Blast-Induced Central Auditory Neurodegeneration Affects Tinnitus Development Regardless of Peripheral Cochlear Damage.

Blast exposure causes serious complications, the most common of which are ear-related symptoms such as hearing loss and tinnitus. The blast shock waves can cause neurodegeneration of the auditory pathway in the brainstem, as well as the cochlea, which is the primary receptor for hearing, leading to blast-induced tinnitus. However, it is still unclear which lesion is more dominant in triggering tinnitus, the peripheral cochlea or the brainstem lesion owing to the complex pathophysiology and the difficulty in objectively measuring tinnitus. Recently, gap detection tests have been developed and are potentially well-suited for determining the presence of tinnitus. In this study, we investigated whether the peripheral cochlea or the central nervous system has a dominant effect on the generation of tinnitus using a blast-exposed mouse model with or without earplugs, which prevent cochlear damage from a blast transmitted via the external auditory canal. The results showed that the earplug (+) group, in which the cochlea was neither physiologically nor histologically damaged, showed a similar extent of tinnitus behavior in a gap prepulse inhibition of acoustic startle reflex test as the earplug (-) group, in which the explosion caused a cochlear synaptic loss in the inner hair cells and demyelination of auditory neurons. In contrast, both excitatory synapses labeled with VGLUT-1 and inhibitory synapses labeled with GAD65 were reduced in the ventral cochlear nucleus, and demyelination in the medial nucleus of the trapezoid body was observed in both groups. These disruptions significantly correlated with the presence of tinnitus behavior regardless of cochlear damage. These results indicate that the lesion in the brainstem could be dominant to the cochlear lesion in the development of tinnitus following blast exposure.

Feasibility of transnasal flexible carbon dioxide laser surgery for laryngopharyngeal lesions.

OBJECTIVE: The fiber-guided carbon dioxide (CO2) laser is a useful device for laryngopharyngeal surgery. The flexible CO2 wave-guide laser has been developed and commercially available for several years. However, the transnasal use of CO2 flexible wave-guided laser surgery through the instrument channel of a flexible endoscope (CO2 TNFLS) is not permitted in Japan. This feasibility study aimed to assess the value and the safety of an in-office CO2 TNFLS procedure. METHODS: Patients with small laryngopharyngeal diseases were enrolled from June 2015. Eligible patients had indications with lesions generally localized superficial lesions such as the benign tumor, leukoplakia, and premalignant lesion-like carcinoma in situ (CIS). Patients were locally well anesthetized using xylocaine. After removing as much of the lesion(s) as possible with flexible forceps, the remainder of the lesions were evaporated using CO2 TNFLS through the instrument channel of a flexible endoscope under local anesthesia. RESULTS: Eighteen surgeries involving 13 patients, including 9 papilloma (7 recurrent respiratory papilloma [RRP]), 2 carcinoma in situ, 1 leukoplakia, and 1 large epiglottic cyst), were performed. Four patients with RRP required multiple surgeries. Except for 3 patients with RRP, all patients achieved disease control without additional intervention. All procedures were completed with no severe adverse events. CONCLUSION: Office-based CO2 TNFLS is safe and feasible for patients with laryngopharyngeal pathologies. It is especially valuable for RRP patients with small lesions to avoid surgery under general anesthesia.

Photobiomodulation rescues the cochlea from noise-induced hearing loss via upregulating nuclear factor κB expression in rats.

Photobiomodulation (PBM) is a noninvasive treatment that can be neuroprotective, although the underlying mechanisms remain unclear. In the present study, we assessed the mechanism of PBM as a novel treatment for noise-induced hearing loss, focusing on the nuclear factor (NF)-κB signaling pathway. Sprague-Dawley rats were exposed to 1-octave band noise centered at 4kHz for 5h (121dB). After noise exposure, their right ears were irradiated with an 808nm diode laser beam at an output power density of 165mW/cm(2) for 30min a day for 5 consecutive days. Measurement of the auditory brainstem response revealed an accelerated recovery of auditory function in the groups treated with PBM compared with the non-treatment group at 4, 7, and 14 days after noise exposure. Immunofluorescent image analysis for inducible nitric oxide synthase and cleaved caspase-3 showed lesser immunoreactivities in outer hair cells in the PBM group compared with the non-treatment group. However, immunofluorescent image analysis for NF-κB, an upstream protein of inducible nitric oxide synthase, revealed greater activation in the PBM group compared with the naïve and non-treatment groups. Western blot analysis for NF-κB also showed stronger activation in the cochlear tissues in the PBM group compared with the naïve and non-treatment groups (p<0.01, each). These data suggest that PBM activates NF-κB to induce protection against inducible nitric oxide synthase-triggered oxidative stress and caspase-3-mediated apoptosis that occur following noise-induced hearing loss.

The beneficial effect of Hangesha-shin-to (TJ-014) in gentamicin-induced hair cell loss in the rat cochlea.

OBJECTIVE: Ototoxic damage caused by aminoglycosides (AG) leads to the loss of cochlear hair cells (HCs). In mammals, mature cochlear HCs are unable to regenerate, and their loss results in permanent hearing deficits. Our objective was to protect the inner ear from damage after an AG challenge. The generation of reactive oxygen species (ROS), one of the earliest events in the process of AG ototoxicity, is considered to play a key role in the initiation of HC death. We examined whether Hangesha-shin-to (TJ-014), a traditional Japanese Kampo medicine considered to be a potent antioxidant, protects HCs from gentamicin (GM)-induced damage. METHODS: Organ of Corti explants removed from postnatal day 3-5 rats were maintained in tissue culture and exposed to 50µM GM for up to 48h. The effects of TJ-014 on GM-induced ototoxicity were assessed by HC counts and immunohistochemistry against cleaved caspase-3, 8-hydroxy-2'-deoxyguanosine (8-OHdG), and a probe reacting to mitochondrial function changes. RESULTS: TJ-014 treatments significantly reduced GM-induced HC loss and immunoreactivities for cleaved caspase-3 and 8-OHdG; these effects were correlated with increasing TJ-014 concentrations. Moreover, TJ-014 protected the mitochondrial membrane potential from GM ototoxicity. CONCLUSION: These findings indicate the potential of TJ-014 to prevent GM-induced cochlear damage involving ROS.

Low-level laser therapy for prevention of noise-induced hearing loss in rats.

Noninvasive low-level laser therapy (LLLT) is neuroprotective, but the mechanism of this effect is not fully understood. In this study, the use of LLLT as a novel treatment for noise-induced hearing loss (NIHL) is investigated. Sprague-Dawley rats were exposed to intense noise and their right ears were irradiated with an 808nm diode laser at an output power density of 110 or 165mW/cm(2) for a 30min period for 5 consecutive days. Measurement of the auditory brainstem response revealed an accelerated recovery of auditory function in the groups treated with LLLT compared with the non-treatment group at days 2, 4, 7 and 14 after noise exposure. Morphological observations also revealed a significantly higher outer hair cell survival rate in the LLLT groups. Immunohistochemical analyses for inducible nitric oxide synthase (iNOS) and cleaved caspase-3 were used to examine oxidative stress and apoptosis. Strong immunoreactivities were observed in the inner ear tissues of the non-treatment group, whereas these signals were decreased in the LLLT group at 165mW/cm(2) power density. Our findings suggest that LLLT has cytoprotective effects against NIHL via the inhibition of iNOS expression and apoptosis.

A traditional Japanese medicine--Hangeshashinto (TJ-14)--alleviates chemoradiation-induced mucositis and improves rates of treatment completion.

PURPOSE: Oral mucositis induced by radiation or chemoradiation can cause devastating quality of life issues for patients undergoing treatment for head and neck cancer. In this study, we investigated the efficacy of a traditional Japanese medicine-Hangeshashinto (TJ-14)-for (chemo)radiation-induced oral mucositis. METHODS: Eighty patients who underwent whole neck radiation of >60 Gy with or without chemotherapy (high-dose cisplatin or low-dose docetaxel) were enrolled in this retrospective study; 40 had received TJ-14 during treatment, and 40 had not (controls). Factors related to alleviation of oral mucositis were identified by multivariate logistic regression analysis. Rates of completion of (chemo)radiation treatments were compared between the patients who received TJ-14 and the control group according to the treatment regimen. The comparison of the nutrition status between groups was also performed. RESULTS: Multivariate analysis indicated that the use of TJ-14 (p = 0.019), gender (p = 0.024), and primary tumor location (p = 0.028) were significant factors associated with the severity of oral mucositis. TJ-14 was associated with a significantly improved rate of completion of chemoradiation with cisplatin (p = 0.002). In the investigation of nutritional status, only serum albumin was significantly maintained better in the TJ-14 group than the control group in terms of mean change before and after (chemo)radiation (p = 0.024). CONCLUSIONS: The present study indicates that TJ-14 is effective for ameliorating oral mucositis induced by (chemo)radiation in patients with head and neck cancers. TJ-14 was associated with improved completion rates of chemoradiation treatments with cisplatin. A randomized controlled trial is necessary to confirm the efficacy of TJ-14 for chemoradiation-induced mucositis in head and neck cancer patients.

Traditional Chinese Medicine for treatment of laryngeal papillomatosis.

OBJECTIVE: The objective of this study was to assess the clinical effectiveness of Traditional Chinese Medicine (TCM) as an adjuvant therapy for recurrent respiratory papillomatosis. DESIGN: The design of this study was a case series. LOCATION AND SUBJECTS: Fifty-one (51) patients with laryngeal papillomatosis who were treated at Keio University Hospital between May 1981 and April 2008 were incorporated in this study. INTERVENTIONS: Individually formulated TCM was orally administered postsurgically to 20 patients with aggressive laryngeal papillomatosis requiring multiple laser ablations (at least biannually) because of frequent recurrence. Eight (8) patients were excluded because of discontinued visits or medication (6 patients), or malignant transformation of the lesion (2 patients). The remaining 12 patients were enrolled in this study. OUTCOME MEASURES: Retrospective chart review and review of the patients' recorded laryngeal images were performed. Clinical response to TCM was measured by the surgical necessity and Derkay's severity score for each patient, followed by statistical analyses. RESULTS: Surgeries were required statistically less often (p = 0.0029) after TCM administration compared with the pre-TCM period. Furthermore, Derkay's severity score was significantly lower (p = 0.022) at the patients' last visit compared with the score before TCM administration. CONCLUSIONS: TCM may be a useful adjuvant therapy to treat aggressive laryngeal papillomatosis. Further studies are necessary to clarify the pharmacological mechanism of TCM in the treatment of laryngeal papillomatosis.

Heme oxygenase-1 expression in the guinea pig cochlea induced by intense noise stimulation.

CONCLUSION: These results suggest that noise induces free radical formation in the cochlea and that, in the guinea pig, heme oxygenase-1 (HO-1) may play an important role in the recovery from noise trauma in the organ of Corti. OBJECTIVE: Free radicals are involved in noise-induced hearing loss. It has been demonstrated that the induction of HO-1 may protect cells exposed to oxidative challenge. The present study was designed to investigate the effect of intense noise exposure on HO-1 induction. MATERIALS AND METHODS: A total of 25 adult guinea pigs (body weight 200-300 g) with a normal Preyers's reflex were used as subjects. Based on preliminary tests, the appropriate intensities and durations of noise were determined that were adequate to induce apparent threshold shifts and lead to various recovery patterns to initial thresholds. The sound was routed through a power amplifier to a speaker, which was positioned directly over the animals in a sound chamber. Auditory brainstem response (ABR) testing, Western blot analysis for HO-1, and immunohistochemical testing were done. RESULTS: Exposure of the guinea pigs to 115 dB SPL octave band noise for 5 h induced HO-1 expression in the organ of Corti. In the organ of Corti, HO-1 expression increased mainly in the outer hair cells. Some expression of HO-1 was observed before and after noise exposure in the supporting cells. HO-1 expression in the organ of Corti was definitely increased in guinea pigs with an intense noise exposure which causes a temporary threshold shift.

Sendai virus vector-mediated transgene expression in the cochlea in vivo.

We injected a recombinant Sendai virus (SeV) vector into the guinea pig cochlea using two different approaches--the scala media and scala tympani--and investigated which cell types took up the vector. The hearing threshold shift and distribution of transfected cells in animals using the scala media approach were different compared to those using the scala tympani approach. SeV can transfect very different types of cells, including stria vascularis, spiral ganglion neurons, and sensory epithelia of the organ of Corti, and fibrocytes of the scala tympani. Because SeV vectors can potentially deliver stimuli to the cochlea to induce hair cell regeneration, it may be a powerful tool for repairing the organ of Corti.