Induction of apoptosis by remoxipride metabolites in HL60 and CD3 4(+/)CD19(-) human bone marrow progenitor cells: potential relevance to remoxipride-induced aplastic anemia

The antipsychotic agent, remoxipride [(S)-(-)-3-bromo-N-[(1-ethyl-2-pyrroli dinyl)methyl]-2,6-dimethoxybenzamide] has been associated with acquired apl astic anemia. We have examined the ability of remoxipride, three pyrrolidin e ring metabolites and five aromatic ring metabolites of the parent compoun d to induce apoptosis in HL60 cells and human bone marrow progenitor (HBMP) cells. Cells were treated for 0-24 h with each compound (0-200 mu M). Apop tosis was assessed by fluorescence microscopy in Hoechst 33342- and propidi um iodide stained cell samples. Results were confirmed by determination of internucleosomal DNA fragmentation using gel electrophoresis for HL60 cell samples and terminal deoxynucleotidyl transferase assay in HBMP cells. The catechol and hydroquinone metabolites, NCQ436 and NCQ344, induced apoptosis in HL60 and HBMP cells in a time- and concentration dependent manner, whil e the phenols, NCR181, FLA873, and FLA797, and the derivatives formed by ox idation of the pyrrolidine ring, FLA838, NCM001, and NCL118, had no effect. No necrosis was observed in cells treated with NCQ436 but NCQ344 had a bip hasic effect in both cell types, inducing apoptosis at lower concentrations and necrosis at higher concentrations. These data show that the catechol a nd hydroquinone metabolites of remoxipride have direct toxic effects in HL6 0 and HBMP cells, leading to apoptosis, while the phenol metabolites were i nactive. Similarly, benzene-derived catechol and hydroquinone, but not phen ol, induce apoptosis in HBMP cells [Moran et al., Mel. Pharmacol., 50 (1996 ) 610-615]. We propose that remoxipride and benzene may induce aplastic ane mia via production of similar reactive metabolites and that the ability of NCQ436 and NCQ344 to induce apoptosis in HBMP cells may contribute to the m echanism underlying acquired aplastic anemia that has been associated with remoxipride. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.