Aldehyde Acrolein Research Articles

Ligand-functionalized surfaces for chemoselective heterogeneous catalysis

Selectivity of multi-pathway surface reactions depends on subtle differences in the activation barriers of competing reactive processes, which is difficult to control. One of the most promising strategies to overcome this problem is to introduce a specific selective interaction between the reactant and the catalytically active site, directing the chemical transformations towards the desired route. This interaction can be imposed via functionalization of a solid catalyst with organic ligands, promoting the desired pathway via steric constrain and/or electronic effects. The microscopic-level understanding of the underlying surface processes is an important prerequisite for rational design of such new class of ligand-functionalized catalytic materials. In this perspective, we present an overview over our recent mechanistic studies on heterogeneous Pd(111) catalysts functionalized with different types of organic ligands for chemoselective hydrogenation of a,b-unsaturated aldehyde acrolein. Employing a combination of real space microscopic (STM) and in operando spectroscopic (IRAS) surface sensitive techniques, we show that self-ordered active ligand layers are formed under operational conditions and identify their chemical nature and the geometric arrangement on the surface turning over. Deposition of a ligand layer renders Pd highly active and nearly 100 % selective toward propenol formation by promoting acrolein adsorption in a specific adsorption configuration via the O atom of the C = O bond. In this adsorption configuration, acrolein can be hydrogenated first to the desired reaction intermediate propenoxy species followed by formation of the target product propenol. Both the reaction intermediate and the final product propenol as well as their time evolution were identified by IRAS and gas phase analysis via quadrupole mass spectrometry (QMS). Particular focus of these studies was on the role of geometric and electronic effects imposed by specific functional groups purposefully introduced in the ligand layer. Obtained atomistic-level insights into the formation and dynamic evolution of the active ligand layer under operational conditions as well as into the role of geometric vs. electronic effects imposed by the ligand provide important input required for controlling chemoselectivity by purposeful surface functionalization.

Neuroprotection by acrolein sequestration through exogenously applied scavengers and endogenous enzymatic enabling strategies in mouse EAE model

We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in MS pathology. In this study, we found that the acrolein scavenger hydralazine (HZ), when applied from the day of induction, can suppress acrolein and alleviate motor and sensory deficits in a mouse experimental autoimmune encephalomyelitis (EAE) model. Furthermore, we also demonstrated that HZ can alleviate motor deficits when applied after the emergence of MS symptoms, making potential anti-acrolein treatment a more clinically relevant strategy. In addition, HZ can reduce both acrolein and MPO, suggesting a connection between acrolein and inflammation. We also found that in addition to HZ, phenelzine (PZ), a structurally distinct acrolein scavenger, can mitigate motor deficits in EAE when applied from the day of induction. This suggests that the likely chief factor of neuroprotection offered by these two structurally distinct acrolein scavengers in EAE is their common feature of acrolein neutralization. Finally, up-and-down regulation of the function of aldehyde dehydrogenase 2 (ALDH2) in EAE mice using either a pharmacological or genetic strategy led to correspondent motor and sensory changes. This data indicates a potential key role of ALDH2 in influencing acrolein levels, oxidative stress, inflammation, and behavior in EAE. These findings further consolidate the critical role of aldehydes in the pathology of EAE and its mechanisms of regulation. This is expected to reinforce and expand the possible therapeutic targets of anti-aldehyde treatment to achieve neuroprotection through both endogenous and exogenous manners.

Changes in Whole Blood Polyamine Levels and Their Background in Age-Related Diseases and Healthy Longevity.

The relationship between polyamines and healthy longevity has received much attention in recent years. However, conducting research without understanding the properties of polyamines can lead to unexpected pitfalls. The most fundamental consideration in conducting polyamine studies is that bovine serum used for cell culture contains bovine serum amine oxidase. Bovine serum amine oxidase, which is not inactivated by heat treatment, breaks down spermine and spermidine to produce the highly toxic aldehyde acrolein, which causes cell damage and activates autophagy. However, no such enzyme activity has been found in humans. Polyamine catabolism does not produce toxic aldehydes under normal conditions, but inflammation and some pathogens provoke an inducible enzyme, spermine oxidase, which only breaks down spermine to produce acrolein, resulting in cytotoxicity and the activation of autophagy. Therefore, spermine oxidase activation reduces spermine concentration and the ratio of spermine to spermidine, a feature recently reported in patients with age-related diseases. Spermine, which is increased by a long-term, continuous high polyamine diet, suppresses aberrant gene methylation and the pro-inflammatory status that progress with age and are strongly associated with the development of several age-related diseases and senescence. Changes in spermine concentration and the spermine/spermidine ratio should be considered as indicators of human health status.

Quantitation by Liquid Chromatography-Nanoelectrospray Ionization-High-Resolution Tandem Mass Spectrometry of Multiple DNA Adducts Related to Cigarette Smoking in Oral Cells in the Shanghai Cohort Study.

We developed a liquid chromatography-nanoelectrospray ionization-high-resolution tandem mass spectrometry (LC-NSI-HRMS/MS) method for simultaneous quantitative analysis of 5 oral cell DNA adducts associated with cigarette smoking: (8R/S)-3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a]purine-10(3H)-one (γ-OH-Acr-dGuo, 1) from acrolein; (6S,8S and 6R,8R)-3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)-one [(6S,8S)γ-OH-Cro-dGuo, 2; and (6R,8R)γ-OH-Cro-dGuo, 3] from crotonaldehyde; 1,N6-etheno-dAdo (4) from acrylonitrile, vinyl chloride, lipid peroxidation, and inflammation; and 8-oxo-dGuo (5) from oxidative damage. Oral cell DNA was isolated in the presence of glutathione to prevent artifact formation. Clear LC-NSI-HRMS/MS chromatograms were obtained allowing quantitation of each adduct using the appropriately labeled internal standards. The accuracy and precision of the method were validated, and the assay limit of quantitation was 5 fmol/μmol dGuo for adducts 1-4 and 20 fmol/μmol for adduct 5. The assay was applied to 80 buccal cell samples selected from those collected in the Shanghai Cohort Study: 40 from current smokers and 40 from never smokers. Significant differences were found in all adduct levels between smokers and nonsmokers. Levels of 8-oxo-dGuo (5) were at least 3000 times greater than those of the other adducts in both smokers and nonsmokers, and the difference between amounts of this adduct in smokers versus nonsmokers, while significant (P = 0.013), was not as great as the differences of the other DNA adducts between smokers and nonsmokers (P-values all less than 0.001). No significant relationship of adduct levels to risk of lung cancer incidence was found. This study provides a new LC-NSI-HRMS/MS methodology for the quantitation of diverse DNA adducts resulting from exposure to the α,β-unsaturated aldehydes acrolein and crotonaldehyde, inflammation, and oxidative damage which are all associated with carcinogenesis. We anticipate application of this assay in ongoing studies of the molecular epidemiology of cancers of the lung and oral cavity related to cigarette smoking.

Acrolein inhalation acutely affects the regulation of mitochondrial metabolism in rat lung

Exposure of the airways to cigarette smoke (CS) is the primary risk factor for developing several lung diseases such as Chronic Obstructive Pulmonary Disease (COPD). CS consists of a complex mixture of over 6000 chemicals including the highly reactive α,β-unsaturated aldehyde acrolein. Acrolein is thought to be responsible for a large proportion of the non-cancer disease risk associated with smoking. Emerging evidence suggest a key role for CS-induced abnormalities in mitochondrial morphology and function in airway epithelial cells in COPD pathogenesis. Although in vitro studies suggest acrolein-induced mitochondrial dysfunction in airway epithelial cells, it is unknown if in vivo inhalation of acrolein affects mitochondrial content or the pathways controlling this. In this study, rats were acutely exposed to acrolein by inhalation (nose-only; 0−4 ppm), 4 h/day for 1 or 2 consecutive days (n = 6/group). Subsequently, the activity and abundance of key constituents of mitochondrial metabolic pathways as well as expression of critical proteins and genes controlling mitochondrial biogenesis and mitophagy were investigated in lung homogenates. A transient decreasing response in protein and transcript abundance of subunits of the electron transport chain complexes was observed following acrolein inhalation. Moreover, acrolein inhalation caused a decreased abundance of key regulators associated with mitochondrial biogenesis, respectively a differential response on day 1 versus day 2. Abundance of components of the mitophagy machinery was in general unaltered in response to acrolein exposure in rat lung. Collectively, this study demonstrates that acrolein inhalation acutely and dose-dependently disrupts the molecular regulation of mitochondrial metabolism in rat lung. Hence, understanding the effect of acrolein on mitochondrial function will provide a scientifically supported reasoning to shortlist aldehydes regulation in tobacco smoke.

Competing Reaction Pathways in Heterogeneously Catalyzed Hydrogenation of Allyl Cyanide: The Chemical Nature of Surface Species.

We present a mechanistic study on the formation of an active ligand layer over Pd(111), turning the catalytic surface highly active and selective in partial hydrogenation of an α,β‐unsaturated aldehyde acrolein. Specifically, we investigate the chemical composition of a ligand layer consisting of allyl cyanide deposited on Pd(111) and its dynamic changes under the hydrogenation conditions. On pristine surface, allyl cyanide largely retains its chemical structure and forms a layer of molecular species with the CN bond oriented nearly parallel to the underlying metal. In the presence of hydrogen, the chemical composition of allyl cyanide strongly changes. At 100 K, allyl cyanide transforms to unsaturated imine species, containing the C=C and C=N double bonds. At increasing temperatures, these species undergo two competing reaction pathways. First, the C=C bond become hydrogenated and the stable N‐butylimine species are produced. In the competing pathway, the unsaturated imine reacts with hydrogen to fully hydrogenate the imine group and produce butylamine. The latter species are unstable under the hydrogenation reaction conditions and desorb from the surface, while the N‐butylimine adsorbates formed in the first reaction pathway remain adsorbed and act as an active ligand layer in selective hydrogenation of acrolein.

ROCK1 Mediates Retinal Glial Cell Migration Promoted by Acrolein.

Objective: Acrolein is a highly reactive aldehyde that covalently binds to cellular macromolecules and subsequently modulates cellular function. Our previous study demonstrated that acrolein induces glial cell migration, a pathological hallmark of diabetic retinopathy; however, the detailed cellular mechanism remains unclear. The purpose of this study was to investigate the role of acrolein in retinal glial cell migration by focusing on rho-associated coiled-coil-containing protein kinases (ROCKs).Methods: Immunofluorescence staining for ROCK isoforms was performed using sections of fibrovascular tissue obtained from the eyes of patients with proliferative diabetic retinopathy (PDR). Rat retinal Müller glial cell line, TR-MUL5, was stimulated with acrolein and the levels of ROCK1 were evaluated using real-time PCR and western blotting. Phosphorylation of the myosin-binding subunit of myosin light chain phosphatase [myosin phosphatase target subunit 1, (MYPT1)] and myosin light chain 2 (MLC2) was assessed. The cell migration rate of TR-MUL5 cells exposed to acrolein and/or ripasudil, a non-selective ROCK inhibitor, was measured using the Oris cell migration assay.Results: ROCK isoforms, ROCK1 and ROCK2, were positively stained in the cytosol of glial cells in fibrovascular tissues. In TR-MUL5 cells, the mRNA expression level of Rock1, but not Rock2, was increased following acrolein stimulation. In line with the PCR data, western blotting showed increase in ROCK1 and cleaved ROCK1 protein in TR-MUL5 cells stimulated with acrolein. N-acetylcysteine (NAC) suppressed acrolein-associated Rock1 upregulation in TR-MUL5 cells. Acrolein augmented the phosphorylation of MYPT1 and MLC2 and increased the cell migration rate of TR-MUL5 cells, both of which were abrogated by ripasudil.Conclusions: Our study demonstrated that ROCK1 mediates the migration of retinal glial cells promoted by the unsaturated aldehyde acrolein.

Understanding Ligand‐Directed Heterogeneous Catalysis: When the Dynamically Changing Nature of the Ligand Layer Controls the Hydrogenation Selectivity

AbstractWe present a mechanistic study on the formation and dynamic changes of a ligand‐based heterogeneous Pd catalyst for chemoselective hydrogenation of α,β‐unsaturated aldehyde acrolein. Deposition of allyl cyanide as a precursor of a ligand layer renders Pd highly active and close to 100 % selective toward propenol formation by promoting acrolein adsorption in a desired configuration via the C=O end. Employing a combination of real‐space microscopic and in‐operando spectroscopic surface‐sensitive techniques, we show that an ordered active ligand layer is formed under operational conditions, consisting of stable N‐butylimine species. In a competing process, unstable amine species evolve on the surface, which desorb in the course of the reaction. Obtained atomistic‐level insights into the formation and dynamic evolution of the active ligand layer under operational conditions provide important input required for controlling chemoselectivity by purposeful surface functionalization.

Understanding Ligand-Directed Heterogeneous Catalysis: When the Dynamically Changing Nature of the Ligand Layer Controls the Hydrogenation Selectivity.

We present a mechanistic study on the formation and dynamic changes of a ligand‐based heterogeneous Pd catalyst for chemoselective hydrogenation of α,β‐unsaturated aldehyde acrolein. Deposition of allyl cyanide as a precursor of a ligand layer renders Pd highly active and close to 100 % selective toward propenol formation by promoting acrolein adsorption in a desired configuration via the C=O end. Employing a combination of real‐space microscopic and in‐operando spectroscopic surface‐sensitive techniques, we show that an ordered active ligand layer is formed under operational conditions, consisting of stable N‐butylimine species. In a competing process, unstable amine species evolve on the surface, which desorb in the course of the reaction. Obtained atomistic‐level insights into the formation and dynamic evolution of the active ligand layer under operational conditions provide important input required for controlling chemoselectivity by purposeful surface functionalization.

Acrolein scavenger dimercaprol offers neuroprotection in an animal model of Parkinson\u2019s disease: implication of acrolein and TRPA1

BackgroundThe mechanisms underlying lesions of dopaminergic (DA) neurons, an essential pathology of Parkinson’s disease (PD), are largely unknown, although oxidative stress is recognized as a key factor. We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in PD pathology, and that acrolein scavenger hydralazine can reduce the elevated acrolein, mitigate DA neuron death, and alleviate motor deficits in a 6-hydroxydopamine (6-OHDA) rat model. As such, we hypothesize that a structurally distinct acrolein scavenger, dimercaprol (DP), can also offer neuroprotection and behavioral benefits.MethodsDP was used to lower the elevated levels of acrolein in the basal ganglia of 6-OHDA rats. The acrolein levels and related pathologies were measured by immunohistochemistry. Locomotor and behavioral effects of 6-OHDA injections and DP treatment were examined using the open field test and rotarod test. Pain was assessed using mechanical allodynia, cold hypersensitivity, and plantar tests. Finally, the effects of DP were assessed in vitro on SK-N-SH dopaminergic cells exposed to acrolein.ResultsDP reduced acrolein and reversed the upregulation of pain-sensing transient receptor potential ankyrin 1 (TRPA1) channels in the substantia nigra, striatum, and cortex. DP also mitigated both motor and sensory deficits typical of PD. In addition, DP lowered acrolein and protected DA-like cells in vitro. Acrolein’s ability to upregulate TRPA1 was also verified in vitro using cell lines.ConclusionsThese results further elucidated the acrolein-mediated pathogenesis and reinforced the critical role of acrolein in PD while providing strong arguments for anti-acrolein treatments as a novel and feasible strategy to combat neurodegeneration in PD. Considering the extensive involvement of acrolein in various nervous system illnesses and beyond, anti-acrolein strategies may have wide applications and broad impacts on human health.

Pathological Role of Unsaturated Aldehyde Acrolein in Diabetic Retinopathy.

With increasing prevalence of diabetes and a progressively aging society, diabetic retinopathy is emerging as one of the global leading causes of blindness. Recent studies have shown that vascular endothelial growth factor (VEGF) plays a central role in the pathogenesis of diabetic retinopathy and anti-VEGF agents have become the first-line therapy for the vision-threatening disease. However, recent studies have also demonstrated that diabetic retinopathy is a multifactorial disease and that VEGF-independent mechanism(s) also underlie much of the pathological changes in diabetic retinopathy. Acrolein is a highly reactive unsaturated aldehyde and is implicated in protein dysfunction. As acrolein is common in air pollutants, previous studies have focused on it as an exogenous causative factor, for instance, in the development of respiratory diseases. However, it has been discovered that acrolein is also endogenously produced and induces cell toxicity and oxidative stress in the body. In addition, accumulating evidence suggests that acrolein and/or acrolein-conjugated proteins are associated with the molecular mechanisms in diabetic retinopathy. This review summarizes the pathological roles and mechanisms of endogenous acrolein production in the pathogenesis of diabetic retinopathy.

Acrolein-Trapping Mechanism of Theophylline in Green Tea, Coffee, and Cocoa: Speedy and Successful.

Increasing evidence has identified the unsaturated aldehyde acrolein (ACR) as the potential factor that causes deoxyribonucleic acid cross-linking and the development of chronic diseases. The objective of this study was to investigate the mechanism by which theophylline (TP) scavenges ACR for the first time. TP efficiently scavenged ACR through forming adducts, which was demonstrated in a system in which TP was incubated with ACR at different ratios for different times for liquid chromatography with tandem mass spectrometry. Then, the mono- and di-ACR-TP adducts were purified, and their structures were elucidated by high-resolution mass spectrometry and nuclear magnetic resonance analysis. We found that the ACR residue on mono-ACR-TP further trapped one more ACR and formed di-ACR-TP adducts. Furthermore, mono- and di-ACR-TP had similar time-dependent ACR-scavenging activity to TP. Finally, we demonstrated that green tea, coffee, and cocoa inhibited ACR by trapping ACR to form mono- and di-ACR-TP adducts during the incubation of green tea, coffee, and cocoa with ACR.

Short‐term e‐cigarette vapor exposure causes vascular oxidative stress and dysfunction ‐ evidence for a close connection to brain damage and a key role of the phagocytic NADPH oxidase (NOX‐2)

BackgroundElectronic (e)‐cigarettes have been marketed as a “healthy” alternative to traditional combustible cigarettes and as an effective method of smoking cessation. There are, however, a paucity of data to support these claims. In fact, e‐cigarettes are implicated in endothelial dysfunction and oxidative stress in the vasculature and the lungs. The mechanisms underlying these side effects remain unclear. Here, we investigated the effects of e‐cigarette vapor on vascular function in smokers and experimental animals to determine the underlying mechanisms.Methods and ResultsAcute e‐cigarette smoking produced a marked impairment of endothelial function in chronic smokers determined by flow‐mediated dilation. In mice, e‐cigarette vapor without nicotine had more detrimental effects on endothelial function, markers of oxidative stress, inflammation and lipid peroxidation than vapor containing nicotine. These effects of e‐cigarette vapor were largely absent in mice lacking phagocytic NADPH oxidase (NOX‐2) or upon treatment with the endothelin receptor blocker macitentan or the FOXO3 activator bepridil. We also established that the e‐cigarette product acrolein, a reactive aldehyde, recapitulated many of the NOX‐2‐dependent effects of e‐cigarette vapor using in vitro blood vessel incubation.ConclusionsE‐cigarette vapor exposure increases vascular, cerebral and pulmonary oxidative stress via a NOX‐2‐dependent mechanism. Our study identifies the toxic aldehyde acrolein as a key mediator of the observed adverse vascular consequences. Thus, e‐cigarettes have the potential to induce marked adverse cardiovascular, pulmonary and cerebrovascular consequences. Since e‐cigarette use is increasing, particularly amongst youth, our data suggest that aggressive steps are warranted to limit the health risks of e‐cigarettes.Support or Funding InformationThe present work was supported by a vascular biology research grant from the Foundation Heart of Mainz and by a vascular biology research grant from the Boehringer Ingelheim Foundation for the collaborative research group „Novel and neglected cardiovascular risk factors: molecular mechanisms and therapeutic implications" to study the effects of environmental risk factors on vascular function and oxidative stress. R. H. holds a PhD stipend of the Max Planck Graduate Center with the Johannes Gutenberg University Mainz. T.M. is PI of the DZHK (German Center for Cardiovascular Research), Partner Site Rhine‐Main, Mainz, Germany.Central scheme: Proposed mechanisms of E‐cigarette mediated cerebro/cardiovascular complications from studies in mice.The described adverse effects are also operative in the disease development and progression of classical cerebro/cardiovascular disease such as stroke, atherosclerosis, hypertension and coronary artery disease. Light blue color items represent pharmacological/genetic interventions.Figure 1

Short-term e-cigarette vapour exposure causes vascular oxidative stress and dysfunction: evidence for a close connection to brain damage and a key role of the phagocytic NADPH oxidase (NOX-2).

AimsElectronic (e)-cigarettes have been marketed as a ‘healthy’ alternative to traditional combustible cigarettes and as an effective method of smoking cessation. There are, however, a paucity of data to support these claims. In fact, e-cigarettes are implicated in endothelial dysfunction and oxidative stress in the vasculature and the lungs. The mechanisms underlying these side effects remain unclear. Here, we investigated the effects of e-cigarette vapour on vascular function in smokers and experimental animals to determine the underlying mechanisms.Methods and resultsAcute e-cigarette smoking produced a marked impairment of endothelial function in chronic smokers determined by flow-mediated dilation. In mice, e-cigarette vapour without nicotine had more detrimental effects on endothelial function, markers of oxidative stress, inflammation, and lipid peroxidation than vapour containing nicotine. These effects of e-cigarette vapour were largely absent in mice lacking phagocytic NADPH oxidase (NOX-2) or upon treatment with the endothelin receptor blocker macitentan or the FOXO3 activator bepridil. We also established that the e-cigarette product acrolein, a reactive aldehyde, recapitulated many of the NOX-2-dependent effects of e-cigarette vapour using in vitro blood vessel incubation.ConclusionsE-cigarette vapour exposure increases vascular, cerebral, and pulmonary oxidative stress via a NOX-2-dependent mechanism. Our study identifies the toxic aldehyde acrolein as a key mediator of the observed adverse vascular consequences. Thus, e-cigarettes have the potential to induce marked adverse cardiovascular, pulmonary, and cerebrovascular consequences. Since e-cigarette use is increasing, particularly amongst youth, our data suggest that aggressive steps are warranted to limit their health risks.

Unsaturated Aldehyde Acrolein Promotes Retinal Glial Cell Migration.

To investigate the effect of the unsaturated aldehyde acrolein on retinal glial cell migration. Müller glial cell markers expression in TR-MUL5 were confirmed by RT-PCR and immunostaining. Cell viability and migration rate of TR-MUL5 cells were assessed after the stimulation with acrolein. DNA microarray analysis was performed to analyze changes in the expression levels of migration-related genes in Müller glial cells stimulated with acrolein. Real-time PCR and ELISA were performed to validate DNA microarray analysis results. Inhibitors of C-X-C motif chemokine ligand 1 (CXCL1), one of the genes highly upregulated after the exposure to acrolein, and blockers of its receptor, CXCR2, were used to investigate the role of the CXCL1-CXCR2 axis on glial cell migration. CXCL1 concentration was measured in vitreous fluid samples obtained from proliferative diabetic retinopathy (PDR) and nondiabetic control eyes. CXCL1 and CXCR2 expression in glial cells of fibrovascular tissues obtained from PDR patients was examined by immunostaining. At a high concentration, acrolein (100 μM) significantly decreased cell viability. However, in moderate, sublethal concentrations (25-50 μM), acrolein induced cell migration and substantially increased the production of CXCL1 in TR-MUL5 cells. CXCL1 concentration was significantly elevated in vitreous fluids of PDR patients, and CXCL1 and CXCR2 were present in glial cells in fibrovascular tissues of PDR patients. CXCL1 stimulation increased glial cell migration in a dose-dependent manner, which was abrogated by the neutralization of the CXCL1-CXCR2 axis. Our data demonstrate that acrolein promotes retinal Müller glial cell migration by enhancing CXCL1 production.

Soluble Vascular Adhesion Protein-1 Mediates Spermine Oxidation as Semicarbazide-Sensitive Amine Oxidase: Possible Role in Proliferative Diabetic Retinopathy

ABSTRACTPurpose/Aim of the study: To explore the possible role of vascular adhesion protein-1 (VAP-1) via its enzymatic function as a semicarbazide-sensitive amine oxidase (SSAO) in the pathogenesis of proliferative diabetic retinopathy (PDR).Materials and Methods: The levels of soluble VAP-1/SSAO and the unsaturated aldehyde acrolein (ACR)-conjugated protein, Nε-(3-formyl-3, 4-dehydropiperidino) lysine adduct (FDP-Lys), were measured in vitreous fluid samples of PDR and non-diabetic patients using ELISA. Recombinant human VAP-1/SSAO (rhVAP-1/SSAO) was incubated with spermine, with or without semicarbazide or RTU-1096 (a specific inhibitor for VAP-1/SSAO). Immunofluorescence assays were performed to assess the localization of VAP-1/SSAO and FDP-Lys in fibrovascular tissues from patients with PDR. The impact of ACR on cultured retinal capillary endothelial cells was assessed using a cell viability assay and total glutathione (GSH) measurements.Results: The levels of sVAP-1/SSAO and FDP-Lys were elevated in the vitreous fluid of patients with PDR. Incubation of rhVAP-1 with spermine resulted in the generation of hydrogen peroxide and FDP-Lys and the production was inhibited by semicarbazide and RTU-1096. In fibrovascular tissues, FDP-Lys and VAP-1/SSAO were present in endothelial cells. ACR stimulation reduced GSH levels in the cultured endothelial cells in a dose-dependent manner and caused cellular toxicity.Conclusions: Our results indicate the pathological role of sVAP-1/SSAO to generate hydrogen peroxide and toxic aldehyde ACR, both of which are associated with oxidative stress, as a consequence of spermine oxidation in eyes with PDR.

Acrolein increases macrophage atherogenicity in association with gut microbiota remodeling in atherosclerotic mice: protective role for the polyphenol-rich pomegranate juice.

The unsaturated aldehyde acrolein is pro-atherogenic, and the polyphenol-rich pomegranate juice (PJ), known for its anti-oxidative/anti-atherogenic properties, inhibits macrophage foam cell formation, the hallmark feature of early atherosclerosis. This study aimed to investigate two unexplored areas of acrolein atherogenicity: macrophage lipid metabolism and the gut microbiota composition. The protective effects of PJ against acrolein atherogenicity were also evaluated. Atherosclerotic apolipoprotein E-deficient (apoE-/-) mice that were fed acrolein (3mg/kg/day) for 1month showed significant increases in serum and aortic cholesterol, triglycerides, and lipid peroxides. In peritoneal macrophages isolated from the mice and in J774A.1 cultured macrophages, acrolein exposure increased intracellular oxidative stress and stimulated cholesterol and triglyceride accumulation via enhanced rates of their biosynthesis and over-expression of key regulators of cellular lipid biosynthesis: sterol regulatory element-binding proteins (SREBPs), 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), and diacylglycerol acyltransferase1 (DGAT1). Acrolein-fed mice demonstrated a major shift in the gut microbiota composition, including a significant phylum-level change in increased Firmicutes and decreased Bacteroidetes. At the family level, acrolein significantly increased the prevalence of Ruminococcaceae and Lachnospiraceae of which the Coprococcus genus was significantly and positively correlated with serum, aortic and macrophage lipid levels and peroxidation. The pro-atherogenic effects of acrolein on serum, aortas, macrophages, and the gut microbiota were substantially abolished by PJ. In conclusion, these findings provide novel mechanisms by which acrolein increases macrophage lipid accumulation and alters the gut microbiota composition in association with enhanced atherogenesis. Moreover, PJ was found as an effective strategy against acrolein atherogenicity.

Acrolein scavengers, cysteamine and N-benzylhydroxylamine, reduces the mouse liver damage after acetaminophen overdose.

Our previous study suggested that the highly toxic α,β-unsaturated aldehyde acrolein, a byproduct of oxidative stress, plays a major role in acetaminophen-induced liver injury. In this study, to determine the involvement of acrolein in the liver injury and to identify novel therapeutic options for the liver damage, we examined two putative acrolein scavengers, a thiol compound cysteamine and a hydroxylamine N-benzylhydroxylamine, in cell culture and in mice. Our results showed that cysteamine and N-benzylhydroxylamine effectively prevented the cell toxicity of acrolein in vitro and acetaminophen-induced liver injury in vivo, which suggested that acrolein is involved in the liver damage, and these two drugs can be potential therapeutic options for this condition.

Inhalation of the reactive aldehyde acrolein promotes antigen sensitization to ovalbumin and enhances neutrophilic inflammation

Acrolein (ACR), an α,β-unsaturated aldehyde and a major component of tobacco smoke, is a highly reactive electrophilic respiratory irritant implicated in asthma pathogenesis and severity. However, few studies have directly investigated the influence of ACR exposure on allergen sensitization and pulmonary inflammation. The present study was designed to examine the impact of ACR inhalation on allergic sensitization to the inhaled antigen ovalbumin (OVA), as well as pulmonary inflammation during subsequent OVA challenge. Adult male C57BL/6 mice were exposed to inhaled OVA (1%, 30 min/day, 4 days/week) and/or ACR (5 ppm, 4 h/day, 4 days/week) over 2 weeks and subsequently challenged with aerosolized OVA (1%, 30 min/day) over three consecutive days. Serum anti-OVA IgG1 levels were increased significantly in animals exposed to both OVA and ACR, compared to animals exposed to either OVA or ACR alone. In addition, differential cell counts and histological analysis revealed an increase in BAL neutrophils in animals exposed to both OVA and ACR. However, exposure to both OVA and ACR did not influence mRNA expression of the cytokines il5, il10, il13 or tnfa, but significantly increased mRNA expression of ccl20. Moreover, ACR exposure enhanced lung mRNA levels of il17f and tgfb1, suggesting development of enhanced inhalation tolerance to OVA. Overall, the findings indicate that ACR inhalation can promote airway-mediated sensitization to otherwise innocuous inhaled antigens, such as OVA, but also enhances immune tolerance, thereby favoring neutrophilic airway inflammation.

Glutathione S-transferase P protects against cyclophosphamide-induced cardiotoxicity in mice

High-dose chemotherapy regimens using cyclophosphamide (CY) are frequently associated with cardiotoxicity that could lead to myocyte damage and congestive heart failure. However, the mechanisms regulating the cardiotoxic effects of CY remain unclear. Because CY is converted to an unsaturated aldehyde acrolein, a toxic, reactive CY metabolite that induces extensive protein modification and myocardial injury, we examined the role of glutathione S-transferase P (GSTP), an acrolein-metabolizing enzyme, in CY cardiotoxicity in wild-type (WT) and GSTP-null mice. Treatment with CY (100–300mg/kg) increased plasma levels of creatine kinase-MB isoform (CK·MB) and heart-to-body weight ratio to a significantly greater extent in GSTP-null than WT mice. In addition to modest yet significant echocardiographic changes following acute CY-treatment, GSTP insufficiency was associated with greater phosphorylation of c-Jun and p38 as well as greater accumulation of albumin and protein–acrolein adducts in the heart. Mass spectrometric analysis revealed likely prominent modification of albumin, kallikrein-1-related peptidase, myoglobin and transgelin-2 by acrolein in the hearts of CY-treated mice. Treatment with acrolein (low dose, 1–5mg/kg) also led to increased heart-to-body weight ratio and myocardial contractility changes. Acrolein induced similar hypotension in GSTP-null and WT mice. GSTP-null mice also were more susceptible than WT mice to mortality associated with high-dose acrolein (10–20mg/kg). Collectively, these results suggest that CY cardiotoxicity is regulated, in part, by GSTP, which prevents CY toxicity by detoxifying acrolein. Thus, humans with low cardiac GSTP levels or polymorphic forms of GSTP with low acrolein-metabolizing capacity may be more sensitive to CY toxicity.