Catalytic mechanism of heparinase II investigated by site-directed mutagenesis and the crystal structure with its substrate.

Heparinase II (HepII) is an 85-kDa dimeric enzyme that depolymerizes both heparin and heparan sulfate glycosaminoglycans through a beta-elimination mechanism. Recently, we determined the crystal structure of HepII from Pedobacter heparinus (previously known as Flavobacterium heparinum) in complex with a heparin disaccharide product, and identified the location of its active site. Here we present the structure of HepII complexed with a heparan sulfate disaccharide product, proving that the same binding/active site is responsible for the degradation of both uronic acid epimers containing substrates. The key enzymatic step involves removal of a proton from the C5 carbon (a chiral center) of the uronic acid, posing a topological challenge to abstract the proton from either side of the ring in a single active site. We have identified three potential active site residues equidistant from C5 and located on both sides of the uronate product and determined their role in catalysis using a set of defined tetrasaccharide substrates. HepII H202A/Y257A mutant lost activity for both substrates and we determined its crystal structure complexed with a heparan sulfate-derived tetrasaccharide. Based on kinetic characterization of various mutants and the structure of the enzyme-substrate complex we propose residues participating in catalysis and their specific roles.

Heparinase 1 selectivity for the 3,6-di-O-sulfo-2-deoxy-2-sulfamido-alpha-D-glucopyranose (1,4) 2-O-sulfo-alpha-L-idopyranosyluronic acid (GlcNS3S6S-IdoA2S) linkages.

Porcine intestinal mucosa heparin was partially depolymerized by recombinant heparinase 1 (heparin lyase 1, originating from Flavobacterium heparinum and expressed in Escherichia coli) and then fractionated, leading to the isolation of 22 homogeneous oligosaccharides with sizes ranging from disaccharide to hexadecasaccharide. The purity of these oligosaccharides was determined by gel electrophoresis, strong anion exchange and reversed-phase ion-pairing high-performance liquid chromatography. The molecular mass of oligosaccharides was determined using electrospray ionization-mass spectrometry and their structures were elucidated using one- and two-dimensional nuclear magnetic resonance spectroscopy at 600 MHz. Five of the characterized oligosaccharides represent new compounds. The most prominent oligosaccharide comprises the common repeating unit of heparin, ΔUA2S-[-GlcNS6S-IdoA2S-](n)-GlcNS6S, where ΔUA is 4-deoxy-α-l-threo-hex-4-eno-pyranosyluronic acid, GlcN is 2-deoxy-2-amino-d-glucopyranose, IdoA is l-idopyranosyluronic acid, S is sulfate and n = 0-7. A second prominent heparin oligosaccharide motif corresponds to ΔUA2S-[GlcNS6S-IdoA2S](n)-GlcNS6S-IdoA-GlcNAc6S-GlcA-GlcNS3S6S (where n = 0-5 and GlcA is d-glucopyranosyluronic acid), a fragment of the antithrombin III binding site in heparin. The prominence of this second set of oligosaccharides and the absence of intact antithrombin III binding sites suggest that the -GlcNS3S6S-IdoA2S- linkage is particularly susceptible to heparinase 1.

Mass balance analysis of contaminated heparin product.

A quantitative analysis of a recalled contaminated lot of heparin sodium injection U.S. Pharmacopeia (USP) was undertaken in response to the controversy regarding the exact nature of the contaminant involved in the heparin (HP) crisis. A mass balance analysis of the formulated drug product was performed. After freeze-drying, a 1-ml vial for injection afforded 54.8±0.3 mg of dry solids. The excipients, sodium chloride and residual benzyl alcohol, accounted for 11.4±0.5 and 0.9±0.5 mg, respectively. Active pharmaceutical ingredient (API) represented 41.5±1.0 mg, corresponding to 75.7 wt% of dry mass. Exhaustive treatment of API with specific enzymes, heparin lyases, and/or chondroitin lyases was used to close mass balance. HP represented 30.5±0.5 mg, corresponding to 73.5 wt% of the API. Dermatan sulfate (DS) impurity represented 1.7±0.3 mg, corresponding to 4.1 wt% of API. Contaminant, representing 9.3±0.1 mg corresponding to 22.4 wt% of API, was found in the contaminated formulated drug product. The recovery of contaminant was close to quantitative (95.6-100 wt%). A single contaminant was unambiguously identified as oversulfated chondroitin sulfate (OSCS).

Structural characterization of heparins from different commercial sources.

Seven commercial heparin active pharmaceutical ingredients and one commercial low molecular weight from different manufacturers were characterized with a view profiling their physicochemical properties. All heparins had similar molecular weight properties as determined by polyacrylamide gel electrophoresis (M(N), 10-11 kDa; M(W), 13-14 kDa; polydispersity (PD), 1.3-1.4) and by size exclusion chromatography (M(N), 14-16 kDa; M (W), 21-25 kDa; PD, 1.4-1.6). one-dimensional (1)H- and (13)C-nuclear magnetic resonance (NMR) evaluation of the heparin samples was performed, and peaks were fully assigned using two-dimensional NMR. The percentage of glucosamine residues with 3-O-sulfo groups and the percentage of N-sulfo groups and N-acetyl groups ranged from 5.8-7.9%, 78-82%, to 13-14%, respectively. There was substantial variability observed in the disaccharide composition, as determined by high performance liquid chromatography (HPLC)-mass spectral analysis of heparin lyase I-III digested heparins. Heparin oligosaccharide mapping was performed using HPLC following separate treatments with heparin lyase I, II, and III. These maps were useful in qualitatively and quantitatively identifying structural differences between these heparins. The binding affinities of these heparins to antithrombin III and thrombin were evaluated by using a surface plasmon resonance competitive binding assay. This study provides the physicochemical and activity characterization necessary for the appropriate design and synthesis of a generic bioengineered heparin.

ELECTRON DETACHMENT DISSOCIATION AND INFRARED MULTIPHOTON DISSOCIATION OF HEPARIN TETRASACCHARIDES.

Heparin glycosaminoglycans (GAGs) present the most difficult glycoform for analytical characterization due to high levels of sulfation and structural heterogeneity. Recent contamination of the clinical heparin supply and subsequent fatalities has highlighted the need for sensitive methodologies of analysis. In the last decade, tandem mass spectrometry has been increasingly applied for the analysis of GAGs, but developments in the characterization of highly sulfated compounds have been minimal due to the low number of cross-ring cleavages generated by threshold ion activation by collisional induced dissociation (CID). In the current work, electron detachment dissociation (EDD) and infrared multiphoton dissociation (IRMPD) are applied to a series of heparin tetrasaccharides. With both activation methods, abundant glycosidic and cross-ring cleavages are observed. The concept of Ionized Sulfate Criteria (ISC) is presented as a succinct method for describing the charge state, degree of ionization and sodium/proton exchange in the precursor ion. These factors contribute to the propensity for useful fragmentation during MS/MS measurements. Precursors with ISC values of 0 are studied here, and shown to yield adequate structural information from ion activation by EDD or IRMPD.

Negative electron transfer dissociation Fourier transform mass spectrometry of glycosaminoglycan carbohydrates.

Electron transfer through gas phase ion-ion reactions has led to the widespread application of electron- based techniques once only capable in ion trapping mass spectrometers. Although any mass analyzer can in theory be coupled to an ion-ion reaction device (typically a 3-D ion trap), some systems of interest exceed the capabilities of most mass spectrometers. This case is particularly true in the structural characterization of glycosaminoglycan (GAG) oligosaccharides. To adequately characterize highly sulfated GAGs or oligosaccharides above the tetrasaccharide level, a high resolution mass analyzer is required. To extend previous efforts on an ion trap mass spectrometer, negative electron transfer dissociation coupled with a Fourier transform ion cyclotron resonance mass spectrometer has been applied to increasingly sulfated heparan sulfate and heparin tetrasaccharides as well as a dermatan sulfate octasaccharide. Results similar to those obtained by electron detachment dissociation are observed.

Structural snapshots of heparin depolymerization by heparin lyase I.

Heparin lyase I (heparinase I) specifically depolymerizes heparin, cleaving the glycosidic linkage next to iduronic acid. Here, we show the crystal structures of heparinase I from Bacteroides thetaiotaomicron at various stages of the reaction with heparin oligosaccharides before and just after cleavage and product disaccharide. The heparinase I structure is comprised of a beta-jellyroll domain harboring a long and deep substrate binding groove and an unusual thumb-resembling extension. This thumb, decorated with many basic residues, is of particular importance in activity especially on short heparin oligosaccharides. Unexpected structural similarity of the active site to that of heparinase II with an (alpha/alpha)(6) fold is observed. Mutational studies and kinetic analysis of this enzyme provide insights into the catalytic mechanism, the substrate recognition, and processivity.

[Clinical Significance of Mean Platelet Volume Determination in Multiple Myeloma].

OBJECTIVE: To investigate the clinical significance of mean platelet volume(MPV) in patients with multiple myeloma(MM). METHODS: The clinical data of 198 patients with MM admitted in our hospital from March 2008 to March 2015 were collected and analyzed. The clinical data included the Ig type, hemoglobin level, platelet count, creatinine, calciumion albumin, ß2-MG, LDH, plasmocytes in bone marrow, MPV, complications such as diabetes, a history of venous thromboembolism (VTE) and arterial events such as coronary artery disease, cerebrovascular disease, thrombosis and blood clotting. All patients were divided into low MPV group (≤8.50 fl) and high MPV group (>8.50 fl). The biochemical parameters and prognosis of the 2 groups were compared. RESULTS: When MPV was 8.50 fl, the higest sensitivety and specificity were 55.56% and 80.00% respectively. The area under curve (AUC) was 0.656 (95% CI: 0.515-0.797), the IgA type, creatinine level and IgH rearrangement in MM patients were related with MPV. The ratio of IgA and IgH rearrangements in patients with low MPV was higher than that in patients with high MPV, and the ratio of patients with creatinine >176.8 µmol/L was lower than that of patients with high MPV (P<0.05). The age, sex, ECOG PS, complications, ISS stage, hemoglobin level, platelet count, calcium ion, albumin, ß2 microglobulin, lactate dehydrogenase and bone marrow plasma cell ratio were not statistically significantly different between the 2 groups. Patients with low MPV had a shorter OS (P=0.039) than those with higher MPV. Univariate analysis showed that MPV, BM plasma cell ratio and age>60 years correleted with OS. Multivariate analysis showed that the low MPV and BM plasma cell ratio were correlated with shorter OS (P<0.05). CONCLUSION: The low MPV is correlated with poor prognosis in patients with MM and may serve as an important indicator for disease progression and prognosis of patients with MM.

Stereocomplex micelle efficiently transports Doxorubicin for enhanced lymphoma suppression in vivo.

The application of Doxorubicin (DOX) in the chemotherapy for lymphoma is seriously hampered by the side effects of DOX, especially the cardiotoxicity and nephrotoxicity. Nanoscale micelle as a promising drug delivery system has gained more and more interest in malignancy chemotherapy. In this study, we successfully fabricated DOX-loaded stereocomplex micelle (SCM/DOX) from the equimolar mixture of the enantiomeric four-armed poly(ethylene glycol)-polylactide (PDM and PLM) copolymers. The SCM/DOX showed proper hydrodynamic size of ~90 nm and slow DOX release in phosphate-buffered saline at pH 7.4. The antitumor activities of DOX, PDM/DOX, PLM/DOX, and SCM/DOX toward lymphoma cells were tested in vitro and in vivo. Our data demonstrated that the SCM/DOX more effectively inhibited the cell proliferation than PDM/DOX, PLM/DOX, and free DOX in vitro. In the in vivo antitumor test, the SCM/DOX more effectively inhibited the growth of EL4 lymphoma, too. In addition, the body weight loss caused by SCM/DOX was alleviated than DOX. More importantly, the cardiotoxicity, nephrotoxicity, and hepatotoxicity caused by DOX in mice were obviously attenuated compared to the free DOX treatment group. Taken together, all the results indicated that the SCM/DOX could inhibit the growth of EL4 lymphoma cells and attenuate the toxicity of DOX more efficiently, which suggested SCM/DOX was promising for the prevention and treatment of lymphoma.

[Efficacy and safety of anagrelide in treatment of essential thrombocythemia: multicenter, randomized controlled clinical trial].

OBJECTIVE: To evaluate the efficacy and safety of anagrelide in essential thrombocythemia (ET). METHODS: Patients who diagnosed as ET according to the World Health Organization classification were enrolled. Each patient was assigned to take anagrelide hydrochloride capsule or hydroxyurea tablet by random 1∶1 ratio. Dose of anagrelide started at 2 mg/d, then increased gradually and the maximum dose was 10 mg/d until the platelet counts dropped to (100-400) × 109/L, one month later gradually reduced to maintain dose. The dose of hydroxyurea was 1000 mg/d at beginning, then increased gradually, when platelet counts dropped to (100-400)×109/L and kept for one month, reduced to maintain dose as 10 mg·kg⁻¹·d⁻¹. The observation period was 12 weeks. RESULTS: A total of 222 patients were enrolled in seventeen centers (including 113 patients treated with anagrelide and 109 with hydroxyurea). Therapy efficacy can be evaluated in 198 patients (including 97 patients administered with anagrelide and 101 with hydroxyurea). At 12th weeks of therapy, the hematologic remission rate was 87.63% (85/97) in anagrelide group and 88.12% (89/107) in hydroxyurea group, the differences between the two groups were not significant (P=0.173). Treatment with anagrelide lowered the platelet counts by a median of 393 (362-1 339) × 109/L from a median of 827 (562-1657) × 109/L at the beginning of the observation to 400(127-1130)×109/L after 12 weeks (P<0.001), which were similar to the treatment result of hydroxyurea by a median drop of 398 (597-1846)× 109/L (P=0.982). The median time to achieving response of anagrelide group was 7 (3-14) days, superior to that of hydroxyurea for 21 (14-28) significantly (P=0.003). Frequency of anagrelide related adverse events was 65.49 % (74/113), including cardiopalmus (36.28% ), headache (21.24% ), fatigue (14.16% ) and dizzy (11.50% ). CONCLUSION: Anagrelide was effective in patients with ET which had similar hematologic remission rate to hydroxyurea and could take effect more quickly than hydroxyurea. Incidence of adverse events was undifferentiated between anagrelide and hydroxyurea, but anagrelide treatment had tolerable adverse effects and no hematologic toxicity.

Binding affinities of vascular endothelial growth factor (VEGF) for heparin-derived oligosaccharides.

Heparin and HS (heparan sulfate) exert their wide range of biological activities by interacting with extracellular protein ligands. Among these important protein ligands are various angiogenic growth factors and cytokines. HS binding to VEGF (vascular endothelial growth factor) regulates multiple aspects of vascular development and function through its specific interaction with HS. Many studies have focused on HS-derived or HS-mimicking structures for the characterization of VEGF165 interaction with HS. Using a heparinase 1-prepared small library of heparin-derived oligosaccharides ranging from hexasaccharide to octadecasaccharide, we systematically investigated the heparin-specific structural features required for VEGF binding. We report the apparent affinities for the association between the heparin-derived oligosaccharides with both VEGF165 and VEGF55, a peptide construct encompassing exclusively the heparin-binding domain of VEGF165. An octasaccharide was the minimum size of oligosaccharide within the library to efficiently bind to both forms of VEGF and a tetradecasaccharide displayed an effective binding affinity to VEGF165 comparable to unfractionated heparin. The range of relative apparent binding affinities among VEGF and the panel of heparin-derived oligosaccharides demonstrate that the VEGF binding affinity likely depends on the specific structural features of these oligosaccharides, including their degree of sulfation, sugar-ring stereochemistry and conformation. Notably, the unique 3-O-sulfo group found within the specific antithrombin binding site of heparin is not required for VEGF165 binding. These findings afford new insight into the inherent kinetics and affinities for VEGF association with heparin and heparin-derived oligosaccharides with key residue-specific modifications and may potentially benefit the future design of oligosaccharide-based anti-angiogenesis drugs.

Asparagine 405 of heparin lyase II prevents the cleavage of glycosidic linkages proximate to a 3-O-sulfoglucosamine residue.

Heparin and heparan sulfate contain a rare 3-O-sulfoglucosamine residue critical for anticoagulation and virus recognition, respectively. The glycosidic linkage proximate to this 3-O-sulfoglucosamine is resistant to cleavage by all heparin lyases (Heps). HepII has a broad specificity. The crystal structure of the wild type HepII identified its active site and showed a close spatial proximity between Asn405 and the 3-OH group of the bound glucosamine residue. In this study, we mutated Asn405 to the less sterically demanding Ala405 or Gly405, which broadened the substrate specificity of HepII and caused it to cleave the resistant linkage proximate to the 3-O-sulfoglucosamine residue.

Heparin mapping using heparin lyases and the generation of a novel low molecular weight heparin.

Seven pharmaceutical heparins were investigated by oligosaccharide mapping by digestion with heparin lyase 1, 2, or 3, followed by high performance liquid chromatography analysis. The structure of one of the prepared mapping standards, ΔUA-Gal-Gal-Xyl-O-CH(2)CONHCH(2)COOH (where ΔUA is 4-deoxy-α-l-threo-hex-4-eno-pyranosyluronic acid, Gal is ß-d-galactpyranose, and Xyl is ß-d-xylopyranose) released from the linkage region using either heparin lyase 2 or heparin lyase 3 digestion, is reported for the first time. A size-dependent susceptibility of site cleaved by heparin lyase 3 was also observed. Heparin lyase 3 acts on the undersulfated domains of the heparin chain and does not cleave the linkages within heparin's antithrombin III binding site. Thus, a novel low molecular weight heparin (LMWH) is afforded on heparin lyase 3 digestion of heparin due to this unique substrate specificity, which has anticoagulant activity comparable to that of currently available LMWH.

[The comparison of CD4(+);CD25(high); Foxp3(+); regulatory T cells between neonatal cord blood and adult peripheral blood.].

AIM: To quantify the proportion of CD4(+);CD25(high); Foxp3(+); regulatory T cells (Treg) in neonatal cord blood and adult peripheral blood, and to explore the clinical significance of Treg in neonatal cord blood. METHODS: The percentage of CD4(+); T cells, and ratio of CD4(+);CD25(+);/CD4(+); and CD4(+);CD25(high);/CD4(+);T cells in mononuclear cells in 30 neonatal cord blood and 27 adult peripheral blood were examinea with flow cytometry (FCM). The expression of Foxp3(+); in CD4(+);CD25(+); and CD4(+);CD25(high); T cells was examined with FCM and RT-PCR, respectively RT-PCR. RESULTS: Compared with adult PBMC, the percentage of CD4(+); T cells was increased in neonatal cord blood(P<0.01); the percentage of CD4(+);CD25(+);/CD4(+); and CD4(+);CD25(high);/CD4(+);T cells were decreased in neonatal cord blood(P<0.05). The percentage of Foxp3(+); cells in CD4(+);CD25(+); and CD4(+);CD25(high); T cells in neonatal cord blood were both lower than that in adult peripheral blood(P<0.01) and the expression level of Foxp3 mRNA was also lower than that in adult peripheral blood(P<0.05). CONCLUSION: There are certain amount CD4(+);CD25(high); Tregs in neonatal cord blood, but the expression levels of Foxp3 are lower than that in adult peripheral blood, which indicate that Tregs might play a distinct role of immunoloregulation.