Alterations in the gut microbiome implicate key taxa and metabolic pathways across inflammatory arthritis phenotypes.

Musculoskeletal diseases affect up to 20% of adults worldwide. The gut microbiome has been implicated in inflammatory conditions, but large-scale metagenomic evaluations have not yet traced the routes by which immunity in the gut affects inflammatory arthritis. To characterize the community structure and associated functional processes driving gut microbial involvement in arthritis, the Inflammatory Arthritis Microbiome Consortium investigated 440 stool shotgun metagenomes comprising 221 adults diagnosed with rheumatoid arthritis, ankylosing spondylitis, or psoriatic arthritis and 219 healthy controls and individuals with joint pain without an underlying inflammatory cause. Diagnosis explained about 2% of gut taxonomic variability, which is comparable in magnitude to inflammatory bowel disease. We identified several candidate microbes with differential carriage patterns in patients with elevated blood markers for inflammation. Our results confirm and extend previous findings of increased carriage of typically oral and inflammatory taxa and decreased abundance and prevalence of typical gut clades, indicating that distal inflammatory conditions, as well as local conditions, correspond to alterations to the gut microbial composition. We identified several differentially encoded pathways in the gut microbiome of patients with inflammatory arthritis, including changes in vitamin B salvage and biosynthesis and enrichment of iron sequestration. Although several of these changes characteristic of inflammation could have causal roles, we hypothesize that they are mainly positive feedback responses to changes in host physiology and immune homeostasis. By connecting taxonomic alternations to functional alterations, this work expands our understanding of the shifts in the gut ecosystem that occur in response to systemic inflammation during arthritis.

The JAK inhibitor baricitinib inhibits oncostatin M induction of proinflammatory mediators in ex-vivo synovial derived cells.

OBJECTIVES: To investigate the ex vivo effect of the JAK1/2 inhibitor baricitinib on expression of pro-inflammatory mediators in rheumatoid arthritis (RA) fibroblast like synoviocytes (FLS) stimulated with TNFα, IL-1ß and oncostatin M (OSM), and in RA synovial membrane cells (SMCs). METHODS: RA and osteoarthritis (OA) SMCs, were isolated from arthroplasty specimens of RA (n=8) and OA (n=8) patients, respectively, using enzymatic digestion followed by cell propagation to obtain RA (n=5) and OA (n=3) FLS. Normal FLS and normal human foreskin fibroblasts (HSF) were purchased from commercial sources. Fibroblasts were stimulated with cytokines with or without baricitinib. RA SMCs were cultured in the presence of baricitinib without stimulation. JAK/STAT activation and levels of mRNA and proteins of the various inflammatory cytokines (IL-6, IL-8, MCP-1, RANTES and IP-10) were determined by qPCR, ELISA and MSD. RESULTS: Baricitinib inhibited OSM-induced JAK signalling in RA synovial fibroblasts and effectively suppressed subsequent expression of the proinflammatory mediators IL-6, MCP-1 and IP-10. However, baricitinib was not effective in altering levels of spontaneously released TNFα, IL-6 and IL-8 in RA SMC. Although both TNFα and IL-1ß signal independently of the JAK/STAT pathway, in HSF, but not in RA FLS, baricitinib significantly inhibited TNFα- and IL-1ß-induced MCP-1 and IP-10 protein levels in a dose dependent manner. Furthermore, baricitinib did not inhibit TNFα- and IL-1ß-induced expression of IL-6, IL-8 and MCP-1 in RA FLS. CONCLUSIONS: These findings are consistent with known signalling pathways employed by OSM, TNFα and IL-1ß, but our data suggest that in HSF, baricitinib may have anti-inflammatory effects via downstream modulation of cytokines and chemokines produced in response to TNFα or IL-1ß.

TLR expression profiles are a function of disease status in rheumatoid arthritis and experimental arthritis.

The role of the innate immune system has been established in the initiation and perpetuation of inflammatory disease, but less attention has been paid to its role in the resolution of inflammation and return to homeostasis. Toll-like receptor (TLR) expression profiles were analysed in tissues with differing disease status in rheumatoid arthritis (RA), ankylosing spondylitis (AS), and in experimental arthritis. TLR gene expression was measured in whole blood and monocytes, before and after TNF blockade. In RA and osteoarthritis synovia, the expression of TLRs was quantified by standard curve qPCR. In addition, four distinct stages of disease were defined and validated in collagen-induced arthritis (CIA), the gold standard animal model for RA - pre-onset, early disease, late disease and immunised mice that were resistant to the development of disease. TLR expression was measured in spleens, lymph nodes, blood cells, liver and the paws (inflamed and unaffected). In RA whole blood, the expression of TLR1, 4 and 6 was significantly reduced by TNF blockade but the differences in TLR expression profiles between responders and non-responders were less pronounced than the differences between RA and AS patients. In RA non-responders, monocytes had greater TLR2 expression prior to therapy compared to responders. The expression of TLR1, 2, 4 and 8 was higher in RA synovium compared to control OA synovium. Circulating cytokine levels in CIA resistant mice were similar to naïve mice, but anti-collagen antibodies were similar to arthritic mice. Distinct profiles of inflammatory gene expression were mapped in paws and organs with differing disease status. TLR expression in arthritic paws tended to be similar in early and late disease, with TLR1 and 2 moderately higher in late disease. TLR expression in unaffected paws varied according to gene and disease status but was generally lower in resistant paws. Disease status-specific profiles of TLR expression were observed in spleens, lymph nodes, blood cells and the liver. Notably, TLR2 expression rose then fell in the transition from naïve to pre-onset to early arthritis. TLR gene expression profiles are strongly associated with disease status. In particular, increased expression in the blood precedes clinical manifestation.

The macrophage marker translocator protein (TSPO) is down-regulated on pro-inflammatory 'M1' human macrophages.

The translocator protein (TSPO) is a mitochondrial membrane protein, of as yet uncertain function. Its purported high expression on activated macrophages, has lent utility to TSPO targeted molecular imaging in the form of positron emission tomography (PET), as a means to detect and quantify inflammation in vivo. However, existing literature regarding TSPO expression on human activated macrophages is lacking, mostly deriving from brain tissue studies, including studies of brain malignancy, and inflammatory diseases such as multiple sclerosis. Here, we utilized three human sources of monocyte derived macrophages (MDM), from THP-1 monocytes, healthy peripheral blood monocytes and synovial fluid monocytes from patients with rheumatoid arthritis, to undertake a detailed investigation of TSPO expression in activated macrophages. In this work, we demonstrate a consistent down-regulation of TSPO mRNA and protein in macrophages activated to a pro-inflammatory, or 'M1' phenotype. Conversely, stimulation of macrophages to an M2 phenotype with IL-4, dexamethasone or TGF-ß1 did not alter TSPO expression, regardless of MDM source. The reasons for this are uncertain, but our study findings add some supporting evidence for recent investigations concluding that TSPO may be involved in negative regulation of inflammatory responses in macrophages.

Filgotinib for the treatment of rheumatoid arthritis.

INTRODUCTION: Biologics were the first targeted therapies for rheumatoid arthritis (RA), having in common high clinical efficacy. Being proteins, they are administered parenterally. The first oral targeted small molecules approved for RA are competitive inhibitors of the Janus kinase (JAK) enzyme family which mediate signalling for a cytokine subset important in RA pathogenesis. Areas covered: Several JAK inhibitors have been developed with differing selectivity for the four JAK enzymes with a view to generating oral, multi-cytokine inhibitors. Here we review the pharmacology and clinical trial data for efficacy and safety of filgotinib, an investigational selective JAK1 inhibitor. We contextualise the contemporary approach to RA management and substantial unmet needs that remain. Expert opinion: The selectivity of filgotinib for JAK1 may have theoretical advantages in terms of limiting toxicity. However, establishing whether this is so before larger numbers of patients are exposed in phase III and beyond in the real word setting, will be difficult. Filgotinib clinical trial data to date has been encouraging with rapid, sustained efficacy with promising safety and tolerability. We are likely to see an expanding choice of approved JAK inhibitors in the clinic but it may not be straightforward to distinguish safety and efficacy differences.

Complement C1q is hydroxylated by collagen prolyl 4 hydroxylase and is sensitive to off-target inhibition by prolyl hydroxylase domain inhibitors that stabilize hypoxia-inducible factor.

Complement C1q is part of the C1 macromolecular complex that mediates the classical complement activation pathway: a major arm of innate immune defense. C1q is composed of A, B, and C chains that require post-translational prolyl 4-hydroxylation of their N-terminal collagen-like domain to enable the formation of the functional triple helical multimers. The prolyl 4-hydroxylase(s) that hydroxylate C1q have not previously been identified. Recognized prolyl 4-hydroxylases include collagen prolyl-4-hydroxylases (CP4H) and the more recently described prolyl hydroxylase domain (PHD) enzymes that act as oxygen sensors regulating hypoxia-inducible factor (HIF). We show that several small-molecule prolyl hydroxylase inhibitors that activate HIF also potently suppress C1q secretion by human macrophages. However, reducing oxygenation to a level that activates HIF does not compromise C1q hydroxylation. In vitro studies showed that a C1q A chain peptide is not a substrate for PHD2 but is a substrate for CP4H1. Circulating levels of C1q did not differ between wild-type mice or mice with genetic deficits in PHD enzymes, but were reduced by prolyl hydroxylase inhibitors. Thus, C1q is hydroxylated by CP4H, but not the structurally related PHD hydroxylases. Hence, reduction of C1q levels may be an important off-target side effect of small molecule PHD inhibitors developed as treatments for renal anemia.

Factor-inhibiting HIF-1 (FIH-1) is required for human vascular endothelial cell survival.

Factor-inhibiting hypoxia-inducible factor (HIF)-1 (FIH-1) is an asparaginyl ß-hydroxylase enzyme that was initially found to hydroxylate the HIF-α, preventing its transcriptional activity and leading to adaptive responses to hypoxia. More recently, other substrates, such as neurogenic locus notch homolog (Notch), have been found to be alternative FIH targets, but the biologic relevance of this regulation was never investigated. Given the key function of Notch in angiogenesis, we here investigate the role of FIH/Notch signaling in endothelial cells. We report that FIH-1 silencing in HUVECs results in reduced growth and increased apoptosis. The knockdown of FIH is associated with increased Notch2 activity, leading to enhanced expression of the Notch target hairy/enhancer-of-split related with YRPW motif protein 1 (Hey-1). Consistent with recent findings showing that Notch2 suppresses survivin (a key inhibitor of apoptosis), FIH targeting in HUVECs leads to selective repression of survivin in endothelial cells, thus promoting cell apoptosis and growth arrest. Our data support the concept that FIH-1 may interact with Notch2 and repress its activity, thereby playing a critical role in controlling the survival of vascular endothelial cells. These findings might pave the way toward novel, antiangiogenic strategies in disorders that are characterized by excessive vascular growth, such as cancer and rheumatoid arthritis.

HIF-1 reduces ischaemia-reperfusion injury in the heart by targeting the mitochondrial permeability transition pore.

AIMS: Hypoxia-inducible factor-1 (HIF-1) has been reported to promote tolerance against acute myocardial ischaemia-reperfusion injury (IRI). However, the mechanism through which HIF-1 stabilization actually confers this cardioprotection is not clear. We investigated whether HIF-1α stabilization protects the heart against acute IRI by preventing the opening of the mitochondrial permeability transition pore (MPTP) and the potential mechanisms involved. METHODS AND RESULTS: Stabilization of myocardial HIF-1 was achieved by pharmacological inhibition of prolyl hydroxylase (PHD) domain-containing enzyme using GSK360A or using cardiac-specific ablation of von Hippel-Lindau protein (VHL(fl/fl)) in mice. Treatment of HL-1 cardiac cells with GSK360A stabilized HIF-1, increased the expression of HIF-1 target genes pyruvate dehydrogenase kinase-1 (PDK1) and hexokinase II (HKII), and reprogrammed cell metabolism to aerobic glycolysis, thereby resulting in the production of less mitochondrial oxidative stress during IRI, and less MPTP opening, effects which were shown to be dependent on HKII. These findings were further confirmed when HIF-1 stabilization in the rat and murine heart resulted in smaller myocardial infarct sizes (both in vivo and ex vivo), decreased mitochondrial oxidative stress, and inhibited MPTP opening following IRI, effects which were also found to be dependent on HKII. CONCLUSIONS: We have demonstrated that acute HIF-1α stabilization using either a pharmacological or genetic approach protected the heart against acute IRI by promoting aerobic glycolysis, decreasing mitochondrial oxidative stress, activating HKII, and inhibiting MPTP opening.

Identification of the angiogenic gene signature induced by EGF and hypoxia in colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) is characterised by hypoxia, which activates gene transcription through hypoxia-inducible factors (HIF), as well as by expression of epidermal growth factor (EGF) and EGF receptors, targeting of which has been demonstrated to provide therapeutic benefit in CRC. Although EGF has been demonstrated to induce expression of angiogenic mediators, potential interactions in CRC between EGF-mediated signalling and the hypoxia/HIF pathway remain uncharacterised. METHODS: PCR-based profiling was applied to identify angiogenic genes in Caco-2 CRC cells regulated by hypoxia, the hypoxia mimetic dimethyloxallylglycine (DMOG) and/or EGF. Western blotting was used to determine the role of HIF-1alpha, HIF-2alpha and MAPK cell signalling in mediating the angiogenic responses. RESULTS: We identified a total of 9 angiogenic genes, including angiopoietin-like (ANGPTL) 4, ephrin (EFNA) 3, transforming growth factor (TGF) ß1 and vascular endothelial growth factor (VEGF), to be upregulated in a HIF dependent manner in Caco-2 CRC cells in response to both hypoxia and the hypoxia mimetic dimethyloxallylglycine (DMOG). Stimulation with EGF resulted in EGFR tyrosine autophosphorylation, activation of p42/p44 MAP kinases and stabilisation of HIF-1α and HIF-2α proteins. However, expression of 84 angiogenic genes remained unchanged in response to EGF alone. Crucially, addition of DMOG in combination with EGF significantly increased expression of a further 11 genes (in addition to the 9 genes upregulated in response to either DMOG alone or hypoxia alone). These additional genes included chemokines (CCL-11/eotaxin-1 and interleukin-8), collagen type IV α3 chain, integrin ß3 chain, TGFα and VEGF receptor KDR. CONCLUSION: These findings suggest that although EGFR phosphorylation activates the MAP kinase signalling and promotes HIF stabilisation in CRC, this alone is not sufficient to induce angiogenic gene expression. In contrast, HIF activation downstream of hypoxia/DMOG drives expression of genes such as ANGPTL4, EFNA3, TGFß1 and VEGF. Finally, HIF activation synergises with EGF-mediated signalling to additionally induce a unique sub-group of candidate angiogenic genes. Our data highlight the complex interrelationship between tumour hypoxia, EGF and angiogenesis in the pathogenesis of CRC.

Hypoxia-induced invadopodia formation: a role for ß-PIX.

During tumour progression, oxygen tension in the microenvironment surrounding tumour cells is reduced, resulting in hypoxia. It is well established that cancer cells resist the negative effects of hypoxia by inducing angiogenesis predominantly via the activity of transcription factor hypoxia-inducible factor-1 (HIF-1). However, more recently HIF-1α has also been linked to increased invasive potential, although the molecular mechanisms remain to be defined. Invasive cancer cells are thought to employ membrane protrusions, termed invadopodia, to achieve matrix degradation. While many invadopodia components have been identified, signalling pathways that link extracellular stimuli to invadopodia formation remain largely unknown. Indeed, the relationship between invadopodia formation and HIF-1α has not been explored. We now report that HIF-1α is a driver of invadopodia formation. Furthermore, we have identified an important, direct and novel link between the Rho family activator ß-PIX, HIF-1α and invadopodia formation. Indeed, we find that ß-PIX expression is essential for invadopodia formation. In conclusion, we identify a new HIF-1α mechanistic pathway and suggest that ß-PIX is a novel downstream signalling mediator during invadopodia formation.

Hypoxia-inducible factor pathway and diseases of the vascular wall.

BACKGROUND: Hypoxia may contribute to the pathogenesis of various diseases of the vascular wall. Hypoxia-inducible factors (HIFs) are nuclear transcriptional factors that regulate the transcription of genes that mediate cellular and tissue homeostatic responses to altered oxygenation. This article reviews the published literature on and discusses the role of the HIF pathway in diseases involving the vascular wall, including atherosclerosis, arterial aneurysms, pulmonary hypertension, vascular graft failure, chronic venous diseases, and vascular malformation. METHODS: PubMed was searched with the terms "hypoxia-inducible factor" or "HIF" and "atherosclerosis," "carotid stenosis," "aneurysm," "pulmonary artery hypertension," "varicose veins," "venous thrombosis," "graft thrombosis," and "vascular malformation." RESULTS: In atherosclerotic plaque, HIF-1α was localized in macrophages and smooth muscle cells bordering the necrotic core. Increased HIF-1α may contribute to atherosclerosis through alteration of smooth muscle cell proliferation and migration, angiogenesis, and lipid metabolism. The expression of HIF-1α is significantly elevated in aortic aneurysms compared with nonaneurysmal arteries. In pulmonary hypertension, HIF-1α contributes to the increase of intracellular K(+) and Ca(2+) leading to vasoconstriction of pulmonary smooth muscle cells. Alteration of the HIF pathway may contribute to vascular graft failure through the formation of intimal hyperplasia. In chronic venous disease, HIF pathway dysregulation contributes to formation of varicose veins and venous thromboembolism. However, whether the activation of the HIF pathway is protective or destructive to the venous wall is unclear. Increased activation of the HIF pathway causes aberrant expression of angiogenic factors contributing to the formation and maintenance of vascular malformations. CONCLUSIONS: Pathologic vascular wall remodelling of many common diseases of the blood vessels has been found to be associated with altered activity of the HIF pathway. Therefore, understanding the role of the HIF pathway in diseases of the vascular wall is important to identify novel therapeutic strategies in the management of these pathologies.

Cell death pattern of a varicose vein organ culture model.

The study aimed to investigate the viability of a varicose vein (VV) organ culture model by assessing cell death pattern. To assess pattern of cell death with time, VV organ cultures were incubated for up to 14 days with regular medium changed. To assess viability, cell death of VV organ cultures treated with sodium azide and their untreated counterparts was assayed. Increased cell death was measured in VV organ cultures from day 0 to 2. Cell death decreased gradually after day 2 and plateaued from day 8 to 14.VV organ cultures treated with sodium azide demonstrated significantly more cell death in tissue (P = 0.001). Cell death measured in cultures treated with sodium azide continued to increase until day 7. In conclusion, this study demonstrated the viability of a VV organ culture model with most cell death occurred within the first two days and then declined to a relatively low level.

Vascular endothelium--role in chronic inflammatory disease.

The vascular endothelial lining of blood vessels plays a key 'target-effector' role in vivo, integrating the body's response to inflammatory cytokines, chemokines and growth factors (derived from both endothelial cells themselves and from other cells such as leukocytes and fibroblasts), to allow leukocyte activation, adhesion and extravasation from the flowing blood into underlying tissue. Endothelial proliferation, through the process of angiogenesis, results in an increased cell surface area for these events to occur, and further functions to deliver oxygen and nutrients, and to remove waste products. In addition to playing an important role in physiology, the endothelium is thus an active participant in inflammatory pathologies. One of the best understood diseases in which inflammation and angiogenesis play a part is rheumatoid arthritis (RA). Blockade of the inflammatory cascade in RA has significant consequences for the vasculature, highlighting the links between reducing endothelial activation and therapeutic benefit in chronic inflammatory disorders.

The effects of doxycycline and micronized purified flavonoid fraction on human vein wall remodeling are not hypoxia-inducible factor pathway-dependent.

BACKGROUND: Doxycycline and micronized purified flavonoid fraction (MPFF) modulate vein wall remodeling that may be associated with hypoxia in varicose veins (VVs), vein graft stenosis, and deep venous thrombosis. We recently reported that in vitro exposure of non-VV (NVVs) and VVs to hypoxic conditions activates the hypoxia-inducible factor (HIF) pathway. This study investigated the in vitro effects of doxycycline and MPFF on the HIF pathway in hypoxic NVVs and VVs. METHODS: Six NVVs and six VVs obtained from surgery were used to prepare vein organ cultures, which were exposed to hypoxia (1% O(2)), with and without MPFF (10(-5) mol/L) or doxycycline (5 µg/mL) for 16 hours. The veins were analyzed for HIF-1α, HIF-2α, and their target gene expression, with real-time polymerase chain reaction and Western blot. The differences between gene expressions were tested with one-way analysis of variance with repeated measures, followed by the Dunnett test for multiple comparisons. P < .05 was considered significant. RESULTS: Treatment of NVV organ cultures exposed to hypoxia with doxycycline or MPFF did not significantly alter the expression of HIF-1α and HIF-2α messenger (m)RNA and protein compared with untreated. Doxycycline also did not significantly affect the expression of HIF-1α and HIF-2α mRNA and protein in VVs exposed to hypoxia compared with untreated VVs. However, MPFF significantly reduced the expression of HIF-1α but not HIF-2α mRNA in VVs exposed to hypoxia compared with untreated VVs. Interestingly, the reduction of the expression of HIF-1α mRNA in VVs by MPFF was not reflected at the protein level. The mRNA expression of HIF target genes, namely glucose transporter-1, carbonic anhydrase-9, vascular endothelial growth factor, B-cell lymphoma 2/adenovirus E1B 19-kDa protein-interacting protein 3, prolyl hydroxylase domain-2, and prolyl hydroxylase domain-3, was not significantly altered in NVVs and VVs exposed to hypoxia and treated with doxycycline or MPFF compared with those untreated. CONCLUSIONS: Doxycycline and MPFF at a concentration corresponding to a therapeutic dose do not alter the activation of the HIF pathway in NVV and VV organ cultures exposed to hypoxia. Our findings suggest vein wall remodeling actions in NVVs and VVs are likely not HIF-dependent.

Prolyl hydroxylase domain enzyme 2 is the major player in regulating hypoxic responses in rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is characterized by hypoxia and the expression of hypoxia-inducible transcription factors (HIFs), which coordinate cellular responses to hypoxia. The objective of this study was to analyze the expression and regulation of prolyl hydroxylase domain (PHD) enzymes and factor-inhibiting HIF-1α (FIH-1), which regulate cellular HIF levels, and to study the roles of these enzymes in RA fibroblast-like synoviocytes (RA FLS). METHODS: The expression of PHD and FIH and downstream target genes was assessed by quantitative polymerase chain reaction and Western blotting. A small interfering RNA (siRNA) approach and an in vitro endothelial cell angiogenesis assay were used to analyze the roles of HIF hydroxylases. RESULTS: In human RA FLS, knockdown of PHD-2, but not knockdown of PHD-1 or FIH-1, dramatically augmented HIF-1α expression, modestly increased HIF-2α protein expression under normoxic conditions, and up-regulated HIF-dependent gene expression. In contrast, silencing of PHD-3 up-regulated HIF-2α but reduced HIF-1α, thereby decreasing the expression of HIF-regulated genes. A similar effect of PHD-2 knockdown was observed in osteoarthritis FLS (OA FLS) but not in nondiseased primary human dermal fibroblasts. These findings correlated with the induction of in vitro angiogenesis by supernatants from RA FLS and OA FLS transfected with siPHD-2 but not by supernatants from nondiseased fibroblasts or from siPHD-3-transfected cells. CONCLUSION: Our data suggest that PHD-2 is the major hydroxylase regulating HIF levels and the expression of angiogenic genes in arthritic cells. PHD-2 appears to regulate responses relevant to arthritis via HIF-α, highlighting the major importance of this enzyme in hypoxia- and angiogenesis-dependent inflammatory diseases such as RA.

Hypoxia--a key regulator of angiogenesis and inflammation in rheumatoid arthritis.

The importance of inflammation in rheumatoid arthritis (RA) is well understood. This knowledge has resulted in the development of anti-inflammatory therapies--either broadly acting (such as steroids) or more specific approaches (such as antibodies against TNF)--with biologic therapies (including TNF inhibitors) revolutionizing the treatment of RA. However, what is less well appreciated in RA are the links between inflammation, blood-vessel formation (angiogenesis) and cellular responses to changes in oxygen tension. Inadequate oxygenation, termed hypoxia, is thought to drive the increase in synovial angiogenesis that occurs in RA, through expression of hypoxia-inducible molecules, including vascular endothelial growth factor (VEGF). This process promotes further infiltration of inflammatory cells and production of inflammatory mediators, perpetuating synovitis. This Review highlights the molecular pathways activated by hypoxia, and how these pathways might interact with inflammatory signaling to promote and maintain synovitis in RA, with a particular focus on the response of macrophages to hypoxia in the context of RA. Successful treatment of RA, for example with anti-TNF antibodies, reduces levels of proangiogenic factors, including VEGF, and leads to normalization of the vasculature. These processes emphasise the close links between hypoxia, angiogenesis and inflammation in this disease and supports the concept that angiogenesis blockade could be of therapeutic benefit in RA.

Increased activation of the hypoxia-inducible factor pathway in varicose veins.

BACKGROUND: Venous hypoxia has been postulated to contribute to varicose vein (VV) formation. Direct measurements of vein wall oxygen tension have previously demonstrated that the average minimum oxygen tensions were significantly lower in VVs compared with non-varicose veins (NVVs). Hypoxia-inducible factors (HIFs) are nuclear transcriptional factors that regulate the expression of several genes of oxygen homeostasis. This study aimed to investigate if hypoxia was associated with VVs by assessing the expression of HIF-1α, HIF-2α, HIF target genes, and upstream HIF regulatory enzymes in VVs and NVVs, and their regulation by hypoxia. METHODS: VVs and NVVs were surgically retrieved and immediately snap-frozen or used for organ culture preparation. The relative expression of HIF-1α, HIF-2α, HIF target genes, and HIF regulatory enzymes in VVs and NVVs was analyzed with quantitative polymerase chain reaction (Q-PCR) and Western blot. VV and NVV organ ex vivo cultures were exposed to 16 hours of normoxia, hypoxia (oxygen tension 1%), or the hypoxia mimetic dimethyloxallyl glycine (DMOG) 1 mM in normoxia. The vein organ cultures were then analyzed for HIF-1α, HIF-2α, and their target gene expression with Q-PCR and Western blot. RESULTS: HIF-1α and HIF-2α mRNA were significantly upregulated in VVs compared with NVVs (89.8 ± 18.6 vs 10.4 ± 7.2 and 384.9 ± 209.4 vs 8.1 ± 4.2, respectively). HIF target gene mRNA expression was also significantly elevated in VVs compared with NVVs, namely glucose transporter-1 (GLUT-1; 8.7 ± 2.1 vs 1.0 ± 0.3), carbonic anhydrase-9 (CA9; 8.5 ± 2.1 vs 2.8 ± 1.2), vascular endothelial growth factor (VEGF; 7.5 ± 2.1 vs 0.9 ± 0.2), and BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 (BNIP-3; 4.5 ± 0.7 vs 1.4 ± 0.3). The upregulation of HIF-1α, HIF-2α, and HIF target genes in VVs was also reflected at protein level. Of the HIF regulatory enzymes, the expression of prolyl-hydroxylase domain (PHD)-2 and PHD-3 was found to be elevated in VVs compared with NVVs. Exposure of VV and NVV organ cultures to hypoxia or DMOG was associated with increases in HIF-1α and HIF-2α protein and HIF target gene expression compared with normoxia only. CONCLUSIONS: The study concluded, we believe for the first time, an increased activation of the HIF pathway, with upregulation of the expression of HIF-1α and HIF-2α transcription factors, and HIF target genes, in VVs compared with NVVs. Exposure of VVs and NVVs to hypoxic conditions was associated with increased expression of HIF-1α and HIF-2α protein and HIF target genes. The data suggest that the HIF pathway may be associated with several pathophysiologic changes in the VV wall, and that hypoxia may be a feature contributing to VV pathogenesis.

Angiogenesis as a therapeutic target in arthritis in 2011: learning the lessons of the colorectal cancer experience.

The paradigm of a therapy aimed at inhibiting the formation of blood vessels, which would consequentially deprive cells and tissues of oxygen and nutrients, was born from the concept pioneered by the late Judah Folkman that blood vessel formation is central to the progression and maintenance of diseases which involve cellular metabolism and tissue expansion, and cancer in particular. The prototype targeted angiogenesis inhibitor anti-vascular endothelial growth factor (VEGF) antibody bevacizumab was approved in 2004 for colorectal cancer, and has since been approved for other cancers. Rheumatoid arthritis (RA) is a chronic inflammatory disease, during which inflamed tissue invades and destroys cartilage and bone. The tissue expansion, invasion, expression of cytokines and growth factors and areas of hypoxia which are a feature of RA have resulted in the hypothesis that angiogenesis inhibition may also be beneficial in RA, drawing on the success of bevacizumab. This review focuses on our current understanding of the importance of angiogenesis in RA, and on the lessons which may be learnt from the clinical experiences of angiogenesis blockade, particularly in colorectal cancer.

Regulation of the angiopoietin-Tie ligand-receptor system with a novel splice variant of Tie1 reduces the severity of murine arthritis.

OBJECTIVES: To determine the function of the angiopoietin (Ang)-Tie ligand-receptor system, and to assess the effect of Tie1-751, a naturally occurring extracellular domain of the Tie1 receptor derived by alternative splicing, in an in vivo model of RA. METHODS: In the murine CIA model, expression of endogenous Ang1, Ang2, Tie1 and Tie2 in whole paws was analysed by quantitative RT-PCR. To assess the effect of inhibition of the Ang-Tie axis, Tie1-751 was expressed and fused to the Fc fragment of human IgG1. The effect of Tie1-751-Fc on human umbilical vein endothelial cell (HUVEC) cytoprotection and migration in response to Ang1, either alone or in combination with VEGF, was investigated. Furthermore, an in vitro angiogenesis assay was used to determine the effect of Tie1-751-Fc on Ang1-mediated angiogenesis. Finally, Tie1-751-Fc was administered in CIA, and the effects on clinical disease and joint architecture of hind foot specimens were determined. RESULTS: Gene expression levels of Ang1, Ang2, and receptors Tie1 and Tie2 in whole paws were significantly increased during the progression of arthritis. Tie1-751-Fc significantly inhibited HUVEC cytoprotection and migration in response to Ang1 alone, or Ang1 in combination with VEGF. Tie1-751-Fc also significantly inhibited angiogenesis induced by a combination of Ang1 plus VEGF. Finally, Tie1-751-Fc, when administered intra-peritoneally to arthritic mice, reduced clinical signs of arthritis, damage to joint architecture and infiltration of blood vessels into the synovium. CONCLUSIONS: Our data demonstrate that the Ang-Tie ligand-receptor system is dysregulated in CIA. Tie1-751, a novel splice variant of the Tie1 receptor, inhibits Ang1/VEGF signalling, suggesting that Ang inhibition may be of therapeutic benefit in inflammatory arthritis.

Novel imatinib derivatives with altered specificity between Bcr-Abl and FMS, KIT, and PDGF receptors.

Imatinib is a clinically important ATP analogue inhibitor that targets the tyrosine kinase domain of the intracellular Abl kinase and the PDGF receptor family. Imatinib has revolutionised the treatment of chronic myeloid leukaemia, which is caused by the oncogene Bcr-Abl and certain solid tumours that harbor oncogenic mutations of the PDGF receptor family. As a leading kinase inhibitor, imatinib also provides an excellent model system to investigate how changes in drug design impact biological activity, which is an important consideration for rational drug design. Herein we report a new series of imatinib derivatives that in general have greater activity against the family of PDGF receptors and poorer activity against Abl, as a result of modifications of the phenyl and N-methylpiperazine rings. These new compounds provide a platform for further drug development against the therapeutically important PDGF receptor family and they also provide insight into the engineering of drugs with altered biological activity.