Removal of As(III)/As(V) from aqueous solution using newly developed thiosalicylic acid coated magnetite [TSA@Fe3O4] nanoparticles.

The aim of this study was to develop an affordable adsorption methodology for removal of As(III)/As(V) from contaminated water. Herein, novel adsorbent TSA@Fe3O4 nanoparticles (NPs) were synthesized by decorating thiosalicylic acid (TSA) on magnetite nanoparticles (Fe3O4 NPs) and employed for removal of As(III)/As(V) species from artificially contaminated natural water systems. TSA@Fe3O4 NPs demonstrated excellent adsorption efficiency (AE) and 98% of As(V) and 93% of As(III) was removed at optimized experimental conditions. The adsorption kinetic and equilibrium isotherm studies were conducted preferentially for As(III) adsorption. Adsorption followed the pseudo-second-order kinetic (R2 = 99%) and adsorption data fitted well in Langmuir isotherm model (R2 = 99%) and maximum adsorption capacity (Qmax = 34.1 mg/g) was calculated for 5 mg/L of As(III) by using 10 mg of TSA@Fe3O4 NPs. The effect of pH, contact time, adsorption dosages, and competitive anions was also examined to identify optimum experimental conditions. The adsorbent was characterized by advanced instrumental techniques to investigate the physicochemical properties and stability of NPs. To comprehend the interactions of As(III) species with adsorbent NPs, NPs were analyzed using XPS and Raman spectroscopy techniques. Both the techniques confirmed that As(III) and As(V) species present simultaneously on adsorbent surface. The TSA@Fe3O4 was regenerated using 0.1 M NaOH. The findings of this study suggested that TSA@Fe3O4 NPs could be considered a potential adsorbent for effective remediation of As(III) and As(V) from contaminated natural water systems.

Silibinin Radiosensitizes EGF Receptor-knockdown Prostate Cancer Cells by Attenuating DNA Repair Pathways.

Emergence of radioresistance in prostate cancer (PCa) cells is a major obstacle in cancer therapy and contributes to the relapse of the disease. EGF receptor (EGFR) signaling plays an important role in the development of radioresistance. Herein, we have assessed the modulatory effects of silibinin on radiation-induced resistance via DNA repair pathways in EGFR-knockdown DU145 cells. shRNA-based silencing of EGFR was done in radioresistant human PCa DU145 cells and effects of ionizing radiation (IR) and silibinin were assessed using clonogenic and trypan blue assays. Furthermore, radiosensitizing effects of silibinin on PCa in context with EGFR were analyzed using flow cytometry, comet assay, and immunoblotting. Silibinin decreased the colony formation ability with an increased death of DU145 cells exposed to IR (5 Gray), with a concomitant decrease in Rad51 protein expression. Silibinin (25 µM) augmented the IR-induced cytotoxic effect in EGFR-knockdown PCa cells, along with induction of G2/M phase cell cycle arrest. Further, we studied homologous recombination (HR) and non-homologous end joining (NHEJ) pathways in silibinin-induced DNA double-strand breaks in EGFR-knockdown DU145 cells. Silibinin down-regulated the expression of Rad51 and DNA-dependent protein kinase proteins without any considerable effect on Ku70 and Ku80 in IR-exposed EGFR-knockdown PCa cells. The pro-survival signaling proteins, phospho-extracellular signal-regulated kinases (ERK)1/2, phospho-Akt and phospho-STAT3 were decreased by silibinin in EGFR-deficient PCa cells. These findings suggest a novel mechanism of silibinin-induced radiosensitization of PCa cells by targeting DNA repair pathways, HR and NHEJ, and suppressing the pro-survival signaling pathways, ERK1/2, Akt and STAT3, in EGFR-knockdown PCa cells.

EGFR-mediated Rad51 expression potentiates intrinsic resistance in prostate cancer via EMT and DNA repair pathways.

AIM: To study the role of EGFR signaling in regulation of intrinsic resistance in prostate cancer. MATERIALS AND METHODS: Radioresistant prostate carcinoma DU145 and PC-3 cells were used to study the effect of shRNA-mediated knockdown of EGFR on intrinsic radioresistance mechanisms. Semi-quantitative PCR, western blotting, growth kinetics, colony formation, transwell migration, invasion and trypan blue assays along with inhibitors erlotinib, NU7441, B02, PD98059 and LY294002 were used. KEY FINDINGS: EGFR knock-down induced morphological alterations along with reduction in clonogenic potential and cell proliferation in DU145 cells. Migratory potential of prostate cancer cells were reduced concomitant with upregulation of epithelial marker, E-cadherin and decreased expression of mesenchymal markers, vimentin and snail. Further, EGFR knock-down decreased the expression of Rad51 and DNA-PK at mRNA as well as protein levels. Likewise, erlotinib, an EGFR inhibitor, and NU7441, a DNA-PK inhibitor increased the expression of E-cadherin and decreased the level of vimentin. Both these inhibitors also decreased the levels of DNA damage regulatory protein Rad51. Further, Rad51 inhibitor, B02, inhibited the clonogenic potential, cell migration and reduced the expression of vimentin, Ku70 and Ku80, and also, B02 radiosensitized DU145 cells. EGFR-regulated expression of Rad51 was found to be mediated via PI3K/Akt and Erk1/2 pathways. SIGNIFICANCE: EGFR was found to regulate DNA damage repair, survival and EMT responses in prostate cancer cells through transcriptional regulation of Rad51. A novel role of EGFR-Erk1/2/Akt-Rad51 axis through modulation of EMT and DNA repair pathways in prostate cancer resistance mechanisms is suggested.

Simulated microgravity triggers DNA damage and mitochondria-mediated apoptosis through ROS generation in human promyelocytic leukemic cells.

The weightlessness or microgravity, a physical factor in space, may adversely affect the health of the space travellers or astronauts. The knowledge about the effect of microgravity on human cancer cells is very limited and poorly understood. Here, we employed rotary cell culture system (RCCS) to induce simulated microgravity (SMG) and examined its effects on human promyelocytic leukemic HL-60 cells. These cells were grown in normal gravity condition (1g) for control purpose. The 72 h exposure of cells to SMG decreased cell proliferation and viability which were accompanied by the reduced expression of PCNA and phosphorylated ERK1/2 and AKT proteins. SMG increased the DNA damage as well as the expression of DNA damage sensing proteins including ATM, ATR, Chk1, Chk2 and γH2A.X. The expression of AP1, XRCC1 and APEX1 regulating BER, XPC regulating NER and MLH1 and PMS2 regulating MMR were downregulated. However, SMG increased the expression of Ku70/80, DNA-PK and Rad51, regulating NHEJ and HR. SMG induced apoptosis and increased the levels of cleaved-poly-(ADP-ribose) polymerase and cleaved-caspase-3. An increase in Bax/Bcl-2 ratio and dissipation of mitochondrial membrane potential were also observed. SMG enhanced reactive oxygen species (ROS) formation which led to the enhanced DNA damage and apoptotic cell death. Overall, SMG induced ROS, DNA damage and differential expression of DNA repair genes, and altered the overall DNA repair capacity which may activate ATM/ATR-Chk1/2 and Ku70/80 and DNA-PK-mediated apoptotic cell death.

Preparation of a novel environmentally friendly hydrophobic deep eutectic solvent ChCl-THY and its application in removal of hexavalent chromium from aqueous solution.

A liquid-liquid extraction methodology was developed for the removal of Cr(VI) from contaminated water using a novel green hydrophobic deep eutectic solvent (DES) as an efficient sole extracting agent. The hydrophobic DES was obtained by mixing choline chloride and thymol in 1:4 molar ratio at 70°C for 10 min and was denoted as ChCl-THY(1:4). The ChCl-THY(1:4) works efficiently for removal of high (20 mg/L) and low (500 µg/L) concentration of Cr(VI) from artificially contaminated natural water with >95% extraction efficiency (E%) at optimized reaction conditions (pH 2-6, 40°C). The DES was characterized by 1 H NMR and FTIR spectroscopy, and the data suggest that interaction occurs between Cl- ion of choline chloride and H atoms of thymol molecules. Physicochemical properties such as density, melting point, moisture, and solubility were studied and discussed. Herein, no sharp melting point was observed for ChCl-THY(1:4) in DSC curve. DES was regenerated using 0.1 M NaOH as stripping agent, and 50%-60% extraction efficiency could be attained in the next cycle. A plausible mechanism of interaction between Cr(VI) species and DES was also explored with the help of FTIR spectroscopy. PRACTITIONER POINTS: A novel hydrophobic DES (ChCl-THY) is prepared by mixing choline chloride and thymol at 1:4 molar ratio. ChCl-THY(1:4) is employed for the first time as sole extracting agent to remove the Cr(VI) from contaminated aqueous solution. >95% extraction efficiency was achieved by ChCl-THY(1:4) in natural water conditions at µg/L and mg/L level of contamination. Both the component used to prepare the DES are naturally abundant; hence, DES is not toxic for biota. The element present in natural water did not show any interference with extraction of Cr(VI).

Flavonoids inhibit chronically exposed arsenic-induced proliferation and malignant transformation of HaCaT cells.

BACKGROUND: Apart from exposure to UV-radiation, studies show relationship between skin cancer and chronic ingestion of arsenic through drinking water. Chemopreventive strategies could help in reducing the toxic effects of arsenic and arsenic-induced skin cancer. METHODS: Cytotoxicity of arsenic on human skin keratinocytes HaCaT cells was evaluated using MTT and trypan blue assays. Arsenic-induced malignant transformant HaCaT cells were selected through soft agar colony assay. Cell cycle progression was analyzed through FACS. The expressions of genes modulated by arsenic were studied through RT-PCR. RESULTS: The lower concentrations (0.1-0.5 µmol/L) of arsenic were non-toxic and transformed HaCaT cells on chronic exposure, and also enhanced the cell proliferation. Silibinin and fisetin reduced the arsenic-induced cell proliferation and malignant transformation. A slight increase in G2-M phase cell population was also observed. The anti-proliferation effects of flavonoids on HaCaT transformants were further enhanced when combined with gamma radiation. Chronic and acute exposure to arsenic modulated the expression of transformation-associated genes including Bcl-2A1, IGFL-1, Rab31, and TNC in HaCaT cells. CONCLUSIONS: Chronic exposure to lower arsenic concentrations caused malignant transformation of skin keratinocytes and that effect was attenuated by flavonoids silibinin and fisetin. Thus, chemoprevention could reduce arsenic-caused detrimental effects on skin cells.