Cytochrome c release

It has been shown in many studies that protective effects of carotenoids can be observed only at small carotenoid concentrations, whereas at high concentrations carotenoids exert pro-oxidant effects via propagation of free radical damage (Chucair et al., 2007 Lowe et al., 1999 Palozza, 1998, 2001 Young and Lowe, 2001). For example, supplementation of rat retinal photoreceptors with small concentrations of lutein and zeaxanthin reduces apoptosis in photoreceptors, preserves mitochondrial potential, and prevents cytochrome c release from mitochondria subjected to oxidative stress induced by paraquat or hydrogen peroxide (Chucair et al., 2007). However, this protective effect has been observed only at low concentrations of xanthophylls, of 0.14 and 0.17 pM for lutein and zeaxanthin, respectively. Higher concentrations of carotenoids have led to deleterious effects (Chucair et al., 2007). 

Necrosis by LDH Mitochondrial transmembrane potential by DiOC6 and JC-1 fluorescence Apoptosis by cytochrome c release Annexin V binding DNA fragmentation by agarose gel electrophoresis... 

Li, S., Takasu, T., Perlman, D. M., Peterson, M. S., Burrichter, D., Avdulov, S., Bitterman, P. B., and Polunovsky, V. A. (2003). Translation factor eIF4E rescues cells from Myc-dependent apoptosis by inhibiting cytochrome c release. J. Biol. Chem. 278, 3015-3022. 

As described earlier, superoxide is a well-proven participant in apoptosis, and its role is tightly connected with the release of cytochrome c. It has been proposed that a switch from the normal four-electron reduction of dioxygen through mitochondrial respiratory chain to the one-electron reduction of dioxygen to superoxide can be an initial event in apoptosis development. This proposal was supported by experimental data. Thus, Petrosillo et al. [104] have shown that mitochondrial-produced oxygen radicals induced the dissociation of cytochrome c from bovine heart submitochondrial particles supposedly via cardiolipin peroxidation. Similarly, it has been found [105] that superoxide elicited rapid cytochrome c release in permeabilized HepG2 cells. In contrast, it was also suggested [106] that it is the release of cytochrome c that inhibits mitochondrial respiration and stimulates superoxide production. 

Skulachev [117] proposed that the released cytochrome c oxidizes superoxide and, by this, exhibits an antioxidant function. This proposal was supported by recent experimental findings by Atlante et al. [118], who suggested that cytochrome c released from mitochondria by oxygen species protected mitochondria through a feedback-like process oxidizing superoxide. The most important physiological inhibitor of apoptosis is multifunctional protein Bcl-2,... 

Classic antioxidants, vitamin E, vitamin C, and others can suppress the activation of apoptosis. For example, ascorbic acid prevented cytochrome c release and caspase activation in human leukemia cells exposed to hydrogen peroxide [128], Pretreatment with A -acctylcystcinc, ascorbate, and vitamin E decreased homocysteine thiolactone-induced apoptosis in human promyelocytic leukemia HL-60 cells [129]. Resveratrol protected rat brain mitochondria from anoxia-reoxygenation damage by the inhibition of cytochrome c release and the reduction of superoxide production [130]. However, it should be mentioned that the proapoptotic effect of ascorbate, gallic acid, or epigallocatechin gallate has been shown in the same human promyelocytic leukemia cells [131]. 

The administration of Qio or quercetin to rats protected against endotoxin-induced shock in rat brain [252]. It was found that the pretreatment with these antioxidants diminished the shock-induced increase in brain MDA and nitric oxide levels. Interesting data have been obtained by Yamamura et al. [253] who showed that ubiquinone Qi0 is able to play a double role in mitochondria. It was found that on the one hand, Q10 enhanced the release of hydrogen peroxide from antimycin A- or calcium-treated mitochondria, but on the other hand, it inhibited mitochondrial lipid peroxidation. It was proposed that Q10 acts as a prooxidant participating in redox signaling and as an antioxidant suppressing permeability transition and cytochrome c release. 

Some other examples of free radical formation in various pathologies are discussed below. (Of course, they are only few examples among many others, which can be found in literature.) Mitochondrial diseases are associated with superoxide overproduction [428] and cytochrome c release [429], For example, mitochondrial superoxide production apparently contributes to hippocampal pathology produced by kainate [430]. It has been found that erythrocytes from iron deficiency anemia are more susceptible to oxidative stress than normal cells but have a good capacity for recovery [431]. The beneficial effects of treatment of iron deficiency anemia with iron dextran and iron polymaltose complexes have been shown [432,433]. 

Many of the morphological and biochemical changes that occur in cells that die by necrosis are very different from those that occur in apoptosis. During necrosis cells swell, mitochondria and endoplasmic reticulum lose their structure and become dysfunctional and the nuclear membrane becomes disrupted (Fig. 35-1). Necrotic death is independent of premitochondrial apoptotic proteins such as Bax, cytochrome c release and caspase activation. Necrosis is further distinguished from apoptosis by the fact that necrosis usually occurs as the result of a traumatic physical injury or stroke and cells die en masse, whereas apoptosis typically occurs in individual cells within a population of surviving neighbors. 

Zhu, S., Stavrovskaya, I. G., Drozda, M. et al. Minocycline inhibits cytochrome c release and delays progression of amyotrophic lateral sclerosis in mice. Nature 417 74—78, 2002. 

Miura, K., Aminova L., and MurayamaY. Fusarenon-X induced apoptosis in HL-60 cells depends on caspase activation and cytochrome c release. Toxicology 172, 103, 2002. 

Granville DJ, Carthy CM, Jiang H, Shore GC, McManus BM, Hunt DW (1998) Rapid cytochrome c release, activation of caspases 3, 6, 7 and 8 followed by Bap31 cleavage in HeLa cells treated with photodynamic therapy. FEBS Lett 437 5-10. 

Darios, F., et ah. Parkin prevents mitochondrial swelling and cytochrome c release in mitochondria-dependent cell death. Hum Mol Genet, 2003, 12(5), 517-26. 

Proapototic signals direct these proteins to mitochondria where they compete with antiapoptotic members of the Bcl-2 family to regulate the cytochrome c release and to determine the fate of the cell life or death (Cosulich et al., 1999). Unlike proapoptotic proteins, the antiapoptotic Bcl-2 proteins reside in the outer mitochondrial membrane, anchored by a hydrophobic stretch of amino acids located at the COOH-termini,... 

Most of the responses which lead to cytochrome c release are triggered by activated proapoptotic members of the Bcl-2 family which are directed to mitochondria, where they insert into the outer membrane. What mediates the specific targeting of these proteins to mitochondria, hi a recent work, Lutter et al. (2000) investigated this question using the proapoptotic Bcl-2 member (tBid) as a tool. These authors estabhshed a hposome model for cytochrome c release and recreated the lipid constitution of mitochondrial outer... 

Figure 3. Possible mechanisms of actions of Bcl-2 members. Two prevailing models through which Bcl-2 membas trigger cytochrome c release have been suggested. In both models phospholipids in the bilayer stnicture either individually and/or collectively induce a conformational change in Bcl-2 members, allowing them to insert into the outer mitochondrial membrane. In model 1 proapoptotic proteins destabilize the outer mitochondrial membrane, oligomerize and form channels through which cytochrome c and other proteins of the intermembrane space can escape.BcI-2 proteins such as Bax or tBid act in concert with other proteins of the BcI-2 family to form channels. In model 2 Bcl-2 members such as Bax interact with residoit proteins in the outer membrane (OM) such as the voltage-dependent anion...

Bradham, C.A., Qian, T., Streetz, K., Trautwein, C., Brenner, D.A., and Lemasters, J.J., 1998, The mitochondrial permeability transition is required for Tumor Necrosis Factor Alpha-mediated apoptosis and cytochrome c release, Molecular and Cellular Biology 18 6353-6364. 

Gross, A., Yin, X.M., Wang, K., Wei, M.C., Jockel, J., Milliman, C., Erdjument-Bromage, H., Tempst, P., and Korsmeyer, SJ., 1999, Caspase cleaved Bid targets mitochondria and is required for cytochrome c release, while BcI-Xl prevents this release but not tumor necrosis factor-Rl/Fas death, 7. Biol. Chem. 274 1156-1163. 

Martinou, I.C., Desagher, S., and Antonsson, B., 2000, Cytochrome c release from mitochondria aU or nothing, iVatore Cell Biology E41-43. 

Nitric oxide-induced apoptosis in human leukemic lines requires mitochondrial hpid degradation and cytochrome c release. Blood 93 2342-2352. 

Zhai, D., Huang, X, Han, X., and Yang, R, 2000, Characterization of tBid-induced cytochrome c release from mitochondria and liposomes, FEES Lett. 472 293-296. 

It is now well estahlished that activation of the caspase cascade is an indispensable and sufficient process in the execution phase of apoptosis (Nunez et al, 1998). As for mitochondria-mediated apoptosis, cytochrome c released from the mitochondrial inner membrane is well known to play an important role in the activation of caspase 9, one of the upstream proteases in the cascade (Zou et al, 1997). For activation of caspase 9, cytochrome c or apoptotic protease activating factor 2 (Apaf 2) induces the formation of the complex between Apaf 1 and caspase 9. The resultant activated caspase 9 then activates caspase 3, which in turn leads to the genomic DNA fragmentation and apoptotic cell death. 

Our model of cytochrome c release during apoptosis is not an alternative mechanism to the Bid/Bax-regulated release of cytochrome c. The voltage-dependent anion channel (VDAC) is known to be converted to a cytochrome c-permeant conduit by Bax. Furthermore, Bax protein can... 

In this chapter, we have postulated that cardiolipin may participate in determination of cell fate by allowing cytochrome c release from mitochondrial inner membrane through its peroxidative damage during apoptotic ceU death. And anti-oxidant mitochondrial enzyme, PHGPx may protect cardiolipin from its peroxidation as well as apoptotic cell death. 

The toxic effect of 7-oxysterols, 25- and 27-hydroxycholesterols and their involvement in LDL cytotoxicity have been extensively studied on the different vascular cell types (Lizard et al, 1999 Aupeix et al, 1995 Clare et al, 1995 Ramasamy et al, 1992). 7a and 7p-hydroxycholesterols, 7-ketocholesterol, 25 and 27-hydroxycholesterol induce apoptosis (Brown and Jessup, 1999 Lizard et al, 1999, 1998 Zhang et al, 1997 Hughes et al, 1994). 7p-hydroperoxycholesterol is one of the most toxic Oxysterols present in oxidized LDL (Brown and Jessup, 1999 Colles et al, 1996). 25-hydroxycholesterol, though less active (Aupeix et al 1995), is able to trigger a cytochrome c release and subsequent caspase activation in CHO cells, but also calcium inaease in relation with apoptosis (Rusinol et al, 2000). 

Bax interacts with the permeability transition pore to induce permeability transition and cytochrome c release in isolated mitochondria, Proc.Natl.Acad.Sci. U.S.A. 95 14681-14686. 

CuvUlier, O., Nava, V.E., Murthy, S.K., Edsall, L.C., Levade, T, MUstien, S. and Spiegel, S., 2001, Sphingosine generation, cytochrome c release, and activation ofcaspase-7 in doxorubidn-induced apoptosis of MCF7 breast adenocarcinoma cells. Cell Death Differ 8 162-171. 

Garcia-Ruiz, C., Colell, A., Paris, R., and Femandez-Checa, J. C., 2000, Direct interaction of GD3 ganghoside with mitochondria generates reactive oxygen species followed by mitochondrial permeabihty transition, cytochrome c release, and caspase activation. Faseb J14 847-858. 

Inoki, Y., Miura, T, Kajimoto, T, Kawase, M., Kawase, Y., Yoshida, Y., Tsuji, S., Kinouchi, T, Endo, H., Kagawa, Y., and Hamamoto, T., 2000, Ganghoside GD3 audits mimetics induce cytochrome c release from mitochondria. Biochem Biophys Res Commun 276 1210-1216. 

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