Nitric oxide released from zwitterionic polyamine/NO adducts inhibits Cu2+‐induced low density lipoprotein oxidation

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Abstract
The effects of nitrix oxide (NO) released from zwitterionic polyamine/NO adducts on Cu2+-induced low density lipoprotein (LDL) oxidation were studied. When each of the two kinds of NO releasing zwitterionic polyamine/NO adducts (NOC5 and NOC7) was incubated at 5 μM with isolated human LDL (0.25 mg/ml) and Cu2+, the formation of thiobarbituric acid reactive substances (TBARS) was inhibited. The duration of inhibition by NOC7 (20 min) and NOC5 (100 min) corresponded to the NO generation lives of respective zwitterionic polyamine/NO adducts. The duration of inhibition was dependent on the amount of NOC5 added (2.5–20 μM). Repeated additions of 5 μM NOC5 at 100 min intervals worked as inhibitor in the same manner. NOC5 broke to inhibit at any process of the Cu2+-induced LDL oxidation reaction. Fragmentation of apolipoprotein B derived from Cu2+-induced LDL oxidation was also prevented by the addition of NOC5. These results clearly indicate that NO inhibits the oxidative modification of LDL induced by Cu2+. NO releasing zwitterionic polyamine/NO adducts are good reagents for NO studies.