Alpha1-antitrypsin deficiency

Alpha1-antitrypsin deficiency is a genetic disorder that affects about one in 2000-5000 individuals. It is clinically characterised by liver disease and early-onset emphysema. Although alpha1 antitrypsin is mainly produced in the liver, its main function is to protect the lung against proteolytic damage from neutrophil elastase. The most frequent mutation that causes severe alpha1-antitrypsin deficiency arises in the SERPINA 1 gene and gives rise to the Z allele. This mutation reduces concentrations in serum of alpha1 antitrypsin by retaining polymerised molecules within hepatocytes: an amount below the serum protective threshold of 11 micromol/L increases risk for emphysema. In addition to the usual treatments for emphysema, infusion of purified alpha1 antitrypsin from pooled human plasma represents a specific treatment and raises the concentrations in serum and epithelial-lining fluid above the protective threshold. Evidence suggests that this approach is safe, slows the decline of lung function, could reduce infection rates, and might enhance survival. However, uncertainty about the cost-effectiveness of this expensive treatment remains.     

Absence of alpha-1-antitrypsin (Pi Null Bellingham) and the early onset of emphysema

Background : Alpha-1-antitrypsin is the body's major inhibitor of human neutrophil elastase, a powerful proteolytic enzyme capable of degrading the common tissue components. There are over 70 genetic variants of alpha-1-antitrypsin, with the Z allele being of greatest clinical relevance. Individuals homozygous for this allele (approximately one in 2500 in Caucasians) have low serum alpha-1-antitrypsin levels (10–20% of normal) and are predisposed to emphysema, especially if they smoke. Much rarer are mutations which result in the complete or almost complete absence of alpha-1-antitrypsin in the serum.
Aim : To determine the cause of complete absence of alpha-1-antitrypsin in a patient who at age 27 years had both emphysema and idiopathic cardiomyopathy.
Methods : Molecular biology techniques were used to sequence the alpha-1-antitrypsin gene. Allele specific amplification was used to show the presence of the mutations in other family members.
Results : Investigation showed that the proband was homozygous for the Pi Null Bellingham variant of alpha-1-antitrypsin due to the mutation Lys 217 (AAG) to Stop (TAG). His grandmother was heterozygous for Pi Null Bellingham and the additional rare variant P Lowell, Asp 256 (GAT) to Val (GTT), a variant that also results in alpha-1-antitrypsin deficiency.
Conclusion : Patients with complete absence of alpha-1-antitrypsin develop premature emphysema not having smoked or after only minimal exposure, and much earlier than the more common Pi Z individuals who have the usual form of alpha-1-antitrypsin deficiency.     

Alpha1-antitrypsin deficiency and hepatic carcinoma.

A patient with homozygous ZZ alpha1-antitrypsin deficiency and severe pulmonary emphysema was discovered to have a mixed hepatocellular and cholangiolar hepatic carcinoma arising in a noncirrhotic liver. Because of the increasing frequency of hepatomas in patients with alpha1-antitrypsin deficiency, it is suggested that a causal relationship may exist.     

Alpha1-antitrypsin deficiency: biological answers to clinical questions

Alpha1-antitrypsin (alpha1AT) deficiency is a common lethal hereditary disorder of white persons of European descent. The condition is characterized by reduced serum levels of alpha1AT, a 52-kDa glycoprotein synthesized chiefly in the liver and, to a lesser extent, by macrophages and neutrophils. Alpha1AT acts as an antiprotease and is the physiological inhibitor of neutrophil serine proteases such as neutrophil elastase cathepsin G and proteinase 3. The clinical manifestations of alpha1AT deficiency occur chiefly in the lung, with a high risk of emphysema occurring by the third or fourth decade of life. Cigarette smoking accelerates the development of emphysema in persons with alpha1AT deficiency. There is also an increased risk of liver disease in alpha1AT deficiency, which occurs mostly in childhood. In this review, we will define further the diagnosis of alpha1AT deficiency and its clinical manifestations and describe the therapeutic strategies that are currently being developed to treat the hepatic and pulmonary disease associated with this condition.     

Interrelationships between neutrophil elastase, serum alpha, -antitrypsin, lung function and chest radiography in patients with chronic airflow obstruction.

We assayed protease and elastase activity of lysosomal granules of purified neutrophil suspensions in 58 patients with chronic irreversible airflow obstruction and compared them to 26 healthy control subjects. Denatured hemoglobin and tritiated elastin were used as substrates for protease and elastase assays. Forty-two patients had M antitrypsin phemotype, five had MS, and 11 had Z variant (five were homozygotes and six were heterozygotes). We did not find significant differences in mean lysosomal elastase or protease activity between patients with normal antitrypsin and control subjects; however, a few patients had concentrations of neutrophil elastase that exceeded the range among control subjects. There was no significant correlation between neutrophil protease or elastase activity and age, smoking, degree of airway obstruction, diffusing capacity, lung elastic recoil, or radiologic presence of emphysema in patients with M and MS antitrypsin. In patients with Z variant antitrypsin, protease and elastase concentrations per unit of lysosomal protein were not significantly different from those in control subjects or M patients; however, both elastase and protease content per 108 neurtophils was significantly higher in homozygous and heterozygous Z patients as compared to normalsubjects and M patients, which suggest an increase in the neutrophil content of protease and elastase in patients with Z antitrypsin deficiency. These results suggest that hte concentrations of protease and elastase in neutrophils do not appear to interact as additive risk factors in the pulmonary impairment of most patients with chronic airflow obstruction, but may be of importance as risk factors in patients with Z or MZ phenotype and in a few patients with M phenotype.     

Serine proteinase inhibitor therapy in alpha(1)-antitrypsin inhibitor deficiency and cystic fibrosis.

Proteinase-antiproteinase imbalances are recognized in several diseases including the two most common lethal hereditary disorders of white populations, alpha(1)-antitrypsin (alpha(1)-AT) deficiency and cystic fibrosis (CF). In alpha(1)-AT deficiency, the type Z variant of alpha(1)-AT forms polymers in the endoplasmic reticulum of hepatocytes resulting in liver disease in childhood. The block in alpha(1)-AT processing in hepatocytes significantly reduces levels of circulating alpha(1)-AT. This may lead in young adults to panacinar emphysema due to insufficient protection of the lower respiratory tract from neutrophil elastase, permitting progressive destruction of the alveoli. In CF, chronic bacterial lung infections due to impaired mucociliary clearance lead to a vigorous influx of neutrophils in the airways. Released levels of neutrophil serine proteinases, particularly elastase, exceed the antiproteinase capacity of endogenous serine proteinase inhibitors in the airways. Progressive proteolytic impairment of multiple defense pathways in addition to endobronchial obstruction and airway wall destruction are thought to be responsible for the reduced life expectancy in CF patients. Strategies to augment the antiproteinase defenses in the airways of patients with severe alpha(1)-AT deficiency or CF include the intravenous or aerosol administration of serine proteinase inhibitors. Studies in both patient groups using plasma-derived or transgenic alpha(1)-AT, recombinant secretory leukoprotease inhibitor or synthetic elastase inhibitors show promising results concerning drug safety and efficacy.     

A study of antielastase activity in the development of pulmonary emphysema in a family with alpha 1-antitrypsin deficiency

The five siblings of a family with alpha 1-antitrypsin deficiency including three of Pi- and two of PiM- phenotypes, were studied for the development of pulmonary emphysema during nine years. The changes of pulmonary function showed significant decrease in FEV1.0 and V50, and increase in RV/TLC. Clinical diagnoses for each patient were assessed by pulmonary function, inhalation and perfusion lung scintigram. Two case of Pi- phenotypes were diagnosed definite pulmonary emphysema 9 years previously, in one case of Pi- emphysema was suspected and two PiM- cases were also suspected of emphysema. alpha 1-antitrypsin and elastase inhibitory capacity (EIC) were investigated in serum and bronchoalveolar lavage fluids (BALF) from four patients with alpha 1-antitrypsin deficiency, healthy non-smokers and smokers. alpha 1-Antitrypsin and EIC in BALF in patients with alpha 1-antitrypsin deficiency were markedly decreased. There were no differences between non-smokers and smokers in alpha 1-antitrypsin and EIC, but EIC in BALF showed a significant correlation with DLCO or %DLCO. These findings suggest that a deficiency of alpha 1-antitrypsin results in insufficient antielastase protection in the lower respiratory tract, and EIC in BALF may be useful for detecting early changes of emphysema.     

Evaluation of the S-type of alpha-1-antitrypsin as an in vivo and in vitro inhibitor of neutrophil elastase

S-type alpha 1-antitrypsin (alpha 1AT) is a deficiency haplotype that differs from the common normal M1 (val213) alpha 1AT haplotype by a single amino acid (glu264 to val264). To evaluate the adequacy of the antineutrophil elastase protection associated with the S homozygous state, alpha 1AT plasma and lung epithelial lining fluid (ELF) levels and antineutrophil elastase function were analyzed in 9 PISS subjects. The plasma alpha 1AT levels of SS subjects were intermediate between that of M1M1 and ZZ subjects (p less than 0.001, all comparisons) and the plasma neutrophil elastase inhibitory capacity paralleled the differences in alpha 1AT concentration (p less than 0.001, all comparisons). The association rate constant for neutrophil elastase of the purified S protein was less than that of the normal molecule (S-type, 7.1 +/- 0.1 X 10(6) M-1 s-1; M1-type, 9.6 +/- 0.2 X 10(6) M-1 s-1; p less than 0.001), but much greater than that for the Z molecule (p less than 0.001). Exposure of the purified S protein to increasing oxidant burdens resulted in a dose-dependent reduction in the ability of the molecule to inhibit neutrophil elastase in a fashion parallel to that of the M1 and Z proteins. Quantification of ELF alpha 1AT levels and antineutrophil elastase capacity demonstrated that the SS ELF parameters were, as in plasma, intermediate between M1 homozygotes and Z homozygotes. Using the association rate constant together with the quantification of ELF alpha 1AT levels, the "in vivo lung inhibition time" was estimated, yielding an assessment of the relative antineutrophil elastase screen of the PISS lower respiratory tract.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of tamoxifen as a therapy to augment alpha-1-antitrypsin concentrations in Z homozygous alpha-1-antitrypsin-deficient subjects

Tamoxifen, an agent that binds to intracytoplasmic estrogen receptors, was evaluated as a possible means of increasing alpha-1-antitrypsin (alpha 1AT) synthesis and/or secretion and thus alpha 1AT serum levels in subjects with the homozygous form of alpha 1AT deficiency. Administration of tamoxifen (10 mg twice daily) to 30 Z homozygotes for a 30-day period was not associated with adverse reactions. However, although serum alpha 1AT levels increased significantly (p less than 0.03), the increase was minor (average pretreatment levels, 32 +/- 1 mg/dl; levels at 30 days of therapy, 35 +/- 1 mg/dl) and far below the "threshold" level of 80 mg/dl considered "protective" against an increased risk for emphysema. Thus, while the concept that increasing alpha 1AT synthesis and/or secretion is a rational goal for treating the Z homozygous form of alpha 1AT deficiency, tamoxifen will not be useful in this regard.     

Airways inflammation in chronic bronchitis: the effects of smoking and alpha1-antitrypsin deficiency.

Airways inflammation in chronic bronchitis is thought predominantly to be a direct consequence of neutrophil recruitment and release of elastase in response to factors such as cigarette smoke. The aims of this study were to assess the role of smoking and determine whether the serum elastase inhibitor alpha1-antitrypsin (alpha1AT) influenced the process. Airways inflammation was compared between patients with chronic obstructive bronchitis with (n=39) and without (n=42) severe alpha1AT deficiency. The authors assessed the sputum concentration of the neutrophil chemoattractants interleukin-8 (IL-8) and leukotriene (LT)B4, myeloperoxidase (MPO) as a marker of neutrophil influx, neutrophil elastase activity and its natural inhibitors, alpha1AT and secretory leukoprotease inhibitor (SLPI). Finally serum alpha1AT was measured to determine the degree of protein leakage (sputum sol serum alpha1AT ratio). Compared to current smokers, the exsmokers had a lower concentration of the chemoattractant IL-8 (p<0.05) and a lower MPO concentration, although this failed to reach conventional statistical significance (p=0.06). Patients with alpha1AT deficiency had greater inflammation in the larger airways with increased LTB4 (p<0.005), MPO (p<0.001), neutrophil elastase activity (p<0.01), protein leak (p<0.001), and were found to have a lower anti-proteinase screen with both reduced sputum alpha1AT (p<0.001) and SLPI concentrations (p<0.05). The reduction in sputum interleukin-8 levels in exsmokers may decrease neutrophil influx and thus explain the slower rate of neutrophil mediated progression of lung disease compared to subjects who continue to smoke. Patients with alpha1-antitrypsin deficiency had greater inflammation suggesting that alpha1-antitrypsin plays an important role in protecting the larger airways from the inflammatory effects of elastase activity and may explain their more rapid progression of disease.     

Degradation of tropoelastin and elastin substrates by human neutrophil elastase, free and bound to alpha2-macroglobulin in serum of the M and Z (Pi) phenotypes for alpha1-antitrypsin.

Human neutrophil elastase degraded tropoelastin approximately 9 times faster than it did solubilized elastin and approximately 19 times faster than it did lung elastin. When bound to alpha2-M, the enzyme retained approximately 6 per cent of its activity toward tropoelastin and solubilized latter observations suggest that alpha2-M--bound elastase, cleared slowly from lung extracellular tissue space, may participate normally in the turnover of soluble precursor (s) of elastin and may contribute to the development of emphysema in alpha1-antitrypsin deficiency.     

Effect of human alpha-antitrypsin in papain-induced emphysema in the hamster.

The possibility that human alpha1-antitrypsin could effectively prevent development of emphysematous lesions produced in hamsters 7 days after exposure to aerosolized papain (3% for 3 hours) was investigated. Pretreatment with intratracheal human alpha1-antitrypsin prevented the appearance of these lesions in a dose-dependent manner. On the other hand, systemic administration of large doses of human alpha1-antitrypsin failed to prevent papain-induced pulmonary lesions, despite a significant increase in serum trypsin inhibitory capacity. These results suggest that intra-alveolar rather than serum concentrations of human alpha1-antitrypsin are critical for preventing the development of pulmonary emphysema in this animal model. It is interesting that although the mechanism by which human alpha1-antitrypsin prevented the papain-induced lesions is unknown, intratracheally administered human alpha1-antitrypsin similarly prevented the development of pulmonary emphysematous lesions induced by 0.1 mg of porcine pancreatic elastase given intratracheally.     

Alpha,-antitrypsin and leukocyte elastase in infected and noninfected sputum.

Leukocyte elastase and alpha 1-antitrypsin have been implicated in the pathogenesis of pulmonary emphysema. The relationship between these proteins has been studied in sputum both qualitatively and quantitatively in bronchitic patients with and without chest infections. Leukocyte elastase was found in 75% of the noninfected samples but was enzymatically inactive, suggesting complete inhibition. During infection, leukocyte elastase and alpha 1-antitrypsin concentrations increased, although the enzyme was only partially inactivated. The proportion of alpha 1-antitrypsin present as "complex" was smaller in the presence of infection, suggesting damage of the protein by excess enzyme.     

Alpha-1-antitrypsin PLowell: a normally functioning variant present in low concentration

Background: Alpha-1-antitrypsin deficiency is associated with a high risk for the development of emphysema, particularly for phenotype Pi ZZ, which is both deficient and an abnormal inhibitor of the powerful proteolytic enzyme, human neutrophil elastase. The rare variant P_Lowell is also expressed at abnormally low levels, but its anti-elastase activity has not been described. Aim: To study the anti-elastase activity of alpha-1-antitrypsin P_Lowdl and compare it to the common M, S and Z proteins. Method: Alpha-1-antitrypsin from a female patient aged 75 years with the rare genotype P_LoweU Null_Bcllingham was studied for its ability to inhibit human neutrophil elastase in a time dependent manner. Results: P_Loweii has near normal function as an inhibitor of human neutrophil elastase with an association rate constant of 7.4 X 10⁶ M'V¹ at 25 °C, similar to that of M and S. Conclusion: Alpha-1-antitrypsin P_L is associated with a severe deficiency of alpha-1-antitrypsin similar to Z, but unlike that protein it has near normal function as an anti-elastase.     

A new deficient variant of alpha1-antitrypsin (MDUARTE). Inability to detect the heterozygous state by antitrypsin phenotyping.

A new molecular variant of alpha1-antitrypsin was discovered in the family of a woman with severe antitrypsin deficiency and bullous emphysema. The variant resembles the Z variant in most respects in that it results in severe antitrypsin deficiency with the homozygous state and intermediate deficiency with the heterozygous state, and is associated with diastase-resistant, periodic acid-Schiff-positive globules in the liver cells. It differs from the usual Z variant, however, by having normal mobility on acid-starch electrophoresis so that the heterozygous state with the normal M form cannot be distinguished by phenotyping procedures on either acid-starch or alkaline-agarose electrophoresis. The variant has been labeled MDUARTE. A review of phenotype patterns in all patients previously classified as having a homozygous ZZ phenotype reveals extra, fast-moving bands on acid-starch suggestive of an MDUARTEZ heterozygous state in 7.9 per cent of such cases. When intermediate antitrypsin deficiency occurs in the presence of a normal phenotype pattern, one must consider that the patient has inherited either a null gene for antitrypsin synthesis or an MDUARTE variant.     

The proteinase–antiproteinase theory of emphysema: A speculative analysis of recent advances into the pathogenesis of emphysema

This review concerns the reasons why only an estimated 10–15% of patients with alpha-1-antitrypsin (A1AT) deficiency develop the destructive lung disease known as emphysema. The arguments presented revolve around the proteinase-antiproteinase balance in the 'microenvironment' of the epithelial space of the lung. Attention is focused on the balance between destructive enzymes such as neutrophil elastase and protective proteins such as A1AT, secretory leucocyte proteinase inhibitor (SLPI), human elastase inhibitor (HEI) and elafin. When neutrophil elastase is already attached to the elastin fibres the smaller molecules SLPI and elafin appear to be better inhibitors of this enzyme than larger inhibitors such as A1AT and HEI. Furthermore, SLPI and elafin may provide the first line of defence against proteinase attack from neutrophil elastase. In trying to explain the variability in the clinical expression of A1AT-deficiency and the development of emphysema, the importance of changes to A1AT, SLPI and elafin molecules induced by smoking and/or oxygen free radicals has been considered. It is possible that emphysema only develops in patients who have SLPI/elafin deficiency as well as A1AT deficiency.     

Differential detection of PAS-positive inclusions formed by the Z, Siiyama, and Mmalton variants of alpha1-antitrypsin

Several point mutations of alpha(1)-antitrypsin cause a perturbation in protein structure with consequent polymerization and intracellular accumulation. The retention of polymers of alpha(1)-antitrypsin within hepatocytes results in protein overload that in turn is associated with juvenile hepatitis, cirrhosis, and hepatocellular carcinoma. The detection of alpha(1)-antitrypsin polymers and understanding the molecular basis of polymer formation is of considerable clinical importance. We have used a monoclonal antibody (ATZ11) that specifically recognizes a conformation-dependent neoepitope on polymerized alpha(1)-antitrypsin to detect polymers within hepatocytes of individuals with alpha(1)-antitrypsin deficiency. Paraffin-embedded liver tissue specimens were obtained from individuals who were homozygous for the Z (Glu342Lys), Mmalton (52Phe del), and Siiyama (Ser53Phe) alleles of alpha(1)-antitrypsin that result in hepatic inclusions and profound plasma deficiency. Immunohistological staining with a polyclonal anti-human alpha(1)-antitrypsin antibody showed hepatic inclusions in all 3 cases, while ATZ11 reacted with hepatic inclusions formed by only Z alpha(1)-antitrypsin. Polymers of plasma M and Z alpha(1)-antitrypsin prepared under different conditions in vitro and polymers of recombinant mutants of alpha(1)-antitrypsin demonstrated that the monoclonal antibody detected a neoepitope on the polymerized protein. It did not detect polymers formed by a recombinant shutter domain mutant (that mirrors the effects of the Siiyama and Mmalton variants), polymers formed by cleaving alpha(1)-antitrypsin at the reactive loop, or C-sheet polymers formed by heating alpha(1)-antitrypsin in citrate. In conclusion, the ATZ11 monoclonal antibody detects Z alpha(1)-antitrypsin in hepatic inclusions by detecting a neoepitope that is specific to the polymeric conformer and that is localized close to residue 342.     

Selective IgA deficiency and Pi ZZ-antitrypsin deficiency. Association with recurrent sinopulmonary infections, emphysema, and bronchiectasis.

We describe a patient in whom selective IgA deficiency and homozygous alpha1-antitrypsin deficiency were discovered. Clinically, the patient suffered from chronic sinopulmonary infections, destructive emphysema, and bronchiectasis. The interrelation of IgA and alpha1-antitrypsin was studied. Twenty-three alpha1-antitrypsin-deficient sera were screened for IgA deficiency. None of these sera were deficient in IgA. Fifteen IgA-deficient sera were screened for alpha1-antitrypsin deficiency. In this group, three patients were found to have variant alpha1-antitrypsin phenotypes. Respiratory infections were a prominent complaint in all three of these patients, with bronchiectasis in two patients. We believe that the combination of IgA and alpha1-antitrypsin deficiencies should be considered in the evaluation of any patient with idiopathic bronchiectasis.     

Alpha-1-antitrypsin and the pathogenesis of emphysema

The review examines the relationship between alpha₁-antitrypsin (α ₁AT) and emphysema. Although other defects occur in subjects with alpha₁-antitrypsin deficiency, it seems likely that a reduction in inhibition due to loss of this inhibitor explains their emphysema. There is a great deal of controversy, however, concerning the role of alpha₁-antitrypsin in subjects without inherited deficiency. There is uncertainty about the presence and function of other elastase inhibitors in the peripheral lung. The function of lungα ₁AT and the presence of elastase activity are dependent upon the techniques used and this probably accounts for different results between research groups. In addition, other relevant factors such as which enzymes cause lung elastolysis, control of neutrophil chemotaxis, and mechanisms of elastin synthesis and repair are less well studied. The overall conclusion is that many aspects of the elastase/antielastase hypothesis of emphysema are poorly understood. Without further information the true role ofα ₁AT will remain largely speculative.     

Protease inhibitors in patients with chronic obstructive pulmonary disease: the alpha-antitrypsin heterozygote controversy.

A group of 163 patients with chronic obstructive pulmonary disease, from the pulmonary service of a large urban hospital, were evaluated for their protease inhibitor (Pi) type by starch gel and crossed immunoelectrophoresis, for serum concentrations of alpha1-antitrypsin and alpha1-antichymotrypsin, and for pulmonary function. Of the patients with emphysema, 17.8% were of Pi type Z; 50% of these were less than 45 years of age, compared to 13% of those of Pi type M. Of all patients with chronic obstructive pulmonary disease, 4.9% were of Pi type Z; 4.9% of patients were of Pi type MZ (heterozygotes) compared with 1.9% of the control population. There was an increased incidence of chronic obstructive pulmonary disease in persons of Pi type MZ, but no increase in persons of Pi type MS. Concentrations of both alpha1-antitrypsin and alpha1-antichymotrypsin were increased and were correlated. No patient had a deficiency of alpha1-antichymotrypsin.