sirolimus and Hearing-Loss

Autophagy plays a pathogenic role in neurodegenerative disease. However, the involvement of autophagy in the pathogenesis of age-related hearing loss (ARHL) remains obscure. Naturally aged C57BL/6J mice were used to identify the role of autophagy in ARHL, and rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, was administered for 34 weeks to explore the potential therapeutic effect of rapamycin in ARHL. We found that the number of autophagosomes and the expression of microtubule-associated protein 1 light chain 3B (LC3B) decreased as the mice aged. The expression of autophagy-related (Atg) proteins, including Beclin1 and Atg5, and the ratio of LC3-II/I was reduced in aged mice, while mTOR activity in aged mice gradually increased. Rapamycin improved the auditory brainstem response (ABR) threshold (at 8, 12, and 24 kHz). Further exploration demonstrated that spiral ganglion neuron (SGN) density was enhanced in response to administration of rapamycin. The rate of apoptosis in the basal turn SGNs was decreased, whereas autophagy activity was increased in the experimental group. Meanwhile, mTOR activity in the experimental group was decreased. Our findings indicate that age-related deficiency in autophagy may lead to increased apoptosis of aged SGNs. Rapamycin enhances autophagy of SGNs by inhibiting mTOR activation, resulting in amelioration of ARHL. Therapeutic strategy targeting autophagy may provide a potential approach for treating ARHL.

Topics: Aging; Animals; Autophagy; Autophagy-Related Protein 5; Beclin-1; Evoked Potentials, Auditory, Brain Stem; Hearing Loss; Male; Mice; Mice, Inbred C57BL; Microtubule-Associated Proteins; Sirolimus; Spiral Ganglion; TOR Serine-Threonine Kinases

Hearing impairments are the most common symptom of congenital defects, and they generally remain intractable to treatment. Pendred syndrome, the most frequent syndromic form of hereditary hearing loss, is associated with mutations in the anion exchanger pendrin. Loss of pendrin function as an anion exchanger is thought to be causative, but rodent models do not exhibit progressive deafness. Here, we report a degenerative phenotype exhibiting mutant pendrin aggregates and increased susceptibility to cellular stresses in cochlear epithelial cells induced from patient-derived induced pluripotent stem cells (iPSCs). These degenerative phenotypes were rescued by site-specific gene corrections. Moreover, low-dose rapamycin and metformin reduced aggregation and cell death. Our results provide an unexpected, comprehensive understanding of deafness due to "degenerative cochlear disease" and may contribute to rational therapeutic development. This iPSC-based disease model provides an approach to the study of pathogenesis and therapeutic development for hereditary hearing loss.

Topics: Adolescent; Adult; Cell Line; Child; Child, Preschool; Cochlea; Female; Goiter, Nodular; Hearing Loss; Hearing Loss, Sensorineural; Human Embryonic Stem Cells; Humans; Induced Pluripotent Stem Cells; Infant, Newborn; Ion Exchange; Membrane Transport Proteins; Metformin; Phenotype; Protein Aggregates; Sirolimus; Sulfate Transporters; Vestibular Aqueduct

Little is known about hearing impairment in patients after organ transplantation. Few cases of hearing loss associated with different immunosuppressants have been published. To evaluate severe hearing impairment in patients after liver transplantation (OLT), all living adult patients in need of a hearing aid were analyzed. Out of 521 transplanted patients, 25 (5%) were identified with hearing aids. Nine (36%) of these patients either suffered from hearing loss prior to OLT or experienced risk factors such as ototoxic drugs. Of the remaining 16 patients who developed severe hearing loss after OLT (64%), half were men. Mean age was 42 +/- 18 years at OLT, which took place 8 +/- 4 years ago. Main transplantation indication was virus-induced cirrhosis (44%). In 14/16 (88%) patients, the hearing aid was bilateral. In 50% of patients, the hearing aid was necessary within 2 years post-OLT. Additional tinnitus was present in 9/16 patients (56%), otalgia in three patients (19%). Four patients (25%) reported a history of sudden deafness. In three of them, an association with high levels of calcineurin inhibitors was found. The proportion of patients receiving tacrolimus (50%) was relatively higher than those receiving cyclosporine (50%) compared to control patients (28% respectively 64%, P < .05). In conclusion, a high incidence of severe hearing loss was found in patients after liver transplantation. In most patients, onset of hearing loss is early and bilateral, suggesting a dose-dependent toxicity. The pathogenetic role of different immunosuppressants remains to be evaluated.

Topics: Adult; Calcineurin Inhibitors; Deafness; Follow-Up Studies; Hearing Aids; Hearing Loss; Humans; Immunosuppressive Agents; Liver Cirrhosis; Liver Transplantation; Postoperative Complications; Retrospective Studies; Sirolimus; Surveys and Questionnaires; Tacrolimus; Time Factors