Nitric oxide-releasing agents and cGMP analogues inhibit murine erythroleukemia cell differentiation and suppress erythroid-specific gene expression: correlation with decreased DNA binding of NF-E2 and altered c-myb mRNA expression.

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.