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PubMed2001

1,N(2)-propanodeoxyguanosine adduct formation in aortic DNA following inhalation of acrolein.

Recent reports indicate that many of the cytotoxic and health-threatening components of environmental tobacco smoke (ETS) reside in the vapor phase of the smoke. We have reported previously that inhalation of 1,3-butadiene, a prominent vapor phase component of ETS, accelerates arteriosclerotic plaque development in cockerels. In this study we asked whether inhaled acrolein, a reactive aldehyde that is also a prominent vapor-phase component of ETS, damages artery-wall DNA and accelerates plaque development. Cockerels inhaled 0, 1, or 10 ppm acrolein mixed with HEPA-filtered air for 6 hr. Half were killed immediately (day 1 group) for detection of the stable, premutagenic 1,N(2)-propanodeoxyguanosine acrolein adduct (AdG3) in aortic DNA via a (32)P-postlabeling/HPLC method, and half were killed after 10 days (day 10 group) for indirect assessment of adduct repair. In the day 1 group, acrolein-DNA adducts were 5 times higher in the 1 and 10 ppm groups than in HEPA-filtered air controls. However, in the day 10 group, adduct levels in the 1 and 10 ppm acrolein groups were reduced to the control adduct level. For the plaque studies, cockerels inhaled 1 ppm acrolein (6 hr/day, 8 weeks), mixed with the same HEPA-filtered air inhaled by controls. Plaque development was measured blind by computerized morphometry. Unlike butadiene inhalation, acrolein inhalation did not accelerate plaque development. Thus, even though repeated exposure to acrolein alone has no effect on plaque size under the exposure conditions described here, a single, brief inhalation exposure to acrolein elicits repairable DNA damage to the artery wall. These results suggest that frequent exposure to ETS may lead to persistent artery-wall DNA damage and thus provide sites on which other ETS plaque accelerants can act.

Acrolein↗
PubMed2003

Increased urinary levels of pentosidine, pyrraline and acrolein adduct in type 2 diabetes.

This study investigates whether urinary levels of pentosidine, pyrraline and acrolein adduct are increased in type 2 diabetes (DM), and whether these levels are correlated with glycemic control and clinical traits. Urinary levels of pentosidine, pyrraline and acrolein adduct in DM patients (n = 100) recruited from the outpatient clinic of our university hospital were compared with those of age- and sex-matched non-diabetic subjects (n = 50). The correlation of these urinary levels with the glycemic control and the clinical traits were examined. Furthermore, the influence of smoking habit on the levels of acrolein adduct was examined. Urinary levels of pentosidine, pyrraline and acrolein adduct were all significantly (p<0.001) higher in the DM group than in the non-DM group (pentosidine (log(pmol/mgCr)), 1.579 +/- 0.147 vs 1.427 +/- 0.142; pyrraline (log(nmol/mgCr)), 0.888 +/- 0.402 vs 0.581 +/- 0.336; acrolein adduct (log(nmol/mgCr)), 2.316 +/- 0.221 vs 2.051 +/- 0.201). Glycemic control parameters, such as fasting plasma glucose (FPG) and HbA1c, were significantly correlated with these urinary levels. Age was correlated with the urinary levels of pentosidine but not with those of pyrraline and acrolein adduct. The urinary albumin excretion rate did not correlate with any of these urinary levels. The levels of acrolein adduct were higher in the subjects with smoking habit than in those without the habit in the DM group as well as in the non-DM group (DM, 2.391 +/- 0.230 and 2.212 +/- 0.190, p=0.0004; Non-DM, 2.120 +/- 0.171 and 1.993 +/- 0.206, p=0.0503). The urinary levels of pentosidine, pyrraline and acrolein adduct were increased in DM and were significantly correlated with glycemic control levels. In addition, smoking habit seems to increase the urinary levels of acrolein adduct.

Acrolein↗
PubMed2006

Acrolein-mediated mechanisms of neuronal death.

It is well known that traumatic injury in the central nervous system can be viewed as a primary injury and a secondary injury. Increases in oxidative stress lead to breakdown of membrane lipids (lipid peroxidation) during secondary injury. Acrolein, an alpha,beta-unsaturated aldehyde, together with other aldehydes, increases as a result of self-propagating lipid peroxidation. Historically, most research on the pathology of secondary injury has focused on reactive oxygen species (ROS) rather than lipid peroxidation products. Little is known about the toxicology and cell death mediated by these aldehydes. In this study, we investigated and characterized certain features of cell death induced by acrolein on PC12 cells as well as cells from dorsal root ganglion (DRG) and sympathetic ganglion in vitro. In the companion paper, we evaluated a possible means to interfere with this toxicity by application of a compound that can bind to and inactivate acrolein. Here we use both light and atomic force microscopy to study cell morphology after exposure to acrolein. Administration of 100 microM acrolein caused a dramatic change in cell morphology as early as 4 hr. Cytoskeletal structures significantly deteriorated after exposure to 100 microM acrolein as demonstrated by fluorescence microscopy, whereas calpain activity increased significantly at this concentration. Cell viability assays indicated significant cell death with 100 microM acrolein by 4 hr. Caspase 3 activity and DNA fragmentation assays were performed and supported the notion that 100 microM acrolein induced PC12 cell death by the mechanism of necrosis, not apoptosis.

Acrolein↗
PubMed1985

Teratogenicity and embryolethality of acrolein and structurally related compounds in rats.

Acrolein, a metabolite of the anticancer agent cyclophosphamide, is teratogenic to rats after intraamniotic administration. It is not known whether acrolein or a metabolite of acrolein is responsible for the teratogenicity of this compound. We assessed the teratogenicity and embryolethality of acrolein and five structurally related compounds: acrylic acid, allyl alcohol, glycidol, glyceraldehyde, and propionaldehyde by intraamniotic injections in Sprague-Dawley rats on day 13 of gestation. All compounds tested were significantly embryolethal with at least one concentration of the drug. Acrolein was the most embryolethal of the drugs, causing a significant increase in resorptions with as little as 0.1 micrograms/fetus; the other drugs were embryolethal at doses 100-10,000 times that of acrolein. Acrolein was also the most teratogenic of the drugs tested; a dose as low as 5 micrograms/fetus caused a significant increase in the incidence of fetal malformations. Of the other compounds tested, only glycidol at a dose of 1,000 micrograms/fetus induced a significant number of malformed fetuses compared to control. These results suggest that it is acrolein itself that is responsible for its teratogenicity.

1-Propanol↗
PubMed1996

Studies on the basis for the toxicity of acrolein mercapturates.

Acrolein, 3-oxopropyl glutathione (oxoPrGSH), and S-3-hydroxypropyl N-acetylcysteine (hydroxyPrMCA) are confirmed metabolic products of cyclophosphamide. Other potential metabolites include the mercapturic acid S-3-oxopropyl N-acetylcysteine (oxoPrMCA), its sulfoxide, and their corresponding diacid forms. The reactivity of acrolein would appear to preclude its movement from the main site of formation (liver) to the sites of toxicity (lung and bladder). However, the rerelease of acrolein from various thiol conjugates via a beta-elimination reaction is possible. It is also possible that the parent conjugate is directly toxic. The current study examined the toxicity of various acrolein-thiol conjugates and related analogs to human lung adenoma A549 cells. The expected enhancement of acrolein, oxoPrMCA, and oxoPrMCA S-oxide toxicity (assessed as cell proliferation by the alamarBlue assay) following a 2-hr exposure of cells treated with diethyl maleate (DEM) to deplete GSH was observed. OxoPrGSH was toxic when present for 24 hr, and this toxicity was also enhanced by pretreatment with DEM. When treated with these conjugates alone, the depletion of intracellular GSH only occurred at doses above those needed to significantly inhibit cell proliferation. There were no changes in protein thiols as determined using the membrane impermeant fluorescent thiol probe para-sulfobenzoyloxybromobimane. The diacid conjugate was not toxic to A549 cells indicating further oxidation products of the mercapturic acids are not a factor in toxicity. ButanoneMCA, an analog of oxoPrMCA that cannot exist in the geminal diol form, inhibited A549 cell growth only slightly less effectively than oxoPrMCA, suggesting the geminal diol is not toxicologically significant. OxoBuMCA, which cannot undergo beta-elimination of acrolein, showed no toxicity to these cells, suggesting that the release of acrolein could be required. Exogenous GSH provided protection from all toxic compounds suggesting that the toxic species is electrophilic. Overall, the data suggest that toxicity, in terms of an inhibition of cell proliferation, is not due to the parent molecule but rather is the result of rereleased acrolein that then affects factors necessary for cell proliferation.

Acetylcysteine↗
PubMed1992

The acrolein cytotoxicity and cytoprotective action of alpha-tocopherol in primary cultured rat hepatocytes.

The influence of acrolein on hepatocytes and the effect of alpha-tocopherol on acrolein cytotoxicity were investigated using primary cultured rat hepatocytes. Hepatocellular injury was dependent on both acrolein concentration in medium and on duration of exposure. Treatment of hepatocytes with 100 microM acrolein resulted in a marked loss of cellular glutathione (GSH) within 15 min, gradual accumulation of cellular lipid peroxide (LPO) and subsequent lactate dehydrogenase (LDH) leakage in the medium from 3 hr after exposure to acrolein. Cellular GSH peroxidase (GSH-Px) activity at 2 hr was significantly decreased. Electron microscopic examination on hepatocytes at 8 hr revealed a marked swelling of mitochondria and ruptures of the plasma membrane. Simultaneous treatment with 100 microM acrolein and 20 microM alpha-tocopherol did not prevent the loss of cellular GSH, though it prevented the LPO accumulation and the LDH leakage. The decrease of cellular GSH-Px activity with acrolein treatment was not mitigated by co-treatment with alpha-tocopherol. Ultrastructural alterations of hepatocytes induced by acrolein were minimized by co-treatment with alpha-tocopherol. In conclusion, acute loss of GSH and GSH-Px may increase cellular LPO and lead to hepatocellular injury, though suppression of cellular LPO accumulation by alpha-tocopherol can prevent the hepatocellular injury, even under condition of lack of GSH and GSH-Px.

Acrolein↗
PubMed1992

Nephrotoxicity of the 1:1 acrolein-glutathione adduct in the rat.

Previous metabolic studies in rats have suggested in vivo formation of the acrolein-glutathione (acrolein-GSH) adduct following administration of the highly reactive alpha, beta-unsaturated aldehyde acrolein. Early studies by several investigators demonstrated that similar compounds such as alpha, beta-unsaturated aldehyde-cysteine adducts have toxic (carcinostatic) activity against Ehrlich ascites tumor cells implanted in mice. The current studies investigated the in vivo toxicity associated with the acrolein-GSH adduct in the male Sprague-Dawley rat. The 1:1 acrolein-GSH adduct was synthesized and characterized by physical-chemical methods. Rats given the acrolein-GSH adduct intravenously at 0.5 or 1 mmol/kg developed nephrotoxicity characterized by glucosuria, proteinuria, elevation in serum urea nitrogen, and gross and histologic changes of the kidney. The toxicity was not affected by pretreatment of rats with pyrazole, an alcohol dehydrogenase inhibitor; disulfiram, an inhibitor of aldehyde dehydrogenases; or probenecid, a renal organic anion transport inhibitor. Administration of a similar but nonaldehydic glutathione conjugate, S-n-propylglutathione, did not result in nephrotoxicity in the rat. The nephrotoxicity induced by the acrolein-GSH adduct was inhibited by acivicin, a gamma-glutamyl-transpeptidase inhibitor. These results indicate that the acrolein-GSH adduct requires processing through the first step of the renal mercapturic acid synthesis pathway to be activated to a toxic species.

Acrolein↗
PubMed1989

Comparative toxicity of allylamine and acrolein in cultured myocytes and fibroblasts from neonatal rat heart.

Allylamine is toxic to the cardiovascular system causing aortic, valvular and myocardial lesions. Acute toxicity is believed to involve metabolism of allylamine to highly reactive acrolein. Comparative toxicity of allylamine and acrolein was evaluated in cardiac fibroblasts and myocytes, which were obtained from neonatal rat hearts by a differential plating technique. Allylamine and acrolein were added directly to serum supplemented culture media (M199). Toxicity was assessed by measuring lactate dehydrogenase (LDH) release as an indicator of cell lysis. Spontaneous beating activity of myocytes, and adenosine 5' triphosphate (ATP) levels of myocytes and fibroblasts were also assessed. Cell lysis occurred 4 h after treatment of myocytes with 0.5 mM allylamine, whereas 20 mM allylamine was required to lyse fibroblasts. Acrolein, at a concentration of 0.05 mM, was equally toxic to fibroblasts and myocytes. Semicarbazide, a benzylamine oxidase inhibitor, protected myocytes from allylamine toxicity, but clorgyline, a monoamine oxidase inhibitor, was ineffective. Semicarbazide was ineffective against acrolein toxicity. Beating activity of myocytes was arrested by 0.05 mM acrolein and 0.5 mM allylamine, although 0.05-0.1 mM allylamine reduced beating activity. Myocyte ATP levels were reduced 4 h after exposure to 0.01 mM acrolein. Allylamine at 0.05 mM reduced ATP in myocytes, but 10 mM allylamine was required to reduce ATP in fibroblasts. ATP levels remained normal in myocytes exposed to 1 mM allylamine in the presence of 0.1 mM semicarbazide. The findings support the hypothesis that the toxicity of allylamine in cultured myocytes is dependent on its metabolism to acrolein, and that cytotoxicity may result from interference with energy production.

Acrolein↗
PubMed1993

Acrolein-induced oxygen radical formation.

The mechanism of acrolein-induced lipid peroxidation is unknown. This study found that acrolein and its glutathione adduct, glutathionylpropionaldehyde, induce oxygen radical formation. These oxygen radicals may be responsible for the induction of lipid peroxidation by acrolein. The enzymes xanthine oxidase and aldehyde dehydrogenase were found to interact with glutathionylpropionaldehyde to produce O2.- and HO(.). Acrolein was oxidized by xanthine oxidase to produce acroleinyl radical and O2(.-). Aldehyde dehydrogenase metabolized acrolein to form O2.- but not acroleinyl radical. The fact that glutathionylpropionaldehyde is a more potent stimulator of oxygen radical formation than acrolein indicates that glutathionylpropionaldehyde is a toxic metabolite of acrolein and may be responsible for some of the in vivo toxicity of acrolein.

Acrolein↗
PubMed2005

The aldehyde acrolein induces apoptosis via activation of the mitochondrial pathway.

Acrolein is a highly reactive alpha,beta-unsaturated aldehyde, which is a product of lipid peroxidation. It is an environmental pollutant that has been implicated in multiple respiratory diseases. Acrolein is produced by the enzymatic oxidative deamination of spermine by amine oxidase. Oxidation products of polyamines have been involved in the inhibition of cell proliferation, apoptosis, and the inhibition of DNA and protein synthesis. The present study investigates the mechanism of cell death induced by acrolein. Acrolein induced apoptosis through a decrease in mitochondrial membrane potential, the liberation of cytochrome c, the activation of initiator caspase-9, and the activation of the effector caspase-7. However, acrolein inhibited enzymatic activity of the effector caspase-3, although a cleavage of pro-caspase-3 occurred. The activation of caspases-9 and -7 was confirmed by the cleavage of their pro-enzyme form by acrolein. Apoptosis was inhibited by an inhibitor of caspase-9, but not by an inhibitor of caspase-3. The induction of apoptosis by acrolein was confirmed morphologically by the condensation of nuclear chromatin and by the cleavage of the inhibitor of caspase activated DNase (ICAD), which leads to the liberation of CAD that causes DNA fragmentation. These results demonstrate that acrolein causes apoptosis through the mitochondrial pathway.

Acrolein↗
PubMed2006

Acrolein is a mitochondrial toxin: effects on respiratory function and enzyme activities in isolated rat liver mitochondria.

Acrolein is an air pollutant from cigarette smoking and other pollutions and also a by-product of lipid peroxidation. Studies have demonstrated that acrolein causes cytotoxicity and genotoxicity, including liver damage and death of hepatocytes. However, the toxic effects and the underlying mechanisms of acrolein on mitochondria, especially, on liver mitochondria, have not been well studied. In the present study, we investigated the toxic effects and mechanisms of acrolein on mitochondria isolated from rat liver by examining mitochondrial respiration, dehydrogenases, complex I, II, III, IV and V, permeability transition, and protein oxidation. Acrolein incubation (10-1000 microM, or 0.02-2 micromol/mg protein) with mitochondria caused dose-dependent inhibition of NADH- and succinate-linked mitochondrial respiration chain, change of mitochondrial permeability transition, increase in protein carbonyls, and selective enzyme inhibition of mitochondrial complex I, II, pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, but no effects on mitochondrial complex III, IV, V and malate dehydrogenase. These results suggest that acrolein is a mitochondrial toxin and that mitochondrial dysfunction caused by acrolein may play an important role in acrolein toxicity such as hepatotoxicity and also smoking-related diseases.

Acrolein↗
PubMed2005

Acrolein-induced cell death in PC12 cells: role of mitochondria-mediated oxidative stress.

Oxidative stress has been implicated in acrolein cytotoxicity in various cell types, including mammalian spinal cord tissue. In this study we report that acrolein also decreases PC12 cell viability in a reactive oxygen species (ROS)-dependent manner. Specifically, acrolein-induced cell death, mainly necrosis, is accompanied by the accumulation of cellular ROS. Elevating ROS scavengers can alleviate acrolein-induced cell death. Furthermore, we show that exposure to acrolein leads to mitochondrial dysfunction, denoted by the loss of mitochondrial transmembrane potential, reduction of cellular oxygen consumption, and decrease of ATP level. This raises the possibility that the cellular accumulation of ROS could result from the increased production of ROS in the mitochondria of PC12 cells as a result of exposure to acrolein. The acrolein-induced significant decrease of ATP production in mitochondria may also explain why necrosis, not apoptosis, is the dominant type of cell death. In conclusion, our data suggest that one possible mechanism of acrolein-induced cell death could be through mitochondria as its initial target. The subsequent increase of ROS then inflicts cell death and further worsens mitochondria function. Such mechanism may play an important role in CNS trauma and neurodegenerative diseases.

Acrolein↗
PubMed2004

Effect of acrolein and glutathione depleting agents on thioredoxin.

Acrolein is a widespread environmental pollutant that reacts rapidly with nucleophiles, especially cellular thiols. In addition to glutathione (GSH), thioredoxin (Trx) and thioredoxin reductase (TR) contain thiol groups and may react with electrophiles. In the present study, A549 cells treated with 5-25 microM acrolein for 30 min lost cellular Trx activity in a dose-dependent fashion. Over 90% of Trx activity was lost at concentrations of 25 microM or greater. In contrast, Trx protein content, as assessed by western blotting, was not altered immediately after the 30 min acrolein treatment. Both Trx activity and protein levels increased 4h after the acrolein treatment. However, Trx activity remained below control levels at 24h. A similar dose-response relationship was seen with TR in A549 cells exposed to acrolein. There was, however, a rapid recovery of TR activity such that it attained normal levels by 4h after doses < or = 75 microM acrolein. Diethyl maleate (DEM), a common but not highly specific, agent used to deplete GSH, also inactivated Trx. A 2 h exposure of A549 cells to 1 mM DEM depleted cellular GSH by ~50% and diminished Trx activity by over 67%. Lower DEM doses (0.125 mM and 0.25 mM) for 1h had no significant effect on GSH but significantly decreased Trx activity 12 and 23%, respectively. Similar to immediately after acrolein exposure, DEM did not affect Trx protein levels. A Trx-1-GFP fusion protein was transfected into A549 cells. While the fusion protein was expressed, the Trx component was inactive by the insulin reducing assay. In summary, Trx and TR are inactivated by acrolein. In addition, the GSH depleting agent DEM inactivates Trx somewhat more effectively than it depletes GSH. The Trx-1-GFP fusion protein, while readily expressed, appears to have little or no activity, perhaps because the small size of Trx-1 (12 kDa) is affected by the larger GFP.

Acrolein↗
PubMed1999

Acrolein toxicity: comparative in vitro study with lung slices and pneumocytes type II cell line from rats.

Toxicological effects of acrolein have been studied in precision-cut rat lung slices and in L2 cells, a rat pneumocyte II cell line. These two models were cultured for 24 h with or without acrolein (0-100 microM in L2 cells; 0-200 microM in lung slices). Treatment with this pneumotoxicant produced a concentration dependent decrease in intracellular ATP levels. Acrolein concentrations higher than 50 microM induced ATP decrease in slices, while this decrease occurred from 10 microM acrolein in L2 cells. Detoxification marker evaluations showed that mostly the glutathione pathway was altered after acrolein treatment in both models. Intracellular glutathione (GSH) levels were drastically increased with an acrolein concentration of 10 microM. This increase was concomitant with glutathione-S-transferase (GST) and glutathione reductase (GRED) activities in L2 cells. After this strong increase, these enzymatic activities as well as GSH levels were quickly decreased. In precision-cut rat lung slices, the induction of the glutathione pathway was less clear-cut. A bell-shaped dose response curve was observed with a maximum for 5 microM acrolein for GST and GRED activities. These differences between acrolein toxic ranges could be explained by the presence of an active detoxification pathway in slices compared to its relative lack in L2 cells.

Acrolein↗
PubMed2006

Formation of acrolein adducts with 2'-deoxyadenosine in calf thymus DNA.

Acrolein is a ubiquitous environmental contaminant that has been found to be mutagenic in prokaryotic and eukaryotic cells. In the present study, we examined the reactions of acrolein with 2'-deoxyadenosine and calf thymus single- and double-stranded DNA in aqueous buffered solutions at physiological conditions. The deoxynucleoside adducts were isolated by reversed-phase liquid chromatography, and their structures were determined by their UV absorbance, mass spectrometry, and 1H and 13C NMR spectroscopy. The reaction of 2'-deoxyadenosine with acrolein resulted in the formation of four structurally different adducts (dAI, dAII, dAIII, dAIV). The structures of the novel acrolein adducts, dAIII and dAIV, were assigned as 3-[N(6)-(2'-deoxyadenosinyl)]propanal (dAIII) and 9-(2'-deoxyribosyl-6-(3-formyl-1,2,5,6-tetrahydropyridyl)purine (dAIV), respectively. The adduct dAIII was found to arise via a Dimroth rearrangement of adduct dAI, while the adduct dAIV was shown to be formed upon further reaction of acrolein with dAIII. In the reaction of acrolein with calf thymus DNA, all studied 2'-deoxyadenosine-acrolein adducts were observed. For the first time, it is shown that the N(6)-adduct and the adducts which are derived from two acrolein units are formed in calf thymus DNA.

Acrolein↗
PubMed1999

Acrolein causes inhibitor kappaB-independent decreases in nuclear factor kappaB activation in human lung adenocarcinoma (A549) cells.

Acrolein is a highly electrophilic alpha,beta-unsaturated aldehyde to which humans are exposed in various situations. In the present study, the effects of sublethal doses of acrolein on nuclear factor kappaB (NF-kappaB) activation in A549 human lung adenocarcinoma cells were investigated. Immediately following a 30-min exposure to 45 fmol of acrolein/cell, glutathione (GSH) and DNA synthesis and NF-kappaB binding were reduced by more than 80%. All parameters returned to normal or supranormal levels by 8 h post-treatment. Pretreatment with acrolein completely blocked 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced activation of NF-kappaB. Cells treated for 1 h with 1 mM diethyl maleate (DEM) showed a 34 and 53% decrease in GSH and DNA synthesis, respectively. DEM also reduced NF-kappaB activation by 64% at 2 h post-treatment, with recovery to within 22% of control at 8 h. Both acrolein and DEM decreased NF-kappaB function approximately 50% at 2 h after treatment with TPA, as shown by a secreted alkaline phosphatase reporter assay. GSH returned to control levels by 8 h after DEM treatment, but proliferation remained significantly depressed for 24 h. Interestingly, DEM caused a profound decrease in NF-kappaB binding, even at doses as low as 0.125 mM that had little effect on GSH. Neither acrolein nor DEM had any effect on the levels of phosphorylated or nonphosphorylated inhibitor kappaB-alpha (IkappaB-alpha). Furthermore, acrolein decreased NF-kappaB activation in cells depleted of IkappaB-alpha by TPA stimulation in the presence of cycloheximide, demonstrating that the decrease in NF-kappaB activation was not the result of increased binding by the inhibitory protein. This conclusion was further supported by the finding that acrolein modified NF-kappaB in the cytosol prior to chemical dissociation from IkappaB with detergent. Together, these data support the conclusion that the inhibition of NF-kappaB activation by acrolein and DEM is IkappaB-independent. The mechanism appears to be related to direct modification of thiol groups in the NF-kappaB subunits.

Acrolein↗
PubMed2005

Acrolein impairs ATP binding cassette transporter A1-dependent cholesterol export from cells through site-specific modification of apolipoprotein A-I.

Acrolein is a highly reactive alpha,beta-unsaturated aldehyde, but the factors that control its reactions with nucleophilic groups on proteins remain poorly understood. Lipid peroxidation and threonine oxidation by myeloperoxidase are potential sources of acrolein during inflammation. Because both pathways are implicated in atherogenesis and high density lipoprotein (HDL) is anti-atherogenic, we investigated the possibility that acrolein might target the major protein of HDL, apolipoprotein A-I (apoA-I), for modification. Tandem mass spectrometric analysis demonstrated that lysine 226, located near the center of helix 10 in apoA-I, was the major site modified by acrolein. Importantly, this region plays a critical role in the cellular interactions and ability of apoA-I to transport lipid. Indeed, we found that conversion of Lys-226 to N(epsilon)-(3-methylpyridinium)lysine by acrolein associated quantitatively with decreased cholesterol efflux from cells via the ATP-binding cassette transporter A1 pathway. In the crystal structure of truncated apoA-I, Glu-234 lies adjacent to Lys-226, suggesting that negatively charged residues might direct the modification of specific lysine residues in proteins. Finally, immunohistochemical studies with a monoclonal antibody revealed co-localization of apoA-I with acrolein adducts in human atherosclerotic lesions. Our observations suggest that acrolein might interfere with normal reverse cholesterol transport by HDL by modifying specific sites in apoA-I. Thus, acrolein might contribute to atherogenesis by impairing cholesterol removal from the artery wall.

ATP Binding Cassette Transporter 1↗
PubMed1988

Inhibition of DNA methylase activity by acrolein.

Acrolein, a reactive metabolite of cyclophosphamide, may be responsible for bladder cancer induced by cyclophosphamide. DNA methylase was isolated from the liver and urothelium of rats by high salt extraction of purified nuclei. Acrolein at 10 microM inhibited liver and bladder DNA methylase activity by 30-50%. Kinetic studies with the liver enzyme showed a competitive type of inhibition with a Ki of 6.7 microM. Both dithiothreitol and glutathione afforded protection to the enzyme when added to the assay. At near equimolar concentrations of glutathione to acrolein, the methylase retained 80-90% activity. An increase in DNA had no effect on the inhibition by acrolein, whereas increased amounts of protein protected against acrolein inhibition, suggesting that acrolein reacted with the DNA methylase protein. On the other hand, DNA that had been reacted with acrolein was unable to serve as a substrate for DNA methylase. As the DNA adducts increased the methylation of the DNA decreased. Thus, acrolein has the ability to react with DNA and the DNA methylase protein, either of which results in inhibition of DNA methylation.

Acrolein↗