NF-kappaB activation and iNOS expression in the synovial membrane of rat temporomandibular joints after induced synovitis

Critical signaling molecules in the temporomandibular joint osteoarthritis under different magnitudes of mechanical stimulation

The mechanical stress environment in the temporomandibular joint (TMJ) is constantly changing due to daily mandibular movements. Therefore, TMJ tissues, such as condylar cartilage, the synovial membrane and discs, are influenced by different magnitudes of mechanical stimulation. Moderate mechanical stimulation is beneficial for maintaining homeostasis, whereas abnormal mechanical stimulation leads to degeneration and ultimately contributes to the development of temporomandibular joint osteoarthritis (TMJOA), which involves changes in critical signaling molecules. Under abnormal mechanical stimulation, compensatory molecules may prevent degenerative changes while decompensatory molecules aggravate. In this review, we summarize the critical signaling molecules that are stimulated by moderate or abnormal mechanical loading in TMJ tissues, mainly in condylar cartilage. Furthermore, we classify abnormal mechanical stimulation-induced molecules into compensatory or decompensatory molecules. Our aim is to understand the pathophysiological mechanism of TMJ dysfunction more deeply in the ever-changing mechanical environment, and then provide new ideas for discovering effective diagnostic and therapeutic targets in TMJOA.

Natural therapeutics and nutraceuticals for lung diseases: Traditional significance, phytochemistry, and pharmacology

BACKGROUND

Lung diseases including chronic obstructive pulmonary disease (COPD), infections like influenza, acute respiratory distress syndrome (ARDS), asthma and pneumonia lung cancer (LC) are common causes of sickness and death worldwide due to their remoteness, cold and harsh climatic conditions, and inaccessible health care facilities.

PURPOSE

Many drugs have already been proposed for the treatment of lung diseases. Few of them are in clinical trials and have the potential to cure infectious diseases. Plant extracts or herbal products have been extensively used as Traditional Chinese Medicine (TCM) and Indian Ayurveda. Moreover, it has been involved in the inhibition of certain genes/protiens effects to promote regulation of signaling pathways. Natural remedies have been scientifically proven with remarkable bioactivities and are considered a cheap and safe source for lung disease.

METHODS

This comprehensive review highlighted the literature about traditional plants and their metabolites with their applications for the treatment of lung diseases through experimental models in humans. Natural drugs information and mode of mechanism have been studied through the literature retrieved by Google Scholar, ScienceDirect, SciFinder, Scopus and Medline PubMed resources against lung diseases.

RESULTS

In vitro, in vivo and computational studies have been explained for natural metabolites derived from plants (like flavonoids, alkaloids, and terpenoids) against different types of lung diseases. Probiotics have also been biologically active therapeutics against cancer, anti-inflammation, antiplatelet, antiviral, and antioxidants associated with lung diseases.

CONCLUSION

The results of the mentioned natural metabolites repurposed for different lung diseases especially for SARS-CoV-2 should be evaluated more by advance computational applications, experimental models in the biological system, also need to be validated by clinical trials so that we may be able to retrieve potential drugs for most challenging lung diseases especially SARS-CoV-2.

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.

Immunohistochemical characterization of early and advanced knee osteoarthritis by NF-κB and iNOS expression

This study was performed to determine the differences in grade of synovitis and expression of NF-κB and iNOS in knee synovial membrane between early and advanced stage of osteoarthritis (OA). Thirty synovial membrane intra-operative biopsies of patients (ten controls, ten with early and ten with advanced OA according to Kellgren-Lawrence radiological score) were immunohistochemically (NF-κB and iNOS) and hystologically (Krenn synovitis score) analyzed and correlated to WOMAC clinical score and pain duration. Krenn synovitis score of patients with radiologically early OA was significantly higher than in patients with advanced OA (p < 0.001). NF-κB expression in both synovial intima (p < 0.001) and subintima (p < 0.001) was also higher in early OA. iNOS expression in subintima was significantly higher in early than in advanced OA (p < 0.001), while in intima iNOS showed no statistical difference between groups (p = 0.07). The lymphocytic nodules, located in synovial subintima, were significantly higher in advanced OA when compared to early OA (p = 0.006) and the control group (p < 0.001). These results suggest that in early OA, there is a localized inflammation of the synovial membrane with high expression of NF-κB and iNOS. In advanced OA, number of expressed factors is reduced, with the exception of intima cells that highly express iNOS, reflecting the ongoing localized inflammatory process of lower degree. In advanced OA, the density of the resident cells is reduced and lymphocytic nodules appear, confirming the important role of adaptive immunity in later OA stage. Clinical significance of this study is better understanding possibilities of preventive measures for synovitis and OA advancement. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1990-1997, 2017.

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

Synovial hyperplasia is a feature of degenerative temporomandibular joint (TMJ) disease. However, the mechanism by which hyperplasia progresses in the TMJ is unknown. Based on the hypothesis that the oxidative stress generated by mechanical loading causes degenerative changes in the TMJ synovium, we investigated the generation of the highly reactive species, peroxynitrite, and the occurrence of DNA damage in the synovium. After condylar hypermobility of rat TMJs, a marker of peroxynitrite, nitrotyrosine, was localized to the nuclei and cytoplasm of the synovial lining cells and fibroblasts in synovitis-induced TMJ. DNA single-strand breaks were found in the nuclei of the synovial cells only after enzyme treatment, whereas DNA double-strand breaks were not detected. These findings indicate that condylar hypermovement induces the proliferation of synovial cells, and suggest that oxidative stress leads to the progression of synovial hyperplasia via DNA damage of the synovial cells in TMJs after mechanical loading.

Alterations in intermediate filaments expression in disc cells from the rat temporomandibular joint following exposure to continuous compressive force

The articular disc in the temporomandibular joint (TMJ) that serves in load relief and stabilizing in jaw movements is a dense collagenous tissue consisting of extracellular matrices and disc cells. The various morphological configurations of the disc cells have given us diverse names, such as fibroblasts, chondrocyte-like cells and fibrochondrocytes; however, the characteristics of these cells have remained to be elucidated in detail. The disc cells have been reported to exhibit heterogeneous immunoreaction patterns for intermediate filaments including glial fibrillary acidic protein (GFAP), nestin and vimentin in the adult rat TMJ. Because these intermediate filaments accumulate in the disc cells as tooth eruption proceeds during postnatal development, it might be surmised that the expression of these intermediate filaments in the disc cells closely relates to mechanical stress. The present study was therefore undertaken to examine the effect of a continuous compressive force on the immunoexpression of these intermediate filaments and an additional intermediate filament - muscle-specific desmin - in the disc cells of the TMJ disc using a rat experimental model. The rats wore an appliance that exerts a continuous compressive load on the TMJ. The experimental period with the appliance was 5 days as determined by previous studies, after which some experimental animals were allowed to survive another 5 days after removal of the appliance. Histological observations demonstrated that the compressive force provoked a remarkable acellular region and a decrease in the thickness of the condylar cartilage of the mandible, and a sparse collagen fiber distribution in the articular disc. The articular disc showed a significant increase in the number of desmin-positive cells as compared with the controls. In contrast, immunopositive cells for GFAP, nestin and vimentin remained unchanged in number as well as intensity. At 5 days after removal of the appliance, both the disc and cartilage exhibited immunohistological and histological features in a recovery process. These findings indicate that the mature articular cells are capable of producing desmin instead of the other intermediate filaments against mechanical stress. The desmin-positive disc cells lacked α-smooth muscle actin (α-SMA) in this study, even though desmin usually co-exists with α-SMA in the vascular smooth muscle cells or pericytes. Because the precursor of a pericyte has such an immunoexpression pattern during angiogenesis, there is a further possibility that the formation of new vessels commenced in response to the extraordinary compressive force.

Sustained inflammation induces degeneration of the temporomandibular joint

The temporomandibular joint (TMJ) undergoes degenerative changes among patients who suffer from arthritis, and yet the pathogenesis of TMJ osteoarthritis and rheumatoid arthritis is poorly understood. We hypothesized that sustained inflammation in the TMJ induces structural abnormalities, and accordingly characterized the disc and synovium in a novel model with double injections of complete Freund's adjuvant (CFA), using behavioral, morphological, cellular, and molecular assessments. Thirty-five days following double CFA injections in seven-week-old female Sprague-Dawley rats, the disc in the CFA-induced inflammation group demonstrated multiple degenerative changes, including marked thickening, opacity, and deformation. The discs in the CFA group further showed significantly greater wet and net weights, and elevated collagen, aggrecan, and total glycosaminoglycan contents. The synovium in the CFA-induced inflammation group showed marked infiltration of mononucleated cells and accumulated sub-synovial adipose tissue. Both the disc and synovium had significantly higher iNOS and IL-1β mRNA expression than controls (saline injections). These findings are consistent with our hypothesis that sustained TMJ inflammation, even within the presently observed 35 days, may be a predisposing factor for structural abnormalities. Insight into TMJ inflammation and degeneration is anticipated to improve our understanding of the pathogenesis of TMJ arthritis and help design clinically relevant strategies for tissue engineering.

The role of nitric oxide in orofacial pain

Nitric oxide (NO) is a free radical gas that has been shown to be produced by nitric oxide synthase (NOS) in different cell types and recognized to act as a neurotransmitter or neuromodulator in the nervous system. NOS isoforms are expressed and/or can be induced in the related structures of trigeminal nerve system, in which the regulation of NOS biosynthesis at different levels of gene expression may allow for a fine control of NO production. Several lines of evidence suggest that NO may play a role through multiple mechanisms in orofacial pain processing. This report will review the latest evidence for the role of NO involved in orofacial pain and the potential cellular mechanisms are also discussed.

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.

Mechanical stretch enhances NF-kappaB-dependent gene expression and poly(ADP-ribose) synthesis in synovial cells

Temporomandibular joint disorders (TMD) show complex symptoms associated with inflammation, pain and degeneration of the peripheral tissues including synovium. Although it is believed that excessive mechanical stress on synovium causes development of TMD, the molecular mechanism by which mechanical stress triggers TMD has still remained unclear. In order to examine the effect of mechanical stress on synoviocytes, rabbit synovial cells were cyclically stretched in vitro. The stretch efficiently increased the gene expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and NF-kappaB responsive reporter gene constructs. The interruption of NF-kappaB activating pathway by inhibitors resulted in the abrogation of those expressions, indicating the pivotal role of NF-kappaB in the mechanical stretch-mediated COX-2 and iNOS expressions. In parallel, the stretch remarkably increased NO production and poly(ADP-ribose) (PAR) synthesis, suggesting that excessive amounts of NO causes DNA injury and in turn activates PAR synthesis by poly(ADP-ribose) polymerase (PARP). The inhibition of PAR synthesis by a PARP inhibitor or a radical scavenger enhanced the mechanical stretch-induced gene expressions in a NF-kappaB-independent manner, implying an involvement of PARP in the gene expression. Taken together, these results demonstrate that mechanical stress on synovial cells not only induces gene expressions of COX-2 and iNOS but also affects PAR synthesis.

[Pathophysiology of acute lung injury in severe burn and smoke inhalation injury]

This review article describes the pathophysiological aspects of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), induced by combined burn and smoke inhalation and examines various therapeutic approaches. The injury results in a fall in arterial oxygenation as a result of airway obstruction, increased pulmonary transvascular fluid flux and loss of hypoxic pulmonary vasoconstriction. The changes in cardiopulmonary function are mediated by reactive oxygen and nitrogen species. Nitric oxide (NO) is generated by both inducible and constitutive isoforms of nitric oxide synthase (NOS). Recently, neuronal NOS emerged as a major component within the pathogenesis of ARDS. NO rapidly combines with the oxygen radical superoxide to form reactive and highly toxic nitrogen species such as peroxynitrite. The control of NO formation involves poly(ADP-ribose) polymerase and its ability to up-regulate the activity of nuclear transcription factors through ribosylation. In addition, present data support a major role of the bronchial circulation in the injury, as blockage of bronchial blood flow will also minimize the pulmonary injury. Current data suggest that cytotoxins and activated cells are formed in the airway and carried to the parenchyma.

CGRP stimulation of iNOS and NO release from trigeminal ganglion glial cells involves mitogen-activated protein kinase pathways

Clinical and basic science data support an integral role of calcitonin gene-related peptide (CGRP) in the pathophysiology of temporomandibular joint disorders. Recently, we have shown that CGRP can stimulate the synthesis and release of nitric oxide (NO) from trigeminal ganglion glial cells. The goal of this study was to determine the role of mitogen-activated protein kinase (MAPK) signaling pathways in CGRP regulation of iNOS expression and NO release from cultured trigeminal ganglion glial cells from Sprague-Dawley rats. CGRP treatment for 2 h significantly increased activity of the MAPK reporter genes, Elk, ATF-2, and CHOP. In addition, CGRP increased nuclear staining for the active forms of the MAPKs: extracellular signal-regulated kinase, c-Jun amino-terminal kinase, and p38. This stimulatory event was not observed in cultures pre-treated with the CGRP receptor antagonist peptide CGRP(8-37). Similarly, pre-treatment with selective MAPK inhibitors repressed increases in reporter gene activity as well as CGRP-induced increases in iNOS expression and NO release mediated by MAPKs. In addition, over-expression of MAPK kinase 1 (MEK1), MEK3, MEK6, and MEK kinase significantly increased iNOS expression and NO production in glial cells. Results from our study provide evidence that CGRP binding to its receptor can stimulate iNOS gene expression via activation of MAPK pathways in trigeminal ganglion glial cells.

Pathophysiology, management and treatment of smoke inhalation injury

Smoke inhalation injury continues to increase morbidity and mortality in burn patients in both the third world and industrialized countries. The lack of uniform criteria for the diagnosis and definition of smoke inhalation injury contributes to the fact that, despite extensive research, mortality rates have changed little in recent decades. The formation of reactive oxygen and nitrogen species, as well as the procoagulant and antifibrinolytic imbalance of alveolar homeostasis, all play a central role in the pathogenesis of smoke inhalation injury. Further hallmarks include massive airway obstruction owing to cast formation, bronchospasm, the increase in bronchial circulation and transvascular fluid flux. Therefore, anticoagulants, antioxidants and bronchodilators, especially when administered as an aerosol, represent the most promising treatment strategies. The purpose of this review article is to provide an overview of the pathophysiological changes, management and treatment options of smoke inhalation injury based on the current literature.

Effect of carbon dioxide on calcitonin gene-related peptide secretion from trigeminal neurons

OBJECTIVE

The goal of this study was to determine whether the physiological effects of carbon dioxide (CO(2)) involve regulation of CGRP secretion from trigeminal sensory neurons.

BACKGROUND

The neuropeptide calcitonin gene-related peptide (CGRP) is implicated in the pathophysiology of allergic rhinosinusitis and migraine. Recent clinical evidence supports the use of noninhaled intranasal delivery of 100% CO(2) for treatment of these diseases. Patients report 2 distinct physiological events: first, a short duration stinging or burning sensation within the nasal mucosa, and second, alleviation of primary symptoms.

METHODS

Primary cultures of rat trigeminal ganglia were utilized to investigate the effects of CO(2) on CGRP release stimulated by a depolarizing stimulus (KCl), capsaicin, nitric oxide, and/or protons. The amount of CGRP secreted into the culture media was determined using a CGRP-specific radioimmunoassay. Intracellular pH and calcium levels were measured in cultured trigeminal neurons in response to CO(2) and stimulatory agents using fluorescent imaging techniques.

RESULTS

Incubation of primary trigeminal ganglia cultures at pH 6.0 or 5.5 was shown to significantly stimulate CGRP release. Similarly, CO(2) treatment of cultures caused a time-dependent acidification of the media, achieving pH values of 5.5-6 that stimulated CGRP secretion. In addition, KCl, capsaicin, and a nitric oxide donor also caused a significant increase in CGRP release. Interestingly, CO(2) treatment of cultures under isohydric conditions, which prevents extracellular acidification while allowing changes in PCO(2) values, significantly repressed the stimulatory effects of KCl, capsaicin, and nitric oxide on CGRP secretion. We found that CO(2) treatment under isohydric conditions resulted in a decrease in intracellular pH and inhibition of the KCl- and capsaicin-mediated increases in intracellular calcium.

CONCLUSIONS

Results from this study provide the first evidence of a unique regulatory mechanism by which CO(2) inhibits sensory nerve activation, and subsequent neuropeptide release. Furthermore, the observed inhibitory effect of CO(2) on CGRP secretion likely involves modulation of calcium channel activity and changes in intracellular pH.

Role of NF-kappaB in TNF-alpha-induced COX-2 expression in synovial fibroblasts from human TMJ

In the temporomandibular joint (TMJ) synovium, cyclo-oxygenase-2 (COX-2) expression has been believed to be directly related to joint pain and synovitis. Here we investigated the role of Nuclear Factor kappaB (NF-kappaB) in the regulation of COX-2 expression in synovial fibroblasts from human TMJ induced by tumor necrosis factor-alpha (TNF-alpha). By reverse-transcriptase/polymerase chain-reaction (RT-PCR) and Western blotting analysis, TNF-alpha induced a dose- and time-dependent increase in COX-2 expression. Electrophoretic mobility shift assay (EMSA) revealed that transient NF-kappaB activation in the COX-2 promoter was triggered by TNF-alpha. In parallel with transient NF-kappaB activation, the rapid translocation of NF-kappaB, particularly the p65 subunit, from the cytoplasm into the nucleus was demonstrated. Pre-treatment with pyrolidine dithiocarbamate (PDTC), one of the NF-kappaB inhibitors, prevented binding to the COX-2 promoter and expression of COX-2 protein in response to TNF-alpha. These findings indicate that activation of NF-kappaB is responsible for TNF-alpha-induced COX-2 expression in synovial fibroblasts from the TMJ.

Capsaicin receptor expression in the rat temporomandibular joint

Experimentally, temporomandibular joint (TMJ) nerve units respond to capsaicin, which is used clinically to treat TMJ pain. However, the existence of capsaicin receptors in the TMJ has not previously been clearly demonstrated. Immunohistochemical analysis has revealed the presence of transient receptor potential vanilloid subtype 1 (TRPV1) expression in the nerves and synovial lining cells of the TMJ. TRPV1-immunoreactive nerves are distributed in the synovial membrane of the joint capsule and provide branches to the joint compartment. The disc periphery is supplied by TRPV1 nerves that are mostly associated with small arterioles, and occasional nerves penetrate to the synovial lining layer. Double immunofluorescence has shown that many TRPV1-immunoreactive nerves are labeled with neuropeptide calcitonin gene-related peptide, whereas few are labeled with IB4-lectin. The results provide evidence for the presence of TRPV1 in both nerves and synovial lining cells, which might thus be involved in the mechanism of nociception and inflammation in the TMJ.

Synovial membrane in the temporomandibular joint--its morphology, function and development

This paper reviews recent findings of the synovial membrane, in particular the morphology, function and development of synovial lining cells, in the temporomandibular joint (TMJ). Electron microscopic studies have confirmed the synovial membrane in TMJ consists of macrophage-like type A cells and fibroblast-like type B cells identical to those in other systematic joints. The macrophage-like type A cells react with anti-macrophage and macrophage-derived substances including the major histocompatibility class II molecule, and show a drastic increase in their number in the inflamed synovial membrane. In addition, they have the ability to produce substances involved in the progression of TMJ inflammation such as nitric oxide and inducible nitric oxide synthase. Observation of osteopetrotic mice revealed that macrophage-like type A cells in TMJ are derived from monocyte lineage. Immunocytochemistry for 25kDa heat shock protein was able to depict the entire shape of fibroblast-like type B cells including their unique processes. The expression of an estrogen receptor alpha-immunoreaction in the fibroblast-like type B cells may explain the etiology of temporomandibular disorders at a higher frequency in females than in males, suggesting that TMJ is a target tissue for estrogen. Furthermore, fibroblast-like type B cells are equipped with a basement membrane to serve as an adhesion molecule for the fibroblast-like type B cells to keep their epithelial arrangement. A clear understanding of the morphology of the intact synovial membrane will serve to clarify the etiology and development of temporomandibular disorders.

Intracerebroventricular injection of erythropoietin enhances sleep in the rat

Systemic injection of erythropoietin (EPO) over several days reduces sleep fragmentation in patients with periodic limb movements in sleep (PLMS). However, there are no studies concerning the effects of EPO on spontaneous sleep. In this study, we determined the effects of intracerebroventricular (i.c.v.) administration of EPO on spontaneous rat sleep. Three doses of EPO (25, 75, and 125 ng) were injected i.c.v. at the onset of the dark period. All doses of EPO increased non-rapid eye movement sleep (NREMS). In addition, high and low doses of EPO (125 and 25 ng) increased rapid eye movement sleep (REMS), but the medium dose of EPO (75 ng) inhibited REMS. Electroencephalogram slow-wave activity during NREMS also increased following the two higher doses of EPO. In contrast, EPO injection during the light period failed to affect sleep. Brain temperature (Tbr) was not affected by any dose of EPO. These results suggest that EPO could be part of the cytokine network involved in sleep regulation.