Lowered Expression of MicroRNAs 221 and 222 Mediate Apoptosis Induced by High Glucose in Human Periodontal Ligament Cells

Cystathionine γ-lyase contributes to exacerbation of periodontal destruction in experimental periodontitis under hyperglycemia

BACKGROUND

Diabetes is one of the major inflammatory comorbidities of periodontitis via 2-way interactions. Cystathionine γ-lyase (CTH) is a pivotal endogenous enzyme synthesizing hydrogen sulfide (H2S), and CTH/H2S is crucially implicated in modulating inflammation in various diseases. This study aimed to explore the potential role of CTH in experimental periodontitis under a hyperglycemic condition.

METHODS

CTH-silenced and normal human periodontal ligament cells (hPDLCs) were cultured in a high glucose and Porphyromonas gingivalis lipopolysaccharide (P.g-LPS) condition. The effects of CTH on hPDLCs were assessed by Cell Counting Kit 8 (CCK8), real-time quantitative polymerase chain reaction (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA). The model of experimental periodontitis under hyperglycemia was established on both Cth-/- and wild-type (WT) mice, and the extent of periodontal destruction was assessed by micro-CT, histology, RNA-Seq, Western blot, tartrate-resistant acid phosphatase (TRAP) staining and immunostaining.

RESULTS

CTH mRNA expression increased in hPDLCs in response to increasing concentration of P.g-LPS stimulation in a high glucose medium. With reference to WT mice, Cth-/- mice with experimental periodontitis under hyperglycemia exhibited reduced bone loss, decreased leukocyte infiltration and hindered osteoclast formation, along with reduced expression of proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in periodontal tissue. RNA-seq-enriched altered NF-κB pathway signaling in healthy murine gingiva with experimental periodontitis mice under hyperglycemia. Accordingly, phosphorylation of p65 (P-p65) was alleviated in CTH-silenced hPDLCs, leading to decreased expression of IL6 and TNF. CTH knockdown inhibited activation of nuclear factor kappa-B (NF-κB) pathway and decreased production of proinflammatory cytokines under high glucose and P.g-LPS treatment.

CONCLUSION

The present findings suggest the potential of CTH as a therapeutic target for tackling periodontitis in diabetic patients.

Role of microRNAs in Diabetes-Associated Periodontitis: A Scoping Review

Aim

Diabetes mellitus (DM), a metabolic disorder, exhibits a bidirectional relationship with periodontitis (PD), and recently, microRNAs (miRNAs) were associated with their progression. This review aims to assess the role of miRNAs in the pathogenesis of DM-associated PD and their plausible application as a biomarker for PD in individuals with DM.

Materials and Methods

The search conducted until September 2023 on Medline (Pubmed), Scopus, Embase, and Web of Science using the keywords "microRNA," "miRNA," or "miR," combined with "Diabetes" and "PD" yielded 100 articles. Only research focusing on the role of miRNAs in the pathogenesis of DM-associated PD and their potential application as biomarkers for both conditions were included. Finally, 14 studies were assessed for any bias, and the collected data included study design, sample size, participant groups, age, sample obtained, PD severity, miRNAs examined, clinical and biochemical parameters related to DM and PD, and primary outcomes.

Results

In vivo studies indicated altered expression of miRNAs-146a, -146b, -155, -200b, -203, and -223, specifically in the comorbid subjects with both conditions. Animal, ex vivo, and in vitro studies demonstrated altered expression of miRNAs-126, -147, -31, -25-3p, -508-3p, -214, 124-3p, -221, -222, and the SIRT6-miR-216/217 axis. These miRNAs impact innate and adaptive immune mechanisms, oxidative stress, hyperglycemia, and insulin sensitivity, thereby promoting periodontal destruction in DM. miRNA-146a emerges as a reliable biomarker of PD in DM, whereas miRNA-155 is a consistent predictor of PD in subjects without DM.

Conclusions

miRNAs exert influence on immuno-inflammation in DM-associated PD. Although they can be biomarkers of PD and DM, their clinical utility is hindered by the absence of standardized tests to evaluate their sensitivity and specificity. Moreover, there has been limited exploration of the role of miRNAs in DM-associated PD through human studies. Future clinical trials are warranted to address this gap, focusing on standardizing sample collection, miRNA sources, and detection methods. This approach will enable the identification of specific miRNAs for DM-associated PD.

High glucose impairs human periodontal ligament cells migration through lowered microRNAs 221 and 222

OBJECTIVE

To investigate the effects of miR-221 and miR-222 and high glucose on human periodontal ligament (PL) cells morphology, cytoskeleton, adhesion, and migration.

BACKGROUND

Chronic hyperglycemia is common in uncontrolled diabetes mellitus (DM) and plays a central role in long-term DM complications, such as impaired periodontal healing. We have previously shown that high glucose increases apoptosis of human PL cells by inhibiting miR-221 and miR-222 and consequently augmenting their target caspase-3. However, other effects of miR-221/222 downregulation on PL cells are still unknown.

METHODS

Cells from young humans' premolar teeth were cultured for 7 days under 5 or 30 mM glucose. Directional and spontaneous migration on fibronectin were studied using transwell and time-lapse assays, respectively. F-actin staining was employed to study cell morphology and the actin cytoskeleton. MiR-221 and miR-222 were inhibited using antagomiRs, and their expressions were evaluated by real-time RT-PCR.

RESULTS

High glucose inhibited PL cells early adhesion, spreading, and migration on fibronectin. Cells exposed to high glucose showed reduced polarization, velocity, and directionality. They formed several simultaneous unstable and short-lived protrusions, suggesting impairment of adhesion maturation. MiR-221 and miR-222 inhibition also reduced migration, decreasing cell directionality but not significantly cell velocity. After miR-221 and miR-222 downregulation cells showed morphological resemblance with cells exposed to high glucose.

CONCLUSION

High glucose impairs human PL cells migration potentially through a mechanism involving reduction of microRNA-221 and microRNA-222 expression. These effects may contribute to the impairment of periodontal healing, especially after surgery and during guided regeneration therapies.

Diabetes mellitus promotes susceptibility to periodontitis-novel insight into the molecular mechanisms

Diabetes mellitus is a main risk factor for periodontitis, but until now, the underlying molecular mechanisms remain unclear. Diabetes can increase the pathogenicity of the periodontal microbiota and the inflammatory/host immune response of the periodontium. Hyperglycemia induces reactive oxygen species (ROS) production and enhances oxidative stress (OS), exacerbating periodontal tissue destruction. Furthermore, the alveolar bone resorption damage and the epigenetic changes in periodontal tissue induced by diabetes may also contribute to periodontitis. We will review the latest clinical data on the evidence of diabetes promoting the susceptibility of periodontitis from epidemiological, molecular mechanistic, and potential therapeutic targets and discuss the possible molecular mechanistic targets, focusing in particular on novel data on inflammatory/host immune response and OS. Understanding the intertwined pathogenesis of diabetes mellitus and periodontitis can explain the cross-interference between endocrine metabolic and inflammatory diseases better, provide a theoretical basis for new systemic holistic treatment, and promote interprofessional collaboration between endocrine physicians and dentists.

Programmed cell death of periodontal ligament cells

The periodontal ligament is a crucial tissue that provides support to the periodontium. Situated between the alveolar bone and the tooth root, it consists primarily of fibroblasts, cementoblasts, osteoblasts, osteoclasts, periodontal ligament stem cells (PDLSCs), and epithelial cell rests of Malassez. Fibroblasts, cementoblasts, osteoblasts, and osteoclasts are functionally differentiated cells, whereas PDLSCs are undifferentiated mesenchymal stem cells. The dynamic development of these cells is intricately linked to periodontal changes and homeostasis. Notably, the regulation of programmed cell death facilitates the clearance of necrotic tissue and plays a pivotal role in immune response. However, it also potentially contributes to the loss of periodontal supporting tissues and root resorption. These findings have significant implications for understanding the occurrence and progression of periodontitis, as well as the mechanisms underlying orthodontic root resorption. Further, the regulation of periodontal ligament cell (PDLC) death is influenced by both systemic and local factors. This comprehensive review focuses on recent studies reporting the mechanisms of PDLC death and related factors.

MicroRNAs: Harbingers and shapers of periodontal inflammation

Periodontal disease is an inflammatory reaction of the periodontal tissues to oral pathogens. In the present review we discuss the intricate effects of a regulatory network of gene expression modulators, microRNAs (miRNAs), as they affect periodontal morphology, function and gene expression during periodontal disease. These miRNAs are small RNAs involved in RNA silencing and post-transcriptional regulation and affect all stages of periodontal disease, from the earliest signs of gingivitis to the regulation of periodontal homeostasis and immunity and to the involvement in periodontal tissue destruction. MiRNAs coordinate periodontal disease progression not only directly but also through long non-coding RNAs (lncRNAs), which have been demonstrated to act as endogenous sponges or decoys that regulate the expression and function of miRNAs, and which in turn suppress the targeting of mRNAs involved in the inflammatory response, cell proliferation, migration and differentiation. While the integrity of miRNA function is essential for periodontal health and immunity, miRNA sequence variations (genetic polymorphisms) contribute toward an enhanced risk for periodontal disease progression and severity. Several polymorphisms in miRNA genes have been linked to an increased risk of periodontitis, and among those, miR-146a, miR-196, and miR-499 polymorphisms have been identified as risk factors for periodontal disease. The role of miRNAs in periodontal disease progression is not limited to the host tissues but also extends to the viruses that reside in periodontal lesions, such as herpesviruses (human herpesvirus, HHV). In advanced periodontal lesions, HHV infections result in the release of cytokines from periodontal tissues and impair antibacterial immune mechanisms that promote bacterial overgrowth. In turn, controlling the exacerbation of periodontal disease by minimizing the effect of periodontal HHV in periodontal lesions may provide novel avenues for therapeutic intervention. In summary, this review highlights multiple levels of miRNA-mediated control of periodontal disease progression, (i) through their role in periodontal inflammation and the dysregulation of homeostasis, (ii) as a regulatory target of lncRNAs, (iii) by contributing toward periodontal disease susceptibility through miRNA polymorphism, and (iv) as periodontal microflora modulators via viral miRNAs.

Cynaroside protects human periodontal ligament cells from lipopolysaccharide-induced damage and inflammation through suppression of NF-κB activation

OBJECTIVE

To investigate whether cynaroside protects human periodontal ligament (hPDL) cells from lipopolysaccharide (LPS)-induced damage and inflammation and to analyze the underlying mechanism.

METHODS

LPS was used to stimulate hPDL and RAW264.7 cells. MTT assay was used to detect cell viability, and protein expression levels were measured via western blot analysis. Nitrite oxide and prostaglandin E₂ were used to quantify the inflammatory response. Alizarin Red S staining was used to detect mineralized nodules.

RESULTS

Cynaroside inhibited the expression of iNOS, COX-2, TNF-α, and IL-6 in LPS-stimulated hPDL and RAW264.7 cells without cytotoxicity. Furthermore, cynaroside significantly suppressed LPS-induced protein expression of matrix metalloproteinase 3. Additionally, cynaroside prevented LPS-induced NF-κB p65 subunit translocation to the nucleus by inhibiting the phosphorylation and degradation of IκB-α. Moreover, cynaroside could restore the mineralization ability of hPDL cells reduced by LPS.

CONCLUSION

Cynaroside protected hPDL cells from LPS-induced damage and inflammation via inhibition of NF-κB activation. These results suggest that cynaroside may be a potential therapeutic agent for the alleviation of periodontitis.