Effects of tenidap on intracellular signal transduction and the induction of proinflammatory cytokines: a review

Apolipoprotein A-IV acts as an endogenous anti-inflammatory protein and is reduced in treatment-naïve allergic patients and allergen-challenged mice

Background

Recent studies pointed to a crucial role for apolipoproteins in the pathogenesis of inflammatory diseases. However, the role of apolipoprotein‐IV (ApoA‐IV) in allergic inflammation has not been addressed thoroughly thus far.

Objective

Here, we explored the anti‐inflammatory effects and underlying signaling pathways of ApoA‐IV on eosinophil effector function in vitro and in vivo.

Methods

Migratory responsiveness, Ca²⁺‐flux and apoptosis of human peripheral blood eosinophils were assessed in vitro. Allergen‐driven airway inflammation was assessed in a mouse model of acute house dust mite‐induced asthma. ApoA‐IV serum levels were determined by ELISA.

Results

Recombinant ApoA‐IV potently inhibited eosinophil responsiveness in vitro as measured by Ca²⁺‐flux, shape change, integrin (CD11b) expression, and chemotaxis. The underlying molecular mechanism involved the activation of Rev‐ErbA‐α and induced a PI3K/PDK1/PKA‐dependent signaling cascade. Systemic application of ApoA‐IV prevented airway hyperresponsiveness (AHR) and airway eosinophilia in mice following allergen challenge. ApoA‐IV levels were decreased in serum from allergic patients compared to healthy controls.

Conclusion

Our data suggest that ApoA‐IV is an endogenous anti‐inflammatory protein that potently suppresses effector cell functions in eosinophils. Thus, exogenously applied ApoA‐IV may represent a novel pharmacological approach for the treatment of allergic inflammation and other eosinophil‐driven disorders.

Investigation of the curative effects of palm vitamin E tocotrienols on autoimmune arthritis disease in vivo

The tocotrienol-rich fraction (TRF) from palm oil contains vitamin E, which possesses potent antioxidant and anti-inflammatory activities. Rheumatoid arthritis (RA) is a chronic joint inflammatory disease characterised by severe joint pain, cartilage destruction, and bone erosion owing to the effects of various pro-inflammatory mediators and cytokines. Here, we investigated the therapeutic effects of TRF in a rat model of collagen-induced arthritis (CIA). Arthritis was induced by a single intradermal injection of collagen type II in Dark Agouti (DA) rats. Rats were then treated with or without TRF by oral gavage from day 28 after the first collagen injection. Arthritic rats supplemented with TRF showed decreased articular index scores, ankle circumferences, paw volumes, and radiographic scores when compared with untreated rats. The untreated arthritic rats showed higher plasma C-reactive protein levels (p < 0.05) and production of pro-inflammatory cytokines than arthritic rats fed TRF. Moreover, there was a marked reduction in the severity of histopathological changes observed in arthritic rats treated with TRF compared with that in untreated arthritic rats. Overall, the results show that TRF had beneficial effects in this rat model of RA.

A systematic review on the role of eicosanoid pathways in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis is characterized by the production of eicosanoids, cytokines, adhesion molecules, infiltration of T and B lymphocytes in the synovium and oxygen reduction accompanied by the cartilage degradation. Eicosanoids are responsible for the progressive destruction of cartilage and bone, however neither steroids, nor the non steroidal anti-inflammatory drugs (NSAIDs), cannot slow down cartilage and bone destruction providing only symptomatic improvement. The current rheumatoid arthritis treatment options include mainly the use of disease-modifying anti-rheumatic drugs, the corticosteroids, the NSAIDs and biological agents.

METHODS

PubMed, Cochrane, and Embase electronic database were used as the main sources for extracting several articles, reviews, original papers in English for further review and analysis on the implication of arachidonic acid metabolites with rheumatoid arthritis and different strategies of targeting arachidonic acid metabolites, different enzymes or receptors for improving the treatment of rheumatoid arthritis patients.

RESULTS

We first focused on the role of individual prostaglandins and leukotrienes, in the inflammatory process of arthritis, concluding with an outline of the current clinical situation of rheumatoid arthritis and novel treatment strategies targeting the arachidonic acid pathway.

CONCLUSIONS

Extended research is necessary for the development of these novel compounds targeting the eicosanoid pathway, by increasing the levels of anti-inflammatory eicosanoids (PGD₂,15dPGJ₂), by inhibiting the production of pro-inflammatory eicosanoids (PGE₂, LTB₄, PGI₂) involved in rheumatoid arthritis or also by developing dual compounds displaying both the COX-2 inhibitor/TP antagonist activity within a single compound.

Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle?

The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.

Opposing effects of tenidap on the volume-regulated anion channel and K(ATP) channel activity in rat pancreatic beta-cells

Tenidap (5-chloro-2-hydroxy-3-(thiophene-2-carbonyl)indole-1-carboxamide) is a non-steroidal anti-inflammatory and anti-rheumatic drug with several cellular actions including inhibition of anion transport processes. Since other anion transport inhibitors have been shown to inhibit activity of the volume-regulated anion channel (VRAC), the present study investigated the effects of tenidap on activity of this channel in pancreatic beta-cells. Membrane potential, VRAC currents and input conductance were recorded from single rat beta-cells in primary culture using perforated patch, conventional whole-cell and cell-attached configurations of the patch-clamp technique. Relative cell volume was measured using a video-imaging method. Tenidap (0.1mM) was found to rapidly hyperpolarise the beta-cell membrane potential and terminate glucose-induced electrical activity. This effect was associated with a pronounced outward current shift at a holding potential of -65mV. Tenidap was found to inhibit activity of the volume-regulated anion channel with IC(50) values of 31 and 43microM for outward and inward currents respectively. Tenidap also markedly increased beta-cell input conductance, representing an activation of the K(ATP) conductance. beta-cell regulatory volume decrease following hypotonically-induced cell swelling was sensitive to inhibition by 50microM tenidap. Tenidap is a potent inhibitor of the volume-regulated anion channel and K(ATP) channel activator in rat pancreatic beta-cells. These actions could at least in part explain the recently reported inhibitory actions of the drug on electrical and secretory activity in the beta-cell, and could also underlie other pharmacological actions of the drug.

Expression of the electrogenic Na+-HCO3--cotransporters NBCe1-A and NBCe1-B in rat pancreatic islet cells

It was recently proposed that, in rat pancreatic islets, the production of bicarbonate accounts for the major fraction of the carbon dioxide generated by the oxidative catabolism of nutrient insulin secretagogues. In search of the mechanism(s) supporting the membrane transport of bicarbonate, the possible role of the electrogenic Na(+)-HCO(3) (-)-cotransporters NBCe1-A and NBCe1-B in rat pancreatic islet cells was investigated. Expression of NBCe1-A and NBCe1-B in rat pancreatic islet cells was documented by RT-PCR, western blotting, and immunocytochemistry. The latter procedure suggested a preferential localization of NBCe1-B in insulin-producing cells. Tenidap (3-100 microM), previously proposed as an inhibitor of NBCe1-A-mediated cotransport in proximal tubule kidney cells, caused a concentration-related inhibition of glucose-stimulated insulin secretion. It also inhibited 2-ketoisocaproate-induced insulin release and to a relatively lesser extent, the secretory response to L: -leucine. Tenidap (50-100 microM) also inhibited the metabolism of D: -glucose in isolated islets, increased (22)Na net uptake by dispersed islet cells, lowered intracellular pH and provoked hyperpolarization of plasma membrane in insulin-producing cells. This study thus reveals the expression of the electrogenic Na(+)-HCO(3) (-)-cotransporters NBCe1-A and NBCe1-B in rat pancreatic islet cells, and is consistent with the participation of such transporters in the process of nutrient-stimulated insulin secretion.

Decreased interleukin-1beta and elastase in the gingival crevicular fluid of individuals undergoing anti-inflammatory treatment for rheumatoid arthritis

BACKGROUND

The primary aim of this study was to compare the inflammatory activity in the gingival crevicular fluid (GCF) in a group of patients with rheumatoid arthritis (RA) and a group of matched controls. Secondarily, we aimed to evaluate the effect of rheumatologic treatment on periodontal inflammation.

METHODS

Seventeen individuals with RA with a mean duration of disease of 12.1 (+/- 9.9) years and the same number of systemically healthy individuals matched for age, gender, periodontal status, and tobacco use were selected. Medication data were registered, and GCF was collected by means of an intracrevicular washing method. Besides clinical registrations, periodontal inflammation was assessed by analysis of the cytokines interleukin (IL)-1beta and -18 and of elastase activity.

RESULTS

Amounts of IL-1beta and total elastase were significantly lower in the patient group. IL-1beta and total elastase had a significant and strong correlation in the RA group (r(s) = 0.883). This correlation was not observed in the control group.

CONCLUSION

The anti-inflammatory treatment taken by RA patients might influence the periodontal inflammation status represented by IL-1beta and elastase in the GCF.

Arthroscopic evaluation of potential structure-modifying drug in osteoarthritis of the knee. A multicenter, randomized, double-blind comparison of tenidap sodium vs piroxicam

OBJECTIVE

To test the hypothesis that tenidap has a structure-modifying effect in human knee osteoarthritis.

DESIGN

STUDY

multicenter, prospective, randomized, double blind, 1 year duration.

PATIENTS

primary painful knee osteoarthritis (ACR criteria) of the medial tibiofemoral compartment, medial joint space width > or =2mm, at least 10% of one cartilage surface of the medial compartment affected by superficial fibrillation or worse at baseline arthroscopy. STUDY MEDICATION: once daily dosage of either tenidap 40 mg, tenidap 120 mg or piroxicam 20mg. STUDY ENDPOINTS: bilateral extended weight-bearing X-rays and knee arthroscopy under local anaesthesia were done at entry and after 1 year. Joint space width was measured in millimeters at the narrowest point of the medial compartment. Chondropathy was scored by using reader's overall assessment (VAS score, 100mm) and Société Française d'Arthroscopie (SFA) score (0-100).

RESULTS

Patients (665) were randomized and 494 completed the study. After 1 year, intra-group radiological changes and radiological difference between both tenidap groups and the piroxicam group did not reach statistical significance. The intra-group arthroscopic deterioration of chondropathy was low, but statistically significant in the three study groups. However, there was no statistically significant difference between both tenidap groups and the piroxicam group.

CONCLUSIONS

This study failed to demonstrate any difference between the treatment arms with regard to the structural progression of medial knee osteoarthritis as measured by radiography and arthroscopy. Arthroscopy did, however, appears to be more sensitive in detecting disease progression than the weight-bearing radiographs with fully extended knees. This study shows that it is possible to complete a large international trial using arthroscopy as an outcome measure of articular cartilage.

Tenidap, a novel anti-inflammatory agent, is an opener of the inwardly rectifying K+ channel hKir2.3

We studied the effect of a novel anti-inflammatory agent, tenidap, on a cloned inwardly rectifying K+ channel, hKir2.3. Tenidap (a) potently potentiated 86Rb+ efflux through hKir2.3 channels expressed in Chinese hamster ovary cells (EC50=402 nM), (b) reversibly and dose-dependently increased whole-cell and macro-patch hKir2.3 currents (maximum whole-cell current response to tenidap was 230+/-27% of control; EC50=1.3 microM.), and (c) caused dose-dependent and Ba2+-sensitive membrane hyperpolarizations and concurrent decreases in input resistance. Potentiation of hKir2.3 by tenidap was unaffected by inhibitors of phospholipase A2, protein kinase C, or arachidonic acid metabolic pathways. The action of tenidap was not intracellular. Tenidap also had little or no effect on currents flowing through hKir2.1, Kv1.5, and micro1 Na+ channels. Our results demonstrate that tenidap is a potent opener of hKir2.3 and suggest that it can serve as a valuable pharmacological tool for studying physiological and pathological processes involving Kir2.3.

Theory and practice of cytokine assessment in immunotoxicology

The tools and concepts of immunotoxicology are increasingly being used in novel ways, such as using toxic reagents to understand immune system function. One of the most potentially useful of these new tools is the assessment of cytokines, the molecules responsible for regulating a variety of processes including immunity, inflammation, apoptosis, and hematopoiesis. Cytokine production or bioactivity may be affected by a variety of toxic mechanisms including direct toxicity to cytokine-producing cells, inhibition of cytokine production, inhibition of cytokine release, induction of immunosuppressive factors, alterations in cellular homeostasis, alterations in cellular activational or transcriptional mechanisms, and miscellaneous or undefined mechanisms. Moreover, alterations in the profile of cytokine production may provide important information regarding the nature of an immunotoxic insult (i.e., TH1 vs TH2 response). Proper evaluation of the role of cytokine modulation in immunotoxicology requires attention to myriad details. Some of the details discussed in this review include the source of the sample to be tested (circulating, local, or ex vivo isolated cells); the potential effects of collection, processing, and storage on the results of the assays; potential variables associated with the source material (matrix effects, relevance, inhibitory substances); and factors influencing the choice of assay used (bioassay, immunoassay, molecular biology technique, flow cytometry, hybrid assays). Other often-overlooked issues are discussed, including species considerations and quality control issues such as the use of reference standards and the expression of results.

Termination of acute-phase response: role of some cytokines and anti-inflammatory drugs

1. The acute-phase response is triggered by changes in intracellular mediators that activate stress-sensitive kinases and transcription factors controlling the synthesis of proinflammatory cytokines such as TNF-alpha, IL-1, IL-8 or IFN-gamma. 2. Natural extinguishing of acute-phase response occurs due to short half-lives of inflammatory mediators and production of anti-inflammatory cytokines such as IL-10, IL-4, IL-13, TGF-beta and some others. 3. Excess proinflammatory cytokines are removed by soluble cytokine receptors and receptor antagonists. 4. Synthesis of proinflammatory mediators and cytokines can be blocked by glucocorticoids, some nonsteroidal anti-inflammatory drugs suppressing cyclooxygenase and by specific inhibitors of cytokine induction. 5. The most promising approach in effective termination of acute-phase response appears to be a combined use of anti-inflammatory cytokines and specific drugs.

Pharmacological modulation of cell adhesion molecules

Cell adhesion molecules mediate the contact between two cells or between cells and the extracellular matrix. They are essential for morphogenesis, organization of tissues and organs, regulation of immune cell responses and migration of inflammatory cells from the blood vessels into inflamed tissues. Many diseases have been shown to be associated with dysfunction or with overexpression of certain adhesion molecules. Increased cell adhesion molecule function and number are found in clinical disorders in which inflammation and immune cells are involved. Several possible therapeutic agents are described here which have been shown to reduce the expression and/or function of cell adhesion molecules. Anti-adhesion treatment can lead to diminished infiltration and activation of inflammatory immune cells resulting in decreased tissue injury and malfunction.

Antifibroproliferative effect of tenidap in chronic antigen-induced arthritis

OBJECTIVE

To determine whether tenidap regulates extracellular matrix metabolism in chronic arthritis.

METHODS

Antigen arthritis was induced in the knees of 30 rabbits. Animals were distributed into 3 groups: untreated, tenidap-treated, and diclofenac-treated rabbits. Three weeks after disease induction, synovial membranes were extracted and processed for histopathologic examination and detection of type I collagen (CI) and fibronectin (FN) by immunoperoxidase. Simultaneously, we analyzed the in vitro effect of tenidap on healthy synovial cell (SC) proliferation, FN expression and synthesis, and expression of transforming growth factor beta1 (TGFbeta1) messenger RNA.

RESULTS

Untreated animals showed synovial lining hyperplasia, cellular infiltration at the sublining, and increased deposition of matrix proteins. These findings were not apparent in tenidap-treated rabbits, where CI and FN had the same distribution as in healthy synovial membranes. In vitro, tenidap inhibited SC proliferation (> or =25 microM) and down-regulated the expression and synthesis of FN in a dose-dependent manner (> or =1 microM). This antifibrotic effect was associated with a reduction of TGFbeta1 message.

CONCLUSION

Tenidap down-regulates the fibroproliferative changes typical of chronic arthritis, an effect that fits the profile of a disease-modifying agent for rheumatoid arthritis.

The mechanisms of action of disease-modifying antirheumatic drugs: a review with emphasis on macrophage signal transduction and the induction of proinflammatory cytokines

1. Rheumatoid arthritis (RA) is probably the most common source of treatable disability. A major problem in modern rheumatology is that the mechanism(s) of action of the currently used disease-modifying antirheumatic drugs (DMARDs) remain unclear. Many of these drugs entered rheumatology mainly through clinical intuition and have been used for decades. 2. The former T-cell-centered paradigm of rheumatoid inflammation has given way to a model of inflammation highlighting the macrophage and its proinflammatory cytokines. In particular, tumor necrosis factor alpha (TNF-alpha) has gained prominence as a central proinflammatory mediator in RA, and antibodies against TNF-alpha have been successfully used in patients with RA. 3. This review will summarize the recent advances in determining the mechanisms of action of the currently used DMARDs, with particular emphasis on their effects on the induction of TNF-alpha and interleukin 1 (IL-1) in mononuclear phagocytes. Although some DMARDs, such as auranofin, antimalarials and tenidap, act as inhibitors of the induction of these cytokines in monocytes or macrophages or both, other drugs, such as methotrexate, D-penicillamine and aurothiomalate, do not seem to affect either TNF-alpha or IL-1. 4. The drugs' effects on proinflammatory cytokine induction are correlated to those on other macrophage responses.

Differential effects of tenidap on the zymosan- and lipopolysaccharide-induced expression of mRNA for proinflammatory cytokines in macrophages

Tenidap is a novel antirheumatic drug that combines cyclooxygenase inhibition with cytokine modulating qualities. We demonstrate here that tenidap inhibits the zymosan-induced expression of both interleukin 1 and tumor necrosis factor alpha in macrophages, at the mRNA and protein levels. The concentration-dependence of the tenidap-induced inhibition of the expression of mRNA for these proinflammatory cytokines agrees with that of its inhibitory effects on zymosan-induced arachidonate mobilization and changes in phosphoprotein pattern. The effects of tenidap on the lipopolysaccharide-induced expression of these cytokines are more complex. Tenidap inhibits the induction of interleukin 1 by lipopolysaccharide or bacteria, but less potently than the interleukin 1-response induced by zymosan. In contrast, the drug markedly potentiates the lipopolysaccharide-induced expression of tumor necrosis factor alpha at both the mRNA and protein levels. The latter effect is demonstrated to be due to cyclooxygenase inhibition and is reversed by prostaglandin E2.