Noise exposure alters cyclooxygenase 1 (COX-1) and 5-lipoxygenase (5-LO) expression in the guinea pig cochlea.
CONCLUSIONS
Changes in the metabolism of arachidonic acid (AA) might be part of a noise-induced compensatory mechanism with regional specificity.


OBJECTIVE
The released imbalance of prostaglandins and leukotrienes, both AA metabolites, might result in altered blood flow regulation in the inner ear and probably contributes to noise-induced hearing loss. The aim of this study was to gain further information about noise-dependent changes in AA metabolism in the mammalian cochlea.


METHODS
In this prospective animal study, 10 male guinea pigs were exposed to tone bursts for 1 h at 70 dB sound pressure level (SPL) (n = 5) or 90 dB SPL (n = 5). Five animals were used as controls. Alterations in cyclooxygenase 1 (COX-1) and 5-lipoxygenase (5-LO) expression were determined by quantitative immunohistochemical analysis in 11 cochlear regions.


RESULTS
COX-1 expression was decreased after both 70 dB SPL and 90 dB SPL exposure in most cell types of the organ of Corti and increased in the nerve fibers of the osseous spiral lamina. 5-LO was lowered after 90 dB SPL exposure, preferentially in the third cochlear turn in the organ of Corti, in the first and second turn in spiral ganglion cells, and in all turns in the stria vascularis.
Heinrich
Ulf-Rüdiger
UR
Department of Otolaryngology, Head and Neck Surgery, Johannes Gutenberg University of Mainz, Medical School, Langenbeckstrasse 1, 55131 Mainz, Germany. heinrich@hno.klinik.uni-mainz.de
Selivanova
Oxana
O
Schmidtmann
Irene
I
Feltens
Ralph
R
Brieger
Jürgen
J
Mann
Wolf J
WJ
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D016718:Arachidonic Acid / Q000378:metabolism; D003051:Cochlea / Q000473:pathology*; D051545:Cyclooxygenase 1 / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology; D006168:Guinea Pigs; D006317:Hearing Loss, Noise-Induced / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D009412:Nerve Fibers / Q000473:pathology; D009925:Organ of Corti / Q000473:pathology; D011446:Prospective Studies; D012583:Schwann Cells / Q000473:pathology; D013136:Spiral Ganglion / Q000473:pathology; D013137:Spiral Lamina / Q000473:pathology; D055493:Spiral Ligament of Cochlea / Q000473:pathology; D013316:Stria Vascularis / Q000473:pathology; D015854:Up-Regulation / Q000502:physiology
D016718:Arachidonic Acid; D001094:Arachidonate 5-Lipoxygenase; D051545:Cyclooxygenase 1