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Antimicrobial Agents and Chemotherapy, March 2007, p. 1022-1027, Vol. 51, No. 3
0066-4804/07/$08.00+0 doi:10.1128/AAC.01175-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Institute for Clinical Pharmacology and Toxicology, Charité Universitätsmedizin Berlin, Campus Benjamin Franklin, Department of Toxicology, Berlin, Germany,1 Institute for Prevention and Nutrition, Prof. Vormann GmbH, Ismaning, Germany2
Received 21 September 2006/ Returned for modification 7 November 2006/ Accepted 20 December 2006
| ABSTRACT |
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| INTRODUCTION |
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A review of quinolone use in children revealed no cases of arthropathy. The vast majority of these patients were treated with ciprofloxacin, and the authors of a previous report discussed the possibility that pefloxacin may be an exception to these findings (1). Recent experience with gatifloxacin administered to children with acute severe otitis media showed that this quinolone seems to be safe for children (13). On the other hand, some clinical case reports describe severe arthropathy in humans also and an extensive number of publications indicate that tendon disorders as a result of the toxic quinolone effects on connective tissue structures can be induced by quinolones under therapeutic conditions (12, 22).
A precise molecular mechanism for the induction of tendon or cartilage lesions by quinolones has not yet been identified, but there is some evidence that free-radical formation and oxidative stress may play a role (16). Pretreatment with the scavenger vitamin E can afford protection against such reactions in vitro (6). The formation of free radicals seems to be mediated via the lack of functionally available magnesium in joint cartilage as a result of the chelation of magnesium ions by quinolones. This idea is supported by several observations; for example, the joint cartilage lesions in juvenile rats induced either by quinolone treatment or by feeding with a magnesium-deficient diet were histologically identical (17). Treatment with low doses of quinolones, which are not chondrotoxic in control rats, acts synergistically with a mild, diet-induced magnesium deficiency (11). The developmental phases most sensitive for the induction of those lesions seem to be identical for both treatments (26).
Considering the role of free-radical formation and magnesium deficiency in quinolone-induced arthropathy, it is of special interest whether supplementation with magnesium and vitamin E may diminish the chondrotoxic effect of quinolones. Supplementation with magnesium can reduce the toxic effects of quinolones on chondrocytes in vitro (4). Preliminary data from our laboratory indicated that the administration of magnesium can reduce the incidence of quinolone-induced joint cartilage lesions in juvenile rats. Combined oral magnesium and vitamin E supplementation prevents quinolone-induced cartilage lesions in rats (21).
The objective of the present study was to investigate whether ciprofloxacin-induced chondrotoxicity in juvenile Wistar rats can be diminished by oral supplementation with either magnesium, vitamin E, or a combination. Magnesium and calcium concentrations in plasma and cartilage as well as vitamin E concentrations in plasma were determined in order to investigate specific concentration changes associated with different diet regimes.
| MATERIALS AND METHODS |
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The animals were examined for clinical abnormalities including motility alterations and weighed during the treatment period. Rats were sacrificed by decapitation on day 34, and tissue samples were collected immediately as follows. Blood was collected and centrifuged to separate plasma. Cartilage samples from the right femoral hip joint were excoriated, rinsed in phosphate-buffered saline buffer, and dried, and sample weights were documented. Plasma and cartilage samples were frozen at 25°C until analysis. The knee joint of the right hind limb was removed, rinsed with phosphate-buffered saline buffer, and fixed in 10% formalin.
The research procedures have complied with all relevant guidelines. Animal tests were approved by the local authority.
Histopathology. Joint samples were decalcified (EDTA solution, pH 7.4; Serva, Heidelberg, Germany), dehydrated in alcohol series, and embedded in paraffin (Paraplast Monoject Scientific, Kildare, Ireland). Sagittal sections of 7 µm were cut with a microtome (model no. 1140; Reichert-Jung, Heidelberg, Germany) and stained with 1% toluidine blue (Merck, Darmstadt, Germany). For each knee, 40 to 50 serial sections from the predilection sites were prepared and examined under a light microscope (Axiophot; Zeiss, Jena, Germany) and microscopic findings were documented on photographs.
The presence of typical quinolone-induced joint cartilage lesions (matrix swelling, cleft formation, the loss of chondrocytes and proteoglycans, and decreased matrix staining) as described before in detail (17, 20) as well as the lengths of those lesions on either femoral or tibial knee joint cartilage was documented and evaluated.
Analysis of magnesium, calcium, and vitamin E concentrations. Magnesium and calcium concentrations in plasma and cartilage were determined by means of atomic absorption spectrophotometry (TYE Unicam SP9; Philips). Before analysis, cartilage from the femoral hip joint was lyophilized, cleansed, dryly incinerated to ash (at 110°C with a plasma processor 200-E; Technics, Munich, Germany), and diluted in 0.175% lanthanum solution. Plasma samples were deproteinized with 0.175% lanthanum-0.5% trichloroacetic acid solution. Vitamin E concentrations in plasma were determined using a fluorescence spectrophotometry method after hexane fluid-fluid extraction.
Data analysis. Results were statistically presented as means ± standard deviations (SD). To calculate the statistical significance of results among treatment groups and the control, Pearson's chi-square test (comparison of numbers of cartilage lesions), Fisher's exact test (comparison of numbers of animals with lesions), and the two-sided Dunnett t test after a one-way analysis of variance (ANOVA; comparison of electrolyte and vitamin E concentrations) were employed using the statistical software SPSS 12.0 (SPSS Inc.) and StatXact 6.1 (Cytel Software Corp.). Statistical significance was assumed for P values of <0.05.
| RESULTS |
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Histopathology. Typical quinolone-induced joint cartilage lesions as described before in detail (17, 20) were found in all four groups, with matrix swelling, cleft formation, the loss of chondrocytes, and reduced stainability (loss of proteoglycans). The histological appearance of lesions was not affected by diet supplementation with magnesium or vitamin E (Fig. 1).
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Concentrations of magnesium, calcium, and vitamin E. The results of the mineral and vitamin E analyses are summarized in Table 2. The magnesium concentration in plasma (mean ± SD) was 0.83 ± 0.10 mmol/liter for rats fed a standard diet (group A) and 0.88 ± 0.08 mmol/liter for rats fed a vitamin E-enriched diet (group B). Plasma magnesium levels were significantly higher in the rats fed a magnesium-enriched diet (group C, 1.28 ± 0.23 mmol/liter; P < 0.01) as well as in the rats fed a magnesium- and vitamin E-enriched diet (group D, 1.15 ± 0.20 mmol/liter; P < 0.01) than in the rats fed the standard diet. The magnesium concentrations in articular cartilage, 33.4 ± 6.4 mmol/kg (dry weight) for group C and 35.5 ± 10.4 mmol/kg for group D, were significantly (P, <0.05 for both groups) higher for rats receiving the magnesium- and magnesium- and vitamin E-enriched diets than for rats receiving the standard diet (group A, 27.7 ± 6.7 mmol/kg).
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Plasma tocopherol concentrations, 146 ± 27.4 nmol/ml for group B and 158 ± 25.8 nmol/ml for group D, were significantly (P, <0.01 for both groups) higher for rats receiving vitamin E or magnesium and vitamin E supplementation than for rats receiving the standard diet (group A, 93.6 ± 21.1 nmol/ml). No significant difference between group A and group C (magnesium supplementation; 88.3 ± 21.8 nmol/ml) was observed.
| DISCUSSION |
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The present study investigated the effect of two subcutaneous ciprofloxacin injections of 600 mg/kg in 34-day-old Wistar rats, fed either a standard diet or diets enriched with magnesium or vitamin E or both. In the group receiving standard feed, altogether 17 joint cartilage lesions in 11 of 12 (92%) rats were induced by the two doses of 600 mg of ciprofloxacin/kg. This result corresponded well with findings revealed from a previous experiment by our group, in which an incidence of 16 cartilage lesions in 11 of 12 rats treated with ciprofloxacin under similar conditions was found (21). In corresponding animal studies with ofloxacin, the following incidences were observed: two doses of ofloxacin at 600 mg/kg, 96% (5); single ofloxacin doses of 300, 600, and 1,200 mg/kg, 0%, 71%, and 100%, respectively (17).
In a study with daily intragastric administration of 400, 800, and 1,200 mg of ciprofloxacin/kg to 4-week-old rats for 7 consecutive days, doses of 800 and 1,200 but not 400 mg of ciprofloxacin/kg induced severe cartilage lesions, such as matrix swelling and the loss of chondrocytes. The thickness of cartilage of the femoral condyle in groups receiving ciprofloxacin doses of 800 and 1,200 mg/kg was significantly decreased compared to that in controls (10).
In previous studies, it was shown that in rats a magnesium-deficient diet can induce joint cartilage lesions that are identical to quinolone-induced cartilage lesions (17). The reduction of the magnesium concentration in joint cartilage via the chelating properties of quinolones was discussed as the underlying mechanism. Thus, it is of special interest whether, in reverse, supplementation with magnesium may diminish the chondrotoxic effect of quinolones in vivo. The promoting effect of vitamin E on cell proliferation and its ability to prevent the propagation of free-radical damage in biological membranes are well known. In an in vitro experiment, vitamin E provided a significant protective effect against the cytotoxicity as well as the lipid peroxidation induced by ciprofloxacin in fibroblast cells (6). Considering the role of free-radical formation in the quinolone-induced arthropathy as indicated by the data published by Simonin and colleagues (16), it was expected that supplementation with the scavenger vitamin E should also be beneficial in reducing the toxic effects of quinolones in immature animals.
In the present study, the number of ciprofloxacin-induced joint cartilage lesions was significantly reduced in the animals receiving a diet supplemented with vitamin E or magnesium or both for 10 days. The effects on lesion incidence of the diets with single supplementation (vitamin E, 41% reduction; magnesium, 65% reduction) were shown to be additive by the results for the group receiving combined supplementation (vitamin E plus magnesium, 82% reduction). The reduction of ciprofloxacin-induced joint lesions after combined magnesium-vitamin E supplementation for 10 days was higher than that in a previous experiment by our group with a 7-day supplementation, in which the incidence of those lesions was reduced by 56% only (21). In this previous study as well as in the present experiment, we used different routes of application for the quinolones and the magnesium (subcutaneous and oral) to avoid pharmacokinetic interactions.
The supplementation of the rats' diets with vitamin E and magnesium for 10 days resulted in magnesium concentrations in plasma and cartilage as well as tocopherol concentrations in plasma that were significantly higher than those in samples from animals receiving the standard diet. No difference in calcium concentrations among the groups was observed. In samples from animal groups fed a magnesium- or magnesium- and vitamin E-enriched diet for 10 days, mean magnesium concentrations were up to 54% (plasma) and 28% (cartilage) higher than magnesium concentrations in samples from animals fed a standard diet. For animals fed a vitamin E- or vitamin E- and magnesium-enriched diet, mean tocopherol concentrations in plasma were up to 67% higher than those for animals fed a standard diet.
The characteristic increases in magnesium and vitamin E concentrations in plasma and cartilage and the decreased incidence of ciprofloxacin-induced joint cartilage lesions after supplementation with magnesium and vitamin E support the suggested role of a (latent) magnesium deficiency in the pathogenesis of quinolone-induced cartilage lesions in rats. Magnesium supplementation seems to counterbalance effectively the magnesium deficiency in the extracellular matrix of cartilage initially induced by the formation of quinolone-magnesium chelates. Vitamin E inhibits lipid peroxidation and protects chondrocytes from oxidative stress (27). Thus, the consequences of a magnesium deficiencyincreased lipid peroxidation, the formation of free radicals in several tissues, and a decrease in the content of the antioxidant vitamin Emay be diminished or even compensated for by either magnesium, vitamin E, or both.
The relevance of data regarding quinolone-induced arthropathy from animal studies for humans is still unclear. Rare but well-documented cases of joint damage in children treated with quinolones have been reported. The few pediatric trials for which data are available included too few patients to identify rare adverse effects on joints or to show a causal relationship between treatment and joint damage (2, 13, 14). The chondrotoxic potentials of different quinolones obviously differ, probably due to differences in pharmacokinetic behaviors as well as different affinities for magnesium (9). The highest incidence of arthropathy in humans reported to date is 14% in patients with cystic fibrosis treated with pefloxacin, whereas in a similar group of juvenile patients treated with ofloxacin, no such findings were observed (12).
In summary, the present study provides data indicating that supplementation with magnesium and vitamin E alone or in combination may relevantly diminish joint cartilage lesions induced by quinolones in immature rats. An additive effect of combined supplementation with magnesium and vitamin E was observed. The data further support the proposed pathomechanism of quinolone-induced arthropathy and its sequence with the lack of functionally available magnesium caused by chelation, which leads to increased oxidative stress and the characteristic destruction of cartilage.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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Published ahead of print on 8 January 2007. ![]()
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