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Periodontitis is one of the most prevalent human inflammatory diseases. It is characterized by periodontal tissue destruction, progressively driven by the host response. In this regard, cytokines associated with tissue destruction, such as interleukin (IL)–6 and IL-23, use a common signaling pathway mediated by STAT3. This transcription factor is also needed for IL-17A production, a key mediator in periodontitis pathogenesis. Although several studies have reported increased activation of STAT3 in experimental periodontitis, a detailed characterization of STAT3 activation in human gingival tissues and its involvement in alveolar bone loss has yet to be explored. Using a cross-sectional study design, we detected increased proportions of pSTAT3-positive cells during periodontitis compared with health, particularly in epithelial cells and T cells. Other cell types of hematopoietic and nonhematopoietic origin also display STAT3 activation in gingival tissues. We detected increased STAT3 phosphorylation and expression of STAT3-related genes during experimental periodontitis. Next, we evaluated the role of STAT3 in alveolar bone destruction using a mouse model of STAT3 loss of function (mut- Stat3 mice). Compared with controls, mut- Stat3 mice had reduced alveolar bone loss following ligature-induced periodontitis. We also evaluated pharmacologic inhibition of STAT3 in ligature-induced periodontitis. Like mut- Stat3 mice, mice treated with STAT3 small-molecule inhibitor had reduced bone loss compared with controls. Our results demonstrate that STAT3 activation is increased in epithelial and T cells during periodontitis and indicate a pathogenic role of STAT3 in inflammatory alveolar bone loss. [ABSTRACT FROM AUTHOR]

Periodontitis is a complex inflammatory disease affecting the supporting structures of teeth and is associated with systemic inflammatory disorders. Regulator of G-protein signaling 12 (RGS12), the largest protein in the RGS protein family, plays a crucial role in the development of inflammation and bone remodeling. However, the role and mechanism(s) by which RGS12 may regulate periodontitis have not been elucidated. Here, we showed that ablation of RGS12 in Mx1+ hematopoietic cells blocked bone loss in the ligature-induced periodontitis model, as evidenced morphometrically and by micro–computed tomography analysis of the alveolar bone. Moreover, hematopoietic cell-specific deletion of RGS12 inhibited osteoclast formation and activity as well as the production of inflammatory cytokines such as IL1β, IL6, and TNFα in the diseased periodontal tissue. In the in vitro experiments, we found that the overexpression of RGS12 promoted the reprogramming of macrophages to the proinflammatory M1 type, but not the anti-inflammatory M2 type, and enhanced the ability of macrophages for migration. Conversely, knockdown of RGS12 in macrophages inhibited the production of inflammatory cytokines and migration of macrophages in response to lipopolysaccharide stimulation. Our results demonstrate for the first time that inhibition of RGS12 in macrophages is a promising therapeutic target for the treatment of periodontitis. [ABSTRACT FROM AUTHOR]

The complement system plays a central role in immunity and inflammation, although certain pathogens can exploit complement to undermine protective immunity. In this context, the periodontal keystone pathogen Porphyromonas gingivalis was previously shown by our group to evade killing by neutrophils or macrophages through exploitation of complement C5a receptor 1 (C5aR1) and complement receptor 3 (CR3). Here, we examined whether P. gingivalis uses complement receptors to also subvert killing by dendritic cells. In line with earlier independent studies, intracellular viable P. gingivalis bacteria could be recovered from mouse bone-marrow-derived dendritic cells (BMDC) or human monocyte-derived dendritic cells (MDDC) exposed to the pathogen. However, in the presence of C5a, the intracellular survival of P. gingivalis was significantly decreased in a C5aR1-dependent way. Further work using wild-type and receptor-knockout BMDC showed that, in the presence of C3a, the C3a receptor (C3aR) similarly enhanced the intracellular killing of P. gingivalis. In contrast, C5aR2, an alternative receptor for C5a (G protein-coupled receptor 77), was associated with increased intracellular P. gingivalis viable counts, consistent with the notion that C5aR2 functions as a negative regulator of C5aR1 activity. Moreover, P. gingivalis failed to use CR3 as a phagocytic receptor in BMDC, in contrast to our earlier findings in macrophages where CR3-mediated uptake promotes P. gingivalis survival. Collectively, these data show that complement receptors mediate cell-type-specific effects on how innate leukocytes handle P. gingivalis, which appears to exploit complement to preferentially evade those cells (neutrophils and macrophages) that are most often encountered in its predominant niche, the periodontal pocket. [ABSTRACT FROM AUTHOR]

Periodontal ligament cells (PDLCs) and macrophages in bone marrow cells have been widely used to investigate novel therapeutic agents to treat periodontitis. Here, we present a protocol for collecting primary mouse PDLCs and bone marrow cells. We detail steps for culturing and differentiation for both cell types and review data analysis for in vitro experiments using primary PDLCs and bone marrow cells. This protocol can be used to explore the impact of novel therapeutic agents using in vitro experiments. For complete details on the use and execution of this protocol, please refer to Sirisereephap et al. 1 ., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Formyl peptide receptor 2 (FPR2) is a receptor for formylated peptides and specific pro-resolving mediators, and is involved in various inflammatory processes. Here, we aimed to elucidate the role of FPR2 in dendritic cell (DC) function and autoimmunity-related central nervous system (CNS) inflammation by using the experimental autoimmune encephalomyelitis (EAE) model. EAE induction was accompanied by increased Fpr2 mRNA expression in the spinal cord. FPR2-deficient ( Fpr2 KO ) mice displayed delayed onset of EAE compared to wild-type (WT) mice, associated with reduced frequencies of Th17 cells in the inflamed spinal cord at the early stage of the disease. However, FPR2 deficiency did not affect EAE severity after the disease reached its peak. FPR2 deficiency in mature DCs resulted in decreased expression of Th17 polarizing cytokines IL6, IL23p19, IL1β, and thereby diminished the DC-mediated activation of Th17 cell differentiation. LPS-activated FPR2-deficient DCs showed upregulated Nos2 expression and nitric oxide (NO) production, as well as reduced oxygen consumption rate and impaired mitochondrial function, including decreased mitochondrial superoxide levels, lower mitochondrial membrane potential and diminished expression of genes related to the tricarboxylic acid cycle and genes related to the electron transport chain, as compared to WT DCs. Treatment with a NO inhibitor reversed the reduced Th17 cell differentiation in the presence of FPR2-deficient DCs. Together, by regulating DC metabolism, FPR2 enhances the production of DC-derived Th17-polarizing cytokines and hence Th17 cell differentiation in the context of neuroinflammation., 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 © 2024 Lim, Neuwirth, Chung, Grossklaus, Soehnlein, Hajishengallis and Chavakis.)

Clonal hematopoiesis of indeterminate potential (CHIP) arises from aging-associated acquired mutations in hematopoietic progenitors, which display clonal expansion and produce phenotypically altered leukocytes. We associated CHIP-DNMT3A mutations with a higher prevalence of periodontitis and gingival inflammation among 4,946 community-dwelling adults. To model DNMT3A-driven CHIP, we used mice with the heterozygous loss-of-function mutation R878H, equivalent to the human hotspot mutation R882H. Partial transplantation with Dnmt3a R878H/+ bone marrow (BM) cells resulted in clonal expansion of mutant cells into both myeloid and lymphoid lineages and an elevated abundance of osteoclast precursors in the BM and osteoclastogenic macrophages in the periphery. DNMT3A-driven clonal hematopoiesis in recipient mice promoted naturally occurring periodontitis and aggravated experimentally induced periodontitis and arthritis, associated with enhanced osteoclastogenesis, IL-17-dependent inflammation and neutrophil responses, and impaired regulatory T cell immunosuppressive activity. DNMT3A-driven clonal hematopoiesis and, subsequently, periodontitis were suppressed by rapamycin treatment. DNMT3A-driven CHIP represents a treatable state of maladaptive hematopoiesis promoting inflammatory bone loss., Competing Interests: Declaration of interests P.N. reports research grants from Allelica, Amgen, Apple, Boston Scientific, Genentech/Roche, and Novartis, personal fees from Allelica, Apple, AstraZeneca, Blackstone Life Sciences, Creative Education Concepts, CRISPR Therapeutics, Eli Lilly & Co, Foresite Labs, Genentech/Roche, GV, HeartFlow, Magnet Biomedicine, Merck, and Novartis, scientific advisory board membership of Esperion Therapeutics, Preciseli, and TenSixteen Bio, scientific co-founder of TenSixteen Bio, equity in MyOme, Preciseli, and TenSixteen Bio, and spousal employment at Vertex Pharmaceuticals, all unrelated to the present work. M.G.N. is an advisory board member of Cell and scientific founder of Lemba, TTxD, and Biotrip., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Consensus statements can be very influential in medicine and public health. Some of these statements use systematic evidence synthesis but others fail on this front. Many consensus statements use panels of experts to deduce perceived consensus through Delphi processes. We argue that stacking of panel members towards one particular position or narrative is a major threat, especially in absence of systematic evidence review. Stacking may involve financial conflicts of interest, but non-financial conflicts of strong advocacy can also cause major bias. Given their emerging importance, we describe here how such consensus statements may be misleading, by analysing in depth a recent high-impact Delphi consensus statement on COVID-19 recommendations as a case example. We demonstrate that many of the selected panel members and at least 35% of the core panel members had advocated towards COVID-19 elimination (zero-COVID) during the pandemic and were leading members of aggressive advocacy groups. These advocacy conflicts were not declared in the Delphi consensus publication, with rare exceptions. Therefore, we propose that consensus statements should always require rigorous evidence synthesis and maximal transparency on potential biases towards advocacy or lobbyist groups to be valid. While advocacy can have many important functions, its biased impact on consensus panels should be carefully avoided., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Cardiometabolic disorders are chief causes of morbidity and mortality, with chronic inflammation playing a crucial role in their pathogenesis. The release of differentiated myeloid cells with elevated pro-inflammatory potential, as a result of maladaptively trained myelopoiesis may be a crucial factor for the perpetuation of inflammation. Several cardiovascular risk factors, including sedentary lifestyle, unhealthy diet, hypercholesterolemia, and hyperglycemia, may modulate bone marrow hematopoietic progenitors, causing sustained functional changes that favour chronic metabolic and vascular inflammation. In the present review, we summarize recent studies that support the function of long-term inflammatory memory in progenitors of the bone marrow for the development and progression of cardiometabolic disease and related inflammatory comorbidities, including periodontitis and arthritis. We also discuss how maladaptive myelopoiesis associated with the presence of mutated hematopoietic clones, as present in clonal hematopoiesis, may accelerate atherosclerosis via increased inflammation., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Complement has long been considered a key innate immune effector system that mediates host defence and tissue homeostasis. Yet, growing evidence has illuminated a broader involvement of complement in fundamental biological processes extending far beyond its traditional realm in innate immunity. Complement engages in intricate crosstalk with multiple pattern-recognition and signalling pathways both in the extracellular and intracellular space. Besides modulating host-pathogen interactions, this crosstalk guides early developmental processes and distinct cell trajectories, shaping tissue immunometabolic and regenerative programmes in different physiological systems. This Review provides a guide to the system-wide functions of complement. It highlights illustrative paradigm shifts that have reshaped our understanding of complement pathobiology, drawing examples from evolution, development of the central nervous system, tissue regeneration and cancer immunity. Despite its tight spatiotemporal regulation, complement activation can be derailed, fuelling inflammatory tissue pathology. The pervasive contribution of complement to disease pathophysiology has inspired a resurgence of complement therapeutics with major clinical developments, some of which have challenged long-held dogmas. We thus highlight major therapeutic concepts and milestones in clinical complement intervention., (© 2023. Springer Nature Limited.)

The limited reserves of neutrophils are implicated in the susceptibility to infection in neonates, however the regulation of neutrophil kinetics in infections in early life remains poorly understood. Here we show that the developmental endothelial locus (DEL-1) is elevated in neonates and is critical for survival from neonatal polymicrobial sepsis, by supporting emergency granulopoiesis. Septic DEL-1 deficient neonate mice display low numbers of myeloid-biased multipotent and granulocyte-macrophage progenitors in the bone marrow, resulting in neutropenia, exaggerated bacteremia, and increased mortality; defects that are rescued by DEL-1 administration. A high IL-10/IL-17A ratio, observed in newborn sepsis, sustains tissue DEL-1 expression, as IL-10 upregulates while IL-17 downregulates DEL-1. Consistently, serum DEL-1 and blood neutrophils are elevated in septic adult and neonate patients with high serum IL-10/IL-17A ratio, and mortality is lower in septic patients with high serum DEL-1. Therefore, IL-10/DEL-1 axis supports emergency granulopoiesis, prevents neutropenia and promotes sepsis survival in early life., (© 2024. The Author(s).)

Aging is associated with increased susceptibility to chronic inflammatory bone loss disorders, such as periodontitis, in large part due to the impaired regenerative potential of aging tissues. DEL-1 exerts osteogenic activity and promotes bone regeneration. However, DEL-1 expression declines with age. Here we show that systemically administered macrolide antibiotics and a non-antibiotic erythromycin derivative, EM-523, restore DEL-1 expression in 18-month-old ("aged") mice while promoting regeneration of bone lost due to naturally occurring age-related periodontitis. These compounds failed to induce bone regeneration in age-matched DEL-1-deficient mice. Consequently, these drugs promoted DEL-1-dependent functions, including alkaline phosphatase activity and osteogenic gene expression in the periodontal tissue while inhibiting osteoclastogenesis, leading to net bone growth. Macrolide-treated aged mice exhibited increased skeletal bone mass, suggesting that this treatment may be pertinent to systemic bone loss disorders. In conclusion, we identified a macrolide-DEL-1 axis that can regenerate bone lost due to aging-related disease., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s).)

Multiple transcription factors are activated in the IL-17 signaling pathway that mediates anti-fungal immunity, although many of them are redundant for protective immunity despite being essential in driving IL-17-mediated autoimmunity. In this issue, Gaffen and colleagues unveil the IκBζ protein as an indispensable transcription factor in IL-17-activated anti-fungal defense., Competing Interests: Declaration of interests The author declares no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Microbial species colonizing host ecosystems in health or disease rarely do so alone. Organisms conglomerate into dynamic heterotypic communities or biofilms in which interspecies and interkingdom interactions drive functional specialization of constituent species and shape community properties, including nososymbiocity or pathogenic potential. Cell-to-cell binding, exchange of signaling molecules, and nutritional codependencies can all contribute to the emergent properties of these communities. Spatial constraints defined by community architecture also determine overall community function. Multilayered interactions thus occur between individual pairs of organisms, and the relative impact can be determined by contextual cues. Host responses to heterotypic communities and impact on host surfaces are also driven by the collective action of the community. Additionally, the range of interspecies interactions can be extended by bacteria utilizing host cells or host diet to indirectly or directly influence the properties of other organisms and the community microenvironment. In contexts where communities transition to a dysbiotic state, their quasi-organismal nature imparts adaptability to nutritional availability and facilitates resistance to immune effectors and, moreover, exploits inflammatory and acidic microenvironments for their persistence., Competing Interests: The authors declare no conflict of interest.

A minimized version of complement factor H (FH), designated mini-FH, was previously engineered combining the N-terminal regulatory domains (short consensus repeat [SCR]1-4) and C-terminal host-surface recognition domains (SCR19-20) of the parent molecule. Mini-FH conferred enhanced protection, as compared with FH, in an ex vivo model of paroxysmal nocturnal hemoglobinuria driven by alternative pathway dysregulation. In the current study, we tested whether and how mini-FH could block another complement-mediated disease, namely periodontitis. In a mouse model of ligature-induced periodontitis (LIP), mini-FH inhibited periodontal inflammation and bone loss in wild-type mice. Although LIP-subjected C3-deficient mice are protected relative to wild-type littermates and exhibit only modest bone loss, mini-FH strikingly inhibited bone loss even in C3-deficient mice. However, mini-FH failed to inhibit ligature-induced bone loss in mice doubly deficient in C3 and CD11b. These findings indicate that mini-FH can inhibit experimental periodontitis even in a manner that is independent of its complement regulatory activity and is mediated by complement receptor 3 (CD11b/CD18). Consistent with this notion, a complement receptor 3-interacting recombinant FH segment that lacks complement regulatory activity (specifically encompassing SCRs 19 and 20; FH19-20) was also able to suppress bone loss in LIP-subjected C3-deficient mice. In conclusion, mini-FH appears to be a promising candidate therapeutic for periodontitis by virtue of its ability to suppress bone loss via mechanisms that both include and go beyond its complement regulatory activity., (Copyright © 2023 by The American Association of Immunologists, Inc.)

Periodontitis and caries are driven by complex interactions between the oral microbiome and host factors, i.e. inflammation and dietary sugars, respectively. Animal models have been instrumental in our mechanistic understanding of these oral diseases, although no single model can faithfully reproduce all aspects of a given human disease. This review discusses evidence that the utility of an animal model lies in its capacity to address a specific hypothesis and, therefore, different aspects of a disease can be investigated using distinct and complementary models. As in vitro systems cannot replicate the complexity of in vivo host-microbe interactions and human research is typically correlative, model organisms-their limitations notwithstanding-remain essential in proving causality, identifying therapeutic targets, and evaluating the safety and efficacy of novel treatments. To achieve broader and deeper insights into oral disease pathogenesis, animal model-derived findings can be synthesized with data from in vitro and clinical research. In the absence of better mechanistic alternatives, dismissal of animal models on fidelity issues would impede further progress to understand and treat oral disease., (© The Author(s) 2023. Published by Oxford University Press on behalf of FEMS.)

Oral microbial communities assemble into complex spatial structures. The sophisticated physical and chemical signaling systems underlying the community enable their collective functional regulation as well as the ability to adapt by integrating environmental information. The combined output of community action, as shaped by both intra-community interactions and host and environmental variables, dictates homeostatic balance or dysbiotic disease such as periodontitis and dental caries. Oral polymicrobial dysbiosis also exerts systemic effects that adversely affect comorbidities, in part due to ectopic colonization of oral pathobionts in extra-oral tissues. Here, we review new and emerging concepts that explain the collective functional properties of oral polymicrobial communities and how these impact health and disease both locally and systemically., Competing Interests: Declaration of interests G.H. is inventor of a patent that describes the use of complement inhibitors in periodontal disease (“Methods of Treating or Preventing Periodontitis and Diseases Associated with Periodontitis”; patent no. 10,668,135). H.K. is inventor of a patent titled “Iron Oxide Nanoparticles and Methods of Use Thereof” (patent no. 62,115,968). R.J.L. is inventor of a patent titled “Bacterial Inhibitors” (patent no. 11,504,414)., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Neutrophils are of key importance in periodontal health and disease. In their absence or when they are functionally defective, as occurs in certain congenital disorders, affected individuals develop severe forms of periodontitis in early age. These observations imply that the presence of immune-competent neutrophils is essential to homeostasis. However, the presence of supernumerary or hyper-responsive neutrophils, either because of systemic priming or innate immune training, leads to imbalanced host-microbe interactions in the periodontium that culminate in dysbiosis and inflammatory tissue breakdown. These disease-provoking imbalanced interactions are further exacerbated by periodontal pathogens capable of subverting neutrophil responses to their microbial community's benefit and the host's detriment. This review attempts a synthesis of these findings for an integrated view of the neutrophils' ambivalent role in periodontal disease and, moreover, discusses how some of these concepts underpin the development of novel therapeutic approaches to treat periodontal disease., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The principle of trained immunity represents innate immune memory due to sustained, mainly epigenetic, changes triggered by endogenous or exogenous stimuli in bone marrow (BM) progenitors (central trained immunity) and their innate immune cell progeny, thereby triggering elevated responsiveness against secondary stimuli. BM progenitors can respond to microbial and sterile signals, thereby possibly acquiring trained immunity-mediated long-lasting alterations that may shape the fate and function of their progeny, for example, neutrophils. Neutrophils, the most abundant innate immune cell population, are produced in the BM from committed progenitor cells in a process designated granulopoiesis. Neutrophils are the first responders against infectious or inflammatory challenges and have versatile functions in immunity. Together with other innate immune cells, neutrophils are effectors of peripheral trained immunity. However, given the short lifetime of neutrophils, their ability to acquire immunological memory may lie in the central training of their BM progenitors resulting in generation of reprogrammed, that is, "trained", neutrophils. Although trained immunity may have beneficial effects in infection or cancer, it may also mediate detrimental outcomes in chronic inflammation. Here, we review the emerging research area of trained immunity with a particular emphasis on the role of neutrophils and granulopoiesis., (© 2022 The Authors. Immunological Reviews published by John Wiley & Sons Ltd.)

In both mice and humans, complement and Th17 cells have been implicated in periodontitis, an oral microbiota-driven inflammatory disease associated with systemic disorders. A recent clinical trial showed that a complement C3 inhibitor (AMY-101) causes sustainable resolution of periodontal inflammation, the main effector of tissue destruction in this oral disease. Although both complement and Th17 are required for periodontitis, it is uncertain how these immune components cooperate in disease development. In this study, we dissected the complement-Th17 relationship in the setting of ligature-induced periodontitis (LIP), a model that previously established that microbial dysbiosis drives Th17 cell expansion and periodontal bone loss. Complement was readily activated in the periodontal tissue of LIP-subjected mice but not when the mice were placed on broad-spectrum antibiotics. Microbiota-induced complement activation generated critical cytokines, IL-6 and IL-23, which are required for Th17 cell expansion. These cytokines as well as Th17 accumulation and IL-17 expression were significantly suppressed in LIP-subjected C3-deficient mice relative to wild-type controls. As IL-23 has been extensively studied in periodontitis, we focused on IL-6 and showed that LIP-induced IL-17 and bone loss required intact IL-6 receptor signaling in the periodontium. LIP-induced IL-6 was predominantly produced by gingival epithelial cells that upregulated C3a receptor upon LIP challenge. Experiments in human gingival epithelial cells showed that C3a upregulated IL-6 production in cooperation with microbial stimuli that upregulated C3a receptor expression in ERK1/2- and JNK-dependent manner. In conclusion, complement links the periodontal microbiota challenge to Th17 cell accumulation and thus integrates complement- and Th17-driven immunopathology in periodontitis., (Copyright © 2022 by The American Association of Immunologists, Inc.)

Inflammation plays a crucial role in the onset and development of atherosclerosis. Periodontitis is a common chronic disease linked to other chronic inflammatory diseases such as atherosclerotic cardiovascular disease (ASCVD). The mechanistic pathways underlying this association are yet to be fully understood. This critical review aims at discuss the role of neutrophils in mediating the relationship between periodontitis and ASCVD. Systemic inflammation triggered by periodontitis could lead to adaptations in hematopoietic stem and progenitor cells (HSPCs) resulting in trained granulopoiesis in the bone marrow, thereby increasing the production of neutrophils and driving the hyper-responsiveness of these abundant innate-immune cells. These alterations may contribute to the onset, progression, and complications of atherosclerosis. Despite the emerging evidence suggesting that the treatment of periodontitis improves surrogate markers of cardiovascular disease, the resolution of periodontitis may not necessarily reverse neutrophil hyper-responsiveness since the hyper-inflammatory re-programming of granulopoiesis can persist long after the inflammatory inducers are removed. Novel and targeted approaches to manipulate neutrophil numbers and functions are warranted within the context of the treatment of periodontitis and also to mitigate its potential impact on ASCVD., 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 © 2022 Irwandi, Chiesa, Hajishengallis, Papayannopoulos, Deanfield and D’Aiuto.)

In this issue of Science Immunology , Barreto de Albuquerque et al. track immune responsiveness to the foodborne pathogen Listeria monocytogenes during oral infection. Their findings extend the notion of compartmentalized immunity within the gastrointestinal tract to the oral cavity and provide previously unkown insights into regional specialization of oral immunity.