Study of potential in vitro and in vivo genotoxicity in hepatocytes of quinolone antibiotics

Cytogenetic alterations in human lymphocyte cultures following exposure to ofloxacin

Ofloxacin (OFX), a second-generation of quinolones, is a broad-spectrum flouroquinolone antibiotic used in the treatment of various bacterial infections. In this article, we aimed to investigate the cytotoxic and genotoxic potentials of OFX in cultured human peripheral lymphocytes. The cytotoxicity and genotoxicity of OFX on human peripheral blood lymphocytes were examined in vitro by sister chromatid exchange (SCE), chromosomal aberrations (CAs) and micronucleus (MN) tests. Cultures were treated with 30, 60 and 120 μg/ml of OFX for 48 h. Dimethylsulfoxide (DMSO) was used as a solvent control. OFX decreased the mitotic index (MI) and nuclear division index (NDI) significantly, especially at higher concentrations (60 and 120 μg/ml) compared with solvent control. OFX significantly induced CAs at all concentrations and SCEs at higher concentrations (60 and 120 μg/ml) compared with solvent control. In conclusion, our results indicated that OFX has cytotoxic, cytostatic and genotoxic potential especially at higher concentrations on human peripheral blood lymphocyte cultures under the experimental conditions.

Assessment of the genotoxicity of quinolone and fluoroquinolones contaminated soil with the Vicia faba micronucleus test

The genotoxicity of quinolone and fluroquinolones was assessed using the micronucleus (MN) test on Vicia faba roots by direct contact exposure to a solid matrix. Plants were exposed to quinolones (nalidixic acid) and fluoroquinolones (ciprofloxacin and enrofloxacin) alone or mixed with artificially contaminated soils. Four different concentrations of each of these antibiotics were tested (0.01, 0.1, 1 and 10 mg/Kg) for nalidixic acid and (0.005, 0.05, 0.5 and 5 mg/Kg) for ciprofloxacin and enrofloxacin. These antibiotics were also used in mixture. Exposure of Vicia faba plants to each antibiotic at the highest two concentrations showed significant MN induction. The lowest two concentrations had no significant genotoxic effect. The mixture of the three compounds induced a significant MN induction whatever the mixture tested, from 0.02 to 20 mg/Kg. The results indicated that a similar genotoxic effect was obtained with the mixture at 0.2 mg/Kg in comparison with each molecule alone at 5-10 mg/Kg. Data revealed a clear synergism of these molecules on Vicia faba genotoxicity.

Genotoxicity of lomefloxacin--an antibacterial drug in somatic and germ cells of Swiss albino mice in vivo

The in vivo genotoxicity of lomefloxacin, a diflourinated antibacterial drug, was evaluated by employing mouse in vivo chromosomal aberration test in bone marrow cells and dominant lethal mutation assay in germ cells. Statistically significant reduction in mitotic index, increase in chromosomal aberrations (CAs)/cell and percent abnormal metaphase was observed only at the highest dose (160 mg/kg b.w.) of the drug. In the dominant lethal mutation assay, a statistically significant decrease in the number of implants/female, compared to vehicle control, was noticed only in the females mated with males treated with 32 mg/kg b.w. during the third week of mating, while statistically significant reduction in live implants/female was noticed at both the doses during the second and third weeks of mating. Nevertheless, no significant change in the number of dead implants/female was observed after lomefloxacin treatment. These results seems to indicate that lomefloxacin is a weak clastogen in the bone marrow cells and non-mutagenic in the germ cells of mouse in vivo.

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.

Effect of quinolone antibiotics on hepatic growth and protein synthesis following partial hepatectomy in rats

Quinolone antibiotics inhibit eukaryotic as well as prokaryotic cell growth and protein synthesis. To determine whether these properties adversely affect hepatic growth and recovery following surgical resection, five groups of healthy, adult male rats (n = 7-8/group) were treated for 10 days with equal volumes of either ofloxacin (50 mg/kg), fleroxacin (25 mg/kg), ciprofloxacin (25 mg/kg), norfloxacin (15 mg/kg) or sterile saline (controls) prior to 70% partial hepatectomy (PH) and daily thereafter until death. Restituted liver mass, DNA and protein synthesis rates were determined at 24, 48 and 72 h PH. The results of the study revealed that all parameters of hepatic regeneration were similar in the five study groups at each time interval. To ensure that an effect on hepatic regeneration was not dose-dependent, additional experiments were performed where 1, 10 and 100 mg/kg ciprofloxacin was administered and DNA synthesis was measured 24 h post-PH. Once again, the results were similar to sterile saline-treated controls. These findings suggest that the quinolone antibiotics are unlikely to have an adverse effect on hepatic recovery following surgical resection of the liver and are safe to use in that setting.

In vitro induction of micronuclei and chromosome aberrations by quinolones: possible mechanisms

The bacterial gyrase inhibitors, ciprofloxacin and PD 124816, were tested for clastogenic and aneugenic activity in V79 Chinese hamster lung cells in vitro. Cells were exposed for 3 h, washed free of drug, and subcultured for assessment of various endpoints. For structural chromosomal aberration (SCA) analysis, cells were incubated for 18 h, and treated with Colcemid for 2 h before harvest. For micronucleus (MN) analysis, treated cells were incubated with cytochalasin B (CYB) for 16 h. Aneugenicity was assessed by utilizing antikinetochore antibody to detect kinetochore-containing (K +) MN. Both quinolones induced significant increases in SCAs and MN, indicating clastogenic activity. With both compounds, however, the MN response was apparent at lower doses, and remained much higher throughout the dose range than the SCA response. The induced MN were predominantly K --, indicating that aneugenicity was not playing a major role in their induction. A possible explanation for the chromosome effects is that cross-reactivity of the gyrase inhibitors with mammalian topoisomerase II interferes with the separation of chromatids at anaphase leading to chromosome breaks and MN. Quinolones are known to inhibit resolution of the normally transient topoisomerase II-DNA cleavable complex, which may result in chromosome stickness. Thus, SCAs detected in metaphase cells may be attributed to quinolone-induced inhibition of topoisomerase II prior to mitosis while MN arise in binucleated cells as a result of this effect which interferes with chromatid separation during anaphase.

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.