Use of in vitro topoisomerase II assays for studying quinolone antibacterial agents

DNA topoisomerase IIIβ promotes cyst generation by inducing cyst wall protein gene expression in Giardia lamblia

Giardia lamblia causes waterborne diarrhoea by transmission of infective cysts. Three cyst wall proteins are highly expressed in a concerted manner during encystation of trophozoites into cysts. However, their gene regulatory mechanism is still largely unknown. DNA topoisomerases control topological homeostasis of genomic DNA during replication, transcription and chromosome segregation. They are involved in a variety of cellular processes including cell cycle, cell proliferation and differentiation, so they may be valuable drug targets. Giardia lamblia possesses a type IA DNA topoisomerase (TOP3β) with similarity to the mammalian topoisomerase IIIβ. We found that TOP3β was upregulated during encystation and it possessed DNA-binding and cleavage activity. TOP3β can bind to the cwp promoters in vivo using norfloxacin-mediated topoisomerase immunoprecipitation assays. We also found TOP3β can interact with MYB2, a transcription factor involved in the coordinate expression of cwp1-3 genes during encystation. Interestingly, overexpression of TOP3β increased expression of cwp1-3 and myb2 genes and cyst formation. Microarray analysis confirmed upregulation of cwp1-3 and myb2 genes by TOP3β. Mutation of the catalytically important Tyr residue, deletion of C-terminal zinc ribbon domain or further deletion of partial catalytic core domain reduced the levels of cleavage activity, cwp1-3 and myb2 gene expression, and cyst formation. Interestingly, some of these mutant proteins were mis-localized to cytoplasm. Using a CRISPR/Cas9 system for targeted disruption of top3β gene, we found a significant decrease in cwp1-3 and myb2 gene expression and cyst number. Our results suggest that TOP3β may be functionally conserved, and involved in inducing Giardia cyst formation.

Demonstration of a potent RET transcriptional inhibitor for the treatment of medullary thyroid carcinoma based on an ellipticine derivative

Dominant-activating mutations in the RET (rearranged during transfection) proto-oncogene, which encodes a receptor tyrosine kinase, is often associated with the development of medullary thyroid carcinoma (MTC). The proximal promoter region of the RET gene consists of a guanine-rich sequence containing five runs of three consecutive guanine residues that serve as the binding site for transcriptional factors. As we have recently shown, this stretch of nucleotides in the promoter region is highly dynamic in nature and tend to form non-B DNA secondary structures called G-quadruplexes, which suppress the transcription of the RET gene. In the present study, ellipticine and its derivatives were identified as excellent RET G-quadruplex stabilizing agents. Circular dichroism (CD) spectroscopic studies revealed that the incorporation of a piperidine ring in an ellipticine derivative, NSC311153 improves its binding with the G-quadruplex structure and the stability induced by this compound is more potent than ellipticine. Furthermore, this compound also interfered with the transcriptional mechanism of the RET gene in an MTC derived cell line, TT cells and significantly decreased the endogenous RET protein expression. We demonstrated the specificity of NSC311153 by using papillary thyroid carcinoma (PTC) cells, the TPC1 cell line which lacks the G-quadruplex forming sequence in the promoter region due to chromosomal rearrangement. The RET downregulation selectively suppresses cell proliferation by inhibiting the intracellular Raf/MEK/ERK and PI3K/Akt/mTOR signaling pathways in the TT cells. In the present study, we also showed that the systemic administration of a water soluble NSC311153 analog in a mouse MTC xenograft model inhibited the tumor growth through RET downregulation.

Synthesis and biological evaluation of naphthoquinone-coumarin conjugates as topoisomerase II inhibitors

Based on previous Topoisomerase II docking studies of naphthoquinone derivatives, a series of naphthoquinone-coumarin conjugates was synthesized through a multicomponent reaction from aromatic aldehydes, 4-hydroxycoumarin and 2-hydroxynaphthoquinone. The hybrid structures were evaluated against the α isoform of human topoisomerase II (hTopoIIα), Escherichia coli DNA Gyrase and E. coli Topoisomerase I. All tested compounds inhibited the hTopoIIα-mediated relaxation of negatively supercoiled circular DNA in the low micromolar range. This inhibition was specific since neither DNA Gyrase nor Topoisomerase I were affected. Cleavage assays pointed out that naphthoquinone-coumarins act by catalytically inhibiting hTopoIIα. ATPase assays and molecular docking studies further pointed out that the mode of action is related to the hTopoIIα ATP-binding site.

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.

Trovafloxacin enhances lipopolysaccharide-stimulated production of tumor necrosis factor-α by macrophages: role of the DNA damage response

Trovafloxacin (TVX) is a drug that has caused idiosyncratic, drug-induced liver injury (IDILI) in humans. In a murine model of IDILI, otherwise nontoxic doses of TVX and the inflammagen lipopolysaccharide (LPS) interacted to produce pronounced hepatocellular injury. The liver injury depended on a TVX-induced, small but significant prolongation of tumor necrosis factor-α (TNF) appearance in the plasma. The enhancement of TNF expression by TVX was reproduced in vitro in RAW 264.7 murine macrophages (RAW cells) stimulated with LPS. The current study was designed to identify the molecular target of TVX responsible for this response in RAW cells. An in silico analysis suggested a favorable binding profile of TVX to eukaryotic topoisomerase II-α (TopIIα), and a cell-free assay revealed that TVX inhibited eukaryotic TopIIα activity. Topoisomerase inhibition is known to lead to DNA damage, and TVX increased the DNA damage marker phosphorylated histone 2A.X in RAW cells. Moreover, TVX induced activation of the DNA damage sensor kinases, ataxia telangiectasia mutated (ATM) and Rad3-related (ATR). The ATR inhibitor NU6027 [6-(cyclohexylmethoxy)-5-nitrosopyrimidine-2,4-diamine] prevented the TVX-mediated increases in LPS-induced TNF mRNA and protein release, whereas a selective ATM inhibitor [2-(4-morpholinyl)-6-(1-thianthrenyl)-4H-pyran-4-one (KU55933)] was without effect. TVX prolonged TNF mRNA stability, and this effect was largely attenuated by NU6027. These results suggest that TVX can inhibit eukaryotic topoisomerase, leading to activation of ATR and potentiation of TNF release by macrophages, at least in part through increased mRNA stability. This off-target effect might contribute to the ability of TVX to precipitate IDILI in humans.

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.

Ciprofloxacin modulates cytokine/chemokine profile in serum, improves bone marrow repopulation, and limits apoptosis and autophagy in ileum after whole body ionizing irradiation combined with skin-wound trauma

Radiation combined injury (CI) is a radiation injury (RI) combined with other types of injury, which generally leads to greater mortality than RI alone. A spectrum of specific, time-dependent pathophysiological changes is associated with CI. Of these changes, the massive release of pro-inflammatory cytokines, severe hematopoietic and gastrointestinal losses and bacterial sepsis are important treatment targets to improve survival. Ciprofloxacin (CIP) is known to have immunomodulatory effect besides the antimicrobial activity. The present study reports that CIP ameliorated pathophysiological changes unique to CI that later led to major mortality. B6D2F1/J mice received CI on day 0, by RI followed by wound trauma, and were treated with CIP (90 mg/kg p.o., q.d. within 2 h after CI through day 10). At day 10, CIP treatment not only significantly reduced pro-inflammatory cytokine and chemokine concentrations, including interleukin-6 (IL-6) and KC (i.e., IL-8 in human), but it also enhanced IL-3 production compared to vehicle-treated controls. Mice treated with CIP displayed a greater repopulation of bone marrow cells. CIP also limited CI-induced apoptosis and autophagy in ileal villi, systemic bacterial infection, and IgA production. CIP treatment led to LD_0/10 compared to LD_20/10 for vehicle-treated group after CI. Given the multiple beneficial activities of CIP shown in our experiments, CIP may prove to be a useful therapeutic drug for CI.

Role of nitric oxide in the chemistry and anticancer activity of etoposide (VP-16,213)

Originally identified as an innate cytotoxin, nitric oxide ((·)NO) formation in tumors can influence chemotherapy and exacerbate cancer progression. Here, we examined the hypothesis that (·)NO generation contributes to cancer cell drug resistance toward the widely used anticancer drug Etoposide (VP-16). The UV-vis spectrum of VP-16 was not changed by exposure of VP-16 to (·)NO in aqueous buffer. In contrast, reddish-orange compound(s) characteristic of o-quinone- and nitroso-VP-16 were readily generated in a hydrophobic medium (chloroform) in an oxygen-dependent manner. Similar products were also formed when the VP-16 radical, generated from VP-16 and horseradish peroxidase/H2O2, was exposed directly to (·)NO in chloroform in the presence of oxygen. Separation and spectral analysis of VP-16 reaction extracts by electron spin resonance and UV-vis indicated the generation of the phenoxy radical and the o-quinone of VP-16, as well as putative nitroxide, iminoxyl, and other nitrogen oxide intermediates. Nitric oxide products of VP-16 displayed significantly diminished topoisomerase II-dependent cleavage of DNA and cytotoxicity to human HL-60 leukemia cells. LPS-mediated induction of nitric oxide synthase in murine macrophages resulted in VP-16 resistance compared to Raw cells. Furthermore, (·)NO products derived from iNOS rapidly reacted with VP-16 leading to decreased DNA damage and cytotoxicity. Together, these observations suggest that the formation of (·)NO in tumors (associated macrophages) can contribute to VP-16 resistance via the detoxification of VP-16.

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.

High-yield production and characterization of biologically active GST-tagged human topoisomerase IIα protein in insect cells for the development of a high-throughput assay

DNA topoisomerase type II enzymes are well-validated targets of anti-bacterial and anti-cancer compounds. In order to facilitate discovery of these types of inhibitors human topoisomerase II in vitro assays can play an important role to support drug discovery processes. Typically, human topoisomerase IIα proteins have been purified from human cell lines or as untagged proteins from yeast cells. This study reports a method for the rapid over-expression and purification of active GST-tagged human topoisomerase IIα using the baculovirus mediated insect cell expression system. Expression of the GST fused protein was observed in the nuclear fraction of insect cells. High yields (40 mg/L i.e. 8 mg/10(9) cells) at >80% purity of this target was achieved by purification using a GST HiTrap column followed by size exclusion chromatography. Functional activity of GST-tagged human topoisomerase IIα was demonstrated by ATP-dependent relaxation of supercoiled DNA in an agarose gel based assay. An 8-fold DNA-dependent increase in ATPase activity of this target compared to its intrinsic activity was also demonstrated in a high-throughput ATPase fluorescence based assay. Human topoisomerase IIα inhibitors etoposide, quercetin and suramin were tested in the fluorescence assay. IC(50) values obtained were in good agreement with published data. These inhibitors also demonstrated ≥ 30-fold potency over the anti-bacterial topoisomerase II inhibitor ciprofloxacin in the assay. Collectively these data validated the enzyme and the high-throughput fluorescence assay as tools for inhibitor identification and selectivity studies.

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.

A Highly Regioselective Synthesis of 8-Hydroxy-3-Sulfanyl-7-Undecyl-5H-[1,2,4]Triazolo[3,4-b][1,3,4]Benzothiadiazole-6,9-Dione and its Derivatives

Regioselective synthesis of novel 8-hydroxy-3-sulfanyl-7-undecyl-5H-[1,2,4]triazolo[3,4-b][1,3,4]benzothiadiazole-6,9-dione (3) by condensation of 2-bromo-3,6-dihydroxy-5-undecyl-1,4-benzoquinone (bromoembelin) (1) with 4-amino-4H-1,2,4-triazole-3,5-dithiol (2) in ethanol. Reaction of 3 with various alkyl, aralkyl and phenacyl halides gave the corresponding thioethers (4).

Type II topoisomerases--inhibitors, repair mechanisms and mutations

Type II topoisomerases are ubiquitous enzymes that play an essential role in the control of replicative DNA synthesis and share structural and functional homology among different prokaryotic and eukaryotic organisms. Antibacterial fluoroquinolones target prokaryotic topoisomerases at concentrations 100- to 1000-fold lower than mammalian enzymes, the preferred targets of anticancer drugs such as etoposide. The mechanisms of action of both of these types of inhibitors involve the fixation of an intermediate reaction step, where the enzyme is covalently bound to an enzyme-mediated DNA double-strand break (DSB). The resulting ternary drug-enzyme-DNA complexes can then be converted to cleavage complexes that block further movement of the DNA replication fork, subsequently inducing stress responses. In haploid prokaryotic cells, stress responses include error-free and error-prone DNA damage repair pathways, such as homologous recombination and translesion synthesis, respectively. The latter can result in the acquisition of point mutations. Diploid mammalian cells are assumed to preferentially use recombination mechanisms for the repair of DSBs, an example of which, non-homologous end joining, is a major error-prone repair mechanism associated with an increased frequency of detectable small deletions, insertions and translocations. However, results obtained from safety testing of novel fluoroquinolones at high concentrations indicate that point mutations may also occur in mammalian cells. Recent data provide evidence for translesion synthesis catalysed by error-prone repair polymerases as a damage-tolerance repair mechanism of DSBs in eukaryotic cells. This paper discusses possible roles of different mechanisms for the repair of DSBs operating in both eukaryotic and prokaryotic cells that result in recombinational rearrangements, deletions/insertions as well as point mutations.

The pentapeptide repeat proteins MfpAMt and QnrB4 exhibit opposite effects on DNA gyrase catalytic reactions and on the ternary gyrase-DNA-quinolone complex

MfpA(Mt) and QnrB4 are two newly characterized pentapeptide repeat proteins (PRPs) that interact with DNA gyrase. The mfpA(Mt) gene is chromosome borne in Mycobacterium tuberculosis, while qnrB4 is plasmid borne in enterobacteria. We expressed and purified the two PRPs and compared their effects on DNA gyrase, taking into account host specificity, i.e., the effect of MfpA(Mt) on M. tuberculosis gyrase and the effect of QnrB4 on Escherichia coli gyrase. Whereas QnrB4 inhibited E. coli gyrase activity only at concentrations higher than 30 microM, MfpA(Mt) inhibited all catalytic reactions of the M. tuberculosis gyrase described for this enzyme (supercoiling, cleavage, relaxation, and decatenation) with a 50% inhibitory concentration of 2 microM. We showed that the D87 residue in GyrA has a major role in the MfpA(Mt)-gyrase interaction, as D87H and D87G substitutions abolished MfpA(Mt) inhibition of M. tuberculosis gyrase catalytic reactions, while A83S modification did not. Since MfpA(Mt) and QnrB4 have been involved in resistance to fluoroquinolones, we measured the inhibition of the quinolone effect in the presence of each PRP. QnrB4 reversed quinolone inhibition of E. coli gyrase at 0.1 microM as described for other Qnr proteins, but MfpA(Mt) did not modify M. tuberculosis gyrase inhibition by fluoroquinolones. Crossover experiments showed that MfpA(Mt) also inhibited E. coli gyrase function, while QnrB4 did not reverse quinolone inhibition of M. tuberculosis gyrase. In conclusion, our in vitro experiments showed that MfpA(Mt) and QnrB4 exhibit opposite effects on DNA gyrase and that these effects are protein and species specific.

QSAR analysis of 1,4-dihydro-4-oxo-1-(2-thiazolyl)-1,8-naphthyridines with anticancer activity

In the present study a quantitative structure activity relationship (QSAR) analysis was applied to a series of 100 of 7- and 3-substituted 1,4-dihydro-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine derivatives. The Chem-X (version 2000) software was used to develop 3D QSAR models. The steric and electrostatic interactions between a probe atom (H(+)) and a set of aligned molecules were assessed using the comparative molecular field analysis method. Statistically relevant models were derived for both electrostatic and steric fields. A 2D model over a restricted series of close structural analogs was derived as well. A number of conclusions on the relationship between the type and size of different substituents and the antitumor activity of the compounds were derived.

Effects of some antibiotics on paraoxonase from human serum in vitro and from mouse serum and liver in vivo

Paraoxonase (PON1, EC 3.1.8.1) is an esterase protein which plays multifunctional role in metabolism. Therefore, in this study the effects of commonly used antibiotics, namely sodium ampicillin, ciprofloxacin, rifamycin SV and clindamycin phosphate, on human PON1 were investigated in vitro and in vivo. Human serum paraoxonase (PON1) was separately purified by ammonium sulfate precipitation and hydrophobic interaction chromatography. The in vitro effects of the antibiotics in purifying human serum paraoxonase was determined using paraoxon as a substrate, and the IC50 values of these drugs exhibiting inhibition effects were found from graphs of hydratase activity % by plotting the concentration of the drugs. It was determined that sodium ampicillin, ciprofloxacin, and clindamycin phosphate were effective inhibitors on human serum PON1, and the inhibition kinetics of interaction of sodium ampicillin, ciprofloxacin, and clindamycin phosphate with the human serum PON1 was also determined, with the Ki of sodium ampicillin, ciprofloxacin, and clindamycin phosphate being 0.00714+/-0.00068, 6.5x10(-6)+/-4.59x10(-7), 0.0291+/-0.0077 mM, respectively. The in vivo effects of the antibiotics on paraoxonase enzyme activity in mouse serum and liver PON1 were also investigated. Mouse liver PON1 activity showed a statistically significant change at 2, 4 and 6 h of drug application in vivo. Sodium ampicillin and clindamycin phosphate exhibited about 80% mouse liver PON1 at 2 or 4 h (p: 0.034, 0.003 and 0.021, respectively). In addition, ciprofloxacin and rifamycin SV only showed inhibition at 4 h incubation. Sodium ampicillin (17.12 mg/kg) lead to a significant decrease in mouse serum PON1 after 4 h drug administration. Ciprofloxacin (3.2 mg/kg), rifamycin SV (3.56 mg/kg) and clindamycin phosphate (2.143 mg/kg) did not exhibit any inhibition effect for the mouse serum PON1, in vivo.

Antimicrobial activities of naphthazarins from Arnebia euchroma

Bioassay-directed fractionation of extract of Arnebia euchroma led to the isolation of alkannin (1), shikonin (2), and their derivatives (3-8) as the active principles against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). The stereochemistry of alpha-methylbutyryl alkannin (8) is revealed for the first time, and the antimicrobial activity of 8 was compared with its corresponding diastereomer (9). The derivatives 3-9 showed stronger anti-MRSA activity [minimum inhibitory concentrations (MICs) ranged from 1.56 to 3.13 microg/mL] than alkannin or shikonin (MIC = 6.25 microg/mL). Anti-MRSA activity of derivatives was bactericidal with minimum bactericidal concentration (MBC)/MIC < or = 2. In a time-kill assay, the bactericidal activity against MRSA was achieved as rapidly as 2 h. The derivatives 3-9 were also active against vancomycin-resistant Enterococcus faecium (F935) and vancomycin-resistant Enterococcus faecalis (CKU-17) with MICs similar to those with MRSA. Aromatic ester derivatives were also synthesized for antimicrobial activity comparison. None of these compounds were active against Gram-negative bacteria tested. Their cytotoxicity was also evaluated on selected cancer cell lines, and they expressed their activity in the range 0.6-5.4 microg/mL (CD(50)). Our results indicate that the ester derivatives of alkannin are potential candidates of anti-MRSA and anti-VRE agents with antitumor activity.

Ciprofloxacin: in vivo genotoxicity studies

The fluoroquinolone ciprofloxacin is widely used in antimicrobial therapy. It inhibits the bacterial gyrase and in high concentrations in vitro also the functionally related eukaryotic topoisomerase-II, which resulted in genotoxic effects in several in vitro tests. In order to evaluate the relevance of these findings, ciprofloxacin was tested in vivo for genotoxic activity using the following test systems: micronucleus test in bone marrow of mice, cytogenetic chromosome analysis in Chinese hamster, dominant lethal assay in male mice and UDS tests in primary rat and mouse hepatocytes in vivo. These results are compared with already published in vitro and in vivo studies with ciprofloxacin. All in vivo genotoxicity revealed no genotoxic effect for ciprofloxacin. In addition, ciprofloxacin was found to be non-carcinogenic in two rodent long-term bioassays. Therefore, ciprofloxacin is considered to be safe for therapeutic use.

Mitochondrial DNA metabolism targeting drugs

Numerous drugs are known to deplete mitochondrial DNA (mtDNA) from mammalian cells. These include DNA polymerase gamma and type II topoisomerase inhibitors, lipophilic cationic compounds, and DNA intercalating and non intercalating agents. The effects of these drugs on mtDNA metabolism will be discussed and potential mechanisms underlying their depletion of mtDNA presented.

Ciprofloxacin inhibition of experimental fracture healing

BACKGROUND

Fluoroquinolones, such as ciprofloxacin, have an adverse effect on growing cartilage and endochondral ossification in children. This study was carried out to determine whether ciprofloxacin also has an adverse effect on the healing of experimental fractures.

METHODS

Sixty male 300-gram Wistar rats were divided equally into three groups, which received ciprofloxacin, cefazolin, or no treatment for three weeks, beginning seven days after production of a closed, nondisplaced, bilateral femoral fracture. The serum concentrations of the ciprofloxacin and the cefazolin were 2.4 and 146 micrograms per milliliter, respectively. Radiographic, histological, and biomechanical studies were used to evaluate fracture-healing.

RESULTS

Radiographs revealed significantly more advanced healing of the control fractures compared with the fractures in the ciprofloxacin-treated group (average stage, 2.1 compared with 1.5, p = 0.01). The cefazolin-treated group was not different from the controls with respect to radiographic healing (average stage, 1.8 compared with 2.1, p = 0.18). Torsional strength-testing of fracture callus exposed to ciprofloxacin revealed a 16 percent decrease in strength compared with the controls (284 compared with 338 newton-millimeters, p = 0.04) and a 49 percent decrease in stiffness (twenty compared with thirty-nine newton-millimeters per degree, p = 0.001). The biomechanical strength in the cefazolin-treated group was not different from that of the controls. Fracture calluses in the animals treated with ciprofloxacin showed abnormalities in cartilage morphology and endochondral bone formation and a significant decrease in the number of chondrocytes compared with the controls (0.77 x 10(4) compared with 1.3 x 10(4) cells per square millimeter, p = 0.004).

CONCLUSIONS

These data suggest that experimental fractures exposed to therapeutic concentrations of ciprofloxacin in serum demonstrate diminished healing during the early stages of fracture repair. The administration of ciprofloxacin during early fracture repair may compromise the clinical course of fracture-healing.

Quinolones inhibit DNA religation mediated by Staphylococcus aureus topoisomerase IV. Changes in drug mechanism across evolutionary boundaries

Quinolones are the most active oral antibacterials in clinical use and act by increasing DNA cleavage mediated by prokaryotic type II topoisomerases. Although topoisomerase IV appears to be the primary cytotoxic target for most quinolones in Gram-positive bacteria, interactions between the enzyme and these drugs are poorly understood. Therefore, the effects of ciprofloxacin on the DNA cleavage and religation reactions of Staphylococcus aureus topoisomerase IV were characterized. Ciprofloxacin doubled DNA scission at 150 nM drug and increased cleavage approximately 9-fold at 5 microM. Furthermore, it dramatically inhibited rates of DNA religation mediated by S. aureus topoisomerase IV. This inhibition of religation is in marked contrast to the effects of antineoplastic quinolones on eukaryotic topoisomerase II, and suggests that the mechanistic basis for quinolone action against type II topoisomerases has not been maintained across evolutionary boundaries. The apparent change in quinolone mechanism was not caused by an overt difference in the drug interaction domain on topoisomerase IV. Therefore, we propose that the mechanistic basis for quinolone action is regulated by subtle changes in drug orientation within the enzyme.drug.DNA ternary complex rather than gross differences in the site of drug binding.

Design and synthesis of modified quinolones as antitumoral acridones

The bacterial topoisomerase II (DNA gyrase) and the mammalian topoisomerase II represent the cellular targets for quinolone antibacterials and a wide variety of anticancer drugs, respectively. In view of the mechanistic similarities and sequence homologies exhibited by the two enzymes, tentative efforts to selectively shift from an antibacterial to an antitumoral activity was made by synthesizing a series of modified tricyclic quinolones, in which the essential 3-carboxylic function is surrogated by phenolic OH and the classic C-6 fluorine atom is replaced by a NH2 group. The resulting 7-amino-9-acridone derivatives were assayed for their antibacterial as well as cytotoxic activities. No antibacterial activity was found. On the other hand, many derivatives showed significant cytotoxic activity against both HL-60 and P388 leukemias and a wide panel of human and rodent solid tumor cells, derivatives 25 and 26 displaying the best overall antiproliferative activity. Against the LoVo cell line, derivative 25 exhibited higher cytotoxic effects than etoposide.

Inhibition of topoisomerase I by naphthoquinone derivatives

Alkannin and shikonin are naturally occurring naphthoquinones. We have tested several derivatives of the title compounds and we have found that naphthoquinones bearing at least one phenolic hydroxyl group are potent inhibitors of topoisomerase I. The ability of the tested compounds to complex Zn++ parallels with a few exceptions their topoisomerase I inhibition properties while their intercalation and redox properties do not.

Topoisomerase IV catalysis and the mechanism of quinolone action

Topoisomerase IV is a bacterial type II topoisomerase that is essential for proper chromosome segregation and is a target for quinolone-based antimicrobial agents. Despite the importance of this enzyme to the survival of prokaryotic cells and to the treatment of bacterial infections, relatively little is known about the details of its catalytic mechanism or the basis by which quinolones alter its enzymatic functions. Therefore, a series of experiments that analyzed individual steps of the topoisomerase IV catalytic cycle were undertaken to address these critical mechanistic issues. The following conclusions were drawn. First, equilibrium levels of DNA cleavage mediated by the bacterial enzyme were considerably (>10-fold) higher than those observed with its eukaryotic counterparts. To a large extent, this reflected decreased rates of DNA religation. Second, the preference of topoisomerase IV for catalyzing DNA decatenation over relaxation reflects increased rates of strand passage and enzyme recycling rather than a heightened recognition of intermolecular DNA helices. Third, quinolones stimulate topoisomerase IV-mediated DNA cleavage both by increasing rates of DNA scission and by inhibiting religation of cleaved DNA. Finally, quinolones inhibit the overall catalytic activity of topoisomerase IV primarily by interfering with enzyme-ATP interactions.

Synthesis and inhibitory activity of novel tri- and tetracyclic quinolines against topoisomerases

A series of isoindolo[2,1-a]- and pyrrolo[1,2-a]quinolines were designed and synthesized for DNA-gyrase and topoisomerase-II inhibition studies. Some of the compounds showed significant activity against the enzymes.

DNA gyrase inhibitory activity of ellagic acid derivatives

Ellagic acid was found to inhibit E. coli DNA gyrase supercoiling with approximately the same potency as nalidixic acid. Tricyclic analogs of ellagic acid, which vary in the number and position of the hydroxy groups as well as their replacement with halogens, have been synthesized. The biological activity of these analogs is discussed.

DNA gyrase inhibitory and antimicrobial activities of some diphenic acid monohydroxamides

The synthesis and inhibitory activity against DNA gyrase of a series of diphenic acid monohydroxamides 4a-f are described. A protocol of two biological assays showed conclusively that inhibition occurs specifically at the DNA-DNA gyrase complex and is not attributable to nonspecific inhibition. In the enzyme assays, 4c was potent as the prototypical quinolone, nalidixic acid (1), with an IC50 value of 58.3 micrograms/mL compared to 52 micrograms/mL for 1. MIC activity against bacterial strains showed a systematic drop for all compounds relative to 1. For compounds 4c-e, the addition of PMBN produced dramatic increases in MIC activity indicating that activity is likely to be related to membrane transport. Molecular modeling of 4a indicates that the diphenic acid monohydroxamides can bind to the DNA-DNA gyrase complex in a similar fashion as that hypothesized for the quinolone series according to the hypothesis suggested by Shen et al. but may not self-associate by pi-pi stacking. In contrast to the quinolone series, as the diphenic acid monohydroxamides are shown by molecular mechanics minimizations to be nonplanar, they may present novel approaches for chemotherapeutic intervention with a potential for decreased side effects.

Attenuation of gentamicin-induced nephrotoxicity in rats by fleroxacin

The effect of fleroxacin on gentamicin-induced nephrotoxicity was evaluated with female Sprague-Dawley rats. Animals were injected during 4 or 10 days with saline (NaCl; 0.9%), gentamicin alone at doses of 10 and 40 mg/kg of body weight/12 h (subcutaneously), fleroxacin alone at a dose of 25 mg/kg/12 h (intraperitoneally), or the combination gentamicin-fleroxacin in the same regimen. Gentamicin induced a dose- and time-dependent renal toxicity as evaluated by gentamicin cortical levels, sphingomyelinase activity in the renal cortex, histopathologic and morphometric analysis, blood urea nitrogen and serum creatinine levels, and cellular regeneration ([3H]thymidine incorporation into DNA of cortical cells). The extent of these changes was significantly reduced when gentamicin was given in combination with fleroxacin. Although the mechanisms by which fleroxacin reduces the nephrotoxic potential of gentamicin are unknown, we propose that the fleroxacin-gentamicin combination enhances exocytosis activity in proximal tubular cells, as suggested by the higher excretion of urinary enzymes and lower cortical levels of gentamicin observed in animals treated with the combination fleroxacin-gentamicin compared with those treated with gentamicin alone. The protective effect of fleroxacin on gentamicin nephrotoxicity should be investigated further.

Quinolone antibiotic photodynamic production of 8-oxo-7, 8-dihydro-2'-deoxyguanosine in cultured liver epithelial cells

To study the basis for the phototoxicity of quinolones, a class of synthetic antibacterials, the photodynamic ability to mediate 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) formation in cultured cells was measured for lomefloxacin (LMX), which is strongly associated with clinical phototoxicity in humans, and ciprofloxacin (CFX), which has few reports of phototoxicity. Adult rat liver (ARL-18) cells were exposed to the quinolones in the presence of UVA and DNA was extracted and analyzed by HPLC with electrochemical detection. Low levels of 8-oxo-dG were found in the DNA of nonirradiated ARL-18 cells and this was increased up to 6-fold in the presence of either LMX (50-400 microM) or up to 3.6-fold in the presence of CFX (50-400 microM) and UVA (20 J/cm2) when compared to the UVA control. Comparing separate experiments with LMX and CFX, LMX produced greater levels of 8-oxo-dG either after dark exposure or after UVA exposure at 20 J/cm2. Also, LMX and CFX were both shown to photodegrade in the presence of UVA, and it was determined that UVA photoinstability alone does not reflect phototoxic potential. These data suggest that the photodynamic potential of LMX and CFX to produce 8-oxo-dG may relate to their human clinical phototoxicity profile. We suggest that the observed clinical phototoxicity is mediated through a UVA photodynamic effect on the quinolone to form reactive oxygen species in the presence of molecular oxygen. The findings indicate that 8-oxo-dG formation can serve as a marker for the potential phototoxicity of new quinolones.

Effect of levofloxacin on glycosaminoglycan and DNA synthesis of cultured rabbit chondrocytes at concentrations inducing cartilage lesions in vivo

We investigated the toxic effect of levofloxacin (LVFX), a quinolone antibacterial agent, on cartilage by examining aspects of its in vivo toxicokinetics and effect on the function of cultured chondrocytes of the femoral articular cartilage from juvenile New Zealand White rabbits. Repeated administration of LVFX (100 mg/kg) orally for 7 days induced focal necrosis and superficial erosion in the articular cartilage of the femoral condyle, but 30 mg/kg did not. Concentrations of LVFX in the cartilage were highest at the first sampling point (30 min) after a single administration, being 4.93 and 12.2 micrograms/g in the 30- and 100-mg/kg groups, respectively. The arthropathic concentration of LVFX in the cartilage was then shown to be 12.2 micrograms/g or more. For an in vitro study, chondrocytes were separated from the articular cartilage of the rabbit femoral condyle and cultured for 7 days until confluence. 35SO4 uptake by cultured chondrocyte sheets was most susceptible to LVFX, decreasing at drug concentrations of 5 micrograms/ml or more in 24- and 48-h cultures but not in a 72-h culture. Furthermore, 3H-thymidine uptake was decreased at concentrations of 10 micrograms/ml or more in a 48-h culture but not in 24- and 72-h cultures. Rhodamine 123 accumulation was susceptible to inhibition in cultured chondrocytes at an LVFX concentration of 10 micrograms/ml or more. These results suggest that LVFX inhibits glycosaminoglycan synthesis initially and DNA synthesis and mitochondrial function secondarily at actual arthropathic concentrations in cultured rabbit chondrocytes but that these changes are reversible and not enough to kill the cells.

Mechanism of action and antitumor activity of (S)-10-(2,6-dimethyl-4-pyridinyl)-9-fluoro-3-methyl-7-oxo-2,3-dihydro-7 H- pyridol[1,2,3-de]-[1,4]benzothiazine-6-carboxylic acid (WIN 58161)

(S)-10-(2,6-Dimethyl-4-pyridinyl)-9-fluoro-3-methyl-7-oxo-2,3-dihydro-7H - pyrido[1,2,3-de][1,4]benzothiazine-6-carboxylic acid (WIN 58161) is an enantiomerically pure quinolone with outstanding bacterial topoisomerase II (DNA gyrase, EC 5.99.1.3) inhibitory and antibacterial activity. Unlike most quinolones, WIN 58161 also exhibits significant inhibitory activity against mammalian topoisomerase II (EC 5.99.1.3). DNA gyrase and topoisomerase II inhibitory activities are enantioselective. Consequently, WIN 58161 and its enantiomer (WIN 58161-2) provide useful tools to probe the contribution of topoisomerase II inhibition to the mechanism of cytotoxicity of quinolones and the potential utility of quinolone-topoisomerase II inhibitors as antitumor agents. WIN 58161 inhibited both highly purified Escherichia coli DNA gyrase and HeLa cell topoisomerase II by the promotion of enzyme-DNA covalent complexes. WIN 58161 did not bind stably to DNA via intercalation and did not enhance the formation of topoisomerase I (EC 5.99.1.2)-DNA covalent complexes. At drug concentrations that are cytotoxic to P388 murine leukemia cells, WIN 58161 promoted intracellular DNA single-strand breaks (SSBs) that exhibited the hallmarks of being mediated by topoisomerase. DNA fragments were complexed with protein, and SSBs were readily resealed at 37 degrees following drug removal. WIN 58161-2 was neither cytotoxic nor did it promote intracellular SSBs in P388. These observations suggest that the mechanism of cytotoxicity of WIN 58161 is predominantly, if not exclusively, a result of topoisomerase II inhibition. When studied in tumor-bearing mice, WIN 58161 exhibited a significant antitumor effect against each of five tumors tested, whereas neither toxicity nor antitumor activity was observed with WIN 58161-2. We conclude from these studies that WIN 58161 represents the prototype of a novel chemical class of topoisomerase II inhibitor with potential clinical utility in treating cancer.

Toxicity of quinolone antimicrobial agents

An approach to minimization of toxicity of a new compound is to elucidate the mechanisms of toxicity of analogous compounds and to clarify their structure-toxicity relationships. A problem with this approach, however, is that such elucidation remains difficult. For quinolones, some improvements in this mechanistic approach have been achieved in the central nervous system (CNS), particularly with regard to their interaction with non-steroidal anti-inflammatory drugs (NSAIDs), and in genotoxicity and phototoxicity studies, particularly in comparison with other toxicities, such as to the cardiovascular, gastrointestinal, bone, reproductive, and developmental systems. This review concentrates on a description of the known effects of quinolones on various organ systems in experimental animals and humans. Given the logarithmic increase in the synthesis of new quinolones, it is questionable whether these drugs share similar safety and efficacy. Nevertheless, this mechanistic approach to the investigation and minimization of toxicity has produced satisfactory results to date and deserves to be continued.

CP-115,953 stimulates cytokine production by lymphocytes

The cytotoxic quinolone CP-115,953 specifically exerts its inhibitory effect upon eukaryotic topoisomerase II. CP-115,953 stimulates DNA cleavage mediated by topoisomerase II with a potency approximately 600 times greater than that of ciprofloxacin, a quinolone antibacterial agent that currently is in clinical use. Because ciprofloxacin has been reported to strongly enhance interleukin-2 production, we considered it important to study the effect of CP-115,953 on interleukin-2 and gamma interferon (IFN-gamma) mRNA and protein expression in mitogen-stimulated human peripheral blood lymphocytes. For comparison, novobiocin and the antineoplastic drug etoposide were also included in the study. CP-115,953 (25 microM) enhanced interleukin-2 mRNA levels up to 8-fold and IFN-gamma mRNA concentrations up to 6.5-fold. In contrast, ciprofloxacin (282 microM) induced mRNAs for interleukin-2 and IFN-gamma up to 20-fold and 7.8-fold, respectively. However, CP-115,953 showed more prolonged kinetics of IFN-gamma mRNA production than ciprofloxacin. At high concentrations (> or = 141 microM), ciprofloxacin was a greater inducer of interleukin-2 production and exhibited a higher level of stimulatory action than CP-115,953 on IFN-gamma synthesis. At low concentrations, however, CP-115,953 (< or = 25 microM) was more potent than ciprofloxacin in inducing interleukin-2 and IFN-gamma synthesis. Etoposide or novobiocin did not influence cytokine mRNA expression. Thus, among the topoisomerase II inhibitors tested, fluoroquinolones are unique in stimulating cytokine synthesis in lymphocyte cultures.

A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase

The activity of 4-quinolone antibacterials at the enzyme target level is based on the well known and reported observations that 4-quinolone antibacterials target the Gyr A subunit of the DNA gyrase holoenzyme, inhibiting supercoiling while facilitating the "cleavable complex". Such inhibition can be observed by running the in vitro DNA gyrase supercoiling inhibition assay or the "cleavable complex" DNA gyrase assay. Although potency of the gyrase inhibitor is dependent on many factors including permeability and pharmacokinetics, the inherent potency of a gyrase inhibitor lies in its activity against the target enzyme. We have examined the binding activity of novel flavones [Bioorganic & Med. Chem. Letters 3:225-230, 1993] to Escherichia coli DNA gyrase and have found differences in binding consistent with inhibition of DNA gyrase supercoiling and ability to facilitate the cleavable complex, but of different rank order. [3H]norfloxacin was used in vitro competition studies with test compounds, pBR322 and E. coli DNA gyrase. Binding affinity results indicate the rank order of greatest to weakest binding (ability to compete with [3H]norfloxacin) of test compounds: Levofloxacin = ciprofloxacin > ofloxacin > norfloxacin > flavone compounds (including ellagic acid, quercetin, and compounds 5a through 5n [Bioorganic & Med. Chem. Letters 3:225-230, 1993]). Such differences in binding ability of the 4-quinolones and flavones to the ternary complex of DNA.DNA gyrase.drug, as compared to the catalytic inhibition and "cleavable complex" data, suggests a more complex binding of flavones than the previously hypothesized models for 4-quinolone binding.

In vitro activity of CP-99,219, a novel 7-(3-azabicyclo[3.1.0]hexyl) naphthyridone antimicrobial

The in vitro activity of CP-99,219 was compared with that of ciprofloxacin and sparfloxacin against 814 clinical bacterial isolates using a microdilution method with brain-heart infusion broth. CP-99,219 was the most potent agent tested against methicillin-resistant, ciprofloxacin-susceptible staphylocci (minimum inhibitory concentration [MIC]90 < or = 0.25 microgram/ml). CP-99,219 was 32-fold and fourfold more potent than ciprofloxacin and sparfloxacin, respectively, against Streptococcus pneumoniae, including strains resistant to penicillin G and erythromycin (MIC90 < or = 0.25 microgram/ml). CP-99,219 was also the most potent agent tested against S. pyogenes and Enterococcus faecalis (MIC90 < or = 0.5 microgram/ml). The activity of CP-99,219 against Enterobacteriaceae was comparable to that of sparfloxacin, with 90% of Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Klebsiella pneumoniae, Citrobacter freundii, C. diversus, Helicobacter pylori, and K. oxytoca being inhibited by < or = 0.5 microgram/ml. Serratia marcescens, Morganella morganii, and Pseudomonas aeruginosa were less susceptible, with MIC90 values to CP-99,219 of 4, 2, and 2 micrograms/ml, respectively. The MIC90 for Bacteroides fragilis was 0.39 microgram/ml for CP-99,219 compared with 12.5 micrograms/ml for ciprofloxacin. CP-99,219 was highly bactericidal at 1 x to 4 x MIC against both Gram-positive and Gram-negative organisms; its activity was similar in nutrient, trypticase soy, and cation-supplemented Mueller-Hinton broths. The spectrum and potency observed with CP-99,219 warrant further testing with this novel quinolone.

Carcinogenicity studies of oxolinic acid in rats and mice

A chronic feeding study was conducted to determine the carcinogenic potential of oxolinic acid, an antimicrobial agent, in rats and mice. Oxolinic acid was administered in the diet to Wistar rats (0, 30, 100, 300 or 1000 ppm; 50 rats/dose/sex) for 104 wk and to ICR mice (0, 50, 150 or 500 ppm; 50 mice/dose/sex) for 78 wk. Clinical signs, body weight, food consumption, autopsy findings and histopathological data were noted. Mortality was unaffected by oxolinic acid administration in neither species. In rats, body weight gain was suppressed in both sexes at 1000 ppm. Histopathological examinations conducted after autopsy at 104 wk revealed a slight increase in benign Leydig cell tumours of the testis at 1000 ppm, which did not appear until late in the lifetime of rats. No other treatment-related neoplastic lesions were observed in rats. Non-neoplastic lesions in males at 1000 ppm included Leydig cell hyperplasia and tubular atrophy of the testes. In mice, decreased body weight gain was observed in both sexes at 500 ppm, but no non-neoplastic or neoplastic lesions attributable to the treatment with oxolinic acid occurred in either sex. In conclusion, oxolinic acid induced benign Leydig cell tumours of the testis in rats at the highest dose level tested (1000 ppm). The no-effect level for tumour induction was confirmed to be 300 ppm (10.9 mg/kg/day) in rats. None was induced in mice.

Comparison of lesions induced by intra-articular injections of quinolones and compounds damaging cartilage components in rat femoral condyles

Twenty-five microliters of a 2% saline solution of levofloxacin (LVFX) or ciprofloxacin (CPFX) was injected every other day for 2 wk into the knee joint space of CD rats (weighing 62.7-86.7 g) from the age of 3 wk. Early in the course of injection, histologic examination revealed chondrocyte necrosis without marked matrix change in the articular cartilage of the femoral condyles adjacent to the intercondylar groove. After 7 injections, the surface and intermediate zones of the articular cartilage showed extensive necrosis, sometimes with cavity formation in the center of the same portion. Papain completely depleted matrix basophilia in all zones throughout the condyle and caused cartilage necrosis with cavity formation. One injection of iodoacetic acid caused necrosis of almost all chondrocytes over the entire condyle, but chondrocytes sometimes remained alive in the portion where cavity formation was induced by quinolones. Chondroitinase depleted the matrix basophilia, and sometimes produced necrotic areas. DNA synthesis inhibitors n-ethylmaleimide, CPT-11, and etoposide (VP-16) caused chondrocyte necrosis, but never caused cavities in the articular cartilage. The DNA synthesis inhibitors n-ethylmaleimide, CPT-11, and hydroxyurea were administered concurrently with po LVFX administration and significantly increased the incidence of LVFX-induced cavity formation. n-Ethylmaleimide was the most effective of all the inhibitors. The quinolone-induced cavity formation is suggested to be site specific in the articular cartilage of rat femoral condyles. The depletion of matrix proteoglycans and chondrocyte necrosis may be necessary, although insufficient, to produce such lesions. Disruption of the collagen framework is suspected to contribute to their development. Involvement of altered DNA metabolism may play a role in the chondrocyte necrosis that occurs early in the specific sites.