Effects of Cholesterol Modulation on Cisplatin-Induced Hearing Loss.

Cisplatin is a widely used and effective anticancer drug. However, it causes permanent sensorineural hearing loss in over 50% of treated patients. There are no FDA-approved therapies to prevent cisplatin-induced hearing loss (CIHL) in adults, highlighting a critical unmet clinical need. Previous studies suggest that statins, commonly prescribed cholesterol-lowering drugs, are associated with reduced incidence and severity of cisplatin-induced hearing loss. Statins are primarily used to lower cholesterol, but they also exert several pleiotropic effects, making the mechanism(s) underlying this protection unclear. Here we examine whether reduced plasma cholesterol confers protection against CIHL independent of statin treatment. We utilized mice lacking serine protease proprotein convertase subtilisin/kexin type 9 (Pcsk9 knockout (KO) mice) as a genetic model of reduced plasma cholesterol. We find that Pcsk9 KO mice are protected against cisplatin-induced hearing loss, as reflected by significantly lower ABR and DPOAE threshold shifts relative to wild type (WT) mice following treatment. Histological analyses confirmed preservation of cochlear outer hair cells (OHCs) in Pcsk9 KO mice treated with cisplatin, whereas WT mice showed significant OHC loss in the high-frequency cochlear regions. Finally, hearing loss positively correlated with baseline plasma cholesterol levels. Together our data demonstrate that systemic cholesterol reduction provides significant protection against CIHL, and they suggest that the protective effect of statins against CIHL is mediated by cholesterol reduction.