Enzymatic Generation of Highly Anticoagulant Bovine Intestinal Heparin

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Imaging of Escherichia coli K5 and glycosaminoglycan precursors via targeted metabolic labeling of capsular polysaccharides in bacteria

The introduction of unnatural chemical moieties into glycosaminoglycans (GAGs) has enormous potential to facilitate studies of the mechanism and application of these critical, widespread molecules. Unnatural N-acetylhexosamine analogs were metabolically incorporated into the capsule polysaccharides of Escherichia coli and Bacillus subtilis via bacterial metabolism. Targeted metabolic labeled hyaluronan and the precursors of heparin and chondroitin sulfate were obtained. The azido-labeled polysaccharides (purified or in capsules) were reacted with dyes, via bioorthogonal chemistry, to enable detection and imaging. Site-specific introduction of fluorophores directly onto cell surfaces affords another choice for observing and quantifying bacteria in vivo and in vitro. Furthermore, azido-polysaccharides retain similar biological properties to their natural analogs, and reliable and predictable introduction of functionalities, such as fluorophores, onto azido-N-hexosamines in the disaccharide repeat units provides chemical tools for imaging and metabolic analysis of GAGs in vivo and in vitro.

Chemobiocatalytic Synthesis of a Low-Molecular-Weight Heparin

Heparin products are widely used clinical anticoagulants essential in the practice of modern medicine. Low-molecular-weight heparins (LMWHs) are currently prepared by the controlled chemical or enzymatic depolymerization of unfractionated heparins (UFHs) that are extracted from animal tissues. In many clinical applications, LMWHs have displaced UFHs and currently comprise over 60% of the heparin market. In the past, our laboratory has made extensive efforts to prepare bioengineered UFHs relying on a chemoenzymatic process to address concerns about animal-sourced UFHs. The current study describes the use of a novel chemoenzymatic process to prepare a chemobiosynthetic LMWH from a low-molecular-weight heparosan. The resulting chemobiocatalytic LMWH matches most of the United States pharmacopeial specifications for enoxaparin, a LMWH prepared through the base-catalyzed depolymerization of animal-derived UFH.

Anion binding to a cationic europium(III) probe enables the first real-time assay of heparan sulfotransferase activity

Sulfotransferases constitute a ubiquitous class of enzymes which are poorly understood due to the lack of a convenient tool for screening their activity. These enzymes use the anion PAPS (adenosine-3'-phosphate-5'-phosphosulfate) as a donor for a broad range of acceptor substrates, including carbohydrates, producing sulfated compounds and PAP (adenosine-3',5'-diphosphate) as a side product. We present a europium(III)-based probe that binds reversibly to both PAPS and PAP, producing a larger luminescence enhancement with the latter anion. We exploit this greater emission enhancement with PAP to demonstrate the first direct real-time assay of a heparan sulfate sulfotransferase using a multi-well plate format. The selective response of our probe towards PAP over structurally similar nucleoside phosphate anions, and over other anions, is investigated and discussed. This work opens the possibility of investigating more fully the roles played by this enzyme class in health and disease, including operationally simple inhibitor screening.

Platelet factor 4 polyanion immune complexes: heparin induced thrombocytopenia and vaccine-induced immune thrombotic thrombocytopenia

BACKGROUND

This is a review article on heparin-induced thrombocytopenia, an adverse effect of heparin therapy, and vaccine-induced immune thrombotic thrombocytopenia, occurring in some patients administered certain coronavirus vaccines.

MAIN BODY/TEXT

Immune-mediated thrombocytopenia occurs when specific antibodies bind to platelet factor 4 /heparin complexes. Platelet factor 4 is a naturally occurring chemokine, and under certain conditions, may complex with negatively charged molecules and polyanions, including heparin. The antibody-platelet factor 4/heparin complex may lead to platelet activation, accompanied by other cascading reactions, resulting in cerebral sinus thrombosis, deep vein thrombosis, lower limb arterial thrombosis, myocardial infarction, pulmonary embolism, skin necrosis, and thrombotic stroke. If untreated, heparin-induced thrombocytopenia can be life threatening. In parallel, rare incidents of spontaneous vaccine-induced immune thrombotic thrombocytopenia can also occur in some patients administered certain coronavirus vaccines. The role of platelet factor 4 in vaccine-induced thrombosis with thrombocytopenia syndrome further reinforces the importance the platelet factor 4/polyanion immune complexes and the complications that this might pose to susceptible individuals. These findings demonstrate, how auxiliary factors can complicate heparin therapy and drug development. An increasing interest in biomanufacturing heparins from non-animal sources has driven a growing interest in understanding the biology of immune-mediated heparin-induced thrombocytopenia, and therefore, the development of safe and effective biosynthetic heparins.

SHORT CONCLUSION

In conclusion, these findings further reinforce the importance of the binding of platelet factor 4 with known and unknown polyanions, and the complications that these might pose to susceptible patients. In parallel, these findings also demonstrate how auxiliary factors can complicate the heparin drug development.

Bioengineered production of glycosaminoglycans and their analogues

Glycosaminoglycans (GAGs) are a class of linear polysaccharides, consisting of alternating disaccharide sequences of uronic acid and hexosamines (or galactose) with and without sulfation. They can interact with various proteins, such as growth factors, receptors and cell adhesion molecules, endowing these with various biological and pharmacological activities. Such activities make GAGs useful in health care products and medicines. Currently, all GAGs, with the exception of hyaluronan, are produced by extraction from animal tissues. However, limited availability, poor control of animal tissues, impurities, viruses, prions, endotoxins, contamination and other problems have increased the interest in new approaches for GAG production. These new approaches include GAGs production by chemical synthesis, chemoenzymatic synthesis and metabolic engineering. One chemically synthesized heparin pentasaccharide, fondaparinux sodium, is in clinical use. Mostly, hyaluronan today is prepared by microbial fermentation, largely replacing hyaluronan from rooster comb. The recent gram scale chemoenzymatic synthesis of a heparin dodecasaccharide suggests its potential to replace currently used animal-sourced low molecular weight heparin (LMWH). Despite these considerable successes, such high-tech approaches still cannot meet worldwide demands for GAGs. This review gives a brief introduction on the manufacturing of unfractionated and low molecular weight heparins, the chemical synthesis and chemoenzymatic synthesis of GAGs and focuses on the progress in the bioengineered preparation of GAGs, particularly heparin.

Preparation of Low Molecular Weight Heparin from a Remodeled Bovine Intestinal Heparin

Bovine intestinal heparins are structurally distinct from porcine intestinal heparins and exhibit lower specific anticoagulant activity (units/mg). The reduced content of N-sulfo, 3-O-sulfo glucosamine, the central and critical residue in heparin's antithrombin III binding site, is responsible for bovine intestinal heparin's reduced activity. Previous studies demonstrate that treatment of bovine intestinal heparin with 3-O-sulfotransferase in the presence of 3'-phosphoadenosine-5'-phosphosulfate afforded remodeled bovine heparin with an enhanced activity reaching the United States Pharmacopeia's requirements. Starting from this remodeled bovine intestinal heparin, we report the preparation of a bovine intestinal low molecular weight heparin having the same structural properties and anti-factor IIa and anti-factor Xa activities of Enoxaparin. Moreover, this bovine intestinal heparin-derived "Enoxaparin" showed comparable platelet factor-4 binding affinity, suggesting that it should exhibit similarly low levels of heparin induced thrombocytopeneia, HIT.

High density fermentation of probiotic E. coli Nissle 1917 towards heparosan production, characterization, and modification

Heparosan is a naturally occurring non-sulfated glycosaminoglycan. Heparosan serves as the substrate for chemoenzymatic synthesis of biopharmaceutically important heparan sulfate and heparin. Heparosan is biologically inert molecule, non-toxic, and non-immunogenic and these qualities of heparosan make it an ideal drug delivery vehicle. The critical-to-quality (CTQ) attributes for heparosan applications include composition of heparosan, absence of any unnatural moieties, and heparosan molecular weight size and unimodal distribution. Probiotic bacteria E. coli Nissle 1917 (EcN) is a natural producer of heparosan. The current work explores production of EcN heparosan and process parameters that may impact the heparosan CTQ attributes. Results show that EcN could be grown to high cell densities (OD₆₀₀ 160-180) in a chemically defined media. The fermentation process is successfully scaled from 5-L to 100-L bioreactor. The chemical composition of heparosan from EcN was confirmed using nuclear magnetic resonance. Results demonstrate that heparosan molecular weight distribution may be influenced by fermentation and purification conditions. Size exclusion chromatography analysis shows that the heparosan purified from fermentation broth results in bimodal distribution, and cell-free supernatant results in unimodal distribution (average molecular weight 68,000 Da). The yield of EcN-derived heparosan was 3 g/L of cell free supernatant. We further evaluated the application of Nissle 1917 heparosan for chemical modification to prepare N-sulfo heparosan (NSH), the first intermediate precursor for heparin and heparan sulfate. KEY POINTS: • High cell density fermentation, using a chemically defined fermentation media for the growth of probiotic bacteria EcN (E. coli Nissle 1917, a natural producer of heparosan) is reported. • Process parameters towards the production of monodispersed heparosan using probiotic bacteria EcN (Nissle 1917) has been explored and discussed. • The media composition and the protocol (SOPs and batch records) have been successfully transferred to contract manufacturing facilities and industrial partners.

Heparosan Chain Characterization: Sequential Depolymerization of E. Coli K5 Heparosan by a Bacterial Eliminase Heparin Lyase III and a Bacterial Hydrolase Heparanase Bp to Prepare Defined Oligomers

Heparosan is a non-sulfated polysaccharide and potential applications include, chemoenzymatic synthesis of heparin and heparan sulfates. Heparosan is produced using microbial cells (natural producers or engineered cells). The characterization of heparosan isolated from both natural producers and engineered-cells are critical steps towards the potential applications of heparosan. Heparosan is characterized using 1) analysis of intact chain size and polydispersity, and 2) disaccharide composition. The current paper describes a novel method for heparosan chain characterization, using heparin lyase III (Hep-3, an eliminase from Flavobacterium heparinum) and heparanase Bp (Hep-Bp, a hydrolase from Burkholderia pseudomallei). The partial digestion of E. coli K5 heparosan with purified His-tagged Hep-3 results in oligomers of defined sizes. The oligomers (degree of polymerization from 2 to 8, DP2-DP8) are completely digested with purified GST-tagged Hep-Bp and analyzed using gel permeation chromatography. Hep-Bp specifically cleaves the linkage between d-glucuronic acid (GlcA) and N-acetyl-d-glucosamine (GlcNAc) but not the linkage between 4-deoxy-α-L-threo-hex-4-enopyranosyluronic acid (deltaUA) and GlcNAc, and results in the presence of a minor resistant trisaccharide (GlcNAc-GlcA-GlcNAc). This method successfully demonstrated the substrate selectivity of Hep-BP on heparosan oligomers. This analytical tool could be applied towards heparosan chain mapping and analysis of unnatural sugar moieties in the heparosan chain.

Processing bovine intestinal mucosa to active heparin removes spiked BSE agent

Heparin is an anticoagulant sourced from animal tissues. In the 1990s, bovine-sourced heparin was withdrawn from the U.S. market due to a theoretical concern that the bovine spongiform encephalopathy (BSE) agent might contaminate crude heparin and spread to humans as variant Creutzfeldt-Jakob disease. Only porcine intestinal heparin is now marketed in the U.S. FDA has encouraged the reintroduction of bovine heparin. We applied a scaled-down laboratory model process to produce heparin as an active pharmaceutical ingredient (API) starting from bovine intestinal mucosa. The process consisted of two phases. To model the first phase, we applied enzymatic proteolysis, anionic resin separation and methanol precipitation of crude heparin. Bovine intestinal mucosa was spiked with BSE or scrapie agents. We assayed BSE- or scrapie-associated prion protein (PrP^TSE) using the Real-Time Quaking-Induced Conversion (RT-QuIC) assay at each step. The process reduced PrP^TSE by 4 log₁₀ and 6 log₁₀ from BSE-spiked and scrapie-spiked mucosa, respectively. To model the entire process, we spiked mucosa with scrapie agent and produced heparin API, reducing PrP^TSE by 6.7 log₁₀. The purification processes removed large amounts of PrP^TSE from the final products. Heparin purification together with careful sourcing of raw materials should allow safely reintroducing bovine heparin in the U.S.

Expression of enzymes for 3'-phosphoadenosine-5'-phosphosulfate (PAPS) biosynthesis and their preparation for PAPS synthesis and regeneration

The synthesis of sulfated polysaccharides involves the sulfation of simpler polysaccharide substrates, through the action sulfotransferases using the cofactor, 3'-phosphoadenosine-5'-phosphosulfate (PAPS). Three enzymes are essential for the in vitro synthesis of PAPS, namely, pyrophosphatase (PPA), adenosine 5'-phosphosulfate kinase (APSK), and ATP sulfurylase (ATPS). The optimized enzyme expression ratio and effect on PAPS synthesis were evaluated using ePathBrick, a novel synthetic biology tool that assemble multiple genes in a single vector. The introduction of multiple promoters and stop codons at different location enable the bacterial system to fine tune expression level of the genes inserted. Recombinant vectors expressing PPA (U39393.1), ATPS (CP021243.1), and PPA (CP047127.1) were used for fermentations and resulted in volumetric yields of 400-1380 mg/L with accumulation of 34-66% in the soluble fraction. The enzymes from soluble fraction, without any further purification, were used for PAPS synthesis. The PAPS was used for the chemoenzymatic synthesis of a heparan sulfate polysaccharide and coupled with a PAPS-ASTIV regeneration system. ASTIV catalyzes the regeneration of PAPS. A recombinant vector expressing the enzyme ASTIV (from Rattus norvegicus) was used for fermentations and resulted in volumetric yield of 1153 mg/L enzyme with accumulation of 48% in the soluble fraction. In conclusion, we have successfully utilized a metabolic engineering approach to optimize the overall PAPS synthesis productivity. In addition, we have demonstrated that the ePathBrick system could be applied towards study and improvement of enzymatic synthesis conditions. In parallel, we have successfully demonstrated an autoinduction microbial fermentation towards the production of mammalian enzyme (ASTIV). KEY POINTS : • ePathBrick used to optimize expression levels of enzymes. • Protocols have been used for the production of recombinant enzymes. • High cell density fed-batch fermentations with high yields of soluble enzymes. • Robust fermentation protocol successfully transferred to contract manufacturing and research facilities.

Cross-Species Analysis of Glycosaminoglycan Binding Proteins Reveals Some Animal Models Are "More Equal" than Others

Glycosaminoglycan (GAG) mimetics are synthetic or semi-synthetic analogues of heparin or heparan sulfate, which are designed to interact with GAG binding sites on proteins. The preclinical stages of drug development rely on efficacy and toxicity assessment in animals and aim to apply these findings to clinical studies. However, such data may not always reflect the human situation possibly because the GAG binding site on the protein ligand in animals and humans could differ. Possible inter-species differences in the GAG-binding sites on antithrombin III, heparanase, and chemokines of the CCL and CXCL families were examined by sequence alignments, molecular modelling and assessment of surface electrostatic potentials to determine if one species of laboratory animal is likely to result in more clinically relevant data than another. For each protein, current understanding of GAG binding is reviewed from a protein structure and function perspective. This combinatorial analysis shows chemokine dimers and oligomers can present different GAG binding surfaces for the same target protein, whereas a cleft-like GAG binding site will differently influence the types of GAG structures that bind and the species preferable for preclinical work. Such analyses will allow an informed choice of animal(s) for preclinical studies of GAG mimetic drugs.

Heparins Sourced From Bovine and Porcine Mucosa Gain Exclusive Monographs in the Brazilian Pharmacopeia

Most of the unfractionated heparin (UFH) consumed worldwide is manufactured using porcine mucosa as raw material (HPI); however, some countries also employ products sourced from bovine mucosa (HBI) as interchangeable versions of the gold standard HPI. Although accounted as a single UFH, HBI, and HPI have differing anticoagulant activities (~100 and 200 IU mg⁻¹, respectively) because of their compositional dissimilarities. The concomitant use of HBI and HPI in Brazil had already provoked serious bleeding incidents, which led to the withdrawal of HBI products in 2009. In 2010, the Brazilian Pharmacopeia (BP) formed a special committee to develop two complementary monographs approaching HBI and HPI separately, as distinct active pharmaceutical ingredients (APIs). The committee has rapidly agreed on requirements concerning the composition and presence of contaminants based on nuclear magnetic resonance and anion-exchange chromatography. On the other hand, consensus on the anticoagulant activity of HBI was the subject of long and intense discussions. Nevertheless, the committee has ultimately agreed to recommend minimum anti-FIIa activities of 100 IU mg⁻¹ for HBI and 180 IU mg⁻¹ for HPI. Upon the approval by the Brazilian Health Authority (ANVISA), the BP published the new monographs for HPI and HBI APIs in 2016 and 2017, respectively. These pioneer monographs represent a pivotal step toward the safest use of HBI and HPI as interchangeable anticoagulants and serve as a valuable template for the reformulation of pharmacopeias of other countries willing to introduce HBI.

Bovine Mucosal Heparins Are Comparable to Porcine Mucosal Heparin at USP Potency Adjusted Levels

Introduction: Bovine mucosal heparins (BMH) are currently being developed for re-introduction for both medical and surgical indications. BMH active pharmaceutical ingredient (API) exhibits a somewhat weaker USP potency when compared to PMHs. We hypothesized that when dosages are normalized based on the USP reference heparin, BMH will exhibit comparable in vitro and in vivo effects to those produced by PMH. Therefore, studies were developed to compare the APIs of bovine and porcine heparin.

Materials and Methods: API versions of PMH were obtained from Celsus Laboratories (Franklin, OH) and Medefil (Glen Ellen, IL). API versions of BMH were obtained from Kin Master (Passo Fundo, Brazil). Each of these heparins was assayed for their molecular weight profile, AT affinity, USP potency, and anticoagulant/antiprotease profiles using standard laboratory methods. In vitro protamine neutralization studies were carried out. Antithrombotic and hemorrhagic effects were measured in rats and pharmacodynamic profiles were assessed in primates.

Results: Size exclusion chromatography demonstrated that the mean molecular weight of BMH was ~15% higher than that of PMH (BMH: 20.1 ± 0.8 kDa and PMH: 17.5 ± 0.7 kDa). BMH exhibited an anti-Xa potency of 130 U/mg while PMH had an anti-Xa potency of 185 U/mg. In the anticoagulant and antiprotease assays, the BMH exhibited lower functionality which was proportional to USP potency. When the BMH was compared with PMH at potency adjusted concentrations, it showed identical concentration-response curves in the aPTT and anti-protease assays. However, in the protamine neutralization studies, BMH required slightly higher amounts of protamine in contrast to PMH. BMH and PMH administered to rats at equivalent anti-Xa unit dosages resulted in comparable antithrombotic activity and prolongation of bleeding time. Similar pharmacodynamic profiles were observed in primates when BMH and PMH were dosed on an anti-Xa U/kg basis.

Conclusion: BMH, when used at comparable anti-Xa unit levels, is comparable to PMH, however, it requires proportionally higher amount of protamine due to the increased mass for adjusting to higher potency. Additional studies on the structural characterization, interactions with PF4 and in vivo neutralization studies are ongoing.

Chemometric analysis of porcine, bovine and ovine heparins

Heparin is a polysaccharide anticoagulant drug isolated from animal tissues. There have been concerns on the safety and security of the heparin supply chain since 2007-8 when a contamination crisis led to its disruption. The current study applies a suite of modern analytical techniques to porcine, bovine and ovine intestinal mucosal heparins. These techniques include structural analysis by nuclear magnetic resonance spectrometry, disaccharide compositional analysis, bottom-up analysis of tetrasaccharides corresponding to heparin's antithrombin III binding site. Chemometric analysis was then applied to understand how these structural differences to predict the animal/tissue source of heparin and to help detect blending of heparins from various sources.

Increased soluble heterologous expression of a rat brain 3-O-sulfotransferase 1 - A key enzyme for heparin biosynthesis

Heparan sulfate (HS), is a glycosaminoglycan (GAG) involved in various biological processes, including blood coagulation, wound healing and embryonic development. HS 3-O-sulfotransferases (3-OST), which transfer the sulfo group to the 3-hydroxyl group of certain glucosamine residues, is a key enzyme in the biosynthesis of a number of biologically important HS chains. The 3-OST-1 isoform is one of the 7 known 3-OST isoforms and is important for the biosynthesis of anticoagulant HS chains. In this study, we cloned 3-OST-1 from the rat brain by reverse transcription-polymerase chain reaction (RT-PCR). After codon optimization and removal of the signal peptide, the recombinant plasmid was transformed into Escherichia coli BL21 (DE3) to obtain a His tagged-3-OST-1 fusion protein. SDS-PAGE analysis showed that the expressed 3-OST-1 was mainly found in inclusion bodies. The 3-OST-1 was purified by Ni affinity column and refolded by dialysis. The activity of obtained 3-OST-1 was 0.04 U/mL with a specific activity of 0.55 U/mg after renaturation. Furthermore, a co-expressed recombinant plasmid pET-28a-3-OST-1 with the chaperone expression system (pGro7) was constructed and transferred to E. coli BL21 (DE3) to co-express recombinant strain E. coli BL21 (DE3)/pET-28a-3-OST-1 + pGro7. The soluble expression of 3-OST-1 was significantly improved in the co-expressed recombinant strain, with enzyme activity reaching 0.06 U/mL and having a specific activity of 0.83 U/mg. N-sulfo, N-acetylheparosan (NSNAH) was modified by the recombinant expressed 3-OST-1 and the product was confirmed by ¹H NMR showing the sulfo group was successfully transferred to NSNAH.