Involvement of NLRP3-inflammasome pathway in noise-induced hearing loss.

The inflammasome is a multiprotein oligomer in the cell cytoplasm and is part of the innate immune system. It plays a crucial role in the pathological process of noise-induced hearing loss (NIHL). However, the mechanisms of NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in NIHL have not been clearly demonstrated. In this study, miniature pigs were exposed to white noise at 120 dB(A) and auditory brainstem response measurements were used to measure their hearing function. Immunofluorescence staining, confocal laser scanning microscopy, western blot assay, and quantitative reverse transcription-polymerase chain reaction were used to analyze inflammasome-related protein distribution and expression. NLRP3, interleukin-1ß, interleukin-18, and cleaved-caspase-1 were highly expressed in the cochlea after 120 dB(A) white noise exposure. Our findings suggest that NLRP3-inflammasomes in the cochlea may be activated after acoustic trauma, which may be an important mechanism of noise-induced hearing loss.

Involvement of Cholesterol Metabolic Pathways in Recovery from Noise-Induced Hearing Loss.

The objective of this study was to explore the molecular mechanisms of acute noise-induced hearing loss and recovery of steady-state noise-induced hearing loss using miniature pigs. We used miniature pigs exposed to white noise at 120 dB (A) as a model. Auditory brainstem response (ABR) measurements were made before noise exposure, 1 day and 7 days after noise exposure. Proteomic Isobaric Tags for Relative and Absolute Quantification (iTRAQ) was used to observe changes in proteins of the miniature pig inner ear following noise exposure. Western blot and immunofluorescence were performed for further quantitative and qualitative analysis of proteomic changes. The average ABR-click threshold of miniature pigs before noise exposure, 1 day and 7 days after noise exposure, were 39.4 dB SPL, 67.1 dB SPL, and 50.8 dB SPL, respectively. In total, 2,158 proteins were identified using iTRAQ. Both gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analyses showed that immune and metabolic pathways were prominently involved during the impairment stage of acute hearing loss. During the recovery stage of acute hearing loss, most differentially expressed proteins were related to cholesterol metabolism. Western blot and immunofluorescence showed accumulation of reactive oxygen species and nuclear translocation of NF-κB (p65) in the hair cells of miniature pig inner ears during the acute hearing loss stage after noise exposure. Nuclear translocation of NF-κB (p65) may be associated with overexpression of downstream inflammatory factors. Apolipoprotein (Apo) A1 and Apo E were significantly upregulated during the recovery stage of hearing loss and may be related to activation of cholesterol metabolic pathways. This is the first study to use proteomics analysis to analyze the molecular mechanisms of acute noise-induced hearing loss and its recovery in a large animal model (miniature pigs). Our results showed that activation of metabolic, inflammatory, and innate immunity pathways may be involved in acute noise-induced hearing loss, while cholesterol metabolic pathways may play an important role in recovery of hearing ability following noise-induced hearing loss.

Distribution and change of peroxynitrite in the guinea pig cochlea following noise exposure.

Nitric oxide (NO)-mediated pathology depends on the formation of reactive intermediates, such as the peroxynitrite (ONOO-). ONOO- can nitrate free tyrosine and tyrosine residues of proteins. Therefore, increases in tyrosine nitration reflect the amount of ONOO- produced by oxidative stress. The distribution of 3-nitrotyrosine (3-NT), an ONOO- marker, in the organ of corti and the cochlear lateral wall tissue from the guinea pig were examined using fluorescence immunohistochemistry. The immunoactivity of 3-NT in the normal guinea pig was compared with animals exposed to 122dBA broadband noise, 4 h/day, for 2 consecutive days. In the normal animals, 3-NT immunoreactivity was found in the outer hair cells (OHCs), inner hair cells (IHCs), pillar cells (PCs), spiral ganglion cells (SPCs) and the marginal cells of stria vascularis in the lateral wall. Sound exposure increased the 3-NT signal in all of the cells and resulted in extensive outer hair cell loss. A quantitative analysis of the 3-NT change in OHCs and marginal cells of lateral wall showed that immunolabeling was significant (P<0.01, n=10) in the noise exposure group compared with that of the control group. Anti-3-NT and propidium iodide double labeling showed that 3-NT was distributed mainly in the apical end of OHCs. In addition, 3-NT was distributed outside of the nucleus of the OHCs and marginal cells. In conclusion, the data indicate that noise exposure leads to a significant production of ONOO- in the cochlear lateral wall and organ of corti. This is consistent with the known increase of NO production by loud sound stress and suggests that NO-derived free radicals participate in the cochlear pathophysiology of noise-induced hearing loss.

Congenital middle ear abnormalities with absence of the oval window: diagnosis, surgery, and audiometric outcomes.

OBJECTIVE: Congenital absence of the oval window (CAOW) is a rare condition in which the stapes footplate fails to develop, resulting in a significant conductive hearing loss in the affected ear. The purpose of this study was to describe the surgical management and outcomes of patients with CAOW undergoing the oval window drill-out (OWD) procedure. MATERIALS AND METHODS: A retrospective chart review of patients with CAOW between 1996 and 2011 was performed. Clinical data of patients who underwent OWD were collected. Seventy-nine patients (103 ears) were confirmed using exploratory tympanotomy as having congenital stapes anomalies and CAOW without any anomalies of the tympanic membrane and external auditory canal. Demographic data, CT findings, operative findings, complications, and preoperative/postoperative audiometry data of patients who underwent OWD were collected. The preoperative and postoperative audiologic findings were analyzed in 42 patients (56 ears) with complete data. RESULTS: Hearing restoration surgery was aborted for various reasons in 14 cases. Six patients underwent revision operations for worsening hearing after their first surgery. The average preoperative 4 tone air conduction threshold was 67 dB; the average 6-month postoperative four tone air conduction threshold was 49 dB, and the average postoperative hearing gain was 18 dB. For the 56 ears, the average 4 tone air conduction threshold 6 months after surgery was significantly lower than the preoperative threshold. CONCLUSION: The oval window drill-out procedure is a viable operation for patients with congenital absence of the oval window, and it is important for surgeons to develop personalized treatment programs to improve patients' hearing with minimal complications.

Noise-induced nitrotyrosine increase and outer hair cell death in guinea pig cochlea.

BACKGROUND: Modern research has provided new insights into the biological mechanisms of noise-induced hearing loss, and a number of studies showed the appearance of increased reactive oxygen species (ROS) and reactive nitrogen species (RNS) during and after noise exposure. This study was designed to investigate the noise exposure induced nitrotyrosine change and the mechanism of outer hair cells death in guinea pig cochlea. METHOD: Thirty guinea pigs were used in this study. The experimental animals were either exposed for 4 hours per day to broadband noise at 122 dB SPL (A-weighted) for 2 consecutive days or perfused cochleae with 5 mg/ml of the SIN1 solutions, an exogenous NO and superoxide donor, for 30 minutes. Then the cochleae of the animals were dissected. Propidium iodide (PI), a DNA intercalating fluorescent probe, was used to trace morphological changes in OHC nuclei. The distribution of nitrotyrosine (NT) in the organ of Corti and the cochlear lateral wall tissue from the guinea pigs were examined using fluorescence immunohistochemistry method. Whole mounts of organ of Corti were prepared. Morphological and fluorescent changes were examined under a confocal microscope. RESULTS: Either after noise exposure or after SIN1 perfusion, outer hair cells (OHCs) death with characteristics of both apoptotic and necrotic degradation appeared. Nitrotyrosine immunolabeling could be observed in the OHCs from the control animals. After noise exposure, NT immunostaining became much greater than the control animals in OHCs. The apoptotic OHC has significant increase of nitrotyrosine in and around the nucleus following noise exposure. In the normal later wall of cochleae, relatively weak nitrotyrosine immunolabeling could be observed. After noise exposure, nitrotyrosine immunoactivity became stronger in stria vascularis. CONCLUSION: Noise exposure induced increase of nitrotyrosine production is associated with OHCs death suggesting reactive nitrogen species participation in the cochlear pathophysiology of noise-induced hearing loss.

[Endolymphatic sac tumor with von Hippel-Lindau disease: report of two cases with testing of von Hippel-Lindau gene].

OBJECTIVE: Endolymphatic sac tumors (ELSTs) are rare in the general population with much higher prevalence in von Hippel-Lindau(VHL) disease. The purpose of this study is to present two cases of endolymphatic sac tumor with VHL disease with analysis of VHL gene and to explore their association with VHL disease using molecular analysis. METHODS: Clinical data of these two patients from different VHL families were studied. DNAs extracted from peripheral bloods were amplified by the polymerase chain reaction using oligonucleotide primers corresponding to the VHL gene, then compared the mutations with the Human Gene Mutation Database. RESULTS: In case 1, 6 family members were enrolled in the study. Among them, three had been identified to have a germline missense point mutation at codon 194 of the VHL gene exon 1 (p.S65W). The little sister of the patient (case 1) underwent vitrectomy for retinal hemangioblastoma 5 years ago in another hospital. The mother of the patient (case 1) was further diagnosed to have a cerebellar hemangioblastoma and renal carcinoma in the following physical examination. Case 2 with her parents were also tested. Codon 499 of the VHL gene exon 3 (p.R167W) were detected in case 2 and her mother, but the mother refused further examination. CONCLUSIONS: The genetic diagnosis plays an important role in early detection of symptomatic patients and suspected patients. Clinical screening for members of the VHL families, and close follow-up of carriers allow an early detection of tumors and the metastasis, which is the most common cause of death of these patients.

Interaction of a calcium channel blocker with noise in cochlear function in guinea pig.

CONCLUSIONS: Both nifedipine and noise exposure had damaging effects on cochlear function. These damaging effects were subtractive rather than additive, suggesting that calcium channel blockers may have a protective role in noise-induced hearing loss. OBJECTIVE: We assessed the interaction of nifedipine, a calcium channel blocker, with noise in cochlear function by evaluating changes in the compound action potential (CAP) threshold after the administration of nifedipine with or without noise exposure. METHODS: Eighty guinea pigs were randomly assigned to eight groups based on those with cochlear perfusion with nifedipine only (0, 0.15, 0.5, and 3 µM, groups 1-4) and noise exposure (groups 5-8). CAP thresholds were recorded using a round window electrode before and 120 min after cochlear perfusion. RESULTS: Cochlear perfusion of different concentrations of nifedipine caused 2.5, 5.5, 28, and 21.5 dB SPL threshold shift, respectively, at 0, 0.15, 0.5, and 3 µM concentrations (groups 1-4). In comparison, the CAP thresholds after nifedipine perfusion with noise exposure were 43.5, 46.5, 20, and 21.5 dB SPL, respectively, in groups 5-8.

Intraoperative CT-guided cochlear implantation in congenital ear deformity.

CONCLUSIONS: Intraoperative computed tomography (iCT)-guided cochlear implantation is practical and effective for correct electrode placement in the cochlea of patients with congenital inner ear and/or complex middle ear malformation. OBJECTIVES: The operation in patients with inner ear and/or complex middle ear malformation including abnormal facial nerve course is difficult. This study evaluated the efficacy of cochlear implantation under the guidance of iCT to insure correct electrode placement. METHODS: This was a prospective interventional case series. Ten patients with severe to profound sensorineural hearing loss due to ear malformations were enrolled, and iCT was used to confirm the right placement of electrodes. RESULTS: Intraoperative CT was performed three times in one patient, twice in two, and once in the others. Interruption of the surgical process for each iCT until resumption of surgery was 9.64 ± 0.63 min. iCT revealed incorrectly positioned cochlear implants in two patients, which were immediately corrected. There were no reoperations due to misplacement of electrodes. iCT helped locate the cochlea in the middle ear of one patient with an abnormal facial nerve course. The overall intervention rate based on iCT findings was 30%. LEVEL OF EVIDENCE: level 4.

[Surgical management and prognosis of iatrogenic peripheral facial nerve injury following middle ear surgery].

OBJECTIVE: To discuss the causes, sites, management strategies and curative effects of accidental facial nerve paralysis in the middle ear surgery. METHODS: Forty two cases with peripheral facial nerve paralysis following middle ear surgery who underwent surgical exploration and reanimation were analyzed. Facial nerve decompression, primary end-to-end anastomosis, interpositional nerve grafts with the great auricular nerve and nerve substitution of facial-hypoglossal anastomosis were applied to restoration of the facial nerve function. The facial nerve function was graded according to House-Brackmann (HB) Grade. RESULTS: The most common operation complicating iatrogenic facial nerve injury was mastoidectomy, and the common sites of the injured facial nerve were the tympanic segment and pyramid segment. The facial nerve exploration showed facial nerve edema in nine cases (21.4%), injury of the facial nerve sheath was observed in 10 cases (23.8%), partial nerve fibers transection was found in four cases (9.5%), total nerve fibers transection was detected in 17 cases (40.5%) and two cases (4.8%) with facial nerve anatomical integrity. Facial nerve re-animation methods include facial nerve decompression in 24 cases (57.1%), end-to-end anastomosis in two cases (4.8%), end-to-end anastomosis after nerve transfer in two cases (4.8%), interpositional nerve grafts with the great auricular nerve in 10 cases (23.8%) and facial-hypoglossal nerve anastomosis in four cases (9.5%). The facial nerve function was graded according to House-Brackmann Grade before and after surgery. Twenty eight patients were followed up more than one year. For the 17 cases who received facial nerve decompression, four cases recovered to House-Brackmann Grade I, 11 cases recovered to House-Brackmann Grade II, two cases recovered to House-Brackmann Grade III. For the five cases who underwent the great auricular nerve grafting, three cases recovered to House-Brackmann Grade II, two cases recovered to House-Brackmann Grade III. For the four cases who received facial-hypoglossal nerve anastomosis recovered to House-Brackmann Grade III. For the two cases who underwent the end-to-end anastomosis recovered to House-Brackmann Grade II. CONCLUSIONS: The tympanic segment and pyramid segment are more vulnerable to be injured during mastoid surgery. The injured facial nerve should be explored and repaired. The methods include facial nerve decompression, end-to-end anastomosis, end-to-end anastomosis after nerve transfer, interpositional nerve grafts with the great auricular nerve and facial-hypoglossal nerve anastomosis.

[Clinical analysis of adenoid cystic carcinoma of external auditory canal].

OBJECTIVE: To explore methods of treatment for adenoid cystic carcinoma of external auditory canal, and discuss the correlating factors that effect prognosis. METHODS: A retrospective analysis of 19 cases of adenoid cystic carcinoma of external auditory canal treated from 1988 to 2004 was carried out. Based on University of Pittsburgh TNM staging system of external auditory canal carcinoma, 19 cases were classified into groups as 5 cases in T1, 2 in T2, 6 in T3, and 6 in T4. Local resection was performed in cases in stage T1 and T2, while radical mastoidectomy or temporal bone resection was performed in stage T3 and T4. Radiotherapy was applied after operation. Relapsed cases with isolated metastasis were treated by surgery. Multiple metastasis were treated with radiotherapy. RESULTS: The follow-up time is from 6 months to 19 years, and the median is 44 months. There're 8 cases with more than 5 years' follow-up. Twelve patients relapsed and 7 had metastasis but 4 died. The cases with positive incisal edge after first operation relapsed even treated with radiotherapy. In recurrent cases, 9 cases received more than 2 operations, 8 more than 3, and 4 received 4 operations. CONCLUSIONS: The adenoid cystic carcinoma of external auditory canal grows insidiously, and relapses frequently. But the patients can live long with neoplasm implanted. A wide surgical excision combined with post operative radiotherapy was proposed, and negative incision edge should be confirmed. Recurrent cases can be treated with several operations to elongate survival. Multiple relapses will cause metastasis more frequently. Metastasis is the main reason to cause death.

[Caspase 3 activation and apoptosis inducing factor translocation in noise exposure induced out hair cells apoptosis].

OBJECTIVE: To investigate the pathway and mechanism of noise exposure induced out hair cells (OHC) apoptosis. METHODS: The cochleae of control and noise exposure group were dissected. The activity of caspase 3, an important mediator of apoptosis, in OHC, was examined with carboxyfluorescein-labeled fluoromethyl ketone (FMK)-peptide inhibitors. The apoptosis inducing factor (AIF) translocation from mitochondria in OHC were further examined by immunohistology method. The nuclei were labeled with PI and the mitochondrion was labeled with Mito-tracker. Whole mount organ of Corti was prepared. Morphological and fluorescent change was observed use confocal microscope. RESULTS: In the normal OHC, AIF is distributed where the mitochondria were located and no activated caspase 3 was observed. After the animals exposed to broadband noise at 122 dB in 4 h/day for 2 days, both apoptosis and necrosis were appeared in OHC. AIF translocated from mitochondrion to nuclei in apoptotic and necrotic OHC following noise exposure. The noise exposure triggered activation of caspase 3 in apoptic hair cells. But no caspase 3 activation appeared in necrotic OHC. CONCLUSIONS: These findings indicated that the caspase-dependent pathway is an important pathway in noise exposure induced apoptosis. And AIF also involves OHC death pathway following noise exposure.

[Phanerogenetic retrocochlear low frequency hearing loss].

OBJECTIVE: To study the pathogenisis of retrocochlear low frequency hearing loss. METHODS: Clinical and audiologic findings [auditory brainstem response (ABR), evoked otoacoustic emission (EOAE), et al] of 29 cases with retrocochlear low frequency hearing loss were studied. RESULTS: The head injury, acoustic neuroma, peripheral neurophathy, hereditary hear loss, multiple sclerosis and brainstem disease can cause retrocochlear low frequency hearing loss. The typical clinical manifestations of retrocochlear low frequency hearing loss were normal EOAE which cannot be suppressed by contralateral white noise, but with abnormal ABR as well as with no acoustic reflex and -SP/AP > 0.44. CONCLUSIONS: The results suggest that phanerogenetic retrocochlear low frequency hearing loss should be a syndrome rather than a disease called "auditory neuropathy". The main lesions of the disease are brainstem, cochlear nuclei and auditory nerve.