Calcineurin inhibitor sparing with mycophenolate mofetil in liver transplantion: a systematic review of randomized controlled trials.

Liver transplant recipients are at high risk of developing acute and chronic renal failure. Moreover, introduction of the model for end-stage liver disease (MELD) score for primary allocation of liver grafts favors patients with pretransplant kidney dysfunction, which in turn have a higher risk of posttransplant renal failure. Calcineurin inhibitors (CNI) further increase the risk of renal failure and therefore sparing CNI with the use of mycophenolate mofetil (MMF) may improve renal function. MMF may either be used de novo in the immediate posttransplant period in combination with low-dose CNI (scenario 1) or patients that receive immunosuppression based on CNI may be converted to MMF in combination with minimization or elimination of CNI (scenario 2). Although many retrospective cohort studies and nonrandomized trials have implicated efficacy of this approach the evidence from randomized controlled studies has not been summarized. In the current review we report the results of a systematic review and meta-analysis of randomized controlled trials.

High predictability of a sustained virological response (87%) in chronic hepatitis C virus genotype 1 infection treatment by combined IL28B genotype analysis and γ-glutamyltransferase/alanine aminotransferase ratio: a retrospective single-center study.

BACKGROUND: Chronic hepatitis C virus genotype 1 (HCV-G1) infection is treated with pegylated interferon-α and ribavirin. Predictive factors for treatment success are even more important now as direct-acting antiviral agents are available. METHODS: Clinical and laboratory parameters were analyzed by uni- and multivariate statistical means in 264 patients with HCV-G1 infections with regard to treatment outcome. RESULTS: The overall sustained virological response (SVR) rate was 44%. Univariate analyses revealed SVRs to be associated with age, high alanine aminotransferase (ALT) and low γ-glutamyltransferase (γ-GT) serum activities, a low pretreatment γ-GT/ALT ratio, rapid virological response (RVR), and absence of steatosis. Multivariate analyses unveiled IL28B rs12979860 genotype (CC vs. CT: OR = 2.8, CI: 1.5-4.9, p = 0.001; CC vs. TT: OR = 7.1, CI: 3.1-16.7, p < 0.001), low pretreatment γ-GT/ALT ratio (OR = 2.5, CI: 1.7-3.3, p < 0.001), age (OR = 0.96, CI: 0.94-0.98, p = 0.001) and RVR (OR = 4.18, CI: 2.85-8.65, p < 0.001) to be significantly related to treatment outcome. Patients with the IL28B rs12979860 CC genotype and a low pretreatment γ-GT/ALT ratio achieved the highest rate of a SVR with the highest predictive values (OR = 26.7, 95% CI: 10-71.1, p < 0.0001). CONCLUSION: The pretreatment γ-GT/ALT ratio significantly enhances the predictability of the IL28B genotype. Employing this combination will help to identify patients who will most likely benefit from an interferon-α-based combination therapy in a nontriaged ordinary setting.

C1 esterase inhibitor gene expression in rat Kupffer cells, peritoneal macrophages and blood monocytes: modulation by interferon gamma.

Kupffer cells (KC) represent the main part of the tissue macrophages. Beside phagocytosis of particulate material, involvement of KC in immunological and inflammatory reactions has been supposed. As C1 esterase inhibitor (C1-INH) is a serine protease inhibitor involved in such processes, the aim of this work was to study C1-INH synthesis in KC and, by comparison, in peritoneal macrophages (PM) and blood monocytes (MC) of the rat. C1-INH synthesis was studied on the protein level by biosynthetic labeling, immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and on the RNA level by Northern blotting of total RNA or by in situ hybridization. KC were found to express C1-INH gene spontaneously. C1-INH synthesis represents 1.3 +/- 0.2% of total protein synthesis at day 1 of culture and the absolute amount each cell synthesis remains constant during the whole time in culture. Transcripts of C1-INH were detected both in freshly isolated and in cultured KC. In contrast, spontaneous C1-INH gene expression was not detectable in freshly isolated PM, but only in cultured PM. In MC, C1-INH was not detectable at any time, whatever. Treatment of the cells with interferon gamma increased C1-INH synthesis in KC and in PM and caused an induction of C1-INH synthesis in MC. The results suggest that constitutive C1-INH synthesis is a functional marker for mature tissue macrophages.

Pretranslational modulation of acute phase hepatic protein synthesis by murine recombinant interleukin 1 (IL-1) and purified human IL-1.

During the acute phase response to tissue injury or inflammation, the concentration of several plasma proteins change. Previous work (29-34) suggested a role for interleukin 1 (IL-1) in the acute phase response. The availability of recombinant-generated mouse IL-1 prompted a study designed to directly test the function of IL-1 and its mechanism of action on hepatic synthesis of two positive acute phase proteins (serum amyloid A [SAA] and complement factor B), and a negative acute phase reactant (albumin). Intravenous injection of purified recombinant-generated murine-IL-1 into C3H/HeJ endotoxin-resistant mice induced a dose-dependent increase in SAA-specific hepatic messenger RNA (mRNA), and an increase in SAA plasma protein concentration. In primary murine hepatocyte cultures, both the recombinant IL-1 and highly purified human IL-1 induced a dose- and time-dependent, reversible increase in expression of the SAA and factor B genes, and a decrease in albumin gene expression. This regulation is pretranslational, since the kinetics and direction of change in specific mRNA for SAA, factor B, and albumin correspond to the changes in synthesis of the respective proteins. Moreover, the effect of IL-1 was specific, since actin gene expression was unaffected, and the IL-1 response was inhibited by antibody specific for IL-1. These data provide direct evidence that a single mediator, IL-1, can effect the positive and negative changes in specific hepatic gene expression characteristic of the acute phase response.

Increased KIT signalling with up-regulation of cyclin D correlates to accelerated proliferation and shorter disease-free survival in gastrointestinal stromal tumours (GISTs) with KIT exon 11 deletions.

Gastrointestinal stromal tumours (GISTs) with deletions in KIT exon 11 are characterized by higher proliferation rates and shorter disease-free survival times, compared to GISTs with KIT exon 11 point mutations. Up-regulation of cyclin D is a crucial event for entry into the G1 phase of the cell cycle, and links mitogenic signalling to cell proliferation. Signalling from activated KIT to cyclin D is directed through the RAS/RAF/ERK, PI3K/AKT/mTOR/EIF4E, and JAK/STATs cascades. ERK and STATs initiate mRNA transcription of cyclin D, whereas EIF4E activation leads to increased translation efficiency and reduced degradation of cyclin D protein. The aim of the current study was to analyse the mRNA and protein expression as well as protein phosphorylation of central hubs of these signalling cascades in primary GISTs, to evaluate whether tumours with KIT exon 11 deletions and point mutations differently utilize these pathways. GISTs with KIT exon 11 deletions had significantly higher mitotic counts, higher proliferation rates, and shorter disease-free survival times. In line with this, they had significantly higher expression of cyclin D on the mRNA and protein level. Furthermore, there was a significantly higher amount of phosphorylated ERK1/2, and a higher protein amount of STAT3, mTOR, and EIF4E. PI3K and phosphorylated AKT were also up-regulated, but this was not significant. Ultimately, GISTs with KIT exon 11 deletions had significantly higher phosphorylation of the central negative cell-cycle regulator RB. Phosphorylation of RB is accomplished by activated cyclin D/CDK4/6 complex, and marks a central event in the release of the cell cycle. Altogether, these observations suggest increased KIT signalling with up-regulation of cyclin D as the basis for the unfavourable clinical course in GISTs with KIT exon 11 deletions.

Gastrointestinal stromal tumors: diagnostics, therapy and beyond?

Amongst the different solid tumors, gastrointestinal stromal tumors (GISTs) can be considered as orphan tumors, as overall, they are rather rare. Up-to now, they do not find mention within epidemiological tumor statistics of the Western population. However, with the combined use of clinical and laboratory diagnostic tools these mesenchymal tumors are not only discovered more often, but also have been recognized as model tumors for the therapy with tyrosine kinase inhibitors. This review tries to give an overview of the clinical presentation and of the diagnostics employed for identifying these tumors. It also summarizes the recent advances in treatment especially in intermediate and high risk cases.

Measuring the effect of a study meal on portal concentrations of glucagon-like peptide 1 (GLP-1) in non diabetic and diabetic patients with liver cirrhosis: transjugular intrahepatic portosystemic stent shunt (TIPSS) as a new method for metabolic measurements.

BACKGROUND: Diabetes in liver cirrhosis is associated with a blunted insulin response, which might be explained by an impaired release of the incretin hormone glucagon-like peptide 1 (GLP-1) into the portal circulation. AIMS: To investigate basal and stimulated portal venous and peripheral GLP-1 concentrations in non-diabetic (ND) and diabetic (D) patients with liver cirrhosis undergoing transjugular intrahepatic portosystemic stent shunt (TIPSS) implantation. PATIENTS AND METHODS: After elective TIPSS portalvenous and peripheral probes were drawn from 10 ND and 10 D patients with stable liver disease during an oral metabolic test and plasma glucose, immunoreactive GLP-1, insulin and C-peptide were measured. RESULTS: The study meal led to a significant rise in portal GLP-1 levels in ND and D. Basal and stimulated portal GLP-1 concentrations were not significantly different between ND and D. Peripheral GLP-1 did not differ significantly from portal venous levels. Insulin response in ND was more pronounced in the portal blood than in the periphery and was absent in D. CONCLUSION: TIPSS allows a direct evaluation of hormonal changes in the portal circulation during an oral metabolic tolerance test. A disturbed GLP-1 secretion does not play a role in blunting the insulin response observed in patients with hepatogenous diabetes.

Histological changes in a model of chronic heart failure induced by multiple sequential coronary microembolization in sheep.

AIM: Valuable models of chronic heart failure to perform histological studies are scarce. The authors aimed at investigating histological changes of the heart, lung, liver and kidneys in a stable and reproducible animal model of chronic heart failure in sheep. METHODS: In 8 sheep (N.=8, 77+/-2 kg) chronic heart failure was induced by multiple sequential microembolization through bolus injection of polysterol microspheres (90 microm, N=25 000) into the left main coronary artery. Microembolization (ME) was repeated up to three times in two to three week intervals until animals started to develop stable signs of heart failure. Therefore, clinical and hemodynamic parameters were measured (Troponin T, heart and respiratory rate, cardiac output) after each embolization. Clinical examination was carried out by a veterinarian. All animals were followed for 3 months after first microembolization and then euthanized for histological examination. Histological data of the heart, lung, liver and the kidneys were analyzed in hematoxylin-eosin (HE) stains (10x, 25x, 100x) at baseline (control group) and at 3 months after first ME. Additionally preparations of heart tissue were stained with Picro-Sirius-Red (PSR) for planimetric quantification. A score from 0 to 4 according to Rassler et al. (2005) was used to assess the degree of lung injury. RESULTS: All animals developed histological signs of heart failure as indicated by island-like, patchy fibrosis of the heart. Planimetric quantification (PSR stain) of the heart revealed a significant increase of the total amount of fibrosis from 8+/-2% (base) to 21+/-4% (3 months) (P<0.05), which was distributed homogeneously throughout the left ventricle (20+/-3% left ventricular [LV] anterior wall, 21+/-4% LV posterior wall, 20+/-4% septum). Histologic analysis of the lung demonstrated a moderate degree of interstitial edema and pronounced peribronchial processes of inflammation with beginning proliferation of fibrotic tissue. Liver tissue showed histological changes in terms of pericentral adiposis as sign of hypoxia in course of lacking perfusion. Signs of liver congestion could be detected histological in form of central-venous accumulation of erythrocytes and dissolution of liver tissue in proximity of the central veins. Kidney preparations illustrated loss of endothelial function and vascular occlusions, caused by microspheres, with decline of renal parenchyma particularly of the tubules. CONCLUSION: Multiple sequential intracoronary microembolization can effectively induce myocardial dysfunction with histological signs of chronic ischemic cardiomyopathy and pathological changes of lung, liver and kidney, which can directly be coursed by chronic heart failure. Thus, the present model may be suitable in experimental work on heart failure and LV assist devices, e.g. for studying the impact of mechanical unloading, mechanisms of recovery and reverse remodeling.

Characterization of gene expression profile in rat Kupffer cells stimulated with IFN-alpha or IFN-gamma.

BACKGROUND AND AIM: Kupffer cells are intrasinusoidal space located macrophages with phagocytic capacity. Interferons are cytokines with antiviral, antiproliferative and immunomodulatory activities which may influence the activity of Kupffer cells. Aim of this study was to evaluate Kupffer cell gene expression after interferon-alpha or interferon-gamma stimulation in order to investigate a link between these cytokines and macrophage activation. METHODS: Rat Kupffer cells were cultured for 24 h and divided into three groups: unstimulated; stimulated with interferon-alpha and stimulated with interferon-gamma. After 8 h stimulation total RNA was extracted and processed according to Affymetrix protocols and hybridised on R34A microarray gene set. Data analyses was performed using Microarray Analysis Suite 5.0 software. Genes showing remarkably different expression in microarray analysis were confirmed by real-time PCR. RESULTS: Nearly 4000 out of the 8800 genes represented in the array were expressed by Kupffer cells. Among these, interferon-alpha up-regulates 91 genes by over two-fold (antiviral, antigen processing and presentation, and tumour suppressor/proapoptotic genes) and down-regulates 72 genes by 50% or more. Interferon-gamma up-regulates 70 genes by over two-fold and down-regulates 78 genes by 50% or more. Most of the genes induced by interferon-alpha are also induced by interferon-gamma. Down-regulated genes include growth factors and genes involved in cell cycle/proliferation. Real-time PCR confirms the results of the array. CONCLUSION: Interferons directly target rat Kupffer cells and are involved in the regulation of a wide variety of genes. Their expression profile shed light onto molecular mechanism of Kupffer cells activation in specific pathways such as antiviral and antitumour processes.

Localization and mRNA steady-state level of cellular fibronectin in rat liver undergoing a CCl4-induced acute damage or fibrosis.

In an attempt to investigate cellular fibronectin synthesis and deposition during acute liver damage and fibrogenesis, we used the presence of the additional type III-related ED-A domain of cellular fibronectin as a characteristic for distinguishing it from the plasma form. Using site-specific antibodies, we localized cellular fibronectin deposition in the necrotic pericentral areas of acutely damaged liver tissue after a single CCl4-gavage, whereas in control liver only trace amounts of cellular fibronectin were detectable along the sinusoids. Upon several CCl4-administrations leading to liver fibrosis, cellular fibronectin deposits were accumulated in the fibrotic septa. Northern blot hybridization using a cDNA representing part of the ED-A domain revealed that in liver tissue, in response to an acute intoxication, cellular fibronectin synthesis was initiated within the first 48 h after CCl4-gavage. By in situ hybridisation transcripts for cellular fibronectin were identified in the necrotic areas of acutely damaged tissue restricted to single, pericentrally located cells, whereas no cellular fibronectin mRNA was detectable in control liver. During fibrogenesis cellular fibronectin transcripts were shown to be synthesized in the immediate vicinity of septa. We conclude that upon acute or chronic intoxication, cellular fibronectin is a member of the accumulating biomatrix and is produced locally by mesenchymal liver cells.

Fasting hyperglucagonemia in patients with transjugular intrahepatic portosystemic shunts (TIPS).

BACKGROUND: Hyperglucagonemia has been described to be associated with insulin resistance in patients with liver cirrhosis. Portosystemic shunts may be involved in the etiology of hyperglucagonemia. To test this hypothesis we investigated fasting peripheral plasma glucagon levels before and after portal decompression by transjugular intrahepatic portosystemic shunting (TIPS). METHODS: Glucagon, insulin, plasma glucose, HbA1c, and C-peptide were determined in peripheral venous samples from 21 non-diabetic (ND)- and 15 diabetic patients (D; 3 treated with insulin, 3 with sulfonylurea, 9 with diet alone) with liver cirrhosis, showing comparable clinical features (gender, age, BMI, creatinine, Child-Pugh-score, complications, and etiology of liver cirrhosis) before, 3 and 9 months after elective TIPS implantation. Insulin resistance was calculated as R (HOMA) according to the homeostasis model assessment (HOMA). RESULTS: Glucagon levels before TIPS were elevated in patients with diabetes compared to patients without diabetes (D: 145.4 +/- 52.1 pg/ml vs. ND: 97.3 +/- 49.8 pg/ml; p = 0.057). 3 and 9 months after TIPS implantation glucagon levels increased significantly in ND (188.9 +/- 80.3 pg/ml and 187.2 +/- 87.6 pg/ml) but not in D (169.6 +/- 62.4 pg/ml and 171.9 +/- 58.4 pg/ml). While plasma glucose, HbA1c, and C-peptide were significantly higher in D than in ND, they did not change significantly 3 and 9 months after TIPS implantation. Insulin was increased in D before TIPS (D: 31.6 +/- 15.9 mU/l vs. ND: 14.8 +/- 7.1 mU/l; p = 0.0001). 3 and 9 months after TIPS insulin significantly increased in ND (26.6 +/- 14.7 mU/l and 23.2 +/- 10.9 mU/l vs. 14.8 +/- 7.1 mU/l before TIPS) but not in D. In ND R (HOMA) also increased from 3.5 +/- 2 mU x mmol/l(2) to 5.7 +/- 3.3 mU x mmol/l(2) after 3 and 5.4 +/- 2.6 mU x mmol/l(2) after 9 months. BMI, liver and kidney function did not change with time. CONCLUSION: In non-diabetic cirrhotic patients TIPS implantation is followed by an increase of glucagon. However, this does not result in a worsening of glycemic control, probably because of a simultaneous increase of insulin.

The bcl, NFkappaB and p53/p21WAF1 systems are involved in spontaneous apoptosis and in the anti-apoptotic effect of TGF-beta or TNF-alpha on activated hepatic stellate cells.

Activated hepatic stellate cells (HSC) are thought to play a pivotal role in development of liver fibrosis which takes place in chronic liver diseases. Previous studies have shown that "activated" rat HSC undergo spontaneous apoptosis probably through the CD95/CD95L pathway. TGF-beta as well as TNF-alpha reduced spontaneous apoptosis and CD95L expression. The aim of this study was to investigate the possible mechanisms responsible for the spontaneous apoptosis and for the anti-apoptotic effect of TGF-beta and TNF-alpha on activated HSC. While bcl-2, bax, NFkappaB and p53 gene expression were spontaneously upregulated, bcl-xL and p21WAF1 gene expression decreased and IkappaB remained unchanged during the activation process in vitro. TGF-beta as well as TNF-alpha induced activation of NFKB and upregulated bcl-xL. The latter was inhibited by overexpression of IkappaB. By suppressing spontaneous apoptosis TGF-beta as well as TNF-alpha inhibited p53 gene expression while that of the p21WAF1 gene was increased. We conclude that TGF-beta as well as TNF-alpha may act as surviving factors for activated rat HSC not only through reduction of CD95L gene expression but also by upregulating the anti-apoptotic factors NFKB, bcl-xL and p21WAF1 and by downregulating the proapoptotic factor p53. The interaction with these factors may lead to the generation of new antifibrotic drugs.

A novel management strategy of steroid-free immunosuppression after liver transplantation: efficacy and safety of tacrolimus and mycophenolate mofetil.

BACKGROUND: Corticosteroids have been used traditionally for immunosuppression after solid organ transplantation. The variety of modern immunosuppressive agents offers the chance to replace drugs with an unfavorable risk-benefit ratio. The objective of this prospective pilot study was to investigate a novel steroid-free immunosuppressive regimen after clinical liver transplantation. METHODS: 30 adult liver graft recipients were included in an intent-to-treat analysis. Dual induction immunosuppression consisted of tacrolimus and mycophenolate mofetil. Prophylactic steroids were not given. Efficacy and safety parameters analyzed were patient and graft survival, incidence and severity of rejection, and adverse events in correlation to immunosuppressive drug levels. RESULTS: Patient and graft survival at 2 years was 86.7 and 83.9%, respectively. Acute rejection occurred in 26.2%, and was associated with subtherapeutic tacrolimus blood levels and diarrhea. All rejections were completely reversible by temporary addition of steroids. Acute renal failure was seen in 10/30 patients, and was related to high tacrolimus blood levels together with primary liver graft dysfunction. 43% of all patients never received any steroids, and 73% were on a steroid-free maintenance regimen. CONCLUSIONS: These results confirm that corticosteroids can be completely avoided from the beginning after liver transplantation. Double drug immunosuppression with tacrolimus and mycophenolate mofetil is effective and safe in terms of patient and graft survival as well as incidence and severity of rejection. In order to avoid under- or over-immunosuppression, which may be caused by impaired absorption or metabolism, close drug monitoring is advised.

Decrease of platelet-endothelial cell adhesion molecule 1-gene-expression in inflammatory cells and in endothelial cells in the rat liver following CCl(4)-administration and in vitro after treatment with TNFalpha.

UNLABELLED: Platelet-endothelial cell adhesion molecule (PECAM-1), a member of the Ig superfamily is strongly expressed at endothelial cell-cell junctions, on most leukocytes and on monocytes. PECAM-1 has been implicated as a key mediator of the transendothelial migration of leukocytes and monocytes. To further define the physiological role of PECAM-1, we studied the modulation of PECAM-1-expression in a model of liver inflammation in both mononuclear cells (MCs) and sinusoidal endothelial cells (SECs). In normal rat liver sections, PECAM-1 immunohistology indicated a sinusoidal pattern similar to the ICAM-1 staining. Both, SECs, small and large MCs isolated from control rats express PECAM-1 as demonstrated by immunocytochemistry, flow cytometry, and Northern blot analysis. Immunohistochemical studies on liver sections from CCl(4)-treated animals indicated, that in the areas of necrosis 24-48 h after a single administration of the toxin, there was an accumulation of LFA-1-, ED1- (marker for rat monocytes) and ICAM-1-positive, but ED2-(marker for tissue macrophages)-negative inflammatory cells. Most of these cells were PECAM-1-negative. In situ hybridization indicated that there is no accumulation of PECAM-1 specific transcripts after CCl(4) treatment within the pericentral region. Immunocytology, flow cytometry, and Northern blot analysis of MCs and SECs isolated at different times after the administration of CCl(4) revealed a decrease of PECAM-1 gene expression in MCs and in SECs, whereas ICAM-1 expression increased. As TNFalpha has been shown to be upregulated early after CCl(4) administration, the influence of TNFalpha on PECAM-gene-expression was analyzed. TNFalpha treatment of cultured rat SECs and of small and large MCs from normal liver decreased PECAM-1 specific transcript level in parallel to the increase of ICAM-1 transcript level. CONCLUSIONS: Early production of TNFalpha after liver injury could induce an increased ICAM-1-expression and a decreased PECAM-1 expression, which might be essential for the transmigration of inflammatory cells into the parenchyma.

Serum leptin levels in hypo- and hyperthyroidism.

Leptin, the product of the ob gene, is an important circulating signal for the regulation of body weight. In the present study the role of immunoreactive leptin (leptin-IR) was investigated in functional thyroid disease. Serum leptin-IR levels of 23 hypothyroid and 19 hyperthyroid patients were compared with 21 controls. Leptin-IR was quantified by a specific RIA. In hyperthyroid patients, leptin-IR was not different from controls. Serum leptin-IR levels were significantly increased in hypothyroid patients (21.0 +/- 2.7 micrograms/l vs controls 10.8 +/- 2.1 micrograms/l, P = 0.0044). When serum leptin of hypothyroid patients was compared with euthyroid controls of the same body mass index the difference was still significant (P = 0.0333 by paired Student's t-test). This might indicate that elevation of the serum leptin level does not merely reflect changes in body weight secondary to hypothyroidism, but might be increased to overcome the gain of body weight caused by hypothyroidism.

A synthetic glucagon-like peptide-1 analog with improved plasma stability.

Glucagon-like peptide-1 (GLP-1) is the most potent endogenous insulin-stimulating hormone. In the present study the plasma stability and biological activity of a GLP-1 analog, [Ser]GLP-1(7-36)amide, in which the second N-terminal amino acid alanine was replaced by serine, was evaluated in vitro and in vivo. Incubation of GLP-1 with human or rat plasma resulted in degradation of native GLP-1(7-36)amide to GLP-1(9-36)amide, while [Ser]GLP-1(7-36)amide was not significantly degraded by plasma enzymes. Using glucose-responsive HIT-T15 cells, [Ser]GLP-1(7-36)amide showed strong insulinotropic activity, which was inhibited by the specific GLP-1 receptor antagonist exendin-4(9-39)amide. Simultaneous i.v. injection of [Ser]GLP-1(7-36)amide and glucose in rats induced a twofold higher increase in plasma insulin levels than unmodified GLP-1(7-36)amide with glucose and a fivefold higher increase than glucose alone. [Ser]GLP-1(7-36)amide induced a 1.5-fold higher increase in plasma insulin than GLP-1(7-36)amide when given 1 h before i.v. application of glucose. The insulinotropic effect of [Ser]GLP-1(7-36)amide was suppressed by i.v. application of exendin-4(9-39)amide. The present data demonstrate that replacement of the second N-terminal amino acid alanine by serine improves the plasma stability of GLP-1(7-36)amide. The insulinotropic action in vitro and in vivo was not impaired significantly by this modification.

Immunoreactive leptin and leptin mRNA expression are increased in rat hypo- but not hyperthyroidism.

In this study, plasma leptin concentrations were measured in rats artificially rendered hyper- or hypothyroid by administration of thyroxine or TRH, by administration of methimazole, or by thyroidectomy. Compared with those in untreated controls, leptin immunoreactivity was not affected in the hyperthyroid state, but was significantly increased in hypothyroid animals. Methimazole administration for longer time periods caused a stepwise increase in plasma leptin immunoreactivity. Greatest leptin concentrations were seen after 28 days of methimazole. Seven days after withdrawal of the methimazole, leptin concentrations no longer differed from those observed in control animals. In hypothyroid animals, expression of leptin mRNA was increased in both retroperitoneal and epididymal adipose tissue, whereas no difference was seen for subcutaneous or mesenteric fat. Incubation of rat leptin with plasma of eu- or hypothyroid rats and subsequent HPLC analysis of leptin plasma peaks gave no indication of an altered hormone stability. We conclude that, in hypothyroid rats, leptin concentrations may be increased as a result of stimulated leptin synthesis in retroperitoneal and epididymal adipose tissue.

Gene regulation of heme oxygenase-1 as a therapeutic target.

Heme oxygenase (HO)-1 is the inducible isoform of the rate-limiting enzyme of heme degradation. HO regulates the cellular content of the pro-oxidant heme and produces catabolites with physiological functions. HO-1 is induced by a host of oxidative stress stimuli, and the activation of HO-1 gene expression is considered to be an adaptive cellular response to survive exposure to environmental stresses. Since overexpression of the HO-1 gene is also protective against the deleterious effects of experimental injuries, the specific induction of HO-1 by 'non-stressful' stimuli, eg. stimuli that are not associated with oxidative stress, such as adenosine 3', 5'-cyclic monophosphate or cyclic guanosine 3',5'-monophosphate, may have important clinical implications. This review summarizes recent advances in the understanding of regulatory mechanisms of HO-1 gene expression, in particular the role of various redox-dependent and redox-independent signaling pathways. Models of experimental injuries are highlighted in which specific overexpression of the HO-1 gene either by targeted gene transfer or by pharmacological modulation has been demonstrated to provide therapeutic effects.

Cellular localization of hepatic cytochrome 1B1 expression and its regulation by aromatic hydrocarbons and inflammatory cytokines.

Cytochrome P450 1B1 (CYP1B1) is an activator of several xenobiotics and is induced in the liver upon experimental exposure to aromatic hydrocarbons. Since its cellular localization and regulation are incompletely clarified, Cyp1B1 expression and inducibility by 9,10-dimethyl-1,2-benzanthracene (DMBA) and inflammatory cytokines were investigated in different rat liver cell populations in vitro and in the liver during hepatocellular injury. Expression of Cyp1B1 was studied by Northern blot analysis in hepatic stellate cells (HSCs), myofibroblasts (MFs), Kupffer cells (KCs), and hepatocytes at various time points of primary cultures and in acutely damaged rat liver (carbon tetrachloride model). Enzyme inducibility was assessed by incubation of cells with DMBA as well as, in the case of HSCs, with tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor beta1 (TGFbeta1). Cyp1B1 messengers were expressed at high levels by HSCs and MFs, whereas constitutive expression was not detectable in KCs or in hepatocytes. Cyp1B1-specific mRNA were expressed at highest levels in HSCs at an early stage of activation (2 days after plating) and were diminished upon further activation. DMBA strongly enhanced Cyp1B1 gene expression in HSCs, MFs, and in hepatocytes at day 3 of primary cultures, but not in hepatocytes at day 1, or in KCs. The inflammatory cytokine TNF-alpha enhanced the Cyp1B1 gene expression in HSCs, either when administered alone or in addition to DMBA, while TGFbeta1 did not affect Cyp1B1 expression, even after DMBA induction. We conclude that HSCs and MFs seem to be the major cellular sources of hepatic Cyp1B1 expression and that the constitutive expression of the Cyp1B1 gene and the responsiveness to DMBA stimulation differ between mesenchymal and parenchymal liver cells, indicating a cell-specific regulation of Cyp1B1 gene expression. Interestingly, TNF-alpha is a potent stimulator of the Cyp1B1 gene in HSCs and acts in concert with DMBA.