Differential metabolism of 4-hydroxynonenal in liver, lung and brain of mice and rats

Cleavage of Hsp70.1 causes lysosomal cell death under stress conditions

Autophagy mediates the degradation of intracellular macromolecules and organelles within lysosomes. There are three types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy. Heat shock protein 70.1 (Hsp70.1) exhibits dual functions as a chaperone protein and a lysosomal membrane stabilizer. Since chaperone-mediated autophagy participates in the recycling of ∼30% cytosolic proteins, its disorder causes cell susceptibility to stress conditions. Cargo proteins destined for degradation such as amyloid precursor protein and tau protein are trafficked by Hsp70.1 from the cytosol into lysosomes. Hsp70.1 is composed of an N-terminal nucleotide-binding domain (NBD) and a C-terminal domain that binds to cargo proteins, termed the substrate-binding domain (SBD). The NBD and SBD are connected by the interdomain linker LL1, which modulates the allosteric structure of Hsp70.1 in response to ADP/ATP binding. After the passage of the Hsp70.1-cargo complex through the lysosomal limiting membrane, high-affinity binding of the positive-charged SBD with negative-charged bis(monoacylglycero)phosphate (BMP) at the internal vesicular membranes activates acid sphingomyelinase to generate ceramide for stabilizing lysosomal membranes. As the integrity of the lysosomal limiting membrane is critical to ensure cargo protein degradation within the acidic lumen, the disintegration of the lysosomal limiting membrane is lethal to cells. After the intake of high-fat diets, however, β-oxidation of fatty acids in the mitochondria generates reactive oxygen species, which enhance the oxidation of membrane linoleic acids to produce 4-hydroxy-2-nonenal (4-HNE). In addition, 4-HNE is produced during the heating of linoleic acid-rich vegetable oils and incorporated into the body via deep-fried foods. This endogenous and exogenous 4-HNE synergically causes an increase in its serum and organ levels to induce carbonylation of Hsp70.1 at Arg469, which facilitates its conformational change and access of activated μ-calpain to LL1. Therefore, the cleavage of Hsp70.1 occurs prior to its influx into the lysosomal lumen, which leads to lysosomal membrane permeabilization/rupture. The resultant leakage of cathepsins is responsible for lysosomal cell death, which would be one of the causative factors of lifestyle-related diseases.

Response of a Human Lens Epithelial Cell Line to Hyperglycemic and Oxidative Stress: The Role of Aldose Reductase

A common feature of different types of diabetes is the high blood glucose levels, which are known to induce a series of metabolic alterations, leading to damaging events in different tissues. Among these alterations, both increased polyol pathway flux and oxidative stress are considered to play relevant roles in the response of different cells. In this work, the effect on a human lens epithelial cell line of stress conditions, consisting of exposure to either high glucose levels or to the lipid peroxidation product 4-hydroxy-2-nonenal, is reported. The occurrence of osmotic imbalance, alterations of glutathione levels, and expression of inflammatory markers was monitored. A common feature of the two stress conditions was the expression of COX-2, which, only in the case of hyperglycemic stress, occurred through NF-κB activation. In our cell model, aldose reductase activity, which is confirmed as the only activity responsible for the osmotic imbalance occurring in hyperglycemic conditions, seemed to have no role in controlling the onset of the inflammatory phenomena. However, it played a relevant role in cellular detoxification against lipid peroxidation products. These results, in confirming the multifactorial nature of the inflammatory phenomena, highlight the dual role of aldose reductase as having both damaging but also protecting activity, depending on stress conditions.

Protocol to study in vitro drug metabolism and identify montelukast metabolites from purified enzymes and primary cell cultures by mass spectrometry

We present an optimized protocol set to study the production of drug metabolites in different in vitro systems. We detail the necessary steps to identify the metabolites of xenobiotics produced in different metabolic-competent systems, from purified enzymes to primary cell cultures. It is coupled to a high-resolution mass spectrometry analytical approach and can be adapted to study any xenobiotic. This protocol was optimized using montelukast, an antagonist of the cysteinyl leukotriene receptor 1, widely used for asthma management. For complete details on the use and execution of this protocol, please refer to Marques et al. (2022).1.

A time differentiated dietary intervention effect on the biomarkers of exposure to pyrethroids and neonicotinoids pesticides

Tailoring medical models to the right person or risk subgroups delivered at the right time is important in personalized medicine/prevention initiatives. The CIRCA-CHEM randomized 2x2 crossover pilot trial investigated whether the consumption of fruits/vegetables within a time-restricted daily window would affect urinary biomarkers of exposure to neonicotinoids (6-chloronicotinic acid, 6-CN) and pyrethroids (3-phenoxybenzoic acid, 3-PBA) pesticides, a biomarker of oxidative damage (4-hydroxynonenal, 4-HNE) and the associated urinary NMR metabolome. A statistically significant difference (p < 0.001) in both creatinine-adjusted 6-CN and 3-PBA levels was observed between the two-time dietary intervention windows (morning vs. evening). In the evening intervention period, pesticides biomarker levels were higher compared to the baseline, whereas in the morning period, pesticide levels remained unchanged. Positive associations were observed between pesticides and 4-HNE suggesting a diurnal chrono-window of pesticide toxicity. The discovery of a chronotoxicity window associated with chrono-disrupted metabolism of food contaminants may find use in personalized medicine initiatives.

Electrophilic Aldehyde 4-Hydroxy-2-Nonenal Mediated Signaling and Mitochondrial Dysfunction

Reactive oxygen species (ROS), a by-product of aerobic life, are highly reactive molecules with unpaired electrons. The excess of ROS leads to oxidative stress, instigating the peroxidation of polyunsaturated fatty acids (PUFA) in the lipid membrane through a free radical chain reaction and the formation of the most bioactive aldehyde, known as 4-hydroxynonenal (4-HNE). 4-HNE functions as a signaling molecule and toxic product and acts mainly by forming covalent adducts with nucleophilic functional groups in proteins, nucleic acids, and lipids. The mitochondria have been implicated as a site for 4-HNE generation and adduction. Several studies clarified how 4-HNE affects the mitochondria's functions, including bioenergetics, calcium homeostasis, and mitochondrial dynamics. Our research group has shown that 4-HNE activates mitochondria apoptosis-inducing factor (AIFM2) translocation and facilitates apoptosis in mice and human heart tissue during anti-cancer treatment. Recently, we demonstrated that a deficiency of SOD2 in the conditional-specific cardiac knockout mouse increases ROS, and subsequent production of 4-HNE inside mitochondria leads to the adduction of several mitochondrial respiratory chain complex proteins. Moreover, we highlighted the physiological functions of HNE and discussed their relevance in human pathophysiology and current discoveries concerning 4-HNE effects on mitochondria.

Diurnal Variation in Biomarkers of Exposure to Endocrine-Disrupting Chemicals and Their Association with Oxidative Damage in Norwegian Adults: The EuroMix Study

Much evidence on the adverse health effects of endocrine-disrupting chemicals (EDCs) has accumulated during recent decades. EDCs are commonly found in various foods and personal care products (PCP). Data documenting a diurnally varying EDC metabolism in humans is scarce. This study examined (i) the time-of-day effect on the diurnal magnitude and variance of urinary biomarkers of exposure to EDCs, and (ii) the association between EDC exposures and oxidative damage in a Norwegian adult subpopulation. This was a cross-sectional panel study using biobanked samples from the EuroMix project. During a typical weekday, participants were asked to collect all day’s urine voids and record dietary and PCP habitual uses in a diary. Collected time stamps of urine voids were classified into three distinct periods in the day (morning 6 a.m.−12 p.m., mid-day 12 p.m.−6 p.m., evening 6 p.m.−6 a.m.). Questionnaires regarding demographic characteristics, personal care product usage, and dietary habits were completed. Urinary levels of EDCs (phthalates, parabens, and bisphenols) were measured using mass spectrometry and adjusted for urinary volume using specific gravity. Urinary 4-hydroxynonenal (4HNE), a lipid peroxidation marker, was measured using an immunoassay kit. Linear mixed-effect models identified EDCs under the influence of a diurnal variation effect that was adjusted for dietary habits and PCP use and examined associations between EDC and 4HNE. p-values were FDR-adjusted. Most phthalates appeared to be diurnally varying with higher urinary levels towards the evening (q < 0.001) than those measured during mid-day; this strong diurnal variation effect was not present for parabens and bisphenols. Significant (q < 0.001) positive associations were observed between all phthalates, parabens, and bisphenols (except bisphenol S) and 4HNE. This study’s findings highlighted the diurnal variation of excretion for certain EDC, but not for others, in real-life conditions. The degree of EDC chronotoxicity in distinct diurnal windows of the day warrants further investigation with longitudinal human studies.

Protective effect of genistein pre-treatment on paraquat hepatotoxicity in rats

Paraquat (PQ), an herbicide widely used in agriculture, is considered a highly toxic compound. In hepatocytes, P-glycoprotein (P-gp/Abcb1) is a canalicular transporter involved in PQ extrusion from the cell. Previously, we demonstrated that genistein (GNT) induces P-gp in rat liver. In this study, the protective role of GNT pretreatment towards hepatic damage in a model of acute intoxication with PQ in rats, was investigated. Wistar rats were randomized in 4 groups: Control, GNT (5 mg/kg/day sc, 4 days), PQ (50 mg/kg/day ip, last day) and GNT+ PQ. Hepatic lipoperoxidation (LPO) was evaluated by the thiobarbituric acid reactive substances method. Hepatic levels of 4-hydroxynonenal protein adducts (4-HNEp-add) and glutathione-S-transferase alpha (GSTα) protein expression were evaluated by Western blotting. Hepatic glutathione levels and plasma levels of alanine transaminase (ALT) and aspartate transaminase (AST) were also measured. Biliary excretion of PQ was studied in vivo and in isolated perfused liver. PQ was quantified by HPLC. PQ significantly increased AST and ALT activities, malondialdehyde and 4-HNEp-add levels, whereby pretreatment with GNT ameliorated this effect. PQ biliary excretion remained unchanged after treatments in both experimental models. Hepatic GSTα expression was augmented in GNT group. GNT pretreatment increased hepatic glutathione levels in PQ + GNT group. These results agree with the lower content of 4-HNEp-adds in GNT + PQ group respect to PQ group. Unexpectedly, increased activity of P-gp did not enhance PQ biliary excretion. Thus, GNT protective mechanism is likely through the induction of GSTα which results in increased 4-HNE metabolism before formation of protein adducts.

Involvement of 4-hydroxy-2-nonenal in the pathogenesis of pulmonary fibrosis

Pulmonary fibrosis is a chronic progressive disease with high incidence, prevalence, and mortality rates worldwide. It is characterized by excessive accumulation of extracellular matrix in the lung parenchyma. The cellular and molecular mechanisms involved in its pathogenesis are complex, and some are still unknown. Several studies indicate that oxidative stress, characterized by overproduction of 4-hydroxy-2-nonenal (4-HNE), is an important player in pulmonary fibrosis. 4-HNE is a highly reactive compound derived from polyunsaturated fatty acids that can react with proteins, phospholipids, and nucleic acids. Thus, many of the altered cellular mechanisms that contribute to this disease can be explained by the participation of 4-HNE. Here, we summarize the current knowledge on the molecular states and signal transduction pathways that contribute to the pathogenesis of pulmonary fibrosis. Furthermore, we describe the participation of 4-HNE in various mechanisms involved in pulmonary fibrosis development, with a focus on the cell populations involved in the initiation, development, and maintenance of the fibrotic process, mainly alveolar cells, endothelial cells, macrophages, and inflammatory cells. Due to its characteristic activity as a second messenger, 4-HNE, in addition to being a consequence of oxidative stress, can support maintenance of the inflammatory and fibrotic process by spreading the effects of reactive oxygen species (ROS). Thus, regulation of 4-HNE levels could be a viable strategy to reduce its effects on the mechanisms involved in pulmonary fibrosis development.

4-Hydroxy-2-nonenal antimicrobial toxicity is neutralized by an intracellular pathogen

Pathogens encounter numerous antimicrobial responses during infection, including the reactive oxygen species (ROS) burst. ROS-mediated oxidation of host membrane poly-unsaturated fatty acids (PUFAs) generates the toxic alpha-beta carbonyl 4-hydroxy-2-nonenal (4-HNE). Although studied extensively in the context of sterile inflammation, research into 4-HNE’s role during infection remains limited. Here, we found that 4-HNE is generated during bacterial infection, that it impacts growth and survival in a range of bacteria, and that the intracellular pathogen Listeria monocytogenes induces many genes in response to 4-HNE exposure. A component of the L. monocytogenes 4-HNE response is the expression of the genes lmo0103 and lmo0613, deemed rha1 and rha2 (reductase of host alkenals), respectively, which code for two NADPH-dependent oxidoreductases that convert 4-HNE to the product 4-hydroxynonanal (4-HNA). Loss of these genes had no impact on L. monocytogenes bacterial burdens during murine or tissue culture infection. However, heterologous expression of rha1/2 in Bacillus subtilis significantly increased bacterial resistance to 4-HNE in vitro and promoted bacterial survival following phagocytosis by murine macrophages in an ROS-dependent manner. Thus, Rha1 and Rha2 are not necessary for 4-HNE resistance in L. monocytogenes but are sufficient to confer resistance to an otherwise sensitive organism in vitro and in host cells. Our work demonstrates that 4-HNE is a previously unappreciated component of ROS-mediated toxicity encountered by bacteria within eukaryotic hosts.

Dietary iso-α-acids prevent acetaldehyde-induced liver injury through Nrf2-mediated gene expression

Acetaldehyde is the major toxic metabolite of alcohol (ethanol) and enhances fibrosis of the liver through hepatic stellate cells. Additionally, alcohol administration causes the accumulation of reactive oxygen species (ROS), which induce hepatocyte injury-mediated lipid peroxidation. Iso-α-acids, called isohumulones, are bitter acids in beer. The purpose of this study was to investigate the protective effects of iso-α-acids against alcoholic liver injury in hepatocytes in mice. C57BL/6N mice were fed diets containing isomerized hop extract, which mainly consists of iso-α-acids. After 7 days of feeding, acetaldehyde was administered by a single intraperitoneal injection. The acetaldehyde-induced increases in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were suppressed by iso-α-acids intake. Hepatic gene expression analyses showed the upregulation of detoxifying enzyme genes, glutathione-S-transferase (GST) and aldehyde dehydrogenase (ALDH). In vitro, iso-α-acids upregulated the enzymatic activities of GST and ALDH and induced the nuclear translocation of nuclear factor-erythroid-2-related factor 2 (Nfe2l2; Nrf2), a master regulator of antioxidant and detoxifying systems. These results suggest that iso-α-acid intake prevents acetaldehyde-induced liver injury by reducing oxidative stress via Nrf2-mediated gene expression.

Age-related alteration in HNE elimination enzymes

4-hydroxynonenal (HNE, 4-hydroxy-2-nonenal) is a primary α,β-unsaturated aldehyde product of lipid peroxidation. The accumulation of HNE increases with aging and the mechanisms are mainly attributable to increased oxidative stress and decreased capacity of HNE elimination. In this review article, we summarize the studies on age-related change of HNE concentration and alteration of HNE metabolizing enzymes (GCL, GST, ALDHs, aldose reductase, and 20S-proteasome), and discuss potential mechanism of age-related decrease in HNE-elimination capacity by focusing on Nrf2 redox signaling.

Dual Substance Use of Electronic Cigarettes and Alcohol

Electronic cigarettes (ECs) are a modern nicotine delivery system that rapidly grew in widespread use, particularly in younger populations. Given the long history of the comorbidity of alcohol and nicotine use, the rising prevalence of ECs raises the question as to their role in the consumption of alcohol. Of the numerous models of ECs available, JUUL is the most popular. This narrative review aims to determine current trends in literature regarding the relationship between EC and alcohol dual use, as well as hypothesize potential pathogenic tissue damage and summarize areas for future study, including second-hand vapor exposure and calling for standardization among studies. In summary, EC users are more likely to participate in hazardous drinking and are at higher risk for alcohol use disorder (AUD). We surmise the pathogenic damage of dual use may exhibit an additive effect, particularly in pathogen clearance from the lungs, increased inflammation and decreased immune response, physical damage to epithelial cells, and exacerbation of chronic obstructive pulmonary disease (COPD)-like illnesses. A better understanding of pathogenic damages is critical to understand the risks placed on dual users when exposed to respiratory pathogens, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

ORY supplementation mitigates acetaminophen-induced acute liver failure in male mice: role of oxidative stress and apoptotic markers

The aim of the present study was to assess the possible protective effect of γ-oryzanol (ORY) supplementation in a model of acute liver failure (ALF) induced by acetaminophen (APAP) in mice. Male Swiss strain mice were supplemented with ORY (10 and 50 mg/kg, per oral route) daily for 7 days. One hour after the last supplementation, animals received APAP (300 mg/kg, intraperitoneal). Twenty-four hours after APAP administration, mice were euthanized, and biochemical and histopathological determinations were performed. Histopathological analysis revealed that APAP caused vascular congestion, loss of cellular structure, and cellular infiltration in hepatocytes. Moreover, it caused oxidative damage (enzymatic and non-enzymatic analysis of oxidative stress), with loss of hepatic function leading to cell apoptosis (apoptotic parameters). ORY supplementation (ORY-10 and ORY-50) protected against all changes in ALF model. Thus, the protective effect of ORY supplementation was due to modulation of antioxidant defenses avoiding the apoptotic process.

Electrophile Signaling and Emerging Immuno- and Neuro-modulatory Electrophilic Pharmaceuticals

With a lipid-rich environment and elevated oxygen consumption, the central nervous system (CNS) is subject to intricate regulation by lipid-derived electrophiles (LDEs). Investigations into oxidative damage and chronic LDE generation in neural disorders have spurred the development of tools that can detect and catalog the gamut of LDE-adducted proteins. Despite these advances, deconstructing the precise consequences of individual protein-specific LDE modifications remained largely impossible until recently. In this perspective, we first overview emerging toolsets that can decode electrophile-signaling events in a protein/context-specific manner, and how the accumulating mechanistic insights brought about by these tools have begun to offer new means to modulate pathways relevant to multiple sclerosis (MS). By surveying the latest data surrounding the blockbuster MS drug dimethyl fumarate that functions through LDE-signaling-like mechanisms, we further provide a vision for how chemical biology tools probing electrophile signaling may be leveraged toward novel interventions in CNS disease.

Can Medicinal Plants and Bioactive Compounds Combat Lipid Peroxidation Product 4-HNE-Induced Deleterious Effects?

The toxic reactive aldehyde 4-hydroxynonenal (4-HNE) belongs to the advanced lipid peroxidation end products. Accumulation of 4-HNE and formation of 4-HNE adducts induced by redox imbalance participate in several cytotoxic processes, which contribute to the pathogenesis and progression of oxidative stress-related human disorders. Medicinal plants and bioactive natural compounds are suggested to be attractive sources of potential agents to mitigate oxidative stress, but little is known about the therapeutic potentials especially on combating 4-HNE-induced deleterious effects. Of note, some investigations clarify the attenuation of medicinal plants and bioactive compounds on 4-HNE-induced disturbances, but strong evidence is needed that these plants and compounds serve as potent agents in the prevention and treatment of disorders driven by 4-HNE. Therefore, this review highlights the pharmacological basis of these medicinal plants and bioactive compounds to combat 4-HNE-induced deleterious effects in oxidative stress-related disorders, such as neurotoxicity and neurological disorder, eye damage, cardiovascular injury, liver injury, and energy metabolism disorder. In addition, this review briefly discusses with special attention to the strategies for developing potential therapies by future applications of these medicinal plants and bioactive compounds, which will help biological and pharmacological scientists to explore the new vistas of medicinal plants in combating 4-HNE-induced deleterious effects.

4-Hydroxy-Trans-2-Nonenal in the Regulation of Anti-Oxidative and Pro-Inflammatory Signaling Pathways

Recent studies indicate that 4-hydroxy-trans-2-nonenal (HNE), a major oxidative stress triggered lipid peroxidation-derived aldehyde, plays a critical role in the pathophysiology of various human pathologies including metabolic syndrome, diabetes, cardiovascular, neurological, immunological, and age-related diseases and various types of cancer. HNE is the most abundant and toxic α, β-unsaturated aldehyde formed during the peroxidation of polyunsaturated fatty acids in a series of free radical-mediated reactions. The presence of an aldehyde group at C1, a double bond between C2 and C3 and a hydroxyl group at C4 makes HNE a highly reactive molecule. These strong reactive electrophilic groups favor the formation of HNE adducts with cellular macromolecules such as proteins and nucleic acids leading to the regulation of various cell signaling pathways and processes involved in cell proliferation, differentiation, and apoptosis. Many studies suggest that the cell-specific intracellular concentrations of HNE dictate the anti-oxidative and pro-inflammatory activities of this important molecule. In this review, we focused on how HNE could alter multiple anti-oxidative defense pathways and pro-inflammatory cytotoxic pathways by interacting with various cell-signaling intermediates.

Xenobiotica-metabolizing enzymes in the lung of experimental animals, man and in human lung models

The xenobiotic metabolism in the lung, an organ of first entry of xenobiotics into the organism, is crucial for inhaled compounds entering this organ intentionally (e.g. drugs) and unintentionally (e.g. work place and environmental compounds). Additionally, local metabolism by enzymes preferentially or exclusively occurring in the lung is important for favorable or toxic effects of xenobiotics entering the organism also by routes other than by inhalation. The data collected in this review show that generally activities of cytochromes P450 are low in the lung of all investigated species and in vitro models. Other oxidoreductases may turn out to be more important, but are largely not investigated. Phase II enzymes are generally much higher with the exception of UGT glucuronosyltransferases which are generally very low. Insofar as data are available the xenobiotic metabolism in the lung of monkeys comes closed to that in the human lung; however, very few data are available for this comparison. Second best rate the mouse and rat lung, followed by the rabbit. Of the human in vitro model primary cells in culture, such as alveolar macrophages and alveolar type II cells as well as the A549 cell line appear quite acceptable. However, (1) this generalization represents a temporary oversimplification born from the lack of more comparable data; (2) the relative suitability of individual species/models is different for different enzymes; (3) when more data become available, the conclusions derived from these comparisons quite possibly may change.

Silibinin ameliorates hepatic lipid accumulation and oxidative stress in mice with non-alcoholic steatohepatitis by regulating CFLAR-JNK pathway

Non-alcoholic steatohepatitis (NASH) is a chronic metabolic syndrome and the CFLAR-JNK pathway can reverse the process of NASH. Although silibinin is used for the treatment of NASH in clinical, its effect on CFLAR-JNK pathway in NASH remains unclear. This study aimed to investigate the effect of silibinin on CFLAR-JNK pathway in NASH models both in vivo and in vitro. The in vivo study was performed using male C57BL/6 mice fed with methionine- choline-deficient diet and simultaneously treated with silibinin for 6 weeks. The in vitro study was performed by using mouse NCTC-1469 cells which were respectively pretreated with oleic acid plus palmitic acid, and adenovirus-down Cflar for 24 h, then treated with silibinin for 24 h. After the drug treatment, the key indicators involved in CFLAR-JNK pathway including hepatic injury, lipid metabolism and oxidative stress were determined. Silibinin significantly activated CFLAR and inhibited the phosphorylation of JNK, up-regulated the mRNA expression of Pparα, Fabp5, Cpt1α, Acox, Scd-1, Gpat and Mttp, reduced the activities of serum ALT and AST and the contents of hepatic TG, TC and MDA, increased the expression of NRF2 and the activities of CAT, GSH-Px and HO-1, and decreased the activities and expression of CYP2E1 and CYP4A in vivo. These effects were confirmed by the in vitro experiments. Silibinin prevented NASH by regulating CFLAR-JNK pathway, and thereby on one hand promoting the β-oxidation and efflux of fatty acids in liver to relieve lipid accumulation, and on the other hand inducing antioxidase activity (CAT, GSH-Px and HO-1) and inhibiting pro-oxidase activity (CYP2E1 and CYP4A) to relieve oxidative stress.

Protective effect of inducible aldo-keto reductases on 4-hydroxynonenal- induced hepatotoxicity

4-Hydroxynonenal (HNE), an end-product of lipid peroxidation generated in response to oxidative stress, has been implicated in the pathophysiology of chronic liver diseases. HNE is very reactive that forms Michael adducts with nucleophilic sites in DNA, lipids and proteins. At high concentrations, HNE causes rapid cell death associated with depletion of sulfhydryl groups and inhibition of key metabolic enzymes. At low concentrations, HNE stimulates expression of genes that are part of an adaptive response. In this study, we show that sub-lethal concentrations of HNE induce mRNA expression levels of heme oxygenase-1 (HO-1) (2.5-fold), NADPH:quinone oxidoreductase (NQO1) (4.5-fold), AKR1C3 (2-fold) and AKR7A2 (3-fold) enzymes. Protein expression levels of AKR1C and AKR7A2 are induced by 2- and 1.5-fold following exposure to HNE. The role of AKR1C3 and AKR7A2 in protecting HepG2 cells against HNE toxicity was investigated through using RNAi. Results show that AKR7A2, but not AKR1C3 contributes to the protection against HNE toxicity in HepG2 cells. Moreover, transcriptional factor nuclear factor erythroid 2 p45-related factor 2 (Nrf2) is activated by HNE through translocation to the nucleus. Overexpressing AKR7A2 could rescue the effect of knocking down Nrf2 on HNE-induced cytotoxicity. Furthermore, a natural compound 7-hydroxycoumain, an AKR7A2 inducer, shows hepatoprotection against HNE via AKR7A2 induction. Hence, the inducible AKR7A2 has provided a new therapeutic target to treat chronic liver disease.

Growth of Triple Negative and Progesterone Positive Breast Cancer Causes Oxidative Stress and Down-Regulates Neuroprotective Transcription Factor NPAS4 and NPAS4-Regulated Genes in Hippocampal Tissues of TumorGraft Mice-an Aging Connection

While the refinement of existing and the development of new chemotherapeutic regimens has significantly improved cancer treatment outcomes and patient survival, chemotherapy still causes many persistent side effects. Central nervous system (CNS) toxicity is of particular concern, as cancer patients experience significant deficits in memory, learning, cognition, and decision-making. These chemotherapy-induced cognitive changes are termed chemo brain, and manifest in more than half of cancer survivors. Moreover, recent studies have emerged suggesting that neurocognitive deficits manifest prior to cancer diagnosis and treatment, and thus may be associated with tumor presence, a phenomenon recently termed “tumor brain.” To dissect the molecular mechanisms of tumor brain, we used TumorGraft^TM models, wherein part of a patient's tumor is grafted into immune-deficient mice. Here, we analyzed molecular changes in the hippocampal tissues of mice carrying triple negative (TNBC) or progesterone receptor positive (PR+BC) xenografts. TNBC growth led to increased oxidative damage, as detected by elevated levels of 4-hydroxy-2-nonenal, a product of lipid peroxidation. Furthermore, the growth of TNBC and PR+BC tumors altered global gene expression in the murine hippocampus and affected multiple pathways implicated in PI3K-Akt and MAPK signaling, as well as other pathways crucial for the proper functioning of hippocampal neurons. TNBC and PR+BC tumor growth also led to a significant decrease in the levels of neuronal transcription factor NPAS4, a regulator that governs the expression of brain-derived neurotrophic factor (BDNF), and several other key brain neurotrophic factors and pro-survival molecules. The decreased expression of ERK1/2, NPAS4, and BDNF are also seen in neurodegenerative conditions and aging, and may constitute an important tumor brain mechanism.

Enzymatic and non-enzymatic detoxification of 4-hydroxynonenal: Methodological aspects and biological consequences

4-Hydroxynonenal (HNE), an electrophilic end-product deriving from lipid peroxidation, undergoes a heterogeneous set of biotransformations including enzymatic and non-enzymatic reactions. The former mostly involve red-ox reactions on the HNE oxygenated functions (phase I metabolism) and GSH conjugations (phase II) while the latter are due to the HNE capacity to spontaneously condense with nucleophilic sites within endogenous molecules such as proteins, nucleic acids and phospholipids. The overall metabolic fate of HNE has recently attracted great interest not only because it clearly determines the HNE disposal, but especially because the generated metabolites and adducts are not inactive molecules (as initially believed) but show biological activities even more pronounced than those of the parent compound as exemplified by potent pro-inflammatory stimulus induced by GSH conjugates. Similarly, several studies revealed that the non-enzymatic reactions, initially considered as damaging processes randomly involving all endogenous nucleophilic reactants, are in fact quite selective in terms of both reactivity of the nucleophilic sites and stability of the generated adducts. Even though many formed adducts retain the expected toxic consequences, some adducts exhibit well-defined beneficial roles as documented by the protective effects of sublethal concentrations of HNE against toxic concentrations of HNE. Clearly, future investigations are required to gain a more detailed understanding of the metabolic fate of HNE as well as to identify novel targets involved in the biological activity of the HNE metabolites. These studies are and will be permitted by the continuous progress in the analytical methods for the identification and quantitation of novel HNE metabolites as well as for proteomic analyses able to offer a comprehensive picture of the HNE-induced adducted targets. On these grounds, the present review will focus on the major enzymatic and non-enzymatic HNE biotransformations discussing both the molecular mechanisms involved and the biological effects elicited. The review will also describe the most important analytical enhancements that have permitted the here discussed advancements in our understanding of the HNE metabolic fate and which will permit in a near future an even better knowledge of this enigmatic molecule.

4-Hydroxynonenal metabolites and adducts in pre-carcinogenic conditions and cancer

4-hydroxy-2-nonenal (HNE) is an amazing reactive compound, originating from lipid peroxidation within cells but also in food and considered as a "second messenger" of oxidative stress. Due to its chemical features, HNE is able to make covalent links with DNA, proteins and lipids. The aim of this review is to give a comprehensive summary of the chemical properties of HNE and of the consequences of its reactivity in relation to cancer development. The formation of exocyclic etheno-and propano-adducts and genotoxic effects are addressed. The adduction to cellular proteins and the repercussions on the regulation of cell signaling pathways involved in cancer development are reviewed, notably on the Nrf2/Keap1/ARE pathway. The metabolic pathways leading to the inactivation/elimination or, on the contrary, to the bioactivation of HNE are considered. A special focus is given on the link between HNE and colorectal cancer development, due to its occurrence in foodstuffs and in the digestive lumen, during digestion.

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

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

Adolescent exposure to MDMA induces dopaminergic toxicity in substantia nigra and potentiates the amyloid plaque deposition in the striatum of APPswe/PS1dE9 mice

MDMA is one of the most used drugs by adolescents and its consumption has been associated with many psychobiological problems, among them psychomotor problems. Moreover, some authors described that early exposure to MDMA may render the dopaminergic neurons more vulnerable to the effects of future neurotoxic insults. Alzheimer disease (AD) is the main cause of dementia in the elderly and a percentage of the patients have predisposition to suffer nigrostriatal alterations, developing extrapyramidal signs. Nigrostriatal dysfunction in the brain of aged APPswe/PS1dE9 (APP/PS1), a mouse model of familiar AD (FAD), has also been described. The aim of the present study was to investigate the consequences of adolescent exposure to MDMA in APP/PS1 mice, on nigrostriatal function on early adulthood. We used a MDMA schedule simulating weekend binge abuse of this substance. Our MDMA schedule produced a genotype-independent decrease in dopaminergic neurons in the substantia nigra that remained at least 3months. Shortly after the injury, wild-type animals showed a decrease in the locomotor activity and apparent DA depletion in striatum, however in the APP/PS1 mice neither the locomotor activity nor the DA levels were modified, but a reduction in dopamine transporter (DAT) expression and a higher levels of oxidative stress were observed. We found that these disturbances are age-related characteristics that this APP/PS1 mice develops spontaneously much later. Therefore, MDMA administration seems to anticipate the striatal dopaminergic dysfunction in this FAD model. The most important outcome lies in a potentiation, by MDMA, of the amyloid beta deposition in the striatum.

Retracted Article: Cell orientation, proliferation, and differentiation on poly(l-lactide) spherulites

We show cytoskeleton and nuclear alignment on PLLA crystallized at 140 °C. Cell proliferation and differentiation were also promoted significantly and we study the effect of polymer spherulites on cell orientation, proliferation and differentiation.

Fabrication, characterization, bioactivity, and biocompatibility of novel mesoporous calcium silicate/polyetheretherketone composites

Composite consisting of polyetheretherketone and mesoporous calcium silicate were fabricated. The composite with improved hydrophilicity, bioactivity and biocompatibility might be a great candidate for bone tissue regeneration.

Alcohol, Aldehydes, Adducts and Airways

Drinking alcohol and smoking cigarettes results in the formation of reactive aldehydes in the lung, which are capable of forming adducts with several proteins and DNA. Acetaldehyde and malondialdehyde are the major aldehydes generated in high levels in the lung of subjects with alcohol use disorder who smoke cigarettes. In addition to the above aldehydes, several other aldehydes like 4-hydroxynonenal, formaldehyde and acrolein are also detected in the lung due to exposure to toxic gases, vapors and chemicals. These aldehydes react with nucleophilic targets in cells such as DNA, lipids and proteins to form both stable and unstable adducts. This adduction may disturb cellular functions as well as damage proteins, nucleic acids and lipids. Among several adducts formed in the lung, malondialdehyde DNA (MDA-DNA) adduct and hybrid malondialdehyde-acetaldehyde (MAA) protein adducts have been shown to initiate several pathological conditions in the lung. MDA-DNA adducts are pre-mutagenic in mammalian cells and induce frame shift and base-pair substitution mutations, whereas MAA protein adducts have been shown to induce inflammation and inhibit wound healing. This review provides an insight into different reactive aldehyde adducts and their role in the pathogenesis of lung disease.

On the role of 4-hydroxynonenal in health and disease

Polyunsaturated fatty acids are susceptible to peroxidation and they yield various degradation products, including the main α,β-unsaturated hydroxyalkenal, 4-hydroxy-2,3-trans-nonenal (HNE) in oxidative stress. Due to its high reactivity, HNE interacts with various macromolecules of the cell, and this general toxicity clearly contributes to a wide variety of pathological conditions. In addition, growing evidence suggests a more specific function of HNE in electrophilic signaling as a second messenger of oxidative/electrophilic stress. It can induce antioxidant defense mechanisms to restrain its own production and to enhance the cellular protection against oxidative stress. Moreover, HNE-mediated signaling can largely influence the fate of the cell through modulating major cellular processes, such as autophagy, proliferation and apoptosis. This review focuses on the molecular mechanisms underlying the signaling and regulatory functions of HNE. The role of HNE in the pathophysiology of cancer, cardiovascular and neurodegenerative diseases is also discussed.

Oxidative stress in severe acute illness

The overall redox potential of a cell is primarily determined by oxidizable/reducible chemical pairs, including glutathione–glutathione disulfide, reduced thioredoxin–oxidized thioredoxin, and NAD⁺–NADH (and NADP–NADPH). Current methods for evaluating oxidative stress rely on detecting levels of individual byproducts of oxidative damage or by determining the total levels or activity of individual antioxidant enzymes. Oxidation–reduction potential (ORP), on the other hand, is an integrated, comprehensive measure of the balance between total (known and unknown) pro-oxidant and antioxidant components in a biological system. Much emphasis has been placed on the role of oxidative stress in chronic diseases, such as Alzheimer's disease and atherosclerosis. The role of oxidative stress in acute diseases often seen in the emergency room and intensive care unit is considerable. New tools for the rapid, inexpensive measurement of both redox potential and total redox capacity should aid in introducing a new body of literature on the role of oxidative stress in acute illness and how to screen and monitor for potentially beneficial pharmacologic agents.