Acute high-dose X-radiation-induced genomic changes in A549 cells

Accidents with ionizing radiation often involve single, acute high-dose exposures that can lead to acute radiation syndrome and late effects such as carcinogenesis. To study such effects at the cellular level, we investigated acute ionizing radiation-induced chromosomal aberrations in A549 adenocarcinoma cells at the genome-wide level by exposing the cells to an acute dose of 6 Gy 240 kV X rays. One sham-irradiated clone and four surviving irradiated clones were recovered by minimal dilution and further expanded and analyzed by chromosome painting and tiling-path array CGH, with the nonirradiated clone 0 serving as the control. Acute X-ray exposure induced specific translocations and changes in modal chromosome number in the four irradiated clones. Array CGH disclosed unique and recurrent genomic changes, predominantly losses, and revealed that the fragile sites FRA3B and FRA16D were preferential regions of genomic alterations in all irradiated clones, which is likely related to radioresistant S-phase progression and genomic stress. Furthermore, clone 4 displayed an increased radiosensitivity at doses >5 Gy. Pairwise comparisons of the gene expression patterns of all irradiated clones to the sham-irradiated clone 0 revealed an enrichment of the Gene Ontology term "M Phase" (P = 6.2 × 10(-7)) in the set of differentially expressed genes of clone 4 but not in those of clones 1-3. Ionizing radiation-induced genomic changes and fragile site expression highlight the capacity of a single acute radiation exposure to affect the genome of exposed cells by inflicting genomic stress.     

Copper oxide nanoparticles induce anticancer activity in A549 lung cancer cells by inhibition of histone deacetylase

Objectives

Copper oxide nanoparticles (CuO NPs) promoting anticancer activity may be due to the regulation of various classes of histone deacetylases (HDACs).

Results

Green-synthesized CuO NPs significantly arrested total HDAC level and also suppressed class I, II and IV HDACs mRNA expression in A549 cells. A549 cells treated with CuO NPs downregulated oncogenes and upregulated tumor suppressor protein expression. CuO NPs positively regulated both mitochondrial and death receptor-mediated apoptosis caspase cascade pathway in A549 cells.

Conclusion

Green-synthesized CuO NPs inhibited HDAC and therefore shown apoptosis mediated anticancer activity in A549 lung cancer cell line.

     

Esomeprazole overcomes paclitaxel-resistance and enhances anticancer effects of paclitaxel by inducing autophagy in A549/Taxol cells

Non-small-cell lung cancer (NSCLC) is one of the most common malignancies, and the occurrence of drug-resistance severely limits the efficacy of anticancer drugs in the treatment of NSCLC. Identification of new agents to reverse drug-resistance in NSCLC treatment is of great importance and urgency both clinically and scientifically. In the present study, we found that A549/Taxol cells displayed a high level of resistance to paclitaxel with the resistance index up to 231. Importantly, esomeprazole could potentiate the antiproliferative effect of paclitaxel in A549/Taxol cells, but not in A549 cells. Further exploration on the underlying mechanisms revealed that esomeprazole decreased the intracellular pH via inhibiting V-ATPase expression in A549/Taxol cells. Meanwhile, esomeprazole pretreatment significantly promoted paclitaxel-induced polymerization of tubulin and enhanced the proportion of G2/M-arrested cells in A549/Taxol cells. Unfortunately, esomeprazole could only result in a slight decrease in the expression of P-gp in A549/Taxol cells. Interestingly, esomeprazole significantly increased paclitaxel-induced apoptosis, which was impeded by the autophagy inhibitor 3-MA in A549/Taxol cells. Taken together, our data suggest that esomeprazole is a promising chemosensitizer against paclitaxel-resistant NSCLC by inducing autophagy. Our study also offers a new strategy to solve the paclitaxel-resistance problem during NSCLC treatment.     

Sanggenon O induced apoptosis of A549 cells is counterbalanced by protective autophagy

Sanggenon O (SO) is a Diels-Alder type adduct extracted from Morus alba, which has been used for its anti-inflammatory action in the Oriental medicine. However, whether it has regulatory effect on human cancer cell proliferation and what the underlying mechanism remains unknown. Here, we found that SO could significantly inhibit the growth and proliferation of A549 cells and induce its pro-apoptotic action through a caspase-dependent pathway. It could also impair the mitochondria which can be reflected by mitochondrial membrane permeabilization. Besides, SQSTM1 up-regulation and autophagic flux measurement demonstrated that exposure to SO led to autophagosome accumulation, which plays a protective role in SO-treated cells. In addition, knocking down of LC3B increased SO triggered apoptotic cell rates. These results indicated that SO has great potential as a promising candidate combined with autophagy inhibitor for the treatment of NSCLC. In conclusion, our results identified a novel mechanism by which SO exerts potent anticancer activity.     

Photosensitization by selected anticancer agents

Novel anticancer anthrapyrazoles and anthracenediones are available as alternatives to the cardiotoxic clinical agents, doxorubicin and daunorubicin. Certain representatives of these new classes of compounds possess photosensitizing properties. The structural features influencing the photophysical parameters of these agents are discussed. Photosensitizing reactions involving singlet oxygen production, free radical formation, decomposition of hydrogen peroxide and organic hydroperoxides, oxidation of certain biochemical electron donors, DNA damage and killing of human leukemic cells in vitro in the presence of photoactive anthrapyrazoles, anthracenediones and anthracyclines are described.     

Conformational changes in the ribosome induced by translational miscoding agents

Ribosomes are dynamic complexes responsible for translating the genetic information encoded in mRNAs to proteins. The accuracy of this process is vital to the survival of an organism, and is often compromised by translational miscoding agents. Aminoglycosides are a group of miscoding agents that bind to the ribosome and reduce the fidelity of translation. Previous studies have shown that aminoglycosides alter the higher order structure of the ribosome. Here, we used a toeprinting assay to how that streptomycin, neomycin, kanamycin, gentamycin, and hygromycin B trigger conformational changes within Escherichia coli ribosome. Miscoding agents viomycin and 30% ethanol also cause similar structural changes within the ribosome. In contrast, antibiotics that do not cause miscoding, such as tetracycline, chloramphenicol, erythromycin, fusidic acid and spectinomycin, do not induce the conformational changes triggered by miscoding agents. Furthermore, ribosomes isolated from strains that are either streptomycin resistant or dependent for growth do not show these conformational changes in the presence of streptomycin. These results correlate structural changes in the ribosome induced by miscoding agents in vitro with their in vivo phenotype.     

Low dose leflunomide activates PI3K/Akt signalling in erythroleukemia cells and reduces apoptosis induced by anticancer agents

Rheumatoid arthritis (RA) is characterized by persistent joint synovial tissue inflammation. Leflunomide is an immunomodulatory agent that has been approved for treatment of active RA. In the past few years, uses other than RA treatment have appeared. Leflunomide has been reported to show antitumor potential through inhibition of cancer cell proliferation. We thus tested the antiproliferative potential of leflunomide on HEL and K562 erythroleukemia cells. The findings summarized in this report demonstrate for the first time that low dose leflunomide prolonged survival and reduced apoptosis induced by several anticancer agents in erythroleukemia cells. We showed that in treated cells, leflunomide reduced the signalling pathways involved in promoting apoptosis by reducing p38 MAPK and JNK basal activity. On the other hand, leflunomide transiently activated the ERK signalling pathway and induced a sustained activation of Akt. We also showed that leflunomide reduced caspase-3 activity and DNA fragmentation induced by anticancer agents. By using an inhibitory strategy, we showed that inhibition of Akt activation but not ERK abolished the protective effect of leflunomide. Thus our findings suggested that leflunomide reduced apoptosis induced by anticancer agents through PI3K/Akt signalling activation.     

Proteins induced by DNA-damaging agents in cultured Drosophila cells

In Drosophila cultured cells, the effects of several DNA-damaging agents on the expression of proteins were investigated. Poly(A+) RNA prepared from both untreated cells and cells treated with DNA-damaging agents was translated in vitro. The translation products were analyzed by two-dimensional electrophoresis. Methyl methanesulfonate, the most potent agent used, induced about 25 proteins, some new and some enhanced pre-existing proteins. Angelicin plus near UV irradiation, 4-nitroquinoline N-oxide and ethyl methanesulfonate were efficient inducers. Mitomycin C, UV irradiation and hydrogen peroxide were poor inducers, inducing only a few proteins at low levels. A tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, and a DNA gyrase inhibitor, nalidixic acid, also were used. In this system they were weak inducers of new proteins. Several of the new or enhanced proteins were common to several agents, but others were agent specific. The distribution of mutagen-induced proteins was compared with that of proteins induced in cells heated at 37 degrees C. Some of the proteins induced by DNA-damaging agents were found to overlap heat-shock proteins. These results suggest that there are sets of induced genes that are regulated differently.     

Structural and functional changes in root cells induced by calcium ionophore A23187

The shifts of Ca²⁺, K⁺ and proton homeostasis of wheat (Triticum aestivum L. M. cv Ljuba) root cells induced by the Ca²⁺-ionophore A23187 caused different responses, depending on the time of exposure to the ionophore. Oxygen consumption and heat production by roots were increased when the Ca²⁺-specific effect of A23187 was expressed. Ultrastructural re-organization of cell organelles was found to follow the ion shifts. The endoplasmic reticulum, Golgi apparatus and mitochondria rearranged their membranes following treatment. The increased ion permeability of root cell membranes is proposed to cause an excessive energy expenditure for the restoration of ion homeostasis.     

DDAH1 plays dual roles in PM2.5 induced cell death in A549 cells

BackgroundDimethylarginine dimethylaminohydrolase 1 (DDAH1) is an enzyme that can degrade asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor. Emerging evidence suggests that alterations in the ADMA–DDAH1 pathway are involved in environmental pollution induced airway inflammation. However, the role of DDAH1 in protection against cytotoxicity of ambient airborne particulate matter is unclear.MethodsWe examined the influence of DDAH1 expression on oxidative stress and cell apoptosis in human type II alveolar epithelial A549 cells exposed to PM_2.5 (particulate matter with an aerodynamic diameter less than 2.5 μM).ResultsWe found that PM_2.5 exposure for 48 h significantly decreased DDAH1 expression. However, knockdown of DDAH1 prior to PM_2.5 exposure actually attenuated the cytotoxicity of PM_2.5. Cytoprotection in DDAH1 deficient cells was due to increased reactive oxygen species, activation of PI3K–AKT and mitogen-activated protein kinase (MAPK) pathways, subsequent activation of nuclear factor erythroid-2-related factor 2 (Nrf2) and this caused a subsequent reduction in PM_2.5 induced oxidative stress relative to control. DDAH1 depletion also repressed the induction of inducible NOS (iNOS) in PM_2.5-exposed cells and knockdown of iNOS protected cells against PM_2.5 induced cell death. Interestingly, overexpression of DDAH1 also exerted a protective effect against the cytotoxicity of PM_2.5 and this was associated with a reduction in oxidative stress and upregulation of the anti-apoptotic protein Bcl-2.ConclusionsOur data indicate that DDAH1 plays dual roles in protection against cytotoxicity of PM_2.5 exposure, apparently by limiting PM_2.5 induced oxidative stress.General significanceOur findings reveal new insights into the role(s) of the DDAH1/ADMA in pulmonary protection against airborne pollutants. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.     

Role of Rad52 in fractionated irradiation induced signaling in A549 lung adenocarcinoma cells

The effect of fractionated doses of γ-irradiation (2Gy per fraction over 5 days), as delivered in cancer radiotherapy, was compared with acute doses of 10 and 2Gy, in A549 cells. A549 cells were found to be relatively more radioresistant if the 10Gy dose was delivered as a fractionated regimen. Microarray analysis showed upregulation of DNA repair and cell cycle arrest genes in the cells exposed to fractionated irradiation. There was intense activation of DNA repair pathway-associated genes (DNA-PK, ATM, Rad52, MLH1 and BRCA1), efficient DNA repair and phospho-p53 was found to be translocated to the nucleus of A549 cells exposed to fractionated irradiation. MCF-7 cells responded differently in fractionated regimen. Silencing of the Rad52 gene in fractionated group of A549 cells made the cells radiosensitive. The above result indicated increased radioresistance in A549 cells due to the activation of Rad52 gene.     

Ruthenium methylimidazole complexes induced apoptosis in lung cancer A549 cells through intrinsic mitochondrial pathway

Ruthenium(II) methylimidazole complexes, with the general formula [Ru(MeIm)₄(N?N)]²⁺ (N?N = tip (RMC1), iip (RMC2), dppz (RMC3), dpq (RMC4); MeIm = 1-methylimidazole, tip = 2-(thiophene-2-yl)-1H-imidazo [4,5-f] [1,10]phenanthroline, iip = 2-(1H-imidazol-4-yl)-1H-imidazo [4,5-f] [1,10]phenanthroline, dppz = dipyrido[3,2-a:2′,3′-c]phenazine, dpq = pyrazino [2,3-f] [1,10]phenanthroline), were synthesized and characterized. As determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, these complexes displayed potent anti-proliferation activity against various cancer cells. RMC1 inhibited the growth of A549 (human lung adenocarcinoma) lung cells through induction of apoptotic cell death, as evidenced by the accumulation of cell population in sub-G1 phase. RMC1 also induced the depletion of mitochondrial membrane potential in A549 cells by regulating the expression of pro-survival and pro-apoptotic Bcl-2 family members. Another experiment showed that Bid protein was also activated by RMC1, which implied that RMC1 could existed two pathways crosstalk, namely, have exogenous death receptor signaling pathway. These results demonstrated that RMC1 induced cancer cell death by acting on both mitochondrial and death receptor apoptotic pathways, suggesting that RMC1 could be a candidate for further evaluation as a chemotherapeutic agent against human cancers.     

Genotoxicity of hydroquinone in A549 cells

Hydroquinone (HQ) is found in natural and anthropogenic sources including food, cosmetics, cigarette smoke, and industrial products. In addition to ingestion and dermal absorption, human exposure to HQ may also occur by inhaling cigarette smoke or polluted air. The adverse effects of HQ on respiratory systems have been studied, but genotoxicity HQ on human lung cells is unclear. The aim of this study was to investigate the cytotoxicity and genotoxicity of HQ in human lung alveolar epithelial cells (A549). We found that HQ induced a dose response in cell growth inhibition and DNA damage which was associated with an increase in oxidative stress. Cytotoxicity results demonstrated that HQ was most toxic after 24 h (LC₅₀?=?33 μM) and less toxic after 1 h exposure (LC₅₀?=?59 μM). Genotoxicity of HQ was measured using the Comet assay, H2AX phosphorylation, and chromosome aberration formation. Results from the comet assay revealed that DNA damage was highest during the earlier hours of exposure (1 and 6 h) and thereafter was reduced. A similar pattern was observed for H2AX phosphorylation suggesting that damage DNA may be repaired in later exposure hours. An increase in chromosomal aberration corresponded with maximal DNA damage which further confirmed the genotoxic effects of HQ. To investigate whether oxidative stress was involved in the cytotoxic and genotoxic effects of HQ, cellular glutathione and 8-Oxo-deoguanisone (8-Oxo-dG) formation were measured. A decrease in the reduced glutathione (GSH) and an increase oxidized glutathione (GSSG) was observed during the early hours of exposure which corresponded with elevated 8-Oxo-dG adducts. Together these results demonstrate that HQ exerts its cytotoxic and genotoxic effects in A549 lung cells, probably through DNA damage via oxidative stress.