Receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell-surface molecules. Blockade of RAGE has been reported to considerably improve liver function and accelerate regeneration after hepatectomy. The aim of this study was to investigate the cell type-specific expression of RAGE, and to examine whether transdifferentiation of hepatic stellate cells (HSC) into myofibroblasts (MFB) is associated with changes in RAGE expression. Northern blot analysis revealed that RAGE mRNA was exclusively expressed by HSC isolated from rat liver, while no transcripts were seen in hepatocytes, Kupffer cells, or sinusoidal endothelial cells. Expression of RAGE mRNA was up-regulated during transdifferentiation of HSC into MFB. Concomitantly, expression of RAGE protein was increased as confirmed by Western blotting and immunohistochemistry. As assessed by radioactive labeling, transforming growth factor beta(1) (TGF-beta(1)) induced a time-dependent 2- to 15-fold increase in the de novo synthesis of RAGE protein, which was completely abolished using PD098059, a specific inhibitor of the mitogen-activated protein kinase (MAPK) kinase. As shown by double-immunofluorescence staining, RAGE colocalized with alpha-smooth muscle actin, and immunoelectron microscopy demonstrated the most prominent labeling for RAGE at filopodial membranes of MFB. In conclusion, this study demonstrates that expression of RAGE is restricted to rat HSC, and that expression is up-regulated during activation of HSC and transition to MFB. The preferential immunogold labeling of RAGE to focal membrane areas of filopodia of MFB is suggestive of a role of RAGE in the spreading and migration of activated HSC/MFB, major players in liver fibrogenesis.
The primary function of mitochondria is respiration, where catabolism of substrates is coupled to ATP synthesis via oxidative phosphorylation. In plants, mitochondrial composition is relatively complex and flexible and has specific pathways to support photosynthetic processes in illuminated leaves. This review begins with outlining current models of mitochondrial composition in plant cells, with an emphasis upon the assembly of the complexes of the classical electron transport chain (ETC). Next, we focus upon the comparative analysis of mitochondrial function from different tissue types. A prominent theme in the plant mitochondrial literature involves linking mitochondrial composition to environmental stress responses, and this review then gives a detailed outline of how oxidative stress impacts upon the plant mitochondrial proteome with particular attention to the role of transition metals. This is followed by an analysis of the signaling capacity of mitochondrial reactive oxygen species, which studies the transcriptional changes of stress responsive genes as a framework to define specific signals emanating from the mitochondrion. Finally, specific mitochondrial roles during exposure to harsh environments are outlined, with attention paid to mitochondrial delivery of energy and intermediates, mitochondrial support for photosynthesis, and mitochondrial processes operating within root cells that mediate tolerance to anoxia and unfavorable soil chemistries. [Formula: see text] [ A. Harvey Millar (Corresponding author)].
Interspecific hybrids of Trifolium medium L. ✕ T. sarosiense Hazsl. and reciprocal hybrids were produced by hand pollinations in a greenhouse. Hybrids of T. medium ✕ T. sarosiense were normal green and intermediate betweenthe two parents for morphological traits, but the reciprocal hybrids showed chlorophyll deficiencies including mottling and chimeras. Seed set from interspecific crosses was lower than from intraspecific crosses, but the small reduction in seed set represents only a minor isolation barrier between the species. All hybrids and both parents were self‐incompatible. Hybrids of T. medium 2n=72 ✕ T. sarosiense 2n=48 and the reciprocal hybrids had 2n=60 chromosomes except for two plants which had 2n=58 chromosomes. Meiotic analysis of chromosomes of T. medium and T. sarosiense revealed mean frequencies of 7.40 I, 32.30 II and 1.34 I, 23.33 lI respectively per PMC at metaphase I of meiosis. The hybrids (2n=60) of T. medium ✕ T. sarosiense and reciprocal exhibited mean frequencies ot 5.30 I, 27.29 II and 4.68 I, 27.66 II, respectively, per PMC at metaphase I. However, the two 2n=58 hybrids had a reduction in bivalents to 25.96 and 26.00, respectively. Mean pollen stainabillty of the two parents was greater than 95%, whereas mean stainability of all hybrids was 89%. Other lines of T. medium were later identified with 2n=64, 68, 70, 72, and 80 chromosomes. The 2n=64 and 80 lines showed mostly 32 II and 40 II, respectively, but cytotypes with 68, 70, and 72 chromosomes had 32 II and an increasing number of univalents. Although the complexity of ploidy level in the T. medium taxa complicates any conclusions concerning phylogenetic relationships, our results indicate strong evolutionary links between T. sarosiense and T. medium .
Aktivierte Hepatische Sternzellen (HSC) entwickeln einen Myofibroblasten-ähnlichen Phänotyp, sezernieren Komponenten der extrazellulären Matrix und spielen daher eine wesentliche Rolle bei der hepatischen Fibrogenese [1]. Die Apoptose aktivierter HSC wird während der Fibrogenese durch stark erhöhte tissue inhibitor of metalloproteinases-1 (TIMP-1)-Spiegel unterdrückt [2]. Die Regeneration der Leber ist charakterisiert durch Apoptose aktivierter HSC und einer Verminderung von TIMP-1 [1]. Kürzlich konnten wir zeigen, dass proteolytisch inaktive Matrix Metalloproteinase-9 (MMP-9) Mutanten, die jedoch weiterhin hochaffin TIMP-1 binden, den Fibrosegrad im CCl4-Maus Modell der toxisch induzierten Fibrose vermindern [3]. Mit der vorliegenden Studie sollen die Mechanismen der durch diese MMP-9 Mutanten induzierten Apoptose in vitro untersucht werden.
Currently, Kentucky's two native Trifolium species, T. sioloniferum and T. reflexum, are each known from only one locality. Historical records indicate that T. stoloniferum was widespread on moist, fertile soils in the Bluegrass Region, and that T. reflexum occurred on drier or less fertile soils in the fomer Big Barrens Region and the Shawnee Hills. Many old records are from areas with open woodland or grass land disturbed by Indians and buffalo (Bison), and recent records are mostly from roadsides or trails through woods. The decline of these species may be attributed to changes in disturbance and consumer patterns since settlement. In cultivation, T. stoloniferum is a vigorous perennial, easily propagated from stolons, but it requires moist, fertile soil, and is sensitive to competition and herbivory. Trifolium reflexum grows more slowly and is typically biennial. The chromosome number of T. solonife rum, reported here for the first time, is the same as other eastern North American species (2n — 16).
Read moreBackground: The Y-box binding protein-1 (YB-1) exerts pleiotropic functions in gene transcription and in translation, e.g. of fibrosis-related genes. Recent in vitro findings point to opposite regulatory effects on fibrogenesis by YB-1 that depend on its subcellular localization. YB-1 might even accomplish opposite functions on gene transcription and mRNA translation of the same gene product, e.g. that of type I collagen (Col1A), a major constituent of the extracellular matrix (ECM) [1]. This led us to in vivo investigations that analyze the outcome of half-maximal YB-1 depletion in a model of liver fibrosis (bile duct ligation (BDL)) and compared the results to renal fibrosis, investigated by unilateral ureteral obstruction (UUO). Additionally, the impact of BDL on kidney damage was assessed.
Read moreAn individually darkened leaf model was used to study protein changes in the Arabidopsis mutant stay-green1 (sgr1) to partially mimic the process of leaf covering senescence that occurs naturally in the shaded rosettes of Arabidopsis plants. Utilizing this controlled and predictable induced senescence model has allowed the direct comparison of sgr1 with Col-0 during the developmental period preceding the retention of chlorophyll and light harvesting complex II (LHCII) in sgr1 and the induction of senescence in Col-0. Quantitative proteomic analysis of soluble leaf proteins from sgr1 and Col-0 before the initiation of senescence has revealed a range of differences in plastid soluble protein abundance in sgr1 when compared to Col-0. Changes were also observed in membrane located machinery for photosystem II (PSII), in Calvin cycle components, proteins involved in redox control of the stromal compartment and ammonia assimilation that differentiated sgr1 during the early stages of the senescence process. The changes in PSII abundance were accompanied with a lower capacity of photosynthetic CO(2) assimilation in sgr1 than Col-0 after return of plants to lighted conditions following 3 and 5 days of darkness. A light-harvesting chlorophyll-a/b binding protein (LHCB2) was retained during the later stages of senescence in sgr1 but this was accompanied by an enhanced loss of oxygen evolving complex (OEC) subunits from PSII, which was confirmed by Western blotting, and an enhanced stability of PSII repair proteins in sgr1, compared to Col-0. Together these data provide insights into the significant differences in the steady-state proteome in sgr1 and its response to senescence, showing this cosmetic stay-green mutant is in fact significantly different to wild-type plants both before and during leaf senescence.
Read moreA human line of spontaneously immortalized keratinocytes (SIK cells) has been derived from ostensibly normal epidermis and has proven useful in dissecting molecular changes associated with immortalization. The original cultures had a normal karyotype and a colony forming efficiency of approximately 3% through 10 passages. At passage 15, after which normal strains ordinarily senesce, these cells continued vigorous growth and gradually increased in colony forming efficiency, stabilizing at approximately 30% by passage 40. During the early stage of increasing colony forming efficiency, the cells acquired a single i(6p) chromosomal aberration and 5- to 10-fold increases in expression of the cell-cycle control proteins cyclin A, cyclin B, and p34cdc2. Additional chromosomal aberrations accumulated at later passages (i(8q) and +7), but the i(6p) and the increased expression of cell-cycle proteins were maintained, raising the possibility that these features were important for immortalization. Regulation of cell growth and differentiation in the cultures appeared minimally altered compared with normal keratinocytes as judged by their microscopic appearance and generation of abortive colonies, sensitivity to growth suppression by transforming growth factor-beta and tetradecanoylphorbol acetate, and dependence upon epidermal growth factor for progressive growth.
Read moreRecently, the need for more standardized operation procedures in experimental liver fibrosis research was suggested due to dramatic changes in European animal welfare rules. Here, we present a short series of standard operation procedures (SOPs) summarizing the most relevant and widely accepted experimental models for the induction of liver injury leading to liver fibrosis. The described procedures are based on the long-term experience of the Collaborative Research Centre 'Organ Fibrosis: From Mechanisms of Injury to Modulation of Disease' (http://www.sfbtrr57.rwth-aachen.de/), which is supported by the German Research Foundation (SFB/TRR57). These SOPs will help to improve standardization of fibrosis models and to increase the comparability of data between different laboratories with the aim of reducing animal experimentation according to the principle that was proposed in 1959 by Russell and Burch as an ethical framework for conducting scientific experiments with animals, namely the replacement, refinement and reduction (3R) principle. In the first section we focus on the carbon tetrachloride (CCl4) model in mice, which is the toxic model of liver fibrosis induction most commonly used worldwide.
Read morePeroxisomes play key roles in energy metabolism, cell signaling, and plant development. A better understanding of these important functions will be achieved with a more complete definition of the peroxisome proteome. The isolation of peroxisomes and their separation from mitochondria and other major membrane systems have been significant challenges in the Arabidopsis (Arabidopsis thaliana) model system. In this study, we present new data on the Arabidopsis peroxisome proteome obtained using two new technical advances that have not previously been applied to studies of plant peroxisomes. First, we followed density gradient centrifugation with free-flow electrophoresis to improve the separation of peroxisomes from mitochondria. Second, we used quantitative proteomics to identify proteins enriched in the peroxisome fractions relative to mitochondrial fractions. We provide evidence for peroxisomal localization of 89 proteins, 36 of which have not previously been identified in other analyses of Arabidopsis peroxisomes. Chimeric green fluorescent protein constructs of 35 proteins have been used to confirm their localization in peroxisomes or to identify endoplasmic reticulum contaminants. The distribution of many of these peroxisomal proteins between soluble, membrane-associated, and integral membrane locations has also been determined. This core peroxisomal proteome from nonphotosynthetic cultured cells contains a proportion of proteins that cannot be predicted to be peroxisomal due to the lack of recognizable peroxisomal targeting sequence 1 (PTS1) or PTS2 signals. Proteins identified are likely to be components in peroxisome biogenesis, beta-oxidation for fatty acid degradation and hormone biosynthesis, photorespiration, and metabolite transport. A considerable number of the proteins found in peroxisomes have no known function, and potential roles of these proteins in peroxisomal metabolism are discussed. This is aided by a metabolic network analysis that reveals a tight integration of functions and highlights specific metabolite nodes that most probably represent entry and exit metabolites that could require transport across the peroxisomal membrane.
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