ubiquinone and Hearing-Loss

Mitoquinone (MitoQ) attenuates amikacin ototoxicity in guinea pigs.. MitoQ, a mitochondria-targeted derivative of the antioxidant ubiquinone, has improved bioavailability and demonstrated safety in humans. Thus, MitoQ is a promising therapeutic approach for protecting against amikacin-induced ototoxicity.. Both oral and subcutaneous administrations of MitoQ were tested. Amikacin-treated guinea pigs (n = 12-18 per group) received water alone (control) or MitoQ 30 mg/l-supplemented drinking water; or injected subcutaneously with 3 to 5 mg/kg MitoQ or saline (control). Auditory brainstem responses and distortion product otoacoustic emissions were measured before MitoQ or control solution administration and after amikacin injections. Cochlear hair cell damage was assessed using scanning electron microscopy and Western blotting.. With oral administration, animals that received 30 mg/l MitoQ had better hearing than controls at only 24 kHz at 3-week (p = 0.017) and 6-week (p = 0.027) post-amikacin. With subcutaneous administration, MitoQ-injected guinea pigs had better hearing than controls at only 24 kHz, 2-week post-amikacin (p = 0.013). Distortion product otoacoustic emission (DPOAE) amplitudes were decreased after amikacin injections, but were not different between treatments (p > 0.05). Electron microscopy showed minor difference in outer hair cell loss between treatments. Western blotting demonstrated limited attenuation of oxidative stress in the cochlea of MitoQ-supplemented guinea pigs.. Oral or subcutaneous MitoQ provided limited protection against amikacin-induced hearing loss and cochlear damage in guinea pigs. Other strategies for attenuating aminoglycoside-induced ototoxicity should be explored.

Topics: Amikacin; Animals; Anti-Bacterial Agents; Antioxidants; Evoked Potentials, Auditory, Brain Stem; Guinea Pigs; Hair Cells, Auditory; Hearing; Hearing Loss; Organophosphorus Compounds; Otoacoustic Emissions, Spontaneous; Ubiquinone

Primary ubiquinone (co-enzyme Q) deficiency results in a wide range of clinical features due to mitochondrial dysfunction. Here, we analyse and characterize two mutations in the ubiquinone biosynthetic gene COQ7. One mutation from the only previously identified patient (V141E), and one (L111P) from a 6-year-old girl who presents with spasticity and bilateral sensorineural hearing loss. We used patient fibroblast cell lines and a heterologous expression system to show that both mutations lead to loss of protein stability and decreased levels of ubiquinone that correlate with the severity of mitochondrial dysfunction. The severity of L111P is enhanced by the particular COQ7 polymorphism (T103M) that the patient carries, but not by a mitochondrial DNA mutation (A1555G) that is also present in the patient and that has been linked to aminoglycoside-dependent hearing loss. We analysed treatment with the unnatural biosynthesis precursor 2,4-dihydroxybenzoate (DHB), which can restore ubiquinone synthesis in cells completely lacking the enzymatic activity of COQ7. We find that the treatment is not beneficial for every COQ7 mutation and its outcome depends on the extent of enzyme activity loss.

Topics: Animals; Base Sequence; Cell Line; Child; Consanguinity; Cytochrome P-450 Enzyme System; DNA Mutational Analysis; DNA, Mitochondrial; Female; Fibroblasts; Hearing Loss; Humans; Hydroxybenzoates; Membrane Proteins; Mice, Knockout; Mitochondrial Proteins; Mixed Function Oxygenases; Mutation; Spastic Paraplegia, Hereditary; Ubiquinone

Objective To determine if mitoquinone (MitoQ) attenuates cisplatin-induced hearing loss in guinea pigs. Study Design Prospective and controlled animal study. Setting Academic, tertiary medical center. Subjects and Methods Guinea pigs were injected subcutaneously with either 5 mg/kg MitoQ (n = 9) or normal saline (control, n = 9) for 7 days and 1 hour before receiving a single dose of 10 mg/kg cisplatin. Auditory brainstem response thresholds were measured before MitoQ or saline administration and 3 to 4 days after cisplatin administration. Results Auditory brainstem response threshold shifts after cisplatin treatment were smaller by 28 to 47 dB in guinea pigs injected with MitoQ compared with those in the control group at all tested frequencies (4, 8, 16, and 24 kHz, P = .0002 to .04). Scanning electron microscopy of cochlear hair cells showed less outer hair cell loss and damage in the MitoQ group. Conclusion MitoQ reduced cisplatin-induced hearing loss in guinea pigs. MitoQ appears worthy of further investigation as a means of preventing cisplatin ototoxicity in humans.

Topics: Animals; Antineoplastic Agents; Antioxidants; Cisplatin; Guinea Pigs; Hearing Loss; Male; Mitochondria; Organophosphorus Compounds; Ubiquinone

Cisplatin (Cpt) is known to induce a high level of oxidative stress, resulting in an increase of reactive oxygen species damaging the inner ear and causing hearing loss at high frequencies. Studies on animal models show that antioxidants may lower Cpt-induced ototoxicity. The aim of this study is to evaluate the ototoxic effects of two different protocols of Cpt administration in a Sprague-Dawley rat model, and to test in the same model the synergic protective effects of a solution of coenzyme Q10 terclatrate and Acuval 400®, a multivitamin supplement containing antioxidant agents and minerals (Acu-Qter). The Cpt was administered intraperitoneally in a single dose (14 mg/kg) or in three daily doses (4.6 mg/kg/day) to rats orally treated or untreated with Acu-Qter for 5 days. The auditory function was assessed by measuring auditory brainstem responses from 2 to 32 kHz at day 0 and 5 days after treatment. Similar hearing threshold and body weight alterations were observed in both Cpt administration protocols, but mortality reduced to zero when Cpt was administered in three daily doses. The Acu-Qter treatment was able to prevent and completely neutralize ototoxicity in rats treated with three daily Cpt doses, supporting the synergic protective effects of coenzyme Q terclatrate and Acuval 400® against Cpt-induced oxidative stress. The administration protocol involving three Cpt doses is more similar to common human chemotherapy protocols, therefore it appears more useful for long-term preclinical studies on ototoxicity prevention.

Topics: Animals; Antineoplastic Agents; Cisplatin; Drug Administration Schedule; Ear, Inner; Hearing Loss; Male; Rats; Rats, Sprague-Dawley; Ubiquinone; Vitamins

Oral supplementation with mitoquinone (MitoQ) prevents gentamicin-induced ototoxicity in guinea pigs.. Antioxidants have been shown to protect against aminoglycoside (AG)-induced ototoxicity. MitoQ, a mitochondria-targeted derivative of the antioxidant ubiquinone, is attached to a lipophilic triphenylphosphonium (TPP) cation, which enables its accumulation inside the mitochondria several hundred-fold over the untargeted antioxidant. MitoQ has improved bioavailability and can reach most tissues and has been used in Parkinson's disease and hepatitis C human trials, which demonstrated that MitoQ can be safely used in humans. Thus, MitoQ is a promising novel therapeutic approach for protecting against AG-induced ototoxicity.. Gentamicin-treated guinea pigs were supplied with water alone (control), decyl-TPP (positive control), or MitoQ-supplemented drinking water. Auditory function was assessed by auditory brainstem response. Cochlear damage was assessed using scanning electron microscopy. Western blotting was performed to evaluate changes in proteins related to apoptosis and oxidative damage in the cochlea.. Threshold shifts at 4 and 8 kHz at 4 and 7 weeks after gentamicin treatment were smaller in animals treated with MitoQ compared with those in the control- and decyl-TPP-treated animals (p < 0.05). Protein carbonyls and levels of the proapoptotic protein Bak were lower (p < 0.05 and p = 0.008, respectively), whereas the level of the antioxidant enzyme manganese superoxide dismutase was higher (p = 0.01) in the cochlea of MitoQ-treated animals. The expression of 3-nitrotyrosine and Hrk were not different between groups (p > 0.05).. Oral supplementation with MitoQ attenuated gentamicin-induced cochlear damage and hearing loss in guinea pigs. MitoQ holds promise as a means for protecting against AG ototoxicity.

Topics: Animals; Antioxidants; Apoptosis; Cochlea; Cochlear Diseases; Evoked Potentials, Auditory, Brain Stem; Gentamicins; Guinea Pigs; Hearing Loss; Mitochondria; Organophosphorus Compounds; Oxidation-Reduction; Oxidative Stress; Superoxide Dismutase; Ubiquinone