Histone deacetylase inhibition protects hearing against acute ototoxicity by activating the Nf-κB pathway

Abstract

Auditory hair cells have repeatedly been shown to be susceptible to ototoxicity from a multitude of drugs including aminoglycoside antibiotics. Here, we found that systemic HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) on adult mice offers almost complete protection against hair cell loss and hearing threshold shifts from acute ototoxic insult from kanamycin potentiated with furosemide. We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic <i>Atoh1</i> induction) hair cell regeneration. Rather, SAHA treatment correlated with RelA acetylation (K310) and subsequent activation of the Nf-<i>κ</i>B pro-survival pathway leading to expression of pro-survival genes such as <i>Cflar</i> (<i>cFLIP</i>) and <i>Bcl2l1</i> (<i>Bcl-xL</i>). In addition, we also detected increased expression of pro-survival genes <i>Cdkn1a</i> (<i>p21</i>) and <i>Hspa1a</i> (<i>Hsp70</i>), and decreased expression of the pro-apoptosis gene <i>Bcl2l11</i> (<i>Bim</i>). These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.