Glycosaminoglycans from a Sea Snake (Lapemis curtus): Extraction, Structural Characterization and Antioxidant Activity.

Sea snakes have wide application prospects in medicine, health food and other fields. Several novel polysaccharides were successfully obtained from the skin and the meat of a sea snake (Lapemis curtus). The structures of polysaccharides LSP3 and LMP3, which were extracted and purified from Lapemis curtus, were determined to be new and highly heterogenic glycosaminoglycans (GAGs) by means of FT-IR, ESI-MS/MS and NMR. LSP3 is a hybrid dermatan sulfate (DS) and composed of 48% 4-sulfated disaccharides (Di4S), 42% 6-sulfated disaccharides (Di6S) and 5% disulfated disaccharides (Di2,6S), while LMP3 is a hybrid chondroitin sulfate (CS) and composed of 70% Di4S, 20% Di6S, and 8% Di2,6S. More importantly, LSP3 and LMP3 showed a strong scavenging ability of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, iron (Fe2+) chelating activity and total antioxidant capacity in vitro, especially LSP3, with high contents of uronic acid and sulfate, which possessed a higher scavenging ability of DPPH radicals than other fractions. These data suggested that the sea snake polysaccharides could be promising candidates for natural antioxidant ingredients.

Fucoidan MF4 from Fucus vesiculosus inhibits Lewis lung cancer via STING-TBK1-IRF3 pathway.

Fucoidan, a sulfated polysaccharide of marine origin found in brown algae and sea cucumbers, has been identified as a neuroprotective compound. In this study, a novel fucoidan MF4 was extracted from Fucus vesiculosus and isolated using Q-Sepharose fast-flow ion-exchange chromatography. The physicochemical properties of MF4 were characterized. MF4 is primarily composed of fucose, xylose, galactose, glucose, and mannose in a molar ratio of 12.3: 4.9: 1.1: 1.0: 1.1, with an average molecular weight of 67.7 kDa. Notably, MF4 demonstrated suppression of LLC tumor growth in vivo. RNA-sequencing analysis revealed that MF4 enhanced the expression of type I interferon-associated downstream genes in macrophages. Furthermore, MF4 increased the levels of phosphorylated TBK1 and IRF3 proteins in vitro. By activating the STING-TBK1-IRF3 signaling pathway, MF4 may enhance the antitumor activity of macrophages. Taken together, MF4 has promising potential as an antitumor and immunomodulatory agent.

The STING-mediated antiviral effect of fucoidan from Durvillaea antarctica.

Fucoidans have attracted increasing attention due to their minimal toxicity and various biological activities, such as antioxidant, anti-inflammatory, anti-tumor and immunomodulatory effects. In this study, the antiviral effect and mechanism of fucoidan (FU) derived from Durvillaea antarctica were explored in vitro. The results demonstrated that FU effectively inhibited the infection of both RNA virus (VSV) and DNA virus (HSV-1). The potential antiviral mechanism of FU is to trigger the production of type I IFN (IFN-I) and IFN-stimulated genes dependent on the cytoplasmic DNA adaptor STING (stimulator of interferon genes), and to enhance innate immune response via activating the STING-TBK1-IRF3 pathway. FU possesses the potential to be an antiviral and immunomodulatory agent in the future.

Design and syntheses of a bimolecular STING agonist based on the covalent STING antagonist.

Cyclic GMP-AMP synthase and stimulator of interferon genes (cGAS-STING) signaling stimulators, an essential innate immunity component, monitor invading pathogen DNA and damaged self-DNA, making them an appealing target for drug development. The natural STING agonist, 2'3'-cGAMP, mounts and stabilizes the STING homodimer to trigger an antiviral or antitumor immune responses. However, cyclic-dinucleotide-based STING agonists show limited clinical effects owing to their short half-lives. To explore whether STING-dimer stabilizers could trigger STING signaling instead of cyclic dinucleotide-based molecules, we analyzed the structural characteristics of STING to design and synthesize a series of compounds based on the covalent STING inhibitor C-170, three of which were 23, 26, and 27, exhibited STING-dependent immune activation, both in vitro and in vivo. Compound 23 could act synergistically with cGAMP and other STING agonists as a promising moderate STING agonist. This indicates that promoting STING dimerization is a promising strategy for designing next-generation STING agonists.

Low molecular-weight polyguluronate phosphate: An immunostimulant by activating splenocyte/macrophage invitro and improving immune response invivo.

The substituents and backbones are two main factors affecting immune activities of polysaccharides. In the present study, we firstly evaluated the immunostimulating effects of phosphorylated, sulfated, H-phosphonated and nitrated derivatives of low-molecular-weight polymannuronate (LPM) and polyguluronate (LPG) on splenocytes and peritoneal macrophages in vitro. The results showed that the phosphate group was the best substituent to enhance the immune activities, and LPG phosphate (LPGP) had much better activity than LPM phosphate (LPMP). Further studies showed that LPGP not only promoted the proliferation of mouse splenocytes in the presence of either LPS or Con A, but also acted as an excellent peritoneal macrophage activator to enhance the cell phagocytosis, energy metabolism, cytokines release and activities of intracellular enzymes. The studies in RAW264.7 cells revealed that LPGP activated the TBK1-IκBα-NF-κB and the TBK1-IRF3 pathway. Moreover, LPGP rescued the immune response in the Cyclophosphamide-treated mice in vivo. In conclusion, LPGP is a potential alginate-based biological response modifier (BRM).

Chitosan coated pH/redox-responsive hyaluronic acid micelles for enhanced tumor targeted co-delivery of doxorubicin and siPD-L1.

The complex tumor microenvironment (TME) makes it difficult for single chemotherapy to achieve satisfactory therapeutic effects. Here, chitosan-coated hyaluronic acid micelles (R/C/D@HAssOA) that co-delivers doxorubicin (DOX) and programmed death-ligand 1 small interfering RNA (siPD-L1) are developed to enhance anti-tumor effect by combination of immunotherapy and chemotherapy. The pH/reduction dual-responsive co-delivery micelles R/C/D@HAssOA are spherical particles about 180 nm, and have good drug loading performance, stability, biocompatibility, and TME-responsive drug release properties. The CD44 receptor targeting HA significantly enhances the cellular uptake of DOX and siPD-L1, and siPD-L1 causes the immune infiltration of CD4+/CD8+ T cells by silencing PD-L1 expression. In vivo studies show that R/C/D@HAssOA exhibits significantly stronger anti-breast cancer effect than that of free DOX and micelles loaded only DOX. Therefore, the dual-stimulus responsive micelles provide a promising strategy for combining chemotherapy and siRNA-based immunotherapy to enhance efficacy.

Inhibition of Histone H3 Lysine-27 Demethylase Activity Relieves Rheumatoid Arthritis Symptoms via Repression of IL6 Transcription in Macrophages.

Rheumatoid arthritis (RA) occurs in about 5 per 1,000 people and can lead to severe joint damage and disability. However, the knowledge of pathogenesis and treatment for RA remains limited. Here, we found that histone demethylase inhibitor GSK-J4 relieved collagen induced arthritis (CIA) symptom in experimental mice model, and the underlying mechanism is related to epigenetic transcriptional regulation in macrophages. The role of epigenetic regulation has been introduced in the process of macrophage polarization and the pathogenesis of inflammatory diseases. As a repressive epigenetic marker, tri-methylation of lysine 27 on histone H3 (H3K27me3) was shown to be important for transcriptional gene expression regulation. Here, we comprehensively analyzed H3K27me3 binding promoter and corresponding genes function by RNA sequencing in two differentially polarized macrophage populations. The results revealed that H3K27me3 binds on the promoter regions of multiple critical cytokine genes and suppressed their transcription, such as IL6, specifically in M-CSF derived macrophages but not GM-CSF derived counterparts. Our results may provide a new approach for the treatment of inflammatory and autoimmune disorders.

The anti-inflammatory activity of specific-sized hyaluronic acid oligosaccharides.

Severe acute inflammatory conditions may cause tissue damage, sepsis, and death. As a critical component of the extracellular matrix, hyaluronic acid (HA) has been reported to possess pro- and anti-inflammatory properties via Toll-like receptors (TLRs). In this study, we prepared different sizes and structures of HA oligosaccharides and derivatives and investigated the effects on inflammation in vitro and in vivo. Our results showed that HA tetra-saccharide was the minimum fragment to enhance inflammation, whereas HA disaccharide competitively blocked TLR4-dependent inflammation. The enzymatic HA disaccharide (ΔHA2) inhibited lipopolysaccharide (LPS)-induced inflammation. Based on structure-activity relationship analysis, we observed that anti-inflammatory activity depended on HAs polymerization degree, acetyl group, and configuration. In addition, we demonstrated that ΔHA2 reduced LPS-induced pro-inflammatory cytokines production in vivo. ΔHA2, a native metabolite of HA polysaccharides, may have a potential role against LPS-mediated inflammatory diseases.

Alginate-chitosan oligosaccharide-ZnO composite hydrogel for accelerating wound healing.

Moist, breathable and antibacterial microenvironment can promote cell proliferation and migration, which is beneficial to wound healing. Here, we fabricated a novel sodium alginate-chitosan oligosaccharide­zinc oxide (SA-COS-ZnO) composite hydrogel by spontaneous Schiff base reaction, using aldehydated sodium alginate (SA), chitosan oligosaccharide (COS), and zinc oxide (ZnO) nanoparticles, which can provide a moist and antibacterial environment for wound healing. The porosity and swelling degree of SA-COS-ZnO hydrogel are 80% and 150%, respectively, and its water vapor permeability is 682 g/m2/24h. The composite hydrogel showed good biocompatibility to blood cells, 3T3 cells, and 293T cells, and significant antibacterial activity against Escherichia coli, Staphylococcus aureus, Candida albicans, and Bacillus subtilis. Moreover, the hydrogel showed a promoting effect on wound healing in a rat scald model. The present study suggests that marine carbohydrates composite hydrogels are promising in wound care management.

Application prospect of polysaccharides in the development of anti-novel coronavirus drugs and vaccines.

Since the outbreak of the novel coronavirus disease COVID-19, caused by the SARS-CoV-2 virus, it has spread rapidly worldwide and poses a great threat to public health. This is the third serious coronavirus outbreak in <20 years, following SARS in 2002-2003 and MERS in 2012. So far, there are almost no specific clinically effective drugs and vaccines available for COVID-19. Polysaccharides with good safety, immune regulation and antiviral activity have broad application prospects in anti-virus, especially in anti-coronavirus applications. Here, we reviewed the antiviral mechanisms of some polysaccharides, such as glycosaminoglycans, marine polysaccharides, traditional Chinese medicine polysaccharides, and their application progress in anti-coronavirus. In particular, the application prospects of polysaccharide-based vaccine adjuvants, nanomaterials and drug delivery systems in the fight against novel coronavirus were also analyzed and summarized. Additionally, we speculate the possible mechanisms of polysaccharides anti-SARS-CoV-2, and propose the strategy of loading S or N protein from coronavirus onto polysaccharide capped gold nanoparticles vaccine for COVID-19 treatment. This review may provide a new approach for the development of COVID-19 therapeutic agents and vaccines.

Sulfated polymannuroguluronate TGC161 ameliorates leukopenia by inhibiting CD4+ T cell apoptosis.

Polysaccharides have aroused considerable interest due to their diverse biological activities and low toxicity. In this study, we evaluated the effect of marine polysaccharide sulfated polymannuroguluronate (TGC161) on the leukopenia induced by chemotherapy. It is found that TGC161 ameliorates the leukopenia. Besides, TGC161 would promote CD4+ T cell differentiation and maturation in the thymus, but does not have a significant effect on precursor cells in bone marrow. Furthermore, TGC161 inhibits CD4+ T cell apoptosis in vitro. Collectively, our findings offer a natural and harmless polysaccharide to ameliorate leukopenia.

Epirubicin-loaded marine carrageenan oligosaccharide capped gold nanoparticle system for pH-triggered anticancer drug release.

Gold nanoparticles (AuNPs) and the pH stimuli-responsive drug delivery system have been extensively applied in cancer treatment. Carrageenan derived from marine red algae shows a promising application prospect for drug delivery as a nanomaterial for its biodegradability, abundance, and non-toxicity. Carrageenan oligosaccharide (CAO) was used as a biocompatible reductant for green synthesis of CAO-AuNPs, and the obtained CAO-AuNPs were further used as a delivery system for pH-triggered delivery of epirubicin (EPI). The EPI-CAO-AuNPs were demonstrated to be spherical and homogeneous with mean diameter of 141 ± 6 nm by means of electron microscopy and Malvern particle size analyzer. Results showed that the release of EPI from EPI-CAO-AuNPs was significant under acidic condition that simulated cancer environment, while it was negligible under physiological pH in vitro. Confocal laser scanning microscope and flow cytometry analysis showed that EPI-CAO-AuNPs were localized in cellular nucleus and induced more apoptosis of HCT-116 and HepG2 cells than free EPI. A new pH-triggered anticancer drug release was achieved by EPI-CAO-AuNPs system for the first time. The developed EPI-CAO-AuNPs nanosystem shows a promising prospect for pH-triggered delivery of antitumor drugs, and our work provides a new idea for targeted drug delivery by using biocompatible marine carbohydrates as nanomaterial.

Preparation, Characterization, and Inhibition of Hyaluronic Acid Oligosaccharides in Triple-Negative Breast Cancer.

Hyaluronic acid (hyaluronan, HA) is a critical component of the extracellular matrix and plays an important biological function of interacting with different molecules and receptors. In this study, both odd- and even-numbered HA oligosaccharides (HAOs) with specific degrees of polymerization (DP) were prepared by different hydrochloric acid hydrolyses, and their structures were characterized by means of HPLC, ESI-MS, and NMR. The data show that the odd-numbered HAOs (DP3-11) have a glucuronic acid reducing end, while the even-numbered HAOs (DP2-10) have an N-acetylglucosamine reducing end. Biological evaluations indicated that all HAOs significantly inhibited the growth and migration of triple-negative breast cancer (TNBC) MDA-MB-231 cells. Among these oligosaccharides, the HA tetrasaccharide (DP4) was confirmed to be the minimum fragment necessary to inhibit MDA-MB-231 cells. Our data suggest that HAOs have potential value in the treatment of TNBC.

Preparation and structural characterization of regioselective 4-O/6-O-desulfated chondroitin sulfate.

The sulfation pattern plays a crucial role in chondroitin sulfate (CS) biological activity, and preparation of CS with defined structure is essential for accurate pharmacological study. In this study, we focused on the preparation of regioselective 4-O/6-O-desulfated CS derived from porcine, employing a dimethyl sulfoxide-methanol (DMSO-MeOH) method and an N-methyl-N-(trimethylsilyl) -trifluoroacetamide (MTSTFA) method CS, respectively. Results showed that the sulfate at C4 position (4-O-S) of N-acetylgalactosamine (GalNAc) was selectively removed by the DMSO-MeOH method, and the sulfate at C6 position (6-O-S) of GalNAc was selectively removed by the MTSTFA method. Structures of desulfated CS were characterized by means of FT-IR, NMR and disaccharide composition analysis. The preparations of regioselective 4-O/6-O-desulfated CS are powerful for the study of structure-activity relationship of CS.