Bilirubin- and Blue-Green Light-Induced Damage of Human Erythrocytes

Abstract

Phototherapy is widely used for neonatal hyperbilirubinemia treatment; however, the most important but not completely recognized issue is the determination of the optimal spectral range of light that provides an effective reduction of bilirubin level in the blood of a newborn with minimal adverse side effects. This study demonstrates that the exposure of radiation from LED sources of blue (emission wavelength λ max = 463 nm, FWHM 20 nm) and green (λ max = 517 nm, FWHM 38 nm) spectral regions to the erythrocyte suspension with the same energy dose (D = 14.4 J/cm 2 ) leads to approximately equally effective hemolysis of erythrocytes. It is concluded that the damage of erythrocyte membranes is caused by the excitation of endogenous porphyrin and flavin photosensitizers contained in the cells in low concentrations, but characterized by high efficiency of singlet oxygen generation. When bilirubin is added to the erythrocyte suspension, a spontaneous (dark) erythrocyte hemolysis intensifies, but the light-induced hemolysis slows down (compared to cells containing no bilirubin). Under the same conditions, the leakage of potassium ions from light-exposed erythrocytes is accelerating, with the light of green spectral region has a more pronounced effect, despite more intense absorption of blue light by bilirubin localized in cells.