An Electron Paramagnetic Resonance Study of the Superoxide-Scavenging and Redox-Modulating Effects of Lecithinized Superoxide Dismutase in the Bloodstream

Lecithinized superoxide dismutase (PC-SOD) was found to have a significantly improved half-life in the bloodstream and better pharmacological effects compared with unmodified SOD. However, there is no direct evidence that parenterally administered PC-SOD decreases superoxide levels in blood and tissues in vivo. In the present study, we investigated the ability of PC-SOD versus unmodified SOD as a superoxide scavenger in mice subjected to oxidative stress. Experiments were performed on a lipopolysaccharide (LPS) mouse model of acute inflammation known to be accompanied by the overproduction of superoxide in the blood. The mice were divided into four groups: untreated (healthy; <i>n</i> = 6), LPS-treated (<i>n</i> = 7), LPS/SOD-treated (<i>n</i> = 6), and LPS/PC-SOD-treated (<i>n</i> = 7) mice. SOD and PC-SOD were injected intravenously. Blood samples were collected at four time intervals and analyzed by electron paramagnetic resonance (EPR) spectroscopy using a nitroxide probe, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (CMP). The following effects were observed: (i) In the blood of healthy mice, the EPR signal was significantly lower compared with the control (<i>p</i> < 0.001) and LPS-treated mice (<i>p</i> < 0.01); (ii) in the blood of LPS-treated mice, the EPR signal was identical to that of the control; and (iii) in the blood of LPS/SOD-treated mice collected immediately after enzyme injection, the EPR signal was significantly lower compared with the control (<i>p</i> < 0.01) and LPS-treated mice (<i>p</i> < 0.05). However, the effect disappeared in the samples collected 30 min and 1 h after enzyme injection. (iv) In LPS/PC-SOD-treated mice, the EPR signal was significantly lower compared with the control (<i>p</i> < 0.01) and LPS-treated mice (<i>p</i> < 0.05), even in the blood samples collected within 1 h after enzyme injection. The data indicate that the blood of healthy mice was characterized by a high reducing capacity, while the blood of LPS-treated mice was characterized by a high oxidative capacity. SOD decreased superoxide production immediately after enzyme injection. However, the effect was short-lived and disappeared within 30 min. PC-SOD effectively decreased superoxide production in the bloodstream of LPS-treated mice and restored the redox balance to the control level even two hours after enzyme injection. The effects of PC-SOD were more pronounced and long-lasting compared with those of SOD. The possible reason is the longer half-life of PC-SOD in the bloodstream, its better stability, and its slower clearance from the circulation due to the increased hydrophobicity of the enzyme and its interaction with plasma proteins. The data are discussed in the context of recent clinical trials showing that PC-SOD is a promising pharmaceutical product for adjuvant therapy of a variety of pathologies accompanied by inflammation, redox imbalance, and oxidative stress.