Aging involves the accumulation of various forms of molecular and cellular damage over time. Key features of aging, such as mitochondrial dysfunction, dysbiosis, and oxidative stress, are closely linked and largely driven by inflammation. This study examines the role of succinate, a key metabolite produced and utilized by cells of both host and microbes, and its receptor, succinate receptor 1 (SUCNR1), in age-related oral dysbiosis and inflammation. We examined young and aged wild-type (WT) and SUCNR1 knockout (KO) mice for this analysis. Our findings revealed significant aging-associated alveolar bone loss and succinate elevation in aged WT mice, along with notable changes in the oral microbiome. Conversely, aged KO mice showed reduced bone loss, lower succinate levels, less inflammation, and better-maintained microbial function. These results suggest that SUCNR1 is crucial in influencing aging-related succinate elevation, oral dysbiosis, and inflammation. Analysis of gene families and pathways in the oral microbiome demonstrated distinct aging-related changes between WT and KO mice, with the functional potential being preserved in the KO-aged group. This study underscores the importance of succinate elevation and signaling through SUCNR1 in regulating inflammation, alveolar bone loss, and shifts in the oral microbiome, offering potential targets for therapeutic interventions in age-related oral health issues.
Animals ; Dysbiosis/metabolism* ; Mice ; Succinic Acid/metabolism* ; Mice, Knockout ; Receptors, G-Protein-Coupled/metabolism* ; Inflammation/metabolism* ; Aging ; Alveolar Bone Loss/metabolism* ; Mouth/microbiology* ; Mice, Inbred C57BL ; Male ; Microbiota

OBJECTIVES: This study aimed to explore the therapeutic effect and mechanism of ginsenoside Rb3 on experimental periodontitis and bone resorption in rats. METHODS: Male SD rats were randomly divided into a control group, a ligation group, an Rb3 group, and a doxycycline (Dox) group for in vivo experiments. A periodontitis model was established by ligating the maxillary second molar, and samples were collected after 3 weeks of drug treatment. Micro-CT assessment of alveolar bone resorption was performed, and hematoxylin-eosin (HE) staining was used to observe pathological changes in periodontal and visceral tissues. Tartrate resistant acid phosphatase (TRAP) staining was applied to detect the formation of osteoclasts in periodontal tissues, and enzyme-linked immunosorbent assay (ELISA) was adopted to detect the serum levels of interleukin (IL)-6, IL-8, immunoglobulin (Ig)M, and IgG. Quantitative polymerase chain reaction (qPCR) was employed to detect the expression of factors related to gingival inflammation and osteoclast formation. Immunofluorescence staining was used to detect phospho-extracellular signal-regulated kinase (p-ERK) expression. In vitro experiments were conducted by pretreating RAW264.7 cells with drugs and adding lipopolysaccharides (LPS) stimulation from Porphyromonas gingivalis (P. gingivalis). IL-1β and IL-6 mRNA expression was detected by qPCR, and Western blot was used to detect the effect of Rb3 on the mitogen-activated protein kinases (MAPKs) signaling pathway. RESULTS: Compared with the control group, the ligation group showed significant periodontitis and bone resorption. Compared with the ligation group, the Rb3 group showed a decrease in alveolar bone resorption and osteoclast formation; p-ERK/ERK ratio, IL-1β, IL-6, and nuclear factor of activated T cells (NFATc1) mRNA levels and downstream gene expression in periodontal tissues; serum IL-6, IL-8, IgG, and IgM levels. Rb3 reduced IL-8 and IL-1β mRNA expression levels and p-ERK/ERK and p-p38 MAPK/p38 MAPK ratios in RAW264.7 cells induced by P. gingivalis LPS stimulation. CONCLUSIONS Rb3 inhibits inflammation and bone resorption in experimental periodontitis in rats. Compared with Dox, Rb3 has better effects in inhibiting pro-inflammatory factors and osteoclast gene expression and may exert anti-inflammatory effects by activating the MAPK signaling pathway.
Animals ; Ginsenosides/therapeutic use* ; Rats, Sprague-Dawley ; Male ; Periodontitis/pathology* ; Rats ; Osteoclasts/drug effects* ; Interleukin-1beta/metabolism* ; Interleukin-6/blood* ; Mice ; Alveolar Bone Loss ; Interleukin-8/blood* ; Immunoglobulin G/blood* ; RAW 264.7 Cells ; Transcription Factors

Periodontitis is a widespread oral disease characterized by continuous inflammation of the periodontal tissue and an irreversible alveolar bone loss, which eventually leads to tooth loss. Four-octyl itaconate (4-OI) is a cell-permeable itaconate derivative and has been recognized as a promising therapeutic target for the treatment of inflammatory diseases. Here, we explored, for the first time, the protective effect of 4-OI on inhibiting periodontal destruction, ameliorating local inflammation, and the underlying mechanism in periodontitis. Here we showed that 4-OI treatment ameliorates inflammation induced by lipopolysaccharide in the periodontal microenvironment. 4-OI can also significantly alleviate inflammation and alveolar bone loss via Nrf2 activation as observed on samples from experimental periodontitis in the C57BL/6 mice. This was further confirmed as silencing Nrf2 blocked the antioxidant effect of 4-OI by downregulating the expression of downstream antioxidant enzymes. Additionally, molecular docking simulation indicated the possible mechanism under Nrf2 activation. Also, in Nrf2^-/- mice, 4-OI treatment did not protect against alveolar bone dysfunction due to induced periodontitis, which underlined the importance of the Nrf2 in 4-OI mediated periodontitis treatment. Our results indicated that 4-OI attenuates inflammation and oxidative stress via disassociation of KEAP1-Nrf2 and activation of Nrf2 signaling cascade. Taken together, local administration of 4-OI offers clinical potential to inhibit periodontal destruction, ameliorate local inflammation for more predictable periodontitis.
Alveolar Bone Loss/prevention & control* ; Animals ; Antioxidants/pharmacology* ; Inflammation ; Kelch-Like ECH-Associated Protein 1/metabolism* ; Mice ; Mice, Inbred C57BL ; Molecular Docking Simulation ; NF-E2-Related Factor 2/metabolism* ; Periodontitis/prevention & control* ; Succinates

Periodontitis is an inflammatory disease involving the destruction of both soft and hard tissue in the periodontal region. Although dysbiosis of the local microbial community initiates local inflammation, over-activation of the host immune response directly activates osteoclastic activity and alveolar bone loss. Many studies have reported on the cytokine network involved in periodontitis and its crucial and pleiotropic effect on the recruitment of specific immunocytes, control of pathobionts and induction or suppression of osteoclastic activity. Nonetheless, particularities in the stimulation of pathogens in the oral cavity that lead to the specific and complex periodontal cytokine network are far from clarified. Thus, in this review, we begin with an up-to-date aetiological hypothesis of periodontal disease and summarize the roles of cytokines in the host immune response. In addition, we also summarize the latest cytokine-related therapeutic measures for periodontal disease.
Alveolar Bone Loss ; etiology ; Cytokines ; metabolism ; physiology ; Humans ; Inflammation ; Periodontal Diseases ; Periodontitis ; immunology ; microbiology ; Tumor Necrosis Factor-alpha ; physiology

Hypoxia (low oxygen level) is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1 (HIF-1). Hypoxia interferes degradation of HIF-1 alpha subunit (HIF-1α), leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit (HIF-1β) and subsequent activation of HIF-1 pathway. Apical periodontitis (periapical lesion) is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a well-characterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine (DMOG) and adenovirus-induced constitutively active HIF-1α (CA-HIF1A). Both DMOG and CA-HIF1A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B (NF-κB) and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.
Alveolar Bone Loss ; metabolism ; prevention & control ; Amino Acids, Dicarboxylic ; pharmacology ; Animals ; Cytokines ; metabolism ; Down-Regulation ; Gene Expression ; drug effects ; Hypoxia-Inducible Factor 1, alpha Subunit ; physiology ; Macrophages ; physiology ; Mice ; NF-kappa B ; metabolism ; Osteogenesis ; physiology ; Periapical Periodontitis ; metabolism ; prevention & control ; Real-Time Polymerase Chain Reaction ; X-Ray Microtomography

Diabetes mellitus (DM) is a complex disease with various systemic and oral complications including periodontitis. Periodontitis is a disease that leads to destruction of the soft and hard tissues of periodontium, which can result in periodontal bone loss and tooth loss. Although the etiology for periodontitis is bacterial plaque, the host immune response also mediates the destruction of periodontal tissues. DM is related to the development, progression and severity of periodontitis. There are several factors potentially contributing to the development of periodontitis in DM patients: 1) altered immune function, 2) hyperglycemia and advanced glycation end products, and 3) altered lipid metabolism. With limited number of studies, the potential mechanisms involved in the development of DM in periodontitis have also been suggested. DM clearly increases the risk of periodontitis and biological mechanisms have been illucidated. Less clear is the impact of periodontitis on the development of DM. It is possible that periodontitis may serve as initiators or propagators of insulin resistance in a way similar to obesity, thereby aggravating glycemic control.
Alveolar Bone Loss ; Diabetes Mellitus ; Glycosylation End Products, Advanced ; Humans ; Hyperglycemia ; Insulin Resistance ; Lipid Metabolism ; Obesity ; Periodontal Diseases* ; Periodontitis ; Periodontium ; Tooth Loss

OBJECTIVEThis study investigates the immune status of T helper (Th) 17 cells in mice with periodontitis.

METHODSSeven-week-old C57BL/6 female mice were randomly divided into the control and periodontitis groups. Each group comprisedfour mice. Experimental periodontitis was induced in mice by oral infection with Porphyromonas gingivalis in the periodontitis group. Phosphate-buffered saline solution was used in the control group. All mice were sacrificed 4 weeks after the last P. gingivalis infection. CD4⁺retinoid-related orphan receptor (ROR) γτ⁺(Th17) cells were analyzed by flow cytometry. The protein expression of Th17 cell-related cytokine interleukin (IL)-17A was detected by enzyme-linked immunosorbentassay (ELISA).

RESULTSFlow cytometry showed that the percentage of CD4⁺RORγτ⁺(Thl7) cells in all CD4⁺ cells and the cell number in gingival tissues, cervical lymph nodes (CLNs), and the peripheral blood obviously increased (P < 0.01) in the periodontitis group. ELISA showed that compared with the control group, the periodontitis group exhibited an obvious increase in the protein expression of IL-17A (P < 0.05).

CONCLUSIONTh17 cell-mediated cell response is enhanced, and the gingival tissues, CLNs, and the peripheral blood are probably the main locations of Thl7 cell-mediated cell response during the development of periodontitis.

Alveolar Bone Loss ; Animals ; Cytokines ; Female ; Flow Cytometry ; Gingiva ; Interleukin-17 ; metabolism ; Mice ; Mice, Inbred C57BL ; Periodontitis ; metabolism ; Porphyromonas gingivalis ; Random Allocation ; T-Lymphocytes, Helper-Inducer

Cellular fibronectin (cFn) is a type of bioactive non-collagen glycoprotein regarded as the main substance used to maintain periodontal attachment. The content of cFn in some specific sites can reflect the progress of periodontitis or peri-implantitis. This study aims to evaluate the expression of cFn messenger RNA (mRNA) in tissues of adult periodontitis and peri-implantitis by real-time fluorescent quantitative polymerase chain reaction (PCR) and to determine its clinical significance. A total of 30 patients were divided into three groups of 10: healthy, adult periodontitis and peri-implantitis. Periodontal tissue biopsies (1 mm×1 mm×1 mm) from each patient were frozen in liquid nitrogen. Total RNA was extracted from these tissues, and the content, purity and integrity were detected. Specific primers were designed according to the sequence, and the mRNA expression levels of cellular fibronectin were detected by real-time PCR. The purity and integrity of the extracted total RNA were both high, and the specificity of amplified genes was very high with no other pollution. The mRNA expression of cFn in the adult periodontitis group (1.526±0.441) was lower than that in the healthy group (3.253±0.736). However, the mRNA expression of cFn in the peri-implantitis group (3.965±0.537) was significantly higher than that in the healthy group. The difference revealed that although both processes were destructive inflammatory reactions in the periodontium, the pathomechanisms were different and the variation started from the transcription level of the cFn gene.
Adult ; Alveolar Bone Loss ; metabolism ; Female ; Fibronectins ; analysis ; genetics ; Gingiva ; metabolism ; Humans ; Male ; Middle Aged ; Peri-Implantitis ; metabolism ; Periodontal Attachment Loss ; metabolism ; Periodontal Index ; Periodontal Pocket ; metabolism ; Periodontitis ; metabolism ; Periodontium ; metabolism ; RNA, Messenger ; analysis ; Real-Time Polymerase Chain Reaction ; Transcription, Genetic ; genetics ; Young Adult

Adult ; Alveolar Bone Loss ; therapy ; Blood Glucose ; metabolism ; Chronic Periodontitis ; blood ; complications ; diagnostic imaging ; therapy ; Dental Scaling ; Diabetes Mellitus, Type 1 ; blood ; complications ; drug therapy ; Diabetes Mellitus, Type 2 ; blood ; complications ; drug therapy ; Humans ; Hypoglycemic Agents ; therapeutic use ; Insulin ; therapeutic use ; Male ; Metformin ; therapeutic use ; Middle Aged ; Patient Education as Topic ; Periodontal Index ; Radiography, Panoramic ; Root Planing ; Sulfonylurea Compounds ; therapeutic use