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

Effect of nonsense-mediated mRNA decay factor SMG9 deficiency on premature aging in zebrafish

SMG9 is an essential component of the nonsense-mediated mRNA decay (NMD) machinery, a quality control mechanism that selectively degrades aberrant transcripts. Mutations in SMG9 are associated with heart and brain malformation syndrome (HBMS). However, the molecular mechanism underlying HBMS remains unclear. We generated smg9 mutant zebrafish (smg9oi7/oi7) that have a lifespan of approximately 6 months or longer, allowing for analysis of the in vivo function of Smg9 in adults in more detail. smg9oi7/oi7 zebrafish display congenital brain abnormalities and reduced cardiac contraction. Additionally, smg9oi7/oi7 zebrafish exhibit a premature aging phenotype. Analysis of NMD target mRNAs shows a trend toward increased mRNA levels in smg9oi7/oi7 zebrafish. Spermidine oxidase (Smox) is increased in smg9oi7/oi7 zebrafish, resulting in the accumulation of byproducts, reactive oxygen species, and acrolein. The accumulation of smox mRNA due to NMD dysregulation caused by Smg9 deficiency leads to increased oxidative stress, resulting in premature aging.

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.

Acrolein increases the concentration of intracellular Zn2⁺ by producing mitochondrial reactive oxygen species in A549 cells

Smoking or occupational exposure leads to low concentrations of acrolein on the surface of the airways. Acrolein is involved in the pathophysiological processes of various respiratory diseases. Reports showed that acrolein induced an increase in mitochondrial reactive oxygen species (mROS). Furthermore, exogenous H₂O₂ was found to increase intracellular Zn2⁺ concentration ([Zn2⁺]ᵢ). However, the specific impact of acrolein on changes in intracellular Zn2⁺ levels has not been fully investigated. Therefore, this study aimed to investigate the effects of acrolein on mROS and [Zn2⁺]ᵢ in A549 cells. We used Mito Tracker Red CM-H2Xros (MitoROS) and Fluozin-3 fluorescent probes to observe changes in mROS and intracellular Zn2⁺. The results revealed that acrolein increased [Zn2⁺]ᵢ in a time- and dose-dependent manner. Additionally, the production of mROS was observed in response to acrolein treatment. Subsequent experiments showed that the intracellular Zn2⁺ chelator TPEN could inhibit the acrolein-induced elevation of [Zn2⁺]ᵢ but did not affect the acrolein-induced mROS production. Conversely, the acrolein-induced elevation of mROS and [Zn2⁺]ᵢ were significantly decreased by the inhibitors of ROS formation (NaHSO₃, NAC). Furthermore, external oxygen free radicals increased both [Zn2⁺]ᵢ levels and mROS production. These results demonstrated that acrolein-induced elevation of [Zn2⁺]ᵢ in A549 cells was mediated by mROS generation, rather than through a pathway where [Zn2⁺]ᵢ elevation leads to mROS production.

The Role of Acrolein in Neurodegenerative Diseases and Its Protective Strategy

Neurodegenerative diseases are characterized by a massive loss of specific neurons, which can be fatal. Acrolein, an omnipresent environmental pollutant, is classified as a priority control contaminant by the EPA. Evidence suggests that acrolein is a highly active unsaturated aldehyde related to many nervous system diseases. Therefore, numerous studies have been conducted to identify the function of acrolein in neurodegenerative diseases, such as ischemic stroke, AD, PD, and MS, and its exact regulatory mechanism. Acrolein is involved in neurodegenerative diseases mainly by elevating oxidative stress, polyamine metabolism, neuronal damage, and plasma ACR-PC levels, and decreasing urinary 3-HPMA and plasma GSH levels. At present, the protective mechanism of acrolein mainly focused on the use of antioxidant compounds. This review aimed to clarify the role of acrolein in the pathogenesis of four neurodegenerative diseases (ischemic stroke, AD, PD and MS), as well as protection strategies, and to propose future trends in the inhibition of acrolein toxicity through optimization of food thermal processing and exploration of natural products.

Comparative study of oral versus parenteral crocin in mitigating acrolein-induced lung injury in albino rats

Acrolein (Ac) is the second most commonly inhaled toxin, produced in smoke of fires, tobacco smoke, overheated oils, and fried foods; and usually associated with lung toxicity. Crocin (Cr) is a natural carotenoid with a direct antioxidant capacity. Yet, oral administration of crocin as a natural rout is doubtful, because of poor absorbability. Therefore, the current study aimed to compare the potential protective effect of oral versus intraperitoneal (ip) crocin in mitigating Ac-induced lung toxicity. 50 Adult rats were randomly divided into 5 equal groups; Control (oral-saline and ip-saline) group, Cr (oral-Cr and ip-Cr) group, Ac group, oral-Cr/Ac group, and ip-Cr/Ac group; for biochemical, histopathological, and immunohistochemical investigations. Results indicated increased oxidative stress and inflammatory biomarkers in lungs of Ac-treated group. Histopathological and immunohistochemical examinations revealed lung edema, infiltration, fibrosis, and altered expression of apoptotic and anti-apoptotic markers. Compared to oral-Cr/Ac group, the ip-Cr/Ac group demonstrated remarkable improvement in the oxidative, inflammatory, and apoptotic biomarkers, as well as the histopathological alterations. In conclusion, intraperitoneal crocin exerts a more protective effect on acrolein-induced lung toxicity than the orally administered crocin.

Protective Effects of Antioxidants on Cyclophosphamide-Induced Ovarian Toxicity

The most common limitation of anticancer chemotherapy is the injury to normal cells. Cyclophosphamide, which is one of the most widely used alkylating agents, can cause premature ovarian insufficiency and infertility since the ovarian follicles are extremely sensitive to their effects. Although little information is available about the pathogenic mechanism of cyclophosphamide-induced ovarian damage, its toxicity is attributed to oxidative stress, inflammation, and apoptosis. The use of compounds with antioxidant and cytoprotective properties to protect ovarian function from deleterious effects during chemotherapy would be a significant advantage. Thus, this article reviews the mechanism by which cyclophosphamide exerts its toxic effects on the different cellular components of the ovary, and describes 24 cytoprotective compounds used to ameliorate cyclophosphamide-induced ovarian injury and their possible mechanisms of action. Understanding these mechanisms is essential for the development of efficient and targeted pharmacological complementary therapies that could protect and prolong female fertility.

Insulin resistance enhances binge ethanol-induced liver injury through promoting oxidative stress and up-regulation CYP2E1

Alcoholic liver disease (ALD) has caused a serious burden on public and personal health in crowd with ethanol abuse. The effects of insulin resistance (IR) on ALD and the mechanisms underlying these responses are still not well understood. In this study, we investigated the changes of liver injury, inflammation, apoptosis, mitochondrial dysfunction and CYP2E1 changes in liver of mice exposed to ethanol with IR or not. We found IR increased the sensitivity of liver injury in mice exposed to ethanol, manifested as the increase serum activities of AST and ALT, the accumulation of triglycerides, the deterioration of liver pathology and increase of inflammatory factors. IR also exacerbated apoptosis and mitochondrial dysfunction in liver of mice exposed to ethanol. The increase of oxidative stress and the decrease of antioxidant defense ability might be responsible for the sensitizing effects of IR on ethanol-induced liver injury, supported by the increase of MDA levels and the decline of GSH/GSSG, the inactivation of antioxidant enzymes SOD, GR through the inhibition of Nrf-2 pathway. The activation of CYP2E1 might be also involved in the sensitizing effects of IR on ethanol induced liver injury in mice. These results demonstrated that IR exhibited a significant pro-oxidative and pro-apoptosis effects to aggravate alcoholic liver injury. Our study helped us to better understand the sensitive role of IR on ALD and suggested that alcohol intake may be more harmful for people with IR.

Acrolein Promotes Aging and Oxidative Stress via the Stress Response Factor DAF-16/FOXO in Caenorhabditis elegans

For this investigation, Caenorhabditis elegans (C. elegans) served, for the first time, as a model organism to evaluate the toxic effect and possible underlying mechanisms under acrolein (ACR) exposure. The results showed that ACR exposure (12.5–100 μM) shortened the lifespan of C. elegans. The reproductive capacity, body length, body width, and locomotive behavior (head thrash) of C. elegans were diminished by ACR, especially the doses of 50 and 100 μM. Furthermore, ACR significantly enhanced the endogenous ROS levels of C. elegans, inhibited the antioxidant-related enzyme activities, and affected the expression of antioxidant related genes. The increasing oxidative stress level promoted the migration of DAF-16 into the nucleus that was related to the DAF-16/FOXO pathway. It was also confirmed by the significant decrease of the lifespan-shortening trend in the daf-16 knockout mutant. In conclusion, ACR exposure induced aging and oxidative stress in C.elegans, resulting in aging-related decline and defense-related DAF-16/FOXO pathways’ activation.

Carnosine quenches the reactive carbonyl acrolein in the central nervous system and attenuates autoimmune neuroinflammation

Background

Multiple sclerosis (MS) is a chronic autoimmune disease driven by sustained inflammation in the central nervous system. One of the pathological hallmarks of MS is extensive free radical production. However, the subsequent generation, potential pathological role, and detoxification of different lipid peroxidation-derived reactive carbonyl species during neuroinflammation are unclear, as are the therapeutic benefits of carbonyl quenchers. Here, we investigated the reactive carbonyl acrolein and (the therapeutic effect of) acrolein quenching by carnosine during neuroinflammation.

Methods

The abundance and localization of acrolein was investigated in inflammatory lesions of MS patients and experimental autoimmune encephalomyelitis (EAE) mice. In addition, we analysed carnosine levels and acrolein quenching by endogenous and exogenous carnosine in EAE. Finally, the therapeutic effect of exogenous carnosine was assessed in vivo (EAE) and in vitro (primary mouse microglia, macrophages, astrocytes).

Results

Acrolein was substantially increased in inflammatory lesions of MS patients and EAE mice. Levels of the dipeptide carnosine (β-alanyl-l-histidine), an endogenous carbonyl quencher particularly reactive towards acrolein, and the carnosine-acrolein adduct (carnosine-propanal) were ~ twofold lower within EAE spinal cord tissue. Oral carnosine treatment augmented spinal cord carnosine levels (up to > tenfold), increased carnosine-acrolein quenching, reduced acrolein-protein adduct formation, suppressed inflammatory activity, and alleviated clinical disease severity in EAE. In vivo and in vitro studies indicate that pro-inflammatory microglia/macrophages generate acrolein, which can be efficiently quenched by increasing carnosine availability, resulting in suppressed inflammatory activity. Other properties of carnosine (antioxidant, nitric oxide scavenging) may also contribute to the therapeutic effects.

Conclusions

Our results identify carbonyl (particularly acrolein) quenching by carnosine as a therapeutic strategy to counter inflammation and macromolecular damage in MS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02306-9.

Wild-type IDH2 protects nuclear DNA from oxidative damage and is a potential therapeutic target in colorectal cancer

Although the role of isocitrate dehydrogenase (IDH) mutation in promoting cancer development has been well-characterized, the impact of wild-type IDH on cancer cells remains unclear. Here we show that the wild-type isocitrate dehydrogenase 2 (IDH2) is highly expressed in colorectal cancer (CRC) cells, and plays an unexpected role in protecting the cancer cells from oxidative damage. Genetic abrogation of IDH2 in CRC cells leads to reactive oxygen species (ROS)-mediated DNA damage and an accumulation of 8-oxoguanine with DNA strand breaks, which activates DNA damage response (DDR) with elevated γH2AX and phosphorylation of ataxia telangiectasia-mutated (ATM) protein, leading to a partial cell cycle arrest and eventually cell senescence. Mechanistically, the suppression of IDH2 results in a reduction of the tricarboxylic acid (TCA) cycle activity due to a decrease in the conversion of isocitrate to α-ketoglutarate (α-KG) with a concurrent decrease in NADPH production, leading to ROS accumulation and oxidative DNA damage. Importantly, abrogation of IDH2 inhibits CRC cell growth in vitro and in vivo, and renders CRC cells more vulnerable to DNA-damaging drugs. Screening of an FDA-approved drug library has identified oxaliplatin as a compound highly effective against CRC cells when IDH2 was suppressed. Our study has uncovered an important role of the wild-type IDH2 in protecting DNA from oxidative damage, and provides a novel biochemical basis for developing metabolic intervention strategy for cancer treatment.

Conjugated linoleic acid protects brain mitochondrial function in acrolein induced male rats

Acrolein (AC) is a toxic substance that can have a neurotoxic effect. It can cause oxidative stress and mitochondrial dysfunction. Conjugated linoleic acid (CLA), a dietary supplement, has many biological functions. Limited information is available about the effect of CLA on AC-induced brain toxicity. Therefore, the present study aims to investigate the effect of CLA on mitochondrial oxidative stress, respiratory enzymes, krebs cycle enzymes and ATP levels in AC treated rat brain. Sprague Dawley male rats were given AC (5 mg/kg i.p.), CLA (200 mg/kg orally) and CLA with AC for six days per week for 30 days. Some oxidative stress parameters and mitochondrial enzymes such as manganese super oxide dismutase, glutathione peroxidase, NADP⁺-dependent isocitrate dehydrogenase (ICDH), alpha-ketoglutarate dehydrogenase (α-KGDH), malate dehydrogenase, reduced glutathione (GSH), lipid peroxidation (LP), protein carbonyl (PC), oxidative phosphorylation (OXPHOS) and tricarboxylic acid cycle (TCA) enzymes, and ATP levels were determined. AC significantly decreased the activities of GSH, antioxidant enzymes, OXPHOS enzymes (complex I and IV), TCA enzymes (ICDH and α-KGDH) and ATP levels. Significant increases were also observed in mitochondrial LP and PC levels in AC group. Co-treatment with AC + CLA improved oxidative stress and mitochondrial dysfunction caused by AC. As a result of our findings, it was observed that CLA was effective in improving oxidative stress and impaired mitochondrial functions in brain tissue by the effect of AC. Considering the association between neurodegenerative diseases and mitochondrial dysfunction, CLA can play a role in the prevention and therapy of neurodegenerative disorders.

N-acetylcysteine is more effective than ellagic acid in preventing acrolein induced dysfunction in mitochondria isolated from rat liver

Acrolein, a common environmental, food, and water pollutant, has been linked to the pathology of several diseases. This toxic substance is an unsaturated aldehyde and a major component of cigarette smoke and also produced during the processing of fat-containing foods. This study aimed to evaluate the protective effect of ellagic acid and N-acetylcysteine (NAC) in acrolein-induced toxicity in mitochondria isolated from the rat liver. The mitochondria were exposed to different concentrations of acrolein for 40 min, then functionality was assessed. Contact with acrolein rapidly and remarkably depleted the intracellular glutathione and antioxidant capacity, because of increased ROS production and lipid peroxidation which may lead to the cell death. Mitochondria were then pre-exposed to different concentrations of ellagic acid, NAC, and IC₅₀ concentration of acrolein. Consistent with the results, acrolein decreased GSH content and increased ROS level and lipid peroxidation, which led to ATP depletion and mitochondrial dysfunction. While ellagic acid has been able to reduce ROS and therefore the permeability of the mitochondrial membrane potential (MMP), presumably via its antioxidant properties, we've not detected its favorable effect on GSH and ATP restoration and also on mitochondrial complex II function. However, NAC strongly decreased ROS, lipid peroxidation and MMP and improved GSH content and complex II activity. These results showed that ellagic acid while reported to possess some cellular protective properties, did not prevent mitochondria from being affected by acrolein during this in vitro study. PRACTICAL APPLICATIONS: Ellagic acid is found in fruits, vegetables, and nuts which are revealed to possess strong antioxidant and protective properties. Mitochondrial dysfunction has been implicated in the pathogenesis of some chronic diseases including cancer, diabetes, liver disease, and neurodegenerative disorders, and presumably, ellagic acid by its mitochondrial protective effects can be helpful in these chronic conditions. Acrolein is an α,β-unsaturated aldehyde that can be produced during cooking at high temperature. By increasing the ROS level and lipid peroxidation and depleting the glutathione content, acrolein induces cellular damage and mitochondrial toxicity. This toxicant is taken into account as a carcinogen and mutagen. In this study, the protective effect of ellagic acid in comparison with N-acetylcysteine has been investigated during the toxicity of acrolein in the rat liver mitochondria to look for evidence of whether it is useful or not through this insult.

An Intensified Acrolein Exposure Can Affect Memory and Cognition in Rat

Acrolein is a clear, colorless liquid and a highly reactive α, β-unsaturated aldehyde. Acrolein, a byproduct and initiator of oxidative stress, has a major role in the pathogenesis of disorders including pulmonary, cardiovascular, atherosclerosis, and neurodegenerative diseases. Environmental or dietary exposure and endogenous production are common sources of acrolein. Widespread exposure to acrolein is a major risk for human health; therefore, we decided to investigate the neurological effects of acrolein. In this study, we used male Sprague-Dawley rats and exposed them orally to acrolein (0.5, 1, 3, and 5 mg/kg/day) for 90 days and investigated the neurobehavioral and electrophysiological disturbances. We also assessed the correlation between neurotoxicity and CSF concentration of acrolein in the rats. The results showed that chronic oral administration of acrolein at 5 mg/kg/day impaired learning and memory in the neurobehavioral tests. In addition, acrolein decreased the release of excitatory neurotransmitters such as glutamate in electrophysiological studies. Our data demonstrated that chronic oral exposure of acrolein at a dose of 5 mg/kg leads to a direct correlation between neurotoxicity and its CSF concentration. In conclusion, exposure to acrolein as a major pollutant in the environment may cause cognitive problems and may have serious neurocognitive effects on humans.

N-alkyl triphenylvinylpyridinium conjugated dihydroartemisinin perturbs mitochondrial functions resulting in enhanced cancer versus normal cell toxicity

Dihydroartemisinin (DHA) is an FDA-approved antimalarial drug that has been repurposed for cancer therapy because of its preferential antiproliferative effects on cancer versus normal cells. Mitochondria represent an attractive target for cancer therapy based on their regulatory role in proliferation and cell death. This study investigates whether DHA conjugated to innately fluorescent N-alkyl triphenylvinylpyridinium (TPVP) perturbs mitochondrial functions resulting in a differential toxicity of cancer versus normal cells. TPVP-DHA treatments resulted in a dose-dependent toxicity of human melanoma and pancreatic cancer cells, whereas normal human fibroblasts were resistant to this treatment. TPVP-DHA treatments resulted in a G₁-delay of the cancer cell cycle, which was also associated with a significant inhibition of the mTOR-metabolic and ERK1/2-proliferative signaling pathways. TPVP-DHA treatments perturbed mitochondrial functions, which correlated with increases in mitochondrial fission. In summary, TPVP mediated mitochondrial targeting of DHA enhanced cancer cell toxicity by perturbing mitochondrial functions and morphology.

Acrolein Aggravates Secondary Brain Injury After Intracerebral Hemorrhage Through Drp1-Mediated Mitochondrial Oxidative Damage in Mice

Clinical advances in the treatment of intracranial hemorrhage (ICH) are restricted by the incomplete understanding of the molecular mechanisms contributing to secondary brain injury. Acrolein is a highly active unsaturated aldehyde which has been implicated in many nervous system diseases. Our results indicated a significant increase in the level of acrolein after ICH in mouse brain. In primary neurons, acrolein induced an increase in mitochondrial fragmentation, loss of mitochondrial membrane potential, generation of reactive oxidative species, and release of mitochondrial cytochrome c. Mechanistically, acrolein facilitated the translocation of dynamin-related protein1 (Drp1) from the cytoplasm onto the mitochondrial membrane and led to excessive mitochondrial fission. Further studies found that treatment with hydralazine (an acrolein scavenger) significantly reversed Drp1 translocation and the morphological damage of mitochondria after ICH. In parallel, the neural apoptosis, brain edema, and neurological functional deficits induced by ICH were also remarkably alleviated. In conclusion, our results identify acrolein as an important contributor to the secondary brain injury following ICH. Meanwhile, we uncovered a novel mechanism by which Drp1-mediated mitochondrial oxidative damage is involved in acrolein-induced brain injury.

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.

Cyclophosphamide in Drosophila promotes genes and transposable elements differential expression and mitochondrial dysfunction

Cyclophosphamide (CPA) is an alkylating agent used for cancer chemotherapy, organ transplantation, and autoimmune disease treatment. Here, mRNA sequencing and high-resolution respirometry were performed to evaluate the alterations of Drosophila melanogaster gene expression fed with CPA under acute (0.1 mg/mL, for 24 h) and chronic (0.05 mg/mL, for 35 days) treatments. Differential expression analysis was performed using Cufflinks-Cuffdiff, DESeq2, and edgeR software. CPA affected genes are involved in several biological functions, including stress response and immune-related pathways, oxi-reduction and apoptotic processes, and cuticle and vitelline membrane formation. In particular, this is the first report of CPA-induced mitochondrial dysfunction caused by the downregulation of genes involved with mitochondria constituents. CPA treatment also changed the transcription pattern of transposable elements (TEs) from the gypsy and copia superfamilies. The results presented here provided evidence of CPA mitochondrial toxicity mechanisms and that CPA can modify TEs transcription in Drosophila flies.

Neuroprotective Effects of Baicalein on Acrolein-induced Neurotoxicity in the Nigrostriatal Dopaminergic System of Rat Brain

Elevated levels of acrolein, an α,β-unsaturated aldehyde are detected in the brain of patients with Parkinson's disease (PD). In the present study, the neuroprotective effect of baicalein (a phenolic flavonoid in the dried root of Scutellaria baicalensis Georgi) on acrolein-induced neurodegeneration of nigrostriatal dopaminergic system was investigated using local infusion of acrolein in the substantia nigra (SN) of rat brain. Systemic administration of baicalein (30 mg/kg, i.p.) significantly attenuated acrolein-induced elevations in 4-hydroxy-2-noneal (a product of lipid peroxidation), N-(3-formyl-3,4-dehydropiperidino)lysine (a biomarker of acrolein-conjugated proteins), and heme-oxygenase-1 levels (a redox-regulated protein) in the infused SN, indicating that baicalein inhibited acrolein-induced oxidative stress and protein conjugation. Furthermore, baicalein reduced acrolein-induced elevations in glial fibrillary acidic protein (a biomarker of activated astrocytes), ED-1 (a biomarker of activated microglia), and mature cathepsin B levels (a cysteine lysosomal protease), suggesting that baicalein attenuated acrolein-induced neuroinflammation. Moreover, baicalein attenuated acrolein-induced caspase 1 activation (a pro-inflammatory caspase) and interleukin-1β levels, indicating that baicalein prevented acrolein-induced inflammasome activation. In addition, baicalein significantly attenuated acrolein-induced caspase 3 activation (a biomarker of apoptosis) as well as acrolein-induced elevation in receptor interacting protein kinase (RIPK) 3 levels (an initiator of necroptosis), indicating that baicalein attenuated apoptosis and necroptosis. At the same time, baicalein mitigated acrolein-induced reduction in dopamine levels in the striatum ipsilateral to acrolein-infused SN. In conclusion, our data suggest that baicalein is neuroprotective via inhibiting oxidative stress, protein conjugation, and inflammation. Furthermore, baicalein prevents acrolein-induced program cell deaths, suggesting that baicalein is therapeutically useful for slowing PD progression.

A comprehensive overview of mitochondrial DNA 4977-bp deletion in cancer studies

Mitochondria are cellular machines essential for energy production. The biogenesis of mitochondria is a highly complex and it depends on the coordination of the nuclear and mitochondrial genome. Mitochondrial DNA (mtDNA) mutations and deletions are suspected to be associated with carcinogenesis. The most described mtDNA deletion in various human cancers is called the 4977-bp common deletion (mDNA⁴⁹⁷⁷) and it has been explored since two decades. In spite of that, its implication in carcinogenesis still unknown and its predictive and prognostic impact remains controversial. This review article provides an overview of some of the cellular and molecular mechanisms underlying mDNA⁴⁹⁷⁷ formation and a detailed summary about mDNA⁴⁹⁷⁷ reported in various types of cancers. The current knowledges of mDNA⁴⁹⁷⁷ as a prognostic and predictive marker are also discussed.

Response of DNA damage genes in acrolein-treated lung adenocarcinoma cells

Acrolein is a α-β-unsaturated aldehyde and is toxic to human upon its exposure from the environment. Sources of exposure to acrolein can be from heating cooking oil, automobile exhaust, tobacco smoke, and plastic waste. Acrolein exposure to lung is a major concern because of its volatile nature and due to its presence in the urban atmospheric air. Acrolein being highly reactive forms DNA and protein adducts, thereby making the cells vulnerable to long-term damage. Such long-term effect can lead to high susceptibility towards malignant transformation as has been reported in cigarette smokers. The response of DNA damaging genes by acrolein can perhaps give an insight to the cause of damage in the DNA by acrolein. The aim of this study was to examine the response of the DNA damage responsive genes by acrolein in A549 lung adenocarcinoma cells. Acrolein treatment at IC50 concentration showed a robust response of the DNA repair genes but eventually failed to rescue the cells from undergoing apoptosis. The cells pretreated with acrolein and followed by growing the same cells in fresh medium in the absence of acrolein did not help the cells to proliferate. These results conclude that exposure to acrolein marks long-lasting damage to DNA, irrespective of the DNA repair response.

Systemic Acrolein Elevations in Mice With Experimental Autoimmune Encephalomyelitis and Patients With Multiple Sclerosis

Demyelination and axonal injury are the key pathological processes in multiple sclerosis (MS), driven by inflammation and oxidative stress. Acrolein, a byproduct and instigator of oxidative stress, has been demonstrated as a neurotoxin in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. However, due to the invasive nature of acrolein detection using immunoblotting techniques, the investigation of acrolein in MS has been limited to animal models. Recently, detection of a specific acrolein-glutathione metabolite, 3-HPMA, has been demonstrated in urine, enabling the noninvasive quantification of acrolein for the first time in humans with neurological disorders. In this study, we have demonstrated similar elevated levels of acrolein in both urine (3-HPMA) and in spinal cord tissue (acrolein-lysine adduct) in mice with EAE, which can be reduced through systemic application of acrolein scavenger hydralazine. Furthermore, using this approach we have demonstrated an increase of 3-HPMA in both the urine and serum of MS patients relative to controls. It is expected that this noninvasive acrolein detection could facilitate the investigation of the role of acrolein in the pathology of MS in human. It may also be used to monitor putative therapies aimed at suppressing acrolein levels, reducing severity of symptoms, and slowing progression as previously demonstrated in animal studies.

Continuous Infusion of Phenelzine, Cyclosporine A, or Their Combination: Evaluation of Mitochondrial Bioenergetics, Oxidative Damage, and Cytoskeletal Degradation following Severe Controlled Cortical Impact Traumatic Brain Injury in Rats

To date, all monotherapy clinical traumatic brain injury (TBI) trials have failed, and there are currently no Food and Drug Administration (FDA)-approved pharmacotherapies for the acute treatment of severe TBI. Due to the complex secondary injury cascade following injury, there is a need to develop multi-mechanistic combinational neuroprotective approaches for the treatment of acute TBI. As central mediators of the TBI secondary injury cascade, both mitochondria and lipid peroxidation-derived aldehydes make promising therapeutic targets. Cyclosporine A (CsA), an FDA-approved immunosuppressant capable of inhibiting the mitochondrial permeability transition pore, and phenelzine (PZ), an FDA-approved monoamine oxidase inhibitor capable of scavenging neurotoxic lipid peroxidation-derived aldehydes, have both been shown to be partially neuroprotective following experimental TBI. Therefore, it follows that the combination of PZ and CsA may enhance neuroprotection over either agent alone through the combining of distinct but complementary mechanisms of action. Additionally, as the first 72 h represents a critical time period following injury, it follows that continuous drug infusion over the first 72 h following injury may also lead to optimal neuroprotective effects. This is the first study to examine the effects of a 72 h subcutaneous continuous infusion of PZ, CsA, and the combination of these two agents on mitochondrial respiration, mitochondrial bound 4-hydroxynonenal (4-HNE), and acrolein, and α-spectrin degradation 72 h following a severe controlled cortical impact injury in rats. Our results indicate that individually, both CsA and PZ are able to attenuate mitochondrial 4-HNE and acrolein, PZ is able to maintain mitochondrial respiratory control ratio and cytoskeletal integrity but together, PZ and CsA are unable to maintain neuroprotective effects.

Acrolein-mediated neuronal cell death and alpha-synuclein aggregation: Implications for Parkinson's disease

Growing evidence suggests that oxidative stress plays a critical role in neuronal destruction characteristic of Parkinson's disease (PD). However, the molecular mechanisms of oxidative stress-mediated dopaminergic cell death are far from clear. In the current investigation, we tested the hypothesis that acrolein, an oxidative stress and lipid peroxidation (LPO) product, is a key factor in the pathogenesis of PD. Using a combination of in vitro, in vivo, and cell free models, coupled with anatomical, functional, and behavioral examination, we found that acrolein was elevated in 6-OHDA-injected rats, and behavioral deficits associated with 6-OHDA could be mitigated by the application of the acrolein scavenger hydralazine, and mimicked by injection of acrolein in healthy rats. Furthermore, hydralazine alleviated neuronal cell death elicited by 6-OHDA and another PD-related toxin, rotenone, in vitro. We also show that acrolein can promote the aggregation of alpha-synuclein, suggesting that alpha-synuclein self-assembly, a key pathological phenomenon in human PD, could play a role in neurotoxic effects of acrolein in PD models. These studies suggest that acrolein is involved in the pathogenesis of PD, and the administration of anti-acrolein scavengers such as hydralazine could represent a novel strategy to alleviate tissue damage and motor deficits associated with this disease.

Idh2 Deficiency Exacerbates Acrolein-Induced Lung Injury through Mitochondrial Redox Environment Deterioration

Acrolein is known to be involved in acute lung injury and other pulmonary diseases. A number of studies have suggested that acrolein-induced toxic effects are associated with depletion of antioxidants, such as reduced glutathione and protein thiols, and production of reactive oxygen species. Mitochondrial NADP⁺-dependent isocitrate dehydrogenase (idh2) regulates mitochondrial redox balance and reduces oxidative stress-induced cell injury via generation of NADPH. Therefore, we evaluated the role of idh2 in acrolein-induced lung injury using idh2 short hairpin RNA- (shRNA-) transfected Lewis lung carcinoma (LLC) cells and idh2-deficient (idh2^-/- ) mice. Downregulation of idh2 expression increased susceptibility to acrolein via induction of apoptotic cell death due to elevated mitochondrial oxidative stress. Idh2 deficiency also promoted acrolein-induced lung injury in idh2 knockout mice through the disruption of mitochondrial redox status. In addition, acrolein-induced toxicity in idh2 shRNA-transfected LLC cells and in idh2 knockout mice was ameliorated by the antioxidant, N-acetylcysteine, through attenuation of oxidative stress resulting from idh2 deficiency. In conclusion, idh2 deficiency leads to mitochondrial redox environment deterioration, which causes acrolein-mediated apoptosis of LLC cells and acrolein-induced lung injury in idh2^-/- mice. The present study supports the central role of idh2 deficiency in inducing oxidative stress resulting from acrolein-induced disruption of mitochondrial redox status in the lung.

Cyclophosphamide leads to persistent deficits in physical performance and in vivo mitochondria function in a mouse model of chemotherapy late effects

Fatigue is the symptom most commonly reported by long-term cancer survivors and is increasingly recognized as related to skeletal muscle dysfunction. Traditional chemotherapeutic agents can cause acute toxicities including cardiac and skeletal myopathies. To investigate the mechanism by which chemotherapy may lead to persistent skeletal muscle dysfunction, mature adult mice were injected with a single cyclophosphamide dose and evaluated for 6 weeks. We found that exposed mice developed a persistent decrease in treadmill running time compared to baseline (25.7±10.6 vs. 49.0±16.8 min, P = 0.0012). Further, 6 weeks after drug exposure, in vivo parameters of mitochondrial function remained below baseline including maximum ATP production (482.1 ± 48.6 vs. 696.2 ± 76.6, P = 0.029) and phosphocreatine to ATP ratio (3.243 ± 0.1 vs. 3.878 ± 0.1, P = 0.004). Immunoblotting of homogenized muscles from treated animals demonstrated a transient increase in HNE adducts 1 week after exposure that resolved by 6 weeks. However, there was no evidence of an oxidative stress response as measured by quantitation of SOD1, SOD2, and catalase protein levels. Examination of mtDNA demonstrated that the mutation frequency remained comparable between control and treated groups. Interestingly, there was evidence of a transient increase in NF-ĸB p65 protein 1 day after drug exposure as compared to saline controls (0.091±0.017 vs. 0.053±0.022, P = 0.033). These data suggest that continued impairment in muscle and mitochondria function in cyclophosphamide-treated animals is not linked to persistent oxidative stress and that alternative mechanisms need to be considered.

Dimercaprol is an acrolein scavenger that mitigates acrolein-mediated PC-12 cells toxicity and reduces acrolein in rat following spinal cord injury

Acrolein is one of the most toxic byproducts of lipid peroxidation, and it has been shown to be associated with multiple pathological processes in trauma and diseases, including spinal cord injury, multiple sclerosis, and Alzheimer's disease. Therefore, suppressing acrolein using acrolein scavengers has been suggested as a novel strategy of neuroprotection. In an effort to identify effective acrolein scavengers, we have confirmed that dimercaprol, which possesses thiol functional groups, could bind and trap acrolein. We demonstrated the reaction between acrolein and dimercaprol in an abiotic condition by nuclear magnetic resonance spectroscopy. Specifically, dimercaprol is able to bind to both the carbon double bond and aldehyde group of acrolein. Its acrolein scavenging capability was further demonstrated by in vitro results that showed that dimercaprol could significantly protect PC-12 cells from acrolein-mediated cell death in a dose-dependent manner. Furthermore, dimercaprol, when applied systemically through intraperitoneal injection, could significantly reduce acrolein contents in spinal cord tissue following a spinal cord contusion injury in rats, a condition known to have elevated acrolein concentration. Taken together, dimercaprol may be an effective acrolein scavenger and a viable candidate for acrolein detoxification.

Acrolein acts as a neurotoxin in the nigrostriatal dopaminergic system of rat: involvement of α-synuclein aggregation and programmed cell death

Clinical studies report significant increases in acrolein (an α,β-unsaturated aldehyde) in the substantia nigra (SN) of patients with Parkinson’s disease (PD). In the present study, acrolein-induced neurotoxicity in the nigrostriatal dopaminergic system was investigated by local infusion of acrolein (15, 50, 150 nmoles/0.5 μl) in the SN of Sprague-Dawley rats. Acrolein-induced neurodegeneration of nigrostriatal dopaminergic system was delineated by reductions in tyrosine hydroxylase (TH) levels, dopamine transporter levels and TH-positive neurons in the infused SN as well as in striatal dopamine content. At the same time, apomorphine-induced turning behavior was evident in rats subjected to a unilateral infusion of acrolein in SN. Acrolein was pro-oxidative by increasing 4-hydroxy-2-nonenal and heme oxygenase-1 levels. Furthermore, acrolein conjugated with proteins at lysine residue and induced α-synuclein aggregation in the infused SN. Acrolein was pro-inflammatory by activating astrocytes and microglia. In addition, acrolein activated caspase 1 in the infused SN, suggesting acrolein-induced inflammasome formation. The neurotoxic mechanisms underlying acrolein-induced neurotoxicity involved programmed cell death, including apoptosis and necroptosis. Compared with well-known Parkinsonian neurotoxins, including 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and rotenone which do not exist in the SN of PD patients, our in vivo study shows that acrolein acts as a Parkinsonian neurotoxin in the nigrostriatal dopaminergic system of rat brain.

Hepatoprotective activity of white horehound (Marrubium vulgare) extract against cyclophosphamide toxicity in male rats

The hepatoprotective activity of Marrubium vulgare against cyclophosphamide toxicity in Wistar rats was evaluated. Adult male rats were divided into 4 groups of 6 each: a control group, a group injected with cyclophosphamide (150 mg·kg−1) for 3 days, a group orally given a M. vulgare aqueous extract ((500 mg of dry leaves)·kg−1·day−1) for 30 days then treated with cyclophosphamide, and a group receiving only M. vulgare for 30 days. After 33 days of treatment, activities of alanine amino transferase (ALAT), aspartate amino transferase (ASAT), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP) were determined in serum. Moreover, lipid peroxidation level and superoxide dismutase (SOD) activities, catalase (CAT) and glutathione peroxidase (GPx) were measured in liver. Alterations of these hepatic biomarkers and increased lipid peroxidation confirmed cyclophosphamide-induced liver toxicity. Cyclophosphamide also decreased the enzymatic defense system against oxidative stress. However, when this drug was administered in rats given M. vulgare extract, all the biological parameters underwent much less alteration. Administration of M. vulgare extract was found to be beneficial by attenuating cyclophosphamide-induced liver damage. The protective effect of the plant is mainly attributed to its antioxidant properties and the existence of phenolic acids and flavonoids, as highlighted by HPLC-based analysis.

Modulation of Hydrogen Peroxide-Induced Oxidative Stress in Human Neuronal Cells by Thymoquinone-Rich Fraction and Thymoquinone via Transcriptomic Regulation of Antioxidant and Apoptotic Signaling Genes

Nigella sativa Linn. (N. sativa) and its bioactive constituent Thymoquinone (TQ) have demonstrated numerous pharmacological attributes. In the present study, the neuroprotective properties of Thymoquinone-rich fraction (TQRF) and TQ against hydrogen peroxide- (H₂O₂-) induced neurotoxicity in differentiated human SH-SY5Y cells were investigated. TQRF was extracted using supercritical fluid extraction while TQ was acquired commercially, and their effects on H₂O₂ were evaluated using cell viability assay, reactive oxygen species (ROS) assay, morphological observation, and multiplex gene expression. Both TQRF and TQ protected the cells against H₂O₂ by preserving the mitochondrial metabolic enzymes, reducing intracellular ROS levels, preserving morphological architecture, and modulating the expression of genes related to antioxidants (SOD1, SOD2, and catalase) and signaling genes (p53, AKT1, ERK1/2, p38 MAPK, JNK, and NF-κβ). In conclusion, the enhanced efficacy of TQRF over TQ was likely due to the synergism of multiple constituents in TQRF. The efficacy of TQRF was better than that of TQ alone when equal concentrations of TQ in TQRF were compared. In addition, TQRF also showed comparable effects to TQ when the same concentrations were tested. These findings provide further support for the use of TQRF as an alternative to combat oxidative stress insults in neurodegenerative diseases.

Acrolein-mediated conduction loss is partially restored by K⁺ channel blockers

Acrolein-mediated myelin damage is thought to be a critical mechanism leading to conduction failure following neurotrauma and neurodegenerative diseases. The exposure and activation of juxtaparanodal voltage-gated K(+) channels due to myelin damage leads to conduction block, and K(+) channel blockers have long been studied as a means for restoring axonal conduction in spinal cord injury (SCI) and multiple sclerosis (MS). In this study, we have found that 100 μM K(+) channel blockers 4-aminopyridine-3-methanol (4-AP-3-MeOH), and to a lesser degree 4-aminopyridine (4-AP), can significantly restore compound action potential (CAP) conduction in spinal cord tissue following acrolein-mediated myelin damage using a well-established ex vivo SCI model. In addition, 4-AP-3-MeOH can effectively restore CAP conduction in acrolein-damaged axons with a range of concentrations from 0.1 to 100 μM. We have also shown that while both compounds at 100 μM showed no preference of small- and large-caliber axons when restoring CAP conduction, 4-AP-3-MeOH, unlike 4-AP, is able to augment CAP amplitude while causing little change in axonal responsiveness measured in refractory periods and response to repetitive stimuli. In a prior study, we show that 4-AP-3-MeOH was able to functionally rescue mechanically injured axons. In this investigation, we conclude that 4-AP-3-MeOH is an effective K(+) channel blocker in restoring axonal conduction following both primary (physical) and secondary (chemical) insults. These findings also suggest that 4-AP-3-MeOH is a viable alternative of 4-AP for treating myelin damage and improving function following central nervous system trauma and neurodegenerative diseases.

Structural and biochemical abnormalities in the absence of acute deficits in mild primary blast-induced head trauma

OBJECTIVE

Blast-induced neurotrauma (BINT), if not fatal, is nonetheless potentially crippling. It can produce a wide array of acute symptoms in moderate-to-severe exposures, but mild BINT (mBINT) is characterized by the distinct absence of acute clinical abnormalities. The lack of observable indications for mBINT is particularly alarming, as these injuries have been linked to severe long-term psychiatric and degenerative neurological dysfunction. Although the long-term sequelae of BINT are extensively documented, the underlying mechanisms of injury remain poorly understood, impeding the development of diagnostic and treatment strategies. The primary goal of this research was to recapitulate primary mBINT in rodents in order to facilitate well-controlled, long-term investigations of blast-induced pathological neurological sequelae and identify potential mechanisms by which ongoing damage may occur postinjury.

METHODS

A validated, open-ended shock tube model was used to deliver blast overpressure (150 kPa) to anesthetized rats with body shielding and head fixation, simulating the protective effects of military-grade body armor and isolating a shock wave injury from confounding systemic injury responses, head acceleration, and other elements of explosive events. Evans Blue-labeled albumin was used to visualize blood-brain barrier (BBB) compromise at 4 hours postinjury. Iba1 staining was used to visualize activated microglia and infiltrating macrophages in areas of peak BBB compromise. Acrolein, a potent posttraumatic neurotoxin, was quantified in brain tissue by immunoblotting and in urine through liquid chromatography with tandem mass spectrometry at 1, 2, 3, and 5 days postinjury. Locomotor behavior, motor performance, and short-term memory were assessed with open field, rotarod, and novel object recognition (NOR) paradigms at 24 and 48 hours after the blast.

RESULTS

Average speed, maximum speed, and distance traveled in an open-field exploration paradigm did not show significant differences in performance between sham-injured and mBINT rats. Likewise, rats with mBINT did not exhibit deficits in maximum revolutions per minute or total run time in a rotarod paradigm. Short-term memory was also unaffected by mBINT in an NOR paradigm. Despite lacking observable motor or cognitive deficits in the acute term, blast-injured rats displayed brain acrolein levels that were significantly elevated for at least 5 days, and acrolein's glutathione-reduced metabolite, 3-HPMA, was present in urine for 2 days after injury. Additionally, mBINT brain tissue demonstrated BBB damage 4 hours postinjury and colocalized neuroinflammatory changes 24 hours postinjury.

CONCLUSIONS

This model highlights mBINT's potential for underlying detrimental physical and biochemical alterations despite the lack of apparent acute symptoms and, by recapitulating the human condition, represents an avenue for further examining the pathophysiology of mBINT. The sustained upregulation of acrolein for days after injury suggests that acrolein may be an upstream player potentiating ongoing postinjury damage and neuroinflammation. Ultimately, continued research with this model may lead to diagnostic and treatment mechanisms capable of preventing or reducing the severity of long-term neurological dysfunction following mBINT.

Enhancement of the acrolein-induced production of reactive oxygen species and lung injury by GADD34

Chronic obstructive pulmonary disease (COPD) is characterized by lung destruction and inflammation. As a major compound of cigarette smoke, acrolein plays a critical role in the induction of respiratory diseases. GADD34 is known as a growth arrest and DNA damage-related gene, which can be overexpressed in adverse environmental conditions. Here we investigated the effects of GADD34 on acrolein-induced lung injury. The intranasal exposure of acrolein induced the expression of GADD34, developing the pulmonary damage with inflammation and increase of reactive oxygen species (ROS). Conversely, the integrality of pulmonary structure was preserved and the generation of ROS was reduced in GADD34-knockout mice. Acrolein-induced phosphorylation of eIF2α in GADD34-knockout epithelial cells by shRNA protected cell death by reducing misfolded protein-caused oxidative stress. These data indicate that GADD34 participates in the development of acrolein-induced lung injury.

Investigation by microarray analysis of effects of cigarette design characteristics on gene expression in human lung mucoepidermoid cancer cells NCI-H292 exposed to cigarette smoke

The effects of tobacco leaf types and the presence or absence of charcoal in the cigarette filters on gene expression were investigated using cigarette prototypes made of either flue-cured (FC) leaf or burley (BLY) leaf and Kentucky Reference 2R4F as a representative blend cigarette with cellulose acetate filters or charcoal filters. NCI-H292, human lung mucoepidermoid carcinoma cell line, was exposed to the total particulate matter (TPM) and gas/vapor phase (GVP) from each prototype for 8h and then the changes in gene expression from microarray data were analyzed. A number of genes associated with oxidative stress, inflammation, DNA damage and xenobiotic response were modified by the two fractions, TPM and GVP, from the three prototypes with cellulose acetate filters. Both TPM and GVP fractions strongly enhanced the gene expression of HMOX1, which is encoding the limiting enzyme in heme degradation and a key regulator of oxidative stress and inflammatory process. Comparing the effects of TPM and GVP fraction, TPM strongly activated Nrf2 pathway-mediated anti-oxidative stress reaction, whereas GVP caused notable DNA damage response. In comparison of FC and BLY, TPM from FC more strongly induced the expression of histone family proteins than that from BLY. GVP from FC markedly induced gene expression associated with HSP70-mediated inflammation relative to that from BLY. Charcoal included in the filter strongly reduced the effects of GVP from each cigarette on gene expression. However, charcoal did not modified the effects of TPM. As a whole, charcoal is a useful material for reducing the biological effects of GVP.

Mechanistic basis for protection of differentiated SH-SY5Y cells by oryzanol-rich fraction against hydrogen peroxide-induced neurotoxicity

BACKGROUND

Apoptosis is often the end result of oxidative damage to neurons. Due to shared pathways between oxidative stress, apoptosis and antioxidant defence systems, an oxidative insult could end up causing cellular apoptosis or survival depending on the severity of the insult and cellular responses. Plant bioresources have received close attention in recent years for their potential role in regulating the pathways involved in apoptosis and oxidative stress in favour of cell survival. Rice bran is a bioactive-rich by-product of rice milling process. It possesses antioxidant properties, making it a promising source of antioxidants that could potentially prevent oxidative stress-induced neurodegenerative diseases.

METHODS

Thus, the present study investigated the neuroprotective properties of oryzanol-rich fraction (ORF) against hydrogen peroxide (H2O2)-induced neurotoxicity in differentiated human neuroblastoma SH-SY5Y cells. ORF was extracted from rice bran using a green technology platform, supercritical fluid extraction system. Furthermore, its effects on cell viability, morphological changes, cell cycle, and apoptosis were evaluated. The underlying transcriptomic changes involved in regulation of oxidative stress, apoptosis and antioxidant defence systems were equally studied.

RESULTS

ORF protected differentiated SH-SY5Y cells against H2O2-induced neurotoxicity through preserving the mitochondrial metabolic enzyme activities, thus reducing apoptosis. The mechanistic basis for the neuroprotective effects of ORF included upregulation of antioxidant genes (catalase, SOD 1 and SOD 2), downregulation of pro-apoptotic genes (JNK, TNF, ING3, BAK1, BAX, p21 and caspase-9), and upregulation of anti-apoptotic genes (ERK1/2, AKT1 and NF-Kβ).

CONCLUSION

These findings suggest ORF may be an effective antioxidant that could prevent oxidative stress-induced neurodegenerative disorders.

Acute systemic accumulation of acrolein in mice by inhalation at a concentration similar to that in cigarette smoke

Cigarette smoke is an important environmental factor associated with a wide array of public health concerns. Acrolein, a component of tobacco smoke and a known toxin to various cell types, may be a key pathological factor mediating the adverse effects linked with tobacco smoke. Although acrolein is known to accumulate in the respiratory system after acute nasal exposure, it is not clear if it accumulates systemically, and less is known in the nervous system. The aim of this study was to assess the degree of acrolein accumulation in the circulation and in the spinal cord following acute acrolein inhalation in mice. Using a laboratory-fabricated inhalation chamber, we found elevated urinary 3-HPMA, an acrolein metabolite, and increased acrolein adducts in the spinal cord after weeks of nasal exposure to acrolein at a concentration similar to that in tobacco smoke. The data indicated that acrolein is absorbed into the circulatory system and some enters the nervous system. It is expected that these findings may facilitate further studies to probe the pathological role of acrolein in the nervous system resulting from smoke and other external sources.

Lithium prevents acrolein-induced neurotoxicity in HT22 mouse hippocampal cells

Acrolein is a highly electrophilic alpha, beta-unsaturated aldehyde to which humans are exposed in many situations and has been implicated in neurodegenerative diseases, such as Alzheimer's disease. Lithium is demonstrated to have neuroprotective and neurotrophic effects in brain ischemia, trauma, neurodegenerative disorders, and psychiatric disorders. Previously we have found that acrolein induced neuronal death in HT22 mouse hippocampal cells. In this study, the effects of lithium on the acrolein-induced neurotoxicity in HT22 cells as well as its mechanism(s) were investigated. We found that lithium protected HT22 cells against acrolein-induced damage by the attenuation of reactive oxygen species and the enhancement of the glutathione level. Lithium also attenuated the mitochondrial dysfunction caused by acrolein. Furthermore, lithium significantly increased the level of phospho-glycogen synthase kinase-3 beta (GSK-3β), the non-activated GSK-3β. Taken together, our findings suggest that lithium is a protective agent for acrolein-related neurotoxicity.

Neuroprotective role of hydralazine in rat spinal cord injury-attenuation of acrolein-mediated damage

Acrolein, an α,β-unsaturated aldehyde and a reactive product of lipid peroxidation, has been suggested as a key factor in neural post-traumatic secondary injury in spinal cord injury (SCI), mainly based on in vitro and ex vivo evidence. Here, we demonstrate an increase of acrolein up to 300%; the elevation lasted at least 2 weeks in a rat SCI model. More importantly, hydralazine, a known acrolein scavenger can provide neuroprotection when applied systemically. Besides effectively reducing acrolein, hydralazine treatment also resulted in significant amelioration of tissue damage, motor deficits, and neuropathic pain. This effect was further supported by demonstrating the ability of hydralazine to reach spinal cord tissue at a therapeutic level following intraperitoneal application. This suggests that hydralazine is an effective neuroprotective agent not only in vitro, but in a live animal model of SCI as well. Finally, the role of acrolein in SCI was further validated by the fact that acrolein injection into the spinal cord caused significant SCI-like tissue damage and motor deficits. Taken together, available evidence strongly suggests a critical causal role of acrolein in the pathogenesis of spinal cord trauma. Since acrolein has been linked to a variety of illness and conditions, we believe that acrolein-scavenging measures have the potential to be expanded significantly ensuring a broad impact on human health.

Aldose reductase regulates acrolein-induced cytotoxicity in human small airway epithelial cells

Aldose reductase (AR), a glucose-metabolizing enzyme, reduces lipid aldehydes and their glutathione conjugates with more than 1000-fold efficiency (Km aldehydes 5-30 µM) relative to glucose. Acrolein, a major endogenous lipid peroxidation product as well as a component of environmental pollutants and cigarette smoke, is known to be involved in various pathologies including atherosclerosis, airway inflammation, COPD, and age-related disorders, but the mechanism of acrolein-induced cytotoxicity is not clearly understood. We have investigated the role of AR in acrolein-induced cytotoxicity in primary human small airway epithelial cells (SAECs). Exposure of SAECs to varying concentrations of acrolein caused cell death in a concentration- and time-dependent manner. AR inhibition by fidarestat prevented the low-dose (5-10 µM) but not the high-dose (>10 µM) acrolein-induced SAEC death. AR inhibition protected SAECs from low-dose (5 µM) acrolein-induced cellular reactive oxygen species (ROS). Inhibition of acrolein-induced apoptosis by fidarestat was confirmed by decreased condensation of nuclear chromatin, DNA fragmentation, comet tail moment, and annexin V fluorescence. Further, fidarestat inhibited acrolein-induced translocation of the proapoptotic proteins Bax and Bad from the cytosol to the mitochondria and that of Bcl2 and BclXL from the mitochondria to the cytosol. Acrolein-induced cytochrome c release from mitochondria was also prevented by AR inhibition. The mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinases 1 and 2, stress-activated protein kinase/c-Jun NH2-terminal kinase, and p38MAPK, and c-Jun were transiently activated in airway epithelial cells by acrolein in a concentration- and time-dependent fashion, which was significantly prevented by AR inhibition. These results suggest that AR inhibitors could prevent acrolein-induced cytotoxicity in the lung epithelial cells.

Determination of urine 3-HPMA, a stable acrolein metabolite in a rat model of spinal cord injury

Acrolein has been suggested to be involved in a variety of pathological conditions. The monitoring of acrolein is of significant importance in delineating the pathogenesis of various diseases. Aimed at overcoming the reactivity and volatility of acrolein, we describe a specific and stable metabolite of acrolein in urine, N-acetyl-S-3-hydroxypropylcysteine (3-HPMA), as a potential surrogate marker for acrolein quantification. Using the LC/MS/MS method, we demonstrated that 3-HPMA was significantly elevated in a dose-dependent manner when acrolein was injected into rats IP or directly into the spinal cord, but not when acrolein scavengers were co-incubated with acrolein solution. A nonlinear mathematic relationship is established between acrolein injected directly into the spinal cord and a correlated dose-dependent increase of 3-HPMA, suggesting the increase of 3-HPMA becomes less apparent as the level of injected acrolein increases. The elevation of 3-HPMA was further detected in the rat spinal cord injury, a pathological condition known to be associated with elevated endogenous acrolein. This finding was further validated by concomitant confirmation of increased acrolein-lysine adducts using established dot immunoblotting techniques. The noninvasive nature of measuring 3-HPMA concentrations in urine allows for long-term monitoring of acrolein in the same animal and ultimately in human clinical studies. Due to wide spread involvement of acrolein in human health, the benefits of this study have the potential to enhance human health significantly.

Proteomic analysis of rat cerebral cortex following subchronic acrolein toxicity

Acrolein, a member of reactive α,β-unsaturated aldehydes, is a major environmental pollutant. Acrolein is also produced endogenously as a toxic by-product of lipid peroxidation. Because of high reactivity, acrolein may mediate oxidative damages to cells and tissues. It has been shown to be involved in a wide variety of pathological states including pulmonary, atherosclerosis and neurodegenerative diseases. In this study we employed proteomics approach to investigate the effects of subchronic oral exposures to 3mg/kg of acrolein on protein expression profile in the brain of rats. Moreover effects of acrolein on malondialdehyde (MDA) levels and reduced glutathione (GSH) content were investigated. Our results revealed that treatment with acrolein changed levels of several proteins in diverse physiological process including energy metabolism, cell communication and transport, response to stimulus and metabolic process. Interestingly, several differentially over-expressed proteins, including β-synuclein, enolase and calcineurin, are known to be associated with human neurodegenerative diseases. Changes in the levels of some proteins were confirmed by Western blot. Moreover, acrolein increases the level of MDA, as a lipid peroxidation biomarker and decreased GSH concentrations, as a non-enzyme antioxidant in the brain of acrolein treated rats. These findings suggested that acrolein induces the oxidative stress and lipid peroxidation in the brain, and so that may contribute to the pathophysiology of neurological disorders.

Magnolol protects against oxidative stress-mediated neural cell damage by modulating mitochondrial dysfunction and PI3K/Akt signaling

Magnolol, an orally available compound from Magnolia officinalis used widely in traditional herbal medicine against a variety of neuronal diseases, possesses potent antioxidant properties and protects the brain against oxidative damage. The aim of the work is to examine the protective mechanisms of magnolol on human neuroblastoma SH-SY5Y cells against apoptosis induced by the neurotoxin acrolein, which can cause neurodegenerative disorders by inducing oxidative stress. By investigating the effect of magnolol on neural cell damage induced by the neurotoxin acrolein, we found that magnolol pretreatment significantly attenuated acrolein-induced oxidative stress through inhibiting reactive oxygen species accumulation caused by intracellular glutathione depletion and nicotinamide adenine dinucleotide phosphate oxidase activation. We next examined the signaling cascade(s) involved in magnolol-mediated antiapoptotic effects. The results showed that acrolein induced SH-SY5Y cell apoptosis by activating mitochondria/caspase and MEK/ERK signaling pathways. Our findings provide the first evidence that magnolol protects SH-SY5Y cells against acrolein-induced oxidative stress and prolongs SH-SY5Y cell survival through regulating JNK/mitochondria/caspase, PI3K/MEK/ERK, and PI3K/Akt/FoxO1 signaling pathways.

Acrolein cytotoxicity in hepatocytes involves endoplasmic reticulum stress, mitochondrial dysfunction and oxidative stress

Acrolein is a common environmental, food and water pollutant and a major component of cigarette smoke. Also, it is produced endogenously via lipid peroxidation and cellular metabolism of certain amino acids and drugs. Acrolein is cytotoxic to many cell types including hepatocytes; however the mechanisms are not fully understood. We examined the molecular mechanisms underlying acrolein hepatotoxicity in primary human hepatocytes and hepatoma cells. Acrolein, at pathophysiological concentrations, caused a dose-dependent loss of viability of hepatocytes. The death was apoptotic at moderate and necrotic at high concentrations of acrolein. Acrolein exposure rapidly and dramatically decreased intracellular glutathione and overall antioxidant capacity, and activated the stress-signaling MAP-kinases JNK, p42/44 and p38. Our data demonstrate for the first time in human hepatocytes, that acrolein triggered endoplasmic reticulum (ER) stress and activated eIF2α, ATF-3 and -4, and Gadd153/CHOP, resulting in cell death. Notably, the protective/adaptive component of ER stress was not activated, and acrolein failed to up-regulate the protective ER-chaperones, GRP78 and GRP94. Additionally, exposure to acrolein disrupted mitochondrial integrity/function, and led to the release of pro-apoptotic proteins and ATP depletion. Acrolein-induced cell death was attenuated by N-acetyl cysteine, phenyl-butyric acid, and caspase and JNK inhibitors. Our data demonstrate that exposure to acrolein induces a variety of stress responses in hepatocytes, including GSH depletion, oxidative stress, mitochondrial dysfunction and ER stress (without ER-protective responses) which together contribute to acrolein toxicity. Our study defines basic mechanisms underlying liver injury caused by reactive aldehyde pollutants such as acrolein.