Isolation, identification and immunosuppressive activity of a new IMM-125 metabolite from human liver microsomes. Identification of its cyclophilin A-IMM-125 metabolite complex by nanospray tandem mass spectrometry.

The isolation from human liver microsomes and identification by electrospray mass spectrometry and tandem mass spectrometry of a new metabolite of IMM-125 resulting from the biotransformation of the amino acid 1 vinylic methyl group to a carboxylic acid, called the IMM-125-COOH metabolite, is described. It was found that the complex of this new metabolite with cyclophilin A is formed less easily than the corresponding cyclophilin A-IMM-125-CH2OH main metabolite and cyclophilin A-IMM-125 complexes. However, when formed, the IMM-125-COOH metabolite-cyclophilin A complex requires more collision-induced dissociation (CID) to dissociate the complex than the complexes formed with the two other ligands. The nanospray tandem mass spectrum of the IMM-125-COOH metabolite-cyclophilin A complex (m/z 1755) gives rise to cyclophilin A-ligand complexes of m/z 1751 by elimination of CO2 and of m/z 1749 by loss of CO2 and H2O or glycerol. Since immunosuppressive activity is known to be dependent on the formation of a binary complex between cyclophilin A and the drug and since the target for the binary complex was found to be the calcium- and calmodulin-dependent protein phosphatase, calcineurin, it could be interesting to measure for structurally related immunosuppressive drugs the CID energy necessary to dissociate the binary complexes in order to evaluate whether a correlation with the phosphatase activity could be derived.

Screening and analysis of polar pesticides in environmental monitoring programmes by coupled-column liquid chromatography and gas chromatography-mass spectrometry.

Screening and analysis of polar pesticides based on coupled-column reversed-phase liquid chromatography (LC-LC) and GC- or LC-MS is a powerful tool in the execution of environmental monitoring programmes. This paper presents a unified approach utilising LC-LC screening followed by GC-MS confirmation. As polar pesticides are not generally amenable to GC a widely applicable derivation technique is used. The results demonstrate that the proposed LC and MS techniques are capable of analysing a wide range of polar pesticides down to levels of 0.1 microgram/l (EU limit for drinking water). LC switching techniques for group analysis or individual compounds rely on the reversed-phase retention and the UV detectability of the pesticides in combination with the choice of the LC columns. Fast miniaturised derivatization prior to GC-MS forms an integral part in the proposed strategy. In order to avoid extraction losses, derivation in the aqueous sample, preferably with electrophoric reagents with enhanced sensitivity in GC-NICI-MS are employed where possible. In this communication, method development and validation fitting in the strategy are evaluated and the results of the combined approach are discussed.

Confirmation of residues of thyreostatic drugs in thyroid glands by multiple mass spectrometry after thin-layer chromatographic screening.

A method is described for the confirmation of high-performance thin layer chromatography (HPTLC) suspect results of residues of thyreostatic drugs in thyroid tissue. The method is based on the infusion of the remainder of the extract used for HPTLC via the electrospray interface into a mass spectrometer operating in the multiple stage mass spectrometry (MSn) mode. The clean-up of the samples was performed with a selective extraction procedure, based on a specific complex formation of the drugs with mercury ions, bound in an affinity column. The thyreostatic drugs were derivatised with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole.

The identification of a nitrosated prodrug of the PDE-5 inhibitor aildenafil in a dietary supplement: a Viagra with a pop.

A new unapproved analogue of sildenafil was detected in capsules of a herbal dietary supplement promoted as a libido enhancing product. Using LC-DAD-MS, MS-MS, HRMS, IR and NMR the analogue was shown to be a derivative of the PDE-5 inhibitor aildenafil with a nitrosamine moiety. A hydrolysis experiment showed that the new analogue was a prodrug of aildenafil and was therefore named nitroso-prodenafil. A capsule contained 108 mg of nitroso-prodenafil which is equivalent to 84 mg of aildenafil and 5.1 mg of nitrogen monoxide (NO). Although it is unknown how much NO can be usefully generated there is 3-fold more NO present than in a 10 mg isorbide nitrate tablet. Both PDE-5 inhibitors and nitrosamines cause vasodilatation by increasing levels of NO. To their coincidental use is warned against because it may cause a fatal drop in blood pressure. In addition, nitrosamines are known carcinogens. This is the first time a PDE-5 inhibitor and a potential NO donor were identified in one molecule. The findings indicate the dangerous level of advancement in medicinal chemistry by producers of unapproved drugs.

Targeted identification of infection-related HLA class I-presented epitopes by stable isotope tagging of epitopes (SITE).

Identification of peptides presented in human leukocyte antigen (HLA) class I molecules after viral infection is of strategic importance for immunology and vaccine development. A powerful strategy aimed at the rapid, unambiguous identification of naturally processed HLA class I-associated peptides, which are induced by viral infection, is presented here. The methodology, stable isotope tagging of epitopes (SITE), is based on metabolic labeling of endogenously synthesized proteins during infection. This is accomplished by culturing virus-infected cells with stable isotope-labeled amino acids that are expected to be anchor residues for the human leukocyte antigen allele of interest. Subsequently, these cells are mixed with an equal number of noninfected cells, which are cultured in normal medium. Finally, peptides are acid-eluted from immunoprecipitated HLA molecules and subjected to two-dimensional nanoscale liquid chromatography-mass spectrometry analysis. Virus-induced peptides are identified through computer-assisted detection of characteristic, binomially distributed ratios of labeled and unlabeled molecules.

Gas chromatographic-mass spectrometric analysis of the loop diuretic torasemide in human urine.

A fast and reliable gas chromatographic-mass spectrometric (GC-MS) method for the identification and determination of the loop diuretic torasemide in human urine is described. The usefulness of different derivatization procedures and reagents was studied. Flash methylation using trimethylanilinium hydroxide was the most convenient and appropriate procedure. The optimal urine isolation method comprised alkaline liquid-liquid extraction with ethyl acetate. After evaporation of the organic layer to dryness, the solid residue was reconstituted in the derivatizing reagent and was directly injected into the GC-MS system. Samples were analysed in the multiple ion detection mode using electron impact ionization. No interferences from other urinary compounds were found. Torasemide gave rise to a derivative that was identified by GC with Fourier transform infrared detection. There was a 70 +/- 5% recovery of torasemide. The coefficient of variation was 5% at a concentration of 0.05 microgram/ml. The method was used for the determination of torasemide in urine samples obtained from a healthy volunteer that had received a single, 10 mg dose of torasemide.

A microcapillary column switching HPLC-electrospray ionization MS system for the direct identification of peptides presented by major histocompatibility complex class I molecules.

A microcapillary column switching high-performance liquid chromatography (HPLC) system was developed for the separation of major histocompatibility complex (MHC) class I associated peptides. Combination of the column switching system with electrospray ionization mass spectrometry (ESIMS) enabled the detection and identification of the peptides at low-femtomole levels. Sample volumes of 30-50 microL were injected and concentrated onto a short, 100-micron-i.d. precolumn. The precolumn was coupled to a 100-micron-i.d. reversed-phase analytical HPLC column via a six-port valve. Peptides were separated on the analytical column using an ESI-compatible mobile phase at a flow rate of 0.5 microL/min. Peptides were eluted directly into the ESI source of either a magnetic sector MS or an ion trap MS. Peptides associated with human leukocyte antigen A*0201 molecules were determined in immunoaffinity-purified extracts from either measles virus infected cells or uninfected cells by microcapillary column switching HPLC-ESIMS. The approach toward detection of virus-specific peptides we used was based on the comparison of ion chromatograms obtained from the LC-MS analysis of extracts from virally infected cells and their uninfected counterparts. In this way, the molecular mass of peptides unique to virus infected cells was obtained. The utility of the system is demonstrated by the identification of a candidate epitope. Microcapillary column switching HPLC was used along with ESI ion trap tandem MS to identify the naturally processed viral peptide KLWESPQEI. This peptide was found to derive from the measles virus nonstructural protein C. The approach described here provides a versatile and sensitive method for the direct identification of viral peptides associated with MHC class I molecules.

Differential protein expression in phenotypic variants of Streptococcus pneumoniae.

Streptococcus pneumoniae undergoes spontaneous phase variation resulting in opaque and transparent colony forms. Differences in colony opacity correlate with differences in virulence: the transparent variants are more capable of colonizing the nasopharynx, whereas the opaque variants show increased virulence during systemic infections. To gain insight into the pathogenesis of pneumococcal disease at the molecular level, protein expression patterns of the phenotypic variants of two pneumococcal strains were compared by high-resolution two-dimensional protein electrophoresis. In comparison with transparent variants, the opaque variants reduced the expression of two proteins and overexpressed one protein. The proteins were identified by mass spectrometric analysis. The protein overexpressed in the opaque phenotype revealed significant homology to elongation factor Ts of Helicobacter pylori. One of the two proteins that were underexpressed in the opaque variants revealed significant homology to the proteinase maturation protein PrtM of Lactocobacillus paracasei, a member of the family of peptidyl-prolyl cis/trans isomerases. A consensus lipoprotein signal sequence suggests that the putative proteinase maturation protein A, designated PpmA, is located at the surface of the pneumococcus and may play a role in the maturation of surface or secreted proteins. The second underexpressed protein was identified as pyruvate oxidase, SpxB. The lower SpxB expression in opaque variants most probably explains the reduced production of hydrogen peroxide, a reaction product of SpxB, in this variant. Since a spxB-defective pneumococcal mutant has decreased ability to colonize the nasopharynx (B. Spellerberg, D. R. Cundell, J. Sandros, B. J. Pearce, I. Idanpaan-Heikkila, C. Rosenow, and H. R. Masure, 1996. Mol. Microbiol. 19:803-813, 1996), our data suggest that SpxB plays an important role in enhancing the ability of transparent variants to efficiently colonize the nasopharynx.

Effects of isoniazid (INH) on the BCG-induced local immune response after intravesical BCG therapy for superficial bladder cancer.

Because recent investigations showed that the use of isoniazid (INH) severely impaired the local immune reaction to intravesical bacillus Calmette-Guérin (BCG) in the bladder of guinea pigs, in this study the effect of INH in man has been investigated. Patients were treated with BCG with or without oral INH. The concentration of free INH in most urine samples of patients treated with BCG/INH was much higher (mean 38.0 +/- 60.9 micrograms INH/ml) than the minimal inhibitory concentration (MIC; 0.1 microgram INH/ml), suggesting at least a bacteriostatic potential of the INH present. However, in vitro studies showed that these urinary concentrations of INH did not kill BCG organisms effectively, even at a concentration of 150 micrograms/ml for 24 h. After the fifth and sixth BCG instillations a significant increase in the concentration of cytokines (IL2, IL6, IL8 and TNFa), IgG and IgA antibodies to BCG and the number of leukocytes in urine was observed. The leukocytes mainly consisted of granulocytes, besides monocytes/macrophages and, in lower amounts, T- and B-lymphocytes and natural killer (NK) cells. The absolute number of granulocytes and the concentration of IgG antibodies after BCG instillation were significantly suppressed by INH, whereas INH appeared to have no effect on the urinary cytokine and IgA antibody concentrations or the total number and phenotype of the leukocytes present. In conclusion, the results of this study indicate that INH does not impair the local immunological stimulation after BCG instillation in man as severely as was observed in the guinea pig and it may be expected that INH does not impair the antitumor efficacy of BCG.

A single naturally processed measles virus peptide fully dominates the HLA-A*0201-associated peptide display and is mutated at its anchor position in persistent viral strains.

We studied the natural MHC class I display of measles virus (MV) epitopes. Peptide ligands associated with HLA-A*0201 were purified from a B lymphoblastoid cell line prior to and after infection with MV. Infection-induced peptides were revealed using microcapillary reversed phase high performance liquid chromatography electrospray ionization/mass spectrometry (microLC-ESI/MS) by subtraction of the "infected" and "uninfected" ion traces. Three naturally processed viral epitopes derived from different MV proteins were identified through tandem MS sequencing. These peptides were expressed at widely divergent levels of HLA-peptide complexes, but had similar binding capacities to HLA-A*0201. The most abundant viral peptide species, identified as residues 84-92 (KLWESPQEI) of the MV nonstructural C protein, was expressed at an unprecedented high density (> 10(5) copies per cell) and was immunogenic in HLA-A2/Kb-transgenic mice. Furthermore, natural mutants of this epitope, occurring in persistent lethal MV strains, were shown to have lost their HLA-A*0201 binding capacity. Thus, here we report for the first time the direct discovery through microLC-ESI/MS of a uniquely dominant viral HLA class I ligand, KLWESPQEI, with features eligible for immune selection pressure.