Liver injury in alpha 1-antitrypsin deficiency

Gene correction in patient-specific iPSCs for therapy development and disease modeling

The discovery that mature cells can be reprogrammed to become pluripotent and the development of engineered endonucleases for enhancing genome editing are two of the most exciting and impactful technology advances in modern medicine and science. Human pluripotent stem cells have the potential to establish new model systems for studying human developmental biology and disease mechanisms. Gene correction in patient-specific iPSCs can also provide a novel source for autologous cell therapy. Although historically challenging, precise genome editing in human iPSCs is becoming more feasible with the development of new genome-editing tools, including ZFNs, TALENs, and CRISPR. iPSCs derived from patients of a variety of diseases have been edited to correct disease-associated mutations and to generate isogenic cell lines. After directed differentiation, many of the corrected iPSCs showed restored functionality and demonstrated their potential in cell replacement therapy. Genome-wide analyses of gene-corrected iPSCs have collectively demonstrated a high fidelity of the engineered endonucleases. Remaining challenges in clinical translation of these technologies include maintaining genome integrity of the iPSC clones and the differentiated cells. Given the rapid advances in genome-editing technologies, gene correction is no longer the bottleneck in developing iPSC-based gene and cell therapies; generating functional and transplantable cell types from iPSCs remains the biggest challenge needing to be addressed by the research field.

Reactive oxygen species and anti-proteinases

Reactive oxygen species (ROS) cause damage to macromolecules such as proteins, lipids and DNA and alters their structure and function. When generated outside the cell, ROS can induce damage to anti-proteinases. Anti-proteinases are proteins that are involved in the control and regulation of proteolytic enzymes. The damage caused to anti-proteinase barrier disturbs the proteinase-anti-proteinases balance and uncontrolled proteolysis at the site of injury promotes tissue damage. Studies have shown that ROS damages anti-proteinase shield of the body by inactivating key members such as alpha-2-macroglobulin, alpha-1-antitrypsin. Hypochlorous acid inactivates α-1-antitrypsin by oxidizing a critical reactive methionine residue. Superoxide and hypochlorous acid are physiological inactivators of alpha-2-macroglobulin. The damage to anti-proteinase barrier induced by ROS is a hallmark of diseases such as atherosclerosis, emphysema and rheumatoid arthritis. Thus, understanding the behaviour of ROS-induced damage to anti-proteinases may helps us in development of strategies that could control these inflammatory reactions and diseases.

[Alpha-1 antitrypsin deficiency: A model of alteration of protein homeostasis or proteostasis]

Chronic obstructive pulmonary disease (COPD) is currently the ninth leading cause of death in France and is predicted to become the third leading cause of worldwide morbidity and mortality by 2020. Risk factors for COPD include exposure to tobacco, dusts and chemicals, asthma and alpha-1 antitrypsin deficiency. This genetic disease, significantly under-diagnosed and under-recognized, affects 1 in 2500 live births and is an important cause of lung and, occasionally, liver disease. Alpha-1 antitrypsin deficiency is a pathology of proteostasis-mediated protein folding and trafficking pathways. To date, there are only palliative therapeutic approaches for the symptoms associated with this hereditary disorder. Therefore, a more detailed understanding is required of the folding and trafficking biology governing alpha-1 antitrypsin biogenesis and its response to drugs. Here, we review the cell biological, biochemical and biophysical properties of alpha-1 antitrypsin and its variants, and we suggest that alpha-1 antitrypsin deficiency is an example of cell autonomous and non-autonomous challenges to proteostasis. Finally, we review emerging strategies that may be used to enhance the proteostasis system and protect the lung from alpha-1 antitrypsin deficiency.

Efficient drug screening and gene correction for treating liver disease using patient-specific stem cells

Patient-specific induced pluripotent stem cells (iPSCs) represent a potential source for developing novel drug and cell therapies. Although increasing numbers of disease-specific iPSCs have been generated, there has been limited progress in iPSC-based drug screening/discovery for liver diseases, and the low gene-targeting efficiency in human iPSCs warrants further improvement. Using iPSC lines from patients with alpha-1 antitrypsin (AAT) deficiency, for which there is currently no drug or gene therapy available, we established a platform to discover new drug candidates and correct disease-causing mutation with a high efficiency. A high-throughput format screening assay, based on our hepatic differentiation protocol, was implemented to facilitate automated quantification of cellular AAT accumulation using a 96-well immunofluorescence reader. To expedite the eventual application of lead compounds to patients, we conducted drug screening utilizing our established library of clinical compounds (the Johns Hopkins Drug Library) with extensive safety profiles. Through a blind large-scale drug screening, five clinical drugs were identified to reduce AAT accumulation in diverse patient iPSC-derived hepatocyte-like cells. In addition, using the recently developed transcription activator-like effector nuclease technology, we achieved high gene-targeting efficiency in AAT-deficiency patient iPSCs with 25%-33% of the clones demonstrating simultaneous targeting at both diseased alleles. The hepatocyte-like cells derived from the gene-corrected iPSCs were functional without the mutant AAT accumulation. This highly efficient and cost-effective targeting technology will broadly benefit both basic and translational applications.

CONCLUSIONS

Our results demonstrated the feasibility of effective large-scale drug screening using an iPSC-based disease model and highly robust gene targeting in human iPSCs, both of which are critical for translating the iPSC technology into novel therapies for untreatable diseases.

Nanodelivery in airway diseases: challenges and therapeutic applications

This review describes the challenges and therapeutic applications of nanodelivery systems for treatment of airway diseases. Therapeutic applications of nanodelivery in airway diseases involve targeted delivery of DNA, short interfering RNA, drugs, or peptides to hematopoietic progenitor cells and pulmonary epithelium to control chronic pathophysiology of obstructive and conformational disorders. The major challenges to nanodelivery involve physiologic barriers such as mucus and alveolar fluid. It is necessary for the nanoparticles to be biodegradable and capable of providing sustained drug delivery to the selected cell type. Once inside the cell, the nanoparticle should be capable of escaping the endocytic degradation machinery. In addition, for effective gene delivery, nuclear entry and chromosomal integration are critical. The strategies to overcome these pathophysiologic barriers are discussed as an attempt to synchronize the efforts of pulmonary biologists, chemists, and clinicians to develop novel nanodelivery therapeutics for airway diseases.

FROM THE CLINICAL EDITOR

Therapeutic applications of nano-delivery in airway diseases involve targeted delivery of DNA, siRNA, drugs or peptides to hematopoietic progenitor cells and pulmonary epithelium. These nano-particles must be biodegradable, capable of providing sustained drug delivery to specific cells, and should escape the endocytic degradation machinery. For effective gene-delivery they should also provide nuclear entry and chromosomal integration.

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.

Alpha-1 antitrypsin Z protein (PiZ) increases hepatic fibrosis in a murine model of cholestasis

Alpha-1 antitrypsin (alpha1-AT) deficiency is the most common genetic cause of liver disease in children. The homozygous alpha1-ATZ mutation (PiZZ) results in significant liver disease in 10% of all affected patients. The alpha1-ATZ mutation also may lead to worse liver injury in the setting of other liver diseases such as cystic fibrosis, nonalcoholic fatty liver disease, and hepatitis C. Although cholestatic injury is common to many forms of liver disease, its effect on the PiZZ phenotype is unknown. To elucidate the interplay of cholestasis and the PiZZ phenotype, we performed bile duct ligation (BDL) on C57BL/6 mice possessing a transgenic alpha1-ATZ mutation and littermate controls. PiZ transgenic mice undergoing BDL developed more liver fibrosis by quantification of Sirius red staining (P = 0.0003) and hydroxyproline (P = 0.007) than wild-type mice after BDL. More activated hepatic stellate cells (HSCs) and apoptotic cells also were observed in the PiZ BDL model. Quantitative real time polymerase chain reaction (PCR) of the endoplasmic reticulum (ER) stress markers CHOP and GRP78 were 4-fold and 2-fold more up-regulated, respectively, in PiZ BDL mice when compared with wild-type BDL mice (P = 0.02, P = 0.02). Increased apoptosis was also noted in PiZ BDL mice by terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) and cleaved caspase-3 histological staining.

CONCLUSION

PiZ transgenic mice are more susceptible to liver fibrosis induced by cholestasis from BDL. Cholestasis therefore may lead to increased fibrosis in alpha1-AT deficiency, and the alpha1-ATZ mutation may act as a modifier gene in patients with concurrent cholestatic liver diseases such as cystic fibrosis.

Beyond the signal sequence: protein routing in health and disease

Receptors, hormones, enzymes, ion channels, and structural components of the cell are created by the act of protein synthesis. Synthesis alone is insufficient for proper function, of course; for a cell to operate effectively, its components must be correctly compartmentalized. The mechanism by which proteins maintain the fidelity of localization warrants attention in light of the large number of different molecules that must be routed to distinct subcellular loci, the potential for error, and resultant disease. This review summarizes diseases known to have etiologies based on defective protein folding or failure of the cell's quality control apparatus and presents approaches for therapeutic intervention.

CuZnSOD deficiency leads to persistent and widespread oxidative damage and hepatocarcinogenesis later in life

Mice deficient in CuZn superoxide dismutase (CuZnSOD) showed no overt abnormalities during development and early adulthood, but had a reduced lifespan and increased incidence of neoplastic changes in the liver. Greater than 70% of Sod1-/- mice developed liver nodules that were either nodular hyperplasia or hepatocellular carcinoma (HCC). Cross-sectional studies with livers collected from Sod1-/- and age-matched +/+ controls revealed extensive oxidative damage in the cytoplasm and, to a lesser extent, in the nucleus and mitochondria from as early as 3 months of age. A marked reduction in cytosolic aconitase, increased levels of 8-oxo dG and F2-isoprostanes, and a moderate reduction in glutathione peroxidase activities and porin levels were observed in all age groups of Sod1-/- mice examined. There were also age-related reductions in Mn superoxide dismutase activities and carbonic anhydrase III. Parallel to the biochemical changes, there were progressive increases in the DNA repair enzyme APEX1, the cell cycle control proteins cyclin D1 and D3, and the hepatocyte growth factor receptor Met. Increased cell proliferation in the presence of persistent oxidative damage to macromolecules likely contributes to hepatocarcinogenesis later in life.

Noninfectious liver disorders: assessment and diagnosis

Infectious hepatitis is often the initial suspect when abnormal serum liver function test results are discovered in primary care settings. However, noninfectious liver disorders may also present with altered liver function tests. Noninfectious liver disorders require careful assessment of patient history, physical findings, and serum laboratory tests to distinguish among entities that have varying clinical implications and treatments.

A novel mode of polymerization of alpha1-proteinase inhibitor

Patients homozygous for the Z mutant form of alpha1-proteinase inhibitor (alpha1-PI) have an increased risk for the development of liver disease because of the accumulation in hepatocytes of inclusion bodies containing linear polymers of mutant alpha1-PI. The most widely accepted model of polymerization proposes that a linear, head-to-tail polymer forms by sequential insertion of the reactive center loop (RCL) of one alpha1-PI monomer between the central strands of the A beta-sheet of an adjacent monomer. This model derives primarily from two observations: peptides that are homologous with the RCL insert into the A beta-sheet of alpha1-PI monomer and this insertion prevents alpha1-PI polymerization. Normal alpha1-PI monomer does not spontaneously polymerize; however, here we show that the disulfide-linked dimer of normal alpha1-PI spontaneously forms linear polymers in buffer. The monomers within this dimer are joined head-to-head. Thus, the arrangement of monomers in these polymers must be different from that predicted by the loop-A sheet model. Therefore, we propose a new model for alpha1-PI polymer. In addition, polymerization of disulfide-linked dimer is not inhibited by the presence of the peptide even though dimer appears to interact with the peptide. Thus, RCL insertion into A beta-sheets may not occur during polymerization of this dimer.

Metabolic liver disease in the young adult

This chapter describes the gene mutations, phenotypes, diagnosis and therapy of the common metabolic liver diseases in young adulthood: haemochromatosis, Wilson disease, alpha(1)-anti-trypsin deficiency and cystic fibrosis. The remarkable variability of the phenotypical expression of the mutated genotypes makes screening recommendations and the establishment of prognosis for these liver disorders in young adults problematical. The diagnosis and therapy of the young adult with metabolic liver disease is discussed, with an emphasis on maintaining quality-of-life and balancing the importance of early intervention with the stigmatization of the diagnosis of potentially life-threatening liver disease. There is a critical need for the development of biochemical markers that would predict the risk of expression of clinical phenotypes and prognosis.

Metabolic effects of infection on protein and energy status

A review of some of the seminal studies of metabolism during various infections indicates that similar patterns of metabolic alterations occur during these illnesses. This patterned metabolic array occurs whether the infection is caused by a gram-positive or a gram-negative bacterium, a rickettsia or a virus, or is respiratory or systemic. In all instances, the previously healthy host responds to infection with cytokine-mediated alterations that appear to occur in proportion to the infectious challenge and to the likelihood of death. These alterations also can occur in the vaccinated host, if the infectious challenge is sufficiently great. Because of their widespread occurrence and seemingly ingrained status, these metabolic alterations may be presumed to be of survival benefit to the host. Whether this patterned array of metabolic sequelae is of benefit to the host, or even to the species, its widespread and systematic occurrence allows it to be of value in assessing the safety and efficacy of vaccines and drugs to prevent or treat a wide variety of infections. In this era of bioterrorism, wherein drugs and vaccines may have to be approved for human use without clinical trials and solely on the basis of animal data, these cytokine-mediated metabolic sequelae can aid in the rational selection of drug and vaccine candidates.

Detection of circulating and endothelial cell polymers of Z and wild type alpha 1-antitrypsin by a monoclonal antibody

Globular inclusions of abnormal alpha1-antitrypsin (AAT) in the endoplasmic reticulum of hepatocytes are a characteristic feature of AAT deficiency of the PiZZ phenotype. Monoclonal antibodies, which contain constant specificity and affinity, are often used for the identification of Z-mutation carriers. A mouse monoclonal antibody (ATZ11) raised against PiZZ hepatocytic AAT was successfully used in enzyme-linked immunosorbent assays (ELISA) and in identification of Z-related AAT globular inclusions by immunohistochemical techniques. Using electrophoresis, Western blotting, and ELISA procedures, we have shown in the present study that this monoclonal antibody specifically detects a conformation-dependent neoepitope on both polymerized and elastase-complexed molecular forms of AAT. The antibody has no apparent affinity for native, latent, or cleaved forms of AAT. The antibody ATZ11 illustrates the structural resemblance between the polymerized form of AAT and its complex with elastase and provides evidence that Z-homozygotes beyond the native form may have at least one more circulating molecular form of AAT, i.e. its polymerized form. In addition, staining of endothelial cells with ATZ11 antibody in both M- and Z-AAT individuals shows that AAT attached to endothelial cells is in a polymerized form. The antibody can be a powerful tool for the study of the molecular profile of AAT, not only in Z-deficiency cases but also in other (patho)physiological conditions.

Hepatocellular carcinoma: predisposing conditions and precursor lesions

The global incidence of HCC is rising; in the United States, its rise is in parallel to that of cirrhosis due to the HCV and obesity epidemics. The lack of adequate treatment for advanced HCC mandates both prevention and early detection of these lesions. The limitations of currently available histopathologic evaluations, serologic markers, and radiographic imaging modalities in detecting HCC and its precursors have been outlined in this review. Refinements of all of these may lead to better HCC detection, earlier intervention, and successful treatment. Randomized controlled trials are necessary to evaluate the most efficacious and cost-effective approach to screening.

Distribution of alpha1-antitrypsin PI S and PI Z frequencies in countries outside Europe: a meta-analysis

The objective of the present study was to review published surveys on allelic frequencies S and Z in countries outside Europe to evaluate the validity of the reported data. Studies on the topic, published from 1965 to May 2001, were retrieved using MEDLINE and bibliographic reference consultations. The criteria for the selection of the studies were the following: 1) sample size >or=250 individuals; 2) alpha1-antitrypsin phenotype determination performed by means of crossed antigen-antibody, isoelectric focusing in polyacrylamide gels, or polymerase chain reaction (PCR); 3) PI type determination performed without any previous screening procedure; 4) S and Z 95% CI of the reported outcomes within the limits of a calculated coefficient of variation. Forty-three out of 85 studies comply with the established criteria for being analysed. Worldwide maps of geographical distributions of PI S and PI Z frequencies have been designed by the authors by adding the data provided by these 43 selected studies to the 70 reported in a recent European meta-analysis.