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PubMed1994

Systemic and liver cytokine activation. Implications for liver regeneration and posthepatectomy endotoxemia and sepsis.

BACKGROUND: The liver is known to be an important site of tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) production during infection, but local changes in these cytokines after liver resection are unknown. DESIGN: Fischer rats were subjected to 70% hepatectomy or sham operation to determine if hepatic resection alters liver cytokine production and subsequent response to infection. RESULTS: During liver regeneration, circulating IL-6 levels were mildly increased but no expression of TNF-alpha or IL-6 could be detected in the regenerating livers. However, the capacity for the regenerating liver to produce cytokines was intact, since intraperitoneal Escherichia coli endotoxin (2 mg/kg) produced liver cytokine messenger RNA levels in hepatectomized animals comparable to those in pair-fed controls. Systemic response to endotoxin and sepsis was also intact after hepatectomy, as circulating cytokine response was similar between hepatectomized and pair-fed animals after endotoxin administration as well as after cecal ligation and puncture. CONCLUSION: Hepatectomy elicits a circulating cytokine response without effects on liver IL-6 or TNF-alpha production. However, cytokine defense mechanisms are intact during noncomplicated liver regeneration, as indicated by normal TNF-alpha and IL-6 responses to endotoxemia or sepsis. Endotoxemia is a more potent stimulus for liver cytokine production than local trauma or liver regeneration, suggesting that not only the proximity to injury but also the severity and mechanisms of injury determine local cytokine responses.

Animals↗
PubMed1993

Liver regeneration after hepatic ischemia and reduced liver autotransplantation in the rat.

Current knowledge of liver regeneration after reduced liver transplantation is limited. Warm ischemia is one component of the reduced liver transplantation procedure that could have an impact on the regenerative response. To study this effect, we performed partial hepatectomy on male Long-Evans rats, with animals divided into four groups: group 1 underwent partial hepatectomy only; group 2 underwent partial hepatectomy and 40 min of ischemia; group 3 underwent partial hepatectomy, 40 min of ischemia and portocaval shunt surgery; and group 4 underwent partial hepatectomy and orthotopic autograft surgery. Group 5 consisted of sham-operated animals. Animals were killed 4, 24, 48, 72 and 96 hr after surgery. Thymidine kinase activity, mitotic index, a liver mass index and ornithine decarboxylase levels were used as parameters of liver regeneration. Aspartate transaminase was recorded. Maximal thymidine kinase and mitotic index were observed in group 1 animals at 24 hr. In groups 2, 3 and 4 maximal thymidine kinase activity and mitotic activity were observed 24 hr later at 48 hr. The magnitude of the peak response in these groups appeared to correlate with the duration of portal venous occlusion, with greatest increases occurring in those groups where portal stasis was most prolonged. The increase in liver mass for these groups was also delayed with respect to group 1 animals. The anticipated peak in ornithine decarboxylase levels was seen at 4 hr in group 1. The ornithine decarboxylase response in the other groups was disorganized, with delay of the recorded peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

c-Myc antisense limits rat liver regeneration and indicates role for c-Myc in regulating cytochrome P-450 3A activity.

Expression of c-myc protein is associated with cell proliferation. The present study uses antisense oligomers to inhibit c-myc expression in the regenerating rat liver after 70% partial hepatectomy (PH). Antisense phosphorodiamidate morpholino oligomers (novel DNA analogs) were administered i.p. immediately after surgery to block expression of c-myc within the first 24 h after PH. A 20-mer PMO complimentary to the c-myc mRNA at the translation start site was an effective sequence (AVI-4126, 5'-ACGTTGAGGGGCATCGTCGC-3'). A single i.p. dose of 0.5 mg/kg AVI-4126 caused reduction of the regenerating liver c-myc protein in a sequence-specific and dose-dependent manner. Inhibition of c-myc expression resulted in reduction of proliferating cell nuclear antigen and arrested cells in the G(0)/G(1) phase of the cell cycle. The ratio of G(2):G(0) cell populations in the regenerating liver 24 h after PH dropped from 29.1 in saline vehicle-treated rats to 18.0 in rats treated with 2.5 mg/kg AVI-4126. The expression of cell cycle checkpoint protein p53 was inhibited with increasing doses of AVI-4126, but expression of p21(waf-1) was unaffected. The activity of cytochrome P-450 3A2 (CYP3A2) was evaluated by immunoblot analysis and erythromycin N-demethylation. AVI-4126 did not alter CYP3A activity in nonhepatectamized animals but showed a dose-dependent decrease in PH rats. We conclude that AVI-4126, antisense oligomer to c-myc, can reduce cell proliferation in the regenerating rat liver. Furthermore, inhibition of c-myc may indirectly influence the expression of CYP3A.

Animals↗
PubMedDate not supplied

Time course and mechanism of alterations in proton relaxation during liver regeneration in the rat.

We studied the proton T1 and T2, water and lipid content of regenerating rat liver from 1 to 7 days after 70% hepatectomy. Liver from normal and sham-operated animals and splenic tissue from all animals were studied as controls. In vivo proton spectroscopy and imaging of liver was performed in a separate group of control and posthepatectomy rats. The T2 of regenerating liver, but not of sham or normal control liver, was prolonged. Changes in T1, relative to normal tissue, were found in liver and spleen of both operated groups. Lipid content, assessed both by extraction of tissue samples and by in vivo spectroscopy, was increased in regenerating tissue but not in controls. Water content was similarly increased in regenerating liver tissue. Changes in water and lipid content appeared to contribute to the alterations in proton relaxation which we observed.

Animals↗
PubMed1994

Liver expression of epidermal growth factor RNA. Rapid increases in immediate-early phase of liver regeneration.

The liver exhibits a remarkable capacity to regenerate its mass following partial removal or after injury. Transmembrane receptors for epidermal growth factor (EGF) are highly expressed in liver cells, which quickly respond to this polypeptide mitogen by activating an intrinsically low rate of cell division. Although EGF appears to regulate liver growth, its significance has remained unclear, and only a small change in serum levels can be detected during hepatocellular proliferation. Using a reverse transcription-polymerase chain reaction assay, we report here the novel finding that EGF RNA transcripts are synthesized in a hepatic cell-specific pattern, appearing in hepatocyte and lipocyte cell types. Our data reveal that within 15 min following a 70% liver removal, EGF RNA levels increase > 10-fold and then diminish below basal levels prior to the first wave of regenerative cell division. Immunoanalysis of metabolically labeled hepatocytes shows that EGF accumulates as a large 60-kDa peptide. These results demonstrate that EGF transcription is a previously unrecognized component of hepatic gene expression, and rapid increases in EGF RNA levels in the immediate-early phase of liver regeneration point to EGF as an autocrine factor in the prereplicative hepatic growth program.

Animals↗
PubMed2002

Cold ischemia decreases liver regeneration after partial liver transplantation in the rat: A TNF-alpha/IL-6-dependent mechanism.

New strategies of partial liver transplantation such as cadaveric split or living related liver transplantation have been developed to overcome organ shortage. Thus, studies on the ability of small partial grafts to regenerate to normal size while maintaining adequate function have become important. Here, we evaluated the effects of cold preservation on hepatocyte proliferation and function in a novel model of partial liver transplantation in rats. Lewis rats subjected to 70% liver resection (control) were compared with rats that underwent total hepatectomy and 30% partial liver transplantation (recipient). Livers were preserved at 4 degrees C for 30 minutes, 10 hours, or 16 hours in University of Wisconsin solution. Seventy percent liver resection was associated with 100% survival, whereas 30-minute, 10-hour, and 16-hour preservation before 30% transplantation resulted in 80%, 40%, and 20% animal survival, respectively. Prolonged time of cold preservation (10 and 16 hours) was associated with a dramatic decrease of all markers of regeneration (P <.05). Tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) levels were also significantly decreased in recipient rats compared with the control group. Finally, pretreatment of recipients with recombinant IL-6 (rIL-6) normalized all markers of regeneration and significantly improved survival in the 10-hour group (90% vs. 40%; P <.05). In conclusion, sustained periods of cold preservation significantly impaired TNF-alpha and IL-6 production, the regenerative ability of the liver, and animal survival. rIL-6 reversed impaired regeneration in the 10-hour cold ischemia group and suggests a primary role of nonparenchymal cells in modulating hepatocyte proliferation in the ischemic liver.

Animals↗
PubMed1970

Amino acid incorporation by isolated rat liver mitochondria during liver regeneration.

Intact mitochondria, isolated from regenerating rat liver 2-3 days after partial hepatectomy, are 2.5-3 times more active in amino acid incorporation than mitochondria from control livers. Liver mitochondria from sham-operated animals showed normal amounts of incorporation. Sterile procedures insured low levels of bacterial contamination; cycloheximide was used to eliminate any contribution by contaminating microsomes. Mitochondria from control and 3-day-old regenerating livers were nearly identical in their concentration of several respiratory chain components, P/O ratios, specific O(2) consumption, and cytochrome c oxidase activities. Small differences were observed in respiratory control ratios but these were shown to be unrelated to the differences observed in amino acid incorporating ability. Differential contamination by lysosomes and differences in lysosome fragility were also shown not to be factors in the increased incorporation by regenerating liver mitochondria. Thus, mitochondria from rapidly growing and dividing mammalian tissues are more active in protein synthesis than mitochondria from tissues that grow and divide more slowly.

Adenosine Triphosphate↗
PubMed2004

[Liver regeneration in living-donor liver transplantation].

Liver regeneration in living-donor liver transplantation is summarized from the authors' data. In donors, liver function tests recovered to within the normal range 2 weeks after surgery regardless of graft type. At 2 weeks, the volumetric recovery of the remnant liver was 65% and 80% of the original volume in right and left lobe donors, respectively. These results suggest that functional recovery occurs earlier than morphologic restoration in donors. In recipients, the factor that affected the regeneration rate in size 4 weeks after transplantation was only implanted graft size; the rate was greater in patients in whom smaller grafts were implanted. In recipients with a rate of two or more, however, high portal vein pressure and flow were observed. Further, persistent low platelet counts and hyperbilirubinemia were seen in those patients. These results indicate that size enlargement may be caused by engorgement, and functional recovery is not achieved concurrently with morphologic restoration, especially in patients with smaller grafts. In patients with fulminant hepatic failure who receive auxiliary partial orthotopic liver transplantation, sequential histopathologic observations of the diseased liver revealed that liver regeneration initiates from cytokeratin 17-positive ductules and at least 1 year is necessary for complete recovery.

Hepatocytes↗
PubMed1977

[Effects of diphtheria and tetanus toxins on liver regeneration in the rat].

The effects of diphtheria toxin and tetanus toxin on the regenerating rat liver were studied. The following parameters were used: liver regeneration percentage, mitotic index, protein content and serum complement C3 fraction level. Diphtheria toxin does not affect the liver regeneration, that what confirms the poor sensitivity of the rat to this toxin. Tetanus toxin inhibits the cellular division, while causes an increase in the cell protein content, resulting in hepatocyte hypertrophy. Both toxins cause a fall of the serum complement C3 fraction.

Animals↗
PubMed1990

Changes in activity and mRNA levels of poly(ADP-ribose) polymerase during rat liver regeneration.

ADP-ribosylation of nuclear proteins, catalysed by the enzyme poly(ADP-ribose) polymerase, is involved in the regulation of different cellular processes of DNA metabolism. To further clarify the role of the enzyme during proliferating activity of mammalian cells, we have studied the control of gene expression in regenerating rat liver. The changes in activity and mRNA levels were analysed during the early and late phases of the compensatory model. When enzyme activity was measured in isolated liver nuclei obtained at different times after hepatectomy, two different phases were observed: an early wave occurring before the onset of DNA synthesis, and a second one, starting several hours after the onset of DNA synthesis and returning to control values at later times. The evaluation of the enzymatic level in nuclear extracts and by activity gel analysis showed a more gradual increase starting 1 day after hepatectomy, in concomitance with the peak of DNA synthesis. By using a specific murine cDNA probe, a significant enhancement of mRNA levels for poly(ADP-ribose) polymerase was observed during liver regeneration, slightly preceding the onset of DNA synthesis. The results obtained show that changes in poly(ADP-ribose) polymerase activity, during liver regeneration, are associated both to early events preceding the increase in DNA synthesis and to later phases of the cell proliferation process.

Animals↗
PubMed1997

Cyclic AMP signalling pathway and cellular proliferation: induction of CREM during liver regeneration.

The CREM gene encodes both activators and repressors of cAMP-induced gene expression. An isoform of CREM encodes the powerful transcriptional repressor ICER (Inducible cAMP Early Repressor), which has been shown to be inducible by virtue of an alternative, intronic promoter. The CREM gene belongs to the early response class and displays a characteristic neuroendocrine cell- and tissue-specific expression. To date ICER inducibility has been described in non-replicating, terminally differentiated tissues. In this paper we document a robust induction of CREM expression in the regenerating rat liver after partial hepatectomy. This represents the first link of inducible CREM expression to the phenomenon of cellular proliferation. Furthermore, it represents the first example of transcriptional activation of a cAMP-responsive factor in the regenerating liver. This has significant physiological relevance since the adenylate cyclase signalling pathway is strongly implicated in liver regeneration. Finally, we show that the repressor ICER is inducible in the hepatoma cell line H35 upon activation of the adenylate cyclase and phosphorylation of the activator CREB.

Animals↗
PubMed2005

betaA- and betaC-activin, follistatin, activin receptor mRNA and betaC-activin peptide expression during rat liver regeneration.

The mRNA expression of two activin growth factor subunits (betaA- and betaC-activin), activin receptor subunits (ActRIIA, ActRIIB) and the activin-binding protein follistatin, and peptide expression of betaA-activin and betaC-activin subunits, were examined in regenerating rat liver after partial hepatectomy (PHx). Liver samples were collected from adult, male Sprague-Dawley rats, 12-240 h (n=3-5 rats per time point) after PHx or from sham-operated controls at the same time points. Hepatocyte mitosis and apoptosis were assessed histologically and by in situ cell death detection. RT and PCR were used to assess relative gene expression. betaA- and betaC-activin peptide immunoreactivity was assessed in liver and serum samples by western blotting, whereas cellular expression was investigated by immunohistochemistry, using specific monoclonal antibodies. betaA- and betaC-activin mRNA dropped to < 50% of sham control values 12 h after PHx and remained at this level until 168 h post-PHx, when betaA-activin expression increased to three times sham control values and betaC-activin mRNA returned to pre-PHx levels. A peak in follistatin expression was observed 24-48 h post-PHx, coincident with an increase in hepatocyte mitosis. No changes were observed in ActRIIA mRNA, whereas ActRIIB expression paralleled that of betaA-activin mRNA. betaC-activin immunoreactive homo- and heterodimers were observed in regenerating liver and serum. Mitotic hepatocytes frequently contained betaC-activin immunoreactivity, whereas apoptotic hepatocytes were often immunoreactive for betaA-activin. We conclude that betaA- and betaC-activin subunit proteins are autocrine growth regulators in regenerating liver and when expressed independently lead to hepatocyte apoptosis or mitosis in a subset of hepatocytes.

Activin Receptors↗
PubMed1988

An S6 kinase activated during liver regeneration is related to the insulin-stimulated S6 kinase in H4 hepatoma cells.

Protein kinase activity toward the 40 S ribosomal protein S6 is activated 6-fold in regenerating rat liver following 70% hepatectomy. The kinase is maximally activated within 2 h after surgery, remains active up to 36 h after surgery, and declines rapidly thereafter. The post-hepatectomy S6 kinase activity exhibits structural and functional similarity to an insulin-stimulated S6 kinase in H4 hepatoma cells. Both S6 kinase activities are cAMP- and Ca2+-independent, and have a requirement for [ethylenebis(oxyethylenenitrilo)]tetraacetic acid. The regenerating liver and the insulin-stimulated H4 hepatoma S6 kinase elute at similar positions when sequentially fractionated by anion-exchange and cation-exchange chromatography. Both enzymes migrate at Mr 70,000 on fast protein liquid chromatography Superose 12 gel filtration. In H4 hepatoma cells, activation of S6 kinase activity is reversed by removal of insulin, and the cells can then be restimulated. Freshly isolated hepatocytes from normal animals show low levels of S6 kinase activity which can be stimulated by epidermal growth factor and insulin. Hepatocytes prepared from regenerating liver remnant have constitutively high levels of S6 kinase activity, which is unresponsive to insulin plus epidermal growth factor and which remains elevated at least 2 h in the absence of exogenously added growth factors. These findings demonstrate S6 protein kinase activation in vivo, in the setting of regulated cell growth; as in cultured cells, activation of S6 kinase probably represents an early step in the pleiotypic response elicited by activation of growth factor receptors.

Animals↗
PubMed1990

Content, pattern and metabolic processing of rat-liver gangliosides during liver regeneration.

During rat liver regeneration, the ganglioside content and distribution undergo significant changes after partial hepatectomy; total liver gangliosides increase remarkably till the 4th day after surgery, thereafter progressively decreasing to reach the values of sham-operated controls at the 12th day. The qualitative pattern is characterized by the 95% relative increase of GD1a at the 4th day and the 40% relative decrease of GD1b. In order to investigate the processes of ganglioside penetration into cells, degradation and biosynthesis, radiolabelled GM1 ([Sph-3H] GM1) was administered. One day after hepatectomy the liver uptake and metabolism of exogenous ganglioside were significantly reduced. Three days post-surgery these parameters were restored to control values; however an increased radioactivity incorporation was found in GD1a, thus suggesting an enhancement of its biosynthesis around the 4th day. The data reported here suggest that in the first two days after partial hepatectomy, the ganglioside degradation is reduced with a consequent increase of ganglioside content; later on the catabolic routes normalize and some biosynthetic processes leading to GD1a are enhanced. GD1a seems to be a marker of a peculiar transition phase of liver regeneration.

Animals↗
PubMed2004

Changes in serum LECT 2 levels during the early period of liver regeneration after adult living related donor liver transplantation.

We investigated changes in serum leukocyte cell-derived chemotaxin2 (LECT2) levels between donors and recipients in the early period during liver regeneration following adult living related donor liver transplantation (LRDLT). Five recipients (three women, two men; 37.0 +/- 15.8 years old), all of whom had end-stage liver failure, underwent LRDLT from healthy five donors (two women, three men; 41.6 +/- 14.3 years old) between June 2000 and February 2001. FK506 and methylprednisolone were used as immunosuppressants for recipients. Serum LECT2 levels decreased immediately after both the hepatectomy in all donors and the implantation of liver graft in all recipients. Donors showed a nadir at 3 to 12 hours, increasing at 24 to 48 hours. The nadir in recipients occurred several hours after the donors. The serum LECT2 levels of donors were significantly higher than those of recipients on day 5 (9.5 +/- 5.9 ng/mL vs 3.1 +/- 2.2 ng/mL, P = .04) and on day 7 (9.3 +/- 3.8 ng/mL vs 3.5 +/- 1.1 ng/mL, P = .04). Serum GPT and GOT levels were inversely proportionate to the serum LECT2 levels. The present studies suggest that LECT2 participates in liver regeneration and injury following hepatectomy.

Adult↗
PubMed1997

Serum transforming growth factor-alpha level can be a parameter for evaluating liver regeneration after partial hepatectomy in patients with liver cancer.

Sensitive and reliable laboratory parameters are necessary to evaluate the degree of liver regeneration serially in patients after partial hepatectomy for liver cancer. We evaluated the serum levels of transforming growth factor-alpha (TGF-alpha) and hepatocyte growth factor (HGF), both of which are potent mitogens for hepatocytes, in 22 hepatectomized patients with liver cancer: 10 patients with hepatocellular carcinoma and 12 patients with metastatic liver tumors. Ten patients who underwent laparotomy for nonhepatic surgery were also studied as surgical controls. The serum TGF-alpha and HGF levels were measured by sandwich enzyme-linked immunosorbent assay techniques. Both the serum TGF-alpha and HGF levels increased after partial hepatectomy. However, there was no correlation between the levels of TGF-alpha and HGF. The maximal level of TGF-alpha achieved in each case correlated significantly with the resected liver volume and the increased volume of the remaining liver. Hepatocyte growth factor showed no such correlations. After nonhepatic surgery, the HGF level also increased significantly, while the TGF-alpha level did not. These results suggest that the serum TGF-alpha level varies depending on the regenerative stimulus to the liver, and that its increase corresponds with the degree of liver regeneration that occurs in patients after partial hepatectomy for liver cancer. In contrast, it is unlikely that the serum HGF level reflects liver regeneration. In conclusion, the serum TGF-alpha level can be used as a parameter for evaluating liver regeneration in patients who have undergone partial hepatectomy.

Carcinoma, Hepatocellular↗
PubMed1991

The gene encoding rat insulinlike growth factor-binding protein 1 is rapidly and highly induced in regenerating liver.

The liver is an epithelioid organ that can regenerate following partial hepatectomy. Although it is composed mainly of hepatocytes, it has a complex, multicellular architecture, implying that intercellular communications must exist during regeneration. As in other mitogen-stimulated cells, immediate-early growth response genes induced in the absence of prior protein synthesis are likely to play an important regulatory role in the regenerative process. Through differential screening of regenerating liver cDNA libraries, we found that one of the most highly expressed immediate-early genes in liver regeneration encodes the rat homolog of the low-molecular-weight insulinlike growth factor (IGF)-binding protein (IGFBP-1). This protein has been implicated in enhancing the mitogenic effect of IGF on tissues. IGFBP-1 gene induction is transcriptionally mediated and specific to regenerating liver, as the gene is not expressed in mitogen-stimulated fibroblasts. IGFBP-1 expression has been shown to increase under low-insulin conditions such as diabetes, and the complex regulation of expression is indicated by our finding that insulin treatment of H35 rat hepatoma cells, which induces proliferation, also causes a rapid decrease in transcription and expression of the IGFBP-1 gene. Of note, IGFBP-1 mRNA is abundant in fetal rat liver, implying that it participates in normal liver growth and development. Although regenerating liver cells continue to produce IGF-I, we did not detect IGF-I receptor mRNA during the first 24 h after hepatectomy. However, some IGFBPs may act to enhance the activity of IGF-I independently of IGF-I receptors. Thus, IGF-1 and IGFBPs may interact with hepatocytes or nonparenchymal liver cells, through either IGF-I or novel receptors. In this way, IGFBP-I and IGF-I could act in a paracrine and/or autocrine fashion in maintaining normal liver architecture during regeneration.

Amino Acid Sequence↗