cytochrome-c-t and mastoparan

Mitochondria, the cells powerhouses, are essential for maintaining cell life, and they also play a major role in regulating cell death, which occurs upon permeabilization of their membranes. Once mitochondrial membrane permeabilization (MMP) occurs, cells die either by apoptosis or necrosis. Key factors regulating MMP include calcium, the cellular redox status (including levels of reactive oxygen species) and the mobilization and targeting to mitochondria of Bcl-2 family members. Contemporary approaches to targeting mitochondria in cancer therapy use strategies that either modulate the action of Bcl-2 family members at the mitochondrial outer membrane or use specific agents that target the mitochondrial inner membrane and the mitochondrial permeability transition (PT) pore. The aim of this review is to describe the major mechanisms regulating MMP and to discuss, with examples, mitochondrial targeting strategies for potential use in cancer therapy.

Topics: Antineoplastic Agents; Apoptosis; Cell Membrane Permeability; Cyclosporine; Cytochromes c; DNA, Mitochondrial; Intercellular Signaling Peptides and Proteins; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitochondrial Permeability Transition Pore; Peptides; Proto-Oncogene Proteins c-bcl-2; Wasp Venoms

Mastoparan (MP), a potent facilitator of mitochondrial permeability transition (PT), could be used as an antitumor agent, if it were encapsulated in a tumor selective delivery system. We recently developed transferrin-modified liposomes (Tf-L) with a pH-sensitive fusogenic peptide (GALA), which delivers an encapsulated fluorescent marker into cytosol efficiently. In this study, we encapsulated MP into Tf-L with GALA for the selective delivery to mitochondria of tumor cells. The MP showed potent PT activity at concentrations above 25 microM in a homogenate of K 562 cells as well as in isolated mitochondria in the presence of phosphate. Tf-L equipped with cholesteryl GALA can release encapsulated sulforhodamine B, while Tf-L failed, as evidenced by confocal laser scanning microscopy. The MP, which was delivered with Tf-L with GALA, released cytochrome c (cyt c) from mitochondria to the cytosol, while free MP released cyt c not only to the cytosol but also extracellulary. These results demonstrate the utility of MP in Tf-L with GALA for cancer therapy.

Topics: Antineoplastic Agents; Cell Death; Cholesterol Esters; Culture Media; Cytochromes c; Cytosol; Dose-Response Relationship, Drug; Endocytosis; Fluorescent Dyes; Humans; Hydrogen-Ion Concentration; Intercellular Signaling Peptides and Proteins; K562 Cells; Liposomes; Mitochondria; Peptides; Receptors, Transferrin; Rhodamines; Transferrin; Wasp Venoms

Activation of neural pathways originating in the cerebellar fastigial nucleus (FN) protects the brain from the deleterious effects of cerebral ischemia and excitotoxicity, a phenomenon termed central neurogenic neuroprotection. The neuroprotection is, in part, mediated by suppression of apoptosis. We sought to determine whether FN stimulation exerts its anti-apoptotic effect through mitochondrial mechanisms. Mitochondria were isolated from the cerebral cortex of rats in which the FN was stimulated for 1 h (100 microA; 1 s on/1 s off), 72 h earlier. Stimulation of the dentate nucleus (DN), a brain region that does not confer neuroprotection, served as control. Mitochondria isolated from FN-stimulated rats exhibited a marked increase in their ability to sequester Ca2+ and an increased resistance to Ca2+-induced membrane depolarization and depression in respiration. FN stimulation also leads to reduction in the release in cytochrome c, induced either by Ca2+ or the mitochondrial toxin mastoparan. Furthermore, in brain slices, FN stimulation reduced the staurosporine-induced insertion of the pro-apoptotic protein Bax into the mitochondria, a critical step in the mitochondrial mechanisms of apoptosis. Collectively, these results provide evidence that FN stimulation protects the mitochondria from dysfunction induced by Ca2+ loading, and inhibits mitochondrial pathways initiating apoptosis. These mitochondrial mechanisms are likely to play a role in the neuroprotection exerted by FN stimulation.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Calcium; Cerebellar Nuclei; Cerebral Cortex; Cytochromes c; Electric Stimulation; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Intracellular Membranes; Male; Membrane Potentials; Mitochondria; Oxygen Consumption; Peptides; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley; Wasp Venoms