Biased accumulation of T lymphocytes with "memory"-type CD45 leukocyte common antigen gene expression on the epithelial surface of the human lung

Expression of alternatively spliced products of the CD45 leukocyte common antigen gene identifies two populations of blood T cells: "naive" T cells (containing CD45R-IV mRNA transcripts, CD45 220, 205 kD surface proteins detected with antibody 2H4) that respond poorly to recall antigens, and "memory" T cells (containing CD45R-0 mRNA transcripts, expressing CD45 180 kD protein, detected with antibody UCHL1) that respond promptly to recall antigens. While blood contains approximately equal numbers of "naive" and "memory" T cells, it is known that UCHL1+ "memory" T cells accumulate at sites of chronic inflammation. To test the concept that "memory" T cells are a feature of the T lymphocyte populations present in tissues chronically exposed to antigens in normals as well as in individuals with chronic inflammation, we evaluated T lymphocytes obtained from blood and the epithelial surface of the lower respiratory tract of normal individuals for the expression of specific CD45 surface protein isoforms and corresponding mRNA transcripts. Flow cytometric analysis of CD45 220, 205, and 180 kD surface proteins demonstrated that lung T cells of normals are dominated by UCHL1+ "memory" cells (86 +/- 2%) while autologous blood T cells have equal proportions of "memory" UCHL1+ and "naive" 2H4+ T cells. In addition, polymerase chain reaction analysis of CD45 mRNA transcripts revealed that the lung cells expressed CD45R-0 mRNA transcripts but 17-fold fewer CD45R-IV mRNA transcripts than autologous blood T cells (p less than 0.01). The pattern of lung T cells being dominated by CD45R-0 mRNA+, UCHL1+ "memory" T cells was also observed in individuals with chronic beryllium disease, an example of a chronic inflammatory disease in which antigen-specific T cells accumulate on the pulmonary epithelial surface. Like the normals, the lung T cells of the beryllium disease patients were dominated by CD45R-0 mRNA transcript+, UCHL1+, T cells. However, on a quantitative basis, the beryllium patients contained far greater numbers of T cells, i.e., the T cell populations on the surface of the normal and inflamed lung are similar in character ("memory" T cells) but differ in numbers (there are far more in the chronic inflammatory state). Thus, T cell populations on the epithelial surface of the normal lung likely reflect the chronic exposure to a diverse set of antigens, with a pattern that is qualitatively similar to that observed among T cells accumulating in response to a single antigen.

Regulation of insulin-like growth factor I gene expression in the human macrophage-like cell line U937

Activated macrophages release tissue forms of insulin-like growth factor I (IGF-I), 20-25-kD products of the IGF-I gene, thus providing an extracellular growth and differentiation signal at sites of inflammation. To examine the control of IGF-I gene expression in mononuclear phagocytes, the human macrophage-like cell line U937 was evaluated at rest and after surface activation with phorbol myristate acetate (PMA) or Ca2+ ionophore. Northern analysis and RNAse protection analysis with 32P-labeled IGF-I-specific probes demonstrated that the IGF-I mRNA transcripts of resting U937 cells were similar in size and amount to those of resting human alveolar macrophages, mononuclear phagocytes known to express the IGF-I gene. Nuclear run-off assays demonstrated that surface activation of U937 cells increased the transcription rate of the IGF-I gene four- to fivefold, a process that was inhibited by cycloheximide, suggesting that active protein synthesis was involved in the activation pathway. Despite this, cytoplasmic IGF-I mRNA levels after surface activation declined markedly, a process blocked by a protein kinase C inhibitor (for PMA activation) or a calmodulin antagonist (for Ca2+ ionophore activation). Like the increased transcription of the IGF-I gene, modulation of IGF-I mRNA transcript levels required active protein synthesis; in the presence of cycloheximide constitutive IGF-I mRNA levels increased and surface activation no longer caused a decrease in transcript number. Interestingly, surface activation caused a rapid release of IGF-I, even in the presence of a protein synthesis inhibitor, suggesting that mononuclear phagocytes have a preformed, stored, releasable pool of IGF-I. Together these observations demonstrate that IGF-I gene expression is complex and probably involves control of transcription rate, cytoplasmic mRNA levels possibly mediated through protein kinase C, calcium influx and calmodulin, and finally, release of preformed IGF-I from a storage pool.

Alveolar macrophages release an insulin-like growth factor I-type molecule

Human alveolar macrophages, when activated, release a progression-type growth factor for fibroblasts that signals "competent" fibroblasts to replicate. The present study demonstrates that this growth activity is an insulin-like growth factor I (IGF-I)-type molecule. Partial purification of medium conditioned by activated alveolar macrophages using ion exchange and gel filtration chromatography revealed an IGF-I molecule as detected by an anti-IGF-I polyclonal antibody and that the specific activity of the progression-type growth activity tracked with the amount of IGF-I present. In a serum-free complementation test, the increase in fibroblast proliferation by alveolar macrophage IGF-I was reduced in a dose-response manner with an anti-IGF-I monoclonal antibody. The alveolar macrophage IGF-I displaced 125I-IGF-I from its receptor in a binding assay utilizing human lung fibroblasts and it stimulated type I IGF receptors purified from human lung fibroblasts to phosphorylate a tyrosine-containing artificial substrate. In contrast to the 7.6-kD serum IGF-I, gel chromatography revealed that the alveolar macrophage IGF-I had an apparent molecular mass of 26 kD, similar to other tissue IGF-Is. Alveolar macrophages expressed IGF-I mRNA transcripts as detected by solution hybridization using a 32P-labeled riboprobe complementary to exons I-II-III of the IGF-I gene. In the context of the known functions of the family of IGF-I molecules in cell growth, IGF-I released by activated alveolar macrophages may play a role in acute and chronic inflammatory disorders.

Metoclopramide suppositories in the treatment of diabetic gastroparesis

Gastroparesis diabeticorum is a common complication that develops in patients with diabetes mellitus. Although the pathogenesis remains unclear, the clinical symptoms of nausea, vomiting, and gastric dilatation frequently respond to metoclopramide hydrochloride, an agent that stimulates gastric emptying in addition to acting centrally as an antiemetic. Occasionally, patients are encountered whose severe gastroparesis is unresponsive to oral metoclopramide and who require intravenous therapy or drainage procedures (eg, pyloroplasty or gastrojejunostomy). Rectal administration of metoclopramide successfully controlled the clinical symptoms of gastroparesis diabeticorum in an outpatient after failure of oral dosing, thus avoiding the need for intravenous therapy. Gastric emptying studies and serum metoclopramide levels following a 25-mg rectal dose of metoclopramide hydrochloride verified the efficacy of therapy.

Copy number of a human type I alpha 2 collagen gene

HpCl, a Charon 4A bacteriophage containing a 16.3-kilobase insert of human genomic DNA, has been identified as representing the 3' portion of the human alpha 2(I) collagen gene by hybrid selected translation and cross-reactivity with characterized sheep and chick collagen genes. Evaluation of HpCl by restriction endonuclease mapping and alpha 2(I) mRNA hybridization demonstrated that the alpha 2(I) mRNA coding regions are separated by noncoding regions including one of 2.7 kilobase pairs near the 3' end of the mRNA coding region. In addition, a 1.8-kilobase XbaI-BamHI fragment containing the 2' a 1.8-kilobase XbaI-BamHI fragment containing the 3' end of the alpha 2(I) mRNA coding region includes a region of DNA that is repeated many times throughout the human genome. Quantification of alpha 2(I) gene number, using the technique of DNA dot hybridization, with two EcoRI fragments from HpClo as probes, demonstrated that HpCl is represented once in the human genome. In this context, it is unlikely that human alpha 2(I) collagen chain production is modulated by differential transcription of multiple alpha 2(I) genes.

Procollagen messenger RNA levels and activity and collagen synthesis during the fetal development of sheep lung, tendon, and skin

The rates of type I collagen synthesis in sheep lung, tendon, and skin were evaluated during the latter half of fetal development and compared with the levels of type I procollagen mRNA, quantified by molecular hybridization with a type I procollagen specific complementary DNA, and with the activity of total procollagen mRNA measured by in vitro cell-free translation. In the lung and tendon, the levels of type I procollagen mRNA and activity of total procollagen mRNA parallel collagen synthesis during development. In the skin, however, type I collagen synthesis declines sharply during fetal development, but both type I procollagen mRNA levels and total procollagen mRNA activity remain at the high levels of early development. These observations suggest that in developing lung and tendon, type I procollagen mRNA levels are likely the major determinants of the levels of type I collagen synthesis. In contrast, the dichotomy between type I procollagen mRNA levels and rates of type I collagen synthesis in the developing sheep skin suggest the skin utilizes mechanisms in addition to mRNA levels to modulate expression of the type I collagen gene.

Procollagen production and procollagen messenger RNA levels and activity in human lung fibroblasts during periods of rapid and stationary growth

The production of procollagen molecules by human diploid fetal lung fibroblasts (HFL-1 cells) remains constant in both rapid and stationary growth phases. However, log phase cells degrade 3-fold more newly synthesized collagen inside the cell prior to secretion than do stationary phase cells. Procollagen mRNA levels, measured by hybridization with a type I procollagen mRNA-specific complementary DNA, are approximately 2-fold higher in confluent cells than in log phase cells. There are no significant differences in the ability of either log phase or confluent HFL-1 cell procollagen mRNA to be translated in an in vitro cell-free translation system. Therefore, the ability of HFL-1 cells to maintain constant collagen production irrespective of the growth status of the cells results from the combined action of a number of regulatory mechanisms, including changes in procollagen mRNA levels, the utilization of procollagen mRNA, and intracellular procollagen degradation.

Secondary structures for splice junctions in eukaryotic and viral messenger RNA precursors

Thermodynamically stable secondary structures have been found for adjacent splice junctions of 17 introns from 10 eukaryotic and viral mRNA precursors. Complementary regions in these structures position the exons to be ligated in a favourable orientation for splicing. The possible role of these structures in a general splicing mechanism in described.

Isolation and characterization of a 15-kilobase genomic sequence coding for part of the Pro alpha 2 chain of sheep type I collagen

DNA fragments, prepared by partial Eco RI digestion of fetal sheep liver genomic DNA, were used to prepare a "library" of amplified genomic sequences with the lambda vector Charon 4A. Several recombinant plaques were identified by their ability to hybridize to 32P-labeled cDNA prepared from fetal sheep tendon type I procollagen mRNA. Two of these recombinant DNA bacteriophages (SpC3 and SpC7) were identified as containing procollagen pro alpha 2 gene sequences by their ability to specifically anneal to procollagen pro alpha 2 mRNA. Restriction endonuclease and hybridization to a cloned pro alpha 2 cDNA demonstrated that approximately half (2.5 kilobases) of the pro alpha 2 mRNA sequence is distributed over 15 kilobases of genomic DNA. Restriction maps of SpC3 and SpC7 demonstrated that these two DNA fragments contain overlapping sequences of the pro alpha 2 gene. Electron microscopy and R-loop analysis of SpC3 revealed that at least 12 to 16 intervening sequences are distributed throughout the length of this gene fragment.