMI as a promising excipient for the production of hydrophobic drugs.

Structural properties and in vitro and in vivo immunomodulatory activity of an arabinofuranan from the fruits of Akebia quinata

In our continuous searching for natural active polysaccharides with immunomodulatory activity, an arabinofuranan (AQP70-3) was isolated and purified from the fruits of Akebia quinata (Houtt.) Decne. by using ion-exchange chromatography and gel permeation chromatography for the first time. AQP70-3 contained both α-l-Araf and β-l-Araf, and the absolute molecular weight was 1.06 × 10⁴ g/mol. The backbone of AQP70-3 comprised →5)-α-l-Araf-(1→, →3,5)-α-l-Araf-(1→, and →2,5)-α-l-Araf-(1→, with branches of →1)-β-l-Arafand →3)-α-l-Araf-(1→ residues. Biological assay suggested that AQP70-3 can stimulate phagocytic activity and promote the levels of nitric oxide (NO), interleukin (IL)-6, IL-1β, and tumor necrosis factor-α (TNF-α) of RAW264.7 cells. Furthermore, AQP70-3 was found to increase the production of reactive oxygen species (ROS) and NO in zebrafish embryo model.

Sulfated modification, characterization, immunomodulatory activities and mechanism of the polysaccharides from Cyclocarya paliurus on dendritic cells

In this study, a crude and purified polysaccharide from Cyclocarya paliurus (CPP, CPP_0.05) were performed with chlorosulfonic acid-pyridine (CSA-Pyr) method to obtain sulfated derivatives (S-CPP, S-CPP_0.05). After comparatively investigating, characterization results showed that the modifications were successful. Polysaccharides were used to culture mouse bone marrow-derived dendritic cells (BM-DCs) to evaluate their immunomodulatory activity and explore mechanism. The functional activity of CPP was significantly stronger than that of the purified polysaccharide CPP_0.05. Meanwhile, S-CPP showed stronger immunomodulatory activity than CPP through determination of cytokine expression levels. We found that p-JNK, p-p38MAPK and NF-κB p65 proteins were significantly increased by stimulus of CPP and S-CPP, blocking TLR2/4 could significantly decreased proteins above which proved that immune regulation effect of CPP and S-CPP on DCs was performed via MAPK and NF-κB signaling pathways by triggering TLR2/4. S-CPP could serve as potential immunomodulatory agents used as complementary medicine or functional foods.

Marine polysaccharides from Gelidium pacificum Okamura and Cereus sinensis reveal prebiotic functions

Many marine polysaccharides as prebiotics can promote host health by modulating gut microbiota. This study investigated the beneficial effects of purified marine plant-derived Gelidium pacificum Okamura polysaccharide (GPOP-1) and marine animal-derived Cereus sinensis polysaccharide (CSP-1) on normal mice by modulating gut microbiota. The composition and diversity of gut microbiota were evaluated using 16S rRNA high-throughput sequencing. The results showed that GPOP-1 and CSP-1 altered the composition of the gut microbiota and promoted the growth of beneficial bacteria. At the genus level, GPOP-1 increased the relative abundance of Bacteroides, Phascolarctobacterium, and decreased the relative abundance of Ruminococcus, Helicobacter, Allobaculum, Dorea and AF12. While CSP-1 increased the relative abundance of Coprococcus, Adlercreutzia, Roseburia, Phascolarctobacterium, and decreased the relative abundance of Bacteroides, Ruminococcus and Oscillospira. The changes in the gut microbiota may affect the body weight, immune organ index and the production of short-chain fatty acids in normal mice. Compared to the normal control group, GPOP-1 decreased average weight gain while CSP-1 increased average weight gain. Furthermore, both GPOP-1 and CSP-1 significantly increased thymus and spleen indexes and total short chain fatty acids production in mice. In summary, GPOP-1 and CSP-1 exerted prebiotic effects on normal mice.

A carrageenan/agarose composite sponge and its immunomodulatory activities toward RAW264.7

A kind of commercial hybrid carrageenan (HC)/agarose composite sponge containing κ-, μ-, ι-, and ν-carrageenan, which could turn into hydrogel and release carrageenan at human body temperature was fabricated for immune stimulation and modulation. Release behavior demonstrated that the hybrid carrageenan contained sponge was mechanically stable and could release carrageenan constantly. RT-PCR and ELISA experiments showed that the leaching liquor of the sponge could stimulate RAW264.7 from M0 state to a polarized state by secreting more anti-inflammatory factor IL-10 than pro-inflammatory ones, such as, IL-6 and TNF-α. Transwell experiments also indicated that the leaching liquor could promote the proliferation of NIH-3T3 by stimulating RAW264.7 of M0 state after 7 days. Results of particle size and intracellular concentration analyses suggested that the released carrageenan might enter into the cellular interior of RAW264.7 in the form of microgels or protein complexes. The sponge would be a promising candidate for skin wound dressing.

Bioactive Polysaccharides from Seaweeds

Bioactive compounds with diverse chemical structures play a significant role in disease prevention and maintenance of physiological functions. Due to the increase in industrial demand for new biosourced molecules, several types of biomasses are being exploited for the identification of bioactive metabolites and techno-functional biomolecules that are suitable for the subsequent uses in cosmetic, food and pharmaceutical fields. Among the various biomasses available, macroalgae are gaining popularity because of their potential nutraceutical and health benefits. Such health effects are delivered by specific diterpenes, pigments (fucoxanthin, phycocyanin, and carotenoids), bioactive peptides and polysaccharides. Abundant and recent studies have identified valuable biological activities of native algae polysaccharides, but also of their derivatives, including oligosaccharides and (bio)chemically modified polysaccharides. However, only a few of them can be industrially developed and open up new markets of active molecules, extracts or ingredients. In this respect, the health and nutraceutical claims associated with marine algal bioactive polysaccharides are summarized and comprehensively discussed in this review.

Anti-oxidant and anti-inflammatory effects of caffeic acid: in vivo evidences in a model of noise-induced hearing loss

SCOPE

The imbalance of cellular redox status, in conjunction with the activation of inflammatory processes, have been considered common predominant mechanisms of noise-induced hearing loss. The identification of novel natural products as potential therapeuticstargeting oxidative stress and inflammatory pathways is an emerging field. Here, we focused on the polyphenol caffeic acid (CA), the major representative of hydroxycinnamic acids and phenolic acid, in order to investigate its protective capacity in a model of sensorineural hearing loss induced by noise.

METHODS AND RESULTS

Hearing loss was induced by exposing animals (Wistar rats) to a pure tone, 120 dB, 10 kHz for 60 min. By using auditory brainstem responses (ABRs) and immunofluorescence analysis, we found that CA protects auditory function and limits cell death in the cochlear middle/basal turn, damaged by noise exposure. Immunofluorescence analysis provided evidence that CA mediates multiple cell protection mechanisms involving both anti-inflammatory and anti-oxidant effects by decreasing NF-κB and IL-1β expression in the cochlea and opposing the oxidative/nitrosative damage induced by noise insult.

CONCLUSIONS

These results demonstrate that the supplementation of polyphenol CA can be considered a valid therapeutic strategy for attenuating noise-induced hearing loss and cochlear damage targeting both inflammatory signalling and cochlear redox balance.

Effects of Nigella sativa seed polysaccharides on type 2 diabetic mice and gut microbiota

Effect of Nigella sativa seed polysaccharides (NSSP) on type 2 diabetic mice and its gut microbiota was investigated on the type 2 diabetic mice model feed by high-fat diet. Fasting blood glucose (FBG), biochemical parameters, expression levels of cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and phosphor-AKT (p-AKT) protein, membrane glucose transporter 4 (GLUT4) in skeletal muscles, as well as the change of gut microbiota profile in mice model were measured. Results showed that the high-dose NSSP could significantly lower the levels of FBG, glycosylated serum protein (GSP), triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), malondialdehyde (MDA), TNF-α, IL-6 and IL-1β, and significantly increased insulin (INS), high-density lipoprotein cholesterol (HDLC), total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT) and the expression levels of p-AKT and GLUT4 in mice. Besides, the high-dose NSSP has significantly increased the abundance of f_Muribaculaceae_Unclassified and Bacteroides, which were significantly suppressed in the mice gut after the treatment of streptozotocin (STZ). These results indicated that NSSP could improve the abnormal state of diabetic mice by regulating the PI3K/AKT signaling pathway with simultaneous changes of the gut microbiota profile.

Mesona chinensis Benth polysaccharides protect against oxidative stress and immunosuppression in cyclophosphamide-treated mice via MAPKs signal transduction pathways

In this study, the immune responses of Mesona chinensis Benth polysaccharides (MP) in vitro and in vivo were investigated. Results showed that MP presented immunomodulatory activities on macrophages and T lymphocytes in vitro. Compared with the cyclophosphamide (Cy)-induced immunosuppressive mice, the body weights, spleen indexes (3.45 to 4.91) and thymus indexes (0.78 to 1.04) of the mice treated with MP were increased, and the peripheral blood levels were recovered. MP treatment also increased superoxide dismutase, glutathione peroxidase and catalase activities, and reduced malondialdehyde levels to enhance the total antioxidant capacity of Cy-treated mice. In addition, MP significantly elevated IL-2, NO, and IFN-γ secretions of splenic lymphocytes and spleen, while MP mainly exerts an immune effect by regulating T lymphocytes. Furthermore, MP possessed the immunomodulatory activity by up-regulating the phosphorylation levels of proteins factors (c-Jun N-terminal kinase, extracellular regulated protein kinase and p38 kinase) in mitogen activated protein kinases signaling pathways. This study suggested that MP may be explored as a natural immune stimulant for functional food and nutraceutical industries.

Radioprotective effects and mechanisms of animal, plant and microbial polysaccharides

Ionizing radiation is increasingly used to successfully diagnose many human health problems, but ionizing radiation may cause damage to organs/tissues in the living organisms such as the spleen, liver, skin, and brain. Many radiation protective agents have been discovered, with the deepening of radiation research. Unfortunately, these protective agents have many side effects, which cause drug resistance, nausea, vomiting, osteoporosis, etc. The polysaccharides extracted from natural sources are widely available and low in toxicity. In vivo and in vitro experiments have demonstrated that polysaccharides have anti-radiation activity through anti-oxidation, immune regulation, protection of hematopoietic system and protection against DNA damage. Recently, some studies have shown that polysaccharides were resistant to radiation. In the review, the anti-radiation activities of polysaccharides from different sources are summarized, and the anti-radiation mechanisms are discussed as well. It can be used to develop more effective anti-radiation management drugs.

Natural polysaccharides with different conformations: extraction, structure and anti-tumor activity

Natural polysaccharides as sustainable polymers are rich sources with good biological safety and various biological functions, which are important research topics in the fields of food and medicine.

Chemical modifications of polysaccharides and their anti-tumor activities

With the rising trend of incidence of cancers, effective therapies are urgently needed to control human malignancies. However, the chemotherapy drugs currently on the market cause serious side effects. Polysaccharides belong to a class of biomacromolecules, which have drawn considerable research interest over the years as it possess anti-cancer activities or can increase the efficacy of conventional chemotherapy drugs with fewer side effects. The antitumor activity of many polysaccharides was significantly increased after modification. Based on these encouraging observations, a great deal of effort has been focused on discovering anti-cancer polysaccharides and modified derivatives for the development of effective therapeutics for various human cancers. This review highlights recent advances on the major chemical modification methods of polysaccharides, and discusses the effect of molecular modification on the physicochemical properties and anti-tumor activities of polysaccharides. Meanwhile, the underlying anti-tumor mechanisms of polysaccharide and its modified derivatives were also discussed.