Angiotensin II Type 1 Receptor Knockdown Impairs Interleukin-1β-Induced Cytokines in Human Periodontal Fibroblasts

Inhibition of gingival fibroblast necroptosis mediated by RIPK3/MLKL attenuates periodontitis

AIM

Necroptosis participates in the pathogenesis of many inflammatory diseases, including periodontitis. Here, we aimed to investigate the role and mechanism of necroptosis inhibitors in attenuating periodontitis.

MATERIALS AND METHODS

The Gene Expression Omnibus (GEO) dataset GSE164241 was re-analysed to identify the role of necroptosis in periodontitis. Gingival specimens from healthy subjects or periodontitis patients were collected to evaluate the expression level of necroptosis-associated proteins. The therapeutic effect of necroptosis inhibitors on periodontitis was assessed in vivo and in vitro. Moreover, Transwell assays and Western blotting and siRNA transfection were used to identify the effects of necroptotic human gingival fibroblasts (hGFs) on THP-1 macrophages.

RESULTS

Re-analysis revealed that gingival fibroblasts (GFs) in periodontitis gingiva showed the highest area under the curve score of necroptosis. Elevated levels of necroptosis-associated proteins were identified in GFs in periodontitis gingiva collected from patients and mice. In ligature-induced periodontitis mice, local administration of receptor interacting protein kinase 3(RIPK3) inhibitor GSK'872 or sh-mixed-lineage kinase domain-like pseudokinase (Mlkl) markedly abrogated necroptosis and rescued periodontitis. Analogously, necroptosis inhibitors alleviated the inflammatory response and release of damage-associated molecular patterns in lipopolysaccharide- or LAZ (LPS + AZD'5582 + z-VAD-fmk, necroptosis inducer)-induced GFs and then reduced THP-1 cell migration and M1 polarization.

CONCLUSIONS

Necroptosis in GFs aggravated gingival inflammation and alveolar bone loss. Necroptosis inhibitors attenuate this process by modulating THP-1 macrophage migration and polarization. This study offers novel insights into the pathogenesis and potential therapeutic targets of periodontitis.

Fibroblasts at the curtain call: from ensemble to principal dancers in immunometabolism and inflammaging

Inflammation is a necessary step in response to injuries, being vital in restoring homeostasis and facilitating tissue healing. Among the cells that play a crucial role in inflammatory responses, stromal cells, including fibroblasts, have an undeniable significance in fine-tuning the magnitude of mediators that directly affect hyper-inflammatory responses and tissue destruction. Fibroblasts, the dominant cells in the gingival connective tissue, are a very heterogeneous population of cells, and more recently they have been receiving well deserved attention as central players and often the 'principal dancers' of many pathological processes ranging from inflammation and fibrosis to altered immunity and cancer. The goal of the current investigation is to dive into the exact role of the stromal fibroblast and the responsible mechanistic factors involved in both regulation and dysregulation of the inflammatory responses. This article reviews the most recent literature on how fibroblasts, in their different activation states or subtypes, play a crucial role in contributing to inflammatory outcomes. We will focus on recent findings on inflammatory diseases. We will also provide connections regarding the stromal-immune relationship, which supports the idea of fibroblast coming out from the 'ensemble' of cell types to the protagonist role in immunometabolism and inflammaging. Additionally, we discuss the current advances in variation of fibroblast nomenclature and division into clusters with their own suggested function and particularities in gene expression. Here, we provide a perspective for the periodontal implications, discussing the fibroblast role in the infection-driven and inflammatory mediated diseases such as periodontitis.

Inflammatory mediators act at renal pericytes to elicit contraction of vasa recta and reduce pericyte density along the kidney medullary vascular network

Introduction: Regardless of initiating cause, renal injury promotes a potent pro-inflammatory environment in the outer medulla and a concomitant sustained decrease in medullary blood flow (MBF). This decline in MBF is believed to be one of the critical events in the pathogenesis of acute kidney injury (AKI), yet the precise cellular mechanism underlying this are still to be fully elucidated. MBF is regulated by contractile pericyte cells that reside on the descending vasa recta (DVR) capillaries, which are the primary source of blood flow to the medulla. Methods: Using the rat and murine live kidney slice models, we investigated the acute effects of key medullary inflammatory mediators TNF-α, IL-1β, IL-33, IL-18, C3a and C5a on vasa recta pericytes, the effect of AT1-R blocker Losartan on pro-inflammatory mediator activity at vasa recta pericytes, and the effect of 4-hour sustained exposure on immunolabelled NG2+ pericytes. Results and discussion: Exposure of rat and mouse kidney slices to TNF-α, IL-18, IL-33, and C5a demonstrated a real-time pericyte-mediated constriction of DVR. When pro-inflammatory mediators were applied in the presence of Losartan the inflammatory mediator-mediated constriction that had previously been observed was significantly attenuated. When live kidney slices were exposed to inflammatory mediators for 4-h, we noted a significant reduction in the number of NG2+ positive pericytes along vasa recta capillaries in both rat and murine kidney slices. Data collected in this study demonstrate that inflammatory mediators can dysregulate pericytes to constrict DVR diameter and reduce the density of pericytes along vasa recta vessels, further diminishing the regulatory capacity of the capillary network. We postulate that preliminary findings here suggest pericytes play a role in AKI.

Is There a Link between COVID-19 and Periodontal Disease? A Narrative Review

The coronavirus disease 2019 (COVID-19) pandemic greatly affected human well-being, social behavior, global economy, and healthcare systems. Everyday clinical practice in dentistry has been adjusted to the increased hazards of aerosol production by routine dental procedures. The objective of this study was to assess the existing literature to determine possible mechanisms of a relationship between COVID-19 and periodontitis, as well as describe findings from relevant epidemiological studies.

Scarce data exist in the literature that directly addresses the relationship between the two diseases. However, several data describe the role of the oral cavity and periodontal tissues as portals of entry of severe acute respiratory syndrome–coronavirus-2 (SARS-CoV-2), and the contribution of cytokines known to be produced in periodontal disease to severe forms of COVID-19. It is also suggested from the current literature that periodontal disease, shown to be associated with systemic diseases such as diabetes mellitus, cardiovascular and respiratory diseases, shares common risk factors with—especially—severe forms of COVID-19.

Further clinical studies are required to establish the relationship between these diseases. Oral hygiene performance and intact periodontal tissues can assist in mitigating the pandemic, and it is suggested that dental practitioners can contribute to identifying at-risk patients.

The Receptor AT1 Appears to Be Important for the Maintenance of Bone Mass and AT2 Receptor Function in Periodontal Bone Loss Appears to Be Regulated by AT1 Receptor

A large number of experimental studies has demonstrated that angiotensin II (Ang II) is involved in key events of the inflammatory process. This study aimed to evaluate the role of Ang II type 1 (AT1) and Ang II type 2 (AT2) receptors on periodontitis. Methods: Experimental periodontitis was induced by placing a 5.0 nylon thread ligature around the second upper left molar of AT1 mice, no-ligature or ligature (AT1-NL and AT1-L), AT2 (AT2-NL or AT2-L) and wild type (WT-NL or L). Alveolar bone loss was scanned using Micro-CT. Cytokines, peptides and enzymes were analyzed from gingival tissues by Elisa and RT-PCR. Results: The blockade of AT1 receptor resulted in bone loss, even in healthy animals. Ang II receptor blockades did not prevent linear bone loss. Ang II and Ang 1-7 levels were significantly increased in the AT2-L (p < 0.01) group compared to AT2-NL and AT1-L. The genic expression of the Mas receptor was significantly increased in WT-L and AT2-L compared to (WT-NL and AT2-NL, respectively) and in AT1-L. Conclusions: Our data suggest that the receptor AT1 appears to be important for the maintenance of bone mass. AT2 receptor molecular function in periodontitis appears to be regulated by AT1.

Is SARS-CoV-2 present in the periodontium? A post-mortem study

Aims To investigate the presence of SARS-CoV-2, the virus responsible for COVID-19 infection, in the periodontal tissues of deceased individuals with a positive SARS-CoV-2 nasopharyngeal swab test.

Sample selection Seven deceased individuals, who were admitted to the intensive care unit of the Hospital das Clínicas of the Medicine School of Sao Paulo University for invasive mechanical ventilation following a positive nasopharyngeal COVID-19 test result, underwent a post-mortem examination. Individuals with comorbidities were included. Exclusion criteria included a current smoking habit.

Design A cross-sectional study involving a videoscope-guided autopsy to obtain a periodontal tissue sample. The plastic body wrapping was incised in the facial region, allowing the insertion of a video endoscope. A single sample of periodontal tissue (junctional epithelium, adjacent oral epithelium and underlying connective tissue) was obtained from the mesial interproximal papilla of the maxillary first molar (or if absent, the mesial tooth). The sample was cleaned using an enzymatic detergent (Riozyme) to mimic the effects of salivary flow and was collected using blunt dissection. The sample was divided into two samples for either histopathological analysis (haematoxylin and eosin stain) or molecular analysis. Real-time reverse transcriptase polymerase chain reaction (rRT-PCR) was used to test for the presence of the envelope (E) gene of SARS-CoV-2. Data on comorbidities, smoking status, period of hospitalisation and time from onset of symptoms to death were also collected.

Data analysis Descriptive analysis was performed and results were presented as a cross tabulation. The presence of SARS-CoV-2 in samples was presented as the rRT-PCR cycle threshold value and the histopathological analysis results were Boolean (that is, presence/absence of vacuolisation or nuclear pleomorphism).

Results A total of seven individuals were examined: four women and three men. The age range was 8-74 years and the range of periods between onset of symptoms and death was 10-31 days. SARS-CoV-2 was detected in five samples, with a mean cycle threshold of 31.38 (range 27.28-36.55). Nuclear pleomorphism and vacuolisation were found in two and three cases, respectively.

Conclusions SARS-CoV-2 genetic material was present in most periodontal tissue samples of individuals with COVID-19. The sample size, however, was small and only included severely ill individuals with prolonged periods of hospitalisation. Consequently, the applicability of the findings to the general population is limited.

Impact of renin-angiotensin system inhibitors and beta-blockers on dental implant stability

BACKGROUND

Current experimental research suggests antihypertensive medication reduces the failure risk of dental implants due to enhanced bone remodeling. However, evidence from clinical studies evaluating the impact of antihypertensive medication on implant stability is lacking.

METHODS

We retrospectively analyzed 377 implants in 196 patients (46 implants inserted in antihypertensive drug users (AH) and 331 implants in non-users (NAH)) for implant stability measured by radiofrequency analysis, and we determined the implant stability quotient (ISQ). AH subgroups were stratified by the use of beta-blockers, renin-angiotensin system (RAS) inhibitors, and both of the aforementioned. The impact of antihypertensive medication on ISQ values at implant insertion (primary stability) and implant exposure (secondary stability) was analyzed by a linear regression model with a regression coefficient and its 95% confidence interval (95% CI), adjusted for potential confounders.

RESULTS

Time between implant insertion and implant exposure was 117.1 ± 56.6 days. ISQ values at insertion were 71.8 ± 8.7 for NAH and 74.1 ± 5.6 for AH, respectively. ISQ at exposure was 73.7 ± 8.1 for NAH and 75.7 ± 5.9 for AH. Regression analysis revealed that none of the AH subgroups were significantly related to ISQ at implant insertion. However, renin-angiotensin system inhibitors (RAS) were significantly associated with higher ISQ values at exposure (reg. coeff. 3.59, 95% CI 0.46-6.71 (p=0.025)).

CONCLUSIONS

Outcome of the present study indicates enhanced bone remodeling and osseointegration following dental implant insertion in patients taking RAS inhibitors than in non-users. Future randomized prospective studies must confirm these indicative results.

Angiotensin-Converting Enzyme 2 as a Possible Correlation between COVID-19 and Periodontal Disease

SARS-CoV-2 propagation in the world has led to rapid growth and an acceleration in the discoveries and publications of various interests. The main focus of a consistent number of studies has been the role of angiotensin-converting enzyme 2 (ACE2) in binding the virus and its role in expression of the inflammatory response after transmission. ACE2 is an enzyme involved in the renin–angiotensin system (RAS), whose key role is to regulate and counter angiotensin-converting enzyme (ACE), reducing the amount of angiotensin II and increasing angiotensin 1–7 (Ang1–7), making it a promising drug target for treating cardiovascular diseases. The classical RAS axis, formed by ACE, angiotensin II (Ang II), and angiotensin receptor type 1 (AT1), activates several cell functions and molecular signalling pathways related to tissue injury and inflammation. In contrast, the RAS axis composed of ACE2, Ang1–7, and Mas receptor (MasR) exerts the opposite effect concerning the inflammatory response and tissue fibrosis. Recent studies have shown the presence of the RAS system in periodontal sites where osteoblasts, fibroblasts, and osteoclasts are involved in bone remodelling, suggesting that the role of ACE2 might have a fundamental function in the under- or overexpression of cytokines such as interleukin-6 (IL-6), interleukin-7 (IL-7), tumour necrosis factor alpha (TNF-α), interleukin-2 (IL-2), interleukin-1 beta (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-beta (TGF-β), associated with a periodontal disorder, mainly during coinfection with SARS-CoV-2, where ACE2 is underexpressed and cannot form the ACE2–Ang1–7–MasR axis. This renders the patient unresponsive to an inflammatory process, facilitating periodontal loss.

Losartan improves the therapeutic effect of metronomic cyclophosphamide in triple negative mammary cancer models

Metronomic chemotherapy refers to the minimum biologically effective doses of a chemotherapy agent given as a continuous regimen without extended rest periods. Drug repurposing is defined as the use of an already known drug for a new medical indication, different from the original one. In oncology the combination of these two therapeutic approaches is called “Metronomics”.

The aim of this work is to evaluate the therapeutic effect of cyclophosphamide in a metronomic schedule in combination with the repurposed drug losartan in two genetically different mice models of triple negative breast cancer.

Our findings showed that adding losartan to metronomic cyclophosphamide significantly improved the therapeutic outcome. In both models the combined treatment increased the mice’s survival without sings of toxicity. Moreover, we elucidated some of the mechanisms of action involved, which include a decrease of intratumor hypoxia, stimulation of the immune response and remodeling of the tumor microenvironment.

The remarkable therapeutic effect, the lack of toxicity, the low cost of the drugs and its oral administration, strongly suggest its translation to the clinical setting in the near future.

Angiotensin II Regulates Proliferation and Function of Stem Cells of Apical Papilla

INTRODUCTION

Stem cells of apical papilla (SCAP) may be affected by inflammatory mediators released by activation with lipopolysaccharide (LPS) from infected pulpal cavities of necrotic immature teeth. Therefore, this study aimed to investigate the presence of a local renin-angiotensin system (RAS) and the role of angiotensin II (Ang II) on the modulation of SCAP in vitro.

METHODS

Primary cultures of SCAP were incubated with LPS (0.1-10 μg/mL) for cell viability and quantification of the chemokine CCL2. Components of RAS were searched by gene expression of angiotensinogen (AGTN), angiotensin converting enzyme (ACE), renin, angiotensin receptor 1 (AT1) and 2 (AT2), and Mas receptor. Ang II was investigated in SCAP supernatants. Immunofluorescence was used to detect AGTN and AT1. Next, cells were treated with Ang II for viability/proliferation assessment, quantification of CCL2 and interleukin 6, and mineralization assay. Data were evaluated by analysis of variance using Tukey post hoc comparisons or the Student t test. P values <.05 were considered to be significant.

RESULTS

LPS increased CCL2 production at 1 and 10 μg/mL. The gene expression of AGTN, renin, ACE, and AT1 was detected, but only ACE was increased by LPS. Ang II peptide was found in SCAP supernatants but unaltered by LPS. Both AGTN and AT1 proteins were detected by immunostaining. Ang II significantly induced SCAP proliferation, increased CCL2 production, down-regulated IL-6 release, and reduced the SCAP mineralization rate.

CONCLUSIONS

A local RAS was found at the apical papilla, and Ang II was able to modulate SCAP function in vitro.

AT1 receptor antagonism promotes bone loss attenuation in experimental periodontitis, blocks inflammatory mediators, and upregulates antioxidant enzymes and bone formation markers

BACKGROUND

The initiation and progression of periodontitis might involve a local renin-angiotensin system in periodontal tissue. This study hypothesized that Losartan treatment could promote protection to rats submitted to experimental periodontitis (EP) by attenuating alveolar bone loss due to reduction in inflammatory cytokines, better reactive oxidant species regulation and maintenance of the balance between bone formation and resorption factors.

METHODS

One hundred and thirty rats were submitted to EP with a silk suture thread (4.0) placed around the lower right first molar for 1, 3, 7, and 14 consecutive days. The study comprised four groups: G1-control without EP; G2-animals with EP treated with water; G3-Losartan-treated animals (treatment started at the same day of EP induction), and G4-animals previously treated with Losartan for 30 days followed by induction of EP and continuity of treatment.

RESULTS

G2 rats had greater bone loss volume, increased number, and thickness and decreased separation of trabeculae. On the other hand, G4 animals showed significant improvements in these parameters. Histological analysis revealed that EP favors inflammatory cell infiltration and junctional epithelium, cementum with alveolar bone crest destruction, but animals pretreated with Losartan (G4) did not show these features. Although the G3 animals did not demonstrate the improvements detected in G4, mRNA expression results were similar. In mandibular tissue, EP promoted mRNA increases for ACE, AT1 receptor, and inflammatory mediators as well as decreases for antioxidant enzymes. However, Losartan treatments attenuated these responses in addition to promoting an increase in bone formation markers and transcription factors.

CONCLUSION

AT1 receptor modulates EP progression.

Developing a periodontal disease antibody array for the prediction of severe periodontal disease using machine learning classifiers

BACKGROUND

The aim of this study was to simultaneously and quantitatively assess the expression levels of 20 periodontal disease-related proteins in gingival crevicular fluid (GCF) from normal controls (NOR) and severe periodontitis (SP) patients with an antibody array.

METHODS

Antibodies against 20 periodontal disease-related proteins were spotted onto a glass slide to create a periodontal disease antibody array (PDD). The array was then incubated with GCF samples collected from 25 NOR and 25 SP patients. Differentially expressed proteins between NOR and SP patients were then used to build receiver operator characteristic (ROC) curves and compare five classification models, including support vector machine, random forest, k nearest neighbor, linear discriminant analysis, and Classification and Regression Trees.

RESULTS

Seven proteins (C-reactive protein, interleukin [IL]-1α, interleukin-1β, interleukin-8, matrix metalloproteinase-13, osteoprotegerin, and osteoactivin) were significantly upregulated in SP patients compared with NOR, while receptor activator of nuclear factor-kappa was significantly downregulated. The highest diagnostic accuracy using a ROC curve was observed for IL-1β with an area under the curve of 0.984. Five of the proteins (IL-1β, IL-8, MMP-13, osteoprotegerin, and osteoactivin) were identified as important features for classification. Linear discriminant analysis had the highest classification accuracy across the five classification models that were tested.

CONCLUSION

This study highlights the potential of antibody arrays to diagnose periodontal disease.