Salivary defense proteins: their network and role in innate and acquired oral immunity

RP-HPLC-ESI-IT Mass Spectrometry Reveals Significant Variations of the Human Salivary Protein Profile Associated with Predominantly Antibody Deficiencies

PURPOSE

Present study is designed to discover potential salivary biomarkers associated with predominantly antibody deficiencies, which include a large spectrum of disorders sharing failure of antibody production, and B cell defects resulting in recurrent infections, autoimmune and inflammatory manifestations, and tumor susceptibility. Understanding and clinical classification of these syndromes is still challenging.

METHODS

We carried out a study of human saliva based on liquid chromatography-mass spectrometry measurements of intact protein mass values. Salivary protein profiles of patients (n = 23) and healthy controls (n = 30) were compared.

RESULTS

Patients exhibited lower abundance of α-defensins 1-4, cystatins S1 and S2, and higher abundance of glutathionylated cystatin B and cystatin SN than controls. Patients could be clustered in two groups on the basis of different levels of cystatin SN, S1 and S2, suggesting that these proteins may play different roles in the disease.

CONCLUSIONS

Quantitative variations of these pro-inflammatory and antimicrobial peptides/proteins may be related to immunodeficiency and infectious condition of the patients. The high incidence of tumors in the group with the highest level of cystatin SN, which is recognized as tumoral marker, appeared an intriguing result deserving of future investigations. Data are available via ProteomeXchange with identifier PXD012688.

RP-HPLC-ESI-IT Mass Spectrometry Reveals Significant Variations of the Human Salivary Protein Profile Associated with Predominantly Antibody Deficiencies

PURPOSE

Present study is designed to discover potential salivary biomarkers associated with predominantly antibody deficiencies, which include a large spectrum of disorders sharing failure of antibody production, and B cell defects resulting in recurrent infections, autoimmune and inflammatory manifestations, and tumor susceptibility. Understanding and clinical classification of these syndromes is still challenging.

METHODS

We carried out a study of human saliva based on liquid chromatography-mass spectrometry measurements of intact protein mass values. Salivary protein profiles of patients (n = 23) and healthy controls (n = 30) were compared.

RESULTS

Patients exhibited lower abundance of α-defensins 1-4, cystatins S1 and S2, and higher abundance of glutathionylated cystatin B and cystatin SN than controls. Patients could be clustered in two groups on the basis of different levels of cystatin SN, S1 and S2, suggesting that these proteins may play different roles in the disease.

CONCLUSIONS

Quantitative variations of these pro-inflammatory and antimicrobial peptides/proteins may be related to immunodeficiency and infectious condition of the patients. The high incidence of tumors in the group with the highest level of cystatin SN, which is recognized as tumoral marker, appeared an intriguing result deserving of future investigations. Data are available via ProteomeXchange with identifier PXD012688.

Measuring the administered dose of particles on the facial mucosa of a realistic human model

Exposure to particulate contaminants can cause serious adverse health effects. Deposition on the facial mucosa is an important path of exposure, but it is difficult to conduct direct dose measurement on real human subjects. In this study, we propose an in vitro method to assess the administered doses of micron-sized particles on the eyes and lips in which computed tomographic scanning and three-dimensional printing were used to create a model that includes a face, oropharynx, trachea, the first five generations of bronchi, and lung volume. This realistic model of a face and airway was exposed to monodispersed fluorescent particles released from an incoming jet. The administered dose of particles deposited upon the eyes and lips, as quantified by fluorescence intensity, was determined via a standard wiping protocol. The results show that, in this scenario, the administered doses normalized by source were 2.15%, 1.02%, 0.88%, 2.13%, and 1.55% for 0.6-, 1.0-, 2.0-, 3.0-, and 5.0-µm particles, respectively. The administered dose of large particles on the mucosa within a given exposure time has great significance. Moreover, the lips suffer a much greater risk of exposure than the eyes and account for more than 80% of total facial mucosa deposition. Our study provides a fast and economical method to assess the administered dose on the facial mucosa on an individual basis.

Cordycepin attenuates Salivary Hypofunction through the Prevention of Oxidative Stress in Human Submandibular Gland Cells

Xerostomia (dry mouth) is a significant age-related condition. Meanwhile, cordycepin, the natural therapeutic agent, has demonstrated an anti-aging effect. Therefore, the present study aimed to investigate the preventive effects of cordycepin on secretory function in an in vitro model of hydrogen peroxide (H₂O₂)-induced salivary hypofunction. After being exposed to H₂O₂, human submandibular gland (HSG) cells were treated with various concentrations of cordycepin (6.25-50 µM) for 24, 48, and 72h. To evaluate cell proliferation and reactive oxygen species (ROS) generation, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide and 2, 7'-dichlorodihydrofluorescein diacetate assays were performed. The amylase activity was kinetically measured by 2-chloro-p-nitrophenol linked with maltotrioside. The expression of salivary, antioxidant and apoptotic markers at mRNA and protein levels were performed by reverse transcriptase polymerase chain reaction (RT-PCR) and immunofluorescence analysis, respectively. We demonstrated that cordycepin (6.25-25 µM) contributed to significant increases in expression of the salivary marker genes, alpha-amylase 1 (AMY1A) and aquaporin-5 (AQP5), and in amylase secretion without changes in cell viability. Under oxidative stress, HSG cells showed remarkable dysfunction. Cordycepin rescued the protective effects partially by decreasing ROS generation and restoring the expression of the salivary proteins, AMY and AQP5 via anti-oxidant and anti-apoptotic activity. In addition, the amount of amylase that was secreted from HSG cells cultured in cordycepin was increased. In conclusion, cordycepin demonstrated a protective effect on H₂O₂ -induced HSG cells by decreasing ROS generation and upregulating the salivary function markers, AMY1A and AQP5, at both the transcriptional and translational levels.

Free light chains as an emerging biomarker in saliva: Biological variability and comparisons with salivary IgA and steroid hormones

BACKGROUND

Salivary free light chains (FLCs) are an emerging biomarker in health and behavioural research. However, little is known regarding biological variability of salivary FLCs and how they relate to other established salivary biomarkers. This study aimed to investigate the diurnal and day-to-day variation of salivary FLCs and their relationship with salivary IgA and steroid hormones.

METHODS

A total of 46 healthy adults participated in studies exploring the biological variability of FLCs. Diurnal variation was investigated by collecting saliva samples immediately upon waking, 0.5 h, 3 h, 6 h, 9 h and 14 h post-waking. Saliva samples were assessed for FLCs, IgA, cortisol and dehydroepiandrosterone (DHEA). Between-day variation in FLCs and IgA was assessed by collecting saliva samples immediately upon waking for seven consecutive days. Participants underwent a dental examination to exclude oral health as a potential confounding variable. Within and between-person day-to day variation was explored in relation to a range of different factors: awakening time, sleep, exercise, well-being and alcohol consumption.

RESULTS

Salivary secretion rates of FLCs decreased following waking and up to 3 h post-waking and then plateaued. This same pattern was observed for IgA. DHEA was stable upon waking and higher levels were seen in the morning with significantly lower levels thereafter. Cortisol levels significantly increased 0.5 h post-waking then continued to decline across the day. FLCs were significantly correlated with IgA but not cortisol or DHEA. Both FLCs and IgA parameters showed day-to-day variability, with coefficients of variation ≥ 40%. Earlier waking time was significantly correlated with higher FLC and IgA secretion rates. Inter-person differences in saliva parameter variability were observed but the degree of variation in FLCs and IgA was related within person. Inter-person day-to-day variation appeared to be uninfluenced by lifestyle or behavioural factors.

CONCLUSIONS

Saliva FLCs secretion exhibits diurnal fluctuation that mirrors IgA fluctuation. Findings strongly indicate salivary FLC secretion is orchestrated by local plasma cells. FLCs and IgA both showed notable variability day-to-day, which was similar within person and influenced by awakening time. FLCs offer a promising adjunct to IgA in the measurement of oral immune activation.

Efficacy and safety of local lysozyme treatment in patients with oral mucositis after chemotherapy and radiotherapy

This observational clinical study was composed of two substudies: a non-comparative one (n = 166), testing only lysozyme-based compounds (LBCs), and a comparative substudy (n = 275), testing both LBCs and bicarbonate-based local compounds (BBCs) on the healing of oral mucositis during radio- or chemotherapy. The density of ulcerations has decreased significantly after the treatment with lysozyme in both substudies. The density of ulcerations in the radiotherapy group was lower in patients treated with LBCs compared to patients treated with BBCs (p < 0.001). In the chemotherapy group, reduction of ulceration density was similar with both LBCs and BBCs. The LBCs reduced pain intensity during the intake of solid food and speech more than BBCs in both patient cohorts (p < 0.05). In the radiotherapy cohort, pain intensity when consuming liquid foods was reduced more with LBCs than with BBCs (p < 0.05). No adverse events were recorded. This study demonstrates the advantages of treating oral mucositis during radiotherapy or chemo-therapy with LBCs.

Salivary antimicrobial proteins and stress biomarkers are elevated during a 6-month mission to the International Space Station

As the international space community plans for manned missions to Mars, spaceflight-associated immune dysregulation has been identified as a potential risk to the health and safety of the flight crew. There is a need to determine whether salivary antimicrobial proteins, which act as a first line of innate immune defense against multiple pathogens, are altered in response to long-duration (>6 mo) missions. We collected 7 consecutive days of whole and sublingual saliva samples from eight International Space Station (ISS) crewmembers and seven ground-based control subjects at nine mission time points, ~180 and ~60 days before launch (L-180/L-60), on orbit at flight days ~10 and ~90 (FD10/FD90) and ~1 day before return (R-1), and at R+0, R+18, R+33, and R+66 days after returning to Earth. We found that salivary secretory (s)IgA, lysozyme, LL-37, and the cortisol-to-dehydroepiandrosterone ratio were elevated in the ISS crew before (L-180) and during (FD10/FD90) the mission. "Rookie" crewmembers embarking on their first spaceflight mission had lower levels of salivary sIgA but increased levels of α-amylase, lysozyme, and LL-37 during and after the mission compared with the "veteran" crew who had previously flown. Latent herpesvirus reactivation was distinct to the ~6-mo mission crewmembers who performed extravehicular activity ("spacewalks"). Crewmembers who shed at least one latent virus had higher cortisol levels than those who did not shed. We conclude that long-duration spaceflight alters the concentration and/or secretion of several antimicrobial proteins in saliva, some of which are related to crewmember flight experience, biomarkers of stress, and latent viral reactivation.NEW & NOTEWORTHY Spaceflight-associated immune dysregulation may jeopardize future exploration-class missions. Salivary antimicrobial proteins act as a first line of innate immune defense. We report here that several of these proteins are elevated in astronauts during an International Space Station mission, particularly in those embarking on their first space voyage. Astronauts who shed a latent herpesvirus also had higher concentrations of salivary cortisol compared with those who did not shed. Stress-relieving countermeasures are needed to preserve immunity and prevent viral reactivation during prolonged voyages into deep space.

Influence of Electronic Cigarettes on Selected Antibacterial Properties of Saliva

The aim of this study was to estimate changes in selected physicochemical properties of saliva collected from users of electronic cigarettes. Methods: The study population consisted of 120 patients (40 users of electronic cigarettes, 40 smokers of traditional cigarettes and 40 non-smokers). Laboratory tests included verification of saliva amount of lysozyme, lactoferrin and IgA. Results: Among e-cigarette users, statistically significant differences were observed in values of lysozyme and lactoferrin; however, no statistically significant differences for the IgA value were found. In the group of traditional cigarette smokers, statistically significant differences were observed among all tested parameters in relation to the control group. In relation to IgA, statistically significant differences were found between e-cigarette users and traditional cigarette smokers, to the disadvantage of the latter. Conclusion: Saliva of e-cigarette users showed changes of antibacterial properties in comparison to the control group and traditional cigarette smokers. Further longitudinal studies on larger study groups should be conducted in order to assess the effect of observed changes in the antibacterial properties of saliva on oral health.

Physical exercise stimulates salivary secretion of cystatins

Physical exercise is known to activate the sympathetic nervous system, which influences the production of saliva from salivary glands. Our examination of saliva collected from highly trained athletes before and after a number of physical competititions showed an increase in the secretion of S-type cystatins and cystatin C as a subacute response to aerobic and anaerobic exercise. The elevation in salivary cystatins was transient and the recovery time course differed from that of amylase and other salivary proteins. An in vitro assay was developed based on a cell line from a human submandibular gland (HSG) that differentiated into acinus-like structures. Treatments with the β-adrenergic agonist isoproterenol caused a shift in the intracellular distribution of S-type cystatins and cystatin C, promoting their accumulation at the outer regions of the acinus prior to release and suggesting the activation of a directional transport involving co-migration of both molecules. In another treatment using non-differentiated HSG cells, it was evident that both expression and secretion of cystatin C increased upon addition of the β-adrenergic agonist, and these effects were essentially eliminated by the antagonist propranolol. The HSG cell line appears to have potential as a model for exploring the mechanism of cystatin secretion, particularly the S-type cystatins that originate primarily in the submandibular glands.

Saliva enhances infection of gingival fibroblasts by herpes simplex virus 1

Oral herpes is a highly prevalent infection caused by herpes simplex virus 1 (HSV-1). After an initial infection of the oral cavity, HSV-1 remains latent in sensory neurons of the trigeminal ganglia. Episodic reactivation of the virus leads to the formation of mucocutaneous lesions (cold sores), but asymptomatic reactivation accompanied by viral shedding is more frequent and allows virus spread to new hosts. HSV-1 DNA has been detected in many oral tissues. In particular, HSV-1 can be found in periodontal lesions and several studies associated its presence with more severe periodontitis pathologies. Since gingival fibroblasts may become exposed to salivary components in periodontitis lesions, we analyzed the effect of saliva on HSV-1 and -2 infection of these cells. We observed that human gingival fibroblasts can be infected by HSV-1. However, pre-treatment of these cells with saliva extracts from some but not all individuals led to an increased susceptibility to infection. Furthermore, the active saliva could expand HSV-1 tropism to cells that are normally resistant to infection due to the absence of HSV entry receptors. The active factor in saliva was partially purified and comprised high molecular weight complexes of glycoproteins that included secretory Immunoglobulin A. Interestingly, we observed a broad variation in the activity of saliva between donors suggesting that this activity is selectively present in the population. The active saliva factor, has not been isolated, but may lead to the identification of a relevant biomarker for susceptibility to oral herpes. The presence of a salivary factor that enhances HSV-1 infection may influence the risk of oral herpes and/or the severity of associated oral pathologies.

An Evolutionary Perspective on the Impact of Genomic Copy Number Variation on Human Health

Copy number variants (CNVs), deletions and duplications of segments of DNA, account for at least five times more variable base pairs in humans than single-nucleotide variants. Several common CNVs were shown to change coding and regulatory sequences and thus dramatically affect adaptive phenotypes involving immunity, perception, metabolism, skin structure, among others. Some of these CNVs were also associated with susceptibility to cancer, infection, and metabolic disorders. These observations raise the possibility that CNVs are a primary contributor to human phenotypic variation and consequently evolve under selective pressures. Indeed, locus-specific haplotype-level analyses revealed signatures of natural selection on several CNVs. However, more traditional tests of selection which are often applied to single-nucleotide variation often have diminished statistical power when applied to CNVs because they often do not show strong linkage disequilibrium with nearby variants. Recombination-based formation mechanisms of CNVs lead to frequent recurrence and gene conversion events, breaking the linkage disequilibrium involving CNVs. Similar methodological challenges also prevent routine genome-wide association studies to adequately investigate the impact of CNVs on heritable human disease. Thus, we argue that the full relevance of CNVs to human health and evolution is yet to be elucidated. We further argue that a holistic investigation of formation mechanisms within an evolutionary framework would provide a powerful framework to understand the functional and biomedical impact of CNVs. In this paper, we review several cases where studies reveal diverse evolutionary histories and unexpected functional consequences of CNVs. We hope that this review will encourage further work on CNVs by both evolutionary and medical geneticists.

Association of salivary levels of immunoglobulin-a and amylase with oral-dental manifestations in patients with controlled and non-controlled type 2 diabetes

Background

Oral health is related to general health and one of the most prevalent chronic diseases is diabetes mellitus. Diabetes can have adverse effects on oral health and vice versa. Saliva analysis can be used as a non-invasive method to obtain information about diseases status like diabetes. The aim of present study was to evaluate the salivary immunoglobulin-A (s-IgA) and salivary amylase levels and their associations with oral-dental manifestations in patients with controlled and non-controlled type 2 diabetes.

Methods

This case-control study was carried out on 90 subjects who referred to the Diabetes Center of Shahid Bahonar Hospital, Kerman University of Medical Sciences, Kerman, Iran. Participants were divided into three groups: 1) uncontrolled diabetic patients (n = 30); 2) controlled diabetic patients (n = 30); and 3) healthy individuals (n = 30). Unstimulated salivary levels of I-A and amylase were measured. All participants underwent a dental and periodontal examination to explore the oral and dental manifestations. T-test, chi-square and ANOVA tests were used for data analysis in SPSS 18.

Results

Significant higher level of s-IgA was found in uncontrolled diabetic patients compared to controlled diabetic (P ≤ 0.0001) and the control group (P = 0.004). Moreover, the mean levels of s-amylase in uncontrolled patients was significantly higher compared to controlled diabetic (P = 0.01) and the control group (P ≤ 0.0001). Uncontrolled diabetic patients with oral candidiasis, erythematous candidiasis, abscesses, or xerostomia had higher s-IgA levels compared to the controlled diabetic participants. Moreover, uncontrolled diabetic patients with oral candidiasis or erythematous candidiasis showed a significant higher levels of s-amylase compared to controlled diabetic patients. Also, significant positive correlations were found between s-IgA and DMFT and s-IgA and PDI (r = 0.444, P = 0.014 and r = 0.386, P = 0.035, respectively).

Conclusion

In conclusion, higher s-amylase and s-IgA concentrations may reflect oral-dental manifestations in T2DM. Moreover, the current findings suggest that s-amylase and s-IgA may serve as a complementary and alternative fluid in screening for diabetes mellitus.

Clinical validity of saliva and novel technology for cancer detection

Cancer, a local disease at an early stage, systemically evolves as it progresses by triggering alterations in surrounding microenvironment, disturbing immune surveillance and further disseminating its molecular contents into circulation. This pathogenic characteristic of cancer makes the use of biofluids such as blood/serum/plasma, urine, tear and cerebrospinal fluids credible surrogates harboring tumor tissue-derived molecular alterations for the detection of cancer. Most importantly, a number of recent reports have credentialed the clinical validity of saliva for the detection of systemic diseases including cancers. In this review, we discussed the validity of saliva as credible biofluid and clinical sample type for the detection of cancers. We have presented the molecular constituents of saliva that could mirror the systemic status of our body and recent findings of salivaomics associated with cancers. Recently, liquid biopsy to detect cancer-derived circulating tumor DNA has emerged as a credible cancer-detection tool with potential benefits in screening, diagnosis and also risk management of cancers. We have further presented the clinical validity of saliva for liquid biopsy of cancers and a new technology platform based on electrochemical detection of cancer-derived ctDNA in saliva with superior sensitivity and point-of-care potential. The clinical utilities of saliva for the detection of cancers have been evidenced, but biological underpinning on the existence of molecular signatures of cancer-origin in saliva, such as via exosomal distribution, should be addressed in detail.

The association of PM2.5 with airway innate antimicrobial activities of salivary agglutinin and surfactant protein D

Fine particulate matter ≤2.5 μm (PM_2.5) is a prominent global public health risk factor that can cause respiratory infection by downregulating the amounts of antimicrobial proteins and peptides (AMPs). Both salivary agglutinin (SAG) and surfactant protein D (SPD) are important AMPs in respiratory mucosal fluid, providing protection against airway pathogen invasion and infection by inducing microbial aggregation and enhancing pathogen clearance. However, the relationship between PM_2.5 and these AMPs is unclear. To better understand the relationship between PM_2.5 and airway innate immune defenses, we review the respiratory antimicrobial activities of SAG and SPD, as well as the adverse effects of PM_2.5 on airway innate antimicrobial defense. We speculate there exists a dual effect between PM_2.5 and respiratory antimicrobial activity, which means that PM_2.5 suppresses respiratory antimicrobial activity through downregulating airway AMPs, while airway AMPs accelerate PM_2.5 clearance by inducing PM_2.5 microbial aggregation. We propose further research on the relationship between PM_2.5 and these AMPs.

Characterization of the bovine salivary gland transcriptome associated with Mycobacterium avium subsp. paratuberculosis experimental challenge

BACKGROUND

Mycobacterium avium subsp. paratuberculosis (MAP), the etiologic agent of Johne's disease is spread between cattle via the fecal-oral route, yet the functional changes in the salivary gland associated with infection remain uncharacterized. In this study, we hypothesized that experimental challenge with MAP would induce stable changes in gene expression patterns in the salivary gland that may shed light on the mucosal immune response as well as the regional variation in immune capacity of this extensive gland. Holstein-Friesian cattle were euthanized 33 months' post oral challenge with MAP strain CIT003 and both the parotid and mandibular salivary glands were collected from healthy control (n = 5) and MAP exposed cattle (n = 5) for histopathological and transcriptomic analysis.

RESULTS

A total of 205, 21, 61, and 135 genes were significantly differentially expressed between control and MAP exposed cattle in dorsal mandibular (M1), ventral mandibular (M2), dorsal parotid (P1) and ventral parotid salivary glands (P2), respectively. Expression profiles varied between the structurally divergent parotid and mandibular gland sections which was also reflected in the enriched biological pathways identified. Changes in gene expression associated with MAP exposure were detected with significantly elevated expression of BoLA DR-ALPHA, BOLA-DRB3 and complement factors in MAP exposed cattle. In contrast, reduced expression of genes such as polymeric immunoglobin receptor (PIGR), TNFSF13, and the antimicrobial genes lactoferrin (LF) and lactoperoxidase (LPO) was detected in MAP exposed animals.

CONCLUSIONS

This first analysis of the transcriptomic profile of salivary glands in cattle adds an important layer to our understanding of salivary gland immune function. Transcriptomic changes associated with MAP exposure have been identified including reduced LF and LPO. These critical antimicrobial and immunoregulatory proteins are known to be secreted into saliva and their downregulation may contribute to disease susceptibility. Future work will focus on the validation of their expression levels in saliva from additional cattle of known infection status as a potential strategy to augment disease diagnosis.

Effects of thermally oxidized canola oil and tannic acid supplementation on nutrient digestibility and microbial metabolites in finishing pigs1

The present study investigated the effects of oxidized canola oil and tannic acid (TA) supplementation on nutrient digestibility and microbial metabolites in finishing pigs. Four experimental diets were formulated to include 5% of either fresh canola oil (0 mEq/kg of peroxide value) or oxidized canola oil (180 mEq/kg of peroxide value). An equal portion of each diet was supplemented with 0.1% TA. Eight pigs (initial body weight of 82.89 ± 2.26 kg) were surgically fitted with a T-cannula at the distal ileum. At the beginning of the experiments, all pigs were fed a nitrogen-free diet for 7 d. Then, they were assigned to 4 dietary treatments according to an incomplete replicated 4 × 3 Latin square design with 3 periods to give 6 replicates per treatment. Each experimental period lasted for 9 d, starting with a 5-d adaptation period followed by 2 consecutive 2-d periods for fecal (day 6 and day 7) and ileal digesta (day 8 and day 9) collection. The inclusion of oxidized oil reduced (P < 0.05) the standardized ileal digestibility (SID) of Pro and the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of NDF. Also, pigs fed the oxidized oil tended to have lower (P ≤ 0.10) lactate and ammonia-nitrogen concentrations in the ileum and lower (P ≤ 0.10) acetate and propionate concentrations in the feces than those fed the fresh oil. The supplementation of 0.1% TA reduced (P < 0.05) the AID of NDF and the ATTD of gross energy, crude protein, and NDF. Additionally, the TA-supplemented diet tended to have a lower (P ≤ 0.10) digestible energy content than the nonsupplemented diet. Pigs fed the TA-supplemented diet showed reduced (P < 0.05) AID and SID of His, Cys, and Pro compared with those fed the nonsupplemented diet. There were interactive effects (P < 0.05) of oxidized oil and TA supplementation on acetate, isovalerate, total short chain fatty acids, and pH level in the ileum. In conclusion, the results indicated that the effects of oxidized oil are greater on microbial activities rather than nutrient digestibility. Although negative effects of dietary TA supplementation were observed in relation to nutrient digestibility, TA supplementation was found to ameliorate these negative effects of oxidized oil on microbial metabolites. Therefore, further studies are required to investigate the interaction between dietary oxidized oil and TA in relation with the gut microbiota in pigs.

Application of Antimicrobial Peptides of the Innate Immune System in Combination With Conventional Antibiotics-A Novel Way to Combat Antibiotic Resistance?

Rapidly growing resistance of pathogenic bacteria to conventional antibiotics leads to inefficiency of traditional approaches of countering infections and determines the urgent need for a search of fundamentally new anti-infective drugs. Antimicrobial peptides (AMPs) of the innate immune system are promising candidates for a role of such novel antibiotics. However, some cytotoxicity of AMPs toward host cells limits their active implementation in medicine and forces attempts to design numerous structural analogs of the peptides with optimized properties. An alternative route for the successful AMPs introduction may be their usage in combination with conventional antibiotics. Synergistic antibacterial effects have been reported for a number of such combinations, however, the molecular mechanisms of the synergy remain poorly understood and little is known whether AMPs cytotoxicy for the host cells increases upon their application with antibiotics. Our study is directed to examination of a combined action of natural AMPs with different structure and mode of action (porcine protegrin 1, caprine bactenecin ChBac3.4, human alpha- and beta-defensins (HNP-1, HNP-4, hBD-2, hBD-3), human cathelicidin LL-37), and egg white lysozyme with varied antibiotic agents (gentamicin, ofloxacin, oxacillin, rifampicin, polymyxin B, silver nanoparticles) toward selected bacteria, including drug-sensitive and drug-resistant strains, as well as toward some mammalian cells (human erythrocytes, PBMC, neutrophils, murine peritoneal macrophages and Ehrlich ascites carcinoma cells). Using “checkerboard titrations” for fractional inhibitory concentration indexes evaluation, it was found that synergy in antibacterial action mainly occurs between highly membrane-active AMPs (e.g., protegrin 1, hBD-3) and antibiotics with intracellular targets (e.g., gentamicin, rifampcin), suggesting bioavailability increase as the main model of such interaction. In some combinations modulation of dynamics of AMP-bacterial membrane interaction in presence of the antibiotic was also shown. Cytotoxic effects of the same combinations toward normal eukaryotic cells were rarely synergistic. The obtained data approve that combined application of antimicrobial peptides with antibiotics or other antimicrobials is a promising strategy for further development of new approach for combating antibiotic-resistant bacteria by usage of AMP-based therapeutics. Revealing the conventional antibiotics that increase the activity of human endogenous AMPs against particular pathogens is also important for cure strategies elaboration.

A novel role of probiotics in improving host defence of elite rugby union athlete: A double blind randomised controlled trial

OBJECTIVE

To examine the effects of a probiotic protocol on the incidence and severity of respiratory and gastrointestinal infections in elite rugby union athletes across an international competition season. Associations were also investigated between salivary biomarkers of stress (cortisol, alpha-amylase) and mucosal immunity (secretory(s)-IgA).

DESIGN

A double-blind RCT was conducted over 27-weeks, divided into three stages: (1) control period; (2) domestic competition; and (3) international competition.

METHODS

Athletes were assigned a probiotic (n = 9) or placebo (n = 10) supplement. Ultrabiotic 60™ or placebo was taken with food twice daily for 17 weeks and SB Floractiv™ 250 mg added twice daily during stage three.

RESULTS

Five infections were diagnosed by the team sports physician across the 27-weeks, three within the intervention period in athletes randomised to the placebo group. No significant group x time interaction effects for salivary cortisol, alpha-amylase or s-IgA were identified over the 27-week time period, although a significant main effect for group and time was identified for salivary cortisol, alpha-amylase, and s-IgA (p < 0.05 for all). When considering stage, significant differences were identified in stage one with s-IgA lower in the probiotic group (p = 0.015). In stage two and three, salivary cortisol was higher in the probiotic group (p = 0.016 and p = 0.001 respectively), and salivary alpha-amylase was higher in the probiotic group in stage three (p = 0.007).

CONCLUSION

The probiotic protocol used in this study was associated with an increase in salivary alpha-amylase supporting its possible role as a host defence peptide.

Salivary Biomarkers in Denture Stomatitis: A Systematic Review

OBJECTIVE

Denture stomatitis (DS) is an oral biofilm-associated inflammation of the denture-bearing mucosa. The objective of this review was to identify and evaluate the quality of evidence on the association between the levels of salivary biomarkers and DS among adults with and without palatal DS.

MATERIALS AND METHODS

Following the PRISMA guidelines, Medline, PubMed, EMBASE, and the Cochrane Central Register for Controlled Trials were searched for eligible studies from the beginning of the archives until December 2018. Experimental and observational studies with adult participants were included that had a control group or subgroup analysis and provided data on salivary biomarkers and DS. Articles in languages other than English or French were excluded. The level of evidence and grades of recommendation were established with the 2011 scale of the Oxford Centre for Evidence-Based Medicine. Additionally, the assessment of methodological quality was conducted with the STROBE statement (Strengthening the Reporting of Observational Studies in Epidemiology) and graded according to the Olmos scale.

RESULTS

From 1,008 citations, 9 studies were included in the systematic review (8 observational, 1 clinical trial). Seven studies suggested a statistically significant difference in the levels of salivary cytokines (IL-6, CCL3, TGF-β, CXCL8, GM-CSF, and TNF-α) between participants with DS and controls (P < 0.05). In contrast, 2 studies concluded that the difference in the levels of several salivary cytokines (IL2, IL12, IFN-g, IL-4, IL-8, IL-10, IL-17, TNF-α, and ICAM-1) between the groups was not statistically significant. The level of evidence for the majority of studies was 3, while the grade of recommendation for all the studies was B, interpreted as "favorable." In terms of methodological quality, most studies met 50% to 80% of STROBE criteria and were graded B.

CONCLUSION

Palatal inflammation in DS is significantly associated with the levels of salivary cytokines.

KNOWLEDGE TRANSFER STATEMENT

The results of this study identified altered levels of specific salivary biomarkers associated with denture stomatitis, which may aid in the early diagnosis and treatment of this disease.

Ambient fine particulate matter inhibits innate airway antimicrobial activity in preschool children in e-waste areas

Ambient fine particulate matter (PM_2.5) is a risk factor for respiratory diseases. Previous studies suggest that PM_2.5 exposure may down-regulate airway antimicrobial proteins and peptides (AMPs), thereby accelerating airway pathogen infection. However, epidemiological research is scarce. Hence, we estimated the associations between individual PM_2.5 chronic daily intake (CDI) and the levels of the airway AMP salivary agglutinin (SAG), as well as peripheral leukocyte counts and pro-inflammatory cytokines, of preschool children in Guiyu (an e-waste area) and Haojiang (a reference area located 31.6 km to the east of Guiyu). We recruited 581 preschool children from Guiyu and Haojiang, of which 222 were included in this study for a matching design (Guiyu: n = 110 vs. Haojiang: n = 112). Air PM_2.5 pollution data was collected to calculate individual PM_2.5 CDI. The mean concentration of PM_2.5 in Guiyu was higher than in Haojiang, resulting in a higher individual PM_2.5 CDI. Concomitantly, saliva SAG levels were lower in Guiyu children (5.05 ng/mL) than in Haojiang children (8.68 ng/mL), and were negatively correlated with CDI. Additionally, peripheral counts of white blood cells, and the concentrations of interleukin-8 and tumor necrosis factor-alpha, in Guiyu children were greater than in Haojiang children, and were positively associated with CDI. Similar results were found for neutrophils and monocytes. To our knowledge, this is the first study on the relationship between PM_2.5 exposure and innate airway antimicrobial activity in children, in an e-waste area, showing that PM_2.5 pollution may weaken airway antimicrobial activity by down-regulation of saliva SAG levels, which might accelerate airway pathogen infection in children.

Real-World Database Examining the Association between Sjögren's Syndrome and Chronic Rhinosinusitis

Objective: To investigate the risk of chronic rhinosinusitis (CRS) among patients with Sjögren’s syndrome (SS). Method: A total of 18,723 patients diagnosed with SS between 1997 and 2011 were retrospectively analyzed. Moreover, 59,568 patients without SS were matched to patients with SS at a 1:4 ratio on the basis of sex, age, urbanization level, income level, and the comorbidities of rhinitis and nasal sepal deviation. Patients were followed up until death or the end of the study period (31 December, 2013). The primary outcome was the occurrence of CRS. Results: The cumulative incidence of CRS was significantly higher in patients with SS than in those without SS (p < 0.001). The adjusted Cox proportional hazard model showed that patients with SS had a significantly higher incidence of CRS (hazard ratio, 2.51; 95% confidence interval, 2.22–2.84; p < 0.001). Sensitivity and subgroup analyses demonstrated SS was an independent risk factor for CRS. The dosage of intranasal corticosteroid spray used was not different between the SS and non-SS groups. Fewer patients with CRS in the SS group underwent sinus surgery (82/407 (20.2%)) than those in the non-SS group (179/667 (26.8%)) and this finding was statistically significant (p = 0.013). The number of operations did not differ significantly between patients with CRS in the SS and non-SS groups. Conclusions: SS is an independent risk factor for CRS. Our study extends the disease spectrum and prompts physicians to be aware of potential CRS occurrence after SS.

Exercise, Immunity, and Illness

It is generally accepted that moderate amounts of exercise improve immune system functions and hence reduce the risk of infection whereas athletes engaged in regular prolonged and/or intensive training have a higher than “normal” incidence of minor infections, especially of the upper respiratory tract (URT, e.g., common cold and influenza). This is likely related to regular acute (and possibly chronic) periods of exercise-induced changes in immune function. URT infections can compromise performance directly if suffered shortly before or during competition or indirectly if suffered at other times via effects on training and/or physiological adaptations. This chapter covers the effects of exercise (acute and chronic), both positive and negative, on immune function and consequent infection risk, and considers the current state-of-the-art for monitoring and assessing this in athletes.

A Secreted Bacterial Peptidylarginine Deiminase Can Neutralize Human Innate Immune Defenses

The keystone oral pathogen Porphyromonas gingivalis is associated with severe periodontitis. Intriguingly, this bacterium is known to secrete large amounts of an enzyme that converts peptidylarginine into citrulline residues. The present study was aimed at identifying possible functions of this citrullinating enzyme, named Porphyromonas peptidylarginine deiminase (PPAD), in the periodontal environment. The results show that PPAD is detectable in the gingiva of patients with periodontitis, and that it literally neutralizes human innate immune defenses at three distinct levels, namely bacterial phagocytosis, capture in neutrophil extracellular traps (NETs), and killing by the lysozyme-derived cationic antimicrobial peptide LP9. As shown by mass spectrometry, exposure of neutrophils to PPAD-proficient bacteria reduces the levels of neutrophil proteins involved in phagocytosis and the bactericidal histone H2. Further, PPAD is shown to citrullinate the histone H3, thereby facilitating the bacterial escape from NETs. Last, PPAD is shown to citrullinate LP9, thereby restricting its antimicrobial activity. The importance of PPAD for immune evasion is corroborated in the infection model Galleria mellonella, which only possesses an innate immune system. Together, the present observations show that PPAD-catalyzed protein citrullination defuses innate immune responses in the oral cavity, and that the citrullinating enzyme of P. gingivalis represents a new type of bacterial immune evasion factor.IMPORTANCE Bacterial pathogens do not only succeed in breaking the barriers that protect humans from infection, but they also manage to evade insults from the human immune system. The importance of the present study resides in the fact that protein citrullination is shown to represent a new bacterial mechanism for immune evasion. In particular, the oral pathogen P. gingivalis employs this mechanism to defuse innate immune responses by secreting a protein-citrullinating enzyme. Of note, this finding impacts not only the global health problem of periodontitis, but it also extends to the prevalent autoimmune disease rheumatoid arthritis, which has been strongly associated with periodontitis, PPAD activity, and loss of tolerance against citrullinated proteins, such as the histone H3.

Impact of salivary hypofunction on incidence of orofungal infections with use of topical steroids for management of oral lichen planus and xerostomia

OBJECTIVES

The aim of this study was to determine if salivary hypofunction increases the incidence of oral fungal infections (OFIs) after topical steroid use for the management of oral lichen planus (OLP).

STUDY DESIGN

Patients with a diagnosis of OLP, treated for at least 2 weeks with topical steroids, had baseline salivary flow evaluations completed, and had a follow-up visit within 5 weeks of steroids being prescribed were assessed. Patients were evaluated for clinical signs of fungal infection at follow-up visits.

RESULTS

Forty-Seven patients (91% female) met the inclusion criteria, with 21.3% developing an OFI after topical steroid use. Demographic characteristics, type of OLP, steroid used, and antifungal used did not impact the development of an OFI. The mean stimulated salivary flow was significantly lower in the group that developed an OFI compared with the group that did not develop an OFI (8.31 mL/15 min vs 15.4 mL/15 min, respectively; P = 0.0006). A higher incidence of OFIs occurred in the low stimulated flow group versus the normal flow group (39% vs 4%, respectively). Most patients in the OFI group received a preventative antifungal (90%).

CONCLUSIONS

OFIs increased after steroid treatment in patients with OLP who had low stimulated salivary flows. Antifungals (90%) were not effective in preventing OFIs in patients with OLP who had salivary hypofunction and were treated with topical steroids.

A genome-wide association study identifies an association between variants in EFCAB4B gene and periodontal disease in an Italian isolated population

BACKGROUND AND OBJECTIVE

Periodontitis in one of the most prevalent dental diseases. Despite numerous studies have investigated its aetiopathogenetic factors, few works have focused on its genetic predisposition and most of them took into account only candidate genes. Therefore, we conducted a Genome Wide Association Study in an Italian isolated population aimed at uncovering genetic variants that predispose to this disorder.

METHODS

Diagnosis of chronic periodontitis was made following the criteria of the American Academy of Periodontology. Patients with chronic periodontitis were grouped into different categories: slight, severe, localized and generalized. A control group composed by people without signs of periodontitis or gingivitis was defined. DNA was genotyped using 370k Illumina chips. Linear mixed model regression was used to test the association between each single nucleotide polymorphism (SNP) (independent variable) and the periodontitis status (dependent variable), controlling for confounders sex, age and smoking. The genomic kinship matrix was also used as random effect.

RESULTS

Four SNPs on the gene EFCAB4B resulted significantly associated to localized periodontitis (P < 5 × 10^-8 ), with the best hit on the rs242016 SNP (P = 1.5 × 10^-8 ).

CONCLUSION

We have identified a novel significant association between the EFCAB4B gene and localized periodontitis. These results open a new perspective in the understanding of genetic factors contributing to this common disorder.

Batch injection analysis towards auxiliary diagnosis of periodontal diseases based on indirect amperometric detection of salivary α-amylase on a cupric oxide electrode

This study describes, for the first time, the use of a batch injection analysis system with amperometric detection (BIA-AD) to indirectly determine salivary α-amylase (sAA) levels in saliva samples for chronic periodontitis diagnosis. A chemical/thermal treatment was explored to generate a CuO film on a Cu electrode surface. This procedure offered good stability (RSD = 0.3%), good repeatability (RSD < 1.3%) and excellent reproducibility (RSD < 1.5%). The sAA concentration levels were determined based on the detection of maltose produced by enzymatic hydrolysis of starch. The analytical performance was investigated, and a linear correlation was observed for a maltose concentration range between 0.5 and 6.0 mmol L^-1 with a correlation coefficient equal to 0.999. The analytical sensitivity and the limit of detection were 48.8 μA/(mmol L^-1) and 0.05 mmol L^-1, respectively. In addition, the proposed system provided an excellent analytical frequency (120 analysis h^-1). The clinical feasibility of the proposed method was investigated by the determination of sAA levels in four saliva samples (two from healthy control persons (C1 and C2) and two from patients with chronic periodontitis (P1 and P2)). The accuracy provided by the BIA-AD system ranged from 93 to 98%. The sAA concentration levels achieved for each sample were compared to the values found by spectrophotometry and there was no statistically significant difference between them at a confidence level of 95%. Finally, the method reported herein emerges as a simple, low cost and promising tool for assisting periodontal diseases diagnosis.

Chemosensate-Induced Modulation of the Salivary Proteome and Metabolome Alters the Sensory Perception of Salt Taste and Odor-Active Thiols

Oral stimulation with chemosensates was found to trigger changes in the composition of the salivary proteome and metabolome, which translate into a functional modulation of odor and taste perception. Orosensory intervention with 6-gingerol induced a significant increase in the abundance of salivary sulfhydryl oxidase 1, which was found to catalyze the oxidative decline of odor-active 2-furfurylthiol, thus resulting in a decrease in the odorant levels in exhaled breath, as shown by PTR-MS, and a reduction of the perceived sulfury after-smell. Therefore, sulfhydryl oxidase 1 may be considered as a component of a molecular network triggering oral cleansing mechanisms after food ingestion. Moreover, oral stimulation with citric acid, followed by targeted metabolomics, was found to induce a strong increase in salivary concentrations of minerals and, in particular, sodium ions, whereas the other metabolites were rather unaffected. Because of the elevated basal levels of salivary sodium after citric acid stimulation, NaCl test stimuli were perceived as significantly less salty, most likely due to the decreased sensory contrast. This indicates the modulation of the salivary proteome and metabolome to be a major perireceptor event in fine-tuning odor and taste sensitivity.

Dynamic Proteome Alteration and Functional Modulation of Human Saliva Induced by Dietary Chemosensory Stimuli

Saliva flow measurements and SDS-PAGE separation of human whole saliva freshly collected after oral stimulation with citric acid (sour), aspartame (sweet), iso-α-acids (bitter), mono sodium l-glutamate (umami), NaCl (salty), 6-gingerol (pungent), hydroxy-α-sanshool (tingling), and hydroxy-β-sanshool (numbing), followed by tryptic digestion, nano-HPLC-MS/MS, and label-free protein quantitation demonstrated a stimulus- and time-dependent influence of the dietary chemosensates on salivation and the salivary proteome composition. Gene ontology enrichment analysis showed evidence for stimulus-induced alterations of the saliva proteome to boot an efficient molecular defense network of the oral cavity, e.g., 6-gingerol increased salivary lactoperoxidase activity, catalyzing the oxidation of thiocyanate to produce the antimicrobial and antifungal hypothiocyanate, from 0.37 ± 0.02 to 0.91 ± 0.05 mU/mL 45 s after stimulation. In comparison, oral citric acid stimulation induced an increase of myeloperoxidase activity, catalyzing the chloride oxidation to generate antimicrobial hypochloride in saliva, from 0.24 ± 0.04 to 0.70 ± 0.1 mU/mL as well as an increase of salivary levels of lysozyme, exhibiting antimicrobial activity on Gram-positive bacteria, from 6.0-10 to 100-150 μg/mL. Finally, microbial growth experiments clearly demonstrated for the first time that the increase of the salivary lysozyme abundance upon oral citric acid stimulation translates into an enhanced biological function, that is an almost complete growth inhibition of the two lysozyme-sensitive Gram-positive bacteria tested.

Peroxidasin contributes to lung host defense by direct binding and killing of gram-negative bacteria

Innate immune recognition is classically mediated by the interaction of host pattern-recognition receptors and pathogen-associated molecular patterns; this triggers a series of downstream signaling events that facilitate killing and elimination of invading pathogens. In this report, we provide the first evidence that peroxidasin (PXDN; also known as vascular peroxidase-1) directly binds to gram-negative bacteria and mediates bactericidal activity, thus, contributing to lung host defense. PXDN contains five leucine-rich repeats and four immunoglobulin domains, which allows for its interaction with lipopolysaccharide, a membrane component of gram-negative bacteria. Bactericidal activity of PXDN is mediated via its capacity to generate hypohalous acids. Deficiency of PXDN results in a failure to eradicate Pseudomonas aeruginosa and increased mortality in a murine model of Pseudomonas lung infection. These observations indicate that PXDN mediates previously unrecognized host defense functions against gram-negative bacterial pathogens.

Novel Two-Component System of Streptococcus sanguinis Affecting Functions Associated with Viability in Saliva and Biofilm Formation

Streptococcus sanguinis is a pioneer species of teeth and a common opportunistic pathogen of infective endocarditis. In this study, we identified a two-component system, S. sanguinis SptRS (SptRS _Ss ), affecting S. sanguinis survival in saliva and biofilm formation. Isogenic mutants of sptR_Ss (SKsptR) and sptS_Ss (SKsptS) showed reduced cell counts in ex vivo assays of viability in saliva compared to those of parent strain SK36 and complemented mutants. Reduced counts of the mutants in saliva were associated with reduced growth rates in nutrient-poor medium (RPMI) and increased susceptibility to the deposition of C3b and the membrane attach complex (MAC) of the complement system, a defense component of saliva and serum. Conversely, sptR_Ss and sptS_Ss mutants showed increased biofilm formation associated with higher levels of production of H₂O₂ and extracellular DNA. Reverse transcription-quantitative PCR (RT-qPCR) comparisons of strains indicated a global role of SptRS _Ss in repressing genes for H₂O₂ production (2.5- to 15-fold upregulation of spxB, spxR, vicR, tpk, and ackA in sptR_Ss and sptS_Ss mutants), biofilm formation, and/or evasion of host immunity (2.1- to 11.4-fold upregulation of srtA, pcsB, cwdP, iga, and nt5e). Compatible with the homology of SptR _Ss with AraC-type regulators, duplicate to multiple conserved repeats were identified in 1,000-bp regulatory regions of downstream genes, suggesting that SptR _Ss regulates transcription by DNA looping. Significant transcriptional changes in the regulatory genes vicR, spxR, comE, comX, and mecA in the sptR_Ss and sptS_Ss mutants further indicated that SptRS _Ss is part of a regulatory network that coordinates cell wall homeostasis, H₂O₂ production, and competence. This study reveals that SptRS _Ss is involved in the regulation of crucial functions for S. sanguinis persistence in the oral cavity.

Electrochemical testing of a novel alloy in natural and artificial body fluids

There is a recent trend in tissue engineering and regenerative medicine to use nanotechnology and bionanomaterials to obtain materials that mimic the surface properties of a natural tissue. From this perspective, nanolevel tissue engineering can be viewed as a novel anatomy of the future. In this paper, a novel titanium-based alloy is studied following this strategy. The alloy nanostructuration is proposed as an improved alternative for restorative prosthodontics or an implantable biomaterial. Tests in (i) standard solution of simulated body fluid (SBF) and (ii) natural saliva were performed to investigate the alloy's electrochemical stability. The results show that nanochannel growth on the alloy surface confers a higher stability than that of the untreated one in both natural and simulated environments.

The effect of saliva on the fate of nanoparticles

OBJECTIVES

The design of nanocarriers for local drug administration to the lining mucosa requires a sound knowledge of how nanoparticles (NPs) interact with saliva. This contact determines whether NPs agglomerate and become immobile due to size- and interaction-filtering effects or adsorb on the cell surface and are internalized by epithelial cells. The aim of this study was to examine the behavior of NPs in saliva considering physicochemical NP properties.

MATERIALS AND METHODS

The salivary pore-size distribution was determined, and the viscosity of the fluid inside of the pores was studied with optical tweezers. Distinct functionalized NPs (20 and 200 nm) were dispersed in saliva and salivary buffers and characterized, and surface-bound MUC5B and MUC7 were analyzed by 1D electrophoresis and immunoblotting. NP mobility was recorded, and cellular uptake studies were performed with TR146 cells.

RESULTS

The mode diameter of the salivary mesh pores is 0.7 μm with a peak width of 1.9 μm, and pores are filled with a low-viscosity fluid. The physicochemical properties of the NPs affected the colloidal stability and mobility: compared with non-functionalized particles, which did not agglomerate and showed a cellular uptake rate of 2.8%, functionalized particles were immobilized, which was correlated with agglomeration and increased binding to mucins.

CONCLUSION

The present study showed that the salivary microstructure facilitates NP adsorption. However, NP size and surface functionalization determine the colloidal stability and cellular interactions.

CLINICAL RELEVANCE

The sound knowledge of NP interactions with saliva enables the improvement of current treatment strategies for inflammatory oral diseases.

The oral microbiome

The human microbiome is receiving a great deal of attention as its role in health and disease becomes ever more apparent. The oral microbiome, perhaps due to the ease with which we can obtain samples, is arguably the most well-studied human microbiome to date. It is obvious, however, that we have only just begun to scratch the surface of the complex bacterial and bacterial–host interactions within this complex community. Here, we describe the factors which are known to influence the development of the seemingly globally conserved, core, oral microbiome and those which are likely to be responsible for the observed differences at the individual level. We discuss the paradoxical situation of maintaining a stable core microbiome which is at the same time incredibly resilient and adaptable to many different stresses encountered in the open environment of the oral cavity. Finally, we explore the interactions of the oral microbiome with the host and discuss the interactions underlying human health and disease.

Salivary proteins and microbiota as biomarkers for early childhood caries risk assessment

Early childhood caries (ECC) is a term used to describe dental caries in children aged 6 years or younger. Oral streptococci, such as Streptococcus mutans and Streptococcus sorbrinus, are considered to be the main etiological agents of tooth decay in children. Other bacteria, such as Prevotella spp. and Lactobacillus spp., and fungus, that is, Candida albicans, are related to the development and progression of ECC. Biomolecules in saliva, mainly proteins, affect the survival of oral microorganisms by multiple innate defensive mechanisms, thus modulating the oral microflora. Therefore, the protein composition of saliva can be a sensitive indicator for dental health. Resistance or susceptibility to caries may be significantly correlated with alterations in salivary protein components. Some oral microorganisms and saliva proteins may serve as useful biomarkers in predicting the risk and prognosis of caries. Current research has generated abundant information that contributes to a better understanding of the roles of microorganisms and salivary proteins in ECC occurrence and prevention. This review summarizes the microorganisms that cause caries and tooth-protective salivary proteins with their potential as functional biomarkers for ECC risk assessment. The identification of biomarkers for children at high risk of ECC is not only critical for early diagnosis but also important for preventing and treating the disease.

Reactivation of peroxidase activity in human saliva samples by polyphenols

OBJECTIVES

The enzyme lactoperoxidase (LPO), which is released into several body fluids like saliva, is an essential part to maintain the oral bacterial homeostasis by catalysing the oxidation of thiocyanate (SCN^-) to hypo-thiocyanite (^-OSCN). The formation of unreactive redox intermediates (like Compound II) leads to a decreased pseudo-halogenating enzyme activity, which is associated with a higher risk for oral infections. According to former studies with bovine LPO selected flavonoids were tested in respect to their potential to reactivate the enzymatic activity in a more physiological, human salivary system.

DESIGN

Saliva samples from healthy donors were collected and characterized by using several gel staining methods and immunoblotting. Afterwards kinetic measurements were performed by applying the TNB-assay to evaluate the pseudo-halogenating salivary peroxidase (SAPX) activity. The measurements were performed in the presence of excess H₂O₂ to simulate pro-inflammatory conditions. Moreover selected flavonoids or an ethanolic extract of Tormentillae rhizoma were applied to test their regenerating effect on the LPO-derived ^-OSCN production.

RESULTS

Despite the complex protein composition of the collected saliva samples, an SAPX-derived pseudo-halogenating activity could be identified. The ^-OSCN regenerating effects of the tested polyphenols were completely comparable to previous in vitro experiments with bovine LPO. Thus, we could show that phenolic substances are suitable to regenerate the peroxidase activity in human saliva samples after H₂O₂-induced inactivation.

CONCLUSION

The studies provide new insights into the effect of pharmaceutical relevant polyphenols on salivary peroxidase activity and thus, suggest this enzyme as a new target for the prevention and therapy of oral inflammatory diseases.

Effect of masticatory stimulation on the quantity and quality of saliva and the salivary metabolomic profile

Background

This study characterized the changes in quality and quantity of saliva, and changes in the salivary metabolomic profile, to understand the effects of masticatory stimulation.

Methods

Stimulated and unstimulated saliva samples were collected from 55 subjects and salivary hydrophilic metabolites were comprehensively quantified using capillary electrophoresis-time-of-flight mass spectrometry.

Results

In total, 137 metabolites were identified and quantified. The concentrations of 44 metabolites in stimulated saliva were significantly higher than those in unstimulated saliva. Pathway analysis identified the upregulation of the urea cycle and synthesis and degradation pathways of glycine, serine, cysteine and threonine in stimulated saliva. A principal component analysis revealed that the effect of masticatory stimulation on salivary metabolomic profiles was less dependent on sample population sex, age, and smoking. The concentrations of only 1 metabolite in unstimulated saliva, and of 3 metabolites stimulated saliva, showed significant correlation with salivary secretion volume, indicating that the salivary metabolomic profile and salivary secretion volume were independent factors.

Conclusions

Masticatory stimulation affected not only salivary secretion volume, but also metabolite concentration patterns. A low correlation between the secretion volume and these patterns supports the conclusion that the salivary metabolomic profile may be a new indicator to characterize masticatory stimulation.

Salivary peptidome profiling analysis for occurrence of new carious lesions in patients with severe early childhood caries

This study aimed to identify differences of peptide profiles in stimulated whole saliva among children with and without occurrence of new carious lesions, and to provide a simple way for early diagnosis and prevention of the relapse of severe early childhood caries (s-ECC). Overall, 26 children aged 3–4 years were selected out from all the children in the kindergarten to be involved in the present study, among them 13 were diagnosed as s-ECC and underwent dental treatment, whilst the other 13 were matched by age and sex as control. Stimulated whole saliva samples were collected before treatment, and at 10 days and 4 months after treatment. During follow-up, 7 of the 13 children with s-ECC showed a relapse, and the new carious lesions were then treated. Salivary peptides were detected using the technique of magnetic beads combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Fifteen peptides showed significant differences in the group without occurrence of new carious lesions (CH group). On comparing the CH group and the other group with occurrence of new carious lesions (CR group), no significant differences were observed before treatment, whereas certain peptides showed significant differences at both 10 days and 4 months after treatment. Two peptides (experimental m/z values: 3162.0 Da and 3290.4 Da) exhibited a consistent tendency in cross-sectional and longitudinal comparisons among these groups; these may be associated with recurrence of s-ECC. Based on our findings, it is concluded that different saliva peptide peaks can be detected in s-ECC using MALDI-TOF MS combined with magnetic beads. Moreover, 2 specific peptides with m/z values 3162.0 Da and 3290.4 Da could be promising salivary protein biomarkers for diagnosis of recurrence of s-ECC.

A New Sugarcane Cystatin Strongly Binds to Dental Enamel and Reduces Erosion

Cystatin B was recently identified as an acid-resistant protein in acquired enamel pellicle; it could therefore be included in oral products to protect against caries and erosion. However, human recombinant cystatin is very expensive, and alternatives to its use are necessary. Phytocystatins are reversible inhibitors of cysteine peptidases that are found naturally in plants. In plants, they have several biological and physiological functions, such as the regulation of endogenous processes, defense against pathogens, and response to abiotic stress. Previous studies performed by our research group have reported high inhibitory activity and potential agricultural and medical applications of several sugarcane cystatins, including CaneCPI-1, CaneCPI-2, CaneCPI-3, and CaneCPI-4. In the present study, we report the characterization of a novel sugarcane cystatin, named CaneCPI-5. This cystatin was efficiently expressed in Escherichia coli, and inhibitory assays demonstrated that it was a potent inhibitor of human cathepsins B, K, and L ( Ki = 6.87, 0.49, and 0.34 nM, respectively). The ability of CaneCPI-5 to bind to dental enamel was evaluated using atomic force microscopy. Its capacity to protect against initial enamel erosion was also tested in vitro via changes in surface hardness. CaneCPI-5 showed a very large force of interaction with enamel (e.g., compared with mucin and casein) and significantly reduced initial enamel erosion. These results suggest that the inclusion of CaneCPIs in dental products might confer protection against enamel erosion.

Unstimulated salivary flow, pH, proteins and oral health in patients with Juvenile Idiopathic Arthritis

Background

There have been inconsistent conclusions regarding salivary abnormalities and their effect on oral health of Juvenile Idiopathic Arthritis (JIA) patients. The purpose of the study was to evaluate the flow rate and selected biochemical parameters of unstimulated whole saliva in correlation to oral health in JIA children.

Methods

Thirty-four JIA patients and 34 age- and sex-matched controls not affected by JIA (C) were divided into two groups: with mixed and permanent dentition. DMFT/dmft, gingival and simplified oral hygiene indices were evaluated. Salivary flow rate, pH, lysozyme, lactoferrin, salivary protein concentrations and peroxidase activity were assessed.

Results

The salivary flow rate was significantly lower in the total JIA group (0.41 ml/min) as compared with the C (0.51 ml/min) and in the permanent dentition of JIA children (0.43 ml/min) as compared with the C (0.61 ml/min). A significantly lower pH was observed in total (6.74), mixed (6.7) and permanent (6.76) dentition of JIA groups in comparison to the C (7.25, 7.21, 7.28 respectively). The specific activity of peroxidase was significantly higher in JIA patients (total 112.72 IU/l, mixed dentition 112.98 IU/l, permanent dentition 112.5 IU/l) than in the C group (total 70.03 IU/l, mixed dentition 71.83 IU/l, permanent dentition 68.61 IU/l). The lysozyme concentration in JIA patients (total and permanent dentition groups) was significantly higher than in the C group. There were no significant differences in lactoferrin and salivary protein concentrations. There were no statistically significant differences in oral status between JIA patients and C, respectively: DMFT = 5.71, dmft = 3.73, OHI-S = 0.95, GI = 0.25 and DMFT 5.71, dmft = 3.73, OHI-S = 0.85, GI = 0.24. The specific activity of peroxidase in the unstimulated whole saliva was inversely correlated with the GI index, whereas the salivary lysozyme concentration was inversely correlated with the dmft index in JIA patients.

Conclusion

In the course of JIA occur a reduction of the resting salivary flow rate and a decrease of saliva pH. In spite of this, no differences in the clinical oral status between the JIA children population and the control group were found. The mobilisation of salivary peroxidase and lysozyme contributes to the maintenance of healthy oral tissues.

Tannins and Tannin-Related Derivatives Enhance the (Pseudo-)Halogenating Activity of Lactoperoxidase

Several hydrolyzable tannins, proanthocyanidins, tannin derivatives, and a tannin-rich plant extract of tormentil rhizome were tested for their potential to regenerate the (pseudo-)halogenating activity, i.e., the oxidation of SCN^- to hypothiocyanite ^-OSCN, of lactoperoxidase (LPO) after hydrogen peroxide-mediated enzyme inactivation. Measurements were performed using 5-thio-2-nitrobenzoic acid in the presence of tannins and related substances in order to determine kinetic parameters and to trace the LPO-mediated ^-OSCN formation. The results were combined with docking studies and molecular orbital analysis. The ^-OSCN-regenerating effect of tannin derivatives relates well with their binding properties toward LPO as well as their occupied molecular orbitals. Especially simple compounds like ellagic acid or methyl gallate and the complex plant extract were found as potent enzyme-regenerating compounds. As the (pseudo-)halogenating activity of LPO contributes to the maintenance of oral bacterial homeostasis, the results provide new insights into the antibacterial mode of action of tannins and related compounds. Furthermore, chemical properties of the tested compounds that are important for efficient enzyme-substrate interaction and regeneration of the ^-OSCN formation by LPO were identified.

Influence of saliva on the oral microbiota

Saliva plays a major role in determining the composition and activity of the oral microbiota, via a variety of mechanisms. Molecules, mainly from saliva, form a conditioning film on oral surfaces, thus providing receptors for bacterial attachment. The attached cells use saliva components, such as glycoproteins, as their main source of nutrients for growth. Oral bacteria work sequentially and in a concerted manner to catabolize these structurally complex molecules. Saliva also buffers the pH in the biofilm to around neutrality, creating an environment which is conducive to the growth of many oral bacteria that provide important benefits to the host. Components of the adaptive and innate host defences are delivered by saliva, and these often function synergistically, and at sublethal concentrations, so a complex relationship develops between the host and the resident microbiota. Dysbiosis can occur rapidly if the flow of saliva is perturbed.

Ability of salivary biomarkers in the prognostic of systemic and buccal inflammation

Nowadays, there is a growing interest in using saliva as an alternative sample for the diagnosis, prediction and progression of several diseases. It has been established that some molecules found in saliva are related to oral inflammatory processes and systemic health status. Furthermore, it is known that saliva is crucial for the carrying out of different functions in the oral cavity and its role in the local modulation of inflammatory and immune response is being thoroughly studied by the health research community. The aim of this review is to analyze the most important biomarkers which have been utilized in biomedicine during the last two decades in order to establish a correlation between certain specific salivary biomarkers and systemic inflammation. Then, we discuss the utility of total proteins, immunoglobulin A and alpha-amylase as biomarkers for the prognostic of local inflammation after oral surgery.

Key words:Inflammation, salivary biomarkers, systemic disease, buccal surgery, total proteins, inmunoglobulin A, Alpha-amylase.

Phenotype and Tissue Residency of Lymphocytes in the Murine Oral Mucosa

The oral mucosa is a critical barrier tissue that harbors a series of distinct immune cell subsets. Immune surveillance in the oral mucosa is important for both local and systemic immunity because the oral cavity is a heavily utilized route of pathogen entry and also serves as site of pathogen propagation. Nonetheless, composition and phenotype of the lymphocyte pool in the oral mucosa have remained poorly characterized. Utilizing a newly established protocol for mucosal immune cell isolation, here, we report that the oral mucosa features a unique cellular composition of immune cells, which differed not only from secondary lymphoid organs but also from mucosal tissues in the gut and lung. We observed profound accumulation of CD11b⁺Ly6C^lo monocytes in the oral mucosa that were maintained independently of T- and B-lymphocytes. Unlike the gut mucosa, the oral mucosa neither contained CD8αα T cells nor was it enriched for CD103⁺CD69⁺ tissue-resident memory CD8 T cells. In fact, a major fraction of T cells circulated and trafficked through the mucosa as revealed by treatment with the S1P1 receptor antagonist, FTY720, a potent inhibitor of lymphocyte migration. Collectively, these results provide a comprehensive picture of immune cells in the oral mucosa as an active site of lymphocyte recruitment and surveillance.

HIV Infection and Compromised Mucosal Immunity: Oral Manifestations and Systemic Inflammation

Mucosal surfaces account for the vast majority of HIV transmission. In adults, HIV transmission occurs mainly by vaginal and rectal routes but rarely via oral route. By contrast, pediatric HIV infections could be as the result of oral route by breastfeeding. As such mucosal surfaces play a crucial role in HIV acquisition, and spread of the virus depends on its ability to cross a mucosal barrier. HIV selectively infects, depletes, and/or dysregulates multiple arms of the human immune system particularly at the mucosal sites and causes substantial irreversible damage to the mucosal barriers. This leads to microbial products translocation and subsequently hyper-immune activation. Although introduction of antiretroviral therapy (ART) has led to significant reduction in morbidity and mortality of HIV-infected patients, viral replication persists. As a result, antigen presence and immune activation are linked to “inflammaging” that attributes to a pro-inflammatory environment and the accelerated aging process in HIV patients. HIV infection is also associated with the prevalence of oral mucosal infections and dysregulation of oral microbiota, both of which may compromise the oral mucosal immunity of HIV-infected individuals. In addition, impaired oral immunity in HIV infection may predispose the patients to periodontal diseases that are associated with systemic inflammation and increased risk of cardiovascular diseases. The purpose of this review is to examine existing evidence regarding the role of innate and cellular components of the oral cavity in HIV infection and how HIV infection may drive systemic hyper-immune activation in these patients. We will also discuss current knowledge on HIV oral transmission, HIV immunosenescence in relation to the oral mucosal alterations during the course of HIV infection and periodontal disease. Finally, we discuss oral manifestations associated with HIV infection and how HIV infection and ART influence the oral microbiome. Therefore, unraveling how HIV compromises the integrity of the oral mucosal tissues and innate immune components of the oral cavity and its association with induction of chronic inflammation are critical for the development of effective preventive interventions and therapeutic strategies.

HIV Infection and Compromised Mucosal Immunity: Oral Manifestations and Systemic Inflammation

Mucosal surfaces account for the vast majority of HIV transmission. In adults, HIV transmission occurs mainly by vaginal and rectal routes but rarely via oral route. By contrast, pediatric HIV infections could be as the result of oral route by breastfeeding. As such mucosal surfaces play a crucial role in HIV acquisition, and spread of the virus depends on its ability to cross a mucosal barrier. HIV selectively infects, depletes, and/or dysregulates multiple arms of the human immune system particularly at the mucosal sites and causes substantial irreversible damage to the mucosal barriers. This leads to microbial products translocation and subsequently hyper-immune activation. Although introduction of antiretroviral therapy (ART) has led to significant reduction in morbidity and mortality of HIV-infected patients, viral replication persists. As a result, antigen presence and immune activation are linked to "inflammaging" that attributes to a pro-inflammatory environment and the accelerated aging process in HIV patients. HIV infection is also associated with the prevalence of oral mucosal infections and dysregulation of oral microbiota, both of which may compromise the oral mucosal immunity of HIV-infected individuals. In addition, impaired oral immunity in HIV infection may predispose the patients to periodontal diseases that are associated with systemic inflammation and increased risk of cardiovascular diseases. The purpose of this review is to examine existing evidence regarding the role of innate and cellular components of the oral cavity in HIV infection and how HIV infection may drive systemic hyper-immune activation in these patients. We will also discuss current knowledge on HIV oral transmission, HIV immunosenescence in relation to the oral mucosal alterations during the course of HIV infection and periodontal disease. Finally, we discuss oral manifestations associated with HIV infection and how HIV infection and ART influence the oral microbiome. Therefore, unraveling how HIV compromises the integrity of the oral mucosal tissues and innate immune components of the oral cavity and its association with induction of chronic inflammation are critical for the development of effective preventive interventions and therapeutic strategies.