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Steatosis is a liver lesion reported with numerous pharmaceuticals. Prior studies showed that severe impairment of mitochondrial fatty acid oxidation (mtFAO) constantly leads to lipid accretion in liver. However, much less is known about the mechanism(s) of drug-induced steatosis in the absence of severe mitochondrial dysfunction, although previous studies suggested the involvement of mild-to-moderate inhibition of mtFAO, increased de novo lipogenesis (DNL), and impairment of very low-density lipoprotein (VLDL) secretion. The objective of our study, mainly carried out in human hepatoma HepaRG cells, was to investigate these 3 mechanisms with 12 drugs able to induce steatosis in human: amiodarone (AMIO, used as positive control), allopurinol (ALLO), d-penicillamine (DPEN), 5-fluorouracil (5FU), indinavir (INDI), indomethacin (INDO), methimazole (METHI), methotrexate (METHO), nifedipine (NIF), rifampicin (RIF), sulindac (SUL), and troglitazone (TRO). Hepatic cells were exposed to drugs for 4 days with concentrations decreasing ATP level by less than 30% as compared to control and not exceeding 100 × Cmax. Among the 12 drugs, AMIO, ALLO, 5FU, INDI, INDO, METHO, RIF, SUL, and TRO induced steatosis in HepaRG cells. AMIO, INDO, and RIF decreased mtFAO. AMIO, INDO, and SUL enhanced DNL. ALLO, 5FU, INDI, INDO, SUL, RIF, and TRO impaired VLDL secretion. These seven drugs reduced the mRNA level of genes playing a major role in VLDL assembly and also induced endoplasmic reticulum (ER) stress. Thus, in the absence of severe mitochondrial dysfunction, drug-induced steatosis can be triggered by different mechanisms, although impairment of VLDL secretion seems more frequently involved, possibly as a consequence of ER stress. [ABSTRACT FROM AUTHOR]

Dengue viruses belong to the Flavivirus family and are responsible for hemorrhagic fever in Human. Dengue virus infection triggers apoptosis especially through the expression of the small membrane (M) protein. Using isolated mitochondria, we found that synthetic peptides containing the C-terminus part of the M ectodomain caused apoptosis-related mitochondrial membrane permeabilization (MMP) events. These events include matrix swelling and the dissipation of the mitochondrial transmembrane potential (ΔΨm). Protein M Flavivirus sequence alignments and helical wheel projections reveal a conserved distribution of charged residues. Moreover, when combined to the cell penetrating HIV-1 Tat peptide transduction domain (Tat-PTD), this sequence triggers a caspase-dependent cell death associated with ΔΨm loss and cytochrome c release. Mutational approaches coupled to functional screening on isolated mitochondria resulted in the selection of a protein M derived sequence containing nine residues with potent MMP-inducing properties on isolated mitochondria. A chimeric peptide composed of a Tat-PTD linked to the 9-mer entity triggers MMP and cell death. Finally, local administration of this chimeric peptide induces growth inhibition of xenograft prostate PC3 tumors in immuno-compromised mice, and significantly enhances animal survival. Together, these findings support the notion of using viral genomes as valuable sources to discover mitochondria-targeted sequences that may lead to the development of new anticancer compounds. [ABSTRACT FROM AUTHOR]

The HIV-1 encoded apoptogenic protein Vpr induces mitochondrial membrane permeabilization (MMP) via interactions with the voltage-dependent anion channel (VDAC) and the adenine nucleotide translocator (ANT). We have designed a peptide, TEAM-VP, composed of two functional domains, one a tumor blood vessel RGD-like ‘homing’ motif and the other an MMP-inducing sequence derived from Vpr. When added to isolated mitochondria, TEAM-VP interacts with ANT and VDAC, reduces oxygen consumption and overcomes Bcl-2 protection to cause inner and outer MMP. TEAM-VP specifically recognizes cell-surface expressed αVβ3 integrins, internalizes, temporarily localizes to lysosomes and progressively co-distributes with the mitochondrial compartment with no sign of lysosomal membrane permeabilization. Finally TEAM-VP reaches mitochondria of angiogenic endothelial cells to induce mitochondrial fission, dissipation of the mitochondrial transmembrane potential (ΔΨm), cytochrome c release and apoptosis hallmarks. Hence, this chimeric peptide constitutes the first example of a virus-derived mitochondriotoxic compound as a candidate to kill selectively tumor neo-endothelia.Cell Death and Differentiation (2007) 14, 422–435. doi:10.1038/sj.cdd.4402018; published online 4 August 2006 [ABSTRACT FROM AUTHOR]

During development as well as in pathological situations, neurons that fail to find appropriate targets or neurotrophic factors undergo cell death. Using primary cortical neurons subjected to acute serum-deprivation (SD), we have examined caspases activation, mitochondrial dysfunction and cell death parameters. Among a panel of metabolic, signaling and caspases inhibitors only those able to interfere with caspase-2 like activity protect primary neurons against SD-induced cell death. In situ detection and subcellular fractionation demonstrate a very early activation of cytosolic caspase-2, which controls Bax cleavage, relocalization and mitochondrial membrane permeabilization (MMP). Both z-VDVAD-fmk and a siRNA specific for caspase-2 abolish Bax changes, mitochondrial membranes permeabilization, as well as cytochrome c release-dependent activation of caspase-9/caspase-3, nuclear alterations, phosphatidylserine exposure, neurites dismantling and neuronal death. Hence, caspase-2 is an early checkpoint for apoptosis initiation in primary neurons subjected to serum deprivation. [ABSTRACT FROM AUTHOR]