Glucose-responsive polymer bearing a novel phenylborate derivative as a glucose-sensing moiety operating at physiological pH conditions

This study is devoted to the development of novel glucose-responsive polymers that operate under physiological conditions (pH 7.4, 37 degrees C), aiming for future use in a self-regulated insulin delivery system to treat diabetes mellitus. The approach involves the use of a newly synthesized phenylborate derivative [4-(1,6-dioxo-2,5-diaza-7-oxamyl) phenylboronic acid, DDOPBA] possessing an appreciably low pK(a) ( approximately 7.8) as a glucose-sensing moiety, as well as the adoption of poly(N-isopropylmethacrylamide), PNIPMAAm, as the main chain that exhibits critical solution behavior in the range close to physiological temperature. Glucose- and pH-dependent changes in the critical solution behavior of the resultant copolymers were investigated at varying temperatures, revealing definite glucose sensitivities near the physiological conditions. Furthermore, DDOPBA moieties in the copolymers maintained constant apparent pK(a) values even when the temperature approaches the critical solution points of the main chain, indicating that spacing of the phenylborate moiety from the polymer backbone is a feasible way to minimize the microenvironment effect caused by a temperature-induced change in the hydration state of the polymer strands.

Dityrosine: preparation, isolation, and analysis

This article describes chromatographic and spectroscopic techniques that have multiple applications in the preparation, isolation, and analysis of dityrosine. A three-step chromatographic procedure facilitates the preparation of 120 mg or more (yield > 26% of theoretical maximum) of dityrosine from the enzyme-catalyzed oxidation of tyrosine. DEAE-cellulose chromatography performed in a boric acid-sodium borate buffer removes most of the contaminating pigments. Two-dimensional pH-dependent chromatography on BioGel P-2 separates dityrosine from tyrosine, residual pigments, salts, etc. Elemental analysis indicates that the purified product is approximately 92% dityrosine by weight. Fast atom bombardment mass spectrometry and two types of reverse-phase high-performance liquid chromatography (HPLC), monitored in fluorescence and absorbance measurements, verify the purity of the dityrosine. The distinctive pH-dependent chromatography of dityrosine on BioGel P-2, with reversible adsorption to the matrix occurring at pH values less than 3, is useful for the isolation of varying quantities of dityrosine and for analysis per se. Affinity chromatography on immobilized phenyl boronate (Matrex Gel PBA-60) is an alternate method for the isolation and determination of dityrosine, which undergoes specific interactions with the boronate moiety and possible hydrophobic association with the phenyl group. Two new reverse-phase HPLC techniques expedite the analysis of picomole quantities of dityrosine. One employs isocratic elution (92% H2O, 8% acetonitrile, and 0.1% trifluoroacetic acid) of an ODS II Spherisorb column, with both fluorometric and spectrophotometric detection. The other procedure may be performed in conjunction with total amino acid analysis. A rapid gradient program, developed with a Phenomenex Ultracarb 20 column, clearly separates dabsylated dityrosine and tyrosine from other dabsylated amino acids. It is especially useful when dityrosine is a trace component.

Inhibition of dipeptidyl aminopeptidase IV (DP-IV) by Xaa-boroPro dipeptides and use of these inhibitors to examine the role of DP-IV in T-cell function

Dipeptidyl peptidase IV (DP-IV; dipeptidyl-peptide hydrolase, EC 3.4.14.5) is a serine protease with a specificity for cleaving Xaa-Pro dipeptides from polypeptides and proteins. It is found in a variety of mammalian cells and tissues, including those of lymphoid origin where it is found specifically on the surface of CD4+ T cells. Although the functional significance of this enzyme has not been established, a role in T-cell activation and immune regulation has been proposed. Here we report that Ala-boroPro and Pro-boroPro, where boroPro is the alpha-amino boronic acid analog of proline, are potent and specific inhibitors of DP-IV, having Ki values in the nanomolar range. Blocking the N terminus of Ala-boroPro abolishes the affinity of this inhibitor for DP-IV, while removal of the N-terminal residue, to give boroPro, reduces the affinity for DP-IV by 5 orders of magnitude. The dipeptide boronic acids exhibit slow-binding kinetics, while boroPro does not. We also report here that low concentrations of Pro-boroPro inhibit antigen-induced proliferation and interleukin 2 production in murine T-cell lines but do not inhibit the response of these T cells to the mitogen concanavalin A. These results indicate that DP-IV plays a role in antigen-induced, but not mitogen-induced, activation of T lymphocytes.

Effect of bortezomib on human neuroblastoma cell growth, apoptosis, and angiogenesis

BACKGROUND

Bortezomib is a selective and reversible inhibitor of the 26S proteasome that shows potent antitumor activity in vitro and in vivo against several human cancers of adulthood. No data are available on bortezomib activity against human pediatric neuroblastoma.

METHODS

Ten neuroblastoma cell lines and suspensions of primary neuroblastoma cells from three patients were tested for sensitivity to bortezomib. Colony formation, cell proliferation, cell cycle progression, and apoptosis were evaluated by a clonogenic assay and by measuring 3H-thymidine incorporation, bromodeoxyuridine uptake, DNA fragmentation, and phosphatidylserine exposure and propidium iodide staining, respectively. Angiogenesis was assessed by the chick embryo chorioallantoic membrane (CAM) assay. Two mouse xenograft models that mimic the growth and spread of neuroblastoma in humans were used to examine in vivo sensitivity of neuroblastoma to bortezomib. All statistical tests were two-sided.

RESULTS

Bortezomib inhibited proliferation and colony formation of neuroblastoma cell lines in a time- and dose-dependent manner. The mean bortezomib concentration that caused 50% inhibition of growth was 6.1 nM (95% confidence interval [CI] = 0.9 to 11.3 nM) at 72 hours. Bortezomib-treated neuroblastoma cells were arrested at G2/M and underwent apoptosis (mean percentage of apoptotic cells in four neuroblastoma cell lines treated with 20 nM bortezomib for 24 hours ranged from 20% to 35%, and caspases were activated by two- to fivefold with respect to untreated cells). Similar results were obtained for primary neuroblastoma cells exposed to bortezomib. Bortezomib inhibited angiogenesis in CAMs stimulated by conditioned medium from neuroblastoma cell lines, by neuroblastoma xenografts, and by primary neuroblastoma biopsy specimens (microvessel area: 2.9 x 10(-2) mm2, 95% CI = 1.8 x 10(-2) to 3.8 x 10(-2) mm2 in CAMs treated with biopsy specimens alone and 1.3 x 10(-2) mm2, 95% CI = 1 x 10(-2) to 1.5 x 10(-2) mm2 in CAMs treated with biopsy specimens plus bortezomib, P = .024). In both mouse models, mice treated with bortezomib lived statistically significantly longer than control mice (mean survival time in the pseudometastatic model: 74.2 versus 50.3 days, P<.001; mean survival time in the orthotopic model: 72.3 versus 50.6 days, P<.001).

CONCLUSIONS

Bortezomib is an effective inhibitor of neuroblastoma cell growth and angiogenesis. These findings provide the rationale for further clinical investigation of bortezomib in pediatric neuroblastoma.

Chemical grafting of molecularly imprinted homopolymers to the surface of microplates. Application of artificial adrenergic receptor in enzyme-linked assay for beta-agonists determination

A technique for coating of microplate wells with a molecularly imprinted polymer (MIP), specific for epinephrine, is presented. 3-Aminophenylboronic acid was polymerized in the presence of epinephrine using oxidation of the monomer by ammonium persulfate. This process resulted in the grafting of a thin polymer layer onto the polystyrene surface of the microplates. The polymer affinity was determined by an enzyme-linked assay using a conjugate of horseradish peroxidase and norepinephrine (HRP-N). It was found that imprinting resulted in increased affinity of the polymer toward HRP-N and epinephrine. Influence of the buffer pH and concentration on the polymer affinity was analyzed. It was shown that the MIP-coated microplates could be used for assay development and drug screening. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to traditional antibodies or receptors, used in ELISA.

The separation of chondroitin sulfate disaccharides and hyaluronan oligosaccharides by capillary zone electrophoresis

We have developed techniques for the separation of unsulfated (2-acetamido-2-deoxy-3-O-(4-deoxy-alpha-L-threo- hex-4-enopyranosyluronicacid)-D-galactose and -D-glucose), monosulfated (2-acetamido-2-deoxy-3- O-(4-deoxy-2-O-sulfo-alpha-L-threo-hex-4-enopyranosyluronic acid)-D-galactose and 2-acetamido-2-deoxy-3-O-(4-deoxy-alpha-L-threo-hex- 4-enopyranosyluronic acid)-4-sulfo-D-galactose and -6-sulfo-D-galactose),disulfated (2-acetamido-2-deoxy-3-O-(4-deoxy-2-O-sulfo-alpha-L-threo-hex-4- enopyranosyluronic acid)-4-sulfo-D-galactose and -6-sulfo-D-galactose and 2-acet-amido-2-deoxy-3-O-(4-deoxy-alpha-L-threo-hex-4-enopy- ranosyluronic acid)-4,6-di-O-sulfo-D-galactose), and trisulfated (2-acetamido-2-deoxy-3-O-(4-deoxy-2-O- sulfo-alpha-L-threo-hex-4-enopyranosyluronic acid)-4,6-di-O-sulfo-D-galactose) isomers of chondroitin using capillary zone electrophoresis. In addition, it is possible to separate oligomers of hyaluronan by similar protocols. These techniques represent a rapid, sensitive, and reproducible technique for the assay of these molecules from digests of connective tissues.

Measurement of urinary 2,3-dinor-thromboxane B2 and thromboxane B2 using bonded-phase phenylboronic acid columns and capillary gas chromatography--negative-ion chemical ionization mass spectrometry

The use of bonded-phase phenylboronic acid columns to selectively extract 2,3-dinor-thromboxane B2 and thromboxane B2 from urine is reported. The compounds were first derivatized as the methoxime and then applied to the phenylboronic acid columns. Subsequent purification by thin-layer chromatography and derivatization to the pentafluorobenzyl ester, trimethylsilyl ether followed by capillary gas chromatography-negative-ion chemical ionization mass spectrometry, monitoring specific ions, allows quantitation in the low-picogram/milliliter range. In healthy male volunteers, the median excretions of 2,3-dinor-thromboxane B2 and thromboxane B2 were 10.3 ng/h (range, 4.5-24 ng/h) and 2.8 ng/h (range, 0.5-7.3 ng/h), respectively. The method offers a noninvasive, specific approach to the study of thromboxane synthesis and platelet function in man. It is much less labor intensive than currently available methods employing electron-impact chromatography-mass spectrometry.

The Rise of Boron-Containing Compounds: Advancements in Synthesis, Medicinal Chemistry, and Emerging Pharmacology

Boron-containing compounds (BCC) have emerged as important pharmacophores. To date, five BCC drugs (including boronic acids and boroles) have been approved by the FDA for the treatment of cancer, infections, and atopic dermatitis, while some natural BCC are included in dietary supplements. Boron's Lewis acidity facilitates a mechanism of action via formation of reversible covalent bonds within the active site of target proteins. Boron has also been employed in the development of fluorophores, such as BODIPY for imaging, and in carboranes that are potential neutron capture therapy agents as well as novel agents in diagnostics and therapy. The utility of natural and synthetic BCC has become multifaceted, and the breadth of their applications continues to expand. This review covers the many uses and targets of boron in medicinal chemistry.

Molecular Boronic Acid-Based Saccharide Sensors

Boronic acids can reversibly bind diols, a molecular feature that is ubiquitous within saccharides, leading to their use in the design and implementation of sensors for numerous saccharide species. There is a growing understanding of the importance of saccharides in many biological processes and systems; while saccharide or carbohydrate sensing in medicine is most often associated with detection of glucose in diabetes patients, saccharides have proven to be relevant in a range of disease states. Herein the relevance of carbohydrate sensing for biomedical applications is explored, and this review seeks to outline how the complexity of saccharides presents a challenge for the development of selective sensors and describes efforts that have been made to understand the underpinning fluorescence and binding mechanisms of these systems, before outlining examples of how researchers have used this knowledge to develop ever more selective receptors.

Pilot trial of a patient-specific cutaneous electrostimulation device (MC5-A Calmare®) for chemotherapy-induced peripheral neuropathy

CONTEXT

Chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting and persistent consequence of numerous classes of antineoplastic agents, affecting up to 30%-40% of patients. To date, there is no effective prevention or therapy. An evolving hypothesis for reducing CIPN pain involves direct nerve stimulation to reduce the pain impulse.

OBJECTIVES

To evaluate the impact on CIPN associated with the MC5-A Calmare® therapy device.

METHODS

The MC5-A Calmare® therapy device is designed to generate a patient-specific cutaneous electrostimulation to reduce the abnormal pain intensity. Sixteen patients from one center received one-hour interventions daily over 10 working days.

RESULTS

Of 18 patients, 16 were evaluable. The mean age of the patients was 58.6 years-four men and 14 women-and the duration of CIPN was three months to eight years. The most common drugs were taxanes, platinums, and bortezomib (Velcade, Millenium Pharmaceuticals, Cambridge MA). At the end of the study (Day 10), a 20% reduction in numeric pain scores was achieved in 15 of 16 patients. The pain score fell 59% from 5.81±1.11 before treatment to 2.38±1.82 at the end of 10 days (P<0.0001 by paired t-test). A daily treatment benefit was seen with a strong statistically significant difference between the pre- and post-daily pain scores (P<0.001). Four patients had their CIPN reduced to zero. A repeated-measures analysis using the scores from all 10 days confirmed these results. No toxicity was seen. Some responses have been durable without maintenance.

CONCLUSION

Patient-specific cutaneous electrostimulation with the MC5-A Calmare® device appears to dramatically reduce pain in refractory CIPN patients with no toxicity. Further studies are underway to define the benefit, mechanisms of action, and optimal schedule.

Early Experience With Meropenem-Vaborbactam for Treatment of Carbapenem-resistant Enterobacteriaceae Infections

Twenty patients with carbapenem-resistant Enterobacteriaceae infections were treated with meropenem-vaborbactam. Thirty-day clinical success and survival rates were 65% (13/20) and 90% (18/20), respectively. Thirty-five percent of patients had microbiologic failures within 90 days. One patient developed a recurrent infection due to meropenem-vaborbactam-nonsusceptible, ompK36 porin mutant Klebsiella pneumoniae.

A modular electrochemical sensor for saccharides

A modular electrochemical saccharide sensor using ferrocene has been prepared which contains two boronic acid receptor groups and hexamethylene linker.

Pathological Mechanisms of Bortezomib-Induced Peripheral Neuropathy

Bortezomib, a first-generation proteasome inhibitor widely used in chemotherapy for hematologic malignancy, has effective anti-cancer activity but often causes severe peripheral neuropathy. Although bortezomib-induced peripheral neuropathy (BIPN) is a dose-limiting toxicity, there are no recommended therapeutics for its prevention or treatment. One of the most critical problems is a lack of knowledge about pathological mechanisms of BIPN. Here, we summarize the known mechanisms of BIPN based on preclinical evidence, including morphological abnormalities, involvement of non-neuronal cells, oxidative stress, and alterations of transcriptional programs in both the peripheral and central nervous systems. Moreover, we describe the necessity of advancing studies that identify the potential efficacy of approved drugs on the basis of pathological mechanisms, as this is a convincing strategy for rapid translation to patients with cancer and BIPN.

Affinity electrophoresis for monitoring terminal phosphorylation and the presence of queuosine in RNA. Application of polyacrylamide containing a covalently bound boronic acid

An affinity electrophoretic method has been developed to study the state of terminal phosphorylation of RNAs and the presence of the hypermodified base Q in tRNA. It is based on the copolymerization of acryloylaminophenylboronic acid into standard polyacrylamide gels and the interaction of this derivative with free cis-diol groups present in the RNA. In the case of terminal phosphorylation, free ribose groups are present either as such, or may be introduced by enzymatic reactions specific for a particular phosphorylation pattern (e.g. using T4 RNA ligase or guanylyltransferase). Additionally, tRNA species containing the Q base may be resolved from Q-lacking tRNAs by boronate affinity electrophoresis. The introduction of a non-destructive, one-step electrophoretic procedure not only offers an alternative to classical analytical methods, but also provides a means of isolating such populations of RNAs for which other methods are unavailable or are less convenient.

Fast Diazaborine Formation of Semicarbazide Enables Facile Labeling of Bacterial Pathogens

Bioorthogonal conjugation chemistry has enabled the development of tools for the interrogation of complex biological systems. Although a number of bioorthogonal reactions have been documented in literature, they are less ideal for one or several reasons including slow kinetics, low stability of the conjugated product, requirement of toxic catalysts, and side reactions with unintended biomolecules. Herein we report a fast (>103 M-1 s-1) and bioorthogonal conjugation reaction that joins semicarbazide to an aryl ketone or aldehyde with an ortho-boronic acid substituent. The boronic acid moiety greatly accelerates the initial formation of a semicarbazone conjugate, which rearranges into a stable diazaborine. The diazaborine formation can be performed in blood serum or cell lysates with minimal interference from biomolecules. We further demonstrate that application of this conjugation chemistry enables facile labeling of bacteria. A synthetic amino acid D-AB3, which presents a 2-acetylphenylboronic acid moiety as its side chain, was found to incorporate into several bacterial species through cell wall remodeling, with particularly high efficiency for Escherichia coli. Subsequent D-AB3 conjugation to a fluorophore-labeled semicarbazide allows robust detection of this bacterial pathogen in blood serum.

Rodent models of chemotherapy-induced peripheral neuropathy

Peripheral neuropathy is a common and dose-limiting side effect of many chemotherapeutic drugs. These include platinum compounds, taxanes, vinca alkaloids, proteasome inhibitors, and others such as thalidomide and suramin. Although many rodent models have been developed using either mice or rats, there is limited consistency in the dose or mode of delivery of the drug; the sex, age, and genetic background of the animal used in the study; and the outcome measures used in evaluation of the peripheral neuropathy. Behavioral assays are commonly used to evaluate evoked sensory responses but are unlikely to be a good representation of the spontaneous sensory paresthesias that the patients experience. Electrophysiologic tests evaluate the integrity of large myelinated populations and are useful in drugs that cause either demyelination or degeneration of large myelinated axons but are insensitive to degeneration of unmyelinated axons in early stages of neuropathy. Histopathologic tools offer an unbiased way to evaluate the degree of axonal degeneration or changes in neuronal cell body but are often time consuming and require processing of the tissue after the study is completed. Nevertheless, use of drug doses and mode of delivery that are relevant to the clinical protocols and use of outcome measures that are both sensitive and objective in evaluation of the length-dependent distal axonal degeneration seen in most chemotherapy-induced peripheral neuropathies may improve the translational utility of these rodent models.

Rapid Cu-Catalyzed [211At]Astatination and [125I]Iodination of Boronic Esters at Room Temperature

Access to 211At- and 125I-radiolabeled compounds in excellent RCCs and RCYs was achieved in just 10 min at room temperature using a Cu catalyst. The reaction conditions are applicable to a broad class of aryl and heteroaryl boronic reagents with varying steric and electronic properties as well as late-stage astatination and iodination of anticancer PARP inhibitors. This protocol eliminates the traditional need for toxic organotin reagents, elevated temperatures, and extended reaction times, providing a more practical and environmentally friendly approach to developing α-emitting radiotherapeutics.

Counterimmunoelectrophoresis of pneumococcal antigens:improved sensitivity for the detection of types VII and XIV

Rapid identification of Streptococcus pneumoniae has been reported using counterimmunoelectrophoresis for the detection of specific capsular antigens in serum, cerebrospinal fluid, and urine. Previous clinical studies have failed to detect type VII or XIV pneumococcal antigen. These two types, however, account for a significant portion of pneumococcal disease. The incorporation of a sulfonated derivative of phenylboronic acid in the buffer system provides a method for the sensitive detection of these types in artificial mixtures without greatly reducing the sensitivity for the detection of other pneumococcal types. A problem with false positives encountered using human serum and barbitalbuffer was reduced by the use of buffer containing sulfonated phenylboronic acid.