Caffeic acid phenethyl ester inhibits diesel exhaust particle-induced inflammation of human middle ear epithelial cells via NOX4 inhibition.
OBJECTIVE
Otitis media is one of the most common diseases in pediatric populations. Recent research on its pathogenesis has focused on air pollution. Chronic exposure to particulate air pollution is associated with the impairment of middle ear function. However, the mechanisms and the underlying inhibitory pathways, especially in the human middle ear, remain unknown. Caffeic acid phenethyl ester (CAPE) is a biologically active ingredient of propolis, a product of honeybee hives, which has anti-oxidative and anti-inflammatory activities. The aim of this study was to evaluate the inhibitory effect of CAPE on diesel exhaust particle (DEP)-induced inflammation of human middle ear epithelial cells and to determine the underlying pathway of the action of CAPE.


METHODS
The inflammatory damage caused by DEPs and the anti-inflammatory effects of CAPE were determined by measuring the levels of tumor necrosis factor alpha and nicotinamide adenine dinucleotide phosphate oxidase (NOX) 4 with real-time reverse transcription polymerase chain reaction and Western blot analysis. The oxidative stress induced by DEPs and the anti-oxidative effects of CAPE were directly evaluated by measuring reactive oxygen species production by use of flow cytometric analysis of 2',7'-dichlorofluorescein diacetate. The effects of CAPE were compared with those of N-acetyl-L-cysteine, which has anti-oxidative and anti-inflammatory effects.


RESULTS
Use of CAPE significantly inhibited DEP-induced up-regulation of tumor necrosis factor alpha and NOX4 expression in a dose- and time-dependent manner. The accumulation of reactive oxygen species induced by DEPs was decreased by pretreatment with CAPE. The anti-inflammatory and anti-oxidative effects of CAPE were similar to those of N-acetyl-L-cysteine.


CONCLUSIONS
The inflammation induced by DEP is reduced by CAPE via the inhibition of NOX4 expression. These findings suggest that CAPE might be used as a therapeutic agent against DEP-induced inflammation of human middle ear epithelial cells.
Division of Brain Korea 21 Program for Biomedical Science, Korea University College of Medicine, Seoul, Korea.
Sun-Young
SY
Jo
Naree
N
Lee
Sung-Moon
SM
Hong
Hak Hyun
HH
Jung
Sung-Won
SW
Chae
D015153:Blotting, Western; D002109:Caffeic Acids / Q000494:pharmacology*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D010033:Otitis Media / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000235:genetics; D052638:Particulate Matter / Q000009:adverse effects*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics*; D015854:Up-Regulation / Q000187:drug effects*; D001335:Vehicle Emissions / Q000506:poisoning
D002109:Caffeic Acids; D016328:NF-kappa B; D052638:Particulate Matter; D012333:RNA, Messenger; D001335:Vehicle Emissions; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; C055494:caffeic acid phenethyl ester; D010626:Phenylethyl Alcohol