Hyperbaric Oxygen Treatment Ameliorates Hearing Loss and Auditory Cortex Injury in Noise Exposed Mice by Repressing Local Ceramide Accumulation

Abstract

Noise-induced hearing loss (NIHL) relates closely to auditory cortex (AC) injury, so countermeasures aiming at the AC recovery would be of benefit. In this work, the effect of hyperbaric oxygen treatment on NIHL was elucidated, which was imposed on mice before (HBOP), during (HBOD) or after (HBOA) noise exposure. Morphology of neurons was assayed by hematoxylin-eosin or Nissl staining. Ceramide (Cer) level was measured through immunohistochemistry analysis. Apoptotic neurons were counted using transferase-mediated dUTP nick end labeling (TUNEL) staining. We demonstrated that the intense, broad band noise raised the threshold of auditory brainstem response, evoked neuronal degeneration or apoptosis and triggered the Cer accumulation in AC, all of which were restored significantly by HBOP, but not HBOD or HBOA. Cer over-generation reversed the advantages of HBOP significantly, while its curtailment recapitulated the effect. Next, noise exposure raised the superoxide or malondialdehyde (MDA) production which was blocked by HBOP or Cer repression. Oxidative control not only attenuated the hearing loss or neurodegeneration but, in turn, reduced the Cer formation significantly. In summary, mutual regulation between Cer and oxidative stress underlies the HBOP’s curative effect on hearing loss and neuronal damage in noise-exposed mice.

Ginsenoside Rd Ameliorates Auditory Cortex Injury Associated With Military Aviation Noise-Induced Hearing Loss by Activating SIRT1/PGC-1α Signaling Pathway

“…Hematoxylin–eosin staining was conducted as described by Su et al (2019) . After deparaffinization in xylene and rehydration in gradient alcohol, 5 μm longitudinal coronal sections were stained with hematoxylin solution for 2 min and then rinsed in distilled water for 1 min.…”

“…The recording electrode was inserted subcutaneously into the middle of the vertical line between the ears on the head, the reference electrode was inserted subcutaneously behind the test ear, and the grounding electrode was inserted into the root of the right hind limb. The sound stimulus was composed of a 15-ms tone burst, with a rise-fall time of 1 ms at frequencies of 2, 4, and 8 kHz (Su et al, 2019). Brainstem auditory evoked responses, which were accumulated 600 times, were stimulated by density alternating short click sounds produced by the potentiometer.…”

“…The left and right brain hemispheres were preserved, respectively, for detection of SOD activity, MDA level, and GSH-Px level. Hematoxylin-Eosin Staining Hematoxylin-eosin staining was conducted as described by Su et al (2019). After deparaffinization in xylene and rehydration in gradient alcohol, 5 µm longitudinal coronal sections were stained with hematoxylin solution for 2 min and then rinsed in distilled water for 1 min.…”

“…Nissl staining was carried out according to the method proposed by Su et al (2019). Sections were deparaffinized using xylene, hydrated with 95%, 85%, and 70% gradient alcohol, and rinsed using running tap water for 2 min.…”

“…The experimental steps of western blotting analysis refer to the articles previously published by our teaching and research department (Cheng et al, 2017;Su et al, 2019). Total auditory cortex protein was extracted with 500 µL…”