Rosmarinic acid up-regulates the noise-activated Nrf2/HO-1 pathway and protects against noise-induced injury in rat cochlea.
Noise-induced hearing loss depends on progressive increase of reactive oxygen species and lipoperoxidative damage in conjunction with the imbalance of antioxidant defenses. The redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in the regulation of cellular defenses against oxidative stress, including heme oxygenase-1 (HO-1) activation. In this work we describe a link between cochlear oxidative stress damage, induced by noise exposure, and the activation of the Nrf2/HO-1 pathway. In our model, noise induces superoxide production and overexpression of the lipid peroxidation marker 4-hydroxy-nonenals (4-HNE). To face the oxidative stress, the endogenous defense system is activated as well, as shown by the slight activation of superoxide dismutases (SODs). In addition, we observed the activation of the Nrf2/HO-1 pathway after noise exposure. Nrf2 appears to promote the maintenance of cellular homeostasis under stress conditions. However, in this model the endogenous antioxidant system fails to counteract noise-induced cell damage and its activation is not effective enough in preventing cochlear damage. The herb-derived phenol rosmarinic acid (RA) attenuates noise-induced hearing loss, reducing threshold shift, and promotes hair cell survival. In fact, RA enhances the endogenous antioxidant defenses, as shown by decreased superoxide production, reduced expression of 4-HNE, and up-regulation of SODs. Interestingly, RA potentiates the Nrf2/HO-1 signaling pathway, as shown by immunohistochemical and Western blot analyses. Thus, protective effects of RA are associated with the induction/activation of the Nrf2-ARE signaling pathway in addition to RA direct scavenging capability.
Department of Head and Neck Surgery, Medical School, Università Cattolica, Largo F. Vito 1, 00168 Rome, Italy.
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Fetoni
Department of Head and Neck Surgery, Medical School, Università Cattolica, Largo F. Vito 1, 00168 Rome, Italy.
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Paciello
Department of Head and Neck Surgery, Medical School, Università Cattolica, Largo F. Vito 1, 00168 Rome, Italy.
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Rolesi
Institute of Human Physiology, Medical School, Università Cattolica, Largo F. Vito 1, 00168, Rome, Italy.
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Eramo
Institute of Pharmacology, Medical School, Università Cattolica, Largo F. Vito 1, 00168, Rome, Italy.
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Mancuso
Institute of Human Physiology, Medical School, Università Cattolica, Largo F. Vito 1, 00168, Rome, Italy.
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Troiani
Department of Head and Neck Surgery, Medical School, Università Cattolica, Largo F. Vito 1, 00168 Rome, Italy.
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Paludetti
D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D002934:Cinnamates / Q000494:pharmacology*; D003051:Cochlea / Q000187:drug effects* / Q000201:enzymology / Q000293:injuries / Q000378:metabolism; D053630:Depsides / Q000494:pharmacology*; D006309:Hearing; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D009622:Noise; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D000097123:Rosmarinic Acid
D000447:Aldehydes; D002934:Cinnamates; D053630:Depsides; D051547:Heme Oxygenase-1; D051267:NF-E2-Related Factor 2; D000097123:Rosmarinic Acid; C495637:Nfe2l2 protein, rat; C027576:4-hydroxy-2-nonenal
Acoustic trauma; Antioxidants; Inner ear; Oxidative stress