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Introduction: Previous reports have proposed that Periodontal disease (PDis) predisposes to Alzheimer's disease (AD), both highly prevalent pathologies among the elderly. The bacteria Aggregatibacter actinomycetemcomitans (Aa), associated with the most aggressive forms of PDis, are classified in different serotypes with distinct virulence according to the antigenicity of their lipopolysaccharide (LPS). Methods: Here, we determined the effects of purified LPS, from serotypes a, b or c of Aa, on primary cultures of microglia or mixed hippocampal cells. Results: We found that both culture types exhibited higher levels of inflammatory cytokines (IL-1ß, IL-6 and TNFα) when treated with serotype b-LPS, compared with controls, as quantified by qPCR and/or ELISA. Also, cultures treated with serotype a-LPS displayed increased mRNA levels of the modulatory cytokines IL-4 and IL-10. Mixed hippocampal cultures treated with serotype b-LPS exhibited severe neuronal morphological changes and displayed increased levels of secreted Aß1-42 peptide. These results indicate that LPS from different Aa serotypes triggers discriminatory immune responses, which differentially affect primary hippocampal cells. Conclusion: Altogether, our results show that treatment with serotype b-LPS triggers the secretion of proinflammatory cytokines by microglia, induces neurite shrinking, and increases the extracellular Aß1-42 levels, all features strongly associated with the etiology of AD.
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BACKGROUND AND OBJECTIVE: Two new T-helper (Th) phenotypes have been recently described and named Th9 and Th22 lymphocytes; however, their role in the pathogenesis of periodontitis remains unclear. This study was aimed to assess whether Th9 and Th22 lymphocytes, through interleukin (IL)-9 and IL-22 production, respectively, are associated with the severity of periodontitis and bone resorption. MATERIAL AND METHODS: Gingival crevicular fluid samples and biopsies were obtained from patients with moderate-to-advanced chronic periodontitis and gingivitis, and healthy controls. The levels for the Th9 and Th22-associated cytokines and master-switch transcription factors Spi-B and aryl hydrocarbon receptor (AhR) were quantified by enzyme-linked immunosorbent assay, real-time reverse-transcription quantitative polymerase chain reaction and flow cytometry. In addition, the osteoclast activity in response to tissue homogenates from periodontitis and healthy samples was analyzed quantifying the number of TRAP-positive cells and areas of bone resorption pits produced, in the presence or absence of recombinant human IL-22 and anti-IL-22 neutralization antibody. RESULTS: Higher levels of IL-22 and AhR were detected in patients with periodontitis compared with gingivitis and healthy individuals. In addition, higher levels of IL-9 and Spi-B were detected in gingivitis patients compared with periodontitis and healthy individuals. In patients with periodontitis, a significant positive correlation was detected between secreted levels of IL-22 and clinical attachment level of the sampled periodontal pockets. When osteoclasts were exposed to tissue homogenates obtained from patients with periodontitis, higher levels of resorptive activity were observed as compared with the same cells exposed to tissue homogenates obtained from healthy individuals, and this increment was dependent on the presence and neutralization of IL-22. CONCLUSION: Increased levels of IL-22 produced by Th22 lymphocytes are associated with the pathogenesis of periodontitis, in particular, with osteoclast resorptive activity and severity of disease.
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Periodontitis Crónica/inmunología , Citocinas/metabolismo , Líquido del Surco Gingival/química , Interleucinas/metabolismo , Osteoclastos/inmunología , Osteoclastos/metabolismo , Receptores de Hidrocarburo de Aril/metabolismo , Adulto , Periodontitis Crónica/patología , Citocinas/análisis , Citocinas/genética , Proteínas de Unión al ADN/análisis , Proteínas de Unión al ADN/metabolismo , Femenino , Expresión Génica , Gingivitis/inmunología , Gingivitis/patología , Humanos , Interleucina-9/análisis , Interleucina-9/metabolismo , Interleucinas/análisis , Masculino , Pérdida de la Inserción Periodontal , Bolsa Periodontal/inmunología , ARN/aislamiento & purificación , ARN Ribosómico 18S/análisis , Receptores de Hidrocarburo de Aril/análisis , Factores de Transcripción/análisis , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Interleucina-22RESUMEN
BACKGROUND AND OBJECTIVE: Porphyromonas gingivalis infection induces apoptosis inhibition in gingival epithelial cells; however, it is not fully understood which bacterial effectors are involved in this process. The aim of this study is to evaluate whether the P. gingivalis lipopolysaccharide (LPS), specifically the O-antigen region, affects adherence, invasion, viability and apoptosis of gingival epithelial cells. MATERIAL AND METHODS: Gingival epithelial cells (OKF6/TERT2 line) were infected by different freshly prepared P. gingivalis clinical isolates, obtained from subjects with chronic periodontitis (CP3 and CP4) and healthy individuals (H1 and H3). Periodontitis and healthy isolates show differences in O-antigen production, as healthy isolates lack the O-antigen region. In addition, cells were infected by a site-specific mutant lacking the O-antigen portion. After 24 h postinfection, cell proliferation, viability and apoptosis were evaluated by Trypan blue, MTS and annexin V assays, respectively. Bacterial invasion, adhesion and proliferation were measured by gentamicin/metronidazole protection assays. Finally, toll-like receptor (TLR)2 and TLR4 mRNA expression was evaluated by quantitative reverse transcription-polymerase chain reaction. Statistical analysis was performed using ANOVA, Tukey's or Dunnett's tests (p < 0.05). RESULTS: At 24 h postinfection, strains lacking the O-antigen region (healthy isolates and O-antigen ligase-deficient strain) were unable to increase proliferation and viability, or decrease apoptosis as compared with strains producing intact LPS (periodontitis isolates and reference strain). However, the presence of the O-antigen neither contributed to changes in the ability of the bacteria to adhere to or invade cells, nor to intracellular survival. The presence of O-antigen also increased the expression of TLR4 (nearly sixfold), which correlated with inhibition of apoptosis. CONCLUSION: The O-antigen region of P. gingivalis LPS is required to increase gingival epithelial cell viability upon infection by bacteria and this increase is attributable to a reduction in apoptosis. Moreover, although bacterial internalization is required, the effects observed are not due to alterations in P. gingivalis adherence, invasion or intracellular survival. Interestingly, inhibition of apoptosis correlates with increased TLR4 expression, suggesting a role for TLR4 in this process.
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Apoptosis/efectos de los fármacos , Encía/efectos de los fármacos , Antígenos O/farmacología , Porphyromonas gingivalis/fisiología , Infecciones Bacterianas , Células Cultivadas , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Expresión Génica , Encía/citología , Encía/metabolismo , Humanos , Lipopolisacáridos/farmacología , Periodontitis , Porphyromonas gingivalis/aislamiento & purificación , ARN Mensajero/metabolismo , Receptor Toll-Like 2/genética , Receptor Toll-Like 2/metabolismo , Receptor Toll-Like 4/genética , Receptor Toll-Like 4/metabolismoRESUMEN
During periodontitis, alveolar bone resorption is associated with activation of T helper type 17 (Th17) lymphocytes and receptor activator of nuclear factor-κB ligand (RANKL) -induced osteoclasts. We previously reported that serotype b of Aggregatibacter actinomycetemcomitans has a higher capacity to trigger Th17-type differentiation and function in activated T lymphocytes and its lipopolysaccharide is a more potent immunogen compared with the other serotypes. This study aimed to investigate whether serotype b of A. actinomycetemcomitans induces higher Th17-associated RANKL production, RANKL-induced osteoclast activation, and antigen-specific memory T lymphocyte proliferation. On naive CD4(+) T lymphocytes stimulated with autologous dendritic cells primed with different A. actinomycetemcomitans serotypes, RANKL production, T-bet, GATA-3, RORC2 and Foxp3 expression, RORC2/RANKL intracellular double-expression, TRAP(+) osteoclast activation, and bone resorption were quantified. The frequency of proliferating memory T lymphocytes in response to A. actinomycetemcomitans serotypes was determined in periodontitis and healthy subjects. Naive CD4(+) T lymphocytes stimulated by serotype b-primed dendritic cells elicited higher levels of RANKL, RORC2, TRAP(+) osteoclasts, and bone resorption than the same cells stimulated with the other serotypes. RANKL positively correlated and co-expressed with RORC2. Memory T lymphocytes responding to serotype b were more frequently detected in periodontitis patients than healthy subjects. These results indicate that serotype b of A. actinomycetemcomitans is associated with higher production of RANKL and these increased levels are associated with Th17 lymphocyte induction, osteoclast activation, and bone resorption.
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Aggregatibacter actinomycetemcomitans/inmunología , Osteoclastos/inmunología , Linfocitos T/inmunología , Antígenos Bacterianos/inmunología , Antígenos Bacterianos/farmacología , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/microbiología , Diferenciación Celular/inmunología , Periodontitis Crónica/inmunología , Periodontitis Crónica/microbiología , Células Dendríticas/inmunología , Factores de Transcripción Forkhead/biosíntesis , Factor de Transcripción GATA3/biosíntesis , Humanos , Memoria Inmunológica/inmunología , Lipopolisacáridos/farmacología , Activación de Linfocitos , Miembro 3 del Grupo F de la Subfamilia 1 de Receptores Nucleares/biosíntesis , Ligando RANK/inmunología , Serogrupo , Linfocitos T/microbiologíaRESUMEN
BACKGROUND AND OBJECTIVE: Based on lipopolysaccharide (LPS) antigenicity, different Aggregatibacter actinomycetemcomitans serotypes have been described. Serotype b strains have demonstrated a stronger capacity to trigger cytokine production on dendritic cells (DCs). As DCs regulate the development of T-lymphocyte lineages, the objective of this investigation was to study the response of T lymphocytes after being stimulated with autologous DCs primed with different bacterial strains belonging to the most prevalent serotypes of A. actinomycetemcomitans in humans: a-c. MATERIAL AND METHODS: Human DCs were primed with increasing multiplicity of infection (10(-1) -10(2) ) or the purified LPS (10-50 ng/mL) of A. actinomycetemcomitans serotypes a-c and then used to stimulate autologous naïve CD4(+) T lymphocytes. The T-helper (Th) type 1, Th2, Th17 and T-regulatory transcription factors T-bet, GATA-3, RORC2 and Foxp3, which are the master-switch genes implied in their specific differentiation, as well as T-cell phenotype-specific cytokine patterns were quantified by real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, the intracellular expression of T-bet/interferon-γ, GATA-3/interleukin-4, RORC2/interleukin-17A and Foxp3/transforming growth factor-ß1 was analysed by double staining and flow cytometry. RESULTS: All the A. actinomycetemcomitans serotypes led to T-lymphocyte activation; however, when T lymphocytes were stimulated with DCs primed with the A. actinomycetemcomitans serotype b strain or their purified LPS, higher levels of Th1- and Th17-associated transcription factors and cytokines were detected compared with similar experiments with the other serotypes. CONCLUSION: These results demonstrate that serotype b of A. actinomycetemcomitans has a higher capacity of trigger Th1 and Th17 phenotype and function and it was demonstrated that their LPS is a more potent immunogen compared with the other serotypes.
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Aggregatibacter actinomycetemcomitans/inmunología , Fenotipo , Serogrupo , Linfocitos T/inmunología , Aggregatibacter actinomycetemcomitans/clasificación , Células Cultivadas , Citocinas/análisis , Ensayo de Inmunoadsorción Enzimática , Citometría de Flujo , Perfilación de la Expresión Génica , Humanos , Inmunofenotipificación , Lipopolisacáridos/inmunología , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Transcripción/análisisRESUMEN
Objetivo: Sobre la base de la antigenicidad del polisacárido O del LPS, en A. actinomycetemcomitans se describen distintos serotipos bacterianos y entre ellos se ha especulado una patogenicidad e inmunogenicidad diferente. El objetivo de este trabajo es analizar las diferencias en la síntesis de citoquinas producidas por células dendríticas cuando son estimuladas con los distintos serotipos de A. actinomycetemcomitans. Metodología: Células dendríticas diferenciadas a partir de monocitos circulantes periféricos humanos fueron estimuladas a MOIs=10-1-10-2 con los serotipos a, b y c de A. Actinomycetemcomitans. Mediante PCR y ELISA se evaluaron los niveles de expresión y secreción de citoquinas. Resultados: En las células dendríticas, la producción de citoquinas fue diferente ante los distintos serotipos de A. actinomycetemcomitans, con mayores niveles de secreción de IL-1beta, IL-6, IL-12, IL-23, IFN-gamma y TNF-alfa cuando el microorganismo estimulante fue la cepa ATCC® 43718 (serotipo b). Conclusión: El serotipo b de A. actinomycetemcomitans posee un mayor potencial inmuno-estimulador de células dendríticas comparado con los otros serotipos bacterianos y potencialmente contribuiría a inducir un patrón de respuesta inmune tipo Th1 y/o Th17 durante las periodontitis.
Objective: A. actinomycetemcomitans expresses a number of virulence factors that contribute to direct tissue damage and, based on the antigenicity of LPS O-polysaccharide, distinct serotypes have been described. The aim of this study was to determine the pattern of cytokine expression and secretion on dendritic cells stimulated with A. actinomycetemcomitans serotypes a, b and c. Methods: Using different multiplicity of infections of the serotypes a, b, and c of A. actinomycetemcomitans, the mRNA expression and secretion levels for cytokines IL-1beta, IL-5, IL-6, IL-10, IL-12, IL-23, TNF-alpha, and IFN-gamma were determined in stimulated dendritic cells using PCR and ELISA. Results: A dose-dependent increase in the secretion levels for IL-1beta, IL-5, IL-6, IL-10, IL-12, IL-23, TNF-alpha, and IFN-gamma was elicited on dendritic cells following stimulation with each of the serotypes of A. actinomycetemcomitans. In addition, A. actinomycetemcomitans serotype b (ATCC® 43718) induced higher levels of IL-1beta, IL-6, IL-12, IL-23, IFN-gamma y TNF-alpha compared with the other strains. Conclusion: These data demonstrate that the distinct A. actinomycetemcomitans LPS O-polysaccharide serotypes induce both quantitative and qualitative differences in the dendritic cell response. Furthermore, the observed dendritic cell response to A. actinomycetemcomitans b serotype was characteristic of a Th1 and Th17 pattern of cytokine expression.
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Aggregatibacter actinomycetemcomitans , Células Dendríticas/metabolismo , Citocinas/biosíntesis , Ensayo de Inmunoadsorción Enzimática , Reacción en Cadena de la PolimerasaRESUMEN
Las periodontitis son un conjunto de patologías de naturaleza inflamatoria y etiología infecciosa producidas por el biofilm patogénico subgingival. Porphyromonas gingivalis y Aggregatibacter actinomycetemcomitans son bacterias periodonto-patógenas que pueden causar daño directo a las estructuras periodontales a través de los diversos factores de virulencia que expresan. Sobre la base de estos factores de virulencia, distintos genotipos y serotipos bacterianos se han descrito, cada uno de ellos con una potencial variable patogenicidad. En esta revisión bibliográfica se describen diferentes factores de virulencia de P. gingivalis y A. actinomycetemcomitans y se discute la variable inmunogenicidad y patogenicidad de los distintos genotipos y serotipos descritos para ellos. Tanto P. gingivalis como A. actinomycetemcomitans poseen diversos factores de virulencia asociados al inicio, progresión y severidad de las periodontitis. En P. gingivalis, los factores de virulencia para los cuales se describen distintos genotipos y/o serotipos son fimbria, LPS y cápsula bacteriana, y en A. actinomycetemcomitans son leucotoxina A, Cdt y LPS. Cada uno de estos distintos genotipos y serotipos induce una respuesta inmuno-inflamatoria diferente en el hospedero y, por lo tanto, se podrían asociar a una variable patogenicidad y podrían determinar las características clínicas de la enfermedad.
Periodontitis represents a heterogenic group of periodontal infections elicited by bacteria residing at the subgingival biofilm. Although this biofilm is constituted by a broad variety of bacterial species, only a limited number has been associated with the periodontitis aetiology, among them Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. Both P. gingivalis and A. actinomycetemcomitans express a number of virulence factors that contribute to direct tissue damage and, based on them, distinct genotypes and serotypes have been described, each one with a potential variable pathogenicity. This review aimed to analyze the different virulence factors described for P. gingivalis and A. actinomycetemcomitans and to discuss the variable immunogenicity and pathogenicity of their serotypes and genotypes. P. gingivalis and A. actinomycetemcomitans express different virulence factors and they determine the initiation, progression, and severity of periodontitis. In P. gingivalis, distinct serotypes and/or genotypes are described based on fimbriae, LPS, and capsule. Additionally, in A. actinomycetemcomitans distinct serotypes and/or genotypes are described based on leucotoxin A, Cdt, and LPS. These distinct serotypes and genotypes induce a differential immunoinflammatory response and, thus, could be associated with variations in pathogenicity and reflected in clinic characteristics of the disease.