Pro-/anti-oxidative properties of dopamine on membrane lipid peroxidation upon X-ray irradiation

Dopamine increased membrane lipid peroxidation in DOPC/DOPS (8:2) liposomes which are consisting of unsaturated lipids, L-alpha-dioleoylphosphatidylcholine (DOPC) and L-alpha-dioleoylphosphatidylserine (DOPS). However, when exposed to X-rays at 4 Gy, membrane lipid peroxidation was mitigated in the presence of dopamine to the same level as an antioxidant butylated hydroxyanisole, as measured by fluorescence spectroscopy. Meanwhile, 2phenylethylamine neither enhanced nor suppressed membrane lipid peroxidation regardless of X-ray irradiation. By the 2,2-diphenyl-1-picrylhydrazyl (DPPH)-method, dopamine showed about 4-fold the antioxidant capacity of trolox, and 2-phenylethylamine had no detectable antioxidant capacity. It was confirmed by liquid chromatography-mass spectrometry (LC-MS) analysis that the oxidation of dopamine to aminochrome was increased by X-ray irradiation at 4 Gy. These results suggest that dopamine is susceptible to autoxidation and promotes the oxidation of unsaturated lipids without X-rays, but upon X-ray irradiation, dopamine is preferentially oxidized to aminochrome together with mitigation of membrane lipid peroxidation.

Automated summary

The study showed that dopamine's impact on membrane lipids depends on whether it is exposed to X-ray irradiation, unlike 2-phenylethylamine which has no effect on membrane lipids regardless of irradiation. Dopamine exhibits strong antioxidant capacity, but it is also oxidized to aminochrome upon X-ray irradiation.