Iron-dependent activation of NF-kappaB in Kupffer cells: a priming mechanism for alcoholic liver disease

Supplementation of Micro- and Macronutrients-A Role of Nutritional Status in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a condition in which the pathological cumulation of fat with coexisting inflammation and damage of hepatic cells leads to progressive dysfunctions of the liver. Except for the commonly well-known major causes of NAFLD such as obesity, dyslipidemia, insulin resistance, or diabetes, an unbalanced diet and imbalanced nutritional status should also be taken into consideration. In this narrative review, we summarized the current knowledge regarding the micro- and macronutrient status of patients suffering from NAFLD considering various diets and supplementation of chosen supplements. We aimed to summarize the knowledge indicating which nutritional impairments may be associated with the onset and progression of NAFLD at the same time evaluating the potential therapy targets that could facilitate the healing process. Except for the above-mentioned objectives, one of the most important aspects of this review was to highlight the possible strategies for taking care of NAFLD patients taking into account the challenges and opportunities associated with the micronutrient status of the patients. The current research indicates that a supplementation of chosen vitamins (e.g., vitamin A, B complex, C, or D) as well as chosen elements such as zinc may alleviate the symptoms of NAFLD. However, there is still a lack of sufficient data regarding healthy ranges of dosages; thus, further research is of high importance in this matter.

Liver Iron Loading in Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is a common chronic liver disease with increasing incidence worldwide. Alcoholic liver steatosis/steatohepatitis can progress to liver fibrosis/cirrhosis, which can cause predisposition to hepatocellular carcinoma. ALD diagnosis and management are confounded by several challenges. Iron loading is a feature of ALD which can exacerbate alcohol-induced liver injury and promote ALD pathologic progression. Knowledge of the mechanisms that mediate liver iron loading can help identify cellular/molecular targets and thereby aid in designing adjunct diagnostic, prognostic, and therapeutic approaches for ALD. Herein, the cellular mechanisms underlying alcohol-induced liver iron loading are reviewed and how excess iron in patients with ALD can promote liver fibrosis and aggravate disease pathology is discussed. Alcohol-induced increase in hepatic transferrin receptor-1 expression and up-regulation of high iron protein in Kupffer cells (proposed) facilitate iron deposition and retention in the liver. Iron is loaded in both parenchymal and nonparenchymal liver cells. Iron-loaded liver can promote ferroptosis and thereby contribute to ALD pathology. Iron and alcohol can independently elevate oxidative stress. Therefore, a combination of excess iron and alcohol amplifies oxidative stress and accelerates liver injury. Excess iron-stimulated hepatocytes directly or indirectly (through Kupffer cell activation) activate the hepatic stellate cells via secretion of proinflammatory and profibrotic factors. Persistently activated hepatic stellate cells promote liver fibrosis, and thereby facilitate ALD progression.

Targeting ferroptosis, a novel programmed cell death, for the potential of alcohol-related liver disease therapy

Ferroptosis is a new iron-dependent cell death mode, which is different from the other types of programmed cell death, such as apoptosis, necrosis, and autophagy. Ferroptosis is characterized by a process in which fatal lipids from lipid peroxidation accumulate in cells and eventually lead to cell death. Alcohol-related liver disease (ALD) is a type of liver injury caused by excessive alcohol intake. Alcohol-related liver disease is a broad-spectrum disease category, which includes fatty liver, steatohepatitis, hepatitis, cirrhosis, and hepatocellular tumors. Recent studies have found that ferroptosis is involved in the pathological development of non-viral liver diseases. Therefore, ferroptosis may be an ideal target for the treatment of non-viral liver diseases. In this review article, we will elaborate the molecular mechanism and regulatory mechanism of ferroptosis, explore the key role of ferroptosis in the Alcohol-related liver disease process, and summarize the existing targeted ferroptosis drugs and their feasibility for the treatment of Alcohol-related liver disease.

Aberrant Transferrin and Ferritin Upregulation Elicits Iron Accumulation and Oxidative Inflammaging Causing Ferroptosis and Undermines Estradiol Biosynthesis in Aging Rat Ovaries by Upregulating NF-Κb-Activated Inducible Nitric Oxide Synthase: First Demonstration of an Intricate Mechanism

We report herein a novel mechanism, unraveled by proteomics and validated by in vitro and in vivo studies, of the aberrant aging-associated upregulation of ovarian transferrin and ferritin in rat ovaries. The ovarian mass and serum estradiol titer plummeted while the ovarian labile ferrous iron and total iron levels escalated with age in rats. Oxidative stress markers, such as nitrite/nitrate, 3-nitrotyrosine, and 4-hydroxy-2-nonenal, accumulated in the aging ovaries due to an aberrant upregulation of the ovarian transferrin, ferritin light/heavy chains, and iron regulatory protein 2(IRP2)-mediated transferrin receptor 1 (TfR1). Ferritin inhibited estradiol biosynthesis in ovarian granulosa cells in vitro via the upregulation of a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and p65/p50-induced oxidative and inflammatory factor inducible nitric oxide synthase (iNOS). An in vivo study demonstrated how the age-associated activation of NF-κB induced the upregulation of iNOS and the tumor necrosis factor α (TNFα). The downregulation of the keap1-mediated nuclear factor erythroid 2-related factor 2 (Nrf2), that induced a decrease in glutathione peroxidase 4 (GPX4), was observed. The aberrant transferrin and ferritin upregulation triggered an iron accumulation via the upregulation of an IRP2-induced TfR1. This culminates in NF-κB-iNOS-mediated ovarian oxi-inflamm-aging and serum estradiol decrement in naturally aging rats. The iron accumulation and the effect on ferroptosis-related proteins including the GPX4, TfR1, Nrf2, Keap1, and ferritin heavy chain, as in testicular ferroptosis, indicated the triggering of ferroptosis. In young rats, an intraovarian injection of an adenovirus, which expressed iron regulatory proteins, upregulated the ovarian NF-κB/iNOS and downregulated the GPX4. These novel findings have contributed to a prompt translational research on the ovarian aging-associated iron metabolism and aging-associated ovarian diseases.

Anti-Inflammatory Effects of the Iron Chelator, DIBI, in Experimental Acute Lung Injury

Iron plays a critical role in the immune response to inflammation and infection due to its role in the catalysis of reactive oxygen species (ROS) through the Haber-Weiss and Fenton reactions. However, ROS overproduction can be harmful and damage healthy cells. Therefore, iron chelation represents an innovative pharmacological approach to limit excess ROS formation and the related pro-inflammatory mediator cascades. The present study was designed to investigate the impact of the iron chelator, DIBI, in an experimental model of LPS-induced acute lung injury (ALI). DIBI was administered intraperitoneally in the early and later stages of lung inflammation as determined by histopathological evaluation. We found that lung tissues showed significant injury, as well as increased NF-κB p65 activation and significantly elevated levels of various inflammatory mediators (LIX, CXCL2, CCL5, CXCL10, IL-1𝛽, IL-6) 4 h post ALI induction by LPS. Mice treated with DIBI (80 mg/kg) in the early stages (0 to 2 h) after LPS administration demonstrated a significant reduction of the histopathological damage score, reduced levels of NF-κB p65 activation, and reduced levels of inflammatory mediators. Intravital microscopy of the pulmonary microcirculation also showed a reduced number of adhering leukocytes and improved capillary perfusion with DIBI administration. Our findings support the conclusion that the iron chelator, DIBI, has beneficial anti-inflammatory effects in experimental ALI.

Iron overload in alcoholic liver disease: underlying mechanisms, detrimental effects, and potential therapeutic targets

Alcoholic liver disease (ALD) is a global public health challenge due to the high incidence and lack of effective therapeutics. Evidence from animal studies and ALD patients has demonstrated that iron overload is a hallmark of ALD. Ethanol exposure can promote iron absorption by downregulating the hepcidin expression, which is probably mediated by inducing oxidative stress and promoting erythropoietin (EPO) production. In addition, ethanol may enhance iron uptake in hepatocytes by upregulating the expression of transferrin receptor (TfR). Iron overload in the liver can aggravate ethanol-elicited liver damage by potentiating oxidative stress via Fenton reaction, promoting activation of Kupffer cells (KCs) and hepatic stellate cells (HSCs), and inducing a recently discovered programmed iron-dependent cell death, ferroptosis. This article reviews the current knowledge of iron metabolism, regulators of iron homeostasis, the mechanism of ethanol-induced iron overload, detrimental effects of iron overload in the liver, and potential therapeutic targets.

HIV-1 infection in sickle cell disease and sickle cell trait: role of iron and innate response

INTRODUCTION

Sickle cell disease (SCD), an inherited hemoglobinopathy, affects primarily African Americans in the U.S.A. In addition, about 15% African Americans carry sickle cell trait (SCT). Despite the risk associated with blood transfusions, SCD patients have lower risk of acquiring HIV-1 infection. SCT individuals might also have some protection from HIV-1 infection.

AREAS COVERED

Here, we will review recent and previous studies with the focus on molecular mechanisms that might underlie and contribute to the protection of individuals with SCD and SCT from HIV-1 infection. As both of these conditions predispose to hemolysis, we will focus our discussion on the effects of systemic and intracellular iron on HIV-1 infection and progression. We will also review changes in iron metabolism and activation of innate antiviral responses in SCD and SCT and their effects on HIV-1 infection.

EXPERT OPINION

Previous studies, including ours, showed that SCD might protect from HIV-1 infection. This protection is likely due to the upregulation of complex protein network in response to hemolysis, hypoxia and interferon signaling. These findings are important not only for HIV-1 field but also for SCD cure efforts as antiviral state of SCD patients may adversely affect lentivirus-based gene therapy efforts.

Alcoholic and Non-Alcoholic Liver Diseases: Promising Molecular Drug Targets and their Clinical Development

Alcoholic and non-alcoholic fatty liver diseases have become a serious concern worldwide. Both these liver diseases have an identical pathology, starting from simple steatosis to cirrhosis and, ultimately to hepatocellular carcinoma. Treatment options for alcoholic liver disease (ALD) are still the same as they were 50 years ago which include corticosteroids, pentoxifylline, antioxidants, nutritional support and abstinence; and for non-alcoholic fatty liver disease (NAFLD), weight loss, insulin sensitizers, lipid-lowering agents and anti-oxidants are the only treatment options. Despite broad research in understanding the disease pathophysiology, limited treatments are available for clinical use. Some therapeutic strategies based on targeting a specific molecule have been developed to lessen the consequences of disease and are under clinical investigation. Therefore, focus on multiple molecular targets will help develop an efficient therapeutic strategy. This review comprises a brief overview of the pathogenesis of ALD and NAFLD; recent molecular drug targets explored for ALD and NAFLD that may prove to be effective for multiple therapeutic regimens and also the clinical status of these promising drug targets for liver diseases.

Depriving Iron Supply to the Virus Represents a Promising Adjuvant Therapeutic Against Viral Survival

Purpose of the review

The ongoing outbreak of novel coronavirus pneumonia (COVID-19) caused by the 2019 novel coronavirus (SARS-CoV-2) in China is lifting widespread concerns. Thus, therapeutic options are urgently needed, and will be discussed in this review.

Recent findings

Iron-containing enzymes are required for viruses most likely including coronaviruses (CoVs) to complete their replication process. Moreover, poor prognosis occurred in the conditions of iron overload for patients upon infections of viruses. Thus, limiting iron represents a promising adjuvant strategy in treating viral infection through oral uptake or venous injection of iron chelators, or through the manipulation of the key iron regulators. For example, treatment with iron chelator deferiprone has been shown to prolong the survival of acquired immunodeficiency syndrome (AIDS) patients. Increasing intracellular iron efflux via increasing iron exporter ferroportin expression also exhibits antiviral effect on human immunodeficiency virus (HIV). The implications of other metals besides iron are also briefly discussed.

Summary

For even though we know little about iron regulation in COVID-19 patients thus far, it could be deduced from other viral infections that iron chelation might be an alternative beneficial adjuvant in treating COVID-19.

miR-374a/Myc axis modulates iron overload-induced production of ROS and the activation of hepatic stellate cells via TGF-β1 and IL-6

The transformation of hepatic stellate cells (HSCs) to activated myofibroblasts plays a critical role in the progression of hepatic fibrosis, while iron-catalyzed production of free radical, including reaction and active oxygen (ROS), and activation and transformation of HSC into a myofibroblasts has been regarded as a major mechanism. In the present study, we attempted to investigate the mechanism of iron overload in hepatic fibrosis from the perspective of regulating HSC activation via oxidative stress and miR-374a/Myc axis. FAC stimulation significantly increased ROS production and TGF-β1 and IL-6 release dose-dependently in hepatocytes. miR-374a could target Myc, a co-transcription factor of both TGF-β1 and IL-6, to negatively regulate Myc expression; FAC stimulation significantly suppressed miR-374a expression, whereas the suppressive effect of FAC stimulation on miR-374a expression could be reversed by ROS inhibitor NAC, indicating that miR-374a could be modulated by iron overload-induced ROS. Via targeting Myc, miR-374a overexpression significantly reduced FAC-induced increases in TGF-β1 and IL-6 levels within L02 cells, whereas the effects of miR-374a overexpression were significantly attenuated via Myc overexpression. Finally, miR-374a overexpression attenuated FAC-induced activity of HSCs by decreasing α-SMA and Collagen I levels whereas Myc overexpression enhanced FAC-induced activity of HSCs by increasing α-SMA and Collagen I levels; the effects of miR-374a overexpression could also be significantly reversed by Myc overexpression, indicating that miR-374a suppresses the activation of HSCs by inhibiting Myc to reduce FAC-induced increases in TGF-β1 and IL-6 release. In conclusion, we demonstrate a novel mechanism of miR-374a/Myc axis modulating iron overload-induced production of ROS and the activation of HSCs via TGF-β1 and IL-6.

Natural compounds in the chemoprevention of alcoholic liver disease

Alcoholic liver disease (ALD), caused by excessive consumption of alcohol, is a major cause of chronic liver disease worldwide. Much effort has been expended to explore the pathogenesis of ALD. Hepatic cell injury, oxidative stress, inflammation, regeneration, and bacterial translocation are all involved in the pathogenesis of ALD. Immediate abstinence is the most important therapeutic treatment for affected individuals. However, the medical treatment for ALD had not advanced in a long period. Intriguingly, an increasing body of research indicates the potential of natural compounds in the targeted therapy of ALD. A plethora of dietary natural products such as flavonoids, resveratrol, saponins, and β-carotene are found to exert protective effects on ALD. This occurs through various mechanisms composed of antioxidative, anti-inflammatory, iron chelation, pro-apoptosis, and/or antiproliferation of hepatic stellate cells and hepatocellular carcinoma cells. In this review, we will summarize current knowledge about the pathogenesis and treatments of ALD and focus on the potential of natural compounds in ALD therapies and underlying mechanisms.

Protective Effects of Taraxasterol against Ethanol-Induced Liver Injury by Regulating CYP2E1/Nrf2/HO-1 and NF-κB Signaling Pathways in Mice

Taraxasterol, a pentacyclic-triterpene compound, is one of the main active components isolated from the traditional Chinese medicinal herb Taraxacum. The objective of this study is to evaluate the protective effects of taraxasterol and its possible underlying mechanisms against ethanol-induced liver injury in mice. ICR mice were fed with Lieber-DeCarli diet containing 5% ethanol for 10 d and then challenged with a single dose of 20% ethanol (5 g/kg BW) by intragastric administration. The mice were intragastrically treated daily with taraxasterol (2.5, 5, and 10 mg/kg). Tiopronin was used as a positive control. The liver index was calculated, and the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in sera were detected. The contents of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH) and the activity of superoxide dismutase (SOD) in the livers were measured. The histopathological changes of liver tissues were observed by hematoxylin and eosin (H&E) staining. The protein expression levels of hepatic cytochrome P450 2E1 (CYP2E1), nuclear factor erythroid 2-related factor 2 (Nrf2), antioxidant protein heme oxygenase-1 (HO-1), and nuclear factor-kappa B (NF-κB) signaling pathway in liver tissues were detected by immunohistochemistry and Western blot methods. Taraxasterol significantly reduced the ethanol-induced increases of liver index, ALT, AST, and TG levels in sera and TG and MDA contents in the livers and hepatic ROS production and suppressed the ethanol-induced decreases of hepatic GSH level and SOD activity. Taraxasterol also significantly inhibited the secretion of proinflammatory cytokines TNF-α and IL-6 induced by ethanol. In addition, taraxasterol improved the liver histopathological changes in mice with ethanol-induced liver injury. Further studies revealed that taraxasterol significantly inhibited the ethanol-induced upregulation of CYP2E1, increased the ethanol-induced downregulation of Nrf2 and HO-1, and inhibited the degradation of inhibitory kappa Bα (IκBα) and the expression level of NF-κB p65 in liver tissues of ethanol-induced mice. These findings suggest that taraxasterol possesses the potential protective effects against ethanol-induced liver injury in mice by exerting antioxidative stress and anti-inflammatory response via CYP2E1/Nrf2/HO-1 and NF-κB signaling pathways.

Protein Phosphatase-1 -targeted Small Molecules, Iron Chelators and Curcumin Analogs as HIV-1 Antivirals

BACKGROUND

Despite efficient suppression of HIV-1 replication, current antiviral drugs are not able to eradicate HIV-1 infection. Permanent HIV-1 suppression or complete eradication requires novel biological approaches and therapeutic strategies. Our previous studies showed that HIV-1 transcription is regulated by host cell protein phosphatase-1. We also showed that HIV-1 transcription is sensitive to the reduction of intracellular iron that affects cell cycle-dependent kinase 2. We developed protein phosphatase 1-targeting small molecules that inhibited HIV-1 transcription. We also found an additional class of protein phosphatase-1-targeting molecules that activated HIV-1 transcription and reported HIV-1 inhibitory iron chelators and novel curcumin analogs that inhibit HIV-1. Here, we review HIV-1 transcription and replication with focus on its regulation by protein phosphatase 1 and cell cycle dependent kinase 2 and describe novel small molecules that can serve as future leads for anti-HIV drug development.

RESULTS

Our review describes in a non-exhaustive manner studies in which HIV-1 transcription and replication are targeted with small molecules. Previously, published studies show that HIV-1 can be inhibited with protein phosphatase-1-targeting and iron chelating compounds and curcumin analogs. These results are significant in light of the current efforts to eradicate HIV-1 through permanent inhibition. Also, HIV-1 activating compounds can be useful for "kick and kill" therapy in which the virus is reactivated prior to its inhibition by the combination antiretroviral therapy.

CONCLUSION

The studies described in our review point to protein phosphatase-1 as a new drug target, intracellular iron as subject for iron chelation and novel curcumin analogs that can be developed for novel HIV-1 transcription- targeting therapeutics.

Significance and In Vivo Detection of Iron-Laden Microglia in White Matter Multiple Sclerosis Lesions

Microglia are resident immune cells that fulfill protective and homeostatic functions in the central nervous system (CNS) but may also promote neurotoxicity in the aged brain and in chronic disease. In multiple sclerosis (MS), an autoimmune demyelinating disease of the CNS, microglia and macrophages contribute to the development of white matter lesions through myelin phagocytosis, and possibly to disease progression through diffuse activation throughout myelinated white matter. In this review, we discuss an additional compartment of myeloid cell activation in MS, i.e., the rim and normal adjacent white matter of chronic active lesions. In chronic active lesions, microglia and macrophages may contain high amounts of iron, express markers of proinflammatory polarization, are activated for an extended period of time (years), and drive chronic tissue damage. Iron-positive myeloid cells can be visualized and quantified with quantitative susceptibility mapping (QSM), a magnetic resonance imaging technique. Thus, QSM has potential as an in vivo biomarker for chronic inflammatory activity in established white matter MS lesions. Reducing chronic inflammation associated with iron accumulation using existing or novel MS therapies may impact disease severity and progression.

Dietary Iron Supplementation Alters Hepatic Inflammation in a Rat Model of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is now the most common liver disease in the world. NAFLD can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and eventually hepatocellular carcinoma. Acquired hepatic iron overload is seen in a number of patients with NAFLD; however, its significance in the pathology of NAFLD is still debated. Here, we investigated the role of dietary iron supplementation in experimental steatohepatitis in rats. Rats were fed a control, high-fat (HF), high-fat high-iron (HFHI) and high-iron (HI) diet for 30 weeks. Blood biochemical, histopathological and gut microbiota analyses were performed. Rats in HF and HFHI groups showed an ALT-dominant elevation of serum transaminases, hepatic steatosis, hepatic inflammation, and upregulation of proinflammatory cytokines. The number of large inflammatory foci, corresponding to lobular inflammation in NASH patients, was significantly higher in HFHI than in HF group; within the lesion, macrophages with intense iron staining were observed. Hepatic expression of TNFα was higher in HFHI than that in HF group. There was no significant change in hepatic oxidative stress, gut microbiota or serum endotoxin levels between HF and HFHI groups. These results suggested that dietary iron supplementation enhances experimental steatohepatitis induced by long-term high-fat diet feeding in rats. Iron-laden macrophages can play an important role in the enhancement of hepatic inflammation.

Root bark of Ulmus davidiana var. japonica restrains acute alcohol-induced hepatic steatosis onset in mice by inhibiting ROS accumulation

Alcohol-induced hepatic steatosis and inflammation are key drivers of alcohol-induced liver injury, mainly caused by oxidative stress. The roots bark of Ulmus davidiana var. japonica is well known for its substantial antioxidative and antitumorigenic potency. In this study, we examined whether this plant can ameliorate alcohol-induced liver injuries characterized by hepatic steatosis and inflammation through its antioxidative activity. C57BL/6J mice were treated with the root bark extract of Ulmus davidiana var. japonica (RUE; 100 mg of extract/kg bodyweight; oral gavage) and alcohol (1 g/kg of bodyweight; oral gavage) for 5 days. Markers of acute alcohol-induced hepatic steatosis were determined and putative molecular mechanisms responsible for the protection of RUE were investigated. RUE noticeably protected against alcohol-induced hepatic steatosis and inflammation. Reactive oxygen species (ROS), over-produced by alcohol, negatively orchestrated various signaling pathways involved in the lipid metabolism and inflammation. These pathways were restored through the ROS scavenging activity of RUE in the liver. In particular, the expression of lipogenic genes (e.g., SREBP-1, ACC, and FAS) and inflammatory cytokines (e.g., IL-1β, and NF-κB p65) significantly decreased with RUE treatment. Conversely, the expression of fatty acid oxidation-related genes (e.g., SIRT1, AMPKα, and PGC1α) were increased in mice treated with RUE. Thus, the results indicate that RUE counteracts and thus attenuates alcoholic hepatic steatosis onset in mice, possibly by suppressing ROS-mediated steatosis and inflammation.

Leishmania and its quest for iron: An update and overview

Parasites of genus Leishmania are the causative agents of complex neglected diseases called leishmaniasis and continue to be a significant health concern globally. Iron is a vital nutritional requirement for virtually all organisms, including pathogenic trypanosomatid parasites, and plays a crucial role in many facets of cellular metabolism as a cofactor of several enzymes. Iron acquisition is essential for the survival of parasites. Yet parasites are also vulnerable to the toxicity of iron and reactive oxygen species. The aim of this review is to provide an update on the current knowledge about iron acquisition and usage by Leishmania species. We have also discussed about host strategy to modulate iron availability and the strategies deployed by Leishmania parasites to overcome iron withholding defences and thus favour parasite growth within host macrophages. Since iron plays central roles in the host's response and parasite metabolism, a comprehensive understanding of the iron metabolism is beneficial to identify potential viable therapeutic opportunities against leishmaniasis.

Early-Phase Alcoholic Liver Disease: An Update on Animal Models, Pathology, and Pathogenesis

Alcoholic liver disease (ALD) remains to be one of the most common etiology of liver disease and is a major cause of morbidity and mortality worldwide. The pathologic stages of ALD comprises of steatosis, steatohepatitis, and fibrosis/cirrhosis. Steatosis and steatohepatitis represents the early phase of ALD and are precursor stages for fibrosis/cirrhosis. Numerous research efforts have been directed at recognizing cofactors interacting with alcohol in the pathogenesis of steatosis and steatohepatitis. This review will elucidate the constellation of complex pathogenesis, available animal models, and microscopic pathologic findings mostly in the early-phase of ALD. The role of endotoxin, reactive oxygen species, alcohol metabolism, and cytokines are discussed. Understanding the mechanisms of early-phase ALD should provide insight into the development of therapeutic strategies and thereby decrease the morbidity and mortality associated with ALD.

Role of Transcription Factors in Steatohepatitis and Hypertension after Ethanol: The Epicenter of Metabolism

Chronic alcohol consumption induces multi-organ damage, including alcoholic liver disease (ALD), pancreatitis and hypertension. Ethanol and ethanol metabolic products play a significant role in the manifestation of its toxicity. Ethanol metabolizes to acetaldehyde and produces reduced nicotinamide adenine dinucleotide (NADH) by cytosolic alcohol dehydrogenase. Ethanol metabolism mediated by cytochrome-P450 2E1 causes oxidative stress due to increased production of reactive oxygen species (ROS). Acetaldehyde, increased redox cellular state and ROS activate transcription factors, which in turn activate genes for lipid biosynthesis and offer protection of hepatocytes from alcohol toxicity. Sterol regulatory element binding proteins (SREBPs) and peroxisome proliferator activated-receptors (PPARs) are two key lipogenic transcription factors implicated in the development of fatty liver in alcoholic and non-alcoholic steatohepatitis. SREBP-1 is activated in the livers of chronic ethanol abusers. An increase in ROS activates nuclear factor erythroid-2-related factor-2 (Nrf2) and hypoxia inducible factor (HIF) to provide protection to hepatocytes from ethanol toxicity. Under ethanol exposure, due to increased gut permeability, there is release of gram-negative bacteria-derived lipopolysaccharide (LPS) from intestine causing activation of immune response. In addition, the metabolic product, acetaldehyde, modifies the proteins in hepatocyte, which become antigens inviting auto-immune response. LPS activates macrophages, especially the liver resident macrophages, Kupffer cells. These Kupffer cells and circulating macrophages secrete various cytokines. The level of tumor necrosis factor-α (TNFα), interleukin-1beta (IL-1β), IL-6, IL-8 and IL-12 have been found elevated among chronic alcoholics. In addition to elevation of these cytokines, the peripheral iron (Fe(2+)) is also mobilized. An increased level of hepatic iron has been observed among alcoholics. Increased ROS, IL-1β, acetaldehyde, and increased hepatic iron, all activate nuclear factor-kappa B (NF-κB) transcription factor. Resolution of increased reactive oxygen species requires increased expression of genes responsible for dismutation of increased ROS which is partially achieved by IL-6 mediated activation of signal transducers and activators of transcription 3 (STAT3). In addition to these transcription factors, activator protein-1 may also be activated in hepatocytes due to its association with resolution of increased ROS. These transcription factors are central to alcohol-mediated hepatotoxicity.

Iron primes 3T3-L1 adipocytes to a TLR4-mediated inflammatory response

OBJECTIVE

Iron participates in several mechanisms involving inflammation and innate immunity, yet the dysregulation of its homeostasis is a major cause of metabolic syndrome. Adipocytes should play a major role in iron metabolism, as an impairment in iron turnover is closely related to insulin resistance, obesity, and type 2 diabetes. The aim of this study was to investigate the role of iron in an in vitro-inflamed adipocyte model.

METHODS

Gene expression of tumor necrosis factor-α, interleukin-6, inflammatory chemokines (CCL3, CCL4, and CXCL12), and molecules involved in iron metabolism were evaluated in an in vitro mouse 3T3-L1 cell model. Cells underwent treatment with FeSO4 heptahydrate and lipopolysaccharide (LPS) stimulation. Toll-like receptor 4 (TLR4) membrane expression, lipid droplet immunohystochemistry, and lipolysis were also evaluated.

RESULTS

Iron sulphate heptahydrate elicited gene expression of hepcidin, hemojuvelin, and ferroportin at different time courses. Additionally, it activated lipolysis but did not trigger any adipokine gene expression. When cells treated with physiological doses of iron were also stimulated with LPS, an enhancement in the LPS-induced gene expression of cytokines and chemokines was observed. The enhancement occurred with different patterns depending on different time courses and investigated genes, showing its maximal effect for IL-6 gene expression.

CONCLUSIONS

FeSO4 heptahydrate at a relatively physiological dose, induced gene expression of iron modulatory proteins and also enhanced RNA transcripts of several inflammatory cytokines and chemokines through a priming/synergistic mechanism involving membrane TLR4.

The utility of iron chelators in the management of inflammatory disorders

Since iron can contribute to detrimental radical generating processes through the Fenton and Haber-Weiss reactions, it seems to be a reasonable approach to modulate iron-related pathways in inflammation. In the human organism a counterregulatory reduction in iron availability is observed during inflammatory diseases. Under pathological conditions with reduced or increased baseline iron levels different consequences regarding protection or susceptibility to inflammation have to be considered. Given the role of iron in development of inflammatory diseases, pharmaceutical agents targeting this pathway promise to improve the clinical outcome. The objective of this review is to highlight the mechanisms of iron regulation and iron chelation, and to demonstrate the potential impact of this strategy in the management of several acute and chronic inflammatory diseases, including cancer.

Iron overload-modulated nuclear factor kappa-B activation in human endometrial stromal cells as a mechanism postulated in endometriosis pathogenesis

OBJECTIVE

To evaluate the effect of iron overload on nuclear factor kappa-B (NF-κB) activation in human endometrial stromal cells (ESCs).

DESIGN

Experimental study.

SETTING

University hospital research laboratory.

PATIENT(S)

Ten healthy women.

INTERVENTION(S)

Isolated ESCs from endometrial biopsies were incubated with 50 μM FeSO(4) or vehicle. The NF-κB inhibitor [5-(p-fluorophenyl)-2-ureido] thiophene-3-carboxamide (TPCA-1), which inhibits IKKβ, the kinase of IκBα (inhibitory protein of NF-κB), was used to prevent iron overload-stimulated NF-κB changes in ESCs.

MAIN OUTCOME MEASURE(S)

NF-κB activation was assessed by p65:DNA-binding activity immunodetection assay. IκBα, p65, and intercellular adhesion molecule (ICAM)-1 proteins expression was evaluated by Western blots. ESC soluble ICAM (sICAM)-1 secretion was measured by ELISA using conditioned medium.

RESULT(S)

Iron overload increased p65:DNA-binding activity and decreased IκBα and p65 cytoplasmic expression in ESCs after 30 minutes of incubation as compared with the basal condition. ESC ICAM-1 expression and sICAM-1 secretion were higher after 24 hours of iron overload treatment than in the absence of treatment. TPCA-1 prevented the iron overload-induced increase of p65:DNA binding and IκBα degradation.

CONCLUSION(S)

Iron overload activates IKKβ in ESCs, stimulating the NF-κB pathway and increasing ICAM-1 expression and sICAM-1 secretion. These results suggest that iron overload induces a proendometriotic phenotype on healthy ESCs, which could participate in endometriosis pathogenesis and development.

The common marmoset as a model for the study of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome. The more clinically concerning form of the disease, nonalcoholic steatohepatitis (NASH), is characterized by steatosis, lobular inflammation, and ballooning degeneration. Here we describe a naturally occurring syndrome in the common marmoset that recapitulates the pathologic findings associated with NAFLD/NASH in humans. Hepatomegaly determined to result from NAFLD was observed in 33 of 183 marmosets. A comprehensive histopathologic assessment performed in 31 marmosets demonstrated that NAFLD was characterized by variably sized, Oil Red O staining cytoplasmic vacuoles and observed primarily in animals with evidence of obesity and insulin resistance. A subset of marmosets (16 of 31) also demonstrated evidence of NASH characterized by multifocal inflammation combined with ballooning hepatocellular degeneration. Marmosets with NASH demonstrated an increase in immunostaining with an antibody targeted against the human leukocyte antigens (HLA)-DP, HLA-DQ, and HLA-DR compared with marmosets without NASH (38.89 cells/10× field vs 12.05 cells/10× field, P = .05). In addition, marmosets with NASH demonstrated increased Ki-67 immunopositive cellular proliferation compared with those without (5.95 cells/10× field vs 1.53 cells/10× field, P = .0002). Finally, animals with NASH demonstrated significantly increased mean circulating serum iron levels (160.47 μg/dl, P = .008) and an increase in numbers of Prussian blue-positive Kupffer cells (9.28 cells/40× field, P = .005) relative to marmosets without NASH (97.75 μg/dl and 1.87 cells/40×, respectively). This study further characterizes the histopathology of NAFLD/NASH and suggests that the marmoset may be a valuable animal model with which to investigate the host and environmental factors contributing to the progression of NAFLD/ NASH.

Sex-specific differences in the development of acute alcohol-induced liver steatosis in mice

AIMS

Results of several animal studies suggest that similar to humans, female rodents are more susceptible to chronic alcohol-induced liver disease (ALD). The aim of the present study was to determine whether female mice are more susceptible to acute alcohol-induced steatosis than male mice and to investigate possible mechanisms involved.

METHODS

Male and female C57BL/6J mice received one single dose of ethanol (6 g/kg bodyweight) or isocaloric maltose-dextrin solution intragastrically. Plasma alcohol concentration, markers of hepatic steatosis, activation of the TLR-4 signaling cascade and triglyceride export as well as lipid peroxidation and of iron metabolism were measured 12 h after acute alcohol intake.

RESULTS

In male and female ethanol-treated mice, plasma alcohol concentrations were still markedly increased 12 h after the alcohol challenge, which was associated with a significant accumulation of lipids in the liver and increase of transaminases in plasma; however, lipid accumulation was ∼3-fold higher in females in comparison with male animals. Expression of MyD88 was only found to be significantly induced in livers of female alcohol-exposed mice, whereas protein levels of ApoB were found to be significantly lower only in livers of female mice exposed to ethanol. Levels of 4-HNE protein adducts and ferritin were induced in livers of male and female ethanol-treated mice.

CONCLUSION

Taken together, these data suggest that female mice are also more susceptible to acute alcohol-induced liver steatosis and that this involves an increased activation of TLR-4-dependent signaling pathways in the liver.

Non-alcoholic steatohepatitis in morbidly obese patients

The hepatic complications of morbid obesity range from steatosis to steatohepatitis (Non-alcoholic steatohepatitis [NASH]), fibrosis, cirrhosis and finally hepatocellular carcinoma. The pathophysiological mechanisms of the progression of a normal liver to a liver showing steatosis and then steatohepatitis are complex, including, per se, insulin-resistance, iron accumulation, oxidative stress and hepatocyte death. An imbalance in anti- and pro-inflammatory factors may be the trigger. These factors can originate from intra- or extrahepatic sites, particularly the adipose tissue and the gut. This review will provide insight into the current diagnosis and understanding of hepatic inflammation including non-invasive markers of NASH (markers of hepatocyte death), intrahepatic mechanisms (regulation of the immune and inflammatory response, hepatocellular iron deposition, hepatocyte death) and extrahepatic factors (from adipose tissue and gut) in morbidly obese patients.

Liver hepcidin mRNA expression is inappropriately low in alcoholic patients compared with healthy controls

BACKGROUND AND AIMS

Hepcidin plays a crucial role in iron metabolism, preventing its absorption at the basolateral enterocyte membrane. Hepcidin regulation is complex and regulated at the transcriptional level. The relation between iron overload and alcoholic liver disease is well known, but its mechanism is not clear. We present an observational, case-control study, aimed at evaluating the effects of alcohol on the expression of hepcidin in human participants. We intended to assess whether iron overload related to alcohol ingestion was caused by hepcidin-impaired expression by determining hepcidin mRNA expression and relating it to iron stores, both in alcoholic patients and in normal controls.

METHODS

We compared liver hepcidin mRNA expression between 25 active drinkers with alcoholic liver disease, without cirrhosis, and 20 healthy controls. All individuals were evaluated for HFE mutations, complete blood count, coagulation, glucose, kidney function, liver function, viral hepatitis, C-reactive protein, interleukin 6, tumor necrosis factor α, and serum iron, ferritin, and transferrin saturation. Total RNA was isolated from liver samples, cDNA was obtained by reverse transcription, and hepatic expression levels of hepcidin were determined by real-time PCR using the comparative Ct method (2(-ΔΔCt)).

RESULTS

Serum ferritin and transferrin saturation were significantly higher in patients. Hepcidin was downregulated in patients compared with the controls by a mean factor of -0.44 (log10 2(-ΔΔCt)) (P=0.009). Hepcidin expression was not significantly different between the several grades of fibrosis, necroinflammatory activity, and liver iron stores. Heavy alcohol consumption caused the highest hepcidin mRNA suppression. The hepcidin mRNA expression/serum ferritin ratio was significantly lower in alcoholic patients (P<0.0001).

CONCLUSION

Hepcidin liver expression is inappropriately low in alcoholic patients with active alcoholism and preserved hepatic function, and we conclude that this is the mechanism for alcohol consumption-associated iron overload in humans.

Accelerated proliferation of hepatocytes in rats with iron overload after partial hepatectomy

Although iron overload is implicated in hepatocarcinogenesis, the precise mechanism was not known yet. In the present study, we investigated the effect of iron overload upon the induction of hepatocyte proliferation after 70% partial hepatectomy (PH) in rats fed with rat chow with 3% carbonyl iron for 3 months. In normal-diet rats, the increase in Ki-67 labeling index (LI) commenced at 24 h post-PH and the LIs of proliferating cell nuclear antigen (PCNA) incorporated 5-bromo-2'-deoxyuridine (BrdU) and phospho-histone H3 reached maximum values at 36 and 48 h after PH, respectively. In iron-overload rats, the above parameters occurred 12 h earlier compared to that of normal-diet rats, shortening the G0-G1 transition. Interestingly, nuclear staining for metallothionein (MT), which is essential for hepatocyte proliferation, was noted even at 0 h in iron-overload rats, while MT expression occurred at 6 h in the normal rats. Moreover, nuclear factor kappa B (NF-κB) expression, which is an essential early event leading to liver regeneration, was detected in Kupffer cells at 0 h in iron-overload rats. These results may indicate that overloaded iron, maybe through the induction of MT and NF-κB, may keep liver as a state ready to regenerate in response to PH, by bypassing signal transduction cascades involved in the initiation of liver regeneration.

Iron metabolism in Nonalcoholic Fatty Liver Disease

Non-Alcoholic Fatty Liver Disease (NAFLD) is a common worldwide clinical and major public health problem affecting both adults and children in developed nations. Increased hepatic iron stores are observed in about one-third of adult NAFLD patients. Iron deposition may occur in parenchymal and/or non-parenchymal cells of the reticuloendothelial system (RES). Similar patterns of iron deposition have been associated with increased severity of other chronic liver diseases including HCV infection and dysmetabolic iron overload, suggesting there may be a common mechanism for hepatic iron deposition in these diseases. In NAFLD, iron may potentiate the onset and progression of disease by increasing oxidative stress and altering insulin signaling and lipid metabolism. The impact of iron in these processes may depend upon the sub-cellular location of iron deposition in hepatocytes or RES cells. Iron depletion therapy has shown efficacy at reducing serum aminotransferase levels and improving insulin sensitivity in subjects with NAFLD.

Accelerated CCl4-induced liver fibrosis in Hjv-/- mice, associated with an oxidative burst and precocious profibrogenic gene expression

Hereditary hemochromatosis is commonly associated with liver fibrosis. Likewise, hepatic iron overload secondary to chronic liver diseases aggravates liver injury. To uncover underlying molecular mechanisms, hemochromatotic hemojuvelin knockout (Hjv-/-) mice and wild type (wt) controls were intoxicated with CCl(4). Hjv-/- mice developed earlier (by 2-4 weeks) and more acute liver damage, reflected in dramatic levels of serum transaminases and ferritin and the development of severe coagulative necrosis and fibrosis. These responses were associated with an oxidative burst and early upregulation of mRNAs encoding α1-(I)-collagen, the profibrogenic cytokines TGF-β1, endothelin-1 and PDGF and, notably, the iron-regulatory hormone hepcidin. Hence, CCl4-induced liver fibrogenesis was exacerbated and progressed precociously in Hjv-/- animals. Even though livers of naïve Hjv-/- mice were devoid of apparent pathology, they exhibited oxidative stress and immunoreactivity towards α-SMA antibodies, a marker of hepatic stellate cells activation. Furthermore, they expressed significantly higher (2-3 fold vs. wt, p<0.05) levels of α1-(I)-collagen, TGF-β1, endothelin-1 and PDGF mRNAs, indicative of early fibrogenesis. Our data suggest that hepatic iron overload in parenchymal cells promotes oxidative stress and triggers premature profibrogenic gene expression, contributing to accelerated onset and precipitous progression of liver fibrogenesis.

Copper chelation by tetrathiomolybdate inhibits lipopolysaccharide-induced inflammatory responses in vivo

Redox-active transition metal ions, such as iron and copper, may play an important role in vascular inflammation, which is an etiologic factor in atherosclerotic vascular diseases. In this study, we investigated whether tetrathiomolybdate (TTM), a highly specific copper chelator, can act as an anti-inflammatory agent, preventing lipopolysaccharide (LPS)-induced inflammatory responses in vivo. Female C57BL/6N mice were daily gavaged with TTM (30 mg/kg body wt) or vehicle control. After 3 wk, animals were injected intraperitoneally with 50 μg LPS or saline buffer and killed 3 h later. Treatment with TTM reduced serum ceruloplasmin activity by 43%, a surrogate marker of bioavailable copper, in the absence of detectable hepatotoxicity. The concentrations of both copper and molybdenum increased in various tissues, whereas the copper-to-molybdenum ratio decreased, consistent with reduced copper bioavailability. TTM treatment did not have a significant effect on superoxide dismutase activity in heart and liver. Furthermore, TTM significantly inhibited LPS-induced inflammatory gene transcription in aorta and heart, including vascular and intercellular adhesion molecule-1 (VCAM-1 and ICAM-1, respectively), monocyte chemotactic protein-1 (MCP-1), interleukin-6, and tumor necrosis factor (TNF)-α (ANOVA, P < 0.05); consistently, protein levels of VCAM-1, ICAM-1, and MCP-1 in heart were also significantly lower in TTM-treated animals. Similar inhibitory effects of TTM were observed on activation of nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) in heart and lungs. Finally, TTM significantly inhibited LPS-induced increases of serum levels of soluble ICAM-1, MCP-1, and TNF-α (ANOVA, P < 0.05). These data indicate that copper chelation with TTM inhibits LPS-induced inflammatory responses in aorta and other tissues of mice, most likely by inhibiting activation of the redox-sensitive transcription factors, NF-κB and AP-1. Therefore, copper appears to play an important role in vascular inflammation, and TTM may have value as an anti-inflammatory or anti-atherogenic agent.

Relationship between the pattern of hepatic iron deposition and histological severity in nonalcoholic fatty liver disease

Previous studies examining the relationship between hepatic iron deposition and histological severity in nonalcoholic fatty liver disease (NAFLD) have been inconclusive. The goal of this study was to examine the relationship between hepatic iron deposition and liver histology in 849 patients enrolled in the Nonalcoholic Steatohepatitis Clinical Research Network. Hepatic iron staining was performed in a central laboratory, and the stains were scored for grade and cellular and parenchymal localization by a central pathology committee; the relationship between the grade and pattern of iron deposition and the clinical, laboratory, and histological variables was examined with univariate and multivariate analyses. Stainable hepatic iron was present in 293 of 849 patients (34.5%) in one of three histological patterns: a hepatocellular (HC) pattern [63/849 (7.4%)], a reticuloendothelial system (RES) cell pattern [91/849 (10.7%)], or a mixed RES/HC pattern [139/849 (16.4%)]. Patients with the RES iron-staining pattern were more likely to have advanced fibrosis compared to those with those with HC iron (P = 0.01). Patients with RES iron were also more likely to have advanced histological features such as fibrosis (P = 0.049), portal inflammation (P = 0.002), HC ballooning (P = 0.006), and definite nonalcoholic steatohepatitis (P = 0.007) compared to those with patients with HC or mixed iron patterns. The presence of RES iron (odds ratio = 1.60, 95% confidence interval = 1.10-2.33, P = 0.015) was independently associated with advanced hepatic fibrosis on multiple regression analysis after adjustments for age, gender, diabetes status, and body mass index.

CONCLUSION

The presence and pattern of hepatic iron deposition are associated with distinct histological features in patients with NAFLD and may have implications for pathophysiology and therapy.

Taraxacum officinale Weber extracts inhibit LPS-induced oxidative stress and nitric oxide production via the NF-κB modulation in RAW 264.7 cells

ETHNOPHARMACOLOGICAL RELEVANCE

The common dandelion (Taraxacum officinale G.H. Weber ex Wiggers, Asteraceae) has been widely used in folklore medicine to treat dyspepsia, heartburn, and spleen and liver disorders.

AIM OF THE STUDY

To compare the antioxidative and anti-inflammatory activities of Taraxacum officinale methanol extract (TOME) and water extract (TOWE) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and assess their constitutional differences, including luteolin, chicoric acid, and total phenol content.

MATERIALS AND METHODS

Antioxidative enzyme activities, nitric oxide (NO) production, and inducible NO synthase (iNOS) and nuclear factor (NF)-κB expression were estimated by biochemical analysis, the Griess reaction, reverse transcription-polymerase chain reaction, western hybridization, and electrophoretic mobility shift assay. High-performance liquid chromatography and the Folin-Ciocalteau method were used to analyze functional phytochemicals and total phenol content.

RESULTS

TOME and TOWE significantly reduced NO production with an IC(50) of 79.9 and 157.5 μg/mL, respectively, without cytotoxicity. Depleted glutathione (GSH) and antioxidative enzyme activities, including superoxide dismutase, catalase, GSH-peroxidase, and GSH-reductase, were restored by dandelion extracts. Both extracts inhibited LPS-stimulated iNOS gene expression and that of its transcription factor, NF-κB, in parallel with nitrite reduction. TOME showed more potent antioxidative and anti-inflammatory capacities than TOWE, which was attributable to its high total phenol, luteolin, and chicoric acid content.

CONCLUSIONS

These results indicate that TOME and TOWE inhibit oxidative stress and inflammatory responses through elevated de novo synthesis of antioxidative enzymes and suppression of iNOS expression by NF-κB inactivation.

Severe iron deficiency blunts the response of the iron regulatory gene Hamp and pro-inflammatory cytokines to lipopolysaccharide

BACKGROUND

Expression of the key iron regulatory hormone hepcidin is increased by some stimuli (iron loading, inflammation) but decreased by others (increased erythropoiesis, iron deficiency). We investigated the response of hepcidin to increased erythropoiesis and iron deficiency in the presence of an acute inflammation to assess the relative strengths of these stimuli.

DESIGN AND METHODS

Sprague-Dawley rats were maintained on control or iron-deficient diets and treated with lipopolysaccharide to induce inflammation or phenylhydrazine to stimulate erythropoiesis. The levels of Hamp, IL-6 and α2m mRNA were determined by qualitative real-time polymerase chain reaction and those of serum interleukin-6 and tumor necrosis factor-α were measured by enzyme-linked immunosorbent assay. Cultured RAW264.7 and HuH7 cells were used in associated studies.

RESULTS

The increase in hepatic hepcidin levels induced by lipopolysaccharide was not affected by phenylhydrazine treatment but was blunted by iron deficiency. Lipopolysaccharide-treated iron-deficient animals also showed lower liver α2m mRNA and reduced serum interleukin-6 and tumor necrosis factor-α, suggesting a more generalized effect of iron deficiency. Similarly, RAW 264.7 cells treated with iron chelators and then stimulated with lipopolysaccharide showed lower IL-6 mRNA than cells treated with lipopolysaccharide alone. Huh7 cells treated with an iron chelator showed a blunted hepcidin response to interleukin-6, suggesting that the response of hepatic parenchymal cells to inflammatory cytokines may also be iron-dependent.

CONCLUSIONS

In any one physiological situation, net hepcidin levels are determined by the relative strengths of competing stimuli. The ability of severe iron deficiency to blunt the response to lipopolysaccharide of both hepcidin and other markers of inflammation suggests that adequate iron levels are necessary for a full acute phase response.

Redox regulation of tumor necrosis factor signaling

Tumor necrosis factor-alpha (TNF) is a key cytokine that has been shown to play important physiologic (e.g., inflammation) and pathophysiologic (e.g., various liver pathologies) roles. In liver and other tissues, TNF treatment results in the simultaneous activation of an apoptotic pathway (i.e., TRADD, RIP, JNK) and a survival pathway mediated by NF-kappaB transcription of survival genes (i.e., GADD45beta, Mn-SOD, cFLIP). The cellular response (e.g., proliferation versus apoptosis) to TNF is determined by the balance between the apoptotic signaling pathway and the NF-kappaB survival pathway stimulated by TNF. Reactive oxygen species (ROS) are important modulators of signaling pathways and can regulate both apoptotic signaling and NF-kappaB transcription triggered by TNF. ROS are important in mediating the sustained activation of JNK, to help mediate apoptosis after TNF treatment. In some cells, ROS are second messengers that mediate apoptosis after TNF stimulation. Conversely, ROS can cause redox modifications that inhibit NF-kappaB activation, which can lead to cell death triggered by TNF. Consequently, the redox status of cells can determine the biologic response that TNF will induce in cells. In many liver pathologies, ROS generated extrinsically (e.g., inflammation) or intrinsically (i.e., drugs, toxins) may act in concert with TNF to promote hepatocyte death and liver injury through redox inhibition of NF-kappaB.

Hepcidin is down-regulated in alcohol loading

BACKGROUND

It is common for alcoholic patients to have excess iron accumulation in the liver, which may contribute to the development of alcoholic liver disease (ALD). However, the mechanism of hepatic iron uptake in ALD is still obscure. Recently, a novel iron-regulatory hormone hepcidin was found that suppresses the absorption of iron from the small intestine and the release of iron from macrophages. To elucidate the contribution of hepcidin toward the hepatic excess iron accumulation in ALD, we examined whether alcohol loading affects hepcidin expression both in ALD patients and in an ethanol-fed mouse model.

METHODS

Serum prohepcidin concentration was quantified by enzyme-linked immunosorbent assay. Hepatic hepcidin-1 and hepcidin-2 mRNA expressions in mouse liver were evaluated by quantitative real-time reverse-transcriptase polymerase chain reaction method. The protein expression of prohepcidin in mouse liver was examined immunohistochemically by rabbit antimouse prohepcidin antibody.

RESULTS

Serum prohepcidin concentration in ALD was significantly lower than that in healthy subjects (p<0.001). Especially, serum prohepcidin concentrations were decreased in the patients whose serum ferritin value was high. In the ethanol-fed mouse model, hepatic hepcidin-1 mRNA expression was significantly lower than that in control (p=0.04). Prohepcidin was expressed in the cytoplasm of hepatocytes of mice liver tissue sections, and its expression was decreased after ethanol loading.

CONCLUSION

Alcohol loading down-regulates hepatic hepcidin expression and leads to the increase of iron absorption from the intestine.

Protein kinase C-zeta (PKC-zeta) regulates Kupffer cell apoptosis during experimental sepsis

BACKGROUND

Kupffer cells play an important role in sepsis-mediated liver injury. We tested the hypothesis that PKC-zeta plays a critical role in Kupffer cell apoptosis during sepsis.

METHODS

Sepsis was induced in rats by cecal ligation and puncture (CLP); 12 h later, livers were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation. Kupffer cells from control rats were infected with AdPKC-zeta DN to inhibit PKC-zeta, or transfected with pCMVPKC-zeta to overexpress PKC-zeta, and then treated with lipopolysaccharide (LPS). Cellular extracts were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation.

RESULTS

During sepsis, PKC-zeta localized in cells positive for the macrophage marker (F4/80). CLP upregulated PKC-zeta protein and activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and increased DNA fragmentation in rat livers (all p<0.001). AdPKC-zeta DN attenuated the LPS-induced upregulation of PKC-zeta activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation in Kupffer cells (all p<0.001), whereas overexpression of PKC-zeta augmented LPS-induced upregulation of IKKbeta, IKKgamma, NF-kappaB, Caspase-3, and DNA fragmentation (p<0.001).

CONCLUSION

PKC-zeta plays an important role in sepsis-induced apoptosis of Kupffer cells via activation of NF-kappaB and Fas/FasL. Manipulating the response of Kupffer cells to cellular stress may have important therapeutic implications.

Role of alcohol in the regulation of iron metabolism

Patients with alcoholic liver disease frequently exhibit increased body iron stores, as reflected by elevated serum iron indices (transferrin saturation, ferritin) and hepatic iron concentration. Even mild to moderate alcohol consumption has been shown to increase the prevalence of iron overload. Moreover, increased hepatic iron content is associated with greater mortality from alcoholic cirrhosis, suggesting a pathogenic role for iron in alcoholic liver disease. Alcohol increases the severity of disease in patients with genetic hemochromatosis, an iron overload disorder common in the Caucasian population. Both iron and alcohol individually cause oxidative stress and lipid peroxidation, which culminates in liver injury. Despite these observations, the underlying mechanisms of iron accumulation and the source of the excess iron observed in alcoholic liver disease remain unclear. Over the last decade, several novel iron-regulatory proteins have been identified and these have greatly enhanced our understanding of iron metabolism. For example, hepcidin, a circulatory antimicrobial peptide synthesized by the hepatocytes of the liver is now known to play a central role in the regulation of iron homeostasis. This review attempts to describe the interaction of alcohol and iron-regulatory molecules. Understanding these molecular mechanisms is of considerable clinical importance because both alcoholic liver disease and genetic hemochromatosis are common diseases, in which alcohol and iron appear to act synergistically to cause liver injury.

Protein kinase C-zeta is critical in pancreatitis-induced apoptosis of Kupffer cells

Protein kinase C-zeta (PKC-zeta) regulates cell death via NF-kappaB; therefore, we tested the hypothesis that PKC-zeta plays a critical role in pancreatitis-induced Kupffer cell apoptosis. Acute pancreatitis was induced in rats by cerulein injection 24 h later, livers were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, and apoptosis was assessed with Caspase-3 and DNA fragmentation. Kupffer cells from unoperated rats were infected with a PKC-zeta domain-negative adenovirus (AdPKCzeta-DN) to inhibit PKC-zeta, or transfected with pCMVPKC-zeta to overexpress PKC-zeta, and then stimulated with pancreatic elastase; cellular extracts were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation. Cerulein-induced pancreatitis upregulated PKC-zeta protein and activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3 and increased DNA fragmentation in rat livers (all p < 0.001 vs control). AdPKCzeta-DN abolished elastase-induced upregulation of PKC-zeta activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3 and DNA fragmentation (all p < 0.001 vs infection control), whereas overexpression of PKC-zeta augmented elastase-induced upregulation of IKKbeta, IKKgamma, Fas/FasL, Caspase-3 and DNA fragmentation (p < 0.001 vs control). PKC-zeta plays a critical role in pancreatitis-induced Kupffer cell apoptosis via NF-kappaB and Fas/FasL. The ability of Kupffer cells to autoregulate their stress response by upregulating their death receptor/ligand and key proapoptotic cell signaling systems warrants further investigation.

Iron overload and cofactors with special reference to alcohol, hepatitis C virus infection and steatosis/insulin resistance

There are several cofactors which affect body iron metabolism and accelerate iron overload. Alcohol and hepatic viral infections are the most typical examples for clarifying the role of cofactors in iron overload. In these conditions, iron is deposited in hepatocytes and Kupffer cells and reactive oxygen species (ROS) produced through Fenton reaction have key role to facilitate cellular uptake of transferrin-bound iron. Furthermore, hepcidin, antimicrobial peptide produced mainly in the liver is also responsible for intestinal iron absorption and reticuloendothelial iron release. In patients with ceruloplasmin deficiency, anemia and secondary iron overload in liver and neurodegeneration are reported. Furthermore, there is accumulating evidence that fatty acid accumulation without alcohol and obesity itself modifies iron overload states. Ineffective erythropoiesis is also an important factor to accelerate iron overload, which is associated with diseases such as thalassemia and myelodysplastic syndrome. When this condition persists, the dietary iron absorption is increased due to the increment of bone marrow erythropoiesis and tissue iron overload will thereafter occurs. In porphyria cutanea tarda, iron is secondarily accumulated in the liver.

Hepatic tumor necrosis factor signaling and nuclear factor-kappaB: effects on liver homeostasis and beyond

The proinflammatory cytokine TNF has a pivotal role in liver pathophysiology because it holds the capacity to induce both hepatocyte cell death and hepatocyte proliferation. This dual effect of TNF on hepatocytes reflects its ability to induce both nuclear factor kappaB (NF-kappaB)-dependent gene expression and cell death. Multiple studies have demonstrated the crucial role of the transcription factor NF-kappaB in the decision between life and death of a hepatocyte. Massive hepatocyte apoptosis preceding embryonic lethality in NF-kappaB-deficient mice constituted the first indication of an essential antiapoptotic function of NF-kappaB in the liver. Although many studies confirmed this crucial cytoprotective role of NF-kappaB in adult liver, a number of genetic studies recently obtained conflicting results on the exact role of NF-kappaB in different mouse models of TNF hepatotoxicity, demonstrating that caution should be taken when interpreting studies using different NF-kappaB-deficient mice in distinct models of liver injury. Recent reports showing a role for hepatic NF-kappaB activation in the proliferation of malignant cells during hepatocarcinogenesis, and in the progression of fatty liver diseases to insulin resistance and type 2 diabetes mellitus demonstrate that NF-kappaB can also have more detrimental effects in the liver. Moreover, its role in the development of the metabolic syndrome emphasizes that hepatic NF-kappaB activation might also have adverse effects on the endocrine system. Therefore, understanding the regulation of hepatic TNF signaling and NF-kappaB activation is of critical therapeutic importance. In this review, we summarize how studies on the role of NF-kappaB in different mouse models of liver pathologies have contributed to this understanding.

Effects of alcohol consumption on iron metabolism in mice with hemochromatosis mutations

BACKGROUND

Alcoholic liver disease is associated with increased hepatic iron accumulation. The liver-derived peptide hepcidin is the central regulator of iron homeostasis and recent animal studies have demonstrated that exposure to alcohol reduces hepcidin expression. This down-regulation of hepcidin in vivo implies that disturbed iron sensing may contribute to the hepatosiderosis seen in alcoholic liver disease. Alcohol intake is also a major factor in expression of the hemochromatosis phenotype in patients homozygous for the C282Y mutation of the HFE gene.

METHODS

To assess the effect of alcohol in mice with iron overload, alcohol was administered to mice with disrupted Hfe and IL-6 genes and Tfr2 mutant mice and their respective 129x1/SvJ, C57BL/6J, and AKR/J wild-type congenic strains. Iron absorption, serum iron levels, and hepcidin expression levels were then measured in these mice compared with water-treated control mice.

RESULTS

Alcohol was shown to have a strain-specific effect in 129x1/SvJ mice, with treated 129x1/SvJ mice showing a significant increase in iron absorption, serum iron levels, and a corresponding decrease in hepcidin expression. C57BL/6J and AKR/J strain mice showed no effect from alcohol treatment. 129x1/SvJ mice heterozygous or homozygous for the Hfe knockout had a diminished response to alcohol. All 3 strains were shown to have high blood alcohol levels.

CONCLUSIONS

The effect of alcohol on iron homeostasis is dependent on the genetic background in mice. In an alcohol-susceptible strain, mutation of the Hfe gene diminished the response of the measured iron indices to alcohol treatment. This indicates that either maximal suppression of hepcidin levels had already occurred as a result of the Hfe mutation or that Hfe was a component of the pathway utilized by EtOH in suppressing hepcidin production and increasing iron absorption.

Primary graft nonfunction and Kupffer cell activation after liver transplantation from non-heart-beating donors in pigs

More extensive use of non-heart-beating donors (NHBD) could reduce mortality on liver transplantation waiting lists, but this is associated with more primary nonfunction (PNF). We assessed which parameters are involved in the development of PNF in livers from NHBD in a previously validated pig liver transplantation model, in which livers were transplanted after exposure to incremental periods of warm ischemia. The risk of PNF was unacceptably high (>50%) when livers were exposed to >30 minutes' warm ischemia before a short cold ischemic period. This study examined how PNF is affected by Kupffer cell activation (beta-galactosidase), the generation of cytokines tumor necrosis factor alpha and interleukin 6, antioxidant mechanisms (ascorbic acid, alpha-tocopherol, reduced glutathione), circulating redox-active iron, and sinusoidal endothelial cell function (hyaluronic acid clearance). Kupffer cells were more activated in PNF recipients, as suggested by higher beta-galactosidase levels (15 minutes after reperfusion), and secondarily, by higher production of tumor necrosis factor alpha and interleukin 6 (180 minutes after reperfusion). In addition, alpha-tocopherol and reduced glutathione were lower, and ascorbic acid and redox-active iron higher in PNF recipients. Finally, PNF grafts displayed progressively decreasing hyaluronic acid clearance (suggesting sinusoidal endothelial cell dysfunction) and parenchymal edema. Consequently, a reduced-flow phenomenon was documented. In grafts from NHBD that are destined to fail, beta-galactosidase activity (a surrogate of Kupffer cell activation) is higher, proinflammatory cytokines are overproduced, some antioxidant mechanisms fail, and circulating redox-active iron is more rapidly released. A no-flow phenomenon is eventually observed in these failing grafts.

Chronic binge ethanol consumption accelerates progression of simian immunodeficiency virus disease

BACKGROUND

While alcohol consumption is known to increase the incidence and severity of infections, the impact of alcohol consumption on human immunodeficiency virus (HIV) disease progression has been difficult to assess. Therefore, we examined the effect of ethanol on simian immunodeficiency virus (SIV) disease progression in a well-defined model utilizing rhesus macaques.

METHODS

Alcohol was administered for 5 hours via an indwelling intragastric catheter to achieve an alcohol concentration of 50 to 60 mM for 4 consecutive days per week for the duration of the study. Control animals received isocaloric sucrose. After 3 months, animals were inoculated intravenously with 10,000 times the ID(50) of SIV(DeltaB670) and followed to end-stage disease.

RESULTS

Plasma SIV ribonucleic acid (RNA) was higher in alcohol-consuming animals compared with sucrose-treated animals during the early asymptomatic stage of disease but not at later time points. This increase in viral set point was associated with more rapid progression to end-stage disease in macaques administered alcohol (median=374 days) compared with sucrose (median=900 days). The decline in blood CD4+ cells was similar in both groups of animals.

CONCLUSIONS

This study indicates that frequent episodes of alcohol intoxication in SIV+ macaques increase viral set point in association with more rapid development of end-stage disease.