[The value of MELD in the allocation of priority for liver transplantation candidates]

Liver transplantation is the most effective treatment for many patients with chronic end-stage liver disease. The discrepancy between the number of donor organs and potential recipients causes marked pre-transplantation mortality and consequently optimal rationalization of organ allocation is essential. The Model for End-Stage Liver Disease (MELD) is an objective and easily reproducible prognostic index of mortality based on three simple analytical variables: bilirubin and serum creatinine and the prothrombin time/International Normalized Ratio (INR) of protrombine time. The implementation of MELD as an organ allocation system has reduced mortality on the waiting list without affecting post-transplantation survival. Nevertheless, this model has some limitations and consequently further investigations should be performed to improve the organ allocation policy in liver transplantation.

Angiotensin II activates I kappaB kinase phosphorylation of RelA at Ser 536 to promote myofibroblast survival and liver fibrosis

BACKGROUND & AIMS

The transcription factor nuclear factor-kappaB (NF)-kappaB promotes survival of hepatic myofibroblasts and fibrogenesis through poorly defined mechanisms. We investigated the activities of angiotensin II and I kappaB kinase (IKK) in regulation of NF-kappaB activity and the role of these proteins in liver fibrosis in rodents and humans.

METHODS

Phosphorylation of the NF-kappaB subunit RelA at serine 536 (P-Ser(536)-RelA) was detected by immunoblot and immunohistochemical analyses. P-Ser(536)-RelA function was assessed using vectors that expressed mutant forms of RelA, cell-permeable blocking peptides, and assays for RelA nuclear transport and apoptosis. Levels of P-Ser(536)-RelA were compared with degree of fibrosis in liver sections from chronically injured rats and patients with hepatitis C virus-mediated fibrosis who had been treated with the AT1 antagonist losartan.

RESULTS

Constitutive P-Ser(536)-RelA is a feature of human hepatic myofibroblasts, both in vitro and in situ in diseased livers. Autocrine angiotensin II stimulated IKK-mediated phosphorylation of RelA at Ser(536), which was required for nuclear transport and transcriptional activity of NF-kappaB. Inhibition of angiotensin II, the angiotensin II receptor type 1 (AT1), or IKK blocked Ser(536) phosphorylation and stimulated myofibroblast apoptosis. Treatment of fibrotic rodent liver with the angiotensin converting enzyme (ACE) inhibitor captopril or the IKK inhibitor sulphasalazine resulted in loss of P-Ser(536)-RelA-positive myofibroblasts and fibrosis regression. In human liver samples, increased numbers of P-Ser(536)-RelA-positive cells were associated with fibrosis that regressed following exposure to losartan.

CONCLUSIONS

An autocrine pathway that includes angiotensin II, IKK, and P-Ser(536)-RelA regulates myofibroblast survival and can be targeted to stimulate therapeutic regression of liver fibrosis.

Hepatic expression of CXC chemokines predicts portal hypertension and survival in patients with alcoholic hepatitis

BACKGROUND & AIMS

Alcoholic hepatitis (AH) is characterized by hepatocellular damage, inflammation, and fibrosis. We performed a prospective study to associate hepatic expression of the CXC subfamily of chemokines with histology findings and prognosis of patients with AH.

METHODS

Liver biopsy samples from 105 patients with AH and 5 normal liver samples (controls) were evaluated for steatosis, inflammation, fibrosis, and cholestasis. Computer-based morphometric analysis assessed the numbers of infiltrating CD3+ T cells and CD15+ cells (neutrophils); terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining was used to quantify apoptosis. Expression of CXC and CC chemokines and selected signaling components were assessed by quantitative reverse-transcription polymerase chain reaction; protein levels of interleukin (IL)-8 and Gro-alpha also were determined by immunohistochemistry. Serum levels of IL-8 and Gro-alpha were measured by enzyme-linked immunosorbent assay. The Cox regression model identified variables associated with mortality.

RESULTS

Most patients (75%) had severe AH; their 90-day mortality rate was 21.9%. In AH liver samples, expression of the CXC subfamily members IL-8, Gro-alpha, CXCL5, CXCL6, CXCL10, and platelet factor 4 was up-regulated and compared with controls. The CC chemokine CCL2, but not CCL5, also was up-regulated. Higher expression levels of IL-8, CXCL5, Gro-gamma, and CXCL6 were associated with worse prognosis. Expression of CXC components correlated with neutrophil infiltration and the severity of portal hypertension. In the multivariate analysis, IL-8 protein levels were an independent predictor of 90-day mortality. IL-8 and Gro-alpha serum levels did not correlate with prognosis.

CONCLUSIONS

Hepatic expression of CXC components correlates with prognosis of patients with AH. Reagents that target CXC chemokines might be developed as therapeutics.

Atorvastatin attenuates angiotensin II-induced inflammatory actions in the liver

Statins exert beneficial effects in chronically damaged tissues. Angiotensin II (ANG II) participates in liver fibrogenesis by inducing oxidative stress, inflammation, and transforming growth factor-beta1 (TGF-beta1) expression. We investigate whether atorvastatin modulates ANG II-induced pathogenic effects in the liver. Male Wistar rats were infused with saline or ANG II (100 ng kg(-1) min(-1)) for 4 wk through a subcutaneous osmotic pump. Rats received either vehicle or atorvastatin (5 mg kg(-1) day(-1)) by gavage. ANG II infusion resulted in infiltration of inflammatory cells (CD43 immunostaining), oxidative stress (4-hydroxynonenal), hepatic stellate cells (HSC) activation (smooth muscle alpha-actin), increased intercellular adhesion molecule (ICAM-1), and interleukin-6 hepatic gene expression (quantitative PCR). These effects were markedly blunted in rats receiving atorvastatin. The beneficial effects of atorvastatin were confirmed in an additional model of acute liver injury (carbon tetrachloride administration). We next explored whether the beneficial effects of atorvastatin on ANG II-induced actions are also reproduced at the cellular level. We studied HSC, a cell type with inflammatory and fibrogenic properties. ANG II (10(-8)M) stimulated cell proliferation, proinflammatory actions (NF-kappaB activation, ICAM-1 expression, interleukin-8 secretion) as well as expression of procollagen-alpha(1(I)) and TGF-beta1. All of these effects were reduced in the presence of atorvastatin (10(-7)M). These results indicate that atorvastatin attenuates the pathogenic events induced by ANG II in the liver both in vivo and in vitro. Therefore, statins could have beneficial effects in conditions characterized by hepatic inflammation.

A new scoring system for prognostic stratification of patients with alcoholic hepatitis

OBJECTIVES

Prognostic stratification of patients with alcoholic hepatitis (AH) may improve the clinical management and facilitate clinical trials. We aimed at developing a scoring system capable of providing prognostic stratification of patients with AH.

METHODS

Patients with biopsy-proven AH were prospectively included between 2000 and 2006. The biochemical, clinical, portal hemodynamic and histological parameters were evaluated. A Cox regression model was used for univariate and multivariate analyses. A predictive score was built using variables obtained at admission identified in the multivariate analysis. The resulting score was validated in an independent prospective cohort.

RESULTS

In total, 103 patients with biopsy-proven AH were included in the study cohort. Age, serum bilirubin, serum creatinine, and international normalized ratio (INR) independently predicted 90-day mortality. We generated the Age, serum Bilirubin, INR, and serum Creatinine (ABIC) score: (age x 0.1) + (serum bilirubin x 0.08) + (serum creatinine x 0.3) + (INR x 0.8). The area under the curve (AUC) was 0.82. Using the Kaplan-Meier analysis with the cutoff values of 6.71 and 9.0, we identified patients with low, intermediate, and high risk of death at 90 days (100%, 70%, and 25% of survival rate, respectively). Using the same cutoff values, the ABIC score also stratified patients according to their risk of death at 1 yr. These results were validated by a confirmatory cohort (N = 80).

CONCLUSIONS

The ABIC score is a new tool that allows the stratification of risk of death in patients with AH at 90 days and 1 yr. This score can help improve the management of these patients and also help to perform clinical trials.

Atomic motions in the alphabeta-merging region of 1,4-polybutadiene: a molecular dynamics simulation study

We present fully atomistic molecular dynamics simulations on 1,4-polybutadiene in a wide temperature range from 200 to 280 K, i.e., in the region where the alpha- and beta-relaxations merge and above. A big computational effort has been performed-especially for the lowest temperatures investigated-to extend the simulation runs to very long times (up to 1 mus for 200 K). The simulated sample has been carefully validated by using previous neutron scattering data on the real sample with similar microstructure. Inspecting the trajectories of the different hydrogens in real space, we have observed a heterogeneous dynamical behavior (each kind of hydrogen moves in a different way) with signatures of combined hopping and diffusive motions in the whole range investigated. The application of a previously proposed model [Colmenero et al., Europhys. Lett. 71, 262 (2005)] is successful and a characterization of the local motions and diffusion is possible. The comparison of our results to those reported in the literature provides a consistent scenario for polybutadiene dynamics and puts into a context the different experimental observations. We also discuss the impact of the hopping processes on the observation and interpretation of experimentally accessible magnitudes and the origin of the deviations from Gaussian behavior in this system.

Bradykinin attenuates hepatocellular damage and fibrosis in rats with chronic liver injury

BACKGROUND & AIMS

Recent studies have suggested that the kallikrein-kinin system regulates tissue fibrogenesis. We hypothesize that bradykinin (BK), the main effector peptide of this system, regulates hepatic fibrogenesis.

METHODS

Kallikrein-kinin system components were studied by quantitative reverse-transcription polymerase chain reaction analysis, immunohistochemistry, and Western blotting. The effect of bradykinin on liver injury was studied by infusing saline or bradykinin (1 and 100 ng/kg/min) through a subcutaneous pump into carbon tetrachloride-treated rats and mice treated with Fas-stimulating antibody. Bradykinin effects were studied in cultured hepatic stellate cells (HSCs) and hepatocytes.

RESULTS

Bradykinin receptors and kallikrein-1 were detected in both normal and fibrotic human livers and HSCs. BK receptors were up-regulated in fibrotic livers and activated HSCs. Bradykinin infusion reduced liver damage, as indicated by decreased aminotransferase serum levels and reduced histologic necroinflammatory score without inducing changes in arterial pressure. Moreover, bradykinin attenuated hepatic fibrosis, as indicated by reduced collagen accumulation, smooth muscle alpha-actin content, as well as decreased pro-collagen-alpha1(I) and transforming growth factor-beta1 gene expression. Bradykinin infusion reduced hepatocellular apoptosis induced by anti-Fas-receptor antibody. HSCs responded to bradykinin with intracellular calcium mobilization. Bradykinin reduced procollagen-alpha1(I) and transforming growth factor-beta1 gene expression and induced matrix metalloproteinase-2 activation. Finally, BK induced prosurvival and proliferative intracellular signaling in primary hepatocytes.

CONCLUSIONS

Bradykinin attenuates liver damage and fibrosis development in a rat model of chronic liver injury. Therefore, activation of the kallikrein-kinin system may be a new therapeutic approach to the management of chronic liver disease.

Segmental dynamics in miscible polymer blends: recent results and open questions

In this short review we summarize the outcome of the large amount of effort made during the past decade from both the experimental and the theoretical point of view in order to understand the effect of blending on the segmental dynamics in polymers. Each of the two families of models proposed-one based on thermally activated concentration fluctuations, the other on chain connectivity effects-account for each of the two main experimental observations: the broadening of the component response with respect to that of the homopolymer and the dynamic heterogeneity, respectively. The complementarity of these approaches, their main achievements and failures, are critically revised. We also include recent results on blends of components with very different mobilities. In the neighbourhood of the glass-transition of the slow polymer, the dynamics of the other component seem to be confined within the frozen chains. We suggest possible ingredients and new routes to be considered in order to elaborate more predictive theoretical frameworks for all these phenomena.

Positron-annihilation-lifetime response and broadband dielectric relaxation spectroscopy: diethyl phthalate

We report the results of a combined phenomenological analysis of the data from positron-annihilation-lifetime spectroscopy (PALS) and the relaxation data from broadband dielectric spectroscopy (BDS) on diethyl phthalate (DEP). The ortho-positronium (o-Ps) lifetime, tau3, as a function of temperature over a temperature range from 67 K up to 300 K is compared with the spectral features and the relaxation parameters of the BDS spectra decomposed into the primary alpha and the secondary beta processes in the temperature range from 140 K up to 380 K by using the Williams-Watts scheme. Phenomenological model-free analysis of the tau3-T plot provides the three characteristic PALS temperatures, where the two most pronounced ones at TgPALS=185 K and Tb2=245 K=1.32TgPALS are related to the glass-liquid transition and the onset of a quasiplateau region, respectively. In the case of a weaker bend effect at Tb1=210 K=1.14TgPALS, a number of new coincidences with changes in the dielectric beta process have been found. They concern the changes in width parameter of the distribution function for the beta relaxation time and the activation energy of the betaeff process, a crossover from the Arrhenius to the non-Arrhenius type of temperature dependence as well as with the onset of a short-time tail of the beta relaxation time distribution and finally, with changes in the relaxation strength of the alpha and betaeff processes. All these findings indicate a close connection of the o -Ps annihilation parameters and relaxation characteristics of BDS response for the DEP matrix.

Route to calculate the length scale for the glass transition in polymers

The occurrence of glass transition is believed to be associated to cooperative motion with a growing length scale with decreasing temperature. We provide a route to calculate the size of cooperatively rearranging regions (CRR) of glass-forming polymers combining the Adam-Gibbs theory of the glass transition with the self-concentration concept. To do so we explore the dynamics of glass-forming polymers in different environments. The material specific parameter alpha connecting the size of the CRR to the configurational entropy is obtained in this way. Thereby, the size of CRR can be precisely quantified in absolute values. This size results to be in the range 1-3nm at the glass transition temperature depending on the glass-forming polymer.

"Self-concentration" effects on the dynamics of a polychlorinated biphenyl diluted in 1,4-polybutadiene

The mobility of isolated polychlorinated biphenyl (PCB54) in 1,4-polybutadiene (PB) has been investigated by means of broadband dielectric spectroscopy. The aim was to provide new insights about the effect of the environment on the dynamics of PCB54. The authors' results indicate that PCB54 structural dynamics is neither independent of the PB matrix nor slaved to the matrix itself. The authors interpret these results as a consequence of the limited size of cooperatively rearranging regions (CRRs) involved in PCB54 structural relaxation possessing an effective concentration different from the macroscopic one. This implies a non-negligible influence of "self-concentration," already proven for the component segmental dynamics in polymer blends, also in the relaxation of binary mixtures involving low molecular weight glass formers. This allowed the evaluation of the size of CRR, which was about 1 nm for PCB54 in PB. This means that the cooperativity extends over the first shell around PCB54 molecules.

Polymer chain dynamics in a random environment: heterogeneous mobilities

We present a neutron scattering investigation on a miscible blend of two polymers with greatly different glass-transition temperatures Tg. Under such conditions, the nearly frozen high-Tg component imposes a random environment on the mobile chain. The results demand the consideration of a distribution of heterogeneous mobilities in the material and demonstrate that the larger scale dynamics of the fast component is not determined by the average local environment alone. This distribution of mobilities can be mapped quantitatively on the spectrum of local relaxation rates measured at high momentum transfers.

Hepatic expression of candidate genes in patients with alcoholic hepatitis: correlation with disease severity

BACKGROUND & AIMS

Alcoholic hepatitis (AH) is a form of acute-on-chronic liver failure for which current therapy is not fully effective. We investigated the hepatic expression of candidate genes in patients with AH to identify new targets for therapy.

METHODS

Hepatic expression of candidate genes (n = 46) was assessed by quantitative polymerase chain reaction in patients with AH (n = 23) and in normal livers (n = 6). Disease severity was assessed by the Maddrey's discriminant function and the occurrence of clinical complications. Histologic analysis included the assessment of myofibroblasts (smooth muscle alpha-actin), collagen deposition (Sirius red), and inflammatory infiltrate (CD43). Portal hypertension was assessed by hepatic venous pressure gradient. Predictive association between gene expression and disease severity was assessed by k-nearest neighbor analysis.

RESULTS

Patients with AH showed profound hepatocellular dysfunction advanced fibrosis, and severe portal hypertension. Livers with AH showed up-regulation of genes encoding extracellular matrix proteins (procollagen I), fibrogenesis mediators, inflammatory cytokines, and apoptosis regulators. Key components of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase were markedly up-regulated, whereas cytochrome p450 2E1 and angiotensinogen were down-regulated. The expression of tissue inhibitor of metalloproteinases-1, growth-related oncogene alpha, and several components of NADPH oxidase (dual oxidases 1 and 2) correlated with histologic findings and parameters indicative of disease severity.

CONCLUSIONS

Genes involved in hepatic fibrogenesis, inflammatory response, and oxidative stress are overexpressed in AH. Some candidate genes correlate with histologic findings and disease severity, suggesting that they may be potential targets for therapy.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Norepinephrine induces calcium spikes and proinflammatory actions in human hepatic stellate cells

Catecholamines participate in the pathogenesis of portal hypertension and liver fibrosis through alpha1-adrenoceptors. However, the underlying cellular and molecular mechanisms are largely unknown. Here, we investigated the effects of norepinephrine (NE) on human hepatic stellate cells (HSC), which exert vasoactive, inflammatory, and fibrogenic actions in the injured liver. Adrenoceptor expression was assessed in human HSC by RT-PCR and immunocytochemistry. Intracellular Ca2+ concentration ([Ca2+]i) was studied in fura-2-loaded cells. Cell contraction was studied by assessing wrinkle formation and myosin light chain II (MLC II) phosphorylation. Cell proliferation and collagen-alpha1(I) expression were assessed by [3H]thymidine incorporation and quantitative PCR, respectively. NF-kappaB activation was assessed by luciferase reporter gene and p65 nuclear translocation. Chemokine secretion was assessed by ELISA. Normal human livers expressed alpha(1A)-adrenoceptors, which were markedly upregulated in livers with advanced fibrosis. Activated human HSC expressed alpha(1A)-adrenoceptors. NE induced multiple rapid [Ca2+]i oscillations (Ca2+ spikes). Prazosin (alpha1-blocker) completely prevented NE-induced Ca2+ spikes, whereas propranolol (nonspecific beta-blocker) partially attenuated this effect. NE caused phosphorylation of MLC II and cell contraction. In contrast, NE did not affect cell proliferation or collagen-alpha1(I) expression. Importantly, NE stimulated the secretion of inflammatory chemokines (RANTES and interleukin-8) in a dose-dependent manner. Prazosin blocked NE-induced chemokine secretion. NE stimulated NF-kappaB activation. BAY 11-7082, a specific NF-kappaB inhibitor, blocked NE-induced chemokine secretion. We conclude that NE stimulates NF-kappaB and induces cell contraction and proinflammatory effects in human HSC. Catecholamines may participate in the pathogenesis of portal hypertension and liver fibrosis by targeting HSC.