New Therapeutic Targets for Alpha-1 Antitrypsin Deficiency.
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ABSTRACT:
SUBMITTER: Lomas DA
PROVIDER: S-EPMC6361470 | biostudies-literature | 2018 Aug
REPOSITORIES: biostudies-literature
Publications
New Therapeutic Targets for Alpha-1 Antitrypsin Deficiency.
Chronic obstructive pulmonary diseases (Miami, Fla.) 20180806 4
Alpha-1antitrypsin deficiency (AATD) results from the intracellular polymerization and retention of mutant alpha-1antitrypsin (AAT) within the endoplasmic reticulum of hepatocytes. This causes cirrhosis whilst the deficiency of circulating AAT predisposes to early onset emphysema. This is an exciting time for researchers in the field with the development of novel therapies based on understanding the pathobiology of disease. I review here augmentation therapy to prevent the progression of lung di ...[more]
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Project description:BACKGROUND:Alpha-1-antitrypsin (AAT) deficiency (AATD) of Z, Mmalton, Siiyama type is associated with liver storage of the mutant proteins and liver disease. The Z variant can be diagnosed on isoelectric focusing (IEF) while Mmalton and Siiyama may be missed or misdiagnosed with this technique. Therefore, molecular analysis is mandatory for their characterization. In particular, that holds true for the Mmalton variant as on IEF profile it resembles the wild M2 subtype. METHODS:This is a retrospective analysis involving review of medical records and of liver biopsy specimens from a series of Mmalton, Z and Siiyama Alpha-1-antitrypsin deficiency patients. The review has been implemented by additional histological stains, electron microscopic observations and 3-D modeling studies of the sites of the mutations. RESULTS:Z, Mmalton and Siiyama liver specimen contained characteristic intrahepatocytic PAS-D globules. The globules differed in the three variants as only Mmalton cases showed dark basophilic precipitates within the AAT inclusions. The precipitates were visualized in haematoxylin-eosin (H.E.) stained preparations and corresponded to calcium precipitates as demonstrated by von Kossa staining. On immunohistochemistry, ZAAT inclusions were stained by polyclonal as well as monoclonal noncommercial anti-AAT antibody (AZT11), whilst Mmalton and Siiyama inclusion bodies remained negative with the monoclonal anti-Z antibody. 3-D protein analysis allowed to predict more severe misfolding of the Mmalton molecule as compared to Z and Siiyama that could trigger anomalous interaction with endoplasmic reticulum chaperon proteins, namely calcium binding proteins. CONCLUSIONS:Mmalton AAT inclusion bodies contain calcium precipitates inside them that allow the differential diagnosis with Siiyama and ZAAT inclusions in routine histological sections. The study has confirmed the specificity of the monoclonal AZT11 for the Z mutant. Thus, the combination of these two features is crucial for the distinction between the three variants and for predicting the genotype, whose confirmation would definitely require molecular analysis. Our study provides new data on the pathomorphogenesis of Mmalton inclusion bodies whose mineralization could play a central role in disease pathogenesis of Mmalton that is distinct from the Z and Siiyama variants. Calcium is known to be a major effector of cell death either via the increased intracellular concentration or the alteration of homeostasis.
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Project description:Alpha 1-antitrypsin (AAT) deficiency, a hereditary disorder characterized by low serum levels of functional AAT, is associated with early development of panacinar emphysema. AAT inhibits serine proteases, including neutrophil elastase, protecting the lung from proteolytic destruction. Cigarette smoke, pollution, and inflammatory cell-mediated oxidation of methionine (M) 351 and 358 inactivates AAT, limiting lung protection. In vitro studies using amino acid substitutions demonstrated that replacing M351 with valine (V) and M358 with leucine (L) on a normal M1 alanine (A) 213 background provided maximum antiprotease protection despite oxidant stress. We hypothesized that a onetime administration of a serotype 8 adeno-associated virus (AAV8) gene transfer vector coding for the oxidation-resistant variant AAT (A213/V351/L358; 8/AVL) would maintain antiprotease activity under oxidant stress compared with normal AAT (A213/M351/M358; 8/AMM). 8/AVL was administered via intravenous (IV) and intrapleural (IPL) routes to C57BL/6 mice. High, dose-dependent AAT levels were found in the serum and lung epithelial lining fluid (ELF) of mice administered 8/AVL or 8/AMM by IV or IPL. 8/AVL serum and ELF retained serine protease-inhibitory activity despite oxidant stress while 8/AMM function was abolished. 8/AVL represents a second-generation gene therapy for AAT deficiency providing effective antiprotease protection even with oxidant stress.
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Project description:BackgroundSevere Alpha-1 Antitrypsin (AAT) deficiency is a hereditary condition caused by mutations in the SERPINA1 gene, which predisposes to lung emphysema and liver disease. It is usually related to PI*Z alleles, and less frequent to rare and null (QO) alleles. Null-AAT alleles represent the end of a continuum of variants associated with profound AAT deficiency and extremely increased risk of emphysema.MethodsA family with severe AAT deficiency was analyzed to achieve genetic diagnosis. The complete exons and introns of the SERPINA1 gene were sequenced and transcriptional analysis by RT-PCR was performed to characterize the effect of splicing variants found in the patients. In addition, a minigene MGserpa1_ex1b-1c was cloned into the pSAD vector to in vitro investigate the independent impact of variants on splicing process.ResultsWe report a new identified null allele (PI*QOMadrid) in two adult siblings with practically no detectable serum AAT. The PI*QOMadrid allele consist of a duplication of the thymine (T) in position +2 of the donor splice site of exon 1C (+2dupT). In these two subjects, PI*QOMadrid occurred in compound heterozygote combination with the previously described variant PI*QOPorto. Both QOMadrid and QOPorto variants are located very close together in a regulatory region of the SERPINA1 gene. Analysis of transcripts revealed that QOMadrid variant prevented the expression of transcripts from exon 1C, and then normally spliced RNA products are not expected in the liver of these patients. In addition, aberrant splicing patterns of both variants were clearly distinguished and quantified by functional in vitro assays lending further support to their pathogenicity.ConclusionFinding pathogenic mutations in non-coding regions of the SERPINA1 highlight the importance that regulatory regions might have in the disease. Regulatory regions should be seriously considered in discordant cases with severe AAT deficiency where no coding mutations were found.
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Project description: Not available
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Project description:PurposeTo report a case of severe bilateral descemetoceles in a patient with alpha-1 antitrypsin (A1AT) deficiency during intensive care unit hospitalization.ObservationsA 42-year-old male presented with sub-acute bilateral vision loss during an intensive care unit hospitalization following liver and kidney transplantations. On exam, this patient's best-corrected visual acuity was 20/80 in both eyes. There were bilateral descemetoceles inferotemporally in both eyes with overlying epithelial defects and dense surrounding punctate epithelial staining. The patient was initially treated with gatifloxacin drops and frequent lubricating ointment. Given the concern for impending perforation, cyanoacrylate glue with bandage contact lens was applied to both eyes. His best corrected visual acuity remained unchanged in the right eye and improved to 20/30 in the left eye. Upon medical stabilization, anterior lamellar graft was performed in the right eye, with plans for the same treatment in the left eye in the future.ConclusionsAs A1AT is found in the tear film and is believed to play a role in regulating protease activity in the cornea, we hypothesize that this patient's A1AT deficiency exacerbated the progression of corneal ulceration leading to severe descemetocele formation.
| S-EPMC6639587 | biostudies-literature
Project description:Alpha-1 antitrypsin (AAT) deficiency (AATD) is an under-recognized hereditary disorder and a significant cause of chronic obstructive pulmonary disease (COPD), a disease that contributes to global mortality. AAT is encoded by the SERPINA1 gene, and severe mutation variants of this gene increase the risk of developing COPD. AATD is more frequently screened for in non-Hispanic White populations. However, AATD is also observed in other ethnic groups and very few studies have documented the mutation frequency in these other ethnic populations. Here, we review the current literature on AATD and allele frequency primarily in Black populations and discuss the possible clinical outcomes of low screening rates in a population that experiences poor health outcomes and whether the low frequency of AATD is related to a lack of screening in this population or a truly low frequency of mutations causing AATD. This review also outlines the harmful SERPINA1 variants, the current epidemiology knowledge of AATD, health inequity in Black populations, AATD prevalence in Black populations, the clinical implications of low screening of AATD in this population, and the possible dangers of not diagnosing or treating AATD.
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Project description:Alpha 1 antitrypsin deficiency is a hereditary condition characterized by low alpha 1 proteinase inhibitor (also known as alpha 1 antitrypsin [AAT]) serum levels. Reduced levels of AAT allow abnormal degradation of lung tissue, which may ultimately lead to the development of early-onset emphysema. Intravenous infusion of AAT is the only therapeutic option that can be used to maintain levels above the protective threshold. Based on its biochemical efficacy, AAT replacement therapy was approved by the US Food and Drug administration in 1987. However, there remained considerable interest in selecting appropriate outcome measures that could confirm clinical efficacy in a randomized controlled trial setting. Using computed tomography as the primary measure of decline in lung density, the capacity for intravenously administered AAT replacement therapy to slow and modify the course of disease progression was demonstrated for the first time in the Randomized, Placebo-controlled Trial of Augmentation Therapy in Alpha-1 Proteinase Inhibitor Deficiency (RAPID) trial. Following these results, an expert review forum was held at the European Respiratory Society to discuss the findings of the RAPID trial program and how they may change the landscape of alpha 1 antitrypsin emphysema treatment. This review summarizes the results of the RAPID program and the implications for clinical considerations with respect to diagnosis, treatment and management of emphysema due to alpha 1 antitrypsin deficiency.
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