title: Ebselen attenuates cisplatin-induced ROS generation through Nrf2 activation in auditory cells.
abstract: Ebselen, an organoselenium compound that acts as a glutathione peroxidase mimetic, has been demonstrated to possess antioxidant and anti-inflammatory activities. However, the molecular mechanism underlying this effect is not fully understood in auditory cells. The purpose of the present study is to investigate the protective effect of ebselen against cisplatin-induced toxicity in HEI-OC1 auditory cells, organotypic cultures of cochlear explants from two-day postnatal rats (P(2)) and adult Balb/C mice. Pretreatment with ebselen ameliorated apoptotic death induced by cisplatin in HEI-OC1 cells and organotypic cultures of Corti's organ. Ebselen pretreatment also significantly suppressed cisplatin-induced increases in intracellular reactive oxygen species (ROS), intracellular reactive nitrogen species (RNS) and lipid peroxidation levels. Ebselen dose-dependently increased the expression level of an antioxidant response element (ARE)-luciferase reporter in HEI-OC1 cells through the translocation of Nrf2 into the nucleus. Furthermore, we found that pretreatment with ebselen significantly restored Nrf2 function, whereas it ameliorated the cytotoxicity of cisplatin in cells transfectants with either a pcDNA3.1 (control) or a DN-Nrf2 (dominant-negative) plasmid. We also observed that Nrf2 activation by ebselen increased the expression of phase II antioxidant genes, including heme oxygenase (HO-1), NAD(P)H:quinine oxidoreductase, and gamma-glutamylcysteine synthetase (gamma-GCS). Treatment with ebselen resulted in an increased expression of HO-1 and intranuclear Nrf2 in hair cells of organotypic cultured cochlea. After intraperitoneal injection with cisplatin, auditory brainstem responses (ABRs) threshold was measured on 8th day in Balb/C mice. ABR threshold shift was marked occurred in mice injected with cisplatin (16 mg/kg, n=5; Click and 8-kHz stimuli, p<0.05; 4, 16 and 32 kHz, p<0.01), whereas that of animal group which was treated with cisplatin and ebselen was not significantly changed. These results suggest that ebselen activates the Nrf2-ARE signaling pathway, which ultimately prevents free radical stresses from cisplatin and further contributes to protect auditory sensory hair cells from free radicals produced by cisplatin.
authors.affiliation: Vestibulocochlear Research Center (VCRC), Department of Microbiology, Wonkwang University College of Medicine, 344-2 Shinyong-dong, Iksan, Jeonbuk 570-749, South Korea.
authors.forename: Se-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Channy
authors.initials: C
authors.lastname: Park
authors.forename: A Lum
authors.initials: AL
authors.lastname: Han
authors.forename: Myung-Ja
authors.initials: MJ
authors.lastname: Youn
authors.forename: Jeong-Han
authors.initials: JH
authors.lastname: Lee
authors.forename: Yunha
authors.initials: Y
authors.lastname: Kim
authors.forename: Eun-Sook
authors.initials: ES
authors.lastname: Kim
authors.forename: Hyung-Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Jin-Kyung
authors.initials: JK
authors.lastname: Kim
authors.forename: Ho-Kyun
authors.initials: HK
authors.lastname: Lee
authors.forename: Sang-Young
authors.initials: SY
authors.lastname: Chung
authors.forename: Hongseob
authors.initials: H
authors.lastname: So
authors.forename: Raekil
authors.initials: R
authors.lastname: Park
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D001393:Azoles / Q000494:pharmacology*; D002461:Cell Line, Transformed; D002945:Cisplatin / Q000633:toxicity; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D054833:Isoindoles; D015227:Lipid Peroxidation / Q000187:drug effects; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009924:Organ Culture Techniques; D009925:Organ of Corti / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D016566:Organoselenium Compounds / Q000494:pharmacology*; D010636:Phenols / Q000378:metabolism; D010936:Plant Extracts / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D001393:Azoles; D054833:Isoindoles; D051267:NF-E2-Related Factor 2; D018696:Neuroprotective Agents; C495636:Nfe2l2 protein, mouse; D016566:Organoselenium Compounds; D010636:Phenols; D010936:Plant Extracts; D017382:Reactive Oxygen Species; C501911:antioxidant biofactor AOB; C042986:ebselen; D008156:Luciferases; D002945:Cisplatin