Nitroxoline resistance is associated with significant fitness loss and diminishes in vivo virulence of Escherichia coli

IMPORTANCE

Antimicrobial resistance (AMR) poses a global threat and requires the exploration of underestimated treatment options. Nitroxoline, an effective broad-spectrum antibiotic, does not suffer from high resistance rates in the clinics but surprisingly, it is not heavily used yet. Our findings provide compelling evidence that Nitroxoline resistance renders bacteria unable to cause an infection in vivo, thereby reinvigorating the potential of Nitroxoline in combating AMR.

Carcinogen 4-Nitroquinoline Oxide (4-NQO) Induces Oncostatin-M (OSM) in Esophageal Cells

BACKGROUND/AIM

The earliest cellular and molecular biologic changes in the esophagus that lead to esophageal cancer were evaluated in a mouse model. We correlated numbers of senescent cells with the levels of expression of potentially carcinogenic genes in sorted side population (SP) cells containing esophageal stem cells and non-stem cells in the non-side population cells in the 4-nitroquinolone oxide (NQO)-treated esophagus.

MATERIALS AND METHODS

We compared stem cells with non-stem cells from the esophagus of mice treated with the chemical carcinogen 4-NQO (100 μg/ml) in drinking water. We also compared gene expression in human esophagus samples treated with 4-NQO (100 μg/ml media) to non-treated samples. We separated and quantitated the relative levels of expression of RNA using RNAseq analysis. We identified senescent cells by luciferase imaging of p16^+/LUC mice and senescent cells in excised esophagus from tdTOMp16+ mice.

RESULTS

A significant increase in the levels of RNA for oncostatin-M was found in senescent cells of the esophagus from 4-NQO-treated mice and human esophagus in vitro.

CONCLUSION

Induction of OSM in chemically-induced esophageal cancer in mice correlates with the appearance of senescent cells.

SNH Amidation of 5-Nitroisoquinoline: Access to Nitro- and Nitroso Derivatives of Amides and Ureas on the Basis of Isoquinoline

For the first time, amides and ureas based on both 5-nitroisoquinoline and 5-nitrosoisoquinoline were obtained by direct nucleophilic substitution of hydrogen in the 5-nitroisoquinoline molecule. In the case of urea and monosubstituted ureas, only 5-nitrosoisoquinoline-6-amine is formed under anhydrous conditions.

Combination Treatment of TRPV4 Agonist with Cisplatin Promotes Vessel Normalization in an Animal Model of Oral Squamous Cell Carcinoma

Background and Objectives: Oral squamous cell carcinoma (OSCC) is the sixth most common malignancy in the world. Transient receptor potential vanilloid 4 (TRPV4) channel has been shown to be involved in angiogenesis in multiple types of tumors. However, not much is known about TRPV4′s involvement in OSCC. Thus, in this study, we investigate the effect of administering a TRPV4 agonist on angiogenesis in OSCC. Materials and Methods: Thirty-six Sprague Dawley (SD) rats were used in this study. 4-nitroquinoline 1-oxide (4NQO) was used to induce OSCC. Cisplatin (an anticancer drug), and GSK1016790A (an agonist for TRPV4) was used in this study. Immunohistochemistry was employed to examine the TRPV4 expression. An RT2 Profiler PCR Array was performed for gene expression analysis of TRPV4, vascular growth factors that correspond directly with angiogenesis, such as angiopoietin (Ang-1 and Ang-2), and tyrosine kinase (Tie-1 and Tie-2) receptors. Tumor vessel maturity was assessed by microvessel density and microvessel-pericyte-coverage index. Results: RT2 profiler PCR array showed significant elevated levels of Ang-1 (2.1-fold change; p < 0.05) and Tie-2 (4.5-fold change; p < 0.05) in OSCC following the administration of a combination of GSK1016790A and cisplatin. Additionally, the combination treatment significantly reduced the microvessel density (p < 0.01) and significantly increased the percentage of microvessels covered with pericytes (p < 0.01) in OSCC. Furthermore, tumor size was significantly reduced (p < 0.05) in rats that received cisplatin alone. The combination treatment also greatly reduced the tumor size; however, the data were not statistically significant. Conclusions: The findings suggest that combining a TRPV4 agonist with cisplatin for treatment of OSCC promote vessels normalization via modulation of Ang-1/Tie-2 pathway.

Transcript Profiling of Nitroxoline-Treated Biofilms Shows Rapid Up-regulation of Iron Acquisition Gene Clusters

Bacterial biofilms are surface-attached communities of slow- or non-replicating cells embedded within a protective matrix of biomolecules. Unlike free-floating planktonic bacteria, biofilms are innately tolerant to conventional antibiotics and are prevalent in recurring and chronic infections. Nitroxoline, a broad-spectrum biofilm-eradicating agent, was used to probe biofilm viability. Transcript profiling (RNA-seq) showed that 452 of 2594 genes (17.4%) in methicillin-resistant Staphylococcus aureus (MRSA) biofilms were differentially expressed after a 2 h treatment of nitroxoline. WoPPER analysis and time-course validation (RT-qPCR) revealed that gene clusters involved in iron acquisition (sbn, isd, MW2101, MW0695, fhu, and feo) were rapidly up-regulated following nitroxoline treatment, which is indicative of iron starvation in MRSA biofilms. In addition, genes related to oligopeptide transporters and riboflavin biosynthesis were found to be up-regulated, while genes related to carotenoid biosynthesis and nitrate assimilation were down-regulated. RT-qPCR experiments revealed that iron uptake transcripts were also up-regulated in established Staphylococcus epidermidis and Acinetobacter baumannii biofilms following nitroxoline treatment. Overall, we show RNA-seq to be an ideal platform to define cellular pathways critical for biofilm survival, in addition to demonstrating the need these bacterial communities have for iron.

Molecular mechanism of in vitro transformation of mammalian cells by chemical carcinogens

BHK21 clone 13 cells transformed by dimethylnitrosamine (DMN) or nitrosomethylurea (NMU) ("alkylating" chemical carcinogens) appear to be restricted by temperature in the expression of their transformed phenotype. When grown at 38.5 degrees C, they exhibit a transformed phenotype (clonal morphology and ability to plate in agar), when grown at 32 degrees C, their phenotype is normal. Conversion from the normal to the transformed phenotype and the reverse is possible by temperature shifts. Conversely of the BHK21 clone 13 cells, of the rat fibroblasts (R111) transformed by 4-nitroquinoline-N-oxide (NQN), some exhibit a transformed phenotype restricted by temperature while others are not restricted by temperature in the expression of transformation. A working hypothesis is proposed suggesting that the phenotype of cells transformed by chemical carcinogens may be determined by the nature of the chemical reaction with the cell DNA. "Alkylating" carcinogens cause prevalently point mutation in bacteria (of the base substitution kind); in the case of transformation of mammalian cells temperature-sensitive phenotypes will be obtained. "Frameshift" carcinogens cause frameshift mutation in bacteria and cells transformed by this class of carcinogens will exhibit a transformed phenotype unrestricted by temperature.

Protection against malignant conversion of chemically induced benign skin papillomas to squamous cell carcinomas in SENCAR mice by a polyphenolic fraction isolated from green tea

Progression of benign tumors to malignant cancer is critical since cancerous lesions are capable of metastatic spread and eventually causing death. Inhibitors of the conversion process, therefore, would likely be useful as cancer chemopreventive agents. In this study, we assessed the protective effect of topical application of a polyphenolic fraction isolated from green tea (GTP) against spontaneous as well as benzoyl peroxide (BPO)- and 4-nitroquinoline-N-oxide (4-NQO)-enhanced malignant conversion of chemically induced skin papillomas in SENCAR mice. Papillomas were induced in SENCAR mice by topical application of 7,12-dimethylbenz(a)anthracene as a tumor-initiating agent followed by twice a week application of 12-O-tetradecanoylphorbol-13-acetate as a tumor-promoting agent. Beginning at the 20th week, when papilloma yield was stabilized, enhanced malignant conversion was achieved by twice weekly topical application of either BPO or 4-NQO, whereas spontaneous malignant conversion was associated with topical application of acetone. In these protocols, preapplication of GTP (6 mg/animal) 30 min prior to skin application of acetone, BPO, or 4-NQO resulted in 14, 31, and 29% protection, respectively, in terms of percentage of mice with carcinomas, and 20, 35, and 43% protection in terms of number of carcinomas/mouse. In these experiments, a BPO- and 4-NQO-enhanced rate of malignant conversion was also found to be decreased significantly by the skin application of GTP; however, such effects of GTP were less profound in the cases of spontaneous malignant conversion. The results of this study suggest that, in addition to its chemopreventive effects against tumor initiation and promotion stages of multistage carcinogenesis, green tea also possesses significant protective effects against tumor progression, specifically tumor progression induced by BPO and 4-NQO.

The N2-guanine adduct but not the C8-guanine or N6-adenine adducts formed by 4-nitroquinoline 1-oxide blocks the 3'-5' exonuclease action of T4 DNA polymerase

When O-acetyl-4-(hydroxyamino)quinoline 1-oxide (Ac-4HAQO) reacts with double-stranded DNA at 37 degrees C the major products, N2-guanine, C8-guanine, and N6-adenine adducts, are formed in the proportions of 5:3:2, respectively. When the reaction is carried out with single-stranded DNA at 0 degree C, the products are found in the ratio 1:7:2. Unique 174-bp DNA fragments were modified in these ways and used as substrates for the 3'-5' exonuclease activity of T4 DNA polymerase. The results obtained showed that the exonuclease is blocked by the N2-guanine adduct but not the other two adducts. Interpretation of the cleavage patterns suggested that the enzyme stopped 2 nucleotides before the N2-guanine adduct. The N2-guanine adduct lies in the minor groove of the DNA double helix, while the other two adducts are found in the major groove. Apparently, only the former hinders progression of the enzyme.

DNA damage activates transcription and transposition of yeast Ty retrotransposons

A set of genes isolated from Saccharomyces cerevisiae showed increased transcript levels after yeast had been exposed to ultraviolet (UV) light or 4-nitroquinoline-1-oxide (4NQO). Included among these DNA damage responsive (DDR) genes were members of the Ty retrotransposon family of yeast. Northern hybridization analysis indicated that maximal levels of a 5.6 kb transcript encoded by the Ty elements accumulated in cells after 4 to 6 h of exposure to 4NQO. The induced levels of transcripts varied from two- to tenfold for different Ty probes although similar kinetics and dose responses were observed for transcripts hybridizing to the different Ty family members. Pulse labeling experiments suggested that the accumulation of Ty transcripts was due, in part, to an increased rate of Ty message synthesis. Transposition of Ty elements to two target loci encoding distinct alcohol dehydrogenase enzymes, ADH2 and ADH4, was examined in cells exposed to increasing doses of UV light or 4NQO. The frequency of Ty insertion into these genetic regions following DNA damaging treatments increased by as much as 17-fold compared with untreated cells. These results provide direct evidence that transposable elements can be activated by physical and chemical mutagens/carcinogens and that transpositional mutagenesis is induced by these agents in S. cerevisiae.

Enhancing effect of high fat diet on 4-nitroquinoline 1-oxide-induced pulmonary tumorigenesis in ICR male mice

The effects of dietary high fat on 4-nitroquinoline 1-oxide (4NQO)-induced lung tumorigenesis were investigated in male ICR mice. Two groups of mice were initially given a single subcutaneous injection of 4NQO at a dose of 15 mg/kg and, thereafter, fed either 20% corn oil-supplemented diet or a standard basal diet. Two further groups were maintained on the high fat diet or standard diet without administration of 4NQO. Mice were killed at weeks 15, 18 and 25 and the incidence of lung tumors at each time point was found to be significantly increased in the 4NQO/high fat diet group as compared to the 4NQO/standard diet group in terms of both incidence of tumor-bearing mice and the number of lesions per mouse. The results thus indicate that dietary high fat can enhance 4NQO-induced lung tumorigenesis in mice.

Histomorphometric analysis of epithelial changes in chemically induced oral mucosal carcinogenesis in rats

Quantitative analysis of rat palatal mucosa after the carcinogen 4- nitroquinoline-1-oxide had been applied to the epithelium for varying periods of time showed that there was a significant increase in epithelial thickness, due largely to an increase in thickness of the basal compartment. This alteration was measurable before epithelial dysplasia could be recognised.

Ia+ epithelial dendritic cells during oral carcinogenesis in the rat

Epithelial dendritic cells (EDC) were examined during the induction and growth of oral squamous cell carcinomas in rats treated with the carcinogen 4-Nitroquinoline N-oxide (4NQO). Acetone-fixed frozen sections of the palate and tongue were stained using an indirect immunoperoxidase technique and a monoclonal antibody to rat Ia (MRC OX-6). After 6 months there was a significant increase in Ia+ EDC/mm2 in non-invasive palatal and lingual epithelium compared with untreated and solvent painted controls. Furthermore, after 9 months there were significantly more Ia+ EDC/mm2 in non-invasive lingual epithelium compared with invasive epithelium or the epithelium overlying/adjacent to squamous cell carcinomas of the tongue. Although there were no significant differences of Ia+ EDC/mm2 between infiltrating epithelium of lingual carcinomas and non-invasive epithelium overlying/adjacent to the tumour, these tissues did contain significantly more Ia+ EDC than lingual epithelium from either solvent-only or untreated controls. The results indicate that treatment with 4NQO stimulates an increase in Ia+ EDC numbers which, although remaining higher than in controls, is not maintained within, or adjacent to, sites of neoplastic change.

H-2-controlled genetic susceptibility to pulmonary adenomas induced by urethane and 4-nitroquinoline 1-oxide in A/Wy congenic strains

The genetic effect of the H-2 complex on the development of chemically induced pulmonary adenomas was clearly demonstrated in H-2 congenic strains with an A/Wy background which had a high susceptibility to pulmonary adenoma. A single subcutaneous injection of either urethane or 4-nitroquinoline 1-oxide was given to nine strains of mice. Among them, the number of adenoma foci per mouse was significantly higher in A/Wy (haplotype H-2a), A/J (H-2a), A.TL (H-2tl) and A.AL (H-2al) than in A.BY (H-2b), A.SW (H-2s), A.CA (H-2f) and A.TH (H-2t2) strains. In addition, the average number of adenoma foci in A/Wy (H-2a) was more than 20 times that in the B10.A (H-2a) strain. Thus, multiplicity of adenoma foci appeared to be regulated by at least two genes, one of which is located in the I or S region in the H-2 complex and the other in the non-H-2 genetic background. The genes in the H-2 complex were distinct from Pas-1 locus, which is probably identical to ptr.

The effect of iron deficiency on early oral carcinogenesis in the rat

In order to further investigate the known influence of iron deficiency on 4NQO oral carcinogenesis in the rat, groups of iron-deficient and iron-sufficient Charles River white rats were painted with carcinogen for 8 weeks or 14 weeks and then left untreated for 32 weeks or 26 weeks respectively. Tumour development and epithelial dysplasia were assessed at the time of killing. Animals painted for 14 weeks showed more severe dysplasia than those painted for 8 weeks, but no significant differences were noted between corresponding iron-deficient and iron-sufficient groups.

Oral epithelial atypia and acantholytic dyskeratosis in rats painted with 4-nitroquinoline N-oxide

Oral epithelial atypia and foci of acantholytic dyskeratosis (FAD) were investigated in 54 rats treated with the carcinogen 0.5% (w/v) 4-nitroquinoline-N-oxide in propylene glycol and in 18 rats treated with propylene glycol only. The palate of each animal was painted 3 times weekly for up to 9 months and rats were killed at monthly intervals. A gradual significant increase in the epithelial atypia indices of the palatal and lingual tissues (anterior and posterior of the intermolar tubercle) was observed with a maximum value of 17-22 of a possible 75 at 28-32 weeks. No significant differences were noted between the atypia indices of the palatal and lingual tissues. FAD were not evident in the palate or lingual tissues before 12 weeks and 16-24 weeks, respectively, and although the palate consistently showed more FAD compared with the lingual tissues the differences were not significant. Features of epithelial atypia and FAD were absent in the 18 control rats treated with propylene glycol only and in 8 untreated control animals. At 28 weeks of 4NQO treatment 2 of 5 rats, at 32 weeks 3 of 4 rats and at 36 weeks 3 of 3 rats had developed infiltrating squamous cell carcinomas in either/both the palate or tongue. The results suggest that epithelial dysplasia and acantholytic dyskeratosis may be late morphological features of a more fundamental change occurring earlier in the process of tumour development.

Verrucous hyperplasia and verrucous carcinoma of the rat oral mucosa. Experimental oral carcinogenesis using 4-nitroquinoline 1-oxide

Verrucous hyperplasia and carcinoma are recognized entities in the human pathology, but not documented experimentally. During application of the carcinogen 4-nitroquinoline 1-oxide to the oral cavity of rats three times a week for a maximum of 18 weeks an increasing frequency of verrucous hyperplasias and carcinomas were noted. The majority of the carcinomas were localized to the palate and 3/4 of these were verrucous carcinomas, with or without anaplastic transformation to infiltrating squamous cell carcinomas. The oral verrucous lesions have all the histological characteristics of their human counterparts. The present experimental study supports the idea that tobacco consumption may represent an important etiological factor in the development of human, oral verrucous carcinomas.

Biomimetic preparation and structure determination of QGI, one of the quinoline-DNA base adducts formed in cells treated with 4-nitroquinoline 1-oxide

One of the quinoline-DNA base adducts, QGI, formed in cells treated with 4-nitroquinoline 1-oxide, was readily prepared in vitro from GMP or dGMP and 4-hydroxy-aminoquinoline 1-oxide in the presence of ATP, L-serine, and seryl tRNA synthetase. Synthetic seryl-AMP could be substituted for the enzymatic activation system for QGI formation. Chemical and spectral analyses of the adduct thus prepared revealed that QGI can be formulated as N4-(guan-8-yl)-4-aminoquinoline 1-oxide, the structure of which is identical with the modified base structure involved in the deoxyguanosine-quinoline adduct, dGIII (nomenclature of Loucheux-Lefebvre et al.) obtained by the chemical modification of deoxyguanosine with monoacetyl and diacetyl derivatives of 4HAQO.

4 Nitroquinoline 1-oxide-induced carcinogenesis in the rat palate

Most reported studies of experimental oral cancer have been carried out in the hamster. This animal is not available in certain countries and there is controversy regarding its suitability as a model for experimental oral carcinogenesis. An attempt was made to reproduce an experimental oral cancer model in rats, using a protocol based on that described by Lekholm and Wallenius (1976). The carcinogen 4 nitroquinoline 1-oxide was applied to the palates of rats for periods of up to 24 weeks. Macroscopic and microscopic examination of carcinogen-treated palatal mucosa was carried out during the experimental period. Verrucous carcinoma-like lesions of the mid-palate and squamous carcinomas of the gingival mucosa were produced, beginning at 16 and 20 weeks respectively. A variety of other macroscopic and microscopic mucosal changes were also observed during the experimental period. The findings are discussed in relation to the work of others.

In vitro DNA reaction with an ultimate carcinogen model of 4-nitroquinoline-1-oxide: the 4-acetoxyaminoquinoline-1-oxide. Enzymatic degradation of the modified DNA

2-3H-Labelled 4-acetoxyaminoquinoline-1-oxide (Ac-4 HAQO), the ultimate carcinogen model of 4-nitroquinoline-1-oxide, was reacted in vitro with native and denatured DNA. We found that Ac-4 HAQO is 2- to 3-fold more reactive than diAc-4 HAQO, another ultimate carcinogen model of 4 NQO which was previously studied [Galiègue et al. (1980) Biochim. Biophys. Acta, 609, 383-391]. Ac-4 HAQO-modified DNA is thermally destabilized: when 1% of the bases of DNA were modified by Ac-4 HAQO, its melting temperature decreased 1.2 degrees C. Enzymatic degradation of Ac-4 HAQO-modified native and denatured DNA's to nucleosides was performed. The hydrolysates were analyzed, first with a simple chromatographic system, and then by h.p.l.c. The compounds recovered from the modified polymers were characterized by h.p.l.c. and a variation in their respective amounts as a function of the secondary structure of DNA was observed. Especially, the N-(deoxyguanosin-(C8-yl)-4-aminoquinoline-1-oxide, the so called dG III adduct, was recovered from DNA, and its amount was evaluated to be approximately 3.5-fold greater in the case of denatured DNA than in the case of native DNA.

Malignancy of 4NQO-induced oral squamous cell carcinomas in the rat

Oral carcinomas in the rat were induced by painting the hard palate three times a week for 22 weeks with the carcinogen 4-nitrochinoline N-oxide (4NQO). The induction resulted almost consistently in highly differentiated squamous cell carcinomas, often showing excessive keratinization. No metastases were recorded from any of the primary tumours. Transplantation experiments, performed on 23 out of a total of 26 induced carcinomas, generally yielded a negative result, only one tumour being transplantable. The biological significance of these features of 4NQO-induced oral rat carcinomas are discussed.

Equilibrium binding of carcinogens and antitumor antibiotics to DNA: site selectivity, cooperativity, allosterism

The equilibrium binding of the carcinogens N-hydroxy-N-acetyl-2-amino-fluorene (HAAF) and 4-nitroquinoline-1-oxide (NQO) to phi X174RF DNA have been studied by phase partition techniques. Both molecules bind in a cooperative manner with only a few carcinogen molecules binding to each phi X174RF DNA molecule. The binding data for both HAAF and NQO fit a model in which two carcinogens cluster into a small number of sites--four sites for HAAF and twelve sites for NQO. Phase partition techniques were also used to study the binding of actinomycin D to both calf thymus DNA and poly (dG-dC) . poly (dG-dC) at much lower r values than had been previously reported. These data exhibit humped Scatchard plots which are indicative of cooperative binding; the overall shape of the Scatchard plots are consistent with a model for drug induced allosteric transitions in the DNA structure. The cooperativity in the actinomycin D binding to calf thymus DNA increases with decreasing sodium chloride concentration, suggesting a role for DNA flexibility in allosteric binding.

Clastogenic effect of 4-nitroquinoline-1-oxide on swine urothelial cells in culture

Swine bladder epithelial cells in culture were treated with 4-nitroquinoline-1-oxide (4NQO) for 4 hr with three different concentrations to examine dose-dependent effects. To study time course effects, they were treated with one concentration for 4 hr and then incubated in 4NQO-free medium for three different periods before harvesting. Three different effects were recorded: (i) a suppression of mitotic activity that was dose-dependent and which continued for more than 30 hr posttreatment; (ii) no marked changes in the proportions of different ploidy classes; and (iii) chromatid gaps, breaks, and exchanges that were dose-dependent. This clastogenic effect decreased with increasing time after treatment.

Nucleic acid base and carcinogen metabolite specificities during intercalative interactions between DNA and 4-nitroquinoline 1-oxide

Intercalation of the carcinogen 4-nitroquinoline 1-oxide (4-NQO) or its metabolic intermediate forms, probably precedes the covalent bond formation of the ultimate carcinogenic form with DNA. A 'complete' empirical-potential energy description of the base-sequence and metabolite specificities of the 4-NQO intercalation process is presented in this work. The important force and structural interaction components are depicted via decomposed energy functions. Energy-minimized intercalated complexes are presented and indicate several interesting characteristics. It is clear that the various intercalated quinoline-metabolites do not generally enter into 'strictly' parallel-planar stacked orientations (unlike the structurally rigid ethidium-intercalated complexes). Intercalation is energetically permitted for six of seven quinoline-metabolites (QMS) studied, although, intercalation into to Pyr(3'-5')Pur sequences is preferred over Pur(3'-5'1Pyr sequences. The three quinoline-metabolites that are more energetically favoured to undergo intercalation than the parent form are also known to enter into the greatest amount of covalent interactions with DNA and its constituents. Thus the present work further suggests the existence of a two-step binding mechanism: intercalation followed by covalent reaction.

Interactions of 4-nitroquinoline 1-oxide with deoxyribodinucleotides

The interactions of 4-nitroquinoline 1-oxide (NQO), a potent mutagen and carcinogen, with several self- and non-self-complementary deoxydinucleotides were probed by using absorption spectra of the charge transfer bands and 1H and 13C NMR spectra. Absorption spectra were analyzed by using Benesi-Hildebrand-type equations to yield stoichiometries and equilibrium constants of complex formation. Non-self complementary dimers form weak l:1 complexes [dpTpG:NQO, K(25 degrees C) = 22 M-1] while self-complementary dimers form strong 2:1 complexes [dpCpG)2:NQO, K(25 degrees C) = 2.2 X 10(4) M-2]. A mixture of dpTpG and dpCpA with NQO gives a 2:1 complexes [dpCpG)2:NQO, K(25 degrees C) = 2.2 X 10(4) M-2]. A mixture of dpTpG and dpCpA, K(25 degrees C) = 8.6 X 10(3) M-2]. Analyses of the changes in 13C and 1H NMR chemical shifts with complex formation gave approximate orientations for the intercalation of NQO with self-complementary dimer minihelixes. In the (dpCpG)2:NQO and (dpGpC)2:NQO complexes, the NO2 group of NQO probably lies in the major grove and the NO2, NO containing NQO ring is stacked near the purine imidazole ring. In the (dpTpA)2:NQO and (dpApT)2NQO complexes, the NO2 seems to project into the minor grove and the NQO benzenoid ring is over the purine imidazole ring.

Antibacterial activity of nitroxoline and sulphamethizole alone and in combination in urinary tract infections

In vitro studies on the antibacterial activity of nitroxoline and sulphamethizole, alone and in combination, were undertaken and minimal inhibitory concentrations (MICs) determined on a range of urinary pathogens. Eighty per cent of the strains tested were sensitive to less than or equal to 16 mg/l of nitroxoline, and all strains, including Pseudomonas aeruginosa and Streptococcus faecalis, were sensitive to less than or equal to 64 mg/l of nitroxoline. No synergism could be demonstrated with sulphamethizole, but the combination was antagonistic when tested against strains of Ps. aeruginosa and Strep. faecalis. An in vivo study on 10 volunteers showed excellent urinary levels of nitroxoline and sulphamethizole after an oral dose of 160 mg of each agent, and 6-hour urinary nitroxoline levels were greater than or equal to 64 mg/l in 9 of the 10 subjects, and sulphamethizole levels were greater than or equal to 64 mg/l in all 10 subjects. Laboratory findings suggest that nitroxoline and sulphamethizole are both suitable agents for use in urinary tract infections caused by organisms sensitive to these agents, but there appears to be litte advantage in using them in combination.

Cytologic comparison of a human fibroblast culture chemically transformed in vitro with its non-neoplastic parent cell strain

Paired cultures of glutaraldehyde-fixed, nontransformed and chemically-transformed human fibroblasts were examined by quantitative microscopy. Significant differences were found to exist between the two cell types with respect to projected cell and nuclear area, dry weight distribution, cell cytoplasmic thickness and intracellular distribution of protein. Quantitative measurements of nuclear DNA failed to reveal a major difference between the two cell populations.

Carcinogenicity of 4-nitrosoquinoline 1-oxide and its possible role in carcinogenesis by 4-nitroquinoline 1-oxide

4-Nitrosoquinoline 1-oxide induced malignant tumors at the subcutaneous site of injection in mice. It affected Escherichia coli to induce the so-called UV-type lesion in cellular DNA. DNA base-quinoline adducts produced by the treatment of mammalian cellular DNA with this carcinogen were proved to be identical with those obtained by the action of 4-nitroquinoline 1-oxide. Although this carcinogen was reactive enough to modify DNA chemically by itself, a different DNA modification took place in a chemical process from thos obtained in the in vivo process.

Interactions of 4-nitroquinoline 1-oxide with four deoxyribonucleotides

The interactions of 4-nitroquinoline 1-oxide (NQO) with the four 5'-deoxyribonucleotides were probed using absorption spectra of the charge transfer bands and 1H and 13C nuclear magnetic resonance (NMR) spectra of nucleotide-NQO mixtures. Spectral data yielded equilibrium constants (K(dpG:NQO) = 16 M-1, K(dpA:NQO) = 12 M-1, K(dpT:NQO) = K(dpC:NQO) = 4 M-1) which suggest the preference of NQO for the guanine residue in a DNA. This is in agreement with the data of Okano, T., et al. [(1969) Gann 60, 295]. From 13C and 1H NMR data on nucleosides, a structure for the dpG:NQO complex is proposed.

Specific changes in the collagen phenotype of BALB 3T3 cells as a result of transformation by sarcoma viruses or a chemical carcinogen

Radioactive proline-labeled procollagen, accumulated during a 3-hr incubation of normal and transformed BALB 3T3 cultures, was treated with pepsin and the resulting collagen components were analyzed by carboxymethyl-cellulose chromatography and sodium dodecyl sulfate/polyacrylamide gel electrophoresis in the presence or absence of reducing agent. Collagen in the medium of three subclones of BALB 3T3 A-31 that exhibited contact-inhibition of growth at confluence, as well as in the medium of one that did not, consisted of alpha(1) and alpha(2) subunits in the ratio of 3:1, suggesting that 3T3 cells synthesize type I collagen, [alpha(1)(I)](2)alpha(2), and another type, which we have designated X, composed of alpha(1) chains, which may or may not be identical to alpha(1)(I). Culture medium from 3T3 transformed by Kirsten or Moloney sarcoma virus contained type I collagen and another type differing from I and X and designated as type Y. The latter appeared to be similar to type III collagen [alpha(1)(III)](3), since it contained intrahelical disulfide bonds. Analysis of intracellular collagen also demonstrated the presence of type III in Ki-3T3 and its absence from 3T3 cells. Collagen components from the medium of a simian virus 40 transformant were identical to those of the contact-inhibited clones, while the collagen from a 4-nitroquinoline-1-oxide-induced transformant was composed mainly of two components differing from alpha(1)(I), alpha(2), or alpha(1)(III). These results suggest that the type of collagen accumulated in transformed cell cultures may be specifically related to the transforming agent.

Main binding sites of the carcinogen, 4-nitroquinoline 1-oxide in nucleic acids

4-Hydroxyaminoquinoline 1-oxide, the reduced metabolite of 4-nitroquinoline 1-oxide, was reacted with homopolyribonucleotides through the catalysis of an activating enzyme. It bound specifically to poly(G), poly(A) and poly(X) but negligibly to poly(C), poly (U) and poly(I). Chromatographic analysis of the acid hydrolysates of carcinogen-bound polynucleotides revealed that the reaction of the carcinogen with polynucleotides yielded two guanine, one adenine and two xanthine adducts. The same kinds of guanine and adenine adducts were found in DNA or RNA isolated from Escherichia coli and mammalian cells that had been exposed to the carcinogen. Analysis of nucleic acids isolated from 4-hydroxyaminoquinoline 1-oxide-treated cells revealed that 4-hydroxy-aminoquinoline reacts in vivo preferentially with guanines, to a less, but significant, extent with adenines and not significantly with pyrimidines.

Interval effect of beta-irradiation and subsequent 4-nitroquinoline 1-oxide painting on skin tumor induction in mice

Skin tumors were produced in female ICR mice by 90Sr-90Y beta-irradiation and subsequent 4-nitroquinoline 1-oxide painting. The doses were chosen so as to produce no tumors with a single agent alone; the interval between two treatments ranged from 11 to 408 days. The tumor induction rate was found to be at almost the same level (average, 12.4%) for each interval. The results indicate the persistence of the latent carcinogenic alterations in the beta-irradiated mouse skin.