4-hydroxynonenal triggers an epidermal growth factor receptor-linked signal pathway for growth inhibition

Reactive Carbonyl Species and Protein Lipoxidation in Atherogenesis

Atherosclerosis is a multifactorial disease of medium and large arteries, characterized by the presence of lipid-rich plaques lining the intima over time. It is the main cause of cardiovascular diseases and death worldwide. Redox imbalance and lipid peroxidation could play key roles in atherosclerosis by promoting a bundle of responses, including endothelial activation, inflammation, and foam cell formation. The oxidation of polyunsaturated fatty acids generates various lipid oxidation products such as reactive carbonyl species (RCS), including 4-hydroxy alkenals, malondialdehyde, and acrolein. RCS covalently bind to nucleophilic groups of nucleic acids, phospholipids, and proteins, modifying their structure and activity and leading to their progressive dysfunction. Protein lipoxidation is the non-enzymatic post-translational modification of proteins by RCS. Low-density lipoprotein (LDL) oxidation and apolipoprotein B (apoB) modification by RCS play a major role in foam cell formation. Moreover, oxidized LDLs are a source of RCS, which form adducts on a huge number of proteins, depending on oxidative stress intensity, the nature of targets, and the availability of detoxifying systems. Many systems are affected by lipoxidation, including extracellular matrix components, membranes, cytoplasmic and cytoskeletal proteins, transcription factors, and other components. The mechanisms involved in lipoxidation-induced vascular dysfunction are not fully elucidated. In this review, we focus on protein lipoxidation during atherogenesis.

Lipid Peroxidation Products Influence Calpain-1 Functionality In Vitro by Covalent Binding

The objective of the current study was to evaluate the effects of lipid peroxidation products, malondialdehyde (MDA), hexenal, and 4-hydroxynonenal (HNE), on calpain-1 function, and liquid chromatography and tandem mass spectrometry (LC-MS/MS) identification of adducts on calpain-1. Calpain-1 activity slightly increased after incubation with 100 μM MDA but not with 500 and 1000 μM MDA. However, calpain-1 activity was lowered by hexenal and HNE at 100, 500, and 1000 μM. No difference in calpain-1 autolysis was observed between the control and 1000 μM MDA. However, 1000 μM hexenal and HNE treatments slowed the calpain-1 autolysis. Adducts of MDA were detected on glutamine, arginine, lysine, histidine, and asparagine residues via Schiff base formation, while HNE adducts were detected on histidine, lysine, glutamine, and asparagine residues via Michael addition. These results are the first to demonstrate that lipid peroxidation products can impact calpain-1 activity in a concentration-dependent manner and may impact the development of meat tenderness postmortem.

IL-10 attenuates OxPCs-mediated lipid metabolic responses in ischemia reperfusion injury

Oxidized phospholipids (OxPLs) promote inflammation as well as low density lipoprotein (LDL) uptake in a variety of physiological and pathological states. Given the anti-inflammatory role of the cytokine IL-10, we investigated its modulatory effect on the production of oxidized phosphatidylcholines (OxPCs) as well as lipid metabolic responses in global myocardial ischemia/reperfusion (I/R) injury. Increased OxPCs levels, by 1-Palmitoyl-2-(5-oxovaleryl)-sn-glycero-3-phosphocholine (POVPC), promoted oxidative stress (OS) and cell death. OxPCs-mediated-OS, resulted in oxidized low-density lipoprotein receptor 1 (LOX-1) activation and upregulated the expression of toll-like receptor 2 (TLR2). IL-10-induced increase in proprotein convertase subtilisin/kexin type 9 (PCSK9) negatively regulated LOX-1 as well as TLR2 inflammatory responses. Under stress conditions, phosphorylation of sterol regulatory element binding protein 1c (SREBP 1c) was prevented by IL-10. The latter also prevented the generation of OxPCs and reduced their ratio (OxPCs/PCs) during injury. LOX-1 activation also promoted SREBP1c-mediated TGF-βRII expression which was inhibited by IL-10. Both fragmented and non-fragmented OxPCs were elevated during I/R and this effect was attenuated by IL-10. The largest impact (two–threefold change at log₂) was on PAzPC, (1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine)—a fragmented OxPC. Thus it appears that among different OxPCs, IL-10 significantly reduces a single molecule (PAzPC)-mediated lipid metabolic responses in cardiomyocytes thereby mitigating inflammation and cell death.

Detection of HNE Modification of Proteins in Aging Mouse Tissues: A Western Blot-Based Approach

4-Hydroxenonenal (HNE) is one of the major α,β-unsaturated aldehyde products of lipid peroxidation. HNE can form conjugates with macromolecules, including protein, and thereby alter their function. HNE and its conjugation with proteins are increased in aging and age-related diseases. To elucidate how HNE is involved in these aging-related pathophysiological changes, it is necessary to assess HNE modification of proteins. Here a simple and convenient Western-blot based method is presented to detect HNE modification of proteins in tissues of aging mice.

Lipoxidation and cancer immunity

Lipoxidation is a well-known reaction between electrophilic carbonyl species, formed during oxidation of lipids, and specific proteins that, in most cases, causes an alteration in proteins function. This can occur under physiological conditions but, in many cases, it has been associated to pathological process, including cancer. Lipoxidation may have an effect in cancer development through their effects in tumour cells, as well as through the alteration of immune components and the consequent modulation of the immune response. The formation of protein adducts affects different proteins in cancer, triggering different mechanism, such as proliferation, cell differentiation and apoptosis, among others, altering cancer progression. The divergent results obtained documented that the formation of lipoxidation adducts can have either anti-carcinogenic or pro-carcinogenic effects, depending on the cell type affected and the specific adduct formed. Moreover, lipoxidation adducts may alter the immune response, consequently causing either positive or negative alterations in cancer progression. Therefore, in this review, we summarize the effects of lipoxidation adducts in cancer cells and immune components and their consequences in the evolution of different types of cancer.

Lipoproteins as targets and markers of lipoxidation

Lipoproteins are essential systemic lipid transport particles, composed of apolipoproteins embedded in a phospholipid and cholesterol monolayer surrounding a cargo of diverse lipid species. Many of the lipids present are susceptible to oxidative damage by lipid peroxidation, giving rise to the formation of reactive lipid peroxidation products (rLPPs). In view of the close proximity of the protein and lipid moieties within lipoproteins, the probability of adduct formation between rLPPs and amino acid residues of the proteins, a process called lipoxidation, is high. There has been interest for many years in the biological effects of such modifications, but the field has been limited to some extent by the availability of methods to determine the sites and exact nature of such modification. More recently, the availability of a wide range of antibodies to lipoxidation products, as well as advances in analytical techniques such as liquid chromatography tandem mass spectrometry (LC-MSMS), have increased our knowledge substantially. While most work has focused on LDL, oxidation of which has long been associated with pro-inflammatory responses and atherosclerosis, some studies on HDL, VLDL and Lipoprotein(a) have also been reported. As the broader topic of LDL oxidation has been reviewed previously, this review focuses on lipoxidative modifications of lipoproteins, from the historical background through to recent advances in the field. We consider the main methods of analysis for detecting rLPP adducts on apolipoproteins, including their advantages and disadvantages, as well as the biological effects of lipoxidized lipoproteins and their potential roles in diseases.

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Lipoproteins can be modified by reactive Lipid Peroxidation Products (rLPPs).

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Lipoprotein lipoxidation is known to occur in several inflammatory diseases.

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Biochemical, immunochemical and mass spectrometry methods can detect rLPP adducts.

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Due to higher information output, MS can facilitate localization of modifications.

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Antibodies against some rLPPs have been used to identify lipoxidation in vivo.

S-metolachlor promotes oxidative stress in green microalga Parachlorella kessleri - A potential environmental and health risk for higher organisms

The estimation of the toxic influences of herbicide products on non-target aquatic organisms is essential for evaluation of environmental contamination. We assessed the effects of the herbicide S-metolachlor (S-MET) on unicellular green microalga Parachlorella kessleri during 4-72 in vitro exposure to concentrations in the range 2-200μg/L. The results have shown that S-MET had a significant effect on algae, even in doses 10 and 20 times lower than the EC50 values obtained for P. kessleri (EC50-72h=1090μg/L). It generates reactive oxygen species in algae, decreases their growth and photosynthetic pigment concentration, changes their ultrastructure and alters the cellular antioxidant defence capacities. The levels of protein adducts with the reactive aldehyde 4-hydroxy-2-nonenal (HNE), the end-product of lipid peroxidation, were significantly elevated in S-MET treated cells revealing the insufficient effectiveness of P. kessleri antioxidant mechanisms and persistent lipid peroxidation. Since algae are fundamental aquatic food component, the damaged algal cells, still capable of dividing while having persistently increased content of HNE upon S-MET contamination could represent an important environmental toxic factor that might further affect higher organisms in the food chain.

Proatherogenic effects of 4-hydroxynonenal

4-hydroxy-2-nonenal (HNE) is a α,β-unsaturated hydroxyalkenal generated by peroxidation of n-6 polyunsaturated fatty acid. This reactive carbonyl compound exhibits a huge number of biological properties that result mainly from the formation of HNE-adducts on free amino groups and thiol groups in proteins. In the vascular system, HNE adduct accumulation progressively leads to cellular dysfunction and tissue damages that are involved in the progression of atherosclerosis and related diseases. HNE contributes to the atherogenicity of oxidized LDL, by forming HNE-apoB adducts that deviate the LDL metabolism to the scavenger receptor pathway of macrophagic cells, and lead to the formation of foam cells. HNE activates transcription factors (Nrf2, NF-kappaB) that (dys)regulate various cellular responses ranging from hormetic and survival signaling at very low concentrations, to inflammatory and apoptotic effects at higher concentrations. Among a variety of cellular targets, HNE can modify signaling proteins involved in atherosclerotic plaque remodeling, particularly growth factor receptors (PDGFR, EGFR), cell cycle proteins, mitochondrial and endoplasmic reticulum components or extracellular matrix proteins, which progressively alters smooth muscle cell proliferation, angiogenesis and induces apoptosis. HNE adducts accumulate in the lipidic necrotic core of advanced atherosclerotic lesions, and may locally contribute to macrophage and smooth muscle cell apoptosis, which may induce plaque destabilization and rupture, thereby increasing the risk of athero-thrombotic events.

4-hydroxynonenal-mediated signaling and aging

4-Hydroxy-2-nonenal (HNE), one of the major α, β-unsaturated aldehydes produced during lipid peroxidation, is a potent messenger in mediating signaling pathways. Lipid peroxidation and HNE production appear to increase with aging. Although the cause and effect relation remains arguable, aging is associated with significant changes in diverse signaling events, characterized by enhanced or diminished responses of specific signaling pathways. In this review we will discuss how HNE may contribute to aging-related alterations of signaling pathways.

Signaling by 4-hydroxy-2-nonenal: Exposure protocols, target selectivity and degradation

4-hydroxy-2-nonenal (HNE), a major non-saturated aldehyde product of lipid peroxidation, has been extensively studied as a signaling messenger. In these studies a wide range of HNE concentrations have been used, ranging from the unstressed plasma concentration to far beyond what would be found in actual pathophysiological condition. In addition, accumulating evidence suggest that signaling protein modification by HNE is specific with only those proteins with cysteine, histidine, and lysine residues located in certain sequence or environments adducted by HNE. HNE-signaling is further regulated through the turnover of HNE-signaling protein adducts through proteolytic process that involve proteasomes, lysosomes and autophagy. This review discusses the HNE concentrations and exposure modes used in signaling studies, the selectivity of the HNE-adduction site, and the turnover of signaling protein adducts.

[Development of Preventive Therapy by Clarification of Mechanisms of Environmental-Factor-Mediated Diseases]

Environmental factors affecting human health are generally classified into physical, chemical and biological factors. In this review article, we focus on ultraviolet (UV) as a physical factor, heavy metals as a chemical factor and Japanese cedar pollens as a biological factor. Since we believe that progress based on both fieldwork research and experimental research is essential in hygiene study, we included the results of both the research approached. We first introduced the mechanism of development of and prevention of UV-mediated skin melanoma in our experimental research after showing our epidemiological research on UV-mediated DNA damage in humans. We then introduced our evaluation of toxicity and development of a remediation system in our experimental research on heavy metals after showing our fieldwork research for the monitoring of drinking water from wells in Asian countries. We finally introduced the results of pathogenic analysis of pollinosis in our clinical study. We would be very happy if young researchers would re-realize the importance of experimental research as well as epidemiological research in hygiene study.

Role of 4-hydroxynonenal-protein adducts in human diseases

SIGNIFICANCE

Oxidative stress provokes the peroxidation of polyunsaturated fatty acids in cellular membranes, leading to the formation of aldheydes that, due to their high chemical reactivity, are considered to act as second messengers of oxidative stress. Among the aldehydes formed during lipid peroxidation (LPO), 4-hydroxy-2-nonenal (HNE) is produced at a high level and easily reacts with both low-molecular-weight compounds and macromolecules, such as proteins and DNA. In particular, HNE-protein adducts have been extensively investigated in diseases characterized by the pathogenic contribution of oxidative stress, such as cancer, neurodegenerative, chronic inflammatory, and autoimmune diseases.

RECENT ADVANCES

In this review, we describe and discuss recent insights regarding the role played by covalent adducts of HNE with proteins in the development and evolution of those among the earlier mentioned disease conditions in which the functional consequences of their formation have been characterized.

CRITICAL ISSUES

Results obtained in recent years have shown that the generation of HNE-protein adducts can play important pathogenic roles in several diseases. However, in some cases, the generation of HNE-protein adducts can represent a contrast to the progression of disease or can promote adaptive cell responses, demonstrating that HNE is not only a toxic product of LPO but also a regulatory molecule that is involved in several biochemical pathways.

FUTURE DIRECTIONS

In the next few years, the refinement of proteomical techniques, allowing the individuation of novel cellular targets of HNE, will lead to a better understanding the role of HNE in human diseases.

Overview on major lipid peroxidation bioactive factor 4-hydroxynonenal as pluripotent growth-regulating factor

The reactive aldehyde 4-hydroxynonenal (HNE) is major bioactive marker of lipid peroxidation generated under oxidative stress from polyunsaturated fatty acids. Biomedical significance of HNE was first revealed in pathogenesis of various degenerative and malignant diseases. Thus, HNE was considered for decades only as cytotoxic molecule, "second toxic messenger of free radicals" responsible for numerous undesirable consequences of oxidative stress. However, the increase of knowledge on physiology of redox signaling revealed also desirable, physiological roles of HNE, especially in the field of cellular signaling pathways regulating proliferation, differentiation, and apoptosis. These pluripotent effects of HNE can be explained by its concentration-dependent interactions with the cytokine networks and complex cellular antioxidant systems also showing cell and tissue specificities. Therefore, this paper gives a comprehensive, yet short overview on HNE as pluripotent growth-regulating factor.

Immune response to chemically modified proteome

Both enzymatic and nonenzymatic PTMs of proteins involve chemical modifications. Some of these modifications are prerequisite for the normal functioning of cell, while other chemical modifications render the proteins as "neo-self" antigens, which are recognized as "non-self" leading to aberrant cellular and humoral immune responses. However, these modifications could be a secondary effect of autoimmune diseases, as in the case of type I diabetes, hyperglycemia leads to protein glycation. The enigma of chemical modifications and immune response is akin to the "chick-and-egg" paradox. Nevertheless, chemical modifications regulate immune response. In some of the well-known autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis, chemically modified proteins act as autoantigens forming immune complexes. In some instances, chemical modifications are also involved in regulating immune response during pathogen infection. Further, the usefulness of proteomic analysis of immune complexes is briefly discussed.

Role of 4-hydroxynonenal and its metabolites in signaling

Available evidence from a multitude of studies on the effects of 4-hydroxynonenal (HNE) on cellular processes seem to converge on some common themes: (i) concentration-dependent opposing effects of HNE on key signaling components (e.g. protein kinase C, adenylate cyclase) predict that certain constitutive levels of HNE may be needed for normal cell functions - lowering of this constitutive HNE level in cells promotes proliferative machinery while an increase in this level promotes apoptotic signaling; (ii) HNE is a common denominator in stress-induced apoptosis caused by H(2)O(2), superoxide, UV, heat or oxidant chemicals such as doxorubicin; and (iii) HNE can modulate ligand-independent signaling by membrane receptors such as EGFR or Fas (CD95) and may act as a sensor of external stimuli for eliciting stress-response. Against a backdrop of various reported effects of HNE, in vitro and in vivo, we have critically evaluated the above mentioned hypotheses suggesting a key role of HNE in signaling.

Therapeutic and protective effects of Caesalpinia gilliesii and Cajanus cajan proteins against acetaminophen overdose-induced renal damage

The present work aims to evaluate the protective and ameliorative effects of two plant-derived proteins obtained from the seeds of Cajanus cajan and Caesalpinia gilliesii(Leguminosae) against the toxic effects of acetaminophen in kidney after chronic dose through determination of certain biochemical markers including total urea, creatinine, and kidney marker enzyme, that is, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In addition histopathological examination of intoxicated and treated kidney with both proteins was performed. The present results show a significant increase in serum total urea and creatinine, while significant decrease in GAPDH. Improvement in all biochemical parameters studied was demonstrated, which was documented by the amelioration signs in rats kidney architecture. Thus, both plant protein extracts can counteract the nephrotoxic process, minimize damage to the kidney, delay disease progression, and reduce its complications.

Apoptosis signalling by 4-hydroxynonenal: a role for JNK–c-Jun/AP-1 pathway

4-Hydroxynonenal (HNE) is one of the most abundant aldehyde components of ox-LDL and it exerts various effects on intracellular and extracellular signaling cascades. In this mini-review, a brief synopsis of HNE-modulated signaling pathways will be presented mainly focused on cell death, including recent studies from our laboratory. The results of a number of studies demonstrate the ability of HNE to induce apoptosis and ROS formation in a dose-dependent manner. Several signaling pathways have been shown to be modulated by HNE, including MAP kinases, PKC isoforms, cell-cycle regulators, receptor tyrosine kinases and caspases. In order to get insight into the mechanisms of apoptotic response by HNE, MAP kinase and caspase activation pathways have been studied in 3T3 fibroblasts; HNE induced early activation of JNK and p38 proteins but down-regulated the basal activity of ERK-1/2. We have shown that HNE-induced release of cytochrome c from mitochondria, caspase-9 and caspase-3 activation. Activation of AP-1 along with increased c-Jun and phospho-c-Jun levels could be inhibited by pretreatment of cells with certain molecules such as resveratrol. Additionally, overexpression of dominant negative c-Jun and JNK1 in 3T3 fibroblasts prevented HNE-induced apoptosis, which indicated a role for JNK-c-Jun/AP-1 pathway. JNK-dependent induction of c-Jun/AP-1 activation data in the literature indicates a critical potential role for JNK in the cellular response against toxic products of lipid peroxidation.

MxA inhibits hepatitis B virus replication by interaction with hepatitis B core antigen

Human MxA, an interferon-inducible cytoplasmic dynamin-like GTPase, possesses antiviral activity against multiple RNA viruses. Recently, MxA has also been demonstrated to have activity against the hepatitis B virus (HBV), a well-known DNA virus responsible for acute and chronic liver disease in humans. We investigated the molecular mechanism for the anti-HBV activity of MxA. Our results demonstrated that in HepG2.2.15 cells, MxA GTPase independently suppressed the production of hepatitis B surface antigen and HBV DNA without changing the level of hepatitis B core antigen (HBcAg) and the distribution of HBV mRNA. MxA significantly reduced the level of the encapsidated pregenomic RNA. Through its central interactive domain, MxA interacted with HBcAg, causing accumulation of the proteins in perinuclear compartments. MxA-HBcAg interaction significantly affected the dynamics of HBcAg by immobilizing HBcAg in the perinuclear structures.

CONCLUSION

MxA displays antiviral activity against HBV involving a mechanism of MxA-HBcAg interaction that may interfere with core particle formation.

Resveratrol enhances solar UV-induced responses in normal human epidermal keratinocytes

Resveratrol (RV) differentially affects UV-induced death/pro-survival pathways in normal and tumor cells. On these grounds, RV-containing topical products have been developed to prevent UV-associated tumorigenesis/damage to human skin. In this study, we evaluated mechanisms of combined effects of RV and low-dose solar simulated UVA+UVB or 6-formylindo[3,2-b]carbazole (FICZ), a product of tryptophan photo-oxidation known to mediate UV effects, on the inflammatory, metabolic and proliferative responses of cultured normal human epidermal keratinocytes (HEK). Applied alone, RV, UV and FICZ induced time- and dose-dependent activation of aryl hydrocarbon receptor (AhR) pathway followed by over-expression of Cyp1A1 (metabolic response), UV and RV induced IL-8 expression (inflammatory response), while RV enhanced also HEK proliferation revealed by MTT assay and (3)H-thymidine incorporation. In the combined treatment, RV synergized with both UV and FICZ, leading to further activation of AhR machine, Cyp1A1 transcription and IL-8 expression, the latter partly AhR-dependent as assessed by AhR silencing. RV enhanced UV-induced NFkappaB activation and nuclear translocation of epidermal growth factor receptor. By contrast, proliferative effect of RV was abolished in the presence of UV, whereas synergic anti-proliferative action of RV+UV was observed in the Nrf2-silenced HEK. Our data suggest cooperative effects of RV-specific and UV-/FICZ-activated transcription factors leading to deregulated inflammatory, metabolic and proliferative responses of HEK.

Metalloproteinase processing of HBEGF is a proximal event in the response of human aortic endothelial cells to oxidized phospholipids

OBJECTIVE

Atherosclerosis is a chronic inflammatory disease initiated by monocyte recruitment and retention in the vessel wall. An important mediator of monocyte endothelial interaction is the chemokine interleukin (IL)-8. The oxidation products of phospholipids, including oxidized 1-palmitoyl-2-arachidonyl-sn-glycerol-3-phosphocholine (Ox-PAPC), accumulate in atherosclerotic lesions and strongly induce IL-8 in human aortic endothelial cells (HAECs). The goal of this study was to identify the proximal events leading to induction of IL-8 by Ox-PAPC in vascular endothelial cells.

METHODS AND RESULTS

In a systems genetics analysis of HAECs isolated from 96 different human donors, we showed that heparin-binding EGF-like growth factor (HBEGF) transcript levels are strongly correlated to IL-8 induction by Ox-PAPC. The silencing and overexpression of HBEGF in HAECs confirmed the role of HBEGF in regulating IL-8 expression. HBEGF has been shown to be stored in an inactive form and activation is dependent on processing by a dysintegrin and metalloproteinases (ADAM) to a form that can activate the epidermal growth factor (EGF) receptor. Ox-PAPC was shown to rapidly induce HBEGF processing and EGF receptor activation in HAECs. Using siRNA we identified 3 ADAMs that regulate IL-8 induction and directly demonstrated that Ox-PAPC increases ADAM activity in the cells using a substrate cleavage assay. We provide evidence for one mechanism of Ox-PAPC activation of ADAM involving covalent binding of Ox-PAPC to cysteine on ADAM. Free thiol cysteine analogs showed inhibition of IL-8 induction by Ox-PAPC, and both a cysteine analog and a cell surface thiol blocker strongly inhibited ADAM activity induction by Ox-PAPC. Using microarray analyses, we determined that this ADAM pathway may regulate at least 30% of genes induced by Ox-PAPC in HAECs.

CONCLUSIONS

This study is the first report demonstrating a role for the ADAM-HBEGF-EGF receptor axis in Ox-PAPC induction of IL-8 in HAECs. These studies highlight a role for specific ADAMs as initiators of Ox-PAPC action and provide evidence for a role of covalent interaction of Ox-PAPC in activation of ADAMs.

Damage of DNA and proteins by major lipid peroxidation products in genome stability

Oxidative stress and lipid peroxidation (LPO) accompanying infections and chronic inflammation may induce several human cancers. LPO products are characterized by carbohydrate chains of different length, reactive aldehyde groups and double bonds, which make these molecules reactive to nucleic acids, proteins and cellular thiols. LPO-derived adducts to DNA bases form etheno-type and propano-type exocyclic rings, which have profound mutagenic potential, and are elevated in several cancer-prone diseases. Adducts of long chain LPO products to DNA bases inhibit transcription. Elimination from DNA of LPO-induced lesions is executed by several repair systems: base excision repair (BER), direct reversal by AlkB family proteins, nucleotide excision repair (NER) and recombination. Modifications of proteins with LPO products may regulate cellular processes like apoptosis, cell signalling and senescence. This review summarizes consequences of LPO products' presence in cell, particularly 4-hydroxy-2-nonenal, in terms of genomic stability.

Plant polyphenols regulate chemokine expression and tissue repair in human keratinocytes through interaction with cytoplasmic and nuclear components of epidermal growth factor receptor system

AIMS

To evaluate mechanisms underlying modulation of inflammatory chemokines in primary human keratinocytes (normal human epidermal keratinocytes) and repair-related processes in wound models by plant polyphenols (PPs) with antioxidant and superoxide scavenging properties (verbascoside [Vb], resveratrol [Rv], polydatin [Pd], quercetin [Qr], and rutin).

RESULTS

Epidermal growth factor receptor (EGFR)-controlled chemokines CXCL8/interleukin 8 (IL-8), CCL2/monocyte chemotactic protein-1 (MCP-1), and CXCL10/interferon gamma-produced protein of 10 kDa (IP-10) were modulated by transforming growth factor alpha (TGF-α) and by the tumor necrosis factor alpha/interferon gamma combination (T/I). EGFR phosphorylation, nuclear translocation, and downstream cytoplasmic signaling pathways (extracellular regulation kinase [ERK]1/2, p38, STAT3, and PI-3K) were studied. All PPs did not affect TGF-α-induced STAT3 phosphorylation, whereas they suppressed T/I-activated NFkappaB and constitutive and T/I-induced but not TGF-α-induced ERK1/2 phosphorylation. Vb and Qr suppressed total EGFR phosphorylation, but they synergized with TGF-α to enhance nuclear accumulation of phosphorylated EGFR. Vb strongly inhibited TGF-α-induced p38 phosphorylation and T/I-induced NFkappaB and activator protein-1 (AP-1) binding to DNA. Vb was an effective inhibitor of T/I-stimulated chemokine synthesis, and it accelerated scratch wound healing in vitro. Anti-inflammatory and wound healing activities of Vb were confirmed in vivo in the full-thickness excision wound. Although Pd and Rv did not affect EGFR activation/translocation, they and Qr synergized with TGF-α and T/I in the induction of IL-8 transcription/synthesis while opposing enhanced MCP-1 and IP-10 transcription/synthesis connected with pharmacologically impaired EGFR functioning.

INNOVATION

PPs perturb the EGFR system in human keratinocytes, and this effect may be implicated in the regulation of inflammatory and repair-related processes in the skin.

CONCLUSION

Anti-inflammatory and wound healing effects of PPs depend on their interaction with EGFR-controlled cytoplasmic and nuclear pathways rather than on their direct redox properties.

AP1 is essential for generation of autophagosomes from the trans-Golgi network

Despite recent advances in understanding the functions of autophagy in developmental and pathological conditions, the underlying mechanism of where and how autophagosomal structures acquire membrane remains enigmatic. Here, we provide evidence that post-Golgi membrane traffic plays a crucial role in autophagosome formation. Increased secretion of constitutive cargo from the trans-Golgi network (TGN) to the plasma membrane induced the formation of microtubule-associated protein light chain 3 (LC3)-positive structures. At the early phase of autophagy, LC3 associated with and then budded off from a distinct TGN domain without constitutive TGN-to-plasma cargo and TGN-to-endosome proteins. The clathrin adaptor protein AP1 and clathrin localized to starvation- and rapamycin-induced autophagosomes. Dysfunction of the AP1-dependent clathrin coating at the TGN but not at the plasma membrane prevented autophagosome formation. Our results thus suggest an essential role of the TGN in autophagosome biogenesis, providing membrane to autophagosomes through an AP1-dependent pathway.

The expression and function of vascular endothelial growth factor in retinal pigment epithelial (RPE) cells is regulated by 4-hydroxynonenal (HNE) and glutathione S-transferaseA4-4

It is well established that 4-hydroxynonenal (HNE) plays a major role in oxidative stress-induced signaling and the toxicity of oxidants. Surprisingly our recent studies also demonstrate that low levels of HNE generated during oxidative stress promote cell survival mechanisms and proliferation. Since the expression and secretion of VEGF is known to be affected by Oxidative stress, during present studies, we have examined dose dependent effect of HNE on VEGF expression and secretion in a model of retinal pigment epithelial (RPE) cells in culture. Results of these studies showed that while inclusion of 0.1 μM HNE in the medium caused increased secretion of VEGF, its secretion and expression was significantly suppressed in the presence of >5 μM HNE in the media. These concentration dependent hormetic effects of HNE on VEGF secretion could be blocked by the over expression of GSTA4-4 indicating that these effects were specifically attributed to HNE and regulated by GSTA4-4. VEGF secreted into the media showed angiogenic properties as indicated by increased migration and tube formation of HUVEC in matrigel when grown in media from RPE cells treated with 1 μM HNE. The corresponding media from GSTA4-4 over expressing RPE cells had no effect on migration and tube formation of HUVEC in matrigel. These results are consistent with earlier studies showing that at low concentrations, HNE promotes proliferative mechanisms and suggest that HNE induces VEGF secretion from RPE cells that acts in a paracrine fashion to induce angiogenic signaling mechanism in the endothelial cells. These findings may suggest a role of HNE and GSTA4-4 in oxidative stress induced proliferative retinopathies.

Control of genetically prescribed protein tyrosine kinase activities by environment-linked redox reactions

Recent observations on environment-linked control of genetically prescribed signaling systems for either cell activation or cell death have been reviewed with a focus on the regulation of activities of protein tyrosine kinases (PTKs). The environment-linked redox reactions seem to primarily affect cell surface receptors and cell membrane lipid rafts, and they induce generation of reactive oxygen species (ROS) in cells. ROS thus generated might upregulate the catalytic activities of PTKs through inactivating protein tyrosine phosphatases that dephosphorylate and inactivate autophosphorylated PTKs. Recent evidence has, however, demonstrated that ROS could also directly oxidize SH groups of genetically conserved specific cysteines on PTKs, sometimes producing disulfide-bonded dimers of PTK proteins, either for upregulation or downregulation of their catalytic activities. The basic role of the redox reaction/covalent bond-mediated modification of protein tertiary structure-linked noncovalent bond-oriented signaling systems in living organisms is discussed.

The balance between 4-hydroxynonenal and intrinsic glutathione/glutathione S-transferase A4 system may be critical for the epidermal growth factor receptor phosphorylation of human esophageal squamous cell carcinomas

Oxidative stress might participate in the carcinogenesis of human esophageal squamous cell carcinomas (hESCC). 4-Hydroxynonenal (HNE) is a major product of membrane lipid peroxidation with short life. It might act as an important mediator through the generation of adducts and activate epidermal growth factor receptor (EGFR) signaling. It is mainly trapped with glutathione (GSH) and catalyzed by glutathione S-transferases (GSTs). This study aimed to elucidate the possible participation of HNE, GSH/GST system, and EGFR signaling in hESCC development. Immunohistochemistry of HNE adducts, EGFR, and phosphorylated EGFR (pEGFR) was performed with hESCC specimens. The effect of HNE on the phosphorylation of EGFR and its downstream PhospholipaseCγ1 (PLCγ1) was investigated with KYSE30 cell-line. Pretreatment with GSH inducer N-acetylcysteine (NAC) or GSH inhibitor Buthionine sulfoximine (BSO) and mandatory transfection of hGSTA4 gene in KYSE30 were conducted to investigate the relationship between HNE and GSH/GST system. Immunoreactants of HNE adducts, EGFR, and pEGFR were increased in hESCC compared to non-cancerous epithelium with positive correlations. The treatment of HNE ligand-independently induced the phosphorylation of EGFR and PLCγ1 accompanying the diminishment of intracellular GSH level. NAC increased GSH contents but BSO decreased in dose-dependent manners. Reflecting changes in GSH, HNE-induced EGFR phosphorylation was suppressed by NAC, whereas it was promoted by BSO. Mandatory expression of hGSTA4 suppressed HNE-induced events. We first demonstrated that the ligand-independent activation of EGFR by the balance between the stimulation of HNE and the prevention of intrinsic GSH/GST system might participate in the development of hESCC.

Plant polyphenols differentially modulate inflammatory responses of human keratinocytes by interfering with activation of transcription factors NFκB and AhR and EGFR-ERK pathway

Molecular mechanisms underlying modulation of inflammatory responses in primary human keratinocytes by plant polyphenols (PPs), namely the glycosylated phenylpropanoid verbascoside, the stilbenoid resveratrol and its glycoside polydatin, and the flavonoid quercetin and its glycoside rutin were evaluated. As non-lethal stimuli, the prototypic ligand for epidermal growth factor receptor (EGFR) transforming growth factor alpha (TGFalpha), the combination of tumor necrosis factor (TNFalpha) and interferon (IFNgamma) (T/I), UVA+UVB irradiation, and bacterial lipopolysaccharide (LPS) were used. We demonstrated differential modulation of inflammatory responses in keratinocytes at signal transduction, gene transcription, and protein synthesis levels as a function of PP chemical structure, the pro-inflammatory trigger used, and PP interaction with intracellular detoxifying systems. The PPs remarkably inhibited constitutive, LPS- and T/I-induced but not TGFalpha-induced ERK phosphorylation. They also suppressed NFkappaB activation by LPS and T/I. Verbascoside and quercetin invariably impaired EGFR phosphorylation and UV-associated aryl hydrocarbon receptor (AhR)-mediated signaling, while rutin, polydatin and resveratrol did not affect EGFR phosphorylation and further activated AhR machinery in UV-exposed keratinocytes. In general, PPs down-regulated gene expression of pro-inflammatory cytokines/enzymes, except significant up-regulation of IL-8 observed under stimulation with TGFalpha. Both spontaneous and T/I-induced release of IL-8 and IP-10 was suppressed, although 50μM resveratrol and polydatin up-regulated IL-8. At this concentration, resveratrol activated both gene expression and de novo synthesis of IL-8 and AhR-mediated mechanisms were involved. We conclude that PPs differentially modulate the inflammatory response of human keratinocytes through distinct signal transduction pathways, including AhR and EGFR.

Interleukin-6 plays a protective role in development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors

AIMS

Cisplatin, a major chemotherapeutic agent, accumulates in proximal tubules of the kidneys and causes acute renal failure dose-dependently. We previously reported that cisplatin induced more severe renal dysfunction in interleukin-6 (IL-6) knockout (IL-6(-/-)) mice than in wild-type (WT) mice. Expression of a pro-apoptotic protein was significantly increased with cisplatin in IL-6(-/-) mice compared to that in WT mice. IL-6, locally expressed in renal tubular cells after cisplatin administration, prevents the development of renal dysfunction at an early stage. In the present study, we focused on downstream signals of IL-6 and oxidative stress induced by cisplatin in order to evaluate the protective role of IL-6 in the development of acute renal failure.

MAIN METHODS

WT and IL-6(-/-) mice were given either cisplatin (30 mg/kg) or saline intraperitoneally. Blood and kidney samples were collected at 24h and 72 h after cisplatin administration. The changes in expression of 4-hydroxy-2-nonenal protein (4-HNE, oxidative stress marker) and cyclooxygenase-2 (cox-2), activities of superoxide dismutases and caspase-3, and phosphorylation of extracellular signal-regulated kinase (ERK) were examined.

KEY FINDINGS

Cisplatin increased the expression of 4-HNE and cox-2, and phosphorylation of ERK in IL-6(-/-) mice than in WT mice. On the other hand, activity of superoxide dismutase, an anti-oxidative enzyme, was significantly decreased in the kidney obtained from IL-6(-/-) mice after cisplatin administration.

SIGNIFICANCE

Our findings suggest that IL-6 plays a protective role in the development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors.

4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase is degraded by cathepsin G in rat neutrophils

Degradation of oxidized or oxidatively modified proteins is an essential part of the antioxidant defenses of cells. 4-Hydroxy-2-nonenal, a major reactive aldehyde formed by lipid peroxidation, causes many types of cellular damage. It has been reported that 4-hydroxy-2-nonenal-modified proteins are degraded by the ubiquitin-proteasome pathway or, in some cases, by the lysosomal pathway. However, our previous studies using U937 cells showed that 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase is degraded by cathepsin G. In the present study, we isolated the 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase-degrading enzyme from rat neutrophils to an active protein fraction of 28 kDa. Using the specific antibody, the 28 kDa protein was identified as cathepsin G. Moreover, the degradation activity was inhibited by cathepsin G inhibitors. These results suggest that cathepsin G plays a crucial role in the degradation of 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase.

Clair DK. p53 Regulates oxidative stress-mediated retrograde signaling: a novel mechanism for chemotherapy-induced cardiac injury

The side effects of cancer therapy on normal tissues limit the success of therapy. Generation of reactive oxygen species (ROS) has been implicated for numerous chemotherapeutic agents including doxorubicin (DOX), a potent cancer chemotherapeutic drug. The production of ROS by DOX has been linked to DNA damage, nuclear translocation of p53, and mitochondrial injury; however, the causal relationship and molecular mechanisms underlying these events are unknown. The present study used wild-type (WT) and p53 homozygous knock-out (p53^−/−) mice to investigate the role of p53 in the crosstalk between mitochondria and nucleus. Injecting mice with DOX (20 mg/kg) causes oxidative stress in cardiac tissue as demonstrated by immunogold analysis of the levels of 4-hydroxy-2′-nonenal (4HNE)-adducted protein, a lipid peroxidation product bound to proteins. 4HNE levels increased in both nuclei and mitochondria of WT DOX-treated mice but only in nuclei of DOX-treated p53^(−/−) mice, implicating a critical role for p53 in causing DOX-induced oxidative stress in mitochondria. The stress-activated protein c-Jun amino-terminal kinase (JNKs) was activated in response to increased 4HNE in WT mice but not p53^(−/−) mice receiving DOX treatment, as determined by co-immunoprecipitation of HNE and pJNK. The activation of JNK in DOX treated WT mice was accompanied by Bcl-2 dissociation from Beclin in mitochondria and induction of type II cell death (autophagic cell death), as evidenced by an increase in LC3-I/LC-3-II ratio and γ-H2AX, a biomarker for DNA damage. The absence of p53 significantly reduces mitochondrial injury, assessed by quantitative morphology, and decline in cardiac function, assessed by left ventricular ejection fraction and fraction shortening. These results demonstrate that p53 plays a critical role in DOX-induced cardiac toxicity, in part, by the induction of oxidative stress mediated retrograde signaling.

Hepatitis B virus X protein stimulates IL-6 expression in hepatocytes via a MyD88-dependent pathway

BACKGROUND & AIMS

Hepatitis B virus (HBV) X protein (HBx) has been implicated in HBV-associated carcinogenesis by activating signal transduction pathways and influencing gene transcription in liver cells. We aimed to investigate the underlying mechanisms for HBx-induced production of interleukin-6 (IL-6), one of the major inflammatory mediators that stimulate hepatocellular carcinoma development.

METHODS

HBx was overexpressed in hepatic and hepatoma cell lines and IL-6 expression levels were measured by quantitative RT-PCR and ELISA. The activation of IRAK-1, ERKs/p38, and NF-κB was determined by Western blotting using specific anti-phosphoprotein antibodies. The role of MyD88 in these processes was analyzed by MyD88 RNAi and expression of an inactive MyD88 mutant.

RESULTS

Expression of HBx in hepatic and hepatoma cells led to a dramatic enhancement of IL-6 synthesis and secretion. Dysfunction of MyD88 in these cells prevented the HBx-triggered IL-6 production. HBx expression also activated downstream signaling proteins of MyD88 including IRAK-1, ERKs/p38, and NF-κB. Inactivation of these signaling molecules blocked IL-6 synthesis as well. HBx-stimulated the expression of MyD88.

CONCLUSIONS

In hepatocytes and hepatoma cells, HBx stimulates the production of IL-6 in a MyD88-dependent manner, indicating that parenchymal liver cells are an additional source of high levels of IL-6 in the HBV-infected liver microenvironment. HBx could be involved in HBV-mediated liver carcinogenesis, through this mechanism of action.

Pathological aspects of lipid peroxidation

Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.

Role of 4-hydroxynonenal in epidermal growth factor receptor-mediated signaling in retinal pigment epithelial cells

Lipid peroxidation (LPO) end-product 4-hydroxynonenal (4-HNE) has been implicated in the mechanism of retinopathy. Lately it has been shown that besides being cytotoxic, 4-HNE plays an important role in oxidative stress-induced signaling. In this study, we have investigated the effect of 4-HNE on epidermal growth factor receptor (EGFR)-mediated signaling, its potential functional consequences, and the regulatory role of the 4-HNE metabolizing isozymes, glutathione S-transferase A4-4 (GSTA4-4) on this signaling in retinal pigment epithelial (RPE) cells. Our results showed that consistent with its known toxicity at relatively higher concentrations, 4-HNE induced cell death in RPE. However, at lower concentrations (as low as 0.1 μM) 4-HNE triggered phosphorylation of EGFR and activation of its down stream signaling components ERK1/2 and Akt that are known to be involved in cell proliferation. These effects of 4-HNE on EGFR could be attenuated by the over expression of GSTA4-4 that reduces intracellular levels of 4-HNE. Our results also indicated that 4-HNE-induced activation of EGFR is a protective mechanism against oxidative stress because EGFR, MEK, and PI3K inhibitors potentiated the toxicity of 4-HNE and also inhibited wound healing in a RPE cell model. These studies suggest that as an initial response to oxidative stress, 4-HNE induces protective mechanism(s) in RPE cells through EGFR-mediated signaling.

Dysfunction of glutathione S-transferase leads to excess 4-hydroxy-2-nonenal and H(2)O(2) and impaired cytokine pattern in cultured keratinocytes and blood of vitiligo patients

Oxidative stress due to increased epidermal levels of H(2)O(2) with consequent inhibition of catalase activity is generally accepted as a leading cytotoxic mechanism of melanocyte loss in vitiligo. Keratinocyte-derived cytokines are considered key factors in the maintenance of melanocyte structure and functions. We hypothesized that abnormal redox control may lead to impaired cytokine production by keratinocytes, thus causing noncytotoxic defects in melanocyte proliferation and melanogenesis. We found significantly suppressed mRNA and protein expression of glutathione-S-transferase (GST) M1 isoform, and higher-than-normal levels of both 4-hydroxy-2-nonenal (HNE)-protein adducts and H(2)O(2) in the cultures of keratinocytes derived from unaffected and affected skin of vitiligo patients, and in their co-cultures with allogeneic melanocytes. GST and catalase activities, as well as glutathione levels, were dramatically low in erythrocytes, whilst HNE-protein adducts were high in the plasma of vitiligo patients. The broad spectrum of major cytokines, chemokines, and growth factors was dysregulated in both blood plasma and cultured keratinocytes of vitiligo patients, when compared to normal subjects. Exogenous HNE added to normal keratinocytes induced a vitiligo-like cytokine pattern, and H(2)O(2) overproduction accompanied by adaptive upregulation of catalase and GSTM1 genes, and transient inhibition of Erk1/2 and Akt phosphorylation. Based on these results, we suggest a novel GST-HNE-H(2)O(2)-based mechanism of dysregulation of cytokine-mediated keratinocyte-melanocyte interaction in vitiligo.

Naphtho[1,2-b]furan-4,5-dione induces apoptosis of oral squamous cell carcinoma: involvement of EGF receptor/PI3K/Akt signaling pathway

Naphtho[1,2-b]furan-4,5-dione (NFD), prepared from 2-hydroxy-1,4-naphthoquinone and chloroacetaldehyde in an efficient one-pot reaction, exerts an anti-tumor effect. This study was performed to elucidate whether the epidermal growth factor (EGF) receptor and phosphatidylinositol-3-kinase (PI3K) signaling pathways are involved in NFD-induced apoptosis of oral squamous cell carcinoma (OSCC). Immunoblot showed that NFD suppressed the phosphorylation of EGF receptor and activation of PI3K/Akt, downstream molecules of EGF receptor signaling pathway, in Ca9-22 cells. The levels of downstream targets of Akt, including phospho-glycogen synthase kinase-3beta (p-GSK-3beta), GSK-3beta, forkhead transcription factor (FKHR), and cyclin D1, were also reduced after NFD treatment. Moreover, inactivation of nuclear factor-kappaB (NF kappaB), modulation of I kappa K beta and I kappaB alpha, up-regulation of Bad, and down-regulation of anti-apoptotic proteins including phospho-Bad, Bcl-X(L), myeloid cell leukemia-1(Mcl-1), and XIAP were found in NFD-treated cells. In addition, NFD treatment disrupted mitochondrial membrane potential (Delta Psi m), resulted in release of cytochrome c, and activation of both caspases-9 and caspase-3. Taken together, these results indicate that NFD induces apoptosis in Ca9-22 cells via inactivation of the EGF receptor-mediated survival pathway.

Naphtho[1,2-b]furan-4,5-dione inactivates EGFR and PI3K/Akt signaling pathways in human lung adenocarcinoma A549 cells

AIMS

Naphtho[1,2-b]furan-4,5-dione (NFD), prepared from 2-hydroxy-1,4-naphthoquinone and chloroacetaldehyde in an efficient one-pot reaction, exhibits an anti-carcinogenic effect. This study was performed to elucidate whether EGFR and PI3K signaling pathways are involved in NFD-induced apoptosis of human lung adenocarcinoma A549 cells.

MAIN METHODS

The effect of NFD on cell viability and apoptosis was measured by the MTT assay and flow cytometry. The phosphorylation levels of EGFR and its regulatory molecules by NFD treatment were studied by immunoblots.

KEY FINDINGS

Immunoblot showed that NFD inhibited EGFR phosphorylation and the activation of PI3K/Akt, downstream molecules of EGFR pathway, in A549 cells. The levels of downstream targets of Akt, including phospho-glycogen synthase kinase-3beta (p-GSK-3beta), GSK-3beta, forkhead transcription factor (FKHR), and cyclin D1, were also reduced after NFD treatment. Moreover, inactivation of nuclear factor-kappaB (NFkappaB), modulation of IkappaKalpha/beta and IkappaBalpha, up-regulation of Bad and Bax, and down-regulation of anti-apoptotic proteins including phospho-Bad, Bcl-2, survivin, and XIAP were also found in NFD-treated cells. In addition, NFD treatment disrupted mitochondrial membrane potential (DeltaPsim) and resulted in release of mitochondrial cytochrome c and activation of both caspases-9 and caspase-3.

SIGNIFICANCE

These findings indicate that EGFR and PI3K/Akt signaling pathways play important roles in NFD-induced apoptosis of A549 cells.

Inactivation of epidermal growth factor receptor and downstream pathways in oral squamous cell carcinoma Ca9-22 cells by cardiotoxin III from Naja naja atra

Cardiotoxin III (1), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has potential therapeutic activity in cancer. Treatment with 1 reduced phosphorylation of EGFR and Akt, as well as ERK in Ca9-22 cells. Moreover, 1-treatment inhibited constitutive activation of STAT3 and STAT5 in a time-dependent manner. Up-regulation of Bax and down-regulation of anti-apoptotic proteins including Bcl-2, Bcl-X(L), and myeloid cell leukemia-1(Mcl-1) were also found in cells treated with 1. In addition, 1-treatment disrupted mitochondrial membrane potential (DeltaPsim) and resulted in release of mitochondrial cytochrome c and activation of both caspases-9 and -3. AG1478, a specific pharmacological inhibitor of EGFR activation, mimics the cytotoxic effects of 1. Taken together, these results showed that 1 causes significant induction of apoptosis in Ca9-22 cells via abolition of the EGFR-mediated survival pathway of these cells. Thus, cardiotoxin III appears to be a potential therapeutic agent for killing oral squamous carcinoma Ca9-22 cells.

Roles of the lipid peroxidation product 4-hydroxynonenal in obesity, the metabolic syndrome, and associated vascular and neurodegenerative disorders

A rising tide of obesity and type 2 diabetes has resulted from the development of technologies that have made inexpensive high calorie foods readily available and exercise unnecessary for many people. Obesity and the metabolic syndrome (insulin resistance, visceral adiposity and dyslipidemia) wreak havoc on cells throughout the body thereby promoting cardiovascular and kidney disease, and degenerative diseases of the brain and body. Obesity and insulin resistance promote disease by increasing oxidative damage to proteins, lipids and DNA as the result of a combination of increased free radical production and an impaired ability of cells to detoxify the radicals and repair damaged molecules. By covalently modifying membrane-associated proteins, the membrane lipid peroxidation product 4-hydroxynonenal (HNE) may play particularly sinister roles in the metabolic syndrome and associated disease processes. HNE can damage pancreatic beta cells and can impair the ability of muscle and liver cells to respond to insulin. HNE may promote atherosclerosis by modifying lipoproteins and can cause cardiac cell damage by impairing metabolic enzymes. An adverse role for HNE in the brain in obesity and the metabolic syndrome is suggested by studies showing that HNE levels are increased in brain cells with aging and Alzheimer's disease. HNE can cause the dysfunction and degeneration of neurons by modifying membrane-associated glucose and glutamate transporters, ion-motive ATPases, enzymes involved in amyloid metabolism, and cytoskeletal proteins. Exercise and dietary energy restriction reduce HNE production and may also increase cellular systems for HNE detoxification including glutathione and oxidoreductases. The recent development of low molecular weight molecules that scavenge HNE suggests that HNE can be targeted in the design of drugs for the treatment of obesity, the metabolic syndrome, and associated disorders.

Effect of 4-hydroxynonenal on Antioxidant Capacity and Apoptosis Induction in Jurkat T Cells

4-Hydroxynonenal (HNE) is one of the major end products of lipid peroxidation and may have either physiological or pathological significance regulating cell proliferation. We studied some biochemical effects of HNE, at various concentrations (0.1-100 microM), on Jurkat T cells incubated thereafter for 24, 48 and 72 h. HNE at low concentrations significantly enhanced the proliferation index, whereas at higher concentrations progressively blocked cell proliferation. Caspase 3 activity increased significantly at HNE concentrations between 1 and 10 microM and decreased at higher concentrations. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Rd) increased progressively with HNE concentrations, particularly GSH-Px. Glucose-6-phosphate dehydrogenase (G6PDH) showed a different pattern, increasing at low HNE (1-5 microM) concentrations and rapidly declined thereafter. These results show that HNE may induce growth inhibition of Jurkat T cells and regulate the activity of typical antioxidant enzymes. Furthermore, the protective effect of doubling the foetal calf serum still points out the risk that cultured cells undergo oxidative stress during incubation.

Radiation-induced lipid peroxidation activates src kinase and triggers nuclear EGFR transport

PURPOSE

Elucidation of the molecular mechanism of radiation-induced activation of src kinase, which initiates EGFR internalization and nuclear transport.

MATERIAL AND METHODS

Radiation-induced src activation was investigated in the bronchial carcinoma cell line A549. Proteins were Western blotted and quantified by the help of specific antibodies. Residual DNA-damage was quantified with gammaH(2)AX-foci analysis. Radiation-induced lipid peroxidation was prevented by acetyl-cysteine.

RESULTS

The radiation-induced src activation and EGFR stabilization could be mimicked by addition of hydroxy-nonenal (HNE), one of the major lipid peroxidation products. Radiation-generated HNE is bound to EGFR and src and correlated with complex formation between both following radiation. Treatment with HNE activated src and stimulated radiation-associated EGFR and caveolin 1 phosphorylations resulting in increased nuclear transport of EGFR. Consequently, radiation-induced phosphorylation and activation of DNA-PK were increased. This phosphorylation was associated with improved removal of residual damage 24h after irradiation. Inhibition of radiation-induced HNE generation by acetyl-cysteine blocked radiation-induced src activation and EGFR phosphorylation.

CONCLUSIONS

HNE generated in response to radiation exposure activates src kinase and is involved in regulation of radiation-stimulated DNA-repair processes.

The chemistry of cell signaling by reactive oxygen and nitrogen species and 4-hydroxynonenal

During the past several years, major advances have been made in understanding how reactive oxygen species (ROS) and nitrogen species (RNS) participate in signal transduction. Identification of the specific targets and the chemical reactions involved still remains to be resolved with many of the signaling pathways in which the involvement of reactive species has been determined. Our understanding is that ROS and RNS have second messenger roles. While cysteine residues in the thiolate (ionized) form found in several classes of signaling proteins can be specific targets for reaction with H(2)O(2) and RNS, better understanding of the chemistry, particularly kinetics, suggests that for many signaling events in which ROS and RNS participate, enzymatic catalysis is more likely to be involved than non-enzymatic reaction. Due to increased interest in how oxidation products, particularly lipid peroxidation products, also are involved with signaling, a review of signaling by 4-hydroxy-2-nonenal (HNE) is included. This article focuses on the chemistry of signaling by ROS, RNS, and HNE and will describe reactions with selected target proteins as representatives of the mechanisms rather attempt to comprehensively review the many signaling pathways in which the reactive species are involved.

Self-regulatory role of 4-hydroxynonenal in signaling for stress-induced programmed cell death

Within the last two decades, 4-hydroxynonenal has emerged as an important second messenger involved in the regulation of various cellular processes. Our recent studies suggest that HNE can induce apoptosis in various cells through the death receptor Fas (CD95)-mediated extrinsic pathway as well as through the p53-dependent intrinsic pathway. Interestingly, through its interaction with the nuclear protein Daxx, HNE can self-limit its apoptotic role by translocating Daxx to cytoplasm where it binds to Fas and inhibits Fas-mediated apoptosis. In this paper, after briefly describing recent studies on various biological activities of HNE, based on its interactions with Fas, Daxx, and p53, we speculate on possible mechanisms through which HNE may affect a multitude of cellular processes and draw a parallel between signaling roles of H(2)O(2) and HNE.

Oxidative stress and covalent modification of protein with bioactive aldehydes

The term "oxidative stress" links the production of reactive oxygen species to a variety of metabolic outcomes, including insulin resistance, immune dysfunction, and inflammation. Antioxidant defense systems down-regulated due to disease and/or aging result in oxidatively modified DNA, carbohydrates, proteins, and lipids. Increased production of hydroxyl radical leads to the formation of lipid hydroperoxides that produce a family of alpha,beta-unsaturated aldehydes. Such reactive aldehydes are subject to Michael addition reactions with the side chains of lysine, histidine, and cysteine residues, referred to as "protein carbonylation." Although not widely appreciated, reactive lipids can accumulate to high levels in cells, resulting in extensive protein modification leading to either loss or gain of function. The use of mass spectrometric methods to identify the site and extent of protein carbonylation on a proteome-wide scale has expanded our view of how oxidative stress can regulate cellular processes.

Lipid peroxidation and redox-sensitive signaling pathways

A growing body of evidence suggests that many of the effects of vascular dysfunction on cardiovascular diseases are mediated by the products of nonenzymatic reactions, such as the peroxidative degradation of polyunsaturated fatty acids (ie, lipid peroxidation). These degradation products are electrophilic reactive compounds and are thought to have a major impact on human health and lifespan by acting on proteins and genes. The oxidized lipids bound to the biomacromolecules can be detected as constituents in human patients with increased risk factors or clinical manifestations of lifestyle-related diseases, such as atherosclerosis. However, it appears that there are several sensor mechanisms in which specific cellular proteins directly interact with these electrophilic molecules. Moreover, a number of lipid peroxidation products have been shown as inducers for activation of the redox-related cell signaling mechanism, which integrate with other signaling pathways to control cellular responses to extracellular stimuli.

Epidermal growth factor upregulates motility of Mat-LyLu rat prostate cancer cells partially via voltage-gated Na+ channel activity

The main aim of this investigation was to determine whether a functional relationship existed between epidermal growth factor (EGF) and voltage-gated sodium channel (VGSC) upregulation, both associated with strongly metastatic prostate cancer cells. Incubation with EGF for 24 h more than doubled VGSC current density. Similar treatment with EGF significantly and dose-dependently enhanced the cells' migration through Transwell filters. Both the patch clamp recordings and the migration assay suggested that endogenous EGF played a similar role. Importantly, co-application of EGF and tetrodotoxin, a highly selective VGSC blocker, abolished 65% of the potentiating effect of EGF. It is suggested that a significant portion of the EGF-induced enhancement of migration occurred via VGSC activity.

Pathogenesis of chronic obstructive pulmonary disease

The pathogenesis of chronic obstructive pulmonary disease (COPD) encompasses a number of injurious processes, including an abnormal inflammatory response in the lungs to inhaled particles and gases. Other processes, such as failure to resolve inflammation, abnormal cell repair, apoptosis, abnormal cellular maintenance programs, extracellular matrix destruction (protease/antiprotease imbalance), and oxidative stress (oxidant/antioxidant imbalance) also have a role. The inflammatory responses to the inhalation of active and passive tobacco smoke and urban and rural air pollution are modified by genetic and epigenetic factors. The subsequent chronic inflammatory responses lead to mucus hypersecretion, airway remodeling, and alveolar destruction. This article provides an update on the cellular and molecular mechanisms of these processes in the pathogenesis of COPD.

4-Hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase is degraded by cathepsin G

Degradation of oxidized or oxidatively modified proteins is an essential part of the antioxidant defenses of cells. 4-Hydroxy-2-nonenal (HNE), a major reactive aldehyde formed by lipid peroxidation, causes many types of cellular damage. It has been reported that HNE-modified proteins are degraded by the ubiquitin-proteasome pathway or, in some cases, by the lysosomal pathway. However, our previous studies using U937 cells showed that HNE-modified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is degraded by an enzyme that is sensitive to a serine protease inhibitor, diisopropyl fluorophosphate (DFP), but not a proteasome inhibitor, MG-132, and that its degradation is not catalyzed in the acidic pH range where lysosomal enzymes are active. In the present study, we purified an HNE-modified GAPDH-degrading enzyme from a U937 cell extract to a final active fraction containing two proteins of 28 kDa (P28) and 27 kDa (P27) that became labeled with [(3)H]DFP. Using peptide mass fingerprinting and a specific antibody, P28 and P27 were both identified as cathepsin G. The degradation activity was inhibited by cathepsin G inhibitors. Furthermore, a cell extract from U937 cells transfected with a cathepsin G-specific siRNA hardly degraded HNE-modified GAPDH. These results suggest that cathepsin G plays a role in the degradation of HNE-modified GAPDH.

Advanced lipid peroxidation end products in oxidative damage to proteins. Potential role in diseases and therapeutic prospects for the inhibitors

Reactive carbonyl compounds (RCCs) formed during lipid peroxidation and sugar glycoxidation, namely Advanced lipid peroxidation end products (ALEs) and Advanced Glycation end products (AGEs), accumulate with ageing and oxidative stress-related diseases, such as atherosclerosis, diabetes or neurodegenerative diseases. RCCs induce the 'carbonyl stress' characterized by the formation of adducts and cross-links on proteins, which progressively leads to impaired protein function and damages in all tissues, and pathological consequences including cell dysfunction, inflammatory response and apoptosis. The prevention of carbonyl stress involves the use of free radical scavengers and antioxidants that prevent the generation of lipid peroxidation products, but are inefficient on pre-formed RCCs. Conversely, carbonyl scavengers prevent carbonyl stress by inhibiting the formation of protein cross-links. While a large variety of AGE inhibitors has been developed, only few carbonyl scavengers have been tested on ALE-mediated effects. This review summarizes the signalling properties of ALEs and ALE-precursors, their role in the pathogenesis of oxidative stress-associated diseases, and the different agents efficient in neutralizing ALEs effects in vitro and in vivo. The generation of drugs sharing both antioxidant and carbonyl scavenger properties represents a new therapeutic challenge in the treatment of carbonyl stress-associated diseases.