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PubMed1995

Poly(adenosine diphosphate ribose) polymerase inhibition prevents necrosis induced by H2O2 but not apoptosis.

BACKGROUND & AIMS: H2O2 causes DNA damage, which activates poly(adenosine diphosphate ribose) polymerase (PARP), a nuclear enzyme that uses nicotinamide adenine dinucleotide (NAD) as a substrate. When DNA strand breaks are extensive, consumption of NAD by PARP can cause adenosine triphosphate depletion. The aim was to study the effect of PARP inhibition on H2O2-induced cell injury in the intestinal epithelial cell line HT-29-18-C1. METHODS: Cell injury was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test and flow cytometric analysis. RESULTS: The PARP inhibitors 3-aminobenzamide and nicotinamide both prevented cell death immediately after exposure to 1 mmol/L H2O2 and loss of cellular NAD and adenosine triphosphate. The inactive structural analogues 3-aminobenzoic acid and nicotinic acid had no such protective effect. H2O2 also caused HT-29 cells to detach from the monolayer up to 24 hours after exposure and die by apoptosis in the incubating medium. Flow cytometric analysis showed that 3-aminobenzamide had no effect on this delayed detachment process. CONCLUSIONS: H2O2 induces two distinct death pathways in HT-29 cells: one that is immediate and may represent necrosis and another that is delayed, causing cell detachment leading to apoptosis. PARP inhibition prevents necrosis but has no effect on delayed cell detachment leading to apoptosis.

Aminobenzoates↗

PubMed1995

Design, synthesis and biological evaluation of benzoic acid mustard derivatives of imidazole-containing and C-terminal carboxamide analogues of distamycin.

The synthesis, DNA binding and biological evaluation of two benzoic acid mustard derivatives of imidazole-containing analogues of distamycin in which the C-terminus is modified to contain a terminal carboxamide are described. The apparent DNA binding constants of compounds 5 and 6 were determined using an ethidium displacement assay, and the results showed that they do not have the AT sequence selectivity of distamycin and they show an acceptance for GC base pairs. Based on their pronounced binding to T4 DNA the data suggest that they bind to the minor groove of DNA. The cytotoxicities of compounds 5 and 6 in human chronic myeloid leukemia cells were determined using a MTT assay, and their IC50 values were 27 and 16 microM, respectively, and higher than the corresponding non-terminal carboxamide-containing analogues 3 and 4. Both compounds were however markedly more active than the non-targeted mustard BAM [N,N-bis (-2-chloroethyl)-4-aminobenzoic acid]. In the NCI panel of cell lines 5 gave a distinctly different pattern of tumor selectivity from 6. While these compounds were shown to alkylate DNA using a CD alkylation assay (35 +/- 10% for 5 and 85 +/- 10% for 6), they produced interstrand crosslinks poorly, even at 100 microM drug concentrations. Based on preliminary data from a polymerase stop assay compounds 3-6 gave different patterns of sequence selection monoalkylation which may contribute to their differing biological activities.

Antineoplastic Agents↗

PubMed1997

Retinal toxicity associated with occupational exposure to the fish anesthetic MS-222.

PURPOSE: To report a case of retinopathy associated with chronic occupational exposure to ethyl-m-aminobenzoic acid methanesulfonate (MS-222), a retinotoxic fish anesthetic. METHOD: Case report with electroretinograms to document changes in visual electrophysiology. RESULTS: An ichthyologist with a long history of skin exposure to MS-222 was initially examined for decreased vision, photophobia, and photopsia. His electroretinogram abnormalities were similar to those seen in animal models of acute MS-222 toxicity. After terminating MS-222 contact for 7 months, his vision returned to normal, and his electroretinogram improved. CONCLUSION: Individuals with occupational exposure to MS-222 should exercise caution to avoid systemic absorption of this retinotoxic compound.

Aminobenzoates↗

PubMed1975

Ability of PABA to protect mammalian skin from ultraviolet light-induced skin tumors and actinic damage.

Application of 50 para-aminobenzoic acid (PABA) to hairless mice one hour prior to ultraviolet light (UVL) irradiation will almost totally protect these animals from developing tumors induced by chronic exposure to UVL in the 290 to 320 nm range in conjunction with a chemical carcinogen. Mice exposed to UVL and not protected by PABA developed primarily squamous cell carcinomas. Two months after cessation of chronic UVL exposure, the non-PABA-treated irradiated mouse skin appeared thickened, yellow, and wrinkled while showing elevated DNA synthesis, hyperplasia, hypergranulosis, and increased amounts of elastotic material. The PABA-treated skin was grossly normal.

Aminobenzoates↗

PubMed1976

Nitrite in meat products determined by fluorescence quenching of p-aminobenzoate ion.

A direct fluorometric method is presented for determining nitrites in meat products by means of quenching. The extracted sodium nitrite is consumed in a diazotization reaction with a measured excess of the fluorescent reagent p-aminobenzoic acid (PABA) in boiling water and at pH less than or equal to 1.4. The amount of decrease in fluorescence (quenching) of PABA, in alkaline medium (pH 11.0) with excitation at 265 nm and fluorescence at 339 nm, is directly related to the amount of nitrite present. The slope for that standard curve is 1% decrease in relative fluorescence intensity per 2.76 ppm NaNO2. Results obtained for a series of 20 meat samples analyzed by this fluorometric method are in good agreement with results obtained by a colorimetric method with an average difference of +/- 6.1 ppm NaNO2.

Aminobenzoates↗

PubMed1995

Muscle weakness during tricaine anesthesia.

An isolated preparation of tadpole tail muscle was used to assess the peripheral effects of tricaine (3-aminobenzoic acid ethyl ester) at anesthetic concentrations and under physiological conditions. The drug effect on the electrically-evoked twitch was tested using short-pulse durations that elicited synaptically mediated effects or longer-duration pulses that stimulated the muscle directly. Tricaine reduced both types of response anesthetic and even subanesthetic concentrations. At steady state concentrations that produced surgical anesthesia in vivo, tricaine reduced the directly evoked response by about half. It is concluded that tricaine anesthesia has a pronounced peripheral effect on neuromuscular function and that direct effect(s) on muscle are a major component.

Aminobenzoates↗

PubMed1991

An arylamine acetyltransferase (AT-I) from Syrian golden hamster liver: cloning, complete nucleotide sequence, and expression in mammalian cells.

A cDNA clone (designated hamAT101) encoding an arylamine acetyltransferase, AT-1, was isolated from a hamster liver lambda gt11 cDNA library using a specific polyclonal antibody raised against AT-1. The cloned cDNA insert consisted of 1181 nucleotides, including an open reading frame of 870 nucleotides encoding 290 amino acid (Mr 33,503). The isolated cDNA displayed high sequence similarity to those of chicken, rabbit, and human acetyltransferases. In Northern blots, the hamAT101 cDNA probe hybridized to an RNA band of 18S in the livers of both slow and rapid acetylator phenotypes. To confirm that hamAT101 cDNA encodes the monomorphic but not the polymorphic protein, the isolated cDNA was expressed in monkey kidney cells (COS-1 cells) using the vector p91023(B). A protein with a molecular weight similar to that of AT-1 was detected upon Western blotting in the 9000 x g supernatant from the transfected cells. The activity toward four different substrates of the 9000 x g supernatant was also examined. In agreement with the results of purified AT-1, the cDNA-expressed protein exhibited a high capacity for N-acetylation of 4-aminoazobenzene and 2-aminofluorene, and O-acetylation of 2-hydroxyamino-6-methyldipyrido [1,2-a:3',2'-d] imidazole, whereas no activity was found for the N-acetylation of p-aminobenzoic acid. These results, in addition to the RNA blot hybridization, indicate that hamAT101 encodes the hamster acetyltransferase AT-1.

Amino Acid Sequence↗

PubMed1978

Phototoxicity to a sunscreen ingredient. Padimate A.

Para-aminobenzoic acid and certain of its esters are widely used in sunscreens. We found that one of these, amyl paradimethylaminobenzoate (padimate A) was capable of provoking phototoxic reactions; With ultraviolet A (UV-A) dosages of about 30 joules/sq cm, a reaction grossly resembling sunburn developed in most subjects. The dominant histological feature was vacuolar degeneration of the epidermis without sunburn cells. Proprietary sunscreens containing padimate A were also shown to produce a similar reaction. Our explanation for the paradox of a sunscreen that promotes "sunburn" is that, as affected users have concluded, the product was ineffective. The similarity between sunburn and a phototoxic response has delayed recognition of this adverse effect until now.

Adolescent↗

PubMedDate not supplied

Design of in vivo cadmium-mobilizing agents: synthesis and properties of monobenzyl meso-2,3-dimercaptosuccinate.

A novel method for the synthesis of monoesters of meso-2,3-dimercaptosuccinic acid (DMSA) is presented which utilizes the reaction of the vicinal sulfhydryl-protected anhydride with the corresponding alcohol in the presence of a base. The product is then treated successively with mercuric chloride to remove the protecting group and form the mercuric complex, and hydrogen sulfide to regenerate thiol groups by removal of mercury as HgS. This strategy was exploited to synthesize monobenzyl meso-2,3-dimercaptosuccinate (MBzDMS), C6H5CH2O(O)CCH(SH)CH(SH)C(O)OH, and demonstrates a feasible synthesis of monoesters difficult to obtain by direct esterification, via the use of the reactive anhydride. The resultant compound was found to be an effective cadminum-mobilizing agent when used with cadmium-exposed rats or mice and when administered by any one of several routes (ip, iv, po). This monobenzyl ester (MBzDMS) of DMSA was found to be somewhat less effective than the corresponding monoisoamyl ester (Mi-ADMS) in mobilizing cadmium from such cadmium deposits. The ability of MBzDMS to mobilize cadmium into the urine is significantly decreased by the coadministration of p-aminobenzoic acid, in support of the hypothesis that MBzDMS enters renal cells via an anion transport system. An analysis of the structural features of vicinal dithiols examined as antagonists for chronic cadmium intoxication allows a hypothesis to be formulated indicating essential features required for the design of effective new cadmium antagonists of this type.

Administration, Oral↗

PubMed1993

Prevention and suppression of experimental allergic encephalomyelitis by an orally active leukocyte recruitment inhibitor, NPC 16570.

An orally active leukocyte recruitment inhibitor, NPC 16570 (N-[9H-fluoren-9-ylethoxycarbonyl]-4-aminobenzoic acid), was evaluated in experimental allergic encephalomyelitis (EAE) in rats. The mean time of disease onset in control animals was 12 +/- 1 days, with peak average clinical scores of 2.5 +/- 0.2, accompanied by perivascular infiltration of inflammatory cells into the CNS. Daily administration (p.o.) of NPC 16570 reduced the clinical severity (by 70%) at 10 and 30 mg/kg, and at 100 mg/kg, no clinical symptoms were detected. When NPC 16570 (100 mg/kg) treatment was initiated 7 days after EAE induction, the severity (75% inhibition) and duration of the disease were attenuated; 2 out of 6 animals showed no overt clinical symptoms and perivascular cell infiltration was prevented, suggesting potential utility in autoimmune diseases.

Administration, Oral↗

PubMed1999

Inhibitors of poly (ADP-ribose) synthetase protect rat cardiomyocytes against oxidant stress.

OBJECTIVE: Inhibitors of poly (ADP-ribose) synthetase (PARS) activity reduce the infarct size caused by regional myocardial ischaemia and reperfusion in the rabbit and rat in vivo. The mechanism of action of these inhibitors is unclear. Here we investigate the effects of the PARS inhibitor 3-aminobenzamide (3-AB) on infarct size caused by ischaemia and reperfusion of the isolated, perfused heart of the rat. We also investigate the role of PARS in the hydrogen peroxide-mediated cell injury/necrosis in rat cardiac myoblasts. METHODS: Rat isolated hearts perfused at constant pressure (80 mmHg) were subjected to 35 min of regional ischaemia and 2 h of reperfusion. Infarct size was determined at the end of the experiment using nitro-blue tetrazolium. 3-AB (300 microM) or 3-aminobenzoic acid (3-ABA, 300 microM) were infused during the reperfusion period. Rat cardiac myoblasts (H9c2 cells) were preincubated with the PARS inhibitors, 3-AB. nicotinamide (Nic) or 1,5-dihydroxyisoquinoline (ISO) or the inactive analogues 3-ABA or nicotinic acid (NicA) prior to exposure with hydrogen peroxide (1 mM). Cell injury was assessed by measuring mitochondrial respiration and cell necrosis by measuring the release of LDH. PARS activity was determined by measuring the incorporation of NAD into nuclear proteins. RESULTS: Regional ischaemia and reperfusion of the isolated rat heart resulted in an infarct size of 54% which was reduced by 3-AB, but not by 3-ABA. Exposure of rat cardiac myoblasts to hydrogen peroxide caused an increase in PARS activity and cell injury/necrosis which was attenuated by pretreatment with the PARS inhibitors. CONCLUSION: Inhibition of the activity of PARS attenuates the cell death associated with oxidant stress in rat cardiac myoblasts and heart.

Aminobenzoates↗

PubMed2000

Endogenous generation of cyanide in neuronal tissue: involvement of a peroxidase system.

In a study of the mechanism by which cyanide is produced in neural tissue, it was hypothesized that nerve cells generate cyanide in a manner similar to that in leukocytes. As in white blood cells, glycine addition enhanced cyanide production in rat pheochromocytoma cells. Because myeloperoxidase catalyses cyanide production in leukocytes, a selective myeloperoxidase inhibitor (aminobenzoic acid hydrazide) was tested and found to inhibit opiate agonist-induced cyanide production in pheochromocytoma cells and also in rat brain. In addition, hydrogen peroxide enhanced cyanide release in pheochromocytoma cells, further suggesting that the process is oxidative in nature. Sonicated rat pheochromocytoma cells did not generate cyanide in response to an agonist acting on surface receptors even though disrupted cells responded to glycine. The mitochondrial fraction from rat brain produced more cyanide in response to glycine than any other fraction. Thus glycine seems to act at an intracellular site to enhance cyanide production and the process seems to involve a peroxidase mechanism similar to that reported for white blood cells.

Aminobenzoates↗

PubMed1999

An improved method for the structural profiling of keratan sulfates: analysis of keratan sulfates from brain and ovarian tumors.

A previously developed method for the structural fingerprinting of keratan sulfates (Brown et al., Glycobiology, 5, 311-317, 1995) has been adapted for use with oligosaccharides fluorescently labeled with 2-aminobenzoic acid following keratanase II digestion. The oligosaccharides are separated by high-pH anion-exchange chromatography on a Dionex AS4A-SC column. This methodology permits quantitative analysis of labeled oligosaccharides which can be detected at the sub-nanogram ( approximately 100 fmol) level. Satisfactory calibration of this method can be achieved using commercial keratan sulfate standards. Keratan sulfates from porcine brain phosphocan and human ovarian tumors have been examined using this methodology, and their structural features are discussed.

Acetylglucosaminidase↗

PubMed2006

Structure elucidation of arabinoxylan isomers by normal phase HPLC-MALDI-TOF/TOF-MS/MS.

Normal phase-high performance liquid chromatography (NP-HPLC) coupled to matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight (MALDI-TOF/TOF) tandem mass spectrometry is evaluated for the detailed structural characterization of various isomers of arabinoxylan (AX) oligosaccharides produced from endo-beta-(1-->4)-xylanase (endoxylanase) digestion of wheat AX. The fragmentation characteristics of these oligosaccharides upon MALDI-TOF/TOF high-energy collision induced dissociation (CID) were investigated using purified AX oligosaccharide standards labeled at the reducing end with 2-aminobenzoic acid (2-AA). A variety of cross-ring cleavages and 'elimination' ions in the fragment ion spectra provided extensive structural information, including Araf substitution patterns along the xylan backbone and comprehensive linkage assignment. The off-line coupling of this MALDI-CID technique to capillary normal phase HPLC enabled the separation and identification of isomeric oligosaccharides (DP 4-8) produced by endoxylanase digestion of AX. Furthermore, this technique was used to characterize structurally different isomeric AX oligosaccharides produced by endoxylanase enzymes with different substrate specificities.

Amination↗

PubMed2006

Probing the substrate specificity of the dengue virus type 2 NS3 serine protease by using internally quenched fluorescent peptides.

The NS3 (dengue virus non-structural protein 3) serine protease of dengue virus is an essential component for virus maturation, thus representing an attractive target for the development of antiviral drugs directed at the inhibition of polyprotein processing. In the present study, we have investigated determinants of substrate specificity of the dengue virus NS3 protease by using internally quenched fluorogenic peptides containing Abz (o-aminobenzoic acid; synonymous to anthranilic acid) and 3-nitrotyrosine (nY) representing both native and chimaeric polyprotein cleavage site sequences. By using this combinatorial approach, we were able to describe the substrate preferences and determinants of specificity for the dengue virus NS2B(H)-NS3pro protease. Kinetic parameters (kcat/K(m)) for the hydrolysis of peptide substrates with systematic truncations at the prime and non-prime side revealed a length preference for peptides spanning the P4-P3' residues, and the peptide Abz-RRRRSAGnY-amide based on the dengue virus capsid protein processing site was discovered as a novel and efficient substrate of the NS3 protease (kcat/K(m)=11087 M(-1) x s(-1)). Thus, while having confirmed the exclusive preference of the NS3 protease for basic residues at the P1 and P2 positions, we have also shown that the presence of basic amino acids at the P3 and P4 positions is a major specificity-determining feature of the dengue virus NS3 protease. Investigation of the substrate peptide Abz-KKQRAGVLnY-amide based on the NS2B/NS3 polyprotein cleavage site demonstrated an unexpected high degree of cleavage efficiency. Chimaeric peptides with combinations of prime and non-prime sequences spanning the P4-P4' positions of all five native polyprotein cleavage sites revealed a preponderant effect of non-prime side residues on the K(m) values, whereas variations at the prime side sequences had higher impact on kcat.

Dengue Virus↗

PubMed1974

Purification of human placental alkaline phosphatase. Salt effects in affinity chromatography.

Human placental alkaline phosphatase was chromatographed on Sepharose derivatives of d- and l-phenylalanine, l-leucine, glycine, aniline and p-aminobenzoic acid in high concentrations of (NH(4))(2)SO(4). Retention on these columns was greatest at the highest concentrations of (NH(4))(2)SO(4). By using decreasing concentrations and changing the types of salts, elution was effected from each of the columns. The (NH(4))(2)SO(4)-mediated retention appeared to be related to the hydrophobic character of the substituted Sepharose, rather than to any specific binding site of the enzyme. It is suggested that this provides a way of controlling hydrophobic affinity chromatography. By use of chromatography on l-phenylalanine-Sepharose and of DEAE-Sephadex chromatography in the presence of Triton X-100 detergent, a preparation of highly purified (1000-fold) human placental alkaline phosphatase was obtained in 22% yield.

Alkaline Phosphatase↗

PubMed1980

cAMP-stimulated cation cotransport in avian erythrocytes: inhibition by "loop" diuretics.

The effect of a series of diuretically active substituted 3-aminobenzoic acid derivatives and related compounds was investigated on a cyclic AMP-activated Na+-K+ cotransport system in avian erythrocytes. A good correlation between the diuretic potency of this class of "loop" diuretics in the dog and their inhibition of cation cotransport in turkey erythrocytes was found. Selected thiazide-type diuretics were found to be ineffective. The most active compound tested (3-benzylamino-4-phenylthio-5-sulfamoylbenzoic acid) had an effective dose50 of 4.6 x 10(-8) M in the avian system, and was about 5 times more potent than bumetanide and 500 times more potent than furosemide in this regard. The diuretics appear to interact directly with the cation transport system itself, and not with some antecedent step in the sequence of events from intracellular cAMP accumulation to stimulation of transport. The compounds tested did not appear to compete at Na+- or K+-binding sites on the transport system. The similarity in the structure-activity relationship of these agents in the avian erythrocyte and the kidney suggests that the avian erythrocyte may be a useful model for analysis both of the diuretic-sensitive transport system of the mammalian kidney, and of the molecular mechanism of loop diuretic action.

Aminobenzoates↗

PubMed1990

Radiolabelling of platelets with technetium-99m.

A method for labelling of platelets with technetium-99m (Tc-99m) is presented. In principle, aminobenzoic acid and tartaric acid are used as reagents, allowing Tc-99m complexes of intermediate chemical stability to be formed. These complexes react rapidly with proteins, such as platelet proteins, when added. We have examined the isolation procedure for the platelets and the labelling procedure using residual aggregational ability and residual content of beta-thromboglobulin (beta-TG) as indicators of damage to the platelets. In its final version the method allowed a 32.6 +/- 2.7% (mean +/- SD) incorporation of Tc-99m into platelets which again showed a 66 +/- 15% residual aggregational ability, tested by 50 mumol/l of ADP, and a 79 +/- 17% residual content of beta-TG releasable by 10 IU/ml of thrombin. In a pilot clinical study involving 28 patients we found labelled autologous platelets useful in detecting lung embolism and deep vein thrombosis.

Adenosine Diphosphate↗