Neoagaro-oligosaccharide monomers inhibit inflammation in LPS-stimulated macrophages through suppression of MAPK and NF-κB pathways

Effect of Chitooligosaccharides on TLR2/NF-κB Signaling in LPS-Stimulated RAW 264.7 Macrophages

Chitooligosaccharides (COSs), degraded products of chitosan or chitin, are attracting growing interest owing to their low degree of polymerization (DP), high solubility, and prominent anti-inflammatory activity. However, the correlation between their structure and anti-inflammatory activities still needs to be explored. In this study, we use LPS-stimulated RAW 264.7 macrophages as an inflammatory model to systematically evaluate COS1-7 for their effects on inflammatory mediators and NF-κB signaling pathways. The results of Griess assay, ELISA, and real-time quantitative PCR show that COSs can inhibit the expression of NO, iNOS, and pro-inflammatory cytokines (IL-6, TNF-α, MCP-1 and IL-1β), thereby attenuating inflammatory signaling. Notably, chitohexaose (COS6) exhibits the most significant anti-inflammatory effect, reducing the mRNA levels of LPS-induced iNOS, IL-6, and IL-1β and the production of IL-6 and TNF-α by more than 50%. Transcriptome, western blotting, and real-time quantitative PCR analysis reveal that COSs can inhibit the activation of the NF-κB signal pathway by down-regulating TLR2 levels. Additionally, molecular docking confirms that COSs retard TLR2/4 dimerization and LPS recognition by TLR4, affecting downstream signaling cascades. In summary, this study provides a valuable insight into the potential anti-inflammatory mechanism of COSs and highlights the possible applications in human health promotion by modulating receptor-mediated signaling pathways.

3,6-Anhydro-L-galactose suppresses mouse lymphocyte proliferation by attenuating JAK-STAT growth factor signal transduction and G1-S cell cycle progression

Recombinant GH16B β-agarase-catalyzed liquefaction of 5-7 %(w/v) melted agarose at 50 °C completely hydrolyzed agarose into neoagarohexaose (NA6) and neoagarotetraose (NA4). Subsequent saccharification by recombinant GH50A β-agarase or recombinant GH50A β-agarase/recombinant GH117A α-neoagarobiose hydrolase at 35 °C converted NA6/NA4 into neoagarobiose (NA2) or 3,6-anhydro-L-galactose (L-AHG)/D-galactose, respectively. Purification of NA6/NA4 and NA2 was achieved by Sephadex G-15 column chromatography, while L-AHG was purified by Sephadex G-10, achieving ≥ 98 % purity. L-AHG (25-200 μg/mL), but not NA2, NA4, or NA6, inhibited the proliferation of immobilized anti-CD3/anti-CD28-activated T cells and immobilized anti-CD40 + soluble anti-IgM + interleukin (IL)-4-activated B cells. This inhibition impacted the G1-S traverse in the cell cycle without influencing CD69 expression and p27Kip1 down-regulation, markers of the exit from G0 into G1 phase in activated lymphocytes. L-AHG impeded cyclin-dependent kinases (CDKs)-driven retinoblastoma phosphorylation, necessary for the G1-S traverse, by reducing the activating phosphorylation of CDKs (CDK4, CDK2, and CDK1) and lowering cyclin D3, cyclin A2 and cyclin B1 levels. Furthermore, L-AHG diminished the production of growth factors, including IL-2 in activated T cells and IL-6 in activated B cells. The antiproliferative effect of L-AHG on T cells was partially restored by exogenous IL-2 but was unaffected by exogenous IL-6 on B cells. L-AHG inhibited the activating phosphorylation of Janus kinase 1 (JAK1), affecting signal transducer and activator of transcription 1 (STAT1) and STAT3 signaling. These results demonstrate that L-AHG may serve as a novel immunosuppressant by impairing JAK-STAT growth factor signaling and G1-S cell cycle progression in T and B lymphocytes.

Boron in wound healing: a comprehensive investigation of its diverse mechanisms

Chronic wounds present a significant clinical challenge due to their prolonged healing time and susceptibility to infection. Boron, a trace element with diverse biological functions, has emerged as a promising therapeutic agent in wound healing. This review article comprehensively investigates the mechanisms underlying the beneficial effects of boron compounds in wound healing. Boron exerts its healing properties through multiple pathways, including anti-inflammatory, antimicrobial, antioxidant, and pro-proliferative effects. Inflammation is a crucial component of the wound-healing process, and boron has been shown to modulate inflammatory responses by inhibiting pro-inflammatory cytokines and promoting the resolution of inflammation. Furthermore, boron exhibits antimicrobial activity against a wide range of pathogens commonly associated with chronic wounds, thereby reducing the risk of infection and promoting wound closure. The antioxidant properties of boron help protect cells from oxidative stress, a common feature of chronic wounds that can impair healing. Additionally, boron stimulates cell proliferation and migration, as well as essential tissue regeneration and wound closure processes. Overall, this review highlights the potential of boron as a novel therapeutic approach for treating chronic wounds, offering insights into its diverse mechanisms of action and clinical implications.

Multi-omics analysis reveals that agaro-oligosaccharides with different degrees of polymerization alleviate colitis in mice by regulating intestinal flora and arginine synthesis

Inflammatory bowel disease (IBD) is a common chronic disease with a complex etiology, characterized by body weight loss, intestinal barrier damage, and an imbalance of intestinal flora, posing a significant threat to people's health. In this work, we studied whether safer natural active agaro-oligosaccharides (AOSs) benefit mice with IBD and elucidated their underlying mechanisms. The findings indicated that oral administration of agarobiose (A2), agarotriose (A3), and agarotetraose (A4) contributed to alleviating body weight loss and colon shortening, as well as enhancing IL-10 levels while reducing IL-6, IL-1β, and TNF-α. AOSs improved colon disruption, reduced the number of goblet cells caused by DSS, and enhanced the expression of Muc2, ZO-1, and occludin-1 to repair the intestinal barrier. It is noteworthy that A3 demonstrated superior outcomes in the evaluated AOSs relative to A2 and A4. This was evidenced by an increase in Bacteroidota and reduced Firmicutes at the phylum level, which corrected DSS-induced intestinal dysbiosis and significantly restored disrupted metabolic pathways, including amino acid and lipid metabolism. The differential metabolites between the AOS treatment groups and the model group were mainly enriched in arginine synthesis with co-regulated critical substances N-acetyl-L-citrulline and N2-acetylornithine, which alleviated colitis. This evidence offers a fresh perspective on the potential application of AOSs as functional foods to improve intestinal inflammation and metabolism.

Oral bomb effect nanotherapeutics alleviate ulcerative colitis through coordinated anti-inflammatory and pro-resolving strategies

Background: Ulcerative colitis (UC) is a debilitating chronic inflammatory bowel disease, and current treatments primarily focus on suppressing inflammation with limited efficacy. However, the resolution of inflammation also plays a crucial role in UC prognosis. Combining anti-inflammatory and pro-inflammatory resolution interventions may be a promising approach for treating UC. Materials and methods: The nano-bomb nanoparticles were validated for their ability to load CD98 siRNA (siCD98) and Annexin A1-mimetic peptides (Ac2-26 peptides), as well as release CO2 upon lysosomal escape. Surface modification with hyaluronic acid (HA) was assessed for its capability to target inflammatory tissues and cells. Biocompatibility and biosafety were evaluated through in vitro and in vivo studies. The anti-inflammatory and pro-resolving effects of siCD98@NPs and Ac2-26@NPs, both individually and in combination, were evaluated by measuring ROS production, pro-inflammatory cytokine expression, CD98 gene expression, and macrophage polarization. Results: These nanoparticles could efficiently load siCD98 and Ac2-26 peptides and release CO2 under acidic pH in the endo/lysosome to deliver drugs to the cytoplasm. HA could effectively target the inflammatory tissue and cells, showing good biocompatibility and biosafety both in vitro and in vivo. siCD98@NPs and Ac2-26@NPs showed anti-inflammatory effects by eliminating the over-production of ROS and down-regulating the expression of pro-inflammatory cytokines (TNF-α and IL-1β) and the CD98 gene; meanwhile, it showed pro-resolving function by inhibiting M0 to pro-inflammatory M1 macrophage conversion, with a more pronounced effect when combined with siCD98 and Ac2-26. The oral administration of chitosan-alginate hydrogel-encapsulated nanoparticles in UC model mice effectively alleviated inflammatory symptoms, reduced the expression of pro-inflammatory cytokines (TNF-α and IL-1β) and the CD98 gene, restored intestinal barrier function, and promoted M1 to M2 polarization, with a more pronounced effect when combined. Conclusion: By combining anti-inflammatory and pro-resolution interventions, these nanoparticles offer a novel therapeutic approach. This study offered a new approach for combination therapy of UC.

Isolation and identification of anti-inflammatory and analgesic polysaccharides from Coix seed (Coix lacryma-jobi L.var. Ma-yuen (Roman.) Stapf)

Coix seed is a nutrient-rich food and traditional Chinese medicine with anti-inflammatory and analgesic properties. Polysaccharides from Coix seed have been rarely investigated for structure and activities. In this study, the analgesic and anti-inflammatory effects were investigated in vivo and in vitro. The results showed that Coix seed had a significant influence on reducing the number of writhing, increasing the pain threshold and alleviating the swelling degree caused by acute inflammation. Column chromatography was used to obtain two active compounds of Coix seed. Compound 1 was (1→6)-α-glucan with a molecular weight of 6.81 × 105 Da. The chemical connection of compound 2 was as follows: α-Frup (2→ [1)-α-Glcp (6]5→1)-α-Glcp (4→1)-α-Glcp, which was isolated in Coix seed for the first time. LPS-induced inflammation in RAW264.7 cells was well inhibited by compounds. These findings offered a preliminary investigation into the analgesic and anti-inflammatory properties of Coix seed, which may be helpful for application.

Agaro-oligosaccharides mitigate deoxynivalenol-induced intestinal inflammation by regulating gut microbiota and enhancing intestinal barrier function in mice

Agarose-derived agaro-oligosaccharides (AgaroS) have been extensively studied in terms of structures and bioactivities; they reportedly possess antioxidant and anti-inflammatory activities that maintain intestinal homeostasis and host health. However, the protective effects of AgaroS on deoxynivalenol (DON)-induced intestinal dysfunction remain unclear. We investigated the effects of AgaroS on DON-induced intestinal dysfunction in mice and explored the underlying protective mechanisms. In total, 32 mice were randomly allocated to four treatments (n = 8 each) for 28 days. From day 1 to day 21, the control (CON) and DON groups received oral phosphate-buffered saline (200 μL per day); the AgaroS and AgaroS + DON groups received 200 mg AgaroS per kg body weight once daily by orogastric gavage. Experimental intestinal injury was induced by adding DON (4.8 mg per kg body weight) via gavage from day 21 to day 28. Phosphate-buffered saline was administered once daily by gavage in the CON and AgaroS groups. Herein, AgaroS supplementation led to a higher final body weight and smaller body weight loss and a lower concentration of plasma inflammatory cytokines, compared with the DON group. The DON group showed a significantly reduced ileal villus height and villus height/crypt depth, compared with the CON and AgaroS + DON groups. However, AgaroS supplementation improved DON-induced intestinal injury in mice. Compared with the DON group, ileal and colonic protein expression levels of claudin, occludin, Ki67, and mucin2 were significantly higher in the AgaroS supplementation group. Colonic levels of the anti-inflammatory cytokine IL-1β tended to be higher in the DON group than in the AgaroS + DON group. AgaroS altered the gut microbiota composition, accompanied by increased production of short-chain fatty acids in mice. In conclusion, our findings highlight a promising anti-mycotoxin approach whereby AgaroS alleviate DON-induced intestinal inflammation by modulating intestinal barrier functional integrity and gut microbiota in mice.

Agarose biodegradation by deep-sea bacterium Vibrio natriegens WPAGA4 with the agarases through horizontal gene transfer

This study aimed to reveal the importance of horizontal gene transfer (HGT) for the agarose-degrading ability and the related degradation pathway of a deep-sea bacterium Vibrio natriegens WPAGA4, which was rarely reported in former works. A total of four agarases belonged to the GH50 family, including Aga3418, Aga3419, Aga3420, and Aga3472, were annotated and expressed in Escherichia coli cells. The agarose degradation products of Aga3418, Aga3420, and Aga3472 were neoagarobiose, while those of Aga3419 were neoagarobiose and neoagarotetraose. The RT-qPCR analysis showed that the expression level ratio of Aga3418, Aga3419, Aga3420, and Aga3472 was stable at about 1:1:1.5:2.5 during the degradation, which indicated the optimal expression level ratio of the agarases for agarose degradation by V. natriegens WPAGA4. Based on the genomic information, three of four agarases and other agarose-degrading related genes were in a genome island with a G + C content that was obviously lower than that of the whole genome of V. natriegens WPAGA4, indicating that these agarose-degrading genes were required through HGT. Our results demonstrated that the expression level ratio instead of the expression level itself of agarase genes was crucial for agarose degradation by V. natriegens WPAGA4, and HGT occurred in the deep-sea environment, thereby promoting the deep-sea carbon cycle and providing a reference for studying the evolution and transfer pathways of agar-related genes.

Enzymatically prepared neoagarooligosaccharides improve gut health and function through promoting the production of spermidine by Faecalibacterium in chickens

Maintaining animal gut health through modulating the gut microbiota is a constant need when antibiotics are not used in animal feed during the food animal production process. Prebiotics is regarded as one of the most promising antibiotic alternatives for such purpose. As an attractive prebiotic, the role and mechanisms of neoagarooligosaccharides (NAOS) in promoting animal growth and gut health have not been elucidated. In this study, we first cloned and expressed marine bacterial β-agarase in yeast to optimize the NAOS preparation and then investigated the role and the underlying mechanisms of the prepared NAOS in improving chicken gut health and function. The marine bacterial β-agarase PDE13B was expressed in Pichia pastoris GS115 and generated even-numbered NAOS. Dietary the prepared NAOS promoted chicken growth and improved intestinal morphology, its barrier, and digestion capabilities, and absorption function. Metagenomic analysis indicated that NAOS modulated the chicken gut microbiota structure and function, and microbial interactions, and promoted the growth of spermidine-producing bacteria especially Faecalibacterium. Through integration of gut metagenome, gut content metabolome, and gut tissue transcriptome, we established connections among NAOS, gut microbes, spermidine, and chicken gut gene expression. The spermidine regulation of genes related to autophagy, immunity, and inflammation was further confirmed in chicken embryo intestinal epithelium cells. We also verified that NAOS can be utilized by Faecalibacterium prausnitzii to grow and produce spermidine in in vitro experiments. Collectively, we provide a systematic investigation of the role of NAOS in regulating gut health and demonstrate the microbial spermidine-mediated mechanism involved in prebiotic effects of NAOS, which lays foundation for future use of NAOS as a new antibiotic alternative in animal production.

Supplementing maternal diet with milk oligosaccharides and probiotics helps develop the immune system and intestinal flora of offsprings

Intestinal flora is very important for improving the development of the immune system in newborns. Maternal diet during pregnancy and lactation is one of the key factors affecting the growth and development of offspring. The objective of the present study was to examine whether supplementation of maternal diet with milk oligosaccharides and Bifidobacterium could influence the development of the intestinal flora and immune system of neonatal mice. In total, 30 pregnant Institute of Cancer Research (ICR) mice were randomly divided into six groups: a control group (basal diet) and five intervention groups (basal diet supplemented with different doses of 2'-fucosyllactose [2'-FL] and Bifidobacterium Bb12) during the pregnancy period. All female mice were monitored for physical health during gavage. After delivery, the number of mice in each litter, any deformity, and the development of the offspring were recorded. The spleen, blood, and fecal samples of six groups of 10-12 day-old offspring were collected. The results demonstrated that maternal milk oligosaccharides and probiotics conferred protective effects against lipopolysaccharide (LPS)-induced immunosuppression in mice offspring by significantly enhancing the immune organ indexes, splenocyte proliferation, immunoglobulin (immunoglobulin G, A, M) production as well as improving the macrophage phagocytosis (p < .05). The abundance of Lactobacilli and Bifidobacteria in the feces of offspring mice in the intervention groups was significantly higher than that of the offspring mice in the control group (p < .05). These findings suggest that the combination of 2'-FL and Bifidobacterium Bb12 displayed synergistic interactions between the two components that could promote the development of the immune system of the offsprings and improve their microbiota through maternal ingestion.

Dietary neoagarotetraose extends lifespan and impedes brain aging in mice via regulation of microbiota-gut-brain axis

INTRODUCTION

Dietary oligosaccharides can impact the gut microbiota and confer tremendous health benefits.

OBJECTIVES

The aim of this study was to determine the impact of a novel functional oligosaccharide, neoagarotetraose (NAT), on aging in mice.

METHODS

8-month-old C57BL/6J mice as the natural aging mice model were orally administered with NAT for 12 months. The preventive effect of NAT in Alzheimer's disease (AD) mice was further evaluated. Aging related indicators, neuropathology, gut microbiota and short-chain fatty acids (SCFAs) in cecal contents were analyzed.

RESULTS

NAT treatment extended the lifespan of these mice by up to 33.3 %. Furthermore, these mice showed the improved aging characteristics and decreased injuries in cerebral neurons. Dietary NAT significantly delayed DNA damage in the brain, and inhibited reduction of tight junction protein in the colon. A significant increase at gut bacterial genus level (such as Lactobacillus, Butyricimonas, and Akkermansia) accompanied by increasing concentrations of SCFAs in cecal contents was observed after NAT treatment. Functional profiling of gut microbiota composition indicated that NAT treatment regulated the glucolipid and bile acid-related metabolic pathways. Interestingly, NAT treatment ameliorated cognitive impairment, attenuated amyloid-β (Aβ) and Tau pathology, and regulated the gut microbiota composition and SCFAs receptor-related pathway of Alzheimer's disease (AD) mice.

CONCLUSION

NAT mitigated age-associated cerebral injury in mice through gut-brain axis. The findings provide novel evidence for the effect of NAT on anti-aging, and highlight the potential application of NAT as an effective intervention against age-related diseases.

Statistical optimization of process variables for agarase production using Microbacterium sp. SS5 strain from non-marine sources

Agar oligosaccharides are thought to be valuable biomolecules with high bioactivity potential, along with a wide range of applications and advantages. The current study aimed to optimize the culture parameters required to produce agarase enzyme and agar oligosaccharides from industrial waste agar. Microbacterium spp. strain SS5 was isolated from a non-marine source and could synthesize oligo derivatives for use in a variety of industries ranging from food to pharmaceuticals. In addition, the strain and culture conditions were optimized to maximize extracellular agarase production. The bacterium grew best at pH 5.0 - 9.0, with an optimal pH of 7.5 - 8.0; temperatures ranging from 25 to 45 °C, with an optimal of 35 °C; and carbon and nitrogen concentrations of 0.5% each. Plackett-Burman experimental design and response surface methods were used to optimize various process parameters for agarase production by Microbacterium spp. strain SS5. Using the Plackett-Burman experimental design, eleven process factors were screened, and agar, beef extract, CaCl2, and beginning pH were found as the most significant independent variables affecting agarase production with confidence levels above 90%. To determine the optimal concentrations of the identified process factors on agarase production, the Box- Behnken design was used. Agarase production by Microbacterium spp. strain SS5 after optimization was 0.272 U/mL, which was determined to be greater than the result obtained from the basal medium (0.132 U/mL) before screening using Plackett-Burman and BBD with a fold increase of 2.06.

Extracellular production of a thermostable Cellvibrio endolytic β-agarase in Escherichia coli for agarose liquefaction

Four GH16 family β-agarases (GH16A, GH16B, GH16C, and GH16D), originated from an agarolytic bacterium Cellvibrio sp. KY-GH-1, were expressed in an Escherichia coli system and their activities were compared. Only GH16B (597 amino acids, 63.8 kDa), with N-terminal 22-amino acid signal sequence, was secreted into the culture supernatant and demonstrated a robust endolytic agarose hydrolyzing activity for producing neoagarotetraose (NA4) and neoagarohexaose (NA6) as end products. The optimal temperature and pH for the enzyme activity were 50 °C and 7.0, respectively. The enzyme was stable up to 50 °C and over a pH range of 5.0-8.0. The kinetic parameters, including Km, Vmax, kcat, and kcat/Km, of GH16B β-agarases for agarose were 14.40 mg/mL, 542.0 U/mg, 576.3 s^-1, and 4.80 × 10⁶ s^-1 M^-1, respectively. The addition of 1 mM MnCl₂ and 15 mM tris(2-carboxyethyl)phosphine enhanced the enzymatic activity. When agarose or neoagaro-oligosaccharides were used as substrates, the end products of enzymatic catalysis were NA4 and NA6, whereas agaropentaose was produced along with NA4 and NA6 when agaro-oligosaccharides were used as substrates. Treatment of 9%[w/v] melted agarose with the enzyme (1.6 µg/mL) under continuous magnetic stirring at 50 °C for 14 h resulted in efficient agarose liquefaction into NA4 and NA6. Purification of NA4 and NA6 from the enzymatic hydrolysate (9%[w/v] agarose, 20 mL) via Sephadex G-15 column chromatography yielded ~ 650 mg NA4/~ 900 mg NA6 (i.e., ~ 85.3% of the theoretical maximum yield). These findings suggest that the recombinant thermostable GH16B β-agarase is useful for agarose liquefaction to produce NA4 and NA6.

In vitro characterization of lactic acid bacterial strains isolated from fermented foods with anti-inflammatory and dipeptidyl peptidase-IV inhibition potential

Probiotics are known to stimulate, modulate, and regulate host immune response by regulating specific sets of genes and improve glucose homeostasis through regulating dipeptidyl peptidase (DPP-IV) activity, but the mechanism behind their protective role is not clearly understood. Therefore, the present study was designed to isolate indigenous lactic acid bacterial (LAB) strains from different fermented food samples, vegetables, and human infant feces exhibiting anti-inflammatory, antioxidant, and DPP-IV inhibitory activity. A total of thirty-six Gram-positive, catalase-negative, and rod-shaped bacteria were isolated and screened for their anti-inflammatory activity using lipopolysaccharide (LPS)-induced inflammation on the murine (RAW264.7) macrophages. Among all, sixteen strains exhibited more than 90% reduction in nitric oxide (NO) production by the LPS-treated RAW264.7 cells. Prioritized strains were characterized for their probiotic attributes as per the DBT-ICMR guidelines and showed desirable probiotic attributes in a species and strain-dependent manner. Accordingly, Lacticaseibacillus rhamnosus LAB3, Levilactobacillus brevis LAB20, Lactiplantibacillus plantarum LAB31, Pediococcus acidilactici LAB8, and Lactiplantibacillus plantarum LAB39 were prioritized. Furthermore, these strains when co-supplemented with LPS and treated on RAW264.7 cells inhibited the mitogen-activated protein kinases (MAPKs), i.e., p38 MAPK, ERK1/2, and SAPK/JNK, cyclooxygenase-2 (COX-2), relative to the LPS-alone-treated macrophages. LAB31 and LAB39 also showed 64 and 95% of DPP-IV inhibitory activity relative to the Lacticaseibacillus rhamnosus GG ATCC 53103, which was used as a reference strain in all the studies. Five prioritized strains ameliorated the LPS-induced inflammation by downregulating the JNK/MAPK pathway and could be employed as an alternative bio-therapeutic strategy in mitigating gut-associated inflammatory conditions. The potential mechanism of action of prioritized LAB strains in preventing the LPS-induced inflammation in RAW 264.7 macrophage cells.

New NSAID Conjugates as Potent and Selective COX-2 Inhibitors: Synthesis, Molecular Modeling and Biological Investigation

New sets of ibuprofen and indomethacin conjugates comprising triazolyl heterocycle were synthesized via click chemistry, adopting an optimized protocol through the molecular hybridization approach affording the targeted agents in good yields. The new non-steroidal anti-inflammatory drug (NSAID) conjugates were designed and synthesized and could be considered as potential drug candidates for the treatment of pain and inflammation. The anti-inflammatory properties were investigated for all the synthesized conjugates. Among 14 synthesized conjugates, four (5a, 5b, 5d, and 5e) were found to have significant anti-inflammatory properties potency 117.6%, 116.5%, 93.8%, and 109.1% in comparison to reference drugs ibuprofen (97.2%) and indomethacin (100%) in the rat paw edema carrageenan test without any ulcerogenic liability. The suppression effect of cytokines IL-6, TNF-α, and iNOS in addition to NO in the LPS-induced RAW264.7 cells supports the promising anti-inflammatory properties observed in the ibuprofen conjugates. In addition, several conjugates showed promising peripheral and central analgesic activity. The selectivity index (SI) of compound 5a (23.096) indicates the significant efficacy and selectivity for COX-2 over COX-1. Molecular modeling (docking and QSAR) studies described the observed biological properties.

In vitro fermentation of seaweed polysaccharides and tea polyphenol blends by human intestinal flora and their effects on intestinal inflammation

A combination of polysaccharides and tea polyphenols can enhance immune activity synergistically, depending on the type and structure of polysaccharides, but the mechanism remains unknown. This study is aimed to investigate the regulating effects of different seaweed polysaccharide (ι-carrageenan, agarose) and tea polyphenol blends on intestinal flora and intestinal inflammation using an in vitro ascending-transverse-descending colon fermentation system and RAW264.7 cell model. The results showed that seaweed polysaccharides in the presence of tea polyphenol were almost completely degraded at transverse colon fermentation for 36 h. Agarose significantly enhanced the butyric acid production content by increasing the abundance of Lachnospiraceae, whereas agarose and tea polyphenol blends did not have a synergistic effect. On the contrary, ι-carrageenan and tea polyphenol blends synergistically increased the abundance of beneficial bacteria (e.g., Bacteroidetes and Bifidobacterium) and promoted the production of short-chain fatty acids (SCFAs), such as isobutyric acid. Such changes tended to alter the impacts of different seaweed polysaccharides and tea polyphenol blends on intestinal inflammation. Among them, ι-carrageenan and tea polyphenol blends were the most effective in inhibiting lipopolysaccharide-induced NO, ROS, IL-6, and TNF-α production in RAW264.7 cells, indicating the alleviated intestinal inflammation. The results suggest that the seaweed polysaccharide and tea polyphenol blends have prebiotic potential and can benefit intestinal health.

Enzymatic preparation and potential applications of agar oligosaccharides: a review

Oligosaccharides derived from agar, that is, agarooligosaccharides and neoagarooligosaccharides, have demonstrated various kinds of bioactivities which have been utilized in a variety of fields. Enzymatic hydrolysis is a feasible approach that principally allows for obtaining specific agar oligosaccharides in a sustainable way at an industrial scale. This review summarizes recent technologies employed to improve the properties of agarase. Additionally, the relationship between the degree of polymerization, bioactivities, and potential applications of agar-derived oligosaccharides for pharmaceutical, food, cosmetic, and agricultural industries are discussed. Engineered agarase exhibited general improvement of enzymatic performance, which is mostly achieved by truncation. Rational and semi-rational design assisted by computational methods present the latest strategy for agarase improvement with greatest potential to satisfy future industrial needs. Agarase immobilized on magnetic Fe3O4 nanoparticles via covalent bond formation showed characteristics well suited for industry. Additionally, albeit with the relationship between the degree of polymerization and versatile bioactivities like anti-oxidants, anti-inflammatory, anti-microbial agents, prebiotics and in skin care of agar-derived oligosaccharides are discussed here, further researches are still needed to unravel the complicated relationship between bioactivity and structure of the different oligosaccharides.

Diverse Galactooligosaccharides Differentially Reduce LPS-Induced Inflammation in Macrophages

The effects of natural and synthetic galactooligosaccharides (GOS) on inflammation were explored by investigating the structure-activity relationship between the degree of GOS polymerization and in vitro anti-inflammatory activity, together with the potential underlying mechanism of their anti-inflammatory effects. The results demonstrated that GOS had strong anti-inflammatory effects in lipopolysaccharide (LPS)-induced RAW264.7 macrophages, including the inhibition of nitric oxide production and the reduced expression of pro-inflammatory mediators (interleukin-1β, interleukin-6, and tumor necrosis factor α), induced nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and proteins related to the Toll-like receptor 4 (TLR4)/nuclear factor (NF)-κB signaling pathway. GOS4, which has the highest degree of polymerization, exerted the strongest anti-inflammatory activity among the GOS examined. More importantly, our findings confirmed the anti-inflammatory effects of GOS on RAW264.7 macrophages via the TLR4/NF-κB pathway. Our experimental results could provide further support for the exploration of GOS in human nutrition and health.

Reactive metal boride nanoparticles trap lipopolysaccharide and peptidoglycan for bacteria-infected wound healing

Bacteria and excessive inflammation are two main factors causing non-healing wounds. However, current studies have mainly focused on the inhibition of bacteria survival for wound healing while ignoring the excessive inflammation induced by dead bacteria-released lipopolysaccharide (LPS) or peptidoglycan (PGN). Herein, a boron-trapping strategy has been proposed to prevent both infection and excessive inflammation by synthesizing a class of reactive metal boride nanoparticles (MB NPs). Our results show that the MB NPs are gradually hydrolyzed to generate boron dihydroxy groups and metal cations while generating a local alkaline microenvironment. This microenvironment greatly enhances boron dihydroxy groups to trap LPS or PGN through an esterification reaction, which not only enhances metal cation-induced bacterial death but also inhibits dead bacteria-induced excessive inflammation both in vitro and in vivo, finally accelerating wound healing. Taken together, this boron-trapping strategy provides an approach to the treatment of bacterial infection and the accompanying inflammation.

Neoagaro-Oligosaccharides Ameliorate Chronic Restraint Stress-Induced Depression by Increasing 5-HT and BDNF in the Brain and Remodeling the Gut Microbiota of Mice

Neoagaro-oligosaccharides (NAOs) belong to the algae oligosaccharides. NAOs have been found to have diverse biological activities. However, the effects of NAOs on depression and their underlying mechanism have not been thoroughly studied. A chronic restraint stress (CRS)-induced C57BL/6J mouse model was used to assess the antidepressant effects of NAOs. Anxiety and depression behaviors were assessed by open field tests (OFT) and forced swimming tests (FST), while interleukin 18 (IL-18), 5-hydroxytryptamine (5-HT) and brain-derived neurotrophic factor (BDNF) were the molecular biomarkers of depression. Fecal microbiota transplantation (FMT) was performed. The results showed that NAO treatment significantly improved the body weight of depressed mice and reduced the central area time in the OFT and immobility time in the FST. NAO treatment decreased the levels of IL-18 in the serum and increased the levels of 5-HT in the serum and whole brain and of BDNF in the whole brain. NAO treatment mitigated the gut microbiota dysbiosis in the depressed mice and reversed the decreased levels of short-chain fatty acids (SCFAs) in the cecum of the depressed mice. FMT indicated that the gut microbiota is, indeed, linked to depression, which was reflected in the changes in weight gain and behaviors. In a word, NAOs effectively reversed the CRS-induced mice model of depression, which depended on the changes in the gut microbiota and SCFAs, as well as its modulation of 5-HT and BDNF.

Characterization of a novel β-agarase from Antarctic macroalgae-associated bacteria metagenomic library and anti-inflammatory activity of the enzymatic hydrolysates

An agarase gene (aga1904) that codes a protein with 640 amino acids was obtained from the metagenomic library of macroalgae-associated bacteria collected from King George Island, Antarctica. Gene aga1904 was expressed in Escherichia coli BL21 (DE3) and recombinant Aga1904 was purified by His Bind Purification kit. The optimal temperature and pH for the activity of Aga1904 were 50°C and 6.0, respectively. Fe³⁺ and Cu²⁺ significantly inhibited the activity of Aga1904. The V_max and K_m values of recombinant Aga1904 were 108.70 mg/ml min and 6.51 mg/ml, respectively. The degradation products of Aga1904 against agarose substrate were mainly neoagarobiose, neoagarotetraose, and neoagarohexaose analyzed by thin layer chromatography. The cellular immunoassay of enzymatic hydrolysates was subsequently carried out, and the results showed that agaro-oligosaccharides dominated by neoagarobiose significantly inhibited key pro-inflammatory markers including, nitric oxide (NO), interleukins 6 (IL-6), and tumor necrosis factor α (TNF-α). This work provides a promising candidate for development recombinant industrial enzyme to prepare agaro-oligosaccharides, and paved up a new path for the exploitation of natural anti-inflammatory agent in the future.

Characterization of a GH50 β-Agarase: A Biotechnological Tool for Preparing Oligosaccharides from Agarose and Porphyran

Agarase is of vital significance for functional agaro-oligosaccharides production from algal dived agarose. Especially, the exolytic agarases have the advantage of obtaining agaro-oligosaccharides with a specific degree of polymerization. Herein, we cloned and expressed a novel glycoside hydrolase (GH) 50 family β-agarase OUC-PgJC50 from Photobacterium gaetbulicola. The degradation pattern analysis indicated that OUC-PgJC50 not only showed an exolytic activity with main products of neoagarotetraose from hydrolyzing agarose but also show a hydrolytic activity to transform neoagarotetraose into neoagarobiose. This is the first time that the discovery of a neoagarotetraose-producing exolytic GH50 β-agarase possesses the activity to transform neoagarotetraose into neoagarobiose, which provided new insight into the recognition of the degradation mode of agarases. Molecular docking and sequence alignment analysis further revealed the His₆₅₄ residue in OUC-PgJC50 may play a vital role in forming a strong force with l-AHG residue at -4 subsite that helps to produce neoagarotetraose from catalyzing agarose. Moreover, the catalytic ability of OUC-PgJC50 toward another agar polysaccharide porphyran was also described that could hydrolyze porphyran into sulfated oligosaccharides, in which the LA6S-d-Gal was the main products. This study is of vital significance for developing the application range of GH50 β-agarases.

Anti-Inflammatory Activity of Oxyresveratrol Tetraacetate, an Ester Prodrug of Oxyresveratrol, on Lipopolysaccharide-Stimulated RAW264.7 Macrophage Cells

Oxyresveratrol (OXY) has been reported for its anti-inflammatory activity; however, the pharmaceutical applications of this compound are limited by its physicochemical properties and poor pharmacokinetic profiles. The use of an ester prodrug is a promising strategy to overcome these obstacles. In previous researches, several carboxylate esters of OXY were synthesized and oxyresveratrol tetraacetate (OXY-TAc) was reported to possess anti-melanogenic and anti-skin-aging properties. In this study, in addition to OXY-TAc, two novel ester prodrugs of OXY, oxyresveratrol tetrapropionate (OXY-TPr), and oxyresveratrol tetrabutyrate (OXY-TBu), were synthesized. Results from the Caco-2-permeation assay suggested that synthesized ester prodrugs can improve the membrane-permeation ability of OXY. The OXY-TAc exhibited the most significant profile, then this prodrug was chosen to observe anti-inflammatory activities with lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Our results showed that OXY-Tac significantly alleviated secretion of several pro-inflammatory mediators (nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α)), mitigated expression of enzyme-regulated inflammation (inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2)), and suppressed the MAPK cascades. Interestingly, the observed anti-inflammatory activities of OXY-TAc were more remarkable than those of its parent compound OXY. Taken together, we demonstrated that OXY-TAc improved physicochemical and pharmacokinetic profiles and enhanced the pharmacological effects of OXY. Hence, the results in the present study would strongly support the clinical utilities of OXY-TAc for the treatment of inflammation-related disorders.

Simultaneous quantification of marine neutral neoagaro-oligosaccharides and agar-oligosaccharides by the UHPLC-MS/MS method: application to the intestinal transport study by using the Caco-2 cell monolayer

A sensitive and robust ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for the first time to simultaneously quantify marine neutral neoagaro-oligosaccharides (NAOS) and agar-oligosaccharides (AOS) with different degrees of polymerization (DP) in Hanks' balanced salt solution (HBSS). The separation was achieved on a BEH amide column using a mobile phase of acetonitrile-10 mmol L^-1 ammonium acetate (58 : 42, v/v) with an isocratic elution program. The total analysis time was 3.5 min. The mass spectra were acquired in the multiple reaction monitoring (MRM) pattern by using a heated-electrospray ionization (H-ESI) source operating in the positive ionization mode. The linear range was 40-20 000 nmol L^-1. The accuracy and precision ranged from 91.5 to 110.0% and 0.9 to 10.4%, respectively. The extraction recovery was consistent and reproducible. The stability was within 90.3-110.8%. The matrix effect, carryover, and dilution integrity were all satisfactory. Moreover, the validated method was successfully applied to the intestinal transport study by using the Caco-2 cell monolayer in vitro. The results revealed that neoagarobiose, neoagarotetraose, neoagarohexaose, agarotriose, agaropentose, and agaroheptose were transported by a paracellular pathway.

Oral Delivery of Pterostilbene by L-Arginine-Mediated "Nano-Bomb" Carrier for the Treatment of Ulcerative Colitis

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) of unknown aetiology affecting the colon and rectum. Pterostilbene (PS) has been reported as an effective antioxidant and anti-inflammatory agent in preclinical IBD models. However, the therapeutic outcomes of PS are limited by potential side effects associated with the systemic exposure and the modest bioavailability afforded by its oral administration. These issues can be improved with the use of intelligent responsive nanoparticles with the ability of lysosome escape, given their high drug delivery capacity and reducing the side effects.

MATERIALS AND METHODS

Herein, the hyaluronic acid (HA)-modified L-arginine CO2 nanoparticles (HA-L-Arg-CO2@NPs) loaded with PS (HA-PS@NPs) are constructed. Under lysosomal pH conditions, HA-PS@NPs liberate CO2 and generate a pH-activated nano-bomb effect to augment the cytosolic delivery of PS.

RESULTS

HA-L-Arg-CO2@NPs show great biocompatibility and the excellent ability to target the colon. Using lipopolysaccharide-induced inflammation in vitro, the prominent anti-inflammatory effect of HA-L-Arg-CO2@NPs and HA-PS@NPs is observed. Further, orally administered HA-L-Arg-CO2@NPs and HA-PS@NPs via the colon-targeted chitosan/alginate (CA) hydrogel downregulate pro-inflammatory cytokines and reduce intestinal permeability, yielding significant outcomes in alleviating the symptoms of UC.

CONCLUSION

This pH-activated "nano-bomb" carrier with therapeutic effect can be exploited as efficient oral drug carriers for UC treatment.

Orally pH-activated "nano-bomb" carrier combined with berberine by regulating gene silencing and gut microbiota for site-specific treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic, relapsing inflammatory bowel disease that features colonic epithelial barrier dysfunction and gut dysbiosis. Preclinical studies demonstrated that inhibiting the overexpression of CD98 via small...

Design and synthesis of ibuprofen-quinoline conjugates as potential anti-inflammatory and analgesic drug candidates

A new set of ibuprofen-quinoline conjugates comprising quinolinyl heterocycle and ibuprofen moieties linked by an alkyl chain were synthesized in good yields utilizing an optimized reaction procedure in a molecular hybridization approach to overcome the drawbacks of the current non-steroidal anti-inflammatory drugs. The synthesized conjugates were screened for their anti-inflammatory, and ulcerogenic properties. Several conjugates were found to have significant anti-inflammatory properties in the carrageenan-induced rat paw edema test without showing any ulcerogenic liability. In addition, most conjugates showed promising peripheral analgesic activity in the acetic acid-induced writhing test as well as central analgesic properties in the in vivo hot plate test. The most promising conjugates were the unsubstituted and 6-substituted fluoro- and chloro-derivatives of 2-(trifluoromethyl)quinoline linked to ibuprofen by a propyl chain. Their anti-inflammatory activity was evaluated against LPS-stimulated inflammatory reactions in RAW264.7 mouse macrophages. In this regard, it was found that most of the conjugates were able to significantly reduce the release and production of nitric oxide in the LPS-stimulated macrophages. The secretion and expression of the pro-inflammatory cytokines IL-6, TNF-α, and inducible nitric oxide synthase (iNOS) were also significantly suppressed.

Characterization and activity enhancement of a novel exo-type agarase Aga575 from Aquimarina agarilytica ZC1

The novel β-agarase gene aga575 from the agarolytic bacterium Aquimarina agarilytica ZC1 is composed of 2142 bp, and the encoded protein Aga575 has the highest amino acid sequence homology of only 65.2% with known agarases. Though carrying a domain of glycoside hydrolase family 42 in the C-terminal, Aga575 should belong to glycoside hydrolase family 50 according to the phylogenetic analysis. Gene aga575 was successfully cloned and overexpressed in Escherichia coli Rosetta (DE3) cells. The recombinant protein had the maximal agarase activity at pH 8.0 and 37 °C. The values K_m and V_max toward agarose were 8.4 mg/mL and 52.2 U/mg, respectively. Aga575 hydrolyzed agarose and neoagarooligosaccharides to yield neoagarobiose as the sole product. The agarose hydrolysis pattern of Aga575 indicated that it was an exo-type β-agarase. Random mutagenesis was carried out to obtain two beneficial mutants M1 (R534G) and M2 (S4R-R424G) with higher activities. The results showed that the agarase activity of mutant M1 and M2 reached 162% and 192% of the wild-type agarase Aga575, respectively. Moreover, the activity of the mixed mutant M1/M2 (S4R-R424G-R534G) increased to 227%. KEY POINTS: • Aga575 is a novel exo-type β-agarase degrading agarose to yield neoagarobiose as the sole product. • Though owning a domain of glycoside hydrolase family GH42, Aga575 should belong to family GH50. • The agarase activity of one mutant increased to 227% of the wild-type Aga575.

Sargahydroquinoic Acid, a Cyclooxygenase-2 Inhibitor, Attenuates Inflammatory Responses by Regulating NF-κB Inactivation and Nrf2 Activation in Lipopolysaccharide-Stimulated Cells

Sargahydroquinoic acid (SHQA) is a major plastoquinone in Sargassum macrocarpum and has shown the capacity to prevent inflammation and oxidative stress. However, the protective mechanisms were unclear. The molecular mechanisms of SHQA on ameliorating inflammation and oxidative stress have been investigated, using lipopolysaccharide (LPS)-stimulated macrophages. SHQA was isolated and purified from S. macrocarpum and the anti-inflammatory mechanisms were explored using LPS-stimulated murine macrophage RAW 264.7 cells. SHQA did not change the expression of cyclooxygenase-2 (COX-2) but inhibited the activity of COX-2. As a result, SHQA significantly diminished the secretions of nitric oxide (NO), prostaglandin E2 (PGE2), and multiple pro-inflammatory cytokines. LPS-induced activation of nuclear factor-κB (NF-κB) was inhibited by SHQA by preventing the degradation of inhibitor κB-α (IκBα). NF-κB activation was also downregulated by the inhibition of Akt phosphorylation in LPS-stimulated cells. Furthermore, SHQA induced the expression of heme oxygenase 1 via Nrf2 activation. These results indicated that SHQA inhibited LPS-induced expressions of inflammatory mediators via suppressing the Akt-mediated NF-κB pathway as well as upregulating the Nrf2/HO-1 pathway. Our findings suggest that SHQA might be a potential therapeutic agent in various inflammatory diseases.

Production of neoagarooligosaccharides by probiotic yeast Saccharomyces cerevisiae var. boulardii engineered as a microbial cell factory

Background

Saccharomyces cerevisiae var. boulardii is a representative probiotic yeast that has been widely used in the food and pharmaceutical industries. However, S. boulardii has not been studied as a microbial cell factory for producing useful substances. Agarose, a major component of red macroalgae, can be depolymerized into neoagarooligosaccharides (NAOSs) by an endo-type β-agarase. NAOSs, including neoagarotetraose (NeoDP4), are known to be health-benefiting substances owing to their prebiotic effect. Thus, NAOS production in the gut is required. In this study, the probiotic yeast S. boulardii was engineered to produce NAOSs by expressing an endo-type β-agarase, BpGH16A, derived from a human gut bacterium Bacteroides plebeius.

Results

In total, four different signal peptides were compared in S. boulardii for protein (BpGH16A) secretion for the first time. The SED1 signal peptide derived from Saccharomyces cerevisiae was selected as optimal for extracellular production of NeoDP4 from agarose. Expression of BpGH16A was performed in two ways using the plasmid vector system and the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system. The production of NeoDP4 by engineered S. boulardii was verified and quantified. NeoDP4 was produced by S. boulardii engineered using the plasmid vector system and CRISPR-Cas9 at 1.86 and 0.80 g/L in a 72-h fermentation, respectively.

Conclusions

This is the first report on NAOS production using the probiotic yeast S. boulardii. Our results suggest that S. boulardii can be considered a microbial cell factory to produce health-beneficial substances in the human gut.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01644-w.

Expression and Characterization of a Novel Cold-Adapted and Stable β-Agarase Gene agaW1540 from the Deep-Sea Bacterium Shewanella sp. WPAGA9

The neoagaro-oligosaccharides, degraded from agarose by agarases, are important natural substances with many bioactivities. In this study, a novel agarase gene, agaW1540, from the genome of a deep-sea bacterium Shewanella sp. WPAGA9, was expressed, and the recombinant AgaW1540 (rAgaW1540) displayed the maximum activity under the optimal pH and temperature of 7.0 and 35 °C, respectively. rAgaW1540 retained 85.4% of its maximum activity at 0 °C and retained more than 92% of its maximum activity at the temperature range of 20-40 °C and the pH range of 4.0-9.0, respectively, indicating its extensive working temperature and pH values. The activity of rAgaW1540 was dramatically suppressed by Cu²⁺ and Zn²⁺, whereas Fe²⁺ displayed an intensification of enzymatic activity. The K_m and V_max of rAgaW1540 for agarose degradation were 15.7 mg/mL and 23.4 U/mg, respectively. rAgaW1540 retained 94.7%, 97.9%, and 42.4% of its maximum activity after incubation at 20 °C, 25 °C, and 30 °C for 60 min, respectively. Thin-layer chromatography and ion chromatography analyses verified that rAgaW1540 is an endo-acting β-agarase that degrades agarose into neoagarotetraose and neoagarohexaose as the main products. The wide variety of working conditions and stable activity at room temperatures make rAgaW1540an appropriate bio-tool for further industrial production of neoagaro-oligosaccharides.

Gut Dysbiosis and IL-21 Response in Patients with Severe COVID-19

Background: The disease severity, ranging from being asymptomatic to having acute illness, and associated inflammatory responses has suggested that alterations in the gut microbiota may play a crucial role in the development of chronic disorders due to COVID-19 infection. This study describes gut microbiota dysbiosis in COVID-19 patients and its implications relating to the disease. Design: A cross sectional prospective study was performed on thirty RT-PCR-confirmed COVID-19 patients admitted to the All India Institute of Medical Sciences, Bhopal, India, between September 10 and 20, 2020. Ten healthy volunteers were recruited as the control group. IFN, TNF, and IL-21 profiling was conducted using plasma samples, and gut bacterial analysis was performed after obtaining the metagenomics data of stool samples. Results: Patients with a variable COVID-19 severity showed distinct gut microflora and peripheral interleukin-21 levels. A low Firmicute/Bacteroidetes ratio, caused by the depletion of the fibre-utilizing bacteria, F. prausnitzii, B. Plebius, and Prevotella, and an increase in Bacteroidetes has associated gut microbiota dysbiosis with COVID-19 disease severity. Conclusions: The loss of the functional attributes of signature commensals in the gut, due to dysbiosis, is a predisposing factor of COVID-19 pathophysiology.

Enzymatic characterization of a novel recombinant 1,3-α-3,6-anhydro-L-galactosidase specific for neoagarobiose hydrolysis into monosaccharides

Two GH117 family α-neoagarobiose hydrolases (GH117A α-NABH and GH117B α-NABH) from the freshwater agar-degrading Cellvibrio sp. KY-GH-1 were expressed and purified as recombinant His-tagged proteins using an Escherichia coli expression system to compare activities. The amino acid sequence of GH117A α-NABH (364 amino acids, 40.9 kDa) showed 35% identity with that of GH117B α-NABH (392 amino acids, 44.2 kDa). GH117A α-NABH, but not GH117B α-NABH, could hydrolyze neoagarobiose (NA2) into monosaccharides 3,6-anhydro-L-galactose (L-AHG) and D-galactose. The presence of GH117A α-NABH homologues in all of the agar-degrading bacteria aligned suggests that GH117A α-NABH hydrolyzing NA2 into L-AHG and D-galactose is an essential component of the agar-degrading enzyme machinery. For GH117A α-NABH-catalyzed hydrolysis, NA2 was the sole substrate among various neoagaro-oligosaccharides (NA2~NA18). GH117A α-NABH appeared to exist as a dimer, and optimal enzymatic temperature and pH were 35 °C and 7.5, respectively. GH117A α-NABH was stable up to 35 °C and at pH 7.5 and unstable beyond 35 °C and outside pH 7.0~7.5. The kinetic parameters K_m, V_max, k_cat, and k_cat/K_m for NA2 were 16.0 mM, 20.8 U/mg, 14.2 s^-1, and 8.9 × 10² s^-1 M^-1, respectively. Combined addition of 5 mM MnSO₄ and 10 mM tris(2-carboxyethyl)phosphine enhanced the enzyme activity by 2.4-fold. The enzyme-mediated hydrolysis of 5.0% NA2 into monosaccharide and purification of L-AHG from hydrolysis products by Sephadex G-10 column chromatography recovered ~ 192 mg L-AHG from 400 mg NA2 (~ 92% of the theoretical maximum yield). These results indicate that the recombinant GH117A α-NABH is NA2-specific and useful to produce L-AHG from NA2. KEY POINTS: • Recombinant GH117A α-NABH (364 aa, 40.9 kDa) purified from E. coli forms a dimer. • The enzyme hydrolyzes only NA2 among various neoagaro-oligosaccharides (NA2~NA18). • The enzyme completely hydrolyzes up to 5% NA2 into monomers under optimal conditions.

Advances in agaro-oligosaccharides preparation and bioactivities for revealing the structure-function relationship

Agaro-oligosaccharides originating from red algae have attracted increasing attention in both basic theoretical research and applied fields due to their excellent bioactivities, which indicates the wide prospects of agaro-oligosaccharides for application in the food, pharmaceutical and cosmetic industries. Thus, a considerable number of studies regarding functional agaro-oligosaccharides preparation as well as the bioactivities exploration have been carried out. Based on these studies, this review first introduced different methods that have been used in agar extraction from red algae, and further provided research progress on arylsulfatase. Then, different methods used for agaro-oligosaccharides production were summarized. Moreover, the abundant bioactivities of agaro-oligosaccharides were described in detail. Finally, this review has discussed current research problems and further provided critical aspects, which may be helpful for revealing the structure-function relationship of agaro-oligosaccharide.

Agar oligosaccharides: A review of preparation, structures, bioactivities and application

Agar, a gelatinous polysaccharide which is in the cell wall of many red algae, is widely used as food and gelling agent. Agar oligosaccharides (AOs), the hydrolysate of agar, show much more kinds of bio-activities because of its lower molecular weight, better water solubility and higher absorption efficiency. It is indicated that AOs with different structure and degree of polymerization, i.e. series of agaro-oligosaccharides and neoagaro-oligosaccharides, can be obtained under different preparation conditions. In addition, the biological activities of AOs are diversely and closely correlated to the composition and structure. This review aims to comprehensively summarize the preparation, structural characteristics and bio-activities of AOs, so as to provide a reference for applications of AOs as marine natural products in pharmacological, cosmetics and nutraceutical fields.

Overview on Microbial Enzymatic Production of Algal Oligosaccharides for Nutraceutical Applications

Global requirement for algal foods is increasing, as they are progressively consumed for its nutrition and health. Macroalgae is a proven source of metabolites, proteins, pigments, bioactive compounds, and algal polysaccharides. The unique polysaccharides such as agar, carrageenan, porphyran, alginate, fucoidan, laminarin, and ulvan are known for its wide range of bioactivities and extensively used for applications from tissue engineering to drug delivery. However, there are few limitations due to its high molecular size, low compatibility, and hydrocolloid nature. Hence, the enzymatically produced algal oligosaccharides have drawn tremendous attention due to its green synthesis, solubility, and lower molecular size. They are reported to have bioactivities including antioxidant, antiglycemic, immunostimulatory, anti-inflammatory, and prebiotic activities, which can be used in the healthcare and nutraceutical industry for the manufacture of functional foods and dietary supplements. However, identification of potential microorganisms, producing polysaccharide hydrolyzing enzymes, remains a major bottle neck for efficient utilization of bioactive algal oligosaccharides. This review summarizes the recent developments in the identification and characterization of microbial enzymes for the production of bioactive algal oligosaccharides. This can improve our understanding of bioactive algal oligosaccharides and pave way for efficient utilization of macroalgae to prevent various chronic diseases.

Novel and emerging prebiotics: Advances and opportunities

Consumers are conscientiously changing their eating preferences toward healthier options, such as functional foods enriched with pre- and probiotics. Prebiotics are attractive bioactive compounds with multidimensional beneficial action on both human and animal health, namely on the gastrointestinal tract, cardiometabolism, bones or mental health. Conventionally, prebiotics are non-digestible carbohydrates which generally present favorable organoleptic properties, temperature and acidic stability, and are considered interesting food ingredients. However, according to the current definition of prebiotics, application categories other than food are accepted, as well as non-carbohydrate substrates and bioactivity at extra-intestinal sites. Regulatory issues are considered a major concern for prebiotics since a clear understanding and application of these compounds among the consumers, regulators, scientists, suppliers or manufacturers, health-care providers and standards or recommendation-setting organizations are of utmost importance. Prebiotics can be divided in several categories according to their development and regulatory status. Inulin, galactooligosaccharides, fructooligosaccharides and lactulose are generally classified as well established prebiotics. Xylooligosaccharides, isomaltooligosaccharides, chitooligosaccharides and lactosucrose are classified as "emerging" prebiotics, while raffinose, neoagaro-oligosaccharides and epilactose are "under development." Other substances, such as human milk oligosaccharides, polyphenols, polyunsaturated fatty acids, proteins, protein hydrolysates and peptides are considered "new candidates." This chapter will encompass actual information about the non-established prebiotics, mainly their physicochemical properties, market, legislation, biological activity and possible applications. Generally, there is a lack of clear demonstrations about the effective health benefits associated with all the non-established prebiotics. Overcoming this limitation will undoubtedly increase the demand for these compounds and their market size will follow the consumer's trend.

Agarase cocktail from agar polysaccharide utilization loci converts homogenized Gelidium amansii into neoagarooligosaccharides

Neoagarooligosaccharides (NAOs) are drawing more and more attention because of their numerous bioactivities, yet limited number of agarases impedes NAOs production from red algae. In this study, predicted agar polysaccharide utilization loci (agar-PUL) were firstly used as inventory for agarase. 6 agarases were identified from agar-PULs and two of them were successfully expressed and analyzed. Then enzyme cocktail (GH16-1:GH16-2:Aga50D = 2:1:1) was proved to have highest synergistic effect. Finally homogenization was applied to G. amansii and proved to be an efficient way to release agar from tissues. When liquid-to-solid ratio was 9 g/150 mL, homogenization time was 20 min, and enzyme cocktail loading was 150 U/150 mL, maximum NAOs production (90.2 mg per 9 g wet G. amansii) could be achieved. Enzyme supported one-step process (ESOP) proposed in study is environment-friendly, time saving, cost saving and none-destructive, therefore has a potential industrial application in red algae utilization.

Characterization and Application of a Recombinant Exolytic GH50A β-Agarase from Cellvibrio sp. KY-GH-1 for Enzymatic Production of Neoagarobiose from Agarose

Neoagarobiose (NA2) is the repeating disaccharide unit of agarose and possesses various promising biological activities. To identify an efficient exolytic β-agarase required for NA2 production from agarose, the GH50A β-agarase gene from agar-degrading Cellvibrio sp. KY-GH-1 was overexpressed as a recombinant His-tagged protein using the Escherichia coli expression system. GH50A β-agarase that consists of 797 amino acids was able to produce predominantly NA2 from agarose at an optimal temperature and pH of 35 °C and 7.5, respectively. The enzyme was stable up to 35 °C and within a pH range of 7.0-9.0. The K m, V max, K cat, and K cat/K m values of the enzyme were 26.5 mg/mL, 16.9 U/mg, 25.2 s-1, and 1.2 × 105 s-1 M-1, respectively. The copresence of 5 mM MnSO4 and 10 mM tris(2-carboxyethyl)phosphine (TCEP) resulted in a 2.5-fold enhancement of the enzyme activity. For NA2 production, neoagaro-oligosaccharides (NAOSs) containing NA4-NA18 were preferred over agarose or agaro-oligosaccharides (AOSs) as substrates. NA2 was produced along with minor amounts of agarotriose (A3) after treatment of AOS with the enzyme, indicating that the exolytic digestion of AOS by the enzyme was initiated by releasing A3 from nonreducing ends. Enzymatic hydrolysis of 0.4% agarose (100 mL) using GH50A β-agarase (20 μg/mL) for 4 h under optimal reaction conditions (5 mM MnSO4, 10 mM TCEP, 35 °C, 20 mM Tris-HCl, and pH 7.5) and purification of NA2 from hydrolysis products by Bio-Gel P-2 column chromatography resulted in the recovery of 216 mg of NA2 (∼54% yield from agarose). Altogether, these results suggest that the recombinant GH50A β-agarase is useful to convert agarose to NA2.

Macroalgal dietary glycans: potential source for human gut bacteria and enhancing immune system for better health

Macroalgae are the diverse group of photosynthetic algae found at the intertidal regions of oceans. Recent advances suggest that macroalgal derived glycans have tremendous potential to maintain gut microbiome and immune system. The human gut bacteria harbor unique arsenals for utilizing a variety of macroalgal glycans, and produce a variety of oligosaccharides in vivo. Those oligosaccharides interact with immune cell receptors, and also are available for microbial fermentation, thus play magnificent roles in balancing the gut homeostasis. However, this area of research is still in infancy condition in term to understand their molecular interactions. For wooing this area, we urge to emphasize more studies on mechanistic level sympathetic of depolymerizing marine dietary glycans by gut bacteria and elucidating molecular aspect of glycans to cell receptors interactions. This will invent new nutraceutical strategies to purposefully manipulate the microbial composition to improve health. Therefore, review focuses on the recent development of mechanistic understanding of human gut bacterial communities for utilizing macroalgal derived glycans. Recent trends of application of glycans in modulating immune system at mechanistic level and their available evidences are discussed.

Marine-polysaccharide degrading enzymes: Status and prospects

Marine-polysaccharide degrading enzymes have recently been studied extensively. They are particularly interesting as they catalyze the cleavage of glycosidic bonds in polysaccharide macromolecules and produce oligosaccharides with low degrees of polymerization. Numerous findings have demonstrated that marine polysaccharides and their biotransformed products possess beneficial properties including antitumor, antiviral, anticoagulant, and anti-inflammatory activities, and they have great value in healthcare, cosmetics, the food industry, and agriculture. Exploitation of enzymes that can degrade marine polysaccharides is in the ascendant, and is important for high-value use of marine biomass resources. In this review, we describe research and prospects regarding the classification, biochemical properties, and catalytic mechanisms of the main types of marine-polysaccharide degrading enzymes, focusing on chitinase, chitosanase, alginate lyase, agarase, and carrageenase, and their product oligosaccharides. The state-of-the-art discussion of marine-polysaccharide degrading enzymes and their properties offers information that might enable more efficient production of marine oligosaccharides. We also highlight current problems in the field of marine-polysaccharide degrading enzymes and trends in their development. Understanding the properties, catalytic mechanisms, and modification of known enzymes will aid the identification of novel enzymes to degrade marine polysaccharides and facilitation of their use in various biotechnological processes.

Expression and Characterization of a GH16 Family β-Agarase Derived from the Marine Bacterium Microbulbifer sp. BN3 and Its Efficient Hydrolysis of Agar Using Raw Agar-Producing Red Seaweeds Gracilaria sjoestedtii and Gelidium amansii as Substrates

Agarases catalyze the hydrolysis of agarose to oligosaccharides which display an array of biological and physiological functions with important industrial applications in health-related fields. In this study, the gene encoding agarase (Aga-ms-R) was cloned from Microbulbifer sp. BN3 strain. Sequence alignment indicated that Aga-ms-R belongs to the GH16 family and contains one active domain and two carbohydrate binding module (CBM) domains. The mature Aga-ms-R was expressed successfully by employing the Brevibacillus system. Purified rAga-ms-R was obtained with a specific activity of 100.75 U/mg. rAga-ms-R showed optimal activity at 50 °C and pH 7.0, and the enzyme activity was stable at 50 °C and also over the pH range of 5.0–9.0. After exposure of rAga-ms-R to 70 °C for 30 min, only partial enzyme activity remained. Thin layer chromatographic analysis of the enzymatic hydrolysate of agar obtained using rAga-ms-R disclosed that the hydrolysate comprised, in a long intermediate-stage of the hydrolysis reaction, mainly neoagarotetraose (NA4) and neoagarohexaose (NA6) but ultimately, predominantly neoagarotetraose and trace amounts of neoagarobiose (NA2). Hydrolysates of the raw red seaweeds Gracilaria sjoestedtii and Gelidium amansii, produced by incubation with rAga-ms-R, were mainly composed of neoagarotetraose. The results demonstrate the high efficiency of rAga-ms-R in producing neoagaraoligosaccharide under low-cost conditions.

Molecular and Microbial Signatures Predictive of Prebiotic Action of Neoagarotetraose in a Dextran Sulfate Sodium-Induced Murine Colitis Model

Neoagarotetraose (NT), a hydrolytic product of agar by β-agarase, is known to possess bioactive properties. However, the mechanisms via which NT alleviates intestinal inflammation remain unknown. In this study, a dextran sulfate sodium (DSS)-induced murine model was developed to evaluate the effect of NT on gut microbiome and microbial metabolism using 16S rRNA gene sequencing and untargeted metabolomics. Our data demonstrate that NT ingestion improved gut integrity and inflammation scores. NT reversed the abundance of Proteobacteria from an elevated level induced by DSS and significantly increased the abundance of Verrucomicrobia. Further, NT significantly increased the abundance of Akkermansia and Lactobacillus and concomitantly decreased that of Sutterella, which were among the important features identified by random forests analysis contributing to classification accuracy for NT supplementation. A microbial signature consisting of Adlercreutzia (denominator) and Turicibacter (numerator) predicted the NT supplementation status. Moreover, NT significantly modulated multiple gut metabolites, particularly those related to histidine, polyamine and tocopherol metabolism. Together, our findings provided novel insights into the mechanisms by which NT modulated the gut microbiome and metabolome and should facilitate the development of NT as a potent prebiotic for colitis management.

Odd-numbered agaro-oligosaccharides alleviate type 2 diabetes mellitus and related colonic microbiota dysbiosis in mice

Agaro- and neoagaro-oligosaccharides with even-numbered sugar units possess a variety of biological activities. However, the effects of the odd-numbered oligosaccharides from Gracilaria agarose (OGAOs) on type 2 diabetes mellitus (T2DM) have not been reported. In this study, we aimed to evaluate the effects of OGAOs on anti-T2DM from different aspects. We found that OGAOs treatment could alleviate oxidative stress, inflammation, and the related hyperglycemia, insulin resistance, lipid accumulation, and obesity in high-fat diet (HFD) induced T2DM. Investigation of the underlying mechanism showed that colitis and colonic microbiota dysbiosis in T2DM mice were ameliorated after OGAOs treatment. First, OGAOs increased the expression of ZO-1, occludin, and AMPK, and suppressed the TLR4/MAPK/NF-κB pathway in colon indicating that OGAOs enhance intestinal integrity and conduct the anti-apoptosis effects to prevent the invasion of toxins and harmful microorganisms. Moreover, the relative abundance of Akkermansia was significantly upregulated in the gut microbiome of T2DM mice associated with a dramatic decrease of the relative abundance of Helicobacter, which are both beneficial for alleviating colitis and T2DM. In addition, Spearman's correlation analysis indicated that changes in the colonic microbiota could regulate oxidative stress, inflammation, and hyperlipidemia. In summary, the underlying mechanism of OGAOs on alleviating colitis and colonic microbiota dysbiosis in T2DM has been intensively studied, illustrating that OGAOs could be further developed as a potential pharmaceutical agent for T2DM.

Implications of agar and agarase in industrial applications of sustainable marine biomass

Agar, a major component of the cell wall of red algae, is an interesting heteropolysaccharide containing an unusual sugar, 3,6-anhydro-L-galactose. It is widely used as a valuable material in various industrial and experimental applications due to its characteristic gelling and stabilizing properties. Agar-derived oligosaccharides or mono-sugars produced by various agarases have become a promising subject for research owing to their unique biological activities, including anti-obesity, anti-diabetic, immunomodulatory, anti-tumor, antioxidant, skin-whitening, skin-moisturizing, anti-fatigue, and anti-cariogenic activities. Agar is also considered as an alternative sustainable source of biomass for chemical feedstock and biofuel production to substitute for the fossil resource. In this review, we summarize various biochemically characterized agarases, which are useful for industrial applications, such as neoagarooligosaccharide or agarooligosaccharide production and saccharification of agar. Additionally, we succinctly discuss various recent studies that have been conducted to investigate the versatile biological activities of agar-derived saccharides and biofuel production from agar biomass. This review provides a basic framework for understanding the importance of agarases and agar-derived saccharides with broad applications in pharmaceutical, cosmetic, food, and bioenergy industries.

Synthesis of crocetin derivatives and their potent inhibition in multiple tumor cells proliferation and inflammatory property of macrophage

Background

Crocetin is a major active component of saffron, which has a wide range of pharmacological effects. However, due to its low solubility, the pharmacological effects of crocetin cannot be better utilized.

Methods

In this study, we modified the chemical structure of crocetin by conjugating with ethylamine and 4-Fluorbenzylamine to enhance its solubility and biological activities. The solubility and the influence of synthesized derivatives on the proliferation of tumor cells and the inflammatory effect of macrophage were investigated.

Results

It was shown that, compared with the crocetin, the synthesized derivatives have much higher solubility. Moreover, the inhibitory effect of the derivatives on varieties of tumor cells, including human ovarian carcinoma cell line, human lung cancer cell line, rat melanoma cell line was enhanced after the modification. Besides that, the derivatives were improved for the anti-inflammatory efficacy with the cytotoxicity decreased.

Conclusions

The synthesized derivatives were shown for their good solubility and the great potential in tumor and inflammation treatment.