Sexual dimorphism in periapical inflammation and bone loss from mitogen-activated protein kinase phosphatase-1 deficient mice

Sex as a Biological Variable in Oral Diseases: Evidence and Future Prospects

The interest of the scientific community on sex and gender differences in health and disease has increased substantially over the past 25 to 30 y as a result of a long process of events and policies in the biomedical field. This is crucial as compelling evidence from human and animal model studies has demonstrated that sex and gender influence health, molecular and cellular processes, and response and predisposition to disease. The present scoping review aims to provide a synthesis of sex differences in oral diseases, ranging from periodontal disease to orofacial pain conditions, from risk of caries development to apical periodontitis. Overall, findings from this review further support a role for sexual dimorphism influencing disease predisposition and/or progression in oral diseases. Of note, this review also highlights the lack of consideration of additional factors such as gender and other psychosocial and external factors potentially influencing oral health and disease. New conceptual frameworks capable of capturing multiple fundamental domains and measurements should be developed in clinical and preclinical studies to inform sex-based individualized preventive and treatment strategies.

Global Noncoding microRNA Profiling in Mice Infected with Partial Human Mouth Microbes (PAHMM) Using an Ecological Time-Sequential Polybacterial Periodontal Infection (ETSPPI) Model Reveals Sex-Specific Differential microRNA Expression

Periodontitis (PD) is a polymicrobial dysbiotic immuno-inflammatory disease. It is more prevalent in males and has poorly understood pathogenic molecular mechanisms. Our primary objective was to characterize alterations in sex-specific microRNA (miRNA, miR) after periodontal bacterial infection. Using partial human mouth microbes (PAHMM) (Streptococcus gordonii, Fusobacterium nucleatum, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia) in an ecological time-sequential polybacterial periodontal infection (ETSPPI) mouse model, we evaluated differential mandibular miRNA profiles by using high-throughput Nanostring nCounter® miRNA expression panels. All PAHMM mice showed bacterial colonization (100%) in the gingival surface, an increase in alveolar bone resorption (p < 0.0001), and the induction of a specific immunoglobin G antibody immune response (p < 0.001). Sex-specific differences in distal organ bacterial dissemination were observed in the heart (82% male vs. 28% female) and lungs (2% male vs. 68% female). Moreover, sex-specific differential expression (DE) of miRNA was identified in PAHMM mice. Out of 378 differentially expressed miRNAs, we identified seven miRNAs (miR-9, miR-148a, miR-669a, miR-199a-3p, miR-1274a, miR-377, and miR-690) in both sexes that may be implicated in the pathogenesis of periodontitis. A strong relationship was found between male-specific miR-377 upregulation and bacterial dissemination to the heart. This study demonstrates sex-specific differences in bacterial dissemination and in miRNA differential expression. A novel PAHMM mouse and ETSPPI model that replicates human pathobiology can be used to identify miRNA biomarkers in periodontitis.

Study of Zuojin Pill in Treating Chronic Atrophic Gastritis by UPLC-Q-TOF/MS Based on Serum and Urine Metabolomics Combined with Network Pharmacology

Zuojin Pill (ZJP) is widely used for the treatment of gastrointestinal diseases, while its specific mechanism has not been systematically investigated. The aim of this study was to explore the therapeutic effects and potential mechanism of ZJP in chronic atrophic gastritis (CAG) through UPLC-Q-TOF/MS-based metabolomics combined with network pharmacology. ZJP and omeprazole significantly reduce contents of IL-1β, IL-6, IL-10, and iNOS and improve pathological characteristics. Metabolomic results indicated that the therapeutic effects of ZJP were mainly related to ten metabolites, namely, choline, L-threonine, hydroxypyruvic acid, creatine, taurine, succinic acid, cis-aconitic acid, citric acid, succinic acid semialdehyde, and uric acid. Pathway analysis showed that the treatment of CAG by ZJP was associated with taurine and hypotaurine metabolism; glyoxylate and dicarboxylate metabolism; glycine, serine, and threonine metabolism; glycerophospholipid metabolism; citrate cycle (TCA cycle), alanine, aspartate, and glutamate metabolism; butanoate metabolism; and purine metabolism. Validation of metabolic markers and key targets of network pharmacology through RT-PCR analysis showed that ZJP significantly downregulated a series of inflammatory markers, such as MAPK1, PKIA, RB1, SCN5A, RXRA, E2F1, PTGS1, IGF2, ADRB1, ADRA1B, PTGS2, and GABRA1. This study was the first to use a combination of metabolomics and network pharmacology to clarify the therapeutic effects of ZJP on CAG and the regulation of multiple metabolic pathways.

Functionalized nanoparticles containing MKP-1 agonists reduce periodontal bone loss

BACKGROUND

Progress over of the past several years has elucidated a role for mitogen-activated protein kinase phosphatase to regulate periodontal inflammation yielding new possibilities for treatment of periodontal diseases. These studies aimed to determine if nanoparticles (NPs) loaded with a pharmacological agent that induces mitogen-activated protein kinase phosphatase have potential clinical utility for management of periodontal inflammation and alveolar bone.

METHODS

Polyethylene glycol (PEG)-polylactide (PLA) (PEG-PLA) NPs were loaded with auranofin (ARN), an antirheumatic drug, to induce mitogen-activated protein kinase phosphatase (MKP)-1 expression in vitro and in vivo. Release kinetics of ARN from NPs was performed by high performance liquid chromatography (HPLC). Fluorescent-labeled NPs were used to show uptake into macrophages by flow cytometry. Real-time quantitative polymerase chain reaction (qPCR) was used to determine dual specificity protein phosphatase (Dusp)-1 mRNA induction by Auranofin-loaded nanoparticles (ARN-NPs) and viability of ARN-NPs was determined by colorimetric in vitro assays. Functional in vitro assays were used to measure functional MKP-1 induction and preclinical models using Aggregatibacter actinomycetemcomitans lipopolysaccharide-induced alveolar bone loss and microcomputed tomography was used to determine in vivo efficacy of functionalized ARN-NPs.

RESULTS

Data indicated that ARN-NPs had reduced cytotoxicity compared with free ARN and Dusp1 mRNA and MKP-1 activity was significantly increased by ARN-NPs in vitro. Flow cytometry indicated rapid uptake into macrophages. Finally, significant bone loss reduction was observed with ARN-NPs compared with control NPs in vivo using an lipopolysaccharide-induced rat model of periodontitis.

CONCLUSION

Results from these studies suggest that developing NPs functionalized with ARN have anti-inflammatory activities and may be a novel adjuvant therapeutic strategy to significantly improve periodontitis therapy and outcomes.

Sexual Dimorphism in Immunity to Oral Bacterial Diseases: Intersection of Neutrophil and Osteoclast Pathobiology

Sex is a biological variable that affects immune responses to bacterial and other types of infectious agents. Males and females are known to have differential oral bacterial disease burden in periodontal and endodontic disease. Understanding that there is a contribution from both sex and gender to these oral diseases, we discuss in this review recent sex-based findings that provide a pathobiological basis for differences observed between males and females. Sexual dimorphism of immune responses with respect to neutrophil trafficking and osteoclast differentiation and formation is presented as a plausible mechanism to explain the sexual differences. We also emphasize that sex, as a biological variable, should be considered in these types of oral immunologic studies.

Dual specificity phosphatase 1 has a protective role in osteoarthritis fibroblast‑like synoviocytes via inhibition of the MAPK signaling pathway

Increasing evidence indicates the important role of inflammation in the pathogenesis and progression of osteoarthritis (OA). Dual specificity phosphatase 1 (DUSP1), a negative regulator of the mitogen‑activated protein kinase (MAPK) signaling pathway, has anti‑inflammatory properties. In the present study, the expression of DUSP1 was investigated in human OA fibroblast‑like synoviocytes (FLSs), human normal FLSs and OA FLSs pretreated with dexamethasone at the mRNA and protein levels. Then, the activation of MAPK pathway proteins and the expression of matrix metalloproteinase‑13 (MMP‑13) and cyclooxygenase‑2 (COX‑2) were measured by western blot analysis in the three groups of cells. Dexamethasone induced the expression of DUSP1 and inhibited the activation of the MAPK pathway and reduced the expression of MMP‑13 and COX‑2 in OA FLSs. However, the role of DUSP1 remained unclear. To clarify this, the effects of overexpression of DUSP1 in OA FLSs were determined using a DUSP1‑overexpressing lentivirus. The results demonstrated that overexpression of DUSP1 in OA FLSs inhibited the activation of the MAPK pathway and expression of OA‑associated mediators. The findings of the present study indicate that DUSP1 has a protective role in OA FLSs and may be a potential target in the treatment of OA.

Sex-based differential regulation of bacterial-induced bone resorption

BACKGROUND AND OBJECTIVE

Periodontal disease pathogenesis is comprised of the complex inflammatory immune response to oral bacterial dysbiosis. Like other inflammatory diseases, there is sexual dimorphism evident in periodontal diseases. During periodontitis, inflammatory chemokines direct neutrophils to migrate to the site of infection to neutralize the pathogen. Interestingly, these same chemokines are also involved in regulating pathogen-induced osteoclast formation. Previous reports show differences in bone turnover and lymphocyte recruitment between sexes. We hypothesize that chemokine expression is differentially regulated by sex and thus results in differential osteoclast formation.

MATERIAL AND METHODS

Male and female mice were utilized to isolate neutrophils based on expression of Ly6G-specific, as well as defined osteoclast progenitors. Cells were stimulated with lipopolysaccharide (LPS; 100 ng/mL) then analyzed for neutrophil infiltration and gene expression. Defined osteoclast progenitors were primed: macrophage-colony stimulating factor (25 ng/mL), receptor activator of NF-κB ligand (50 ng/mL), then stimulated with LPS. Osteoclasts were enumerated via TRAP stain and mRNA isolated for gene expression analysis via quantitative polymerase chain reaction.

RESULTS

In response to LPS, male neutrophils in vitro respond with increased chemokine expression and significantly more osteoclast formed in response to LPS compared to females.

CONCLUSIONS

Findings support observations in humans regarding a sexual dimorphism in oral bacterial infections of alveolar bone loss. Males have a strong inflammatory response to bacterial infection, resulting in increased inflammatory microenvironment, reduced pathogenic bacteria clearance and increased osteoclast-driven bone loss in response to differential expression of key chemokines.

Mitogen-activated protein kinase phosphatase-1: function and regulation in bone and related tissues

In this review, we have highlighted work that has clearly demonstrated that mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1), a negative regulator of MAPKs, is an important signaling mediator in bone, muscle, and fat tissue homeostasis and differentiation. Further, we examined recent studies with particular focus on MKP-1 overexpression or deletion and its impact on tissues connected to bone. We also summarized regulation of MKP-1 by known skeletal regulators like parathyroid hormone (PTH)/PTH-related peptide (PTHrP) and bone morphogenic proteins. MKP-1's integration into the pathophysiological state of osteoporosis, osteoarthritis, rheumatoid arthritis, obesity, and muscular dystrophy are examined to emphasize possible involvement of MKP-1 both at the molecular level and in disease complications such as sarcopenia- or diabetes-related osteoporosis. We predict that understanding the mechanism of MKP-1-mediated signaling in bone-muscle-fat crosstalk will be a key in coordinating their activities and developing therapeutics to improve clinical outcomes for diseases associated with advanced age.

Use of micro-computed tomography for the assessment of periapical lesions in small rodents: a systematic review

This systematic review aimed to evaluate the literature on the acquisition-, reconstruction- and analysis parameters of micro-computed tomography (micro-CT) for the assessment of periapical lesions in rats and mice, and to illustrate the effect of variation in these parameters. The PubMed database was searched from 2000 to January 2015 (English-language publications) for reports on the use of micro-CT to evaluate periapical lesions in rats and mice. QUADAS criteria were used to rate the quality of the studies. To illustrate the effect of variations in acquisition-, reconstruction-, and analysis parameters on images of periapical lesions, micro-CT examination of two hemi-mandibles of mice, with periapical lesions around the first molar was undertaken. Twenty-one studies were identified, which analysed periapical lesions in rats or mice using micro-CT. According to the QUADAS, no study was classified as high-, seven were classified as moderate-, and 14 as low quality. The effect of variation in parameters was that voxel size may interfere with image sharpness, reconstruction may interfere with image sharpness and contrast, and inadequate plane orientation may alter the size of the periapical lesion. Nonpersonalized ROIs resulted in areas that were not part of the periapical lesion. Changing the limits of the threshold for bone-tissue visualization increased lesion size. There is no defined protocol for acquiring and analysing micro-CT images of periapical lesions in rats and mice. Furthermore, acquisition-, reconstruction- and analysis parameters are not adequately explained, which may compromise the scientific impact of the studies.

Three-Dimensional Micro-Computed Tomography Analyses of Induced Periapical Lesions in Transgenic Mice

The aim of this study was to evaluate the three-dimensional (3D) parameters given by the micro-computed tomography (µCT) analysis of experimentally induced periapical lesions in wild type (WT) and knockout mice for the interleukin 22 (IL-22 KO). Periapical lesions were induced in the mandibular first molars of wild type and IL-22 KO mice (n = 12 teeth/group). The animals were euthanized after the experimental periods of 7, 21 and 42 days. The mandibles were removed and exposed to µCT scanning. The analyses were performed by the CTAn software for the tree-dimensional parameters: Tissue Volume (TV), Lesion Volume (LV), Tissue Surface (TS), Lesion Surface (LS), Intersection Surface (IS), and Trabecular Pattern factor (Tb.Pf). After that, the tissue was subjected to routine histologic procedures and to immunohistochemistry analysis. Statistical analysis was performed in the GraphPad software. A t-test was used to compare the differences between the groups with significance level of 5%. The evaluation of the 3D parameters showed statistical significant difference between the groups only at the latest period of periapical lesion development (42 days), for the TV, LV, TS, LS and IS parameters. The immunohistochemistry evaluation confirmed the immunostaining for IL-22 only in the WT mice, surrounding the periapical lesion. There were no differences regarding the trabecular alveolar bone (Tb.Pf) that could influence the lesion development. In conclusion, the 3D parameters showed that the absence of IL-22 leads to detectable differences at 42 days of lesion progression, resulting in smaller periapical lesions.

Intermittent administration of parathyroid hormone ameliorates periapical lesions in mice

INTRODUCTION

Intermittent administration of parathyroid hormone (PTH) promotes oral osseous wound healing and protects against ligature-induced alveolar bone loss. However, its therapeutic value on periapical periodontitis is unknown. The goal of this study was to determine the effect of intermittent PTH administration on the progression of periapical periodontitis.

METHODS

Seven lymphotoxin alpha-deficient mice received pulp exposures of mandibular first and second molars. Exposed pulp in the right mandible was covered with plaque-contaminated fibrin, whereas exposed pulp in the left mandible was left open. After 4 weeks, the periapical tissues were examined to determine the effect of plaque-contaminated fibrin to induce periapical lesions. Fourteen mice received pulp exposure covered with plaque-contaminated fibrin. PTH (40 μg/kg/d) was administered intermittently to half of the mice for 3 weeks beginning 1 week after pulp exposure. The remaining half received saline injections as the vehicle control. At sacrifice, mandibles and tibiae were harvested and processed for histologic examination. Evaluation of neutrophils and blood vessels was performed after staining with immunofluorescence, and periradicular bone was histomorphometrically analyzed.

RESULTS

The exposed pulp covered with plaque-contaminated fibrin resulted in significantly larger periapical lesions compared with the control. Intermittent PTH administration reduced the size of periapical lesions significantly. Significantly less neutrophil infiltration around the root apex was found in PTH-treated animals compared with the control.

CONCLUSIONS

PTH treatment suppressed periapical inflammation by reducing neutrophil infiltration and protected against tissue destruction by periapical periodontitis.

Estradiol induces osteoprotegerin expression by human dental pulp cells

Estrogen deficiency is associated with increased inflammation related periapical bone resorption. The present study aimed to evaluate the effect and intracellular mechanism(s) of estrogen on osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) expression in human dental pulp cells (HDPs). HDPs were treated with estradiol at a concentration of 0.1-10 μM. The results showed that estradiol induced OPG expression at both the mRNA and protein levels in a dose-dependent manner. However, no influence on RANKL expression was observed. An estrogen receptor (ER) inhibitor failed to attenuate the estradiol-induced OPG expression. Furthermore, ER-α and ER-β agonists did not simulate estradiol's effects on OPG expression by HDPs. However, a significant OPG upregulation was observed in HDPs treated with an estradiol-BSA conjugate or a GPR30 agonist. An ERK inhibitor significantly enhanced estradiol-induced OPG expression, whereas a p38 inhibitor markedly attenuated this expression. In conclusion, OPG expression by HDPs may be regulated by estradiol binding a membrane receptor and the balance between the ERK and p38 signaling pathways.

Simvastatin inhibits LPS-induced alveolar bone loss during metabolic syndrome

Studies in recent years have shown a positive relationship between metabolic syndrome (MS) and periodontal disease (PD). Given that patients with MS take statins to reduce cholesterol, and statins also have anti-inflammatory effects, it is important to determine if statin intake hinders the progression of MS-associated PD. In this study, PD was induced in Zucker fat rats (ZFRs), an animal model for MS, and in control lean rats by periodontal injection of Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS), while simvastatin was given to some of the rats via gavage. After 4 wk of treatment, alveolar bone loss was determined by micro-computed tomography. To explore the underlying mechanisms, we determined the effect of simvastatin on tissue inflammation and the expression of molecules involved in osteoclastogenesis. Results showed that while bone loss was increased by LPS in both ZFRs and the control lean rats, it was significantly more in the former than the latter. Simvastatin effectively alleviated bone loss in both ZFRs and the control rats. Results also showed that LPS stimulated leukocyte tissue infiltration and expression of molecules for osteoclastogenesis, but simvastatin significantly modulated the stimulation. This study demonstrated that simvastatin inhibited LPS-induced alveolar bone loss and periodontal tissue inflammation in rats with MS.