Analysis of the stress response in oral lesions by using Nrf2 gene knockout mouse

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The purpose of this study is to analyze how the transcription factor Nrf2 is associated with oral diseases. As fundamental study, we investigated the role of Nrf2 against oxidative stress and confirmed that the oxidative stress proteins, such as hemeoxygenase, peroxireoxin MSP23, A170, are under control of Nrf2 regulation. We also found MSP23 was induced by BHA treatment. Through these experiments we found the phenotype of Nrf2 mice was the decolorization of the maxillary incisor. We analyzed this phenomenon to know the significance of Nrf2 in oral desease. At first the incisor samples were fixed in ethanol and dehydraded by critical point drying method, and we observed the suface of the incisors with scanning electron microscope. There was no difference among the homo, hetero and wild type mice. We quantified the Ca, P, and Fe ion content with energy disparative micro X ray analysis and found there were significant difference among the mice. Iron ion content decreased significantly in knockout mice, though Ca and P content was not different. We estimated the association the iron ion and oral disease caused by nrf2 gene disruption. To know how the iron acted on the incisor decolorization, we investigated the ferritin and iron ion localization by using in situ hybridization, immunohistochemistry and iron staining. We found there were abnormal iron deposition and the ameloblast was damaged. Our results suggested Nrf2 affected on the oral diseases through abnormal iron deposition.