Association of a genetic polymorphism (-44 C/G SNP) in the human DEFB1 gene with expression and inducibility of multiple beta-defensins in gingival keratinocytes

The Potential Role of Epigenetic Modifications on Different Facets in the Periodontal Pathogenesis

Periodontitis is a chronic inflammatory disease that affects the supporting structures of teeth. In the literature, the association between the pathogenicity of bacteria and environmental factors in this regard have been extensively examined. In the present study, we will shed light on the potential role that epigenetic change can play on different facets of its process, more particularly the modifications concerning the genes involved in inflammation, defense, and immune systems. Since the 1960s, the role of genetic variants in the onset and severity of periodontal disease has been widely demonstrated. These make some people more susceptible to developing it than others. It has been documented that the wide variation in its frequency for various racial and ethnic populations is due primarily to the complex interplay among genetic factors with those affecting the environment and the demography. In molecular biology, epigenetic modifications are defined as any change in the promoter for the CpG islands, in the structure of the histone protein, as well as post-translational regulation by microRNAs (miRNAs), being known to contribute to the alteration in gene expression for complex multifactorial diseases such as periodontitis. The key role of epigenetic modification is to understand the mechanism involved in the gene-environment interaction, and the development of periodontitis is now the subject of more and more studies that attempt to identify which factors are stimulating it, but also affect the reduced response to therapy.

β-defensin 1 Gene Polymorphisms are Associated with Kidney Disease in Northwestern Mexicans with Type 2 Diabetes

Diabetic kidney disease (DKD) is one of the more limiting complications to the quality of life of diabetes mellitus patients. Studies including cultured cells, animal models, and case-control studies highlight the role of human β-defensin-1 (hBD-1) in diabetes.This study assessed the association of hBD-1 gene (DEFB1) functional variations -52 G/A (rs1799946), -44 C/G (rs1800972) and -20 G/A (rs11362) with type 2 diabetes mellitus (T2DM) in order to investigate its effects on genetic susceptibility and progression to DKD in a Mexican population. A total of 214 T2DM patients with and without DKD (n = 102 and n = 112, respectively) and 117 healthy subjects participated in this case-control study. Genotyping was made by PCR-RFLPs. Clinical and biochemical parameters of all patients were measured. There was no statistically significant difference in genotype or allele frequencies between patients and healthy individuals. Nevertheless, compared with patients without DKD, DKD patients have a reduced prevalence of AA genotype of -52 G/A (OR = 0.307, 95% CI = 0.104-0.905, p =.026), as well as a higher frequency of GA genotype of -20 G/A variant (OR = 1.875, 95%CI = 1.031-3.409, p = .038). Our results suggest that rs1799946 and rs11362 could be useful variants to stratify T2DM Mexican patients in order to prescribe closer follow-up to prevent or retard DKD. Further tests in different ethnic groups are encouraged.

DEFB1 gene polymorphisms modify vitiligo extent and response to NB-UVB phototherapy

Human beta defensin-1(hBD-1); an antimicrobial peptide, has immune regulatory effects which may be involved in autoimmunity. The aims were to evaluate the association between defensin beta 1 (DEFB1) (-44 C/G) and (-20 G/A) gene polymorphisms with the risk of vitiligo development, the extent of the disease and the response to NB-UVB treatment in a sample of Egyptian population. 178 active nonsegmental vitiligo patients and 182 control subjects were included in this prospective case control study. Vitiligo extent was evaluated using vitiligo area scoring index (VASI). Gene polymorphisms in all participants were studied by RFLP PCR technique. Patients were treated by three narrowband UVB (NB-UVB) treatment sessions per week. After 12 weeks, the patients were reevaluated clinically to assess the extent of the disease using VASI scoring again and to evaluate the type of repigmentation, if any. AA genotype of DEFB1 (-20G/A) has a protective role against vitiligo development, while (DEFB1 -44 C/G) GG genotype and G allele increase the risk of vitiligo development about two folds. Patients carrying polymorphism in DEFB1 (-20G/A) only showed the lowest VASI scores (14.23 ± 2.77) and the highest percentage of improvement (66.12 ± 18.01%), while patients carrying polymorphism in DEFB1(-44 C/G) only showed the highest baseline VASI scores (38.87 ± 6.7) and the lowest therapeutic response (23.79 ± 19.42%) among all patients groups. Different DEFB1 gene polymorphisms may modify the risk of vitiligo development, the disease extent and the response to NB-UVB phototherapy.

Acne Vulgaris is Associated with the Human β-Defensin 1-Gene Polymorphisms in Han Chinese Ethnic Group Patients

Objective

To study the relationship between the single nucleotide polymorphisms (SNPs) of the human β-defensin 1-gene (DEFB1) and the genetic susceptibility of acne vulgaris in the Han Chinese ethnic group.

Methods

A total of 104 patients with acne vulgaris and 126 healthy participants were included in our study. We analyzed the association between acne vulgaris and the polymorphisms in the DEFB1 G-52A, C-44G, and G-20A gene. We then analyzed the relationship between the different genotypes and the susceptibility to acne vulgaris.

Results

The frequency of DEFB1 C-44G genetic polymorphisms between the acne vulgaris group and the control group was significantly different (P < 0.05). The frequency of DEFB1 G-20A genetic polymorphisms between the acne vulgaris group and the control group was also significantly different (P < 0.05).

Conclusion

The −44G or −20A allele showed a low expression in acne vulgaris, which has already been shown to correlate with the low risk of acne vulgaris among Chinese Han patients. This further supports the contribution of the DEFB1 gene to the pathogenesis of acne.

Regulatory SNP rs5743417 impairs constitutive expression of human β-defensin 1 and has high frequency in Africans and Afro-Americans

The prediction of regulatory single nucleotide polymorphisms (rSNPs) in proximal promoters of disease-related genes could be a useful tool for personalized medicine in both patient stratification and customized therapy. Using our previously reported method of rSNPs prediction (currently a software called SNPClinic v.1.0) as well as with PredictSNP tool, we performed in silico prediction of regulatory SNPs in the antimicrobial peptide human β-defensin 1 gene in three human cell lines from 1,000 Genomes Project (1kGP), namely A549 (epithelial cell line), HL-60 (neutrophils) and T_H 1 (lymphocytes). These predictions were run in a proximal pseudo-promoter comprising all common alleles on each polymorphic site according to the 1,000 Genomes Project data (1kGP: ALL). Plasmid vectors containing either the major or the minor allele of a putative rSNP rs5743417 (categorized as regulatory by SNPClinic and confirmed by PredictSNP) and a non-rSNP negative control were transfected to lung A549 human epithelial cell line. We assessed functionality of rSNPs by qPCR using the Pfaffl method. In A549 cells, minor allele of the SNP rs5743417 G→A showed a significant reduction in gene expression, diminishing DEFB1 transcription by 33% when compared with the G major allele (p-value = .03). SNP rs5743417 minor allele has high frequency in Gambians (8%, 1kGP population: GWD) and Afro-Americans (3.3%, 1kGP population: ASW). This SNP alters three transcription factors binding sites (TFBSs) comprising SREBP2 (sterols and haematopoietic pathways), CREB1 (cAMP, insulin and TNF pathways) and JUND (apoptosis, senescence and stress pathways) in the proximal promoter of DEFB1. Further in silico analysis reveals that this SNP also overlaps with GS1-24F4.2, a lincRNA gene complementary to the X Kell blood group related 5 (XKR5) mRNA. The potential clinical impact of the altered constitutive expression of DEFB1 caused by rSNP rs5743417 in DEFB1-associated diseases as tuberculosis, COPD, asthma, cystic fibrosis and cancer in African and Afro-American populations deserves further research.

Relationship between β-defensin-1 gene polymorphism and susceptibility and prognosis of acute respiratory distress syndrome

OBJECTIVE

The 1st exon 5' noncoding region rs1799946 (-52A/G), rs1800972 (-44C/G), rs11362 (-20A/G) 3 single-nucleotide polymorphisms (SNPs) on human β-defensin-1 (HBD-1) gene affect its transcription and posttranscriptional mRNA stability then affect the activity of HBD-1. This study was to investigate the effects of HBD-1 gene rs1799946, rs1800972, and rs11362 locus SNPs on genetic susceptibility and prognosis of acute respiratory distress syndrome (ARDS).

METHODS

A total of 300 patients with ARDS (ARDS group) and 240 patients who were admitted to the intensive care unit and had a high risk of ARDS but did not progress to ARDS (control group) were included in this study. The genotypes of HBD-1 gene rs1799946, rs1800972, and rs11362 locus and serum HBD-1 were detected. Patients were followed for 60 days with development of ARDS as a primary outcome, ARDS-related mortality and organ dysfunction were secondary outcomes.

RESULTS

HBD-1 gene rs1799946 and rs11362 gene mutations were not risk factors for ARDS (P > .05). Mutation allele G of rs1800972 locus in HBD-1 gene was a risk factor for ARDS. There was no significant difference in serum HBD-1 levels between patients with different genotypes of rs1799946 and rs11362 locus in the HBD-1 gene (P > .05). HBD-1 gene rs1800972 locus wild type, heterozygous, and mutant homozygous serum levels of HBD-1 gradually decreased, the difference was statistically significant (P < .001). The 60-day survival rate of subjects with wild type, heterozygous, and mutant homozygote at the rs1800972 locus of HBD-1 gene decreased sequentially (81.7%, 48.9%, and 39.7%), and the difference was statistically significant (P < .05).

CONCLUSION

The SNP of rs1800972 (-44C/G) in HBD-1 gene is associated with the risk of ARDS. The rs1800972 locus G allele carriers are more likely to develop ARDS and have a poor prognosis.

Human beta defensin-1 is involved in the susceptibility to adeno-tonsillar hypertrophy

INTRODUCTION

Innate immunity molecules are known to play a pivotal role in the homeostasis of the oral mucosa, permitting the presence of commensal microflora and, at the same time, providing a first line of defense against pathogens attempting to invade the oral cavity. Tonsils represent the local immune tissue in oral cavity, being able to provide a non-specific response to pathogens; however, in the presence of microbes or foreign materials present in the mouth tonsils could became infected and develop chronic inflammation, thus leading to hypertrophy. The etiology of the disease is multifactorial depending upon environmental and host factors, the latter including molecules of mucosal innate immunity.

METHODS

Ninety-five children with adeno-tonsillar hypertrophy subjected to adeno-tonsillectomy were recruited at the pediatric otorhinolaryngology service of the Institute for Maternal and Child Health IRCCS Burlo Garofolo, Trieste (Italy). The specimen discarded from the surgery were used for genomic DNA extraction and genotyping, for mRNA extraction and gene expression analysis, finally the samples were cut and used to prepare slides to perform immunohistochemistry.

RESULTS

Functional polymorphisms within DEFB1 gene, encoding the human beta defensin-1 (hBD-1), were analyzed finding association between DEFB1 rare haplotypes and susceptibility to adeno-tonsillar hypertrophy. DEFB1 mRNA expression was detected in the tonsils and the hBD-1 protein was localized at the epithelia of tonsils mainly in the proximity of the basal lamina.

CONCLUSION

Our findings lead us to hypothesize an involvement of hBD-1 mediated innate immunity in the modulation of the susceptibility towards adeno-tonsillar hypertrophy development.

DEFB1 polymorphisms and HIV-1 mother-to-child transmission in Zambian population

Introduction: Human Beta Defensin-1 (hBD-1) is a component of the innate immune system, the first line of defence against pathogens, already reported as involved in the susceptibility to HIV-1 infection and HIV-1 mother-to-child transmission (MTCT) in different populations. We investigated the role of DEFB1 gene (encoding for hBD-1) functional polymorphisms in the susceptibility to HIV-1 MTCT in a population from Zambia. Methods: Four selected polymorphisms within DEFB1 gene, three at the 5' untranslated region (UTR), namely -52G > A (rs1799946), -44C > G (rs1800972) and -20G > A (rs11362) and one in the 3'UTR, c.*87A > G (rs1800972), were genotyped in 101 HIV-1 positive mothers (26 transmitters -27% and 75 not transmitters -73%) and 331 infants born to HIV-1 infected mothers (85 HIV-1 positive -26% and 246 exposed but not infected -74%). Results: DEFB1 c.*87-A allele was more frequent among HIV- children with respect to HIV+ (with intrauterine MTCT). Concerning DEFB1 haplotypes, GCGA haplotype resulted more represented in HIV- than HIV+ infants and DEFB1 ACGG haplotype presented increased frequency in HIV- children respect to HIV+ (with intra-partum MTCT) (p = .02, p = .002 and p = .006, respectively). Conclusions: DEFB1 polymorphisms were significantly associated with decreased risk of HIV-1 infection acquisition in the studied Zambian population suggesting that they may play a role in HIV-1 MTCT.

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.

The oral cavity microbiota: between health, oral disease, and cancers of the aerodigestive tract

Many studies show that the human microbiome plays a critical role in the chronic pathologies of obesity, inflammatory bowel diseases, and diabetes. More recently, the interaction between cancer and the microbiome has been highlighted. Most studies have focused on the gut microbiota because it represents the most extensive bacterial community, and the body of evidence correlating it with gut syndromes is increasing. However, in the strict sense, the gastrointestinal (GI) tract begins in the oral cavity, and special attention should be paid to the specific flora of this cavity. This study reviewed the current knowledge about the various microbial ecosystems of the upper part of the GI tract and discussed their potential link to carcinogenesis. The overall composition of the microbial communities, as well as the presence or absence of "key species", in relation to carcinogenesis is addressed. Alterations in the oral microbiota can potentially be used to predict the risk of cancer. Molecular advances and the further monitoring of the microbiota will increase our understanding of the role of the microbiota in carcinogenesis and open new perspectives for future therapeutic and prophylactic modalities.

The Interplay between Defensins and Microbiota in Crohn's Disease

Crohn's disease (CD) is a chronic inflammation of the intestinal mucosa, characterized by periods of acute recurrence and remission. Depending on the specific region affected, CD is classified as ileal CD or colonic CD. It is largely accepted that the intestinal microbiota is involved in the onset of the pathology. Indeed, a reduced immune tolerance to components of the intestinal commensal microbiota and inflammation of the intestinal barrier typifies patients with CD. Several studies have shown defective expression of intestinal antimicrobial peptides (AMPs) in patients with CD compared to controls, particularly defensins. A reduction in α-defensins is observed in ileal CD, while β-defensins are increased in colonic CD. In addition to an immunological basis, the disease is frequently associated with genetic alterations including mutations of NOD2 gene. Several therapeutic strategies to circumvent the dysfunction observed in CD are currently under investigation. These include the use of delivery systems to administer endogenous AMPs and the engineering of peptidomimetics that could ameliorate the severity of CD. In this review, the role defensins play in CD and the strategies aimed at overcoming bacterial resistance will be discussed.

Caries and Innate Immunity: DEFB1 Gene Polymorphisms and Caries Susceptibility in Genetic Isolates from North-Eastern Italy

Background: The DEFB1 gene, encoding for the constitutively expressed human β-defensin 1 (hBD1) antimicrobial peptide is a potential candidate when studying genetic susceptibility to caries. DEFB1 genetic variations have been reported as contributing to hBD1 production impairment, leading to a greater susceptibility to be infected by oral pathogens, also leading to periodontitis. Methods: We analysed 5 DEFB1 polymorphisms, namely 3 functional single-nucleotide polymorphisms (SNPs) at the 5′-untranslated region (UTR), -52G>A (rs1799946), -44C>G (rs1800972), and -20G>A (rs11362), 2 SNPs at the 3′-UTR, c*5G>A (rs1047031) and c*87A>G (rs1800971) SNP located in potential miRNA binding sites, looking for possible correlations with the risk to develop caries in 654 adult subjects from isolated populations of north-eastern Italy. Dental caries prevalence was evaluated with the DMFT (decayed, missing, filled teeth) index, calculated after an accurate oral examination. DEFB1 SNP genotyping was performed with an Illumina 370k high-density SNP array. Results: Two DEFB1 SNPs were significantly associated with the DMFT index: the strongest association emerged from rs11362 SNP (p = 0.008). In particular G/G homozygous individuals showed a higher DMFT index compared to both G/A heterozygous and A/A homozygous individuals; rs1799946 SNP was also significantly associated with DMFT (p = 0.030), and individuals homozygous for the T allele had a higher DMFT value compared to heterozygous C/T and homozygous C/C individuals. Conclusions: Our study replicated, on a larger number of individuals, previous findings showing the association between two 5′-UTR SNPs in the DEFB1 gene and DMFT, suggesting that these polymorphisms could be considered as potential markers for assessing the risk to develop caries.

Ratio of T-Helper Type 1 (Th1) to Th17 Cytokines in Whole Blood Is Associated With Human β-Defensin 3 Expression in Skin and Persistent Staphylococcus aureus Nasal Carriage

BACKGROUND

 Nasal colonization has gained attention as an effect modifier in Staphylococcus aureus vaccine trials, suggesting interference of carriage with T-cell immunity. Likewise, T-cell signals may be involved in regulating effectors of epithelial innate defense.

METHODS

 Whole blood from 43 persistent carriers and 49 noncarriers was stimulated with viable S. aureus T-helper type 1 (Th1), Th2, and Th17 cytokine expression was measured, compared between carrier groups, and linked with data on human β-defensin 3 (hBD-3) messenger RNA (mRNA) in skin while adjusting for transcriptionally relevant promoter haplotypes.

RESULTS

 Compared with carriers, stimulated whole blood from noncarriers contained on average 60% more interferon γ mRNA (P = .031) and 19% less interleukin 17A (IL-17A) mRNA (P = .11), resulting in, on average, a 90% higher IFN-γ to IL-17A mRNA ratio (P = .003). In a multivariable model, per duplication of the mRNA template, the risk of being a carrier increased by 93% for IL-17A (odds ratio [OR], 1.93; 95% confidence interval [CI], 1.10-3.41; P = .023) and decreased by 35% for IFN-γ (OR, 0.65; 95% CI, 0.47-0.91; P = .01). Independent of carriage and DEFB promotor haplotype, a 1-unit increase in the IFN-γ to IL-17A mRNA ratio (mean ± SD, 5.93 ± 1.60) led to a 24% increase in hBD-3 transcription in experimentally wounded human skin (P = .003).

CONCLUSIONS

 A low Th1 to Th17 mRNA ratio increases the propensity for persistent S. aureus nasal colonization, with downregulated hBD-3 transcription providing a potential link.

DEFB1 polymorphisms and susceptibility to recurrent tonsillitis in Italian children

INTRODUCTION

The tonsils are secondary lymphoid organs fundamental for immune system response against pathogens within the oral cavity. Tonsillitis refers to inflammation of the pharyngeal tonsils that may include the adenoids and the lingual tonsils and that can be acute, recurrent, and chronic. Viral or bacterial infections, as well as immunologic factors are the main trigger to tonsillitis and disease's chronicity: the host immune responses, especially the innate one, could play an important role in susceptibility to the disease.

OBJECTIVES

The current study aims at investigating the role of functional polymorphisms in the 5'UTR (c.-52G>A, c.-44G>C and c.-20G>A) of DEFB1 gene, encoding for the antimicrobial peptide human beta-defensin 1, in the predisposition to recurrent tonsillitis in children from North Eastern Italy.

RESULTS

No significant correlation was found between DEFB1 allele, genotype and haplotype frequencies and recurrent tonsillitis susceptibility with the exception of an increased risk to disease development in patients carrying DEFB1 rare haplotypes.

CONCLUSION

Our results may suggest that DEFB1 polymorphisms alone may not influence pathology susceptibility, however they could possibly concur, together with other factors involved in the genetic control of innate immune system, in the predisposition towards recurrent tonsillitis.

Defensin gene variation and HIV/AIDS: a comprehensive perspective needed

Both α- and β-defensins have anti-human immunodeficiency virus activity. These defensins achieve human immunodeficiency virus inhibition through a variety of mechanisms, including direct binding with virions, binding to and modulation of host cell-surface receptors with disruption of intracellular signaling, and functioning as chemokines or cytokines to augment and alter adaptive immune responses. Polymorphisms in the defensin genes have been associated with susceptibility to human immunodeficiency virus infection and disease progression. However, the roles that these defensins and their genetic polymorphisms have in influencing human immunodeficiency virus/acquired immunodeficiency syndrome outcomes are not straightforward and, at times, appear contradictory. Differences in populations, study designs, and techniques for genotyping defensin gene polymorphisms may have contributed to this lack of clarity. In addition, a comprehensive approach, where both subfamilies of defensins and their all-inclusive genetic polymorphism profiles are analyzed, is lacking. Such an approach may reveal whether the human immunodeficiency virus inhibitory activities of α- and β-defensins are based on parallel or divergent mechanisms and may provide further insights into how the genetic predisposition for susceptibility or resistance to human immunodeficiency virus/acquired immunodeficiency syndrome is orchestrated between these molecules.

Association of Polymorphisms in Innate Immunity Genes TLR9 and DEFB1 with Human Longevity

The distribution of polymorphic variants of innate immunity genes TLR9 (+2848G>A) and DEFB1(-20G>A; -44C>G; -52G>A) was evaluated in long-living individuals. No significant differences were found in the distribution of genotypes and alleles of the TLR9 gene. The following features were revealed: increase in the frequency of AA and GG genotypes and decrease in the frequency of the AG genotype of the DEFB1(-20G>A) gene; increase in the frequency of the CC genotype and C allele and decrease in the frequency of CG and GG genotypes and G allele of the DEFB1(44C>G) gene; and increase in the frequency of AA and AG genotypes and A allele and decrease in the frequency of the GG genotypes and G allele of the DEFB1(-52G>A) gene. Genotypes and alleles of the DEFB1 gene found in long-living individuals can be considered as the factors that increase the probability of longevity and favorable course of age-related diseases.

Ascorbic acid, ultraviolet C rays, and glucose but not hyperthermia are elicitors of human β-defensin 1 mRNA in normal keratinocytes

Hosts' innate defense systems are upregulated by antimicrobial peptide elicitors (APEs). Our aim was to investigate the effects of hyperthermia, ultraviolet A rays (UVA), and ultraviolet C rays (UVC) as well as glucose and ascorbic acid (AA) on the regulation of human β-defensin 1 (DEFB1), cathelicidin (CAMP), and interferon-γ (IFNG) genes in normal human keratinocytes (NHK). The indirect in vitro antimicrobial activity against Staphylococcus aureus and Listeria monocytogenes of these potential APEs was tested. We found that AA is a more potent APE for DEFB1 than glucose in NHK. Glucose but not AA is an APE for CAMP. Mild hypo- (35°C) and hyperthermia (39°C) are not APEs in NHK. AA-dependent DEFB1 upregulation below 20 mM predicts in vitro antimicrobial activity as well as glucose- and AA-dependent CAMP and IFNG upregulation. UVC upregulates CAMP and DEFB1 genes but UVA only upregulates the DEFB1 gene. UVC is a previously unrecognized APE in human cells. Our results suggest that glucose upregulates CAMP in an IFN-γ-independent manner. AA is an elicitor of innate immunity that will challenge the current concept of late activation of adaptive immunity of this vitamin. These results could be useful in designing new potential drugs and devices to combat skin infections.

Gene polymorphism of β-defensin-1 is associated with susceptibility to periodontitis in Japanese

Periodontitis is a multifactorial disease associated with genetic and environmental factors. Single-nucleotide polymorphisms (SNPs) are associated with susceptibility to common diseases such as diabetes and periodontitis. Although the oral cavity is exposed to various organisms, the conditions are well controlled by innate and acquired immune systems. Antimicrobial peptides (AMPs) play an important role in the innate immune system; however, the association of AMP-SNPs with periodontitis has not been fully elucidated. This study investigated the relationship between AMP-SNPs and periodontitis in Japanese. One hundred and five Japanese subjects were recruited, which included patients with aggressive, severe, moderate and mild periodontitis, and age-matched healthy controls. Genomic DNA was isolated from peripheral blood and genotypes of SNPs of β-defensin-1 and lactoferrin genes (DEFB1: rs1799946, rs1800972 and rs11362; and LTF: rs1126478) were investigated using the PCR-Invader assay. Protein level of AMPs in gingival crevicular fluid (GCF) was quantified by ELISA. Case-control studies revealed that the -44 CC genotype of DEFB1 (rs1800972) was associated with periodontitis (OR 2.51), particularly with severe chronic periodontitis (OR 4.15) and with combined severe and moderate chronic periodontitis (OR 4.04). No statistical differences were found in other genotypes. The β-defensin-1 concentrations in GCF were significantly lower in subjects with the -44 CC genotype of DEFB1 than in those without this genotype. No significant differences between GCF concentrations of AMPs and other genotypes were detected. The -44 CC genotype of the β-defensin-1 gene (DEFB1 rs1800972) may be associated with susceptibility to chronic periodontitis in Japanese.

Antimicrobial peptides and gut microbiota in homeostasis and pathology

We survive because we adapted to a world of microorganisms. All our epithelial surfaces participate in keeping up an effective barrier against microbes while not initiating ongoing inflammatory processes and risking collateral damage to the host. Major players in this scenario are antimicrobial peptides (AMPs). Such broad-spectrum innate antibiotics are in part produced by specialized cells but also widely sourced from all epithelia as well as circulating inflammatory cells. AMPs belong to an ancient defense system found in all organisms and participated in a preservative co-evolution with a complex microbiome. Particularly interesting interactions between host barrier and microbiota can be found in the gut. The intestinal cell lining not only has to maintain a tightly regulated homeostasis during its high-throughput regeneration, but also a balanced relationship towards an extreme number of mutualistic or commensal inhabitants. Recent research suggests that advancing our understanding of the circumstances of such balanced and sometimes imbalanced interactions between gut microbiota and host AMPs should have therapeutic implications for different intestinal disorders.

Impaired β-defensin expression in human skin links DEFB1 promoter polymorphisms with persistent Staphylococcus aureus nasal carriage

BACKGROUND

Genetically determined variation in the expression of innate defense molecules may explain differences in the propensity to be colonized with Staphylococcus aureus.

METHODS

We determined S. aureus nasal carriage in 603 volunteers; analyzed polymorphisms in the DEFB1 promoter at positions -52 G>A (rs1799946), -44 C>G (rs1800972), and -20 G>A (rs11362); and measured the content of human β-defensin 1 (hBD-1) and hBD-3 messenger RNA (mRNA) in 192 samples of healthy and experimentally wounded human skin.

RESULTS

Compared with GGG at the positions -52/-44/-20, the ACG haplotype was more common among persistent S. aureus nasal carriers (odds ratio, 1.93; 95% confidence interval [CI], 1.2-3.1; P = .006) and was associated with reduced expression of hBD-1 (GGG>ACG>GCA; P < .001) and hBD-3 (GGG>GCA>ACG; P = .04) in skin when measured 72 hours after wounding. Furthermore, a 50% decrease in hBD-1 and hBD-3 mRNA expression in wounded skin increased the odds of persistent carriage by 1.45 (95% CI, .93-2.26; P = .1) and 1.48 (95% CI, 1.01-2.17; P = .04), respectively. Adjustment for known risk factors of persistent S. aureus carriage did not substantially change the associations of both DEFB1 haplotypes and β-defensin expression with S. aureus colonization.

CONCLUSIONS

DEFB1 polymorphisms may promote persistent S. aureus colonization by altering β-defensin expression in keratinocytes of human skin.

Variation in human β-defensin genes: new insights from a multi-population study

Human β-defensin 2 (hBD-2) and hBD-3, encoded by DEFB4 and DEFB103A, respectively, have shown anti-HIV activity, and both genes exhibit copy number variation (CNV). Although the role of hBD-1, encoded by DEFB1, in HIV-1 infection is less clear, single nucleotide polymorphisms (SNPs) in DEFB1 may influence viral loads and disease progression. We examined the distribution of DEFB1 SNPs and DEFB4/103A CNV, and the relationship between DEFB1 SNPs and DEFB4/103A CNV using samples from two HIV/AIDS cohorts from the United States (n = 150) and five diverse populations from the Coriell Cell Repositories (n = 46). We determined the frequencies of 10 SNPs in DEFB1 using a post-PCR, oligonucleotide ligation detection reaction-fluorescent microsphere assay, and CNV in DEFB4/103A by real-time quantitative PCR. There were noticeable differences in the frequencies of DEFB1 SNP alleles and haplotypes among various racial/ethnic groups. The DEFB4/103A copy numbers varied from 2 to 8 (median, 4), and there was a significant difference between the copy numbers of self-identified whites and blacks in the US cohorts (Mann-Whitney U-test P = 0.04). A significant difference was observed in the distribution of DEFB4/103A CNV among DEFB1 -52G/A and -390T/A genotypes (Kruskal-Wallis P = 0.017 and 0.026, respectively), while not in the distribution of DEFB4/103A CNV among -52G/A_-44C/G_-20G/A diplotypes. These observations provide additional insights for further investigating the complex interplay between β-defensin genetic polymorphisms and susceptibility to, or the progression or severity of, HIV infection/disease.

Antimicrobial peptide elicitors: New hope for the post-antibiotic era

Antimicrobial peptides or host defense peptides are fundamental components of human innate immunity. Recent and growing evidence suggests they have a role in a broad range of diseases, including cancer, allergies and susceptibility to infection, including HIV/AIDS. Antimicrobial peptide elicitors (APEs) are physical, biological or chemical agents that boost human antimicrobial peptide expression. The current knowledge of APEs and their potential use in the treatment of human infectious diseases are reviewed, and a classification system for APEs is proposed. The efficient use of APEs in clinical practice could mark the beginning of the urgently needed post-antibiotic era, but further trials assessing their efficacy and safety are required.

Human polymorphisms as clinical predictors in leprosy

Genetic and serum markers in human host can predict leprosy susceptibility per se as well as be useful in classification and/or prediction of clinical variants and immunological responses in leprosy. Adequate and timely assessment of potential risks associated with these 38 host leprosy genes could diminish epidemiological burden and improve life quality of patients with this still prevalent mycobacterial disease.

Biological approaches to the development of novel periodontal therapies--consensus of the Seventh European Workshop on Periodontology

BACKGROUND

Periodontitis remains a major public health issue and current management approaches have failed to impact upon the most high-risk proportion of the population and those with the most severe disease. The objective of this session was to assess if and how, current understanding of periodontitis provides the opportunity to develop new preventive and therapeutic strategies.

MATERIALS AND METHODS

Based on the current understanding of the pathophysiology of periodontal diseases, the Workshop discussed the potential of antimicrobial peptides, probiotics, pro-resolving lipid mediators, and micronutritional approaches. Evidence-based position papers and expert discussions formed the basis of deliberations.

RESULTS AND DISCUSSION

Current preventive and treatment approaches are only partially effective, and this appears due to the therapeutic focus remaining primarily upon biofilm management rather than embracing a pivotal role for inflammation as a driver of biofilm composition as well as tissue damage. There is a need to develop new, more effective, and efficient preventive and treatment approaches for gingivitis and periodontitis, which embrace recent advances in understanding of host modulation and inflammation resolution, as well as direct management of the microbiota.

Persistent nasal carriage of Staphylococcus aureus is associated with deficient induction of human beta-defensin 3 after sterile wounding of healthy skin in vivo

Persistent nasal carriage of Staphylococcus aureus is the primary reservoir for this pathogen and a risk factor for infection. The nares of 12 to 30% of healthy individuals are persistently colonized with staphylococci. Elucidating the yet enigmatic determinants of this phenomenon is of major public health interest. We hypothesized that differences in the levels of antimicrobial peptides (AMPs) that are found in human skin and have pronounced antistaphylococcal activity may contribute to this phenomenon. We compared constitutive and induced mRNA levels of RNase 7 and human β-defensin 3 (HBD-3) in healthy and experimentally wounded gluteal skin of 60 volunteers after ascertaining their carrier status through repeated nasal cultures. We found that levels of HBD-3 expression in skin of persistent nasal carriers of S. aureus were lower: induced levels in carriers were 63% (95% confidence interval, 43 to 94%; P = 0.02) and constitutive levels were 76% (95% confidence interval, 52 to 110%; P = 0.14) of those found in noncarriers. No such associations were present for RNase 7. In conjunction with existing knowledge, these findings suggest that healthy individuals with deficient HBD-3 expression in keratinocytes are more prone to persistent nasal colonization with S. aureus.

Defensins couple dysbiosis to primary immunodeficiency in Crohn’s disease

Antimicrobial peptides, including defensins, are essential effectors in host defence and in the maintenance of immune homeostasis. Clinical studies have linked the defective expression of both α- and β-defensin to the reduced killing of certain microorganisms by the intestinal mucosa of patients suffering from ileal and colonic Crohn’s disease (CD), respectively. Only recently have the events leading to defective expression of defensins in CD been further elucidated, and are discussed herein. These events may account for CD-associated alterations in the microbiome and may subsequently precipitate the development of granulomatous inflammatory lesions in genetically-predisposed patients. We also address how these discoveries may pave the way for the development of a molecular medicine aimed at restoring gut barrier function in CD.

The role of keratinocytes in defense against infection

PURPOSE OF REVIEW

The discovery of increasing numbers of epithelial antimicrobial peptides (AMPs), cytokines that specifically induce AMPs in epithelial cells, and mechanisms of its regulation point toward a central role of the keratinocyte as effector cell of the epithelial innate defense system. This review summarizes recent progress in understanding the keratinocyte's role in combating infection that can help to understand why skin is usually covered with microbes but normally not infected.

RECENT FINDINGS

The AMP LL-37 has been identified as regulator of keratinocyte apoptosis. The hypothesis of a direct defense function of keratinocytes, combating bacterial, fungal, virus and parasite infection, is strengthened. The discovery of an IL-22-producing T-lymphocyte subpopulation implicates a role in AMP induction of keratinocytes. Multiple studies are adding to our understanding of how skin keratinocytes are interacting in skin barrier defects and with the microflora. Although in atopic patients AMP production is not generally impaired, in hyperIgE syndrome a lack of Th17 cytokines causes local Staphylococcus aureus infection due to a defective keratinocyte defense system. Ultraviolet radiation induces AMPs and thus may have beneficial effects to combat skin infection.

SUMMARY

There is better understanding of the keratinocyte's role in the skin's innate defense system, and these data can help to generate therapeutics that can activate this defense system.

Peroxisome proliferator-activated receptor gamma activation is required for maintenance of innate antimicrobial immunity in the colon

Crohn's disease (CD), a major form of human inflammatory bowel disease, is characterized by primary immunodeficiencies. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is essential for intestinal homeostasis in response to both dietary- and microbiota-derived signals. Its role in host defense remains unknown, however. We show that PPARgamma functions as an antimicrobial factor by maintaining constitutive epithelial expression of a subset of beta-defensin in the colon, which includes mDefB10 in mice and DEFB1 in humans. Colonic mucosa of Ppargamma mutant animals shows defective killing of several major components of the intestinal microbiota, including Candida albicans, Bacteroides fragilis, Enterococcus faecalis, and Escherichia coli. Neutralization of the colicidal activity using an anti-mDefB10 blocking antibody was effective in a PPARgamma-dependent manner. A functional promoter variant that is required for DEFB1 expression confers strong protection against Crohn's colitis and ileocolitis (odds ratio, 0.559; P = 0.018). Consistently, colonic involvement in CD is specifically linked to reduced expression of DEFB1 independent of inflammation. These findings support the development of PPARgamma-targeting therapeutic and/or nutritional approaches to prevent colonic inflammation by restoring antimicrobial immunity in CD.

The sound of silence: human beta-defensin-1 gene untranslated SNPs change the predicted mRNA secondary structure in a length-dependent manner

This study investigated how 5'-UTR of DEFB1 gene (encoding for the human beta-defensin-1) affects mRNA secondary structure and its correlation with translation efficiency in the susceptibility of diseases. It was possible to determine DEFB1 mRNA folding under the influence of 5'-UTR SNPs haplotypes and putative alternative transcript lengths. Different DEFB1 mRNAs that fold in a pattern that is haplotype and length-dependent are potentially able to drive changes in peptide expression dynamics.