Light-induced protoporphyrin release from erythrocytes in erythropoietic protoporphyria.

Abstract

A B S T R A C T The photohemolysis of normal erythrocytes incubated with protoporphyrin is reduced in the presence of albumin. When globin is added to normal erythrocytes loaded with protoporphyrin, protoporphyrin is bound to globin. During irradiation protoporphyrin moves from globin to the erythrocyte membrane and photohemolysis is initiated.Erythrocytes in patients with erythropoietic protoporphyria contain large amounts of protoporphyrin bound to hemoglobin. Upon irradiation of these cells in the absence of albumin, 40% of protoporphyrin and 80% of hemoglobin is released after 240 kJ/m2. The released protoporphyrin is hemoglobin bound. In contrast, when albumin is present only 8% of hemoglobin is released whereas protoporphyrin is released to 76%. The released protoporphyrin is albumin bound.A hypothesis for the release of erythrocyte protoporphyrin in erythropoietic protoporphyria without simultaneous hemolysis is proposed: Upon irradiation protoporphyrin photodamages its binding sites on hemoglobin, moves through the plasma membrane, and is bound to albumin in plasma.

Dual‐wavelength excitation for fluorescence‐based quantification of zinc protoporphyrin IX and protoporphyrin IX in whole blood

“…Additionally, the difference between these spectra is shown, and is referred to subsequently as a "difference spectrum". In Figure 2, the differences of the two spectra at 593 nm and at 627 nm are highlighted by arrows: as the excitation wavelength 407 nm approaches the PPIX excitation maximum at 397 nm [2] and is far off the ZnPP excitation maximum at 424 nm [2,45], the emission spectrum F 407 shows a pronounced PPIX fluorescence emission peak, which is found at 627 nm in accordance with the literature [23,27,38,42], compared to the lower ZnPP fluorescence peak at 593 nm [2,23,27]. The difference in the range 520 nm-570 nm becomes nearly zero, which shows that the background fluorescence is virtually eliminated by calculating the difference spectrum.…”

“…This is the case for 425 nm (the ZnPP fluorescence excitation maximum, emission maximum at 593 nm [2,27]) and 407 nm as a corresponding wavelength with identical oxygenized heme absorption [41], but substantially lower ZnPP excitation efficiency. Moreover, as the excitation wavelength at 407 nm approaches the PPIX excitation maximum at 397 nm [2], the emission spectrum shows a pronounced PPIX fluorescence emission peak, which is found at 627 nm [23,27,38,42]. As the PPIX excitation efficiency is much lower at 425 nm, the PPIX fluorescence emission peak is not eliminated in the difference spectrum and can be evaluated along with the ZnPP signal.…”

The photodynamic and non-photodynamic actions of porphyrins

“…The effect of porphyrins as exogenous and endogenous sensitizers has been studied in a wide variety of biological environments and targets for the phototoxic damage, i.e., lipid and protein solutions (6,7), isolated erythrocyte membranes (8)(9)(10), whole erythrocytes (11-13), subcellular organelles (5,14,15), mammalian tissue and cell cultures (16)(17)(18) as well as animal (19,20) and human (21) models.…”

Accumulation of iron in erythroblasts of patients with erythropoietic protoporphyria

“…The reason for iron deficiency in EPP is unknown. Iron loss caused by photohaemolysis of erythrocytes [25] may contribute to this condition. Intravascular haemolysis cannot be excluded in some of the EPP patients ( Table 1).…”