Effect of Hyp delivery system on PKCα activity: What will happen after pkcα gene silencing and Hyp photo-activation?

Low density lipoproteins (LDL) are considered as suitable natural in vivo delivery system for hydrophobic photosensitizers (pts) such as hypericin (Hyp) and it was shown that over expression of LDL-receptors in tumor cells can be used for specific targeting. Activation of pts by irradiation results in a formation of reactive oxygen species (ROS) at the place of light application and starts destructive mechanism. PKCα plays a key role in the cell survival and its overexpression was observed in glioma cell lines. In the present study we aim to present the effectivity of the pts delivery in the glioma cells and consequences of silencing pkcα gene on cell death/survival after Hyp photo-activation. Pts can be delivered through two pathways: endocytosis - when cells are incubated with LDL/Hyp complex and Hyp transport through cellular membrane without any carrier. Preliminary results show that incubation of cells with or without LDL leads to PKCα activation. Photo-activated Hyp seems to be more effective in terms of apoptosis induction when compared to photo-activated LDL/Hyp complex. We have evaluated the influence of photo-activated Hyp on cell death in non-transfected and transfected (PKCα-) human glioma cells (U87-MG). Level of ROS production and type of cell death was notably affected by silencing pkca gene resulting in significant increase of necrosis after Hyp photo-activation.

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