Antibacterial and lipopolysaccharide (LPS)-neutralising activity of human cationic antimicrobial peptides against periodontopathogens

Human β-defensins and their synthetic analogs: Natural defenders and prospective new drugs of oral health

As a family of cationic host defense peptides, human β-defensins (HBDs) are ubiquitous in the oral cavity and are mainly synthesized primarily by epithelial cells, serving as the primary barrier and aiming to prevent microbial invasion, inflammation, and disease while maintaining physiological homeostasis. In recent decades, there has been great interest in their biological functions, structure-activity relationships, mechanisms of action, and therapeutic potential in oral diseases. Meanwhile, researchers are dedicated to improving the properties of HBDs for clinical application. In this review, we first describe the classification, structural characteristics, functions, and mechanisms of HBDs. Next, we cover the role of HBDs and their synthetic analogs in oral diseases, including dental caries and pulp infections, periodontitis, peri-implantitis, fungal/viral infections and oral mucosal diseases, and oral squamous cell carcinoma. Finally, we discuss the limitations and challenges of clinical translation of HBDs and their synthetic analogs, including, but not limited to, stability, bioavailability, antimicrobial activity, resistance, and toxicity. Above all, this review summarizes the biological functions, mechanisms of action, and therapeutic potential of both natural HBDs and their synthetic analogs in oral diseases, as well as the challenges associated with clinical translation, thus providing substantial insights into the laboratory development and clinical application of HBDs in oral diseases.

Applications of peptides in nanosystems for diagnosing and managing bacterial sepsis

Sepsis represents a critical medical condition stemming from an imbalanced host immune response to infections, which is linked to a significant burden of disease. Despite substantial efforts in laboratory and clinical research, sepsis remains a prominent contributor to mortality worldwide. Nanotechnology presents innovative opportunities for the advancement of sepsis diagnosis and treatment. Due to their unique properties, including diversity, ease of synthesis, biocompatibility, high specificity, and excellent pharmacological efficacy, peptides hold great potential as part of nanotechnology approaches against sepsis. Herein, we present a comprehensive and up-to-date review of the applications of peptides in nanosystems for combating sepsis, with the potential to expedite diagnosis and enhance management outcomes. Firstly, sepsis pathophysiology, antisepsis drug targets, current modalities in management and diagnosis with their limitations, and the potential of peptides to advance the diagnosis and management of sepsis have been adequately addressed. The applications have been organized into diagnostic or managing applications, with the last one being further sub-organized into nano-delivered bioactive peptides with antimicrobial or anti-inflammatory activity, peptides as targeting moieties on the surface of nanosystems against sepsis, and peptides as nanocarriers for antisepsis agents. The studies have been grouped thematically and discussed, emphasizing the constructed nanosystem, physicochemical properties, and peptide-imparted enhancement in diagnostic and therapeutic efficacy. The strengths, limitations, and research gaps in each section have been elaborated. Finally, current challenges and potential future paths to enhance the use of peptides in nanosystems for combating sepsis have been deliberately spotlighted. This review reaffirms peptides' potential as promising biomaterials within nanotechnology strategies aimed at improving sepsis diagnosis and management.

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.

Effect of Processing Methods of Human Saliva on the Proteomic Profile and Protein-Mediated Biological Processes

The use of saliva as a protein source prior to microbiological and biological assays requires previous processing. However, the effect of these processing methods on the proteomic profile of saliva has not been tested. Stimulated human saliva was collected from eight healthy volunteers. Non-processed saliva was compared with 0.22 μm filtered, 0.45 μm filtered, and pasteurized saliva, by liquid chromatography-mass spectrometry. Data are available via ProteomeXchange with identifier PXD039248. The effect of processed saliva on microbial adhesion was tested using bacterial and fungus species and in biological cell behavior using HaCaT immortalized human keratinocytes. Two hundred and seventy-eight proteins were identified in non-processed saliva, of which 54 proteins (≈19%) were exclusive. Saliva processing reduced identified proteins to 222 (≈80%) for the 0.22 μm group, 219 (≈79%) for the 0.45 μm group, and 201 (≈72%) for the pasteurized saliva, compared to non-processed saliva. The proteomic profile showed similar molecular functions and biological processes. The different saliva processing methods did not alter microbial adhesion (ANOVA, p > 0.05). Interestingly, pasteurized saliva reduced keratinocyte cell viability. Saliva processing methods tested reduced the proteomic profile diversity of saliva but maintained similar molecular functions and biological processes, not interfering with microbial adhesion and cell viability, except for pasteurization, which reduced cell viability.

Prevotella: An insight into its characteristics and associated virulence factors

Prevotella species, a gram-negative obligate anaerobe, is commonly associated with human infections such as dental caries and periodontitis, as well as other conditions such as chronic osteomyelitis, bite-related infections, rheumatoid arthritis and intestinal diseases like ulcerative colitis. This generally harmless commensal possesses virulence factors such as adhesins, hemolysins, secretion systems exopolysaccharide, LPS, proteases, quorum sensing molecules and antibiotic resistance to evolve into a well-adapted pathogen capable of causing successful infection and proliferation in the host tissue. This review describes several of these virulence factors and their advantage to Prevotella spp. in causing inflammatory diseases like periodontitis. In addition, using genome analysis of Prevotella reference strains, we examined other putative virulence determinants which can provide insights as biomarkers and be the targets for effective interventions in Prevotella related diseases like periodontitis.

FM-CATH, A Novel Cathelicidin From Fejervarya Multistriata, Shows Therapeutic Potential for Treatment of CLP-Induced Sepsis

Sepsis is an exacerbated inflammatory reaction induced by severe infection. As important defensive molecules in innate immunity, several AMPs are reported to prevent septic shock. In this study, we characterized a novel cathelicidin, FM-CATH, from the frog skin of F. multistriata. FM-CATH was found to adopt an amphipathic α-helix structural in membrane-mimetic environments and possess favorable antimicrobial effects against bacteria and fungus. In addition, it triggered the agglutination of bacteria. It could also strongly bind to LPS and LTA. Additionally, FM-CATH affected the enzymatic activities of thrombin, plasmin, β-tryptase, and tPA, leading to coagulation inhibition in vitro and in vivo. Finally, we observed that FM-CATH improved survival rate and inhibited pathological alteration, bacterial count, serum biochemistry, and pro-inflammatory cytokine expression in the cecal ligation and puncture-induced sepsis mice. Taken together, these findings suggest that FM-CATH might be served as a promising agent for the treatment of sepsis.

Bacterial-Specific Aggregation and Killing of Immunomodulatory Host Defense Peptides

This study involves the design and development of disulfide bridge-linked antimicrobial peptides using the host defense protein Angiogenin 4 (chAng4) as a template. The mini peptides derived from chAng4 (mCA4s) were evaluated for their antibacterial efficacies in various pathogenic bacterial strains, and the role of the oxidation state of thiols in the peptide sequence and its implication on antibacterial properties were explored. A remarkable property of these synthetic mCA4 peptides is their capability to flocculate bacteria and mediate bacterial-specific killing, in the absence of any other external stimulus. mCA4s were further evaluated for their cellular uptake, hemolytic activities, toxicities, and immunomodulatory activities in different eukaryotic cell lines. The results indicate that disulfide bridge-containing cationic amphipathic peptides show superior antibacterial efficacies, are nontoxic and nonhemolytic, and mediate bacterial flocculation and killing, in the absence of external stimuli.

Rational Design of Dipicolylamine-Containing Carbazole Amphiphiles Combined with Zn2+ as Potent Broad-Spectrum Antibacterial Agents with a Membrane-Disruptive Mechanism

Antibiotic resistance has become one of the most urgently important problems facing healthcare providers. A novel series of dipicolylamine-containing carbazole amphiphiles with strong Zn²⁺ chelating ability were synthesized, biomimicking cationic antimicrobial peptides. Effective broad-spectrum 16 combined with 12.5 μg/mL Zn²⁺ was identified as the most promising antimicrobial candidate. 16 combined with 12.5 μg/mL Zn²⁺ exhibited excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria (MICs = 0.78-3.125 μg/mL), weak hemolytic activity, and low cytotoxicity. Time-kill kinetics and mechanism studies revealed 16 combined with 12.5 μg/mL Zn²⁺ had rapid bacterial killing properties, as evidenced by disruption of the integrity of bacterial cell membranes, effectively preventing bacterial resistance development. Importantly, 16 combined with 12.5 μg/mL Zn²⁺ showed excellent in vivo efficacy in a murine keratitis model caused by Staphylococcus aureus ATCC29213 or Pseudomonas aeruginosa ATCC9027. Therefore, 16 combined with 12.5 μg/mL Zn²⁺ could be a promising candidate for treating bacterial infections.

Antimicrobial Peptides: A New Hope in Biomedical and Pharmaceutical Fields

Antibiotics are essential drugs used to treat pathogenic bacteria, but their prolonged use contributes to the development and spread of drug-resistant microorganisms. Antibiotic resistance is a serious challenge and has led to the need for new alternative molecules less prone to bacterial resistance. Antimicrobial peptides (AMPs) have aroused great interest as potential next-generation antibiotics, since they are bioactive small proteins, naturally produced by all living organisms, and representing the first line of defense against fungi, viruses and bacteria. AMPs are commonly classified according to their sources, which are represented by microorganisms, plants and animals, as well as to their secondary structure, their biosynthesis and their mechanism of action. They find application in different fields such as agriculture, food industry and medicine, on which we focused our attention in this review. Particularly, we examined AMP potential applicability in wound healing, skin infections and metabolic syndrome, considering their ability to act as potential Angiotensin-Converting Enzyme I and pancreatic lipase inhibitory peptides as well as antioxidant peptides. Moreover, we argued about the pharmacokinetic and pharmacodynamic approaches to develop new antibiotics, the drug development strategies and the formulation approaches which need to be taken into account in developing clinically suitable AMP applications.

Characteristics of Treponema denticola lipooligosaccharide in presence of hemin and quorum-sensing molecule

OBJECTIVES

The study aimed to examine the diverse bioactivity of lipooligosaccharide extracted from T. denticola cultured in the presence of hemin and quorum-sensing inhibitor.

DESIGN

T. denticola was cultured in the presence or absence hemin or 2(5 H)-furanone, and lipooligosaccharide from T. denticola cultured in various conditions was extracted using an extraction kit. To investigate bioactivity of the lipooligosaccharide, human gingival fibroblasts (HGFs) were treated with the extracted lipooligosaccharide in the presence or absence of Tannerella forsythia lipopolysaccharide. The induction of cytokine expressions was investigated by real-time RT-PCR and ELISA, and the signaling pathway was examined by immunoblotting. To investigate antagonistic mechanisms of the lipooligosaccharide, HGFs were cotreated with fluorescence-labeled T. forsythia lipopolysaccharide and the extracted lipooligosaccharide. Binding of T. forsythia lipopolysaccharide to the cell was analyzed by a flow cytometer.

RESULTS

Lipooligosaccharide induced a low level of cytokine expression at high concentration of hemin or 2(5 H)-furanone. Lipooligosaccharide extracted from T. denticola cultured in higher concentration of hemin and 2(5 H)-furanone had a greater inhibitory effect on induction of cytokine expression by T. forsythia lipopolysaccharide. Further, lipooligosaccharide inhibited the activation of NF-κB and mitogen-activated protein kinase signaling pathways by T. forsythia lipopolysaccharide. Lipooligosaccharide inhibited the binding of T. forsythia lipopolysaccharide to HGFs in the presence of CD14 and LBP.

CONCLUSIONS

The characteristics of T. denticola lipooligosaccharide may be altered by bacterial communication and host factors.

Therapeutic Potential of Antimicrobial Peptides in Polymicrobial Biofilm-Associated Infections

It is widely recognized that many chronic infections of the human body have a polymicrobial etiology. These include diabetic foot ulcer infections, lung infections in cystic fibrosis patients, periodontitis, otitis, urinary tract infections and even a proportion of systemic infections. The treatment of mixed infections poses serious challenges in the clinic. First, polymicrobial communities of microorganisms often organize themselves as biofilms that are notoriously recalcitrant to antimicrobial therapy and clearance by the host immune system. Secondly, a plethora of interactions among community members may affect the expression of virulence factors and the susceptibility to antimicrobials of individual species in the community. Therefore, new strategies able to target multiple pathogens in mixed populations need to be urgently developed and evaluated. In this regard, antimicrobial or host defense peptides (AMPs) deserve particular attention as they are endowed with many favorable features that may serve to this end. The aim of the present review is to offer a comprehensive and updated overview of studies addressing the therapeutic potential of AMPs in mixed infections, highlighting the opportunities offered by this class of antimicrobials in the fight against polymicrobial infections, but also the limits that may arise in their use for this type of application.

Human β-defensin-3 participates in intra-amniotic host defense in women with labor at term, spontaneous preterm labor and intact membranes, and preterm prelabor rupture of membranes

Objective: Human β-defensin-3 (HBD-3) has a broad spectrum of antimicrobial activity, and activity and, therefore, plays a central role in host defense mechanisms against infection. Herein, we determined whether HBD-3 was a physiological constituent of amniotic fluid during midtrimester and at term and whether the concentration of this defensin was increased in amniotic fluid of women with spontaneous preterm labor and intact membranes and those with preterm prelabor rupture of membranes (pPROM) with intra-amniotic inflammation or intra-amniotic infection.Methods: Amniotic fluid was collected from 219 women in the following groups: (1) midtrimester who delivered at term (n = 35); (2) with or without spontaneous labor at term (n = 50); (3) spontaneous preterm labor with intact membranes who delivered at term (n = 29); (4) spontaneous preterm labor with intact membranes who delivered preterm with or without intra-amniotic inflammation or intra-amniotic infection (n = 69); and (5) pPROM with or without intra-amniotic infection (n = 36). Amniotic fluid HBD-3 concentrations were determined using a sensitive and specific ELISA kit.Results: (1) HBD-3 is a physiological constituent of amniotic fluid; (2) the amniotic fluid concentration of HBD-3 did not change with gestational age (midtrimester versus term not in labor); (3) amniotic fluid concentrations of HBD-3 were higher in women with spontaneous labor at term than in those without labor; (4) in the absence of intra-amniotic inflammation, amniotic fluid concentrations of HBD-3 were similar between women with spontaneous preterm labor who delivered preterm and those who delivered at term; (5) among patients with spontaneous preterm labor who delivered preterm, amniotic fluid concentrations of HBD-3 were greater in women with intra-amniotic infection than in those without this clinical condition; (6) among patients with spontaneous preterm labor, amniotic fluid concentrations of HBD-3 were higher in women with intra-amniotic inflammation or intra-amniotic infection who delivered preterm than in those without these clinical conditions who delivered at term; and (7) women with pPROM and intra-amniotic infection had higher median amniotic fluid concentrations of HBD-3 than those without this clinical condition.Conclusion: Human β-defensin-3 is a physiological constituent of amniotic fluid and increases during the process of labor at term. Amniotic fluid concentrations of HBD-3 were increased in women with spontaneous preterm labor with intact membranes or pPROM with intra-amniotic inflammation or intra-amniotic infection, indicating that this defensin participates in the host defense mechanisms in the amniotic cavity against microorganisms or danger signals. These findings provide insight into the soluble host defense mechanisms against intra-amniotic inflammation and intra-amniotic infection.

Association between genetic polymorphisms in the promoter region of the defensin beta 1 gene and persistent apical periodontitis

AIM

To evaluate the association between the promoter region of defensin beta 1 (DEFB1) genetic polymorphisms and persistent apical periodontitis (PAP) in Brazilian patients.

METHODOLOGY

Seventy-three patients with post-treatment PAP (PAP group) and 89 patients with root filled teeth with healed and healthy periradicular tissues (healed group) were included (all teeth had apical periodontitis lesions at the beginning of the treatment). Patients who had undergone at least 1 year of follow-up after root canal treatment were recalled, and their genomic DNA was extracted from saliva. Two single nucleotide polymorphisms (SNPs) in DEFB1 at the g. -52G>A (rs1799946) and g. -20G>A (rs11362) positions were analysed using real-time polymerase chain reaction. The chi-squared test was performed, and the odds ratios were calculated using Epi Info 3.5.2. Logistic regression analysis in the codominant model, using the time of follow-up as a variable, was used to evaluate the SNP-SNP interaction. All tests were performed with an established alpha of 0.05 (P = 0.05).

RESULTS

For the rs11362 polymorphism in the codominant and recessive models, patients who carried two copies of the T allele had a significantly lower risk of developing PAP (P = 0.040 and P = 0.031, respectively). For the rs1799946 polymorphism in DEFB1 in the codominant and recessive models, carrying one copy of the T allele significantly increased the risk of developing PAP (P = 0.007 and P = 0.031, respectively). In the logistic regression, both polymorphisms were associated with PAP as well as the SNP-SNP interaction (P < 0.0001).

CONCLUSIONS

Polymorphisms in DEFB1 genes were associated with the development of post-treatment persistent apical periodontitis.

Comparison of gingival crevicular fluid and serum human beta-defensin-2 levels between periodontal health and disease

BACKGROUND

The aim of this study was to evaluate the levels of serum and gingival crevicular fluid (GCF) human beta-defensin-2 (hBD-2), an antimicrobial peptide that takes roles in inflammatory diseases, in patients with chronic periodontitis (CP).

SUBJECTS AND METHODS

A total of one hundred and one individuals, 59 controls and 42 patients with CP, participated in this study. Clinical index measurements were recorded during the periodontal examination, and radiographic evaluation was also performed. The serum and gingival crevicular fluid (GCF) samples were taken from all of the participants, and the hBD-2 levels were determined biochemically by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In our study, hBD-2 GCF levels in CP (stages II-IV periodontitis based on the new 2018 classification of periodontal diseases) group (2.77 ng/30 s) were higher than in the periodontally healthy (2.51 ng/30 s; p = .047) individuals. In contrast, serum hBD-2 levels in CP (2.92 ng/ml) were lower compared with those in healthy controls (7.75 ng/ml, p < .001).

CONCLUSION

Interestingly, our results showed that while higher hBD-2 GCF levels are associated with CP, lower serum hBD-2 levels were detected in CP.

Escherichia coli Lipopolysaccharide Modulates Biological Activities of Human-β-Defensin Analogues but Not Non-Ribosomally Synthesized Peptides

Human-β-defensins (HBD1-3) are antibacterial peptides containing three disulphide bonds. In the present study, the effect of Escherichia coli lipopolysaccharide (LPS) on the antibacterial activities of HBD2-3, C-terminal analogues having a single disulphide bond, Phd1-3, and their corresponding myristoylated analogues MPhd1-3 were investigated. The effect of LPS on the activities of linear amphipathic peptides melittin, LL37 and non-ribosomally synthesized peptides, polymyxin B, alamethicin, gramicidin A, and gramicidin S was also examined. The antibacterial activity of HBD 2-3, Phd1-3, and MPhd1-3 in the presence of LPS against E. coli and Staphylococcus aureus was inhibited. While LPS inhibited the antibacterial activity of LL37, the inhibition of melittin activity was partial. The hemolytic activity exhibited by MPhd1, MPhd3, melittin, and LL37 was inhibited in the presence of LPS. HBD2-3, Phd1-3, and MPhd1-3 also showed endotoxin neutralizing activity. The antibacterial and hemolytic activities of polymyxin B, alamethicin, gramicidin A, and gramicidin S were not inhibited in the presence of LPS. Fluorescence assays employing dansyl cadaverine showed that HBD2-3 and defensin analogues bind to LPS more strongly as compared to alamethicin, gramicidin A, and gramicidin S. Electron microscopy images indicated that peptides disintegrate the structure of LPS. The inhibition of the antibacterial activity of native defensins and analogues in the presence of LPS indicates that the initial interaction with the bacterial surface is similar. The native defensin sequence or structure is also not essential, although cationic charges are necessary for binding to LPS. Hydrophobic interaction is the main driving force for association of non-ribosomally synthesized polymyxin B, alamethicin, gramicidin A, and gramicidin S with LPS. It is likely that these peptides rapidly insert into membranes and do not interact with the bacterial cell surface, whereas cationic peptides such as β-defensin and their analogues, melittin and LL37, first interact with the bacterial cell surface and then the membrane. Our results suggest that evaluating interaction of antibacterial and hemolytic peptides with LPS is a compelling way of elucidating the mechanism of bacterial killing or hemolysis.

Endodontic biofilms: contemporary and future treatment options

Apical periodontitis is a biofilm-mediated infection. The biofilm protects bacteria from host defenses and increase their resistance to intracanal disinfecting protocols. Understanding the virulence of these endodontic microbiota within biofilm is essential for the development of novel therapeutic procedures for intracanal disinfection. Both the disruption of biofilms and the killing of their bacteria are necessary to effectively treat apical periodontitis. Accordingly, a review of endodontic biofilm types, antimicrobial resistance mechanisms, and current and future therapeutic procedures for endodontic biofilm is provided.

Antimicrobial Peptides and Nanotechnology, Recent Advances and Challenges

Antimicrobial peptides are sequences of amino acids, which present activity against microorganisms. These peptides were discovered over 70 years ago, and are abundant in nature from soil bacteria, insects, amphibians to mammals and plants. They vary in amino acids number, the distance between amino acids within individual peptide structure, net charge, solubility and other physical chemical properties as well as differ in mechanism of action. These peptides may provide an alternative treatment to conventional antibiotics, which encounter resistance such as the peptide nisin applied in treating methicillin resistant Staphylococcus aureus (MRSA) or may behave synergistically with known antibiotics against parasites for instance, nisin Z when used in synergy with ampicillin reported better activity against Pseudomonas fluorescens than when the antibiotic was alone. AMPs are known to be active against viruses, bacteria, fungi and protozoans. Nanotechnology is an arena which explores the synthesis, characterization and application of an array of delivery systems at a one billionth of meter scale. Such systems are implemented to deliver drugs, proteins, vaccines, and peptides. The role of nanotechnology in delivering AMPs is still at its early development stage. There are challenges of incorporating AMPs into drug delivery system. This review intends to explore in depth, the role of nanotechnology in delivering AMPs as well as presenting the current advances and accompanying challenges of the technology.

Beta-defensin 1, aryl hydrocarbon receptor and plasma kynurenine in major depressive disorder: metabolomics-informed genomics

Major depressive disorder (MDD) is a heterogeneous disease. Efforts to identify biomarkers for sub-classifying MDD and antidepressant therapy by genome-wide association studies (GWAS) alone have generally yielded disappointing results. We applied a metabolomics-informed genomic research strategy to study the contribution of genetic variation to MDD pathophysiology by assaying 31 metabolites, including compounds from the tryptophan, tyrosine, and purine pathways, in plasma samples from 290 MDD patients. Associations of metabolite concentrations with depressive symptoms were determined, followed by GWAS for selected metabolites and functional validation studies of the genes identified. Kynurenine (KYN), the baseline plasma metabolite that was most highly associated with depressive symptoms, was negatively correlated with severity of those symptoms. GWAS for baseline plasma KYN concentrations identified SNPs across the beta-defensin 1 (DEFB1) and aryl hydrocarbon receptor (AHR) genes that were cis-expression quantitative trait loci (eQTLs) for DEFB1 and AHR mRNA expression, respectively. Furthermore, the DEFB1 locus was associated with severity of MDD symptoms in a larger cohort of 803 MDD patients. Functional studies demonstrated that DEFB1 could neutralize lipopolysaccharide-stimulated expression of KYN-biosynthesizing enzymes in monocytic cells, resulting in altered KYN concentrations in the culture media. In addition, we demonstrated that AHR was involved in regulating the expression of enzymes in the KYN pathway and altered KYN biosynthesis in cell lines of hepatocyte and astrocyte origin. In conclusion, these studies identified SNPs that were cis-eQTLs for DEFB1 and AHR and, which were associated with variation in plasma KYN concentrations that were related to severity of MDD symptoms.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

Transplantation of periodontal ligament cell sheets expressing human β‑defensin‑3 promotes anti‑inflammation in a canine model of periodontitis

Periodontitis is a chronic oral inflammatory disease caused by microorganisms. Human β-defensin-3 (HBD-3) is an endogenous antimicrobial peptide that inhibits a broad spectrum of microorganisms. Cell sheet technology has been widely applied in tissue and organ reconstructions. In the current study, it was aimed to investigate the anti-inflammatory effect of periodontal tissue engineered by HBD-3 gene-modified periodontal ligament cell (PDLC) sheets, and to identify a suitable method of promoting the regeneration of periodontal tissues. Western blot analysis and antimicrobial tests were used to confirm the expression of HBD-3. The effect of the cell sheets on anti-inflammatory activity and bone remodeling in a dog model of periodontitis was demonstrated by immunohistochemistry. The results demonstrated that the transfected PDLCs stably expressed HBD-3. Periodontal pathogens were susceptible to the antimicrobial activity of the cell sheets. In addition, the cell sheets relieved the bone resorption caused by inflammation in the in vivo model. HBD-3 may potentially be applied in the treatment of periodontitis and may function as osteogenic promoter via its anti-inflammatory effect.

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.

The Effect of Nonsurgical Periodontal Therapy on HNP1-3 Level in Gingival Crevicular Fluid of Chronic Periodontitis Patients

The rich bacterial flora of oral cavity is controlled by innate immune response, including antibacterial peptides and among them human neutrophil peptides 1–3 (HNP1-3). The knowledge of the involvement of HNPs in innate and acquired immunity of the periodontium is fragmentary. The aim of the study was to assess alterations in HNP1-3 levels in the gingival crevicular fluid (GCF) of chronic periodontitis patients before and after nonsurgical periodontal therapy. Nineteen patients with chronic periodontitis were qualified to the study. After periodontal examination, one site with pocket depth (PD) ≥4 mm was selected. All the patients received periodontal treatment involving scaling and root planing with additional systemic antibiotic therapy (Amoxicillin 375 mg three times daily and Metronidazole 250 mg three times daily for 7 days). Prior to therapy, 3 and 6 months after it, clinical periodontal parameters were measured and GCF was collected from previously chosen site. The level of HNP1-3 in GCF was determined by means of a commercially available enzyme-linked immunoassay kit. The periodontal therapy caused a statistically significant (p < 0.001) decrease in all the assessed clinical parameters at the sites of sample collection except for bleeding on probing. The level of HNP1-3 per measure point showed a statistically significant increase (baseline—3 months: p = 0.05, baseline—6 months: p = 0.007). Within the limits of the study, it can be stated that nonsurgical periodontal therapy with additional systemic administration of Amoxicillin and Metronidazole increases the level of HNP1-3 in GCF.

LL-37-derived membrane-active FK-13 analogs possessing cell selectivity, anti-biofilm activity and synergy with chloramphenicol and anti-inflammatory activity

Although the human-derived antimicrobial peptide (AMP) LL-37 has potent antimicrobial and anti-inflammatory activities, its therapeutic application is limited by its low cell selectivity and high production cost due to its large size. To overcome these problems, we tried to develop novel LL-37-derived short α-helical AMPs with improved cell selectivity and without a significant loss of anti-inflammatory activity relative to that of parental LL-37. Using amino acid substitution, we designed and synthesized a series of FK13 analogs based on the sequence of the 13-meric short FK13 peptide (residues 17-29 of LL-37) that has been identified as the region responsible for the antimicrobial activity of LL-37. Among the designed FK13 analogs, FK-13-a1 and FK-13-a7 showed high cell selectivity and retained the anti-inflammatory activity. The therapeutic index (a measure of cell selectivity) of FK-13-a1 and FK-13-a7 was 6.3- and 2.3-fold that of parental LL-37, respectively. Furthermore, FK-13-a1 and FK-13-a7 displayed more potent antimicrobial activity against antibiotic-resistant bacteria including MRSA, MDRPA, and VREF, than did LL-37. In addition, FK-13-a1 and FK-13-a7 exhibited greater synergistic effects with chloramphenicol against MRSA and MDRPA and were more effective anti-biofilm agents against MDRPA than LL-37 was. Moreover, FK-13-a1 and FK-13-a7 maintained their activities in the presence of physiological salts and human serum. SYTOX green uptake, membrane depolarization and killing kinetics revealed that FK13-a1 and FK13-a7 kills microbial cells by permeabilizing the cell membrane and damaging membrane integrity. Taken together, our results suggest that FK13-a1 and FK13-a7 can be developed as novel antimicrobial/anti-inflammatory agents.

β-defensin 3 modulates macrophage activation and orientation during acute inflammatory response to Porphyromonas gingivalis lipopolysaccharide

β-defensin 3, a multifunctional antimicrobial peptide, has immuno-regulatory activities. We investigated the modulatory mechanism of human β-defensin 3 (hBD3) on acute inflammatory response resulted from Porphyromonas gingivalis lipopolysaccharide (P.g-LPS), which plays a pro-inflammatory role in periodontal infection and its derived systemic inflammation. P.g-LPS was administrated to mice and murine macrophages alone or along with hBD3. P.g-LPS could lead to acute inflammation as soon as 2h. And it was observed that hBD3 significantly decreased the production of pro-inflammatory biomarkers of in response to P.g-LPS in vivo and in vitro in the early stage. Interestingly, although hBD3 as well as P.g-LPS stimulated the expression of TLR2 mRNA in macrophages in this study, hBD3 exhibited suppressive effect on the downstream NF-κB signaling pathway activated by P.g-LPS. And above all, hBD3 could polarize macrophages into M2 phenotype and this contributed to its anti-inflammatory property. These results indicated that hBD3 could have therapeutic effect on systemic inflammation associated with periodontal infections via modulating macrophage activation and orientation.

Human β-defensin 3 suppresses Porphyromonas gingivalis lipopolysaccharide-induced inflammation in RAW 264.7 cells and aortas of ApoE-deficient mice

Human beta-defensin 3 (hBD3) is an antimicrobial peptide showing immunomodulatory effect on both innate and acquired immune response. Atherosclerosis is an inflammatory disease characterized by accumulation of lipids in the vascular wall. In this study, we evaluated whether hBD3 could attenuate the atherosclerosis development accelerated by Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) with apolipoprotein E-deficient (ApoE(-/-)) mice. We observed that, in vivo, hBD3 inhibited serum MCP-1, sICAM-1 levels of ApoE-deficient mice exposed to Pg-LPS in a chronic inflammation model. Serum levels of total cholesterol (TC) and low-density lipoprotein (LDL) were also markedly reduced with hBD3 intervention. In addition, thinned vascular walls, less macrophage infiltration and the formation of atherosclerotic lesions were observed in the hBD3-treated group. Furthermore, in vitro, hBD3 profoundly suppressed the production of TNF-α and IL-6 in RAW 264.7 cells induced by Pg-LPS in a dose-dependent manner. Moreover, hBD3 attenuated the phosphorylation of p38 and ERK1/2 in the mitogen-activated protein kinase (MAPK) pathway. Taken together, our work has revealed that hBD3 exhibits potent anti-inflammatory properties both in vitro and in vivo, and this effect might be correlated with inhibition of MAPK pathway.

Potential Use of Antimicrobial Peptides as Vaginal Spermicides/Microbicides

The concurrent increases in global population and sexually transmitted infection (STI) demand a search for agents with dual spermicidal and microbicidal properties for topical vaginal application. Previous attempts to develop the surfactant spermicide, nonoxynol-9 (N-9), into a vaginal microbicide were unsuccessful largely due to its inefficiency to kill microbes. Furthermore, N-9 causes damage to the vaginal epithelium, thus accelerating microbes to enter the women's body. For this reason, antimicrobial peptides (AMPs), naturally secreted by all forms of life as part of innate immunity, deserve evaluation for their potential spermicidal effects. To date, twelve spermicidal AMPs have been described including LL-37, magainin 2 and nisin A. Human cathelicidin LL-37 is the most promising spermicidal AMP to be further developed for vaginal use for the following reasons. First, it is a human AMP naturally produced in the vagina after intercourse. Second, LL-37 exerts microbicidal effects to numerous microbes including those that cause STI. Third, its cytotoxicity is selective to sperm and not to the female reproductive tract. Furthermore, the spermicidal effects of LL-37 have been demonstrated in vivo in mice. Therefore, the availability of LL-37 as a vaginal spermicide/microbicide will empower women for self-protection against unwanted pregnancies and STI.

Unique features of human cathelicidin LL-37

Cathelicidins are antimicrobial peptides produced by humans and animals in response to various pathogenic microbes. This review intends to provide a brief overview of the expression, structure, properties and function of human cathelicidin LL-37 which may be a therapeutic agent against a variety of bacterial and viral diseases, cancers, and hard-to-heal wounds. Cathelicidins act as a primary defense against bacteria and other pathogens in the case of inflammation. They are able to kill bacteria and fungi, inhibit and destroy bacterial biofilms, and possess antiviral and antiparasitics properties. They can also play a role in angiogenesis, wound healing, and the regulation of apoptosis. The host defense peptide LL-37 has emerged as a novel modulator of tumor growth and metastasis in carcinogenesis of various types of cancers. LL-37 is an antimicrobial peptide able of inducing various effects. It acts as an anti- and pro- inflammatory factor. Cathelicidins are able to directly and selectively destroy membranes of various microbes and cancer cells, but they do not attack normal cells. The role of cathelicidins in cancer is double-sided. They play an important role in killing cancer cells and may provide a new possibility for the development of cancer therapeutics. However, they also can participate in carcinogenesis. Due to its activity spectrum LL-37 could be applied in pharmacotherapy. Cathelicidin peptides could serve as a template for the development of modern anti-microbial and anti-viral drugs. LL-37 is an excellent candidate to develop into therapeutics for infected wounds.

Antagonistic effect of peptidoglycan of Streptococcus sanguinis on lipopolysaccharide of major periodontal pathogens

Streptococcus sanguinis is often found in subgingival biofilm including periodontopathogens, and is correlated with a delay in colonization by periodontopathogens. However, the effect of S. sanguinis on inflammation induced by periodontopathogens is poorly understood. Thus, this study investigated the effect of S. sanguinis peptidoglycan (PGN) on induction of TNF-α, IL-6, and IL-8 expression by lipopolysaccharide (LPS) of periodontal pathogens. LPS was extracted from Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythia, and PGN was isolated from S. sanguinis. THP-1 cells, a monocytic cell-line, were cotreated with LPS of the periodontal pathogens and S. sanguinis PGN, and then the expression of inflammatory cytokines was analyzed by real-time RT-PCR. To analyze the underlying mechanism, the binding assay of the LPS to CD14 or LPS-binding protein (LBP) was performed in the presence or absence of the PGN after coating recombinant human CD14 and LBP on EIA plate. The PGN inhibited the binding of LPS to CD14 and LBP in a dose-dependent manner. Also, THP-1 cells were co-treated with the LPS in the presence of N-acetylmuramic acid and N-acetylglucosamine, as components of PGN, and the competition binding assay to CD14 and LBP was performed. N-acetylmuramic acid inhibited the induction of inflammatory cytokine expression by LPS and the binding of LPS to CD14 or LBP whereas N-acetylglucosamine did not show such effect. Collectively, the results suggest that S. sanguinis PGN inhibited the cytokine expression induced by the LPS of periodontopathogens due to the inhibition of LPS binding to LBP and CD14. N-acetylmuramic acid of PGN may play a role in inhibition of the LPS binding of periodontopathogens to CD14 and LBP.

Synergistic anti-inflammatory activity of the antimicrobial peptides human beta-defensin-3 (hBD-3) and cathelicidin (LL-37) in a three-dimensional co-culture model of gingival epithelial cells and fibroblasts

Given the spread of antibiotic resistance in bacterial pathogens, antimicrobial peptides that can also modulate the immune response may be a novel approach for effectively controlling periodontal infections. In the present study, we used a three-dimensional (3D) co-culture model of gingival epithelial cells and fibroblasts stimulated with Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS) to investigate the anti-inflammatory properties of human beta-defensin-3 (hBD-3) and cathelicidin (LL-37) and to determine whether these antimicrobial peptides can act in synergy. The 3D co-culture model composed of gingival fibroblasts embedded in a collagen matrix overlaid with gingival epithelial cells had a synergistic effect with respect to the secretion of IL-6 and IL-8 in response to LPS stimulation compared to fibroblasts and epithelial cells alone. The 3D co-culture model was stimulated with non-cytotoxic concentrations of hBD-3 (10 and 20 µM) and LL-37 (0.1 and 0.2 µM) individually and in combination in the presence of A. actinomycetemcomitans LPS. A multiplex ELISA assay was used to quantify the secretion of 41 different cytokines. hBD-3 and LL-37 acted in synergy to reduce the secretion of GRO-alpha, G-CSF, IP-10, IL-6, and MCP-1, but only had an additive effect on reducing the secretion of IL-8 in response to A. actinomycetemcomitans LPS stimulation. The present study showed that hBD-3 acted in synergy with LL-37 to reduce the secretion of cytokines by an LPS-stimulated 3D model of gingival mucosa. This combination of antimicrobial peptides thus shows promising potential as an adjunctive therapy for treating inflammatory periodontitis.

Transcriptional responses of Treponema denticola to other oral bacterial species

The classic organization by Socransky and coworkers categorized the oral bacteria of the subgingival plaque into different complexes. Treponema denticola, Porphyromonas gingivalis and Tannerella forsythia are grouped into the red complex that is highly correlated with periodontal disease. Socransky's work closely associates red with orange complex species such as Fusobacterium nucleatum and Prevotella intermedia but not with members of the other complexes. While the relationship between species contained by these complexes is in part supported by their ability to physically attach to each other, the physiological consequences of these interactions and associations are less clear. In this study, we employed T. denticola as a model organism to analyze contact-dependent responses to interactions with species belonging to the same complex (P. gingivalis and T. forsythia), the closely associated orange complex (using F. nucleatum and P. intermedia as representatives) and the unconnected yellow complex (using Streptococcus sanguinis and S. gordonii as representatives). RNA was extracted from T. denticola alone as well as after pairwise co-incubation for 5 hrs with representatives of the different complexes, and the respective gene expression profiles were determined using microarrays. Numerous genes related to motility, metabolism, transport, outer membrane and hypothetical proteins were differentially regulated in T. denticola in the presence of the tested partner species. Further analysis revealed a significant overlap in the affected genes and we identified a general response to the presence of other species, those specific to two of the three complexes as well as individual complexes. Most interestingly, many predicted major antigens (e.g. flagella, Msp, CTLP) were suppressed in responses that included red complex species indicating that the presence of the most closely associated species induces immune-evasive strategies. In summary, the data presented here provide an in-depth understanding of the transcriptional responses triggered by contact-dependent interactions between microorganisms inhabiting the periodontal pocket.

LPS inmobilization on porous and non-porous supports as an approach for the isolation of anti-LPS host-defense peptides

Lipopolysaccharides (LPSs) are the major molecular component of the outer membrane of Gram-negative bacteria. This molecule is recognized as a sign of bacterial infection, responsible for the development of local inflammatory response and, in extreme cases, septic shock. Unfortunately, despite substantial advances in the pathophysiology of sepsis, there is no efficacious therapy against this syndrome yet. As a consequence, septic shock syndrome continues to increase, reaching mortality rates over 50% in some cases. Even though many preclinical studies and clinical trials have been conducted, there is no Food and Drug Administration-approved drug yet that interacts directly against LPS. Cationic host-defense peptides (HDPs) could be an alternative solution since they possess both antimicrobial and antiseptic properties. HDPs are small, positively charged peptides which are evolutionarily conserved components of the innate immune response. In fact, binding to diverse chemotypes of LPS and inhibition of LPS-induced pro-inflammatory cytokines from macrophages have been demonstrated for different HDPs. Curiously, none of them have been isolated by their affinity to LPS. A diversity of supports could be useful for such biological interaction and suitable for isolating HDPs that recognize LPS. This approach could expand the rational search for anti-LPS HDPs.

A comprehensive summary of LL-37, the factotum human cathelicidin peptide

Cathelicidins are a group of antimicrobial peptides. Since their discovery, it has become clear that they are an exceptional class of peptides, with some members having pleiotropic effects. Not only do they possess an antibacterial, antifungal and antiviral function, they also show a chemotactic and immunostimulatory/-modulatory effect. Moreover, they are capable of inducing wound healing, angiogenesis and modulating apoptosis. Recent insights even indicate for a role of these peptides in cancer. This review provides a comprehensive summary of the most recent and relevant insights concerning the human cathelicidin LL-37.

Influence of periodontal status and periodontopathogens on levels of oral human β-defensin-2 in saliva

BACKGROUND

Expression patterns of human β-defensin-2 (HBD-2) mRNA or HBD-2 protein concentration and periodontal diseases have been a focus of scientific research. This study compares the salivary levels of HBD-2 protein concentration of healthy patients and patients with gingivitis and chronic periodontitis (CP) and correlates these levels with the presence of periodontopathogens.

METHODS

A total of 89 patients were enrolled in this study: 31 periodontally healthy, 27 with gingivitis, and 31 with CP. Plaque and gingival indices, probing depth, and clinical attachment level were measured. The presence of Campylobacter rectus, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Prevotella intermedia was evaluated qualitatively by conventional polymerase chain reaction. HBD-2 quantification in saliva was performed using an immune enzymatic assay. Frequency of periodontopathogens and HBD-2 protein concentration was assessed. Association between HBD-2 protein concentration (≥100 pg/mL) and the simultaneous presence of one to two, three to four, or five to six periodontopathogens was tested.

RESULTS

Although periodontally healthy individuals and patients with gingivitis showed similar HBD-2 levels, the CP group displayed an increased level of HBD-2. P. gingivalis, P. intermedia, T. forsythia, and T. denticola were more prevalent in CP; however, their mere presence was not related to the increased levels of HBD-2 (Pearson correlation and multinomial logistic regression model).

CONCLUSIONS

Salivary HBD-2 protein concentration was higher in patients with CP compared with healthy individuals or patients with gingivitis. These different protein concentrations were not related to the frequency of periodontopathogens. Clinical inflammatory profile had a higher impact on salivary HBD-2 levels than bacteria.

The yin and yang of human Beta-defensins in health and disease

Rapidly evolving research examining the extended role of human beta-defensins (hBDs) in chemoattraction, innate immune-mediated response, and promotion of angiogenesis suggest that the collective effects of hBDs extend well beyond their antimicrobial mechanism(s). Indeed, the numerous basic cellular functions associated with hBDs demonstrate that these peptides have dual impact on health, as they may be advantageous under certain conditions, but potentially detrimental in others. The consequences of these functions are reflected in the overexpression of hBDs in diseases, such as psoriasis, and recently the association of hBDs with pro-tumoral signaling. The mechanisms regulating hBD response in health and disease are still being elucidated. Clearly the spectrum of function now attributed to hBD regulation identifies these molecules as important cellular regulators, whose appropriate expression is critical for proper immune surveillance; i.e., expression of hBDs in proximity to areas of cellular dysregulation may inadvertently exacerbate disease progression. Understanding the mechanism(s) that regulate contextual signaling of hBDs is an important area of concentration in our laboratories. Using a combination of immunologic, biochemical, and molecular biologic approaches, we have identified signaling pathways associated with hBD promotion of immune homeostasis and have begun to dissect the inappropriate role that beta-defensins may assume in disease.

Antimicrobial peptide control of pathogenic microorganisms of the oral cavity: a review of the literature

Antimicrobial peptides, molecules produced in many different organisms, have high biocidal activity against several microorganisms. However, several questions about these molecules remain unclear. Therefore, this report details a systematic survey of the literature on the use of antimicrobial peptides against oral pathogens and indicates which peptides and microorganisms are most extensively studied. Articles were located using the PubMed and Science Direct databases with the following inclusion criteria: publication date between 2002 and 2011; keywords "biofilm OR biological film OR biological layer OR bacterial growth" AND "peptide" AND "oral cavity OR mouth OR buccal mucosa OR oral mucosa OR mouth mucosa"; and abstract in English. A total of 73 articles were selected after refinement of the data. An increase in publications focusing on the use of antimicrobial peptides against oral microorganisms was observed. In addition, the peptides produced by cells of the oral mucosa (defensins, LL-37 and histatins) as well as Streptococcus mutans (among cariogenic bacteria) and Porphyromonas gingivalis (among periodontal bacteria) were the most studied subjects. It was concluded that the use of antimicrobial peptides as a tool for microbial control is of increasing importance, likely due to its widespread use, mechanism of action, and low rates of bacterial resistance.

Specificity of antimicrobial peptide LL-37 to neutralize periodontopathogenic lipopolysaccharide activity in human oral fibroblasts

BACKGROUND

The antimicrobial peptide LL-37 is known to have a potent lipopolysaccharide (LPS)-neutralizing activity in various cell types. Because of observed heterogeneity within periodontopathogenic LPS, the authors hypothesized that LL-37 had specificity to neutralize such LPS activity. The present study, therefore, aims to investigate the LPS-neutralizing activity of LL-37 to various periodontopathogenic LPS in interleukin-8 (IL-8) production after challenging them in human oral fibroblasts.

METHODS

Human periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) were cultured from biopsies of periodontal ligament and gingival tissues. After cell confluence in 24-well plates, LPS (10 μg/mL) from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans were added with or without LL-37 (10 μg/mL). After 18 hours, the supernatant was collected and analyzed in IL-8 production by enzyme-linked immunosorbent assay.

RESULTS

All periodontopathogenic LPS statistically significantly induced IL-8 production in both PDLF and GF (P <0.01). After neutralization with LL-37, both PDLF and GF showed a statistically significant reduction in IL-8 production compared with LPS-treated groups without LL-37 (P <0.01), and the percentage of reduction in IL-8 production in PDLF appeared to be higher than in GF. In addition, the percentage of reduction in IL-8 production varied considerably according to each periodontopathogenic LPS.

CONCLUSIONS

The antimicrobial peptide LL-37 had an ability to suppress periodontopathogenic LPS-induced IL-8 production in both PDLF and GF. Its LPS-neutralizing activity revealed specificity to periodontopathogenic LPS and seemed to be dependent on the heterogeneity within LPS between different genera.

Understanding the roles of gingival beta-defensins

Gingival epithelium produces β-defensins, small cationic peptides, as part of its contribution to the innate host defense against the bacterial challenge that is constantly present in the oral cavity. Besides their functions in healthy gingival tissues, β-defensins are involved in the initiation and progression, as well as restriction of periodontal tissue destruction, by acting as antimicrobial, chemotactic, and anti-inflammatory agents. In this article, we review the common knowledge about β-defensins, coming from in vivo and in vitro monolayer studies, and present new aspects, based on the experience on three-dimensional organotypic culture models, to the important role of gingival β-defensins in homeostasis of the periodontium.

Antibacterial and neutralizing effect of human β-defensins on Enterococcus faecalis and Enterococcus faecalis lipoteichoic acid

INTRODUCTION

Enterococcus faecalis is frequently found in the root canal of teeth, is a major microorganism of endodontic therapy failure, and is associated with chronic apical periodontitis. Human β-defensins (HBDs) are known to play critical roles in defending the host against infectious microbes and producing dental pulp in healthy and patients. The purpose of the present study was to investigate the bactericidal and neutralizing effects of HBDs on E. faecalis and E. faecalis lipoteichoic acid (Ef LTA) as a major virulence factor of E. faecalis.

METHODS

HBD-1, -2, -3, and -4 were synthesized and investigated the susceptibility against E. faecalis. Also, the neutralizing effects of HBDs on cytokine and intercellular adhesion molecule 1 (ICAM-1) expression by activity of E. faecalis and Ef LTA were analyzed using enzyme-linked immunosorbent assay and flow cytometry.

RESULTS

HBD-1 and -2 were weakly susceptible, and HBD-3 and HBD-4 were strongly susceptible to E. faecalis. All of the HBDs exhibited neutralizing effects on the activity of Ef LTA, and HBD-3 strongly neutralized the activity of E. faecalis in tumor necrosis factor-α, interleukin-8, and ICAM-1 expression. The neutralizing effects of HBDs were to inhibit E. faecalis or Ef LTA binding to the host cells.

CONCLUSIONS

These results suggest that the induction of HBDs might have great potential as endodontic therapeutic agents.