Relationships between oral MUC1 expression and salivary hormones in burning mouth syndrome

Development of New Models of Oral Mucosa to Investigate the Impact of the Structure of Transmembrane Mucin-1 on the Mucosal Pellicle Formation and Its Physicochemical Properties

The mucosal pellicle (MP) is a biological film protecting the oral mucosa. It is composed of bounded salivary proteins and transmembrane mucin MUC1 expressed by oral epithelial cells. Previous research indicates that MUC1 expression enhances the binding of the main salivary protein forming the MP, MUC5B. This study investigated the influence of MUC1 structure on MP formation. A TR146 cell line, which does not express MUC1 natively, was stably transfected with genes coding for three MUC1 isoforms differing in the structure of the two main extracellular domains: the VNTR domain, exhibiting a variable number of tandem repeats, and the SEA domain, maintaining the two bound subunits of MUC1. Semi-quantification of MUC1 using dot blot chemiluminescence showed comparable expression levels in all transfected cell lines. Semi-quantification of MUC5B by immunostaining after incubation with saliva revealed that MUC1 expression significantly increased MUC5B adsorption. Neither the VNTR domain nor the SEA domain was influenced MUC5B anchoring, suggesting the key role of the MUC1 N-terminal domain. AFM-IR nanospectroscopy revealed discernible shifts indicative of changes in the chemical properties at the cell surface due to the expression of the MUC1 isoform. Furthermore, the observed chemical shifts suggest the involvement of hydrophobic effects in the interaction between MUC1 and salivary proteins.

Salivary biomarkers in burning mouth syndrome: A systematic review and meta-analysis

The objective of this systematic review was to evaluate which salivary biomarkers are altered in patients with burning mouth syndrome (BMS) compared to a control group (CG). A comprehensive literature search was conducted in four databases. Case-control studies evaluating salivary biomarkers in BMS patients were included. Risk of bias was assessed using the Newcastle-Ottawa tool. RevMan was used for meta-analysis. Seventeen studies were selected. The included studies collected 54 different biomarkers. Of these biomarkers, only three (cortisol, α-amylase, and dehydroepiandrosterone) were analyzed in three or more studies. Dehydroepiandrosterone obtained contradictory results among the studies. However, cortisol and α-amylase levels were found to be higher in BMS patients. Cortisol was the only biomarker which could be included for meta-analysis. Cortisol levels were significantly higher in the BMS group compared to the CG (Mean Difference = 0.39; 95% CI [0.14-0.65]; p = 0.003). In conclusion, different studies investigated salivary biomarkers in patients with BMS compared to a CG, with controversial results. Meta-analysis, confirmed by trial-sequential analysis, showed how cortisol levels were significantly higher in BMS. Cortisol emerges as an interesting salivary biomarker in BMS, but future properly designed studies are needed to evaluate its role in diagnosis and/or response to treatment.

Changes in the Oral Cavity in Menopausal Women-A Narrative Review

Oral health awareness during the menopausal period is essential to minimize the inevitable inconveniences which may occur due to hormonal changes. The decrease in estrogen hormone concentration impacts the oral mucosa in a similar way to the vaginal mucosa due to the presence of estrogen receptors in both of these structures. An estrogen deficiency also affects the maturation process of the oral mucosal epithelium and can lead to its thinning and atrophy, making it more susceptible to local mechanical injuries, causing a change in pain tolerance and problems in the use of removable prosthetic restorations. Mucosal epithelium during the menopausal period is more vulnerable to infections, candidiasis, burning mouth syndrome, oral lichen planus (OLP), or idiopathic neuropathy. Moreover, salivary glands are also hormone-dependent which leads to changes in saliva secretion and its consistency. In consequence, it may affect teeth and periodontal tissues, resulting in an increased risk of caries and periodontal disease in menopausal women. Due to the large variety of complaints and symptoms occurring in the oral cavity, menopausal women constitute a significant group of patients who should receive special preventive and therapeutic care from doctors and dentists in this particular period.

Evaluation of serum neuron specific enolase levels among patients with primary and secondary burning mouth syndrome

INTRODUCTION

Burning mouth syndrome is a painful condition of the oral cavity with ambiguous pathogenesis and diagnosis. Neuron-specific enolase is increased in several conditions including peripheral neuropathy of diabetes, ophthalmopathies, spinal cord injuries and tumors. Evidence on association of burning mouth syndrome and neuron-specific enolase is limited.

AIM

This study aims to evaluate neuron-specific enolase levels in primary and secondary burning mouth syndrome patients and compare the levels of neuron-specific enolase with associated conditions in secondary burning mouth syndrome.

METHODS

One hundred and twenty-eight patients of more than 18 years of age with no gender predilection and having clinical symptoms of burning mouth syndrome and 135 healthy subjects were included. All the patients fulfilled Scala's criteria for the diagnosis of burning mouth syndrome, including "primary" (idiopathic) and "secondary" (resulting from identified precipitating factors) burning mouth syndrome patients. Blood samples were obtained from burning mouth syndrome patients. Serum neuron-specific enolase was evaluated using enzyme-linked immunosorbent assay. To compare means and standard deviations, among primary and secondary burning mouth syndrome, data was analysed with analysis of variance and multiple comparisons test.

RESULTS

The mean age of the study participants for burning mouth syndrome and healthy subjects was 53.30 and 51.6 years, respectively. Amongst the secondary burning mouth syndrome group, 32 (25%) of the patients had menopause, 15 (11.7%) had diabetes, eight (6.2%) of the patients had nutritional deficiency, seven (5.4%) had combined diabetes, menopause, and depression, six (4.6%) had combined diabetes and depression, four (3.1%) were diagnosed with Sjögren's syndrome. A minor percentage of 2.3% (three) had gastroesophageal reflux disease, while the remaining three (2.3%) patients in the secondary burning mouth syndrome group were on anti-depressants. There was a statistically significant increase in the levels of neuron-specific enolase in primary burning mouth syndrome as compared to the secondary burning mouth syndrome and healthy groups. Among the subgroups of secondary burning mouth syndrome, diabetic individuals showed a significant increase in neuron-specific enolase level when compared with other conditions in the secondary burning mouth syndrome patients.Discussion and conclusion: The raised serum neuron-specific enolase levels in patients suffering from primary burning mouth syndrome highlight a possible neuropathic mechanism. It was also increased in the sub-group of secondary burning mouth syndrome patients having diabetes. Although it cannot be ascertained whether the deranged values in the diabetic group were due to burning mouth syndrome or due to diabetes, the raised quantity of neuron-specific enolase in the primary burning mouth syndrome group is a reliable diagnostic indicator. Future studies on the assessment of neuron-specific enolase levels as a diagnostic tool for onset and management of primary and secondary burning mouth syndrome are recommended.

Neuropathic and Psychogenic Components of Burning Mouth Syndrome: A Systematic Review

The pathophysiology of primary burning mouth syndrome (BMS) has been extensively debated but is poorly understood despite a large number of hypotheses attempting to explain its etiopathogenic mechanisms. The aim of the present work was to systematically review papers that could provide arguments in favour of the neuropathic and psychogenic components of primary BMS for a better understanding of the disease. This systematic review (SR) was registered in PROSPERO (CRD42021224160). The search was limited to articles in English or French from 1990 to 01 December 2020. A total of 113 articles were considered for data extraction. We divided them into four subgroups: pharmacological and nonpharmacological management studies (n = 23); neurophysiological studies (n = 35); biohistopathological studies (n = 25); and questionnaire-based studies (n = 30). Several of these studies have shown neuropathic involvement at various levels of the neuraxis in BMS with the contribution of quantitative sensory testing (QST), functional brain imaging, and biohistopathological or pharmacologic studies. On the other hand, the role of psychological factors in BMS has also been the focus of several studies and has shown a link with psychiatric disorders such as anxiety and/or depression symptoms. Depending on the patient, the neuropathic and psychogenic components may exist simultaneously, with a preponderance of one or the other, or exist individually. These two components cannot be dissociated to define BMS. Consequently, BMS may be considered nociplastic pain.

Is a neuropathic mechanism involved in the perception of oral dryness?

OBJECTIVES

The aim of the present study was to review the existing phenomena which could affect subjective oral dryness and to consider the possibility that neural processing is involved in the perception of oral dryness.

DESIGN

A comprehensive review of scientific literatures relevant to contributing factors of dry mouth symptoms including salivary parameters related with oral dryness and role of neural mechanisms in perception of dry mouth symptoms was conducted.

RESULTS

Several previous reports suggested the possibility of neural processing mechanisms in perception of oral dryness. The decreased pain threshold in the oral cavity of rats with dry tongue and complaints of subjective oral dryness in patients with burning mouth syndrome, of which lacked an actual decrease in salivary output and mucosal wetness, could support this idea. Sensory changes in the oral mucosa and oral dryness may have a bi-directional influence that patients with oral dryness would be more subject to neuropathic pain in the oral mucosa, and those with neuropathic pain in the oral cavity could have complaints associated with higher levels of dry mouth symptoms.

CONCLUSION

A bi-directional influence between sensory change in the oral mucosa and subjective oral dryness could be assumed. We suggest the administration of neuropathic pain medications for controlling subjective oral dryness in patients without objective sign of hyposalivation.

Perspectives on Astringency Sensation: An Alternative Hypothesis on the Molecular Origin of Astringency

Flavor is one of the main drivers of food consumption and acceptability. It is associated with pleasure feels during eating. Flavor is a multimodal perception corresponding to the functional integration of information from the chemical senses: olfaction, gustation, and nasal and oral somatosensory inputs. As a result, astringency, as a sensation mediated by the trigeminal nerves, influences food flavor. Despite the importance of astringency in food consumer acceptance, the exact chemosensory mechanism of its detection and the nature of the receptors activated remain unknown. Herein, after reviewing the current hypotheses on the molecular origin of astringency, we proposed a ground-breaking hypothesis on the molecular mechanisms underpinning this sensation as a perspective for future research.

Salivary Hormones and Quality of Life in Female Postmenopausal Burning Mouth Patients-A Pilot Case-Control Study

The objective of our study was to investigate salivary levels of estradiol, progesterone and dehydroepiandrosterone (DHEA), and quality of life, in female postmenopausal women with burning mouth syndrome. The study included new patients diagnosed with burning mouth syndrome and excluded local and systemic causes. Unstimulated saliva samples were taken in the morning from 9 AM and 11 AM and immediately frozen for hormone analysis. The patients filled out a self-perceived quality of life questionnaire Oral Health Impact Profile-14 and determined the intensity of mucosal symptoms according to the visual-analog scale grading 0 to 10. A total of 40 patients were included. The study group had significantly lower levels of salivary estradiol. No difference was observed in levels of progesterone and DHEA between the groups. The levels of salivary hormones did not exhibit a significant correlation according to the Spearman correlation test with a self-perceived quality of life questionnaire (OHIP-14) in the study group or in the control group. Further research on a larger number of patients is needed to verify these results. This information might help to enable more precise and efficient treatment.

Relationships between subjective taste sensations and electrogustometry findings in patients with taste disorders

This study aimed to examine the relationships between subjective taste sensations and electrogustometry (EGM) findings in patients with taste disturbances according to the presence of burning mouth (BM) symptoms. Forty-six patients were included and asked to complete a questionnaire that contained questions on subjective taste sensations for the four basic taste qualities and the pattern of taste disorders such as ageusia, hypogeusia and dysgeusia. EGM was performed to measure detection thresholds. To examine the influence of BM symptoms, patients were divided into two groups: patients with and without BM symptoms. The patients consisted of 11 men and 35 women. The group without BM symptoms (n=26) had significantly lower degrees of subjective taste sensations for all taste qualities and higher correlation levels between subjective taste sensations and EGM thresholds than the group with BM symptoms (n=20). The patterns of taste disorders also showed more significant associations with the levels of subjective taste sensations in the patients without BM symptoms compared with those with BM symptoms. In conclusion, patients with taste disorders without BM symptoms had more severe taste disturbances than those with BM symptoms. The pathophysiology of taste disturbances differs according to the presence or absence of BM symptoms.

Blood contamination in salivary diagnostics: current methods and their limitations

The use of saliva samples in clinical studies has increased. However, the diagnostic value of whole saliva is compromised in the presence of blood contamination, owing to the higher levels of analytes in blood compared with those in saliva. The aim of this study was to review the existing methods and their limitations for measuring the levels of blood contamination in saliva. A literature search was performed using Web of Science, SCOPUS, and PubMed databases and 49 articles dealing with salivary diagnostics and measurements of blood contamination were included. Five methods for measuring the degree of blood components in saliva were discussed, including "visual inspection", use of "strip for urinalysis", and detection of plasma proteins such as "hemoglobin", "albumin", and "transferrin". Each method has its limitations, and transferrin has been regarded as the most reliable and valid marker for blood contamination in saliva. However, transferrin in whole saliva may not be solely a product of blood, and its level in whole saliva can be influenced by several factors such as age, gonadal hormones, salivary flow rate, chewing performance, and oral microorganisms. In conclusion, when quantitatively analyzing whole saliva samples, the influence of blood contamination should be considered.

Hygiene protocols for the treatment of denture-related stomatitis: local and systemic parameters analysis - a randomized, double-blind trial protocol

Background

Denture-related stomatitis (DS) is chronic multifactorial inflammation, strongly related to the presence of the biofilm that is the complex structure formed by microorganisms held together by a mucus-like matrix of carbohydrate that adheres to different surfaces, including the denture surface. DS has recently been correlated with deleterious cardiovascular alterations. The potential effect of hygiene protocols in the control of DS and randomized clinical trials that address this oral condition with cardiovascular complications are important in clinical decision-making.

Material/design

A clinical trial, randomized, double-blind, and with parallel groups, will be conducted in Brazil The sample will consist of 100 patients without teeth in both arches, users of at least maxillary complete dentures, and diagnosed with DS, who will be allocated to groups (n = 25 per group) according to the different hygiene protocols: (1) brushing of the palate and immersion of the prosthesis in 0.25% sodium hypochlorite solution (positive control); (2) brushing of the palate and immersion of the prosthesis in 0.15% triclosan solution; (3) brushing of the palate and immersion of the prosthesis in lactose monohydrate; or (4) brushing the palate with citric acid and immersing the prosthesis in lactose monohydrate. The response variables will be heart rate variability and alteration of blood pressure (systemic level), remission of DS, removal of biofilm, reduction of microbial load (colony-forming units (CFU)), mouth and prosthesis odor level, expression of MUC1, proinflammatory cytokines, C-reactive protein (CRP), viscosity, pH and salivary flow (locally); patient-centred qualitative analysis will also be undertaken. Measurements will be performed at baseline and 10 days after the interventions. The results obtained will be statistically analyzed as pertinent, with a level of significance of 0.05.

Discussion

This study will provide a guideline for clinical practice regarding the use of hygiene protocols in the treatment of oral diseases (DS) mediated by biofilm. Also, it may provide evidence of correlation of oral manifestation with cardiac risk.

Trial registration

Brazilian Registry of Clinical Trials, RBR-4hhwjb. Registered on 9 November 2018.

Salivary biomarkers of inflammation and oxidative stress in healthy adults

OBJECTIVES

Diagnostic value of saliva depends on the reproducibility of data in repeatedly collected samples and predictable correlations between saliva and blood. We aimed to investigate the reliability, blood reflectance, and influence of blood contamination in the analysis of inflammatory and oxidative stress biomarkers in saliva samples.

DESIGN

In total, 37 healthy young male participants (26.7 ± 2.2 years) were included. Unstimulated whole saliva and blood samples were collected on the first visit, and saliva samples were collected again after 2-3 days. The concentrations of total protein and inflammatory [C-reactive protein (CRP), IL-1β, IL-6, and TNF-α] and oxidative stress [8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and total antioxidant capacity (TAC)] biomarkers in saliva and blood, and as well as blood contamination biomarkers (transferrin and hemoglobin) in saliva were analyzed.

RESULTS

The intra-class correlations of all examined biomarkers except TNF-α were fair to excellent. Significant positive correlations between CRP and IL-6 and between total protein and TAC were stable in the saliva samples collected on different days. Notably, IL-6 was the only biomarker that showed a significant correlation between saliva and blood. As the concentration of salivary transferrin increased, the saliva/blood ratios of total protein and TAC also increased. The concentration of salivary hemoglobin did not affect the saliva/blood ratios of biomarkers.

CONCLUSIONS

The findings of this study are limited to healthy young males. For clinical applications, studies on salivary diagnostics should be performed for individual disease and health conditions, demographic characteristics, and biomarkers.

Oral epithelial MUC1 and oral health

OBJECTIVES

To provide information about MUC1, epithelial membrane-bound mucin, in terms of its role in oral health.

DESIGN

The expression and functional roles of MUC1 in the oral mucosa and salivary glands were reviewed. Information on the modulation of oral mucosal epithelial MUC1 expression compared with that of endometrial epithelial MUC1 expression was also reviewed. In addition, the possible associations between oral mucosal epithelial MUC1 and oral diseases were explored.

RESULTS

MUC1 is expressed in the oral mucosa and major and minor salivary glands. Protection of oral mucosal surfaces is believed to be the main function of oral mucosal epithelial MUC1. Its role in the salivary glands is thought to facilitate salivary flow through the ductal system. Information on the role of MUC1 in signal transduction and modulation of immune function in the oral cavity is sparse. However, the possible roles of MUC1 in dry mouth conditions, burning mouth syndrome, dental caries, and oral candidiasis have been suggested.

CONCLUSIONS

Despite limited information, it is clear that oral epithelial MUC1 plays an important role in oral health. Further research evaluating the physiological and pathological roles of MUC1 in the oral cavity is warranted.

Recent Advances in the Etiology and Treatment of Burning Mouth Syndrome

Burning mouth syndrome (BMS) is a debilitating condition that has a striking female predilection. Although the oral mucosa is normal in appearance, patients with BMS experience oral burning that most commonly localizes to the lips and tongue. BMS is a diagnosis of exclusion, and all underlying pathoses associated with allodynia must be ruled out prior to rendering the diagnosis. The etiopathogenesis of BMS remains poorly understood, and thus patient management is challenging. Data indicate that oral and systemic factors both contribute to the development and persistence of the condition. Of particular interest, emerging work identifies structural and functional deficits within the nervous system that may lead to a more mechanistic understanding of BMS pathology. In addition, several novel findings suggest that circadian rhythm dysfunction may be a previously unappreciated yet clinically significant driver of disease. Circadian rhythm controls pain perception, mood, and sleep and plays a key role in the regulation of the hypothalamic-pituitary-adrenal axis. Since these are altered in patients with BMS, this may be reflective of underlying circadian dysfunction. While evidence-based treatment strategies for BMS are lacking, current treatment approaches consist of local and systemic medications, such as clonazepam, alpha lipoic acid, capsaicin, low-level laser therapy, gabapentin, and amitriptylin. In addition, the use of cognitive behavioral therapy is reported. This review provides an overview of the recent literature related to the etiology and treatment of BMS and identifies current challenges facing researchers and clinicians alike.