Multiple Apical Periodontitis Influences Serum Levels of Cytokines and Nitric Oxide

Apical periodontitis as an aggravating factor for the severity of rheumatoid arthritis: An animal study

AIM

The present study investigated the influence of apical periodontitis (AP) on the severity of rheumatoid arthritis (RA) using a Wistar rat model.

METHODOLOGY

Forty male Wistar rats were distributed across four groups (n = 10) based on the induction of RA and AP: Control, RA, AP, and RA + AP. RA was induced through two immunisations with type II collagen emulsified in incomplete Freund's adjuvant, followed by one immunisation with complete Freund's adjuvant. After 21 days of RA induction, AP was induced by exposing the pulp of four molars. Animals were euthanized after 28 days of pulp exposure. Through the experiment, visual and behavioural assessments tracked RA development and the knees and hind paw joints were measured. Micro-computed tomography scans of knees and hind paws, as well as mandibles and maxillae, were conducted to evaluate RA severity and the presence of AP, respectively. Serum samples were collected to analyse proinflammatory cytokines (IL-1β, IL-2, IL-17, and TNF-α). Non-parametric data were analysed using the Kruskal-Wallis test followed by Student-Newman-Keuls test, while one-way anova followed by Tukey's test was performed for parametric data. A significance level of 5% was employed.

RESULTS

All molars submitted to access cavity developed AP. All joints subjected to arthritis induction developed the disease, with AP + RA demonstrating a higher arthritis severity when compared to the RA group (p < .05). RA + AP group displayed a significantly larger hind paw and knee circumference compared to the RA group (p < .05). Micro-CT images of RA and RA + AP groups revealed joints with erosions and bone deformities, with a significantly lower bone surface density, lower trabecular number and higher trabecular separation in the hind paw and a significantly lower percent bone volume and higher trabecular separation in the knees of RA + AP group compared to RA group (p < .05). RA + AP group exhibited a significantly higher level of TNF-α and a lower level of IL-2 compared to all other groups (p < .05). Both RA and RA + AP groups had significantly higher IL-17 levels (p < .05), while there was no significant difference in IL-1β levels among the groups (p > .05).

CONCLUSION

The findings from this study underscore a possible relationship between apical periodontitis and the exacerbation of rheumatoid arthritis.

The role of infection in signalling root resorption: A narrative review

BACKGROUND

Root resorption consists of complex, multistep processes that involve cell signalling caused by inflammation and stromal cells, which promotes the secretion of receptor activator of nuclear factor κB ligand/ macrophage-colony stimulating factor (RANKL/M-CSF) resulting in a resorptive process.

OBJECTIVE

The aim of this narrative review was to analyse the literature related to root resorption resulting from microbial infection and to comparing it with non-microbial infection.

METHODS

An electronic literature search was performed using the PubMed database and applying keywords of articles published in English. Eligible papers were reviewed to reveal the descriptions of bone and root resorption processes. The abstracts were searched manually to identify articles about infection-stimulating bone and root resorption.

RESULTS

Three main types of root resorption were identified, two associated with primary bacterial infection and one secondary to bacterial infection. These include external inflammatory resorption, internal inflammatory resorption and external cervical (invasive) resorption.

DISCUSSION

The magnitude of cytokine involvement that promotes resorption and M-CSF/RANKL production depends on multiple factors, including pathogen virulence, site of infection and host genetic factors that activate the inflammation at the infection site. Two mechanisms activate the resorption mechanisms-the canonical and non-canonical pathways that can activate clastic cells independently of the RANKL/RANK canonical pathways.

CONCLUSIONS

Two pathways of root resorption co-exist in the body. When resorption is caused by infection, chronic inflammation due to bacterial infection prolongs the secretions of pro-inflammatory cytokines that intensify root and bone resorption. The second pathway is bacterial independent of the non-infection root resorption that is part of the wound healing process, which is limited in time due to its innate ability.

Effects of melatonin against experimentally induced apical periodontitis in rats

Apical periodontitis is an inflammatory condition resulting from microbial invasion in the root canal system, causing periapical tissue destruction and bone resorption. This study investigated melatonin's effects, known for its antioxidant and anti-inflammatory properties, on experimentally induced apical periodontitis in rats. Three groups of rats were studied: control, apical periodontitis and apical periodontitis with melatonin treatment. Proinflammatory cytokines and enzyme levels in blood serum were measured, and micro-CT analysis assessed bone resorption. Results showed significantly elevated cytokines and enzyme levels in the apical periodontitis group compared to the control. However, in the melatonin-treated group, these levels were significantly reduced (p < 0.01-0.001). Micro-CT analysis indicated decreased periapical resorption cavity volume and surface area with melatonin treatment. This suggests that systemic melatonin administration can mitigate inflammation and reduce bone resorption in experimentally induced apical periodontitis in rats, potentially holding promise for human endodontic disease treatment pending further research.

Systemic administration of propranolol reduces bone resorption and inflammation in apical periodontitis of chronically stressed rats

AIM

To evaluate the effect of systemic administration of propranolol on the severity of apical periodontitis (AP) in chronically stressed rats.

METHODOLOGY

Twenty-four 70-day-old male Wistar rats (Rattus norvegicus, albinus) were distributed into three groups (n = 8): rats with AP without stressful conditions (AP-Control), rats with AP and submitted to a chronic unpredictable stress (CUS) protocol (AP + S) and rats with AP and submitted to a CUS protocol treated with propranolol (AP + S + PRO). Stress procedures were applied daily until the end of the experiment. After 3 weeks of CUS, AP was induced in all groups by exposing the pulpal tissue of mandibular and maxillary first molars to the oral environment. Propranolol treatment was administered orally once a day for the entire period of the experiment. Rats were sacrificed at 42 days, and the blood was collected for stress biomarkers serum dosage by multiplex assay. Mandibles were removed and submitted to microtomography and histopathological analyses. Periapical tissue surrounding the upper first molar was homogenized and subjected to RT-PCR analysis to evaluate the mRNA expression of RANKL, TRAP and OPG. Parametric data were assessed using one-way ANOVA followed by Tukey's test while the nonparametric data were analysed by the Kruskal-Wallis followed by Dunn's test. Significance level was set at 5% (p < .05) for all assessed parameters.

RESULTS

Micro-CT revealed statistically significant differences in bone resorption which was greater in the AP + S group (p < .05), but no differences were observed between the Control and AP + S + PRO groups (p > .05). The AP + S + PRO group had a lower intensity and extent of inflammatory infiltrate compared to the AP + S group with smaller areas of bone loss (p < 0.05). The gene expression of RANKL and TRAP was significantly higher in the stressed group AP + S compared to the control group (p < .05), and a significantly higher OPG expression was observed in AP + S + PRO compared to the AP + S group (p < .05).

CONCLUSIONS

Oral administration of propranolol had a significant effect on the AP severity in stressed rats, suggesting an anti-inflammatory effect and a protective role on bone resorption of AP in stressed animals. Further research is necessary to fully comprehend the underlying mechanisms.

Increase Toll-like receptors 2 and 4 in apical periodontitis of rats with chronic liver disease

The aim of this study was to evaluate the influence of liver fibrosis (LF) on the expression of Toll-like receptors (TLR) 2 and 4 in apical periodontitis (AP) in Wistar rats. Forty Wistar rats were allocated in the following groups (n = 10): C-control; AP-apical periodontitis; LF-liver fibrosis; AP + LF-rats with AP and LF. LF and AP were induced by established methodologies. Histological, bacteriological, and immunohistochemical analyses were performed according to pre-established scores. For comparisons between AP and AP + LF groups, the Mann-Whitney test was used (P < .05). The livers of the LF and AP + LF groups showed generalized portal inflammatory infiltrate and collagen fibers confirming the presence of LF. Histopathological analysis in the maxilla of the AP + LF group showed areas of necrosis comprising the entire dental pulp and periapical tissue surrounded by a more intense inflammatory infiltrate than observed in the AP group (P = 0.032). A significant number of specimens in the AP + LF group showed microorganisms beyond the apical foramen adhered to the extraradicular biofilm, demonstrating greater invasion compared to the AP group (P = .008). Immunohistochemical analysis showed a large number of cells immunoreactive for TLR2 and TLR4 in the AP + LF group, compared to the AP group (P < 0.05). Liver fibrosis favors the inflammation and contamination of microorganisms in apical periodontitis and triggers the expression of TLR2 and TLR4, modulating innate immunity response in periapical lesions.

Correlation Between Proinflammatory Cytokine Expression and Clinical Data in Apical Granuloma

INTRODUCTION

This study was intended to evaluate the expression of inflammatory cytokines commonly secreted by CD4+ T cells (IL-2, IL-5, IL-17, TGF-β, TNF-α, and IFN-γ) in apical granulomas and correlate with the clinical conditions and time elapsed since root canal treatment.

METHODS

Eighteen biopsy specimens obtained by periradicular surgery of teeth with post-treatment apical periodontitis and diagnosed as apical granuloma were available from the oral pathology laboratory. Silanized slides containing paraffin sections were used for immunohistochemical reactions. Images were analyzed by using an optical microscopy and each slide was subdivided into 5 fields at high magnification.

RESULTS

IFN-γ and TGF-β were the cytokines with the highest expression levels. There were statistically significant differences when comparing IL-2 and IFN-γ (P < .05), and IL-2 and TGF-β (P < .05). Comparison between the detected cytokines and clinical data and time of treatment demonstrated significant correlation (P < .05) between lower expression of IL-2 and the presence of painful symptoms, absence of sinus tract, and treatments performed more than 4 years before. It was also possible to observe a significant correlation between lower expression of IL-5 and treatments performed less than 4 years before (P < .05).

CONCLUSION

IFN-γ and TGF-β were highly expressed in apical granulomas. However, only IL-2 and IL-5 levels were associated with clinical data and time since previous root canal treatment.

Experimental apical periodontitis alters salivary biochemical composition and induces local redox state disturbances in the salivary glands of male rats

OBJECTIVES

The objective was to evaluate the effects of experimental apical periodontitis on the inflammatory, functional, biochemical, and redox parameters of the parotid and submandibular glands in rats.

MATERIALS AND METHODS

Twenty 12-week-old male Wistar rats were randomly divided into two groups (n = 10): a control group and apical periodontitis group. After 28 days, the saliva was collected for salivary flow rate and biochemistry composition. Both glands were sampled for quantification of the tumor necrosis factor-alpha (TNF-α) and biochemical analyses of redox state.

RESULTS

TNF-α concentrations were higher in both salivary glands adjacent to the periapical lesions in animals with apical periodontitis and also compared to the control group. The apical periodontitis group increased the salivary amylase, chloride, potassium, calcium, and phosphate. The total oxidant capacity increased in the parotid gland adjacent to the periapical lesions in the same rat and compared to the control group. Conversely, the total antioxidant capacity of the parotid glands on both sides in the apical periodontitis group was lower than that in the control group. Furthermore, glutathione peroxidase activity increased in the submandibular gland adjacent to the apical periodontitis group compared to the control group.

CONCLUSIONS

Experimental apical periodontitis alters salivary biochemical composition, in addition to increasing inflammatory marker and inducing local disturbances in the redox state in the parotid and submandibular glands of male rats.

CLINICAL RELEVANCE

Apical periodontitis could exacerbate the decline in oral health by triggering dysfunction in the salivary glands.

Effects of N-acetyl-L-cysteine against apical periodontitis in rats with adriamycin-induced cardiomyopathy and nephropathy

AIM

This study aimed to investigate the potential protective effects of N-acetyl-L-cysteine (NAC) against apical periodontitis (AP) in rats with adriamycin (ADR)-induced kidney and heart diseases.

METHODOLOGY

Fourty-eight Wistar albino rats were divided into six groups: (1) Control group, (2) ADR group (1 mg/kg/day ip for 10 days), (3) AP Group (1st mandibular molar tooth), (4) AP + ADR Group, (5) AP + NAC group (150 mg/kg/day ip), and (6) AP + ADR + NAC group. After 3 weeks, the rats were decapitated and blood and tissue samples (heart, kidney, and jaw) were collected. Tissue samples were evaluated by biochemical (inflammatory cytokines and hemodynamic parameters) and radiological analyses. One-way anova with Tukey post hoc tests was used to compare data, considering p < .05 as statistically significant.

RESULTS

The serum levels of TNF-α, IL-1β, BUN, Creatinine, CK, and LDH were elevated in the test groups compared with the control group, and treatment with NAC reduced these levels (p < .05). Heart and kidney tissue analysis showed a higher heart-to-body weight ratio (HW/BW) and kidney-to-body weight ratio (KW/BW) in the test groups compared with the control group (p < .05). No significant differences in HW/BW and KW/BW were found between the control and AP + NAC groups. Volumetric apical bone resorption analysis showed an increase in periapical radiolucencies in AP-induced groups indicating apical periodontitis. NAC treatment reduced the total area and volume of resorption cavities (p < .05).

CONCLUSIONS

The results suggest that NAC's antioxidant and anti-inflammatory effects can reduce adriamycin-mediated heart and kidney damage and may have a positive effect on apical periodontitis in individuals with nephropathy and cardiomyopathy.

Primary apical periodontitis correlates to elevated levels of interleukin-8 in a Swedish population: A report from the PAROKRANK study

AIM

To explore associations between root filled teeth, primary and secondary apical periodontitis, and levels of inflammatory markers in blood from patients with a first myocardial infarction and matched controls.

METHODOLOGY

Between May 2010 and February 2014, 805 patients with a first myocardial infarction and 805 controls, matched for sex, age, and postal code area, were recruited to the multicentre case-control study PAROKRANK (periodontitis and its relation to coronary artery disease). All participants underwent a physical and oral examination, as well as blood sampling. Using panoramic radiography, root filled teeth, primary apical periodontitis, and secondary apical periodontitis were assessed by three independent observers. Blood samples were analysed with enzyme-linked immunosorbent assay method for the following inflammatory markers: interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-12p70, tumour necrosis factor-α, and high-sensitivity C-reactive protein (hsCRP). Additionally, white blood cell count and plasma-fibrinogen were analysed. Associations between endodontic variables and the levels of inflammatory markers were statistically analysed with Mann-Whitney U-test and Spearman correlation, adjusted for confounding effects of baseline factors (sex, age, myocardial infarction, current smoking, diabetes, family history of cardiovascular disease, education, marital status, and periodontal disease).

RESULTS

Mean age of the cohort was 62 years, and 81% were males. Root fillings were present in 8.4% of the 39 978 examined teeth and were associated with higher levels of hsCRP, fibrinogen, and leukocyte count, but lower levels of IL-2 and IL-12p70. After adjusting for confounders, root filled teeth remained associated with higher levels of fibrinogen, but lower levels of IL-1β, IL-2, IL-6, and IL-12p70. Primary apical periodontitis was found in 1.2% of non-root filled teeth and associated with higher levels of IL-8 (correlation 0.06, p = .025). Secondary apical periodontitis was found in 29.6% of root filled teeth but did not relate to the levels of any of the inflammatory markers.

CONCLUSIONS

This study supports the notion that inflammation at the periapex is more than a local process and that systemic influences cannot be disregarded. Whether the observed alterations in plasma levels of inflammatory markers have any dismal effects on systemic health is presently unknown but, considering the present results, in demand of further investigation.

Effects of Nd: YAG laser on tumour necrosis factor-alpha, interleukin-1beta and interferon-gamma levels in teeth with apical periodontitis: A clinical study

This study aimed to evaluate the levels of tumour necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and interferon-gamma (IFN-γ) with asymptomatic apical periodontitis (AP). A total of 60 participants were randomly divided into two groups: the conventional irrigation (control) and the Nd: YAG laser irradiation. The interstitial fluids were obtained after root canal cleaning (day 0) and 1 week later (day 7). The TNF-α, IL-1β and IFN-γ levels were assayed using the enzyme-linked immunosorbent assay. The Mann-Whitney U, continuity correction chi-square, Pearson chi-square and Fisher exact tests were used. An increased level of cytokines on day 7 in the control group was observed, without statistically significant differences (p > 0.05). All cytokine levels decreased over time in the laser group. Only the IL-1β level showed a significant difference (p < 0.05). Nd: YAG irradiation has a positive effect on decreasing the proinflammatory cytokine level and may help to control infection in teeth with AP.

Effects of cigarette smoke inhalation on the immune-inflammatory profile of experimental apical periodontitis in rats

OBJECTIVE

To evaluate the effects of cigarette smoke inhalation on the immune-inflammatory profile of experimental apical periodontitis in rats.

METHODOLOGY

In total, 32 male Wistar rats were divided into four groups (n = 8): AP-induced apical periodontitis; S-cigarette smoke inhalation; APS-induced AP and cigarette smoke inhalation; and C (control)-neither AP nor cigarette smoke inhalation. To induce cigarette smoke inhalation, the animals were kept in a chamber filled with tobacco smoke for 8 min thrice a day for 50 days. AP was induced 20 days after inhalation initiation by exposing their coronary pulp to their oral environment for 30 days. After animals were euthanized, their right hemimaxillae were removed for histopathological, semi-quantitative and immunohistochemical (F4/80, CD206 and iNOS) analyses.

RESULTS

Quantitative data showed a moderate number of inflammatory infiltrates in AP and an intense number in APS (p < .05). Comparing F4/80+ cells showed no statistically significant differences among groups, but we found more CD206+ cells in AP than in C and S (p > .05). INOS+ immunostaining showed a significant increase in AP and APS, when compared with C and S (p < .05). APS had more iNOS+ cells than AP (p < .05).

CONCLUSION

Cigarette smoke inhalation worsened AP, leading to a predominantly pro- inflammatory profile in our experimental model.

Evaluation of Serum Levels of Cytokines in Acute Apical Abscess: A Longitudinal Observational Study

INTRODUCTION

Cytokine levels are related to the aethiopathogenia of acute apical abscesses (AAA); however, the specific cytokine profiles in these cases are unclear. This study aimed to investigate the changes in systemic cytokine levels in patients with AAA and trismus onset, postantibiotic treatment, and postroot canal disinfection.

METHODS

In total, 46 AAA patients with trismus and 32 control subjects were included. After seven days of antibiotic therapy, root canal disinfection was performed in the AAA patients. The serum levels of cytokines were evaluated at basal, seven, and 14 days after endodontic treatment. Quantification of cytokines from T helper (Th) 1, Th2, Th17, and regulatory T cells profiles was determined using the BioPlex MagPix system, and the obtained data were analyzed using SPSS statistical software (P < .05).

RESULTS

AAA patients showed higher tumor necrosis factor-alpha (TNF-α), interleukin (IL) -6, and IL-10 levels than control subjects, at basal measurement (P < .05); there were similar levels of interferon gamma, IL-1β, IL-4, and IL-17 between groups (P > .05). IL-6 and IL-10 levels decreased after antibiotic treatment (P < .05), which was also associated with clinical improvement in patients with AAA and trismus. Patients with AAA had a positive correlation with higher serum levels of IL-6 and IL-10. In addition, TNF-α levels decreased only after antibiotic and endodontic treatment.

CONCLUSIONS

In conclusion, patients with AAA had increased systemic serum levels of TNF-α, IL-6, and IL-10. Moreover, increased levels of IL-6 and IL-10 are associated with acute inflammatory symptoms. However, IL-6 and IL-10 levels decreased after antibiotic treatment, while TNF-α levels decreased after antibiotic and endodontic treatment.

Effectiveness of probiotics in apical periodontitis progression: A scoping review and implications for research

To synthesise the current knowledge on the effects of probiotics in apical periodontitis progression by a scoping review of animal and human studies. Reporting was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. The literature search and screening was performed on PubMed and Scopus databases by two independent reviewers selecting human and animal studies that evaluated the effectiveness of probiotics in reducing the severity of apical periodontitis. Two animal studies with 3 publications met the eligibility criteria for qualitative synthesis. The most common probiotics were Lactobacillus rhamnosus and Lactobacillus acidophilus orally administered for gavage in Wistar rats with induced apical periodontitis. Overall, probiotics significantly reduced inflammation and bone resorption with an improvement in the apical periodontitis progression. Although results in animal studies are promising, the use of probiotics in apical periodontitis progression requires caution due to the insufficient available evidence.

Modulatory influence of melatonin on apical periodontitis in Wistar rats fed a high-fat diet

OBJECTIVE

This study aimed to evaluate the influence of high-fat diet (HFD) and melatonin (MEL) treatment on the progression of inflammation and alveolar bone resorption (ABR) in rats with AP.

DESIGN

Forty male Wistar rats were divided into four groups: apical periodontitis (AP), HFDAP, APMEL and HFDAPMEL. The animals were fed an HFD or standard diet for 107 days. On the 7th day, the rats were subjected to AP, and after 70 days, the rats in the MEL groups were treated with MEL for 30 days. Post treatment, the animals were euthanized, and their jaws were retrieved for evaluation of bone resorption, intensity of the inflammatory response, and immunohistochemical analysis including tartrate-resistant acid phosphatase (TRAP) and interleukin-1β (IL-1β) levels and tumor necrosis factor (TNF)-α expression.

RESULTS

The APMEL group showed reduction in the inflammatory infiltrate and IL-1β expression relation to HFDAP, while the TNF-α levels did not differ among the groups. The HFDAP group showed an increase in the ABR. MEL reduced the TRAP levels in the APMEL and HFDAPMEL groups.

CONCLUSIONS

while MEL could reduce TRAP levels in the APMEL and HFDAPMEL groups, the reduction in the HFDAPMEL group was smaller than that in the APMEL group, demonstrating that the interaction between AP and HFD decreased the anti-resorptive effects of MEL.

Inflammatory profile of apical periodontitis exacerbated by cigarette smoke inhalation: Histological and immunohistochemical analysis in rats

AIM

The aim of this study was to evaluate the effects of cigarette smoke inhalation (CSI) on inflammation, pro-inflammatory mediators and haematological parameters in rats with induced apical periodontitis (AP).

METHODOLOGY

Thirty-two 3-month-old male Wistar rats were divided into four experimental groups (n = 8): C-Control; S-rats with CSI; AP-rats with AP; and SAP-rats with CSI + AP. Animals in groups S and SAP inhaled cigarette smoke by remaining inside a smoking chamber for 8 min, three times daily, for 50 days. After 20 days of smoke inhalation, animals in AP and SAP groups had the pulps of the lower right first molar exposed to oral environment for 30 days to induce AP. In these subsequent 30 days, animals in group S and SAP continued with CSI. On Day 50, animals were euthanized and mandibles were histologically processed to assess inflammatory infiltrate, immunohistochemical interleukins (IL-1β, IL-6 and TNF-α), and blood samples collected for laboratory analysis. The Mann-Whitney test was performed for non-parametric data and the pairwise analyses of Student's t-test for parametric data, with a significance level of p < .050.

RESULTS

Inflammatory infiltrate was moderate in AP group and more severe in the SAP (p = .010). The interleukins IL-6, IL-1β and TNF-α were higher in SAP group (p < .001) when compared to the AP group. A greater number of red blood cells (p = .010), haemoglobin (p = .007) and neutrophils (p = .014) were observed in the SAP group in comparison with the AP group.

CONCLUSION

Cigarette smoke inhalation induced a more severe inflammatory infiltrate, with increased levels of pro-inflammatory cytokines and changes in haematological parameters in rats with induced AP. Thus, CSI aggravated AP, exacerbating the inflammatory response.

DNER and GNL2 are differentially m6A methylated in periodontitis in comparison with periodontal health revealed by m6A microarray of human gingival tissue and transcriptomic analysis

OBJECTIVE

This study aims to investigate the differences in the epigenomic patterns of N6-methyladenosine (m6A) methylation in gingival tissues between patients with periodontitis (PD) and healthy controls, identifying potential biomarkers.

BACKGROUND

As a multifactorial disease, PD involves multiple genetic and environmental effects. The m6A modification is the most prevalent internal mRNA modification and linked to various inflammatory diseases. However, the m6A modification pattern and m6A-related signatures in PD remain unclear.

MATERIALS AND METHODS

An m6A microarray of human gingival tissues was conducted in eight subjects: four diagnosed with PD and four healthy controls. Microarray analysis was performed to identify the differentially m6A methylated mRNAs (DMGs) and the differentially expressed mRNAs (DEGs). The differentially methylated and expressed mRNAs (DMEGs) were subjected to functional enrichment analysis by Metascape. The weighted gene co-expression network analysis (WGCNA) algorithm, the least absolute shrinkage and selection operator (LASSO) regression, and univariate logistic regression were performed to identify potential biomarkers. The cell type localization of the target genes was determined using single-cell RNA-seq (scRNA-seq) analysis. The m6A methylation level and gene expression of hub genes were subsequently verified by m6A methylated RNA immunoprecipitation (MeRIP) and quantitative real-time PCR (qRT-PCR).

RESULTS

In total, 458 DMGs, 750 DEGs, and 279 DMEGs were identified based on our microarray. Pathway analyses conducted for the DMEGs revealed that biological functions were mainly involved in the regulation of stem cell differentiation, ossification, circadian rhythm, and insulin secretion pathways. Besides, the genes involved in crucial biological processes were mainly expressed in fibroblast and epithelial cells. Furthermore, the m6A methylation and expression levels of two hub biomarkers (DNER and GNL2) were validated.

CONCLUSION

The current study exhibited a distinct m6A epitranscriptome, identified and verified two PD-related biomarkers (DNER and GNL2), which may provide novel insights into revealing the new molecular mechanisms and latent targets of PD.

Melatonin decreases plasma TNF-α and improves nonenzymatic antioxidant defence and insulin sensitivity in rats with apical periodontitis fed a high-fat diet

AIM

To analyse the effects of melatonin (ME) treatment on oxidative stress and insulin resistance (IR) in rats with apical periodontitis (AP) fed a high-fat diet (HFD).

METHODOLOGY

Eighty 60-day-old rats were divided into eight groups: control (CN), AP, HFD with AP (HFDAP), control with ME (CNME), AP with ME (APME), HFD with ME (HFDME) and HFD with AP+ME (HFDAPME). The animals from the HFD groups were fed a HFD throughout the experimental period. On day 7, the animals from the AP groups were subjected to experimental AP, and after 70 days, the ME groups were treated for 30 days. Glycaemia, insulinaemia, homeostatic model assessment for IR index, tumour necrosis factor-α (TNF-α), and interleukin-6 were analysed in plasma using biochemical tests and enzyme-linked immunosorbent assay. Thiobarbituric acid-reactive substances (TBARS), carbonyl protein (CP), superoxide dismutase (SOD), catalase, glutathione peroxidase, glutathione (GSH) and total antioxidant capacity (ferric reducing antioxidant power [FRAP]) were analysed in the gastrocnemius muscle.

RESULTS

(1) Association of AP and HDF exacerbated IR, and ME treatment improved this alteration; (2) AP and HFD and their association showed increased TNF-α, and ME reversed it; (3) TBARS increased in the AP and HFDAP groups, and ME reversed only in the group with the association of disease and diet; (4) CP increased in all HFD groups and improved in the ME groups; (5) GSH activity decreased in all experimental groups, and ME increased this parameter only in the CN and AP groups; (6) FRAP did not change between the groups, but ME treatment increased its activity in the AP and HFD groups; (7) ME increased SOD in the CN and AP groups.

CONCLUSION

Apical periodontitis and HFD promoted IR, and the association of AP with diet promoted IR exacerbation; this resistance might have been caused by an increase in TNF-α. AP promoted more intense changes in lipid oxidative damage than in protein oxidative damage. In non-enzymatic antioxidant defence, it was observed that both AP and HFD and their association promoted a decrease in GSH levels. Overall, ME treatment reversed changes such as oxidative stress and IR.

Early life stress exacerbates bone resorption and inhibits anxiety-like behaviour induced by apical periodontitis in rats

AIM

To evaluate the influence of the early life stress (ELS) on the severity of the apical periodontitis (AP) in Wistar rats.

METHODOLOGY

Forty male Wistar rats were divided into four groups (n = 10): Control rats; AP-rats with AP; ELS-rats subject to ELS; AP + ELS-rats exposed to ELS and subject to AP. ELS was induced by maternal separation (MS) for a period of 3 h for 21 consecutive days. AP was induced via pulp exposure of the first and second right maxillary molars to the oral environment for 40 days. Three days before euthanasia, all rats underwent behavioural analysis to measure anxiety levels by elevated zero maze. Then, the rats were euthanized and the maxillas were removed to assess the occurrence and severity of AP. The periapical region was evaluated for the intensity of the inflammatory infiltrate and the extent of bone loss. The Mann-Whitney test was performed for nonparametric data, and the Tukey's or Student's t-test was performed for parametric data (p < .05).

RESULTS

The intensity of the inflammatory infiltrate was significantly larger in the AP + ELS group when compared with AP group (p < .05). The AP + ELS group exhibited significantly greater alveolar bone loss, with a periapical lesion size of 103.5 ± 29.88, compared with 72.3 ± 22.28 in the AP group (p < .05). Rats with AP displayed higher anxiety-like behaviour in relation to the control group (p < .05). However, exposure to ELS abolished the AP-induced increased anxiety-like 'behaviour' throughout, since that rats from AP + ELS group attended more the open arms than non-stressed rats with AP (p < .05).

CONCLUSION

Early life stress is predictive of the severity of AP exacerbating the inflammatory process and increasing periapical bone resorption.

Melatonin decreases IRF-3 protein expression in the gastrocnemius muscle, reduces IL-1β and LPS plasma concentrations, and improves the lipid profile in rats with apical periodontitis fed on a high-fat diet

To evaluate the effects of melatonin (MEL) on the expression of toll-like receptor-4 (TLR4); myeloid differentiation primary response protein-88 (MyD88); TIR-domain-containing adapter-inducing interferon-β (TRIF); IFN regulatory-factor-3 (IRF-3); nuclear factor kappa-B (NF-κB); plasma concentrations of interleukin-1β (IL-1β) and lipopolysaccharide (LPS); and lipid profile of rats with apical periodontitis (AP) fed on a high-fat diet (HFD). Eighty 60-day-old rats were divided into eight groups: control, AP, HFD, HFDAP, CNMEL, APMEL, HFDMEL and HFDAPMEL. HFD groups were fed on a HFD for 107 days. On day 7, experimental AP was induced in the AP groups, and after 70 days, MEL (5 mg/kg) was administered to the MEL groups for 30 days. Plasma concentrations of LPS and IL-1β were analyzed using enzyme-linked immunosorbent assay, and the lipid profile was analyzed using biochemical tests. The expression of proteins involved in the TLR4 pathway (TLR4, MyD88, TRIF, IRF-3 and NF-κB) in the gastrocnemius muscle (GM) was evaluated using western blotting and qRT-PCR. Treatment with MEL decreased IRF-3 protein expression in GM and IL-1β plasma concentration in the APMEL and HFDMEL groups. Reduction in LPS plasma concentration was reported only in the HFDMEL group. Additionally, a decrease in LDL and an increase in HDL were observed in the HFDMEL and HFDAPMEL groups. Treatment with MEL exhibited anti-inflammatory and anti-hyperlipidemic effects attributed to HFD and AP by reducing the plasma concentrations of IL-1β and LPS in addition to reducing IRF-3 protein expression in the GM, which is associated with the production of inflammatory cytokines.

Curcumin reduces inflammation in rat apical periodontitis

AIM

To evaluate the effect of systemic curcumin administration on the severity of apical periodontitis (AP).

METHODOLOGY

Forty male Wistar rats weighing 250-280g each, age 2.5 months, were distributed into four groups (n=10): control untreated rats (C), control rats treated with curcumin (CUR), rats with pulp exposure-induced apical periodontitis (AP), and rats with pulp exposure-induced apical periodontitis treated with curcumin (AP-CUR). Curcumin treatment was administered orally once daily for 15 days before pulp exposure and continued for 30 days after pulp exposure. The rats were sacrificed at 30 days, and the jaws were collected and reconstructed in a program specific for micro-CT. The jaws were processed for analysis of the inflammatory process using Haemotoxylin and Eosin staining and immunohistochemical assays for interleukin tumour necrosis factor alpha (TNF-α), interleukin (Il)-6, and Il-1β. Tartrate-resistant acid phosphatase (TRAP) and osteocalcin (OCN) staining were used to analyze the resorptive process on the bone surface of periapical area. Kruskal-Wallis with Dunn's test was performed for nonparametric data, and ANOVA with Tukey's test for parametric data, p < .05.

RESULTS

Micro-CT revealed no statistically significant differences in bone resorption between the AP and AP-CUR groups (p > .05). The levels of inflammatory cell infiltration and immunoreactivity for the proinflammatory cytokines TNF-α, Il-6, and Il-1β were significantly higher in the periapical lesions of the AP group than in the AP-CUR group (p < .05). The number of TRAP-positive multinucleated cells was higher in the AP group than in the AP-CUR group (p < .05). In OCN-positive cells, no differences were observed between the AP and AP-CUR groups (p > .05).

CONCLUSIONS

Oral supplementation with curcumin had a significant effect on the AP severity in rats, suggesting an anti-inflammatory effect of curcumin on AP development.

Oral inflammatory burden and carotid atherosclerosis among stroke patients

INTRODUCTION

This study aimed to test the hypothesis that oral inflammatory burden (OIB) is independently associated with the carotid atherosclerotic burden (CAB) among individuals with ischemic stroke (IS) or transient ischemic attack (TIA).

METHODS

This cross-sectional observational study included 240 hospital patients with the diagnosis of IS or TIA. The main exposures were apical periodontitis (AP), root canal treatment (RCT), and crestal alveolar (periodontal) bone loss (BL), and the main outcome was the CAB. Exposure and outcome variables were measured through a head and neck multidetector computed tomography angiography and CAB was dichotomized in <50% and ≥50% vessel occlusion. OIB scored as a composite measure of the endodontic and periodontal disease exposure. Hospital health records provided information on socio-demographic and medical covariates. Prevalence ratios (PR) were calculated through Poisson regression models, estimating the relationship between the oral exposures and CAB, with =5%.

RESULTS

Mean age was 62.15 ± 13.1 years, with 56.7% males. Univariate analyses showed that AP≥2 (PR=1.83,95%CI=1.05-3.17) and endodontic burden (EB) (AP &/or RCT≥2) (PR=1.98,95%CI=1.13-3.47) were associated with CAB ≥50%. Multivariate models, adjusted for socio-demographic and medical covariates, revealed that pooled periodontal and endodontic parameters (OIB= BL ≥5mm & EB ≥2) was independently associated with CAB ≥50% (PR=2.47,95%CI= 1.04-5.87).

CONCLUSION

A higher OIB was independently associated with increased levels of CAB among IS or TIA hospital patients. The combination of endodontic and periodontal parameters strengthened the observed association and should be evaluated in future studies on the relationship between oral health and cardiovascular outcomes.

Apical periodontitis promotes insulin resistance and alters adaptive immunity markers in rats

•

Periapical lesions promotes higher T-bet expression and lower GATA3 and FOXP3 expression.

•

Periapical lesion promotes increased GATA3 and decreased FOXP3 expression in the group with 4 periapical lesions (4PL)

•

The adaptive immune system, with a predominance of the Th1 polarization, may be involved in the development of insulin resistance in rats with Periapical lesions.

Objective

Apical periodontitis (AP) is a chronic or acute inflammatory disease usually developed from endodontic infections, predominantly due to gram-negative anaerobic bacteria invading the dental pulp. This study aimed to evaluate lymphocyte markers to assess the involvement of adaptive immunity in insulin resistance (IR) in a rat model of AP.

Design.

Forty-five male Wistar albino rats were divided into 3 groups (control, 1AP and 4AP). AP was induced in the upper right first molar (1AP), and in the first and second upper and lower right molars (4AP). The spleen was collected to evaluate the expression of transcription factors involved in lymphocyte polarization, including T-bet (Th1), GATA3 (Th2), and FOXP3 (Treg). Blood samples were assessed for serum cytokine levels transcribed by the respective lymphocyte polarizations, INF-γ (Th1), IL-4 (Th2) and TGF-β (Treg). In addition, glucose and insulin levels were measured to evaluate IR by the HOMA-IR method.

Results

The results showed higher T-bet expression on AP groups, along with lower GATA3 and FOXP3 expression in the 1AP, in addition to increased GATA3 and decreased FOXP3 expression in the 4AP group compared to the CN group. There was no difference in the INF-γ levels, while IL-4 was decreased in the AP groups. Taken together, these results suggest that the adaptive immune system, with a predominance of the Th1 polarization, may be involved in the development of IR in rats with AP.

Conclusions

AP promotes increase in the expression of T-bet (4AP) and decrease of FOXP3 expressions and IL-4 levels (1AP and 4AP). However, depending on the number of lesions (1 or 4 lesions), the expression of GATA3 appears differently. Thus, innate immunity and adaptive immunity may contribute to the IR observed in rats with AP.

Periapical lesions in two inbred strains of rats differing in immunological reactivity

AIM

To investigate the influence of strain differences in immune responses on the pathogenesis of experimental periapical lesions in Dark Agouti (DA) and Albino Oxford (AO) inbred strains of rats.

METHODOLOGY

Periapical lesions were induced in male DA and AO rats by pulp exposure of the first mandibular right molars to the oral environment. Animals were killed 21 days after pulp exposure. The mandibular jaws were retrieved and prepared for radiographic, pathohistological, immunohistochemical analysis, real-time PCR and flow cytometry. Blood samples and the supernatant of periapical lesions were collected for measurement of cytokines and oxidative stress marker levels. Statistical analysis was performed using the Kruskal-Wallis H and Mann-Whitney U non-parametric tests or parametric One-Way anova and Independent Samples T-test to determine the differences between groups depending on the normality of the data. A significant difference was considered when p values were <.05.

RESULTS

DA rats developed significantly larger (p < .05) periapical lesions compared to AO rats as confirmed by radiographic and pathohistological analysis. The immunohistochemical staining intensity for CD3 was significantly greater in periapical lesions of DA rats compared to AO rats (p < .05). In DA rats, periapical lesions had a significantly higher (p < .05) percentage of CD3+ cells compared to AO rats. Also, the percentage of INF-γ, IL-17 and IL-10 CD3+CD4+ cells was significantly higher in DA rats (p < .05). DA rats had a significantly higher Th17/Th10 ratio. RT-PCR expression of IL-1β, INF-γ and IL-17 genes was significantly higher in periapical lesions of DA compared to AO rats (p < .05). The receptor activator of nuclear factor kappa-Β ligand/osteoprotegerin ratio was higher in DA compared to AO rats with periapical lesions (p < .05). Systemic levels of TNF-α and IL-6 were significantly higher in DA compared to AO rats (p < .05). Levels of lipid peroxidation measured as thiobarbituric acid reactive substances and reduced glutathione were significantly higher (p < .05) in the supernatant in the periapical lesions of DA rats.

CONCLUSION

After pulp exposure, DA rats developed much larger periapical lesions compared to AO rats. Genetically determined differences in immunopathology have been demonstrated to be a significant element defining the severity of periapical lesions.

Serum levels of inflammatory markers and HbA1c in patients with type 2 diabetes and apical periodontitis: Preliminary findings

This pilot study assessed the glycaemic control and the serum levels of inflammatory mediators in type 2 diabetes (T2DM) patients with apical periodontitis (AP). Thirty individuals were divided into four groups: Healthy (H); with AP (AP); with T2DM (T2DM); and with T2DM and AP (T2DM-AP). Demographic and pharmacological data were registered. The body mass index (BMI) and the levels of glycated haemoglobin (HbA1c) and IL-1β, IL-6, IL-10, CCL3 and CCL4 were evaluated. AP areas were determined radiographically. Mean age was 64 ± 12 years, with 63% females. Most T2DM patients were under treatment with metformin and antihypertensives. BMI and H1bAc were significantly higher in T2DM patients in relation to H and AP groups. The AP areas were larger in the T2DM-AP group, compared with the AP group. These preliminary findings suggest no influence of AP on glycaemic control or inflammatory levels amongst T2DM patients, although T2DM increased the AP severity.

Effect of red wine or its polyphenols on induced apical periodontitis in rats

AIM

To evaluate the effect of red wine consumption or its polyphenols on the inflammation/resorption processes associated with apical periodontitis in rats.

METHODOLOGY

Thirty-two three-month-old Wistar rats had apical periodontitis induced in four first molars and were then arranged into four groups: control (C)-rats with apical periodontitis; wine (W)-rats with apical periodontitis receiving 4.28 ml/kg of red wine; resveratrol+quercetin (R+Q)-rats with apical periodontitis receiving 4.28 ml/kg of a solution containing 1.00 mg/L of quercetin and 0.86 mg/L of resveratrol and alcohol (ALC)-rats with apical periodontitis receiving the alcoholic dose contained in the wine. The oral gavage treatments were administered daily, from day 0 to day 45. On the 15th day, apical periodontitis was induced, and on the 45th day, the animals were euthanized. Histological, immunohistochemical (RANKL, OPG, TRAP, IL-10, TNF-⍺ and IL-1β) and micro-computed tomography for bone resorption analysis were performed in the jaws. The Kruskal-Wallis with Dunn's test was performed for nonparametric data, and the anova with Tukey's test for parametric data, p < .05.

RESULTS

The median score of the inflammatory process was significantly lower in the R+Q group (1) compared to the C (2) (p = .0305) and ALC (3) (p = .0003) groups, and not different from the W (1.5) group. The immunolabeling for OPG was significantly higher in the R+Q group (p = .0054) compared to all groups; the same was observed for IL-10 (p = .0185), different from groups C and ALC. The R+Q group had the lowest TRAP cell count (p < .0001), followed by the W group, both inferior to C and ALC groups. The lowest bone resorption value was in the R+Q group (0.50mm³  ± 0.21mm³ ), significantly lower (p = .0292) than the C group (0.88mm³  ± 0.10mm³ ). The W group (0.60 mm³  ± 0.25 mm³ ) and R+Q group had less bone resorption compared to the ALC group (0.97 mm³  ± 0.22 mm³ ), p = .0297 and p = .0042, respectively.

CONCLUSION

Red wine administration to rats for 15 days before induction of apical periodontitis decreased inflammation, TRAP marking and periapical bone resorption compared to alcohol. Resveratrol-quercetin administration reduced the inflammatory process in apical periodontitis, periapical bone resorption, and altered the OPG, IL-10 and TRAP expression compared to C and ALC groups.

Evolution of endodontic medicine: a critical narrative review of the interrelationship between endodontics and systemic pathological conditions

Endodontics has gained emphasis in the scientific community in recent years due to the increase in clinical and in animal models studies focused on endodontic medicine, which aims to evaluate the interrelationship between systemic and periapical tissues pathological conditions. These studies have shown that systemic changes can boost the pathogenesis of endodontic infection, favoring its development and progression. A contrary relationship is reported in numerous studies that affirm the potential of endodontic infection to trigger systemic damage and may lead to the worsening of pre-existing pathologies. Recently, the potential of filling materials to develop systemic changes such as neurological alterations had been evaluated, also showing that systemic diseases can negatively influence tissue responses to filling materials after endodontic treatment. Despite advances in endodontic medicine studies, there are still gaps in knowledge on the mechanisms of interactions between apical periodontitis (AP) and systemic diseases and much research to be done. In this sense, this critical narrative literature review aimed to show the evolution of studies in endodontic medicine to help the endodontist to know the role of systemic diseases in the pathogenesis of AP and the possible interference in the repair of periapical tissues after endodontic treatment, as well as to evidence the systemic complications that can be triggered or aggravated in the presence of endodontic infection.

Excessive caffeine intake increases bone resorption associated with periapical periodontitis in rats

AIM

To evaluate the effect of excessive caffeine intake on the inflammation/resorption processes associated with periapical periodontitis (PP) in rats.

METHODOLOGY

Sixteen Wistar rats were used. Periapical periodontitis was induced in the four first molars in each animal. The animals were arranged into two groups: control (C)-rats with periapical periodontitis; and caffeine (CAF)-rats with periapical periodontitis under caffeine administration protocol. The CAF animals received 10 mg/100 g of body weight/day of caffeine via gavage starting fifteen days before PP induction and continuing for thirty more days until euthanasia. On the 30th day, the animals were euthanized and the jaws removed for microcomputed tomography, histological and immunohistochemical analysis for RANKL, OPG, TRAP, IL-10, TNF-⍺ and IL-1β. The Mann-Whitney test was performed for nonparametric data, and Student's t test was performed for parametric data, using p < .05.

RESULTS

There was no significant difference in the weight change between the groups. The median score of the inflammatory process was significantly greater in the CAF group (3) compared with the C group (2), p = .0256. Bone resorption was greater in the group consuming caffeine (1.08 ± 0.15 mm³ ) compared with the C group (0.88 ± 0.10 mm³ ), p = .0346. The immunolabelling for RANKL, TRAP and IL-1β was significantly higher in the CAF group when compared to the control, p < .05. No differences were found for the OPG, IL-10 and TNF-⍺ immunolabelling.

CONCLUSION

Excessive caffeine exposure via gavage in rats was able to exacerbate the volume of periapical bone destruction, and the inflammatory pattern deriving from periapical periodontitis altering the expression of RANKL, IL-1β and TRAP.

Inflammatory profile of apical periodontitis associated with liver fibrosis in rats: histological and immunohistochemical analysis

AIM

To investigate the effects of liver fibrosis (LF) on the pro-inflammatory mediators and periapical bone resorption of apical periodontitis (AP) in rats.

METHODOLOGY

Forty male Wistar rats were distributed into four groups: C - control, AP - rats with AP, LF - rats with LF, AP + LF - rats with AP and LF. LF was induced by carbon tetrachloride administration for 8 weeks and surgical bile duct ligation for 4 weeks; AP was induced in the teeth of rats by dental pulp exposure to the oral environment for 30 days. Jaws and livers were removed after euthanasia. Haematoxylin and Eosin (H&E) and Picrosirius Red (PSR) staining were used to confirm fibrosis in the livers. The jaws were analysed using H&E staining, immunohistochemical assays of interleukin (IL)-1β, IL-6 and tumour necrosis factor-alpha (TNF-α). Student's t-test and Mann-Whitney's U-test were used for statistical analysis (P < 0.05).

RESULTS

Inflammatory infiltrate was moderate in the AP group and severe in the AP + LF group (P < 0.05). Periapical bone resorption was significantly larger in the AP + LF group compared with the AP group (P < 0.05). IL-1β, IL-6 and TNF-α levels were significantly higher in AP + LF group when compared to the AP group (P < 0.05).

CONCLUSION

More intense inflammatory infiltrate, greater amounts of pro-inflammatory cytokines and increased periapical bone resorption were observed in the presence of liver fibrosis in rats with exposed pulps.

Dietary supplementation with multi-strain formula of probiotics modulates inflammatory and immunological markers in apical periodontitis

Objective

The aim of this study was to evaluate whether probiotics multi-strain formula affects the development of apical periodontitis (AP) induced in rats.

Methodology

16 Wistar rats were divided in two groups (n=8): rats with AP fed with regular diet (Control-C (CG)); rats with AP, fed with regular diet and supplemented with multi-strain formula (one billion colony-forming units (CFU)): GNC Probiotic Complex (PCG) ( Lactobacillus acidophilus, Lactobacillus salivaris, Lactobacillus plantarum, Lactobacillus rhamnosus, Bifidobacterium bifidum, Bifidobacterium animalis subs. lactis and Streptococcus thermofilus ). AP was induced in the upper and lower first molars by dental pulp exposure to the oral environment. PCG was administered orally through gavage for 30 days during the AP development. After this period the animals were euthanized and the mandibles were removed and processed for histologic analysis, and immunochemical assays for interleukin (IL)-6, IL-10, IL-1β, RANKL, OPG, and TRAP. The Mann–Whitney U test and Student’s t test were performed (P<.05).

Results

The CG showed more intense inflammatory infiltrate than the PCG group (P<.05). IL-1β, IL 6 and RANKL decreased in the PCG group compared with CG (P<.05). The IL-10 level increased in the PCG group (P<.05). The OPG level was similar in both groups (P>.05). The number of mature osteoclasts (TRAP-positive multinucleated cells) was lower in PCG group when compared to the CG (P<.05).

Conclusion

Probiotic Complex modulates inflammation and bone resorption in apical periodontitis.

Effects of chronic apical periodontitis on the inflammatory response of the aorta in hyperlipemic rats

OBJECTIVES

To study the effects of chronic apical periodontitis (CAP) on the inflammatory response and initial lesion of aorta in hyperlipemic rats.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats aged 14 weeks were randomly divided into 4 experimental groups (n = 8), namely, normal diet (ND), high-fat diet (HFD), CAP, and HFD + CAP. The rats were raised under controlled conditions and fed with diet specified for each group. All subjects were euthanatized after 14 weeks for histopathological analysis. Serum cytokines were analyzed to assess changes in gene and protein expression of aorta via enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Results were analyzed by one-way ANOVA.

RESULTS

Low-density lipoprotein cholesterol levels in rats in HFD + CAP group were significantly higher than those in other groups. By comparison, low-density lipoprotein cholesterol levels in rats in both the HFD and HFD + CAP groups were significantly lower than those in the other groups. No significant difference among all groups was observed in terms of CRP level. However, levels of IL-2, IL-6, and IL-10 increased in the experimental CAP rats compared with the control rats. mRNA expression levels of MCP-1, TLR-4, and NF-κB p65 were markedly elevated in rats in the HFD group compared with those in rats in the ND group. TLR-4 mRNA expression was significantly higher in rats in the HFD + CAP group than that in rats in the HFD group.

CONCLUSIONS

CAP mediated the high expression of cytokines and induced the initial inflammatory response in the aorta. Apical periodontitis may affect the level of inflammatory cytokines (IL-2, IL-6, and IL-10) depending on the immune response.

CLINICAL RELEVANCE

CAP may trigger a systemic inflammatory response and affect the aorta of patients.

Omega-3 Fatty Acids Alter Systemic Inflammatory Mediators Caused by Apical Periodontitis

INTRODUCTION

This study investigated the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on serum inflammatory mediators of rats with pulp exposure-induced apical periodontitis.

METHODS

Forty male Wistar rats were divided into the following groups: control, untreated rats (C); control rats treated with ω-3 PUFAs (C-O); rats with pulp exposure-induced apical periodontitis (AP); and rats with pulp exposure-induced apical periodontitis treated with ω-3 PUFAs (AP-O). ω-3 PUFAs were administered orally once a day for 15 days before pulp exposure and continued for 30 days after pulp exposure. The rats were sacrificed, and then blood and jaw samples were collected. Blood analysis was conducted to determine the total number of leukocytes including neutrophils, monocytes, and lymphocytes. Proinflammatory cytokines tumor necrosis factor alpha, interleukin (IL) 6, and IL-17 were quantified by enzyme-linked immunosorbent assay. Histologic analysis was performed to confirm the development of apical periodontitis. The data were statistically evaluated using analysis of variance and the Tukey posttest. The significance level was set at 5%.

RESULTS

The development of apical periodontitis was confirmed in all infected groups. Bone destruction was larger in the AP group compared with the AP-O group (P < .05). Blood analysis showed that the AP and AP-O groups showed higher numbers of lymphocytes, leukocytes, monocytes, eosinophils, and expressions of tumor necrosis factor alpha and IL-6 compared with the C and C-O groups (P < .05). In contrast, the presence of leukocytes, lymphocytes, and the expression of IL-6 decreased in the AP-O group compared with the AP group (P < .05).

CONCLUSIONS

ω-3 PUFA supplementation influences the systemic effects caused by apical periodontitis, decreasing the number of leukocytes, lymphocytes, and IL-6 in rat blood.

Physiopathology of nitric oxide in the oral environment and its biotechnological potential for new oral treatments: a literature review

OBJECTIVES

A narrative review on the NO properties and their relationship with the oral environment describing NO's molecular origin, role, and perspectives regarding oral pathological, physiological, and regenerative processes for future applications and possible use as prevention or treatment in dentistry.

MATERIALS AND METHODS

Pubmed was searched using the word "nitric oxide." Reviews, clinical studies, and experimental studies were eligible for the screening process. Similar search procedures were then performed with the additional search words "conservative dentistry," "orthodontics," "endodontics," "implants," "periodontics," "oral cancer," "pulp revascularization," and "oral surgery." Furthermore, references of included articles were examined to identify further relevant articles.

RESULTS

There is a relationship between NO production and oral diseases such as caries, periodontal diseases, pulp inflammation, apical periodontitis, oral cancer, with implants, and orthodontics. Studies on this relationship and uses of NO, in diagnosis, prevention, and treatment, are being developed. Also, some NO and oral cavity patents have already registered.

CONCLUSIONS

The understanding of how NO can interfere in oral health maintenance or disease processes can contribute to elucidate the disease development and optimize treatment approaches.

CLINICAL RELEVANCE

NO has considerable biotechnological potential and can contribute to improving diagnostics and treating the oral environment. As a biomarker, NO has an important role in the early diagnosis of diseases. Regarding treatments, NO can possibly be used as a regulator of inflammation, anti-biofilm action, replacing antibiotics, inducing apoptosis of cancerous cells, and contributing to the angiogenesis. All these studies are initial considerations regarding the relationship between NO and dentistry.

Relationship between apical periodontitis and atherosclerosis in rats: lipid profile and histological study

AIM

To investigate the relationship between apical periodontitis and atherosclerosis in rats by lipid profile and carotid artery intima tunic measurement, and histological and histometric evaluation of periapical lesions.

METHODOLOGY

Forty male Wistar rats were allocated into four groups: control (C), with apical periodontitis (AP), with atherosclerosis (AT) and with AP and AT (AP + AT). Atherosclerosis was induced using a high-lipid diet associated with a surgical ligature in the carotid artery and a super dosage of vitamin D₃ . AP was induced via pulp exposure to the oral environment. At 45 and 75 days, serum levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were measured. The maxillary and mandibular jaws and carotid artery were collected and processed for histological analysis. The Kruskal-Wallis or Mann-Whitney test was performed for nonparametric data, and the Tukey's or Student's t-test was performed for parametric data (P < 0.05).

RESULTS

In nonatherosclerotic animals, the induction of apical periodontitis increased TG levels significantly, from 63.1 ± 11.4 mg dL^-1 in group C to 88.2 ± 7.9 mg dL^-1 in the AP group (P < 0.05). The induction of AP was associated with a trend for higher TC and LDL-C levels in atherosclerotic animals (P > 0.05); however, it only significantly increased TG levels, from 93.2 ± 18.0 mg dL^-1 in AT group to 121.9 ± 14.5 mg dL^-1 in the AP + AT group (P < 0.05). Animals in the AP + AT group had a 36.5% increase in the thickness of the carotid intima tunic when compared with the AT group (P < 0.05). The intensity of the inflammatory infiltrate was significantly larger in the AP + AT group when compared with AP group (P < 0.05). The AP + AT group exhibited significantly greater alveolar bone loss, with a periapical lesion size of 206.4 ± 56.3 × 10⁴ μm² , compared with 151.4 ± 49.1 × 10⁴ μm² in the AP group (P < 0.05).

CONCLUSION

Apical periodontitis influenced triglyceride levels, increasing them even in the absence of atherosclerosis, and influenced the increase in the thickness of the carotid artery intima tunic in the presence of atherosclerosis. Atherosclerosis intensified the inflammatory reaction and increased bone resorption in periapical lesions.

Nitric Oxide in Dental Pulp Tissue: From Molecular Understanding to Clinical Application in Regenerative Endodontic Procedures

Nitric oxide (NO), which is synthesized by the enzyme NO synthase (NOS), is a versatile endogenous molecule with multiple biological effects on many tissues and organs. In dental pulp tissue, NO has been found to play multifaceted roles in regulating physiological activities, inflammation processes, and tissue repair events, such as cell proliferation, neuronal degeneration, angiogenesis, and odontoblastic differentiation. However, there is a deficiency of detailed discussion on the NO-mediated interactions between inflammation and reparative/regenerative responses in wounded dental pulp tissue, which is a central determinant of ultimate clinical outcomes. Thus, the purpose of this review is to outline the current molecular understanding on the roles of Janus-faced molecule NO in dental pulp physiology, inflammation, and reparative activities. Based on this knowledge, advanced physicochemical techniques designed to manipulate the therapeutic potential of NOS and NO production in endodontic regeneration procedures are further discussed. Impact statement The interaction between inflammation and reparative/regenerative responses is very important for regenerative endodontic procedures, which are biologically based approaches intended to replace damaged tissues. Inside dental pulp tissue, endogenous nitric oxide (NO) is generated mainly by immunocompetent cells and dental pulp cells and mediates not only inflammatory/immune activities but also signaling cascades that regulate tissue repair and reconstruction, indicating its involvement in both tissue destruction and regeneration. Thus, it is feasible that NO acts as one of the indicators and modulators in dental pulp repair or regeneration under physiological and pathological conditions.

Effects of different alcohol concentrations on the development of apical periodontitis in rats

AIM

To investigate the effect of different alcohol concentrations on the development of apical periodontitis (AP) in rats.

METHODS

Forty Wistar rats were arranged into five groups: (C) - control rats receiving sterile water as the only liquid; (G5) - animals receiving an alcohol solution at 5%, (G10) - alcohol solution at 10%, (G15) - alcohol solution at 15%, and (G20) - alcohol solution at 20%. The alcoholic solution or water was given to the groups as the sole source of hydration throughout the 30 days of the experiment. AP was induced in the mandibular molars on the first day. In the end, the animals were euthanized for histopathological and IL-1b, RANKL, OPG, and TRAP analyses. The Kruskal-Wallis test was used for nonparametric data, and ANOVA followed by the Tukey test were performed for parametric data, p < 0.05.

RESULTS

G15 and G20 had a greater chronic inflammatory infiltrate (Score 3) and AP size bigger (1.59 ± 0.41 and 1.83 ± 0.38, respectively) than the C, G5 and G10 (p < 0.05). No significant difference was found in the IL-1b analyses. The G15 and G20 showed the highest immunolabeling pattern for RANKL and the lowest for OPG. The G20 had greater TRAP cells per mm (4.70 ± 0.99) compared to the C, G5, and G10 (p < 0.05). Furthermore, G15 presented 3.92 ± 0.64 TRAP cells/mm, higher than C (p < 0.05).

CONCLUSIONS

G5 and G10 did not exert a protective or aggravating effect on the AP development. However, G15 and G20 had a significant effect on the AP severity, exacerbating the inflammation and osteoclast markers.

Systemic administration of probiotics reduces the severity of apical periodontitis

AIM

To evaluate the effect of systemic administration of probiotics on the severity of apical periodontitis (AP).

METHODOLOGY

Twenty-four male Wistar rats were used. AP was induced in the maxillary left/right first molars. The animals were arranged into groups: Control, Lactobacillus rhamnosus, and Lactobacillus acidophilus. Probiotics were administered orally for gavage (10⁹ colony-forming units diluted in 5 mL of water for 30 days) during the development of AP. After 30 days, cardiac puncture was performed to analyse the complete blood count. Moreover, microbiological analysis of the root canal contents and saliva was performed. Then, the animals were euthanized and the jaw removed for histopathological and IL-10, IL-1β and IL-6 immunolabeling analyses. After the Shapiro-Wilk test of normality, the Kruskal-Wallis followed by Dunn's test was performed for nonparametric data, and analysis of variance followed by the Tukey test was performed for parametric data (P < 0.05).

RESULTS

No significance difference was observed in the blood profiles and in the counts of microorganisms from the saliva samples among the groups (P > 0.05). Total microorganism counts in the root canal, the inflammatory infiltrate and the immunostaining for IL-1β and IL-6 in AP were significantly lower in the probiotic groups when compared with the control group (P < 0.05). IL-10 was significantly more immunolabled in the probiotic groups than in the control group (P < 0.05).

CONCLUSION

Supplementation with probiotics (Lactobacillus rhamnosus and Lactobacillus acidophilus) had a significant effect on the severity of apical periodontitis in rats, demonstrating the anti-inflammatory effect of probiotics on the development of apical periodontitis.

NLRP6 suppresses the inflammatory response of human periodontal ligament cells by inhibiting NF-κB and ERK signal pathways

AIM

To explore the function and mechanisms of NLRP6 (NOD-, LRR- and pyrin domain-containing 6) in the inflammatory response of human periodontal ligament cells (HPDLCs).

METHODOLOGY

Tissues associated with apical periodontitis were obtained from three patients who underwent endodontic microsurgery. The expression of NLRP6 in 3 human apical periodontitis tissues and HPDLCs was examined by immunohistochemistry and immunofluorescence, respectively. The expressions of NLRP6, Phospho(p)- p65, p65, IκB-α, p- IκB-α, ERK, p- ERK, NLRP3, Pro interleukin (IL)-1β, Pro caspase-1 and apoptosis-associated speck-like protein containing a CARD (ASC) were examined by western blot. The gene expression and secretion of proinflammatory cytokines were detected using quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Data were analysed statistically with independent sample t-tests.

RESULTS

NLRP6 was expressed in inflammatory periapical tissues and HPDLCs. Lipopolysaccharide (LPS) from Escherichia coli induced NLRP6 in HPDLCs (P < 0.05). After silencing NLRP6, E. coli LPS-induced activation of NF-κB and ERK signalling was enhanced, which was also accompanied by elevated levels of IL-6 and tumour necrosis factor-α (TNF-α) (P < 0.05). Moreover, knockdown of NLRP6 led to up-regulation of NLRP3, Pro IL-1β and Pro caspase-1 (P < 0.05), whereas down-regulation of ASC (P < 0.05), which may contribute to unchanged levels of IL-1β in HPDLCs inflammation.

CONCLUSION

NLRP6 was functionally expressed in inflamed periapical tissues and HPDLCs. NLRP6 negatively regulated the production of IL-6 and TNF-α in HPDLCs inflammation by inhibiting NF-κB and ERK signal pathways.

Effects of alpha-lipoic acid therapy on experimentally induced apical periodontitis: a biochemical, histopathological and micro-CT analysis

AIM

To investigate the possible therapeutic effects of alpha-lipoic acid (ALA) in a model of chronic apical periodontitis in rats by analysing biochemical, histopathological and micro-CT parameters.

METHODOLOGY

The study was approved by the Animal Ethics Committee of the Near East University. Thirty-two Wistar rats were divided into four groups of eight rats each: Control Group; ALA Group; AP Group; AP + ALA Group. In the AP and AP + ALA groups, the pulp chambers of the mandibular first molars were surgically exposed and were left open to the oral environment for 4-weeks to allow the establishment of periapical lesions. The rats in the Control and AP groups were treated intraperitoneally with saline solution (with a daily dose of 100 mg kg^-1 , for 28 days after periapical lesion induction). The rats in the ALA and AP + ALA groups were treated intraperitoneally with ALA (with a daily dose of 100 mg kg^-1 , for 28 days after periapical lesion induction). After decapitation, the trunk blood was collected for the assessment of biochemical parameters. The mandibles were surgically removed and dissected for histopathologic analysis and further scanned with micro-CT. Groups of data were compared with a two-way analysis of variance (two-way anova) followed by Sidak's multiple comparison tests. Values of P < 0.05 were regarded as significant.

RESULTS

TNF-α, IL-1β, MMP-1, MMP-2 levels were significantly lower in AP + ALA group compared with AP group (P < 0.05). There was a significant difference between the AP and AP + ALA groups according to assessment of the inflammatory scores (P < 0.05). The periapical inflammatory infiltrates were significantly more severe (P < 0.05) in the AP group. The AP + ALA group exhibited lower values both in terms of surface area and volume of resorption cavities than the AP group and this difference was significant (P < 0.05).

CONCLUSION

alpha-lipoic acid treatment provided therapeutic effects on the inhibition of periapical bone loss.

Protective effect of alpha-lipoic acid against apical periodontitis-induced cardiac injury in rats

This study was designed to assess the possible protective effect of alpha-lipoic acid (ALA) on apical periodontitis (AP)-induced cardiac injury. Wistar albino rats were randomized into four groups: control; ALA; AP; and ALA + AP. Rats of the control and ALA groups were not endodontically treated, but saline and ALA (100 mg kg^-1 ) were administered. In rats of the AP and ALA + AP groups, the pulp chambers of mandibular first molar teeth were exposed and left open for 30 d to induce AP. Saline and ALA (100 mg kg^-1 ) were administered intraperitoneally every 24 h during the experiment. At the end of the experiment, the rats were killed. Establishment of AP was verified by radiographic and histopathological evaluation. Serum alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatine kinase (CK), and superoxide dismutase (SOD) activities were determined using an automated biochemical analyzer, and the structural cardiac injury was assessed pathologically. Serum ALP, LDH, and CK activities were elevated, and SOD activities were decreased, in the AP group. The changed enzyme activities were significantly normalized by treatment with ALA. We conclude that ALA administration alleviated the AP-induced heart injury and improved cardiac structure and function, and therefore this agent may be of potential therapeutic value in protecting cardiac tissue from systemic injury caused by AP.

Inflammatory profile of chronic apical periodontitis: a literature review

Apical periodontitis caused by root canal infection is the most frequent pathological lesion in the jaws, mainly manifested as periapical granulomas and cysts. Understanding of the formation and progression of apical periodontitis as well as the identification of inflammatory biomarkers can help increase the knowledge of pathogenic mechanisms, improve the diagnosis and provide support for different therapeutic strategies. The objective of the present article is to review inflammatory biomarkers such as cytokines, chemokines, inflammatory cells, neuropeptides, RANK/RANKL/OPG system and other inflammatory markers and to relate these systems to the development and progression of pathological conditions related to apical periodontitis.

The Presence and involvement of interleukin-17 in apical periodontitis

Apical periodontitis (AP) is a chronic inflammatory disease characterized by periapical tissue inflammation and destruction of the associated alveolar bone. It is caused by microbial infections within the root canal and the resultant host immune responses in the periapical tissues. The proinflammatory cytokine interleukin (IL)-17 has been shown to play an important role in many inflammatory diseases. There is increasing evidence of the presence of IL-17 in AP, which might be associated with disease pathogenesis. Moreover, several animal studies indicate the potential role of IL-17 in periapical inflammation and the resultant bone resorption in AP. This article reviews recent studies regarding the collective in vitro, in vivo and clinical evidence of the presence and involvement of IL-17 in AP. A search related to IL-17 in apical periodontitis was conducted on PubMed, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts that were included. A total of 25 papers were identified, of the 25 included articles, 7 involved laboratory studies on cell cultures, 11 involved animal experimentations, and 7 were observational studies using human clinical samples. In conclusion, evidence for the presence of IL-17 in AP from human and animal models is clear. However, there is relatively little information currently available that would highlight the specific role of IL-17 in AP.

Omega 3 Fatty Acids Reduce the Triglyceride Levels in Rats with Apical Periodontitis

The aim of this study was to evaluate the influence of the prophylactic and therapeutic supplementation with omega 3 polyunsaturated fatty acids (w-3 PUFAs) on the lipid profile and periapical bone resorption in rats with apical periodontitis. Forty male rats were divided into groups: control rats (C), rats treated with w-3 PUFAs (C+O), rats with pulp exposure-induced apical periodontitis (AP), and rats with AP treated with w-3 PUFAs (AP+O). The administration of w-3 PUFAs was carried out orally once a day for 15 days before pulp exposure and, subsequently, for an additional 30 days after pulp exposure. AP was induced by exposing pulpal tissues to the oral environment. The samples were collected after 30 days. Triglycerides and cholesterol levels were enzymatically measured using the Trinder method. The jaws were collected and submitted for histological analysis. Two-way analysis of variance and Kruskal-Wallis tests were used for statistical analysis, and the significance was set at p<0.05. The triglyceride levels of the AP group were significantly higher than those of the C, C+O and AP+O groups (p<0.05). However, the difference in the cholesterol levels among the groups was not significant (p>0.05). Rats with AP showed larger areas of bone resorption as well as higher inflammatory intensity compared with rats with AP supplemented with w-3 PUFAs. It may be concluded that the presence of multiple AP foci increased the triglyceride levels. In addition, omega 3 supplementation might reduce these levels in rats with AP, as well as the bone resorption areas of periapical tissues.

Evaluation of chemokines and receptors in gnotobiotic root canal infection by F. nucleatum and E. faecalis

The present study aims to evaluate the longitudinal effects of induced experimental infections in gnotoxenic animals on the expression of inflammatory chemokines and their receptors in periradicular tissues. The null hypothesis tested was that Enterococcus faecalis and Fusobacterium nucleatum had no effect on CCR5, CCL5, CXCL10, CCL2/MCP-1, CXCR2 and CCR1 expression. Two groups of five animals (n = 5) aged between 8 and 12 weeks were used in this study. The animals were anaesthetized, and coronary access was performed in the first molar on the right and left sides. Microorganisms were inoculated into the left molar, and the right molar was sealed without contamination to function as a control. Animals were sacrificed 7 and 14 days after infection, and periapical tissues were collected. The cytokine mRNA expression levels were assessed using real-time PCR. The chemokine mRNA expression levels demonstrated that the experimental infection was capable of inducing increased chemokine expression on day 7 compared to that on day 14, except for CCR5 and CCL5, which showed no changes. The gnotoxenic animal model proved to be effective and allowed evaluation of the immune response against a known infection. Additionally, this study demonstrates that gene expression of chemokines and their receptors against the experimental infection preferentially prevailed during the initial phase of induction of the periradicular alteration (i.e., on day 7 post-infection).

Concentration-dependent effect of bleaching agents on the immunolabelling of interleukin-6, interleukin-17 and CD5-positive cells in the dental pulp

AIM

To evaluate lymphocyte-like cell activation (CD5-positive cells) and the expression of interleukin (IL)-6 and IL-17 in the pulp after tooth bleaching with two concentrations of hydrogen peroxide (H₂ O₂ ).

METHODOLOGY

The right and left maxillary molars from 40 rats were treated randomly with bleaching gel with 20% H₂ O₂ (BLUE group, 1 application of 50 min), 35% H₂ O₂ (MAXX group, three applications of 15 min), or placebo gel (control). After 2 and 30 days, the rats were killed (n = 10), and the jaws were processed for histological and immunohistochemistry analysis of the pulp tissue. The scores of inflammation and immunolabelling (IL-6/IL-17) were submitted to Mann-Whitney and Kruskal-Wallis followed Dunn tests, respectively; anova tests were used for comparisons of number of CD5-positive cells and pulp chamber area values (P < 0.05).

RESULTS

At 2 days, 60% of specimens of the BLUE group were associated with moderate inflammation in pulp horns, and in the MAXX group with necrosis (P < 0.05). At 30 days, the pulp was organized, and tertiary dentine was formed. The MAXX group had superior immunolabelling of IL-17 at 2 days differing significantly from other groups (P < 0.05). At 2 days, 90% of the specimens of the BLUE group had moderate immunolabelling of IL-6, and 50% of the MAXX group had severe immunolabelling, both significantly different from the control (P < 0.05). There was no significant difference between the groups at 30 days (P > 0.05). CD5-positive cells were present at 2 and 30 days, particularly in the bleached groups (P < 0.05), without significant difference between time periods (P > 0.05).

CONCLUSIONS

IL-6 and IL-17 participated in inflammation in the pulp tissue of rats after tooth bleaching, particularly at 2 days. The immunolabelling was greater with increasing H₂ O₂ concentration. This process was accompanied by the prolonged activation of CD5-positive cells.

Omega-3 Fatty Acids Reduce Inflammation in Rat Apical Periodontitis

INTRODUCTION

The effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on pro- and anti-inflammatory mediators were evaluated in a rat model of pulp exposure-induced apical periodontitis (AP).

METHODS

Twenty-eight male Wistar rats were divided into 4 groups: control, untreated rats (group C); control rats treated with ω-3 PUFAs (group C-O); rats with pulp exposure-induced AP (group AP); and rats with pulp exposure-induced AP treated with ω-3 PUFAs (group AP-O). Omega-3 PUFAs were administered orally once a day for 15 days before pulp exposure; this treatment was continued for 30 days after pulp exposure. The rats were sacrificed 30 days after pulp exposure, and their dissected jaws were subjected to immunohistochemical analysis to detect immunoreactivity for tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1β, IL-17, and IL-10 on the periapical bone surface. The results were statistically evaluated using analysis of variance and the Tukey post-test. The significance level was set at 5%.

RESULTS

Immunoreactivity for the proinflammatory cytokines TNF-α, IL-6, IL-1β, and IL-17 was higher in the AP group than in the AP-O, C, and C-O groups (P < .05). Immunoreactivity for the anti-inflammatory cytokine IL-10 was lower in the AP group than in the AP-O group (P < .05).

CONCLUSIONS

Supplementation with ω-3 PUFAs can modulate the inflammatory response in rat AP, decreasing levels of TNF-α, IL-6, IL-1β, and IL-17 but increasing levels of IL-10.