Effect of resveratrol in acute cochlear damage caused by 3-nitropropionic acid

Abstract

Introduction: 3-Nitropropionic acid (3-NP), a mitochondrial toxin, induces the acute hearing loss by impairing mitochondrial energy generation. Resveratrol is known to have potent protective effects against ototoxicity from various sources as an antioxidant. The aim of the present study is to investigate the protective effect of resveratrol against 3-NP-induced acute cochlear damage.

Methods: Fifteen male Sprague-Dawley rats were divided into 3 groups. In group A, the 3-NP (500 mM, 4 μl, intratympanically) was injected, and in group B, only resveratrol (10 mg/kg, 5 days, intraperitoneally) was administered. In group C, resveratrol pretreatment (10 mg/kg, 5 days, intraperitoneally) was performed before 3-NP injection. The auditory brainstem response (ABR) was recorded at 8, 16, and 32 kHz before and after treatment. And, 4 weeks after treatment, the histological analysis of cochleae from each group was performed to investigate changes of cochlear cells.

Results: After 3-NP exposure (group A), ABR thresholds were significantly elevated compared to those treated with only resveratrol (group B) which showed normal findings. However, resveratrol pretreatment before 3-NP exposure (group C) led to a significant decrease of ABR thresholds. Histological analysis of group A revealed loss of fibrocytes in the spiral ligament (SL), hair cells and supporting cells in the organ of Corti, stellate fibrocytes and interdental cells in the spiral limbus, and spiral ganglion (SG) cells, whereas group B and C demonstrated normal findings. In addition, the thickness of stria vascularis in group A and C were decreased compared to that in group B, and that of group A was the thinnest. When investigating the cell counts of the fibrocytes in SL and the ganglion cells in SG area, those of group A was significantly decreased compared to those in group B and C.

Conclusions: These results suggest that resveratrol may have a protective effect against 3-NP-induced acute cochlear damage.