Progression of radiographic changes in the temporomandibular joints of patients with rheumatoid arthritis in relation to inflammatory markers and mediators in the blood

Exploring the Role of Serotonin as an Immune Modulatory Component in Cardiovascular Diseases

Serotonin, also known as 5-hydroxytryptamine (5-HT) is a well-known neurotransmitter in the central nervous system (CNS), but also plays a significant role in peripheral tissues. There is a growing body of evidence suggesting that serotonin influences immune cell responses and contributes to the development of pathological injury in cardiovascular diseases, such as atherosclerosis, as well as other diseases which occur as a result of immune hyperactivity. In particular, high levels of serotonin are able to activate a multitude of 5-HT receptors found on the surface of immune cells, thereby influencing the process of atherosclerotic plaque formation in arteries. In this review, we will discuss the differences between serotonin production in the CNS and the periphery, and will give a brief outline of the function of serotonin in the periphery. In this context, we will particularly focus on the effects of serotonin on immune cells related to atherosclerosis and identify caveats that are important for future research.

Serum serotonin levels are elevated in patients with increased risk of rheumatoid arthritis

Background

Even though serotonin (5-HT) has been ascribed immunomodulatory features, very little is known about its role in chronic inflammatory diseases. Serotonin is implicated in inflammation and increased levels have been associated with progression of bone erosions in RA.

Objective

To investigate serum serotonin levels in patients with increased risk of rheumatoid arthritis (RA) and patients with recent-onset disease. Moreover, we aimed to determine the prognostic value of serotonin for arthritis development and the disease course.

Methods

Two prospective observational patient cohorts were studied; anti-citrullinated protein antibody (ACPA) -positive patients with musculoskeletal pain without clinical arthritis (n = 82) and patients with early RA (n = 412). Serotonin levels were measured by enzyme-linked immunosorbent assay (ELISA) in baseline serum samples from both cohorts, and longitudinally in at-risk individuals.

Results

Compared to healthy controls (median 65 ng/ml), serotonin levels were significantly higher in both at-risk individuals (median 111 ng/ml, p < 0.0001) and patients with early RA (median 135 ng/ml, p < 0.0001). No significant differences were found between at-risk individuals and patients with early RA. At-risk individuals progressing to arthritis had similar levels as those not progressing, and no significant differences were seen over time. Baseline levels in early RA did not associate with mean 28-joint disease activity scores during 3 years follow-up.

Conclusion

Serum serotonin levels are elevated both at, and prior to, onset of RA. However, increased serotonin is not prognostic for arthritis development or disease course.

The impact of occlusal support on temporomandibular disorders: a literature review

Temporomandibular disorders are a multifactorial disease. Occlusal support and the number of teeth in dentition have significant effects on the masticatory system. The current study aims to review the role of occlusal support in association with findings of temporomandibular disorders. Data sources were PubMed, Web of Science and Google Scholar, with 1411 citations published over the period 1992–2019. The selection criteria stipulated that articles must have reported the association between the number of teeth, occlusal unit, occlusal support and temporomandibular disorders. A total of 15 full-text articles was finally accessed for eligibility in the current review. The studies on temporomandibular disorders were collected from various sources, including articles reporting temporomandibular disorder symptoms ( n=1), temporomandibular disorder signs ( n=5), temporomandibular joint osseous changes ( n=1), temporomandibular joint dysfunction using the Helkimo index ( n=2), and temporomandibular disorder classification ( n=6). Of these articles, significant associations were found between: the number of missing teeth and temporomandibular disorders ( n=5); the number of occlusal units and occlusal supports and temporomandibular disorders ( n=3); the position of the lost occlusal units and temporomandibular disorders ( n=1). Loss of the occlusal unit has more impact on temporomandibular disorders than the loss of posterior teeth. The total loss of unilateral occlusal support seems to be an aetiological factor for temporomandibular disorders, and maintenance of balanced posterior occlusal support has a role in the prevention and management of temporomandibular disorders.

Amino Acid Metabolism in Rheumatoid Arthritis: Friend or Foe?

In mammals, amino acid metabolism has evolved to act as a critical regulator of innate and adaptive immune responses. Rheumatoid arthritis (RA) is the most common form of inflammatory arthropathy sustained by autoimmune responses. We examine here the current knowledge of tryptophan and arginine metabolisms and the main immunoregulatory pathways in amino acid catabolism, in both RA patients and experimental models of arthritis. We found that l-tryptophan (Trp) metabolism and, in particular, the kynurenine pathway would exert protective effects in all experimental models and in some, but not all, RA patients, possibly due to single nucleotide polymorphisms in the gene coding for indoleamine 2,3-dioxygenase 1 (IDO1; the enzyme catalyzing the rate-limiting step of the kynurenine pathway). The function, i.e., either protective or pathogenetic, of the l-arginine (Arg) metabolism in RA was less clear. In fact, although immunoregulatory arginase 1 (ARG1) was highly induced at the synovial level in RA patients, its true functional role is still unknown, possibly because of few available preclinical data. Therefore, our analysis would indicate that amino acid metabolism represents a fruitful area of research for new drug targets for a more effective and safe therapy of RA and that further studies are demanding to pursue such an important objective.

Comprehensive Assessment of Orofacial Health and Disease Related Parameters in Adolescents with Juvenile Idiopathic Arthritis-A Cross-Sectional Study

Background: The aim of this cross-sectional study was to investigate oral health and functional status of adolescents with juvenile idiopathic arthritis (JIA) and its possible link to disease specific parameters. Methods: Patients with JIA were recruited (November 2012–October 2014) and disease specific information was extracted from patients’ records. Oral examination included: dental findings (decayed-, missing- and filled-teeth-index (dmf-t/DMF-T)), gingival inflammation (papilla-bleeding-index (PBI)) and periodontal screening index (PSI). Functional examination followed Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Additionally, modified Helkimo’s Clinical Dysfunction Index and radiographic scoring were recorded. Results: 59 JIA patients were included. The mean dmf-t/DMF-T was 2.6. Only one patient showed no signs of gingival inflammation, while 57.6% had a maximum PSI of 2 or less. Positive functional findings were assessed clinically in more than half of the patients. Major diagnosis by RDC/TMD was osteoarthrosis. Patients with at least one positive anamnestic or clinical functional finding revealed significantly higher radiographic scores (CI = 0.440, p = 0.022). Patients with increased c-reactive-protein had a significantly higher PBI (Z = –2.118, p = 0.034) and increased radiographic scores (CI = 0.408, p = 0.043). Conclusions: Adolescents suffering from JIA show high levels of caries experience and gingival inflammation. Temporomandibular joint dysfunction is often seen in JIA patients. Consequently, special dental care programs would be recommendable.

The Efficacy of Platelets Rich Plasma Injection in the Superior Joint Space of the Tempromandibular Joint Guided by Ultra Sound in Patients with Non-reducing Disk Displacement

OBJECTIVE

The objective of this study was to determine average improvement during the rest and active mouth opening after ultrasound guided platelets rich plasma injection in the tempromandibular superior joint space for the patients complaining from non-reducing disk displacement.

PATIENTS AND METHODS

Thirty-four patients with non-reducing disk displacement underwent guided ultrasound injection of platelet rich plasma to the upper joint space. The extent of maximal mouth opening, chewing efficiency, sound intensity of the TMJ, and tenderness of the TMJ and the masticatory muscles at rest, motion and mastication were thoroughly assessed at the beginning of the study and scheduled for next follow-up at 1st, 3rd, and 6th months.

RESULTS

Injection with platelets rich plasma was significantly more effective in improvements of the extent of maximal mouth opening, statistics result demonstrated a significant reduction in the VAS values of pain at rest, motion and mastication compared to the baseline VAS values.

CONCLUSION

PRP injection to the upper temporomandibular joint space provided improvement in signs and symptoms of patient with non-reducing disk displacement of the temporomandibular joint.

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.

The role of serotonin and its receptors in activation of immune responses and inflammation

Serotonin or 5-hydroxytryptamine (5-HT) is a neurotransmitter and hormone that contributes to the regulation of various physiological functions by its actions in the central nervous system (CNS) and in the respective organ systems. Peripheral 5-HT is predominantly produced by enterochromaffin (EC) cells of the gastrointestinal (GI) tract. These gut-resident cells produce much more 5-HT than all neuronal and other sources combined, establishing EC cells as the main source of this biogenic amine in the human body. Peripheral 5-HT is also a potent immune modulator and affects various immune cells through its receptors and via the recently identified process of serotonylation. Alterations in 5-HT signalling have been described in inflammatory conditions of the gut, such as inflammatory bowel disease. The association between 5-HT and inflammation, however, is not limited to the gut, as changes in 5-HT levels have also been reported in patients with allergic airway inflammation and rheumatoid arthritis. Based on searches for terms such as '5-HT', 'EC cell', 'immune cells' and 'inflammation' in pubmed.gov as well as by utilizing pertinent reviews, the current review aims to provide an update on the role of 5-HT in biological functions with a particular focus on immune activation and inflammation.

Impact of 5-HT₃ receptor antagonists on peripheral and central diseases

In this article we discuss the novel pharmacological aspects of 5-HT(3) receptor antagonists. Commonly used to counteract chemotherapy-induced emesis, these agents now appear to be reaching out for newer indications. Studies have reported neuroprotective and anti-inflammatory properties in vitro and in vivo. 5-HT(3) receptor antagonists can modulate the immune-inflammatory axis through blockade of 5-HT(3) receptors present on immune cells. We review evidence addressing the effects of these drugs on peripheral inflammatory diseases, including asthma, rheumatoid diseases, inflammatory bowel disease and sepsis in addition to diabetes and CNS disorders, including Alzheimer's disease (AD), seizure and stroke.

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.

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.

Measuring persistent temporomandibular joint nociception in rats and two mice strains

Temporomandibular joint (TMJ) pain has been reported to last for prolonged periods in humans. In rodents a variety of methods have been used to measure TMJ nociception, but for most of these methods the period of measurement has been minutes to a couple of hours. In addition, most measurement protocols required restraint or training of the animal. Previous studies from our laboratory demonstrated that feeding behavior, particularly meal duration, was an indicator of TMJ nociception in unrestrained and untrained male and female Sprague-Dawley rats for up to two days. In this study, we first found that injection of complete Freund's adjuvant (CFA) into the TMJ of rats significantly lengthened meal duration for 19 days and also decreased meal frequency for 42 days. Interestingly, the meal duration varied significantly from day to day within the 19 day period. TMJ interleukin-1 beta (IL-1 beta) and calcitonin gene-related peptide (CGRP) were significantly elevated in the TMJ tissues of CFA-injected animals and the level of these markers was attenuated as the meal duration decreased with time. Control animals injected with saline into the TMJ or CFA into the knee did not show a significant lengthening in meal duration but did show a decrease in meal frequency. In a second study, DBA/1LacJ mice given TMJ CFA injections showed a significantly lengthened meal duration on four of the seven days measured using end-of-the meal definition of 5 or 10 min. No other meal pattern changed significantly. Two days post-CFA injection, the DBA/1LacJ mice showed significantly elevated interleukin-6 (IL-6), but not elevated IL-1 beta. Seven days post-injection, both IL-6 and IL-1 beta were significantly elevated. No change in CGRP was detected. In this study C57Bl/6 mice also received TMJ CFA injections, but they did not show a lengthening in any meal pattern or significant increases in IL-1 beta, IL-6 or CGRP. Our data show, for the first time, that meal duration can be used to measure CFA-induced nociception in the TMJ over the course of several weeks in unrestrained rats and for up to seven days in the DBA/1LacJ mouse strain. In addition, C57Bl/6 mice are resistant to CFA-induced TMJ nociception at the same dose used in the DBA/1LacJ mice.

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

PURPOSE

The aim of this study was to investigate the relation between plasma level of glutamate and extent of radiographic bone erosion of the temporomandibular joint (TMJ) in patients with early rheumatoid arthritis (RA) in relation to inflammatory disease activity as well as estradiol and testosterone.

MATERIALS AND METHODS

A total of 47 patients (29 women and 18 men) of whom 24 were seropositive were included shortly after being diagnosed with RA. Radiographic signs of bone tissue resorption (erosions) in the TMJ were recorded by cone-beam CT images, and an erosion score (0 to 24) was calculated for each patient. Venous blood was analyzed for rheumatoid factor, C-reactive protein, erythrocyte sedimentation rate, leukocyte particle count, glutamate, estradiol, and testosterone. Nonparametric statistical methods were used in the analysis.

RESULTS

Resorptive changes of the TMJ were found in a major part of the patients. There was a significant positive correlation between plasma level of glutamate and extension of radiographic erosions that was strongest in the patients with low levels of C-reactive protein, estradiol, or testosterone. By contrast, erosions were correlated with C-reactive protein in patients with high levels of estradiol. The highest levels of glutamate were found in patients with low levels of C-reactive protein and estradiol.

CONCLUSIONS

This study shows that a majority of patients with early RA presents radiographic signs of bone tissue resorption of the TMJ and that circulating glutamate is associated with the extent of these changes. The relationship between glutamate and bone resorption seems to be influenced by systemic inflammatory activity as well as estradiol and testosterone levels.

Interleukin‐1β influences the effect of infliximab on temporomandibular joint pain in rheumatoid arthritis

OBJECTIVES

The aim of this study was to investigate the influence of plasma and synovial fluid tumour necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), IL-6, soluble TNF receptor II (TNF-sRII), IL-1 receptor antagonist (IL-1ra), soluble IL-1 receptor II (IL-1sRII) and IL-10 on the effect of the TNFalpha antibody infliximab on temporomandibular joint (TMJ) pain in patients with active rheumatoid arthritis (RA).

METHODS

Fifteen patients with TMJ pain taking methotrexate were included in the study. The effect of intravenous infusions of infliximab was assessed after 14 or 22 weeks. TMJ resting and movement pain was assessed by a visual analogue scale (VAS) (0-100 mm) and samples of venous blood and TMJ synovial fluid were collected before and after treatment.

RESULTS

The effect of infliximab on TMJ pain was influenced by pretreatment plasma levels of IL-1beta, IL-1ra, and IL-10 as well as pretreatment levels of TMJ synovial fluid IL-1sRII. High pretreatment levels of these cytokines and receptors as well as the presence of rheumatoid factor (RF) were associated with no or minor reduction in TMJ pain after treatment.

CONCLUSIONS

Systemic treatment of RA with a combination of infliximab and methotrexate seems to be insufficient to alleviate TMJ pain in patients with RF or high pretreatment plasma levels of IL-1beta.

Gingivitis and periodontitis are related to repeated high levels of circulating tumor necrosis factor-alpha in patients with rheumatoid arthritis

BACKGROUND

Several studies have indicated a relationship between rheumatoid arthritis and periodontal disease. The aim of this study was to investigate the association between the circulating proinflammatory mediators tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta, prostaglandin E(2), serotonin, rheumatoid factor, and periodontitis in patients with rheumatoid arthritis.

METHODS

Nineteen patients, 17 women and two men, with rheumatoid arthritis were included. These patients had been examined repeatedly (average of three times) with regard to inflammatory markers and mediators from blood samples. Their teeth, excluding third molars, were examined with regard to number, clinical attachment level (CAL), probing depth (PD), and gingival bleeding on probing (BOP). Assessment of furcation involvement and increased tooth mobility was also made. All patients were non-smokers. Thirty healthy individuals, 20 women and 10 men, were included as a reference regarding TNF-alpha.

RESULTS

Patients with high levels of time-averaged TNF-alpha from repeated plasma samples had a higher frequency of BOP as well as increased CAL and PD compared to those with low levels.

CONCLUSION

Gingivitis and periodontitis are related to high levels of circulating TNF-alpha in patients with rheumatoid arthritis.

Serotonin mediates PGE2 overexpression through 5-HT2A and 5-HT3 receptor subtypes in serum-free tissue culture of macrophage-like synovial cells

Serotonin antagonists show impressive analgesic efficacy in rheumatoid arthritis, osteoarthritis (OA) or fibromyalgia; however, this effect is not well understood. We examined the mechanism of serotonin-induced inflammation and its antagonists in OA. Serotonin receptor subtypes and COX-2 were analysed by RT-PCR from synovial tissue. Serum-free cultures were stimulated with 10 muM serotonin and/or the antagonists ketanserin (5-HT(2A)), tropisetron (5-HT(3)) and parecoxib (COX-2). Prostaglandin E(2) (PGE(2)), tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta) and leukotriene B4 (LTB4) were measured by an immunoassay in the supernatants. RT-PCR results showed mRNA for 5-HT(2A) and 5-HT(3) receptors, and COX-2. PGE(2) in the supernatants increased by 261.2% +/- 56.7 (mean +/- SEM; P = 0.007) in response to serotonin. TNF-alpha, IL-1beta and LTB4 levels did not change. Ketanserin, tropisetron and parecoxib suppressed PGE(2). The serotonin-induced PGE(2) overexpression appeared thus to be mediated by 5-HT(2A) and 5-HT(3) receptors. This activation might involve COX-2. The findings may explain the potent benefit of 5-HT(3) antagonists.

Injection of sodium hyaluronate compared to a corticosteroid in the treatment of patients with temporomandibular joint osteoarthritis: a CT evaluation

OBJECTIVE

Osseous changes in the temporomandibular joint (TMJ) were evaluated using computed tomography (CT) examinations before and after TMJ injections of sodium hyaluronate or a corticosteroid in patients with osteoarthritis (OA).

STUDY DESIGN

Forty patients were randomly allocated into 2 groups for 2 intra-articular injections with either sodium hyaluronate or a corticosteroid. Bilateral TMJ examinations with high resolution CT were obtained in 36 patients before and 6 months after treatment. Treated and contralateral TMJs were evaluated for the presence of osteoarthritic osseous abnormalities by 2 reviewers independently.

RESULTS

Progression, regression, and no changes of osseous abnormalities were demonstrated in 13, 9, and 14 TMJs, respectively, 6 months after treatment. There was no significant difference between the groups.

CONCLUSIONS

Progression/regression and no changes of osteoarthritic abnormalities were observed on CT examinations in both the treated and the contralateral TMJs after treatment with intra-articular injection with sodium hyaluronate or corticosteroid.

Reduction of temporomandibular joint pain after treatment with a combination of methotrexate and infliximab is associated with changes in synovial fluid and plasma cytokines in rheumatoid arthritis

The aims were to investigate the effect of intravenous infusions of the tumor necrosis factor-alpha (TNF-alpha) antibody infliximab on symptoms and signs of temporomandibular joint (TMJ) involvement in relation to effects on synovial fluid and plasma proinflammatory TNF-alpha, interleukin-1beta (IL-1beta) and interleukin-6 as well as antiinflam matory soluble TNF receptor II (TNF-sRII), interleukin-1 receptor antagonist (IL-1ra), soluble IL-1 receptor II (IL-1sRII) and interleukin-10 (IL-10) in patients with active rheumatoid arthritis (RA). Nineteen patients with TMJ involvement taking methotrexate were included in the study. TMJ and general joint pain intensity as well as pain on mandibular movements, tenderness to digital palpation, pressure pain threshold and maximum mouth-opening capacity were assessed in a clinical examination. The effect of infliximab was assessed after 2 and 14 or 22 weeks. TMJ synovial fluid and venous blood were collected for cytokine analysis at all occasions while determination of erythrocyte sedimentation rate and C-reactive protein were performed at baseline and at long-term follow-up only. Reduction of TMJ pain was associated with raised levels of synovial fluid TNF-sRII and IL-1sRII as well as raised plasma levels of IL-1ra and IL-10. Decreased erythrocyte sedimentation rate was associated with decreased tenderness to digital palpation. Reduced general joint pain intensity was associated with reduced plasma levels of IL-6 and C-reactive protein. In conclusion, systemic treatment with a combination of infliximab and methotrexate reduces TMJ pain in RA in association with an increase in anti-inflammatory cytokines and receptors in synovial fluid and plasma.