Structure-Activity Relationships of Low Molecular Weight Alginate Oligosaccharide Therapy against Pseudomonas aeruginosa

Low molecular weight alginate oligosaccharides have been shown to exhibit anti-microbial activity against a range of multi-drug resistant bacteria, including Pseudomonas aeruginosa. Previous studies suggested that the disruption of calcium (Ca2+)-DNA binding within bacterial biofilms and dysregulation of quorum sensing (QS) were key factors in these observed effects. To further investigate the contribution of Ca2+ binding, G-block (OligoG) and M-block alginate oligosaccharides (OligoM) with comparable average size DPn 19 but contrasting Ca2+ binding properties were prepared. Fourier-transform infrared spectroscopy demonstrated prolonged binding of alginate oligosaccharides to the pseudomonal cell membrane even after hydrodynamic shear treatment. Molecular dynamics simulations and isothermal titration calorimetry revealed that OligoG exhibited stronger interactions with bacterial LPS than OligoM, although this difference was not mirrored by differential reductions in bacterial growth. While confocal laser scanning microscopy showed that both agents demonstrated similar dose-dependent reductions in biofilm formation, OligoG exhibited a stronger QS inhibitory effect and increased potentiation of the antibiotic azithromycin in minimum inhibitory concentration and biofilm assays. This study demonstrates that the anti-microbial effects of alginate oligosaccharides are not purely influenced by Ca2+-dependent processes but also by electrostatic interactions that are common to both G-block and M-block structures.

Enzymatic depolymerization of alginate by two novel thermostable alginate lyases from Rhodothermus marinus

Alginate (alginic acid) is a linear polysaccharide, wherein (1→4)-linked β-D-mannuronic acid and its C5 epimer, α-L-guluronic acid, are arranged in varying sequences. Alginate lyases catalyze the depolymerization of alginate, thereby cleaving the (1→4) glycosidic linkages between the monomers by a β-elimination mechanism, to yield unsaturated 4-deoxy-L-erythro-hex-4-enopyranosyluronic acid (Δ) at the non-reducing end of resulting oligosaccharides (α-L-erythro configuration) or, depending on the enzyme, the unsaturated monosaccharide itself. In solution, the released free unsaturated monomer product is further hydrated in a spontaneous (keto-enol tautomerization) process to form two cyclic stereoisomers. In this study, two alginate lyase genes, designated alyRm3 and alyRm4, from the marine thermophilic bacterium Rhodothermus marinus (strain MAT378), were cloned and expressed in Escherichia coli. The recombinant enzymes were characterized, and their substrate specificity and product structures determined. AlyRm3 (PL39) and AlyRm4 (PL17) are among the most thermophilic and thermostable alginate lyases described to date with temperature optimum of activity at ∼75 and 81°C, respectively. The pH optimum of activity of AlyRm3 is ∼5.5 and AlyRm4 at pH 6.5. Detailed NMR analysis of the incubation products demonstrated that AlyRm3 is an endolytic lyase, while AlyRm4 is an exolytic lyase, cleaving monomers from the non-reducing end of oligo/poly-alginates.

Evaluation of the Effect of Mannuronic Acid as a Novel NSAID With Immunosuppressive Properties on Expression of SOCS1, SOCS3, SHIP1, and TRAF6 Genes and Serum Levels of IL-6 and TNF-α in Patients With Multiple Sclerosis

Multiple sclerosis (MS) is described as a chronic inflammatory, demyelinating disease of the central nervous system on an autoimmune basis, which is the most frequent reason for nontraumatic disability in youth. The efficacy and safety of β-D-nannuronic acid (M2000) as a novel immunosuppressive drug (patented PCT/EP2017/067920) has been shown in an experimental model of MS and also in a phase 2 clinical trial. The effects of M2000 on SOCS1, SOCS3, TRAF6, and SHIP1 gene expression and also serum levels of IL-6 and TNF-α in secondary progressive multiple sclerosis patients have been assessed in this study. In this study, 14 secondary progressive multiple sclerosis patients and 14 healthy subjects (as the control group) were recruited from the phase 2 clinical trial (Clinical Trial identifier, IRCT2016111313739N6). Gene expression of SOCS1, SOCS3, TRAF6, and SHIP1 was measured at baseline and after 6 months of therapy with M2000 using a quantitative real-time polymerase chain reaction method. Furthermore, the serum levels of IL-6 and TNF-α were assessed by the enzyme-linked immunosorbent assay method. Our results showed that the gene expression of SOCS1, SOCS3, and SHIP1 was increased after 6 months of therapy with M2000 in MS patients. Moreover, the serum levels of IL-6 and TNF-α of patients declined compared with baseline, but this was not statistically significant. The results of this study demonstrated that M2000, with immunosuppressive properties, could upregulate SOCS1, SOCS3, and SHIP1 genes in patients with secondary progressive multiple sclerosis.

Cardioprotective effect of β-d-mannuronic acid (M2000) as a novel NSAID on gene expression of oxLDL scavenger receptors in the experimental diabetic model

CONTEXT

The investigations have shown that patients with diabetes have the elevated levels of glucose and oxLDL. These two play an important role in increased expression levels of oxLDL scavenger receptors on the surface of macrophages and endothelial cells that leads to deposition of oxLDL and macrophages in vascular walls.

OBJECTIVE

The present study intends to show the effects of β-d-mannuronic acid (M2000) on the expression profile of ox-LDL scavenger receptors (including SR-A, LOX-1, CD36, and CD68) in an experimental model of diabetes.

MATERIALS AND METHODS

Eighteen Sprague-Dawley rats were randomly divided into three 6-member groups of the healthy control, diabetic control, and treated rats by M2000. Diabetes was induced in rats by intraperitoneal (IP) administration of 60 mg/kg streptozotocin. The treated rats were given daily intraperitoneal injections of M2000 with a dose of 25 mg/kg for 28 days and at the end of the 28th day, their aortas were removed. The qRT-PCR technique was then used to evaluate the expression levels of the proposed gene.

RESULTS

The gene expression levels of the SR-A, LOX-1, CD36, and CD68 significantly declined in the diabetic group that received M2000 compared with untreated diabetic rats.

CONCLUSIONS

The M2000, as a novel NSAID is able to modify by lowering the gene expression levels of SR-A, LOX-1, CD36, and CD68 in treated rats compared to the untreated diabetic group, which may play an important role in preventing the complications that could lead to a cardioprotective efficacy.

Anti-aging effects of M2000 (β-D-mannuronic acid) as a novel immunosuppressive drug on the enzymatic and non-enzymatic oxidative stress parameters in an experimental model

BACKGROUND

The anti-aging property of β-D-mannuronic acid (M2000) as a novel non-steroidal anti-inflammatory and immunosuppressive agent was investigated on several determinants relative to the oxidative stress in an animal model.

METHODS

Sprague-Dawley rats were used for evaluating the safety and efficacy properties of M2000 on some oxidative stress enzymes, including the following: mitochondrial superoxide dismutase (SOD2), catalase (CAT), glutathione peroxidase (GPX1), glutathione S-transferase (GST), myeloperoxidase (MPO), and inducible nitric oxide synthase (iNOS) gene expression by real-time PCR. Malondialdehyde (MDA), carbonyl protein (PCO) (the lipid and protein oxidation marker, respectively), and total antioxidant capacity (TAC) were tested in serum by biochemical analysis. In addition, cortisol as a steroid hormone was surveyed by chemiluminescence immunoassay after 12 weeks of M2000 consumption. The rats were sacrificed 3 months after daily oral administration of M2000.

RESULTS

Our findings revealed the favorable effects of M2000 on several antioxidant enzyme and gene expression, including SOD2, CAT, GPX1, and GST; however, our results were not statistically significant. Moreover, there was no significant difference in MDA and PCO as lipid and protein oxidation markers, TAC, and cortisol compared with the control group following M2000 consumption. A slight weight increase in the M2000-treated group was also observed.

CONCLUSIONS

Our data showed the anti-aging property of M2000 as a novel designed non-steroidal anti-inflammatory drug (NSAID) with immunosuppressive property on various oxidative stress determinants.

Systematic study of alginate-based microcapsules by micropipette aspiration and confocal fluorescence microscopy

Micropipette aspiration and confocal fluorescence microscopy were used to study the structure and mechanical properties of calcium alginate hydrogel beads (A beads), as well as A beads that were additionally coated with poly-L-lysine (P) and sodium alginate (A) to form, respectively, AP and APA hydrogels. A beads were found to continue curing for up to 500 h during storage in saline, due to residual calcium chloride carried over from the gelling bath. In subsequent saline washes, micropipette aspiration proved to be a sensitive indicator of gel weakening and calcium loss. Aspiration tests were used to compare capsule stiffness before and after citrate extraction of calcium. They showed that the initial gel strength is largely due to the calcium alginate gel cores, while the long term strength is solely due to the poly-L-lysine-alginate polyelectrolyte complex (PEC) shells. Confocal fluorescence microscopy showed that calcium chloride exposure after PLL deposition led to PLL redistribution into the hydrogel bead, resulting in thicker but more diffuse and weaker PEC shells. Adding a final alginate coating to form APA capsules did not significantly change the PEC membrane thickness and stiffness, but did speed the loss of calcium from the bead core.