Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human gene therapy for diseases involving leukocytes would be facilitated by the identification of specific promoter/enhancer sequences capable of directing high levels of tissue and stage-specific expression of the requisite cDNA when used in a retroviral vector. We tested the promoter sequences from the leukocyte integrin CD11a (LFA-1), CD11b (Mac-1), and CD18 subunits in retroviral vectors to express a reporter gene, adenosine deaminase, in the human leukocyte cell lines K562 and HL-60. The leukocyte integrins are expressed in leukocytes, and they are inducible in HL-60 cells, a model system for myeloid differentiation. Although the leukocyte integrin promoter/enhancer sequences direct the expression of reporter genes in myeloid lineage cell lines in transient transfection assays, in these studies, the leukocyte integrin promoters direct low levels of reporter gene expression following retroviral-mediated transduction in K562 and HL-60 cells and selection of stable integrants. Treatment of HL-60 cells transduced with retroviral vectors containing the leukocyte integrin promoters with retinoic acid or phorbol myristate acetate results in less than a two-fold increase in reporter gene expression. These studies indicate that: (i) expression from the leukocyte integrin promoters from stable integrants in retroviral vectors does not parallel the results observed in transient transfection assays, and (ii) additional promoter/enhancer sequences will likely be required for these promoters to direct high levels of tissue and stage-specific expression in retroviral vectors.
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PMID:Expression from leukocyte integrin promoters in retroviral vectors. 794 33

An early event associated with neutrophil-dependent tissue damage involves the adhesion of neutrophils to the vascular endothelium and the subsequent release of oxygen-derived free radicals and granule constituents. Elevations in intracellular cAMP are known to inhibit free radical release but not lysosomal enzyme release. The role of cAMP in FMLP-induced neutrophil adhesion was examined in this study by using an in vitro model of neutrophil-endothelial cell adhesion. FMLP stimulated a time- and concentration-dependent increase in human neutrophil adhesion to HUVEC. FMLP-mediated adhesion was inhibited by a diverse group of cAMP modulators: forskolin, isoproterenol, phosphodiesterase IV inhibitors (rolipram and Ro 20-1724), but not phosphodiesterase III inhibitors (milrinone and bemoradan). Endogenous adenosine has previously been shown to mediate FMLP-induced increases in cAMP enhanced in the presence of Ro 20-1724. In this study, adenosine deaminase prevented the inhibitory effects observed with rolipram and Ro 20-1724, implicating endogenous adenosine as a co-modulator of inhibition. FMLP stimulated neutrophil shape change and the surface expression of the beta 2 integrins CD11b/CD18 and CD11a/CD18. Both these responses were inhibited by rolipram but not bemoradan. With the use of 4,4'-diisothiocyanostilbene-2,2'disulfonic acid, we showed that mobilization of the intracellular pool of CD11b/CD18 paralleled adhesion. We conclude that neutrophil-endothelial cell adhesion is attenuated by elevating neutrophil intracellular cAMP and that inhibition of neutrophil CD11b/CD18 surface expression by cAMP accounts for this observed inhibition of adhesion.
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PMID:Inhibition of chemotactic peptide-induced neutrophil adhesion to vascular endothelium by cAMP modulators. 799 50

All nonsteroidal antiinflammatory drugs (NSAIDs) inhibit neutrophil aggregation (homotypic cell-cell adhesion) and do so without affecting expression of CD11b/CD18. Since the first step in acute inflammation is a critical interaction between neutrophils and the vascular endothelium (heterotypic cell-cell adhesion), we determined whether NSAIDs diminish the adherence of neutrophils to the endothelium. At antiinflammatory concentrations (0.5-5 mM) sodium salicylate, an NSAID that does not inhibit prostaglandin synthesis, inhibited stimulated but not unstimulated neutrophil adherence to endothelial cells (IC50 < 1 mM, P < 0.00001). Salicylates have previously been shown to inhibit oxidative phosphorylation and, predictably, sodium salicylate inhibited oxidative phosphorylation, as evidenced by depletion of ATP stores (875 +/- 75 pmol/10(6) PMN, [2.92 +/- 0.25 mM]) in stimulated (FMLP, 0.1 microM) but not resting neutrophils treated with antiinflammatory doses of sodium salicylate (EC50 = 1 mM, P < 0.00001). Indomethacin and piroxicam (10 and 30 microM) only minimally decreased ATP concentrations in stimulated and resting neutrophils. ATP is metabolized to adenosine, and we have previously demonstrated that both endogenously released (180-200 nM) and exogenous adenosine (IC50 = 250 nM) inhibit stimulated neutrophil adherence to endothelial cells. To determine whether the increased metabolism of ATP and the resultant increase in adenosine release were responsible for inhibition of neutrophil adhesion to endothelium, we determined whether addition of adenosine deaminase (ADA, 0.125 IU/ml), an enzyme that converts extracellular adenosine to its inactive metabolite, inosine, affected inhibition of neutrophil adhesion to endothelium by stimulated neutrophils. ADA significantly reversed inhibition of neutrophil adherence to endothelium by sodium salicylate (0.5-5 mM, P < 0.00001). This suggests that sodium salicylate inhibits neutrophil adherence by increasing adenosine release. Whereas indomethacin and piroxicam (10-50 microM) also inhibited stimulated neutrophil adherence to endothelial cells, ADA did not affect their inhibition of adherence. These studies demonstrate a heretofore unexpected antiinflammatory mechanism for salicylates: salicylates increase ATP hydrolysis and thereby enhance release of adenosine. Moreover, these data are consistent with the hypothesis that NSAIDs differ from one another with respect to their mechanisms of action.
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PMID:Nonsteroidal antiinflammatory agents inhibit stimulated neutrophil adhesion to endothelium: adenosine dependent and independent mechanisms. 808 28