Comparative Metabolomics Reveals the Microenvironment of Common T-Helper Cells and Differential Immune Cells Linked to Unique Periapical Lesions

Heterogeneity of T cells in periapical lesions and in vitro validation of the proangiogenic effect of GZMA on HUVECs

AIM

T cells are key immunomodulatory cells in periapical lesions. This study aimed to explore the roles of T cells in chronic apical periodontitis (CAP) using single-cell RNA sequencing and to further investigate Granzyme A (GZMA) in angiogenesis regulation.

METHODOLOGY

A total of five CAP samples were collected for single-cell RNA sequencing. We performed subcluster and lineage-tracing analyses for T cells. According to differential gene expression, distinct biological functions enriched in T cells of CAP were presented by gene set enrichment analysis (GSEA) and compared with healthy gingiva (data obtained from the GEO database). CellChat was used to explore potential ligand-receptor interactions between T cells and endothelial cells in CAP. The coculture of primary human umbilical vein endothelial cells (HUVECs) and Jurkat T cells, as well as the addition of GZMA recombinant protein, was used to validate the predicted pair of GZMA and coagulation factor II thrombin receptor (F2R) by RT-PCR, angiogenesis and migration assays.

RESULTS

A transcriptomic atlas of 44 746 individual cells was constructed from the periapical lesions of five patients with CAP by single-cell RNA-seq, and eight cell types were identified. We identified nine subsets of T cells and deciphered the cellular heterogeneity of T cells in CAP at the functional level by subclustering and GSEA. Lineage tracing revealed a distinct lineage of T cells in CAP and predicted the transition of the T cellular state upon CAP. GSEA revealed multiple biological processes and relevant angiogenesis genes upregulated in CAP T cells. GZMA-F2R pairs were predicted by cell-cell interactions in CAP. High expression of GZMA and F2R was observed in the coculture of HUVECs and Jurkat T cells, and the proangiogenic capacity of the GZMA recombinant protein was emphasized by in vitro experiments.

CONCLUSIONS

Our study provides novel insights into the heterogeneity of T cells in periapical lesions and reveals the potential role of GZMA in T cells in regulating angiogenesis in HUVECs.

Reduction of NrF2 as coadjuvant during the development of persistent periapical lesions

BACKGROUND

Persistent periapical lesions (PPL) are the result of pulpar necrosis induced by bacterial infection resulting in bone degradation and culminating with the loss of dental piece. Pathological changes in the peripapice are associated with the presence of free radicals. The transcription factor Nrf2 is the main regulator of the endogenous antioxidant response against oxidative stress and has been implicated in the regulation of osteoclastogenesis.The aim is to determine the oxidative condition in samples from patients with Persistent Periapical Injuries as a detonating factor of tissue damage.

MATERIAL AND METHODS

An observational, descriptive, cross-sectional study was carried out in samples with PPL (cases) and samples by removal of third molars (controls) obtained in the clinic of the specialty in endodontics, University of Guadalajara. Samples were submitted to histological staining with Hematoxylin-Eosin, lipoperoxide analysis, Superoxide Dismutase (SOD), Glutathione-Peroxidase (GPx) and Catalase (CAT) activities were determined by immunoenzymatic assays and NrF2 by Western Blot analysis.

RESULTS

Samples from PPL patients histologically showed an increased presence of lymphocytes, plasma cells, and eosinophils, as well as a decrease in extracellular matrix proteins and fibroblast cells. There was a rise in lipid peroxidation, GPx and SOD activities, but an important decline (36%) in Catalase activity was observed (p<0.005); finally, NrF2-protein was diminished at 10.41%. All comparisons were between cases vs controls.

CONCLUSIONS

The alterations in antioxidants endogenous NrF2-controlled are related to osseous destruction in patients with PPL.

Molecular pathogenicity of 1-nonadecene and L-lactic acid, unique metabolites in radicular cysts and periapical granulomas

Recently, 1-nonadecene and L-lactic acid were identified as unique metabolites in radicular cysts and periapical granuloma, respectively. However, the biological roles of these metabolites were unknown. Therefore, we aimed to investigate the inflammatory and mesenchymal-epithelial transition (MET) effects of 1-nonadecene, and the inflammatory and collagen precipitation effects of L-lactic acid on both periodontal ligament fibroblasts (PdLFs) and peripheral blood mononuclear cells (PBMCs). PdLFs and PBMCs were treated with 1-nonadecene and L-lactic acid. Cytokines' expression was measured using quantitative real-time polymerase chain reaction (qRT-PCR). E-cadherin, N-cadherin, and macrophage polarization markers were measured using flow cytometry. The collagen, matrix metalloproteinase (MMP)-1, and released cytokines were measured using collagen assay, western blot, and Luminex assay, respectively. In PdLFs, 1-nonadecene enhances inflammation through the upregulation of some inflammatory cytokines including IL-1β, IL-6, IL-12A, monocyte chemoattractant protein (MCP)-1, and platelet-derived growth factor (PDGF) α. 1-Nonadecene also induced MET through the upregulation of E-cadherin and the downregulation of N-cadherin in PdLFs. 1-Nonadecene polarized macrophages to a pro-inflammatory phenotype and suppressed their cytokines' release. L-lactic acid exerted a differential impact on the inflammation and proliferation markers. Intriguingly, L-lactic acid induced fibrosis-like effects by enhancing collagen synthesis, while inhibiting MMP-1 release in PdLFs. These results provide a deeper understanding of 1-nonadecene and L-lactic acid's roles in modulating the microenvironment of the periapical area. Consequently, further clinical investigation can be employed for target therapy.

Human Archaeological Dentin as Source of Polar and Less Polar Metabolites for Untargeted Metabolomic Research: The Case of Yersinia pestis

Metabolomic approaches, such as in clinical applications of living individuals, have shown potential use for solving questions regarding the past when applied to archaeological material. Here, we study for the first time the potential of this Omic approach as applied to metabolites extracted from archaeological human dentin. Dentin obtained from micro sampling the dental pulp of teeth of victims and non-victims of Yersinia pestis (plague) from a 6th century Cambridgeshire site are used to evaluate the potential use of such unique material for untargeted metabolomic studies on disease state through liquid chromatography hyphenated to high-resolution mass spectrometry (LC-HRMS). Results show that small molecules of both likely endogenous and exogenous sources are preserved for a range of polar and less polar/apolar metabolites in archaeological dentin; however, untargeted metabolomic profiles show no clear differentiation between healthy and infected individuals in the small sample analysed (n = 20). This study discusses the potential of dentin as a source of small molecules for metabolomic assays and highlights: (1) the need for follow up research to optimise sampling protocols, (2) the requirements of studies with larger sample numbers and (3) the necessity of more databases to amplify the positive results achievable with this Omic technique in the archaeological sciences.

SARS-CoV-2-free residual proteins mediated phenotypic and metabolic changes in peripheral blood monocytic-derived macrophages in support of viral pathogenesis

The large-scale dissemination of coronavirus disease-2019 (COVID-19) and its serious complications have pledged the scientific research communities to uncover the pathogenesis mechanisms of its etiologic agent, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Methods of unveiling such mechanisms are rooted in understanding the viral agent's interactions with the immune system, including its ability to activate macrophages, due to their suggested role in prolonged inflammatory phases and adverse immune responses. The objective of this study is to test the effect of SARS-CoV-2-free proteins on the metabolic and immune responses of macrophages. We hypothesized that SARS-CoV-2 proteins shed during the infection cycle may dynamically induce metabolic and immunologic alterations with an inflammatory impact on the infected host cells. It is imperative to delineate such alterations in the context of macrophages to gain insight into the pathogenesis of these highly infectious viruses and their associated complications and thus, expedite the vaccine and drug therapy advent in combat of viral infections. Human monocyte-derived macrophages were treated with SARS-CoV-2-free proteins at different concentrations. The phenotypic and metabolic alterations in macrophages were investigated and the subsequent metabolic pathways were analyzed. The obtained results indicated that SARS-CoV-2-free proteins induced concentration-dependent alterations in the metabolic and phenotypic profiles of macrophages. Several metabolic pathways were enriched following treatment, including vitamin K, propanoate, and the Warburg effect. These results indicate significant adverse effects driven by residual viral proteins that may hence be considered determinants of viral pathogenesis. These findings provide important insight as to the impact of SARS-CoV-2-free residual proteins on the host cells and suggest a potential new method of management during the infection and prior to vaccination.

Plasma Rich in Growth Factors in the Treatment of Endodontic Periapical Lesions in Adult Patients: 3-Dimensional Analysis Using Cone-Beam Computed Tomography on the Outcomes of Non-Surgical Endodontic Treatment Using A-PRF+ and Calcium Hydroxide: A Retrospective Cohort Study

The study presents results of periapical lesion healing after one-visit root canal treatment (RCT) with Advanced Platelet Rich Fibrin plus (A-PRF+) application compared to a two-visit RCT with an inter-appointment calcium hydroxide filling. The comparison was made based on CBCT-Periapical Index (PAI) lesion volume changes and the occurrence of post endodontic pain. The results of 3D radiographic healing assessments based on volume reduction criteria were different from the CBCT-PAI. Based on volume changes, the healing assessment criteria-9 cases from the Study Group and six cases in the Control Group were defined as healed. Based on the CBCT-PAI healing assessment criteria, 8 cases from the Study Group and 9 cases from the Control Group were categorized as healed. The volumes of apical radiolucency were, on average, reduced by 85.93% in the Study Group and by 72.31% in the Control Group. Post-endodontic pain occurred more frequently in the Control than in the Study Group. The highest score of pain in the Study Group was five (moderate pain, n = 1), while in the Control Group, the highest score was eight (severe pain, n = 2). In the 6-month follow-up, CBCT scans showed a better healing tendency for patients in the Study Group.

Phenolic Contents and Antioxidant Activity of Citrullus colocynthis Fruits, Growing in the Hot Arid Desert of the UAE, Influenced by the Fruit Parts, Accessions, and Seasons of Fruit Collection

Citrullus colocynthis (Cucurbitaceae) is an important medicinal plant traditionally used in the United Arab Emirates (UAE). In a recent study, it has been reported that different individuals of the same population of C. colocynthis, growing in the hot arid desert of the UAE, exhibited variations in their fruit size, color, and stripe pattern. In addition, these plants differed genetically, and their seeds showed variation in size, color, and germination behavior (hereinafter, these individuals are referred to as accessions). In the present study, the total phenolic content (TPC) and antioxidant activity of different fruit parts (rinds, pulps, and seeds) of three different accessions with significant genetic variations, from a single C. colocynthis population, were assessed in response to different seasonal environments. Green fruits were collected in summer and winter from three accessions growing in the botanic garden of the University of Sharjah, UAE. Methanolic extracts from different fruit parts were prepared. The TPC was qualitatively determined by a Folin–Ciocalteu assay, while the antioxidant capacity was analyzed using the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging ability. The metabolic profiling of the antioxidant metabolites was determined using a gas chromatograph coupled to mass spectrometry (GC–MS), associated with a literature search. The results showed that the TPC and the DPPH free radical scavenging activity varied between seasons, accessions, and fruit parts. The highest phenolics were in rinds, but the highest antioxidant activities were in seeds during the summer, reflecting the role of these compounds in protecting the developed seeds from harsh environmental conditions. The metabolomic analysis revealed the presence of 28 metabolites with significant antioxidant activities relevant to fruit parts and season. Collectively, the formation of phenolics and antioxidant activity in different fruit parts is environmentally and genetically dependent.

Estimating the viral loads of SARS-CoV-2 in the oral cavity when complicated with periapical lesions

Background

The oral cavity represents a main entrance of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Angiotensin-converting enzyme 2 (ACE-2), neuropilin-1 (NRP-1), and transmembrane serine protease 2 (TMPRSS2) are essential for the entry of SARS-CoV-2 to the host cells. Both ACE-2 and NRP-1 receptors and TMPRSS2 have been identified in the oral cavity. However, there is limited knowledge about the impact of periapical lesions and their metabolites on the expression of these critical genes. This study aims to measure the impact of periapical lesions and their unique fatty acids (FAs) metabolites on the expression of the aforementioned genes, in addition to interleukin 6 (IL-6) gene and hence SARS-CoV-2 infection loads can be estimated.

Methods

Gene expression of ACE-2, NRP-1, TMPRSS2, and IL-6 was performed in periapical lesions in comparison to healthy oral cavity. Since FAs are important immunomodulators required for the lipid synthesis essential for receptors synthesis and viral replication, comparative FAs profiling was determined in oral lesions and healthy pulp tissues using gas chromatography–mass spectrometry (GC–MS). The effect of major identified and unique FAs was tested on mammalian cells known to express ACE-2, NRP-1, and TMPRSS2 genes.

Results

Gene expression analysis indicated that ACE-2, NRP-1, and TMPRSS2 were significantly upregulated in healthy clinical samples compared to oral lesions, while the reverse was true with IL-6 gene expression. Saturated and monounsaturated FAs were the major identified shared and unique FAs, respectively. Major shared FAs included palmitic, stearic and myristic acids with the highest percentage in the healthy oral cavity, while unique FAs included 17-octadecynoic acid in periapical abscess, petroselinic acid and l-lactic acid in periapical granuloma, and 1-nonadecene in the radicular cyst. Computational prediction showed that the binding affinity of identified FAs to ACE-2, TMPRSS2 and S protein were insignificant. Further, FA-treated mammalian cells showed significant overexpression of ACE-2, NRP-1 and TMPRSS2 genes except with l-lactic acid and oleic acid caused downregulation of NRP-1 gene, while 17-octadecynoic acid caused insignificant effect.

Conclusion

Collectively, a healthy oral cavity is more susceptible to viral infection when compared to that complicated with periapical lesions. FAs play important role in viral infection and their balance can affect the viral loads. Shifting the balance towards higher levels of palmitic, stearic and 1-nonadecene caused significant upregulation of the aforementioned genes and hence higher viral loads. On the other hand, there is a reverse correlation between inflammation and expression of SARS-CoV-2 receptors. Therefore, a mouth preparation that can reduce the levels of palmitic, stearic and 1-nonadecene, while maintaining an immunomodulatory effect can be employed as a future protection strategy against viral infection.