Sulfation patterns in heparin and heparan sulfate: effects on the proliferation of bovine pulmonary artery smooth muscle cells

N-desulfated and reacetylated modification of heparin modulates macrophage polarization

Heparin as a widely used anticoagulant drug has potent anti-inflammatory effects, which have been rarely reported to be involved in macrophage polarization. Furthermore, the effects of structural modifications of heparin on the plasticity of macrophage functions have not been clearly understood. In this study, the N-desulfated reacetylated derivative of heparin (NDeSAcH) was prepared and its immunoregulatory effects of macrophage polarization were evaluated. The findings indicated that NDeSAcH could effectively promote the release of more nitric oxide (NO), interleukin (IL)-6 and tumor necrosis factor-α (TNF-α) in RAW264.7 cells than heparin. Moreover, the production of NO, IL-6 and TNF-α was significantly inhibited by NDeSAcH in LPS-induced RAW264.7 cells, while the secretion of transforming growth factor-β (TGF-β) was suppressed in M2 macrophages. The N-desulfated and reacetylated group of heparin was proved to have two-side adjusting effects on the polarization of macrophages. This study suggested that NDeSAcH might be a promising candidate for modulating macrophage polarization and treating inflammation-related diseases.

Phase separation on cell surface facilitates bFGF signal transduction with heparan sulphate

Liquid-liquid phase separation (LLPS) plays important roles in various cellular processes, facilitating membrane-less organelles construction, chromatin condensation, signal transduction on inner membrane and many other processes. Current perception is that LLPS relies on weak multivalent interactions and crowded environments intracellularly. In this study, we demonstrate that heparan sulfate can serve as a platform to induce the phase separation of basic fibroblast growth factor on cell surface. The phase separation model provides an alternative mechanism how bFGF is enriched to its receptors, therefore triggering the signaling transduction. The research provides insights on the mechanism how growth factors can be recruited to cell surface by heparan sulfate and execute their functions, extending people’s view on phase separation from intracellular to extracellular proteins at cellular level.

Liquid-liquid phase separation (LLPS) is reported to occur in the intracellular environment. Here the authors show that heparan sulphate serves as a platform for basic fibroblast growth factor to undergo LLPS on the cell surface, therefore facilitating downstream signalling

Binding ability of methylene blue with heparin dependent on its sulfate level rather than its sulfation location or basic saccharide structure

Methylene blue (MB) is one of the most common cationic dyes to detect heparin. As the sulfate residue presented in heparin was the main contributor to bind with MB, the UV performance of the MB with selectively desulfated heparin derivatives was investigated. It was found that the sulfate residue in different heparin analogues did not show the equal ability to attract MB binding. The stoichiometry of sulfate with MB among the heparin and derivatives was verified as a non-constant number. For the two selectively desulfated heparin derivatives: sulfate elimination at 6-O (6-OdeS) and N-acetylated heparin (N-deS-Acetyl), the MB to sulfate ratios were significantly higher than for heparin. For the not fully diminished sulfate at 2-O heparin derivative (2-OdeS), the MB-SO₃^- ratio of 2-OdeS was between 6-OdeS, N-deS-Acetlyl and heparin. Although in a distinct sulfation position, the MB-SO₃^- ratio of 6-OdeS and N-deS-Acetyl was almost equal, which agreed with the comparable total desulfation degree between 6-OdeS and N-deS-Acetyl. In addition, compared to heparin groups, the non-desulfated gs-HP showed no significantly different MB-SO₃^- ratio with heparin. The above results demonstrated that compared with the sulfate location and glycan composition of heparin, the content of sulfate was the most essential factor for the MB binding.

Rationale for the Role of Heparin and Related GAG Antithrombotics in COVID-19 Infection

The SARS-CoV-2 pandemic has focused attention on prevention, restriction and treatment methods that are acceptable worldwide. This means that they should be simple and inexpensive. This review examines the possible role of glycosaminoglycan (GAG) antithrombotics in the treatment of COVID-19. The pathophysiology of this disease reveals a complex interplay between the hemostatic and immune systems that can be readily disrupted by SARS-CoV-2. Some of the GAG antithrombotics also possess immune-modulatory actions and since they are relatively inexpensive they could play an important role in the management of COVID-19 and its complications.

Genetic engineering approaches to improve posttranslational modification of biopharmaceuticals in different production platforms

The number of approved biopharmaceuticals, where product quality attributes remain of major importance, is increasing steadily. Within the available variety of expression hosts, the production of biopharmaceuticals faces diverse limitations with respect to posttranslational modifications (PTM), while different biopharmaceuticals demand different forms and specifications of PTMs for proper functionality. With the growing toolbox of genetic engineering technologies, it is now possible to address general as well as host- or biopharmaceutical-specific product quality obstacles. In this review, we present diverse expression systems derived from mammalians, bacteria, yeast, plants, and insects as well as available genetic engineering tools. We focus on genes for knockout/knockdown and overexpression for meaningful approaches to improve biopharmaceutical PTMs and discuss their applicability as well as future trends in the field.

Developing force fields when experimental data is sparse: AMBER/GAFF-compatible parameters for inorganic and alkyl oxoanions

We present a set of Lennard-Jones parameters for classical, all-atom models of acetate and various alkylated and non-alkylated forms of sulfate, sulfonate and phosphate ions, optimized to reproduce their interactions with water and with the physiologically relevant sodium, ammonium and methylammonium cations. The parameters are internally consistent and are fully compatible with the Generalized Amber Force Field (GAFF), the AMBER force field for proteins, the accompanying TIP3P water model and the sodium model of Joung and Cheatham. The parameters were developed primarily relying on experimental information - hydration free energies and solution activity derivatives at 0.5 m concentration - with ab initio, gas phase calculations being used for the cases where experimental information is missing. The ab initio parameterization scheme presented here is distinct from other approaches because it explicitly connects gas phase binding energies to intermolecular interactions in solution. We demonstrate that the original GAFF/AMBER parameters often overestimate anion-cation interactions, leading to an excessive number of contact ion pairs in solutions of carboxylate ions, and to aggregation in solutions of divalent ions. GAFF/AMBER parameters lead to excessive numbers of salt bridges in proteins and of contact ion pairs between sodium and acidic protein groups, issues that are resolved by using the optimized parameters presented here.

Upregulated expression of STIM2, TRPC6, and Orai2 contributes to the transition of pulmonary arterial smooth muscle cells from a contractile to proliferative phenotype

Pulmonary arterial hypertension (PAH) is a progressive disease that, if left untreated, eventually leads to right heart failure and death. Elevated pulmonary arterial pressure (PAP) in patients with PAH is mainly caused by an increase in pulmonary vascular resistance (PVR). Sustained vasoconstriction and excessive pulmonary vascular remodeling are two major causes for elevated PVR in patients with PAH. Excessive pulmonary vascular remodeling is mediated by increased proliferation of pulmonary arterial smooth muscle cells (PASMC) due to PASMC dedifferentiation from a contractile or quiescent phenotype to a proliferative or synthetic phenotype. Increased cytosolic Ca(2+) concentration ([Ca(2+)]cyt) in PASMC is a key stimulus for cell proliferation and this phenotypic transition. Voltage-dependent Ca(2+) entry (VDCE) and store-operated Ca(2+) entry (SOCE) are important mechanisms for controlling [Ca(2+)]cyt. Stromal interacting molecule proteins (e.g., STIM2) and Orai2 both contribute to SOCE and we have previously shown that STIM2 and Orai2, specifically, are upregulated in PASMC from patients with idiopathic PAH and from animals with experimental pulmonary hypertension in comparison to normal controls. In this study, we show that STIM2 and Orai2 are upregulated in proliferating PASMC compared with contractile phenotype of PASMC. Additionally, a switch in Ca(2+) regulation is observed in correlation with a phenotypic transition from contractile PASMC to proliferative PASMC. PASMC in a contractile phenotype or state have increased VDCE, while in the proliferative phenotype or state PASMC have increased SOCE. The data from this study indicate that upregulation of STIM2 and Orai2 is involved in the phenotypic transition of PASMC from a contractile state to a proliferative state; the enhanced SOCE due to upregulation of STIM2 and Orai2 plays an important role in PASMC proliferation.

Non-anticoagulant derivatives of heparin for the management of asthma: distant dream or close reality?

INTRODUCTION

Approximately 300 million people worldwide are currently affected by asthma. Improvements in the understanding of the mechanisms involved in such inflammatory airway disorders has led to the recognition of new therapeutic approaches. Heparin, a widely used anticoagulant, has been shown to be beneficial in the management of asthma. It belongs to the family of highly sulphated polysaccharides referred to as glycosaminoglycans, containing a heterogeneous mixture of both anticoagulant and non-anticoagulant polysaccharides. Experimental findings have suggested that heparin has potential anti-asthmatic properties owing to the ability of its non-anticoagulant oligosaccharides to bind and modulate the activity of a wide range of biological molecules involved in the inflammatory process.

AREAS COVERED

This review focuses on the potential mechanisms of action and clinical application of heparin as an anti-inflammatory agent for the management of asthma.

EXPERT OPINION

Heparin may play a significant role in the management of asthma. However, these properties are often hindered by the presence of anticoagulant oligosaccharides, which possess a significant risk of bleeding. Therefore, its therapeutic potential must be explored using well-designed clinical studies that focus on identifying and isolating the anti-inflammatory oligosaccharides of heparin and further elucidating the structure and mechanisms of actions of these non-anticoagulant oligosaccharides.

Glycosaminoglycan overproduction in the aorta increases aortic calcification in murine chronic kidney disease

Background

Vascular calcification accompanying chronic kidney disease increases the mortality and morbidity associated with cardiovascular disorders, but no effective therapy is available. We hypothesized that glycosaminoglycans may contribute to osteoblastic differentiation of vascular smooth muscle cells during vascular calcification.

Methods and Results

We used exostosin‐like glycosyltranferase 2–deficient (EXTL2 knockout) mice expressing high levels of glycosaminoglycans in several organs including the aorta. We performed 5/6 subtotal nephrectomy and fed the mice a high‐phosphate diet to induce chronic kidney disease. Overexpression of glycosaminoglycans in the aorta enhanced aortic calcification in chronic kidney disease in EXTL2 knockout mice. Ex vivo and in vitro, matrix mineralization in aortic rings and vascular smooth muscle cells of EXTL2 knockout mice was augmented. Furthermore, removal of glycosaminoglycans in EXTL2 knockout and wild‐type mice‐derived vascular smooth muscle cells effectively suppressed calcium deposition in a high‐phosphate environment.

Conclusions

These results illustrate an important role for glycosaminoglycans in the development of vascular calcification. Manipulation of glycosaminoglycan expression may have beneficial effects on the progression of vascular calcification in chronic kidney disease patients.

Anti-proliferative effects of O-acyl-low-molecular-weight heparin derivatives on bovine pulmonary artery smooth muscle cells

Heparin (HP) inhibits the growth of several cell types in vitro including bovine pulmonary artery (BPA) smooth muscle cells (SMCs). In initial studies we discovered that an O-hexanoylated low-molecular-weight (LMW) HP derivative having acyl groups with 6-carbon chain length was more potent inhibitor of BPA-SMCs than the starting HP. We prepared several O-acylated LMWHP derivatives having 4-, 6-, 8-, 10-, 12-, and 18- carbon acyl chain lengths to determine the optimal acyl chain length for maximum anti-proliferative properties of BPA-SMCs. The starting LMWHP was prepared from unfractionated HP by sodium periodate treatment followed by sodium borohydride reduction. The tri-n-butylammonium salt of this LMWHP was O-acylated with butanoic, hexanoic, octanoic, decanoic, dodecanoic, and stearyl anhydrides separately to give respective O-acylated LMWHP derivatives. Gradient polyacrylamide gel electrophoresis (PAGE) was used to examine the average molecular weights of those O-acylated LMWHP derivatives. NMR analysis indicated the presence of one O-acyl group per disaccharide residue. Measurement of the inhibition of BPA-SMCS as a function of O-acyl chain length shows two optima, at a carbon chain length of 6 (O-hexanoylated LMWHP) and at a carbon chain length 12-18 (O-dodecanoyl and O-stearyl LMWHPs). A solution competition SPR study was performed to test the ability of different O-acylated LMWHP derivatives to inhibit fibroblast growth factor (FGF) 1 and FGF2 binding to surface-immobilized heparin. All the LMWHP derivatives bound to FGF1 and FGF2 but each exhibited slightly different binding affinity.

Bioactivity screening of partially desulfated low-molecular-weight heparins: a structure/activity relationship study

A series of size-defined low-molecular-weight heparins were generated by regioselective chemical modifications and profiled for their in vitro and in vivo activities. The compounds displayed reduced anti-coagulant activity, demonstrated varying affinities toward angiogenic growth factors (fibroblast growth factor-2, vascular endothelial growth factor and stromal cell-derived factor-1α), inhibited the P-selectin/P-selectin glycoprotein ligand-1 interaction and, notably, exhibited anti-tumor efficacy in a murine melanoma experimental metastasis model. Our results demonstrate that modulating specific sequences, especially the N-domains (-NS or -NH(2) or -NHCOCH(3)) in these polysaccharide sequences, has a major impact on the participation in a diverse range of biological activities. These results also suggest that the 6-O-sulfates, but not the 2-O-sulfates, critically affect the binding of a desulfated derivative to certain angiogenic proteins as well as its ability to inhibit P-selectin-mediated B16F10 melanoma metastases. Furthermore, N-desulfation followed by N-acetylation regenerates the affinity/inhibition properties to different extents in all the compounds tested in the in vitro assays. This systematic study lays a conceptual foundation for detailed structure function elucidation and will facilitate the rational design of targeted heparan sulfate proteoglycan-based anti-metastatic therapeutic candidates.

Molecular regulation of contractile smooth muscle cell phenotype: implications for vascular tissue engineering

The molecular regulation of smooth muscle cell (SMC) behavior is reviewed, with particular emphasis on stimuli that promote the contractile phenotype. SMCs can shift reversibly along a continuum from a quiescent, contractile phenotype to a synthetic phenotype, which is characterized by proliferation and extracellular matrix (ECM) synthesis. This phenotypic plasticity can be harnessed for tissue engineering. Cultured synthetic SMCs have been used to engineer smooth muscle tissues with organized ECM and cell populations. However, returning SMCs to a contractile phenotype remains a key challenge. This review will integrate recent work on how soluble signaling factors, ECM, mechanical stimulation, and other cells contribute to the regulation of contractile SMC phenotype. The signal transduction pathways and mechanisms of gene expression induced by these stimuli are beginning to be elucidated and provide useful information for the quantitative analysis of SMC phenotype in engineered tissues. Progress in the development of tissue-engineered scaffold systems that implement biochemical, mechanical, or novel polymer fabrication approaches to promote contractile phenotype will also be reviewed. The application of an improved molecular understanding of SMC biology will facilitate the design of more potent cell-instructive scaffold systems to regulate SMC behavior.

Heparin inhibits pulmonary artery smooth muscle cell proliferation through guanine nucleotide exchange factor-H1/RhoA/Rho kinase/p27

Ras homolog gene family member A (RhoA) through Rho kinase kinase (ROCK), one of its downstream effectors, regulates a wide range of cell physiological functions, including vascular smooth muscle cell (SMC) proliferation, by degrading cyclin-dependent kinase inhibitor, p27. Our previous studies found that heparin inhibition of pulmonary artery SMC (PASMC) proliferation and pulmonary hypertension was dependent on p27 up-regulation. To investigate whether ROCK, a regulator of p27, is involved in regulation of heparin inhibition of PASMC proliferation, we analyzed ROCK expression in the lungs from mice and from human PASMCs exposed to hypoxia, and investigated the effect of ROCK expression in vitro by RhoA cDNA transfection. We also investigated the effect of guanine nucleotide exchange factor (GEF)-H1, an upstream regulator of RhoA, on heparin inhibition of PASMC proliferation by GEF-H1 cDNA transfection. We found that: (1) hypoxia increased ROCK expression in mice and PASMCs; (2) overexpression of RhoA diminished the inhibitory effect of heparin on PASMC proliferation and down-regulated p27 expression; and (3) overexpression of GEF-H1 negated heparin inhibition of PASMC proliferation, which was accompanied by increased GTP-RhoA and decreased p27. This study demonstrates that the RhoA/ROCK pathway plays an important role in heparin inhibition on PASMC proliferation, and reveals that heparin inhibits PASMC proliferation through GEF-H1/RhoA/ROCK/p27 signaling pathway, by down-regulating GEF-H1, RhoA, and ROCK, and then up-regulating p27.

Effect of carboxyl-reduced heparin on the growth inhibition of bovine pulmonary artery smooth muscle cells

Heparin (HP) inhibits the proliferation of bovine pulmonary artery smooth muscle cells (BPASMC's), among other cell types in vitro. In order to develop a potential therapeutic agent to reverse vascular remodeling, we are involved in deciphering the relationship between the native HP structure and its antiproliferative potency. We have previously reported the influence of the molecular size and the effects of various O-sulfo and N-acetyl groups of HP on growth-inhibitory activity. In this study, to understand the influence of carboxyl groups in the HP structure required for endogenous activity, a chemically modified derivative of native HP was prepared by converting the carboxyl groups of hexuronic acid residues in HP to primary hydroxyl groups. This modification procedure involves the treatment of HP with N-(3-dimethylaminopropyl)-N-ethylcarbodiimide followed by reduction with NaBH(4) to yield carboxyl-reduced heparin (CR-HP). When compared to the antiproliferative potency of native HP on cultured BPASMC's at three dose levels (1, 10, and 100 microg/mL), the CR-HP showed significantly less potency at all the doses. These results suggest that hexuronic acid residues in both major and variable sequences in HP are essential for the antiproliferative properties of native HP.

Significance of the 2-O-sulfo group of L-iduronic acid residues in heparin on the growth inhibition of bovine pulmonary artery smooth muscle cells

Heparin inhibits the growth of several cell types in vitro, including bovine pulmonary artery smooth muscle cells (BPASMCs). To understand more about the heparin structure required for endogenous activity, chemically modified derivatives of native heparin and glycol-split heparin, namely, 2-O-desulfonated iduronic/glucuronic acid residues in heparin, and 2-O-desulfonated iduronic residues in glycol-split heparin were prepared. These were assayed for their antiproliferative potency on cultured BPASMCs. All of the 2-O-desulfonated heparin derivatives had significantly decreased less antiproliferative activity on BPASMCs. These results suggest that the 2-O-sulfo group of iduronic acid residues in heparin's major sequence is essential for the antiproliferative properties of heparin. The size of heparin does not affect the growth-inhibitory properties of heparin on BPASMCs at the three dose levels examined.

Temporal and functional changes in glycosaminoglycan expression during osteogenesis

Heparan sulfate proteoglycans (HSPGs) are complex and labile macromolecular moieties on the surfaces of cells that control the activities of a range of extracellular proteins, particularly those driving growth and regeneration. Here, we examine the biosynthesis of heparan sulfate (HS) sugars produced by cultured MC3T3-E1 mouse calvarial pre-osteoblast cells in order to explore the idea that changes in HS activity in turn drive phenotypic development during osteogenesis. Cells grown for 5 days under proliferating conditions were compared to cells grown for 20 days under mineralizing conditions with respect to their phenotype, the forms of HS core protein produced, and their HS sulfotransferase biosynthetic enzyme levels. RQ-PCR data was supported by the results from the purification of day 5 and day 20 HS forms by anionic exchange chromatography. The data show that cells in active growth phases produce more complex forms of sugar than cells that have become relatively quiescent during active mineralization, and that these in turn can differentially influence rates of cell growth when added exogenously back to preosteoblasts.

Bone-specific heparan sulfates induce osteoblast growth arrest and downregulation of retinoblastoma protein

The heparan sulfate (HSs) sugars of the extracellular matrix (ECM) play a key role during both development and wound repair in regulating the flow of growth and adhesive factors across their cell surface receptors. The aim of this study was to assess the structural and functional differences of HS chains extracted from the conditioned media (soluble), cell surface, and ECM of primary human osteoblast cultures, and to analyze their effects on osteoblast cell growth. HS chains from these compartments were characterized through a combination of enzymatic degradation, anion exchange chromatography, and molecular sieving. Although the chains were all approximately the same size, they varied systematically in their sulfate content, suggesting differences in their protein-binding domains. When added to pre-confluent hFOB1.19 osteoblast cultures, HS doses exceeding 500 ng/ml inhibited proliferation, without affecting viability, irrespective of their origin. Furthermore, HS doses of 500 ng/ml also downregulated retinoblastoma, Cyclin A and CDK1 protein expression, indicating that high doses of osteoblast HS negatively regulate cell cycle, resulting in growth arrest; when high doses of HS were withdrawn after a prolonged period, linear cell growth was reestablished. Thus, despite differences in sulfation, HS from either the soluble, cell surface, or matrix compartments of primary human osteoblast cultures are functionally similar with respect to their effects on growth. Binding assays revealed that the HS chains bound TGFbeta1, a known inhibitor of osteoprogenitor growth, at higher affinity than a suite of other bone-related, heparin-binding growth factors. Overcoming such sugar-mediated inhibition may prove important for wound repair.

Selectively desulfated heparin inhibits P-selectin-mediated adhesion of human melanoma cells

Accumulating evidence has suggested that one of the mechanisms by which heparin inhibits metastasis is by blocking the P-selectin-based interaction of platelets with tumor cells. Here we demonstrate that the sulfate groups at C6/N and especially C6, but not C2 and C3, of heparin play a critical role in P-selectin recognition and that 2-O,3-O-desulfated heparin can block P-selectin-mediated A375 human melanoma cell adhesion. Our findings show that chemical modification of heparin, especially 2-O,3-O-desulfation, may result in a therapeutic agent that is anti-metastatic because it blocks unwanted P-selectin-dependent adhesion but that lacks dose-limiting anticoagulant effects.