Abstract

IntroductionNoise-induced hearing loss (NIHL) is an increasing problem in society and accounts for a third of all cases of acquired hearing loss. NIHL is caused by formation of reactive oxygen species (ROS) in the cochlea causing oxidative stress. Hydrogen gas (H2) can alleviate the damage caused by oxidative stress and can be easily administered through inhalation.ObjectivesTo present a protocol for untargeted metabolomics of guinea pig perilymph and investigate the effect of H2 administration on the perilymph metabolome of noise exposed guinea pigs.MethodsThe left ear of guinea pigs were exposed to hazardous impulse noise only (Noise, n = 10), noise and H2 (Noise + H2, n = 10), only H2 (H2, n = 4), or untreated (Control, n = 2). Scala tympani perilymph was sampled from the cochlea of both ears. The polar component of the perilymph metabolome was analyzed using a HILIC-UHPLC-Q-TOF–MS-based untargeted metabolomics protocol. Multivariate data analysis (MVDA) was performed separately for the exposed- and unexposed ear.ResultsMVDA allowed separation of groups Noise and Noise + H2 in both the exposed and unexposed ear and yielded 15 metabolites with differentiating relative abundances. Seven were found in both exposed and unexposed ear data and included two osmoprotectants. Eight metabolites were unique to the unexposed ear and included a number of short-chain acylcarnitines.ConclusionsA HILIC-UHPLC-Q-TOF–MS-based protocol for untargeted metabolomics of perilymph is presented and shown to be fit-for-purpose. We found a clear difference in the perilymph metabolome of noise exposed guinea pigs with and without H2 treatment.

Highlights

  • Noise-induced hearing loss (NIHL) is an increasing problem in society and accounts for a third of all cases of acquired hearing loss

  • We present an LCMS-based untargeted metabolomics protocol for perilymph applied to a guinea pig model of the attenuating effect of ­H2 on NIHL

  • The quality control (QC) sample is a composite of all samples in the study which includes a number of sample groups not presented in this paper, this likely explains the slight offset of the cluster from the origin in the plot

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Summary

Introduction

Noise-induced hearing loss (NIHL) is an increasing problem in society and accounts for a third of all cases of acquired hearing loss. NIHL is caused by formation of reactive oxygen species (ROS) in the cochlea causing oxidative stress. Objectives To present a protocol for untargeted metabolomics of guinea pig perilymph and investigate the effect of H­ 2 administration on the perilymph metabolome of noise exposed guinea pigs. The polar component of the perilymph metabolome was analyzed using a HILIC-UHPLC-Q-TOF–MS-based untargeted metabolomics protocol. Multivariate data analysis (MVDA) was performed separately for the exposed- and unexposed ear. Conclusions A HILIC-UHPLC-Q-TOF–MS-based protocol for untargeted metabolomics of perilymph is presented and shown to be fit-for-purpose. Noise exposure can lead to pathological changes in the cochlea causing hearing impairment. One key mechanism is the formation of reactive oxygen species (ROS) leading to oxidative stress in the inner ear (Henderson et al 2006; Le et al 2017). More knowledge about the molecular mechanisms surrounding the protective effect is needed

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