title: Rottlerin induces cyclooxygenase-2 upregulation through an ATF4 and reactive oxygen species-independent pathway in HEI-OC1 cells.
abstract: Hearing loss can be caused by infection, inflammation, loud noise and ototoxic drugs. The induction of cyclooxygenase-2 (COX‑2) expression is an important event during the cellular inflammatory response. The present study investigated the effect of rottlerin on CO-2 mRNA and protein expression in HEI-OC1 cells. Cell viability was determined using an MTT assay. Western blotting was used to examine the expression of COX‑2, endoplasmic reticulum stress-associated transcription factors and activation of the MAPK pathway. ROS was measured using the fluorescent probe 2', 7'-dichlorodihydrofluorescein diacetate. Treatment with the natural protein kinase C δ inhibitor, rottlerin, was shown to increase COX‑2 expression at the protein and mRNA levels in a dose‑dependent manner. Rottlerin was shown to induce increased reactive oxygen species (ROS) generation, however, ROS were not critical for rottlerin‑induced upregulation of COX‑2 expression in HEI‑OC1 cells. In addition, rottlerin was shown to increase the phosphorylation of p38 mitogen-activated protein kinase (MAPK). The pharmacological inhibition of p38MAPK and suppression of activating transcription factor 4 (an ER stress‑associated transcription factor) expression by small interfering RNA inhibited rottlerin-induced COX‑2 upregulation. Furthermore, COX‑2 expression levels were increased further when cells were treated with rottlerin and interleukin‑1β or protein kinase C activator, PMA. In conclusion, the results of the present study demonstrated that rottlerin is a novel inducer of COX‑2 expression and identified the mechanisms involved in this process. Rottlerin may be considered a potential activator of repair and remodeling.
authors.affiliation: Department of Immunology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Seon Min
authors.initials: SM
authors.lastname: Woo
authors.affiliation: Department of Otolaryngology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Woo Keun
authors.initials: WK
authors.lastname: Lee
authors.affiliation: Department of Immunology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Kyoung-Jin
authors.initials: KJ
authors.lastname: Min
authors.affiliation: Department of Otolaryngology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Dong Eun
authors.initials: DE
authors.lastname: Kim
authors.affiliation: Department of Otolaryngology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Soon Hyung
authors.initials: SH
authors.lastname: Park
authors.affiliation: Department of Otolaryngology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Sung Il
authors.initials: SI
authors.lastname: Nam
authors.affiliation: Department of Immunology, School of Medicine, Keimyung University, Daegu 700712, Republic of Korea.
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
mesh_terms: D000098:Acetophenones / Q000494:pharmacology*; D051701:Activating Transcription Factor 4 / Q000378:metabolism*; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology*; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D053583:Interleukin-1beta / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D053583:Interleukin-1beta; D017382:Reactive Oxygen Species; D051701:Activating Transcription Factor 4; C085746:rottlerin; D051546:Cyclooxygenase 2; D048051:p38 Mitogen-Activated Protein Kinases