Influence of cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphisms in periodontitis

Transcriptional and post-transcriptional regulation of checkpoint genes on the tumour side of the immunological synapse

Cancer is a disease of the genome, therefore, its development has a clear Mendelian component, demonstrated by well-studied genes such as BRCA1 and BRCA2 in breast cancer risk. However, it is known that a single genetic variant is not enough for cancer to develop leading to the theory of multistage carcinogenesis. In many cases, it is a sequence of events, acquired somatic mutations, or simply polygenic components with strong epigenetic effects, such as in the case of brain tumours. The expression of many genes is the product of the complex interplay between several factors, including the organism's genotype (in most cases Mendelian-inherited), genetic instability, epigenetic factors (non-Mendelian-inherited) as well as the immune response of the host, to name just a few. In recent years the importance of the immune system has been elevated, especially in the light of the immune checkpoint genes discovery and the subsequent development of their inhibitors. As the expression of these genes normally suppresses self-immunoreactivity, their expression by tumour cells prevents the elimination of the tumour by the immune system. These discoveries led to the rapid growth of the field of immuno-oncology that offers new possibilities of long-lasting and effective treatment options. Here we discuss the recent advances in the understanding of the key mechanisms controlling the expression of immune checkpoint genes in tumour cells.

Armed to the Teeth-The Oral Mucosa Immunity System and Microbiota

The oral cavity is inhabited by a wide spectrum of microbial species, and their colonization is mostly based on commensalism. These microbes are part of the normal oral flora, but there are also opportunistic species that can cause oral and systemic diseases. Although there is a strong exposure to various microorganisms, the oral mucosa reduces the colonization of microorganisms with high rotation and secretion of various types of cytokines and antimicrobial proteins such as defensins. In some circumstances, the imbalance between normal oral flora and pathogenic flora may lead to a change in the ratio of commensalism to parasitism. Healthy oral mucosa has many important functions. Thanks to its integrity, it is impermeable to most microorganisms and constitutes a mechanical barrier against their penetration into tissues. Our study aims to present the role and composition of the oral cavity microbiota as well as defense mechanisms within the oral mucosa which allow for maintaining a balance between such numerous species of microorganisms. We highlight the specific aspects of the oral mucosa protecting barrier and discuss up-to-date information on the immune cell system that ensures microbiota balance. This study presents the latest data on specific tissue stimuli in the regulation of the immune system with particular emphasis on the resistance of the gingival barrier. Despite advances in understanding the mechanisms regulating the balance on the microorganism/host axis, more research is still needed on how the combination of these diverse signals is involved in the regulation of immunity at the oral mucosa barrier.

Systemic administration of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4)-Ig abrogates alveolar bone resorption in induced periodontitis through inhibition of osteoclast differentiation and activation: An experimental investigation

BACKGROUND/OBJECTIVES

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical immunoregulatory molecule expressed on T cells. CTLA-4 also binds to the surfaces of monocytes and macrophages, precursors of osteoclasts. Research on rheumatoid arthritis demonstrated that CTLA-4 suppresses inflammation and bone resorption. However, its effects on alveolar bone have yet to be understood. The purpose of this study was to investigate the role and potential mechanism of CTLA-4 in bone resorption in periodontitis.

MATERIALS AND METHODS

In vivo, the effects of systemic administration of CTLA-4 immunoglobulin fusion protein (CTLA-4-Ig) on alveolar bone resorption were investigated using a periodontitis mouse model. A total of 20 C57BL/6J mice were randomly assigned to two groups according to the administration modes. Periodontitis was induced by placing a ligature around the left maxillary second molar. The contralateral tooth was left un-ligated. In the CTLA-4-Ig (+) group, CTLA-4-Ig was administered by intraperitoneal injection at 1 and 3 days after ligature placement. Animals in the CTLA-4-Ig (-) group were given only phosphate-buffered saline each time. At 5 days after ligature placement, bone resorption was assessed by micro-computed tomography and histological examination, and the prevalence of osteoclast-like cells was assessed by tartrate-resistant acid phosphatase (TRAP) staining. In vitro, the effects of CTLA-4-Ig on osteoclasts were evaluated. Viability of RAW 264.7 cells treated with receptor activator of nuclear factor-κB ligand (RANKL) and CTLA-4-Ig was tested by WST-1 assay. Osteoclast-like cells were enumerated by TRAP staining, and osteoclast activity was evaluated by resorption pit assay. Gene expression levels of osteoclast differentiation markers (macrophage-colony stimulating factor receptor, carbonic anhydrase II, cathepsin K, and Trap) and protein phosphatase 2A (PP2A), a major serine-threonine phosphatase, were assessed by quantitative real-time polymerase chain reaction. The effect of CTLA-4-Ig on the nuclear factor-κB (NF-κB) activation was assessed by enzyme-linked immunosorbent assay.

RESULTS

In vivo, ligature-induced bone resorption and the numbers of osteoclast-like cells were significantly decreased by the administration of CTLA-4-Ig. In vitro, treatment with RANKL and CTLA-4-Ig had no significant effect on cell viability. CTLA-4-Ig significantly reduced the prevalence and activation of osteoclast-like cells and decreased the expressions of osteoclast differentiation markers, compared with the RANKL-treated control. CTLA-4-Ig significantly suppressed RANKL-induced phosphorylation of NF-κB p65 but increased PP2A expression.

CONCLUSION

These results suggest that CTLA-4-Ig abrogates bone resorption in induced periodontitis, possibly via inhibition of osteoclast differentiation and activation. The regulation of the NF-κB pathway and PP2A expression may be one mechanism by which CTLA-4-Ig suppresses osteoclast behavior.

Oral Dysbiosis and Autoimmunity: From Local Periodontal Responses to an Imbalanced Systemic Immunity. A Review

The current paradigm of onset and progression of periodontitis includes oral dysbiosis directed by inflammophilic bacteria, leading to altered resolution of inflammation and lack of regulation of the inflammatory responses. In the construction of explanatory models of the etiopathogenesis of periodontal disease, autoimmune mechanisms were among the first to be explored and historically, for more than five decades, they have been described in an isolated manner as part of the tissue damage process observed in periodontitis, however direct participation of these mechanisms in the tissue damage is still controversial. Autoimmunity is affected by genetic and environmental factors, leading to an imbalance between the effector and regulatory responses, mostly associated with failed resolution mechanisms. However, dysbiosis/infection and chronic inflammation could trigger autoimmunity by several mechanisms including bystander activation, dysregulation of toll-like receptors, amplification of autoimmunity by cytokines, epitope spreading, autoantigens complementarity, autoantigens overproduction, microbial translocation, molecular mimicry, superantigens, and activation or inhibition of receptors related to autoimmunity by microorganisms. Even though autoreactivity in periodontitis is biologically plausible, the associated mechanisms could be related to non-pathologic responses which could even explain non-recognized physiological functions. In this review we shall discuss from a descriptive point of view, the autoimmune mechanisms related to periodontitis physio-pathogenesis and the participation of oral dysbiosis on local periodontal autoimmune responses as well as on different systemic inflammatory diseases.

Th2 cell regulatory and effector molecules single nucleotide polymorphisms and periodontitis

To investigate the association between T helper 2 (Th2) cell regulatory and effector molecules' genetic polymorphisms and periodontitis. Single nucleotide polymorphisms (SNPs) of 11 Th2 cell regulatory or effector molecules genes (CD28, CTLA4, IL4, IL5, IL6, IL9, IL10, IL13, IL4R, GATA3, STAT6, and rs1537415; total 130 SNPs) were studied in Chinese nonsmokers (163 periodontitis-free controls, 141 periodontitis patients) using Sequenom iPlex assays. SNPs potentially associated with periodontitis (adjusted allelic P < 0.1) in this cross-sectional study were further investigated via meta-analysis. Allele G of rs4553808 in promoter of CTLA4 was more frequently detected in periodontitis than controls (P < 0.005), but did not remain significant after age and gender adjustment. Haplotype (GTT) in a block of three CTLA4 SNPs (rs4553808, rs16840252, rs5742909) was significantly associated with periodontitis. Meta-analysis of SNPs identified indicated allele T of CTLA4 rs5742909 (3 studies; 461 control, 369 periodontitis) and allele G of IL6 rs1800796 (18 studies; 2760 control, 2442 periodontitis) were significantly associated with periodontitis (OR = 1.44 and OR = 1.30, respectively). Within limitations of this study, a haplotype of CTLA4 concerning Th2 cell regulation, may be associated with periodontitis in Chinese nonsmokers followed. Meta-analysis indicated rs5742909 of CTLA4 and rs1800796 of IL6 appeared significantly associated with periodontitis.

Comparative analysis of blood and saliva expression profiles in chronic and refractory periodontitis patients

Background

This study aimed to identify characteristic representative genes through a comparative analysis of gene expression profiles in the blood and saliva of chronic periodontitis (CP) and refractory periodontitis (RP) patients to provide new treatment strategies that may be helpful in the treatment of different forms of periodontitis.

Methods

GSE43525 was downloaded from Gene Expression Omnibus. In the dataset, thirteen samples were from blood including 4 controls, 4 CP and 5 RP samples, and ten samples were from saliva including 3 controls, 4 CP and 3 RP samples. After comparing the CP and RP samples, differentially expressed genes (DEGs) between these two types of periodontitis in the blood and saliva samples were identified by an LIMMA package. Then, functional and pathway enrichment analyses were performed by DAVID and KOBAS, respectively. The significantly associated miRNAs in CP and RP were searched by WebGestalt.

Results

In total, 213 DEGs in CP and 45 DEGs in RP were identified. Functional enrichment showed that the DEGs of CP were mainly enriched in ribosome and regulation of apoptosis-related pathways in blood as well as saliva, while the DEGs of RP were significantly enriched in immune responses and response to organic substance-related pathways. Several miRNAs, such as miR-381 and miR-494, were identified as being closely associated with CP. In addition, CD24, EST1, MTSS1, ING3, CCND2 and SYNE2 might be potential targets for diagnosis and treatment of CP.

Conclusion

The identified DEGs and miRNAs might be potential targets for the treatment of chronic and refractory periodontitis.