Pathogenesis of chronic liver injury and hepatocellular carcinoma in alpha-1-antitrypsin deficiency

Proteasome hyperactivation rewires the proteome enhancing stress resistance, proteostasis, lipid metabolism and ERAD in C. elegans

Proteasome dysfunction is implicated in the pathogenesis of neurodegenerative diseases and age-related proteinopathies. Using a C. elegans model, we demonstrate that 20S proteasome hyperactivation, facilitated by 20S gate-opening, accelerates the targeting of intrinsically disordered proteins. This leads to increased protein synthesis, extensive rewiring of the proteome and transcriptome, enhanced oxidative stress defense, accelerated lipid metabolism, and peroxisome proliferation. It also promotes ER-associated degradation (ERAD) of aggregation-prone proteins, such as alpha-1 antitrypsin (ATZ) and various lipoproteins. Notably, our results reveal that 20S proteasome hyperactivation suggests a novel role in ERAD with broad implications for proteostasis-related disorders, simultaneously affecting lipid homeostasis and peroxisome proliferation. Furthermore, the enhanced cellular capacity to mitigate proteostasis challenges, alongside unanticipated acceleration of lipid metabolism is expected to contribute to the longevity phenotype of this mutant. Remarkably, the mechanism of longevity induced by 20S gate opening appears unique, independent of known longevity and stress-resistance pathways. These results support the therapeutic potential of 20S proteasome activation in mitigating proteostasis-related disorders broadly and provide new insights into the complex interplay between proteasome activity, cellular health, and aging.

Characterization of hepatic inflammatory changes in a C57BL/6J mouse model of alpha1-antitrypsin deficiency

Alpha-1 antitrypsin deficiency (AATD) is a genetic disease caused by a hepatic accumulation of mutant alpha-1 antitrypsin (ZAAT). Individuals with AATD are prone to develop a chronic liver disease that remains undiagnosed until late stage of the disease. Here, we sought to characterize the liver pathophysiology of a human transgenic mouse model for AATD with a manifestation of liver disease compared with normal transgenic mice model. Male and female transgenic mice for normal (Pi*M) and mutant variant (Pi*Z) human alpha-1 antitrypsin at 3 and 6 mo of age were subjected to this study. The progression of hepatic ZAAT accumulation, hepatocyte injury, steatosis, liver inflammation, and fibrotic features were monitored by performing an in vivo study. We have also performed a Next-Gene transcriptomic analysis of the transgenic mice liver tissue 16 h after lipopolysaccharide (LPS) administration to delineate liver inflammatory response in Pi*Z mice as compared with Pi*M. Our results show hepatic ZAAT accumulation, followed by hepatocyte ballooning and liver steatosis developed at 3 mo in Pi*Z mice compared with the mice carrying normal variant of human alpha-1 antitrypsin. We observed higher levels of hepatic immune cell infiltrations in both 3- and 6-mo-old Pi*Z mice compared with Pi*M as an indication of liver inflammation. Liver fibrosis was observed as accumulation of collagen in 6-mo-old Pi*Z liver tissues compared with Pi*M control mice. Furthermore, the transcriptomic analysis revealed a dysregulated liver immune response to LPS in Pi*Z mice compared with Pi*M. Of particular interest for translational work, this study aims to establish a mouse model of AATD with a strong manifestation of liver disease that will be a valuable in vivo tool to study the pathophysiology of AATD-mediated liver disease. Our data suggest that the human transgenic mouse model of AATD could provide a suitable model for the evaluation of therapeutic approaches and preventive reagents against AATD-mediated liver disease.NEW & NOTEWORTHY We have characterized a mouse model of human alpha-1 antitrypsin deficiency with a strong manifestation of liver disease that can be used as an in vivo tool to test preventive and therapeutic reagents. Our data explores the altered immunophenotype of alpha-1 antitrypsin-deficient liver macrophages and suggests a relationship between acute inflammation, immune response, and fibrosis.

Disease Status at Diagnosis in Danish Children with α 1 -antitrypsin Deficiency

OBJECTIVES

The aim of this cross-sectional study was to assess the state of disease at the time of diagnosis in Danish children with α 1 -antitrypsin deficiency as Denmark has a high prevalence of ZZ-homozygosity.

METHODS

Children either heterozygous, compound heterozygous, or homozygous for Z- and S-variants in the SERPINA1 -gene were included. Clinical characteristics, SERPINA1 -genotype, and blood serum (S) concentrations were recorded concurrently with genetic testing. Serum liver marker concentrations were compared using T tests and Wilcoxon-Mann-Whitney tests. Generalized estimating equation (GEE) linear regression models, both univariable and multivariable adjusted for age and sex, were applied to identify correlations with serum α 1 -antitrypsin (S-AAT). The relationship between S-AAT concentration and genotype was assessed using logistic regression with GEE.

RESULTS

The study included 183 of 225 children genetically tested for alpha-1-antitrypsin deficiency (AATD). Of these, 36.6% were homozygous for the Z-variant. Of the heterozygotes, 89.7% had a ZM genotype and the remaining had either an MS genotype or were compound heterozygous. At diagnosis, ZZ-homozygous children had higher serum concentrations of liver enzymes and conjugated bilirubin, but lower concentrations of S-AAT compared with heterozygotes. Serum concentrations of conjugated bilirubin and liver enzymes were negatively associated with S-AAT. Children under 6 months of age had higher total S-bilirubin concentrations than children over 6 months of age.

CONCLUSIONS

A low S-AAT concentration is a strong indicator of homozygosity, and homozygous children have higher enzymatic and cholestatic parameters compared with heterozygous children at diagnosis. This underlines the importance of measuring the S-AAT concentration in children with prolonged neonatal jaundice.

Hepatocellular carcinoma (HCC): Epidemiology, etiology and molecular classification

Hepatocellular carcinoma (HCC), the primary malignancy of hepatocytes, is a diagnosis with bleak outcome. According to National Cancer Institute's SEER database, the average five-year survival rate of HCC patients in the US is 19.6% but can be as low as 2.5% for advanced, metastatic disease. When diagnosed at early stages, it is treatable with locoregional treatments including surgical resection, Radio-Frequency Ablation, Trans-Arterial Chemoembolization or liver transplantation. However, HCC is usually diagnosed at advanced stages when the tumor is unresectable, making these treatments ineffective. In such instances, systemic therapy with tyrosine kinase inhibitors (TKIs) becomes the only viable option, even though it benefits only 30% of patients, provides only a modest (~3months) increase in overall survival and causes drug resistance within 6months. HCC, like many other cancers, is highly heterogeneous making a one-size fits all option problematic. The selection of liver transplantation, locoregional treatment, TKIs or immune checkpoint inhibitors as a treatment strategy depends on the disease stage and underlying condition(s). Additionally, patients with similar disease phenotype can have different molecular etiology making treatment responses different. Stratification of patients at the molecular level would facilitate development of the most effective treatment option. With the increase in efficiency and affordability of "omics"-level analysis, considerable effort has been expended in classifying HCC at the molecular, metabolic and immunologic levels. This review examines the results of these efforts and the ways they can be leveraged to develop targeted treatment options for HCC.

CHOP and c-JUN up-regulate the mutant Z α1-antitrypsin, exacerbating its aggregation and liver proteotoxicity

α₁-Antitrypsin (AAT) encoded by the SERPINA1 gene is an acute-phase protein synthesized in the liver and secreted into the circulation. Its primary role is to protect lung tissue by inhibiting neutrophil elastase. The Z allele of SERPINA1 encodes a mutant AAT, named ATZ, that changes the protein structure and leads to its misfolding and polymerization, which cause endoplasmic reticulum (ER) stress and liver disease through a gain-of-function toxic mechanism. Hepatic retention of ATZ results in deficiency of one of the most important circulating proteinase inhibitors and predisposes to early-onset emphysema through a loss-of-function mechanism. The pathogenetic mechanisms underlying the liver disease are not completely understood. C/EBP-homologous protein (CHOP), a transcription factor induced by ER stress, was found among the most up-regulated genes in livers of PiZ mice that express ATZ and in human livers of patients homozygous for the Z allele. Compared with controls, juvenile PiZ/Chop ^-/- mice showed reduced hepatic ATZ and a transcriptional response indicative of decreased ER stress by RNA-Seq analysis. Livers of PiZ/Chop ^-/- mice also showed reduced SERPINA1 mRNA levels. By chromatin immunoprecipitations and luciferase reporter-based transfection assays, CHOP was found to up-regulate SERPINA1 cooperating with c-JUN, which was previously shown to up-regulate SERPINA1, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. In summary, CHOP and c-JUN up-regulate SERPINA1 transcription and play an important role in hepatic disease by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.

Alpha-1 Antitrypsin Deficiency and Pulmonary Morbidity in Patients with Primary Immunodeficiency Disease: A Single-Center Experience

Background

Alpha-1 antitrypsin deficiency (AATD) is of importance in the pathogenesis of pulmonary emphysema, chronic obstructive pulmonary diseases (COPD), and bronchiectasis. Various pulmonary disorders are a typical feature of primary immunodeficiency disease (PID). This includes recurrent pulmonary infections, immunodysregulation, and autoinflammatory diseases. As a result, incidence of acute and chronic pulmonary diseases is higher. Interestingly, pulmonary morbidity in PID and AATD share similar features. To study the coexistence of AATD in patients suffering from PID, we performed the underlying investigation.

Methods

We evaluated a study group of 149 patients (n = 149) with PID. In total, serum AAT concentrations were available for 110 patients (n = 110). For the identified patients, we analyzed both clinical associations and interactions.

Results

Among the investigated patients, reduced serum AAT levels were detected in 7 patients. With regard to the genotype, PI∗ZZ was found in 2 patients, whereas PI∗MZ was observed in 5 patients. Independent of the underlying phenotype, obstructive lung diseases were found in 2 patients with PI∗ZZ and 2 patients with PI∗MZ.

Conclusions

In Germany, the estimated percentage for PI∗ZZ and PI∗MZ is 0.01% and 1.9%, respectively. As demonstrated, the ratio in our study group was even higher. We identified seven patients with AATD. Since AATD contributes to pulmonary morbidity in PID patients, systematic underdiagnosis of the coexistence might yield a strong clinical impact. Hence, AAT analysis should be offered to all patients with confirmed PID diagnoses. To strengthen this finding, we suggest the investigation of larger databases.

α-1 Antitrypsin Genotype-Phenotype Discrepancy in a 42-Year-Old Man Who Carries the Null-Allele

BACKGROUND

Alpha-1-antitrypsin (A1AT) deficiency is a hereditary condition caused by mutations in the SERPINA1 gene and associated with lung emphysema and liver disease. Laboratory testing in suspected A1AT deficiency involves quantifying serum A1AT concentration and identification of specific alleles by genotyping and phenotyping. The aim of this report was to present a case of the null allele carrier with consequent genotype/phenotype/concentration discrepancies and potential misclassification of the Z variant in a 42-year-old white man presenting with symptoms of chronic obstructive pulmonary disease (COPD).

METHOD

Serum A1AT concentration was measured using an immunoturbidimetric assay. A1AT phenotype was determined using isoelectric focusing followed with immunofixation (IEF-IF). Genotyping specifically for the S and Z allele was performed by melting curve analysis using real-time PCR and checked by an alternative PCR-RFLP method. Genotype/phenotype ambiguity and discrepancy were amended using gene sequencing.

RESULTS

Laboratory testing revealed highly reduced A1AT concentration (less than 0.30 g/L), mild to moderate deficient genotype (Pi*Z allele: M/Z and Pi*S allele: M/M) and severe deficient Z homozygous phenotype (Pi ZZ). After repeated sampling, the same discordant results were verified by these tests. Further sequencing revealed two clinically relevant and defective variants: rs199422210 (a rare null allele) and rs28929474 (the Z allele).

CONCLUSION

Due to inability of genotyping kit probes to detect null/Z allele combination (which mimics the Pi ZZ phenotype), our patient was misclassified as mild to moderate deficient Pi*MZ heterozygote. In all unclear cases, whole-gene sequencing is highly recommended in order to determine definitive cause of A1AT deficiency.

Pharmaceutical Research for Inherited Metabolic Disorders of the Liver Using Human Induced Pluripotent Stem Cell and Genome Editing Technologies

Orthotopic liver transplantation, rather than drug therapy, is the major curative approach for various inherited metabolic disorders of the liver. However, the scarcity of donated livers is a serious problem. To resolve this, there is an urgent need for novel drugs to treat inherited metabolic disorders of the liver. This requirement, in turn, necessitates the establishment of suitable disease models for many inherited metabolic disorders of the liver that currently lack such models for drug development. Recent studies have shown that human induced pluripotent stem (iPS) cells generated from patients with inherited metabolic disorders of the liver are an ideal cell source for models that faithfully recapitulate the pathophysiology of inherited metabolic disorders of the liver. By using patient iPS cell-derived hepatocyte-like cells, drug efficacy evaluation and drug screening can be performed. In addition, genome editing technology has enabled us to generate functionally recovered patient iPS cell-derived hepatocyte-like cells in vitro. It is also possible to identify the genetic mutations responsible for undiagnosed liver diseases using iPS cell and genome editing technologies. Finally, a combination of exhaustive analysis, iPS cells, and genome editing technologies would be a powerful approach to accelerate the identification of novel genetic mutations responsible for undiagnosed liver diseases. In this review, we will discuss the usefulness of iPS cell and genome editing technologies in the field of inherited metabolic disorders of the liver, such as alpha-1 antitrypsin deficiency and familial hypercholesterolemia.

The endoplasmic reticulum co-chaperone ERdj3/DNAJB11 promotes hepatocellular carcinoma progression through suppressing AATZ degradation

AIM

The co-chaperone ERdj3/DNAJB11 is involved in the endoplasmic reticulum stress response observed in cancer cells. We hypothesized that ERdj3 functions as a hepatocellular carcinoma (HCC) oncogene by inhibiting AATZ degradation.

MATERIALS & METHODS

ERdj3 and AATZ expressions were analyzed in 84 HCC patients. Cell proliferation, epithelial-mesenchymal transition marker expression, migration and invasiveness were assessed in HepG2 and Huh-7 cells. A murine xenograft tumor model was constructed.

RESULTS

ERdj3 is upregulated in HCC tumors and cell lines. Tumor ERdj3 levels are positively associated with cirrhosis, enhanced HCC status, inferior survival outcomes and AATZ levels. ERdj3 suppresses AATZ degradation. ERdj3 overexpression enhances proliferation, epithelial-mesenchymal transition marker expression, migration, invasiveness and xenograft tumor growth in an AATZ-dependent manner.

CONCLUSION

ERdj3 enhances HCC progression through suppressing AATZ degradation.

Chemotherapy for Hepatocellular Carcinoma: Current Evidence and Future Perspectives

Hepatocarcinogenesis is a multistep process, heralded by abnormalities in cell differentiation and proliferation and sustained by an aberrant neoangiogenesis. Understanding the underlying molecular pathogenesis leading to hepatocellular carcinoma is a prerequisite to develop new drugs that will hamper or block the steps of these pathways. As hepatocellular carcinoma has higher arterial vascularization than normal liver, this could be a good target for novel molecular therapies. Introduction of the antiangiogenic drug sorafenib into clinical practice since 2008 has led to new perspectives in the management of this tumor. The importance of this drug lies not only in the modest gain of patients' survival, but in having opened a roadmap towards the development of new molecules and targets. Unfortunately, after the introduction of sorafenib, during the last years, a wide number of clinical trials on antiangiogenic therapies failed in achieving significant results. However, many of these trials are still ongoing and promise to improve overall survival and progression-free survival. A recent clinical trial has proven regorafenib effective in patients showing tumor progression under sorafenib, thus opening new interesting therapeutic perspectives. Many other expectations have been borne from the discovery of the immune checkpoint blockade, already known in other solid malignancies. Furthermore, a potential role in hepatocellular carcinoma therapy may derive from the use of branched-chain amino acids and of nutritional support. This review analyses the biomolecular pathways of hepatocellular carcinoma and the ongoing studies, the actual evidence and the future perspectives concerning drug therapy in this open field.

Is severe progressive liver disease caused by alpha-1-antitrypsin deficiency more common in children or adults?

The classical form of alpha-1-antitrypsin deficiency (A1ATD) is known to cause liver disease in children and adults, but there is relatively little information about the risk of severe, progressive liver disease and the need for liver transplantation. To better understand how newly evolving pharmacological, genetic, and cellular therapies may be targeted according to risk for progressive liver disease, we sought to determine the age distribution of A1ATD as a cause of severe liver disease, as defined by the need for liver transplantation. Using 3 US liver transplantation databases for the period 1991-2012, we found 77.2% of 1677 liver transplants with a reported diagnosis of A1ATD were adults. The peak age range was 50-64 years. Using 2 of the databases which included specific A1AT phenotypes, we found that many of these adults who undergo liver transplantation with A1ATD as the diagnosis are heterozygotes and have other potential causes of liver disease, most notably obesity and ethanol abuse. However, even when these cases are excluded and only ZZ and SZ phenotypes are considered, severe liver disease requiring transplantation is more than 2.5 times as likely in adults. The analysis also showed a markedly increased risk for males. In the pediatric group, almost all of the transplants are done in children less than 5 years of age. In conclusion, A1ATD causes progressive liver disease most commonly in adults with males in the highest risk category. In the pediatric group, children less than 5 years of age are highest in risk. These results suggest that A1ATD most commonly causes liver disease by mechanisms similar to age-dependent degenerative diseases and more rarely in children by powerful modifiers. Liver Transplantation 22 886-894 2016 AASLD.

New advances in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the leading cause of deaths in cirrhotic patients and the third cause of cancer related deaths. Most HCC are associated with well known underlying risk factors, in fact, HCC arise in cirrhotic patients in up to 90% of cases, mainly due to chronic viral hepatitis and alcohol abuse. The worldwide prevention strategies are conducted to avoid the infection of new subjects and to minimize the risk of liver disease progression in infected patients. HCC is a condition which lends itself to surveillance as at-risk individuals can readily be identified. The American and European guidelines recommended implementation of surveillance programs with ultrasound every six months in patient at-risk for developing HCC. The diagnosis of HCC can be based on non-invasive criteria (only in cirrhotic patient) or pathology. Accurately staging patients is essential to oncology practice. The ideal tumour staging system in HCC needs to account for both tumour characteristics and liver function. Treatment allocation is based on several factors: Liver function, size and number of tumours, macrovascular invasion or extrahepatic spread. The recommendations in terms of selection for different treatment strategies must be based on evidence-based data. Resection, liver transplant and interventional radiology treatment are mainstays of HCC therapy and achieve the best outcomes in well-selected candidates. Chemoembolization is the most widely used treatment for unresectable HCC or progression after curative treatment. Finally, in patients with advanced HCC with preserved liver function, sorafenib is the only approved systemic drug that has demonstrated a survival benefit and is the standard of care in this group of patients.

Deficient and Null Variants of SERPINA1 Are Proteotoxic in a Caenorhabditis elegans Model of α1-Antitrypsin Deficiency

α1-antitrypsin deficiency (ATD) predisposes patients to both loss-of-function (emphysema) and gain-of-function (liver cirrhosis) phenotypes depending on the type of mutation. Although the Z mutation (ATZ) is the most prevalent cause of ATD, >120 mutant alleles have been identified. In general, these mutations are classified as deficient (<20% normal plasma levels) or null (<1% normal levels) alleles. The deficient alleles, like ATZ, misfold in the ER where they accumulate as toxic monomers, oligomers and aggregates. Thus, deficient alleles may predispose to both gain- and loss-of-function phenotypes. Null variants, if translated, typically yield truncated proteins that are efficiently degraded after being transiently retained in the ER. Clinically, null alleles are only associated with the loss-of-function phenotype. We recently developed a C. elegans model of ATD in order to further elucidate the mechanisms of proteotoxicity (gain-of-function phenotype) induced by the aggregation-prone deficient allele, ATZ. The goal of this study was to use this C. elegans model to determine whether different types of deficient and null alleles, which differentially affect polymerization and secretion rates, correlated to any extent with proteotoxicity. Animals expressing the deficient alleles, Mmalton, Siiyama and S (ATS), showed overall toxicity comparable to that observed in patients. Interestingly, Siiyama expressing animals had smaller intracellular inclusions than ATZ yet appeared to have a greater negative effect on animal fitness. Surprisingly, the null mutants, although efficiently degraded, showed a relatively mild gain-of-function proteotoxic phenotype. However, since null variant proteins are degraded differently and do not appear to accumulate, their mechanism of proteotoxicity is likely to be different to that of polymerizing, deficient mutants. Taken together, these studies showed that C. elegans is an inexpensive tool to assess the proteotoxicity of different AT variants using a transgenic approach.

Liver tumors in children with metabolic disorders

Hepatic neoplasia is a rare but serious complication of metabolic diseases in children. The risk of developing neoplasia, the age at onset, and the measures to prevent it differ in the various diseases. We review the most common metabolic disorders that are associated with a heightened risk of developing hepatocellular neoplasms, with a special emphasis on reviewing recent advances in the molecular pathogenesis of the disorders and pre-clinical therapeutic options. The cellular and genetic pathways driving carcinogenesis are poorly understood, but best understood in tyrosinemia.

The aggregation-prone intracellular serpin SRP-2 fails to transit the ER in Caenorhabditis elegans

Familial encephalopathy with neuroserpin inclusions bodies (FENIB) is a serpinopathy that induces a rare form of presenile dementia. Neuroserpin contains a classical signal peptide and like all extracellular serine proteinase inhibitors (serpins) is secreted via the endoplasmic reticulum (ER)-Golgi pathway. The disease phenotype is due to gain-of-function missense mutations that cause neuroserpin to misfold and aggregate within the ER. In a previous study, nematodes expressing a homologous mutation in the endogenous Caenorhabditis elegans serpin, srp-2, were reported to model the ER proteotoxicity induced by an allele of mutant neuroserpin. Our results suggest that SRP-2 lacks a classical N-terminal signal peptide and is a member of the intracellular serpin family. Using confocal imaging and an ER colocalization marker, we confirmed that GFP-tagged wild-type SRP-2 localized to the cytosol and not the ER. Similarly, the aggregation-prone SRP-2 mutant formed intracellular inclusions that localized to the cytosol. Interestingly, wild-type SRP-2, targeted to the ER by fusion to a cleavable N-terminal signal peptide, failed to be secreted and accumulated within the ER lumen. This ER retention phenotype is typical of other obligate intracellular serpins forced to translocate across the ER membrane. Neuroserpin is a secreted protein that inhibits trypsin-like proteinase. SRP-2 is a cytosolic serpin that inhibits lysosomal cysteine peptidases. We concluded that SRP-2 is neither an ortholog nor a functional homolog of neuroserpin. Furthermore, animals expressing an aggregation-prone mutation in SRP-2 do not model the ER proteotoxicity associated with FENIB.

Alpha-1-antitrypsin deficiency: from genoma to liver disease. PiZ mouse as model for the development of liver pathology in human

BACKGROUND & AIMS

Homozygous individuals with alpha-1-antitrypsin deficiency (AATD) type PiZ have an increased risk of chronic liver disease and hepatocellular carcinoma (HCC). It is noteworthy that HCCs are composed by hepatocytes without accumulation of AAT, but the reason for this remains unclear. The aim of this study was to determine liver pathology in PiZ mice, focusing the attention on the distribution of AAT globules in normal liver, regenerative foci and neoplastic nodules.

METHODS

Liver of 79 PiZ mice and 18 wild type (Wt) was histologically analysed for steatosis, clear cell foci, hyperplasia and neoplasia. The expression of human-AAT transgene and murine AAT, in non-neoplastic liver and in hyperplastic/neoplastic nodules was tested by qPCR and qRT-PCR. RT-PCR was used to study expression of hepatic markers: albumin, α-foetoprotein, transthyretin, AAT, glucose-6-phospate, tyrosine aminotransferase.

RESULTS

Liver pathology was seen more frequently in PiZ (47/79) than in Wt (5/18) and its development was age related. In older PiZ mice (18-24 m), livers showed malignant tumours (HCC and angiosarcoma) (17/50), hyperplastic nodules (28/50), non-specific changes (33/50), whereas only 9/50 were normal. Both human-AATZ DNA and mRNA showed no differences between tumours/nodules and normal liver, while murine-AAT mRNA was reduced in tumours/nodules.

CONCLUSION

Accumulation of AAT is associated with an increased risk of liver nodules. The presence of globule-devoid hepatocytes and the reduced expression of murine-AAT mRNA in hyperplastic and neoplastic nodules suggest that these hepatic lesions in AATD could originate from proliferating dedifferentiated cells, lacking AAT storage and becoming capable of AFP re-expression.

Capitalizing on the autophagic response for treatment of liver disease caused by alpha-1-antitrypsin deficiency and other genetic diseases

Alpha-1-antitrypsin deficiency (ATD) is one of the most common genetic causes of liver disease and is a prototype of liver diseases caused by the pathologic accumulation of aggregated mutant alpha-1-antitrypsin Z (ATZ) within liver cells. In the case of ATD-associated liver disease, the resulting “gain-of-function” toxicity can lead to serious clinical manifestations, including cirrhosis and hepatocellular carcinoma. Currently, the only definitive therapy for ATD-associated liver disease is liver transplantation, but recent efforts have demonstrated the exciting potential for novel therapies that target disposal of the mutant protein aggregates by harnessing a cellular homeostasis mechanism called autophagy. In this review, we will summarize research advances on autophagy and genetic liver diseases. We will discuss autophagy enhancer strategies for liver disease due to ATD and another genetic liver disease, inherited hypofibrinogenemia, caused by the proteotoxic effects of a misfolded protein. On the basis of recent evidence that autophagy plays a role in cellular lipid degradation, we also speculate about autophagy enhancer strategies for treatment of hepatic lipid storage diseases such as cholesterol ester storage disease.

A genome-wide RNAi screen identifies potential drug targets in a C. elegans model of α1-antitrypsin deficiency

α1-Antitrypsin deficiency (ATD) is a common genetic disorder that can lead to end-stage liver and lung disease. Although liver transplantation remains the only therapy currently available, manipulation of the proteostasis network (PN) by small molecule therapeutics offers great promise. To accelerate the drug-discovery process for this disease, we first developed a semi-automated high-throughput/content-genome-wide RNAi screen to identify PN modifiers affecting the accumulation of the α1-antitrypsin Z mutant (ATZ) in a Caenorhabditis elegans model of ATD. We identified 104 PN modifiers, and these genes were used in a computational strategy to identify human ortholog-ligand pairs. Based on rigorous selection criteria, we identified four FDA-approved drugs directed against four different PN targets that decreased the accumulation of ATZ in C. elegans. We also tested one of the compounds in a mammalian cell line with similar results. This methodology also proved useful in confirming drug targets in vivo, and predicting the success of combination therapy. We propose that small animal models of genetic disorders combined with genome-wide RNAi screening and computational methods can be used to rapidly, economically and strategically prime the preclinical discovery pipeline for rare and neglected diseases with limited therapeutic options.

Latin American Association for the Study of the Liver (LAASL) clinical practice guidelines: management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world and the third most common cause of cancer death, and accounts for 5.6% of all cancers. Nearly 82% of the approximately 550,000 liver cancer deaths each year occur in Asia. In some regions, cancer-related death from HCC is second only to lung cancer. The incidence and mortality of HCC are increasing in America countries as a result of an ageing cohort infected with chronic hepatitis C, and are expected to continue to rise as a consequence of the obesity epidemic. Clinical care and survival for patients with HCC has advanced considerably during the last two decades, thanks to improvements in patient stratification, an enhanced understanding of the pathophysiology of the disease, and because of developments in diagnostic procedures and the introduction of novel therapies and strategies in prevention. Nevertheless, HCC remains the third most common cause of cancer-related deaths worldwide. These LAASL recommendations on treatment of hepatocellular carcinoma are intended to assist physicians and other healthcare providers, as well as patients and other interested individuals, in the clinical decision-making process by describing the optimal management of patients with liver cancer.

Z α1-antitrypsin confers a proinflammatory phenotype that contributes to chronic obstructive pulmonary disease

RATIONALE

Severe α1-antitrypsin deficiency caused by the Z variant (Glu342Lys; ZZ-AT) is a well-known genetic cause for emphysema. Although severe lack of antiproteinase protection is the critical etiologic factor for ZZ-AT-associated chronic obstructive pulmonary disease (COPD), some reports have suggested enhanced lung inflammation as a factor in ZZ-AT homozygotes.

OBJECTIVES

To provide molecular characterization of inflammation in ZZ-AT.

METHODS

Inflammatory cell and cytokine profile (nuclear factor-κB, IL-6, tumor necrosis factor-α), intracellular polymerization of Z-AT, and endoplasmic reticulum (ER) stress markers (protein kinase RNA-like ER kinase, activator transcription factor 4) were assessed in transgenic mice and transfected cells in response to cigarette smoke, and in explanted lungs from ZZ and MM individuals with severe COPD.

MEASUREMENTS AND MAIN RESULTS

Compared with M-AT, transgenic Z-AT mice lungs exposed to cigarette smoke had higher levels of pulmonary cytokines, neutrophils, and macrophages and an exaggerated ER stress. Similarly, the ER overload response was greater in lungs from ZZ-AT homozygotes with COPD, and was particularly found in pulmonary epithelial cells. Cigarette smoke increased intracellular Z-AT polymers, ER overload response, and proinflammatory cytokine release in Z-AT-expressing pulmonary epithelial cells, which could be prevented with an inhibitor of polymerization, an antioxidant, and an inhibitor of protein kinase RNA-like ER kinase.

CONCLUSIONS

We show here that aggregation of intracellular mutant Z-AT invokes a specific deleterious cellular inflammatory phenotype in COPD. Oxidant-induced intracellular polymerization of Z-AT in epithelial cells causes ER stress, and promotes excess cytokine and cellular inflammation. This pathway is likely to contribute to the development of COPD in ZZ-AT homozygotes, and therefore merits further investigation.

UDP-glucose:glycoprotein glucosyltransferase (UGGT1) promotes substrate solubility in the endoplasmic reticulum

The N-glycans promote solubility in the ER even for mutant glycoproteins, such as mutant α1-antitrypsin. This study shows that enzymatic monoglucosylation activity of the enzyme UGGT1 and lectin chaperone abundance are required for N-glycans to provide maximum solubility to the misfolded substrate.

Protein folding in the endoplasmic reticulum (ER) is error prone, and ER quality control (ERQC) processes ensure that only correctly folded proteins are exported from the ER. Glycoproteins can be retained in the ER by ERQC, and this retention contributes to multiple human diseases, termed ER storage diseases. UDP-glucose:glycoprotein glucosyltransferase (UGGT1) acts as a central component of glycoprotein ERQC, monoglucosylating deglucosylated N-glycans of incompletely folded glycoproteins and promoting subsequent reassociation with the lectin-like chaperones calreticulin and calnexin. The extent to which UGGT1 influences glycoprotein folding, however, has only been investigated for a few selected substrates. Using mouse embryonic fibroblasts lacking UGGT1 or those with UGGT1 complementation, we investigated the effect of monoglucosylation on the soluble/insoluble distribution of two misfolded α1-antitrypsin (AAT) variants responsible for AAT deficiency disease: null Hong Kong (NHK) and Z allele. Whereas substrate solubility increases directly with the number of N-linked glycosylation sites, our results indicate that additional solubility is conferred by UGGT1 enzymatic activity. Monoglucosylation-dependent solubility decreases both BiP association with NHK and unfolded protein response activation, and the solubility increase is blocked in cells deficient for calreticulin. These results suggest that UGGT1-dependent monoglucosylation of N-linked glycoproteins promotes substrate solubility in the ER.

Quantitative proteomic analyses of cerebrospinal fluid using iTRAQ in a primate model of iron deficiency anemia

Iron deficiency affects nearly 2 billion people worldwide, with pregnant women and young children being most severely impacted. Sustained anemia during the first year of life can cause cognitive, attention and motor deficits, which may persist despite iron supplementation. We conducted iTRAQ analyses on cerebrospinal fluid (CSF) from infant monkeys (Macaca mulatta) to identify differential protein expression associated with early iron deficiency. CSF was collected from 5 iron-sufficient and 8 iron-deficient anemic monkeys at weaning age (6-7 months) and again at 12-14 months. Despite consumption of iron-fortified food after weaning, which restored hematological indices into the normal range, expression of 5 proteins in the CSF remained altered. Most of the proteins identified are involved in neurite outgrowth, migration or synapse formation. The results reveal novel ways in which iron deficiency undermines brain growth and results in aberrant neuronal migration and connections. Taken together with gene expression data from rodent models of iron deficiency, we conclude that significant alterations in neuroconnectivity occur in the iron-deficient brain, which may persist even after resolution of the hematological anemia. The compromised brain infrastructure could account for observations of behavioral deficits in children during and after the period of anemia.

The delicate balance between secreted protein folding and endoplasmic reticulum-associated degradation in human physiology

Protein folding is a complex, error-prone process that often results in an irreparable protein by-product. These by-products can be recognized by cellular quality control machineries and targeted for proteasome-dependent degradation. The folding of proteins in the secretory pathway adds another layer to the protein folding "problem," as the endoplasmic reticulum maintains a unique chemical environment within the cell. In fact, a growing number of diseases are attributed to defects in secretory protein folding, and many of these by-products are targeted for a process known as endoplasmic reticulum-associated degradation (ERAD). Since its discovery, research on the mechanisms underlying the ERAD pathway has provided new insights into how ERAD contributes to human health during both normal and diseases states. Links between ERAD and disease are evidenced from the loss of protein function as a result of degradation, chronic cellular stress when ERAD fails to keep up with misfolded protein production, and the ability of some pathogens to coopt the ERAD pathway. The growing number of ERAD substrates has also illuminated the differences in the machineries used to recognize and degrade a vast array of potential clients for this pathway. Despite all that is known about ERAD, many questions remain, and new paradigms will likely emerge. Clearly, the key to successful disease treatment lies within defining the molecular details of the ERAD pathway and in understanding how this conserved pathway selects and degrades an innumerable cast of substrates.

Novel treatment strategies for liver disease due to α1-antitrypsin deficiency

Alpha1-antitrypsin (AT) deficiency is the most common genetic cause of liver disease in children and is also a cause of chronic hepatic fibrosis, cirrhosis, and hepatocellular carcinoma in adults. Recent advances in understanding how mutant AT molecules accumulate within hepatocytes and cause liver cell injury have led to a novel strategy for chemoprophylaxis of this liver disease. This strategy involves a class of drugs, which enhance the intracellular degradation of mutant AT and, because several of these drugs have been used safely in humans for other indications, the strategy can be moved immediately into clinical trials. In this review, we will also report on advances that provide a basis for several other strategies that could be used in the future for treatment of the liver disease associated with AT deficiency.

Polymorphisms of hemochromatosis, and alpha-1 antitrypsin genes in Egyptian HCV patients with and without hepatocellular carcinoma

Hereditary hemochromatosis and alpha-1antitrypsin deficiency are genetic diseases characterized by endoplasmic reticulum (ER) stress with subsequent development of liver disease. Our aim was to estimate the frequency of hemochromatosis gene (HFE) mutant alleles (C282Y and H63D) and alpha-1 antitrypsin S/Z variants among Egyptian HCV cirrhotic patients and in hepatocellular carcinoma patients and to evaluate their effects on disease progression. HFE and alpha-1 antitrypsin polymorphisms were characterized in 200 Egyptian patients with HCV infection (100 patients complicated with cirrhosis, 100 patients with HCC) and 100 healthy subjects who had no history of any malignancy. The frequencies of HD genotype of H63D mutation were significantly increased in HCC patients compared to control group and to cirrhosis group. Also, the frequencies of DD genotype were significantly increased In HCC group compared to control group and to cirrhosis group. Our results suggested that Carriers of the D allele of H63D mutation were significantly more likely to develop HCC.

Functions of autophagy in hepatic and pancreatic physiology and disease

Autophagy is a lysosomal pathway that degrades and recycles intracellular organelles and proteins to maintain energy homeostasis during times of nutrient deprivation and to remove damaged cell components. Recent studies have identified new functions for autophagy under basal and stressed conditions. In the liver and pancreas, autophagy performs the standard functions of degrading mitochondria and aggregated proteins and regulating cell death. In addition, autophagy functions in these organs to regulate lipid accumulation in hepatic steatosis, trypsinogen activation in pancreatitis, and hepatitis virus replication. This review discusses the effects of autophagy on hepatic and pancreatic physiology and the contribution of this degradative process to diseases of these organs. The discovery of novel functions for this lysosomal pathway has increased our understanding of the pathophysiology of diseases in the liver and pancreas and suggested new possibilities for their treatment.

Intracellular production of recombinant serpins in yeast

Yeast are a valuable system for recombinant serpin production due to their ability to synthesize large amounts of heterologous gene products as well as their expression of folding chaperones and lack of endogenous serpin genes. In this chapter, we describe a method for intracellular expression of cytoplasmic serpins in the yeast Pichia pastoris. We also give details on how this system can be exploited to produce polymer-forming mutants of secretory serpins.

Hepatic neoplasia and metabolic diseases in children

Hepatic neoplasia is a rare but serious complication of metabolic diseases in children. The risk of developing neoplasia, the age at onset, and the measures to prevent it differ in various diseases. This article reviews the most common metabolic disorders in humans that are associated with neoplasms, with a special emphasis on the molecular etiopathogenesis of this process. The cellular pathways driving carcinogenesis are poorly understood, but best known in tyrosinemia.

Z α-1 antitrypsin deficiency and the endoplasmic reticulum stress response

The serine proteinase inhibitor α-1 antitrypsin (AAT) is produced principally by the liver at the rate of 2 g/d. It is secreted into the circulation and provides an antiprotease protective screen throughout the body but most importantly in the lung, where it can neutralise the activity of the serine protease neutrophil elastase. Mutations leading to deficiency in AAT are associated with liver and lung disease. The most notable is the Z AAT mutation, which encodes a misfolded variant of the AAT protein in which the glutamic acid at position 342 is replaced by a lysine. More than 95% of all individuals with AAT deficiency carry at least one Z allele. ZAAT protein is not secreted effectively and accumulates intracellularly in the endoplasmic reticulum (ER) of hepatocytes and other AAT-producing cells. This results in a loss of function associated with decreased circulating and intrapulmonary levels of AAT. However, the misfolded protein acquires a toxic gain of function that impacts on the ER. A major function of the ER is to ensure correct protein folding. ZAAT interferes with this function and promotes ER stress responses and inflammation. Here the signalling pathways activated during ER stress in response to accumulation of ZAAT are described and therapeutic strategies that can potentially relieve ER stress are discussed.

Modeling inherited metabolic disorders of the liver using human induced pluripotent stem cells

Human induced pluripotent stem (iPS) cells hold great promise for advancements in developmental biology, cell-based therapy, and modeling of human disease. Here, we examined the use of human iPS cells for modeling inherited metabolic disorders of the liver. Dermal fibroblasts from patients with various inherited metabolic diseases of the liver were used to generate a library of patient-specific human iPS cell lines. Each line was differentiated into hepatocytes using what we believe to be a novel 3-step differentiation protocol in chemically defined conditions. The resulting cells exhibited properties of mature hepatocytes, such as albumin secretion and cytochrome P450 metabolism. Moreover, cells generated from patients with 3 of the inherited metabolic conditions studied in further detail (alpha1-antitrypsin deficiency, familial hypercholesterolemia, and glycogen storage disease type 1a) were found to recapitulate key pathological features of the diseases affecting the patients from which they were derived, such as aggregation of misfolded alpha1-antitrypsin in the endoplasmic reticulum, deficient LDL receptor-mediated cholesterol uptake, and elevated lipid and glycogen accumulation. Therefore, we report a simple and effective platform for hepatocyte generation from patient-specific human iPS cells. These patient-derived hepatocytes demonstrate that it is possible to model diseases whose phenotypes are caused by pathological dysregulation of key processes within adult cells.

A novel monoclonal antibody to characterize pathogenic polymers in liver disease associated with alpha1-antitrypsin deficiency

Alpha(1)-antitrypsin is the most abundant circulating protease inhibitor. The severe Z deficiency allele (Glu342Lys) causes the protein to undergo a conformational transition and form ordered polymers that are retained within hepatocytes. This causes neonatal hepatitis, cirrhosis, and hepatocellular carcinoma. We have developed a conformation-specific monoclonal antibody (2C1) that recognizes the pathological polymers formed by alpha(1)-antitrypsin. This antibody was used to characterize the Z variant and a novel shutter domain mutant (His334Asp; alpha(1)-antitrypsin King's) identified in a 6-week-old boy who presented with prolonged jaundice. His334Asp alpha(1)-antitrypsin rapidly forms polymers that accumulate within the endoplasmic reticulum and show delayed secretion when compared to the wild-type M alpha(1)-antitrypsin. The 2C1 antibody recognizes polymers formed by Z and His334Asp alpha(1)-antitrypsin despite the mutations directing their effects on different parts of the protein. This antibody also recognized polymers formed by the Siiyama (Ser53Phe) and Brescia (Gly225Arg) mutants, which also mediate their effects on the shutter region of alpha(1)-antitrypsin.

CONCLUSION

Z and shutter domain mutants of alpha(1)-antitrypsin form polymers with a shared epitope and so are likely to have a similar structure.

Proteomic analysis of differentially expressed proteins in peripheral cholangiocarcinoma

Cholangiocarcinoma is an adenocarcinoma of the liver which has increased in incidence over the last thirty years to reach similar levels to other liver cancers. Diagnosis of this disease is usually late and prognosis is poor, therefore it is of great importance to identify novel candidate markers and potential early indicators of this disease as well as molecules that may be potential therapeutic targets. We have used a proteomic approach to identify differentially expressed proteins in peripheral cholangiocarcinoma cases and compared expression with paired non-tumoral liver tissue from the same patients. Two-dimensional fluorescence difference gel electrophoresis after labeling of the proteins with cyanines 3 and 5 was used to identify differentially expressed proteins. Overall, of the approximately 2,400 protein spots visualised in each gel, 172 protein spots showed significant differences in expression level between tumoral and non-tumoral tissue with p < 0.01. Of these, 100 spots corresponding to 138 different proteins were identified by mass spectrometry: 70 proteins were over-expressed whereas 68 proteins were under-expressed in tumoral samples compared to non-tumoral samples. Among the over-expressed proteins, immunohistochemistry studies confirmed an increased expression of 14-3-3 protein in tumoral cells while α-smooth muscle actin and periostin were shown to be overexpressed in the stromal myofibroblasts surrounding tumoral cells. α-Smooth muscle actin is a marker of myofibroblast differentiation and has been found to be a prognostic indicator in colon cancer while periostin may also have a role in cell adhesion, proliferation and migration and has been identified in other cancers. This underlines the role of stromal components in cancer progression and their interest for developing new diagnostic or therapeutic tools.

Characteristics of hepatocellular carcinoma in a murine model of alpha-1-antitrypsin deficiency

AIM

Individuals with homozygous (ZZ) alpha-1-antitrypsin (alpha1AT) deficiency are at an increased risk for liver damage, cirrhosis and hepatocellular carcinoma (HCC). The transgenic PiZ mouse, expressing the human alpha1AT mutant Z gene, is a valuable model for this disease. We studied PiZ mice in order to identify and characterize mechanisms involved in the development of HCC.

METHODS

Tumor incidence and histology were studied, gene expression levels were surveyed with microarrays, RNA quantified with quantitative real time polymerase chain reaction and protein levels determined with immunoblots and immunohistochemistry.

RESULTS

By 16-19 months of age, approximately 69% of the PiZ mice had developed tumors. HCC was present with no evidence of benign adenomas as pre-cancerous lesions. Tumors showed abnormal mitochondria, variable levels of steatosis, globular inclusions of alpha1AT mutant Z protein and metastases. PiZ mice that subsequently developed liver tumors had higher serum levels of alpha1AT mutant Z protein than those that did not develop tumors. Cyclin D1, a cell cycle protein, was upregulated in PiZ livers without tumors compared to Wt. cFOS, a component of AP-1 that may be involved in transforming cells and MCAM, an adhesion molecule likely involved in tumorigenesis and metastases, were elevated in tumors compared with livers without tumors.

CONCLUSION

In the PiZ model, many of the histological characteristics of HCC recapitulated features seen in human HCC, whether from individuals with homozygous ZZ liver disease or from unrelated causes in individuals that were not homozygous ZZ. The accumulation of mutant Z protein altered the regulation of several genes driving proliferation and tumorigenesis.

Role of autophagy in liver physiology and pathophysiology

Autophagy is a highly conserved intracellular degradation pathway by which bulk cytoplasm and superfluous or damaged organelles are enveloped by double membrane structures termed autophagosomes. The autophagosomes then fuse with lysosomes for degradation of their contents, and the resulting amino acids can then recycle back to the cytosol. Autophagy is normally activated in response to nutrient deprivation and other stressors and occurs in all eukaryotes. In addition to maintaining energy and nutrient balance in the liver, it is now clear that autophagy plays a role in liver protein aggregates related diseases, hepatocyte cell death, steatohepatitis, hepatitis virus infection and hepatocellular carcinoma. In this review, I discuss the recent findings of autophagy with a focus on its role in liver pathophysiology.

Genetic modifiers of liver disease in cystic fibrosis

CONTEXT

A subset (approximately 3%-5%) of patients with cystic fibrosis (CF) develops severe liver disease with portal hypertension.

OBJECTIVE

To assess whether any of 9 polymorphisms in 5 candidate genes (alpha(1)-antitrypsin or alpha(1)-antiprotease [SERPINA1], angiotensin-converting enzyme [ACE], glutathione S-transferase [GSTP1], mannose-binding lectin 2 [MBL2], and transforming growth factor beta1 [TGFB1]) are associated with severe liver disease in patients with CF.

DESIGN, SETTING, AND PARTICIPANTS

Two-stage case-control study enrolling patients with CF and severe liver disease with portal hypertension (CFLD) from 63 CF centers in the United States as well as 32 in Canada and 18 outside of North America, with the University of North Carolina at Chapel Hill as the coordinating site. In the initial study, 124 patients with CFLD (enrolled January 1999-December 2004) and 843 control patients without CFLD were studied by genotyping 9 polymorphisms in 5 genes previously studied as modifiers of liver disease in CF. In the second stage, the SERPINA1 Z allele and TGFB1 codon 10 genotype were tested in an additional 136 patients with CFLD (enrolled January 2005-February 2007) and 1088 with no CFLD.

MAIN OUTCOME MEASURES

Differences in distribution of genotypes in patients with CFLD vs patients without CFLD.

RESULTS

The initial study showed CFLD to be associated with the SERPINA1 Z allele (odds ratio [OR], 4.72; 95% confidence interval [CI], 2.31-9.61; P = 3.3 x 10(-6)) and with TGFB1 codon 10 CC genotype (OR, 1.53; 95% CI, 1.16-2.03; P = 2.8 x 10(-3)). In the replication study, CFLD was associated with the SERPINA1 Z allele (OR, 3.42; 95% CI, 1.54-7.59; P = 1.4 x 10(-3)) but not with TGFB1 codon 10. A combined analysis of the initial and replication studies by logistic regression showed CFLD to be associated with SERPINA1 Z allele (OR, 5.04; 95% CI, 2.88-8.83; P = 1.5 x 10(-8)).

CONCLUSIONS

The SERPINA1 Z allele is a risk factor for liver disease in CF. Patients who carry the Z allele are at greater risk (OR, approximately 5) of developing severe liver disease with portal hypertension.

Single nucleotide polymorphism-mediated translational suppression of endoplasmic reticulum mannosidase I modifies the onset of end-stage liver disease in alpha1-antitrypsin deficiency

Inappropriate accumulation of the misfolded Z variant of alpha1-antitrypsin in the hepatocyte endoplasmic reticulum (ER) is a risk factor for the development of end-stage liver disease. However, the genetic and environmental factors that contribute to its etiology are poorly understood. ER mannosidase I (ERManI) is a quality control factor that plays a critical role in the sorting and targeting of misfolded glycoproteins for proteasome-mediated degradation. In this study, we tested whether genetic variations in the human ERManI gene influence the age at onset of end-stage liver disease in patients homozygous for the Z allele (ZZ). We sequenced all 13 exons in a group of unrelated Caucasian ZZ transplant recipients with different age at onset of the end-stage liver disease. Homozygosity for the minor A allele at 2484G/A (refSNP ID number rs4567) in the 3'-untranslated region was prevalent in the infant ZZ patients. Functional studies indicated that rs4567(A), but not rs4567(G), suppresses ERManI translation under ER stress conditions.

CONCLUSION

These findings suggest that the identified single-nucleotide polymorphism can accelerate the onset of the end-stage liver disease associated with alpha1-antitrypsin deficiency and underscore the contribution of biosynthetic quality control as a modifier of genetic disease.

The association of family history of liver cancer with hepatocellular carcinoma: a case-control study in the United States

BACKGROUND/AIMS

The study aimed at addressing the connection between positive family history of liver cancer and hepatocellular carcinoma (HCC) development in the USA.

METHODS

At The University of Texas M.D. Anderson Cancer Center, 347 patients with pathologically confirmed HCC and 1075 healthy controls were studied. All subjects were interviewed for their family history of cancer, including the number of relatives with cancer, the type of cancer, the individual's relationship with the relative, and the age at which the relative was diagnosed.

RESULTS

Independently of hepatitis B virus (HBV) and hepatitis C virus (HCV), a history of liver cancer in first degree relatives was significantly associated with HCC development (AOR=4.1 [95% CI, 1.3-12.9]). Multiple relatives with liver cancer were only observed among HCC patients with chronic HBV/HCV infection. Affected siblings with liver cancer is significantly associated with HCC development with and without HBV/HCV infection; (AOR=5.7 [95% CI, 1.2-27.3]) and (AOR=4.3 [95% CI, 1.01-20.9]), respectively. Individuals with HBV/HCV and a family history of liver cancer were at higher risk for HCC (AOR=61.9 [95% CI, 6.6-579.7]).

CONCLUSIONS

First degree family history of liver cancer is associated with HCC development in the USA. Further research exploring the genetic-environment interactions associated with risk of HCC is warranted.

New insight into serpin polymerization and aggregation

We recently solved the crystallographic structure of a dimeric form of the serpin antithrombin which has fundamentally changed the way we think about serpin polymerization. Like for other diseases that have protein deposition as a hallmark, the serpinopathies are associated with discrete inter-protomer linkage followed by subsequent association into larger fibrils and aggregates. Polymerization of the serpins is an off-pathway event that occurs during folding in the endoplasmic reticulum. Our structure reveals the nature of the polymerogenic folding intermediate, the reason that the inter-protomer linkage is hyperstable, and suggests a mechanism of lateral association of polymers into soluble fibrils and insoluble aggregates. While the basis of cellular toxicity is still unclear, novel therapeutic approaches targeting the folding intermediate or the lateral association event are now conceivable.

Modeling molecular and cellular aspects of human disease using the nematode Caenorhabditis elegans

As an experimental system, Caenorhabditis elegans offers a unique opportunity to interrogate in vivo the genetic and molecular functions of human disease-related genes. For example, C. elegans has provided crucial insights into fundamental biologic processes, such as cell death and cell fate determinations, as well as pathologic processes such as neurodegeneration and microbial susceptibility. The C. elegans model has several distinct advantages, including a completely sequenced genome that shares extensive homology with that of mammals, ease of cultivation and storage, a relatively short lifespan and techniques for generating null and transgenic animals. However, the ability to conduct unbiased forward and reverse genetic screens in C. elegans remains one of the most powerful experimental paradigms for discovering the biochemical pathways underlying human disease phenotypes. The identification of these pathways leads to a better understanding of the molecular interactions that perturb cellular physiology, and forms the foundation for designing mechanism-based therapies. To this end, the ability to process large numbers of isogenic animals through automated work stations suggests that C. elegans, manifesting different aspects of human disease phenotypes, will become the platform of choice for in vivo drug discovery and target validation using high-throughput/content screening technologies.

Dysfunctional glycogen storage in a mouse model of alpha1-antitrypsin deficiency

Autophagy is an intracellular pathway that contributes to the degradation and recycling of unfolded proteins. Based on the knowledge that autophagy affects glycogen metabolism and that alpha(1)-antitrypsin (AAT) deficiency is associated with an autophagic response in the liver, we hypothesized that the conformational abnormalities of the Z-AAT protein interfere with hepatocyte glycogen storage and/or metabolism. Compared with wild-type mice (WT), the Z-AAT mice had lower liver glycogen stores (P < 0.001) and abnormal activities of glycogen-related enzymes, including acid alpha-glucosidase (P < 0.05) and the total glycogen synthase (P < 0.05). As metabolic consequences, PiZ mice demonstrated lower blood glucose levels (P < 0.05), lower body weights (P < 0.001), and lower fat pad weights (P < 0.001) compared with WT. After the stress of fasting or partial hepatectomy, PiZ mice had further reduced liver glycogen and lower blood glucose levels (both P < 0.05 compared WT). Finally, PiZ mice exhibited decreased survival after partial hepatectomy (P < 0.01 compared with WT), but this was normalized with postoperative dextrose supplementation. In conclusion, these observations are consistent with the general concept that abnormal protein conformation and degradation affects other cellular functions, suggesting that diseases in the liver might benefit from metabolic compensation if glycogen metabolism is affected.

Autophagic disposal of the aggregation-prone protein that causes liver inflammation and carcinogenesis in alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin (AT) deficiency is a relatively common autosomal co-dominant disorder, which causes chronic lung and liver disease. A point mutation renders aggregation-prone properties on a hepatic secretory protein in such a way that the mutant protein is retained in the endoplasmic reticulum of hepatocytes rather than secreted into the blood and body fluids where it ordinarily functions as an inhibitor of neutrophil proteases. A loss-of-function mechanism allows neutrophil proteases to degrade the connective tissue matrix of the lung causing chronic emphysema. Accumulation of aggregated mutant AT in the endoplasmic reticulum of hepatocytes causes liver inflammation and carcinogenesis by a gain-of-toxic function mechanism. However, genetic epidemiology studies indicate that many, if not the majority of, affected homozygotes are protected from liver disease by unlinked genetic and/or environmental modifiers. Studies performed over the last several years have demonstrated the importance of autophagy in disposal of mutant, aggregated AT and raise the possibility that predisposition to, or protection from, liver injury and carcinogenesis is determined by the balance of de novo biogenesis of the mutant AT molecule and its autophagic disposal.