TLR2 promoter hypermethylation creates innate immune dysbiosis

Investigation of the functional role of human Interleukin-8 gene haplotypes by CRISPR/Cas9 mediated genome editing

Interleukin-8 (IL-8) gene polymorphisms have been considered as susceptibility factors in periodontal disease. However, the functional roles of IL-8 gene haplotypes have not been investigated. Here, we demonstrate for the first time the use of the CRISPR/Cas9 system to engineer the IL-8 gene, and tested the functionality of different haplotypes. Two sgRNAs vectors targeting the IL-8 gene and the naked homologous repair DNA carrying different haplotypes were used to successfully generate HEK293T cells carrying the AT genotype at the first SNP - rs4073 (alias -251), TT genotype at the second SNP - rs2227307 (alias +396), TC or CC genotypes at the third SNP - rs2227306 (alias +781) at the IL-8 locus. When stimulated with Poly I:C, ATC/TTC haplotype, cells significantly up-regulated the IL-8 at both transcriptional and translational levels. To test whether ATC/TTC haplotype is functional, we used a trans-well assay to measure the transmigration of primary neutrophils incubated with supernatants from the Poly I:C stimulation experiment. ATC/TTC haplotype cells significantly increased transmigration of neutrophils confirming the functional role for this IL-8 haplotype. Taken together, our data provides evidence that carriage of the ATC/TTC haplotype in itself may increase the influx of neutrophils in inflammatory lesions and influence disease susceptibility.

Epigenetic mechanisms involved in modulation of inflammatory diseases

PURPOSE OF REVIEW

The activation of inflammatory response is dependent upon genetic factors and epigenetic control mechanisms. This overview will highlight recent advances in the understanding of epigenetic dynamics during cellular inflammation.

RECENT FINDINGS

There is a growing body of evidence indicating that alterations of the chromatin state associate with an increased risk of chronic disease development and inflammation. Epigenetic alterations respond rapidly to environmental changes and have a profound effect on gene regulatory cross-wirings and transcriptional regulation.

SUMMARY

Systematic dissection of the mechanisms underlying epigenetic effects during inflammatory response is a critical step toward elucidation of the cell's molecular processes and holds potential for the development of novel therapies for the treatment of chronic diseases.

Neonatal lipopolysaccharide exposure does not diminish the innate immune response to a subsequent lipopolysaccharide challenge in Holstein bull calves

The innate immune response following experimental mastitis is quite variable between individual dairy cattle. An inflammatory response that minimizes collateral damage to the mammary gland while still effectively resolving the infection following pathogen exposure is beneficial to dairy producers. The ability of a lipopolysaccharide (LPS) exposure in early life to generate a low-responding phenotype and thus reduce the inflammatory response to a later-life LPS challenge was investigated in neonatal bull calves. Ten Holstein bull calves were randomly assigned to either an early life LPS (ELL) group (n=5) or an early life saline (ELS) group (n=5). At 7d of age, calves received either LPS or saline, and at 32d of age, all calves were challenged with an intravenous dose of LPS to determine the effect of the early life treatment (LPS or saline) on the immune response generated toward a subsequent LPS challenge. Dermal fibroblast and monocyte-derived macrophage cultures from each calf were established at age 20 and 27d, respectively, to model sustained effects from the early life LPS exposure on gene expression and protein production of components within the LPS response pathway. The ELL calves had greater levels of plasma IL-6 and tumor necrosis factor-α than the ELS calves following the early life LPS or saline treatments. However, levels of these 2 immune markers were similar between ELL and ELS calves when both groups were subsequently challenged with LPS. A comparison of the in vitro LPS responses of the ELL and ELS calves revealed similar patterns of protein production and gene expression following an LPS challenge of both dermal fibroblast and monocyte-derived macrophage cultures established from the treatment groups. Whereas an early life exposure to LPS did not result in a dampened inflammatory response toward a later LPS challenge in these neonatal bull calves, the potential that exposure to inflammation or stress in early life or in utero can create an offspring with a low-responding phenotype as an adult is intriguing and has been documented in rodents. Further work is needed to determine if an inflammatory exposure in utero in a dairy animal would result in a low-responding innate immune phenotype.

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

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

The role of Toll-like receptors in periodontitis

Periodontitis is a common infectious disease. Recent studies have indicated that the progression of periodontitis may be regulated by interactions between host immunity and periodontopathic bacteria. Although periodontopathic bacteria can destroy periodontal tissue, a dysfunctional host immune response triggered by the bacteria can lead to more severe and persistent destruction. Toll-like receptors (TLRs), a type of pattern recognition receptor (PRR) that recognizes pathogens, have been implicated in host innate immune responses to periodontopathic bacteria and in the activation of adaptive immunity. TLR-targeted drugs may hold promise to treat periodontal disease. This review summarizes recent studies on the role of TLRs in periodontitis and discusses areas needing further research. We believe TLRs may be an effective biomarker for the prevention, diagnosis, and treatment of periodontitis in the near future.

Epigenetic Modifications of Histones in Periodontal Disease

Periodontitis is a chronic infectious disease driven by dysbiosis, an imbalance between commensal bacteria and the host organism. Periodontitis is a leading cause of tooth loss in adults and occurs in about 50% of the US population. In addition to the clinical challenges associated with treating periodontitis, the progression and chronic nature of this disease seriously affect human health. Emerging evidence suggests that periodontitis is associated with mechanisms beyond bacteria-induced protein and tissue degradation. Here, we hypothesize that bacteria are able to induce epigenetic modifications in oral epithelial cells mediated by histone modifications. In this study, we found that dysbiosis in vivo led to epigenetic modifications, including acetylation of histones and downregulation of DNA methyltransferase 1. In addition, in vitro exposure of oral epithelial cells to lipopolysaccharides resulted in histone modifications, activation of transcriptional coactivators, such as p300/CBP, and accumulation of nuclear factor-κB (NF-κB). Given that oral epithelial cells are the first line of defense for the periodontium against bacteria, we also evaluated whether activation of pathogen recognition receptors induced histone modifications. We found that activation of the Toll-like receptors 1, 2, and 4 and the nucleotide-binding oligomerization domain protein 1 induced histone acetylation in oral epithelial cells. Our findings corroborate the emerging concept that epigenetic modifications play a role in the development of periodontitis.

Fine-tuning of Th17 Cytokines in Periodontal Disease by IL-10

Periodontitis (PD) is a chronic disease caused by the host inflammatory response to bacteria colonizing the oral cavity. In addition to tolerance to oral microbiome, a fine-tuned balance of IL-10 levels is critical to efficiently mount antimicrobial resistance without causing immunopathology. Clinical and animal studies support that adaptive T-helper (Th) cytokines are involved in the pathogenesis of alveolar bone destruction in PD. However, it remains unclear what type of Th response is related to human PD progression and what role IL-10 has on this process. We addressed the contribution of IL-10 in limiting Th1 and Th17 inflammatory response in murine and human PD. Through a combination of basic and translational approaches involving selected cytokine-deficient mice as well as human genetic epidemiology, our results demonstrate the requirement for IL-10 in fine-tuning the levels of Th17 (IL-17A and IL-17F) cytokines in experimental and human PD. Of novelty, we found that IL-17F correlated with protection in murine and human PD and was positively regulated by IL-10. To our knowledge, this is the first demonstration of the protective role for IL-17F in PD, its positive regulation by IL-10, and the potential differential role for IL-17A and IL-17F in periodontal disease.

Toll-Like Receptor 9-Mediated Inflammation Triggers Alveolar Bone Loss in Experimental Murine Periodontitis

Chronic periodontitis is a local inflammatory disease induced by a dysbiotic microbiota and leading to destruction of the tooth-supporting structures. Microbial nucleic acids are abundantly present in the periodontium, derived through release after phagocytic uptake of microbes and/or from biofilm-associated extracellular DNA. Binding of microbial DNA to its cognate receptors, such as Toll-like receptor 9 (TLR9), can trigger inflammation. In this study, we utilized TLR9 knockout (TLR9(-/-)) mice and wild-type (WT) controls in a murine model of Porphyromonas gingivalis-induced periodontitis and report the first in vivo evidence that TLR9 signaling mediates the induction of periodontal bone loss. P. gingivalis-infected WT mice exhibited significantly increased bone loss compared to that in sham-infected WT mice or P. gingivalis-infected TLR9(-/-) mice, which were resistant to bone loss. Consistent with this, the expression levels of interleukin 6 (IL-6), tumor necrosis factor (TNF), and receptor-activator of nuclear factor kappa B ligand (RANKL) were significantly elevated in the gingival tissues of the infected WT mice but not in infected TLR9(-/-) mice compared to their levels in controls. Ex vivo studies using splenocytes and bone marrow-derived macrophages revealed significantly diminished cytokine production in TLR9(-/-) cells relative to the cytokine production in WT cells in response to P. gingivalis, thereby implicating TLR9 in inflammatory responses to this organism. Intriguingly, compared to the cytokine production in WT cells, TLR9(-/-) cells exhibited significantly decreased proinflammatory cytokine production upon challenge with lipopolysaccharide (LPS) (TLR4 agonist) or Pam3Cys (TLR2 agonist), suggesting possible cross talk between TLR9, TLR4, and TLR2. Collectively, our results provide the first proof-of-concept evidence implicating TLR9-triggered inflammation in periodontal disease pathogenesis, thereby identifying a new potential therapeutic target to control periodontal inflammation.

Chemokine function in periodontal disease and oral cavity cancer

The chemotactic cytokines, or chemokines, comprise a superfamily of polypeptides with a wide range of activities that include recruitment of immune cells to sites of infection and inflammation, as well as stimulation of cell proliferation. As such, they function as antimicrobial molecules and play a central role in host defenses against pathogen challenge. However, their ability to recruit leukocytes and potentiate or prolong the inflammatory response may have profound implications for the progression of oral diseases such as chronic periodontitis, where tissue destruction may be widespread. Moreover, it is increasingly recognized that chronic inflammation is a key component of tumor progression. Interaction between cancer cells and their microenvironment is mediated in large part by secreted factors such as chemokines, and serves to enhance the malignant phenotype in oral and other cancers. In this article, we will outline the biological and biochemical mechanisms of chemokine action in host–microbiome interactions in periodontal disease and in oral cancer, and how these may overlap and contribute to pathogenesis.

Odanacatib, A Cathepsin K-Specific Inhibitor, Inhibits Inflammation and Bone Loss Caused by Periodontal Diseases

BACKGROUND

Periodontitis is a bacteria-induced inflammatory disease mainly affecting periodontal tissues, leading to periodontal inflammation, bone breakdown, and loss of the tooth. The main obstacle for treating periodontitis effectively is the difficulty in finding a target that can inhibit bone loss and inflammation simultaneously. Recent studies showed that cathepsin K (CTSK) might have functions in the immune system besides its role in osteoclasts. Thus, targeting CTSK would have a potential therapeutic effect in both the bone system and the immune system during the progression of periodontitis.

METHODS

In the current study, a small molecular inhibitor (odanacatib [ODN]) is explored to inhibit the function of CTSK in a bacteria-induced periodontitis mouse model.

RESULTS

The application of ODN decreased the number of osteoclasts, macrophages, and T cells, as well as the expression of Toll-like receptors (TLRs) in the periodontitis lesion area. Furthermore, lack of CTSK inhibited the expression of TLR4, TLR5, and TLR9 and their downstream cytokine signaling in the gingival epithelial cells in periodontitis lesions, demonstrating that the innate immune response was inhibited in periodontitis.

CONCLUSION

The present results show that inhibition of CTSK can prevent bone loss and the immune response during the progression of periodontitis, indicating that CTSK is a promising target for treating inflammatory diseases such as periodontitis by affecting both osteoclasts and the immune system.