Effect of low radiation dose on the expression and location of aquaporins in rat submandibular gland

Side effects of different head and neck radiotherapy doses on wistar rat's behavior

Radiotherapy (RT) is a common treatment for head and neck tumors. However, it causes several physical and behavioral side effects, and no study has assessed the emotional effects in rats. Therefore, the present study evaluated the influence of head and neck RT on the behavior and body weight gain in Wistar rats. Fifty-four male Wistar rats were allocated into six groups (n = 9) according to the irradiation dose, which was applied at the first day of the experiment: RT-7.5 (single dose of 7.5 Gy); RT-10 (single dose of 10 Gy); RT-15 (single dose of 15 Gy); RT-30 (single dose of 30 Gy); Control (without RT). The animals were irradiated in the region of the right face, and behavioral tests and weighing were performed on days one, seven, and 28. The open field and Y-maze tests were undertaken to analyze the animal's behavior. The dose of 30 Gy was lethal when applied to the head and neck region. The irradiated animals had less weight gain when compared to the control ones, but there was no statistical difference. In the open field and Y-maze tests, lower mobility of animals in the RT groups was observed both on day seven and at the end of the experiment (day 28) when compared to the control rats (p < 0.05). It was possible to conclude that the different doses of radiation induced depressive behavior in the animals, and that the weight gain tended to be lower in the irradiated groups, however, without statistical difference.

Clinical management of salivary gland hypofunction in patients with head and neck cancer: a scoping review of physical salivary stimulation methods

OBJECTIVE(S)

This scoping review aims to map the scientific literature on the therapies currently available for physical salivary stimulation in individuals with hyposalivation caused by radiotherapy.

STUDY DESIGN

Studies were included when they comprised the target population of adult individuals receiving radiotherapy of the head and neck region and who developed or were at risk of developing hyposalivation. Two reviewers selected the studies and extracted data on the type of physical salivary stimulation therapy used, the degree of glandular tissue involvement, and the percentage of salivary flow alteration. Therapies were classified according to either prophylactic application (before/during radiotherapy) or therapeutic application (post-radiotherapy).

RESULTS

Sixteen articles were included: 4 tested transcutaneous electrical nerve stimulation (TENS), 3 studied low-level lasers, 7 researched acupunctures, and 2 investigated acupuncture-like TENS. The outcomes of the prophylactic studies indicated beneficial effects (similar salivary flow or reduced salivary flow loss), although most studies did not include a comparable control group. Therapeutic studies presented conflicting results.

CONCLUSION(S)

Prophylactic therapies of physical salivary stimulation may produce better effects than therapeutic applications. However, the protocols best indicated could not be defined. Well-designed, controlled clinical trials should be researched in the future to support the clinical recommendation of any of these treatments.

Insights into the Function of Aquaporins in Gastrointestinal Fluid Absorption and Secretion in Health and Disease

Aquaporins (AQPs), transmembrane proteins permeable to water, are involved in gastrointestinal secretion. The secretory products of the glands are delivered either to some organ cavities for exocrine glands or to the bloodstream for endocrine glands. The main secretory glands being part of the gastrointestinal system are salivary glands, gastric glands, duodenal Brunner's gland, liver, bile ducts, gallbladder, intestinal goblet cells, exocrine and endocrine pancreas. Due to their expression in gastrointestinal exocrine and endocrine glands, AQPs fulfill important roles in the secretion of various fluids involved in food handling. This review summarizes the contribution of AQPs in physiological and pathophysiological stages related to gastrointestinal secretion.

Aquaporins in Glandular Secretion

Exocrine and endocrine glands deliver their secretory product, respectively, at the surface of the target organs or within the bloodstream. The release of their products has been shown to rely on secretory mechanisms often involving aquaporins (AQPs). This chapter will provide insight into the role of AQPs in secretory glands located within the gastrointestinal tract, including salivary glands, gastric glands, duodenal Brunner's glands, liver, gallbladder, intestinal goblets cells, and pancreas, as well and in other parts of the body, including airway submucosal glands, lacrimal glands, mammary glands, and eccrine sweat glands. The involvement of AQPs in both physiological and pathophysiological conditions will also be highlighted.

Effect of vitamin E and supragingival scaling on salivary gland function in patients with differentiated thyroid cancer treated with 131I

OBJECTIVE

The aim of this study was to evaluate the effect of vitamin E and supragingival scaling with vitamin C on the salivary glands of patients with differentiated thyroid carcinoma after 131I treatment.

METHODS

A total of 89 prospective patients with differentiated thyroid carcinoma were enrolled and randomly divided into the following groups: vitamin E group (n = 30, group A), vitamin C group (n = 30, group B) and supragingival scaling with vitamin C group (n = 29, group C). Using functional indices (e.g. maximum uptake fraction, uptake index, excretion fraction, secretion time and excretion rate), changes in the salivary gland functions before and a month after 131I treatment were assessed by dynamic imaging of salivary gland.

RESULTS

We compared the before and after 131I therapy results of the three groups. In group A (P  < 0.05), the excretion fraction and excretion rate of the left parotid gland were significantly higher, and the uptake index of the bilateral submandibular glands was significantly lower. No significant changes in salivary gland functional parameters were observed in group B (P > 0.05). The uptake index of the bilateral parotid glands and the excretion rate of the left parotid gland were significantly higher in group C (P < 0.05). The degree of serum amylase level reduction decreased significantly in group C (P < 0.05).

CONCLUSION

Vitamin E showed a protective effect on parotid excretion function in patients with differentiated thyroid carcinoma who underwent 131I treatment. Supragingival scaling may be a promising radiation protector because it is associated with a protective effect on the salivary gland functions.

Does laser photobiomodulation prevent hyposalivation in patients undergoing head and neck radiotherapy? A systematic review and meta-analysis of controlled trials

INTRODUCTION

Head and neck radiotherapy can cause hypofunction of the salivary glands. Many studies report that laser photobiomodulation (PBM) is able to minimize radiation-induced hyposalivation, yet there is no consensus about its effects.

OBJECTIVE

To carry out a meta-analysis of controlled clinical trials that used PBM to prevent radiation-induced hyposalivation.

METHODS

A systematic search was performed through Embase, Medline/PubMed, Cochrane, EBSCO, Scopus, LILACS and Web of Science databases. The strategy included comparisons of the effect of PBM with placebo/clinical follow-up on unstimulated and/or stimulated salivary flow in patients undergoing head and neck radiotherapy.

RESULTS

Six clinical trials were included, five of which were used for meta-analysis. Evidence was observed between the use of PBM and increased unstimulated salivary flow (MD 0.20 mL/min, 95 % Cl 0.10-0.30, I² = 96 %, p < 0.00001) and in stimulated salivary flow (MD 0.27 mL/min, 95 % CI 0.08-0.46, I² = 95 %, p < 0.00001).

CONCLUSION

PBM appears to minimize radiation-induced hyposalivation.

Experimental Animal Model Systems for Understanding Salivary Secretory Disorders

Salivary secretory disorders are life-disrupting pathologic conditions with a high prevalence, especially in the geriatric population. Both patients and clinicians frequently feel helpless and get frustrated by the currently available therapeutic strategies, which consist mainly of palliative managements. Accordingly, to unravel the underlying mechanisms and to develop effective and curative strategies, several animal models have been developed and introduced. Experimental findings from these models have contributed to answer biological and biomedical questions. This review aims to provide various methodological considerations used for the examination of pathological fundamentals in salivary disorders using animal models and to summarize the obtained findings. The information provided in this review could provide plausible solutions for overcoming salivary disorders and also suggest purpose-specific experimental animal systems.

Evaluation of Aquaporins 1 and 5 Expression in Rat Parotid Glands After Volumetric Modulated Arc Radiotherapy and Use of Low-Level Laser Therapy at Different Times

Introduction: This experimental study investigated the mRNA expression of aquaporins (AQPs) 1 and 5 in the parotid glands of rats irradiated with volumetric modulated arc therapy (VMAT) and subjected to low-level laser therapy (LLLT) at different time points. Methods: The sample consisted of 30 Wistar rats (Rattus norvegicus) divided into the following groups: control, LLLT alone (LG), radiotherapy alone (RG), and experimental groups that received LLLT at 24 hours (early experimental group [EEG], n=12) and 120 hours (late experimental group [LEG], n=12) after radiotherapy. VMAT was delivered at a single dose (12 Gy) and LLLT was performed with an aluminium-gallium-arsenide diode laser (660 nm, 100 mW), spot area of 0.0028 cm2, energy of 2 J/cm² applied to 3 spots in the region corresponding to the right parotid gland, for 10 consecutive days. The right parotid gland was resected and prepared for RNA extraction. The gene expression of AQPs was evaluated by quantitative polymerase chain reaction (qPCR) using specific TaqMan probes, with the HPRT gene as an internal control. Results: The lowest AQP1 gene expression was 0.83 (0.27) with the use of LLLT 24 hours after radiotherapy (EEG), and the highest was 1.56 (0.80) with the use of LLLT alone (LG). Likewise, the lowest AQP5 gene expression was found in the EEG (mean = 0.88; SD = 0.49) and the highest in the LG (mean = 1.29; SD = 0.33). Conclusion: The use of LLLT after radiotherapy may contribute to the maintenance and an increase of these proteins, even when used at a later time point after radiotherapy.

Insight into Salivary Gland Aquaporins

The main role of salivary glands (SG) is the production and secretion of saliva, in which aquaporins (AQPs) play a key role by ensuring water flow. The AQPs are transmembrane channel proteins permeable to water to allow water transport across cell membranes according to osmotic gradient. This review gives an insight into SG AQPs. Indeed, it gives a summary of the expression and localization of AQPs in adult human, rat and mouse SG, as well as of their physiological role in SG function. Furthermore, the review provides a comprehensive view of the involvement of AQPs in pathological conditions affecting SG, including Sjögren's syndrome, diabetes, agedness, head and neck cancer radiotherapy and SG cancer. These conditions are characterized by salivary hypofunction resulting in xerostomia. A specific focus is given on current and future therapeutic strategies aiming at AQPs to treat xerostomia. A deeper understanding of the AQPs involvement in molecular mechanisms of saliva secretion and diseases offered new avenues for therapeutic approaches, including drugs, gene therapy and tissue engineering. As such, AQP5 represents a potential therapeutic target in different strategies for the treatment of xerostomia.