Effects of aging on endotoxin tolerance induced by lipopolysaccharides derived from Porphyromonas gingivalis and Escherichia coli

Associations between immune-inflammatory markers, age, and periodontal status: a cross-sectional study

Since periodontal disease is associated with many systemic diseases, it is important to evaluate its effects on host responses in elderly individuals. To this end, this study investigated salivary interleukin (IL)-17, IL-18, toll-like receptor (TLR) 2, TLR4, and tumor necrosis factor-alpha (TNF-α) levels in patient groups with different periodontal health statuses and immunologically evaluated the relationship between age and periodontal health status. A total of 60 individuals aged 18-40 years (young individuals) and 60 individuals aged 65 years or older (elderly individuals) were included in this study. According to periodontal disease status, the patients were divided into periodontally healthy, gingivitis, and periodontitis subgroups. Clinical periodontal parameters, including probing depth (PD), clinical attachment level (CAL), plaque index (PI), and gingival index (GI), were recorded. Saliva samples were collected and analyzed using ELISA to determine the levels of IL-17, IL-18, TLR2, TLR4, and TNF-α. Higher clinical periodontal parameter (PD, CAL, PI, and GI) and inflammatory marker (IL-17, IL-18, TNF-α, TLR2, and TLR4) levels were found in patients with periodontitis than those in periodontally healthy individuals and patients with gingivitis (P < 0.05). Salivary inflammatory marker levels were significantly higher in elderly individuals than those in young individuals in all subgroups (P < 0.05). A positive correlation was found between inflammatory marker levels and clinical periodontal parameters, but there was no correlation between TLR2 and PI or GI. This study suggests a significant increase in host response to periodontal disease as the disease progresses, with the levels of cytokines and TLR expression exhibiting an increasing trend with age. Increased IL-17, IL-18, TLR2, TLR4, and TNF-α levels in elderly individuals in all periodontal health subgroups might suggest the role of these cytokines and TLR pathway in the pathogenesis of periodontal diseases.

DAMPs and alarmin gene expression patterns in aging healthy and diseased mucosal tissues

Introduction

Periodontitis is delineated by a dysbiotic microbiome at sites of lesions accompanied by a dysregulated persistent inflammatory response that undermines the integrity of the periodontium. The interplay of the altered microbial ecology and warning signals from host cells would be a critical feature for maintaining or re-establishing homeostasis in these tissues.

Methods

This study used a nonhuman primate model (Macaca mulatta) with naturally-occurring periodontitis (n = 34) and experimental ligature-induced periodontitis (n = 36) to describe the features of gene expression for an array of damage-associate molecular patterns (DAMPs) or alarmins within the gingival tissues. The animals were age stratified into: ≤3 years (Young), 7-12 years (Adolescent), 12-15 years (Adult) and 17-23 years (Aged). Gingival tissue biopsies were examined via microarray. The analysis focused on 51 genes representative of the DAMPs/alarmins family of host cell warning factors and 18 genes associated with tissue destructive processed in the gingival tissues. Bacterial plaque samples were collected by curette sampling and 16S rRNA gene sequences used to describe the oral microbiome.

Results

A subset of DAMPs/alarmins were expressed in healthy and naturally-occurring periodontitis tissues in the animals and suggested local effects on gingival tissues leading to altered levels of DAMPs/alarmins related to age and disease. Significant differences from adult healthy levels were most frequently observed in the young and adolescent animals with few representatives in this gene array altered in the healthy aged gingival tissues. Of the 51 target genes, only approximately ⅓ were altered by ≥1.5-fold in any of the age groups of animals during disease, with those increases observed during disease initiation. Distinctive positive and negative correlations were noted with the DAMP/alarmin gene levels and comparative expression changes of tissue destructive molecules during disease across the age groups. Finally, specific correlations of DAMP/alarmin genes and relative abundance of particular microbes were observed in health and resolution samples in younger animals, while increased correlations during disease in the older groups were noted.

Conclusions

Thus, using this human-like preclinical model of induced periodontitis, we demonstrated the dynamics of the activation of the DAMP/alarmin warning system in the gingival tissues that showed some specific differences based on age.

Endotoxin Tolerance Acquisition and Altered Hepatic Fatty Acid Profile in Aged Mice

(1) Background: Aging is linked to an altered immune response and metabolism. Inflammatory conditions, such as sepsis, COVID-19, and steatohepatitis are more prevalent in the elderly and steatosis is linked both to severe COVID-19 and sepsis. We hypothesized that aging is linked to a loss of endotoxin tolerance, which normally protects the host from excessive inflammation, and that this is accompanied by elevated levels of hepatic lipids. (2) Methods: An in vivo lipopolysaccharide (LPS) tolerance model in young and old mice was used and the cytokine serum levels were measured by ELISA. Cytokine and toll-like receptor gene expression was determined by qPCR in the lungs and the liver; hepatic fatty acid composition was assessed by GC–MS. (3) Results: The old mice showed a distinct potential for endotoxin tolerance as suggested by the serum cytokine levels and gene expression in the lung tissue. Endotoxin tolerance was less pronounced in the livers of the aged mice. However, the fatty acid composition strongly differed in the liver tissues of the young and old mice with a distinct change in the ratio of C18 to C16 fatty acids. (4) Conclusions: Endotoxin tolerance is maintained in advanced age, but changes in the metabolic tissue homeostasis may lead to an altered immune response in old individuals.

Oxidative Stress Inhibits Endotoxin Tolerance and May Affect Periodontitis

Periodontal disease is caused by dysbiosis of the dental biofilm and the host inflammatory response. Various pathogenic factors, such as proteases and lipopolysaccharides (LPSs) produced by bacteria, are involved in disease progression. Endotoxin tolerance is a function of myeloid cells, which sustain inflammation and promote tissue regeneration upon prolonged stimulation by endotoxins such as LPS. The role of endotoxin tolerance is gaining attention in various chronic inflammatory diseases, but its role in periodontal disease remains elusive. Oxidative stress, one of the major risk factors for periodontal disease, promotes disease progression through various mechanisms, of which only some are known. The effect of oxidative stress on endotoxin tolerance has not yet been studied, and we postulated that endotoxin tolerance regulation may be an additional mechanism through which oxidative stress influences periodontal disease. This study aimed to reveal the effect of oxidative stress on endotoxin tolerance and that of endotoxin tolerance on periodontitis progression. The effect of oxidative stress on endotoxin tolerance was analyzed in vitro using peritoneal macrophages of mice and hydrogen peroxide (H₂O₂). The results showed that oxidative stress inhibits endotoxin tolerance induced by Porphyromonas gingivalis LPS in macrophages, at least partially, by downregulating LPS-elicited negative regulators of Toll-like receptor (TLR) signaling. A novel oxidative stress mouse model was established using SMP30KO mice incapable of ascorbate biosynthesis. Using this model, we revealed that oxidative stress impairs endotoxin tolerance potential in macrophages in vivo. Furthermore, gingival expression of endotoxin tolerance-related genes and TLR signaling negative regulators was decreased, and symptoms of ligature-induced periodontitis were aggravated in the oxidative stress mouse model. Our findings suggest that oxidative stress may contribute to periodontitis progression through endotoxin tolerance inhibition.

Periodontal Treatment and Usual Care for Nonalcoholic Fatty Liver Disease: A Multicenter, Randomized Controlled Trial

INTRODUCTION

Periodontal disease is associated with nonalcoholic fatty liver disease (NAFLD). We evaluated periodontal treatment efficacy in patients with NAFLD and periodontal disease.

METHODS

This multicenter, 2-arm, randomized study recruited adult patients with NAFLD and periodontitis, alanine aminotransferase levels ≥40 U/L, and equivalent steatosis grade ≥1. Forty eligible patients (18 men and 22 women) were randomly assigned to 2 groups (scaling and root planning [SRP; n = 20] and tooth brushing [n = 20] groups) stratified by age and sex. The primary and secondary endpoints were changes in alanine aminotransferase levels and serum Porphyromonas gingivalis IgG antibody titers from baseline to 12 weeks, respectively. Efficacy analysis was performed using an intention-to-treat approach ( t test). This trial was registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN000022079).

RESULTS

We observed a significantly higher decrease in absolute alanine aminotransferase levels and P. gingivalis IgG antibody titers in the SRP group than in the tooth brushing group (-12 vs 1 U/L; mean difference [δ], -12; 95% confidence interval [CI], -20 to -5; P = 0.002). The decrease in P. gingivalis IgG antibody titer was significantly higher in the SRP group than in the tooth brushing group (FDC381, -1.6 [2.5]; δ, -1.6; 95% CI, -2.7 to -0.4; P = 0.0092; SU63, -1.7 [2.0]; δ, -1.7; 95% CI, -2.7 to -0.7). No life-threatening events or treatment-related deaths occurred.

DISCUSSION

Periodontal treatment induced significant short-term and mid-term reductions in liver enzyme levels and antibody titers. Further research is warranted to clearly define SRP efficacy and tolerability in patients with NAFLD and periodontitis.

Cardiac alterations following experimental hip fracture - inflammaging as independent risk factor

Background

Cardiac injuries following trauma are associated with a worse clinical outcome. So-called trauma-induced secondary cardiac injuries have been recently described after experimental long bone fracture even in absence of direct heart damage. With the progressive aging of our society, the number of elderly trauma victims rises and therefore the incidence of hip fractures increases. Hip fractures were previously shown to be associated with adverse cardiac events in elderly individuals, which have mainly been attributed to pre-conditioned cardiac diseases. The aim of the present study was to investigate the effect of hip fractures on the heart in healthy young and middle-aged mice.

Materials and Methods

Young (12-week-old) and middle-aged (52-week-old) female C57BL/6 mice either received an intramedullary stabilized proximal femur fracture or sham treatment. The observation time points included 6 and 24 h. Systemic levels of pro-inflammatory mediators as well as local inflammation and alterations in myocardial structure, metabolism and calcium homeostasis in left ventricular tissue was analyzed following hip fracture by multiplex analysis, RT-qPCR and immunohistochemistry.

Results

After hip fracture young and middle-aged mice showed increased systemic IL-6 and KC levels, which were significantly elevated in the middle-aged animals. Furthermore, the middle-aged mice showed enhanced myocardial expression of HMGB1, TLR2/4, TNF, IL1β and NLRP3 as well as considerable alterations in the myocardial expression of glucose- and fatty acid transporters (HFABP, GLUT4), calcium homeostasis proteins (SERCA) and cardiac structure proteins (desmin, troponin I) compared to the young animals following hip fracture.

Conclusion

Young and middle-aged mice showed local myocardial alterations, which might predispose for the development of secondary cardiac injury following hip fracture. Age and the age-associated phenomenon of ‘inflammaging’ seemed to be an independent risk factor aggravating and accelerating cardiac alterations following hip fracture.

Does Oral Endotoxin Contribute to Systemic Inflammation?

The oral microbiome, with a unique emphasis on Porphyromonas gingivalis has been associated with a constellation of inflammatory diseases such as cardiovascular disease, rheumatoid arthritis, Alzheimer's disease, type II diabetes, and non-alcoholic associated fatty liver disease. Periodontal disease has also been shown to induce “leaky gut” leading to metabolic endotoxemia. Several recent studies investigating the habitants of the blood microbiome have found the majority of species appear to be derived from oral and skin bacterial communities in otherwise healthy individuals. Many of the same pathologies associated with perturbations of oral health, such as cardiovascular disease, show alterations to the composition of the blood microbiome as well as circulating neutrophil phenotypes. Gingival inflammation is associated with activated blood neutrophil phenotypes that can exacerbate a distal inflammatory insult which may explain the connection between oral and systemic inflammatory conditions. While in the oral cavity, neutrophils encounter oral microbes that are adept in manipulating neutrophil activity which can re-enter the vasculature thereafter. Endotoxin from oral microbes can differ significantly depending on bacterial community and state of oral health to alter cellular LPS tolerance mechanisms which may contribute to the primed neutrophil phenotype seen in periodontitis and provide a mechanism by which the oral-microbes can affect systemic health outcomes. This review synthesizes the studies between inflammatory diseases and oral health with emphasis on microbiome and corresponding lipopolysaccharides in immune tolerance and activation.

Semaphorin 3A promotes the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells in inflammatory environments by suppressing the Wnt/β-catenin signaling pathway

After periodontal treatment, the local inflammatory environment surrounding periodontal tissues cannot be entirely eliminated. The means by which alveolar bone repair and regeneration are promoted in inflammatory environments have important clinical significance. As a powerful protein that promotes the differentiation of osteocytes, semaphorin 3A (Sema3A) shows potential for bone regeneration therapy. However, the effect of Sema3A on osteogenic differentiation in an inflammatory environment, as well as the underlying mechanism, have not yet been explored. We used lentivirus to transduce rat bone marrow-derived mesenchymal stem cells (rBMSCs) to stably overexpress Sema3A. Lipopolysaccharide from Escherichia coli (E. coli LPS) was used to stimulate rBMSCs to establish an inflammatory environment. ALP staining, Alizarin red staining, ALP activity tests, quantitative RT-PCR (qRT-PCR), and Western blotting were used to elucidate the effect of Sema3A on the osteogenesis of rBMSCs in inflammatory environments. XAV939 and LiCl were used to determine whether the Wnt/β-catenin signaling pathway was involved in attenuating the inhibition of Sema3A-induced osteogenic differentiation by LPS. The qRT-PCR and Western blot results demonstrated that the lentiviral vector (LV-NC) and lentiviral-Sema3A (LV-Sema3A) were successfully transduced into rBMSCs. An inflammatory environment could be established by stimulating rBMSCs with 1 μg/ml E. coli LPS. After Sema3A overexpression, mineral deposition was exacerbated, and the BSP and Runx2 gene and protein expression levels were increased. Furthermore, E. coli LPS activated the Wnt/β-catenin signaling pathway and decreased rBMSC osteogenesis, but these effects were attenuated by Sema3A. In conclusion, Sema3A could protect BMSCs from LPS-mediated inhibition of osteogenic differentiation in inflammatory environments by suppressing the Wnt/β-catenin pathway.

Association between the Frequency of Daily Toothbrushing and Development of Nonalcoholic Fatty Liver Disease

Background &amp; Aim: This study aimed to evaluate the association between the frequency of daily toothbrushing and the development of nonalcoholic fatty liver disease (NAFLD).

METHODS

A retrospective longitudinal study was conducted from 2005 to 2012 at the Center for Preventive Medicine at St. Luke's International Hospital, Japan. Data on all participants who underwent a health checkup during the study period were collected. NAFLD was diagnosed by abdominal ultrasonography, and all participants who were diagnosed with NAFLD at the time of their initial visit, consumed alcohol in any amount, or had received only one health checkup were excluded. The questionnaire for the frequency of daily toothbrushing was conducted as part of health checkups. The primary outcome was the risk of developing NAFLD according to the frequency of daily toothbrushing (1-2 times a day or 3 times a day) compared to those who brush teeth once or less than once a day.

RESULTS

Data were collected from 25,804 people. A total of 3,289 (12.7%) participants developed NAFLD. The mean age was 45.2 years, and 6,901 (26.7%) of the participants were male. The risk of developing NAFLD significantly decreased with increased frequency of daily toothbrushing. Adjusted odds ratios (ORs) are as follows: brushing teeth 1-2 times a day (OR: 0.85, 95% confidence interval [CI]: 0.77-0.95) and 3 times a day (OR: 0.74, 95% CI: 0.67-0.82).

CONCLUSION

Frequent toothbrushing was shown to significantly reduce the risk of developing NAFLD.

Contribution of Porphyromonas gingivalis lipopolysaccharide to experimental periodontitis in relation to aging

Aging is associated with increased prevalence and severity of pathogenic outcomes of periodontal disease, including soft tissue degeneration and bone loss around the teeth. Although lipopolysaccharide (LPS) derived from the key periodontal pathogen Porphyromonas gingivalis (Pg) plays an important role in the promotion of inflammation and osteoclastogenesis via toll-like receptor (TLR)4 signaling, its pathophysiological role in age-associated periodontitis remains unclear. This study investigated the possible effects of Pg-LPS on RANKL-primed osteoclastogenesis and ligature-induced periodontitis in relation to aging using young (2 months old) and aged (24 months old) mice. To the best of our knowledge, our results indicated that expression of TLR4 was significantly diminished on the surface of osteoclast precursors isolated from aged mice compared with that of young mice. Furthermore, our data demonstrated that the TLR4 antagonist (TAK242) dramatically decreased the numbers of tartrate-resistant acid phosphatase positive (TRAP+) osteoclasts differentiated from RANKL-primed young osteoclast precursors (OCPs) compared with those isolated from aged mice in response to Pg-LPS. In addition, using a ligature-induced periodontitis mouse model, we demonstrated that Pg-LPS elevated (1) secretion of senescence-associated secretory phenotype (SASP) markers, including the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, as well as osteoclastogenic RANKL, and (2) the number of OCPs and TRAP+ osteoclasts in the periodontal lesion induced in young mice. In contrast, Pg-LPS had little, or no, effect on the promotion of periodontitis inflammation induced in aged mice. Altogether, these results indicated that periodontal disease in older mice occurs in a manner independent of canonical signaling elicited by the Pg-LPS/TLR4 axis.

Septic acute kidney injury: a review of basic research

Sepsis is a major cause of acute kidney injury (AKI) among patients in the intensive care unit. However, the numbers of basic science papers for septic AKI account for only 1% of all publications on AKI. This may be partially attributable to the specific pathophysiology of septic AKI as compared to that of the other types of AKI because it shows only modest histological changes despite functional decline and often requires real-time functional analysis. To increase the scope of research in this field, this article reviews the basic research information that has been reported thus far on the subject of septic AKI, mainly from the viewpoint of functional dysregulation, including some knowledge acquired with multiphoton intravital imaging. Moreover, the efficacy and limitation of the potential novel therapies are discussed. Finally, the author proposes several points that should be considered when designing the study, such as monitoring the long-term effects of the intervention and reflecting the clinical settings for identifying the molecular mechanisms and for challenging the intervention effects.

Effects of Endotoxin Tolerance Induced by Porphyromonas gingivalis Lipopolysaccharide on Inflammatory Responses in Neutrophils

Periodontitis is a dental plaque-induced chronic inflammatory disease. Long-term exposure of the host to periodontal pathogens leads to a hyporesponsive state to the following stimulations, which is described as endotoxin tolerance. Neutrophils are the most abundant innate immune cells in the body. To clarify the roles of endotoxin tolerance in periodontitis, inflammatory responses in Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS)-tolerized neutrophils were explored in this study. Here, apoptosis and respiratory burst in neutrophils upon single or repeated P. gingivalis LPS stimulations were explored by flow cytometry. Cytokine production (TNF-α, IL-8, and IL-10) in tolerized neutrophils or neutrophils co-cultured with peripheral blood mononuclear cells was determined by ELISA. Phagocytosis of P. gingivalis by tolerized neutrophils was also assayed by flow cytometry. In addition, quality and quantitation of neutrophil extracellular trap (NET) formation were detected using immunofluorescence microscope and microplate reader, respectively. The protein expressions of extracellular signal-regulated kinase1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (p38 MAPK) were examined to identify possible mechanisms for the abovementioned changes. Tolerance induced by P. gingivalis LPS significantly suppressed apoptosis, reactive oxygen species (ROS) generation, and phagocytosis in neutrophils (p < 0.05). In both neutrophils alone and co-culture system, repeated P. gingivalis LPS stimulations significantly decreased TNF-α production, but increased IL-10 secretion (p < 0.05). Moreover, in tolerized neutrophils, NET formations were strengthened and there were more released extracellular DNA (p < 0.05). In P. gingivalis LPS-tolerized neutrophils, phosphorylation of ERK1/2 was suppressed compared with that in non-tolerized cells. Taken together, immune responses in neutrophils were reprogrammed by P. gingivalis LPS-induced tolerance, which might be related with the development of inflammation in periodontal tissues. Moreover, ERK1/2 might play important roles in endotoxin tolerance triggered by P. gingivalis LPS.

Efficacy and safety of PERIOdontal treatment versus usual care for Nonalcoholic liver disease: protocol of the PERION multicenter, two-arm, open-label, randomized trial

Background

We report the first protocol for a multicenter, randomized comparison study to compare the efficacies of periodontal scaling and root-planing treatment against that of tooth-brushing treatment for nonalcoholic fatty liver disease (NAFLD) (PERION: PERIOdontal treatment for NAFLD). Nonalcoholic steatohepatitis (NASH) is an advanced form of NAFLD, which can progress to cirrhosis and hepatocellular carcinoma. Increased endotoxemia is associated with the progression of NAFLD. Periodontal bacteria possess endotoxins; Porphyromonas gingivalis is well-known as a major pathogenic bacterium in periodontitis, and serum antibody levels for P. gingivalis are high in patients with periodontitis. Several reports have indicated that P. gingivalis is related to NAFLD. This study aims to investigate the effect of periodontal treatment for liver damage, P. gingivalis infection, and endotoxemia on patients with NAFLD.

Methods

We will include adult patients (20–85 years old) with NAFLD, alanine aminotransferase (ALT) ≥ 40 IU/L, and equivalent steatosis grade ≥ 1 (target sample size, n = 40 patients; planned number of patients with outcome data, n = 32). Participants will be randomly assigned to one of two groups: a scaling and root-planing group or tooth-brushing as the usual group. The primary outcome will be the change in ALT levels from baseline to 12 weeks; the key secondary outcome will be the change in the serum immunoglobulin G (IgG) antibody titer for P. gingivalis at 12 weeks.

Discussion

This study should determine whether periodontal treatment decreases liver damage, P. gingivalis infection, and endotoxemia in patients with NAFLD.

Trial registration

University Hospital Medical Information Network (UMIN) Clinical Trials Registry, ID: UMIN000022079.

Toll-like receptor 4 agonist and antagonist lipopolysaccharides modify innate immune response in rat brain circumventricular organs

Background

The circumventricular organs (CVOs) are blood-brain-barrier missing structures whose activation through lipopolysaccharide (LPS) is a starting point for TLR-driven (Toll-like receptors) neuroinflammation. The aim of this study was to evaluate in the CVO area postrema (AP), subfornical organ (SFO), and median eminence (ME), the inflammatory response to two TLR4 agonists: LPS from Escherichia coli (EC-LPS), the strongest endotoxin molecule described, and LPS from Porphyromonas gingivalis (PG-LPS), a pathogenic bacteria present in the periodontium related to neuroinflammation in neurodegenerative/psychiatric diseases. The response to LPS from the cyanobacteria Rhodobacter sphaeroides (RS-LPS), a TLR4 antagonist with an interesting anti-inflammatory potential, was also assessed.

Methods

LPSs were intraperitoneally administered to Wistar rats and, as indicatives of neuroinflammation in CVOs, the cellular localization of the nuclear factor NF-κB was studied by immunofluorescence, and microglia morphology was quantified by fractal and skeleton analysis.

Results

Data showed that EC-LPS increased NF-κB nuclear translocation in the three CVOs studied and PG-LPS only induced NF-κB nuclear translocation in the ME. RS-LPS showed no difference in NF-κB nuclear translocation compared to control. Microglia in the three CVOs showed an ameboid-shape after EC-LPS exposure, whereas PG-LPS only elicited a mild tendency to induce an ameboid shape. On the other hand, RS-LPS produced a markedly elongated morphology described as “rod” microglia in the three CVOs.

Conclusions

In conclusion, at the doses tested, EC-LPS induces a stronger neuroinflammatory response than PG-LPS in CVOs, which might be related to their different potency as TLR4 agonists. The non-reduction of basal NF-κB activation and induction of rod microglia by RS-LPS, a cell morphology only present in severe brain injury and infections, suggests that this molecule must be carefully studied before being proposed as an anti-inflammatory treatment for neuroinflammation related to neurodegenerative/psychiatric diseases.

Age and sex determine CD4+ T cell stimulatory and polarizing capacity of rat splenic dendritic cells

The study investigated influence of sex and age on splenic myeloid dendritic cells (DCs) from Dark Agouti rats. Freshly isolated DCs from young males exhibited less mature phenotype and greater endocytic capacity compared with those from age-matched females. Upon LPS stimulation in vitro they were less potent in stimulating allogeneic CD4+ cells in mixed leukocyte reaction (MLR), due to lower expression of MHC II, and greater NO and IL-10 production. In accordance with higher TGF-β production, young male rat DCs were less potent in stimulating IL-17 production in MLR than those from young females. Irrespective of sex, endocytic capacity and responsiveness of DCs to LPS stimulation in culture, judging by their allostimulatory capacity in MLR decreased with age, reflecting decline in MHC II surface density followed by their greater NO production; the effects more prominent in females. Additionally, compared with LPS-stimulated DCs from young rats, those from sex-matched aged rats were more potent in stimulating IL-10 production in MLR, whereas capacity of DCs from aged female and male rats to stimulate IL-17 production remained unaltered and decreased, respectively. This reflected age-related shift in IL-6/TGF-β production level ratio in LPS-stimulated DC cultures towards TGF-β, and sex-specific age-related remodeling CD4+ cell cytokine pathways. Additionally, compared with LPS-stimulated DCs from young rats, those cells from sex-matched aged rats were less potent in stimulating IFN-γ production in MLR, the effect particularly prominent in MLRs encompassing male rat DCs. The study showed that stimulatory and polarizing capacity of DCs depends on rat sex and age.

Immune Mechanisms Underlying Susceptibility to Endotoxin Shock in Aged Hosts: Implication in Age-Augmented Generalized Shwartzman Reaction

In recent decades, the elderly population has been rapidly increasing in many countries. Such patients are susceptible to Gram-negative septic shock, namely endotoxin shock. Mortality due to endotoxin shock remains high despite recent advances in medical care. The generalized Shwartzman reaction is well recognized as an experimental endotoxin shock. Aged mice are similarly susceptible to the generalized Shwartzman reaction and show an increased mortality accompanied by the enhanced production of tumor necrosis factor (TNF). Consistent with the findings in the murine model, the in vitro Shwartzman reaction-like response is also age-dependently augmented in human peripheral blood mononuclear cells, as assessed by enhanced TNF production. Interestingly, age-dependently increased innate lymphocytes with T cell receptor-that intermediate expression, such as that of CD8⁺CD122⁺T cells in mice and CD57⁺T cells in humans, may collaborate with macrophages and induce the exacerbation of the Shwartzman reaction in elderly individuals. However, endotoxin tolerance in mice, which resembles a mirror phenomenon of the generalized Shwartzman reaction, drastically reduces the TNF production of macrophages while strongly activating their bactericidal activity in infection. Importantly, this effect can be induced in aged mice. The safe induction of endotoxin tolerance may be a potential therapeutic strategy for refractory septic shock in elderly patients.

Tolerance induced by Porphyromonas gingivalis may occur independently of TLR2 and TLR4

OBJECTIVE

Periodontitis is a microbe-induced chronic inflammatory disease. Previous exposure of the host to bacteria or their virulence factors leads to refractory responses to further stimuli, which is called tolerance. Porphyromonas gingivalis (P. gingivalis) is one of the most important pathogenic microorganisms associated with periodontitis, and is a potent inducer of pro- and anti-inflammatory cytokines. The aim of this study was to explore the roles and possible mechanisms of tolerance induced by P. gingivalis.

METHODS

THP-1-derived macrophages were pretreated with 1x108 colony-forming units/ml P. gingivalis ATCC 33277 or 21 clinical isolates from moderate to severe chronic periodontitis patients (24 h), washed (2 h) and treated with P. gingivalis ATCC 33277 or the same clinical isolates again (24 h). Levels of pro-inflammatory cytokines TNF-α and IL-1β and anti-inflammatory cytokine IL-10 in supernatants were detected by ELISA. Moreover, to identify the possible mechanisms for the changes in cytokine secretion, Toll-like receptor 2 (TLR2) and TLR4 protein expressions were explored in these cells by flow cytometry.

RESULTS

After repeated challenge with P. gingivalis ATCC 33277 or clinical isolates, production of TNF-α and IL-1β in macrophages was decreased significantly compared with that following a single stimulation (p<0.05), while only comparable levels of IL-10 were detected in P. gingivalis ATCC 33277 or clinical isolate-tolerized cells (p>0.05). In addition, there was interstrain variability in the ability to induce IL-1β and IL-10 production after repeated P. gingivalis stimulation. However, no significant changes in TLR2 or TLR4 were detected in macrophages that were repeatedly treated with P. gingivalis ATCC 33277 or clinical isolates compared with those stimulated with P. gingivalis only once (p>0.05).

CONCLUSIONS

Repeated P. gingivalis stimulation triggered tolerance, which might contribute to limiting periodontal inflammation. However, tolerance induced by P. gingivalis might develop independently of TLR2 and TLR4 and be related to molecules in signaling pathways downstream of TLR2 and TLR4.

Human periodontal ligament cells exhibit no endotoxin tolerance upon stimulation with Porphyromonas gingivalis lipopolysaccharide

Background/Objectives

Endotoxin tolerance is characterized by a state of hyporesponsiveness after confrontation with endotoxins such as lipopolysaccharides (LPS) at low concentrations. The aim of this study was to investigate, whether pretreatment with Porphyromonas gingivalis leads to endotoxin tolerance induction and possible alterations in toll‐like receptor (TLR) 2‐ and 4‐induced response in human periodontal ligament cells (hPDLCs).

Material and Methods

Primary hPDLCs were pretreated with P. gingivalis (0.1 or 0.3 μg/mL) LPS for 24 hours and afterwards treated with one of the following stimuli: P. gingivalis LPS (1 μg/mL); TLR4 agonist Escherichia coli LPS (0.1 μg/mL; 1 μg/mL); TLR2 agonist Pam3CSK4 (0.1 μg/mL; 1 μg/mL). The protein expression of interleukin (IL)‐6, IL‐8 and monocyte chemotactic protein‐1 was analyzed with quantitative polymerase chain reaction and enzyme‐linked immunosorbent assay. Gene expression levels of TLR2 and TLR4 were determined by quantitative polymerase chain reaction.

Results

Pretreatment of cells with low concentrations of P. gingivalis LPS did not result in lower production of IL‐6, IL‐8 and monocyte chemotactic protein‐1 compared to control group. In some cases, pretreated cells exhibited lower gene expression levels of TLR2 and TLR4 compared to non‐pretreated cells.

Conclusion

The results of this study implicate that hPDLCs do not develop endotoxin tolerance. Furthermore, the amplitude of the inflammatory response shows no significant dependency on TLR2 and TLR4 expression levels.

Comparative analysis of microbial sensing molecules in mucosal tissues with aging

Host-bacterial interactions at mucosal surfaces require recognition of the bacteria by host cells enabling targeted responses to maintain tissue homeostasis. It is now well recognized that an array of host-derived pattern recognition receptors (PRRs), both cell-bound and soluble, are critical to innate immune engagement of microbes via microbial-associated molecular patterns (MAMP). This report describes the use of a nonhuman primate model to evaluate changes in the expression of these sensing molecules related to aging in healthy gingival tissues. Macaca mulatta aged 3-24 years were evaluated clinically and gingival tissues obtained, RNA isolated and microarray analysis conducted for gene expression of the sensing pattern recognition receptors (PRRs). The results demonstrated increased expression of various PRRs in healthy aging gingiva including extracellular (CD14, CD209, CLEC4E, TLR4), intracellular (NAIP, IFIH1, DAI) and soluble (PTX4, SAA1) PRRs. Selected PRRs were also correlated with both bleeding on probing (BOP) and pocket depth (PD) in the animals. These findings suggest that aged animals express altered levels of various PRRs that could affect the ability of the tissues to interact effectively with the juxtaposed microbial ecology, presumably contributing to an enhanced risk of periodontitis even in clinically healthy oral mucosal tissues with aging.

Porphyromonas gingivalis suppresses adaptive immunity in periodontitis, atherosclerosis, and Alzheimer's disease

Porphyromonas gingivalis, a keystone pathogen in chronic periodontitis, has been found to associate with remote body organ inflammatory pathologies, including atherosclerosis and Alzheimer’s disease (AD). Although P. gingivalis has a plethora of virulence factors, much of its pathogenicity is surprisingly related to the overall immunosuppression of the host. This review focuses on P. gingivalis aiding suppression of the host’s adaptive immune system involving manipulation of cellular immunological responses, specifically T cells and B cells in periodontitis and related conditions. In periodontitis, this bacterium inhibits the synthesis of IL-2 and increases humoral responses. This reduces the inflammatory responses related to T- and B-cell activation, and subsequent IFN-γ secretion by a subset of T cells. The T cells further suppress upregulation of programmed cell death-1 (PD-1)-receptor on CD⁺cells and its ligand PD-L1 on CD11b⁺-subset of T cells. IL-2 downregulates genes regulated by immune response and induces a cytokine pattern in which the Th17 lineage is favored, thereby modulating the Th17/T-regulatory cell (Treg) imbalance. The suppression of IFN-γ-stimulated release of interferon-inducible protein-10 (IP-10) chemokine ligands [ITAC (CXCL11) and Mig (CXCL9)] by P. gingivalis capsular serotypes triggers distinct T cell responses and contributes to local immune evasion by release of its outer membrane vesicles. In atherosclerosis, P. gingivalis reduces Tregs, transforms growth factor beta-1 (TGFβ-1), and causes imbalance in the Th17 lineage of the Treg population. In AD, P. gingivalis may affect the blood–brain barrier permeability and inhibit local IFN-γ response by preventing entry of immune cells into the brain. The scarcity of adaptive immune cells in AD neuropathology implies P. gingivalis infection of the brain likely causing impaired clearance of insoluble amyloid and inducing immunosuppression. By the effective manipulation of the armory of adaptive immune suppression through a plethora of virulence factors, P. gingivalis may act as a keystone organism in periodontitis and in related systemic diseases and other remote body inflammatory pathologies.

Innate immune responses in the ageing lung

The world is undergoing an unprecedented shift in demographics, with the number of individuals over the age of 60 years projected to reach 2 billion or more by 2050, representing 22% of the global population. Elderly people are at a higher risk for chronic disease and more susceptible to infection, due in part to age-related dysfunction of the immune system resulting from low-grade chronic inflammation known as 'inflamm-ageing'. The innate immune system of older individuals exhibits a diminished ability to respond to microbial threats and clear infections, resulting in a greater occurrence of many infectious diseases in elderly people. In particular, the incidence of and mortality from lung infections increase sharply with age, with such infections often leading to worse outcomes, prolonged hospital stays and life-threatening complications, such as sepsis or acute respiratory distress syndrome. In this review, we highlight research on bacterial pneumonias and pulmonary viral infections and discuss age-related changes in innate immunity that contribute to the higher rate of these infections in older populations. By understanding more clearly the innate immune defects in elderly individuals, we can design age-specific therapies to address lung infections in such a vulnerable population.

Senescent endothelial cells: Potential modulators of immunosenescence and ageing

Recent studies have demonstrated that the accumulation of senescent endothelial cells may be the primary cause of cardiovascular diseases. Because of their multifunctional properties, endothelial cells actively take part in stimulating the immune system and inflammation. In addition, ageing is characterized by the progressive deterioration of immune cells and a decline in the activation of the immune response. This results in a loss of the primary function of the immune system, which is eliminating damaged/senescent cells and neutralizing potential sources of harmful inflammatory reactions. In this review, we discuss cellular senescence and the senescence-associated secretory phenotype (SASP) of endothelial cells and summarize the link between endothelial cells and immunosenescence. We describe the possibility that age-related changes in Toll-like receptors (TLRs) and microRNAs can affect the phenotypes of senescent endothelial cells and immune cells via a negative feedback loop aimed at restraining the excessive pro-inflammatory response. This review also addresses the following questions: how do senescent endothelial cells influence ageing or age-related changes in the inflammatory burden; what is the connection between ECs and immunosenescence, and what are the crucial hypothetical pathways linking endothelial cells and the immune system during ageing.

Toll-like Receptor function of murine macrophages, probed by cytokine induction, is biphasic and is not impaired globally with age

Aging is associated with a waning of normal immune function. This "immunosenescence" is characterized by a diverse repertoire of seemingly discreet and unbalanced immune alterations. A number of studies have suggested that aging-associated alterations in innate immune responsiveness, especially responsiveness dependent on Toll-like Receptor (TLR) engagement, are causally involved. We find, however, that the magnitude and dose-dependency of responsiveness to TLR engagement (assessed with respect to cytokine production) in distinct populations of murine macrophages are not altered generally with animal age or as a consequence of immunosenescence. Responses elicited with a wide array of TLR agonists were examined by extensive functional analyses, principally on the level of the individual cell. These studies reveal an intriguing "all-or-nothing" response behavior of macrophages, independent of animal age. Although reports to the contrary have been cited widely, aging-associated immune decline cannot be attributed to widespread alterations in the extents of TLR-dependent innate immune macrophage responses.

Porphyromonas gingivalis Outer Membrane Vesicles Induce Selective Tumor Necrosis Factor Tolerance in a Toll-Like Receptor 4- and mTOR-Dependent Manner

Porphyromonas gingivalis is an important member of the anaerobic oral flora. Its presence fosters growth of periodontal biofilm and development of periodontitis. In this study, we demonstrated that lipophilic outer membrane vesicles (OMV) shed from P. gingivalis promote monocyte unresponsiveness to live P. gingivalis but retain reactivity to stimulation with bacterial DNA isolated from P. gingivalis or AIM2 ligand poly(dA·dT). OMV-mediated tolerance of P. gingivalis is characterized by selective abrogation of tumor necrosis factor (TNF). Neutralization of interleukin-10 (IL-10) during OMV challenge partially restores monocyte responsiveness toP. gingivalis; full reactivity toP. gingivalis can be restored by inhibition of mTOR signaling, which we previously identified as the major signaling pathway promoting Toll-like receptor 2 and Toll-like receptor 4 (TLR2/4)-mediated tolerance in monocytes. However, despite previous reports emphasizing a central role of TLR2 in innate immune recognition of P. gingivalis, our current findings highlight a selective role of TLR4 in the promotion of OMV-mediated TNF tolerance: only blockade of TLR4-and not of TLR2-restores responsiveness toP. gingivalis Of further note, OMV-mediated tolerance is preserved in the presence of cytochalasin B and chloroquine, indicating that triggering of surface TLR4 is sufficient for this effect. Taking the results together, we propose that P. gingivalis OMV contribute to local immune evasion of P. gingivalis by hampering the host response.

Age-associated metabolic dysregulation in bone marrow-derived macrophages stimulated with lipopolysaccharide

Macrophages are major contributors to age-associated inflammation. Metabolic processes such as oxidative phosphorylation, glycolysis and the urea cycle regulate inflammatory responses by macrophages. Metabolic profiles changes with age; therefore, we hypothesized that dysregulation of metabolic processes could contribute to macrophage hyporesponsiveness to LPS. We examined the intracellular metabolome of bone marrow-derived macrophages from young (6-8 wk) and old (18-22 mo) mice following lipopolysaccharide (LPS) stimulation and tolerance. We discovered known and novel metabolites that were associated with the LPS response of macrophages from young mice, which were not inducible in macrophages from old mice. Macrophages from old mice were largely non-responsive towards LPS stimulation, and we did not observe a shift from oxidative phosphorylation to glycolysis. The critical regulatory metabolites succinate, γ-aminobutyric acid, arginine, ornithine and adenosine were increased in LPS-stimulated macrophages from young mice, but not macrophages from old mice. A shift between glycolysis and oxidative phosphorylation was not observed during LPS tolerance in macrophages from either young or old mice. Metabolic bottlenecks may be one of the mechanisms that contribute to the dysregulation of LPS responses with age.

Bone morphogenetic protein receptor type II deficiency and increased inflammatory cytokine production. A gateway to pulmonary arterial hypertension

RATIONALE

Mutations in bone morphogenetic protein receptor type II (BMPR-II) underlie most cases of heritable pulmonary arterial hypertension (PAH). However, disease penetrance is only 20-30%, suggesting a requirement for additional triggers. Inflammation is emerging as a key disease-related factor in PAH, but to date there is no clear mechanism linking BMPR-II deficiency and inflammation.

OBJECTIVES

To establish a direct link between BMPR-II deficiency, a consequentially heightened inflammatory response, and development of PAH.

METHODS

We used pulmonary artery smooth muscle cells from Bmpr2(+/-) mice and patients with BMPR2 mutations and compared them with wild-type controls. For the in vivo model, we used mice heterozygous for a null allele in Bmpr2 (Bmpr2(+/-)) and wild-type littermates.

MEASUREMENTS AND MAIN RESULTS

Acute exposure to LPS increased lung and circulating IL-6 and KC (IL-8 analog) levels in Bmpr2(+/-) mice to a greater extent than in wild-type controls. Similarly, pulmonary artery smooth muscle cells from Bmpr2(+/-) mice and patients with BMPR2 mutations produced higher levels of IL-6 and KC/IL-8 after lipopolysaccharide stimulation compared with controls. BMPR-II deficiency in mouse and human pulmonary artery smooth muscle cells was associated with increased phospho-STAT3 and loss of extracellular superoxide dismutase. Chronic lipopolysaccharide administration caused pulmonary hypertension in Bmpr2(+/-) mice but not in wild-type littermates. Coadministration of tempol, a superoxide dismutase mimetic, ameliorated the exaggerated inflammatory response and prevented development of PAH.

CONCLUSIONS

This study demonstrates that BMPR-II deficiency promotes an exaggerated inflammatory response in vitro and in vivo, which can instigate development of pulmonary hypertension.

The effects of Twist-2 on liver endotoxin tolerance induced by a low dose of lipopolysaccharide

Endotoxin tolerance is an important mechanism for preventing uncontrolled inflammatory cytokine production in bacterial sepsis. However, its molecular mechanisms remain largely unknown. It was reported that Twist-2 protein was a negative regulator for cytokine signaling by repressing the nuclear factor (NF)-κB-dependent cytokine pathway. However, the relationship between Twist-2 and endotoxin tolerance is unclear. Endotoxin tolerance models of BABL/c mice and isolated Kupffer cells (KCs) were established to observe the changes of Twist-2 during endotoxin tolerance. Then, Twist-2 shRNA was used to specifically inhibit Twist-2 gene in KCs to further explore the role of Twist-2 in endotoxin tolerance. The expression of Twist-2 was analyzed by immunohistochemistry, reverse transcription polymerase chain reaction, and Western blotting, respectively. The responses to lipopolysaccharide were assessed by the activation of nuclear factor-κB and the production of tumor necrosis factor-α. The histopathologic changes in the liver of the non-endotoxin tolerance group were more serious than those of the endotoxin tolerance group. Endotoxin tolerance also led to less activation of nuclear factor-κB, lower expression levels of tumor necrosis factor-α mRNA, and more expression of Twist-2 than those of non-endotoxin tolerance group in liver and KCs. Moreover, the inhibitive effects partly weaken in KCs transfected with Twist-2 shRNA. Twist-2 was involved in endotoxin tolerance through inhibiting NF-κB trans-activation and cytokines transcriptional activities. It may be a new target for the clinical treatment of sepsis and other inflammatory diseases.

Posttranscriptional Suppression of Lipopolysaccharide-Stimulated Inflammatory Responses by Macrophages in Middle-Aged Mice: A Possible Role for Eukaryotic Initiation Factor 2 α

The intensities of macrophage inflammatory responses to bacterial components gradually decrease with age. Given that a reduced rate of protein synthesis is a common age-related biochemical change, which is partially mediated by increased phosphorylation of eukaryotic initiation factor-2 α (eIF-2 α ), we investigated the mechanism responsible for the deterioration of macrophage inflammatory responses, focusing specifically on the age-related biochemical changes in middle-aged mice. Peritoneal macrophages isolated from 2-month-old (young) and 12-month-old (middle-aged) male BALB/c mice were stimulated with lipopolysaccharide (LPS). Although LPS-stimulated secretion of tumor necrosis factor- α (TNF- α ) by the macrophages from middle-aged mice was significantly lower than that from young mice, LPS caused marked increases in levels of TNF- α mRNA in macrophages from middle-aged as well as young mice. Moreover, LPS evoked similar levels of phosphorylation of c-Jun N-terminal kinase (JNK) and nuclear factor- κ B (NF- κ B) in young and middle-aged mice. In contrast, the basal level of phosphorylated eIF-2 α in macrophages from middle-aged mice was higher than that in macrophages from young mice. Salubrinal, an inhibitor of the phosphatase activity that dephosphorylates eIF-2 α , suppressed the LPS-stimulated inflammatory responses in a murine macrophage cell line RAW264.7. These results suggest that posttranscriptional suppression of macrophage inflammatory responses during middle age requires phosphorylation of eIF-2 α .

TEGDMA and filler particles from dental composites additively attenuate LPS-induced cytokine release from the macrophage cell line RAW 264.7

OBJECTIVES

Due to incomplete curing and material degradation, cells in the oral cavity may be exposed to monomers and filler particles from dental composite fillings. The objective of the present study was to investigate if combined exposures to particles and a methacrylate monomer from composite fillings resulted in additive effects on the macrophage immune response.

MATERIAL AND METHODS

Two filler particles, Nanosilica (12 nm) and Quartz (1 μm), were studied at concentrations 0.5-4 μg/cm(2), while the methacrylate monomer triethyleneglycol dimethacrylate (TEGDMA) was applied at 5 and 50 μM. RAW 264.7 macrophages were exposed to monomers and/or particles for 24 h, with a subsequent 24 h combined exposure to monomers and/or particles and the bacterial factor lipopolysaccharide (LPS) to stimulate an immune response. Release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were measured as well as the cellular viability.

RESULTS

Co-exposure to Nanosilica and Quartz resulted in an additive attenuation of the LPS-induced IL-1β release. Moreover, co-exposure to TEGDMA and both types of filler particles also resulted in an additive attenuation, although with a weak synergistic trend. The cellular viability and TNF-α release were not significantly affected by the exposures.

CONCLUSION

The present findings emphasize the necessity of considering effects of combined exposure to dental degradation products in future risk assessments.

CLINICAL RELEVANCE

Attenuated cytokine release could have implications for the macrophage immune response and result in impaired bacterial clearance. Further studies are necessary to determine implications for formation of dental biofilms and caries development.

Glycogen synthase kinase 3 inhibitor attenuates endotoxin-induced liver injury

BACKGROUND/AIMS

Endotoxin (lipopolysaccharide, LPS)-induced acute liver injury was attenuated by endotoxin tolerance (ET), which is characterized by phosphatidylinositol 3-kinase pathway/Akt signaling. Glycogen synthase kinase 3 (GSK-3) acts downstream of phosphatidylinositol 3-kinase pathway/Akt and GSK-3 inhibitor protects against organic injury. This study evaluates the hypothesis that ET attenuated LPS-induced liver injury through inhibiting GSK-3 functional activity and downstream signaling.

METHODS

Sprague-Dawley rats with or without low-dose LPS pretreatment were challenged with or without large dose of LPS and subsequently received studies. Serum tumor necrosis factor-alpha, interleukin-10, alanine aminotransferase, lactate dehydrogenase, and total bilirubin levels were analyzed, morphology of liver tissue was performed, glycogen content, myeloperoxidase content, phagocytosis activity of Kupffer cells, and the expression and inhibitory phosphorylation as well as kinase activity of GSK-3 were examined. Survival after LPS administration was also determined.

RESULTS

LPS induced significant increases of serum TNF-α, alanine aminotransferase, lactate dehydrogenase, and total bilirubin (P < 0.05), which were companied by obvious alterations in liver: the injury of liver tissue, the decrease of glycogen, the infiltration of neutrophils, and the enhancement of phagocytosis of Kupffer cells (P < 0.05). LPS pretreatment significantly attenuated these alterations, promoted the inhibitory phosphorylation of GSK-3 and inhibited its kinase activity, and improved the survival rate (P < 0.05).

CONCLUSIONS

ET attenuated LPS-induced acute liver injury through inhibiting GSK-3 functional activity and its downstream signaling.

Toll like receptor signaling in "inflammaging": microRNA as new players

The age-related changes of immune system functions are complex phenomena incompletely understood. The acquired immune system shows a functional decline in ability to respond to new pathogens during aging, whereas serum levels of inflammatory cytokines are increased with age. The source of this age-related systemic chronic inflammation, named inflammaging, was mainly attributed to the progressive activation of immune cells over time. However, recent studies have shown that the process of cellular senescence can be an important additional contributor to chronic inflammation, since senescent cells acquire a phenotype named “senescence-associated secretory phenotype” (SASP), characterized by the enhanced secretion of many inflammation modulators. Pathogen-associated molecular pattern receptors, in particular Toll-like receptors (TLRs), are key molecules in the response of innate immunity cells to pathological stimuli. An intriguing and innovative hypothesis is that the dysfunction of TLRs signaling and the acquisition of SASP can be two interconnected phenomena. The TLR family, including receptors and co-effector molecules, do not show a consistent age-dependent change across model systems. However, there is evidence for impaired downstream signaling events, including inhibition of positive and activation of negative modulators of TLR signaling. MicroRNAs (miRNAs) are a newly discovered class of gene regulators acting as post-transcriptional repressors of a number of genes. The miRNA property to finely-tune gene expression makes them right for immune system regulation, which requires precise control for proper activity. We reviewed evidences suggesting that miRNAs can modulate TLR signaling mainly by three different mechanisms: 1) miRNAs can directly target components of the TLR signaling system, 2) miRNA expression can be directly regulated by TLRs pathway activation and 3) miRNAs can directly activate the RNA-sensing TLRs, like TLR-8, in humans. We also reviewed how TLR signaling is modulated by miRNAs during aging, and how an impaired miRNAs/TLR signaling interaction in immune system cells and related cells, i.e. endothelial cells and adipocytes, can contribute to inflammaging observed in normal aging. Interestingly, this impairment appears accelerated in presence of the majors age-related diseases, such as cardiovascular diseases, diabetes, neurodegenerative diseases and cancers.