Acrolein-an α,β-Unsaturated Aldehyde: A Review of Oral Cavity Exposure and Oral Pathology Effects

Acrolein-Triggered Ferroptosis and Protection by Intermittent Fasting via the AMPK/NRF2-CLOCK/BMAL1 Pathway

Environmental pollution significantly exacerbates various diseases, particularly those affecting the cardiovascular and respiratory systems. Our previous studies have shown that acrolein, an environmental pollutant, promotes atherosclerosis by downregulating the circadian clock genes (CLOCK/BMAL1) and disrupting circadian rhythm. We have also found that intermittent fasting (IF), closely linked to the circadian clock, may mitigate atherosclerosis induced by acrolein. Ferroptosis, a newly identified form of regulated cell death, is associated with the acceleration of atherosclerotic development, but its relationship with the circadian clock is not well understood. In this study, we explored the potential of IF to alleviate ferroptosis by modulating the circadian clock. Our in vivo experiments revealed that IF reversed ferroptosis and upregulated CLOCK/BMAL1 in APOE-/- mice. In human umbilical vein endothelial cells (HUVECs), we discovered that acrolein-induced ferroptosis leads to cell death, while short-term starvation (STS, IF cell model) reversed this effect. Acrolein also suppressed the expression of AMP-activated protein kinase (AMPK), nuclear factor erythroid 2-related factor 2 (NRF2), and CLOCK/BMAL1, which were restored by subsequent STS treatments. Additionally, the overexpression of CLOCK/BMAL1 mitigated ferroptosis, consistent with findings from CLOCK gene knockout experiments. Notably, CLOCK/BMAL1 and AMPK/NRF2 were found to be mutually regulated. Concurrently, the AMPK and NRF2 signaling pathways may be interdependent and act in concert. In conclusion, our findings suggest that IF modulates the CLOCK/BMAL1-AMPK/NRF2 pathway to alleviate acrolein-induced ferroptosis, offering a potential strategy to address health issues related to environmental pollution.

E-Cigarette effects on oral health: A molecular perspective

Electronic cigarettes (e-cigarettes) have emerged as a potential alternative to traditional smoking and may aid in tobacco harm reduction and smoking cessation. E-cigarette use has notably increased, especially among young non-tobacco users, raising concerns due to the unknown long-term health effects. The oral cavity is the first and one of the most crucial anatomical sites for the deposition of e-cigarette aerosols. E-cigarette aerosols contain nicotine, flavors, volatile organic compounds, heavy metals, carcinogens, and other hazardous substances. These aerosols impact the oral cavity, disrupting host-microbial interactions and triggering gingivitis and systemic diseases. Furthermore, oral inflammation and periodontitis can be caused by proinflammatory cytokines induced by e-cigarette aerosols. The toxic components of e-cigarette aerosols increase the cellular reactive oxygen species (ROS) levels, reduce antioxidant capacity, increase DNA damage, and disrupt repair processes, which may further contribute to harmful effects on oral epithelum, leading to inflammatory and pre-malignant oral epithelial lesions. In this review, we analyze the toxicological properties of compounds in e-cigarette aerosols, exploring their cytotoxic, genotoxic, and inflammatory effects on oral health and delving into the underlying molecular mechanisms. Further research is essential to understand the impact of e-cigarettes on oral health and make informed regulatory decisions based on reliable scientific evidence.

Novel fluorescent nanoplatform for all-in-one sensing and removal of acrolein: An ultrasensitive probe to evaluate its removal efficiency

As a highly toxic aldehyde, acrolein is widely found in diet and environment, and can be produced endogenously, posing a serious threat to human health. Herein, we designed a novel fluorescent nanoplatform integrating carbon dots‑manganese dioxide (CDs-MnO2) and glutathione (GSH) for all-in-one sensing and removal of acrolein. By converting Mn4+ to free Mn2+, GSH inhibited the inner filter effect (IFE) of MnO2 nanosheets, and the Michael addition of acrolein with GSH inhibited the GSH-induced Mn4+ conversion, forming an "off-on-off" fluorescence response of CDs. The developed fluorescent nanoplatform exhibited high sensitivity (LOD was 0.067 μM) and selectivity for the simultaneous detection and removal of acrolein. The combination of CDs-MnO2 hydrogels with smartphones realized the point-of-care detection of acrolein, yielding satisfactory results (recovery rates varied between 97.01-104.65%, and RSD ranged from 1.42 to 4.16%). Moreover, the capability of the nanoplatform was investigated for on-site evaluating acrolein scavengers' efficacy, demonstrating excellent potential for practical application.

Elimination of Acrolein by Disodium 5'-Guanylate or Disodium 5'-Inosinate at High Temperature and Its Application in Roasted Pork Patty

Acrolein (ACR) is a highly active, simple unsaturated aldehyde found in various high-temperature processed foods. Its long-term accumulation in the human body increases the risk of chronic diseases. Animal and plant foodstuffs are rich in disodium 5'-guanylate (GMP) and disodium 5'-inosinate (IMP), which are authorized flavor enhancers. Herein, we used liquid chromatography with tandem mass spectrometry to explore the reaction-active kinetics and pathway of the interaction between GMP/IMP and ACR and validated it in roasted pork patties. Our results suggested that GMP and IMP could efficiently eliminate ACR by forming ACR adducts (GMP-ACR, IMP-ACR). In addition, IMP exhibited a higher reaction rate, whereas GMP had a good trapping capacity at a later stage. As carriers of GMP and IMP, dried mushrooms and shrimp exhibited an effective ACR-trapping ability in the ACR model and roasted pork patty individually and in combination. Adding 10% of dried mushroom or shrimp alone or 5% of dried mushroom and shrimp in combination eliminated up to 53.9%, 55.8%, and 55.2% ACR in a roasted pork patty, respectively. This study proposed a novel strategy to eliminate the generation of ACR in roasted pork patties by adding foodstuffs rich in GMP and IMP.

Diet as a Source of Acrolein: Molecular Basis of Aldehyde Biological Activity in Diabetes and Digestive System Diseases

Acrolein, a highly reactive α,β-unsaturated aldehyde, is a compound involved in the pathogenesis of many diseases, including neurodegenerative diseases, cardiovascular and respiratory diseases, diabetes mellitus, and the development of cancers of various origins. In addition to environmental pollution (e.g., from car exhaust fumes) and tobacco smoke, a serious source of acrolein is our daily diet and improper thermal processing of animal and vegetable fats, carbohydrates, and amino acids. Dietary intake is one of the main routes of human exposure to acrolein, which is a major public health concern. This review focuses on the molecular mechanisms of acrolein activity in the context of its involvement in the pathogenesis of diseases related to the digestive system, including diabetes, alcoholic liver disease, and intestinal cancer.

The Tobacco Smoke Component, Acrolein, as a Major Culprit in Lung Diseases and Respiratory Cancers: Molecular Mechanisms of Acrolein Cytotoxic Activity

Acrolein, a highly reactive unsaturated aldehyde, is a ubiquitous environmental pollutant that seriously threatens human health and life. Due to its high reactivity, cytotoxicity and genotoxicity, acrolein is involved in the development of several diseases, including multiple sclerosis, neurodegenerative diseases such as Alzheimer’s disease, cardiovascular and respiratory diseases, diabetes mellitus and even the development of cancer. Traditional tobacco smokers and e-cigarette users are particularly exposed to the harmful effects of acrolein. High concentrations of acrolein have been found in both mainstream and side-stream tobacco smoke. Acrolein is considered one of cigarette smoke’s most toxic and harmful components. Chronic exposure to acrolein through cigarette smoke has been linked to the development of asthma, acute lung injury, chronic obstructive pulmonary disease (COPD) and even respiratory cancers. This review addresses the current state of knowledge on the pathological molecular mechanisms of acrolein in the induction, course and development of lung diseases and cancers in smokers.

Rutin alleviated acrolein-induced cytotoxicity in Caco-2 and GES-1 cells by forming a cyclic hemiacetal product

Acrolein (ACR), an α, β-unsaturated aldehyde, is a toxic compound formed during food processing, and the use of phenolics derived from dietary materials to scavenge ACR is a hot spot. In this study, rutin, a polyphenol widely present in various dietary materials, was used to investigate its capacity to scavenge ACR. It was shown that more than 98% of ACR was eliminated under the conditions of reaction time of 2 h, temperature of 80 °C, and molar ratio of rutin/ACR of 2/1. Further structural characterization of the formed adduct revealed that the adduct of rutin to ACR to form a cyclic hemiacetal compound (RAC) was the main scavenging mechanism. Besides, the stability of RAC during simulated in vitro digestion was evaluated, which showed that more than 83.61% of RAC was remained. Furthermore, the cytotoxicity of RAC against Caco-2 and GES-1 cells was significantly reduced compared with ACR, where the IC50 values of ACR were both below 20 μM while that of RAC were both above 140 μM. And the improvement of the loss of mitochondrial membrane potential (MMP) by RAC might be one of the detoxification pathways. The present study indicated that rutin was one of the potential ACR scavengers among natural polyphenols.

Origin and Fate of Acrolein in Foods

Acrolein is a highly toxic agent that may promote the occurrence and development of various diseases. Acrolein is pervasive in all kinds of foods, and dietary intake is one of the main routes of human exposure to acrolein. Considering that acrolein is substantially eliminated after its formation during food processing and re-exposed in the human body after ingestion and metabolism, the origin and fate of acrolein must be traced in food. Focusing on molecular mechanisms, this review introduces the formation of acrolein in food and summarises both in vitro and in vivo fates of acrolein based on its interactions with small molecules and biomacromolecules. Future investigation of acrolein from different perspectives is also discussed.

Mechanisms of acrolein induces toxicity in human umbilical vein endothelial cells: Oxidative stress, DNA damage response, and apoptosis

Acrolein is a ubiquitous environmental pollutant that produced by the incomplete combustion of cigarette smoke, forest fires, petroleum fuels, plastic materials, and cooking fumes. Inhalation is a common form of people exposure to acrolein, increasing evidence demonstrates that acrolein impairs the cardiovascular system by targeting vascular endothelial cells. However, the molecular mechanism of the cytotoxicity of acrolein exposure on vascular endothelial cells remains unclear. This work focused on the toxicity of acrolein on human umbilical vein endothelial cells (HUVECs). The molecular mechanism was studied based on oxidative stress, DNA damage response (DDR), and mitochondrial apoptosis pathways. After HUVECs were treated with 12.5, 25, and 50 μM acrolein for 24 h, cell viability, cell colony formation, mitochondrial membrane potential, and adenosine triphosphate content significantly reduced, and acrolein increased intracellular reactive oxygen species, apoptosis rate, and 8-hydroxy-2 deoxyguanosine (8-OHdG) level. Furthermore, p38MAPK and c-Jun N-terminal kinase signaling pathways were activated in response to oxidative stress. Moreover, acrolein induced G0/G1phase arrest, promoted the expression of γ-H2AX, activated the DDR signaling pathway (Ataxia-Telangiectasia-Mutated [ATM] and Rad-3-related/Chk1 and ATM/Chk2), and triggered the consequent cell cycle checkpoints. Finally, the protein expression of Bax/Bcl-2 and cleaved Caspase-3 was up-regulated, suggesting apoptosis was induced by triggering the mitochondrial apoptosis pathway. All these results indicated that acrolein induced HUVECs cytotoxicity by regulating oxidative stress, DNA damage, and apoptosis. This study provides a novel perspective on the mechanism of acrolein-induced cardiovascular toxicity, it will be helpful for the prevention of acrolein-induced cardiovascular disease.

Design of a naphthalimide-based probe for acrolein detection in foods and cells

Acrolein is a highly toxic agent that can be generated exogenously and endogenously. Therefore, a highly specific and sensitive probe for acrolein with potential applications in acrolein detection must be developed. In this research, a novel fluorescent probe named "probe for acrolein detection" (Pr-ACR) was designed and synthesized based on a naphthalimide fluorophore skeleton, and a thiol group (-SH) was introduced into its structure for acrolein recognition. The -SH traps acrolein via Michael addition and the resultant interaction product of the probe inhibits the photoinduced electron transfer process and produce a strong fluorescence at 510 nm. The probe showed high sensitivity and specificity for acrolein. HPLC-MS/MS analysis verified that it can be used to quantify acrolein in foods, such as soda crackers, red wine, and baijiu, with a fluorescence spectrophotometer. After methyl esterification, the methyl esterified probe (mPr-ACR) successfully visualised acrolein in Hela cells under a laser scanning confocal microscope. This finding proved that Pr-ACR and mPr-ACR are potential tools for the detection and visualisation of acrolein from different sources.

Apiaceous vegetables protect against acrolein-induced pulmonary injuries through modulating hepatic detoxification and inflammation in C57BL/6 male mice

Acrolein (Acr) is a reactive aldehyde in the environment. Acr causes oxidative stress and a cascade of catalytic events and has, thereby, been associated with increased risk of pulmonary diseases. Whether apiaceous vegetables (API) consumption can prevent Acr-induced pulmonary toxicity has not yet been explored hence, we investigated the effects of API on Acr-induced pulmonary damages in C57BL/6J mice. The mice were assigned into either negative control [NEG group; American Institute of Nutrition (AIN)-93G diet only], positive control (POS group; AIN-93G+Acr) or API intervention group (API group; AIN-93G+21% API+Acr). After 1 week of dietary intervention, the POS and API mice were exposed to Acr (10 µmol/kg body weight/day) for 5 days. During the exposure period, assigned diets remained the same. Prominent indicators lung of toxicity of POS mice were found, including mucus accumulation, macrophage infiltration, and hemorrhage, all of which were ameliorated by the API. Serum and lung inflammation markers, such as a tumor necrosis factor alpha were also increased by Acr while reduced by API. In the liver, API upregulated expression of glutathione S-transferases, which enhanced the metabolism of Acr into water-soluble 3-hydroxypropyl mercapturic acid for excretion. This is consistent with observed reductions in serum Acr-protein adducts. Taken together, our results suggest that API may provide protection against Acr-induced pulmonary damages and inflammation via enhancement of the hepatic detoxification of Acr.

The correlation between the level of 3-hydroxypropyl mercapturic acid, CYP2B6 polymorphisms, and hematuria occurrences after cyclophosphamide administration and its bioanalytical methods: A systematic review

BACKGROUND

Cyclophosphamide (CPA) is a cytotoxic prodrug that needs to be metabolized by cytochrome P450 enzymes, like CYP2B6. Unfortunately, CYP2B6 is a very polymorphic enzyme and can cause a change in 3-hydroxypropyl mercapturic acid (3-HPMA), the most found CYP metabolite in urine levels. Change in 3-HPMA levels can also indicate the level change in its precursor, acrolein, which is responsible for the hematuria incidence after CPA administration.This review's purpose is to obtain a conclusion about the optimal 3-HPMA analysis method in urine after the administration of cyclophosphamide using liquid chromatography-tandem mass spectrometry (LC-MS/MS) through literature review from previous studies. Also, this review was written to examine the relationship between levels of 3-HPMA in urine, polymorphisms of CYP2B6 enzymes, and the incidence of hematuria after cyclophosphamide administration in cancer patients.

METHODS

Major databases, such as Universitas Indonesia's library database ScienceDirect, PubMed/Medline, Frontiers Media, and Google Scholar database, were used to find both published and unpublished studies without a time limit until 2020. Studies on pharmacokinetics, pharmacodynamics, drug therapy monitoring of cyclophosphamide, bioanalysis, and polymerase chain reaction (PCR) published in Indonesian and English were included. Meanwhile, non-related studies or studies written in other languages besides Indonesian and English were excluded. Two independent reviewers screened the titles, abstracts, and full-text manuscripts. Data obtained from eligible sources were used to answer the purpose of this review in a narrative form.

RESULTS

The authors found 436 related studies from various databases and websites. Then, the authors narrowed it down into 62 pieces of literature by removing the duplicates and reviewing the abstracts and full-text manuscripts. Out of 62 sources, the authors found 30 studies that explained 3-HPMA analysis using LC/MS-MS, CYP2B6 polymorphisms, and hematuria occurrences. The authors used those 30 studies to build a conclusion regarding the purpose of this study. We strengthened the results with some additional information from the other 32 eligible sources.

CONCLUSIONS

The authors conclude that according to literature searches from previous studies, the optimal 3-HPMA analysis method in urine after cyclophosphamide administration using LC-MS/MS is using triple quadrupole LC-MS/MS; source of positive ion electrospray ionization (ESI); mobile phase combination of 0.1% formic acid in water (A) - 0.1% formic acid in acetonitrile (90:10 v/v) (B); the Acquity® BEH C18 column (2.1 × 100 mm; 1.7 μm); injection volume of 10 μl; flow rate of 0.2 ml/minute; gradient elution method. Detection was carried out using mass spectrometry with m/z ratio of 222.10 > 90 for 3-HPMA and m/z 164.10 > 122 for n-acetylcysteine (NAC). The optimum sample preparation method is acidification and dilution ratio of 1:5 v/v. Also, there is a relationship between 3-HPMA levels, CYP2B6 polymorphisms, and the occurrences of hematuria after the administration of cyclophosphamide, which is a type of CYP2B6 polymorph, namely CYP2B6∗6, can increase cyclophosphamide hydroxylation so that it can increase the levels of acrolein and 3-HPMA, as its metabolites, and risk of hematuria.

ETHICS AND DISSEMINATION

This research does not use human participants, human data, or human tissue for being directly studied for the review. Therefore, ethics approval and consent to participate are not applicable.

REGISTRATION

This research has not been registered yet.

Identification of adducts formed between acrolein and alanine or serine in fried potato crisps and the cytotoxicity-lowering effect of acrolein in three cell lines

In physiological and thermally-processed conditions, alanine and serine efficiently eliminate acrolein to generate two main adducts, 2-(5-formyl-3,6-dihydropyridin-1(2H)-yl) propanoic acid and 2-(5-formyl-3,6-dihydropyridin-1(2H)-yl)-3-hydroxypropanoic acid, with amounts of 81.6 ± 4.24 μg/kg and 23.72 ± 0.40 μg/kg in fried potato crisps, respectively. Adduct formation markedly decreased the cytotoxicity of acrolein against Caco-2, GES-1 and HUVEC cells. The cell viability of them remained approximately100% after incubation with 200 µmolL^-1 adducts, while the IC₅₀ values for acrolein in the three cells were 66, 54, and 16 µmolL^-1 respectively. The adducts express the protective effects by tremendous reduction of cell apoptosis, reactive oxygen species (ROS) production, and DNA damage.

Cardiac toxicity of acrolein exposure in embryonic zebrafish (Danio rerio)

Acrolein is a widely distributed pollutant produced from various sources such as industrial waste, organic combustion, and power plant emissions. It is also intentionally released into irrigation canals to control invasive aquatic plants. Zebrafish (Danio rerio) has a good reputation for being an attractive model organism for developmental and toxicological research. In this study, zebrafish embryos were exposed to acrolein to investigate the cardiotoxic effects. The 96-h LC₅₀ (median lethal concentration) value of acrolein was determined as 654.385 μg/L. Then, the embryos were treated with the sublethal experimental concentrations of acrolein (1, 4, 16, 64, and 256 μg/L) for 96 h. Embryos were examined at 48, 72, and 96 h post-fertilization (hpf). Acrolein affected the cardiac morphology and function of the embryos. Sinus venosus-bulbus arteriosus (SV-BA) distance of 64 μg/L and 256 μg/L acrolein groups was elongated compared with the control samples. Immunostaining with MF20 antibody clearly exhibited that the atrium positioned posterior to the ventricle which indicated cardiac looping inhibition. Histological preparations also showed the mispositioning and the lumens of the chambers narrowed. Acrolein-induced increased heart rate was noted in the 4, 16, 64, and 256 μg/L treatment groups. Taken together, these results indicated that acrolein disrupted the heart development and cardiac function in zebrafish, suggesting that its water-borne risks should be considered seriously.

Interaction of Acrylamide, Acrolein, and 5-Hydroxymethylfurfural with Amino Acids and DNA

Acrylamide, acrolein, and 5-hydroxymethylfurfural (HMF) are food-borne toxicants produced during the thermal processing of food. The α,β-unsaturated carbonyl group or aldehyde group in their structure can react easily with the amino, imino, and thiol groups in amino acids, proteins, and DNA via Michael addition and nucleophilic reactions in food and in vivo. This work reviews the interaction pathways of three toxins with amino acids and the cytotoxicity and changes after the digestion and absorption of the resulting adducts. Their interaction with DNA is also discussed. Amino acids ubiquitously exist in foods and are added as nutrients or used to control these food-borne toxicants. Hence, the interaction widely occurring in foods would greatly increase the internal exposure of these toxins and their derived compounds after food intake. This review aims to encourage further investigation on toxin-derived compounds, including their types, exposure levels, toxicities, and pharmacokinetics.

Formation of di-cysteine acrolein adduct decreases cytotoxicity of acrolein by ROS alleviation and apoptosis intervention

Acrolein (ACR) is a toxic contaminant for humans. Our previous research indicated that l-cysteine (Cys) decreased the cytotoxicity of acrolein possibly via adduct formation, but which adduct contributed to the toxicity-lowering effect remains unknown. In this work, we identified a di-cysteine acrolein adduct (ACR-di-Cys) and investigated its toxicity against human bronchial epithelial cell line HBE and colon cancer cell line Caco-2. ACR-di-Cys tremendously decreased acrolein-induced cytotoxicity via alleviating ROS and apoptosis intervention. In the condition of no presence of free cysteine, however, this adduct can convert to mono-ACR-Cys in PBS solution by losing a molecule of cysteine conjugated at CC bond. ACR-mono-Cys showed much higher toxicity than ACR-di-Cys, and even higher than acrolein after 48 h exposure. This study indicated that cysteine can react with acrolein to form adducts with different acrolein-detoxifying capacity, and a sufficient intake of cysteine or cysteine-containing proteins can maximize the detoxifying effect for acrolein via the formation of a highly detoxifying agent, ACR-di-Cys.

Elevated levels of lead exposure and impact on the anti-inflammatory ability of oral sialic acids among preschool children in e-waste areas

The oral health of preschool children in an electronic waste (e-waste) area is susceptible to lead (Pb) exposure increasing the risk of dental caries and causing periodontitis and other oral diseases. The aim of the present study is to investigate the relationship between chronic exposure to Pb and oral anti-inflammatory potential of preschool children. For this analysis, 574 preschool children from 2.5 to 6 years of age were recruited between November and December 2017, in which 357 preschool children were from Guiyu (n = 357), an e-waste-contaminated town, and 217 from Haojiang Shantou. We measured the levels of child blood Pb, salivary sialic acid, serum interleukin-6 (IL-6) and serum tumor necrosis factor-α (TNF-α), and investigated the prevalence of dental caries in deciduous teeth. The medians of blood Pb levels, serum IL-6 and TNF-α were significantly higher in the Guiyu children than in Haojiang children. Concomitantly, salivary sialic acids were lower in the Guiyu children [9.58 (3.97, 18.42) mg/dL] than in Haojiang [17.57 (5.95, 24.23) mg/dL]. Additionally, the prevalence of dental caries in deciduous teeth was significantly higher in the Guiyu children than in Haojiang (62.5% vs. 53.9%). Blood Pb levels were negatively correlated with salivary sialic acids, in which IL-6 played as a mediator of the association between blood Pb levels and saliva sialic acid concentrations according to the mediation model. To our knowledge, this is the first report on the potential association between chronic Pb exposure and the anti-inflammatory ability of oral sialic acids among preschool children. These results suggest that the chronic Pb exposure can reduce salivary sialic acid levels, attenuate oral anti-inflammatory potential and increase the potential risk of dental caries in deciduous teeth among preschool children in an e-waste site.

Short-chain lipid peroxidation products form covalent adducts with pyruvate kinase and inhibit its activity in vitro and in breast cancer cells

Pyruvate kinase catalyses the last step in glycolysis and has been suggested to contribute to the regulation of aerobic glycolysis in cancer cells. It can be inhibited by oxidation of cysteine residues in vitro and in vivo, which is relevant to the more pro-oxidant state in cancer and proliferating tissues. These conditions also favour lipid peroxidation and the formation of electrophilic fragmentation products, including short-chain aldehydes that can covalently modify proteins. However, as yet few studies have investigated their interactions with pyruvate kinase, so we investigated the effects of three different aldehydes, acrolein, malondialdehyde and 4-hydroxy-2(E)-hexenal (HHE), on the structure and activity of the enzyme. Analysis by LC-MS/MS showed unique modification profiles for each aldehyde, but Cys152, Cys423 and Cys474 were the residues most susceptible to electrophilic modification. Analysis of enzymatic activity under these conditions showed that acrolein was the strongest inhibitor, and at incubation times longer than 2 h, pathophysiological concentrations induced significant effects. Treatment of MCF-7 cells with the aldehydes caused similar losses of pyruvate kinase activity to those observed in vitro, and at lower concentrations than those required to cause cell death, with time and dose-dependent effects; acrolein adducts on Cys152 and Cys358 were detected. Cys358 and Cys474 are located at or near the allosteric or active sites, and formation of adducts on these residues probably contributes to loss of activity at low treatment concentrations. This study provides the first detailed analysis of the structure-activity relationship of C3 and C6 aldehydes with pyruvate kinase, and suggests that reactive short-chain aldehydes generated in diseases with an oxidative aetiology or from environmental exposure such as smoking could be involved in the metabolic alterations observed in cancer cells, through alteration of pyruvate kinase activity.

Identification of acrolein metabolites in human buccal cells, blood, and urine after consumption of commercial fried food

SCOPE

Acrolein is a highly electrophilic α,β-unsaturated aldehyde and is associated with human diseases. It is formed by Maillard reaction during food processing and could be detected in the emissions of overheated cooking oils. Consequently, humans are at risk of acrolein exposure through consumption of such prepared food.

METHODS AND RESULTS

We conducted three human studies that healthy subjects (21-30 years) were served fried foods including fried chicken and French fries from three commercial fast food restaurants. Acrolein-related metabolites including urinary 3-hydroxypropyl mercapturic acid (3-HPMA), serum acrolein-protein conjugates (Acr-FDP), and buccal acrolein-induced DNA damages (Acr-dG adducts) along with GSH levels in serum or buccal cells were investigated for different times after consumption.

CONCLUSION

Urinary 3-HPMA levels were increased after 2-hr consumption of fried food with an elimination half-life of 10 hr. In addition, increased Acr-dG adducts in oral cavity were inversely correlated to buccal glutathione (GSH) levels after consumption. However, there was no significant change in systemic GSH levels or Acr-FDP adducts in serum. These results indicate that exposure of acrolein from consuming fried food affects local oral cavity homeostasis. This may provide a possible link between intake of fried food and increased risk of upper aerodigestive tract cancers.

Acrolein Is Involved in the Synergistic Potential of Cigarette Smoking- and Betel Quid Chewing-Related Human Oral Cancer

BACKGROUND

Cigarette smoking (CS) and betel quid (BQ) chewing are two known risk factors and have synergistic potential for the development of oral squamous cell carcinoma (OSCC) in Taiwan. The p53 mutation characteristics in OSCC (G to A or G to T mutations) are similar to that of acrolein-induced DNA damage. Acrolein is a major cigarette-related carcinogen that preferentially causes p53 mutations and inhibits DNA repair function in lung cancer. We hypothesize that acrolein is associated with OSCC carcinogenesis.

METHODS

A total of 97 patients with OSCC and 230 healthy subjects with CS and/or BQ chewing histories were recruited. Slot blot analysis of Acr-dG adducts, an indicator of acrolein-induced DNA damage in buccal DNA, and LC/MS-MS analysis of 3-HPMA levels, urinary Acr metabolites, were performed.

RESULTS

Our results showed that the level of Acr-dG adducts in buccal cells was 1.4-fold higher in patients with OSCC than in healthy subjects with CS and/or BQ chewing histories (P < 0.001). In addition, in healthy subjects, CS and BQ chewing were associated with significantly higher levels of 3-HPMA, indicating that CS and BQ chewing promotes acrolein absorption. However, 3-HPMA levels in patients with OSCC were significantly lower than those in healthy subjects, indicating impaired acrolein metabolism.

CONCLUSIONS

In this study, we provide a novel mechanism by which increased acrolein uptake and impaired metabolism may contribute to the synergistic potential of CS and BQ-induced OSCC.

IMPACT

Elevated acrolein-induced DNA damage (Acr-dG adducts) detected in buccal swabs may serve as an early indicator to identify patients at risk of developing OSCC.

Lamisil (terbinafine) toxicity: Determining pathways to bioactivation through computational and experimental approaches

Lamisil (terbinafine) may cause idiosyncratic liver toxicity through a proposed toxicological mechanism involving the reactive metabolite 6,6-dimethyl-2-hepten-4-ynal (TBF-A). TBF-A toxicological relevance remains unclear due to a lack of identification of pathways leading to and competing with TBF-A formation. We resolved this knowledge gap by combining computational modeling and experimental kinetics of in vitro hepatic N-dealkylation of terbinafine. A deep learning model of N-dealkylation predicted a high probability for N-demethylation to yield desmethyl-terbinafine followed by N-dealkylation to TBF-A and marginal contributions from other possible pathways. We carried out steady-state kinetic experiments with pooled human liver microsomes that relied on development of labeling methods to expand metabolite characterization. Those efforts revealed high levels of TBF-A formation and first order decay during metabolic reactions; actual TBF-A levels would then reflect the balance between those processes as well as reflect the impact of stabilizing adduction with glutathione and other biological molecules. Modeling predictions and experimental studies agreed on the significance of N-demethylation and insignificance of N-denaphthylation in terbinafine metabolism, yet differed on importance of direct TBF-A formation. Under steady-state conditions, the direct pathway was the most important source of the reactive metabolite with a Vmax/Km of 4.0 pmol/min/mg protein/µM in contrast to model predictions. Nevertheless, previous studies show that therapeutic dosing leads to accumulation of desmethyl-terbinafine in plasma, which means that likely sources for TBF-A would draw from metabolism of both the major metabolite and parent drug based on our modeling and experimental studies. Through this combination of novel modeling and experimental approaches, we are the first to identify pathways leading to generation of TBF-A for assessing its role in idiosyncratic adverse drug interactions.

Protective effects of curcumin on acrolein-induced neurotoxicity in HT22 mouse hippocampal cells

BACKGROUND

Aging is one of the most important inevitable risk factors of Alzheimer disease (AD). Oxidative stress plays a critical role in the process of aging. Curcumin has been proposed to improve neural damage, especially neurodegenerative injury, through its antioxidant and anti-inflammatory properties. Therefore, we investigated the effects of curcumin on acrolein-induced AD-like pathologies in HT22 cells.

METHODS

HT22 murine hippocampal neuronal cells were treated with 25 μM acrolein for 24 h with or without pre-treating with curcumin at the selected optimum concentration (5 μg/mL) for 30 min. Cell viability and apoptosis were measured by CCK8 assay and flow cytometric analysis. Levels of glutathione (GSH), superoxide dismutase (SOD), and malondialdehyde (MDA) were detected by a GSH assay kit or commercial assay kits, respectively. Alterations in the expression of BDNF/TrkB and key enzymes involved in amyloid precursor protein (APP) metabolism were assessed by western blotting.

RESULTS

Data showed that curcumin significantly reversed acrolein-induced oxidative stress indicated by depletion of GSH and SOD, and elevation of MDA. The findings also suggested curcumin's potential in protecting HT22 cells against acrolein through regulating the BDNF/TrkB signaling. In addition, acrolein-induced reduction in A-disintegrin and metalloprotease, and the increase of amyloid precursor protein, β-secretase, and receptor for advanced glycation end products were reversed either, and most of them were nearly restored to the control levels by curcumin.

CONCLUSION

These findings demonstrate the protective effects of curcumin on acrolein-induced neurotoxicity in vitro, which further suggests its potential role in the treatment of AD.

A mass spectrometry approach for the identification and localization of small aldehyde modifications of proteins

Lipids containing polyunsaturated fatty acids are primary targets of oxidation, which produces reactive short-chain aldehydes that can covalently modify proteins, a process called lipoxidation. Improved mass spectrometry (MS) methods for the analysis of these adducts in complex biological systems are needed. Lysozyme and human serum albumin (HSA) were used as model proteins to investigate lipoxidation products formed by two short-chain aldehydes, acrolein and pentanal, which are unsaturated and saturated aldehydes respectively. The adducts formed were stabilized by NaBH₄ or NaBH₃CN reduction and analysed by MS. Analysis of intact modified lysozyme showed a pentanal modification resulting from Schiff's base formation (+70 Da), and up to 8 acrolein adducts, all resulting from Michael addition (+58 Da). Analysis of tryptic digests identified specific histidine, cysteine and lysine residues modified in both lysozyme and HSA, and determined characteristic amino acid-specific fragmentations. Eight different internal fragment ions were found that could be used as general diagnostic ions for pentanal- and acrolein-modified amino acids. The combined use of intact protein analysis and LC-MS/MS methods provided a powerful tool for the identification and localization of aldehyde-protein adducts, and the diagnostic ions will facilitate the development of targeted MS methods for analysis of adducts in more complex samples.

Caloric restriction ameliorates acrolein-induced neurotoxicity in rats

OBJECTIVE

Acrolein, a highly reactive unsaturated aldehyde, is a ubiquitous environmental pollutant and oxidative damage induced by acrolein is hypothesized to involve in the etiology of Alzheimer's disease (AD). Calorie restriction (CR) is the only non-genetic intervention that has consistently been verified to retard aging by ameliorating oxidative stress. Therefore, we investigated the effects of CR on acrolein-induced neurotoxicity in Sprague-Dawley (SD) rats.

METHODS

A total of 45 weaned and specific-pathogen-free SD rats (male, weighing 180-220 g) were gavage-fed with acrolein (2.5 mg/kg/day) and fed ab libitum of 10 g/day or 7 g/day (representing 30% CR regimen), or gavage-fed with same volume of tap water and fed al libitum as vehicle control for 12 weeks. After behavioral test conducted by Morris Water Maze, SD rats were sacrificed and brain tissues were prepared for histochemical evaluation and Western blotting to detect alterations in oxidative stress, BDNF/TrkB pathway and key enzymes involved in amyloid precursor protein (APP) metabolism.

RESULTS

Treatment with 30% CR in SD rats significantly attenuated acrolein-induced cognitive impairment. Oxidative damage including deletion of glutathione and superoxide dismutase and sharp rise in malondialdehyde were notably improved by 30% CR. Further study suggested that 30% CR showed protective effects against acrolein by modulating BDNF/TrkB signaling pathways. Moreover, 30% CR restored acrolein-induced changes of APP, β-secretase, α-secretase and receptor for advanced glycation end products.

CONCLUSION

These findings suggest that CR may provide a promising approach for the treatment of AD, targeting acrolein.

Chemistry and analysis of HNE and other prominent carbonyl-containing lipid oxidation compounds

The process of lipid oxidation generates a diverse array of small aldehydes and carbonyl-containing compounds, which may occur in free form or esterified within phospholipids and cholesterol esters. These aldehydes mostly result from fragmentation of fatty acyl chains following radical oxidation, and the products can be subdivided into alkanals, alkenals (usually α,β-unsaturated), γ-substituted alkenals and bis-aldehydes. Isolevuglandins are non-fragmented di-carbonyl compounds derived from H₂-isoprostanes, and oxidation of the ω-3-fatty acid docosahexenoic acid yield analogous 22 carbon neuroketals. Non-radical oxidation by hypochlorous acid can generate α-chlorofatty aldehydes from plasmenyl phospholipids. Most of these compounds are reactive and have generally been considered as toxic products of a deleterious process. The reactivity is especially high for the α,β-unsaturated alkenals, such as acrolein and crotonaldehyde, and for γ-substituted alkenals, of which 4-hydroxy-2-nonenal and 4-oxo-2-nonenal are best known. Nevertheless, in recent years several previously neglected aldehydes have been investigated and also found to have significant reactivity and biological effects; notable examples are 4-hydroxy-2-hexenal and 4-hydroxy-dodecadienal. This has led to substantial interest in the biological effects of all of these lipid oxidation products and their roles in disease, including proposals that HNE is a second messenger or signalling molecule. However, it is becoming clear that many of the effects elicited by these compounds relate to their propensity for forming adducts with nucleophilic groups on proteins, DNA and specific phospholipids. This emphasizes the need for good analytical methods, not just for free lipid oxidation products but also for the resulting adducts with biomolecules. The most informative methods are those utilizing HPLC separations and mass spectrometry, although analysis of the wide variety of possible adducts is very challenging. Nevertheless, evidence for the occurrence of lipid-derived aldehyde adducts in biological and clinical samples is building, and offers an exciting area of future research.