Anti-inflammatory Effects of Novel Polysaccharide Sacran Extracted from Cyanobacterium Aphanothece sacrum in Various Inflammatory Animal Models

The Clinical Promise of Microalgae in Rheumatoid Arthritis: From Natural Compounds to Recombinant Therapeutics

Rheumatoid arthritis (RA) is an invalidating chronic autoimmune disorder characterized by joint inflammation and progressive bone damage. Dietary intervention is an important component in the treatment of RA to mitigate oxidative stress, a major pathogenic driver of the disease. Alongside traditional sources of antioxidants, microalgae-a diverse group of photosynthetic prokaryotes and eukaryotes-are emerging as anti-inflammatory and immunomodulatory food supplements. Several species accumulate therapeutic metabolites-mainly lipids and pigments-which interfere in the pro-inflammatory pathways involved in RA and other chronic inflammatory conditions. The advancement of the clinical uses of microalgae requires the continuous exploration of phytoplankton biodiversity and chemodiversity, followed by the domestication of wild strains into reliable producers of said metabolites. In addition, the tractability of microalgal genomes offers unprecedented possibilities to establish photosynthetic microbes as light-driven biofactories of heterologous immunotherapeutics. Here, we review the evidence-based anti-inflammatory mechanisms of microalgal metabolites and provide a detailed coverage of the genetic engineering strategies to enhance the yields of endogenous compounds and to develop innovative bioproducts.

The Analgesic and Anti-inflammatory Effects of Partially Purified Polysaccharide Fractions of Cell-free Medium and Biomass of Spirulina platensis PCST5

Background

Spirulina is a cyanobacteria species containing various bioactive compounds. Spirulina is a known source of nutrients in some traditional diets. Different activities have been reported for various extracts of S. platensis.

Objectives

In this study, the polysaccharide content of culture media and biomass extract of one species of Spirulina was partially purified, and its analgesic and anti-inflammatory effects were evaluated.

Methods

Spirulina platensis PCST5 was cultured in a sterile Zarouk medium at 27°C and 16/8h of light/ dark exposure cycle for 25 days. Then, the polysaccharide content of biomass and cell-free culture medium samples (BPSs and CFPSs, respectively) was partially purified. The analgesic and anti-inflammatory effects were evaluated using animal models.

Results

16S rRNA gene analysis confirmed that the organism was genetically similar to Spirulina platensis. The CFPSs (30 and 100 mg/kg) and BPSs (30 mg/kg) significantly reduced pain-related behaviors in rats. Similarly, all samples could significantly reduce carrageenan-induced paw inflammation volume compared with the control group. Our results suggest Spirulina's polysaccharide fractions (CFPSs and BPSs) had significant analgesic and anti-inflammatory effects.

Conclusions

Since Spirulina is a readily available source of bioactive compounds, finding such potent anti-inflammatory and anti-nociceptive compounds can provide promising leads for novel drug development.

Carrageenophyte Kappaphycus malesianus Inhibits Microglia-Mediated Neuroinflammation via Suppression of AKT/NF-κB and ERK Signaling Pathways

Neuroinflammation is an inflammatory response in any part of the central nervous system triggered by the activation of microglia and astrocytes to produce proinflammatory cytokines in the brain. However, overproduction of proinflammatory cytokines further contributes to the development of neurodegenerative disorders. Red seaweed, Kappaphycus malesianus, is a predominant carrageenophyte commercially cultivated in Semporna, Sabah, Malaysia. It is an important source of raw material for kappa-carrageenan productions in the food, pharmaceutical and cosmetics industries. However, no studies have been conducted focusing on the antineuroinflammatory effects of K. malesianus. The aim of the present study was to investigate the effect of the antineuroinflammatory activity of K. malesianus extracts (ethyl acetate, ethanol and methanol) on lipopolysaccharide-stimulated BV2 microglia and the underlying mechanisms involved in the regulation of neuroinflammatory pathways. Extract with the most promising antineuroinflammatory activity was analyzed using liquid chromatography-mass spectrometry (LC-MS). Our results show that methanol extract has a convincing antineuroinflammatory effect by suppressing both AKT/NF-κB and ERK signaling pathways to inhibit the expression of all proinflammatory cytokines without causing a cytotoxicity effect. LC-MS analysis of methanol extract revealed two compounds: prosopinine and eplerenone. Our findings indicated that metabolites of K. malesianus are potent antineuroinflammatory agents with respect to prevention of neurological disorders.

Cyanobacterial secondary metabolites towards improved commercial significance through multiomics approaches

Cyanobacteria are ubiquitous photosynthetic prokaryotes responsible for the oxygenation of the earth's reducing atmosphere. Apart from oxygen they are producers of a myriad of bioactive metabolites with diverse complex chemical structures and robust biological activities. These secondary metabolites are known to have a variety of medicinal and therapeutic applications ranging from anti-microbial, anti-viral, anti-inflammatory, anti-cancer, and immunomodulating properties. The present review discusses various aspects of secondary metabolites viz. biosynthesis, types and applications, which highlights the repertoire of bioactive constituents they harbor. Majority of these products have been produced from only a handful of genera. Moreover, with the onset of various OMICS approaches, cyanobacteria have become an attractive chassis for improved secondary metabolites production. Also the intervention of synthetic biology tools such as gene editing technologies and a variety of metabolomics and fluxomics approaches, used for engineering cyanobacteria, have significantly enhanced the production of secondary metabolites.

The Use of Megamolecular Polysaccharide Sacran in Food and Biomedical Applications

Natural polymer is a frequently used polymer in various food applications and pharmaceutical formulations due to its benefits and its biocompatibility compared to synthetic polymers. One of the natural polymer groups (i.e., polysaccharide) does not only function as an additive in pharmaceutical preparations, but also as an active ingredient with pharmacological effects. In addition, several natural polymers offer potential distinct applications in gene delivery and genetic engineering. However, some of these polymers have drawbacks, such as their lack of water retention and elasticity. Sacran, one of the high-molecular-weight natural polysaccharides (megamolecular polysaccharides) derived from Aphanothece sacrum (A. sacrum), has good water retention and elasticity. Historically, sacran has been used as a dietary food. Moreover, sacran can be applied in biomedical fields as an active material, excipient, and genetic engineering material. This article discusses the characteristics, extraction, isolation procedures, and the use of sacran in food and biomedical applications.

Anti-inflammatory Activity of Bioactive Compounds from Microalgae and Cyanobacteria by Focusing on the Mechanisms of Action

Microalgae and cyanobacteria are the potentially valuable source of bioactive compounds applied in the various industries and human usage in different fields of pharmaceutical, nutraceutical, and cosmetic disciplines. One of the interesting aspects is their application as the anti-inflammatory agents for treatment of inflammation related mal-conditions. Natural compounds are of great importance in the treatment of inflammations to reduce the reaction of immune system against pathogens, toxic compounds and damaged cells. A wide range of different metabolites with various chemical structures, including small molecules and peptides and proteins, polysaccharides, fatty acids and their derivatives have been found in microalgae and cyanobacteria which have anti-inflammatory activity. In this review, we summarized different metabolites with anti-inflammatory activity that were extracted from these microorganisms and their mechanisms. The bioactive compounds from microalgae and cyanobacteria have exhibited anti-inflammatory activity through different mechanisms acting intra- or extra- cellularly. So, they could be considered as promising anti-inflammatory agents in treatment of related diseases.

Anti-Inflammatory Activity of Exopolysaccharides from Phormidium sp. ETS05, the Most Abundant Cyanobacterium of the Therapeutic Euganean Thermal Muds, Using the Zebrafish Model

The Euganean Thermal District (Italy) represents the oldest and largest thermal center in Europe, and its therapeutic mud is considered a unique product whose beneficial effects have been documented since Ancient Roman times. Mud properties depend on the heat and electrolytes of the thermal water, as well as on the bioactive molecules produced by its biotic component, mainly represented by cyanobacteria. The investigation of the healing effects of compounds produced by the Euganean cyanobacteria represents an important goal for scientific validation of Euganean mud therapies and for the discovering of new health beneficial biomolecules. In this work, we evaluated the therapeutic potential of exopolysaccharides (EPS) produced by Phormidium sp. ETS05, the most abundant cyanobacterium of the Euganean mud. Specifically, Phormidium EPS resulted in exerting anti-inflammatory and pro-resolution activities in chemical and injury-induced zebrafish inflammation models as demonstrated using specific transgenic zebrafish lines and morphometric and expression analyses. Moreover, in vivo and in vitro tests showed no toxicity at all for the EPS concentrations tested. The results suggest that these EPS, with their combined anti-inflammatory and pro-resolution activities, could be one of the most important therapeutic molecules present in the Euganean mud and confirm the potential of these treatments for chronic inflammatory disease recovery.

[Potential Use of Sacran for Dermal and Oral Preparations]

Sacran, a new polysaccharide isolated from cyanobacterium Aphanothece sacrum (Sur.) Okada, is known to have potential as an active pharmaceutical ingredient (API) for the treatment of atopic dermatitis, various types of dermatitis, skin wound, hemorrhoids and corneal epithelium disorder. In the present studies, the effects of sacran on skin injury and skin pain induced by stratum corneum tape-stripping and gastric ulcer induced by indomethacin, a non-steroidal anti-inflammatory drug (NSAID), and hydrochloride/ethanol (HCl/EtOH) in mice were investigated. Sacran solution 0.05% (w/v) showed greater reduction of skin injury and skin pain induced by stratum corneum tape-stripping, compared to that of 0.01% (w/v) and 0.1% (w/v) sacran solutions. In addition, the inhibitory effects of 0.05% (w/v) sacran on skin injury and skin pain induced by tape-stripping were significantly superior to 0.05% (w/v) hyaluronic acid solution. On the other hand, 1.0% (w/v) sacran solution significantly inhibited gastric ulcer formation induced by indomethacin, compared with 1% (w/v) dextran solution and the inhibitory effect of sacran was comparable to that of the positive control omeprazole. In addition, 1% (w/v) and 2% (w/v) sacran solution reduced HCl/EtOH-induced gastric ulcer in mice, with the alleviative effect of sacran was comparable to or greater than that of the positive control sodium alginate. These results suggest that sacran has potential as API to treat skin injury and pain induced by tape-stripping and gastric ulcer induced by NSAIDs and EtOH.

[Unidirectionally-oriented Membrane Formation of Supra-polysaccharides Sacran and Application to Drug Delivery System]

　The geometric structures of soft materials can be controlled on the macro-scale using interfacial or mechanical instability, e.g., fingering patterns of viscous liquid and buckling patterns of gels during swelling/deswelling. These patterns can be used as smart materials for capturing/releasing and mass-transportation applications. Here we introduce the emergence of a uniaxially oriented membrane by drying an aqueous liquid-crystalline solution, composed of megamolecular supra-polysaccharides "sacran", from a limited space. By controlling the geometries of the evaporation front, multiple nuclei emerge that grow into upright membranes with uniaxial orientation. Notably, the uniaxially orientated membrane composed of rod-like microdomains is rationally formed along the dynamic three-phase contact line. Besides, the membrane macroscopically partitions the three-dimensional cuboid cell for evaporating the aqueous solution. We envision that such a uniaxially oriented membrane can be used as soft biomaterials such as dialysis membranes with directional controllability in medical and pharmaceutical fields.

[Potential Use of Sacran Hydrogels as Wound Dressing Material]

　A wound dressing is one of the essential approaches to prevent further harm to cutaneous wounds as well as to promote wound healing. Therefore, to achieve ideal wound healing, the development of advanced dressing materials is necessary. Sacran, a novel megamolecular polysaccharide derived from the cyanobacterium Aphanothece sacrum, has a very high molecular weight that exceeds 10⁷ g/mol and water-superabsorbent capacity. Recently, we demonstrated that sacran exerts anti-inflammatory activity by ameliorating the skin barrier function in patients with atopic dermatitis. In this study, to develop and characterize sacran hydrogel films (Sac-HGFs) for wound dressing materials, we prepared a physically crosslinked-Sac-HGFs, and evaluated their physicochemical properties, cytotoxicity, skin hydration and wound healing ability. Additionally, we encapsulated curcumin, as a model drug for wound healing, into Sac-HGFs by complexation with 2-hydroxypropyl-γ-cyclodextrin (HP-γ-CyD), and investigated their potential for wound dressing application. Sac-HGF has potentially good properties for wound dressing application, due to not only the moisturizing effect but also the anti-inflammatory effect of sacran. Additionally, Sac-HGF has the potential to deliver water soluble complex of curcumin/HP-γ-CyD at the wound site and thereby promote wound healing. These findings may be useful information for preparation of wound dressing materials using sacran, CyDs and drugs.

[Anti-inflammatory Effect of Sacran on Atopic Dermatitis]

　Atopic dermatitis (AD) is a chronic skin disease characterized by inflammation, pruritus, and eczematous lesions. Recently, sacran, a new polysaccharide isolated from cyanobacterium Aphanothece sacrum (Sur.) OKADA discovered by Suringar in the 19th century, has received considerable attention as a novel biomaterial. Previously, it was reported that sacran exhibits potent anti-inflammatory effects for skin diseases produced by various stimulants with optimum effective concentrations at 0.01% (w/v) and 0.05% (w/v) in rats and mice. Importantly, we demonstrated clinically that almost all of the average scores for AD symptoms in patient treated with sacran solutions were improved. In AD model mice, sacran treatment markedly down-regulated inflammatory cytokine and chemokine mRNA levels compared with non-treated controls. Furthermore, sacran solution significantly suppressed inflammation response in RAW264.7 cells. In RBL-2H3 cells, the sacran solution significantly lowered degranulation. Taken together, our studies suggest sacran may have the potential to improve AD through functional recovery of skin barrier and anti-inflammatory effects.

Anti-allergic and Profilaggrin (ProFLG)-mRNA expression modulatory effects of sacran

Atopic dermatitis (AD) is a skin disorder characterized by filaggrin (FLG) defect. We evaluated sacran's effects on dust-mite extracts (DME)-induced AD-like disease and also its effect on profilaggrin (proFLG) in a murine model of 2,4-dinitroflurobenze (DNFB)-induced contact hypersensitivity. In the murine AD-like disease model, allergic NC/Nga mice (N=60) were randomly divided into five treatment groups of 12 animals each: 0.2% and 1%sacran; 0.1% Tacrolimus; Vaseline and buffer-treated controls. Blood samples were drawn and serum levels of representative Th-1, Th-2 and also Th-17 (IL-17A) cytokines were assayed by Cytometric Bead Array (CBA). In the contact hypersensitivity model, diseased NC/Nga mice (N=20) were divided into four groups of five mice each [0.05%sacran, 0.05% chondroitin sulfate (CS), 0.5% prednisolone (PD), non-treated control group] and were treated for 14days. Skin biopsies were performed for the measurement of proFLG-mRNA by real-time PCR. Sacran solutions and 0.1%Tacrolimus reduced disease severity, suppressed histological changes and decreased the serum Th-1 (IFN-γ, TNF-α, IL-2) and Th-2 (IL-4, IL-6, IL-10) cytokines in allergic mice (vs. controls). Additionally, a marked increase of proFLG-mRNA expression was observed in 0.05%sacran group (vs. control 0.05% CS and 0.5% PD groups). Thus, Sacran might be useful as a natural skin barrier enhancer and anti-allergic agent.

Ternary complexes of folate-PEG-appended dendrimer (G4)/α-cyclodextrin conjugate, siRNA and low-molecular-weight polysaccharide sacran as a novel tumor-selective siRNA delivery system

We previously developed a tumor-selective siRNA carrier by preparing polyamidoamine dendrimer (generation 4, G4) conjugates with α-cyclodextrin and folate-polyethylene glycol (Fol-PαC (G4)). In the present study, we developed ternary complexes of Fol-PαC (G4)/siRNA with low-molecular-weight-sacrans to achieve more effective siRNA transfer activity. Among the different molecular-weight sacrans, i.e. sacran 100, 1000 and 10,000 (MW 44,889Da, 943,692Da and 1,488,281Da, respectively), sacran 100 significantly increased the cellular uptake and the RNAi effects of Fol-PαC (G4)/siRNA binary complex with negligible cytotoxicity in KB cells (folate receptor-α positive cells). In addition, the ζ-potential and particle size of Fol-PαC (G4)/siRNA complex were decreased by the ternary complexation with sacran 100. Importantly, the in vivo RNAi effect of the ternary complex after the intravenous administration to tumor-bearing BALB/c mice was significantly higher than that of the binary complex. In conclusion, Fol-PαC (G4)/siRNA/sacran 100 ternary complex has a potential as a novel tumor-selective siRNA delivery system.

Enhancing effect of γ-cyclodextrin on wound dressing properties of sacran hydrogel film

A wound dressing is one of the essential approaches for preventing further harm to cutaneous wounds as well as promoting wound healing. Therefore, to achieve ideal wound healing, the development of advanced dressing materials is necessary. Recently, we revealed that a novel megamolecular polysaccharide, sacran, has potential properties as a biomaterial in a physically cross-linked hydrogel film (HGF) for wound dressing application. In this study, to enhance the wound-healing properties of sacran hydrogel film (Sac-HGF) further, we fabricated and characterized novel Sac-HGFs containing cyclodextrins (CyDs). The sacran/α-CyD film (Sac/α-CyD-HGF) and sacran/γ-CyD HGF (Sac/γ-CyD-HGF), but not sacran/β-CyD HGF (Sac/β-CyD-HGF), were well prepared without surface roughness. Powder X-ray diffraction (XRD) patterns of the Sac/γ-CyD-HGFs showed a totally amorphous state compared to that shown by Sac/α-CyD-HGFs. Furthermore, the addition of γ-CyD to Sac-HGFs significantly increased the swelling ratio, porosity, and moisture content of the HGFs, compared to those of the Sac-HGF without CyDs. The Sac/γ-CyD-HGFs were not cytotoxic against NIH3T3 cells, a murine fibroblast cell line. Notably, the Sac/γ-CyD-HGFs significantly improved wound healing in mice, compared to that achieved with the Sac-HGF without γ-CyD. These results suggest that γ-CyD has the potential to promote the wound healing ability of Sac-HGF.