Alpha 1-antitrypsin deficiency and emphysema caused by homozygous inheritance of non-expressing alpha 1-antitrypsin genes

Alpha1-antitrypsin deficiency in Greece: Focus on rare variants

PURPOSE

A1Antitrypsin deficiency (AATD) pathogenic mutations are expanding beyond the PI*Z and PI*S to a multitude of rare variants.

AIM

to investigate genotype and clinical profile of Greeks with AATD.

METHODS

Symptomatic adult-patients with early-emphysema defined by fixed airway obstruction and computerized-tomography scan and lower than normal serum AAT levels were enrolled from reference centers all over Greece. Samples were analyzed in the AAT Laboratory, University of Marburg-Germany.

RESULTS

Included are 45 adults, 38 homozygous or compound heterozygous for pathogenic variants and 7 heterozygous. Homozygous were 57.9% male, 65.8% ever-smokers, median (IQR) age 49.0(42.5-58.5) years, AAT-levels 0.20(0.08-0.26) g/L, FEV1(%predicted) 41.5(28.8-64.5). PI*Z, PI*Q0, and rare deficient allele's frequency was 51.3%, 32.9%,15.8%, respectively. PI*ZZ genotype was 36.8%, PI*Q0Q0 21.1%, PI*MdeficientMdeficient 7.9%, PI*ZQ0 18.4%, PI*Q0Mdeficient 5.3% and PI*Zrare-deficient 10.5%. Genotyping by Luminex detected: p.(Pro393Leu) associated with MHeerlen (M1Ala/M1Val); p.(Leu65Pro) with MProcida; p.(Lys241Ter) with Q0Bellingham; p.(Leu377Phefs*24) with Q0Mattawa (M1Val) and Q0Ourem (M3); p.(Phe76del) with MMalton (M2), MPalermo (M1Val), MNichinan (V) and Q0LaPalma (S); p.(Asp280Val) with PLowell (M1Val); PDuarte (M4), YBarcelona (p.Pro39His). Gene-sequencing (46.7%) detected Q0GraniteFalls, Q0Saint-Etienne, Q0Amersfoort(M1Ala), MWürzburg, NHartfordcity and one novel-variant (c.1A>G) named Q0Attikon.Heterozygous included PI*MQ0Amersfoort(M1Ala), PI*MMProcida, PI*Mp.(Asp280Val), PI*MOFeyzin. AAT-levels were significantly different between genotypes (p = 0.002).

CONCLUSION

Genotyping AATD in Greece, a multiplicity of rare variants and a diversity of rare combinations, including unique ones were observed in two thirds of patients, expanding knowledge regarding European geographical trend in rare variants. Gene sequencing was necessary for genetic diagnosis. In the future the detection of rare genotypes may add to personalize preventive and therapeutic measures.

Alpha1-antitrypsin deficiency: An updated review

Alpha1-antitrypsin deficiency (AATD) is a rare autosomal recessive disease associated with the homozygous Z variant of the SERPINA1 gene. Clinical expression of AATD, reported 60 years ago associate a severe deficiency, pulmonary emphysema and/or liver fibrosis. Pulmonary emphysema is due to the severe alpha1-antitrypsin deficiency of the ZZ homozygous status and is favored by smoking. Liver fibrosis is due to the ZZ homozygous status and is favored by obesity and excessive chronic alcohol intake, with a risk of liver cancer. Diagnosis is based on serum level and either isoelectric focusing determination of the biochemical phenotype or PCR detection of some variants. SERPINA1 gene sequencing is necessary in case of discrepancies between the results of these tests. No treatment is available for the liver disease in AATD. Although no specific trial has been performed, COPD in AATD should be treated as per COPD recommendations. Based on a randomized clinical trial, augmentation therapy is indicated in non-smoking adults less than 70 years of age with emphysema at chest CT, confirmed homozygous AATD, and FEV1 between 35% and 70% of predicted. In contrast Z heterozygosis (MZ or SZ) brings a risk of lung or liver disease only in association with further risk factors. Early detection, in all patients with COPD and chronic liver disease, is critical for the correct information of Z variant carriers. News ways of correcting the liver production of alpha1-antitrypsin will modify the care of AATD patients.

Distribution of alpha1 antitrypsin rare alleles in six countries: Results from the Progenika diagnostic network

BACKGROUND

Knowledge of the frequency of rare SERPINA1 mutations could help in the management of alpha1 antitrypsin deficiency (AATD). The present study aims to assess the frequencies of rare and null alleles and their respiratory and hepatic pathogenicity.

METHODS

This is a secondary analysis of a study that evaluated the viability of the Progenika diagnostic genotyping system in six different countries by analyzing 30,827 samples from cases of suspected AATD. Allele-specific genotyping was carried out with the Progenika A1AT Genotyping Test which analyses 14 mutations in buccal swabs or dried blood spots samples. SERPINA1 gene sequencing was performed for serum AAT-genotype discrepancies or by request of the clinician. Only cases with rare mutations were included in this analysis.

RESULTS

There were 818 cases (2.6%) carrying a rare allele, excluding newly identified mutations. All were heterozygous except for 20 that were homozygous. The most frequent alleles were the M-like alleles, PI*M_malton and PI*M_heerlen. Of the 14 mutations included in the Progenika panel, there were no cases detected of PI*S_iiyama, PI*Q0_{granite falls} and PI*Q0_west. Other alleles not included in the 14-mutation panel and identified by gene sequencing included PI*M_würzburg, PI*Z_bristol, and PI*Z_wrexham, and the null alleles PI*Q0_porto, PI*Q0_madrid, PI*Q0_brescia, and PI*Q0_kayseri.

CONCLUSIONS

The Progenika diagnostic network has allowed the identification of several rare alleles, some unexpected and not included in the initial diagnostic panel. This establishes a new perspective on the distribution of these alleles in different countries. These findings may help prioritize allele selection for routine testing and highlights the need for further research into their pathogenetic role.

Identification of small-molecule elastase inhibitors as antagonists of IL-36 cytokine activation

IL‐1 family cytokines act as apical initiators of inflammation in many settings and can promote the production of a battery of inflammatory cytokines, chemokines and other inflammatory mediators in diverse cell types. IL‐36α, IL‐36β and IL‐36γ, which belong to the extended IL‐1 family, have been implicated as key initiators of skin inflammation in psoriasis. IL‐36γ is highly upregulated in lesional skin from psoriatic individuals, and heritable mutations in the natural IL‐36 receptor antagonist result in a severe form of psoriasis. IL‐36 family cytokines are initially expressed as inactive precursors that require proteolytic processing for activation. The neutrophil granule‐derived protease elastase proteolytically processes and activates IL‐36α and IL‐36γ, increasing their biological activity ~ 500‐fold, and also robustly activates IL‐1α and IL‐33 through limited proteolytic processing. Consequently, inhibitors of elastase activity may have potential as anti‐inflammatory agents through antagonizing the activation of multiple IL‐1 family cytokines. Using in silico screening approaches, we have identified small‐molecule inhibitors of elastase that can antagonize activation of IL‐36γ by the latter protease. The compounds reported herein may have utility as lead compounds for the development of inhibitors of elastase‐mediated activation of IL‐36 and other IL‐1 family cytokines in inflammatory conditions, such as psoriasis.

Suppressing IL-36-driven inflammation using peptide pseudosubstrates for neutrophil proteases

Sterile inflammation is initiated by molecules released from necrotic cells, called damage-associated molecular patterns (DAMPs). Members of the extended IL-1 cytokine family are important DAMPs, are typically only released through necrosis, and require limited proteolytic processing for activation. The IL-1 family cytokines, IL-36α, IL-36β, and IL-36γ, are expressed as inactive precursors and have been implicated as key initiators of psoriatic-type skin inflammation. We have recently found that IL-36 family cytokines are proteolytically processed and activated by the neutrophil granule-derived proteases, elastase, and cathepsin G. Inhibitors of IL-36 processing may therefore have utility as anti-inflammatory agents through suppressing activation of the latter cytokines. We have identified peptide-based pseudosubstrates for cathepsin G and elastase, based on optimal substrate cleavage motifs, which can antagonize activation of all three IL-36 family cytokines by the latter proteases. Human psoriatic skin plaques displayed elevated IL-36β processing activity that could be antagonized by peptide pseudosubstrates specific for cathepsin G. Thus, antagonists of neutrophil-derived proteases may have therapeutic potential for blocking activation of IL-36 family cytokines in inflammatory conditions such as psoriasis.

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.

Autoprocessing of neutrophil elastase near its active site reduces the efficiency of natural and synthetic elastase inhibitors

An imbalance between neutrophil-derived proteases and extracellular inhibitors is widely regarded as an important pathogenic mechanism for lung injury. Despite intense efforts over the last three decades, attempts to develop small-molecule inhibitors for neutrophil elastase have failed in the clinic. Here we discover an intrinsic self-cleaving property of mouse neutrophil elastase that interferes with the action of elastase inhibitors. We show that conversion of the single-chain (sc) into a two-chain (tc) neutrophil elastase by self-cleavage near its S1 pocket altered substrate activity and impaired both inhibition by endogenous α-1-antitrypsin and synthetic small molecules. Our data indicate that autoconversion of neutrophil elastase decreases the inhibitory efficacy of natural α-1-antitrypsin and small-molecule inhibitors, while retaining its pathological potential in an experimental mouse model. The so-far overlooked occurrence and properties of a naturally occurring tc-form of neutrophil elastase necessitates the redesign of small-molecule inhibitors that target the sc-form as well as the tc-form of neutrophil elastase.

Coordinated DNA methylation and gene expression changes in smoker alveolar macrophages: specific effects on VEGF receptor 1 expression

Cigarette smoking is implicated in numerous diseases, including emphysema and lung cancer. The clinical expression of lung disease in smokers is not well explained by currently defined variations in gene expression or simple differences in smoking exposure. Alveolar macrophages play a critical role in the inflammation and remodeling of the lung parenchyma in smoking-related lung disease. Significant gene expression changes in alveolar macrophages from smokers have been identified. However, the mechanism for these changes remains unknown. One potential mechanism for smoking-altered gene expression is via changes in cytosine methylation in DNA regions proximal to gene-coding sequences. In this study, alveolar macrophage DNA from heavy smokers and never smokers was isolated and methylation status at 25,000 loci determined. We found differential methylation in genes from immune-system and inflammatory pathways. Analysis of matching gene expression data demonstrated a parallel enrichment for changes in immune-system and inflammatory pathways. A significant number of genes with smoking-altered mRNA expression had inverse changes in methylation status. One gene highlighted by this data was the FLT1, and further studies found particular up-regulation of a splice variant encoding a soluble inhibitory form of the receptor. In conclusion, chronic cigarette smoke exposure altered DNA methylation in specific gene promoter regions in human alveolar macrophages.

Alpha-1-antitrypsin deficiency panniculitis

Alpha-1-antitrypsin deficiency is a congenital error of metabolism linked to pulmonary (emphysema) and liver (cirrhosis) disease. Since 1972, panniculitis has been associated with this deficiency, initially related to Weber-Christian syndrome and finally as a differentiated entity. Clinical manifestations typically consist of wide nodular lesions on the trunk and proximal extremities that evolve to ulceration and drainage. Histopathologically it presents as a mixed septal-lobular panniculitis pattern with some typical findings referred. Differential diagnosis from other types of panniculitis and neutrophilic dermatosis must be established. Different treatments, including tetracyclines, dapsone, and alpha-1-antitrypsin repositioning, have shown variable efficacy in controlling this disease.

Alpha one antitrypsin deficiency: from gene to treatment

Alpha1-antitrypsin deficiency is a genetic disorder which contributes to the development of chronic obstructive pulmonary disease, bronchiectasis, liver cirrhosis and panniculitis. The discovery of alpha1-antitrypsin and its function as an antiprotease led to the protease-antiprotease hypothesis, which goes some way to explaining the pathogenesis of emphysema. This article will review the clinical features of alpha1-antitrypsin deficiency, the genetic mutations known to cause it, and how they do so at a molecular level. Specific treatments for the disorder based on this knowledge will be reviewed, including alpha1-antitrypsin replacement, gene therapy and possible future therapies, such as those based on stem cells.

Alpha-1-Antitrypsin Deficiency: Current Concepts

Since the condition was first described four decades ago, alpha-1-antitrypsin (A1AT) deficiency has served as a model for other disease processes. A1AT is the archetypal serpin designed to ensnare proteases, a process that involves significant conformational change within the molecule. Mutations in the A1AT gene lead to misfolding of the protein and accumulation within the endoplasmic reticulum of hepatocytes resulting in two different pathologic processes. First, the accumulation of mutant A1AT protein has a directly toxic effect on the liver, resulting in hepatitis and cirrhosis. Second, the resultant decrease in circulating A1AT results in protease-antiprotease imbalance at the lung surface and emphysema ensues. A1AT deficiency therefore can be seen as two distinct disease processes: a conformational disease of the liver and a protease-antiprotease imbalance of the lung. This two-stage model of disease in A1AT deficiency is elegant in its simplicity and goes a long way to explaining the clinical manifestations that occur in patients with the condition. However, some aspects of the disease are not readily explained. Recent findings suggest that there is more to the lung damage in A1AT deficiency than simple proteolytic insult and that the presence of the mutant protein itself is proinflammatory and may indeed cause chronic injury to the cells that produce it. This review discusses some of the emerging concepts in alpha-1-antitrypsin research and outlines the implications these new ideas may have for treatment of this condition.

Alpha1-antitrypsin deficiency. 2: genetic aspects of alpha(1)-antitrypsin deficiency: phenotypes and genetic modifiers of emphysema risk

The genetic aspects of AAT deficiency and the variable manifestations of lung disease in PI Z individuals are reviewed. The role of modifying genetic factors which may interact with environmental factors (such as cigarette smoking) is discussed, and directions for future research are presented.

Retinoic acid inhibits elastase-induced injury in human lung epithelial cell lines

The protective effects of retinoic acid on elastase-induced lung epithelial cell injury were studied using elastase extracted from purulent human sputum, the BEAS-2B human bronchial epithelial cell line, A549 human type II lung cell line, and primary cultures of human tracheal epithelial cells. Elastase decreased viability of BEAS-2B cells, A549 cells, and human tracheal epithelial cells in concentration- and time-dependent fashions. Elastase also induced apoptosis of BEAS-2B cells, A549 cells, and the tracheal epithelial cells detected with cell death detection enzyme-linked immunosorbent assay and terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) methods. Retinoic acid alone did not affect the viability of BEAS-2B cells, A549 cells, or the tracheal epithelial cells, and did not induce apoptosis of the cells. However, retinoic acid prevented the decreases in the viability and reduced apoptosis of BEAS-2B cells, A549 cells, and the tracheal epithelial cells induced by elastase. Likewise, retinoic acid inhibited caspase 3 activity in BEAS-2B cells and A549 cells induced by elastase, as well as proteolytic activity of elastase. Furthermore, caspase 3 inhibitor inhibited the elastase-induced apoptosis of the cells. These findings suggest that retinoic acid may inhibit elastase-induced lung epithelial cell injury partly through the inhibition of proteolytic activity of elastase and through the inhibition of caspase 3 activity by elastase. Retinoic acid may, therefore, have protective effects against the elastase-induced lung injury and subsequent development of pulmonary emphysema.

Pathogenesis and management of virus infection-induced exacerbation of senile bronchial asthma and chronic pulmonary emphysema

The number of senile patients with therapy resistant bronchial asthma, chronic pulmonary emphysema increases due to the habit of smoking and increased number of older people, and these inflammatory pulmonary diseases are the leading causes of death worldwide. Rhinoviruses cause the majority of common colds, and provoke exacerbations of bronchial asthma and chronic pulmonary emphysema. Here, I review the pathogenesis and management of rhinovirus infection-induced exacerbation of senile bronchial asthma and chronic pulmonary emphysema.

Polymers of alpha(1)-antitrypsin are chemotactic for human neutrophils: a new paradigm for the pathogenesis of emphysema

Plasma deficiency of alpha(1)-antitrypsin is most commonly due to the Z mutation ((342)Glu--> Lys) and is associated with early-onset panlobular emphysema. The lung disease in these patients is attributed to the relative deficiency of circulating alpha(1)-antitrypsin resulting in uncontrolled neutrophil-derived proteolytic activity. We have previously demonstrated that the local deficiency of Z alpha(1)-antitrypsin is exacerbated by the formation of polymers within the lung and now show that this polymerization not only inactivates alpha(1)-antitrypsin but also converts the molecule to a chemoattractant for human neutrophils. The chemotactic action of polymeric alpha(1)-antitrypsin was substantially greater than that seen with other conformers, was of similar magnitude to C5a, and was apparent over a range of physiologically relevant concentrations (EC(50) 0.0045 +/- 0.002 mg/ml). The biologic activity of polymeric alpha(1)-antitrypsin was confirmed by the demonstration that polymers, but not native alpha(1)-antitrypsin, induced neutrophil shape change and stimulated myeloperoxidase release and neutrophil adhesion. Polymeric alpha(1)-antitrypsin had no effect on basal or N-formyl-Met-Leu-Phe- stimulated superoxide anion release or constitutive apoptosis. The chemotactic properties of polymeric alpha(1)-antitrypsin may provide an explanation for the excessive neutrophils found in the lungs of Z alpha(1)-antitrypsin homozygotes and suggests a new paradigm for the pathogenesis of emphysema in these patients.

Molecular mechanisms of alpha1-antitrypsin null alleles

Alpha1-antitrypsin (alpha1-AT) is the most abundant circulating inhibitor of serine proteases and therefore is essential to normal protease-anti-protease homeostasis. Inheritance of two parental alpha1-AT deficiency alleles is associated with a substantially increased risk for development of emphysema and liver disease. In very rare circumstances individuals may inherit alpha1-AT null alleles. Null alpha1-AT alleles are characterized by the total absence of serum alpha1-AT. These alleles represent the extreme end in a continuum of alleles associated with alpha1-AT deficiency. The molecular mechanisms responsible for absence of serum alpha1-AT include splicing abnormalities, deletion of alpha1-AT coding exons and premature stop codons. While these alleles comprise only a small proportion of alpha1-AT alleles associated with profound alpha1-AT deficiency, studies of their molecular mechanisms provide valuable insights into the structure, gene expression and intracellular transport of alpha1-AT.

Microsatellite polymorphism in the heme oxygenase-1 gene promoter is associated with susceptibility to emphysema

Cigarette smoke, containing reactive oxygen species, is the most important risk factor for chronic pulmonary emphysema (CPE). Heme oxygenase-1 (HO-1) plays a protective role as an antioxidant in the lung. A (GT)n dinucleotide repeat in the 5'-flanking region of human HO-1 gene shows length polymorphism and could modulate the level of gene transcription. To investigate the correlation between the length of the (GT)n repeat and susceptibility to the development of CPE, we screened the frequencies of alleles with varying numbers of (GT)n repeats in the HO-1 gene in 101 smokers with CPE and in 100 smokers without CPE. Polymorphisms of the (GT)n repeat were grouped into three classes: class S alleles (<25 repeats), class M alleles (25-29 repeats), and class L alleles (>/=30 repeats). The proportion of allele frequencies in class L, as well as the proportion of genotypic frequencies in the group with class L alleles (L/L, L/M, and L/S), was significantly higher in the smokers with CPE than in smokers without CPE. Moreover, we analyzed the promoter activities of the HO-1 gene carrying different (GT)n repeats (n=16, 20, 29, and 38), by transient-transfection assay in cultured cell lines. H2O2 exposure up-regulated the transcriptional activity of the HO-1 promoter/luciferase fusion genes with (GT)16 or (GT)20 but did not do so with (GT)29 or (GT)38. These findings suggest that the large size of a (GT)n repeat in the HO-1 gene promoter may reduce HO-1 inducibility by reactive oxygen species in cigarette smoke, thereby resulting in the development of CPE.

Inhibition of human neutrophil elastase. 4. Design, synthesis, X-ray crystallographic analysis, and structure-activity relationships for a series of P2-modified, orally active peptidyl pentafluoroethyl ketones

A series of P2-modified, orally active peptidic inhibitors of human neutrophil elastase (HNE) are reported. These pentafluoroethyl ketone-based inhibitors were designed using pentafluoroethyl ketone 1 as a model. Rational structural modifications were made at the P3, P2, and activating group (AG) portions of 1 based on structure-activity relationships (SAR) developed from in vitro (measured Ki) data and information provided by modeling studies that docked inhibitor 1 into the active site of HNE. The modeling-based design was corroborated with X-ray crystallographic analysis of the complex between 1 and porcine pancreatic elastase (PPE) and subsequently the complex between 1 and HNE.

Alpha 1-antitrypsin nonsense mutation associated with a retained truncated protein and reduced mRNA

alpha 1-Antitrypsin (alpha 1AT) provides the major protection in the lung against neutrophil elastase-mediated proteolysis. Inheritance of alpha 1AT deficiency alleles is associated with an increased risk of emphysema and liver disease. alpha 1AT null alleles cause the total absence of serum alpha 1AT and represent the ultimate in a continuum of alleles associated with alpha 1AT deficiency. The molecular mechanisms responsible for absence of serum alpha 1AT include splicing abnormalities, deletion of alpha 1AT coding exons, and premature stop codons. We identified an Italian individual with asthma, emphysema, and a very low level of serum alpha 1AT. DNA sequencing demonstrated the Mprocida deficiency allele and a novel null allele, QOtrastevere (c654 G-->A, W194Z), a nonsense mutation near the intron 2 (IVS2) splice acceptor site. To determine the molecular basis of QOtrastevere and specifically to evaluate whether this nonsense mutation interfered with mRNA processing by altered splicing, we used a Chinese hamster ovary cell line permanently transfected with QOtrastevere or normal M alpha 1AT with and without IVS2. Northern blot analysis demonstrated that the normal M construct, with or without IVS2, expressed alpha 1AT mRNA of a similar size. The nonsense mutation was associated with moderately reduced alpha 1AT mRNA regardless of the presence or absence of IVS2. Reduction in alpha 1AT mRNA regardless of the opportunity for splicing supports a translational-translocation model as the cause of reduced alpha 1AT mRNA rather than the nuclear scanning model. Pulse-chase studies followed by immunoprecipitation demonstrated an endoplasmic reticulum-retained 31 kDa QOtrastevere alpha 1AT, which was rapidly degraded. Although mRNA content was moderately reduced, retention and rapid intracellular degradation of the truncated form are the major mechanisms for the absence of secreted alpha 1AT.

Association between polymorphism in gene for microsomal epoxide hydrolase and susceptibility to emphysema

BACKGROUND

The first-pass metabolism of foreign compounds in the lung is an important protective mechanism against oxidative stress. We investigated whether polymorphisms in the gene for microsomal epoxide hydrolase (mEPHX), an enzyme involved in this protective process, had any bearing on individual susceptibility to the development of chronic obstructive pulmonary disease (COPD) and emphysema.

METHODS

We designed PCR-based genotyping assays to detect variant forms of mEPHX that confer slow and fast activity. We used these assays to screen 203 blood-donor controls and groups of patients with asthma (n = 57), lung cancer (n = 50), COPD (n = 68), and emphysema (n = 94), who were attending specialised clinics in Edinburgh, UK.

FINDINGS

The proportion of individuals with innate slow mEPHX activity (homozygotes) was significantly higher in both the COPD group and the emphysema group than in the control group (COPD 13 [19%] vs control 13 [6%]; emphysema 21 [22%] vs 13 [6%]). The odds ratios for homozygous slow activity versus all other phenotypes were 4.1 (95% CI 1.8-9.7) for COPD and 5.0 (2.3-10.9) for emphysema.

INTERPRETATION

Genetic polymorphisms in xenobiotic enzymes may have a role in individual susceptibility to oxidant-related lung disease. Epoxide derivatives of cigarette-smoke components may be the cause of some of the lung damage characteristic of these diseases.

Effective treatment with alpha 1-protease inhibitor of chronic cutaneous vasculitis associated with alpha 1-antitrypsin deficiency

The primary serum proteinase inhibitor is alpha 1-antitrypsin, and deficiency of this enzyme has been associated with a variety of systemic and cutaneous disorders. We report cutaneous vasculitis in a 49-year-old man with alpha 1-antitrypsin deficiency. His condition persisted despite treatment with colchicine, prednisone, and antibiotics but has been controlled by the administration of alpha 1-protease inhibitor.

Expression of human growth hormone fusion genes in cultured lung endothelial cells and in the lungs of mice

We sought to develop genetic therapy for acute lung diseases by introducing genes into lung cells in vivo that were only transiently expressed. To that end, we introduced a gene encoding a physiologically relevant secreted human protein into bovine lung endothelial cells in culture and into the lungs of mice using the technique of lipofection. We exposed cultured endothelial cells to a plasmid containing the coding region for human growth hormone (hGH) driven by a metallothionein (MT) promoter. In cells lipofected with the plasmid containing the MT promoter, expression of the hGH gene in medium was low (peak = 30 ng hGH/24 h/60-mm dish), but expression was markedly increased by addition of either dexamethasone (peak = 91) or cadmium (peak = 120). Lipofection with the same construct except a thymidine kinase promoter showed no cadmium response. We gave mice 5,000 ppm ZnSO4 in their drinking water and 24 h later injected intravenously plasmid containing the MT promoter complexed to liposomes. Mice were killed 1, 3, and 5 days after injection, and hGH production by minced lung, liver, and kidneys was determined in vitro. Neither kidneys nor liver produced detectable hGH. However, hGH was produced by the lungs, beginning on day 1, peaking on day 3 (approximately 1.0 ng hGH/24 h/g tissue), and declining by day 5. Lungs from mice injected either with DNA alone or with liposome alone did not produce hGH. mRNA specific for hGH was demonstrated in the lungs by polymerase chain reaction amplification of cDNA followed by agarose gel electrophoreses.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatic endoplasmic reticulum storage diseases

Endoplasmic Reticulum Storage Diseases (ERSD) represent a novel group of inborn errors of metabolism affecting secretory proteins and resulting in hepatocytic storage and plasma deficiency of the corresponding protein. The hepatocellular storage is due to a molecular abnormality hindering the translocation of the abnormal protein from the rough (RER) to the smooth endoplasmic reticulum (SER). The molecular abnormality is genetically determined; hence it is hereditary, congenital, familial and permanent. The storage is selective and exclusive for the mutant protein and predisposes to the development of chronic cryptogenic liver disease. ERSD include alpha-1-antitrypsin deficiency, fibrinogen storage and alpha-1-antichymotrypsin deficiency. Basically, the diagnosis of ERSD is a morphological one: immunohistochemistry and electron microscopy are essential tools for their identification.

Clinical pharmacokinetics of alpha 1-antitrypsin in homozygous PiZ deficient patients

A pharmacokinetic study of alpha 1-antitrypsin (ATT) was performed in 2 groups of homozygous PiZ-deficient patients (treated and untreated) and 1 group of healthy volunteers. The distribution of the 131I-labelled protein corresponds to a 3-compartment model. The intravenously administered protein diffused quickly to the extravascular compartment where some retention occurred. No significant difference in AAT metabolism was observed between the 3 groups. The half-life of the injected protein is slightly longer than 2.5 days. The AAT protein was not stored. These results confirm the observations collected during the clinical trials. That is, a weekly infusion is necessary to obtain stable serum AAT concentrations. Monthly infusions are unable to maintain a 'plateau' phase. The periodicity may be limited to every 2 weeks.

Molecular basis for hereditary antithrombin III quantitative deficiencies: a stop codon in exon IIIa and a frameshift in exon VI

Antithrombin III (AT III) is an inhibitor of serine protease (serpin) comprising 432 amino acids. Quantitative AT III deficiencies are associated with a high risk of thrombotic disease. Although this risk is smaller in patients with qualitative AT III deficiencies, the molecular defects characterizing the latter have been the subject of many studies. However, in quantitative AT III deficiencies, only three mutations have been described: Pro 407 to Leu and A1a404 to Thr (both located in the C-terminal part of the AT III molecule) and also a frameshift in exon IIIa. Using the asymmetric polymerase chain reaction (PCR) and genomic DNA analysis by direct sequencing, we detected two mutations in three unrelated families: (i) a C----T transition in exon IIIa in two families, leading to the replacement of the codon corresponding to Arg 129 by a stop codon, and (ii) in the third family, insertion of an adenine in the codon corresponding to Phe 408, a highly conserved serpin amino acid. This insertion altered the reading frame and led to the appearance of a premature stop signal. Patients of all three families were heterozygous for their abnormality. These results show that asymmetric PCR and genomic DNA analysis by direct sequencing permit fast identification of the molecular basis of quantitative AT III deficiencies. It is concluded that in many cases the absence of AT III gene product probably results from point mutation, as previously observed for another serpin, alpha-1-antitrypsin.

Identification of PiZ gene products in liver tissue by a monoclonal antibody specific for the Z mutant of alpha 1-antitrypsin

Globular inclusions of abnormal alpha 1-antitrypsin (AAT) in the rough endoplasmic reticulum of hepatocytes is a characteristic feature of AAT deficiency of the PiZ phenotype. It is also seen in some rare M-like Pi types (including M-Cagliari) having low plasma AAT levels and M-like mobility on isoelectric focusing. In this report the ability of a monoclonal antibody (ATZ 11) raised against PiZ hepatocytic AAT to identify AAT inclusions by immunohistochemical techniques is evaluated. The antibody was found to specifically and selectively identify the PiZ gene products in hepatocytes, but not M-Cagliari AAT. Application of the method thus allows distinction of PiZ gene carriers from PiM-like subjects in the absence of serum protein analysis.

DNA polymorphisms associated with a new alpha 1-antitrypsin PIQ0 variant (PIQ0riedenburg)

A new PIQ0 variant (PIQ0riedenburg) is described; it is caused by a complete deletion of the alpha 1-antitrypsin (alpha 1 AT) gene. The deletion gives rise to four new restriction fragment length polymorphisms (RFLPs) detected with a genomic probe of the 5' region of the gene. Analysis of the RFLPs indicates that the deletion starts immediately upstream of exon Ic. The deletion extends into the 3' flanking region of the gene but does not include the alpha 1 AT-related gene (the PIL gene), which is located 12 kb downstream of the alpha 1 AT gene.

The epidemiology of alpha 1-antitrypsin deficiency

Alpha 1-protease inhibitor can exist as over 70 different biochemical variants (the Pi system) which are inherited as autosomal-codominant alleles. The majority of these variants are of no clinical significance. Epidemiologically, the most abundant are Pi types M, S, and Z. Homozygotes of type Z have only 10%-20% of the normal serum concentration of the inhibitor and have an increased risk of developing pulmonary emphysema. Cigarette smoking is the most important risk factor. A minority of Pi Z homozygotes (10%-20%) develop a form of neonatal hepatitis and a proportion of these suffer from liver cirrhosis in adult life. Heterozygotes of Pi type SZ have about one third of the normal serum alpha 1-protease inhibitor concentration but this phenotype does not in itself appear to be a significant emphysema risk factor. Heterozygotes of Pi type MZ are thought to have a moderately increased risk of developing emphysema but only if they smoke; there is also evidence for an increased risk of cirrhosis among subjects of type MZ. No excessive risk appears to be attached to the MS phenotype. Cumulative survival curves have suggested that type Z homozygotes have a poor prognosis but such estimates are based on clinic or hospital patients who already have respiratory symptoms. Calculations based on population frequencies however, suggest that about 90% of the total number of type Z subjects are not accounted for in such surveys. Their whereabouts remains unclear at present; some will undoubtedly have died of liver or lung disease but it is possible that the majority escape and live undetected among the general population.

Highly variable clinical course in severe alpha 1-antitrypsin deficiency--use of polymerase chain reaction for the detection of rare deficiency alleles

Among 20 individuals with severe alpha 1-antitrypsin (alpha 1AT) deficiency we observed extremely variable clinical phenotypes ranging from rapidly progressive lung disease fatal at the age of 42 years to an asymptomatic individual with normal lung function at the age of 50 years. Eighteen subjects, including the asymptomatic one, carried the deficient Pi ZZ phenotype as determined by isoelectric focusing (IEF). Their mean alpha 1AT serum level was 36.7 +/- 7.7 mg/dl. DNA restriction analysis showed that all of them had the classical Pi Z-allele-associated DNA haplotype, thus confirming the IEF data. Obviously not all Pi ZZ individuals will have clinical sequelae caused by this genotype. The important differences in clinical course observed could not be explained by smoking habits alone. Probably additional factors are pertinent to the pathogenesis of the lung disease associated with alpha 1AT deficiency (defects in other genes, environmental influences other than smoking). In two patients with very low alpha 1AT serum levels definitive phenotyping by IEF was not possible. Therefore we investigated the molecular basis of their deficiency using polymerase chain reaction (PCR) amplification of the coding exons of their alpha 1AT genes and direct sequencing of the amplification products. Sequence data analysis showed that one of these patients, who had initially been phenotyped as Pi ZZ by IEF, had in fact the genotype Pi QObellinghamZ, thus explaining her low alpha 1AT serum level of 20 mg/dl. The other patient (alpha 1AT serum level 3.7 mg/dl) exhibited the rare genotype Pi MheerlenQOgranite falls. Despite his nearly complete alpha 1AT deficiency, he suffered from only moderately severe pulmonary disease at the age of 42 years.

Histopathology of alpha 1-antitrypsin liver disease in a transgenic mouse model

Transgenic mice were constructed using human alpha 1-antitrypsin M and Z genomic clones. Livers of the M lineage mice showed slight cellular pleomorphism and immunohistochemically demonstrable finely granular alpha 1-antitrypsin material in hepatocytes. Z lineage mice with five gene copies per haploid mouse genome (Z#1) demonstrated fine granular alpha 1-antitrypsin material and a few large globules. In contrast, Z lineage mice with 12 gene copies per haploid mouse genome (Z#2) demonstrated hepatocytes filled with homogeneous, eosinophilic globules that were strongly reactive with diastase and periodic acid-Schiff and antibody to alpha 1-antitrypsin. Scattered microscopic polymorphonuclear leukocyte accumulations were seen that contained extracellular alpha 1-antitrypsin material, but there was neither histological nor serological evidence of mouse infectious hepatitis. In young animals, small clusters of hepatocytes lacking alpha 1-antitrypsin material were seen. These cells were the dominant population in older animals and formed nodular arrangements. Fibrosis was not demonstrable in neonatal and young animals or in any of the controls, but perisinusoidal fibrosis was seen in older Z#2 mice. Groups of hepatocytes without alpha 1-antitrypsin material showed dysplastic changes. We conclude that the transgenic mouse is a reliable and useful model in which to study the effects of alpha 1-antitrypsin in the liver because it demonstrates changes similar to those in the human disease.

Alpha 1-antitrypsin and survival in pancreatic cancer

The association between serum levels of alpha 1-antitrypsin (a1AT) at the time of diagnosis and survival was studied in a group of 44 patients with confirmed pancreas cancer. All 44 patients were followed until time of death, which occurred in all cases from pancreas cancer, with a median time of 3 months and a range of 0.5 to 16 months. Cox's proportional hazards model was utilized in the analysis controlling for sex, age and tobacco smoking. Males, older patients and smokers have higher fatality rates, but none of these relations was statistically significant. By contrast, there was a statistically highly significant association of increased levels of serum a1AT, at the time of diagnosis of the cancer of pancreas, with shorter survival; patients with serum a1AT higher by 100mg/100ml had a 57% higher fatality rate. These results indicate that serum a1AT represents a clinically interesting prognostic factor in pancreas cancer.

Molecular basis of alpha 1-antitrypsin deficiency and emphysema associated with the alpha 1-antitrypsin Mmineral springs allele

The Mmineral springs alpha 1-antitrypsin (alpha 1AT) allele, causing alpha 1AT deficiency and emphysema, is unique among the alpha 1AT-deficiency alleles in that it was observed in a black family, whereas most mutations causing alpha 1AT deficiency are confined to Caucasian populations of European descent. Immobilized pH gradient analysis of serum demonstrated that alpha 1AT Mmineral springs migrated cathodal to the normal M2 allele. Evaluation of Mmineral springs alpha 1AT as an inhibitor of neutrophil elastase, its natural substrate, demonstrated markedly lower than normal function. Characterization of the alpha 1AT Mmineral springs gene demonstrated that it differed from the common normal M1(Ala213) allele by a single-base substitution causing the amino acid substitution Gly-67 (GGG)----Glu-67 (GAG). Capitalizing on the fact that this mutation creates a polymorphism for the restriction endonuclease AvaII, family analysis demonstrated that the Mmineral springs alpha 1AT allele was transmitted in an autosomal-codominant fashion. Evaluation of genomic DNA showed that the index case was homozygous for the alpha 1AT Mmineral springs allele. Cytoplasmic blot analysis of blood monocytes of the Mmineral springs homozygote demonstrated levels of alpha 1AT mRNA transcripts comparable to those in cells of a normal M1 (Val213) homozygote control. Evaluation of in vitro translation of Mmineral springs alpha 1AT mRNA transcripts demonstrated a normal capacity to direct the translation of alpha 1AT. Evaluation of secretion of alpha 1AT by the blood monocytes by pulse-chase labeling with [35S]methionine, however, demonstrated less secretion by the Mmineral springs cells than normal cells. To characterize the posttranslational events causing the alpha 1AT-secretory defect associated with the alpha 1AT Mmineral springs gene, retroviral gene transfer was used to establish polyclonal populations of murine fibroblasts containing either a normal human M1 alpha 1AT cDNA or an Mmineral springs alpha 1AT cDNA and expressing comparable levels of human alpha 1AT mRNA transcripts. Pulse-chase labeling of these cells with [35S]methionine demonstrated less secretion of human alpha 1AT from the Mmineral springs cells than from the M1 cells, and evaluation of cell lysates also demonstrated lower amounts of intracellular human alpha 1AT in the Mmineral springs cells than in the normal M1 control cells. Thus, the Gly-67 --> Glu mutation that characterizes Mmineral springs causes reduced alpha 1AT secretion on the basis of aberrant posttranslational alpha 1AT biosynthesis by a mechanism distinct from that associated with the alpha 1AT Z allele, whereby intracellular aggregation of the mutant protein is etiologic of the alpha 1AT-secretory defect. Furthermore, for the alpha 1AT protein that does reach the circulation, this mutation markedly affects the ability of the molecule to inhibit neutrophil elastase; i.e., the alpha 1AT Mmineral springs allele predisposes to emphysema on the basis of serum apha 1AT deficiency coupled with alpha AT dysfunction.

Molecular basis of alpha 1-antitrypsin deficiency and emphysema associated with the alpha 1-antitrypsin Mmineral springs allele

The Mmineral springs alpha 1-antitrypsin (alpha 1AT) allele, causing alpha 1AT deficiency and emphysema, is unique among the alpha 1AT-deficiency alleles in that it was observed in a black family, whereas most mutations causing alpha 1AT deficiency are confined to Caucasian populations of European descent. Immobilized pH gradient analysis of serum demonstrated that alpha 1AT Mmineral springs migrated cathodal to the normal M2 allele. Evaluation of Mmineral springs alpha 1AT as an inhibitor of neutrophil elastase, its natural substrate, demonstrated markedly lower than normal function. Characterization of the alpha 1AT Mmineral springs gene demonstrated that it differed from the common normal M1(Ala213) allele by a single-base substitution causing the amino acid substitution Gly-67 (GGG)----Glu-67 (GAG). Capitalizing on the fact that this mutation creates a polymorphism for the restriction endonuclease AvaII, family analysis demonstrated that the Mmineral springs alpha 1AT allele was transmitted in an autosomal-codominant fashion. Evaluation of genomic DNA showed that the index case was homozygous for the alpha 1AT Mmineral springs allele. Cytoplasmic blot analysis of blood monocytes of the Mmineral springs homozygote demonstrated levels of alpha 1AT mRNA transcripts comparable to those in cells of a normal M1 (Val213) homozygote control. Evaluation of in vitro translation of Mmineral springs alpha 1AT mRNA transcripts demonstrated a normal capacity to direct the translation of alpha 1AT. Evaluation of secretion of alpha 1AT by the blood monocytes by pulse-chase labeling with [35S]methionine, however, demonstrated less secretion by the Mmineral springs cells than normal cells. To characterize the posttranslational events causing the alpha 1AT-secretory defect associated with the alpha 1AT Mmineral springs gene, retroviral gene transfer was used to establish polyclonal populations of murine fibroblasts containing either a normal human M1 alpha 1AT cDNA or an Mmineral springs alpha 1AT cDNA and expressing comparable levels of human alpha 1AT mRNA transcripts. Pulse-chase labeling of these cells with [35S]methionine demonstrated less secretion of human alpha 1AT from the Mmineral springs cells than from the M1 cells, and evaluation of cell lysates also demonstrated lower amounts of intracellular human alpha 1AT in the Mmineral springs cells than in the normal M1 control cells. Thus, the Gly-67 --> Glu mutation that characterizes Mmineral springs causes reduced alpha 1AT secretion on the basis of aberrant posttranslational alpha 1AT biosynthesis by a mechanism distinct from that associated with the alpha 1AT Z allele, whereby intracellular aggregation of the mutant protein is etiologic of the alpha 1AT-secretory defect. Furthermore, for the alpha 1AT protein that does reach the circulation, this mutation markedly affects the ability of the molecule to inhibit neutrophil elastase; i.e., the alpha 1AT Mmineral springs allele predisposes to emphysema on the basis of serum apha 1AT deficiency coupled with alpha AT dysfunction.

Alpha 1-antitrypsin and survival in hepatocellular carcinoma

The association between serum levels of alpha 1-antitrypsin (alpha 1 AT) at the time of diagnosis and survival was studied in a group of 78 patients with confirmed hepatocellular carcinoma (HCC). All 78 patients were followed until the time of death, which occurred in all instances from HCC, with a median time of 6 months and a range of 1-117 months. Cox's proportional hazards model was utilised in the analysis controlling for sex, age, HBsAg status and logarithmically transformed values of alpha-fetoprotein (alpha-FP). Older patients and patients positive for HBsAg have suggestively higher fatality rates (0.05 less than P less than 0.10) whereas in these data sex and AFP levels were not important prognostic factors. Increased levels of serum at alpha 1AT at the time of diagnosis of HCC were statistically significantly (P less than 0.05) related with shorter survival, patients with higher serum alpha 1AT by 200 mg 100 ml-1 having an expected survival time shorter by about 25%.

Genetic studies on a new deficiency gene (PI*Ztun) at the PI locus

During a study of the alpha 1 antitrypsin (AAT) protein and its locus (PI) by high resolution isoelectric focusing and direct molecular analysis of 106 PIZ probands and their families, a new allele (Ztun) was identified that resembles Z in many of its properties. Two sibs, both compound heterozygotes for Ztun and Z, showed similar evidence of mild liver involvement that was indistinguishable from that associated with classical ZZ homozygotes. The Ztun protein appeared to be deficient in the plasma to about the same degree as the Z protein. Allele specific oligonucleotide analysis of amplified genomic DNA indicated that the new allele is the result of a mutation in exon V that is identical to the classical G----A transition at codon 342 that results in the Glu----Lys substitution characteristic of the Z allele. An analysis of DNA haplotypes constructed from polymorphic restriction enzyme recognition sites in and around the PI locus confirmed that Ztun probably represents a new mutation at codon 342 that has occurred on an M2-like genetic background.

Alpha-1-antitrypsin deficiency: accumulation or degradation of mutant variants within the hepatic endoplasmic reticulum

Recent molecular and biochemical analyses of several alpha-1-antitrypsin variants suggest that the severe deficiency or complete absence of this protease inhibitor from serum results predominantly from the retention of mutant variants within the hepatic endoplasmic reticulum where they can accumulate or undergo intracellular degradation. Additional studies have demonstrated that the accumulation of the insoluble PiZ variant within this subcellular compartment acts as an etiologic agent for the development of liver disease in transgenic mice.

Alpha 1-antitrypsin deficiency caused by the alpha 1-antitrypsin Nullmattawa gene. An insertion mutation rendering the alpha 1-antitrypsin gene incapable of producing alpha 1-antitrypsin

alpha 1-Antitrypsin (alpha 1AT) deficiency is a hereditary disorder associated with reduced serum alpha 1AT levels and the development of pulmonary emphysema. An alpha 1AT gene is defined as "Null" when no alpha 1AT in serum is attributed to that alpha 1AT gene. Although all alpha 1AT Null genes have identical phenotypic consequences (i.e. no detectable alpha 1AT in the serum), different genotypic mechanisms can cause the Null state. This study defines the molecular basis for the alpha 1AT gene Nullmattawa, identified and cloned from genomic DNA of an individual with the Null-Null phenotype and emphysema resulting from the heterozygous inheritance of the Nullmattawa and Nullbellingham genes. Sequencing of exons Ic-V and all exon-intron junctions of the Nullmattawa gene demonstrated it was identical to the common normal M1(Val213) alpha 1AT gene except for the insertion of a single nucleotide within the coding region of exon V, causing a 3' frameshift with generation of a premature stop signal. Family analysis using oligonucleotide probes specific for the Nullmattawa sequence demonstrated the gene was inherited in an autosomal fashion. Examination of blood monocytes demonstrated that a normal-sized, 1.8-kb alpha 1AT mRNA transcript is associated with the Nullmattawa gene and in vitro translation of mRNA with the Nullmattawa mutation showed it translated at a normal rate but produced a truncated alpha 1AT protein. Additionally, retroviral transfer of the alpha 1AT Nullmattawa cDNA to murine fibroblasts demonstrated no detectable intracellular or secreted alpha 1AT, despite the presence of alpha 1AT Nullmattawa mRNA transcripts. These findings are consistent with the concept that the molecular pathophysiology of Nullmattawa is likely manifested at a posttranslational level. The identification of the Nullmattawa gene supports the concept that Null alpha 1AT alleles represent a heterogenous group in which very different mechanisms cause the identical phenotypic state.

Elastase inhibitor. Characterization of the human elastase inhibitor molecule associated with monocytes, macrophages, and neutrophils

A fast-acting inhibitor of serine elastase has been detected at high levels in human neutrophils, fresh monocytes, matured monocytes, and macrophages. The elastase inhibitor was isolated from large scale cultures of the monocyte-like cell line U937 by DNase chromatography, disulfide exchange, Phenyl-Sepharose, Red A-agarose, and DEAE HPLC chromatography with an average yield of 480 micrograms from 1.8 x 10(10) cells. The isolated polypeptide was verified as elastase inhibitor by its ability to (a) form a covalent complex with elastase; and (b) inhibit the elastinolytic activity of elastase. The purified elastase inhibitor molecule is unique, i.e., physiochemical and/or functional properties distinguish it from all other serine proteinase inhibitors. Treatment with iodoacetamide abrogates the ability of the molecule to form a complex with elastase, thereby providing evidence for the presence of an essential cysteine residue. Based on functional criteria, this elastase inhibitor has been grouped with the proteinase inhibitors of the serpin superfamily. The purified elastase inhibitor is a single polypeptide of Mr approximately 42,000. The NH2 terminus appears to be blocked. Compositional analyses indicates five cysteine residues per molecule of approximately 360 amino acid residues. Negligible levels of carbohydrate were detected on gas-liquid chromatography. This finding and the insensitivity of the molecule to peptide N-glycosidase F treatment strongly indicate that the elastase inhibitor is a nonglycosylated protein.

Structure of human neutrophil elastase in complex with a peptide chloromethyl ketone inhibitor at 1.84-A resolution

Human neutrophil elastase (HNE) has been implicated as a major contributor to tissue destruction in various disease states, including emphysema. The structure of HNE, at neutral pH, in complex with methoxysuccinyl-Ala-Ala-Pro-Ala chloromethyl ketone (MSACK), has been solved and refined to an R factor of 16.4% at 1.84-A resolution. Results are consistent with the currently accepted mechanism of peptide chloromethyl ketone inhibition of serine proteases, in that MSACK cross-links the catalytic residues His-57 and Ser-195. The structure of the HNE-MSACK complex is compared with that of porcine pancreatic elastase in complex with L-647,957, a beta-lactam inhibitor of both elastases. The distribution of positively charged residues on HNE is highly asymmetric and may play a role in its specific association with the underlying negatively charged proteoglycan matrix of the neutrophil granules in which the enzyme is stored.

Widespread expression of human alpha 1-antitrypsin in transgenic mice revealed by in situ hybridization

In situ hybridization is a powerful means of identifying sites of gene expression. We used this technique to examine the spatial and developmental control of transcription of the human alpha 1-antitrypsin (alpha 1 AT) gene in transgenic mice carrying this gene and extensive 5'- and 3'-flanking sequences. In addition to expression in yolk sac and liver, human alpha 1AT RNA was detected in gut, stomach, pancreas, nasal epithelium, pharynx, bronchi, spinal ganglia, and ossifying cartilage of transgenic fetuses at 14.5 days post coitum (dpc). In transgenic adults, expression was no longer found in the pancreas but was found in the kidney and salivary gland. In each tissue, expression was confined to a specific cell population. This pattern of alpha 1AT expression was found to correlate with that seen in several fetal and adult human tissues. These results suggest a wider role of alpha 1AT in human physiology and development than previously suspected, and they demonstrated the potential value of this approach in delineating the physiological role of human proteins. Expression of the endogenous alpha 1AT gene in mice was confined to a limited, but overlapping, set of tissues, suggesting that the cis-acting DNA sequences that regulate the expression of the human and mouse genes interact differently with transcription factors present in mouse cells.

Molecular basis of alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin (A1AT) deficiency is an autosomal hereditary disorder associated with a major reduction in serum A1AT levels. Clinically, A1AT deficiency is associated with emphysema in adults and, less commonly, liver disease in neonates. A1AT is a 52-kDa, 394-amino acid, single-chain glycoprotein normally present in serum at 150 to 350 mg/dl. The A1AT gene, composed of seven exons dispersed over 12 kb of chromosomal segment 14q31-32.3, is expressed in hepatocytes and mononuclear phagocytes. The A1AT protein, a member of the class of protease inhibitor proteins known as serpins (serine protease inhibitors), is a globular molecule composed of nine alpha-helices and three beta-pleated sheets. The major function of A1AT is to inhibit neutrophil elastase; A1AT does so through an active site centered around Met358 contained within an external stressed loop on the surface of the molecule. A1AT is a highly pleomorphic protein with greater than 75 variants determined at the protein and/or gene level. These variants can be categorized into four groups according to their serum A1AT level and function: normal, deficient, dysfunctional, and absent. There are two important salt bridges within the A1AT molecule (Glu342-Lys290; Glu263-Lys387); a mutation in the A1AT gene causing disruption of either salt bridge causes distinct molecular pathology resulting in reduced serum A1AT levels. Clinically relevant variants can be distinguished by a combination of isoelectric focusing of serum, restriction fragment length analysis of genomic DNA, oligonucleotide probes, and direct sequencing of the variant A1AT genes.

Natural history of alpha-1-protease inhibitor deficiency

Alpha-1-protease inhibitor (A1PI) exists in over 30 biochemical variants (the Pi system), inherited as autosomal codominant alleles. Homozygotes of Pi type Z have only 10 to 20 percent of the normal serum A1PI concentration and have a high risk of developing pulmonary emphysema. A1PI is an inactivator of polymorph lysosomal elastase, the unopposed action of which may damage the lung. Cigarette smoking is an important additional risk factor. Neonatal hepatitis occurs in 10 to 20 percent of Pi type Z persons, and cirrhosis develops in a number of them in later childhood or in adult life. In heterozygotes of Pi type MZ, pulmonary or hepatic disease may also develop, though they are at lesser risk than type Z homozygotes. Specific A1PI replacement therapy derived from human plasma is now available and has been administered to Pi type Z patients by weekly intravenous infusion without adverse effects. A controlled clinical trial would be desirable, though this would be attended by organizational and economic problems.