Hydrophobized triphenyl phosphonium derivatives for the preparation of mitochondriotropic liposomes: choice of hydrophobic anchor influences cytotoxicity but not mitochondriotropic effect.

CONTEXT: Nanocarrier-based strategies to achieve delivery of bioactives specifically to the mitochondria are being increasingly explored due to the importance of mitochondria in critical cellular processes. OBJECTIVE: To test the ability of liposomes modified with newly synthesized triphenylphosphonium (TPP)-phospholipid conjugates and to test their use in overcoming the cytotoxicity of stearyl triphenylphosphonium (STPP)-modified liposomes when used for delivery of therapeutic molecules to the mitochondria. METHODS: TPP-phospholipid conjugates with the dioleoyl, dimyristoyl or dipalmitoyl lipid moieties were synthesized and liposomes were prepared with these conjugates in a 1 mol% ratio. The subcellular distribution of the liposomes was tested by confocal microscopy. Furthermore, the liposomes were tested for their effect on cell viability using a MTS assay, on cell membrane integrity using a lactate dehydrogenase assay and on mitochondrial membrane integrity using a modified JC-1 assay. RESULTS: The liposomes modified with the new TPP-phospholipid conjugates exhibited similar mitochondriotropism as STPP-liposomes but they were more biocompatible as compared to the STPP liposomes. While the STPP-liposomes had a destabilizing effect on cell and mitochondrial membranes, the liposomes modified with the TPP-phospholipid conjugates did not demonstrate any such effect on biomembranes. CONCLUSIONS: Using phospholipid anchors in the synthesis of TPP-lipid conjugates can provide liposomes that exhibit the same mitochondrial targeting ability as STPP but with much higher biocompatibility.

Synthesis of triphenylphosphonium phospholipid conjugates for the preparation of mitochondriotropic liposomes.

Surface modification of liposomes with a ligand is facilitated by the conjugation of the ligand to a hydrophobic molecule that serves to anchor the ligand to the liposomal bilayer. We describe here a simple protocol to conjugate a triphenylphosphonium group to several commercially available functionalized phospholipids. The resulting triphenylphosphonium conjugated lipids can be used to prepare liposomes that preferentially associate with mitochondria when exposed to live mammalian cells in culture.

Design, synthesis and biological evaluation of a series of thioamides as non-nucleoside reverse transcriptase inhibitors.

A series of thioamides were designed as bio-isosteres to the non-nucleoside reverse transcriptase inhibitor trovirdine by replacement of the thiourea NH groups with methylene groups. Eight thioamides were synthesized and in vitro tested for inhibitory effects on the activity of HIV-1 reverse transcriptase wild and mutant types. Three of the 8-thioamides exhibited enzyme inhibitory activities with IC(50) values below 100 microM. While compound (2) exhibited activity against the mutant strain L100I with IC(50) of 70.1 microM, compound (4) showed activity against the mutant strain K103N with IC(50) of 92.7 microM, and compound (8) with activity against the wild type enzyme with IC(50) of 8.9 microM. Each of the three thioamides could serve as a lead compound for further activity optimization.

Design, synthesis, and biological testing of thiosalicylamides as a novel class of calcium channel blockers.

The current research aimed to investigate the importance of the heterocyclic ring system in the structure of the cardiovascular drug diltiazem for its calcium channel blocking activity. The manuscript describes the design, synthesis, and biological testing of a total of 10 S-(p-methoxybenzyl), N-substituted thiosalicylamides as a series of non-cyclic compounds derived from diltiazem's structure. The new compounds maintained all diltiazem pharmacophores except the thiazepine ring system. In vitro evaluation of the new series for calcium channel blocking effects revealed moderate activities with IC50 values in the range of 4.8-56.0 microM. The data suggest that the ring system is not essential for activity; however, its absence leads to a considerable drop of activity relative to that of diltiazem (IC50=0.3 microM). Compounds of the current series showed optimum activity when the aliphatic alkyl chain on the salicylamide nitrogen is part of a piperidine or piperazine ring system substituted at the terminal nitrogen with a benzyl group.