Brain-derived neurotrophic factor in chronic periodontitis

Dynamic changes in macrophage polarization during the resolution phase of periodontal disease

AIM

Polarization of macrophages (Mφ) is a well-controlled axis with considerable consequences in both the pro-inflammatory and resolution phases of inflammation. We aimed to determine if periodontal therapy may instigate M1 to M2 Mφ polarization favoring resolution of inflammation within periodontal tissues.

METHODS

Gingival biopsies were excised from subjects diagnosed with Stage III, Grade B periodontitis before and 4-6 weeks after nonsurgical periodontal therapy. Total RNA was isolated and pro- and anti-inflammatory markers associated with Mφ polarization assessed by RT-qPCR. Mice were subject to ligature-induced periodontitis and gingival tissues collected after 8 days in-situ or 10 days after ligature removal and M1 and M2 Mφ markers examined by RT-qPCR and flow cytometry.

RESULTS

In human samples, improvement in clinical parameters posttherapy correlates with reduced bacterial burden, downregulation in M1 (TNF-α, STAT1, CXCL10, and miR-155), and elevated levels of M2 (STAT6, TGM2, CCL22, and IL-10) Mφ markers. In a murine model of resolution of LIP, we observed reduced levels of M1 Mφ markers cox2, iNOS2, F4/80+CD80+, and F4/80+CD86+ and elevated levels of M2-like Mφ markers tgm2, arg1, F4/80+CD206+ and F4/80+CD163+ corroborated human findings.

CONCLUSION

Resolution of periodontal inflammation is associated with M1 to M2 Mφ polarization after nonsurgical periodontal therapy. Assessment of Mφ markers can provide relevant clinical information on the successful response of periodontal therapy and may be used to target nonresponders.

Parkinson's disease is positively associated with periodontal inflammation

BACKGROUND

Parkinson's disease (PA) affects 1% of the global population above 60 years. PA pathogenesis involves severe neuroinflammation that impacts systemic and local inflammatory changes. We tested the hypothesis that PA is associated with periodontal tissue inflammation promoting a greater systemic inflammatory burden.

METHODS

We recruited 60 patients with Stage III, Grade B periodontitis (P) with and without PA (n = 20 for each). We also included systemically and periodontally healthy individuals as controls (n = 20). Clinical periodontal parameters were recorded. Serum, saliva, and gingival crevicular fluid (GCF) samples were collected to measure the inflammatory and neurodegenerative targets (YKL-40, fractalkine, S100B, alpha-synuclein, tau, vascular cell adhesion protein-1 (VCAM-1), brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL).

RESULTS

Parkinson's patients in this study had mild to moderate motor dysfunctions, which did not prevent them from performing optimal oral hygiene control. Periodontal parameters and GCF volume were significantly higher in the P and P+PA groups than in the control group. PA was associated with significantly increased bleeding on probing (BOP) compared to P-alone (p < 0.05), while other clinical parameters were similar between P and P+PA groups. In saliva and serum, YKL-40 levels were higher in the P+PA group than in P and C groups (p < 0.001). GCF NfL levels from shallow sites were significantly higher in the P+PA group compared to the C group (p = 0.0462). GCF S100B levels from deep sites were higher in the P+PA group than in healthy individuals (p = 0.0194).

CONCLUSION

The data suggested that PA is highly associated with increased periodontal inflammatory burden-bleeding upon probing and inflammatory markers-in parallel with PA-related neuroinflammation.

Expression Pattern and Value of Brain-Derived Neurotrophic Factor in Periodontitis

BACKGROUND

Periodontitis is a common human disease with an increasing incidence. Brain-derived neurotrophic factor (BDNF) is known to play a crucial role in the regeneration of periodontal tissue; however, the expression, methylation level, molecular function, and clinical value of BDNF in periodontitis require further investigation. This study aimed to investigate the expression and potential functions of BDNF in periodontitis.

METHODS

RNA expression and methylation data were obtained from the Gene Expression Omnibus (GEO) database, and the expression and methylation levels of BDNF were compared between periodontitis and normal tissues. In addition, bioinformatics analysis was performed to investigate the downstream molecular functions of BDNF. Finally, Reverse transcription Quantitative real-time polymerase chain reaction was performed to determine the level of BDNF expression in periodontitis and normal tissues.

RESULTS

GEO database analysis revealed that BDNF was hypermethylated in periodontitis tissues and that its expression was downregulated. Reverse transcription Quantitative real-time polymerase chain reaction confirmed that BDNF expression was downregulated in periodontitis tissues. Several genes that interact with BDNF were determined using a protein-protein interaction network. Functional analysis of BDNF revealed that it was enriched in the Gene Ontology terms cytoplasmic dynein complex, glutathione transferase activity, and glycoside metabolic process. Kyoto Encyclopedia of Genes and Genomes analysis suggested that BDNF was associated with the mechanistic target of rapamycin signaling pathway, fatty acid metabolism, the Janus kinase-signal transducer and activator of transcription signaling pathway, glutathione metabolism, and others. Furthermore, the level of BDNF expression was correlated with the immune infiltration degree of B cells and CD4⁺ T cells.

CONCLUSIONS

This study shown that BDNF was hypermethylated and downregulated in periodontitis tissues, which could be a biomarker and treatment target of periodontitis.

Mental health and periodontal and peri-implant diseases

Mental health disorders, particularly depression and anxiety, affect a significant number of the global population. Several pathophysiological pathways for these disorders have been identified, including the hypothalamic-pituitary-adrenal axis, autonomic nervous system, and the immune system. In addition, life events, environmental factors, and lifestyle affect the onset, progression, and recurrence of mental health disorders. These may all overlap with periodontal and/or peri-implant disease. Mental health disorders are associated with more severe periodontal disease and, in some cases, poorer healing outcomes to nonsurgical periodontal therapy. They can result in behavior modification, such as poor oral hygiene practices, tobacco smoking, and alcohol abuse, which are also risk factors for periodontal disease and, therefore, may have a contributory effect. Stress has immunomodulatory effects regulating immune cell numbers and function, as well as proinflammatory cytokine production. Stress markers such as cortisol and catecholamines may modulate periodontal bacterial growth and the expression of virulence factors. Stress and some mental health disorders are accompanied by a low-grade chronic inflammation that may be involved in their relationship with periodontal disease and vice versa. Although the gut microbiome interacting with the central nervous system (gut-brain axis) is thought to play a significant role in mental illness, less is understood about the role of the oral microbiome. The evidence for mental health disorders on implant outcomes is lacking, but may mainly be through behaviourial changes. Through lack of compliance withoral hygiene and maintenance visits, peri-implant health can be affected. Increased smoking and risk of periodontal disease may also affect implant outcomes. Selective serotonin reuptake inhibitors have been linked with higher implant failure. They have an anabolic effect on bone, reducing turnover, which could account for the increased loss.

Metagenomic Analysis Reveals a Mitigating Role for Lactobacillus paracasei and Bifidobacterium animalis in Experimental Periodontitis

Probiotics have aroused increasing concern as an intervention strategy for periodontitis (PD), but their underlying mechanism of action remains poorly characterized. Regarding the significance of oral microbiota dysbiosis related to PD, we predicted that the preventive activity of probiotics may be influenced by suppressing the bacterial pathogenicity. Herein, we investigated the effects of Lactobacillus paracasei L9 (L9) and Bifidobacterium animalis A6 (A6) on PD using a rat model, and demonstrated a regulatory effect of probiotics on oral flora from a metagenomics perspective. Oral administration of A6 or L9 effectively relieved gingival bleeding, periodontal inflammatory infiltration, and alveolar bone resorption. In addition, A6 or L9 treatment reduced the inflammatory response and increased the expression of anti-inflammatory cytokines, which we expected to ameliorate alveolar bone resorption as mediated by the receptor activator of the nuclear factor-κB ligand/OPG signaling pathway. More importantly, using metagenomic sequencing, we showed that probiotics significantly altered the taxonomic composition of the subgingival microbiome, and reduced the relative proportions of pathogenic bacterial genera such as Streptococcus, Fusobacterium, Veillonella, and Escherichia. Both probiotics significantly inhibited levels of bacterial virulence factors related to adherence, invasion, exoenzyme, and complement protease functions that are strongly correlated with the pathogenesis of PD. Our overall results suggest that A6 and L9 may constitute promising prophylactic agents for PD, and should thus be further explored in the future.

Metagenomic Analysis Reveals a Mitigating Role for Lactobacillus paracasei and Bifidobacterium animalis in Experimental Periodontitis

Probiotics have aroused increasing concern as an intervention strategy for periodontitis (PD), but their underlying mechanism of action remains poorly characterized. Regarding the significance of oral microbiota dysbiosis related to PD, we predicted that the preventive activity of probiotics may be influenced by suppressing the bacterial pathogenicity. Herein, we investigated the effects of Lactobacillus paracasei L9 (L9) and Bifidobacterium animalis A6 (A6) on PD using a rat model, and demonstrated a regulatory effect of probiotics on oral flora from a metagenomics perspective. Oral administration of A6 or L9 effectively relieved gingival bleeding, periodontal inflammatory infiltration, and alveolar bone resorption. In addition, A6 or L9 treatment reduced the inflammatory response and increased the expression of anti-inflammatory cytokines, which we expected to ameliorate alveolar bone resorption as mediated by the receptor activator of the nuclear factor-κB ligand/OPG signaling pathway. More importantly, using metagenomic sequencing, we showed that probiotics significantly altered the taxonomic composition of the subgingival microbiome, and reduced the relative proportions of pathogenic bacterial genera such as Streptococcus, Fusobacterium, Veillonella, and Escherichia. Both probiotics significantly inhibited levels of bacterial virulence factors related to adherence, invasion, exoenzyme, and complement protease functions that are strongly correlated with the pathogenesis of PD. Our overall results suggest that A6 and L9 may constitute promising prophylactic agents for PD, and should thus be further explored in the future.

Metagenomic Analysis Reveals a Mitigating Role for Lactobacillus paracasei and Bifidobacterium animalis in Experimental Periodontitis

Probiotics have aroused increasing concern as an intervention strategy for periodontitis (PD), but their underlying mechanism of action remains poorly characterized. Regarding the significance of oral microbiota dysbiosis related to PD, we predicted that the preventive activity of probiotics may be influenced by suppressing the bacterial pathogenicity. Herein, we investigated the effects of Lactobacillus paracasei L9 (L9) and Bifidobacterium animalis A6 (A6) on PD using a rat model, and demonstrated a regulatory effect of probiotics on oral flora from a metagenomics perspective. Oral administration of A6 or L9 effectively relieved gingival bleeding, periodontal inflammatory infiltration, and alveolar bone resorption. In addition, A6 or L9 treatment reduced the inflammatory response and increased the expression of anti-inflammatory cytokines, which we expected to ameliorate alveolar bone resorption as mediated by the receptor activator of the nuclear factor-κB ligand/OPG signaling pathway. More importantly, using metagenomic sequencing, we showed that probiotics significantly altered the taxonomic composition of the subgingival microbiome, and reduced the relative proportions of pathogenic bacterial genera such as Streptococcus, Fusobacterium, Veillonella, and Escherichia. Both probiotics significantly inhibited levels of bacterial virulence factors related to adherence, invasion, exoenzyme, and complement protease functions that are strongly correlated with the pathogenesis of PD. Our overall results suggest that A6 and L9 may constitute promising prophylactic agents for PD, and should thus be further explored in the future.

The Complex Molecular Picture of Gut and Oral Microbiota-Brain-Depression System: What We Know and What We Need to Know

Major depressive disorder (MDD) is a complex mental disorder where the neurochemical, neuroendocrine, immune, and metabolic systems are impaired. The microbiota-gut-brain axis is a bidirectional network where the central and enteric nervous systems are linked through the same endocrine, immune, neural, and metabolic routes dysregulated in MDD. Thus, gut-brain axis abnormalities in MDD patients may, at least in part, account for the symptomatic features associated with MDD. Recent investigations have suggested that the oral microbiome also plays a key role in this complex molecular picture of relationships. As on one hand there is a lot of what we know and on the other hand little of what we still need to know, we structured this review focusing, in the first place, on putting all pieces of this complex puzzle together, underlying the endocrine, immune, oxidative stress, neural, microbial neurotransmitters, and metabolites molecular interactions and systems lying at the base of gut microbiota (GM)-brain-depression interphase. Then, we focused on promising but still under-explored areas of research strictly linked to the GM and potentially involved in MDD development: (i) the interconnection of GM with oral microbiome that can influence the neuroinflammation-related processes and (ii) gut phageome (bacteria-infecting viruses). As conclusions and future directions, we discussed potentiality but also pitfalls, roadblocks, and the gaps to be bridged in this exciting field of research. By the development of a broader knowledge of the biology associated with MDD, with the inclusion of the gut/oral microbiome, we can accelerate the growth toward a better global health based on precision medicine.

The role of PHF8 and TLR4 in osteogenic differentiation of periodontal ligament cells in inflammatory environment

BACKGROUND

Histone methylation is considered to play an important role in the occurrence and development of periodontitis. Plant homeodomain finger protein 8 (PHF8), a histone demethylase, has been shown to regulate inflammation and osteogenic differentiation of bone marrow stromal cells (BMSCs). This study aimed to detect the functions of PHF8 and TLR4 in osteogenic differentiation in an inflammatory environment induced by Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) METHODS: A periodontitis mouse model was established, and the mice were treated with TAK-242. Immunohistochemical staining was used to detect the expression of PHF8 in periodontal tissue. Periodontal ligament cells (PDLCs) were treated with mineralization induction medium supplemented with Pg-LPS and/or TAK-242, and a Cell Counting Kit-8 (CCK-8) assay was used to detect the proliferation of PDLCs. Real-time PCR and western blotting were used to detect the mRNA and protein expression levels, respectively, of PHF8, toll-like receptor 4 (TLR4) and the other osteogenic markers alkaline phosphatase (ALP), osteocalcin (OCN), Special AT-rich sequence-binding protein 2 (Satb2) and Runt-related transcription factor 2 (Runx2) RESULTS: Periodontitis reduced PHF8 expression in periodontal tissue, and TAK-242 partially reversed this downregulation. An in vitro experiment revealed that the mRNA and protein expression levels of PHF8 were significantly upregulated during the osteogenic differentiation of PDLCs. Alizarin red staining showed that the mineralized nodules of PDLCs in osteogenic induction group were more than those in control group. Real-time PCR and western blot results indicated that Pg-LPS inhibited PHF8 expression and upregulated TLR4 expression in PDLCs. TAK-242 inhibited TLR4 and partially reversed the inhibition of PHF8 expression and osteogenic differentiation induced by Pg-LPS in PDLCs CONCLUSION: PHF8 and TLR4 play important roles in periodontitis. Pg-LPS inhibits the expression of PHF8 via upregulation of TLR4 and might further inhibit the osteogenic differentiation of PDLCs. However, the specific mechanisms involved remain to be explored.

Blood and tissue levels of lncRNAs in periodontitis

Periodontitis is a complex disorder that affects a large number of human beings from different ethnic groups. This condition has been associated with dysregulation of a number of genes, among them are long noncoding RNAs (lncRNAs). In the current study, we assessed the expression of four lncRNAs (BDNF-AS, MIAT, MIR137HG, and PNKY) as well as BDNF in the peripheral blood and gingival tissues obtained from patients with periodontitis and healthy subjects. The expression of BDNF was significantly lower in blood samples of male patients with periodontitis compared with male controls (posterior β of RE = -4.754, p = .048). However, there was no significant difference in the expression of BDNF in tissue samples from the cases and controls. The expression of BDNF-AS was significantly lower in the tissue samples of patients compared with control tissue samples (posterior β of RE = -2.151, p = .019). Such an expression difference was detected between male subgroups as well (posterior β of RE = -3.679, p = .009). However, expression of this lncRNA was not different in blood samples obtained from patients compared with healthy subjects. The expression of PNKY was significantly higher in tissue samples obtained from female patients compared with sex-matched controls (posterior β of RE = 6.23, p = .037). Blood levels of this lncRNA were not different between cases and controls. There was no significant difference either in the tissue expression or in blood expression of MIR137HG or MIAT between cases and controls. The current study indicates the putative role of BDNF, BDNF-AS, and PNKY in the pathophysiology of periodontitis and potentiates these genes as candidates for functional studies.

Identification of Potential Candidate Genes of Oral Cancer in Response to Chronic Infection With Porphyromonas gingivalis Using Bioinformatical Analyses

Recent investigations revealed the relationship between chronic periodontitis, Porphyromonas gingivalis and cancer. However, host genes that change in response to chronic infection with P. gingivalis and may contribute to oral cancer have remained largely unknown. In the present study, we aimed to comprehensively analyze microarray data obtained from the chronic infection model of immortalized oral epithelial cells that were persistently exposed to P. gingivalis for 15 weeks. Using protein-protein interaction (PPI) networks and Ingenuity Pathway Analysis (IPA), we identified hub genes, major biological processes, upstream regulators and genes potentially involved in tumor initiation and progression. We also validated gene expression and demonstrated genetic alteration of hub genes from clinical samples of head and neck cancer. Overall, we utilized bioinformatical methods to identify IL6, STAT1, LYN, BDNF, C3, CD274, PDCD1LG2, and CXCL10 as potential candidate genes that might facilitate the prevention and treatment of oral squamous cell carcinoma (OSCC), the most common type of head and neck squamous cell carcinoma (HNSCC).

Role of neurodevelopment involved genes in psychiatric comorbidities and modulation of inflammatory processes in Alzheimer's disease

INTRODUCTION

With the increase of the population's average age, Alzheimer's disease (AD) is becoming one of the most disabling diseases worldwide. Recently, neurodevelopment processes have been involved in the AD etiopathogenesis. Genetic studies in this field could contribute to our knowledge and suggest new molecular targets for possible treatments.

METHODS

Our primary aim was to investigate the associations among single nucleotide polymorphisms (SNPs) within neurodevelopment related genes (BDNF, ST8SIA2, C15orf32, NCAPG2, ESYT2, WDR60, LOC154822, VIPR2, GSK3B, NR1I2, ZNF804A, SP4) and AD. A number of exploratory analyses was also performed to evaluate the associations with the presence of behavioral and psychiatric symptoms of dementia (BPSD), as well as with variations in hematological parameters. Two independent samples were investigated, one of 228 Greek subjects and one sample of 229 Italian subjects, including 156Alzheimer's Disease patients CE patients and 301 healthy controls. All patients were affected by late onset AD (LOAD).

RESULTS

None of the analyzed SNPs was associated with AD in our samples. In the exploratory analyses, several genetic variants were associated with inflammation parameters in the Greek sample and in the merged one, suggesting a relationship among these genes and the modulation of inflammation and the immune response. Other exploratory analyses showed associations among several SNPs and psychiatric symptomatology in the Greek sample, suggesting a possible modulation of these variants on psychiatric comorbidities in AD.

CONCLUSIONS

Although we failed to find a direct relationship between AD and the genetic variants investigated, possible connections with inflammation and psychiatric symptoms were suggested.