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

Abstract

Expression of the a1-proteinase inhibitor (a1PI) gene was studied in human mononuclear cells. Using RNA blot and dot hybridization, a1PI mRNA was detected in human peripheral blood monocytes, bronchoalveolar and breast milk macrophages, but not in B or T lymphocytes. Using incorporation of a radiolabeled amino acid precursor, synthesis and secretion of a1PI were demonstrated in human monocytes and macrophages, but not in lymphocytes. In addition, a1PI was secreted in functionally active form as shown by complexing with serine proteases. Biosynthesis of a1PI by mononuclear phagocytes was greatest during the first 24 hr in culture and progressively decreased over the next 10 days. The reduction in a1PI biosynthesis in vitro involved a mechanism acting at the pretranslational level as a1PI mRNA content also progressively declined over 10 days in culture. The ease of sampling human monocytes and macrophages now permits examination of the biochemical defect in homozygous PiZ and PiS a1PI deficiencies and study of the functional significance of locally produced aIPI in normal tissues and sites of injury or inflammation.a1-proteinase inhibitor (a1PI), a single-chain 55-kDa glycoprotein, is a major serine proteinase inhibitor in human plasma. It is characterized by a remarkable degree of polymorphic variition. Two of the variants, PiZ a1PI and PiS a1PI, are associated with moderately to severely diminished plasma levels and, in many cases, the development of chronic disease in liver and/or lung (1-3).Although it is generally considered a tissue-specific product of the liver, several recent studies have suggested that a1PI is also produced by human mononuclear cells (4-8).Other plasma proteins, including many of the complement proteins, a-2-macroglobulin, lysozyme, and plasminogen activator, that are predominantly synthesized by the liver are also synthesized by monocytes and macrophages, and the products are thought to have important functions in regulation of local tissue injury (9-13). Unfortunately, technical limitations in separation of mononuclear cell subpopulations, biosynthetic labeling, and analytical methods in previous reports (4-8) have prevented definitive identification of a1PI biosynthesis in human mononuclear cells. In the present study, we provide evidence for transcription of the aPI gene and translation, postsynthetic processing, and secretion of a1PI in a functionally active form in human peripheral blood monocytes, bronchoalveolar and breast milk macrophages, but not in B or T lymphocytes. MATERIALSDulbecco's modified Eagle's medium (DME medium), DME medium lacking methionine, RPMI 1640 medium, RPMI 1640 lacking methionine, Hanks' balanced salt solution, and fetal bovine serum were purchased from GIBCO and medium 199 was from M. A. Bioproducts (Walkersville, MD).[35S]Methionine (specific radioactivity, -1000 Ci/mmol; 1 Ci = 37 GBq) and [32P]deoxycytidine triphosphate (specific radioactivity, =3000 Ci/mmol) were obtained from New England Nuclear and 14C-methylated protein standards were from ...

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.

“…Confluent monolayers of human peripheral blood monocytes were established from eight normal PiMM volunteers and eight PiZZ individuals (with a wide range of hepatic and/or pulmonary involvement) using adherence of dextran-purified leukocytes on siliconized glass as described (13). The diagnosis of homozygous PiZZ a1PI deficiency was based on isoelectric focusing, serum levels, and family studies.…”

Identification of Differentially Secreted Biomarkers Using LC-MS/MS in Isogenic Cell Lines Representing a Progression of Breast Cancer

“…Both proteins are serine proteinase inhibitors produced by various tumor cells. While AAT is primarily secreted by the liver [23], it is also secreted by monocytes and certain types of tumors [24][25][26], and is associated with inflammation, infection and other malignant diseases. Its C-terminal fragment can potentiate proliferation, invasiveness and NF-κB (nuclear factor kappa B) activity in breast cancer cells [27].…”

Recombinant adeno-associated virus-mediated alpha-1 antitrypsin gene therapy prevents type I diabetes in NOD mice

“…9 AAT is primarily synthesized in the liver, but can also be produced by extrahepatic cells, including pancreatic islets, neutrophils, monocytes, macrophages, alveolar macrophages, intestinal epithelial cells, carcinoma cells and the cornea. [10][11][12][13][14][15] Normal serum levels of AAT in humans are 11-30 mM (0.8-2.4 mg/ml). During inflammation, infection and malignant diseases, AAT levels, as an acute phase reactant, can rise by 3-to 4-fold.…”