Inactivation of ricin by constituents present in a skin decontamination lotion

Ricin is a proteinaceous toxin, listed on the schedules of both the chemical and biological weapons conventions. The ease of accessibility to the Ricinus communis plant and toxin extraction makes ricin a viable concern for use of intentional release and causal effects. The adverse effects following exposure to the toxin are caused by the bipartite molecular structure of ricin which allows binding to the mammalian cell surface, enter via endocytic uptake, and deliver the catalytically active polypeptide into the cell cytosol where it irreversibly inhibits protein synthesis, causing cell death. In the present study, the inactivation effectiveness of RSDL® (Reactive Skin Decontamination Lotion) and its individual inactivating constituents (Potassium 2,3-butanedione monoximate (KBDO) and 2,3-butanedione (DAM)) was evaluated for ricin using a number of read out systems including a cytotoxicity assay, quantitative sandwich ELISA test, and a mass spectrometry-based assay. The results demonstrate that RSDL is able to abolish ricin activity after an incubation time of 30 min as determined in the cytotoxicity assay, and after 2 min as determined in the ELISA assay. Mass spectrometric analysis provided evidence that RSDL is able to induce cleavage of the disulfide linkage between the A- and B- polypeptide chain of ricin which is crucial to the inactivation of the toxin, but this seems not the only mechanism of inactivation. Follow on studies would assist to elucidate the details of the toxin inactivation because it is possible that additional generic mechanisms are in place for denaturation with the RSDL lotion components. This may also provide a promise for testing and inactivation with RSDL of other protein toxins.

Protein adduct formation by glucuronide metabolites of permethrin

Biomonitoring of exposure to the insecticide permethrin is usually performed by analysis of its urinary metabolites 3-phenoxybenzoic acid (3-PBA) or cis/ trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (Cl 2 CA). We are engaged in the development of a methodology to assess the cumulative internal dose of exposure to permethrin, which is based on the assumption that (reactive) glucuronide conjugates of the major permethrin metabolites 3-PBA and Cl 2 CA will form persistent (weeks to months) adducts to proteins, in analogy with the glucuronide conjugates of structurally related drugs. The 3-PBA and Cl 2 CA beta-glucuronide metabolites of permethrin have been successfully chemically and enzymatically synthesized. Their identities have been assessed by means of (1)H NMR spectroscopy and liquid chromatography-tandem mass spectrometry. The reactivity of these metabolites with various amino acids, peptides, and albumin in human plasma has been studied. Several distinct adducts could be identified by liquid chromatography-tandem mass spectrometry. After pronase digestion of albumin isolated from exposed human plasma, various lysine derivatives resulted with favorable mass spectrometric and chromatographic properties. Covalent binding was quantified by using [(14)C]-3-PBA glucuronide; >1.5% of total radioactivity was bound to proteins. It is envisaged that the obtained results can form a firm basis for the development of a protein adduct-based methodology for biomonitoring exposure to permethrin. In view of the widespread use of permethrin, the toxicological relevance of protein binding by its metabolites will be addressed in more detail in future work.

Verification of exposure to cholinesterase inhibitors: generic detection of OPCW Schedule 1 nerve agent adducts to human butyrylcholinesterase

Phosphylated butyrylcholinesterase is one of the most important biomarkers to verify an exposure to nerve agents, and it can be analyzed with liquid chromatography-tandem mass spectrometry (LC-MS-MS) by detection of a phosphylated nonapeptide that results after digestion of butyrylcholinesterase (BuChE) with pepsin. For a sensitive analysis (low degree of BuChE inhibition), the identity of the cholinesterase inhibitor has to be known in order to use the LC-MS-MS instrument in the most sensitive selected reaction monitoring mode. In practice, the identity of the cholinesterase inhibitor will not be known beforehand, and the number of possible organophosphates is greater than 1000. However, the number of possible molecular masses of organophosphates is approximately 170. A method for which only 34 transitions in the multiple reaction monitoring mode have to be acquired in order to screen for an exposure to all Organization for the Prohibition of Chemical Weapons Schedule 1 nerve agents was developed.

Verification of Exposure to Organophosphates: Generic Mass Spectrometric Method for Detection of Human Butyrylcholinesterase Adducts

We present a generic mass spectrometric method to verify exposure to organophosphates, based on the chemical conversion of the phosphylated peptides obtained after pepsin digestion of human butyrylcholinesterase (HuBuChE) to a common precursor peptide. After exposure of plasma to various organophosphates (nerve agents, pesticides), HuBuChE was isolated from plasma by procainamide affinity-based solid-phase extraction. Upon subsequent pepsin digestion, the respective phosphylated nonapeptides could be identified in the digests. After treatment of the pepsin digests with Ba(OH)2 in the presence of a nucleophilic tag (a thiol or amine), the phosphylated nonapeptides were transformed into a common tagged nonapeptide that could be analyzed sensitively by means of LC tandem MS. So far, best results were obtained with 2-(3-aminopropylamino)ethanol as nucleophilic tag. By applying the presented method, HuBuChE inhibition can now be monitored accurately by mass spectrometry, without advance knowledge of the structure of the inhibitor.

Standard operating procedure for immunuslotblot assay for analysis of DNA/sulfur mustard adducts in human blood and skin

A standard operating procedure has been developed for an immunoslotblot assay of sulfur mustard adducts to DNA in human blood and skin for use in a field laboratory. A minimum detectable level of exposure of human blood in vitro (> or = 50 nM) sulfur mustard is feasible with the assay. In the case of human skin, a 1 s exposure to saturated sulfur mustard vapor (830 mg/m(-3)) could still be detected.

Procedure for Monitoring Exposure to Sulfur Mustard Based on Modified Edman Degradation of Globin

A procedure for the modified Edman degradation of globin for determination of sulfur mustard adducts to the N-terminal valine residue in human hemoglobin has been developed for use under field laboratory conditions. The minimum detectable exposure level of human blood (in vitro) to sulfur mustard using this procedure is 100 nM. The interindividual and intraindividual variabilities of the procedure were acceptable (standard deviation < 10% and < 20%, respectively). The procedure could be properly set up and carried out in another laboratory within one working day, demonstrating its robustness.

Retrospective Detection of Exposure to Sulfur Mustard: Improvements on an Assay for Liquid Chromatography-Tandem Mass Spectrometry Analysis of Albumin/Sulfur Mustard Adducts

We here report on the further development of the method comprising the pronase digestion of albumin alkylated by sulfur mustard and the subsequent mass spectrometric analysis of an adducted tripeptide. This includes significant improvements in both the albumin isolation procedure and the automation of the microliquid chromatography-electrospray-tandem mass spectrometric analysis. We also report on the results of a small reference range study, in which we have established that there are no detectable interferences in sera from unexposed individuals.

Solid-phase synthesis of polymyxin B1 and analogues via a safety-catch approach

As part of a program towards the development of novel antibiotics, a convenient method for solid-phase synthesis of the cyclic cationic peptide polymyxin B1 and analogues thereof is described. The methodology, based on cleavage-by-cyclization using Kenner's safety-catch linker, yields crude products with purities ranging from 37-67%. Antibacterial assays revealed that analogues 23-26, in which the (S)-6-methyloctanoic acid moiety is replaced with shorter acyl chains, exhibit distinct antimicrobial activity. The results suggest that the length of the acyl chain is rather critical for antimicrobial activity. On the other hand, substitution of the hydrophobic ring-segment D-Phe-6/Leu-7 in polymyxin B1 with dipeptide mimics (i.e. analogues 27-33) resulted in almost complete loss of antimicrobial activity.

Biomonitoring of exposure to chemical warfare agents: a review

In this report an overview of the methods currently available for detection of exposure to a number of chemical warfare agents (CWA), i.e., sulfur mustard, lewisite and nerve agents, is presented. Such methods can be applied for various purposes, e.g., diagnosis and dosimetry of exposure of casualties, confirmation of nonexposure, verification of nonadherence to the Chemical Weapons Convention, health surveillance, and forensic purposes. The methods are either based on mass spectrometric or immunochemical analysis of CWA adducts with DNA or proteins or based on mass spectrometric analysis of urine or plasma metabolites that result from hydrolysis and/or glutathione conjugation. Several of the methods have been successfully applied to actual cases.

Retrospective detection of exposure to organophosphorus anti-cholinesterases: mass spectrometric analysis of phosphylated human butyrylcholinesterase

In this paper a novel and general procedure is presented for detection of organophosphate-inhibited human butyrylcholinesterase (HuBuChE), which is based on electrospray tandem mass spectrometric analysis of phosphylated nonapeptides obtained after pepsin digestion of the enzyme. The utility of this method is exemplified by the positive analysis of serum samples from Japanese victims of the terrorist attack with sarin in the Tokyo subway in 1995.

Diagnosis and dosimetry of exposure to sulfur mustard: development of a standard operating procedure for mass spectrometric analysis of haemoglobin adducts: exploratory research on albumin and keratin adducts

Experiments were carried out to develop a standard operating procedure for analysis of sulfur mustard adducts to the N-terminal valine in haemoglobin and to explore adduct formation with albumin and keratin. In the first approach, gas chromatography-negative chemical ionization/mass spectrometry (GC-NCI/MS) of the thiohydantoin sample subsequent to the modified Edman degradation was performed using a thermodesorption/cold trap (TCT) injection technique (detection limit for in vitro exposure of human blood to sulfur mustard: 30 nM). In the second approach, the crude thiohydantoin sample was purified by solid-phase extraction procedures. In the third approach, the procedure was shortened significantly by performing the Edman degradation for 2 h at 60 degrees C. Upon exposure of human blood to various concentrations of [14C]sulfur mustard, ca. 20% was covalently bound to albumin. One of the tryptic fragments (T5 containing an alkylated cysteine (HETE-(A-L-V-L-I-A-F-A-Q-Y-L-Q-Q-C-P-F-E-D-H-V-K); MW 2536 Da) could be detected sensitively with liquid chromatography/tandem mass spectrometry analysis (detection limits: > or =15 pg absolute and 1 microM for in vitro exposure of human blood). Upon exposure of human callus (suspensions in 0.9% NaCl; 500 mg ml(-1)) to various concentrations of [14C]sulfur mustard we found 15-20% of the added radioactivity covalently bound to keratin. Upon incubation with base, 80% of the bound radioactivity was split off as [14C]thiodiglycol. This result opens the way for sensitive mass spectrometric detection of sulfur mustard exposure of skin by gas chromatography/mass spectrometry of (derivatized) thiodiglycol.

In vitro adduct formation of phosgene with albumin and hemoglobin in human blood

The development of procedures for retrospective detection and quantitation of exposure to phosgene, based on adducts to hemoglobin and albumin, is described. Upon incubation of human blood with [(14)C]phosgene (0-750 microM), a significant part of radioactivity (0-13%) became associated with globin and albumin. Upon Pronase digestion of globin, one of the adducts was identified as the pentapeptide O=C-(V-L)-S-P-A, representing amino acid residues 1-5 of alpha-globin, with a hydantoin function between N-terminal valine and leucine. Micro-LC/tandem MS analyses of tryptic as well as V8 protease digests identified one of the adducts to albumin as a urea resulting from intramolecular bridging of lysine residues 195 and 199. The adducted tryptic fragment could be sensitively analyzed by means of micro-LC/tandem MS with multiple-reaction monitoring (MRM), enabling the detection in human blood of an in vitro exposure level of >/=1 microM phosgene.

Biomonitoring of exposure to lewisite based on adducts to haemoglobin

The development of a procedure for retrospective detection and quantitation of exposure to the arsenical dichloro(2-chlorovinyl)arsine (lewisite; L1) has been initiated. Upon incubation of human blood with [14C]L1 (20 nM-0.2 mM) in vitro, more than 90% of the total radioactivity was found in the erythrocytes and 25-50% of the radioactivity becomes associated with globin. Evidence was obtained for the presence of several binding sites. One type of binding was identified as L1-induced crosslinking of cysteine residues 93 and 112 of the beta-globin chain. A method was developed for extraction of bound and unbound 2-chlorovinylarsonous acid (CVAA), a major metabolite of L1, from whole blood after treatment with 2,3-dimercapto-1-propanol (BAL). Subsequent to derivatization with heptafluorobutyryl imidazole, the CVAA-BAL derivative could be analysed at a 40-fmol level by means of gas chromatography-mass spectroscopy (GC-MS) under electron impact conditions. With this procedure, in vitro exposure of human blood to 1 nM L1 could be determined. The same procedure was applied to the analysis of human urine samples spiked with CVAA. In vivo exposure of guinea pigs could be established at least 240 h after subcutaneous administration of the agent (0.25 mg/kg) by the determination of bound and unbound CVAA in the blood. In the urine of these animals, CVAA could be detected for 12 h after exposure.

Alkylation of human serum albumin by sulfur mustard in vitro and in vivo: mass spectrometric analysis of a cysteine adduct as a sensitive biomarker of exposure

To develop a mass spectrometric assay for the detection of sulfur mustard adducts with human serum albumin, the following steps were performed: quantitation of the binding of the agent to the protein by using [(14)C]sulfur mustard and analysis of acidic and tryptic digests of albumin from blood after exposure to sulfur mustard for identification of alkylation sites in the protein. The T5 fragment containing an alkylated cysteine could be detected in the tryptic digest with micro-LC/tandem MS analysis. Attempts to decrease the detection limit for in vitro exposure of human blood by analysis of the alkylated T5 fragment were not successful. After Pronase treatment of albumin, S-[2-[(hydroxyethyl)thio]ethyl]Cys-Pro-Phe was analyzed by means of micro-LC/tandem MS, allowing a detection limit for in vitro exposure of human blood of 10 nM, which is 1 order of magnitude lower than that obtained by means of modified Edman degradation. The analytical procedure could be successfully applied to the analysis of albumin samples from Iranian victims of the Iran-Iraq war.

Quantitative analysis of O-isopropyl methylphosphonic acid in serum samples of Japanese citizens allegedly exposed to sarin: estimation of internal dosage

A convenient and rapid micro-anion exchange liquid chromatography (LC) tandem electrospray mass spectrometry (MS) procedure was developed for quantitative analysis in serum of O-isopropyl methylphosphonic acid (IMPA), the hydrolysis product of the nerve agent sarin. The mass spectrometric procedure involves negative or positive ion electrospray ionization and multiple reaction monitoring (MRM) detection. The method could be successfully applied to the analysis of serum samples from victims of the Tokyo subway attack and of an earlier incident at Matsumoto, Japan. IMPA levels ranging from 2 to 135 ng/ml were found. High levels of IMPA appear to correlate with low levels of residual butyrylcholinesterase activity in the samples and vice versa. Based on our analyses, the internal and exposure doses of the victims were estimated. In several cases, the doses appeared to be substantially higher than the assumed lethal doses in man.

Verification of exposure to sulfur mustard in two casualties of the Iran-Iraq conflict

The exposure of two Iranian victims of the Iran-Iraq conflict (1980-1988) to sulfur mustard was established by immunochemical and mass spectrometric analysis of blood samples taken 22 and 26 days after alleged exposure. One victim suffered from skin injuries compatible with sulfur mustard intoxication but did not have lung injuries; the symptoms of the other victim were only vaguely compatible with sulfur mustard intoxication. Both patients recovered. Immunochemical analysis was based on detection of the N7-guanine adduct of the agent in DNA from lymphocytes and granulocytes, whereas the N-terminal valine adduct in globin was determined by gas chromatography-mass spectrometry after a modified Edman degradation. The valine adduct levels correspond with those found in human blood after in vitro treatment with 0.9 microM sulfur mustard.

Synthesis and mass spectrometric identification of the major amino acid adducts formed between sulphur mustard and haemoglobin in human blood

As part of a program to develop methods for the verification of alleged exposure to sulphur mustard, we synthesized and characterized three amino acid adducts presumably formed by alkylation of haemoglobin: 4-(2-hydroxyethylthioethyl)-L-aspartate, 5-(2-hydroxyethylthioethyl)L-glutamate and N1- and N3-(2-hydroxyethylthioethyl)-L-histidine. Suitable derivatization methods for GC/MS analysis were developed for these adducts as well as for the cysteine and the N-terminal valine adduct. Incubation of human blood with [35S]sulfur mustard in vitro followed by acidic hydrolysis of isolated globin and derivatization with Fmoc-Cl afforded three radioactive peaks upon HPLC analysis, one of which coeluted with the synthetic Fmoc derivative of N1/N3-(2-hydroxyethylthioethyl)-L-histidine. After pronase digestion of globin the adducts of histidine, glutamic acid, aspartic acid, cysteine and N-terminal valine could be tentatively identified and quantitated. Final identification was obtained from GC/MS analysis. The most abundant adduct, N1/N3-(2-hydroxyethylthioethyl)-L-histidine, could not be sensitively analysed by GC/MS. A convenient LC-tandem MS procedure was developed for this compound, enabling the detection of exposure of human blood to 10 microM sulphur mustard in vitro.

Characterization of sulfur mustard induced structural modifications in human hemoglobin by liquid chromatography--tandem mass spectrometry

In this paper we describe the use of tandem mass spectrometry to identify modified sites in human hemoglobin after in vitro exposure to bis(2-chloroethyl) sulfide (sulfur mustard). Globin isolated from human whole blood which had been exposed to sulfur mustard was degraded with trypsin, and the digests were analyzed by micro LC/MS. Alkylated tryptic fragments (alpha-T1, alpha-T4, alpha-T6, alpha-T9, beta-T1, beta-T9, beta-T10, beta-T11, and beta-T10-S-S-beta-T12) could be tentatively assigned upon comparison with a digest from nonexposed globin. Subsequent tandem mass spectrometry of these peptides allowed unambiguous assignment of 5 specific modified residues: alpha-Val-1, alpha-His-20, beta-Val-1, beta-His-77, and beta-His-97. The results demonstrate the usefulness of microbore LC in combination with tandem mass spectrometry for the structural determination of chemically modified peptides and proteins.

Monitoring of in vitro and in vivo exposure to sulfur mustard by GC/MS determination of the N-terminal valine adduct in hemoglobin after a modified Edman degradation

We report that exposure to the chemical warfare agent sulfur mustard can be monitored by means of a modified Edman degradation involving selective release of the N-terminal valine adduct of hemoglobin with the agent. The degree of alkylation of the N-terminal valine in human hemoglobin is approximately 1-2% of the total alkylation induced in hemoglobin upon treatment of human blood with sulfur mustard. After modified Edman degradation, followed by derivatization with heptafluorobutyric anhydride, the obtained pentafluorophenyl thiohydantion derivative of the valine adduct could be analyzed at a > or = 0.5 fmol level by means of GC/MS under negative ion chemical ionization conditions. Applying this procedure, in vitro exposure of human blood to > or = 0.1 microM of sulfur mustard could be determined. In vivo exposure of guinea pigs could also be established at 48 h after intoxication intravenously with 0.5 mg/kg (0.06 LD50) of the agent.

Solid-phase synthesis of peptide haptens containing a cysteine-sulfur mustard adduct

Solid-phase synthesis of peptide haptens containing 2-[2-(S-cysteinyl)ethanol has been achieved by solution-phase synthesis of a properly protected S-alkylated cysteine derivative and subsequent solid-phase incorporation.

Selective and potent inhibition of different hepatic UDP-glucuronosyltransferase activities by omega,omega,omega-triphenylalcohols and UDP derivatives

A homologous series of omega,omega,omega-triphenylalcohols and corresponding omega,omega,omega-triphenylalkyl-UDP derivatives was synthesized and tested as inhibitors of UDP-glucuronosyltransferase (UGT) activity in rat liver microsomes, with 1-naphthol, testosterone and bilirubin as substrates. Introduction of the UDP moiety in the triphenylalcohols increased their inhibition potency markedly toward the isoforms which glucuronidate 1-naphthol and testosterone, but strongly decreased that toward bilirubin. The inhibiting potency of the UDP-derivatives increased as a function of the length of the hydrocarbon chain. The best inhibitor 7,7,7-triphenylheptyl-UDP showed an I50 of 30 and 10 microM for 1-naphthol and testosterone glucuronidation, respectively; even a 1 mM concentration of the compound had little, if any, effect on bilirubin glucuronidation. The inhibition by 7,7,7-triphenylheptyl-UDP was mixed-type toward 1-naphthol, and non competitive toward testosterone (apparent K(i) 30 microM and 1.7 microM, respectively); on the other hand, the inhibition was competitive toward the common substrate UDP-glucuronic acid (apparent K(i) 1.9-1.2 microM). In addition, 7,7,7-triphenylheptyl-UDP (0.25-0.50 mM) almost inhibited glucuronidation of 1-naphthol and testosterone catalyzed by the recombinant rat liver UGT-2B1 and human liver UGT-1A1, whose cDNA has been expressed in V79 cells. In conclusion, the data indicate that 7,7,7-triphenyheptyl-UDP interacted competitively with the UDP binding site of UGT. The results also indicate that it is possible to design transition state analogue inhibitors with specificity for different UGT forms.

Selective inhibition of glucuronidation by 2,2,2-triphenylethyl-UDP in isolated rat hepatocytes: conjugation of harmol, 3,3',5-triiodothyronine, and N-hydroxy-2-acetylaminofluorene

2,2,2-Triphenylethyl-UDP (TPEU) was synthesized as an analogue of the transition state of the glucuronidation reaction catalyzed by UDP-glucuronosyltransferase; it contains both a uridine and an acceptor substrate moiety. It inhibits rat liver microsomal UDP-glucuronosyltransferase [Eur. J. Biochem. 188:309-312 (1990)]. In the present work, TPEU was tested as an inhibitor of glucuronidation in intact rat hepatocytes. Two phenols (harmol and 3,3',5-triiodothyronine) and a hydroxamic acid (N-hydroxy-2-acetylaminofluorene) were used as substrates for glucuronidation. The glucuronidation of these substrates was strongly decreased by TPEU at 0.3-5 mM. Up to 5 mM TPEU did not kill the cells, as shown by unimpaired trypan blue exclusion at the end of the incubation. When glucuronidation was inhibited, the sulfation of harmol increased, as did the production of reactive species generated from N-hydroxy-2-acetylaminofluorene that bind to cellular macromolecules. This indicates that a decreased substrate consumption by loss of glucuronidation leads to increased conversion by competing pathways. The results show, therefore, that TPEU is an effective inhibitor of glucuronidation in this cellular system in vitro.

Inhibition of UDP-glucuronosyltransferase activity by possible transition-state analogues in rat-liver microsomes

A series of possible transition state analogues of the glucuronidation reaction catalyzed by UDP-glucuronosyltransferase were tested for their inhibitory effect on glucuronidation of various substrates in a rat liver microsomal fraction. In general 4-nitrophenol glucuronidation was more effectively inhibited than that of 1-naphthol, bilirubin or testosterone. 2-(1-Naphthyl)ethyl-UDP and 2,2,2-(triphenyl)ethyl-UDP were the most effective inhibitors. Their inhibitory effect was competitive towards both UDP-glucuronic acid and 4-nitrophenol. These compounds were much more effective inhibitors than UDP; therefore addition of a lipophilic group enhances the inhibitory potency of UDP. The various UDP derivatives showed differences in their abilities to inhibit the glucuronidation of the four acceptor substrates, supporting the concept that the different forms of UDP-glucuronosyl transferase have different active sites.