Tumor necrosis factor-alpha increases the steady-state reduction of cytochrome b of the mitochondrial respiratory chain in metabolically inhibited L929 cells

Role of Angiotensin II in Non-Alcoholic Steatosis Development

Fatty liver is a multifactorial disease characterized by excessive accumulation of lipids in hepatocytes (steatosis), insulin resistance, oxidative stress, and inflammation. This disease has a major public health impact because it is the first stage of a chronic and degenerative process in the liver that can lead to steatohepatitis, cirrhosis, and liver cancer. Although this disease is mainly diagnosed in patients with obesity, type 2 diabetes mellitus, and dyslipidemia, recent evidence indicates that vasoactive hormones such as angiotensin II (ANGII) not only promote endothelial dysfunction (ED) and hypertension, but also cause fatty liver, increase adipose tissue, and develop a pro-steatotic environment characterized by a low-grade systemic pro-inflammatory and pro-oxidant state, with elevated blood lipid levels. The role of ANGII in lipid accumulation has been little studied, so this review aims to summarize existing reports on the possible mechanism of action of ANGII in inducing lipid accumulation in hepatocytes.

Autocrine positive feedback of tumor necrosis factor from activated microglia proposed to be of widespread relevance in chronic neurological disease

Over a decade's experience of post-stroke rehabilitation by administering the specific anti-TNF biological, etanercept, by the novel perispinal route, is consistent with a wide range of chronically diminished neurological function having been caused by persistent excessive cerebral levels of TNF. We propose that this TNF persistence, and cerebral disease chronicity, largely arises from a positive autocrine feedback loop of this cytokine, allowing the persistence of microglial activation caused by the excess TNF that these cells produce. It appears that many of these observations have never been exploited to construct a broad understanding and treatment of certain chronic, yet reversible, neurological illnesses. We propose that this treatment allows these chronically activated microglia to revert to their normal quiescent state, rather than simply neutralizing the direct harmful effects of this cytokine after its release from microglia. Logically, this also applies to the chronic cerebral aspects of various other neurological conditions characterized by activated microglia. These include long COVID, Lyme disease, post-stroke syndromes, traumatic brain injury, chronic traumatic encephalopathy, post-chemotherapy, post-irradiation cerebral dysfunction, cerebral palsy, fetal alcohol syndrome, hepatic encephalopathy, the antinociceptive state of morphine tolerance, and neurogenic pain. In addition, certain psychiatric states, in isolation or as sequelae of infectious diseases such as Lyme disease and long COVID, are candidates for being understood through this approach and treated accordingly. Perispinal etanercept provides the prospect of being able to treat various chronic central nervous system illnesses, whether they are of infectious or non-infectious origin, through reversing excess TNF generation by microglia.

Grape seed extract proanthocyanidin antagonizes aristolochic acid I-induced liver injury in rats by activating PI3K-AKT pathway

Aristolochic acid is internationally recognized as a carcinogen. It has been shown that the main toxic mechanism of aristolochic acid on the liver and kidney is the induction of ROS-induced oxidative stress damage. To investigate whether proanthocyanidins (GSPE), a natural antioxidant product from grape seed extract, could antagonize AA-I-induced liver injury. Thirty-two SD rats were selected and divided into aristolochic acid exposure group (AA-I), normal control group, GSPE group and GSPE intervention group. The protective effects of GSPE on AA-I liver injury were evaluated by examining the body weight, liver index, liver function and liver pathological sections of rats. The results of body weight, liver index, liver function and liver pathological sections of rats showed that GSPE had antagonistic effects on AA-I-induced liver injury. antioxidant enzyme activity in the GSPE intervention group was significantly higher than that in the aristolochic acid group, apoptotic cells were significantly lower than that in the aristolochic acid group, protein and mRNA expression of PI3K-AKT and BCL-2 were significantly higher than that in the aristolochic acid group, BAX, The protein and mRNA expression of BAX, CASPAES-3, CASPAES-9 were significantly lower than those of the aristolochic acid group. GSPE can antagonize aristolochic acid-induced hepatotoxicity, and its mechanism of action is to antagonize aristolochic acid I-induced liver injury by inhibiting PI3K-AKT pathway-mediated hepatocyte apoptosis.

Chronic cerebral aspects of long COVID, post-stroke syndromes and similar states share their pathogenesis and perispinal etanercept treatment logic

The chronic neurological aspects of traumatic brain injury, post-stroke syndromes, long COVID-19, persistent Lyme disease, and influenza encephalopathy having close pathophysiological parallels that warrant being investigated in an integrated manner. A mechanism, common to all, for this persistence of the range of symptoms common to these conditions is described. While TNF maintains cerebral homeostasis, its excessive production through either pathogen-associated molecular patterns or damage-associated molecular patterns activity associates with the persistence of the symptoms common across both infectious and non-infectious conditions. The case is made that this shared chronicity arises from a positive feedback loop causing the persistence of the activation of microglia by the TNF that these cells generate. Lowering this excess TNF is the logical way to reducing this persistent, TNF-maintained, microglial activation. While too large to negotiate the blood-brain barrier effectively, the specific anti-TNF biological, etanercept, shows promise when administered by the perispinal route, which allows it to bypass this obstruction.

How diseases caused by parasites allowed a wider understanding of disease in general: my encounters with parasitology in Australia and elsewhere over the last 50 years

This is an account of how it can prove possible to carve a reasonable scientific career by following what brought most scientific thrill rather than pursue a safe, institution-directed, path. The fascination began when I noticed, quite unexpectedly, that the normal mouse immune response causes Babesia microti to die, en masse, inside circulating red cells. It eventuated that prior Bacillus Calmette Guerin infection caused the same outcome, even before the protozoal infection became patent. It also rendered mice quite immune, long term. I acquired an obsession about this telling us how little we know. Surrounded by basic immunologists, parasitologists and virologists in London, I had been given, in the days that funding was ample, the opportunity to follow any promising lead with a free hand. Through Bacillus Calmette Guerin, this meant stumbling through a set of phenomena that were in their infancies, and could be explained only through nebulous novel soluble mediators such as TNF, described the following year as causing the in vivo necrosis of tumours in mice. Beginning with malarial disease pathogenesis, I followed TNF wherever it led, into innate immunity, acute and chronic infections, neurophysiology and neurodegenerative diseases, in all of which states awareness of the role of this cytokine is still growing fast. Many of these steps can be illustrated and expanded upon in parasitic diseases. Covering the importance of TNF in the pathogenesis of neurodegenerative disease has proved to be highly illuminating, scientifically and otherwise. But the insights it has given me into understanding the temptations to which patent-owners can succumb when faced with opportunities to put money before people is not for the faint hearted. Clearly, parasitologists inhabit a much more common-good yet science-orientated, civilised, world.

Background to new treatments for COVID-19, including its chronicity, through altering elements of the cytokine storm

Anti-tumour necrosis factor (TNF) biologicals, Dexamethasone and rIL-7 are of considerable interest in treating COVID-19 patients who are in danger of, or have become, seriously ill. Yet reducing sepsis mortality by lowering circulating levels of TNF lost favour when positive endpoints in earlier simplistic models could not be reproduced in well-conducted human trials. Newer information with anti-TNF biologicals has encouraged reintroducing this concept for treating COVID-19. Viral models have had encouraging outcomes, as have the effects of anti-TNF biologicals on community-acquired COVID-19 during their long-term use to treat chronic inflammatory states. The positive outcome of a large scale trial of dexamethasone, and its higher potency late in the disease, harmonises well with its capacity to enhance levels of IL-7Rα, the receptor for IL-7, a cytokine that enhances lymphocyte development and is increased during the cytokine storm. Lymphoid germinal centres required for antibody-based immunity can be harmed by TNF, and restored by reducing TNF. Thus the IL-7- enhancing activity of dexamethasone may explain its higher potency when lymphocytes are depleted later in the infection, while employing anti-TNF, for several reasons, is much more logical earlier in the infection. This implies dexamethasone could prove to be synergistic with rIL-7, currently being trialed as a COVID-19 therapeutic. The principles behind these COVID-19 therapies are consistent with the observed chronic hypoxia through reduced mitochondrial function, and also the increased severity of this disease in ApoE4-positive individuals. Many of the debilitating persistent aspects of this disease are predictably susceptible to treatment with perispinal etanercept, since they have cerebral origins.

Epidermal growth factor receptor and integrins meet redox signaling through P66shc and Rac1

This review examines the concerted role of Epidermal Growth Factor Receptor (EGFR) and integrins in regulating Reactive oxygen species (ROS) production through different signaling pathways. ROS as such are not always deleterious to the cells but they also act as signaling molecules, that regulates numerous indespensible physiological fuctions of life. Many adaptor proteins, particularly Shc and Grb2, are involved in mediating the downstream signaling pathways stimulated by EGFR and integrins. Integrin-induced activation of EGFR and subsequent tyrosine phosphorylation of a class of acceptor sites on EGFR leads to alignment and tyrosine phosphorylation of Shc, PLCγ, the p85 subunit of PI-3 K, and Cbl, followed by activation of the downstream targets Erk and Akt/PKB. Functional interactions between these receptors result in the activation of Rac1 via these adaptor proteins, thereby leading to Reactive Oxygen Species. Both GF and integrin activation can produce oxidants independently, however synergistically there is increased ROS generation, suggesting a mutual cooperation between integrins and GFRs for redox signalling. The ROS produced further promotes feed-forward stimulation of redox signaling events such as MAPK activation and gene expression. This relationship has not been reviewed previously. The literature presented here can have multiple implications, ranging from looking at synergistic effects of integrin and EGFR mediated signaling mechanisms of different proteins to possible therapeutic interventions operated by these two receptors. Furthermore, such mutual redox regulation of crosstalk between EGFR and integrins not only add to the established models of pathological oxidative stress, but also can impart new avenues and opportunities for targeted antioxidant based therapeutics.

N-Adamantyl Phthalimidine: A New Thalidomide-like Drug That Lacks Cereblon Binding and Mitigates Neuronal and Synaptic Loss, Neuroinflammation, and Behavioral Deficits in Traumatic Brain Injury and LPS Challenge

Neuroinflammation contributes to delayed secondary cell death following traumatic brain injury (TBI), has the potential to chronically exacerbate the initial insult, and represents a therapeutic target that has largely failed to translate into human efficacy. Thalidomide-like drugs have effectively mitigated neuroinflammation across cellular and animal models of TBI and neurodegeneration but are complicated by adverse actions in humans. We hence developed N-adamantyl phthalimidine (NAP) as a new thalidomide-like drug to mitigate inflammation without binding to cereblon, a key target associated with the antiproliferative, antiangiogenic, and teratogenic actions seen in this drug class. We utilized a phenotypic drug discovery approach that employed multiple cellular and animal models and ultimately examined immunohistochemical, biochemical, and behavioral measures following controlled cortical impact (CCI) TBI in mice. NAP mitigated LPS-induced inflammation across cellular and rodent models and reduced oligomeric α-synuclein and amyloid-β mediated inflammation. Following CCI TBI, NAP mitigated neuronal and synaptic loss, neuroinflammation, and behavioral deficits, and is unencumbered by cereblon binding, a key protein underpinning the teratogenic and adverse actions of thalidomide-like drugs in humans. In summary, NAP represents a new class of thalidomide-like drugs with anti-inflammatory actions for promising efficacy in the treatment of TBI and potentially longer-term neurodegenerative disorders.

2-aryl benzimidazole conjugate induced apoptosis in human breast cancer MCF-7 cells through caspase independent pathway

Apoptosis is a representative form of programmed cell death, which has been assumed to be critical for cancer prevention. Thus, any agent that can induce apoptosis may be useful for cancer treatment and apoptosis induction is arguably the most potent defense against cancer promotion. In our previous studies, 2-aryl benzimidazole conjugates were synthesized and evaluated for their antiproliferative activity and one of the new molecule (2f) was considered as a potential lead. This lead molecule showed significant antiproliferative activity against human breast cancer cell line, MCF-7. The results of the present study revealed that this compound arrested the cell cycle at G2/M phase. Topoisomerase II inhibition assay and Western blot analysis suggested that this compound effectively inhibits topoisomerase II activity which leads to apoptotic cell death. Apoptosis induction in MCF-7 cells was further confirmed by loss of mitochondrial membrane potential (∆Ψm), release of cytochrome c from mitochondria, an increase in the level of apoptosis inducing factor (AIF), generation of reactive oxygen species (ROS), up regulation of proapoptotic protein Bax and down regulation of anti apoptotic protein Bcl-2. Apoptosis assay using Annexin V-FITC assay also suggested that this compound induced cell death by apoptosis. However, compound 2f induced apoptosis could not be reversed by Z-VAD-FMK (a pan-caspase inhibitor) demonstrated that the 2f induced apoptosis was caspase independent. Further, 2f treatment did not activate caspase-7 and caspase-9 activity, suggesting that this compound induced apoptosis in breast cancer cells via a caspase independent pathway. Most importantly, this compound was less toxic towards non-tumorigenic breast epithelial cells, MCF-10A. Furthermore, docking studies also support the potentiality of this molecule to bind to the DNA topoisomerase II.

Zanthoxylum ailanthoides Suppresses Oleic Acid-Induced Lipid Accumulation through an Activation of LKB1/AMPK Pathway in HepG2 Cells

Zanthoxylum ailanthoides (ZA) has been used as folk medicines in East Asian and recently reported to have several bioactivity; however, the studies of ZA on the regulation of triacylglycerol (TG) biosynthesis have not been elucidated yet. In this study, we examined whether the methanol extract of ZA (ZA-M) could reduce oleic acid- (OA-) induced intracellular lipid accumulation and confirmed its mode of action in HepG2 cells. ZA-M was shown to promote the phosphorylation of AMPK and its upstream LKB1, followed by reduction of lipogenic gene expressions. As a result, treatment of ZA-M blocked de novo TG biosynthesis and subsequently mitigated intracellular neutral lipid accumulation in HepG2 cells. ZA-M also inhibited OA-induced production of reactive oxygen species (ROS) and TNF-α, suggesting that ZA-M possess the anti-inflammatory feature in fatty acid over accumulated condition. Taken together, these results suggest that ZA-M attenuates OA-induced lipid accumulation and inflammation through the activation of LKB1/AMPK signaling pathway in HepG2 cells.

Role of mitochondria and mitochondria-targeted agents in non-alcoholic fatty liver disease

Mitochondria play a pivotal role in the fatty acid oxidation and have been found to be affected early during the macrovesicular fat accumulation in the hepatocytes. The fatty infiltration is the primary cause of oxidative stress and inflammation in the non-alcoholic fatty liver disease (NAFLD), which can lead to the peroxidation of phospholipids, such as cardiolipin. Oxidative stress-induced damage to mitochondrial DNA can result in the impairment of oxidative phosphorylation and further increases the generation of reactive oxygen species. The mitochondrial damage may eventually lead to apoptotic death of hepatocytes. The apoptosis along with the generated cytokines from the stellate and Kupffer cells further augment the fibrotic changes to advance the disease. Hence, alleviation of the mitochondrial impairment, particularly in the early stages of NAFLD, may prevent the progression of the disease. Among the various experimentally studied mitochondrial-targeted agents, triphenylphosphonium cation ligated ubiquinone Q10 and vitamin E, Szeto-Scheller peptides, and superoxide dismutase mimetic-salen manganese complexes (EUK-8 and EUK-134) have been found to be most promising. In addition to these mitochondrial-targeted agents, a novel area of therapy called mitotherapy have also emerged. However, clinical studies conducted so far are still fragmentary to validate their efficacy. This review article discusses the mitochondria-targeted molecules and their potential role in the treatment of NAFLD.

The meteorology of cytokine storms, and the clinical usefulness of this knowledge

The term cytokine storm has become a popular descriptor of the dramatic harmful consequences of the rapid release of polypeptide mediators, or cytokines, that generate inflammatory responses. This occurs throughout the body in both non-infectious and infectious disease states, including the central nervous system. In infectious disease it has become a useful concept through which to appreciate that most infectious disease is not caused directly by a pathogen, but by an overexuberant innate immune response by the host to its presence. It is less widely known that in addition to these roles in disease pathogenesis these same cytokines are also the basis of innate immunity, and in lower concentrations have many essential physiological roles. Here we update this field, including what can be learned through the history of how these interlinking three aspects of biology and disease came to be appreciated. We argue that understanding cytokine storms in their various degrees of acuteness, severity and persistence is essential in order to grasp the pathophysiology of many diseases, and thus the basis of newer therapeutic approaches to treating them. This particularly applies to the neurodegenerative diseases.

Aristolochia manshuriensis Kom ethyl acetate extract protects against high-fat diet-induced non-alcoholic steatohepatitis by regulating kinase phosphorylation in mouse

Aristolochia manshuriensis Kom (AMK) is an herb used as a traditional medicine; however, it causes side effects such as nephrotoxicity and carcinogenicity. Nevertheless, AMK can be applied in specific ways medicinally, including via ingestion of low doses for short periods of time. Non-alcoholic steatohepatitis (NASH) induced the hepatocyte injury and inflammation. The protective effects of AMK against NASH are unclear; therefore, in this study, the protective effects of AMK ethyl acetate extract were investigated in a high-fat diet (HFD)-induced NASH model. We found decreased hepatic steatosis and inflammation, as well as increased levels of lipoproteins during AMK extract treatment. We also observed decreased hepatic lipid peroxidation and triglycerides, as well as suppressed hepatic expression of lipogenic genes in extract-treated livers. Treatment with extract decreased the activation of c-jun N-terminal kinase 1/2 (JNK1/2) and increased the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). These results demonstrate that the protective effect of the extract against HFD-induced NASH occurred via reductions in reactive oxygen species production, inflammation suppression, and apoptosis related to the suppression of JNK1/2 activation and increased ERK1/2 phosphorylation. Taken together, these results indicate that that ethyl acetate extract of AMK has potential therapeutic effects in the HFD-induced NASH mouse model.

NADPH oxidase is implicated in the pathogenesis of oxidative phosphorylation dysfunction in mice fed a high-fat diet

The aim of this study was to evaluate the role of NADPH oxidase (NADPHox) in the pathogenesis of oxidative phosphorylation (OXPHOS) dysfunction as found in mice fed a high-fat diet (HFD). C57BL/6J mice were distributed in four groups: WT/SCD: six wild-type (WT) mice fed a standard chow diet (SCD); WT/HFD, six WT mice fed a HFD; NOX2(-/-)/SCD, six NADPHox-deficient mice on a SCD; (4) NOX2(-/-)/HFD, six NADPHox-deficient mice on a HFD. After 32 weeks, we studied the liver for: histology; OXPHOS complex activity; fully assembled OXPHOS complexes and their subunits; gene expression of OXPHOS subunits; oxidative and nitrosative stress; and oxidative DNA damage. In the liver of WT/HFD mice, we found a significant decreased in the activity of all OXPHOS complexes, in fully assembled complexes, in the amount of OXPHOS subunits, and in gene expression of mitochondrial DNA-encoded subunits. 8-hydroxy-2'-deoxyguanosine was only increased in mitochondrial DNA. The liver of NOX(-/-)/HFD mice showed mild steatosis but no non-alcoholic steatohepatitis (NASH) lesions were found. OXPHOS activity, OXPHOS subunits, and assembly of subunits into OXPHOS complexes were normal in these mice. We conclude that this study shows that NADPH deficiency protects mice from developing OXPHOS dysfunction and NASH caused by a HFD.

Hydroxytyrosol prevents metabolic impairment reducing hepatic inflammation and restoring duodenal integrity in a rat model of NAFLD

The potential mechanisms of action of polyphenols in nonalcoholic fatty liver disease (NAFLD) are overlooked. Here, we evaluate the beneficial therapeutic effects of hydroxytyrosol (HT), the major metabolite of the oleuropein, in a nutritional model of insulin resistance (IR) and NAFLD by high-fat diet. Young male rats were divided into three groups receiving (1) standard diet (STD; 10.5% fat), (2) high-fat diet (HFD; 58.0% fat) and (3) HFD+HT (10 mg/kg/day by gavage). After 5 weeks, the oral glucose tolerance test was performed, and at 6th week, blood sample and tissues (liver and duodenum) were collected for following determinations. The HT-treated rats showed a marked reduction in serum AST, ALT and cholesterol and improved glucose tolerance and insulin sensitivity, reducing homeostasis model assessment index. HT significantly corrected the metabolic impairment induced by HFD, increasing hepatic peroxisome proliferator activated receptor PPAR-α and its downstream-regulated gene fibroblast growth factor 21, the phosphorylation of acetyl-CoA carboxylase and the mRNA carnitine palmitoyltransferase 1a. HT also reduced liver inflammation and nitrosative/oxidative stress decreasing the nitrosylation of proteins, reactive oxygen species production and lipid peroxidation. Moreover, HT restored intestinal barrier integrity and functions (fluorescein isothiocyanate-dextran permeability and mRNA zona occludens ZO-1). Our data demonstrate the beneficial effect of HT in the prevention of early inflammatory events responsible for the onset of IR and steatosis, reducing hepatic inflammation and nitrosative/oxidative stress and restoring glucose homeostasis and intestinal barrier integrity.

Amyloid β: one of three danger-associated molecules that are secondary inducers of the proinflammatory cytokines that mediate Alzheimer's disease

This review concerns how the primary inflammation preceding the generation of certain key damage-associated molecular patterns (DAMPs) arises in Alzheimer's disease (AD). In doing so, it places soluble amyloid β (Aβ), a protein hitherto considered as a primary initiator of AD, in a novel perspective. We note here that increased soluble Aβ is one of the proinflammatory cytokine-induced DAMPs recognized by at least one of the toll-like receptors on and in various cell types. Moreover, Aβ is best regarded as belonging to a class of DAMPs, as do the S100 proteins and HMBG1, that further exacerbate production of these same proinflammatory cytokines, which are already enhanced, and induces them further. Moreover, variation in levels of other DAMPs of this same class in AD may explain why normal elderly patients can exhibit high Aβ plaque levels, and why removing Aβ or its plaque does not retard disease progression. It may also explain why mouse transgenic models, having been designed to generate high Aβ, can be treated successfully by this approach.

A Neurologist's Guide to TNF Biology and to the Principles behind the Therapeutic Removal of Excess TNF in Disease

Tumor necrosis factor (TNF) is an ancient and widespread cytokine required in small amounts for much physiological function. Higher concentrations are central to innate immunity, but if unchecked this cytokine orchestrates much chronic and acute disease, both infectious and noninfectious. While being a major proinflammatory cytokine, it also controls homeostasis and plasticity in physiological circumstances. For the last decade or so these principles have been shown to apply to the central nervous system as well as the rest of the body. Nevertheless, whereas this approach has been a major success in treating noncerebral disease, its investigation and potential widespread adoption in chronic neurological conditions has inexplicably stalled since the first open trial almost a decade ago. While neuroscience is closely involved with this approach, clinical neurology appears to be reticent in engaging with what it offers patients. Unfortunately, the basic biology of TNF and its relevance to disease is largely outside the traditions of neurology. The purpose of this review is to facilitate lowering communication barriers between the traditional anatomically based medical specialties through recognition of shared disease mechanisms and thus advance the prospects of a large group of patients with neurodegenerative conditions for whom at present little can be done.

Dysfunctional mitochondrial bioenergetics and the pathogenesis of hepatic disorders

The liver is involved in a variety of critical biological functions including the homeostasis of glucose, fatty acids, amino acids, and the synthesis of proteins that are secreted in the blood. It is also at the forefront in the detoxification of noxious metabolites that would otherwise upset the functioning of the body. As such, this vital component of the mammalian system is exposed to a notable quantity of toxicants on a regular basis. It therefore comes as no surprise that there are over a hundred disparate hepatic disorders, encompassing such afflictions as fatty liver disease, hepatitis, and liver cancer. Most if not all of liver functions are dependent on energy, an ingredient that is primarily generated by the mitochondrion, the power house of all cells. This organelle is indispensable in providing adenosine triphosphate (ATP), a key effector of most biological processes. Dysfunctional mitochondria lead to a shortage in ATP, the leakage of deleterious reactive oxygen species (ROS), and the excessive storage of fats. Here we examine how incapacitated mitochondrial bioenergetics triggers the pathogenesis of various hepatic diseases. Exposure of liver cells to detrimental environmental hazards such as oxidative stress, metal toxicity, and various xenobiotics results in the inactivation of crucial mitochondrial enzymes and decreased ATP levels. The contribution of the latter to hepatic disorders and potential therapeutic cues to remedy these conditions are elaborated.

In vivo biodistribution and toxicity of Gd2O3:Eu3+ nanotubes in mice after intraperitoneal injection

To better understand the potential impact of Gd₂O₃:Eu³⁺ nanotubes on human health, we investigated their biodistribution, subacute toxicity, and hepatic injury in mice under different dosages (4.0, 40.0, and 400.0 mg kg⁻¹).

Oxidative stress, cardiolipin and mitochondrial dysfunction in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is today considered the most common form of chronic liver disease, affecting a high proportion of the population worldwide. NAFLD encompasses a large spectrum of liver damage, ranging from simple steatosis to steatohepatitis, advanced fibrosis and cirrhosis. Obesity, hyperglycemia, type 2 diabetes and hypertriglyceridemia are the most important risk factors. The pathogenesis of NAFLD and its progression to fibrosis and chronic liver disease is still unknown. Accumulating evidence indicates that mitochondrial dysfunction plays a key role in the physiopathology of NAFLD, although the mechanisms underlying this dysfunction are still unclear. Oxidative stress is considered an important factor in producing lethal hepatocyte injury associated with NAFLD. Mitochondrial respiratory chain is the main subcellular source of reactive oxygen species (ROS), which may damage mitochondrial proteins, lipids and mitochondrial DNA. Cardiolipin, a phospholipid located at the level of the inner mitochondrial membrane, plays an important role in several reactions and processes involved in mitochondrial bioenergetics as well as in mitochondrial dependent steps of apoptosis. This phospholipid is particularly susceptible to ROS attack. Cardiolipin peroxidation has been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions, including NAFLD. In this review, we focus on the potential roles played by oxidative stress and cardiolipin alterations in mitochondrial dysfunction associated with NAFLD.

High-fat diet decreases activity of the oxidative phosphorylation complexes and causes nonalcoholic steatohepatitis in mice

Nonalcoholic fatty liver disease (NAFLD) is the most frequent histological finding in individuals with abnormal liver-function tests in the Western countries. In previous studies, we have shown that oxidative phosphorylation (OXPHOS) is decreased in individuals with NAFLD, but the cause of this mitochondrial dysfunction remains uncertain. The aims of this study were to determine whether feeding mice a high-fat diet (HFD) induces any change in the activity of OXPHOS, and to investigate the mechanisms involved in the pathogenesis of this defect. To that end, 30 mice were distributed between five groups: control mice fed a standard diet, and mice on a HFD and treated with saline solution, melatonin (an antioxidant), MnTBAP (a superoxide dismutase analog) or uric acid (a scavenger of peroxynitrite) for 28 weeks intraperitoneously. In the liver of these mice, we studied histology, activity and assembly of OXPHOS complexes, levels of subunits of these complexes, gene expression of these subunits, oxidative and nitrosative stress, and oxidative DNA damage. In HFD-fed mice, we found nonalcoholic steatohepatitis, increased gene expression of TNFα, IFNγ, MCP-1, caspase-3, TGFβ1 and collagen α1(I), and increased levels of 3-tyrosine nitrated proteins. The activity and assembly of all OXPHOS complexes was decreased to about 50–60%. The amount of all studied OXPHOS subunits was markedly decreased, particularly the mitochondrial-DNA-encoded subunits. Gene expression of mitochondrial-DNA-encoded subunits was decreased to about 60% of control. There was oxidative damage to mitochondrial DNA but not to genomic DNA. Treatment of HFD-fed mice with melatonin, MnTBAP or uric acid prevented all changes observed in untreated HFD-fed mice. We conclude that a HFD decreased OXPHOS enzymatic activity owing to a decreased amount of fully assembled complexes caused by a reduced synthesis of their subunits. Antioxidants and antiperoxynitrites prevented all of these changes, suggesting that nitro-oxidative stress played a key role in the pathogenesis of these alterations. Treatment with these agents might prevent the development of NAFLD in humans.

Chemoprevention of nonalcoholic fatty liver disease by dietary natural compounds

Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver disease that is not from excess alcohol consumption, but is often associated with obesity, type 2 diabetes, and metabolic syndrome. NAFLD pathogenesis is complicated and involves oxidative stress, lipotoxicity, mitochondrial damage, insulin resistance, inflammation, and excessive dietary fat intake, which increase hepatic lipid influx and de novo lipogenesis and impair insulin signaling, thus promoting hepatic triglyceride accumulation and ultimately NAFLD. Overproduction of proinflammatory adipokines from adipose tissue also affects hepatic metabolic function. Current NAFLD therapies are limited; thus, much attention has been focused on identification of potential dietary substances from fruits, vegetables, and edible plants to provide a new strategy for NAFLD treatment. Dietary natural compounds, such as carotenoids, omega-3-PUFAs, flavonoids, isothiocyanates, terpenoids, curcumin, and resveratrol, act through a variety of mechanisms to prevent and improve NAFLD. Here, we summarize and briefly discuss the currently known targets and signaling pathways as well as the role of dietary natural compounds that interfere with NAFLD pathogenesis.

Superoxide release from contracting skeletal muscle in pulmonary TNF-α overexpression mice

Chronic obstructive pulmonary disease (COPD) often results in increased levels of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, which circulates in the blood. However, it is not clear whether pulmonary TNF-α overexpression (a COPD mimic) induces excessive reactive oxygen species (ROS) formation in skeletal muscle and thereby may contribute to the muscle impairment often seen in COPD. We hypothesized that ROS generation in contracting skeletal muscle is elevated when there is TNF-α overproduction in the lung and that this can induce muscle dysfunction. Cytochrome c (cyt c) in the perfusate was used to assay superoxide (O2(·-)) release from isolated contracting soleus muscles from transgenic mice of pulmonary TNF-α overexpression (Tg(+)) and wild-type (WT) mice. Our results showed that Tg(+) muscle released significantly higher levels of O2(·-) than WT during a period of intense contractile activity (in nmol/mg wt; 17.5 ± 2.3 vs. 4.4 ± 1.3, respectively; n = 5; P < 0.05). In addition, the soleus muscle demonstrated a significantly reduced fatigue resistance in Tg(+) mice compared with WT mice. Perfusion of the contracting soleus muscle with superoxide dismutase, which specifically scavenges O2(·-) in the perfusate, resulted in significantly less cyt c reduction, thereby indicating that the type of ROS released from the Tg(+) muscles is O2(·-). Our results demonstrate that pulmonary TNF-α overexpression leads to a greater O2(·-) release from contracting soleus muscle in Tg(+) compared with WT and that the excessive formation of O2(·-) in the contracting muscle of Tg(+) mice leads to earlier fatigue.

The aqueous extract of Ficus religiosa induces cell cycle arrest in human cervical cancer cell lines SiHa (HPV-16 Positive) and apoptosis in HeLa (HPV-18 positive)

Natural products are being extensively explored for their potential to prevent as well as treat cancer due to their ability to target multiple molecular pathways. Ficus religiosa has been shown to exert diverse biological activities including apoptosis in breast cancer cell lines. In the present study, we report the anti-neoplastic potential of aqueous extract of F. religiosa (FRaq) bark in human cervical cancer cell lines, SiHa and HeLa. FRaq altered the growth kinetics of SiHa (HPV-16 positive) and HeLa (HPV-18 positive) cells in a dose-dependent manner. It blocked the cell cycle progression at G1/S phase in SiHa that was characterized by an increase in the expression of p53, p21 and pRb proteins with a simultaneous decrease in the expression of phospho Rb (ppRb) protein. On the other hand, in HeLa, FRaq induced apoptosis through an increase in intracellular Ca(2+) leading to loss of mitochondrial membrane potential, release of cytochrome-c and increase in the expression of caspase-3. Moreover, FRaq reduced the migration as well as invasion capability of both the cervical cancer cell lines accompanied with downregulation of MMP-2 and Her-2 expression. Interestingly, FRaq reduced the expression of viral oncoproteins E6 and E7 in both the cervical cancer cell lines. All these data suggest that F. religiosa could be explored for its chemopreventive potential in cervical cancer.

Alterations in the redox state and liver damage: hints from the EASL Basic School of Hepatology

The importance of a correct balance between oxidative and reductive events has been shown to have a paramount effect on cell function for quite a long time. However, in spite of this body of rapidly growing evidence, the implication of the alteration of the redox state in human disease has been so far much less appreciated. Liver diseases make no exception. Although not fully comprehensive, this article reports what discussed during an EASL Basic School held in 2012 in Trieste, Italy, where the effect of the alteration of the redox state was addressed in different experimental and human models. This translational approach resulted in further stressing the concept that this topic should be expanded in the future not only to better understand how oxidative stress may be linked to a liver damage but also, perhaps more important, how this may be the target for better, more focused treatments. In parallel, understanding how alteration of the redox balance may be associated with liver damage may help define sensitive and ideally early biomarkers of the disorder.

Mitochondrial electron transport chain in heavy metal-induced neurotoxicity: effects of cadmium, mercury, and copper

To clarify the role of mitochondrial electron transport chain (mtETC) in heavy-metal-induced neurotoxicity, we studied action of Cd²⁺, Hg²⁺, and Cu²⁺ on cell viability, intracellular reactive oxygen species formation, respiratory function, and mitochondrial membrane potential of rat cell line PC12. As found, the metals produced, although in a different way, dose- and time-dependent changes of all these parameters. Importantly, Cd²⁺ beginning from 10 [mu]M and already at short incubation time (3 h) significantly inhibited the FCCP-uncoupled cell respiration; besides, practically the complete inhibition of the respiration was reached after 3 h incubation with 50 [mu]M Hg²⁺ or 500 [mu]M Cd²⁺, whereas even after 48 h exposure with 500 [mu]M Cu²⁺, only a 50% inhibition of the respiration occurred. Against the Cd²⁺-induced cell injury, not only different antioxidants and mitochondrial permeability transition pore inhibitors were protective but also such mtETC effectors as FCCP and stigmatellin (complex III inhibitor). However, all mtETC effectors used did not protect against the Hg²⁺- or Cu²⁺-induced cell damage. Notably, stigmatellin was shown to be one of the strongest protectors against the Cd²⁺-induced cell damage, producing a 15–20% increase in the cell viability. The mechanisms of the mtETC involvement in the heavy-metal-induced mitochondrial membrane permeabilization and cell death are discussed.

Some inflammatory cytokine levels, iron metabolism and oxidan stress markers in subjects with nonalcoholic steatohepatitis

OBJECTIVES

The relation between nonalcoholic steatohepatitis and iron metabolism is still controversial. Free fatty acids, iron, and other sources of oxidative stress probably result in cell damage, and necroinflammation mediated by various cytokines.

DESIGN AND METHODS

Sixty patients were diagnosed with NASH were included in the study, and the patient group was divided into three subgroups. Iron metabolism markers, inflammatory cytokines, including TNF-α, IL-6 and IL-8, MDA and nitric oxide levels were measured.

RESULTS

Serum ferritin, inflammatory cytokines, and oxidative stress markers were significantly higher in the patient group. Among three patient groups, divided according to the results of ultrasonic examination, there were significant changes with regard to these parameters.

CONCLUSION

The study results suggest that liver iron and fat accumulation, oxidant stres, and inflammatory cytokines are closely related. Therefore, levels of serum ferritin, MDA, IL-6, TNF-α and IL-8 could represent the indices of activity and progression of NASH.

Melatonin improves mitochondrial respiratory chain activity and liver morphology in ob/ob mice

In previous studies, we have shown that mitochondrial respiratory chain (MRC) activity is decreased in patients with nonalcoholic steatohepatitis and in ob/ob mice and that peroxynitrite plays a pathogenic role. The present study examined whether melatonin, a peroxynitrite scavenger, prevents: (i) the in vitro effects of peroxynitrite on normal mitochondrial proteins and (ii) the development of nonalcoholic liver disease, MRC dysfunction and proteomic changes found in the mitochondrial complexes from ob/ob mice. We studied MRC activity, assembly of mitochondrial complexes and its subunits in normal mitochondrial proteins exposed to peroxynitrite in the absence and presence of melatonin. The same studies were done in mitochondrial proteins from ob/ob mice untreated and treated with melatonin. Preincubation of mitochondrial proteins from wild-type mice with melatonin prevented 3-tyrosine nitration of these proteins, eliminated the reduction in the MRC activity, the defect in the assembly of mitochondrial complexes and degradation of their subunits induced by peroxynitrite in vitro. Moreover, treatment of ob/ob mice with 10 mg/kg/day melatonin for 12 wk reduced oxidative and nitrosative stress, prevented the loss of MRC activity, protected their complexes and subunits from degradation, and favored assembling of mitochondrial complexes. In addition, this treatment improved fatty liver, decreased hepatic triglyceride concentration and increased apolipoprotein B100 in liver tissue. In conclusion, melatonin prevents the effects of peroxynitrite on mitochondrial proteins in vitro and administration of melatonin to ob/ob mice normalizes liver morphology, mitochondrial dysfunction and assembly of MRC complexes.

Pathogenesis and biomarkers of carcinogenesis in ulcerative colitis

One of the most serious complications of ulcerative colitis is the development of colorectal cancer. Screening patients with ulcerative colitis by standard histological examination of random intestinal biopsy samples might be inefficient as a method of cancer surveillance. This Review focuses on the current understanding of the pathogenesis of ulcerative colitis-associated colorectal cancer and how this knowledge can be transferred into patient management to assist clinicians and pathologists in identifying patients with ulcerative colitis who have an increased risk of colorectal cancer. Inflammation-driven mechanisms of DNA damage, including the generation and effects of reactive oxygen species, microsatellite instability, telomere shortening and chromosomal instability, are reviewed, as are the molecular responses to genomic stress. We also discuss how these mechanisms can be translated into usable biomarkers. Although progress has been made in the understanding of inflammation-driven carcinogenesis, markers based on these findings possess insufficient sensitivity or specificity to be usable as reliable biomarkers for risk of colorectal cancer development in patients with ulcerative colitis. However, screening for mutations in p53 could be relevant in the surveillance of patients with ulcerative colitis. Several other new biomarkers, including senescence markers and α-methylacyl-CoA-racemase, might be future candidates for preneoplastic markers in ulcerative colitis.

Increase of reduced nicotinamide adenine dinucleotide fluorescence lifetime precedes mitochondrial dysfunction in staurosporine-induced apoptosis of HeLa cells

In vivo noninvasive detection of apoptosis represents a new tool that may yield a more definite diagnosis, a more accurate prognosis, and help improve therapies for human diseases. The intrinsic fluorescence of reduced nicotinamide adenine dinucleotide (NADH) may be a potential optical biomarker for the apoptosis detection because NADH is involved in the respiration for the mitochondrial membrane potential (ΔΨ) formation and adenosine-5'-triphosphate (ATP) synthesis, and the depletion of ΔΨ and ATP level is the hallmark of apoptosis. We have previously observed the NADH fluorescence lifetime change is associated with staurosporine (STS)-induced mitochondria-mediated apoptosis. However, its relationship with mitochondrial functions such as ΔΨ, ATP, and oxygen consumption rate is not clear. In this study, we investigated this relationship. Our results indicate that the NADH fluorescence lifetime increased when ΔΨ and ATP levels were equal to or higher than their values of controls and decreased before the depletion of ΔΨ and ATP, and the oxygen consumption rate did not change. These findings suggest that the increased NADH fluorescence lifetime in STS-induced cell death occurred before the depletion of ΔΨ and ATP and activation of caspase 3, and was not simply caused by cellular metabolic change. Furthermore, the NADH fluorescence lifetime change is associated with the pace of apoptosis.

Mitochondrial rejuvenation after induced pluripotency

Background

As stem cells of the early embryo mature and differentiate into all tissues, the mitochondrial complement undergoes dramatic functional improvement. Mitochondrial activity is low to minimize generation of DNA-damaging reactive oxygen species during pre-implantation development and increases following implantation and differentiation to meet higher metabolic demands. It has recently been reported that when the stem cell type known as induced pluripotent stem cells (IPSCs) are re-differentiated for several weeks in vitro, the mitochondrial complement progressively re-acquires properties approximating input fibroblasts, suggesting that despite the observation that IPSC conversion “resets” some parameters of cellular aging such as telomere length, it may have little impact on other age-affected cellular systems such as mitochondria in IPSC-derived cells.

Methodology/Principal Findings

We have examined the properties of mitochondria in two fibroblast lines, corresponding IPSCs, and fibroblasts re-derived from IPSCs using biochemical methods and electron microscopy, and found a dramatic improvement in the quality and function of the mitochondrial complement of the re-derived fibroblasts compared to input fibroblasts. This observation likely stems from two aspects of our experimental design: 1) that the input cell lines used were of advanced cellular age and contained an inefficient mitochondrial complement, and 2) the re-derived fibroblasts were produced using an extensive differentiation regimen that may more closely mimic the degree of growth and maturation found in a developing mammal.

Conclusions/Significance

These results — coupled with earlier data from our laboratory — suggest that IPSC conversion not only resets the “biological clock”, but can also rejuvenate the energetic capacity of derived cells.

Mechanisms of non-alcoholic steatohepatitis: pathophysiology and molecular biology

Non-alcoholic steatohepatitis (NASH), characterized by liver fatty infiltration, inflammation, hepatocellular injury and fibrosis, may easily develop into liver cirrhosis and hepatocellular carcinoma. The increased flow of FFAs (free fatty acids) to the liver and the de novo lipogenesis in the liver lead to fat overload. Lipotoxicity can induce oxidative stress, inflammatory reaction and apoptosis. Subsequently chronic liver injury activates a fibrogenic response that accelerates the evolution of NASH towards end-stage liver disease. Further research on pathophysiology and molecular biology is beneficial to clinical diagnosis and management of NASH.

Oxidative stress and hepatic injury

Oxidative stress, initiated by reactive oxygen species, is the collective pathophysiological mechanism of many hepatopathies. Oxidative stress results in hepatic injury mainly by priming lipid peroxidation to change the function of biological membrane, covalent immobilization of biomacromolecules and destroying the enzyme activity considering cytokine (TNF-α and NF-κB) interaction. The role of oxidative stress in many hepatopathies such as fatty liver desease, viral hepatitis, hepatic fibrosis is innegligible.

Mitochondrial complex III is involved in proapoptotic BAK-induced microvascular endothelial cell hyperpermeability

It has been shown that the intrinsic mitochondrial apoptotic cascade is activated in vascular hyperpermeability after conditions such as hemorrhagic shock. Studies from our laboratory demonstrated mitochondrial reactive oxygen species (ROS) formation in endothelial cells during vascular hyperpermeability. We hypothesized that the participation of mitochondrial ROS in the intrinsic apoptotic cascade results in microvascular endothelial cell hyperpermeability. The purpose of this study was to identify the site(s) of ROS formation in the mitochondrial complex(es) that leads to hyperpermeability. Rat lung microvascular endothelial cell monolayers were pretreated with inhibitors of the complex(es) (I-V) before the activation of the mitochondrial apoptotic cascade using the proapoptotic peptide BAK (BH3). Inhibitors of the xanthine oxidase, nicotinamide adenine dinucleotide phosphate (reduced form) oxidase, NOS, and cytochrome P-450 monooxygenase were also studied. The hyperpermeability was determined by the fluorescence of fluorescein isothiocyanate-albumin that leaked across endothelial cells and ROS production by 2',7& rime;-dichlorofluorescein diacetate. Cytochrome c levels were also measured. BAK (BH3)-transfected cells showed increased ROS, cytosolic cytochrome c, and hyperpermeability (P<0.05). Complex III inhibitors antimycin A (10 microM) and stigmatellin (10 microM) attenuated BAK (BH3)-mediated ROS formation and hyperpermeability (P<0.05). The complex III inhibition decreased BAK (BH3)-mediated cytochrome c release. The results suggest that mitochondrial ROS formation, particularly at respiratory chain complex III, is involved in BAK-induced monolayer hyperpermeability.

Phyllanthus urinaria ameliorates the severity of nutritional steatohepatitis both in vitro and in vivo

Hepatic oxidative stress plays a critical role in metabolic forms of steatohepatitis. Phyllanthus urinaria, an herbal medicine, has been reported to have potential antioxidant properties. We tested the effects of P. urinaria on nutritional steatohepatitis both in vitro and in vivo. Immortalized normal hepatocytes (AML-12) or primary hepatocytes were exposed to control, the methionine-and-choline-deficient (MCD) culture medium, in the presence or absence of P. urinaria for 24 hours. Hepatocyte triglyceride, release of alanine aminotransferase, lipoperoxides, and reactive oxygen species production were determined. Age-matched C57BL/6 and db/db mice were fed control or MCD diet for 10 days with or without P. urinaria. Hepatic steatosis, necroinflammation, triglycerides, and lipid peroxide levels were determined. Hepatic expression of inflammatory factors and lipid regulatory mediators were assayed. P. urinaria reduced steatosis and alanine aminotransferase (ALT) levels in culture of hepatocytes in a dose-dependent manner. Phyllanthus prevented MCD-induced hepatic fat accumulation and steatohepatitis in mice. This effect was associated with repressed levels of hepatic lipid peroxides, reduced expression of cytochrome P450-2E1, pro-inflammatory tumor necrosis factor alpha, interleukin-6, dampened activation of inflammatory c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-kappaB), increased expression of lipolytic cytochrome P450 (Cyp4a10), and suppressed transcriptional activity of lipogenic CCAAT/enhancer binding protein beta (C/EBPbeta). Hepatic acyl co-enzyme A oxidase that regulated hepatic beta-oxidation of fatty acid and other lipid regulators were not affected by P. urinaria. In conclusion, P. urinaria effectively alleviated the steatohepatitis induced by the MCD, probably through dampening oxidative stress, ameliorating inflammation, and decreasing lipid accumulation.

Molecular basis and mechanisms of progression of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH), a cause of cirrhosis and hepatocellular carcinoma, is characterized by fatty infiltration of the liver, inflammation, hepatocellular damage and fibrosis. Progress has been made in understanding the molecular and cellular mechanisms implicated in the pathogenesis of this condition, therefore, we here review recent developments regarding the basic mechanisms of NASH development. Accumulation of triglycerides in the hepatocytes is the result of increased inflow of free fatty acids and de novo lipogenesis. Steatosis leads to lipotoxicity, which causes apoptosis, necrosis, generation of oxidative stress and inflammation. The resulting chronic injury activates a fibrogenic response that leads eventually to end-stage liver disease. A better understanding of these mechanisms is crucial for the design of novel diagnostic and therapeutic strategies.

Herpes simplex virus type 1 infection induces oxidative stress and the release of bioactive lipid peroxidation by-products in mouse P19N neural cell cultures

To determine whether herpes simplex virus type 1 (HSV-1) infection causes oxidative stress and lipid peroxidation in cultured neural cells, mouse P19 embryonal carcinoma cells were differentiated into cells with neural phenotypes (P19N cells) by retinoic acid and were then infected with HSV-1. Cellular levels of reactive oxygen species (ROS) and the release of lipid peroxidation by-products into the tissue culture medium were then measured by the generation of fluorescent markers hydroxyphenyl fluorescein and a stable chromophore produced by lipid peroxidation products, malondialdehyde (MDA) and hydroxyalkenals (4-HAEs; predominantly 4-hydroxy-2-nonenal [HNE]), respectively. HSV-1 infection increased ROS levels in neural cells as early as 1 h post infection (p.i.) and ROS levels remained elevated at 24 h p.i. This viral effect required viral entry and replication as heat- and ultraviolet light-inactivated HSV-1 were ineffective. HSV-1 infection also was associated with increased levels of MDA/HAE in the culture medium at 2 and 4 h p.i., but MDA/HAE levels were not different from those detected in mock infected control cultures at 1, 6, and 24 h p.i. HSV-1 replication in P19N cells was inhibited by the antioxidant compound ebselen and high concentrations of HNE added to the cultures, but was increased by low concentrations of HNE. These findings indicate that HSV-1 infection of neural cells causes oxidative stress that is required for efficient viral replication. Furthermore, these observations raise the possibility that soluble, bioactive lipid peroxidation by-products generated in infected neural cells may be important regulators of HSV-1 pathogenesis in the nervous system.

Nonalcoholic fatty liver disease and mitochondrial dysfunction

Nonalcoholic fatty liver disease (NAFLD) includes hepatic steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. NAFLD is the most common liver disorder in the United States and worldwide. Due to the rapid rise of the metabolic syndrome, the prevalence of NAFLD has recently dramatically increased and will continue to increase. NAFLD has also the potential to progress to hepatocellular carcinoma (HCC) or liver failure. NAFLD is strongly linked to caloric overconsumption, physical inactivity, insulin resistance and genetic factors. Although significant progress in understanding the pathogenesis of NAFLD has been achieved in years, the primary metabolic abnormalities leading to lipid accumulation within hepatocytes has remained poorly understood. Mitochondria are critical metabolic organelles serving as “cellular power plants”. Accumulating evidence indicate that hepatic mitochondrial dysfunction is crucial to the pathogenesis of NAFLD. This review is focused on the significant role of mitochondria in the development of NAFLD.

Release of arachidonic acid induced by tumor necrosis factor-alpha in the presence of caspase inhibition: evidence for a cytosolic phospholipase A2alpha-independent pathway

Stimulation of L929 cells with tumor necrosis factor-alpha (TNFalpha) caused cell death accompanied by a release of arachidonic acid (AA). Although the inhibition of caspases has been shown to cause necrosis in TNFalpha-treated L929 cells, its role in the TNFalpha-induced release of AA has not been elucidated. The release of AA is tightly regulated by phospholipase A(2) (PLA(2)). To find out the mechanisms underlying the TNFalpha-induced release of AA, we investigated the relationship between TNFalpha stimulation and PLA(2) regulation with and without zVAD, an inhibitor of caspases. In the present study, we found that treatment with TNFalpha and zVAD stimulated release of AA and cell death in C12 cells (a variant of L929 cells lacking alpha type of cytosolic PLA(2) (cPLA(2)alpha)). Stimulation with TNFalpha/zVAD also caused the release of AA from L929-cPLA(2)alpha-siRNA cells. Treatment with pyrrophenone (a selective inhibitor of cPLA(2)alpha) completely inhibited the TNFalpha-induced release of AA, but only partially inhibited the TNFalpha/zVAD-induced response in L929 cells. The TNFalpha/zVAD-induced release of AA from C12 and L929-cPLA(2)alpha-siRNA cells was pyrrophenone-insensitive, but inhibited by treatment with butylated hydroxyanisole (BHA, an antioxidant). Treatment with dithiothreitol, which inactivates secretory PLA(2) activity, decreased the amount of AA released by TNFalpha/zVAD. TNFalpha/zVAD appears to stimulate release of AA from C12 cells in a cPLA(2)alpha-independent, BHA-sensitive manner. The possible roles of secretory PLA(2) and reactive oxygen species from different pools in the release of AA and cell death were discussed.

Effects of rosiglitazone on the liver histology and mitochondrial function in ob/ob mice

Insulin resistance is present in almost all patients with nonalcoholic steatohepatitis (NAFLD), and mitochondrial dysfunction likely plays a critical role in the progression of fatty liver into nonalcoholic steatohepatitis. Rosiglitazone, a selective ligand of peroxisome proliferator-activated receptor gamma (PPARgamma), is an insulin sensitizer drug that has been used in a number of insulin-resistant conditions, including NAFLD. The aim of this study was to analyze the effects of rosiglitazone on the liver histology and mitochondrial function in a model of NAFLD. All studies were carried out in wild-type and leptin-deficient (ob/ob) C57BL/6J mice. Ob/ob mice were treated with 1 mg/kg/day, and activity of mitochondrial respiratory chain (MRC), beta-oxidation, lipid peroxidation, glutathione content in mitochondria, and 3-tyrosine-nitrated proteins in mitochondria were measured. In addition, histological and ultrastructural changes induced by rosiglitazone were also noted. Rosiglitazone treatment increased liver steatosis, particularly microvesicular steatosis. In these animals, mitochondria were markedly swollen with cristae peripherally placed. In ob/ob mice, this drug increased PPARgamma protein expression and lipid peroxide content in liver tissue and decreased glutathione concentration in mitochondria. Rosiglitazone suppressed the activity of complex I of the MRC in ob/ob mice, but did not affect beta-oxidation. 3-Tyrosine nitrated mitochondrial proteins, significantly increased in ob/ob mice, were not modified by rosiglitazone treatment.

CONCLUSION

Treatment of ob/ob mice with rosiglitazone did not reverse histological lesions of NAFLD or improve MRC activity. On the contrary, rosiglitazone reduced activity of complex I and increased oxidative stress and liver steatosis.

A growing burden: the pathogenesis, investigation and management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic disorder in western countries, and its incidence is increasing. This review outlines the significant health burden posed by NAFLD and discusses what is presently known about its pathogenesis, including the roles of the metabolic syndrome, obesity, insulin resistance, hepatic steatosis, reactive oxygen species, inflammatory cytokines and adipocytokines. The way in which NAFLD is clinically diagnosed is described, and areas of uncertainty surrounding its investigation are identified, before discussing the relative merits of the limited treatment options available and looking ahead to potential therapeutic strategies for the future.

Integrin-mediated cell adhesion and spreading engage different sources of reactive oxygen species

The tightly regulated production of intracellular reactive oxygen species (ROS) participates in several biologic processes such as cellular growth, programmed cell death, senescence, and adhesion. It is increasingly evident that the same enzymatic processes that were originally linked to ROS generation during host defence or apoptosis execution are also involved in redox-mediated signal transduction. We investigated in murine NIH3T3 fibroblasts the contribution of a variety of redox-dependent events during signal transduction initiated by integrin engagement due to fibronectin stimulation and report that a mitochondrial ROS release occurs, strictly confined to the early phase of extracellular matrix (ECM) contact (10 min). Besides, 5-lipoxygenase (5-LOX) is engaged by integrin receptor ligation as another ROS source, contributing to the more-intense, second ROS burst (45 min), possibly orchestrating the spreading of cells in response to ECM contact. To define a potential mechanism for ROS signaling, we demonstrate that on integrin recruitment, the Src homology-2 domain-containing phosphatase 2 (SHP-2) undergoes a reversible oxidization/inactivation to which mitochondrial and 5-lipoxygenase ROS contribute differentially. In keeping with a key role of oxidants during integrin signaling, the inactivation of SHP-2 prevents the dephosphorylation and inactivation of SHP-2 substrates (p125FAK and SHPS-1), thus enabling the continued propagation of the signal arising by integrin engagement.

Tumor necrosis factor-alpha is a potent endogenous mutagen that promotes cellular transformation

Tumor necrosis factor-alpha (TNF-alpha) is an important inflammation cytokine without known direct effect on DNA. In this study, we found that TNF-alpha can cause DNA damages through reactive oxygen species. The mutagenic effect of TNF-alpha is comparable with that of ionizing radiation. TNF-alpha treatment in cultured cells resulted in increased gene mutations, gene amplification, micronuclei formation, and chromosomal instability. Antioxidants significantly reduced TNF-alpha-induced genetic damage. TNF-alpha also induced oxidative stress and nucleotide damages in mouse tissues in vivo. Moreover, TNF-alpha treatment alone led to increased malignant transformation of mouse embryo fibroblasts, which could be partially suppressed by antioxidants. As TNF-alpha is involved in chronic inflammatory diseases, such as chronic hepatitis, ulcerative colitis, and chronic skin ulcers, and these diseases predispose the patients to cancer development, our results suggest a novel pathway through which TNF-alpha promotes cancer development through induction of gene mutations, in addition to the previously reported mechanisms, in which nuclear factor-kappaB activation was implicated.

Uric acid and anti-TNF antibody improve mitochondrial dysfunction in ob/ob mice

The mechanisms responsible for low mitochondrial respiratory chain (MRC) activity in the liver of patients with nonalcoholic steatohepatitis are unknown. In this study, we examined the cause of this dysfunction in ob/ob mice. Forty-six mice were distributed in six groups: group I: C57BL/6J mice; group II: C57BL/6J Lep(-/-) mice (ob/ob); group III, ob/ob mice treated with manganese [III] tetrakis (5,10,15,20 benzoic acid) porphyrin (MnTBAP); group IV, ob/ob mice treated with IgG1 immunoglobulin; group V, ob/ob mice treated with anti-TNF antibody; group VI: ob/ob mice treated with uric acid. In liver tissue, we measured MRC activity, fatty acid beta-oxidation, tumor necrosis factor (TNF), inducible nitric oxide synthase (iNOS), 3-tyrosine-nitrated proteins, 3-tyrosine-nitrated mitochondrial proteins, including cytochrome c and ND4 subunit of complex I. MRC activity was decreased in ob/ob mice. TNF levels, iNOS protein expression, and tyrosine nitrated proteins were markedly increased in the liver of ob/ob mice. In these animals, mitochondrial proteins were markedly tyrosine nitrated, particularly the ND4 subunit of complex I and cytochrome c. Treatment of these animals with uric acid, a peroxynitrite scavenger, anti-TNF antibody, or MnTBAP decreased tyrosine nitrated proteins, improved the activity of MRC complexes, and led to a marked regression of hepatic steatosis and inflammation. In conclusion, MRC dysfunction and liver lesions found in ob/ob mice are likely to reflect the tyrosine nitration of mitochondrial proteins by peroxynitrite or a peroxynitrite-derivate radical. Increased hepatic TNF and iNOS expression might enhance peroxynitrite formation and inhibition of MRC complexes.

Production of lipid peroxidation products in osteoarthritic tissues: new evidence linking 4-hydroxynonenal to cartilage degradation

OBJECTIVE

The lipid peroxidation product 4-hydroxynonenal (HNE) is prominently produced in osteoarthritic (OA) synovial cells, but its specific contribution to cartilage destruction is not understood. This study was designed to test whether HNE signaling and binding are involved in OA cartilage degradation through type II collagen (CII) and matrix metalloproteinase 13 (MMP-13) modulation.

METHODS

HNE levels in synovial fluid and in isolated OA chondrocytes treated with free radical donors were determined by enzyme-linked immunosorbent assay. The formation of the HNE/CII adducts was measured in cartilage explants by immunoprecipitation. Levels of CII and MMP-13 messenger RNA and protein were determined by reverse transcription-polymerase chain reaction, Western blotting, and by the use of commercial kits.

RESULTS

Levels of HNE/protein adducts were higher in OA synovial fluid compared with normal synovial fluid and were higher in OA chondrocytes treated with free radical donors compared with untreated cells. In cartilage explants, HNE induced CII cleavage, as established by the generation of neoepitopes. The level of HNE/CII adducts was increased in OA cartilage explants incubated with free radical donors. Modification of CII by HNE accelerated its degradation by active MMP-13. In isolated OA chondrocytes, HNE inhibited the expression of CII and tissue inhibitor of metalloproteinases 1 and induced MMP-13 mainly through activation of p38 MAPK. In vitro, HNE binding to MMP-13 activated this enzyme at a molar ratio of 1:100 (MMP-13 to HNE).

CONCLUSION

The increased level of HNE in OA cartilage and the ability of HNE to induce transcriptional and posttranslational modifications of CII and MMP-13 suggest that this aldehyde could play a role in OA.

Reactive oxygen species production by mitochondria in endothelial cells exposed to reoxygenation after hypoxia and glucose depletion is mediated by ceramide

In endothelium, reoxygenation after hypoxia (H/R) has been shown to induce production of reactive oxygen species (ROS) by complex III of the mitochondrial respiratory chain. The purpose of the present study was to test the involvement of ceramide in this phenomenon. Human umbilical vein endothelial cells underwent 2 h of hypoxia (Po2, ∼20 mmHg) without glucose and 1 h of reoxygenation (Po2, ∼120 mmHg) with glucose. ROS production was measured by the fluorescent marker 2′,7′-dichlorodihydrofluorescein diacetate, and cell death by propidium iodide. We showed that 1) after 1 h of reoxygenation, fluorescence had risen and that ROS production was inhibited by desipramine, an inhibitor of sphingomyelinase, an enzyme responsible for ceramide production (126 ± 7% vs. 48 ± 12%, P < 0.05); 2) administration of ceramide ( N-acetylsphingosine) per se (i.e., in the absence of H/R) induced ROS production (65 ± 3%), which was inhibited by complex III inhibitor: antimycin A (24 ± 3%, P < 0.0001), or stigmatellin (31 ± 2%, P < 0.0001); 3) hypoxia/reoxygenation-induced ROS production was not affected by either ceramide-activated protein kinase inhibitor dimethyl aminopurine or mitochondrial permeability transition inhibitor cyclosporin A but was significantly inhibited by the antiapoptotic protein Bcl-2 (82 ± 8%, P < 0.05); 4) ceramide-induced ROS production was also inhibited by Bcl-2 (41 ± 4%, P < 0.0001). These results demonstrate that in endothelial cells submitted to hypoxia and glucose depletion followed by reoxygenation with glucose, the pathway implicated in mitochondrial complex III ROS production is ceramide dependent and is decreased by the antiapoptotic protein Bcl-2.