奧勒岡精油嗅覺刺激可調控口腔菌叢，活化 Nrf2/HO-1 抗氧化路徑與降低牙齦氧化壓力，改善口腔功能

Abstract

口腔菌叢 (oral microbiota) 是人體内第二大微生物菌叢。維持口腔菌叢的菌相平衡 (eubiosis) 不僅有助於維護口腔健康，更對促進人體各系統之健康發展有莫大的助益。先前研究已證實嗅覺刺激 (olfactory stimulation) 可有效調節腸道菌叢(gut microbiota)，且具有顯著的抗氧化能力 (anti-oxidative activity)，因此本研究即旨在探討嗅覺刺激是否亦能有效改善口腔菌叢，抑低牙齦氧化壓力，成功達到提升或促進口腔功能的目的。本研究使用成年雄性 Wistar 大鼠，利用擴香儀釋放奧勒岡 (Origanum vulgare) 精油進行嗅覺刺激。嗅覺刺激每次持續一小時，每日兩次，連續兩週。16S rRNA 菌相定序分析結果顯示，嗅覺刺激可有效改善口腔菌叢，顯著提升菌相的豐富度 (richness) 與歧異性(diversity)。西方墨點反應的結果亦顯示，嗅覺刺激可巨幅活化 Nrf2/HO-1 抗氧化訊息傳遞路徑，進而誘使下游抗氧化酵素 (anti-oxidative enzymes) 的活性同步增強。生物組織能量 (bioenergetics) 的研究結果與菌叢分析和生化實驗所獲致的成果相當吻合，無論是細胞色素氧化酵素(cytochrome oxidase)、Na+/K+ ATPase 活性表現與咀嚼肌細胞內的鈣離子強度 (代表咀嚼肌收縮功能)，在嗅覺刺激後皆顯著增加。此外，掃描式電子顯微鏡的型態分析亦進一步證實，接受嗅覺刺激的實驗鼠，其齒槽骨骨小樑 (alveolar trabeculae)之平均厚度顯著大於對照組。綜合上述研究成果我們推斷，嗅覺刺激可透過改善口腔菌叢，增強抗氧化活性，提升咀嚼肌的生物組織能量，以及強化齒槽骨結構，成功達到促進口腔健康與對抗口腔疾病發生的潛在效益。

The oral microbiota constitutes the second most extensive microbial community in the body. Maintaining eubiosis of the oral microbiota will not only support oral health but also significantly contribute to the development of overall well-being. Concerning olfactory stimulation (OS) possesses significant microbial modulating and anti-oxidative effects, the present study aims to determine whether OS would successfully improve oral microbiota, depress oxidative stress, and subsequently give rise to the betterment of oral bioenergetics. Adult male Wistar rats underwent OS by inhaling the essential oil of Origanum vulgare dispersed by a nebulizer diffuser twice daily for two weeks, with each session lasting for one hour, were used in this study. Data from 16S rRNA sequencing revealed that OS effectively improves the oral microbial composition, as indicated by increased richness and diversity compared to that of untreated rats. Immunoblotted results also showed that OS significantly enhanced the Nrf2/HO-1 signaling pathway, and consequently up-regulates the activities of several downstream anti-oxidative enzymes. Bioenergetic data corresponded well with both microbial and biochemical findings, in which considerably higher cytochrome oxidase expression, Na+/K+ ATPase activity, and intracellular Ca2+ intensity was all detected in the mastication muscles of OS rats compared to those of untreated ones. Moreover, morphological data from scanning electron microscopy further showed that the averaged trabecular thickness of alveolar bone was much higher in OS rats than in untreated ones. As OS successfully improves oral microbiota, enhances anti-oxidative activity, increases bioenergetics of mastication muscle, and strengthens microarchitecture of alveolar bone, applying OS may serve as a promising strategy to preserve oral function or to counter the pathogenesis of oral diseases.