Hsp70/Bmi1-FoxO1-SOD Signaling Pathway Contributes to the Protective Effect of Sound Conditioning against Acute Acoustic Trauma in a Rat Model

Figure 1

Chronogram of the experiment in vivo (a) and in vitro (b). (a) 114 rats were available in the experiment in vivo, but there were six animals that were excluded based on the exclusion criteria (tympanitis) or died during experiments. Rats were exposed to a pure tone of 1 kHz at 85 dB SPL (SC) for 24 hours; then, some of them and others were exposed to white noise at 115 dB SPL (NE) for 6 hours per day over two consecutive days with anesthesia; they were allowed to rest for 3 hours between SC and NE with anesthesia. Hearing was evaluated with auditory brainstem responses (ABRs) before 1 day prior to exposure and 1 day after exposure. At the end of the study in vivo, cochleae were dissected and processed for histology analysis. (b) The spiral ganglion neuron cells (SGNs) from 256 neonatal rats were harvested and then cultured on culture dishes for 48 h; next, AD-Hspa4 (Hsp70-overexpressing adenovirus) and 1 μM PTC-209 (a small-molecule inhibitor of Bmi1) were, respectively, added to the appropriate cells and incubated for 72 hours at 37°C. At the end of the study in vitro, SGNs were processed for histology analysis.

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