Hydrochemical characteristics and potential health risks of nitrate, fluoride, and uranium in Kota district, Rajasthan, India.

This study examines the uranium, fluoride, and nitrate dispositions in groundwater as well as potential health risks in Kota district, Rajasthan, India. Total 198 groundwater samples were collected in both dry and wet periods and analyzed for physicochemical parameters along with U, F-, and NO3- using standard methods. Results indicate that the electrical conductivity, total dissolved solids, total hardness, alkalinity, Ca2+, Mg2+, HCO3-, Cl-, NO3-, and F- exceed the WHO standard limits of drinking water in both periods. Uranium concentration is at the broader of drinking water permissible limit (30 µg/L) and found about 1.05 times more. Nitrate and fluoride concentrations ranged from 9.8 to 412.0 mg/L and 0.1 to 4.0 mg/L for the dry season, while in the wet period, they varied from 10.0 to 954.0 mg/L and 0.1 to 3.5 mg/L, respectively. Correlation studies show a significantly strong positive correlation between uranium and total alkalinity and carbonate. Natural background levels (NBLs) were explored to assess the source of groundwater pollution. It shows that the second inflection points of NBLs estimated for NO3-, F-, and U are about 168 mg/L, 1.2 mg/L, and 7.3 µg/L, respectively, during the experimental period. The USEPA technique was used to evaluate the non-carcinogenic health risks associated with consuming the NO3- and F--contaminated groundwater. The health risks in Kota district show that children are more at risk than adults. The risk assessment of uranium reveals that the excess cancer risk (ECR) and hazard quotient (HQ) are found to be below the standard limits, but a high concentration of uranium (31.6 µg/L) is observed at Amarpura village of Digod block. This study will provide a baseline of uranium, fluoride, and nitrate dispositions in groundwater for simulating mass transport model and safe use of drinking water.

Development of highly selective fluorescent ferrocenyl-iminopyridine chemosensor for biologically relevant Fe3.

Design, synthesis, characterization, and ion detection studies of two ferrocene-appended Schiff bases namely N-(2-[ferrocenylamino]ethyl)-5-nitropyridin-2-amine (1) and ferrocenylamino-1H-imidazole-4-carboxamide (2) been reported. Both the chemosensors have been thoroughly characterized using Fourier transfer infrared, 1 H and 13 C nuclear magnetic resonance, high resolution mass spectrometry, and ultraviolet/visible (UV/visible) and fluorescence spectral techniques. Probes 1 and 2 were designed with the aim of appending the ferrocenyl group with pyridine ring having an amine substitution (for 1) and imidazole ring with an amide substitution (for 2). Interaction of these probes with a series of cations and anions was examined through UV/vis and fluorescence spectral techniques. Probe 2 exhibited an insignificant response towards anions and loss of selectivity for cations, whereas 1 displayed highly selective detection towards biologically important Fe3+ in 2:1 (probe:cation) stoichiometry. Notably, none of the cations and anions could interfere the selectivity of Fe3+ ensured by 1 in aqueous medium. The limit of detection for Fe3+ detection using 1 was determined to be 0.2 ppm. The results strongly suggest that 1 could find promising future application as a chemosensor for Fe3+ in biological systems for quantification and qualitative analysis.

A zinc (II) complex comprising an aminoethyl-nitropyridine-derived N,N,O-donor Schiff base ligand serves as an efficient ON-OFF probe for Cu(II).

A new fluorescent zinc (II) complex-based probe 1 encompassing a Schiff's base (E)-2-methoxy-6-((2-[5-nitropyridin-2-ylamino]ethylimino)methyl)phenol (HL) was designed, synthesized, and used for the highly selective detection of Cu2+ . Ligand HL and complex 1 were characterized using various spectroscopic techniques such as 1 H, 13 C-NMR, and FTIR spectroscopy, high-resolution mass spectronomy (HRMS), UV/visible light spectroscopy, and fluorescence studies. Ligand HL did not exhibit any considerable change in fluorescence in the presence of various cations. Notably, its Zn(II) complex 1 exhibited highly selective 'TURN-OFF' fluorescence signalling towards Cu2+ that remained uninterrupted with competing analytes. Probe 1 interacted with Cu2+ in 1:2 (1:Cu2+ ) stoichiometry as estimated through a Job's plot. Moreover, the selectivity of 1 was further confirmed through the interaction of the 1 + Cu2+ complex with some possible interfering metal ions inducing an insignificant response. Additionally, the association and quenching constant were determined to be 3.30 × 104 M-1 and 0.21 × 105 M-1 through the Benesi-Hildebrand method and Stern-Volmer plot, respectively.

Novel DNA methyltransferase-1 (DNMT1) depleting anticancer nucleosides, 4'-thio-2'-deoxycytidine and 5-aza-4'-thio-2'-deoxycytidine.

PURPOSE: Currently approved DNA hypomethylating nucleosides elicit their effects in part by depleting DNA methyltransferase I (DNMT1). However, their low response rates and adverse effects continue to drive the discovery of newer DNMT1 depleting agents. Herein, we identified two novel 2'-deoxycytidine (dCyd) analogs, 4'-thio-2'-deoxycytidine (T-dCyd) and 5-aza-4'-thio-2'-deoxycytidine (aza-T-dCyd) that potently deplete DNMT1 in both in vitro and in vivo models of cancer and concomitantly inhibit tumor growth. METHODS: DNMT1 protein levels in in vitro and in vivo cancer models were determined by Western blotting and antitumor efficacy was evaluated using xenografts. Effects on CpG methylation were evaluated using methylation-specific PCR. T-dCyd metabolism was evaluated using radiolabeled substrate. RESULTS: T-dCyd markedly depleted DNMT1 in CCRF-CEM and KG1a leukemia and NCI-H23 lung carcinoma cell lines, while it was ineffective in the HCT-116 colon or IGROV-1 ovarian tumor lines. On the other hand, aza-T-dCyd potently depleted DNMT1 in all of these lines indicating that dCyd analogs with minor structural dissimilarities induce different DNMT1 turnover mechanisms. Although T-dCyd was deaminated to 4'-thio-2'-deoxyuridine, very little was converted to 4'-thio-thymidine nucleotides, suggesting that inhibition of thymidylate synthase would be minimal with 4'-thio dCyd analogs. Both T-dCyd and aza-T-dCyd also depleted DNMT1 in human tumor xenografts and markedly reduced in vivo tumor growth. Interestingly, the selectivity index of aza-T-dCyd was at least tenfold greater than that of decitabine. CONCLUSIONS: Collectively, these data show that 4'-thio modified dCyd analogs, such as T-dCyd or aza-T-dCyd, could be a new source of clinically effective DNMT1 depleting anticancer compounds with less toxicity.

Inhibition of herpesvirus replication by 5-substituted 4'-thiopyrimidine nucleosides.

A series of 4'-thionucleosides were synthesized and evaluated for activities against orthopoxviruses and herpesviruses. We reported previously that one analog, 5-iodo-4'-thio-2'-deoxyuridine (4'-thioIDU), exhibits good activity both in vitro and in vivo against two orthopoxviruses. This compound also has good activity in cell culture against many of the herpesviruses. It inhibited the replication of herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus with 50% effective concentrations (EC(50)s) of 0.1, 0.5, and 2 microM, respectively. It also inhibited the replication of human cytomegalovirus (HCMV) with an EC(50) of 5.9 microM but did not selectively inhibit Epstein-Barr virus, human herpesvirus 6, or human herpesvirus 8. While acyclovir-resistant strains of HSV-1 and HSV-2 were comparatively resistant to 4'-thioIDU, it retained modest activity (EC(50)s of 4 to 12 microM) against these strains. Some ganciclovir-resistant strains of HCMV also exhibited reduced susceptibilities to the compound, which appeared to be related to the specific mutations in the DNA polymerase, consistent with the observed incorporation of the compound into viral DNA. The activity of 4'-thioIDU was also evaluated using mice infected intranasally with the MS strain of HSV-2. Although there was no decrease in final mortality rates, the mean length of survival after inoculation increased significantly (P < 0.05) for all animals receiving 4'-thioIDU. The findings from the studies presented here suggest that 4'-thioIDU is a good inhibitor of some herpesviruses, as well as orthopoxviruses, and this class of compounds warrants further study as a therapy for infections with these viruses.

Activities of certain 5-substituted 4'-thiopyrimidine nucleosides against orthopoxvirus infections.

As part of a program to identify new compounds that have activity against orthopoxviruses, a number of 4'-thionucleosides were synthesized and evaluated for their efficacies against vaccinia and cowpox viruses. Seven compounds that were active at about 1 microM against both viruses in human cells but that did not have significant toxicity were identified. The 5-iodo analog, 1-(2-deoxy-4-thio-beta-d-ribofuranosyl)-5-iodouracil (4'-thioIDU), was selected as a representative molecule; and this compound also inhibited viral DNA synthesis at less than 1 microM but only partially inhibited the replication of a recombinant vaccinia virus that lacked a thymidine kinase. This compound retained complete activity against cidofovir- and ST-246-resistant mutants. To determine if this analog had activity in an animal model, mice were infected intranasally with vaccinia or cowpox virus and treatment with 4'-thioIDU was given intraperitoneally or orally twice daily at 50, 15, 5, or 1.5 mg/kg of body weight beginning at 24 to 120 h postinfection and was continued for 5 days. Almost complete protection (87%) was observed when treatment with 1.5 mg/kg was begun at 72 h postinfection, and significant protection (73%) was still obtained when treatment with 5 mg/kg was initiated at 96 h. Virus titers in the liver, spleen, and kidney were reduced by about 4 log(10) units and about 2 log(10) units in mice infected with vaccinia virus and cowpox virus, respectively. These results indicate that 4'-thioIDU is a potent, nontoxic inhibitor of orthopoxvirus replication in cell culture and experimental animal infections and suggest that it may have potential for use in the treatment of orthopoxvirus infections in animals and humans.

Synthesis and anticancer evaluation of 4'-C-methyl-2'-fluoro arabino nucleosides.

As part of an ongoing program to develop novel antitumor agents over the years, we have synthesized and evaluated a number of 4'-C-substituted nucleosides. A few years ago, we reported the first synthesis of 4'-C-hydroxymethyl-2'-fluoro arabino nucleosides, which did not exhibit any cytotoxicity. In our exploration of related compounds, we synthesized and evaluated the 4'-C-methyl-2'-fluoro arabino nucleosides in both the purine and pyrimidine series. In the pyrimidine series, 1-(4-C-methyl-2-fluoro-beta-D-arabinofuranosyl) cytosine (13) was found to be highly cytotoxic and had significant antitumor activity in mice implanted with human tumor xenografts. The synthesis and anticancer activity of this series of nucleosides are reported.

Clofarabine acts as radiosensitizer in vitro and in vivo by interfering with DNA damage response.

PURPOSE: Combination treatment with radiotherapy and chemotherapy has emerged as the dominant form of cancer adjuvant regimens in recent years. Clofarabine, a newly approved drug for pediatric leukemia, is a second-generation purine nucleoside analogue that can block DNA synthesis and inhibit DNA repair. Therefore, we hypothesized that clofarabine could work synergistically with radiotherapy to increase the tumor cell response. METHODS AND MATERIALS: The effects of clofarabine on radiosensitivity have been established in several tumor cell lines in vitro and in vivo using colony-forming assays and tumor xenografts. The effect of clofarabine on the DNA damage response was also studied in vitro by measuring gamma-H2AX focus formation. RESULTS: Clonogenic survival was significantly reduced in irradiated cells treated with clofarabine, demonstrating the strong radiosensitizing effect of clofarabine. Furthermore, clofarabine displayed a radiosensitizing effect that was greater than gemcitabine or 5-fluorouracil. We also found that low doses of clofarabine can prolong the presence of radiation-induced gamma-H2AX nuclear focus formation, and high doses of clofarabine can induce DNA double-strand breaks, suggesting that clofarabine can interfere with DNA damage response pathways. In addition, clofarabine-induced radiosensitization was also established in vivo using a colorectal cancer model, DLD-1, in athymic nude mice. When combined with fractionated radiotherapy, a moderate dose of clofarabine led to a significant increase in tumor growth inhibition. CONCLUSION: Clofarabine acts as a powerful radiosensitizer both in vitro and in vivo by interfering with the DNA damage response.

Antiangiogenic activity of 4'-thio-beta-D-arabinofuranosylcytosine.

4'-Thio-beta-D-arabinofuranosylcytosine (T-araC), a new-generation deoxycytidine nucleoside analogue, showed significant efficacy against numerous solid tumors in preclinical studies and entered clinical development for cancer therapy. It is a structural analogue of cytarabine (araC), a clinically used drug in the treatment of acute myelogenous leukemia, which has no or very limited efficacy against solid tumors. In comparison with araC, the excellent in vivo activity of T-araC against solid tumors suggests that, in addition to inhibition of DNA synthesis, T-araC may target cellular signaling pathways, such as angiogenesis, in solid tumors. We studied T-araC and araC for their antiangiogenic activities in vitro and in vivo. Both compounds inhibited human endothelial cell proliferation with similar IC50s. However, only T-araC inhibited endothelial cell migration and differentiation into capillary tubules. T-araC also abrogated endothelial cell extracellular signal-regulated kinase (ERK) 1/2 phosphorylation, a key signaling molecule involved in cellular processes of angiogenesis. Results from chick chorioallantoic membrane angiogenesis assays revealed that T-araC significantly inhibited the development of new blood vessels in vivo, whereas araC showed much less effect. The findings of this study show a role of T-araC in antiangiogenesis and suggest that T-araC combines antiproliferative and antiangiogenic activity in one molecule for a dual mechanism of drug action to achieve the excellent in vivo efficacy against several solid tumors. This study also provides important information for optimizing dosage and sequence of T-araC administration in clinical investigations by considering T-araC as both an antiproliferative and an antiangiogenic agent.

Synthesis and biological activity of 4'-thio-L-xylofuranosyl purine nucleosides.

A series of some new 4'-thio-L-xylofuranosyl nucleosides were prepared and evaluated as potential anticancer agents. A versatile sugar intermediate for direct coupling with the purine moiety is also synthesized by an efficient and high-yielding route. Proof of structure and configuration at all chiral centers of the nucleosides was obtained by proton NMR. All target compounds were evaluated in a series of human cancer cell lines in vitro. The details of the synthesis of the carbohydrate precursor 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-L-xylofuranose (6) and corresponding purine nucleosides are presented in the manuscript.

Phosphorylation of 4'-thio-beta-D-arabinofuranosylcytosine and its analogs by human deoxycytidine kinase.

4'-thio-beta-D-arabinofuranosylcytosine (T-araC) exhibits excellent in vivo antitumor activity against a variety of solid tumors despite its structural similarity to beta-D-arabinofuranosylcytosine (araC), an agent which is poorly active against solid tumors in vivo. It is of great interest to elucidate why these compounds show a profound difference in antitumor activity. Because deoxycytidine kinase (dCK) is the critical enzyme in the activation of both compounds, here we report the differences in the substrate characteristics with human dCK between these compounds. The catalytic efficiency (V(max)/K(m)) of araC was 100-fold higher than that of T-araC using either ATP or UTP as the phosphate donor. However, V(max) values of araC and T-araC were similar when UTP was the phosphate donor. Since UTP is believed to be the true phosphate donor for dCK in intact cells, these data indicated that the rates of phosphorylation of these two compounds at high pharmacologically relevant concentrations would be similar. This prediction was confirmed in intact cell experiments, which supported the hypothesis that UTP is the physiological phosphate donor for dCK phosphorylation in cells. The relative lack of importance of phosphate donor to the phosphorylation of T-araC by dCK revealed important insights into the activation of this compound in human cells at pharmacological doses. These studies indicated that replacement of the 4'-oxygen with sulfur significantly reduced the substrate activity of nucleoside analogs with dCK and that the superior activity of T-araC with respect to araC against solid tumors was not due to superior activity with dCK.

Synthesis and anti-cancer activity of some novel 5-azacytosine nucleosides.

1-O-Acetyl-2-deoxy-3,5-di-O-toluoyl-4-thio-D-erythro-pentofuranose and 2-deoxy-1,3,5-tri-O-acetyl-4-thio-L-threo-pentofuranose were coupled with 5-azacytosine to obtain alpha and beta anomers of nucleosides. All four nucleosides were reduced to the corresponding dihydro derivatives and deblocked to give target compounds. All eight target compounds were evaluated in a series of human cancer cell lines in culture. Only 2'-deoxy-4'-thio-5-azacytidine (3beta) was found to be cytotoxic in all the cell lines and was further evaluated in vivo. Details of the synthesis and biological activity are reported.