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PubMed2006

2-Aminoethyl diphenylborinate analogues: selective inhibition for store-operated Ca2+ entry.

Capacitative calcium entry (CCE), the mechanism that replenishes the internal Ca2+ stores with Ca2+ from the extracellular milieu in response to depletion of the store, is mediated by Ca2+ channels in the plasma membrane generally referred to as store-operated channels (SOCs). However, the roles of SOCs in the more physiological context have been fully elucidated. 2-Aminoethyl diphenylborinate (2-APB) strongly inhibits SOCs, as well as inositol-1,4,5 trisphosphate (IP3) receptors. In the present study, we screened a library of 166 2-APB analogues for effects on CCE and IP3-induced Ca2+ release in order to discover specific SOC inhibitors, and found that some blocked both store-operated and receptor-operated Ca2+ influx more strongly and selectively than 2-APB. Indeed, these new compounds ceased the prolonged intracellular Ca2+ oscillations induced by a low concentration of ATP in CHO-K1 cells. These novel SOC inhibitors will be valuable pharmacological and biochemical tools for elucidating the physiological roles.

Animals↗

PubMed1991

DNA interaction with metal complexes and salts of substituted boranes and hydroborates in murine and human tumor cell lines.

A series of metal complexes and sodium salts of substituted boranes and hydroborates was shown to have cytotoxicity in murine and human tumor screens. Most of these agents were active against the growth of L-1210, Tmolt3 and Hela-S3. Selected agents demonstrated activity against the growth of monolayer human cell lines derived from solid tumors. Interestingly, many of the compounds demonstrated even lower ED50 values in the solid tumor than the L-1210 leukemic screen. Four compounds, Cu2(m-CH3)3NBH2CO2)4.2(CH3)NBH2COOH (I), [Fe3O((CH3)3NBH2CO2)6(CH3OH)3]NO3.CH3CN (II), cis-[Co(en)2((CH3)3N.BH2CO2)2]Cl.2.5 H2O.0.5 CH3OH (V), and Na(CH3)3NBH2CO2.0.25 CH3OH (IX) were shown preferentially to inhibit DNA synthesis of L-1210 cells with only moderate inhibition of RNA and protein synthesis. In preliminary studies these agents effectively inhibited the activities of regulatory enzymes involved in the purine pathway and nucleoside kinases resulting in the suppression of d(NTP) pool levels. The boron derivatives also caused L-1210 DNA strand scission. These drugs may act together to inhibit DNA synthesis and induce cytotoxicity.

Animals↗

PubMed1994

Inhibition of lipid biosynthesis induces the expression of the pspA gene.

Treatment of Escherichia coli with diazaborine strongly induces the synthesis of a 28 kDa protein which is associated with the cytoplasmic membrane. The partial amino acid sequence proved that this protein is identical to the phage shock protein PspA. The kinetics of the expression of the pspA gene were determined in an E. coli strain which carried a pspA-lacZ fusion in the chromosome. PspA synthesis is independent of the growth phase. It is, however, strongly induced when fatty acid biosynthesis is inhibited by diazaborine or cerulenin. Treatment with either compound also causes dose-dependent inhibition of phospholipid biosynthesis whose degree correlates with the induction of PspA. Another cause of induction of PspA synthesis is treatment of E. coli with globomycin, which is an inhibitor of the processing of lipoproteins.

Anti-Bacterial Agents↗

PubMed2001

2-Aminoethoxydiphenyl borate directly inhibits store-operated calcium entry channels in human platelets.

In this study, we examined 2-aminoethoxydiphenyl borate (2APB) as an inhibitor of Ca(2+) influx in human platelets. 2APB was found to inhibit thrombin-mediated intracellular Ca(2+) mobilization rapidly in platelets incubated in the absence of extracellular Ca(2+). This result supports an intracellular action of 2APB on inositol 1,4,5-trisphosphate (IP(3))-receptor Ca(2+) channels. 2APB was without effect on the ability of thapsigargin to mobilize intracellular Ca(2+). This result suggests that the efflux of Ca(2+) from the endoplasmic reticulum mediated by thapsigargin is not via IP(3) Ca(2+) channels. However, 2APB was able to prevent the entry of Ca(2+) and Sr(2+) through thapsigargin-activated, store-operated Ca(2+) channels (SOCC). This result supports a direct inhibitory effect of 2APB on SOCC. 2APB was also able to block the entry of Sr(2+), Ba(2+), and Mn(2+) entry into unstimulated platelets, which suggests that 2APB was inhibiting the Ca(2+) influx channels directly. The capacity of 2APB to prevent Ca(2+) influx and Sr(2+) influx was rapid because it occurred immediately upon addition to the platelets. The inhibition of Ca(2+) and Sr(2+) influx by 2APB was similar to that seen with the cell-impermeable nonselective Ca(2+)-channel blocker La(3+) or the Ca(2+) chelator EGTA. Diphenylboronic anhydride and 2,2-diphenyltetrahydrofuran, two compounds that are structurally similar to 2APB, also inhibited Ca(2+) influx. It was concluded that 2APB was a rapid and effective direct inhibitor of SOCC in human platelets; as such, it cannot be used to support the involvement of IP(3) receptors in the activation of SOCC.

Barium↗

PubMed2005

Synthesis, cellular uptake and animal toxicity of a tetra(carboranylphenyl)-tetrabenzoporphyrin.

A water-soluble nido-carboranyl-tetrabenzoporphyrin has been synthesized in 43% overall yield, by condensation of butanopyrrole with a carboranylbenzaldehyde, followed by metal insertion, oxidation, demetallation and deboronation reactions. This compound accumulated within human glioblastoma T98G cells to a significant higher extent than a structurally related nido-carboranylporphyrin, and localized preferentially in the cell lysosomes. Animal toxicity studies using male and female BALB/c mice revealed that both compounds are non-toxic even at a dose of 160 mg/kg, administered intraperitoneally as a single injection at a concentration of 4 mg/mL. It is concluded that the tetra(carboranylphenyl)-tetrabenzoporphyrin is a promising new sensitizer for the treatment of malignant tumors.

Animals↗

PubMed2023

Anticancer benzoxaboroles block pre-mRNA processing by directly inhibiting CPSF3.

A novel class of benzoxaboroles was reported to induce cancer cell death but the mechanism was unknown. Using a forward genetics platform, we discovered mutations in cleavage and polyadenylation specific factor 3 (CPSF3) that reduce benzoxaborole binding and confer resistance. CPSF3 is the endonuclease responsible for pre-mRNA 3'-end processing, which is also important for RNA polymerase II transcription termination. Benzoxaboroles inhibit this endonuclease activity of CPSF3 in vitro and also curb transcriptional termination in cells, which results in the downregulation of numerous constitutively expressed genes. Furthermore, we used X-ray crystallography to demonstrate that benzoxaboroles bind to the active site of CPSF3 in a manner distinct from the other known inhibitors of CPSF3. The benzoxaborole compound impeded the growth of cancer cell lines derived from different lineages. Our results suggest benzoxaboroles may represent a promising lead as CPSF3 inhibitors for clinical development.

Cleavage And Polyadenylation Specificity Factor↗

PubMedDate not supplied

Specific killing of human melanoma cells with an efficient 10B-compound on monoclonal antibodies.

We previously established methods which have enabled us to target a sufficient number of 10B atoms on human melanoma cells to destroy them by thermal neutron irradiation. Monoclonal antibodies were here used as vector of 10B atoms on the target cell. Thermal neutrons require at least 10(9) 10B atoms to destroy the cell. In order to accumulate an adequate number of 10B atoms on target cells, our first approach was to make an effective compound that contains 12 atoms of 10B in a molecule. The second step was to conjugate the compound with an avidin molecule (10B12-avidin). One molecule of the 10B12-avidin carries about 30 atoms of 10B. This 10B12-avidin can be specifically targeted on human melanoma cells by biotinated monoclonal antibodies specific for the cells. Furthermore, the number of 10B atoms on target cells can be augmented by a hapten-antihapten monoclonal antibody system. The cultured human melanoma cells treated with these methods were damaged by thermal neutron irradiation. This is the first study that indicates thermal neutrons do injure target cells boronated by monoclonal antibodies.

Antibodies, Monoclonal↗

PubMed1971

Demonstration of imino acids as products of the reactions catalyzed by D- and L-amino acid oxidases.

It had long been thought, but never demonstrated, that imino acids are formed in the reactions catalyzed by D- and L-amino acid oxidases (EC 1.4.3.3 and 1.4.3.2). The formation of imino acids is now shown directly by allowing the amino acid oxidase reaction to proceed in the presence of NaBH(4), when the imino acid is reduced to the corresponding racemic amino acid. Thus, when NaBH(4) is added to a mixture of D-amino acid oxidase and D-alanine, a significant amount of L-alanine is formed. Analogous results are obtained using L-amino acid oxidase and L-leucine. Since D-amino acid oxidase is active in the presence of NaBH(4), L-alanine continues to be formed until most of the D-isomer is oxidized by the enzyme. This reaction provides a new method for inverting the configuration of an amino acid. When NaBH(4) is added to a system containing D-amino acid oxidase plus D-alanine and L-lysine, free epsilon-N-(1-carboxyethyl)-L-lysine is formed. When bovine serum albumin is substituted for L-lysine, the same compound results upon acid hydrolysis. It is concluded that the amino acid oxidase reaction produces a free imino acid, which may be reduced by NaBH(4) to a racemic amino acid or may form Schiff's bases by reaction with the epsilon-amino groups of proteins and of free lysine.

Alanine↗

PubMed2002

Quantitative analysis of triphenylboron in environmental water samples by liquid chromatography/mass spectrometry.

Liquid chromatography/mass spectrometry (LC/MS) has been applied to the analysis of triphenylboron, which has been produced as a substitute for organotin compounds, in water. Although commercial triphenylboron compounds are produced as pyridinyl complexes, the chemical form in water is supposed to be mainly triphenylboron after liberating pyridine. The triphenylborons were extracted from water with an Empore C18 extraction disk under acidic condition, and the extracts were introduced directly into a liquid chromatograph-mass spectrometer equipped with a negative ion electrospray ionization interface. Identification of the compounds was performed with specific ions produced from the triphenylboron, and a quantitative analysis was carried out using the peak areas. The average recoveries from distilled water, seawater and river water at 0.30 ng/ml were 92.3, 100 and 85.3%, respectively. A detection limit of 0.023 ng/ml for triphenylboron was achieved.

Boron Compounds↗

PubMed2004

Variable solid state aggregations in a series of (isocyanide)gold(I) halides with the novel trimethylamine-isocyanoborane adduct.

This paper provides evidence that the degree of aurophilic character and resulting solid state arrangement observed in (isocyanide)gold(I) halides is in part dependent on the nature of halide substituent. In particular, we report here the synthesis of a series of novel (isocyanide)gold(I) halides involving trimethylamine-isocyanoborane, an unusual 'zwitterionic' isocyanide that is comparable to the more familiar methyl isocyanide, but potentially more strongly Lewis basic. The reaction of chloro(dimethyl sulfide)gold(I) and the isocyanoborane species, (RNC)(R =(H3C)3NB(H)2), gives the novel crystalline adduct [(RNC)AuCl] (1). Treatment of 1 in an organic phase with aqueous KBr effected substitution of the chloride to give the bromide analogue [(RNC)AuBr] (2). The structures of 1 and 2 were determined by X-ray crystallography to be isostructural, consisting of a zigzag topology of chains of monomers, where adjacent gold(I) centres interact aurophilically. However, similar reaction of 1 with KI solution affords the unusual and unexpected compound, [(RNC)2Au][AuI2] (3). This iodide 3, is a linear chain polymer of alternating anion, cation units that is formed via ligand redistribution. The complexes 1-3 all fluoresce in the presence of UV light; the fluorescence of 3 being most prevalent at room temperature. The free trimethylamine-isocyanoborane ligand, the dimeric structures of compounds 1,2 and the thermodynamic stabilities of the dimers in the gas phase were studied by density functional and ab initio calculations at various levels of theory. The theoretical results are compared to the corresponding experimental data.

Boron Compounds↗

PubMed2003

Oxygen-promoted Pd(II) catalysis for the coupling of organoboron compounds and olefins.

Reported herein is a mild and efficient Pd(II) catalysis, leading to the formation of carbon-carbon bonds between a broad spectrum of organoboron compounds and alkenes. Molecular oxygen was employed to reoxidize the resultant Pd(0) species back to Pd(II) during catalytic cycles. This oxygen protocol promoted the desired Pd(II) catalysis, whereas it retarded competing Pd(0) catalytic pathways such as Heck or Suzuki couplings. [reaction: see text]

Alkenes↗

PubMed2007

Pravastatin induces thrombomodulin expression in TNFalpha-treated human aortic endothelial cells by inhibiting Rac1 and Cdc42 translocation and activity.

Expression of functionally active thrombomodulin (TM) on the luminal surface of endothelial cells is critical for vascular thromboresistance. The 3-hydroxyl-3-methyl coenzyme A reductase inhibitor, pravastatin, can protect the vasculature in a manner that is independent of its lipid-lowering activity. We examined the effect of pravastatin on TM expression by human aortic endothelial cells (HAECs) with subsequent tumor necrosis factor alpha (TNFalpha) stimulation and investigated the signaling pathways involved. TNFalpha treatment attenuated TM expression in HAECs in a time-dependent manner. Pravastatin upregulated TM levels in TNFalpha-treated HAECs. Specific inhibition of geranylgeranyltransferase-I or the Rho family by GGTI-286 or TcdB, respectively, enhanced TM expression in TNFalpha-treated HAECs, whereas MAP kinase inhibitors, inactivation of Rho by Clostridium botulinum C3 exoenzyme, or the Rho kinase inhibitor, Y-27632, had no effect. In TNFalpha-treated HAECs, pravastatin inhibited Rac1 and Cdc42 activation and their translocation to the cell membrane. Blocking the transcriptional activation of NF-kappaB prevented the TNFalpha-induced downregulation of TM. The pravastatin-induced increase in TM expression in TNFalpha-treated HAECs was mediated through inhibition of NF-kappaB activation. Pravastatin regulates TM expression by inhibiting the activation of the Rho family proteins, Rac1 and Cdc42, and the transcription factor, NF-kappaB. The increase in endothelial TM activity in response to pravastatin constitutes a novel pleiotropic (nonlipid-related) effect of this commonly used compound and may be of clinical significance in disorders in which deficient endothelial TM plays a pathophysiological role.

Amides↗

PubMed1995

Method for measuring the activities of cholesteryl ester transfer protein (lipid transfer protein).

A continuous recording fluorescence assay was developed for cholesteryl ester transfer protein (CETP). The assay measures the increase in fluorescence accompanying the relocation of fluorescent lipids, cholesteryl esters and triglycerides, from a donor emulsion to an acceptor emulsion. In the absence of CETP, the quantum yields of the fluorescent lipids is low because their high concentrations in the donor emulsions result in self-quenching. CETP catalyzes the redistribution of the fluorescent lipids from the donor to the acceptor emulsions and fluorescence increases substantially. Efficient sonication and incorporation of apolipoproteins from human HDL into the emulsions significantly increased the transfer rates. Under optimal conditions, the redistribution of fluorescent compounds reaches equilibrium within < 30 min and the kinetics of this process are consistent with a simple, first-order reaction pathway. The redistribution kinetics support a mechanism of adsorption --> exchange --> desorption --> diffusion.

Boron Compounds↗

PubMed2006

Effects of subacute boric acid administration on rat kidney tissue.

BACKGROUND/AIMS: Boron is used in manufacturing processes and numerous consumer products. Clarification of boron toxicity is important because of industrial and consumer exposure to boron and boron-containing compounds. The aim of this study was to observe effects of subacute boric acid administration on rat kidney tissue. MATERIALS AND METHODS: A total of 96 male albino Sprague-Dawley rats were used in this study. Seventy-two rats were selected for the experimental group and 24 rats constituted the control group. Experimental group rats were divided into three groups for exposure to three different doses of orally administered boric acid (100-275-400 mg/kg/day). Kidney tissues were removed at the 10th, 30th, and 45th day after sacrificing the rats. Kidney weights, kidney boron concentration and histopathological changes were determined. RESULTS: In the experimental group, a significant accumulation of boron in kidney tissue was seen, but there was a significant drop in boron concentration on the 45th day compared with the 30th day. Histopathological degenerative changes were observed especially in the proximal tubule cells that were dose- and time-dependent. CONCLUSION: Subacute boric acid exposure caused dose-dependent histopathological changes in kidney tissue.

Administration, Oral↗

PubMed1995

The disposition, tissue distribution, and cellular transport of N-[[(trimethylamino)boryl]carbonyl]-L-phenylalanine methyl ester in CF1 mice.

The disposition and tissue distribution of 14C-labeled N-[[(trimethylamino)boryl]carbonyl]-L-phenylalanine methyl esther (1) determined in CF1 mice following i.v., p.o., and i.p. administration. Compound 1 was found to undergo rapid and extensive metabolism, and the majority of the radioactivity was found in the skin and carcass regardless of the route of administration. Approximately 55% of the radioactivity was recovered in urine and feces after 78 h; however, excretion via these routes was not complete. Degradation of compound 1 occurred at the amide bond at low pH (0.8) but at the ester bond a physiological pH. This difference in degradation was reflected in elevation of the blood radioactivity levels after p.o. administration compared to i.p. and i.v. administration.

Administration, Oral↗

PubMed1970

Interactions of p-nitrobenzene diazonium fluoroborate and analogs with the active sites of acetylcholine-receptor and -esterase.

p-Nitrobenzene diazonium fluoroborate (NDF) is a potent inhibitor of the carbamylcholine-induced depolarization of the electroplax and of acetylcholinesterase. It probably forms covalent bonds with the acetylcholine-receptor and -esterase at the active site of the proteins. Its inhibitory strength is at least the same as that of trimethylammonium diazonium fluoroborate (TDF). The p-acetoxy analog, with its weaker electron-withdrawing group, is about ten times weaker as an inhibitor than the trimethylammonium or p-nitro analogs, both of which have strong electron-withdrawing groups. After treatment of the electroplax preparation with dithiothreitol, NDF remains an irreversible receptor-inhibitor, while TDF becomes a potent reversible receptor-activator. TDF is self-inhibitory: applied before reduction, it no longer depolarizes. Although the first observations on TDF suggested that the compound labels both proteins by virtue of the steric complementary of its trimethylammonium group to a negative subsite in the proteins, the present study indicates that it is the positively charged diazonium group that reacts with the active sites of the proteins to form a covalent bond with an appropriate amino-acid residue.

Acetylcholinesterase↗

PubMed1984

Mass spectral and HPLC analysis of biological compounds with diphenylborinic acid.

Diphenylborinic acid is shown to react with a variety of polyfunctional molecules of biological interest to give products which are easily identifiable by mass spectrometry. The diphenylborinate adducts of amino acids possess extraordinary stability and are separable by reverse phase chromatography. The stability of products is discussed with regard to the nature and stereochemical arrangement of the functional groups involved in complex formation.

Amino Acids↗

PubMed1996

Distribution and biophysical properties of fluorescent lipids on the surface of adult Schistosoma mansoni.

The properties of 4 fluorescent lipid compounds in the surface membrane of adult male Schistosoma mansoni worms were examined by fluorescent microscopy and fluorescent recovery after photobleaching (FRAP). The data suggest that the probes N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s- indacene-3-pentanoyl) sphingosine (BODIPY FL ceramide) and PKH2 pass through the outer membrane and enter structures in or below the membrane. In contrast 5-(N-octadecanoyl)aminofluorescein (AF18) and N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s- indacene-3-pentanoyl) sphingosylphosphocholine (BODIPY FL sphingomyelin) insert into the outer monolayer. The DL values of these latter 2 compounds, 8:83 +/- 2.35 x 10(-9)cm(2)s(-1) and 2.76 +/- 0.53 x 10(-9)cm(2)s(-1), respectively, suggest that they enter different domains. Furthermore, it was observed that both BODIPY FL ceramide and BODIPY FL sphingomyelin entered particular structures in or under the surface membrane. The possible nature of these particles is discussed.

Animals↗