Depletion Of Cardiolipin Research Articles

Malarial infection develops mitochondrial pathology and mitochondrial oxidative stress to promote hepatocyte apoptosis

Activation of the mitochondrial apoptosis pathway by oxidative stress has been implicated in hepatocyte apoptosis during malaria. Because mitochondria are the source and target of reactive oxygen species (ROS), we have investigated whether hepatocyte apoptosis is linked to mitochondrial pathology and mitochondrial ROS generation during malaria. Malarial infection induces mitochondrial pathology by inhibiting mitochondrial respiration, dehydrogenases, and transmembrane potential and damaging the ultrastructure as evident from transmission electron microscopic studies. Mitochondrial GSH depletion and formation of protein carbonyl indicate that mitochondrial pathology is associated with mitochondrial oxidative stress. Fluorescence imaging of hepatocytes documents intramitochondrial superoxide anion (O 2 − ) generation during malaria. O 2 − inactivates mitochondrial aconitase to release iron from iron–sulfur clusters, which forms the hydroxyl radical ( OH) interacting with H 2O 2 produced concurrently. Malarial infection inactivates mitochondrial aconitase, and carbonylation of aconitase is evident from Western immunoblotting. The release of iron has been documented by fluorescence imaging of hepatocytes using Phen Green SK, and mitochondrial OH generation has been confirmed. During malaria, the depletion of cardiolipin and formation of the mitochondrial permeability transition pore favor cytochrome c release to activate caspase-9. Interestingly, mitochondrial OH generation correlates with the activation of both caspase-9 and caspase-3 with the progress of malarial infection, indicating the critical role of OH.

Effective elimination of fludarabine-resistant CLL cells by PEITC through a redox-mediated mechanism

AbstractChronic lymphocytic leukemia (CLL) is the most common adult leukemia, and resistance to fludarabine-based therapies is a major challenge in CLL treatment. Because CLL cells are known to have elevated levels of reactive oxygen species (ROS), we aimed to test a novel ROS-mediated strategy to eliminate fludarabine-resistant CLL cells based on this redox alteration. Using primary CLL cells and normal lymphocytes from patients (n = 58) and healthy subjects (n = 12), we showed that both fludarabine-resistant and -sensitive CLL cells were highly sensitive to β-phenylethyl isothiocyanate (PEITC) with mean IC50 values of 5.4 μM and 5.1 μM, respectively. Normal lymphocytes were significantly less sensitive to PEITC (IC50 = 27 μM, P < .001). CLL cells exhibited intrinsically higher ROS level and lower cellular glutathione, which were shown to be the critical determinants of CLL sensitivity to PEITC. Exposure of CLL cells to PEITC induced severe glutathione depletion, ROS accumulation, and oxidation of mitochondrial cardiolipin leading to massive cell death. Such ROS stress also caused deglutathionylation of MCL1, followed by a rapid degradation of this cell survival molecule. Our study demonstrated that the natural compound PEITC is effective in eliminating fludarabine-resistant CLL cells through a redox-mediated mechanism with low toxicity to normal lymphocytes, and warrants further clinical evaluation.

Melatonin protects against common deletion of mitochondrial DNA‐augmented mitochondrial oxidative stress and apoptosis

Defected mitochondrial respiratory chain (RC), in addition to causing a severe ATP deficiency, often augments reactive oxygen species (ROS) generation in mitochondria (mROS) which enhances pathological conditions and diseases. Previously, we demonstrated a potent endogenously RC defect-augmented mROS associated dose-dependently with a commonly seen large-scale deletion of 4977 base pairs of mitochondrial DNA (mtDNA), i.e. the common deletion (CD). As current treatments for CD-associated diseases are rather supplementary and ineffective, we investigated whether melatonin, a potential mitochondrial protector, provides beneficial protection for CD-augmented mitochondrial oxidative stress and apoptosis particularly upon the induction of a secondary oxidative stress. Detailed mechanistic investigations were performed by using laser scanning dual fluorescence imaging microscopy to provide precise spatial and temporal resolution of mitochondrial events at single cell level. We demonstrate, for the first time, that melatonin significantly prevents CD-augmented mROS formation under basal conditions as well as at early time-points upon secondary oxidative stress induced by H2O2 exposure. Thus, melatonin prevents mROS-mediated depolarization of mitochondrial membrane potential (DeltaPsim) and subsequent opening of the mitochondrial permeability transition pore (MPTP) and cytochrome c release. Moreover, melatonin prevents depletion of cardiolipin which appears to be crucial for postponing later MPTP opening, disruption of the mitochondrial membrane and apoptosis. Finally, the protection provided by melatonin is superior to those caused by the suppression of mitochondrial Ca2+ regulators including the mitochondrial Na+-Ca2) exchanger, the MPTP, and the mitochondrial Ca2+ uniporter and by antioxidants including vitamin E and mitochondria-targeted coenzyme Q, MitoQ. As RC defect-augmented endogenous mitochondrial oxidative stress is centrally involved in a variety of pathological conditions and diseases, melatonin thus may serve as a therapeutic drug to benefit many clinical conditions that involve malfunction of the mitochondria.

Alterations in Myocardial Cardiolipin Content and Composition Occur at the Very Earliest Stages of Diabetes: A Shotgun Lipidomics Study

Recently, we have identified the dramatic depletion of cardiolipin (CL) in diabetic myocardium 6 weeks after streptozotocin (STZ) injection that was accompanied by increases in triacylglycerol content and multiple changes in polar lipid molecular species. However, after 6 weeks in the diabetic state, the predominant lipid hallmarks of diabetic cardiomyopathy were each present concomitantly, and thus, it was impossible to identify the temporal course of lipid alterations in diabetic myocardium. Using the newly developed enhanced shotgun lipidomics approach, we demonstrated the dramatic loss of abundant CL molecular species in STZ-treated hearts at the very earliest stages of diabetes accompanied by a profound remodeling of the remaining CL molecular species including a 16-fold increase in the content of 18:2-22:6-22:6-22:6 CL. These alterations in CL metabolism occur within days after the induction of the diabetic state and precede the triacylglycerol accumulation manifest in diabetic myocardium. Similarly, in ob/ob mice, a dramatic and progressive redistribution from 18:2 FA-containing CL molecular species to 22:6 FA-containing CL molecular species was also identified. Collectively, these results demonstrate alterations in CL hydrolysis and remodeling at the earliest stages of diabetes and are consistent with a role for alterations in CL content in precipitating mitochondrial dysfunction in diabetic cardiomyopathy.

Depletion of cardiolipin and cytochrome c during ischemia increases hydrogen peroxide production from the electron transport chain

Mitochondrial electron transport is a major source of reactive oxygen species (ROS) during cardiac ischemia and reperfusion. In the isolated rabbit heart, 30 and 45 min of ischemia decrease the contents of cardiolipin and cytochrome c in subsarcolemmal mitochondria (SSM) located beneath the plasma membrane. In contrast, interfibrillar mitochondria (IFM) in the interior of the myocyte do not sustain a decrease in cardiolipin. We proposed that the depletion of cardiolipin and the accompanying cytochrome c loss during ischemia were critical events that amplified ROS production by mitochondria. The total production of H 2O 2 was measured in submitochondrial particles (SMP) prepared from rabbit heart SSM and IFM after 0, 15, 30, and 45 min of ischemia. With NADH as substrate, total H 2O 2 production was increased only in SMP from SSM after 30 and 45 min ischemia, when ischemia decreased the content of cardiolipin and cytochrome c. In contrast, ischemia did not augment H 2O 2 generation in SMP from IFM with preserved cardiolipin and cytochrome c content. Thus, during the evolution of ischemic injury, H 2O 2 production from the electron transport chain increased after depletion of cardiolipin and the loss of cytochrome c.

Chlamydia pneumoniae infected macrophages exhibit enhanced plasma membrane fluidity and show increased adherence to endothelial cells

Chlamydia pneumoniae, an intracellular prokaryote, is known to have requirement for some lipids which it is incapable of synthesizing, and these lipids have important fluidizing roles in plasma membrane. We decided to examine if the trafficking of these lipids to C. pneumoniae alters the physicochemical properties of macrophage plasma membrane, affects the expression of genes and proteins of enzymes associated with metabolism of some of these lipids and assess if Ca2+ signaling usually induced in macrophages infected with C. pneumoniae modulates the genes of these selected enzymes. Chlamydia pneumoniae induced the depletion of macrophage membrane cholesterol, phosphatidylinositol and cardiolipin but caused an increase in phosphotidylcholine resulting in a relative increase in total phospholipids. There was increased membrane fluidity, enhanced macrophage fragility and heightened adherence of macrophages to endothelial cells despite the application of inhibitor of adhesion molecules. Also, there was impairment of macrophage 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase gene and protein expression independent of Ca2+ signaling, while phospholipase C gene and protein were up-regulated in a manner minimally dependent on Ca2+ signaling. The implications of these findings are that macrophages infected with C. pneumoniae have altered membrane physicochemical characteristics which may render them atherogenic.