Effects of ofloxacin on chondrogenesis in murine cartilage organoid culture

Effects of TNFR1 gene silencing on early apoptosis of marbofloxacin-treated chondrocytes from juvenile dogs

Quinolones (QNs)-induced cartilaginous lesions in juvenile animals by chondrocyte apoptosis is an important toxic effect, which results in the restriction of their use in pediatrics. However, limited data about QNs chondrotoxicity are available for evaluation of the potential toxicity in both animals and human cartilage. To explore whether tumor necrosis factor/its receptor (TNF/TNFR1) signaling pathway is involved in the early apoptosis of marbofloxacin-induced chondrocytes, canine juvenile chondrocytes were treated with 0, 20, 50 and 100 μg/mL marbofloxacin. Results showed that the apoptosis rates of the chondrocytes at 2, 8 and 24 h were significantly increased in a concentration- and time-dependent manner (P <  0.05). The mRNA levels of apoptosis-related factors in TNF/TNFR1 signaling pathways and the protein levels of TNFα and TNFR1 were increased in canine chondrocytes treated with 20-100 μg/mL marbofloxacin (P <  0.05) while TNFR1 gene silencing significantly decreased the chondrocyte apoptosis and inhibited the mRNA expression of TNF/TNFR1 downstream signaling molecules after 100 μg/mL marbofloxacin treatment at 8 h (P <  0.01). It was confirmed that activated TNF/TNFR1 signaling pathway may play a leading role in the early apoptosis of marbofloxacin-induced canine juvenile chondrocytes, which is helpful for clinical estimation or prevention of the risk of QNs.

Toxic effects of levofloxacin on rat annulus fibrosus cells: an in-vitro study

BACKGROUND

Fluoroquinolones are in wide clinical use as safe and effective antibiotics. Articular cartilage, tendons, and epiphyseal growth plates have been recognized as targets of fluoroquinolone-induced connective tissue toxicity. However, the effects of fluoroquinolones on annulus fibrosus (AF) cells are still unknown.

MATERIAL/METHODS

The main objective of this study was to investigate the effects of levofloxacin, a typical fluoroquinolone antibiotic drug, on rat AF cells in vitro. Rat annulus fibrosus (RAF) cells were treated with levofloxacin at different concentrations (0, 10, 20, 30, 40, 60, 80, and 90 μg/ml) and were assessed to determine the possible cytotoxic effects of levofloxacin. Inverted phase-contrast microscopy was used to accomplish the morphological observation of apoptosis of treated cells. Western blot and real-time quantitative RT-PCR (qPCR) was used to explore the expression of active caspase-3 and MMP-3. Flow cytometry was used to measure the apoptotic incidences.

RESULTS

Our study showed that levofloxacin, with concentrations at 30, 60, and 90 μg/ml, induced dose-dependent RAF cell apoptosis and higher expression of caspase-3 and MMP-3. More apoptotic cells were observed by inverted phase-contrast microscopy. Moreover, levofloxacin increased the activity of caspase-3, and it also reduced cell viability with different concentrations ranging from 10 to 80 μg/ml.

CONCLUSIONS

Our study results suggest that levofloxacin has cytotoxic effects on RAF cells, characterized by enhancing apoptosis and reducing cell viability, and indicate a potential toxic effect of fluoroquinolones on RAF cells.

Effects of ofloxacin on integrin expression on epiphyseal mouse chondrocytes in vitro

Quinolone-induced arthropathy is an important toxic effect in immature animals that has led to restrictions of the therapeutic use of these antimicrobial agents. The effects of ofloxacin on epiphyseal chondrocytes from 17-day-old mouse foetuses were studied in vitro. Adhesion of the cells to culture dishes was impaired in a concentration-dependent manner and was first perceptible at a concentration of 10 mg ofloxacin/litre medium. A closer analysis by immunomorphological methods showed that the expression of several integrin receptors (beta1, alpha3, alpha5beta1, alphavbeta3) on the chondrocytes was reduced. Again, first alterations occurred at the rather low concentration of 10 mg ofloxacin/litre medium, and at 30 mg ofloxacin/litre medium alpha3- and alpha5beta1 integrins were demonstrable on 50% or less of the cultured cells. Based on these findings in vitro, a new hypothesis for the mechanism of the chondrotoxicity of quinolones is proposed: the ability of these antimicrobials to form chelate complexes with divalent cations could explain why the integrin receptors on chondrocytes are altered after quinolone exposure, since it is well known that the function of the integrin receptor depends on calcium or magnesium ions. Further investigations are under way to study the effects of quinolones on integrin receptors in cartilage in more detail.

Effects of enrofloxacin and magnesium deficiency on matrix metabolism in equine articular cartilage

OBJECTIVE

To investigate the effects of enrofloxacin and magnesium deficiency on explants of equine articular cartilage.

SAMPLE POPULATION

Articular cartilage explants and cultured chondrocytes obtained from adult and neonatal horses.

PROCEDURE

Full-thickness explants and cultured chondrocytes were incubated in complete or magnesium-deficient media containing enrofloxacin at concentrations of 0, 1, 5, 25, 100, and 500 microg/ml. Incorporation and release of sulfate 35S over 24 hours were used to assess glycosaminoglycan (GAG) synthesis and degradation. An assay that measured binding of dimethylmethylene blue dye was used to compare total GAG content between groups. Northern blots of RNA from cultured chondrocytes were probed with equine cDNA of aggrecan, type-II collagen, biglycan, decorin, link protein, matrix metalloproteinases 1, 3, and 13, and tissue inhibitor of metalloproteinase 1.

RESULTS

A dose-dependent suppression of 35S incorporation was observed. In cartilage of neonates, 35S incorporation was substantially decreased at enrofloxacin concentrations of 25 mg/ml. In cartilage of adult horses, 35S incorporation was decreased only at enrofloxacin concentrations of > or =100 microg/ml. Magnesium deficiency caused suppression of 35S incorporation. Enrofloxacin or magnesium deficiency did not affect GAG degradation or endogenous GAG content. Specific effects of enrofloxacin on steady-state mRNA for the various genes were not observed.

CONCLUSION AND CLINICAL RELEVANCE

Enrofloxacin may have a detrimental effect on cartilage metabolism in horses, especially in neonates.

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.

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.