Anti-HBV activity and mechanism of marine-derived polyguluronate sulfate (PGS) in vitro

Neuroprotective effect of acetoxypachydiol against oxidative stress through activation of the Keap1-Nrf2/HO-1 pathway

BACKGROUND

Excessive oxidative stress in the brain is an important pathological factor in neurological diseases. Acetoxypachydiol (APHD) is a lipophilic germacrane-type diterpene extracted as a major component from different species of brown algae within the genus Dictyota. There have been no previous reports on the pharmacological activity of APHD. The present research aims to explore the potential neuroprotective properties of APHD and its underlying mechanisms.

METHODS

The possible mechanism of APHD was predicted using a combination of molecular docking and network pharmacological analysis. PC12 cells were induced by H2O2 and oxygen-glucose deprivation/reoxygenation (OGD/R), respectively. Western blot, flow cytometry, immunofluorescence staining, and qRT-PCR were used to investigate the antioxidant activity of APHD. The HO-1 inhibitor ZnPP and Nrf2 gene silencing were employed to confirm the influence of APHD on the signaling cascade involving HO-1, Nrf2, and Keap1 in vitro.

RESULTS

APHD exhibited antioxidant activity in both PC12 cells subjected to H2O2 and OGD/R conditions by downregulating the release of LDH, the concentrations of MDA, and ROS, and upregulating SOD, GSH-Px, and GSH concentrations. APHD could potentially initiate the Keap1-Nrf2/HO-1 signaling cascade, according to the findings from network pharmacology evaluation and molecular docking. Furthermore, APHD was observed to increase Nrf2 and HO-1 expression at both mRNA and protein levels, while downregulating the protein concentrations of Keap1. Both Nrf2 silencing and treatment with ZnPP reversed the neuroprotective effects of APHD.

CONCLUSIONS

APHD activated antioxidant enzymes and downregulated the levels of LDH, MDA, and ROS in two cell models. The neuroprotective effect is presumably reliant on upregulation of the Keap1-Nrf2/HO-1 pathway. Taken together, APHD from brown algae of the genus Dictyota shows potential as a candidate for novel neuroprotective agents.

Synthesis of sulfated alginate from its tributylammonium salt: Comparing the sulfating agents H2SO4-DCC and SO3·py

Direct comparison of the sulfating agents H2SO4-DCC and SO3·py for the synthesis of sulfated alginate (S-Alg) as well as detailed characterisation of the products that form is lacking. This study involving three researchers used the tributylammonium salt of alginate (T-Alg) as a common substrate for the sulfation reactions. It was found that the use of H2SO4-DCC resulted in poor control of the degree of sulfation (DS) and that the S-Alg polymers contained nitrogen (determined by elemental analysis) as a result of formation of an unwanted N-acylurea adduct. Additionally, a large reduction in chain length was confirmed. In contrast, the use of SO3·py gave reasonable control over DS, resulted in high yields, showed no contamination and no clear change in chain length. Detailed characterisation of such S-Alg polymers by 1H NMR, 13C NMR and 1H,13C-HSQC NMR confirmed sulfation at C2 and C3 with a preference for C2.

Sulfated Polysaccharides from Seaweeds: A Promising Strategy for Combatting Viral Diseases-A Review

The limited availability of treatments for many infectious diseases highlights the need for new treatments, particularly for viral infections. Natural compounds from seaweed are attracting increasing attention for the treatment of various viral diseases, and thousands of novel compounds have been isolated for the development of pharmaceutical products. Seaweed is a rich source of natural bioactive compounds, including polysaccharides. The discovery of algal polysaccharides with antiviral activity has significantly increased in the past few decades. Furthermore, unique polysaccharides isolated from seaweeds, such as carrageenan, alginates, fucoidans, galactans, laminarians, and ulvans, have been shown to act against viral infections. The antiviral mechanisms of these agents are based on their inhibition of DNA or RNA synthesis, viral entry, and viral replication. In this article, we review and provide an inclusive description of the antiviral activities of algal polysaccharides. Additionally, we discuss the challenges and opportunities for developing polysaccharide-based antiviral therapies, including issues related to drug delivery and formulation. Finally, this review highlights the need for further research for fully understanding the potential of seaweed polysaccharides as a source of antiviral agents and for developing effective treatments for viral diseases.

Strongylocentrotus nudus egg polysaccharide (SEP) suppresses HBV replication via activation of TLR4-induced immune pathway

Chronic hepatitis B virus (HBV) infection is a worldwide public health problem that causes significant liver-related morbidity and mortality. In our previous study, Strongylocentrotus nudus eggs polysaccharide (SEP), extracted from sea urchins, had immunomodulatory and antitumor effects. Whether SEP has anti-HBV activity is still obscure. This study demonstrated that SEP decreased the secretion of hepatitis B surface antigen (HBsAg) and e antigen (HBeAg), as well as the replication and transcription of HBV both in vitro and in vivo. Immunofluorescence and immunohistochemistry results showed that the level of HBV core antigen (HBcAg) was clearly reduced by SEP treatment. Mechanistically, RT-qPCR, western blot, and confocal microscopy analysis showed that SEP significantly increased the expression of toll-like receptor 4 (TLR4) and co-localization with TLR4. The downstream molecules of TLR4, including NF-κb and IRF3, were activated and the expression of IFN-β, TNF-α, IL-6, OAS, and MxA were also increased, which could suppress HBV replication. Moreover, SEP inhibited other genotypes of HBV and hepatitis C virus (HCV) replication in vitro. In summary, SEP could be investigated as a potential anti-HBV drug capable of modulating the innate immune.

Transcriptomics based identification of S100A3 as the key anti-hepatitis B virus factor of 16F16

More than 250 million people worldwide have chronic hepatitis B virus (HBV) infections, resulting in over 1 million annual fatalities because HBV cannot be adequately treated with current antivirals. Hepatocellular carcinoma (HCC) risk is elevated in the presence of the HBV. Novel and powerful medications that specifically target the persistent viral components are needed to remove infection. This study aimed to use HepG2.2.15 cells and the rAAV-HBV1.3 C57BL/6 mouse model established in our laboratory to examine the effects of 16F16 on HBV. The transcriptome analysis of the samples was performed to examine the impact of 16F16 therapy on host factors. We found that the HBsAg and HBeAg levels significantly decreased in a dose-dependent manner following the 16F16 treatment. 16F16 also showed significant anti-hepatitis B effects in vivo. The transcriptome analysis showed that 16F16 regulated the expression of several proteins in HBV-producing HepG2.2.15 cells. As one of the differentially expressed genes, the role of S100A3 in the anti-hepatitis B process of 16F16 was further investigated. The expression of the S100A3 protein significantly decreased following the 16F16 therapy. And upregulation of S100A3 caused an upregulation of HBV DNA, HBsAg, and HBeAg in HepG2.2.15 cells. Similarly, knockdown of S100A3 significantly reduced the levels of HBsAg, HBeAg, and HBV DNA. Our findings proved that S100A3 might be a new target for combating HBV pathogenesis. 16F16 can target several proteins involved in HBV pathogenesis, and may be a promising drug precursor molecule for the treatment of HBV.

Inhibitory activities of alginate phosphate and sulfate derivatives against SARS-CoV-2 in vitro

Alginate derivatives have been demonstrated remarkable antiviral activities. Here we firstly identified polymannuronate phosphate (PMP) as a highly potential anti-SARS-CoV-2 agent. The structure-activity relationship showed polymannuronate monophosphate (PMPD, Mw: 5.8 kDa, P%: 8.7 %) was the most effective component to block the interaction of spike to ACE2 with an IC₅₀ of 85.5 nM. Surface plasmon resonance study indicated that PMPD could bind to spike receptor binding domain (RBD) with the KD value of 78.59 nM. Molecular docking further suggested that the probable binding site of PMPD to spike RBD protein is the interaction interface between spike and ACE2. PMPD has the potential to inhibit the SARS-CoV-2 infection in an independent manner of heparan sulfate proteoglycans. In addition, polyguluronate sulfate (PGS) and propylene glycol alginate sodium sulfate (PSS) unexpectedly showed 3CLpro inhibition with an IC₅₀ of 1.20 μM and 1.42 μM respectively. The polyguluronate backbone and sulfate group played pivotal roles in the 3CLpro inhibition. Overall, this study revealed the potential of PMPD as a novel agent against SARS-CoV-2. It also provided a theoretical basis for further study on the role of PGS and PSS as 3CLpro inhibitors.

Process and applications of alginate oligosaccharides with emphasis on health beneficial perspectives

Alginates are linear polymers comprising 40% of the dry weight of algae possess various applications in food and biomedical industries. Alginate oligosaccharides (AOS), a degradation product of alginate, is now gaining much attention for their beneficial role in food, pharmaceutical and agricultural industries. Hence this review was aimed to compile the information on alginate and AOS (prepared from seaweeds) during 1994-2020. As per our knowledge, this is the first review on the potential use of alginate oligosaccharides in different fields. The alginate derivatives are grouped according to their applications. They are involved in the isolation process and show antimicrobial, antioxidant, anti-inflammatory, antihypertension, anticancer, and immunostimulatory properties. AOS also have significant applications in prebiotics, nutritional supplements, plant growth development and others products.

Multifaceted role of natural sources for COVID-19 pandemic as marine drugs

COVID-19, which is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has quickly spread over the world, posing a global health concern. The ongoing epidemic has necessitated the development of novel drugs and potential therapies for patients infected with SARS-CoV-2. Advances in vaccination and medication development, no preventative vaccinations, or viable therapeutics against SARS-CoV-2 infection have been developed to date. As a result, additional research is needed in order to find a long-term solution to this devastating condition. Clinical studies are being conducted to determine the efficacy of bioactive compounds retrieved or synthesized from marine species starting material. The present study focuses on the anti-SARS-CoV-2 potential of marine-derived phytochemicals, which has been investigated utilizing in in silico, in vitro, and in vivo models to determine their effectiveness. Marine-derived biologically active substances, such as flavonoids, tannins, alkaloids, terpenoids, peptides, lectins, polysaccharides, and lipids, can affect SARS-CoV-2 during the viral particle's penetration and entry into the cell, replication of the viral nucleic acid, and virion release from the cell; they can also act on the host's cellular targets. COVID-19 has been proven to be resistant to several contaminants produced from marine resources. This paper gives an overview and summary of the various marine resources as marine drugs and their potential for treating SARS-CoV-2. We discussed at numerous natural compounds as marine drugs generated from natural sources for treating COVID-19 and controlling the current pandemic scenario.

Advances in Research on Antiviral Activities of Sulfated Polysaccharides from Seaweeds

In recent years, various viral diseases have suddenly erupted, resulting in widespread infection and death. A variety of biological activities from marine natural products have gradually attracted the attention of people. Seaweeds have a wide range of sources, huge output, and high economic benefits. This is very promising in the pharmaceutical industry. In particular, sulfated polysaccharides derived from seaweeds, considered a potential source of bioactive compounds for drug development, have shown antiviral activity against a broad spectrum of viruses, mainly including common DNA viruses and RNA viruses. In addition, sulfated polysaccharides can also improve the body’s immunity. This review focuses on recent advances in antiviral research on the sulfated polysaccharides from seaweeds, including carrageenan, galactan, fucoidan, alginate, ulvan, p-KG03, naviculan, and calcium spirulan. We hope that this review will provide new ideas for the development of COVID-19 therapeutics and vaccines.

Novel Molecular Therapeutics Targeting Signaling Pathway to Control Hepatitis B Viral Infection

Numerous canonical cellular signaling pathways modulate hepatitis B virus (HBV) replication. HBV genome products are known to play a significant role in regulating these cellular pathways for the liver’s viral-related pathology and physiology and have been identified as the main factor in hepatocarcinogenesis. Signaling changes during viral replication ultimately affect cellular persistence, multiplication, migration, genome instability, and genome damage, leading to proliferation, evasion of apoptosis, block of differentiation, and immortality. Recent studies have documented that numerous signaling pathway agonists or inhibitors play an important role in reducing HBV replication in vitro and in vivo, and some have been used in phase I or phase II clinical trials. These optional agents as molecular therapeutics target cellular pathways that could limit the replication and transcription of HBV or inhibit the secretion of the small surface antigen of HBV in a signaling-independent manner. As principle-based available information, a combined strategy including antiviral therapy and immunomodulation will be needed to control HBV infection effectively. In this review, we summarize recent findings on interventions of molecular regulators in viral replication and the interactions of HBV proteins with the components of the various targeting cellular pathways, which may assist in designing novel agents to modulate signaling pathways to prevent HBV replication or carcinogenesis.

Algae and Their Metabolites as Potential Bio-Pesticides

An increasing human population necessitates more food production, yet current techniques in agriculture, such as chemical pesticide use, have negative impacts on the ecosystems and strong public opposition. Alternatives to synthetic pesticides should be safe for humans, the environment, and be sustainable. Extremely diverse ecological niches and millions of years of competition have shaped the genomes of algae to produce a myriad of substances that may serve humans in various biotechnological areas. Among the thousands of described algal species, only a small number have been investigated for valuable metabolites, yet these revealed the potential of algal metabolites as bio-pesticides. This review focuses on macroalgae and microalgae (including cyanobacteria) and their extracts or purified compounds, that have proven to be effective antibacterial, antiviral, antifungal, nematocides, insecticides, herbicides, and plant growth stimulants. Moreover, the mechanisms of action of the majority of these metabolites against plant pests are thoroughly discussed. The available information demonstrated herbicidal activities via inhibition of photosynthesis, antimicrobial activities via induction of plant defense responses, inhibition of quorum sensing and blocking virus entry, and insecticidal activities via neurotoxicity. The discovery of antimetabolites also seems to hold great potential as one recent example showed antimicrobial and herbicidal properties. Algae, especially microalgae, represent a vast untapped resource for discovering novel and safe biopesticide compounds.

Antiviral Strategies Using Natural Source-Derived Sulfated Polysaccharides in the Light of the COVID-19 Pandemic and Major Human Pathogenic Viruses

Only a mere fraction of the huge variety of human pathogenic viruses can be targeted by the currently available spectrum of antiviral drugs. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak has highlighted the urgent need for molecules that can be deployed quickly to treat novel, developing or re-emerging viral infections. Sulfated polysaccharides are found on the surfaces of both the susceptible host cells and the majority of human viruses, and thus can play an important role during viral infection. Such polysaccharides widely occurring in natural sources, specifically those converted into sulfated varieties, have already proved to possess a high level and sometimes also broad-spectrum antiviral activity. This antiviral potency can be determined through multifold molecular pathways, which in many cases have low profiles of cytotoxicity. Consequently, several new polysaccharide-derived drugs are currently being investigated in clinical settings. We reviewed the present status of research on sulfated polysaccharide-based antiviral agents, their structural characteristics, structure-activity relationships, and the potential of clinical application. Furthermore, the molecular mechanisms of sulfated polysaccharides involved in viral infection or in antiviral activity, respectively, are discussed, together with a focus on the emerging methodology contributing to polysaccharide-based drug development.

The direct and indirect effects of bioactive compounds against coronavirus

Emerging viruses are known to pose a threat to humans in the world. COVID‐19, a newly emerging viral respiratory disease, can spread quickly from people to people via respiratory droplets, cough, sneeze, or exhale. Up to now, there are no specific therapies found for the treatment of COVID‐19. In this sense, the rising demand for effective antiviral drugs is stressed. The main goal of the present study is to cover the current literature about bioactive compounds (e.g., polyphenols, glucosinolates, carotenoids, minerals, vitamins, oligosaccharides, bioactive peptides, essential oils, and probiotics) with potential efficiency against COVID‐19, showing antiviral activities via the inhibition of coronavirus entry into the host cell, coronavirus enzymes, as well as the virus replication in human cells. In turn, these compounds can boost the immune system, helping fight against COVID‐19. Overall, it can be concluded that bioactives and the functional foods containing these compounds can be natural alternatives for boosting the immune system and defeating coronavirus.

Protective effects of sulfated polysaccharides from Lentinula edodes on the lung and liver of MODS mice

In this work, the effects of sulfated polysaccharides from Lentinula edodes (SPLE) on zymosan (ZYM)-induced multiple organ dysfunction syndrome (MODS) mice were investigated. Using the MODS mice model, biochemical works have already shown that in mice treated with SPLE, the lung parameters of GGT, C3 and hs-CRP were down-regulated and the hepatic parameters of TC, TG, ALT and AST, HDLC, LDL-C and VLDL-C were improved, the serum levels of CK, Cr and Amy were decreased, and the levels of inflammatory factors such as TNF-α, IL-1β, IL-6 and IL-10 were also reduced, the activity of antioxidant enzymes SOD and CAT enhanced, and the content of MDA was reduced. In addition, histopathology of the lung and liver confirmed the beneficial effects of SPLE on MODS mice, indicating that SPLE played a role in protecting the organ function of MODS mice. In addition, SPLE was characterized as a sulfated β-glucan linked by β-type glycosidic bonds. These conclusions indicated that SPLE had effective antioxidant and anti-inflammatory activities, and could be used as a functional food and medicine to prevent MODS.

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.

Hepatocyte steatosis inhibits hepatitis B virus secretion via induction of endoplasmic reticulum stress

The effects of hepatocyte steatosis on hepatitis B virus (HBV) DNA replication and HBV-related antigen secretion are incompletely understood. The aims of this study are to explore the effects and mechanism of hepatocyte steatosis on HBV replication and secretion. Stearic acid (SA) and oleic acid (OA) were used to induce HepG2.2.15 cell steatosis in this study. The expressions of glucose-regulated protein 78 (GRP78), phosphorylation of protein kinase R-like endoplasmic reticulum (ER) kinase (p-PERK), and eukaryotic translation initiation factor 2α (p-eIF2α) were detected by Western blotting (WB). HBV DNA, HBsAg, and HBeAg in the supernatant were determined by real-time fluorescent polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay. Intracellular HBV DNA, HBsAg level, and HBV RNA were measured by real-time fluorescent PCR, WB, and real-time quantitative reverse transcriptase-PCR, respectively. The results showed that SA and OA significantly increased intracellular lipid droplets and triglyceride levels. SA and OA significantly induced GRP78, p-PERK, and p-eIF2α expressions from 24 to 72 h. 4-phenylbutyric acid (PBA) alleviated ER stress induced by SA. SA promoted intracellular HBsAg and HBV DNA accumulation; however, it inhibited the transcript of HBV 3.5 kb mRNA and S mRNA. The secretion of HBsAg and HBV DNA inhibited by SA or OA could be partially restored by pretreatment with PBA but not by inhibiting GRP78 expression with siRNA. Hepatocyte steatosis inhibits HBsAg and HBV DNA secretion via induction of ER stress in hepatocytes, but not via induction of GRP78.

Anti-HBV Activities of Polysaccharides from Thais clavigera (Küster) by In Vitro and In Vivo Study

Hepatitis B virus (HBV) infection remains a major global health problem. It is therefore imperative to develop drugs for anti-hepatitis B with high-efficiency and low toxicity. Attracted by the observations and evidence that the symptoms of some patients from the Southern Fujian, China, suffering from hepatitis B were alleviated after daily eating an edible marine mollusk, Thais clavigera (Küster 1860) (TCK). Water-soluble polysaccharide from TCK (TCKP1) was isolated and characterized. The anti-HBV activity of TCKP1 and its regulatory pathway were investigated on both HepG2.2.15 cell line and HBV transgenic mice. The data obtained from in vitro studies showed that TCKP1 significantly enhanced the production of IFN-α, and reduced the level of HBV antigens and HBV DNA in the supernatants of HepG2.2.15 cells in a dose-dependent manner with low cytotoxicity. The result of the study on the HBV transgenic mice further revealed that TCKP1 significantly decreased the level of transaminases, HBsAg, HBeAg, and HBV DNA in the serum, as well as HBsAg, HBeAg, HBV DNA, and HBV RNA in the liver of HBV transgenic (HBV-Tg) mice. Furthermore, TCKP1 exhibited equivalent inhibitory effect with the positive control tenofovir alafenamide (TAF) on the markers above except for HBV DNA even in low dosage in a mouse model. However, the TCKP1 high-dose group displayed stronger inhibition of transaminases and liver HBsAg, HBeAg, and HBV RNA when compared with those of TAF. Meanwhile, inflammation of the liver was, by pathological observation, relieved in a dose-dependent manner after being treated with TCKP1. In addition, elevated levels of interleukin-12 (IL-12) and interferon γ (IFN-γ), and reduced level of interleukin-4 (IL-4) in the serum were observed, indicating that the anti-HBV effect of TCKP1 was achieved by potentiating immunocyte function and regulating the balance of Th1/Th2 cytokines.

Advances in Targeting HPV Infection as Potential Alternative Prophylactic Means

Infection by oncogenic human papillomavirus (HPV) is the primary cause of cervical cancer and other anogenital cancers. The majority of cervical cancer cases occur in low- and middle- income countries (LMIC). Concurrent infection with Human Immunodeficiency Virus (HIV) further increases the risk of HPV infection and exacerbates disease onset and progression. Highly effective prophylactic vaccines do exist to combat HPV infection with the most common oncogenic types, but the accessibility to these in LMIC is severely limited due to cost, difficulties in accessing the target population, cultural issues, and maintenance of a cold chain. Alternative preventive measures against HPV infection that are more accessible and affordable are therefore also needed to control cervical cancer risk. There are several efforts in identifying such alternative prophylactics which target key molecules involved in early HPV infection events. This review summarizes the current knowledge of the initial steps in HPV infection, from host cell-surface engagement to cellular trafficking of the viral genome before arrival in the nucleus. The key molecules that can be potentially targeted are highlighted, and a discussion on their applicability as alternative preventive means against HPV infection, with a focus on LMIC, is presented.

Hepatocyte Endoplasmic Reticulum Stress Inhibits Hepatitis B Virus Secretion and Delays Intracellular Hepatitis B Virus Clearance After Entecavir Treatment

Background: The aim of this study was to explore the effects of endoplasmic reticulum (ER) stress on hepatitis B virus (HBV) replication and the antiviral effect of entecavir (ETV).

Methods: Thapsigargin (TG) and stearic acid (SA) were used to induce ER stress in HepG2.2.15 cells and HepAD38 cells that contained an integrated HBV genome, while ETV was used to inhibit HBV replication. The expression levels of glucose-regulated protein 78 (GRP78) and phosphorylated eukaryotic translation initiation factor 2 subunit alpha (p-eIF2α) were measured by western blotting. Intracellular HBV DNA was determined by qPCR; HBsAg by western blotting; HBV RNA by real-time RT-qPCR; HBsAg and HBeAg in supernatants by enzyme-linked immunosorbent assay (ELISA); and HBV DNA in supernatants by qPCR.

Results: TG and SA induced ER stress in HepG2.2.15 cells and HepAD38 cells from 12 to 48 h post treatment. However, 4-phenylbutyric acid (PBA) partly alleviated the TG-induced ER stress. Moreover, TG inhibited HBsAg, HBeAg, and HBV DNA secretion from 12 to 48 h, while different concentrations of SA inhibited HBsAg and HBV DNA secretion at 48 h. TG promoted intracellular HBV DNA and HBsAg accumulation and the transcription of the HBV 3.5-kb mRNA and S mRNA. PBA treatment restored the secretion of HBsAg and HBV DNA. Finally, ER stress accelerated extracellular HBV DNA clearance but delayed intracellular HBV DNA clearance after ETV treatment.

Conclusions: Hepatocyte ER stress promoted intracellular HBV DNA and HBsAg accumulation by inhibiting their secretion. Our study also suggested that hepatocyte ER stress delayed intracellular HBV DNA clearance after ETV treatment.

Neddylation inhibitor MLN4924 has anti-HBV activity via modulating the ERK-HNF1α-C/EBPα-HNF4α axis

Hepatitis B virus (HBV) infection is a major public health problem. The high levels of HBV DNA and HBsAg are positively associated with the development of secondary liver diseases, including hepatocellular carcinoma (HCC). Current treatment with nucleos(t)ide analogues mainly reduces viral DNA, but has minimal, if any, inhibitory effect on the viral antigen. Although IFN reduces both HBV DNA and HBsAg, the serious associated side effects limit its use in clinic. Thus, there is an urgent demanding for novel anti‐HBV therapy. In our study, viral parameters were determined in the supernatant of HepG2.2.15 cells, HBV‐expressing Huh7 and HepG2 cells which transfected with HBV plasmids and in the serum of HBV mouse models with hydrodynamic injection of pAAV‐HBV1.2 plasmid. RT‐qPCR and Southern blot were performed to detect 35kb mRNA and cccDNA. RT‐qPCR, Luciferase assay and Western blot were used to determine anti‐HBV effects of MLN4924 and the underlying mechanisms. We found that treatment with MLN4924, the first‐in‐class neddylation inhibitor currently in several phase II clinical trials for anti‐cancer application, effectively suppressed production of HBV DNA, HBsAg, 3.5kb HBV RNA as well as cccDNA. Mechanistically, MLN4924 blocks cullin neddylation and activates ERK to suppress the expression of several transcription factors required for HBV replication, including HNF1α, C/EBPα and HNF4α, leading to an effective blockage in the production of cccDNA and HBV antigen. Our study revealed that neddylation inhibitor MLN4924 has impressive anti‐HBV activity by inhibiting HBV replication, thus providing sound rationale for future MLN4924 clinical trial as a novel anti‐HBV therapy.

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.

The inhibitory effects and mechanisms of polymannuroguluronate sulfate against human papillomavirus infection in vitro and in vivo

Human papillomaviruses (HPVs) are non-enveloped DNA viruses that infect epithelia and can cause a wide variety of benign and pre-malignant epithelial tumours. The sulfated polysaccharides such as carrageenans were reported to be able to interfere with the binding process of HPV to the cell surface. In this study, brown seaweed derived polysaccharides polymannuroguluronate sulfate (PMGS) were prepared, and their anti-HPV effects were explored in vitro and in vivo. The results indicated that PMGS effectively inhibited high-risk HPV16 and HPV45 infection with very low toxicity. PMGS may inactivate HPV particles or block the binding and entry process of HPV through direct interaction with viral capsid proteins. PMGS can enter into HeLa cells and down-regulate the expression levels of viral oncogene proteins E6 and E7. In addition, PMGS also dramatically inhibited HPV infection on the skin of BALB/c Nude Mice. Thus, marine derived polysaccharide PMGS possessed anti-HPV activities in vitro and in vivo, and may block HPV infection via targeting viral capsid L1 protein, suggesting that it has great potential to be developed into a novel anti-HPV agent in the future.

Antiviral activity of a polysaccharide from Radix Isatidis (Isatis indigotica Fortune) against hepatitis B virus (HBV) in vitro via activation of JAK/STAT signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatitis B virus (HBV) infection frequently results in both acute and chronic hepatitis and poses serious threats to human health worldwide. Despite the availability of effective HBV vaccine and anti-HBV drugs, apparently inevitable side effects and resistance have limited its efficiency, thus prompt the search for new anti-HBV agents. The traditional Chinese medicine Radix Isatidis has been used for thousands of years, mainly for the treatment of viral and bacterial infection diseases including hepatitis.

AIM OF THE STUDY

In this study, antiviral activities of a Radix Isatidis (Isatis indigotica Fortune) polysaccharide (RIP) were evaluated in vitro model using the HepG2.2.15 cell line and the underlying mechanism was elucidated with the aim of developing a novel anti-HBV therapeutic agent.

MATERIALS AND METHODS

Structure features of the purified polysaccharide RIP were investigated by a combination of chemical and instrumental analysis. Drug cytotoxicity was assessed using the MTT assay. The contents of HBsAg, HBeAg, intracellular and extracellular IFN-α level were measured using respective commercially available ELISA kit. The HBV DNA expression was evaluated by real-time quantitative polymerase chain reaction (PCR) and the relevant proteins involved in TFN/JAK/STAT signaling pathways were examined by western blot assay.

RESULTS

MTT assay showed that RIP had no toxicity on HepG2.2.15 cell line below the concentration 400 μg/ml at Day 3, 6 and 9. Furthermore, RIP at the concentration of 50, 100 and 200 μg/ml significantly reduced extracellular and intracellular level of HBsAg, HBeAg and HBV DNA in HepG2.2.15 cells in a time and dose-dependent manner. Moreover, RIP also enhanced the production of IFN-α in HepG2.2.15 cell via activation of JAK/STAT signal pathway and induction of antiviral proteins, as evidenced by the increased protein expression of p-STAT-1, p-STAT-2, p-JAK1, p-TYK2, OAS1, and Mx in HepG2.2.15 cells. In addition, the over expression of SOCS-1 and SOCS-3 was significantly abolished under same conditions.

CONCLUSIONS

These results suggested that the HBV inhibitory effect of RIP was possibly due to the activation of IFN-α-dependent JAK/STAT signal pathway and induction of the anti-HBV protein expression.

Advances in Research on the Bioactivity of Alginate Oligosaccharides

Alginate is a natural polysaccharide present in various marine brown seaweeds. Alginate oligosaccharide (AOS) is a degradation product of alginate, which has received increasing attention due to its low molecular weight and promising biological activity. The wide-ranging biological activity of AOS is closely related to the diversity of their structures. AOS with a specific structure and distinct applications can be obtained by different methods of alginate degradation. This review focuses on recent advances in the biological activity of alginate and its derivatives, including their anti-tumor, anti-oxidative, immunoregulatory, anti-inflammatory, neuroprotective, antibacterial, hypolipidemic, antihypertensive, and hypoglycemic properties, as well as the ability to suppress obesity and promote cell proliferation and regulate plant growth. We hope that this review will provide theoretical basis and inspiration for the high-value research developments and utilization of AOS-related products.

The inhibitory effects and mechanisms of 3,6-O-sulfated chitosan against human papillomavirus infection

High-risk human papillomavirus (HPV) infection can lead to the development of cervical cancers that are a significant health burden worldwide. The heparin-like polysaccharides such as dextran sulfate and carrageenan were reported to be able to prevent the binding of HPV to the cell surface. In this study, a 3,6-O-sulfated chitosan (36S) was prepared, and its anti-HPV effects were explored. The results showed that 36S effectively inhibited multiple genital HPV genotypes in different cell lines with low cytotoxicity. 36S may possibly block HPV adsorption via direct binding to the viral capsid proteins. 36S could enter into Hela cells and down-regulate cellular PI3K/Akt/mTOR pathway which is associated with autophagy. Thus, marine derived sulfated chitosan 36S possessed broad anti-HPV activities in vitro, and may possibly inhibit HPV infection by targeting viral capsid protein and host PI3K/Akt/mTOR pathway, suggesting that 36S merits further investigation as a novel anti-HPV agent.

Polyguluronate sulfate (PGS) attenuates immunological liver injury in vitro and in vivo

Hepatocyte damage, especially immunological liver injury, is a key process in the pathogenesis of hepatitis virus-induced liver diseases. The aim of this study was to investigate the protective effects of polyguluronate sulfate (PGS) against immunological liver damage. The results showed that PGS significantly reduced the H₂O₂-induced oxidative stress and increased the cell viability in HepG2 hepatocytes. PGS also suppressed the production of malondialdehyde (MDA), lactate dehydrogenase (LDH), TNF-α, and IL-6, while up-regulating the activity of SOD in HepG2 cells. Further, PGS (150 and 300mg/kg/day) significantly attenuated the elevation of serum glutamate pyruvate transaminase (ALT), aspartate aminotransferase (AST), total bilirubin (TBiL), in addition to liver MDA and NO levels in Con A-induced immunological liver injury within mice (P<0.05). Significant improvements of organ indexes (liver, spleen, and thymus) were observed in PGS-treated mice. PGS also significantly reduced the disorganization of hepatocytes and decreased the inflammatory cell infiltration caused by Con A treatment, suggesting that PGS was able to attenuate Con A-induced liver injury. In conclusion, PGS possesses significant hepatoprotective effects on immunological liver injury in vitro and in vivo, and this may be related to its antioxidant activities.

Synthesis of Fucoidan-Mimetic Glycopolymers with Well-Defined Sulfation Patterns via Emulsion Ring-Opening Metathesis Polymerization

The approach developed here offers distinct and well-defined glycopolymers for deciphering the biological roles of natural bioactive polysaccharides. Fucose monomers were chemically synthesized and decorated with specific sulfation patterns including unsulfate, monosulfate, disulfate, and trisulfate groups. The six fucoidan-mimetic glycopolymers (18-23) were successfully fabricated through microwave-assisted ring-opening metathesis polymerization (ROMP) in an emulsion system. The molecular weight (M_w), polydispersity index (PDI), and multiple functional groups were fully characterized by SEC-MALLS-RI and NMR spectroscopy. Three glycopolymers (19, 21, 23) associated with 2-O-sulfation exhibited better inhibitory effects on the H1N1 virus, while glycopolymers (19, 20) with monosulfate groups were more effective against the H3N2 virus. These findings would promote the development of novel anti-influenza A virus (IAV) drugs based on natural fucoidans.

Propylene glycol guluronate sulfate (PGGS) reduces lipid accumulation via AMP-activated kinase activation in palmitate-induced HepG2 cells

Cardiovascular disease (CVD) is the No. 1 cause of death worldwide. Hyperlipidemia is one of the major risk factors for CVD. Maintaining lipid homeostasis is an effective way to prevent CVD. We prepared propylene glycol guluronate sulfate (PGGS), a sulfated polysaccharide, and investigated its effect on lipid metabolism in HepG2 cells. We found that total cholesterol (TC) and triglycerides (TG) were significantly decreased in the cells after PGGS treatment. We have also shown that the AMPK signaling is activated after PGGS treatment as evidenced by changes in the expression of many AMPK downstream targets including SREBP-1c, SIRT-1, CPT1, PPARα, and FAS. Our results have demonstrated that PGGS is a potentially novel lipid-lowering agent for CVD prevention.

Cholyl-l-lysine-carboxylbutyryl adriamycin prodrugs targeting chemically induced liver injury

By use of carboxylbutyryl as a linker, adriamycin (ADR) and cholyl-l-Lys (an anti-inflammatory agent) were covalently conjugated and N^α-cholyl-N^ε-(N-carbonylpropionoadriamycin)-l-Lys (BCBALys) was constructed as a liver-targeting nano-delivery system to release cholyl-l-Lys and protect the liver from CCl₄-induced injury. In ultrapure water and rat plasma, 10^-6 M BCBALys formed nanoparticles of 42-231 nm in diameter and ∼116 nm in height. In a CCl₄-injured mouse model, however, only 2 µmol kg^-1 of BCBALys effectively protected the liver of the mice from injury, and the mouse liver histology showed no hepatic architecture loss and inflammatory cell infiltration. BCBALys selectively accumulated in the liver of CCl₄-injured mice, but not in other vital organs, and released cholyl-l-Lys. These data demonstrated that BCBALys exhibited high efficacy for treating CCl₄-induced liver injury in a targeted manner. The chemical mechanism of BCBALys nanoparticle formation and the pharmacological mechanism of BCBALys mouse liver protection from CCl₄-induced injury were also revealed by experiments.