Up-regulation of microsomal prostaglandin E synthase 1 in osteoarthritic human cartilage: critical roles of the ERK-1/2 and p38 signaling pathways

Influenza A virus selectively elevates prostaglandin E2 formation in pro-resolving macrophages

Respiratory influenza A virus (IAV) infections are major health concerns worldwide, where bacterial superinfections substantially increase morbidity and mortality. The underlying mechanisms of how IAV impairs host defense remain elusive. Macrophages are pivotal for the innate immune response and crucially regulate the entire inflammatory process, occurring as inflammatory M1- or pro-resolving M2-like phenotypes. Lipid mediators (LM), produced from polyunsaturated fatty acids by macrophages, are potent immune regulators and impact all stages of inflammation. Using LM metabololipidomics, we show that human pro-resolving M2-macrophages respond to IAV infections with specific and robust production of prostaglandin (PG)E2 along with upregulation of cyclooxygenase-2 (COX-2), which persists after co-infection with Staphylococcus aureus. In contrast, cytokine/interferon production in macrophages was essentially unaffected by IAV infection, and the functionality of M1-macrophages was not influenced. Conclusively, IAV infection of M2-macrophages selectively elevates PGE2 formation, suggesting inhibition of the COX-2/PGE2 axis as strategy to limit IAV exacerbation.

Flavonoid diversity and roles in the lipopolysaccharide-mediated inflammatory response of monocytes and macrophages

Targeting lipopolysaccharide (LPS)/toll-like receptor 4 signaling in mononuclear phagocytes has been explored for the treatment of inflammation and inflammation-related disorders. However, only a few key targets have been translated into clinical applications. Flavonoids, a class of ubiquitous plant secondary metabolites, possess a privileged scaffold which serves as a valuable template for designing pharmacologically active compounds directed against diseases with inflammatory components. This perspective provides a general overview of the diversity of flavonoids and their multifaceted mechanisms that interfere with LPS-induced signaling in monocytes and macrophages. Focus is placed on flavonoids targeting MD-2, IκB kinases, c-Jun N-terminal kinases, extracellular signal-regulated kinase, p38 MAPK and PI3K/Akt or modulating LPS-related gene expression.

(9S,13R)-12-oxo-phytodienoic acid attenuates inflammation by inhibiting mPGES-1 and modulating macrophage polarization via NF-κB and Nrf2/HO-1 pathways

Non-steroidal anti-inflammatory drugs (NSAIDs) relieve inflammation by suppressing prostaglandin E₂/cyclooxygenase 2 (PGE₂/COX-2) with cardiovascular and gastrointestinal bleeding risk. Theoretically, suppressing PGE₂ through inhibiting the terminal synthase microsomal prostaglandin E₂ synthase-1 (mPGES-1) instead of upstream COX-2 is ideal for inflammation. Here, (9S,13R)-12-oxo-phytodienoic acid (AA-24) extracted from Artemisia anomala was first screened as an anti-inflammatory candidate and decreased inducible nitric oxide synthase (iNOS), nitric oxide (NO), mPGES-1, and PGE₂ without affecting COX-1/2, thromboxane A₂ (TXA₂) and prostaglandin I₂ (PGI₂). Besides, AA-24 suppressed the differentiation of M0 macrophages to M1 phenotype but enhanced it to M2 phenotype, blocked the activation of NF-κB pathway, and increased the activation of Nrf2 and heme oxygenase-1 (HO-1). Moreover, AA-24 selectively inhibited mPGES-1 and reduced inflamed paw edema in carrageenan-induced mice. In conclusion, AA-24 attenuates inflammation by inhibiting mPGES-1 and modulating macrophage polarization via the NF-κB and Nrf2/HO-1 pathways and could be a promising candidate for developing anti-inflammatory drugs.

Vicenin 3 ameliorates ECM degradation by regulating the MAPK pathway in SW1353 chondrocytes

Aberrant destruction of the articular extracellular matrix (ECM) has been considered to be one of the pathological features of osteoarthritis (OA) which results in chondrocyte changes and articular cartilage degeneration. The MAPK signaling pathway serves a key role by releasing cartilage-degrading enzymes from OA chondrocytes. However, the use of MAPK inhibitors for OA is hindered by their potential long-term toxicity. Vicenin 3 is one of the major components of the Jian-Gu injection which is effective in the clinical treatment of OA. However, its potential impact on OA remain poorly understood. Therefore, the present study aimed to assess the effects of vicenin 3 on interleukin (IL)-1β-treated SW1353 chondrocytes, which mimic the microenvironment of OA. These chondrocytes were pretreated with vicenin 3 (0, 5 and 20 µM) for 1 h and subsequently stimulated with IL-1β (10 ng/ml) for 24 h. Nitric oxide (NO) production was measured using the Griess reaction, whereas the production of prostaglandin E2 (PGE2), matrix metalloproteinases (MMPs), A disintegrin-like and metalloproteinase with thrombospondin motifs (ADAMTSs), collagen type II and aggrecan were measured using ELISA. The mRNA expression of MMPs and ADAMTSs were measured using reverse transcription-quantitative PCR. The protein expression levels of MAPK were measured using western blotting. Vicenin 3 was found to significantly inhibit IL-1β-induced production of NO and PGE. Increments in the expression levels of MMP-1, MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 induced by IL-1β, in addition to the IL-1β-induced degradation of collagen type II and aggrecan, were all reversed by vicenin 3 treatment. Furthermore, vicenin 3 suppressed IL-1β-stimulated MAPK activation, an effect that was similar to that exerted by SB203580, a well-known p38 MAPK inhibitor. In conclusion, vicenin 3 may confer therapeutic potential similar to that of the p38 MAPK inhibitor for the treatment of OA.

Chondroprotective effect of Alpinia oxyphylla extract in experimentally induced cartilage degradation in rabbit articular cartilage explants

Alpinia oxyphylla is a widely used medicinal herb for diarrhea, gastralgia, tumors, hypertention, and cerebrovascular disorders. Here, we evaluated the chondroprotective effect of A. oxyphylla dried fruit ethanol extract (AOE) against cartilage degradation in rabbit articular cartilage explants. Treatment of interleukin-1α (IL-1α) and plasminogen increased degraded collagen release in culture supernatants, but pretreatment of AOE (50, 100, 200 µg/ml) inhibited the collagen release in dose-dependent manner. To examine the mechanism of action of AOE on chondroprotection, the level of matrix metalloproteinases-3 (MMP-3), matrix metalloproteinases-13 (MMP-13), tissue inhibitor of metalloprotease-1 (TIMP-1), and inflammatory mediators like prostaglandin E₂ (PGE₂ ) and nitric oxide (NO) was evaluated. AOE inhibited upregulation of MMP-3 and MMP-13 and downregulation of TIMP-1 and also reduced increase of PGE₂ and NO level induced by exposure of IL-1α and plasminogen. These results indicate that AOE show chondroprotective effect through inhibiting collagen degradation via regulating MMPs, TIMP-1, and inflammatory mediators. PRACTICAL APPLICATIONS: Osteoarthritis (OA) is a one of the most common chronic disorders in elderly persons. Because the regenerative power of joint articular cartilage is very low, treatment of OA is difficult to expect complete recovery. Therefore, there is a need to develop a therapeutic agent that can safely and effectively inhibit the cartilage destruction. For the first time, we exhibited the inhibitory effect of AOE on collagen degradation through regulating MMPs and TIMP-1 in articular cartilage explants. These findings support AOE could be used as herbal therapeutic application for protecting articular cartilage to prevent OA.

Composition and Acute Inflammatory Response from Tetraponera rufonigra Venom on RAW 264.7 Macrophage Cells

Tetraponera rufonigra (Arboreal Bicoloured Ant) venom induces pain, inflammation, and anaphylaxis in people and has an increased incident in Southeast Asia regions. The bioactive components and mechanism of action of the ant venom are still limited. The aim of this research was to identify the protein composition and inflammatory process of the ant venom by using RAW 264.7 macrophage cells. The major venom proteins are composed of 5' nucleotidase, prolyl endopeptidase-like, aminopeptidase N, trypsin-3, venom protein, and phospholipase A₂ (PLA₂). The venom showed PLA₂ activity and represented 0.46 μg of PLA₂ bee venom equivalent/μg crude venom protein. The venom induced cytotoxic in a dose- and time-dependent manner with IC₂₀ approximately at 4.01 µg/mL. The increased levels of COX-2 and PGE₂ were observed after 1 h of treatment correlating with an upregulation of COX-2 expression. Moreover, the level of mPGES-1 expression was obviously increased after 12 h of venom induction. Hence, our results suggested that the induction of COX-2/mPGEs-1 pathway could be a direct pathway for the ant venom-induced inflammation.

Genome-wide gene expression analysis of a murine model of prostate cancer progression: Deciphering the roles of IL-6 and p38 MAPK as potential therapeutic targets

Background

Prostate cancer (PCa) is the most commonly diagnosed cancer and the second leading cause of cancer-related deaths among adult males globally. The poor prognosis of PCa is largely due to late diagnosis of the disease when it has already progressed to an advanced stage marked by androgen-independence, thus necessitating new strategies for early detection and treatment. We construe that these direly needed advances are limited by our poor understanding of early events in the progression of PCa and that would thus represent ideal targets for early intervention. To begin to fill this void, we interrogated molecular “oncophenotypes” that embody the transition of PCa from an androgen-dependent (AD) to–independent (AI) state.

Methods

To accomplish this aim, we used our previously established AD and AI murine PCa cell lines, PLum-AD and PLum-AI, respectively, which recapitulate primary and progressive PCa morphologically and molecularly. We statistically surveyed global gene expressions in these cell lines by microarray analysis. Differential profiles were functionally interrogated by pathways, gene set enrichment and topological gene network analyses.

Results

Gene expression analysis of PLum-AD and PLum-AI transcriptomes (n = 3 each), revealed 723 differentially expressed genes (392 upregulated and 331 downregulated) in PLum-AI compared to PLum-AD cells. Gene set analysis demonstrated enrichment of biological functions and pathways in PLum-AI cells that are central to tumor aggressiveness including cell migration and invasion facilitated by epithelial-to-mesenchymal transition (EMT). Further analysis demonstrated that the p38 mitogen-activated protein kinase (MAPK) was predicted to be significantly activated in the PLum-AI cells, whereas gene sets previously associated with favorable response to the p38 inhibitor SB203580 were attenuated (i.e., inversely enriched) in the PLum-AI cells, suggesting that these aggressive cells may be therapeutically vulnerable to p38 inhibition. Gene set and gene-network analysis also alluded to activation of other signaling networks particularly those associated with enhanced EMT, inflammation and immune function/response including, but not limited to Tnf, IL-6, Mmp 2, Ctgf, and Ptges. Accordingly, we chose SB203580 and IL-6 to validate their effect on PLum-AD and PLum-AI. Some of the common genes identified in the gene-network analysis were validated at the molecular and functional level. Additionally, the vulnerability to SB203580 and the effect of IL-6 were also validated on the stem/progenitor cell population using the sphere formation assay.

Conclusions

In summary, our study highlights pathways associated with an augmented malignant phenotype in AI cells and presents new high-potential targets to constrain the aggressive malignancy seen in the castration-resistant PCa.

Adaptive Molecular Evolution of AKT3 Gene for Positive Diversifying Selection in Mammals

The V-Akt Murine Thymoma Viral Oncogene Homolog 3 (AKT3) gene is of the serine/threonine-protein kinase family and influences the production of milk fats and cholesterol by acting on the sterol administrative area restricting protein (SREBP). The AKT3 gene is highly preserved in animals, and during lactation in cattle, its expression increases. The AKT3 gene is expressed in the digestive system, mammary gland, and immune cells. A phylogenetic investigation was performed to clarify the evolutionary role of AKT3, by maximum probability. The AKT3 gene sequence data of various mammalian species was evident even with animals undergoing breeding selection. From 39 mammalian species studied, there was a signal of positive diversifying selection with Hominidae at 13Q, 16G, 23R, 24P, 121P, 294K, 327V, 376L, 397K, 445T, and 471F among other codon sites of the AKT3 gene. These sites were codes for amino acids such as arginine, proline, lysine, and leucine indicating major roles for the function of immunological proteins, and in particular, the study highlighted the importance of changes in gene expression of AKT3 on immunity.

miR-574-5p as RNA decoy for CUGBP1 stimulates human lung tumor growth by mPGES-1 induction

MicroRNAs (miRs) are important posttranscriptional regulators of gene expression. Besides their well-characterized inhibitory effects on mRNA stability and translation, miRs can also activate gene expression. In this study, we identified a novel noncanonical function of miR-574-5p. We found that miR-574-5p acts as an RNA decoy to CUG RNA-binding protein 1 (CUGBP1) and antagonizes its function. MiR-574-5p induces microsomal prostaglandin E synthase-1 (mPGES-1) expression by preventing CUGBP1 binding to its 3'UTR, leading to an enhanced alternative splicing and generation of an mPGES-1 3'UTR isoform, increased mPGES-1 protein expression, PGE₂ formation, and tumor growth in vivo. miR-574-5p-induced tumor growth in mice could be completely inhibited with the mPGES-1 inhibitor CIII. Moreover, miR-574-5p is induced by IL-1β and is strongly overexpressed in human nonsmall cell lung cancer where high mPGES-1 expression correlates with a low survival rate. The discovered function of miR-574-5p as a CUGBP1 decoy opens up new therapeutic opportunities. It might serve as a stratification marker to select lung tumor patients who respond to the pharmacological inhibition of PGE₂ formation.-Saul, M. J., Baumann, I., Bruno, A., Emmerich, A. C., Wellstein, J., Ottinger, S. M., Contursi, A., Dovizio, M., Donnini, S., Tacconelli, S., Raouf, J., Idborg, H., Stein, S., Korotkova, M., Savai, R., Terzuoli, E., Sala, G., Seeger, W., Jakobsson, P.-J., Patrignani, P., Suess, B., Steinhilber, D. miR-574-5p as RNA decoy for CUGBP1 stimulates human lung tumor growth by mPGES-1 induction.

PDE4 inhibitor rolipram inhibits the expression of microsomal prostaglandin E synthase-1 by a mechanism dependent on MAP kinase phosphatase-1

Phosphodiesterase‐4 (PDE4) inhibitors have recently been introduced to the treatment of COPD and psoriatic arthritis. Microsomal prostaglandin E synthase‐1 (mPGES‐1) is an inducible enzyme synthesizing PGE₂, the most abundant prostanoid related to inflammation and inflammatory pain. mPGES‐1 is a potential drug target for novel anti‐inflammatory treatments aiming at an improved safety profile as compared to NSAIDs. Here we investigated the effect of the PDE4 inhibitor rolipram on the expression of mPGES‐1 in macrophages; and a potential mediator role in the process for MAP kinase phosphatase‐1 (MKP‐1) which is an endogenous factor limiting the activity of the proinflammatory MAP kinases p38 and JNK. The expression of mPGES‐1 was decreased, whereas that of MKP‐1 was enhanced by rolipram in wild‐type murine macrophages. Interestingly, rolipram did not reduce mPGES‐1 expression in peritoneal macrophages from MKP‐1‐deficient mice. A reduced phosphorylation of JNK, but not p38 MAP kinase, was specifically associated with the decreased expression of mPGES‐1. Accordingly, mPGES‐1 expression was suppressed by JNK but not p38 inhibitor. These findings underline the significance of the increased MKP‐1 expression and decreased JNK phosphorylation associated with the downregulated expression of mPGES‐1 by PDE4 inhibitors in inflammation.

Anti-Inflammatory Effect of Geniposide on Osteoarthritis by Suppressing the Activation of p38 MAPK Signaling Pathway

It has been suggested that the activation of the p38 mitogen activated protein kinases (MAPKs) signaling pathway plays a significant role in the progression of OA by leading to the overexpression of proinflammatory cytokines, chemokines, and signaling enzymes in human osteoarthritis chondrocytes. However, most p38 MAPK inhibitors applied for OA have been thought to be limited due to their potential long-term toxicities. Geniposide (GE), an iridoid glycoside purified from the fruit of the herb, has been widely used in traditional medicine for the treatment of a variety of chronic inflammatory diseases. In this study, we evaluated the inhibition effect of geniposide on the inflammatory progression of the surgically induced osteoarthritis and whether the protective effect of geniposide on OA is related to the inhibition of the p38 MAPK signaling pathway. In vitro, geniposide attenuated the expression of inflammatory cytokines including interleukin-1 (IL-1), tumor necrosis factor (TNF-α), and nitric oxide (NO) production as well as matrix metalloproteinase- (MMP-) 13 in chondrocytes isolated from surgically induced rabbit osteoarthritis model. Additionally, geniposide markedly suppressed the expression of IL-1, TNF-α, NO, and MMP-13 in the synovial fluid from the rabbits with osteoarthritis. More importantly, our results clearly demonstrated that the inhibitory effect of geniposide on surgery-induced expression of inflammatory mediators in osteoarthritis was closely associated with the suppression of the p38 MAPK signaling pathways. Our study demonstrates that geniposide may have therapeutic potential to serve as an alternative agent for the p38 MAPK inhibition for the treatment of OA due to its inherent features of biological activities and low toxicity as a traditional Chinese medicine.

Microsomal Prostaglandin E Synthase-1 Expression in Inflammatory Conditions Is Downregulated by Dexamethasone: Seminal Role of the Regulatory Phosphatase MKP-1

Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible enzyme situated downstream of cyclo-oxygenase-2, promoting the excessive PGE₂ production in inflammation. Dexamethasone is known to suppress mPGES-1 but the mechanisms regulating mPGES-1 expression remain poorly known. MKP-1 is a phosphatase controlling the proinflammatory MAP kinase pathways p38 and JNK, thus limiting the inflammatory responses. We have now investigated the role of MKP-1 and MAP kinases p38 and JNK in the regulation of mPGES-1 expression by dexamethasone. Dexamethasone increased MKP-1 and decreased mPGES-1 expression in J774 macrophages and in peritoneal macrophages from wild-type but not from MKP-1 deficient mice. Dexamethasone also reduced p38 and JNK phosphorylation along with enhancement of MKP-1, while inhibition of JNK reduced mPGES-1 expression. These findings were also translated to in vivo conditions as dexamethasone downregulated mPGES-1 expression in paw inflammation in wild-type but not in MKP-1 deficient mice. In conclusion, dexamethasone was found to downregulate mPGES-1 expression through enhanced MKP-1 expression and reduced JNK phosphorylation in inflammatory conditions. The results extend the understanding on the regulation of mPGES-1 expression and highlight the potential of MKP-1 as an anti-inflammatory drug target.

Small molecule therapeutics for inflammation-associated chronic musculoskeletal degenerative diseases: Past, present and future

Inflammation-associated chronic musculoskeletal degenerative diseases (ICMDDs) like osteoarthritis and tendinopathy often results in morbidity and disability, with consequent heavy socio-economic burden. Current available therapies such as NSAIDs and glucocorticoid are palliative rather than disease-modifying. Insufficient systematic research data on disease molecular mechanism also makes it difficult to exploit valid therapeutic targets. Small molecules are designed to act on specific signaling pathways and/or mechanisms of cellular physiology and function, and have gradually shown potential for treating ICMDDs. In this review, we would examine and analyze recent developments in small molecule drugs for ICMDDs, suggest possible feasible improvements in treatment modalities, and discuss future research directions.

The nuclear factor-erythroid 2-related factor/heme oxygenase-1 axis is critical for the inflammatory features of type 2 diabetes-associated osteoarthritis

Epidemiological findings support the hypothesis that type 2 diabetes mellitus (T2DM) is a risk factor for osteoarthritis (OA). Moreover, OA cartilage from patients with T2DM exhibits a greater response to inflammatory stress, but the molecular mechanism is unclear. To investigate whether the antioxidant defense system participates in this response, we examined here the expression of nuclear factor-erythroid 2-related factor (Nrf-2), a master antioxidant transcription factor, and of heme oxygenase-1 (HO-1), one of its main target genes, in OA cartilage from T2DM and non-T2DM patients as well as in murine chondrocytes exposed to high glucose (HG). Ex vivo experiments indicated that Nrf-2 and HO-1 expression is reduced in T2DM versus non-T2DM OA cartilage (0.57-fold Nrf-2 and 0.34-fold HO-1), and prostaglandin E₂ (PGE₂) release was increased in samples with low HO-1 expression. HG-exposed, IL-1β-stimulated chondrocytes had lower Nrf-2 levels in vitro, particularly in the nuclear fraction, than chondrocytes exposed to normal glucose (NG). Accordingly, HO-1 levels were also decreased (0.49-fold) in these cells. The HO-1 inducer cobalt protoporphyrin IX more efficiently attenuated PGE₂ and IL-6 release in HG+IL-1β-treated cells than in NG+IL-1β-treated cells. Greater reductions in HO-1 expression and increase in PGE₂/IL-6 production were observed in HG+IL-1β-stimulated chondrocytes from Nrf-2^-/- mice than in chondrocytes from wild-type mice. We conclude that the Nrf-2/HO-1 axis is a critical pathway in the hyperglucidic-mediated dysregulation of chondrocytes. Impairments in this antioxidant system may explain the greater inflammatory responsiveness of OA cartilage from T2DM patients and may inform treatments of such patients.

Low-grade inflammation as a key mediator of the pathogenesis of osteoarthritis

Osteoarthritis (OA) has long been viewed as a degenerative disease of cartilage, but accumulating evidence indicates that inflammation has a critical role in its pathogenesis. Furthermore, we now appreciate that OA pathogenesis involves not only breakdown of cartilage, but also remodelling of the underlying bone, formation of ectopic bone, hypertrophy of the joint capsule, and inflammation of the synovial lining. That is, OA is a disorder of the joint as a whole, with inflammation driving many pathologic changes. The inflammation in OA is distinct from that in rheumatoid arthritis and other autoimmune diseases: it is chronic, comparatively low-grade, and mediated primarily by the innate immune system. Current treatments for OA only control the symptoms, and none has been FDA-approved for the prevention or slowing of disease progression. However, increasing insight into the inflammatory underpinnings of OA holds promise for the development of new, disease-modifying therapies. Indeed, several anti-inflammatory therapies have shown promise in animal models of OA. Further work is needed to identify effective inhibitors of the low-grade inflammation in OA, and to determine whether therapies that target this inflammation can prevent or slow the development and progression of the disease.

Explore the variation of MMP3, JNK, p38 MAPKs, and autophagy at the early stage of osteoarthritis

Osteoarthritis is a chronic disease characterized by cartilage degeneration and chondrocyte apoptosis. Mitogen-activated protein kinase (MAPK) signaling pathway plays a key role in regulating OA process. Autophagy has an important effect on the OA process, and it is believed to be regulated by MAPKs. To reveal the mechanism and the effect of JNK and p38 MAPKs on matrix metalloproteinase 3 (MMP3) and autophagy in OA, the study established OA model in rabbits, used the measurement of the Osteoarthritis Research Society International scoring system to evaluate OA model, and conducted general observation, histological observation, and Western blotting of JNK, phosphorylate-JNK (P-JNK), p38, phosphorylate-p38 (P-p38), MMP3, and light-chain 3 (LC3)-II/LC3-I to explore the variation of JNK, p38 MAPKs, and autophagy at the early stage of OA. With OA progressing at the early stage, MMP3, P-p38, and P-JNK were gradually upregulated from the baseline to the peak in study groups when compared with the control group; JNK and p38 variated of turbulence without statistical difference; and LC3-II/LC3-I had a decreasing tendency from the 0- to 15-day group. This study identifies that compromised autophagy may be related to the OA progress and that JNK and p38 MAPKs have positive regulation on MMP3 and negative regulation on autophagy. It also implicates a new therapeutic strategy for OA and other degenerate diseases based on selective MAPK inhibitors, reduction of MMP3, and autophagy.

Can Small Chemical Modifications of Natural Pan-inhibitors Modulate the Biological Selectivity? The Case of Curcumin Prenylated Derivatives Acting as HDAC or mPGES-1 Inhibitors

Curcumin, or diferuloylmethane, a polyphenolic molecule isolated from the rhizome of Curcuma longa, is reported to modulate multiple molecular targets involved in cancer and inflammatory processes. On the basis of its pan-inhibitory characteristics, here we show that simple chemical modifications of the curcumin scaffold can regulate its biological selectivity. In particular, the curcumin scaffold was modified with three types of substituents at positions C-1, C-8, and/or C-8' [C5 (isopentenyl, 5-8), C10 (geranyl, 9-12), and C15 (farnesyl, 13, 14)] in order to make these molecules more selective than the parent compound toward two specific targets: histone deacetylase (HDAC) and microsomal prostaglandin E2 synthase-1 (mPGES-1). From combined in silico and in vitro analyses, three selective inhibitors by proper substitution at position 8 were revealed. Compound 13 has improved HDAC inhibitory activity and selectivity with respect to the parent compound, while 5 and 9 block the mPGES-1 enzyme. We hypothesize about the covalent interaction of curcumin, 5, and 9 with the mPGES-1 binding site.

Prostaglandin E synthase is upregulated by Gas6 during cancer-induced venous thrombosis

Venous thromboembolism is a common complication of cancer. Based on recent evidence that (1) growth arrest-specific 6 (Gas6) regulates the expression of tissue factor during venous thrombosis, and (2) cancer promotes a procoagulant milieu, we hypothesize that Gas6 may be involved in cancer-induced coagulopathy. Venous thrombi were induced in both wild-type (WT) and Gas6-deficient ((-/-)) mice with cancer. WT mice with cancer developed larger thrombi than their healthy counterparts; these larger thrombi induced by cancer were not seen in Gas6(-/-) mice. Whole genome microarray analysis of differential gene expression in WT and Gas6(-/-) endothelial cells exposed to M27 murine lung carcinoma cells reveal that Gas6 increases prostaglandin E synthase (Ptges) expression in endothelial cells. This was confirmed using real-time polymerase chain reaction and immunofluorescence staining. Culture of WT endothelial cells with M27 increases the secretion of prostaglandin E2 (PGE2), the enzymatic product of Ptges, in WT but not in Gas6(-/-) endothelial cells. In WT endothelial cells, Ptges expression was regulated through extracellular signal-regulated kinase 1/2 phosphorylation (ERK1/2). In vitro, PGE2 activates platelets after binding to its receptor, EP3. In vivo, EP3 receptor antagonism reversed the effect of cancer-induced thrombosis in WT mice. These results show that Gas6, through upregulation of PGE2, contributes to cancer-induced venous thrombosis.

Elucidating new structural features of the triazole scaffold for the development of mPGES-1 inhibitors

Halogen bonding as a new key interaction is useful for the design of novel triazole derivatives as mPGES-1 inhibitors.

Ghrelin receptor (GHS-R1a) and its constitutive activity in somatotroph adenomas: a new co-targeting therapy using GHS-R1a inverse agonists and somatostatin analogs

CONTEXT

The ghrelin receptor GHS-R1a is highly expressed in human somatotroph adenomas and exhibits unusually high basal signaling activity. In humans, the suppression of this constitutive activity by mutation induces a short stature.

OBJECTIVE

Using a GHS-R1a inverse agonist, modified substance P (MSP), we explored the role of GHS-R1a constitutive activity in GH hypersecretion from somatotroph adenomas and as a putative therapeutic target.

DESIGN

The effects of MSP were assessed on GH secretion from 19 human somatotroph tumors in vitro. Moreover, these effects were compared with those of octreotide (somatostatin receptor subtype 2 [sst2] agonist) and with the combination of both drugs. Expression and localization of GHS-R1a and sst2 were studied.

RESULTS

For all tumors, MSP inhibited GH secretion in a dose-dependent manner from 13 to 64%. Moreover, MSP enhanced octreotide-induced GH inhibition. For five tumors, the effects of combined MSP plus octreotide treatment were significantly higher than the sum of effects of each drug alone. MSP increased the membrane localization of GHS-R1a and of microdomains colocalizing sst2-GHS-R1a, highlighting the cooperation between the two drugs.

CONCLUSIONS

The GHS-R1a inverse agonist could open new therapeutic options for acromegalic patients, particularly patients partially sensitive to octreotide whose GH secretion is not completely controlled by the sst2 agonist.

Protective role of frizzled-related protein B on matrix metalloproteinase induction in mouse chondrocytes

Introduction

Our objective was to investigate whether a lack of frizzled-related protein B (FrzB), an extracellular antagonist of the Wnt signaling pathways, could enhance cartilage degradation by facilitating the expression, release and activation of matrix metalloproteinases (MMPs) by chondrocytes in response to tissue-damaging stimuli.

Methods

Cartilage explants from FrzB^−/− and wild-type mice were challenged by excessive dynamic compression (0.5 Hz and 1 MPa for 6 hours). Load-induced glycosaminoglycan (GAG) release and MMP enzymatic activity were assessed. Interleukin-1β (IL-1β) (10, 100 and 1000 pg/mL for 24 hours) was used to stimulate primary cultures of articular chondrocytes from FrzB^−/− and wild-type mice. The expression and release of MMP-3 and −13 were determined by RT-PCR, western blot and ELISA. The accumulation of β-catenin was assessed by RT-PCR and western blot.

Results

Cartilage degradation, as revealed by a significant increase in GAG release (2.8-fold, P = 0.014) and MMP activity (4.5-fold, P = 0.014) by explants, was induced by an excessive load. Load-induced MMP activity appeared to be enhanced in FrzB^−/− cartilage explants compared to wild-type (P = 0.17). IL-1β dose-dependently induced Mmp-13 and −3 gene expression and protein release by cultured chondrocytes. IL-1β-mediated increase in MMP-13 and −3 was slightly enhanced in FrzB^−/− chondrocytes compared to wild-type (P = 0.05 and P = 0.10 at gene level, P = 0.17 and P = 0.10 at protein level, respectively). Analysis of Ctnn1b and Lef1 gene expression and β-catenin accumulation at protein level suggests that the enhanced catabolic response of FrzB^−/− chondrocytes to IL-1β and load may be associated with an over-stimulation of the canonical Wnt/β-catenin pathway.

Conclusions

Our results suggest that FrzB may have a protective role on cartilage degradation and MMP induction in mouse chondrocytes by attenuating deleterious effects of the activation of the canonical Wnt/β-catenin pathway.

Connexin43 hemichannels mediate small molecule exchange between chondrocytes and matrix in biomechanically-stimulated temporomandibular joint cartilage

OBJECTIVE

Connexin (Cx) 43 hemichannels play a role in mechanotransduction. This study was undertaken in order to determine if Cx43 hemichannels were activated in rat temporomandibular joint (TMJ) chondrocytes under mechanical stimulation.

METHODS

Sprague-Dawley rats were stimulated dental-mechanically. Cx43 expression in rat TMJ cartilage was determined with immunohistochemistry and real-time PCR, and Cx43 hemichannel opening was evaluated by the extra- and intracellular levels of prostaglandin E2 (PGE2). Both primary rat chondrocytes and ATDC5 cells were treated with fluid flow shear stress (FFSS) to induce hemichannel opening. The Cx43 expression level was then determined by real-time PCR or Western blotting, and the extent of Cx43 hemichannel opening was evaluated by measuring both PGE2 release and cellular dye uptake.

RESULTS

Cx43 expression and intra- and extracellular PGE2 levels were increased in mechanically-stimulated rat TMJ cartilage compared to the unstimulated control. The FFSS treatment increased Cx43 expression and induced Cx43 hemichannel opening in primary rat chondrocytes and ATDC5 cells indicated by enhanced PGE2 release and dye uptake. Furthermore, the Cx43 hemichannel opening could be blocked by the addition of 18β-glycyrrhetinic acid, a Cx channel inhibitor, Cx43-targeting siRNA, or by withdrawal of FFSS stimulation. The migration of cytosolic Cx43 protein to the plasma membrane in ATDC5 cells was still significant after 8 h post 2-h FFSS treatment, and the Cx43 protein level was still high at 48 h, which returned to control levels at 72 h after treatment.

CONCLUSION

Cx43 hemichannels are activated and mediate small molecule exchange between TMJ chondrocytes and matrix under mechanical stimulation.

Lysine-specific demethylase 1-mediated demethylation of histone H3 lysine 9 contributes to interleukin 1β-induced microsomal prostaglandin E synthase 1 expression in human osteoarthritic chondrocytes

Introduction

Microsomal prostaglandin E synthase 1 (mPGES-1) catalyzes the terminal step in the biosynthesis of PGE₂, a critical mediator in the pathophysiology of osteoarthritis (OA). Histone methylation plays an important role in epigenetic gene regulation. In this study, we investigated the roles of histone H3 lysine 9 (H3K9) methylation in interleukin 1β (IL-1β)-induced mPGES-1 expression in human chondrocytes.

Methods

Chondrocytes were stimulated with IL-1β, and the expression of mPGES-1 mRNA was evaluated using real-time RT-PCR. H3K9 methylation and the recruitment of the histone demethylase lysine-specific demethylase 1 (LSD1) to the mPGES-1 promoter were evaluated using chromatin immunoprecipitation assays. The role of LSD1 was further evaluated using the pharmacological inhibitors tranylcypromine and pargyline and small interfering RNA (siRNA)-mediated gene silencing. The LSD1 level in cartilage was determined by RT-PCR and immunohistochemistry.

Results

The induction of mPGES-1 expression by IL-1β correlated with decreased levels of mono- and dimethylated H3K9 at the mPGES-1 promoter. These changes were concomitant with the recruitment of the histone demethylase LSD1. Treatment with tranylcypromine and pargyline, which are potent inhibitors of LSD1, prevented IL-1β-induced H3K9 demethylation at the mPGES-1 promoter and expression of mPGES-1. Consistently, LSD1 gene silencing with siRNA prevented IL-1β-induced H3K9 demethylation and mPGES-1 expression, suggesting that LSD1 mediates IL-1β-induced mPGES-1 expression via H3K9 demethylation. We show that the level of LSD1 was elevated in OA compared to normal cartilage.

Conclusion

These results indicate that H3K9 demethylation by LSD1 contributes to IL-1β-induced mPGES-1 expression and suggest that this pathway could be a potential target for pharmacological intervention in the treatment of OA and possibly other arthritic conditions.

Potential role of hyaluronic acid on bone in osteoarthritis: matrix metalloproteinases, aggrecanases, and RANKL expression are partially prevented by hyaluronic acid in interleukin 1-stimulated osteoblasts

OBJECTIVE

To determine the effect of hyaluronic acid (HA) on proteolytic enzymes and bone remodeling mediators induced by interleukin 1β (IL-1β) and related to cartilage catabolism in murine osteoblasts.

METHODS

Osteoblasts were obtained from Swiss mice and cultured for 3 weeks. HA-treated osteoblasts were incubated with 100 μg/ml HA during the last week of culture, then stimulated with IL-1β (10 ng/ml) for 24 h. The expression of matrix metalloproteinases 3 and 13 (MMP-3 and MMP-13), ADAMTS-4 and ADAMTS-5, tissue inhibitor of metalloproteinases (TIMP), osteoprotegerin, and receptor activator of nuclear factor-κB ligand (RANKL) was determined by real-time polymerase chain reaction. MMP-3 and MMP-13 release was assessed by Western blot analysis.

RESULTS

IL-1β increased the mRNA levels of MMP-3 and MMP-13 and ADAMTS-4 and ADAMTS-5 and release of MMP-3 and MMP-13. Seven days of HA treatment significantly prevented the IL-1β-increased mRNA levels of MMP-3 (-61%, p < 0.01), MMP-13 (-56%, p < 0.01), ADAMTS-4 (-58%, p < 0.05), ADAMTS-5 (-52%, p < 0.01), and RANKL (-49%, p < 0.05), but not TIMP. As well, IL-1β-induced production of MMP-3 and MMP-13 was inhibited, by 27% (p < 0.01) and 40% (p < 0.01), respectively.

CONCLUSION

In an inflammatory context in murine osteoblasts, HA can inhibit the expression of MMP and ADAMTS. Because HA can counteract the production of these mediators in chondrocytes, its beneficial effect in osteoarthritis may be due to its action on cartilage and subchondral bone.

Interleukin-1β inhibits synthesis of 5-lipooxygenase in lipopolysaccharide-stimulated equine whole blood

Interleukin-1β (IL-1β) is a pro-inflammatory cytokine. It induces the synthesis of prostaglandin E2 (PGE2) catalyzed by cyclooxygenase (COX) and microsomal prostaglandin E synthase (m-PGES). Besides its pro-inflammatory properties, PGE2 also exhibits anti-inflammatory properties by inhibiting synthesis of 5-lipooxygenase (5-LO) products which are in themselves, pro-inflammatory mediators. Thus, inhibition of 5-LO products is beneficial in regulating immune-responses and pro-inflammatory processes. To investigate the hypothesis that IL-1β is responsible for the increase in the synthesis of PGE2 and in the reduction of 5-LO products, equine whole blood (EWB) was treated with lipopolysaccharide (LPS). In vitro treatment of EWB with LPS resulted in increased expression of IL-1β while expression of 5-LO was suppressed. Quantification of eicosanoids using liquid-chromatography-mass spectrometry/multiple reaction monitoring (LC-MS/MRM) showed increased concentrations of prostaglandins and decreased 5-LO products in LPS-treated EWB. Pretreatment of EWB with IL-1β followed by calcium ionophore A23187 (CI) reduced synthesis of 5-LO products. However, pretreatment of EWB with COX-2 inhibitor (NS-398) or m-PGES-1 inhibitor (CAY 10526) and IL-1β followed with CI resulted in a significant (p<0.0001) increase in 5-LO products. Pretreatment of EWB with phospholipase C inhibitor (U73122) followed with LPS reduced PGE2 production but increased 5-LO products. The result of this study indicated that increased PGE2 production led to reduction in 5-LO products in LPS-treated EWB via IL-1β. However, other pathways, cytokines and mediators may be involved in inhibiting 5-LO products but the present study did not include those other potential pathways. Inhibition of 5-LO products by PGE2 in EWB may regulate the initiation and pathogenesis of inflammatory responses in the horse.

The role of prostaglandin E2 in human vascular inflammation

Prostaglandins (PG) are the product of a cascade of enzymes such as cyclooxygenases and PG synthases. Among PG, PGE2 is produced by 3 isoforms of PGE synthase (PGES) and through activation of its cognate receptors (EP1-4), this PG is involved in the pathophysiology of vascular diseases. Some anti-inflammatory drugs (e.g. glucocorticoids, nonsteroidal anti-inflammatory drugs) interfere with its metabolism or effects. Vascular cells can initiate many of the responses associated with inflammation. In human vascular tissue, PGE2 is involved in many physiological processes, such as increasing vascular permeability, cell proliferation, cell migration and control of vascular smooth muscle tone. PGE2 has been shown to contribute to the pathogenesis of atherosclerosis, abdominal aortic aneurysm but also in physiologic/adaptive processes such as angiogenesis. Understanding the roles of PGE2 and its cognate receptors in vascular diseases could help to identify diagnostic and prognostic biomarkers. In addition, from these recent studies new promising therapeutic approaches like mPGES-1 inhibition and/or EP4-antagonism should be investigated.

Potential directions for drug development for osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a frustrating disease for both patient and physician because neither cause nor cure is known and there are currently no disease-modifying drugs.

OBJECTIVE

To review current therapeutic approaches as well as new findings regarding OA pathoetiology that could form the basis of future direction for the development of drugs to prevent or slow down disease progression.

METHODS

After reviewing disease progression in human OA, as demonstrated by histological analyses, the reasons for cartilage erosion are explored and possible therapeutic approaches are highlighted.

RESULTS/CONCLUSIONS

OA may be an epigenetic disease. This new concept can explain many aspects of the disease and provide reasons why therapeutic approaches until now have met with little success.

New findings in osteoarthritis pathogenesis: therapeutic implications

This review focuses on the new perspectives which can provide insight into the crucial pathways that drive cartilage-bone physiopathology. In particular, we discuss the critical signaling and effector molecules that can activate cellular and molecular processes in both cartilage and bone cells and which may be relevant in cross talk among joint compartments: growth factors (bone morphogenetic proteins and transforming growth factor), hypoxia-related factors, cell-matrix interactions [discoidin domain receptor 2 (DDR2) and syndecan 4], signaling molecules [WNT, Hedgehog (Hh)]. With the continuous progression of our knowledge on the molecular pathways involved in cartilage and bone changes in osteoarthritis (OA), an increasing number of potentially effective candidates for OA therapy are already under scrutiny in clinical trials to ascertain their possible safe use in an attempt to identify molecules active in slowing or halting OA progression and reducing joint pain. We then review the principal molecules currently under clinical investigation.

Advances in deoxynivalenol toxicity mechanisms: the brain as a target

Deoxynivalenol (DON), mainly produced by Fusarium fungi, and also commonly called vomitoxin, is a trichothecene mycotoxin. It is one of the most abundant trichothecenes which contaminate cereals consumed by farm animals and humans. The extent of cereal contamination is strongly associated with rainfall and moisture at the time of flowering and with grain storage conditions. DON consumption may result in intoxication, the severity of which is dose-dependent and may lead to different symptoms including anorexia, vomiting, reduced weight gain, neuroendocrine changes, immunological effects, diarrhea, leukocytosis, hemorrhage or circulatory shock. During the last two decades, many studies have described DON toxicity using diverse animal species as a model. While the action of the toxin on peripheral organs and tissues is well documented, data illustrating its effect on the brain are significantly less abundant. Yet, DON is known to affect the central nervous system. Recent studies have provided new evidence and detail regarding the action of the toxin on the brain. The purpose of the present review is to summarize critical studies illustrating this central action of the toxin and to suggest research perspectives in this field.

Microsomal Prostaglandin E2 Synthase-1

The prostanoids and leukotrienes (LTs) formed from arachidonic acid (AA) via the cyclooxygenase (COX)-1/2 and 5-lipoxygenase (5-LO) pathway, respectively, mediate inflammatory responses, chronic tissue remodelling, cancer, asthma and autoimmune disorders, but also possess homeostatic functions in the gastrointestinal tract, uterus, brain, kidney, vasculature and host defence. Based on the manifold functions of these eicosanoids, the clinical use of non-steroidal anti-inflammatory drugs (NSAIDs), a class of drugs that block formation of all prostanoids, is hampered by severe side-effects including gastrointestinal injury, renal irritations and cardiovascular risks. Therefore, anti-inflammatory agents interfering with eicosanoid biosynthesis require a well-balanced pharmacological profile to minimize these on-target side-effects. Current anti-inflammatory research aims at identifying compounds that can suppress the massive formation of pro-inflammatory prostaglandin (PG)E2 without affecting homeostatic PGE2 and PGI2 synthesis. The inducible microsomal prostaglandin E2 synthase-1 (mPGES-1) is one promising target enzyme. We will give an overview about the structure, regulation and function of mPGES-1 and then present novel inhibitors of mPGES-1 that may possess a promising pharmacological profile.

Proinflammatory actions of visfatin/nicotinamide phosphoribosyltransferase (Nampt) involve regulation of insulin signaling pathway and Nampt enzymatic activity

Visfatin (also termed pre-B-cell colony-enhancing factor (PBEF) or nicotinamide phosphoribosyltransferase (Nampt)) is a pleiotropic mediator acting on many inflammatory processes including osteoarthritis. Visfatin exhibits both an intracellular enzymatic activity (nicotinamide phosphoribosyltransferase, Nampt) leading to NAD synthesis and a cytokine function via the binding to its hypothetical receptor. We recently reported the role of visfatin in prostaglandin E(2) (PGE(2)) synthesis in chondrocytes. Here, our aim was to characterize the signaling pathways involved in this response in exploring both the insulin receptor (IR) signaling pathway and Nampt activity. IR was expressed in human and murine chondrocytes, and visfatin triggered Akt phosphorylation in murine chondrocytes. Blocking IR expression with siRNA or activity using the hydroxy-2-naphthalenyl methyl phosphonic acid tris acetoxymethyl ester (HNMPA-(AM)(3)) inhibitor diminished visfatin-induced PGE(2) release in chondrocytes. Moreover, visfatin-induced IGF-1R(-/-) chondrocytes released higher concentration of PGE(2) than IGF-1R(+/+) cells, a finding confirmed with an antibody that blocked IGF-1R. Using RT-PCR, we found that visfatin did not regulate IR expression and that an increased insulin release was also unlikely to be involved because insulin was unable to increase PGE(2) release. Inhibition of Nampt activity using the APO866 inhibitor gradually decreased PGE(2) release, whereas the addition of exogenous nicotinamide increased it. We conclude that the proinflammatory actions of visfatin in chondrocytes involve regulation of IR signaling pathways, possibly through the control of Nampt enzymatic activity.

Phase 2 enzyme inducer sulphoraphane blocks prostaglandin and nitric oxide synthesis in human articular chondrocytes and inhibits cartilage matrix degradation

OBJECTIVE

We explored the inhibitory effect of sulphoraphane (SFN), a potent inducer of Phase 2 enzymes, on cytokine-induced prostaglandin E(2) (PGE2) and nitric oxide (NO) production and cartilage degradation in articular chondrocytes. The regulatory mechanism of SFN on nuclear factor (NF)-κB was investigated.

METHODS

Chondrocytes were obtained from patients with knee OA. Chondrocytes were stimulated with IL-1β or TNF-α with or without pre-incubation with SFN. Production of PGE2 and NO was evaluated by the Griess reaction and an ELISA. The expression of microsomal PGE synthase (mPGES), cyclo-oxygenase (COX)-2 and inducible NO synthase (iNOS) was evaluated by real-time RT-PCR and western blot analysis. The regulation of NF-κB activity was explored using luciferase and chromatin immunoprecipitation assays as well as a western blot for phosphorylated IκB kinase (IKK), IκB and the degradation of IκB. Proteoglycan and type II collagen degradation products released from explant cultures were analysed using the dimethylmethylene blue assay and an ELISA for C-terminal telopeptides of type II collagen.

RESULTS

SFN inhibited the production of PGE2 and NO induced by IL-1β and TNF-α. At a concentration as low as 5 μM, SFN completely inhibited mPGES, COX-2 and iNOS at the mRNA and protein levels, and proteoglycan and type II collagen degradation product release in explant culture. Various signalling pathways required for the NF-κB activation were affected by SFN.

CONCLUSION

SFN inhibited a broad range of catabolic mechanisms in articular chondrocytes. SFN may be a safe and effective candidate drug for the inhibition of cartilage degradation in arthritic diseases.

A potential role of chondroitin sulfate on bone in osteoarthritis: inhibition of prostaglandin E₂ and matrix metalloproteinases synthesis in interleukin-1β-stimulated osteoblasts

OBJECTIVES

To determine the effect of chondroitin sulfate (CS) on inflammatory mediators and proteolytic enzymes induced by interleukin-1β (IL-1β) and related to cartilage catabolism in murine osteoblasts.

DESIGN

Osteoblasts were obtained by enzymatic digestion of calvaria from Swiss mice and cultured for 3 weeks as a primary culture. Cells were then stimulated with IL-1β (1 or 10 ng/ml). CS-treated osteoblasts were incubated with 100 μg/ml of CS during the last week of culture w/o IL-1β for the last 24 h. Expressions of cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-1 (mPGES-1), 15-PG dehydrogenase (15-PGDH), matrix metalloproteinases-3 and -13 (MMP-3 and -13), osteoprotegerin (OPG) and receptor activator of nuclear factor-kappa B ligand (RANKL) were determined by real-time polymerase chain reaction (PCR). PGE₂, MMP-3 and MMP-13 release were assessed in the medium by enzyme-linked immunosorbent assay or western-blotting.

RESULTS

IL-1β increased COX-2, mPGES-1, MMP-3, MMP-13, RANKL expressions, decreased 15-PGDH expression, and increased PGE₂, MMP-3 and MMP-13 release. Interestingly, 7 days of CS treatment significantly counteracted IL-1β-induced expression of COX-2 (-62%, P<0.001), mPGES-1 (-63%, P<0.001), MMP-3 (-39%, P=0.08), MMP-13 (-60%, P<0.001) and RANKL (-84%, P<0.001). Accordingly, IL-1β-induced PGE₂, MMP-3 and MMP-13 releases were inhibited by 86% (P<0.001), 58%(P<0.001) and 38% (P<0.01) respectively.

CONCLUSIONS

In conclusion, our data demonstrate that, in an inflammatory context, CS inhibits the production of PGE₂ and MMPs. Since CS has previously been shown to counteract the production of these mediators in chondrocytes, we speculate that the beneficial effect of CS in Osteoarthritis (OA) could not only be due to its action on cartilage but also on subchondral bone.

MicroRNA-199a* regulates the expression of cyclooxygenase-2 in human chondrocytes

OBJECTIVE

Cyclooxygenase-2 (COX-2) expression is associated with the pathogenesis of chronic inflammation and pain in osteoarthritis (OA). A study was undertaken to determine whether interleukin-1β (IL-1β)-mediated induction of COX-2 can be regulated by microRNAs (miRNAs) in OA.

METHODS

Human chondrocytes were stimulated with IL-1β in vitro. Total RNA was prepared using Trizol reagent. Gene expression was quantified using TaqMan Assays and miRNA targets were identified using bioinformatics. Transfection with reporter construct and premiRNA and antimiRNA was employed to verify suppression of target mRNA. Expression of COX-2 proteins was determined by immunoblotting. The role of activated p38-MAPKs was evaluated using specific inhibitor.

RESULTS

The 3'UTR of COX-2 mRNA contained the 'seed-matched' sequences for miR-199a* and miR-101_3. Increased expression of COX-2 correlated with the downregulation of miR-199a* and miR-101_3 in IL-1β-stimulated normal and OA chondrocytes. miR-199a* directly suppressed the luciferase activity of a COX-2 3'UTR reporter construct and inhibited the IL-1β-induced expression of COX-2 protein in OA chondrocytes. Modulation of miR-199a* expression also caused significant inhibition of IL-1β-induced upregulation of mPGES1 and prostaglandin E(2) production in OA chondrocytes. Activation of p38-MAPK downregulated the expression of miR-199a* and induced COX-2 expression. Treatment with antimiR-101_3 increased COX-2 expression in IL-1β-stimulated chondrocytes, but overexpression of miR-101_3 had no significant effect on COX-2 protein expression.

CONCLUSIONS

miR-199a* is a direct regulator of COX-2 expression in OA chondrocytes. IL-1β-induced activation of p38-MAPK correlates inversely with miR199a* expression levels. miR-199a* may be an important regulator of human cartilage homeostasis and a new target for OA therapy.

Rose hip and its constituent galactolipids confer cartilage protection by modulating cytokine, and chemokine expression

Background

Clinical studies have shown that rose hip powder (RHP) alleviates osteoarthritis (OA). This might be due to anti-inflammatory and cartilage-protective properties of the complete RHP or specific constituents of RHP. Cellular systems (macrophages, peripheral blood leukocytes and chondrocytes), which respond to inflammatory and OA-inducing stimuli, are used as in vitro surrogates to evaluate the possible pain-relief and disease-modifying effects of RHP.

Methods

(1) Inflammatory processes were induced in RAW264.7 cells or human peripheral blood leukocytes (PBL) with LPS. Inflammatory mediators (nitric oxide (NO), prostaglandin E₂ (PGE₂) and cytokines/chemokines) were determined by the Griess reaction, EIA and multiplex ELISA, respectively. Gene expression was quantified by RT-PCR. RHP or its constituent galactolipid, GLGPG (galactolipid (2S)-1, 2-di-O-[(9Z, 12Z, 15Z)-octadeca-9, 12, 15-trienoyl]-3-O-β-D-galactopyranosyl glycerol), were added at various concentrations and the effects on biochemical and molecular parameters were evaluated. (2) SW1353 chondrosarcoma cells and primary human knee articular chondrocytes (NHAC-kn) were treated with interleukin (IL)-1β to induce in vitro processes similar to those occurring during in vivo degradation of cartilage. Biomarkers related to OA (NO, PGE₂, cytokines, chemokines, metalloproteinases) were measured by multiplex ELISA and gene expression analysis in chondrocytes. We investigated the modulation of these events by RHP and GLGPG.

Results

In macrophages and PBL, RHP and GLGPG inhibited NO and PGE₂ production and reduced the secretion of cytokines (TNF-α, IFN-γ, IL-1β, IL-6, IL-12) and chemokines (CCL5/RANTES, CXCL10/IP-10). In SW1353 cells and primary chondrocytes, RHP and GLGPG diminished catabolic gene expression and inflammatory protein secretion as shown by lower mRNA levels of matrix metalloproteinases (MMP-1, MMP-3, MMP-13), aggrecanase (ADAMTS-4), macrophage inflammatory protein (MIP-2, MIP-3α), CCL5/RANTES, CXCL10/IP-10, IL-8, IL-1α and IL-6. The effects of GLGPG were weaker than those of RHP, which presumably contains other chondro-protective substances besides GLGPG.

Conclusions

RHP and GLGPG attenuate inflammatory responses in different cellular systems (macrophages, PBLs and chondrocytes). The effects on cytokine production and MMP expression indicate that RHP and its constituent GLGPG down-regulate catabolic processes associated with osteoarthritis (OA) or rheumatoid arthritis (RA). These data provide a molecular and biochemical basis for cartilage protection provided by RHP.

Blocking TREM-1 signaling prolongs survival of mice with Pseudomonas aeruginosa induced sepsis

TREM-1 is a recently discovered receptor expressed on neutrophils and macrophages. Blocking of TREM-1 signaling improves the survival of mice with bacterial sepsis. However, the precise mechanism by which TREM-1 modulates the inflammatory responses is poorly defined. In this study, we investigated the role of TREM-1 in Pseudomonas aeruginosa-induced peritonitis. Our results showed that TREM-1 was not expressed on lymphocytes but emerged on the cell surface of neutrophils and peritoneal macrophages. Blockade of TREM-1 signaling significantly prolonged survival of mice with P. aeruginosa-induced peritonitis. However, blocking TREM-1 signaling had no effect on macrophage phagocytosis in vitro. Interestingly, the expression of the costimulatory molecules CD40 and CD86 on macrophages was significantly decreased after blocking TREM-1 signaling. Furthermore, interfering with TREM-1 engagement led to significant reduction of pro-inflammatory mediators such as IL-1, TNF-α, MCP-1 and IFN-γ. Therefore, our results showed that TREM-1 could be a potential therapeutic target for bacterial sepsis.

Evidence for regulated interleukin-4 expression in chondrocyte-scaffolds under in vitro inflammatory conditions

Objective

To elucidate the anti-inflammatory and anabolic effects of regulated expression of IL-4 in chondrocyte-scaffolds under in vitro inflammatory conditions.

Methods

Mature articular chondrocytes from dogs (n = 3) were conditioned through transient transfection using pcDNA3.1.cIL-4 (constitutive) or pCOX-2.cIL-4 (cytokine-responsive) plasmids. Conditioned cells were seeded in alginate microspheres and rat-tail collagen type I matrix (CaReS®) to generate two types of tissue-engineered 3-dimensional scaffolds. Inflammatory arthritis was simulated in the packed chondrocytes through exogenous addition of recombinant canine (rc) IL-1β (100 ng/ml) plus rcTNFα (50 ng/ml) in culture media for 96 hours. Harvested cells and culture media were analyzed by various assays to monitor the anti-inflammatory and regenerative (anabolic) properties of cIL-4.

Results

cIL-4 was expressed from COX-2 promoter exclusively on the addition of rcIL-1β and rcTNFα while its expression from CMV promoter was constitutive. The expressed cIL-4 downregulated the mRNA expression of IL-1β, TNFα, IL-6, iNOS and COX-2 in the cells and inhibited the production of NO and PGE₂ in culture media. At the same time, it up-regulated the expression of IGF-1, IL-1ra, COL2a1 and aggrecan in conditioned chondrocytes in both scaffolds along with a diminished release of total collagen and sGAG into the culture media. An increased amount of cIL-4 protein was detected both in chondrocyte cell lysate and in concentrated culture media. Neutralizing anti-cIL-4 antibody assay confirmed that the anti-inflammatory and regenerative effects seen are exclusively driven by cIL-4. There was a restricted expression of IL-4 under COX-2 promoter possibly due to negative feedback loop while it was over-expressed under CMV promoter (undesirable). Furthermore, the anti-inflammatory /anabolic outcomes from both scaffolds were reproducible and the therapeutic effects of cIL-4 were both scaffold- and promoter-independent.

Conclusions

Regulated expression of therapeutic candidate gene(s) coupled with suitable scaffold(s) could potentially serve as a useful tissue-engineering tool to devise future treatment strategies for osteoarthritis.

Interleukin-1 beta affects cyclooxygenase-2 expression and cartilage metabolism in mandibular condyle

Extracellular matrix degradation in mandibular condylar cartilage is mediated by various cytokines in the temporomandibular joint (TMJ). Interleukin-1 beta (IL-1β) is detected in joint structures with pathologic status, and participates in catabolic action in the extracellular matrix. The purpose of this study was to investigate the effects of IL-1β on cyclooxygenase-2 (COX-2) expression and cartilage metabolism using cultured chondrocytes from mandibular condyle. Articular chondrocytes from the porcine mandibular condylar cartilage around the surface were cultured and treated with 0-10 ng/ml IL-1β or 0-1000 ng/ml prostaglandin (PGE(2)) for 0-24h. The mRNA levels of COX-2, MMP-1, -3, and -13 were evaluated by real-time PCR analysis. The protein levels of PGE(2) and MMPs were examined by ELISA and Western blot analysis, respectively. The expression levels of COX-2 and PGE(2) were enhanced by exogenous IL-1β in chondrocytes. The mRNA levels of MMP-1, -3, and -13 were up-regulated by PGE(2) treatment dose-dependently. It is shown that the expression of COX-2/PGE(2) was enhanced by IL-1β in articular chondrocytes from mandibular condyle, and that MMP-1, -3, and -13 were induced by PGE(2), suggesting that IL-1β-induced COX-2/PGE(2) play a crucial role in catabolic processes of mandibular condylar cartilage under inflammatory conditions.

Angiotensin II differentially modulates cyclooxygenase-2, microsomal prostaglandin E2 synthase-1 and prostaglandin I2 synthase expression in adventitial fibroblasts exposed to inflammatory stimuli

AIMS

To assess whether angiotensin II (Ang II) modulates key enzymes of the cyclooxygenase (COX)-2/prostanoid pathway, including prostaglandin E synthase-1 (mPGES-1) and prostacyclin synthase (PGIS) in rat aortic adventitial fibroblasts in the presence or absence of an inflammatory stimulus [interleukin (IL)-1β].

METHODS AND RESULTS

Fibroblasts stimulated with IL-1β (10 ng/ml, 24 h) and/or Ang II (0.1 μmol/l, 24 h) were used. IL-1β up-regulated COX-2 and mPGES-1 (protein and mRNA) and increased PGI2 and PGE2 release, without altering PGIS protein expression. Ang II did modify neither COX-2 and mPGES-1 expression nor prostanoid levels, but it induced PGIS expression. Interestingly, Ang II further enhanced IL-1β-induced COX-2 expression and PGI2 release and concomitantly reduced IL-1β-induced mPGES-1 expression. The AT1 receptor antagonist losartan prevented the effects of Ang II on IL-1β-induced COX-2 or mPGES-1 expression. IL-1β activated p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK)1/2 pathways, and coincubation with Ang II resulted in a higher and more sustained phosphorylation of both MAPK. Inhibition of either p38 MAPK (SB203580) or ERK1/2 (PD98059) reduced COX-2 and mPGES-1 expression in cells treated with IL-1β or the combination of IL-1β and Ang II. Ang II did not modify COX-2 transcriptional activity but increased COX-2 mRNA stability in IL-1β-treated cells; by contrast, it increased PGIS mRNA levels through a transcriptional mechanism.

CONCLUSION

Ang II differentially modulates key enzymes involved in prostanoid biosynthesis thereby altering the balance between PGI2/PGE2 in vascular cells exposed to inflammatory stimuli.

Microsomal prostaglandin e synthase-1 in rheumatic diseases

Microsomal prostaglandin E synthase-1 (mPGES-1) is a well-recognized target for the development of novel anti-inflammatory drugs that can reduce symptoms of inflammation in rheumatic diseases and other inflammatory conditions. In this review, we focus on mPGES-1 in rheumatic diseases with the aim to cover the most recent advances in the understanding of mPGES-1 in rheumatoid arthritis, osteoarthritis, and inflammatory myopathies. Novel findings regarding regulation of mPGES-1 cell expression as well as enzyme inhibitors are also summarized.

Selenomethionine inhibits IL-1β inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2) expression in primary human chondrocytes

OBJECTIVE

Several lines of evidence show that selenium (Se) has potential protective effects in osteoarthritis (OA), however the exact mechanism is still unclear. As interleukin-1β (IL-1β) is one of the key proinflammatory cytokines contributing to the progression in OA, we investigated the effect of Se in neutralizing the inflammatory effects of IL-1β on nitric oxide (NO) and prostaglandin E₂ (PGE₂) production, and the signaling pathways involved.

METHODS

Isolated primary human chondrocytes were pretreated with selenomethionine (SeMet) (0.5 μM SeMet) for 24 h then co-treated without or with IL-1β (10 pg/ml or 50 pg/ml) for another 24 h followed by RNA isolation. Gene expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2) was determined by quantitative Real Time-Polymerase Chain Reaction. Culture media concentrations of NO and PGE₂ were determined by nitrite (NO₂⁻) assay and immunoassay respectively. For analysis of cell signaling pathways, chondrocytes were pretreated with SeMet then stimulated with IL-1β for 0-45 min. The activity of IL-1β signaling pathways was determined by Western blot screening of phosphorylation states of signal transduction proteins.

RESULTS

SeMet inhibited chondrocyte gene expression of IL-1β induced iNOS (31-54%, P=0.031) and COX2 (50-65%, P=0.031) with corresponding reductions in both NO (19-47%, P=0.031) and PGE₂ (24-32%, P=0.031) production. Pretreatment with SeMet attenuated IL-1β induced activation of p38 MAPK (39%, P=0.039) but not the extracellular signal-regulated kinase pathways (ERK) 1/2, c-Jun N-terminal kinases (JNK) or nuclear factor κB (NFκB).

CONCLUSIONS

This study elucidates one potential protective mechanism of Se, namely through the alteration of cell signaling and downstream transcription of pro-inflammatory effects of IL-1β.

Potential roles of microsomal prostaglandin E synthase-1 in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease which primarily affects the synovial joints leading to inflammation, pain and joint deformities. Nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids, both of which inhibit cyclooxygenase (COX), have been extensively used for treating RA patients. Prostaglandin E synthase (PGES) is a specific biosynthetic enzyme that acts downstream of COX and converts prostaglandin (PG) H(2) to PGE(2). Among PGES isozymes, microsomal PGES-1 (mPGES-1) has been shown to be induced in a variety of cells and tissues under inflammatory conditions. The induction of mPGES-1 in the synovial tissue of RA patients is closely associated with the activation of the tissue by proinflammatory cytokines. Although selective mPGES-1 inhibitors have not yet been widely available, mice lacking mPGES-1 (mPGES-1(-/-) mice) have been generated to evaluate the physiological and pathological roles of mPGES-1 in vivo. Recent studies utilizing mPGES-1(-/-) mice have demonstrated the significance of mPGES-1 in the process of chronic inflammation and evocation of humoral immune response in autoimmune arthritis models. These recent findings highlight mPGES-1 as a novel therapeutic target for the treatment of autoimmune inflammatory diseases, including RA. Currently, both natural and synthetic chemicals are being tested for inhibition of mPGES-1 activity to produce PGE(2). The present review focuses on the recent advances in understanding the role of mPGES-1 in the pathophysiology of RA.

Differential effects of p38MAP kinase inhibitors on the expression of inflammation-associated genes in primary, interleukin-1beta-stimulated human chondrocytes

BACKGROUND AND PURPOSE

A main challenge in the therapy of osteoarthritis (OA) is the development of drugs that will modify the disease. Reliable test systems are necessary to enable an efficient screening of therapeutic substances. We therefore established a chondrocyte-based in vitro cell culture model in order to characterize different p38MAPK inhibitors.

EXPERIMENTAL APPROACH

Interleukin-1beta (IL-1beta)-stimulated human OA chondrocytes were treated with the p38MAPK inhibitors Birb 796, pamapimod, SB203580 and the new substance CBS-3868. Birb 796- and SB203580-treated cells were analysed in a genome-wide microarray analysis. The efficacy of all inhibitors was characterized by quantitative gene expression analysis and the quantification of PGE(2) and NO release.

KEY RESULTS

Microarray analysis revealed inhibitor-specific differences in gene expression. Whereas SB203580 had a broad effect on chondrocytes, Birb 796 counteracted the IL-1beta effect more specifically. All p38MAPK inhibitors significantly inhibited the IL-1beta-induced gene expression of COX-2, mPGES1, iNOS, matrix metalloproteinase 13 (MMP13) and TNFRSF11B, as well as PGE(2) release. Birb 796 and CBS-3868 showed a higher efficacy than SB203580 and pamapimod at inhibiting the expression of COX-2 and MMP13 genes, as well as PGE(2) release. In the case of mPGES1 and TNFRSF11B gene expression, CBS-3868 exceeded the efficacy of Birb 796.

CONCLUSIONS AND IMPLICATIONS

Our test system could differentially characterize inhibitors of the same primary pharmaceutical target. It reflects processes relevant in OA and is based on chondrocytes that are mainly responsible for cartilage degradation. It therefore represents a valuable tool for drug screening in between functional in vitro testing and in vivo models.