Expression of the alpha 1-proteinase inhibitor gene in human monocytes and macrophages

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.

Characterization of mononuclear-phagocyte terminal maturation by mRNA phenotyping using a set of cloned cDNA probes

The terminal step in the maturation of mononuclear cells from circulating monocytes to resident macrophages is accompanied by dramatic changes in cell morphology and physiology. Applying a cultivation system which allows peripheral monocytes to undergo terminal maturation in vitro under absolutely endotoxin-free conditions, we have determined the pattern of expression of a set of eight genes by mRNA phenotyping. The results can be summarized as follows: the two protease inhibitors alpha 1-antitrypsin and alpha 2-macroglobulin show a inverse pattern of expression. alpha 1-Antitrypsin mRNA is repressed, alpha 2-macroglobulin mRNA is strongly induced during maturation to macrophages. Therefore, these two genes are excellent markers of the terminal maturation. In addition, ferritin-light-chain mRNA progressively increases during the course of differentiation, providing a further marker for maturation. Gene expression as a function of activation was studied in mononuclear cells stimulated with bacterial endotoxin (lipopolysaccharide). In monocytes, complement-factor-B, interleukin-1 and interleukin-6 mRNAs are drastically induced upon lipopolysaccharide activation whereas lysozyme RNA is strongly repressed. However, the ability of all four genes to respond to endotoxin was markedly diminished or abolished in mature macrophages, indicating that susceptibility to a certain type of activation may be restricted to a specific stage of maturation. Our data show that mRNA phenotyping is excellently suited for the characterization of the differentiation and activation state of mononuclear phagocytes.

Synthesis of stress proteins is increased in individuals with homozygous PiZZ alpha 1-antitrypsin deficiency and liver disease

Individuals who are homozygous for the protease inhibitor phenotype Z (PiZ) genetic variant of alpha 1-antitrypsin (alpha 1-AT) have reduced plasma concentrations of alpha 1-AT, and are susceptible to premature development of pulmonary emphysema. A subset of this population develops chronic liver disease. The reduction in plasma concentrations of alpha 1-AT results from a selective defect in secretion as the abnormal PiZ alpha 1-AT protein accumulates within the cell. It has recently been shown in several experimental systems that the heat shock/stress response, a response characterized by the synthesis of a family of highly evolutionarily conserved proteins during thermal or chemical stress, may also be activated by the presence of abnormal proteins within the cell. Therefore, we predicted that the heat shock/stress response would be induced in the absence of thermal or chemical stress in alpha 1-AT-synthesizing cells of PiZZ individuals. In the following study, however, we show that net synthesis of proteins in the heat shock/stress gene family (SP90, SP70, ubiquitin) is increased only in a subset of the population, PiZZ individuals with liver disease. It is not significantly increased in PiZZ individuals with emphysema or in those without apparent tissue injury. Net synthesis of stress proteins is not increased in individuals with another variant of the alpha 1-AT gene (PiS alpha 1-AT) and is not increased in individuals with severe liver disease but a normal alpha 1-AT haplotype (PiM alpha 1-AT). These results demonstrate that the synthesis of stress proteins is increased in a subset of individuals with homozygous PiZZ alpha 1-AT deficiency, those also having liver disease.

Ribonuclease A cleavage combined with the polymerase chain reaction for detection of the Z mutation of the alpha-1-antitrypsin gene

Homozygous inheritance of the Z mutation (exon V, Glu342GAG----Lys342AAG), the most common cause of alpha-1-antitrypsin (alpha 1AT) deficiency, is associated with a high risk for emphysema and liver disease. This study presents a rapid and accurate approach to definitive genotypic diagnosis of the Z homozygous state using a combination of polymerase chain reaction amplification of exon V of the alpha 1AT gene and ribonuclease cleavage of an exon V-specific antisense RNA probe. Taking advantage of the concept that ribonuclease A will cleave at points of mismatch of RNA-DNA hybrids, a 0.79 kb antisense RNA probe was designed with complementarity to the sense strand of exon V of the alpha 1AT gene (the site of the Z mutation) along with small regions of the 5' and 3' flanking sequences. After amplification of exon V of the alpha 1AT gene from genomic DNA by the polymerase chain reaction, the amplified DNA was analyzed by hybridization to a 32P-labeled exon V antisense RNA probe followed by digestion with RNase A. Any substitution mutations resulting in DNA-RNA mismatch were detected by evaluation with polyacrylamide gel electrophoresis under denaturing conditions followed by autoradiography (expected fragment lengths: 0.33 kb when the exon V probe hybridized to the normal amplified genomic DNA, 0.25 and 0.08 kb fragments when the exon V probe hybridized to the amplified genomic DNA with the Z mutation). Double-blinded evaluation of genomic DNA of 36 individuals (phenotypes MM n = 14, MZ n = 5, ZZ n = 16, ZNull n = 1; included among the "M" alleles were representatives of all the major normal M alleles) demonstrated definitive diagnosis of the Z mutation with absolute specificity for all 36 specimens, i.e., ZZ homozygotes, MZ heterozygotes, and normals were all detected accurately. This approach should be useful not only for screening for the Z mutation of the alpha 1AT gene, but by this type of analysis, mutational alterations of the alpha 1AT gene can be screened for without prior knowledge of the sequence changes and without complex cloning and sequencing methods.

Interferon beta 2/interleukin 6 modulates synthesis of alpha 1-antitrypsin in human mononuclear phagocytes and in human hepatoma cells

The cytokine IFN beta 2/IL-6 has recently been shown to regulate the expression of genes encoding hepatic acute phase plasma proteins. INF beta 2/IL-6 has also been shown to be identical to MGI-2, a protein that induces differentiation of bone marrow precursor cells toward mature granulocytes and monocytes. Accordingly, we have examined the effect of IFN beta 2/IL-6 on expression of the IL-1- and tumor necrosis factor-unresponsive acute phase protein alpha 1-antitrypsin (alpha 1 AT) in human hepatoma-derived hepatocytes and in human mononuclear phagocytes. Purified human fibroblast and recombinant IFN beta 2/IL-6 each mediate a specific increase in steady-state levels of alpha 1 AT mRNA and a corresponding increase in net synthesis of alpha 1 AT in primary cultures of human peripheral blood monocytes as well as in HepG2 and Hep3B cells. Thus, the effect of IFN beta 2/IL-6 on alpha 1 AT gene expression in these cells is primarily due to an increase in accumulation of alpha 1 AT mRNA and can be distinguished from the direct, predominantly translational effect of bacterial lipopolysaccharide on expression of this gene in monocytes and macrophages. The results indicate that IFN beta 2/IL-6 regulates acute phase gene expression, specifically alpha 1 AT gene expression, in extrahepatic as well as hepatic cell types.

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.

Interferon beta 2/B-cell stimulating factor 2/interleukin 6 affects glycosylation of acute phase proteins in human hepatoma cell lines

Undefined monocyte-derived cytokines have previously been shown to affect glycan processing in glycoproteins secreted by human hepatoma cell lines. Hep 3B cells, when incubated with the cytokine interferon beta 2/B-cell stimulating factor 2/interleukin 6, secreted forms of alpha 1-protease inhibitor, ceruloplasmin, and alpha-fetoprotein with increased reactivity with concanavalin A (Con A) while incubation of Hep G2 cells with this cytokine led to secretion of forms of these proteins with decreased reactivity with Con A, reflecting changes in their oligosaccharide chains. The difference in response of these two transformed cell lines to this cytokine undoubtedly reflects differences in their intracellular glycan processing mechanisms. Changes in glycosylation patterns were dissociated from changes in rate of synthesis: this cytokine caused increased synthesis of alpha 1-protease inhibitor and ceruloplasmin, and decreased synthesis of alpha-fetoprotein in both cell lines.

Effect of cytokines on glycosylation of acute phase proteins in human hepatoma cell lines

The effects of various cytokines on synthesis and microheterogeneity of carbohydrate structure of alpha 1-proteinase inhibitor (PI) and alpha-fetoprotein (AFP) in the human hepatoma cell lines Hep 3B and Hep G2 were studied. In both lines, crude cytokine preparations from LPS-activated human monocytes (CM) and several cell lines led to increased PI and decreased AFP synthesis, while recombinant interleukin 1 (IL-1), recombinant tumor necrosis factor (TNF) and hepatocyte stimulating factor preparations (HSF) affected AFP but not PI production. Several of the crude cytokine preparations, but not IL-1, TNF, or HSF, caused Hep 3B cells to secrete forms of PI and AFP showing increased reactivity with Con A upon testing by affinity electrophoresis, while decreased reactivity with Con A was seen in these proteins secreted by Hep G2 cells. Determination of molecular size of PI inducing activity in CM showed a sharp peak at about 17 kD while AFP inhibiting activity was present in a very broad range of molecular size fractions maximal at 17-30 kD. Changes in patterns of glycosylation of these proteins were attributable to cytokines of about 30 kD in Hep 3B and 44 kD in Hep G2 cells. These findings demonstrate the existence of a family of glycosylation regulating cytokines, and suggest that distinct mechanisms within hepatocytes, responsive to different cytokines, may lead to increased or decreased Con A binding of glycoproteins and to altered gene expression.

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.

Multiple tissues express alpha 1-antitrypsin in transgenic mice and man

Hepatocytes are considered to be the predominant source of alpha 1-antitrypsin (AAT), the major antiprotease in human plasma. The development of emphysema in the hereditary PiZ AAT deficiency state suggests that inhibition of leukocyte elastase in the lung is a major function of this protein. In addition, patients with AAT deficiency are at increased risk for developing cholestasis in infancy and chronic liver disease as adults. The mechanism for hepatic cell injury, however, is not understood. Transgenic mice that express the normal human AAT gene demonstrate abundant AAT in hepatocytes and specific cell types of numerous nonhepatic tissues. Immunoperoxidase techniques have previously disclosed AAT in many of the cell types seen in transgenic mice; however, the issue of local synthesis vs. endocytosis in these cell types has remained unresolved. In this study, AAT mRNA was seen in a variety of tissues in the transgenic mouse. Immunoelectron microscopy of renal tubular and small intestinal epithelial cells in the transgenic mice demonstrated AAT within the cisternae of the rough endoplasmic reticulum, as in hepatocytes. These findings support the possibility of local synthesis in the various cell types. The results suggest that in addition to maintaining tissue integrity in the lung, the protease/antiprotease balance may have physiological functions in other organs as well.

Elastase regulates the synthesis of its inhibitor, alpha 1-proteinase inhibitor, and exaggerates the defect in homozygous PiZZ alpha 1 PI deficiency

The net balance of neutrophil elastase, an enzyme that degrades many components of the extracellular matrix, and its inhibitor, alpha-1-proteinase inhibitor (alpha 1 PI), is thought to be a critical determinant in the development of destructive lung disease, especially in individuals with homozygous alpha 1 PI deficiency. Synthesis and secretion of alpha 1 PI has been recently demonstrated in cells of mononuclear phagocyte lineage, including peripheral blood monocytes and tissue macrophages. In this study we show that alpha 1 PI gene expression in human monocytes and bronchoalveolar macrophages is affected by a novel mechanism, whereby elastase directly regulates the synthesis of its inhibitor. In nanomolar concentrations, neutrophil or pancreatic elastase mediates a dose- and time-dependent increase in steady state levels of alpha 1 PI mRNA and in the rate of synthesis of alpha 1 PI in human monocytes and bronchoalveolar macrophages. Antisera to neutrophil elastase or pretreatment of elastase with the serine proteinase inhibitor diisopropylfluorophosphate abrogates the effect of elastase on alpha 1 PI expression. Elastase also stimulates the synthesis of alpha 1 PI in monocytes from homozygous PiZZ alpha 1 PI-deficient individuals, but has no effect on the rate of secretion; hence, the enzyme mediates an effect on alpha 1 PI that increases the intracellular accumulation of inhibitor and exaggerates the intrinsic defect in secretion of alpha 1 PI that characterizes the homozygous PiZZ alpha 1 PI deficiency.

The inhibitory complex of human alpha 1-proteinase inhibitor and human leukocyte elastase is a neutrophil chemoattractant

An inhibitor-proteinase complex consisting of human alpha 1-PI and human leukocyte elastase is chemotactic for human neutrophils. The chemotactic activity is optimal at 1 nM and is associated only with the alpha 1-PI portion of the complex. Neither HLE in the complex, free HLE, nor native alpha 1-PI possesses chemotactic activity for human neutrophils. alpha 1-PI in complex is hydrolyzed at the Met-358-Ser-359 bond. The chemotactic activity is associated with the Mr 4,200 fragment of alpha 1-PI that has Ser-359 as its NH2 terminus. The region of the HLE-alpha 1-PI complex that stimulates chemotaxis appears to be the same as that of the Mr 4,200 fragment generated by hydrolysis of the Pro-357-Met-358 bond during proteolytic inactivation of alpha 1-PI. The data suggest the presence of a neutrophil surface receptor bound by alpha 1-PI after the formation of a complex with HLE or after proteolytic degradation. This receptor may play a role in clearance of these modified alpha 1-PI molecules.

Alpha 1-proteinase inhibitor in psoriasis: reduced activity in symptom-free patients and during flare

The aim of this study was to quantitate the active fraction of the alpha 1-proteinase inhibitor (alpha 1-PI) in psoriasis. Serum proteinase inhibitory capacity was measured vs porcine pancreatic elastase of a known active fraction against its specific substrate (Suc-Ala3-pNA). The inhibitory capacity was determined in 21 symptom-free patients, 134 patients with skin lesions, and 23 healthy volunteers. Alpha 1-PI was found to be significantly decreased in symptom-free patients and in those with stationary lesions, in a manner similar to the reduced activity of neutrophil proteinases, elastase, and cathepsin G. The synthesis of alpha 1-PI was stimulated during the appearance of active psoriatic lesions, but to a much lesser degree in patients with early onset (less than or equal to 21 years) than in patients with late onset of psoriasis (greater than 21 years). The early onset subgroup differed by a more frequent familial occurrence of psoriasis and a more severe course of the disease. The data indicate that the regulation of the proteinase-alpha 1-PI system in psoriasis is abnormal and this may contribute to the pathogenesis of the disease. The decreased alpha 1-PI during flare may be responsible for the disease activity, at least in patients with early onset of psoriasis.

Z-type alpha 1-antitrypsin is less competent than M1-type alpha 1-antitrypsin as an inhibitor of neutrophil elastase

Alpha 1-antitrypsin (alpha 1AT) deficiency resulting from homozygous inheritance of the Z-type alpha 1AT gene is associated with serum alpha 1AT levels of less than 50 mg/dl and the development of emphysema in the third to fourth decades. Despite the overwhelming evidence that the emphysema of PiZZ individuals develops because of a "deficiency" of alpha 1AT and hence an insufficient antineutrophil elastase defense of the lung, epidemiologic evidence has shown that levels of alpha 1AT of only 80 mg/dl protect the lung from an increased risk of emphysema. With this background, we hypothesized that homozygous inheritance of the Z-type may confer an added risk beyond a simple deficiency of alpha 1AT by virtue of an inability of the Z-type alpha 1AT molecule to inhibit neutrophil elastase as effectively as the common M1-type molecule. To evaluate this hypothesis, the functional status of alpha 1AT from PiZZ individuals (n = 10) was compared with that of alpha 1AT from PiM1M1 individuals (n = 7) for its ability to inhibit neutrophil elastase (percent inhibition) as well as its association rate constant for neutrophil elastase (K association). Plasma alpha 1AT concentration, measured by radial immunodiffusion, was 34 +/- 1 mg/dl in PiZZ patients vs. 237 +/- 14 mg/dl for PiM1M1 plasma, a sevenfold difference. When titrated against neutrophil elastase, the present inhibition of PiZZ plasma was significantly less than Pi M1M1 plasma (ZZ 78 +/- 1% vs. M1M1 95 +/- 1%, P less than 0.001) as was purified Z type alpha 1AT (ZZ, 63 +/- 2% vs. M1M1 86 +/- 2%, P less than 0.001). Sodium dodecyl sulfate (SDS) gel comparisons of the complexes formed with M1-type alpha 1AT and Z-type alpha 1AT with elastase demonstrated the Z alpha 1AT-elastase complexes were less stable than the M1 alpha 1AT-elastase complexes, thus releasing some of the enzyme to continue to function as a protease. Consistent with these observations, the K association of purified Z-type alpha 1AT for neutrophil elastase was lower than that of M1-type alpha 1AT (ZZ 4.5 +/- 0.3 X 10(6) M-1s-1 vs. M1M1 9.7 +/- 0.4 X 10(6) M-1s-1, P less than 0.001), suggesting that for the population of alpha 1AT molecules, the active Z-type molecules take more than twice as long as the active M1-type alpha 1AT to inhibit neutrophil elastase. Consequently, not only is there less alpha1AT in PiZZ individuals, but the population of Z-type alpha1AT molecules is less competent as an inhibitor of neutrophil elastase than M1-type alpha1AT molecules. This combination of defects suggests that PiZZ individuals have far less functional antielastase protection than suggested by the reduced concentrations of alpha1AT alone, further explaining their profound risk for development of emphysema.

Lipopolysaccharide modulates the expression of alpha 1 proteinase inhibitor and other serine proteinase inhibitors in human monocytes and macrophages

alpha 1 Proteinase inhibitor (PI) is the principle inhibitor of neutrophil elastase, an enzyme that degrades many components of the extracellular matrix. Expression and regulation of alpha 1 PI, therefore, affects the delicate balance of elastase and antielastase, which is critical to turnover of connective tissue during homeostasis, tissue injury, and repair. In this study we show that expression of alpha 1 PI in human monocytes and macrophages is regulated during activation by LPS. LPS mediates a concentration- and time-dependent increase in the rate of synthesis of alpha 1 PI in mononuclear phagocytes. There is a 4.5-8.7-fold increase in functionally active inhibitor delivered to the cell culture fluid of monocytes. The effect of LPS is specific in that it is neutralized by an mAb to the lipid A moiety. The increase in expression of alpha 1 PI mediated by LPS occurs in the context of other specific changes in the expression of serine proteinase inhibitor genes in mononuclear phagocytes. There is an increase in the rate of synthesis of C1 inhibitor and a decrease in synthesis of alpha 2 macroglobulin. Regulation of alpha 1 PI by LPS is distinctive in that it is largely determined by a change in the efficiency of translation of alpha 1 PI mRNA. LPS has no effect on the rate of posttranslational processing and/or secretion of alpha 1 PI and, therein, causes greater intracellular accumulation of alpha 1 PI in mononuclear phagocytes from individuals with homozygous PiZZ alpha 1 PI deficiency.

The human alpha 1-antitrypsin gene is transcribed from two different promoters in macrophages and hepatocytes

In order to investigate the mechanism of expression of the human alpha 1-antitrypsin (alpha 1-AT) gene in macrophages, we have characterized the alpha 1-AT transcriptional units in these cells and discovered that there is a macrophage-specific promoter located approximately 2000 bp upstream of the hepatocyte-specific promoter. Transcription from the two alpha 1-AT promoters is mutually exclusive: the macrophage promoter is silent in hepatocytes and the hepatocyte promoter is silent in macrophages. In addition, in macrophages two distinct mRNAs are generated transcript by alternative splicing. These results suggest that alpha 1-AT gene transcription responds to two different cell-specific regulatory mechanisms.

Clonal gene therapy: transplanted mouse fibroblast clones express human alpha 1-antitrypsin gene in vivo

A retroviral vector was used to insert human alpha 1-antitrypsin (alpha 1AT) complementary DNA into the genome of mouse fibroblasts to create a clonal population of mouse fibroblasts secreting human alpha 1AT. After demonstrating that this clone of fibroblasts produced alpha 1AT after more than 100 population doublings in the absence of selection pressure, the clone was transplanted into the peritoneal cavities of nude mice. When the animals were evaluated 4 weeks later, human alpha 1AT was detected in both sera and the epithelial surface of the lungs. The transplanted clone of fibroblasts could be recovered from the peritoneal cavities of those mice and demonstrated to still be producing human alpha 1AT. Thus, even after removal of selective pressure, a single clone of retroviral vector-infected cells that expressed an exogenous gene in vitro, continued to do so in vivo, and when recovered, continued to produce the product of the exogenous gene.

Species- and tissue-specific expression of human alpha 1-antitrypsin in transgenic mice

alpha 1-Antitrypsin (alpha 1AT) is an abundant serum protein whose major site of synthesis is in the hepatocyte. alpha 1AT transcripts are also present, albeit at a lower level, in a variety of other human tissues. This pattern of expression is partly related to initiation of transcription at sites with distinct tissue specificities. The mouse alpha 1AT gene, in contrast, is more strictly liver specific in its expression. To explore the regulation of the alpha 1AT gene we have microinjected a cosmid insert carrying the human gene into fertilized mouse eggs. In three lines obtained from transgenic mice, inheritance of copies of the human gene is accompanied by a high serum concentration of the human protein. Human alpha 1AT RNA accumulates to the highest level in liver of transgenic animals. The presence of transcripts in other tissues indicates that the human pattern of expression is maintained, whereas the temporal activity of the introduced gene parallels that of the endogenous one during mouse embryogenesis.

Molecular basis for the deficiency of complement 1 inhibitor in type I hereditary angioneurotic edema

Hereditary angioneurotic edema (HANE) results from deficiency of complement 1 inhibitor (C1 INH). In type I HANE, C1 INH is present in serum at levels 5-30% of normals. Using cultured monocytes and biosynthetic labeling of proteins, C1 INH was detected in supernatants of cells from HANE patients at levels 20% of those detected in normals. The intracellular reduction of C1 INH in patients' monocytes approached 50%. The study of C1 INH messenger RNA (mRNA) by Northern blot analysis indicated that in HANE patients' monocytes a message of normal size is present at about half the concentration of that from normal cells. One of the patients analyzed showed the presence of a genetically inherited abnormal mRNA (1.9 kb) in addition to the normal mRNA (2.1 kb). Southern blot analysis of DNA from peripheral blood leukocytes did not show any difference in quantity or in sizes of endonuclease restriction fragments between patients and normals. The defect(s), therefore, in type I HANE is pretranslational, but is not due to a deletion or to a major chromosomal rearrangement.

Plasminogen activator-specific inhibitors produced by human monocytes/macrophages

Human monocytes/macrophages produce plasminogen activator-specific inhibitors (PAIs) that form covalent complexes with urokinase-type plasminogen activator (uPA). We have characterized two functionally and antigenically related forms of PAIs produced by resting and phorbol myristate acetate (PMA)-treated U 937 cells: an Mr 40,000 form, presumably nonglycosylated, with a pI of 5.2, that is constitutively synthetized by these cells and that remains predominantly intracellular; a PMA-induced form of heterogeneous Mr (50,000-65,000) with a pI of 4.7, that is preferentially secreted; this PAI is glycosylated with terminal sialic acid residue(s). Biosynthetic labeling experiments demonstrated that both PAIs are synthetized by U 937 cells. They are inactivated upon treatment with propanol, heat, and acid; the covalent and equimolar complexes formed between these PAIs and 125I-uPA are dissociated by ammonium hydroxide, suggesting that the PAIs are linked to uPA via an ester bond. Human peripheral blood monocytes/macrophages also produce the two forms of PAI. These PAIs are clearly different from the main plasma protease inhibitors and they are both antigenically related to the PAI-2 characterized in human placenta.

Biosynthesis of complement C1 inhibitor by Hep G2 cells. Reactivity of different glycosylated forms of the inhibitor with C1s

The biosynthesis of C1 Inh (C1 inhibitor) was studied in a human hepatoma cell line (Hep G2) by metabolic labelling, immunoprecipitation with anti-(C1 Inh) serum, analysis on SDS/polyacrylamide gel slabs and fluorography. Two forms of C1 Inh are secreted by Hep G2: a minor form of Mr 90,000 and a major form of Mr approximately 100,000. The latter form is also found in small amounts intracellularly in co-existence with an 80,000-Mr form. Accumulation of the 80,000-Mr C1 Inh is favoured when the cells are labelled at 23 degrees C instead of 37 degrees C or when they are treated with monensin. In the presence of tunicamycin, a compound that blocks the formation of N-asparagine-linked oligosaccharide chains, a decrease in Mr of both secreted and intracellular major forms is observed, indicating that secreted and intracellular C1 Inh contain N-linked oligosaccharide units. The 100,000 Mr secreted C1 Inh is sensitive to endoglycosidase F but resistant to endoglycosidase H, and it incorporates [3H]galactose, [3H]glucosamine and [3H]galactosamine, indicating the presence of both N-linked oligosaccharides of the complex type and O-linked oligosaccharides. The intracellular C1 Inh contains N-linked oligosaccharide units of the high-mannose type as demonstrated by endoglycosidase H-sensitivity. The functional activity of C1 Inh during its biosynthesis was tested by studying its reactivity towards C1s. Both secreted and intracellular C1 Inh form covalent-like complexes with purified plasma C1s. The underglycosylated C1 Inh secreted in presence of tunicamycin is still reactive with purified C1s. These results clearly show that sugars are not essential for this inhibitory activity of C1 Inh.

Expression of the alpha-1-antitrypsin gene in mononuclear phagocytes of normal and alpha-1-antitrypsin-deficient individuals

To evaluate the contribution of mononuclear phagocytes, and particularly alveolar macrophages, to alpha-1-antitrypsin (alpha 1AT) production in normal and alpha 1AT-deficient individuals, Northern analysis with a human alpha 1AT complementary DNA was used to demonstrate that alpha 1AT messenger RNA (mRNA) can be detected in liver, blood monocytes, and alveolar macrophages. Quantification of alpha 1AT mRNA expression demonstrated that: (a) type PiMM monocytes and alveolar macrophages expressed, respectively, 200-fold and 70-fold less alpha 1AT mRNA per cell than the liver; (b) the level of expression of the alpha 1AT gene was increased during the in vitro maturation of blood monocytes; and (c) blood monocyte and alveolar macrophage levels of expression of the alpha 1AT gene were the same in PiMM and PiZZ individuals. However, the amount of newly synthesized alpha 1AT secreted by ZZ alveolar macrophages was 10 times lower than that secreted by MM alveolar macrophages. Thus, mononuclear phagocytes of PiZZ individuals express a secretory defect in alpha 1AT in a fashion similar to hepatocytes. Not only do mononuclear phagocytes provide a readily accessible cell to evaluate the regulation of alpha 1AT gene expression, but these cells may contribute to the levels of alpha 1AT present in the lower respiratory tract in the normal and ZZ states.

A lymphokine regulates expression of alpha-1-proteinase inhibitor in human monocytes and macrophages

Biosynthesis and secretion of alpha-1-proteinase inhibitor (alpha 1 PI) has been demonstrated in primary cultures of human mononuclear phagocytes, making it possible to study regulation of alpha 1 PI in normal (PiMM) and homozygous-deficient (PiZZ) individuals. In this study, expression of alpha 1 PI by blood monocytes, bronchoalveolar, and breast milk macrophages decreased during 1 wk in culture whereas expression of other secreted proteins increased. The addition of crude supernatants from mitogen-stimulated peripheral blood mononuclear cells to confluent monolayers of mononuclear phagocytes after 1 wk in culture resulted in a 2- to 2.5-fold increase in alpha 1 PI expression. The increase in alpha 1 PI expression was dose- and time-dependent, and involved a mechanism acting at a pretranslational level as shown by an increase in specific messenger RNA content corresponding to the increase in synthesis and secretion of alpha 1 PI. Although alpha 1 PI was expressed in native form and in forms complexed with serine protease by monocytes early in culture, it was expressed in its native form alone when monocytes were incubated with the lymphokine after 1 wk in culture. The regulating factor had the characteristics of a polypeptide and was derived from T lymphocytes, but it was not interferon-alpha, -beta, -gamma, or interleukin 2. This lymphokine also stimulated synthesis of alpha 1 PI in monocytes of homozygous-deficient PiZZ individuals, but had minimal effect on secretion, thereby increasing the intracellular accumulation of the inhibitor and exaggerating the defect in secretion of alpha 1 PI in these individuals. Regulation of mononuclear phagocyte alpha 1 PI expression by a lymphokine provides a model for further analysis of the effect of enhanced synthesis on a defect in posttranslational processing/secretion and for analysis of differential regulation of protease and inhibitor expressed in the same cells.

Evaluation of "at risk" alpha 1-antitrypsin genotype SZ with synthetic oligonucleotide gene probes

Alpha 1-antitrypsin (alpha 1AT), a 52,000-mol-wt serum glycoprotein produced by hepatocytes and mononuclear phagocytes, functions as the major inhibitor of neutrophil elastase. The alpha 1AT haplotype S is associated with childhood liver disease and/or adult emphysema when inherited with the Z haplotype to give the phenotype SZ. To accurately identify the SZ phenotype at the level of genomic DNA, four 32P-labeled 19-mer synthetic oligonucleotide probes were prepared; two to identify the M and S difference in exon III, and two to identify the M and Z difference in exon V. These probes were hybridized with various cloned DNAs and genomic DNAs cut with the restriction endonucleases BgII and EcoRI; the genomic DNAs represented all six possible phenotype combinations of the M, S, and Z haplotypes (MM, MS, MZ, SS, ZZ, and SZ). Using the four probes to evaluate 42 samples of genomic DNA, the "at risk" SZ and ZZ phenotypes were correctly identified in all cases, as were the "not at risk" phenotypes SS, MS, MM, and MZ, demonstrating that both exon III and exon V directed probes are necessary to properly identify all of the major "at risk" alpha 1AT genes. However, when used to evaluate a very rare family carrying a null allele, these four oligonucleotide probes misidentified the "at risk" null-null and S null phenotypes as "not at risk" MM and SM combinations. These observations indicate that oligonucleotide gene probes yielded reliable and accurate assessment of "at risk" alpha 1AT genotypes in almost all situations, but in the context of prenatal diagnosis and genetic counseling this approach must be used with caution and in combination with family studies so as not to misidentify rare genotypes that may be associated with a risk for disease.

A fast-acting elastase inhibitor in human monocytes

A proteinase inhibitor active against neutrophil and pancreatic elastase was detected in extracts of cultured human monocytes and the human monocyte-like cell line U937. This component forms a covalent complex with the active site of elastase; the complex is stable in boiling sodium dodecyl sulfate solution, and is susceptible to nucleophilic cleavage. The activity of the elastase inhibitor is not detected in extracts of freshly isolated monocytes, but becomes detectable when the monocytes are allowed to mature in culture, with maximum levels occurring at 5-7 d. The monocyte inhibitor is fast-acting; its reaction with 125I-labeled elastase is complete in less than 1 min at 37 degrees C. Analysis by electrophoresis and studies using a heteroantiserum to alpha 1-proteinase inhibitor demonstrated that the elastase inhibitor of monocytes/U937 cells is not identical to alpha 1-proteinase inhibitor, the major elastase inhibitor of blood plasma. The extent of conversion of 125I-elastase to the 125I-elastase-inhibitor complex is proportional to the amount of U937 extract or cultured monocyte extract, indicating that this reaction can serve to quantify the elastase inhibitor. The elastase inhibitor is an abundant component in mature monocytes, with greater than or equal to 1.5 X 10(6) molecules/cell (greater than or equal to 12 micrograms per 10(8) cells, greater than 0.1% of total cell protein). Its mol wt is estimated at 50,000. Thus, the monocyte inhibitor should be classified as a putative regulator of neutrophil (and monocyte) elastase activity at inflammatory sites. This designation is based on the properties of the molecule, including its high concentration in maturing monocytes, its affinity for elastase, and its fast reaction with this enzyme.

The cellular defect in alpha 1-proteinase inhibitor (alpha 1-PI) deficiency is expressed in human monocytes and in Xenopus oocytes injected with human liver mRNA

To determine the basis for low serum concentrations of alpha 1-proteinase inhibitor (alpha 1PI) in individuals with homozygous alpha 1PI deficiency (hereafter referred to as PiZZ), biosynthesis and secretion of alpha 1PI were studied in Xenopus oocytes microinjected with hepatic mRNA and in blood monocytes (an extrahepatic site of alpha 1PI gene expression). Although both the usual alpha 1PI (hereafter referred to as PiMM) and PiZZ alpha 1PI were secreted in functionally active form, the rate of secretion of alpha 1PI was significantly and selectively decreased in Xenopus oocytes injected with PiZZ liver mRNA and in monocytes from PiZZ individuals. The apparent size of alpha 1PI in the intracellular compartment of Xenopus oocytes injected with PiZZ liver mRNA was different from the corresponding intracellular PiMM alpha 1PI in oocytes injected with PiMM liver mRNA. There were also differences in the relative ratio of native and complexed alpha 1PI secreted by monocytes from individuals with PiMM and PiZZ phenotypes.

Analysis of effects of lipopolysaccharide and interferon on murine macrophages: modulation of elastase secretion in vitro

Macrophages are able to produce and secrete elastase in response to a variety of agents which induce macrophage differentiation. In this study, we compared elastase levels in macrophage cultures derived from lipopolysaccharide (LPS)-responsive and LPS-hyporesponsive mice. After the in vivo administration of fluid thioglycolate, both types of macrophages exhibited increased secretion of elastase, and further enhancement was observed after in vitro stimulation with colchicine or phorbol myristic acetate or ingestion of latex beads. In contrast, phenol- and water-extracted, protein-free preparations of LPS (Ph-LPS) markedly inhibited elastase secretion below basal levels in LPS-responsive macrophages. The LPS-induced inhibition was reversible with polymyxin B and was not observed in Ph-LPS-stimulated C3H/HeJ (LPS-hyporesponsive) macrophage cultures. Stimulation of either LPS-responsive or -hyporesponsive macrophage cultures with interferon (IFN) also resulted in a significant reduction in elastase secretion below basal levels. LPS-induced inhibition of elastase secretion could be reversed and elastase secretion could be augmented in the presence of an antibody directed against IFN-alpha/beta. These findings suggest that LPS induces the production of both elastase and IFN, and that the latter product acts to suppress secretion of the proteinase.

Regulation of alpha 1 proteinase inhibitor function by rabbit alveolar macrophages. Evidence for proteolytic rather than oxidative inactivation

Rabbit alveolar macrophages were cultured in an environment conducive to the secretion of both reactive oxygen and proteinases, so that the relative importance of proteolytic and oxidative inactivation of alpha 1-proteinase inhibitor by alveolar macrophages could be evaluated. The inactivation of alpha 1-proteinase inhibitor was proportional to its proteolysis, and there was no detectable inactivation in the absence of proteolysis. Although the live macrophages were capable of secreting reactive oxygen, they did not inactivate alpha 1-proteinase inhibitor by oxidation. The inactivation of alpha 1-proteinase inhibitor by proteolysis was proportional to the secretion of elastinolytic activity by the alveolar macrophages. The inability of the alveolar macrophages to oxidize alpha 1-proteinase inhibitor was attributed to the methionine in the macrophages, in secreted proteins, and in the culture medium competing for oxidants. The data suggest that proteolytic inactivation of alpha 1-proteinase inhibitor may be important in vivo and that the methionine concentration in vivo may protect alpha 1-proteinase inhibitor from significant oxidative inactivation.