The
pyrrolopyrimidine U101033E is a therapeutic compound potentially useful in
stroke,
head injury and other oxidative stress conditions. Electron paramagnetic resonance (EPR) techniques of spin labeling and spin trapping in conjunction with measures of
lipid and
protein oxidation have been used to investigate the proposed
antioxidant capacity of
U101033E. We report potent
antioxidant activity of this agent in aqueous cell-free
solution as measured by spin trapping.
U101033E significantly (P<0.005) reduces the formation of the EPR active spin trap
N-t-butyl-alpha-phenylnitrone (PBN)-radical adduct by 17.1% at a concentration of 1 microM, four orders of magnitude less than the concentration of PBN. As measured by the decrease in signal intensity of
lipid-resident
nitroxide stearate spin probes, an EPR assay for lipid peroxidation, this
pyrrolopyrimidine compound efficiently protected against
hydroxyl radical-induced lipid peroxidation in cortical synaptosomal membranes deep within the membrane bilayer, but not closer to the membrane surface. In addition,
U101033E partially prevents synaptosomal
protein oxidation in the presence of Fe(II); however,
U101033E demonstrates some
protein oxidative effects itself. These results are supportive of the proposed role of
U101033E as a
lipid-specific
antioxidant, especially for protection against lipid peroxidation that occurs deep within the membrane bilayer, but raise some potential concerns about the oxidative nature of this agent toward
proteins.