Tsuyoshi Takemoto

Maintenance of Olfactory Neurogenesis Requires HSF1, a Major Heat Shock Transcription Factor in Mice *

Heat shock transcription factors (HSFs) play roles not only in heat shock response but also in development of the reproductive organs, brain, and lens. Here, we analyzed sensory organs and found abnormalities of the olfactory epithelium in adult HSF1-null mice, which is developmentally related to the lens. The olfactory epithelium was normal until postnatal 3 weeks but was not maintained later than 4 weeks in HSF1-null mice. The olfactory epithelium was atrophied with increased cell death of olfactory sensory neurons. Analysis of the epithelium revealed that induction of HSP expression and reduction of LIF expression are lacking in adult HSF1-null mice. We found that DNA binding activity of HSF1 is induced in the olfactory epithelium later than 4 weeks and that HSF1 binds directly to Lif gene and inhibits its expression. HSF4 has opposing effects on LIF expression and olfactory neurogenesis. These data indicate that HSF1 is required for the precise expression of Hsp and cytokine genes that is obligatory for maintenance of olfactory neurogenesis in adult mice and suggest that stress-related processes are involved in its maintenance.

Geranylgeranylacetone, a heat shock protein inducer, prevents acoustic injury in the guinea pig

Geranylgeranylacetone (GGA) used widely as anti-ulcer agent is accepted as an inducer of the heat shock proteins (Hsps) at gastric mucosa, liver, heart, and brain. However, there have been no reports that GGA could induce Hsps in the cochlea leading up to the oto-protection. The purpose of the present study was to investigate whether single oral dose of GGA could induce Hsps at cochlea and oral administration had protective effect to the cochlea against noise trauma. We used Hartley guinea pigs and investigated the expression of Hsp70, 40, and 27 in cochlea by Western blot analysis. To evaluate cochlear function, we assessed thresholds of the auditory brain stem response (ABR). For histological assessment, we observed the sensory epithelium using surface preparation technique. GGA (600 mg/kg) or vehicle was given orally to animals. Western blot analysis showed that the expressions of Hsp 70, 40, and 27 were increased 24-48 h after administration of single dose of GGA, whereas there was less expression in the animals given vehicle. In the animals given GGA once a day for a week before sound exposure (130 dB SPL octave band noise with a center frequency of 4 kHz) for 3 h, their ABR threshold elevations were lowered significantly. In addition, significantly fewer defects were observed on outer hair cells of organ of Corti in the animals treated by GGA than those of the animals without GGA. This result shows that pretreatment by GGA have a potential to prevent cochlea damage against the intense noise.

Attenuation of progressive hearing loss in a model of age-related hearing loss by a heat shock protein inducer, geranylgeranylacetone.

Mechanisms of age-related hearing loss (ARHL) have not been elucidated as aging processes are extremely complex. Although oxidative stress and apoptotic cell death are involved in progression of ARHL, number of trial to treat ARHL is limited. Heat shock response is characterized by induction of heat shock proteins (HSPs) in response to stresses such as heat shock, which diminishes during aging. HSPs act as molecular chaperones, and some HSPs also inhibit apoptotic pathways. Here, we examined age-related expression of HSPs in the cochlea of ARHL model DBA/2J mice and control CBA/N mice. Western blot assay revealed that CBA/N mice showed constant expression of Hsp70 and Hsp110 with age, but not in DBA/2J mice. The result suggests that pharmacological upregulation of HSPs might attenuate ARHL. We administered DBA/2J mice with food containing geranylgeranylacetone (GGA) that induces HSPs in the cochlea, and found that its administration suppresses ARHL examined by ABR test and histological examination though protection is specific for the apical part of the cochlea. These results demonstrate that dietary supplementation of GGA could be an effective therapeutic strategy for treatment of ARHL.

Cochlear Administration of Adenosine Triphosphate Facilitates Recovery from Acoustic Trauma (Temporary Threshold Shift)

Background: Adenosine triphosphate (ATP) has often been used in the treatment of acoustic trauma although evidence supporting its clinical use was lacking. The aim of this study was to evaluate the chronic effects of ATP on acoustic trauma in guinea pigs. Methods: We infused ATP into the perilymph of the guinea pig cochlea concurrently with intense noise exposure to investigate the effect of ATP on the process of recovery after acoustic trauma. We assessed auditory brainstem response (ABR) thresholds to evaluate cochlear function. Results: After noise exposure (120 dB SPL, 5 h), ABR thresholds showed an increase of approximately 50 dB SPL that returned to normal after 14 days. Cochlear function in ATP-treated ears recovered more quickly than in control ears. The effect of ATP was inhibited by the administration of the ATP receptor antagonist: pyridoxal- phosphate-6-azophenyl-2′,4′-disulfonic acid. Conclusion: These results suggest that ATP mitigates the effects of noise trauma through the ATP receptor.

Novel method for homogeneous gene transfer to the inner ear

Viral vectors are widely used in gene therapy due to their efficiency. In this paper we describe a novel method for transfecting the whole inner ear of a guinea pig using adenoviral vectors. Very small perforations are made in both the cochlea and lateral semicircular canal, into which 50 μl of adenoviral suspension (8.9×108 plaque forming unit (PFU)/ml) is gently infused. Any excess suspension flows out through the perforation in the semicircular canal and therefore makes no contact with the central nervous system. Our method can therefore be utilized to perform homogeneous gene transfer and may eliminate any effects on other organs, such as the contralateral ear.

The systemic application of diazepam facilitates the reacquisition of a well-balanced vestibular function in a unilateral vestibular re-input model with intracochlear tetrodotoxin infusion using an osmotic pump

Diazepam is a popular medicine used in the treatment of acute vertigo. In the past, many studies investigating the effect of diazepam in peripheral vestibular destruction have been reported. However, no previous study has yet investigated the effect of diazepam on a model with a transient and reversible vestibular function similar to recurrent vertigo as seen in Menieres disease. We thus made a peripheral vestibular re-input model by the unilateral intracochlear administration of tetrodotoxin (TTX) using an osmotic pump and then examined the influence of diazepam on the vestibular system in this model. Hartley white guinea pigs were intracochlearly administered with TTX on the right side for 3 days by an osmotic pump. Animals were divided into three groups, TTX alone (control group (n = 7)), TTX and an intraperitoneal diazepam injection once a day for 3 days (diazepam group (n = 6)) and vehicle injection (vehicle group (n = 6)). A caloric response and vestibuloocular reflex (VOR) were observed at 7 and 14 days after completing 3 days of TTX administration. Seven days after vestibular re-input, a directional preponderance of the nystagmus (DP) to the TTX-treated side was observed in the control and vehicle groups on VOR examination. DP was not observed in the diazepam group on any examined day. The R/L time ratio of caloric response showed no statistical difference between three groups on any examined day. These results suggest that diazepam may thus be useful for patients in an acute stage of peripheral vestibular vertigo by decreasing their vertiginous symptoms.