Too old to fight? Aging and its toll on innate immunity

Impact of aging on TREM-1 responses in the periodontium: a cross-sectional study in an elderly population

Background

Aging is associated with altered immune response, which increases susceptibility to infections. sTREM-1 is involved in the amplification of the inflammatory response to bacterial infection. The present cross-sectional study aims to investigate local sTREM-1 levels in gingival crevicular fluid (GCF) as well as key periodontal pathogen levels in the subgingival plaque in an elderly cohort with periodontal health, gingivitis, and chronic periodontitis (CP).

Methods

Subjects were 51 systemically healthy, elderly individuals (mean age, 68 ± 4.5 years) who had undergone full-mouth periodontal examinations. Subgingival plaque and GCF samples were collected from the healthy sites of participants without periodontal disease (n = 17), the sites with gingival inflammation from patients with gingivitis (n = 19), and the periodontitis sites of patients with CP (n = 15). GCF volumes were measured by an electronic impedance device, and total protein levels were assessed by a flouremetric assay. sTREM-1 levels in GCF were measured by enzyme-linked immunosorbent assay. The subgingival plaque total bacteria, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, and Prevotella intermedia levels were determined by quantitative real-time polymerase chain reaction. Statistical analysis was performed using nonparametric methods.

Results

GCF volume, total protein concentrations, and sTREM-1 levels in GCF were similar among the groups (p > 0.05). Significantly higher T. forsythia levels were observed in subgingival plaque samples harvested from patients with gingivitis and CP, than in those from healthy participants (p < 0.05). However, the subgingival levels of the other four periodontal pathogens and total bacteria were not statistically different among the groups (p > 0.05).

Conclusions

Our findings suggest that there are no differences in GCF volume, total protein, and sTREM-1 levels between healthy and periodontally diseased elderly adults. We found only limited differences in the studied subgingival microbial profile. This finding indicates an already deregulated, local inflammatory response in this elderly cohort, on which bacterial biofilm challenge may have a limited further impact.

Caveolin-1 serves as a negative effector in senescent human gingival fibroblasts during Fusobacterium nucleatum infection

It is well established that aging is associated with increased susceptibility to infectious diseases. Fusobacterium nucleatum is a well-known bacterial species that plays a central bridging role between early and late colonizers in the human oral cavity. Further, the ability of F. nucleatum to invade gingival fibroblasts (GFs) is critical to the development of periodontal diseases. However, the mechanisms underlying the age-related infection of GFs by F. nucleatum remain unknown. We used young (fourth passage) and senescent (22nd passage) GFs to investigate the mechanisms of F. nucleatum infection in aged GFs and first observed increased invasion of F. nucleatum in senescent GFs. We also found that the co-localization of caveolin-1 (Cav-1), a protein marker of aging, with F. nucleatum and the knockdown of Cav-1 in GFs reduced F. nucleatum invasion. Additionally, F. nucleatum infection triggered the production of reactive oxygen species (ROS) through activation of NADPH oxidase in GFs, but senescent GFs exhibited significantly lower levels of NADPH oxidase activity and ROS production compared with young GFs in both the uninfected and infected conditions. Also, senescent GFs exhibited a decline in proinflammatory cytokine production and extracellular signal regulated kinase (ERK) phosphorylation following F. nucleatum infection. Interestingly, the knockdown of Cav-1 in senescent GFs increased NADPH oxidase activity and caused the upregulation of interleukin-6 and interleukin-8 and the phosphorylation of ERK. Collectively, the increased expression of Cav-1 might play a critical role in F. nucleatum invasion and could hinder the host response in senescent GFs.

Experimental mucositis and experimental gingivitis in persons aged 70 or over. Clinical and biological responses

Objectives

To compare in persons aged 70 years or older the clinical and inflammatory changes occurring around implants and natural teeth during and after a phase of undisturbed plaque accumulation.

Material and methods

Twenty partially edentulous participants with titanium implants refrained from oral hygiene practices while being clinically monitored in weekly intervals for 21 days. Teeth and implants were then cleaned, oral hygiene resumed, and the participants were further monitored for 3 weeks. Twelve biomarkers were assessed in gingival and peri‐implant crevicular fluid (GCF, PCF).

Results

During 3 weeks of oral hygiene abstention, the gingival index (GI) continuously increased. On day 21, there were significantly more sites with GI >1 at implants than at teeth. After restarting oral hygiene, the GI decreased markedly in both groups. Throughout the experiment, the plaque index was significantly higher on teeth than on implants.

The different biomarkers reacted variably. IL‐1β increased significantly with plaque accumulation. IL‐1β, GM‐CSF, TNF‐α, and IFN‐γ were significantly higher in GCF compared to PCF at day 21. IL‐8 decreased significantly in GCF up to day 14. MIP‐1β decreased significantly in GCF, but not in PCF. At the 3‐week follow‐up, the levels of all biomarkers assessed in GCF and PCF had returned to baseline values.

Conclusions

In an elderly cohort, plaque accumulation induced an inflammatory reaction around both teeth and implants. Although there was less plaque accumulation on implants, the peri‐implant mucosa showed a stronger clinical response than gingiva.

Immune system transcriptome in gingival tissues of young nonhuman primates

BACKGROUND AND OBJECTIVE

Young/adolescent humans harbor many microorganisms associated with periodontal disease in adults and show substantial gingival inflammatory responses. However, younger individuals do not demonstrate the soft- and hard-tissue destruction that hallmark periodontitis.

MATERIAL AND METHODS

This study evaluated responses to the oral microbial ecology in gingival tissues from clinically healthy young Macaca mulatta (< 3 years of age) compared with older animals (5-23 years of age). RNA was isolated from the tissues and analyzed for the transcriptome using the Rhesus Macaque GeneChip (Affymetrix).

RESULTS

Global transcriptional profiling of four age groups revealed a subset of 159 genes that were differentially expressed across at least one of the age comparisons. Correlation metrics generated a relevance network abstraction of these genes. Partitioning of the relevance network revealed seven distinct communities comprising functionally related genes associated with host inflammatory and immune responses. A group of genes was identified that were selectively increased/decreased or positively/negatively correlated with gingival profiles in the animals. A principal components analysis created metagenes of expression profiles for classifying the 23 animals.

CONCLUSION

The results provide novel system-level insights into gene-expression differences in gingival tissues from healthy young animals, weighted toward host responses associated with anti-inflammatory biomolecules or those linked with T-cell regulation of responses. The combination of the regulated microenvironment may help to explain the apparent 'resistance' of younger individuals to developing periodontal disease.

Effect of Aging on Periodontal Inflammation, Microbial Colonization, and Disease Susceptibility

Periodontitis is a chronic inflammatory disease induced by a biofilm that forms on the tooth surface. Increased periodontal disease is associated with aging. We investigated the effect of aging on challenge by oral pathogens, examining the host response, colonization, and osteoclast numbers in aged versus young mice. We also compared the results with mice with lineage-specific deletion of the transcription factor FOXO1, which reduces dendritic cell (DC) function. Periodontitis was induced by oral inoculation of Porphyromonas gingivalis and Fusobacterium nucleatum in young (4 to 5 mo) and aged (14 to 15 mo) mice. Aged mice as well as mice with reduced DC function had decreased numbers of DCs in lymph nodes, indicative of a diminished host response. In vitro studies suggest that reduced DC numbers in lymph nodes of aged mice may involve the effect of advanced glycation end products on DC migration. Surprisingly, aged mice but not mice with genetically altered DC function had greater production of antibody to P. gingivalis, greater IL-12 expression, and more plasma cells in lymph nodes following oral inoculation as compared with young mice. The greater adaptive immune response in aged versus young mice was linked to enhanced levels of P. gingivalis and reduced bacterial diversity. Thus, reduced bacterial diversity in aged mice may contribute to increased P. gingivalis colonization following inoculation and increased periodontal disease susceptibility, reflected by higher TNF levels and osteoclast numbers in the periodontium of aged versus young mice.

Effects of aging in the expression of NOD-like receptors and inflammasome-related genes in oral mucosa

The molecular changes underlying the higher risk of chronic inflammatory disorders during aging remain incompletely understood. Molecular variations in the innate immune response related to recognition and interaction with microbes at mucosal surfaces could be involved in aging-related inflammation. We developed an ontology analysis of 20 nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) and seven inflammasome-related genes (IRGs) in healthy and inflamed/periodontitis oral mucosal tissues from young, adolescent, adult, and aged non-human primates (Macaca mulatta) using the GeneChip(®) Rhesus Macaque Genome array. Validation of some of the significant changes was done by quantitative reverse transcription-polymerase chain reaction. The expression of NLRB/NAIP, NLRP12, and AIM2 increased with aging in healthy mucosa whereas NLRC2/NOD2 expression decreased. Although higher expression levels of some NLRs were generally observed with periodontitis in adult mucosal tissues (e.g. NLRB/NAIP, NLRP5, and NLRX1), various receptors (e.g. NLRC2/NOD2 and NLRP2) and the inflammasome adaptor protein ASC, exhibited a significant reduction in expression in aged periodontitis tissues. Accordingly, the expression of NLR-activated innate immune genes, such as HBD3 and IFNB1, was impaired in aged but not adult periodontitis tissues. Both adult and aged tissues showed significant increase in interleukin-1β expression. These findings suggest that the expression of a subset of NLRs appears to change with aging in healthy oral mucosa, and that aging-related oral mucosal inflammation could involve an impaired regulation of the inflammatory and antimicrobial response associated with downregulation of specific NLRs and IRGs.

Role of nitro-oxidative stress in the pathogenesis of experimental rat periodontitis

Background and aims

Periodontitis is a common chronic adult condition that implicates oxidative damage to gingival tissue, periodontal ligament and alveolar bone. This study aimed at assessing the association between the nitro-oxidative stress and the periodontal tissues destructions in experimental rat periodontitis.

Methods

Periodontitis was induced in 15 male albino rats by repetitive lesions to the gingiva adjacent to the inferior incisors, performed daily, for 16 days. On D1, D3, D6, D8, and D16 the onset and evolution of periodontitis were monitored by clinical and histopathological examinations; blood was collected and serum nitro-oxidative stress was evaluated through total nitrites and nitrates, total oxidative status, total antioxidant capacity, and oxidative stress index.

Results

The results demonstrated that there was a graded and continuous increase in serum levels of total nitrites and nitrates, total oxidative status and oxidative stress index, which was consistent with the severity of periodontal destructions during periodontitis progression. However, total antioxidant capacity was not significantly influenced by the disease progression.

Conclusions

In experimental rat periodontitis, the systemic nitro-oxidative stress was associated with the severity of periodontal destructions assessed clinically and histopathologically. Therefore, systemic nitro-oxidative stress parameters might be used as diagnostic tools in periodontitis.

Clinical profile of patients with advanced age and inflammatoric dilated cardiomyopathy on endomyocardial biopsy

BACKGROUND

Endomyocardial biopsy (EMB) is an important tool when patients with inflammatoric cardiomyopathy (DCMi) are evaluated. We aimed to assess the clinical profile of elderly patients with DCMi on EMB.

METHODS

Retrospective study of all consecutive patients hospitalized from January 2007 to December 2011 with clinical suspicion of DCMi undergoing EMB. Patients with evidence of DCMi on EMB (Group 1 ≥ 70 years, n = 85; Group 3 < 70 years; n = 418) were compared to patients of the same age group without evidence of DCMi on EMB (Group 2 ≥ 70 years, n = 45; Group 4 < 70 years; n = 147).

RESULTS

Among 24,275 patients treated at our institution during the study period, 695 had clinical suspicion of DCMi and underwent EMB; 503 (2.1%) patients had DCMi on EMB. There were more male patients in Group 1, mean age was 74 ± 2.8 years, mean ejection fraction was 38% ± 14%. On presentation, signs of hemodynamic compromise (NYHA functional class III/IV, low cardiac output/index, and low cardiac power index) were more frequent in Group 1. EMB revealed viral genome in 78% of the patients, parvovirus B19 (PVB) was frequently encountered in both age groups (Group 1: 69.4% vs. Group 2: 59.6%); detection of more than one viral genome was more frequent in Group 1 (21.2% vs. 11.2%; P = 0.02) whereas the extent of immune response was significantly lower in individuals with advanced age.

CONCLUSIONS

In patients ≥ 70 years with DCMi on EMB signs of hemodynamic compromise, detection of multiple viral genomes together with an overall lower extent of immune response were more frequently observed.

Immunosenescence in renal transplantation: a changing balance of innate and adaptive immunity

PURPOSE OF REVIEW

With global demographic changes and an overall improved healthcare, more older end-stage renal disease (ESRD) patients receive kidney transplants. At the same time, organs from older donors are utilized more frequently. Those developments have and will continue to impact allocation, immunosuppression and efforts improving organ quality.

RECENT FINDINGS

Findings mainly outside the field of transplantation have provided insights into mechanisms that drive immunosenescence and immunogenicity, thus providing a rationale for an age-adapted immunosuppression and relevant clinical trials in the elderly. With fewer rejections in the elderly, alloimmune responses appear to be characterized by a decline in effectiveness and an augmented unspecific immune response.

SUMMARY

Immunosenescence displays broad and ambivalent effects in elderly transplant recipients. Those changes appear to compensate a decline in allospecific effectiveness by a shift towards an augmented unspecific immune response. Immunosuppression needs to target those age-specific changes to optimize outcomes in elderly transplant recipients.

Differential Gene Expression Profiles Reflecting Macrophage Polarization in Aging and Periodontitis Gingival Tissues

Recent evidence has determined a phenotypic and functional heterogeneity for macrophage populations. This plasticity of macrophage function has been related to specific properties of subsets (M1 and M2) of these cells in inflammation, adaptive immune responses and resolution of tissue destructive processes. This investigation hypothesized that targeted alterations in the distribution of macrophage phenotypes in aged individuals, and with periodontitis would be skewed towards M1 inflammatory macrophages in gingival tissues. The study used a non-human primate model to evaluate gene expression profiles as footprints of macrophage variation in healthy and periodontitis gingival tissues from animals 3-23 years of age and in periodontitis tissues in adult and aged animals. Significant increases in multiple genes reflecting overall increases in macrophage activities were observed in healthy aged tissues, and were significantly increased in periodontitis tissues from both adults and aged animals. Generally, gene expression patterns for M2 macrophages were similar in healthy young, adolescent and adult tissues. However, modest increases were noted in healthy aged tissues, similar to those seen in periodontitis tissues from both age groups. M1 macrophage gene transcription patterns increased significantly over the age range in healthy tissues, with multiple genes (e.g. CCL13, CCL19, CCR7 and TLR4) significantly increased in aged animals. Additionally, gene expression patterns for M1 macrophages were significantly increased in adult health versus periodontitis and aged healthy versus periodontitis. The findings supported a significant increase in macrophages with aging and in periodontitis. The primary increases in both healthy aged tissues and, particularly periodontitis tissues appeared in the M1 phenotype.

Can oral infection be a risk factor for Alzheimer's disease?

Alzheimer's disease (AD) is a scourge of longevity that will drain enormous resources from public health budgets in the future. Currently, there is no diagnostic biomarker and/or treatment for this most common form of dementia in humans. AD can be of early familial-onset or sporadic with a late-onset. Apart from the two main hallmarks, amyloid-beta and neurofibrillary tangles, inflammation is a characteristic feature of AD neuropathology. Inflammation may be caused by a local central nervous system insult and/or by peripheral infections. Numerous microorganisms are suspected in AD brains ranging from bacteria (mainly oral and non-oral Treponema species), viruses (herpes simplex type I), and yeasts (Candida species). A causal relationship between periodontal pathogens and non-oral Treponema species of bacteria has been proposed via the amyloid-beta and inflammatory links. Periodontitis constitutes a peripheral oral infection that can provide the brain with intact bacteria and virulence factors and inflammatory mediators due to daily, transient bacteremias. If and when genetic risk factors meet environmental risk factors in the brain, disease is expressed, in which neurocognition may be impacted, leading to the development of dementia. To achieve the goal of finding a diagnostic biomarker and possible prophylactic treatment for AD, there is an initial need to solve the etiological puzzle contributing to its pathogenesis. This review therefore addresses oral infection as the plausible etiology of late-onset AD (LOAD).

RNA regulators of host immunity and pathogen adaptive responses in the oral cavity

The recent explosion of RNA-seq studies has resulted in a newfound appreciation for the importance of riboregulatory RNAs in the posttranscriptional control of eukaryotic and prokaryotic genetic networks. The current review will explore the role of trans-riboregulatory RNAs in various adaptive responses of host and pathogen in the oral cavity.

Immunosenescence in monocytes, macrophages, and dendritic cells: lessons learned from the lung and heart

In the absence of an immune challenge, healthy, aged individuals have a significantly higher basal inflammatory state where circulating levels of cytokines, including IL-6, TNF-α and IL-1β, are elevated [1]. This progressive pro-inflammatory state, termed "inflamm-aging", affects the phenotype/function of cells present in the aged as well as renders the older individuals more susceptible to a poor prognosis after systemic insults. Although it is important to understand the mechanisms that underlie the progression of disease, most preclinical analyses of disease therapies are performed in young adult mice that have an intact, functional immune system. Oftentimes, this is not necessarily representative of the immune disposition in the aged, let alone diseased, aged. Herein, two distinct responses that are not only commonly associated with aging but that also have dendritic cells and/or monocytes and macrophages as key players are discussed: pulmonary infection and myocardial infarction. Although studies of pulmonary infection in the aged have progressed significantly, studies of monocytes and macrophages in inflammation and cardiac injury following ischemia in the aged have not been as forthcoming. Nonetheless, several elegant studies have established the dynamic role of monocytes and macrophages post infarction. These will be discussed in light of what is known with aging.

Influence of age on manifestation, VC and TLCO values, and bronchoalveolar lavage cell counts of sarcoidosis and extrinsic allergic alveolitis

INTRODUCTION

Immune response probably changes during human life, being influenced by cumulative exposure to environmental factors and individual genetic background.

METHODS

Patients investigated for suspected interstitial lung disease were prospectively enrolled. After completing the diagnostic process, 121 patients were diagnosed extrinsic allergic alveolitis (EAA) and 136 sarcoidosis. Three groups according to age were established (<30 years, 30-60 years, >60 years), clinical manifestation, vital capacity (VC), forced expired volume in 1 s (FEV1 ), lung diffusing capacity for carbon monoxide-transfer factor (TLCO ) and bronchoalveolar lavage fluid (BALF) differential cell count were compared among the groups.

RESULTS

Age subgroups of EAA patients did not significantly differ in lung functions. In the group above 60 years, non-significantly higher neutrophils and eosinophils counts and CD4/CD8 ratio were observed. Sarcoidosis patients were significantly younger than EAA group and had significantly better lung functions (VC, FEV1 , TLCO ). Patients with sarcoidosis above 60 years of age had significantly higher percentages of neutrophils in BALF compared with younger patients. BALF percentage of neutrophils positively correlated with age.

CONCLUSIONS

Presented results may support the hypothesis that reactivity of immune system changes during the life, which may result in different manifestation of interstitial lung diseases according to age.

Aging and its Impact on Innate Immunity and Inflammation: Implications for Periodontitis

The elderly exhibit increased susceptibility to a number of inflammatory or degenerative pathologies. Aging is similarly thought to be associated with increased prevalence and severity of periodontitis, although the underlying causes are poorly understood. Among the plausible mechanisms whereby aging could contribute to increased susceptibility to periodontitis are age-dependent alterations in the innate immune and inflammatory status of the host. This hypothesis is supported by studies in humans and animal models outlined in this Review. Indeed, innate immune cells isolated from elderly subjects exhibit age-related cell-intrinsic defects that could predispose the elderly to deregulated immune and inflammatory responses. Moreover, the investigation of age-related alterations in the tissue environment where recruited inflammatory cells ultimately function could provide complementary, if not better, insights into the impact of aging on periodontitis. Integrative approaches combining in vitro and in vivo mechanistic models are underway and can potentially contribute to targeted molecular therapies that can reverse or mitigate the effects of aging on periodontitis and other inflammatory diseases.

Comparative analysis of gingival tissue antigen presentation pathways in ageing and periodontitis

AIM

Gingival tissues of periodontitis lesions contribute to local elevations in mediators, including both specific T cell and antibody immune responses to oral bacterial antigens. Thus, antigen processing and presentation activities must exist in these tissues to link antigen-presenting cells with adaptive immunity. We hypothesized that alterations in the transcriptome of antigen processing and presentation genes occur in ageing gingival tissues and that periodontitis enhances these differences reflecting tissues less capable of immune resistance to oral pathogens.

MATERIALS AND METHODS

Rhesus monkeys (n = 34) from 3 to 23 years of age were examined. A buccal gingival sample from healthy or periodontitis sites was obtained, total RNA isolated, and microarray analysis was used to describe the transcriptome.

RESULTS

The results demonstrated increased transcription of genes related to the MHC class II and negative regulation of NK cells with ageing in healthy gingival tissues. In contrast, both adult and ageing periodontitis tissues showed decreased transcription of genes for MHC class II antigens, coincident with up-regulation of MHC class I-associated genes.

CONCLUSION

These transcriptional changes suggest a response of healthy ageing tissues through the class II pathway (i.e. endocytosed antigens) and altered responses in periodontitis that could reflect host-associated self-antigens or targeting cytosolic intracellular microbial pathogens.

Immunomicrobial pathogenesis of periodontitis: keystones, pathobionts, and host response

Recent studies have uncovered novel mechanisms underlying the breakdown of periodontal host-microbe homeostasis, which can precipitate dysbiosis and periodontitis in susceptible hosts. Dysbiotic microbial communities of keystone pathogens and pathobionts are thought to exhibit synergistic virulence whereby not only can they endure the host response but can also thrive by exploiting tissue-destructive inflammation, which fuels a self-feeding cycle of escalating dysbiosis and inflammatory bone loss, potentially leading to tooth loss and systemic complications. Here, I discuss new paradigms in our understanding of periodontitis, which may shed light into other polymicrobial inflammatory disorders. In addition, I highlight gaps in knowledge required for an integrated picture of the interplay between microbes and innate and adaptive immune elements that initiate and propagate chronic periodontal inflammation.

Bacterial behaviors associated with the quorum-sensing peptide pheromone ('alarmone') in streptococci

Streptococci are among the predominant bacterial species living in the human body. They are normally harmless bacteria, but have the ability to cause diverse infections, ranging from mild (e.g., tooth decay and sore throat) to life-threatening (e.g., endocarditis and meningitis). Streptococci have evolved various means of coping with the deleterious effects of environmental stressors and avoiding the host immune system. Recently, several studies have shown that streptococci colonizing the mouth and upper respiratory tract are able to mount complex stress responses in order to persist and successfully survive competition in their ecological niche. Using a small quorum-sensing peptide pheromone acting as a stress-inducible 'alarmone', oral streptococci synchronize the gene expression of a specific group of cells to coordinate important biological activities.

Neutrophil homeostasis and periodontal health in children and adults

This review summarizes the current state of knowledge on neutrophil basic biology and discusses how the breakdown of neutrophil homeostasis affects periodontal health. The homeostasis of neutrophils is tightly regulated through coordinated bone marrow production, release into the circulation, transmigration to and activation in peripheral tissues, and clearance of senescent neutrophils. Dysregulation of any of these homeostatic mechanisms at any age can cause severe periodontitis in humans and animal models. Accordingly, both impaired and excessive neutrophil activity (in terms of numbers or immune function) can precipitate periodontitis. Neutrophil defects of congenital origin (e.g., congenital neutropenia, leukocyte adhesion deficiency, and Chediak-Higashi syndrome) are associated with cutaneous and systemic infections and early-onset forms of periodontitis affecting both the primary and permanent dentitions of children. However, the strong association between congenital neutrophil disorders and early-onset periodontitis is not currently adequately explained mechanistically. This suggests the operation of as-yet-unknown molecular mechanisms, although the available body of evidence leaves no doubt that neutrophils are integral to periodontal tissue homeostasis and health.

Neutrophil heterogeneity in health and disease: a revitalized avenue in inflammation and immunity

Leucocytes form the principal cellular components of immunity and inflammation, existing as multiple subsets defined by distinct phenotypic and functional profiles. To date, this has most notably been documented for lymphocytes and monocytes. In contrast, as neutrophils are traditionally considered, to be short-lived, terminally differentiated cells that do not re-circulate, the potential existence of distinct neutrophil subsets with functional and phenotypic heterogeneity has not been widely considered or explored. A growing body of evidence is now challenging this scenario, and there is significant evidence for the existence of different neutrophil subsets under both physiological and pathological conditions. This review will summarize the key findings that have triggered a renewed interest in neutrophil phenotypic changes, both in terms of functional implications and consequences within disease models. Special emphasis will be placed on the potential pro- and anti-inflammatory roles of neutrophil subsets, as indicated by the recent works in models of ischaemia–reperfusion injury, trauma, cancer and sepsis.

Role of complement in host-microbe homeostasis of the periodontium

Complement plays a key role in immunity and inflammation through direct effects on immune cells or via crosstalk and regulation of other host signaling pathways. Deregulation of these finely balanced complement activities can link infection to inflammatory tissue damage. Periodontitis is a polymicrobial community-induced chronic inflammatory disease that can destroy the tooth-supporting tissues. In this review, we summarize and discuss evidence that complement is involved in the dysbiotic transformation of the periodontal microbiota and in the inflammatory process that leads to the destruction of periodontal bone. Recent insights into the mechanisms of complement involvement in periodontitis have additionally provided likely targets for therapeutic intervention against this oral disease.

Increased nucleic Acid receptor expression in chronic periodontitis

BACKGROUND

Nucleic acid sensing has emerged as one of the important components of the immune system triggering inflammation. The aim of this study is to determine the expression of bacterial DNA sensors, including Toll-like receptor 9 (TLR-9), DNA-dependent activator of interferon-regulatory factors (DAI), and absent in melanoma 2 (AIM2) in chronic periodontitis (CP versus healthy) (H) tissues.

METHODS

Thirty-five CP and 27 H gingival biopsies were included. Real-time quantitative polymerase chain reaction was performed to determine mRNA levels of AIM2, DAI, and TLRs (TLR-1 through TLR-9). The difference in gene expression for each sensor between CP and H tissues was calculated using analysis of covariance. The Spearman test was used to determine correlations among innate receptors. The expression of TLR-9, AIM2, and DAI in gingival tissues was further confirmed using immunohistochemistry.

RESULTS

The present results reveal statistically significant upregulation of TLR-9 (P <0.006), DAI (P <0.001), and TLR-8 (P <0.01) in CP tissues compared to H sites. Although mRNA expression was not changed significantly between groups for other receptors, the present results reveal significant correlations between receptors (P <0.05), suggesting that cooperation between multiple components of the host immune system may influence the overall response. Immunohistochemistry further confirmed expression of TLR-9, AIM2, and DAI in gingival tissues.

CONCLUSIONS

This study highlights a possible role for nucleic acid receptors in periodontal inflammation. Future investigations will determine whether cytoplasmic receptors and their ligands can be targeted to improve clinical outcomes in periodontitis.

Evaluation of salivary biomarker profiles following non-surgical management of chronic periodontitis

OBJECTIVES

Soluble toll-like receptor-2 (sTLR-2) and cytokines in saliva were assessed as clinical markers for chronic periodontitis in a longitudinal study.

MATERIALS AND METHODS

Unstimulated whole saliva was collected from 20 periodontally healthy individuals and 20 patients with chronic periodontitis at diagnosis and at 1 and 6 weeks following scaling and root planing (SRP). Biomarkers including the cytokines (IL-4, IL-6, IL-10, and IL-17), sTLR-2, and sCD14 in saliva were measured by enzyme-linked immunosorbent assay. Mann-Whitney U-test and Student's t-test were used to determine the significance between healthy and chronic periodontitis groups and that between pre- and post-SRP samples, respectively.

RESULTS

Salivary sTLR-2, IL-17, and IL-10 levels were significantly lower and those of sCD14, IL-6, and IL-4 were significantly higher in patients with chronic periodontitis as compared with healthy controls. Furthermore, sTLR-2 and IL-4 in saliva reached levels comparable to those of healthy individuals at 6-week re-evaluation visit, implicating a correlation of the two markers with the disease process.

CONCLUSIONS

Our data suggest that salivary sTLR-2 is a potential prognostic or maintenance marker for chronic periodontitis. The observed variability of salivary cytokines is consistent with the role of these cytokines in the progression of chronic periodontitis.

Perinatal epigenetic determinants of cognitive and metabolic disorders

Multiple cues from the environment of our indirect and immediate ancestors, which often persist throughout the prenatal period and adulthood, are shaping our phenotypes through either direct, parent-to-child influences, or transgenerational inheritance. These effects are due to gene-environment interactions, which are intended to be a predictive tool and a mechanism of quick adaptation to the environment, as compared with genetic variations that are inherited over many generations. In certain circumstances the influences induced by the gene-environment interactions can have deleterious effects upon the health status, in the context of a radical change in the environment that does not fit with the predicted conditions, via epigenetic alterations. Conversely the best fit to the expected environment might have a delayed aging process and a longer life span. This review will touch upon the Developmental Origins of Health and Disease (DoHAD) concept, while discussing recent advances in the understanding of metabolic and cognitive disruptions, with a focus on epigenetic factors, their transgenerational effects, and the consequences they might have upon the onset of chronic disease and premature exitus.

Local complement-targeted intervention in periodontitis: proof-of-concept using a C5a receptor (CD88) antagonist

When excessively activated or deregulated, complement becomes a major link between infection and inflammatory pathology including periodontitis. This oral inflammatory disease is associated with a dysbiotic microbiota, leads to the destruction of bone and other tooth-supporting structures, and exerts an adverse impact on systemic health. We have previously shown that mice deficient either in complement C5a receptor (C5aR; CD88) or TLR2 are highly and similarly resistant to periodontitis, suggesting that a cross-talk between the two receptors may be involved in the disease process. In this paper, we show that C5aR and TLR2 indeed synergize for maximal inflammatory responses in the periodontal tissue and uncover a novel pharmacological target to abrogate periodontitis. Using two different mouse models of periodontitis, we show that local treatments with a C5aR antagonist inhibited periodontal inflammation through downregulation of TNF, IL-1β, IL-6, and IL-17 and further protected against bone loss, regardless of the presence of TLR2. These findings not only reveal a crucial cooperation between C5aR and TLR2 in periodontal inflammation but also provide proof-of-concept for local targeting of C5aR as a powerful candidate for the treatment of human periodontitis.

Reduced neutrophil superoxide production among healthy older adults in response to acute psychological stress

Ageing is associated with higher morbidity and mortality, and declining immune function, termed immunesenescence. The present study examined the effects of an acute laboratory psychological stress task on innate immunity, specifically neutrophil function, among older adults. The two functional assays used were phagocytosis of Escherichia coli and stimulated superoxide production. Participants were 17 (11 female) older adults (mean age 75.7, SD=7.06 years). Blood samples to determine neutrophil function by flow cytometry were taken at the end of resting baseline, during an acute stress task and during recovery. The stress task was an 8-minute time-pressured mental arithmetic challenge with social evaluation. There was a significant reduction in neutrophil superoxide production, p=.017, η(2)(p)=.240, associated with the stress task relative to baseline, but no effect on phagocytosis. The results of this study could contribute to explaining the increased risk of infection in older adults, particularly those subject to frequent stress exposures. Future research is needed to explore the underlying mechanisms of acute stress effects on human neutrophil function in older adults in greater detail.

Inhibition of Porphyromonas gingivalis-induced periodontal bone loss by CXCR4 antagonist treatment

Microbial pathogens have evolved mechanisms to proactively manipulate innate immunity, thereby improving their fitness in mammalian hosts. We have previously shown that Porphyromonas gingivalis exploits CXC-chemokine receptor-4 (CXCR4) to instigate a subversive crosstalk with Toll-like receptor 2 that inhibits leukocyte killing of this periodontal pathogen. However, whether CXCR4 plays a role in periodontal disease pathogenesis has not been previously addressed. Here, we hypothesized that CXCR4 is required for P. gingivalis virulence in the periodontium and that treatment with AMD3100, a potent CXCR4 antagonist, would inhibit P. gingivalis-induced periodontitis. Indeed, mice given AMD3100 via osmotic minipumps became resistant to induction of periodontal bone loss following oral inoculation with P. gingivalis. AMD3100 appeared to act in an antimicrobial manner, because mice treated with AMD3100 were protected against P. gingivalis colonization and the associated elevation of the total microbiota counts in the periodontal tissue. Moreover, even when administered 2 weeks after infection, AMD3100 halted the progression of P. gingivalis-induced periodontal bone loss. Therefore, AMD3100 can act in both preventive and therapeutic ways and CXCR4 antagonism could be a promising novel approach to treat human periodontitis.

Clinical profile of orofacial infections: an experience from two primary care dental practices

Objectives: Orofacial infections are common reasons for dental consultations worldwide. However, there is scarcity of data on clinico-epidemiological profiles reported from primary care dental practices. To address this issue, a study was done to characterize the clinical pattern, age groups affected and sex predilection of orofacial infections in the primary care dental practice. Study design: Clinical data was evaluated from random electronic files of patients for whom antimicrobials were prescribed at two Dental Practices in UK between January 2009 and December 2010. Results: 200 case records were studied. 104 (52%) cases were females. Mean age was 37.2 (+/-15.1) years. 107 (53.5%) cases belonged to age group 21-40 years. Posterior teeth were involved in 112 (56%) cases. Types of disease were as follows: dentoalveolar abscess 63(31.5%), pulpitis 27(13.5%), apical periodontitis 21(10.5%), pericoronitis 21(10.5%), dry socket 13(6.5%), periodontitis 9(4.5%) infected root stump 5(2.5%), facial swelling 5(2.5%) and infections unspecified 36(18%) cases. Conclusions: Orofacial infections affect both sexes equally. 21-40 years is the commonest age-group affected. Dentoalveolar abscess is the commonest infection followed by unspecified infections and pulpitis.

Key words:Orofacial infections, primary care dental practice, dentoalveolar abscess and pulpitis.

Innate immunosenescence: effect of aging on cells and receptors of the innate immune system in humans

Components of the innate immune response, including neutrophils and macrophages, are the first line of defense against infections. Their role is to initiate an inflammatory response, phagocyte and kill pathogens, recruit natural killer cells (NK), and facilitate the maturation and migration of dendritic cells that will initiate the adaptive immune response. Extraordinary advances have been made in the last decade on the knowledge of the receptors and mechanisms used by cells of the innate immunity not only to sense and eliminate the pathogen but also to communicate each other and collaborate with cells of adaptive immunity to mount an effective immune response. The analysis of innate immunity in elderly humans has evidenced that aging has a profound impact on the phenotype and functions of these cells. Thus altered expression and/or function of innate immunity receptors and signal transduction leading to defective activation and decreased chemotaxis, phagocytosis and intracellular killing of pathogens have been described. The phenotype and function of NK cells from elderly individuals show significant changes that are compatible with remodeling of the different NK subsets, with a decrease in the CD56bright subpopulation and accumulation of the CD56dim cells, in particular those differentiated NK cells that co-express CD57, as well as a decreased expression of activating natural cytotoxicity receptors. These alterations can be responsible of the decreased production of cytokines and the lower per-cell cytotoxicity observed in the elderly. Considering the relevance of these cells in the initiation of the immune response, the possibility to reactivate the function of innate immune cells should be considered in order to improve the response to pathogens and to vaccination in the elderly.

The leukocyte integrin antagonist Del-1 inhibits IL-17-mediated inflammatory bone loss

Aging is linked to greater susceptibility to chronic inflammatory diseases, several of which, including periodontitis, involve neutrophil-mediated tissue injury. Here we found that aging-associated periodontitis was accompanied by lower expression of Del-1, an endogenous inhibitor of neutrophil adhesion dependent on the integrin LFA-1, and by reciprocal higher expression of interleukin 17 (IL-17). Consistent with that, IL-17 inhibited gingival endothelial cell expression of Del-1, thereby promoting LFA-1-dependent recruitment of neutrophils. Young Del-1-deficient mice developed spontaneous periodontitis that featured excessive neutrophil infiltration and IL-17 expression; disease was prevented in mice doubly deficient in Del-1 and LFA-1 or in Del-1 and the IL-17 receptor. Locally administered Del-1 inhibited IL-17 production, neutrophil accumulation and bone loss. Therefore, Del-1 suppressed LFA-1-dependent recruitment of neutrophils and IL-17-triggered inflammatory pathology and may thus be a promising therapeutic agent for inflammatory diseases.

Paradigm shift in the pharmacological management of periodontal diseases

It is becoming clear that variations in inflammatory response are a major determinant in susceptibility to periodontitis. However, our understanding of the relationship of the causal agents in periodontitis to the pathogenesis is not as clear as we once thought, and thus therapies based on etiopathogenesis are similarly in question. We are entering a new era of therapeutic discovery that may have a major impact on our management of the periodontal diseases. Fundamentally, periodontitis is an irreversible condition and once both soft and hard tissues are lost, the healthy periodontal architecture cannot be completely or predictably rebuilt. The discovery of new families of lipid mediators of resolution of inflammation (the lipoxins) and eicosapentaenoic-acid- and docosahexaenoic-acid-derived chemical mediators (the resolvins and protectins) opens new avenues to designing resolution-targeted therapies to control the unwanted side effects of excessive inflammation. The novel protective and therapeutic actions of pro-resolution lipid mediators following microbial challenge are mediated by regulation of the local and systemic inflammatory response that has a direct impact on the organization of the biofilm (plaque) and suggests a new paradigm in clinical periodontal therapeutics.

Neutrophils in periodontal inflammation

Neutrophils (also called polymorphonuclear leukocytes) are the most abundant leukocytes whose primary purpose as anti-microbial professional phagocytes is to kill extracellular pathogens. Neutrophils and macrophages are phagocytic cell types that along with other cells effectively link the innate and adaptive arms of the immune response, and help promote inflammatory resolution and tissue healing. Found extensively within the gingival crevice and epithelium, neutrophils are considered the key protective cell type in the periodontal tissues. Histopathology of periodontal lesions indicates that neutrophils form a 'wall' between the junctional epithelium and the pathogen-rich dental plaque which functions as a robust anti-microbial secretory structure and as a unified phagocytic apparatus. However, neutrophil protection is not without cost and is always considered a two-edged sword in that overactivity of neutrophils can cause tissue damage and prolong the extent and severity of inflammatory periodontal diseases. This review will cover the innate and inflammatory functions of neutrophils, and describe the importance and utility of neutrophils to the host response and the integrity of the periodontium in health and disease.

Neutrophil function and cortisol:DHEAS ratio in bereaved older adults

Bereavement is a common life event for older adults and is associated with increased risk of morbidity and mortality, though the underlying reasons for this link are poorly understood. Although physical and emotional stressors and ageing are known to suppress immunity, few studies have explored the impact of bereavement upon immunity in the older population. We therefore hypothesised that the emotional stress of bereavement would suppress immune function, specifically neutrophil bactericidal activity, in older adults. A between-subjects design was used to examine the effect of recent bereavement (<2 months) on neutrophil function in elders. Participants were 24 bereaved and 24 age- and sex-matched non-bereaved controls all aged 65+ years. Neutrophil phagocytosis of Escherichia coli (E. coli) and stimulated superoxide production were assessed. Cortisol and dehydroepiandrosterone-sulphate (DHEAS) levels were determined in serum to assess potential mechanisms. Depressive and anxiety symptoms were measured by questionnaire. Neutrophil superoxide production was significantly reduced among the bereaved when challenged with E. coli (p=0.05), or phorbol 12-myristate 13-acetate (p=0.009). Further, the bereaved group had a significantly higher cortisol:DHEAS ratio compared to controls (p=0.03). There was no difference in neutrophil phagocytosis between the two groups. The psychological questionnaire results showed that the bereaved had significantly greater depressive and anxiety symptoms than the non-bereaved. The emotional stress of bereavement is associated with suppressed neutrophil superoxide production and with a raised cortisol:DHEAS ratio. The stress of bereavement exaggerates the age-related decline in HPA axis and combines with immune ageing to further suppress immune function, which may help to the explain increased risk of infection in bereaved older adults.

Respiratory disease and the role of oral bacteria

The relationship between oral health and systemic conditions, including the association between poor oral hygiene, periodontal disease, and respiratory disease, has been increasingly debated over recent decades. A considerable number of hypotheses have sought to explain the possible role of oral bacteria in the pathogenesis of respiratory diseases, and some clinical and epidemiological studies have found results favoring such an association. This review discusses the effect of oral bacteria on respiratory disease, briefly introduces the putative biological mechanisms involved, and the main factors that could contribute to this relationship. It also describes the role of oral care for individuals who are vulnerable to respiratory infections.

The C5a receptor impairs IL-12-dependent clearance of Porphyromonas gingivalis and is required for induction of periodontal bone loss

The C5a anaphylatoxin receptor (C5aR; CD88) is activated as part of the complement cascade and exerts important inflammatory, antimicrobial, and regulatory functions, at least in part, via crosstalk with TLRs. However, the periodontal pathogen Porphyromonas gingivalis can control C5aR activation by generating C5a through its own C5 convertase-like enzymatic activity. In this paper, we show that P. gingivalis uses this mechanism to proactively and selectively inhibit TLR2-induced IL-12p70, whereas the same pathogen-instigated C5aR-TLR2 crosstalk upregulates other inflammatory and bone-resorptive cytokines (IL-1β, IL-6, and TNF-α). In vivo, the ability of P. gingivalis to manipulate TLR2 activation via the C5a-C5aR axis allowed it to escape IL-12p70-dependent immune clearance and to cause inflammatory bone loss in a murine model of experimental periodontitis. In the latter regard, C5aR-deficient or TLR2-deficient mice were both resistant to periodontal bone loss, in stark contrast with wild-type control mice, which is consistent with the interdependent interactions of C5aR and TLR2 in P. gingivalis immune evasion and induction of bone-resorptive cytokines. In conclusion, P. gingivalis targets C5aR to promote its adaptive fitness and cause periodontal disease. Given the current availability of safe and effective C5aR antagonists, pharmacological blockade of C5aR could act therapeutically in human periodontitis and reduce associated systemic risks.

Complement and periodontitis

Although the complement system is centrally involved in host defense, its overactivation or deregulation (e.g., due to inherent host genetic defects or due to pathogen subversion) may excessively amplify inflammation and contribute to immunopathology. Periodontitis is an oral infection-driven chronic inflammatory disease which exerts a systemic impact on health. This paper reviews evidence linking complement to periodontal inflammation and pathogenesis. Clinical and histological observations show a correlation between periodontal inflammatory activity and local complement activation. Certain genetic polymorphisms or deficiencies in specific complement components appear to predispose to increased susceptibility to periodontitis. Animal model studies and in vitro experiments indicate that periodontal bacteria can either inhibit or activate distinct components of the complement cascade. Porphyromonas gingivalis, a keystone species in periodontitis, subverts complement receptor 3 and C5a anaphylatoxin receptor signaling in ways that promote its adaptive fitness in the presence of non-productive inflammation. Overall, available evidence suggests that complement activation or subversion contributes to periodontal pathogenesis, although not all complement pathways or functions are necessarily destructive. Effective complement-targeted therapeutic intervention in periodontitis would require determining the precise roles of the various inductive or effector complement pathways. This information is essential as it may reveal which specific pathways need to be blocked to counteract microbial evasion and inflammatory pathology or, conversely, kept intact to promote host immunity.