Restitution of Endothelial Function and Nitric Oxide Bioavailability in Aging Vasculature
Advanced age is associated with endothelial dysfunction and increased risk for cardiovascular diseases. However, the molecular mechanisms of the L-arginine/endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) pathway for this dysfunction are not clear. We determined whether a deficient NO bioactivity in aged rats results from eNOS uncoupling, producing superoxide (O 2 - ) and subsequently peroxynitrite (ONOO - ) rather than NO, and whether this effect may be antagonized by L-arginine. The kinetics of NO/O 2 - /ONOO - release were recorded ex vivo in single endothelial cells from aortas of old and young rats by tandem electrochemical NO/O 2 - /ONOO - -nanosensors before and after long-term and short-term supplementations with D-/L-arginine stereoisomers. We also tested the integrity of the L-arginine/eNOS/NO pathway by analyzing eNOS expression and activity together with changes in the concentrations of L-arginine, N G ,N G ’ -dimethylarginine (ADMA), and L-glutamine in endothelium. The aged endothelium elicited a greater potency of NO production through increased eNOS protein levels and enzyme activities compared with young endothelium. Paradoxically, due to decreased L-arginine (˜5.5-fold) and increased ADMA (˜3-fold) intracellular levels (without changes in L-glutamine concentrations), the aged endothelium exhibited reduced release of bioactive NO with concomitant increases in the eNOS-dependent release of both O 2 - and ONOO-. These age-dependent effects were reversed by supplementation with L-arginine, but not D-arginine, and were associated with restored L-arginine/ADMA concentration ratios in endothelium. Reduction of NO bioavailabilty in aged vascular endothelium is caused by an excess of O 2 - , produced by upregulated uncoupled eNOS under conditions of diminished intracellular L-arginine concentrations. The age-related uncoupling of eNOS may be reversed by L-arginine supplementation and statins treatment.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:nitric oxide superoxide peroxynitrite aging endothelium enos uncoupling
Date of Publication:01/01/2004