cyclic-gmp and hexamethylene-bisacetamide

Differentiation of murine erythroleukemia (MEL) cells induced by hexamethylene bisacetamide (HMBA) and DMSO was inhibited by several structurally unrelated nitric oxide (NO)-releasing agents and two membrane-permeable cGMP analogues. Since the effect of the NO-releasing agents was augmented by a cGMP phosphodiesterase inhibitor, at least some of their effect appeared to be mediated by activation of cytosolic guanylate cyclase. The drugs did not globally block differentiation since hemin-induced differentiation was undisturbed. In HMBA-treated cells, the NO-releasing agents and cGMP analogues reduced beta-globin and delta-aminolevulinate synthetase mRNA expression and inhibited the late down-regulation of c-myb mRNA that is required for HMBA-induced differentiation of MEL cells; the regulation of c-myc mRNA was not changed by the drugs. Nuclear run-off analyses showed that the drugs inhibited the HMBA-induced changes in beta-globin and c-myb transcription rates, and transient transfection of a reporter gene construct demonstrated that the drugs inhibited HMBA-inducible enhancer function of the alpha-globin control region, which contains binding sites for the erythroid transcription factors NF-E2 and GATA-1. The NO-releasing agents and cGMP analogues largely prevented HMBA-induced increases in DNA binding of NF-E2, whereas DNA binding of GATA-1 and SP-1 was not affected. The inhibition of erythroid gene expression by NO and cGMP analogues may be physiologically important under conditions of high NO production by endothelial cells and macrophages, i.e. during acute or chronic inflammation.

Topics: 5-Aminolevulinate Synthetase; Acetamides; Animals; Base Sequence; Cell Differentiation; Cell Line; Cell Nucleus; Chloramphenicol O-Acetyltransferase; Cyclic GMP; Dimethyl Sulfoxide; DNA-Binding Proteins; Erythroid-Specific DNA-Binding Factors; GATA1 Transcription Factor; Gene Expression Regulation, Neoplastic; Globins; Leukemia, Erythroblastic, Acute; Mice; Molecular Sequence Data; Molsidomine; NF-E2 Transcription Factor; NF-E2 Transcription Factor, p45 Subunit; Nitric Oxide; Nuclear Proteins; Oligonucleotide Probes; Oncogenes; Phosphodiesterase Inhibitors; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-myb; Purinones; Recombinant Proteins; RNA, Messenger; Thionucleotides; Trans-Activators; Transcription Factors; Transcription, Genetic; Transfection; Tumor Cells, Cultured

1. The changes in electrophoretic distribution of cytosolic protein kinases have been studied in relation to proliferation, differentiation and transformation in murine erythroleukaemic cells, using a non-denaturing polyacrylamide gel electrophoresis system. 2. Native molecular masses of the major forms were determined by Ferguson plots. 3. A two dimensional electrophoresis method was developed for determination of the subunit molecular masses. 4. These studies suggest that the major bands of activity contain components which may correspond to cGMP dependent protein kinase, cAMP dependent protein kinase and protein kinase C. 5. On hexamethylene bisacetamide induced differentiation of the cells, changes in proportions of the different forms were observed.

Topics: Acetamides; Animals; Cell Differentiation; Cell Division; Cyclic AMP; Cyclic GMP; Cytosol; Electrophoresis, Gel, Two-Dimensional; Electrophoresis, Polyacrylamide Gel; Histones; Leukemia, Erythroblastic, Acute; Mice; Molecular Weight; Phosphorylation; Protein Kinase C; Protein Kinases