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Biomedical subjects

P Heyder

Publications and source records attributed to P Heyder.

7 recordsLinked to original sources
PubMed2005

Induction of apoptosis by spermine-metabolites in primary human blood cells and various tumor cell lines.

Polyamines are involved in the regulation of cellular growth and survival by interacting with processes like translation, transcription or ion transport. The aim of our study was to analyze whether polyamines induce apoptosis in hematopoetic cells and to investigate the molecular mechanisms involved. We found an induction of apoptosis by spermine in primary human cells and malignant tumor cell lines. Spermine-treatment resulted in an intracellular increase of reactive oxygen species. Apoptosis was mediated by a collapse of mitochondrial membrane potential, a decrease in Bcl-2 expression and a release of apoptosis mediating molecules from mitochondrial intermembrane space (cytochrome C, Smac/DIABLO). Spermine-mediated apoptosis was caspase-dependent. To test whether spermine mediates apoptosis through metabolites we analyzed the effects of several molecules that interfere with its catabolism. Aminoguanidine, an inhibitor of serum amine oxidase, aldehyde-dehydrogenase, which degrades aldehydes to less reactive molecules or N-acetyl-cysteine, a glutathion precursor, significantly inhibited spermine-mediated apoptosis. From these data we conclude that spermine-derived aldehydes and intracellular accumulation of reactive oxygen species result in mitochondria mediated apoptosis.

Acetylcysteine↗
PubMed2005

Microparticles shed from different antigen-presenting cells display an individual pattern of surface molecules and a distinct potential of allogeneic T-cell activation.

Various cells such as platelets, lymphocytes, endothelial cells, red blood cells and monocytes do release surface-derived microparticles (mps). We analysed mp isolated from supernatants of cultured antigen-presenting human cells (APCs) and human cell lines. Particle sizing by dynamic light scattering revealed a characteristic size of the particles ranging from 80 nm to 300 nm in viable cells and from 400 nm to 1200 nm in irradiated cells. Employing flow-cytometry, we observed partly an altered surface protein composition of the mp compared to their cellular source. Mp originating from dendritic cells (DCs) differed in their surface composition from those released from monocytes and monocyte-derived macrophages. In functional assays, these mp stimulated alloreactive T-cells. The treatment of the cells with either UV-B or lipopolysaccharide strongly influenced the quantity, the immunostimulatory features and the surface composition of the mp. Mp from apoptotic macrophages were able to reduce the stimulatory capacity of vital macrophages but not of DC. Apoptotic mps from DC, on the other hand, were always stimulatory. This is the first report regarding the study of mp released from DC and compared with those released from other APC.

Antigen-Presenting Cells↗
PubMed2004

UV irradiation inhibits ABC transporters via generation of ADP-ribose by concerted action of poly(ADP-ribose) polymerase-1 and glycohydrolase.

ATP-binding cassette (ABC) transporters are involved in the transport of multiple substrates across cellular membranes, including metabolites, proteins, and drugs. Employing a functional fluorochrome export assay, we found that UVB irradiation strongly inhibits the activity of ABC transporters. Specific inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1) restored the function of ABC transporters in UVB-irradiated cells, and PARP-1-deficient cells did not undergo UVB-induced membrane transport inhibition. These data suggest that PARP-1 activation is necessary for ABC transporter functional downregulation. The hydrolysis of poly(ADP-ribose) by poly(ADP-ribose) glycohydrolase (PARG) was also required, since specific PARG inhibitors, which limit the production of ADP-ribose molecules, restored the function of ABC transporters. Furthermore, ADP-ribose molecules potently inhibited the activity of the ABC transporter P-glycoprotein. Hence, poly(ADP-ribose) metabolism appears to play a novel role in the regulation of ABC transporters.

ATP-Binding Cassette Transporters↗
PubMed2002

Apoptosis of the teratocarcinoma cell line Tera-1 leads to the cleavage of HERV-K10gag proteins by caspases and/or granzyme B.

Redistribution, post-translational modifications and coclustering with viral antigens contribute to the immunogenicity of apoptotic cell-derived autoantigens. Almost all known targets of the humoral autoimmune response in systemic lupus erythematosus (SLE) are cleaved by caspases or granzyme B during apoptosis. Antibodies against retroviral proteins can frequently be detected in the sera of SLE patients without overt retroviral infections. These antibodies may represent cross-reactive antibodies or may have been induced by proteins encoded by endogenous retroviral sequences. We used Tera-1 cells that abundantly express a group-specific antigen of human endogenous retroviruses, HERV-K10gag polyprotein, to investigate its processing during apoptosis. Tera-1 cells induced to undergo apoptosis showed an altered HERV-K10gag processing compared with viable cells. In addition, granzyme B was able to cleave HERV-K10gag isolated from viable Tera-1 cells. Similar to nuclear autoantigens, endogenous retroviral proteins are cleaved during the execution phase of apoptosis. These post-translational modifications may result in the generation of T-cell neoepitopes or a changed epitope hierarchy of retroviral proteins. Therefore, immunogenicity of retroviral antigens in SLE patients may result from a similar mechanism as described for nuclear autoantigens.

Amino Acid Sequence↗
PubMed2001

A heterologous 3-D coculture model of breast tumor cells and fibroblasts to study tumor-associated fibroblast differentiation.

The objective of our study was to establish spheroid cocultures as a valid 3-D in vitro model mimicking tumor-fibroblast interactions in scirrhous breast tumors. The experimental setup was designed to verify if in cocultures (a) adherence and migration reflect the invasive potential of breast tumor cells, (b) breast tumor cells induce tumor-associated fibroblast differentiation, and (c) tumor-derived fibroblasts better reflect the in vivo situation than normal skin fibroblasts. Only one (SK-BR-3) out of five tumor cell types showed extensive fibroblast infiltration, MCF-7 cells frequently invaded fibroblast spheroids; BT474, T47D, and ZR-75-1 were noninvasive. While tumor cell invasion was independent of fibroblast origin, tumor-associated myofibroblast differentiation defined by alpha-SMA expression was demonstrated for tumor-derived but not normal skin fibroblasts in coculture indicating that (a) tumor cell invasion and myofibroblast differentiation are autonomous processes and (b) cocultures with tumor-derived fibroblasts resemble advanced stages of desmoplastic carcinomas while cocultures with normal skin fibroblasts rather reflect the early tumor development. The latter is also implied by fibroblast-associated alterations in tumor cell morphology and ECM distribution in the system. By using RNA arbitrarily primed PCR and cells isolated from cocultures by fluorescence-activated and magnetic cell separation, peripheral myelin protein PMP22/SR13 has been identified as a novel candidate with potential relevance in the interaction between tumor cell and normal fibroblast since PMP22 mRNA was significantly reduced in normal skin fibroblasts in coculture with BT474 cells.

Breast Neoplasms↗
PubMed2001

Complement binding is an early feature of necrotic and a rather late event during apoptotic cell death.

The phagocytosis of dying cells is an integral feature of apoptosis and necrosis. There are many receptors involved in recognition of dying cells, however, the molecular mechanisms of the scavenging process remain elusive. The activation by necrotic cells of complement is well established, however, the importance of complement in the scavenging process of apoptotic cells was just recently described. Here we report that the complement components C3 and C4 immediately bound to necrotic cells. The binding of complement was much higher for lymphocytes compared to granulocytes. In case of apoptotic cell death complement binding was a rather late event, which in lymphocytes was preceded by secondary necrosis. Taken together complement binding is an immediate early feature of necrosis and a rather late event during apoptotic cell death. We conclude that complement may serve as an opsonin for fragments of apoptotic cells that have escaped regular scavenging mechanisms.

Apoptosis↗