Antimicrobial peptides of the oral cavity

Machine learning enabled design features of antimicrobial peptides selectively targeting peri-implant disease progression

Peri-implantitis is a complex infectious disease that manifests as progressive loss of alveolar bone around the dental implants and hyper-inflammation associated with microbial dysbiosis. Using antibiotics in treating peri-implantitis is controversial because of antibiotic resistance threats, the non-selective suppression of pathogens and commensals within the microbial community, and potentially serious systemic sequelae. Therefore, conventional treatment for peri-implantitis comprises mechanical debridement by nonsurgical or surgical approaches with adjunct local microbicidal agents. Consequently, current treatment options may not prevent relapses, as the pathogens either remain unaffected or quickly re-emerge after treatment. Successful mitigation of disease progression in peri-implantitis requires a specific mode of treatment capable of targeting keystone pathogens and restoring bacterial community balance toward commensal species. Antimicrobial peptides (AMPs) hold promise as alternative therapeutics through their bacterial specificity and targeted inhibitory activity. However, peptide sequence space exhibits complex relationships such as sparse vector encoding of sequences, including combinatorial and discrete functions describing peptide antimicrobial activity. In this paper, we generated a transparent Machine Learning (ML) model that identifies sequence-function relationships based on rough set theory using simple summaries of the hydropathic features of AMPs. Comparing the hydropathic features of peptides according to their differential activity for different classes of bacteria empowered predictability of antimicrobial targeting. Enriching the sequence diversity by a genetic algorithm, we generated numerous candidate AMPs designed for selectively targeting pathogens and predicted their activity using classifying rough sets. Empirical growth inhibition data is iteratively fed back into our ML training to generate new peptides, resulting in increasingly more rigorous rules for which peptides match targeted inhibition levels for specific bacterial strains. The subsequent top scoring candidates were empirically tested for their inhibition against keystone and accessory peri-implantitis pathogens as well as an oral commensal bacterium. A novel peptide, VL-13, was confirmed to be selectively active against a keystone pathogen. Considering the continually increasing number of oral implants placed each year and the complexity of the disease progression, prevalence of peri-implant diseases continues to rise. Our approach offers transparent ML-enabled paths towards developing antimicrobial peptide-based therapies targeting the changes in the microbial communities that can beneficially impact disease progression.

Macrophages immunomodulation induced by Porphyromonas gingivalis and oral antimicrobial peptides

Porphyromonas gingivalis is a keystone pathogen associated with periodontitis development, a chronic inflammatory pathology characterized by the destruction of the supporting teeth structure. Macrophages are recruited cells in the inflammatory infiltrate from patients with periodontitis. They are activated by the P. gingivalis virulence factors arsenal, promoting an inflammatory microenvironment characterized by cytokine production (TNF-α, IL-1β, IL-6), prostaglandins, and metalloproteinases (MMPs) that foster the tissular destruction characteristic of periodontitis. Furthermore, P. gingivalis suppresses the generation of nitric oxide, a potent antimicrobial molecule, through its degradation, and incorporating its byproducts as a source of energy. Oral antimicrobial peptides can contribute to controlling the disease due to their antimicrobial and immunoregulatory activity, which allows them to maintain homeostasis in the oral cavity. This study aimed to analyze the immunopathological role of macrophages activated by P. gingivalis in periodontitis and suggested using antimicrobial peptides as therapeutic agents to treat the disease.

Physical and chemical properties of saliva and its role in Early Childhood caries - A systematic review and meta-analysis

Background

Early Childhood Caries is a chronic disease of childhood and salivary parameters are considered as one of the prime etiological factors of Early Childhood Caries.

Aim

To develop a systematic review based on the relation between physical and chemical properties of saliva and Early childhood caries by comparing children with and without Early childhood caries.

Methods

PubMed, Cochrane, Lilacs, Embase, Scopus, and additional manual search was done up to April 2021 to identify the original cross-sectional observational studies published in English. The risk of bias and quality of the included papers were assessed based on New castle Ottawa guidelines.

Results

From a total of 1709 identified studies, only 22 articles were included in this systematic review and 10 studies were qualified for meta-analysis. Eight studies were classified as ''moderate risk of bias'' and fourteen studies were classified as ''high risk of bias''.

Conclusion

There was a significant difference in physical and chemical properties of saliva in children with and without Early childhood caries. Since wide disparity were evident in available studies, further studies are needed to arrive to a definitive conclusion.

The neutralising and stimulatory effects of antimicrobial peptide LL-37 in human gingival fibroblasts

OBJECTIVES

To investigate the effects of LL-37, a broad spectrum antimicrobial peptide expressed in periodontal tissues, on human gingival fibroblast responsiveness to microbial challenge and to explore the direct effects of LL-37 on human gingival fibroblasts.

DESIGN

The effect of LL-37 on bacterial lipopolysaccharide-induced expression of Interleukin (IL-6) and chemokine C-X-C motif ligand (CXCL) 8 was determined by enzyme linked immunosorbent assay (ELISA). LL-37's influence on bacterial lipopolysaccharide-induced IκBα degradation was investigated by western blot. DNA microarray analysis initially determined the direct effects of LL-37 on gene expression, these findings were subsequently confirmed by quantitative polymerase chain reaction and ELISA analysis of selected genes.

RESULTS

Bacterial lipopolysaccharide-induced IL-6 and CXCL8 production by human gingival fibroblasts was significantly reduced in the presence of LL-37 at concentrations in the range of 1-10 µg/ml. LL-37 led to a reduction in lipopolysaccharide-induced IκBα degradation by Escherichia coli lipopolysaccharide and Porphyromonas gingivalis lipopolysaccharide (10 µg/ml). LL-37 (50 µg/ml) significantly altered the gene expression of 367 genes in human gingival fibroblasts by at least 2-fold. CXCL1, CXCL2, CXCL3, Interleukin-24 (IL-24), CXCL8, Chemokine (C-C motif) Ligand 2, and Suppressor of Cytokine Signalling 3 mRNA were significantly upregulated by LL-37. LL-37 also significantly stimulated expression of CXCL8, hepatocyte growth factor and CXCL1 at the protein level.

CONCLUSION

LL-37 plays an important regulatory role in the immunomodulatory activity of gingival fibroblasts by inhibiting lipopolysaccharide -induced expression of inflammatory cytokines and directly stimulating the expression of an array of bioactive molecules involved in inflammation and repair.

Induction of Endogenous Antimicrobial Peptides to Prevent or Treat Oral Infection and Inflammation

Antibiotics are often used to treat oral infections. Unfortunately, excessive antibiotic use can adversely alter oral microbiomes and promote the development of antibiotic-resistant microorganisms, which can be difficult to treat. An alternate approach could be to induce the local transcription and expression of endogenous oral antimicrobial peptides (AMPs). To assess the feasibility and benefits of this approach, we conducted literature searches to identify (i) the AMPs expressed in the oral cavity; (ii) the methods used to induce endogenous AMP expression; and (iii) the roles that expressed AMPs may have in regulating oral inflammation, immunity, healing, and pain. Search results identified human neutrophil peptides (HNP), human beta defensins (HBD), and cathelicidin AMP (CAMP) gene product LL-37 as prominent AMPs expressed by oral cells and tissues. HNP, HBD, and LL-37 expression can be induced by micronutrients (trace elements, elements, and vitamins), nutrients, macronutrients (mono-, di-, and polysaccharides, amino acids, pyropeptides, proteins, and fatty acids), proinflammatory agonists, thyroid hormones, and exposure to ultraviolet (UV) irradiation, red light, or near infrared radiation (NIR). Localized AMP expression can help reduce infection, inflammation, and pain and help oral tissues heal. The use of a specific inducer depends upon the overall objective. Inducing the expression of AMPs through beneficial foods would be suitable for long-term health protection. Additionally, the specialized metabolites or concentrated extracts that are utilized as dosage forms would maintain the oral and intestinal microbiome composition and control oral and intestinal infections. Inducing AMP expression using irradiation methodologies would be applicable to a specific oral treatment area in addition to controlling local infections while regulating inflammatory and healing processes.

Investigation of human β-defensins 1, 2 and 3 in human saliva by molecular dynamics

Human β-defensins present in saliva have a broad spectrum of antimicrobial activities that work against infections in oral cavity. To provide a better understanding of these molecules' properties and functions at the molecular level, we have investigated and compared the important structural properties of human β-defensin-1, -2 and -3 using molecular dynamics simulations. Our results have shown that human β-defensin-3 has a more flexible structure in water than the other two because of its high hydrophilicity, low β-sheet content and high repulsive forces between its charged residues. Moreover, we found that the location of the salt bridges is important in protein's stability in water. Molecular dynamics simulations of human β-defensins 1, 2 and 3 revealed that the hbd-3 is more flexible in water than hbd-1 and hbd-2.

Long-term prognosis of burning mouth syndrome following treatment

The purpose of this study was to evaluate the long-term prognosis of patients with burning mouth syndrome (BMS) after the termination or discontinuation of treatment and to identify the clinical characteristics that might affect that prognosis. Of 769 patients with an oral burning sensation, 202 with primary BMS who had been treated for at least 3 months were included. Among them, 28 patients who responded to the treatment and 25 patients who did not were assigned to responder and non-responder groups, respectively. Based on telephone interviews, the responders were classified into relapse and non-relapse subgroups, and the non-responder group into persistence and remission subgroups. The majority of responders reported no oral discomfort since their last visit. Compared with the non-relapse subgroup, the relapse subgroup had significantly higher levels of xerostomia at the first visit (P = 0.026) and taste disturbance at the last visit (P = 0.015). The majority of non-responders reported persistent oral discomfort since their last visit. No significant differences were found in the characteristics of oral symptoms between the persistence and remission subgroups. In conclusion, the treatment outcomes in the majority of responders and non-responders were maintained following treatment. Xerostomia and taste disturbance were associated with relapse of oral discomfort in the responders.

Antimicrobial and anti-inflammatory activity of Cystatin C on human gingival fibroblast incubated with Porphyromonas gingivalis

Background

Periodontal disease is considered one of the most prevalent chronic infectious diseases, often leading to the disruption of tooth-supporting tissues, including alveolar bone, causing tooth mobility and loss. Porphyromonas gingivalis is considered the major etiological agent of this disease, having a plethora of virulence factors, including, lipopolysaccharides (LPS), hemolysins, and proteinases. Antimicrobial peptides are one of the main components of the innate immune response that inhibit the growth of P. gingivalis. The aim of this study was to analyze the antimicrobial activity of cystatin C and to assess the effect on the inflammatory and anti-inflammatory cytokines, the production of reactive oxygen species, and in the release of nitric oxide by human gingival fibroblasts incubated with P. gingivalis in the presence and absence of cystatin C.

Methods

P. gingivalis ATCC 33277 was exposed to cystatin C for 24h and co-cultured with human gingival fibroblasts (HGFs) ATCC CRL-2014. The effect of cystatin on growth of P. gingivalis and HGFs was evaluated. Pro-inflammatory (TNFα, IL-1β) and anti-inflammatory (IL-10) cytokines were determined by ELISA in the supernatants of HGFs incubated with P. gingivalis exposed to cystatin C. Additionally, nitrites and reactive oxygen species (ROS) production were evaluated.

Results

Cystatin Cinhibited the growth of P. gingivalis without affecting HGFs. Incubation of HGFs with P. gingivalis led to a significant increase of TNF-α and IL-1β. In contrast, HGFs incubated with P. gingivalis exposed to cystatin C showed a decreased production of both cytokines, whereas IL-10 was enhanced. Incubation of HGFs with P. gingivalis led to an increase of nitric oxide (NO) and ROS production, which was reduced in the presence of the peptide.

Conclusions

Cystatin C inhibits the growth of P. gingivalis and decreases the inflammatory cytokines, ROS, and NO production during infection of HGFs with P. gingivalis. Knowledge on the antimicrobial and immunomodulatory properties of cystatin C could aid in the design of new therapeutic approaches to facilitate the elimination of this bacterium to improve the treatment of periodontal disease.

Regulation of LL-37 in Bone and Periodontium Regeneration

The goal of regenerative therapy is to restore the structure and function of the lost tissues in the fields of medicine and dentistry. However, there are some challenges in regeneration therapy such as the delivery of oxygen and nutrition, and the risk of infection in conditions such as periodontitis, osteomyelitis, etc. Leucine leucine-37 (LL-37) is a 37-residue, amphipathic, and helical peptide found only in humans and is expressed throughout the body. It has been shown to induce neovascularization and vascular endothelial growth factor (VEGF) expression. LL-37 also stimulates the migration and differentiation of mesenchymal stem cells (MSCs). Recent studies have shown that LL-37 plays an important role in the innate defense system through the elimination of pathogenic microbes and the modulation of the host immune response. LL-37 also manifests other functions such as promoting wound healing, angiogenesis, cell differentiation, and modulating apoptosis. This review summarizes the current studies on the structure, expression, and function of LL-37 and highlights the contributions of LL-37 to oral cavity, periodontium, and bone regeneration.

Could AMPs and B-cells be the missing link in understanding periodontitis?

Periodontal diseases are common inflammatory conditions characterized by bone loss in response to simultaneous bacterial aggression and host defenses. The etiology of such diseases is still not completely understood, however. It has been shown that specific pathogens involved in the build-up of dysbiotic biofilms participate actively in the establishment of periodontitis. This multifactorial pathology also depends on environmental factors and host characteristics, especially defenses. The immune response to the pathogens seems to be critical in preventing the disease from starting but also contributes to tissue damage. It is known that small molecules known as antimicrobial peptides (AMPs) are key actors in the innate immune response. They not only target microbes, but also act as immuno-modulators. They can help to recruit or activate cells such as neutrophils, monocytes, dendritic cells, or lymphocytes. AMPs have already been described in the periodontium, and their expression seems to be connected to disease activity. Alpha and beta defensins and LL37 are the AMPs most frequently linked to periodontitis. Additionally, leukocyte infiltrates, especially B-cells, have also been linked to the severity of periodontitis. Indeed, the particular subpopulations of B-cells in these infiltrates have been linked to inflammation and bone resorption. A link between B-cells and AMP could be relevant to understanding B-cells' action. Some AMP receptors, such as chemokines receptors, toll-like receptors, or purinergic receptors, have been shown to be expressed by B-cells. Consequently, the action of AMPs on B-cell subpopulations could participate to B-cell recruitment, their differentiation, and their implication in both periodontal defense and destruction.

Dental Materials for Oral Microbiota Dysbiosis: An Update

The balance or dysbiosis of the microbial community is a major factor in maintaining human health or causing disease. The unique microenvironment of the oral cavity provides optimal conditions for colonization and proliferation of microbiota, regulated through complex biological signaling systems and interactions with the host. Once the oral microbiota is out of balance, microorganisms produce virulence factors and metabolites, which will cause dental caries, periodontal disease, etc. Microbial metabolism and host immune response change the local microenvironment in turn and further promote the excessive proliferation of dominant microbes in dysbiosis. As the product of interdisciplinary development of materials science, stomatology, and biomedical engineering, oral biomaterials are playing an increasingly important role in regulating the balance of the oral microbiome and treating oral diseases. In this perspective, we discuss the mechanisms underlying the pathogenesis of oral microbiota dysbiosis and introduce emerging materials focusing on oral microbiota dysbiosis in recent years, including inorganic materials, organic materials, and some biomolecules. In addition, the limitations of the current study and possible research trends are also summarized. It is hoped that this review can provide reference and enlightenment for subsequent research on effective treatment strategies for diseases related to oral microbiota dysbiosis.

Transcriptome Analysis of Monocytes and Fibroblasts Provides Insights Into the Molecular Features of Periodontal Ehlers-Danlos Syndrome

Periodontal Ehlers–Danlos syndrome (pEDS) is a rare hereditary disorder characterized by severe early-onset periodontitis with premature tooth loss, pretibial hyperpigmentation, and skin fragility. It is caused by mutant variants in the C1R and C1S genes that result in C4 cleavage and local complement cascade activation, as well as other possible consequences. However, the exact functional consequences of this activation remain unclear. To shed light on molecular mechanisms underlying pEDS and to identify novel molecular targets that may expand treatment strategies, we performed transcriptome profiling by RNA sequencing of monocytes and gingival fibroblasts from two patients with pEDS. Compared to normal controls, differential expression of genes was found only in monocytes but not gingival fibroblasts. Most of the significant genes were enriched in biological processes such as neutrophil-mediated immunity, response to bacterium, TNF-α and IL-17 pathway which are related to inflammation response and immune response. In disease ontology enrichment analysis, genes related to periodontal host defense, inflammatory response, skin disease, and vascular development, including MMP9, VEGFA, IL10, IL1A, IL1B, IL2RA, and IL6, were significantly enriched and also validated by qPCR and ELISA. Overall, the present study provides the transcriptomic data of pEDS for the first time and the distinct molecular features in monocytes of pEDS might serve as a tool to better understand the disease.

Gingival Transcriptome of Innate Antimicrobial Factors and the Oral Microbiome With Aging and Periodontitis

The epithelial barrier at mucosal sites comprises an important mechanical protective feature of innate immunity, and is intimately involved in communicating signals of infection/tissue damage to inflammatory and immune cells in these local environments. A wide array of antimicrobial factors (AMF) exist at mucosal sites and in secretions that contribute to this innate immunity. A non-human primate model of ligature-induced periodontitis was used to explore characteristics of the antimicrobial factor transcriptome (n = 114 genes) of gingival biopsies in health, initiation and progression of periodontal lesions, and in samples with clinical resolution. Age effects and relationship of AMF to the dominant members of the oral microbiome were also evaluated. AMF could be stratified into 4 groups with high (n = 22), intermediate (n = 29), low (n = 18) and very low (n = 45) expression in healthy adult tissues. A subset of AMF were altered in healthy young, adolescent and aged samples compared with adults (e.g., APP, CCL28, DEFB113, DEFB126, FLG2, PRH1) and were affected across multiple age groups. With disease, a greater number of the AMF genes were affected in the adult and aged samples with skewing toward decreased expression, for example WDC12, PGLYRP3, FLG2, DEFB128, and DEF4A/B, with multiple age groups. Few of the AMF genes showed a >2-fold increase with disease in any age group. Selected AMF exhibited significant positive correlations across the array of AMF that varied in health and disease. In contrast, a rather limited number of the AMF significantly correlated with members of the microbiome; most prominent in healthy samples. These correlated microbes were different in younger and older samples and differed in health, disease and resolution samples. The findings supported effects of age on the expression of AMF genes in healthy gingival tissues showing a relationship to members of the oral microbiome. Furthermore, a dynamic expression of AMF genes was related to the disease process and showed similarities across the age groups, except for low/very low expressed genes that were unaffected in young samples. Targeted assessment of AMF members from this large array may provide insight into differences in disease risk and biomolecules that provide some discernment of early transition to disease.

Antimicrobial and Antibiofilm Properties of Bioceramic Materials in Endodontics

Microbes are prevalent in the root canals of necrotic teeth, and they are the cause of primary and post-treatment apical periodontitis. Bacteria can dwell within the infected root canal system as surface-adherent biofilm structures, which exhibit high resistance to antimicrobial agents. Bioceramic materials, with their biocompatible nature and excellent physico-chemical properties, have been widely used in dental applications, including endodontics. This review focuses on the application of bioceramic technology in endodontic disinfection and the antibiofilm effects of endodontic bioceramic materials. Different bioceramic materials have shown different levels of antibiofilm effects. New supplements have emerged to potentially enhance the antibiofilm properties of bioceramics aiming to achieve the goal of microbial elimination in the root canal system.

Cationic Antimicrobial Peptides Are Leading the Way to Combat Oropathogenic Infections

Oral dental infections are one of the most common diseases affecting humans, with caries and periodontal disease having the highest incidence. Caries and periodontal disease arise from infections caused by oral bacterial pathogens. Current misuse and overuse of antibiotic treatments have led to the development of antimicrobial resistance. However, recent studies have shown that cationic antimicrobial peptides are a promising family of antibacterial agents that are active against oral pathogenic bacteria and also possess less propensity for development of antimicrobial resistance. This timely Review has a focus on two primary subjects: (i) the oral bacterial pathogens associated with dental infections and (ii) the current development of antimicrobial peptides targeting oral pathogens.

Suppressive effects of gecko cathelicidin on biofilm formation and cariogenic virulence factors of Streptococcus mutans

OBJECTIVE

The aims of this study were to investigate the effectivity of gecko cathelicidin Gj-CATH2 on biofilm formation and cariogenic virulence factors of S. mutans, and preliminary explore its function mechanisms.

DESIGN

Minimum inhibitory concentration and bacterial killing kinetics assays were performed to assess the antimicrobial effect of Gj-CATH2.The influence of Gj-CATH2 on S. mutans biofilm formation was determined by crystal violet staining method and observed by SEM. The effects of Gj-CATH2 on exopolysaccharides (EPS) synthesis, bacterial aggregation, acidogenicity and aciduricity of S. mutans were also investigated. Quantitative real-time PCR was conducted to acquire the expression profile of related genes.

RESULTS

Gj-CATH2 showed strong bactericidal and anti-biofilm effects on S. mutans. SEM confirmed the reduction of the dense structure in S. mutans biofilm in Gj-CATH2-treated groups. Gj-CATH2 significantly inhibited EPS synthesis, cell aggregation, acid production of S. mutans, but showed no influence on its acid proof. Furthermore, the expression of genes related to biofilm formation (gtfB/C/D, gbpB/D), quorum sensing system (luxS and comD/E) and acidogenicity (ldh) was significantly suppressed by Gj-CATH2. Gj-CATH2 also displayed advantageous resistance in human saliva and exhibited negligible toxicity against mammalian cells.

CONCLUSIONS

Gj-CATH2 inhibited S. mutans biofilm formation by targeting the bacterial adhesion and the biofilm maturation stages. Gj-CATH2 significantly suppressed virulence factors production of S. mutans, resulting in decreased EPS synthesis and reduced acidogenicity of bacteria. These findings suggest Gj-CATH2 might be a promising agent for clinical application in prevention of dental caries.

Drug Delivery (Nano)Platforms for Oral and Dental Applications: Tissue Regeneration, Infection Control, and Cancer Management

The oral cavity and oropharynx are complex environments that are susceptible to physical, chemical, and microbiological insults. They are also common sites for pathological and cancerous changes. The effectiveness of conventional locally-administered medications against diseases affecting these oral milieus may be compromised by constant salivary flow. For systemically-administered medications, drug resistance and adverse side-effects are issues that need to be resolved. New strategies for drug delivery have been investigated over the last decade to overcome these obstacles. Synthesis of nanoparticle-containing agents that promote healing represents a quantum leap in ensuring safe, efficient drug delivery to the affected tissues. Micro/nanoencapsulants with unique structures and properties function as more favorable drug-release platforms than conventional treatment approaches. The present review provides an overview of newly-developed nanocarriers and discusses their potential applications and limitations in various fields of dentistry and oral medicine.

LL-37 and hBD-2 in the gingival crevicular fluid of smokers and nonsmokers with periodontitis

Abstract Introduction The association between smoking and periodontal diseases has been described in clinical and epidemiological studies. Objective The aim of this study was to compare the LL-37 and human β-defensin-2 (hBD-2) levels in crevicular fluid of patients with generalized periodontitis in smokers (S) and nonsmokers (NS). Material and method A total of 35 patients with generalized periodontitis stages III and IV, 15 NS (11 female, 4 male) and 20 S (7 female and 13 male), were included in the study. The evaluated clinical parameters were bleeding on probing (BOP), probing depth (PD) and clinical attachment level (CAL). Enzyme-linked immunosorbent assays were performed to quantify the LL-37 and hBD-2 levels in the gingival crevicular fluid of these patients. The results were analyzed statistically with the level of significance set at 5%. Result In relation to periodontal clinical parameters, no statistically significant difference was observed for BOP and PD between groups S and NS. There was a higher CAL in the S group than in the NS group (p = 0.0095). There was no statistically significant difference between the levels of LL-37 and hBD-2 when comparing groups S and NS (p>0.05). Conclusion It was concluded that smokers have a higher clinical attachment loss than nonsmokers, but that smoking did not influence the levels of LL-37 and hBD-2 in the gingival crevicular fluid in periodontitis.

Emerging Contact-Killing Antibacterial Strategies for Developing Anti-Biofilm Dental Polymeric Restorative Materials

Polymeric materials are the first choice for restoring tooth cavities, bonding tooth-colored fillings, sealing root canal systems, and many other dental restorative applications. However, polymeric materials are highly susceptible to bacterial attachment and colonization, leading to dental diseases. Many approaches have been investigated to minimize the formation of biofilms over polymeric restorative materials and at the tooth/material interfaces. Among them, contact-killing compounds have shown promising results to inhibit dental biofilms. Contact-killing compounds can be immobilized within the polymer structure, delivering a long-lasting effect with no leaching or release, thus providing advantages compared to release-based materials. This review discusses cutting-edge research on the development of contact-killing compounds in dental restorative materials to target oral pathogens. Contact-killing compounds in resin composite restorations, dental adhesives, root canal sealers, denture-based materials, and crown cements have all demonstrated promising antibacterial properties. Contact-killing restorative materials have been found to effectively inhibit the growth and activities of several oral pathogens related to dental caries, periodontal diseases, endodontic, and fungal infections. Further laboratory optimization and clinical trials using translational models are needed to confirm the clinical applicability of this new generation of contact-killing dental restorative materials.

Which salivary components can differentiate metabolic obesity?

Background

Obesity is a multifactorial disease and represents a global and relevant health problem. The aim of the study was to assess the concentration of pro-inflammatory cytokines (tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8)) and other selected proteins as well as enzymes (soluble intercellular adhesion molecule 1 (sICAM1), calprotectin, matrix metalloproteinase-9 (MMP-9), matrix metalloproteinase-2 (MMP-2), toll like receptor 2 (TLR2)) detectable in the saliva of women who varied in body composition. It was debated whether there are marker factors in saliva that could indicate metabolic obesity.

Methods and findings

The pilot study included 10 women with obesity (BMI>30 kg/m2) and 6 women with normal body weight (control group). The levels of TNF-α, IL-8, sICAM1, calprotectin, MMP-9, MMP-2, and TLR2 were checked by using the ELISA technique. We proved that women with metabolic obesity had significantly increased concentrations of IL-8, calprotectin, and MMP-2 in comparison with healthy subjects. Significant positive correlations of BMI with TNF-α, IL-8, and MMP-2 were observed. Similarly, the content of fat (in kg and %) in the bodies of the women correlated positively with TNF-α, IL-8, and MMP-2. Whereas, the visceral adipose tissue (VAT) correlated positively only with TNF-α and MMP-2, similarly to VAT/SAT. The WHR (waist hip ratio) was also positively correlated with TNF-α and MMP-2. Interestingly, we found that the level of insulin positively correlated with TNF- α concentration, which additionally confirmed metabolic obesity.

Conclusions

We found that positive correlations of body mass index were observed only with salivary concentrations of TNF-α, MMP-2, and IL-8. Thus, it is worth conducting a study among a larger number of people taking into account these three salivary components.

The parotid secretory protein BPIFA2 is a salivary surfactant that affects lipopolysaccharide action

NEW FINDINGS

What is the central question of this study? The salivary protein BPIFA2 binds lipopolysaccharide, but its physiological function is not known. This study uses a new knockout mouse model to explore the physiological role of BPIFA2 in the oral cavity and systemic physiology. What is the main finding and its importance? BPIFA2 is a crucial surfactant in mouse saliva. In its absence, saliva exhibits the surface tension of water. Depletion of BPIFA2 affects salivary and ingested lipopolysaccharide and leads to systemic sequelae that include increased insulin secretion and metabolomic changes. These results suggest that the lipopolysaccharide-binding activity of BPIFA2 affects the activity of ingested lipopolysaccharide in the intestine and that BPIFA2 depletion causes mild metabolic endotoxaemia.

ABSTRACT

Saliva plays important roles in the mastication, swallowing and digestion of food, speech and lubrication of the oral mucosa, antimicrobial and anti-inflammatory activities, and the control of body temperature in grooming animals. The salivary protein BPIFA [BPI fold containing family A member 2; former names: parotid secretory protein (PSP), SPLUN2 and C20orf70] is related to lipid-binding and lipopolysaccharide (LPS)-binding proteins expressed in the mucosa. Indeed, BPIFA2 binds LPS, but the physiological role of BPIFA2 remains to be determined. To address this question, Bpifa2 knockout (Bpifa2^{tm1(KOMP)Vlcg} ) (KO) mice were phenotyped, with emphasis on the saliva and salivary glands. Stimulated whole saliva collected from KO mice was less able to spread on a hydrophobic surface than wild-type saliva, and the surface tension of KO saliva was close to that of water. These data suggest that BPIFA2 is a salivary surfactant that is mainly responsible for the low surface tension of mouse saliva. The reduced surfactant activity of KO saliva did not affect consumption of dry food or grooming, but saliva from KO mice contained less LPS than wild-type saliva. Indeed, mice lacking BPIFA2 responded to ingested LPS with an increased stool frequency, suggesting that BPIFA2 plays a role in the solubilization and activity of ingested LPS. Consistent with these findings, BPIFA2-depleted mice also showed increased insulin secretion and metabolomic changes that were consistent with a mild endotoxaemia. These results support the distal physiological function of a salivary protein and reinforce the connection between oral biology and systemic disease.

The role of innate lymphoid cells in response to microbes at mucosal surfaces

Innate lymphoid cells (ILCs) are a lymphocyte population that is mostly resident at mucosal surfaces. They help to induce an appropriate immune response to the microbiome at homeostasis. In healthy people, the mucosal immune system works symbiotically with organisms that make up the microbiota. ILCs play a critical role in orchestrating this balance, as they can both influence and in turn be influenced by the microbiome. ILCs also are important regulators of the early response to infections by diverse types of pathogenic microbes at mucosal barriers. Their rapid responses initiate inflammatory programs, production of antimicrobial products and repair processes. This review will focus on the role of ILCs in response to the microbiota and to microbial infections of the lung and intestine.

Antimicrobial Effect of a Peptide Containing Novel Oral Spray on Streptococcus mutans

Objective

To investigate the antibacterial effect of a novel antimicrobial peptide containing oral spray GERM CLEAN on Streptococcus mutans (S. mutans) in vitro and further explore the related mechanisms at phenotypic and transcriptional levels.

Methods

The disk diffusion method was used to preliminarily appraise the antimicrobial effect of GERM CLEAN. The minimal inhibitory concentration (MIC) of GREM CLEAN towards S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method.

Results

The diameter (10.18 ± 1.744 mm) of inhibition zones formed by GERM CLEAN preliminarily indicated its inhibitory effect on the major cariogenic bacteria S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method. gtfB, gtfC, gtfD, and ldh were significantly repressed by treating with GERM CLEAN, and this was consistent with our phenotypic results.

Conclusion

The novel antimicrobial peptide containing oral spray GERM CLEAN has an anti-Streptococcus mutans effect and the inhibitory property may be due to suppression of the virulence factors of S. mutans including adhesive, acidogenicity, EPS, and biofilm formation.Streptococcus mutans effect and the inhibitory property may be due to suppression of the virulence factors of S. mutans including adhesive, acidogenicity, EPS, and biofilm formation.S. mutans was determined by the broth dilution method.

Antibacterial Activity of Indolicidin-Coated Silver Nanoparticles in Oral Disease

(1) Background: In dentistry, silver nanoparticles (AgNPs) have progressively earned great interest as antimicrobial drugs and are widely used in several biomedical fields. Recent progress in the analysis of complex bacterial communities has demonstrated the richness of the oral microbiota and the presence of numerous previously unexplained strains. Several efforts have been dedicated to the investigation of antimicrobial peptides (AMPs). Those peptides are a widespread group of small peptides against invading microbes. We report the production of a hybrid molecule composed of AgNPs and indolicidin, a well-known antibacterial peptide. (2) Methods: Spectroscopy and microscopy were used to analyze the optical features and to determine the size of the generated AgNPs. The AgNP antibacterial activity was evaluated versus oral Gram-positive and Gram-negative bacteria. (3) Results: The coated nanoparticles’ antibacterial activity strongly inhibited the growth of microorganisms, with very low minimum inhibitory concentration (MIC) values in the range of 5–12.5 μg/mL. We hypothesize that this effect depended on the specific characteristics of the metal surface coated with indolicidin. The second result was that the coated nanoparticles observed cellular toxicity, was lower with respect to the toxicity of peptide and the naked AgNPs when used individually. (4) New investigations regarding antimicrobial effect of AgNPs coated with AMPs in oral infections are an urgent task.

Oral Candidiasis: A Disease of Opportunity

Oral candidiasis, commonly referred to as “thrush,” is an opportunistic fungal infection that commonly affects the oral mucosa. The main causative agent, Candida albicans, is a highly versatile commensal organism that is well adapted to its human host; however, changes in the host microenvironment can promote the transition from one of commensalism to pathogen. This transition is heavily reliant on an impressive repertoire of virulence factors, most notably cell surface adhesins, proteolytic enzymes, morphologic switching, and the development of drug resistance. In the oral cavity, the co-adhesion of C. albicans with bacteria is crucial for its persistence, and a wide range of synergistic interactions with various oral species were described to enhance colonization in the host. As a frequent colonizer of the oral mucosa, the host immune response in the oral cavity is oriented toward a more tolerogenic state and, therefore, local innate immune defenses play a central role in maintaining Candida in its commensal state. Specifically, in addition to preventing Candida adherence to epithelial cells, saliva is enriched with anti-candidal peptides, considered to be part of the host innate immunity. The T helper 17 (Th17)-type adaptive immune response is mainly involved in mucosal host defenses, controlling initial growth of Candida and inhibiting subsequent tissue invasion. Animal models, most notably the mouse model of oropharyngeal candidiasis and the rat model of denture stomatitis, are instrumental in our understanding of Candida virulence factors and the factors leading to host susceptibility to infections. Given the continuing rise in development of resistance to the limited number of traditional antifungal agents, novel therapeutic strategies are directed toward identifying bioactive compounds that target pathogenic mechanisms to prevent C. albicans transition from harmless commensal to pathogen.

Effects of non-surgical periodontal therapy on inflammatory markers of psoriasis: A randomized controlled trial

AIM

The purpose of this randomized controlled clinical study was to evaluate the effect of non-surgical mechanical periodontal therapy on the inflammatory status and severity of psoriasis in subjects with psoriasis.

MATERIAL AND METHODS

The study population consisted of 92 periodontitis patients with psoriasis vulgaris suffering from an untreated periodontal disease. Two randomized groups were formed from these patients: immediate periodontal therapy (test group, n = 46) and delayed periodontal therapy (control group, n = 46). Periodontal clinical measures, on salivary interleukin 2, interleukin 6 and secretory immunoglobulin A levels and the Psoriasis Area and Severity Index (PASI) scores were evaluated at baseline and on the 8th week in control and test groups.

RESULTS

Eight weeks after completion of non-surgical periodontal therapy (test group) or initial examination (control group), a significant decrease was observed in interleukin 2, interleukin 6 level and in PASI score, whereas a significant increase was observed in secretory immunoglobulin A levels in the test group (p < .05).

CONCLUSION

Within the limits of this study, the results suggest that effective periodontal therapy improves the psoriasis condition in patients afflicted by both diseases.

Ability of S100 proteins and matrix metalloproteinase-9 to identify periodontitis in a ligature-induced periodontitis dog model

AIMS

The present study aimed to monitor the levels of selected salivary biomarkers during the development and treatment of periodontitis and to evaluate their ability to identify periodontitis in dogs.

MATERIALS AND METHODS

A total of 15 beagle dogs were divided into a control group (no ligature), group 1 (ligature on six teeth), and group 2 (ligature on 12 teeth). The experimental periods consisted of 8 weeks of periodontitis induction and 4 weeks of treatment. Clinical measurements and the sampling of saliva were performed every 4 weeks. The levels of S100A8, S100A9, S100A8/A9, and matrix metalloproteinase (MMP)-9 were measured by enzyme-linked immunosorbent assay.

RESULTS

All experimental animals and two control animals developed periodontitis, which was successfully treated. All salivary biomarkers were significantly increased in periodontitis with high diagnostic power (c-index ≥ 0.944) and were able to identify animals with periodontitis on a single tooth. Whereas the levels of salivary S100A8/A9 recovered to levels in health, those of S100A8, S100A9, and MMP-9 in periodontitis stability remained significantly higher than in health.

CONCLUSION

Salivary S100A8, S100A9, S100A8/A9, and MMP-9 may be used for the screening of periodontitis in dogs, but with caution of other conditions that can affect their levels in saliva.

Threats to adhesive/dentin interfacial integrity and next generation bio-enabled multifunctional adhesives

Nearly 100 million of the 170 million composite and amalgam restorations placed annually in the United States are replacements for failed restorations. The primary reason both composite and amalgam restorations fail is recurrent decay, for which composite restorations experience a 2.0-3.5-fold increase compared to amalgam. Recurrent decay is a pernicious problem-the standard treatment is replacement of defective composites with larger restorations that will also fail, initiating a cycle of ever-larger restorations that can lead to root canals, and eventually, to tooth loss. Unlike amalgam, composite lacks the inherent capability to seal discrepancies at the restorative material/tooth interface. The low-viscosity adhesive that bonds the composite to the tooth is intended to seal the interface, but the adhesive degrades, which can breach the composite/tooth margin. Bacteria and bacterial by-products such as acids and enzymes infiltrate the marginal gaps and the composite's inability to increase the interfacial pH facilitates cariogenic and aciduric bacterial outgrowth. Together, these characteristics encourage recurrent decay, pulpal damage, and composite failure. This review article examines key biological and physicochemical interactions involved in the failure of composite restorations and discusses innovative strategies to mitigate the negative effects of pathogens at the adhesive/dentin interface. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2466-2475, 2019.

The effect of smoking on gingival crevicular fluid peptidoglycan recognition protein-1 level following initial periodontal therapy in chronic periodontitis

OBJECTIVE

To determine the effect of smoking on peptidoglycan recognition protein (PGRP)-1 levels in gingival crevicular fluid (GCF) in smokers and non-smokers with chronic periodontitis (CP) following initial periodontal therapy.

SUBJECTS AND METHODS

A total of 40 patients with CP (20 smokers (S + CP) and 20 non-smokers (S-CP)) and 40 subjects with healthy periodontium (20 smokers (S + PH) and 20 non-smokers (S-PH)), comprising 80 subjects, were included in this study. Baseline GCF samples were obtained from all subjects, and clinical periodontal measurements were recorded. In patients who had received initial periodontal therapy, GCF samples were obtained and all clinical periodontal measurements were recorded again during the 6th-8th weeks. GCF PGRP-1 levels were analyzed by enzyme-linked immunosorbent assay.

RESULTS

At baseline, GCF PGRP-1 levels were significantly higher in both groups with CP than in both groups with healthy periodontium, whereas these levels were significantly lower in S + CP than in S-CP. GCF PGRP-1 levels decreased significantly in both CP groups after periodontal therapy, and this reduction was significantly greater in non-smokers than in smokers.

CONCLUSION

Smoking might have a suppressive effect on GCF PGRP-1 levels in CP. Initial periodontal therapy is effective in decreasing GCF PGRP-1 levels in both smokers and non-smokers with CP.

Peptide and non-peptide mimetics as potential therapeutics targeting oral bacteria and oral biofilms

The development of the oral biofilm requires a complex series of interactions between host tissues and the colonizing bacteria as well as numerous interspecies interactions between the organisms themselves. Disruption of normal host-microbe homoeostasis in the oral cavity can lead to a dysbiotic microbial community that contributes to caries or periodontal disease. A variety of approaches have been pursued to develop novel potential therapeutics that are active against the oral biofilm and/or target specific oral bacteria. The structure and function of naturally occurring antimicrobial peptides from oral tissues and secretions as well as external sources such as frog skin secretions have been exploited to develop numerous peptide mimetics and small molecule peptidomimetics that show improved antimicrobial activity, increased stability and other desirable characteristics relative to the parent peptides. In addition, a rational and minimalist approach has been developed to design small artificial peptides with amphipathic α-helical properties that exhibit potent antibacterial activity. Furthermore, with an increased understanding of the molecular mechanisms of beneficial and/or antagonistic interspecies interactions that contribute to the formation of the oral biofilm, new potential targets for therapeutic intervention have been identified and both peptide-based and small molecule mimetics have been developed that target these key components. Many of these mimetics have shown promising results in in vitro and pre-clinical testing and the initial clinical evaluation of several novel compounds has demonstrated their utility in humans.

Effect of mechanically stimulated saliva on initial human dental biofilm formation

This study evaluated the impact of mechanically stimulated saliva on initial bacterial colonization. Interaction between oral bacteria and both unstimulated and stimulated saliva was examined in vitro by laying labeled bacteria over SDS-PAGE-separated salivary proteins. The effects of chewing on in vivo biofilm, microbial composition, and spatial arrangement were examined in two human volunteers using an intraoral stent containing retrievable enamel chips. In vitro experiments showed that bacterial binding to proteins from stimulated saliva was lower than that to proteins from unstimulated saliva. Lack of binding activity was noted with Streptococcus mutans and Lactobacillus casei. Human Oral Microbe Identification Microarray (HOMIM) analyses revealed a consistent chewing-related increase in the binding of Streptococcus anginosus and Streptococcus gordonii. Immunofluorescence microscopy demonstrated the presence of multi-species colonies and cells bearing different serotypes of the coaggregation-mediating streptococcal cell-surface receptor polysaccharides (RPS). Differences in bacterial colonization were noted between the two volunteers, while the type 4 RPS-reactive serotype was absent in one volunteer. Cells reacting with antibody against Rothia or Haemophilus were prominent in the early biofilm. While analysis of the data obtained demonstrated inter-individual variations in both in vitro and in vivo bacterial binding patterns, stimulating saliva with multiple orosensory stimuli may modulate oral bacterial colonization of tooth surfaces.

Effect of scaling and root planing on gingival crevicular fluid levels of adrenomedullin in chronic periodontitis patients with and without diabetes mellitus type 2: A clinico-biochemical study

Background

Increased plasma adrenomedullin levels are usually observed in certain conditions such as diabetes mellitus (DM).

Aims and Objectives

To gauge adrenomedullin values in the gingival crevicular fluid (GCF) of healthy individuals, chronic periodontitis (CP) patients with and without DM, and diabetics without any periodontal involvement, prior and after periodontal therapy.

Materials and Methods

A total of 120 subjects were segregated into four categories of 30 each: Group 1 (healthy subjects), Group 2 (CP without DM), Group 3 (patients with CP and DM), and Group 4 (diabetics without any periodontal involvement). GCF was collected from all the patients. Nonsurgical periodontal therapy was done in Group 2 and Group 3 patients, followed up for 6 weeks, and GCF was obtained again from the same site. Enzyme-linked immunosorbent assay was used to evaluate the samples.

Results

Adrenomedullin level in the GCF was high in diabetics without any periodontal involvement than in healthy individuals and significantly elevated in those with CP and DM. Reduced adrenomedullin was noted 6 weeks postperiodontal therapy.

Conclusion

Adrenomedullin levels being higher in diabetics without any periodontal involvement than healthy controls suggest a link between DM and adrenomedullin. Furthermore, infection plays a noteworthy role in the elevation of adrenomedullin, indicating its role in periodontal disease progression.

Activity and characterization of a pH-sensitive antimicrobial peptide

Antimicrobial peptides (AMPs) have been an area of great interest, due to the high selectivity of these molecules toward bacterial targets over host cells and the limited development of bacterial resistance to these molecules throughout evolution. Previous work showed that when Histidine was incorporated into the peptide C18G it lost antimicrobial activity. The role of pH on activity and biophysical properties of the peptide was investigated to explain this phenomenon. Minimal inhibitory concentration (MIC) results demonstrated that decreased media pH increased antimicrobial activity. Trichloroethanol (TCE) quenching and red-edge excitation spectroscopy (REES) showed a clear pH dependence on peptide aggregation in solution. Trp fluorescence was used to monitor binding to lipid vesicles and demonstrated the peptide binds to anionic bilayers at all pH values tested, however, binding to zwitterionic bilayers was enhanced at pH 7 and 8 (above the His pKa). Dual Quencher Analysis (DQA) confirmed the peptide inserted more deeply in PC:PG and PE:PG membranes, but could insert into PC bilayers at pH conditions above the His pKa. Bacterial membrane permeabilization assays which showed enhanced membrane permeabilization at pH 5 and 6 but vesicle leakage assays indicate enhanced permeabilization of PC and PC:PG bilayers at neutral pH. The results indicate the ionization of the His side chain affects the aggregation state of the peptide in solution and the conformation the peptide adopts when bound to bilayers, but there are likely more subtle influences of lipid composition and properties that impact the ability of the peptide to form pores in membranes.

A tooth-binding antimicrobial peptide to prevent the formation of dental biofilm

Dental caries is primarily caused by pathogenic bacteria infection, and Streptococcus mutans is considered a major cariogenic pathogen. Moreover, antimicrobial peptides have been considered an alternative to traditional antibiotics in treating caries. This study aimed to design a tooth-binding antimicrobial peptide and evaluate its antimicrobial efficacy against S. mutans. An antimicrobial peptide of polyphemusin I (PI) was modified by grafting a tooth-binding domain of diphosphoserine (Ser(p)-Ser(p)-) to create the peptide of Ser(p)-Ser(p)-polyphemusin I (DPS-PI). PI and DPS-PI were synthesized by Fmoc solid-phase peptide synthesis. The minimum inhibitory concentration of PI and DPS-PI against S. mutans were tested. Scanning electron microscopy (SEM) were used to observe the growth of S. mutans on PI and DPS-PI treated enamel surfaces. The growth of S. mutans was evaluated by optical density (OD) at 590 nm. Inhibition of dental plaque biofilm development in vivo were investigated. The cytocompatibility to bone mesenchymal stem cells (BMSCs) was tested. The MIC of PI and DPS-PI were 40 and 80 μg/ml, respectively. SEM images showed that S. mutans were sparsely distributed on the DPS-PI treated enamel surface. OD findings indicated that DPS-PI maintained its inhibition effect on S. mutans growth after 24 h. The incisor surfaces of rabbits treated with DPS-PI developed significantly less dental plaque biofilm than that on PI treated surfaces. The DPS-PI had good biocompatibility with the cells. We successfully constructed a novel tooth-binding antimicrobial peptide against S. mutans in vitro and inhibited dental plaque biofilm development in vivo. DPS-PI may provide a feasible alternative to conventional antibiotics for the prevention and treatment of dental caries. Dental caries is primarily caused by pathogenic bacteria infection, and Streptococcus mutans is considered a major cariogenic pathogen. A tooth-binding antimicrobial peptide was designed by grafted diphosphoserine (-Ser(p)-Ser(p)-) to the structure of polyphemusin I. This novel tooth-binding antimicrobial peptide can inhibit dental plaque biofilm development and thus provide a feasible alternative to conventional antibiotics for the prevention and treatment of dental caries.

Peptide Mediated Antimicrobial Dental Adhesive System

The most common cause for dental composite failures is secondary caries due to invasive bacterial colonization of the adhesive/dentin (a/d) interface. Innate material weakness often lead to an insufficient seal between the adhesive and dentin. Consequently, bacterial by-products invade the porous a/d interface leading to material degradation and dental caries. Current approaches to achieve antibacterial properties in these materials continue to raise concerns regarding hypersensitivity and antibiotic resistance. Herein, we have developed a multi-faceted, bio-functionalized approach to overcome the vulnerability of such interfaces. An antimicrobial adhesive formulation was designed using a combination of antimicrobial peptide and a ε-polylysine resin system. Effector molecules boasting innate immunity are brought together with a biopolymer offering a two-fold biomimetic design approach. The selection of ε-polylysine was inspired due to its non-toxic nature and common use as food preservative. Biomolecular characterization and functional activity of our engineered dental adhesive formulation were assessed and the combinatorial formulation demonstrated significant antimicrobial activity against Streptococcus mutans. Our antimicrobial peptide-hydrophilic adhesive hybrid system design offers advanced, biofunctional properties at the critical a/d interface.

Human salivary proteins and their peptidomimetics: Values of function, early diagnosis, and therapeutic potential in combating dental caries

Saliva contains a large number of proteins that play various crucial roles to maintain the oral health and tooth integrity. This oral fluid is proposed to be one of the most important host factors, serving as a special medium for monitoring aspects of microorganisms, diet and host susceptibility involved in the caries process. Extensive salivary proteomic and peptidomic studies have resulted in considerable advances in the field of biomarkers discovery for dental caries. These salivary biomarkers may be exploited for the prediction, diagnosis, prognosis and treatment of dental caries, many of which could also provide the potential templates for bioactive peptides used for the biomimetic management of dental caries, rather than repairing caries lesions with artificial materials. A comprehensive understanding of the biological function of salivary proteins as well as their derived biomimetic peptides with promising potential against dental caries has been long awaited. This review overviewed a collection of current literature and addressed the majority of different functions of salivary proteins and peptides with their potential as functional biomarkers for caries risk assessment and clinical prospects for the anti-caries application.

Multi-species oral biofilm promotes reconstructed human gingiva epithelial barrier function

Since the oral mucosa is continuously exposed to abundant microbes, one of its most important defense features is a highly proliferative, thick, stratified epithelium. The cellular mechanisms responsible for this are still unknown. The aim of this study was to determine whether multi-species oral biofilm contribute to the extensive stratification and primed antimicrobial defense in epithelium. Two in vitro models were used: 3D reconstructed human gingiva (RHG) and oral bacteria representative of multi-species commensal biofilm. The organotypic RHG consists of a reconstructed stratified gingiva epithelium on a gingiva fibroblast populated hydrogel (lamina propria). Biofilm was cultured from healthy human saliva, and consists of typical commensal genera Granulicatella and major oral microbiota genera Veillonella and Streptococcus. Biofilm was applied topically to RHG and host–microbiome interactions were studied over 7 days. Compared to unexposed RHG, biofilm exposed RHG showed increased epithelial thickness, more organized stratification and increased keratinocyte proliferation. Furthermore biofilm exposure increased production of RHG anti-microbial proteins Elafin, HBD2 and HBD3 but not HBD1, adrenomedullin or cathelicidin LL-37. Inflammatory and antimicrobial cytokine secretion (IL-6, CXCL8, CXCL1, CCL20) showed an immediate and sustained increase. In conclusion, exposure of RHG to commensal oral biofilm actively contributes to RHG epithelial barrier function.

Glycan recognition at the saliva - oral microbiome interface

The mouth is a first critical interface where most potentially harmful substances or pathogens contact the host environment. Adaptive and innate immune defense mechanisms are established there to inactivate or eliminate pathogenic microbes that traverse the oral environment on the way to their target organs and tissues. Protein and glycoprotein components of saliva play a particularly important role in modulating the oral microbiota and helping with the clearance of pathogens. It has long been acknowledged that glycobiological and glycoimmunological aspects play a pivotal role in oral host-microbe, microbe-host, and microbe-microbe interactions in the mouth. In this review, we aim to delineate how glycan-mediated host defense mechanisms in the oral cavity support human health. We will describe the role of glycans attached to large molecular size salivary glycoproteins which act as a first line of primordial host defense in the human mouth. We will further discuss how glycan recognition contributes to both colonization and clearance of oral microbes.

Host defense peptides: An insight into the antimicrobial world

A serious challenge to antimicrobial therapies has emerged due to rapid increase in drug-resistant infections creating an urge for the development of alternative therapeutics. Antimicrobial peptides (AMPs) have gained importance because of their broad-spectrum antimicrobial activities and mediator-like functions linking innate and adaptive immune responses. The multidimensional properties of these peptides hold promising potentials as prophylactic and antimicrobial agents. This review discusses various AMPs and their role in combating microorganisms and infections along with its clinical implication.

Antimicrobial peptide gene expression in periodontitis patients: A pilot study

AIM

Antimicrobial peptides (AMPs) are one of the most active components of innate immunity and have characteristics that could place them at the heart of the pathogenesis of periodontal disease. This study investigated differences in the expression of AMP coding genes obtained using a simple harvesting technique, gingival smear, between two groups of patients: chronic periodontitis subjects versus healthy ones.

MATERIALS AND METHODS

Twenty-three patients were enrolled in two groups: 12 were diagnosed with moderate or severe generalized chronic periodontitis, and 11 were diagnosed as clinically healthy. Gingival smears were retrieved and studied using reverse transcription-quantitative PCR (RT-qPCR) after mRNA purification.

RESULTS

Fifteen gene expressions were obtained using real-time RT-qPCR. Three AMP genes, histatin 3 (HTN3), α-defensin 4 (DEFA4) and lysozyme C (LYZ), presented different expression levels in periodontitis patients compared with healthy subjects. The relative expression level of DEFA4 appeared to be a protective factor against periodontitis.

CONCLUSION

Gingival smears studied by RT-qPCR may be used to assess the expression of AMPs coding genes. A lack of expression of DEFA4 could be a potential indicator of periodontitis status.

Sensitivity of caries pathogens to antimicrobial peptides related to caries risk

OBJECTIVES

Antimicrobial peptides (AMPs) represent important facets of the immune system controlling infectious diseases. However, pathogens show varying susceptibilities to AMPs. This study investigates the susceptibilities of strains of Streptococcus mutans (SM), Actinomyces naeslundii (AN), and Lactobacillus spp. (LB) towards AMPs and if there are correlations between the appearance of such high-risk strains and clinical caries status.

MATERIAL AND METHODS

Plaque samples were collected from patients along with clinical examinations. Bacterial strains were identified via selective media, matrix-assisted laser desorption/ionization analysis-time of flight (MALDI-TOF), and arbitrary-primed-PCR (AP-PCR). Each strain was tested for susceptibility to LL-37, HBD-2, HNP-1, and HNP-3 or phosphate-buffered saline as negative control in a biofilm model on hydroxylapatite discs. Survival rates and resulting risk classification for each strain were determined. Correlations were calculated between the number of high-risk strains (all/S. mutans) appearing in patients and their clinical caries status.

RESULTS

Forty-seven patients were included with mean DMFT values of 11.4 ± 8.7. A total of 8 different SM, 30 LB, and 47 AN strains were detected. One-way ANOVA indicated that type/concentration of AMPs had major influence on reductions of Lactobacilli and Actinomyces. Seventeen strains of AN, 2 of SM, and 6 of LB had low susceptibilities to AMPs. The number of such strains in patients showed significant positive correlations to the DMFT values (all p = 0.001; r = 0.452; S. mutans p < 0.0001, r = 0.558).

CONCLUSION

The occurrence of low susceptible strains to AMPs seems to correlate with the individual caries status.

CLINICAL RELEVANCE

The results may lead to new ways to identify individuals with increased caries risk.

Salivary proteomics of healthy dogs: An in depth catalog

Objective

To provide an in-depth catalog of the salivary proteome and endogenous peptidome of healthy dogs, evaluate proteins and peptides with antimicrobial properties, and compare the most common salivary proteins and peptides between different breed phylogeny groups.

Methods

36 healthy dogs without evidence of periodontal disease representing four breed phylogeny groups, based upon single nucleotide polymorphism haplotypes (ancient, herding/sighthound, and two miscellaneous groups). Saliva collected from dogs was pooled by phylogeny group and analyzed using nanoscale liquid chromatography-tandem mass spectrometry. Resulting tandem mass spectra were compared to databases for identification of endogenous peptides and inferred proteins.

Results

2,491 proteins and endogenous peptides were found in the saliva of healthy dogs with no periodontal disease. All dog phylogeny groups’ saliva was rich in proteins and peptides with antimicrobial functions. The ancient breeds group was distinct in that it contained unique proteins and was missing many proteins and peptides present in the other groups.

Conclusions and clinical relevance

Using a sophisticated nanoscale liquid chromatography-tandem mass spectrometry, we were able to identify 10-fold more salivary proteins than previously reported in dogs. Seven of the top 10 most abundant proteins or peptides serve immune functions and many more with various antimicrobial mechanisms were found. This is the most comprehensive analysis of healthy canine saliva to date, and will provide the groundwork for future studies analyzing salivary proteins and endogenous peptides in disease states.

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.

Salivary Proteome Patterns Affecting Human Salt Taste Sensitivity

To investigate the role of perireceptor events in inter-individual variability in salt taste sensitivity, 31 volunteers were monitored in their detection functions for sodium chloride (NaCl) and classified into sensitive (0.6-1.7 mmol/L), medium-sensitive (1.8-6.9 mmol/L), and nonsensitive (7.0-11.2 mmol/L) subjects. Chemosensory intervention of NaCl-sensitive (S⁺) and nonsensitive (S^-) panellists with potassium chloride, ammonium chloride, and sodium gluconate showed the salt taste sensitivity to be specific for NaCl. As no significant differences were found between S⁺ and S^- subjects in salivary sodium and protein content, salivary proteome differences and their stimulus-induced dynamic changes were analyzed by tryptic digestion, iTRAQ labeling, and liquid chromatography-tandem mass spectrometry analysis. Differences in the salivary proteome between S⁺ and S^- subjects were found primarily in resting saliva and were largely independent of the dynamic alterations observed upon salt stimulation. Gene ontology enrichment analysis of key proteins, i.e., immunoglobulin heavy constant y1, myeloblastin, cathepsin G, and kallikrein, revealed significantly increased serine-type endopeptidase activity for the S⁺ group, while the S^- group exhibited augmented cysteine-type endopeptidase inhibitor activity by increased abundances in lipocalin-1 and cystatin-D, -S, and -SN, respectively. As proteases have been suggested to facilitate transepithelial sodium transport by cleaving the y-subunit of the epithelial sodium channel (ENaC) and protease inhibitors have been shown to reduce ENaC-mediated sodium transport, the differentially modulated proteolytic activity patterns observed in vivo for S⁺ and S^- subjects show evidence of them playing a crucial role in affecting human NaCl sensitivity.

The role of natural antimicrobial peptides during infection and chronic inflammation

Natural antimicrobial peptides (AMPs), a family of small polypeptides that are produced by constitutive or inducible expression in organisms, are integral components of the host innate immune system. In addition to their broad-spectrum antibacterial activity, natural AMPs also have many biological activities against fungi, viruses and parasites. Natural AMPs exert multiple immunomodulatory roles that may predominate under physiological conditions where they lose their microbicidal properties in serum and tissue environments. Increased drug resistance among microorganisms is occurring far more quickly than the discovery of new antibiotics. Natural AMPs have shown promise as 'next generation antibiotics' due to their broad-spectrum curative effects, low toxicity, the fact that they are not residual in animals, and the low rates of resistance exhibited by many pathogens. Many types of synthetic AMPs are currently being tested in clinical trials for the prevention and treatment of various diseases such as chemotherapy-associated infections, diabetic foot ulcers, catheter-related infections, and other conditions. Here, we provide an overview of the types and functions of natural AMPs and their role in combating microorganisms and different infectious and inflammatory diseases.