Photo-oxidation of Cardiolipin and Cytochrome c with Bilayer-Embedded Pc 4

摘要

Singlet oxygen, ¹O2, is produced by absorption of red light by the phthalocyanine dye, Pc 4, followed by energy transfer to dissolved triplet molecular oxygen, ³O2. In tissues, Pc 4 concentrates in lipid bilayers, and particularly in mitochondrial membranes due to its positive charge. Illumination of cells and tissues with red light following uptake of Pc 4 results in cell death. The potential initial chemical steps that result in cellular dysfunction have been characterized in this study. Both unsaturated acyl chains of phospholipids and proteins are identified as targets of oxidation. Tetra-linoleoyl cardiolipin was oxidized in both liposomes and mitochondria following Pc 4 mediated ¹O2 generation. Evidence for formation of both mono and bis hydroperoxide adducts of single linoleoyl side chains is provided by ESI-MS and ESI-MS/MS. Similarly illumination of Pc 4 into liposomes and mitochondria resulted in cytochrome c oxidation as detected by oxidation of H²⁶ in the peptide, H²⁶*KTGPNLHGLFGK, further supporting the potential use of this peptide as a biomarker for the presence of mitochondrial oxidative stress characteristic of ¹O2 in vivo []. These observations provide evidence that formation of lipid hydroperoxides and/or protein oxidation can be the initial chemical steps in Pc 4 mediated induction of apoptosis in PDT.