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Dive into the research topics where Wanja M. Bernhardt is active.

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Featured researches published by Wanja M. Bernhardt.


Journal of Clinical Investigation | 2007

Hypoxia promotes fibrogenesis in vivo via HIF-1 stimulation of epithelial-to-mesenchymal transition

Debra F. Higgins; Kuniko Kimura; Wanja M. Bernhardt; Nikita Shrimanker; Yasuhiro Akai; Bernd Hohenstein; Yoshihiko Saito; Randall S. Johnson; Matthias Kretzler; Clemens D. Cohen; Kai-Uwe Eckardt; Masayuki Iwano; Volker H. Haase

Hypoxia has been proposed as an important microenvironmental factor in the development of tissue fibrosis; however, the underlying mechanisms are not well defined. To examine the role of hypoxia-inducible factor-1 (HIF-1), a key mediator of cellular adaptation to hypoxia, in the development of fibrosis in mice, we inactivated Hif-1alpha in primary renal epithelial cells and in proximal tubules of kidneys subjected to unilateral ureteral obstruction (UUO) using Cre-loxP-mediated gene targeting. We found that Hif-1alpha enhanced epithelial-to-mesenchymal transition (EMT) in vitro and induced epithelial cell migration through upregulation of lysyl oxidase genes. Genetic ablation of epithelial Hif-1alpha inhibited the development of tubulointerstitial fibrosis in UUO kidneys, which was associated with decreased interstitial collagen deposition, decreased inflammatory cell infiltration, and a reduction in the number of fibroblast-specific protein-1-expressing (FSP-1-expressing) interstitial cells. Furthermore, we demonstrate that increased renal HIF-1alpha expression is associated with tubulointerstitial injury in patients with chronic kidney disease. Thus, we provide clinical and genetic evidence that activation of HIF-1 signaling in renal epithelial cells is associated with the development of chronic renal disease and may promote fibrogenesis by increasing expression of extracellular matrix-modifying factors and lysyl oxidase genes and by facilitating EMT.


Journal of The American Society of Nephrology | 2010

Inhibition of Prolyl Hydroxylases Increases Erythropoietin Production in ESRD

Wanja M. Bernhardt; Michael S. Wiesener; Paul Scigalla; James Chou; Roland E. Schmieder; Volkmar Günzler; Kai-Uwe Eckardt

The reasons for inadequate production of erythropoietin (EPO) in patients with ESRD are poorly understood. A better understanding of EPO regulation, namely oxygen-dependent hydroxylation of the hypoxia-inducible transcription factor (HIF), may enable targeted pharmacological intervention. Here, we tested the ability of fibrotic kidneys and extrarenal tissues to produce EPO. In this phase 1 study, we used an orally active prolyl-hydroxylase inhibitor, FG-2216, to stabilize HIF independent of oxygen availability in 12 hemodialysis (HD) patients, six of whom were anephric, and in six healthy volunteers. FG-2216 increased plasma EPO levels 30.8-fold in HD patients with kidneys, 14.5-fold in anephric HD patients, and 12.7-fold in healthy volunteers. These data demonstrate that pharmacologic manipulation of the HIF system can stimulate endogenous EPO production. Furthermore, the data indicate that deranged oxygen sensing--not a loss of EPO production capacity--causes renal anemia.


American Journal of Pathology | 2008

2-Methoxyestradiol Inhibits Hypoxia-Inducible Factor-1α and Suppresses Growth of Lesions in a Mouse Model of Endometriosis

Christian M. Becker; Nadine Rohwer; Tae Funakoshi; Thorsten Cramer; Wanja M. Bernhardt; Amy E. Birsner; Judah Folkman; Robert J. D'Amato

Endometriosis, the presence of ectopic endometrial tissue outside the uterine cavity, is a common disease affecting women during their reproductive years. Current therapeutic success is often unsatisfactory because of limited insight into disease mechanisms. Nevertheless, angiogenesis plays an essential role in the pathogenesis of the disease, making it a potential novel target for therapy. In the current study, we demonstrate in an established mouse model of endometriosis that transient hypoxia in transplanted endometriosis-like lesions results in the up-regulation of hypoxia-inducible factor-1alpha (HIF-1alpha), leading to the expression of vascular endothelial growth factor (VEGF), a key player in endometriosis-associated angiogenesis. Systemic treatment with the angiogenesis inhibitor 2-methoxyestradiol suppressed HIF-1alpha expression in vivo, resulting in a decreased downstream expression of HIF-1alpha target genes, such as for VEGF, phosphoglycerate kinase, and glucose transporter-1. 2-Methoxyestradiol also suppressed VEGF-induced vascular permeability, as demonstrated in a modified Miles assay. Finally, systemic treatment with 2-methoxyestradiol significantly inhibited the growth of endometriosis-like lesions in a dose-dependent manner. In conclusion, hypoxia appears to play an important role in the pathogenesis of endometriosis and endometriosis-associated angiogenesis, and the angiogenesis inhibitor 2-methoxyestradiol may be a potential candidate for systemic treatment in the future.


Journal of The American Society of Nephrology | 2008

HIF Activation Protects From Acute Kidney Injury

Alexander Weidemann; Wanja M. Bernhardt; Bernd Klanke; Christoph Daniel; Björn Buchholz; Valentina Câmpean; Kerstin Amann; Christina Warnecke; Michael S. Wiesener; Kai-Uwe Eckardt; Carsten Willam

The contribution of hypoxia to cisplatin-induced renal tubular injury is controversial. Because the hypoxia-inducible factor (HIF) pathway is a master regulator of adaptation to hypoxia, we measured the effects of cisplatin on HIF accumulation in vitro and in vivo, and tested whether hypoxic preconditioning is protective against cisplatin-induced injury. We found that cisplatin did not stabilize HIF-1alpha protein in vitro or in vivo under normoxic conditions. However, hypoxic preconditioning of cisplatin-treated proximal tubular cells in culture reduced apoptosis in an HIF-1alpha-dependent fashion and increased cell proliferation as measured by BrdU incorporation. In vivo, rats preconditioned with carbon monoxide before cisplatin administration had significantly better renal function than rats kept in normoxic conditions throughout. Moreover, the histomorphological extent of renal damage and tubular apoptosis was reduced by the preconditional treatment. Therefore, development of pharmacologic agents to induce renal HIF might provide a new approach to ameliorate cisplatin-induced nephrotoxicity.


Proceedings of the National Academy of Sciences of the United States of America | 2009

Donor treatment with a PHD-inhibitor activating HIFs prevents graft injury and prolongs survival in an allogenic kidney transplant model.

Wanja M. Bernhardt; U. Gottmann; F. Doyon; Björn Buchholz; Valentina Campean; Johannes Schödel; A. Reisenbuechler; S. Klaus; M. Arend; L. Flippin; Carsten Willam; Michael S. Wiesener; B. Yard; Christina Warnecke; Kai-Uwe Eckardt

Long-term survival of renal allografts depends on the chronic immune response and is probably influenced by the initial injury caused by ischemia and reperfusion. Hypoxia-inducible transcription factors (HIFs) are essential for adaptation to low oxygen. Normoxic inactivation of HIFs is regulated by oxygen-dependent hydroxylation of specific prolyl-residues by prolyl-hydroxylases (PHDs). Pharmacological inhibition of PHDs results in HIF accumulation with subsequent activation of tissue-protective genes. We examined the effect of donor treatment with a specific PHD inhibitor (FG-4497) on graft function in the Fisher–Lewis rat model of allogenic kidney transplantation (KTx). Orthotopic transplantation of the left donor kidney was performed after 24 h of cold storage. The right kidney was removed at the time of KTx (acute model) or at day 10 (chronic model). Donor animals received a single dose of FG-4497 (40 mg/kg i.v.) or vehicle 6 h before donor nephrectomy. Recipients were followed up for 10 days (acute model) or 24 weeks (chronic model). Donor preconditioning with FG-4497 resulted in HIF accumulation and induction of HIF target genes, which persisted beyond cold storage. It reduced acute renal injury (serum creatinine at day 10: 0.66 ± 0.20 vs. 1.49 ± 1.36 mg/dL; P < 0.05) and early mortality in the acute model and improved long-term survival of recipient animals in the chronic model (mortality at 24 weeks: 3 of 16 vs. 7 of 13 vehicle-treated animals; P < 0.05). In conclusion, pretreatment of organ donors with FG-4497 improves short- and long-term outcomes after allogenic KTx. Inhibition of PHDs appears to be an attractive strategy for organ preservation that deserves clinical evaluation.


PLOS ONE | 2010

Activation of Hypoxia Inducible Factor 1 Is a General Phenomenon in Infections with Human Pathogens

Nadine Werth; Christiane Beerlage; Christian Rosenberger; Amir S. Yazdi; Markus Edelmann; Amro Amr; Wanja M. Bernhardt; Christof von Eiff; Karsten Becker; Andrea Schäfer; Andreas Peschel; Volkhard A. J. Kempf

Background Hypoxia inducible factor (HIF)-1 is the key transcriptional factor involved in the adaptation process of cells and organisms to hypoxia. Recent findings suggest that HIF-1 plays also a crucial role in inflammatory and infectious diseases. Methodology/Principal Findings Using patient skin biopsies, cell culture and murine infection models, HIF-1 activation was determined by immunohistochemistry, immunoblotting and reporter gene assays and was linked to cellular oxygen consumption. The course of a S. aureus peritonitis was determined upon pharmacological HIF-1 inhibition. Activation of HIF-1 was detectable (i) in all ex vivo in biopsies of patients suffering from skin infections, (ii) in vitro using cell culture infection models and (iii) in vivo using murine intravenous and peritoneal S. aureus infection models. HIF-1 activation by human pathogens was induced by oxygen-dependent mechanisms. Small colony variants (SCVs) of S. aureus known to cause chronic infections did not result in cellular hypoxia nor in HIF-1 activation. Pharmaceutical inhibition of HIF-1 activation resulted in increased survival rates of mice suffering from a S. aureus peritonitis. Conclusions/Significance Activation of HIF-1 is a general phenomenon in infections with human pathogenic bacteria, viruses, fungi and protozoa. HIF-1-regulated pathways might be an attractive target to modulate the course of life-threatening infections.


Methods in Enzymology | 2007

Organ Protection by Hypoxia and Hypoxia‐Inducible Factors

Wanja M. Bernhardt; Christina Warnecke; Carsten Willam; Tetsuhiro Tanaka; Michael S. Wiesener; Kai-Uwe Eckardt

Since the first description of a protective effect of hypoxic preconditioning in the heart, the principle of reducing tissue injury in response to ischemia by prior exposure to hypoxia was confirmed in a number of cells and organs. However, despite impressive preclinical results, hypoxic preconditioning has so far failed to reach clinical application. Nevertheless, it remains of significant interest to induce genes that are normally activated during hypoxia and ischemia as part of an endogenous escape mechanism prior to or during the early phase of an ischemic insult. This approach has recently been greatly facilitated by the identification of hypoxia-inducible factors (HIFs), transcription factors that operate as a master switch in the cellular response to hypoxia. Far more than 100 target genes are regulated by HIF, including genes such as erythropoietin and hemoxygenase-1, which have been shown to be tissue-protective. The identification of small molecule inhibitors of the oxygen-sensing HIF-prolyl hydroxlases now offers the possibility to mimic the hypoxic response by pharmacological stabilization of HIF in order to achieve organ protection. Oxygen-independent activation of HIF is therefore a promising therapeutic strategy for the prevention of organ injury and failure.


American Journal of Pathology | 2009

HIF-prolyl hydroxylases in the rat kidney: physiologic expression patterns and regulation in acute kidney injury.

Johannes Schödel; Bernd Klanke; Alexander Weidemann; Björn Buchholz; Wanja M. Bernhardt; Marko Bertog; Kerstin Amann; Christoph Korbmacher; Michael S. Wiesener; Christina Warnecke; Armin Kurtz; Kai-Uwe Eckardt; Carsten Willam

Hypoxia-inducible transcription factors (HIFs) play important roles in the response of the kidney to systemic and regional hypoxia. Degradation of HIFs is mediated by three oxygen-dependent HIF-prolyl hydroxylases (PHDs), which have partially overlapping characteristics. Although PHD inhibitors, which can induce HIFs in the presence of oxygen, are already in clinical development, little is known about the expression and regulation of these enzymes in the kidney. Therefore, we investigated the expression levels of the three PHDs in both isolated tubular cells and rat kidneys. All three PHDs were present in the kidney and were expressed predominantly in three different cell populations: (a) in distal convoluted tubules and collecting ducts (PHD1,2,3), (b) in glomerular podocytes (PHD1,3), and (c) in interstitial fibroblasts (PHD1,3). Higher levels of PHDs were found in tubular segments of the inner medulla where oxygen tensions are known to be physiologically low. PHD expression levels were unchanged in HIF-positive tubular and interstitial cells after induction by systemic hypoxia. In rat models of acute renal injury, changes in PHD expression levels were variable; while cisplatin and ischemia/reperfusion led to significant decreases in PHD2 and 3 expression levels, no changes were seen in a model of contrast media-induced nephropathy. These results implicate the non-uniform expression of HIF-regulating enzymes that modify the hypoxic response in the kidney under both regional and temporal conditions.


European Journal of Heart Failure | 2006

Stabilization of hypoxia inducible factor rather than modulation of collagen metabolism improves cardiac function after acute myocardial infarction in rats

Sebastian Philipp; Jan Steffen Jürgensen; Jens Fielitz; Wanja M. Bernhardt; Alexander Weidemann; Bernhard Pilz; Rainer Dietz; Vera Regitz-Zagrosek; Kai-Uwe Eckardt; Roland Willenbrock

Prolyl hydroxylase domain‐containing enzymes (PHD) hydroxylate a proline residue that controls the degradation of hypoxia inducible factor (HIF). Hypoxia inhibits this hydroxylation thus increasing HIF levels. HIF is upregulated in ischemic tissues, growing tumors and in nonischemic, mechanically stressed myocardium. Pharmacological inhibition of prolyl 4‐hydroxylase (P4‐H) stabilizes HIF‐protein in vitro and may modulate collagen turnover. The aims of this study were to investigate whether inhibition of P4‐H protects myocardium against ischemia, and whether the observed effects are related to modulation of collagen metabolism or due to the stabilization of HIF.


Experimental Cell Research | 2008

The specific contribution of hypoxia-inducible factor-2α to hypoxic gene expression in vitro is limited and modulated by cell type-specific and exogenous factors

Christina Warnecke; Alexander Weidemann; Melanie Volke; Ruth Schietke; Xiaoqing Wu; Thomas Hackenbeck; Wanja M. Bernhardt; Carsten Willam; Kai-Uwe Eckardt; Michael S. Wiesener

Cellular integrity in hypoxia is dependent on molecular adaptations dominated by the heterodimeric transcription factor hypoxia-inducible factor (HIF). The HIF complex contains one of two alternative oxygen-regulated alpha-subunits considered to play distinct roles in the hypoxia response. Although HIF-2alpha may be more important in tumour biology and erythropoiesis, the spectrum of individual target genes is still insufficiently characterized. We therefore performed an Affymetrix gene array on Hep3B cells stimulated with a hypoxia-mimetic and transfected with either HIF-1alpha or HIF-2alpha siRNA. 271 transcripts were found to be induced HIF-dependently, including most previously identified HIF targets and a number of novel genes. Most were influenced by HIF-1alpha knock-down, whereas a smaller number were regulated by HIF-2alpha. Validation of a selection of genes by RNase protection confirmed the hypoxic regulation and HIF-1alpha- or HIF-2alpha-dependency in most cases, with the latter showing a lower amplitude. Many HIF-2alpha targets also responded to HIF-1alpha knock-down. Interestingly, regulation by HIF-2alpha was markedly influenced not only by cell type, but also by cell culture conditions, features that were not shared with HIF-1alpha-regulated genes. Thus, HIF-2alpha effects are modulated by a number of intrinsic and extrinsic factors which may be most relevant in tumour cells.

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Dive into the Wanja M. Bernhardt's collaboration.

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Kai-Uwe Eckardt

University of Erlangen-Nuremberg

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Michael S. Wiesener

University of Erlangen-Nuremberg

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Carsten Willam

University of Erlangen-Nuremberg

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Christina Warnecke

University of Erlangen-Nuremberg

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Nicolai Burzlaff

University of Erlangen-Nuremberg

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B. Motsch

University of Erlangen-Nuremberg

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C. Heim

University of Erlangen-Nuremberg

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M. Weyand

University of Erlangen-Nuremberg

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