Hydroxynonenal Causes Hepatocyte Death by Disrupting Lysosomal Integrity in Nonalcoholic Steatohepatitis

BACKGROUND & AIMS

The lipid oxidation is a key factor for damaging hepatocytes and causing cell death. However, the mechanisms underlying hepatocyte death and the role of the most popular lipid peroxidation product 4-hydroxy-2-nonenal (HNE) in nonalcoholic steatohepatitis (NASH) remains unclear.

METHODS

We demonstrated using hepatoma cell lines, a NASH mouse model, HNE-treated monkeys, and biopsy specimens from patients with NASH that HNE induced hepatocyte death by disintegrating the lysosomal limiting membrane.

RESULTS

The degree of HNE deposition in human NASH hepatocytes was more severe in cases with high lobular inflammation, ballooning, and fibrosis scores, and was associated with enlargement of the staining of lysosomes in hepatocytes. In in vitro experiments, HNE activated μ-calpain via G-protein coupled receptor (GPR) 120. The resultant rupture/permeabilization of the lysosomal limiting membrane induced the leakage of cathepsins from lysosomes and hepatocyte death. The blockade of G-protein coupled receptor 120 (GPR120) or μ-calpain expression suppressed lysosomal membrane damage and hepatocyte death by HNE. Alda-1, which activates aldehyde dehydrogenase 2 to degrade HNE, prevented HNE-induced hepatocyte death. Intravenous administration of HNE to monkeys for 6 months resulted in hepatocyte death by a mechanism similar to that of cultured cells. In addition, intraperitoneal administration of Alda-1 to choline-deficient, amino-acid defined treated mice for 8 weeks inhibited HNE deposition, decreased liver inflammation, and disrupted lysosomal membranes in hepatocytes, resulting in improvement of liver fibrosis.

CONCLUSIONS

These results provide novel insights into the mechanism of hepatocyte death in NASH and will contribute to the development of new therapeutic strategies for NASH.

Differential Effects of 2-Deoxyglucose and Glucose Deprivation on 4-Hydroxynonenal Dependent Mitochondrial Dysfunction in Primary Neurons

Mitochondrial dysfunction and metabolic decline are prevalent features of aging and age-related disorders, including neurodegeneration. Neurodegenerative diseases are associated with a progressive loss of metabolic homeostasis. This pathogenic decline in metabolism is the result of several factors, including decreased mitochondrial function, increased oxidative stress, inhibited autophagic flux, and altered metabolic substrate availability. One critical metabolite for maintaining neuronal function is glucose, which is utilized by the brain more than any other organ to meet its substantial metabolic demand. Enzymatic conversion of glucose into its downstream metabolites is critical for maintaining neuronal cell growth and overall metabolic homeostasis. Perturbation of glycolysis could significantly hinder neuronal metabolism by affecting key metabolic pathways. Here, we demonstrate that the glucose analogue 2-deoxyglucose (2DG) decreases cell viability, as well as both basal and maximal mitochondrial oxygen consumption in response to the neurotoxic lipid 4-hydroxynonenal (HNE), whereas glucose deprivation has a minimal effect. Furthermore, using a cell permeabilization assay we found that 2DG has a more pronounced effect on HNE-dependent inhibition of mitochondrial complex I and II than glucose deprivation. Importantly, these findings indicate that altered glucose utilization plays a critical role in dictating neuronal survival by regulating the mitochondrial response to electrophilic stress.

4-Hydroxy-2-Nonenal Promotes Cardiomyocyte Necroptosis via Stabilizing Receptor-Interacting Serine/Threonine-Protein Kinase 1

Background: Necroptosis is a vital regulator of myocardial ischemia/reperfusion (MI/R) injury. Meanwhile, 4-hydroxy-2-nonenal (4-HNE) is abundantly increased during MI/R injury. However, whether 4-HNE induces cardiomyocyte necroptosis during MI/R remains unknown. Methods: To observe the relationship between 4-HNE and necroptosis during MI/R, C57BL/6 mice and aldehyde dehydrogenase 2-transgenic (ALDH2-Tg) mice were both exposed to left anterior descending artery ligation surgery to establish MI/R injury models. For further study, isolated mouse hearts and H9c2 cells were both treated with 4-HNE to elucidate the underlying mechanisms. Results: Necroptosis and 4-HNE were both upregulated in I/R-injured hearts. Cardiomyocyte necroptosis was significantly decreased in I/R-injured hearts from ALDH2-Tg mice as compared with that of wild-type mice. In vitro studies showed that necroptosis was enhanced by 4-HNE perfusion in a time- and concentration-dependent manner. Knockdown of receptor-interacting serine/threonine-protein kinase 1 (RIP1) using small interfering RNA (siRNA) prevented 4-HNE-induced cardiomyocyte necroptosis, manifesting that RIP1 played a key role in the upregulation of cell necroptosis by 4-HNE. Further studies found that 4-HNE reduced the protein degradation of RIP1 by preventing K48-polyubiquitination of RIP1. Conclusion: 4-HNE contributes to cardiomyocyte necroptosis by regulating ubiquitin-mediated proteasome degradation of RIP1.

Curcumin Attenuates Sarcopenia in Chronic Forced Exercise Executed Aged Mice by Regulating Muscle Degradation and Protein Synthesis with Antioxidant and Anti-inflammatory Effects

The aim of the current study is to investigate the effects of spray dry powders of Curcuma longa containing 40% curcumin (CM-SD), as a new aqueous curcumin formula, on sarcopenia in chronic forced exercise executed 10 month old ICR mice. CM-SD (80 and 40 mg/kg) increased calf thicknesses and strengths, total body and calf protein amounts, and muscle weights in both gastrocnemius and soleus muscles. mRNA expressions regarding muscle growth and protein synthesis were induced, while those of muscle degradation significantly declined in CM-SD treatment. CM-SD decreased serum biochemical markers, lipid peroxidation, and reactive oxygen species and increased endogenous antioxidants and enzyme activities. It also reduced immunoreactive myofibers for apoptosis and oxidative stress markers but increased ATPase in myofibers. These results suggest that CM-SD can be an adjunct therapy to exercise-based remedy that prevents muscle disorders including sarcopenia by anti-apoptosis, anti-inflammation, and antioxidation-mediated modulation of gene expressions related to muscle degradation and protein synthesis.

SOD2 deficiency in cardiomyocytes defines defective mitochondrial bioenergetics as a cause of lethal dilated cardiomyopathy

Electrophilic aldehyde (4-hydroxynonenal; 4-HNE), formed after lipid peroxidation, is a mediator of mitochondrial dysfunction and implicated in both the pathogenesis and the progression of cardiovascular disease. Manganese superoxide dismutase (MnSOD), a nuclear-encoded antioxidant enzyme, catalyzes the dismutation of superoxide radicals (O2•-) in mitochondria. To study the role of MnSOD in the myocardium, we generated a cardiomyocyte-specific SOD2 (SOD2Δ) deficient mouse strain. Unlike global SOD2 knockout mice, SOD2Δ mice reached adolescence; however, they die at ~4 months of age due to heart failure. Ultrastructural analysis of SOD2Δ hearts revealed altered mitochondrial architecture, with prominent disruption of the cristae and vacuole formation. Noninvasive echocardiographic measurements in SOD2Δ mice showed dilated cardiomyopathic features such as decreased ejection fraction and fractional shortening along with increased left ventricular internal diameter. An increased incidence of ventricular tachycardia was observed during electrophysiological studies of the heart in SOD2Δ mice. Oxidative phosphorylation (OXPHOS) measurement using a Seahorse XF analyzer in SOD2Δ neonatal cardiomyocytes and adult cardiac mitochondria displayed reduced O2 consumption, particularly during basal conditions and after the addition of FCCP (H+ ionophore/uncoupler), compared to that in SOD2fl hearts. Measurement of extracellular acidification (ECAR) to examine glycolysis in these cells showed a pattern precisely opposite that of the oxygen consumption rate (OCR) among SOD2Δ mice compared to their SOD2fl littermates. Analysis of the activity of the electron transport chain complex identified a reduction in Complex I and Complex V activity in SOD2Δ compared to SOD2fl mice. We demonstrated that a deficiency of SOD2 increases reactive oxygen species (ROS), leading to subsequent overproduction of 4-HNE inside mitochondria. Mechanistically, proteins in the mitochondrial respiratory chain complex and TCA cycle (NDUFS2, SDHA, ATP5B, and DLD) were the target of 4-HNE adduction in SOD2Δ hearts. Our findings suggest that the SOD2 mediated 4-HNE signaling nexus may play an important role in cardiomyopathy.

Oxidative contribution of air pollution to extrinsic skin ageing

•Epidemiological evidence links exposure to poor air quality to lentigines and wrinkles. •Experimental studies provide mechanistic explanations involving oxidative stress. •Polluted air may hasten skin ageing through indirect systemic effects via the lung and/or direct effects on cutaneous tissue. •Prevention measures would need to combine strategies that target both ‘routes’. •Air pollution is one of several environmental stressors that combined, may have additive/synergistic effects on the skin.

The Disposal of Reactive Carbonyl Species through Carnosine Conjugation: What We Know Now

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Reactive Carbonyl Species are electrophiles generated by the oxidative cleavage of lipids and sugars. Such compounds have been described as important molecules for cellular signaling, whilst their accumulation has been found to be cytotoxic as they may trigger aberrant modifications of proteins (a process often referred to as carbonylation).

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A correlation between carbonylation of proteins and human disease progression has been shown in ageing, diabetes, obesity, chronic renal failure, neurodegeneration and cardiovascular disease. However, the fate of reactive carbonyl species is still far from being understood, especially concerning the mechanisms responsible for their disposal as well as the importance of this in disease progression.

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In this context, some data have been published on phase I and phase II deactivation of reactive carbonyl species. In the case of phase II mechanisms, the route involving glutathione conjugation and subsequent disposal of the adducts has been extensively studied both in vitro and in vivo for some of the more representative compounds, e.g. 4-hydroxynonenal.

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There is also emerging evidence of an involvement of carnosine as an endogenous alternative to glutathione for phase II conjugation. However, the fate of carnosine conjugates is still poorly investigated and, unlike glutathione, there is little evidence of the formation of carnosine adducts in vivo. The acquisition of such data could be of importance for the development of new drugs, since carnosine and its derivatives have been proposed as potential therapeutic agents for the mitigation of carbonylation associated with disease progression.

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Herein, we wish to review our current knowledge of the binding of reactive carbonyl species with carnosine together with the disposal of carnosine conjugates, emphasizing those aspects still requiring investigation such as conjugation reversibility and enzyme assisted catalysis of the reactions.

Involvement of 4-hydroxy-2-nonenal in pollution-induced skin damage

The effects of environmental insults on human health are a major global concern. Some of the most noxious pollutants that humans are exposed to include ozone (O₃ ), particulate matter (PM), and cigarette smoke (CS). Since the skin is the first line of defense against environmental insults, it is considered one of the main target organs for the harmful insults of air pollution. Thus, there is solid evidence that skin pathologies such as premature aging, atopic dermatitis (AD), and psoriasis are associated with pollutant exposure; all of these skin conditions are also associated with an altered redox status. Therefore, although the mechanisms of action and concentrations of O₃ , PM, and CS that we are exposed to differ, exposure to all of these pollutants is associated with the development of similar skin conditions due to the fact that all of these pollutants alter redox homeostasis, increasing reactive oxygen species production and oxidative stress. A main product of oxidative stress, induced by exposure to the aforementioned pollutants, is 4-hydroxy-2-nonenal (HNE), which derives from the oxidation of ω-6 polyunsaturated fatty acids. HNE is a highly reactive compound that can form adducts with cellular proteins and even DNA; it is also an efficient cell signaling molecule able to regulate mitogen-activated protein kinase pathways and the activity of redox-sensitive transcription factors such as Nrf2, AP1, and NFκB. Therefore, increased levels of HNE in the skin, in response to pollutants, likely accelerates skin aging and exacerbates existing skin inflammatory conditions; thus, targeting HNE formation could be an innovative cosmeceutical approach for topical applications.

Effects of Phenelzine Administration on Mitochondrial Function, Calcium Handling, and Cytoskeletal Degradation after Experimental Traumatic Brain Injury

Traumatic brain injury (TBI) results in the production of peroxynitrite (PN), leading to oxidative damage of lipids and protein. PN-mediated lipid peroxidation (LP) results in production of reactive aldehydes 4-hydroxynonenal (4-HNE) and acrolein. The goal of these studies was to explore the hypothesis that interrupting secondary oxidative damage following a TBI via phenelzine (PZ), analdehyde scavenger, would protect against LP-mediated mitochondrial and neuronal damage. Male Sprague-Dawley rats received a severe (2.2 mm) controlled cortical impact (CCI)-TBI. PZ was administered subcutaneously (s.c.) at 15 min (10 mg/kg) and 12 h (5 mg/kg) post-injury and for the therapeutic window/delay study, PZ was administered at 1 h (10 mg/kg) and 24 h (5 mg/kg). Mitochondrial and cellular protein samples were obtained at 24 and 72 h post-injury (hpi). Administration of PZ significantly improved mitochondrial respiration at 24 and 72 h compared with vehicle-treated animals. These results demonstrate that PZ administration preserves mitochondrial bioenergetics at 24 h and that this protection is maintained out to 72 hpi. Additionally, delaying the administration still elicited significant protective effects. PZ administration also improved mitochondrial Ca2+ buffering (CB) capacity and mitochondrial membrane potential parameters compared with vehicle-treated animals at 24 h. Although PZ treatment attenuated aldehyde accumulation post-injury, the effects were insignificant. The amount of α-spectrin breakdown in cortical tissue was reduced by PZ administration at 24 h, but not at 72 hpi compared with vehicle-treated animals. In conclusion, these results indicate that acute PZ treatment successfully attenuates LP-mediated oxidative damage eliciting multiple neuroprotective effects following TBI.

Pink1 attenuates propofol-induced apoptosis and oxidative stress in developing neurons

BACKGROUND

The underlying mechanisms of propofol-induced neurotoxicity in developing neurons are still not completely understood. We examined the role of PTEN-induced kinase 1 (Pink1), an antioxidant protein, in propofol-induced apoptosis in developing neurons.

MATERIALS AND METHODS

Primary hippocampal neurons isolated from neonatal Sprague-Dawley rats were exposed to propofol 20 μM for 2, 4, 6 and 12 h. Subsequently, neurons underwent overexpression and knockdown of Pink1, followed by propofol exposure (20 μM, 6 h). Neuron apoptosis was detected by terminal transferase deoxyuridine triphosphate-biotin nick-end labeling (TUNEL). Reactive oxygen species (ROS) production in neurons was detected by using a 2,7-dichlorodihydro-fluorescein diacetate probe and target protein or mRNA levels were analyzed by Western blotting or real-time polymerase chain reaction.

RESULTS

Propofol treatment time-dependently increased the number of TUNEL-positive neurons and the expression levels of cleaved caspase-3 and B-cell lymphoma 2 (BcL-2) associated X protein, but decreased expression levels of BcL-2. Furthermore, propofol treatment time-dependently reduced the expression levels of Pink1 mRNA and protein. ROS production and the markers of oxidative stress, 2,4-dinitrophenol and 4-hydroxynonenal, were increased by propofol treatment. However, these propofol-induced changes were significantly restored by Pink1 overexpression.

CONCLUSIONS

Pink1 plays an important role in neuronal apoptosis induced by propofol. Our results may provide some new insights in propofol-induced neurotoxicity in developing neurons.

Direct 1O2 optical excitation: A tool for redox biology

Molecular oxygen (O2) displays very interesting properties. Its first excited state, commonly known as singlet oxygen (1O2), is one of the so-called Reactive Oxygen Species (ROS). It has been implicated in many redox processes in biological systems. For many decades its role has been that of a deleterious chemical species, although very positive clinical applications in the Photodynamic Therapy of cancer (PDT) have been reported. More recently, many ROS, and also 1O2, are in the spotlight because of their role in physiological signaling, like cell proliferation or tissue regeneration. However, there are methodological shortcomings to properly assess the role of 1O2 in redox biology with classical generation procedures. In this review the direct optical excitation of O2 to produce 1O2 will be introduced, in order to present its main advantages and drawbacks for biological studies. This photonic approach can provide with many interesting possibilities to understand and put to use ROS in redox signaling and in the biomedical field.

Regulation of autophagy, mitochondrial dynamics, and cellular bioenergetics by 4-hydroxynonenal in primary neurons

The production of reactive species contributes to the age-dependent accumulation of dysfunctional mitochondria and protein aggregates, all of which are associated with neurodegeneration. A putative mediator of these effects is the lipid peroxidation product 4-hydroxynonenal (4-HNE), which has been shown to inhibit mitochondrial function, and accumulate in the postmortem brains of patients with neurodegenerative diseases. This deterioration in mitochondrial quality could be due to direct effects on mitochondrial proteins, or through perturbation of the macroautophagy/autophagy pathway, which plays an essential role in removing damaged mitochondria. Here, we use a click chemistry-based approach to demonstrate that alkyne-4-HNE can adduct to specific mitochondrial and autophagy-related proteins. Furthermore, we found that at lower concentrations (5-10 μM), 4-HNE activates autophagy, whereas at higher concentrations (15 μM), autophagic flux is inhibited, correlating with the modification of key autophagy proteins at higher concentrations of alkyne-4-HNE. Increasing concentrations of 4-HNE also cause mitochondrial dysfunction by targeting complex V (the ATP synthase) in the electron transport chain, and induce significant changes in mitochondrial fission and fusion protein levels, which results in alterations to mitochondrial network length. Finally, inhibition of autophagy initiation using 3-methyladenine (3MA) also results in a significant decrease in mitochondrial function and network length. These data show that both the mitochondria and autophagy are critical targets of 4-HNE, and that the proteins targeted by 4-HNE may change based on its concentration, persistently driving cellular dysfunction.

Bathing effects of east saline groundwater concentrates on allergic (atopic) dermatitis-like skin lesions induced by 2,4-dinitrochlorobenzene in hairless mice

In the present study, it was evaluated whether east saline groundwater concentration solution (ESGWc) exerted a favorable inhibitory effect on 2,4-dinitrochlorobenzene (DNCB)-induced allergic/atopic-like dermatitis (AD). AD was induced and boosted by sensitization with DNCB via topical application on the dorsal back skins. Mice with DNCB-induced AD were bathed in 100-, 200- and 400-fold diluted ESGWc. After 6 weeks bathing, changes to body weight, clinical skin severity scores, scratching behavior, serum total immunoglobulin (Ig)E levels, submandibular lymph node and spleen weights, splenic cytokine levels, skin cytokine mRNA expressions, antioxidant defense systems and superoxide anion productions were recorded to determine the effects of bathing on the histopathology of dorsal back skin tissues. All DNCB-induced mice demonstrated that the induction of AD through IgE-mediated hypersensitivities, oxidative stresses, activation of MMP and apoptosis of keratinocytes resulted in no significant differences in body weight between the different groups at each time point following initial sensitization. However, markers of DNCB-induced AD were significantly inhibited (P<0.05) in a concentration-dependent manner following bathing in all concentrations of ESGWc. The results obtained in the present study suggest that bathing in ESGWc may have favorable protective effects against DNCB-induced AD due to favorable systemic and local immunomodulatory effects, active cytoprotective anti-apoptotic effects, inhibitory effects of matrix metalloproteinase activity, and anti-inflammatory and antioxidative effects.

Activation of AMPK by Buddleja officinalis Maxim. Flower Extract Contributes to Protecting Hepatocytes from Oxidative Stress

The Buddleja officinalis Maxim. flower is used in traditional Chinese and Korean medicine to treat inflammation, vascular diseases, headache, and stroke, as well as enhance liver function. This research investigated the effects of B. officinalis Maxim. flower extract (BFE) on hepatotoxicity. The cytoprotective effects and mechanism of BFE against severe mitochondrial dysfunction and H₂O₂ production in hepatotoxicity induced by coadministration of arachidonic acid (AA) and iron were observed in the HepG2 cell line. In addition, we performed blood biochemical, histopathological, and histomorphometric analyses of mice with carbon tetrachloride- (CCl₄-) induced acute liver damage. BFE inhibited the AA + iron-mediated hepatotoxicity of HepG2 cells. Moreover, it inhibited mitochondrial dysfunction, H₂O₂ production, and glutathione depletion mediated by AA + iron in the same cells. Meanwhile, the cytoprotective effects of BFE against oxidative stress were associated with the activation of AMP-activated protein kinase (AMPK). In particular, based on the histopathological observations, BFE (30 and 100 mg/kg) showed clear hepatoprotective effects against CCl₄-induced acute hepatic damage. Furthermore, it inhibited 4-hydroxynonenal and nitrotyrosine immunoreactivity in hepatocytes. These results provide evidence that BFE has beneficial hepatoprotective effects against hepatic damage via the activation of AMPK pathway. Accordingly, BFE may have therapeutic potential for diverse liver disorders.

Hepatoprotective effects of hoveniae semen cum fructus extracts in ethanol intoxicated mice

[Purpose]

The objective of this study was to evaluate the hepatoprotective effects of Hoveniae Semen Cum Fructus extract in ethanol induced hepatic damages.

[Methods]

Hepatic damages were induced by oral administration of ethanol and then Hoveniae Semen Cum Fructus extract was administered.

[Results]

Following Hoveniae Semen Cum Fructus extract administration, body and liver weights were increased, while aspartate aminotransferase, alanine aminotransferase, albumin, γ-glutamyl transferase, and triglyceride levels in the serum, triglyceride contents, tumor necrosis factor -α level, cytochrome (CY) P450 2E1 activity in the liver and mRNA expression of hepatic lipogenic genes, and Nitrotyrosine and 4-HNE-immunolabelled hepatocytes were decreased. However, mRNA expression of genes involved in fatty acid oxidation was increased. Also, as a protective mechanism for hepatic antioxidant defense systems, decreased liver MDA contents, increased glutathione contents, increased dismutase and catalase activities were observed when compared to the ethanol control.

[Conclusion]

Hoveniae Semen Cum Fructus extract favorably protected against liver damages, mediated by its potent anti-inflammatory and anti-steatosis properties through the augmentation of the hepatic antioxidant defense system by NF-E2-related factor-2 activation, and down-regulation of the mRNA expression of hepatic lipogenic genes or up-regulation of the mRNA expression of genes involved in fatty acid oxidation.

Compensatory renal hypertrophy and the handling of an acute nephrotoxicant in a model of aging

Aging often results in progressive losses of functioning nephrons, which can lead to a significant reduction in overall renal function. Because of age-related pathological changes, the remaining functional nephrons within aged kidneys may be unable to fully counteract physiological and/or toxicological challenges. We hypothesized that when the total functional renal mass of aged rats is reduced by 50%, the nephrons within the remnant kidney do not fully undergo the functional and physiological changes that are necessary to maintain normal fluid and solute homeostasis. We also tested the hypothesis that the disposition and handling of a nephrotoxicant are altered significantly in aged kidneys following an acute, 50% reduction in functional renal mass. To test these hypotheses, we examined molecular indices of renal cellular hypertrophy and the disposition of inorganic mercury (Hg(2+)), a model nephrotoxicant, in young control, young uninephrectomized (NPX), aged control and aged NPX Wistar rats. We found that the process of aging reduces the ability of the remnant kidney to undergo compensatory renal growth. In addition, we found that an additional reduction in renal mass in aged animals alters the disposition of Hg(2+) and potentially alters the risk of renal intoxication by this nephrotoxicant. To our knowledge, this study represents the first report of the handling of a nephrotoxicant in an aged animal following a 50% reduction in functional renal mass.

The neuroprotection of hypoxic preconditioning on rat brain against traumatic brain injury by up-regulated transcription factor Nrf2 and HO-1 expression

Hypoxic preconditioning (HPC) increases the inherent tolerance of brain tissue suffering from severe hypoxia or ischemia insult by stimulating the protective ability of the brain. However, little is known concerning the effect of HPC on traumatic brain injury (TBI). We designed this study to investigate the effect of HPC on TBI and explore its underlying mechanisms. We found that HPC significantly alleviates neurological dysfunction, lessens brain edema, reduces cell apoptosis, increases neuronal survival, up-regulates the expressions of Nrf2 and HO-1, and decreases the inducer of protein carbonyls, 4-hydroxy-2-nonenal, and 8-hydroxy-2-deoxyguanosine in the brain tissue of rats 24h after brain injury. However, no influence was observed in normal rats after only 3d of hypoxic training. Results further indicated that HPC protects the brain against traumatic damage. This protective effect may be achieved by up-regulating Nrf2 and HO-1 expression and alleviating oxidative stress damage.

4-Hydroxy-nonenal-A Bioactive Lipid Peroxidation Product

This review on recent research advances of the lipid peroxidation product 4-hydroxy-nonenal (HNE) has four major topics: I. the formation of HNE in various organs and tissues, II. the diverse biochemical reactions with Michael adduct formation as the most prominent one, III. the endogenous targets of HNE, primarily peptides and proteins (here the mechanisms of covalent adduct formation are described and the (patho-) physiological consequences discussed), and IV. the metabolism of HNE leading to a great number of degradation products, some of which are excreted in urine and may serve as non-invasive biomarkers of oxidative stress.

Bathing Effects of Various Seawaters on Allergic (Atopic) Dermatitis-Like Skin Lesions Induced by 2,4-Dinitrochlorobenzene in Hairless Mice

We evaluated the preventive effects of four types of seawater collected in Republic of Korea on hairless mice with 2,4-dinitrochlorobenzene- (DNCB-) induced allergic/atopic dermatitis (AD). The anti-inflammatory effects were evaluated by measuring tumor necrosis factor- (TNF-) α and interleukins (ILs). Glutathione (GSH), malondialdehyde (MDA), superoxide anion, and inducible nitric oxide synthase (iNOS) were measured to evaluate the antioxidant effects. Caspase-3 and poly (ADP-ribose) polymerase (PARP) were observed to measure the antiapoptotic effects; matrix metalloproteinase- (MMP-) 9 levels were also evaluated. Mice with AD had markedly higher clinical skin severity scores and scratching behaviors; higher TNF-α and ILs (1β, 10, 4, 5, and 13) levels; higher MDA, superoxide anion, caspase-3, PARP, and MMP-9 levels; and greater iNOS activity. However, the severity of AD was significantly decreased by bathing in seawaters, but it did not influence the dermal collagen depositions and skin tissue antioxidant defense systems. These results suggest that bathing in all four seawaters has protective effects against DNCB-induced AD through their favorable systemic and local immunomodulatory effects, active cytoprotective antiapoptotic effects, inhibitory effects of MMP activity and anti-inflammatory and antioxidative effects.

Schisandrae Fructus Supplementation Ameliorates Sciatic Neurectomy-Induced Muscle Atrophy in Mice

The objective of this study was to assess the possible beneficial skeletal muscle preserving effects of ethanol extract of Schisandrae Fructus (EESF) on sciatic neurectomy- (NTX-) induced hindlimb muscle atrophy in mice. Here, calf muscle atrophy was induced by unilateral right sciatic NTX. In order to investigate whether administration of EESF prevents or improves sciatic NTX-induced muscle atrophy, EESF was administered orally. Our results indicated that EESF dose-dependently diminished the decreases in markers of muscle mass and activity levels, and the increases in markers of muscle damage and fibrosis, inflammatory cell infiltration, cytokines, and apoptotic events in the gastrocnemius muscle bundles are induced by NTX. Additionally, destruction of gastrocnemius antioxidant defense systems after NTX was dose-dependently protected by treatment with EESF. EESF also upregulated muscle-specific mRNAs involved in muscle protein synthesis but downregulated those involved in protein degradation. The overall effects of 500 mg/kg EESF were similar to those of 50 mg/kg oxymetholone, but it showed more favorable antioxidant effects. The present results suggested that EESF exerts a favorable ameliorating effect on muscle atrophy induced by NTX, through anti-inflammatory and antioxidant effects related to muscle fiber protective effects and via an increase in protein synthesis and a decrease in protein degradation.

Pink1 protects cortical neurons from thapsigargin-induced oxidative stress and neuronal apoptosis

Apoptosis mediates the precise and programmed natural death of neurons and is a physiologically important process in neurogenesis during maturation of the central nervous system. However, premature apoptosis and/or an aberration in apoptosis regulation are implicated in the pathogenesis of neurodegeneration. Thus, it is important to identify neuronal pathways/factors controlling apoptosis. Pink1 [phosphatase and tensin homologue (PTEN)-induced kinase 1] is a ubiquitously expressed gene and has been reported to have a physiological role in mitochondrial maintenance, suppressing mitochondrial oxidative stress, fission and autophagy. However, how Pink1 is involved in neuronal survival against oxidative stress remains not well understood. In the present paper, we demonstrate that thapsigargin, a specific irreversible inhibitor of endoplasmic reticulum (ER) calcium-ATPase, could lead to dramatic oxidative stress and neuronal apoptosis by ectopic calcium entry. Importantly, the neuronal toxicity of thapsigargin inhibits antioxidant gene Pink1 expression. Although Pink1 knockdown enhances the neuronal apoptosis by thapsigargin, its overexpression restores it. Our findings have established the neuronal protective role of Pink1 against oxidative stress and afford rationale for developing new strategy to the therapy of neurodegenerative diseases.

Pink1 (PTEN-induced kinase 1) have a physiological role in mitochondrial maintenance, suppressing mitochondrial oxidative stress, fission, and autophagy. Our findings indicated that thapsigargin induced oxidative stress and neuronal apoptosis in cultured neurons is at least partly mediated inactivation of Pink1.

Inhibition of glycolysis attenuates 4-hydroxynonenal-dependent autophagy and exacerbates apoptosis in differentiated SH-SY5Y neuroblastoma cells

How cellular metabolic activities regulate autophagy and determine the susceptibility to oxidative stress and ultimately cell death in neuronal cells is not well understood. An important example of oxidative stress is 4-hydroxynonenal (HNE), which is a lipid peroxidation product that is formed during oxidative stress, and accumulates in neurodegenerative diseases causing damage. The accumulation of toxic oxidation products such as HNE, is a prevalent feature of neurodegenerative diseases, and can promote organelle and protein damage leading to induction of autophagy. In this study, we used differentiated SH-SY5Y neuroblastoma cells to investigate the mechanisms and regulation of cellular susceptibility to HNE toxicity and the relationship to cellular metabolism. We found that autophagy is immediately stimulated by HNE at a sublethal concentration. Within the same time frame, HNE induces concentration dependent CASP3/caspase 3 activation and cell death. Interestingly, both basal and HNE-activated autophagy, were regulated by glucose metabolism. Inhibition of glucose metabolism by 2-deoxyglucose (2DG), at a concentration that inhibited autophagic flux, further exacerbated CASP3 activation and cell death in response to HNE. Cell death was attenuated by the pan-caspase inhibitor Z-VAD-FMK. Specific inhibition of glycolysis using koningic acid, a GAPDH inhibitor, inhibited autophagic flux and exacerbated HNE-induced cell death similarly to 2DG. The effects of 2DG on autophagy and HNE-induced cell death could not be reversed by addition of mannose, suggesting an ER stress-independent mechanism. 2DG decreased LAMP1 and increased BCL2 levels suggesting that its effects on autophagy may be mediated by more than one mechanism. Furthermore, 2DG decreased cellular ATP, and 2DG and HNE combined treatment decreased mitochondrial membrane potential. We conclude that glucose-dependent autophagy serves as a protective mechanism in response to HNE.

Inhibition of UVB-induced skin damage by exopolymers from Aureobasidium pullulans SM-2001 in hairless mice

Because antioxidants from natural sources may be an effective approach to the treatment and prevention of UV radiation-induced skin damage, the effects of purified exopolymers from Aureobasidium pullulans SM-2001 ('E-AP-SM2001') were evaluated in UVB-induced hairless mice. E-AP-SM2001 consists of 1.7% β-1,3/1,6-glucan, fibrous polysaccharides and other organic materials, such as amino acids, and mono- and di-unsaturated fatty acids (linoleic and linolenic acids) and shows anti-osteoporotic and immunomodulatory effects, through antioxidant and anti-inflammatory mechanisms. Hairless mice were treated topically with vehicle, E-AP-SM2001 stock and two and four times diluted solutions once per day for 15 weeks against UVB irradiation (three times per week at 0.18 J/cm(2) ). The following parameters were evaluated in skin samples: myeloperoxidase (MPO) activity, cytokine levels [interleukin (IL)-1β and IL-10], endogenous antioxidant content (glutathione, GSH), malondialdehyde (MDA) levels, superoxide anion production; matrix metalloproteases (MMP-1, -9 and -13), GSH reductase and Nox2 (gp91phox) mRNA levels, and immunoreactivity for nitrotyrosine (NT), 4-hydroxynonenal (HNE), caspase-3, and cleaved poly(ADP-ribose) polymerase (PARP). Photoageing was induced by UVB irradiation through ROS-mediated inflammation, which was related to the depletion of endogenous antioxidants, activation of MMPs and keratinocyte apoptosis. Topical treatment with all three doses of E-AP-SM2001 and 5 nm myricetin attenuated the UV-induced depletion of GSH, activation of MMPs, production of IL-1β, the decrease in IL-10 and keratinocyte apoptosis. In this study, E-AP-SM2001 showed potent inhibitory effects against UVB-induced skin photoageing. Thus, E-AP-SM2001 may be useful as a functional ingredient in cosmetics, especially as a protective agent against UVB-induced skin photoageing.

Reactive carbonyl species in vivo: generation and dual biological effects

Reactive carbonyls are widespread species in living organisms and mainly known for their damaging effects. The most abundant reactive carbonyl species (RCS) are derived from oxidation of carbohydrates, lipids, and amino acids. Chemical modification of proteins, nucleic acids, and aminophospholipids by RCS results in cytotoxicity and mutagenicity. In addition to their direct toxicity, modification of biomolecules by RCS gives rise to a multitude of adducts and cross links that are increasingly implicated in aging and pathology of a wide range of human diseases. Understanding of the relationship between metabolism of RCS and the development of pathological disorders and diseases may help to develop effective approaches to prevent a number of disorders and diseases. On the other hand, constant persistence of RCS in cells suggests that they perform some useful role in living organisms. The most beneficial effects of RCS are their establishment as regulators of cell signal transduction and gene expression. Since RCS can modulate different biological processes, new tools are required to decipher the precise mechanisms underlying dual effects of RCS.

Erythrocyte shape abnormalities, membrane oxidative damage, and β-actin alterations: an unrecognized triad in classical autism

Autism spectrum disorders (ASDs) are a complex group of neurodevelopment disorders steadily rising in frequency and treatment refractory, where the search for biological markers is of paramount importance. Although red blood cells (RBCs) membrane lipidomics and rheological variables have been reported to be altered, with some suggestions indicating an increased lipid peroxidation in the erythrocyte membrane, to date no information exists on how the oxidative membrane damage may affect cytoskeletal membrane proteins and, ultimately, RBCs shape in autism. Here, we investigated RBC morphology by scanning electron microscopy in patients with classical autism, that is, the predominant ASDs phenotype (age range: 6–26 years), nonautistic neurodevelopmental disorders (i.e., “positive controls”), and healthy controls (i.e., “negative controls”). A high percentage of altered RBCs shapes, predominantly elliptocytes, was observed in autistic patients, but not in both control groups. The RBCs altered morphology in autistic subjects was related to increased erythrocyte membrane F₂-isoprostanes and 4-hydroxynonenal protein adducts. In addition, an oxidative damage of the erythrocyte membrane β-actin protein was evidenced. Therefore, the combination of erythrocyte shape abnormalities, erythrocyte membrane oxidative damage, and β-actin alterations constitutes a previously unrecognized triad in classical autism and provides new biological markers in the diagnostic workup of ASDs.

Regulation and therapeutic strategies of 4-hydroxy-2-nonenal metabolism in heart disease

4-Hydroxy-2-nonenal (4-HNE), a reactive aldehyde, is generated from polyunsaturated fatty acids (PUFAs) in biological membranes. Reactive oxygen species (ROS) generated during oxidative stress react with PUFAs to form aldehydes like 4-HNE, which inactivates proteins and DNA by forming hybrid covalent chemical addition compounds called adducts. The ensuing chain reaction results in cellular dysfunction and tissue damage. It includes a wide spectrum of events ranging from electron transport chain dysfunction to apoptosis. In addition, 4-HNE directly depresses contractile function, enhances ROS formation, modulates cell signaling pathways, and can contribute to many cardiovascular diseases, including atherosclerosis, myocardial ischemia-reperfusion injury, heart failure, and cardiomyopathy. Therefore, targeting 4-HNE could help reverse these pathologies. This review will focus on 4-HNE generation, the role of 4-HNE in cardiovascular diseases, cellular targets (especially mitochondria), processes and mechanisms for 4-HNE-induced toxicity, regulation of 4-HNE metabolism, and finally strategies for developing potential therapies for cardiovascular disease by attenuating 4-HNEinduced toxicity.

A chemoproteomic platform to quantitatively map targets of lipid-derived electrophiles

Cells produce electrophilic products with the potential to modify and affect the function of proteins. Chemoproteomic methods have provided a means to qualitatively inventory proteins targeted by endogenous electrophiles; however, ascertaining the potency and specificity of these reactions to identify the most sensitive sites in the proteome to electrophilic modification requires more quantitative methods. Here, we describe a competitive activity-based profiling method for quantifying the reactivity of electrophilic compounds against 1000+ cysteines in parallel in the human proteome. Using this approach, we identify a select set of proteins that constitute “hot spots” for modification by various lipid-derived electrophiles, including the oxidative stress product 4-hydroxynonenal (HNE). We show that one of these proteins, ZAK kinase, is labeled by HNE on a conserved, active site-proximal cysteine, resulting in enzyme inhibition to create a negative feedback mechanism that can suppress the activation of JNK pathways by oxidative stress.

Cellular metabolic and autophagic pathways: traffic control by redox signaling

It has been established that the key metabolic pathways of glycolysis and oxidative phosphorylation are intimately related to redox biology through control of cell signaling. Under physiological conditions glucose metabolism is linked to control of the NADH/NAD redox couple, as well as providing the major reductant, NADPH, for thiol-dependent antioxidant defenses. Retrograde signaling from the mitochondrion to the nucleus or cytosol controls cell growth and differentiation. Under pathological conditions mitochondria are targets for reactive oxygen and nitrogen species and are critical in controlling apoptotic cell death. At the interface of these metabolic pathways, the autophagy-lysosomal pathway functions to maintain mitochondrial quality and generally serves an important cytoprotective function. In this review we will discuss the autophagic response to reactive oxygen and nitrogen species that are generated from perturbations of cellular glucose metabolism and bioenergetic function.

Melatonin affects conjugation of 4-hydroxynonenal with glutathione in liver of pacu, a hypoxia-tolerant fish

In cytosol from liver of pacu, Piaractus mesopotamicus, a hypoxia-tolerant fish that dwells in Pantanal, we found an enzyme activity capable of modulating the alkenal 4-hydroxy-2-nonenal (HNE) by conjugating it with glutathione (GST-HNE activity). HNE is a downstream metabolite from the oxidation of polyunsaturated fatty acids by reactive oxygen species arisen from mitochondria of animal cells. HNE production may increase more intensively under oxidative stress. Harmful effects to cell survival may occur when HNE increases over 10(-4) M. Pacus submitted to hypoxia in July (cold season in Pantanal) showed 40% less of this GST-HNE conjugating activity in their liver cytosol. Injecting pacus subjected to hypoxia during the cold season with a summer physiological dose of melatonin caused their liver cytosolic GST-HNE activity to increase up to the levels found in the warm season. From October to March (warm season in Pantanal), pacus are prone to oxidative stress particularly during potamodromous active oxygen-demanding swimming, when they migrate up rivers to spawn. Thus, our findings point out that the higher levels of melatonin in circulation during the summer are important to avoid the increase of 4-HNE inside liver cells of this fish species.

Isoprostanes and 4-hydroxy-2-nonenal: markers or mediators of disease? Focus on Rett syndrome as a model of autism spectrum disorder

Lipid peroxidation, a process known to induce oxidative damage to key cellular components, has been implicated in several diseases. Following three decades of explorations mainly on in vitro models reproducible in the laboratories, lipid peroxidation has become increasingly relevant for the interpretation of a wide range of pathophysiological mechanisms in the clinical setting. This cumulative effort has led to the identification of several lipid peroxidation end-products meeting the needs of the in vivo evaluation. Among these different molecules, isoprostanes and 4-hydroxy-2-nonenal protein adducts appear to be particularly interesting. This review shows how specific oxidation products, deriving from polyunsaturated fatty acids precursors, are strictly related to the clinical manifestations and the natural history of Rett syndrome, a genetically determined neurodevelopmental pathology, currently classified among the autism spectrum disorders. In our experience, Rett syndrome offers a unique setting for physicians, biologists, and chemists to explore the borders of the lipid mediators concept.

Placental ABC transporters, cellular toxicity and stress in pregnancy

The human placenta, in addition to its roles as a nutrient transfer and endocrine organ, functions as a selective barrier to protect the fetus against the harmful effects of exogenous and endogenous toxins. Members of the ATP-binding cassette (ABC) family of transport proteins limit the entry of xenobiotics into the fetal circulation via vectorial efflux from the placenta to the maternal circulation. Several members of the ABC family, including proteins from the ABCA, ABCB, ABCC and ABCG subfamilies, have been shown to be functional in the placenta with clinically significant roles in xenobiotic efflux. However, recent findings suggest that these transporters also protect placental tissue by preventing the cellular accumulation of cytotoxic compounds such as lipids, sterols and their derivatives. Such protective functions are likely to be particularly important in pregnancies complicated by inflammatory or oxidative stress, where the generation of toxic metabolites is enhanced. For example, ABC transporters have been shown to protect against the harmful effects of hypoxia and oxidative stress through increased expression and efflux of oxysterols and glutathione conjugated xenobiotics. However, this protective capacity may be diminished in response to the same stressors. Several studies in primary human trophoblast cells and animal models have demonstrated decreased expression and activity of placental ABC transporters with inflammatory, oxidative or metabolic stress. Several clinical studies in pregnancies complicated by inflammatory conditions such as preeclampsia and gestational diabetes support these findings, although further studies are required to determine the clinical relevance of the relationships between placental ABC transporter expression and activity, and placental function in stressed pregnancies. Such studies are necessary to fully understand the consequences of pregnancy disorders on placental function and viability in order to optimise pregnancy care and maximise fetal growth and health.

Metabolic impact of 4-hydroxynonenal on macrophage-like RAW 264.7 function and activation

Metabolic profiling of macrophage metabolic response upon exposure to 4-hydroxynonenal (HNE) demonstrates that HNE does not simply inactivate superoxide-generating enzymes but also could be responsible for the impairment of downfield signaling pathways. Multianalyte microphysiometry (MAMP) was employed to simultaneously measure perturbations in extracellular acidification, lactate production, and oxygen consumption for the examination of aerobic and anaerobic pathways. Combining the activation of oxidative burst with phorbol myristate acetate (PMA) and the immunosuppression with HNE, the complex nature of HNE toxicity was determined to be concentration- and time-dependent. Further analysis was utilized to assess the temporal effect of HNE on reactive oxygen species (ROS) production and on protein kinase C (PKC). Increased levels of HNE with decreasing PKC activity suggest that PKC is a target for HNE adductation prior to oxidative burst. Additionally, localization of PKC to the cell membrane was prevented with the introduction of HNE, demonstrating a consequence of HNE adductation on NADPH activation. The impairment of ROS by HNE suggests that HNE has a greater role in foam cell formation and tissue damage than is already known. Although work has been performed to understand the effect of HNE's regulation of specific signaling pathways, details regarding its involvement in cellular metabolism as a whole are generally unknown. This study examines the impact of HNE on macrophage oxidative burst and identifies PKC as a key protein for HNE suppression and eventual metabolic response.

Identification of mammary epithelial cells subject to chronic oxidative stress in mammary epithelium of young women and teenagers living in USA: implication for breast carcinogenesis

Current knowledge of changes in the mammary epithelium relevant to breast carcinogenesis is limited to when histological changes are already present because of a lack of biomarkers needed to identify where such molecular changes might be ongoing at earlier during the of decades-long latent stages of breast carcinogenesis. Breast reduction tissues from young women and teenagers, representative of USA's high breast cancer incidence population, were studies using immunocytochemistry and targeted PCR arrays in order to learn whether a marker of chronic oxidative-stress [protein adducts of 4-hydroxy-2-nonenal (4HNE)] can identify where molecular changes relevant to carcinogenesis might be taking place prior to any histological changes. 4HNE-immunopositive (4HNE+) mammary epithelial cell-clusters were identified in breast tissue sections from most women and from many teenagers (ages 14-30 y) and, in tissues from women ages 17-27 y with many vs. few 4HNE+ cells, the expression of 30 of 84 oxidative-stress associated genes was decreased and only one was increased > 2-fold. This is in contrast to increased expression of many of these genes known to be elicited by acute oxidative-stress. The findings validate using 4HNE-adducts to identify where molecular changes of potential relevance to carcinogenesis are taking place in histologically normal mammary epithelium and highlight differences between responses to acute vs. chronic oxidative-stress. We posit that the altered gene expression in 4HNE+ tissues reflect adaptive responses to chronic oxidative-stress that enable some cells to evade mechanisms that have evolved to prevent propagation of cells with oxidatively-damaged DNA and to accrue heritable changes needed to establish a cancer.

Hydroxyalkenals and oxidized phospholipids modulation of endothelial cytoskeleton, focal adhesion and adherens junction proteins in regulating endothelial barrier function

Lipid peroxidation of polyunsaturated fatty acids generates bioactive aldehydes, which exhibit pro- and anti-inflammatory effects in cells and tissues. Accumulating evidence indicates that 4-hydroxynonenal (4-HNE), a major aldehyde derived from lipid peroxidation of n-6 polyunsaturated fatty acids trigger signals that modulates focal adhesion and adherens junction proteins thereby inducing endothelial barrier dysfunction. Similarly, oxidized phospholipids (Ox-PLs) generated by lipid peroxidation of phospholipids with polyunsaturated fatty acids have been implicated in atherogenesis, inflammation and gene expression. Interestingly, physiological concentration of Ox-PLs is anti-inflammatory and protect against endotoxin- and ventilator-associated acute lung injury. Thus, excess generation of bioactive hydroxyalkenals and Ox-PLs during oxidative stress contributes to pathophysiology of various diseases by modulating signaling pathways that regulate pro- and anti-inflammatory responses and barrier regulation. This review summarizes the role of 4-HNE and Ox-PLs affecting cell signaling pathways and endothelial barrier dysfunction through modulation of the activities of proteins/enzymes by Michael adducts formation, enhancing the level of protein tyrosine phosphorylation of the target proteins, and by reorganization of cytoskeletal, focal adhesion, and adherens junction proteins. A better understanding of molecular mechanisms of hydroxyalkenals- and Ox-PLs-mediated pro-and anti-inflammatory responses and barrier function may lead to development of novel therapies to ameliorate oxidative stress related cardio-pulmonary disorders.

The protective role of natural phytoalexin resveratrol on inflammation, fibrosis and regeneration in cholestatic liver injury

Liver injuries can trigger a cascade of inflammatory responses and as a result, initiate the process of hepatic regeneration and fibrogenesis. Resveratrol (RSV) has multiple health-promoting benefits. This study evaluated the potential protective effects and mechanism of RSV as related to cholestatic liver injury. RSV was given (4 mg/kg/day, i.p.) for either 3 days or 7 days after bile duct ligation (BDL) injury. RSV significantly reduced serum ALT, AST but not T-bil on Day 3. At this early stage of injury, RSV significantly reduced TNF-α and IL-6 mRNA and decreased the number of Kupffer cells (CD68(+) ) recruited in the injured liver. RSV decreased hepatic fibrosis and reduced collagen Iα1 and TIMP-1 mRNA on Day 7. At the later stages of injury, RSV increased the number of Ki67(+) hepatocytes indicating that RSV promoted hepatocyte proliferation. Additionally, it resulted in decreased expression of 4-hydroxynonenal and increased expression of the hepatocyte growth factor protein and mRNA in the RSV-treated BDL group. Meanwhile, RSV reduced the mortality rate of BDL mice. In conclusion, RSV attenuated inflammation and reduced Kupffer cells activation. RSV decreased fibrosis and promoted hepatocyte regeneration, which increased the survival of BDL mice. RSV was beneficial for the treatment of cholestatic liver injury.

Knockout and transgenic mice in glutathione transferase research

Glutathione transferases (GSTs) are a multigene family of ubiquitously expressed, polymorphic enzymes responsible for the metabolism of a wide range of both endogenous and exogenous substrates, play a central role in the adaptive response to chemical and oxidative stress, and are subject to regulation by a range of structurally unrelated chemicals. In this review, we present a current summary of knockout mouse models in the GST field, discussing some of the issues pertaining to orthologous proteins between mice and humans, the potential confounding issues related to genetic background, and also cover new transgenic models in the increasingly important area of humanization.