Bernhard Brüne

Goethe-Universität Frankfurt am Main, Frankfurt, Hesse, Germany

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Publications (273)1252.56 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Hypoxia promotes progression of hepatocellular carcinoma (HCC), not only affecting tumor cell proliferation and invasion, but also angiogenesis and thus, increasing the risk of metastasis. Hypoxia inducible factors (HIF)-1α and -2α cause adaptation of tumors to hypoxia, still with uncertainties towards the angiogenic switch. We created a stable knockdown of HIF-1α and HIF-2α in HepG2 cells and generated cocultures of HepG2 spheroids with embryonic bodies as an in vitro tumor model mimicking the cancer microenvironment. The naturally occuring oxygen and nutrient gradients within the cocultures allow us to question the role of distinct HIF isoforms in regulating HCC angiogenesis. In cocultures with a HIF-2α knockdown, angiogenesis was attenuated, while the knockdown of HIF-1α was without effect. Microarray analysis identified plasminogen activator inhibitor 1 (PAI-1) as a HIF-2α target gene in HepG2 cells. The knockdown of PAI-1 in HepG2 cells also lowered angiogenesis. Blocking plasmin, the downstream target of PAI-1, with aprotinin in HIF-2α knockdown (k/d) cells proved a cause-effect relation and restored angiogenesis, with no effect on control cocultures. Suggestively, HIF-2α increases PAI-1 to lower concentrations of active plasmin, thereby supporting angiogenesis. We conclude that the HIF-2α target gene PAI-1 favors the angiogenic switch in HCC. Copyright © 2014. Published by Elsevier Inc.
    Experimental cell research. 12/2014;
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    ABSTRACT: Macrophages play important roles in many diseases and are frequently found in hypoxic areas. A chronic hypoxic microenvironment alters global cellular protein expression but molecular details remain poorly understood. Although hypoxia inducible factor (HIF) is an established transcription factor allowing adaption to acute hypoxia, responses to chronic hypoxia are more complex. Based on a two-dimensional differential gel electrophoresis (2D-DIGE) approach, we aimed to identify proteins that are exclusively expressed under chronic but not acute hypoxia (1% O2). One of the identified proteins was cathepsin B (CTSB) and a knockdown of either HIF-1α or -2α in primary human macrophages pointed to a HIF-2α-dependency. Although ChIP experiments confirmed HIF-2 binding to a CTSB enhancer in acute hypoxia, an increase of CTSB mRNA was only evident under chronic hypoxia. Along those lines, CTSB mRNA stability increased at 48 h but not at 8 h of hypoxia. However, RNA stability at 8 h hypoxia was enhanced by a knockdown of tristetraprolin (TTP). Inactivation of TTP under prolonged hypoxia was facilitated by c-jun N-terminal kinase (JNK) and inhibition of this kinase lowered CTSB mRNA levels and stability. We postulate a TTP-dependent mechanism to explain delayed expression of CTSB under chronic hypoxia. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Molecular and cellular biology. 12/2014;
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    ABSTRACT: Macrophages (MΦ) often accumulate in hypoxic areas, where they significantly influence disease progression. Anti-inflammatory cytokines, such as IL-10, generate alternatively activated macrophages that support tumor growth. To understand how alternative activation affects the transcriptional profile of hypoxic macrophages, we globally mapped binding sites of hypoxia-inducible factor (HIF)-1α and HIF-2α in primary human monocyte-derived macrophages prestimulated with IL-10. 713 HIF-1 and 795 HIF-2 binding sites were identified under hypoxia. Pretreatment with IL-10 altered the binding pattern, with 120 new HIF-1 and 188 new HIF-2 binding sites emerging. HIF-1 binding was most prominent in promoters, while HIF-2 binding was more abundant in enhancer regions. Comparison of ChIP-seq data obtained in other cells revealed a highly cell type specific binding of HIF. In MΦ HIF binding occurred preferentially in already active enhancers or promoters. To assess the roles of HIF on gene expression, primary human macrophages were treated with siRNA against HIF-1α or HIF-2α, followed by genome-wide gene expression analysis. Comparing mRNA expression to the HIF binding profile revealed a significant enrichment of hypoxia-inducible genes previously identified by ChIP-seq. Analysis of gene expression under hypoxia alone and hypoxia/IL-10 showed the enhanced induction of a set of genes including PLOD2 and SLC2A3, while another group including KDM3A and ADM remained unaffected or was reduced by IL-10. Taken together IL-10 influences the DNA binding pattern of HIF and the level of gene induction. Copyright © 2014. Published by Elsevier B.V.
    Biochimica et biophysica acta. 11/2014; 1849(1):10-22.
  • Michaela Jung, Christina Mertens, Bernhard Brüne
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    ABSTRACT: Macrophages are central in regulating iron homeostasis, which is tightly linked to their versatile role during innate immunity. They sequester iron by phagocytosis of senescent erythrocytes and represent a major source of available iron in the body. Macrophage iron homeostasis is coupled to the functional heterogeneity and plasticity of these cells, with their extreme roles during inflammation, immune modulation, and resolution of inflammation. It is now appreciated that the macrophage polarization process dictates expression profiles of genes involved in iron metabolism. Therefore, macrophages have evolved a multitude of mechanisms to sequester, transport, store, and release iron. A new, enigmatic protein entering the iron scene and affecting the macrophage phenotype is lipocalin-2. Iron sequestration in macrophages depletes the microenvironment, thereby limiting extracellular pathogen or tumor growth, while fostering inflammation. In contrast, iron release from macrophages contributes to bystander cell proliferation, which is important for tissue regeneration and repair. This dichotomy is also reflected by the dual role of lipocalin-2 in macrophages. Unfortunately, the iron release macrophage phenotype is also a characteristic of tumor associated macrophages and stimulates tumor cell survival and growth. Iron sequestration versus its release is now appreciated to be associated with the macrophage polarization program and can be used to explain a number of biological functions attributed to distinct macrophage phenotypes. Here we discuss macrophage iron homeostasis with a special focus on lipocalin-2 related to the formation and function of tumor associated macrophages.
    Immunobiology 09/2014; · 2.81 Impact Factor
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    ABSTRACT: Lipopolysaccharide (LPS)-induced activation of TLR4 (toll-like receptor 4) is followed by a subsequent overwhelming inflammatory response, a hallmark of the first phase of sepsis. Therefore, counteracting excessive innate immunity by autophagy is important to contribute to the termination of inflammation. However, the exact molecular details of this interplay are only poorly understood. Here, we show that PELI3/Pellino3 (pellino E3 ubiquitin protein ligase family member 3), which is an E3 ubiquitin ligase and scaffold protein in TLR4-signaling, is impacted by autophagy in macrophages (MΦ) after LPS stimulation. We noticed an attenuated mRNA expression of proinflammatory Il1b (interleukin 1, β) in Peli3 knockdown murine MΦ in response to LPS treatment. The autophagy adaptor protein SQSTM1/p62 (sequestosome 1) emerged as a potential PELI3 binding partner in TLR4-signaling. siRNA targeting Sqstm1 and Atg7 (autophagy related 7), pharmacological inhibition of autophagy by wortmannin as well as blocking the lysosomal vacuolar-type H(+)-ATPase by bafilomycin A 1 augmented PELI3 protein levels, while inhibition of the proteasome had no effect. Consistently, treatment to induce autophagy by MTOR (mechanistic target of rapamycin (serine/threonine kinase)) inhibition or starvation enhanced PELI3 degradation and reduced proinflammatory Il1b expression. PELI3 was found to be ubiquitinated upon LPS stimulation and point mutation of PELI3-lysine residue 316 (Lys316Arg) attenuated Torin2-dependent degradation of PELI3. Immunofluorescence analysis revealed that PELI3 colocalized with the typical autophagy markers MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 β) and LAMP2 (lysosomal-associated membrane protein 2). Our observations suggest that autophagy causes PELI3 degradation during TLR4-signaling, thereby impairing the hyperinflammatory phase during sepsis.
    Autophagy 08/2014; 10(11). · 12.04 Impact Factor
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    ABSTRACT: Emerging lines of evidence indicate that production of reactive oxygen species (ROS) at distinct sites of the nociceptive system contributes to the processing of neuropathic pain. However, the mechanisms underlying ROS production during neuropathic pain processing are not fully understood. We here detected the ROS-generating NADPH oxidase isoform Nox2 in macrophages of dorsal root ganglia (DRGs) in mice. In response to peripheral nerve injury, Nox2-positive macrophages were recruited to DRGs, and ROS production was increased in a Nox2-dependent manner. Nox2-deficient mice displayed reduced neuropathic pain behavior after peripheral nerve injury, whereas their immediate responses to noxious stimuli were normal. Moreover, injury-induced upregulation of tumor necrosis factor α was absent and ATF3-induction was reduced in DRGs of Nox2-deficient mice suggesting an attenuated macrophage-neuron signaling. These data suggest that Nox2-dependent ROS production in macrophages recruited to DRGs contributes to neuropathic pain hypersensitivity, underlining the observation that Nox-derived ROS exert specific functions during the processing of pain.
    Pain 08/2014; · 5.64 Impact Factor
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    ABSTRACT: -Vitamin D deficiency in humans is frequent and has been associated with inflammation. The role of the active hormone, 1,25-dihydroxy-vitamin D3 (1,25-VitD3) in the cardiovascular system is controversial. High doses induce vascular calcification; vitamin D3 deficiency, however, has been linked to cardiovascular disease as the hormone has anti-inflammatory properties. We therefore hypothesized that 1,25-VitD3 promotes regeneration after vascular injury.
    Circulation 07/2014; · 15.20 Impact Factor
  • Dmitry Namgaladze, Bernhard Brüne
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    ABSTRACT: Macrophage polarization elicits various metabolic alterations which in turn influence the polarized phenotype. Activation of glycolytic metabolism accompanies and supports macrophage pro-inflammatory M1 polarization. In contrast, M2 polarization of murine macrophages in response to the Th2 cytokine interleukin-4 (IL-4) was linked to the up-regulation of mitochondrial oxidative metabolism and fatty acid oxidation (FAO), which was necessary for coining an IL-4-polarized phenotype. Here we investigated whether similar mechanisms operate in human macrophages stimulated with IL-4. IL-4 causes only moderate changes of mitochondrial oxidative metabolism and FAO, correlating with an unaltered expression of peroxisome proliferator-activated receptor-γ coactivator 1 α/β (PGC-1α/β), the master transcriptional regulators of mitochondrial biogenesis. Furthermore, attenuating FAO had no effect on IL-4-induced polarization-associated gene expression. Apparently, FAO is dispensable for IL-4-induced polarization of human macrophages, pointing to fundamental differences in the metabolic requirements of macrophage phenotype alterations between mice and humans.
    Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 06/2014; · 4.13 Impact Factor
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    ABSTRACT: Aim: During sepsis macrophages are alternatively activated towards a M2-like phenotype upon contact with apoptotic cells or their secretion products. Simultaneously NADPH oxidase dependent ROS formation is attenuated, thus contributing to immune paralysis. However the exact mechanism remains elusive. Herein we provide mechanistic insights into diminished mRNA stability of the NADPH oxidase Nox2 upon macrophage M2 polarization and thereby reduced ROS formation in sepsis. Results: Murine J774A.1 macrophages were stimulated with conditioned medium of apoptotic T cells, which reduced Nox2 mRNA and protein expression, consequently decreasing ROS-production. A mRNA pulldown approach coupled to mass spectrometry analysis identified the RNA binding protein SYNCRIP attached to the Nox2 mRNA 3´UTR. The binding of SYNCRIP to the 3´UTR of Nox2 mRNA is attenuated after treatment with conditioned medium of apoptotic T cells, followed by Nox2 mRNA destabilization. In in vivo models of polymicrobial sepsis such as cecal ligation and puncture SYNCRIP was strongly downregulated, which was associated with a decreased Nox2 expression in peritoneal macrophages. Innovation: Downregulation of SYNCRIP in macrophages following contact to material of apoptotic cells destabilized Nox2 mRNA and impaired ROS formation, thereby contributing to a M2 phenotype shift of macrophages in sepsis. Conclusion: M2 polarization of macrophages in sepsis results in an attenuated SYNCRIP binding to the 3'UTR of Nox2 mRNA, destabilizing Nox2 mRNA abundance and expression. Consequently, ROS formation needed to fight against recurrent infections is impaired. In conclusion SYNCRIP regulated Nox2 mRNA degradation mediates the hypoinflammatory phase of sepsis.
    Antioxidants and Redox Signaling 05/2014; · 7.19 Impact Factor
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    ABSTRACT: The objective of this study was to investigate, whether the naturally occurring polyphenol resveratrol (Res) enhances the anti-tumor activities of the chemotherapeutic agent oxaliplatin (Ox) in a cell culture model of colorectal cancer, also with regard to a possible inflammatory response and cytotoxic side-effects. Res and Ox in combination synergistically inhibit cell growth of Caco-2 cells, which seems to be due to the induction of different modes of cell death and further leads to an altered cytokine profile of cocultured macrophages. Moreover, combinatorial treatment does not affect non-transformed cells as severe cytotoxicity is not detected in human foreskin fibroblasts and platelets.
    Apoptosis 04/2014; · 4.07 Impact Factor
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    ABSTRACT: Deregulation of the phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR)-70kDa ribosomal protein S6 kinase 1 (p70(S6K)) pathway is commonly observed in many tumors. This pathway controls proliferation, survival, and translation, and its overactivation is associated with poor prognosis for tumor-associated survival. Current efforts focus on the development of novel inhibitors of this pathway. In a cell-based high-throughput screening assay of 15 272 pure natural compounds, we identified pomiferin triacetate as a potent stabilizer of the tumor suppressor programmed cell death 4 (Pdcd4). Mechanistically, pomiferin triacetate appeared as a general inhibitor of the PI3K-Akt-mTOR-p70(S6K) cascade. Interference with this pathway occurred downstream of Akt but upstream of p70(S6K). Specifically, mTOR kinase emerged as the molecular target of pomiferin triacetate, with similar activities against mTOR complexes 1 and 2. In an in vitro mTOR kinase assay pomiferin triacetate dose-dependently inhibited mTOR with an IC50 of 6.2 μM. Molecular docking studies supported the interaction of the inhibitor with the catalytic site of mTOR. Importantly, pomiferin triacetate appeared to be highly selective for mTOR compared to a panel of 17 lipid and 50 protein kinases tested. As a consequence of the mTOR inhibition, pomiferin triacetate efficiently attenuated translation. In summary, pomiferin triacetate emerged as a novel and highly specific mTOR inhibitor with strong translation inhibitory effects. Thus, it might be an interesting lead structure for the development of mTOR- and translation-targeted anti-tumor therapies.
    Biochemical pharmacology 02/2014; · 4.25 Impact Factor
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    ABSTRACT: miRNA let-7e is involved in stem cell differentiation, and metalloproteinases are among its potential target genes. We hypothesized that the inhibitory action of let-7e on regulation of MMP9 expression could represent a crucial mechanism during differentiation of adipose-derived stem cells (ASCs). ASCs were differentiated with all-trans retinoic acid (ATRA) to promote differentiation, and the effect of let-7 silencing during differentiation was tested. Results indicate that ASCs cultured with ATRA differentiated into cells of the epithelial lineage. We found that ASCs cultured with ATRA or transfected with miRNA let-7e expressed epithelial markers such as cytokeratin-18 and early renal organogenesis markers such as Pax2, Wt1, Wnt4 and megalin. Conversely, the specific knockdown of miRNA let-7e in ASCs significantly decreased the expression of these genes, indicating its vital role during the differentiation process. Using luciferase reporter assays, we also showed that MMP9 is a direct target of miRNA let-7e. Thus, our results suggest that miRNA let-7e acts as a matrix metalloproteinase-9 (MMP9) inhibitor and differentiation inducer in ASCs.
    Cell Death & Disease 02/2014; 5:e1048. · 6.04 Impact Factor
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    ABSTRACT: Saturated fatty acids (SFAs) such as palmitate activate inflammatory pathways and elicit an endoplasmic reticulum (ER) stress response in macrophages, thereby contributing to the development of insulin resistance linked to the metabolic syndrome. This study addressed the question of whether or not mitochondrial fatty acid β-oxidation (FAO) affects macrophage responses to SFA. We modulated the activity of carnitine palmitoyl transferase 1A (CPT1A) in macrophage-differentiated THP-1 monocytic cells using genetic or pharmacological approaches, treated the cells with palmitate and analysed the proinflammatory and ER stress signatures. To inhibit FAO, we created THP-1 cells with a stable knockdown (KD) of CPT1A and differentiated them to macrophages. Consequently, in CPT1A-silenced cells FAO was reduced. CPT1A KD in THP-1 macrophages increased proinflammatory signalling, cytokine expression and ER stress responses after palmitate treatment. In addition, in human primary macrophages CPT1A KD elevated palmitate-induced inflammatory gene expression. Pharmacological inhibition of FAO with etomoxir recapitulated the CPT1A KD phenotype. Conversely, overexpression of a malonyl-CoA-insensitive CPT1A M593S mutant reduced inflammatory and ER stress responses to palmitate in THP-1 macrophages. Macrophages with a CPT1A KD accumulated diacylglycerols and triacylglycerols after palmitate treatment, while ceramide accumulation remained unaltered. Moreover, lipidomic analysis of ER phospholipids revealed increased palmitate incorporation into phosphatidylethanolamine and phosphatidylserine classes associated with the CPT1A KD. Our data indicate that FAO attenuates inflammatory and ER stress responses in SFA-exposed macrophages, suggesting an anti-inflammatory impact of drugs that activate FAO.
    Diabetologia 02/2014; · 6.49 Impact Factor
  • Dmitry Namgaladze, Bernhard Brüne
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    ABSTRACT: Macrophage polarization elicits various metabolic alterations which in turn influence the polarized phenotype. Activation of glycolytic metabolism accompanies and supports macrophage pro-inflammatory M1 polarization. In contrast, M2 polarization of murine macrophages in response to the Th2 cytokine interleukin-4 (IL-4) was linked to the up-regulation of mitochondrial oxidative metabolism and fatty acid oxidation (FAO), which was necessary for coining an IL-4-polarized phenotype. Here we investigated whether similar mechanisms operate in human macrophages stimulated with IL-4. IL-4 causes only moderate changes of mitochondrial oxidative metabolism and FAO, correlating with an unaltered expression of peroxisome proliferator-activated receptor-γ coactivator 1 α/β (PGC-1α/β), the master transcriptional regulators of mitochondrial biogenesis. Furthermore, attenuating FAO had no effect on IL-4-induced polarization-associated gene expression. Apparently, FAO is dispensable for IL-4-induced polarization of human macrophages, pointing to fundamental differences in the metabolic requirements of macrophage phenotype alterations between mice and humans.
    Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 01/2014; · 4.13 Impact Factor
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    ABSTRACT: Rapid alterations in protein expression are commonly regulated by adjusting translation. In addition to cap-dependent translation, which is e.g. induced by pro-proliferative signaling via the mammalian target of rapamycin (mTOR)-kinase, alternative modes of translation, such as internal ribosome entry site (IRES)-dependent translation, are often enhanced under stress conditions, even if cap-dependent translation is attenuated. Common stress stimuli comprise nutrient deprivation, hypoxia, but also inflammatory signals supplied by infiltrating immune cells. Yet, the impact of inflammatory microenvironments on translation in tumor cells still remains largely elusive. In the present study, we aimed at identifying translationally deregulated targets in tumor cells under inflammatory conditions. Using polysome profiling and microarray analysis, we identified cyp24a1 (1,25-dihydroxyvitamin D3 24-hydroxylase) to be translationally upregulated in breast tumor cells co-cultured with conditioned medium of activated monocyte-derived macrophages (CM). Using bicistronic reporter assays, we identified and validated an IRES within the 5' untranslated region (5'UTR) of cyp24a1, which enhances translation of cyp24a1 upon CM treatment. Furthermore, IRES-dependent translation of cyp24a1 by CM was sensitive to phosphatidyl-inositol-3-kinase (PI3K) inhibition, while constitutive activation of Akt sufficed to induce its IRES activity. Our data provide evidence that cyp24a1 expression is translationally regulated via an IRES element, which is responsive to an inflammatory environment. Considering the negative feedback impact of cyp24a1 on the vitamin D responses, the identification of a novel, translational mechanism of cyp24a1 regulation might open new possibilities to overcome the current limitations of vitamin D as tumor therapeutic option.
    PLoS ONE 01/2014; 9(1):e85314. · 3.53 Impact Factor
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    ABSTRACT: Lipoxins belong to the family of so-called pro-resolving endogenous lipid mediators which are derived from arachidonic acid and play a key role in the counter-regulation of inflammation. Arachidonic acid is also precursor of multiple pro-inflammatory lipid mediators, such as prostaglandins and leukotrienes, which are simultaneously present in biological compartments. The close structural relationship between several of these lipid mediators and the absence of blank matrix samples enormously complicates the unequivocal identification of these compounds. The determination of lipoxin A4 has been accomplished by chromatographic separation using a C18 reversed phase column and tandem mass spectrometry detection. Samples were liquid-liquid extracted with ethyl acetate before injection. Identification of the analyte was done based on three criteria: retention time, ratio of the m/z transitions and MS/MS spectrum. To avoid false positive results due to endogenous interferences, the extracted samples were re-injected into a chiral Lux Amylose-2 chromatographic column. The authors recommend the use of chiral chromatography in the determination of pro-resolving lipid mediators, together with transition area ratio and fragmentation spectra to improve selectivity for identification and quantitation purposes.
    Talanta 01/2014; 127:82–87. · 3.50 Impact Factor
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    ABSTRACT: Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated inflammatory autoimmune disease model of multiple sclerosis (MS). The inflammatory process is initiated by activation and proliferation of T cells and monocytes and by their subsequent migration into the central nervous system (CNS), where they induce demyelination and neurodegeneration. Prostaglandin E2 (PGE2)-synthesized by cyclooxygenase 2 (COX-2)- has both pro- and anti-inflammatory potential, which is translated via four different EP receptors. We hypothesized that PGE2 synthesized in the preclinical phase by peripheral immune cells exerts pro-inflammatory properties in the EAE model. To investigate this, we used a bone marrow transplantation model, which enables PGE2 synthesis or EP receptor expression to be blocked specifically in peripheral murine immune cells. Our results reveal that deletion of COX-2 or its EP4 receptor in bone marrow-derived cells leads to a significant delay in the onset of EAE. This effect is due to an impaired preclinical inflammatory process indicated by a reduced level of the T cell activating interleukin-6 (IL-6), reduced numbers of T cells and of the T cell secreted interleukin-17 (IL-17) in the blood of mice lacking COX-2 or EP4 in peripheral immune cells. Moreover, mice lacking COX-2 or EP4 in bone marrow-derived cells show a reduced expression of matrix metalloproteinase 9 (MMP9), which results in decreased infiltration of monocytes and T cells into the CNS. In conclusion, our data demonstrate that PGE2 synthesized by monocytes in the early preclinical phase promotes the development of EAE in an EP4 receptor dependent manner.
    Biochemical pharmacology 12/2013; · 4.25 Impact Factor
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    ABSTRACT: Prostacyclin is an important mediator of peripheral painsensation. Here, we investigated its potential participation in mediating neuropathic pain and found that prostacyclin receptor (IP)-knockout mice exhibit markedly decreased pain behaviour. Application of an IP-antagonist to the injury site or selective IP-deficiency in myeloid cells mimicked the antinociceptive effect observed in IP-knockout mice. At the site of nerve injury IP was expressed in interleukin (IL) 1beta-containing resident macrophages, which were less frequent in IP knockout mice. Local administration of the IP-agonist cicaprost inhibited macrophage migration in vitro and promoted accumulation of IP- and IL1beta-expressing cells as well as an increase of IL1beta-concentrations at the application site in vivo. Fittingly, the IL1-receptor antagonist anakinra (IL-1ra) decreased neuropathic pain behaviour in wild type, but not in IP-knockout mice. Finally, continuous, but not single administration, of the cyclooxygenase inhibitor meloxicam early after nerve injury decreased pain behaviour and the number of resident macrophages. Thus, early synthesis of prostacyclin at the site of injury causes accumulation of IL1beta-expressing macrophages as a key step for neuropathic pain after traumatic injury.
    Pain 12/2013; · 5.64 Impact Factor
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    ABSTRACT: Aims: The present study assessed the functions of the transcription factor hypoxia inducible factor (HIF) in sensory neurons in models of acute, inflammatory, ischemic and neuropathic pain. The alpha subunit, HIF1α was specifically deleted in neurons of the dorsal root ganglia by mating HIF1α-flfl mice with SNScre mice. Results: SNS-HIF1α-/- mice were more sensitive to noxious heat and cold pain stimulation than HIF1α-flfl control mice. They also showed heightened first-phase nociceptive responses in the formalin and capsaicin tests with increased numbers of cFos positive neurons in the dorsal horn, and intensified hyperalgesia in early phases after paw inflammation and hind limb ischemia/reperfusion. The behavioral cold and heat pain hypersensitivity was explained by increased calcium fluxes upon transient receptor potential channel activation in primary sensory neurons of SNS-HIF1α-/- mice and lowered electrical activation thresholds of sensory fibers. SNS-HIF1α-/- mice however, developed less neuropathic pain after sciatic nerve injury, associated with an abrogation of HIF1-mediated gene upregulation. Innovation: The results suggest that HIF1α is protective in terms of acute heat and cold pain but in case of ongoing activation in injured neurons it may promote the development of neuropathic pain. Conclusion: The duality of HIF1 in pain regulation may impact on the side effects of drugs targeting HIF1, which are being developed e.g. as anticancer agents. Specifically in patients with cancer neuropathy however, temporary HIF1 inhibition might provide a welcome combination of growth and pain reduction.
    Antioxidants & Redox Signaling 10/2013; · 8.20 Impact Factor
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    ABSTRACT: Hypoxia inducible factors (HIFs) are important mediators of the cellular adaptive response during acute hypoxia. The role of HIF-1 and HIF-2 during prolonged periods of hypoxia, i.e. chronic hypoxia is less defined. Therefore, we used human THP-1 macrophages with a knockdown of either HIF-1α, HIF-2α, or both HIFα-subunits, incubated them for several days under hypoxia (1% O2), and analyzed responses to hypoxia using 2D-DIGE coupled to MS/MS-analysis. Chronic hypoxia was defined as a time point when the early but transient accumulation of HIFα-subunits and mRNA expression of classical HIF target genes returned towards basal levels, with a new steady state that was constant from 72h onwards. From roughly 800 spots, that were regulated comparing normoxia to chronic hypoxia, about 100 proteins were unambiguously assigned during MS/MS-analysis. Interestingly, a number of glycolytic genes were up-regulated, while a number of inner mitochondrial membrane proteins were down-regulated independently of HIF-1α or HIF-2α. Chronic hypoxic conditions depleted the mitochondrial mass by autophagy, which occurred independently of HIF proteins. Macrophages tolerate periods of chronic hypoxia very well and adaptive responses occur, at least in part, independently of HIF-1α and/or HIF-2α and comprise mitophagy as a pathway of particular importance.
    Biochimica et Biophysica Acta 10/2013; · 4.66 Impact Factor

Publication Stats

8k Citations
1,252.56 Total Impact Points

Institutions

  • 2005–2014
    • Goethe-Universität Frankfurt am Main
      • Institute of Biochemistry
      Frankfurt, Hesse, Germany
  • 2005–2013
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany
  • 2006–2011
    • Università degli Studi di Teramo
      • Faculty of Veterinary Medicine
      Teramo, Abruzzo, Italy
  • 2005–2006
    • Università degli Studi di Urbino "Carlo Bo"
      • Istituto di Farmacologia e Farmacognosia
      Urbino, The Marches, Italy
  • 2001–2005
    • Technische Universität Kaiserslautern
      • Fachgebiet Zellbiologie
      Kaiserslautern, Rhineland-Palatinate, Germany
  • 1995–2005
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Faculty of Medicine
      Erlangen, Bavaria, Germany
  • 2003
    • Universität zu Lübeck
      • Institut für Physiologie
      Lübeck, Schleswig-Holstein, Germany
  • 2002
    • Sapienza University of Rome
      Roma, Latium, Italy
    • Università della Calabria
      • Department of Pharmaco-Biology
      Rende, Calabria, Italy
  • 1999
    • Case Western Reserve University School of Medicine
      Cleveland, Ohio, United States
  • 1997
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
  • 1987–1997
    • Universität Konstanz
      Constance, Baden-Württemberg, Germany
  • 1996
    • National Public Health Institute
      Helsinki, Southern Finland Province, Finland
  • 1993
    • Research Triangle Park Laboratories, Inc.
      Raleigh, North Carolina, United States
  • 1991
    • Karolinska Institutet
      • Institutet för miljömedicin - IMM
      Solna, Stockholm, Sweden