Synthesis of triphenylphosphonium phospholipid conjugates for the preparation of mitochondriotropic liposomes

Repurposing of MitoTam: Novel Anti-Cancer Drug Candidate Exhibits Potent Activity against Major Protozoan and Fungal Pathogens

Many of the currently available anti-parasitic and anti-fungal frontline drugs have severe limitations, including adverse side effects, complex administration, and increasing occurrence of resistance. The discovery and development of new therapeutic agents is a costly and lengthy process. Therefore, repurposing drugs with already established clinical application offers an attractive, fast-track approach for novel treatment options. In this study, we show that the anti-cancer drug candidate MitoTam, a mitochondria-targeted analog of tamoxifen, efficiently eliminates a wide range of evolutionarily distinct pathogens in vitro, including pathogenic fungi, Plasmodium falciparum, and several species of trypanosomatid parasites, causative agents of debilitating neglected tropical diseases. MitoTam treatment was also effective in vivo and significantly reduced parasitemia of two medically important parasites, Leishmania mexicana and Trypanosoma brucei, in their respective animal infection models. Functional analysis in the bloodstream form of T. brucei showed that MitoTam rapidly altered mitochondrial functions, particularly affecting cellular respiration, lowering ATP levels, and dissipating mitochondrial membrane potential. Our data suggest that the mode of action of MitoTam involves disruption of the inner mitochondrial membrane, leading to rapid organelle depolarization and cell death. Altogether, MitoTam is an excellent candidate drug against several important pathogens, for which there are no efficient therapies and for which drug development is not a priority.

Mitochondrial targeted astaxanthin liposomes for myocardial ischemia-reperfusion injury based on oxidative stress

Myocardial ischemia-reperfusion injury (MI/RI) refers to the clinical state of decreased coronary blood flow caused by various causes. The main pathogenesis of MI/RI is mitochondrial oxidative damage. In this study, we designed a novel mitochondrial targeted astaxanthin (AST) liposome, namely, STPP-AST-LIP, targeting mitochondria of H9c2 myocardial cells. STPP-AST-LIP not only reduced the production of mitochondrial reactive oxygen species (ROS), but also increased the survival rate of MI/RI H9c2 cells. In addition, rat experiments further confirmed that STPP-AST-LIP could improve myocardial cardiac function in MI/RI rats, significantly inhibited apoptosis of myocardial cells, and had a protective effect on the heart of rats after MI/RI.

Mitochondria-targeting nanoparticles for enhanced microwave ablation of cancer

Although microwave ablation is widely used in the treatment of hepatocellular carcinoma, it is only recommended for the therapy of cancer with a diameter of 3 cm or less because of the limited heat transmission radius. Mitochondria play an important role in the apoptotic events of tumor cells. Here, we developed mitochondria-targeting zirconia (ZrO2) complex nanoparticles (MZCNs) as nanoagents for efficient cancer therapy by microwave ablation. The MZCNs are composed of ZrO2 nanoparticles encapsulating the microwave-sensitive ionic liquid (IL) and co-decorated with the mitochondria-targeting molecule of triphenylphosphonium (TPP), and the tumor cell-targeting peptide iRGD. The cell experiment results reveal that the amount of MZCNs accumulated in the tumor is obviously increased by the synergistically targeted delivery of TPP and iRGD peptide after administration by intravenous injection. Besides, the in vitro experiments demonstrate that MZCNs are distributed preferentially in the mitochondria with the assistance of TPP molecules. More importantly, the in vivo experiments in mice administered with MZCNs show that the effective area with a temperature above 42 °C was about 2.8-fold larger than that of the controls due to the targeting effect and better microwave sensitivity of the MZCNs. As such, the cancer in mice can be eradicated without recurrence, demonstrating the MZCNs as promising nanoagents for efficient cancer therapy by microwave ablation.

Mitochondria-Targeted Triphenylphosphonium-Based Compounds: Syntheses, Mechanisms of Action, and Therapeutic and Diagnostic Applications

Mitochondria are recognized as one of the most important targets for new drug design in cancer, cardiovascular, and neurological diseases. Currently, the most effective way to deliver drugs specifically to mitochondria is by covalent linking a lipophilic cation such as an alkyltriphenylphosphonium moiety to a pharmacophore of interest. Other delocalized lipophilic cations, such as rhodamine, natural and synthetic mitochondria-targeting peptides, and nanoparticle vehicles, have also been used for mitochondrial delivery of small molecules. Depending on the approach used, and the cell and mitochondrial membrane potentials, more than 1000-fold higher mitochondrial concentration can be achieved. Mitochondrial targeting has been developed to study mitochondrial physiology and dysfunction and the interaction between mitochondria and other subcellular organelles and for treatment of a variety of diseases such as neurodegeneration and cancer. In this Review, we discuss efforts to target small-molecule compounds to mitochondria for probing mitochondria function, as diagnostic tools and potential therapeutics. We describe the physicochemical basis for mitochondrial accumulation of lipophilic cations, synthetic chemistry strategies to target compounds to mitochondria, mitochondrial probes, and sensors, and examples of mitochondrial targeting of bioactive compounds. Finally, we review published attempts to apply mitochondria-targeted agents for the treatment of cancer and neurodegenerative diseases.

Trypanocidal action of bisphosphonium salts through a mitochondrial target in bloodstream form Trypanosoma brucei

Lipophilic bisphosphonium salts are among the most promising antiprotozoal leads currently under investigation. As part of their preclinical evaluation we here report on their mode of action against African trypanosomes, the etiological agents of sleeping sickness. The bisphosphonium compounds CD38 and AHI-9 exhibited rapid inhibition of Trypanosoma brucei growth, apparently the result of cell cycle arrest that blocked the replication of mitochondrial DNA, contained in the kinetoplast, thereby preventing the initiation of S-phase. Incubation with either compound led to a rapid reduction in mitochondrial membrane potential, and ATP levels decreased by approximately 50% within 1 h. Between 4 and 8 h, cellular calcium levels increased, consistent with release from the depolarized mitochondria. Within the mitochondria, the Succinate Dehydrogenase complex (SDH) was investigated as a target for bisphosphonium salts, but while its subunit 1 (SDH1) was present at low levels in the bloodstream form trypanosomes, the assembled complex was hardly detectable. RNAi knockdown of the SDH1 subunit produced no growth phenotype, either in bloodstream or in the procyclic (insect) forms and we conclude that in trypanosomes SDH is not the target for bisphosphonium salts. Instead, the compounds inhibited ATP production in intact mitochondria, as well as the purified F₁ ATPase, to a level that was similar to 1 mM azide. Co-incubation with azide and bisphosphonium compounds did not inhibit ATPase activity more than either product alone. The results show that, in T. brucei, bisphosphonium compounds do not principally act on succinate dehydrogenase but on the mitochondrial F_oF₁ ATPase.

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Bisphosphonium salts display highly promising antiprotozoal activity.

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It has been reported that, in Leishmania, they act on the mitochondrial SDH complex.

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We show that in Trypanosoma brucei SDH is not essential and not the drug target.

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Instead, we present strong evidence that the F1F0 ATPase is the target.