title: Evidence that cisplatin-induced auditory damage is attenuated by downregulation of pro-inflammatory cytokines via Nrf2/HO-1.
abstract: Recently, we demonstrated that pro-inflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6 played a critical role in cisplatin-induced cochlear injury and that flunarizine, known as a T-type Ca(2+) channel antagonist, induced a cytoprotective effect against cisplatin cytotoxicity in HEI-OC1 cells by the activation of NF-E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) cascade through PI3K-Akt signaling but calcium-independent pathway. We report here that flunarizine markedly attenuates cisplatin-induced pro-inflammatory cytokine secretion and their messenger RNA transcription as well as cisplatin cytotoxicity through the activation of Nrf2/HO-1 and downregulation of NF-kappaB. In HEI-OC1 cells, overexpression of Nrf2/HO-1 by gene transfer or pharmacological approaches attenuated cisplatin-induced cytotoxicity and pro-inflammatory cytokine production. On the contrary, inhibition of Nrf2/HO-1 signaling by pharmacological inhibitors or specific small interfering RNAs significantly abolished the beneficial effects of flunarizine. Flunarizine also attenuated cisplatin-mediated MAPK activation and pharmacological inhibition of MAPKs, especially MEK1/ERK, blocked cisplatin-induced NF-kappaB activation in HEI-OC1 cells. Furthermore, WT-Nrf2 overexpression effectively blocked MAPK activation after cisplatin exposure. Finally, orally administrated Sibelium, the trade name of flunarizine, suppressed the increase of pro-inflammatory cytokines by cisplatin in both serum and cochleas of mice, whereas it increased HO-1 expression in cochleas. These results indicate that flunarizine induces a protective effect against cisplatin ototoxicity through the downregulation of NF-kappaB by Nrf2/HO-1 activation and the resulting inhibition of pro-inflammatory cytokine production in vitro and in vivo.
authors.affiliation: Vestibulocochlear Research Center & Department of Microbiology, School of Medicine, Wonkwang University School of Medicine, 344-7 Shinyong-dong, Iksan, Jeonbuk 570-749, South Korea.
authors.forename: HongSeob
authors.initials: H
authors.lastname: So
authors.forename: HyungJin
authors.initials: H
authors.lastname: Kim
authors.forename: Yunha
authors.initials: Y
authors.lastname: Kim
authors.forename: Eunsook
authors.initials: E
authors.lastname: Kim
authors.forename: Hyun-Ock
authors.initials: HO
authors.lastname: Pae
authors.forename: Hun-Taeg
authors.initials: HT
authors.lastname: Chung
authors.forename: Hye-Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Kang-Beom
authors.initials: KB
authors.lastname: Kwon
authors.forename: Kang-Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Haa-Yung
authors.initials: HY
authors.lastname: Lee
authors.forename: Sung-Kyun
authors.initials: SK
authors.lastname: Moon
authors.forename: Raekil
authors.initials: R
authors.lastname: Park
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D002945:Cisplatin / Q000633:toxicity*; D016207:Cytokines / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005444:Flunarizine / Q000494:pharmacology; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects* / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009925:Organ of Corti / Q000187:drug effects / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000970:Antineoplastic Agents; D002121:Calcium Channel Blockers; D016207:Cytokines; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; C495636:Nfe2l2 protein, mouse; D012333:RNA, Messenger; D051547:Heme Oxygenase-1; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D002945:Cisplatin; D005444:Flunarizine