Roles and mechanisms of oxidative pathways in cardiovascular disease

The primary goals of this thesis work were to further define the roles and mechanisms of oxidant related events during cardiac and vascular disease, particularly with respect to nitric oxide related actions, and to define potential anti-oxidant therapeutic strategies. In initial studies angiotensin II (ANGII) was administered to rats with a short term (3-day) sub-pressor dose and vascular tissues were then studied. Selective reductions in NO-dependent endothelial dysfunction was observed in ANGII treated animals, and this dysfunction was associated with endothelium specific prevalence of protein 3-nitrotyrosine (3-NT, a stable biomarker of tissue peroxynitrite formation). A novel image analysis technique was developed to quantify the extent of endothelial immunostaining, and a significant inverse correlation between endothelium mediated relaxant response and 3-NT immunoreactivity was observed. Endothelial peroxynitrite formation may therefore participate in (or initiate) early vascular effects of ANGII. Isolated endothelial cells showed that ANG II induced concentration and time dependent increases in protein nitration, demonstrating the direct in vitro action of ANG II in eliciting this response. Time dependent protein nitration was also observed in isolated endothelial cells in the absence of ANG II stimulation, and endothelial cell lysates were shown to possess enzymatic activity in modifying nitrated protein requiring a serum cofactor(s). These data suggest that nitration of protein tyrosine residues may be a regulated process through nitration/denitration mechanisms rather than a contemporary view of it being a cytotoxic phenomenon.;Cardiac remodeling is a key event in progressive heart disease involving selective myocyte dropout and fetal gene expression, but the initiating events are not well defined. Short-term (3-day) administration ANG II or TNF alone at physiologically relevant concentrations induced significant TUNEL positive nuclei (apoptosis marker) and 4-fold increases in LV atrial natriuretic peptide mRNA (fetal gene marker). In contrast, the combination of ANG II and TNF caused only changes in fetal gene expression. These changes in vivo were independent of hemodynamic or cardiac size changes, and not related to cardiac NOS II induction. Our findings suggest that important interactions between ANG II and TNF exist in vivo, and that induction of NOS II is not associated with these early hormonal influences.