The Regulation Of HP?CD On Hair Cell Sphingolipids Metabolism And Cell Fate Decision

According to the latest WHO report in 2015,there are around 466 million people suffer from hearing loss worldwide,the number of patients who suffered is expected to increase to 900 million by 2050.Sensorineural deafness mainly due to the damage of cochlear hair cells,spiral ganglion neuron injury or auditory central neuron system disorder.Current research shows that sensorineural deafness is mainly related to noise and chemicals.With the rapid development of society,drug discovery and wildly used in the pharmaceutical industry is increasing rapidly.The side effect of ototoxicity,especially of chemicals,is showing with the accumulation in organisms.Cyclodextrin is the family of cyclic oligosaccharide which is extracted from starch.The ring of Cyclodextrins is often depicted as a cup-shaped toroid.Due to the inside of the molecule is more hydrophobic and the outside of the ring is hydrophilic,the solubility and stabilization compound guest was enhanced which were sequestered.As a derivative of cyclodextrin,hydroxypropyl-?-cyclodextrin(HP?CD),which is widely used in food,agriculture,daily chemicals and medicine.Niemann-Pick disease type C(NP-C)is mainly caused by the mutation of the NPC gene which leads to the accumulation of cholesterol and sphingolipids.HP?CD can effectively reduce the accumulation of cholesterol and sphingolipids to maintain the normal physiological activity of cells,due to the cholesterol and sphingolipids chelating properties.The first case report of HP?CD ototoxicity came from NPC Human patients with NPC1 mutations which have disease-related hearing loss.According to previous studies,the dysfunction of mitochondria and reactive oxygen species were increased significantly after HP?CD was transported into the cytosol via endocytosis.The prestin was especially accumulated on the plasma membrane which plays an essential role in electromotile activity,might a potential damaged target of HP?CD.OHCs from prestin knockout mice are partially prevented from HP?CD ototoxicity.However,the detailed mechanism of intracellular injury and the protection in prestin knockout mice remain unclear.In this paper,the HP?CD Acute injury model and chronic model were established and hired to investigate the detail mechanism of OHCs impairment.In the acute injury model,five weeks CBA/J mice were hired to investigate the cochlea hair cells and ribbon synapses damage.The result shows that the OHCs were damaged in a dose-dependent way following base to apex region of the cochlea,even IHCs in hook region were partially lost after a higher dose(6000mg/kg)injection.After a lower dose of HP?CD(4000mg/kg)injection,still,some mice were not affected according to the auditory measurement and whole-mount immunolabeling results which is consistence with previous reports.Even ABR and DPOAE threshold were not affected after 1000mg/kg HP?CD injection,the ribbon synapses were partially lost in the middle and high-frequency region.The damage of ribbon synapses was also the following dose-dependent way.The damage of OHCs occurred rapidly.After a single injection of 5000mg/kg HP?CD 13 hours,OHCs were damaged and autophagy maker LC3-II were increased significantly.Next,a chronic HP?CD injury model was established to evaluate the detail mechanism because of the severe hair cell damage is hard to protect in the acute model.Finally,the Metabolomics analysis was hired to investigate the sphingolipids metabolic change in HEI-OC1 cells.the sphingosines were reduced,ceramides and sphingomyelin were increased significantly after HP?CD treatment.These indicate the regulation of HP?CD on sphingolipids.This study provides new clues and basis for further study of the HP?CD ototoxicity mechanism.