Alpha-1-antitrypsin deficiency: diagnosis and treatment (literature review)

Недостаточность альфа-1-антитрипсина - наследственное заболевание, характеризующееся низким уровнем белка альфа-1-антитрипсина (A1AT) в крови. В основном дефицит A1AT проявляется в виде хронической обструктивной болезни легких (ХОБЛ), эмфиземы, а также поражения печени и сосудов. А1АТ является главным ингибитором сериновых протеаз в крови человека. Недостаточность А1АТ обусловлена мутациями в гене SERPINA1. Наиболее распространенными аллельными вариантами в гене SERPINA1 являются S (p.Glu288Val) и Z (р.Glu366Lys), однако в клинической практике большинство случаев тяжелого дефицита А1АТ связаны с генотипом PIZZ. У пациентов с PIZZ патология легких представляет собой фенотип «потери функции», так как дефицит A1AT приводит к ускоренному разрушению паренхимы легких, приводящему к эмфиземе. При Z-мутации 85% синтезированного белка блокируется в гепатоцитах из-за неправильного сворачивания и полимеризации. Накопление полимеризованного белка в эндоплазматической сети гепатоцитов в свою очередь приводит к хроническим заболеваниям печени у некоторых пациентов: циррозу и злокачественным новообразованиям печени. Дефицит А1АТ является довольно распространенным заболеванием, но выявляется лишь незначительная часть лиц с данной патологией. Недостаточность А1АТ зачастую ошибочно диагностируется как ХОБЛ, бронхиальная астма или криптогенное заболевание печени. Задержка в установлении диагноза составляет обычно более 5 лет (в среднем около 8 лет) что, как правило, связано с плохой осведомленностью врачей, недооценкой его распространенности и вариабельностью клинических проявлений. В настоящее время для лечения дефицита А1АТ с легочными проявлениями возможно применение аугментационной терапии, основанной на внутривенном введении очищенного человеческого А1АТ. Также активно ведется поиск новых препаратов, способных улучшить прогноз у пациентов с патологией печени. Современные подходы в лечении дефицита А1АТ, сосредоточенные на генной терапии, становятся перспективным направлением в лечении как легочной, так и печеночной патологии при дефиците А1АТ. Alpha-1 antitrypsin deficiency is a genetic disorder characterized by low level of alfa-1-antitripsin protein (A1AT) in the blood. Usually, A1AT deficiency results in chronic obstructive pulmonary disease (COPD), emphysemas, liver disease and vessels damaging. A1AT is the main inhibitor of serine proteases in human blood. A1AT deficiency is caused by mutations in the gene SERPINA1. The most common SERPINA1 allelic variants are S (p.Glu288Val) and Z (p.Glu366Lys). However, the most of documented severe cases of A1AD are associated with PIZZ genotype. PIZZ genotype patients have loss-of-function phenotype due to accelerated lung parenchyma destruction resulting in emphysema. Z mutation genotype leads to blocking of 85% synthesized protein in hepatocytes due to wrong folding and polymerization. Accumulation of the bodied protein in hepatocytes endoplasmic reticulum results in chronic liver disease, cirrhosis and other liver pathologies. A1AT deficiency is a common disorder, however, this diagnosis is established in a small part of the patients. A1AT deficiency is often misdiagnosed as COPD, asthma or сryptogenic liver disease. Usually, due to underestimating the prevalence of the disease and its unspecific symptoms, the diagnosis delay is more than 5 years (on average about 8 years). Nowadays it is possible to treat lung form of A1AT deficiency used the augmentation therapy, that bases on intravenous infusions of pure human A1AT. Also, the active development of new drugs to improve the prognosis in the patients with liver pathology is ongoing. Modern approaches of A1AT deficiency treatment, focused on gene therapy, are becoming a promising direction in the managing of both pulmonary and hepatic pathology with A1AT deficiency.

SUN-221 Subclinical Alpha-1 Antitrypsin Deficiency Is Associated with Increased Free Cortisol Fraction in Plasma and Altered Glucocorticoid Delivery to Tissues

Background Corticosteroid Binding Globulin (CBG) binds >85% of plasma cortisol and controls the circulating free cortisol pool. Proteolytic cleavage by neutrophil elastase is proposed to reduce CBG binding affinity and increase free cortisol availability to inflamed tissues. The CORtisol NETwork (CORNET) consortium found that genetic variation at a locus spanning SERPINA1 (encoding alpha-1 antitrypsin, A1AT, the endogenous inhibitor of neutrophil elastase) and SERPINA6 (CBG) contributes to morning total plasma cortisol variation. We hypothesised that A1AT deficiency increases CBG cleavage and hence free plasma cortisol, resulting in increased tissue cortisol delivery in adipose and in HPA axis negative feedback. We tested this in recall-by-genotype studies of people who are heterozygous for inactivating mutations in SERPINA1. Methods 16 healthy carriers of one of the two most common A1AT-deficiency single nucleotide polymorphisms (rs17580 & rs28929474) and 16 age-, gender- and BMI-matched controls were recruited from the Generation Scotland Biobank. Participants underwent combined receptor antagonist stimulation of the HPA axis (‘CRASH’) testing using RU486 400mg and spironolactone 200mg, or placebo in a double blind randomised crossover design. Plasma free cortisol was measured by isotopic dilution and ultrafiltration, total cortisol by LC-MS/MS, total CBG by ELISA, CBG binding capacity by radioligand displacement assay, and ACTH by immunoassay. Serum A1AT was measured by ELISA. Tissue cortisol (LC-MS/MS) and expression of glucocorticoid dependent transcripts (qPCR) were measured in subcutaneous adipose samples collected by needle biopsy. Results Serum A1AT was confirmed lower in those with heterozygous mutations vs wild type controls (411.3 +/- 27.44 vs 565.1 +/- 23.38 mg/dL, p=0.0002). No measurable differences in total CBG or CBG binding capacity were observed. However, plasma free cortisol fraction was higher in those carrying A1AT mutations (16.13 +/- 0.2 vs 13.88 +/- 0.04 %, p<0.0001). Adipose cortisol concentrations were not significantly different but expression of glucocorticoid responsive genes e.g. PER1 was 54% higher (p=0.014) in A1AT-deficient subjects. Plasma cortisol was elevated during CRASH testing in both groups, with the increment versus placebo tending to be lower in A1AT-deficient subjects (82.5 +/- 6.7 vs 126.7 +/- 6.8 nM). Conclusion Alpha-1 antitrypsin mutation heterozygosity, common in the general population, is associated with higher free cortisol fraction, consistent with enhanced cleavage of CBG. This is associated with evidence of enhanced delivery of glucocorticoid to adipose tissues but reduced HPA negative feedback, suggesting tissue-specific control of cortisol delivery by CBG.

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.

Functional characterization of the mouse Serpina1 paralog DOM-7

The generation of authentic mouse-models for human α1-antitrypsin (A1AT)-deficiency is difficult due to the high complexity of the mouse Serpina1 gene locus. Depending on the exact mouse strain, three to five paralogs are expressed, with different proteinase inhibitory properties. Nowadays with CRISPR-technology, genome editing of complex genomic loci is feasible and could be employed for the generation of A1AT-deficiency mouse models. In preparation of a CRISPR/Cas9-based genome-engineering approach we identified cDNA clones with a functional CDS for the Serpina1-paralog DOM-7. Here, we show that DOM-7 functionally inhibits neutrophil elastase (ELANE) and chymotrypsin, and therefore needs to be considered when aiming at the generation of A1AT-deficient models.

Gastroenterology

This chapter explores gastroenterology, including healthy, enjoyable eating, mouth observations, endoscopy and biopsy, dysphagia, nausea and vomiting, dyspepsia and peptic ulcer disease, gastro-oesophageal reflux disease (GORD), upper gastrointestinal bleeding, diarrhoea, constipation, ulcerative colitis (UC), Crohn’s disease, gastrointestinal malabsorption, Coeliac disease, irritable bowel syndrome (IBS), nutritional disorders, chronic pancreatitis, carcinoma of the pancreas, carcinoid tumours, jaundice, liver failure, cirrhosis, viral hepatitis, alcoholism, primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), autoimmune hepatitis (AIH), non-alcoholic fatty liver disease (NAFLD), Wilson’s disease/hepatolenticular degeneration, liver tumours, hereditary haemochromatosis (HH), and α‎1-antitrypsin (A1AT) deficiency.

Autophagy induced by exogenous bile acids is therapeutic in a model of α-1-AT deficiency liver disease

The bile acid nor-ursodeoxycholic acid (norUDCA) has many biological actions, including antiapoptotic effects. Homozygous PIZZ α-1-antitrypsin (A1AT)-deficient humans are known to be at risk for liver disease, cirrhosis, and liver cancer as a result of the accumulation of the toxic, A1AT mutant Z protein within hepatocytes. This accumulation triggers cell death in the hepatocytes with the largest mutant Z-protein burdens, followed by compensatory proliferation. Proteolysis pathways within the hepatocyte, including autophagy, act to reduce the intracellular burden of A1AT Z protein. We hypothesized that norUDCA would reduce liver cell death and injury in A1AT deficiency. We treated groups of PiZ transgenic mice and wild-type mice with norUDCA or vehicle, orally, and examined the effects on the liver. The PiZ mouse is the best model of A1AT liver injury and recapitulates many features of the human liver disease. Mice treated with norUDCA demonstrated reduced hepatocellular death by compensatory hepatocellular proliferation as determined by bromodeoxyuridine incorporation (3.8% control, 0.88% treated, P < 0.04). Ki-67 staining as a marker for hepatocellular senescence and death was also reduced ( P < 0.02). Reduced apoptotic signaling was associated with norUDCA, including reduced cleavage of caspases-3, -7, and -8 (all P < 0.05). We determined that norUDCA was associated with a >70% reduction in intrahepatic mutant Z protein ( P < 0.01). A 32% increase in hepatic autophagy associated with norUDCA was the likely mechanism. norUDCA administration is associated with increased autophagy, reduced A1AT protein accumulation, and reduced liver injury in a model of A1AT deficiency.