A Novel Triphenylphosphonium Carrier to Target Mitochondria without Uncoupling Oxidative Phosphorylation

Abstract

Mitochondrial dysfunction is an underlying pathology in numerous diseases. Delivery of diagnostic and therapeutic cargo directly into mitochondria is a powerful approach to study and treat these diseases. The triphenylphosphonium (TPP+) moiety is the most widely used mitochondriotropic carrier. However, studies have shown that TPP+ is not inert; TPP+ conjugates uncouple mitochondrial oxidative phosphorylation. To date, all efforts toward addressing this problem have focused on modifying lipophilicity of TPP+-linker-cargo conjugates to alter mitochondrial uptake, albeit with limited success. We show that structural modifications to the TPP+ phenyl rings that decrease electron density on the phosphorus atom can abrogate uncoupling activity as compared to the parent TPP+ moiety and prevent dissipation of mitochondrial membrane potential. These alterations of the TPP+ structure do not negatively affect the delivery of cargo to mitochondria. Results here identify the 4-CF3-phenyl TPP+ moiety as an inert mitochondria-targeting carrier to safely target pharmacophores and probes to mitochondria.

Alkyl vs. aryl modifications: a comparative study on modular modifications of triphenylphosphonium mitochondrial vectors

“…In summary, the MMP was affected from incubation with all TPP + salts, which were known to induce proton leaks and affect mitochondrial respiration. 41,42 The effects appear to be correlated with the lipophilicity of the nine salts, with no significant difference between alkyl chain extension and aryl methylation. Removal of TPP + from the cell medium results in a slow restoration of the MMP, with no further cell death observed.…”

Small Molecule Modulation of the Archetypal UbiB protein COQ8

“…Negative impacts of TPP compounds on bioenergetics were reported in the low μM range, including for MitoQ 32 . Efforts are underway to decrease this toxicity by developing modified lipophilic cations 48 , which could inform future efforts to improve our TPP-UNC-CA157 inhibitor.…”

Inhibiting succinate release worsens cardiac reperfusion injury by enhancing mitochondrial reactive oxygen species generation

“…Mitochondrial ROS generation was measured using the probe mitoSOX 39,40 (tetraphenylphosphonium-conjugated dihydroethidium, TPP + -DHE) at a concentration of 1.5 µM, since the TPP + moiety is known to uncouple mitochondria at concentrations >2.5 µM [41][42][43] . Hearts subject to conditions (i-vii) described above were equilibrated for 10 min., loaded with 1.5 µM mitoSOX for 5 min.…”