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Cytotoxicity of Tetracyclines in Human Tympanic Membrane Fibroblasts
Carolyn O Dirain1, Patrick J Antonelli
1Department of Otolaryngology, College of Medicine, University of Florida, Gainesville, Florida.
Hypothesis:
Tetracyclines are less cytotoxic to tympanic membrane (TM) fibroblasts than quinolones.
Background:
Use of quinolone ear drops after tympanostomy tube placement and for acute otitis externa has been linked to an increased risk of TM perforation. This has been verified in animal models. Cell culture studies have shown quinolones to be highly toxic to TM fibroblasts. Tetracyclines are a potential alternative to quinolones as they have been used to treat acute otitis externa and are thought to be nontoxic to the inner ear. We aimed to determine if tetracyclines are cytotoxic to TM fibroblasts.
Methods:
Human TM fibroblasts were treated with 1:10 dilutions of ofloxacin 0.3%, ciprofloxacin 0.3%, doxycycline 0.3 and 0.5%, minocycline 0.3 and 0.5%, tetracycline 0.3 and 0.5%, or dilute HCl (control), twice within 24 hours or four times within 48 hours. After 2 hours of treatment, cells were returned to growth media. Cells were observed with phase-contrast microscopy until cytotoxicity was measured.
Results:
Fibroblasts had lower survival with ciprofloxacin 0.3% and doxycycline 0.5% treatment compared with the control after 24 and 48 hours (all p < 0.0001). Fibroblasts treated with minocycline 0.5% had increased cell survival after 24 hours. Minocycline 0.3 and 0.5% showed increased TM fibroblast survival after 48 hours (all p < 0.0001). Phase-contrast images mirrored the cytotoxicity findings.
Conclusions:
Tetracyclines are less toxic to cultured TM fibroblasts than ciprofloxacin. Fibroblast tetracycline toxicity is drug and dose specific. Minocycline shows the most promise for possible otic applications in which fibroblast toxicity is a concern.
Insights
Tetracyclines are less toxic to tympanic membrane fibroblasts than quinolones. Minocycline demonstrated the most promise for otic applications due to its low cytotoxicity.
Area of Science:
- Ototoxicity research
- Fibroblast cell culture
- Pharmacological safety
Background:
- Quinolone ear drops are linked to tympanic membrane perforation.
- Quinolones exhibit high toxicity to tympanic membrane fibroblasts.
- Tetracyclines are a potential alternative with presumed lower toxicity.
Purpose of the Study:
- To evaluate the cytotoxicity of tetracyclines on human tympanic membrane fibroblasts.
- To compare the toxicity of tetracyclines with quinolones in a cellular model.
Main Methods:
- Human tympanic membrane fibroblasts were exposed to various concentrations of ofloxacin, ciprofloxacin, doxycycline, minocycline, and tetracycline.
- Treatments were administered twice within 24 hours or four times within 48 hours.
- Cell viability was assessed using phase-contrast microscopy after a 2-hour exposure and return to growth media.
Main Results:
- Ciprofloxacin and doxycycline (0.5%) significantly reduced fibroblast survival.
- Minocycline (0.3% and 0.5%) demonstrated increased TM fibroblast survival at 24 and 48 hours.
- Cytotoxicity findings were consistent with phase-contrast microscopy observations.
Conclusions:
- Tetracyclines are less cytotoxic to cultured TM fibroblasts than ciprofloxacin.
- The toxicity of tetracyclines to fibroblasts is specific to the drug and its concentration.
- Minocycline shows potential for otic applications where minimizing fibroblast toxicity is crucial.
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