Characterization and antioxidant activities of glycosaminoglycans from dried leech

Dried leech (Whitmania pigra whitman) has been widely used as a traditional animal-based Chinese medicine. Dried leech extracts have been reported to have various biological activities that are often associated with mammalian glycosaminoglycans. However, their presence and possible structural characteristics within dried leech were previously unknown. In this study, glycosaminoglycans were isolated from dried leech for the first time and their structures were analyzed by the combination of Fourier-transform infrared spectroscopy, liquid chromatography-ion trap/time-of-flight mass spectrometry and polyacrylamide gel electrophoresis. Heparan sulfate and chondroitin sulfate/dermatan sulfate were detected in dried leech with varied disaccharide compositions and possess a heterogeneous structure. Heparan sulfate species possess an equal amount of total 2-O-sulfated, N-sulfated and acetylated disaccharides, while chondroitin sulfate /dermatan sulfate contain high content of 4-O-sulfated disaccharides. Also, the quantitative analysis revealed that the contents of heparan sulfate and chondroitin/dermatan sulfate in dried leech varied significantly, with chondroitin/dermatan sulfate being by far the most abundant. This novel structural information could help clarify the possible involvement of these polysaccharides in the biological activities of the dried leech. Furthermore, leech glycosaminoglycans showed a strong ABTS radical scavenging ability, which suggests the potential of leech polysaccharides for exploitation in the nutraceutical and pharmaceutical industries.

State-of-the-art glycosaminoglycan characterization

Glycosaminoglycans (GAGs) are heterogeneous acidic polysaccharides involved in a range of biological functions. They have a significant influence on the regulation of cellular processes and the development of various diseases and infections. To fully understand the functional roles that GAGs play in mammalian systems, including disease processes, it is essential to understand their structural features. Despite having a linear structure and a repetitive disaccharide backbone, their structural analysis is challenging and requires elaborate preparative and analytical techniques. In particular, the extent to which GAGs are sulfated, as well as variation in sulfate position across the entire oligosaccharide or on individual monosaccharides, represents a major obstacle. Here, we summarize the current state-of-the-art methodologies used for GAG sample preparation and analysis, discussing in detail liquid chromatograpy and mass spectrometry-based approaches, including advanced ion activation methods, ion mobility separations and infrared action spectroscopy of mass-selected species.

Pathogenesis of COVID-19 described through the lens of an undersulfated and degraded epithelial and endothelial glycocalyx

The glycocalyx surrounds every eukaryotic cell and is a complex mesh of proteins and carbohydrates. It consists of proteoglycans with glycosaminoglycan side chains, which are highly sulfated under normal physiological conditions. The degree of sulfation and the position of the sulfate groups mainly determine biological function. The intact highly sulfated glycocalyx of the epithelium may repel severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) through electrostatic forces. However, if the glycocalyx is undersulfated and 3-O-sulfotransferase 3B (3OST-3B) is overexpressed, as is the case during chronic inflammatory conditions, SARS-CoV-2 entry may be facilitated by the glycocalyx. The degree of sulfation and position of the sulfate groups will also affect functions such as immune modulation, the inflammatory response, vascular permeability and tone, coagulation, mediation of sheer stress, and protection against oxidative stress. The rate-limiting factor to sulfation is the availability of inorganic sulfate. Various genetic and epigenetic factors will affect sulfur metabolism and inorganic sulfate availability, such as various dietary factors, and exposure to drugs, environmental toxins, and biotoxins, which will deplete inorganic sulfate. The role that undersulfation plays in the various comorbid conditions that predispose to coronavirus disease 2019 (COVID-19), is also considered. The undersulfated glycocalyx may not only increase susceptibility to SARS-CoV-2 infection, but would also result in a hyperinflammatory response, vascular permeability, and shedding of the glycocalyx components, giving rise to a procoagulant and antifibrinolytic state and eventual multiple organ failure. These symptoms relate to a diagnosis of systemic septic shock seen in almost all COVID-19 deaths. The focus of prevention and treatment protocols proposed is the preservation of epithelial and endothelial glycocalyx integrity.

Analysis of the Glycosaminoglycan Chains of Proteoglycans

Glycosaminoglycans (GAGs) are heterogeneous, negatively charged, macromolecules that are found in animal tissues. Based on the form of component sugar, GAGs have been categorized into four different families: heparin/heparan sulfate, chondroitin/dermatan sulfate, keratan sulfate, and hyaluronan. GAGs engage in biological pathway regulation through their interaction with protein ligands. Detailed structural information on GAG chains is required to further understanding of GAG-ligand interactions. However, polysaccharide sequencing has lagged behind protein and DNA sequencing due to the non-template-driven biosynthesis of glycans. In this review, we summarize recent progress in the analysis of GAG chains, specifically focusing on techniques related to mass spectroscopy (MS), including separation techniques coupled to MS, tandem MS, and bioinformatics software for MS spectrum interpretation. Progress in the use of other structural analysis tools, such as nuclear magnetic resonance (NMR) and hyphenated techniques, is included to provide a comprehensive perspective.

Structural analysis of glycosaminoglycans from Oviductus ranae

Oviductus ranae (O.ran.) has been widely used as a tonic and a traditional animal-based Chinese medicine. O.ran. extracts have been reported to have numerous biological activities, including activities that are often associated with mammalian glycosaminoglycans such as anti-inflammatory, antiosteoperotic, and anti-asthmatic. Glycosaminoglycans are complex linear polysaccharides ubiquitous in mammals that possess a wide range of biological activities. However, their presence and possible structural characteristics within O.ran. were previously unknown. In this study, glycosaminoglycans were isolated from O.ran. and their disaccharide compositions were analyzed by liquid chromatography-ion trap/time-of-flight mass spectrometry (LC-MS-ITTOF). Heparan sulfate (HS)/heparin (HP), chondroitin sulfate (CS)/dermatan sulfate (DS) and hyaluronic acid (HA) were detected in O.ran. with varied disaccharide compositions. HS species contain highly acetylated disaccharides, and have various structures in their constituent chains. CS/DS chains also possess a heterogeneous structure with different sulfation patterns and densities. This novel structural information could help clarify the possible involvement of these polysaccharides in the biological activities of O.ran..

Preparation and characterization of partial de-O-sulfation of heparin oligosaccharide library

The O-sulfation, including 2-O- and 6-O-sulfation, in heparan sulfate (HS) have important biological and pathophysiological roles. Therefore, the ability to chemically generate a series of oligosaccharides, which have a similar structure to the naturally-occurring, 2-O- and 6-O-sulfating oligosaccharides from HS, would greatly contribute to investigating their natural role in HS. In this study, a heparin oligosaccharide library, including dp2, dp4 and dp6, were prepared from the chemical modification of the fully sulfated dp2, dp4 and dp6. Chemical reaction conditions were optimized to generate different patterns of 2-O- and 6-O-sulfated oligosaccharides, then the disaccharide composition and structure of the library was detected by high-performance liquid chromatography-ion trap/time-of-flight mass spectrometry (LC-IT-TOF/MS) analysis. This provides a foundation for further structural and functional studies of O-sulfated groups in HS.

MS/IR, a new MS-based hyphenated method for analysis of hexuronic acid epimers in glycosaminoglycans

We report an original MS-based hyphenated method for the elucidation of the epimerization in GAG fragments. It consists of measuring simultaneously the MS/MS spectrum and the gas phase IR spectrum to gain direct structural information. This is possible using a customized MS instrument, modified to allow injection of a tunable IR laser inside of the instrument for in situ spectroscopy of trapped ions. The proof of principle of this approach is performed in the case of a hyaluronic acid tetrasaccharide standard. In addition, we provide the reference IR fingerprint of glucuronic and Iduronic monosaccharide standards. Remarkably, we show that the gas phase IR fingerprint of reference hexuronic acid monosaccharides proves to be transposable to oligosaccharides. Therefore, the method presented here is predictive and allows structural elucidation of unknown GAG fragments, even in the absence of referenced standards.