In vivo altered unfolded protein response and apoptosis in livers from lipopolysaccharide-challenged cirrhotic rats.
ABSTRACT Endoplasmic reticulum (ER)-related unfolded protein response (UPR) is mediated by PKR-like ER kinase (PERK), ATF6 and IRE1. PERK phosphorylates eukaryotic translation initiation factor-2alpha (eIF2alpha) to attenuate protein synthesis, including in NF-kappaB-dependent antiapoptotic proteins. We hypothesized that an altered UPR in the liver may sensitize cirrhotic livers to LPS-induced, TNFalpha-mediated apoptosis. Thus, we examined in vivo UPR and NF-kappaB activity in livers from cirrhotic and normal LPS-challenged rats.
Livers were harvested in rats that did or did not receive LPS.
Under baseline conditions, no UPR was found in normal livers while PERK/eIF2alpha and ATF6 pathways were activated in cirrhotic livers. After LPS, in normal livers, the PERK/eIF2alpha pathway was transiently activated. ATF6 and IRE1 were activated. In cirrhotic livers, the PERK/eIF2alpha pathway remained elevated. ATF6 and IRE1 pathways were altered. LPS-induced, NF-kappaB-dependent antiapoptotic proteins increased in normal livers whereas their expression was blunted at the posttranscriptional level in cirrhotic livers.
Cirrhotic livers exhibit partial UPR activation in the basal state and full UPR, although altered, after LPS challenge. Sustained eIF2alpha phosphorylation, a hallmark of cirrhotic liver UPR, is associated with a lack of LPS-induced accumulation of NF-kappaB-dependent antiapoptotic proteins which may sensitize cirrhotic livers to LPS/TNFalpha-mediated apoptosis.
- SourceAvailable from: Vanessa Stadlbauer[Show abstract] [Hide abstract]
ABSTRACT: Bacterial infections are very common and represent one of the most important reasons of progression of liver failure, development of liver-related complications, and mortality in patients with cirrhosis. In fact, bacterial infections may be a triggering factor for the occurrence of gastrointestinal bleeding, hypervolemic hyponatremia, hepatic encephalopathy, kidney failure, and development of acute-on-chronic liver failure. Moreover, infections are a very common cause of repeated hospitalizations, impaired health-related quality of life, and increased healthcare costs in cirrhosis. Bacterial infections develop as a consequence of immune dysfunction that occurs progressively during the course of cirrhosis. In a significant proportion of patients, infections are caused by gramnegative bacteria from intestinal origin, yet grampositive bacteria are a frequent cause of infection, particularly in hospitalized patients. In recent years, infections caused by multidrug-resistant bacteria are becoming an important clinical problem in many countries. The reduction of the negative clinical impact of infections in patients with cirrhosis may be achieved by a combination of prophylactic measures, such as administration of antibiotics, to reduce the occurrence of infections in high-risk groups together with early identification and management of infection once it has developed. Investigation on the mechanisms of altered gut microflora, translocation of bacteria, and immune dysfunction may help develop more effective and safe methods of prevention compared to those that are currently available. Moreover, research on biomarkers of early infection may be useful in early diagnosis and treatment of infections. The current manuscript reports and in-depth review and a position statement on bacterial infections in cirrhosis.Journal of Hepatology 02/2014; · 9.86 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: When cells are subjected to stress by changes in their extracellular environment, unfolded proteins accumulate in the endoplasmic reticulum (ER), causing ER stress. This initiates the unfolded protein response (UPR), a signal transduction cascade aiming at restoring cellular homeostasis. The UPR and angiogenesis are involved in the pathogenesis of many diseases such as cancer, pulmonary diseases and chronic liver diseases (CLDs) such as alcoholic liver disease, non-alcoholic steatohepatitis and hepatitis B. This review summarizes the upcoming knowledge of the interaction between the UPR and angiogenesis in physiological angiogenesis and in different CLDs and other diseases. This article is protected by copyright. All rights reserved.Liver international: official journal of the International Association for the Study of the Liver 01/2014; · 3.87 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Alcohol-induced liver disease increasingly contributes to human mortality worldwide. Alcohol-induced endoplasmic reticulum (ER) stress and disruption of cellular protein homeostasis have recently been established as a significant mechanism contributing to liver diseases. The alcohol-induced ER stress occurs not only in cultured hepatocytes but also in vivo in the livers of several species including mouse, rat, minipigs, zebrafish, and humans. Identified causes for the ER stress include acetaldehyde, oxidative stress, impaired one carbon metabolism, toxic lipid species, insulin resistance, disrupted calcium homeostasis, and aberrant epigenetic modifications. Importance of each of the causes in alcohol-induced liver injury depends on doses, duration and patterns of alcohol exposure, genetic disposition, environmental factors, cross-talks with other pathogenic pathways, and stages of liver disease. The ER stress may occur more or less all the time during alcohol consumption, which interferes with hepatic protein homeostasis, proliferation, and cell cycle progression promoting development of advanced liver diseases. Emerging evidence indicates that long-term alcohol consumption and ER stress may directly be involved in hepatocellular carcinogenesis (HCC). Dissecting ER stress signaling pathways leading to tumorigenesis will uncover potential therapeutic targets for intervention and treatment of human alcoholics with liver cancer.International journal of hepatology. 01/2014; 2014:513787.