Hepatic regeneration induces transient acute phase reaction: systemic elevation of acute phase reactants and soluble cytokine receptors

Validation of a surgical model for posthepatectomy liver failure in rats

BACKGROUND

The upper limit for liver resections in rats is approximately 90%. In the early postoperative phase, mortality increases. The aim of the present study was to validate the rat model of 90% partial hepatectomy (PH) as a model of post-hepatectomy liver failure (PHLF). Further, we wanted to test a quantitative scoring system as a detector of lethal outcomes caused by PHLF in rats.

METHODS

Sixty-eight rats were randomized to 90% PH, sham operation, or no surgery. Further, block randomization was performed based on time of euthanization: 12, 24, or 48 h after surgery. A general distress score (GDS) ≥10 during the day or ≥6 at midnight prompted early euthanization and classification as nonsurvivor. Animals euthanized as planned were classified as survivors. During euthanization, blood and liver tissue were collected, and liver-specific biochemistry was evaluated.

RESULTS

Based on the biochemical results, all animals subjected to 90% PH experienced PHLF. Seventeen rats were euthanized due to irreversible PHLF. The GDS increased for nonsurvivors within 12-18 h after surgery. The mean time for euthanization was 27 h after surgery.

CONCLUSION

Based on the GDS and liver-specific biochemistry, we concluded that the model of 90% PH seems to be a proper model for investigating PHLF in rats. As a high GDS is associated with increased mortality, the GDS appears to be valuable in detecting lethal outcomes caused by PHLF in rats.

New insights into IL-6 family cytokines in metabolism, hepatology and gastroenterology

IL-6 family cytokines are defined by the common use of the signal-transducing receptor chain glycoprotein 130 (gp130). Increasing evidence indicates that these cytokines are essential in the regulation of metabolic homeostasis as well as in the pathophysiology of multiple gastrointestinal and liver disorders, thus making them attractive therapeutic targets. Over the past few years, therapies modulating gp130 signalling have grown exponentially in several clinical settings including obesity, cancer and inflammatory bowel disease. A newly engineered gp130 cytokine, IC7Fc, has shown promising preclinical results for the treatment of type 2 diabetes, obesity and liver steatosis. Moreover, drugs that modulate gp130 signalling have shown promise in refractory inflammatory bowel disease in clinical trials. A deeper understanding of the main roles of the IL-6 family of cytokines during homeostatic and pathological conditions, their signalling pathways, sources of production and target cells will be crucial to the development of improved treatments. Here, we review the current state of the role of these cytokines in hepatology and gastroenterology and discuss the progress achieved in translating therapeutics targeting gp130 signalling into clinical practice.

IL-6 Trans-signaling Controls Liver Regeneration After Partial Hepatectomy

Interleukin-6 (IL-6) is critically involved in liver regeneration after partial hepatectomy (PHX). Previous reports suggest that IL-6 trans-signaling through the soluble IL-6/IL-6R complex is involved in this process. However, the long-term contribution of IL-6 trans-signaling for liver regeneration after PHX is unknown. PHX-induced generation of the soluble IL-6R by ADAM (a disintegrin and metallo) proteases enables IL-6 trans-signaling, in which IL-6 forms an agonistic complex with the soluble IL-6 receptor (sIL-6R) to activate all cells expressing the signal-transducing receptor chain glycoprotein 130 (gp130). In contrast, without activation of ADAM proteases, IL-6 in complex with membrane-bound IL-6R and gp130 activates classic signaling. Here, we describe the generation of IL-6 trans-signaling mice, which exhibit boosted IL-6 trans-signaling and abrogated classic signaling by genetic conversion of all membrane-bound IL-6R into sIL-6R proteins phenocopying hyperactivation of ADAM-mediated shedding of IL-6R as single substrate. Importantly, although IL-6R deficient mice were strongly affected by PHX, survival and regeneration of IL-6 trans-signaling mice was indistinguishable from control mice, demonstrating that IL-6 trans-signaling fully compensates for disabled classic signaling in liver regeneration after PHX. Moreover, we monitored the long-term consequences of global IL-6 signaling inhibition versus IL-6 trans-signaling selective blockade after PHX by IL-6 monoclonal antibodies and soluble glycoprotein 130 as fragment crystallizable fusion, respectively. Both global IL-6 blockade and selective inhibition of IL-6 trans-signaling results in a strong decrease of overall survival after PHX, accompanied by decreased signal transducer and activator of transcription 3 phosphorylation and proliferation of hepatocytes. Mechanistically, IL-6 trans-signaling induces hepatocyte growth factor production by hepatic stellate cells. Conclusion: IL-6 trans-signaling, but not classic signaling, controls liver regeneration following PHX.

Liver regeneration is dependent on the extent of hepatectomy

BACKGROUND

The upper limit for the size of hepatectomy is approximately 90% in rats. The aim of the study was to assess quantitatively using stereological methods the impact on liver function, regeneration rate (RR), and hepatocyte proliferation of varying hepatectomy size in a rat model.

MATERIALS AND METHODS

A total of 104 male Wistar rats were subjected to 30%, 70%, or 90% partial hepatectomy, sham operation, or no operation. Euthanization and harvesting of liver tissue and blood took place at postoperative days 1, 3, and 5 (n = 8 per group). Liver-specific biochemistry and RR were evaluated. Hepatocyte proliferation was estimated by immunohistochemical staining for Ki-67 antigen using unbiased stereological principles.

RESULTS

Liver RR in the 90% group increased by a 6.6 fold during the 5 postoperative days compared with only a minor increase in both the 70% and 30% partial hepatectomy groups. The highest number of Ki-67-positive hepatocytes was observed in the 70% group at postoperative day 1 and for the 90% group at postoperative day 3. Prothrombin-proconvertin ratio was significantly lower in the 90% group 1 d after surgery compared with all other groups, however, nearly normalized at postoperative day 5.

CONCLUSIONS

We show that liver RR and the number of proliferating hepatocytes increase, whereas the initial hepatic synthetic capacity decreases with increasing hepatectomy size.

A disintegrin and metalloproteinase 17 regulates TNF and TNFR1 levels in inflammation and liver regeneration in mice

A disintegrin and metalloproteinase 17 (ADAM17), or tumor necrosis factor (TNF)-α-converting enzyme, is a key metalloproteinase and physiological convertase for a number of putative targets that play critical roles in cytokine and growth factor signaling. These interdependent pathways are essential components of the signaling network that links liver function with the compensatory growth that occurs during liver regeneration following 2/3 partial hepatectomy (PH) or chemically induced hepatotoxicity. Despite identification of many soluble factors needed for efficient liver regeneration, very little is known about how such ligands are regulated in the liver. To directly study the role of ADAM17 in the liver, we employed two cell-specific ADAM17 knockout (KO) mouse models. Using lipopolysaccharide (LPS) as a robust stimulus for TNF release, we found attenuated levels of circulating TNF in myeloid-specific ADAM17 KO mice (ADAM17 m-KO) and, unexpectedly, in mice with hepatocyte-specific ADAM17 deletion (ADAM17 h-KO), indicating that ADAM17 expression in both cell types plays a role in TNF shedding. After 2/3 PH, induction of TNF, TNFR1, and amphiregulin (AR) was significantly attenuated in ADAM17 h-KO mice, implicating ADAM17 as the primary sheddase for these factors in the liver. Surprisingly, the extent and timing of hepatocyte proliferation were not affected after PH or carbon tetrachloride injection in ADAM17 h-KO or ADAM17 m-KO mice. We conclude that ADAM17 regulates TNF, TNFR1, and AR in the liver, and its expression in both hepatocytes and myeloid cells is important for TNF regulation after LPS injury or 2/3 PH, but is not required for liver regeneration.

Iron-regulatory gene expression during liver regeneration

BACKGROUND

In rat, the first 18-24 h after partial hepatectomy (PH) are characterized by an acute-phase reaction, after which liver regeneration predominates. Interleukin-6 (IL-6) induces the iron hormone hepcidin, which blocks iron uptake and may compromise iron uptake in the growing liver. The expressions of hepcidin and the iron-regulatory pathway of hepcidin gene expression during the late phase of liver regeneration are unknown.

AIM

To characterize the expression pattern of hepcidin and the iron-sensing pathway of hepcidin regulation during liver regeneration.

METHODS

Rats were subjected to PH or sham operation. Liver weights, number of S-phase nuclei, and serum levels of iron and IL-6 were determined. Messenger-RNA levels of hepcidin, ferritin, hemojuvelin, transferrin receptor 1 and 2, HFE, divalent metal transporter 1, ferroportin, and ceruloplasmin were determined with qPCR at different time points. Protein levels of STAT3 and SMAD4 were determined with western blot.

RESULTS

During the acute-phase response, IL-6 release induced STAT3 protein and hepcidin mRNA, whereas mRNA levels of proteins in the iron-sensing pathway (HFE, hemojuvelin, and transferrin receptor 2) decreased. The mRNA levels of proteins involved in cellular iron uptake were increased and cellular iron export unchanged. During liver regeneration >24 h after PH, gene expressions in the iron-sensing pathway were continuously suppressed and hepcidin mRNA levels declined 3-7 days after surgery.

CONCLUSIONS

Hepcidin gene expression peaks during the acute-phase response, but a sustained down-regulation of the iron-sensing pathway of hepcidin regulation gradually reduces hepcidin gene expression until regeneration is complete, thereby promoting iron mobilization to the regenerating liver.

Early hepatocyte DNA synthetic response posthepatectomy is modulated by IL-6 trans-signaling and PI3K/AKT activation

BACKGROUND & AIMS

Interleukin-6 (IL-6) is a crucial factor in liver regeneration following partial hepatectomy (PH); however, the role of IL-6 and IL-6 trans-signaling in particular, in hepatocyte mitosis remains controversial. IL-6 trans-signaling relies upon the release of the soluble IL-6R (sIL-6R), which binds IL-6 to form an agonistic IL-6/sIL-6R complex. Herein we have examined the hypothesis that IL-6 trans-signaling plays a crucial and distinct role in liver regeneration following PH.

METHODS

The specific IL-6/sIL-6R antagonist, sgp130Fc, was expressed in mice and analyzed for its effect on hepatocyte mitosis following PH. Alternatively, we examined the effect of the IL-6/sIL-6R super-agonist, Hyper-IL-6, or IL-6 expressed either alone or in combination with hepatocyte growth factor (HGF) on hepatocyte mitosis in the absence of PH.

RESULTS

Following PH, the dramatic rise of circulating IL-6 levels is accompanied by a concurrent ∼2-fold increase in circulating sIL-6R levels. Ectopic expression of sgp130Fc reduced hepatocyte mitosis by about 40% at early times following PH, while substantially reducing AKT, but not STAT3, activation. But, ectopic Hyper-IL-6 expression in mice without PH was not mitogenic to hepatocytes in vivo. Rather, Hyper-IL-6, but not IL-6, markedly increased HGF-induced hepatocyte mitosis. This cooperative effect correlated with greater resistance of HIL-6 than IL-6 to HGF-mediated reduction of AKT activation, rather than changes in STAT3 or MAPK signaling, and was completely blocked by PI3K inhibition.

CONCLUSIONS

Following PH, IL-6/sIL-6R cooperates with growth factors, through a PI3K/AKT-dependent mechanism to promote entry of hepatocytes into the cell cycle.

Protein profilings in mouse liver regeneration after partial hepatectomy using iTRAQ technology

Liver is unique in its capability to regenerate after an injury. Liver regeneration after a 2/3 partial hepatectomy served as a classical model and is adopted frequently to study the mechanism of liver regeneration. In the present study, semiquantitative analysis of protein expression in mouse liver regeneration following partial hepatectomy was performed using an iTRAQ technique. Proteins from pre-PHx control livers and livers regenerating for 24, 48 and 72 h were extracted and inspected using 4-plex isotope labeling, followed by liquid chromatography fractionation, mass spectrometry and statistical differential analysis. A total of 827 proteins were identified in this study. There were 270 proteins for which quantitative information was available at all the time points in both biologically duplicate experiments. Among the 270 proteins, Car3, Mif, Adh1, Lactb2, Fabp5, Es31, Acaa1b and LOC100044783 were consistently down-regulated, and Mat1a, Dnpep, Pabpc1, Apoa4, Oat, Hpx, Hp and Mt1 were up-regulated by a factor of at least 1.5 from that of the controls at one time point or more. The regulation of each differential protein was also demonstrated by monitoring its time-dependent expression changes during the regenerating process. We believe this is the first report to profile the protein changes in liver regeneration utilizing the iTRAQ proteomic technique.

Gene modulation associated with inhibition of liver regeneration in hepatitis B virus X transgenic mice

AIM: To analyze the modulation of gene expression profile associated with inhibition of liver regeneration in hepatitis B X (HBx)-expressing transgenic mice.

METHODS: Microarray technology was performed on liver tissue obtained from 4 control (LacZ) and 4 transgenic mice (HBx-LacZ), 48 h after partial hepatectomy. The significance of the normalized log-ratios was assessed for each gene, using robust t-tests under an empirical Bayes approach. Microarray hybridization data was verified on selected genes by quantitative PCR.

RESULTS: The comparison of gene expression patterns showed a consistent modulation of the expression of 26 genes, most of which are implicated in liver regeneration. Up-regulated genes included DNA repair proteins (Rad-52, MSH6) and transmembrane proteins (syndecan 4, tetraspanin), while down-regulated genes were connected to the regulation of transcription (histone deacetylase, Zfp90, MyoD1) and were involved in the cholesterol metabolic pathway and isoprenoid biosynthesis (farnesyl diphosphate synthase, Cyp7b1, geranylgeranyl diphosphate synthase, SAA3).

CONCLUSION: Our results provide a novel insight into the biological activities of HBx, implicated in the inhibition of liver regeneration.

The early acute phase response after burn injury in mice

In the hours immediately after burn injury, the body enters into an acute phase reaction characterized, in part, by the augmentation of cytokine and acute phase protein production. This reaction has been poorly characterized in the 24 hours immediately after injury. To better understand the early acute phase response, 8- to 10-week-old BALB/C female mice were subjected to a 15% total body surface area (TBSA). Hepatic levels of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 were monitored. In addition, the circulating level of serum amyloid A, an acute phase protein, also was measured at the same time points. Tumor necrosis factor-alpha levels peaked 2 hours after burn injury, whereas interleukin-1beta had a biphasic response, increasing 2 hours after injury and again at 12 hours. Interleukin-6 and serum amyloid A were not increased until 12 hours after injury and began to decline at 24 hours. These results demonstrate that within the liver, the acute phase response after burn injury initially involves tumor necrosis factor-alpha and interleukin-1beta, whereas interleukin-6 is not involved until later and that systemic serum amyloid A levels are not increased until interleukin-6 is also increased.

Expression patterns and action analysis of genes associated with blood coagulation responses during rat liver regeneration

AIM: To study the blood coagulation response after partial hepatectomy (PH) at transcriptional level.

METHODS: After PH of rats, the associated genes with blood coagulation were obtained through reference to the databases, and the gene expression changes in rat regenerating liver were analyzed by the Rat Genome 230 2.0 array.

RESULTS: It was found that 107 genes were associated with liver regeneration. The initially and totally expressing gene numbers occurring in initiation phase of liver regeneration (0.5-4 h after PH), G₀/G₁ transition (4-6 h after PH), cell proliferation (6-66 h after PH), cell differentiation and structure-function reconstruction (66-168 h after PH) were 44, 11, 58, 7 and 44, 33, 100, 71 respectively, showing that the associated genes were mainly triggered in the forepart and prophase, and worked at different phases. According to their expression similarity, these genes were classified into 5 groups: only up-, predominantly up-, only down-, predominantly down-, up- and down-regulation, involving 44, 8, 36, 13 and 6 genes, respectively, and the total times of their up- and down-regulation expression were 342 and 253, respectively, demonstrating that the number of the up-regulated genes was more than that of the down- regulated genes. Their time relevance was classified into 15 groups, showing that the cellular physiological and biochemical activities were staggered during liver regeneration. According to gene expression patterns, they were classified into 29 types, suggesting that their protein activities were diverse and complex during liver regeneration.

CONCLUSION: The blood coagulation response is enhanced mainly in the forepart, prophase and anaphase of liver regeneration, in which the response in the forepart, prophase of liver regeneration can prevent the bleeding caused by partial hepatectomy, whereas that in the anaphase contributes to the structure-function reorganization of regenerating liver. In the process, 107 genes associated with liver regeneration play an important role.

Protection against lung damage in reduced-size liver transplantation

OBJECTIVE

This study examined the effect of ischemic preconditioning on pulmonary damage associated with reduced-size orthotopic liver transplantation (ROLT) and attempted to identify the underlying protective mechanisms.

DESIGN

Randomized and controlled animals study.

SETTING

Experimental laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Lung damage was evaluated in ROLT with or without preconditioning. Nitric oxide and interleukin (IL)-1 actions were altered pharmacologically.

MEASUREMENTS AND MAIN RESULTS

IL-1, tumor necrosis factor (TNF)-alpha, soluble TNF receptors (sTNFR), and inflammatory response in lung were measured after ROLT. Our results indicate the involvement of IL-1 in the lung damage following ROLT. Ischemic preconditioning, mediated by nitric oxide, reduced IL-1 release and protected against lung damage. Nitric oxide synthesis inhibition in the preconditioned group led to increased IL-1 levels and increased lung damage following ROLT, whereas the addition of IL-1 receptor antagonist protected against the injurious effects of nitric oxide inhibition. In addition, nitric oxide pretreatment gave similar results in terms of IL-1alpha and lung protection to those found in preconditioning. The benefits to the lung attributable to IL-1 inhibition might be linked to the effect of this cytokine on sTNFR, an endogenous mechanism that modulates systemic TNF actions. In fact, strategies aimed at inhibiting IL-1 action, including IL-1 receptor antagonist, ischemic preconditioning, and nitric oxide donor, increased systemic sTNFR2 and decreased free TNF, following ROLT. Similarly, nitric oxide synthesis inhibition in the preconditioned group, which increased IL-1alpha and lung damage, reduced systemic sTNFR2 and increased free TNF levels. These injurious effects were avoided when IL-1 action was inhibited.

CONCLUSIONS

Ischemic preconditioning and pharmacologic strategies that simulate its benefits protected against lung damage in an experimental model of ROLT. Our results also suggest a potential relationship between nitric oxide, IL-1, and TNF/sTNF in the benefits of preconditioning on the lung damage associated with ROLT.

Microarray analysis of thioacetamide-treated type 1 diabetic rats

It is well known that diabetes imparts high sensitivity to numerous hepatotoxicants. Previously, we have shown that a normally non-lethal dose of thioacetamide (TA, 300 mg/kg) causes 90% mortality in type 1 diabetic (DB) rats due to inhibited tissue repair allowing progression of liver injury. On the other hand, DB rats exposed to 30 mg TA/kg exhibit delayed tissue repair and delayed recovery from injury. The objective of this study was to investigate the mechanism of impaired tissue repair and progression of liver injury in TA-treated DB rats by using cDNA microarray. Gene expression pattern was examined at 0, 6, and 12 h after TA challenge, and selected mechanistic leads from microarray experiments were confirmed by real-time RT-PCR and further investigated at protein level over the time course of 0 to 36 h after TA treatment. Diabetic condition itself increased gene expression of proteases and decreased gene expression of protease inhibitors. Administration of 300 mg TA/kg to DB rats further elevated gene expression of proteases and suppressed gene expression of protease inhibitors, explaining progression of liver injury in DB rats after TA treatment. Inhibited expression of genes involved in cell division cycle (cyclin D1, IGFBP-1, ras, E2F) was observed after exposure of DB rats to 300 mg TA/kg, explaining inhibited tissue repair in these rats. On the other hand, DB rats receiving 30 mg TA/kg exhibit delayed expression of genes involved in cell division cycle, explaining delayed tissue repair in these rats. In conclusion, impaired cyclin D1 signaling along with increased proteases and decreased protease inhibitors may explain impaired tissue repair that leads to progression of liver injury initiated by TA in DB rats.

Activity and expression of various isoforms of uridine diphosphate glucuronosyltransferase are differentially regulated during hepatic regeneration in rats

PURPOSE

Glucuronidation pathway is very important in the detoxification of endogenous and exogenous compounds. The objective of this study was to evaluate the activity and expression of various hepatic uridine diphosphate glucuronosyltransferases (UGTs) in rats at various time points after initiation of hepatic regeneration by partial hepatectomy (PHx).

METHODS

The mRNA expression of various UGTs was evaluated using real-time polymerase chain reaction (real-time PCR) with specific primers. The in vitro activity of UGTs was evaluated using different substrates such as estradiol (UGT1A1), acetaminophen (UGT1A6/7), morphine (UGT2B1), testosterone (UGT2B1/3/6), androsterone (UGT2B2), and (-)-borneol (UGT2B12).

RESULTS

Whereas the activity and mRNA expression of UGT1A1, UGT2B1, UGT2B1/3/6, UGT2B2, and UGT2B12 were lower, the activity and mRNA expression of UGT1A6/7 were preserved during hepatic regeneration. The mRNA expression of UGT2B8 was down-regulated, whereas the mRNA expression of UGT1A5 and UGT1A8 was not altered by PHx. The mRNA expression of UGT1A2 and UGT1A3 was increased during hepatic regeneration.

CONCLUSION

UGT-mediated drug-metabolizing ability of the liver was altered differentially in the regenerating rat liver. Individualized dosing regimen for different UGT substrates may be needed when using such substrates of these enzymes in patients with a regenerating liver, especially during the early postoperative period. However, the glucuronide conjugating capacity of the liver in the donor of a living donor liver transplantation is expected to completely return to normal with time after surgery.

Transient changes in the expression pattern of key enzymes for bile acid synthesis during rat liver regeneration

Changes in the expression patterns of genes involved in bile acid (BA) synthesis were investigated during rat liver regeneration that follows two-thirds partial hepatectomy. BAs in bile were measured by GC-MS and the absolute and relative abundance of specific mRNAs in the liver by RT-real-time quantitative PCR. Cyclin E mRNA, used as an indicator of liver cell proliferation, peaked at day 1. The levels of mRNA of alpha-fetoprotein transcription factor (FTF) and small heterodimer partner (SHP) were first reduced (day 1) and then (days 2-3) increased, when those of farnesoid X receptor (FXR) were also transiently enhanced. The early (day 1) up-regulation of Cyp7a1, and Cyp8b1, together with the down-regulation of Cyp27, was consistent with an increased proportion of cholic acid versus chenodeoxycholic acid and a progressive recovery in total BAs secretion. The transient appearance of flat BAs (allo-BAs plus Delta4-unsaturated-BAs) during rat liver regeneration was probably due to the changes in the expression ratio of steroid 5alpha- versus 5beta-reductase. Both were first (day 1) down-regulated and then up-regulated (5alpha-reductase more than 5beta-reductase). In conclusion, changes in the expression patterns of nuclear receptors and enzymes involved in BA synthesis are consistent with the transient modifications that occur in BA pool during rat liver regeneration.

Comportamento do fator de necrose tumoral e da proteína C reativa em hepatectomia simultânea com colectomia em ratos

OBJETIVO: Observar o comportamento do fator de necrose tumoral-a (TNFalfa) e da proteína C reativa (PCR) em cirurgias simultâneas de fígado e intestino. MÉTODO: Para este objetivo foi desenvolvido um modelo experimental, no qual foram operados quarenta ratos da raça Wistar, divididos em quatros grupos: grupo controle, grupo 1 com ratos submetidos à hepatectomia a 70%, grupo 2 com ratos submetidos à colectomia e grupo 3 com cirurgia simultânea de hepactetomia e colectomia. Em todos os grupos foram dosados TNFalfa e PCR uma hora após o procedimento. Os animais foram mortos em seguida. RESULTADOS: Os valores encontrados mostraram alteração nas dosagens desses elementos nos diversos grupos, sendo que no grupo 3 houve aumento significativo do TNFalfa e queda de PCR. CONCLUSÃO: Quanto mais complexo se tornou o ato cirúrgico os níveis sangüíneos de TFNalfa aumentaram e os níveis sangüíneos da PCR diminuíram significativamente.

Pharmacokinetics of tacrolimus and mycophenolic acid are altered, but recover at different times during hepatic regeneration in rats

Hepatic regeneration is very critical to the success of living donor liver transplantation, which allows a reduced size liver to grow in size to accommodate the requirements of both the donor and the recipient. The objectives of this study were to evaluate 1) the hepatic metabolism of the two immunosuppressive drugs, tacrolimus and mycophenolic acid (MPA), and 2) the pharmacokinetics of tacrolimus and mycophenolic acid at various time points after initiation of hepatic regeneration by partial hepatectomy in rats. The hepatic intrinsic clearance of tacrolimus was decreased to 70% and 51% of the control level at the 24th h and the 6th day, respectively, but returned to normal level by day 14. The total body clearance of tacrolimus was reduced transiently but recovered completely by day 18. The hepatic intrinsic clearance of MPA was decreased to 52% and 51% of that in control rats at the 24th h and the 6th day, respectively, but recovered to normal level by day 14. The total body clearance of MPA was reduced at the 24th h but recovered by day 6. The magnitude of reduction in the clearance of tacrolimus and MPA was much smaller than what was predicted from in vitro data. The elimination clearance of MPA glucuronide was also impaired during hepatic regeneration but recovered to normal level with time. In conclusion, the pharmacokinetics of tacrolimus and mycophenolic acid were altered during hepatic regeneration but recovered completely at different rates over time. Caution must be exercised in extrapolating in vitro data to in vivo conditions during hepatic regeneration.

Modulation of plasma fibrinogen levels in acute-phase response after hepatectomy

In acute-phase response, the use of amino acids is redirected to supporting the synthesis of proteins for host defence and tissue repair. Fibrinogen is one of these proteins, and its plasma levels commonly increase in acute-phase conditions. After hepatectomy, this pattern may be modified by the variable impact of postoperative liver dysfunction. Our study was performed to specifically assess and quantify this aspect. Data were collected prospectively on 82 hepatectomized patients; 62 recovered normally, 20 had major complications (most commonly sepsis). Plasma fibrinogen and a large series of complementary variables were determined preoperatively and at postoperative days 1, 3 and 7 in all patients and until recovery, or death in those with complications. Multiple regression analysis showed that postoperative changes in fibrinogen (deltaFIB, micromol/l) were simultaneously related to the number of resected liver segments (NSEG), total bilirubin (BIL, micromol/l), aspartate aminotransferase (AST, U/l, n.v. 5-45), albumin (ALB, g/l), prothrombin activity (PA, % of standard reference), age (AGE, years) and basal preoperative fibrinogen (PFIB, micromol/l): deltaFIB = -0.51(NSEG) - 0.71(Log(n)BIL) - 0.74(Log(n)AST) + 0.11(ALB) + 0.09(PA) - 0.06(AGE) - 0.55(PFIB) + 7.74 (n=362, r2=0.68, p<0.001). In addition, an early postoperative tendency for low fibrinogen was associated with the subsequent development of complications or death. Our study quantifies the impact of size of hepatectomy and dysfunction of residual liver in modulating postoperative fibrinogen level and suggests that failure of fibrinogen to increase may signal an unfavorable condition limiting up-regulation of acute-phase response and increasing liability to complications.

Effect of hyperbaric oxygenation on the regeneration of the liver after partial hepatectomy in rats

The aim of the present study was to assess the influence of hyperbaric oxygenation (HBO) on rat liver regeneration before and after partial hepatectomy. Rats were sacrificed 54 h after 15% hepatectomy, liver and body weights were measured, and serum alanine transaminase (ALT) and aspartate transaminase (AST) activity and albumin levels were determined. The lipid peroxide level, as indicated by malondialdehyde production in the remnant liver was measured, and liver sections were analyzed by light microscopy. Five groups of 10 rats in each group were studied. The preHBO and pre-hyperbaric pressure (preHB) groups were treated before partial hepatectomy with 100% O2 and 21% O2, respectively, at 202,650 pascals, daily for 3 days (45 min/day). The control group was not treated before partial hepatectomy and recovered under normal ambient conditions after the procedure. Groups postHBO and postHB were treated after partial hepatectomy with HBO and HB, respectively, three times (45 min/day). The preHBO group presented a significant increase in the initiation of the regeneration process of the liver 54 h postoperatively. The liver/body weight ratio was 0.0618 +/- 0.0084 in the preHBO compared to 0.0517 +/- 0016 g/g in the control animals (P = 0.016). In addition, the preHBO group showed significant better liver function (evaluated by the lowest serum ALT and AST activities, P = 0.002 and P = 0.008, respectively) and showed a significant decrease in serum albumin levels compared to control (P < 0.001). Liver lipid peroxide concentration was lowest in the preHBO group (P < 0.001 vs control and postHBO group) and light microscopy revealed that the composition of liver lobules in the preHBO group was the closest to normal histological features. These results suggest that HBO pretreatment was beneficial for rat liver regeneration after partial hepatectomy.

The role of transsignalling via the agonistic soluble IL-6 receptor in human diseases

The activation of cells that do not express the membrane bound interleukin-6 6 receptor (IL-6R) by IL-6 and the soluble IL-6 receptor (sIL-6R) is termed transsignalling. Transsignalling may be an pathogenetic factor in human diseases as diverse as multiple myeloma (MM), Castleman's disease, prostate carcinoma, Crohn's disease, systemic sclerosis, Still's disease, osteoporosis and cardiovascular diseases. IL-6 and sIL-6R may directly or indirectly enhance their own production on endothelial or bone marrow stromal cells. Positive feedback autocrine loops thus created in affected organs may either cause or maintain disease progression. In autoimmune or vasculitic disease, the ability of the IL-6/sIL-6R complex to inhibit apoptosis of autoreactive T-cells may be central to the development of tissue specific autoimmunity. The anti-apoptotic effect of the IL-6/sIL-6R complex may be involved in tumour genesis and resistance to chemotherapy. Only in rare cases, where counterregulation has failed, there is a notable systemic effect of IL-6/sIL-6R. Appropriate animal models are necessary to establish the pathogenetic role of the IL-6/sIL-6R complex. A specific treatment option for diseases influenced by the sIL-6R could be based on gp130-Fc, a soluble gp130 (sgp130) linked to the Fc-fragment of IgG1. gp130-Fc has shown efficacy in vivo in animal models of Crohn's disease.