Targeting cytochrome C oxidase in mitochondria with Pt(II)-porphyrins for Photodynamic Therapy

TL;DR

This study explores targeting mitochondrial cytochrome C oxidase with Pt(II)-porphyrins for photodynamic therapy, demonstrating disruption of mitochondrial function and potential induction of apoptosis in cancer cells.

Contribution

It introduces a novel cationic photosensitizer, Pt(II)-TMPyP, that specifically binds to and disrupts cytochrome C oxidase in mitochondria during PDT.

Findings

Pt(II)-TMPyP binds to COX in mitochondria

Disruption of mitochondrial cristae observed after PDT

Potential induction of apoptosis through cytochrome C release

Abstract

Mitochondria are the power house of living cells, where the synthesis of the chemical "energy currency" adenosine triphosphate (ATP) occurs. Oxidative phosphorylation by a series of membrane protein complexes I to IV, that is, the electron transport chain, is the source of the electrochemical potential difference or proton motive force (PMF) of protons across the inner mitochondrial membrane. The PMF is required for ATP production by complex V of the electron transport chain, i.e. by FoF1-ATP synthase. Destroying cytochrome C oxidase (COX; complex IV) in Photodynamic Therapy (PDT) is achieved by the cationic photosensitizer Pt(II)-TMPyP. Electron microscopy revealed the disruption of the mitochondrial christae as a primary step of PDT. Time resolved phosphorescence measurements identified COX as the binding site for Pt(II)-TMPyP in living HeLa cells. As this photosensitizer competed with cytochrome C in binding to COX, destruction of COX might not only disturb ATP synthesis but could expedite the release of cytochrome C to the cytosol inducing apoptosis.