Ciprofloxacin-induced G2 arrest and apoptosis in TK6 lymphoblastoid cells is not dependent on DNA double-strand break formation

Advancements in Synthetic Strategies and Biological Effects of Ciprofloxacin Derivatives: A Review

Ciprofloxacin is a widely used antibiotic in the fluoroquinolone class. It is widely acknowledged by various researchers worldwide, and it has been documented to have a broad range of other pharmacological activities, such as anticancer, antiviral, antimalarial activities, etc. Researchers have been exploring the synthesis of ciprofloxacin derivatives with enhanced biological activities or tailored capability to target specific pathogens. The various biological activities of some of the most potent and promising ciprofloxacin derivatives, as well as the synthetic strategies used to develop them, are thoroughly reviewed in this paper. Modification of ciprofloxacin via 4-oxo-3-carboxylic acid resulted in derivatives with reduced efficacy against bacterial strains. Hybrid molecules containing ciprofloxacin scaffolds displayed promising biological effects. The current review paper provides reported findings on the development of novel ciprofloxacin-based molecules with enhanced potency and intended therapeutic activities which will be of great interest to medicinal chemists.

Fluoroquinolones upregulate insulin-like growth factor-binding protein 3, inhibit cell growth and insulin-like growth factor signaling

Fluoroquinolones (FQs), commonly known for their antibiotic properties, exhibit additional pharmacological potential with anti-proliferative effects on various malignant cell types and immunomodulatory responses. Despite these observed effects, the precise mechanisms of action remain elusive. This study elucidates the biological impact of FQs on insulin-like growth factor-binding protein 3 (IGFBP-3) productions in a p53-dependent manner. Cultured cells and mouse models treated with FQs demonstrated increased IGFBP-3 mRNA expression and protein secretion. The FQ-induced IGFBP-3 was identified to impede cell growth by inhibiting IGF-I signaling and exerting effects through an IGF-independent pathway. Notably, FQ-mediated suppression of cell proliferation was reversed in p53-null and p53 knockdown cells, suggesting the pivotal role of p53 in FQ-induced IGFBP-3 production and IGFBP-3-mediated growth inhibition. Additionally, ciprofloxacin, a clinically used FQ, exhibited the induction of tumor cell apoptosis and attenuation of tumor growth in a syngeneic mouse hepatocellular carcinoma (HCC) model. These findings unveil a novel mechanism through which FQs act as anti-proliferative agents, prompting further exploration of their potential utility or derivative compounds in cancer treatment and prevention.

Degradation of ciprofloxacin in aqueous solution using ozone microbubbles: spectroscopic, kinetics, and antibacterial analysis

Ciprofloxacin (CIP) has been listed in the last version of the surface water due to its ability to kill human cells by inhibiting the activity of DNA topoisomerase IV. Thus, CIP, along with other antibiotic pollution has become a serious threat to the environment and public health. Ozonation has been used as an advanced technique that is applied in wastewater treatment to remove CIP, but the primary limitation of this method is the low solubility of ozone in water. This study is the first report of CIP removal in a scale-up of its aqueous solution using a self-developed aerator pump-enhanced ozonation (APO) system, which only employs a propeller and a zigzag arrangement of meshes. This aerator pump decreased the size of ozone bubbles by 90% and increased the effective ozone solubility to 0.47 ppm. The mechanism of degradation of CIP is attributed to an oxidation reaction of the antibiotic with reactive oxygen species, such as hydroxyl, oxygen, and hydroperoxyl radicals, generated on the surface of the ozone microbubbles. It was found that the rate and efficiency of degradation of CIP using the APO system were 3.64 × 10⁻³/min and 83.5%, respectively, which is higher compared with those of conventional flow ozonation (FO) systems (1.47 × 10⁻³/min and 60.9%). The higher degradation efficiency of CIP by the APO system was also revealed by its higher electrical energy efficiency (0.146 g/kWh), compared to that of the FO system (0.106 g/kWh). The degradation of CIP was also monitored by the resulting antibacterial activity against Escherichia coli and Staphylococcus aureus.

Exploring quinolone scaffold: Unravelling the chemistry of anticancer drug design

Globally, cancer is considered as the major leading cause in decreasing the patient health care system of human beings. The growing threat from drug-resistant cancers makes heterocyclic moieties as an urgent need to develop more successful candidates for anti-cancer therapy. In view of outstanding pharmacological activities Quinolone and its derivatives have attracted more attention towards drug designing and biological evaluation in the search of new drug molecules. The inspired researchers attempted efforts in order to discover quinolone based analogs due to its wide range of biological activities. Due to immense pharmacological importance, distinct synthetic methods have been executed to attain new drug entities from quinolones and all the reported molecules have shown constructive anticancer activity. Some of the synthetic protocol like, one pot synthesis, post-Ugi-transformation, catalysed based synthesis, enzyme-based synthesis and nano-catalyst based synthetic procedures are also discussed as recent advancement in production of quinolone derivatives. In this review, recent synthetic approaches in the medicinal chemistry of quinolones and potent quinolone derivatives on the basis of structural activity relationship are outlined. Moreover, their major methods and modifications are discussed.

Novel Mannich bases of ciprofloxacin with improved physicochemical properties, antibacterial, anticancer activities and caspase-3 mediated apoptosis

The design, synthesis and identification of a novel series of Mannich bases of ciprofloxacin was reported. Naphthol derivatives 2a and 2b showed highly potent cytotoxic activity among the tested compounds. Compound 2a showed broad spectrum antiproliferative activity with GI₅₀ of 2.5-6.79 µM with remarkable selectivity towards renal and prostate cancers with selectivity ratios ranging from 0.17 to 6.79. Independently, 2a showed outstanding activity against colon cancer HOP-92 cell lines with IC₅₀ of 6.66 µM while 2b showed highly potent activity against ovarian cancer cell lines with IC₅₀ of 0.97 µM. Results showed that 2b induced cell cycle arrest at G2/M phase and apoptosis; compound 2b showed over-expression of caspase-3 protein level (449.2 ± 7.95) compared to doxorubicin (578.7 ± 14.4 pg/mL). Meanwhile, compounds 2a and 2b experienced outstanding activity against both Gram-positive and Gram-negative microorganisms. Interestingly, compound 2j experienced high activity against Escherichia coli and Pseudomonas aeruginosa with MIC of 0.036 and 0.043, respectively. Compound 2d revealed 27 folds and 22 folds, respectively increasing of activity over ciprofloxacin against Staphylococcus aureus and MRSA(reference strain). Compound 2d showed high activity against Staphylococcus aureus, MRSA (reference strain) and MRSA (clinical strain) with MIC of 0.57, 0.52, 0.082 µg/mL, respectively. Interestingly, the most active tested compounds were found to have promising physicochemical and drug likeness properties. The Mannich bases 2j, 2d and 2g showed promising antibacterial activities, while naphthols 2a and 2b showed promising antiproliferative and antibacterial activities that require further optimization.

Selective inhibitory effects of HYIpro-3-1 on CYP1A2 in human liver microsomes

CYP1A2 is one of the main Cytochrome P450 enzymes in the human liver associated with the metabolism of several xenobiotics. CYP1A2 is especially involved in the metabolic activation of different procarcinogens. Therefore, the development of cancer may be inhibited by inhibiting CYP1A2 activity. Here, the inhibitory effect of HYIpro-3-1 and its derivatives on CYP1A2 activity in human liver microsomes (HLM) was studied through LC-MS/MS using a cocktail assay. Among the four compounds, HYIpro-3-1 showed the most selective and strongest inhibitory effect on CYP1A2 at IC₅₀ values of 0.1 µM in HLMs and inhibition was confirmed using purified human CYP1A2. It was determined that inhibition is reversible because the inhibitory effect of HYIpro-3-1 is not dependent on preincubation time. HYIpro-3-1 showed a typical pattern of competitive inhibition for CYP1A2-catalyzed phenacetin O-deethylation, based on the Lineweaver-Burk plot, with a Ki value of 0.05 μM in HLMs; the secondary plot also showed a linear pattern. In our study, HYIpro-3-1 was proposed as a novel inhibitor with the capacity to selectively inhibit CYP1A activity in HLMs.

Novel urea linked ciprofloxacin-chalcone hybrids having antiproliferative topoisomerases I/II inhibitory activities and caspases-mediated apoptosis

A novel series of urea-linked ciprofloxacin (CP)-chalcone hybrids 3a-j were synthesized and screened by NCI-60 cancer cell lines as potential cytotoxic agents. Interestingly, compounds 3c and 3j showed remarkable antiproliferative activities against both colon HCT-116 and leukemia SR cancer cells compared to camptothecin, topotecan and staurosporine with IC₅₀ = 2.53, 2.01, 17.36, 12.23 and 3.1 μM for HCT-116 cells, respectively and IC₅₀ = 0.73, 0.64, 3.32, 13.72 and 1.17 μM for leukemia SR cells, respectively. Also, compounds 3c and 3j exhibited inhibitory activities against Topoisomerase (Topo) I with % inhibition = 51.19% and 56.72%, respectively, compared to camptothecin (% inhibition = 60.05%) and Topo IIβ with % inhibition = 60.81% and 60.06%, respectively, compared to topotecan (% inhibition = 71.09%). Furthermore, compound 3j arrested the cell cycle of leukemia SR cells at G2/M phase. It induced apoptosis both intrinsically and extrinsically via activation of proteolytic caspases cascade (caspases-3, -8, and -9), release of cytochrome C from mitochondria, upregulation of proapoptotic Bax and down-regulation of Bcl-2 protein level. Thus, the new ciprofloxacin derivative 3j could be considered as a potential lead for further optimization of antitumor agent against leukemia and colorectal carcinoma.

Potential adverse effects of ciprofloxacin and tetracycline on ARPE-19 cell lines

Background

We aim to determine the possible adverse effects of ciprofloxacin (CPFX) and tetracycline (TETRA), as examples of bactericidal and bacteriostatic agents, respectively, on cultured human retinal pigment epithelial cells (ARPE-19).

Methods

Cells were treated with 30, 60 and 120 µg/mL of CPFX and TETRA. Cell metabolism was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. JC-1 dye (5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide) assay was conducted to measure the mitochondrial membrane potential (MMP). The level of reactive oxygen species (ROS) was measured using the -2’,7’-dichlorodihydrofluorescein diacetate assay (H2DCFDA). Quantitative real-time PCR was performed to analyse the gene expression levels associated with apoptosis (BAX, BCL2-L13, BCL2, Caspase 3, Caspase 7 and Caspase 9), inflammatory (interleukin-1β (IL-1β), IL-6, IL-33, transforming growth factor-α (TGF-α), TGF-β1 and TGF-β2) and antioxidant pathways (SOD2, SOD3, GPX3 and NOX4), along with the mitochondrial DNA (mtDNA) copy numbers.

Results

Results illustrated that while all three concentrations of CPFX decreased cellular viability of ARPE-19 during all incubation periods, the 120 µg/mL TETRA resulted in increased cellular viability. At 48 and 72 hours, levels of MMP and ROS decreased significantly with each antibiotic. BAX, BCL2-L13, CASP-7, CASP-9, SOD2 and GPX3 genes overexpressed by either antibiotics. There was higher expression of IL-6 and IL-1B with TETRA treatment. The level of mtDNA decreased using both treatments.

Conclusions

Clinically relevant concentrations of CPFX and TETRA have detrimental impacts on ARPE-19 cell lines in vitro, including upregulation of genes related to apoptosis, inflammation and antioxidant pathways. Additional studies are warranted to investigate if these harmful effects might be seen in retinal degeneration models in vivo.

Cumulative effects of ciprofloxacin and pilocarpine on cytotoxicity and G0 phase arrest in hepatoma-derived Hep G2 cell line

OBJECTIVES

Uncontrolled cell proliferation was caused by multiple deficient pathways that inhibition of one pathway may result to activate an alternative pathway. Therefore, combination of drugs which targeted multiple pathways could be beneficial to overcome drug resistance. Ciprofloxacin (CPF) cytotoxicity was widely investigated on cancer cell lines, and results revealed hepatoma-derived Hep G2 cells are relatively resistant. So, this study aimed to increase CPF cytotoxicity by rational design of a supplement which targeted Ca²⁺ homoeostasis as major hub in unchecked proliferation.

METHODS

Cells were treated by CPF and/or pilocarpine (PILO), and cell cycle distribution, caspases activity and regulatory proteins were evaluated.

KEY FINDINGS

MTT and flow cytometry analysis confirmed administration of CPF + PILO causes more cytotoxicity. CPF-exposed cells accumulated in S phase due to DNA damages while PILO + CPF imposed G0 stage arrest through cyclin D1 and P-Akt downregulation. Caspase 8 was activated in cells treated by CPF but accompaniment of PILO with CPF led to activation of caspase 9, 8 and 3 and ROS overproduction.

CONCLUSIONS

Ciprofloxacin imposed mitochondrial-independent apoptosis while PILO + CPF caused mitochondrial-dependent and independent apoptosis simultaneously. Consequently, coadministration of PILO and CPF causes intense cytotoxic effects through targeting the mitochondria, DNA gyrase enzyme and other unknown mechanisms.

Repositioning of fluoroquinolones from antibiotic to anti-cancer agents: An underestimated truth

Increasing development costs and higher failure rate in clinical trials has reduced the repertoire of newer drugs in the market for clinical use. The most appropriate approach to end the search for newer drugs is "Repositioning", as it requires less time and money to explore new indication of existing drug or failed drug. In the past, several drugs have been repositioned for different indication but the full potential remains unharnessed. With rise in cancer prevalence and treatment costs, it is imperative to search for newer drugs and the use of repositioning approach may help us. Fluoroquinolones has been used as antibiotics for over four decades now, but recent research highlighted their use as pharmacological compounds with multifaceted implication. Repositioning of fluoroquinolones into anti-cancer molecule seems to be a highly plausible option owing to their profound immunomodulatory, pro-apoptotic, anti-proliferative and anti-metastatic potential. The present review provides a comprehensive account of the recent and past explorations pertaining to the anti-cancer activity of fluoroquinolones and also discusses the various approaches that are being considered to remodel them for the treatment of cancer.

Design, Synthesis and Biological Evaluation of Ciprofloxacin- Peptide Conjugates as Anticancer Agents

Cancer has emerged as a leading cause of death throughout the world. Peptides are a novel class of anticancer agents that can specifically target cancer cells with low toxicity to normal tissues and thus, offer new opportunities for future cancer treatment. On the other hand, Ciprofloxacin, an antibiotic, also known to its anticancer property for enabling cell cycle arrest and creating double strand breaks in nucleic acid can trigger apoptosis of cancer cells. Thus, joining anticancer peptides with Ciprofloxacin may be good idea to get benefit of the both compounds' properties and therefore gives better anticancer agents. The aim of this study was to synthesize Ciprofloxacin- cytotoxic peptide conjugates and to investigate the anticancer activity of the resultant compounds. The conjugates were prepared by solid phase peptide synthesis technique using Fmoc strategy. Anticancer activity of these compounds was examined on three cancer cell lines, HT-29, MCF-7, MDA-MB-231 as well as skin fibroblast cells as a control, employing MTT test. Our results showed that the cytotoxic activity of the synthesized compounds against cancer cells was raised considerably without producing a high toxicity on normal cells. Moreover, Ciprofloxacin-peptide conjugates showed selectivity against different kinds of breast cancer cells, especially on those with triple negative receptors. Therefore, it can be suggested that the strategy of making Ciprofloxacin- peptide conjugates as cytotoxic agents with safety profiles on the normal cells, rise promise to find better chemotherapeutic candidates to combat cancer.

Effect of Ciprofloxacin on Susceptibility to Aortic Dissection and Rupture in Mice

Importance

Fluoroquinolones are among the most commonly prescribed antibiotics. Recent clinical studies indicated an association between fluoroquinolone use and increased risk of aortic aneurysm and dissection (AAD). This alarming association has raised concern, especially in patients with AAD with risk of rupture and in individuals at risk for developing AAD.

Objective

To examine the effect of ciprofloxacin on AAD development in mice.

Design, Setting, and Participants

In a mouse model of moderate, sporadic AAD, 4-week-old male and female C57BL/6J mice were challenged with a high-fat diet and low-dose angiotensin infusion (1000 ng/min/kg). Control unchallenged mice were fed a normal diet and infused with saline. After randomization, challenged and unchallenged mice received ciprofloxacin (100 mg/kg/d) or vehicle through daily gavage during angiotensin or saline infusion. Aortic aneurysm and dissection development and aortic destruction were compared between mice. The direct effects of ciprofloxacin on aortic smooth muscle cells were examined in cultured cells.

Results

No notable aortic destruction was observed in unchallenged mice that received ciprofloxacin alone. Aortic challenge induced moderate aortic destruction with development of AAD in 17 of 38 mice (45%) and severe AAD in 9 (24%) but no rupture or death. However, challenged mice that received ciprofloxacin had severe aortic destruction and a significantly increased incidence of AAD (38 of 48 [79%]; P = .001; χ2 = 10.9), severe AAD (32 of 48 [67%]; P < .001; χ2 = 15.7), and rupture and premature death (7 of 48 [15%]; P = .01; χ2 = 6.0). The increased AAD incidence was observed in different aortic segments and was similar between male and female mice. Compared with aortic tissues from challenged control mice, those from challenged mice that received ciprofloxacin showed decreased expression of lysyl oxidase, an enzyme that is critical in the assembly and stabilization of elastic fibers and collagen. These aortas also showed increased matrix metalloproteinase levels and activity, elastic fiber fragmentation, and aortic cell injury. In cultured smooth muscle cells, ciprofloxacin treatment significantly reduced lysyl oxidase expression and activity, increased matrix metalloproteinase expression and activity, suppressed cell proliferation, and induced cell death. Furthermore, ciprofloxacin-a DNA topoisomerase inhibitor-caused nuclear and mitochondrial DNA damage and the release of DNA into the cytosol, subsequently inducing mitochondrial dysfunction, reactive oxygen species production, and activation of the cytosolic DNA sensor STING, which we further showed was involved in the suppression of lysyl oxidase expression and induction of matrix metalloproteinase expression.

Conclusions and Relevance

Ciprofloxacin increases susceptibility to aortic dissection and rupture in a mouse model of moderate, sporadic AAD. Ciprofloxacin should be used with caution in patients with aortic dilatation, as well as in those at high risk for AAD.

New antiproliferative 7-(4-(N-substituted carbamoylmethyl)piperazin-1-yl) derivatives of ciprofloxacin induce cell cycle arrest at G2/M phase

New N-4-piperazinyl derivatives of ciprofloxacin 2a-g were prepared and tested for their cytotoxic activity. The primary in vitro one dose anticancer assay experienced promising cytotoxic activity against different cancer cell lines especially non-small cell lung cancer. Independently, compounds 2b, 2d, 2f and 2g showed anticancer activity against human non-small cell lung cancer A549 cells (IC50=14.8, 24.8, 23.6 and 20.7μM, respectively) compared to the parent ciprofloxacin (IC50 >100μM) and doxorubicin as a positive control (IC50=1μM). The flow cytometric analysis for 2b showed dose dependent G2/M arrest in A549 cells. Also, 2b increased the expression of p53 and p21 and decreased the expression of cyclin B1 and Cdc2 proteins in A549 cells without any effect on the same proteins expression in WI-38 cells. Specific inhibition of p53 by pifithrin-α reversed the G2/M phase arrest induced by the 2b compound, suggesting contribution of p53 to increase. Taken together, 2b induced G2/M phase arrest via p53/p21 dependent pathway. The results indicate that 2b can be used as a lead compound for further development of new derivatives against non-small cell lung cancer.

Enrofloxacin enhances the effects of chemotherapy in canine osteosarcoma cells with mutant and wild-type p53

Adjuvant chemotherapy improves survival time in dogs receiving adequate local control for appendicular osteosarcoma, but most dogs ultimately succumb to metastatic disease. The fluoroquinolone antibiotic enrofloxacin has been shown to inhibit survival and proliferation of canine osteosarcoma cells in vitro. Others have reported that fluoroquinolones may modulate cellular responses to DNA damaging agents and that these effects may be differentially mediated by p53 activity. We therefore determined p53 status and activity in three canine osteosarcoma cell lines and examined the effects of enrofloxacin when used alone or in combination with doxorubicin or carboplatin chemotherapy. Moresco and Abrams canine osteosarcoma cell lines contained mutations in p53, while no mutations were identified in the D17 cells or in a normal canine osteoblast cell line. The addition of enrofloxacin to either doxorubicin or carboplatin resulted in further reductions in osteosarcoma cell viability; this effect was apparent regardless of p53 mutational status or downstream activity.

Copper(i) complexes with phosphine derived from sparfloxacin. Part II: a first insight into the cytotoxic action mode

A first insight into the cytotoxic action mode of copper(i) iodide or copper(i) thiocyanate complexes with a phosphine derivative of sparfloxacin (a 3^rdgeneration fluoroquinolone antibiotic agent) and 2,9-dimethyl-1,10-phenanthroline or 2,2′-biquinoline as auxiliary ligands.

A "Double-Edged" Scaffold: Antitumor Power within the Antibacterial Quinolone

In the late 1980s, reports emerged describing experimental antibacterial quinolones having significant potency against eukaryotic Type II topoisomerases (topo II) and showing cytotoxic activity against tumor cell lines. As a result, several pharmaceutical companies initiated quinolone anticancer programs to explore the potential of this class in comparison to conventional human topo II inhibiting antitumor drugs such as doxorubicin and etoposide. In this review, we present a modern re-evaluation of the anticancer potential of the quinolone class in the context of today's predominantly pathway-based (rather than cytotoxicity-based) oncology drug R&D environment. The quinolone eukaryotic SAR is comprehensively discussed, contrasted with the corresponding prokaryotic data, and merged with recent structural biology information which is now beginning to help explain the basis for that SAR. Quinolone topo II inhibitors appear to be much less susceptible to efflux-mediated resistance, a current limitation of therapy with conventional agents. Recent advances in the biological understanding of human topo II isoforms suggest that significant progress might now be made in overcoming two other treatment-limiting disadvantages of conventional topo II inhibitors, namely cardiotoxicity and drug-induced secondary leukemias. We propose that quinolone class topo II inhibitors could have a useful future therapeutic role due to the continued need for effective topo II drugs in many cancer treatment settings, and due to the recent biological and structural advances which can now provide, for the first time, specific guidance for the design of a new class of inhibitors potentially superior to existing agents.

Ciprofloxacin as a potential radio-sensitizer to tumor cells and a radio-protectant for normal cells: differential effects on γ-H2AX formation, p53 phosphorylation, Bcl-2 production, and cell death

Ionizing radiation increases cell mortality in a dose-dependent manner. Increases in DNA double strand breaks, γ-H2AX, p53 phophorylation, and protein levels of p53 and Bax also occur. We investigated the ability of ciprofloxacin (CIP), a widely prescribed antibiotic, to inhibit DNA damage induced by ionizing radiation. Human tumor TK6, NH32 (p53 (-/-) of TK6) cells, and human normal peripheral blood mononuclear cells (PBMCs) were exposed to 2-8 Gy (60)Co-γ-photon radiation. γ-H2AX (an indicator of DNA strand breaks), phosphorylated p53 (responsible for cell-cycle arrest), Bcl-2 (an apoptotic protein, and cell death were measured. Ionizing irradiation increased γ-H2AX amounts in TK6 cells (p53(+/+)) within 1 h in a radiation dose-dependent manner. CIP pretreatment and posttreatment effectively inhibited the increase in γ-H2AX. CIP pretreatment reduced Bcl-2 production but promoted p53 phosphorylation, caspase-3 activation and cell death. In NH32 cells, CIP failed to significantly inhibit the radiation-induced γ-H2AX increase, suggesting that CIP inhibition involves in p53-dependent mechanisms. In normal healthy human PBMCs, CIP failed to block the radiation-induced γ-H2AX increase but effectively increased Bcl-2 production, but blocked the phospho-p53 increase and subsequent cell death. CIP increased Gadd45α, and enhanced p21 protein 24 h postirradiation. Results suggest that CIP exerts its effect in TK6 cells by promoting p53 phosphorylation and inhibiting Bcl-2 production and in PBMCs by inhibiting p53 phosphorylation and increasing Bcl-2 production. Our data are the first to support the view that CIP may be effective to protect normal tissue cells from radiation injury, while enhancing cancer cell death in radiation therapy.

Ciprofloxacin is an inhibitor of the Mcm2-7 replicative helicase

Most currently available small molecule inhibitors of DNA replication lack enzymatic specificity, resulting in deleterious side effects during use in cancer chemotherapy and limited experimental usefulness as mechanistic tools to study DNA replication. Towards development of targeted replication inhibitors, we have focused on Mcm2-7 (minichromosome maintenance protein 2-7), a highly conserved helicase and key regulatory component of eukaryotic DNA replication. Unexpectedly we found that the fluoroquinolone antibiotic ciprofloxacin preferentially inhibits Mcm2-7. Ciprofloxacin blocks the DNA helicase activity of Mcm2-7 at concentrations that have little effect on other tested helicases and prevents the proliferation of both yeast and human cells at concentrations similar to those that inhibit DNA unwinding. Moreover, a previously characterized mcm mutant (mcm4chaos3) exhibits increased ciprofloxacin resistance. To identify more potent Mcm2-7 inhibitors, we screened molecules that are structurally related to ciprofloxacin and identified several that compromise the Mcm2-7 helicase activity at lower concentrations. Our results indicate that ciprofloxacin targets Mcm2-7 in vitro, and support the feasibility of developing specific quinolone-based inhibitors of Mcm2-7 for therapeutic and experimental applications.

Oxidative DNA damage is involved in ochratoxin A-induced G2 arrest through ataxia telangiectasia-mutated (ATM) pathways in human gastric epithelium GES-1 cells in vitro

Ochratoxin A (OTA), one of the most abundant mycotoxin food contaminants, is classified as "possibly carcinogenic to humans." Our previous study showed that OTA could induce a G2 arrest in immortalized human gastric epithelium cells (GES-1). To explore the putative roles of oxidative DNA damage and the ataxia telangiectasia-mutated (ATM) pathways on the OTA-induced G2 arrest, the current study systematically evaluated the roles of reactive oxygen species (ROS) production, DNA damage, and ATM-dependent pathway activation on the OTA-induced G2 phase arrest in GES-1 cells. The results showed that OTA exposure elevated intracellular ROS production, which directly induced DNA damage and increased the levels of 8-OHdG and DNA double-strand breaks (DSBs). In addition, it was found that OTA treatment induced the phosphorylation of the ATM protein, as well as its downstream molecules Chk2 and p53, in response to DNA DSBs. Inhibition of ATM by the pharmacological inhibitor caffeine or siRNA effectively prevented the activation of ATM-dependent pathways and rescued the G2 arrest elicited by OTA. Finally, pretreatment with the antioxidant N-acetyl-L-cysteine (NAC) reduced the OTA-induced DNA DSBs, ATM phosphorylation, and G2 arrest. In conclusion, the results of this study suggested that OTA-induced oxidative DNA damage triggered the ATM-dependent pathways, which ultimately elicited a G2 arrest in GES-1 cells.

Relationship of cellular topoisomerase IIα inhibition to cytotoxicity and published genotoxicity of fluoroquinolone antibiotics in V79 cells

Fluoroquinolone (FQ) antibiotics are bacteriocidal through inhibition of the bacterial gyrase and at sufficient concentrations in vitro, they can inhibit the homologous eukaryotic topoisomerase (TOPO) II enzyme. FQ exert a variety of genotoxic effects in mammalian systems through mechanisms not yet established, but which are postulated to involve inhibition of TOPO II enzymes. To assess the relationship of inhibition of cell nuclear TOPO II to cytotoxicity and reported genotoxicity, two FQ, clinafloxacin (CLFX) and lomefloxacin (LOFX), having available genotoxicity data showing substantial differences with CLFX being more potent than LOFX, were selected for study. The relative inhibitory activities of these FQ on nuclear TOPO IIα in cultured Chinese hamster lung fibroblasts (V79 cells) over dose ranges and at equimolar concentrations were assessed by measuring nuclear stabilized cleavage complexes of TOPO IIα-DNA. Cytotoxicity was measured by relative cell counts. Both FQ inhibited V79 cell nuclear TOPO IIα. The lowest-observed-adverse-effect levels for TOPO IIα inhibition were 55 μM for CLFX, and 516 μM for LOFX. The no-observed-adverse-effect-levels were 41 μM for CLFX, and 258 μM for LOFX. At equimolar concentrations (175 μM), CLFX was more potent than LOFX. Likewise, CLFX was more cytotoxic than LOFX. Thus, the two FQ, inhibited TOPO IIα in intact V79 cells, differed in their potencies and exhibited no-observed-adverse-effect levels. These findings are in concordance with published genotoxicity data and observed cytotoxicity.

Piperonal ciprofloxacin hydrazone induces growth arrest and apoptosis of human hepatocarcinoma SMMC-7721 cells

AIM

To investigate the cytotoxic effects of piperonal ciprofloxacin hydrazone (QNT4), a novel antibacterial fluoroquinolone derivative, against human hepatocarcinoma SMMC-7721 cells.

METHODS

Human hepatocarcinoma cells (SMMC-7721), human breast adenocarcinoma cells (MCF-7) and human colon adenocarcinoma cells (HCT-8) were tested. The effects of QNT4 on cell proliferation were examined using MTT assay. Cell apoptosis was determined using Hoechst 33258 fluorescence staining, TUNEL assay and agarose gel electrophoresis. The topoisomerase II activity was measured using agarose gel electrophoresis with the DNA plasmid pBR322 as the substrate. Mitochondrial membrane potential (Δψm) was measured using a high content screening imaging system. Protein expression of caspase-9, caspase-8, caspase-3, p53, Bcl-2, Bax, and cytochrome c was detected with Western blot analysis.

RESULTS

Treatment with QNT4 (0.625-10 μmol/L) potently inhibited the proliferation of the cancer cells in time- and dose-dependent manners (the IC(50) value at 24 h in SMMC-7721 cells, MCF-7 cells and HCT-8 cells was 2.956±0.024, 3.710±0.027, and 3.694±0.030 μmol/L, respectively). Treatment of SMMC-7721 cells with QNT4 (0.2146, 2.964, and 4.600 μmol/L) for 24 h dose-dependently increased the percentage of apoptotic cells, elicited characteristic DNA "ladder" bands, and decreased the mitochondrial membrane potential. QNT4 dose-dependently increased topoisomerase II-mediated DNA breaks while inhibiting DNA relegation, thus keeping the DNA in fragments. Treatment of SMMC-7721 cells with QNT4 significantly increased cytochrome c in the cytosol, and decreased cytochrome c in the mitochondrial compartment. QNT4 (3-7.39 μmol/L) significantly increased the protein expression of p53, Bax, caspase-9, caspase-3, and the cleaved activated forms of caspase-9 and caspase-3 in SMMC-7721 cells. In contrast, the expression of Bcl-2 was decreased, while caspase-8 had no significant change.

CONCLUSION

QNT4 induced the apoptosis of SMMC-7721 cells via inhibiting topoisomerase II activity and modulating mitochondrial-dependent pathways.

Ciprofloxacin as a prophylactic agent against prostate cancer: a "two hit" hypothesis

More evidence indicate that prostate inflammation can lead to prostate cancer development. Prostate cancer affects elderly men. Prostate cancer prophylaxis is an important issue because life expectancy is very long now. Ciprofloxacin is an antibacterial agent used mainly in urinary tract infections and prostate inflammation. This drug acts also against cancer cells by the inhibition of topoisomerase II. These properties should allow it to inhibit the development of prostate cancer. Firstly, ciprofloxacin can stop the acute and chronic prostate inflammation which can lead to cancer development. Secondly, ciprofloxacin can potentially kill prostate cancer cells in their early stage of development. Ciprofloxacin accumulates mainly in the prostate after oral intake thus ciprofloxacin seems to be a perfect candidate as a prophylactic agent.

Topoisomerase IIalpha maintains genomic stability through decatenation G(2) checkpoint signaling

Topoisomerase IIalpha (topoIIalpha) is an essential mammalian enzyme that topologically modifies DNA and is required for chromosome segregation during mitosis. Previous research suggests that inhibition of topoII decatenatory activity triggers a G(2) checkpoint response, which delays mitotic entry because of insufficient decatenation of daughter chromatids. Here we examine the effects of both topoIIalpha and topoIIbeta on decatenatory activity in cell extracts, DNA damage and decatenation G(2) checkpoint function, and the frequencies of p16(INK4A) allele loss and gain. In diploid human fibroblast lines, depletion of topoIIalpha by small-interfering RNA was associated with severely reduced decatenatory activity, delayed progression from G(2) into mitosis and insensitivity to G(2) arrest induced by the topoII catalytic inhibitor ICRF-193. Furthermore, interphase nuclei of topoIIalpha-depleted cells showed increased frequencies of losses and gains of the tumor suppressor genetic locus p16(INK4A). This study shows that the topoIIalpha protein is required for decatenation G(2) checkpoint function, and inactivation of decatenation and the decatenation G(2) checkpoint leads to abnormal chromosome segregation and genomic instability.

Revised genetic requirements for the decatenation G2 checkpoint: the role of ATM

The decatenation G2 checkpoint is proposed to delay cellular progression from G2 into mitosis when intertwined daughter chromatids are insufficiently decatenated. Previous studies indicated that the ATM- and Rad3-related (ATR) checkpoint kinase, but not the ataxia telangiectasia-mutated (ATM) kinase, was required for decatenation G2 checkpoint function. Here, we show that the method used to quantify decatenation G2 checkpoint function can influence the identification of genetic requirements for the checkpoint. Normal human diploid fibroblast (NHDF) lines responded to the topoisomerase II (topo II) catalytic inhibitor ICRF-193 with a stringent G2 arrest and a reduction in the mitotic index. While siRNA-mediated depletion of ATR and CHEK1 increased the mitotic index in ICRF-193 treated NHDF lines, depletion of these proteins did not affect the mitotic entry rate, indicating that the decatenation G2 checkpoint was functional. These results suggest that ATR and CHEK1 are not required for the decatenation G2 checkpoint, but may influence mitotic exit after inhibition of topo II. A re-evaluation of ataxia telangiectasia (AT) cell lines using the mitotic entry assay indicated that ATM was required for the decatenation G2 checkpoint. Three NHDF cell lines responded to ICRF-193 with a mean 98% inhibition of the mitotic entry rate. Examination of the mitotic entry rates in AT fibroblasts upon treatment with ICRF-193 revealed a significantly attenuated decatenation G2 checkpoint response, with a mean 59% inhibition of the mitotic entry rate. In addition, a normal lymphoblastoid line exhibited a 95% inhibition of the mitotic entry rate after incubation with ICRF-193, whereas two AT lymphoblastoid lines displayed only 36% and 20% inhibition of the mitotic entry rate. Stable depletion of ATM in normal human fibroblasts with short hairpin RNA also attenuated decatenation G2 checkpoint function by an average of 40%. Western immunoblot analysis demonstrated that treatment with ICRF-193 induced ATM autophosphorylation and ATM-dependent phosphorylation of Ser15-p53 and Thr68 in Chk2, but no appreciable phosphorylation of Ser139-H2AX or Ser345-Chk1. The results suggest that inhibition of topo II induces ATM to phosphorylate selected targets that contribute to a G2 arrest independently of DNA damage.

Does ciprofloxacin have an obverse and a reverse?

Ciprofloxacin is an antibiotic that belongs to fluoroquinoles, characterized by broad spectrum of action against pathogens, especially Gram(-) aerobic bacilli. For a long time, it has been thought that ciprofloxacin has an effect only on bacterial cells. Now it is known, that this drug can significantly affect eukaryotic cells including human cancer cells. Its bactericidal action relay on inhibition of topoisomerase II, enzyme responsible for alterations in 3D structure of DNA during replication, transcription and chromatin condensation. Thanks to that, ciprofloxacin can induce cell cycle arrest and apoptosis of cancer cells. The effectiveness of ciprofloxacin was confirmed in several in vitro studies on tumor cell lines such as: human bladder cells, leukaemic cell lines, human osteosarcoma cells, human prostate cancer cells, human colorectal carcinoma cells and human non-small cell lung cancer cell line. Ciprofloxacin is particularly effective against non-small cell lung cancer mainly due to accumulation of ciprofloxacin in lung tissue after intravenous administration and its toxicity against lung cancer lines in vitro in a concentration and time-dependent manner.

Fluoroquinolones lower constitutive H2AX and ATM phosphorylation in TK6 lymphoblastoid cells via modulation of the intracellular redox status

Accumulation of reactive oxygen species (ROS)-induced damage and mutations in the genomic DNA is considered the primary etiology of aging and age-related pathologies including cancer. Strategies aimed at slowing these conditions often involve protecting against oxidative DNA damage via modulation of the intracellular redox state. Recently, a biomarker of DNA double-strand breaks (DSBs), serine 139-phosphorylated histone H2AX (gammaH2AX), and its upstream mediator, activated PI-3-related kinase, ATM (ATM(P1981)), were shown to be constitutively expressed in cells and modulated by antioxidant treatment. Thus, both constitutive histone H2AX phosphorylation (CHP) and constitutive ATM activation (CAA) are thought to reflect a cell's response to endogenous ROS-induced DSBs. In the present study, we investigated the effects of a battery of fluoroquinolone (FQ) compounds, namely ciprofloxacin, enrofloxacin, gatifloxacin, lomefloxacin and ofloxacin, on CHP and CAA in human TK6 lymphoblastoid cells. All FQs tested reduced CHP and CAA compared to controls following 6 and 24 h treatment with CAA being more sensitive to their effects at both time points. In addition, intracellular ROS levels and mitochondrial activities were also lowered in FQ-treated cells at 6 and 24 h.We presume that FQs mediate this effect via a combination of ROS-scavenging and mitochondrial suppression and therefore may protect against the onset or may slow the progression of numerous oxidative pathophysiological conditions.