The use of salivary biomarkers in occupational and environmental medicine

Salivary diagnostics: a brief review

Early detection of disease plays a crucial role for treatment planning and prognosis. Saliva has great potential as a diagnostic fluid and offers advantage over serum and other biological fluids by an economic and noninvasive collection method for monitoring of systemic health and disease progression. The plethora of components in this fluid can act as biomarkers for diagnosis of various systemic and local diseases. In this review paper, we have emphasized the role of salivary biomarkers as diagnostic tools.

DNA methylation as a long-term biomarker of exposure to tobacco smoke

BACKGROUND

Most biomarkers of exposure tend to have short half-lives. This includes cotinine, a metabolite of nicotine widely used to assess smoke exposure. Cotinine is thus unsuitable as a determinant of past exposure to cigarette smoke.

METHODS

We used bisulphite pyrosequencing of a set of four genomic loci (AHRR, 6p21, and two at 2q37) that had differential DNA methylation levels in peripheral blood DNA dependent on tobacco exposure to create a predictive model of smoking status.

RESULTS

Combining four gene loci into a single methylation index provided high positive predictive and sensitivity values for predicting former smoking status in both test (n = 81) and validation (n = 180) sample sets.

CONCLUSIONS

This study provides a direct molecular measure of prior exposure to tobacco that can be performed using the quantitative approach of bisulphite pyrosequencing. Epigenetic changes that are detectable in blood may more generally act as molecular biomarkers for other exposures that are also difficult to quantify in epidemiological studies.

Otoacoustic emission sensitivity to exposure to styrene and noise

The ototoxic effect of the exposure to styrene is evaluated, also in the presence of simultaneous exposure to noise, using otoacoustic emissions as biomarkers of mild cochlear damage. Transient-evoked and distortion product otoacoustic emissions were recorded and analyzed in a sample of workers (15 subjects) exposed to styrene and noise in a fiberglass manufacturing facility and in a control group of 13 non-exposed subjects. Individual exposure monitoring of the airborne styrene concentrations was performed, as well as biological monitoring, based on the urinary concentration of two styrene metabolites, the Mandelic and Phenylglyoxylic acids. Noise exposure was evaluated using wearable phonometers, and hearing loss with pure tone audiometry. Due to their different job tasks, one group of workers was exposed to high noise and low styrene levels, another group to higher styrene levels, close to the limit of 20 ppm, and to low noise levels. A significant negative correlation was found between the otoacoustic emission levels and the concentration of the styrene urinary metabolites. Otoacoustic emissions, and particularly distortion products, were able to discriminate the exposed workers from the controls, providing also a rough estimate of the slope of the dose-response relation between otoacoustic levels and styrene exposure.

Acetylcholinesterase as a biomarker in environmental and occupational medicine: new insights and future perspectives

Acetylcholinesterase (AChE) is a key enzyme in the nervous system. It terminates nerve impulses by catalysing the hydrolysis of neurotransmitter acetylcholine. As a specific molecular target of organophosphate and carbamate pesticides, acetylcholinesterase activity and its inhibition has been early recognized to be a human biological marker of pesticide poisoning. Measurement of AChE inhibition has been increasingly used in the last two decades as a biomarker of effect on nervous system following exposure to organophosphate and carbamate pesticides in occupational and environmental medicine. The success of this biomarker arises from the fact that it meets a number of characteristics necessary for the successful application of a biological response as biomarker in human biomonitoring: the response is easy to measure, it shows a dose-dependent behavior to pollutant exposure, it is sensitive, and it exhibits a link to health adverse effects. The aim of this work is to review and discuss the recent findings about acetylcholinesterase, including its sensitivity to other pollutants and the expression of different splice variants. These insights open new perspective for the future use of this biomarker in environmental and occupational human health monitoring.

Salivary hexosaminidase in smoking alcoholics with bad periodontal and dental states

BACKGROUND

A sensitive alcohol marker, β-hexosaminidase (HEX), in the saliva of alcoholics, is investigated for the first time.

METHODS

The activity, specific-activity and output of total HEX and its isoenzymes HEX A and HEX B were measured in the saliva of healthy controls (C), alcohol-dependent non-smokers (ANS), and alcohol-dependent smokers (AS).

RESULTS

We observed a significantly increased activity/specific-activity and output of HEX A in the ANS and AS groups, due to the inflammatory state of the oral-cavity/salivary-glands. Significantly increased activity of HEX A contributed to an increase in the salivary activity of the total HEX in the ANS group. A significant decrease in the activity/specific-activity of HEX B in AS seemed to be due to HEX B inactivation by cigarette smoke. We noticed a tendency for deteriorated dental state (lower decayed-missing-filled-teeth index - DMFT), worse periodontal state (higher gingival index - GI and papilla-bleeding index - PBI) in AS, and worse periodontal state (higher GI) in ANS, as compared to the controls. We found no differences in the salivary protein concentrations between all groups and decreased salivary flow in both alcoholic groups as compared to the controls. In alcoholics, the area under the curve (AUC) for HEX A activity/specific-activity was significantly greater than for HEX and HEX B. The salivary HEX A activity/specific-activity had good/excellent sensitivity and specificity in smoking and non-smoking alcoholics, whereas salivary HEX and HEX B had poor/fair sensitivity and specificity.

CONCLUSIONS

Salivary HEX A may be helpful in the diagnosis of chronic alcohol intoxication, even in smokers.

Implementing Self-collection of Biological Specimens With a Diverse Sample

Collecting saliva is the most noninvasive way to detect changing levels of cortisol (Adam & Kumari, 2009; Soo-Quee Koh & Choon-Huat Koh, 2007), a stress hormone of interest to behavioral and health scientists, where there are benefits from multiple samples taken over a period of days. Various self-collection strategies have been employed, ranging from treated cards to cotton swabs and passive drool methods. The current study investigates the effectiveness of a variety of reminder techniques in encouraging adherence with procedures requiring 4 samples per day on 3 separate days of passive drool collection among African American and European American young adults. The findings suggest that direct texts were associated with the greatest level of adherence, while phone reminders were most effective when controlling for total number of contacts. Results indicate that both traditional and novel reminder methods can positively influence adherence, even with challenging populations.

Mining the salivary proteome with grating-coupled surface plasmon resonance imaging and surface plasmon coupled emission microarrays

Biological indicators have numerous and widespread utility in personalized medicine, but the measurement of these indicators also poses many technological and practical challenges. Blood/plasma has typically been used as the sample source with which to measure these indicators, but the invasiveness associated with sample procurement has led to increased interest in saliva as an attractive alternative. However, there are unique issues associated with the measurement of saliva biomarkers. These issues are compounded by the imperfect correlation between saliva and plasma with respect to biomarker profiles. In this manuscript, we address the technical challenges associated with saliva biomarker quantification. We describe a high-content microarray assay that employs both grating-coupled surface plasmon resonance imaging and surface plasmon-coupled emission modalities in a highly sensitive assay with a large dynamic range. This powerful approach provides the tools to map the proteome of saliva, which in turn should greatly enhance the utility of salivary biomarker profiles in personalized medicine.

Observations on saliva osmolality during progressive dehydration and partial rehydration

A need exists to identify dehydrated individuals under stressful settings beyond the laboratory. A predictive index based on changes in saliva osmolality has been proposed, and its efficacy and sensitivity was appraised across mass (water) losses from 1 to 7%. Twelve euhydrated males [serum osmolality: 286.1 mOsm kg(-1) H(2)O (SD 4.3)] completed three exercise- and heat-induced dehydration trials (35.6°C, 56% relative humidity): 7% dehydration (6.15 h), 3% dehydration (with 60% fluid replacement: 2.37 h), repeat 7% dehydration (5.27 h). Expectorated saliva osmolality, measured at baseline and at each 1% mass change, was used to predict instantaneous hydration state relative to mass losses of 3 and 6%. Saliva osmolality increased linearly with dehydration, although its basal osmolality and its rate of change varied among and within subjects across trials. Receiver operating characteristic curves indicated a good predictive power for saliva osmolality when used with two, single-threshold cutoffs to differentiate between hydrated and dehydrated individuals (area under curve: 3% cutoff = 0.868, 6% cutoff = 0.831). However, when analysed using a double-threshold detection technique (3 and 6%), as might be used in a field-based monitor, <50% of the osmolality data could correctly identify individuals who exceeded 3% dehydration. Indeed, within the 3-6% dehydration range, its sensitivity was 64%, while beyond 6% dehydration, this fell to 42%. Therefore, while expectorated saliva osmolality tracked mass losses within individuals, its large intra- and inter-individual variability limited its predictive power and sensitivity, rendering its utility questionable within a universal dehydration monitor.

Biomarkers of immunotoxicity for environmental and public health research

The immune response plays an important role in the pathophysiology of numerous diseases including asthma, autoimmunity and cancer. Application of biomarkers of immunotoxicity in epidemiology studies and human clinical trials can improve our understanding of the mechanisms that underlie the associations between environmental exposures and development of these immune-mediated diseases. Immunological biomarkers currently used in environmental health studies include detection of key components of innate and adaptive immunity (e.g., complement, immunoglobulin and cell subsets) as well as functional responses and activation of key immune cells. The use of high-throughput assays, including flow cytometry, Luminex, and Multi-spot cytokine detection methods can further provide quantitative analysis of immune effects. Due to the complexity and redundancy of the immune response, an integrated assessment of several components of the immune responses is needed. The rapidly expanding field of immunoinformatics will also aid in the synthesis of the vast amount of data being generated. This review discusses and provides examples of how the identification and development of immunological biomarkers for use in studies of environmental exposures and immune-mediated disorders can be achieved.

Salivary Biomarkers of Stress Among Teachers in an Urban Setting

The aim of this study was to determine the prevalence of job stress among secondary school teachers using Karasek Job Content Questionnaire (JCQ), the association between salivary cortisol, salivary IgA, and sociodemographic characteristics, and the association between log cortisol, IgA levels, and job strain categories. A cross-sectional study was undertaken using JCQ and salivary cortisol and IgA samples. Cluster sampling was done yielding 302 respondents. The prevalence of stress among all teachers was 20.2%. Being a Malay, teaching experience of 5 to 10 years, and those without a supervisor’s support had higher prevalence of high job strain. Teachers in the 31 to 40 years age bracket, educating handicapped children with the absence of supervisor support exhibited higher stress levels with lower log salivary IgA levels. Further studies must be conducted using salivary biomarkers to study the in-depth relationship of stress, extending into other occupational groups.

Effects of smoking on trace metal levels in saliva

OBJECTIVES

To compare the salivary levels of trace metals between non-smokers and smokers using inductively coupled plasma mass spectroscopy (ICP-MS). The effect of pretreatment methods on the accuracy of ICP-MS analysis and daily variations in trace metal levels in saliva were also investigated.

SUBJECTS AND METHODS

The participants were 10 male non-smokers (mean age: 27.4 ± 3.4 years) and 30 male smokers (mean age: 26.5 ± 4.1 years). Unstimulated whole saliva was collected. Salivary flow rate, the number of metal restorations in the oral cavity, the level of blood contamination in the saliva and the levels of cotinine and trace metals in the saliva of each participant were determined.

RESULTS

Direct dilution of saliva samples with nitric acid showed the most accurate ICP-MS results. Trace metal levels in saliva showed wide daily variations. They were not affected by the number of metal restorations. Trace metal concentrations of saliva samples without blood contamination were much lower than the previously reported values. Salivary levels of cotinine and aluminum were significantly increased in smokers.

CONCLUSIONS

Saliva can be a medium for trace metal analysis. Salivary levels of cotinine and aluminum can be useful markers to evaluate smoking status.

Single-walled carbon nanotube chemoresistive label-free immunosensor for salivary stress biomarkers

The present work is focused on the development, analytical characterization and evaluation of selective and sensitive SWNT-chemiresistor immunosensor for the label-free detection of salivary α-amylase (SAA). SWNTs were aligned to bridge lithographically patterned gold microelectrodes using AC dielectrophoresis followed by functionalization with anti-SAA antibodies. The nano-immunosensors exhibited excellent sensitivity over the clinically relevant range (19 to 308 U ml(-1)) with a limit of detection (LOD) of 6 µg ml(-1) (0.6 U ml(-1)) and 7.8 µg ml(-1) (0.78 U ml(-1)) in phosphate buffer and artificial saliva, respectively, and no interference from other components of saliva. This label-free nano-immunosensor technology has potential application in clinical diagnosis for stress biomarkers expressed in human saliva at the point-of-care.

Saliva and serum eosinophil cationic protein in asthmatic children and adolescents with and without allergic sensitization

Saliva eosinophil cationic protein (ECP) is higher in asthmatic adults than in healthy ones. However, its relationship with asthma severity, other atopic conditions and allergic sensitization have not been reported. Saliva collection is painless, readily acceptable to children and parents, and can be a potentially useful body fluid to measure asthma biomarkers. We recruited 102 physician-diagnosed young asthmatic subjects from outpatient clinics with change in FEV(1) > or = 12% with inhaled salbutamol and collected data on asthma severity, concurrent allergic rhinitis (AR) and atopic dermatitis (AD), and medication used (bronchodilator and corticosteroid). We measured whole saliva and serum ECP and performed skin prick tests (SPT) for three dust mites (Dermatophagoides pteronyssisinus, Dermatophagoides farinae and Blomia tropicalis) and two cockroaches (Periplaneta americana and Blatella germanica). Median salivary ECP was 84.6 microg/l (inter-quartile range [IQR]: 40.9-147.9) and median serum ECP was 14.7 microg/l (IQR: 6.4-32.1). Serum ECP was only higher in children whose sleep was disturbed by asthma in the past year than those who were not (geometric mean [GM]: 18.9 vs. 11.1 microg/l, relative mean difference [RMD]: 1.71 [95%CI: 1.09-2.69]). Serum ECP was increased among asthmatic children on inhaled corticosteroid than those not using them (GM: 15.6 vs. 8.1 microg/l, RMD: 1.93 [95%CI: 1.11-3.39]). Salivary ECP was not associated with asthma severity, concurrence of atopic conditions, medications used, or any SPT parameter. Saliva ECP did not correlate with serum ECP (r(s) = 0.032, p = 0.790). Salivary and serum ECP did not correlate with wheal size for any skin prick test.

Expressão das metaloproteinases da matriz 2 e 9 na saliva de pacientes com doença pulmonar obstrutiva crônica

O aumento da expressão das metaloproteinases da matriz extracelular (MPM) é considerado um importante fator no desenvolvimento da doença pulmonar obstrutiva crônica (DPOC). O presente estudo teve como objetivo avaliar os níveis de expressão da MPM-2 e MPM-9 na saliva de pacientes com DPOC em comparação com indivíduos saudáveis, verificando a viabilidade de usar a saliva para a caracterização de biomarcadores específicos em DPOC. Foram selecionados pacientes com DPOC (n=16) e controles saudáveis (n=9). Em ambos os grupos foram realizados teste espirométrico e obtidas amostras de saliva de cada indivíduo. Os níveis de MPM-2 e MPM-9 na saliva foram determinados pela técnica Western blot. A MPM-2 e a MPM-9 foram significativamente maiores em pacientes com DPOC do que no grupo de indivíduos saudáveis. Foi encontrada moderada correlação negativa entre a concentração de MPM-2 e o volume expiratório forçado no primeiro segundo (r= -0,582, p=0,014) em pacientes com DPOC. Estes resultados abrem novas perspectivas para o estudo específico de biomarcadores na saliva para predizer e monitorar a obstrução ao fluxo aéreo em pacientes com DPOC.

An application of salivary DNA in twin research of Chinese children

Since saliva collection is noninvasive, painless and inexpensive, it may become an alternative to obtain genomic DNA, which is critical to evaluate zygosity and the role of genetic factors in twin research. This study provided a rough description of salivary DNA in Chinese twin children, and presented the DNA yield and quality extracted from saliva in a large-scale children sample, which supplied an example for saliva sample using in genetic epidemiology. Three milliliters of saliva was collected from 356 twin children aged 6 to 15, and DNA was extracted by a commercial DNA isolation kit. The DNA yield and purity was determined by spectrophotometry at 260 nm and 280 nm. The zygosity determination of the same-sex twins and the assay of Polymerase Chain Reaction-Restriction Fragment Length Polymorphism indicated the quality of salivary DNA. The amount of extracted DNA from three milliliters of saliva was about 34.91 microg (2.20 approximately 122.04 microg), average OD(260/280) values was 1.84. Saliva DNA is a reliable sample for the determination of twins' zygosity. We conclude that saliva may be a feasible and reliable source of DNA for genetic epidemiology studies, especially for twin research.

Salivary cortisol and psychosocial hazards at work

BACKGROUND

Experimental and clinical evidence suggest that stress can lead to ill-health through the disregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Studies to date have produced equivocal results likely due to different methodologies and failure to account for confounding factors. This investigation aimed to assess the relation between self-reported work-related stressors and salivary cortisol and to clarify the role of the potential confounders.

METHODS

Thirty-six call-handlers completed a self-administered job content questionnaire and collected seven daily salivary samples on two workdays and a weekend. The diurnal salivary cortisol output was expressed as cortisol awakening response (CAR), and cortisol output in the rest of the day. Salivary cortisol data were normalized by means of square root transformation. The generalized estimating equations method was used to assess the relation between job strain and cortisol levels after adjusting for gender, weekdays and adherence to the sampling schedule.

RESULTS

Job strain significantly influenced the total amount of cortisol response to waking (high strain vs. low strain: 1.1 (0.3-2.0) nmol/L). The cortisol response to waking showed gender-specific differences [women excreting greater cortisol than men: 1.1 (0.3-1.9) nmol/L], and weekday differences [workdays vs. weekend: 1.0 (0.3-1.6) nmol/L]. Non-compliance with the sampling protocol was associated with lower salivary cortisol than in adherent subjects.

CONCLUSIONS

Our results provide further evidence for the HPA axis involvement in the physiological response to work stress. The measure of the CAR showed to be the sensitive index to assess the physiological response to psychosocial factors. Gender, weekday, and protocol compliance were confounding factors.

Non-invasive matrices in human biomonitoring: a review

Humans and other living organisms are exposed to a variety of chemical pollutants that are released into the environment as a consequence of anthropogenic activities. Environmental pollutants are incorporated into the organism by different routes and can then be stored and distributed in different tissues, which leads to an internal concentration that can induce different alterations, adverse effects and/or diseases. Control measures should be taken to avoid these effects and human biomonitoring is a very useful tool that can contribute to this aim. Human biomonitoring uses different matrices to measure the target chemicals depending on the chemical, the amount of matrix necessary for the analysis and the detection limit (LOD) of the analytical technique. Blood is the ideal matrix for most chemicals due to its contact with the whole organism and its equilibrium with organs and tissues where chemicals are stored. However, it has an important disadvantage of being an invasive matrix. The development of new methodology and modern analytical techniques has allowed the use of other matrices that are less or non-invasive, such as saliva, urine, meconium, nails, hair, and semen or breast milk. The presence of a chemical in these matrices reflects an exposure, but correlations between levels in non-invasive matrices and blood must be established to ensure that these levels are related to the total body burden. The development of new biomarkers that are measurable in these matrices will improve non-invasive biomonitoring. This paper reviews studies that measure Cd, Pb, Hg, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides and phthalates in non-invasive matrices, the most used techniques for measurements and what alternative techniques are available.

The effect of cotton-based collection methods on eosinophil cationic protein (ECP) concentrations detected in saliva

Background:

Salivary eosinophil cationic protein (ECP) level has the potential to be an assessment tool for asthma. Its measurement is not well-established and needs standardization. We studied how passive drool (PD) and two commercial devices, Salivette^® (cotton-based device) and Sorbette^® (cellulose–cotton-based-device), may affect ECP levels during collection among healthy subjects.

Methods:

Study I (n = 10) involved direct sampling of healthy adult subjects with Salivette^® and Sorbette^®. Study II (n = 33) involved ‘indirect’ sampling of previously collected PD by both devices.

Results:

In study I, ECP levels were detected in all PD samples but only in three with Sorbette^® and none with Salivette^® (collection order: PD, Sorbette^® and Salivette^®). We changed the order of collection (Salivette^®, Sorbette^®, PD) and the results were similar (ECP levels detected in all PD samples, three with Sorbette^® and only one with Salivette^®). In study II, ECP levels in saliva collected by PD was 12.8 μg/L (median) and using Sorbette^® and Salivette^® were < 2.0 μg/L and 3.4 μg/L respectively (p < 0.01). ECP levels in PD correlated with Sorbette^® (r_s = 0.79, p < 0.01) and Salivette^® (r_s = 0.62, p < 0.01).

Conclusion:

Compared to PD, saliva collected using cotton or cellulose-based collection devices resulted in lower measurable ECP levels.

Saliva as an analytical tool to measure occupational exposure to toluene

OBJECTIVE

To describe a sensitive and rapid method for the determination of toluene in saliva. Biomonitoring of toluene exposure is commonly performed by determination of urinary hippuric acid, o-cresol or toluene itself. The analysis of blood toluene has been verified as another method for biomonitoring. However, drawing blood is invasive and can often not be performed at the workplace for hygienic reasons. Sampling of saliva may be non-invasive, easy to perform and a viable alternative for biomonitoring in the workplace.

METHODS

We measured the solvent concentration in saliva specimens of 5 healthy volunteers studied in the laboratory and a group of 36 workers exposed to toluene in the synthetic leather industry. Saliva was collected into Salivette (Sarstedt, Germany) devices by sterile cotton rolls placed in the mouth and then squeezed into pre-weighted vials. Environmental toluene was collected for the duration of a work-shift by Radiello (FSM, Italy) passive samplers. Toluene in urine and saliva (head space analysis) and in environmental samples was measured by GC-MS.

RESULTS

Environmental toluene levels ranged from 0.22 to 57.20 mg/m(3), while the concentrations of the solvent in saliva and urine ranged from 0.12 to 18.30 microg/L, and from 0.47 to 26.64 microg/L, respectively. The correlation coefficients (r) between biological and environmental levels of toluene were 0.77 and 0.93, respectively, for saliva and urine samples.

CONCLUSION

This preliminary study suggests that saliva may offer many advantages over 'classical' biological fluids such as blood as it is readily accessible and collectible: therefore saliva toluene may be considered as a possible biomarker of exposure to toluene.