PRDX6 alleviates lipopolysaccharide-induced inflammation and ferroptosis in periodontitis

Modulation of NRF2/KEAP1 Signaling by Phytotherapeutics in Periodontitis

Periodontitis affects up to 40% of adults over 60 years old and is a consequence of gingivitis. Periodontitis is characterized by a chronic inflammation, periodontal damage, and alveolar bone resorption. The nuclear factor erythroid 2-related factor 2 (NFE2L2 or NRF2)/Kelch-like ECH-Associated Protein 1 (KEAP1) (NRF2/KEAP1) signaling pathway plays a key role in periodontitis by modulating redox balance and inflammation of the periodontium. However, NRF2 expression is decreased in gingival tissues of patients with periodontitis while oxidative stress is significantly increased in this pathology. Oxidative stress and lipopolysaccharide (LPS) produced by gram-negative bacteria favor the production of inflammatory causing periodontal inflammation and favoring alveolar bone. In this review, we analyzed the current literature regarding the role of natural and synthetic compounds in modulating the NRF2/KEAP1 pathway in in vitro and in vivo models of periodontitis in order to evaluate new potential treatments of periodontitis that can improve the outcome of this disease.

ALDH2 alleviates inflammation and facilitates osteogenic differentiation of periodontal ligament stem cells in periodontitis by blocking ferroptosis via activating Nrf2

This paper elucidated the effects and mechanisms of aldehyde dehydrogenase 2 (ALDH2) on periodontitis. Rat model of periodontitis and periodontal ligament stem cell (PDLSC) model of periodontitis were constructed. PDLSC were transfected by ALDH2 overexpression vectors, and then treated by ML385 (Nrf2 inhibitor), ferrostatin-1 (ferroptosis inhibitor) and FIN56 (ferroptosis inducer), respectively. ALDH2, nuclear factor erythroid 2-related factor 2 (Nrf2) and glutathione peroxidase 4 (GPX4) proteins was evaluated by immunohistochemistry and Western blot. Ferroptosis-related factors, including Fe2+ and glutathione (GSH), were assessed by commercial kits. Pro-inflammatory factors (interleukin-6 [IL-6] and tumor necrosis factor-α [TNF-α]) and osteogenic differentiation-related proteins (osteocalcin [OCN] and runt-related transcription factor 2 [RUNX2]) were scrutinized by commercial kits and Western blot. In both periodontal tissues of periodontitis rats and PDLSC model of periodontitis, down-regulated ALDH2, Nrf2, GPX4 and GSH, but elevated Fe2+ level was discovered. ALDH2 overexpression in PDLSC resulted in an increase in Nrf2 expression. In PDLSC model of periodontitis, ALDH2 increased GPX4 and GSH levels, decreased Fe2+, IL-6 and TNF-α levels, and elevated OCN and RUNX2 expression. However, these effects of ALDH2 were counteracted by ML385. Additionally, the suppression of ALDH2 on IL-6 and TNF-α levels and promotion of it on OCN and RUNX2 expression in PDLSC model of periodontitis was further intensified by ferrostatin-1, but reversed by FIN56. ALDH2 may alleviate inflammation and facilitate osteogenic differentiation of PDLSC in periodontitis by hindering ferroptosis via activating Nrf2, suggesting it to be a promising candidate for treating periodontitis.

ATF3 affects osteogenic differentiation in inflammatory hPDLSCs by mediating ferroptosis via regulating the Nrf2/HO-1 signaling pathway

Activating transcription factor 3 (ATF3) has been identified as a regulator associated with osteoblast differentiation. However, the effects of ATF3 on the osteogenic differentiation and proliferation of human periodontal stem cells (hPDLSCs) in periodontitis have not been reported. With the purpose of establishing an in vitro model of periodontitis, hPDLSCs were challenged with lipopolysaccharide (LPS). The Cell Counting Kit-8 assay was applied to assess cell viability, while reverse transcription-quantitative PCR and western blotting were employed to detect ATF3 expression. Inflammatory release was assessed using ELISA, together with western blotting. Lipid peroxidation was explored using the C11 BODIPY 581/591 probe, biochemical kits, thiobarbituric acid reactive substances (TBARS) assay and DCFH-DA staining. Iron and Fe2+ levels, and the expression levels of ferroptosis-related proteins were measured using corresponding kits and western blotting. Osteogenic differentiative capability was evaluated using alkaline phosphatase staining, Alizarin red staining and western blotting. The expression levels of proteins associated with Nrf2/HO-1 signaling were identified using western blotting. The results indicated that ATF3 expression was upregulated in LPS-induced hPDLSCs. The knockdown of ATF3 alleviated the LPS-induced inflammatory response in hPDLSCs, together with increased levels of TNF-α, IL-6, IL-1β, Cox-2 and iNOS, and decreased levels of IL-10. ATF3 silencing also led to lower TBARS production rate, and reduced levels of reactive oxygen species, iron, Fe2+, ACSL4 and TFR1, whereas it elevated the levels of SLC7A11 and GPX4. In addition, ATF3 silencing promoted hPDLSC mineralization and cell differentiation, and elevated the levels of OCN2, RUNX2 and BMP2. Additionally, ATF3 depletion upregulated the expression levels of proteins related with Nrf2/HO-1 signaling. The Nrf2 inhibitor ML385 partially counteracted the effects of ATF3 interference on the LPS-challenged inflammatory response, lipid peroxidation, ferroptosis as well as osteogenic differentiative capability in hPDLSCs. In summary, the results revealed that ATF3 silencing suppressed inflammation and ferroptosis, while it improved osteogenic differentiation in LPS-induced hPDLSCs by regulating Nrf2/HO-1 signaling, which may provide promising therapeutic targets for the treatment of periodontitis.

PRDX6 alleviated heart failure by inhibiting doxorubicin-induced ferroptosis through the JAK2/STAT1 pathway inactivation

Peroxiredoxin 6 (PRDX6) is a protective biomarker associated with ferroptosis in heart failure (HF). This study investigated the specific mechanism of PRDX6 on doxorubicin (DOX)-induced ferroptosis in HF. Wistar rats and H9c2 cells were induced by DOX to construct HF models. Pathological changes and collagen deposition in myocardium were investigated using HE and Masson staining. PRDX6 levels, indexes of ferroptosis, and JAK2/STAT1 pathway were detected by qRT-PCR, Western blot, and biochemical kits. DOX promoted heart weight/body weight, increased inflammation and collagen deposition, increased PTGS2 and MDA levels, and decreased SLC7A11, GPX4, FTH1, and PRDX6 levels in myocardium. PRDX6 overexpression reduced PTGS2, MDA, Fe2+, and LDH levels, inhibited JAK2 and STAT1 phosphorylation, and increased SLC7A11, GPX4, and FTH1 levels in DOX-added H9c2 cells. RO8191 and erastin reversed the inhibition of PRDX6 on ferroptosis through the JAK2/STAT1 pathway. Overall, PRDX6 alleviated HF by inhibiting DOX-induced ferroptosis through the JAK2/STAT1 pathway inactivation.

Role of ferroptosis in Porphyromonas gingivalis-induced impairment of epithelial junction

Objectives

This study aims to clarify the effect of ferroptosis by P. gingivalis on periodontal epithelium impairment and potential mechanisms.

Materials and methods

The expression of epithelial junction proteins (CDH1, OCLN, ZO-1), FTL and GPX4 in healthy and periodontitis tissues was analyzed using bioinformatics analysis and validated in vivo. An in vitro model was constructed to evaluate ferroptosis by mitochondria morphology, content of iron and GSH, and level of lipid peroxidation, FTL, GPX4 and SLC7A11. The iron concentration was changed with iron chelator DFO and iron supplementation FAC. The epithelial impairment was assessed by protein expression. To investigate the mechanism, si-MYB (a negative transcription factor of SLC7A11) and GPX4 inhibitor RSL3 were employed.

Results

CDH1, OCLN, ZO-1 and GPX4 expression was decreased, while FTL expression was elevated in periodontitis tissues. Infected cells showed ferroptosis change of the mitochondria with higher level of lipid peroxidation, iron, FTL and lower level of GPX4, GSH, SLC7A11. FAC augmented ferroptosis and weakened epithelial junction, while DFO exhibited a counteractive effect. Silencing MYB rescued SLC7A11, GPX4 and epithelial junction proteins, which was hindered by RSL3.

Conclusions

Our study demonstrated that P. gingivalis weakened the oral epithelial barrier by causing ferroptosis via inhibiting SLC7A11/GSH/GPX4 axis.

Development of a classification model and an immune-related network based on ferroptosis in periodontitis

BACKGROUND AND OBJECTIVES

Periodontitis is an immunoinflammatory disease characterized by irreversible periodontal attachment loss and bone destruction. Ferroptosis is a kind of immunogenic cell death that depends on the participation of iron ions and is involved in various inflammatory and immune processes. However, information regarding the relationship between ferroptosis and immunomodulation processes in periodontitis is extremely limited. The purpose of this study was to investigate the correlation between ferroptosis and immune responses in periodontitis.

METHODS

Gene expression profiles of gingivae were collected from the Gene Expression Omnibus data portal. After detecting differentially expressed ferroptosis-related genes (FRGs), we used univariate logistic regression analysis followed by logistic least absolute shrinkage and selection operator (LASSO) regression to establish a ferroptosis-related classification model in an attempt to accurately distinguish periodontitis gingival tissues from healthy samples. The infiltration level of immunocytes in periodontitis was then assessed through single-sample gene-set enrichment analysis. Subsequently, we screened out immune-related genes by weighted correlation network analysis and protein-protein interaction (PPI) analysis and constructed an immune-related network based on FRGs and immune-related genes.

RESULTS

A total of 24 differentially expressed FRGs were detected, and an 8-FRG combined signature constituted the classification model. The established model showed outstanding discriminating ability according to the results of receiver operating characteristic (ROC) curve analysis. In addition, the periodontitis samples had a higher degree of immunocyte infiltration. Activated B cells had the strongest positive correlation while macrophages had a strong negative correlation with certain FRGs, and we found that XBP1, ALOX5 and their interacting genes might be crucial genes in the immune-related network.

CONCLUSIONS

The FRG-based classification model had a satisfactory determination ability, which could bring new insights into the pathogenesis of periodontitis. Those genes in the immune-related network, especially hub genes along with XBP1 and ALOX5, would have the potential to serve as promising targets of immunomodulatory treatments for periodontitis.

Identification of ferroptosis, necroptosis, and pyroptosis-associated genes in periodontitis-affected human periodontal tissue using integrated bioinformatic analysis

Introduction: Periodontitis is a chronic inflammatory oral disease that destroys soft and hard periodontal support tissues. Multiple cell death modes including apoptosis, necroptosis, pyroptosis, and ferroptosis play a crucial role in the pathogenicity of inflammatory diseases. This study aimed to identify genes associated with ferroptosis, necroptosis, and pyroptosis in different cells present in the periodontium of periodontitis patients. Methods: Gingival tissues' mRNA sequencing dataset GSE173078 of 12 healthy control and 12 periodontitis patients' and the microarray dataset GSE10334 of 63 healthy controls and 64 periodontitis patients' were obtained from Gene Expression Omnibus (GEO) database. A total of 910 differentially expressed genes (DEGs) obtained in GSE173078 were intersected with necroptosis, pyroptosis, and ferroptosis-related genes to obtain the differential genes associated with cell death (DCDEGs), and the expression levels of 21 differential genes associated with cell death were verified with dataset GSE10334. Results: Bioinformatic analysis revealed 21 differential genes associated with cell death attributed to ferroptosis, pyroptosis, and necroptosis in periodontitis patients compared with healthy controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that 21 differential genes associated with cell death were related to various cellular and immunological pathways including inflammatory responses, necroptosis, and osteoclast differentiation. Additionally, the single-cell RNA (scRNA) sequencing data GSE171213 of 4 healthy controls and 5 periodontitis patients' periodontal tissue was analyzed to obtain cell clustering and cell types attributed to differential genes associated with cell death. We found that among 21 DCDEGs, SLC2A3, FPR2, TREM1, and IL1B were mainly upregulated in neutrophils present in the periodontium of periodontitis patients. Gene overlapping analysis revealed that IL-1B is related to necroptosis and pyroptosis, TREM1 and FPR2 are related to pyroptosis, and SLC2A3 is related to ferroptosis. Finally, we utilized the CIBERSORT algorithm to assess the association between DCDEGs and immune infiltration phenotypes, based on the gene expression profile of GSE10334. The results revealed that the upregulated SLC2A3, FPR2, TREM1, and IL1B were positively correlated with neutrophil infiltration in the periodontium. Discussion: The findings provide upregulated SLC2A3, FPR2, TREM1, and IL1B in neutrophils as a future research direction on the mode and mechanism of cell death in periodontitis and their role in disease pathogenicity.

Ferroptosis: A New Development Trend in Periodontitis

Periodontitis is a chronic inflammatory disease associated with bacterial biofilm. It is characterized by loss of periodontal support tissue and has long been considered as a "silent disease". Because it is difficult to prevent and has a health impact that can not be ignored, researchers have been focusing on a mechanism-based treatment model. Ferroptosis is an iron-dependent regulatory form of cell death, that directly or indirectly affects glutathione peroxidase through different signaling pathways, resulting in a decrease in cell antioxidant capacity, accumulation of reactive oxygen species and lipid peroxidation, which cause oxidative cell death and tissue damage. Recently, some studies have proven that iron overload, oxidative stress, and lipid peroxidation exist in the process of periodontitis. Based on this, this article reviews the relationship between periodontitis and ferroptosis, in order to provide a theoretical reference for future research on the prevention and treatment of periodontal disease.