Occlusional Modifications Reversibly Alter Aquaporin 5 Expression and Localization in Rat Salivary Glands

Application of anti-vascular endothelial growth factor antibody restores the function of saliva secretion in a type 2 diabetes mouse model

OBJECTIVES

Xerostomia, a common complication of type 2 diabetes, leads to an increased risk of caries, dysphagia, and dysgeusia. Although anti-vascular endothelial growth factor (VEGF) antibodies, such as ranibizumab (RBZ), have been used to treat diabetic retinopathy, their effects on the salivary glands are unknown. This study evaluated the effects of RBZ on salivary glands to reduce inflammation and restore salivary function in a mouse model of type 2 diabetes.

METHODS

Male KK-Ay mice with type 2 diabetes (10-12 weeks old) were used. The diabetes mellitus (DM) group received phosphate-buffered saline, while the DM + RBZ group received an intraperitoneal administration of RBZ (100 μg/kg) 24 h before the experiment.

RESULTS

Ex vivo perfusion experiments showed a substantial increase in salivary secretion from the submandibular gland (SMG) in the DM + RBZ group. In addition, the mRNA expression levels of TNF-α and IL-1β were considerably lower in this group. In contrast, those of aquaporin 5 were substantially higher in the DM + RBZ group, as revealed by quantitative reverse transcription PCR. Furthermore, the number of lymphocyte infiltration spots in the SMG was notably lower in the DM + RBZ group. Finally, intracellular Ca2+ signaling in acinar cells was considerably higher in the DM + RBZ group than that in the DM group.

CONCLUSION

Treating a type 2 diabetic mouse model with RBZ restored salivary secretion through its anti-inflammatory effects.

Molar extraction alters gastric mucosa and ghrelin expression in rat stomach: A preliminary study

Objectives:

Ghrelin is a key regulator of food intake and is considered a hunger hormone that affects cognition, memory, glucose metabolism, and antidepressant effects. Altered occlusion, such as a loss of molars, has been thought to retard digestive function. However, the association between occlusion and digestive function remains poorly understood. Here, we aimed to explore the effect of bilateral maxillary molar extraction on the gastrointestinal mucosa of growing rats and the expression of ghrelin and its receptor, growth hormone secretagogue receptor (GHSR).

Material and Methods:

Twenty-four male 5-week-old Wistar rats were divided into control (CON) and experimental (EXP) groups (n = 12/group). The rats in the EXP group underwent extraction of the bilateral maxillary first, second, and third molars under general anesthesia. Rats in the CON group underwent a sham operation. All rats in both the CON and EXP groups were fed a powder diet and water ad libitum. The body weight of all rats was monitored throughout the EXP period. Rats in both the CON and EXP groups were euthanized on days 14 and 28, and the stomachs were isolated and subjected to histological analysis. Paraffin serial sections were prepared using a microtome for hematoxylin-eosin and immunohistochemical staining using anti-ghrelin and anti-GHSR antibodies. The distribution and expression of ghrelin-immunopositive and GHSR cells were detected and observed under a light microscope. Data were statistically analyzed using t-tests (P < 0.05).

Results:

There were no significant differences in body weight between the CON and EXP groups throughout the EXP period. Histological analysis showed that the area of the submucosa (ASM), and the number of ghrelinimmunopositive cells were significantly decreased in the EXP group compared with the CON group on day 14. Alternatively, there was no significant difference in the ASM and the number of ghrelin-immunopositive cells between the CON and EXP groups on day 28, whereas the number of ghrelin receptors showed no differences across groups. Furthermore, the number of eosinophilic blood cells significantly increased in the EXP group on days 14 and 28.

Conclusion:

Our findings suggest that bilateral maxillary molar extraction may trigger stomach mucosal changes and alter digestive function through ghrelin expression in rats. This is the first report that occlusal deficiency could alter ghrelin expression in the mucosa of the rat stomach, thus raising concerns about the consequential role of ghrelin.

Mechanism, Prevention, and Treatment of Radiation-Induced Salivary Gland Injury Related to Oxidative Stress

Radiation therapy is a common treatment for head and neck cancers. However, because of the presence of nerve structures (brain stem, spinal cord, and brachial plexus), salivary glands (SGs), mucous membranes, and swallowing muscles in the head and neck regions, radiotherapy inevitably causes damage to these normal tissues. Among them, SG injury is a serious adverse event, and its clinical manifestations include changes in taste, difficulty chewing and swallowing, oral infections, and dental caries. These clinical symptoms seriously reduce a patient’s quality of life. Therefore, it is important to clarify the mechanism of SG injury caused by radiotherapy. Although the mechanism of radiation-induced SG injury has not yet been determined, recent studies have shown that the mechanisms of calcium signaling, microvascular injury, cellular senescence, and apoptosis are closely related to oxidative stress. In this article, we review the mechanism by which radiotherapy causes oxidative stress and damages the SGs. In addition, we discuss effective methods to prevent and treat radiation-induced SG damage.