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

Serotonin Signaling Through the 5-HT1B Receptor and NADPH Oxidase 1 in Pulmonary Arterial Hypertension

OBJECTIVE

Serotonin can induce human pulmonary artery smooth muscle cell (hPASMC) proliferation through reactive oxygen species (ROS), influencing the development of pulmonary arterial hypertension (PAH). We hypothesize that in PASMCs, serotonin induces oxidative stress through NADPH-oxidase-derived ROS generation and reduced Nrf-2 (nuclear factor [erythroid-derived 2]-like 2) antioxidant systems, promoting vascular injury.

APPROACH AND RESULTS

HPASMCs from controls and PAH patients, and PASMCs from Nox1^-/- mice, were stimulated with serotonin in the absence/presence of inhibitors of Src kinase, the 5-HT_1B receptor, and NADPH oxidase 1 (Nox1). Markers of fibrosis were also determined. The pathophysiological significance of our findings was examined in vivo in serotonin transporter overexpressing female mice, a model of pulmonary hypertension. We confirmed thatserotonin increased superoxide and hydrogen peroxide production in these cells. For the first time, we show that serotonin increased oxidized protein tyrosine phosphatases and hyperoxidized peroxiredoxin and decreased Nrf-2 and catalase activity in hPASMCs. ROS generation was exaggerated and dependent on cellular Src-related kinase, 5-HT_1B receptor, and the serotonin transporter in human pulmonary artery smooth muscle cells from PAH subjects. Proliferation and extracellular matrix remodeling were exaggerated in human pulmonary artery smooth muscle cells from PAH subjects and dependent on 5-HT_1B receptor signaling and Nox1, confirmed in PASMCs from Nox1^-/- mice. In serotonin transporter overexpressing mice, SB216641, a 5-HT_1B receptor antagonist, prevented development of pulmonary hypertension in a ROS-dependent manner.

CONCLUSIONS

Serotonin can induce cellular Src-related kinase-regulated Nox1-induced ROS and Nrf-2 dysregulation, contributing to increased post-translational oxidative modification of proteins and activation of redox-sensitive signaling pathways in hPASMCs, associated with mitogenic responses. 5-HT_1B receptors contribute to experimental pulmonary hypertension by inducing lung ROS production. Our results suggest that 5-HT_1B receptor-dependent cellular Src-related kinase-Nox1-pathways contribute to vascular remodeling in PAH.

MEF2D haploinsufficiency downregulates the NRF2 pathway and renders photoreceptors susceptible to light-induced oxidative stress

Gaining mechanistic insight into interaction between causative factors of complex multifactorial diseases involving photoreceptor damage might aid in devising effective therapies. Oxidative stress is one of the potential unifying mechanisms for interplay between genetic and environmental factors that contribute to photoreceptor pathology. Interestingly, the transcription factor myocyte enhancer factor 2d (MEF2D) is known to be important in photoreceptor survival, as knockout of this transcription factor results in loss of photoreceptors in mice. Here, using a mild light-induced retinal degeneration model, we show that the diminished MEF2D transcriptional activity in Mef2d^+/- retina is further reduced under photostimulation-induced oxidative stress. Reactive oxygen species cause an aberrant redox modification on MEF2D, consequently inhibiting transcription of its downstream target, nuclear factor (erythroid-derived 2)-like 2 (NRF2). NRF2 is a master regulator of phase II antiinflammatory and antioxidant gene expression. In the Mef2d heterozygous mouse retina, NRF2 is not up-regulated to a normal degree in the face of light-induced oxidative stress, contributing to accelerated photoreceptor cell death. Furthermore, to combat this injury, we found that activation of the endogenous NRF2 pathway using proelectrophilic drugs rescues photoreceptors from photo-induced oxidative stress and may therefore represent a viable treatment for oxidative stress-induced photoreceptor degeneration, which is thought to contribute to some forms of retinitis pigmentosa and age-related macular degeneration.

Dual signaling evoked by oxidized LDLs in vascular cells

The oxidative theory of atherosclerosis relies on the modification of low density lipoproteins (LDLs) in the vascular wall by reactive oxygen species. Modified LDLs, such as oxidized LDLs, are thought to participate in the formation of early atherosclerotic lesions (accumulation of foam cells and fatty streaks), whereas their role in advanced lesions and atherothrombotic events is more debated, because antioxidant supplementation failed to prevent coronary disease events and mortality in intervention randomized trials. As oxidized LDLs and oxidized lipids are present in atherosclerotic lesions and are able to trigger cell signaling on cultured vascular cells and macrophages, it has been proposed that they could play a role in atherogenesis and atherosclerotic vascular remodeling. Oxidized LDLs exhibit dual biological effects, which are dependent on extent of lipid peroxidation, nature of oxidized lipids (oxidized phospholipids, oxysterols, malondialdehyde, α,β-unsaturated hydroxyalkenals), concentration of oxidized LDLs and uptake by scavenger receptors (e.g. CD36, LOX-1, SRA) that signal through different transduction pathways. Moderate concentrations of mildly oxidized LDLs are proinflammatory and trigger cell migration and proliferation, whereas higher concentrations induce cell growth arrest and apoptosis. The balance between survival and apoptotic responses evoked by oxidized LDLs depends on cellular systems that regulate the cell fate, such as ceramide/sphingosine-1-phosphate rheostat, endoplasmic reticulum stress, autophagy and expression of pro/antiapoptotic proteins. In vivo, the intimal concentration of oxidized LDLs depends on the influx (hypercholesterolemia, endothelial permeability), residence time and lipid composition of LDLs, oxidative stress intensity, induction of defense mechanisms (antioxidant systems, heat shock proteins). As a consequence, the local cellular responses to oxidized LDLs may stimulate inflammatory or anti-inflammatory pathways, angiogenic or antiangiogenic responses, survival or apoptosis, thereby contributing to plaque growth, instability, complication (intraplaque hemorrhage, proteolysis, calcification, apoptosis) and rupture. Finally, these dual properties suggest that oxLDLs could be implicated at each step of atherosclerosis development, from early fatty streaks to advanced lesions, depending on the nature and concentration of their oxidized lipid content.

An overview of the role of lipid peroxidation-derived 4-hydroxynonenal in osteoarthritis

BACKGROUND

Over the years, many theories have been proposed and examined to better explain the etiology and development of osteoarthritis (OA). The characteristics of joint destruction are one of the most important aspects in disease progression. Therefore, investigating different factors and signaling pathways involved in the alteration of extracellular matrix (ECM) turnover, and the subsequent catabolic damage to cartilage holds chief importance in understanding OA development. Among these factors, reactive oxygen species (ROS) have been at the forefront of the physiological and pathophysiological OA investigation.

FINDINGS

In the last decades, research studies provided an enormous volume of data supporting the involvement of ROS in OA. Most interestingly, published data regarding the effect of exogenous antioxidant therapy in OA lack conclusive results from clinical trials to back up in vitro data. Accordingly, it is rational to suggest that there are other reactive species in OA that are not taken into account. Thus, our present review is focused on our current understanding of the involvement of lipid peroxidation-derived 4-hydroxynonenal (HNE) in OA.

CONCLUSION

Our findings, like those in the literature, illustrate the central role played by HNE in the regulation of a number of factors involved in joint homeostasis. HNE could thus be considered as an attractive therapeutic target in OA.

Quality and freshness of human bone marrow-derived mesenchymal stem cells decrease over time after trypsinization and storage in phosphate-buffered saline

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) have been studied for their therapeutic potential. However, evaluating the quality of hBM-MSCs before transplantation remains a challenge. We addressed this issue in the present study by investigating deformation, the expression of genes related to reactive oxygen species (ROS) generation, changes in amino acid profiles, and membrane fluidity in hBM-MSCs. Deformability and cell size were decreased after storage for 6 and 12 h, respectively, in phosphate-buffered saline. Intracellular ROS levels also increased over time, which was associated with altered expression of genes related to ROS generation and amino acid metabolism. Membrane fluidity measurements revealed higher Laurdan generalized polarization values at 6 and 12 h; however, this effect was reversed by N-acetyl-l-cysteine-treatment. These findings indicate that the quality and freshness of hBM-MSCs is lost over time after dissociation from the culture dish for transplantation, highlighting the importance of using freshly trypsinized cells in clinical applications.

Superoxide is the critical driver of DOPAL autoxidation, lysyl adduct formation, and crosslinking of α-synuclein

Parkinson's disease has long been associated with redox imbalance and oxidative stress in dopaminergic neurons. The catecholaldehyde hypothesis proposes that 3,4-dihydroxyphenylacetaldehyde (DOPAL), an obligate product of dopamine catabolism, is a central nexus in a network of pathways leading to disease-state neurodegeneration, owing to its toxicity and potent ability to oligomerize α-synuclein, the main component of protein aggregates in Lewy bodies. In this work we examine the connection between reactive oxygen species and DOPAL autoxidation. We show that superoxide propagates a chain reaction oxidation, and that this reaction is dramatically inhibited by superoxide dismutase. Moreover, superoxide dismutase prevents DOPAL from forming dicatechol pyrrole adducts with lysine and from covalently crosslinking α-synuclein. Given that superoxide is a major radical byproduct of impaired cellular respiration, our results provide a possible mechanistic link between mitochondrial dysfunction and synuclein aggregation in dopaminergic neurons.

4-Hydroxynonenal Contributes to Angiogenesis through a Redox-Dependent Sphingolipid Pathway: Prevention by Hydralazine Derivatives

The neovascularization of atherosclerotic lesions is involved in plaque development and may contribute to intraplaque hemorrhage and plaque fragilization and rupture. Among the various proangiogenic agents involved in the neovascularization process, proatherogenic oxidized LDLs (oxLDLs) contribute to the formation of tubes via the generation of sphingosine 1-phosphate (S1P), a major mitogenic and proangiogenic sphingolipid mediator. In this study, we investigated whether 4-hydroxynonenal (4-HNE), an aldehydic lipid oxidation product abundantly present in oxLDLs, contributes to their proangiogenic properties. Immunofluorescence analysis of human atherosclerotic lesions from carotid endarterectomy showed the colocalization of HNE-adducts with CD31, a marker of endothelial cells, suggesting a close relationship between 4-HNE and neovessel formation. In vitro, low 4-HNE concentration (0.5-1 µM) elicited the formation of tubes by human microvascular endothelial cells (HMEC-1), whereas higher concentrations were not angiogenic. The formation of tubes by 4-HNE involved the generation of reactive oxygen species and the activation of the sphingolipid pathway, namely, the neutral type 2 sphingomyelinase and sphingosine kinase-1 (nSMase2/SK-1) pathway, indicating a role for S1P in the angiogenic signaling of 4-HNE. Carbonyl scavengers hydralazine and bisvanillyl-hydralazone inhibited the nSMase2/SK1 pathway activation and the formation of tubes on Matrigel® evoked by 4-HNE. Altogether, these results emphasize the role of 4-HNE in the angiogenic effect of oxLDLs and point out the potential interest of pharmacological carbonyl scavengers to prevent the neovascularization process.

Aldehyde Oxidase 4 Plays a Critical Role in Delaying Silique Senescence by Catalyzing Aldehyde Detoxification

The Arabidopsis (Arabidopsis thaliana) aldehyde oxidases are a multigene family of four oxidases (AAO1-AAO4) that oxidize a variety of aldehydes, among them abscisic aldehyde, which is oxidized to the phytohormone abscisic acid. Toxic aldehydes are generated in plants both under normal conditions and in response to stress. The detoxification of such aldehydes by oxidation is attributed to aldehyde dehydrogenases but never to aldehyde oxidases. The feasibility of the detoxification of aldehydes in siliques via oxidation by AAO4 was demonstrated, first, by its ability to efficiently oxidize an array of aromatic and aliphatic aldehydes, including the reactive carbonyl species (RCS) acrolein, hydroxyl-2-nonenal, and malondialdehyde. Next, exogenous application of several aldehydes to siliques in AAO4 knockout (KO) Arabidopsis plants induced severe tissue damage and enhanced malondialdehyde levels and senescence symptoms, but not in wild-type siliques. Furthermore, abiotic stresses such as dark and ultraviolet C irradiation caused an increase in endogenous RCS and higher expression levels of senescence marker genes, leading to premature senescence of KO siliques, whereas RCS and senescence marker levels in wild-type siliques were hardly affected. Finally, in naturally senesced KO siliques, higher endogenous RCS levels were associated with enhanced senescence molecular markers, chlorophyll degradation, and earlier seed shattering compared with the wild type. The aldehyde-dependent differential generation of superoxide and hydrogen peroxide by AAO4 and the induction of AAO4 expression by hydrogen peroxide shown here suggest a self-amplification mechanism for detoxifying additional reactive aldehydes produced during stress. Taken together, our results indicate that AAO4 plays a critical role in delaying senescence in siliques by catalyzing aldehyde detoxification.

Sodium fluoride induces hypertension and cardiac complications through generation of reactive oxygen species and activation of nuclear factor kappa beta

Human exposure to sodium fluoride through its daily usage is almost inevitable. Cardiovascular and renal dysfunction has been associated with fluoride toxicity. Therefore, this study investigated the mechanism of action of sodium fluoride (NaF) induced hypertension and cardiovascular complications Forty male albino rats of an average of 10 rats per group were used. Group A received clean tap water. Toxicity was induced in Group B to D by administering graded doses of NaF through drinking water ad libitum for 10 days at 150 ppm, 300 ppm, and 600 ppm concentration respectively. Following administration of NaF, there was significant increase in systolic pressure, diastolic pressure and mean arterial pressure. Markers of oxidative stress; malondialdehyde, hydrogen peroxide, advance oxidation protein products, and protein carbonyl were significantly increased in dose-dependent pattern in the cardiac and renal tissues of rats together with significant decrease in the GST activity in NaF-treated rats compared to the control. Also serum markers of inflammation, cardiac, and renal damage including myeloperoxidase, xanthine oxidase, blood urea nitrogen, creatinine, Lactate dehydrogenase (LDH), and Creatinine kinase myocardial band (CK-MB) significantly increased indicating induction of oxidative stress, renal, and cardiac damage after exposure. Histopathology of the kidney and heart revealed aberrations in the histological architecture in NaF-treated rats. Also, immunohistochemistry showed higher expression of nuclear factor kappa beta (NF-kB) in the cardiac and renal tissues of rats administered NaF. Combining all, these results indicate NaF-induced hypertension through generation of reactive oxygen species and activation of renal and cardiac NF-kB expressions. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1089-1101, 2017.

Effects of ferric citrate supplementation on advanced glycation end products in a rat model of streptozotocin/nicotinamide-induced diabetes

SCOPE

Diabetes is associated with the increased risks of anemia and activation of advanced glycation end products (AGEs) and the receptor for AGEs (RAGE). However, the effects of pharmacological doses of iron supplementation on AGE metabolism are less clear. The aim was to investigate the effect of ferric citrate supplementation on AGE metabolism.

METHODS AND RESULTS

Diabetes was induced in overnight starved rats by intraperitoneal injections of 40 mg/kg streptozotocin and 120 mg/kg nicotinamide. Diabetic rats were fed a standard diet or pharmacological doses of ferric citrate (0.5, 1, 2, and 3 g of ferric iron/kg diet) for 10 weeks. Ferric citrate supplementation showed a dose-related effect on the hepatic steatosis score, malondialdehyde, cathepsin D, and glyoxalase I. A Western blot analysis revealed that >1 g of ferric iron suppressed hepatic AGE receptor 1 and high-mobility group-box 1 expressions but increased heme oxygenase-1 and RAGE expressions. Further analysis showed that high doses of ferric iron triggered sterol regulatory element-binding protein 1c, p38-mitogen-activated protein kinase, and nuclear factor-κB protein expressions.

CONCLUSION

Overall, the present results suggest a dose-related effect of ferric citrate supplementation on AGE metabolism, and this effect was more evident at high iron doses (>1 g of ferric iron/kg diet).

Wheat germ agglutinin-conjugated liposomes incorporated with cardiolipin to improve neuronal survival in Alzheimer's disease treatment

Curcumin (CRM) and nerve growth factor (NGF) were entrapped in liposomes (LIP) with surface wheat germ agglutinin (WGA) to downregulate the phosphorylation of kinases in Alzheimer’s disease (AD) therapy. Cardiolipin (CL)-conjugated LIP carrying CRM (CRM-CL/LIP) and also carrying NGF (NGF-CL/LIP) were used with AD models of SK-N-MC cells and Wistar rats after an insult with β-amyloid peptide (Aβ). We found that CRM-CL/LIP inhibited the expression of phosphorylated p38 (p-p38), phosphorylated c-Jun N-terminal kinase (p-JNK), and p-tau protein at serine 202 and prevented neurodegeneration of SK-N-MC cells. In addition, NGF-CL/LIP could enhance the quantities of p-neurotrophic tyrosine kinase receptor type 1 and p-extracellular signal-regulated kinase 5 for neuronal rescue. Moreover, WGA-grafted CRM-CL/LIP and WGA-grafted NGF-CL/LIP significantly improved the permeation of CRM and NGF across the blood–brain barrier, reduced Aβ plaque deposition and the malondialdehyde level, and increased the percentage of normal neurons and cholinergic activity in the hippocampus of AD rats. Based on the marker expressions and in vivo evidence, current LIP carriers can be promising drug delivery systems to protect nervous tissue against Aβ-induced apoptosis in the brain during the clinical management of AD.

[Protein molecular aging: which role in physiopathology?]

Protein molecular aging corresponds to all modifications affecting proteins during their biological life, which lead to the alteration of their structural and functional properties. This phenomenon participates in cell and tissue aging and is therefore involved in the aging of human organism. It is also amplified in various chronic diseases such as diabetes mellitus or chronic kidney disease, where it participates in the development of long-term complications. This review aims at describing the main reactions responsible for molecular aging, their impact on protein properties and the parameters which could influence this phenomenon. A general scheme explaining its role in physiopathology is also proposed.

Angiogenesis in the atherosclerotic plaque

Atherosclerosis is a multifocal alteration of the vascular wall of medium and large arteries characterized by a local accumulation of cholesterol and non-resolving inflammation. Atherothrombotic complications are the leading cause of disability and mortality in western countries. Neovascularization in atherosclerotic lesions plays a major role in plaque growth and instability. The angiogenic process is mediated by classical angiogenic factors and by additional factors specific to atherosclerotic angiogenesis. In addition to its role in plaque progression, neovascularization may take part in plaque destabilization and thromboembolic events. Anti-angiogenic agents are effective to reduce atherosclerosis progression in various animal models. However, clinical trials with anti-angiogenic drugs, mainly anti-VEGF/VEGFR, used in anti-cancer therapy show cardiovascular adverse effects, and require additional investigations.

Determination of glucose exchange rates and permeability of erythrocyte membrane in preeclampsia and subsequent oxidative stress-related protein damage using dynamic-19F-NMR

The cause of the pregnancy condition preeclampsia (PE) is thought to be endothelial dysfunction caused by oxidative stress. As abnormal glucose tolerance has also been associated with PE, we use a fluorinated-mimic of this metabolite to establish whether any oxidative damage to lipids and proteins in the erythrocyte membrane has increased cell membrane permeability. Data were acquired using ¹⁹F Dynamic-NMR (DNMR) to measure exchange of 3-fluoro-3-deoxyglucose (3-FDG) across the membrane of erythrocytes from 10 pregnant women (5 healthy control women, and 5 from women suffering from PE). Magnetisation transfer was measured using the 1D selective inversion and 2D EXSY pulse sequences, over a range of time delays. Integrated intensities from these experiments were used in matrix diagonalisation to estimate the values of the rate constants of exchange and membrane permeability. No significant differences were observed for the rate of exchange of 3-FDG and membrane permeability between healthy pregnant women and those suffering from PE, leading us to conclude that no oxidative damage had occurred at this carrier-protein site in the membrane.

Cross-talk between lipid and protein carbonylation in a dynamic cardiomyocyte model of mild nitroxidative stress

Reactive oxygen and nitrogen species (ROS/RNS) play an important role in the regulation of cardiac function. Increase in ROS/RNS concentration results in lipid and protein oxidation and is often associated with onset and/or progression of many cardiovascular disorders. However, interplay between lipid and protein modifications has not been simultaneously studied in detail so far. Biomolecule carbonylation is one of the most common biomarkers of oxidative stress. Using a dynamic model of nitroxidative stress we demonstrated rapid changes in biomolecule carbonylation in rat cardiomyocytes. Levels of carbonylated species increased as early as 15min upon treatment with the peroxynitrite donor, 3-morpholinosydnonimine (SIN-1), and decreased to values close to control after 16h. Total (lipids+proteins) vs. protein-specific carbonylation showed different dynamics, with a significant increase in protein-bound carbonyls at later time points. Treatment with SIN-1 in combination with inhibitors of proteasomal and autophagy/lysosomal degradation pathways allowed confirmation of a significant role of the proteasome in the degradation of carbonylated proteins, whereas lipid carbonylation increased in the presence of autophagy/lysosomal inhibitors. Electrophilic aldehydes and ketones formed by lipid peroxidation were identified and relatively quantified using LC-MS/MS. Molecular identity of reactive species was used for data-driven analysis of their protein targets. Combination of different enrichment strategies with LC-MS/MS analysis allowed identification of more than 167 unique proteins with 332 sites modified by electrophilic lipid peroxidation products. Gene ontology analysis of modified proteins demonstrated enrichment of several functional categories including proteins involved in cytoskeleton, extracellular matrix, ion channels and their regulation. Using calcium mobilization assays, the effect of nitroxidative stress on the activity of several ion channels was further confirmed.

Modified Lipids and Lipoproteins in Chronic Kidney Disease: A New Class of Uremic Toxins

Chronic kidney disease (CKD) is associated with an enhanced oxidative stress and deep modifications in lipid and lipoprotein metabolism. First, many oxidized lipids accumulate in CKD and were shown to exert toxic effects on cells and tissues. These lipids are known to interfere with many cell functions and to be pro-apoptotic and pro-inflammatory, especially in the cardiovascular system. Some, like F2-isoprostanes, are directly correlated with CKD progression. Their accumulation, added to their noxious effects, rendered their nomination as uremic toxins credible. Similarly, lipoproteins are deeply altered by CKD modifications, either in their metabolism or composition. These impairments lead to impaired effects of HDL on their normal effectors and may strongly participate in accelerated atherosclerosis and failure of statins in end-stage renal disease patients. This review describes the impact of oxidized lipids and other modifications in the natural history of CKD and its complications. Moreover, this review focuses on the modifications of lipoproteins and their impact on the emergence of cardiovascular diseases in CKD as well as the appropriateness of considering them as actual mediators of uremic toxicity.

Rescuing cholinergic neurons from apoptotic degeneration by targeting of serotonin modulator-and apolipoprotein E-conjugated liposomes to the hippocampus

β-Amyloid (Aβ)-targeting liposomes (LIP) with surface serotonin modulator (SM) and apolipoprotein E (ApoE) were utilized to facilitate the delivery of nerve growth factor (NGF) across the blood-brain barrier (BBB) for neuroprotection in the hippocampus. The therapeutic efficacy of SM- and ApoE-grafted LIP carrying NGF (NGF-SM-ApoE-LIP) was assessed by an in vitro Alzheimer's disease (AD) model of degenerated SK-N-MC cells and an in vivo AD model of Aβ-insulted Wistar rats. The experimental evidences revealed that the modified SM and ApoE on the surface of LIP increased the permeation of NGF across the BBB without serious damage to structural integrity of tight junction. When compared with free NGF, NGF-SM-ApoE-LIP upregulated the expression of phosphorylated neurotrophic tyrosine kinase receptor type 1 on cholinergic neurons and significantly improved their survival. In addition, NGF-SM-ApoE-LIP could reduce the secretion of acetylcholinesterase and malondialdehyde and rescue hippocampal neurons from apoptosis in rat brains. The synergistic effect of SM and ApoE is promising in the induction of NGF to inhibit the neurotoxicity of Aβ and NGF-SM-ApoE-LIP can be a potent antiapoptotic pharmacotherapy for clinical care of patients with AD.

Protein lipid modifications--More than just a greasy ballast

Covalent lipid modifications of proteins are crucial for regulation of cellular plasticity, since they affect the chemical and physical properties and therefore protein activity, localization, and stability. Most recently, lipid modifications on proteins are increasingly attracting important regulatory entities in diverse signaling events and diseases. In all cases, the lipid moiety of modified proteins is essential to allow water-soluble proteins to strongly interact with membranes or to induce structural changes in proteins that are critical for elemental processes such as respiration, transport, signal transduction, and motility. Until now, roughly about ten lipid modifications on different amino acid residues are described at the UniProtKB database and even well-known modifications are underrepresented. Thus, it is of fundamental importance to develop a better understanding of this emerging and so far under-investigated type of protein modification. Therefore, this review aims to give a comprehensive and detailed overview about enzymatic and nonenzymatic lipidation events, will report their role in cellular biology, discuss their relevancy for diseases, and describe so far available bioanalytical strategies to analyze this highly challenging type of modification.

Intracellular Activation of Complement 3 Is Responsible for Intestinal Tissue Damage during Mesenteric Ischemia

Intestinal ischemia followed by reperfusion leads to local and remote organ injury attributed to inflammatory response during the reperfusion phase. The extent to which ischemia contributes to ischemia/reperfusion injury has not been thoroughly studied. After careful evaluation of intestinal tissue following 30 min of ischemia, we noticed significant local mucosal injury in wild-type mice. This injury was drastically reduced in C3-deficient mice, suggesting C3 involvement. Depletion of circulating complement with cobra venom factor eliminated, as expected, injury recorded at the end of the reperfusion phase but failed to eliminate injury that occurred during the ischemic phase. Immunohistochemical studies showed that tissue damage during ischemia was associated with increased expression of C3/C3 fragments primarily in the intestinal epithelial cells, suggesting local involvement of complement. In vitro studies using Caco2 intestinal epithelial cells showed that in the presence of LPS or exposure to hypoxic conditions the cells produce higher C3 mRNA as well as C3a fragment. Caco2 cells were also noted to produce cathepsins B and L, and inhibition of cathepsins suppressed the release of C3a. Finally, we found that mice treated with a cathepsin inhibitor and cathepsin B-deficient mice suffer limited intestinal injury during the ischemic phase. To our knowledge, our findings demonstrate for the first time that significant intestinal injury occurs during ischemia prior to reperfusion and that this is due to activation of C3 within the intestinal epithelial cells in a cathepsin-dependent manner. Modulation of cathepsin activity may prevent injury of organs exposed to ischemia.

Hyperlipidemia-Mediated Increased Advanced Lipoxidation End Products Formation, an Important Factor Associated with Decreased Erythrocyte Glucose-6-Phosphate Dehydrogenase Activity in Mild Nonproliferative Diabetic Retinopathy

OBJECTIVES

The present study aimed to evaluate the role of hyperlipidemia in increased formation of advanced lipoxidation end products (ALEs) and to evaluate whether there is any relationship between ALEs generation and erythrocyte glucose-6-phosphate dehydrogenase (G6PD) activity in cases of mild nonproliferative diabetic retinopathy (MNPDR).

METHODS

In this study, we enrolled 100 patients with type 2 diabetes and MNPDR, 100 subjects with type 2 diabetes but without retinopathy (DNR) and 90 normal individuals without diabetes as healthy controls (HCs). Erythrocyte nicotinamide dinucleotide phosphate (NADPH), G6PD activity, serum total cholesterol, low- and high-density lipoprotein (LDL, HDL) and triglyceride levels were determined by photometric assay. Serum malondialdehyde (MDA) protein adduct and hexanoyl-lysine (HEL) were measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

A robust linear relationship was observed between MDA protein adduct and LDL or cholesterol or triglyceride levels, and HEL and LDL or cholesterol or triglyceride levels in subjects with MNPDR (p=0.0001). A significant inverse association was observed between erythrocyte G6PD activity and serum MDA protein adductor HEL levels in subjects with MNPDR (p=0.0001).

CONCLUSIONS

Hyperlipidemia is an important factor that is associated with increased ALEs formation in persons with MNPDR. Increased ALEs generation was associated with decreased G6PD activity and low NADPH levels in cases of MNPDR, suggesting their detrimental role in the occurrence of early NPDR.

Galectin-3 and IL-33/ST2 axis roles and interplay in diet-induced steatohepatitis

Immune reactivity and chronic low-grade inflammation (metaflammation) play an important role in the pathogenesis of obesity-associated metabolic disorders, including type 2 diabetes and nonalcoholic fatty liver disease (NAFLD), a spectrum of diseases that include liver steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Increased adiposity and insulin resistance contribute to the progression from hepatic steatosis to NASH and fibrosis through the development of proinflammatory and profibrotic processes in the liver, including increased hepatic infiltration of innate and adaptive immune cells, altered balance of cytokines and chemokines, increased reactive oxygen species generation and hepatocellular death. Experimental models of dietary-induced NAFLD/NASH in mice on different genetic backgrounds or knockout mice with different immune reactivity are used for elucidating the pathogenesis of NASH and liver fibrosis. Galectin-3 (Gal-3), a unique chimera-type β-galactoside-binding protein of the galectin family has a regulatory role in immunometabolism and fibrogenesis. Mice deficient in Gal-3 develop pronounced adiposity, hyperglycemia and hepatic steatosis, as well as attenuated liver inflammation and fibrosis when fed an obesogenic high-fat diet. Interleukin (IL)-33, a member of the IL-1 cytokine family, mediates its effects through the ST receptor, which is present on immune and nonimmune cells and participates in immunometabolic and fibrotic disorders. Recent evidence, including our own data, suggests a protective role for the IL-33/IL-33R (ST2) signaling pathway in obesity, adipose tissue inflammation and atherosclerosis, but a profibrotic role in NASH development. The link between Gal-3 and soluble ST2 in myocardial fibrosis and heart failure progression has been demonstrated and we have recently shown that Gal-3 and the IL-33/ST2 pathway interact and both have a profibrotic role in diet-induced NASH. This review discusses the current evidence on the roles of Gal-3 and the IL-33/ST2 pathway and their interplay in obesity-associated hepatic inflammation and fibrogenesis that may be of interest in the development of therapeutic interventions to prevent and/or reverse obesity-associated hepatic inflammation and fibrosis.

Carbonylated proteins exposed to UVA and to blue light generate reactive oxygen species through a type I photosensitizing reaction

BACKGROUND

Carbonylated proteins (CPs) are generated by the reaction of basic amino acid residues in proteins with aldehyde compounds produced during lipid peroxidation. CPs in the stratum corneum (SC) impact skin conditions such as skin moisture functions including water content and transepidermal water loss (TEWL). In addition, CPs can be frequently seen in the SC from sun-exposed sites compared with sun-protected sites.

OBJECTIVE

The aim of this study was to reveal whether CPs could be a generation source of reactive oxygen species (ROS) in the SC following exposure to ultraviolet (UV) radiation and to identify the type of ROS and its generation mechanism.

METHODS

ROS generation was detected using a methyl cypridina luciferin analog (MCLA) chemiluminescence system and an ESR spin-trapping method. CPs in porcine SC, in a keratin film and in bovine serum albumin (BSA) were prepared by reaction with acrolein. Levels of protein carbonylation were quantified by detecting aldehyde residues.

RESULTS

CP levels in the SC were increased in a UVA energy-dependent manner. That result suggested that a source of ROS generation existed in the SC initiated and produced the carbonylation of SC proteins. Carbonylated BSA and carbonylated porcine SC sheets exhibited fluorescence spectra at an excitation wavelength of 430nm and an emission wavelength of 520nm. Irradiation of the SC with UVA increased protein carbonylation and the amount of autofluorescence in the SC. ROS generation in the SC caused by UVA and by short-wavelength visible light (blue light, 400-470nm) was detected by the MCLA chemiluminescence system. Artificially carbonylated porcine SCs and keratin films had increases of chemiluminescence intensity after exposure to both light sources as well. The addition of superoxide dismutase to the MCLA system completely abolished the incremental chemiluminescence intensity after both UVA and blue light exposure of the SC. In addition, acrolein-treated BSA gave ESR signals like hydroxyl radicals (OH) converted from superoxide anion radicals (O₂^-) during irradiation with a xenon arc lamp containing UVA and visible light. From the sum of these results, we consider that CPs are produced from O₂^- initially generated from exposure to UVA and blue light.

CONCLUSION

CPs are excited by absorbing sunlight, particularly UVA and blue light, and result in the generation of O₂^- through a CPs progress new protein carbonylation in stratum corneum through ROS generation. photosensitizing reaction. Further, the results suggest that the O₂^- produces CPs in the SC through lipid peroxidation in the sebum, and finally affects skin conditions including color and moisture functions.

4-hydroxynonenal regulates mitochondrial function in human small airway epithelial cells

Prolonged exposure to oxidative stress causes Acute Lung Injury (ALI) and significantly impairs pulmonary function. Previously we have demonstrated that mitochondrial dysfunction is a key pathological factor in hyperoxic ALI. While it is known that hyperoxia induces the production of stable, but toxic 4-hydroxynonenal (4-HNE) molecule, it is unknown how the reactive aldehyde disrupts mitochondrial function. Our previous in vivo study indicated that exposure to hyperoxia significantly increases 4-HNE-Protein adducts, as well as levels of MDA in total lung homogenates. Based on the in vivo studies, we explored the effects of 4-HNE in human small airway epithelial cells (SAECs). Human SAECs treated with 25 μM of 4-HNE showed a significant decrease in cellular viability and increased caspase-3 activity. Moreover, 4-HNE treated SAECs showed impaired mitochondrial function and energy production indicated by reduced ATP levels, mitochondrial membrane potential, and aconitase activity. This was followed by a significant decrease in mitochondrial oxygen consumption and depletion of the reserve capacity. The direct effect of 4-HNE on the mitochondrial respiratory chain was confirmed using Rotenone. Furthermore, SAECs treated with 25 μM 4-HNE showed a time-dependent depletion of total Thioredoxin (Trx) proteins and Trx activity. Taken together, our results indicate that 4-HNE induces cellular and mitochondrial dysfunction in human SAECs, leading to an impaired endogenous antioxidant response.

Antioxidant-Enhancing Property of the Polar Fraction of Mangosteen Pericarp Extract and Evaluation of Its Safety in Humans

Crude extract from the pericarp of the mangosteen (mangosteen extract [ME]) has exhibited several medicinal properties in both animal models and human cell lines. Interestingly, the cytotoxic activities were always observed in nonpolar fraction of the extract whereas the potent antioxidant was often found in polar fraction. Although it has been demonstrated that the polar fraction of ME exhibited the antioxidant activity, the safety of the polar fraction of ME has never been thoroughly investigated in humans. In this study, we investigated the safety of oral administration of the polar fraction of ME in 11 healthy Thai volunteers. During a 24-week period of the study, only minor and tolerable side effects were reported; no serious side effects were documented. Blood chemistry studies also showed no liver damage or kidney dysfunction in all subjects. We also demonstrated antioxidant property of the polar fraction of ME both in vitro and in vivo. Interestingly, oral administration of the polar fraction of ME enhanced the antioxidant capability of red blood cells and decreased oxidative damage to proteins within red blood cells and whole blood.

Breads Fortified with Freeze-Dried Vegetables: Quality and Nutritional Attributes. Part II: Breads Not Containing Oil as an Ingredient

The present article describes the second part of a study investigating the effect of adding vegetables on the nutritional, physico-chemical, and oxidative properties of wheat bread, and specifically focuses on bread that does not contain oil as an added ingredient. Wheat flour breads fortified with freeze-dried carrot, tomato, beetroot or broccoli were developed and assessed for their nutritional composition, antioxidant potential, oxidative stability, and storage properties. Using a simulated in vitro model, the study also examined the impact of vegetable addition on the oxidative stability of macronutrients during gastro-intestinal digestion. Adding vegetables improved the nutritional and functional attributes of the oil-free breads. However, they demonstrated a lower antioxidant potential compared to their oil-containing counterparts. Similarly, the textural and storage properties of the oil-free vegetable breads were poorer compared to the oil-containing breads. As expected, in the absence of oil the oil-free breads were associated with lower lipid oxidation both in their fresh form and during gastro-intestinal digestion. Adding vegetables reduced protein oxidation in the fresh oil-free breads but had no effect during gastro-intestinal digestion. The impact of vegetables on macronutrient oxidation in the oil-free breads during digestion appears to be vegetable-specific with broccoli exacerbating it and the others having no effect. Of the evaluated vegetables, beetroot showed the most promising nutritional and physico-chemical benefits when incorporated into bread that does not contain added oil.

Relevance of peroxynitrite formation and 3-nitrotyrosine on spermatozoa physiology

HIGHLIGHTS

Male fertility decline has been attributed, in part, to increased oxidative stress.Here we will focus on spermatozoa ROS, namely O2•-, NO and ONOO- and their contribution to protein tyrosine nitration, namely by 3-NT formation.An in depth review will be made on the methods used to detect protein oxidation.Detecting 3-NT in sperm proteins will have a crucial clinical impact, namely on the follow up of anti-oxidant therapies.

ABSTRACT

Infertility is a clinical condition that affects around 15% of reproductive-aged couples worldwide. Around half of these cases are due to male factors, the most owing to idiopathic causes. The increase of reactive oxygen species (ROS), which leads to oxidative stress (OS), has been discussed in the last years as a possible cause of male idiopathic infertility. Superoxide anion (O2 •-) and nitric oxide (NO) can react with each other contributing to the formation of peroxynitrite (ONOO-). This molecule can then act on spermatozoa proteins, leading to nitration of protein tyrosines - addition of a nitro (NO2) group - that is then manifested by the formation of 3-nitrotyrosine (3-NT). In turn, 3-NT may be responsible for the alteration or inactivation of the protein function.This review will focus on the description of spermatozoa ROS, namely O2 •-, NO and ONOO- and in their contribution to protein tyrosine nitration, namely by 3-NT formation. Previous results about the effect of ONOO- and 3-NT in spermatozoa will be presented, as well as, the methods that can be performed to detect the protein oxidation by these species. The impact of measuring, at the clinical level, 3-NT, considered a marker of OS, in spermatozoa will be discussed.

Upstream Pathways Controlling Mitochondrial Function in Major Psychosis: A Focus on Bipolar Disorder

Mitochondrial dysfunction is commonly observed in bipolar disorder (BD) and schizophrenia (SCZ) and may be a central feature of psychosis. These illnesses are complex and heterogeneous, which is reflected by the complexity of the processes regulating mitochondrial function. Mitochondria are typically associated with energy production; however, dysfunction of mitochondria affects not only energy production but also vital cellular processes, including the formation of reactive oxygen species, cell cycle and survival, intracellular Ca(2+) homeostasis, and neurotransmission. In this review, we characterize the upstream components controlling mitochondrial function, including 1) mutations in nuclear and mitochondrial DNA, 2) mitochondrial dynamics, and 3) intracellular Ca(2+) homeostasis. Characterizing and understanding the upstream factors that regulate mitochondrial function is essential to understand progression of these illnesses and develop biomarkers and therapeutics.

4-Hydroxy-2-nonenal: a critical target in oxidative stress?

In this perspective, we summarize and discuss critical advancements in the study of 4-hydroxy-2-nonenal (4-HNE) as it relates to diseases and clinical complications either caused or exacerbated by oxidative stress. Since its identification in 1980, 4-HNE has been extensively studied with an emphasis on its formation, its role in pathology, and its targets. As a reactive aldehyde, and a product of lipid peroxidation, studies corroborate its ability to disrupt signal transduction and protein activity, as well as induce inflammation and trigger cellular apoptosis in conditions of oxidative stress. Notably, we discuss the role of natural enzymes involved in the regulation of 4-HNE, and how they can be applied to its detoxification in various physiological conditions.

CNDP1 genotype and renal survival in pediatric nephropathies

BACKGROUND

The risk of developing type II diabetic nephropathy (DN) is lower in patients carrying the CNDP1 Mannheim polymorphism (homozygosity for the five leucine repeat), resulting in decreased activity of the histidine-dipeptide metabolizing enzyme carnosinase. The role of CNDP1 in other nephropathies is still unknown.

METHODS

To evaluate the impact of the CNDP1 Mannheim allele on pediatric chronic kidney disease (CKD), we prospectively followed the long-term clinical outcome of 272 children with non-diabetic kidney disease (glomerulopathies n=32, non-glomerular kidney disease n=240).

RESULTS

Renal failure progression was independent of CNDP1 genotype in the total cohort of CKD children. However, in patients with glomerulopathies, only 39% of patients homozygous for the CNDP1 Mannheim polymorphism attained the primary renal endpoint as compared to 77% of patients with any other CNDP1 genotype (p=0.06).

CONCLUSIONS

Our findings in pediatric CKD patients suggest that the nephroprotective effect of the CNDP1 Mannheim variant is not restricted to patients with diabetic nephropathy.

Expression and oxidative modifications of plasma proteins in autism spectrum disorders: Interplay between inflammatory response and lipid peroxidation

PURPOSE

A role for inflammation and oxidative stress is reported in autism spectrum disorders (ASDs). Here, we tested possible changes in expression and/or oxidative status for plasma proteins in subjects with ASDs.

EXPERIMENTAL DESIGN

To evaluate protein expression and protein adducts of lipid peroxidation-derived aldehyde, analysis of plasma proteins was performed in 30 subjects with ASDs and compared with 30 healthy controls with typical development, using a proteomic approach.

RESULTS

Significant changes were evidenced for a total of 12 proteins. Of these, ten were identified as proteins involved in the acute inflammatory response including alpha-2-macroglobulin, alpha-1-antitrypsin, haptoglobin, fibrinogen, serum transferrin, prealbumin, apolipoprotein A-I apolipoprotein A-IV, apolipoprotein J, and serum albumin. In addition, significant changes occurred for two immunoglobulins alpha and gamma chains.

CONCLUSIONS AND CLINICAL RELEVANCE

Our present data indicate that an inflammatory response, coupled with increased lipid peroxidation, is present in subjects with ASDs. This information can provide new insight into the identification of potential plasma protein biomarkers in autism.

Toxic Dopamine Metabolite DOPAL Forms an Unexpected Dicatechol Pyrrole Adduct with Lysines of α-Synuclein

Parkinson's disease has long been known to involve the loss of dopaminergic neurons in the substantia nigra and the coincidental appearance of Lewy bodies containing oligomerized forms of α-synuclein. The "catecholaldehyde hypothesis" posits a causal link between these two central pathologies mediated by 3,4-dihydroxyphenylacetaldehyde (DOPAL), the most toxic dopamine metabolite. Here we determine the structure of the dominant product in reactions between DOPAL and α-synuclein, a dicatechol pyrrole lysine adduct. This novel modification results from the addition of two DOPAL molecules to the Lys sidechain amine through their aldehyde moieties and the formation of a new carbon-carbon bond between their alkyl chains to generate a pyrrole ring. The product is detectable at low concentrations of DOPAL and its discovery should provide a valuable chemical basis for future studies of DOPAL-induced crosslinking of α-synuclein.

The Pivotal Role of Aldehyde Toxicity in Autism Spectrum Disorder: The Therapeutic Potential of Micronutrient Supplementation

Autism spectrum disorder (ASD) is characterized by social and communication impairments as well as by restricted, repetitive patterns of behavior and interests. Genomic studies have not revealed dominant genetic errors common to all forms of ASD. So ASD is assumed to be a complex disorder due to mutations in hundreds of common variants. Other theories argue that spontaneous DNA mutations and/or environmental factors contribute to as much as 50% of ASD. In reviewing potential genetic linkages between autism and alcoholism, it became apparent that all theories of ASD are consistent with aldehyde toxicity, in which endogenous and exogenous aldehydes accumulate as a consequence of mutations in key enzymes. Aldehyde toxicity is characterized by cell-localized, micronutrient deficiencies in sulfur-containing antioxidants, thiamine (B1), pyridoxine (B6), folate, Zn²⁺, possibly Mg²⁺, and retinoic acid, causing oxidative stress and a cascade of metabolic disturbances. Aldehydes also react with selective cytosolic and membrane proteins in the cell of origin; then some types migrate to damage neighboring cells. Reactive aldehydes also form adducts with DNA, selectively mutating bases and inducing strand breakage. This article reviews the relevant genomic, biochemical, and nutritional literature, which supports the central hypothesis that most ASD symptoms are consistent with symptoms of aldehyde toxicity. The hypothesis represents a paradigm shift in thinking and has profound implications for clinical detection, treatment, and even prevention of ASD. Insight is offered as to which neurologically afflicted children might successfully be treated with micronutrients and which children are unlikely to be helped. The aldehyde toxicity hypothesis likely applies to other neurological disorders.

Cellular oxidative damage is more sensitive to biosynthetic rate than to metabolic rate: A test of the theoretical model on hornworms (Manduca sexta larvae)

We develop a theoretical model from an energetic viewpoint for unraveling the entangled effects of metabolic and biosynthetic rates on oxidative cellular damage accumulation during animal's growth, and test the model by experiments in hornworms. The theoretical consideration suggests that most of the cellular damages caused by the oxidative metabolism can be repaired by the efficient maintenance mechanisms, if the energy required by repair is unlimited. However, during growth a considerable amount of energy is allocated to the biosynthesis, which entails tradeoffs with the requirements of repair. Thus, the model predicts that cellular damage is more influenced by the biosynthetic rate than the metabolic rate. To test the prediction, we induced broad variations in metabolic and biosynthetic rates in hornworms, and assayed the lipid peroxidation and protein carbonyl. We found that the increase in the cellular damage was mainly caused by the increase in biosynthetic rate, and the variations in metabolic rate had negligible effect. The oxidative stress hypothesis of aging suggests that high metabolism leads to high cellular damage and short lifespan. However, some empirical studies showed that varying biosynthetic rate, rather than metabolic rate, changes animal's lifespan. The conflicts between the empirical evidence and the hypothesis are reconciled by this study.

Inflammation-related alterations of lipids after spinal cord injury revealed by Raman spectroscopy

Spinal cord injury (SCI) triggers several lipid alterations in nervous tissue. It is characterized by extensive demyelination and the inflammatory response leads to accumulation of activated microglia/macrophages, which often transform into foam cells by accumulation of lipid droplets after engulfment of the damaged myelin sheaths. Using an experimental rat model, Raman microspectroscopy was applied to retrieve the modifications of the lipid distribution following SCI. Coherent anti-Stokes Raman scattering (CARS) and endogenous two-photon fluorescence (TPEF) microscopies were used for the detection of lipid-laden inflammatory cells. The Raman mapping of CH2 deformation mode intensity at 1440  cm(−1) retrieved the lipid-depleted injury core. Preserved white matter and inflammatory regions with myelin fragmentation and foam cells were localized by specifically addressing the distribution of esterified lipids, i.e., by mapping the intensity of the carbonyl Raman band at 1743  cm(−1), and were in agreement with CARS/TPEF microscopy. Principal component analysis revealed that the inflammatory regions are notably rich in saturated fatty acids. Therefore, Raman spectroscopy enabled to specifically detect inflammation after SCI and myelin degradation products.

Effect of long-term ingestion of weakly oxidised flaxseed oil on biomarkers of oxidative stress in LDL-receptor knockout mice

The effect of oxidised fatty acids on atherosclerosis progression is controversial. Thus, our objective was to evaluate the effect of long-term consumption of weakly oxidised PUFA from flaxseed oil on oxidative stress biomarkers of LDL-receptor(-/-) mice. To test our hypothesis, mice were separated into three groups. The first group received a high-fat diet containing fresh flaxseed oil (CONT-), the second was fed the same diet prepared using heated flaxseed oil (OXID), and the third group received the same diet containing fresh flaxseed oil and had diabetes induced by streptozotocin (CONT+). Oxidative stress, aortic parameters and non-alcoholic fatty liver disease were assessed. After 3 months, plasma lipid profile, glucose levels, body weight, energy intake and dietary intake did not differ among groups. Likewise, oxidative stress, plasma malondialdehyde (MDA), hepatic MDA expressed as nmol/mg portion (ptn) and antioxidant enzymes did not differ among the groups. Hepatic linoleic acid, α-linolenic acid, arachidonic acid and EPA acid declined in the OXID and CONT+ groups. Aortic wall thickness, lumen and diameter increased only in the OXID group. OXID and CONT+ groups exhibited higher concentrations of MDA, expressed as μmol/mg ptn per %PUFA, when compared with the CONT- group. Our results suggest that ingestion of oxidised flaxseed oil increases hepatic MDA concentration and is potentially pro-atherogenic. In addition, the mean MDA value observed in all groups was similar to those reported in other studies that used xenobiotics as oxidative stress inducers. Thus, the diet applied in this study represents an interesting model for further research involving antioxidants.

Nutrient-Deprived Retinal Progenitors Proliferate in Response to Hypoxia: Interaction of the HIF-1 and mTOR Pathway

At a cellular level, nutrients are sensed by the mechanistic Target of Rapamycin (mTOR). The response of cells to hypoxia is regulated via action of the oxygen sensor Hypoxia-Inducible Factor 1 (HIF-1). During development, injury and disease, tissues might face conditions of both low nutrient supply and low oxygen, yet it is not clear how cells adapt to both nutrient restriction and hypoxia, or how mTOR and HIF-1 interact in such conditions. Here we explore this question in vivo with respect to cell proliferation using the ciliary marginal zone (CMZ) of Xenopus. We found that both nutrient-deprivation and hypoxia cause retinal progenitors to decrease their proliferation, yet when nutrient-deprived progenitors are exposed to hypoxia there is an unexpected rise in cell proliferation. This increase, mediated by HIF-1 signalling, is dependent on glutaminolysis and reactivation of the mTOR pathway. We discuss how these findings in non-transformed tissue may also shed light on the ability of cancer cells in poorly vascularised solid tumours to proliferate.

Multifunctional diamine AGE/ALE inhibitors with potential therapeutical properties against Alzheimer's disease

An important part of pathogenesis of Alzheimer's disease (AD) is attributed to the contribution of AGE (Advanced Glycation Endproducts) and ALE (Advanced Lipid peroxidation Endproducts). In order to attenuate the progression of AD, we designed a new type of molecules that consist of two trapping parts for reactive carbonyl species (RCS) and reactive oxygen species (ROS), precursors of AGE and ALE, respectively. These molecules also chelate transition metals, the promoters of ROS formation. In this paper, synthesis of the new AGE/ALE inhibitors and evaluation of their physicochemical and biological properties (carbonyl trapping capacity, antioxidant activity, Cu(2+)-chelating capacity, cytotoxicity and protective effect against in vitro MGO-induced apoptosis in the model AD cell-line PC12) are described. It is found that compounds 40b and 51e possess promising therapeutic potentials for treating AD.

Lipid peroxidation is associated with poor control of type-2 diabetes mellitus

BACKGROUND

Hyperglycemia increases oxidative stress through the overproduction of reactive oxygen species, which results in an imbalance between free radicals and the antioxidant defense system of the cells. A positive correlation was reported between lipid peroxide levels and diabetic complication.

OBJECTIVES

The aim of the present study was to investigate the state of oxidative stress in controlled and uncontrolled diabetic patients.

METHODS

One hundred thirty nine participants were included in this study, grouped as: Group-I: Healthy Control group of non-diabetic normal subjects, Group-II: Controlled type-2 DM group of subjects with type-2 DM and HbA1c≤8% and Group-III: Uncontrolled type-2 DM group of subjects with type-2 DM and HbA1c>8%. Fasting blood glucose, 2h postprandial glucose, MDA and HbA1c were quantified. The association between diabetic control and lipid peroxidation (malondialdehyde) was evaluated.

RESULTS

The mean HbA1c increased significantly in uncontrolled type-2 DM subjects compared to controlled type-2 DM group. Lipid peroxidation as expressed in MDA was significantly increased in uncontrolled type-2 DM group compared to controlled type-2 DM, both groups show significant elevation in this parameter compared to healthy subjects. There is a significant positive correlation between MDA and HbA1c in the studied subjects.

CONCLUSION

The core problem during diabetes is poor glycemic control, which leads to protein glycation, lipid peroxidation, oxidative stress and finally varieties of complications. Periodic evaluation of lipid peroxidation products in diabetes mellitus is recommended as it could contribute to the early identification and management of oxidative stress.

EGCG Inhibited Lipofuscin Formation Based on Intercepting Amyloidogenic β-Sheet-Rich Structure Conversion

BACKGROUND

Lipofuscin (LF) is formed during lipid peroxidation and sugar glycosylation by carbonyl-amino crosslinks with biomacrolecules, and accumulates slowly within postmitotic cells. The environmental pollution, modern dietary culture and lifestyle changes have been found to be the major sources of reactive carbonyl compounds in vivo. Irreversible carbonyl-amino crosslinks induced by carbonyl stress are essentially toxiferous for aging-related functional losses in modern society. Results show that (-)-epigallocatechin gallate (EGCG), the main polyphenol in green tea, can neutralize the carbonyl-amino cross-linking reaction and inhibit LF formation, but the underlying mechanism is unknown.

METHODS AND RESULTS

We explored the mechanism of the neutralization process from protein, cell, and animal levels using spectrofluorometry, infrared spectroscopy, conformation antibodies, and electron microscopy. LF demonstrated an amyloidogenic β-sheet-rich with antiparallel structure, which accelerated the carbonyl-amino crosslinks formation and disrupted proteolysis in both PC12 cells and D-galactose (D-gal)-induced brain aging mice models. Additionally, EGCG effectively inhibited the formation of the amyloidogenic β-sheet-rich structure of LF, and prevented its conversion into toxic and on-pathway aggregation intermediates, thereby cutting off the carbonyl-amino crosslinks.

CONCLUSIONS

Our study indicated that the amyloidogenic β-sheet structure of LF may be the core driving force for carbonyl-amino crosslinks further formation, which mediates the formation of amyloid fibrils from native state of biomacrolecules. That EGCG exhibits anti-amyloidogenic β-sheet-rich structure properties to prevent the LF formation represents a novel strategy to impede the development of degenerative processes caused by ageing or stress-induced premature senescence in modern environments.

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.