[show abstract][hide abstract] ABSTRACT: Langerhans cells (LCs) are dendritic cells (DCs) residing in epithelia, where they critically regulate immunity and tolerance. The p14 adaptor molecule is part of the late endosomal/lysosomal adaptor and MAPK and mTOR activator/regulator (LAMTOR) complex, thereby contributing to the signal transduction of the "extracellular signaling-regulated kinase" (ERK) and the "mammalian target of rapamycin" (mTOR) cascade. Furthermore, p14 represents an important regulator for endosomal sorting processes within the cell. Mutated, dysfunctional p14 leads to a human immunodeficiency disorder with endosomal/lysosomal defects in immune cells. Since p14 participates in the regulation of endosomal trafficking, growth factor signaling and cell proliferation, we investigated the role of p14 in mouse DCs/LCs using a conditional knock out mouse model. p14-deficient animals displayed a virtually complete loss of LCs in the epidermis early after birth due to impaired proliferation and increased apoptosis of LCs. Repopulation analysis after application of contact sensitizer leads to the recruitment of a transient LC population, predominantly consisting of short-term LCs. The underlying molecular mechanism involves the p14-mediated disruption of the LAMTOR complex which results in the malfunction of both ERK and mTOR signal pathways. Hence, we conclude that p14 acts as a novel and essential regulator of LC homeostasis in vivo.
[show abstract][hide abstract] ABSTRACT: Dysregulation of the insulin-like growth factor (IGF) axis is implicated in the development of benign prostatic hyperplasia (BPH) and prostate cancer (PCa), two of the most common diseases affecting elderly males. PCa is the second leading cause of male-related cancer death in Western societies. Although distinct pathologies, BPH and PCa are both characterized by extensive stromal remodeling, in particular fibroblast-to-myofibroblast differentiation thought to be induced by elevated local production of transforming growth factor beta 1 (TGFβ1). We previously showed that TGFβ1-mediated fibroblast-to-myofibroblast differentiation of primary human prostatic stromal cells (PrSCs) resulted in dsyregulation of several components of the IGF axis, including induction of IGF binding protein 3 (IGFBP3). Using isoform-specific lentiviral-mediated knockdown, we demonstrate herein that IGFBP3 is essential for TGFβ1-mediated differentiation. Whilst recombinant human IGFBP3 alone was not sufficient to induce differentiation, IGFBP3 synergistically potentiated TGFβ1-mediated stromal remodeling predominantly via an IGF-independent mechanism. Consistent with these in vitro findings, IGFBP3 immunohistochemistry revealed elevated levels of IGFBP3 in the hyperplastic fibromuscular stroma of BPH specimens and in the tumor-adjacent stroma of high-grade PCa. Collectively, these data indicate that dysregulation of the stromal IGF axis, in particular elevated IGFBP3, plays a crucial role in fibroblast-to-myofibroblast differentiation in the diseased prostatic stroma and indicate the therapeutic potential of inhibiting stromal remodeling and the resulting dysregulation of the stromal IGF axis as a novel strategy for the treatment of advanced PCa and BPH.
[show abstract][hide abstract] ABSTRACT: Lipocalin-2 (Lcn2) expression contributes to ischemia and reperfusion injury (IRI) by enhancing pro-inflammatory responses. The aim of this work was to elucidate the regulation of Lcn2 during hypoxia and its effects on the expression of key chemokines and adhesion molecules. Lcn2 wt and Lcn2(-/-) mice were used in a heterotopic heart transplantation model. Quantitative RT-PCR was applied for chemokine gene expression analysis. Reporter gene studies were used to elucidate the regulation of the Lcn2 promoter by hypoxia. HIF-1β expression led to a 2.4-fold induction of the Lcn2 promoter. Apart from an earlier onset of granulocyte infiltration in the Lcn2 wt setting after 2 h of reperfusion compared with the Lcn2(-/-) setting (P < 0.013), exogenous application of recombinant Lcn2 revealed a trend toward increase of granulocyte infiltration. Analyzed chemokines were expressed significantly higher in the Lcn2 wt setting at 2 h of reperfusion (P ≤ 0.05). The number of apoptotic cells observed in Lcn2(-/-) grafts was significantly higher than in the Lcn2 wt setting. Our results indicate that Lcn2 affects granulocyte infiltration in the reperfused graft by modulating the expression of chemokines, their receptors and the apoptotic rate.
Transplant International 05/2013; · 3.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: Reactive oxygen species (ROS) generated by NADPH oxidases play an important role in cellular signal transduction regulating cell proliferation, survival and differentiation. NADPH oxidase 4 (Nox4) induces cellular senescence in human endothelial cells; however, intracellular targets for Nox4 remained elusive. Here we show that Nox4 induces mitochondrial dysfunction in human endothelial cells. Nox4 depletion induced alterations in mitochondrial morphology, stabilized mitochondrial membrane potential, and decreased production of hydrogen peroxide in mitochondria. High-resolution respirometry in permeabilized cells combined with native polyacrylamide gel electrophoresis demonstrated that Nox4 specifically inhibits the activity of mitochondrial electron transport chain complex I, and this was associated with a decreased concentration of complex I subunits. These data suggest a new pathway by which sustained Nox4 activity decreases mitochondrial function.
[show abstract][hide abstract] ABSTRACT: Tetrahydrobiopterin has been shown to efficiently abrogate ischemia reperfusion injury (IRI). However, it is unclear, whether its beneficial action relies on cofactor activity of one of the five known tetrahydrobiopterin-dependent reactions or on its antioxidative capacity. We therefore compared tetrahydrobiopterin with the pterin derivate tetrahydroneopterin (similar biochemical properties, but no nitric oxide synthase cofactor activity) and the antioxidants vitamin C and 5-methyltetrahydrofolate. Donor mice were pretreated with tetrahydrobiopterin, tetrahydroneopterin, vitamin C, or 5-methyltetrahydrofolate. Pancreatic grafts were subjected to 16-h cold ischemia time and implanted in syngeneic recipients. Untreated and nontransplanted animals served as controls. Following 2-h reperfusion, microcirculation was analyzed by intravital fluorescence microscopy. Graft damage was assessed by histology and nitrotyrosine immunostaining, and tetrahydrobiopterin levels were determined by HPLC. Recipient survival served as ultimate readout. Prolonged cold ischemia time resulted in microcirculatory breakdown. Only tetrahydrobiopterin pretreatment succeeded to preserve the capillary net, whereas all other compounds showed no beneficial effects. Along with increased intragraft tetrahydrobiopterin levels during recovery and implantation, only tetrahydrobiopterin pretreatment led to significant reduction of IRI-related parenchymal damage enabling recipient survival. These results show a striking superiority of tetrahydrobiopterin in preventing lethal IRI compared with related compounds and suggest nitric oxide synthases as treatment target.
Transplant International 07/2012; 25(10):1084-1095. · 3.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: The setup of an islet isolation facility designed along the rules of good manufacturing practice (GMP) is a technically challenging, cost and time intensive process. ( 1) Consequently, several institutions have decided to perform transplantation of islets isolated at another center with an already standing expertise. Such a solution includes the necessity to transport the isolated islets from the isolation to the transplantation facility. In spite of its importance, an ideal solution for the transport of the isolated human islets has still not been established. Here, we present an islet transport device suited to transport human islet cells under reproducible conditions and minimized cell stress. The transport simulation of the human islets was performed in a transfused "rotary transport system for islets" termed "ROTi." Besides measuring standard metabolic (LDH, lactate, glucose) and physical parameters (pH, dissolved oxygen and temperature), we used five different live stains in combination with real time live confocal microscopy to document islet quality parameters. As live stains we added tetramethylrhodamine methyl ester, cell permeant acetoxymethylester, propidium iodide, annexin-fitc and fluorescent wheat germ agglutinin, and assessed mitochondrial membrane potentials, calcium levels, cell death, apoptosis or cell morphology, respectively. We compared the viability of human islets after 24 h incubation in the ROTi device to an incubation simulating "standard" shipment of islets in 50 ml tubes. All cell viability parameters studied (mitochondrial membrane potentials, calcium content, apoptosis, cell death as well as cell morphology) documented a significantly better cell viability in the ROTi fraction compared with the simulated "standard" shipment fraction. Besides maintaining islet cell viability, the ROTi bears the advantage of a better reproducibility of islet transport conditions.
[show abstract][hide abstract] ABSTRACT: Despite recent advances in therapy, multiple myeloma, the second most common hematologic tumor in the Western world, is still incurable. Identification of substances that display a wide range of tumor-killing activities and target cancer-specific pathways constitute a basis for the development of novel therapies. In this study, we investigate the cytotoxic effect of the natural substance cnicin in multiple myeloma. Cnicin treatment reveals potent antiproliferative effects and induces cell death in cell lines and primary myeloma cells even in the presence of survival cytokines and the tumor microenvironment. Other cell lines of hematopoietic origin also succumb to cell death whereas stromal cells and endothelial cells are unaffected. We show that activation of caspases, accumulation of reactive oxygen species and downregulation of nuclear factor kappa-light-chain-enhancer of activated B cell contribute to the cytotoxic effects of cnicin. Microarray analysis reveals downregulation of Pim-2, a serine/threonine kinase. We provide evidence that Pim-2 constitutes a new survival kinase for myeloma cells in vitro and is highly expressed in malignant but not in normal plasma cells in vivo. Combining cnicin with current standard or experimental therapeutics leads to enhanced cell death. Thus, our data indicate that cnicin induces myeloma cell death via several pathways and reveals Pim-2 as a novel target. These findings provide a rational for further evaluation of cnicin as a new anti-tumor drug and underline the potential of sesquiterpene lactones in tumor therapy.
Journal of Molecular Medicine 12/2011; 90(6):681-93. · 4.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: The B lymphocyte adaptor molecule of 32 kDa (Bam32) is strongly induced during the maturation of dendritic cells (DC). Most known functions of Bam32 are related to the signaling of the B cell receptor for Ag. Because DC do not express receptors specific for Ags, we aim at characterizing the role of Bam32 in human monocyte-derived DC in this study. Our results show that binding of allogeneic T cells to mature DC causes accumulation of Bam32 on the contact sites and that this translocation is mimicked by Ab-mediated engagement of MHC class I. Silencing of Bam32 in mature monocyte-derived DC results in an enhanced proliferation of CD8(+) T cells in an Ag-specific T cell proliferation assay. Further studies identify galectin-1 as an intracellular binding partner of Bam32. Regulating immune responses via regulatory T cell (Treg) modulation is one of the many immunological activities attributed to galectin-1. Therefore, we assayed mixed leukocyte reactions for Treg expansion and found fewer Treg in reactions stimulated with DC silenced for Bam32 compared to reactions stimulated with DC treated with a nontarget control. Based on our findings, we propose a role for Bam32 in the signaling of MHC class I molecules in professional Ag-presenting DC for the regulation of CD8(+) T cell activation. It is distinct from that of MHC class I recognized by CD8(+) T cells leading to target [corrected] cell death. Thus, our data pinpoint a novel level of T cell regulation that may be of biological relevance.
The Journal of Immunology 09/2011; 187(8):3972-8. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Pancreatic cancer (PaCa) is the fourth leading cause of cancer deaths in Western societies, with pancreatic ductal adenocarcinomas (PDACs) accounting for >90% of such cases. PDAC is a heterogeneous disease that includes a subset showing overexpression of the secreted glycoprotein Dickkopf-related protein 3 (Dkk-3), a protein shown to be downregulated in various cancers of different tissues. The biological function of Dkk-3 in this subset was studied using the Dkk-3 expressing PANC-1 cell line as a model for PDACs. The influence of Dkk-3 overexpression and knockdown on cellular differentiation and proliferation of PANC-1 was investigated. Confocal microscopy showed that Dkk-3 was expressed in a fraction of PANC-1 cells. While lentiviral-mediated overexpression of DKK3 did not alter cellular proliferation, knockdown of DKK3 resulted in significant reduction of cellular proliferation and concomitant induction of cell cycle inhibitors CDKN2B (p15INK4b), CDKN1A (p21CIP1) and CDKN1B (p27KIP1). In parallel, pancreatic epithelial cell differentiation markers AMY2A, CELA1, CTRB1, GCG, GLB1 and INS were significantly upregulated. PANC-1 cells differentiated using exendin-4 showed analogous induction of cell cycle inhibitors and differentiation markers. Thus, we conclude that Dkk-3 is required to maintain a highly dedifferentiated and consequently proliferative state in PANC-1, indicating a similar function in the Dkk-3 overexpressing subset of PDACs. Therefore, Dkk-3 represents a potential target for the treatment of Dkk-3-positive subtypes of PaCa to drive cells into cell cycle arrest and differentiation.
International Journal of Oncology 08/2011; 40(1):40-6. · 2.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dickkopf (dkk) genes belong to the family of secreted wnt-inhibitors with conserved cysteine-rich domains. In contrast to the prototype dkk1, dkk3 does not modulate canonical Wnt/β-catenin signalling. Until now, neither functions nor interaction partners of dkk3 in lower vertebrates have been described. In this study we cloned two dkk3 homologues dkk3a(dkk3l) and dkk3b(dkk3) and a dkk1 homologue dkk1a of the zebrafish and studied their expression patterns during embryonic development in comparison to the known dkk1b gene. Moreover, mutants with defects in hedgehog signalling (smo), notch (mib) signalling, nodal signalling (Zoep) or retinoic acid synthesis (neckless) were analyzed for changes in dkk3 gene expression. In situ hybridization analyses showed a dynamic expression of dkk1a and dkk1b primarily in epidermal structures of the otic vesicle, lens, branchial arches and fin folds. While dkk1a was expressed mainly in deep tissues, dkk1b expression was mainly found in protrusions at the outer surface of the branchial arch epidermis. In contrast, dkk3 genes showed expression in different tissues. Strong signals for dkk3a(dkk3l) were present in various neuronal structures of the head, whereas dkk3b(dkk3) expression was restricted mainly to endocrine cells of the pancreas and to the brachial arches. In summary, both dkk3 genes display a unique and distinct expression pattern in late embryonic development, pointing to a specific role during neuronal and pancreatic cell differentiation.
[show abstract][hide abstract] ABSTRACT: Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) regulates cell proliferation and survival by extracellular interaction and inactivation of the growth factor IGF-I. Beyond that, IGF-independent actions mediated by intracellular IGFBP-3 including nuclear-IGFBP-3, have also been described. We here show, using both confocal and electron microscopy and cell fractionation, that the extracellular addition of IGFBP-3 to living cells results in rapid uptake and nuclear delivery of IGFBP-3, by yet partly unknown mechanisms. IGFBP-3 is internalized through a dynamin-dependent pathway, traffics through endocytic compartments and is finally delivered into the nucleus. We observed docking of IGFBP-3 containing structures to the nuclear envelope and found IGFBP-3 containing dot-like structures to permeate the nuclear envelope. In summary, our findings establish the pathway by which this tumor suppressor protein is delivered from extracellular space to the nucleus.
International Journal of Cancer 08/2011; 130(7):1544 - 1557. · 6.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Insulin-like growth factor binding proteins (IGFBPs) are key regulators of insulin-like growth factor (IGF) mediated signal transduction and thereby can profoundly influence cellular phenotypes and cell fate. Whereas IGFBPs are extracellular proteins, intracellular activities were described for several IGFBP family members, such as IGFBP-3, which can be reinternalized by endocytosis and reaches the nucleus through routes that remain to be fully established. Within the family of IGFBPs, IGFBP-6 is unique for its specific binding to IGF-II. IGFBP-6 was described to possess additional IGF-independent activities, which have in part been attributed to its translocation to the nucleus; however, cellular uptake of IGFBP-6 was not described. To further explore IGFBP-6 functions, we developed a new method for the purification of native human IGFBP-6 from cell culture supernatants, involving a four-step affinity purification procedure, which yields highly enriched IGFBP-6. Whereas protein purified in this way retained the capacity to interact with IGF-II and modulate IGF-dependent signal transduction, our data suggest that, unlike IGFBP-3, human IGFBP-6 is not readily internalized by human tumor cells. To summarize, this work describes a novel and efficient method for the purification of native human insulin-like growth factor binding protein 6 (IGFBP-6) from human cell culture supernatants, applying a four-step chromatography procedure. Intactness of purified IGFBP-6 was confirmed by IGF ligand Western blot and ability to modulate IGF-dependent signal transduction. Cellular uptake studies were performed to further characterize the purified protein, showing no short-term uptake of IGFBP-6, in contrast to IGFBP-3.
Journal of Cell Communication and Signaling 03/2011; 5(4):277-89.
[show abstract][hide abstract] ABSTRACT: Reactive oxygen species (ROS) are involved in the regulation of many physiological processes. However, overproduction of ROS under various cellular stresses results in cell death and organ injury and thus contributes to a broad spectrum of diseases and pathological conditions. The existence of different cellular sources for ROS and the distinct properties of individual ROS (their reactivity, lifetime, etc.) require adequate detection methods. We therefore compared different models of cellular stress and various ROS-sensitive dyes-2',7'-dichlorodihydrofluorescein diacetate (DCF-DA), MitoSOX™, and MitoTracker® red CM-H(2)XRos-using a confocal fluorescent imaging approach, which has the advantage of not only detecting but also of localizing intracellular sources for ROS. Confocal acquisition of DCF-DA fluorescence can be combined with ROS detection by the mitochondria-specific probes MitoSOX™ and MitoTracker® red CM-H(2)XRos. Specificity was controlled using various antioxidants such as Trolox and N-acetylcysteine. Using different fluorescent ROS-sensitive probes, we detected higher ROS production equally under cell starvation (IL-3 or serum depletion), hypoxia-reoxygenation, or treatment of cells with prooxidants. The detected increase in ROS was approximately threefold in IL-3-depleted 32D cells, approximately 3.5-fold in serum-deprived NIH cells, and 2.5-fold to threefold in hypoxic HL-1 cells, and these findings agree well with previously published spectrofluorometric measurements. In some cases, electron spin resonance (ESR) spectroscopy was used for the validation of results from confocal fluorescent imaging. Our data show that confocal fluorescent imaging and ESR data are in good agreement. Under cellular stress, mitochondrial ROS are released into the cytoplasm and may participate in many processes, but they do not escape from the cell.
Analytical and Bioanalytical Chemistry 02/2011; 400(8):2383-90. · 3.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: The reticulon Nogo-B participates in cellular and immunological processes in murine macrophages. Since leukocytes are an essential part of the immune system in health and disease, we decided to investigate the expression of Nogo-A, Nogo-B and Nogo-C in different human immune cell subpopulations. Furthermore, we analyzed the localization of Nogo-B in human monocyte-derived macrophages by indirect immunofluorescence stainings to gain further insight into its possible function.
We describe an association of Nogo-B with cytoskeletal structures and the base of filopodia, but not with focal or podosomal adhesion sites of monocyte-derived macrophages. Nogo-B positive structures are partially co-localized with RhoA staining and Rac1 positive membrane ruffles. Furthermore, Nogo-B is associated with the tubulin network, but not accumulated in the Golgi region. Although Nogo-B is present in the endoplasmic reticulum, it can also be translocated to large cell protrusions or the trailing end of migratory cells, where it is homogenously distributed.
Two different Nogo-B staining patterns can be distinguished in macrophages: firstly we observed ER-independent Nogo-B localization in cell protrusions and at the trailing end of migrating cells. Secondly, the localization of Nogo-B in actin/RhoA/Rac1 positive regions supports an influence on cytoskeletal organization. To our knowledge this is the first report on Nogo-B expression at the base of filopodia, thus providing further insight into the distribution of this protein.
[show abstract][hide abstract] ABSTRACT: Recently, EpCAM has attracted major interest as a target for antibody- and vaccine-based cancer immunotherapies. In breast cancer, the EpCAM antigen is overexpressed in 30-40% of all cases and this increased expression correlates with poor prognosis. The use of EpCAM-specific monoclonal antibodies is a promising treatment approach in these patients.
In order to explore molecular changes following EpCAM overexpression, we investigated changes of the transcriptome upon EpCAM gene expression in commercially available human breast cancer cells lines Hs578T and MDA-MB-231. To assess cell proliferation, a tetrazolium salt based assay was performed. A TCF/LEF Reporter Kit was used to measure the transcriptional activity of the Wnt/β-catenin pathway. To evaluate the accumulation of β-catenin in the nucleus, a subcellular fractionation assay was performed.
For the first time we could show that expression profiling data of EpCAM transfected cell lines Hs578TEpCAM and MDA-MB-231EpCAM indicate an association of EpCAM overexpression with the downregulation of the Wnt signaling inhibitors SFRP1 and TCF7L2. Confirmation of increased Wnt signaling was provided by a TCF/LEF reporter kit and by the finding of the nuclear accumulation of ß-catenin for MDA-MB-231 EpCAM but not Hs578T EpCAM cells. In Hs578T cells, an increase of proliferation and chemosensitivity to Docetaxel was associated with EpCAM overexpression.
These data show a cell type dependent modification of Wnt signaling components after EpCAM overexpression in breast cancer cell lines, which results in marginal functional changes. Further investigations on the interaction of EpCAM with SFRP1 and TCF7L2 and on additional factors, which may be causal for changes upon EpCAM overexpression, will help to characterize unique molecular properties of EpCAM-positive breast cancer cells.
[show abstract][hide abstract] ABSTRACT: Dickkopf-3 (Dkk3) has been proposed as tumour suppressor gene and a marker for tumour blood vessels. We analysed the expression and function of Dkk3 in platelets and megakaryocytes from healthy controls and patients with BCR-ABL1-negative myeloproliferative neoplasms (MPN). Dkk3 protein and gene expression in platelets was compared with endothelial and other blood cell populations by ELISA, real-time PCR, and immunofluorescence. Moreover, megakaryocytes were isolated from bone marrow aspirates by CD61 microbeads. Immunohistochemical studies of Dkk3 expression were performed in essential thrombocythemia (ET), polycythemia vera (PV), primary myelofibrosis (PMF) and control reactive bone marrow cases (each n=10). Compared to all other blood cell populations platelets showed the highest concentration of Dkk3 protein (150 ± 19 ng/mg total protein). A strong DKK3 gene and protein expression was also observed in isolated megakaryocytes. Dkk3 co-localised with VEGF in α-granules of platelets and was released similar to VEGF upon stimulation. Addition of recombinant Dkk3 had no influence on blood coagulation (aPTT, INR) and platelet aggregation. Significantly more Dkk3+ megakaryocytes/mm2 could be found in bone marrow biopsies from patients with MPN (ET 40 ± 10, PV 31 ± 4, PMF 22 ± 3) than in controls (15 ± 3). The mean proportion of Dkk3+ megakaryocytes was increased in MPN as well (ET 83% ± 15%; PV 84% ± 12%; PMF 77% ± 8%) compared to controls (53% ± 11%). Dkk3+ megakaryocytes correlated with microvessel density in PV and PMF. We conclude that Dkk3 might be involved in the pathogenesis of MPN.
Thrombosis and Haemostasis 10/2010; 105(1):72-80. · 6.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: Depletion of the nitric oxide synthase cofactor tetrahydrobiopterin (H4B) during ischemia and reperfusion is associated with severe graft pancreatitis. Since clinically feasible approaches to prevent ischemia reperfusion injury (IRI) by H4B-substitution are missing we investigated its therapeutic potential in a murine pancreas transplantation model using different treatment regimens. Grafts were subjected to 16 h cold ischemia time (CIT) and different treatment regimens: no treatment, 160 μM H4B to perfusion solution, H4B 50 mg/kg prior to reperfusion and H4B 50 mg/kg before recovery of organs. Nontransplanted animals served as controls. Recipient survival and endocrine graft function were assessed. Graft microcirculation was analyzed 2 h after reperfusion by intravital fluorescence microscopy. Parenchymal damage was assessed by histology and nitrotyrosine immunohistochemistry, H4B tissue levels by high pressure liquid chromatography (HPLC). Compared to nontransplanted controls prolonged CIT resulted in significant microcirculatory deterioration. Different efficacy according to route and timing of administration could be observed. Only donor pretreatment with H4B resulted in almost completely abrogated IRI-related damage showing graft microcirculation comparable to nontransplanted controls and restored intragraft H4B levels, resulting in significant reduction of parenchymal damage (p < 0.002) and improved survival and endocrine function (p = 0.0002 each). H4B donor pretreatment abrogates ischemia-induced parenchymal damage and represents a promising strategy to prevent IRI following pancreas transplantation.
American Journal of Transplantation 10/2010; 10(10):2231-40. · 6.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Alkylglycerol monooxygenase (glyceryl-ether monooxygenase, EC 188.8.131.52) is the only enzyme known to cleave the O-alkyl bond of ether lipids which are essential components of brain membranes, protect the eye from cataract, interfere or mediate signalling processes, and are required for spermatogenesis. Along with phenylalanine hydroxylase, tyrosine hydroxylase, tryptophan hydroxylase, and nitric oxide synthase, alkylglycerol monooxygenase is one of five known enzymatic reactions which depend on tetrahydrobiopterin. Although first described in 1964, no sequence had been assigned to this enzyme so far since it lost activity upon protein purification attempts. A functional library screen using pools of plasmids of a rat liver expression library transfected to CHO cells was also unsuccessful. We therefore selected human candidate genes by bioinformatic approaches and by proteomic analysis of partially purified enzyme and tested alkylglycerol monooxygenase activity in CHO cells transfected with expression plasmids. Transmembrane protein 195, a predicted membrane protein with unassigned function which occurs in bilateral animals, was found to encode for tetrahydrobiopterin-dependent alkylglycerol monooxygenase. This sequence assignment was confirmed by injection of transmembrane protein 195 cRNA into Xenopus laevis oocytes. Transmembrane protein 195 shows no sequence homology to aromatic amino acid hydroxylases or nitric oxide synthases, but contains the fatty acid hydroxylase motif. This motif is found in enzymes which contain a diiron center and which carry out hydroxylations of lipids at aliphatic carbon atoms like alkylglycerol monooxygenase. This sequence assignment suggests that alkylglycerol monooxygenase forms a distinct third group among tetrahydrobiopterin-dependent enzymes.
Proceedings of the National Academy of Sciences 08/2010; 107(31):13672-7. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Tetrahydrobiopterin (BH4) is an essential cofactor for the nitric oxide (NO) synthases and represents a critical determinant of NO production. BH4 depletion during ischemia leads to the uncoupling of the synthases, thus contributing to reperfusion injury due to increased superoxide formation. To examine whether BH4 supplementation attenuates ischemia-reperfusion injury, we clamped the left renal arteries of male Lewis rats immediately following right-side nephrectomy. BH4 tissue levels significantly decreased after 45 min of warm ischemia compared with levels in non-ischemic controls. Histopathology demonstrated significant tubular damage and increased peroxynitrite formation. Intravital fluorescent microscopy found perfusion deficits in the microvasculature and leakage of the capillary mesh. Supplemental BH4 treatment before ischemia significantly reduced ischemia-induced renal dysfunction, and decreased tubular histologic injury scores and peroxynitrite generation. BH4 also significantly improved microcirculatory parameters such as functional capillary density and diameter. These protective effects of BH4 on microvasculature were significantly correlated with its ability to abolish peroxynitrite formation. We suggest that BH4 significantly protects against acute renal failure following ischemia reperfusion. Whether BH4 has a therapeutic potential will require more direct testing in humans.
Kidney International 02/2010; 77(8):681-9. · 7.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: We present a novel efficient procedure for high level purification of human IGFBP-3. Insulin-like growth factor-binding proteins (IGFBPs) are key regulators of insulin-like growth factor mediated signal transduction and thereby can profoundly influence cellular phenotypes. Certain IGFBPs, including IGFBP-3, have also been described to possess additional IGF-independent activities, which rely, at least in part, on their nuclear localization. However, the mechanisms of IGF-independent biological activities of IGFBP-3 are not well understood. For the study of these functions, recombinant IGFBP-3 is used. However, it has traditionally been difficult to obtain recombinant protein in sufficient quality and quantity. Here we describe a new procedure for the purification of recombinant IGFBP-3 from cell culture supernatants involving a two-step affinity purification procedure. Using this new protocol, we obtained pure IGFBP-3 free of any visible contaminants. We also provide evidence that the protein purified in this way retains biological activity, to bind IGF and modulate IGF-dependent signal transduction. We also show that the purified protein produced by the new procedure is readily internalized by human fibroblasts, suggesting that this protein is also suitable to study intracellular trafficking of IGFBP-3.
Protein Expression and Purification 02/2010; 71(2):160-7. · 1.43 Impact Factor