The Mallory body: morphological, clinical and experimental studies (Part 1 of a literature survey)

Monitoring physiological processes of fast-growing broilers during the whole life cycle: Changes of redox-homeostasis effected to trassulfuration pathway predicting the development of non-alcoholic fatty liver disease

In the broiler industry, the average daily gain and feed conversion ratio are extremely favorable, but the birds are beginning to approach the maximum of their genetic capacity. However, as a consequence of strong genetic selection, the occurrence of certain metabolic diseases, such as myopathies, ascites, sudden cardiac death and tibial dyschondroplasia, is increasing. These metabolic diseases can greatly affect the health status and welfare of birds, as well as the quality of meat. The main goal of this study was to investigate the changes in the main parameters of redox homeostasis during the rearing (1-42 days of age) of broilers with high genetic capacity, such as the concentrations of malondialdehyde, vitamin C, vitamin E, and reduced glutathione, the activities of glutathione peroxidase and glutathione reductase, and the inhibition rate of superoxide dismutase. Damage to the transsulfuration pathway during growth and the reason for changes in the level of homocysteine were investigated. Further, the parameters that can characterize the biochemical changes occurring in the birds were examined. Our study is the first characterize plasma albumin saturation. A method was developed to measure the levels of other small molecule thiol components of plasma. Changes in redox homeostasis induce increases in the concentrations of tumor necrosis factor alpha and inflammatory interleukins interleukin 2, interleukin 6 and interleukin 8 in broilers reared according to current large-scale husbandry technology and feeding protocols. A significant difference in all parameters tested was observed on the 21st day. The concentrations of cytokines and homocysteine increased, while the concentrations of glutathione and cysteine in the plasma decreased. Our findings suggest that observed changes in the abovementioned biochemical indices have a negative effect on poultry health.

Ethanol Exposure to Ethanol-Oxidizing HEPG2 Cells Induces Intracellular Protein Aggregation

Background: Aggresomes are collections of intracellular protein aggregates. In liver cells of patients with alcoholic hepatitis, aggresomes appear histologically as cellular inclusions known as Mallory–Denk (M–D) bodies. The proteasome is a multicatalytic intracellular protease that catalyzes the degradation of both normal (native) and abnormal (misfolded and/or damaged) proteins. The enzyme minimizes intracellular protein aggregate formation by rapidly degrading abnormal proteins before they form aggregates. When proteasome activity is blocked, either by specific inhibitors or by intracellular oxidants (e.g., peroxynitrite, acetaldehyde), aggresome formation is enhanced. Here, we sought to verify whether inhibition of proteasome activity by ethanol exposure enhances protein aggregate formation in VL-17A cells, which are recombinant, ethanol-oxidizing HepG2 cells that express both alcohol dehydrogenase (ADH) and cytochrome P450 2E1 (CYP2E1). Methods: We exposed ethanol-non-oxidizing HepG2 cells (ADH−/CYP2E1−) or ethanol-oxidizing VL-17A (ADH+/CYP2E1+) to varying levels of ethanol for 24 h or 72 h. After these treatments, we stained cells for aggresomes (detected microscopically) and quantified their numbers and sizes. We also conducted flow cytometric analyses to confirm our microscopic findings. Additionally, aggresome content in liver cells of patients with alcohol-induced hepatitis was quantified. Results: After we exposed VL-17A cells to increasing doses of ethanol for 24 h or 72 h, 20S proteasome activity declined in response to rising ethanol concentrations. After 24 h of ethanol exposure, aggresome numbers in VL-17A cells were 1.8-fold higher than their untreated controls at all ethanol concentrations employed. After 72 h of ethanol exposure, mean aggresome numbers were 2.5-fold higher than unexposed control cells. The mean aggregate size in all ethanol-exposed VL-17A cells was significantly higher than in unexposed control cells but was unaffected by the duration of ethanol exposure. Co-exposure of cells to EtOH and rapamycin, the latter an autophagy activator, completely prevented EtOH-induced aggresome formation. In the livers of patients with alcohol-induced hepatitis (AH), the staining intensity of aggresomes was 2.2-fold higher than in the livers of patients without alcohol use disorder (AUD). Conclusions: We conclude that ethanol-induced proteasome inhibition in ethanol-metabolizing VL-17A hepatoma cells causes accumulation of protein aggregates. Notably, autophagy activation removes such aggregates. The significance of these findings is discussed.

Identifying amyloid-related diseases by mapping mutations in low-complexity protein domains to pathologies

Proteins including FUS, hnRNPA2, and TDP-43 reversibly aggregate into amyloid-like fibrils through interactions of their low-complexity domains (LCDs). Mutations in LCDs can promote irreversible amyloid aggregation and disease. We introduce a computational approach to identify mutations in LCDs of disease-associated proteins predicted to increase propensity for amyloid aggregation. We identify several disease-related mutations in the intermediate filament protein keratin-8 (KRT8). Atomic structures of wild-type and mutant KRT8 segments confirm the transition to a pleated strand capable of amyloid formation. Biochemical analysis reveals KRT8 forms amyloid aggregates, and the identified mutations promote aggregation. Aggregated KRT8 is found in Mallory-Denk bodies, observed in hepatocytes of livers with alcoholic steatohepatitis (ASH). We demonstrate that ethanol promotes KRT8 aggregation, and KRT8 amyloids co-crystallize with alcohol. Lastly, KRT8 aggregation can be seeded by liver extract from people with ASH, consistent with the amyloid nature of KRT8 aggregates and the classification of ASH as an amyloid-related condition.

A Novel Mechanism for NF-κB-activation via IκB-aggregation: Implications for Hepatic Mallory-Denk-Body Induced Inflammation

Mallory-Denk-bodies (MDBs) are hepatic protein aggregates associated with inflammation both clinically and in MDB-inducing models. Similar protein aggregation in neurodegenerative diseases also triggers inflammation and NF-κB activation. However, the precise mechanism that links protein aggregation to NF-κB-activation and inflammatory response remains unclear. Herein we find that treating primary hepatocytes with MDB-inducing agents (N-methylprotoporphyrin (NMPP), protoporphyrin IX (PPIX), or Zinc-protoporphyrin IX (ZnPP)) elicited an IκBα-loss with consequent NF-κB activation. Four known mechanisms of IκBα-loss i.e. the canonical ubiquitin-dependent proteasomal degradation (UPD), autophagic-lysosomal degradation, calpain degradation and translational inhibition, were all probed and excluded. Immunofluorescence analyses of ZnPP-treated cells coupled with 8 M urea/CHAPS-extraction revealed that this IκBα-loss was due to its sequestration along with IκBβ into insoluble aggregates, thereby releasing NF-κB. Through affinity pulldown, proximity biotinylation by antibody recognition, and other proteomic analyses, we verified that NF-κB subunit p65, which stably interacts with IκBα under normal conditions, no longer binds to it upon ZnPP-treatment. Additionally, we identified 10 proteins that interact with IκBα under baseline conditions, aggregate upon ZnPP-treatment, and maintain the interaction with IκBα after ZnPP-treatment, either by cosequestering into insoluble aggregates or through a different mechanism. Of these 10 proteins, the nucleoporins Nup153 and Nup358/RanBP2 were identified through RNA-interference, as mediators of IκBα-nuclear import. The concurrent aggregation of IκBα, NUP153, and RanBP2 upon ZnPP-treatment, synergistically precluded the nuclear entry of IκBα and its consequent binding and termination of NF-κB activation. This novel mechanism may account for the protein aggregate-induced inflammation observed in liver diseases, thus identifying novel targets for therapeutic intervention. Because of inherent commonalities this MDB cell model is a bona fide protoporphyric model, making these findings equally relevant to the liver inflammation associated with clinical protoporphyria.

Glucocorticosteroids for people with alcoholic hepatitis

BACKGROUND

Alcoholic hepatitis is a form of alcoholic liver disease characterised by steatosis, necroinflammation, fibrosis, and complications to the liver. Typically, alcoholic hepatitis presents in people between 40 and 50 years of age. Alcoholic hepatitis can be resolved if people abstain from drinking, but the risk of death will depend on the severity of the liver damage and abstinence from alcohol. Glucocorticosteroids have been studied extensively in randomised clinical trials to assess their benefits and harms. However, the results have been contradictory.

OBJECTIVES

To assess the benefits and harms of glucocorticosteroids in people with alcoholic hepatitis.

SEARCH METHODS

We identified trials through electronic searches in Cochrane Hepato-Biliary's (CHB) Controlled Trials Register, CENTRAL, MEDLINE, Embase, LILACS, and Science Citation Index Expanded. We looked for ongoing or unpublished trials in clinical trials registers and pharmaceutical company sources. We also scanned reference lists of the studies retrieved. The last search was 18 January 2019.

SELECTION CRITERIA

Randomised clinical trials assessing glucocorticosteroids versus placebo or no intervention in people with alcoholic hepatitis, irrespective of year, language of publication, or format. We considered trials with adults diagnosed with alcoholic hepatitis, which could have been established through clinical or biochemical diagnostic criteria or both. We defined alcoholic hepatitis as mild (Maddrey's score less than 32) and severe (Maddrey's score 32 or more). We allowed cointerventions in the trial groups, provided they were similar.

DATA COLLECTION AND ANALYSIS

We followed Cochrane methodology, performing the meta-analyses using Review Manager 5. We presented the results of dichotomous outcomes as risk ratios (RR) and of continuous outcomes as mean difference (MD), with 95% confidence intervals (CI). We used both the fixed-effect and the random-effects models for meta-analyses. Whenever there were significant discrepancies in the results, we reported the more conservative point estimate of the two. We considered a P value of 0.01 or less, two-tailed, as statistically significant if the required information size was reached for our three primary outcomes (all-cause mortality, health-related quality of life, and serious adverse events during treatment) and our post hoc decision to include analyses of mortality at more time points. We presented heterogeneity using the I² statistic. If trialists used intention-to-treat analysis to deal with missing data, we used these data in our primary analysis; otherwise, we used the available data. We assessed the bias risk of the trials using bias risk domains and the certainty of the evidence using GRADE.

MAIN RESULTS

Sixteen trials fulfilled our inclusion criteria. All trials but one were at overall high risk of bias. Fifteen trials (one of which was an abstract) provided data for analysis (927 participants received glucocorticosteroids and 934 participants received placebo or no intervention). Glucocorticosteroids were administered orally or parenterally for a median 28 days (range 3 days to 12 weeks). The participants were between 25 and 70 years old, had different stages of alcoholic liver disease, and 65% were men. Follow-up, when reported, was up to the moment of discharge from the hospital, until they died (median of 63 days), or for at least one year. There was no evidence of effect of glucocorticosteroids on all-cause mortality up to three months following randomisation (random-effects RR 0.90, 95% CI 0.70 to 1.15; participants = 1861; trials = 15; very low-certainty evidence) or on health-related quality of life up to three months, measured with the European Quality of Life - 5 Dimensions - 3 Levels scale (MD -0.04 points, 95% CI -0.11 to 0.03; participants = 377; trial = 1; low-certainty evidence). There was no evidence of effect on the occurrence of serious adverse events during treatment (random-effects RR 1.05, 95% CI 0.85 to 1.29; participants = 1861; trials = 15; very low-certainty evidence), liver-related mortality up to three months following randomisation (random-effects RR 0.89, 95% CI 0.69 to 1.14; participants = 1861; trials = 15; very low-certainty evidence), number of participants with any complications up to three months following randomisation (random-effects RR 1.04, 95% CI 0.86 to 1.27; participants = 1861; very low-certainty evidence), and number of participants of non-serious adverse events up to three months' follow-up after end of treatment (random-effects RR 1.99, 95% CI 0.72 to 5.48; participants = 160; trials = 4; very low-certainty evidence). Based on the information that we collected from the published trial reports, only one of the trials seems not to be industry-funded, and the remaining 15 trials did not report clearly whether they were partly or completely funded by the industry.

AUTHORS' CONCLUSIONS

We are very uncertain about the effect estimate of no difference between glucocorticosteroids and placebo or no intervention on all-cause mortality and serious adverse events during treatment because the certainty of evidence was very low, and low for health-related quality of life. Due to inadequate reporting, we cannot exclude increases in adverse events. As the CIs were wide, we cannot rule out significant benefits or harms of glucocorticosteroids. Therefore, we need placebo-controlled randomised clinical trials, designed according to the SPIRIT guidelines and reported according to the CONSORT guidelines. Future trials ought to report depersonalised individual participant data, so that proper individual participant data meta-analyses of the effects of glucocorticosteroids in subgroups can be conducted.

Hepatic stress associated with pathologies characterized by disturbed glucose production

The liver is an organ with many facets, including a role in energy production and metabolic balance, detoxification and extraordinary capacity of regeneration. Hepatic glucose production plays a crucial role in the maintenance of normal glucose levels in the organism i.e. between 0.7 to 1.1 g/l. The loss of this function leads to a rare genetic metabolic disease named glycogen storage disease type I (GSDI), characterized by severe hypoglycemia during short fasts. On the contrary, type 2 diabetes is characterized by chronic hyperglycemia, partly due to an overproduction of glucose by the liver. Indeed, diabetes is characterized by increased uptake/production of glucose by hepatocytes, leading to the activation of de novo lipogenesis and the development of a non-alcoholic fatty liver disease. In GSDI, the accumulation of glucose-6 phosphate, which cannot be hydrolyzed into glucose, leads to an increase of glycogen stores and the development of hepatic steatosis. Thus, in these pathologies, hepatocytes are subjected to cellular stress mainly induced by glucotoxicity and lipotoxicity. In this review, we have compared hepatic cellular stress induced in type 2 diabetes and GSDI, especially oxidative stress, autophagy deregulation, and ER-stress. In addition, both GSDI and diabetic patients are prone to the development of hepatocellular adenomas (HCA) that occur on a fatty liver in the absence of cirrhosis. These HCA can further acquire malignant traits and transform into hepatocellular carcinoma. This process of tumorigenesis highlights the importance of an optimal metabolic control in both GSDI and diabetic patients in order to prevent, or at least to restrain, tumorigenic activity during disturbed glucose metabolism pathologies.

Glucocorticosteroids for people with alcoholic hepatitis

BACKGROUND

Alcoholic hepatitis is a form of alcoholic liver disease, characterised by steatosis, necroinflammation, fibrosis, and potential complications to the liver disease. Typically, alcoholic hepatitis presents in people between 40 and 50 years of age. Alcoholic hepatitis can be resolved if people abstain from drinking, but the risk of death will depend on the severity of the liver damage and abstinence from alcohol. Glucocorticosteroids are used as anti-inflammatory drugs for people with alcoholic hepatitis. Glucocorticosteroids have been studied extensively in randomised clinical trials in order to assess their benefits and harms. However, the results have been contradictory.

OBJECTIVES

To assess the benefits and harms of glucocorticosteroids in people with alcoholic hepatitis.

SEARCH METHODS

We identified trials through electronic searches in Cochrane Hepato-Biliary's (CHB) Controlled Trials Register, CENTRAL, MEDLINE, Embase, LILACS, and Science Citation Index Expanded. We looked for ongoing or unpublished trials in clinical trials registers and pharmaceutical company sources. We also scanned reference lists of the studies retrieved. The last search was 20 October 2016.

SELECTION CRITERIA

Randomised clinical trials assessing glucocorticosteroids versus placebo or no intervention in people with alcoholic hepatitis, irrespective of year, language of publication, or format. We considered trials with adult participants diagnosed with alcoholic hepatitis, which could have been established through clinical or biochemical diagnostic criteria or both. We defined alcoholic hepatitis as mild (Maddrey's score less than 32) and severe (Maddrey's score 32 or more). We allowed co-interventions in the trial groups, provided they were similar.

DATA COLLECTION AND ANALYSIS

We followed Cochrane and CHB methodology, performing the meta-analyses using Review Manager 5 and Trial Sequential Analysis. We presented the results of dichotomous outcomes as risk ratios (RR) and those of the continuous outcomes as mean difference (MD). We applied both the fixed-effect model and the random-effects model meta-analyses. Whenever there were significant discrepancies in the results, we reported the more conservative point estimate of the two. We considered a P value of 0.01 or less, two-tailed, as statistically significant if the required information size was reached due to our three primary outcomes (all-cause mortality, health-related quality of life, and serious adverse events during treatment) and our post hoc decision to include analyses of mortality at more time points. We presented heterogeneity using the I² statistic. If trialists used intention-to-treat analysis to deal with missing data, we used these data in our primary analysis; otherwise, we used the available data. We assessed the bias risk of the trials using bias risk domains and the quality of the evidence using GRADE.

MAIN RESULTS

Sixteen trials fulfilled the inclusion criteria. All trials were at high risk of bias. Fifteen trials provided data for analysis (927 participants received glucocorticosteroids and 934 participants received placebo or no intervention). The glucocorticosteroids were administered orally or parenterally for a median of 28 days (range 3 days to 12 weeks). The participants were between 25 and 70 years old, had different stages of alcoholic liver disease, and 65% were men. The follow-up of trial participants, when it was reported, was up to the moment of discharge from the hospital, until they died (a median of 63 days), or for at least a year. There was no evidence of effect of glucocorticosteroids on all-cause mortality up to three months following randomisation neither with traditional meta-analysis (random-effects RR 0.90, 95% CI 0.70 to 1.15; participants = 1861; trials = 15; I² = 45% (moderate heterogeneity) nor with Trial Sequential Analysis. Meta-analysis showed no evidence of effect on health-related quality of life up to three months (MD -0.04 points; 95% CI -0.11 to 0.03; participants = 377; trial = 1; low-quality evidence), measured with the European Quality of Life - 5 Dimensions-3 Levels (EQ- 5D-3L) scale. There was no evidence of effect on the occurrence of serious adverse events during treatment, neither with traditional meta-analysis (random-effects RR 1.05, 95% CI 0.85 to 1.29; participants = 1861; trials = 15; I² = 36% (moderate heterogeneity), liver-related mortality up to three months following randomisation (random-effects RR 0.89, 95% CI 0.69 to 1.14; participants = 1861; trials = 15; I² = 46% (moderate heterogeneity), frequency of any complications up to three months following randomisation (random-effects RR 1.04, 95% CI 0.86 to 1.27; participants = 1861; I² = 42% (moderate heterogeneity), and frequency of non-serious adverse events up to three months' follow-up after end of treatment (random-effects RR 1.99, 95% CI 0.72 to 5.48; participants = 160; trials = 4; I² = 0% (no heterogeneity) nor with Trial Sequential Analysis. Nine of the trials were industry-funded.

AUTHORS' CONCLUSIONS

We found no evidence of a difference between glucocorticosteroids and placebo or no intervention on all-cause mortality, health-related quality of life, and serious adverse events during treatment. The risk of bias was high and the quality of evidence was very low or low. Therefore, we are very uncertain about this effect estimate. Due to inadequate reporting, we cannot exclude increases in adverse events. As the confidence intervals were wide, we cannot rule out significant benefits and harms of glucocorticosteroids. Therefore, we need placebo-controlled, randomised clinical trials, designed according to the SPIRIT guidelines and reported according to the CONSORT guidelines. Future trials ought to report depersonalised individual participant data, so that proper individual participant data meta-analyses of the effects of glucocorticosteroids in subgroups can be conducted.

The Pathology of Alcoholic Liver Disease

The term "alcoholic liver disease" encompasses a spectrum of pathologic conditions ranging from isolated steatosis to established cirrhosis. Within this spectrum, varying degrees of inflammation, hepatocellular ballooning degeneration, hepatocyte necrosis, cholestasis, and fibrosis may be encountered. This article reviews the characteristic histologic features of the many forms of alcoholic liver disease. Histologic scoring systems are described, and diseases with overlapping morphologic features and comorbid conditions are also discussed.

Taurine Attenuates Hepatic Inflammation in Chronic Alcohol-Fed Rats Through Inhibition of TLR4/MyD88 Signaling

Accumulating evidence indicates that overconsumption of ethanol contributes in many ways to the pathogenesis of hepatic injury. Although studies indicate that taurine decreases lipogenesis, oxidative stress, and inflammatory cytokines, the protective effect of taurine against alcohol-induced liver injury is still unclear. To clarify the precise signaling involved in the beneficial effect of taurine on alcohol-induced liver injury, rats were randomly divided into four treatment groups: (1) control (Ctl), (2) alcohol (Alc), (3) Alc+taurine (Tau), and (4) Alc+silymarin (Sil). The Tau and Sil groups had lower lymphocyte infiltration and significantly lower TLR-4/MyD88 and IκB/NFκB compared to the Alc group. The inducible nitric oxide synthase (iNOS), C-reactive protein (CRP), tumor necrosis factors (TNF)-α, interleukin (IL)-6, and IL-1β were also significantly lower in the Tau and Sil groups than in the Alc group. The experimental results indicated that hepatoprotection against alcohol-induced inflammation may be mediated by decreased TLR-4/MyD88 signaling.

Autophagy in hepatic fibrosis

Hepatic fibrosis is a leading cause of morbidity and mortality worldwide. Hepatic fibrosis is usually associated with chronic liver diseases caused by infection, drugs, metabolic disorders, or autoimmune imbalances. Effective clinical therapies are still lacking. Autophagy is a cellular process that degrades damaged organelles or protein aggregation, which participates in many pathological processes including liver diseases. Autophagy participates in hepatic fibrosis by activating hepatic stellate cells and may participate as well through influencing other fibrogenic cells. Besides that, autophagy can induce some liver diseases to develop while it may play a protective role in hepatocellular abnormal aggregates related liver diseases and reduces fibrosis. With a better understanding of the potential effects of autophagy on hepatic fibrosis, targeting autophagy might be a novel therapeutic strategy for hepatic fibrosis in the near future.

Alcohol induced hepatic degeneration in a hepatitis C virus core protein transgenic mouse model

Hepatitis C virus (HCV) has become a major public health issue. It is prevalent in most countries. HCV infection frequently begins without clinical symptoms, before progressing to persistent viremia, chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) in the majority of patients (70% to 80%). Alcohol is an independent cofactor that accelerates the development of HCC in chronic hepatitis C patients. The purpose of the current study was to evaluate ethanol-induced hepatic changes in HCV core-Tg mice and mutant core Tg mice. Wild type (NTG), core wild-Tg mice (TG-K), mutant core 116-Tg mice (TG-116) and mutant core 99-Tg mice (TG-99) were used in this investigation. All groups were given drinking water with 10% ethanol and 5% sucrose for 13 weeks. To observe liver morphological changes, we performed histopathological and immunohistochemical examinations. Histopathologically, NTG, TG-K and TG-116 mice showed moderate centrilobular necrosis, while severe centrilobular necrosis and hepatocyte dissociation were observed in TG-99 mice with increasing lymphocyte infiltration and piecemeal necrosis. In all groups, a small amount of collagen fiber was found, principally in portal areas. None of the mice were found to have myofibroblasts based on immunohistochemical staining specific for α-SMA. CYP2E1-positive cells were clearly detected in the centrilobular area in all groups. In the TG-99 mice, we also observed cells positive for CK8/18, TGF-β1 and phosphorylated (p)-Smad2/3 and p21 around the necrotic hepatocytes in the centrilobular area (p < 0.01). Based on our data, alcohol intake induced piecemeal necrosis and hepatocyte dissociation in the TG-99 mice. These phenomena involved activation of the TGF-β1/p-Smad2/3/p21 signaling pathway in hepatocytes. Data from this study will be useful for elucidating the association between alcohol intake and HCV infection.

A myriad of pathways to NASH

Nonalcoholic steatohepatitis (NASH) is defined histopathologically by the presence of macrovesicular steatosis, cellular ballooning, and inflammation. NASH represents a complex multifactorial disease that typically occurs within the context of the metabolic syndrome. NASH lacks homogeneity, and other forms of NASH can present atypically. Less than 50% of patients with NASH respond to pharmacologic treatment, which speaks to this heterogeneity. The authors discuss drugs, disease entities, and nutritional states that can cause or exacerbate underlying NASH indirectly through worsening insulin resistance or directly by interfering with lipid metabolism, promoting oxidative injury, or activating inflammatory pathways.

Alcoholic hepatitis: a clinician's guide

Alcoholic hepatitis is a frequent reason for admission and a common consultation request for hepatologists and gastroenterologists. Although it seems to occur acutely, it is usually subacute and often superimposed on underlying alcoholic cirrhosis. Typically patients have a background of drinking on a daily basis, but, in response to a life crisis, patients have started drinking massively.

Changes in IL12A methylation pattern in livers from mice fed DDC

Mallory-Denk body (MDB) formation is a component of alcoholic and non alcoholic hepatitis. Proteins of the TLR pathway were shown to be involved in the formation of MDBs, in mice fed DDC. TLR genes are upregulated and SAMe supplementation prevents this up regulation and prevented the formation of MDBs. DNA of livers from control mice, from mice fed DDC 10weeks, refed 1week with DDC and with DDC+SAMe were extracted and used to study the methylation pattern of genes involves in the TLR pathway. A PCR array was used to analyze it. Using PCR arrays for the mouse TLR pathway,24 genes were found whose expression of IL12A was regulated by the methylation of its gene. DDC fed for 10weeks reduced the methylation of the IL12A gene expression. This expression was also reduced when DDC was refed. However, when SAMe was fed, the intermediate level methylation of IL12A was up regulated to the intermediate level and the methylation of the promoter decreased compared to DDC refeeding or DDC 10weeks. IL12A is known to induce the production of IFNg by NK and L(T). We showed in a previous publication that IFNg is one of the major cytokines involved in the induction of MDB formation. The low expression of IL12A associated with the intermediate methylation of its promoter could explain one step in the mechanism which leads to the formation of MDBs.

The cytoskeleton in nonalcoholic steatohepatitis: 100 years old but still youthful

The hepatocellular cytoskeleton consists of three filamentous systems: microfilaments, microtubules and keratins (Ks). While the alterations in microfilaments and microtubules during nonalcoholic steatohepatitis (NASH) are largely unexplored, K8/K18 reorganization into Mallory-Denk bodies (MDBs) represents a NASH hallmark, and serological K18 fragments constitute an established tool to monitor NASH severity. To commemorate the 100th anniversary of the first description of MDBs, this article summarizes the composition and function of the hepatocellular cytoskeleton, as well as the importance of cytoskeletal alterations in NASH. The significance of MDBs in clinical routine is illustrated, as are the findings from MDB mouse models, which shape our current view of MDB pathogenesis. Even after 100 years, the cytoskeleton represents a fascinating but greatly understudied area of NASH biology.

Alcoholic liver disease and exacerbation by malnutrition and infections: what animal models are currently available?

Alcoholic liver disease remains a frequent and serious problem for increasing numbers of patients. Research has expanded our molecular understanding of the cellular basis of disease progression; however, translation into therapy is still hampered by a lack of suitable animal models for alcoholic liver disease, as well as from consequences of related liver damage due to malnutrition, hepatitis C virus infection, or abuse of other substances. Many patients with liver disease do not simply consume too much alcohol; they also suffer from comorbidities such as obesity or viral hepatitis, and/or may be addicted to other drugs besides alcohol. This review will summarize the currently available animal models to study liver disease due to either single causes or combinations of liver toxic substances/infections and alcohol.

Strategies for the early detection of drug-induced hepatic steatosis in preclinical drug safety evaluation studies

Hepatic steatosis is characterized by the accumulation of lipid droplets in the liver. Although relatively benign, simple steatosis can eventually lead to the development of steatohepatitis, a more serious condition characterized by fibrosis, cirrhosis, and eventual liver failure if the underlying cause is not eliminated. According to the "two hit" theory of steatohepatitis, the initial hit involves fat accumulation in the liver, and a second hit leads to inflammation and subsequent tissue injury. Because some xenobiotics target liver fatty acid metabolism, especially mitochondrial β-oxidation, it is important to avoid potential drug candidates that can contribute to either the initiation of liver steatosis or progression to the more injurious steatohepatitis. The gold standard for the detection of these types of hepatic effects is histopathological examination of liver tissue. In animal studies, these examinations are slow, restricted to a single sampling time, and limited tissue sections. Recent literature suggests that rapid in vitro screening methods can be used early in the drug R&D process to identify compounds with steatotic potential. Further, progress in the identification of potential serum or plasma protein biomarkers for these liver changes may provide additional in vivo tools to the preclinical study toxicologist. This review summarizes recent developments for in vitro screening and in vivo biomarker detection for steatotic drug candidates.

Alcoholic hepatitis 2010: A clinician’s guide to diagnosis and therapy

Alcoholic hepatitis (AH) remains a common and life threatening cause of liver failure, especially when it is severe. Although the adjective “acute” is frequently used to describe this form of liver injury, it is usually subacute and has been developing for weeks to months before it becomes clinically apparent. Patients with this form of alcoholic liver disease usually have a history of drinking heavily for many years. While certain aspects of therapy, mainly nutritional support and abstinence are well established, significant debate has surrounded the pharmacologic treatment of AH, and many institutions practice widely varying treatment protocols. In recent years a significant amount of literature has helped focus on the details of treatment, and more data have accumulated regarding risks and benefits of pharmacologic treatment. In particular, the efficacy of pentoxifylline has become increasingly apparent, and when compared with the risks associated with prednisolone, has brought this drug to the forefront of therapy for severe AH. This review will focus on the clinical and laboratory diagnosis and pharmacologic therapies that should be applied during hospitalization and continued into outpatient management. We conclude that the routine use of glucocorticoids for severe AH poses significant risk with equivocal benefit, and that pentoxifylline is a better, safer and cheaper alternative. While the full details of nutritional support lie beyond the scope of this article, nutrition is a cornerstone of therapy and must be addressed in every patient diagnosed with AH. Finally, while traditional psychosocial techniques play a major role in post-hospitalization care of alcoholics, we hope to make the medical clinician realize his or her role in reducing recidivism rates with early and frequent outpatient visits and with the use of baclofen to reduce alcohol craving.

The role of cytokines in UbD promoter regulation and Mallory-Denk body-like aggresomes

Mallory-Denk bodies (MDBs) are found in chronic liver diseases. Previous studies showed that diethyl-1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate (DDC) induced formation of MDBs and the up regulation of UbD expression in mouse liver. UbD is a protein over expressed in hepatocellular carcinomas. It is a potential preneoplastic marker in the mouse. It is hypothesized that inflammatory cytokines play a critical role in UbD up regulation and MDB formation. TNFa and IFNg treatment of HCC cell line Hepa 1-6, induced the expression of UbD and the expression of genes coding for the immunoproteasome (LMP2, LMP7, and MECL-1 subunits). TNFa and IFNg induced the activity of the UbD promoter, using a luciferase assay. The cotreatment with TNFa and IFNg induced the activity of the UbD promoter through an Interferon Sequence Responsive Element (ISRE). In addition, long term treatment with TNFa and IFNg induced the formation of MDB-like aggresomes in Hepa 1-6 cells, which emphasizes the role of inflammation in the formation of MDBs leading to the formation of liver tumors, in the mouse. Identifying the mechanism that regulates gene expression of UbD supports the hypothesis that down regulation of UbD and the proinflammatory gene expression would prevent MDB and HCC formations. Previous studies indicate that S-adenosylmethionine or betaine prevented IFNg induced UbD and MDB formations.

Toward unraveling the complexity of simple epithelial keratins in human disease

Simple epithelial keratins (SEKs) are found primarily in single-layered simple epithelia and include keratin 7 (K7), K8, K18-K20, and K23. Genetically engineered mice that lack SEKs or overexpress mutant SEKs have helped illuminate several keratin functions and served as important disease models. Insight into the contribution of SEKs to human disease has indicated that K8 and K18 are the major constituents of Mallory-Denk bodies, hepatic inclusions associated with several liver diseases, and are essential for inclusion formation. Furthermore, mutations in the genes encoding K8, K18, and K19 predispose individuals to a variety of liver diseases. Hence, as we discuss here, the SEK cytoskeleton is involved in the orchestration of several important cellular functions and contributes to the pathogenesis of human liver disease.

Mallory-Denk-bodies: lessons from keratin-containing hepatic inclusion bodies

Inclusion bodies are characteristic morphological features of various neuronal, muscular and other human disorders. They share common molecular constituents such as p62, chaperones and proteasome subunits. The proteins within aggregates are misfolded with increased beta-sheet structure, they are heavily phosphorylated, ubiquitinylated and partially degraded. Furthermore, involvement of proteasomal system represents a common feature of virtually all inclusions. Multiple aggregates contain intermediate filament proteins as their major constituents. Among them, Mallory-Denk bodies (MDBs) are the best studied. MDBs represent hepatic inclusions observed in diverse chronic liver diseases such as alcoholic and non-alcoholic steatohepatitis, chronic cholestasis, metabolic disorders and hepatocellular neoplasms. MDBs are induced in mice fed griseofulvin or 3,5-diethoxycarbonyl-1,4-dihydrocollidine and resolve after discontinuation of toxin administration. The availability of a drug-induced model makes MDBs a unique tool for studying inclusion formation. Our review summarizes the recent advances gained from this model and shows how they relate to observations in other aggregates. The MDB formation-underlying mechanisms include protein misfolding, chaperone alterations, disproportional protein expression with keratin 8>keratin 18 levels and subsequent keratin 8 crosslinking via transglutaminase. p62 presence is crucial for MDB formation. Proteasome inhibitors precipitate MDB formation, whereas stimulation of autophagy with rapamycin attenuates their formation.

The genetic background modulates susceptibility to mouse liver Mallory-Denk body formation and liver injury

Mallory-Denk bodies (MDBs) are hepatocyte inclusions found in several liver diseases and consist primarily of keratins 8 and 18 (K8/K18) and ubiquitin that are cross-linked by transglutaminase-2. We hypothesized that genetic variables contribute to the extent of MDB formation, because not all patients with an MDB-associated liver disease develop inclusions. We tested this hypothesis using five strains of mice (FVB/N, C3H/He, Balb/cAnN, C57BL/6, 129X1/Sv) fed for three months (eight mice per strain) the established MDB-inducing agent 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). MDB formation was compared using hematoxylin-and-eosin staining, or immunofluorescence staining with antibodies to K8/K18/ubiquitin, or biochemically by blotting with antibodies to transglutaminase-2/p62 proteins and to K8/K18/ubiquitin to detect keratin cross-linking. DDC feeding induced MDBs in all mouse strains, but there were dramatic strain differences that quantitatively varied 2.5-fold (P < 0.05). MDB formation correlated with hepatocyte ballooning, and most ballooned hepatocytes had MDBs. Immunofluorescence assessment was far more sensitive than hematoxylin-and-eosin staining in detecting small MDBs, which out-numbered (by approximately 30-fold to 90-fold) but did not parallel their large counterparts. MDB scores partially reflected the biochemical presence of cross-linked keratin-ubiquitin species but not the changes in liver size or injury in response to DDC. The extent of steatosis correlated with the total (large+small) number of MDBs, and there was a limited correlation between large MDBs and acidophil bodies.

CONCLUSION

Mouse MDB formation has important genetic contributions that do not correlate with the extent of DDC-induced liver injury. If extrapolated to humans, the genetic contributions help explain why some patients develop MDBs whereas others are less likely to do so. Detection and classification of MDBs using MDB-marker-selective staining may offer unique links to specific histological features of DDC-induced liver injury.

"Toxic memory" via chaperone modification is a potential mechanism for rapid Mallory-Denk body reinduction

The cytoplasmic hepatocyte inclusions, Mallory-Denk bodies (MDBs), are characteristic of several liver disorders, including alcoholic and nonalcoholic steatohepatitis. In mice, MDBs can be induced by long-term feeding with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) for 3 to 4 months or rapidly reformed in DDC-induced then recovered mice by DDC refeeding or exposure to a wide range of toxins for only 5 to 7 days. The molecular basis for such a rapid reinduction of MDBs is unknown. We hypothesized that protein changes retained after DDC priming contribute to the rapid MDB reappearance and associate with MDB formation in general terms. Two-dimensional differential-in-gel-electrophoresis coupled with mass spectrometry were used to characterize protein changes in livers from the various treatment groups. The alterations were assessed by real-time reverse-transcription polymerase chain reaction and confirmed by immunoblotting. DDC treatment led to pronounced charged isoform changes in several chaperone families, including Hsp25, 60, 70, GRP58, GRP75, and GRP78, which lasted at least for 1 month after discontinuation of DDC feeding, whereas changes in other proteins normalized during recovery. DDC feeding also resulted in altered expression of Hsp72, GRP75, and Hsp25 and in functional impairment of Hsp60 and Hsp70 as determined using a protein complex formation and release assay. The priming toward rapid MDB reinduction lasts for at least 3 months after DDC discontinuation, but becomes weaker after prolonged recovery. MDB reinduction parallels the rapid increase in p62 and Hsp25 levels as well as keratin 8 cross-linking that is normally associated with MDB formation.

CONCLUSION

Persistent posttranslational modifications in chaperone proteins, coupled with protein cross-linking and altered chaperone expression and function likely contribute to the "toxic memory" of DDC-primed mice. We hypothesize that similar changes are important contributors to inclusion body formation in several diseases.

Intermediate filament cytoskeleton of the liver in health and disease

Intermediate filaments (IFs) represent the largest cytoskeletal gene family comprising approximately 70 genes expressed in tissue specific manner. In addition to scaffolding function, they form complex signaling platforms and interact with various kinases, adaptor, and apoptotic proteins. IFs are established cytoprotectants and IF variants are associated with >30 human diseases. Furthermore, IF-containing inclusion bodies are characteristic features of several neurodegenerative, muscular, and other disorders. Acidic (type I) and basic keratins (type II) build obligatory type I and type II heteropolymers and are expressed in epithelial cells. Adult hepatocytes contain K8 and K18 as their only cytoplasmic IF pair, whereas cholangiocytes express K7 and K19 in addition. K8/K18-deficient animals exhibit a marked susceptibility to various toxic agents and Fas-induced apoptosis. In humans, K8/K18 variants predispose to development of end-stage liver disease and acute liver failure (ALF). K8/K18 variants also associate with development of liver fibrosis in patients with chronic hepatitis C. Mallory-Denk bodies (MDBs) are protein aggregates consisting of ubiquitinated K8/K18, chaperones and sequestosome1/p62 (p62) as their major constituents. MDBs are found in various liver diseases including alcoholic and non-alcoholic steatohepatitis and can be formed in mice by feeding hepatotoxic substances griseofulvin and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). MDBs also arise in cell culture after transfection with K8/K18, ubiquitin, and p62. Major factors that determine MDB formation in vivo are the type of stress (with oxidative stress as a major player), the extent of stress-induced protein misfolding and resulting chaperone, proteasome and autophagy overload, keratin 8 excess, transglutaminase activation with transamidation of keratin 8 and p62 upregulation.

From Mallory to Mallory–Denk bodies: What, how and why?

Frank B. Mallory described cytoplasmic hyaline inclusions in hepatocytes of patients with alcoholic hepatitis in 1911. These inclusions became known as Mallory bodies (MBs) and have since been associated with a variety of other liver diseases including non-alcoholic fatty liver disease. Helmut Denk and colleagues described the first animal model of MBs in 1975 that involves feeding mice griseofulvin. Since then, mouse models have been instrumental in helping understand the pathogenesis of MBs. Given the tremendous contributions made by Denk to the field, we propose renaming MBs as Mallory-Denk bodies (MDBs). The major constituents of MDBs include keratins 8 and 18 (K8/18), ubiquitin, and p62. The relevant proteins and cellular processes that contribute to MDB formation and accumulation include the type of chronic stress, the extent of stress-induced protein misfolding and consequent proteasome overload, a K8-greater-than-K18 ratio, transamidation of K8 and other proteins, presence of p62 and autophagy. Although it remains unclear whether MDBs serve a bystander, protective or injury promoting function, they do serve an important role as histological and potential progression markers in several liver diseases.

Proteomic analysis of the response of human lung cells to uranium

The industrial use of uranium and particularly of depleted uranium, has pinpointed the need to review its chemical impact on human health. A proteomic approach was used to evaluate the response of a human lung cell line (A549) to uranium. We established the first 2-D reference map of the A549 cell line, identifying 87 spots corresponding to 81 major proteins. Uranium treatment triggered differential expression of 18 spots, of which 14 corresponded to fragments of cytokeratin 8 (CK8) and cytokeratin (CK18) and 1 to peroxiredoxin 1. We probed several hypotheses regarding CK cleavage, and observed that it did not result from caspase or calpain activity. Furthermore, we showed that the fragments are recognised by an anti-ubiquitin antibody (KM691). These results suggest a regulatory pathway involving CK ubiquitinylation or dysfunction in the proteasome-ubiquitin system in response to uranium exposure in human lung cells.

The role of laminin–integrin signaling in triggering MB formation. An in vivo and in vitro study

It is still unclear as to how hepatocytes perceive external factors and transduce the signals which initiate MB formation. To investigate this phenomenon, the model of MB formation in liver in vivo and in primary culture of hepatocytes derived from drug-primed mice was used. Control mice were fed the control diet (group 1). MBs were induced in the livers of mice fed diethyl-1, 4-dihydro-2, 4, 6-trimethyl-3, 5-pyridinedicarboxylate (DDC) for 10 weeks (group 2). The induced MBs completely disappeared after the withdrawal of DDC for 4 weeks (group 3). Newly formed MBs were numerous after DDC was refed for 1 week (group 4). Relative mRNA abundance was determined by quantitative real-time RT-PCR in the liver from the mice. The expression of integrin alpha(6) and beta(2) was significantly increased in the livers of DDC-treated (group 2) and drug refed mice (group 4), when compared with the livers from controls (group 1) and DDC-withdrawn (group 3) mice. The increased mRNA of these two integrin genes was associated with the increased expression of laminin (a ligand for integrin alpha(6)beta(1) and alpha(6)beta(4)), Icam1 (a ligand of alphaLbeta2), Src, MEKK1, and ERK1. Primary cultures of isolated DDC-primed hepatocytes (group 4 mice were withdrawn from DDC-CMZ for 4-6 weeks) produced significantly more MBs on laminin-coated coverslips compared with plastic uncoated, fibronectin-, collagen-, or fibrinogen-coated coverslips. U0126, an inhibitor of MEK1 protein, significantly reduced the phosphorylated forms of ERK1/2 and MB formation in vitro. In conclusion, the current study revealed an association between MB formation and integrin-mediated signaling in vivo. The data indicate that laminin-integrin signaling which activates ERK, triggered MB formation in vitro, and an inhibitor of the signaling cascade reduced MB formation.

Heat shock protein 70 expression, keratin phosphorylation and Mallory body formation in hepatocytes from griseofulvin-intoxicated mice

Background

Keratins are members of the intermediate filaments (IFs) proteins, which constitute one of the three major cytoskeletal protein families. In hepatocytes, keratin 8 and 18 (K8/18) are believed to play a protective role against mechanical and toxic stress. Post-translational modifications such as phosphorylation and glycosylation are thought to modulate K8/18 functions. Treatment of mouse with a diet containing griseofulvin (GF) induces, in hepatocytes, modifications in organization, expression and phosphorylation of K8/18 IFs and leads, on the long term, to the formation of K8/18 containing aggregates morphologically and biochemically identical to Mallory bodies present in a number of human liver diseases. The aim of the present study was to investigate the relationship between the level and localization of the stress inducible heat shock protein 70 kDa (HSP70i) and the level and localization of K8/18 phosphorylation in the liver of GF-intoxicated mice. The role of these processes in Mallory body formation was studied, too. The experiment was carried out parallely on two different mouse strains, C3H and FVB/n.

Results

GF-treatment induced an increase in HSP70i expression and K8 phosphorylation on serines 79 (K8 S79), 436 (K8 S436), and K18 phosphorylation on serine 33 (K18 S33) as determined by Western blotting. Using immunofluorescence staining, we showed that after treatment, HSP70i was present in all hepatocytes. However, phosphorylated K8 S79 (K8 pS79) and K8 S436 (K8 pS436) were observed only in groups of hepatocytes or in isolated hepatocytes. K18 pS33 was increased in all hepatocytes. HSP70i colocalized with MBs containing phosphorylated K8/18. Phophorylation of K8 S79 was observed in C3H mice MBs but was not present in FVB/n MBs.

Conclusions

Our results indicate that GF intoxication represents a stress condition affecting all hepatocytes, whereas induction of K8/18 phosphorylation is not occurring in every hepatocyte. We conclude that, in vivo, there is no direct relationship between GF-induced stress and K8/18 phosphorylation on the studied sites. The K8/18 phosphorylation pattern indicates that different cell signaling pathways are activated in subpopulations of hepatocytes. Moreover, our results demonstrate that, in distinct genetic backgrounds, the induction of K8/18 phosphorylation can be different.

Wilson disease

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism. Since daily copper intake exceeds the body's requirements, effective means of excreting excess copper are essential. These are accomplished by ATP7B, a new member of the cation-transporting p-type ATPase family, which is mainly expressed in the liver and mediates both copper secretion into plasma (coupled with ceruloplasmin synthesis) and its excretion into bile. Thus far, more than 200 mutations of the WD gene have been detected, causing impairment of ATP7B function and, ultimately, copper accumulation. Excess copper, however, induces free-radical reactions and lipid peroxidation. Resultant liver damage leads to steatosis, inflammation, cirrhosis, and, occasionally, fulminant liver failure. The diagnosis of WD is commonly made on the basis of typical clinical and laboratory findings, including low serum ceruloplasmin, increased urinary copper excretion, and increased hepatic copper content. Since liver morphology is non-specific, and copper histochemistry may lead to both false-negative and false-positive results, the pathologist usually only suspects the disease or assists in its confirmation. Although the value of molecular genetic testing is limited due to the high number of possible gene mutations, polymerase chain reaction may be useful for the evaluation of family members of homozygous index patients.

Hepatic adenomatosis in glycogen storage disease type Ia: report of a case with unusual histology

Hepatic adenomatosis is a well-known complication of glycogen storage disease type Ia (von Gierke disease). Although most of these tumors have an appearance similar to sporadic hepatocellular adenomas, unusual histologic features have been reported, including Mallory hyaline, varying degrees of fibrosis, and aggregates of neutrophils. We report the fourth case of Mallory hyaline in the adenomas of glycogen storage disease type Ia in a 28-year-old woman undergoing segmental hepatectomy for enlarging liver nodules. Other prominent findings included steatohepatitis and nonspecific granulomatous inflammation--2 findings that are commonly seen in sporadic adenomas but not, to our knowledge, previously reported in glycogen storage disease type Ia.

Cancer-associated cleavage of cytokeratin 8/18 heterotypic complexes exposes a neoepitope in human adenocarcinomas

The intermediate filament network in simple glandular epithelial cells predominantly consists of heterotypic complexes of cytokeratin 8 (K8) and cytokeratin 18 (K18). In contrast to other cytokeratins, K8 and K18 are persistently expressed during malignant transformation, but changes in cell morphology are accompanied by alterations in the intermediate filament network. To study molecular changes, K8 and K18 were purified from surgically removed colon cancer and normal epithelia tissues. Western blotting and amino acid sequencing revealed the presence of abundant K8 and K18 fragments, truncated at the N terminus, from cancerous, but not normal, epithelial cells. The fragmentation pattern indicates proteolysis mediated by several enzymes, including trypsin-like enzymes. The cancer-associated forms of K8 and K18 are specifically recognized by the human antibody, COU-1, cloned from the B cells of a cancer patient. We demonstrate that COU-1 recognizes a unique conformational epitope presented only by a complex between K8 and K18. The epitope is revealed after proteolytic removal of the head domain of either K8 or K18. A large panel of recombinant K8 and K18 fragments, deleted N- or C-terminally, allowed for the localization of the COU-1 epitope to the N-terminal part of the rod domains. Using surface plasmon resonance, the affinity of COU-1 for this epitope was determined to be 10(9) x m(-1), i.e. more than 2 orders of magnitude higher than for intact heterotypic K8/K18 complexes. The cellular distribution of truncated K8/K18 heterotypic complexes in viable adenocarcinomas cells was probed using COU-1 showing small fibrillar structures distinct from those of intact K8/K18 complexes. Previously we demonstrated the binding and subsequent internalization of recombinant Fab COU-1 to live cancer cells. We have thus characterized a cancer neoepitope recognized by the humoral immune system. The results have biological as well as clinical implications.

Molecular misreading of the ubiquitin B gene and hepatic mallory body formation

BACKGROUND & AIMS

Molecular misreading of the ubiquitin B gene has been documented in the cerebral cortex of patients with Alzheimer's disease and Down syndrome. This novel process consists of the unfaithful conversion of genomic information into aberrant transcripts and its subsequent translation into +1 proteins.

METHODS

Because Mallory bodies (MBs) also contain ubiquitinated proteins, we stained 11 autopsied and 6 biopsied MB-containing livers from patients with steatohepatitis with an antibody to ubiquitin(+1) to look for the presence of mutant (ubiquitin(+1)) protein. Antibodies to wild-type ubiquitin were used to document the presence of MBs in all cases.

RESULTS

Ubiquitin(+1) immunoreactivity was detected in all MB-containing livers with steatohepatitis; no ubiquitin(+1) immunoreactivity was found in 13 MB-free liver controls. A subpopulation (about one third of the MBs) of the MB-containing hepatocytes in autopsied livers showed ubiquitin(+1) immunoreactivity (i.e., ubiquitin and ubiquitin(+1) colocalized in MBs). MB-containing liver biopsy specimens showed colocalization of ubiquitin and ubiquitin(+1) in every MB. Western blot analysis showed an ubiquitin(+1) band of 11 kilodaltons. Molecular misreading of the ubiquitin B gene (DeltaGU) was shown in one of the livers, which contained numerous MBs using an expression cloning strategy.

CONCLUSIONS

The results showed that molecular misreading of the ubiquitin B gene occurred in hepatocytes in virtually all of the MB-containing livers tested. Ubiquitin(+1) protein was only found within the MBs and therefore may act by interfering with the degradation of the MBs because ubiquitin(+1) may inhibit proteolytic function of the proteasome.

Sequence of events in the assembly of Mallory body components in mouse liver: clues to the pathogenesis and significance of Mallory body formation

BACKGROUND/AIMS

Chronic intoxication of mice with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or griseofulvin (GF) results in appearance of Mallory bodies (MBs) and alterations of the keratin cytoskeleton, which are reversible upon drug withdrawal but recur after readministration within 2-3 days.

METHODS

DDC- or GF-treated and recovered mice were reintoxicated with the original drugs but also colchicine and lumicolchicine. Cytoskeletal alterations of hepatocytes and MB formation were monitored by immunofluorescence microscopy using keratin, MB-specific antibodies, antibodies to phosphoepitopes and to HSP70. Keratin 8/18 mRNA expression and protein levels were determined by competitive reverse transcription-polymerase chain reaction, in situ-hybridization and western blotting.

RESULTS

Duration of pretreatment was important for the efficiency of MB triggering. Rapid increase of keratin 8/18 mRNA and proteins was found in all reintoxicated mice concomitant with MB formation, whereby keratin 8 prevailed over keratin 18. Keratins and a protein with heat shock characteristics (M(M) 120-1 antigen) were the earliest detectable MB components, whereas ubiquitination and phosphorylation followed later.

CONCLUSIONS

Overproduction of keratins is a major but not the only step responsible for MB formation. Additional components (e.g. M(M) 120-1 antigen) and excess of keratin 8 over keratin 18 are essential.

Lactation affects expression of intermediate filaments in human breast epithelium

The human breast contains two epithelial lineages, luminal epithelial and myoepithelial. Specific patterns of expression of intermediate filaments have previously been demonstrated in the resting breast. To determine how terminal differentiation and lactation influenced expression of intermediate filaments in breast epithelial cells, we used Western blot analysis to measure the levels of vimentin, alpha-smooth muscle actin, keratin 14, and keratin 18 in the resting and lactating breast. Confocal immunofluorescence was used to determine the subcellular site of localization of the intermediate filaments. Vimentin was localised to myoepithelial cells in both the resting and lactating gland. There was a four-fold increase in vimentin protein levels in lactating tissue relative to resting tissue, and this may be related to increased cellular activity of the myoepithelial cells which surround secretory alveoli. Alpha-smooth muscle actin and keratin 14 were detected in myoepithelial cells, and similar levels of expression were found in lactating and resting tissue. In the resting breast, keratin 18 and keratin 8 were detected in luminal epithelial cells in a filamentous form, whereas in lactating tissue it was present in a punctate form in luminal cells and also seen as granules in the lumen of alveoli. Our results indicate that intermediate filament expression patterns are altered in the lactating human breast, and this may reflect their role in the fully functional gland.

Identification of Mrj, a DnaJ/Hsp40 family protein, as a keratin 8/18 filament regulatory protein

To elucidate the function of keratins 8 and 18 (K8/18), major components of the intermediate filaments of simple epithelia, we searched for K8/18-binding proteins by screening a yeast two-hybrid library. We report here that human Mrj, a DnaJ/Hsp40 family protein, directly binds to K18. Among the interactions between DnaJ/Hsp40 family proteins and various intermediate filament proteins that we tested using two-hybrid methods, Mrj specifically interacted with K18. Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells. Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70. Mrj bound to K18 through its C terminus and interacted with Hsp/c70 via its N terminus, which contains the J domain. Microinjection of anti-Mrj antibody resulted in the disorganization of K8/18 filaments, without effects on the organization of actin filaments and microtubules. Taken together, these results suggest that Mrj may play an important role in the regulation of K8/18 filament organization as a K18-specific co-chaperone working together with Hsp/c70.

Isolation and characterization of an antigenically distinct 68-kd protein from nonviral intracytoplasmic inclusions in Boa constrictors chronically infected with the inclusion body disease virus (IBDV: Retroviridae)

The relationship between a retroviral infection and the development of nonviral intracytoplasmic inclusion bodies was studied in a Boa constrictor model. Twelve juvenile age- and size-matched inclusion body disease (IBD)-negative boas were randomly divided into three groups. Each group was inoculated intraperitoneally with 1 ml of an IBD virus (IBDV)-infected liver homogenate or 1 ml of normal boa liver homogenate (sham-inoculated control) or was left untreated. All boas were monitored for development of IBD by daily examination and serial liver biopsy over 1 year. The 4 IBDV-inoculated boas became IBDV and inclusion positive by 10 weeks postinoculation. The average size and density of inclusion bodies increased with the duration of infection. Ultrastructurally, inclusion bodies <2 microm in diameter consisted of intracytoplasmic aggregates of granular electron-dense material that were not membrane limited. Larger inclusions (3-6 microm in diameter) were characterized as membrane-bound aggregates of amorphous to granular electron-dense material admixed with membranelike fragments. The sham-inoculated and untreated control snakes did not become inclusion or IBDV positive. Direct comparison of the protein electrophoretograms of IBDV-infected and normal boa tissues demonstrated a prominent 68-kd protein band unique to infected inclusion-positive tissues. Monoclonal antibodies directed against the 68-kd protein band specifically labeled inclusion bodies. The results of this study demonstrate that IBD inclusions represent an intracytoplasmic accumulation of an antigenically distinct IBDV-associated protein.

Early perturbations in keratin and actin gene expression and fibrillar organisation in griseofulvin-fed mouse liver

BACKGROUND/AIMS

Long-term feeding of mice with a diet containing griseofulvin results in the formation of Mallory bodies, keratin K8 and K18 containing aggregates in hepatocytes. These bodies are biochemically and morphologically identical to the Mallory bodies that emerge in several human liver disorders. The aim of this study was to examine the contribution of K8 and K18 and actin to Mallory body formation.

METHODS

Mice were fed griseofulvin over a period ranging from 1 day to 20 months. Hepatocyte morphology was monitored by immunocytochemistry, gene expression by Northern and run-off transcription assays, and protein level by Western blotting.

RESULTS

Griseofulvin feeding induced a series of morphological alterations in hepatocytes that could be grouped into 3 phases: appearance of cholestasis during the first week (phase I), partial hepatocyte recovery at 3 months (phase II), and development of typical Mallory bodies after 3 to 5 months (phase III). All these cellular alterations were associated with perturbations in keratin and actin fibrillar status, coupled with increases in K8, K18 and actin mRNA steady-state level and, in K8 and K18 protein content. The transcriptional activity of the genes was not affected.

CONCLUSIONS

Perturbations in keratin and actin gene expression and fibrillar organisation constitute early events in the griseofulvin-induced pathological process that in the long-term leads to Mallory body formation. The higher keratin and actin mRNA levels reflect significant increases in mRNA stability taking place at the early phase of griseofulvin intoxication in hepatocytes.

Estrogen induces cytokeratin aggregation in primary cultures of Armenian hamster hepatocytes

The effect of estrogen administration to cultured Armenian hamster was studied. Isolated Armenian hamster hepatocytes were cultured in RPMI medium supplemented with beta-estradiol (E2). Beta-estradiol treatment for 24-48 hr induced cytoplasmic inclusion bodies which by immunocytochemistry were positive for cytokeratin (CK) 8, CK 18, and ubiquitin but negative for CK 7 and CK 19. These inclusion bodies appeared as filamentous tangles or amorphous aggregates when observed by electron microscopy. F-actin, tubulin, and desmosomes were not influenced by the presence of the inclusion bodies. Addition of ethanol to culture medium increased the incidence of the inclusion formation. In combination with 0.5% ethanol 1 microM of E2 induced five to six times more inclusion bodies, while the number of inclusion bodies decreased when epidermal growth factor (EGF) was added to the medium in combination with E2. This reduction effect was nullified by treatment with anti-EGF receptor antibody. These findings suggest that E2 treatment to Armenian hamster hepatocytes in vitro induces Mallory body-like inclusions whose incidence can be influenced by addition of ethanol or EGF to the culture medium.

Keratins turn over by ubiquitination in a phosphorylation-modulated fashion

Keratin polypeptides 8 and 18 (K8/18) are intermediate filament (IF) proteins that are expressed in glandular epithelia. Although the mechanism of keratin turnover is poorly understood, caspase-mediated degradation of type I keratins occurs during apoptosis and the proteasome pathway has been indirectly implicated in keratin turnover based on colocalization of keratin-ubiquitin antibody staining. Here we show that K8 and K18 are ubiquitinated based on cotransfection of His-tagged ubiquitin and human K8 and/or K18 cDNAs, followed by purification of ubiquitinated proteins and immunoblotting with keratin antibodies. Transfection of K8 or K18 alone yields higher levels of keratin ubiquitination as compared with cotransfection of K8/18, likely due to stabilization of the keratin heteropolymer. Most of the ubiquitinated species partition with the noncytosolic keratin fraction. Proteasome inhibition stabilizes K8 and K18 turnover, and is associated with accumulation of phosphorylated keratins, which indicates that although keratins are stable they still turnover. Analysis of K8 and K18 ubiquitination and degradation showed that K8 phosphorylation contributes to its stabilization. Our results provide direct evidence for K8 and K18 ubiquitination, in a phosphorylation modulated fashion, as a mechanism for regulating their turnover and suggest that other IF proteins could undergo similar regulation. These and other data offer a model that links keratin ubiquitination and hyperphosphorylation that, in turn, are associated with Mallory body deposits in a variety of liver diseases.

Cytokeratin 8 protects from hepatotoxicity, and its ratio to cytokeratin 18 determines the ability of hepatocytes to form Mallory bodies

In alcoholic hepatitis, a severe form of alcohol-induced toxic liver injury, as well as in experimental intoxication of mice with the porphyrinogenic drugs griseofulvin and 3,5-diethoxycarbonyl-1, 4-dihydrocollidine, hepatocytes form cytoplasmic protein aggregates (Mallory bodies; MBs) containing cytokeratins (CKs) and non-CK components. Here we report that mice lacking the CK8 gene and hence CK intermediate filaments in hepatocytes, but still expressing the type I partner, ie, the CK18 gene, do not form MBs but suffer from extensive porphyria and progressive toxic liver damage, leading to the death of a considerable number of animals (7 of 12 during 12 weeks of intoxication). Our observations show that 1) in the absence of CK8 as well as in the situation of a relative excess of CK18 over CK8 no MBs are formed; 2) the loss of CK8 is not compensated by other type II CKs; and 3) porphyria and toxic liver damage are drastically enhanced in the absence of CK8. Our results point to a protective role of CKs in certain types of toxic liver injury and suggest that MBs by themselves are not harmful to hepatocytes but may be considered as a product of a novel defense mechanism in hepatocytes.

Hepatocyte cytokeratins are hyperphosphorylated at multiple sites in human alcoholic hepatitis and in a mallory body mouse model

Alcoholic hepatitis (AH) is associated with cytokeratin 8 and 18 (CK8/18) accumulation as cytoplasmic inclusion bodies, termed Mallory bodies (MBs). Studies with MB mouse models and cultured hepatocytes suggested that CK8/18 hyperphosphorylation might be involved in MB formation. However, no data exist on phosphorylation of CK8/18 in human AH. In this study, antibodies that selectively recognize phosphorylated epitopes of CK8 or CK18 were used to analyze CK8/18 phosphorylation states in normal human and murine livers, human AH biopsies, and livers of 3,5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC)-intoxicated mice, the last serving as model for MB induction. Hepatocyte cytokeratins become hyperphosphorylated at multiple sites in AH and in DDC-intoxicated mice. Hyperphosphorylation of CK8/18 occurred rapidly, after 1 day of DDC intoxication and preceded architectural changes of the cytoskeleton. In long-term DDC-intoxicated mice as well as in human AH, MBs preferentially contain hyperphosphorylated CK8/18 as compared with the cytoplasmic cytokeratin intermediate filament network suggesting that CK8/18 hyperphosphorylation may play a contributing role in MB pathogenesis. Furthermore, the site-specific phosphorylation of cytokeratin in different stages of MB induction provides indirect evidence for the involvement of a variety of protein kinases known to be activated in stress responses, mitosis, and apoptosis.

The cytoskeleton of digestive epithelia in health and disease

The mammalian cell cytoskeleton consists of a diverse group of fibrillar elements that play a pivotal role in mediating a number of digestive and nondigestive cell functions, including secretion, absorption, motility, mechanical integrity, and mitosis. The cytoskeleton of higher-eukaryotic cells consists of three highly abundant major protein families: microfilaments (MF), microtubules (MT), and intermediate filaments (IF), as well as a growing number of associated proteins. Within digestive epithelia, the prototype members of these three protein families are actins, tubulins, and keratins, respectively. This review highlights the important structural, regulatory, functional, and unique features of the three major cytoskeletal protein groups in digestive epithelia. The emerging exciting biological aspects of these protein groups are their involvement in cell signaling via direct or indirect interaction with a growing list of associated proteins (MF, MT, IF), the identification of several disease-causing mutations (IF, MF), the functional role that they play in protection from environmental stresses (IF), and their functional integration via several linker proteins that bridge two or potentially all three of these groups together. The use of agents that target specific cytoskeletal elements as therapeutic modalities for digestive diseases offers potential unique areas of intervention that remain to be fully explored.