A long-linker conjugate of fluorescein and triphenylphosphonium as mitochondria-targeted uncoupler and fluorescent neuro- and nephroprotector.

BACKGROUND: Limited uncoupling of oxidative phosphorylation is known to be beneficial in various laboratory models of diseases. Linking a triphenyl-phosphonium cation to fluorescein through a decyl (C10) spacer yields a fluorescent uncoupler, coined mitoFluo, that selectively accumulates in energized mitochondria (Denisov et al., Chem.Commun. 2014). METHODS: Proton-transport activity of mitoFluo was tested in liposomes reconstituted with bacteriorhodopsin. To examine the uncoupling action on mitochondria, we monitored mitochondrial membrane potential in parallel with oxygen consumption. Neuro- and nephroprotecting activity was detected by a limb-placing test and a kidney ischemia/reperfusion protocol, respectively. RESULTS: We compared mitoFluo properties with those of its newly synthesized analog having a short (butyl) spacer (C4-mitoFluo). MitoFluo, but not C4-mitoFluo, caused collapse of mitochondrial membrane potential resulting in stimulation of mitochondrial respiration. The dramatic difference in the uncoupling activity of mitoFluo and C4-mitoFluo was in line with the difference in their protonophoric activity on a lipid membrane. The accumulation of mitoFluo in mitochondria was more pronounced than that of C4-mitoFluo. MitoFluo decreased the rate of ROS production in mitochondria. MitoFluo was effective in preventing consequences of brain trauma in rats: it suppressed trauma-induced brain swelling and reduced a neurological deficit. Besides, mitoFluo attenuated acute kidney injury after ischemia/reperfusion in rats. CONCLUSIONS: A long alkyl linker was proved mandatory for mitoFluo to be a mitochondria- targeted uncoupler. MitoFluo showed high protective efficacy in certain models of oxidative stress-related diseases. GENERAL SIGNIFICANCE: MitoFluo is a candidate for developing therapeutic and fluorescence imaging agents to treat brain and kidney pathologies.

Structure-activity relationships of furazano[3,4-b]pyrazines as mitochondrial uncouplers.

Chemical mitochondrial uncouplers are lipophilic weak acids that transport protons into the mitochondrial matrix via a pathway that is independent of ATP synthase, thereby uncoupling nutrient oxidation from ATP production. These uncouplers have potential for the treatment of diseases such as obesity, Parkinson's disease, and aging. We have previously identified a novel mitochondrial protonophore, named BAM15, which stimulates mitochondrial respiration across a broad dosing range compared to carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). Herein, we report our investigations on the structure-activity relationship profile of BAM15. Our studies demonstrate the importance of the furazan, pyrazine, and aniline rings as well as pKa in maintaining its effective protonophore activity.

Synthesis of prenylated quinolinecarboxylic acid derivatives and their anti-obesity activities.

Mitochondrial uncoupling is one of the therapeutic strategies used to control energy metabolism in various metabolic diseases and in obesity. Ppc-1 (1), a prenylated quinolinecarboxylic acid isolated from cellular slime molds, shows uncoupling activity in vitro and anti-obesity activity in vivo. In this study, we synthesized Ppc-1 (1) and its derivatives, and revealed the structure-activity relationship of uncoupling activities. The triprenylated compound 18 showed mitochondrial uncoupling activity that was more potent than that of Ppc-1 (1). Compound 18 also suppressed weight gain in mice without undesired effects such as lesions on tissues. These results indicate that compound 18 could be used as a seed compound for new anti-obesity drugs.

Antiproliferative and uncoupling effects of delocalized, lipophilic, cationic gallic acid derivatives on cancer cell lines. Validation in vivo in singenic mice.

Tumor cells principally exhibit increased mitochondrial transmembrane potential (ΔΨ(m)) and altered metabolic pathways. The therapeutic targeting and delivery of anticancer drugs to the mitochondria might improve treatment efficacy. Gallic acid exhibits a variety of biological activities, and its ester derivatives can induce mitochondrial dysfunction. Four alkyl gallate triphenylphosphonium lipophilic cations were synthesized, each differing in the size of the linker chain at the cationic moiety. These derivatives were selectively cytotoxic toward tumor cells. The better compound (TPP(+)C10) contained 10 carbon atoms within the linker chain and exhibited an IC50 value of approximately 0.4-1.6 µM for tumor cells and a selectivity index of approximately 17-fold for tumor compared with normal cells. Consequently, its antiproliferative effect was also assessed in vivo. The oxygen consumption rate and NAD(P)H oxidation levels increased in the tumor cell lines (uncoupling effect), resulting in a ΔΨ(m) decrease and a consequent decrease in intracellular ATP levels. Moreover, TPP(+)C10 significantly inhibited the growth of TA3/Ha tumors in mice. According to these results, the antineoplastic activity and safety of TPP(+)C10 warrant further comprehensive evaluation.

Synthesis and biological evaluation of 2-hydroxy-3-[(2-aryloxyethyl)amino]propyl 4-[(alkoxycarbonyl)amino]benzoates.

A series of twenty substituted 2-hydroxy-3-[(2-aryloxyethyl)amino]propyl 4-[(alkoxycarbonyl)amino]benzoates were prepared and characterized. As similar compounds have been described as potential antimycobacterials, primary in vitro screening of the synthesized carbamates was also performed against two mycobacterial species. 2-Hydroxy-3-[2-(2,6-dimethoxyphenoxy)ethylamino]-propyl 4-(butoxycarbonylamino)benzoate hydrochloride, 2-hydroxy-3-[2-(4-methoxyphenoxy)ethylamino]-propyl 4-(butoxycarbonylamino)benzoate hydrochloride, and 2-hydroxy-3-[2-(2-methoxyphenoxy)ethylamino]-propyl 4-(butoxycarbonylamino)benzoate hydrochloride showed higher activity against M. avium subsp. paratuberculosis and M. intracellulare than the standards ciprofloxacin, isoniazid, or pyrazinamide. Cytotoxicity assay of effective compounds was performed using the human monocytic leukaemia THP-1 cell line. Compounds with predicted amphiphilic properties were also tested for their effects on the rate of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. All butyl derivatives significantly stimulated the rate of PET, indicating that the compounds can induce conformational changes in thylakoid membranes resulting in an increase of their permeability and so causing uncoupling of phosphorylation from electron transport.

Substituted alpha-(phenylhydrazono)phenylacetonitrile derivatives. Part 2: Synthesis and biological activity of pro-pesticides.

Pro-pesticides of alpha-(2,6-dichloro-4-trifluoromethylphenylhydrazono)-4-nitrophenylacetonitrile have been prepared and tested against mite and insect pests. Variations in potency and spectrum were observed depending on the choice of cleavable pro-moiety. Cleavage of the pro-moiety was demonstrated in one case by measuring the rate of increase in the uncoupling activity using a mitochondrial preparation. Irradiation experiments have demonstrated a rapid isomerisation of the planar Z isomer to the E isomer, which is reversible.

Fluoride curcumin derivatives: new mitochondrial uncoupling agents.

The mitochondrial effects of two fluoride curcumin derivatives were studied. They induced the collapse of mitochondrial membrane potential (DeltaPsi), increased mitochondrial respiration, and decreased O(2)*- production and promoted Ca(2+) release. These effects were reversed by the recoupling agent 6-Ketocholestanol, but not by cyclosporin A, an inhibitor of the permeability transition pore (PTP), suggesting that these compounds act as uncoupling agents. This idea was reinforced by the analysis of the physico-chemical properties of the compounds indicating, that they are mainly in the anionic form in the mitochondrial membrane. Moreover, they are able to induce PTP opening by promoting the oxidation of thiol groups and the release of cytochrome c, making these two molecules potential candidates for induction of apoptosis.

Synthesis and structure--activity relationship of nonyl 3-acyldithiocarbazates and related compounds for uncoupling activities.

Various nonyl 3-substituted-dithiocarbazates, methyl and dimethyl derivatives of nonyl 3-benzoyldithiocarbazate, nonyl 2-substituted-dithiocarbamates, and benzaldehyde nonyldithiocarbohydrazone were synthesized and their uncoupling activities of oxidative phosphorylation in mitochondria were examined. The results indicate that the presence of the thiocarbamoyl structure with the potential SH group is a requisite for uncoupling activity. The presence of a C=O group and a hydrophobic aromatic ring significantly increases the uncoupling activity.

Syntheses and uncoupling activities of alkyl dithiocarbazates and alkyl pyridinecarbonyldithiocarbazates.

A series of alkyl dithiocarbazates, alkyl 3-picolinoyldithiocarbazates, alkyl 3-nicotinoyldithiocarbazates, alkyl 3-isonicotinoyldithiocarbazates, and alkyl 3-picolinoyl-2-methyldithiocarbazates was prepared. These alkyl pyridinecarbonyldithiocarbazates were shown to be uncouplers of oxidative phosphorylation in mitochondria. The finding that uncoupling activity increased with increase in the length of the alkyl chains of the compounds indicates that hydrophobicity influences the activity. The nonyl derivatives had the highest activity. The results also suggested that a dissociable acidic proton is necessary for the uncoupling activity.