Endogenous glutamate in association with inflammatory and hormonal factors modulates bone tissue resorption of the temporomandibular joint in patients with early rheumatoid arthritis

Sex diferences in serum and synovial fluid C-reactive protein concentration in healthy dogs

Differences between serum C-reactive protein (SCRP) and synovial fluid C-reactive protein (SFCRP) concentrations in healthy animals may be influenced by the sex of the individual and associated with various factors. The objective of this study was to evaluate the disparities in SCRP and SFCRP concentrations between females and males, as well as within each sex. Sixty healthy dogs (N = 60), comprising both sexes, were enrolled in the study. Peripheral blood and knee synovial fluid samples were collected for SCRP and SFCRP analysis, respectively. Serum C-reactive protein (SCRP) and SFCRP concentrations were measured, with mean of 9.61 ± 4.96 mg/L for SCRP and 1.28 ± 3.05 mg/L for SFCRP. Notably, SFCRP concentrations were consistently lower than SCRP concentrations in both sexes. Statistically significant differences were observed between sexes for both SCRP (P = 0.021) and SFCRP (P = 0.007). Further analysis within females revealed statistically significant differences between SCRP and SFCRP concentrations (P = 0.002), whereas in males, such differences were not significant (P = 0.175). Additionally, weak correlations were found between SCRP and SFCRP concentrations for both sexes (females r = 0.07; males r = 0.29). Joint capsule thickness was assessed using ultrasonography, revealing thicker joint capsules in males. A robust positive association was noted between joint capsule thickness and the SFCRP concentration in both sexes. These findings offer valuable insights into the dynamics of CRP in the context of joint health in male and female patients, elucidating the underlying pathological mechanisms of joint disease and inflammation. Overall, this underscores the importance of considering sex-specific factors in the assessment and management of joint health, as well as in the design and interpretation of studies involving SFCRP concentrations.

Neuroendocrine Influencers and Associated Factors That Shape Jaw Movement and Growth in Temporomandibular Joint Disorder Management: A Systematic Review of Clinical and Radiographic Evidence

OBJECTIVE

To investigate the influence of endogenous and exogenous neuroendocrine analogues on the range and motion of jaw movement, mandibular growth, and factors affecting condylar guidance in patients with temporomandibular joint disorders using clinical assessment and radiographic imaging.

MATERIAL AND METHODS

Eligible articles were extracted from eleven databases in early 2023 and screened following PRISMA protocols. Certainty of evidence and potential biases were assessed using the GRADE approach.

RESULTS

Nineteen articles were screened, with four deemed to be of high quality, eight of moderate quality, and the remaining seven of low to very low quality. Corticosteroids improve maximal incisal opening but not TMJ disorder symptoms. Higher doses worsen jaw movement and cause osseous deformity. Growth hormone affects occlusal development, and delayed treatment affects arch width. Sex hormone correlation with TMJ disorder is complex, with some studies showing a correlation between menstrual cycle phases and pain/limited mobility.

CONCLUSIONS

The evaluation of neuroendocrine influencers in relation to jaw movement in patients with temporomandibular joint disorders involves the complex interplay of potentially confounding factors that each require careful consideration to ensure accurate diagnoses and evaluations.

Is there an association between rheumatoid arthritis and bone changes in the temporomandibular joint diagnosed by cone-beam computed tomography? A systematic review and meta-analysis

OBJECTIVES

Evaluate the relation of rheumatoid arthritis (RA) and bone changes in the temporomandibular joint diagnosed by cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

This systematic review and meta-analysis were recorded in the PROSPERO database, using the CRD42020153246 protocol. The electronic searches were performed in the following databases: Pubmed, Scopus, Web of Science, Lilacs, Cochrane, and Open Grey. Cross-sectional studies that evaluated patients with RA with bone changes in the temporomandibular joint diagnosed by CBCT, without language restriction or publication date, were included. Meta-analysis was performed in Stata Software (StataCorp, TX, USA, version 12.0), using the metan, and a random effects model, and the risk of different bone alterations occurring in adults with and without arthritis was estimated using odds ratios (ORs) as a pooled measure of effect. Forest plots were used to present the isolated and the pooled effects (ORs and 95% CI).

RESULTS

Six studies were used for qualitative synthesis and 2 studies for quantitative synthesis. All studies diagnosed higher prevalence changes in the bone structures of the TMJ of RA patients, described as erosion, flattening, sclerosis, and osteophytes. Meta-analysis showed that the chance of bone changes occurring in components of the TMJ is greater in individuals who have RA.

CONCLUSION

There is an association between RA and bone changes in TMJ structures diagnosed through CBCT, as RA patients were more likely to have osteoarthritic changes in this joint.

CLINICAL RELEVANCE

Understanding the existence of an association between bone alterations in TMJ and RA can assist in the management of patients.

Increased Risk of Temporomandibular Joint Disorder in Patients with Rheumatoid Arthritis: A Longitudinal Follow-Up Study

We evaluated the incidence of temporomandibular disorder (TMD) in patients with rheumatoid arthritis (RA) and examined the association between TMD and RA, through longitudinal follow-up. Population data from the Korean National Health Insurance Service-Health Screening Cohort from 2002 to 2015 was used. From 514,866 subjects, 3122 with RA were matched with 12,488 controls in a 1:4 ratio. The crude and adjusted models (for obesity, smoking, alcohol consumption, blood pressure, blood glucose, total cholesterol, and Charlson Comorbidity Index scores) were calculated. Chi-square tests, Kaplan-Meier (KM) analysis, and two-tailed analyses were used for statistical analysis. Stratified Cox proportional hazard models were used to assess the hazard ratios (HR) and 95% confidence intervals (CI) for TMD in the RA group, compared to those in the control group. The adjusted HR for TMD in RA was 2.52 (95% CI = 1.70–3.74), compared to the control group. The results were consistent with the subgroup analyses, according to age and sex, except in men older than 60 years of age. KM analysis showed similar results. Hence, we found that patients with RA have a higher risk of TMD, and should be observed for symptoms of the initial stage of TMD to prevent the risk of aggravation.

Long-term Changes of Temporomandibular Joint Osteoarthritis on Computed Tomography

This study aimed to understand long-term changes of the osteoarthritic temporomandibular joint (TMJ) condyle using computed tomography (CT) and to verify its correlation with clinical characteristics of temporomandibular disorders. Eighty-nine patients (152 joints; 76 female, 13 male) who had taken follow-up CTs (mean follow-up period: 644.58 ± 325.71 days) at least once in addition to their initial evaluation were selected. Cross-sectional demographic and clinical data and longitudinal CT images were collected. Data were analyzed by analysis of variance and logistic regression. Overall destructive change index (number of TMJ condyle sections in which destructive change was observed) decreased from 1.56 to 0.66. Improvement was seen in 93 joints (61.2%) and 27 joints (17.8%) worsened. In the pain positive group, both initial and final destructive change index were significantly higher compared to the pain negative group (p = 0.04). Occlusal stabilization splint therapy and nonsteroidal anti-inflammatory drug administration showed a significant effect on improving the prognosis of TMJ osteoarthritis (p = 0.015 and 0.011). In conclusion, TMJ osteoarthritis showed long-term improvement in the majority of cases. TMJ osteoarthritis accompanied by pain showed unfavorable prognosis with additional bone destruction. Occlusal stabilization splint and nonsteroidal anti-inflammatory drug administration were beneficial on the prognosis of TMJ osteoarthritis.

Crosstalk between Fas and S1P1 signaling via NF-kB in osteoclasts controls bone destruction in the TMJ due to rheumatoid arthritis

Rheumatoid arthritis (RA) mainly affects various joints of the body, including the temporomandibular joint (TMJ), and it involves an infiltration of autoantibodies and inflammatory leukocytes into articular tissues and the synovium. Initially, the synovial lining tissue becomes engaged with several kinds of infiltrating cells, including osteoclasts, macrophages, lymphocytes, and plasma cells. Eventually, bone degradation occurs. In order to elucidate the best therapy for RA, a comprehensive study of RA pathogenesis needs to be completed. In this article, we discuss a Fas-deficient condition which develops into RA, with an emphasis on the role of sphingosine 1-phosphate (S1P)/S1P receptor 1 signaling which induces the migration of osteoclast precursor cells. We describe that Fas/S1P1 signaling via NF-κB activation in osteoclasts is a key factor in TMJ-RA severity and we discuss a strategy for blocking nuclear translocation of the p50 NF-κB subunit as a potential therapy for attenuating osteoclastogenesis.

Evaluation of the Prevalence of Temporomandibular Joint Involvement in Rheumatoid Arthritis Using Research Diagnostic Criteria for Temporomandibular Disorders

OBJECTIVES

Temporomandibular joint (TMJ) disorders, known as TMDs, are significant public health problems and may result in pain and disability. In order to determine the prevalence of clinical/subjective TMD in rheumatoid arthritis (RA), we used the research diagnostic criteria (RDC)/TMD axes. We assessed the anti-cyclic citrullinated protein (anti-CCP)-related TMD in RA for the first time.

MATERIALS AND METHODS

Fifty-two RA patients were compared to 47 healthy controls with regard to complete blood count (CBC), serology, acute phase reactants (APR), and TMJ dysfunction.

RESULTS

The anti-CCP antibody showed a significant correlation with the development of clinical TMD (P=0.001, 95% confidence interval (CI)=12.4%-35.6%). A prevalence of 50% was calculated through the RDC/TMD for such disorders. In RA patients, statistically significant differences were observed between the groups with and without clinical TMD regarding psychological depression and physical symptoms.

CONCLUSIONS

According to the results, a significant correlation was found between the anti-CCP antibody and TMD. Therefore, when this antibody is detected in the blood serum, the treatment must be initiated. The RDC/TMD used in this study assessed the prevalence of TMJ dysfunction in conformity with RA-associated TMJ findings previously obtained through other conventional methods.

Osseous changes in the temporomandibular joint in rheumatoid arthritis: A cone-beam computed tomography study

Purpose

To evaluate osseous changes of temporomandibular joint (TMJ) in patients with rheumatoid arthritis (RA) using cone-beam computed tomography (CBCT) and to correlate the imaging findings with the severity of TMJ dysfunction, clinical findings, and laboratory findings.

Materials and Methods

This study consisted of 28 subjects, including 14 RA patients and 14 controls, who were scheduled to undergo CBCT imaging for the diagnosis of a complaint not related to or affecting the TMJ. The Fonseca's questionnaire was used to assess the severity of TMJ dysfunction. Rheumatoid factor (RF) and the erythrocyte sedimentation rate (ESR) were assessed in the RA patients. CBCT was then performed in all subjects and osseous TMJ abnormalities were assessed.

Results

According to the Fonseca's questionnaire, 14.3% of the patients had no TMJ dysfunction, while 50%, 21.4%, and 14.3% had mild, moderate, and severe dysfunction, respectively. RF was positive in 64.3% of patients, and the ESR level was high in 100%. Imaging findings revealed a statistically significantly higher prevalence of erosion (85.7%), flattening (89.3%), osteophyte formation (32.1%), subchondral cyst (32.1%), sclerosis (64.3%), and condylar irregularities (28.6%) in the RA patients than in the controls. No correlations were found between CBCT findings and the clinical findings, the severity of TMJ dysfunction, disease duration, or laboratory results.

Conclusion

RA patients might show extensive osseous abnormalities with no/mild clinical signs or symptoms of TMJ dysfunction that necessitate TMJ imaging for these patients. CBCT is a valuable and efficient modality that can assess osseous TMJ changes in RA patients.

Neurotransmitter signalling via NMDA receptors leads to decreased T helper type 1-like and enhanced T helper type 2-like immune balance in humans

Given the pivotal roles that CD4⁺ T cell imbalance plays in human immune disorders, much interest centres on better understanding influences that regulate human helper T-cell subset dominance in vivo. Here, using primary CD4⁺ T cells and short-term T helper type 1 (Th1) and Th2-like lines, we investigated roles and mechanisms by which neurotransmitter receptors may influence human type 1 versus type 2 immunity. We hypothesized that N-methyl-d-aspartate receptors (NMDA-R), which play key roles in memory and learning, can also regulate human CD4⁺ T cell function through induction of excitotoxicity. Fresh primary CD4⁺ T cells from healthy donors express functional NMDA-R that are strongly up-regulated upon T cell receptor (TCR) mediated activation. Synthetic and physiological NMDA-R agonists elicited Ca²⁺ flux and led to marked inhibition of type 1 but not type 2 or interleukin-10 cytokine responses. Among CD4⁺ lines, NMDA and quinolinic acid preferentially reduced cytokine production, Ca²⁺ flux, proliferation and survival of Th1-like cells through increased induction of cell death whereas Th2-like cells were largely spared. Collectively, the findings demonstrate that (i) NMDA-R is rapidly up-regulated upon CD4⁺ T cell activation in humans and (ii) Th1 versus Th2 cell functions such as proliferation, cytokine production and cell survival are differentially affected by NMDA-R agonists. Differential cytokine production and proliferative capacity of Th1 versus Th2 cells is attributable in part to increased physiological cell death among fully committed Th1 versus Th2 cells, leading to increased Th2-like dominance. Hence, excitotoxicity, beyond its roles in neuronal plasticity, may contribute to ongoing modulation of human T cell responses.

Vitamin D prenatal programming of childhood metabolomics profiles at age 3 y

Background: Vitamin D deficiency is implicated in a range of common complex diseases that may be prevented by gestational vitamin D repletion. Understanding the metabolic mechanisms related to in utero vitamin D exposure may therefore shed light on complex disease susceptibility.Objective: The goal was to analyze the programming role of in utero vitamin D exposure on children's metabolomics profiles.Design: First, unsupervised clustering was done with plasma metabolomics profiles from a case-control subset of 245 children aged 3 y with and without asthma from the Vitamin D Antenatal Asthma Reduction Trial (VDAART), in which pregnant women were randomly assigned to vitamin D supplementation or placebo. Thereafter, we analyzed the influence of maternal pre- and postsupplement vitamin D concentrations on cluster membership. Finally, we used the metabolites driving the clustering of children to identify the dominant metabolic pathways that were influential in each cluster.Results: We identified 3 clusters of children characterized by 1) high concentrations of fatty acids and amines and low maternal postsupplement vitamin D (mean ± SD; 27.5 ± 11.0 ng/mL), 2) high concentrations of amines, moderate concentrations of fatty acids, and normal maternal postsupplement vitamin D (34.0 ± 14.1 ng/mL), and 3) low concentrations of fatty acids, amines, and normal maternal postsupplement vitamin D (35.2 ± 15.9 ng/mL). Adjusting for sample storage time, maternal age and education, and both child asthma and vitamin D concentration at age 3 y did not modify the association between maternal postsupplement vitamin D and cluster membership (P = 0.0014). Maternal presupplement vitamin D did not influence cluster membership, whereas the combination of pre- and postsupplement concentrations did (P = 0.03).Conclusions: Young children can be clustered into distinct biologically meaningful groups by their metabolomics profiles. The clusters differed in concentrations of inflammatory mediators, and cluster membership was influenced by in utero vitamin D exposure, suggesting a prenatal programming role of vitamin D on the child's metabolome. This trial was registered at clinicaltrials.gov as NCT00920621.

Temporomandibular joint diagnostics using CBCT

The present review will give an update on temporomandibular joint (TMJ) imaging using CBCT. It will focus on diagnostic accuracy and the value of CBCT compared with other imaging modalities for the evaluation of TMJs in different categories of patients; osteoarthritis (OA), juvenile OA, rheumatoid arthritis and related joint diseases, juvenile idiopathic arthritis and other intra-articular conditions. Finally, sections on other aspects of CBCT research related to the TMJ, clinical decision-making and concluding remarks are added. CBCT has emerged as a cost- and dose-effective imaging modality for the diagnostic assessment of a variety of TMJ conditions. The imaging modality has been found to be superior to conventional radiographical examinations as well as MRI in assessment of the TMJ. However, it should be emphasized that the diagnostic information obtained is limited to the morphology of the osseous joint components, cortical bone integrity and subcortical bone destruction/production. For evaluation of soft-tissue abnormalities, MRI is mandatory. There is an obvious need for research on the impact of CBCT examinations on patient outcome.

Deficient cytokine control modulates temporomandibular joint pain in rheumatoid arthritis

The aim was to investigate how endogenous cytokine control of tumor necrosis factor (TNF) influences temporomandibular joint (TMJ) pain in relation to the role of anti-citrullinated peptide antibodies (ACPA) in patients with rheumatoid arthritis (RA). Twenty-six consecutive patients with TMJ RA were included. Temporomandibular joint pain intensity was assessed at rest, on maximum mouth opening, on chewing, and on palpation. Mandibular movement capacity and degree of anterior open bite (a clinical sign of structural destruction of TMJ tissues) were also assessed. Systemic inflammatory activity was assessed using the Disease Activity Score in 28 joints (DAS28) for rheumatoid arthritis. Samples of TMJ synovial fluid and blood were obtained and analyzed for TNF, its soluble receptor, soluble TNF receptor II (TNFsRII), and ACPA. A high concentration of TNF in relation to the concentration of TNFsRII in TMJ synovial fluid was associated with TMJ pain on posterior palpation on maximum mouth opening. The ACPA concentration correlated significantly to the TNF concentration, but not to the TNFsRII concentration, indicating that increased inflammatory activity is mainly caused by an insufficient increase in anti-inflammatory mediators. This study indicates that TMJ pain on palpation in patients with RA is related to a deficiency in local cytokine control that contributes to increased inflammatory activity, including sensitization to mechanical stimuli over the TMJ.

Tumor necrosis factor mediates temporomandibular joint bone tissue resorption in rheumatoid arthritis

OBJECTIVE

To investigate if TNF, IL-1 or their endogenous controls, in relation to ACPA, are associated with radiological signs of ongoing temporomandibular joint (TMJ) bone tissue resorption and disc displacement in RA patients.

METHODS

Twenty-two consecutive outpatients with TMJ of RA were included. Systemic inflammatory activity was assessed by DAS28. The number of painful regions in the body and ESR, CRP, RF and ACPA were analyzed. TMJ synovial fluid and blood samples were obtained and analyzed for TNF, TNFsRII, IL-1ra, IL-1sRII and ACPA. The ratios between the mediators and their endogenous control receptors were used in the statistical analysis. Magnetic resonance imaging was performed in closed- and open-mouth positions and evaluated regarding disc position and presence of condylar and temporal erosions of the TMJ.

RESULTS

A high TNF level in relation to TNFsRII in TMJ synovial fluid correlated to the degree of TMJ condylar erosion. A high IL-1ra level in relation to TNF in TMJ synovial fluid was also correlated to the degree of TMJ condylar erosion. The total degree of TMJ condylar erosion was correlated with the number of painful regions.

CONCLUSION

This study indicates that TNF in TMJ synovial fluid mediates TMJ cartilage and bone tissue resorption in RA. The study also suggests that the degree of endogenous cytokine control is of importance for development of bone tissue destruction.

Expanding the taxonomy of the diagnostic criteria for temporomandibular disorders

There is a need to expand the current temporomandibular disorders' (TMDs) classification to include less common but clinically important disorders. The immediate aim was to develop a consensus-based classification system and associated diagnostic criteria that have clinical and research utility for less common TMDs. The long-term aim was to establish a foundation, vis-à-vis this classification system, that will stimulate data collection, validity testing and further criteria refinement. A working group [members of the International RDC/TMD Consortium Network of the International Association for Dental Research (IADR), members of the Orofacial Pain Special Interest Group (SIG) of the International Association for the Study of Pain (IASP), and members from other professional societies] reviewed disorders for inclusion based on clinical significance, the availability of plausible diagnostic criteria and the ability to operationalise and study the criteria. The disorders were derived from the literature when possible and based on expert opinion as necessary. The expanded TMDs taxonomy was presented for feedback at international meetings. Of 56 disorders considered, 37 were included in the expanded taxonomy and were placed into the following four categories: temporomandibular joint disorders, masticatory muscle disorders, headache disorders and disorders affecting associated structures. Those excluded were extremely uncommon, lacking operationalised diagnostic criteria, not clearly related to TMDs, or not sufficiently distinct from disorders already included within the taxonomy. The expanded TMDs taxonomy offers an integrated approach to clinical diagnosis and provides a framework for further research to operationalise and test the proposed taxonomy and diagnostic criteria.

Impact of temporomandibular joint pain in rheumatoid arthritis

To investigate the impact of temporomandibular joint (TMJ) pain on daily activities and quality of life in relation to systemic inflammatory activity in patients with rheumatoid arthritis (RA), thirty-three consecutive outpatients with RA were included. TMJ pain intensity at rest, on maximum mouth opening, and on chewing was assessed on a 0–10 numerical rating scale. TMJ palpatory tenderness, degree of anterior open bite, the impact of TMJ pain on daily activities and quality of life were also assessed. The systemic inflammatory activity was estimated by the disease activity score 28 (DAS28), blood levels of inflammatory markers and number of painful musculoskeletal regions. TMJ pain at rest, on maximum mouth opening, and on chewing as well as DAS28 was correlated with the impact of the TMJ pain on daily activities and quality of life. Partial correlations showed a significant interaction between TMJ pain on movement and DAS28 that explained the TMJ pain impact on daily activities and quality of life to a significant degree. This study indicates that both current TMJ pain intensity and systemic inflammatory activity play roles in the impact of TMJ pain on daily living and quality of life in RA.

Serotonin acts as a novel regulator of interleukin-6 secretion in osteocytes through the activation of the 5-HT(2B) receptor and the ERK1/2 signalling pathway

Interleukin-6 (IL-6) is a potent stimulator of osteoclastic bone resorption. Osteocyte secretion of IL-6 plays an important role in bone metabolism. Serotonin (5-HT) has recently been reported to regulate bone metabolism. The aim of this study was to evaluate the effect of serotonin on osteocyte expression of IL-6. The requirement for the 5-HT receptor(s) and the role of the extracellular signal-regulated kinase 1/2 (ERK1/2) in serotonin-induced IL-6 synthesis were examined. In this study, real-time PCR and ELISA were used to analyse IL-6 gene and protein expression in serotonin-stimulated MLO-Y4 cells. ERK1/2 pathway activation was determined by Western blot. We found that serotonin significantly activated the ERK1/2 pathway and induced IL-6 mRNA expression and protein synthesis in cultured MLO-Y4 cells. However, these effects were abolished by pre-treatment of MLO-Y4 cells with a 5-HT2B receptor antagonist, RS127445 or the ERK1/2 inhibitor, PD98059. Our results indicate that serotonin stimulates osteocyte secretion of IL-6 and that this effect is associated with activation of 5-HT2B receptor and the ERK1/2 pathway. These findings provide support for a role of serotonin in bone metabolism by indicating serotonin regulates bone remodelling by mediating an inflammatory cytokine.

Regional 3D superimposition to assess temporomandibular joint condylar morphology

OBJECTIVES

To investigate the reliability of regional three-dimensional registration and superimposition methods for assessment of temporomandibular joint condylar morphology across subjects and longitudinally.

METHODS

The sample consisted of cone beam CT scans of 36 patients. The across-subject comparisons included 12 controls, mean age 41.3 ± 12.0 years, and 12 patients with temporomandibular joint osteoarthritis, mean age 41.3 ± 14.7 years. The individual longitudinal assessments included 12 patients with temporomandibular joint osteoarthritis, mean age 37.8 ± 16.7 years, followed up at pre-operative jaw surgery, immediately after and one-year post-operative. Surface models of all condyles were constructed from the cone beam CT scans. Two previously calibrated observers independently performed all registration methods. A landmark-based approach was used for the registration of across-subject condylar models, and temporomandibular joint osteoarthritis vs control group differences were computed with shape analysis. A voxel-based approach was used for registration of longitudinal scans calculated x, y, z degrees of freedom for translation and rotation. Two-way random intraclass correlation coefficients tested the interobserver reliability.

RESULTS

Statistically significant differences between the control group and the osteoarthritis group were consistently located on the lateral and medial poles for both observers. The interobserver differences were ≤0.2 mm. For individual longitudinal comparisons, the mean interobserver differences were ≤0.6 mm in translation errors and 1.2° in rotation errors, with excellent reliability (intraclass correlation coefficient >0.75).

CONCLUSIONS

Condylar registration for across-subjects and longitudinal assessments is reliable and can be used to quantify subtle bony differences in the three-dimensional condylar morphology.

Blood glutamate scavenging: insight into neuroprotection

Brain insults are characterized by a multitude of complex processes, of which glutamate release plays a major role. Deleterious excess of glutamate in the brain's extracellular fluids stimulates glutamate receptors, which in turn lead to cell swelling, apoptosis, and neuronal death. These exacerbate neurological outcome. Approaches aimed at antagonizing the astrocytic and glial glutamate receptors have failed to demonstrate clinical benefit. Alternatively, eliminating excess glutamate from brain interstitial fluids by making use of the naturally occurring brain-to-blood glutamate efflux has been shown to be effective in various animal studies. This is facilitated by gradient driven transport across brain capillary endothelial glutamate transporters. Blood glutamate scavengers enhance this naturally occurring mechanism by reducing the blood glutamate concentration, thus increasing the rate at which excess glutamate is cleared. Blood glutamate scavenging is achieved by several mechanisms including: catalyzation of the enzymatic process involved in glutamate metabolism, redistribution of glutamate into tissue, and acute stress response. Regardless of the mechanism involved, decreased blood glutamate concentration is associated with improved neurological outcome. This review focuses on the physiological, mechanistic and clinical roles of blood glutamate scavenging, particularly in the context of acute and chronic CNS injury. We discuss the details of brain-to-blood glutamate efflux, auto-regulation mechanisms of blood glutamate, natural and exogenous blood glutamate scavenging systems, and redistribution of glutamate. We then propose different applied methodologies to reduce blood and brain glutamate concentrations and discuss the neuroprotective role of blood glutamate scavenging.

Glutamate signaling in healthy and diseased bone

Bone relies on multiple extracellular signaling systems to maintain homeostasis of its normal structure and functions. The amino acid glutamate is a fundamental extracellular messenger molecule in many tissues, and is used in bone for both neural and non-neural signaling. This review focuses on the non-neural interactions, and examines the evolutionarily ancient glutamate signaling system in the context of its application to normal bone functioning and discusses recent findings on the role of glutamate signaling as they pertain to maintaining healthy bone structure. The underlying mechanisms of glutamate signaling and the many roles glutamate plays in modulating bone physiology are featured, including those involved in osteoclast and osteoblast differentiation and mature cell functions. Moreover, the relevance of glutamate signaling systems in diseases that affect bone, such as cancer and rheumatoid arthritis, is discussed, and will highlight how the glutamate system may be exploited as a viable therapeutic target. We will identify novel areas of research where knowledge of glutamate communication mechanisms may aid in our understanding of the complex nature of bone homeostasis. By uncovering the contributions of glutamate in maintaining healthy bone, the reader will discover how this complex molecular signaling system may advance our capacity to treat bone pathologies.

Osteoarthritis-like damage of cartilage in the temporomandibular joints in mice with autoimmune inflammatory arthritis

OBJECTIVE

To study temporomandibular joint (TMJ) involvement in an autoimmune murine model of rheumatoid arthritis (RA), a disease characterized by inflammatory destruction of the synovial joints. Although TMJ dysfunction is frequently found in RA, TMJ involvement in RA remains unclear, and TMJ pathology has not been studied in systemic autoimmune animal models of RA.

METHODS

Proteoglycan (PG) aggrecan-induced arthritis (PGIA) was generated in genetically susceptible BALB/c mice. TMJs and joint tissues/cartilage were harvested for histological and immunohistochemical analyses and RNA isolation for quantitative polymerase chain-reaction. Serum cytokine levels were measured in mice with acute or chronic arthritis, and in non-arthritic control animals.

RESULTS

Despite the development of destructive synovitis in the limbs, little or no synovial inflammation was found in the TMJs of mice with PGIA. However, the TMJs of arthritic mice showed evidence of aggrecanase- and matrix metalloproteinase-mediated loss of glycosaminoglycan-containing aggrecan, and in the most severe cases, structural damage of cartilage. Serum levels of pro-inflammatory cytokines, including interleukin (IL)-1β, were elevated in arthritic animals. Expression of the IL-1β gene was also high in the inflamed limbs, but essentially normal in the TMJs. Local expression of genes encoding matrix-degrading enzymes (aggrecanases and stromelysin) was upregulated to a similar degree in both the limbs and the TMJs.

CONCLUSION

We propose that constantly elevated levels of catabolic cytokines, such as IL-1β, in the circulation (released from inflamed joints) create a pro-inflammatory milieu within the TMJ, causing local upregulation of proteolytic enzymes and subsequent loss of aggrecan from cartilage.

The effects of estrogen and progesterone on blood glutamate levels: evidence from changes of blood glutamate levels during the menstrual cycle in women

The gonadal steroids estrogen and progesterone have been shown to have neuroprotective properties against various neurodegenerative conditions. Excessive concentrations of glutamate have been found to exert neurotoxic properties. We hypothesize that estrogen and progesterone provide neuroprotection by the autoregulation of blood and brain glutamate levels. Venous blood samples (10 ml) were taken from 31 men and 45 women to determine blood glutamate, estrogen, progesterone, glucose, glutamate-pyruvate transaminase (GPT), and glutamate-oxaloacetate transaminase (GOT) levels, collected on Days 1, 7, 12, and 21 of the female participants' menstrual cycle. Blood glutamate concentrations were higher in men than in women at the start of menstruation (P < 0.05). Blood glutamate levels in women decreased significantly on Days 7 (P < 0.01), 12 (P < 0.001), and 21 (P < 0.001) in comparison with blood glutamate levels on Day 1. There was a significant decrease in blood glutamate levels on Days 12 (P < 0.001) and 21 (P < 0.001) in comparison with blood glutamate levels on Day 7. Furthermore, there was an increase in blood glutamate levels on Day 21 compared with Day 12 (P < 0.05). In women, there were elevated levels of estrogen on Days 7 (P < 0.05), 12, and 21 (P < 0.001), and elevated levels of progesterone on Days 12 and 21 (P < 0.001). There were no differences between men and women with respect to blood glucose concentrations. Concentrations of GOT (P < 0.05) and GPT (P < 0.001) were significantly higher in men than in women during the entire cycle. The results of this study demonstrate that blood glutamate levels are inversely correlated to levels of plasma estrogen and progesterone.

Quantification of condylar resorption in temporomandibular joint osteoarthritis

OBJECTIVE

This study was performed to determine the condylar morphologic variation of osteoarthritic (OA) and asymptomatic temporomandibular joints (TMJs) and to determine its correlation with pain intensity and duration.

STUDY DESIGN

Three-dimensional surface models of mandibular condyles were constructed from cone-beam computerized tomography images of 29 female patients with TMJ OA (Research Diagnostic Criteria for Temporomandibular Disorders group III) and 36 female asymptomatic subjects. Shape correspondence was used to localize and quantify the condylar morphology. Statistical analysis was performed with multivariate analysis of covariance analysis, using Hotelling T(2) metric based on covariance matrices, and Pearson correlation.

RESULTS

The OA condylar morphology was statistically significantly different from the asymptomatic condyles (P < .05). Three-dimensional morphologic variation of the OA condyles was significantly correlated with pain intensity and duration.

CONCLUSION

Three-dimensional quantification of condylar morphology revealed profound differences between OA and asymptomatic condyles, and the extent of the resorptive changes paralleled pain severity and duration.

Temporomandibular joint bone tissue resorption in patients with early rheumatoid arthritis can be predicted by joint crepitus and plasma glutamate level

The aim was to investigate whether bone tissue resorption in early RA is related to crepitus of the temporomandibular joint (TMJ) and systemic levels of inflammatory mediators and markers and sex steroid hormones. Twentynine women and 18 men with recently diagnosed RA were examined for TMJ bone erosions with computerized tomography and TMJ crepitus was assessed. Blood samples were analyzed for glutamate, 5-HT, TNF, IL-1β, IL-6, VEGF, inflammatory markers, and estradiol, progesterone and testosterone. The TMJ erosion score was positively correlated to glutamate, and TMJ crepitus where crepitus, glutamate and ESR explained 40% of the variation in the bone erosion score. In the patients without crepitus, bone erosion score was positively correlated to glutamate, which was not the case in the patients with crepitus. In conclusion, the results of this study show that TMJ bone tissue resorption can be predicted by TMJ crepitus and glutamate in early RA.