Activation of SIRT3 by the NAD+ Precursor Nicotinamide Riboside Protects from Noise-Induced Hearing Loss
- •The NAD+ precursor NR prevents noise-induced hearing loss
- •NR can be administered after acoustic trauma to prevent hearing loss
- •Prevention of noise-induced hearing loss by NAD+ and NR is dependent upon SIRT3
- •NAD+ and NR prevent noise-induced neurite retraction in the cochlea
Intense noise exposure causes hearing loss by inducing degeneration of spiral ganglia neurites that innervate cochlear hair cells. Nicotinamide adenine dinucleotide (NAD+) exhibits axon-protective effects in cultured neurons; however, its ability to block degeneration in vivo has been difficult to establish due to its poor cell permeability and serum instability. Here, we describe a strategy to increase cochlear NAD+ levels in mice by administering nicotinamide riboside (NR), a recently described NAD+ precursor. We find that administration of NR, even after noise exposure, prevents noise-induced hearing loss (NIHL) and spiral ganglia neurite degeneration. These effects are mediated by the NAD+-dependent mitochondrial sirtuin, SIRT3, since SIRT3-overexpressing mice are resistant to NIHL and SIRT3deletion abrogates the protective effects of NR and expression of NAD+ biosynthetic enzymes. These findings reveal that administration of NR activates a NAD+-SIRT3 pathway that reduces neurite degeneration caused by noise exposure.