Dynamic photodamage of red blood cell induced by CisDiMPyP porphyrin.

It is well-known that oxidative damage in red blood cell (RBC) usually causes morphological changes and increased membrane rigidity. Although many studies have focused on investigating how RBC responds to a photodynamic stimulus, the intermediate steps between membrane damage and hemolysis are not reported. To give a comprehensive insight into changes of RBC membrane property under different oxidative damage levels, we employed the photoactivation of CisDiMPyP porphyrin that primarily generates singlet oxygen 1 O2 as oxidant species. We found that there were distinguishable characteristic damages depending on the 1 O2 flux over the membrane, in a way that each impact of photooxidative damage was categorized under three damage levels: mild (maintaining the membrane morphology and elasticity), moderate (membrane elongation and increased membrane elasticity) and severe (wrinkle-like deformation and hemolysis). When sodium azide (NaN3 ) was used as a singlet oxygen quencher, delayed cell membrane alterations and hemolysis were detected. The delay times showed that 1 O2 indeed plays a key role that causes RBC photooxidation by CisDiMPyP. We suggest that the sequence of morphological changes (RBC discoid area expansion, wrinkle-like patterns, and hemolysis) under photooxidative damage occurs due to damage to the lipid membrane and cytoskeletal network proteins.