Modulation of NAD⁺ biosynthesis activates SIRT1 and resists cisplatin-induced ototoxicity

Cisplatin, the most widely used platinum-based anticancer drug, often causes progressive and irreversible sensorineural hearing loss in cancer patients. However, the precise mechanism underlying cisplatin-associated ototoxicity is still unclear. Nicotinamide adenine dinucleotide (NAD(+)), a co-substrate for the sirtuin family and PARPs, has emerged as a potent therapeutic molecular target in various diseases. In our investigates, we observed that NAD(+) level was changed in the cochlear explants of mice treated with cisplatin. Supplementation of a specific inhibitor (TES-1025) of alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSD), a rate-limiting enzyme of NAD(+) de novo synthesis pathway, promoted SIRT1 activity, increased mtDNA contents and enhanced AMPK expression, thus significantly reducing hair cells loss and deformation. The protection was blocked by EX527, a specific SIRT1 inhibitor. Meanwhile, the use of NMN, a precursor of NAD(+) salvage synthesis pathway, had shown beneficial effect on hair cell under cisplatin administration, effectively suppressing PARP1. In vivo experiments confirmed the hair cell protection of NAD(+) modulators in cisplatin treated mice and zebrafish. In conclusion, we demonstrated that modulation of NAD(+) biosynthesis via the de novo synthesis pathway and the salvage synthesis pathway could both prevent ototoxicity of cisplatin. These results suggested that direct modulation of cellular NAD(+) levels could be a promising therapeutic approach for protection of hearing from cisplatin-induced ototoxicity. (C) 2021 Published by Elsevier B.V.