Cytosolic phospholipase A2 regulates TNF-induced production of joint destructive effectors in synoviocytes

AAV mediated repression of Neat1 lncRNA combined with F8 gene augmentation mitigates pathological mediators of joint disease in haemophilia

Haemophilic arthropathy (HA), a common comorbidity in haemophilic patients leads to joint pain, deformity and reduced quality of life. We have recently demonstrated that a long non-coding RNA, Neat1 as a primary regulator of matrix metalloproteinase (MMP) 3 and MMP13 activity, and its induction in the target joint has a deteriorating effect on articular cartilage. In the present study, we administered an Adeno-associated virus (AAV) 5 vector carrying an short hairpin (sh)RNA to Neat1 via intra-articular injection alone or in conjunction with systemic administration of a capsid-modified AAV8 (K31Q) vector carrying F8 gene (F8-BDD-V3) to study its impact on HA. AAV8K31Q-F8 vector administration at low dose, led to an increase in FVIII activity (16%-28%) in treated mice. We further observed a significant knockdown of Neat1 (~40 fold vs. untreated injured joint, p = 0.005) in joint tissue of treated mice and a downregulation of chondrodegenerative enzymes, MMP3, MMP13 and the inflammatory mediator- cPLA2, in mice receiving combination therapy. These data demonstrate that AAV mediated Neat1 knockdown in combination with F8 gene augmentation can potentially impact mediators of haemophilic joint disease.

Inflammatory arthritis and eye diseases: a Mendelian randomization study

Objectives

The aim of this study was to determine causal associations between inflammatory arthritis and eye diseases (disorders of sclera, cornea, iris, and ciliary body [DSCIC] and disorders of choroid and retina [DCR]).

Methods

Genome-wide association studies' summary data of rheumatoid arthritis (RA) from a large-scale meta-analysis were used to identify genetically predicted RA. UK Biobank source data predicted ankylosing spondylitis (AS), psoriatic arthritis (PsA), and juvenile idiopathic arthritis (JIA). Furthermore, data from the FinnGen Biobank were used to identify genetically predicted eye diseases. Two-sample Mendelian randomization analysis was used to assess the causal relationship between inflammatory arthritis and eye diseases in the European population. Inverse-variance weighting (IVW) was used as the primary method, while MR-Egger, weighted median, and MR-PRESSO outlier test were used to detect heterogeneity and pleiotropy.

Results

Genetically determined RA was indeed observed to have a causal effect on DSCIC (odds ratio [OR] = 1.084, p = 2.353 × 10-10) and DCR (OR = 1.151, p = 1.584 × 10-19). AS was causally associated with DSCIC (OR = 1.068, p < 2.024 × 10-8). In addition, PsA was also found to have a causal association with an increased risk of 17.9% for the development of DSCIC (OR = 1.179, p = 0.003). On the flip side, DSCIC increased the risk of JIA (OR = 2.276, p = 0.003).

Conclusion

Our study provided genetic evidence for the causal associations of RA, AS, and PsA with an increased risk of DSCIC, and a causal association between RA and DCR was also identified. In addition, DSCIC greatly increased the risk of JIA.

Bovine tumor necrosis factor-alpha Increases IL-6, IL-8, and PGE2 in bovine fibroblast-like synoviocytes by metabolic reprogramming

Lameness is a common condition in dairy cattle caused by infectious or noninfectious agents. Joint lesions are the second most common cause of lameness and can be diagnosed in association with the presentation of digit injuries. Fibroblast-like synoviocyte (FLS) are predominant cells of synovia and play a key role in the pathophysiology of joint diseases, thus increasing the expression of proinflammatory mediators. Tumor necrosis factor-alpha (TNF-α) is a potent proinflammatory cytokine involved in cyclooxygenase 2 (COX-2) and proinflammatory cytokine expression in FLS. Previously, TNF-α was demonstrated to increase hypoxia-inducible Factor 1 (HIF-1), a transcription factor that rewires cellular metabolism and increases the expression of interleukin (IL)-6 in bovine FLS (bFLS). Despite this, the proinflammatory effects of TNF-α in bFLS on metabolic reprogramming have been poorly studied. We hypothesized that TNF-α increases glycolysis and in this way controls the expression of IL-6, IL-8, and COX-2 in bFLS. Results first, gas chromatography/mass spectrometry (GC/MS)-based untargeted metabolomics revealed that bTNF-α altered the metabolism of bFLS, increasing glucose, isoleucine, leucine, methionine, valine, tyrosine, and lysine and decreasing malate, fumarate, α-ketoglutarate, stearate, palmitate, laurate, aspartate, and alanine. In addition, metabolic flux analysis using D-glucose-¹³C₆ demonstrated an increase of pyruvate and a reduction in malate and citrate levels, suggesting a decreased flux toward the tricarboxylic acid cycle after bTNF-α stimulation. However, bTNF-α increased lactate dehydrogenase subunit A (LDHA), IL-6, IL-8, IL-1β and COX-2 expression, which was dependent on glycolysis and the PI3K/Akt pathway. The use of FX11 and dichloroacetate (DCA), an inhibitor of LDHA and pyruvate dehydrogenase kinase (PDK) respectively, partially reduced the expression of IL-6. Our results suggest that bTNF-α induces metabolic reprogramming that favors glycolysis in bFLS and increases IL-6, IL-8, IL-1β and COX-2/PGE2.

Integrated metabolomics and network analysis reveal changes in lipid metabolisms of tripterygium glycosides tablets in rats with collagen-induced arthritis

Tripterygium glycosides tablets (TGT) are the commonly used preparation for rheumatoid arthritis (RA). However, the changes in TGT on RA are still unclear at the metabolic level. This study aimed to reveal the biological processes of TGT in collagen-induced arthritis (CIA) rats through integrated metabolomics and network analysis. First, the CIA model in rats was established, and the CIA rats were given three doses of TGT. Then, the endogenous metabolites in the serum from normal rats, CIA rats, and CIA rats treated with varying doses of TGT were detected by UHPLC-QTOF-MS/MS. Next, univariate and multivariate statistical analyses were performed to find the differential metabolites. Finally, differential metabolites, metabolic pathways, and hub genes were analyzed integrally to reveal the biological processes of TGT in CIA rats. The paw diameter, arthritis score, immunoglobulin G (IgG) concentration, CT image, and histological assay showed that TGT had evident therapeutic effects on CIA rats. Untargeted metabolomics revealed that TGT could ameliorate the down-regulation of lipid levels in CIA rats. Four key differential metabolites were found including LysoP(18:0), LysoPA(20:4), LysoPA(18:2), and PS(O-20:0/17:1). The glycerophospholipid metabolic pathway was perturbed in treating CIA with TGT. A total of 24 genes, including PLD1, LPCAT4, AGPAT1, and PLA2G4A, were found to be the hub genes of TGT in CIA rats. In conclusion, the integrated analysis provided a novel and holistic perspective on the biological processes of TGT in CIA rats, which could give helpful guidance for further TGT on RA. Future studies based on human samples are necessary.

Tocopheryl Phosphate Inhibits Rheumatoid Arthritis-Related Gene Expression In Vitro and Ameliorates Arthritic Symptoms in Mice

Anti-rheumatoid arthritis (RA) effects of α-tocopherol (α-T) have been shown in human patients in a double-blind trial. However, the effects of α-T and its derivatives on fibroblast-like synoviocytes (FLS) during the pathogenesis of RA remain unclear. In the present study, we compared the expression levels of genes related to RA progression in FLS treated with α-T, succinic ester of α-T (TS), and phosphate ester of α-T (TP), as determined via RT-PCR. The mRNA levels of interleukin (IL)-6, tumor necrosis factor-α (TNF-α), matrix metalloproteinase (MMP)-3, and MMP-13 were reduced by treatment with TP without cytotoxicity, while α-T and TS did not show such effects. Furthermore, intraperitoneal injection of TP ameliorated the edema of the foot and joint and improved the arthritis score in laminarin-induced RA model mice. Therefore, TP exerted anti-RA effects through by inhibiting RA-related gene expression.

Inhibition of Cytosolic Phospholipase A2α Induces Apoptosis in Multiple Myeloma Cells

Cytosolic phospholipase A2α (cPLA2α) is the rate-limiting enzyme in releasing arachidonic acid and biosynthesis of its derivative eicosanoids. Thus, the catalytic activity of cPLA2α plays an important role in cellular metabolism in healthy as well as cancer cells. There is mounting evidence suggesting that cPLA2α is an interesting target for cancer treatment; however, it is unclear which cancers are most relevant for further investigation. Here we report the relative expression of cPLA2α in a variety of cancers and cancer cell lines using publicly available datasets. The profiling of a panel of cancer cell lines representing different tissue origins suggests that hematological malignancies are particularly sensitive to the growth inhibitory effect of cPLA2α inhibition. Several hematological cancers and cancer cell lines overexpressed cPLA2α, including multiple myeloma. Multiple myeloma is an incurable hematological cancer of plasma cells in the bone marrow with an emerging requirement of therapeutic approaches. We show here that two cPLA2α inhibitors AVX420 and AVX002, significantly and dose-dependently reduced the viability of multiple myeloma cells and induced apoptosis in vitro. Our findings implicate cPLA2α activity in the survival of multiple myeloma cells and support further studies into cPLA2α as a potential target for treating hematological cancers, including multiple myeloma.

Fascin1 mediated release of pro-inflammatory cytokines and invasion/migration in rheumatoid arthritis via the STAT3 pathway

Rheumatoid arthritis (RA) is a chronic, multi-factorial disease characterized by Synovial hyperplasia, chronic inflammation, and autoimmune reaction. Fascin1 overexpression has been implicated in cancer, immune, and inflammatory diseases. However, the relationship between Fascin1 and rheumatoid arthritis (RA) has not yet been determined. We investigated whether Fascin1 could modulate pro-inflammatory cytokine secretion and the proliferation, apoptosis, and invasion/migration of fibroblast-like synoviocytes (RA-FLSs). Fascin 1 was suppressed with a short interfering (si)RNA approach. Functional analysis contained MTT assay, flow cytometry,Transwell™ assays, wound healing, Quantitative polymerase chain reaction and western blotting were used to detect cell proliferation,apoptosis ratio, invasion/ migration, the mRNA and protein expression of the realted markers, respectively. Overexpression of fascin1 was observed in RA-FLSs group compared with control group. Fascin1 expression positively correlated with changes in the expression of RA disease activity markers (RF, CRP, and DAB28, respectively). We also observed a significant positive correlation between Fascin1 and STAT3 mRNA levels in RA- FLSs.Fascin1 silencing attenuated the expression of pro-inflammatory cytokines; reduced FLS proliferation in vitro; and increased apoptosis ratio and bax, cleaved PARP, and caspase-3 expression. si- Fascin1 transfection delayed RA-FLS invasion/migration and reversed the epithelial- mesenchymal transition. These data suggest that Fascin1 exerts positive effects on the proliferation, cell cycle, and invasion/migration of RA-FLSs by activating signal transducer and activator of transcription 3 signaling.After all, Fascin1 contributed to RA development.

Research Progress of Therapeutic Enzymes and Their Derivatives: Based on Herbal Medicinal Products in Rheumatoid Arthritis

Rheumatoid arthritis (RA) acts as one of the most common, agnogenic and chronic inflammatory-autoimmune disorder which is characterized by persistent synovitis, cartilage destruction, and joint deformities, leads to a wide range of disabilities, and increased mortality, thus imposing enormous burdens. Several drugs with anti-inflammatory and immunomodulatory properties such as celecoxib, diclofenac and methotrexate are being selected as conventional drugs in the allopathic system of medicine for the treatment of RA in clinic. However, there are some serious side effects more or less when using these drugs because of their short poor bioavailability and biological half-life for a long time. These shortcomings greatly promote the exploration and application of new low- or no-toxicity drugs for treating the RA. Meanwhile, a growing number of studies demonstrate that several herbs present certain anti-inflammatory and anti-arthritic activities through different enzymes and their derivatives, which indicate that they are promising therapeutic strategies when targeting these mediators based on herbal medicinal products in RA research. This review article summarizes the roles of the main enzymes and their derivatives during the pathogenesis of RA, and clearly clarifies the explicit and potential targeted actions of herbal medicinal products that have anti-RA activity. Our review provides timely and critical reference for the scientific rationale use of herbal medicinal products, with the increasing basic research and clinical application of herbal medicinal products by patients with RA.

Critical Involvement of Calcium-Dependent Cytosolic Phospholipase A2α in Aortic Valve Interstitial Cell Calcification

The involvement of calcium-dependent cytosolic phospholipase A2α (cPLA2α) in aortic valve calcification is not exhaustively elucidated. Here, cPLA2α expression in aortic valve interstitial cell (AVIC) pro-calcific cultures simulating either metastatic or dystrophic calcification was estimated by qPCR, Western blotting, and counting of cPLA2α-immunoreactive cells, with parallel ultrastructural examination of AVIC calcific degeneration. These evaluations also involved pro-calcific AVIC cultures treated with cPLA2α inhibitor dexamethasone. cPLA2α over-expression resulted for both types of pro-calcific AVIC cultures. Compared to controls, enzyme content was found to increase by up to 300% and 186% in metastatic and dystrophic calcification-like cultures, respectively. Increases in mRNA amounts were also observed, although they were not as striking as those in enzyme content. Moreover, cPLA2α increases were time-dependent and strictly associated with mineralization progression. Conversely, drastically lower levels of enzyme content resulted for the pro-calcific AVIC cultures supplemented with dexamethasone. In particular, cPLA2α amounts were found to decrease by almost 88% and 48% in metastatic and dystrophic calcification-like cultures, respectively, with mRNA amounts showing a similar trend. Interestingly, these drastic decreases in cPLA2α amounts were paralleled by drastic decreases in mineralization degrees, as revealed ultrastructurally. In conclusion, cPLA2α may be regarded as a crucial co-factor contributing to AVIC mineralization in vitro, thus being an attractive potential target for designing novel therapeutic strategies aimed to counteract onset or progression of calcific aortic valve diseases.

Fexofenadine inhibits TNF signaling through targeting to cytosolic phospholipase A2 and is therapeutic against inflammatory arthritis

OBJECTIVE

Tumour necrosis factor alpha (TNF-α) signalling plays a central role in the pathogenesis of various autoimmune diseases, particularly inflammatory arthritis. This study aimed to repurpose clinically approved drugs as potential inhibitors of TNF-α signalling in treatment of inflammatory arthritis.

METHODS

In vitro and in vivo screening of an Food and Drug Administration (FDA)-approved drug library; in vitro and in vivo assays for examining the blockade of TNF actions by fexofenadine: assays for defining the anti-inflammatory activity of fexofenadine using TNF-α transgenic (TNF-tg) mice and collagen-induced arthritis in DBA/1 mice. Identification and characterisation of the binding of fexofenadine to cytosolic phospholipase A2 (cPLA2) using drug affinity responsive target stability assay, proteomics, cellular thermal shift assay, information field dynamics and molecular dynamics; various assays for examining fexofenadine inhibition of cPLA2 as well as the dependence of fexofenadine's anti-TNF activity on cPLA2.

RESULTS

Serial screenings of a library composed of FDA-approved drugs led to the identification of fexofenadine as an inhibitor of TNF-α signalling. Fexofenadine potently inhibited TNF/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB) signalling in vitro and in vivo, and ameliorated disease symptoms in inflammatory arthritis models. cPLA2 was isolated as a novel target of fexofenadine. Fexofenadine blocked TNF-stimulated cPLA2 activity and arachidonic acid production through binding to catalytic domain 2 of cPLA2 and inhibition of its phosphorylation on Ser-505. Further, deletion of cPLA2 abolished fexofenadine's anti-TNF activity.

CONCLUSION

Collectively, these findings not only provide new insights into the understanding of fexofenadine action and underlying mechanisms but also provide new therapeutic interventions for various TNF-α and cPLA2-associated pathologies and conditions, particularly inflammatory rheumatic diseases.

Evaluation of 12 GWAS-drawn SNPs as biomarkers of rheumatoid arthritis response to TNF inhibitors. A potential SNP association with response to etanercept

Research in rheumatoid arthritis (RA) is increasingly focused on the discovery of biomarkers that could enable personalized treatments. The genetic biomarkers associated with the response to TNF inhibitors (TNFi) are among the most studied. They include 12 SNPs exhibiting promising results in the three largest genome-wide association studies (GWAS). However, they still require further validation. With this aim, we assessed their association with response to TNFi in a replication study, and a meta-analysis summarizing all non-redundant data. The replication involved 755 patients with RA that were treated for the first time with a biologic drug, which was either infliximab (n = 397), etanercept (n = 155) or adalimumab (n = 203). Their DNA samples were successfully genotyped with a single-base extension multiplex method. Lamentably, none of the 12 SNPs was associated with response to the TNFi in the replication study (p > 0.05). However, a drug-stratified exploratory analysis revealed a significant association of the NUBPL rs2378945 SNP with a poor response to etanercept (B = -0.50, 95% CI = -0.82, -0.17, p = 0.003). In addition, the meta-analysis reinforced the previous association of three SNPs: rs2378945, rs12142623, and rs4651370. In contrast, five of the remaining SNPs were less associated than before, and the other four SNPs were no longer associated with the response to treatment. In summary, our results highlight the complexity of the pharmacogenetics of TNFi in RA showing that it could involve a drug-specific component and clarifying the status of the 12 GWAS-drawn SNPs.

Therapeutic potential of arachidonyl trifluromethyl ketone, a cytosolic phospholipaseA2 IVA specific inhibitor, in cigarette smoke condensate-induced pathological conditions in alveolar type I & II epithelial cells

Cigarette smoke is responsible for multiple disorders and causes almost 10 million annual deaths globally but underlying mechanisms are still underexplored. Continuous exposure of Cigarette smoke condensate (CSC) leads to cytosolic phospholipase A2 (cPLA2) mediated high free radicals where cPLA2s seems to play crucial role in generated various patho-physiological conditions such as chronic inflammation, oxidative stress and cancer. In this view, we assessed the therapeutic potential of arachidonyl trifluromethyl ketone (ATK), a cPLA2 inhibitor, via pharmacological inhibition of most expressible CSC-induced cPLA2 group IVA in type-I and type-II alveolar epithelial cells. The In Vitro inhibitory effect of ATK on CSC-induced PLA2 activity and its cellular role were assessed in terms of cell viability, fluorescein diacetate (FDA) dye uptake assay for membrane integrity, reactive oxygen species (ROS)/reactive nitrogen species (RNS) levels and pro apoptotic as well as anti apoptosis markers via flow cytometry, along with extracellular signal-regulated kinases (ERK) levels using enzyme-linked immunosorbent assay (ELISA). The experimental findings demonstrated that ATK acts as potent inhibitor of cPLA2 activity and shown its effectiveness as therapeutic agent by significantly mimicking CSC-induced levels of free radicals, primary apoptosis, ratio of pro-apoptotic/apoptotic proteins and levels of ERK whereas protected cells from loss of cell viability and membrane integrity. Thus, this study is an important step towards the opening up of avenues for the applicability of the cPLA2 isoform specific inhibitors such as ATK for pre-clinical and clinical studies and could be beneficial during smoking-induced lung pathological conditions.

Cytosolic group IVA phospholipase A2 inhibitors, AVX001 and AVX002, ameliorate collagen-induced arthritis

Background

Cytosolic phospholipase A2 group IVA (cPLA2α)-deficient mice are resistant to collagen-induced arthritis, suggesting that cPLA2α is an important therapeutic target. Here, the anti-inflammatory effects of the AVX001 and AVX002 cPLA2α inhibitors were investigated.

Methods

In vitro enzyme activity was assessed by a modified Dole assay. Effects on inhibiting IL-1β-induced release of arachidonic acid (AA) and prostaglandin E2 (PGE2) were measured using SW982 synoviocyte cells. In vivo effects were studied in prophylactic and therapetic murine collagen-induced arthritis models and compared to methotrexate (MTX) and Enbrel, commonly used anti-rheumatic drugs. The in vivo response to treatment was evaluated in terms of the arthritis index (AI), histopathology scores and by plasma levels of PGE2 following 14 and 21 days of treatment.

Results

Both cPLA2α inhibitors are potent inhibitors of cPLA2α in vitro. In synoviocytes, AVX001 and AVX002 reduce, but do not block, release of AA or PGE2 synthesis. In both CIA models, the AI and progression of arthritis were significantly lower in the mice treated with AVX001, AVX002, Enbrel and MTX than in non- treated mice. Several histopathology parameters of joint damage were found to be significantly reduced by AVX001 and AVX002 in both prophylactic and therapeutic study modes; namely articular cavity and peripheral tissue inflammatory cell infiltration; capillary and synovial hyperplasia; articular cartilage surface damage; and periostal and endochondral ossification. In comparison, MTX did not significantly improve any histopathology parameters and Enbrel only improved ossification. Finally, as a biomarker of inflammation and as an indication that AVX001 and AVX002 blocked the cPLA2α target, we determined that plasma levels of PGE2 were significantly reduced in response to the AVX inhibitors and MTX, but not Enbrel.

Conclusions

AVX001 and AVX002 display potent anti-inflammatory activity and disease-modifying properties in cellular and in vivo models. The in vivo effects of AVX001 and AVX002 were comparable to, or superior, to those of MTX and Enbrel. Taken together, this study suggests that cPLA2α inhibitors AVX001 and AVX002 are promising small molecule disease-modifying anti-rheumatic therapies.

Polyphenolic extract from extra virgin olive oil inhibits the inflammatory response in IL-1β-activated synovial fibroblasts

The polyphenolic extract (PE) from extra virgin olive oil (EVOO) has been shown to possess important anti-inflammatory and joint protective properties in murine models of rheumatoid arthritis (RA). This study was designed to evaluate the effects of PE on IL-1β-activated human synovial fibroblasts SW982 cell line. PE from EVOO treatment inhibited IL-1β-induced matrix metalloproteases (P&lt;0·001), TNF-α and IL-6 production (P&lt;0·001). Similarly, IL-1β-induced cyclo-oxygenase-2 and microsomal PGE synthase-1 up-regulations were down-regulated by PE (P&lt;0·001). Moreover, IL-1β-induced mitogen-activated protein kinase (MAPK) phosphorylation and NF-κB activation were ameliorated by PE (P&lt;0·001). These results suggest that PE from EVOO reduces the production of proinflammatory mediators in human synovial fibroblasts; particularly, these protective effects could be related to the inhibition of MAPK and NF-κB signalling pathways. Taken together, PE from EVOO probably could provide an attractive complement in management of diseases associated with over-activation of synovial fibroblasts, such as RA.

Tussilagone, a major active component in Tussilago farfara, ameliorates inflammatory responses in dextran sulphate sodium-induced murine colitis

Inflammatory bowel disease (IBD) is a chronically relapsing inflammatory disorder of the gastrointestinal tract. Current IBD treatments are associated with poor tolerability and insufficient therapeutic efficacy, prompting the need for alternative therapeutic approaches. Recent advances suggest promising interventions based on a number of phytochemicals. Herein, we explored the beneficial effects of tussilagone, a major component of Tussilago farfara, in mice subjected to acute colitis induced by dextran sulfate sodium (DSS). Treatment with tussilagone resulted in a significant protective effect against DSS-induced acute colitis in mice via amelioration of weight loss, and attenuation of colonic inflammatory damage. Additionally, the expression of tumor necrosis factor-α and interleukin-6 and the activity of myeloperoxidase in colonic tissues were significantly reduced in tussilagone-treated mice. Furthermore, immunohistochemical analysis revealed that tussilagone treatment reduced the numbers of nuclear factor-kappa B (NF-κB) and increased the numbers of nuclear factor erythroid 2-related factor 2 (Nrf2) in nuclei of colonic tissues. Taken together, tussilagone treatment attenuated DSS-induced colitis in mice through inhibiting the activation of NF-κB and inducing Nrf2 pathways, indicating that tussilagone is a potent therapeutic candidate for treatment of intestinal inflammation.

PGE2 enhanced TNFα-mediated IL-8 induction in monocytic cell lines and PBMC

BACKGROUND & PURPOSE

Recent studies suggested a role of prostaglandin E₂ (PGE₂) in the expression of the chemokine IL-8 by monocytes. The function of EP4 receptor for TNFα-induced IL-8 expression was studied in monocytic cell lines.

EXPERIMENTAL APPROACH

IL-8 mRNA and protein induction as well as IL-8 promoter activity and transcription factor activation were assessed in monocytic cell lines, primary blood mononuclear cells (PBMC) and transgenic HEK293 cells expressing the EP4 receptor.

KEY RESULTS

In monocytic cell lines THP-1, MonoMac and U937 PGE₂ had only a marginal impact on IL-8 induction but strongly enhanced TNFα-induced IL-8 mRNA and protein synthesis. Similarly, in PBMC IL-8 mRNA induction was larger by simultaneous stimulation with TNFα and PGE₂ than by either stimulus alone. The EP4 receptor subtype was the most abundant EP receptor in all three cell lines and in PBMC. Stimulation of THP-1 cells with an EP4 specific agonist enhanced TNFα-induced IL-8 mRNA and protein formation to the same extent as PGE₂. In HEK293 cells expressing EP4, but not in wild type HEK293 cells lacking EP4, PGE₂ enhanced TNFα-induced IL-8 protein and mRNA synthesis. In THP-1 cells, the enhancement of TNFα-mediated IL-8 mRNA induction by PGE₂ was mimicked by a PKA-activator. Furthermore in these cells PGE₂ induced expression of transcription factor C/EBPß, enhanced NF-κB activation by TNFα and inhibited TNFα-mediated AP-1 activation. PGE₂ and TNFα synergistically activated transcription factor CREB, induced C/EBPß expression and enhanced the activity of an IL-8 promoter fragment containing -223 bp upstream of the transcription start site.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that a combined stimulation of TNFα and PGE₂/EP4 signal chains in monocytic cells leads to maximal IL-8 promoter activity, as well as IL-8 mRNA and protein induction, by activating the PKA/CREB/C/EBPß as well as NF-κB signal chains.

Oleuropein down-regulated IL-1β-induced inflammation and oxidative stress in human synovial fibroblast cell line SW982

Rheumatoid arthritis (RA) is a chronic and systemic inflammatory autoimmune disease mainly characterized by aggressive hyperproliferation of synovial fibroblasts (SFs). It is accompained by a massive infiltration of inflammatory immune cells inducing progressive matrix degradation, destruction of cartilage and bone erosion through the production of inflammatory mediators. Oleuropein is the most prevalent phenolic component in olive leaves, seed, pulp and peel of unripe olives and is responsible for the characteristic bitter taste of unprocessed olives. This secoiridoid possesses well-documented pharmacological properties, including antioxidant and anti-inflammatory properties, and is available as a food supplement in Mediterranean countries. However, to date, anti-arthritic effects of oleuropein on SFs have not been yet elucidated. Thus, the aim of the present study was to investigate the potential effects of oleuropein, on IL-1β-induced production of inflammatory mediators and oxidative stress in the human synovial sarcoma cell line (SW982). In order to gain a better insight into mechanisms of action, signaling pathways were also explored. Cell viability was determined using the sulforhodamine B (SRB) assay. The expression of inflammatory cytokines IL-6, TNF-α, MMP-1 and MMP-3 was evaluated by ELISA. Moreover, changes in the protein expression of cyclooxygenase (COX)-2, microsomal prostaglandin E synthase-1 (mPGES-1) as well as mitogen-activated protein kinase (MAPKs), nuclear factor kappa B (NF-κB), and nuclear factor-erythroid 2-related and heme oxygenase-1 (HO-1) signalling pathways were analysed by western blot. Oleuropein exerted anti-inflammatory and anti-oxidant effects via down-regulation of MAPK and NF-κB signaling pathways and induction of Nrf2-linked HO-1 controlling the production of inflammatory mediators decreasing IL-6 and TNF-α cytokines, MMP-1 and MMP-3 levels and mPGES-1 and COX-2 overexpression. Thus, oleuropein might provide a basis for developing a new dietary strategy for the prevention and management of RA.

Cytosolic phospholipase A2 (cPLA2) IVA as a potential signature molecule in cigarette smoke condensate induced pathologies in alveolar epithelial lineages

BACKGROUND

Smoking is one of the leading causes of millions of deaths worldwide. During cigarette smoking, most affected and highly exposed cells are the alveolar epithelium and generated oxidative stress in these cells leads to death and damage. Several studies suggested that oxidative stress causes membrane remodeling via Phospholipase A2s but in the case of cigarette smokers, mechanistically study is not yet fully defined. In view of present perspective, we evaluated the involvement of cytosolic phospholipase A2 (cPLA2) IVA as therapeutic target in cigarette smoke induced pathologies in transformed type I and type II alveolar epithelial cells.

METHODS

Transformed type I (WI26) and type II (A549) alveolar epithelial cells were used for the present study. Cigarette smoke condensate (CSC) was prepared from most commonly used cigarette (Gold Flake with filter) by the Indian population. CSC-induced molecular changes were evaluated through cell viability using MTT assay, reactive oxygen species (ROS) measurement using 2,7 dichlorodihydrofluorescin diacetate (DCFH-DA), cell membrane integrity using fluorescein diacetate (FDA) and ethidium bromide (EtBr) staining, super oxide dismutase (SOD) levels, cPLA2 activity and molecular involvement of specific cPLA2s at selected 24 h time period.

RESULTS

CSC-induced response on both type of epithelial cells shown significantly reduction in cell viability, declined membrane integrity, with differential escalation of ROS levels in the range of 1.5-15 folds and pointedly increased cPLA2 activity (p < 0.05). Likewise, we observed distinction antioxidant potential in these two types of lineages as type I cells had considerably higher SOD levels when compared to type II cells (p < 0.05). Further molecular expression of all cPLA2s increased significantly in a dose dependent manner, specifically cytosolic phospholipase A2 IVA with maximum manifestation of 3.8 folds. Interestingly, CSC-induced ROS levels and cPLA2s expression were relatively higher in A549 cells as compared to WI26 cells.

CONCLUSIONS

The present study indicates that among all cPLA2s, specific cPLA2 IVA are the main enzymes involved in cigarette smoke induced anomalies in type I and type II lung epithelial cells and targeting them holds tremendous possibilities in cigarette smoke induced lung pathologies.

Inhibition of Cytosolic Phospholipase A2α (cPLA2α) by Medicinal Plants in Relation to Their Phenolic Content

The cytosolic phospholipase A2α(cPLA2α) is one of the potential targets for anti-inflammatory drugs, since this enzyme plays a key role in the inflammation processes seen in health disorders, like asthma, allergic reactions, arthritis and neuronal diseases. In this study, cPLA2α inhibition by 43 methanol extracts from medicinal plants rich in polyphenols was determined. The eight most active extracts were derived from Ribes nigrum (IC50 of 27.7 μg/mL), Ononis spinosa (IC50 of 39.4 μg/mL), Urtica dioica (IC50 of 44.32 μg/mL), Betula sp. (IC50 of 58.02 μg/mL), Sanguisorba officinalis (IC50 of 76.25 μg/mL), Orthosiphon stamineus (IC50 of 78.83 μg/mL), Petasites hybridus (IC50 of 81.02 μg/mL) and Tussilago farfara (IC50 of 123.28 μg/mL). Additionally, the antioxidant activities of these extracts were determined with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and their phenolic content with the Folin-Ciocalteu reagent. Antioxidant activity showed a non-linear, positive correlation to the phenolic content, but no correlation of PLA2 inhibition with phenolic content could be established. This study provides evidence that cPLA2α may be a relevant target for anti-inflammatory agents.

Cytosolic phospholipase A2 modulates TLR2 signaling in synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovitis leading to destruction of cartilage and bone. PLA2 enzymes are key players in inflammation regulating the release of unsaturated fatty acids such as arachidonic acid (AA), a precursor of pro-inflammatory eicosanoids. Several lines of evidence point to toll-like receptors (TLRs) as drivers of synovitis and joint destruction in RA. However, few studies have addressed the implication of PLA2 activity downstream TLR activation in the synovium. Here, we aimed to characterize PLA2 enzyme involvement in TLR2-induced signaling in synovial fibroblast-like cells. TLRs1-7 and a range of sPLA2, iPLA2 and cPLA2 enzymes were found to be transcriptionally expressed in cultured synoviocytes. Activation of TLR2/1 and TLR2/6 led to phosphorylation of cPLA2α at Ser⁵⁰⁵, and induced AA release and PGE₂ production; effects that were attenuated by cPLA2α inhibitors. In contrast, sPLA2 inhibitors did not affect AA or PGE₂ release. cPLA2α inhibitors furthermore attenuated TLR-induced expression of IL-6, IL-8 and COX2. COX1/2 inhibitors attenuated TLR2/6-induced IL-6 transcription and protein production comparable to cPLA2α inhibition. Moreover, exogenously PGE₂ added alone induced IL-6 production and completely rescued IL-6 transcription when added simultaneously with FSL-1 in the presence of a cPLA2α inhibitor. Our results demonstrate for the first time that cPLA2α is involved in TLR2/1- and TLR2/6-induced AA release, PGE₂ production and pro-inflammatory cytokine expression in synoviocytes, possibly through COX/PGE₂-dependent pathways. These findings expand our understanding of cPLA2α as a modulator of inflammatory molecular mechanisms in chronic diseases such as RA.

Inhibition of group IVA cytosolic phospholipase A2 by thiazolyl ketones in vitro, ex vivo, and in vivo

Group IVA cytosolic phospholipase A2 (GIVA cPLA2) is the rate-limiting provider of pro-inflammatory mediators in many tissues and is thus an attractive target for the development of novel anti-inflammatory agents. In this work, we present the synthesis of new thiazolyl ketones and the study of their activities in vitro, in cells, and in vivo. Within this series of compounds, methyl 2-(2-(4-octylphenoxy)acetyl)thiazole-4-carboxylate (GK470) was found to be the most potent inhibitor of GIVA cPLA2, exhibiting an XI(50) value of 0.011 mole fraction in a mixed micelle assay and an IC50 of 300 nM in a vesicle assay. In a cellular assay using SW982 fibroblast-like synoviocytes, it suppressed the release of arachidonic acid with an IC50 value of 0.6 μM. In a prophylactic collagen-induced arthritis model, it exhibited an anti-inflammatory effect comparable to the reference drug methotrexate, whereas in a therapeutic model, it showed results comparable to those of the reference drug Enbrel. In both models, it significantly reduced plasma PGE2 levels.

The eye: a window of opportunity in rheumatoid arthritis?

Rheumatoid arthritis (RA), the most common autoimmune disorder associated with dry eye syndrome, is also associated with sight-threatening ocular diseases such as peripheral ulcerative keratitis, scleritis and corneal melts. Tissue damage on the ocular surface of patients with RA is autoimmune-mediated. Findings from patients with dry eye have implicated defects in innate immunity (Toll-like receptors, S100A and resident antigen-presenting cells), cytokines, chemokines and T helper (TH)-cell subsets (including TH1 and TH17) in disease pathogenesis. Some of these features are probably important in dry eye related to RA, which can occur at a different time from articular disease and is more clinically severe than idiopathic dry eye. Ocular surface immune factors can be influenced by the systemic immune landscape. Depending on the severity of ocular inflammation in RA, treatment can include ciclosporin, topical corticosteroids, tacrolimus, autologous serum and systemic immunosuppression. Tissue damage is treated by inhibiting matrix metalloproteinases. Potential therapeutic strategies benefit from an improved understanding of ocular surface immunology, and include targeting of T-cell subsets, B-cell signalling or cytokines.