Protective effect of astaxanthin nanoemulsion on mammalian inner ear hair cells.

Background: Aminoglycoside antibiotics are used for treating certain acute infections. However, these drugs cause ototoxicity by inducing inner ear hair cell death. Aims/Objectives: We investigated the protective effect of a nanoemulsion of the carotenoid astaxanthin on mammalian inner ear hair cells against neomycin-induced ototoxicity. Material and Methods: Dose-response relationship, quantification of hair cell loss, and reactive oxygen species production were assayed in response to neomycin with and without astaxanthin in cultured utricles of CBA/N mice. In addition, auditory brain response (ABR) and hair cell loss after exposure to the nanoformulation and loud noise were examined in vivo in guinea pigs. Results: Astaxanthin suppressed neomycin-induced reduction of hair cells by reducing the production of hydroxy radicals. Furthermore, hair cell loss in the second rotation of the cochlea was significantly lower in the astaxanthin group than in the noise-only group. Conclusions and Significance: The blood-labyrinth barrier limits the successful delivery of drugs for inner ear complications. However, in the nanoemulsion form, astaxanthin can penetrate the round window (fenestra ovale) membrane, enabling topical administration. Thus, astaxanthin nanoemulsion could be useful in treating ototoxicity in individuals with inner ear complications.

Effect of preservation on the physical and chemical properties of the temporal fascia.

OBJECTIVE: The temporal fascia has been widely used in tympanoplasty. In addition, the preserved fascia has been also used in the ear surgery. In this study, we planned the experiments to determine whether physical and chemical properties of the fascia preserved at a low temperature. METHODS: Preserved temporal fasciae from 21 patients were used in this study. The thickness of the temporal fascia was measured under a 3D laser microscope. The tensile strength was evaluated using a tensile tester. In addition, the chemical property evaluated was the biologic antioxidative potential of samples. RESULTS: The results showed that the strength of the fascia was not affected by the retention period. The thick fascia tended to show the less tensile strength. The intensity was highest in middle-aged donors when compared to young and older donor. The antioxidative potentials did not affect the preservation. CONCLUSION: The results suggested that the preserved temporal fascia could be safely used for tympanoplasty.

Protective effect of an astaxanthin nanoemulsion against neomycin-induced hair-cell damage in zebrafish.

Objective: The cause of those hair cells disorder is oxidative stress due to free radicals. In particular, hair cells are very susceptible to aminoglycosides. Antioxidant is known to reduce the generation of oxygen-derived free radicals. Various antioxidant is marketed, and different dosage form is developed with the same drug. Using a zebra fish lateral line, we report hair cell protection effect of astaxanthin from neomycin-induced trauma. Methods: Zebrafish larvae were exposed to the astaxanthin nanoemulsion or to the suspension for 1 h, or were left unexposed. Subsequently, the larvae were exposed to neomycin for 1 h by adding the neomycin solution. Results were calculated as the mean hair-cell survival as a percentage of the control. Results: Hair cells were not protected in the group treated with astaxanthin suspension and neomycin. On the other hand, there was dose-dependent protection against neomycin-induced hair-cell death in the zebrafish lateral-line hair cells in the group treated with nano astaxanthin. Conclusion: The results of the current study performed using a zebra fish lateral-line, nano astaxanthin protected sensory hair cells against neomycin-induced death. This suggests that nano-astaxanthin is more efficiently absorbed in the body than astaxanthin, and may be useful as a protective drug for the inner ear.