Nucleotide sequence of cloned rat serum albumin messenger RNA

Suppression of C/EBPalpha expression in periportal hepatoblasts may stimulate biliary cell differentiation through increased Hnf6 and Hnf1b expression

The expression of C/EBPalpha, which may govern transcription of mature hepatocyte marker genes, was suppressed in periportal hepatoblasts in mouse liver development, leading to biliary cell differentiation. This study was undertaken to analyze how inactivation of the Cebpa gene affects biliary cell differentiation and gene expression of the regulatory genes for that differentiation, including Hnf1b and Hnf6. In the knockout mouse liver at midgestation stages, pseudoglandular structures were abundantly induced in the parenchyma with elevated expression of Hnf6 and Hnf1b mRNAs. The wild-type liver parenchyma expressed mRNAs of these transcription factors at low levels, though periportal biliary progenitors had strong expression of them. These results suggest that expression of Hnf6 and Hnf1b is downstream of C/EBPalpha action in fetal liver development, and that the suppression of C/EBPalpha expression in periportal hepatoblasts may lead to expression of Hnf6 and Hnf1b mRNAs. Immunohistochemical studies with biliary cell markers in knockout livers demonstrated that differentiated biliary epithelial cells were confined to around the portal veins. The suppression of C/EBPalpha expression may result in upregulation of Hnf6 and Hnf1b gene expression, but be insufficient for biliary cell differentiation. When liver fragments of Cebpa-knockout fetuses, in which hepatoblasts were contained as an endodermal component, were transplanted in the testis of Scid (Prkdc) male mice, almost all hepatoblasts gave rise to biliary epithelial cells. Wild-type hepatoblasts constructed mature hepatic tissue accompanied by biliary cell differentiation. These results also demonstrate that the suppression of C/EBPalpha expression may stimulate biliary cell differentiation.

Synthesis of acute phase proteins in rats with cirrhosis exposed to lipopolysaccharide

BACKGROUND

In patients with cirrhosis, infection is frequent and a leading cause of death. This is secondary to various immunologic abnormalities in both the innate and the adaptive immune system. However, it remains unclear whether cirrhosis affects the inflammatory systemic component of the innate immunity, 'the acute phase response', mostly effectuated by the liver itself. We hypothesized that rats with cirrhosis raise a reduced acute phase response induced by lipopolysaccharide (LPS).

RESULTS

We examined the acute phase response induced by intraperitoneal injection of a low dose of LPS, in sham operated control animals and in rats with liver cirrhosis induced by bile duct ligation (BDL). We measured the serum concentrations of the most important acute phase proteins and their liver tissue gene expressions, assessed by mRNA levels. The BDL-model itself increased the serum concentration of alpha1-acid glycoprotein (alpha1AGP) and haptoglobin. LPS was lethal to 25% of the cirrhotic animals and to none of the controls. Twenty-four hours after LPS, the serum concentration of alpha1AGP and haptoglobin, the mRNA level of these acute phase proteins and of alpha2-macroglobulin and thiostatin rose to the same level in the animals with cirrhosis and in controls.

CONCLUSION

In rats with experimental cirrhosis LPS caused high mortality. In the survivors, the cirrhotic liver still synthesized acute phase proteins as the normal liver, indicating a normal hepatic contribution to this part of the acute phase response.

Dietary PUFA modulate the expression of proliferation and differentiation markers in Morris 3924A hepatoma cells

The effect of dietary polyunsaturated fatty acids on the expression of differentiation and proliferation markers in Morris 3924A hepatoma cells was investigated. ACT/I rats were conditioned 10 days with diets enriched with linoleic acid or alpha-linolenic acid before subcutaneous hepatoma cell transplantation. After 19 days from the inoculum, the mRNA levels of liver-enriched transcription factors and of their target genes were quantified. Both linoleic acid- and linolenic acid-enriched diets induced a decrease of beta-actin, AFP, PCNA, c-myc and of hepatocyte nuclear factors HNF-1alpha and HNF-4alpha mRNA levels in tumor tissue whereas HNF-3beta expression was induced by both dietary treatments. Only the alpha-linolenic acid-enriched diet was effective in reducing c-jun and increasing albumin mRNA levels. Since albumin is a C/EBPalpha target gene, C/EBPalpha gene transcription was evaluated at both protein and mRNA levels. It was found that alpha-linolenic acid-enriched diet did not enhance the C/EBPalpha mRNA content in hepatoma tissue while inducing C/EBPalpha protein expression with an isoform pattern similar to the hepatic phenotype. This evidence implies that alpha-linolenic acid or one of its metabolic products induce albumin synthesis in hepatoma cells by modulating C/EBPalpha gene expression at post-transcriptional level.

Novel Method to Examine Hepatocyte-Specific Gene Expression in a Functional Coculture System

To mimic native tissue function, coculture systems are an extremely useful model. In many cases, differentiated functions can be maintained only through the interactions of various cell types. Therefore, methods for examining the interactions between cocultured cells are necessary. The assessment of cell-to-cell cross-talk at the level of gene expression is one such method to examine interactions between different cell types. However, it is generally difficult to determine the gene expression of specific cell types in coculture without first separating cell populations. To overcome these obstacles, we have established a novel method to determine gene expression levels of a targeted cell population in coculture, using species-specific primers. With this approach, we were able to determine hepatocyte-specific gene expression of Fao cells (a rat hepatocyte cell line) in culture with human umbilical vein endothelial cells (HUVECs). Expression of both albumin and apolipoprotein A-I (apoA-I) increased time dependently for 10 days and maintained significantly higher expression in the coculture system as compared with isolated Fao cells. This indicates that hepatocyte function increased gradually in our coculture system and could be maintained long-term, suggesting that the construction of mature cell-to-cell communication between the two cell lines required a considerable amount of time. The expression of HNF-4 and HNF-1alpha, which are liver-enriched transcription factors, did not differ between the monolayer and cocultured Fao cells, suggesting that expression of HNF-4 and HNF-1alpha was not responsible for the increased expression albumin and apoA-I. Our findings suggest that this novel method for the detection of gene expression of targeted cell populations can be a useful tool in determining the molecular mechanisms that regulate communication between different cell types.

Role of uroguanylin, a Peptide with natriuretic activity, in rats with experimental nephrotic syndrome

Uroguanylin induces natriuresis and diuresis in vivo as well as in vitro and is found mainly in the intestine and the kidney. However, the roles of uroguanylin in nephrotic syndrome, which is associated with sodium and water retention, have not been determined. Therefore, changes in the urine and plasma concentration of immunoreactive uroguanylin (ir-uroguanylin) and its mRNA expression in the kidney and intestine were examined using rats with puromycin aminonucleoside (PAN)-induced nephrosis. Male Sprague-Dawley rats were separated into control and nephrotic groups, and then the urinary excretion of sodium, protein, and ir-uroguanylin was examined over time. The plasma levels and renal and intestinal mRNA expression of uroguanylin at the periods of sodium retention and remarkable natriuresis also were evaluated. The sequential changes of urinary ir-uroguanylin excretion in the nephrotic group were similar to those of urinary sodium excretion. When the urinary excretion of ir-uroguanylin and sodium peaked, the plasma level of ir-uroguanylin also increased compared with that of the control group. Uroguanylin mRNA expression in the kidney increased during the period of sodium retention and then decreased during the period of remarkable natriuresis. Uroguanylin mRNA expression in the small intestines of control and nephrotic rats were identical. However, in a unilateral PAN-induced proteinuria, uroguanylin expression significantly increased in the PAN-perfused kidney compared with that in the opposite kidney. Considering the natriuretic effect of uroguanylin, these results suggested that uroguanylin plays an important role as a natriuretic factor in nephrotic syndrome via both the circulation and the kidney itself.

Posttranscriptional regulation of albumin gene expression by branched-chain amino acids in rats with acute liver injury

We previously demonstrated that the integration of albumin mRNA into functional polysomes was regulated by the supply of branched-chain amino acids (BCAA) in the liver of galactosamine-treated rats. To study the mechanism of this regulation, we investigated interaction between rat liver proteins and albumin transcripts. When albumin transcript was incubated with ribosome salt wash (RSW) extracts prepared from liver, a specific RNA-protein complex (p65) formed. Competition experiments showed that a pyrimidine-rich sequence in the coding region of albumin mRNA was required for the formation of p65. The level of p65 was increased in the RSW extracts prepared from liver of galactosamine-treated rats infused with a standard amino acid formula, compared with a BCAA-enriched amino acid formula. The protein in p65 appears to be polypyrimidine tract-binding protein (PTB), because the formation of p65 was reduced in the RSW extracts pre-incubated with anti-PTB antibody. In cell-free translation analysis, immunodepletion of PTB from rabbit reticulocyte lysate caused an increase in albumin translation. These results suggest that binding of PTB to albumin mRNA suppresses its translation. A supply of BCAA may interfere with this binding and improve the translation efficiency of albumin mRNA in injured liver.

Suppression of C/EBP alpha expression in biliary cell differentiation from hepatoblasts during mouse liver development

BACKGROUND/AIMS

Intrahepatic biliary cell differentiation takes place in periportal hepatoblasts under the influence of the subjacent mesenchyme, which leads to the suppression of mature hepatocyte marker expression. This study was undertaken to analyze C/EBP alpha and beta expression, which may govern transcription of mature hepatocyte marker genes, during mouse liver development with special attention given to biliary differentiation.

METHODS

Expression of C/EBP alpha and beta was immunohistochemically examined. Expression of alpha-fetoprotein, albumin and urea cycle enzymes, the genes of which have CCAAT motifs in their upstream regulatory sequences, was examined immunohistochemically or by using in situ hybridization.

RESULTS

C/EBP alpha started to be expressed in endodermal cells of 9.5-day liver primordium, and continued to be expressed in hepatoblasts and hepatocytes throughout development. Although biliary cell progenitors transiently expressed mature hepatocyte markers, their expression of C/EBP alpha was weak or totally absent. The signals of C/EBP beta in hepatocytes were weak in fetal liver, but became stronger with postnatal development. Differentiated epithelial cells of intrahepatic biliary structures did not express C/EBP alpha.

CONCLUSIONS

These data suggest that the suppression of C/EBP alpha expression may be prerequisite to biliary cell differentiation in the hepatoblast population and one of its earliest signs.

Establishing of two in vitro models of epithelial cells from the apocrine secreting rat coagulating gland

Apocrine secretion is an alternative export pathway for proteins and was described especially for accessory sex glands of rodents and men. This mechanism is not as well characterized as the classical merocrine (eccrine) export. In the rat coagulating gland both secretion modes were observed, and several proteins were identified to be released by these two pathways. To obtain more data on the apocrine secretion mode, we established two culture models of the rat coagulating gland: primary epithelial cells and an organ culture system. The in vitro models were characterized with immunocytochemistry, electron microscopy and RT-PCR. The polarity of primary and passaged epithelial cells (passage 8) was proven by the detection of occludin, E-cadherin and beta-actin. The gland tissue pieces showed good maintenance after 1-week culture. Finally we demonstrated that the epithelial cells of both culture models are still expressing and producing apocrine and merocrine proteins. Using these two culture models for the rat coagulating gland, it is now possible to initiate studies on the apocrine secretion mechanism in vitro.

Postnatal changes in gene expression of retinal dehydrogenase and retinoid receptors in liver of rats

Retinoic acid (RA) plays important roles in cellular differentiation and proliferation in various tissues including the liver. To explore a possible role of RA in the postnatal development of hepatic function, we analyzed RA-generation enzyme activity and the RA-related hepatic gene expressions in the suckling and weaning rats. At 5 days after birth, retinal dehydrogenase (RALDH) activity in the liver was relatively high. Its activity decreased by 70% until day 17, and then it gradually increased to a high level by the completion of weaning period. Northern blot analysis showed that RALDH2 mRNA levels decreased in the suckling period, whereas RALDH1 mRNA levels increased in the weaning period. Retinoid X receptor alpha (RXRalpha) mRNA levels increased in the suckling period and attained to a higher level at 17 days after birth. Retinoic acid receptor alpha (RARalpha) mRNA level showed only a slight and temporary increase on day 13. The mRNA levels of hepatocyte nuclear factors (HNF-4 and HNF-1alpha) exhibited parallel increases around suckling-weaning period, and the transcript levels of albumin, a typical target gene of the hepatocyte nuclear factors, increased during the suckling-weaning transition period. Electrophoretic mobility shift assay using a putative nuclear receptor-binding element on rat HNF-1 alpha gene revealed that HNF-4 homodimer, but not RXRalpha homodimer, bound to this element. These results suggest that postnatal expressions of hepatocyte-specific genes might be up-regulated by retinoid receptors, which may be related with the alterations of RALDH expression during postnatal development in the liver.

Autoprotection against acetaminophen toxicity in cultured rat hepatocytes: the effect of pretreatment and growth factors

To evaluate the effect of acetaminophen pretreatment and growth factors on acetaminophen hepatotoxicity in cultured rat hepatocytes, rat hepatocytes in primary culture were exposed to acetaminophen 8 mM after pretreatment with either acetaminophen 1 mM, treatment with growth factors (EGF and HGF), or no treatment. Growth response was measured by changes in DNA, [3H]thymidine incorporation and mRNA of growth related proteins, cell damage by leakage of LDH to the medium and changes in ATP, and protection against toxicity by changes in glutathione, cytochrome p450 and the expression of glutathione-S-transferase and Cyp1A2. Pretreatment with acetaminophen induced growth response, weaker than that of growth factors, but pretreatment and growth factors reduced cell damage equally effectively. Glutathione and glutathione-S-transferase increased more by growth factors than by pretreatment, but both conditions reduced Cyp1A2 to near zero. Pretreatment and growth factors protect against acetaminophen toxicity by suppressing the expression of Cyp1A2, thereby reducing the production of the intermediate N-acetyl-p-benzoquinone imine (NAPQI). Suppression of Cyp1A2 expression by pretreatment is assumed to be due to a growth-stimulating effect of low concentrations of acetaminophen.

Enhancement of albumin expression in bone tissues with healing rat fractures

The characterization of 66 kDa protein molecule, a major protein component which is produced from femoral-diaphyseal tissues with fracture healing (Igarashi and Yamaguchi [2002] Int. J. Mol. Med. 9:503-508), was investigated. Weaning rats were killed at 7 and 14 days after femoral fracture. When the femoral-diaphyseal tissues with fracture healing were cultured for 48 h in a serum-free medium, many proteins in the bone tissues were released into the medium. Analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that a protein molecule of approximately 66 kDa was markedly increased in culture medium from bone tissues with fracture healing. N-terminal sequencing of 66 kDa protein indicated that its N-terminus was identical to that of rat albumin. Western blot analysis of medium 66 kDa protein showed expression of albumin. This expression was significantly enhanced by fracture healing. The expression of albumin was seen in the diaphyseal (cortical bone) and metaphyseal (trabecular bone) tissues of rat femur. When the femoral-diaphyseal tissues obtained at 7 days after femoral fracture were cultured in a serum-free medium containing either vehicle, parathyroid hormone (1-34) (10(-7) M), insulin-like growth factor-I (10(-8) M) or zinc acexamate (10(-4) M), medium albumin was significantly increased in the presence of those bone-stimulating factors. The addition of albumin (0.5 or 1.0 mg/ml of medium) caused a significant increase in calcium and deoxyribonucleic acid contents in the femoral-diaphyseal and -metaphyseal tissues obtained from normal rats in vitro. The present study demonstrates that fracture healing induces a remarkable production of albumin which is a major protein component produced from femoral-diaphyseal tissues of rats, and that albumin has an anabolic effect on bone components.

Monitoring of developing graft-versus-host disease mediated by herpes simplex virus thymidine kinase gene-transduced T cells

Introduction of the HSV-Tk suicide gene into allogeneic T cells offers the possibility to control developing host-reactive cells within the context of allogeneic bone marrow transplantation (BMT). Sensitive quantitative detection methods are a prerequisite to monitor genetically modified T cells in peripheral blood and tissues to study their involvement in graft-versus-host disease (GVHD)-induced lesions as well as their disappearance or persistence after ganciclovir (GCV)-induced suicide. We monitored the alloreactivity of HSV-Tk-transduced T cells after BMT by studying their in vivo distribution and quantity in peripheral blood and in tissues in a WAG/Rij into Brown Norway fully mismatched rat allogeneic BMT model. Genetically modified T cells were quantified in blood and tissues by fluorescence-activated cell sorting, immunohistochemical analysis, and real-time quantitative polymerase chain reaction (PCR) analysis. A significant increase in the number of allogeneic HSV-Tk(+) T cells was found in particular in spleen and lymph nodes and large numbers were found in tongue, skin, and intestines. In blood, an increase in HSV-Tk(+) T cells closely preceded clinical symptoms of GVHD. Real-time quantitative PCR proved to be a fast and accurate tool by which to quantify transduced T cells both in blood and tissues. This enables the study of the in vivo alloreactivity of retrovirus-transduced cells and the response of HSV-Tk-expressing T cells to GCV-induced suicide therapy. Furthermore, we showed the potential use to study specific cause-effect relationships in a broad range of animal and clinical studies involving genetically engineered cells.

Transferrin receptor gene expression and transferrin-bound iron uptake are increased during postischemic rat liver reperfusion

Iron-catalyzed production of reactive oxygen species is a cause of liver injury after ischemia/reperfusion (I/R). The aim of the present study was to address the regulation of transferrin receptor (TfR), which mediates cellular iron uptake, during I/R. The molecular mechanisms controlling TfR gene expression in vivo during I/R of rat liver were investigated by molecular biology procedures. We also analyzed transferrin-bound iron uptake into surviving liver slices. Increased amounts of TfR protein and messenger RNA (mRNA) were found 2 to 6 hours after reestablishment of blood supply. RNA bandshift analysis showed that iron regulatory protein (IRP) activity was decreased in the first hours of reperfusion, thus indicating that IRP-mediated mRNA stabilization was not involved in early TfR upregulation. On the contrary, increased transcription of the TfR gene in isolated nuclei was observed during reperfusion; during the ischemic phase this was preceded by enhanced binding of hypoxia inducible factor (HIF-1) to a DNA sequence derived from the TfR promoter. TfR2 mRNA levels were also enhanced after reperfusion. The increased expression of TfR at the cell surface resulted in increased uptake of transferrin-bound-iron into surviving liver slices; however, iron was not incorporated into ferritin. In conclusion, HIF-1 mediated activation of TfR gene transcription and IRP-mediated increase of TfR mRNA stability ensure a steady induction of TfR, and hence higher iron uptake in reperfused rat liver. TfR-mediated entry of the metal into liver cells may represent a source of catalytically active iron, which may play a role in reperfusion damage.

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.

Liver gene regulation in rats following both 70 or 90% hepatectomy and endotoxin treatment

BACKGROUND

The metabolic state effect of liver failure on liver gene regulation was evaluated in a rat model.

METHODS

Following 70 or 90% hepatectomy and lipopolysaccharide or vehicle treatment at intervals up to 24 h, the liver remnants were analyzed for mRNA levels for acute-phase, liver-specific and growth-related proteins.

RESULTS

After 70% hepatectomy mRNA for alpha 1-acid glycoprotein, alpha 2-macroglobulin, thiostatin and fibrinogen, haptoglobin increased three- to sevenfold (P < 0.05), and mRNA for cyclin D and histone 3 increased seven- and 15-fold (P < 0.05), respectively. After lipopolysaccharide injection and 70% hepatectomy were done, mRNA for acute-phase proteins raised significantly (P < 0.05), more to five to 20-fold, while mRNA for growth-related proteins raised significantly (P < 0.05) less to three- to fourfold. After 90% hepatectomy, acute-phase protein mRNA increased five- to ninefold (P < 0.05) more than after 70% hepatectomy, while mRNA for histone 3 and cyclin D did not increase within 24 h, which indicates a delayed growth after 90% hepatectomy. In 90% of hepatectomized rats treated with lipopolysaccharide, acute-phase protein mRNA raised three- to sixfold (P < 0.05) less than after vehicle treatment.

CONCLUSION

In endotoxemia from liver failure, the synthesis of acute-phase proteins is upregulated by gene regulation at the expense of that for regeneration, which may be an appropriate response for immediate survival. In severe liver failure, endotoxin may interfere with the appropriate gene regulation.

Hepatocyte growth factor induces differentiation of adult rat bone marrow cells into a hepatocyte lineage in vitro

Bone marrow (BM) cells originally include alpha-fetoprotein (AFP)- and c-Met [a receptor for hepatocyte growth factor (HGF)]-expressing cells. In vitro treatment of BM cells with HGF induced albumin-expressing hepatocyte-like cells. Furthermore, those hepatocyte-like cells expressed cytokeratins 8 and 18, which are typically expressed in normal adult hepatocytes. These findings demonstrate that BM cells include AFP-expressing hepatic progenitor cells that can be differentiated into hepatocytes by HGF in culture, indicating that such cultures are useful resources for cell transplantation therapy for liver diseases.

Long-term differentiated function of heterotopically transplanted hepatocytes on three-dimensional polymer matrices

Hepatocyte transplantation using porous matrices is under investigation as an alternative therapy for certain liver diseases. For this purpose, long-term function of transplanted hepatocytes is mandatory. This problem has not been sufficiently investigated yet. In this study Lewis rats were used as donors and recipients. Stimulated (group A, portocaval shunt) or unstimulated (group B) hepatocytes were transplanted into prevascularized polyvinyl-alcohol matrices. Cell-free matrices served as controls (group C). Matrices were harvested between 1 h and 1 year after implantation and analyzed by morphometry; albumin RNA in situ hybridization; and cytokeratin-, actin-, desmin-, and macrophage-specific antigen immunohistology. The hepatocyte number significantly decreased within the first week following implantation. Between 1 month and 1 year after transplantation a significant increase in hepatocyte number was noted in groups A and B. Albumin transcripts of transplanted hepatocytes were at normal levels at all times except for group B after 1 year. The immunohistology suggested engraftment of nonparenchymal liver cells. We conclude that 3-dimensional matrices provide a sufficient environment for long-term engraftment of transplanted liver cells. The hepatocytes are able, despite suboptimal initial engraftment, to repopulate the scaffold for at least half of the recipient's life span and maintain cell-specific function after sufficient stimulation.

Investigation of albumin-synthesizing ability in rat cirrhotic liver-derived hepatocytes using primary hepatocyte culture

BACKGROUND/AIMS

In cirrhosis, despite a decrease in the total number of hepatocytes, a normal serum albumin level is maintained during the compensatory stage of the disease in many cases. Therefore, to elucidate the mechanism in hepatocytes related to the regulation of the serum albumin level, the albumin-synthesizing ability of individual hepatocytes was investigated in cirrhotic rats.

METHODS

Cirrhotic rats were prepared by oral administration of furfural to male Wistar rats for 20 weeks. Albumin-synthesizing abilities of liver and of isolated hepatocyte culture were evaluated by measuring the albumin concentration in blood and culture supernatant. Expressions of albumin mRNA were compared using Northern blotting. Furthermore, transcriptional activity of the albumin gene was measured using the promoter domain of the gene.

RESULTS

The total number of hepatocytes in rat cirrhotic liver was significantly decreased compared to that in normal rat liver. However, there were no significant differences in levels of serum albumin or albumin mRNA expression between cirrhotic and normal liver. In primary hepatocyte culture, albumin mRNA expression, the amount of albumin secretion and the albumin promoter activity were clearly enhanced in cirrhotic hepatocytes compared to normal hepatocytes.

CONCLUSION

Although the total number of hepatocytes was decreased in the rat cirrhosis models used in this study, the serum albumin level was maintained and albumin-synthesizing ability was enhanced at the transcriptional level in the individual hepatocytes. These results suggest that the maintenance of serum albumin levels in compensated cirrhosis may be due to enhanced albumin synthesis by the hepatocytes.

Is there an optimal concentration of cotransplanted islets of Langerhans for stimulation of hepatocytes in three dimensional matrices?

BACKGROUND

Hepatocyte transplantation using three-dimensional matrices is under investigation as an alternative therapy for several liver diseases. For sufficient transplantation results hepatotrophic stimulation is necessary. We investigated the stimulatory effect of cotransplanted pancreatic islets in different ratios.

METHODS

Lewis rats were used as donors and recipients. A portocaval shunt (group A) or sham operation (groups B-G) was performed 1 week before hepatocyte transplantation. Four polyvinyl-alcohol matrices each containing 1.25 x 10(7) hepatocytes (groups A and B) or 1.25 x 10(7) hepatocytes and 125 (C), 250 (D), 500 (E), or 750 (F) islets were implanted between small bowel mesenteric leaves. In group G, medium soaked matrices were implanted. One month after implantation, specimens were harvested and investigated using albumin-RNA in situ hybridization, and insulin, glucagon, and bromodesoxy uridine immunohistochemistry. The hepatocyte area was assessed using image analysis.

RESULTS

Hepatocyte area and proliferation ratio increased depending on the number of cotransplanted islets with a peak at 40 islets per 1 million hepatocytes (group E). Cotransplantation of islets in higher concentrations did not further increase hepatocyte area or proliferation ratio. Hepatocytes in all groups expressed albumin RNA at normal transcription levels as compared to standard liver sections. Islets displayed insulin and glucagon in physiological distribution.

DISCUSSION

Three-dimensional matrices provide a sufficient environment for transplanted hepatocytes and islets. The hepatotrophic effect of cotransplanted islets is comparable to portocaval shunting and has a saturation limit at 40 islets per 1 million hepatocytes. For further application of islet cotransplantation, this ratio seems to be preferable.

Effects of LPS on transport of indocyanine green and alanine uptake in perfused rat liver

Lipopolysaccharide (LPS) initiates cholestasis. Whether this process is mediated by tumor necrosis factor-alpha (TNF-alpha) and whether the cholestatic response to LPS is associated with intrahepatic accumulation of possibly toxic substances are under debate. To study these questions the hepatic uptake and biliary excretion of indocyanine green (ICG) was examined in the isolated perfused rat liver 18 h after intravenous treatment of rats with either saline, 1 mg/kg body wt LPS, or LPS and intraperitoneal pentoxifylline (POF) (n = 6 in each group). POF inhibits TNF-alpha release after LPS administration. LPS induced a typical acute-phase response with increased mRNA for acute-phase proteins, reduced albumin mRNA, and increased hepatic uptake of alanine. Intrinsic hepatic clearance of ICG in controls (1.01 +/- 0.05 ml. min(-1). g liver(-1)) was similarly decreased by LPS alone (0.62 +/- 0.04 ml. min(-1). g(-1); P = 0.002 vs. control) or combined with POF (0.66 +/- 0.06 ml. min(-1). g(-1)). A kinetic analysis indicated that LPS reduced both uptake and excretion processes in a balanced manner, so that intrahepatic ICG content was unaffected or even slightly reduced, as confirmed by measurement of ICG contents in the perfused livers. In livers from parallel-treated nonperfused rats, mRNA for the organic anion transporting protein-1 (Oatp1, which is likely to mediate ICG uptake) was unaffected by LPS, whereas the concentration of Oatp1 protein was reduced. Thus LPS induced an acute-phase response that included downregulation of ICG uptake by reduction of Oatp1 protein concentration, possibly at a posttranscriptional level. TNF-alpha appears not to be the mediator because POF did not modify these LPS effects.

Growth factors and gene expression in cultured rat hepatocytes

BACKGROUND/AIM

The aim of this study was to evaluate the effect of replication on function variables in cultured hepatocytes.

METHODS

Isolated rat hepatocytes were cultured in HCM medium and plated on collagen-coated dishes at cell densities from 0.2 x 10(5) (subconfluent) to 1.0 x 10(5) x cm(-2) (confluent) with and without addition of hepatocyte growth factor, epidermal growth factor and insulin-like growth factor-I. The synthesis rate was measured for DNA, albumin, urea, and glucose together with mRNA levels (Northern blots) for albumin, urea cycle enzymes, and acute phase and "house-keeping" proteins.

RESULTS

In subconfluent culture the synthesis of DNA and urea was higher (118% and 112%, respectively), and of albumin and glucose lower (40% and 67%, respectively) than in confluent culture. The mRNA levels of carbamoylphosphate synthase, argininosuccinate synthetase, argininosuccinate lyase, arginase, a2-macroglobulin, beta-fibrinogen, and albumin were lower (23%, 58%, 77%, 33%, 12%, 50%, and 51%, respectively) in subconfluent culture compared with confluent culture. Relatively increased levels were found for beta-actin (109%) and alpha-tubulin (136%). In subconfluent culture hepatocyte growth factor increased the DNA synthesis rate 6-fold, epidermal growth factor 3-fold, and insulin-like growth factor-I 2-fold; that of albumin, urea and glucose was not increased significantly. In confluent culture the effect of growth factors on synthesis rates was not significant, and the growth factors had little influence on mRNA levels.

CONCLUSIONS

Hepatocytes produce urea at the same rate in subconfluent as in confluent culture in spite of a lower mRNA level of urea cycle enzymes. Hepatocyte growth factor and epidermal growth factor increase DNA synthesis markedly in subconfluent culture only, without significantly changing the ratio between subconfluent and confluent culture of other variables. This suggests that active replication is not an important cause of the relatively low liver-specific function of hepatocytes in subconfluent culture.

Serum albumin as a potential carrier for the apocrine secretion of proteins in the rat coagulating gland

A protein of 66k was purified to homogeneity from the total secretion of rat coagulating gland. Its close structural relationship to serum albumin was demonstrated by N-terminal amino acid sequence analysis, proteolytic fingerprinting and Western blotting studies using polyclonal antibodies raised against the 66k protein and rat serum albumin. Immunofluorescence staining showed that the 66k protein was localised in the cytoplasm of coagulating gland epithelial cells from which it is released via apocrine blebs. Performing immunoelectron microscopy, the 66k protein was by no means detectable in the endoplasmic reticulum and the Golgi apparatus. Reverse transcription-PCR, Northern blotting studies and in situ hybridisation experiments demonstrated that mRNA of albumin is not expressed by coagulating gland epithelial cells. Therefore, intravascular albumin should be transferred into the epithelial cells of the rat coagulating gland followed by secretion via aposomes. Furthermore, overlay blots proved that the 66k protein binds to the apocrine proteins carbonic anhydrase II and secretory transglutaminase and vice versa. In contrast, no binding was evident to the merocrine 115k protein and to cytoplasmic resident proteins e.g. lactate dehydrogenase. These findings point to the assumption that serum albumin taken up from extracellular sources could function as a selective carrier for cytoplasmic proteins destined for apocrine secretion.

Expression and localization of hepatocyte domain-specific plasma membrane proteins in hepatoma × fibroblast hybrids and in hepatoma dedifferentiated variants

We have studied two aspects of the plasma membrane of hepatocytes, highly differentiated epithelial cells that exhibit a particular and complex polarity. Using a genetic approach, we have distinguished between the expression/regulation of proteins specific for all three hepatocyte membrane domains and their organization into discrete domains. For this analysis we used a panel of previously isolated cell clones, derived from the differentiated rat hepatoma line H4IIEC3, and that present different expression patterns for liver-specific genes. This panel was composed of (1) differentiated clones, (2) chromosomally reduced hepatoma-fibroblast hybrids characterized by a pleiotropic extinction/reexpression of liver-specific genes and (3) dedifferentiated variant and revertant clones. The expression of 16 hepatocyte membrane polarity markers was studied by western blotting and immunolocalization. Even though cells of differentiated clones express all of these polarity markers, they are not polarized, and are therefore suitable for studying the regulation of plasma membrane protein expression, and for identifying gene products implicated in the establishment of membrane polarity. In hepatoma-fibroblast hybrids the expression of four markers, three apical (dipeptidylpeptidase IV, alkaline phosphodiesterase B10 and polymeric IgA receptor) and one lateral (E-cadherin), is down-regulated in extinguished clones and restored in reexpressing subclones, as previously reported for liver-specific functions. The dipeptidylpeptidase IV mRNA was undetectable or strongly reduced in extinguished hybrids, but expressed at a robust level in some of the reexpressing clones. Concerning the dedifferentiated variants, each has its own pattern of membrane marker expression (loss of expression of three to six markers), that differs from that of extinguished hybrids. Revertant cells express all of the membrane markers examined. Among all of these hepatoma derivatives, only cells of reexpressing hybrids are polarized, and form bile canaliculi-like structures, with spherical and even, for one clone, long tubular and branched forms. All apical markers examined are confined in these canalicular structures, whereas the other markers are excluded from them, and present on the rest of the membrane (basolateral markers) or at the cell-cell contacts (lateral markers). Cells of reexpressing hybrids also express simple epithelial polarity. Thus the expression of only a few hepatocyte-domain-specific plasma membrane proteins is subject to down-regulation, as is the case for liver-specific genes so far studied, and the expression of polarity markers and the formation of poles are dissociable events.

A new assay for albumin and hemoglobin adducts of 1,2- and 1,4-benzoquinones

A new method has been developed to detect mono-S-substituted cysteinyl adducts of 1,2- and 1,4-benzoquinone (BQ) in hemoglobin (Hb) and albumin (Alb). After reacting the protein with trifluoroacetic anhydride and methanesulfonic acid, the resulting isomers of O,O',S-tris-trifluoroacetyl-hydroquinone and -catechol are extracted and detected by gas-chromatography-mass spectrometry in the negative-ion chemical ionization mode. The limit of detection of the assay is about 20 pmol adduct/g protein. This assay was employed to quantitate mono-S-substituted background adducts in human and rat Hb and Alb and benzene-specific adducts in Hb and Alb from F344 rats following a single oral dosage of 50-400 mg [13C6]benzene/kg body wt. In Alb, a dose-related increase in both [13C6]1,2- and [13C6]1,4-BQ adducts was observed with [[13C6]]1,4-BQ-Alb] >> [[13C6]1,2-BQ-Alb]. The formation of [13C6]1,2-BQ-Alb was linear with increasing dosage of benzene with a slope of 2.3 (pmol adduct/g protein)/(mg/kg body wt.) (S.E. = 0.18, R2 = 0.91). However, at dosages above about 100 mg [13C6]benzene/kg body wt., the levels of 1,4-BQ-Alb were greater than proportional to the dosage. Mono-S-substituted adducts of [13C6]1,2-BQ and [13C6]1,4-BQ were not detected in Hb. The background ([12C6]) adducts of 1,2- and 1,4-BQ in 20 F344 rats were estimated (in nmol adduct/g of protein) to be 3.9 (S.E. = 0.23) and 4.9 (S.E. = 0.30) in Hb and 2.7 (S.E. = 0.24) and 11.4 (S.E. = 0.60) in Alb. At the highest dosage of 400 mg [13C6]benzene/kg body wt., background levels of 1,2-BQ-Alb were about 4-fold higher than those of the benzene-specific adducts whereas the benzene-specific levels of 1,4-BQ-Alb were about 7-fold higher than those of the background adducts. Background levels of 1,2- and 1,4-BQ adducts in 10 portions of commercial human proteins were found to be (in nmol adduct/g of protein) 1.6 (S.E. = 0.05) and 0.85 (S.E. = 0.04) in Hb and 1.6 (S.E. = 0.06) and 8.9 (S.E. = 0.36) in Alb.

Regulation of cyclin G1 during murine hepatic regeneration following Dipin-induced DNA damage

Cyclin G1 has been linked to both positive and negative growth regulation. The expression of cyclin G1 is induced by transforming growth factor beta1 and p53, as well as by multiple mitogenic stimuli in mammalian cells in culture. However, the physiological role of cyclin G1 remains unclear. To examine the cell-cycle regulation of cyclin G1 in vivo, two models of coordinated cell proliferation induced by partial hepatectomy (PH) in the presence or absence of DNA damage were used. To introduce DNA damage, mice were treated with the alkylating drug, 1,4-bis[N,N'-di(ethylene)-phosphamide]piperazine (Dipin) 2 hours before PH. Cell-cycle progression was monitored by 5-bromo-2-deoxyuridine (BrdU) incorporation into the DNA, the frequency of mitoses, the expression of cell-cycle control genes, and by flow cytometry. Dipin treatment resulted in cell-cycle arrest at the G2/M boundary without affecting G0/G1 and G1/S transitions. While the hepatocytes progressively entered G2 phase arrest, the cyclin G1 mRNA and protein levels increased more than five- and eightfold, respectively. Cyclin G1 had a nuclear localization in all interphase cells with clear absence from nucleoli. In contrast, during mitosis, cyclin G1 was undetectable by immunohistochemistry. Taken together, our data provide evidence for a putative role of cyclin G1 in G2/M checkpoint control.

Zinc regulation of insulin-like growth factor-I (IGF-I), growth hormone receptor (GHR) and binding protein (GHBP) gene expression in rat cultured hepatocytes

Dietary zinc depletion in vivo attenuates growth, decreases circulating insulin-like growth factor-I (IGF-I) and liver growth hormone (GH) receptors (GHR). In order to investigate a direct role of zinc in the regulation of IGF-I, GHR and GH binding protein (GHBP) gene expression, we evaluated the response of their mRNAs to changes in zinc availability in primary culture of rat hepatocytes. Exposition of cells to the zinc chelator DTPA (diethylenetriaminepenta-acetic acid) did not decrease IGF-I and GHBP mRNAs while it strongly inhibited metallothionein (MT) gene expression. On the other hand, zinc excess (50 vs. 1.5 microM) decreased IGF-I, GHR and GHBP mRNAs while it stimulated MT mRNA. However, the response of IGF-I to GH was not affected by the exposure to DTPA nor zinc excess. Furthermore, zinc repletion of primary cultured hepatocytes isolated from zinc-deprived rats did not increase IGF-I nor GHR/GHBP mRNAs. Therefore, our results suggest that the IGF-I decline induced in vivo by zinc deficiency is not caused by reduced extracellular zinc availability at the hepatocyte level. Although IGF-I and MT gene expression is down-regulated by dietary zinc depletion, underlying mechanisms of regulation are different for both genes.

Differentiation and antiproliferation effects of retinoic acid receptor beta in hepatoma cells

Evidence indicates that the retinoic acid receptor beta (RARbeta) gene might be a tumor suppressor gene. Previously, we have shown that the expression of the RARbeta gene was either inhibited or downregulated in tumorigenic hepatoma cell lines such as McA-RH8994. McA-RH8994 cells expressed RARalpha and gamma and three types of retinoid X receptor (RXRalpha, beta and gamma), but not RARbeta mRNA. To further analyze the molecular mechanisms which might account for RARbeta gene inactivation, the rat RARbeta gene promoter was cloned from McA-RH8994 cells and no mutation was detected. By transient transfection, McA-RH8994 cells contained the necessary factors to activate the RARbeta gene. To study the possible roles of RARbeta in hepatoma cells, the expression of the RARbeta gene was restored in McA-RH8994 cells by stable transfection. A RARbeta positive cell line named McA-RH8994beta was characterized. The results demonstrated that expression of the RARbeta gene resulted in increased sensitivity of the hepatoma cells to the antiproliferative effect of retinoic acid (RA). Furthermore, expression of RARbeta resulted in a spontaneous differentiation of the hepatoma cells. These data indicate that RARbeta plays important roles in differentiation and antiproliferation.

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.

Induction by peroxisome proliferators and triiodothyronine of serine:pyruvate/alanine:glyoxylate aminotransferase of rat liver

In rat liver, a single serine:pyruvate/alanine:glyoxylate aminotransferase (SPT or SPT/AGT) gene is transcribed from two transcription initiation sites. Transcription from the upstream site generates the mRNA encoding the precursor for mitochondrial SPT (pSPTm) and is markedly enhanced by the administration of glucagon or cAMP. In this report we show the increase in the downstream transcript, the peroxisomal SPT (SPTp) mRNA, caused by peroxisome proliferators and triiodothyronine (T3). In the case of T3, the pSPTm mRNA was also increased 72 h after a single administration of the hormone in addition to an earlier increase in SPTp mRNA.

Cloning and molecular characterization of cDNA encoding a mouse male-enhanced antigen-2 (Mea-2): a putative family of the Golgi autoantigen

The male-enhanced antigen-2 (Mea-2) gene was originally identified with a monoclonal histocompatibility Y (H-Y) antibody (mAb4VII). There is no report of the full length cDNA encode for Mea-2 product until this report. In this study, we isolated the full length mouse Mea-2 cDNA by screening a testis cDNA library with a PCR-amplified Mea-2 product, and direct PCR amplification of its upstream sequences from the cDNA library. The primary structure of the Mea-2 peptide, deduced from this nucleotide sequence, shows that it encode a 150 kDa protein, of 1325 amino acid residues, which contained five putative N-glycosylation sites and four leucine zipper motifs. A data bank search indicated that it has high homology with a human Golgi autoantigen (golgin-160) both in its nucleotides (78%) and amino acids sequence (83%). This suggests that Mea-2 gene product may encode a golgi structural protein. In situ hybridization analysis suggested that the Mea-2 gene is expressed in spermatids during spermatogenesis as already shown by Mea-1, suggesting that Mea-2 gene product as well as Mea-1 have also some role for spermatogenesis.

Early stage of human adenovirus type 12-inoculated retinal tissue of F344 newborn rat

To elucidate the pathogenesis of adenovirus type 12 (Ad12)-induced rat retinal tumor, an experimental animal model of human retinoblastoma (RB), DNA analysis, in situ hybridization and immunohistochemistry were performed. The adenovirus oncogene E1A was detected in the host genome by Southern blot hybridization. Examined retinal tissues did not show any histological changes, but the number of retinal cells immunoreactive with an antibody to proliferating cell nuclear antigen (PCNA) increased with the course of study. In in situ hybridization, E1A gene expression was recognized at the inner granular layer of the retina at an early stage after virus inoculation, and subsequently, N-myc gene expression was recognized at the same region. No alteration was found in the retinoblastoma susceptibility gene (Rb gene) expression. The product of the virus oncogene integrated into the host genome could induce an increase in N-myc expression, without any abnormality of the Rb gene itself. Results from the present study could be useful in clarifying the tumorigenesis of this experimental model.

Expression of liver-specific functions in rat hepatocytes following sublethal and lethal acetaminophen poisoning

AIM

In order to study the short-term effect of moderate and severe reduction of liver function by acetaminophen poisoning of different severity on gene expression for liver-specific functions, rats were given 3.75 and 7.5 g per kg body weight acetaminophen intragastrically. The lower dose is associated with low mortality; after the higher dose, most rats die at between 12 and 24 h.

METHODS

In the morning, 1 1/2, 3, 6, 9, and 12 h after the injection, the rats were killed and RNA was extracted from liver tissue. By slot-blot hybridization mRNA steady-state levels were determined for enzymes involved in metabolic liver functions, i.e. ureagenesis, gluconeogenesis, and drug metabolism, for acute phase proteins, "house-keeping" proteins, and for proteins related to liver regeneration. Results were expressed as per cent of the level in similarly fasted, untreated rats of the same stock

RESULTS

After the smaller dose of acetaminophen, most of the examined mRNA levels were increasing during the experimental period, being two- to four-fold elevated in relation to control after 6 to 12 h. Rats receiving the lethal dose either showed no or a later and smaller increase, and in several cases a fall towards the end of the experiment. The greatest differences were seen for mRNA of arginase, beta-fibrinogen, alpha 1-acid glycoprotein, alpha-tubulin, histone 3, TGF beta, and cyclin d, i.e. proteins associated with acute phase response and liver cell replication and maintenance.

CONCLUSIONS

It is concluded that reversible intoxication with acetaminophen induces an adaptive modulation of mRNA expression of liver functions and regeneration which is lacking after severe intoxication. This adaptation, with emphasis on acute phase response and regeneration, may be crucial for recovery after acetaminophen intoxication. If this also applies to the intoxication in man, estimates of the corresponding variables may be clues to the prognosis of acetaminophen-induced fulminant hepatic failure.

Expression of messenger RNA for liver functions following 70% and 90% hepatectomy

AIMS/METHODS

The effect of moderate and severe reduction of the functional liver mass on gene expression for liver functions was studied in rats following 70% and 90% hepatectomy. At intervals up to 24 h after operation rats were killed and RNA was extracted from the remaining liver tissue. By slot-blot hybridization mRNA steady-state levels were determined for enzymes involved in metabolic 'liver-specific' functions, acute phase proteins, 'house-keeping', and growth-related proteins. Results were expressed as per cent of levels in a pool from fed control rats of the same gender and age.

RESULTS

Among 'liver-specific' metabolic functions only expression of gluconeogenesis, represented by phosphoenol carboxykinase mRNA, was augmented initially, followed by a fall to very low values after 90% hepatectomy. The drug metabolizing system represented by CYP2B1/2 mRNA was reduced to half of the control values. Expression of urea synthesis, as reflected by carbamoylphosphate synthetase mRNA, showed a gradual decline after 90% hepatectomy, in contrast to rising levels of argininosuccinate lyase and arginase mRNA, possibly serving polyamine rather than urea synthesis. The mRNA level of the acute phase protein alpha 1-acid glycoprotein showed a smaller and later rise in 90% than in 70% hepatectomized rats, whereas that of alpha 2-macroglobulin only increased after 90% hepatectomy like the 'house-keeping' beta-actin mRNA. A rise in histone 3, which coincides with mitosis, was only seen after 70% hepatectomy, indicating that after 90% hepatectomy the response to growth-stimulating factors is weak or delayed, supported by a delayed rise in cyclin d and low levels of growth hormone receptor mRNA.

CONCLUSIONS

It is concluded that attempts by gene regulation to adapt liver functions to a reduction of the liver mass depend on the amount of liver tissue lost. When the loss is nearly fatal, compensation for normal metabolic functions may be abandoned for efforts to regenerate, which, however, may be delayed or after all be too weak.

Effects of insulin, dexamethasone and cytokines on alpha 1-acid glycoprotein gene expression in primary cultures of normal rat hepatocytes

While the effects of insulin, dexamethasone and cytokines on alpha 1-acid glycoprotein gene expression have been investigated in various hepatoma cell lines, the individual and combined effects of these components on the expression of this gene have been rarely studied in cultured normal rat hepatocytes. In this cell model, we have shown that mRNA levels of alpha 1-acid glycoprotein were not decreased at least during the first 24 h of culture under basal conditions. During these short-term cultures, the expression of alpha 1-acid glycoprotein in normal hepatocytes showed a high degree of responsiveness to dexamethasone alone (20-fold increase) and to dexamethasone associated with various cytokines (interleukin-1 beta, interleukin-6 and tumor necrosis factor alpha) with a 40 to 100-fold increase depending on the cytokine. Insulin alone did not modify alpha 1-acid glycoprotein mRNA; however, this hormone exerted a positive effect (about 50% increase) in the presence of dexamethasone or dexamethasone with cytokines. These results indicate that the regulation of alpha 1-acid glycoprotein in cultured normal rat hepatocytes presents major differences when compared to reported observations in rat hepatoma cell lines.

Albumin binding and time action of acylated insulins in various species

Insulins acylated with fatty acids at the epsilon-amino group of LysB29 constitute a new class of insulin analogs, which are prolonged-acting due to albumin binding. In the present study it is shown that the affinity of fatty acid acylated insulins for albumin varies considerably (> 50-fold) among species. The relative affinities of acylated insulin for albumin in human, pig, and rabbit serum are about 1:1:5:35. The several fold higher binding affinity in rabbit serum than in pig serum is reflected in a relatively more protracted effect after sc injection in rabbits than in pigs. Due to the similar binding affinities in pig serum and human serum, the pig model should provide a useful estimate of the degree of protraction of acylated insulin in humans. The results emphasize that species differences in ligand binding can be of major importance in the preclinical evaluation of highly albumin bound drugs.

Genomic sequence analysis of the bovine male-enhanced antigen-1 (Mea-1) and differential localization of its transcripts and products during spermatogenesis

The male-enhanced antigen-1 (Mea-1) gene was previously isolated from a bovine testicular cDNA library. In the present study, we cloned the full-length bovine genomic Mea-1 gene and compared this with the Mea-1 cDNA. The 1035-nucleotide bovine mRNA for Mea-1 (excluding the poly (A) tail) is encoded in three exons distributed over 3123 base pairs of the genome. Analysis of the 5' flanking sequence by primer extension mapping identified two main transcription start sites and several minor ones. The 5' region contained transcription-related sequences such as TATA/CAAT boxes, GC-rich regions, and several cis elements. When chloramphenicol acetyltransferase (CAT) activities of 5'-deleted clones were measured in CHO, TM4, and BALB/3T3 cells, a critical region for transcription was identified around -249 to -113 bp region from transcription start site. In situ hybridization and immunohistochemistry indicate that transcripts of the Mea-1 gene were localized in primary and secondary spermatocytes, and spermatids, but the protein products were detected only in spermatids. Intensive transcription of Mea-1 gene and specific localization of the gene product suggest that Mea-1 may play a important role in the late stage of spermatogenesis.

Induction of the acyl-coenzyme A synthetase gene by fibrates and fatty acids is mediated by a peroxisome proliferator response element in the C promoter

The long-chain acyl-coenzyme A synthetase (ACS) gene gives rise to three transcripts containing different first exons preceded by specific regulatory regions A, B, and C. Exon-specific oligonucleotide hybridization indicated that only A-ACS mRNA is expressed in rat liver. Fibrate administration induced liver C-ACS strongly and A-ACS mRNA to a lesser extent. B-ACS mRNA remained undetectable. In primary rat hepatocytes and Fa-32 hepatoma cells C-ACS mRNA increased after treatment with fenofibric acid, alpha-bromopalmitate, tetradecylthioacetic acid, or alpha-linolenic acid. Nuclear run-on experiments indicated that fenofibric acid and alpha-bromopalmitate act at the transcriptional level. Transient transfections showed a 3.4-, 2.3-, and 2.2-fold induction of C-ACS promoter activity after fenofibric acid, alpha-bromopalmitate, and tetradecylthioacetic acid, respectively. Unilateral deletion and site-directed mutagenesis identified a peroxisome proliferator activator receptor (PPAR)-responsive element (PPRE) mediating the responsiveness to fibrates and fatty acids. This ACS PPRE contains three imperfect half sites spaced by 1 and 3 oligonucleotides and binds PPAR.retinoid X receptor heterodimers in gel retardation assays. In conclusion, the regulation of C-ACS mRNA expression by fibrates and fatty acids is mediated by PPAR.retinoid X receptor heterodimers interacting through a PPRE in the C-ACS promoters. PPAR therefore occupies a key position in the transcriptional control of a pivotal enzyme controlling the channeling of fatty acids into various metabolic pathways.

DNase I-hypersensitive sites in the chromatin of rat growth hormone gene locus and enhancer activity of regions with these sites

In this study, a determination was made of the chromatin structure of the rat growth hormone (GH) gene locus by DNase I sensitivity analysis using GC [GH+, prolactin (PRL)-], 235 (GH-, PRL+), GH3 (GH+, PRL+) and liver (GH-, PRL-) cells. From 7 kb upstream from the transcription start site to 19 kb downstream from the polyadenylation site, two major DNase I-hypersensitive sites (M-DHS; UIA, UIIA) and three M-DHS (DIA, DII, DIII) were found within 2 kb upstream and 7 kb downstream regions, respectively. Two minor DHS (m-DHS; UIB, UIIB) in the upstream region and one m-DHS (DIB) downstream were shown to be associated with M-DHS. Thus, a total of five M-DHS and three m-DHS were mapped on the rat GH gene locus. Among these, five (UIIB, UIA, UIB, DIB, DIA) including two (UIA, DIA) M-DHS were specific for GH-producing cells. UIIA and DIII were M-DHS only in PRL-producing 235 cells while the major hypersensitivity of DII was detected in GH-producing cells and liver cells. Assessment of the enhancing activity of the DHS regions indicated novel enhancers in one upstream and two downstream regions that function well with the GH promoter in GC cells. These enhancers, each appearing different, coincided with m-DHS but not M-DHS in GC cells, and were not activated by Pit-1. Based on these observations, the following functions of five M-DHS and three m-DHS regions were defined: enhancer; locus control region (LCR); switch region serving for conversion from GH/PRL-producing cells to PRL-producing cells; and a region having a structural function in chromatin.

Non-iron mediated alteration in hepatic transferrin gene expression in the nephrotic rat

Both transferrin and the iron it carries are lost in the urine in the nephrotic syndrome. Patients may develop hypochromic microcytic anemia and synthesis of transferrin, a protein regulated in large part by iron availability, is increased. Transferrin synthesis has also been reported to be increased in liver slices from rats with hereditary analbuminemia, and their plasma transferrin levels are increased, suggesting that transferrin synthesis may be stimulated by processes other than iron depletion in this hypoalbuminemic condition. Transferrin metabolism was studied in rats with Heymann nephritis (HN), in a strain of Sprague-Dawley (SD) rats with hereditary analbuminemia [Nagase analbuminemic rats (NAR)], and in normal SD rats. Plasma transferrin concentration and mass was decreased significantly in HN, but increased in NAR. Transferrin synthesis was increased both in NAR (measured either as the disappearance of [125I] labeled transferrin or as the incorporation of [3H] phenylalanine) and in HN (incorporation of [3H] phenylalanine). The fractional rate of transferrin catabolism was unchanged in NAR. Thus transferrin mass was increased in NAR entirely as a consequence of increased synthesis. Transferrin and albumin synthesis correlated with one another in both HN and SD (P < 0.001). Transferrin mRNA was increased in both HN and NAR and was unaffected by administration of iron to HN. Hepatic transferrin and albumin mRNA levels were also correlated positively in HN and SD, suggesting that increased hepatic synthesis of both proteins might be responding to the same stimuli. Transferrin gene transcription was increased in both HN and NAR and was unaffected by administration of iron to HN. Transferrin mRNA was not increased in the testis in either HN or NAR, suggesting that augmentation in transferrin gene expression is driven by a non-iron dependent process and is confined to the liver.

Activation of Jun kinase is an early event in hepatic regeneration

Compensatory hepatic regeneration after partial hepatectomy (PH) is dependent upon the extent of resection. This study analyzes the regulation of the AP-1 transcription factor c-Jun during hepatic regeneration. There is a progressive increase in c-jun mRNA levels after sham operation, one-third PH, and two-thirds PH. A concomitant increase in AP-1 binding activity is also observed. The c-Jun protein is a major constituent of the AP-1 complex in quiescent and early regenerating liver. The activity of c-Jun nuclear kinase (JNK), which phosphorylates the activation domain of the c-Jun protein, is markedly stimulated after one-third PH. JNK1 or an immunologically related kinase is a constituent of this stimulated JNK activity after PH. When primary cultures of adult rat hepatocytes are incubated with epidermal growth factor or transforming growth factor-alpha, AP-1 transcriptional activity is increased and the activation domain of the c-Jun protein is further potentiated. Phosphopeptide mapping of the endogenous c-Jun protein in proliferating cultured hepatocytes demonstrates phosphorylation of the c-Jun activation domain. Combining the results of these in vivo and culture studies, we conclude that the minimal stimulation of one-third PH activates JNK, which phosphorylates the c-Jun activation domain in hepatocytes, resulting in enhanced transcription of AP-1-dependent genes.

Studies on non-covalent associations of immunosuppressive drugs with serum albumin using pneumatically assisted electrospray ionization mass spectrometry

Pneumatically assisted electrospray ionization (ion-spray) mass spectrometry was employed in the detection of non-covalent interactions of immunosuppressive drugs with proteins. Non-covalent complexes of albumin (rat and bovine) with FK506, dihydro-FK506, and FK520 were observed. No complexation was detected between albumin and cyclosporin A (CsA), even at a protein-ligand molar ratio of 1:20. It is suggested that the lack of detection of an albumin-CsA non-covalent complex may be attributed to dissociation of the weakly associated species during ion vaporization. Nonetheless, preliminary results indicate that ion-spray mass spectrometry has potential in qualitative evaluation of drug-plasma protein interaction.

Distribution of albumin, alpha 1-inhibitor 3 and their respective mRNAs in periportal and perivenous rat hepatocytes isolated by the digitonin-collagenase technique

The expression of albumin and alpha 1-inhibitor 3 genes was investigated in rat cell suspensions enriched in periportal (n = 10) and perivenous (n = 10) hepatocytes obtained by the digitonin-collagenase technique. The degree of enrichment of the cell suspensions was assessed: (1) by enzymic assays for the periportal marker alanine aminotransferase and for the perivenous marker glutamine synthetase; and (2) by their content of mRNAs for the periportal marker hepatic glutaminase and for glutamine synthetase. The existence of an antegrade intra-lobular gradient for albumin and alpha 1-inhibitor 3 mRNAs was demonstrated, with periportal:perivenous ratios of 2.33 and 3.80, respectively. However, no gradient was demonstrated for the respective protein contents with corresponding ratios of 0.98 and 1.21. A certain degree of overlap existed between periportal and perivenous suspensions for their content in albumin and alpha 1-inhibitor 3 mRNAs. A morphometrical analysis of the surface of digitonin-permeabilized hepatic tissue revealed that this overlap could be explained by a variable extent of permeabilization of the mediolobular zone from one rat to another and from one lobule to another in a given animal. These results suggest that while the digitonin-collagenase technique is well suited for studies in vitro of proteins expressed in sharp intra-lobular gradients or restricted to an intra-lobular compartment, it is not completely reliable for proteins distributed in continuous moderate intra-lobular gradients, such as albumin and alpha 1-inhibitor 3.

Cytochalisin D exerts stimulatory and inhibitory effects on insulin-induced glucokinase mRNA expression in hepatocytes

The microfilament cytoskeleton is postulated to have a role in the localization, transport and anchorage of certain specific mRNAs. We investigated the effects of cytochalasin D, a fungal metabolite that binds to actin and disrupts the microfilament structure, on insulin-induced expression of glucokinase mRNA in rat hepatocyte cultures. Cytochalasin-D significantly potentiates insulin-induced glucokinase mRNA expression at 100 nM concentration but counteracts glucokinase expression at 2-20 microM. The latter effect is at least in part due to an increase in glucokinase mRNA degradation. This effect of cytochalasin D cannot be accounted for by an increase in cAMP and is also not due to a non-specific effect on mRNA degradation since albumin mRNA levels were not affected by cytochalasin-D and actin mRNA and tubulin mRNA levels were increased. Measurement of glucokinase mRNA release from digitonin-permeabilized hepatocytes suggests that cytochalasin D does not cause acute dissociation of glucokinase mRNA from its binding site. The increased degradation of glucokinase mRNA suggests involvement of the cytoskeleton in glucokinase mRNA stability. However, an additional effect of cytochalasin D on the insulin signalling mechanism cannot be excluded.

Heat shock response in the liver: expression and regulation of the hsp70 gene family and early response genes after in vivo hyperthermia

Heat shock response in cultured cells has been studied extensively; however few data are available on heat shock response in an intact organ of a living animal. In this study we analyzed the kinetics of expression of the heat shock protein 70 gene family (heat shock protein 70, heat shock cognate protein 73 and glucose-regulated protein 78) in the liver of the thermally stressed rat. New synthesis of heat shock protein 70 and heat shock cognate protein 73 was shown in liver slices pulse labeled in vitro with 35S-methionine. Accumulation of heat shock protein 70 and heat shock cognate protein 73 proteins was shown in total cellular extracts. 32P-labeled complementary DNA probes encoding heat shock protein 70, heat shock cognate protein 73 and glucose-regulated protein 78 were used to show that the levels of the corresponding messenger RNAs increase as a fraction of total RNA and in polysomes at different extents and with different kinetics. The induction of heat shock protein 70 and heat shock cognate protein 73 messenger RNAs reflected the increase in the synthesis of the corresponding proteins. Run-on transcription analysis indicated that the expression of heat shock protein 70 and heat shock cognate protein 73 genes was mainly regulated at the transcriptional level. On the contrary, both transcriptional and posttranscriptional regulatory mechanisms can explain the induction of the glucose-regulated protein 78 gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Amelioration of diabetic nephropathy by treatment with monoclonal antibodies against glycated albumin

The pathogenesis of diabetic nephropathy is incompletely understood, but increased nonenzymatic glycation of proteins is considered an important contributory factor. Glycated albumin, which is increased in diabetic sera and is preferentially transported into the renal glomerulus, induces an increase in Type IV collagen production and a decrease in proliferative capacity by mesangial cells in culture. These effects resemble the abnormalities that characterize the glomerular mesangium in diabetes and are prevented by monoclonal antibodies that specifically react with Amadori adducts in glycated albumin. To explore the possibility that the in vitro effects of glycated albumin on mesangial cell biology pertain to the in vivo situation, we examined the effect of treatment with the A717 monoclonal antibodies on glomerular functional and structural changes in a rodent model of genetic diabetes, the db/db mouse. Weekly parenteral antibody administration reduced the elevated albumin excretion and attenuated the mesangial expansion that were observed in the untreated db/db mice that served as controls. Monoclonal antibody treatment also was shown to lower plasma concentrations of glycated albumin in diabetic mice. Thus, reducing glycated albumin concentrations and/or blocking its biologically active epitopes has a salutary influence on the pathogenesis of diabetic nephropathy. The findings indicate that glycated albumin participates in the development of the glomerular lesion in the db/db mouse, and suggest a new approach to the therapy of this complication of diabetes.