Urinary prostanoids are elevated by anti-TNF and anti-IL6 receptor disease-modifying antirheumatic drugs but are not predictive of response to treatment in early rheumatoid arthritis

BACKGROUND

Disease-modifying antirheumatic drugs (DMARDs) are widely used for treating rheumatoid arthritis (RA). However, there are no established biomarkers to predict a patient's response to these therapies. Prostanoids, encompassing prostaglandins, prostacyclins, and thromboxanes, are potent lipid mediators implicated in RA progression. Nevertheless, the influence of DMARDs on prostanoid biosynthesis in RA patients remains poorly understood. This study aims to assess the impact of various DMARDs on urinary prostanoids levels and to explore whether urinary prostanoid profiles correlate with disease activity or response to therapy.

METHODS

This study included 152 Swedish female patients with early RA, all rheumatoid factor (RF) positive, enrolled in the NORD-STAR trial (registration number: NCT01491815). Participants were randomized into four therapeutic regimes: methotrexate (MTX) combined with (i) prednisolone (arm ACT), (ii) TNF-α blocker certolizumab pegol (arm CZP), (iii) CTLA-4Ig abatacept (arm ABA), or (iv) IL-6R blocker tocilizumab (arm TCZ). Urine samples, collected before start of treatment and at 24 weeks post-treatment, were analyzed for tetranor-prostaglandin E metabolite (tPGEM), tetranor-prostaglandin D metabolite (tPGDM), 2,3-dinor thromboxane B2 (TXBM), 2,3-dinor-6-keto prostaglandin F1a (PGIM), leukotriene E4 (LTE4) and 12-hydroxyeicosatetraenoic acid (12-HETE) using liquid chromatography-mass spectrometry (LC-MS). Generalized estimating equation (GEE) models were used to analyze the change in urinary eicosanoids and their correlations to clinical outcomes.

RESULTS

Patients receiving MTX combined with CZP or TCZ exhibited significant elevations in urinary tPGEM and TXBM levels after 24 weeks of treatment. Other eicosanoids did not show significant alterations in response to any treatment. Baseline urinary eicosanoid levels did not correlate with baseline clinical disease activity index (CDAI) levels, nor with changes in CDAI from baseline to week 24. Their levels were also similar between patients who achieved CDAI remission and those with active disease at week 24.

CONCLUSIONS

Treatment with anti-TNF or anti-IL6R agents in early RA patients leads to an increased systemic production of proinflammatory and prothrombotic prostanoids. However, urinary eicosanoid levels do not appear to be predictive of the response to DMARDs therapy.

In early rheumatoid arthritis, anticitrullinated peptide antibodies associate with low number of affected joints and rheumatoid factor associates with systemic inflammation

OBJECTIVES

To investigate how individual rheumatoid arthritis (RA) autoantibodies associate with individual signs and symptoms at the time of RA diagnosis.

METHODS

IgA, IgG, IgM rheumatoid factor (RF), antibodies against cyclic citrullinated peptide version 2 (anti-CCP2) and 16 individual antibodies against citrullinated protein (ACPA) reactivities were analysed centrally in baseline sera from 1600 patients with RA classified according to the 1987 American College of Rheumatology (ACR) criteria. These results were related to C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), number of swollen and tender joints (SJC and TJC), 28-joint disease activity scores (DAS28 and DAS28CRP), global disease activity evaluated by the patients and Health Assessment Questionnaire, all obtained at baseline.

RESULTS

Individually, all autoantibodies except immunoglobulin G (IgG) RF associated with low SJC and TJC and with high ESR. In IgM RF-negative patients, ACPA associated strictly with low number of swollen and tender joints. This association persisted in multiple regression and stratified analyses where IgM and IgA RF instead associated with inflammation expressed as ESR. Among subjects without any ACPA peptide reactivity, there was no association between RF isotypes and ESR. The effect of RF on ESR increased with the number of ACPA reactivities, especially for IgM RF. In patients fulfilling the 1987 ACR criteria without taking RF into account, associations between IgM RF and high ESR, as well as between ACPA and low joint counts, remained.

CONCLUSION

Whereas ACPA associate with low counts of affected joints in early RA, RF associates with elevated measures of systemic inflammation in an ACPA-dependent manner. This latter finding corroborates in vitro models of ACPA and RF in immune complex-induced inflammation. These phenotypic associations are independent of classification criteria.

The anti-inflammatory and vasoprotective properties of mPGES-1 inhibition offer promising therapeutic potential

INTRODUCTION

Prostaglandin E2 (PGE2) is produced by cyclooxygenases (COX-1/2) and the microsomal prostaglandin E synthase 1 (mPGES-1). PGE2 is pro-inflammatory in diseases such as rheumatoid arthritis, cardiovascular disorders, and cancer. While Nonsteroidal anti-inflammatory drugs (NSAIDs) targeting COX can effectively reduce inflammation, their use is limited by gastrointestinal and cardiovascular side effects resulting from the blockade of all prostanoids. To overcome this limitation, selective inhibition of mPGES-1 is being explored as an alternative therapeutic strategy to inhibit PGE2 production while sparing or even upregulating other prostaglandins. However, the exact timing and location of PGH2 conversion to PGD2, PGI2, TXB2 or PGF2α, and whether it hinders or supports the therapeutic effect of mPGES-1 inhibition, is not fully understood.

AREAS COVERED

The article briefly describes prostanoid history and metabolism with a strong focus on the vascular effects of prostanoids. Recent advances in mPGES-1 inhibitor development and results from pre-clinical and clinical studies are presented. Prostanoid shunting after mPGES-1 inhibition is highlighted and particularly discussed in the context of cardiovascular diseases.

EXPERT OPINION

The newest research demonstrates that inhibition of mPGES-1 is a potent anti-inflammatory treatment strategy and beneficial and safer regarding cardiovascular side effects compared to NSAIDs. Inhibitors of mPGES-1 hold great potential to advance to the clinic and there are ongoing phase-II trials in endometriosis.

Microsomal prostaglandin E synthase-1 inhibition promotes shunting in arachidonic acid metabolism during inflammatory responses in vitro

Microsomal Prostaglandin E Synthase 1 (mPGES-1) is the key enzyme for the generation of the pro-inflammatory lipid mediator prostaglandin E₂ (PGE₂), which contributes to several pathological features of many diseases. Inhibition of mPGES-1 has been shown to be a safe and effective therapeutic strategy in various pre-clinical studies. In addition to reduced PGE₂ formation, it is also suggested that the potential shunting into other protective and pro-resolving prostanoids may play an important role in resolution of inflammation. In the present study, we analysed the eicosanoid profiles in four in vitro inflammation models and compared the effects of mPGES-1 inhibition with those of cyclooxygenase-2 (Cox-2) inhibition. Our results showed a marked shift to the PGD₂ pathway under mPGES-1 inhibition in A549 cells, RAW264.7 cells and mouse bone marrow-derived macrophages (BMDMs), whereas enhanced prostacyclin production was observed in rheumatoid arthritis synovial fibroblasts (RASFs) treated with an mPGES-1 inhibitor. As expected, Cox-2 inhibition completely suppressed all prostanoids. This study suggests that the therapeutic effects of mPGES-1 inhibition may be mediated by modulation of other prostanoids in addition to PGE₂ reduction.

Microsomal prostaglandin E synthase-1 inhibition prevents adverse cardiac remodelling after myocardial infarction in mice

BACKGROUND AND PURPOSE

Heart failure with reduced ejection fraction (HFrEF) is a major consequence of myocardial infarction (MI). The microsomal prostaglandin E synthase-1 (mPGES-1)/PGE₂ pathway has been shown to constrain reperfusion injury after acute myocardial ischaemia. However, it is unknown whether pharmacological inhibition of mPGES-1, a target with lower risk of thrombosis compared with selective inhibition of cyclooxygenase-2, affects chronic cardiac remodelling after MI.

EXPERIMENTAL APPROACH

Mice were subjected to left anterior descending coronary artery ligation, followed by intraperitoneal treatment with the mPGES-1 inhibitor compound III (CIII) or 118, celecoxib (cyclooxygenase-2 inhibitor) or vehicle, once daily for 28 days. Urinary prostanoid metabolites were measured by liquid chromatography-tandem mass spectrometry.

KEY RESULTS

Chronic administration of CIII improved cardiac function in mice after MI compared with vehicle or celecoxib. CIII did not affect thrombogenesis or blood pressure. In addition, CIII reduced infarct area, augmented scar thickness, decreased collagen I/III ratio, decreased the expression of fibrosis-related genes and increased capillary density in the ischaemic area. Shunting to urinary metabolites of PGI₂ , not thromboxane B₂ or PGD₂ , after inhibition of mPGES-1 was positively correlated with cardiac function after MI. CIII administration significantly increased urinary PGI₂ /PGE₂ metabolite ratio compared to vehicle or celecoxib. The PGI₂ /PGE₂ metabolite ratio correlated positively with ejection fraction, fractional shortening and scar thickness. Treatment with 118 also improved cardiac function.

CONCLUSION AND IMPLICATIONS

Inhibition of mPGES-1 prevented chronic adverse cardiac remodelling via an augmented PGI₂ /PGE₂ metabolite ratio and therefore represents a potential therapeutic strategy for development of HFrEF after MI.

Autoantigenic properties of the aminoacyl tRNA synthetase family in idiopathic inflammatory myopathies

OBJECTIVES

Autoantibodies are thought to play a key role in the pathogenesis of idiopathic inflammatory myopathies (IIM). However, up to 40% of IIM patients, even those with clinical manifestations of anti-synthetase syndrome (ASSD), test seronegative to known myositis-specific autoantibodies. We hypothesized the existence of new potential autoantigens among human cytoplasmic aminoacyl tRNA synthetases (aaRS) in patients with IIM.

METHODS

Plasma samples from 217 patients with IIM according to 2017 EULAR/ACR criteria, including 50 patients with ASSD, 165 without, and two with unknown ASSD status were identified retrospectively, as well as age and gender-matched sera from 156 population controls, and 219 disease controls. Patients with previously documented ASSD had to test positive for at least one of the five most common anti-aaRS autoantibodies (anti-Jo1, -PL7, -PL12, -EJ, and -OJ) and present with one or more of the following clinical manifestations: interstitial lung disease, myositis, arthritis, Raynaud's phenomenon, fever, or mechanic's hands. Demographics, laboratory, and clinical data of the IIM cohort (ASSD and non-ASSD) were compared. Samples were screened using a multiplex bead array assay for presence of autoantibodies against a panel of 117 recombinant protein variants, representing 33 myositis-related proteins, including all nineteen cytoplasmic aaRS. Prospectively collected clinical data for the IIM cohort were retrieved and compared between groups within the IIM cohort and correlated with the results of the autoantibody screening. Principal component analysis was used to analyze clinical manifestations between ASSD, non-ASSD groups, and individuals with novel anti-aaRS autoantibodies.

RESULTS

We identified reactivity towards 16 aaRS in 72 of the 217 IIM patients. Twelve patients displayed reactivity against nine novel aaRS. The novel autoantibody specificities were detected in four previously seronegative patients for myositis-specific autoantibodies and eight with previously detected myositis-specific autoantibodies. IIM individuals with novel anti-aaRS autoantibodies (n = 12) all had signs of myositis, and they had either muscle weakness and/or muscle enzyme elevation, 2/12 had mechanic's hands, 3/12 had interstitial lung disease, and 2/12 had arthritis. The individuals with novel anti-aaRS and a pathological muscle biopsy all presented widespread up-regulation of major histocompatibility complex class I. The reactivities against novel aaRS could be confirmed in ELISA and western blot. Using the multiplex bead array assay, we could confirm previously known reactivities to four of the most common aaRS (Jo1, PL12, PL7, and EJ (n = 45)) and identified patients positive for anti-Zo, -KS, and -HA (n = 10) that were not previously tested. A low frequency of anti-aaRS autoantibodies was also detected in controls.

CONCLUSION

Our results suggest that most, if not all, cytoplasmic aaRS may become autoantigenic. Autoantibodies against new aaRS may be found in plasma of patients previously classified as seronegative with potential high clinical relevance.

Autoantibodies targeting malondialdehyde-modifications in rheumatoid arthritis regulate osteoclasts via inducing glycolysis and lipid biosynthesis

Proteins subjected to post-translational modifications, such as citrullination, carbamylation, acetylation or malondialdehyde (MDA)-modification are targeted by autoantibodies in seropositive rheumatoid arthritis (RA). Epidemiological and experimental studies have both suggested the pathogenicity of such humoral autoimmunity, however, molecular mechanisms triggered by anti-modified protein antibodies have remained to be identified. Here we describe in detail the pathways induced by anti-MDA modified protein antibodies that were obtained from synovial B cells of RA patients and that possessed robust osteoclast stimulatory potential and induced bone erosion in vivo. Anti-MDA antibodies boosted glycolysis in developing osteoclasts via an FcγRI, HIF-1α and MYC-dependent mechanism and subsequently increased oxidative phosphorylation. Osteoclast development required robust phosphoglyceride and triacylglyceride biosynthesis, which was also enhanced by anti-MDA by modulating citrate production and expression of the glycerol-3-phosphate dehydrogenase 1 (GPD1) and glycerol-3-phosphate acyltransferase 2 (GPAT2) genes. In summary, we described novel metabolic pathways instrumental for osteoclast differentiation, which were targeted by anti-MDA antibodies, accelerating bone erosion, a central component of RA pathogenesis.

Biosynthesis of prostaglandin 15dPGJ2 -glutathione and 15dPGJ2-cysteine conjugates in macrophages and mast cells via MGST3

Inhibition of microsomal prostaglandin E synthase-1 (mPGES-1) results in decreased production of proinflammatory PGE₂ and can lead to shunting of PGH₂ into the prostaglandin D₂ (PGD₂)/15-deoxy-Δ^12,14-prostaglandin J₂ (15dPGJ₂) pathway. 15dPGJ₂ forms Michael adducts with thiol-containing biomolecules such as GSH or cysteine residues on target proteins and is thought to promote resolution of inflammation. We aimed to elucidate the biosynthesis and metabolism of 15dPGJ₂ via conjugation with GSH, to form 15dPGJ₂-glutathione (15dPGJ₂-GS) and 15dPGJ₂-cysteine (15dPGJ₂-Cys) conjugates and to characterize the effects of mPGES-1 inhibition on the PGD₂/15dPGJ₂ pathway in mouse and human immune cells. Our results demonstrate the formation of PGD₂, 15dPGJ₂, 15dPGJ₂-GS, and 15dPGJ₂-Cys in RAW264.7 cells after lipopolysaccharide stimulation. Moreover, 15dPGJ₂-Cys was found in lipopolysaccharide-activated primary murine macrophages as well as in human mast cells following stimulation of the IgE-receptor. Our results also suggest that the microsomal glutathione S-transferase 3 is essential for the formation of 15dPGJ₂ conjugates. In contrast to inhibition of cyclooxygenase, which leads to blockage of the PGD₂/15dPGJ₂ pathway, we found that inhibition of mPGES-1 preserves PGD₂ and its metabolites. Collectively, this study highlights the formation of 15dPGJ₂-GS and 15dPGJ₂-Cys in mouse and human immune cells, the involvement of microsomal glutathione S-transferase 3 in their biosynthesis, and their unchanged formation following inhibition of mPGES-1. The results encourage further research on their roles as bioactive lipid mediators.

Where traditional Chinese medicine meets Western medicine in the prevention of rheumatoid arthritis

Chinese medicine has a long tradition of use against rheumatoid arthritis (RA). The formulations are based on combinations of typically 5-10 plants, which are usually boiled and administered as a decoction or tea. There are few clinical trials performed so the clinical evidence is sparse. One fundamental of traditional medicine is to prevent disease. RA is an autoimmune, inflammatory and chronic disease that primarily affects the joints of 0.5%-1% of the population. In two out of three of the cases, the patients are characterised by the presence of autoantibodies such as the rheumatoid factor and the more disease-specific autoantibody against citrullinated proteins, so-called 'ACPA' (anticitrullinated protein/peptide antibodies). ACPA positivity is also strongly associated with specific variations in the HLA-DRB1 gene, the shared epitope alleles. Together with smoking, these factors account for the major risks of developing RA. In this review, we will summarise the background using certain plant-based formulations based on Chinese traditional medicine for the treatment and prevention of RA and the strategy we have taken to explore the mechanisms of action. We also summarise the major pathophysiological pathways related to RA and how these could be analysed. Finally, we summarise our ideas on how a clinical trial using Chinese herbal medicine to prevent RA could be conducted.

Helminthic dehydrogenase drives PGE2 and IL-10 production in monocytes to potentiate Treg induction

Immunoregulation of inflammatory, infection‐triggered processes in the brain constitutes a central mechanism to control devastating disease manifestations such as epilepsy. Observational studies implicate the viability of Taenia solium cysts as key factor determining severity of neurocysticercosis (NCC), the most common cause of epilepsy, especially in children, in Sub‐Saharan Africa. Viable, in contrast to decaying, cysts mostly remain clinically silent by yet unknown mechanisms, potentially involving Tregs in controlling inflammation. Here, we show that glutamate dehydrogenase from viable cysts instructs tolerogenic monocytes to release IL‐10 and the lipid mediator PGE₂. These act in concert, converting naive CD4⁺ T cells into CD127⁻CD25^hiFoxP3⁺CTLA‐4⁺ Tregs, through the G protein‐coupled receptors EP2 and EP4 and the IL‐10 receptor. Moreover, while viable cyst products strongly upregulate IL‐10 and PGE₂ transcription in microglia, intravesicular fluid, released during cyst decay, induces pro‐inflammatory microglia and TGF‐β as potential drivers of epilepsy. Inhibition of PGE₂ synthesis and IL‐10 signaling prevents Treg induction by viable cyst products. Harnessing the PGE₂‐IL‐10 axis and targeting TGF‐ß signaling may offer an important therapeutic strategy in inflammatory epilepsy and NCC.

Longitudinal assessment of reactivity and affinity profile of anti-Jo1 autoantibodies to distinct HisRS domains and a splice variant in a cohort of patients with myositis and anti-synthetase syndrome

Background

To address the reactivity and affinity against histidyl-transfer RNA synthetase (HisRS) autoantigen of anti-Jo1 autoantibodies from serum and bronchoalveolar lavage fluid (BALF) in patients with idiopathic inflammatory myopathies/anti-synthetase syndrome (IIM/ASSD). To investigate the associations between the reactivity profile and clinical data over time.

Methods

Samples and clinical data were obtained from (i) 25 anti-Jo1⁺ patients (19 sera with 16 longitudinal samples and 6 BALF/matching sera at diagnosis), (ii) 29 anti-Jo1⁻ patients (25 sera and 4 BALF/matching sera at diagnosis), and (iii) 27 age/gender-matched healthy controls (24 sera and 3 BALF/matching sera). Reactivity towards HisRS full-length (HisRS-FL), three HisRS domains (WHEP, antigen binding domain (ABD), and catalytic domain (CD)), and the HisRS splice variant (SV) was tested. Anti-Jo1 IgG reactivity was evaluated by ELISA and western blot using IgG purified from serum by affinity chromatography. In paired serum-BALF, anti-Jo1 IgG and IgA reactivity was analyzed by ELISA. Autoantibody affinity was measured by surface plasmon resonance using IgG purified from sera. Correlations between autoantibody reactivity and clinical data were evaluated at diagnosis and longitudinally.

Results

Anti-Jo1 IgG from serum and BALF bound HisRS-FL, WHEP, and SV with high reactivity at the time of diagnosis and recognized both conformation-dependent and conformation-independent HisRS epitopes. Anti-HisRS-FL IgG displayed high affinity early in the disease. At the time of IIM/ASSD diagnosis, the highest autoantibody levels against HisRS-FL were found in patients ever developing interstitial lung disease (ILD) and arthritis, but with less skin involvement. Moreover, the reactivity of anti-WHEP IgG in BALF correlated with poor pulmonary function.

Levels of autoantibodies against HisRS-FL, HisRS domains, and HisRS splice variant generally decreased over time. With some exceptions, longitudinal anti-HisRS-FL antibody levels changed in line with ILD activity.

Conclusion

High levels and high-affinity anti-Jo1 autoantibodies towards HisRS-FL were found early in disease in sera and BALF. In combination with the correlation of anti-HisRS-FL antibody levels with ILD and ILD activity in longitudinal samples as well as of anti-WHEP IgG in BALF with poor pulmonary function, this supports the previously raised hypothesis that the lung might have a role in the immune reaction in anti-Jo1-positive patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02745-6.

Formation, Signaling and Occurrence of Specialized Pro-Resolving Lipid Mediators-What is the Evidence so far?

Formation of specialized pro-resolving lipid mediators (SPMs) such as lipoxins or resolvins usually involves arachidonic acid 5-lipoxygenase (5-LO, ALOX5) and different types of arachidonic acid 12- and 15-lipoxygenating paralogues (15-LO1, ALOX15; 15-LO2, ALOX15B; 12-LO, ALOX12). Typically, SPMs are thought to be formed via consecutive steps of oxidation of polyenoic fatty acids such as arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid. One hallmark of SPM formation is that reported levels of these lipid mediators are much lower than typical pro-inflammatory mediators including the monohydroxylated fatty acid derivatives (e.g., 5-HETE), leukotrienes or certain cyclooxygenase-derived prostaglandins. Thus, reliable detection and quantification of these metabolites is challenging. This paper is aimed at critically evaluating i) the proposed biosynthetic pathways of SPM formation, ii) the current knowledge on SPM receptors and their signaling cascades and iii) the analytical methods used to quantify these pro-resolving mediators in the context of their instability and their low concentrations. Based on current literature it can be concluded that i) there is at most, a low biosynthetic capacity for SPMs in human leukocytes. ii) The identity and the signaling of the proposed G-protein-coupled SPM receptors have not been supported by studies in knock-out mice and remain to be validated. iii) In humans, SPM levels were neither related to dietary supplementation with their ω-3 polyunsaturated fatty acid precursors nor were they formed during the resolution phase of an evoked inflammatory response. iv) The reported low SPM levels cannot be reliably quantified by means of the most commonly reported methodology. Overall, these questions regarding formation, signaling and occurrence of SPMs challenge their role as endogenous mediators of the resolution of inflammation.

Omega-3 fatty acids decrease CRYAB, production of oncogenic prostaglandin E2 and suppress tumor growth in medulloblastoma

AIMS

Medulloblastoma (MB) is one of the most common malignant central nervous system tumors of childhood. Despite intensive treatments that often leads to severe neurological sequelae, the risk for resistant relapses remains significant. In this study we have evaluated the effects of the ω3-long chain polyunsaturated fatty acids (ω3-LCPUFA) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on MB cell lines and in a MB xenograft model.

MAIN METHODS

Effects of ω3-LCPUFA treatment of MB cells were assessed using the following: WST-1 assay, cell death probes, clonogenic assay, ELISA and western blot. MB cells were implanted into nude mice and the mice were randomized to DHA, or a combination of DHA and EPA treatment, or to control group. Treatment effects in tumor tissues were evaluated with: LC-MS/MS, RNA-sequencing and immunohistochemistry, and tumors, erythrocytes and brain tissues were analyzed with gas chromatography.

KEY FINDINGS

ω3-LCPUFA decreased prostaglandin E2 (PGE₂) secretion from MB cells, and impaired MB cell viability and colony forming ability and increased apoptosis in a dose-dependent manner. DHA reduced tumor growth in vivo, and both PGE₂ and prostacyclin were significantly decreased in tumor tissue from treated mice compared to control animals. All ω3-LCPUFA and dihomo-γ-linolenic acid increased in tumors from treated mice. RNA-sequencing revealed 10 downregulated genes in common among ω3-LCPUFA treated tumors. CRYAB was the most significantly altered gene and the downregulation was confirmed by immunohistochemistry.

SIGNIFICANCE

Our findings suggest that addition of DHA and EPA to the standard MB treatment regimen might be a novel approach to target inflammation in the tumor microenvironment.

Effects of microsomal prostaglandin E synthase-1 (mPGES-1) inhibition on resistance artery tone in patients with end stage kidney disease

BACKGROUND

Inhibition of the microsomal prostaglandin (PG) E₂ synthase (mPGES-1) introduces a promising anti-inflammatory treatment approach by specifically reducing PGE₂ . The microvasculature is a central target organ for early manifestations of cardiovascular disease. Therefore, a better understanding of the prostaglandin system and characterising the effects of mPGES-1 inhibition in this vascular bed are of interest.

EXPERIMENTAL APPROACH

The effects of mPGES-1 inhibition on constriction and relaxation of resistance arteries (Ø100-400μm) from patients with end stage kidney disease (ESKD) and controls (Non-ESKD) were studied using wire-myography in combination with immunological and mass-spectrometry based analyses.

KEY RESULTS

Inhibition of mPGES-1 in arteries from ESKD patients and Non-ESKD controls significantly reduced adrenergic vasoconstriction, which was not affected by the COX-2 inhibitors NS-398 and Etoricoxib or the COX-1/COX-2 inhibitor Indomethacin, tested in Non-ESKD controls. Correspondingly, a significant increase of acetylcholine-induced dilatation was observed for mPGES-1 inhibition only. In IL-1β treated arteries, inhibition of mPGES-1 significantly reduced PGE₂ levels while PGI₂ levels remained unchanged. In contrast, COX-2 inhibition blocked the formation of both prostaglandins. Blockage of PGI₂ signaling with an IP receptor antagonist did not restore the reduced constriction, neither did blocking of PGE₂ -EP4 or signaling through PPARγ. A biphasic effect was observed for PGE₂ , inducing dilatation at nmol and constriction at μmol concentrations. Immunohistochemistry demonstrated expression of mPGES-1, COX-1, PGIS, weak expression for COX-2 as well as receptor expression for PGE₂ (EP1-4), thromboxane (TP) and PGI₂ (IP) in ESKD and Non-ESKD.

CONCLUSION

Our study demonstrates vasodilating effects following mPGES-1 inhibition in human microvasculature and suggests that several pathways besides shunting to PGI₂ may be involved.

An anti-inflammatory eicosanoid switch mediates the suppression of type-2 inflammation by helminth larval products

Eicosanoids are key mediators of type-2 inflammation, e.g., in allergy and asthma. Helminth products have been suggested as remedies against inflammatory diseases, but their effects on eicosanoids are unknown. Here, we show that larval products of the helminth Heligmosomoides polygyrus bakeri (HpbE), known to modulate type-2 responses, trigger a broad anti-inflammatory eicosanoid shift by suppressing the 5-lipoxygenase pathway, but inducing the cyclooxygenase (COX) pathway. In human macrophages and granulocytes, the HpbE-driven induction of the COX pathway resulted in the production of anti-inflammatory mediators [e.g., prostaglandin E₂ (PGE₂) and IL-10] and suppressed chemotaxis. HpbE also abrogated the chemotaxis of granulocytes from patients suffering from aspirin-exacerbated respiratory disease (AERD), a severe type-2 inflammatory condition. Intranasal treatment with HpbE extract attenuated allergic airway inflammation in mice, and intranasal transfer of HpbE-conditioned macrophages led to reduced airway eosinophilia in a COX/PGE₂-dependent fashion. The induction of regulatory mediators in macrophages depended on p38 mitogen-activated protein kinase (MAPK), hypoxia-inducible factor-1α (HIF-1α), and Hpb glutamate dehydrogenase (GDH), which we identify as a major immunoregulatory protein in HpbE Hpb GDH activity was required for anti-inflammatory effects of HpbE in macrophages, and local administration of recombinant Hpb GDH to the airways abrogated allergic airway inflammation in mice. Thus, a metabolic enzyme present in helminth larvae can suppress type-2 inflammation by inducing an anti-inflammatory eicosanoid switch, which has important implications for the therapy of allergy and asthma.

Serum-circulating His-tRNA synthetase inhibits organ-targeted immune responses

His-tRNA synthetase (HARS) is targeted by autoantibodies in chronic and acute inflammatory anti-Jo-1-positive antisynthetase syndrome. The extensive activation and migration of immune cells into lung and muscle are associated with interstitial lung disease, myositis, and morbidity. It is unknown whether the sequestration of HARS is an epiphenomenon or plays a causal role in the disease. Here, we show that HARS circulates in healthy individuals, but it is largely undetectable in the serum of anti-Jo-1-positive antisynthetase syndrome patients. In cultured primary human skeletal muscle myoblasts (HSkMC), HARS is released in increasing amounts during their differentiation into myotubes. We further show that HARS regulates immune cell engagement and inhibits CD4+ and CD8+ T-cell activation. In mouse and rodent models of acute inflammatory diseases, HARS administration downregulates immune activation. In contrast, neutralization of extracellular HARS by high-titer antibody responses during tissue injury increases susceptibility to immune attack, similar to what is seen in humans with anti-Jo-1-positive disease. Collectively, these data suggest that extracellular HARS is homeostatic in normal subjects, and its sequestration contributes to the morbidity of the anti-Jo-1-positive antisynthetase syndrome.

Identifying novel B-cell targets for chronic inflammatory autoimmune disease by screening of chemical probes in a patient-derived cell assay

B-cell secretion of autoantibodies drives autoimmune diseases, including systemic lupus erythematosus and idiopathic inflammatory myositis. Few therapies are presently available for treatment of these patients, often resulting in unsatisfactory effects and helping only some of the patients. We developed a screening assay for evaluation of novel targets suspending B-cell maturation into antibody secreting cells, which could contribute to future drug development. The assay was employed for testing 43 high quality chemical probes and compounds inhibiting under-explored protein targets, using primary cells from patients with autoimmune disease. Probes inhibiting bromodomain family proteins and histone methyl transferases demonstrated abrogation of B-cell functions to a degree comparable to a positive control, the JAK inhibitor tofacitinib. Inhibition of each target rendered a specific functional cell and potential disease modifying effect, indicating specific epigenetic protein targets as potential new intervention points for future drug discovery and development efforts.

Inhibition of mPGES-1 attenuates efficient resolution of acute inflammation by enhancing CX3CL1 expression

Despite the progress to understand inflammatory reactions, mechanisms causing their resolution remain poorly understood. Prostanoids, especially prostaglandin E2 (PGE2), are well-characterized mediators of inflammation. PGE2 is produced in an inducible manner in macrophages (Mϕ) by microsomal PGE2-synthase-1 (mPGES-1), with the notion that it also conveys pro-resolving properties. We aimed to characterize the role of mPGES-1 during resolution of acute, zymosan-induced peritonitis. Experimentally, we applied the mPGES-1 inhibitor compound III (CIII) once the inflammatory response was established and confirmed its potent PGE2-blocking efficacy. mPGES-1 inhibition resulted in an incomplete removal of neutrophils and a concomitant increase in monocytes and Mϕ during the resolution process. The mRNA-seq analysis identified enhanced C-X3-C motif receptor 1 (CX3CR1) expression in resident and infiltrating Mϕ upon mPGES-1 inhibition. Besides elevated Cx3cr1 expression, its ligand CX3CL1 was enriched in the peritoneal lavage of the mice, produced by epithelial cells upon mPGES-1 inhibition. CX3CL1 not only increased adhesion and survival of Mϕ but its neutralization also completely reversed elevated inflammatory cell numbers, thereby normalizing the cellular, peritoneal composition during resolution. Our data suggest that mPGES-1-derived PGE2 contributes to the resolution of inflammation by preventing CX3CL1-mediated retention of activated myeloid cells at sites of injury.

Phosphodiesterase 4A confers resistance to PGE2-mediated suppression in CD25+ /CD54+ NK cells

Inadequate persistence of tumor‐infiltrating natural killer (NK) cells is associated with poor prognosis in cancer patients. The solid tumor microenvironment is characterized by the presence of immunosuppressive factors, including prostaglandin E2 (PGE2), that limit NK cell persistence. Here, we investigate if the modulation of the cytokine environment in lung cancer with IL‐2 or IL‐15 renders NK cells resistant to suppression by PGE2. Analyzing Cancer Genome Atlas (TCGA) data, we found that high NK cell gene signatures correlate with significantly improved overall survival in patients with high levels of the prostaglandin E synthase (PTGES). In vitro, IL‐15, in contrast to IL‐2, enriches for CD25⁺/CD54⁺ NK cells with superior mTOR activity and increased expression of the cAMP hydrolyzing enzyme phosphodiesterase 4A (PDE4A). Consequently, this distinct population of NK cells maintains their function in the presence of PGE2 and shows an increased ability to infiltrate lung adenocarcinoma tumors in vitro and in vivo. Thus, strategies to enrich CD25⁺/CD54⁺ NK cells for adoptive cell therapy should be considered.

Extracellular miR-574-5p Induces Osteoclast Differentiation via TLR 7/8 in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and joint destruction. Cell-derived small extracellular vesicles (sEV) mediate cell-to-cell communication in the synovial microenvironment by carrying microRNAs (miRs), a class of small non-coding RNAs. Herein, we report that sEV from synovial fluid promote osteoclast differentiation which is attributed to high levels of extracellular miR-574-5p. Moreover, we demonstrate for the first time that enhanced osteoclast maturation is mediated by Toll-like receptor (TLR) 7/8 signaling which is activated by miR-574-5p binding. This is a novel mechanism by which sEV and miRs contribute to RA pathogenesis and indicate that pharmacological inhibition of extracellular miR-574-5p might offer new therapeutic strategies to protect osteoclast-mediated bone destruction in RA.

Chinese Herbal Formula Huayu-Qiangshen-Tongbi Decoction Compared With Leflunomide in Combination With Methotrexate in Patients With Active Rheumatoid Arthritis: An Open-Label, Randomized, Controlled, Pilot Study

Background: Traditional Chinese Medicine is complementary and an alternative to modern medicine. The combination therapies of herbal products with disease-modifying anti-rheumatic drugs are gradually and widely adopted in the management of rheumatoid arthritis (RA) in China. Purpose: To evaluate the efficacy and safety of Huayu-Qiangshen-Tongbi (HQT) decoction, a Chinese medicine formula, combined with methotrexate (MTX) in the treatment of patients with active RA, in comparison with the combination therapy of MTX with leflunomide (LEF). Methods: This pilot study was a monocenter, open-label, randomized controlled trial with two parallel arms. Ninety patients with active RA were randomly allocated to receive either HQT at a dose of 250 ml twice daily or LEF at a dose of 20 mg once daily, and all participants received MTX at a dose of 10-15 mg once weekly. The primary efficacy endpoint was the proportion of patients who achieved a 20% improvement in the American College of Rheumatology criteria (ACR20) after a 24-week treatment. Results: 84.4% (76/90) patients completed the 24-week observation. In the intention-to-treat analysis, the percentage values of patients achieving the ACR20 response criteria were 72.1% (31/43) in MTX + HQT group and 74.4% (32/43) in MTX + LEF group (p = 0.808). No significant difference was observed in other parameters, including ACR50, ACR70, clinical disease activity index good responses, European League Against Rheumatism good response, remission rate, and low disease activity rate. The results of the per-protocol analysis showed consistency with those of the intention-to-treat analysis. The mean change from baseline at week 24 for the van der Heijde modified total sharp score had no significant difference between two groups (3.59 ± 4.75 and 1.34 ± 8.67 in the MTX + HQT group and MTX + LEF group, respectively, p = 0.613). The frequency of adverse events was similar in both groups (11 cases in the MTX + HQT and 17 cases in the MTX + LEF, p > 0.05). Conclusions: In patients with active RA, treatment with the combination of HQT and MTX was associated with improvement in signs, symptoms, and physical function. With a beneficial clinical response and acceptable tolerability, HQT or other Chinese medicine formula may be a good therapeutic option in combination with MTX for RA treatment. Trial registration: Chinese Clinical Trails Registry, ChiCTR-INR-16009031, Registered on 15th August 2016, http://www.chictr.org.cn/enindex.aspx.

Mechanistic definition of the cardiovascular mPGES-1/COX-2/ADMA axis

AIMS

Cardiovascular side effects caused by non-steroidal anti-inflammatory drugs (NSAIDs), which all inhibit cyclooxygenase (COX)-2, have prevented development of new drugs that target prostaglandins to treat inflammation and cancer. Microsomal prostaglandin E synthase-1 (mPGES-1) inhibitors have efficacy in the NSAID arena but their cardiovascular safety is not known. Our previous work identified asymmetric dimethylarginine (ADMA), an inhibitor of endothelial nitric oxide synthase, as a potential biomarker of cardiovascular toxicity associated with blockade of COX-2. Here, we have used pharmacological tools and genetically modified mice to delineate mPGES-1 and COX-2 in the regulation of ADMA.

METHODS AND RESULTS

Inhibition of COX-2 but not mPGES-1 deletion resulted in increased plasma ADMA levels. mPGES-1 deletion but not COX-2 inhibition resulted in increased plasma prostacyclin levels. These differences were explained by distinct compartmentalization of COX-2 and mPGES-1 in the kidney. Data from prostanoid synthase/receptor knockout mice showed that the COX-2/ADMA axis is controlled by prostacyclin receptors (IP and PPARβ/δ) and the inhibitory PGE2 receptor EP4, but not other PGE2 receptors.

CONCLUSION

These data demonstrate that inhibition of mPGES-1 spares the renal COX-2/ADMA pathway and define mechanistically how COX-2 regulates ADMA.

Anti-Citrullinated Protein Antibody Specificities, Rheumatoid Factor Isotypes, and Incident Cardiovascular Events in Patients With Rheumatoid Arthritis

OBJECTIVE

To investigate the relationship between anti-citrullinated protein antibodies (ACPAs), specific ACPA subspecificities, rheumatoid factor (RF) isotypes, and incident cardiovascular (CV) events in patients with rheumatoid arthritis (RA).

METHODS

Serum samples from Swedish patients with new-onset RA (diagnosed within 1 year of symptom onset between 1996 and 2009) were centrally typed for anti-cyclic citrullinated peptide 2 (anti-CCP2) antibodies, 20 ACPA subspecificities, and RF isotypes. Patients were followed up longitudinally in nationwide registers to monitor the occurrence of acute coronary syndrome (ACS), stroke, CV-related death, and major adverse CV events (MACE). The association between each serologic marker and CV outcome, and the impact of adjustment for the Disease Activity Score in 28 joints (DAS28), smoking status, and income at baseline, were assessed using Cox proportional hazards models. In addition, associations of serologic markers with all-cause mortality were explored.

RESULTS

In total, 2,814 patients with RA were included in the study. The median follow-up was 13 years, during which the CV end points of ACS, stroke, or CV-related death were reported to occur in 375 patients. Occurrence and/or levels of anti-CCP2 were associated with risk of incident ACS (hazard ratio [HR] 1.46, 95% confidence interval [95% CI] 1.03-2.06), stroke (HR 1.47, 95% CI 1.03-2.10), CV-related death (P = 0.024 for association with anti-CCP2 levels), and MACE (HR 1.34, 95% CI 1.06-1.70). Similarly, an association with the number of ACPA subspecificities was observed; however, this could not be attributed to any individual or group of ACPA subspecificities. Presence of IgM-RF was associated with all CV end points except ACS, and IgA-RF was exclusively associated with CV-related death. Adjustment for smoking status, income, and DAS28 scores decreased most of the HRs, whereas IgA-RF remained associated with CV-related death (HR 1.61, 95% CI 1.05-2.48). All of the assessed serologic makers were associated with all-cause mortality.

CONCLUSION

RF isotypes and ACPAs are associated with future CV events in patients with RA. ACPA levels and number of subspecificities seem more important than the occurrence of particular subspecificities, and these associations were not explained by a history of ever smoking.

Generation and validation of recombinant antibodies to study human aminoacyl-tRNA synthetases

Aminoacyl-tRNA synthetases (aaRSs) have long been viewed as mere housekeeping proteins and have therefore often been overlooked in drug discovery. However, recent findings have revealed that many aaRSs have noncanonical functions, and several of the aaRSs have been linked to autoimmune diseases, cancer, and neurological disorders. Deciphering these roles has been challenging because of a lack of tools to enable their study. To help solve this problem, we have generated recombinant high-affinity antibodies for a collection of thirteen cytoplasmic and one mitochondrial aaRSs. Selected domains of these proteins were produced recombinantly in Escherichia coli and used as antigens in phage display selections using a synthetic human single-chain fragment variable library. All targets yielded large sets of antibody candidates that were validated through a panel of binding assays against the purified antigen. Furthermore, the top-performing binders were tested in immunoprecipitation followed by MS for their ability to capture the endogenous protein from mammalian cell lysates. For antibodies targeting individual members of the multi-tRNA synthetase complex, we were able to detect all members of the complex, co-immunoprecipitating with the target, in several cell types. The functionality of a subset of binders for each target was also confirmed using immunofluorescence. The sequences of these proteins have been deposited in publicly available databases and repositories. We anticipate that this open source resource, in the form of high-quality recombinant proteins and antibodies, will accelerate and empower future research of the role of aaRSs in health and disease.

Descriptive Proteome Analysis to Investigate Context-Dependent Treatment Responses to OXPHOS Inhibition in Colon Carcinoma Cells Grown as Monolayer and Multicellular Tumor Spheroids

We have previously identified selective upregulation of the mevalonate pathway genes upon inhibition of oxidative phosphorylation (OXPHOS) in quiescent cancer cells. Using mass spectrometry-based proteomics, we here investigated whether these responses are corroborated on the protein level and whether proteomics could yield unique insights into context-dependent biology. HCT116 colon carcinoma cells were cultured as monolayer cultures, proliferative multicellular tumor spheroids (P-MCTS), or quiescent (Q-MCTS) multicellular tumor spheroids and exposed to OXPHOS inhibitors: nitazoxanide, FCCP, oligomycin, and salinomycin or the HMG-CoA-reductase inhibitor simvastatin at two different doses for 6 and 24 h. Samples were processed using an in-depth bottom-up proteomics workflow resulting in a total of 9286 identified protein groups. Gene set enrichment analysis showed profound differences between the three cell systems and confirmed differential enrichment of hypoxia, OXPHOS, and cell cycle progression-related protein responses in P-MCTS and Q-MCTS. Treatment experiments showed that the observed drug-induced alterations in gene expression of metabolically challenged cells are not translated directly to the protein level, but the results reaffirmed OXPHOS as a selective vulnerability of quiescent cancer cells. This work provides rationale for the use of deep proteome profiling to identify context-dependent treatment responses and encourages further studies investigating metabolic processes that could be co-targeted together with OXPHOS to eradicate quiescent cancer cells.

Presence of autoantibodies in "seronegative" rheumatoid arthritis associates with classical risk factors and high disease activity

Background

Rheumatoid arthritis (RA) is classified as seropositive or seronegative, depending on the presence/absence of rheumatoid factor (RF), primarily IgM RF, and/or anti-citrullinated protein antibodies (ACPA), commonly detected using anti-cyclic citrullinated peptide (CCP) assays. Known risk factors associate with the more severe seropositive form of RA; less is known about seronegative RA. Here, we examine risk factors and clinical phenotypes in relation to presence of autoantibodies in the RA subset that is traditionally defined as seronegative.

Methods

Anti-CCP2 IgG, 19 ACPA fine-specificities, IgM/IgG/IgA RF, anti-carbamylated-protein (CarP) antibodies, and 17 other autoantibodies, were analysed in 2755 RA patients and 370 controls. Antibody prevalence, levels, and co-occurrence were examined, and associations with risk factors and disease activity during 5 years were investigated for different antibody-defined RA subsets.

Results

Autoantibodies were detected in a substantial proportion of the traditionally defined seronegative RA subset, with ACPA fine-specificities found in 30%, IgA/IgG RF in 9.4%, and anti-CarP antibodies in 16%, with a 9.6% co-occurrence of at least two types of RA-associated autoantibodies. HLA-DRB1 shared epitope (SE) associated with the presence of ACPA in anti-CCP2-negative RA; in anti-CCP2-positive RA, the SE association was defined by six ACPA fine-specificities with high co-occurrence. Smoking associated with RF, but not with ACPA, in anti-CCP2-negative RA. Presence of ACPA and RF, but not anti-CarP antibodies, in conventionally defined “seronegative” RA, associated with worse clinical outcome.

Conclusions

“Seronegative” RA is not truly a seronegative disease subset. Additional screening for ACPA fine-specificities and IgA/IgG RF defines a group of patients that resembles seropositive patients with respect to risk factors and clinical picture and may contribute to earlier diagnosis for a subset of anti-CCP2−/IgM RF− patients with a high need for active treatment.

Establishment of an in vitro 3D model for neuroblastoma enables preclinical investigation of combined tumor-stroma drug targeting

The majority of anti-cancer therapies target the proliferating tumor cells, while the tumor stroma, principally unaffected, survives, and provide a niche for surviving tumor cells. Combining tumor cell and stroma-targeting therapies thus have a potential to improve patient outcome. The neuroblastoma stroma contains cancer-associated fibroblasts expressing microsomal prostaglandin E synthase-1 (mPGES-1). mPGES-1-derived prostaglandin E₂ (PGE₂ ) is known to promote tumor growth through increased proliferation and survival of tumor cells, immune suppression, angiogenesis, and therapy resistance, and we, therefore, hypothesize that mPGES-1 constitutes an interesting stromal target. Here, we aimed to develop a relevant in vitro model to study combination therapies. Co-culturing of neuroblastoma and fibroblast cells in 3D tumor spheroids mimic neuroblastoma tumors with regard to the cyclooxygenase/mPGES-1/PGE₂ pathway. Using the spheroid model, we show that the inhibition of fibroblast-derived mPGES-1 enhanced the cytotoxic effect of doxorubicin and vincristine and significantly reduced tumor cell viability and spheroid growth. Cyclic treatment with vincristine in combination with an mPGES-1 inhibitor abrogated cell repopulation. Moreover, inhibition of mPGES-1 potentiated the cytotoxic effect of vincristine on established neuroblastoma allografts in mice. In conclusion, we established a 3D neuroblastoma model, highlighting the potential of combining stromal targeting of mPGES-1 with tumor cell targeting drugs like vincristine.

Anti-Inflammatory Properties of Chemical Probes in Human Whole Blood: Focus on Prostaglandin E2 Production

We screened 57 chemical probes, high-quality tool compounds, and relevant clinically used drugs to investigate their effect on pro-inflammatory prostaglandin E2 (PGE2) production and interleukin-8 (IL-8) secretion in human whole blood. Freshly drawn blood from healthy volunteers and patients with systemic lupus erythematosus (SLE) or dermatomyositis was incubated with compounds at 0.1 or 1 µM and treated with lipopolysaccharide (LPS, 10 µg/ml) to induce a pro-inflammatory condition. Plasma was collected after 24 h for lipid profiling using liquid chromatography tandem mass spectrometry (LC-MS/MS) and IL-8 quantification using enzyme-linked immunosorbent assay (ELISA). Each compound was tested in at least four donors at one concentration based on prior knowledge of binding affinities and in vitro activity. Our screening suggested that PD0325901 (MEK-1/2 inhibitor), trametinib (MEK-1/2 inhibitor), and selumetinib (MEK-1 inhibitor) decreased while tofacitinib (JAK inhibitor) increased PGE2 production. These findings were validated by concentration-response experiment in two donors. Moreover, the tested MEK inhibitors decreased thromboxane B2 (TXB2) production and IL-8 secretion. We also investigated the lysophophatidylcholine (LPC) profile in plasma from treated whole blood as these lipids are potentially important mediators in inflammation, and we did not observe any changes in LPC profiles. Collectively, we deployed a semi-high throughput and robust methodology to investigate anti-inflammatory properties of new chemical probes.

Proteomics-Based Characterization of miR-574-5p Decoy to CUGBP1 Suggests Specificity for mPGES-1 Regulation in Human Lung Cancer Cells

MicroRNAs (miRs) are one of the most important post-transcriptional repressors of gene expression. However, miR-574-5p has recently been shown to positively regulate the expression of microsomal prostaglandin E-synthase-1 (mPGES-1), a key enzyme in the prostaglandin E₂ (PGE₂) biosynthesis, by acting as decoy to the RNA-binding protein CUG-RNA binding protein 1 (CUGBP1) in human lung cancer. miR-574-5p exhibits oncogenic properties and promotes lung tumor growth in vivo via induction of mPGES-1-derived PGE₂ synthesis. In a mass spectrometry-based proteomics study, we now attempted to characterize this decoy mechanism in A549 lung cancer cells at a cellular level. Besides the identification of novel CUGBP1 targets, we identified that the interaction between miR-574-5p and CUGBP1 specifically regulates mPGES-1 expression. This is supported by the fact that CUGBP1 and miR-574-5p are located in the nucleus, where CUGBP1 regulates alternative splicing. Further, in a bioinformatical approach we showed that the decoy-dependent mPGES-1 splicing pattern is unique. The specificity of miR-574-5p/CUGBP1 regulation on mPGES-1 expression supports the therapeutic strategy of pharmacological inhibition of PGE₂ formation, which may provide significant therapeutic value for NSCLC patients with high miR-574-5p levels.

sRNA scr5239 Involved in Feedback Loop Regulation of Streptomyces coelicolor Central Metabolism

In contrast to transcriptional regulation, post-transcriptional regulation and the role of small non-coding RNAs (sRNAs) in streptomycetes are not well studied. Here, we focus on the highly conserved sRNA scr5239 in Streptomyces coelicolor. A proteomics approach revealed that the sRNA regulates several metabolic enzymes, among them phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme of the central carbon metabolism. The sRNA scr5239 represses pepck at the post-transcriptional level and thus modulates the intracellular level of phosphoenolpyruvate (PEP). The expression of scr5239 in turn is dependent on the global transcriptional regulator DasR, thus creating a feedback loop regulation of the central carbon metabolism. By post-transcriptional regulation of PEPCK and in all likelihood other targets, scr5239 adds an additional layer to the DasR regulatory network and provides a tool to control the metabolism dependent on the available carbon source.

Biological characterization of new inhibitors of microsomal PGE synthase-1 in preclinical models of inflammation and vascular tone

BACKGROUND AND PURPOSE

Microsomal PGE synthase-1 (mPGES-1), the inducible synthase that catalyses the terminal step in PGE₂ biosynthesis, is of high interest as therapeutic target to treat inflammation. Inhibition of mPGES-1 is suggested to be safer than traditional NSAIDs, and recent data demonstrate anti-constrictive effects on vascular tone, indicating new therapeutic opportunities. However, there is a lack of potent mPGES-1 inhibitors lacking interspecies differences for conducting in vivo studies in relevant preclinical disease models.

EXPERIMENTAL APPROACH

Potency was determined based on the reduction of PGE₂ formation in recombinant enzyme assays, cellular assay, human whole blood assay, and air pouch mouse model. Anti-inflammatory properties were assessed by acute paw swelling in a paw oedema rat model. Effect on vascular tone was determined with human ex vivo wire myography.

KEY RESULTS

We report five new mPGES-1 inhibitors (named 934, 117, 118, 322, and 323) that selectively inhibit recombinant human and rat mPGES-1 with IC₅₀ values of 10-29 and 67-250 nM respectively. The compounds inhibited PGE₂ production in a cellular assay (IC₅₀ values 0.15-0.82 μM) and in a human whole blood assay (IC₅₀ values 3.3-8.7 μM). Moreover, the compounds blocked PGE₂ formation in an air pouch mouse model and reduced acute paw swelling in a paw oedema rat model. Human ex vivo wire myography analysis showed reduced adrenergic vasoconstriction after incubation with the compounds.

CONCLUSION AND IMPLICATIONS

These mPGES-1 inhibitors can be used as refined tools in further investigations of the role of mPGES-1 in inflammation and microvascular disease.

Microsomal prostaglandin E synthase-1 promotes lung metastasis via SDF-1/CXCR4-mediated recruitment of CD11b+Gr1+MDSCs from bone marrow

BACKGROUND

Accumulation of myeloid-derived suppressor cells (MDSCs) to tumors is related to cancer prognosis. We investigated the contribution of host stromal microsomal prostaglandin E synthase-1 (mPGES-1) to the accumulation of MDSCs in metastasized lungs of prostate cancer in mice.

MATERIAL AND METHODS

Eight-week-old male C57Bl/6 wild type (WT) mice and mPGES-1 knock out mice (mPGES-1KO) were injected with RM9 murine prostate cancer cell line (5 × 10⁶ cells/mL). Lung metastasis was evaluated by the number of colonies, the weight of the lung, and the number of MDSCs (CD11b⁺Gr1⁺ cells) in the lung.

RESULTS

Intravenous injections of RM9, a murine prostate cancer cell line to WT mice revealed that lung metastasis and accumulation of MDCSs were suppressed with treatments with a Gr1 antibody, a COX-2 inhibitor, and an mPGES-1 inhibitor. Lung metastasis and accumulation of CD11b⁺Gr1⁺MDSCs were suppressed in mPGES-1KO mice. The mRNA level of stromal cell-derived factor-1 (SDF-1) in the lung and the number of accumulated SDF-1-expressing CD11b⁺Gr1⁺ MDSCs were elevated at an early stage in lung metastasis of C-X-C chemokine receptor type 4 (CXCR4)-expressing RM9 in an mPGES-1-dependent manner. The number of CXCR4-expressing CD11b⁺Gr1⁺MDSCs in WT mice was higher than that in mPGES-1KO mice. RM9 lung metastasis and accumulation of CD11b⁺Gr1⁺MDSCs were suppressed by CXCR4 antibody in WT mice but not in mPGES-1KO. WT mice transplanted with mPGES-1 KO bone marrow (BM) showed a significant reduction in lung metastasis and accumulation of CD11b⁺Gr1⁺MDSCs.

CONCLUSION

These results suggest that mPGES-1 enhances tumor metastasis by inducing accumulation of BM-derived MDSCs. Selective mPGES-1 inhibitors might, therefore, represent valuable therapeutic tools for the suppression of tumor metastasis.

Distinct HLA Associations with Rheumatoid Arthritis Subsets Defined by Serological Subphenotype

Rheumatoid arthritis (RA) is the most common immune-mediated arthritis. Anti-citrullinated peptide antibodies (ACPA) are highly specific to RA and assayed with the commercial CCP2 assay. Genetic drivers of RA within the MHC are different for CCP2-positive and -negative subsets of RA, particularly at HLA-DRB1. However, aspartic acid at amino acid position 9 in HLA-B (B^pos-9) increases risk to both RA subsets. Here we explore how individual serologies associated with RA drive associations within the MHC. To define MHC differences for specific ACPA serologies, we quantified a total of 19 separate ACPAs in RA-affected case subjects from four cohorts (n = 6,805). We found a cluster of tightly co-occurring antibodies (canonical serologies, containing CCP2), along with several independently expressed antibodies (non-canonical serologies). After imputing HLA variants into 6,805 case subjects and 13,467 control subjects, we tested associations between the HLA region and RA subgroups based on the presence of canonical and/or non-canonical serologies. We examined CCP2(+) and CCP2(−) RA-affected case subjects separately. In CCP2(−) RA, we observed that the association between CCP2(−) RA and B^pos-9 was derived from individuals who were positive for non-canonical serologies (omnibus_p = 9.2 × 10⁻¹⁷). Similarly, we observed in CCP2(+) RA that associations between subsets of CCP2(+) RA and B^pos-9 were negatively correlated with the number of positive canonical serologies (p = 0.0096). These findings suggest unique genetic characteristics underlying fine-specific ACPAs, suggesting that RA may be further subdivided beyond simply seropositive and seronegative.

Urinary prostaglandin D2 and E2 metabolites associate with abdominal obesity, glucose metabolism, and triglycerides in obese subjects

Obesity is associated with low-grade chronic inflammation, which contributes to the development of the metabolic syndrome and its associated complications, such as insulin resistance and type-2 diabetes. Limited data from animal and human studies support local generation of pro-inflammatory prostanoid lipid mediators in white adipose tissue. However, the link between systemic prostanoid levels and parameters characterizing the metabolic syndrome is missing in human obesity. Therefore, we performed a targeted lipidomic analysis using urine samples from obese human subjects (n = 45) and show for the first time in humans that urinary prostanoid levels correlate with metabolic parameters that indicate a dysregulated glucose and triglyceride metabolism. We identified tetranor-PGDM and tetranor-PGEM as the two major urinary prostanoid metabolites in obese subjects with levels of 247 ± 31 and 23.3 ± 4.0 pmol/mg creatinine, respectively. Tetranor-PGDM was significantly associated with serum triglycerides, while tetranor-PGEM was associated with abdominal obesity as defined by an increased waist-to-hip ratio (WHR), with glycated hemoglobin (HbA1c), and with impaired oral glucose tolerance. These results confirm the previously established notion of low-grade chronic inflammation in obesity and further identify an association of the prostanoid pathway with obesity-associated dyslipidemia, abdominal obesity, and insulin resistance.

Inhibition of mPGES-1 or COX-2 Results in Different Proteomic and Lipidomic Profiles in A549 Lung Cancer Cells

Pharmacological inhibition of microsomal prostaglandin E synthase (mPGES)-1 for selective reduction in prostaglandin E₂ (PGE₂) biosynthesis is protective in experimental models of cancer and inflammation. Targeting mPGES-1 is envisioned as a safer alternative to traditional non-steroidal anti-inflammatory drugs (NSAIDs). Herein, we compared the effects of mPGES-1 inhibitor Compound III (CIII) with the cyclooxygenase (COX)-2 inhibitor NS-398 on protein and lipid profiles in interleukin (IL)-1β-induced A549 lung cancer cells using mass spectrometry. Inhibition of mPGES-1 decreased PGE₂ production and increased PGF_2α and thromboxane B₂ (TXB₂) formation, while inhibition of COX-2 decreased the production of all three prostanoids. Our proteomics results revealed that CIII downregulated multiple canonical pathways including eIF2, eIF4/P70S6K, and mTOR signaling, compared to NS-398 that activated these pathways. Moreover, pathway analysis predicted that CIII increased cell death of cancer cells (Z = 3.8, p = 5.1E-41) while NS-398 decreased the same function (Z = -5.0, p = 6.5E-35). In our lipidomics analyses, we found alterations in nine phospholipids between the two inhibitors, with a stronger alteration in the lysophospholipid (LPC) profile with NS-398 compared to CIII. Inhibition of mPGES-1 increased the concentration of sphinganine and dihydroceramide (C_16:0DhCer), while inhibition of COX-2 caused a general decrease in most ceramides, again suggesting different effects on cell death between the two inhibitors. We showed that CIII decreased proliferation and potentiated the cytotoxic effect of the cytostatic drugs cisplatin, etoposide, and vincristine when investigated in a live cell imaging system. Our results demonstrate differences in protein and lipid profiles after inhibition of mPGES-1 or COX-2 with important implications on the therapeutic potential of mPGES-1 inhibitors as adjuvant treatment in cancer. We encourage further investigations to illuminate the clinical benefit of mPGES-1 inhibitors in cancer.

Circulating Levels of Interferon Regulatory Factor-5 Associates With Subgroups of Systemic Lupus Erythematosus Patients

Systemic Lupus Erythematosus (SLE) is a heterogeneous autoimmune disease, which currently lacks specific diagnostic biomarkers. The diversity within the patients obstructs clinical trials but may also reflect differences in underlying pathogenesis. Our objective was to obtain protein profiles to identify potential general biomarkers of SLE and to determine molecular subgroups within SLE for patient stratification. Plasma samples from a cross-sectional study of well-characterized SLE patients (n = 379) and matched population controls (n = 316) were analyzed by antibody suspension bead array targeting 281 proteins. To investigate the differences between SLE and controls, Mann–Whitney U-test with Bonferroni correction, generalized linear modeling and receiver operating characteristics (ROC) analysis were performed. K-means clustering was used to identify molecular SLE subgroups. We identified Interferon regulating factor 5 (IRF5), solute carrier family 22 member 2 (SLC22A2) and S100 calcium binding protein A12 (S100A12) as the three proteins with the largest fold change between SLE patients and controls (SLE/Control = 1.4, 1.4, and 1.2 respectively). The lowest p-values comparing SLE patients and controls were obtained for S100A12, Matrix metalloproteinase-1 (MMP1) and SLC22A2 (p_adjusted = 3 × 10⁻⁹, 3 × 10⁻⁶, and 5 × 10⁻⁶ respectively). In a set of 15 potential biomarkers differentiating SLE patients and controls, two of the proteins were transcription factors, i.e., IRF5 and SAM pointed domain containing ETS transcription factor (SPDEF). IRF5 was up-regulated while SPDEF was found to be down-regulated in SLE patients. Unsupervised clustering of all investigated proteins identified three molecular subgroups among SLE patients, characterized by (1) high levels of rheumatoid factor-IgM, (2) low IRF5, and (3) high IRF5. IRF5 expressing microparticles were analyzed by flow cytometry in a subset of patients to confirm the presence of IRF5 in plasma and detection of extracellular IRF5 was further confirmed by immunoprecipitation-mass spectrometry (IP-MS). Interestingly IRF5, a known genetic risk factor for SLE, was detected extracellularly and suggested by unsupervised clustering analysis to differentiate between SLE subgroups. Our results imply a set of circulating molecules as markers of possible pathogenic importance in SLE. We believe that these findings could be of relevance for understanding the pathogenesis and diversity of SLE, as well as for selection of patients in clinical trials.

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.

Divergent roles of prostacyclin and PGE2 in human tendinopathy

BACKGROUND

Tendon disease is a significant global healthcare burden whereby patients experience pain and disability; however, the mechanisms that underlie inflammation and pain are poorly understood. Herein, we investigated the role of prostaglandins as important mediators of inflammation and pain in tissues and cells derived from patients with tendinopathy.

METHODS

We studied supraspinatus and Achilles tendon biopsies from symptomatic patients with tendinopathy or rupture. Tendon-derived stromal cells (CD45negCD34neg) isolated from tendons were cultured and treated with interleukin-1β (IL-1β) to investigate prostaglandin production.

RESULTS

Diseased tendon tissues showed increased expression of prostacyclin receptor (IP) and enzymes catalyzing the biosynthesis of prostaglandins, including cyclooxygenase-1 (COX-1), COX-2, prostacyclin synthase (PGIS), and microsomal prostaglandin E synthase-1 (mPGES-1). PGIS co-localized with cells expressing Podoplanin, a marker of stromal fibroblast activation, and the nociceptive neuromodulator NMDAR-1. Treatment with IL-1β induced release of the prostacyclin metabolite 6-keto PGF1α in tendon cells isolated from diseased supraspinatus and Achilles tendons but not in cells from healthy comparator tendons. The same treatment induced profound prostaglandin E2 (PGE2) release in tendon cells derived from patients with supraspinatus tendon tears. Incubation of IL-1β treated diseased tendon cells with selective mPGES-1 inhibitor Compound III, reduced PGE2, and simultaneously increased 6-keto PGF1α production. Conversely, COX blockade with naproxen or NS-398 inhibited both PGE2 and 6-keto PGF1α production. Tendon biopsies from patients in whom symptoms had resolved showed increased PTGIS compared to biopsies from patients with persistent tendinopathy.

CONCLUSIONS

Our results suggest that PGE2 sustains inflammation and pain while prostacyclin may have a protective role in human tendon disease.

Two subgroups in systemic lupus erythematosus with features of antiphospholipid or Sjögren's syndrome differ in molecular signatures and treatment perspectives

Background

Previous studies and own clinical observations of patients with systemic lupus erythematosus (SLE) suggest that SLE harbors distinct immunophenotypes. This heterogeneity might result in differences in response to treatment in different subgroups and obstruct clinical trials. Our aim was to understand how SLE subgroups may differ regarding underlying pathophysiology and characteristic biomarkers.

Methods

In a cross-sectional study, including 378 well-characterized SLE patients and 316 individually matched population controls, we defined subgroups based on the patients’ autoantibody profile at inclusion. We selected a core of an antiphospholipid syndrome-like SLE (aPL+ group; positive in the lupus anticoagulant (LA) test and negative for all three of SSA (Ro52 and Ro60) and SSB antibodies) and a Sjögren’s syndrome-like SLE (SSA/SSB+ group; positive for all three of SSA (Ro52 and Ro60) and SSB antibodies but negative in the LA test). We applied affinity-based proteomics, targeting 281 proteins, together with well-established clinical biomarkers and complementary immunoassays to explore the difference between the two predefined SLE subgroups.

Results

The aPL+ group comprised 66 and the SSA/SSB+ group 63 patients. The protein with the highest prediction power (receiver operating characteristic (ROC) area under the curve = 0.89) for separating the aPL+ and SSA/SSB+ SLE subgroups was integrin beta-1 (ITGB1), with higher levels present in the SSA/SSB+ subgroup. Proteins with the lowest p values comparing the two SLE subgroups were ITGB1, SLC13A3, and CERS5. These three proteins, rheumatoid factor, and immunoglobulin G (IgG) were all increased in the SSA/SSB+ subgroup. This subgroup was also characterized by a possible activation of the interferon system as measured by high KRT7, TYK2, and ETV7 in plasma. In the aPL+ subgroup, complement activation was more pronounced together with several biomarkers associated with systemic inflammation (fibrinogen, α-1 antitrypsin, neutrophils, and triglycerides).

Conclusions

Our observations indicate underlying pathogenic differences between the SSA/SSB+ and the aPL+ SLE subgroups, suggesting that the SSA/SSB+ subgroup may benefit from IFN-blocking therapies while the aPL+ subgroup is more likely to have an effect from drugs targeting the complement system. Stratifying SLE patients based on an autoantibody profile could be a way forward to understand underlying pathophysiology and to improve selection of patients for clinical trials of targeted treatments.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1836-8) contains supplementary material, which is available to authorized users.

Mass spectrometry-based analysis of cerebrospinal fluid from arthritis patients-immune-related candidate proteins affected by TNF blocking treatment

Background

Signs of inflammation in cerebrospinal fluid (CSF) of rheumatoid arthritis patients correlate positively with fatigue, a central nervous system (CNS)-related symptom that can be partially suppressed by TNF blockade. This suggests a possible role for CNS inflammation in arthritis that may be affected by TNF blockade. We therefore investigated the effects of TNF blockade on the arthritis CSF proteome and how candidate proteins related to clinical measures of disease activity and inflammation.

Methods

Mass spectrometry-based quantitative proteomic analysis was performed on CSF from seven polyarthritis patients before and during infliximab treatment. Treatment-associated proteins were identified using univariate (Wilcoxon signed rank test) and multivariate (partial least squares discriminant analysis (PLS-DA)) strategies. Relations between selected candidate proteins and clinical measures were investigated using the Spearman correlations. Additionally, selected proteins were cross-referenced to other studies investigating human CSF in a thorough literature search to ensure feasibility of our results.

Results

Univariate analysis of arthritis CSF proteome revealed a decrease of 35 proteins, predominantly involved in inflammatory processes, following TNF blockade. Seven candidate proteins, Contactin-1 (CNTN1), fibrinogen gamma chain (FGG), hemopexin (HPX), cell adhesion molecule-3 (CADM3), alpha-1B-glycoprotein (A1BG), complement factor B (CFB), and beta-2-microglobulin (B2M), were selected for further studies based on identification by both univariate and multivariate analyses and reported detection in human CSF and known associations to arthritis. Decreased levels of FGG and CFB in CSF after treatment showed strong correlations with both erythrocyte sedimentation rate and disability scores, while CNTN1 and CADM3 were associated with pain.

Conclusion

Several immune-related proteins in the CSF of arthritis patients decreased during TNF blockade, including FGG and CFB that both correlated strongly with systemic inflammation. Our findings stress that also intrathecal inflammatory pathways are related to arthritis symptoms and may be affected by TNF blockade.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1846-6) contains supplementary material, which is available to authorized users.

Targeting the COX/mPGES-1/PGE2 Pathway in Neuroblastoma

The importance of prostaglandin E₂ in cancer progression is well established, but research on its role in cancer has so far mostly been focused on epithelial cancer in adults while the knowledge about the contribution of prostaglandin E₂ to childhood malignancies is limited. Neuroblastoma, an extracranial solid tumor of the sympathetic nervous system, mainly affects young children. Patients with tumors classified as high-risk have poor survival despite receiving intensive treatment, illustrating a need for new treatments complimenting existing ones. The basis of neuroblastoma treatment e.g. chemotherapy and radiation therapy, target the proliferating genetically unstable tumor cells leading to treatment resistance and relapses. The tumor microenvironment is an avenue, still to a great extent, unexplored and lacking effective targeted therapies. Cancer-associated fibroblasts is the main source of prostaglandin E₂ in neuroblastoma contributing to angiogenesis, immunosuppression and tumor growth. Prostaglandin E₂ is formed from its precursor arachidonic acid in a two-step enzymatic reaction. Arachidonic acid is first converted by cyclooxygenases into prostaglandin H₂ and then further converted by microsomal prostaglandin E synthase-1 into prostaglandin E₂. We believe targeting of microsomal prostaglandin E synthase-1 in cancer-associated fibroblasts will be an effective future therapeutic strategy in fighting neuroblastoma.