LA-ICP-MS for Pu source identification at Mayak PA, the Urals, Russia

Information on Pu in environmental samples is traditionally based on the determination of the (240+239)Pu activity via Alpha Spectrometry (AS). A large number of alpha spectrometry sources (planchettes) containing radiochemically separated Pu are therefore stored worldwide and are available for further analyses. These archive samples represent a resource from which valuable information on isotopic composition of alpha emitters including Pu can be obtained. The relative abundances of Pu isotopes can be used to trace specific Pu sources and characterize the relative contributions of different Pu sources in a sample. Thus, in addition to the total (239+240)Pu activity, determination of the (240)Pu/(239)Pu ratio can provide valuable information on the nature of the Pu emitting sources. The Pu isotopic ratios can be determined by mass spectrometry techniques such as Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICPMS) or Accelerator Mass Spectrometry (AMS) that require dissolution and complete destruction of the material deposited on the planchettes. In this study Laser Ablation (LA)-quadrupole-ICP-MS has been employed for the analysis of (239)Pu/(240)Pu ratios from alpha-planchettes prepared from samples originating from the Mayak PA nuclear facility, Russia. The results are compared with data from AMS and show that the (240)Pu/(239)Pu ratios obtained by LA-ICP-MS can be utilized to distinguish weapons-grade Pu from civil reprocessing sources. Moreover, isotope ratio mapping can also be performed across the planchettes, allowing e.g. the visualization of possible inhomogeneities in the Pu-isotope distribution on their surface. Thus, this solid sample technique can be applied to extract additional information from existing archives of samples.

Functional characteristics of neonatal rat β cells with distinct markers

Neonatal β cells are considered developmentally immature and hence less glucose responsive. To study the acquisition of mature glucose responsiveness, we compared glucose-regulated redox state, insulin synthesis, and secretion of β cells purified from neonatal or 10-week-old rats with their transcriptomes and proteomes measured by oligonucleotide and LC-MS/MS profiling. Lower glucose responsiveness of neonatal β cells was explained by two distinct properties: higher activity at low glucose and lower activity at high glucose. Basal hyperactivity was associated with higher NAD(P)H, a higher fraction of neonatal β cells actively incorporating (3)H-tyrosine, and persistently increased insulin secretion below 5 mM glucose. Neonatal β cells lacked the steep glucose-responsive NAD(P)H rise between 5 and 10 mM glucose characteristic for adult β cells and accumulated less NAD(P)H at high glucose. They had twofold lower expression of malate/aspartate-NADH shuttle and most glycolytic enzymes. Genome-wide profiling situated neonatal β cells at a developmental crossroad: they showed advanced endocrine differentiation when specifically analyzed for their mRNA/protein level of classical neuroendocrine markers. On the other hand, discrete neonatal β cell subpopulations still expressed mRNAs/proteins typical for developing/proliferating tissues. One example, delta-like 1 homolog (DLK1) was used to investigate whether neonatal β cells with basal hyperactivity corresponded to a more immature subset with high DLK1, but no association was found. In conclusion, the current study supports the importance of glycolytic NADH-shuttling in stimulus function coupling, presents basal hyperactivity as novel property of neonatal β cells, and provides potential markers to recognize intercellular developmental differences in the endocrine pancreas.

Glucose regulates rat beta cell number through age-dependent effects on beta cell survival and proliferation

Background

Glucose effects on beta cell survival and DNA-synthesis suggest a role as regulator of beta cell mass but data on beta cell numbers are lacking. We examined outcome of these influences on the number of beta cells isolated at different growth stages in their population.

Methods

Beta cells from neonatal, young-adult and old rats were cultured serum-free for 15 days. Their number was counted by automated whole-well imaging distinguishing influences on cell survival and on proliferative activity.

Results

Elevated glucose (10–20 versus 5 mmol/l) increased the number of living beta cells from 8-week rats to 30%, following a time- and concentration-dependent recruitment of quiescent cells into DNA-synthesis; a glucokinase-activator lowered the threshold but did not raise total numbers of glucose-recruitable cells. No glucose-induced increase occurred in beta cells from 40-week rats. Neonatal beta cells doubled in number at 5 mmol/l involving a larger activated fraction that did not increase at higher concentrations; however, their higher susceptibility to glucose toxicity at 20 mmol/l resulted in 20% lower living cell numbers than at start. None of the age groups exhibited a repetitively proliferating subpopulation.

Conclusions

Chronically elevated glucose levels increased the number of beta cells from young-adult but not from old rats; they interfered with expansion of neonatal beta cells and reduced their number. These effects are attributed to age-dependent differences in basal and glucose-induced proliferative activity and in cellular susceptibility to glucose toxicity. They also reflect age-dependent variations in the functional heterogeneity of the rat beta cell population.

Impact of a standardized nurse observation protocol including MEWS after Intensive Care Unit discharge

BACKGROUND

Analysis of in-hospital mortality after serious adverse events (SAE's) in our hospital showed the need for more frequent observation in medical and surgical wards. We hypothesized that the incidence of SAE's could be decreased by introducing a standard nurse observation protocol.

AIM

To investigate the effect of a standard nurse observation protocol implementing the Modified Early Warning Score (MEWS) and a color graphic observation chart.

METHODS

Pre- and post-intervention study by analysis of patients records for a 5-day period after Intensive Care Unit (ICU) discharge to 14 medical and surgical wards before (n=530) and after (n=509) the intervention.

RESULTS

For the total study population the mean Patient Observation Frequency Per Nursing Shift (POFPNS) during the 5-day period after ICU discharge increased from .9993 (95% C.I. .9637-1.0350) in the pre-intervention period to 1.0732 (95% C.I. 1.0362-1.1101) (p=.005) in the post-intervention period. There was an increased risk of a SAE in patients with MEWS 4 or higher in the present nursing shift (HR 8.25; 95% C.I. 2.88-23.62) and the previous nursing shift (HR 12.83;95% C.I. 4.45-36.99). There was an absolute risk reduction for SAE's within 120h after ICU discharge of 2.2% (95% C.I. -0.4-4.67%) from 5.7% to 3.5%.

CONCLUSION

The intervention had a positive impact on the observation frequency. MEWS had a predictive value for SAE's in patients after ICU discharge. The drop in SAE's was substantial but did not reach statistical significance.

Contribution of postnatally formed small beta cell aggregates to functional beta cell mass in adult rat pancreas

AIMS/HYPOTHESIS

Neogenesis of beta cells and their clustering to small aggregates is a key process in prenatal development of beta cell mass. We investigated the contribution of postnatally formed small aggregates to functional beta cell mass in adult rats.

METHODS

Conditions were defined for (1) counting total beta cell number in pancreases with relative error of <10% and (2) determining their distribution over aggregates of different size and over functionally different subpopulations.

RESULTS

Pancreases of 10-week-old male Wistar rats contained 2.8 ± 0.2 × 10⁶ beta cells, of which >90% was generated postnatally, involving: (1) neo-formation of 30,000 aggregates with diameter <50 μm including single cells; and (2) growth of 5,500 aggregates to larger sizes, accounting for 90% of the increase in cell number, with number of growing aggregates in the tail 50% greater than elsewhere. At 10 weeks, 86% of aggregates were <50 μm; compared with aggregates >200 μm, their beta cells exhibited a higher basal insulin content that was also resistant to glibenclamide-induced degranulation. The pool of Ki67-positive beta cells was sixfold larger than at birth and distributed over all aggregate sizes.

CONCLUSIONS/INTERPRETATION

We describe a method for in situ counting of beta cell numbers and subpopulations with low relative error. In adult rats, >90% of beta cells and beta cell aggregates are formed after birth. Aggregates <50 μm are more than 100-fold more abundant than aggregates >200 μm, which are selected for isolated islet studies. Their topographic and functional properties contribute to the functional heterogeneity of the beta cell population; their growth to larger aggregates with characteristic beta cell functions may serve future metabolic needs.

Specificity in beta cell expression of L-3-hydroxyacyl-CoA dehydrogenase, short chain, and potential role in down-regulating insulin release

A loss-of-function mutation of the mitochondrial beta-oxidation enzyme l-3-hydroxyacyl-CoA dehydrogenase, short chain (HADHSC), has been associated with hyperinsulinemic hypoglycemia in man. It is still unclear whether loss of glucose homeostasis in these patients (partly) results from a dysregulation of beta cells. This study examines HADHSC expression in purified rat beta cells and investigates whether its selective suppression elevates insulin release. Beta cells expressed the highest levels of HADHSC mRNA and protein of all examined tissues, including those with high rates of mitochondrial beta-oxidation. On the other hand, beta cells expressed relatively low levels of other beta-oxidation enzymes (acyl-CoA dehydrogenase short, medium, and long chain and acetyl-coenzyme A acyltransferase 2). HADHSC expression was sequence-specifically silenced by RNA interference, and the effects were examined on glucose-stimulated insulin secretion following 48-72 h of suppression. In both rat beta cells and in the beta cell line INS1 832-13, HADHSC silencing resulted in elevated insulin release at low and at high glucose concentrations, which appeared not to be caused by increased rates of glucose metabolism or an inhibition in fatty acid oxidation. These data indicate that the normal beta cell phenotype is characterized by a high expression of HADHSC and a low expression of other beta-oxidation enzymes. Down-regulation of HADHSC causes an elevated secretory activity suggesting that this enzyme protects against inappropriately high insulin levels and hypoglycemia.

Essential role of chicken ovalbumin upstream promoter-transcription factor II in insulin secretion and insulin sensitivity revealed by conditional gene knockout

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) has been implicated in the control of blood glucose by its potent effect on expression and signaling of various nuclear receptors. To understand the role of COUP-TFII in glucose homeostasis, conditional COUP-TFII-deficient mice were generated and crossed with mice expressing Cre under the control of rat insulin II gene promoter, resulting in deletion of COUP-TFII in pancreatic beta-cells. Homozygous mutants died before birth for yet undetermined reasons. Heterozygous mice appeared healthy at birth and showed normal growth and fertility. When challenged intraperitoneally, the animals had glucose intolerance associated with reduced glucose-stimulated insulin secretion. Moreover, these heterozygous mice presented a mild increase in fasting and random-fed circulating insulin levels. In accordance, islets isolated from these animals exhibited higher insulin secretion in low glucose conditions and markedly decreased glucose-stimulated insulin secretion. Their pancreata presented normal microscopic architecture and insulin content up to 16 weeks of study. Altered insulin secretion was associated with peripheral insulin resistance in whole animals. It can be concluded that COUP-TFII is a new, important regulator of glucose homeostasis and insulin sensitivity.

Plasticity of the beta cell insulin secretory competence: preparing the pancreatic beta cell for the next meal

It is well established that the acute rise in plasma glucose and in the incretin hormones glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (7-36) amide (GLP-1), as occurs during a meal, is of pivotal importance in regulating the minute-to-minute output of insulin from pancreatic beta cells. In addition to this well studied acute effect, both glucose and incretin hormones have been recently observed to determine the future secretory responsiveness of the cells. Such plasticity of the insulin secretory competence would imply that glucose and incretins not only act during the present meal, but also help to prepare the beta cells to function during the subsequent meal. Evidence supporting this hypothesis is growing as a result of physiological studies of cultured beta cells (either primary cells or beta cell lines), as well as from an increasing number of large-scale gene expression studies, exploring transcriptional and post-transcriptional events in genes regulated by glucose and incretins. On the basis of this hypothesis, one can speculate that genetic or environmental disturbances of plasticity of the insulin secretory competence is one aspect of beta cell dysfunction that can contribute to the aetiology of type 2 diabetes.

Differential modulation of rat hepatic stellate phenotype by natural and synthetic retinoids

Activation of hepatic stellate cells (HSC) is a central event in the pathogenesis of liver fibrosis during chronic liver injury. We examined the expression of retinoic acid (RAR) and retinoid X receptors (RXR) during HSC activation and evaluated the influence of natural and synthetic retinoic acids (RA) on the phenotype of culture-activated HSC. The expression of the major RAR/RXR subtypes and isoforms was analyzed by Northern hybridization. Presence of functional receptor proteins was established by gel shift analysis. Retinoic acids, RAR, and RXR selective agonists and an RAR antagonist were used to evaluate the effects of retinoid signalling on matrix synthesis by Northern blotting and immunoprecipitation, and on cell proliferation by BrdU incorporation. The 9-cisRA and synthetic RXR agonists reduced HSC proliferation and synthesis of collagen I and fibronectin. All-trans RA and RAR agonists both reduced the synthesis of collagen I, collagen III, and fibronectin, but showed a different effect on cell proliferation. Synthetic RAR agonists did not affect HSC proliferation, indicating that ATRA inhibits cell growth independent of its interaction with RARs. In contrast, RAR specific antagonists enhance HSC proliferation and demonstrate that RARs control proliferation in a negative way. In conclusion, natural RAs and synthetic RAR or RXR specific ligands exert differential effects on activated HSC. Our observations may explain prior divergent results obtained following retinoid administration to cultured stellate cells or to animals subjected to fibrogenic stimuli.

Effect of HMG-CoA reductase inhibitors on proliferation and protein synthesis by rat hepatic stellate cells

BACKGROUND/AIMS

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors called statins, have besides their cholesterol-lowering function, therapeutic value in conditions such as neo-angiogenesis and atherosclerosis. We investigated the effect of two statins on the proliferation rate and protein steady state levels of hepatic stellate cells (HSC).

METHODS

Cellular DNA synthesis under the influence of statins and/or platelet derived growth factor (PDGF) and mevalonate was evaluated by measuring BrdU incorporation. Synthesis of collagens type I, III, IV and fibronectin was quantified by ELISA. Additionally, we examined the influence of simvastatin on isoprenylation of Ras and RhoA proteins.

RESULTS

Lovastatin and simvastatin induced a dose-dependent inhibition of the proliferation rate of HSC. Subsequent addition of PDGF and/or mevalonate, after long-term exposure of simvastatin to HSC, did not reverse simvastatins' antiproliferative effect. Lovastatin and simvastatin reduced the protein steady state level of collagens type I (-40%), III (-45%) and IV (-27%). Membrane bound Ras steady state levels decreased under the influence of simvastatin. Membrane bound RhoA remained unaltered, whereas, cytosolic RhoA protein level was strongly reduced.

CONCLUSIONS

Our data showed that lovastatin and simvastatin inhibited HSC proliferation and collagen steady state levels by mechanisms independent of their lipid reducing activities.

PPARbeta regulates vitamin A metabolism-related gene expression in hepatic stellate cells undergoing activation

Activation of cultured hepatic stellate cells correlated with an enhanced expression of proteins involved in uptake and storage of fatty acids (FA translocase CD36, Acyl-CoA synthetase 2) and retinol (cellular retinol binding protein type I, CRBP-I; lecithin:retinol acyltransferases, LRAT). The increased expression of CRBP-I and LRAT during hepatic stellate cells activation, both involved in retinol esterification, was in contrast with the simultaneous depletion of their typical lipid-vitamin A (vitA) reserves. Since hepatic stellate cells express high levels of peroxisome proliferator activated receptor beta (PPARbeta), which become further induced during transition into the activated phenotype, we investigated the potential role of PPARbeta in the regulation of these changes. Administration of L165041, a PPARbeta-specific agonist, further induced the expression of CD36, B-FABP, CRBP-I, and LRAT, whereas their expression was inhibited by antisense PPARbeta mRNA. PPARbeta-RXR dimers bound to CRBP-I promoter sequences. Our observations suggest that PPARbeta regulates the expression of these genes, and thus could play an important role in vitA storage. In vivo, we observed a striking association between the enhanced expression of PPARbeta and CRBP-I in activated myofibroblast-like hepatic stellate cells and the manifestation of vitA autofluorescent droplets in the fibrotic septa after injury with CCl4 or CCl4 in combination with retinol.

Peroxisome proliferator-activated receptor-beta signaling contributes to enhanced proliferation of hepatic stellate cells

BACKGROUND & AIMS

The peroxisome proliferator-activated nuclear receptors (PPAR-alpha, PPAR-beta, and PPAR-gamma), which modulate the expression of genes involved in energy homeostasis, cell cycle, and immune function, may play a role in hepatic stellate cell activation. Previous studies focused on the decreased expression of PPAR-gamma in hepatic stellate cell activation but did not investigate the expression and role of the PPAR-alpha and -beta isotypes. The aim of this study was to evaluate the expression of the different PPARs during hepatic stellate cell activation in vitro and in situ and to analyze possible factors that might contribute to their expression. In a second part of the study, the effect of a PPAR-beta agonist on acute liver injury was evaluated.

METHODS

The effects of PPAR isotype-specific ligands on hepatic stellate cell transition were evaluated by bromodeoxyuridine incorporation, gel shifts, immunoprecipitation, and use of antisense PPAR-beta RNA-expressing adenoviruses. Tumor necrosis factor alpha-induced PPAR-beta phosphorylation and expression was evaluated by metabolic labeling and by using specific P38 inhibitors.

RESULTS

Hepatic stellate cells constitutively express high levels of PPAR-beta, which become further induced during culture activation and in vivo fibrogenesis. No significant expression of PPAR-alpha or -gamma was found. Stimulation of the P38 mitogen-activated protein kinase pathway modulated the expression of PPAR-beta. Transcriptional activation of PPAR-beta by L165041 enhanced hepatic stellate cell proliferation. Treatment of rats with a single bolus of CCl(4) in combination with L165041 further enhanced the expression of fibrotic markers.

CONCLUSIONS

PPAR-beta is an important signal-transducing factor contributing to hepatic stellate cell proliferation during acute and chronic liver inflammation.

Actin filament formation, reorganization and migration are impaired in hepatic stellate cells under influence of trichostatin A, a histone deacetylase inhibitor

BACKGROUND/AIMS

Previously, trichostatin A (TSA), a histone deacetylase inhibitor, has been shown to exhibit strong antifibrotic characteristics in hepatic stellate cells (HSC), which are known to play a central role in chronic liver diseases. TSA retained a more quiescent phenotype in spite of culture conditions that favor transdifferentiation into activated HSC.

METHODS

To identify TSA-sensitive genes, differential mRNA display, Northern and Western blot analysis were used and genes were functionally validated by using contraction and motility assays.

RESULTS

TSA prevented new actin filament formation by down-regulation of two nucleating proteins, actin related protein 2 (Arp2) and Arp3, and by up-regulation of adducin like protein 70 (ADDL70) and gelsolin, two capping proteins. RhoA, a key mediator in the development of the actin cytoskeleton, decreased following TSA exposure. Expression of proteins of Class III intermediate filaments was affected by TSA. Furthermore, F-actin and G-actin were expressed heterogeneously under influence of TSA. Functionally, TSA treatment abrogated migration of quiescent HSC, while migration was reduced in transitional HSC. The endothelin-1-induced contractility properties of HSC was not affected by TSA.

CONCLUSIONS

These data indicate that TSA affects the development of the actin cytoskeleton in quiescent HSC and thereby abrogates the process of HSC transdifferentiation.

Trichostatin A, a histone deacetylase inhibitor, suppresses collagen synthesis and prevents TGF-beta(1)-induced fibrogenesis in skin fibroblasts

Excessive production of collagens by alpha-smooth muscle actin (alpha-SMA)-positive myofibroblasts leads to fibrotic skin diseases, such as hypertrophic scarring. This process is characterized by an imbalance between extracellular matrix (ECM) synthesis and degradation, while transforming growth factor beta (TGF-beta(1)), known to be a key mediator of fibrogenesis, is up-regulated. In this study we have investigated the possible antifibrogenic effect of Trichostatin A (TSA), a histone deacetylase inhibitor, on rat skin fibroblasts in culture. mRNA steady-state levels and de novo protein synthesis of procollagen types I and III and alpha-SMA were inhibited when skin fibroblasts were treated with 100 nM TSA with or without TGF-beta(1). While the transcription rate of the procollagen alpha1(I) gene was increased following TSA or TGF-beta(1) treatment, TSA abrogated the stimulatory effect of TGF-beta(1) on procollagen alpha1(I) transcription when both compounds were added simultaneously. The reduction of procollagen alpha1(I) and alpha1(III) mRNA steady-state levels by TSA did not require de novo protein synthesis, while the effect of TSA on alpha-SMA mRNA steady-state levels was cycloheximide-sensitive. Interestingly, TSA affected TGF-beta(1) and its downstream mediators, i.e., the Smad family proteins. TSA strongly induced in a biphasic way the expression of 5'TG3' interacting factor (TGIF), a known endogenous corepressor molecule of the TGF-beta(1) signaling pathway. Addition of exogenous TGF-beta(1) did not interfere with the effect of TSA on the TGIF mRNA level. Our study shows that inhibition of histone deacetylases by TSA reduces expression of fibrosis-related genes in skin fibroblasts and this coincides by alterations in the TGF-beta(1) signaling pathway.

Somatostatin suppresses endothelin-1-induced rat hepatic stellate cell contraction via somatostatin receptor subtype 1

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are considered therapeutic targets to decrease portal hypertension. To elucidate some of the hemodynamic effects of somatostatin (SST) on portal pressure, the presence and function of SST receptors (SSTRs) on HSCs were investigated.

METHODS

SSTR messenger RNA expression, and SSTR presence was investigated using reverse-transcription polymerase chain reaction, real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. The function of SSTRs was studied by examining the effects of SST and specific SSTR agonists on endothelin-1(ET-1)-induced HSC contraction.

RESULTS

Specific amplicons for SSTR subtypes 1, 2, and 3 were demonstrated in rat liver and in activated HSCs. The presence of SSTR subtypes 1, 2, and 3 was confirmed by Western blotting. With immunohistochemistry, a strong staining of HSCs was obtained for SSTR subtypes 1, 2, and 3 in CCl4-treated rats, but not in normal rat liver. Incubation of HSCs on collagen gels with buffer, 10(-8) mol/L SST, and 2 x 10(-8) mol/L ET-1 resulted in collagen surface area decreases of 5.5% +/- 3.3%, 6.8% +/- 4.4%, and 49.8% +/- 8.3%, respectively. Relative contraction of gels preincubated with 10(-8) mol/L SST followed by 2 x 10(-8) mol/L ET-1 or vice versa as compared with maximal contraction (100%) with 2 x 10(-8) mol/L ET-1 were 72.6% +/- 17.9% and 76.2% +/- 12.6%, respectively (P < 0.05). SSTR agonist 1, but not SSTR agonist 2 or 3, was able to counteract the contractile effect of ET-1. CONCLUSIONA: Activated rat HSCs bear SSTR subtypes 1, 2, and 3. SST causes significant partial inhibition of ET-1-induced contraction of activated HSCs, mainly by stimulation of SSTR subtype 1.

Influence of aldosterone on collagen synthesis and proliferation of rat cardiac fibroblasts

1. Previous in vivo studies in men and experimental animal models have shown that hyperaldosteronemia is correlated with cardiac fibrosis due to increased total collagen synthesis. As yet, it is unclear whether aldosterone has direct pro-fibrogenic effect on cardiac fibroblasts, the fibrogenic effector cell in the myocardium, and if so which procollagens specifically are synthesized at higher rates. 2. The present study aims at establishing whether de novo collagen synthesis by cardiac fibroblasts is enhanced following exposure for 2x24 h to pharmacological (10(-7) - 10(-8) M), near-physiological (10(-9) M) or physiological (10(-10) - 10(-11) M) aldosterone concentrations. During the last 24 h, cells were metabolically labelled with [35S]-methionine/[35S]-cysteine. Labelled procollagens were immunoprecipitated quantitatively using antibodies against specific procollagens. Contrary to expectations, 10(-7) M aldosterone inhibited significantly de novo synthesis of procollagens type I and IV (-35% and -42%, respectively). For procollagen type III, only a tendency towards inhibition was observed. At lower concentrations of aldosterone (10(-8) - 10(-10) M), synthesis of procollagens type I, III or IV was unaffected. 3. Cellular DNA synthesis under influence of aldosterone was evaluated by measuring BrdU incorporation. Cells were treated with aldosterone, while BrdU was added during the last 16 h of treatment. Aldosterone had no demonstrable effect on cellular proliferation. 4. Reverse transcription-polymerase chain reaction (RT - PCR) clearly demonstrated the presence of mineralocorticoid receptor mRNA in cardiac fibroblasts. 5. In spite of the expression of the mineralocorticoid receptor by cultured cardiac fibroblasts, the pro-fibrogenic effect of aldosterone as observed in vivo, is not likely to be due to a direct effect of this hormone in cardiac fibroblasts.

Trichostatin A, lead compound for development of antifibrogenic drugs

Eukaryotic gene expression has mainly been studied in the context of trans-acting transcription factors and their interaction with regulatory cis-elements. Evidence is accumulating, that the higher order structure of chromatin also plays an essential role in eukaryotic gene expression. Hepatic stellate cells are the major cellular source of extracellular matrix synthesis in chronic liver diseases leading to fibrosis. We explored the antifibrogenic effect of the histone deacetylase inhibitor trichostatin A (TSA) on hepatic stellate cells in vitro. Primary hepatic stellate cells as well as activated, subcultured stellate cells were exposed to 10(-7) M-10(-9) M TSA. Collagens type I and III, and smooth muscle alpha-actin (alpha-SMA), a marker for transdifferentiation, were investigated at the protein and mRNA level by performing Northern hybridisation and quantitative immunoprecipitation. The antiproliferative effect was examined by 3H-thymidine incorporation and cell counting. Hyperacetylation of histone H4 was demonstrated by acid urea Triton-X-100 (AUT) polyacrylamide gel electrophoresis. TSA at 10(-7) M retarded the morphological changes characteristics for activation of primary stellate cells. Synthesis of collagens type I and III, and alpha-SMA was strongly inhibited at both protein and mRNA level. The proliferation rate of primary hepatic stellate cells was strongly suppressed by 10(-7) M TSA. Hyperacetylation of histone H4 showed to be maximal at 10(-7) M TSA. Primary hepatic stellate cells were more affected by TSA than subcultured stellate cells.

In vitro and in vivo activation of rat hepatic stellate cells results in de novo expression of L-type voltage-operated calcium channels

Following chronic liver injury, hepatic stellate cells (HSCs) transdifferentiate into myofibroblast-like cells, which develop contractile properties and contribute to increased resistance to blood flow. We investigated whether this phenotypic activation includes changes in the expression of L-type voltage-operated Ca2+ channels (VOCC), which mediate Ca2+ influx and regulate cell contraction in vascular cell types. Rat HSCs were studied in the quiescent phenotype and after their activation in vitro (cultured on plastic for 14 days) and in vivo (isolated from rats with CCl(4)-induced cirrhosis). Patch-clamp studies showed Ca2+ currents through L-type VOCC in HSCs activated both in vitro and in vivo, whereas no currents were detected in quiescent HSCs. Moreover, binding studies with (3)H-isradipine, a specific L-type VOCC antagonist, showed a large number of binding sites in activated HSCs, while no specific binding was found in quiescent HSCs. Finally, messenger RNA (mRNA) encoding L-type VOCC was not detected in quiescent HSCs as assessed by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis, whereas it was present in activated HSCs. Stimulation of L-type VOCC with KCl resulted in a marked increase in [Ca2+](i) followed by cell contraction in HSCs activated both in vitro and in vivo, whereas no effects were observed in quiescent HSCs. We conclude that the activation of HSCs is associated with up-regulation of L-type VOCC that mediate Ca2+ influx and cell contraction. These results may be relevant to the pathogenesis of portal hypertension.

Effect of aldosterone on collagen steady state levels in primary and subcultured rat hepatic stellate cells

BACKGROUND/AIMS

Activation of the renin-angiotensin-aldosterone system can lead to collagen accumulation and reactive myocardial fibrosis. This study aims at evaluating the effect of aldosterone on extracellular matrix synthesis by rat hepatic stellate cells.

METHODS

Cultured cells were treated with different concentrations of aldosterone (10(-6)-10(-10) M) and metabolically labeled with 35S-methionine/35S-cysteine. Procollagen types I, III and IV, laminin and fibronectin were specifically immunoprecipitated and quantified by phosphor imaging. Using the reverse transcription-polymerase chain reaction, we investigated the expression of the mineralocorticoid receptor in hepatic stellate cells.

RESULTS

Quantitation showed that 10(-6) M aldosterone induced procollagen type I synthesis significantly, whereas procollagen type IV expression was significantly affected by 10(-9) and 10(-10) M aldosterone, both in primary hepatic stellate cells. RT-PCR experiments clearly demonstrated a lack of expression of the mineralocorticoid receptor in hepatic stellate cells.

CONCLUSION

We demonstrated that aldosterone altered moderately procollagen type I and IV synthesis by primary hepatic stellate cells, but not by activated stellate cells which are the principal cellular sources of extracellular matrix proteins in chronic liver disease. Moreover, hepatic stellate cells do not express the mineralocorticoid receptor, suggesting that the observed modest changes of extracellular matrix synthesis are probably due to mineralocorticoid receptor unrelated mechanisms.

Renal antioxidant enzymes and fibrosis-related markers in the rat adriamycin model

Excessive generation of reactive oxygen intermediates can induce changes in the cellular antioxidant defence system. In this study we examine the antioxidant enzyme status and the expression of fibrosis-related marker proteins in the Adriamycin model of chronic renal failure in the rat. Twenty weeks after Adriamycin treatment, rats have overt nephrotic syndrome and renal failure with development of tubulo-interstitial fibrosis and glomerulosclerosis. Lipids accumulate in blood and in both glomeruli and tubulo-interstitial tissue. Desmin and alpha-smooth muscle actin expression increases in glomeruli and in the tubulo-interstitial area. Renal cortex antioxidant enzyme activities are decreased 20 weeks after Adriamycin injection (to 41% for catalase, to 56% for total superoxide dismutase and to 69% for glutathione peroxidase). The mRNA levels of catalase, Cu/Zn-superoxide dismutase and glutathione peroxidase-1 evaluated by Northern blot are decreased by more than 50% for catalase, Cu/Zn-superoxide dismutase and glutathione peroxidase-1. We conclude that in the rat Adriamycin-induced model of chronic renal failure with fibrosis, the combination of decreased antioxidant enzyme status in renal cortex with high concentrations of lipids in blood and renal tissue facilitates oxidative damage. Development of fibrosis is paralleled by increased expression of desmin and alpha-smooth muscle actin.

Antioxidant enzyme gene expression in rats with remnant kidney induced chronic renal failure

Reactive oxygen intermediates play a role in chronic renal injury and glomerulosclerosis. We investigate changes in renal cortex antioxidant enzyme gene expression in the rat remnant-kidney model of chronic renal failure and compare the new data to enzyme activities published earlier. Antioxidant enzyme gene expression is evaluated by Northern blot analysis of cortex mRNA, using cDNA probes for catalase, copper/zinc-containing superoxide dismutase, and glutathione peroxidase. Catalase gene expression decreases during development of renal failure; this decrease is accompanied by decreased catalase activity during the glomerulosclerosis phase of the remnant-kidney model. Copper/zinc superoxide dismutase and glutathione peroxidase gene expression remain at a normal level during progression of the model, whereas their activities show a temporary decrease in the early remnant kidney. In the remnant-kidney model, catalase seems to be more vulnerable to reactive oxygen intermediates than superoxide dismutase and glutathione peroxidase. Our results show that antioxidant enzyme activity and gene expression do not change in the same direction at all times during disease development and that all antioxidant enzymes do not respond in the same way.

All-trans and 9-cis retinoic acid alter rat hepatic stellate cell phenotype differentially

BACKGROUND

Hepatic stellate cells exert specific functions in the liver: storage of large amounts of retinyl esters, synthesis and breakdown of hepatic extracellular matrix, secretion of a variety of cytokines, and control of the diameter of the sinusoids.

AIMS

To examine the influence of all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9RA) on extracellular matrix production and proliferation of activated hepatic stellate cells.

METHODS

Cells were isolated using collagenase/pronase, purified by centrifugation in nycodenz, and cultured for two weeks. At this time point the cells exhibited the activated phenotype. Cells were exposed to various concentrations of ATRA and 9RA. The expression of procollagens I, III, and IV, of fibronectin and of laminin were analysed by immunoprecipitation and northern hybridisation.

RESULTS

ATRA exerted a significant inhibitory effect on the synthesis of procollagens type I, III, and IV, fibronectin, and laminin, but did not influence stellate cell proliferation, whereas 9RA showed a clear but late effect on proliferation. 9RA increased procollagen I mRNA 1.9-fold, but did not affect the expression of other matrix proteins.

CONCLUSION

Results showed that ATRA and 9RA exert different, often contrary effects on activated stellate cells. These observations may explain prior divergent results obtained following retinoid administration to cultured stellate cells or in animals subjected to fibrogenic stimuli.

Class VI intermediate filament protein nestin is induced during activation of rat hepatic stellate cells

Hepatic stellate cells are considered to be liver-specific pericytes that play a key role in liver fibrosis. Because these cells express desmin and smooth muscle alpha-actin, they were assumed to be of myogenic origin. This hypothesis became doubtful when it was reported that stellate cells also express glial fibrillary acidic protein and neural cell adhesion molecule. In the present study, we show that activated stellate cells express nestin, a class VI intermediate filament protein originally identified as a marker for neural stem cells. Expression of nestin was first studied during spontaneous activation of stellate cells in culture. Immunohistochemistry showed that nestin-positive stellate cells already appeared at day 3, and nearly all the cells became positive for nestin at day 6 and 15. The immunoreaction was present in filaments except in dividing cells. The presence of messenger RNA transcript for nestin was shown by reverse transcription polymerase chain reaction and sequencing of amplified complementary DNA. We then compared the presence of nestin with that of other intermediate filament proteins and smooth muscle alpha-actin. Immunoblotting showed that the relative concentrations of nestin, desmin, and vimentin increased between day 2 and 6 in primary culture. After the initial increase vimentin leveled off, while nestin and desmin showed a tendency to decrease. This pattern was quite different from that of glial fibrillary acidic protein, which kept declining, and smooth muscle alpha-actin, which increased continuously up to day 13 in culture. We then studied the presence of nestin in normal and CCl4-injured rat liver. In normal liver, minimal immunoreaction for nestin was observed within the liver parenchyma. During induction of fibrosis by carbon tetrachloride, nestin-positive stellate cells appeared at 6 weeks, which was late in comparison with the induction of desmin and smooth muscle alpha-actin. We conclude that nestin is induced in stellate cells during transition from the quiescent to the activated phenotype; culture activation is a stronger stimulus than in vivo activation by injection of CCl4. Taken together with reports on expression of glial fibrillary acidic protein and neural cell adhesion molecule by stellate cells, new experimental studies on the embryonic origin of these cells are required.

Purification of rat hepatic stellate cells by side scatter-activated cell sorting

In this study, we present a new method to obtain pure, viable, freshly isolated hepatic stellate cells. Stellate cells were purified by cell sorting using their high side scatter (SSC) of incident light. Purity of the cells was established by light and transmission electron microscopy (TEM). Starting from stellate cells that were 50% to 70% enriched by centrifugation in 11% Nycodenz, the cell purity after sorting was found to be 96.6% +/- 2.9%. Viability of the sorted cells was 90.8% +/- 2.2% as measured by the Trypan blue exclusion test and was confirmed by cell culturing. Per hour of sorting, 1.4 +/- 0.4 million stellate cells were obtained. Sorting runs of up to 4 hours were practically feasible, resulting in yields of 5 to 6 million cells per rat liver. Cells attached to plastic substratum within 24 hours. Subsequently, they spread and underwent spontaneous transition into myofibroblast-like cells. The purity of sorted cells was documented by reverse-transcriptase polymerase chain reaction (RT-PCR) experiments using specific primer pairs for messenger RNA (mRNA) species that were only present in parenchymal (preproalbumin), endothelial (endothelial cell nitric oxide synthase [eNOS]), stellate (desmin), or Kupffer cells (77- to 88-kd fucose receptor). Contaminating mRNA species were absent in sorted stellate cells. Next, we examined freshly sorted stellate cells by Western blotting to confirm the presence of relevant cytoskeletal proteins. Cells were positive for vimentin, desmin, and glial fibrillary acidic protein (GFAP), but negative for alpha-smooth muscle actin (alpha-SMA). Sorted and cultured cells were immunophenotyped for the presence of collagen types I, III, and IV, laminin, and the cytoskeletal proteins, alpha-SMA, desmin, vimentin, and GFAP. At 90 hours in culture, cells expressed all the investigated extracellular matrix proteins. Desmin was present in 82% +/- 1%, vimentin in 96% +/- 2.5%, and GFAP in 91% +/- 4.5% of cells. Alpha-SMA was present in 91% +/- 2% of cultured cells. We conclude that cell sorting based on SSC of incident light is a convenient method to obtain virtually pure stellate cells that can be used for direct analysis or for culturing. Although the yields obtained with this method are lower than with standard methods, and additional equipment is required, SSC-activated sorting offers the possibility of very pure cells when essential for analyses based on sensitive detection methods such as RT-PCR.