Regulation of salivary gland function by autonomic nerves

Ictal Hypersalivation and Salivary Gland Enlargement in a Patient With Acquired Frontal Lobe Epilepsy

Hypersalivation is a well-known ictal semiology of benign Rolandic epilepsy and other childhood epilepsy syndromes. There are also occasional reports of adults with temporal, parietal, or frontal lobe epilepsy in which hypersalivation is a prominent seizure manifestation. Notably lacking are reports linking salivary gland enlargement to ictal hypersalivation. A 33-year-old man with frontal lobe epilepsy due to a ruptured aneurysm presented with focal seizures and facial swelling. The only seizures he had in the past were generalized tonic-clonic seizures. Eight days prior to admission, he started having focal seizures characterized by pronounced hypersalivation, speech arrest, impaired awareness, and left upper extremity posturing or automatism. Seizure frequency increased from five to 30 per day. Four days prior to admission, his face started to swell up, and his family thought he had mumps. Computed tomography (CT) of the head showed encephalomalacia in the inferomedial cortex of the right frontal lobe, the same lesion seen in his old CT images. Maxillofacial CT revealed enlargement of the parotid and submandibular glands. Although electroencephalography (EEG) showed seizure onset in the right frontal region, the initial ictal discharge on the scalp may represent seizure propagation from a focus near the zone of encephalomalacia. After seizure freedom was achieved with antiepileptic drugs, the patient’s salivary glands decreased in size and returned to normal.

The salivary glands as a dose limiting organ of PSMA- targeted radionuclide therapy: A review of the lessons learnt so far

At present, prostate cancer remains the second most occurring cancer in men, in Europe. Treatment efficacy for therapy of advanced metastatic disease, and metastatic castration-resistant prostate cancer in particular is limited. Prostate-specific membrane antigen (PSMA) is a promising therapeutic target in prostate cancer, seeing the high amount of overexpression on prostate cancer cells. Clinical investigation of PSMA-targeted radionuclide therapy has shown good clinical efficacy. However, adverse effects are observed of which salivary gland hypofunction and xerostomia are among the most prominent. Salivary gland toxicity is currently the dose-limiting side effect for PSMA-targeted radionuclide therapy, and more specifically for PSMA-targeted alpha therapy. To date, mechanisms underlying the salivary gland uptake of PSMA-targeting compounds and the subsequent damage to the salivary glands remain largely unknown. Furthermore, preventive strategies for salivary gland uptake or strategies for treatment of salivary gland toxicity are needed. This review focuses on the current knowledge on uptake mechanisms of PSMA-targeting compounds in the salivary glands and the research performed to investigate different strategies to prevent or treat salivary gland toxicity.

Standardizing salivary lactoferrin measurements to obtain a robust diagnostic biomarker for Alzheimer's disease

The search for new, robust, and reproducible biomarkers for Alzheimer's disease (AD) diagnosis is a challenge. We recently reported that salivary lactoferrin (Lf) could be presented as new biomarker candidate for AD, being both non-invasive and cost-effective, as well as having appropriate diagnostic performance for the clinical detection of AD subjects. Saliva is an attractive sample type for biomarker-based testing approaches for several other diseases; however, its composition may change under certain circumstances. It is therefore critical to maintain a consistent salivary handling protocol, considering possible extrinsic factors that may influence salivary Lf concentration. In this work, we analyzed salivary Lf concentration under different handling conditions and donor-dependent factors including age, inter-diurnal variations, physical activity, and pharmacological treatments. Our aim was to evaluate the influence of such conditions on salivary Lf concentration. In conclusion, we found that most of these extrinsic factors should be considered in the future when using Lf as a predictive biomarker for AD.

Use of a non-invasive biomarker salivary alpha-amylase to assess the role of probiotics in sleep regulation and stress attenuation in surgical patients: A randomised double-blind clinical trial

BACKGROUND AND AIMS

The influence of gut microbiota on human behaviour, stress and sleep is currently a novel topic of research. A prospective double-blind randomised trial was planned to find out whether probiotics by alteration of the gut microbiome can allay surgery-related stress and improve sleep.

METHODS

A total of 160 elective surgical patients were randomised to receive either probiotic or placebo capsule twice daily for four and a half consecutive preoperative days. They were subjected to the Perceived Stress Scale (PSS) questionnaire, a psychomotor vigilance task (PVT) and estimation of salivary alpha-amylase (SAA), a well-known biomarker of stress on the evening of admission and on the evening just before the day of scheduled surgery. Data were analysed using Chi-square test, Student's t-test and Mann-Whitney test.

RESULTS

On comparing between the two groups, there was a significant difference in PSS scores, SAA levels and PVT scores after probiotic/placebo therapy. There was a decrease in the PSS scores by 11.38% (P < 0.05) and SAA levels by 11.38% (P < 0.05) and an increase in the PVT scores (12.13%, P < 0.05) following probiotic treatment.There was a mean difference of 52.85 in SAA levels in probiotic group and - 69.32 in placebo group with a definite fall in SAA levels in probiotic group, which showed that these patients had reduced stress levels and improved psychomotor vigilance implying improved sleep.

CONCLUSION

Gut microbiome alteration with probiotics results in lowering of psychological stress and sleep improvement in the preoperative period in surgical patients.

Muscarinic Receptors and BK Channels Are Affected by Lipid Raft Disruption of Salivary Gland Cells

Activity-dependent fluid secretion is the most important physiological function of salivary glands and is regulated via muscarinic receptor signaling. Lipid rafts are important for G-protein coupled receptor (GPCR) signaling and ion channels in plasma membranes. However, it is not well understood whether lipid raft disruption affects all membrane events or only specific functions in muscarinic receptor-mediated water secretion in salivary gland cells. We investigated the effects of lipid raft disruption on the major membrane events of muscarinic transcellular water movement in human salivary gland (HSG) cells. We found that incubation with methyl-β-cyclodextrin (MβCD), which depletes lipid rafts, inhibited muscarinic receptor-mediated Ca²⁺ signaling in HSG cells and isolated mouse submandibular acinar cells. However, MβCD did not inhibit a Ca²⁺ increase induced by thapsigargin, which activates store-operated Ca²⁺ entry (SOCE). Interestingly, MβCD increased the activity of the large-conductance Ca²⁺-activated K⁺ channel (BK channel). Finally, we found that MβCD did not directly affect the translocation of aquaporin-5 (AQP5) into the plasma membrane. Our results suggest that lipid rafts maintain muscarinic Ca²⁺ signaling at the receptor level without directly affecting the activation of SOCE induced by intracellular Ca²⁺ pool depletion or the translocation of AQP5 into the plasma membrane.

Salivary Proteome Changes in Response to Acute Psychological Stress Due to an Oral Exam Simulation in University Students: Effect of an Olfactory Stimulus

The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is also regulated by ANS. In this study, we explored salivary proteome changes produced in thirty-eight University students by a test stress, which simulated an oral exam. Students underwent a relaxation phase followed by the stress test during which an electrocardiogram was recorded. To evaluate the effect of an olfactory stimulus, half of the students were exposed to a pleasant odor diffused in the room throughout the whole session. Saliva samples were collected after the relaxation phase (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis, and patterns at different times were compared. Spots differentially expressed were trypsin digested and identified by mass spectrometry. Western blot analysis was used to validate proteomic results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of α-amylase, polymeric immunoglobulin receptor (PIGR), and immunoglobulin α chain (IGHA) secretion were observed after the stress test was performed in the two conditions. Moreover, the presence of pleasant odor reduced the acute social stress affecting salivary proteome changes. Therefore, saliva proteomic analysis was a useful approach to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers.

In Vivo Monitoring of Acetylcholine Release from Nerve Endings in Salivary Gland

Simple Summary

Stimulation of the parasympathetic nervous system results in the secretion of saliva. Previous studies have demonstrated acetylcholine content in homogenate obtained from salivary glands. Acetylcholine in homogenate, however, includes that stored in the cells, as well as that released in the interstitial fluid. The activity of the parasympathetic nervous system is mainly determined by the amount of acetylcholine released. We established an in vivo microdialysis method for monitoring the acetylcholine released from nerve endings in the salivary glands in rats. The results of the present study demonstrated that acetylcholine levels in the dialysate reflect acetylcholine levels in the interstitial fluid of the submandibular gland, and that an increase in the acetylcholine level in the dialysate depends predominantly on the release of acetylcholine from the parasympathetic nerve endings.

Abstract

A microdialysis technique was used to monitor acetylcholine levels in the local interstitial fluid in rat submandibular glands, with the aim of determining parasympathetic nerve activity in vivo. The dialysis probe housed a 10 × 0.22 mm semipermeable membrane (molecular weight cutoffs: 50,000 Da). When the probe was perfused at 2 μL/min in vitro, the mean relative recovery of acetylcholine was 41.7% ± 2.5%. The dialysis probes were implanted in the submandibular glands of anesthetized rats and perfusion with Ringer’s solution, at 2 μL/min, was performed. Acetylcholine concentrations in the dialysate were measured by high-performance liquid chromatography and electrochemical detection. The results revealed the following: (1) that mixing Eserine with Ringer’s solution allowed acetylcholine in the salivary glands to be quantified; (2) that acetylcholine concentrations in the dialysate were highly variable and unstable over the first 120 min after probe implantation, but reached a nearly stable level (4.8 ± 2.7 nM) thereafter in the presence of 100 µM of Eserine; and (3) that electrical stimulation of the chorda tympani nerve, or perfusion with high potassium Ringer’s solution, significantly increased acetylcholine concentrations in the dialysate. These results indicate that the present microdialysis technique offers a powerful tool for detecting changes in parasympathetic activity within the salivary glands.

Disease-Induced Changes in Salivary Gland Function and the Composition of Saliva

Although the physiological control of salivary secretion has been well studied, the impact of disease on salivary gland function and how this changes the composition and function of saliva is less well understood and is considered in this review. Secretion of saliva is dependent upon nerve-mediated stimuli, which activate glandular fluid and protein secretory mechanisms. The volume of saliva secreted by salivary glands depends upon the frequency and intensity of nerve-mediated stimuli, which increase dramatically with food intake and are subject to facilitatory or inhibitory influences within the central nervous system. Longer-term changes in saliva secretion have been found to occur in response to dietary change and aging, and these physiological influences can alter the composition and function of saliva in the mouth. Salivary gland dysfunction is associated with different diseases, including Sjögren syndrome, sialadenitis, and iatrogenic disease, due to radiotherapy and medications and is usually reported as a loss of secretory volume, which can range in severity. Defining salivary gland dysfunction by measuring salivary flow rates can be difficult since these vary widely in the healthy population. However, saliva can be sampled noninvasively and repeatedly, which facilitates longitudinal studies of subjects, providing a clearer picture of altered function. The application of omics technologies has revealed changes in saliva composition in many systemic diseases, offering disease biomarkers, but these compositional changes may not be related to salivary gland dysfunction. In Sjögren syndrome, there appears to be a change in the rheology of saliva due to altered mucin glycosylation. Analysis of glandular saliva in diseases or therapeutic interventions causing salivary gland inflammation frequently shows increased electrolyte concentrations and increased presence of innate immune proteins, most notably lactoferrin. Altering nerve-mediated signaling of salivary gland secretion contributes to medication-induced dysfunction and may also contribute to altered saliva composition in neurodegenerative disease.

Effect of High Fat and Fructo-Oligosaccharide Consumption on Immunoglobulin A in Saliva and Salivary Glands in Rats

Consumption of indigestible dietary fiber increases immunoglobulin A (IgA) levels in saliva. The purpose of this study is to clarify the synergistic effect of the intake of a high amount of fats and indigestible dietary fiber on IgA levels in saliva and submandibular glands (SMG). Seven-week-old Wistar rats were fed a low-fat (60 g/kg) fiberless diet, low-fat fructo-oligosaccharide (FOS, 30 g/kg) diet, high-fat (220 g/kg) fiberless diet, or high-fat FOS diet for 70 days. The IgA flow rate of saliva (IgA FR-saliva) was higher in the low-fat FOS group than in the other groups (p < 0.05). Furthermore, the concentration of tyrosine hydroxylase (a marker of sympathetic nerve activation) in the SMG was higher in the low-fat FOS group (p < 0.05) and positively correlated with the IgA FR-saliva (rs = 0.68. p < 0.0001. n = 32) in comparison to that in the other groups. These findings suggest that during low-fat FOS intake, salivary IgA levels may increase through sympathetic nerve activation.

Salivary Biomarkers of Oxidative Stress and Inflammation in Stroke Patients: From Basic Research to Clinical Practice

Cerebral stroke is a serious worldwide health problem, as can be seen by the global epidemic of the disease. In this disorder, when the blood flow is compromised by ruptures or blocked arteries, sudden death of neurons is observed as a result of a lack of oxygen and nutrients. Numerous severe problems and frequent complications also exist in stroke patients; therefore, there is an urgent need to develop new therapeutic, diagnostic, and prognostic methods for the disease. At present, the diagnosis of stroke is based on a neurological examination, medical history, and neuroimaging, due to the fact that rapid and noninvasive diagnostic tests are unavailable. Nevertheless, oxidative stress and inflammation are considered key factors in stroke pathogenesis. Oxygen free radicals are responsible for oxidation of lipids, proteins, and DNA/RNA, which in turn contributes to oxidative damage of the brain. Toxic products of the oxidation reactions act cytostatically on the cell by damaging cell membranes and leading to neuronal death by apoptosis or necrosis. Thus, it seems that redox/inflammatory biomarkers might be used in the diagnosis of the disease. Nowadays, saliva is of increasing interest in clinical laboratory medicine. Redox biomarkers could be obtained easily, noninvasively, cheaply, and stress-free from saliva. This minireview is aimed at presenting the current knowledge concerning the use of salivary biomarkers of oxidative stress and inflammation in the diagnosis and prognosis of stroke.

Muscarinic inhibition of salivary glands with glycopyrronium bromide does not reduce the uptake of PSMA-ligands or radioiodine

RATIONALE

Salivary glands are highly perfused and express the prostate-specific membrane antigen (PSMA) receptor as well as the sodium-iodide symporter. As a consequence, treatment with ¹⁷⁷Lu/²²⁵Ac-PSMA for prostate cancer or ¹³¹I for thyroid cancer leads to a high radiation dose in the salivary glands, and patients can be confronted with persistent xerostomia and reduced quality of life. Salivation can be inhibited using an antimuscarinic pharmaceutical, such as glycopyrronium bromide (GPB), which may also reduce perfusion. The primary objective of this work was to determine if inhibition with GPB could provide a considerable (> 30%) reduction in the accumulation of administered ¹²³I or ⁶⁸Ga-PSMA-11 in salivary glands.

METHODS

Ten patients who already received a whole-body ⁶⁸Ga-PSMA-11 PET/CT scan for (re)staging of prostate cancer underwent a repeat PET/CT scan with tracer administration at 90 min after intravenous injection of 0.2 mg GPB. Four patients in follow-up after thyroid cancer, who had been treated with one round of ablative ¹³¹I therapy with curative intent and had no signs of recurrence, received ¹²³I planar scintigraphy at 4 h after tracer administration without GPB and a repeated scan at least one week later, with tracer administration at 30 min after intramuscular injection of 0.4 mg GPB. Tracer uptake in the salivary glands was quantified on PET and scintigraphy, respectively, and values with and without GPB were compared.

RESULTS

No significant difference in PSMA uptake in the salivary glands was seen without or with GPB (Mean SUL_mean parotid glands control 5.57, intervention 5.72, p = 0.50. Mean SUL_mean submandibular glands control 6.25, intervention 5.89, p = 0.12). Three out of 4 patients showed increased ¹²³I uptake in the salivary glands after GPB (Mean counts per pixel control 8.60, intervention 11.46).

CONCLUSION

Muscarinic inhibition of salivation with GPB did not significantly reduce the uptake of PSMA-ligands or radioiodine in salivary glands, and can be dismissed as a potential strategy to reduce toxicity from radionuclide therapies.

Case Report: Deep Cerebellar Stimulation for Tremor and Dystonia

Background: The cerebellum plays an important role in the pathogenesis and pathophysiology of movement disorders, including tremor and dystonia. To date, there have been few reports on deep cerebellar stimulation.

Case Report: The patient was a 35-year-old previously healthy man with no history of movement disorders. He developed a tremor and stiffness in his left hand at the age of 27 years, which was diagnosed as a dystonic tremor. We performed right thalamotomy, which resulted in a complete resolution of the tremor; however, the dystonia persisted. Subsequently, the patient developed left foot dystonia with inversion and a newly developed tremor in the right hand and foot. The patient underwent left ventralis intermedius (VIM) deep brain stimulation (VIM-DBS) and left pallidothalamic tract DBS (PTT-DBS). Left VIM-DBS completely resolved the right hand and foot tremor, and PTT-DBS significantly improved the left hand and foot dystonia. Three months postoperatively, the patient developed an infection and wound disruption at the surgical site. We performed palliative surgery for deep cerebellar stimulation via the posterior cranial region, which was not infected. The surgery was performed under general anesthesia with the patient lying in the prone position. Eight contact DBS electrodes were used. The placement of electrodes extended from the superior cerebellar peduncle to the dentate nucleus. Both the right hand and foot tremor improved with right cerebellar stimulation. Further, both the left hand and foot dystonia improved with left cerebellar stimulation. Right and left cerebellar stimulation led to no improvement in the left hand and foot dystonia and right hand and foot tremor, respectively. Stimulation-induced complications observed in the patient included dizziness, dysphagia, and dysarthria. After the surgery, the patient developed hypersalivation and hyperhidrosis in the left side of the body, both of which did not improve with adjustments of stimulation parameters. At the 6-month follow-up, the tremor and dystonia had almost completely resolved.

Conclusion: Deep cerebellar stimulation deserves consideration as a potential treatment for tremor and dystonia.

Activation of the cholinergic antiinflammatory reflex by occipitoatlantal decompression and transcutaneous auricular vagus nerve stimulation

CONTEXT

The parasympathetic-mediated inflammatory reflex inhibits excessive proinflammatory cytokine production. Noninvasive techniques, including occipitoatlantal decompression (OA-D) and transcutaneous auricular vagus nerve stimulation (taVNS), have been demonstrated to increase parasympathetic tone.

OBJECTIVES

To test the hypothesis that OA-D and taVNS increase parasympathetic nervous system activity and inhibit proinflammatory cytokine mobilization and/or production.

METHODS

Healthy adult participants were randomized to receive OA-D (5 min of OA-D followed by 10 min of rest; n=8), taVNS (15 min; n=9), or no intervention (15 min, time control; n=10) on three consecutive days. Before and after these interventions, saliva samples were collected for determination of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor α (TNF-α). Arterial blood pressure and the electrocardiogram were recorded for a 30-min baseline, throughout the intervention, and during a 30-min recovery period to derive heart rate and blood pressure variability markers as indices of vagal and sympathetic control.

RESULTS

OA-D and taVNS increased root mean square of successive RR interval differences (RMSSD) and high frequency heart rate variability, which are established markers for parasympathetic modulation of cardiac function. In all three groups, the experimental protocol was associated with a significant increase in salivary cytokine concentrations. However, the increase in IL-1β was significantly less in the taVNS group (+66 ± 13 pg/mL; p<0.05) than in the time control group (+142 ± 24 pg/mL). A similar trend was observed in the taVNS group for TNF-α (+1.7 ± 0.3 pg/mL vs. 4.1 ± 1.3 pg/mL; p<0.10). In the OA-D group baseline IL-6, IL-8, and TNF-α levels on the third study day were significantly lower than on the first study day (IL-6: 2.3 ± 0.4 vs. 3.2 ± 0.6 pg/mL, p<0.05; IL-8: 190 ± 61 vs. 483 ± 125 pg/mL, p <0.05; TNF-α: 1.2 ± 0.3 vs. 2.3 ± 0.4 pg/mL, p<0.05). OA-D decreased mean blood pressure from the first (100 ± 8 mmHg) to the second (92 ± 6 mmHg; p<0.05) and third (93 ± 8 mmHg; p<0.05) study days and reduced low frequency spectral power of systolic blood pressure variability (19 ± 3 mmHg² after OA-D vs. 28 ± 5 mmHg² before OA-D; p<0.05), a marker of sympathetic modulation of vascular tone. OA-D also increased baroreceptor-heart rate reflex sensitivity from the first (13.7 ± 3.0 ms/mmHg) to the second (18.4 ± 4.3 ms/mmHg; p<0.05) and third (16.9 ± 4.2 ms/mmHg; p<0.05) study days.

CONCLUSIONS

Both OA-D and taVNS elicited antiinflammatory responses that were associated with increases in heart rate variability-derived markers for parasympathetic function. These findings suggest that OA-D and taVNS activate the parasympathetic antiinflammatory reflex. Furthermore, an antihypertensive effect was observed with OA-D that may be mediated by reduced sympathetic modulation of vascular tone and/or increased baroreceptor reflex sensitivity.

Associations of salivary total antioxidant capacity with cortical amyloid beta burden, cortical glucose uptake and cognitive function in normal aging

BACKGROUND

Recognizing vulnerability to Alzheimer's disease (AD) requires from non-invasive, simple, and inexpensive markers that can be easily obtained in primary care settings. While saliva meets all these requirements, there is lack of evidence linking salivary constituents to in vivo AD pathology in aging.

METHODS

We examined the potential of salivary total antioxidant capacity (TAC) for identifying global cortical amyloid-beta (Aβ) burden, deficits in regional glucose uptake, and poorer cognition in 71 cognitively normal older adults. We further assessed whether salivary TAC-related cognitive performance was associated with higher Aβ load and lower cortical glucose consumption.

RESULTS

Linear regression analyses adjusted by age, sex, years of education, and ApoE4 status showed that salivary TAC was associated with slower processing speed and poorer sustained attention, as well as with higher Aβ load and lower glucose metabolism in cortical regions vulnerable to cognitive aging and AD. Results also revealed that lower scores in processing speed and sustained attention were associated with greater Aβ burden and lower regional glucose consumption, respectively.

CONCLUSIONS

Together, these findings support the use of salivary TAC for preventive screening and detection of cerebral vulnerability to AD. Further research is needed to evaluate the utility of salivary TAC as a clinical marker.

Ghrelin and oral diseases

Eating food is one of the most complicated behaviours in mammals, especially humans. The primary function of ghrelin is regulation of the appetite level and its stimulation. It is also responsible for the body's energy balance and glucose homeostasis. Ghrelin has been shown to affect many brain structures, which confirms the presence of ghrelin receptors in the brain. Studies are also conducted to assess the possible role of ghrelin in anxiety states and in memory disorders and motor dysfunctions. Ghrelin has been found in saliva and salivary glands, teeth and gums, and in the taste buds of the tongue epithelium; it is also secreted by mucosal cells and gingival fibroblasts. The presence of ghrelin in developmental enamel, especially in odontoblasts and ameloblasts, may suggest its regulatory role in the development of teeth. Patients with chronic periodontitis have significantly higher concentrations of ghrelin in the peripheral blood serum, as compared to the control group. Ghrelin plays a special role in the proliferation of cancer cells and in the development of neoplastic metastases. The abundant presence of ghrelin receptors in cancer cells is considered an important target in the treatment of neoplasms. Ghrelin is a hormone whose multidirectional mechanism of action has not yet been fully understood. However, its ubiquitous occurrence in the human body and its very diverse participation in metabolic processes may prove to be a significant obstacle in achieving the expected clinical effect of ghrelin as an effective drug in selected disease units.

The Relationship Between Salivary Redox, Diet, and Food Flavor Perception

The mouth is the gateway for entrance of food and microorganisms into the organism. The oral cavity is bathed by saliva, which is thus the first fluid that food and microorganisms will face after their entrance. As a result, saliva plays different functions, including lubrication, predigestion, protection, detoxification, and even transport of taste compounds to chemoreceptors located in the taste buds. To ensure its function of protection, saliva contains reactive harmful compounds such as reactive oxygen species that are controlled and neutralized by the antioxidant activity of saliva. Several antioxidant molecules control the production of molecules such as reactive oxygen compounds, neutralize them and/or repair the damage they have caused. Therefore, a balance between reactive oxidant species and antioxidant compounds exists. At the same time, food can also contain antioxidant compounds, which can participate in the equilibrium of this balance. Numerous studies have investigated the effects of different food components on the antioxidant capacity of saliva that correspond to the ability of saliva to neutralize reactive oxygen species. Contradictory results have sometimes been obtained. Moreover, some antioxidant compounds are also cofactors of enzymatic reactions that affect flavor compounds. Recent studies have considered the salivary antioxidant capacity to explain the release of flavor compounds ex vivo or in vivo. This article aims to review the effect of food on the antioxidant capacity of saliva and the impact of salivary antioxidant capacity on flavor perception after a brief presentation of the different molecules involved.

Salivary Gland Dysfunction in Patients with Chronic Heart Failure Is Aggravated by Nitrosative Stress, as Well as Oxidation and Glycation of Proteins

Chronic heart failure (HF) is an important clinical, social, and economic problem. A key role in HF progression is played by oxidative stress. Free oxygen radicals, formed under the conditions of hypoxia and reperfusion, participate in myocardial stunning and other forms of post-reperfusion damage. HF patients also suffer from disorders connected with saliva secretion. However, still little is known about the mechanisms that impair the secretory function of salivary glands in these patients. In the presented study, we were the first to compare the antioxidant barrier, protein glycoxidation, and nitrosative/nitrative stress in non-stimulated (non-stimulated whole saliva (NWS)) and stimulated (SWS) saliva of HF patients. The study included 50 HF patients with normal saliva (NS) secretion (n = 27) and hyposalivation (HS) (n = 23), as well as an age- and gender-matched control group (n = 50). We demonstrated that, in NWS of HF patients with HS, the concentration of low-molecular-weight non-enzymatic antioxidants decreased (↓total polyphenols, ↓ascorbic acid, ↓reduced glutathione, ↓albumin) compared to HF patients with normal saliva (NS) secretion, as well as the control group (except albumin). We also observed increased content of protein glycoxidation products (↑dityrosine, ↑kynurenine, ↑glycophore) in NWS and SWS of HF patients with HS compared to healthy controls. Interestingly, the content of dityrosine, N-formylkynurenine, and glycophore in NWS was also significantly higher in HF patients with HS compared to those with NS secretion. The concentration of NO was considerably lower, while the levels of peroxynitrite and nitrotyrosine were significantly higher in NWS and SWS of HF subjects with HS compared to the controls. Salivary gland dysfunction occurs in patients with chronic HF with the submandibular salivary glands being the least efficient. Oxidative/nitrosative stress may be one of the mechanisms responsible for the impairment of salivary gland secretory function in HF patients.

Endocannabinoid reactivity to acute stress: Investigation of the relationship between salivary and plasma levels

The endogenous cannabinoid (eCB) system has been shown in animal models to regulate the initiation and termination of central nervous responses to stress. In human studies, the role of peripherally measured eCBs is much less clear and the effect in salivary eCBs has not been studied. In this study, we use a novel method to quantify cortisol and eCBs arachidonoyl ethanolamide (AEA) and 2-arachidonoyl glycerol (2-AG) in human saliva, as well as in plasma samples. Forty-five females and 32 males completed a mixed physiological/psychosocial stress-induction study where saliva, and blood samples in males, were collected at baseline, immediately following, 30-minutes following, and 45-minutes following stress induction. Cortisol significantly increased after stress, but there were sex differences in the cortisol response to stress, with females having higher cortisol after stress compared to males. There was a significant increase in salivary levels of 2-AG immediately following stress induction, but no effect of AEA. Salivary AEA was higher in males compared to females. Surprisingly, there was no effect of stress on plasma AEA or 2-AG levels in the male cohort, though small effect sizes for 2-AG were observed, which is consistent with most other human literature. This study is the first to show that the eCB system is active in human saliva and is responsive to acute stress, possibly as part of the sympathetic nervous system response.

The Origins of Salivary Vitamin A, Vitamin B12 and Vitamin D-Binding Proteins

Vitamin A- (retinol), vitamin B₁₂- (haptocorrin) and vitamin D-binding proteins are the major circulatory transporters of their respective ligands; they are also constituents of the salivary proteome, the origins of which, remain unclear. The aim of this study was to explore how these proteins enter saliva and their relationship (if any) with vitamin status. Firstly, the three vitamin-binding proteins were quantified in resting whole mouth saliva and chewing-stimulated saliva from healthy donors (n = 10) to determine if they enter the mouth by salivary secretion or from the circulation. Secondly paired whole mouth saliva and serum samples were analysed from healthy donors (n = 14) to determine the relationships between the vitamin-binding proteins and vitamin status. Salivary output of all three vitamin-binding proteins studied increased when secretion was stimulated, suggesting they are secreted by the salivary glands. Whilst retinol-binding protein and haptocorrin were secreted by all major salivary glands, vitamin D-binding protein was restricted to the mucus glands. Salivary vitamin-binding protein concentrations were not found to be indicative of systemic vitamin status.

First Bite Syndrome After Parotidectomy: A Case Series and Review of Literature

INTRODUCTION

First bite syndrome (FBS) is a rare but potentially debilitating complication observed after surgery involving the upper cervical region. Patients classically complain of severe facial pain in the ipsilateral parotid region with the first few bites of a meal.

OBJECTIVE

The aim of this study is to shed light on the incidence and potential risk factors of FBS, including a series of cases depicting FBS observed after parotidectomy.

METHODS

Retrospective review of 419 patients who underwent parotidectomy at a single tertiary care facility between December 2016 and June 2020.

RESULTS

With a mean follow-up time of 16.5 months, 8 (2%) patients were documented to have symptoms of FBS after parotid gland surgery. Six of these patients underwent partial parotidectomy by dissection of the deep lobe of the parotid (DLP).

CONCLUSION

Patients undergoing dissection of the DLP are particularly at risk for the development of FBS. All patients should be appropriately counseled during informed consent discussions, especially in high-risk cases.

Salivary Gland Dysfunction in Stroke Patients Is Associated with Increased Protein Glycoxidation and Nitrosative Stress

Stroke is one of the leading causes of disability and death worldwide. Despite intensive medical care, many of the complaints directly threatening the patient's life marginalize their dental needs after the stroke. Recent studies indicate reduced saliva secretion in stroke patients in addition to the increased incidence of caries and periodontal disease. Since oxidative stress plays a vital role in the pathogenesis of salivary gland hypofunction and neurodegenerative disorders (including stroke), this is the first to evaluate the relationship between salivary gland activity and protein glycoxidation and nitrosative damage. The content of glycation and protein oxidation products and nitrosative stress was assessed in nonstimulated (NWS) and stimulated (SWS) whole saliva of stroke patients with normal salivary secretion and hyposalivation (reduced saliva production). The study included 30 patients in the stroke's subacute phase and 30 healthy controls matched by age and sex. We have shown that stroke patients with hyposalivation show increased contents of protein glycation (↑Amadori products and ↑advanced glycation end products), glycoxidation (↑dityrosine), and nitration (↑nitrotyrosine) products compared to stroke cases with normal salivary secretion and control group. Interestingly, higher oxidative/nitrosative stress was found in NWS, which strongly correlates with salivary flow rate, total protein content, and salivary amylase activity. Such relationships were not observed in the control group. Summarizing, oxidative and nitrosative stress may be one of the mechanisms responsible for the impairment of saliva secretion in stroke patients. However, extraglandular sources of salivary oxidative stress in stroke patients cannot be excluded. Further studies to assess salivary gland hypofunction in stroke cases are necessary.

Aluminum-Induced Toxicity in Salivary Glands of Mice After Long-term Exposure: Insights into the Redox State and Morphological Analyses

Several studies indicate aluminum (Al) as a potent toxicant, mainly related to central nervous system disorders. However, investigations about the Al effects over salivary glands are still scarce. In this way, the present study aimed to investigate whether the Al chloride (AlCl₃) is able of triggering oxidative stress in parotid and submandibular glands of mice and also, if any morphological impairment is observed. For this, twenty mice were divided into two groups: Exposed group (EG), which received 18.5 mg/kg of AlCl₃ by intragastric gavage for 60 days and control group (CG), which received distilled water by intragastric gavage during the same period of time. After that, levels of reduced glutathione (GSH) and malonaldehyde (MDA) were analyzed and we performed morphological analyses by evaluating the area of parenchyma, stroma, acini, and ducts in both glands. Statistical analyses were performed by Student's t test and two-way ANOVA, adopting p < 0.05. No abnormal body weight was observed and data indicates that although both major salivary glands are susceptible to Al-induced oxidative stress, by increasing MDA and reducing GSH, only submandibular glands decreased the parenchyma and increased stroma area. Moreover, the submandibular glands showed smaller total area of acini and higher total area of ducts, in comparison with the control group. Notably, AlCl₃ induces oxidative stress in both glands, however, submandibular glands showed to be more susceptible to Al effects than parotid glands. Our study gives evidences about Al toxicity in parotid and submandibular glands and claims for new investigations to understand more mechanisms of Al-induced toxicity.

Building a Functional Salivary Gland for Cell-Based Therapy: More than Secretory Epithelial Acini

A few treatment options exist for patients experiencing xerostomia due to hyposalivation that occurs as a result of disease or injury to the gland. An opportunity for a permanent solution lies in the field of salivary gland replacement through tissue engineering. Recent success emboldens in the vision of producing a tissue-engineered salivary gland composed of differentiated salivary epithelial cells that are able to differentiate to form functional units that produce and deliver saliva to the oral cavity. This vision is augmented by advances in understanding cellular mechanisms that guide branching morphogenesis and salivary epithelial cell polarization in both acinar and ductal structures. Growth factors and other guidance cues introduced into engineered constructs help to develop a more complex glandular structure that seeks to mimic native salivary gland tissue. This review describes the separate epithelial phenotypes that make up the gland, and it describes their relationship with the other cell types such as nerve and vasculature that surround them. The review is organized around the links between the native components that form and contribute to various aspects of salivary gland development, structure, and function and how this information can drive the design of functional tissue-engineered constructs. In addition, we discuss the attributes of various biomaterials commonly used to drive function and form in engineered constructs. The review also contains a current description of the state-of-the-art of the field, including successes and challenges in creating materials for preclinical testing in animal models. The ability to integrate biomolecular cues in combination with a range of materials opens the door to the design of increasingly complex salivary gland structures that, once accomplished, can lead to breakthroughs in other fields of tissue engineering of epithelial-based exocrine glands or oral tissues.

Cranial osteopathic treatment and stress-related effects on autonomic nervous system measured by salivary markers: A pilot study

BACKGROUND

Variations in the concentration of salivary alpha amylase (sAA) may indicate a change in the autonomic nervous system functionality. In osteopathic medicine it has long been stated that the osteopathic manipulative treatment (OMT) can modulate the autonomic nervous system. Studies carried out on the compression of the fourth ventricle (CV4) have shown a positive effect in reducing the sympathetic tone. The goal of this pilot study is measuring the physiological response of the sAA levels after CV4 technique.

METHODS

90 subjects were randomly assigned to a sham, a control or a CV4 group. Randomization accounted for sex and score in the STAI-2 (form Y) questionnaire. Each subject completed the STAI-1 (form Y) questionnaire to evaluate the anxiety of the moment. sAA activity and saliva flow rate were measured. Saliva was collected before, immediately after and 30 min after treatment.

RESULTS

Within group analysis revealed that sAA activity increased significantly immediately after the technique application only in the CV4 group (p = 0,05). Between groups analysis show a significant difference of the sAA activity in the CV4 group respect the control group (p < 0,05), but no significant difference between CV4 and sham group (p > 0,05). The effect in the CV4 group after the intervention is highly variable and appeared to be related to the level of stress measured with the STAI-Y1 questionnaire (p = 0,002).

CONCLUSIONS

This study shows a positive effect of the CV4 procedure on sAA activity even if not significantly different from the sham procedure, probably due to the confounding effect of stress variability between groups.

Ethanol binge drinking during pregnancy and its effects on salivary glands of offspring rats: oxidative stress, morphometric changes and salivary function impairments

OBJECTIVES

To investigate the biochemical and morphological effects of ethanol (EtOH) binge drinking during pregnancy on parotid glands (PG), submandibular glands (SMG), and saliva of offspring rats.

METHODS

Pregnant Wistar rats (n = 8) were exposed to EtOH consumption (3 g/kg/day - 20 % w/v) for three consecutive days. The saliva of 40-day-old offspring rats was collected to determine amylase activity and total protein concentration. PG and SMG were collected to performe oxidative biochemistry, morphometric and immunohistochemistry analyses (Student's t-test, p < .05).

RESULTS

EtOH consumption during pregnancy significantly decreased the total protein concentration and decreased amylase activity. In the PG, the EtOH group showed increased lipid peroxidation and decreased antioxidant capacity against peroxyl. In the SMG, the EtOH group showed increased lipid peroxidation and NOx metabolite levels. PG exposed to EtOH showed a decrease of acini, ducts, and total parenchymal area. SMG exposed to EtOH showed an increase in the total stromal area. The expression of CK-19 and Vimentin were found not different between groups.

CONCLUSIONS

For the first time, a three-day EtOH binge-drinking protocol during pregnancy is associated with oxidative stress and morphometric alterations in the salivary glands of offspring rats and with the functional reduction of the main salivary enzyme (amylase).

CLINICAL RELEVANCE

EtOH consumption during pregnancy altered the morphology and physiology of the salivary glands of offspring rats.

Evaluation of Psychological Stress Marker in Partially Edentulous Indian Adults Restored with Fixed Dental Prosthesis - A Prospective Cohort Study

Background

Clinical studies have established mastication as a stress relaxation behavior in humans. Absence of teeth compromises mastication, increasing psychologic stress in individuals depicted by many physiologic changes in body. Quantitative level of psychologic stress bio-markers serve as indicators of underlying physical ailment. Lesser literatures are available in determining the role of alpha amylase stress bio marker in partially edentulous clinical situations.

Aim

The purpose of this clinical study was to evaluate the levels of salivary alpha-amylase (sAA) stress biomarker in partially edentulous subjects before and after restoration with fixed dental prosthesis.

Material and Methods

Forty partially edentulous patients with missing mandibular first molar were selected for this study. Two questionnaires, state trait anxiety inventory (STAI) and perceived stress scale (PSS) was used to evaluate stress and anxiety levels of participants. The recruited participants were treated with metal ceramic fixed dental prosthesis (FDP). A visual analog scale (VAS) was used to determine the patient satisfaction .Unstimulated salivary samples were collected preoperative, 3rd and 6th month post FDP placement. Level of sAA was estimated. Data obtained in the form of mean ± SD was subjected to statistical analysis using paired sample t-test (α=.05).

Results

The salivary alpha amylase level was highest with mean of 36.73 μM/min/mg ptn before restoration with FDP. In the third month after prosthesis placement, the enzyme values decreased to16.62 μM/min/mg ptn and least value of 8.58 μM/min/mg ptn was detected in sixth month (P < 0.05).

Conclusion

The salivary alpha amylase stress biomarker decreased after tooth replacement with FDP.

Salivary Biomarkers for Diagnosis of Inflammatory Bowel Diseases: A Systematic Review

Saliva as a biological fluid has a remarkable potential in the non-invasive diagnostics of several systemic disorders. Inflammatory bowel diseases are chronic inflammatory disorders of the gastrointestinal tract. This systematic review was designed to answer the question “Are salivary biomarkers reliable for the diagnosis of inflammatory bowel diseases?”. Following the inclusion and exclusion criteria, eleven studies were included (according to PRISMA statement guidelines). Due to their heterogeneity, the potential salivary markers for IBD were divided into four groups: oxidative status markers, inflammatory cytokines, microRNAs and other biomarkers. Active CD patients manifest decreased activity of antioxidants (e.g., glutathione, catalase) and increased lipid peroxidation. Therefore, malondialdehyde seems to be a good diagnostic marker of CD. Moreover, elevated concentrations of proinflammatory cytokines (such as interleukin 1β, interleukin 6 or tumour necrosis factor α) are associated with the activity of IBD. Additionaly, selected miRNAs are altered in saliva (overexpressed miR-101 in CD; overexpressed miR-21, miR-31, miR-142-3p and underexpressed miR-142-5p in UC). Among other salivary biomarkers, exosomal PSMA7, α-amylase and calprotectin are detected. In conclusion, saliva contains several biomarkers which can be used credibly for the early diagnosis and regular monitoring of IBD. However, further investigations are necessary to validate these findings, as well as to identify new reliable salivary biomarkers.

Diverse epithelial cell populations contribute to the regeneration of secretory units in injured salivary glands

Salivary glands exert exocrine secretory function to provide saliva for lubrication and protection of the oral cavity. Its epithelium consists of several differentiated cell types, including acinar, ductal and myoepithelial cells, that are maintained in a lineage-restricted manner during homeostasis or after mild injuries. Glandular regeneration following a near complete loss of secretory cells, however, may involve cellular plasticity, although the mechanism and extent of such plasticity remain unclear. Here, by combining lineage-tracing experiments with a model of severe glandular injury in the mouse submandibular gland, we show that de novo formation of acini involves induction of cellular plasticity in multiple non-acinar cell populations. Fate-mapping analysis revealed that, although ductal stem cells marked by cytokeratin K14 and Axin2 undergo a multipotency switch, they do not make a significant contribution to acinar regeneration. Intriguingly, more than 80% of regenerated acini derive from differentiated cells, including myoepithelial and ductal cells, that appear to dedifferentiate to a progenitor-like state before re-differentiation into acinar cells. The potential of diverse cell populations serving as a reserve source for acini widens the therapeutic options for hyposalivation.

RELATIONSHIP between prandial drinking behavior and supersensitivity of salivary glands after superior salivatory nucleus lesions in RATS

Prandial drinking, an increase in the number of drinking responses and secondary or non-homeostatic polydipsia in the presence of dry food, is typically associated with a deficit in salivary secretion. This study investigates the degree of salivary gland supersensitivity to pilocarpine administration after lesions to the superior salivatory nucleus (SSN), the site of origin of the parasympathetic preganglionic neurons that innervate the submandibular-sublingual (S-S) salivary glands. The main aim was to determine if there is a relationship between the degree of glandular supersensitivity, as an index of secretory deficit, and the development of prandial drinking in lesioned rats. Results showed that following SSN lesions two subgroups of rats were obtained. One subgroup exhibited prandial drinking but the other was similar to the control group. The SSN-lesioned prandial drinking subgroup presented significantly greater supersensitivity than the SSN-lesioned non-prandial drinking rats; the non-prandial drinking subgroup, in turn, presented significantly more supersensitivity than controls. Additionally, S-S supersensitivity observed in rats that exhibited prandial drinking due to the sectioning of chorda tympani efferent axons was compared to that observed in rats exhibiting prandial drinking due to SSN lesions. It was found that both groups presented the same S-S supersensitivity curve. These results indicate that SSN lesions produce a gradation of S-S supersensitivity values that appear to run parallel to the degree of glandular secretory deficit caused by the lesions. Thus, only the rats with greater secretory deficit (greater supersensitivity) develop prandial drinking. These data support the idea that there is in fact a functional link between the lateral reticular formation of the brainstem (the region associated with the SSN) and S-S salivary glands.

Levels of Interleukin-6 in Saliva, but Not Plasma, Correlate with Clinical Metrics in Huntington's Disease Patients and Healthy Control Subjects

Growing evidence suggests that inflammatory responses, in both the brain and peripheral tissues, contribute to disease pathology in Huntington's disease (HD), an inherited, progressive neurodegenerative disorder typically affecting adults in their 30-40 s. Hence, studies of inflammation-related markers in peripheral fluids might be useful to better characterize disease features. In this study, we measured levels of C-reactive protein (CRP), Interleukin-6 (IL-6), interleukin 1 beta (IL-1B), and alpha-amylase (AA) in saliva and plasma from n = 125 subjects, including n = 37 manifest HD patients, n = 36 premanifest patients, and n = 52 healthy controls, using immunoassays. We found increases in salivary levels of IL-6, IL-1B and CRP across different disease groups and increased levels of IL-6 in the plasma of HD patients as compared to premanifest patients and controls. The levels of salivary IL-6 were significantly correlated with each of the other salivary markers, as well as with IL-6 levels measured in plasma. Further, salivary IL-6 and IL-1B levels were significantly positively correlated with Total Motor Score (TMS) and chorea scores and negatively correlated with Total Functional Capacity (TFC) in HD patients, whereby in healthy control subjects, IL-6 was significantly negatively correlated with Montreal Cognitive Assessment (MoCA) and the Symbol Digit Modalities test (SDM). Interestingly, the plasma levels of IL-6 did not show similar correlations to any clinical measures in either HD or control subjects. These findings suggest that salivary IL-6 is particularly relevant as a potential non-invasive biomarker for HD symptoms. The advent of an effective, dependable salivary biomarker would meet the urgent need for a less invasive means of identifying and monitoring HD disease progression.

Expression of aquaporin 5 during murine palatine glands development: a light and electron microscopic immunocytochemical study

Although aquaporin 5 (AQP5) seems to play a role in cytodifferentiation and cell proliferation during the development of salivary glands, its distribution during minor salivary glands development has been scarcely reported. This study examined the temporal-spatial distribution of AQP5 in the developing rat palatine glands using light and electron microscopy. At embryonic (E) age E18, AQP5 labeling was observed on the cell membranes of some terminal bulb cells. After lumenization at E20, AQP5 labeled the apical membrane in acini where a lumen existed, in addition to displaying positive diffuse cytoplasmic and cell membrane staining. At the electron microscopic level, AQP5 labeled the supranuclear cytoplasm and the luminal microvilli along the apical membrane. At birth, AQP5 was also localized to the lateral membranes associated ultrastructurally with the microvilli of intercellular canaliculi. After postnatal (PN) day PN7, mucous acini and serous demilunes showed reactivity. AQP5 reached peak reactivity around PN13 with a similar staining pattern in all acini, but had reduced dramatically by PN21. Thereafter, AQP5 reactivity was mainly associated with serous cells in adults. In conclusion, the transitory expression of AQP5 during palatine glands development may reflect changing physiological functions of the secretory cells and/or AQP5 throughout the maturation of the glands.

Comprehensive Evaluation of the Oral Health Status, Salivary Gland Function, and Oxidative Stress in the Saliva of Patients with Subacute Phase of Stroke: A Case-Control Study

This is the first study to assess, comprehensively, the oral health status; salivary glands’ function and enzymatic and non-enzymatic antioxidant defense; and oxidative damage to proteins and lipids in the non-stimulated (NWS) and stimulated (SWS) whole saliva of stroke patients. The study included 30 patients in the subacute phase of the stroke and an age and gender-matched control group. We showed that the activity of antioxidant enzymes (catalase and salivary peroxidase) was significantly higher in both NWS and SWS of stroke patients, similarly to uric acid concentration. However, in the study group, the reduced glutathione (GSH) concentration in SWS decreased. The contents of protein glycooxidation products (advanced glycation end products (AGE) and protein oxidation products (AOPP)) and lipid hydroperoxides were significantly higher in NWS and SWS of stroke patients. In the study group there was also a decrease in stimulated saliva secretion and total protein content. Interestingly, products of protein and lipid oxidation correlate negatively with SWS flow. The ROC analysis showed that salivary GSH with 100% specificity and 100% sensitivity differentiates the analyzed groups (AUC = 1.0). To sum up, in subacute stroke patients there are redox imbalances and oxidative damage to proteins and lipids in non-stimulated and stimulated saliva. Stroke patients also suffer from salivary gland dysfunction.

Decreased salivary lactoferrin levels are specific to Alzheimer's disease

BACKGROUND

Evidences of infectious pathogens in Alzheimer's disease (AD) brains may suggest a deteriorated innate immune system in AD pathophysiology. We previously demonstrated reduced salivary lactoferrin (Lf) levels, one of the major antimicrobial proteins, in AD patients.

METHODS

To assess the clinical utility of salivary Lf for AD diagnosis, we examine the relationship between salivary Lf and cerebral amyloid-β (Aβ) load using amyloid-Positron-Emission Tomography (PET) neuroimaging, in two different cross-sectional cohorts including patients with different neurodegenerative disorders.

FINDINGS

The diagnostic performance of salivary Lf in the cohort 1 had an area under the curve [AUC] of 0•95 (0•911-0•992) for the differentiation of the prodromal AD/AD group positive for amyloid-PET (PET⁺) versus healthy group, and 0•97 (0•924-1) versus the frontotemporal dementia (FTD) group. In the cohort 2, salivary Lf had also an excellent diagnostic performance in the health control group versus prodromal AD comparison: AUC 0•93 (0•876-0•989). Salivary Lf detected prodromal AD and AD dementia distinguishing them from FTD with over 87% sensitivity and 91% specificity.

INTERPRETATION

Salivary Lf seems to have a very good diagnostic performance to detect AD. Our findings support the possible utility of salivary Lf as a new non-invasive and cost-effective AD biomarker.

FUNDING

Instituto de Salud Carlos III (FIS15/00780, FIS18/00118), FEDER, Comunidad de Madrid (S2017/BMD-3700; NEUROMETAB-CM), and CIBERNED (PI2016/01) to E.C.; Spanish Ministry of Economy and Competitiveness (SAF2017-85310-R) to J.L.C., and (PSI2017-85311-P) to M.A.; International Centre on ageing CENIE-POCTEP (0348_CIE_6_E) to M.A.; Instituto de Salud Carlos III (PIE16/00021, PI17/01799), to H.B.

Prevention and treatment of radiotherapy-induced side effects

Radiotherapy remains a mainstay of cancer treatment, being used in roughly 50% of patients. The precision with which the radiation dose can be delivered is rapidly improving. This precision allows the more accurate targeting of radiation dose to the tumor and reduces the amount of surrounding normal tissue exposed. Although this often reduces the unwanted side effects of radiotherapy, we still need to further improve patients' quality of life and to escalate radiation doses to tumors when necessary. High-precision radiotherapy forces one to choose which organ or functional organ substructures should be spared. To be able to make such choices, we urgently need to better understand the molecular and physiological mechanisms of normal tissue responses to radiotherapy. Currently, oversimplified approaches using constraints on mean doses, and irradiated volumes of normal tissues are used to plan treatments with minimized risk of radiation side effects. In this review, we discuss the responses of three different normal tissues to radiotherapy: the salivary glands, cardiopulmonary system, and brain. We show that although they may share very similar local cellular processes, they respond very differently through organ-specific, nonlocal mechanisms. We also discuss how a better knowledge of these mechanisms can be used to treat or to prevent the effects of radiotherapy on normal tissue and to optimize radiotherapy delivery.

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

Background

Aquaporin 5 (AQP5) is a water channel–forming protein that plays a key role in saliva secretion. A decrease in masticatory function associated with the molar extraction adversely affects the submandibular salivary gland (SMG) in rats, inducing hypertrophic changes in the acinar cells and the expression of AQP5 in acinar cells or intercalated duct of the SMG. However, changes in AQP5 expression and localization in the SMG in association with occlusal modification have not been fully characterized.

Methods

We examined the influence of the decline and recovery of masticatory function on expression and localization of AQP5 in the rat SMG by inserting and removing an incisor bite plate (IBP). Thirty 5-week-old male Wistar rats were randomly divided into IBP (n = 12), recovery (REC) (n = 6), and control (CON) (n = 12) groups. Each rat in both the IBP and REC groups was fitted with the IBP on its maxillary incisors. Rats without the IBPs served as controls. All rats were fed powder diet and water ad libitum. Rats in the IBP and CON groups were sacrificed after 14 (n = 6) and 28 (n = 6) days after the IBP attachment. In the REC group, the IBP was detached on the 14th day and sacrificed on 28th day after the IBP attachment. AQP5 mRNA expression was quantified by reverse transcription–polymerase chain reaction. Changes in the localization of AQP5 were tracked by immunohistochemical staining.

Results

Attachment of IBP resulted in a decrease in the expression of AQP5 in the IBP group. Changes in the localization of AQP5 were observed between 14 and 28 days in the IBP group. In contrast, changes in the expression and localization of AQP5 were not observed in the REC group.

Conclusion

Findings suggested that a loss of molar occlusion, due to the IBP attachment, altered AQP5 expression and localization in the rat SMG. However, removal of the bite plate allowed the recovery of both AQP5 expression and its normal localization in the SMGs.

Childhood trauma and type D personality: The endocrine and cardiovascular effects on stress reactivity

Both exaggerated and blunted cardiovascular stress reactions are associated with health problems. Moreover, early life experiences and personality traits affect stress responses. Regarding the childhood traumas and type D personality, this study aimed to compare the endocrine and cardiovascular reactions against acute laboratory stress. Results showed that the simultaneous existence of childhood traumatic experiences and type D personality leads to exaggerated stress reactivity, while each factor results in a blunted cardiovascular response. Although the cardiovascular responses are dampened in type D personality people, their endocrine reactions are exaggerated. The underlying mechanisms of blunted cardiovascular reactivity differ between childhood trauma and type D personality groups.

Novel Potent Muscarinic Receptor Antagonists: Investigation on the Nature of Lipophilic Substituents in the 5- and/or 6-Positions of the 1,4-Dioxane Nucleus

A series of novel 1,4-dioxane analogues of the muscarinic acetylcholine receptor (mAChR) antagonist 2 was synthesized and studied for their affinity at M₁–M₅ mAChRs. The 6-cyclohexyl-6-phenyl derivative 3b, with a cis configuration between the CH₂N⁺(CH₃)₃ chain in the 2-position and the cyclohexyl moiety in the 6-position, showed pK_i values for mAChRs higher than those of 2 and a selectivity profile analogous to that of the clinically approved drug oxybutynin. The study of the enantiomers of 3b and the corresponding tertiary amine 33b revealed that the eutomers are (2S,6S)-(−)-3b and (2S,6S)-(−)-33b, respectively. Docking simulations on the M₃ mAChR-resolved structure rationalized the experimental observations. The quaternary ammonium function, which should prevent the crossing of the blood–brain barrier, and the high M₃/M₂ selectivity, which might limit cardiovascular side effects, make 3b a valuable starting point for the design of novel antagonists potentially useful in peripheral diseases in which M₃ receptors are involved.

Salivary lubricity (ex vivo) enhances upon moderate exercise: A pilot study

•

Moderate intensity exercise leads to enhanced lubrication performance of saliva.

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Such enhanced lubrication performance was sustained after 60 min of rest.

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Protein content and α-amylase activity in saliva was elevated post-exercise.

•

Protein content and α-amylase activity returned to baseline with an hour.

•

Effects of exercise on salivary mucin (MUC5B) content was not observed.

Objective

This study sought to examine the effects of moderate intensity exercise on lubrication performance of saliva. We hypothesized that exercise would result in enhanced salivary lubricity by direct sympathetic stimulation of the salivary proteins.

Study design

In total, 11 healthy young pre-menopausal female participants (mean age: 24.4 ± 1.8 years, BMI: 22.1 ± 1.9 kg/m²) were included in a within-subjects repeated measures experimental design. Unstimulated whole saliva was collected at rest (S₀), immediately after 45 min of moderate intensity cycling at ∼70 % maximum heart rate (mean: 133.4 ± 0.8 bpm) or time-match quiet rest (S₁), and after a 60 min of recovery period (S₂). Ex vivo salivary lubricity were measured using soft tribology. Total protein content, mucin (MUC5B) concentration, and α-amylase activity were determined.

Results

Tribology results revealed that moderate intensity exercise resulted in enhanced lubricity of saliva with an order-of-magnitude lower friction coefficients in the boundary regime at S₁ and S_2, with frictional forces being significantly lower at S₁ (p < 0.001) and S₂ (p < 0.001) as compared to the Control procedure. Total protein and α-amylase secretion also increased in the Exercise procedure at S₁ (p < 0.05), but concentrations returned to baseline levels at S₂.

Conclusions

Moderate intensity exercise leads to an increase in α-amylase and total protein secretion resulting in enhanced lubrication performance of the saliva. However, the lubrication performance was not related to MUC5B content, suggesting the role of other proteinaceous species acting as lubricants. This proof-of-concept study serves as the first step to design exercise interventions in populations with dry mouth conditions.

Mouth-Watering Results: Clinical Need, Current Approaches, and Future Directions for Salivary Gland Regeneration

Permanent damage to the salivary glands and resulting hyposalivation and xerostomia have a substantial impact on patient health, quality of life, and healthcare costs. Currently, patients rely on lifelong treatments that alleviate the symptoms, but no long-term restorative solutions exist. Recent advances in adult stem cell enrichment and transplantation, bioengineering, and gene transfer have proved successful in rescuing salivary gland function in a number of animal models that reflect human diseases and that result in hyposalivation and xerostomia. By overcoming the limitations of stem cell transplants and better understanding the mechanisms of cellular plasticity in the adult salivary gland, such studies provide encouraging evidence that a regenerative strategy for patients will be available in the near future.

Relationship between impaired parasympathetic vasodilation and hyposalivation in parotid glands associated with type 2 diabetes mellitus

We examined the relationship between hemodynamics in the three major salivary glands and salivary secretion in urethane-anesthetized and sympathectomized type 2 diabetic and nondiabetic rats via laser speckle imaging and by collecting the saliva. Lingual nerve stimulation elicited rapid increases in glandular blood flow and induced salivary secretion from the three glands in both diabetic and nondiabetic rats. In the parotid gland, the magnitude of blood flow increase and salivary secretion was significantly lower in the diabetic rats when compared with the nondiabetic rats; however, this was not observed in the other glands. Although the intravenous administration of acetylcholine increased blood flow in the parotid gland in a dose-dependent manner, the response was significantly lower in the diabetic rats when compared with the nondiabetic rats. Similarly, mRNA expression levels of M1 and M3 muscarinic acetylcholine receptors in the parotid gland were relatively lower in the diabetic rats compared with the nondiabetic rats. Our results indicate that type 2 diabetes impairs parasympathetic vasodilation and salivary secretion in the parotid gland and suggest that disturbances in the cholinergic vasodilator pathway may contribute to the underlying mechanisms involved in the disruption of parasympathetic nerve-mediated glandular vasodilation.

Salivary Gland Dysfunction, Protein Glycooxidation and Nitrosative Stress in Children with Chronic Kidney Disease

This study is the first to evaluate protein glycooxidation products, lipid oxidative damage and nitrosative stress in non-stimulated (NWS) and stimulated whole saliva (SWS) of children with chronic kidney disease (CKD) divided into two subgroups: normal salivary secretion (n = 18) and hyposalivation (NWS flow < 0.2 mL min-1; n = 12). Hyposalivation was observed in all patients with severe renal failure (4-5 stage CKD), while saliva secretion > 0.2 mL/min in children with mild-moderate CKD (1-3 stage) and controls. Salivary amylase activity and total protein content were significantly lower in CKD children with hyposalivation compared to CKD patients with normal saliva secretion and control group. The fluorescence of protein glycooxidation products (kynurenine, N-formylkynurenine, advanced glycation end products), the content of oxidative damage to lipids (4-hydroxynonneal, 8-isoprostanes) and nitrosative stress (peroxynitrite, nitrotyrosine) were significantly higher in NWS, SWS, and plasma of CKD children with hyposalivation compared to patients with normal salivary secretion and healthy controls. In CKD group, salivary oxidation products correlated negatively with salivary flow rate, -amylase activity and total protein content; however, salivary oxidation products do not reflect their plasma level. In conclusion, children with CKD suffer from salivary gland dysfunction. Oxidation of salivary proteins and lipids increases with CKD progression and deterioration of salivary gland function.

In Vitro Salivary Protein Adsorption Profile on Titanium and Ceramic Surfaces and the Corresponding Putative Immunological Implications

Immune responses triggered by implant abutment surfaces contributed by surface-adsorbed proteins are critical in clinical implant integration. How material surface-adsorbed proteins relate to host immune responses remain unclear. This study aimed to profile and address the immunological roles of surface-adsorbed salivary proteins on conventional implant abutment materials. Standardized polished bocks (5 × 5 × 1 mm3) were prepared from titanium and feldspathic ceramic. Salivary acquired pellicle formed in vitro was examined by liquid chromatography-tandem mass spectrometry and gene ontology (GO) analysis to identify and characterize the adsorbed proteins. Out of 759 proteins identified from pooled saliva samples, 396 were found to be attached to the two materials tested-369 on titanium and 298 on ceramic, with 281 common to both. GO annotation of immune processes was undertaken to form a protein-protein interaction network, and 14 hub proteins (≥6 interaction partners) (coding genes: B2M, C3, CLU, DEFA1, HSP90AA1, HSP90AB1, LTF, PIGR, PSMA2, RAC1, RAP1A, S100A8, S100A9, and SLP1) were identified as the key proteins connecting multiple (6-9) immune processes. The results offered putative immunological prospects of implant abutment material surface-adsorbed salivary proteins, which could potentially underpin the dynamic nature of implant-mucosal/implant-microbial interactions.

Isometric exercise facilitates attention to salient events in women via the noradrenergic system

The locus coeruleus (LC) regulates attention via the release of norepinephrine (NE), with levels of tonic LC activity constraining the intensity of phasic LC responses. In the current fMRI study, we used isometric handgrip to modulate tonic LC-NE activity in older women and in young women with different hormone statuses during the time period immediately after the handgrip. During this post-handgrip time, an oddball detection task was used to probe how changes in tonic arousal influenced functional coordination between the LC and a right frontoparietal network that supports attentional selectivity. As expected, the frontoparietal network responded more to infrequent target and novel sounds than to frequent sounds. Across participants, greater LC-frontoparietal functional connectivity, pupil dilation, and faster oddball detection were all positively associated with LC MRI structural contrast from a neuromelanin-sensitive scan. Thus, LC structure was related to LC functional dynamics and attentional performance during the oddball task. We also found that handgrip influenced pupil and attentional processing during a subsequent oddball task. Handgrip decreased subsequent tonic pupil size, increased phasic pupil responses to oddball sounds, speeded oddball detection speed, and increased frontoparietal network activation, suggesting that inducing strong LC activity benefits attentional performance in the next few minutes, potentially due to reduced tonic LC activity. In addition, older women showed a similar benefit of handgrip on frontoparietal network activation as younger women, despite showing lower frontoparietal network activation overall. Together these findings suggest that a simple exercise may improve selective attention in healthy aging, at least for several minutes afterwards.

Decreased basal and stimulated salivary parameters by histopathological lesions and secretory dysfunction of parotid and submandibular glands in rats with type 2 diabetes

Patients with type 2 diabetes mellitus (T2DM) present with dry mouth, polydipsia and taste impairment due to salivary secretion disorder. However, the underlying functional mechanism of T2DM remains unknown. The present study found that T2DM rats had significantly lower salivary flow rate and salivary alpha amylase activity, and attenuated salivary secretion responses to acid stimulation compared with control rats. Histopathological observation found that T2DM rats had inflammatory cell infiltration with increased expressions of IL-6 and TNF-α, oxidative stress, including decreased total superoxide dismutase activity and increased malondialdehyde content, and decreased expressions of β1 adrenergic receptor, cholinergic receptor, aquaporin-5 and protein kinase A in salivary glands, in particular the parotid gland. These results indicated that parotid gland impairment was more severe compared with submandibular gland impairment. Reduced salivary secretion may be associated with histopathological lesions and decreased regulation in secretory pathways in salivary glands.

Alpha-Lipoic Acid Ameliorates Radiation-Induced Salivary Gland Injury by Preserving Parasympathetic Innervation in Rats

Radiation therapy is a standard treatment for patients with head and neck cancer. However, radiation exposure to the head and neck induces salivary gland (SG) dysfunction. Alpha lipoic acid (ALA) has been reported to reduce radiation-induced toxicity in normal tissues. In this study, we investigated the effect of ALA on radiation-induced SG dysfunction. Male Sprague-Dawley rats were assigned to the following treatment groups: control, ALA only (100 mg/kg, intraperitoneally), irradiation only, and ALA administration 24 h or 30 min prior to irradiation. The neck area, including SGs, was irradiated evenly at 2 Gy/min (total dose, 18 Gy) using a photon 6 MV linear accelerator. The rats were sacrificed at 2, 6, 8, and 12 weeks after irradiation. Radiation decreased SG weight, saliva secretion, AQP5 expression, parasympathetic innervation (GFRα2 and AchE expression), regeneration potentials (Shh and Ptch expression), salivary trophic factor levels (brain-derived neurotrophic factor and neurturin), and stem cell expression (Sca-1). These features were restored by treatment with ALA. This study demonstrated that ALA can rescue radiation-induced hyposalivation by preserving parasympathetic innervation and regenerative potentials.

A Case-Control Study of Salivary Redox Homeostasis in Hypertensive Children. Can Salivary Uric Acid be a Marker of Hypertension?

Oxidative stress plays a critical role in the pathogenesis of hypertension; however, there are no data on salivary redox homeostasis and salivary gland function in children with hypertension. A total of 53 children with hypertension and age- and sex-matched controls were classified for the study. The antioxidant barrier and oxidative/nitrosative stress were evaluated in non-stimulated (NWS) and stimulated (SWS) whole saliva, plasma, and erythrocytes, with Student's t-test and Mann-Whitney U-test used for statistical analysis. We demonstrated that the activities of superoxide dismutase, catalase, and peroxidase were significantly higher in NWS, SWS, and erythrocytes of children with hypertension, similar to oxidative damage in proteins (advanced glycation end products) and lipids (malondialdehyde) as well as nitrosative stress markers (peroxynitrite and nitrotyrosine). The level of uric acid (UA) was significantly higher in NWS, SWS, and plasma of children with hypertension. UA concentration in SWS correlated positively with systolic and diastolic blood pressure and UA content in plasma. This parameter differentiates children with hypertension from healthy controls (AUC = 0.98) with a high degree of sensitivity (94%) and specificity (94%). Stimulated salivary flow was significantly lower in the hypertension group, similar to total protein content and salivary amylase activity. In summary, childhood hypertension is associated with hyposalivation as well as disturbances in antioxidant defense and enhanced oxidative/nitrosative damage both in the plasma/erythrocytes as well as saliva. Salivary UA may be a potential biomarker of hypertension in children.

Restoration of Cyclo-Gly-Pro-induced salivary hyposecretion and submandibular composition by naloxone in mice

Cyclo-Gly-Pro (CGP) attenuates nociception, however its effects on salivary glands remain unclear. In this study, we investigated the acute effects of CGP on salivary flow and composition, and on the submandibular gland composition, compared with morphine. Besides, we characterized the effects of naloxone (a non-selective opioid receptor antagonist) on CGP- and morphine-induced salivary and glandular alterations in mice. After that, in silico analyses were performed to predict the interaction between CGP and opioid receptors. Morphine and CGP significantly reduced salivary flow and total protein concentration of saliva and naloxone restored them to the physiological levels. Morphine and CGP also reduced several infrared vibrational modes (Amide I, 1687-1594cm^-1; Amide II, 1594-1494cm^-1; CH₂/CH₃, 1488-1433cm^-1; C = O, 1432-1365cm^-1; PO₂ asymmetric, 1290-1185cm^-1; PO₂ symmetric, 1135-999cm^-1) and naloxone reverted these alterations. The in silico docking analysis demonstrated the interaction of polar contacts between the CGP and opioid receptor Cys219 residue. Altogether, we showed that salivary hypofunction and glandular changes elicited by CGP may occur through opioid receptor suggesting that the blockage of opioid receptors in superior cervical and submandibular ganglions may be a possible strategy to restore salivary secretion while maintaining antinociceptive action due its effects on the central nervous system.

Long-Term Oral Administration of LLHK, LHK, and HK Alters Gene Expression Profile and Restores Age-Dependent Atrophy and Dysfunction of Rat Salivary Glands

Xerostomia, also known as dry mouth, is caused by a reduction in salivary secretion and by changes in the composition of saliva associated with the malfunction of salivary glands. Xerostomia decreases quality of life. In the present study, we investigated the effects of peptides derived from β-lactoglobulin C on age-dependent atrophy, gene expression profiles, and the dysfunction of salivary glands. Long-term oral administration of Leu⁵⁷-Leu⁵⁸-His⁵⁹-Lys⁶⁰ (LLHK), Leu⁵⁸-His⁵⁹-Lys⁶⁰ (LHK) and His⁵⁹-Lys⁶⁰ (HK) peptides induced salivary secretion and prevented and/or reversed the age-dependent atrophy of salivary glands in older rats. The transcripts of 78 genes were upregulated and those of 81 genes were downregulated by more than 2.0-fold (p ≤ 0.05) after LHK treatment. LHK upregulated major salivary protein genes such as proline-rich proteins (Prpmp5, Prb3, Prp2, Prb1, Prp15), cystatins (Cst5, Cyss, Vegp2), amylases (Amy1a, Amy2a3), and lysozyme (Lyzl1), suggesting that LLHK, LHK, and HK restored normal salivary function. The AP-2 transcription factor gene (Tcfap2b) was also induced significantly by LHK treatment. These results suggest that LLHK, LHK, and HK-administration may prevent and/or reverse the age-dependent atrophy and functional decline of salivary glands by affecting gene expression.

Ganglionic Acetylcholine Receptor Antibodies and Autonomic Dysfunction in Autoimmune Rheumatic Diseases

Autonomic neuropathy has been reported in autoimmune rheumatic diseases (ARD) including Sjögren’s syndrome, systemic sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. However, the pathophysiological mechanism underlying autonomic dysfunction remains unknown to researchers. On the other hand, autoimmune autonomic ganglionopathy (AAG) is an acquired immune-mediated disorder, which causes dysautonomia that is mediated by autoantibodies against ganglionic acetylcholine receptors (gAChRs). The purpose of this review was to describe the characteristics of autonomic disturbance through previous case reports and the functional tests used in these studies and address the importance of anti-gAChR antibodies. We have established luciferase immunoprecipitation systems to detect antibodies against gAChR in the past and determined the prevalence of gAChR antibodies in various autoimmune diseases including AAG and rheumatic diseases. Autonomic dysfunction, which affects lower parasympathetic and higher sympathetic activity, is usually observed in ARD. The anti-gAChR antibodies may play a crucial role in autonomic dysfunction observed in ARD. Further studies are necessary to determine whether anti-gAChR antibody levels are correlated with the severity of autonomic dysfunction in ARD.