Proteome analysis of rat hepatic stellate cells

Erythrophagocytosis by liver macrophages (Kupffer cells) promotes oxidative stress, inflammation, and fibrosis in a rabbit model of steatohepatitis: implications for the pathogenesis of human nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. Here, we report a molecular aspect of this disease elucidated using rabbits fed a cholesterol-rich high-fat diet and exhibiting insulin resistance. The liver in this model showed steatohepatitis with fibrosis and high mRNA expression for some cytokines, heme oxygenase-1, transforming growth factor-beta1, and collagen alpha1(I). Erythrocytes isolated from the model showed marked fragility and the externalization of phosphatidylserine (PS) on the outer leaflet of the membrane and were frequently engulfed by Kupffer cells/macrophages in the hepatic sinusoids. Expression of milk fat globule-epidermal growth factor (EGF)-factor 8, a PS-binding protein, was augmented in the liver. In culture, RAW 264.7 cells engulfed erythrocytes oxidized by tert-butyl hydroperoxide, a process that was inhibited by anti-milk fat globule-EGF-factor 8 antibody. In addition, PS-positive erythrocytes appeared entrapped in the model liver in ex vivo perfusion experiments. Finally, in specimens from NASH patients, the aggregation of erythrocytes in inflammatory hepatic sinusoids was notable. These results indicate that the engulfment of PS-externalized, apoptotic signal-positive, erythrocytes by hepatic macrophages may lead to the deposition of iron derived from hemoglobin in the liver and be involved in the pathogenesis of steatohepatitis.

The Contribution of Methotrexate Exposure and Host Factors on Transcriptional Variance in Human Liver

Long-term administration of methotrexate (MTX) for management of chronic inflammatory diseases is associated with risk of liver damage. In this study, we examined the transcriptional profiles of livers from patients treated with MTX. The possibility that expression signatures correlate with grade of fibrosis or underlying rheumatic disease was evaluated. Twenty-seven patients taking MTX were accrued for this study. Ten non-MTX-exposed normal liver specimens were used as controls. Global mRNA expression was assayed using oligonucleotide arrays. A total of 205 genes were significantly altered in MTX-exposed livers. Six of these genes were validated by qPCR. Two genes, CLN8 and ANKH that map to chromosomal locations previously associated with rheumatoid arthritis, were found to be elevated in MTX-exposed samples. Subsequent pathway analysis indicates that MTX exposure is associated with the following key alterations: (1) upregulation of lipid biosynthetic genes, consistent with MTX-induced steatosis, (2) downregulation of proinflammatory chemokines, consistent with the anti-inflammatory effects of MTX, and (3) elevation of complement pathway gene expression. Complement 5, shown earlier to be correlated with liver fibrosis in mice, was found to be elevated (twofold) in MTX-exposed livers. In conclusion, we have found the expression of a number of genes associated with rheumatic disease and/or MTX exposure to be significantly different. Differences in complement expression provide the rationale for future correlative studies between MTX-induced liver fibrosis and C5 alleles in order to identify patients with increased risk for fibrosis.

Regulation of myofibroblast transdifferentiation by DNA methylation and MeCP2: implications for wound healing and fibrogenesis

Myofibroblasts are critical cellular elements of wound healing generated at sites of injury by transdifferentiation of resident cells. A paradigm for this process is conversion of hepatic stellate cells (HSC) into hepatic myofibroblasts. Treatment of HSC with DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-azadC) blocked transdifferentiation. 5-azadC also prevented loss of IkappaBalpha and PPARgamma expression that occurs during transdifferentiation to allow acquisition of proinflammatory and profibrogenic characteristics. ChIP analysis revealed IkappaBalpha promoter is associated with transcriptionally repressed chromatin that converts to an active state with 5-azadC treatment. The methyl-CpG-binding protein MeCP2 which promotes repressed chromatin structure is selectively detected in myofibroblasts of diseased liver. siRNA knockdown of MeCP2 elevated IkappaBalpha promoter activity, mRNA and protein expression in myofibroblasts. MeCP2 interacts with IkappaBalpha promoter via a methyl-CpG-dependent mechanism and recruitment into a CBF1 corepression complex. We conclude that MeCP2 and DNA methylation exert epigenetic control over hepatic wound healing and fibrogenesis.

Characterization of vitamin A-storing cells in mouse fibrous kidneys using Cygb/STAP as a marker of activated stellate cells

The expression of the cytoglobin/stellate cell activation-associated protein (Cygb/STAP) was recently confirmed in all splanchnic vitamin A-storing cells--including hepatic stellate cells (HSCs)--in normal conditions. In the hepatic fibrous lesion, the expression of Cygb/STAP has been shown to be upregulated in activated HSCs and myofibroblasts (MFs), which have synthesized extracellular matrices. Furthermore, splanchnic vitamin A-storing cells have been reported to be distributed in the kidney. In this study, we clarify the contribution of vitamin A-storing cells to renal fibrosis by focusing on Cygb/ STAP. Adult mice were subjected to unilateral ureteral obstruction (UUO) and kidneys were harvested 1, 3, 7, and 10 days after UUO. Numbers of Cygb/STAP-immunopositive cells as well as Cygb/STAP mRNA 3 days after UUO (UUO day 3 kidney) increased. Vitamin A-autofluorescence was observed in intertubular spaces of controls but gradually declined in a time-dependent manner after UUO. Cygb/STAP+ cells were not completely identical with alpha-smooth muscle actin (alphaSMA)-positive cells in the control or UUO day 7 kidneys. Immunohistochemical analysis for Cygb/STAP and fibulin-2 (Fib), a specific marker for distinguishing MFs from activated HSCs, revealed that the number of Fib+STAP+ cells (MFs) and Fib-STAP+ cells (splanchnic vitamin A-storing cells) significantly increased in UUO day 3 and UUO day 7 kidneys compared with the controls. Our present findings support the concept that Cygb/STAP can be a unique marker for splanchnic fibroblast-like cells, namely the vitamin A-storing cell lineage, and suggest that splanchnic vitamin A-storing cells contribute to renal fibrogenesis in the obstructed kidney.

Ito Cells Are Liver-Resident Antigen-Presenting Cells for Activating T Cell Responses

Here we identified Ito cells (hepatic stellate cells, HSC), known for storage of vitamin A and participation in hepatic fibrosis, as professional liver-resident antigen-presenting cells (APC). Ito cells efficiently presented antigens to CD1-, major histocompatibility complex (MHC)-I-, and MHC-II-restricted T cells. Ito cells presented lipid antigens to CD1-restricted T lymphocytes such as natural killer T (NKT) cells and promoted homeostatic proliferation of liver NKT cells through interleukin-15. Moreover, Ito cells presented antigenic peptides to CD8(+) and CD4(+) T cells and mediated crosspriming of CD8(+) T cells. Peptide-specific T cells were activated by transgenic Ito cells presenting endogenous neoantigen. Upon bacterial infection, Ito cells elicited antigen-specific T cells and mediated protection. In contrast to other liver cell types that have been implicated in induction of immunological tolerance, our data identify Ito cells as professional intrahepatic APCs activating T cells and eliciting a multitude of T cell responses specific for protein and lipid antigens.

A proteomics study of the response of North Ronaldsay sheep to copper challenge

Background

The objective of this proteomics study was to identify proteins that changed expression as a result of copper challenge in the uniquely copper sensitive North Ronaldsay sheep and further, to compare those changes in expression with the more copper tolerant Cambridge breed. Such data gives us a proteome-centered perspective of the pathogenesis of copper-induced oxidative stress in this breed.

Results

Many proteins respond to copper challenge, but this study focuses on those exhibiting a differential response between the two breeds, related to liver copper content. As copper accumulated in the tissue, the pattern of expression of several proteins was markedly different, in North Ronaldsay sheep as compared to the Cambridge breed.

Conclusion

The pattern of changes was consistent with the greatly enhanced susceptibility of North Ronaldsay sheep to copper-induced oxidative stress, focused on mitochondrial disturbance with consequent activation of hepatic stellate cells. The expression profiles were sufficiently complex that the response could not simply be explained as a hypersensitivity to copper in North Ronaldsay sheep.

Gene expression during chemically induced liver fibrosis: effect of halofuginone on TGF-beta signaling

Hepatic fibrosis is associated with the activation of stellate cells (HSCs), the major source of extracellular matrix (ECM) proteins. Transforming growth factor-beta (TGF-beta), signaling via Smad3, is the most profibrogenic cytokine and the major promoter of ECM synthesis. Halofuginone, an inhibitor of liver fibrosis, inhibits TGF-beta-dependent Smad3 phosphorylation in human HSCs in culture. We have used transcriptional profiling to evaluate the effect of halofuginone on gene expression during the progression of thioacetamide (TAA)-induced liver fibrosis in the rat and have focused on genes that are associated with TGF-beta. TAA treatment causes alterations in the expression of 7% of liver genes. Halofuginone treatment prevents the changes in the expression of 41% of these genes and results in the inhibition of HSC activation and collagen synthesis. During the early stages of the disease, halofuginone affects genes involved in alcohol, lipid, protein, and phosphate metabolism and cell adhesion and, at later stages, in the cell cycle (cell development, differentiation, cell proliferation, and apoptosis). The activation of TGF-beta-dependent genes, such as tartrate-resistant acid phosphatase, its putative substrate osteopontin, stellate cell activation-association protein, and fibrillin-1, during chemically induced fibrosis is prevented by halofuginone. This study thus highlights the role of TGF-beta signaling in liver fibrosis and especially its potential for pharmacological intervention. Halofuginone, which has demonstrated efficacy and tolerance in animals and humans, could become an effective and novel therapy for liver fibrosis.

Phosphoprotein analysis: from proteins to proteomes

Characterization of protein modification by phosphorylation is one of the major tasks that have to be accomplished in the post-genomic era. Phosphorylation is a key reversible modification occurring mainly on serine, threonine and tyrosine residues that can regulate enzymatic activity, subcellular localization, complex formation and degradation of proteins. The understanding of the regulatory role played by phosphorylation begins with the discovery and identification of phosphoproteins and then by determining how, where and when these phosphorylation events take place. Because phosphorylation is a dynamic process difficult to quantify, we must at first acquire an inventory of phosphoproteins and characterize their phosphorylation sites. Several experimental strategies can be used to explore the phosphorylation status of proteins from individual moieties to phosphoproteomes. In this review, we will examine and catalogue how proteomics techniques can be used to answer specific questions related to protein phosphorylation. Hence, we will discuss the different methods for enrichment of phospho-proteins and -peptides, and then the various technologies for their identification, quantitation and validation.

Mitochondrial involvement in genetically determined transition metal toxicity II. Copper toxicity

Copper, like iron, is an essential transition metal ion in which its redox reactivity, whilst essential for the activity of mitochondrial enzymes, can also be a source of harmful reactive oxygen species if not chelated to biomolecules. Therefore, both metals are sequestered by protein chaperones and moved across membranes by protein transporters with the excess held in storage proteins for future use. In the case of copper, the storage proteins in the mitochondria are a distinct ceruloplasmin and metallothionein (MT). If the cell accumulates too much copper or copper is needed by other cells, then copper can be chaperoned to the trans-Golgi secretory compartment where it is transported into the Golgi by ATP-dependent pumps ATP7A/B. In liver, the copper is then incorporated into ceruloplasmin in vesicles that travel to the plasma membrane and release ceruloplasmin into the plasma. This paper reviews the genetic basis for diseases associated with copper deficit or excess, particularly those attributed to defective ATP7A/B transporters, with special emphasis on pathologies related to a loss of mitochondrial function.

High glucose concentration induces elevated expression of anti-oxidant and proteolytic enzymes in cultured human retinal pigment epithelial cells

We investigated the differential protein expression patterns of retinal pigment epithelial (RPE) cells exposed to increased glucose concentrations. Cultured human RPE cells (ARPE-19) were exposed for 4 days with normal blood glucose concentration (5.5 mM D-glucose), followed by exposure to either normal (5.5 mM) or high (33 mM) concentrations of D-glucose for 48h. Protein extracts of glucose-treated RPE cells were then subjected to comparative proteome analysis based on 2-D gel electrophoresis. Protein spots were visualized by silver staining. The differentially expressed proteins were excised and digested in-gel with trypsin, then analysed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The expression levels of cathepsin B, glutathione peroxidase and heat shock protein 27 were increased, and that of protein disulfide isomerase decreased in high glucose treated RPE compared to normal glucose. The isoelectric point of copper/zinc-containing superoxide dismutase (Cu/Zn-SOD) shifted toward acidic region in response to high glucose. Cu/Zn-SOD activity in high glucose group was significantly lower than that in normal glucose group (P<0.05, Mann-Whitney U-test). Systematic survey of protein expression has revealed that RPE cells respond to acute, pathologically high glucose levels by the elevated expression of anti-oxidant and proteolytic enzymes.

Cryopreservation of hepatic stellate cells

BACKGROUND/AIMS

Isolated rat hepatic stellate cells (HSC) are taken as a valuable in vitro model to study hepatic fibrogenesis, biotransformation of pharmaceutics, gene expression, transcription factors controlling HSC behaviour, and for the establishment of long-term cultures. Consequently, methods for the isolation and maintenance of HSC cultures are well documented. However, there is ongoing controversial discussion directed on the existence and cellular origin of different HSC subpopulations. Thus, there is a continuing need for developing methods allowing the exchange of HSC isolates between different laboratories. A practical solution to this problem is cryopreservation and banking of HSC.

METHODS

We here describe for the first time the successful establishment of a methodology for long-term cryopreservation and recovery of primary, non-activated HSC from rats. We have optimised critical factors for HSC-banking including prefreeze processing, freezing rate, freezing medium, final cooling temperature, and thawing conditions. We found that DMSO gave far superior attachment and viability on thawing than other cryoprotectants. The viability and cellular characteristics of thawed cells was comparatively analysed by light- and electron microscopic analysis, proliferation assay, Oil Red O-staining, apoptosis testing, and evaluation of marker proteins for fibrogenic activities.

RESULTS

In summary, our data reveal no significant differences in the biochemical and cellular properties between cryopreserved/thawed and freshly isolated HSC.

CONCLUSIONS

According to these results, we suggest that cryoprotected HSC retain functional integrity thereby allowing banking and comfortable exchange of these cells between different laboratories.

Mechanisms of liver fibrosis

Liver fibrosis represents a significant health problem worldwide of which no acceptable therapy exists. The most characteristic feature of liver fibrosis is excess deposition of type I collagen. A great deal of research has been performed to understand the molecular mechanisms responsible for the development of liver fibrosis. The activated hepatic stellate cell (HSC) is the primary cell type responsible for the excess production of collagen. Following a fibrogenic stimulus, HSCs change from a quiescent to an activated, collagen-producing cell. Numerous changes in gene expression are associated with HSC activation including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses in understanding the molecular basis of collagen gene regulation have revealed a complex process offering the opportunity for multiple potential therapeutic strategies. However, further research is still needed to gain a better understanding of HSC activation and how this cell maintains its fibrogenic nature. In this review we describe many of the molecular events that occur following HSC activation and collagen gene regulation that contribute to the fibrogenic nature of these cells and provide a review of therapeutic strategies to treat this disease.

Phosphopeptide-selective column-switching RP-HPLC with a titania precolumn

A methodology of phosphopeptide-selective analysis coupled with column-switching HPLC utilizing titania as precolumn media is presented. Phosphopeptides were selectively enriched on titania packing within a protein/peptide mixture without any additional procedure, and analyzed by column-switching high-performance liquid chromatography. First, phospho-compounds were separated from complex mixtures by trapping them under acidic conditions on a titania packing, where non-phosphorylated compounds were effused out of the precolumn. Subsequently, phospho-compounds were desorbed from the titania column under a specific condition and analyzed. The behavior of phospho-compounds on a titania surface, especially adsorption/desorption, was precisely examined and optimized. A phosphoric buffer was successively employed for the elution of phosphopeptides on a titania surface by competition with the free phosphate group. From the successes of a selective concentration/analysis of phosphopeptides with column-switching HPLC with a titania precolumn, a novel phosphopeptide-selective RP-HPLC analysis has been shown to have an application possibility as a tool for phosphoproteomics.

The Greater Susceptibility of North Ronaldsay Sheep Compared with Cambridge Sheep to Copper-induced Oxidative Stress, Mitochondrial Damage and Hepatic Stellate Cell Activation

Sheep of the semi-feral North Ronaldsay (copper-sensitive) and domesticated Cambridge (copper-tolerant) breeds were compared in respect of pathological changes and protein expression in the liver as a result of excessive dietary copper. Acute mitochondrial damage and hepatic stellate cell (HSC) activation with collagen synthesis occurred in response to moderate copper overload in North Ronaldsay but not in Cambridge sheep. Mitochondrial degradative changes occurred either as ballooning degeneration and rupture with subsequent autophagic degradation or as mitochondrial matrical condensation (pyknosis). In North Ronaldsay sheep prolonged exposure to copper produced mitochondrial hyperplasia and hypertrophy, and nuclear damage with necrosis. Cytosolic isocitrate dehydrogenase (IDH), an enzyme responsive to oxidative stress, was induced in the liver of Cambridge sheep receiving a Cu-supplemented diet but was undetectable in the non-supplemented control sheep. Conversely, IDH was detected at similar levels in both control and copper-supplemented North Ronaldsay sheep, indicating a lower threshold response, and an enhanced susceptibility, to oxidative stress. "Upregulation" of mitochondrial thioredoxin-dependent peroxidase reductase (antioxidant protein-1) in the hepatic cytosol of the North Ronaldsay (but not Cambridge) sheep affirmed the increased susceptibility of the mitochondria to Cu-induced oxidative stress in this breed. Likewise the upregulation of cathepsin-D indicated increased lysosomal activity and HSC activation. The findings may be relevant to copper toxicosis in human infants.

Effects and regulation of osteopontin in rat hepatic stellate cells

Using a cDNA microarray, we identified osteopontin (OPN) as one of the genes upregulated in cultured activated hepatic stellate cells (HSCs). Northern and western blot analyses showed that OPN was increasingly expressed during the progressive activation of cultured rat HSCs, and a significant increase in OPN was observed in carbon tetrachloride-induced rat liver fibrosis. In biliary atresia, OPN protein was predominantly expressed in Kupffer cells and HSCs in the necrotic areas. Incubation of HSCs with recombinant OPN-induced significant proliferative and migratory effects, and induced matrix metalloproteinase 2 production and activation. Moreover, OPN increased type I collagen production and type II transforming growth factor-beta receptor mRNA and protein. In conclusion, this study shows that OPN is expressed in activated HSCs and suggests that the upregulation of OPN might be a central pathway of HSC activation.

Isolation and characterization of a microsomal acid retinyl ester hydrolase

Previous work demonstrated both acid and neutral, bile salt-independent retinyl ester hydrolase activities in rat liver homogenates. Here we present the purification, identification, and characterization of an acid retinyl ester hydrolase activity from solubilized rat liver microsomes. Purification to homogeneity was achieved by sequential chromatography using SP-Sepharose cation exchange, phenyl-Sepharose hydrophobic interaction, concanavalin A-Sepharose affinity and Superose 12 gel filtration chromatography. The isolated protein had a monomer molecular mass of approximately 62 kDa, as measured by mass spectrometry. Gel filtration chromatography of the purified protein revealed a native molecular mass of approximately 176 kDa, indicating that the protein exists as a homotrimeric complex in solution. The purified protein was identified as carboxylesterase ES-10 (EC 3.1.1.1) by N-terminal Edman sequencing and extensive LC-MS/MS sequence analysis and cross-reaction with an anti-ES-10 antibody. Glycosylation analysis revealed that only one of two potential N-linked glycosylation sites is occupied by a high mannose-type carbohydrate structure. Using retinyl palmitate in a micellar assay system the enzyme was active over a broad pH range and displayed Michaelis-Menten kinetics with a K(m) of 86 microm. Substrate specificity studies showed that ES-10 is also able to catalyze hydrolysis of triolein. Cholesteryl oleate was not a substrate for ES-10 under these assay conditions. Real time reverse transcriptase-PCR and Western blot analysis revealed that ES-10 is highly expressed in liver and lung. Lower levels of ES-10 mRNA were also found in kidney, testis, and heart. A comparison of mRNA expression levels in liver demonstrated that ES-10, ES-4, and ES-3 were expressed at significantly higher levels than ES-2, an enzyme previously thought to play a major role in retinyl ester metabolism in liver. Taken together these data indicate that carboxylesterase ES-10 plays a major role in the hydrolysis of newly-endocytosed, chylomicron retinyl esters in both neutral and acidic membrane compartments of liver cells.

Effect of S-adenosyl-L-methionine on the activation, proliferation and contraction of hepatic stellate cells

Inhibition of hepatic stellate cell activation is an important clinical aspect for the control of liver inflammation, fibrosis and cirrhosis. S-adenosyl-L-methionine (SAM), an intermediate product of L-methionine metabolism, is a precursor of glutathione and an endogenous methyl donor. Although the hepato-protective action of SAM has been reported in several animal models, the effect of SAM on the function of hepatic stellate cells has not been elucidated. Using a primary-culture model of hepatic stellate cells, we found that SAM blunts the activation process as indicated by the suppression of expression of collagen alpha1(I) and smooth muscle alpha-actin. SAM also hampers the DNA synthesis of hepatic stellate cells stimulated with a dimer of platelet-derived growth factor-B via the inhibition of phosphorylation of PDGF receptor-beta and down-stream signaling pathways. SAM additionally inhibits the contraction of hepatic stellate cells by disturbing the formation of F-actin stress fibers and phosphorylated myosin light chains. Thus, SAM regulates the activation of hepatic stellate cells and may clinically contribute to therapy targeted at human liver fibrosis.

Galectin-1 is an inductor of pancreatic stellate cell activation

Pancreatic stellate cells (PSCs) play a key role in the development of pancreatic fibrosis, a pathological feature of chronic pancreatitis and pancreatic cancer. Here, we show that activation of rat PSCs in vitro is associated with increased expression of galectin-1 (gal-1) and that gal-1 modulates PSC function. Expression of the lectin was stimulated by fetal calf serum and platelet-derived growth factor. PSCs exposed to exogenous gal-1 proliferated at a higher rate and synthesised more collagen than controls. Gal-1-dependent collagen synthesis was blocked by lactose but not by cellobiose, suggesting that gal-1 acts on PSCs through targeting beta-galactoside-containing glycoconjugates. Analysis of gal-1 signalling in PSCs revealed an activation of the extracellular signal-regulated kinases 1 and 2 and enhanced DNA binding of AP-1 transcription factors. Together, our data implicate gal-1 in PSC activation and suggest further studies to analyse the role of endogenous lectins in the development of pancreatic fibrosis in vivo.

Suppressive effects ofPlatycodon grandiflorum on the progress of carbon tetrachloride-lnduced hepatic fibrosis

The suppressive effects of Platycodi Radix (Changkil: CK), the root of Platycodon grandiflorum A. DC (Campanulaceae), on the progress of acute carbon tetrachloride (CCl4)-induced hepatic fibrosis were investigated in the rat. CK significantly suppressed CCl4-induced hepatic necrosis and inflammation, as determined by the serum enzymatic activities of alanine and aspartate aminotransferase and serum tumor necrosis factor-alpha levels, in dose-dependent manners. In addition, the increased hepatic fibrosis after acute CCl4 treatment was suppressed by the administration of CK. CK also significantly prevented the elevation of hepatic alpha1 (I) procollagen (type I collagen) mRNA and alpha-smooth muscle actin (alpha-SMA) expressions in the liver of CCl4-intoxicated rats and also suppressed the induction of alpha-SMA and type I collagen in cultured hepatic stellate cells, in dose-dependent manners. These results suggest that the suppressive effects of CK against the progress of acute CCl4-induced hepatic fibrosis possibly involve mechanisms related to its ability to block both hepatic inflammation and the activation of hepatic stellate cells.

Proteomics to display tissue repair opposing injury response to LPS-induced liver injury

AIM: To examine the protein expression alterations in liver injury/repair network regulation as a response to gut-derived lipopolysaccharide (LPS) treatment, in order to anticipate the possible signal molecules or biomarkers in signaling LPS-related liver injury.

METHODS: Male BALB/c mice were treated with intra-peritoneal (i.p.) LPS (4 mg/kg) and sacrificed at 0, 6, 24 and 30 h to obtain livers. The livers were stained with hematoxylin and eosin for histopathologic analyses. Total liver protein was separated by two-dimensional gel electrophoresis (2-DE). The peptide mass of liver injury or repair related proteins were drawn up and the protein database was searched to identify the proteins.

RESULTS: Observations were as follows: (1) TRAIL-R2 was down regulated in livers of LPS-treated mice. TNFAIP1 was significantly up regulated at 6 h, then down-regulated at 24, 30 h with silent expression during senescent stage. (2) The amount of metaxin 2 and mitochondria import inner membrane translocase subunit TIM8a (TIMM8A) was increased upon treatment with LPS. (3) P34 cdc2 kinase was significantly up-regulated 30 h after LPS administration with silent expression during senescent, 6, 24 h treated stage. (4) The amount of proteasome activator 28 alpha subunit (PA28), magnesium dependent protein phosphatase (MDPP) and lysophospholipase 2 was decreased 6 h after LPS treatment but recovered or up-regulated 24 and 30 h after LPS treatment.

CONCLUSION: LPS-treated mouse liver displaying a time-dependent liver injury can result in expression change of some liver injury or repair related proteins.

Induction of myofibroblast MMP-9 transcription in three-dimensional collagen I gel cultures: regulation by NF-kappaB, AP-1 and Sp1

Chronic liver injury leads to a progressive wound healing response that eventually results in hepatic fibrosis characterised by net deposition of fibrillar extracellular matrix (ECM) and a qualitative shift from type IV to type I/III collagen. The pivotal cellular event underlying this response is hepatic stellate cell (HSC) activation towards a myofibroblast-like phenotype. Activated HSC contribute to ECM remodelling via secretion of type I/III collagens and matrix metalloproteinases (MMPs). Previous studies showed that three-dimensional (3D) contact of activated HSC with type I collagen further stimulates the ECM remodelling properties of HSC by inducing the type IV gelatinase, MMP-9. The aim of the current study was to confirm transcriptional activation of the MMP-9 gene and identify transcription factors regulating this response. Gelatin zymography and Northern blotting were used to confirm induction of MMP-9 protein and mRNA expression in primary rat HSC cultured in a three-dimensional collagen I gel lattice. MMP-9 promoter studies in transfected HSC and electrophoretic mobility shift assay (EMSA) were employed to study transcriptional events. Both NF-kappaB and AP-1 DNA were induced in HSC cultured in 3D collagen I gels and binding sites for these factors in the MMP-9 promoter were crucial for induction of transcription. By contrast removal of an Sp1 site in the promoter enhanced transcription, while over-expression of either Sp1 or Sp3 repressed transcription. It is concluded that 3D contact of activated HSC with collagen I stimulates MMP-9 expression by elevating NF-kappaB and AP-1 activities which are able to overcome the repressive influence of Sp1/Sp3 on MMP-9 gene transcription.

Herb medicine Inchin-ko-to (TJ-135) regulates PDGF-BB-dependent signaling pathways of hepatic stellate cells in primary culture and attenuates development of liver fibrosis induced by thioacetamide administration in rats

BACKGROUND/AIMS

We studied the effect of Inchin-ko-to (TJ-135), a herb medicine that has been clinically used for liver cirrhosis in Japan, on liver fibrosis in a rat model and on the function of stellate cells.

METHODS

Rat liver fibrosis was generated by thioacetamide (TAA) administration. DNA synthesis was assessed by 5-bromo-2'-deoxyuridine incorporation assay. Protein expression was analysed by western blotting. Collagen and fibronectin mRNA expression were analysed by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

TJ-135 improved liver fibrosis induced in rats by TAA administration. TJ-135 reduced collagen deposition and the expression of smooth muscle alpha-actin in fibrotic liver tissues and decreased the serum level of hyaluronic acid. In primary-cultured stellate cells, TJ-135 suppressed DNA synthesis and the expression of collagen alpha 1(I), collagen III, and fibronectin mRNAs. It hampered DNA synthesis and migration of PDGF-BB-stimulated stellate cells through inhibiting phosphorylation of PDGF receptor-beta and down-stream signaling pathways. Among TJ-135 components, 3-methyl-1,6,8-trihydroxyanthraquinone (emodin) derived from Rhei rhizoma was found to be the most active molecule.

CONCLUSIONS

TJ-135 and emodin regulate PDGF-dependent events in stellate cells and attenuate the development of liver fibrosis. Their clinical use may be beneficial for the therapy of human liver fibrosis.

Typing of hepatic nonparenchymal cells using fibulin-2 and cytoglobin/STAP as liver fibrogenesis-related markers

Fibulin-2 and cytoglobin/stellate cell activation-associated protein (Cygb/STAP) are considered to be markers of hepatic myofibroblasts (MFs) and stellate cells (HSCs), respectively. The aim of the present study was to characterize the nonparenchymal cells (NPCs) of normal rat livers and carbon tetrachloride-induced fibrotic rat livers with respect to the expression of these two proteins. NPCs in normal (Glisson's capsules) and fibrotic (fibrotic septa) connective tissues were immunohistochemically categorized into four cell types in terms of the expression of fibulin-2 and Cygb/STAP: fibulin-2 and Cygb/STAP double-positive (Fib(+)/STAP(+)); fibulin-2-positive and Cygb/STAP-negative (Fib(+)/STAP(-)); Fib(-)/STAP(+); and Fib(-)/STAP(-). The Glisson's capsules had Fib(+)/STAP(+) and Fib(-)/STAP(-) cell occupancy rates of 45.5% and 54.5%, respectively, but did not contain Fib(+)/STAP(-) or Fib(-)/STAP(+) cells. On the other hand, the fibrotic septa contained Fib(+)/STAP(+), Fib(-)/STAP(+), and Fib(-)/STAP(-) cells at occupancy rates of 35.0%, 50.5%, and 9.1%, respectively, but did not contain Fib(+)/STAP(-) cells. Thus, fibrosis is characterized by a dramatic increase in Fib(-)/STAP(+) NPCs, and a dramatic decrease in Fib(-)/STAP(-) NPCs. Fib(+)/STAP(+) NPCs are located uniformly in Glisson's capsules and peripherally in fibrotic septa. The present study strongly suggests that Fib(+)/STAP(+) and Fib(-)/STAP(+) NPCs correspond to MFs and activated HSCs, respectively, both of which may contribute to liver fibrogenesis.

Induction of cell death in activated hepatic stellate cells by targeted gene expression of the thymidine kinase/ganciclovir system

Liver fibrosis is the result from a relative imbalance between synthesis and degradation of matrix proteins. Following liver injury of any etiology, hepatic stellate cells undergo a response known as activation, which is the transition of quiescent cells into proliferative, fibrogenic, and contractile myofibroblasts. Upon this cellular transdifferentiation the effector cell becomes the major source of fibrillar and non-fibrillar matrix proteins resulting in excessive scar formation and cirrhosis, the end stage of fibrosis. Concomitant with progressive liver fibrosis, the tissue inhibitor of metalloproteinases-1 (TIMP-1) is strongly activated in hepatic stellate cells. We have developed a recombinant replication-defective adenovirus in which the TIMP-1 promoter is coupled to the herpes simplex virus thymidine kinase gene rendering activated hepatic stellate cells susceptible to ganciclovir. This novel targeted suicide gene approach was validated in a culture model considered to reflect an accelerated time course of the cellular and molecular events that occur during liver fibrosis. We demonstrate that transfer of the suicide gene to culture-activated hepatic stellate cells results in a strong expression of the respective transgene as assessed by Northern blot and Western blot analyses. The enzyme catalyzed the proper conversion of its prodrug subsequently initiating programmed cell death as estimated by caspase-3 assay and Annexin V-Fluos staining. Altogether, these results indicate that induction of programmed cell death is a promising approach to eliminate fibrogenic HSC.

Halofuginone, an inhibitor of collagen synthesis by rat stellate cells, stimulates insulin-like growth factor binding protein-1 synthesis by hepatocytes

BACKGROUND/AIMS

Halofuginone, an inhibitor of collagen synthesis, prevented and caused resolution of established hepatic fibrosis. A genomic approach in vivo was used to search for additional genes responsible for halofuginone mode of action.

METHODS

Fibrosis was induced in rats by thioacetamide (TAA) and evaluated by collagen type I gene expression and the levels of collagen, tissue inhibitors of metalloproteinases-2 and smooth-muscle actin. Halofuginone was given in the diet. cDNA from liver biopsies was hybridized on Atlas arrays comprising of 588 genes. The results were confirmed by Northern blots and in situ hybridization.

RESULTS

Insulin-like growth factor binding protein-1 (IGFBP-1) was one of the 13 genes differentially expressed in the fibrotic liver after halofuginone treatment. After 2 and 4 weeks, halofuginone prevented the TAA-induced down-regulation of IGFBP-1 gene expression. Halofuginone also prevented the TAA-dependent changes in IGFBP-3 gene expression. Halofuginone affected IGFBP-1 synthesis in rat hepatocytes and cells of hepatocyte origin and caused time- and dose-dependent increases in the IGFBP-1 gene expression and synthesis by HepG2 cells. The IGFBP-1 secreted by HepG2-inhibited stellate cell motility.

CONCLUSIONS

Halofuginone is an anti-fibrotic drug that inhibits collagen synthesis by stellate cells and preventing alteration in the synthesis of IGFBPs by hepatic cells.

Cytoglobin/STAP, its unique localization in splanchnic fibroblast-like cells and function in organ fibrogenesis

Cytoglobin/stellate cell activation-associated protein (Cygb/STAP) consists of a new class of hexacoordinate globin superfamily, which was recently discovered by a proteome analysis on the rat hepatic stellate cells. Unlike haemoglobin, myoglobin, and neuroglobin, Cygb/STAP is ubiquitously expressed in several organs, although its detailed localization has not been clarified. Immunohistochemistry and immunoelectron microscopy revealed that Cygb/STAP is uniquely localized in fibroblast-like cells in splanchnic organs, namely the vitamin A-storing cell lineage, but neither in epithelial cells, endothelial cells, muscle cells, blood cells, macrophages, nor dermal fibroblasts. The expression of Cygb/STAP was upregulated in fibrotic lesions of the pancreas and kidney in which activated fibroblast-like cells or myofibroblasts are known to increase in number. In cultured hepatic stellate cells, Cygb/STAP expression was augmented by the stimulation with sera, platelet-derived growth factor-BB, and transforming growth factor-beta 1. Overexpression of Cygb/STAP in NIH 3T3 cells induced the cells to lessen migratory activities and increase the expression of collagen alpha1(I) mRNA. These results indicate that Cygb/STAP is a tissue globin uniquely localized in splanchnic fibroblastic cell lineage and may play a role in fibrotic organ disorder.

Carbenoxolone inhibits DNA synthesis and collagen gene expression in rat hepatic stellate cells in culture

BACKGROUND/AIMS

This study using primary-cultured rat hepatic stellate cells (HSCs) was aimed to reveal the effect of carbenoxolone and the other gap-junction blockers on the proliferation and activation of HSCs.

METHODS

HSC morphology was microscopically evaluated. DNA synthesis was determined by [3H]thymidine incorporation. Expression of HSC activation markers and cell cycle-related proteins was evaluated by Western blot. Collagen alpha1(I) mRNA expression was evaluated by quantitative reverse transcription polymerase chain reaction.

RESULTS

Carbenoxolone triggered the morphological change of activated HSCs without inducing apoptosis. Culture-induced DNA synthesis was suppressed to 22.6 and 8.51%, respectively, by 40 and 80 microM carbenoxolone. The other gap-junction blockers failed to affect the morphology and the DNA synthesis of activated HSCs. Carbenoxolone decreased the expression of cyclins D1/2 and cyclin-dependent kinases 4/6. Platelet-derived growth factor (PDGF)-BB-elicited DNA synthesis was reduced to 45.6 and 3.27%, respectively, by 40 and 80 microM carbenoxolone. Phosphorylation of c-Raf, MEK and mitogen-activated protein kinase, but not PDGF receptor beta, under PDGF-BB stimulation was attenuated by carbenoxolone. Collagen alpha1(I) mRNA expression was significantly reduced. In addition, carbenoxolone suppressed the activation process of quiescent HSCs.

CONCLUSIONS

Carbenoxolone reduced the DNA synthesis and the expression of collagen alpha1(I) mRNA in activated HSCs independently of its pharmacological action as gap-junction blocker.

Interferon alfa down-regulates collagen gene transcription and suppresses experimental hepatic fibrosis in mice

The equilibrium between the production and degradation of collagen is rigorously controlled by a number of growth factors and cytokines. Interferon alfa (IFN-alpha) is now widely used for the treatment of chronic hepatitis C, which can improve serum levels of fibrotic markers and the degree of hepatic fibrosis, not only in patients who responded to therapy but also in those in whom it is ineffective. These findings may suggest that IFN-alpha possesses direct antifibrotic effects in addition to its antiviral activity. However, in contrast to IFN-gamma, which has been shown to suppress collagen gene transcription, little is known about the mechanisms responsible for the antifibrotic effects of IFN-alpha. Here, we report that IFN-alpha, when administered into transgenic mice harboring the alpha2(I) collagen gene (COL1A2) promoter sequence, significantly repressed promoter activation and prevented the progression of hepatic fibrosis induced by carbon tetrachloride injection. Transient transfection assays indicated that IFN-alpha decreased the steady-state levels of COL1A2 messenger RNA (mRNA) and inhibited basal and TGF-beta/Smad3-stimulated COL1A2 transcription in activated hepatic stellate cells (HSC). These inhibitory effects of IFN-alpha on COL1A2 transcription were exerted through the interaction between phosphorylated Stat1 and p300. Blocking of the IFN-alpha signal by overexpressing the intracellular domain-deleted IFN receptor increased basal COL1A2 transcription and abolished the inhibitory effects of IFN-alpha. In conclusion, our results indicate that IFN-alpha antagonizes the TGF-beta/Smad3-stimulated COL1A2 transcription in vitro and suppresses COL1A2 promoter activation in vivo, providing a molecular basis for antifibrotic effects of IFN-alpha.

Stimulation of proliferation of rat hepatic stellate cells by galectin-1 and galectin-3 through different intracellular signaling pathways

We found that the expression of galectin-1 and galectin-3 was significantly up-regulated in hepatic stellate cells (HSCs) both in the course of their transdifferentiation into myofibroblasts, a process of "self-activation," and in the fibrosis of liver tissues. Recombinant galectin-1 and galectin-3 stimulated the proliferation of cultured HSCs via the MEK1/2-ERK1/2 signaling pathway. However, galectin-3 utilized protein kinases C and A to induce this process, whereas galectin-1 did not. We also found that thiodigalactoside, a potent inhibitor of beta-galactoside binding, attenuated the effects of both galectins. In addition, galectin-1, but not galectin-3, promoted the migration of HSCs. Thus, it appears that galectin-1 and galectin-3, generated by activated HSCs, could participate in beta-galactoside binding and induce different intracellular signaling pathways leading to the proliferation of HSCs.

Apoptosis of T cells in the hepatic fibrotic tissue of the rat: a possible inducing role of hepatic myofibroblast-like cells

Apoptosis of T cells contributes to the immune homeostasis in inflamed organs. A prominent T-cell infiltration is usually seen in human chronic active hepatitis, being associated with liver fibrosis. In order to demonstrate T-cell apoptosis in the hepatic fibrotic tissue, we induced T-cell infiltration in the fibrotic liver of the rat by injecting concanavalin A (Con A), a T-cell mitogen. Lymphocytes increased in number with a peak at 1 day, preferentially distributing in the fibrotic tissue rather than the parenchyma. They consisted of CD4-positive and CD8-positive cells, and gave the feature of lymphoblasts. Double staining for CD3 and TUNEL demonstrated that T cells underwent apoptosis. Apoptotic cells were more frequent in the fibrotic livers than the normal livers, and were spatially associated with alpha-smooth muscle actin-positive myofibroblast-like cells that possibly derived from hepatic stellate cells (HSCs) and portal fibroblasts through activation. In vitro experiments demonstrated that lymphocyte apoptosis was more frequently induced in the co-culture of Con A-activated splenic T cells/activated HSCs compared to that induced in activated T cells/quiescent HSCs or resting T cells/activated HSCs. The present results indicate that T cells which have extravasated and infiltrated the hepatic fibrotic tissue undergo apoptosis probably through an interaction with myofibroblast-like cells, suggesting the regulatory role of the latter cells in T-cell accumulation in the fibrotic liver.

Characterization of human stellate cell activation-associated protein and its expression in human liver

This study cloned cDNA of human homologue (hSTAP) of rat stellate cell activation-associated protein (rSTAP). hSTAP gene is on chromosome 17q and is composed of four exons. Various types of cells including hepatic stellate cells expressed hSTAP mRNA. Recombinant hSTAP was a heme protein with the activity of peroxidase. hSTAP can be used as a marker of quiescent stellate cells in human liver.

PAV-1, a new rat hepatic stellate cell line converts retinol into retinoic acid, a process altered by ethanol

During liver fibrogenesis or long term culture, hepatic stellate cells (HSCs) evolved from "quiescent" to activated phenotype called "myofibroblast-like", a transition prevented by retinoic acid (RA). Little is known about RA generation by HSCs. Our study aimed to check the ability of these cells to produce RA from retinol (Rol) and the alterations of this metabolic step by ethanol. To study this metabolic pathway, primary cultures of HSCs represent the most physiological model but technically suffer several drawbacks. To circumvent these problems, an immortalized rat HSC line (named PAV-1) has been established. We validated PAV-1 cell line as a convenient model to study retinoids metabolism by HSCs. Then, we showed that PAV-1 cells express Rol-binding proteins (RBPs), enzymes and nuclear receptors involved in RA signaling pathway. We also demonstrated in situ generation of functional all-trans-RA (ATRA), using transient transfections with a RA-sensitive reporter gene, in situ modulation of tissue transglutaminase (tTG) activity and HPLC experiments. This production was Rol dose-dependent; 4-methylpyrazole, citral, and ethanol-inhibited which argues in favor of an enzymatic process.In conclusion, we first demonstrate in situ RA generation from Rol in a newly immortalized rat HSC line, named PAV-1. Inhibition of RA production by ethanol in PAV-1 and recent data, suggesting fundamental role of RA to prevent fibrosis development in the liver, allow us to hypothesize that Rol metabolism could be a primary target for ethanol during development of hepatic fibrosis.

Three-dimensional examination of hepatic stellate cells in rat liver and response to endothelin-1 using confocal laser scanning microscopy

BACKGROUND AND AIM

Hepatic stellate cells (HSC) are located in the space of Disse and are considered to participate in the regulation of sinusoidal flow. The contractility of quiescent HSC in normal liver has remained controversial, unlike activated HSC in injured liver. The aim of the present study was to examine the morphological changes in quiescent HSC in response to endothelin-1 (ET-1) perfusion.

METHODS

Sections (50 micro m thick) obtained from 15 normal rat livers with or without ET-1 perfusion (1 or 400 nmol/L) were stained immunohistochemically with antiglial fibrillary acidic protein (GFAP) antibody and then examined using confocal laser scanning microscopy. For examination of HSC, hepatic lobules were divided into three anatomic regions from the portal areas to the central veins. The length of HSC cytoplasmic processes and area of the sinusoids relative to the section area, excluding portal tracts and central veins, were measured.

RESULTS

The GFAP-positive HSC were distributed relatively evenly in the hepatic lobules and those in region 2 (the area between periportal and pericentral areas) tended to have longer cytoplasmic processes. Perfusion of 1 or 400 nmol/L ET-1 for 25 min resulted in swelling of the cell bodies of GFAP-positive HSC and condensation of the intermediate filaments compared with those perfused with buffer only. Although narrowing of the sinusoidal lumen was observed in each region after perfusion with 400 nmol/L ET-1, there was no apparent shortening of the cytoplasmic processes of HSC. These findings were also confirmed quantitatively.

CONCLUSION

In the normal rat liver, quiescent HSC are not involved in the regulation of sinusoidal blood flow in response to ET-1.

Monitoring the effects of drug treatment in rat models of disease by serum protein analysis

In this review we list from literature investigations on rat serum proteins using electrophoretic techniques in connection with drug testing. From our own research work, we provide annotated two-dimensional maps of rat serum proteins under control and experimental conditions. Emphasis is on species-specific components and on the effects of acute and chronic inflammation. We discuss our project of structural proteomics on rat serum as a minimally invasive approach to pharmacological investigation, and we outline a typical experimental plan for drug testing according to the above guidelines. We then report in detail on the results of our trials of anti-inflammatory drugs on adjuvant arthritis, an animal model of disease resembling in many aspects human rheumatoid arthritis. We demonstrate a correlation between biochemical parameters and therapeutic findings and outline the advantages of the chosen methodological approach, which proved also sensitive in revealing "side effects" of the test drugs. In an appendix we describe our experimental protocol when performing two-dimensional electrophoresis of rat serum.

Regulation of cultured rat hepatocyte proliferation by stellate cells

BACKGROUND/AIMS

This study using primary culture models was aimed to reveal the stellate cell-derived factors that regulate hepatocyte proliferation.

METHODS

Rat hepatocytes and stellate cells were cultured in serum-free Williams-E medium. We prepared hepatocyte mono-culture and two different co-cultures of hepatocytes and stellate cells; (1) co-culture on the same surface (Co-mix.) and (2) co-culture without contact between hepatocytes and stellate cells using a culture insert (Co-sep.). The change in the number and the DNA synthesis of hepatocytes was evaluated.

RESULTS

The number of hepatocytes decreased to 76% of the original number after 48 h of starting mono-culture, while it remained at 106% in mixed co-culture (Co-mix.) and increased to 135% in separated co-culture (Co-sep.). The hepatocyte DNA synthesis was enhanced by carbenoxolone in Co-mix. and reduced by NK1 in each co-culture. PD153035 had no effect. Heparitinase-I (20 mU/ml) and sodium chrolate (25 mM) reduced the hepatocyte DNA synthesis in Co-sep. to 71.8 and 61.6%, respectively. Activation of mitogen-activated protein kinase was induced in hepatocytes stimulated by conditioned mediums.

CONCLUSIONS

Hepatocyte proliferation was stimulated in the presence of stellate cells through hepatocyte growth factor, extracellular heparan sulfate (HS), and HS proteoglycan, and might be negatively regulated by gap junction-dependent mechanism.

Kupffer cell-mediated recruitment of rat dendritic cells to the liver: roles of N-acetylgalactosamine-specific sugar receptors

BACKGROUND & AIMS

Tissue recruitment of dendritic cells (DCs) is essential for antigen presentation. This study aimed to examine cellular and molecular mechanisms for DC recruitment to the liver.

METHODS

Purified rat DCs were injected into circulation and their traffics were analyzed in normal and Kupffer cell-depleted rats by intravital confocal microscopy and immunohistology. Affinities of DCs to sinusoidal cells were examined by a cell-binding assay. DC precursor recruitment was induced by particulate injection.

RESULTS

Both DC precursors and DCs at the antigen-transporting stage could be recruited to the liver, and their majority initially showed a selective binding to Kupffer cells. In the Kupffer cell-depleted rats, DCs could neither be recruited to the liver nor adhere to sinusoidal walls. Pretreatment with varied monosaccharides showed that sugar residues consisting of N-acetylgalactosamine were necessary for this binding. The binding was calcium-dependent, implying the C-type lectin involvement. Furthermore, DCs could endocytose N-acetylgalactosamine polymers in a receptor-specific manner.

CONCLUSIONS

The DC-Kupffer cell binding through N-acetylgalactosamine-specific C-type lectin-like receptors is crucial for DC recruitment to the liver. Rat DCs at least partly possess receptors for endocytosis of galactosylated antigens. These DC receptors as well as Kupffer cell lectins are presumably responsible for this binding.

Disease fingerprinting with cDNA microarrays reveals distinct gene expression profiles in lethal type 1 and type 2 cytokine-mediated inflammatory reactions

Development of polarized immune responses controls resistance and susceptibility to many microorganisms. However, studies of several infectious, allergic, and autoimmune diseases have shown that chronic type-1 and type-2 cytokine responses can also cause significant morbidity and mortality if left unchecked. We used mouse cDNA microarrays to molecularly phenotype the gene expression patterns that characterize two disparate but equally lethal forms of liver pathology that develop in Schistosoma mansoni infected mice polarized for type-1 and type-2 cytokine responses. Hierarchical clustering analysis identified at least three groups of genes associated with a polarized type-2 response and two linked with an extreme type-1 cytokine phenotype. Predictions about liver fibrosis, apoptosis, and granulocyte recruitment and activation generated by the microarray studies were confirmed later by traditional biological assays. The data show that cDNA microarrays are useful not only for determining coordinated gene expression profiles but are also highly effective for molecularly "fingerprinting" diseased tissues. Moreover, they illustrate the potential of genome-wide approaches for generating comprehensive views on the molecular and biochemical mechanisms regulating infectious disease pathogenesis.

Regulation of cell growth by redox-mediated extracellular proteolysis of platelet-derived growth factor receptor beta

Redox-regulated processes are important elements in various cellular functions. Reducing agents, such as N-acetyl-l-cysteine (NAC), are known to regulate signal transduction and cell growth through their radical scavenging action. However, recent studies have shown that reactive oxygen species are not always involved in ligand-stimulated intracellular signaling. Here, we report a novel mechanism by which NAC blocks platelet-derived growth factor (PDGF)-induced signaling pathways in hepatic stellate cells, a fibrogenic player in the liver. Unlike in vascular smooth muscle cells, we found that reducing agents, including NAC, triggered extracellular proteolysis of PDGF receptor-beta, leading to desensitization of hepatic stellate cells toward PDGF-BB. This effect was mediated by secreted mature cathepsin B. In addition, type II transforming growth factor-beta receptor was also down-regulated. Furthermore, these events seemed to cause a dramatic improvement of rat liver fibrosis. These results indicated that redox processes impact the cell's response to growth factors by regulating the turnover of growth factor receptors and that "redox therapy" is promising for fibrosis-related disease.

Characterization of a stellate cell activation-associated protein (STAP) with peroxidase activity found in rat hepatic stellate cells

A proteome approach for the molecular analysis of the activation of rat stellate cell, a liver-specific pericyte, led to the discovery of a novel protein named STAP (stellate cell activation-associated protein). We cloned STAP cDNA. STAP is a cytoplasmic protein with molecular weight of 21,496 and shows about 40% amino acid sequence homology with myoglobin. STAP was dramatically induced in in vivo activated stellate cells isolated from fibrotic liver and in stellate cells undergoing in vitro activation during primary culture. This induction was seen together with that of other activation-associated molecules, such as smooth muscle alpha-actin, PDGF receptor-beta, and neural cell adhesion molecule. The expression of STAP protein and mRNA was augmented time dependently in thioacetamide-induced fibrotic liver. Immunoelectron microscopy and proteome analysis detected STAP in stellate cells but not in other hepatic constituent cells. Biochemical characterization of recombinant rat STAP revealed that STAP is a heme protein exhibiting peroxidase activity toward hydrogen peroxide and linoleic acid hydroperoxide. These results indicate that STAP is a novel endogenous peroxidase catabolizing hydrogen peroxide and lipid hydroperoxides, both of which have been reported to trigger stellate cell activation and consequently promote progression of liver fibrosis. STAP could thus play a role as an antifibrotic scavenger of peroxides in the liver.

Expression profiling of acetaminophen liver toxicity in mice using microarray technology

Drug-induced hepatotoxicity causes significant morbidity and mortality and is a major concern in drug development. This is due, in large part, to insufficient knowledge of the mechanism(s) of drug-induced liver injury. In order to address this problem, we have evaluated the modulation of gene expression within the livers of mice treated with a hepatotoxic dose of acetaminophen (APAP) using high-density oligonucleotide microarrays capable of determining the expression profile of >11,000 genes and expressed sequence tags (ESTs). Significant alterations in gene expression, both positive and negative, were noted within the livers of APAP-treated mice. APAP-induced toxicity affected numerous aspects of liver physiology causing, for instance, >twofold increased expression of genes that encode for growth arrest and cell cycle regulatory proteins, stress-induced proteins, the transcription factor LRG-21, suppressor of cytokine signaling (SOCS)-2-protein, and plasminogen activator inhibitor-1 (PAI-1). A number of these and other genes and ESTs were detectable within the liver only after APAP treatment suggesting their potential importance in propagating or preventing further toxicity. These data provide new directions for mechanistic studies that may lead to a better understanding of the molecular basis of drug-induced liver injury and, ultimately, to a more rational design of safer drugs.

A unique charge-coupled device/xenon arc lamp based imaging system for the accurate detection and quantitation of multicolour fluorescence

In recent years the use of fluorescent dyes in biological applications has dramatically increased. The continual improvement in the capabilities of these fluorescent dyes demands increasingly sensitive detection systems that provide accurate quantitation over a wide linear dynamic range. In the field of proteomics, the detection, quantitation and identification of very low abundance proteins are of extreme importance in understanding cellular processes. Therefore, the instrumentation used to acquire an image of such samples, for spot picking and identification by mass spectrometry, must be sensitive enough to be able, not only, to maximise the sensitivity and dynamic range of the staining dyes but, as importantly, adapt to the ever changing portfolio of fluorescent dyes as they become available. Just as the available fluorescent probes are improving and evolving so are the users application requirements. Therefore, the instrumentation chosen must be flexible to address and adapt to those changing needs. As a result, a highly competitive market for the supply and production of such dyes and the instrumentation for their detection and quantitation have emerged. The instrumentation currently available is based on either laser/photomultiplier tube (PMT) scanning or lamp/charge-coupled device (CCD) based mechanisms. This review briefly discusses the advantages and disadvantages of both System types for fluorescence imaging, gives a technical overview of CCD technology and describes in detail a unique xenon/are lamp CCD based instrument, from PerkinElmer Life Sciences. The Wallac-1442 ARTHUR is unique in its ability to scan both large areas at high resolution and give accurate selectable excitation over the whole of the UV/visible range. It operates by filtering both the excitation and emission wavelengths, providing optimal and accurate measurement and quantitation of virtually any available dye and allows excellent spectral resolution between different fluorophores. This flexibility and excitation accuracy is key to multicolour applications and future adaptation of the instrument to address the application requirements and newly emerging dyes.