Comprehensive analysis of differential gene expression profiles on carbon tetrachloride-induced rat liver injury and regeneration

Ccrn4l as a pre-dose marker for prediction of cisplatin-induced hepatotoxicity susceptibility

Clinical cisplatin use is often limited by its drug-induced liver injury (DILI). Particularly, individual differences in susceptibility to DILI can cause life-threatening medical conditions. This study aimed to uncover the inherent genetic factors determining individual variations in hepatotoxicity susceptibility. Rats were subjected to liver biopsy and a 3-week postoperative recovery period before cisplatin administration. At 2 days post-treatment with cisplatin, the rats exhibited histopathological and serum biochemical alterations in the liver, and changes in hydrogen peroxide and cytochrome P450-2E1 levels. Based on these results of liver-related biochemical markers, 32 rats were grouped into the susceptible (top five) and resistant (bottom five) groups. Using RNA-sequencing, we compared gene expressions in the liver pre-biopsied from these two groups before cisplatin treatment and found 161 differently expressed genes between the Susceptible and Resistant groups. Among them, the clock-controlled Ccrn4l responsible for 'rhythmic process' was identified as a common gene downregulated inherently prior to drug exposure in both cisplatin- and acetaminophen-sensitive animals. Additionally, low Ccrn4l levels before cisplatin treatment in the Susceptible group were maintained even after treatment, with decreased antioxidants, increased nitration, and apoptosis. The relationship of Ccrn4l with catalase and mitochondrial RNAs in the liver was confirmed by correlation of their hepatic levels among individuals and similar patterns of circadian variation in their mRNA expression. Remarkably, Ccrn4l knockdown promoted cisplatin-induced mitochondrial dysfunction in WB-F344 cells with antioxidant catalase and apoptosis-related Bax changes. Inherent individual hepatic Ccrn4l level might be a novel factor affecting cisplatin-induced hepatotoxicity susceptibility, possibly through regulation of mitochondrial and antioxidant functions.

Inflammation-associated suppression of metabolic gene networks in acute and chronic liver disease

Inflammation has been recognized as essential for restorative regeneration. Here, we analyzed the sequential processes during onset of liver injury and subsequent regeneration based on time-resolved transcriptional regulatory networks (TRNs) to understand the relationship between inflammation, mature organ function, and regeneration. Genome-wide expression and TRN analysis were performed time dependently in mouse liver after acute injury by CCl₄ (2 h, 8 h, 1, 2, 4, 6, 8, 16 days), as well as lipopolysaccharide (LPS, 24 h) and compared to publicly available data after tunicamycin exposure (mouse, 6 h), hepatocellular carcinoma (HCC, mouse), and human chronic liver disease (non-alcoholic fatty liver, HBV infection and HCC). Spatiotemporal investigation differentiated lobular zones for signaling and transcription factor expression. Acute CCl₄ intoxication induced expression of gene clusters enriched for inflammation and stress signaling that peaked between 2 and 24 h, accompanied by a decrease of mature liver functions, particularly metabolic genes. Metabolism decreased not only in pericentral hepatocytes that underwent CCl₄-induced necrosis, but extended to the surviving periportal hepatocytes. Proliferation and tissue restorative TRNs occurred only later reaching a maximum at 48 h. The same upstream regulators (e.g. inhibited RXR function) were implicated in increased inflammation and suppressed metabolism. The concomitant inflammation/metabolism TRN occurred similarly after acute LPS and tunicamycin challenges, in chronic mouse models and also in human liver diseases. Downregulation of metabolic genes occurs concomitantly to induce inflammation-associated genes as an early response and appears to be initiated by similar upstream regulators in acute and chronic liver diseases in humans and mice. In the acute setting, proliferation and restorative regeneration associated TRNs peak only later when metabolism is already suppressed.

Hyperammonaemia induces hepatic injury with alteration of gene expression profiles

BACKGROUND

Hyperammonaemia is a serious metabolic disorder commonly observed in patients with hepatic failure. However, it is unknown whether hyperammonaemia has a direct adverse effect on the hepatocytes and thereby serves as both a cause and effect of hepatic failure.

AIMS

The purposes were to determine whether hepatic injury can be caused by hyperammonaemia, and if so, screen the key genes involved in hyperammonaemia.

METHODS

Hyperammonaemic rats were established via intragastric administration of the ammonium chloride solution. The liver tissues were assessed via biochemistry, histology, immunohistochemistry and microarray analysis. Selected genes were confirmed by quantitative RT-PCR.

RESULTS

Administration of the ammonium chloride caused the hyperammonaemia, accompanied with the changes of plasma markers indicating hepatic injury. A pathological assessment demonstrated increased apoptosis and higher level of cyclin D1 and cyclin A in hyperammonaemic rat liver. Microarray was performed on the liver samples and 198 differentially expressed genes were identified in hyperammonaemic rats and validated by quantitative RT-PCR. These genes were associated with many vital functional classes and belonged to different signal transduction pathways.

CONCLUSIONS

This study demonstrates that hyperammonaemia can directly induce hepatic injury via the hepatocyte apoptosis. Gene expression profile may provide the possible explanations and mechanisms for the hepatic injury induced by hyperammonaemia.

Transcriptomic responses of European flounder (Platichthys flesus) liver to a brominated flame retardant mixture

Male European flounder (Platichthys flesus) were exposed to a technical mixture of brominated diphenyl ethers (PDBEs, DE-71, Pentamix) that had been purified to remove contaminating dioxins. Controls were exposed to carrier solvent alone. Fish were exposed to decadally increasing concentrations of Pentamix via both sediment and spiked food. The GENIPOL P. flesus cDNA microarray, differentially expressed gene profiling (DEG) and quantitative PCR were employed to detect hepatic transcriptional differences between exposed fish and controls. Gene transcriptional changes were more sensitive to Pentamix exposure than biomarkers measured previously. Pentamix exposure induced transcripts coding for enzymes of xenobiotic metabolism (CYP1A, aldo-keto reductases) and elicited endocrine disruption (vitellogenin and thyroid hormone receptor alpha), with effects on CYP1A and VTG occurring at the highest exposure. Ontology analysis clearly showed dose-responsive changes indicative of oxidative stress, induction of mitochondrial dysfunction, and apoptosis. We conclude that exposure to PBDEs in both sediment and food has a significant adverse effect on a broad range of crucial biochemical processes in the livers of this widely distributed estuarine fish species, the flounder.

Conditional genetic elimination of hepatocyte growth factor in mice compromises liver regeneration after partial hepatectomy

Hepatocyte growth factor (HGF) has been shown to be indispensable for liver regeneration because it serves as a main mitogenic stimulus driving hepatocytes toward proliferation. We hypothesized that ablating HGF in adult mice would have a negative effect on the ability of hepatocytes to regenerate. Deletion of the HGF gene was achieved by inducing systemic recombination in mice lacking exon 5 of HGF and carrying the Mx1-cre or Cre-ER(T) transgene. Analysis of liver genomic DNA from animals 10 days after treatment showed that a majority (70-80%) of alleles underwent cre-induced genetic recombination. Intriguingly, however, analysis by RT-PCR showed the continued presence of both unrecombined and recombined forms of HGF mRNA after treatment. Separation of liver cell populations into hepatocytes and non-parenchymal cells showed equal recombination of genomic HGF in both cell types. The presence of the unrecombined form of HGF mRNA persisted in the liver in significant amounts even after partial hepatectomy (PH), which correlated with insignificant changes in HGF protein and hepatocyte proliferation. The amount of HGF produced by stellate cells in culture was indirectly proportional to the concentration of HGF, suggesting that a decrease in HGF may induce de novo synthesis of HGF from cells with residual unrecombined alleles. Carbon tetrachloride (CCl4)-induced regeneration resulted in a substantial decrease in preexisting HGF mRNA and protein, and subsequent PH led to a delayed regenerative response. Thus, HGF mRNA persists in the liver even after genetic recombination affecting most cells; however, PH subsequent to CCl4 treatment is associated with a decrease in both HGF mRNA and protein and results in compromised liver regeneration, validating an important role of this mitogen in hepatic growth.

1H NMR-based metabonomics approach in a rat model of acute liver injury and regeneration induced by CCl4 administration

The administration of carbon tetrachloride (CCl(4)) has been established as a model of toxin-induced acute and chronic liver injury. In the present study, we investigate the progression of the biochemical response to acute CCl(4)-induced liver injury, capturing metabolic variations during both toxic insult and regeneration using NMR-based metabonomic analysis of liver tissue and plasma. A single dose of CCl(4) (1 mL/kg BW) was intraperitoneally administered to male Wister rats sacrificed every 12h up to 72 h post treatment, while healthy animals served as controls. Acquired (1)H NMR spectra of liver tissue extracts and plasma samples were explored with multivariate analysis and the resulted models were correlated with conventional biochemical and histopathological indices of toxicity for monitoring the progression of experimental injury. The metabonomic analysis resulted in discrimination between the subjects under toxic insult (up to 36 h) and those at the regenerative phase (peaked at 48 h). At 72 h normalization of liver's pathology similar to the controls group was apparent. Principal component analysis (PCA) trajectories highlighted the time points of the greater degree of toxic insult and the regenerative state. A number of metabolites such as glucose, lactate, choline, formate exhibited variations suggesting CCl(4) induced impairment in essential biochemical pathways as energy metabolism, lipid biosynthesis and transmethylation reactions. The latter provides new evidence of B12 and folate pathways deficiency, indicative of new mechanistic implications possibly by direct inhibition of B12 dependent enzymes by the chlorinated radicals of CCl(4) metabolism.

Cholesterol: recapitulation of its active role during liver regeneration

Liver regeneration is a compensatory hyperplasia produced by several stimuli that promotes proliferation in order to provide recovery of the liver mass and architecture. This process involves complex signalling cascades that receive feedback from autocrine and paracrine pathways, recognized by parenchymal as well as non-parenchymal cells. Nowadays the dynamic role of lipids in biological processes is widely recognized; however, a systematic analysis of their importance during liver regeneration is still missing. Therefore, in this review we address the role of lipids including the bioactive ones such as sphingolipids, but with special emphasis on cholesterol. Cholesterol is not only considered as a structural component but also as a relevant lipid involved in the control of the intermediate metabolism of different liver cell types such as hepatocytes, hepatic stellate cells and Kupffer cells. Cholesterol plays a significant role at the level of specific membrane domains, as well as modulating the expression of sterol-dependent proteins. Moreover, several enzymes related to the catabolism of cholesterol and whose activity is down regulated are related to the protection of liver tissue from toxicity during the process of regeneration. This review puts in perspective the necessity to study and understand the basic mechanisms involving lipids during the process of liver regeneration. On the other hand, the knowledge acquired in this area in the past years, can be considered invaluable in order to provide further insights into processes such as general organogenesis and several liver-related pathologies, including steatosis and fibrosis.

Mass spectrometry-based quantification of myocardial protein adducts with acrolein in an in vivo model of oxidative stress

Acrolein (ACR) exposure leads to the formation of protein-ACR adducts. Protein modification by ACR has been associated with various chronic diseases including cardiovascular and neurodegenerative diseases. Here, we report an analytical strategy that enables the quantification of Michael-type protein adducts of ACR in mitochondrial proteome samples using liquid chromatography in combination with tandem mass spectrometry and selected ion monitoring (LC-MS/MS SRM) analysis. Our approach combines site-specific identification and relative quantification at the peptide level of protein-ACR adducts in relation to the unmodified protein thiol pool. Treatment of 3-month-old rats with CCl(4) , an established in vivo model of acute oxidative stress, resulted in significant increases in the ratios of distinct ACR-adducted peptides to the corresponding unmodified thiol-peptides obtained from proteins that were isolated from cardiac mitochondria. The mitochondrial proteins that were found adducted by ACR were malate dehydrogenase, NADH dehydrogenase [ubiquinone] flavoprotein 1, cytochrome c oxidase subunit VIb isoform 1, ATP synthase d chain, and ADP/ATP translocase 1. The findings indicate that protein modification by ACR has potential value as an index of mitochondrial oxidative stress.

Transcriptional response of hepatic largemouth bass (Micropterus salmoides) mRNA upon exposure to environmental contaminants

Microarrays enable gene transcript expression changes in near-whole genomes to be assessed in response to environmental stimuli. We utilized oligonucleotide microarrays and subsequent gene set enrichment analysis (GSEA) to assess patterns of gene expression changes in male largemouth bass (Micropterus salmoides) hepatic tissues after a 96 h exposure to common environmental contaminants. Fish were exposed to atrazine, cadmium chloride, PCB 126, phenanthrene and toxaphene via intraperitoneal injection with target body burdens of 3.0, 0.00067, 2.5, 50 and 100 µg g(-1), respectively. This was conducted in an effort to identify potential biomarkers of exposure. The expressions of 4, 126, 118, 137 and 58 mRNA transcripts were significantly (P ≤ 0.001, fold change ≥2×) affected by exposure to atrazine, cadmium chloride, PCB 126, phenanthrene and toxaphene exposures, respectively. GSEA revealed that none, four, five, five and three biological function gene ontology categories were significantly influenced by exposure to these chemicals, respectively. We observed that cadmium chloride elicited ethanol metabolism responses, and along with PCB 126 and phenanthrene affected transcripts associated with protein biosynthesis. PCB 126, phenanthrene and toxaphene also influenced one-carbon compound metabolism while PCB 126 and phenanthrene affected mRNA transcription and mRNA export from the nucleus and may have induced an antiestrogenic response. Atrazine was found to alter the expression of few hepatic transcripts. This work has highlighted several biological processes of interest that may be helpful in the development of gene transcript biomarkers of chemical exposure in fish.

Gene expression profiling in the lung tissue of cynomolgus monkeys in response to repeated exposure to welding fumes

Many in the welding industry suffer from bronchitis, lung function changes, metal fume fever, and diseases related to respiratory damage. These phenomena are associated with welding fumes; however, the mechanism behind these findings remains to be elucidated. In this study, the lungs of cynomolgus monkeys were exposed to MMA-SS welding fumes for 229 days and allowed to recover for 153 days. After the exposure and recovery period, gene expression profiles were investigated using the Affymetrix GeneChip Human U133 plus 2.0. In total, it was confirmed that 1,116 genes were up-or downregulated (over 2-fold changes, P\0.01) for the T1 (31.4 ± 2.8 mg/m3) and T2 (62.5 ± 2.7 mg/m3) dose groups. Differentially expressed genes in the exposure and recovery groups were analyzed, based on hierarchical clustering, and were imported into Ingenuity Pathways Analysis to analyze the biological and toxicological functions. Functional analysis identified genes involved in immunological disease in both groups. Additionally, differentially expressed genes in common between monkeys and rats following welding fume exposure were compared using microarray data, and the gene expression of selected genes was verified by real-time PCR. Genes such as CHI3L1, RARRES1, and CTSB were up-regulated and genes such as CYP26B1, ID4, and NRGN were down-regulated in both monkeys and rats following welding fume exposure. This is the first comprehensive gene expression profiling conducted for welding fume exposure in monkeys, and these expressed genes are expected to be useful in helping to understand transcriptional changes in monkey lungs after welding fume exposure.

Toxicity and recovery in the pregnant mouse after gestational exposure to the cyanobacterial toxin, cylindrospermopsin

Cylindrospermopsin (CYN) is a tricyclic alkaloid toxin produced by fresh water cyanobacterial species worldwide. CYN has been responsible for both livestock and human poisoning after oral exposure. This study investigated the toxicity of CYN to pregnant mice exposed during different segments of gestation. The course of recovery and individual responses to the toxin were evaluated. Adverse effects of CYN were monitored up to 7 weeks post-dosing by clinical examination, histopathology, biochemistry and gene expression. Exposure on gestational days (GD) 8-12 induced significantly more lethality than GD13-17 exposure. Periorbital, gastrointestinal and distal tail hemorrhages were seen in both groups. Serum markers indicative of hepatic injury (alanine amino transferase, aspartate amino transferase and sorbitol dehydrogenase) were increased in both groups; markers of renal dysfunction (blood urea nitrogen and creatinine) were elevated in the GD8-12 animals. Histopathology was observed in the liver (centrilobular necrosis) and kidney (interstitial inflammation) in groups exhibiting abnormal serum markers. The expression profiles of genes involved in ribosomal biogenesis, xenobiotic and lipid metabolism, inflammatory response and oxidative stress were altered 24 h after the final dose. One week after dosing, gross, histological and serum parameters had returned to normal, although increased liver/body weight ratio and one instance of gastrointestinal bleeding was found in the GD13-17 group. Gene expression changes persisted up to 2 weeks post-dosing and returned to normal by 4 weeks. Responses of individual animals to CYN exposure indicated highly significant inter-animal variability within the treated groups.

Progress in developing rat models of hepatic encephalopathy

Hepatic encephalopathy is a serious complication of acute and chronic liver diseases and has a high mortality rate. The pathogenesis of hepatic encephalopathy remains unclear, and there is no means of prevention or effective cure for the disease. Therefore, there is an urgent need for the basic and clinical research of hepatic encephalopathy to elucidate its pathogenesis. The development of animal models is important for elucidating the pathogenesis of hepatic encephalopathy and providing new avenues for diagnosis and therapy of the disease. Among a variety of animal models, rat model is applied most widely for similarity to humans, repeatability, reliability, applicability, controllability, simplicity and economy. In this paper, we briefly review various rat models of hepatic encephalopathy that have different origins.

In vitro assay for drug-induced hepatosteatosis using rat primary hepatocytes, a fluorescent lipid analog and gene expression analysis

To evaluate new drugs' potential for hepatosteatosis, we developed a cell-based assay using a fluorescent fatty acid analog: BODIPY558/568 C12. Rat primary hepatocytes were exposed to positive reference compounds [cyclosporine A (CsA), clofibrate (CFR), tetracycline (TC), valproic acid (VPA), carbon tetrachloride (CCl4), tamoxifen (TMX)] in the presence of BODIPY558/568 C12. The formation of fluorscecent particles or lipid droplets in the cytoplasm was confirmed by confocal laser scanning microscopy and electron microscopy respectively. The accumulation of BODIPY558/568 C12 was measured by fluorometry and high content imaging method. All positive reference compounds increased fluorescent particles in number and fluorescence intensity. High content imaging was more sensitive and selective method than fluorometry to detect fluorescent particles. Gene expression analysis of the hepatocytes showed two patterns: genes related to lipid metabolism/synthesis were down-regulated by oxidative stress inducing compounds: CsA, TC and TMX, and up-regulated by peroxisome proliferator-activated receptor-alpha agonists: CFR and VPA. From these findings, we concluded that the cell-based assay developed in this study is an appropriate method to predict drugs' potential for hepatosteatosis, and gene expression analysis is useful to profile the mechanism of the hepatosteatosis.

Microarray-based analysis of the lung recovery process after stainless-steel welding fume exposure in Sprague-Dawley rats

Repeated exposure to welding fumes promotes a reversible increase in pulmonary disease risk, but the molecular mechanisms by which welding fumes induce lung injury and how the lung recovers from such insults are unclear. In the present study, pulmonary function and gene-expression profiles in the lung were analyzed by Affymetrix GeneChip microarray after 30 days of consecutive exposure to manual metal arc welding combined with stainless-steel (MMA-SS) welding fumes, and again after 30 days of recovery from MMA-SS fume exposure. In total, 577 genes were identified as being either up-regulated or down-regulated (over twofold changes, p < 0.05) in the lungs of low-dose or high-dose groups. Differentially expressed genes were classified based on a k-means clustering algorithm and biological functions and molecular networks were further analyzed using Ingenuity Pathways Analysis. Among the genes affected by exposure to or recovery from MMA-SS fumes, the transcriptional changes of 13 genes that were highly altered by treatment were confirmed by quantitative real-time PCR. Notably, Mmp12, Cd5l, Ccl7, Cxcl5, and Spp1 related to the immune response were up-regulated only in the exposure group, whereas Trem2, IgG-2a, Igh-1a, and Igh were persistently up-regulated in both the exposure and recovery groups. In addition, several genes that might play a role in the repair process of the lung were up-regulated exclusively in the recovery group. Collectively, these data may help elucidate the molecular mechanism of the recovery process of the lung after welding fume exposure.

Effects of bone marrow stem cell transplantation on acute hepatic injury induced by carbon tetrachloride in rats

AIM: To observe the effects of bone marrow mesenchymal stem cells (BMSCs) on restoration of acute liver injury induced by carbon tetrachloride (CCl₄) in rats via RhoA-ROCK signaling pathway.

METHODS: BMSCs were isolated from male Sprague-Dawley (SD) rats, cultured and purified in a BMSCs culture system in vitro using their adherent characteristics. Rats were divided into 3 groups: normal control (N, n = 10), CCl₄ (C group for short hereafter, n = 10) and CCl₄ plus BMSCs (T group for short hereafter, n = 10). All the rats were sampled at the appointed time and various target markers were determined as follows: hematoxylin and eosin (HE) staining, as well as the index changes of liver's enzymology, were applied for evaluating the improvement of hepatic histological damage. The expression of RhoA mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR), and the expression of RhoA protein was assayed by Western blot.

RESULTS: In the T group, liver function of CCl₄-induced acute hepatic injury after BMSCs transplantation was improved markedly as compared with the C group (1 d, ALT: 89.70 ± 3.09 vs 147.59 ± 6.83; AST: 263.67 ± 17.05 vs 472.68 ± 19.04, P < 0.01 or 0.05; 7 d, ALT: 42.38 ± 14.31 vs 92.75 ± 6.70; AST: 173.85 ± 16.80 vs 260.41 ± 25.35, all P < 0.05), consistent with the improvement of hepatic histology. Little expression of RhoA was detected in the normal control group. In the C group, both mRNA and protein of RhoA were increased significantly as compared with normal control (1.39 ± 0.046 vs 0.57 ± 0.010, 1.23 ± 0.020 vs 0.35 ± 0.036, both P < 0.01), then was decreased slowly. In the T groups, the expression mRNA and protein of RhoA were obviously decreased, in concomitant with the restoration of liver histology and function, as compared with C group.

CONCLUSION: Rho-ROCK signaling pathways are involved in the process of acute hepatic injury in rats induced by CCl₄. BMSCs transplantation may accelerate the restoration of acute liver injury by inhibition of RhoA-ROCK signaling pathway.

Differential expression of the genes involved in amino acids and nitrogen metabolisms during liver regeneration of mice

AIM

Liver regeneration is a highly coordinated response to hepatic injury or resection that is controlled by the body's overall requirement for liver function. The level of circulating amino acids in blood increases after acute liver injury and administration of amino acid mixtures induces hepatic DNA replication. These findings suggest a close connection between amino acid metabolism and hepatic proliferation. However, the underlying molecular mechanisms have not been completely elucidated. Here, we applied a cDNA micro-array technique to analyze expression profiles of the genes associated with nitrogen and amino acid metabolism during liver regeneration in mice following treatment with CCl(4).

METHODS

Seventy-nine genes were identified for their significantly altered expression patterns at different stages of liver damage and regeneration.

RESULTS

We observed that the numbers of down-regulated genes were remarkably higher than that of up-regulated genes at 1.5 days following carbon tetrachloride administration when hepatic DNA replication was most active, indicating the existence of a counter balance between cell proliferation and liver metabolism functions.

CONCLUSIONS

Our results suggest that suppression of amino acids metabolism after acute liver injury results in the accumulation of amino acids in plasma that serves as a driving force for liver regeneration.

Paraoxonase-1 is related to inflammation, fibrosis and PPAR delta in experimental liver disease

BACKGROUND

Paraoxonase-1 (PON1) is an antioxidant enzyme synthesized by the liver. It protects against liver impairment and attenuates the production of the pro-inflammatory monocyte chemoattractant protein-1 (MCP-1). We investigated the relationships between hepatic PON1 and MCP-1 expression in rats with liver disease and explored the possible molecular mechanisms involved.

METHODS

CCl4 was administered for up to 12 weeks to induce liver damage. Serum and hepatic levels of PON1 and MCP-1, their gene and protein expression, nuclear transcription factors, and histological and biochemical markers of liver impairment were measured.

RESULTS

High levels of PON1 and MCP-1 expression were observed at 12th week in the hepatocytes surrounding the fibrous septa and inflammatory areas. CCl4-administered rats had an increased hepatic PON1 concentration that was related to decreased gene transcription and inhibited protein degradation. Decreased PON1 gene transcription was associated with PPARdelta expression. These changes were accompanied by increased hepatic MCP-1 concentration and gene expression. There were significant direct relationships between hepatic PON1 and MCP-1 concentrations (P = 0.005) and between PON1 and the amount of activated stellate cells (P = 0.001).

CONCLUSION

Our results from this experimental model suggest a hepato-protective role for PON1 against inflammation, fibrosis and liver disease mediated by MCP-1.

Paraoxonase-1 is related to inflammation, fibrosis and PPAR delta in experimental liver disease

BACKGROUND

Paraoxonase-1 (PON1) is an antioxidant enzyme synthesized by the liver. It protects against liver impairment and attenuates the production of the pro-inflammatory monocyte chemoattractant protein-1 (MCP-1). We investigated the relationships between hepatic PON1 and MCP-1 expression in rats with liver disease and explored the possible molecular mechanisms involved.

METHODS

CCl4 was administered for up to 12 weeks to induce liver damage. Serum and hepatic levels of PON1 and MCP-1, their gene and protein expression, nuclear transcription factors, and histological and biochemical markers of liver impairment were measured.

RESULTS

High levels of PON1 and MCP-1 expression were observed at 12th week in the hepatocytes surrounding the fibrous septa and inflammatory areas. CCl4-administered rats had an increased hepatic PON1 concentration that was related to decreased gene transcription and inhibited protein degradation. Decreased PON1 gene transcription was associated with PPARdelta expression. These changes were accompanied by increased hepatic MCP-1 concentration and gene expression. There were significant direct relationships between hepatic PON1 and MCP-1 concentrations (P = 0.005) and between PON1 and the amount of activated stellate cells (P = 0.001).

CONCLUSION

Our results from this experimental model suggest a hepato-protective role for PON1 against inflammation, fibrosis and liver disease mediated by MCP-1.

Identification of differentially expressed genes during proliferative response of the liver induced by follistatin

The liver mass is controlled strictly and maintained constant in normal and pathological situations. An exception is observed after an administration of follistatin, which induces proliferation in intact liver. In the present study, we identified genes differentially expressed in proliferating liver caused by overexpression of follistatin-288. Adenovirus vector encoding follistatin-288 (Ad-FS) or green fluorescent protein was injected intraperitoneally in rats. Changes in the liver weight, expression of follistatin and nuclear bromodeoxyuridine labeling were measured. Samples taken on day 5 and day 7 were used to prepare RNA for microarray analysis. The expression of the genes was confirmed by quantitative reverse transcriptase PCR. After the injection of Ad-FS follistatin mRNA peaked on day 3, which was followed by progressive increase in the protein expression. A peak in bromodeoxyuridine labeling was observed on day 7. Microarray data from day 5 and day 7 samples showed that follistatin modified the expression of 907 genes, of which 575 were overexpressed and 332 were downregulated taking into consideration a two fold change reference compared to control rats. In particular, significant increases and time related changes in gene expression after the Ad-FS injection were found in nine genes including growth differentiation factor 15 and fibroblast growth factor 21. This study confirmed that follistatin induced proliferation in intact liver, and identified candidate genes involved in follistatin-induced liver cell growth.

Mercapturic acid conjugates of 4-hydroxy-2-nonenal and 4-oxo-2-nonenal metabolites are in vivo markers of oxidative stress

Oxidative stress-induced lipid peroxidation leads to the formation of cytotoxic and genotoxic 2-alkenals, such as 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE). Lipid-derived reactive aldehydes are subject to phase-2 metabolism and are predominantly found as mercapturic acid (MA) conjugates in urine. This study shows evidence for the in vivo formation of ONE and its phase-1 metabolites, 4-oxo-2-nonen-1-ol (ONO) and 4-oxo-2-nonenoic acid (ONA). We have detected the MA conjugates of HNE, 1,4-dihydroxy-2-nonene (DHN), 4-hydroxy-2-nonenoic acid (HNA), the lactone of HNA, ONE, ONO, and ONA in rat urine by liquid chromatography-tandem mass spectrometry comparison with synthetic standards prepared in our laboratory. CCl(4) treatment of rats, a widely accepted animal model of acute oxidative stress, resulted in a significant increase in the urinary levels of DHN-MA, HNA-MA lactone, ONE-MA, and ONA-MA. Our data suggest that conjugates of HNE and ONE metabolites have value as markers of in vivo oxidative stress and lipid peroxidation.

Changes of the hepatic proteome in murine models for toxically induced fibrogenesis and sclerosing cholangitis

We investigated the changes in the hepatic proteome in murine models for toxic-induced fibrogenesis and sclerosing cholangitis. A comprehensive comparison of protein changes observed is made and the mechanistical basis of the expression changes is discussed. Hepatic fibrosis was induced by repetitive intraperitoneal CCl4 treatment of BALB/c mice or developed spontaneously in BALB/c-ATP-binding cassette, subfamily B, member 4 (Abcb4) knock out mice. Fibrosis was verified by a morphometric score and assessment of hydroxyproline content of liver tissue, respectively. The innovative difference in-gel electrophoresis (DIGE) technique was used to analyse protein expression levels of the mouse proteome. Results were confirmed by Western blotting and real-time RT-PCR. In CCl4-induced fibrosis 20 out of 40 and in BALB/c-Abcb4(-/-) mice 8 out of 28 differentially expressed proteins were identified utilizing DIGE. Only two proteins, selenium-binding protein (Sbp2) and carbonic anhydrase 3, have been unidirectionally expressed (i.e. down-regulated) in both models. Relevant differences in the pathogenesis of toxically induced liver fibrosis and sclerosing cholangitis exist. The only novel protein with regard to liver fibrosis depicting a unidirectional expression pattern in both animal models was Sbp2. An explicit protein function could not be clarified yet.

Development of the GENIPOL European flounder (Platichthys flesus) microarray and determination of temporal transcriptional responses to cadmium at low dose

We have constructed a high density, 13 270-clone cDNA array for the sentinel fish species European flounder (Platichthys flesus), combining clones from suppressive subtractive hybridization and a liver cDNA library; DNA sequences of 5211 clones were determined. Fish were treated by single intraperitoneal injection with 50 micrograms cadmium chloride per kilogram body weight, a dose relevant to environmental exposures, and hepatic gene expression changes were determined at 1, 2, 4, 8, and 16 days postinjection in comparison to saline-treated controls. Gene expression responses were confirmed by real-time reverse transcription polymerase chain reaction (RT-PCR). Blast2GO gene ontology analysis highlighted a general induction of the unfolded protein response, response to oxidative stress, protein synthesis, transport, and degradation pathways, while apoptosis, cell cycle, cytoskeleton, and cytokine genes were also affected. Transcript levels of cytochrome P450 1A (CYP1A) were repressed and vitellogenin altered, real-time PCR showed induction of metallothionein. We thus describe the establishment of a useful resource for ecotoxicogenomics and the determination of the temporal molecular responses to cadmium, a prototypical heavy metal pollutant.

Drinking of Salvia officinalis tea increases CCl(4)-induced hepatotoxicity in mice

In a previous study, the drinking of a Salvia officinalis tea (prepared as an infusion) for 14 days improved liver antioxidant status in mice and rats where, among other factors, an enhancement of glutathione-S-transferase (GST) activity was observed. Taking in consideration these effects, in the present study the potential protective effects of sage tea drinking against a situation of hepatotoxicity due to free radical formation, such as that caused by carbon tetrachloride (CCl(4)), were evaluated in mice of both genders. Contrary to what was expected, sage tea drinking significantly increased the CCl(4)-induced liver injury, as seen by increased plasma transaminase levels and histology liver damage. In accordance with the previous study, sage tea drinking enhanced significantly GST activity. Additionally, glutathione peroxidase was also significantly increased by sage tea drinking. Since CCl(4) toxicity results from its bioactivation mainly by cytochrome P450 (CYP) 2E1, the expression level of this protein was measured by Western Blot. An increase in CYP 2E1 protein was observed which may explain, at least in part, the potentiation of CCl(4)-induced hepatotoxicity conferred by sage tea drinking. The CCl(4)-induced hepatotoxicity was higher in females than males. In conclusion, our results indicate that, although sage tea did not have toxic effects of its own, herb-drug interactions are possible and may affect the efficacy and safety of concurrent medical therapy with drugs that are metabolized by phase I enzymes.

Comprehensive analysis of differential gene expression profiles on d-galactosamine-induced acute mouse liver injury and regeneration

Microarray analysis of RNA from d-galactosamine (GalN)-administered mouse livers was performed to establish a global gene expression profile during injury and regeneration stages at two different doses. A single dose of GalN at 266 or 26.6 mg/kg body weight was given intraperitoneally, and the liver samples were obtained after 6, 24, and 72 h. Histopathologic studies enabled the classification of the D-galactosamine effect into injury (6, 24 h) and regeneration (72 h) stages. By using the Applied Biosystems mouse genome survey microarray, a total of 7267 out of 33,315 (21.8%) genes were found to be statistically reliable at p<0.05 by two-way ANOVA, and 1469 (4.4%) probes at false discovery rate <5% by significance analysis of microarray. Among the statistically reliable clones by both analytical methods, 389 genes were differentially expressed when compared with non-treated control, with more than a 1.625-fold difference (which equals 0.7 in log(2) scale) at one or more GalN treatment conditions and with less than 1.625-fold difference at all three vehicle-treated conditions. Three hundred thirty six genes and 13 genes were identified as injury- and regeneration-specific genes, respectively, showing that most of the transcriptomic changes were seen during the injury stage. Furthermore, multiple genes involved in protein synthesis and degradation, mRNA processing and binding, and cell cycle regulation showed variable transcript levels upon acute GalN administration.

Comprehensive analysis of differential gene expression profiles on diclofenac-induced acute mouse liver injury and recovery

Microarray analysis of RNA from diclofenac-administered mouse livers was performed to establish a global gene expression profile during injury and recovery stages at two different doses. A single dose of diclofenac at 9.5 mg/kg or 0.95 mg/kg body weight was given orally, and the liver samples were obtained after 6, 24, and 72 h. Histopathologic studies enabled the classification of the diclofenac effect into injury (6, 24 h) and recovery (72 h) stages. By using the Applied Biosystems Mouse Genome Survey Microarray, a total of 7370 out of 33,315 (22.1%) genes were found to be statistically reliable at p<0.05 by two-way ANOVA, and 602 (1.8%) probes at false discovery rate <5% by Significance Analysis of Microarray. Among the statistically reliable clones by both analytical methods, 49 genes were differentially expressed with more than a 1.625-fold difference (which equals 0.7 in log(2) scale) at one or more treatment conditions. Forty genes and two genes were identified as injury- and recovery-specific genes, respectively, showing that most of the transcriptomic changes were seen during the injury stage. Furthermore, multiple genes involved in oxidative stress, eicosanoid synthesis, apoptosis, and ATP synthesis showed variable transcript levels upon acute diclofenac administration.

The antitumor effect of LJ-529, a novel agonist to A3 adenosine receptor, in both estrogen receptor-positive and estrogen receptor-negative human breast cancers

Agonists to A3 adenosine receptor (A3AR) have been reported to inhibit cell growth and/or induce apoptosis in various tumors. We tested the effect of a novel A3AR agonist generically known as LJ-529 in breast cancer cells. Anchorage-dependent cell growth and in vivo tumor growth were attenuated by LJ-529, independently of its estrogen receptor (ER) alpha status. In addition, apoptosis was induced as evidenced by the activation of caspase-3 and c-poly(ADP)ribose polymerase. Furthermore, the Wnt signaling pathway was down-regulated and p27(kip) was induced by LJ-529. In ER-positive cells, the expression of ER was down-regulated by LJ-529, which might have additionally contributed to attenuated cell proliferation. In ER-negative, c-ErbB2-overexpressing SK-BR-3 cells, the expression of c-ErbB2 and its downstream extracellular signal-regulated kinase pathway were down-regulated by LJ-529. However, such effect of LJ-529 acted independently of its receptor because no A3AR was detected by reverse transcription-PCR in all four cell lines tested. In conclusion, our novel findings open the possibility of LJ-529 as an effective therapeutic agent against both ER-positive and ER-negative breast cancers, particularly against the more aggressive ER-negative, c-ErbB2-overexpressing types.

Ribosomal protein gene regulation: what about plants?

The ribosome is an intricate ribonucleoprotein complex with a multitude of protein constituents present in equimolar amounts. Coordination of the synthesis of these ribosomal proteins (r-proteins) presents a major challenge to the cell. Although most r-proteins are highly conserved, the mechanisms by which r-protein gene expression is regulated often differ widely among species. While the primary regulatory mechanisms coordinating r-protein synthesis in bacteria, yeast, and animals have been identified, the mechanisms governing the coordination of plant r-protein expression remain largely unexplored. In addition, plants are unique among eukaryotes in carrying multiple (often more than two) functional genes encoding each r-protein, which substantially complicates coordinate expression. A survey of the current knowledge regarding coordinated systems of r-protein gene expression in different model organisms suggests that vertebrate r-protein gene regulation provides a valuable comparison for plants.

Differential gene expression profiles in the steatosis/fibrosis model of rat liver by chronic administration of carbon tetrachloride

Global gene expression profile was analyzed by microarray analysis of rat liver RNA after chronic carbon tetrachloride (CCl(4)) administration. Rats received 0.5 ml CCl(4)/kg three times a week, and the liver samples were obtained after 0, 30, 60, and 90 days of injection. Histopathologic studies of liver tissues enabled the classification of the CCl(4) effect into mild and severe fatty liver/steatosis (30 and 60 days, respectively) and fibrosis/cirrhosis (90 days) stages. The expression levels of 4,900 clones on a custom rat gene microarray were analyzed and the results were confirmed by semi-quantitative RT-PCR. Four hundred thirty-eight clones were differentially expressed with more than a 1.625-fold difference (which equals 0.7 in log2 scale) at one or more time points. Multiple genes involved in lipid metabolism and ribosome biogenesis showed differential transcript levels upon chronic CCl(4) administration, which was previously seen in acute rat model as well. In addition, a total of 149 clones were identified as fibrosis/cirrhosis-specific genes by either fold changes or Significance Analysis of Microarrays. In conclusion, we report microarray analysis results in rat liver upon chronic CCl(4) administration with a full chronological profile that not only covered fatty liver/steatosis but also later points of fibrosis/cirrhosis. These data will provide the insight of specific gene expression profiles that is implicated in the multistep process of fatty liver/steatosis and fibrosis/cirrhosis after chronic hepatotoxin exposure.