Oxidative Stress-induced DNA Damage in the Synovial Cells of the Temporomandibular Joint in the Rat

The Nrf2 Pathway Alleviates Overloading Force-Induced TMJ Degeneration by Downregulating Oxidative Stress Reactions

Objective

Oxidative stress is involved in the mechanisms associated with temporomandibular joint (TMJ) diseases. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a crucial oxidative stress marker, but the specific mechanisms of its regulation in the early stages of mandibular condylar cartilage (MCC) degeneration remain unclear. This study aimed to explore the regulatory role of Nrf2 and its related oxidative stress signaling pathway in the early stage of MCC degeneration.

Materials and Methods

Overloading force-induced MCC degeneration was performed in wild-type and Nrf2 knockout mice, as well as in mice after treatment with the Nrf2 activator cardamonin. Changes in MCC degeneration and the expression of oxidative stress markers in the corresponding situations were observed.

Results

Nrf2 and NADPH oxidase 2 (NOX2) expression were elevated during early MCC degeneration induced by an overloading force. MCC degeneration was aggravated when Nrf2 was knocked out, accompanied by increased NOX2 and superoxide dismutase 2 (SOD2) expression. The MCC degeneration process was alleviated after cardamonin treatment, with activation of the Nrf2 pathway and decreased NOX2 and SOD2 expression.

Conclusion

Early MCC degeneration is accompanied by mild oxidative stress progression. Activated Nrf2 and related pathways could alleviate the degeneration of MCC.

BNTA attenuates temporomandibular joint osteoarthritis progression by directly targeting ALDH3A1: An in vivo and in vitro study

BNTA is known to have a therapeutic effect on knee osteoarthritis and inflammatory osteoclastogenesis. However, the protective effect of BNTA regarding temporomandibular mandibular joint osteoarthritis (TMJOA) and its underlying mechanism and physiological target remains unclear. In the present study, BNTA ameliorated cartilage degradation and inflammation responses in monosodium iodoacetate (MIA)-induced TMJOA in vivo. In IL-1β-induced condylar chondrocytes, BNTA prevents oxidative stress, inflammatory responses and increasing synthesis of cartilage extracellular matrix through activating nuclear factor-E2-related factor 2 (NRF2) signaling. Suppression of NRF2 signaling abolishes the protective effect of BNTA in TMJOA. Notably, BNTA may bind directly to ALDH3A1 and act as a stabilizer, as evidenced by drug affinity responsive target stability assay (DARTS), cellular thermal shift assay (CETSA) and molecular docking results. Further investigation of the underlying molecular and cellular mechanism infers a positive correlation of ALDH3A1 regulating NRF2 signaling. In conclusion, BNTA may attenuate TMJOA progression via the ALDH3A1/NRF2 axis, inferring that BNTA is a therapeutic target for treating temporomandibular mandibular joint osteoarthritis.

The Attenuating Effect of Low-Intensity Pulsed Ultrasound on Hypoxia-Induced Rat Chondrocyte Damage in TMJ Osteoarthritis Based on TMT Labeling Quantitative Proteomic Analysis

Temporomandibular joint osteoarthritis (TMJOA) is a degenerative disease with a complex and multifactorial etiology. An increased intrajoint pressure or weakened penetration can exacerbate the hypoxic state of the condylar cartilage microenvironment. Our group previously simulated the hypoxic environment of TMJOA in vitro. Low-intensity pulsed ultrasound (LIPUS) stimulation attenuates chondrocyte matrix degradation via a hypoxia-inducible factor (HIF) pathway-associated mechanism, but the mode of action of LIPUS is currently poorly understood. Moreover, most recent studies investigated the pathological mechanisms of osteoarthritis, but no biomarkers have been established for assessing the therapeutic effect of LIPUS on TMJOA with high specificity, which results in a lack of guidance regarding clinical application. Here, tandem mass tag (TMT)-based quantitative proteomic technology was used to comprehensively screen the molecular targets and pathways affected by the action of LIPUS on chondrocytes under hypoxic conditions. A bioinformatic analysis identified 902 and 131 differentially expressed proteins (DEPs) in the <1% oxygen treatment group compared with the control group and in the <1% oxygen + LIPUS stimulation group compared with the <1% oxygen treatment group, respectively. The DEPs were analyzed by gene ontology (GO), KEGG pathway and protein-protein interaction (PPI) network analyses. By acting on extracellular matrix (ECM)-associated proteins, LIPUS increases energy production and activates the FAK signaling pathway to regulate cell biological behaviors. DEPs of interest were selected to verify the reliability of the proteomic results. In addition, this experiment demonstrated that LIPUS could upregulate chondrogenic factors (such as Sox9, Collagen Ⅱ and Aggrecan) and increase the mucin sulfate content. Moreover, LIPUS reduced the hydrolytic degradation of the ECM by decreasing the MMP3/TIMP1 ratio and vascularization by downregulating VEGF. Interestingly, LIPUS improved the migration ability of chondrocytes. In summary, LIPUS can regulate complex biological processes in chondrocytes under hypoxic conditions and alter the expression of many functional proteins, which results in reductions in hypoxia-induced chondrocyte damage. ECM proteins such as thrombospondin4, thrombospondin1, IL1RL1, and tissue inhibitors of metalloproteinase 1 play a central role and can be used as specific biomarkers determining the efficacy of LIPUS and viable clinical therapeutic targets of TMJOA.

Role of Photobiomodulation Therapy in Modulating Oxidative Stress in Temporomandibular Disorders. A Systematic Review and Meta-Analysis of Human Randomised Controlled Trials

This systematic review and meta-analysis (PROSPERO registration; ref CRD 42020198921) aimed to govern photobiomodulation therapy (PBMT) efficacy in temporomandibular disorder (TMD). PRISMA guidelines and Cochrane Collaboration recommendations were followed. Differences in pain reduction assessment by qualitative measurement with visual analogue scale pain (VAS), pressure threshold (PPT) and maximum mouth opening (MMO) were calculated with 95% confidence intervals and pooled in a random effects model with a subgroup analysis, evaluating the role of follow-up duration. Heterogeneity was analysed using Q and I² tests. Publication bias was assessed by visual examination of funnel plot symmetry. Qualitative analysis revealed 46% of the 44 included studies showed a high risk of bias. Meta-analysis on 32 out of 44 studies revealed statistically significant intergroup differences (SSID) for VAS (SMD = -0.55; 95% CI = -0.82 to -0.27; Z = 3.90 (p < 0.001)), PPT (SMD = -0.45; 95% CI = -0.89 to 0.00; Z = 1.97 (p = 0.05)) and MMO (SMD = -0.45; 95% CI = -0.89 to 0.00; Z = 1.97 (p = 0.05)), favouring PBMT compared to control treatment strategies. Sensitivity analysis revealed SSID (SMD = -0.53; 95% CI = -0.73 to -0.32; Z = 5.02 (p < 0.0001)) with low heterogeneity (Τ² = 0.02; χ² = 16.03 (p = 0.31); I² = 13%). Hence, this review, for first time, proposed suggested recommendations for PBMT protocols and methodology for future extensive TMD research.

Mandibular lateral deviation induces alteration in vascular endothelial growth factor expression and oxidative stress/nitric oxide generation in rat condyle, synovial membrane and masseter muscle

OBJECTIVE

We aimed to investigate alteration in cellular signaling mediated by vascular endothelial growth factor (VEGF) and parameters of oxidative stress/nitric oxide generation, superoxide dismutase (SOD) and neuronal nitric oxide synthase (nNOS), underlying altered functional mechanical loading of TMJ (temporomandibular joint) during lateral mandibular deviation.

DESIGN

Thirty-eight 5-week-old male Wistar rats were divided into experimental group, which received acrylic resin appliance that shifted mandible to the left during closure, and control group. Computed tomography and histomorphometry were used for condyle analyses, while samples of condyle, synovial membrane and m. masseter were analyzed with enzyme-linked immunosorbent assay and spectrophotometry to determine VEGF and nNOS protein concentrations, and SOD activity.

RESULTS

Experimental group of rats developed smaller and asymmetrical mandibles. Less of new bone and cartilage formation and larger bone marrow cavities area were found in the experimental group. Higher VEGF expression in condyle and m. masseter as well as higher nNOS expression in m. masseter and synovial membrane were found in the experimental compared to the control group. Alteration of SOD activity was found in m. masseter and synovial membrane in the experimental group.

CONCLUSIONS

Lateral mandibular deviation induces mandibular and condylar morphological changes as well as significant cellular signaling alterations in condyle, synovial membrane and masticatory muscle. Cellular VEGF protein overexpression and oxidative stress/nitric oxide disbalance could be the mechanisms underlying unbalanced functional TMJ loading due to mandibular deviation.

Dual-energy X-ray absorptiometry pitfalls in Thalassemia Major

BACKGROUND

Low mineral mass and reduced bone strength with increased fracture risk are the main causes of morbidity in Thalassemia Major (TM). The pathogenesis is multifactorial and includes ineffective erythropoiesis with medullary expansion, multiple endocrine dysfunctions, direct iron bone deposition, deferoxamine-induced bone dysplasia, and reduced physical activity associated with disease complications. Dual-energy X-ray absorptiometry (DXA) is the "gold standard" for bone mineral density (BMD) assessment and for bone strength and quality evaluation. This method identifies patients at greater risk of fragility fractures, guiding treatment and monitoring response to therapy. In TM, DXA shows limitations concerning BMD calculation accuracy and fracture risk prediction. One of the main challenges in the assessment of bone health in patients with TM is the accurate interpretation of densitometric results.

PURPOSE

This review investigates the major pitfalls in DXA implementation and interpretation in TM.

METHODS

Available literature has been assessed.

CONCLUSIONS

DXA shows limitations in assessing bone mineral "status" in TM, especially in the paediatric population, due to the peculiar characteristics of bone architecture and deformities associated with the disease. A radiological technique adjustment in this population is mandatory.

Exogenous nitric oxide stimulates the odontogenic differentiation of rat dental pulp stem cells

Nitric oxide (NO) is thought to play a pivotal regulatory role in dental pulp tissues under both physiological and pathological conditions. However, little is known about the NO functions in dental pulp stem cells (DPSCs). We examined the direct actions of a spontaneous NO gas-releasing donor, NOC-18, on the odontogenic capacity of rat DPSCs (rDPSCs). In the presence of NOC-18, rDPSCs were transformed into odontoblast-like cells with long cytoplasmic processes and a polarized nucleus. NOC-18 treatment increased alkaline phosphatase activity and enhanced dentin-like mineralized tissue formation and the expression levels of several odontoblast-specific genes, such as runt related factor 2, dentin matrix protein 1 and dentin sialophosphoprotein, in rDPSCs. In contrast, carboxy-PTIO, a NO scavenger, completely suppressed the odontogenic capacity of rDPSCs. This NO-promoted odontogenic differentiation was activated by tumor necrosis factor-NF-κB axis in rDPSCs. Further in vivo study demonstrated that NOC-18-application in a tooth cavity accelerated tertiary dentin formation, which was associated with early nitrotyrosine expression in the dental pulp tissues beneath the cavity. Taken together, the present findings indicate that exogenous NO directly induces the odontogenic capacity of rDPSCs, suggesting that NO donors might offer a novel host DPSC-targeting alternative to current pulp capping agents in endodontics.

Role of Glutathione-S-transferases in neurological problems

INTRODUCTION

Role of Glutathione-S-transferases (GSTs) has been well explored in the cellular detoxification process, regulation of redox homeostasis and S-glutothionylation of target proteins like JNK, ASK1 etc. However, altered levels or functions of this enzyme or their subtypes have emerged in the development of several pathologies diseases such as Alzheimer's disease, Parkinson's disease, cancer and related conditions. Oxidative stress is one of the possible pathological events that contributes significantly to activation of degenerating cascades inside neuronal cells. The central nervous system is highly sensitive to oxidative stress because of low levels or capacities of antioxidant enzymes. The brain is highly metabolic in nature making it susceptible to oxidative stress. Areas covered: The present review provides a comprehensive overview of the multiple connections of GSTs within diverse neurological diseases including cancer. Furthermore, the authors have made significant efforts to discuss the regulation of different GST isoforms that have been associated with various pathological processes such as glioblastoma, Alzheimer's disease, Parkinson's disease, stroke and epilepsy. Expert opinion: Though GSTs have been one of the key areas of scientific research over the last few decades, much remains to be elucidated about their physiological functions as well as pathological involvement of GSTs and their polymorphic variants.

Effects of 2-amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP) on histopathology, oxidative stress, and expression of c-fos, c-jun and p16 in rat stomachs

2-Amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP) is one of the most abundant heterocyclic amines (HCAs) generated from overcooking meat at high temperatures. To understand the possible mechanism of PhIP-associated stomach cancer, the effects of PhIP on morphology, oxidative stress, gene expression of c-fos, c-jun and p16 in rat stomachs were investigated. The results showed that (1) 15mg/kg body weight PhIP induced obvious histopathological changes in gastric mucosa; (2) PhIP (10 and/or 15mg/kg) significantly decreased superoxide dismutase (SOD) and glutathioneperoxidase (GPx) activities, while increased catalase (CAT) activity compared with the control. With the elevated doses of PhIP, malondialdehyde (MDA) contents, protein carbonyl (PCO) contents and DNA-protein crosslinks (DPC) coefficients were significantly raised in a dose-dependent manner; (3) PhIP at the doses of 10mg/kg and/or 15mg/kg significantly inhibited p16 mRNA and protein expression, whereas enhanced c-fos and c-jun expression relative to control. The data indicated that PhIP could cause stomach injury, oxidative stress in rat stomachs as well as the activation of c-fos and c-jun and inactivation of p16, which may play a role in the pathogenesis of PhIP-associated stomach cancer.

The spine in β-thalassemia syndromes

STUDY DESIGN

Literature review.

OBJECTIVE

To present a comprehensive overview of spinal involvement in patients with β-thalassemia, aiming to orient the spinal surgeon to these potentially disabling complications.

SUMMARY OF BACKGROUND DATA

β-thalassemia, an inherited disorder of hemoglobin synthesis, is the most common monogenetic disease worldwide. Patients with thalassemia major (TM) suffer a severe anemia that requires regular blood transfusions for survival and iron chelation therapy to control transfusional iron overload. Thalassemia intermedia is a phenotype of thalassemia with a milder course and anemia, wherein most patients remain transfusion independent. Spinal involvement related to disease course and treatment is common in patients with thalassemia syndromes, yet it has not been constructively reviewed in the literature.

METHODS

Potentially relevant studies were identified from an electronic search of MEDLINE (1966 to the second week of May 2010).

RESULTS

In patients with TM, genetic and acquired risk factors lead to osteoporosis, pathologic fractures of the spine, and back pain. Osteoporosis in TM patients is progressive; thus, early diagnosis and treatment are recommended. Bisphosphonates are relatively safe and effective in this patient population. Characteristic intervertebral disc degeneration is also seen in patients with TM who have evidence of severe iron overload or those who receive the subcutaneous iron chelator deferoxamine. Spinal asymmetry and overt scoliosis are common in patients with TM. The prognosis seems favorable, with many patients showing spontaneous resolution without the need for intervention. In patients with thalassemia intermedia, ineffective erythropoiesis drives extramedullary hematopoietic tissue formation, which is mostly evident on magnetic resonance imaging. Paraspinal involvement is of greatest concern because of the associated spinal cord compression. Several treatment options have been described, including transfusion therapy, laminectomy, radiotherapy, and the use of fetal hemoglobin-inducing agents that decrease the hematopoietic drive.

CONCLUSION

Current knowledge supports that spinal involvement in patients with β-thalassemia is common and diverse yet still requires further prospective evaluation.

Genetic polymorphisms in folate pathway enzymes, DRD4 and GSTM1 are related to temporomandibular disorder

Background

Temporomandibular disorder (TMD) is a multifactorial syndrome related to a critical period of human life. TMD has been associated with psychological dysfunctions, oxidative state and sexual dimorphism with coincidental occurrence along the pubertal development. In this work we study the association between TMD and genetic polymorphisms of folate metabolism, neurotransmission, oxidative and hormonal metabolism. Folate metabolism, which depends on genes variations and diet, is directly involved in genetic and epigenetic variations that can influence the changes of last growing period of development in human and the appearance of the TMD.

Methods

A case-control study was designed to evaluate the impact of genetic polymorphisms above described on TMD. A total of 229 individuals (69% women) were included at the study; 86 were patients with TMD and 143 were healthy control subjects. Subjects underwent to a clinical examination following the guidelines by the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Genotyping of 20 Single Nucleotide Polymorphisms (SNPs), divided in two groups, was performed by multiplex minisequencing preceded by multiplex PCR. Other seven genetic polymorphisms different from SNPs (deletions, insertions, tandem repeat, null genotype) were achieved by a multiplex-PCR. A chi-square test was performed to determine the differences in genotype and allelic frequencies between TMD patients and healthy subjects. To estimate TMD risk, in those polymorphisms that shown significant differences, odds ratio (OR) with a 95% of confidence interval were calculated.

Results

Six of the polymorphisms showed statistical associations with TMD. Four of them are related to enzymes of folates metabolism: Allele G of Serine Hydoxymethyltransferase 1 (SHMT1) rs1979277 (OR = 3.99; 95%CI 1.72, 9.25; p = 0.002), allele G of SHMT1 rs638416 (OR = 2.80; 95%CI 1.51, 5.21; p = 0.013), allele T of Methylentetrahydrofolate Dehydrogenase (MTHFD) rs2236225 (OR = 3.09; 95%CI 1.27, 7.50; p = 0.016) and allele A of Methionine Synthase Reductase (MTRR) rs1801394 (OR = 2.35; 95CI 1.10, 5.00; p = 0.037). An inflammatory oxidative stress enzyme, Gluthatione S-Tranferase Mu-1(GSTM1), null allele (OR = 2.21; 95%CI 1.24, 4.36; p = 0.030) and a neurotransmission receptor, Dopamine Receptor D4 (DRD4), long allele of 48 bp-repeat (OR = 3.62; 95%CI 0.76, 17.26; p = 0.161).

Conclusions

Some genetic polymorphisms related to folates metabolism, inflammatory oxidative stress, and neurotransmission responses to pain, has been significantly associated to TMD syndrome

Bone disease and skeletal complications in patients with β thalassemia major

Increased survival in patients with β thalassemia major (TM) allowed for several complications of the disease and its treatment to manifest, one of which is bone disease. Osteoporosis in this patient population results from a variety of genetic and acquired factors. Early diagnosis and prevention are essential and several measures have been evaluated for management including bisphosphonates. Fracture prevalence in TM patients seems to be clustered in mid adulthood, and is related to vitamin D deficiency and low bone mineral density. Fracture healing in patients with TM does not seem to be different from that in normal individuals. Bone and joint pain are a common manifestation of the underlying pathophysiology or may be related to iron chelator intake. Intervertebral disc changes are seen in patients who are heavily iron overloaded or those who are chelated with deferoxamine. Spinal deformity is common in TM, yet the prognosis is benign with spontaneous resolution frequently observed. Further research is warranted to evaluate the mechanisms, clinical implications, and optimal management of bone disease in this patient population.

Effects of hyaluronan on carrageenan-induced synovitis in rat TMJ

Nitric oxide is one of many proinflammatory mediators that are involved in temporomandibular joint (TMJ) inflammatory disorder and is synthesized by inducible nitric oxide synthase (iNOS). iNOS is transcriptionally regulated by nuclear factor-κB (NF-κB) in cases of inflammation, proliferation, and apoptosis. It has also been reported that nitric oxide is positively regulated by carrageenan and negatively regulated by hyaluronan in the knee joint. The aim of this study was to histologically evaluate how inflammation and cell proliferation of the synovial membrane are affected by the exogenous administration of carrageenan and hyaluronan in the rat TMJ by investigating iNOS, NF-κB, and anti proliferating cell nuclear antigen (PCNA) immunoreactivity. As results, immunoreactive cells to iNOS, NF-κB, and PCNA were normally localized only in the synovial membrane of wild type TMJs. The numbers of immunoreactive cells were extensively larger in the carrageenan-injected synovial membranes exhibiting excessive folding, and smaller in the hyaluronan-injected synovial membranes showing a few folds. These results indicate that a carrageenan injection induced inflammation and cell proliferation especially in the synovial membrane and that hyaluronan relieved the inflammation by decreasing inflammatory molecules in the synovial membrane.

Effect of sulfur dioxide on expression of proto-oncogenes and tumor suppressor genes from rats

Sulfur dioxide (SO(2)) is a ubiquitous air pollutant that is present in low concentrations in the urban air, and in higher concentrations in the working environment. In the present study, male Wistar rats were housed in exposure chambers and treated with 14.00 +/- 1.01, 28.00 +/- 1.77 and 56.00 +/- 3.44 mg m(-3) SO(2) for 6 h/day for 7 days, while control group was exposed to filtered air in the same condition. The mRNA and protein levels of proto-oncogenes (c-fos, c-jun, c-myc, and Ki-ras) and tumor suppressor genes (p53, Rb, and p16) were analyzed in lungs using a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay and Western blot analysis. The results showed that mRNA and protein levels of c-fos, c-jun, c-myc, Ki-ras, and p53 in lungs were increased in a dose-dependent manner, while mRNA and protein levels of Rb and p16 were decreased in lungs of rats after SO(2) inhalation. These results lead to a conclusion that SO(2) exposure could activate expressions of proto-oncogenes and suppress expressions of tumor suppressor genes, which might relate to the molecular mechanism of cocarcinogenic properties and potential carcinogenic effects of SO(2). According to previous studies, the results also indicated that promoter genes of apoptosis and tumor suppressor genes could produce apoptotic signals to antagonize the growth signals that arise from oncogenes. Understanding its molecular controls will benefit development of treatments for many diseases.

Condyle-disk-fossa position and relationship to clinical signs and symptoms of temporomandibular disorders in women

OBJECTIVE

The aim of the present study was to assess the disk-condyle-fossa relationship through magnetic resonance imaging and determine its association with clinical signs and symptoms of temporomandibular disorder in patients with myofascial pain and disk displacement (with and without reduction).

STUDY DESIGN

Sixty-two female patients with complaints of pain were clinically examined using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and divided into the following groups: Group I, myofascial pain (n = 19); Group IIa, disk displacement with reduction (n = 32); and Groups IIb and IIc, disk displacement without reduction (n = 11). Classification of disk position was based on the positioning on a clock face (> or < than 11 o'clock) and condylar excursion was determined as (1) the proximal side of the apex of the articular eminence; (2) at the level of the articular eminence; and (3) beyond the apex of the articular eminence. Condylar position was determined in the sagittal images based on Gelb's template (normal, posteriorly displaced). Pain was assessed using a visual analogue scale (VAS). The univariate logistic regression, Mann-Whitney, Kruskall-Wallis and Pearson's correlation tests were used in the statistical analysis (P < or = .05).

RESULTS

No significant association was found between the independent variables (condylar position, disk position, and condylar excursion) and the dependent variables (pain, maximal opening of the mouth, maximal lateral movement). However, there was a significant association between increased condyle excursion and pain (P = .035) and also maximum mouth opening movement was associated with lateral movement (P = .01; r = 0.31).

CONCLUSIONS

Increase in condyle excursion may significantly influence pain perception in TMD patients. The type of dysfunction and severity of alterations on the imaging exams were not related to the severity of pain or range of motion of the mandible.

Aging-dependent regulation of antioxidant enzymes and redox status in chronically loaded rat dorsiflexor muscles

This study compares changes in the pro-oxidant production and buffering capacity in young and aged skeletal muscle after exposure to chronic repetitive loading (RL). The dorsiflexors from one limb of young and aged rats were loaded 3 times/week for 4.5 weeks using 80 maximal stretch-shortening contractions per session. RL increased H2O2 in tibialis anterior muscles of young and aged rats and decreased the ratio of reduced/oxidized glutathione and lipid peroxidation in aged but not young adult animals. Glutathione peroxidase (GPx) activity decreased whereas catalase activity increased with RL in muscles from young and aged rats. RL increased CuZn superoxide disumutase (SOD) and Mn SOD protein concentration and CuZn SOD activity in muscles from young but not aged animals. There were no changes in protein content for GPx-1 and catalase or messenger RNA for any of the enzymes studied. These data show that aging reduces the adaptive capacity of muscles to buffer increased pro-oxidants imposed by chronic RL.

Melatonin: potential functions in the oral cavity

BACKGROUND

Melatonin is synthesized and secreted by the pineal gland and other organs. The pattern of melatonin secretion is controlled by an endogenous circadian timing system and conveys information about the light-dark cycle to the organism, thereby organizing its seasonal and circadian rhythms. Melatonin has powerful antioxidant effects, functions in an immunomodulatory role, may protect against certain cancers, delays some age-related processes, stimulates the synthesis of type I collagen fibers, and promotes bone formation.

METHODS

An extensive review was made (e.g., using PubMed, Science Direct, and Web of Knowledge) of the literature.

RESULTS

Melatonin, which is released into the saliva, may have important implications for dental disorders, especially in periodontal disease. Diseases of the periodontium are known to be aggravated by free radicals and by alterations in the immune response to microorganisms that are present in plaque. In response to periodontal inflammation, the blood and salivary levels of melatonin may increase.

CONCLUSION

Melatonin may play a role in protecting the oral cavity from tissue damage that is due to oxidative stress, and it may contribute to the regeneration of alveolar bone through the stimulation of type I collagen fiber production and the modulation of osteoblastic and osteoclastic activity.

Sequential expression of endothelial nitric oxide synthase, inducible nitric oxide synthase, and nitrotyrosine in odontoblasts and pulp cells during dentin repair after tooth preparation in rat molars

Nitric oxide (NO) stimulates osteoblast differentiation, but whether NO contributes to odontoblast differentiation during dentin repair is unknown. By using reverse transcription/polymerase chain reaction and immunostaining, we investigated the gene expression and/or immunolocalization of endothelial NO synthase (eNOS), inducible NOS (iNOS), and nitrotyrosine (a biomarker for NO-derived peroxinitrite), and alkaline phosphatase (ALP) and osteocalcin (early and terminal differentiation markers of odontoblasts, respectively) in dental pulp tissue after rat tooth preparation. At the early stage (1-3 days) post-preparation, markedly increased expression of iNOS and nitrotyrosine was found in odontoblasts and pulp cells beneath the cavity, whereas eNOS expression was significantly decreased. ALP mRNA expression was significantly increased after 1 day but decreased after 3 days, whereas ALP activity was weak in the dentin-pulp interface under the cavity after 1 day but strong after 3 days. Osteocalcin mRNA expression was significantly increased at this stage. At 7 days post-preparation, tertiary dentin was formed under the cavity. All the molecules studied were expressed at control levels in odontoblasts/pulp cells beneath the cavity. These findings show that abundant NO is released from odontoblasts and pulp cells at an early stage after tooth preparation and indicate that, after tooth preparation, the up-regulation of iNOS and nitrotyrosine in odontoblasts is synchronized with increased cellular expression of ALP and osteocalcin. Therefore, the NO synthesized by iNOS after tooth preparation probably participates in regulating odontoblast differentiation during tertiary dentinogenesis.

The Relationship Between Temporomandibular Joint Synovitis and Adhesions: Pathogenic Mechanisms and Clinical Implications for Surgical Management

PURPOSE

The purpose of this investigation was to determine the relationship between arthroscopically diagnosed synovitis and adhesions in a population of patients with significant limitation of mandibular opening and temporomandibular joint pain.

PATIENTS AND METHODS

Temporomandibular joint arthroscopy was performed on 126 joints in 80 patients (female:male = 5.7:1; mean age = 35.5 years; mean duration of symptoms = 50 months). All patients were diagnosed with severe temporomandibular joint disease recalcitrant to conservative therapy. Each joint was evaluated arthroscopically for the presence of synovitis and adhesions. Chi-squared analysis was performed to determine if there was a significant relationship between the presence of synovitis and adhesions.

RESULTS

Diagnostic arthroscopic examination showed the following: no synovitis and no adhesions in 18/126 joints (14%), no synovitis with adhesions present in 33/126 joints (26%), synovitis with no adhesions in 13/126 joints (10%), and synovitis and adhesions present in 62/126 joints (49%). Statistical analysis showed a significant relationship between arthroscopically diagnosed synovitis and adhesions.

CONCLUSION

Synovitis and adhesions are commonly present in the temporomandibular joints of patients requiring arthroscopic surgery due to painful limitation of mandibular movement. Excessive mechanical stress on the temporomandibular joint leads to maladaptive responses in the articular and synovial tissues, ultimately leading to synovitis, osteoarthritis and the formation of adhesions. An understanding of the pathogenic mechanisms that lead to synovitis, osteoarthritis and adhesions has important clinical implications for the nonsurgical as well as surgical management of patients suffering from these disorders.

A multifaceted molecule, nitric oxide in oral and periodontal diseases

Nitric oxide (NO) is a molecule with multiple effects on different tissues. NO takes important roles in vasodilatation, bacterial challenge and cytokine stimulation, regulation of mineralized tissue function, neurotransmission, and platelet aggregation, etc. However, under pathological conditions, NO has damaging effects. NO is synthesized by NO synthases (NOS) and inducible isoform of NOS (iNOS) is closely related to the pathophysiological characteristics of inflammatory diseases such as periodontal diseases. The expression of iNOS has been investigated in salivary gland-related diseases, temporomandibular joint disorders and oral cancer as well. The beneficial and damaging effects of NO in diseases related with periodontal, dental and maxillofacial area are discussed in this review. The biological pathways involved with NO and NO inhibitors may be good drug targets to have a role in the future management of patients with diseases in orofacial region.

Degenerative disc disease as a cause of back pain in the thalassaemic population: a case-control study using MRI and plain radiographs

PURPOSE

The aim of this study was to test our observation that back pain in thalassemic patients could be caused by premature and extensive lumbar degenerative disc disease, when compared to non-thalassemic patients with back pain.

METHODS AND MATERIALS

Sixteen thalassemic patients with their sex- and age-matched controls were recruited into the study, 12 with thalassemia major, and 4 with thalassemia intermedia. Both the thalassemia patients and control subjects suffered from back pain, which was subjective rather than measured/pain scored. All subjects underwent magnetic resonance (MR) imaging of the lumbar spine, and 11 of the cases and 8 controls had lumbar spine radiographs. Each lumbar disc was scored for radiographic appearances and MR features of disc degeneration and disc protrusion. Proportion values for these parameters and median scores were derived at each disc level, and were analyzed and compared.

RESULTS

There was a statistically-significant difference between proportion values of cases and controls for the MR features (P value=0.01, n=16) and the radiographic features (P value=0.01, n=11 cases, n=8 controls) of disc degeneration. The median disc level scores for the thalassemic group were uniformly high across all lumbar discs, and at all levels except at L 4/5. The control group conversely demonstrated a predilection for disc degeneration at L4/5 level.

CONCLUSION

The distribution of lumbar disc degeneration in thalassemic patients with back pain is more extensive, severe and multi-level in nature compared to matched controls, and disc degeneration should be considered as a significant cause of back pain in this population group.