Abstract
With the aim of discovering an effective method to treat dry mouth, we analyzed the effects of quercetin on salivary secretion and its mechanism of action. We created a mouse model with impaired salivary secretion by exposure to radiation and found that impaired secretion is suppressed by quercetin intake. Moreover, secretion levels were enhanced in quercetin-fed normal mice. To elucidate the mechanisms of these effects on salivary secretion, we conducted an analysis using mouse submandibular gland tissues, a human salivary gland epithelial cell line (HSY), and mouse aortic endothelial cells (MAECs). The results showed that quercetin augments aquaporin 5 (AQP5) expression and calcium uptake, and suppresses oxidative stress and inflammatory responses induced by radiation exposure, suggesting that quercetin intake may be an effective method to treat impaired salivary secretion.
Highlights
Dry mouth, which is caused by decreased salivary secretion levels, exhibits marked dryness and is known to be a risk factor for infections and aspiration pneumonia [1].Several causes of impaired salivary secretion have been reported, including radiation therapy to the head and neck area, as well as Sjögren’s syndrome, an autoimmune disease
Compared to the control group, the salivary secretion levels were significantly lower from 3 week after starting until completion (Fig. 1A), and these results were in agreement with previous reports that studied the radiation-induced impaired salivary secretion in mice [14]
Our findings demonstrated that while the irradiated group had significantly elevated TNF-α and IL-10 expression, the quercetin-fed group showed a clear decrease in TNF-α expression when compared to the groups that were not given quercetin, and IL-10 showed a decreasing trend in the quercetin-fed group (Fig. 2A & B)
Summary
Dry mouth, which is caused by decreased salivary secretion levels, exhibits marked dryness and is known to be a risk factor for infections and aspiration pneumonia [1]. Several causes of impaired salivary secretion have been reported, including radiation therapy to the head and neck area, as well as Sjögren’s syndrome, an autoimmune disease. Chronic inflammation in localized gland tissue [2], involvement of oxidative stress [3], and microvascular disorders of the salivary gland [4] have been reported as mechanisms of impairment. Previous studies have reported that catechin, a polyphenol, is effective against radiation-induced salivary gland impairment [10] and that resveratrol, another polyphenol, suppresses reductions in salivary secretion [11]. The detailed effects of PLOS ONE | DOI:10.1371/journal.pone.0116008 January 28, 2015
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