Activation of SIRT3 by the NAD+ Precursor Nicotinamide Riboside Protects from Noise-Induced Hearing Loss

Summary 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 SIRT3 deletion 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.