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Immune therapeutic exosomes, derived exogenously from dendritic cells (DCs), the 'directors' of the immune response, are receiving favorable safety and tolerance profiles in phase I and II clinical trials for a growing number of inflammatory and neoplastic diseases. DC-derived exosomes (EXO), the focus of this review, can be custom tailored with immunoregulatory or immunostimulatory molecules for specific immune cell targeting. Moreover, the relative stability, small size and rapid uptake of EXO by recipient immune cells offer intriguing options for therapeutic purposes. This necessitates an in-depth understanding of mechanisms of EXO biogenesis, uptake and routing by recipient immune cells, as well as their in vivo biodistribution. Against this backdrop is recognition of endogenous exosomes, secreted by all cells, the molecular content of which is reflective of the metabolic state of these cells. In this regard, exosome biogenesis and secretion is regulated by cell stressors of chronic inflammation and tumorigenesis, including dysbiotic microbes, reactive oxygen species and DNA damage. Such cell stressors can promote premature senescence in young cells through the senescence associated secretory phenotype (SASP). Pathological exosomes of the SASP amplify inflammatory signaling in stressed cells in an autocrine fashion or promote inflammatory signaling to normal neighboring cells in paracrine, without the requirement of cell-to-cell contact. In summary, we review relevant lessons learned from the use of exogenous DC exosomes for immune therapy, as well as the pathogenic potential of endogenous DC exosomes.

Dendritic cell (DC)-derived exosomes (DC EXO), natural nanoparticles of endosomal origin, are under intense scrutiny in clinical trials for various inflammatory diseases. DC EXO are eobiotic, meaning they are well-tolerated by the host; moreover, they can be custom-tailored for immune-regulatory or -stimulatory functions, thus presenting attractive opportunities for immune therapy. Previously we documented the efficacy of immunoregulatory DCs EXO (regDCs EXO) as immunotherapy for inflammatory bone disease, in an in-vivo model. We showed a key role for encapsulated TGFβ1 in promoting a bone sparing immune response. However, the on- and off-target effects of these therapeutic regDC EXO and how target signaling in acceptor cells is activated is unclear. In the present report, therapeutic regDC EXO were analyzed by high throughput proteomics, with non-therapeutic EXO from immature DCs and mature DCs as controls, to identify shared and distinct proteins and potential off-target proteins, as corroborated by immunoblot. The predominant expression in regDC EXO of immunoregulatory proteins as well as proteins involved in trafficking from the circulation to peripheral tissues, cell surface binding, and transmigration, prompted us to investigate how these DC EXO are biodistributed to major organs after intravenous injection. Live animal imaging showed preferential accumulation of regDCs EXO in the lungs, followed by spleen and liver tissue. In addition, TGFβ1 in regDCs EXO sustained downstream signaling in acceptor DCs. Blocking experiments suggested that sustaining TGFβ1 signaling require initial interaction of regDCs EXO with TGFβ1R followed by internalization of regDCs EXO with TGFβ1-TGFβ1R complex. Finally, these regDCs EXO that contain immunoregulatory cargo and showed biodistribution to lungs could downregulate the main severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) target receptor, ACE2 on recipient lung parenchymal cells via TGFβ1 in-vitro. In conclusion, these results in mice may have important immunotherapeutic implications for lung inflammatory disorders., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Elashiry, Elsayed, Elashiry, Rashid, Ara, Arbab, Elawady, Hamrick, Liu, Zhi, Lucas, Vazquez and Cutler.)

Enterococcus faecalis , long implicated in serious systemic infections and failure of root canal treatment, is a persistent inhabitant of oral periapical lesions. Dendritic cells (DCs) and other innate immune cells patrol the oral mucosa for infecting microbes. Dendritic cells are efficient at capturing microbes when immature, whereupon they can transform into potent antigen-presenting cells upon full maturation. Autophagy, a sophisticated intracellular process first described for elimination of damaged organelles, regulates DC maturation and other important immune functions of DCs. The present study examined how E. faecalis influences the differentiation of murine bone marrow-derived stem cells (BMSCs) into functional DCs in the presence of the cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Although the viability and differentiation of DCs were not affected by E. faecalis , expression of the autophagy-related proteins ATG7, Beclin1, and LC3bI/II were significantly suppressed in an mTOR-dependent manner. Ultrastructurally, E. faecalis was identified in single-membrane vacuoles, some of which were in the process of binary fission. Bacterium-containing autophagosomes were absent within the cytoplasm. Accessory molecules (major histocompatibility complex class II [MHC-II], CD80, and CD86) and anti-inflammatory cytokine (transforming growth factor β1 [TGF-β1]) were suppressed in E. faecalis -induced DCs, while IL-1β, tumor necrosis factor alpha (TNF-α), and IL-12 levels were upregulated. When pulsed with ovalbumin (OVA), the E. faecalis -induced DCs showed reduction in CD4 + OVA-specific OT-II T cell proliferation. It is concluded that E. faecalis promotes the differentiation of bone marrow stem cells into CD11c-positive DCs with aberrant immune functions while retaining the capability of proinflammatory cytokine induction., (Copyright © 2020 American Society for Microbiology.)

Mucosal health and disease is mediated by a complex interplay between the microbiota ("spark") and the inflammatory response ("flame"). Pathobionts, a specific class of microbes, exemplified by the oral microbe Porphyromonas gingivalis , live mostly "under the radar" in their human hosts, in a cooperative relationship with the indigenous microbiota. Dendritic cells (DCs), mucosal immune sentinels, often remain undisturbed by such microbes and do not alert adaptive immunity to danger. At a certain tipping point of inflammation, an "awakening" of pathobionts occurs, wherein their active growth and virulence are stimulated, leading to a dysbiosis. Pathobiont becomes pathogen, and commensal becomes accessory pathogen. The local inflammatory outcome is the Th17-mediated degenerative bone disease, periodontitis (PD). In systemic circulation of PD subjects, inflammatory DCs expand, carrying an oral microbiome and promoting Treg and Th17 responses. At distant peripheral sites, comorbid diseases including atherosclerosis, Alzheimer's disease, macular degeneration, chronic kidney disease, and others are reportedly induced. This review will review the immunobiology of DCs, examine the complex interplay of microbes and DCs in the pathogenesis of PD and its comorbid inflammatory diseases, and discuss the role of apoptosis and autophagy in this regard. Overall, the pathophysiological mechanisms of DC-mediated chronic inflammation and tissue destruction will be summarized.

Dendritic cells are an important link between innate and adaptive immune response. The role of dendritic cells in bone homeostasis, however, is not understood. Osteoporosis medications that inhibit osteoclasts have been associated with osteonecrosis, a condition limited to the jawbone, thus called medication-related osteonecrosis of the jaw. We propose that disruption of the local immune response renders the oral microenvironment conducive to osteonecrosis. We tested whether zoledronate (Zol) treatment impaired dendritic cell (DC) functions and increased bacterial load in alveolar bone in vivo and whether DC inhibition alone predisposed the animals to osteonecrosis. We also analyzed the role of Zol in impairment of differentiation and function of migratory and tissue-resident DCs, promoting disruption of T-cell activation in vitro. Results demonstrated a Zol induced impairment in DC functions and an increased bacterial load in the oral cavity. DC-deficient mice were predisposed to osteonecrosis following dental extraction. Zol treatment of DCs in vitro caused an impairment in immune functions including differentiation, maturation, migration, antigen presentation, and T-cell activation. We conclude that the mechanism of Zol-induced osteonecrosis of the jaw involves disruption of DC immune functions required to clear bacterial infection and activate T cell effector response., (© 2020 Federation of American Societies for Experimental Biology.)

Objective: To compare the myeloid and plasmacytoid DC counts and maturation status among subjects with/without generalized periodontitis (GP) and type 2 diabetes mellitus (T2DM)., Methods: The frequency and maturation status of myeloid and plasmacytoid blood DCs were analyzed by flow cytometry in four groups of 15 subjects: healthy controls, T2DM with generalized CP (T2DM + GP), prediabetes with GP (PD + GP), and normoglycemics with GP (NG + GP). RT-PCR was used to determine levels of Porphyromonas gingivalis in the oral biofilms and within panDCs. The role of exogenous glucose effects on differentiation and apoptosis of healthy human MoDCs was explored in vitro., Results: Relative to controls and to NG + GP, T2DM + GP showed significantly lower CD1c + and CD303 + DC counts, while CD141 + DCs were lower in T2DM + GP relative to controls. Blood DC maturation required for mobilization and immune responsiveness was not observed. A statistically significant trend was observed for P. gingivalis levels in the biofilms of groups as follows: controls 

As fundamental processes of immune homeostasis, autophagy, and apoptosis must be maintained to mitigate risk of chronic inflammation and autoimmune diseases. Periodontitis is a chronic inflammatory disease characterized by oral microbial dysbiosis, and dysregulation of dendritic cell (DC) and T cell responses. The aim of this study was to elucidate the underlying mechanisms by which the oral microbe Porphyromonas gingivalis ( P. gingivalis ) manipulates dendritic cell signaling to perturb both autophagy and apoptosis. Using a combination of Western blotting, flow cytometry, qRT-PCR and immunofluorescence analysis, we show a pivotal role for the minor (Mfa1) fimbriae of P. gingivalis in nuclear/cytoplasmic shuttling of Akt and FOXO1 in human monocyte-derived DCs. Mfa1-induced Akt nuclear localization and activation ultimately induced mTOR. Activation of the Akt/mTOR axis downregulated intracellular LC3II, also known as Atg8, required for autophagosome formation and maturation. Use of allosteric panAkt inhibitor MK2206 and mTOR inhibitor rapamycin confirmed the role of Akt/mTOR signaling in autophagy inhibition by P. gingivalis in DCs. Interestingly, this pathway was also linked to induction of the anti-apoptotic protein Bcl2, decreased caspase-3 cleavage and decreased expression of pro-apoptotic proteins Bax and Bim, thus promoting longevity of host DCs. Addition of ABT-199 peptide to disrupt the interaction of antiapoptotic Bcl2 and its proapoptotic partners BAK/BAX restored apoptotic death to P. gingivalis- infected DC cells. In summary, we have identified the underlying mechanism by which P. gingivalis promotes its own survival and that of its host DCs., (Copyright © 2019 Meghil, Tawfik, Elashiry, Rajendran, Arce, Fulton, Schoenlein and Cutler.)

Periodontitis (PD) is a common dysbiotic inflammatory disease that leads to local bone deterioration and tooth loss. PD patients experience low-grade bacteremias with oral microbes implicated in the risk of heart disease, cancer, and kidney failure. Although Th17 effectors are vital to fighting infection, functional imbalance of Th17 effectors and regulatory T cells (Tregs) promote inflammatory diseases. In this study, we investigated, in a small pilot randomized clinical trial, whether expansion of inflammatory blood myeloid dendritic cells (DCs) and conversion of Tregs to Th17 cells could be modulated with antibiotics (AB) as part of initial therapy in PD patients. PD patients were randomly assigned to either 7 d of peroral metronidazole/amoxicillin AB treatment or no AB, along with standard care debridement and chlorhexidine mouthwash. 16s ribosomal RNA analysis of keystone pathogen Porphyromonas gingivalis and its consortium members Fusobacterium nucleatum and Streptococcus gordonii confirmed the presence of all three species in the reservoirs (subgingival pockets and blood DCs) of PD patients before treatment. Of the three species, P. gingivalis was reduced in both reservoirs 4-6 wk after therapy. Further, the frequency of CD1C + CCR6 + myeloid DCs and IL-1R1 expression on IL-17A + FOXP3 + CD4 + T cells in PD patients were reduced to healthy control levels. The latter led to decreased IL-1β-stimulated Treg plasticity in PD patients and improvement in clinical measures of PD. Overall, we identified an important, albeit short-term, beneficial role of AB therapy in reducing inflammatory DCs and Treg-Th17 plasticity in humans with PD., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Years of human microbiome research have confirmed that microbes rarely live or function alone, favoring diverse communities. Yet most experimental host-pathogen studies employ single species models of infection. Here, the influence of three-species oral microbial consortium on growth, virulence, invasion and persistence in dendritic cells (DCs) was examined experimentally in human monocyte-derived dendritic cells (DCs) and in patients with periodontitis (PD). Cooperative biofilm formation by Streptococcus gordonii, Fusobacterium nucleatum and Porphyromonas gingivalis was documented in vitro using growth models and scanning electron microscopy. Analysis of growth rates by species-specific 16s rRNA probes revealed distinct, early advantages to consortium growth for S. gordonii and F. nucleatum with P. gingivalis, while P. gingivalis upregulated its short mfa1 fimbriae, leading to increased invasion of DCs. F. nucleatum was only taken up by DCs when in consortium with P. gingivalis. Mature consortium regressed DC maturation upon uptake, as determined by flow cytometry. Analysis of dental plaques of PD and healthy subjects by 16s rRNA confirmed oral colonization with consortium members, but DC hematogenous spread was limited to P. gingivalis and F. nucleatum. Expression of P. gingivalis mfa1 fimbriae was increased in dental plaques and hematogenous DCs of PD patients. P. gingivalis in the consortium correlated with an adverse clinical response in the gingiva of PD subjects. In conclusion, we have identified polymicrobial synergy in a three-species oral consortium that may have negative consequences for the host, including microbial dissemination and adverse peripheral inflammatory responses.

Chronic periodontitis (CP) is a microbial dysbiotic disease linked to increased risk of oral squamous cell carcinomas (OSCCs). To address the underlying mechanisms, mouse and human cell infection models and human biopsy samples were employed. We show that the 'keystone' pathogen Porphyromonas gingivalis, disrupts immune surveillance by generating myeloid-derived dendritic suppressor cells (MDDSCs) from monocytes. MDDSCs inhibit CTLs and induce FOXP3 + T regs through an anti-apoptotic pathway. This pathway, involving pAKT1, pFOXO1, FOXP3, IDO1 and BIM, is activated in humans with CP and in mice orally infected with Mfa1 expressing P. gingivalis strains. Mechanistically, activation of this pathway, demonstrating FOXP3 as a direct FOXO1-target gene, was demonstrated by ChIP-assay in human CP gingiva. Expression of oncogenic but not tumor suppressor markers is consistent with tumor cell proliferation demonstrated in OSCC-P. gingivalis cocultures. Importantly, FimA + P. gingivalis strain MFI invades OSCCs, inducing inflammatory/angiogenic/oncogenic proteins stimulating OSCCs proliferation through CXCR4. Inhibition of CXCR4 abolished Pg-MFI-induced OSCCs proliferation and reduced expression of oncogenic proteins SDF-1/CXCR4, plus pAKT1-pFOXO1. Conclusively, P. gingivalis, through Mfa1 and FimA fimbriae, promotes immunosuppression and oncogenic cell proliferation, respectively, through a two-hit receptor-ligand process involving DC-SIGN +hi /CXCR4 +hi , activating a pAKT +hi pFOXO1 +hi BIM -low FOXP3 +hi and IDO +hi - driven pathway, likely to impact the prognosis of oral cancers in patients with periodontitis.

Dendritic cells (DCs) are specialized antigen-presenting cells that play a pivotal role in the pathogenesis of periodontitis. The use of animal models to study the role of DCs in periodontitis has been limited by lack of a method for sustained depletion of DCs. Hence, the objectives of this study were to validate the zDC-DTR knockin mouse model of conventional DCs (cDCs) depletion, as well as to investigate whether this depletion could be sustained long enough to induce alveolar bone loss in this model. zDC-DTR mice were treated with different dose regimens of diphtheria toxin (DT) to determine survival rate. A loading DT dose of 20ng/bw, followed and maintained with doses of 10ng/bm every 3days for up to 4weeks demonstrated 80% survival. Animals were weighed weekly and peripheral blood was obtained to confirm normal neutrophil counts. Five animals per group were euthanized at baseline, 24h, 1 and 4weeks. Bone marrow (BM), spleen (SP) and gingival tissue (GT) were harvested, and cells were isolated, separated and stained for Pre-DCs precursors (CD45R - MHCII + CD11c + Flt3 + CD172a + ) in BM, cDCs (CD11c + MHCII + CD209 + ) in spleen, and DCs in GT (CD45R + MHCII + CD11c + DC-SIGN/CD209 + ). Pre-DCs in BM were significantly depleted at 24h and depletion maintained for up to 4weeks, as compared to blank (PBS) controls. Circulating cDCs in spleen demonstrated a non-significant trend to deplete in 1week with high variability among mice. GT also showed a similar non-significant trend to deplete in 24h. The zDC-DTR model seems to be viable for evaluating the role of DCs immune homeostasis disruption and alveolar bone loss pathogenesis in response to long-term oral infection., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Targeting of myeloid-dendritic cell receptor DC-SIGN by numerous chronic infectious agents, including Porphyromonas gingivalis, is shown to drive-differentiation of monocytes into dysfunctional mDCs. These mDCs exhibit alterations of their fine-tuned homeostatic function and contribute to dysregulated immune-responses. Here, we utilize P. gingivalis mutant strains to show that pathogen-differentiated mDCs from primary human-monocytes display anti-apoptotic profile, exhibited by elevated phosphorylated-Foxo1, phosphorylated-Akt1, and decreased Bim-expression. This results in an overall inhibition of DC-apoptosis. Direct stimulation of complex component CD40 on DCs leads to activation of Akt1, suggesting CD40 involvement in anti-apoptotic effects observed. Further, these DCs drove dampened CD8 + T-cell and Th1/Th17 effector-responses while inducing CD25 + Foxp3 + CD127 - Tregs. In vitro Treg induction was mediated by DC expression of indoleamine 2,3-dioxygenase, and was confirmed in IDO-KO mouse model. Pathogen-infected &CMFDA-labeled MoDCs long-lasting survival was confirmed in a huMoDC reconstituted humanized mice. In conclusion, our data implicate PDDCs as an important target for resolution of chronic infection.

Dendritic cells are potent antigen-capture and antigen-presenting cells that play a key role in the initiation and regulation of the adaptive immune response. This process of immune homeostasis, as maintained by dendritic cells, is susceptible to dysregulation by certain pathogens during chronic infections. Such dysregulation may lead to disease perpetuation with potentially severe systemic consequences. Here we discuss in detail how intracellular pathogens exploit dendritic cells and escape degradation by altering or evading autophagy. This novel mechanism explains, in part, the chronic, persistent nature observed in several immuno-inflammatory diseases, including periodontal disease. We also propose a hypothetical model of the plausible role of autophagy in the context of periodontal disease. Promotion of autophagy may open new therapeutic strategies in the search of a 'cure' for periodontal disease in humans., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Signaling via pattern recognition receptors (PRRs) expressed on professional antigen presenting cells, such as dendritic cells (DCs), is crucial to the fate of engulfed microbes. Among the many PRRs expressed by DCs are Toll-like receptors (TLRs) and C-type lectins such as DC-SIGN. DC-SIGN is targeted by several major human pathogens for immune-evasion, although its role in intracellular routing of pathogens to autophagosomes is poorly understood. Here we examined the role of DC-SIGN and TLRs in evasion of autophagy and survival of Porphyromonas gingivalis in human monocyte-derived DCs (MoDCs). We employed a panel of P. gingivalis isogenic fimbriae deficient strains with defined defects in Mfa-1 fimbriae, a DC-SIGN ligand, and FimA fimbriae, a TLR2 agonist. Our results show that DC-SIGN dependent uptake of Mfa1+P. gingivalis strains by MoDCs resulted in lower intracellular killing and higher intracellular content of P. gingivalis. Moreover, Mfa1+P. gingivalis was mostly contained within single membrane vesicles, where it survived intracellularly. Survival was decreased by activation of TLR2 and/or autophagy. Mfa1+P. gingivalis strain did not induce significant levels of Rab5, LC3-II, and LAMP1. In contrast, P. gingivalis uptake through a DC-SIGN independent manner was associated with early endosomal routing through Rab5, increased LC3-II and LAMP-1, as well as the formation of double membrane intracellular phagophores, a characteristic feature of autophagy. These results suggest that selective engagement of DC-SIGN by Mfa-1+P. gingivalis promotes evasion of antibacterial autophagy and lysosome fusion, resulting in intracellular persistence in myeloid DCs; however TLR2 activation can overcome autophagy evasion and pathogen persistence in DCs.

Several intracellular pathogens, including a key etiological agent of chronic periodontitis, Porphyromonas gingivalis, infect blood myeloid dendritic cells (mDCs). This infection results in pathogen dissemination to distant inflammatory sites (i.e., pathogen trafficking). The alteration in chemokine-chemokine receptor expression that contributes to this pathogen trafficking function, particularly toward sites of neovascularization in humans, is unclear. To investigate this, we utilized human monocyte-derived DCs (MoDCs) and primary endothelial cells in vitro, combined with ex vivo-isolated blood mDCs and serum from chronic periodontitis subjects and healthy controls. Our results, using conditional fimbria mutants of P. gingivalis, show that P. gingivalis infection of MoDCs induces an angiogenic migratory profile. This profile is enhanced by expression of DC-SIGN on MoDCs and minor mfa-1 fimbriae on P. gingivalis and is evidenced by robust upregulation of CXCR4, but not secondary lymphoid organ (SLO)-homing CCR7. This disruption of SLO-homing capacity in response to respective chemokines closely matches surface expression of CXCR4 and CCR7 and is consistent with directed MoDC migration through an endothelial monolayer. Ex vivo-isolated mDCs from the blood of chronic periodontitis subjects, but not healthy controls, expressed a similar migratory profile; moreover, sera from chronic periodontitis subjects expressed elevated levels of CXCL12. Overall, we conclude that P. gingivalis actively "commandeers" DCs by reprogramming the chemokine receptor profile, thus disrupting SLO homing, while driving migration toward inflammatory vascular sites.

Maintenance of blood DC homeostasis is essential to preventing autoimmunity while controlling chronic infection. However, the ability of bacteremic pathogens to directly regulate blood DC homeostasis has not been defined. One such bacteremic pathogen, Porphyromonas gingivalis, is shown by our group to survive within mDCs under aerobic conditions and therein, metastasize from its oral mucosal niche. This is accompanied by expansion of the blood mDC pool in vivo, independently of canonical DC poietins. We presently know little of how this bacteremic pathogen causes blood DC expansion and the pathophysiological significance. This work shows that optimum differentiation of MoDCs from primary human monocytes, with or without GM-CSF/IL-4, is dependent on infection with P. gingivalis strains expressing the DC-SIGN ligand mfa-1. DC differentiation is lost when DC-SIGN is blocked with its ligand HIV gp120 or knocked out by siRNA gene silencing. Thus, we have identified a novel, noncanonical pathway of DC differentiation. We term these PDDCs and show that PDDCs are bona fide DCs, based on phenotype and phagocytic activity when immature and the ability to up-regulate accessory molecules and stimulate allo-CD4(+) T cell proliferation when matured. The latter is dependent on the P. gingivalis strain used to initially "educate" PDDCs. Moreover, we show that P. gingivalis-infected, conventional MoDCs become resistant to apoptosis and inflammatory pyroptosis, as determined by levels of Annexin V and caspase-8, -3/7, and -1. Taken together, we provide new insights into how a relatively asymptomatic bacteremia may influence immune homeostasis and promote chronic inflammation.

The low-grade oral infection chronic periodontitis (CP) has been implicated in coronary artery disease risk, but the mechanisms are unclear. In this study, a pathophysiological role for blood dendritic cells (DCs) in systemic dissemination of oral mucosal pathogens to atherosclerotic plaques was investigated in humans. The frequency and microbiome of CD19(-)BDCA-1(+)DC-SIGN(+) blood myeloid DCs (mDCs) were analyzed in CP subjects with or without existing acute coronary syndrome and in healthy controls. FACS analysis revealed a significant increase in blood mDCs in the following order: healthy controls < CP < acute coronary syndrome/CP. Analysis of the blood mDC microbiome by 16S rDNA sequencing showed Porphyromonas gingivalis and other species, including (cultivable) Burkholderia cepacia. The mDC carriage rate with P. gingivalis correlated with oral carriage rate and with serologic exposure to P. gingivalis in CP subjects. Intervention (local debridement) to elicit a bacteremia increased the mDC carriage rate and frequency in vivo. In vitro studies established that P. gingivalis enhanced by 28% the differentiation of monocytes into immature mDCs; moreover, mDCs secreted high levels of matrix metalloproteinase-9 and upregulated C1q, heat shock protein 60, heat shock protein 70, CCR2, and CXCL16 transcripts in response to P. gingivalis in a fimbriae-dependent manner. Moreover, the survival of the anaerobe P. gingivalis under aerobic conditions was enhanced when within mDCs. Immunofluorescence analysis of oral mucosa and atherosclerotic plaques demonstrate infiltration with mDCs, colocalized with P. gingivalis. Our results suggest a role for blood mDCs in harboring and disseminating pathogens from oral mucosa to atherosclerosis plaques, which may provide key signals for mDC differentiation and atherogenic conversion.

The pathogenesis of a number of chronic inflammatory diseases has been linked to dysregulated functioning of nuclear transcription factor (NF)-kappaB. In the present study, we examine NF-kappaB activation in human oral mucosal tissues of chronic periodontitis (CP) patients. Electrophoretic mobility shift assay and DNA-binding enzyme-linked immunosorbent assays indicate elevated levels of transcriptionally repressive p50 subunits and an increased p50/p65 ratio in CP tissues compared to healthy controls. Because Porphyromonas gingivalis has been recognized to be a causal factor in CP, we used P. gingivalis lipopolysaccharide (LPS) for in vitro studies with monocyte-derived dendritic cells (MoDCs). Porphyromonas gingivalis LPS, unlike Escherichia coli LPS, induced an increased p50/p65 ratio in MoDCs. Using blocking antibodies, we demonstrated that while both Toll-like receptor 2 (TLR2) and TLR4 are required for MoDC maturation by P. gingivalis LPS, only TLR4 signaling is sufficient to induce cytokine secretion. Our results suggest that increased levels of transcriptionally repressive p50 may be characteristic of CP and might be a result of suboptimal NF-kappaB activation and dendritic cell maturation by P. gingivalis, a bacterium implicated in CP.

The oral mucosal pathogen Porphyromonas gingivalis expresses at least two adhesins: the 67-kDa mfa-1 (minor) fimbriae and the 41-kDa fimA (major) fimbriae. In periodontal disease, P. gingivalis associates in situ with dermal dendritic cells (DCs), many of which express DC-SIGN (DC-specific ICAM-3 grabbing nonintegrin; CD209). The cellular receptors present on DCs that are involved in the uptake of minor/major fimbriated P. gingivalis, along with the effector immune response induced, are presently unclear. In this study, stably transfected human DC-SIGN(+/-) Raji cell lines and monocyte-derived DCs (MoDCs) were pulsed with whole, live, wild-type Pg381 or isogenic major (DPG-3)-, minor (MFI)-, or double fimbriae (MFB)-deficient mutant P. gingivalis strains. The influence of blocking Abs, carbohydrates, full-length glycosylated HIV-1 gp120 envelope protein, and cytochalasin D on the uptake of strains and on the immune responses was determined in vitro. We show that the binding of minor fimbriated P. gingivalis strains to Raji cells and MoDCs is dependent on DC-SIGN, whereas the double fimbriae mutant strain does not bind. Binding to DC-SIGN on MoDCs is followed by the internalization of P. gingivalis into DC-SIGN-rich intracellular compartments, and MoDCs secrete low levels of inflammatory cytokines and remain relatively immature. Blocking DC-SIGN with HIV-1 gp120 prevents the uptake of minor fimbriated strains and deregulates the expression of inflammatory cytokines. Moreover, MoDCs promote a Th2 or Th1 effector response, depending on whether they are pulsed with minor or major fimbriated P. gingivalis strains, respectively, suggesting distinct immunomodulatory roles for the two adhesins of P. gingivalis.

Porphyromonas gingivalis is a fimbriated mucosal pathogen implicated in chronic periodontitis (CP). The fimbriae are required for invasion of the gingival mucosa and for induction of CP in animal models of periodontitis. CP is associated with infection of immature dendritic cells (DCs) by P. gingivalis in situ and with increased numbers of dermal DCs (DDCs) and mature DCs in the lamina propria. The role of fimbriae in gaining entry into human DCs and how this modulates the inflammatory and effector immune responses, however, have not been explored. To address this, we generated monocyte-derived DCs (MDDCs) in vitro which phenotypically and functionally resemble DDCs. We show here that virulent fimbriated P. gingivalis 381, in contrast to its fimbria-deficient mutant, P. gingivalis DPG3, efficiently gains entry to MDDCs in a manner dependent on active cell metabolism and cytoskeletal rearrangement. In addition, uptake of 381, unlike DPG3, induces DCs to undergo maturation, upregulate costimulatory molecules, and secrete inflammation cytokines interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha, IL-10, and IL-12. Moreover, MDDCs pulsed with 381 also stimulated a higher autologous mixed lymphocyte reaction and induced a Th1-type response, with gamma interferon (IFN-gamma) being the main cytokine. Monocytes used as controls demonstrated fimbria-dependent uptake of 381 as well but produced low levels of inflammatory cytokines compared to MDDCs. When MDDCs were pulsed with recombinant fimbrillin of P. gingivalis (10 micro g/ml), maturation of MDDCs was also induced; moreover, matured MDDCs induced proliferation of autologous CD4(+) T cells and release of IFN-gamma. Thus, these results establish the significance of P. gingivalis fimbriae in the uptake of P. gingivalis by MDDCs and in induction of immunostimulatory Th1 responses.

Understanding how mucosal pathogens modulate the immune response may facilitate the development of vaccines for disparate human diseases. In the present study, human monocyte-derived DC (MDDC)were pulsed with LPS of the oral pathogen Porphyromonas gingivalis and Escherichia coli 25922 and analyzed for: (i) production of Th-biasing/inflammatory cytokines; (ii) maturation/costimulatory molecules; and (iii) induction of allogeneic CD4+ and naive CD45RA+ T cell proliferation and release of Th1 or Th2 cytokines. We show that E. coli LPS-pulsed MDDC released Th1-biasing cytokines - consisting of high levels of IL-12 p70, IFN-gamma-inducible protein 10 (IP-10) - but also TNF-alpha, IL-10, IL-6 and IL-1beta. In contrast, no IL-12 p70 or IP-10, and lower levels of TNF-alpha and IL-10 were induced by P. gingivalis LPS. These differences were sustained at LPS doses that yielded nearly equivalent maturation of MDDC; moreover the T cell response was consistent: E. coli LPS-pulsed MDDC induced higher T cell proliferation, and T cells released more IFN-gamma and IL-2, but less IL-5 than T cells co-cultured with P. gingivalis LPS pulsed-MDDC. IL-13 was secreted by naive CD45RA+CD45RO-CD4+ T cells in response to P. gingivalisLPS-pulsed MDDC. These results suggest that human MDDC can be polarized by LPS from the mucosal pathogen P. gingivalis to induce a Th2 effector response in vitro.

Porphyromonas gingivalis (Pg) and its gingipain proteases contribute to Alzheimer's disease (AD) pathogenesis through yet unclear mechanisms. Cellular secretion of small extracellular vesicles or exosomes (EXO) increases with aging as part of the senescence-associated secretory phenotype (SASP). We have shown that EXO isolated from Pg-infected dendritic cells contain gingipains and other Pg antigens and transmit senescence to bystander gingival cells, inducing alveolar bone loss in mice in vivo. Here, EXO were isolated from the gingiva of mice and humans with/without periodontitis (PD) to determine their ability to penetrate the blood–brain barrier (BBB) in vitro and in vivo. PD was induced by Pg oral gavage for 6 weeks in C57B6 mice. EXO isolated from the gingiva or brain of donor Pg-infected (PD EXO) or control animals (Con EXO) were characterized by NTA, Western blot, and TEM. Gingival PD EXO or Con EXO were labeled and injected into the gingiva of uninfected WT mouse model. EXO biodistribution in brains was tracked by an in vivo imaging system (IVIS) and confocal microscopy. The effect of human PD EXO on BBB integrity and permeability was examined using TEER and FITC dextran assays in a human in vitro 3D model of the BBB. Pg antigens (RGP and Mfa-1) were detected in EXO derived from gingival and brain tissues of donor Pg-infected mice. Orally injected PD EXO from donor mice penetrated the brains of recipient uninfected mice and colocalized with hippocampal microglial cells. IL-1β and IL-6 were expressed in human PD EXO and not in Con EXO. Human PD EXO promoted BBB permeability and penetrated the BBB in vitro. This is the first demonstration that microbial-induced EXO in the oral cavity can disseminate, cross the BBB, and may contribute to AD pathogenesis. [ABSTRACT FROM AUTHOR]

Exosomes (exos) contain molecular cargo of therapeutic and diagnostic value for cancers and other inflammatory diseases, but their therapeutic potential for periodontitis (PD) remains unclear. Dendritic cells (DCs) are the directors of immune response and have been extensively used in immune therapy. We previously reported in a mouse model of PD that custom murine DC-derived exo subtypes could reprogram the immune response toward a bone-sparing or bone-loss phenotype, depending on immune profile. Further advancement of this technology requires the testing of human DC-based exos with human target cells. Our main objective in this study is to test the hypothesis that human monocyte-derived dendritic cell (MoDC)-derived exos constitute a well-tolerated and effective immune therapeutic approach to modulate human target DC and T cell immune responses in vitro. MoDC subtypes were generated with TGFb/IL-10 (regulatory (reg) MoDCs, CD86lowHLA-DRlowPDL1high), E. coli LPS (stimulatory (stim) MoDCs, CD86highHLA-DRhighPDL1low) and buffer (immature (i) MoDCs, CD86lowHLA-DRmedPDL1low). Exosomes were isolated from different MoDC subtypes and characterized. Once released from the secreting cell into the surrounding environment, exosomes protect their prepackaged molecular cargo and deliver it to bystander cells. This modulates the functions of these cells, depending on the cargo content. RegMoDCexos were internalized by recipient MoDCs and induced upregulation of PDL1 and downregulation of costimulatory molecules CD86, HLADR, and CD80, while stimMoDCexos had the opposite influence. RegMoDCexos induced CD25+Foxp3+ Tregs, which expressed CTLA4 and PD1 but not IL-17A. In contrast, T cells treated with stimMoDCexos induced IL-17A+ Th17 T cells, which were negative for immunoregulatory CTLA4 and PD1. T cells and DCs treated with iMoDCexos were immune 'neutral', equivalent to controls. In conclusion, human DC exos present an effective delivery system to modulate human DC and T cell immune responses in vitro. Thus, MoDC exos may present a viable immunotherapeutic agent for modulating immune response in the gingival tissue to inhibit bone loss in periodontal disease. [ABSTRACT FROM AUTHOR]

As the aging population grows, chronic age-related bone degenerative diseases become more prevalent and severe. One such disease, periodontitis (PD), rises to 70.1% prevalence in Americans 65 years and older. PD has been linked to increased risk of other age-related diseases with more serious mortality and morbidity profiles such as Alzheimer's disease and cardiovascular disease, but the cellular and biological mechanisms remain unclear. Recent in vitro studies from our group indicate that murine dendritic cells (DCs) and T cells are vulnerable to immune senescence. This occurs through a distinct process involving invasion of DCs by dysbiotic pathogen Porphyromonas gingivalis (Pg) activating the senescence associated secretory phenotype (SASP). Exosomes of the Pg-induced SASP transmit senescence to normal bystander DC and T cells, ablating antigen presentation. The biological significance of these findings in vivo and the mechanisms involved were examined in the present study using young (4-5mo) or old (22-24mo) mice subjected to ligature-induced PD, with or without dysbiotic oral pathogen and injection of Pg-induced DC exosomes. Senescence profiling of gingiva and draining lymph nodes (LN) corroborates role of advanced age and PD in elevation of senescence biomarkers beta galactosidase (SA-ß-Gal), p16 INK4A p21Waf1/Clip1, IL6, TNF?, and IL1ß, with attendant increase in alveolar bone loss, reversed by senolytic agent rapamycin. Immunophenotyping of gingiva and LN revealed that myeloid CD11c+ DCs and T cells are particularly vulnerable to senescence in vivo under these conditions. Moreover, Pg-induced DC exosomes were the most potent inducers of alveolar bone loss and immune senescence, and capable of overcoming senescence resistance of LN T cells in young mice. We conclude that immune senescence, compounded by advanced age, and accelerated by oral dysbiosis and its induced SASP exosomes, plays a pivotal role in the pathophysiology of experimental periodontitis. [ABSTRACT FROM AUTHOR]

Extensive research in humans and animal models has begun to unravel the complex mechanisms that drive the immunopathogenesis of periodontitis. Neutrophils mount an early and rapid response to the subgingival oral microbiome, producing destructive enzymes to kill microbes. Chemokines and cytokines are released that attract macrophages, dendritic cells, and T cells to the site. Dendritic cells, the focus of this review, are professional antigen-presenting cells on the front line of immune surveillance. Dendritic cells consist of multiple subsets that reside in the epithelium, connective tissues, and major organs. Our work in humans and mice established that myeloid dendritic cells are mobilized in periodontitis. This occurs in lymphoid and nonlymphoid oral tissues, in the bloodstream, and in response to Porphyromonas gingivalis. Moreover, the dendritic cells mature in situ in gingival lamina propria, forming immune conjugates with cluster of differentiation (CD) 4+ T cells, called oral lymphoid foci. At such foci, the decisions are made as to whether to promote bone destructive T helper 17 or bone-sparing regulatory T cell responses. Interestingly, dendritic cells lack potent enzymes and reactive oxygen species needed to kill and degrade endocytosed microbes. The keystone pathogen P. gingivalis exploits this vulnerability by invading dendritic cells in the tissues and peripheral blood using its distinct fimbrial adhesins. This promotes pathogen dissemination and inflammatory disease at distant sites, such as atherosclerotic plaques. Interestingly, our recent studies indicate that such P. gingivalis-infected dendritic cells release nanosized extracellular vesicles called exosomes, in higher numbers than uninfected dendritic cells do. Secreted exosomes and inflammasome-related cytokines are a key feature of the senescence-associated secretory phenotype. Exosomes communicate in paracrine with neighboring stromal cells and immune cells to promote and amplify cellular senescence. We have shown that dendritic cell-derived exosomes can be custom tailored to target and reprogram specific immune cells responsible for inflammatory bone loss in mice. The long-term goal of these immunotherapeutic approaches, ongoing in our laboratory and others, is to promote human health and longevity. [ABSTRACT FROM AUTHOR]

Porphyromonas gingivalis (P. gingivalis) is a unique pathogen implicated in severe forms of periodontitis (PD), a disease that affects around 50% of the US population. P. gingivalis is equipped with a plethora of virulence factors that it uses to exploit its environment and survive. These include distinct fimbrial adhesins that enable it to bind to other microbes, colonize inflamed tissues, acquire nutrients, and invade cells of the stroma and immune system. Most notable for this review is its ability to invade dendritic cells (DCs), which bridge the innate and adaptive immune systems. This invasion process is tightly linked to the bridging functions of resultant DCs, in that it can disable (or stimulate) the maturation function of DCs and cytokines that are secreted. Maturation molecules (e.g., MHCII, CD80/CD86, CD40) and inflammatory cytokines (e.g., IL-1b, TNFa, IL-6) are essential signals for antigen presentation and for proliferation of effector T-cells such as Th17 cells. In this regard, the ability of P. gingivalis to coordinately regulate its expression of major (fimA) and minor (mfa-1) fimbriae under different environmental influences becomes highly relevant. This review will, therefore, focus on the immunoregulatory role of P. gingivalis fimbriae in the invasion of DCs, intracellular signaling, and functional outcomes such as alveolar bone loss and immune senescence. [ABSTRACT FROM AUTHOR]

Periodontitis is a disease of ageing or inflammaging, and is comorbid with other more severe age-related chronic diseases. With advanced age comes an increase in accumulation of senescent cells that release soluble and insoluble pro-inflammatory factors collectively termed the senescence associated secretory phenotype (SASP). In the present report, we examined whether immune cells typical of those at the oral mucosa-microbe interface, are vulnerable to cellular senescence (CS) and the role of dysbiotic oral pathogen Porphyromonas gingivalis. Bone marrow-derived dendritic cells (DCs) from young (yDCs) and old (oDCs) mice were co-cultured in vitro with CS inducer doxorubicin or P.gingivalis (Pg) , plus or minus senolytic agent rapamycin. CS profiling revealed elevated CS mediators SA-β-Gal, p16 INK4A, p53, and p21Waf1/Clip1 in oDCs, or yDCs in response to doxorubicin or P. gingivalis , reversible with rapamycin. Functional studies indicate impaired maturation function of oDCs, and yDC exposed to P. gingivalis ; moreover, OVA-driven proliferation of CD4+ T cells from young OTII transgenic mice was impaired by oDCs or yDCs+Pg. The SASP of DCs, consisting of secreted exosomes and inflammasome-related cytokines was further analyzed. Exosomes of DCs cocultured with P. gingivalis (PgDCexo) were purified, quantitated and characterized. Though typical in terms of size, shape and phenotype, PgDCexo were 2-fold greater in number than control DCs, with several important distinctions. Namely, PgDCexo were enriched in age-related miRNAs, and miRNAs reported to disrupt immune homeostasis through negative regulation of apoptosis and autophagy functions. We further show that PgDCexo were enriched in P. gingivalis fimbrial adhesin protein mfa1 and in inflammasome related cytokines IL-1β, TNFα and IL-6. Functionally PgDCexo were readily endocytosed by recipient yDCs, amplifying functional impairment in maturation and ability to promote Ova-driven proliferation of OTII CD4+ T cells from young mice. In conclusion P. gingivalis induces premature (autocrine) senescence in DCs by direct cellular invasion and greatly amplifies senescence, in paracrine, of bystander DCs by secretion of inflammatory exosomes. The implications of this pathological pathway for periodontal disease in vivo is under investigation in mouse models. [ABSTRACT FROM AUTHOR]

Chronic bone degenerative diseases represent a major threat to the health and well-being of the population, particularly those with advanced age. This study isolated exosomes (EXO), natural nano-particles, from dendritic cells, the "directors" of the immune response, to examine the immunobiology of DC EXO in mice, and their ability to reprogram immune cells responsible for experimental alveolar bone loss in vivo. Distinct DC EXO subtypes including immune-regulatory (regDC EXO), loaded with TGFB1 and IL10 after purification, along with immune stimulatory (stimDC EXO) and immune "null" immature (iDCs EXO) unmodified after purification, were delivered via I.V. route or locally into the soft tissues overlying the alveolar bone. Locally administrated regDC EXO showed high affinity for inflamed sites, and were taken up by both DCs and T cells in situ. RegDC EXO-encapsulated immunoregulatory cargo (TGFB1 and IL10) was protected from proteolytic degradation. Moreover, maturation of recipient DCs and induction of Th17 effectors was suppressed by regDC EXO, while T-regulatory cell recruitment was promoted, resulting in inhibition of bone resorptive cytokines and reduction in osteoclastic bone loss. This work is the first demonstration of DC exosome-based therapy for a degenerative alveolar bone disease and provides the basis for a novel treatment strategy. [ABSTRACT FROM AUTHOR]

Recent epidemiological studies link Periodontal disease(PD) to age-related macular degeneration (AMD). We documented earlier that Porphyromonas gingivalis(Pg), keystone oral-pathobiont, causative of PD, efficiently invades human gingival epithelial and blood-dendritic cells. Here, we investigated the ability of dysbiotic Pg-strains to invade human-retinal pigment epithelial cells(ARPE-19), their survival, intracellular localization, and the pathological effects, as dysfunction of RPEs leads to AMD. We show that live, but not heat-killed Pg-strains adhere to and invade ARPEs. This involves early adhesion to ARPE cell membrane, internalization and localization of Pg within single-membrane vacuoles or cytosol, with some nuclear localization apparent. No degradation of Pg or localization inside double-membrane autophagosomes was evident, with dividing Pg suggesting a metabolically active state during invasion. We found significant downregulation of autophagy-related genes particularly, autophagosome complex. Antibiotic protection-based recovery assay further confirmed distinct processes of adhesion, invasion and amplification of Pg within ARPE cells. This is the first study to demonstrate invasion of human-RPEs, begin to characterize intracellular localization and survival of Pg within these cells. Collectively, invasion of RPE by Pg and its prolonged survival by autophagy evasion within these cells suggest a strong rationale for studying the link between oral infection and AMD pathogenesis in individuals with periodontitis. [ABSTRACT FROM AUTHOR]

The pathogenesis of a number of chronic inflammatory diseases has been linked to dysregulated functioning of nuclear transcription factor (NF)-κB. In the present study, we examine NF-κB activation in human oral mucosal tissues of chronic periodontitis (CP) patients. Electrophoretic mobility shift assay and DNA-binding enzyme-linked immunosorbent assays indicate elevated levels of transcriptionally repressive p50 subunits and an increased p50/p65 ratio in CP tissues compared to healthy controls. Because Porphyromonas gingivalis has been recognized to be a causal factor in CP, we used P. gingivalis lipopolysaccharide (LPS) for in vitro studies with monocyte-derived dendritic cells (MoDCs). Porphyromonas gingivalis LPS, unlike Escherichia coli LPS, induced an increased p50/p65 ratio in MoDCs. Using blocking antibodies, we demonstrated that while both Toll-like receptor 2 (TLR2) and TLR4 are required for MoDC maturation by P. gingivalis LPS, only TLR4 signaling is sufficient to induce cytokine secretion. Our results suggest that increased levels of transcriptionally repressive p50 may be characteristic of CP and might be a result of suboptimal NF-κB activation and dendritic cell maturation by P. gingivalis, a bacterium implicated in CP. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinase-9 (MMP-9) cleaves collagen, allowing leukocytes to traffic toward the vasculature and the lymphatics. When MMP-9 is unregulated by tissue inhibitor of metalloproteinase-1 (TIMP-1), this can lead to tissue destruction. Dendritic cells (DCs) infiltrate the oral mucosa increasingly in chronic periodontitis, characterized by infection with several pathogens including Porphyromonas gingivalis. In this study, human monocyte-derived DCs were pulsed with different doses of lipopolysaccharide of P. gingivalis 381 and of Escherichia coli type strain 25922, as well as whole live isogenic fimbriae-deficient mutant strains of P. gingivalis 381. Levels of induction of MMP-9 and TIMP-1, as well as interleukin-10 (IL-10), which reportedly inhibits MMP-9 induction, were measured by several approaches. Our results reveal that lipopolysaccharide of P. gingivalis, compared with lipopolysaccharide from E. coli type strain 25922, is a relatively potent inducer of MMP-9, but a weak inducer of TIMP-1, contributing to a high MMP-9/TIMP-1 ratio. Whole live P. gingivalis strain 381, major fimbriae mutant DPG-3 and double mutant MFB were potent inducers of MMP-9, but minor fimbriae mutant MFI was not. MMP-9 induction was inversely proportional to IL-10 induction. These results suggest that lipopolysaccharide and the minor and the major fimbriae of P. gingivalis may play distinct roles in induction by DCs of MMP-9, a potent mediator of local tissue destruction and leukocyte trafficking. [ABSTRACT FROM AUTHOR]

An estimated 80 million US adults have one or more types of cardiovascular diseases. Atherosclerosis is the single most important contributor to cardiovascular diseases; however, only 50% of atherosclerosis patients have currently identified risk factors. Chronic periodontitis, a common inflammatory disease, is linked to an increased cardiovascular risk. Dendritic cells (DCs) are potent antigen presenting cells that infiltrate arterial walls and may destabilize atherosclerotic plaques in cardiovascular disease. While the source of these DCs in atherosclerotic plaques is presently unclear, we propose that dermal DCs from peripheral inflamed sites such as CP tissues are a potential source. This review will examine the role of the opportunistic oral pathogen Porphyromonas gingivalis in invading DCs and stimulating their mobilization and misdirection through the bloodstream. Based on our published observations, combined with some new data, as well as a focused review of the literature we will propose a model for how P. gingivalis may exploit DCs to gain access to systemic circulation and contribute to coronary artery disease. Our published evidence supports a significant role for P. gingivalis in subverting normal DC function, promoting a semimature, highly migratory, and immunosuppressive DC phenotype that contributes to the inflammatory development of atherosclerosis and, eventually, plaque rupture. [ABSTRACT FROM AUTHOR]

Immune therapeutic exosomes, derived exogenously from dendritic cells (DCs), the 'directors' of the immune response, are receiving favorable safety and tolerance profiles in phase I and II clinical trials for a growing number of inflammatory and neoplastic diseases. DC-derived exosomes (EXO), the focus of this review, can be custom tailored with immunoregulatory or immunostimulatory molecules for specific immune cell targeting. Moreover, the relative stability, small size and rapid uptake of EXO by recipient immune cells offer intriguing options for therapeutic purposes. This necessitates an in-depth understanding of mechanisms of EXO biogenesis, uptake and routing by recipient immune cells, as well as their in vivo biodistribution. Against this backdrop is recognition of endogenous exosomes, secreted by all cells, the molecular content of which is reflective of the metabolic state of these cells. In this regard, exosome biogenesis and secretion is regulated by cell stressors of chronic inflammation and tumorigenesis, including dysbiotic microbes, reactive oxygen species and DNA damage. Such cell stressors can promote premature senescence in young cells through the senescence associated secretory phenotype (SASP). Pathological exosomes of the SASP amplify inflammatory signaling in stressed cells in an autocrine fashion or promote inflammatory signaling to normal neighboring cells in paracrine, without the requirement of cell-to-cell contact. In summary, we review relevant lessons learned from the use of exogenous DC exosomes for immune therapy, as well as the pathogenic potential of endogenous DC exosomes. [ABSTRACT FROM AUTHOR]

El artículo trata la relación de entre las células dendríticas de la mucosa oral y la periodontitis. Informa que las células dendríticas acumulan y presentan antígenos fácilmente y que activan la respuesta inmunitaria del hospedador. Nota que mantener la homeostasis inmunitaria en la boca es difícil, dado la cantidad de bacterias y otros microbios que hospeda.

We recently reported that the oral mucosal pathogen Porphyromonas gingivalis, through its 67-kDa Mfa1 (minor) fimbria, targets the C-type lectin receptor DC-SIGN for invasion and persistence within human monocyte-derived dendritic cells (DCs). The DCs respond by inducing an immunosuppressive and Th2-biased CD4+ T-cell response. We have now purified the native minor fimbria by ion-exchange chromatography and sequenced the fimbria by tandem mass spectrometry (MS/MS), confirming its identity and revealing two putative N-glycosylation motifs as well as numerous putative O-glycosylation sites. We further show that the minor fimbria is glycosylated by ProQ staining and that glycosylation is partially removed by treatment with β(1-4)-galactosidase, but not by classic N- and O-linked deglycosidases. Further monosaccharide analysis by gas chromatography-mass spectrometry (GC-MS) confirmed that the minor fimbria contains the DC-SIGN-targeting carbohydrates fucose (1.35 nmol/mg), mannose (2.68 nmol/mg), N-acetylglucosamine (2.27 nmol/mg), and N-acetylgalactosamine (0.652 nmol/mg). Analysis by transmission electron microscopy revealed that the minor fimbria forms fibers approximately 200 nm in length that could be involved in targeting or cross-linking DC-SIGN. These findings shed further light on molecular mechanisms of invasion and immunosuppression by this unique mucosal pathogen. [ABSTRACT FROM AUTHOR]