Multiple free-radical scavenging capacity in serum

Abstract

We have developed a method to determine serum scavenging-capacity profile against multiple free radical species, namely hydroxyl radical, superoxide radical, alkoxyl radical, alkylperoxyl radical, alkyl radical, and singlet oxygen. This method was applied to a cohort of chronic kidney disease patients. Each free radical species was produced with a common experimental procedure; i.e., uv/visible-light photolysis of free-radical precursor/sensitizer. The decrease in free-radical concentration by the presence of serum was quantified with electron spin resonance spin trapping method, from which the scavenging capacity was calculated. There was a significant capacity change in the disease group (n = 45) as compared with the healthy control group (n = 30). The percent values of disease's scavenging capacity with respect to control group indicated statistically significant differences in all free-radical species except alkylperoxyl radical, i.e., hydroxyl radical, 73 ± 12% (p = 0.001); superoxide radical, 158 ± 50% (p = 0.001); alkoxyl radical, 121 ± 30% (p = 0.005); alkylperoxyl radical, 123 ± 32% (p>0.1); alkyl radical, 26 ± 14% (p = 0.001); and singlet oxygen, 57 ± 18% (p = 0.001). The scavenging capacity profile was illustrated using a radar chart, clearly demonstrating the characteristic change in the disease group. Although the cause of the scavenging capacity change by the disease state is not completely understood, the profile of multiple radical scavenging capacities may become a useful diagnostic tool.

Keywords: ESR spin trapping; MULTIS; chronic kidney disease; multiple free radical; serum.

Fig. 1

ESR spectra of various spin adducts produced after photolysis of precursors/sensitizers (Table 1): A) hydroxyl radical adduct of CYPMPO; B) superoxide radical adduct of CYPMPO; C) t-butoxyl radical adduct of CYPMPO; D) t-butyl peroxyl radical adduct of CYPMPO; E) methyl radical adduct of CYPMPO; and F) TEMPOL radical formed after the reaction of singlet oxygen with 4-OH-TEMP.

Fig. 2

A radar chart illustration of the relative scavenging capacity data listed in Table 3. Percent changes in the capacity of the CKD group (thick lines) are shown with respect to the control group. Error bars are shown in each free radical species and the numbers marked with asterisk showed statistically significant difference from the control group.