Increased mitochondrial cytochrome c levels and mitochondrial hyperpolarization precede camptothecin-induced apoptosis in Jurkat cells

Abstract

Mitochondria play a central role in apoptosis through release of cytochrome c and activation of caspases. In the present study, we showed that, in Jurkat human T cells, camptothecininduced apoptosis is preceded by (i) an increase in cytochrome c and subunit IV of cytochrome c oxidase (COX IV) levels in mitochondria; and (ii) an elevation of the mitochondrial membrane potential (DC m ). These events are followed by cytochrome c release into the cytosol, cytochrome c and COX IV depletion from mitochondria, externalization of phosphatidylserine (PS), disruption of DC m , caspase activation, poly(ADP-ribose)polymerase cleavage and DNA fragmentation. The pan-caspase inhibitor z-VAD.fmk blocked camptothecin-induced PS externalization, disruption of DC m and DNA fragmentation, suggesting that these events are mediated by caspase activation. In contrast, z-VAD did not prevent cytochrome c release, despite preventing cytochrome c and COX IV depletion from mitochondria. Together, these data suggest that mitochondrial cytochrome c and COX IV enrichment are early events preceding the onset of apoptosis and that cytochrome c release is upstream of caspase activation and loss of DC m . Furthermore, prevention by z-VAD of cytochrome c and COX IV depletion in mitochondria suggests the possibility that a caspase-like activity in mitochondria is involved in the proteolytic depletion of respiratory chain proteins. Activation of this activity may play an important role in drug-induced apoptosis.

Nitric oxide, mitochondrial hyperpolarization, and T cell activation☆

“…Transient MHP is an early event preceding caspase activation, phosphatidylserine (PS) externalization, and disruption of Δψ m in Fas- [6] and H 2 O 2 -induced apoptosis of Jurkat human leukemia T cells and normal human peripheral blood lymphocytes (PBL) [8]. These observations were widely confirmed and extended to other apoptosis pathways [9,10,11,12,13,14]. Transient MHP is also triggered by activation of T cells by Con A [6] and CD3/CD28 costimulation [15] via ROI-and Ca 2+ -dependent production of NO [16].…”

Camptothecin induced mitochondrial dysfunction leading to programmed cell death in unicellular hemoflagellate Leishmania donovani

“…This result is reminiscent of those of other investigators, who concluded that an early increase in Dc m is a common event in the process of apoptosis in a variety of cells with different proapoptotic stimuli including CPT. [33][34][35] We have shown that mitochondrial hyperpolarization in leishmanial cells is prevented by treatment with oligomycin prior to the treatment with CPT. From this result it is confirmed that F 0 -F 1 ATPase-like protein in leishmanial cells plays a very important role in the increase of mitochondrial membrane potential.…”

Expression of the oncogenic NPM-ALK chimeric protein in human lymphoid T-cells inhibits drug-induced, but not Fas-induced apoptosis

“…In drug-induced apoptosis, accumulating evidence shows that cytochrome c release from mitochondria into the cytosol is an early event preceeding the activation of caspases (Sanchez-Alcazar et al, 2000). In contrast, in most cells, Fas and other death receptors directly activate caspases-8 and -3 via a mitochondria-independent pathway.…”