Formation of phosphatidic acid in stressed mitochondria

Free radical fragmentation and oxidation in the polar part of lysophospholipids: Results of the study of blood serum of healthy donors and patients with acute surgical pathology

The interaction of reactive oxygen species with cell membrane lipids is usually considered in the context of lipid peroxidation in the nonpolar component of the membrane. In this work, for the first time, data were obtained indicating that damage to human cell membranes can occur in the polar part of lysophospholipids at the interface with the aqueous environment due to free radical fragmentation (FRF) processes. FRF products, namely 1-hexadecanoyloxyacetone (PAc) and 1-octadecanoyloxyacetone (SAc), were identified in human serum, and a GC-MS method was developed to quantify PAc and SAc. The content of FRF products in serum samples of 52 healthy donors was found to be in the range of 1.98-4.75 μmol/L. A linear regression equation, CPAc&SAc (μmol/L) = 0.51 + 0.064 × years, was derived to describe the relationship between age and content of FRF products. In 70 patients with acute surgical pathology in comparison with the control group of healthy donors, two distinct clusters with different concentration levels of FRF products were revealed. The first cluster: groups of 43 patients with various localized inflammatory-destructive lesions of hollow organ walls and bacterial translocation (septic inflammation) of abdominal cavity organs. These patients showed a 1.5-1.9-fold (p = 0.012) decrease in the total concentration of PAc and SAc in serum. In the second cluster: groups of 27 patients with ischemia-reperfusion tissue damage (aseptic inflammation), - a statistically significant increase in the concentration of FRF products was observed: in 2.2-4.0 times (p = 0.0001). The obtained data allow us to further understand the role of free-radical processes in the damage of lipid molecules. FRF products can potentially be used as markers of the degree of free-radical damage of hydroxyl containing phospholipids.

In Vivo Antitumoral Effects of Linseed Oil and Its Combination With Doxorubicin

Linseed oil (LO) is known for its exceptional nutritional value due to the high content of alpha-linolenic acid (ALA), an essential omega-3 polyunsaturated fatty acid; its anticarcinogenic effect has been established in several experimental and epidemiological studies. As an adjuvant of chemotherapeutic agents, LO and other ALA-rich vegetable oils have been studied in only a handful of studies at the experimental level. However, the efficacy of antitumoral therapy using doxorubicin (Dox) in combination with ALA and ALA-rich substrates has not yet been investigated. In this work, the antitumor activity of LO in a wide dose range was studied with monotherapy and combined with Dox in animal models with Pliss lymphosarcoma (PLS) and Lewis lung adenocarcinoma (LLC). It was founded the daily oral administration of LO (1, 3, and 10 ml per 1 kg) to rats (PLS) and 6 ml/kg to mice (LLC) for 11–12 days from 7 days after subcutaneous transplantation of tumors has a stable statistically significant effect on the dynamics of tumor growth, reducing the intensity of tumor growth and increasing the frequency of complete tumor regressions (CR) compared with the control. LO showed high antimetastatic activity in the LLC model. Furthermore, LO at a dose of 3 ml/kg potentiates the antitumor effect of Dox in the PLS model, reducing the volume of tumors at the end of treatment by 2.0 times (p = 0.013), the value of the tumor growth index by 1.6 times (p < 0.03) and increasing the frequency of CR 60 days after the start of therapy by 3.5 times (p = 0.019) compared with the use of Dox alone. The combination of Dox and LO or fish oil allows growing efficiency therapy of LLC in comparison with Dox alone, increasing the frequency of CR to 73.68% and 94.4%, respectively, and reducing the frequency of metastasis to zero.

Extracellular Vesicles and Damage-Associated Molecular Patterns: A Pandora's Box in Health and Disease

Sterile inflammation develops as part of an innate immunity response to molecules released upon tissue injury and collectively indicated as damage-associated molecular patterns (DAMPs). While coordinating the clearance of potential harmful stimuli, promotion of tissue repair, and restoration of tissue homeostasis, a hyper-activation of such an inflammatory response may be detrimental. The complex regulatory pathways modulating DAMPs generation and trafficking are actively investigated for their potential to provide relevant insights into physiological and pathological conditions. Abnormal circulating extracellular vesicles (EVs) stemming from altered endosomal-lysosomal system have also been reported in several age-related conditions, including cancer and neurodegeneration, and indicated as a promising route for therapeutic purposes. Along this pathway, mitochondria may dispose altered components to preserve organelle homeostasis. However, whether a common thread exists between DAMPs and EVs generation is yet to be clarified. A deeper understanding of the highly complex, dynamic, and variable intracellular and extracellular trafficking of DAMPs and EVs, including those of mitochondrial origin, is needed to unveil relevant pathogenic pathways and novel targets for drug development. Herein, we describe the mechanisms of generation of EVs and mitochondrial-derived vesicles along the endocytic pathway and discuss the involvement of the endosomal-lysosomal in cancer and neurodegeneration (i.e., Alzheimer's and Parkinson's disease).

Free-radical and biochemical reactions involving polar part of glycerophospholipids

The review summarizes and critically discusses data on biochemical and free-radical transformations of glycerophospholipids. The results presented therein demonstrate that hydroxyl-containing glycerophospholipids, such as cardiolipin, lyso-lipids and others, can undergo fragmentation upon interaction with radical agents forming the biologically active products. Hydrolysis of glycerophospholipids catalyzed by different phospholipases was shown to yield compounds, which can be involved in the free-radical fragmentation leading to significant changes in structures of original lipids.

Effects of quinones and nitroazoles on free-radical fragmentation of glycerol-1-phosphate and 1,2-dimyristoyl-glycero-3-phosphatidyl-glycerol

Effects of quinones and azoles on the formation of steady-state radiolysis products in aqueous solutions of glycerol-1-phosphate and aqueous dispersions of 1,2-dimyristoyl-glycero-3-phosphatidyl-glycerol has been investigated. The data obtained by LC-MS-ESI and spectrophotometric measurements shows that the compounds having quinoid structures, including the antitumor agent doxorubicin, and azoles having nitro groups effectively inhibit free-radical fragmentation of glycerol-1-phosphate and 1,2-dimyristoyl-glycero-3-phosphatidyl-glycerol, decreasing the radiation-chemical yields of either inorganic phosphate or phosphatidic acid respectively. The observed effects of blocking free-radical processes are believed to be related to the ability of the tested compounds to oxidize α-hydroxyl-containing carbon-centered radicals of starting substrates, which give rise to fragmentation reaction. The possibility of using the discovered properties of quinones, doxorubicin and nitroazoles to provide practical solutions in oncological radiotherapy and pathophysiology is discussed.

Actein alleviates 2,3,7,8-tetrachlorodibenzo-p-dioxin-mediated cellular dysfunction in osteoblastic MC3T3-E1 cells

The environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is known to affect bone metabolism. We evaluated the protective effects of the triterpene glycoside actein from the herb black cohosh against TCDD-induced toxicity in MC3T3-E1 osteoblastic cells. We found that TCDD significantly reduced cell viability and increased apoptosis and autophagy in MC3T3-E1 osteoblastic cells (P < .05). In addition, TCDD treatment resulted in a significant increase in intracellular calcium concentration, mitochondrial membrane potential collapse, reactive oxygen species (ROS) production, and cardiolipin peroxidation, whereas pretreatment with actein significantly mitigated these effects (P < .05). The effects of TCDD on extracellular signal-related kinase (ERK), aryl hydrocarbon receptor, aryl hydrocarbon receptor repressor, and cytochrome P450 1A1 levels in MC3T3-E1 cells were significantly inhibited by actein. The levels of superoxide dismutase, ERK1, and nuclear factor kappa B mRNA were also effectively restored by pretreatment with actein. Furthermore, actein treatment resulted in a significant increase in alkaline phosphatase (ALP) activity and collagen content, as well as in the expression of genes associated with osteoblastic differentiation (ALP, type I collagen, osteoprotegerin, bone sialoprotein, and osterix). This study demonstrates the underlying molecular mechanisms of cytoprotection exerted by actein against TCDD-induced oxidative stress and osteoblast damage.

Neurotoxicity of Copper

Copper is an essential trace metal that is required for several important biological processes, however, an excess of copper can be toxic to cells. Therefore, systemic and cellular copper homeostasis is tightly regulated, but dysregulation of copper homeostasis may occur in disease states, resulting either in copper deficiency or copper overload and toxicity. This chapter will give an overview on the biological roles of copper and of the mechanisms involved in copper uptake, storage, and distribution. In addition, we will describe potential mechanisms of the cellular toxicity of copper and copper oxide nanoparticles. Finally, we will summarize the current knowledge on the connection of copper toxicity with neurodegenerative diseases.

Mitochondrial lipids in neurodegeneration

Mitochondrial dysfunction is a common feature of many neurodegenerative diseases, including proteinopathies such as Alzheimer's or Parkinson's disease, which are characterized by the deposition of aggregated proteins in the form of insoluble fibrils or plaques. The distinct molecular processes that eventually result in mitochondrial dysfunction during neurodegeneration are well studied but still not fully understood. However, defects in mitochondrial fission and fusion, mitophagy, oxidative phosphorylation and mitochondrial bioenergetics have been linked to cellular demise. These processes are influenced by the lipid environment within mitochondrial membranes as, besides membrane structure and curvature, recruitment and activity of different proteins also largely depend on the respective lipid composition. Hence, the interaction of neurotoxic proteins with certain lipids and the modification of lipid composition in different cell compartments, in particular mitochondria, decisively impact cell death associated with neurodegeneration. Here, we discuss the relevance of mitochondrial lipids in the pathological alterations that result in neuronal demise, focussing on proteinopathies.

Polychlorinated biphenyl quinone induces mitochondrial-mediated and caspase-dependent apoptosis in HepG2 cells

Polychlorinated biphenyl (PCB) quinones are known to cause toxic effects, but their mechanisms are quite unclear. In this study, we examined whether 2,3,5-trichloro-6-phenyl-[1,4]benzoquinone, PCB29-pQ, induces cell death via apoptosis pathway. Our result showed PCB29-pQ exposure decreased HepG2 cell viability in a time-dependent manner. Lactate dehydrogenase leakage assay also implied the cytotoxicity of PCB29-pQ. 4',6-Diamidino-2-phenylindole dihydrochloride staining and flow cytometry assays both confirmed PCB29-pQ caused dose-dependent apoptotic cell death in HepG2 cells. Furthermore, we found that PCB29-pQ exposure increased cellular reactive oxygen species (ROS) level, decreased mitochondrial membrane potential and induced the translocation of cytochrome c from mitochondria into cytosol in HepG2 cells. Moreover, PCB29-pQ exposure induced B-cell lymphoma 2 (Bcl-2) downregulation and Bcl-2-associated X (Bax) upregulation, poly(ADP-ribose) polymerase cleavage, accompanied with the increased caspase-3/9 and p53 expressions. Taking together, these results suggested PCB29-pQ induced HepG2 cells apoptosis through a ROS-driven, mitochondrial-mediated and caspase-dependent pathway.

Free-radical Destruction of Sphingolipids Resulting in 2-hexadecenal Formation

The action of hypochlorous acid (HOCl) and γ-radiation on aqueous lysosphingolipid dispersions was found to produce 2-hexadecenal (Hex). This process includes the stages of formation of nitrogen-centered radicals from the starting molecules and the subsequent fragmentation of these radicals via the rupture of C–C and O–H bonds. These findings prove the existence of a nonenzymatic pathway of sphingolipid destruction leading to the formation of Hex, which possesses a wide spectrum of biological activity. Analysis of the effect of HOCl on transplantable rat glioma C6 cells and human embryonic kidney 293 cells points to the formation of Hex. This suggests that the described mechanism of free-radical destruction of sphingolipids may be replicated on cell culture under the stress of active chlorine forms.

Wilson's disease: a comprehensive review of the molecular mechanisms

Wilson’s disease (WD), also known as hepatolenticular degeneration, is an autosomal recessive inherited disorder resulting from abnormal copper metabolism. Reduced copper excretion causes an excessive deposition of the copper in many organs such as the liver, central nervous system (CNS), cornea, kidney, joints, and cardiac muscle where the physiological functions of the affected organs are impaired. The underlying molecular mechanisms for WD have been extensively studied. It is now believed that a defect in P-type adenosine triphosphatase (ATP7B), the gene encoding the copper transporting P-type ATPase, is responsible for hepatic copper accumulation. Deposited copper in the liver produces toxic effects via modulating several molecular pathways. WD can be a lethal disease if left untreated. A better understanding of the molecular mechanisms causing the aberrant copper deposition and organ damage is the key to developing effective management approaches.

A new pathway for mitochondrial quality control: mitochondrial-derived vesicles

The last decade has been marked by tremendous progress in our understanding of the cell biology of mitochondria, with the identification of molecules and mechanisms that regulate their fusion, fission, motility, and the architectural transitions within the inner membrane. More importantly, the manipulation of these machineries in tissues has provided links between mitochondrial dynamics and physiology. Indeed, just as the proteins required for fusion and fission were identified, they were quickly linked to both rare and common human diseases. This highlighted the critical importance of this emerging field to medicine, with new hopes of finding drugable targets for numerous pathologies, from neurodegenerative diseases to inflammation and cancer. In the midst of these exciting new discoveries, an unexpected new aspect of mitochondrial cell biology has been uncovered; the generation of small vesicular carriers that transport mitochondrial proteins and lipids to other intracellular organelles. These mitochondrial-derived vesicles (MDVs) were first found to transport a mitochondrial outer membrane protein MAPL to a subpopulation of peroxisomes. However, other MDVs did not target peroxisomes and instead fused with the late endosome, or multivesicular body. The Parkinson's disease-associated proteins Vps35, Parkin, and PINK1 are involved in the biogenesis of a subset of these MDVs, linking this novel trafficking pathway to human disease. In this review, we outline what has been learned about the mechanisms and functional importance of MDV transport and speculate on the greater impact of these pathways in cellular physiology.

Tetrachlorobenzoquinone induces acute liver injury, up-regulates HO-1 and NQO1 expression in mice model: the protective role of chlorogenic acid

Tetrachlorobenzoquinone (TCBQ) is an active metabolite of pentachlorophenol (PCP). Although PCP has been investigated extensively, there are only a few reports describing the toxicity effect of TCBQ, and no report regarding TCBQ-induced liver injury in vivo. In the current study, we aimed to examine the acute hepatic toxicity of TCBQ in the mice model. Chlorogenic acid (CGA) exhibits promising antioxidant activity in the past studies, thus, the second aim of this study was to evaluate the protective effect of CGA on TCBQ-induced liver injury. Our results indicated TCBQ-intoxication caused marked liver cell necrosis and inflammation but not apoptosis, and this damage was alleviated by CGA treatment. Meantime, TCBQ-intoxication enhanced serum ALT, AST activities, TBIL content, hepatic oxidative stress and lipid peroxidation, decreased GSH content and inhibited the activities of antioxidant enzymes. Western blot and immunohistochemical analysis showed that TCBQ marked up-regulated HO-1 and NQO1 expression. On the other hand, pretreatment of CGA reduced TCBQ-induced liver damage remarkably. Taking together, these results revealed that TCBQ has strong hepatic toxic effect, and at least a part of this effect is initiated by free radical and relieved with CGA administration.

Structural and metabolic changes in Atp7b-/- mouse liver and potential for new interventions in Wilson's disease

Wilson's disease (WD) is caused by ATP7B mutations and results in copper accumulation and toxicity in liver and brain tissues. The specific mechanisms underlying copper toxicity are still poorly understood. Mouse models have revealed new insights into pathomechanisms of hepatic WD. Mitochondrial damage is observed in livers of WD patients and in mouse models; copper induces fragmentation of mitochondrial membrane lipids, particularly cardiolipin, with deleterious effects on both mitochondrial integrity and function. Copper accumulation also induces chronic inflammation in WD livers, which is followed by regeneration in parts of the liver and occasionally neoplastic proliferation. Gene expression studies using microarrays have aided our understanding of the molecular basis of these changes. Copper overload alters cholesterol biosynthesis in hepatocytes resulting in reduced liver and serum cholesterol. Experiments are currently underway to elucidate the link between copper and cholesterol metabolism. These findings may facilitate the development of specific therapies to ameliorate WD progression.

Protective effects of lipoic acid and mesna on cyclophosphamide-induced haemorrhagic cystitis in mice

The protective roles of lipoic acid (LA)/vitamin C (VC) and mesna on preventing cyclophosphamide (CYP)-induced haemorrhagic cystitis (HC) were investigated. Swiss mice were divided into five groups randomly. HC was induced by a single dose of CYP injection (150-mg kg(-1) bodyweight). Group I was injected with saline (four times in total) throughout as control group. Group II received CYP and three equal doses of saline. Group III received CYP and three doses of mesna, whereas Group IV (or Group V) received CYP, mesna + two doses of VC (or LA). All injections were performed intraperitoneally. After 24 h of cystitis induction, the bladders were collected for all the experiments. Histological characterization showed that CYP injection resulted in severe HC. Reactive oxygen species (ROS) and thiobarbituric acid reactive substances' levels were increased in CYP group. The activities of antioxidant enzymes, e.g. superoxide dismutase, catalase, glutathione S-transferase and glutathione peroxidase, were inhibited significantly in CYP groups, respectively. In addition, activation of c-jun N-terminal kinases (JNK) and p38 mitogen-activated protein kinase (MAPK) may be involved in the mechanism of CYP-induced HC but not extracellular signal regulated kinases (ERK). Significant suppression of p38 phosphorylation on Group V suggests that LA and mesna may have synergistic beneficial effect. In Groups III-V, all the parameters of HC and oxidative stress were inhibited significantly. Taking together, we found that these results illustrated that ROS play an important role on CYP-induced HC and the administration of LA/VC with mesna may have therapeutic potential against CYP-induced bladder HC.

Fragmentation of mitochondrial cardiolipin by copper ions in the Atp7b-/- mouse model of Wilson's disease

Cellular copper overload as found in Wilson's disease may disturb mitochondrial function and integrity. Atp7b(-/-) mice accumulate copper in the liver and serve as an animal model for this inherited disease. The molecular mechanism of copper toxicity in hepatocytes is poorly understood. Total mitochondrial lipids from liver of wild-type mice were subjected to oxidative stress by the Cu(2+)/H(2)O(2)/ascorbate system. Phosphatidic acid (PA) and phosphatidylhydroxyacetone (PHA) were detected as cardiolipin fragmentation products by thin-layer chromatography combined with MALDI-TOF mass spectrometry in oxidized samples, but not in unperturbed ones. The formation of PA and PHA in copper-treated model membrane correlated well with the decrease of cardiolipin. Mitochondrial lipids from Atp7b(-/-) mice of different age were analyzed for the presence of PA. While 32-weeks old wild-type (control) and Atp7b(-/-) mice did not show any PA, there was a steady increase in the amount of this lipid in Atp7b(-/-) mice in contrast to control with increasing age. Hepatocytes from elder Atp7b(-/-)mice contained morphologically changed mitochondria unlike cells from wild-type animals of the same age. We concluded that free-radical fragmentation of cardiolipin with the formation of PA is a likely mechanism that damages mitochondria under conditions of oxidative stress due to copper overload. Our findings are relevant for better understanding of molecular mechanisms for liver damage found in Wilson's disease.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced cytotoxicity accompanied by oxidative stress in rat Sertoli cells: Possible role of mitochondrial fractions of Sertoli cells

TCDD, as an endocrine disruptor, is known to impair testicular functions and fertility. To elucidate the mechanism(s) underlying the testicular effects of TCDD, the potential toxicity of TCDD on Sertoli cells was investigated. Furthermore, the study aims to delineate whether mitochondrial fractions of Sertoli cells are involved in mediating the testicular effects of TCDD. Adult rat Sertoli cells were incubated with (5, 10 or 15nM) of TCDD for 6, 12 or 24h. Cell viability, lactate and LDH leakage into media along with lipid peroxidation, ROS generation, SOD, CAT, GPx, GR, γ-GT and β-glucuronidase activities, GSH content and Δψ(m) were measured. Superoxide anion production, COX and cardiolipin content were measured in mitochondrial fractions. Cell viability was significantly decreased while lactate and LDH leakage into media were increased. ROS generation along with lipid peroxidation was also increased. SOD, CAT, GPx, GR activities and GSH content were significantly decreased. γ-GT and β-glucuronidase activities were also decreased. Superoxide anion production was increased while COX activity and cardiolipin content were decreased in mitochondrial fractions. Moreover, the Δψ(m) was significantly decreased as measured in Sertoli cells. In conclusion, TCDD impairs Sertoli cell functions and this effect is, at least in part, attributed to oxidative stress. We have also found that TCDD increases mitochondrial superoxide anion production and decreases Δψ(m), COX activity and mitochondrial cardiolipin content. Our findings suggest that mitochondria may play an important role in ROS production, leading to the TCDD-induced oxidative stress response and resulting toxicological consequences in rat Sertoli cells.

Degradation of phospholipids by oxidative stress--exceptional significance of cardiolipin

The aim of this study was to investigate the effect of oxidative stress on mitochondrial phospholipids. In this context, this study investigated (i) the content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and cardiolipin (CL), (ii) the correlation of CL degradation with mitochondrial function and (iii) the correlation of CL degradation and CL oxidation. Oxidative stress induced by iron/ascorbate caused a dramatic decrease of these phospholipids, in which CL was the most sensitive phospholipid. Even moderate oxidative stress by hypoxia/reoxygenation caused a decrease in CL that was parallelled by a decrease in active respiration of isolated rat heart mitochondria. The relation between oxidative stress, CL degradation and CL oxidation was studied by in vitro treatment of commercially available CL with superoxide anion radicals and H2O2. The degradation of CL was mediated by H2O2 and required the presence of cytochrome c. Other peroxidases such as horse radish peroxidase and glutathione peroxidase had no effect. Cytochrome c in the presence of H2O2 caused CL oxidation. The data demonstrate that oxidative stress may cause degradation of phospholipids by oxidation, in particular CL; resulting in mitochondrial dysfunction.