Calcium ions potentiate lipoxygenase activity of cytochrome c at the physiological pH

Linoleic Acid-Enriched Diet Increases Mitochondrial Tetralinoleoyl Cardiolipin, OXPHOS Protein Levels, and Uncoupling in Interscapular Brown Adipose Tissue during Diet-Induced Weight Gain

Cardiolipin (CL) is a phospholipid unique to the inner mitochondrial membrane that supports respiratory chain structure and function and is demonstrated to be influenced by types of dietary fats. However, the influence of dietary fat on CL species and how this best supports mitochondrial function in brown adipose tissue (BAT), which exhibits an alternative method of energy utilization through the uncoupling of the mitochondrial proton gradient to generate heat, is not well understood. Therefore, the aim of our study was to evaluate metabolic parameters, interscapular BAT CL quantity, species, and mitochondrial function in mice consuming isocaloric moderate-fat diets with either lard (LD; similar fatty acid profile to western dietary patterns) or safflower oil high in linoleic acid (SO), shown to be metabolically favorable in large clinical meta-analyses. Mice fed the SO diet exhibited decreased adiposity, improved insulin sensitivity, and enrichment of LA-containing CL species in BAT CL. Furthermore, mice fed the SO diet exhibit higher levels of OXPHOS complex proteins and increased oxygen consumption in BAT. Our findings demonstrate that dietary consumption of LA-rich oil improves metabolic parameters, increases LA-containing CL species, and improves BAT function when compared to the consumption of lard in mice during diet-induced weight gain.

Linoleate-Rich Safflower Oil Diet Increases Linoleate-Derived Bioactive Lipid Mediators in Plasma, and Brown and White Adipose Depots of Healthy Mice

Polyunsaturated fats are energy substrates and precursors to the biosynthesis of lipid mediators of cellular processes. Adipose tissue not only provides energy storage, but influences whole-body energy metabolism through endocrine functions. How diet influences adipose-lipid mediator balance may have broad impacts on energy metabolism. To determine how dietary lipid sources modulate brown and white adipose tissue and plasma lipid mediators, mice were fed low-fat (15% kcal fat) isocaloric diets, containing either palm oil (POLF) or linoleate-rich safflower oil (SOLF). Baseline and post body weight, adiposity, and 2-week and post fasting blood glucose were measured and lipid mediators were profiled in plasma, and inguinal white and interscapular brown adipose tissues. We identified over 30 species of altered lipid mediators between diets and found that these changes were unique to each tissue. We identified changes to lipid mediators with known functional roles in the regulation of adipose tissue expansion and function, and found that there was a relationship between the average fold difference in lipid mediators between brown adipose tissue and plasma in mice consuming the SOLF diet. Our findings emphasize that even with a low-fat diet, dietary fat quality has a profound effect on lipid mediator profiles in adipose tissues and plasma.

The Cytotoxic Action of Cytochrome C/Cardiolipin Nanocomplex (Cyt-CL) on Cancer Cells in Culture

PURPOSE

The effect of existing anti-cancer therapies is based mainly on the stimulation of apoptosis in cancer cells. Here, we have demonstrated the ability of a catalytically-reactive nanoparticle-based complex of cytochrome c with cardiolipin (Cyt-CL) to induce the apoptosis and killing of cancer cells in a monolayer cell culture.

METHODS

Cyt-CL nanoparticles were prepared by complexing CytC with different molar excesses of CL. Following characterization, cytotoxicity and apoptosis inducing effects of nanoparticles were investigated. In an attempt to identify the anticancer activity mechanism of Cyt-CL, pseudo-lipoxygenase and lipoperoxidase reaction kinetics were measured by chemiluminescence.

RESULTS

Using chemiluminescence, we have demonstrated that the Cyt-CL complex produces lipoperoxide radicals in two reactions: by decomposition of lipid hydroperoxides, and by lipid peroxidation under the action of H₂O₂. Antioxidants inhibited the formation of lipid radicals. Cyt-CL nanoparticles, but not the CytC alone, dramatically enhanced the level of apoptosis and cell death in two cell lines: drug-sensitive (A2780) and doxorubicin-resistant (A2780-Adr). The proposed mechanism of the cytotoxic action of Cyt-CL involves either penetration through the cytoplasm and outer mitochondrial membrane and catalysis of lipid peroxidation reactions at the inner mitochondrial membrane, or/and activation of lipid peroxidation within the cytoplasmic membrane.

CONCLUSIONS

Here we propose a new type of anticancer nano-formulation, with an action based on the catalytic action of Cyt-CL nanoparticles on the cell membrane and and/or mitochondrial membranes that results in lipid peroxidation reactions, which give rise to activation of apoptosis in cancer cells, including multidrug resistant cells.

Acetaminophen inhibits cytochrome c redox cycling induced lipid peroxidation

Cytochrome (cyt) c can uncouple from the respiratory chain following mitochondrial stress and catalyze lipid peroxidation. Accumulating evidence shows that this phenomenon impairs mitochondrial respiratory function and also initiates the apoptotic cascade. Therefore, under certain conditions a pharmacological approach that can inhibit cyt c catalyzed lipid peroxidation may be beneficial. We recently showed that acetaminophen (ApAP) at normal pharmacologic concentrations can prevent hemoprotein-catalyzed lipid peroxidation in vitro and in vivo by reducing ferryl heme to its ferric state. We report here, for the first time, that ApAP inhibits cytochrome c-catalyzed oxidation of unsaturated free fatty acids and also the mitochondrial phospholipid, cardiolipin. Using isolated mitochondria, we also showed that ApAP inhibits cardiolipin oxidation induced by the pro-apoptotic protein, tBid. We found that the IC(50) of the inhibition of cardiolipin oxidation by ApAP is similar in both intact isolated mitochondria and cardiolipin liposomes, suggesting that ApAP penetrates well into the mitochondria. Together with our previous results, the findings presented herein suggest that ApAP is a pleiotropic inhibitor of peroxidase catalyzed lipid peroxidation. Our study also provides a potentially novel pharmacological approach for inhibiting the cascade of events that can result from redox cycling of cyt c.

Role of calcium-induced mitochondrial hydroperoxide in induction of apoptosis of RBL2H3 cells with eicosapentaenoic acid treatment

Eicosapentaenoic acid (EPA) was previously shown to induce caspase-independent apoptosis in rat basophilic leukemia cells (RBL2H3 cells) by translocation of apoptosis-inducing factor (AIF) [Free Radic Res (2005) 39, 225-235]. Here, we attempted to investigate the mechanism of EPA-induced apoptosis. A rapid and sustained increase in calcium was observed in mitochondria at 2 h after the addition of EPA prior to apoptosis. Coincidently, hydroperoxide was generated in the mitochondria after exposure to EPA. Production of mitochondrial hydroperoxide was significantly reduced by ruthenium red, an inhibitor of mitochondrial calcium uniporter, and BAPTA-AM, a cytoplasmic calcium chelator, indicating that generation of hydroperoxide is triggered by an accumulation of calcium in the mitochondria. The production of mitochondrial hydroperoxide was markedly attenuated by overexpression of phospholipid hydroperoxide glutathione peroxidase (PHGPx) in the mitochondria. Apoptosis was therefore, significantly prevented through inhibition of mitochondrial hydroperoxide generation with mitochondrial PHGPx, ruthenium red or BAPTA-AM. However, accumulation of calcium in the mitochondria was not prevented by mitochondrial PHGPx although apoptosis was blocked, indicating that elevated calcium does not directly induce apoptosis. Taken together, our results show that calcium-dependent hydroperoxide accumulation in the mitochondria is critical in EPA-induced apoptosis.

Doxorubicin as an antioxidant: maintenance of myocardial levels of lycopene under doxorubicin treatment

The mechanism of doxorubicin-induced cardiotoxicity remains controversial. Wistar rats (n=96) were randomly assigned to a control (C), lycopene (L), doxorubicin (D), or doxorubicin+lycopene (DL) group. The L and DL groups received lycopene (5 mg/kg body wt/day by gavage) for 7 weeks. The D and DL groups received doxorubicin (4 mg/kg body wt intraperitoneally) at 3, 4, 5, and 6 weeks and were killed at 7 weeks for analyses. Myocardial tissue lycopene levels and total antioxidant performance (TAP) were analyzed by HPLC and fluorometry, respectively. Lycopene metabolism was determined by incubating (2)H(10)-lycopene with intestinal mucosa postmitochondrial fraction and lipoxygenase and analyzed with HPLC and APCI mass spectroscopy. Myocardial tissue lycopene levels in DL and L were similar. TAP adjusted for tissue protein were higher in myocardium of D than those of C (P=0.002). Lycopene metabolism study identified a lower oxidative cleavage of lycopene in D as compared to those of C. Our results showed that lycopene was not depleted in myocardium of lycopene-supplemented rats treated with doxorubicin and that higher antioxidant capacity in myocardium and less oxidative cleavage of lycopene in intestinal mucosa of doxorubicin-treated rats suggest an antioxidant role of doxorubicin rather than acting as a prooxidant.

Effect of cytochrome c on the linoleic acid-degrading activity of porcine leukocyte 12-lipoxygenase

Hemoproteins are known to have quasilipoxygenase activity that converts linoleic acid (LA) to its hydroperoxides. However, it is not still clear whether, like lipoxygenases, hemoproteins can produce LA hydroperoxides when the LA is part of a mixture containing many different saturated and unsaturated fatty acids. In this study, we found that such hemoprotein as cytochrome c (Cyt c) did not produce LA hydroperoxides from the phospholipase A(2) (PL-A(2)) hydrolysis products of egg yolk phosphatidylcholine (PC). We also found that traces of hydroperoxides and a high concentration of the target unsaturated fatty acid (LA) needs to be present in a fatty acid mixture before the quasi-lipoxygenase activity of Cyt c becomes apparent. We also attempted to elucidate how Cyt c interact with porcine leukocyte 12-lipoxygenase (12-LOX). Hemoproteins are known to possess pseudo-lipohydroperoxidase activity, and can remove the hydroperoxides of unsaturated fatty acids from a reaction mixture. However, we found that Cyt c catalyzed the reaction by which hydroperoxides degrade LA, and thus enhanced the LA-degrading activity of 12-LOX. This hemoprotein-induced promotion of the ability of 12-LOX to degrade LA was observed even when the reaction mixture contained many different saturated and unsaturated fatty acids.

Rapid reversed-phase high-performance liquid chromatographic determination of the regiospecificity of lipoxygenase products on linoleic acid

A new reversed-phase high-performance liquid chromatography method for the separation of regioisomeric products from lipoxygenase acting on linoleic acid was studied. The addition of salts to the mobile phase improved the retention and separation behaviour of 13-hydroperoxy-9,11-octadecadienoic acid and 9-hydroperoxy-10,12-octadecadienoic acid with respect to the results obtained with other mobile phases reported in the literature. The effect of the pH and ionic strength of the buffer on the retention times, capacity factor and separation factor of these lipoxygenase products were also studied. The pH optimum coincided with the pKa of linoleic acid (close to 7 depending on the fatty acid concentration). Phosphate concentrations close to 100 mM considerably reduced the retention times and led to better separation of the mixture of both products. Finally, this method was applied to the identification and separation of two linoleic acid hydroxides (13-hydroxy-9,11-octadecadienoic acid and 9-hydroxy-10,12-octadecadienoic acid) obtained by the reduction of their corresponding hydroperoxides.

Nitric Oxide–Induced Apoptosis in Human Leukemic Lines Requires Mitochondrial Lipid Degradation and Cytochrome C Release

We have previously shown that nitric oxide (NO) stimulates apoptosis in different human neoplastic lymphoid cell lines through activation of caspases not only via CD95/CD95L interaction, but also independently of such death receptors. Here we investigated mitochondria-dependent mechanisms of NO-induced apoptosis in Jurkat leukemic cells. NO donor glycerol trinitrate (at the concentration, which induces apoptotic cell death) caused (1) a significant decrease in the concentration of cardiolipin, a major mitochondrial lipid; (2) a downregulation in respiratory chain complex activities; (3) a release of the mitochondrial protein cytochrome c into the cytosol; and (4) an activation of caspase-9 and caspase-3. These changes were accompanied by an increase in the number of cells with low mitochondrial transmembrane potential and with a high level of reactive oxygen species production. Higher resistance of the CD95-resistant Jurkat subclone (APO-R) cells to NO-mediated apoptosis correlated with the absence of cytochrome c release and with less alterations in other mitochondrial parameters. An inhibitor of lipid peroxidation, trolox, significantly suppressed NO-mediated apoptosis in APO-S Jurkat cells, whereas bongkrekic acid (BA), which blocks mitochondrial permeability transition, provided only a moderate antiapoptotic effect. Transfection of Jurkat cells with bcl-2 led to a complete block of apoptosis due to the prevention of changes in mitochondrial functions. We suggest that the mitochondrial damage (in particular, cardiolipin degradation and cytochrome c release) induced by NO in human leukemia cells plays a crucial role in the subsequent activation of caspase and apoptosis.

Nitric Oxide–Induced Apoptosis in Human Leukemic Lines Requires Mitochondrial Lipid Degradation and Cytochrome C Release

We have previously shown that nitric oxide (NO) stimulates apoptosis in different human neoplastic lymphoid cell lines through activation of caspases not only via CD95/CD95L interaction, but also independently of such death receptors. Here we investigated mitochondria-dependent mechanisms of NO-induced apoptosis in Jurkat leukemic cells. NO donor glycerol trinitrate (at the concentration, which induces apoptotic cell death) caused (1) a significant decrease in the concentration of cardiolipin, a major mitochondrial lipid; (2) a downregulation in respiratory chain complex activities; (3) a release of the mitochondrial protein cytochrome c into the cytosol; and (4) an activation of caspase-9 and caspase-3. These changes were accompanied by an increase in the number of cells with low mitochondrial transmembrane potential and with a high level of reactive oxygen species production. Higher resistance of the CD95-resistant Jurkat subclone (APO-R) cells to NO-mediated apoptosis correlated with the absence of cytochrome c release and with less alterations in other mitochondrial parameters. An inhibitor of lipid peroxidation, trolox, significantly suppressed NO-mediated apoptosis in APO-S Jurkat cells, whereas bongkrekic acid (BA), which blocks mitochondrial permeability transition, provided only a moderate antiapoptotic effect. Transfection of Jurkat cells with bcl-2 led to a complete block of apoptosis due to the prevention of changes in mitochondrial functions. We suggest that the mitochondrial damage (in particular, cardiolipin degradation and cytochrome c release) induced by NO in human leukemia cells plays a crucial role in the subsequent activation of caspase and apoptosis.