Apicomplexan UCHL3 retains dual specificity for ubiquitin and Nedd8 throughout evolution

Post-translational modification of proteins by ubiquitin or ubiquitin-like polypeptides such as Nedd8 controls cellular functions including protein degradation, the cell cycle and transcription. Here we have used an activity-based chemical probe that covalently labels ubiquitin hydrolases. We identify four such enzymes from Toxoplasma gondii by mass spectrometry. The homologue of mammalian UCHL3 was cloned from both T. gondii and Plasmodium falciparum and we show that both enzymes possess deubiquitinating as well as deNeddylating activity. A phylogenetic analysis of the UCHL3 amino acid sequences from several eukaryotes suggests that dual specificity for ubiquitin and Nedd8 was present in the ancestral eukaryotic UCHL3 and has been conserved throughout evolution. Finally, the structural characterization of UCHL3 from T. gondii shows a unique insertion at the surface of this enzyme, which may be involved in novel interactions with other proteins. The characterization of these apicomplexan UCHL3s adds to our understanding of the ubiquitin and Nedd8 pathways in these parasites.

Scrambling of phospholipids activates red cell membrane cholesterol

Cholesterol is predicted to associate more strongly with the outer than the inner leaflet of plasma membrane bilayers based on the relative in vitro affinities of their phospholipids. Complex formation with the high-affinity species (especially saturated sphingomyelins) is said to reduce the chemical activity (escape potential or fugacity) of the sterol. We therefore tested the hypothesis that scrambling the sidedness of plasma membrane phospholipids of intact cells will increase the chemical activity of outer surface cholesterol. Upon activating the plasma membrane scramblase in intact human red cells by introducing ionomycin to raise cytoplasmic Ca++, phosphatidylserine became exposed and, concomitantly, the chemical activity of exofacial cholesterol was increased. (This was gauged by its susceptibility to cholesterol oxidase and its rate of transfer to cyclodextrin.) Similar behavior was observed in human fibroblasts. Two other treatments known to activate cell surface cholesterol (namely, exposure to glutaraldehyde and to low-ionic-strength buffer) also brought phosphatidylserine to the cell surface but by a Ca++-independent mechanism. Given that phospholipid scrambling is important in blood coagulation and apoptosis, the concomitant activation of cell surface cholesterol could contribute to these and other pathophysiological signaling processes.

Bone Matrix Formation in Osteogenic Cultures Derived from Human Embryonic Stem Cells in Vitro

Bone matrix production and mineralization involves sophisticated mechanisms, including the initial formation of an organic extracellular matrix into which inorganic hydroxyapatite crystals are later deposited. Human embryonic stem (hES) cells offer a potential to study early developmental processes and provide an unlimited source of cells. In this study, four different hES cell lines were used, and two different approaches to differentiate hES cells into the osteogenic lineage were taken. Undifferentiated cells were cultured either in suspension, facilitating the formation of embryoid bodies (EBs), or in monolayer, and both methods were in the presence of osteogenic supplements. Novel to our osteogenic differentiation study was the use of commercially available human foreskin fibroblasts to support the undifferentiated growth of the hES cell colonies, and their propagation in serum replacement-containing medium. Characterization of the osteogenic phenotype revealed that all hES cell lines differentiated toward the mesenchymal lineage, because T-Brachyury, Flt-1, and bone morphogenetic protein-4 could be detected. Main osteoblastic marker genes Runx2, osterix, bone sialoprotein, and osteocalcin were up-regulated. Alizarin Red S staining demonstrated the formation of bone-like nodules, and bone sialoprotein and osteocalcin were localized to these foci by immunohistochemistry. Cells differentiated in monolayer conditions exhibited greater osteogenic potential compared to those from EB-derived cells. We conclude that in vitro hES cells can produce a mineralized matrix possessing all the major bone markers, the differentiation of pluripotent hES cells to an osteogenic lineage does not require initiation via EB formation, and that lineage potential is not dependent on the mode of differentiation induction but on a cell line itself.

Analysis of stress responsive genes induced by single-walled carbon nanotubes in BJ Foreskin cells

Nanotechnology is finding its use as a potential technology in consumer products, defense, electronics, and medical applications by exploiting the properties of nanomaterials. Single-walled carbon nanotubes are novel forms of these nanomaterials with potential for large applications. However, the toxicity studies on this material are not explored in detail and therefore limiting its use. It has been earlier reported that single-walled carbon nanotubes induces oxidative stress and also dictates activation of specific signaling pathway in keratinocytes. The present study explores the effect of single-walled carbon nanotubes on stress genes in human BJ Foreskin cells. The results show induction of oxidative stress in BJ Foreskin cells by single-walled carbon nanotubes and increase in stress responsive genes. The genes included inducible genes like HMOX1, HMOX2, and Cyp1B1. In addition we validated increase for four genes by SWCNT, namely ATM, CCNC, DNAJB4, and GADD45A by RT-PCR. Moreover results of the altered stress related genes have been discussed and that partially explains some of the toxic responses induced by single-walled carbon nanotubes.

Development and characteristics of a human cell assay for screening agents for melanoma prevention

This paper describes the development and initial evaluation of a human cell assay to identify potentially efficacious agents for preventing melanoma. Four human cell lines were used: normal melanocytes, a radial growth-phase-like melanoma cell line (WM3211), a vertical growth-phase-like melanoma cell line (Lu1205), and 83-2c, a cell strain cloned from metastatic melanoma. Four endpoints were evaluated in ultraviolet B-treated cells: annexin V, human leukocyte antigen-DR; E-cadherin, and N-cadherin. Annexin V was induced by nimesulide, 4-hydroxyphenylretinamide, and difluoromethylornithine in ultraviolet-B-treated radial growth-phase-like melanoma cells. None of the agents inhibited human leukocyte antigen-DR expression in ultraviolet-B-treated radial growth-phase-like melanoma cells, the only cells that strongly expressed human leukocyte antigen-DR. E-cadherin was overexpressed only in radial growth-phase-like melanoma cells relative to melanocytes, and ultraviolet B exposure dramatically reduced this expression. E-cadherin was only induced by difluoromethylornithine in ultraviolet-B-treated radial growth-phase-like melanoma cells. N-cadherin was over- expressed in all melanoma cell lines relative to melanocytes. In this study, all candidate preventive agents inhibited N-cadherin in ultraviolet B-treated radial growth-phase-like melanoma cells. Four agents inhibited N-cadherin in ultraviolet B-treated vertical growth-phase-like melanoma cells. The mean ratios of N-cadherin to E-cadherin levels and specific endpoint responses for both the radial growth-phase-like melanoma and vertical growth-phase-like melanoma cells were used to rank the agents. Agents were evaluated at clinically relevant concentrations. The rankings were difluoromethylornithine>4-hydroxyphenylretinamide>nimesulide>9-cis-retinoic acid>polyphenon E. Diphenylhydramine, D-mannitol, and nordihydroguaiaretic acid were inactive. The results of these initial studies suggest that ultraviolet-B-treated radial growth-phase-like melanoma cells are the most responsive to chemopreventive agents, and may be the cell line of choice for screening melanoma prevention agents.

A Novel Approach for Harvesting Lymphatic Endothelial Cells from Human Foreskin Dermis

BACKGROUND

The lymphatic system plays an important role on tissue fluid and protein transportation, immune cell trafficking, lipid absorption, and even cancer metastasis, according to recent research. Disorders of the lymphatic system may lead to extremity edema and fibrosis. To investigate the physiological and pathophysiological characteristics of the lymphatic system, isolation and culture of lymphatic endothelial cells (LECs) in vitro are critical, although they remain difficult. The authors introduce a novel approach for harvesting LECs from child foreskin dermis.

METHODS AND RESULTS

After dispase digestion to remove epidermis, instead of the scrape procedure as described previously, collagenase was used to digest and harvest all the dermal cells, including vessel endothelial cells. Immunomagnetic beads were then applied to isolate CD34()/CD31(+)cells. These cells were characterized as LECs by immunofluorescent and RT-PCR with LECs specific markers including Prox-1, LYVE-1, and VEGFR-3. Proliferation of isolated cells in response to angiogenic factors and hypoxia were tested. Cells exhibited their typical cobblestone morphology as monolayer cultures under standard growth conditions and were propagated for at least seven passages without their characteristics being altered. LECs specifically responded to various stimuli, especially to VEGFs.

CONCLUSIONS

Using collagenase digestion procedure followed by immunomagnetic beads sorting, human dermal LECs could be harvested successfully.

The effect of Na+-K+ ATPase inhibition by ouabain on histamine release from human cutaneous mast cells

BACKGROUND

There are controversial reports on the effect of sodium-potassium adenosine triphosphatase (Na+-K+ ATPase) inhibition on mast cell mediator release. Some of them have indicated that ouabain (strophanthin G), a specific Na+-K+ ATPase inhibitor, inhibited the release, whereas the others have shown that ouabain had no effect or even had a stimulatory effect on the mediator secretion. Most of these studies have utilized animal-derived mast cells. The aim of this study was to determine the effect of Na+-K+ ATPase inhibition on human skin mast cells.

METHODS

Unpurified and purified mast cells were obtained from newborn foreskins and stimulated by calcium ionophore A23187 (1 microM) for 30 min following a 1 hr incubation with various concentrations (10(-4) to 10(-8) M) of ouabain. Histamine release was assayed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results indicated that ouabain had no significant effect on the non-immunologic histamine release from human skin mast cells, in vitro.

CONCLUSIONS

Na+-K+ ATPase inhibition by ouabain had no significant effect on the non-immunologic histamine release from human cutaneous mast cells and suggested differences between human and animal mast cells.

Distinct sets of developmentally regulated genes that are expressed by human oocytes and human embryonic stem cells

OBJECTIVE

To identify genes that are expressed differently during final oocyte maturation and early embryonic development in humans.

DESIGN

Comparison of gene expression profiles of human germinal vesicle oocytes (hGVO), human embryonic stem cells (hESC) and human foreskin fibroblasts.

SETTING

Research centers and a fertility unit in a university hospital.

PATIENT(S)

Fifty-five healthy women donated 76 hGVO.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Gene expression profiles were analyzed and compared with the use of microarray and reverse-transcription polymerase chain reaction.

RESULT(S)

Altogether, 10,183 genes were expressed in hGVO, and 45% of these genes were unclassified by biologic function. Four oocyte-specific genes (MATER, ZAR1, NPM2 and FIGLA) were detected in hGVO for the first time. Known components of 4 signaling pathways (MOS-MPF, transforming growth factor-beta, WNT, and NOTCH) were also found expressed in hGVO, with some components detected in hGVO for the first time. Distinct sets of genes that were revealed by comparison of expression profiles between hGVO, hESC, and human foreskin fibroblasts appear to be involved in oocyte maturation and early embryonic development.

CONCLUSION(S)

We obtained, for the first time, a large amount of information on gene expression of hGVO as compared with hESC. These data, from a unique research material-human oocytes, can now be used to understand the molecular mechanisms of early human development.

Core-shell type of nanoparticles composed of poly[(n-butyl cyanoacrylate)-co-(2-octyl cyanoacrylate)] copolymers for drug delivery application: Synthesis, characterization and in vitro degradation

Core-shell type of nanoparticles (NPs) with manipulated degradation rate and balanced hydrophilic/hydrophobic properties were designed and characterized. The NPs based on the copolymers of n-butyl cyanoacrylate (BCA) and 2-octyl cyanoacrylate (OCA) were prepared by anion emulsion polymerization in 0.01N HCl solution with pluronic F127 as the stabilizer. These NPs were spherical in shape and with size smaller than 100 nm in a narrow distribution. The particle size, zeta potential, molecular weight, hydrophobicity and degradation rate of the copolymer depended on its composition significantly. In vitro chemical hydrolytic studies indicated that the degradation rate of the NPs could be controlled over 200-fold by adjusting the BCA/OCA ratio. Differential scanning calorimetry (DSC) measurements verified the existence of copolymer with tapered structure which was induced by the reactivity difference of the monomers. A BCA/OCA core-shell structure is postulated that the OCA rich segments were mainly located in the core of the NPs. The cytotoxicity of poly(2-octyl cyanoactylate) (POCA) is quite lower than that of poly(n-butyl cyanoacrylate) (PBCA) and the toxicity of poly(BCA-co-OCA) NPs is similar to that of PBCA NPs.

p53 Is Preferentially Recruited to the Promoters of Growth Arrest Genes p21 and GADD45 during Replicative Senescence of Normal Human Fibroblasts

Replicative senescence is the terminal growth arrest that most normal human cells enter into after a fixed number of divisions in vitro, limiting the proliferative potential of a cell and preventing genomic instability caused by critically short telomeres. Thus, senescence presents a tumor-suppressive mechanism and a barrier to tumor formation. However, senescent cells are inherently resistant to apoptosis and, as they accumulate in aging tissues, may contribute to organ dysfunction and promote tumor progression as part of the stromal environment. Replicative life span in normal human cells can be extended by inactivation of the tumor suppressor gene p53 or its direct target, the cyclin-dependent kinase inhibitor p21, suggesting a direct role for this pathway in senescence. However, p53 recruitment to promoters of target genes during replicative senescence has not been shown in live cells. In this study, we used chromatin immunoprecipitation to determine that p53 preferentially occupied the promoters of growth arrest genes p21 and GADD45 in senescent normal human diploid fibroblasts but not the promoters of other target genes that recruited p53 following doxorubicin-induced DNA damage, such as apoptosis regulators TNFRSF10b, TNFRSF6, and PUMA. This differential recruitment of p53 in senescent versus doxorubicin-treated fibroblasts was accompanied by differences in post-translational modification of p53. These data provide mechanisms for both the growth arrest mediated by p53 and the resistant nature of senescent cells to apoptosis despite p53 activity.

Comparison of ultraviolet B-induced imbalance of antioxidant status in foreskin- and abdominal skin-derived human fibroblasts

Ultraviolet B radiation (UVB) is involved in the development of deleterious cutaneous damage. Several changes could be attributed to UVB-induced reactive oxygen species attacks in fibroblasts. However dermal cells from young and adult skin could respond differently to oxidative stress. So antioxidant status and its consequences on cytotoxicity and apoptosis were compared in child foreskin fibroblasts (FF) and adult abdominal skin fibroblasts (AF) in response to UVB. Basal levels of lipid peroxidation tended to be higher in AF than in FF, which could be related to a reshaping of antioxidant defences (higher catalase and lower superoxide dismutase activities). AF and FF appeared to react similarly to high UVB doses as regards cytotoxicity and apoptosis which increased significantly 24h after exposure. The enhancement of cell death could be due to the inherent oxidative stress: glutathione appeared significantly decreased in both cell populations. As a consequence AF, but not FF, presented significantly increased levels of lipid peroxidation, which could be explained by the pre-cited differences of basal antioxidant defences. These results suggest that AF and FF do not respond to UVB by the same pathway.

Tissue-specific transcription profiles of sex steroid biosynthesis enzymes and the androgen receptor

17beta-hydroxysteroid dehydrogenase (17beta-HSD) and 5alpha-reductase isoenzymes play a crucial role in the formation and metabolism of sex steroids. Not only the key androgens testosterone and dihydrotestosterone but also their precursors are potent activators of the androgen receptor and are, therefore, likely to act as determinants of male sexual differentiation and maturation in a differentially regulated way. The aim of the present study was to relatively quantify the expression of the mRNA of 17beta-HSD isoenzymes, namely, type 1, 2, 3, 4, 5, 7, and 10, together with the 5alpha-reductase type 1 and 2, and the androgen receptor in normal human males and females. RNA was isolated from peripheral blood cells of both sexes and from genital skin fibroblasts (GSFs) of two different localizations (foreskin and scrotal skin) obtained from phenotypically normal males. mRNA expression was semi-quantified by quantitative reverse-transcriptase polymerase chain reaction with the LightCycler Instrument (Roche). The examined enzymes show statistically significant differences in their transcription pattern between the blood and the GSF RNA samples. Within the GSF samples, there are also significant variations between the two examined localizations in the transcription of 17beta-HSD type 1, 2, 4, and 5 as well as for the androgen receptor. We found large interindividual variation of enzyme transcription patterns in all investigated tissues. In peripheral blood cells, no sex-specific differences were seen. We conclude that sex steroid enzymes are expressed not only in genital primary target tissues but also in peripheral blood. The expression in different target tissues may contribute to both the individual sexual and tissue-specific phenotype in humans.

Cytoskeletal components of an invasion machine--the apical complex of Toxoplasma gondii

The apical complex of Toxoplasma gondii is widely believed to serve essential functions in both invasion of its host cells (including human cells), and in replication of the parasite. The understanding of apical complex function, the basis for its novel structure, and the mechanism for its motility are greatly impeded by lack of knowledge of its molecular composition. We have partially purified the conoid/apical complex, identified approximately 200 proteins that represent 70% of its cytoskeletal protein components, characterized seven novel proteins, and determined the sequence of recruitment of five of these proteins into the cytoskeleton during cell division. Our results provide new markers for the different subcompartments within the apical complex, and revealed previously unknown cellular compartments, which facilitate our understanding of how the invasion machinery is built. Surprisingly, the extreme apical and extreme basal structures of this highly polarized cell originate in the same location and at the same time very early during parasite replication.

[Experimental study on biological character changes of human epidermal cells during proliferation culture in vitro]

[Abstract]

OBJECTIVE

The study was (1) to investigate the biological character changes of human epidermal cells during proliferation culture in vitro and (2) to provide data for construction of engineered skin.

METHODS

The foreskin was collected from 20 healthy children. The epidermal cells were isolated with digestion of the foreskin and cultured in vitro. Growth curve was obtained from the data of cell counting. Cell growth kinetics was observed. Meanwhile, clonal analysis and cell size measurement was performed. The rate of keratin 19 (K19) and involucrin expression-positive cells was counted by flow cytometer. Expression of K19 and involucrin mRNA was detected by RT-PCR.

RESULTS

When passaged to P6, the keratinocytes from child foreskin could be expanded by (700 +/- 37) times. Flow cytometer results showed that the percentage of K19 expression-positive cells decreased from (66.97 +/- 3.14)% to (4.65 +/- 1.38)% while the percentage of involucrin expression-positive cells increased from (11.65 +/- 1.62)% to (97.03 +/- 2.66)% at P0 and P6 respectively. RT-PCR results showed that expression of K19 mRNA decreased from P0 to P6 while involucrin mRNA kept stable with passage in vitro.

CONCLUSIONS

Human epidermal cells of passage 5 maintain proliferation phenotype, which are suitable for skin tissue engineering. Decrease of proliferation phenotype content is partially responsible for the proliferation capacity loss of in vitro cultured epidermal cells.