Yongkang Ou

Activation of miR-34a/SIRT1/p53 signaling contributes to cochlear hair cell apoptosis: implications for age-related hearing loss

The molecular mechanisms underlying age-related hearing loss are not fully understood, and currently, there is no treatment for this disorder. MicroRNAs have recently been reported to be increasingly associated with age-related diseases and are emerging as promising therapeutic targets. In this study, miR-34a/Sirtuin 1 (SIRT1)/p53 signaling was examined in cochlear hair cells during aging. MiR-34a, p53 acetylation, and apoptosis increased in the cochlea of C57BL/6 mice with aging, whereas an age-related decrease in SIRT1 was observed. In the inner ear HEI-OC1 cell line, miR-34a overexpression inhibited SIRT1, leading to an increase in p53 acetylation and apoptosis. Moreover, miR-34a knockdown increased SIRT1 expression and diminished p53 acetylation, and apoptosis. Additionally, resveratrol, an activator of SIRT1, significantly rescued miR-34a overexpression-induced HEI-OC1 cell death and significantly reduced hearing threshold shifts and hair cell loss in C57BL/6 mice after a 2-month administration. Our results support a link between age-related cochlear hair cell apoptosis and miR-34a/SIRT1/p53 signaling, which may serve as a potential target for age-related hearing loss treatment.

SIRT1 expression in the cochlea and auditory cortex of a mouse model of age-related hearing loss.

SIRT1 is a highly conserved NAD(+)-dependent protein deacetylase known to have protective effects against a variety of age-related diseases. However, there is a lack of information concerning SIRT1 expression in the cochlea and auditory cortex of C57BL/6 mice, a mouse model of age-related hearing loss. Using RT-PCR and immunohistochemistry, we show that SIRT1 is abundantly expressed in the inner hair cells, strial marginal cells, strial intermediate cells, type I and type IV fibrocytes of the spiral ligament and spiral ganglion neurons. In addition, moderate SIRT1 is also detected in the outer hair cells and neurons of the auditory cortex. Associated with elevated hearing thresholds and hair cells loss during aging, there is also a significant reduction of SIRT1 expression in the cochlea and auditory cortex. The expression pattern of SIRT1 in the peripheral and central auditory system suggests that SIRT1 may play an important role in auditory function and therefore may serve as a protective molecule against age-related hearing loss.

The Treatment for Postirradiation Otitis Media With Effusion: A Study of Three Methods

Objective: To explore treatments for postirradiation otitis media with effusion (OME) in patients with nasopharyngeal carcinoma.

Circulating miR-34a levels correlate with age-related hearing loss in mice and humans.

Age-related hearing loss (AHL) is a progressive neurodegenerative disease that is largely silent in its initial stages. There is no sensitive blood biomarker for diagnosis or early detection of AHL. MicroRNAs (miRNAs or miRs) are abundant and highly stable in blood, and have been recently described as powerful circulating biomarkers in a wide range of diseases. In the present study, we identified concordant increases in miR-34a levels in the cochlea, auditory cortex, and plasma of C57BL/6 mice during aging. These increases were accompanied by elevated hearing thresholds and greater loss of hair cells. Levels of miR-34a targets, silent information regulator 1 (SIRT1), B-cell lymphoma-2 (Bcl-2), and E2F transcription factor 3 (E2F3), in the cochlea, auditory cortex, and plasma decreased with aging inversely to miR-34a. Moreover, plasma miR-34a levels were significantly higher in patients with AHL compared with controls who had normal hearing and had a receiver-operating characteristic curve that distinguished AHL patients from controls. However, SIRT1, Bcl-2, and E2F3 showed no correlation with AHL in humans. In summary, circulating miR-34a level may potentially serve as a useful biomarker for early detection of AHL.

Surgical treatment of osteoradionecrosis of the temporal bone in patients with nasopharyngeal carcinoma.

OBJECTIVE To investigate methods of treating diffuse osteoradionecrosis of the temporal bone in cases of nasopharyngeal carcinoma, following radiotherapy. STUDY DESIGN Retrospective. METHODS Fourteen post-irradiation nasopharyngeal carcinoma patients (n = 14 ears) with diffuse osteoradionecrosis received surgical treatment from March 1994 to May 2005. The patients underwent radical mastoidectomy (five ears), extensive radical mastoidectomy (one ear), or radical mastoidectomy and obliteration with local vascularised fascia flaps (eight ears). RESULTS Six ears fully recovered; two ears were still infectious but sequestrum had not re-formed; five ears (50 per cent) still had repeated suppuration and did not epithelialise; and one ear had local re-formation of sequestrum requiring periodic dressing changes. CONCLUSION Diffuse osteoradionecrosis of the temporal bone following radiotherapy for nasopharyngeal carcinoma is difficult to treat surgically. The main objective of surgery is to facilitate drainage and to prevent complications. Radical mastoidectomy and obliteration with local vascularised flaps is an effective method.

Hypoxia-Inducible Factor and Vascular Endothelial Growth Factor Pathway for the Study of Hypoxia in a New Model of Otitis Media with Effusion

The hypoxia-inducible factor and vascular endothelial growth factor (HIF-VEGF) pathway in hypoxic conditions of the middle ear due to dysfunction of the eustachian tube is still unknown, but it is considered as one pathogenetic mechanism in otitis media. This study was designed to investigate the possible involvement of the HIF-VEFG pathway in otitis media with effusion induced by dysfunction of the eustachian tube. We adopted a soft palate approach to obstruct the orifice of the eustachian tube to establish otitis media in a rat model. Auditory evoked brainstem response and tympanometry were used as hearing function tests, hypoxia-related factors were examined by reverse transcriptase polymerase chain reaction (RT-PCR). The expression of hypoxia-related proteins was detected by Western blot and immunostaining. The model of otitis media with effusion was successfully induced by cauterizing the orifice of the eustachian tube. RT-PCR showed up-regulation of hypoxia-related factors in cauterized ears. Western blot and immunostaining showed that the expression of hypoxia-related proteins in cauterized ears was increased. Hypoxia-induced vascular proliferation and an increase in permeability may be one pathogenetic mechanism of otitis media due to dysfunction of the eustachian tube.

Effect of the combination of balloon Eustachian tuboplasty and tympanic paracentesis on intractable chronic otitis media with effusion

OBJECTIVE To evaluate the effect of the combination of balloon Eustachian tuboplasty (BET) and tympanic paracentesis (TP) on intractable chronic otitis media with effusion (COME). METHODS Ninety patients with intractable COME were included and randomly assigned to three groups: BET only (30 patients), BET+paracentesis (30 patients), and paracentesis only (30 patients). Otic endoscopic findings and tympanograms were recorded before the surgery and at the month 1, month 3, and month 6 follow-up evaluations. RESULTS Both the BET only and BET+paracentesis groups achieved better outcomes than the paracentesis group. The BET+paracentesis group exhibited better otic endoscopic scores than the BET only group (p<0.05) at 1month post-operation. However, no significant difference was found at month 3 or month 6 post-operation. No significant difference in the tympanograms was observed between these two groups at month 1, month 3, or month 6 post-operation. The otic endoscopic sign scores improved from month 1 to month 6 in the BET only group and from month 1 to month 3 in the BET+paracentesis group. The conversion of type B tympanograms improved from month 1 to month 6 in the BET and BET+paracentesis groups but not in the paracentesis only group. CONCLUSIONS Our results suggested that the combination of BET and TP was effective for intractable COME and can help shorten the recovery period for middle ear effusion.

NMDA receptors are involved in the regulation of BMP4-mediated survival in rat cochlear epithelial cells.

Bone morphogenic protein (BMP4) and the N-methyl-d-aspartic acid (NMDA) receptor both participate in the regulation of cochlear sensory epithelial cell survival. However, whether the NMDA receptor is involved in the BMP4 pathway has not been fully elucidated in rat cochlear sensory epithelial cells. Here, we show that after 3 days of culture with exogenous BMP4, the number of surviving cells in the treated group was less than that in the control group. The apoptosis rate was higher and the percentage of cells in S-phase was lower in the experimental group than in other control group. When the cells were cultured with noggin for 3 days, the results were opposite of those observed with BMP4. When BMP4-treated cells were supplemented with APV for 3 days, the number of viable cells and the percentage of those in S-phase were greater compared to the BMP4-only group. Additionally, the apoptosis rate was lower in the BMP4+APV cells than in the cells cultured with BMP4 only. Meanwhile, the number of NR2B-positive cells, as revealed by the NR2B mRNA and protein levels, was greater in the BMP4 group than in the control group. These results suggest that BMP4 may affect the expression of NR2B, thus playing a role in regulating the survival of cochlear epithelial cells.

miR-34a/Bcl-2 signaling pathway contributes to age-related hearing loss by modulating hair cell apoptosis

MicroRNAs, such as miR-34, have been reported to influence age-related diseases. In this study, we explored the role of the miR-34a/Bcl-2 signaling pathway in age-related hearing loss (AHL). Using an AHL mouse model (C57BL/6), we found that the expression of miR-34a in the cochlea increased with age, whereas expression of Bcl-2 decreased. Increasing the amount of a miR-34a mimetic in a mouse auditory cell line (HEI-OC1) inhibited Bcl-2, leading to enhanced apoptosis; in contrast, miR-34a inhibition produced the opposite effect. Our results support a link between age-related cochlear hair cell apoptosis and miR-34a/Bcl-2 signaling. The latter may thus serve as a potential target for AHL therapy.

Plasma brain-derived neurotrophic factor levels are increased in patients with tinnitus and correlated with therapeutic effects.

Tinnitus is the perception of sound without an external source and is known to be associated with altered neuronal excitability in the auditory system. Tinnitus severity can be assessed by various psychometric instruments and there is no objective measures developed to evaluate tinnitus severity and therapeutic effects so far. Brain-derived nerve growth factor (BDNF) is believed in playing a key role in regulating neuronal excitability in the brain. To determine whether BDNF correlates with tinnitus induction and severity, we described plasma BDNF levels in patients with tinnitus and healthy controls and evaluated the correlation between plasma BDNF levels and tinnitus severity measured by Tinnitus Handicap Inventory (THI) and Visual Analog Scale (VAS). Moreover, alteration of plasma BDNF levels before and after tinnitus retraining therapy (TRT) in patients with severe tinnitus was also analyzed. We found plasma BDNF levels were elevated in patients with tinnitus compared with healthy controls. In addition, plasma BDNF levels in patients with severe tinnitus were decreased significantly after effective TRT. However, plasma BDNF levels were not correlated with tinnitus loudness and tinnitus severity measured by THI and VAS. These findings support plasma BDNF as a marker for activity changes in the auditory system and could possibly evaluate therapeutic effects in patients with tinnitus.