Sodium Butyrate Reduces Gentamicin-induced Hearing Loss

Part one:The effect of putting absorbable gelatin sponge on round window niche on the hearing of normal albino guinea pigs[Objective] Study if the local administration of absorbable gelatin sponge by theround window niche would cause changes in the auditory brainstem response (ABR) threshold of normal albino guinea pig’s.[Methods]Five healthy albino guinea pigs, single ear surgery. Open the auditory vesicle with microscopic drill, soak0.3mm3absorbable gelatin sponge with10ul perilymph and place on the round window niche, and then suture the subcutaneous tissue and skin. Do the ABR test immediately.[Results] Paired Samples T Test demonstrates there is significant difference in the ABR threshold values of the five animals tested before and after surgery.(P<0.01).[Conclusion] This experiment confirmed that the round window niche administration changed the normal conduction, and hence affected albino guinea pig’s ABR thresholds. In the next experiment, only the effect of the local administration on the ABR threshold will be considered.Part two:The toxicity of sodium butyrate by round window-dosing[Objective] Investigate if the sodium butyrate(NaB) administration through the round window will damage the hair cell.[Methods] Five healthy albino guinea pigs, single ear surgery. Open the auditory vesicle with microscopic drill, soak0.3mm3absorbable gelatin sponge with10ul NaB (100mg/ml) and place on the round window niche for14days. Then test the ABR, carry out immunological studies, observe under the scanning electron microscope, and do statistical analyses to examine its toxicity.[Results] One-way ANOVA demonstrates there is no significant difference in the ABR threshold values before and after applying NaB(P>0.05). Immunological studies suggest that there is no missing of hair cells; scanning electron microscope demonstrate that the appearance of hair cell is normal.[Conclusion] NaB will not damage the normal albino guinea pig’s hearing, or hair cells. This experiment confirmed that sodium butyrate(NaB) administration through the round window is nontoxic. The following experiment will verify whether round window administration could have a protective effect on gentamicin-induced hearing loss.Part three:Investigate the protective effect of NaB on gentamicin-induced hearing loss[Objective] Investigate if NaB has a protective effect on gentamicin-induced hearing loss.[Methods] Ten healthy male albino guinea pigs, who are allowed to drink and eat freely during the experiment. After testing the ABR of normal hearing, carry out the binaural surgery. Soak0.3mm3absorbable Gelatin Sponge with10μl NaB (100mg/ml)(the protective agent) and place on the round window niche on the right side of each animal, and soak with10μl perilymph and place on the left side as the control.3days later, gentamicin was administrated by intramuscular injection once daily for5consecutive days (200mg/kg).3days after injection ended, guinea pigs were killed and randomly selected for auditory brain responses (ABRs), cochlear sensory epithelia surface preparation, hair cell counts, immunological studies, and statistical analyses.[Results] Paired Samples T Test demonstrates there is significant difference of ABR threshold values between sodium butyrate group and perilymph group(P<0.01). Basilar membrane stretched, phalloidin staining showed:The second turn of basilar membrane, sodium butyrate group hair cell loss is less than that of the perilymph group.Scanning electron microscopy:in the control group hair cell loss seriously. Remnants of hair cell cilia swelling, lodging, disorganized, lost hair cells normally connection. Meanwhile, the inner hair cells is loss and cilia lodging and swelling. Protective agent sodium butyrate group outer hair cell loss and cilia swelling was significantly reduced than the control group. Hair cell loss rate count, the control group, outer hair cells, from the top turn about10-40%start reduction,55%from the top reduce significiantly,70%from the top there is almost no outer hair cells. Inner hair cells from the top turn about60%begin to reduce,70%from the top reduce significiantly,80%from the top there is almost no hair cells. Given protective agent sodium butyrate group, outer hair cells, from the top turn about55-65%start reduction,70%from the top reduce significiantly,80%from the top there is almost no outer hair cells. Inner hair cells from the top turn about70%begin to reduce,75%from the top reduce significiantly,80%from the top there is almost no hair cells.Immunofluorescence assay shows:1. Normal albino guinea pig given sodium butyrate (NaB), the HDAC1expression is reduced.2. Withing the time extension of inreamuscular gentamicin, HDAC1fluorescence brightness, and expression increased.3.Transformaed cell the expression of HDAC1is increased.4. Five days after inreamuscular gentamicin, the nuclear dissolved and disappeared. The HDAC1expression showed the same changes.5. Given protective agent sodium butyrate group after five days, although the nuclear dissappear, but the majority of nuclear eumorphism. HDAC1fluorescence brightness, and expression compared with the control group decreased.[Conclusion] NaB has a protective effect to gentamicin-induced hearing loss. And this protective effect may through the way to inhibit histone deacetylases.