Salivary secretion in health and disease

Saliva is a complex fluid produced by 3 pairs of major salivary glands and by hundreds of minor salivary glands. It comprises a large variety of constituents and physicochemical properties, which are important for the maintenance of oral health. Saliva not only protects the teeth and the oropharyngeal mucosa, it also facilitates articulation of speech, and is imperative for mastication and swallowing. Furthermore, saliva plays an important role in maintaining a balanced microbiota. Thus, the multiple functions provided by saliva are essential for proper protection and functioning of the body as a whole and for the general health. A large number of diseases and medications can affect salivary secretion through different mechanisms, leading to salivary gland dysfunction and associated oral problems, including xerostomia, dental caries and fungal infections. The first part of this review article provides an updated insight into our understanding of salivary gland structure, the neural regulation of salivary gland secretion, the mechanisms underlying the formation of saliva, the various functions of saliva and factors that influence salivary secretion under normal physiological conditions. The second part focuses on how various diseases and medical treatment including commonly prescribed medications and cancer therapies can affect salivary gland structure and function. We also provide a brief insight into how to diagnose salivary gland dysfunction.     

The effect of saliva specimen collection, handling and storage protocols on hepatitis C virus (HCV) RNA detection by PCR

OBJECTIVES: Commercial assays can now be adapted to detect salivary anti-hepatitis C virus (HCV) antibodies, increasing the potential of saliva as a non-invasive diagnostic specimen suited to surveillance and epidemiological studies. However, current diagnostic algorithms involve confirmation of HCV infection by RT-PCR. Manipulation and storage conditions of serum can influence the stability of viral RNA. This study examined whether varying specimen collection, handling and storage protocols also affected subsequent HCV RNA detection by RT-PCR applied to saliva specimens. METHODS: Whole unstimulated saliva, together with saliva samples collected in two commercially available devices (Salivette and Omnisal) were obtained from 50 HCV seropositive intravenous drug users. The specimens were subjected to a number of handling and storage conditions, including heat treatment and prolonged storage, then examined for HCV RNA by RT-PCR using primers derived from the 5' non-coding region (5'NCR). RESULTS: HCV RNA was detected in saliva samples from 25 (50%) of the patients. No single collection device or handling procedure identified all the subjects with HCV RNA positive saliva though whole saliva yielded the greatest number of positive results. CONCLUSIONS: Collection and processing of saliva specimens for RT-PCR analysis is complex. At present, detection of salivary HCV RNA by PCR is not sufficiently sensitive for use as a diagnostic tool in epidemiological studies.     

Salivary alterations in type 2 (non-insulin-dependent) diabetes mellitus and hypertension

OBJECTIVES: The aim of this study was to determine whether saliva output and composition are altered in type 2 diabetes mellitus by comparison with a healthy, non-medicated control group, and also a group of hypertensives. METHODS: From a community-dwelling cohort of Mexican American and European American subjects enrolled in the OH:SALSA oral aging study, we identified 233 subjects with type 2 diabetes mellitus, 227 with hypertension, and 240 healthy control subjects. We collected unstimulated whole (UW) and submandibular/ sublingual (US) saliva, as well as stimulated parotid (SP) and submandibular/ sublingual (SS) saliva. Flow rates were determined, yeast carriage was assayed in UW saliva, and SP and SS saliva samples were analyzed for protein composition. ELISA was used to determine concentrations of an array of specific protein components, with both antimicrobial and other activities. RESULTS: Both diabetic and hypertensive subjects had reduced output of both stimulated and unstimulated submandibular/sublingual saliva. 30% of the diabetic subjects had high oral yeast counts (> or =1000 cfu/mL) compared with 17% of the healthy subjects and 20% of the hypertensives. Significant increases in the concentrations of a number of the protein components were found in the diabetic subjects, specifically, SP lactoferrin, myeloperoxidase (MPO), and salivary peroxidase (SPO), as well as SS total protein, albumin, lactoferrin and secretory IgA. CONCLUSIONS: The pattern of decreased flow rates and increased protein concentrations were similar, but consistently greater in diabetics than hypertensives, suggesting that disease-specific mechanisms may be responsible. Diabetics may be more prone to oral dryness and infections than non-diabetics.     

Does the neuromotor abnormality type affect the salivary parameters in individuals with cerebral palsy?

J Oral Pathol Med (2010) 39 : 770–774 Background: Previous studies reported alterations in salivary flow rate and biochemical parameters of saliva in cerebral palsy (CP) individuals; however, none of these considered the type of neuromotor abnormality among CP individuals, thus it remains unclear whether the different anatomical and extended regions of the brain lesions responsible for the neurological damage in CP might include disruption of the regulatory mechanism of saliva secretion as part of the encephalopathy. The aim of this study was to evaluate salivary flow rate, pH and buffer capacity in saliva of individuals with CP, aged 3–16 years, with spastic neuromotor abnormality type and clinical patterns of involvement. Methods: Sixty‐seven individuals with CP spasticity movement disorder, were divided in two groups according to age (3–8‐ and 9–16‐years‐old) and compared with 35 sibling volunteers with no neurological damage, divided in two groups according to age (3–8‐ and 9–16‐years‐old). Whole saliva was collected under slight suction and pH and buffer capacity were determined using a digital pHmeter. Buffer capacity was measured by titration using 0.01N HCL, and flow rate was calculated in ml/min. Results: In both age groups studied, whole saliva flow rate, pH and buffer capacity were significantly lower in the spastic CP group (P < 0.05). The clinical patterns of involvement did not influence the studied parameters. Conclusion: These findings show that individuals with spastic cerebral palsy present lower salivary flow rate, pH and buffer capacity that can increase the risk of oral disease in this population.     

“Search less,verify more”—Reviewing salivary biomarkers in oral cancer detection

Oral squamous cell carcinoma is one of the commonest head and neck malignancies with approximately 350 000 cases reported annually and a mortality rate of 50% often attributed to late clinical presentation. Due to the close relationship between saliva bio-fluid and tumour lesions, optimizing salivary biomarkers for disease detection and screening provides a major new research direction in diagnostic oral oncology. As inter-tumour heterogeneity and intra-tumour heterogeneity are common within oral cavity neoplasms, it is unlikely that a single diagnostic or “risk-stratifying” saliva biomarker will suffice for universal translation to clinical practice. Therefore, this article highlights a number of promising saliva biomarker combinations for oral cavity cancer detection that require further research and validation to determine their true diagnostic potential.     

Salivary and mucosal immune responses to HIV and its co-pathogens

The profound effects that HIV induces in systemic immunity have been well characterised, but the situation with regard to mucosal immune responses is less clear. Oral cavity fluids have been used as a marker of the mucosal immune system. Whole and parotid saliva IgA, IgA1 and IgA2 concentrations have been found to be lower in both HIV infection and AIDS subjects, whereas serum IgA and IgA subclasses are markedly raised, suggesting a dichotomy between systemic and secretory immunity. Salivary antibodies to HIV can be readily detected and secretory IgA antibody can be neutralising to some strains of HIV. HIV vaccines can also induce antibody responses in saliva, but vaccination routes other than parenteral immunisation are needed. Antibody responses to oral microbes have also been studied and it has been shown that IgA, IgA1 and IgA2 subclass antibody titres to Candida albicans and to Streptococcus mut-ans are increased in whole or parotid saliva from HIV patients, but reduced in AIDS patients, suggesting a compensatory response which is overcome with progressive immunodeficiency. The avidity of salivary IgA antibodies to Candida in HIV seems unimpaired, whereas relative avidities of serum antibodies in HIV patients with candidiasis are lowered. Non-specific factors which may inhibit Candida and other opportunist pathogens are also found in saliva. The candidacidal, myelomonocytic protein calprotectin is present in saliva at levels which are biologically active, although levels are lowered in HIV infection. Overall, HIV infection appears to be associated with disregulation of a number of immune factors at the mucosal surface, but the ability of patients with HIV infection to mount specific antibody secretory responses seems to be relatively intact until late in infection.     

健康人与慢性牙周炎患者唾液蛋白质量浓度及白蛋白与球蛋白比值的变化

目的 对健康人1 d内唾液总蛋白、白蛋白、球蛋白质量浓度的变化及白蛋白与球蛋白比值（A/G）进行检测、分析,确定唾液蛋白成分较稳定的时间段,并比较此时间段健康人与慢性牙周炎患者非刺激性全唾液中的蛋白质量浓度及A/G的变化,为以唾液为基础的疾病诊断学方法建立和临床应用提供参照。方法 分别采集37名健康受试者（健康组）8:00、9:30、11:30、13:00、16:30、21:00的全唾液,并取24名慢性牙周炎患者（牙周炎组）早晨的全唾液。使用BCA法在酶标仪上检测总蛋白质量浓度,用GF-D800型半自动生化分析仪检测唾液白蛋白的质量浓度,然后计算球蛋白质量浓度及A/G。使用SPSS 19.0统计软件对所得数据进行统计学分析。结果 唾液蛋白成分在早晨（8:00）空腹时较为稳定。在这段时间,健康组总蛋白（1 354.35±389.52）μg•mL-1、白蛋白（139.55±27.19）μg•mL-1、球蛋白（1 211.80±360.73）μg•mL-1、A/G 0.126 3±0.041 7;牙周炎组总蛋白（2 611.56±231.62）μg•mL-1、白蛋白（296.27±17.34）μg•mL-1、球蛋白（2 315.69±221.67）μg•mL-1、A/G 0.156 2±0.017 3。健康组总蛋白、白蛋白、球蛋白的质量浓度在1 d内不同时间存在明显差异（P<0.05）,主要体现在饭前与饭后的差异,但A/G在1 d内基本稳定。对健康组与牙周炎组的唾液蛋白及A/G进行比较,牙周炎组的唾液总蛋白、白蛋白、球蛋白质量浓度较健康组明显升高,但A/G无明显差异。结论 唾液蛋白成分在早晨空腹时较其他时段稳定,可为样本采集时间提供参考。慢性牙周炎患者的唾液总蛋白、白蛋白、球蛋白质量浓度较健康人明显升高。     

Detection of anti-HIV antibodies in saliva

It is sometimes difficult in clinical practice to identify carriers of the AIDS virus. Such identification is of unquestionable value in oral pathology, both for determining the pathogenests of certain lesions and for assessing their significance to the patient. We evaluated several commercially available diagnostic techniques for the detection of anti-HIV antibodies in serum, and examined the feasibility of adapting such techniques to tests on saliva. The technique chosen for experimental adaptation required only slight modifications for use with this medium. We compared the results obtained in serum from intravenous drug users with a western blot assay designed to detect p24 viral protein, against the findings with a test designed to detect salivary antibodies. The likelihood of cross-reactions in saliva containing high concentrations of other antiviral antibodies was also studied. The specificity and sensitivity of the modified saliva test were 100% and 96% respectively, and no cross-reactions were observed.     

Saliva as a diagnostic fluid

In the last 10 years, the use of saliva as a diagnostic fluid has become somewhat of a translational research success story. Technologies are now available enabling saliva to be used to diagnose disease and predict disease progression. This review describes some important recent advances in salivary diagnostics and barriers to application and advancement. This review will also stimulate future research activity.     

Comparison of antioxidant enzymes activity and the concentration of uric acid in the saliva of patients with oral cavity cancer,odontogenic cysts and healthy subjects

J Oral Pathol Med (2011) 40 : 726–730 Chronic inflammation is related to oxidative stress and is still believed to be the cause of carcinogenesis. Patients with oral cavity cancer (OCC) exhibited lower total antioxidant capacity, uric acid (UA) concentration, salivary peroxidise (SPO) and superoxide dismutase (SOD) activity in their saliva than did healthy subjects. This could be a risk factor for tumour induction. Odontogenic cysts also arise in response to locally acting proinflammatory factors, for example, a gangrenous tooth. Furthermore, cyst development is accompanied by chronic inflammation. There are some reports in the literature concerning primary tumours such as squamous cell carcinomas arising from odontogenic cysts. The reason for this transformation is still unknown. The aim of this study was to compare the status of the antioxidant defence system in the saliva of the group with odontogenic cysts and OCC with that of the healthy control. Saliva samples were collected in the morning. SOD, SPO activity and UA concentration were determined using standard methods. Patients with odontogenic cysts and OCC exhibited lower activity of major antioxidants in their saliva (SPO, UA) than did healthy people. SOD activity and age are the main factors that distinguish these diseases. Discriminant function analysis showed that once data such as antioxidant status of saliva, age and smoking status are known 80% cases can be correctly classified as healthy, 80% as having odontogenic cysts and 40% as cancerous. To conclude, the decrease in concentrations of major antioxidants in the saliva of patients with cysts may increase the risk of neoplastic transformation especially in advanced age.     

Variability of flow rate when collecting stimulated human parotid saliva

The aim of this study was to estimate the accuracy and reproducibility of citric‐acid‐stimulated parotid saliva sampling. In healthy volunteers a strong correlation (r² = 0.79) between flow rates from the left and right parotid gland was observed. In patients with Sjögren's syndrome this correlation (r² = 0.90) was even stronger. The intraindividual variation in healthy volunteers was 23.3 ± 5.9%. Increasing the number of collections did not reduce this variation significantly. In head and neck cancer patients, to estimate whether repeated measurements result in more reliable baseline values for use in clinical studies, repeated collections did not result in a significant reduction of intrapatient variation, similar to the results with the healthy volunteers. Thus, notwithstanding the good agreement between left and right flow rates, a high variation in parotid flow rates has to be considered when planning clinical trials evaluating the effects of treatment on salivary gland functioning.     

唾液蛋白质糖基化及其与全身和口腔疾病关系的研究进展

蛋白质糖基化是重要的蛋白质翻译后修饰方式之一,通过赋予蛋白质各种结构和功能特征而在生命活动中扮演重要角色。唾液作为一种获取简单且无创的生理物质,包含有来自血清、龈沟液、口咽黏膜分泌物的成分。近年来随着相关研究的深入,人们对唾液的认识被不断更新。研究发现,唾液蛋白质可以作为一些疾病的诊断指标,唾液中蛋白质糖基化修饰也与多种疾病状态密切相关。本文就唾液蛋白质糖基化及其与全身和口腔疾病关系的研究进展作一综述。     

Specific antibodies against Actinobacillus actinomycetemcomitans in serum and saliva of patients with advanced periodontitis

The aim of the present study was to discover any possible correlation between specific antibodies against Actinobacillus actinomycetemcomitans (A.a.) in serum and saliva. The test group consisted of 38 patients aged 31–68 yr (mean 49) with advanced periodontitis. Twenty-nine subjects aged 23–67 yr, without periodontal destruction, formed a control group with a reference level of specific salivary antibodies against A.a. A subgingival plaque sample for culturing A.a. , a specimen of stimulated whole saliva, and a sample of venous blood were taken from each subject of the test group. Specific IgG and IgA antibodies against A.a. were determined from serum and stimulated whole saliva by means of the ELISA test. Fifteen of the patients (39%) had cultivable A.a. Six of the 15 A.a. culture-positive patients and one of the 29 reference subjects exhibited very high antibody titers against A.a. in saliva. Specific IgG and IgA antibodies in saliva correlated highly significantly with the corresponding antibody values in serum among the patients in the test group. It was concluded that among patients with severe adult periodontitis, the less invasive saliva sample has a diagnostic value equal to that of the serum sample concerning specific antibodies against A.a.     

Inhibitory effects of whole and parotid saliva on immunomodulators

Based on the presence of cytokines in whole saliva and their association with resistance and susceptibility to infectious disease, the present study was designed to evaluate the diagnostic potential of a large panel of cytokines and chemokines in saliva. Despite the endogenous presence of Th1/Th2 and pro-inflammatory cytokines and several chemokines in whole and parotid saliva of most individuals tested, the detection of known concentrations of several recombinant cytokines and chemokines was inhibited immediately following their addition to each type of saliva. In contrast, purified immunoglobulins were unaffected by either whole or parotid saliva. Further studies revealed that the inhibition of immunoreactivity involved sequestration of the majority of cytokines affected and degradation of chemokines. These results suggest that absolute concentrations of cytokines/chemokines may not be fully detectable in saliva. Therefore, the diagnostic value of any cytokine/chemokine is questionable and should be evaluated independently as such.     

A modified device for collection and flow-rate measurement of submandibular-sublingual saliva

The aims of the present study were to measure stimulated submandibular-sublingual (SM-SL) salivary flow rate with a modified Block-Brottman collection device, and, further, to evaluate the reliability of measurements of stimulated SM-SL salivary flow rate by means of this modified Block-Brottman device, as compared to measurements of parotid flow rate using modified Carlson-Crittenden cups. Twenty-nine healthy female volunteers, aged 36±7 yr, were included. Saliva stimulation was achieved by application of a 3% citric acid solution to the rims of the tongue four times/min, for 3 s every 15 s. On 3 consecutive days, stimulated parotid and SM-SL salivas were collected for 2 min at 07.30, before breakfast (morning value), and at 10.00, 2 h after a standard breakfast (lunchtime values). SM-SL saliva was also collected on one occasion for 2 min ± 3. For parotid and SM-SL saliva, the mean stimulated flow rates were in the morning, 1.50±0.83 and 2.25±1.12 ml/min, and at lunchtime, 1.71±1.16 and 2.54±1.01 ml/min, respectively. For both salivas, lunchtime values were significantly higher than morning values by about 13–14%. Comparing parotid and SM-SL saliva flow rates, we found the SM-SL saliva flow rate to exceed the parotid flow rate by about 50% both in the morning and at lunchtime. Variations in flow rate were analyzed by means of ANOVA. Interindividual variance and variance between measurement days and times of day made up 88% of parotid and 83% of SM-SL total variance. By calculating the variation coefficient, we found this to be smaller for SM-SL salivary flow rate measurements as compared to parotid flow rate measurements. In conclusion, the results of the present study indicate that our method of collecting stimulated submandibular-sublingual saliva by means of a modified Block-Brottman collection device is as reliable as the method of collecting stimulated parotid saliva by means of modified Carlson-Crittenden cups, and is thus a useful method for future studies of changes in submandibular-sublingual salivary production.     

Age-related changes in salivary antibodies to commensal oral and gut biota

The prevalence of mucosally derived infections appears to increase with age, suggesting dysfunction at the mucosal surfaces. The present investigation was undertaken to examine any age-related changes in secretion rates and concentrations of secretory antibodies in whole and parotid saliva in a healthy adult population. A total of 116 subjects were subdivided into the following age groups: 20–39 years, 40–59 years, 60–79 years and 80 years and over. Specific immunoglobulin A (IgA), IgG and IgM antibodies in whole and parotid saliva to Streptococcus mutans (serotype c), Actinomyces viscosus NCTC 10951, and Escherichia coli NCTC 10418 were quantified by enzyme-linked immunosorbent assay. IgA antibodies to all three organisms examined increased with age in both whole and parotid saliva, whereas IgG antibody levels to S. mutans in whole saliva were significantly decreased with age. IgG antibodies to E. coli in parotid saliva were reduced in older age groups. IgM antibody levels to S. mutans were reduced with age in both secretions, whereas IgM antibodies to A. viscosus were greatest in the oldest age groups. No significant changes with age were observed in salivary IgM antibody levels to E. coli. No significant reduction in the secretion rates of IgA antibodies were observed in parotid or whole saliva, whereas IgG and IgM antibody secretion rates to all three microorganisms were reduced in most age groups in both whole and parotid saliva. The results of this investigation have demonstrated age-related changes with salivary antibodies, but, whereas salivary IgG and IgM antibodies showed decreases, salivary IgA levels generally increased with age. This suggests that the ability to form IgA antibody responses is not impaired with increased age, and that secretion rates and functional properties of antibodies may be as important as concentrations in protection against mucosal infective diseases.     

基于唾液代谢组学的口腔疾病研究新进展

唾液代谢组学是以唾液为研究对象,定性定量分析生物体内代谢物的变化以研究生物体疾病与健康的新兴学科。在口腔医学领域,采用唾液代谢组学研究发现,唾液代谢物与多种口腔疾病之间存在着联系。本文对近年来以唾液代谢组学为研究手段进行口腔疾病相关研究的进展进行综述,包括在口腔鳞状细胞癌、口腔黏膜癌前病变（口腔扁平苔藓和口腔黏膜白斑）、复发性阿弗他溃疡、原发性舍格伦综合征、早期儿童龋病、牙周炎、慢性根尖周炎、正畸后牙根吸收等方面的研究,对通过唾液代谢组学筛选出的相关差异代谢物和信号通路进行总结,通过这些差异代谢物,可以构建口腔疾病预测模型,对口腔疾病进行早期筛查、预后判断以及发病机制的研究。唾液代谢组学有望为口腔疾病的诊断提供一种无创性的方法,具有重要的临床意义。