Identification of the unknown transformation products derived from clarithromycin and carbamazepine using liquid chromatography/high-resolution mass spectrometry.

RATIONALE: A comprehensive study of the environmental fate of pollutants is more and more required, above all on new contaminants, i.e. pharmaceuticals. As high-resolution mass spectrometry (HRMS(n)) may be a suitable analytical approach for characterization of unknown compounds, its performance was evaluated in this study. METHODS: The analyses were carried out using liquid chromatography (LC) (electrospray ionization (ESI) in positive mode) coupled with a LTQ-Orbitrap analyzer. High-resolution mass spectrometry was employed to assess the evolution of the drug transformation processes over time; accurate masses of protonated molecular ions and sequential product ions were reported with an error below 5 millimass units, which guarantee the correct assignment of their molecular formula in all cases, while their MS(2) and MS(3) spectra showed several structurally diagnostic ions that allowed characterization of the different transformation products (TPs) and to distinguish the isobaric species. RESULTS: The simulation of phototransformation occurring in the aquatic environment and identification of biotic and abiotic transformation products of the two pharmaceuticals were carried out in heterogeneous photocatalysis using titanium dioxide, aimed to recreate conditions similar to those found in the environmental samples. Twenty-eight main species were identified after carbamazepine transformation and twenty-nine for clarithromycin. CONCLUSIONS: This study demonstrates that HRMS, combined with LC, is a technique able to play a key role in the evaluation of the environmental fate of pollutants and allows elucidation of the transformation pathways followed by the two drugs.

Characterization of phenazone transformation products on light-activated TiO2 surface by high-resolution mass spectrometry.

The paper examines the transformation of phenazone (2,3-dimethyl-1-phenyl-3-pyrazolin-5-one), a widely used analgesic and antipyretic drug, under simulated solar irradiation in pure water, using titanium dioxide, and in river water. High-resolution mass spectrometry was employed to monitor the evolution of photoinduced processes. Initially, laboratory experiments were performed to simulate drug-transformation pathways in aqueous solution, using TiO(2) as photocatalyst. Thirteen main phenazone transformation products were detected, and full analysis of their MS and MS(n) spectra identified the diverse isobaric species. All these transformation products were themselves easily degraded, and no compounds were recognized to remain until 1h of irradiation. From these findings, a tentative degradation pathway is proposed to account for the photoinduced transformation of phenazone in natural waters. These simulation experiments were verified in the field, seeking phenazone in River Po water samples.

Inhibition of HMGI-C protein synthesis suppresses retrovirally induced neoplastic transformation of rat thyroid cells.

Elevated expression of the three high-mobility group I (HMGI) proteins (HMGI, HMGY, and HMGI-C) has previously been correlated with the presence of a highly malignant phenotype in epithelial and fibroblastic rat thyroid cells and in experimental thyroid, lung, mammary, and skin carcinomas. Northern (RNA) blot and run-on analyses demonstrated that the induction of HMGI genes in transformed thyroid cells occurs at the transcriptional level. An antisense methodology to block HMGI-C protein synthesis was then used to analyze the role of this protein in the process of thyroid cell transformation. Transfection of an antisense construct for the HMGI-C cDNA into normal thyroid cells, followed by infection with transforming myeloproliferative sarcoma virus or Kirsten murine sarcoma virus, generated cell lines that expressed significant levels of the retroviral transforming oncogenes v-mos or v-ras-Ki and removed the dependency on thyroid-stimulating hormones. However, in contrast with untransfected cells or cells transfected with the sense construct, those containing the antisense construct did not demonstrate the appearance of any malignant phenotypic markers (growth in soft agar and tumorigenicity in athymic mice). A great reduction of the HMGI-C protein levels and the absence of the HMGI(Y) proteins was observed in the HMGI-C antisense-transfected, virally infected cells. Therefore, the HMGI-C protein seems to play a key role in the transformation of these thyroid cells.

Changes in nuclear proteins on transformation of rat epithelial thyroid cells by a murine sarcoma retrovirus.

Two-dimensional electrophoresis has been used to document changes in nuclear proteins following viral transformation of an epithelial cell line exhibiting differentiation markers. After transformation, these markers are lost, and the cells become tumorigenic and capable of growth in soft agar. A sharp rise in the phosphorylation of histones H1, H2A, and ubiquitinated H2A is seen on transformation, together with the appearance of three phosphorylated proteins that are extractable by perchloric acid and appear related to high mobility group Protein 14, a constituent of active chromatin. Since comparison is made between normal and transformed cells that are each grown to confluence and since there is little difference between their observed growth rates, the changes seen represent intrinsic differences between the cell lines and are thus a direct reflection of the process of transformation.

Expression of HMGI(Y) proteins in squamous intraepithelial and invasive lesions of the uterine cervix.

The expression of nuclear proteins high mobility group (HMG) I and HMGY was investigated in intraepithelial and invasive lesions of the uterine cervix. Human carcinoma cell lines C-41, ME-180, and CaSki were used for testing protein expression in neoplastic cells from the cervix. Morphological grading of the dysplasias (CIN 1, CIN 2, and CIN 3) and invasive carcinomas from formalin-fixed paraffin-embedded samples parallels the degree of nuclear immunostaining obtained using a polyclonal antibody raised against the amino-terminal region of HMGI(Y) proteins. The immunostaining obtained with HMGI(Y) antibody was compared with that observed using the antibody Ki-67, and the results were similar. We suggest the use of HMGI(Y) antibody in clinical oncology as a useful marker of intraepithelial lesions and invasive carcinomas.

Human colorectal carcinomas express high levels of high mobility group HMGI(Y) proteins.

A correlation has previously been demonstrated between the presence of the three HMGI proteins (HMGI, HMGY, and HMGI-C) and the expression of a highly malignant phenotype in epithelial and fibroblastic rat thyroid cells; this being subsequently extended to experimental thyroid, lung, prostate, mammary, and skin carcinomas. Recently, we have demonstrated that expression of HMGI and HMGY proteins, coded for by the HMGI(Y) gene, is associated with the malignant phenotype of human thyroid neoplasias. Here, we show that HMGI(Y) gene expression is present both at the RNA and protein level in human colorectal carcinoma cell lines and tissues examined in this study. Conversely, no HMGI(Y) proteins were detected in normal intestinal mucosa. Therefore, these results suggest an involvement of HMGI and HMGY proteins overexpression in colorectal tumorigenesis.

Detection of high mobility group I HMGI(Y) protein in the diagnosis of thyroid tumors: HMGI(Y) expression represents a potential diagnostic indicator of carcinoma.

Hyperplastic or neoplastic proliferative lesions of thyroid follicular epithelium consist of a spectrum, ranging from nodular hyperplasia to undifferentiated (anaplastic) carcinoma, and usually present as palpable thyroid nodules. Thyroid nodules are a common occurrence in the general population, but only a small proportion of them are eventually diagnosed as carcinoma. The difficulty in objectively identifying those thyroid nodules that are malignant to avoid unnecessary surgery, combined with the range and effectiveness of the available therapeutic options in those patients who do, indeed, have thyroid carcinoma, has prompted the search for tumor markers and prognostic indicators. The high mobility group I (HMGI) proteins represent a class of nuclear proteins involved in the regulation of chromatin structure and function. HMGI(Y), one of the members of this class, is expressed at high levels during embryogenesis and in malignant tumors but at generally low levels in normal adult human tissues. Previous work on a limited number of thyroid samples suggested that the detection of the HMGI(Y) proteins may provide a clinically useful diagnostic tool. To verify this assumption, we analyzed HMGI(Y) expression by a combination of immunohistochemistry and reverse transcription-PCR in 358 thyroid tissue samples that were representative of the spectrum of thyroid tumor pathology. HMGI(Y) was detectable in 18 of 19 follicular carcinomas, 92 of 96 papillary carcinomas, and 11 of 11 undifferentiated (anaplastic) carcinomas but in only 1 of 20 hyperplastic nodules, 44 of 200 follicular adenomas, and 0 of 12 normal tissue samples. The correlation between HMGI(Y) expression and a diagnosis of carcinoma was highly significant (P < 0.0001). We also prospectively collected and analyzed for HMGI(Y) expression by immunohistochemistry and reverse transcription-PCR in 12 fine needle aspiration biopsies from 10 patients who subsequently underwent surgical removal of a solitary thyroid nodule. HMGI(Y) was detectable only in the four fine needle aspiration biopsies, corresponding to the thyroid nodules that were definitively diagnosed as carcinomas after surgery (two follicular carcinomas and two papillary carcinomas). The remaining eight samples (six follicular adenomas and two samples consisting of normal follicular cells) were negative. The findings of this study confirm the differential expression of HMGI(Y) in thyroid neoplasia and indicate the HMGI(Y) protein as a potential marker for thyroid carcinoma.

The expression of the high mobility group HMGI (Y) proteins correlates with the malignant phenotype of human thyroid neoplasias.

High Mobility Group I (HMGI) proteins are nuclear proteins involved in the regulation of chromatin structure and function. Elevated expression of the HMGI proteins (HMGI, HMGY and HMGI-C) has been correlated with the presence of a highly malignant phenotype in epithelial and fibroblastic rat thyroid cells, and in several experimental carcinomas. Here, we demonstrate that HMGI and HMGY proteins are expressed in human thyroid carcinomas and thyroid carcinoma cell lines, but not in adenomas, goiters, normal thyroid tissues and cells. These results indicate a correlation between HMGI and HMGY expression and the malignant phenotype of thyroid neoplasias, suggesting that these proteins may be used as markers in thyroid cancer.

High level expression of the HMGI (Y) gene during embryonic development.

The HMGI protein family includes three proteins, named HMG-I, HMG-Y and HMGI-C. The first two proteins are coded for by the same gene, HMGI (Y), through an alternative splicing mechanism. Their expression is elevated in neoplastic tissues and cells and this overexpression has a causal role in the process of cellular neoplastic transformation. We demonstrate that the HMGI (Y) gene is expressed at very low levels in normal adult tissues, whereas in embryonic tissues it is expressed at high levels comparable to those detected in neoplastic tissues. Specifically, a very high expression of the HMGI (Y) gene was detected in all embryonic tissues at 8.5 dpc. Then in the following days, even though the gene is expressed essentially in all tissues, an abundant gene expression was restricted to some tissues. These results indicate an important role of the HMGI (Y) gene in development.

Molluscan sperm proteins: Ensis minor.

The three major proteins, EM1, EM5 and EM6, from the mature sperm of the bivalve mollusc Ensis minor have been partially sequenced in order to establish which category they belong to and their potential for phosphorylation. Protein EM1 is protamine-like with about 50% basic amino acids, some of which are included in SK(R) repeats. Three SPXX potential phosphorylation sites were observed in the N-terminal domain. EM1 does not fold (Giancotti et al. (1983) Eur. J. Biochem. 136, 509-516). Protein EM6 (approx. 270 residues) is histone H1-like, having a globular domain homologous to other H1 family proteins. The N-domain of EM6 contains SK(R) repeats like EM1, but there are few, if any, SPXX sites in the chain. Proteins EM1 and EM6 are the two proteins specific for mature sperm. Protein EM5, of about 150 residues and present at lower levels than EM1 and EM6, is also an H1-family molecule. A sequence from its globular domain shows close homology to chicken H5 and to sea urchin somatic H1. Its presence may relate to the existence of a low level of nucleosomal structure.

Fluorescence of buried tyrosine residues in proteins.

Histone H1 contains only one tyrosine and no tryptophan. The intrinsic fluorescence of the tyrosine rises by about 400% as the protein folds from a random coil to a globular structure (Giancotti, V., Fonda, M. and Crane-Robinson, C. (1977) Biophys. Chem. 6, 379-383). Measurements of external quenching by a large variety of quenchers shows very much reduced quenching in the folded state as compared to the disordered. It is concluded that the tyrosine is a buried residue. This is supported by the observation that the fluorescence of modified amino-tyrosyl H1 is similar to that of buried tyrosines in ribonuclease. The classification of tyrosine fluorescence in tryptophan-free proteins (Cowgill, R.W. (1976) in Biochemical Fluorescence Concepts, Vol. 2 to include the case of residues buried in a hydrophobic environment and having a relative quantum yield RTyr, greater than unity.

The chromatin of sea urchin sperm.

Digestion of sea urchin sperm nuclei with micrococcal nuclease yields nucleosomal monomer fragments of 151 and 164 base pairs. Prior trypsin treatment of the sperm chromatin does not alter the size of these monomer DNA fragments despite the fact that the H1 histone is reduced to a limit globular peptide of about 83 residues. Heterologous reconstitution experiments show that this peptide is capable of protecting an extra 22 base pairs beyond the core particle in a chromatosome. Nuclease digestion of reconstitutes from DNA and sperm core histones yields a core monomer of about 141 base pairs. It is concluded that this sperm chromatin contains a chromatosome of 164 bp essentially similar to that observed in the more usual chromatins. Edman degradation of the H1 limit peptide shows its sequence to be closely analogous to the corresponding peptide of calf H1 and chicken H5. Circular dichroism studies of histone H1 from the sperm of three sea urchin species demonstrate the presence of trypsin-sensitive helical regions outside the globular domain that are absent in calf H1 and chicken H5.

Isolation and characterization of the gene coding for murine high-mobility-group protein HMGI-C.

The HMGI-C protein is a nuclear factor expressed in human and rodent neoplastic cells which has been shown to be involved in the process of cell transformation. We have previously isolated the cDNA encoding murine HMGI-C and now we report the cloning and analysis of the mouse Hmgi-c gene. The gene is at least 50 kb long, contains five exons, and each of the three DNA-binding domains is encoded by a different exon. The location of exon-intron junctions was determined and shown to follow the GT-AG rule. The sequence revealed that the overall organization is similar to the gene encoding human HMGI(Y), the other member of the HMGI family, suggesting that HMGI genes probably evolved through gene duplication and exon shuffling events from an ancestral gene. A highly homologous pseudogene is also present in the mouse genome. Our results on Hmgi-c structure provide basic information to carry out further studies on the regulation of its expression.

Intranuclear distribution of HMGI/Y proteins. An immunocytochemical study.

The intranuclear distribution of HMGI/Y proteins was analyzed by immunofluorescent staining in several cell lines using a polyclonal antibody that stained a fibrogranular network. In actively growing 3T3 fibroblasts, HMGI/Y proteins were mainly localized to heterochromatin masses, whereas in quiescent cells they were more diffusely distributed. Double labeling experiments showed a co-localization of HMGI/Y with DNA topoisomerase IIalpha. These results are in agreement with previously published biochemical data and indicate a possible involvement of HMGI/Y proteins in several nuclear functions, including chromatin organization and gene expression.

Calorimetry of DNA-dye interactions in aqueous solution I. Proflavine and ethidium bromide.

The results of an investigation on the interaction of proflavine and of ethidium bromide with DNA (calf thymus) in dilute aqueous solution are reported. The binding of the two dyes by DNA has been studied by means of microcalorimetric and of equilibrium dialysis measurements. Data on the thermodynamics of dimerization of both proflavine and ethidium bromide in aqueous solution obtained on the basis of spectroscopic and/or calorimetric experiments are also reported. The enthalpy data show that dye-dimerization and dye "strong" interaction with DNA are energetically favourable and quite similar while only in the latter case the phenomenon is also entropy driven. This is taken as further evidence in support of the concept that "strong" interaction-of both proflavine and ethidium bromide with DNA means dye molecules intercalation into the native, double helical structure of the biopolymer.

Tyrosine fluorescence of two tryptophan-free proteins: histones H1 and H5.

The fluorescence intensity of the single tyrosine residue in histone H1 increases from RTYR = 0.3 to RTYR = 1.3 as the protein undergoes a conformational change from the random coil state to a folded form. Enhanced fluorescence in the folded state has not been observed before in ap protein. Histone H5 shows no change in fluorescence intensity on folding. This is interpreted as a result of compensation between enhanced and reduced fluorescence in the three tyrosine residues.

Intrinsic and extrinsic fluorescence of histones H2A and H2B: a conformational study.

Intrinsic and extrinsic fluorescence measurements suggest that H2A and H2B histones, in a partially secondary structure, self-aggregate into assemblies in which some tyrosine groups are buried in a hydrophobic environment and show enhanced fluorescence, 2-p-toluidinylnaphthalene-6-sulfonate (TNS) indicates heterogeneity among the binding sites whose number depends on the pH values of the solutions. Warfarin, used as hydrophobic probe, shows that during the process of self-association and cross-complexing of the two histones there is the covering of some hydrophobic sites of the proteins.

Sodium butyrate affects the cytotoxic and mutagenic response of V79 Chinese hamster cells to the genotoxic agents, daunorubicin and U.V. radiation.

It has been suggested that conditions which lead to modifications in the chromatin structure could be responsible for an increased accessibility of DNA to genotoxic agents in eukaryotic cells. With this in mind, the cytotoxic and mutagenic activity of the anthracycline antibiotic, daunorubicin, and of UV radiation was assayed on V79 Chinese hamster cells pretreated or not with 5 mM sodium butyrate, an agent known to induce modifications in the chromatin structure: this treatment in fact proved to induce the hyperacetylation of the core histones, and moreover to enhance the cytotoxic response of the cells to both daunorubicin and UV radiation and the mutagenic response to daunorubicin.

A method for silver staining HMG chromosomal proteins in polyacrylamide electrophoretic gels.

A method is presented for sensitive staining of the HMG14 and 17 proteins in polyacrylamide gels pre-stained with Coomassie Blue R250. The procedure involves binding negatively and positively charged polycyclic aromatic compounds to the proteins followed by staining with silver using the method of Wray et al. (1981).

Fate of selected pharmaceuticals in river waters.

The aqueous environmental fate of two antibiotics, lincomycin and clarithromycin, and an antiepileptic drug, carbamazepine, was investigated by monitoring drugs decomposition and identifying intermediates in Po river water (North Italy). Initially, control experiments in the dark and under illumination were performed on river water spiked with drugs to simulate all possible transformation processes occurring in the aquatic system. Under illumination, these pharmaceuticals were degraded and transformed into numerous organic intermediate compounds. Several species were formed and characterised by analysing MS and MS(n) spectra and by comparison with parent molecule fragmentation pathways. River water was sampled at three sampling points in an urban area. The selected pharmaceuticals were detected in all samples. Eight transformation products identified in the laboratory simulation were found in natural river water from carbamazepine degradation, three from clarithromycin and two from lincomycin. Their transformation occurring in aquatic system mainly involved mono- and poly-hydroxylation followed by oxidation of the hydroxyl groups.