Changes in apolipoprotein B and oxidized low-density lipoprotein levels in gingival crevicular fluids as a result of periodontal tissue conditions

Effects of oxidized LDL versus IL-1ß/TNF-ɑ/INFɣ on human gingival mesenchymal stem cells properties

AIMS

Oxidized low-density lipoprotein (oxLDL) is an important player in the course of metabolic inflammatory diseases. oxLDL was identified in the gingival crevicular fluid, denoting possible associations between oxLDL-induced inflammation and periodontal disease. The current investigation compared for the first-time direct effects of oxLDL to a cytokine cocktail of IL-1ß/TNF-ɑ/INF-γ on gingival mesenchymal stem cells' (G-MSCs) attributes.

METHODS

Human third passage G-MSCs, isolated from connective tissue biopsies (n = 5) and characterized, were stimulated in three groups over 7 days: control group, cytokine group (IL-1β[1 ng/mL], TNF-α[10 ng/mL], IFN-γ[100 ng/mL]), or oxLDL group (oxLDL [50 μg/mL]). Next Generation Sequencing and KEGG pathway enrichment analysis, stemness gene expression (NANOG/SOX2/OCT4A), cellular proliferation, colony-formation, multilinear potential, and altered intracellular pathways were investigated via histochemistry, next-generation sequencing, and RT-qPCR.

RESULTS

G-MSCs exhibited all mesenchymal stem cells' characteristics. oxLDL group and cytokine group displayed no disparities in their stemness markers (p > .05). Next-generation-sequencing revealed altered expression of the TXNIP gene in response to oxLDL treatment compared with controls (p = .04). Following an initial boosting for up to 5 days by inflammatory stimuli, over 14 day, cellular counts [median count ×10-5 (Q25/Q75)] were utmost in control - [2.6607 (2.0804/4.5357)], followed by cytokine - [0.0433 (0.0026/1.4215)] and significantly lowered in the oxLDL group [0.0274 (0.0023/0.7290); p = .0047]. Osteogenic differentiation [median relative Ca2+ content(Q25/Q75)] was significantly lower in cytokine - [0.0066 (0.0052/0.0105)] compared to oxLDL - [0.0144 (0.0108/0.0216)] (p = .0133), with no differences notable for chondrogenic and adipogenic differentiation (p > .05).

CONCLUSIONS

Within the current investigation's limitations, in contrast to cytokine-mediated inflammation, G-MSCs appear to be minimally responsive to oxLDL-mediated metabolic inflammation, with little negative effect on their differentiation attributes and significantly reduced cellular proliferation.

Causal relationship between circulating lipid traits and periodontitis: univariable and multivariable Mendelian randomization

Introduction

The correlation between dyslipidemia and periodontitis is revealed through epidemiological studies. However, the results are affected by several confounding factors. This study aims to elucidate the genetic causal association between circulating lipid traits and periodontitis by two-sample Mendelian randomization (MR) analysis.

Methods

After the different screening processes, two cohorts of circulating lipid traits from the UK Biobank were used as exposure data, including five circulating lipid traits. The Periodontitis cohort was selected from the GeneLifestyle Interactions in Dental Endpoints (GLIDE) consortium as outcome data. In univariable MR, the inverse variance weighted (IVW) was used in conjunction with six additional analytical methods to assess causality. The Cochran Q test, IGX 2 statistic, MR-PRESSO, and MR-Egger intercept were used to quantify heterogeneity and pleiotropy. The multivariable MR-IVW (MVMR-IVW) and MVMR-robust were mainly used as analytical methods in the multiple MR analyses.

Results

The IVW estimates showed that genetically predicted Apolipoprotein A1 (apo A1) [odds ratio (OR)=1.158, 95% confidence interval (CI)=1.007-1.331, P-value=0.040] was potentially associated with the risk of periodontitis, but the statistical power of the results was low. Multivariable MR analysis did not reveal any significant causal relationship between apo A1 and periodontitis (OR=0.72, 95% CI=0.36-1.41, P-value=0.34). In the validation cohort, there was also no significant causal relationship between apo A1 and periodontitis (OR=1.079, 95% CI=0.903-1.290, P-value=0.401). Meanwhile, genetically predicted Apolipoprotein B (apo B), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) (all P-values>0.05) were not significantly associated with the risk of periodontitis causal inference.

Conclusion

This MR analysis was unable to provide genetic evidence for the influence of these five circulating lipid traits on periodontitis. However, a more extensive study with a more comprehensive circulating lipid profile and periodontitis data is needed due to study limitations.

The etiological consideration of oxidized low-density lipoprotein in periodontitis

BACKGROUND

Epidemiologically, correlations between periodontal disease activity and CVD/serum lipid-related condition have been reported. Known mediators of these links include triglycerides, oxidized LDL (oxLDL) and inflammatory cytokines such as TNF-α supplied by adipocytes as well as oxidative degeneration products of these lipids. In this review, we focused on oxidized LDL and considered the relationship between periodontal disease and systemic conditions.

HIGHLIGHT

The degree of oxidation in the periodontal pocket can be evaluated by analyzing the Gingival Cervicular Fluid (GCF), which can be easily collected with paperpoint. The oxLDL/LDL ratio in GCF has been shown to be 17 times as high as that in blood, and IL-8 and IL-1β were also abundantly found in GCF. Periodontal treatment significantly lowers oxLDL levels in not only GCF but also plasma. In addition, there has been growing body of evidence that periodontal infections by periodontopathic bacteria affect arteriosclerosis. On the other hands, neutrophil extracellular traps (NETs), a form of innate immune responses, reportedly play a role as a defense mechanism in the periodontal pockets. However, the regulatory mechanism of NETs in periodontal pocket is still unknown. Recently, NETs induced by oxidized cholesterol have been reported to be involved in inflammatory damage to vascular endothelial cells.

CONCLUSION

Further understanding of the newly discovered roles of oxLDL in the defense and destruction of periodontal tissues are anticipated.

Diagnostic potential and future directions of matrix metalloproteinases as biomarkers in gingival crevicular fluid of oral and systemic diseases

Gingival crevicular fluid (GCF) is a physiological fluid and an inflammatory serum exudate derived from the gingival plexus of blood vessels and mixed with host tissues and subgingival plaque flows. In addition to proteins, GCF contains a diverse population of cells, including desquamated epithelial cells, cytokines, electrolytes, and bacteria from adjacent plaques. Recently, matrix metalloproteinases(MMPs), which are endopeptidases that are active against extracellular macromolecules, in GCF have been revealed as potential utility biomarkers for the diagnosis and follow-up of oral and systemic diseases, thereby facilitating the early evaluation of malignancy risk and the monitoring of disease progression and treatment response. Tissue inhibitors of metalloproteinases (TIMPs) are specific inhibitors of matrixins that participate in the regulation of local activities of MMPs in tissues. This review provides an overview of the latest findings on the diagnostic and prognostic values of MMPs and TIMPs in GCF of oral and systemic diseases, including periodontal disease, pulpitis, peri-implantitis and cardiovascular disease as well as the extraction, detection and analytical methods for GCF.

Maintaining a protective state for human periodontal tissue

Periodontitis, caused by infection with periodontal pathogens, is primarily characterized by inflammatory bone resorption and destruction of connective tissue. Simply describing periodontitis as a specific bacterial infection cannot completely explain the various periodontal tissue destruction patterns observed. Periodontal tissue damage is thought to be caused by various factors. In recent years, research goals for periodontal pathogens have shifted from searching for specific pathogens to investigating mechanisms that damage periodontal tissues. Bacteria interact directly with the host in several ways, influencing expression and activity of molecules that evade host defenses, and destroying local tissues and inhibiting their repair. The host's innate and acquired immune systems are important defense mechanisms that protect periodontal tissues from attack and invasion of periodontal pathogens, thus preventing infection. Innate and acquired immunity have evolved to confront the microbial challenge, forming a seamless defense network in periodontal tissues. In the innate immune response, host cells quickly detect, via specialized receptors, macromolecules and nucleic acids present on bacterial cell walls, and this triggers a protective, inflammatory response. The work of this subsystem of host immunity is performed mainly by phagocytes, beta-defensin, and the complement system. In addition, the first line of defense in oral innate immunity is the junctional epithelium, which acts as a physical barrier to the entry of oral bacteria and other nonself substances. In the presence of a normal flora, junctional epithelial cells differentiate actively and proliferate apically, with concomitant increase in chemotactic factor expression recruiting neutrophils. These immune cells play an important role in maintaining homeostasis and the protective state in periodontal tissue because they eliminate unwanted bacteria over time. Previous studies indicate a mechanism for attracting immune cells to periodontal tissue with the purpose of maintaining a protective state; although this mechanism can function without bacteria, it is enhanced by the normal flora. A better understanding of the relationship between the protective state and its disruption in periodontal disease could lead to the development of new treatment strategies for periodontal disease.

The Significance of Oxidized Low-Density Lipoprotein in Body Fluids as a Marker Related to Diseased Conditions

Oxidatively modified low-density lipoprotein (oxLDL) is known to be involved in various diseases, including cardiovascular diseases. The presence of oxLDL in the human circulatory system and in atherosclerotic lesions has been demonstrated using monoclonal antibodies. Studies have shown the significance of circulating oxLDL in various systemic diseases, including acute myocardial infarction and diabetic mellitus. Several different enzyme-linked immunosorbent assay (ELISA) procedures to measure oxLDL were utilized. Evidence has been accumulating that reveals changes in oxLDL levels under certain pathological conditions. Since oxLDL concentration tends to correlate with low-density lipoprotein (LDL)-cholesterol, the ratio of ox-LDL and LDL rather than oxLDL concentration alone has also been focused. In addition to circulating plasma, LDL and oxLDL are found in gingival crevicular fluid (GCF), where the ratio of oxLDL to LDL in GCF is much higher than in plasma. LDL and oxLDL levels in GCF show an increase in diabetic patients and periodontal patients, suggesting that GCF might be useful in examining systemic conditions. GCF oxLDL increased when the teeth were affected by periodontitis. It is likely that oxLDL levels in plasma and GCF could reflect oxidative stress and transfer efficacy in the circulatory system.