Effects of analogues of 4,6,4???-trymethylangelicin on erythroid differentiation and NF-kB activity

Recently we demonstrated that 4,6,4’-trimethylangelicin (TMA) is a strong inhibitor of NF-kB and IL-8 gene expression in cystic fibrosis cells (Tamanini et al., 2011) and it is able to induce erythroid differentiation and increase of gamma-globin gene expression (Lampronti et al., 2009). To verify whether these effects can be differentially retained in TMA derivatives, we have characterized 26 synthetic analogues. The effects on erythroid differentiation was analyzed on human leukemic K562 cells following detection of the proportion of benzidine positive (hemoglobin containing cells). The effects on NF-kB-mediated induction of pro-inflammatory genes was first verified by eletrophoretic mobility shift assay (EMSA). The most active NF-kB inhibitors were then tested for the ability to inhibit NF- kB-directed upregulation of IL-8 gene expression in cystic fibrosis IB3- 1 cells treated with TNF-α. The obtained results demonstrate that some compounds (e.g. 4-hydroxymethyl-6,4’-dimethyl angelicin) inhibit NF- kB/DNA interactions (IC50 = 40μM) and strongly induce erythroid differentiation (50% benzidine-positive cells); on the contrary, other compounds (e.g. 4,6,4’,5’-tetramethyl angelicin, 4-methoxymethyl- 6,4’-dimethyl angelicin and 6-chloro-4,4’-dimethyl angelicin) inhibit NF-kB/DNA interactions (IC50 = 12μM), with low or no effects on erythoid differentiation; on the other hands 4-methyl-5-methoxy angelicin was found to be capable to induce erythroid differentiation (30% benzidine-positive cells) without inhibitory effects on NF- kB/DNA interactions. Therefore, the effects on inhibition of NF-kB and induction of erythroid differentiation can be separately operating in TMA analogues, allowing the identification of functional groups possibly involved in these biological effects. Interestingly, 4,6,4’,5’- tetramethyl angelicin was able to inhibit the NF-kB-directed upregulation of IL-8 in TNF-α treated IB3-1 cells.