Protective effect of extractive and biotechnological chondroitin in insulin amyloid and advanced glycation end product-induced toxicity

Biotechnological advances in the synthesis of modified chondroitin towards novel biomedical applications

Chondroitin sulfate (CS) is a well-known glycosaminoglycan present in a large variety of animal tissues, with an outstanding structural heterogeneity mainly related to molecular weight and sulfation pattern. Recently, few microorganisms, eventually engineered, proved able to synthesize the CS biopolymer backbone, composed of d-glucuronic acid and N-acetyl-d-galactosamine linked through alternating β-(1-3)- and β-(1-4)-glycosidic bonds, and secrete the biopolymers generally unsulfated and possibly decorated with other carbohydrates/molecules. Enzyme catalyzed/assisted methods and chemical tailored protocols allowed to obtain a variety of macromolecules not only resembling the natural extractive ones, but even enlarging the access to unnatural structural features. These macromolecules have been investigated for their bioactivity in vitro and in vivo establishing their potentialities in an array of novel applications in the biomedical field. This review aims to present an overview of the advancements in: i) the metabolic engineering strategies and the biotechnological processes towards chondroitin manufacturing; ii) the chemical approaches applied to obtain specific structural features and targeted decoration of the chondroitin backbone; iii) the biochemical and biological properties of the diverse biotechnological-sourced chondroitin polysaccharides reported so far, unraveling novel fields of applications.

BDE-209 disrupted the blood-testis barrier integrity by inhibiting estrogen receptor α signaling pathway in Sprague-Dawley rats

Deca brominated diphenyl ether (BDE-209) is a widely used flame retardant with endocrine-disrupting activity which reportedly caused sperm quality decline and damaged blood-testis barrier (BTB). However, whether BDE-209 exposure led to BTB integrity dysfunction through affecting microtubule cytoskeletal organization and junctions was not well-elucidated. This study aimed to investigate the role of estrogen receptor α (ERα) in BDE-209-mediated perturbation of BTB integrity. Male rats and primary culture Sertoli cells were co-treated with BDE-209 and propylpyrazoletriol (PPT). The data demonstrated that BDE-209 impaired BTB integrity by reducing crucial tight junction-related proteins with ZO-1 and Occludin. Furthermore, the data suggested that BDE-209 diminished the apical ectoplasmic specialization markers with Eps8 and Formin1. In addition, BDE-209 damaged BTB ultrastructure including tight junctions and ectoplasmic specialization structures with broken tight junctions and the absence of actin microfilaments. Further experiments revealed that ERα was triggered in BDE-209-treated Sertoli cells. Unexpectedly, we found that PPT rescued BDE-209-mediated disruption of BTB integrity including tight junction and apical ectoplasmic specialization by activating ERα in Sertoli cells. Taken together, these findings indicated that intratesticular BDE-209 exposure perturbed BTB integrity and destroyed BTB structure by blocking ERα pathway. Our findings provide a new therapeutic target for male reproductive dysfunction.

Microbiological-Chemical Sourced Chondroitin Sulfates Protect Neuroblastoma SH-SY5Y Cells against Oxidative Stress and Are Suitable for Hydrogel-Based Controlled Release

Chondroitin sulfates (CS) are a class of sulfated glycosaminoglycans involved in many biological processes. Several studies reported their protective effect against neurodegenerative conditions like Alzheimer’s disease. CS are commonly derived from animal sources, but ethical concerns, the risk of contamination with animal proteins, and the difficulty in controlling the sulfation pattern have prompted research towards non-animal sources. Here we exploited two microbiological-chemical sourced CS (i.e., CS-A,C and CS-A,C,K,L) and Carbopol 974P NF/agarose semi-interpenetrating polymer networks (i.e., P.NaOH.0 and P.Ethanol.0) to set up a release system, and tested the neuroprotective role of released CS against H₂O₂-induced oxidative stress. After assessing that our CS (1–100 µM) require a 3 h pre-treatment for neuroprotection with SH-SY5Y cells, we evaluated whether the autoclave type (i.e., N- or B-type) affects hydrogel viscoelastic properties. We selected B-type autoclaves and repeated the study after loading CS (1 or 0.1 mg CS/0.5 mL gel). After loading 1 mg CS/0.5 mL gel, we evaluated CS release up to 7 days by 1,9-dimethylmethylene blue (DMMB) assay and verified the neuroprotective role of CS-A,C (1 µM) in the supernatants. We observed that CS-A,C exhibits a broader neuroprotective effect than CS-A,C,K,L. Moreover, sulfation pattern affects not only neuroprotection, but also drug release.

Lysosome purinergic receptor P2X4 regulates neoangiogenesis induced by microvesicles from sarcoma patients

The tumor microenvironment modulates cancer growth. Extracellular vesicles (EVs) have been identified as key mediators of intercellular communication, but their role in tumor growth is largely unexplored. Here, we demonstrate that EVs from sarcoma patients promote neoangiogenesis via a purinergic X receptor 4 (P2XR4) -dependent mechanism in vitro and in vivo. Using a proteomic approach, we analyzed the protein content of plasma EVs and identified critical activated pathways in human umbilical vein endothelial cells (HUVECs) and human progenitor hematopoietic cells (CD34+). We then showed that vessel formation was due to rapid mitochondrial activation, intracellular Ca²⁺ mobilization, increased extracellular ATP, and trafficking of the lysosomal P2XR4 to the cell membrane, which is required for cell motility and formation of stable branching vascular networks. Cell membrane translocation of P2XR4 was induced by proteins and chemokines contained in EVs (e.g. Del-1 and SDF-1). Del-1 was found expressed in many EVs from sarcoma tumors and several tumor types. P2XR4 blockade reduced EVs-induced vessels in angioreactors, as well as intratumor vascularization in mouse xenografts. Together, these findings identify P2XR4 as a key mediator of EVs-induced tumor angiogenesis via a signaling mediated by mitochondria-lysosome-sensing response in endothelial cells, and indicate a novel target for therapeutic interventions.

Hydroxytyrosol Selectively Affects Non-Enzymatic Glycation in Human Insulin and Protects by AGEs Cytotoxicity

Hydroxytyrosol (HT), the major phenolic compound in olive oil, is attracting increasing interest for its beneficial properties including a notable antioxidant and anti-inflammatory power. In this study, using a combination of biophysical and cell biology techniques, we have tested the role of HT in the formation of advanced glycation end-products (AGEs). AGEs have a key role in clinical sciences as they have been associated to diabetes, neurodegenerative and cardiovascular diseases. In addition, as the incidence of Alzheimer’s disease (AD) is strongly increased in diabetic patients, AGE formation is supposed to be involved in the development of the pathological hallmarks of AD. Our data show that HT selectively inhibits protein glycation reaction in human insulin, and it is able to counteract the AGE-induced cytotoxicity in human neurotypical cells by acting on SIRT1 level and oxidative stress, as well as on inflammatory response. This study identifies new beneficial properties for HT and suggests it might be a promising molecule in protecting against the AGE-induced toxicity, a key mechanism underlying the development and progression of neurodegenerative disorders.

Gelatin-biofermentative unsulfated glycosaminoglycans semi-interpenetrating hydrogels via microbial-transglutaminase crosslinking enhance osteogenic potential of dental pulp stem cells

Gelatin hydrogels by microbial-transglutaminase crosslinking are being increasingly exploited for tissue engineering, and proved high potential in bone regeneration. This study aimed to evaluate, for the first time, the combination of enzymatically crosslinked gelatin with hyaluronan and the newly developed biotechnological chondroitin in enhancing osteogenic potential. Gelatin enzymatic crosslinking was carried out in the presence of hyaluronan or of a hyaluronan–chondroitin mixture, obtaining semi-interpenetrating gels. The latter proved lower swelling extent and improved stiffness compared to the gelatin matrix alone, whilst maintaining high stability. The heteropolysaccharides were retained for 30 days in the hydrogels, thus influencing cell response over this period. To evaluate the effect of hydrogel composition on bone regeneration, materials were seeded with human dental pulp stem cells and osteogenic differentiation was assessed. The expression of osteocalcin (OC) and osteopontin (OPN), both at gene and protein level, was evaluated at 7, 15 and 30 days of culture. Scanning electron microscopy (SEM) and two-photon microscope observations were performed to assess bone-like extracellular matrix (ECM) deposition and to observe the cell penetration depth. In the presence of the heteropolysaccharides, OC and OPN expression was upregulated and a higher degree of calcified matrix formation was observed. Combination with hyaluronan and chondroitin improved both the biophysical properties and the biological response of enzymatically crosslinked gelatin, fastening bone deposition.

Production and purification of higher molecular weight chondroitin by metabolically engineered Escherichia coli K4 strains

The capsular polysaccharide obtained from Escherichia coli K4 is a glycosaminoglycan-like molecule, similar to chondroitin sulphate, that has established applications in the biomedical field. Recent efforts focused on the development of strategies to increase K4 polysaccharide fermentation titers up to technologically attractive levels, but an aspect that has not been investigated so far, is how changes in the molecular machinery that produces this biopolymer affect its molecular weight. In this work, we took advantage of recombinant E. coli K4 strains that overproduce capsular polysaccharide, to study whether the inferred pathway modifications also influenced the size of the produced polymer. Fed-batch fermentations were performed up to the 22 L scale, in potentially industrially applicable conditions, and a purification protocol that allows in particular the recovery of high molecular weight unsulphated chondroitin, was developed next. This approach allowed to determine the molecular weight of the purified polysaccharide, demonstrating that kfoF overexpression increased polymer size up to 133 kDa. Higher polysaccharide titers and size were also correlated to increased concentrations of UDP-GlcA and decreased concentrations of UDP-GalNAc during growth. These results are interesting also in view of novel potential applications of higher molecular weight chondroitin and chondroitin sulphate in the biomedical field.

Hydroxytyrosol Inhibits Protein Oligomerization and Amyloid Aggregation in Human Insulin

Hydroxytyrosol (HT), one of the main phenolic components of olive oil, has attracted considerable interest for its biological properties, including a remarkable antioxidant and anti-inflammatory power and, recently, for its ability to interfere with the amyloid aggregation underlying several human diseases. We report here a broad biophysical approach and cell biology techniques that allowed us to characterize the molecular mechanisms by which HT affects insulin amyloid aggregation and the related cytotoxicity. Our data show that HT is able to fully inhibit insulin amyloid aggregation and this property seems to be ascribed to the stabilization of the insulin monomeric state. Moreover, HT completely reverses the toxic effect produced by amyloid insulin aggregates in neuroblastoma cell lines by fully inhibiting the production of toxic amyloid species. These findings suggest that the beneficial effects of olive oil polyphenols, including HT, may arise from multifunctional activities and suggest possible a application of this natural compound in the prevention or treatment of amyloid-associated diseases.

Understanding the self-assembly pathways of a single chain variant of monellin: A first step towards the design of sweet nanomaterials

Peptides and proteins possess an inherent tendency to self-assemble, prompting the formation of amyloid aggregates from their soluble and functional states. Amyloids are linked to many devastating diseases, but self-assembling proteins can also represent formidable tools to produce new and sustainable biomaterials for biomedical and biotechnological applications. The mechanism of fibrillar aggregation, which influences the morphology and the properties of the protein aggregates, depend on factors such as pH, ionic strength, temperature, agitation, and protein concentration. We have here used intensive mechanical agitation, with or without beads, to prompt the aggregation of the single-chain derivative of the plant protein monellin, named MNEI, which is a well characterized sweet protein. Transmission electron microscopy confirmed the formation of fibrils several micrometers long, morphologically different from the previously characterized fibers of MNEI. Changes in the protein secondary structures during the aggregation process were monitored by Fourier transform infrared spectroscopy, which detected differences in the conformation of the final aggregates obtained under mechanical agitation. Moreover, soluble oligomers could be detected in the early phases of aggregation by polyacrylamide gel-electrophoresis. These findings emphasize the existence of multiple pathways of fibrillar aggregation for MNEI, which could be exploited for the design of innovative protein-based biomaterials.

Marine Biocompounds for Neuroprotection-A Review

While terrestrial organisms are the primary source of natural products, recent years have witnessed a considerable shift towards marine-sourced biocompounds. They have achieved a great scientific interest due to the plethora of compounds with structural and chemical properties generally not found in terrestrial products, exhibiting significant bioactivity ten times higher than terrestrial-sourced molecules. In addition to the antioxidant, anti-thrombotic, anti-coagulant, anti-inflammatory, anti-proliferative, anti-hypertensive, anti-diabetic, and cardio-protection properties, marine-sourced biocompounds have been investigated for their neuroprotective potential. Thus, this review aims to describe the recent findings regarding the neuroprotective effects of the significant marine-sourced biocompounds.

Targeting soluble tumor necrosis factor as a potential intervention to lower risk for late-onset Alzheimer's disease associated with obesity, metabolic syndrome, and type 2 diabetes

Background

Insulin impairment and inflammation are two features common to type 2 diabetes and Alzheimer’s disease; however, the molecular and signaling interactions underlying this relationship are not well understood. Mounting evidence point to the associations between the disruption of metabolite processing in insulin impairment and neurodegenerative conditions such as Alzheimer’s. Although the brain depends partially on metabolites processed in the periphery, to date, little is known about how soluble tumor necrosis factor signaling (solTNF) impacts integrated peripheral immune and metabolic feedback signals in states of energy overload and insulin insensitivity.

Methods

C57Bl/6J mice were fed a high-fat high-carbohydrate diet (HFHC) for 14 weeks. The brain-permeant biologic XPro1595® was used to block solTNF-dependent pathways. Metabolic and immune alterations were evaluated in the gut, liver, and brain. Behavioral tests were performed. Untargeted metabolomics was carried out in the plasma and liver.

Results

HFHC diet promotes central insulin impairment and dysregulation of immune-modulatory gene expressed in the brain. Alteration of metabolites associated with type 2 diabetes and Alzheimer’s such as butanoate, glutamate, biopterin, branched-chain amino acids, purines, and proteoglycan metabolism was observed in HFHC-fed mice. solTNF inhibition ameliorates hepatic metabolic disturbances and hepatic and intestinal lipocalin-2 levels, and decreases insulin impairment in the brain and behavioral deficits associated with HFHC diet.

Conclusions

Our novel findings suggest that HFHC diet impacts central insulin signaling and immune-metabolic interactions in a solTNF-dependent manner to increase the risk for neurodegenerative conditions. Our novel findings indicate that selective solTNF neutralization can ameliorate peripheral and central diet-induced insulin impairment and identify lipocalin-2 as a potential target for therapeutic intervention to target inflammation and insulin disturbances in obesogenic environments. Collectively, our findings identify solTNF as a potential target for therapeutic intervention in inflammatory states and insulin disturbances in obesogenic environments to lower risk for AD.

Molecular weight determination of heparosan- and chondroitin-like capsular polysaccharides: figuring out differences between wild -type and engineered Escherichia coli strains

Heparin and chondroitin sulfate are used as anti-thrombic and anti-osteoarthritis drugs, respectively, but their pharmacological actions depend on their structural characteristics such as their sulfation grade and their molecular weight. In the last years, new fermentation-based biotechnological approaches have tried to obtain heparin and chondroitin sulfate starting from the heparosan and chondroitin-like capsular polysaccharides produced by Escherichia coli K5 and K4. The study of the microbial capsular polysaccharide molecular weight is critical to obtain nature-like or structural tailor cut glycosaminoglycan homologues. However, so far, it has been scarcely investigated. In this paper, for the first time, a new protocol was set up to determine the molecular weights of the capsular polysaccharides of three wild-type and three engineered E. coli K5 and K4 strains. The protocol includes a small-scale downstream train to purify the intact polysaccharides, directly from the fermentation broth supernatants, by using ultrafiltration membranes and anion exchange chromatography, and it couples size exclusion chromatography analyses with triple detector array. In the purification high recovery (> 85.0%) and the removal of the main contaminant, the lipopolysaccharide, were obtained. The averaged molecular weights of the wild-type capsular polysaccharides ranged from 51.3 to 90.9 kDa, while the engineered strains produced polysaccharides with higher molecular weights, ranging from 68.4 to 130.6 kDa, but with similar polydispersity values between 1.1 and 1.5.

Pinocembrin Protects from AGE-Induced Cytotoxicity and Inhibits Non-Enzymatic Glycation in Human Insulin

Advanced glycation end products (AGEs) are the end products of the glycation reaction and have a great importance in clinical science for their association with oxidative stress and inflammation, which play a major role in most chronic diseases, such as cardiovascular disease, neurodegenerative diseases, and diabetes. Their pathogenic effects are generally induced by the interaction between AGEs and the receptor for advanced glycation end product (RAGE) on the cell surface, which triggers reactive oxygen species production, nuclear factor kB (NF-kB) activation, and inflammation. Pinocembrin, the most abundant flavonoid in propolis, has been recently proven to interfere with RAGE activation in Aβ–RAGE-induced toxicity. In the present study, we investigated the ability of pinocembrin to interfere with RAGE signaling pathways activated by AGEs. Interestingly, pinocembrin was able to inhibit oxidative stress and NF-kB activation in cells exposed to AGEs. In addition, it was able to block caspase 3/7 and 9 activation, thus suggesting an active role of this molecule in counteracting AGE–RAGE-induced toxicity mediated by NF-kB signaling pathways. The ability of pinocembrin to affect the glycation reaction has been also tested. Our data suggest that pinocembrin might be a promising molecule in protecting from AGE-mediated pathogenesis.