Experiments were performed to evaluate the hypothesis that ACE (
angiotensin-converting enzyme) inhibition (
enalapril) suppresses 3-NT (3-nitrotyrosine) production in the renal cortex during the early stage of Type 1 DM (
diabetes mellitus) in the rat.
Enalapril was administered chronically for 2 weeks to subsets of STZ (
streptozotocin)-induced DM and vehicle-treated
sham rats. O(2)(-) (
superoxide anion) and NO(x) (nitrate+nitrite) levels were measured in the media bathing renal cortical slices after 90 min incubation in vitro. SOD (
superoxide dismutase) activity and 3-NT content were measured in the renal cortex homogenate. Renal cortical nitrated
protein was identified by proteomic analysis. Renal cortical production of O(2)(-) and 3-NT was increased in DM rats; however,
enalapril suppressed these changes. DM rats also exhibited elevated renal cortical NO(x) production and SOD activity, and these changes were magnified by
enalapril treatment. 2-DE (two-dimensional gel electrophoresis)-based Western blotting revealed more than 20 spots with positive 3-NT immunoreactivity in the renal cortex of DM rats.
Enalapril treatment blunted the DM-induced increase in
tyrosine nitration of three
proteins ACO2, GDH1 and
MMSDH (
aconitase 2,
glutamate dehydrogenase 1 and methylmalonate-semialdehyde
dehydrogenase), each of which resides in mitochondria. These data are consistent with
enalapril preventing DM-induced
tyrosine nitration of
mitochondrial proteins by a mechanism involving suppression of
oxidant production and enhancement of
antioxidant capacity, including SOD activation.