title: Impact of SOD in eNOS uncoupling: a two-edged sword between hydrogen peroxide and peroxynitrite.
abstract: In endothelial cell dysfunction, the uncoupling of eNOS results in higher superoxide (O(2)(•-)) and lower NO production and a reduction in NO availability. Superoxide reacts with NO to form a potent oxidizing agent peroxynitrite (ONOO(-)) resulting in nitrosative and nitroxidative stresses and dismutates to form hydrogen peroxide. Studies have shown superoxide dismutase (SOD) plays an important role in reduction of O(2)(•-) and ONOO(-) during eNOS uncoupling. However, the administration or over-expression of SOD was ineffective or displayed deleterious effects in some cases. An understanding of interactions of the two enzyme systems eNOS and SOD is important in determining endothelial cell function. We analyzed complex biochemical interactions involving eNOS and SOD in eNOS uncoupling. A computational model of biochemical pathway of the eNOS-related NO and O(2)(•-) production and downstream reactions involving NO, O(2)(•-), ONOO(-), H(2)O(2) and SOD was developed. The effects of SOD concentration on the concentration profiles of NO, O(2)(•-), ONOO(-) and H(2)O(2) in eNOS coupling/uncoupling were investigated. The results include (i) SOD moderately improves NO production and concentration during eNOS uncoupling, (ii) O(2)(•-) production rate is independent of SOD concentration, (iii) Increase in SOD concentration from 0.1 to 100 μM reduces O(2)(•-) concentration by 90% at all [BH(4)]/[TBP] ratios, (iv) SOD reduces ONOO(-) concentration and increases H(2)O(2) concentration during eNOS uncoupling, (v) Catalase can reduce H(2)O(2) concentration and (vi) Dismutation rate by SOD is the most sensitive parameter during eNOS uncoupling. Thus, SOD plays a dual role in eNOS uncoupling as an attenuator of nitrosative/nitroxidative stress and an augmenter of oxidative stress.
authors.affiliation: Department of Biomedical Engineering, Wayne State University, Detroit, MI, USA. s.kar@wayne.edu
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Kar
authors.forename: Bhagyesh
authors.initials: B
authors.lastname: Bhandar
authors.forename: Mahendra
authors.initials: M
authors.lastname: Kavdia
mesh_terms: D001708:Biopterins / Q000494:pharmacology; D002478:Cells, Cultured; D003198:Computer Simulation; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D030421:Peroxynitrous Acid / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D013481:Superoxides; D030421:Peroxynitrous Acid; D001708:Biopterins; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D052250:Nitric Oxide Synthase Type III; D013482:Superoxide Dismutase