Coenzyme Q10 protects hair cells against aminoglycoside

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.

Antibiotic Therapy and Athletes: Is the Mitochondrial Dysfunction the Real Achilles’ Heel?

It is widely recognized that athletes consume oral antibiotics almost twice as often as observed in the non-sports population in order to reduce as much as possible the period of inactivity due to bacterial diseases. However, increasing evidences have demonstrated the ability of some classes of antibiotics to induce muscle weakness, pain, and a feeling of fatigue upon resuming physical activity conditions that considerably limit the athletic performance of athletes, ascribable to alterations in the biochemical mechanisms underlying normal musculoskeletal activity, such as mitochondrial respiration. For this reason, tailoring a treatment plan for effective antibiotics that limit an athlete’s risk is paramount to their safety and ability to maintain adequate athletic performance. The present review illustrates and critically analyzes the evidence on the use of antibiotics in sports, deepening the molecular mechanisms underlying the onset and development of muscle–tendon alterations in athletes as well as delineating the pharmacological strategies aimed at counteracting such adverse events.

Ameliorative effect of taxifolin on gentamicin-induced ototoxicity via down-regulation of apoptotic pathways in mouse cochlear UB/OC-2 cells

BACKGROUND

Taxifolin is a flavanonol with efficacious cytoprotective properties, such as anti-inflammatory, antioxidant, anticancer, hepatoprotective, and nephroprotective effects. However, the potential protective effects of taxifolin against gentamicin-induced ototoxicity have not been confirmed. In this study, the possible mechanisms underlying the effects of taxifolin on gentamicin-induced death of UB/OC-2 cochlear cells were investigated.

METHODS

Mouse cochlear UB/OC-2 cells with or without taxifolin pretreatment were exposed to gentamicin, and the effects on cytotoxicity, reactive oxygen species (ROS) production, mitochondrial permeability transition, and apoptotic marker expression were examined using biochemical techniques, flow cytometry, western blotting, and fluorescent staining.

RESULTS

Little or no apparent effect of taxifolin on cell viability was observed at concentrations less than 40 μM. Further investigations showed that gentamicin significantly inhibited cell viability in a concentration-dependent manner. Pretreatment with taxifolin attenuated gentamicin-induced lactate dehydrogenase release, as well as cellular cytotoxicity. In addition, taxifolin significantly prevented gentamicin-induced cell damage by decreasing ROS production, stabilizing mitochondrial membrane potential, and downregulating the mitochondrial pathway of apoptosis.

CONCLUSION

In summary, pretreatment with taxifolin is effective for mitigating gentamicin-induced apoptotic cell death mediated by the mitochondrial pathway. Our data suggest that taxifolin provides a new approach to combat gentamicin-induced ototoxicity.

Fetal bovine serum inhibits neomycin-induced apoptosis of hair cell-like HEI-OC-1 cells by maintaining mitochondrial function

Aging and exposure to noise or ototoxic drugs are major causes of hair cell death leading to human hearing loss, and many agents have been developed to protect hair cells from apoptosis. Fetal bovine serum (FBS) is a fundamental ingredient in the culture medium of hair cell-like House Ear Institute Organ of Corti 1 (HEI-OC-1) cells, but there have been no reports about the function of FBS in HEI-OC-1 cell apoptosis. In this study, we found that FBS deprivation alone significantly increased HEI-OC-1 cell apoptosis in the absence of neomycin exposure and that the presence of FBS significantly inhibited HEI-OC-1 cell apoptosis after neomycin exposure compared to FBS-deprived cells. Further, we found that the protective effect of FBS was dose dependent and more effective than the growth factors B27, N2, EGF, bFGF, IGF-1, and heparan sulfate. We also found that FBS deprivation significantly disrupted the expression level of mitochondrial proteins, increased pro-apoptotic gene expression, decreased the mitochondrial membrane potential, and increased reactive oxygen species accumulation in HEI-OC-1 cells after neomycin exposure. These findings indicate that FBS is involved in maintaining the level of mitochondrial proteins, maintaining the balance of oxidant gene expression, and preventing the accumulation of ROS, and thus FBS maintains normal mitochondrial function and inhibits apoptosis in HEI-OC-1 cells after neomycin exposure.

Toward Cochlear Therapies

Sensorineural hearing impairment is the most common sensory disorder and a major health and socio-economic issue in industrialized countries. It is primarily due to the degeneration of mechanosensory hair cells and spiral ganglion neurons in the cochlea via complex pathophysiological mechanisms. These occur following acute and/or chronic exposure to harmful extrinsic (e.g., ototoxic drugs, noise...) and intrinsic (e.g., aging, genetic) causative factors. No clinical therapies currently exist to rescue the dying sensorineural cells or regenerate these cells once lost. Recent studies have, however, provided renewed hope, with insights into the therapeutic targets allowing the prevention and treatment of ototoxic drug- and noise-induced, age-related hearing loss as well as cochlear cell degeneration. Moreover, genetic routes involving the replacement or corrective editing of mutant sequences or defected genes are showing promise, as are cell-replacement therapies to repair damaged cells for the future restoration of hearing in deaf people. This review begins by recapitulating our current understanding of the molecular pathways that underlie cochlear sensorineural damage, as well as the survival signaling pathways that can provide endogenous protection and tissue rescue. It then guides the reader through to the recent discoveries in pharmacological, gene and cell therapy research towards hearing protection and restoration as well as their potential clinical application.

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.

Coenzyme Q10 inhibits the aging of mesenchymal stem cells induced by D-galactose through Akt/mTOR signaling

Increasing evidences indicate that reactive oxygen species are the main factor promoting stem cell aging. Recent studies have demonstrated that coenzyme Q10 (CoQ10) plays a positive role in organ and cellular aging. However, the potential for CoQ10 to protect stem cell aging has not been fully evaluated, and the mechanisms of cell senescence inhibited by CoQ10 are still poorly understood. Our previous study had indicated that D-galactose (D-gal) can remarkably induce mesenchymal stem cell (MSC) aging through promoting intracellular ROS generation. In this study, we showed that CoQ10 could significantly inhibit MSC aging induced by D-gal. Moreover, in the CoQ10 group, the expression of p-Akt and p-mTOR was clearly reduced compared with that in the D-gal group. However, after Akt activating by CA-Akt plasmid, the senescence-cell number in the CoQ10 group was significantly higher than that in the control group. These results indicated that CoQ10 could inhibit D-gal-induced MSC aging through the Akt/mTOR signaling.