Liver Disease in Alpha-1 Antitrypsin Deficiency: Current Understanding and Future Therapy

Alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin deficiency (AATD) is a rare hereditary condition caused by decreased plasma and tissue levels of alpha-1 antitrypsin (AAT) that can lead to serious lung and liver disease in children and adults. AATD patients face challenges such as under diagnosis, clinical variability, and limited treatment options for liver disease. Early detection and biomarkers for predicting outcomes are needed to improve patient outcome. Currently, the only approved pharmacological therapy is augmentation therapy, which can delay the progression of emphysema. However, alternative strategies such as gene therapy, induced pluripotent stem cells, and prevention of AAT polymerization inside hepatocytes are being investigated. This review aims to summarize and update current knowledge on AATD, identify areas of controversy, and formulate questions for further research.

Sirtuin3 promotes the degradation of hepatic Z alpha-1 antitrypsin through lipophagy

BACKGROUND

Alpha-1 antitrypsin deficiency (AATD) is a genetic disease caused by misfolding and accumulation of mutant alpha-1 antitrypsin (ZAAT) in the endoplasmic reticulum of hepatocytes. Hepatic ZAAT aggregates acquire a toxic gain-of-function that impacts the endoplasmic reticulum which is theorized to cause liver disease in individuals with AATD who present asymptomatic until late-stage cirrhosis. Currently, there is no treatment for AATD-mediated liver disease except liver transplantation. In our study of mitochondrial RNA, we identified that Sirtuin3 (SIRT3) plays a role in the hepatic phenotype of AATD.

METHODS

Utilizing RNA and protein analysis in an in vitro AATD model, we investigated the role of SIRT3 in the pathophysiology of AATD-mediated liver disease while also characterizing our novel, transgenic AATD mouse model.

RESULTS

We show lower expression of SIRT3 in ZAAT-expressing hepatocytes. In contrast, the overexpression of SIRT3 increases hepatic ZAAT degradation. ZAAT degradation mediated by SIRT3 appeared independent of proteasomal degradation and regular autophagy pathways. We observed that ZAAT-expressing hepatocytes have aberrant accumulation of lipid droplets, with ZAAT polymers localizing on the lipid droplet surface in a direct interaction with Perilipin2, which coats intracellular lipid droplets. SIRT3 overexpression also induced the degradation of lipid droplets in ZAAT-expressing hepatocytes. We observed that SIRT3 overexpression induces lipophagy by enhancing the interaction of Perilipin2 with HSC70. ZAAT polymers then degrade as a consequence of the mobilization of lipids through this process.

CONCLUSIONS

In this context, SIRT3 activation may eliminate the hepatic toxic gain-of-function associated with the polymerization of ZAAT, providing a rationale for a potential novel therapeutic approach to the treatment of AATD-mediated liver disease.

Liver disease progression in patients with alpha-1 antitrypsin deficiency and protease inhibitor ZZ genotype with or without lung disease

BACKGROUND

Alpha-1 antitrypsin deficiency (AATD) is caused by mutations in SERPINA1, which encodes alpha-1 antitrypsin, a protease inhibitor (Pi). Individuals with AATD and the homozygous Pi*ZZ genotype have variable risk of progressive liver disease but the influence of comorbid lung disease is poorly understood.

AIMS

To characterise patients with AATD Pi*ZZ and liver disease (AATD-LD-Pi*ZZ) with or without lung disease and describe liver disease-related clinical events longitudinally.

METHODS

This was an observational cohort study of patients in the Mayo Clinic Healthcare System (January 2000-September 2021). Patients were identified using diagnosis codes and natural language processing. Fibrosis stage (F0-F4) was assessed using a hierarchical approach at baseline (90 days before or after the index date) and follow-up. Clinical events associated with liver disease progression were assessed.

RESULTS

AATD-LD-Pi*ZZ patients with lung disease had a longer median time from AATD diagnosis to liver disease diagnosis versus those without lung disease (2.2 vs. 0.2 years, respectively). Compared to those without lung disease, patients with lung disease had a longer time to liver disease-related clinical events (8.5 years and not reached, respectively). AATD-LD-Pi*ZZ patients without lung disease were more likely to undergo liver transplantation compared with those with lung disease.

CONCLUSION

In patients with AATD and lung disease, there is a delay in the diagnosis of comorbid liver disease. Our findings suggest that liver disease may progress more rapidly in patients without comorbid lung disease.

Population genetic testing and SERPINA1 sequencing identifies unidentified alpha-1 antitrypsin deficiency alleles and gene-environment interaction with hepatitis C infection

Alpha-1 antitrypsin deficiency (AATD), a relatively common autosomal recessive genetic disorder, is underdiagnosed in symptomatic individuals. We sought to compare the risk of liver transplantation associated with hepatitis C infection with AATD heterozygotes and homozygotes and determine if SERPINA1 sequencing would identify undiagnosed AATD. We performed a retrospective cohort study in a deidentified Electronic Health Record (EHR)-linked DNA biobank with 72,027 individuals genotyped for the M, Z, and S alleles in SERPINA1. We investigated liver transplantation frequency by genotype group and compared with hepatitis C infection. We performed SERPINA1 sequencing in carriers of pathogenic AATD alleles who underwent liver transplantation. Liver transplantation was associated with the Z allele (ZZ: odds ratio [OR] = 1.31, p<2e-16; MZ: OR = 1.02, p = 1.2e-13) and with hepatitis C (OR = 1.20, p<2e-16). For liver transplantation, there was a significant interaction between genotype and hepatitis C (ZZ: interaction OR = 1.23, p = 4.7e-4; MZ: interaction OR = 1.11, p = 6.9e-13). Sequencing uncovered a second, rare, pathogenic SERPINA1 variant in six of 133 individuals with liver transplants and without hepatitis C. Liver transplantation was more common in individuals with AATD risk alleles (including heterozygotes), and AATD and hepatitis C demonstrated evidence of a gene-environment interaction in relation to liver transplantation. The current AATD screening strategy may miss diagnoses whereas SERPINA1 sequencing may increase diagnostic yield for AATD, stratify risk for liver disease, and inform clinical management for individuals with AATD risk alleles and liver disease risk factors.

Disease progression in patients with PI*ZZ alpha-1 antitrypsin deficiency

BACKGROUND AND OBJECTIVE

Alpha-1 antitrypsin deficiency (AATD) is an uncommon but underdiagnosed cause of cirrhosis and lacks medical treatment options. It is important to recognize risk factors that contribute to disease progression and liver transplantation. We aimed to assess if age, sex, or smoking status was associated with liver or lung disease progression.

METHODS

Forty-three patients with ZZ-AATD cirrhosis were consecutively sampled from an Institutional Review Board-approved registry of 240 patients with AATD of any genotype seen as outpatients in the Cleveland Clinic between 1999 and 2019. To determine the association between risk factors and lung or liver disease progression, linear mixed-effects models with fixed effects for linear time, risk factor, and time-by-risk factor interaction, and the random intercepts for intra-patient correlation were used.

RESULTS

Based on the mixed-effects model analysis, there was a significant association between liver disease progression and smoking history, and no association with age or sex. There was no association between lung disease progression and age, sex, or smoking history. However, smoking history was significantly associated with lower forced expiratory volume values.

CONCLUSION

This study found that in a cohort of patients with PI*ZZ genotype AATD (ZZ-AATD) and cirrhosis, smoking history was associated with liver disease progression, whereas age and sex were not.

Assessing Patients with Alpha-1 Antitrypsin Deficiency for Corneal Refractive Surgery: A Review and Clinical Experience

Alpha-1 Antitrypsin Deficiency (AATD) is an autosomal inheritable disorder that impairs the protease inhibitor alpha-1 antitrypsin. This disorder presents with various systemic effects, including liver cirrhosis, centrilobular emphysema, and ocular manifestations. Performing corneal refractive surgery in patients with AATD raises concerns regarding the increased rates of corneal erosions, corneal ulcerations, potential developing descemetoceles, and other ocular manifestations. Patient outcomes for laser-assisted in situ keratomileuses (LASIK), photorefractive keratectomy (PRK), small incision lenticule extraction (SMILE), and other ocular corrective surgeries are lacking in this population. This article provides experiences performing corneal refractive surgery, discusses the current understanding of AATD, including its ocular manifestations, and explores factors to consider when evaluating patients for corneal procedures. The aim of this paper is to address the manifestations of AATD prior to performing corrective vision surgery.

Alpha-1 antitrypsin deficiency: A re-surfacing adult liver disorder

Alpha-1 antitrypsin deficiency (AATD) arises from mutations in the SERPINA1 gene encoding alpha-1 antitrypsin (AAT) that lead to AAT retention in the endoplasmic reticulum of hepatocytes, causing proteotoxic liver injury and loss-of-function lung disease. The homozygous Pi∗Z mutation (Pi∗ZZ genotype) is responsible for the majority of severe AATD cases and can precipitate both paediatric and adult liver diseases, while the heterozygous Pi∗Z mutation (Pi∗MZ genotype) is an established genetic modifier of liver disease. We review genotype-related hepatic phenotypes/disease predispositions. We also describe the mechanisms and factors promoting the development of liver disease, as well as approaches to evaluate the extent of liver fibrosis. Finally, we discuss emerging diagnostic and therapeutic approaches for the clinical management of this often neglected disorder.

Tumor-microenvironmental-response Bi-functional molecules for efficient imaging and anti-tumor activity therapy

To improve the visualization and potency of anticancer agents, the diagnosis and treatment integration bi-functional molecules were constructed based on active candidate BD7, approved drug Linifanib, and monoclonal antibody Bevacizumab. Commercial available Rhodamine B was inducted to realize imaging-aided diagnosis and target efficiency monitoring for cancer cells. In order to maintain the anticancer activity of drugs, disulfide bond was incorporated as releasable group based on tumor microenviroment. After design, synthesis and structure characterization of title compounds, various biological evaluation and cancer cell imaging analysis were carried out. The results indicated that these title diagnosis and treatment integration bi-functional molecules exhibited comparable potency with that of corresponding parent drug. Meanwhile, these agents afforded good performance in cell imaging and could be used to differentiate cancer cells from normal ovarian cells in real time. Further optimization of these bi-functional molecules is ongoing to improve the potency and precision and will be reported in due course. Our findings are expected to achieve efficient screening and real-time prognostic monitoring under the premise of high anti-tumor activity for clinical application.

Alpha-1 Antitrypsin Z Variant (AAT PI*Z) as a Risk Factor for Intrahepatic Cholestasis of Pregnancy

Background: Intrahepatic cholestasis of pregnancy (ICP; prevalence 0.2–15.6%) is the most common pregnancy-related liver disorder. It may have serious consequences for a pregnancy, including increased risk of preterm delivery, meconium staining of amniotic fluid, fetal bradycardia, distress, and fetal demise. In cases of high bile acids (>100μmol/L), patients have 10-fold increase in the risk of stillbirth. Biophysical methods of fetal monitoring, such as cardiotocography, ultrasonography, or Doppler have been proven unreliable for risk prediction in the course of intrahepatic cholestasis. Therefore, we believe extensive research for more specific, especially early, markers should be carried out. By analogy with cholestasis in children with inherited alpha-1 antitrypsin deficiency (AATD), we hypothesized the SERPINA1 Z pathogenic variant might be related to a higher risk of cholestasis in pregnancy. This study aimed to investigate the most common AATD variants (Z and S SERPINA1 alleles) in a group of cholestatic pregnant women.

Results: The Z carrier frequency was calculated to be 6.8%, which is much higher compared to the general population [2.3%; the Chi-squared test with Yates correction is 6.8774 (p=0.008)].

Conclusion: Increased prevalence of SERPINA1 PI*Z variant in a group of women with intrahepatic cholestasis may suggest a possible genetic origin of a higher risk of intrahepatic cholestasis in pregnancy.

Liver disease with unknown etiology - have you ruled out alpha-1 antitrypsin deficiency?

Although a less well-known consequence of alpha-1 antitrypsin deficiency (AATD) liver disease is the second leading cause of death among patients with the condition. The alpha-1 antitrypsin (AAT) protein is produced by hepatocytes within the liver, which retain pathological variants of AAT instead of secreting the proteinase inhibitor into the systemic circulation. This intracellular retention is caused by inefficient folding and polymerization of mutant AAT and the accumulation of these AAT aggregates leads to diverse manifestations of liver disease, which can present differently in both children and adults. The progression from hepatocyte apoptosis to liver inflammation, fibrosis and cirrhosis, and liver failure is still not fully understood, but in older patients, liver disease can surpass lung disease as the principal cause of death. Liver function tests (LFTs) can measure plasma levels of liver enzymes to assess liver function but require careful interpretation. Non-invasive tests are being developed that can detect early liver disease, but liver biopsy is still the gold standard for assessing liver fibrosis once abnormal LFTs have been detected in a patient. Currently, there is no licensed treatment for AATD-related liver disease (intravenous AAT therapy is not indicated for this purpose), but liver transplantation is associated with positive outcomes and may even slow emphysema progression. Therefore, new strategies are being developed to address treatment of AATD-related liver disease, such as accelerating degradation of mutant AAT and assisting hepatocytes in the folding and secretion of mutant AAT, but these approaches remain at early stages of development.

Intrahepatic cholangiocarcinoma in a non-cirrhotic liver in a patient with homozygous ZZ alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin (AAT) deficiency, which is an under-recognised metabolic genetic disorder, is known to cause severe lung disease and liver cirrhosis in about 10%–15% of cases. Patients with AAT deficiency are at a higher risk for developing hepatocellular carcinoma, both in cirrhotic and in non-cirrhotic livers. In this case report, a 48-year-old woman with homozygous ZZ AAT deficiency presented with abdominal pain, and by imaging, an abnormal area in the liver was found. The initial differential diagnosis consisted of benign abnormalities but a malignancy could not be ruled out. Finally, this abnormality turned out to be an intrahepatic cholangiocarcinoma (iCCA) in a non-cirrhotic liver. Since this type of tumour has been very infrequently described to be associated with AAT deficiency, the question remains whether alpha-1 trypsin accumulation in the hepatocytes was responsible for the development of iCCA. However, other associated factors for developing an iCCA were ruled out.

The Autophagy Pathway: A Critical Route in the Disposal of Alpha 1-Antitrypsin Aggregates That Holds Many Mysteries

The maintenance of proteome homeostasis, or proteostasis, is crucial for preserving cellular functions and for cellular adaptation to environmental challenges and changes in physiological conditions. The capacity of cells to maintain proteostasis requires precise control and coordination of protein synthesis, folding, conformational maintenance, and clearance. Thus, protein degradation by the ubiquitin–proteasome system (UPS) or the autophagy–lysosomal system plays an essential role in cellular functions. However, failure of the UPS or the autophagic process can lead to the development of various diseases (aging-associated diseases, cancer), thus both these pathways have become attractive targets in the treatment of protein conformational diseases, such as alpha 1-antitrypsin deficiency (AATD). The Z alpha 1-antitrypsin (Z-AAT) misfolded variant of the serine protease alpha 1-antitrypsin (AAT) is caused by a structural change that predisposes it to protein aggregation and dramatic accumulation in the form of inclusion bodies within liver hepatocytes. This can lead to clinically significant liver disease requiring liver transplantation in childhood or adulthood. Treatment of mice with autophagy enhancers was found to reduce hepatic Z-AAT aggregate levels and protect them from AATD hepatotoxicity. To date, liver transplantation is the only curative therapeutic option for patients with AATD-mediated liver disease. Therefore, the development and discovery of new therapeutic approaches to delay or overcome disease progression is a top priority. Herein, we review AATD-mediated liver disease and the overall process of autophagy. We highlight the role of this system in the regulation of Z-variant degradation and its implication in AATD-medicated liver disease, including some open questions that remain challenges in the field and require further elucidation. Finally, we discuss how manipulation of autophagy could provide multiple routes of therapeutic benefit in AATD-mediated liver disease.

Alpha-1 Antitrypsin Deficiency-Mediated Liver Toxicity: Why Do Some Patients Do Poorly? What Do We Know So Far?

Alpha-1 antitrypsin deficiency (AATD) is a rare genetic disease caused by mutations in the SERPINA1 gene and is associated with a decreased level of circulating alpha-1 antitrypsin (AAT). Among all the known mutations in the SERPINA1 gene, homozygous for the Z allele is well-known to result in both lung and liver disease. Unlike the lung injury that occurs in adulthood with the environment (notably, tobacco) as a co-factor, the hepatic damage is more complicated. Despite a common underlying gene mutation, the liver disease associated with AATD presents a considerable variability in the age-of-onset and severity, ranging from transient neonatal cholestasis (in early childhood) to cirrhosis and liver cancer (in childhood and adulthood). Given that all the cofactors- genetics and/or environmental- have not been fully identified, it is still impossible to predict which individuals with AATD may develop severe liver disease. The discovery of these modifiers represents the major challenge for the detection, diagnosis, and development of new therapies to provide alternative options to liver transplantation. The aim of this current review is to provide an updated overview of our knowledge on why some AATD patients associated with liver damage progress poorly.

Clinical considerations in individuals with α1-antitrypsin PI*SZ genotype

α₁-Antitrypsin deficiency (AATD), characterised by reduced levels or functionality of α₁-antitrypsin (AAT), is a significantly underdiagnosed genetic condition that predisposes individuals to lung and liver disease. Most of the available data on AATD are based on the most common, severe deficiency genotype (PI*ZZ); therefore, treatment and monitoring requirements for individuals with the PI*SZ genotype, which is associated with a less severe AATD, are not as clear. Recent genetic data suggest the PI*SZ genotype may be significantly more prevalent than currently thought, due in part to less frequent identification in the clinic and less frequent reporting in registries. Intravenous AAT therapy, the only specific treatment for patients with AATD, has been shown to slow disease progression in PI*ZZ individuals; however, there is no specific evidence for AAT therapy in PI*SZ individuals, and it remains unclear whether AAT therapy should be considered in these patients. This narrative review evaluates the available data on the PI*SZ genotype, including genetic prevalence, the age of diagnosis and development of respiratory symptoms compared with PI*ZZ individuals, and the impact of factors such as index versus non-index identification and smoking history. In addition, the relevance of the putative 11 µM “protective threshold” for AAT therapy and the risk of liver disease in PI*SZ individuals is explored. The purpose of this review is to identify open research questions in this area, with the aim of optimising the future identification and management of PI*SZ individuals.

Individuals with α₁-antitrypsin (AAT) PI*SZ genotype appear to have an increased risk for lung and liver disease, although definitive evidence is lacking; smoking is a major risk factor for lung disease. The role of AAT therapy requires further study.http://bit.ly/2TxxFD0

Knowledge of Rare Respiratory Diseases among Paediatricians and Medical School Students

Alpha-1-antitrypsin deficiency (AATD) and primary ciliary dyskinesia (PCD) are underdiagnosed rare diseases showing a median diagnostic delay of five to ten years, which has negative effects on patient prognosis. Lack of awareness and education among healthcare professionals involved in the management of these patients have been suggested as possible causes. Our aim was to assess knowledge of these diseases among paediatricians and medical school students to determine which knowledge areas are most deficient. A survey was designed with questions testing fundamental aspects of the diagnosis and treatment of AATD and PCD. A score equal to or greater than 50% of the maximum score was set as the level necessary to ensure a good knowledge of both diseases. Our results indicate a profound lack of knowledge of rare respiratory diseases among paediatric professionals and medical students, suggesting that it is necessary to increase rare respiratory diseases training among all physicians responsible for suspecting and diagnosing them; this will allow early diagnosis and the setup of preventive measures and appropriate early-stage treatment. The first step in closing this knowledge gap could be to include relevant material in the medical syllabus.

Liver Involvement in Children with Alpha-1 Antitrypsin Deficiency: A Multicenter Study

PURPOSE

Alpha-1 antitrypsin deficiency (A1ATD) in one of the most common genetic causes of liver disease in children. We aimed to analyze the clinical characteristics and outcomes of patients with A1ATD.

METHODS

This study included patients with A1ATD from five pediatric hepatology units. Demographics, clinical findings, genetics, and outcome of the patients were recorded (n=25).

RESULTS

Eight patients (32.0%) had homozygous PiZZ genotype while 17 (68.0%) had heterozygous genotype. Patients with PiZZ genotype had lower alpha-1 antitrypsin levels than patients with PiMZ genotype (37.6±7.7 mg/dL vs. 66.5±22.7 mg/dL, p=0.0001). Patients with PiZZ genotype were diagnosed earlier than patients with PiMZ genotype, but this was not significant (13±6.8 months vs. 23.7±30.1 months, p=0.192). Follow-up revealed the death of one patient (12.5%) with a homozygous mutation, and revealed that one patient had child A cirrhosis, five patients (62.5%) had chronic hepatitis, and one patient (12.5%) was asymptomatic. Nine of the 17 patients with a heterozygous mutation had chronic hepatitis (52.9%), two (11.7%) had child A cirrhosis, and six (35.2%) were asymptomatic. Overall, 18 (72%) of the 25 children had liver pathology in the long-term.

CONCLUSION

Although prevalence is rare, patients with liver disorders should be checked for alpha-1 antitrypsin levels. Moreover, long-term follow-up is essential because most patients have a liver pathology.

NullCanada: A novel α1-antitrypsin allele with in cis variants Glu366Lys and Ile100Asn

BACKGROUND

α₁-Antitrypsin (A1AT) deficiency predisposes patients to pulmonary disease due to inadequate protection against human neutrophil elastase released during inflammatory responses. A1AT deficiency is caused by homozygosity or compound heterozygosity for A1AT variants; individuals with A1AT deficiency most commonly have at least one Z variant allele (c.1096G > A (Glu366Lys)). Null variants that result in complete absence of A1AT in the plasma are much rarer. With one recent exception, all reported A1AT variants are characterized by a single pathogenic variant.

CASE

An 8 years old patient from Edmonton, Alberta, Canada, was investigated for A1AT deficiency. His A1AT phenotype was determined to be M (wild type)/Null by isoelectric focusing (IEF) but M/Z by targeted genotyping. Gene sequencing revealed two heterozygous variants: Z and Ile100Asn (c.299 T > A). The Ile100Asn substitution is predicted to disrupt the secondary structure of an α-helix in which it resides and the neighbouring tertiary structure, resulting in intracellular degradation of A1AT prior to hepatocyte secretion.

METHODS

Family testing was conducted to verify potential inheritance of an A1AT allele carrying the two mutations in cis, as this arrangement of the mutations would explain "Z" detection by genotyping but not by IEF. Molecular modeling was used to assess the effect of the variants on A1AT structure and stability.

DISCUSSION

Carrier status for a novel variant Null_Canada with in cis mutations (c.[299 T > A;1096G > A], p.[(Ileu100Asn;Glu366Lys)]) was confirmed. A sibling was identified as having A1AT deficiency on the basis of compound heterozygosity for two alleles: Null_Canada and the common Z allele. A separate pedigree from the Maritimes was subsequently recognized as carrying Null_Canada.

CONCLUSION

In cis mutations such as Null_Canada may be more common than previously described due to failure to detect such mutations using historical testing methods. Combined approaches that include gene sequencing and segregation studies allow recognition of rare A1AT variants, including in cis mutations.

Up-regulation of miR-498 inhibits cell proliferation, invasion and migration of hepatocellular carcinoma by targeting FOXO3

BACKGROUND

To unravel the fundamental role of miR-498 in the context of hepatocellular carcinoma cells and understands underlying potential mechanism.

METHODS

Relative viability was interrogated using MTT method and cell proliferation was determined with colony formation assay. The protein levels of cleaved Caspase-3, Bcl-2, Cyclin D, CDK4, FOXO3 and β-actin were analyzed by western blotting. Cell invasion and migration was evaluated by transwell assay and wound healing, respectively. The relative abundance of Cyclin D, CDK4, FOXO3 and miR-498 transcripts was measured using real-time PCR. The regulatory action of miR-498 on FOXO3 expression was analyzed with luciferase reporter.

RESULTS

Ectopic over-expression of miR-498 significantly inhibited viability and proliferation, suppressed cell migration and invasion, delayed cell cycle progression. We further identified FOXO3 as downstream target gene of miR-498, and positively modulated FOXO3 translation in miR-498-proficient cells consequently contributed to its anti-tumoral properties.

CONCLUSIONS

Our data highlighted the tumor suppressor role of miR-498-FOXO3 signaling in hepatocellular carcinoma cells, which might hold promise for therapeutic exploitation.

Identification and Replication of Six Loci Associated With Gallstone Disease

Gallstone disease is a common complex disease that confers a substantial economic burden on society. The genetic underpinnings of gallstone disease remain incompletely understood. We aimed to identify genetic associations with gallstone disease using publicly available data from the UK Biobank and two large Danish cohorts. We extracted genetic associations with gallstone disease from the Global Biobank Engine (GBE), an online browser of genome-wide associations in UK Biobank participants (14,940 cases and 322,268 controls). Significant associations (P < 5 × 10^-8 ) were retested in two Copenhagen cohorts (comprising 1,522 cases and 18,266 controls). In the Copenhagen cohorts, we also tested whether a genetic risk score was associated with gallstone disease and whether individual gallstone loci were associated with plasma levels of lipids, lipoproteins, and liver enzymes. We identified 19 loci to be associated with gallstone disease in the GBE. Of these, 12 were replicated in the Copenhagen cohorts, including six previously unknown loci (in hepatocyte nuclear factor 4 alpha [HNF4A], fucosyltransferase 2, serpin family A member 1 [SERPINA1], jumonji domain containing 1C, AC074212.3, and solute carrier family 10A member 2 [SLC10A2]) and six known loci (in adenosine triphosphate binding cassette subfamily G member 8 [ABCG8], sulfotransferase family 2A member 1, cytochrome P450 7A1, transmembrane 4 L six family member 4, ABCB4, and tetratricopeptide repeat domain 39B). Five of the gallstone associations are protein-altering variants, and three (HNF4A p.Thr139Ile, SERPINA1 p.Glu366Lys, and SLC10A2 p.Pro290Ser) conferred per-allele odds ratios for gallstone disease of 1.30-1.36. Individuals with a genetic risk score >2.5 (prevalence 1%) had a 5-fold increased risk of gallstones compared to those with a score <1.0 (11%). Of the 19 lithogenic loci, 11 and ten exhibited distinct patterns of association with plasma levels of lipids and liver enzymes, respectively. Conclusion: We identified six susceptibility loci for gallstone disease.

SERPINA1 Z allele is associated with cystic fibrosis liver disease

PURPOSE

The SERPINA1 Z allele is associated with cystic fibrosis (CF)-related liver disease (CFLD), a common manifestation in patients with CF. We estimated CFLD incidence based on the SERPINA1 genotype in 3328 CF patients with CFLD-phenotype information.

METHODS

The associations of SERPINA1 Z (rs28929474) and S (rs17580) alleles with age at CFLD onset and the development of CFLD-related complications (severe liver disease with cirrhosis, portal hypertension, esophageal varices) were analyzed.

RESULTS

Overall, 3% of patients carried the SERPINA1 Z allele and 13% carried the S allele. The cumulative incidence of CFLD increased more rapidly in patients carrying the Z allele (hazard ratio [HR] = 1.6; 95% confidence interval [CI] = 1.1-2.4, P = 0.019), reaching 47% by age 25 compared with 30% in noncarriers. Increased risk was similar for patients with severe CFLD (HR = 1.5, 95% CI = 0.7-3.2, P = 0.31) but failed to reach significance due to a limited sample size of Z-allele carriers. No significant effect was found for the S allele.

CONCLUSION

CF patients carrying the SERPINA1 Z allele had an increased risk of developing CFLD and related complications compared with noncarriers. Routine SERPINA1 Z genotyping upon CF diagnosis is warranted for identifying patients worthy of closer liver disease monitoring.

Alpha1-Antitrypsin Deficiency: Transition of Care for the Child With AAT Deficiency into Adulthood

IMPORTANCE

Alpha1-antitrypsin (AAT) deficiency is a common, but an underdiagnosed genetic condition, affecting 1 in 1500 individuals. It can present insidiously with liver disease in children. Although clinical practice guidelines exist for the management of AAT deficiency, especially with regards to pulmonary involvement, there are no published recommendations that specifically relate to the management of the liver disease and monitoring for lung disease associated with this condition, particularly in children.

OBJECTIVE

To review the literature on the management of AAT deficiency-associated liver disease in adults and children.

EVIDENCE REVIEW

A systematic search for articles indexed in PubMed and published was undertaken. Some earlier selected landmark references were included in the review. Search terms included: "alpha1-antitrypsin deficiency"; "liver disease"; "end-stage liver disease"; "liver transplantation" and "preventative management". Recommendations for the management of children with suspected or confirmed AAT deficiency were made according to the Strength of Recommendation Taxonomy scale.

FINDINGS

Liver complications arising from AAT deficiency result from the accumulation of mutated AAT protein within hepatocytes. Liver disease occurs in 10% of children, manifested by cholestasis, pruritus, poor feeding, hepatomegaly, and splenomegaly, but the presentation is highly variable. A diagnostic test for AAT deficiency is recommended for these children. Baseline liver function tests should be obtained to assess for liver involvement; however, the only curative treatment for AAT deficiency-associated liver disease is organ transplantation. Conclusion and Relevance: There should be a greater vigilance for AAT deficiency testing among pediatricians. Diagnosis should prompt assessment of liver involvement. Children with AATdeficiency- associated liver disease should be referred to a liver specialist and monitored throughout their lifetimes for the symptoms of AAT-deficiency-related pulmonary involvement.

Alpha-1-Antitrypsin Deficiency Liver Disease

In homozygous ZZ alpha-1-antitrypsin (AAT) deficiency, the liver synthesizes large quantities of AAT mutant Z, which folds improperly during biogenesis and is retained within the hepatocytes and directed into intracellular proteolysis pathways. These intracellular polymers trigger an injury cascade, which can lead to liver injury. This is highly variable and not all patients develop liver disease. Although not fully described, there is likely a strong influence of genetic and environmental modifiers of the injury cascade and of the fibrotic response. With improved understanding of liver injury mechanisms, new strategies for treatment are now being explored.

Intrapleural Gene Therapy for Alpha-1 Antitrypsin Deficiency-Related Lung Disease

Alpha-1 antitrypsin deficiency (AATD) manifests primarily as early-onset emphysema caused by the destruction of the lung by neutrophil elastase due to low amounts of the serine protease inhibitor alpha-1 antitrypsin (AAT). The current therapy involves weekly intravenous infusions of AAT-derived from pooled human plasma that is efficacious, yet costly. Gene therapy applications designed to provide constant levels of the AAT protein are currently under development. The challenge is for gene therapy to provide sufficient amounts of AAT to normalize the inhibitor level and anti-neutrophil elastase capacity in the lung. One strategy involves administration of an adeno-associated virus (AAV) gene therapy vector to the pleural space providing both local and systemic production of AAT to reach consistent therapeutic levels. This review focuses on the strategy, advantages, challenges, and updates for intrapleural administration of gene therapy vectors for the treatment of AATD.

Hepatic-targeted RNA interference provides robust and persistent knockdown of alpha-1 antitrypsin levels in ZZ patients

BACKGROUND & AIMS

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder causing pulmonary and liver disease. The PiZ mutation in AAT (SERPINA1) results in mis-folded AAT protein (Z-AAT) accumulating in hepatocytes, leading to fibrosis and cirrhosis. RNAi-based therapeutics silencing production of hepatic Z-AAT might benefit patients with AATD-associated liver disease. This study evaluated an RNAi therapeutic to silence production of AAT.

METHODS

Part A of this double-blind first-in-human study randomized 54 healthy volunteers (HVs) into single dose cohorts (two placebo: four active), receiving escalating doses of the investigational agent ARC-AAT from 0.38 to 8.0 mg/kg or placebo. Part B randomized 11 patients with PiZZ (homozygous for Z-AAT) genotype AATD, who received up to 4.0 mg/kg of ARC-AAT or placebo. Patients with baseline FibroScan® >11 kPa or forced expiratory volume in one second (FEV1) <60% were excluded. Assessments included safety, pharmacokinetics, and change in serum AAT concentrations.

RESULTS

A total of 36 HVs received ARC-AAT and 18 received placebo (part A). Seven PiZZ individuals received ARC-AAT and four received placebo (part B). A dose response in serum AAT reduction was observed at doses ≥4 mg/kg with similar relative reductions in PiZZ patients and HVs at 4 mg/kg and a maximum reduction of 76.1% (HVs) vs. 78.8% (PiZZ) at this dose. The time it took for serum AAT to return to baseline was similar for HV and PiZZ. There were no notable differences between HV and PiZZ safety parameters. The study was terminated early because of toxicity findings related to the delivery vehicle (ARC-EX1) seen in a non-human primate study.

CONCLUSION

PiZZ patients and HVs responded similarly to ARC-AAT. Deep and durable knockdown of hepatic AAT production based on observed reduction in serum AAT concentrations was demonstrated.

LAY SUMMARY

Accumulation of abnormal proteins in the livers of patients with alpha-1 antitrypsin deficiency may lead to decreased liver function and potentially liver failure. Therapeutics targeting the production of these abnormal proteins may be used to prevent or treat liver disease in patients with alpha-1 antitrypsin deficiency.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02363946.

Retrospective analysis of children with α-1 antitrypsin deficiency

BACKGROUND

α-1 Antitrypsin (AAT) deficiency is the most frequently occurring genetic liver disorder. The association among classical α-1 antitrypsin deficiency (AATD), chronic liver disease, and cirrhosis is common in adult patients but rare in children.

AIM

To assess the clinical characteristics of children with AATD and to compare symptoms between homozygous and heterozygous children.

MATERIALS AND METHODS

The study included 20 children who were found to have mutant Pi alleles. AAT phenotyping was conducted on patients with a low serum AAT level. The exclusion criteria included infectious, anatomic, and metabolic conditions. Symptoms on presentation, physical examination findings, laboratory values, liver biopsy results, and follow-up periods were recorded for each patient.

RESULTS

The patients included six (30%) girls and 14 (70%) boys, with a mean age of 6.3±5.1 (1-16) years. The PiZZ phenotype was present in eight (40%) and PiMZ in 12 (60%) patients. The most frequent symptom was elevated liver function test results. Three patients were referred with neonatal cholestasis and one with compensated cirrhosis. Eight patients underwent liver biopsy; all patients except one had periodic acid-Schiff-positive diastase-resistant globules in the hepatocytes. The mean follow-up period was 34±33 (12-101) months. At the end of follow-up, all patients with PiZZ were found to have chronic hepatitis, and one with cirrhosis. On the contrary, two patients with PiMZ were found to have chronic hepatitis.

CONCLUSION

Children with classical AATD commonly have chronic liver disease. In heterozygous (PiMZ) children with AATD, enzyme levels can normalize with occasional fluctuations, sometimes causing delayed diagnosis.

Amelioration of Alpha-1 Antitrypsin Deficiency Diseases with Genome Editing in Transgenic Mice

Alpha-1 antitrypsin deficiency (AATD) is a hereditary liver disease caused by mutations in the SERPINA1 serine protease inhibitor gene. Most severe patients are homozygous for PiZ alleles (PiZZ; amino acid E324K), which lead to protein aggregates in hepatocytes and reduced circulating levels of AAT. The liver aggregates typically lead to fibrosis, cirrhosis, and hepatocellular carcinoma, and the reduced circulating AAT levels can lead to emphysema and chronic obstructive pulmonary diseases. In this study, two CRISPR/Cas9 gene editing approaches were used to decrease liver aggregates and increase systemic AAT-M levels in the PiZ transgenic mouse. In the first approach, AAT expression in hepatocytes was reduced more than 98% following the systemic delivery of AAV8-CRISPR targeting exon 2 of hSERPINA1, leading to reduced aggregates in hepatocytes. In the second approach, a second adeno-associated virus, which provided the donor template to correct the Z mutation, was also administered. These treated mice had reduced AAT expression (> 98%) and a low level (5%) of wildtype AAT-M mRNA. Taken together, this study shows that CRISPR gene editing can efficiently reduce liver expression of AAT-Z and restore modest levels of wildtype AAT-M in a mouse model of AATD, raising the possibility of CRISPR gene editing therapeutic for AATD.

Successful Outcome and Biliary Drainage in an Infant with Concurrent Alpha-1-Antitrypsin Deficiency and Biliary Atresia

We describe the rare instance of concomitant biliary atresia and alpha-1-antitrypsin deficiency and the first documented successful portoenterostomy in this scenario. The potential for dual pathology must be recognized and underscores that prompt diagnosis of biliary atresia, despite concomitant alpha-1-antitrypsin deficiency, is essential to afford potential longstanding native liver function.

Alpha-1 antitrypsin Pi*SZ genotype: estimated prevalence and number of SZ subjects worldwide

The alpha-1 antitrypsin (AAT) haplotype Pi*S, when inherited along with the Pi*Z haplotype to form a Pi*SZ genotype, can be associated with pulmonary emphysema in regular smokers, and less frequently with liver disease, panniculitis, and systemic vasculitis in a small percentage of people, but this connection is less well established. Since the detection of cases can allow the application of preventive measures in patients and relatives with this congenital disorder, the objective of this study was to update the prevalence of the SZ genotype to achieve accurate estimates of the number of Pi*SZ subjects worldwide, based on studies performed according to the following criteria: 1) samples representative of the general population, 2) AAT phenotyping characterized by adequate methods, and 3) selection of studies with reliable results assessed with a coefficient of variation calculated from the sample size and 95% confidence intervals. Studies fulfilling these criteria were used to develop tables and maps with an inverse distance-weighted (IDW) interpolation method, to provide numerical and geographical information of the Pi*SZ distribution worldwide. A total of 262 cohorts from 71 countries were included in the analysis. With the data provided by these cohorts, a total of 1,490,816 Pi*SZ were estimated: 708,792 in Europe; 582,984 in America and Caribbean; 85,925 in Africa; 77,940 in Asia; and 35,176 in Australia and New Zealand. Remarkably, the IDW interpolation maps predicted the Pi*SZ prevalence throughout the entire world even in areas lacking real data. These results may be useful to plan strategies for future research, diagnosis, and management of affected individuals.

Autophagy in Hepatocytes in Infants With Alpha-1 ATD and Different Liver Disease Outcomes: A Retrospective Analysis

OBJECTIVES

It is unclear whether a distinct activity of pathways removing the antitrypsin (AT) protein in Alpha-1-Antitrypsin Deficiency (α1ATD) are associated with an unfavorable predisposition to liver disease in the future. The aim of this study was to determine whether liverspecific activity of AT protein disposal occurs at infancy in α1ATD with PiZZ phenotype (ATZ).

METHODS

Liver samples of 17 infants with unfavorable ATZ outcome (Group I, n = 8, median age  = 0.35 year) and good outcome (Group II, n = 9, 0.17 year), and 9 with biliary atresia (BA, median age = 0.17 year) as control, were enrolled. For each subject were investigated autophagy activity by mRNA, protein expression (Calnexin, Beclin-1, p62, and Parkin), and hepatocyte ultrastructure with morphometric analyses.

RESULTS

No significant differences in gene expression in the liver of infants were found between the 2 ATZ groups. Although a correlation between patients' age and protein expression was observed, the ATZ groups differed Parkin immunohistochemical expression. Moreover, the hepatocytes in ATZ infants with unfavorable outcome were characterized by low Parkin expression and the presence of isolated mitophagosoms and numerous enlarged mitochondria. The mentioned findings differed in patients with BA.

CONCLUSIONS

Thus, mentioned specific features occurring at infancy may suggest association with poor liver outcome. Parkin low expression could have a potential for disease prognosis and treatment; however, further studies in a greater number of patients are needed.

Liver Involvement in Patients With PiZZ-Emphysema, Candidates for Lung Transplantation

Information about the prevalence and nature of liver disorders in adults with alpha1-antitrypsin deficiency is scarce. At our center, systematic liver biopsy screening is part of the evaluation before lung transplantation (LT) in the emphysema patients with the PiZZ phenotype. Our aim was to report our experience with this prospective screening. Clinical, liver function, and imaging parameters as well as liver histology data were analyzed for 23 consecutive adult patients with PiZZ severe emphysema referred to our center for consideration of LT from 2006 to 2014. Overall 20 (87%) featured chronic liver disease characterized by a chronic inflammation and/or a significant portal fibrosis on histology. Two of the 23 patients (8.7%) had septal fibrosis according to the Metavir and Ishak scores and met our definition of severe chronic liver disease. They were both clinically asymptomatic with normal liver function tests. On abdominal ultrasonography, the liver appeared normal in one patient and with abnormal contours in the other. Our data indicate that in adults with PiZZ-related emphysema being evaluated for LT, most patients had some histologic involvement. The prevalence of severe liver dysfunction is <10%.

Measuring the Effect of Histone Deacetylase Inhibitors (HDACi) on the Secretion and Activity of Alpha-1 Antitrypsin

Alpha-1 antitrypsin deficiency (AATD) is a protein conformational disease with the most common cause being the Z-variant mutation in alpha-1 antitrypsin (Z-AAT). The misfolded conformation triggered by the Z-variant disrupts cellular proteostasis (protein folding) systems and fails to meet the endoplasmic reticulum (ER) export metrics, leading to decreased circulating AAT and deficient antiprotease activity in the plasma and lung. Here, we describe the methods for measuring the secretion and neutrophil elastase (NE) inhibition activity of AAT/Z-AAT, as well as the response to histone deacetylase inhibitor (HDACi), a major proteostasis modifier that impacts the secretion and function of AATD from the liver to plasma. These methods provide a platform for further therapeutic development of proteostasis regulators for AATD.

Pathophysiology of Alpha-1 Antitrypsin Deficiency Liver Disease

Classical alpha-1 antitrypsin (a1AT) deficiency is an autosomal recessive disease associated with an increased risk of liver disease in adults and children, and with lung disease in adults (Teckman and Jain, Curr Gastroenterol Rep 16(1):367, 2014). The vast majority of the liver disease is associated with homozygosity for the Z mutant allele, the so-called PIZZ. These homozygous individuals synthesize large quantities of a1AT mutant Z protein in the liver, but the mutant protein folds improperly during biogenesis and approximately 85% of the molecules are retained within the hepatocytes rather than appropriately secreted. The resulting low, or "deficient," serum level leaves the lungs vulnerable to inflammatory injury from uninhibited neutrophil proteases. Most of the mutant Z protein molecules retained within hepatocytes are directed into intracellular proteolysis pathways, but some molecules remain in the endoplasmic reticulum for long periods of time. Some of these molecules adopt an unusual aggregated or "polymerized" conformation (Duvoix et al., Rev Mal Respir 31(10):992-1002, 2014). It is thought that these intracellular polymers trigger a cascade of intracellular injury which can lead to end-organ liver injury including chronic hepatitis, cirrhosis, and hepatocellular carcinoma (Lindblad et al., Hepatology 46(4):1228-1235, 2007). The hepatocytes with the largest accumulations of mutant Z polymers undergo apoptotic death and possibly other death mechanisms. This intracellular death cascade appears to involve ER stress, mitochondrial depolarization, and caspase cleavage, and is possibly linked to autophagy and redox injury. Cells with lesser burdens of mutant Z protein proliferate to maintain the liver cell mass. This chronic cycle of cell death and regeneration activates hepatic stellate cells and initiates the process of hepatic fibrosis. Cirrhosis and hepatocellular carcinoma then result in some patients. Since not all patients with the same homozygous PIZZ genotype develop end-stage disease, it is hypothesized that there is likely to be a strong influence of genetic and environmental modifiers of the injury cascade and of the fibrotic response.

A Library of Rare α1-Antitrypsin (AAT) Variant Phenotypes to Aid in the Diagnosis of AAT Deficiency

OBJECTIVES

α1-Antitrypsin (AAT) deficiency is a hereditary disorder due to defective production of the serine protease inhibitor, AAT, which can cause lung and liver diseases. Severity of disease depends particularly on the phenotypic representation of AAT variants in the patient.

METHODS

In this study, we present determination of seven common and nine rare variant phenotypes of AAT using pediatric samples collected in Texas Children's Hospital to address the knowledge gap in the identification of rare variants. We tested 16 different AAT variants that had been stored in a -80 °C freezer over the years to add to the reference library of AAT variants. The gold-standard isoelectric focusing electrophoresis method was used for analysis and interpretation of AAT variants. Each variant was inspected visually by comparing multiple bands, unique to phenotypic identity, with a previously identified pattern.

RESULTS

Seven common M, S, and Z variants were identified as M1M1, M2M2, M1M2, MS, SS, SZ, and ZZ. Nine rare variants were identified as FM, FS, FZ, PM, XM, YM, IM, TS, and EP. These were interpreted independently and in a blinded manner by an experienced technologist and two clinical chemists from two different institutions.

CONCLUSIONS

Our results add to the reference library to identify the rare variant phenotypes of AAT protein. This report will guide clinical laboratories for proper assessment of rare variants and in turn contribute to accurate diagnosis and management of AAT deficiency.

Gene Therapy for Alpha-1 Antitrypsin Deficiency Lung Disease

Alpha-1 antitrypsin (AAT) deficiency, characterized by low plasma levels of the serine protease inhibitor AAT, is associated with emphysema secondary to insufficient protection of the lung from neutrophil proteases. Although AAT augmentation therapy with purified AAT protein is efficacious, it requires weekly to monthly intravenous infusion of AAT purified from pooled human plasma, has the risk of viral contamination and allergic reactions, and is costly. As an alternative, gene therapy offers the advantage of single administration, eliminating the burden of protein infusion, and reduced risks and costs. The focus of this review is to describe the various strategies for AAT gene therapy for the pulmonary manifestations of AAT deficiency and the state of the art in bringing AAT gene therapy to the bedside.

Challenges and Prospects for Alpha-1 Antitrypsin Deficiency Gene Therapy

Alpha-1 antitrypsin (AAT) is a protease inhibitor belonging to the serpin family. A number of identified mutations in the SERPINA1 gene encoding this protein result in alpha-1 antitrypsin deficiency (AATD). A decrease in AAT serum concentration or reduced biological activity causes considerable risk of chronic respiratory and liver disorders. As a monogenic disease, AATD appears to be an attractive target for gene therapy, particularly for patients with pulmonary dysfunction, where augmentation of functional AAT levels in plasma might slow down respiratory disease development. The short AAT coding sequence and its activity in the extracellular matrix would enable an increase in systemic serum AAT production by cellular secretion. In vitro and in vivo experimental AAT gene transfer with gamma-retroviral, lentiviral, adenoviral, and adeno-associated viral (AAV) vectors has resulted in enhanced AAT serum levels and a promising safety profile. Human clinical trials using intramuscular viral transfer with AAV1 and AAV2 vectors of the AAT gene demonstrated its safety, but did not achieve a protective level of AAT >11 μM in serum. This review provides an in-depth critical analysis of current progress in AATD gene therapy based on viral gene transfer. The factors affecting transgene expression levels, such as site of administration, dose and type of vector, and activity of the immune system, are discussed further as crucial variables for optimizing the clinical effectiveness of gene therapy in AATD subjects.

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.

Suspecting and Testing for Alpha-1 Antitrypsin Deficiency-An Allergist's and/or Immunologist's Perspective

Alpha-1 antitrypsin deficiency (AATD) is a hereditary, monogenic disorder with no unique clinical features. AATD can be difficult to diagnose as patients commonly present with respiratory symptoms often mistaken for other respiratory syndromes such as asthma or smoking-related chronic obstructive pulmonary disease. In addition, symptoms related to AATD may also affect other organs, including the liver, vasculature, and skin. The severity of AATD varies between individuals, and in severe cases, the irreversible lung damage can develop into emphysema. Early diagnosis is critical to enable the implementation of lifestyle changes and therapeutic options that can slow further deterioration of pulmonary tissue. Once AATD is suspected, a range of tests are available (serum alpha-1 proteinase inhibitor [A1-PI] level measurement, phenotyping, genotyping, gene sequencing) for confirming AATD. Currently, intravenous infusion of A1-PI is the only therapy that directly addresses the underlying cause of AATD, and has demonstrated efficacy in a recent randomized, placebo-controlled trial. This review discusses the etiology, testing, and management of AATD from the allergist's and/or immunologist's perspective. It aims to raise awareness of the condition among physicians who care for people with obstructive lung disorders and are therefore likely to see patients with obstructive lung disease that may, in fact, prove to be AATD.

Liver disease in the adolescent

This article discusses common liver diseases in the adolescent. Briefly reviewed is the evaluation of the adolescent with new-onset liver enzyme elevation. Then the article discusses common liver diseases, such as nonalcoholic fatty liver disease, hepatitis, metabolic disease, biliary atresia, cystic fibrosis, and inherited disorders of cholestasis. Finally, a management approach to the adolescent with liver disease is outlined, noting the challenges that must be addressed to effectively care for not only liver disease in the adolescent but also the patient as a whole.

Role of alpha-1 antitrypsin in human health and disease

Alpha-1 antitrypsin (AAT) deficiency is an under-recognized hereditary disorder associated with the premature onset of chronic obstructive pulmonary disease, liver cirrhosis in children and adults, and less frequently, relapsing panniculitis, systemic vasculitis and other inflammatory, autoimmune and neoplastic diseases. Severe AAT deficiency mainly affects Caucasian individuals and has its highest prevalence (1 : 2000-1 : 5000 individuals) in Northern, Western and Central Europe. In the USA and Canada, the prevalence is 1: 5000-10 000. Prevalence is five times lower in Latin American countries and is rare or nonexistent in African and Asian individuals. The key to successful diagnosis is by measuring serum AAT, followed by the determination of the phenotype or genotype if low concentrations are found. Case detection allows implementation of genetic counselling and, in selected cases, the application of augmentation therapy. Over the past decade, it has been demonstrated that AAT is a broad-spectrum anti-inflammatory, immunomodulatory, anti-infective and tissue-repair molecule. These new capacities are promoting an increasing number of clinical studies, new pharmacological formulations, new patent applications and the search for alternative sources of AAT (including transgenic and recombinant AAT) to meet the expected demand for treating a large number of diseases, inside and outside the context of AAT deficiency.

Stress-responsive regulation of mitochondria through the ER unfolded protein response

The endoplasmic reticulum (ER) and mitochondria form physical interactions involved in the regulation of biologic functions including mitochondrial bioenergetics and apoptotic signaling. To coordinate these functions during stress, cells must coregulate ER and mitochondria through stress-responsive signaling pathways such as the ER unfolded protein response (UPR). Although the UPR is traditionally viewed as a signaling pathway responsible for regulating ER proteostasis, it is becoming increasingly clear that the protein kinase RNA (PKR)-like endoplasmic reticulum kinase (PERK) signaling pathway within the UPR can also regulate mitochondria proteostasis and function in response to pathologic insults that induce ER stress. Here, we discuss the contributions of PERK in coordinating ER-mitochondrial activities and describe the mechanisms by which PERK adapts mitochondrial proteostasis and function in response to ER stress.

α1 Antitrypsin deficiency: current best practice in testing and augmentation therapy

α1 Antitrypsin deficiency (AATD) increases the risk of chronic obstructive pulmonary disease (COPD), liver disease and other conditions. Although it is not a rare disease, it is a condition rarely diagnosed because of unawareness by most healthcare providers who manage subjects at risk. Testing recommendations have been published and strongly suggest testing all subjects with confirmed COPD, cryptogenic liver cirrhosis, subjects with incompletely reversible airflow obstruction and siblings of affected individuals. Testing strategies usually imply a combination of measures of α1 antitrypsin (AAT) levels, phenotyping and genotyping, techniques that have been facilitated for in-office use by development of testing kits using dried blood spots. Early detection of subjects is crucial to apply effective preventive measures and early institution of therapy. The only specific Food and Drug Administration - approved therapy for this condition is lifelong weekly intravenous AAT replacement (augmentation therapy). Observational studies strongly suggest a beneficial effect of augmentation therapy in slowing lung function decline and randomized trials suggest a beneficial effect in slowing the progression of emphysema over time as measured by computed tomography. In addition, augmentation therapy has been shown to modulate systemic inflammatory responses and affect markers of elastin degradation. As new markers of disease progression are discovered, new doses of AAT replacement are tested and sub-phenotypes of disease are described, treatment recommendations are likely to change towards a more individualized therapeutic approach.

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.

Using antisense technology to develop a novel therapy for α-1 antitrypsin deficient (AATD) liver disease and to model AATD lung disease

Alpha-1 antitrypsin (AAT) is a serum protease inhibitor that belongs to the serpin superfamily. Mutations in AAT are associated with α-1 antitrypsin deficiency (AATD), a rare genetic disease with two distinct manifestations: AATD lung disease and AATD liver disease. AATD lung disease is caused by loss-of-function of AAT and can be treated with plasma-derived AAT. AATD liver disease is due to the aggregation and retention of mutant AAT protein in the liver; the only treatment available for AATD liver disease is liver transplantation. Here we demonstrate that antisense oligonucleotides (ASOs) targeting human AAT efficiently reduce levels of both short and long human AAT transcript in vitro and in transgenic mice, providing a novel therapy for AATD liver disease. In addition, ASO-mediated depletion of mouse AAT may offer a useful animal model for the investigation of AATD lung disease.

α-1-Antitrypsin deficiency: clinical variability, assessment, and treatment

The recognition of α-1-antitrypsin deficiency, its function, and its role in predisposition to the development of severe emphysema was a watershed in our understanding of the pathophysiology of the condition. This led to the concept and development of intravenous replacement therapy used worldwide to protect against lung damage induced by neutrophil elastase. Nevertheless, much remained unknown about the deficiency and its impact, although in recent years the genetic and clinical variations in manifestation have provided new insights into assessing impact, efficacy of therapy, and development of new therapeutic strategies, including gene therapy, and outcome measures, such as biomarkers and computed tomography. The current article reviews this progress over the preceding 50 years.