Nuclear export of phosphorylated C/EBPbeta mediates the inhibition of albumin expression by TNF-alpha

Prognostic impact of blood urea nitrogen to albumin ratio on patients with sepsis: a retrospective cohort study

To investigate the ability of the ratio of blood urea nitrogen (BUN) to serum albumin ratio (BAR) in patients with sepsis in intensive care units (ICUs) to predict the prognosis of short-and long-term death. Data are from the Marketplace for Intensive Care Medical Information IV (MIMIC-IV v2.0) database for patients with sepsis as defined by SEPSIS-3. The primary outcome was 30-day mortality and the secondary outcome was 360-day mortality. Kaplan-Meier (KM) survival curves were plotted to describe differences in BAR mortality in different subgroups and area under the curve (AUC) analysis was performed to compare the predictive value of sequential organ failure assessment (SOFA), BAR, blood urea nitrogen (BUN) and albumin. Multivariate Cox regression models and subgroup analysis were used to determine the correlation between BAR and 30-day mortality and 360-day mortality. A total of 7656 eligible patients were enrolled in the study with a median BAR of 8.0 mg/g, including 3837 in the ≤ 8.0 group and 3819 in the BAR > 8.0 group, with 30-day mortality rates of 19.1% and 38.2% (P < 0.001) and 360-day mortality rates of 31.1% and 55.6% (P < 0.001). Multivariate Cox regression models showed an increased risk of death for 30-day mortality (HR = 1.219, 95% CI 1.095-1.357; P < 0.001) and 360-day mortality (HR = 1.263, 95% CI 1.159-1.376; P < 0.001) in the high BAR group compared to the low BAR group. For the 30-day outcome, the area under the curve (AUC) was 0.661 for BAR and 0.668 for 360-day BAR. In the subgroup analysis, BAR remained an isolated risk factor for patient death. As a clinically inexpensive and readily available parameter, BAR can be a valuable forecaster of prognosis in patients with sepsis in the intensive care unit.

An Insight into Wheat Germ Oil Nutrition, Identification of Its Bioactive Constituents and Computer-Aided Multidimensional Data Analysis of Its Potential Anti-Inflammatory Effect via Molecular Connections

Wheat germ oil (WGO) is the richest source of unexplored antioxidants and anti-inflammatory compounds. In this study, we identified the constituents of WGO by gas chromatography-mass spectrometry (GC-MS). The physicochemical and pharmacokinetic behaviors were evaluated for the top 12 constituents with the common target FABP4. Three fatty acids with significant anti-inflammatory activity were evaluated for their interaction with FABP4 by molecular docking. The molecular mechanisms involved in anti-inflammatory responses were analyzed by various in-silico analytical tools and multidimensional data analysis. WGO showed anti-inflammatory activities via FABP4 interacting physically with target genes (77.84%) and by co-expressing with 8.01% genes. Primary targets for inflammatory pathways were PPARα, PPARγ, LPL, LEP, and ADIPOQ, as depicted by gene network enrichment analysis. The key pathways implicated were the metabolism of lipids, PPAR signaling, cellular response to alcohol, oxygen and nitrogen pathway, inflammatory response pathway, and regulation of the inflammatory pathway. The common transcription factors implicated were HNF1, AP2α, CEBP, FOX, STATS, MYC, Zic, etc. In this study, we found that WGO possesses anti-inflammatory potential via FABP4 binding to PPARα, PPARγ, LPL, LEP, and ADIPOQ gene expression by regulatory transcription factors HNF, AP2α, and CEPB.

Using Machine Learning to Develop and Validate an In-Hospital Mortality Prediction Model for Patients with Suspected Sepsis

Background: Early recognition of sepsis and the prediction of mortality in patients with infection are important. This multi-center, ED-based study aimed to develop and validate a 28-day mortality prediction model for patients with infection using various machine learning (ML) algorithms. Methods: Patients with acute infection requiring intravenous antibiotic treatment during the first 24 h of admission were prospectively recruited. Patient demographics, comorbidities, clinical signs and symptoms, laboratory test data, selected sepsis-related novel biomarkers, and 28-day mortality were collected and divided into training (70%) and testing (30%) datasets. Logistic regression and seven ML algorithms were used to develop the prediction models. The area under the receiver operating characteristic curve (AUROC) was used to compare different models. Results: A total of 555 patients were recruited with a full panel of biomarker tests. Among them, 18% fulfilled Sepsis-3 criteria, with a 28-day mortality rate of 8%. The wrapper algorithm selected 30 features, including disease severity scores, biochemical parameters, and conventional and few sepsis-related biomarkers. Random forest outperformed other ML models (AUROC: 0.96; 95% confidence interval: 0.93–0.98) and SOFA and early warning scores (AUROC: 0.64–0.84) in the prediction of 28-day mortality in patients with infection. Additionally, random forest remained the best-performing model, with an AUROC of 0.95 (95% CI: 0.91–0.98, p = 0.725) after removing five sepsis-related novel biomarkers. Conclusions: Our results demonstrated that ML models provide a more accurate prediction of 28-day mortality with an enhanced ability in dealing with multi-dimensional data than the logistic regression model.

Evaluation of early antibiotic use in patients with non-severe COVID-19 without bacterial infection

OBJECTIVES

The use of antibiotics was common in some countries during the early phase of the coronavirus disease 2019 (COVID-19) pandemic, but adequate evaluation remains lacking. This study aimed to evaluate the effect of early antibiotic use in patients with non-severe COVID-19 admitted without bacterial infection.

METHODS

This multi-centre retrospective cohort study included 1,373 inpatients with non-severe COVID-19 admitted without bacterial infection. Patients were divided into two groups according to their exposure to antibiotics within 48 h of admission. The outcomes were progression to severe COVID-19, length of stay >15 days and mortality rate. A mixed-effect Cox model and random effect logistic regression were used to explore the association between early antibiotic use and outcomes.

RESULTS

During the 30-day follow-up period, the proportion of patients who progressed to severe COVID-19 in the early antibiotic use group was almost 1.4 times that of the comparison group. In the mixed-effect model, the early use of antibiotics was associated with higher probability of developing severe COVID-19 and staying in hospital for >15 days. However, there was no significant association between early use of antibiotics and mortality. Analysis with propensity-score-matched cohorts displayed similar results. In subgroup analysis, patients receiving any class of antibiotic were at increased risk of adverse health outcomes. Azithromycin did not improve disease progression and length of stay in patients with COVID-19.

CONCLUSIONS

It is suggested that antibiotic use should be avoided unless absolutely necessary in patients with non-severe COVID-19, particularly in the early stages.

KPT-330 Prevents Aortic Valve Calcification via a Novel C/EBPβ Signaling Pathway

[Figure: see text].

Effects of Albumin Infusion on Serum Levels of Albumin, Proinflammatory Cytokines (TNF-α, IL-1, and IL-6), CRP, and MMP-8; Tissue Expression of EGRF, ERK1, ERK2, TGF-β, Collagen, and MMP-8; and Wound Healing in Sprague Dawley Rats

In this study, we sought to determine the roles of albumin in wound healing, which is infused both pre- and postoperatively in malnourished patients presenting with hypoalbuminemia. For the purposes of the study, we used 25 male Sprague Dawley rats of predetermined weight and age, which were initially maintained in a standard environment and fed the same diet for 7 days prior to being segregated into one of the following five groups: A, control, normal protein feed (20% casein); B, hypoalbuminemia, 25% rat albumin infusion prior to surgery; C, hypoalbuminemia, normal protein feed (20% casein); D, hypoalbuminemia, 25% rat albumin infusion after surgery; and E, hypoalbuminemia, low-protein feed (casein 2%). The animals in all five groups were subjected to four deep incisions in their dorsal muscle fascia. On days 1, 3, 5, and 7 after surgery, ELISA was used to determine serum levels of TNF-α, IL-1, IL-6, CRP, and MMP-8, whereas immunohistochemistry was used to determine the tissue expression of EGFR, ERK1, ERK2, TGF-β, collagen, and MMP-8. Significant reductions in serum levels of TNF-α, IL-1, and CRP were detected in the groups receiving albumin infusion and the high-casein diet (P < 0.05). The administration of albumin and a high-casein diet also increased the tissue expression of EGFR, ERK1, ERK2, TGF-β, and collagen and decreased that of MMP-8 relative to the hypoalbuminemia control (P < 0.05). We propose that the administration of albumin promoted NF-κB signaling which, in turn, induced the transduction and transcription of factors involved in wound healing. Albumin infusion and dietary proteins play vital roles in accelerating the wound healing process, as they can contribute to correcting the hypoalbuminemic state. These findings provide insights that will contribute to our understanding of wound healing, particularly in malnourished patients.

Serum albumin as a risk factor for death in patients with prolonged sepsis: An observational study

PURPOSE

The aim of this study was to evaluate an association between nutritional biomarkers and prognosis in septic patients.

METHODS

We retrospectively searched the association between nutritional biomarkers including serum albumin (Alb), total protein (TP), total cholesterol (T-chol), and cholinesterase (ChE), and prognosis for septic patients treated in the ICU for >7 days. We used time-dependent Cox proportional hazard regression analysis to resolve the difference of the statistical weight of each day's data for all 14 consecutive days among individual sepsis patients. The covariates were based on the minimum moving values determined from 1 day, 3 days, 7 days, and 14 days of serial data. The values of these covariates and ICU survival were considered as outcomes.

RESULTS

We included 136 septic patients. The decreases in the values of Alb, TP, T-chol, and ChE were significantly associated with the risk of death in the septic patients (p < .05). Especially, the daily changes of Alb were significantly associated with mortality during the ICU stay (p < .05).

CONCLUSIONS

We found that the changes in serial data of the nutritional markers of Alb, TP, T-chol, and ChE reflected the higher risk of death in patients with prolonged sepsis.

Both high and low plasma glutamine levels predict mortality in critically ill patients

PURPOSE

Plasma amino acids are important indicators for understanding human kinetics and amino acid dynamics. We aimed to investigate the association between the plasma glutamine levels and the mortality rates and determine whether plasma glutamine can predict the prognosis of critically ill patients.

METHODS

The clinical records of adult patients who were admitted to an ICU were retrospectively evaluated to investigate the plasma levels of amino acids, including glutamine.

RESULTS

Two hundred fourteen patients were included in this study (male, 62%; median age, 64 years; range 20-97 years). The patients' diagnoses included sepsis (45%), trauma (14%), cardiovascular disease (9%), fulminant hepatitis (9%), burns (4%), and others (19%). The mortality rates in patients with plasma glutamine <400 nmol/mL (group L; 39%, 28/71) or ≥700 nmol/mL (group H; 50%, 15/30) were significantly higher (p < 0.05 and p < 0.01, respectively) than those in patients with plasma glutamine levels of 400-700 nmol/mL (group M; 21%, 24/113). Among patients with sepsis, the mortality rates of group L (46%) and group H (67%) were significantly higher (p < 0.05 or p < 0.01, respectively) in comparison with group M (26%).

CONCLUSION

Both lower and higher plasma glutamine levels were risk factors for mortality in critically ill patients.

The Janus-Faced Role of Antioxidants in Cancer Cachexia: New Insights on the Established Concepts

Chronic inflammation and excessive loss of skeletal muscle usually occur during cancer cachexia, leading to functional impairment and delaying the cure of cancer. The release of cytokines by tumor promotes the formation of reactive oxygen species (ROS), which in turn regulate catabolic pathways involved in muscle atrophy. ROS also exert a dual role within tumor itself, as they can either promote proliferation and vascularization or induce senescence and apoptosis. Accordingly, previous studies that used antioxidants to modulate these ROS-dependent mechanisms, in cancer and cancer cachexia, have obtained contradictory results, hence the need to gather the main findings of these studies and draw global conclusions in order to stimulate more oriented research in this field. Based on the literature reviewed in this paper, it appears that antioxidant supplementation is (1) beneficial in cancer cachectic patients with antioxidant deficiencies, (2) most likely harmful in cancer patients with adequate antioxidant status (i.e., lung, gastrointestinal, head and neck, and esophageal), and (3) not recommended when undergoing radiotherapy. At the moment, measuring the blood levels of antioxidants may help to identify patients with systemic deficiencies. This approach is simple to realize but could not be a gold standard method for cachexia, as it does not necessarily reflect the redox state in other organs, like muscle.

F-BOX proteins in cancer cachexia and muscle wasting: Emerging regulators and therapeutic opportunities

Cancer cachexia is a debilitating metabolic syndrome accounting for fatigue, an impairment of normal activities, loss of muscle mass associated with body weight loss eventually leading to death in majority of patients with advanced disease. Cachexia patients undergoing skeletal muscle atrophy show consistent activation of the SCF ubiquitin ligase (F-BOX) family member Atrogin-1 (also known as MAFBx/FBXO32) alongside the activation of the muscle ring finger protein1 (MuRF1). Other lesser known F-BOX family members are also emerging as key players supporting muscle wasting pathways. Recent work highlights a spectrum of different cancer signaling mechanisms impacting F-BOX family members that feed forward muscle atrophy related genes during cachexia. These novel players provide unique opportunities to block cachexia induced skeletal muscle atrophy by therapeutically targeting the SCF protein ligases. Conversely, strategies that induce the production of proteins may be helpful to counter the effects of these F-BOX proteins. Through this review, we bring forward some novel targets that promote atrogin-1 signaling in cachexia and muscle wasting and highlight newer therapeutic opportunities that can help in the better management of patients with this devastating and fatal disorder.

C/EBPβ and C/EBPδ transcription factors: Basic biology and roles in the CNS

CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ are transcription factors of the basic-leucine zipper class which share phylogenetic, structural and functional features. In this review we first describe in depth their basic molecular biology which includes fascinating aspects such as the regulated use of alternative initiation codons in the C/EBPβ mRNA. The physical interactions with multiple transcription factors which greatly opens the number of potentially regulated genes or the presence of at least five different types of post-translational modifications are also remarkable molecular mechanisms that modulate C/EBPβ and C/EBPδ function. In the second part, we review the present knowledge on the localization, expression changes and physiological roles of C/EBPβ and C/EBPδ in neurons, astrocytes and microglia. We conclude that C/EBPβ and C/EBPδ share two unique features related to their role in the CNS: whereas in neurons they participate in memory formation and synaptic plasticity, in glial cells they regulate the pro-inflammatory program. Because of their role in neuroinflammation, C/EBPβ and C/EBPδ in microglia are potential targets for treatment of neurodegenerative disorders. Any strategy to reduce C/EBPβ and C/EBPδ activity in neuroinflammation needs to take into account its potential side-effects in neurons. Therefore, cell-specific treatments will be required for the successful application of this strategy.

Polyunsaturated fatty acids augment tumoricidal action of 5-fluorouracil on gastric cancer cells by their action on vascular endothelial growth factor, tumor necrosis factor-α and lipid metabolism related factors

INTRODUCTION

Gastric cancer is the second most common cause of cancer-related mortality worldwide. 5-fluorouracil (5-FU) is a commonly used anti-cancer drug. Various polyunsaturated fatty acids (PUFAs) are known to have tumoricidal action both in vitro and in vivo. Though PUFAs are known to augment the cytotoxic action of anti-cancer drugs, the exact mechanism is not clear.

MATERIAL AND METHODS

The human gastric cancer cell line MGC (undifferentiated) and human gastric cancer cell line SGC (semi-differentiated) were either 5-FU alone or a combination of 5-FU + PUFAs and their proliferation, and ability to secrete tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) and lipid metabolism-related factors lipoprotein lipase (LPL), peroxisome proliferator-activated-γ (PPAR-γ), and CCAAT enhancer-binding protein (C/EBP) were investigated and analyzed.

RESULTS

It was noted that combined treatment of 5-FU + PUFAs on gastric carcinoma (MGC and SGC) cells produced a significant growth inhibitory action compared with either agent alone by inhibiting the production of TNF-α and VEGF and a simultaneous increase in the expression of LPL, PPAR-γ, and C/EBP.

CONCLUSIONS

Based on the results of the present study, it is concluded that PUFAs enhance the tumoricidal action of the anti-cancer drug 5-FU by acting on anti-angiogenic factors and enzymes involved in lipid metabolism.

Cancer cachexia update in head and neck cancer: Pathophysiology and treatment

The pathophysiology of cancer cachexia remains complex. A comprehensive literature search was performed up to April 2013 using PubMed, the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, and the Google search engine. In this review, we focus on the different mediators of impaired anabolism and upregulated catabolism that alter the skeletal muscle homeostasis resulting in the wasting of cancer cachexia. We present recent evidence of targeted treatment modalities from clinical trials along with their potential mechanisms of action. We also report on the most current evidence from randomized clinical trials using multimodal treatments in patients with cancer cachexia, but also the evidence from head and neck cancer-specific trials. A more complete understanding of the pathophysiology of the syndrome may lead to more effective targeted therapies and improved outcomes for patients.

Pancreatic cancer-induced cachexia is Jak2-dependent in mice

Cancer cachexia syndrome is observed in 80% of patients with advanced-stage cancer, and it is one of the most frequent causes of death. Severe wasting accounts for more than 80% in patients with advanced pancreatic cancer. Here we wanted to define, by using an microarray approach and the Pdx1-cre;LSL-Kras(G12D) ;INK4a/arf(fl/fl) mice model, the pathways involved in muscle, liver, and white adipose tissue wasting. These mice, which develop systematically pancreatic cancer, successfully reproduced many human symptoms afflicted with this disease, and particularly cachexia. Using the profiling analysis of pancreatic cancer-dependent cachectic tissues we found that Jak2/Stat3 pathways, p53 and NFkB results activated. Thus, our interest was focused on the Jak2 pathways because it is pharmacologically targetable with low toxicity and FDA approved drugs are available. Therefore, Pdx1-cre;LSL-Kras(G12D) ;INK4a/arf(fl/fl) mice were treated with the Jak2 inhibitor AG490 compound daily starting at 7 weeks old and for a period of 3 weeks and animals were sacrificed at 10 weeks old. Body weight for control mice was 27.84 ± 2.14 g, for untreated Pdx1-cre;LSL-Kras(G12D) ;INK4a/arf(fl/fl) was 14.97 ± 1.99 g, whereas in animals treated with the AG490 compound the weight loss was significantly less to 24.53 ± 2.04 g. Treatment with AG490 compound was efficient since phosphorylation of Jak2 and circulating interleukin-6 (IL6) levels were significantly reduced in cachectic tissues and in mice respectively. In conclusion, we found that Jak2/Stat3-dependent intracellular pathway plays an essential role since its pharmacological inhibition strongly attenuates cachexia progression in a lethal transgenic pancreatic cancer model.

Transcription factor C/EBP-β mediates downregulation of dipeptidyl-peptidase III expression by interleukin-6 in human glioblastoma cells

Dipeptidyl-peptidase III (DPP III) is a cytosolic metallo-aminopeptidase implicated in various physiological and pathological processes. A previous study from our laboratory indicated an elevated expression of DPP III in glioblastoma (U87MG) cells. In the present study we investigated the role of interleukin-6 (IL-6), a pleiotropic cytokine produced by glial tumors, in the regulation of DPP III expression. Immunohistochemistry, western blotting and quantitative RT-PCR were used for quantitation of DPP III and IL-6 in human glioblastoma cells and tumors. Cell transfections and DPP III promoter reporter assays were performed to study the transcriptional regulation of DPP III by IL-6. Promoter deletion analysis, site directed mutagenesis, chromatin immunoprecipitation assays and small interfering RNA (siRNA) technology was employed to elucidate the molecular mechanism of IL-6 mediated regulation of DPP III expression in glioblastoma cells. Our results for the first time demonstrate a negative correlation (r = 0.632, P = 0.01) between DPP III and IL-6 in both human tumors and cultured glioblastoma cells. Treatment of U87MG cells with IL-6 significantly decreased DPP III expression with a concomitant increase in the levels of transcription factor CCAAT/enhancer binding protein beta (C/EBP-β). Deletion/mutagenesis of C/EBP-β binding motif of DPP III promoter significantly increased its activity and abolished its responsiveness to IL-6. This effect could also be mimicked by C/EBP-β siRNA. In conclusion our study for the first time demonstrates C/EBP-β mediated transcriptional downregulation of DPP III by IL-6. Our results demonstrating a negative correlation between IL-6 and DPP III taken together with the previously reported prognostic significance of this cytokine in glioblastoma suggests that DPP III may prove useful as a prognostic marker.

CCAAT-enhancer binding protein-β expression and elevation in Alzheimer's disease and microglial cell cultures

CCAAT-enhancer binding proteins are transcription factors that help to regulate a wide range of inflammatory mediators, as well as several key elements of energy metabolism. Because C/EBPs are expressed by rodent astrocytes and microglia, and because they are induced by pro-inflammatory cytokines that are chronically upregulated in the Alzheimer’s disease (AD) cortex, we have investigated whether C/EBPs are expressed and upregulated in the AD cortex. Here, we demonstrate for the first time that C/EBPβ can be detected by Western blots in AD and nondemented elderly (ND) cortex, and that it is significantly increased in AD cortical samples. In situ, C/EBPβ localizes immunohistochemically to microglia. In microglia cultured from rapid autopsies of elderly patient’s brains and in the BV-2 murine microglia cell line, we have shown that C/EBPβ can be upregulated by C/EBP-inducing cytokines or lipopolysaccharide and exhibits nuclear translocation possibly indicating functional activity. Given the known co-regulatory role of C/EBPs in pivotal inflammatory mechanisms, many of which are present in AD, we propose that upregulation of C/EBPs in the AD brain could be an important orchestrator of pathogenic changes.

The transcription factor CCAAT enhancer-binding protein β protects rat cerebellar granule neurons from apoptosis through its transcription-activating isoforms

CCAAT enhancer-binding protein β is a transcription factor that is involved in many brain processes, although its role in neuronal survival/death remains unclear. By using primary cultures of rat cerebellar granule neurons, we have shown here that CCAAT enhancer-binding protein β is present as all of its isoforms: the transcriptional activators liver activator proteins 1 and 2, and the transcriptional inhibitor liver inhibitory protein. We have also shown that liver activator protein 1 undergoes post-translational modifications, such as phosphorylation and sumoylation. These isoforms have different subcellular localizations, liver activator protein 2 being found in the cytosolic fraction only, liver inhibitory protein in the nucleus only, and liver activator protein 1 in both fractions. Through neuronal apoptosis induction by shifting mature cerebellar granule neurons to low-potassium medium, we have demonstrated that nuclear liver activator protein 1 expression decreases and its phosphorylation disappears, whereas liver inhibitory protein levels increase in the nuclear fraction, suggesting a pro-survival role for liver activator protein transcriptional activation and a pro-apoptotic role for liver inhibitory protein transcriptional inhibition. To confirm this, we transfected cerebellar granule neurons with plasmids expressing liver activator protein 1, liver activator protein 2, or liver inhibitory protein respectively, and observed that both liver activator proteins, which increase CCAAT-dependent transcription, but not liver inhibitory protein, counteracted apoptosis, thus demonstrating the pro-survival role of liver activator proteins. These data significantly improve our current understanding of the role of CCAAT enhancer-binding protein β in neuronal survival/apoptosis.

Tumor necrosis factor-α promotes bile ductular transdifferentiation of mature rat hepatocytes in vitro

We previously showed that mature hepatocytes could transdifferentiate into bile ductular cells when placed in a collagen-rich microenvironment. To explore the mechanism of transdifferentiation, we examined whether inflammatory cytokines affected the phenotype of hepatocytes in a three-dimensional culture system. Spheroidal aggregates of rat hepatocytes were embedded within a type I collagen gel matrix and cultured in the presence of various cytokines. In the control, hepatocytes gradually lost expression of albumin, tyrosine aminotransferase, and hepatocyte nuclear factor (HNF)-4α, while aberrantly expressed bile ductular markers, including cytokeratin 19 (CK 19) and spermatogenic immunoglobulin superfamily (SgIGSF). Among the cytokines examined, tumor necrosis factor (TNF)-α inhibited expression of albumin and HNF-4α, both at mRNA and protein levels. After culturing for 2 weeks with TNF-α, hepatocytic spheroids were transformed into extensively branching tubular structures composed of CK 19- and SgIGSF-positive small cuboidal cells. These cells responded to secretin with an increase in secretion and expressed functional bile duct markers. TNF-α also induced the phosphorylation of Jun N-terminal kinase (JNK) and c-Jun, and the morphogenesis was inhibited by SP600125, a specific JNK inhibitor. Furthermore, in chronic rat liver injury induced by CCl(4) , ductular reaction in the centrilobular area demonstrated strong nuclear staining of phosphorylated c-Jun. Our results demonstrate that TNF-α promotes the ductular transdifferentiation of hepatocytes and suggest a role of TNF-α in the pathogenesis of ductular reaction.

TNF stimulates nuclear export and secretion of IL-15 by acting on CRM1 and ARF6

Interleukin (IL)-15 is a ubiquitously expressed cytokine that in the basal state is mainly localized intracellularly, including the nucleus. Unexpectedly, tumor necrosis factor-α (TNF) time-dependently induced nuclear export of IL-15Rα and IL15. This process was inhibited by leptomycine B (LMB), a specific inhibitor of nuclear export receptor chromosomal region maintenance 1 (CRM1). In the presence of TNF, LMB co-treatment led to accumulation of both IL-15Rα and IL-15 in the nucleus of HeLa cells, suggesting that CRM1 facilitates nuclear export and that TNF enhances CRM1 activity. Once in the cytoplasm, IL-15 showed partial co-localization with late endosomes but very little with other organelles tested 4 h after TNF treatment. IL-15Rα showed co-localization with both early and late endosomes, and to a lesser extent with endoplasmic reticulum and Golgi. This indicates different kinetics and possibly different trafficking routes of IL-15 from its specific receptor. The TNF-induced secretion of IL-15 was attenuated by pretreatment of cells by brefeldin A that inhibits ER-to-Golgi transport, or by use of domain negative ADP-ribosylation factor 6 (ARF6) that interferes with exocytotic sorting. We conclude that TNF abolishes nuclear localization of IL-15 and IL-15Rα by acting on CRM1, and it facilitates exocytosis of IL-15 with the involvement of ARF6.

Differential expression of candidate virus receptors in human T lymphocytes prone or resistant to infection with patient-derived hepatitis C virus

Accumulated evidence implies that hepatitis C virus (HCV) infects not only the liver but also the immune system. A lymphocyte-specific CD5 molecule was recently identified as essential for infection of T cells with native, patient-derived HCV. To assess whether the proposed hepatocyte receptors may also contribute to HCV lymphotropism, expression of scavenger receptor-class B type 1 (SR-B1), claudin-1 (CLDN-1), claudin-6 (CLDN-6), occludin (OCLN), CD5 and CD81 was examined by real-time RT-PCR and the respective proteins quantified by immunoblotting in HCV-prone and resistant T cell lines, peripheral blood mononuclear cells (PBMC), primary T cells and their subsets, and compared to hepatoma Huh7.5 and HepG2 cells. SR-B1 protein was found in T and hepatoma cell lines but not in PBMC or primary T lymphocytes, CLDN-1 in HCV-resistant PM1 T cell line and hepatoma cells only, while CLDN-6 equally in the cells investigated. OCLN protein occurred in HCV-susceptible Molt4 and Jurkat T cells and its traces in primary T cells, but not in PBMC. CD5 was displayed by HCV-prone T cell lines, primary T cells and PBMC, but not by non-susceptible T and hepatoma cell lines, while CD81 in all cell types except HepG2. Knocking-down OCLN in virus-prone T cell line inhibited HCV infection, while de novo infection downregulated OCLN and CD81, and upregulated CD5 without modifying SR-B1 expression. Overall, while no association between SR-B1, CLDN-1 or CLDN-6 and the susceptibility to HCV was found, CD5 and CD81 expression coincided with virus lymphotropism and that of OCLN with permissiveness of T cell lines but unlikely primary T cells. This study narrowed the range of factors potentially utilized by HCV to infect T lymphocytes amongst those uncovered using laboratory HCV and Huh7.5 cells. Together with the demonstrated role for CD5 in HCV lymphotropism, the findings indicate that virus utilizes different molecules to enter hepatocytes and lymphocytes.

The emerging role of C/EBPs in glucocorticoid signaling: lessons from the lung

Glucocorticoids (GCs) have been successfully used in the treatment of inflammatory diseases for decades. However, there is a relative GC resistance in several inflammatory lung disorders, such as chronic obstructive pulmonary disease (COPD), but still the mechanism(s) behind this unresponsiveness remains unknown. Interaction between transcription factors and the GC receptor contribute to GC effects but may also provide mechanisms explaining steroid resistance. CCAAT/enhancer-binding protein (C/EBP) transcription factors are important regulators of pulmonary gene expression and have been implicated in inflammatory lung diseases such as asthma, pulmonary fibrosis, cystic fibrosis, sarcoidosis, and COPD. In addition, several studies have indicated a role for C/EBPs in mediating GC effects. In this review, we discuss the different mechanisms of GC action as well as the function of the lung-enriched members of the C/EBP transcription factor family. We also summarize the current knowledge of the role of C/EBP transcription factors in mediating the effects of GCs, with emphasis on pulmonary effects, and their potential role in mediating GC resistance.

Phosphorylation prevents C/EBPβ from the calpain-dependent degradation

CCAAT/enhancer-binding protein (C/EBP) β plays an important role in proliferation and differentiation of 3T3-L1 preadipocytes. C/EBPβ is sequentially phosphorylated during the 3T3-L1 adipocyte differentiation program, first by MAPK/Cyclin A/cdk2 on Thr(188) and subsequently by GSK3β on Ser(184) or Thr(179). Dual phosphorylation is critical for the gain of DNA binding activity of C/EBPβ. In this manuscript, we found that phosphorylation also contributed to the stability of C/EBPβ. Both ex vivo and in vitro experiments showed that phosphorylation by MAPK/Cyclin A/cdk2 and GSK3β protected C/EBPβ from μ-calpain-mediated proteolysis, while phosphorylation on Thr(188) by MAPK/Cyclin A/cdk2 contributed more to the stabilization of C/EBPβ, Further studies indicated that phosphorylation mimic C/EBPβ was insensitive to both calpain accelerator and calpain inhibitor. Thus, phosphorylation might contribute to the stability as well as the gain of DNA binding activity of C/EBPβ.

Cyclooxygenase inhibitors protect D-galactosamine/lipopolysaccharide induced acute hepatic injury in experimental mice model

We investigated the protective effects of two non-steroid anti-inflammatory drugs, indomethacin (COX-1 and COX-2 inhibitors) and nimesulide (specific COX-2 inhibitor) on the hepatic injury induced by lipopolysaccharide in d-galactosamine sensitized (Gal/LPS) mice. ICR male mice were injected with a single dose of Gal/LPS with or without pre-treatment of 3mg/kg indomethacin or 30 mg/kg nimesulide (single i.p. injection). Sixteen hours later, blood and liver tissues of mice were collected for histological, molecular, and biochemical analyses. Our results showed marked reduction of hepatic necrosis, serum ALT, and tissue TBARS levels in both indomethacin- and nimesulide-pre-treated mice when compared with Gal/LPS-treated mice. Western blot and RT-PCR analysis showed decreased levels of iNOS mRNA, iNOS protein, and nitrotyrosine formation in both COX inhibitor pre-treated groups when compared with Gal/LPS-treated group. There was an inverse relationship between COX-1 and COX-2 expressions, as well as between COX-2 and C/EBP-α expressions in COX inhibitors groups, Gal/LPS and control groups. COX inhibitors reduced the expression of TNF-α mRNA and the activity of NF-κB which were elevated by Gal/LPS treatment. We conclude that COX inhibitors protected the liver from Gal/LPS-induced hepatotoxicity. COX inhibitors could be considered as potential agents in the prevention of acute liver failure and sepsis.

C/EBPβ-Thr217 phosphorylation signaling contributes to the development of lung injury and fibrosis in mice

Background

Although C/EBPβ^ko mice are refractory to Bleomycin-induced lung fibrosis the molecular mechanisms remain unknown. Here we show that blocking the ribosomal S-6 kinase (RSK) phosphorylation of the CCAAT/Enhancer Binding Protein (C/EBP)-β on Thr217 (a RSK phosphoacceptor) with either a single point mutation (Ala217), dominant negative transgene or a blocking peptide containing the mutated phosphoacceptor ameliorates the progression of lung injury and fibrosis induced by Bleomycin in mice.

Methodology/Principal Findings

Mice expressing the non-phosphorylatable C/EBPβ-Ala217 transgene had a marked reduction in lung injury on day-13 after Bleomycin exposure, compared to C/EBPβ^wt mice, judging by the decrease of CD68⁺ activated monocytes/macrophages, bone marrow-derived CD45⁺ cells and lung cytokines as well as by the normal surfactant protein-C expression by lung pneumocytes. On day-21 after Bleomycin treatment, C/EBPβ^wt mice but not mice expressing the dominant negative C/EBPβ-Ala217 transgene developed severe lung fibrosis as determined by quantitative collagen assays. All mice were of identical genetic background and back-crossed to the parental wild-type inbreed FVB mice for at least ten generations. Treatment of C/EBPβ^wt mice with a cell permeant, C/EBPβ peptide that inhibits phosphorylation of C/EBPβ on Thr217 (40 µg instilled intracheally on day-2 and day-6 after the single Bleomycin dose) also blocked the progression of lung injury and fibrosis induced by Bleomycin. Phosphorylation of human C/EBPβ on Thr266 (human homologue phosphoacceptor) was induced in collagen-activated human lung fibroblasts in culture as well as in activated lung fibroblasts in situ in lungs of patients with severe lung fibrosis but not in control lungs, suggesting that this signaling pathway may be also relevant in human lung injury and fibrosis.

Conclusions/Significance

These data suggest that the RSK-C/EBPβ phosphorylation pathway may contribute to the development of lung injury and fibrosis.

Paraneoplastic syndrome in haemophagocytic histiocytic sarcoma in a dog

A case of metastatic splenic haemophagocytic histiocytic sarcoma (HHS) in a 6-year-old neutered male flat-coated retriever is described. The main clinical findings were hypoalbuminaemia and regenerative anaemia. The diagnosis was based on histological features and expression of CD11d by the neoplastic cells. Tumour cells were shown to produce interleukin (IL)-6, to phagocytose erythrocytes and to take up albumin, as demonstrated by immunohistochemistry and ultrastructural examination. Quantitative polymerase chain reaction identified increased IL-6 gene expression in affected organs. These findings suggest that neoplastic cells are responsible for the clinical features of HHS, by removing erythrocytes and albumin from the blood and releasing cytokines, such as IL-6.

Role for tumor necrosis factor-α in JC virus reactivation and progressive multifocal leukoencephalopathy

JCV causes the CNS demyelinating disease progressive multifocal leukoencephalopathy (PML). After primary infection, JCV persists in a latent state, where viral protein expression and replication are not detectable. NF-κB and C/EBPβ regulate the JCV promoter via a control element, κB, suggesting proinflammatory cytokines may reactivate JCV to cause PML, e.g., in HIV-1/AIDS. Since HIV-1 induces cytokines in brain, including TNF-α, we examined a role for TNF-α in JCV regulation. TNF-α stimulated both early and late JCV transcription. Further, the κB element conferred TNF-α response to a heterologous promoter. Immunohistochemistry of HIV+/PML revealed robust labeling for TNF-α and TNFR-1. These data suggest TNF-α stimulation of κB may contribute to JCV reactivation in HIV+/PML.

Molecular symbiosis of CHOP and C/EBP beta isoform LIP contributes to endoplasmic reticulum stress-induced apoptosis

Induction of the transcription factor CHOP (CCAAT-binding homologous protein; GADD 153) is a critical cellular response for the transcriptional control of endoplasmic reticulum (ER) stress-induced apoptosis. Upon nuclear translocation, CHOP upregulates the transcription of proapoptotic factors and downregulates antiapoptotic genes. Transcriptional activation by CHOP involves heterodimerization with other members of the basic leucine zipper transcription factor (bZIP) family. We show that the bZIP protein C/EBP beta isoform LIP is required for nuclear translocation of CHOP during ER stress. In early ER stress, LIP undergoes proteasomal degradation in the cytoplasmic compartment. During later ER stress, LIP binds CHOP in both cytoplasmic and nuclear compartments and contributes to its nuclear import. By using CHOP-deficient cells and transfections of LIP-expressing vectors in C/EBP beta(-/-) mouse embryonic fibroblasts (MEFs), we show that the LIP-CHOP interaction has a stabilizing role for LIP. At the same time, CHOP uses LIP as a vehicle for nuclear import. LIP-expressing C/EBP beta(-/-) MEFs showed enhanced ER stress-induced apoptosis compared to C/EBP beta-null cells, a finding in agreement with the decreased levels of Bcl-2, a known transcriptional control target of CHOP. In view of the positive effect of CHOP-LIP interaction in mediating their proapoptotic functions, we propose this functional cooperativity as molecular symbiosis between proteins.

Nucleolar retention of a translational C/EBPalpha isoform stimulates rDNA transcription and cell size

The messenger RNA of the intronless CEBPA gene is translated into distinct protein isoforms through the usage of consecutive translation initiation sites. These translational isoforms have distinct functions in the regulation of differentiation and proliferation due to the presence of different N-terminal sequences. Here, we describe the function of an N-terminally extended protein isoform of CCAAT enhancer-binding protein α (C/EBPα) that is translated from an alternative non-AUG initiation codon. We show that a basic amino-acid motif within its N-terminus is required for nucleolar retention and for interaction with nucleophosmin (NPM). In the nucleoli, extended-C/EBPα occupies the ribosomal DNA (rDNA) promoter and associates with the Pol I-specific factors upstream-binding factor 1 (UBF-1) and SL1 to stimulate rRNA synthesis. Furthermore, during differentiation of HL-60 cells, endogenous expression of extended-C/EBPα is lost concomitantly with nucleolar C/EBPα immunostaining probably reflecting the reduced requirement for ribosome biogenesis in differentiated cells. Finally, overexpression of extended-C/EBPα induces an increase in cell size. Altogether, our results suggest that control of rRNA synthesis is a novel function of C/EBPα adding to its role as key regulator of cell growth and proliferation.

Modulation of JC virus transcription by C/EBPbeta

The polyomavirus JC (JCV) causes the demyelinating disease progressive multifocal leukoencephalopathy (PML). Infection by JCV is very common in childhood after which the virus enters a latent state, which is poorly understood. Under conditions of severe immunosuppression, especially AIDS, JCV may reactivate to cause PML. Expression of JC viral proteins is regulated by the JCV non-coding control region (NCCR), which contains an NF-kappaB binding site previously shown to activate transcription. We now report that C/EBPbeta inhibits basal and NF-kappaB-stimulated JCV transcription via the same site. Gel shift analysis showed C/EBPbeta bound to this region in vitro and ChIP assays confirmed this binding in vivo. Further, a ternary complex of NF-kappaB/p65, C/EBPbeta-LIP and JCV DNA could be detected in co-immunoprecipitation experiments. Mutagenesis analysis of the JCV NCCR indicated p65 and C/EBPbeta-LIP bound to adjacent but distinct sites and that both sites regulate basal and p65-stimulated transcription. Thus C/EBPbeta negatively regulates JCV, which together with NF-kappaB activation, may control the balance between JCV latency and activation leading to PML. This balance may be regulated by proinflammatory cytokines in the brain.

The importance of being flexible: the case of basic region leucine zipper transcriptional regulators

Large volumes of protein sequence and structure data acquired by proteomic studies led to the development of computational bioinformatic techniques that made possible the functional annotation and structural characterization of proteins based on their primary structure. It has become evident from genome-wide analyses that many proteins in eukaryotic cells are either completely disordered or contain long unstructured regions that are crucial for their biological functions. The content of disorder increases with evolution indicating a possibly important role of disorder in the regulation of cellular systems. Transcription factors are no exception and several proteins of this class have recently been characterized as premolten/molten globules. Yet, mammalian cells rely on these proteins to control expression of their 30,000 or so genes. Basic region:leucine zipper (bZIP) DNA-binding proteins constitute a major class of eukaryotic transcriptional regulators. This review discusses how conformational flexibility "built" into the amino acid sequence allows bZIP proteins to interact with a large number of diverse molecular partners and to accomplish their manifold cellular tasks in a strictly regulated and coordinated manner.

Decreased Jun-D and myogenin expression in muscle wasting of human cachexia

Muscle wasting is a critical feature of patients afflicted by acquired immune deficiency syndrome (AIDS), cancer, or chronic inflammatory diseases. In a mouse model of muscle wasting, TNF-alpha induces oxidative stress and nitric oxide synthase-2 (NOS2) and decreases myogenin, Jun-D, and creatinine kinase muscle isoform (CKM) expression. Here, we studied 12 patients with muscle wasting due to cancer (N = 10) or AIDS (N = 2) and 4 control subjects. We show that in skeletal muscle of cachectic patients there is 1) increased expression and activity of the TNF-alpha signaling, including TNF-alpha mRNA, activation of TNFR1, and TNF-alpha-associated to TNFR1; 2) increased oxidative stress, as determined by the presence of malondialdehyde-lysine adducts; 3) increased NOS2 mRNA and protein; 4) decreased expression of Jun-D, myogenin, myosin, and CKM mRNA and protein; 5) impaired CKM-E box binding activities, associated with decreased Jun-D/myogenin activities; and 6) oxidative modification and ubiquitination of Jun-D. These studies show that these molecular pathways are modulated in association with muscle wasting in patients with cancer or AIDS, and whether or not they cause muscle wasting remains to be determined.

Severe hepatocellular injury with apoptosis induced by a hepatitis C polymerase inhibitor

GOALS

To describe the mechanisms of severe hepatocellular injury with apoptosis in 2 patients receiving hepatitis C virus (HCV)-796.

BACKGROUND

HCV-796 is a hepatitis C polymerase inhibitor approved by the US Food and Drug Administration for a phase 2 study of the treatment of hepatitis C in combination with PEG-Interferon and ribavirin.

RESULTS

The injury occurred after more than 12 weeks of treatment, with a >20-fold increase in serum alanine aminotransferase and aspartate aminotransferase, and a marked increase in total (and direct) bilirubin in the absence of cholestasis. There was no evidence of autoimmune or viral hepatitis. Involvement of the mitochondrial apoptotic pathway was demonstrated by (1) release of cytochrome C into the cytosol; (2) association of cytochrome C with apoptotic protease activating factor-1 in the cytosol; (3) activation of initiator caspase 9; (4) activation of effector caspase 3; (5) increased serum caspase-3 cleaved cytokeratin-18 peptide; (6) nuclear fragmentation; (7) mitochondrial structural abnormalities; (8) expression of light chain 3 B, an indicator of autophagy; (9) probable autophagy of mitochondria by autophagosomes; and (10) probable phagocytosis of apoptotic hepatocytes by activated macrophages. Immunoglobulin G immune complexes were identified in the hepatocytes and localized to the endoplasmic reticulum and Golgi of these patients after the drug-induced liver disease, reflecting a primary or secondary target. Hepatitis C treatment was discontinued at weeks 15 and 19 in patients 1 and 2, respectively. After more than 6 months off the medication, both patients normalized the serum alanine aminotransferase, aspartate aminotransferase, and total bilirubin with undetectable HCV RNA.

CONCLUSIONS

HCV-796 may cause severe hepatocellular injury and apoptosis, with a marked immune reaction in susceptible patients.

Cyclic regulation of transcription factor C/EBP beta in human endometrium

BACKGROUND

The transcription factor CCAAT/enhancer-binding protein (C/EBP) beta is a critical mediator of murine endometrial function during embryo implantation. Our objective is to characterize changes in C/EBP beta mRNA abundance and protein localization over the normal human menstrual cycle.

METHODS

Fifty normally cycling volunteers without reproductive disorders were randomized to undergo endometrial sampling on a specific cycle day, with secretory phase samples timed using urinary LH surge. Samples were assessed for relative C/EBP beta mRNA expression using quantitative real-time RT-PCR and for C/EBP beta protein localization using immunohistochemistry. The semiquantitative histologic scoring (HSCORE) system was used to compare staining intensity in each tissue compartment between each cycle phase.

RESULTS

C/EBP beta mRNA expression by whole endometrium peaks in the late secretory phase and is significantly higher than that in the proliferative and mid-secretory phases. A marked increase in nuclear C/EBP beta protein immunostaining is seen in stromal cells beginning about cycle day 20, coincident with the start of endometrial receptivity. This increased staining continues for the remainder of the cycle.

CONCLUSION

In the normal human menstrual cycle, C/EBP beta mRNA and protein expression also change, with increased nuclear immunostaining in the mid-secretory phase, suggesting a possible role for C/EBP beta in human endometrial receptivity.

The tumour necrosis factor-alpha-mediated suppression of the CCAAT/enhancer binding protein-alpha gene transcription in hepatocytes involves inhibition of autoregulation

Tumour necrosis factor-alpha (TNF-alpha) is a key regulator of the immune and inflammatory responses along with numerous other cellular changes during physiological and pathophysiological conditions. The cellular actions of TNF-alpha are associated with both the activation and the inhibition of gene transcription. In contrast to gene activation, the mechanisms underlying the TNF-alpha-mediated transcriptional inhibition remain largely unclear. We have investigated this aspect using the transcription factor CCAAT/enhancer binding protein-alpha (C/EBPalpha) as a model gene. TNF-alpha decreased the expression of C/EBPalpha mRNA and protein in the human hepatoma Hep3B cell line. The activity of the proximal promoter of both the human and the Xenopus C/EBPalpha genes in transfected Hep3B cells was inhibited by TNF-alpha. Transient transfection assays using various Xenopus C/EBPalpha promoter-luciferase DNA constructs showed that a C/EBP recognition sequence was essential for the TNF-alpha response. Electrophoretic mobility shift assays showed that C/EBPalpha bound to this site and co-transfection assays revealed that it was a major activator of the promoter and its transactivation potential was reduced by TNF-alpha. The potential role of nuclear factor kappaB (NF-kappaB) in the response was also investigated in the light of its pivotal role in TNF-alpha signalling. Inhibition of NF-kappaB using pharmacological agents or by transfection of a plasmid specifying for a superrepressor attenuated the TNF-alpha-inhibited C/EBPalpha promoter activity. In addition, an involvement of NF-kappaB in DNA-protein interactions at the C/EBP recognition sequence was identified.

THOC5 couples M-CSF receptor signaling to transcription factor expression

THOC5 is a nuclear/cytoplasmic protein member of the spliceosome complex which potentiates C/EBP expression in adipocyte differentiation. As C/EBP family members are important regulators of myelopoiesis and THOC5 is highly expressed in neutrophil/macrophage progenitor cells we assessed the role of THOC5 in cytokine-stimulated monocytic development. M-CSF stimulated maturation of the NFS60 cell line was associated with enhanced THOC5 expression and phosphorylation. THOC5 was also shown to form a complex with C/EBPbeta. Ectopic expression of THOC5 mimicked M-CSF mediated cell maturation and enhanced protein expression of the myeloid transcription factors C/EBPbeta, C/EBPalpha, Pu-1 and also GAB2 (a PI-3 Kinase and macrophage development regulator). Increased THOC5 expression also mimicked M-CSF stimulated increases in the lipid second messenger PtdInsP(3). Inhibition of THOC5-induced increases in PtdInsP(3) levels abrogated the elevated levels of C/EBPbeta. Thus THOC5 expression can potentiate receptor signalling to transcription factor expression and monocyte differentiation.

Effects of infliximab and parenteral nutrition on albumin and fibrinogen synthesis rates in pediatric Crohn disease

OBJECTIVES

Tumor necrosis factor-alpha (TNF-alpha) may play a significant role in growth disturbance in pediatric Crohn disease. The aim of this study was to determine the effects of anti-TNF-alpha therapy on albumin and fibrinogen synthesis during both fasting and parenteral nutrition infusion in pediatric patients with active Crohn disease.

PATIENTS AND METHODS

Children with active Crohn disease scheduled for their initial dose of infliximab underwent assessment immediately before and 2 weeks following infliximab infusion. Using the stable isotope [d5] phenylalanine, rates of fractional and absolute albumin and fibrinogen synthesis were calculated. Measurements were made in both the fasting and parenterally fed states.

RESULTS

Fifteen children (mean age 14.9 +/- 0.3) completed the study. The mean serum albumin changed from 3.59 +/- 0.08 to 3.66 +/- 0.04 g/dL, and the mean fibrinogen level decreased from 230 +/- 17 to 187 +/- 8 mg/dL (P < 0.05) following infliximab therapy. During fasting, there were no changes in albumin and fibrinogen synthesis rates following infliximab. During parenteral nutrition infusion, the fractional albumin synthesis rate changed from 11.8% to 15.1%/day (P = 0.06), and the absolute albumin synthesis rate increased from 192 to 248 mg x kg(-1) x day(-1) (P < 0.05), whereas no changes in fibrinogen synthesis rates were observed. Synthesis rates of albumin and fibrinogen were increased during parenteral nutrition infusion compared with the fasting state.

CONCLUSIONS

Following infliximab therapy, during parenteral nutrition infusion, albumin synthesis increased significantly. Conversely, serum fibrinogen levels decreased following infliximab therapy in the absence of significant change in synthesis rates.

NF-IL6 (C/EBPbeta) induces HIV-1 replication by inhibiting cytidine deaminase APOBEC3G

T cell activation is crucial for the productive HIV-1 infection of primary T cells; however, little is known about the host molecules involved in this process. We show that the host transcription factor NF-IL6 (also called C/EBPbeta) renders primary CD4(+) T cells highly permissive for HIV-1 replication. NF-IL6 facilitates reverse transcription of the virus by binding to and inhibiting the antiviral cytidine deaminase APOBEC3G. A mutation in NF-IL6 at Ser-288 weakened its binding to APOBEC3G and strongly inhibited HIV-1 replication. NF-IL6 also induced the replication of a Vif-deficient strain of HIV-1 in nonpermissive HUT78 cells. These data indicate that NF-IL6 is a natural inhibitor of APOBEC3G that facilitates HIV-1 replication. Host factors, such as NF-IL6, that are involved in early HIV-1 replication are potential targets for anti-HIV-1 therapy. Our findings shed light on the activation of HIV-1 replication by T cell host molecules and reveal a unique regulation of DNA deamination by APOBEC3G and NF-IL6.

Induction of sodium iodide symporter gene and molecular characterisation of HNF3 beta/FoxA2, TTF-1 and C/EBP beta in thyroid carcinoma cells

Thyroid carcinoma cells often do not express thyroid-specific genes including sodium iodide symporter (NIS), thyroperoxidase (TPO), thyroglobulin (TG), and thyrotropin-stimulating hormone receptor (TSHR). Treatment of thyroid carcinoma cells (four papillary and two anaplastic cell lines) with histone deacetylase inhibitors (SAHA or VPA) modestly induced the expression of the NIS gene. The promoter regions of the thyroid-specific genes contained binding sites for hepatocyte nuclear factor 3 β (HNF3β)/forkhead box A2 (FoxA2), thyroid transcription factor 1 (TTF-1), and CCAAT/enhancer binding protein β (C/EBPβ). Quantitative reverse transcription-polymerase chain reaction (RT–PCR) showed decreased expression of HNF3β/FoxA2 and TTF-1 mRNA in papillary thyroid carcinoma cell lines, when compared with normal thyroid cells. Forced expression of these genes in papillary thyroid carcinoma cells inhibited their growth. Furthermore, the CpG island in the promoter region of HNF3β/FoxA2 was aberrantly methylated; and treatment with 5-aza-2-deoxycytidine (5-Az) induced its expression. Immunohistochemical staining showed that C/EBPβ was localised in the nucleus in normal thyroid cells but was detected in the cytoplasm in papillary thyroid carcinoma cells. Subcellular fractionation of papillary thyroid carcinoma cell lines also demonstrated high levels of expression of C/EBPβ in the cytoplasm, suggesting that a large proportion of C/EBPβ protein is inappropriately localised in the cytoplasm. In summary, these findings reveal novel abnormalities in thyroid carcinoma cells

Direct infection and replication of naturally occurring hepatitis C virus genotypes 1, 2, 3 and 4 in normal human hepatocyte cultures

BACKGROUND

Hepatitis C virus (HCV) infection afflicts about 170 million individuals worldwide. However, the HCV life cycle is only partially understood because it has not been possible to infect normal human hepatocytes in culture. The current Huh-7 systems use cloned, synthetic HCV RNA expressed in hepatocellular carcinoma cells to produce virions, but these cells cannot be infected with naturally occurring HCV obtained from infected patients.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we describe a human hepatocyte culture permissible to the direct infection with naturally occurring HCV genotypes 1, 2, 3 and 4 in the blood of HCV-infected patients. The culture system mimics the biology and kinetics of HCV infection in humans, and produces infectious virions that can infect naïve human hepatocytes.

CONCLUSIONS/SIGNIFICANCE

This culture system should complement the existing systems, and may facilitate the understanding of the HCV life cycle, its effects in the natural host cell, the hepatocyte, as well as the development of novel therapeutics and vaccines.

A novel domain of BRCA1 interacts with p53 in breast cancer cells

The interactions between BRCA1 and p53 are relevant for understanding hereditary breast and ovarian cancer. Although in vitro studies reported that BRCA1 (amino acids 224-500) and the second BRCT domain of the BRCA1 C-terminus may interact with p53, quantitative biophysical measurements indicate that these regions of BRCA1 do not bind efficiently to p53. Here we show that BRCA1 interacts with p53 in vivo in breast cancer cells, through another BRCA1 domain (amino acids 772-1292). Expression of a truncated BRCA1 (amino acids 772-1292) stimulated p53 DNA-binding and transcription activities and apoptosis, recapitulating some effects of DNA damage. These results suggest that a novel domain of BRCA1 may interact with p53 in breast cancer cells.

Deprivation of protein or amino acid induces C/EBPbeta synthesis and binding to amino acid response elements, but its action is not an absolute requirement for enhanced transcription

A nutrient stress signalling pathway is triggered in response to protein or amino acid deprivation, namely the AAR (amino acid response), and previous studies have shown that C/EBPbeta (CCAAT/enhancer-binding protein beta) expression is up-regulated following activation of the AAR. DNA-binding studies, both in vitro and in vivo, have revealed increased C/EBPbeta association with AARE (AAR element) sequences in AAR target genes, but its role is still unresolved. The present results show that in HepG2 human hepatoma cells, the total amount of C/EBPbeta protein, both the activating [LAP* and LAP (liver-enriched activating protein)] and inhibitory [LIP (liver-enriched inhibitory)] isoforms, was increased in histidine-deprived cells. Immunoblotting of subcellular fractions and immunostaining revealed that most of the C/EBPbeta was located in the nucleus. Consistent with these observations, amino acid limitation caused an increase in C/EBPbeta DNA-binding activity in nuclear extracts and chromatin immunoprecipitation revealed an increase in C/EBPbeta binding to the AARE region in vivo, but at a time when transcription from the target gene was declining. A constant fraction of the basal and increased C/EBPbeta protein was phosphorylated on Thr(235) and the phospho-C/EBPbeta did bind to an AARE. Induction of AARE-enhanced transcription was slightly greater in C/EBPbeta-deficient MEFs (mouse embryonic fibroblasts) or C/EBPbeta siRNA (small interfering RNA)-treated HepG2 cells compared with the corresponding control cells. Transient expression of LAP*, LAP or LIP in C/EBPbeta-deficient fibroblasts caused suppression of increased transcription from an AARE-driven reporter gene. Collectively, the results demonstrate that C/EBPbeta is not required for transcriptional activation by the AAR pathway but, when present, acts in concert with ATF3 (activating transcription factor 3) to suppress transcription during the latter stages of the response.

Loss of c/EBP-beta activity promotes the adaptive to apoptotic switch in hypoxic cortical neurons

Understanding the mechanisms governing the switch between hypoxia-induced adaptive and pathological transcription may reveal novel therapeutic targets for stroke. Using an in vitro hypoxia model that temporally separates these divergent responses, we found apoptotic signaling was preceded by a decline in c/EBP-beta activity and was associated with markers of ER-stress including transient eIF2alpha phosphorylation, and the delayed induction of the bZIP proteins ATF4 and CHOP-10. Pretreatment with the eIF2alpha phosphatase inhibitor salubrinal blocked the activation of caspase-3, indicating that ER-related stress responses are integral to this transition. Delivery of either full-length, or a transcriptionally inactive form of c/EBP-beta protected cultures from hypoxic challenge, in part by inducing levels of the anti-apoptotic protein Bcl-2. These data indicate that the pathologic response in cortical neurons induced by hypoxia involves both the loss of c/EBP-beta-mediated survival signals and activation of pro-death pathways originating from the endoplasmic reticulum.

A ribosomal S-6 kinase-mediated signal to C/EBP-beta is critical for the development of liver fibrosis

Background

In response to liver injury, hepatic stellate cell (HSC) activation causes excessive liver fibrosis. Here we show that activation of RSK and phosphorylation of C/EBPβ on Thr217 in activated HSC is critical for the progression of liver fibrosis.

Methodology/Principal Findings

Chronic treatment with the hepatotoxin CCl₄ induced severe liver fibrosis in C/EBPβ^+/+ mice but not in mice expressing C/EBPβ-Ala217, a non-phosphorylatable RSK-inhibitory transgene. C/EBPβ-Ala217 was present within the death receptor complex II, with active caspase 8, and induced apoptosis of activated HSC. The C/EBPβ-Ala217 peptides directly stimulated caspase 8 activation in a cell-free system. C/EBPβ^+/+ mice with CCl₄-induced severe liver fibrosis, while continuing on CCl₄, were treated with a cell permeant RSK-inhibitory peptide for 4 or 8 weeks. The peptide inhibited RSK activation, stimulating apoptosis of HSC, preventing progression and inducing regression of liver fibrosis. We found a similar activation of RSK and phosphorylation of human C/EBPβ on Thr266 (human phosphoacceptor) in activated HSC in patients with severe liver fibrosis but not in normal livers, suggesting that this pathway may also be relevant in human liver fibrosis.

Conclusions/Significance

These data indicate that the RSK-C/EBPβ phosphorylation pathway is critical for the development of liver fibrosis and suggest a potential therapeutic target.

C/EBPbeta associates with caspase 8 complex proteins and modulates apoptosis in hepatic stellate cells

GOALS

To analyze the role of C/EBPbeta phosphorylation on hepatic stellate cell survival/cell death.

BACKGROUND

Activation and survival of stellate cells is critical for the development of liver fibrosis. C/EBPbeta phosphorylation regulates stellate cell survival by affecting caspase 8 activation. The mechanisms responsible for these effects are unknown.

STUDY

We study the effects of caspase 8 activators signaling through death receptors. In addition, we assess the role of C/EBPbeta phosphorylation on the susceptibility of stellate cells to apoptotic stimuli. Finally, we investigated whether C/EBPbeta is associated with the caspase 8 complex protein FLIP, a critical inhibitor of caspase 8.

RESULTS

Primary mouse stellate cells from C/EBPbeta wild type and the phosphorylation mimic C/EBPbetaGlu transgenic mice were treated with lipopolysaccharide [an inducer of tumor necrosis factor-alpha (TNF-alpha)], FAS, or TNF-alpha. Stellate cell apoptosis was determined by assessing the binding of annexin-V to exposed phosphatidylserine of plasma membranes. TNF-alpha and FAS, but not lipopolysaccharide, induced annexin-V binding at 6 hours in C/EBPbeta wild type stellate cell. However, the stimulation of apoptosis by TNF-alpha and FAS was markedly blocked in C/EBPbetaGlu stellate cells (P<0.001). Stellate cells activated on a collagen type 1 matrix expressed both C/EBPbeta and FLIPL. Treatment of stellate cells with a MAP kinase kinase1 (MEK1) inhibitor blocked FLIPL cellular localization, suggesting that MEK1 signaling through C/EBPbeta modulates FLIP activity. The colocalization of C/EBPbeta and FLIPL was disrupted by activation of the FAS receptor, by blocking the association of C/EBPbeta with the long form of FLIP, FLIPL.

CONCLUSIONS

The MAPK-RSK-C/EBPbeta signaling may modulate stellate cell survival through caspase 8-associated protein FLIPL. This step is critical for liver fibrosis and if blocked with competitor peptides may prevent fibrogenesis.

Tamoxifen Induction of CCAAT Enhancer-binding Protein α Is Required for Tamoxifen-induced Apoptosis

Low concentrations of tamoxifen or its active metabolite 4-hydroxytamoxifen (OHT) induce estrogen receptor alpha (ERalpha)-dependent apoptosis. To analyze the pathway of OHT-ERalpha-induced apoptosis, we developed stably transfected lines of HeLa cells expressing wild-type ER and an inactive mutant ERalpha unable to bind estrogen response elements. HeLa cells expressing the mutant ERalpha and HeLa cells expressing wild-type ERalpha in which the ER was knocked down with an ER-specific small interfering RNA were not killed by Tam or OHT, suggesting that estrogen response element-mediated transcription is required for Tam- and OHT-induced apoptosis. Microarray analysis to identify a gene(s) whose expression is important in OHT-ER-mediated apoptosis identified 19 mRNAs that OHT up-regulated by >1.6-fold and 15 down-regulated mRNAs. Gene function and the time course of induction by OHT-ERalpha led us to further investigate CCAAT enhancer-binding protein alpha (C/EBPalpha), which has roles in cell cycle progression and apoptosis, and p21. Quantitative reverse transcription-PCR, Western blot analysis, and RNA interference knockdown suggest that cell cycle arrest resulting from OHT-ERalpha induction of p21 may facilitate apoptosis. OHT-ERalpha, but not E2-ERalpha, induced C/EBPalpha mRNA and protein. RNA interference knockdown of C/EBPalpha nearly abolished OHT-ERalpha-induced apoptosis. We isolated stable cell lines that were resistant to OHT-induced apoptosis, contain full-length functional ERalpha, and undergo apoptosis in response to etoposide. In these OHT-resistant cell lines both before and after OHT treatment, C/EBPalpha levels are much lower than in OHT-sensitive cells. These studies establish a novel molecular site responsible for Tam- and OHT-ERalpha-induced apoptosis of cancer cells.