Isobutyramide Research Articles

A Combination of Hydroxyurea and Isobutyramide to Induce Fetal Hemoglobin in Transgenic Mice Is More Hematotoxic Than the Individual Agents

ABSTRACT: Pharmacologic agents such as hydroxyurea (HU), N, 3–4 trihydroxybenzamide (didox), and isobutyramide (ISB) can elevate γ-globin as a potential treatment for the β-hemoglobinopathies. In these experiments, transgenic mice with 5′HS2 from the human β-globin locus control region, the fetal (Aγ), and adult (βs) globin genes were used. Mice were treated with HU, didox, or ISB individually, or with combinations of HU or didox with ISB. The aim was to determine whether these drugs have synergistic effects on the induction of fetal hemoglobin (HbF) and whether the combination regimens are more hematotoxic. In the combination regimens, injections of HU or didox for five weeks were concomitant with ISB treatment every other day for the final three weeks of treatment. The combination of HU+ISB was more hematotoxic than the individual drugs based on significantly increased percentages of reticulocytes and reduced hemoglobin, indicating that caution should be taken in treatments involving combinations of these types of drugs. The didox+ISB combination was not more hematotoxic than the individual drugs. HbF was not induced in the groups treated with the combinations of HU or didox with ISB compared to the individual agents. There was a negligible effect on the percentage of HbF and an unexpected negative effect on the percentage of F cells. The results also have implications for future testing of HbF-inducing drugs in mouse models. In control mice that were phlebotomized but not treated with any drugs, increased percentages of F cells were observed, indicating that blood sampling can cause this effect. In addition, increases in the percentage of F cells did not correlate with increases in the percentage of HbF, indicating that monitoring F cells alone is not a sufficient measure of HbF induction.

Evidence for inner-sphere coordinated alkoxide ion intermediates in the catalytic mechanism of Co(II) substituted liver alcohol dehydrogenase

Substitution of certain divalent transition metal ions, i.e. Co(II), Ni(II), Cu(II) and Fe(II), for the active site ion of horse liver alcohol dehydrogenase yields catalytically active enzyme derivatives [1–4]. Since catalysis occurs via inner-sphere coordination of substrate [3,5,6], the ligand-to-metal charge-transfer (LMCT) and d-d electronic transitions of these metal ions are useful spectroscopic probes of the chemical events occurring during catalysis [1, 2, 7]. As will be shown in this report, when reaction is monitored via rapid-scanning, stopped-flow (RSSF) UV-visible spectroscopy, the resulting time-resolved spectra (3000 nm to 700 nm) provide detailed temporal information about transient intermediates formed during catalysis. We report here evidence from RSSF spectroscopy for the existence of ternary enzymeNAD+alkozide ion intermediates both in the Co(II)E-catalyzed reduction of aldehydes and in the Co(II)E-catalyzed oxidation of alcohols.