Figure 5.

Amino endoperoxide compounds upregulate OH levels in cancer cells. (a) Levels of OH (expressed as fold change) in MDA-MB-231 cells suspended in the presence of the four amino endoperoxides at indicated concentrations for 0.5 h measured using TA. (b) Representative EPR spectra of BMPO-OH spin adduct from MDA-MB-231 suspended in the presence 4-Me. For ·OH adduct, spectrometer parameters were: modulation frequency, 100 kHz; scan range, 100 G; field set, 350 G; microwave power, 10 mW; modulation amplitude, 1 G; time constant, 5 ms; and scan time 5.14 s. The EPR spectra represent the averaged signals of 10 scans. Dimethylthiourea was used as negative controls for ·OH measurements. (c) EPR signal intensity expressed as percentage of control at 3410 G from MDA-MB-231 cells in (b). Each experiment was independently performed three times with triplicates. The concentration 0 indicates vehicle control and its ·OH value was set as 1. Error bars, S.E.M. Comparison was performed against cognate vehicle controls. n.s. represents not significant, *P<0.05, **P<0.01