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Biomedical subjects

Maria Wartenberg

Publications and source records attributed to Maria Wartenberg.

At least 19 recordsLinked to original sources
PubMed2006

Polyphenols prevent cell shedding from mouse mammary cancer spheroids and inhibit cancer cell invasion in confrontation cultures derived from embryonic stem cells.

The prognosis of cancer disease is worsened upon shedding of tumor cells from the primary tumor, which escape to the blood stream and form metastases at distant sites within the body. Inhibition of cell shedding from the primary tumor could therefore be exploited to avoid metastasis and delay the progression of the cancer disease. In the present study, we investigated the effects of the polyphenols resveratrol, baicalein, epicatechin, epigallocatechin and polyphenon 60 on cell shedding from multicellular tumor spheroids of the murine mammacarcinoma cell line 4T1, cell invasion into embryonic stem cell-derived tissues, generation of reactive oxygen species (ROS) and expression of matrix metalloproteinase 9 (MMP-9). With increasing tumor spheroid growth MMP-9 expression was upregulated and cells detached from tumor spheroids and formed subspheroids that displayed pronounced ROS generation. Upon incubation with polyphenols tumor growth was arrested and cell shedding was totally abolished. Polyphenol treatment decreased ROS generation and downregulated MMP-9 expression. Furthermore, polyphenols significantly inhibited invasion of tumor cells into embryonic stem cell-derived, vascularized tissues. Our data suggest, that polyphenols inhibit cell shedding and invasion by their anti-oxidative capacity and downregulation of MMP-9 expression.

Animals↗
PubMed2006

Embryonic stem cells utilize reactive oxygen species as transducers of mechanical strain-induced cardiovascular differentiation.

Growing stem cells are subjected to mechanical forces, which may initiate differentiation programs. Mechanical strain stimulated cardiovascular differentiation of mouse embryonic stem (ES) cells as evaluated by quantification of contracting cardiac foci and capillary areas, respectively. Mechanical strain rapidly elevated intracellular reactive oxygen species (ROS). After 24 h up-regulation of NADPH oxidase subunits p22-phox, p47-phox, p67-phox, and Nox-4 as well as Nox-1 and Nox-4 mRNA was observed. In parallel, mechanical strain increased hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) mRNA and protein as well as MEF2C and GATA-4 mRNA, which are involved in cardiovascular development. Furthermore, phosphorylation of extracellular-regulated kinase 1,2 (ERK1,2), p38, and c-jun N-terminal kinase (c-Jun NH2-terminal kinase (JNK)) was observed. Stimulation of cardiovascular commitment, HIF-1alpha, VEGF, and MEF2C expression as well as MAPK activation were abolished by free radical scavengers, whereas GATA-4 expression was increased. Cardiomyogenesis was inhibited by the p38 inhibitor SB203580, the ERK1,2 inhibitor UO126, and the JNK inhibitor SP600125. Vasculogenesis/angiogenesis was blunted following inhibition of ERK1,2 and JNK, whereas p38 inhibition was ineffective. Our data outline a role of ROS as mechanotransducing molecules in mechanical strain-stimulated cardiovascular differentiation of ES cells, and point toward a microenvironment of elevated ROS required for signaling cascades initiating cardiovascular differentiation programs.

Animals↗
PubMed2006

Novel Nox inhibitor VAS2870 attenuates PDGF-dependent smooth muscle cell chemotaxis, but not proliferation.

OBJECTIVE: Reactive oxygen species (ROS) produced by NAD(P)H oxidases (Nox) play a significant role in the pathophysiology of cardiovascular diseases. Expression and activity of NAD(P)H oxidases are regulated by growth factors such as angiotensin II and platelet-derived growth factor (PDGF). We characterized the effects of the novel Nox inhibitor VAS2870 on PDGF-dependent ROS liberation and cellular events in vascular smooth muscle cells (VSMC). METHODS AND RESULTS: PDGF-BB increased NAD(P)H oxidase activity (lucigenin-enhanced chemiluminescence) and intracellular ROS levels (detected by confocal laserscanning microscopy using 2,7-DCF) to 229+/-9% and 362+/-54% at 1 and 2 h, respectively. Preincubation with VAS2870 (10 and 20 microM) completely abolished PDGF-mediated NAD(P)H oxidase activation and ROS production. Since ROS are involved in various growth factor-induced cellular functions, the influence of VAS2870 on PDGF-induced DNA synthesis and chemotaxis was determined. PDGF promoted a 4.2+/-0.2-fold increase of VSMC migration (modified Boyden chamber, p<0.01) and increased DNA synthesis by maximally 3.2+/-0.4-fold (BrdU incorporation, p<0.01) in a concentration-dependent manner. Preincubation with VAS2870 (0.1-20 microM) did not affect PDGF-induced cell cycle progression. However, it abolished PDGF-dependent chemotaxis of VSMC in a concentration-dependent manner (100% inhibition at 10 microM). These findings were related to PDGF-dependent signaling events. Western blot analyses using phospho-specific antibodies revealed that the downstream signaling molecules Akt, Erk, and Src were activated by PDGF. However, VAS2870 blocked PDGF-dependent activation of Src, but not of Akt and Erk, in a concentration-dependent manner. CONCLUSIONS: VAS2870 effectively suppresses growth factor-mediated ROS liberation in VSMC. Furthermore, it completely inhibits PDGF-dependent VSMC migration, whereas it does not affect DNA synthesis. These divergent effects reflect the critical role of Src activity, which-in contrast to Akt and Erk-appears to be redox-sensitive and is absolutely required for PDGF-induced chemotaxis, but not cell cycle progression.

Animals↗
PubMed2006

Regulation of cardiotrophin-1 expression in mouse embryonic stem cells by HIF-1alpha and intracellular reactive oxygen species.

Cardiomyogenesis in differentiating mouse embryonic stem (ES) cells is promoted by cardiotrophin-1 (CT-1), a member of the IL-6 interleukin superfamily that acts through the tall gp130 cytokine receptor. We show that prooxidants (menadione, hydrogen peroxide) as well as chemical (CoCl2) and physiological (1% O2) hypoxia increased CT-1 as well as HIF-1alpha protein and mRNA expression in embryoid bodies, indicating that CT-1 expression is regulated by reactive oxygen species (ROS) and hypoxia. Treatment with either prooxidants or chemical hypoxia increased gp130 phosphorylation and protein expression of NADPH oxidase subunits p22-phox, p47-phox, p67-phox, as well as Nox1 and Nox4 mRNA. Consequently, inhibition of NADPH oxidase activity by diphenylen iodonium chloride (DPI) and apocynin abolished prooxidant- and chemical hypoxia-induced upregulation of CT-1. Prooxidants and chemical hypoxia activated ERK1,2, JNK and p38 as well as PI3-kinase. The proxidant- and CoCl2-mediated upregulation of CT-1 was significantly inhibited in the presence of the ERK1,2 antagonist UO126, the JNK antagonist SP600125, the p38 antagonist SKF86002, the PI3-kinase antagonist LY294002, the Jak-2 antagonist AG490 as well as in the presence of free radical scavengers. Moreover, developing embryoid bodies derived from HIF-1alpha-/- ES cells lack cardiomyogenesis, and prooxidants as well as chemical hypoxia failed to upregulate CT-1 expression. Our results demonstrate that CT-1 expression in ES cells is regulated by ROS and HIF-1alpha and imply a crucial role of CT-1 in the survival and proliferation of ES-cell-derived cardiac cells.

Animals↗
PubMed2006

Confrontation cultures of embryonic stem cells with multicellular tumor spheroids to study tumor-induced angiogenesis.

Human embryonic stem cells efficiently differentiate blood vessels, which allows using this in vitro model to study the interaction of blood vessels with adjacent tissues. Herein, we introduce confrontation cultures of human embryonic stem cells with multicellular tumor spheroids to investigate molecular mechanisms of tumor-induced angiogenesis. Vascularization of tumor tissue by the host is a prerequisite for tumor growth, which has led to the development of antiangiogenic therapy. This promising anti-cancer therapy intends to reduce, halt, or even regress tumor growth by deprivation from blood, oxygen, and nutrient supply. Confrontation cultures of human embryonic stem cells with multicellular tumor spheroids allow the investigation of the time course of endothelial cell invasion into the tumor tissue, the concomitant analysis of changes in angiogenesis-related gene expression, and analysis of the cellular microenvironment (i.e., pericellular oxygen pressure, tissue pH, and levels of tissue reactive oxygen species). The in vitro model of confrontation cultures is suitable for routine screening of antiangiogenic agents in pre-clinical trials and may be used to replace animal experiments applied in antiangiogenesis research.

Animal Use Alternatives↗
PubMed2005

Feed forward cycle of hypotonic stress-induced ATP release, purinergic receptor activation, and growth stimulation of prostate cancer cells.

ATP is released in many cell types upon mechanical strain, the physiological function of extracellular ATP is largely unknown, however. Here we report that ATP released upon hypotonic stress stimulated prostate cancer cell proliferation, activated purinergic receptors, increased intracellular [Ca(2+)](i), and initiated downstream signaling cascades that involved MAPKs ERK1/2 and p38 as well as phosphatidylinositol 3-kinase (PI3K). MAPK activation, the calcium response as well as induction of cell proliferation upon hypotonic stress were inhibited by preincubation with the ATP scavenger apyrase, indicating that hypotonic stress-induced signaling pathways are elicited by released ATP. Hypotonic stress increased prostaglandin E(2) (PGE(2)) synthesis. Consequently, ATP release was inhibited by antagonists of PI3K (LY294002 and wortmannin), phospholipase A(2) (methyl arachidonyl fluorophosphonate (MAFP)), cyclooxygenase-2 (COX-2) (indomethacin, etodolac, NS398) and 5,8,11,14-eicosatetraynoic acid (ETYA), which are involved in arachidonic acid metabolism. Furthermore, ATP release was abolished in the presence of the adenylate cyclase (AC) inhibitor MDL-12,330A, indicating regulation of ATP-release by cAMP. The hypotonic stress-induced ATP release was significantly blunted when the ATP-mediated signal transduction cascade was inhibited on different levels, i.e. purinergic receptors were blocked by suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), the Ca(2+) response was inhibited upon chelation of intracellular Ca(2+) by 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), and ERK1,2 as well as p38 were inhibited by UO126 and SB203580, respectively. In summary our data demonstrate that hypotonic stress initiates a feed forward cycle of ATP release and purinergic receptor signaling resulting in proliferation of prostate cancer cells.

Adenosine Triphosphate↗
PubMed2005

Reactive oxygen species-linked regulation of the multidrug resistance transporter P-glycoprotein in Nox-1 overexpressing prostate tumor spheroids.

Expression of the multidrug resistance (MDR) transporter P-glycoprotein (P-gp) has been demonstrated to be regulated by hypoxia-inducible factor-1alpha (HIF-1alpha) and inhibited by intracellular reactive oxygen species (ROS). Herein, P-gp and HIF-1alpha expression were investigated in multicellular prostate tumor spheroids overexpressing the ROS-generating enzyme Nox-1 in comparison to the mother cell line DU-145. In Nox-1-overexpressing tumor spheroids (DU-145Nox1) generation of ROS as well as expression of Nox-1 was significantly increased as compared to DU-145 tumor spheroids. ROS generation was significantly inhibited in the presence of the NADPH-oxidase antagonists diphenylen-iodonium chloride (DPI) and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF). Albeit growth kinetic of DU-145Nox1 tumor spheroids was decreased as compared to DU-145 spheroids, elevated expression of Ki-67 was observed indicating increased cell cycle activity. In DU-145Nox1 tumor spheroids, expression of HIF-1alpha as well as P-gp was significantly decreased as compared to DU-145 spheroids, which resulted in an increased retention of the anticancer agent doxorubicin. Pretreatment with the free radical scavengers vitamin E and vitamin C increased the expression of P-gp as well as HIF-1alpha in Nox-1-overexpressing cells, whereas no effect of free radical scavengers was observed on mdr-1 mRNA expression. In summary, the data of the present study demonstrate that the development of P-gp-mediated MDR is abolished under conditions of elevated ROS levels, suggesting that the MDR phenotype can be circumvented by modest increase of intracellular ROS generation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Mimicry of a constitutively active pre-B cell receptor in acute lymphoblastic leukemia cells.

Pre-B cells undergo apoptosis unless they are rescued by pre-B cell receptor-dependent survival signals. We previously showed that the BCR-ABL1 kinase that is expressed in pre-B lymphoblastic leukemia bypasses selection for pre-B cell receptor-dependent survival signals. Investigating possible interference of BCR-ABL1 with pre-B cell receptor signaling, we found that neither SYK nor SLP65 can be phosphorylated in response to pre-B cell receptor engagement. Instead, Bruton's tyrosine kinase (BTK) is constitutively phosphorylated by BCR-ABL1. Activated BTK is essential for survival signals that otherwise would arise from the pre-B cell receptor, including activation of PLCgamma1, autonomous Ca2+ signaling, STAT5-phosphorylation, and up-regulation of BCLX(L). Inhibition of BTK activity specifically induces apoptosis in BCR-ABL1+ leukemia cells to a similar extent as inhibition of BCR-ABL1 kinase activity itself. However, BCR-ABL1 cannot directly bind to full-length BTK. Instead, BCR-ABL1 induces the expression of a truncated splice variant of BTK that acts as a linker between the two kinases. As opposed to full-length BTK, truncated BTK lacks kinase activity yet can bind to BCR-ABL1 through its SRC-homology domain 3. Acting as a linker, truncated BTK enables BCR-ABL1-dependent activation of full-length BTK, which initiates downstream survival signals and mimics a constitutively active pre-B cell receptor.

Adolescent↗
PubMed2005

Regulation of the multidrug resistance transporter P-glycoprotein in multicellular prostate tumor spheroids by hyperthermia and reactive oxygen species.

Hyperthermia is an important component of many cancer treatment protocols. In our study the regulation of the multidrug resistance (MDR) transporter P-glycoprotein by hyperthermia was studied in multicellular prostate tumor spheroids. Hyperthermia treatment of small (50-100 microm) tumor spheroids significantly increased P-glycoprotein and mdr-1 mRNA expression with a maximum effect at 42 degrees C, whereas only moderate elevation of P-glycoprotein was found in large (350-450 microm) tumor spheroids. Hyperthermia caused an elevation of intracellular reactive oxygen species (ROS). Inhibition of ROS generation with NADPH-oxidase inhibitors diphenylen iodonium (DPI) and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF) abolished P-glycoprotein expression but did not affect its transcript levels following heat treatment. This indicates that P-glycoprotein levels are controlled by regulating its translation rate or stability. Hyperthermia incubation resulted in a differential activation of p38 mitogen-activated protein kinase (MAPK), extracellular regulated kinase 1,2 (ERK1,2), and c-jun N-terminal kinase (JNK) immediately, 4 hr and 24 hr after treatment. Furthermore, upregulation of hypoxia-inducible factor 1alpha (HIF-1alpha) was observed. Elevation of HIF-1alpha and P-glycoprotein expression following hyperthermia treatment were abolished upon coadministration of the p38 inhibitor SB203580. In contrast the JNK inhibitor SP600125 and the ERK1,2 inhibitor UO126 resulted in increase of HIF-1alpha and P-glycoprotein in the control as well as the hyperthermia-treated samples, indicating negative regulation of intrinsic HIF-1alpha and P-glycoprotein expression by ERK1,2 and JNK signaling cascades. In summary our data demonstrate that hyperthermia-induced upregulation of P-glycoprotein and HIF-1alpha is mediated by activation of p38, whereas ERK1,2 and JNK are involved in repression of P-glycoprotein and HIF-1alpha under control conditions.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Redox control of angiogenic factors and CD31-positive vessel-like structures in mouse embryonic stem cells after direct current electrical field stimulation.

The molecular mechanisms driving angiogenesis in tissues derived from embryonic stem (ES) cells are currently unknown. Herein we investigated the effects of direct current (DC) electrical field treatment on endothelial cell differentiation and angiogenesis of mouse ES cells. Treatment of ES cell-derived embryoid bodies with field strengths ranging from 250 V/m to 750 V/m, applied for 60 s, dose-dependently increased the capillary area staining positive for the endothelial-specific marker platelet endothelial cell adhesion molecule-1 (PECAM-1), indicating stimulation of endothelial cell differentiation and angiogenesis. Consequently, increased expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) within 24 h was observed. Electric field treatment raised reactive oxygen species (ROS) generation for at least 48 h, which was blunted by NADPH-oxidase inhibitors diphenylen iodonium chloride (DPI) as well as 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), and increased the expression of NADPH-oxidase subunits p22-phox, p47-phox, p67-phox, and gp91-phox within 24 h. Electrical field treatment resulted in activation of extracellular regulated kinase 1,2 (ERK1,2), p38, as well as c-Jun NH2-terminal kinase (JNK). Pretreatment with the JNK inhibitor SP600125 resulted in a significant decrease in capillary areas under control conditions as well as under conditions of electrical field treatment, whereas the p38 inhibitor SB203580 was without effects. By contrast, the ERK1,2 antagonist UO126 inhibited electrical field-induced angiogenesis, whereas angiogenesis under control conditions was unimpaired. The increase in capillary areas and VEGF expression as well as activation of JNK and ERK1,2 was significantly inhibited in the presence of the free radical scavenger vitamin E underscoring the role of ROS in electrical field-induced angiogenesis of ES cells.

Angiogenesis Inducing Agents↗
PubMed2005

Tracing the pre-B to immature B cell transition in human leukemia cells reveals a coordinated sequence of primary and secondary IGK gene rearrangement, IGK deletion, and IGL gene rearrangement.

The BCR-ABL1 kinase expressed in acute lymphoblastic leukemia (ALL) drives malignant transformation of pre-B cells and prevents further development. We studied whether inhibition of BCR-ABL1 kinase activity using STI571 can relieve this differentiation block. STI571 treatment of leukemia patients induced expression of the Ig L chain-associated transcription factors IRF4 and SPIB, up-regulation of RAG1 and RAG2, Ckappa and Clambda germline transcription, and rearrangement of Ig kappa L chain (IGK) and Ig lambda L chain (IGL) genes. However, STI571-treated pre-B ALL cells expressed lambda L, but almost no kappa L chains. This could be explained by STI571-induced rearrangement of the kappa-deleting element (KDE), which can delete productively rearranged Vkappa-Jkappa joints. Amplifying double-strand breaks at recombination signal sequences within the IGK, KDE, and IGL loci revealed a coordinated sequence of rearrangement events induced by STI571: recombination of IGK gene segments was already initiated within 1 h after STI571 treatment, followed by KDE-mediated deletion of Vkappa-Jkappa joints 6 h later and, ultimately, IGL gene rearrangement after 12 h. Consistently, up-regulation of Ckappa and Clambda germline transcripts, indicating opening of IGK and IGL loci, was detected after 1 and 6 h for IGK and IGL, respectively. Continued activity of the recombination machinery induced secondary IGK gene rearrangements, which shifted preferential usage of upstream located Jkappa- to downstream Jkappa-gene segments. Thus, inhibition of BCR-ABL1 in pre-B ALL cells 1) recapitulates early B cell development, 2) directly shows that IGK, KDE, and IGL genes are rearranged in sequential order, and 3) provides a model for Ig L chain gene regulation in the human.

B-Lymphocytes↗
PubMed2004

Involvement of reactive oxygen species in cardiotrophin-1-induced proliferation of cardiomyocytes differentiated from murine embryonic stem cells.

Cardiotrophin-1 (CT-1) is a cytokine that is involved in the growth and survival of cardiac cells. In the present study, we demonstrate that treatment of embryoid bodies grown from pluripotent murine embryonic stem (ES) cells with CT-1 significantly stimulated cardiomyogenesis and increased nuclear expression of the proliferation marker Ki-67. The increase in Ki-67 expression was inhibited upon pretreatment with the free radical scavenger vitamin E, indicating a role for reactive oxygen species (ROS) in the signaling cascade. CT-1 treatment of cardiac cells raised intracellular ROS in ES cell-derived cardiomyocytes. ROS were presumably generated by an NADPH-oxidase since ROS generation was down-regulated upon preincubation with the NADPH-oxidase inhibitor diphenylen iodonium chloride (DPI) and LY294002, which inhibits phosphatidylinositol 3 kinase (PI3-kinase). CT-1 activated nuclear factor-kappaB (NF-kappaB) and induced phosphorylation of the Janus kinase signal transducer-2 (Jak-2), the signal transducer and activator of transcription-3 (STAT-3) as well as the extracellular signal-regulated kinase 1,2 (ERK1/2). STAT-3 and ERK1/2 phosphorylation as well as NF-kappaB activation were inhibited by pretreatment with the Jak-2 antagonist AG490, the ERK1/2 inhibitor PD98059, the free radical scavenger vitamin E, the NADPH-oxidase inhibitor DPI, as well as by LY294002. PD98059 failed to inhibit Jak-2 phosphorylation, indicating that the ERK and the Jak/STAT signaling cascade interact on a level downstream of Jak-2. It is concluded that CT-1 stimulates the proliferation of ES cell-derived cardiomyocytes by signaling pathways that involve ROS as signaling molecules in the signal transduction cascade.

Animals↗
PubMed2004

The BCR-ABL1 kinase bypasses selection for the expression of a pre-B cell receptor in pre-B acute lymphoblastic leukemia cells.

The BCR-ABL1 kinase expressed in acute lymphoblastic leukemia (ALL) drives malignant transformation of human pre-B cells. Comparing genome-wide gene expression profiles of BCR-ABL1+ pre-B ALL and normal bone marrow pre-B cells by serial analysis of gene expression, many genes involved in pre-B cell receptor signaling are silenced in the leukemia cells. Although normal pre-B cells are selected for the expression of a functional pre-B cell receptor, BCR-ABL1+ ALL cells mostly do not harbor a productively rearranged IGH allele. In these cases, we identified traces of secondary VH gene rearrangements, which may have rendered an initially productive VH region gene nonfunctional. Even BCR-ABL1+ ALL cells harboring a functional VH region gene are unresponsive to pre-B cell receptor engagement and exhibit autonomous oscillatory Ca2+ signaling activity. Conversely, leukemia subclones surviving inhibition of BCR-ABL1 by STI571 restore responsiveness to antigen receptor engagement and differentiate into immature B cells expressing immunoglobulin light chains. BCR-ABL1 kinase activity is linked to defective pre-B cell receptor signaling and the expression of a truncated isoform of the pre-B cell receptor-associated linker molecule SLP65. Also in primary leukemia cells, truncated SLP65 is expressed before but not after treatment of the patients with STI571. We conclude that inhibition of BCR-ABL1 reconstitutes selection for leukemia cells expressing a functional (pre-) B cell receptor.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Regulation of intrinsic prion protein by growth factors and TNF-alpha: the role of intracellular reactive oxygen species.

Function and regulation of the intrinsic prion protein (PrPc) are largely unknown. In the present study the regulation of PrPc expression by growth factors and cytokines that increase intracellular reactive oxygen species (ROS) levels was studied in glioma and neuroblastoma cells grown as multicellular tumor spheroids. PrPc protein was significantly increased when glioma spheroids were treated with either ATP, nerve growth factor (NGF), epidermal growth factor (EGF), or tumor necrosis factor alpha (TNF-alpha), whereas mRNA levels as evaluated by Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) remained unchanged. ATP, NGF, EGF, and TNF-alpha raised intracellular ROS levels as evaluated using the redox-sensitive fluorescence dye 2'7'-dichlorodihydrofluorescein diacetate (H2DCFDA). The observed elevation in PrPc was completely abolished in the presence of the free radical scavengers vitamin E and ebselen, as well as following pretreatment with the NADPH-oxidase inhibitor diphenylen iodonium chloride (DPI), indicating that PrPc levels are regulated by intracellular ROS. The correlation of PrPc expression to the intracellular ROS levels was investigated by the use of neuroblastoma cells overexpressing either mutant V210I PrP, or wild-type PrPc. It was observed that the intracellular redox state was significantly reduced in PrPc as well as V210I PrP overexpressing cells as compared to non-transfected cells. Consequently, the observed elevation of ROS following treatment with ATP was completely abolished in PrP overexpressing cells. Our data are in line with the assumption that PrPc plays a role as free radical scavenger and/or sensor molecule for oxidative stress.

Adenosine Triphosphate↗
PubMed2003

T lymphoid differentiation in human bone marrow.

The unique role of the thymus in the development of T cells was established >4 decades ago. To elucidate how uncommitted lymphoid progenitor cells are instructed to migrate from bone marrow to the thymus to undergo T lymphoid differentiation, we generated and analyzed a genome-wide gene expression profile of CD7+ CD10+ human bone marrow T cell lineage precursors (TLPs) by using the serial analysis of gene expression technique. Unexpectedly, the serial analysis of gene expression profile identified a high number of (pre-) T cell receptor antigen (TCR)-related transcripts in bone marrow TLPs. To determine the configuration of the TCRbeta locus in these cells at a quantitative level, we sorted and analyzed bone marrow TLPs from five donors by single-cell PCR. Similar proportions of TLPs harbored TCRbeta germ-line alleles, D-J, or V-DJ gene rearrangements. Thus, bone marrow TLPs are heterogenous with respect to TCRbeta rearrangement status, suggesting an active recombination machinery that is consistent with the expression of RAG1, RAG2, and TdT in this population. As a hallmark of ongoing TCRbeta V-DJ rearrangement, we could amplify broken-ended recombination-signal sequence DNA intermediates from bone marrow TLPs, but not from mature T cells by ligation-mediated PCR. Approximately half of the TCRbeta rearrangements were compatible with the expression of a functional pre-TCR, which is in agreement with surface expression of pre-Talpha on bone marrow TLPs as shown by confocal laser microscopy and flow cytometry. At a frequency <0.5% of mononucleated cells in human bone marrow, this population is rare, yet it exemplifies T lymphoid differentiation in the human already before immigration into the thymus.

Base Sequence↗
PubMed2003

Cardiac specific differentiation of mouse embryonic stem cells.

Embryonic stem (ES) cells may represent an alternative source of functionally intact cardiomyocytes for the causal treatment of cardiovascular diseases. However, this requires cardiac-specific differentiation of stem cells and the selection of pure lineages consisting of early embryonic cardiomyocytes. Therefore, an understanding of the basic mechanisms of heart development is essential for selective differentiation of embryonic stem cells into cardiac cells. The development of cardiac cells from embryonic stem cells is regulated by several soluble factors and signalling molecules together with cardiac specific transcription factors such as the zinc-finger GATA proteins and Nkx-2.5. GATA-4 and Nkx-2.5 seem to be essential for heart development. The use of enhanced green fluorescent protein (EGFP) under the control of cardiac-specific promoters in combination with the ES cell system has allowed for the functional characterisation of cardiac precursor cells. Embryonic stem cell-derived cardiomyocytes developmentally express similar cardiac-specific proteins, ion channels and signalling molecules to that of adult cardiomyocytes. Furthermore, identification of growth factors and signalling molecules under cell culture conditions is crucial for the selective cardiac differentiation of embryonic stem cells. Therefore, serum-free culture conditions have to be established in order to examine the influence of different growth factors and signalling molecules on cardiac development and/or formation from ES cells. Although significant progress has been made in generating cardiac cell lineage by the combination of genetically manipulative methods with selective culture conditions for cell transplantation therapy, one of the remaining future challenges for transplantation in humans is the immunological rejection of the engrafted cardiomyocytes.

Animals↗
PubMed2003

Reactive oxygen species-mediated regulation of eNOS and iNOS expression in multicellular prostate tumor spheroids.

Nitric oxide (NO) generated by either endothelial nitric oxide synthase (eNOS) or inducible nitric oxide synthase (iNOS) may be involved in prostate tumorigenesis through the inhibition of reactive oxygen species (ROS)-induced apoptosis. Multicellular DU-145 prostate tumor spheroids endogenously generated NO that paralleled the production of ROS. With increasing spheroid size, eNOS expression was downregulated, whereas an upregulation of iNOS expression was observed. In parallel, NO generation declined, as evaluated by the NO indicator diaminofluorescein-2 diacetate (DAF-2DA), suggesting that NO generation in DU-145 tumor spheroids is mainly mediated by eNOS. Elevation of ROS by treatment of tumor spheroids with either buthionine sulfoximine (BSO) or hydrogen peroxide resulted in upregulation of eNOS, whereas iNOS was downregulated. Furthermore, eNOS expression was increased by epidermal growth factor (EGF) in a redox-sensitive manner. Upregulation of eNOS after treatment with hydrogen peroxide was apparently transduced through receptor tyrosine kinase signaling pathways since it was abolished by the protein kinase C (PKC) inhibitor bisindolylmaleimide-1 (BIM-1), the p21(ras) inhibitor S-trans-trans-farnesylthiosalicylic acid (FTS), the c-Raf inhibitor ZM 336372 and PD98059, which inhibits ERK1/2 activation. Endogenous NO may serve to escape from oxidative stress-induced apoptosis since treatment of tumor spheroids with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl 3-oxide (carboxy-PTIO) as well as the NO synthase inhibitor N-omega-amino-L-arginine (L-NAA) increased cleaved caspase-3. Consequently, lowering intracellular NO levels with either L-NAA or PTIO significantly raised ROS levels, indicating that endogenously generated NO may play a role as a ROS scavenger, thereby protecting exponentially growing tumor spheroids from ROS-induced apoptosis.

Antioxidants↗