We have derived cells from the Chinese hamster V79 cell line by conditioning them with repeated low doses of hydrogen peroxide (H(2)O(2)). This mimics the physiological condition where cells are repeatedly exposed to low levels of oxidants. In an attempt to characterize such cells, we have exposed both conditioned cells (V79(C)) and the parental V79 cells (V79(P)) to different types of cytotoxic agents and compared their sensitivity to cell killing. The V79(C) cells were found to be stably resistant to killing by agents that produced toxicity through oxidative stress, e.g. H(2)O(2) and cisplatin. It was also found that the lipid peroxidation produced by these agents were considerably lower in the V79(C) cells. Thus, the difference in sensitivity could be due to lesser extent of damage to these cells. V79(C) cells had greater antioxidant defense through higher GSH content and greater activity of enzymes such as Cu-Zn superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), which provided protection from damage. Enzyme activities were also assayed at different times after treatment with various cytotoxic agents; there was a relatively large increase in SOD activity which perhaps plays a key role in determining the resistance of the V79(C) cells to killing.

The use of mobile phone related technologies will continue to increase in the foreseeable future worldwide. This has drawn attention to the probable interaction of radiofrequency electromagnetic radiation with different biological targets. Studies have been conducted on various organisms to evaluate the alleged ill-effect on health. We have therefore attempted to review those work limited to in vitro cultured cells where irradiation conditions were well controlled. Different investigators have studied varied endpoints like DNA damage, cell cycle arrest, reactive oxygen species (ROS) formation, cellular morphology and viability to weigh the genotoxic effect of such radiation by utilizing different frequencies and dose rates under various irradiation conditions that include continuous or pulsed exposures and also amplitude- or frequency-modulated waves. Cells adapt to change in their intra and extracellular environment from different chemical and physical stimuli through organized alterations in gene or protein expression that result in the induction of stress responses. Many studies have focused on such effects for risk estimations. Though the effects of microwave radiation on cells are often not pronounced, some investigators have therefore combined radiofrequency radiation with other physical or chemical agents to observe whether the effects of such agents were augmented or not. Such reports in cultured cellular systems have also included in this review. The findings from different workers have revealed that, effects were dependent on cell type and the endpoint selection. However, contradictory findings were also observed in same cell types with same assay, in such cases the specific absorption rate (SAR) values were significant.

Like likes like! A novel fluorescent C2 -symmetric guanosine-based dinucleoside has been engineered by chemical ligation of two guanosine units with a biocompatible dansyl tag. The nucleoside exhibits high selectivity for c-myc G-quadruplex DNA through fluorescence enhancement over duplex DNA and other promoter G-quadruplexes (see scheme). It stains the nucleus preferentially, arrests the cell cycle at the G2/M phase, inhibits cell growth, and induces apoptosis in A375 cancer cells.

Several acridine derivatives have been screened for their therapeutic potential and some are already established as antiprotozoan, antibacterial or anticancer agents. However, phenyl derivative at C-9 position of acridine had remained unexplored for their biological activity so far. In this report, we present our findings with 9-phenyl acridine (ACPH) as an anticancer agent. Both A375 and HeLa, two human cancer cell lines, were more sensitive to ACPH than normal cells namely human lymphocytes and also Chinese hamster V79 cells. ACPH also led to regression of tumour volume in mice. In A375 cells, we have shown that it caused DNA damage and blocked cell cycle progression at G(2)-M phase. Treatment with ACPH led to lowering of mitochondrial potential, upregulation of bax, release of cytochrome C and activation of caspase 3. As a new agent showing lower toxicity to normal cells and greater sensitivity towards cancerous cell line, ACPH shows promise as an effective cancer chemotherapeutic agent. ACPH treatment resulted in apoptotic death of cells through mitochondria-mediated caspase-dependent pathway.

Acridines and their derivatives are well-known probes for nucleic acids as well as being relevant in the field of drug development to establish new chemotherapeutic agents. We have shown from molecular modelling studies that 9-phenyl acridine and some of its derivatives can act as inhibitors of topoisomerase I and thus have potential to act as anticancer agents. Rational design of new compounds for therapeutics requires knowledge about their structural stability and interactions with various cellular macromolecules. In this regard it is important to know how these molecules would interact with DNA. Here we report the interaction of 9-phenyl acridine (ACPH) with calf thymus DNA (CT-DNA) based on various biophysical and molecular modelling studies. Spectrophotometric studies indicated that ACPH binds to CT-DNA. DNA melting studies revealed that binding of ACPH to CT-DNA resulted in a small increase in melting temperature, which is unlikely in case of classical intercalator; rather, it indicates external binding. Viscosity measurements show that ACPH exhibits groove binding. Competitive binding of ACPH to CT-DNA pre-bound to ethidium bromide (EB) showed slow quenching. Measurement of the binding constant of ACPH by fluorescent intercalator displacement (FID) assay corroborated the notion that there was groove binding. Molecular modelling studies also supported this finding. Results indicate that binding of ACPH is through partial intercalation in the minor groove of DNA.

Chinese hamster V79 cells were conditioned by repeated treatment with low doses of hydrogen peroxide. After this treatment, the conditioned cells were compared to parental V79 cells with regard to different endpoints. It was found that, compared to parental cells, the conditioned cells tolerated low serum concentrations better, they suffered from higher levels of aneuploidy, and they showed enhanced antioxidant defense. When exposed to gamma-rays, they suffered from lipid peroxidation to a lesser extent, were more resistant to cell killing, exhibited higher mutation frequency at the HGPRT locus, and showed lower frequency of apoptosis. These cells also induced antioxidant enzymes in response to gamma-ray exposure that differently was from than the parental cells. Overall, the data suggest a stable adaptive response in the conditioned cells.

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