Brain infarction correlates more closely with acrolein than with reactive oxygen species

Measurement of acrolein concentrations in postmortem specimens as an indicator for stroke diagnosis

Acrolein, a polyamine produced from spermine during brain infarction, has recently been used in clinical settings for brain infarction risk assessment. However, few studies have investigated the diagnostic usefulness of acrolein measurement in postmortem specimens. In this study, we measured the acrolein concentration in postmortem specimens to assess its potential as a marker for stroke diagnosis. Acrolein concentrations in the serum and urine were measured using an enzyme-linked immunosorbent assay in 25, 19, 21, and 93 brain infarction, subarachnoid hemorrhage, cerebral hemorrhage, and control cases, respectively. No correlations or significant differences were observed between the acrolein concentrations in blood or urine, age, time since death, or sex. However, the serum acrolein concentrations increased significantly in cases of brain infarction, subarachnoid hemorrhage, and cerebral hemorrhage compared with non-stroke cases, with diagnostic cutoff values of 117.1, 119.9, and 130.3 nmol/mL, respectively. Conversely, the urinary acrolein concentrations decreased in specimens from subarachnoid hemorrhage and cerebral hemorrhage cases, suggesting dilution due to higher urine volumes. In conclusion, our findings suggest that serum acrolein concentration remains unaffected by the time elapsed after death. Moreover, the measurement of serum acrolein in postmortem specimens is effective in diagnosing stroke.

NF-E2-related factor 1 suppresses the expression of a spermine oxidase and the production of highly reactive acrolein

Polyamines (putrescine, spermidine, and spermine) are among the most abundant intracellular small molecular metabolites, with concentrations at the mM level. The ratios of these three molecules remain constant under physiological conditions. Stress (i.e. polyamine overload, oxidative stress, aging, infection, etc.) triggers the catabolic conversion of spermine to spermidine, ultimately yielding acrolein and hydrogen peroxide. The potential of acrolein to induce DNA damage and protein denaturation is 1,000 times greater than that of reactive oxygen species. We have shown that these polyamine metabolic pathways also involve the nuclear factor erythroid-2-related factor 1 (NRF1) transcription factor. In our chemically-inducible, liver-specific Nrf1-knockout mice, the polyamine catabolic pathway dominated the anabolic pathway, producing free acrolein and accumulating acrolein-conjugated proteins in vivo. This metabolic feature implicates SMOX as an important causative enzyme. Chromatin immunoprecipitation and reporter assays confirmed that NRF1 directly suppressed Smox expression. This effect was also observed in vitro. Ectopic overexpression of SMOX increased the accumulation of free acrolein and acrolein-conjugated proteins. SMOX knockdown reversed the accumulation of free acrolein and acrolein-conjugated proteins. Our results show that NRF1 typically suppresses Smox expression when NRF1 is downregulated, SMOX is upregulated, and polyamine metabolic pathways are altered, producing low molecular weight polyamines and acrolein.

SMOX Inhibition Preserved Visual Acuity, Contrast Sensitivity, and Retinal Function and Reduced Neuro-Glial Injury in Mice During Prolonged Diabetes

Diabetic retinopathy, a major cause of vision loss, is characterized by neurovascular changes in the retina. The lack of effective treatments to preserve vision in diabetic patients remains a significant challenge. A previous study from our laboratory demonstrated that 12-week treatment with MDL 72527, a pharmacological inhibitor of spermine oxidase (SMOX, a critical regulator of polyamine metabolism), reduced neurodegeneration in diabetic mice. Utilizing the streptozotocin-induced diabetic mouse model and MDL 72527, the current study investigated the effectiveness of SMOX inhibition on the measures of vision impairment and neuro-glial injury following 24 weeks of diabetes. Reductions in visual acuity, contrast sensitivity, and inner retinal function in diabetic mice were improved by MDL 72527 treatment. Diabetes-induced changes in neuronal-specific class III tubulin (Tuj-1), synaptophysin, glutamine synthetase, and vimentin were attenuated in response to SMOX inhibition. In conclusion, our findings show that SMOX inhibition improved visual acuity, contrast sensitivity, and inner retinal function and mitigated diabetes-induced neuroglial damage during long-term diabetes. Targeting SMOX signaling may provide a potential strategy for reducing retinal neuronal damage and preserving vision in diabetes.

Deep Resequencing of the 1q22 Locus in Non-Lobar Intracerebral Hemorrhage

OBJECTIVE

Genome-wide association studies have identified 1q22 as a susceptibility locus for cerebral small vessel diseases, including non-lobar intracerebral hemorrhage (ICH) and lacunar stroke. In the present study, we performed targeted high-depth sequencing of 1q22 in ICH cases and controls to further characterize this locus and prioritize potential causal mechanisms, which remain unknown.

METHODS

A total of 95,000 base pairs spanning 1q22, including SEMA4A, SLC25A44, and PMF1/PMF1-BGLAP were sequenced in 1,055 spontaneous ICH cases (534 lobar and 521 non-lobar) and 1,078 controls. Firth regression and Rare Variant Influential Filtering Tool analysis were used to analyze common and rare variants, respectively. Chromatin interaction analyses were performed using Hi-C, chromatin immunoprecipitation followed by sequencing, and chromatin interaction analysis with paired-end tag databases. Multivariable Mendelian randomization assessed whether alterations in gene-specific expression relative to regionally co-expressed genes at 1q22 could be causally related to ICH risk.

RESULTS

Common and rare variant analyses prioritized variants in SEMA4A 5'-UTR and PMF1 intronic regions, overlapping with active promoter and enhancer regions based on ENCODE annotation. Hi-C data analysis determined that 1q22 is spatially organized in a single chromatin loop, and that the genes therein belong to the same topologically associating domain. Chromatin immunoprecipitation followed by sequencing and chromatin interaction analysis with paired-end tag data analysis highlighted the presence of long-range interactions between the SEMA4A-promoter and PMF1-enhancer regions prioritized by association testing. Multivariable Mendelian randomization analyses demonstrated that PMF1 overexpression could be causally related to non-lobar ICH risk.

INTERPRETATION

Altered promoter-enhancer interactions leading to PMF1 overexpression, potentially dysregulating polyamine catabolism, could explain demonstrated associations with non-lobar ICH risk at 1q22, offering a potential new target for prevention of ICH and cerebral small vessel disease. ANN NEUROL 2024;95:325-337.

Deep resequencing of the 1q22 locus in non-lobar intracerebral hemorrhage

Objective

Genome-wide association studies have identified 1q22 as a susceptibility locus for cerebral small vessel diseases (CSVDs), including non-lobar intracerebral hemorrhage (ICH) and lacunar stroke. In the present study we performed targeted high-depth sequencing of 1q22 in ICH cases and controls to further characterize this locus and prioritize potential causal mechanisms, which remain unknown.

Methods

95,000 base pairs spanning 1q22 , including SEMA4A, SLC25A44 and PMF1 / PMF1-BGLAP were sequenced in 1,055 spontaneous ICH cases (534 lobar and 521 non-lobar) and 1,078 controls. Firth regression and RIFT analysis were used to analyze common and rare variants, respectively. Chromatin interaction analyses were performed using Hi-C, ChIP-Seq and ChIA-PET databases. Multivariable Mendelian randomization (MVMR) assessed whether alterations in gene-specific expression relative to regionally co-expressed genes at 1q22 could be causally related to ICH risk.

Results

Common and rare variant analyses prioritized variants in SEMA4A 5'-UTR and PMF1 intronic regions, overlapping with active promoter and enhancer regions based on ENCODE annotation. Hi-C data analysis determined that 1q22 is spatially organized in a single chromatin loop and that the genes therein belong to the same Topologically Associating Domain. ChIP-Seq and ChIA-PET data analysis highlighted the presence of long-range interactions between the SEMA4A -promoter and PMF1 -enhancer regions prioritized by association testing. MVMR analyses demonstrated that PMF1 overexpression could be causally related to non-lobar ICH risk.

Interpretation

Altered promoter-enhancer interactions leading to PMF1 overexpression, potentially dysregulating polyamine catabolism, could explain demonstrated associations with non-lobar ICH risk at 1q22 , offering a potential new target for prevention of ICH and CSVD.

Molecular Characteristics of Toxicity of Acrolein Produced from Spermine

Acrolein (CH₂=CH-CHO), an unsaturated aldehyde produced from spermine, is one of the major contributors to oxidative stress. Acrolein has been found to be more toxic than reactive oxygen species (H₂O₂ and •OH), and it can be easily conjugated with proteins, bringing about changes in nature of the proteins. Acrolein is detoxified by glutathione in cells and was found to be mainly produced from spermine through isolating two cell lines of acrolein-resistant Neuro2a cells. The molecular characteristics of acrolein toxicity and tissue damage elicited by acrolein were investigated. It was found that glyceraldehyde-3-phosphate dehydrogenase (GAPDH); cytoskeleton proteins such as vimentin, actin, α- and β-tubulin proteins; and apolipoprotein B-100 (ApoB100) in LDL are strongly damaged by acrolein conjugation. In contrast, activities of matrix metalloproteinase-9 (MMP-9) and proheparanase (proHPSE) are enhanced, and antibody-recognizing abilities of immunoglobulins are modified by acrolein conjugation, resulting in aggravation of diseases. The functional changes of these proteins by acrolein have been elucidated at the molecular level. The findings confirmed that acrolein is the major contributor causing tissue damage in the elderly.

Urinary Amino Acid-Conjugated Acrolein and Taurine as New Biomarkers for Detection of Dementia

BACKGROUND

Dementia, including Alzheimer's disease (AD), is one of the serious diseases at advanced age, and its early detection is important for maintaining quality of life (QOL).

OBJECTIVE

In this study, we sought novel biomarkers for dementia in urine.

METHODS

Samples of urine were collected from 57 control subjects without dementia, 62 mild cognitive impairment (MCI) patients, and 42 AD patients. Mini-Mental State Examination (MMSE) was evaluated when subjects were examined by medical doctors. Urinary amino acid (lysine)-conjugated acrolein (AC-Acro) was measured using N ɛ-(3-formyl-3, 4-dehydropiperidine) lysine (FDP-Lys) ELISA kit, and taurine content was measured using a taurine assay kit. Values were normalized by creatinine content which was measured with the colorimetric assay kit.

RESULTS

We found that urinary amino acid (lysine)-conjugated acrolein (AC-Acro) and taurine negatively correlated with MMSE score and are significantly lower in dementia patients compared to the normal subjects. When AC-Acro and taurine were evaluated together with age using an artificial neural network model, median relative risk values for subjects with AD, subjects with mild cognitive impairment, and control subjects were 0.96, 0.53, and 0.06, respectively.

CONCLUSION

Since urine is relatively easy to collect, our findings provide a novel biomarker for dementia without invasiveness.

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.

Serum Spermidine in Relation to Risk of Stroke: A Multilevel Study

The relationship between serum spermidine levels and future cardiovascular disease risk has not yet been well elucidated in the general population based on community studies. Using a nested case-control study, we estimated the association between serum spermidine level and future stroke. New stroke cases had higher baseline levels of spermidine than controls [182.8 (141.8–231.5) vs. 152.0 (124.3–193.0), P < 0.001]. After multivariable adjustment, individuals with spermidine ≥ 205.9 nmol/L (T3) higher risks of stroke (HR 5.02, 95% CI 1.58–16.02) with the lowest quartile (< 136.9 nmol/L) as reference. The association between serum spermidine levels and risk of stroke seemed to be consistent and was reproducible in our cross-sectional studies. In addition, comparisons of the areas under receiver operator characteristics curves confirmed that a model including spermidine had better discrimination than without (0.755 vs. 0.715, P = 0.04). Here we report a close relationship exists between serum spermidine levels and risk of stroke.

Unique Chemistry, Intake, and Metabolism of Polyamines in the Central Nervous System (CNS) and Its Body

Polyamines (PAs) are small, versatile molecules with two or more nitrogen-containing positively charged groups and provide widespread biological functions. Most of these aspects are well known and covered by quite a number of excellent surveys. Here, the present review includes novel aspects and questions: (1) It summarizes the role of most natural and some important synthetic PAs. (2) It depicts PA uptake from nutrition and bacterial production in the intestinal system following loss of PAs via defecation. (3) It highlights the discrepancy between the high concentrations of PAs in the gut lumen and their low concentration in the blood plasma and cerebrospinal fluid, while concentrations in cellular cytoplasm are much higher. (4) The present review provides a novel and complete scheme for the biosynthesis of Pas, including glycine, glutamate, proline and others as PA precursors, and provides a hypothesis that the agmatine pathway may rescue putrescine production when ODC knockout seems to be lethal (solving the apparent contradiction in the literature). (5) It summarizes novel data on PA transport in brain glial cells explaining why these cells but not neurons preferentially accumulate PAs. (6) Finally, it provides a novel and complete scheme for PA interconversion, including hypusine, putreanine, and GABA (unique gliotransmitter) as end-products. Altogether, this review can serve as an updated contribution to understanding the PA mystery.

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

A new nitronyl nitroxide radical with salicylic acid framework attenuates blood-brain barrier disruption and oxidative stress in a rat model of middle cerebral artery occlusion

OBJECTIVES

A new nitronyl nitroxide radical with a salicylic acid framework (SANR) has been demonstrated to exert antioxidant effects in the previous study by our team. The current study has assessed the protective effect of SANR on cerebral ischemia and reperfusion (I/R) in rat models.

METHODS

Sprague-Dawley rats were randomly divided into four groups: sham, I/R, 10, and 20 mg/kg SANR + I/R groups. A total of 120 min of middle cerebral artery occlusion (MCAO) caused cerebral ischemia. Survival rates were calculated, and neurological deficits were evaluated by a blinded experimenter. Cerebral infarct area, apoptosis cells, and blood-brain barrier (BBB) leakage were measured by 2,3,5-triphenyltetrazolium chloride staining, terminal deoxynucleotidyl transferase dUTP nick-end labeling, and Evans blue assay, respectively. Reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and 8-hydroxy-2-deoxyguanosine (8-OHdG) also were detected to assess oxidation damage caused by cerebral I/R.

RESULTS

Treatment with SANR significantly promoted survival of rats with cerebral I/R injury. SANR meliorated neurologic deficit and infarct area, improved BBB permeability, and reduced neuronal apoptosis. SANR also reduced ROS levels and the content of MDA and increased SOD and GSH-Px activity in a dose-dependent manner. Furthermore, SANR could inhibit the expression of 8-OHdG.

CONCLUSION

Our results suggested that SANR has a neuroprotective effect against cerebral I/R injury, and its effect mechanism is related to the antioxidant function.

Transgenic Mouse Overexpressing Spermine Oxidase in Cerebrocortical Neurons: Astrocyte Dysfunction and Susceptibility to Epileptic Seizures

Polyamines are organic polycations ubiquitously present in living cells. Polyamines are involved in many cellular processes, and their content in mammalian cells is tightly controlled. Among their function, these molecules modulate the activity of several ion channels. Spermine oxidase, specifically oxidized spermine, is a neuromodulator of several types of ion channel and ionotropic glutamate receptors, and its deregulated activity has been linked to several brain pathologies, including epilepsy. The Dach-SMOX mouse line was generated using a Cre/loxP-based recombination approach to study the complex and critical functions carried out by spermine oxidase and spermine in the mammalian brain. This mouse genetic model overexpresses spermine oxidase in the neocortex and is a chronic model of excitotoxic/oxidative injury and neuron vulnerability to oxidative stress and excitotoxic, since its phenotype revealed to be more susceptible to different acute oxidative insults. In this review, the molecular mechanisms underlined the Dach-SMOX phenotype, linked to reactive astrocytosis, neuron loss, chronic oxidative and excitotoxic stress, and susceptibility to seizures have been discussed in detail. The Dach-SMOX mouse model overexpressing SMOX may help in shedding lights on the susceptibility to epileptic seizures, possibly helping to understand the mechanisms underlying epileptogenesis in vulnerable individuals and contributing to provide new molecular mechanism targets to search for novel antiepileptic drugs.

Functional roles of polyamines and their metabolite acrolein in eukaryotic cells

Among low molecular weight substances, polyamines (spermidine, spermine and their precursor putrescine) are present in eukaryotic cells at the mM level together with ATP and glutathione. It is expected therefore that polyamines play important roles in cell proliferation and viability. Polyamines mainly exist as a polyamine-RNA complex and regulate protein synthesis. It was found that polyamines enhance translation from inefficient mRNAs. The detailed mechanisms of polyamine stimulation of specific kinds of protein syntheses and the physiological functions of these proteins are described in this review. Spermine is metabolized into acrolein (CH2 = CH-CHO) and hydrogen peroxide (H2O2) by spermine oxidase. Although it is thought that cell damage is mainly caused by reactive oxygen species (O2-, H2O2, and •OH), it was found that acrolein is much more toxic than H2O2. Accordingly, the level of acrolein produced becomes a useful biomarker for several tissue-damage diseases like brain stroke. Thus, the mechanisms of cell toxicity caused by acrolein are described in this review.

Role of Transglutaminase 2 in Cell Death, Survival, and Fibrosis

Transglutaminase 2 (TG2) is a ubiquitously expressed enzyme catalyzing the crosslinking between Gln and Lys residues and involved in various pathophysiological events. Besides this crosslinking activity, TG2 functions as a deamidase, GTPase, isopeptidase, adapter/scaffold, protein disulfide isomerase, and kinase. It also plays a role in the regulation of hypusination and serotonylation. Through these activities, TG2 is involved in cell growth, differentiation, cell death, inflammation, tissue repair, and fibrosis. Depending on the cell type and stimulus, TG2 changes its subcellular localization and biological activity, leading to cell death or survival. In normal unstressed cells, intracellular TG2 exhibits a GTP-bound closed conformation, exerting prosurvival functions. However, upon cell stimulation with Ca²⁺ or other factors, TG2 adopts a Ca²⁺-bound open conformation, demonstrating a transamidase activity involved in cell death or survival. These functional discrepancies of TG2 open form might be caused by its multifunctional nature, the existence of splicing variants, the cell type and stimulus, and the genetic backgrounds and variations of the mouse models used. TG2 is also involved in the phagocytosis of dead cells by macrophages and in fibrosis during tissue repair. Here, we summarize and discuss the multifunctional and controversial roles of TG2, focusing on cell death/survival and fibrosis.

Spermidine at supraphysiological doses induces oxidative stress and granulosa cell apoptosis in mouse ovaries

Given that spermidine is associated with aging-related diseases and it is a potential target for delaying aging, functional studies on supraphysiological levels of spermidine are required. Our previous studies showed that the granulosa layer arranged irregular and the follicular oocytes were shrunk in female mice injected intraperitoneally with spermidine at 150 mg/kg (Body weight) after 24 h. It indicated that supraphysiological levels of spermidine induced ovarian damage in female mice. The objective of this study was to investigate the effect of acute administration of supraphysiological spermidine on the ovary and granulosa cells in mice. The results showed that treatment with spermidine at 150 mg/kg (intraperitoneal) significantly increased the levels of both H₂O₂ and malondialdehyde and reduced total antioxidant capacity and the activities of catalase and superoxide dismutase in mouse ovaries. The contents of putrescine and spermine increased significantly in the ovaries of mice treated with spermidine. Treatment with spermidine at 150 mg/kg increased the apoptotic rate and reactive oxygen species levels of granulosa cells in mouse ovaries. Furthermore, the protein expression of P53, CASPASE 8 (Cleaved/Pro), CASPASE 9 (Cleaved/Pro) and CASPASE 3 (Cleaved/Pro) in granulosa cells of mice treated with spermidine were significantly upregulated, while BCL2 expression was significantly downregulated. In summary, our study demonstrates for the first time that spermidine at supraphysiological doses causes ovarian oxidative stress and induces granulosa cell apoptosis via the P53 and/or BCL2-CASPASEs pathway.

Acrolein: A Potential Mediator of Oxidative Damage in Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of vision loss among working-age adults. Extensive evidences have documented that oxidative stress mediates a critical role in the pathogenesis of DR. Acrolein, a product of polyamines oxidation and lipid peroxidation, has been demonstrated to be involved in the pathogenesis of various human diseases. Acrolein’s harmful effects are mediated through multiple mechanisms, including DNA damage, inflammation, ROS formation, protein adduction, membrane disruption, endoplasmic reticulum stress, and mitochondrial dysfunction. Recent investigations have reported the involvement of acrolein in the pathogenesis of DR. These studies have shown a detrimental effect of acrolein on the retinal neurovascular unit under diabetic conditions. The current review summarizes the existing literature on the sources of acrolein, the impact of acrolein in the generation of oxidative damage in the diabetic retina, and the mechanisms of acrolein action in the pathogenesis of DR. The possible therapeutic interventions such as the use of polyamine oxidase inhibitors, agents with antioxidant properties, and acrolein scavengers to reduce acrolein toxicity are also discussed.

Disease-associated acrolein: A possible diagnostic and therapeutic substrate for in vivo synthetic chemistry

Acrolein, a highly reactive α,β-unsaturated aldehyde, is a compound to which humans are exposed in many different situations and often causes various human diseases. This paper summarizes the reports over the past twenty-five years regarding disease-associated acrolein detected in clinical patients and the role acrolein plays in various diseases. In several diseases, it was found that the increased acrolein acts as a pathogenetic factor. Thus, we propose the utility of over-produced acrolein as a substrate for a promising therapeutic or diagnostic method applicable to a wide range of diseases based on an in vivo synthetic chemistry strategy.

Structural change and degradation of cytoskeleton due to the acrolein conjugation with vimentin and actin during brain infarction

We have found recently that dendritic spine extension is inhibited through acrolein conjugation with α- and β-tubulin proteins during brain infarction. In this current study, we looked for other acrolein-conjugated proteins in the 100,000g precipitate fraction, to clarify how cytoskeleton structure is modified by acrolein. Acrolein-conjugated proteins were sought from acrolein-treated mouse FM3A and Neuro2a cells and from tissues isolated from mouse brain infarction. It was found that vimentin was conjugated with acrolein, and the conjugated amino acid residue was Cys328, which is the only Cys residue in vimentin. It was also found that Cys207, 257, 285, and Lys118 in actin, another cytoskeleton protein, were conjugated with acrolein. The structure and localization of vimentin and actin filaments were changed greatly in infarct brain in photochemically induced thrombosis model mice and in acrolein-treated Neuro2a cells. In addition, degradation of cytoskeleton proteins was accelerated in the order vimentin > tubulin > actin in mouse brain infarction. These findings indicate that a dysfunction of the cytoskeleton by acrolein is strongly involved in the tissue damage during brain infarction, together with the apoptosis caused by glyceraldehyde-3-phosphate dehydrogenase and protein degradation by matrix metalloproteinase-9.

Pathological Role of Unsaturated Aldehyde Acrolein in Diabetic Retinopathy

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

Association between 10 urinary heavy metal exposure and attention deficit hyperactivity disorder for children

Attention deficit hyperactivity disorder (ADHD) is associated with heavy metal exposure during adolescent development. However, the direct clinical evidence is limited. To investigate the possible association between environmental heavy metal exposure and ADHD, a case-control study was conducted with children aged 6-14 years in Guangzhou, China. Results showed that median concentrations of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo), tin (Sn), barium (Ba), and lead (Pb) in the urine of the case group were significantly higher than those of the control group. Children with ADHD had significantly higher levels of 8-OHdG and MDA compared with those from the control group. In addition, correlations between urinary Co, Ni, Cu, Mo, and Sn were significantly correlated with 8-OHdG and MDA concentrations in urine. After the case and control groups were combined together and the first quartile was used as the reference category, odds ratios (ORs) of ADHD for children increased significantly with the quartile increasing of urinary Co, Cu, and Sn. Our study provides a clinical evidence that Co, Cu, and Sn exposure, particularly Sn exposure, may be an environmental risk of the incurrence of ADHD for children. Furthermore, Co, Ni, Cu, Mo, and Sn exposures were significantly correlated with DNA and lipid damage.

Development of an ELISA for Measurement of Urinary 3-Hydroxypropyl Mercapturic Acid (3-HPMA), the Marker of Stroke

We previously observed an inverse correlation between stroke and urinary 3-hydroxypropyl mercapturic acid (3-HPMA), an acrolein-glutathione metabolite, through its measurement by liquid chromatography with tandem mass spectrometry (LC-MS/MS). However, the cost of equipment for LC-MS/MS and its maintenance fee is very expensive and a cost-efficient method is required. In this study, we have developed a sensitive enzyme-linked immunosorbent assay (ELISA) system to measure 3-HPMA using a chicken antibody recognizing 3-HPMA-conjugated chicken albumin as antigen. Linearity to measure 3-HPMA was obtained from 0 to 10 μM, indicating that this ELISA system is useful for measurement of urine 3-HPMA. It was confirmed that 3-HPMA in urine of stroke patients decreased significantly compared with that of control subjects using the ELISA system. Using the ELISA kit, it became possible to evaluate the risk of brain stroke by not only plasma but also by urine. These results confirm that shortage of glutathione to detoxify acrolein is one of the major causes of stroke incidence. Our method contributes to maintenance of quality of life (QOL) of the elderly.

Acrolein is involved in ischemic stroke-induced neurotoxicity through spermidine/spermine-N1-acetyltransferase activation

BACKGROUND AND PURPOSE

Ischemic stroke is the most common type of cerebrovascular event and is responsible for approximately 85% of all strokes in Taiwan. Neurons contain high concentrations of polyamines, which are prone to various pathological states in the brain and are perturbed after cerebral ischemia. Acrolein, an α,β-unsaturated aldehyde, has been suggested as the primary culprit of neuronal damage in stroke patients. However, the mechanism by which acrolein induces neuronal damage during ischemic stroke is not clear.

METHODS

Urinary 3-hydroxypropyl mercapturic acid (3-HPMA), an acrolein-glutathione (GSH) metabolite, plasma acrolein-protein conjugates (Acr-PC) and plasma GSH levels were analyzed to correlate disease severity and prognosis of stroke patients compared with control subjects. In vivo middle cerebral artery occlusion (MCAO) animal models and an in vitro oxygen glucose deprivation (OGD) stroke model were used to investigate the mechanisms of acrolein-induced neuronal damage.

RESULTS

A deregulated acrolein metabolism, including significantly increased plasma Acr-PC levels, decreased urinary 3-HPMA levels and decreased plasma GSH levels, was found in stroke patients compared to control subjects. We further observed that acrolein was produced during ischemia resulting in brain damage in in vivo MCAO animal model. The induction of acrolein in neuronal cells during OGD occurred due to the increased expression of spermidine/spermine N1-acetyltransferase (SSAT) by NF-kB pathway activation. In addition, acrolein elicited a vicious cycling of oxidative stress resulting in neurotoxicity. Finally, N-acetylcysteine effectively prevented OGD-induced neurotoxicity by scavenging acrolein.

CONCLUSION

Overall, our current results demonstrate that acrolein is a culprit of neuronal damage through GSH depletion in stroke patients. The mechanism underlying the role of acrolein in stroke-related neuronal damage occurs through SSAT-induced polyamine oxidation by NF-kB pathway activation. These results provide a novel mechanism of neurotoxicity in stroke patients, aid in the development of neutralizing or preventive measures, and further our understanding of neural protection.

Inhibition of dendritic spine extension through acrolein conjugation with α-, β-tubulin proteins

We have recently found that conjugation of acrolein with a 50 kDa protein(s) is strongly associated with tissue damage during brain infarction. In the current study, the identity and function of the 50 kDa protein(s) conjugated with acrolein during brain infarction were investigated. The 50 kDa protein(s) conjugated with acrolein were identified as α- and β-tubulins. Ten cysteine residues in α- and β-tubulins (Cys25, 295, 347 and 376 in α-tubulin and Cys12, 129, 211, 239, 303 and 354 in β-tubulin) were mainly conjugated with acrolein. Since two cysteine residues of α-tubulin (Cys347 and 376) and four cysteine residues of β-tubulin (Cys12, 129, 239 and 354) were located at the interaction site of α- and β-tubulins, association between α- and β-tubulins to form microtubules was strongly inhibited by conjugation with acrolein. Accordingly, dendritic spine extension consisting of microtubules was greatly inhibited in acrolein-treated Neuro2a cells. The results strongly suggest that acrolein contributes to the functional losses in brain signaling through its conjugation with α- and β-tubulins.

Assessing acrolein for determination of the severity of brain stroke, dementia, renal failure, and Sjögren's syndrome

It was found recently that acrolein (CH₂=CH-CHO), mainly produced from spermine, is more toxic than ROS (reactive oxygen species, O₂^-·, H₂O₂, and ·OH). In this review, we describe how the seriousness of brain infarction, dementia, renal failure, and Sjӧgren's syndrome is correlated with acrolein. In brain infarction and dementia, it was possible to identify incipient patients with high sensitivity and specificity by measuring protein-conjugated acrolein (PC-Acro) in plasma together with IL-6 and CRP in brain infarction and Aβ_40/42 in dementia. The level of PC-Acro in plasma and saliva correlated with the seriousness of renal failure and Sjӧgren's syndrome, respectively. Thus, development of acrolein scavenger medicines containing SH-group such as N-acetylcysteine derivatives is important to maintain QOL (quality of life) of the elderly.

Urinary acrolein metabolite levels in severe acute alcoholic hepatitis patients

Alcohol-associated liver disease (ALD) remains a major health concern worldwide. Alcohol consumption gives rise to reactive/toxic acrolein, a pathogenic mediator of liver injury in experimental ALD. Elevated acrolein adducts and metabolites are detectable in blood and urine. This study evaluates the major urinary acrolein metabolite, 3-hydroxypropylmercapturic acid (HPMA), in patients with acute alcoholic hepatitis (AAH) and examines its association with disease severity and markers of hepatic inflammation and injury. Urine HPMA was significantly higher in patients with severe [model for end-stage liver disease (MELD) ≥ 20] AAH compared with nonsevere AAH (MELD ≤ 19) or non-alcohol-consuming controls, suggesting that urine HPMA is a novel noninvasive biomarker in severe AAH. The association between HPMA and MELD in patients with AAH was nonlinear. In patients with nonsevere AAH, there was a positive trend, although not significant, whereas in severe AAH the association was negative, indicative of extensive injury and glutathione depletion. Consistent with the multifactorial etiology of ALD, our data identified strong combined effects of HPMA and proinflammatory cytokines on hepatocyte cell death, thereby supporting the pathogenic role of acrolein in liver injury. HPMA, together with IL-1β, showed robust associations with cytokeratin 18 caspase-cleaved fragment (CK18-M30; adjusted R² = 0.812, P = 0.016) and cytokeratin 18 full-length protein (CK18-M65; adjusted R² = 0.670, P = 0.048); similarly, HPMA, with IL-8, correlated with CK18-M30 (adjusted R² = 0.875, P = 0.007) and CK18-M65 (adjusted R² = 0.831, P = 0.013). The apoptosis index (CK18-M30:CK18-M65 ratio) strongly correlated with HPMA, together with IL-1β (adjusted R² = 0.777, P = 0.022) or tumor necrosis factor-α (TNFα; adjusted R² = 0.677, P = 0.046). In patients with severe AAH, IL-1β, IL-8, and TNFα are the predominant proinflammatory cytokines that interact with HPMA and play important mediating roles in influencing the extent/pattern of liver cell death. NEW & NOTEWORTHY This is the first study to examine the urinary acrolein metabolite 3-hydroxypropylmercapturic acid (HPMA) in alcoholic liver disease. HPMA was higher in patients with severe acute alcoholic hepatitis (AAH) compared with controls or nonsevere AAH and may be a novel selective, noninvasive biomarker for severe AAH. Consistent with the multifactorial etiology of alcohol-associated liver disease, we identified strong combined effects of HPMA and proinflammatory cytokines (IL-1β, IL-8, and TNFα) on the extent/pattern of liver cell death, thereby supporting the pathogenic role of acrolein.

Polyamine catabolism and oxidative damage

Polyamines (PAs) are indispensable polycations ubiquitous to all living cells. Among their many critical functions, PAs contribute to the oxidative balance of the cell. Beginning with studies by the Tabor laboratory in bacteria and yeast, the requirement for PAs as protectors against oxygen radical-mediated damage has been well established in many organisms, including mammals. However, PAs also serve as substrates for oxidation reactions that produce hydrogen peroxide (H2O2) both intra- and extracellularly. As intracellular concentrations of PAs can reach millimolar concentrations, the H2O2 amounts produced through their catabolism, coupled with a reduction in protective PAs, are sufficient to cause the oxidative damage associated with many pathologies, including cancer. Thus, the maintenance of intracellular polyamine homeostasis may ultimately contribute to the maintenance of oxidative homeostasis. Again, pioneering studies by Tabor and colleagues led the way in first identifying spermine oxidase in Saccharomyces cerevisiae. They also first purified the extracellular bovine serum amine oxidase and elucidated the products of its oxidation of primary amine groups of PAs when included in culture medium. These investigations formed the foundation for many polyamine-related studies and experimental procedures still performed today. This Minireview will summarize key innovative studies regarding PAs and oxidative damage, starting with those from the Tabor laboratory and including the most recent advances, with a focus on mammalian systems.

Protective Effects of Brain Infarction by N-Acetylcysteine Derivatives

BACKGROUND AND PURPOSE

We recently found that acrolein (CH₂=CH-CHO) is more strongly involved in brain infarction compared with reactive oxygen species. In this study, we looked for acrolein scavengers with less side effects.

METHODS

Photochemically induced thrombosis model mice were prepared by injection of Rose Bengal. Effects of N-acetylcysteine (NAC) derivatives on brain infarction were evaluated using the public domain National Institutes of Health image program.

RESULTS

NAC, NAC ethyl ester, and NAC benzyl ester (150 mg/kg) were administered intraperitoneally at the time of induction of ischemia, or these NAC derivatives (50 mg/kg) were administered 3× at 24-h intervals before induction of ischemia and 1 more administration at the time of induction of ischemia. The size of brain infarction decreased in the order NAC benzyl ester>NAC ethyl ester>NAC in both experimental conditions. Detoxification of acrolein occurred through conjugation of acrolein with glutathione, which was catalyzed by glutathione S-transferases, rather than direct conjugation between acrolein and NAC derivatives. The level of glutathione S-transferases at the locus of brain infarction was in the order of administration of NAC benzyl ester>NAC ethyl ester>NAC>no NAC derivatives, suggesting that NAC derivatives stabilize glutathione S-transferases.

CONCLUSIONS

The results indicate that detoxification of acrolein by NAC derivatives is caused through glutathione conjugation with acrolein catalyzed by glutathione S-transferases, which can be stabilized by NAC derivatives. This is a new concept of acrolein detoxification by NAC derivatives.

N1-Nonyl-1,4-diaminobutane ameliorates brain infarction size in photochemically induced thrombosis model mice

Inhibitors for polyamine oxidizing enzymes, spermine oxidase (SMOX) and N1-acetylpolyamine oxidase (PAOX), were designed and evaluated for their effectiveness in a photochemically induced thrombosis (PIT) mouse model. N1-Nonyl-1,4-diaminobutane (C9-4) and N1-tridecyl-1,4-diaminobutane (C13-4) competitively inhibited the activity of PAOX and SMOX in a manner comparable to N1,N4-bis(2,3-butadienyl)-1,4-butanediamine (MDL72527), an irreversible inhibitor of both enzymes. The two compounds were then tested for their effects in the PIT model. Both intraperitoneal (i.p.) and intracerebroventricular (i.c.v.) administration of C9-4 decreased infarct volumes significantly. By contrast, C13-4 reduced the volume of brain infarction by i.c.v. administration, but no reduction was observed after i.p. administration. C9-4 administered by i.p. injection reduced the volume of brain infarction significantly at doses of more than 3 mg/kg, and the dosage of 5 mg/kg or 10 mg/kg demonstrated the most potent effect and were more effective than equivalent doses of the other inhibitors such as MDL72527 and N-benzylhydroxylamine. I.P. injection of 5 mg/kg of C9-4 provided a therapeutic time window of longer than 12 h. This report demonstrates that C9-4 is a potent inhibitor of the polyamine oxidizing enzymes and is useful lead compound for candidate drugs with a long therapeutic time window, to be used in the treatment of ischemic stroke.

Pre-Treatment with Metformin in Comparison with Post-Treatment Reduces Cerebral Ischemia Reperfusion Induced Injuries in Rats

Objective

To explore the effects of pre versus post ischemic treatment with metformin after global cerebral ischemia in rats.

Methods

Male Wister rats underwent forebrain ischemia by bilateral common carotid artery occlusion for 17 min. Metformin (200 mg/kg) or vehicle was given orally by gavage for 7-14 days. Rats were divided into: control, metformin pre-treatment, metformin post-treatment and metformin pre and post continuous treatment groups. Cerebral infarct size, histopathology, myeloperoxidase and serum malondialdehyde were measured 7 days after ischemia.

Results

Histopathological analysis showed that metformin pre-treatment significantly decreased leukocyte infiltration, myeloperoxidase activity and also malondialdehyde level. Metformin pre-treatment and metformin post-treatment reduced infarct size compared with the control group, but it was not significant in the pre and post continuous treatment group.

Conclusion

Our findings suggest that pre-treatment with metformin in comparison with post-treatment in experimental stroke can reduce the extent of brain damage and is more neuroprotective at least in part by inhibiting oxidative stress and inflammation.

Acrolein toxicity at advanced age: present and future

It is thought that tissue damage at advanced age is mainly caused by ROS (reactive oxygen species, O2-, H2O2, and ·OH). However, it was found that acrolein (CH2=CH-CHO) is more toxic than ROS, and is mainly produced from spermine (SPM), one of the polyamines, rather than from unsaturated fatty acids. Significant amounts of SPM are present normally as SPM-ribosome complexes, and contribute to protein synthesis. However, SPM was released from ribosomes due to the degradation of ribosomal RNA by ·OH or the binding of Ca2+ to ribosomes, and acrolein was produced from free SPM by polyamine oxidases, particularly by SPM oxidase. Acrolein inactivated several proteins such as GAPDH (glycelaldehyde-3-phosphate dehydrogenase), and also stimulated MMP-9 (matrix metalloproteinase-9) activity. Acrolein-conjugated GAPDH translocated to nucleus, and caused apoptosis like nitrosylated GAPDH. Through acrolein conjugation with several proteins, acrolein causes tissue damage during brain stroke, dementia, renal failure, and primary Sjögren's syndrome. Thus, development of acrolein scavengers with less side effects is very important to maintain QOL (quality of life) of elderly people.

Acrolein: An Effective Biomarker for Tissue Damage Produced from Polyamines

It is thought that the major factor responsible for cell damage is reactive oxygen species (ROS), but our recent studies have shown that acrolein (CH₂=CH-CHO) produced from spermine and spermidine is more toxic than ROS. Thus, (1) the mechanism of acrolein production during brain stroke, (2) one of the mechanisms of acrolein toxicity, and (3) the role of glutathione in acrolein detoxification are described in this chapter.

Spermine oxidase promotes bile canalicular lumen formation through acrolein production

Spermine oxidase (SMOX) catalyzes oxidation of spermine to generate spermidine, hydrogen peroxide (H2O2) and 3-aminopropanal, which is spontaneously converted to acrolein. SMOX is induced by a variety of stimuli including bacterial infection, polyamine analogues and acetaldehyde exposure. However, the physiological functions of SMOX are not yet fully understood. We investigated the physiological role of SMOX in liver cells using human hepatocellular carcinoma cell line HepG2. SMOX localized to the bile canalicular lumen, as determined by F-actin staining. Knockdown of SMOX reduced the formation of bile canalicular lumen. We also found that phospho-Akt (phosphorylated protein kinase B) was localized to canalicular lumen. Treatment with Akt inhibitor significantly reduced the formation of bile canalicular lumen. Acrolein scavenger also inhibited the formation of bile canalicular lumen. PTEN, phosphatase and tensin homolog and an inhibitor of Akt, was alkylated in a SMOX-dependent manner. Our results suggest that SMOX plays a central role in the formation of bile canalicular lumen in liver cells by activating Akt pathway through acrolein production.

Polyamines: therapeutic perspectives in oxidative stress and inflammatory diseases

Polyamines are naturally occurring aliphatic compounds, particularly essential elements for biological functions. These compounds play a central role in regulating molecular pathways which are responsible for cellular proliferation, growth, and differentiation. Importantly, excessive polyamine catabolism can lead to a prominent source of oxidative stress which increases inflammatory response and thought to be involved in several diseases including stroke, renal failure, neurological disease, liver disease, and even cancer. Moreover, polyamine supplementation increases life span in model organisms and may encounter oxidative stress via exerting its potential anti-oxidant and anti-inflammatory properties. The revealed literature indicates that an emerging role of polyamine biosynthetic pathway could be a novel target for drug development against inflammatory diseases. In this review, we expand the knowledge on the metabolism of polyamines, and its anti-oxidant and anti-inflammatory activities which might have future implications against inflammatory diseases in humans and animals.

Urinary 3-hydroxypropyl mercapturic acid (3-HPMA) concentrations in dogs with acute spinal cord injury due to intervertebral disc herniation

The aim of this study was to investigate urinary 3-hydroxypropyl mercapturic acid (3-HPMA), a metabolite of acrolein, as a novel biomarker in acute spinal cord injury (ASCI) due to intervertebral disc herniation in dogs. Urine from 10 client-owned dogs with ASCI collected at presentation and 10 control dogs was analyzed for 3-HPMA. The median urinary 3-HPMA concentration in ASCI dogs was significantly higher than in control dogs, but was not correlated with the severity of ASCI. The median urinary 3-HPMA concentration in intact dogs was higher than in neutered dogs. Higher urinary 3-HPMA concentrations in dogs after ASCI support a role for acrolein, a cytotoxic by-product of lipid peroxidation, in canine ASCI. Urinary 3-HPMA could be used as a biomarker in future clinical trials to measure the effect of therapeutic intervention of reducing acrolein after ASCI.

Decrease in acrolein toxicity based on the decline of polyamine oxidases

We have shown recently that acrolein is strongly involved in cell damage during brain infarction and chronic renal failure. To study the mechanism of acrolein detoxification, we tried to isolate Neuro2a cells with reduced sensitivity to acrolein toxicity (Neuro2a-ATD cells). In one cell line, Neuro2a-ATD1, the level of glutathione (GSH) was increased. We recently isolated a second cell line, Neuro2a-ATD2, and found that acrolein-producing enzymes [polyamine oxidases (PAO); i.e. acetylpolyamine oxidase (AcPAO), and spermine oxidase (SMO)] are reduced in this cell line due to changes at the level of transcription. In the Neuro2a-ATD2 cells, the IC50 of acrolein increased from 4.2 to 6.8μM, and the levels of FosB and C/EBPβ - transcription factors involved in the transcription of AcPAO and SMO genes - were reduced. Transfection of siRNAs for FosB and C/EBPβ reduced the levels of AcPAO and SMO, respectively. In addition, the synthesis of FosB and AcPAO was also decreased by siRNA for C/EBPβ, because C/EBPβ is one of the transcription factors for the FosB gene. It was also found that transfection of siRNA for C/EBPβ decreased SMO promoter activity in Neuro2a cells but not in ATD2 cells confirming that a decrease in C/EBPβ is involved in the reduced SMO activity in Neuro2a-ATD2 cells. Furthermore, transfection of the cDNA for AcPAO or SMO into Neuro2a cells increased the toxicity of acrolein. These results suggest that acrolein is mainly produced from polyamines by PAO.

Acrolein Is a Pathogenic Mediator of Alcoholic Liver Disease and the Scavenger Hydralazine Is Protective in Mice

BACKGROUND & AIMS

Alcoholic liver disease (ALD) remains a major cause of morbidity and mortality, with no Food and Drug Administration-approved therapy. Chronic alcohol consumption causes a pro-oxidant environment and increases hepatic lipid peroxidation, with acrolein being the most reactive/toxic by-product. This study investigated the pathogenic role of acrolein in hepatic endoplasmic reticulum (ER) stress, steatosis, and injury in experimental ALD, and tested acrolein elimination/scavenging (using hydralazine) as a potential therapy in ALD.

METHODS

In vitro (rat hepatoma H4IIEC cells) and in vivo (chronic+binge alcohol feeding in C57Bl/6 mice) models were used to examine alcohol-induced acrolein accumulation and consequent hepatic ER stress, apoptosis, and injury. In addition, the potential protective effects of the acrolein scavenger, hydralazine, were examined both in vitro and in vivo.

RESULTS

Alcohol consumption/metabolism resulted in hepatic accumulation of acrolein-protein adducts, by up-regulation of cytochrome P4502E1 and alcohol dehydrogenase, and down-regulation of glutathione-s-transferase-P, which metabolizes/detoxifies acrolein. Alcohol-induced acrolein adduct accumulation led to hepatic ER stress, proapoptotic signaling, steatosis, apoptosis, and liver injury; however, ER-protective/adaptive responses were not induced. Notably, direct exposure to acrolein in vitro mimicked the in vivo effects of alcohol, indicating that acrolein mediates the adverse effects of alcohol. Importantly, hydralazine, a known acrolein scavenger, protected against alcohol-induced ER stress and liver injury, both in vitro and in mice.

CONCLUSIONS

Our study shows the following: (1) alcohol consumption triggers pathologic ER stress without ER adaptation/protection; (2) alcohol-induced acrolein is a potential therapeutic target and pathogenic mediator of hepatic ER stress, cell death, and injury; and (3) removal/clearance of acrolein by scavengers may have therapeutic potential in ALD.

Transglutaminase 2 has opposing roles in the regulation of cellular functions as well as cell growth and death

Transglutaminase 2 (TG2) is primarily known as the most ubiquitously expressed member of the transglutaminase family with Ca²⁺-dependent protein crosslinking activity; however, this enzyme exhibits multiple additional functions through GTPase, cell adhesion, protein disulfide isomerase, kinase, and scaffold activities and is associated with cell growth, differentiation, and apoptosis. TG2 is found in the extracellular matrix, plasma membrane, cytosol, mitochondria, recycling endosomes, and nucleus, and its subcellular localization is an important determinant of its function. Depending upon the cell type and stimuli, TG2 changes its subcellular localization and biological activities, playing both anti- and pro-apoptotic roles. Increasing evidence indicates that the GTP-bound form of the enzyme (in its closed form) protects cells from apoptosis but that the transamidation activity of TG2 (in its open form) participates in both facilitating and inhibiting apoptosis. A difficulty in the study and understanding of this enigmatic protein is that opposing effects have been reported regarding its roles in the same physiological and/or pathological systems. These include neuroprotective or neurodegenerative effects, hepatic cell growth-promoting or hepatic cell death-inducing effects, exacerbating or having no effect on liver fibrosis, and anti- and pro-apoptotic effects on cancer cells. The reasons for these discrepancies have been ascribed to TG2's multifunctional activities, genetic variants, conformational changes induced by the immediate environment, and differences in the genetic background of the mice used in each of the experiments. In this article, we first report that TG2 has opposing roles like the protagonist in the novel Dr. Jekyll and Mr. Hyde, followed by a summary of the controversies reported, and finally discuss the possible reasons for these discrepancies.

Aggravation of brain infarction through an increase in acrolein production and a decrease in glutathione with aging

We previously reported that tissue damage during brain infarction was mainly caused by inactivation of proteins by acrolein. This time, it was tested why brain infarction increases in parallel with aging. A mouse model of photochemically induced thrombosis (PIT) was studied using 2, 6, and 12 month-old female C57BL/6 mice. The size of brain infarction in the mouse PIT model increased with aging. The volume of brain infarction in 12 month-old mice was approximately 2-fold larger than that in 2 month-old mice. The larger brain infarction in 12 month-old mice was due to an increase in acrolein based on an increase in the activity of spermine oxidase, together with a decrease in glutathione (GSH), a major acrolein-detoxifying compound in cells, based on the decrease in one of the subunits of glutathione biosynthesizing enzymes, γ-glutamylcysteine ligase modifier subunit, with aging. The results indicate that aggravation of brain infarction with aging was mainly due to the increase in acrolein production and the decrease in GSH in brain.

A ratiometric fluorescent formaldehyde probe for bioimaging applications

The first ratiometric fluorescent formaldehyde probe (RFFP) has been engineered for bio-applications.

Acrolein, a highly toxic aldehyde generated under oxidative stress in vivo, aggravates the mouse liver damage after acetaminophen overdose

Although acetaminophen-induced liver injury in mice has been extensively studied as a model of human acute drug-induced hepatitis, the mechanism of liver injury remains unclear. Liver injury is believed to be initiated by metabolic conversion of acetaminophen to the highly reactive intermediate N-acetyl p-benzoquinoneimine, and is aggravated by subsequent oxidative stress via reactive oxygen species (ROS), including hydrogen peroxide (H2O2) and the hydroxyl radical (•OH). In this study, we found that a highly toxic unsaturated aldehyde acrolein, a byproduct of oxidative stress, has a major role in acetaminophen-induced liver injury. Acetaminophen administration in mice resulted in liver damage and increased acrolein-protein adduct formation. However, both of them were decreased by treatment with N-acetyl-L-cysteine (NAC) or sodium 2-mercaptoethanesulfonate (MESNA), two known acrolein scavengers. The specificity of NAC and MESNA was confirmed in cell culture, because acrolein toxicity, but not H2O2 or •OH toxicity, was inhibited by NAC and MESNA. These results suggest that acrolein may be more strongly correlated with acetaminophen-induced liver injury than ROS, and that acrolein produced by acetaminophen-induced oxidative stress can spread from dying cells at the primary injury site, causing damage to the adjacent cells and aggravating liver injury.

Practical fluorescence detection of acrolein in human plasma via a two-step tethering approach

Acrolein, a cytotoxic α,β-unsaturated aldehyde and disease biomarker, was determined in plasma by means of a novel tethering strategy using Michael addition of the compound to a fluorescent dye, followed by immobilization of the product on microbeads via the aldehyde moiety. Elevation of blood acrolein was detected in mice treated with an anticancer agent cyclophosphamide, which releases acrolein upon activation. This method should be suitable for high-throughput diagnostic and clinical application.

Polyphenol extract from Phellinus igniarius protects against acrolein toxicity in vitro and provides protection in a mouse stroke model

The basidiomycetous mushroom Phellinus igniarius (L.) Quel. has been used as traditional medicine in various Asian countries for many years. Although many reports exist on its anti-oxidative and anti-inflammatory activities and therapeutic effects against various diseases, our current knowledge of its effect on stroke is very limited. Stroke is a neurodegenerative disorder in which oxidative stress is a key hallmark. Following the 2005 discovery by Igarashi's group that acrolein produced from polyamines in vivo is a major cause of cell damage by oxidative stress, we now describe the effects of anti-oxidative extracts from P. igniarius on symptoms of experimentally induced stroke in mice. The toxicity of acrolein was compared with that of hydrogen peroxide in a mouse mammary carcinoma cell line (FM3A). We found that the complete inhibition of FM3A cell growth by 5 μM acrolein could be prevented by crude ethanol extract of P. igniarius at 0.5 μg/ml. Seven polyphenol compounds named 3,4-dihydroxybenzaldehyde, 4-(3,4-dihydroxyphenyl-3-buten-2one, inonoblin C, phelligridin D, inoscavin C, phelligridin C and interfungin B were identified from this ethanolic extract by LCMS and 1H NMR. Polyphenol-containing extracts of P. igniarius were then used to prevent acrolein toxicity in a mouse neuroblastoma (Neuro-2a) cell line. The results suggested that Neuro-2a cells were protected from acrolein toxicity at 2 and 5 μM by this polyphenol extract at 0.5 and 2 μg/ml, respectively. Furthermore, in mice with experimentally induced stroke, intraperitoneal treatment with P. igniarius polyphenol extract at 20 μg/kg caused a reduction of the infarction volume by 62.2% compared to untreated mice. These observations suggest that the polyphenol extract of P. igniarius could serve to prevent ischemic stroke.

L-Arginine and its metabolites in kidney and cardiovascular disease

L-Arginine is a semi essential amino acid synthesised from glutamine, glutamate and proline via the intestinal-renal axis in humans and most mammals. L-Arginine degradation occurs via multiple pathways initiated by arginase, nitric-oxide synthase, Arg: glycine amidinotransferase, and Arg decarboxylase. These pathways produce nitric oxide, polyamines, proline, glutamate, creatine and agmatine with each having enormous biological importance. Several disease are associated to an L-arginine impaired levels and/or to its metabolites: in particular various L-arginine metabolites may participate in pathogenesis of kidney and cardiovascular disease. L-Arginine and its metabolites may constitute both a marker of pathology progression both the rationale for manipulating L-arginine metabolism as a strategy to ameliorate these disease. A large number of studies have been performed in experimental models of kidney disease with sometimes conflicting results, which underlie the complexity of Arg metabolism and our incomplete knowledge of all the mechanisms involved. Moreover several lines of evidence demonstrate the role of L-arg metabolites in cardiovascular disease and that L-arg administration role in reversing endothelial dysfunction, which is the leading cause of cardiovascular diseases, such as hypertension and atherosclerosis. This review will discuss the implication of the mains L-arginine metabolites and L-arginine-derived guanidine compounds in kidney and cardiovascular disease considering the more recent literature in the field.

Polyamines and their metabolites as diagnostic markers of human diseases

Polyamines, putrescine, spermidine and spermine, are ubiquitous in living cells and are essential for eukaryotic cell growth. These polycations interact with negatively charged molecules such as DNA, RNA, acidic proteins and phospholipids and modulate various cellular functions including macromolecular synthesis. Dysregulation of the polyamine pathway leads to pathological conditions including cancer, inflammation, stroke, renal failure and diabetes. Increase in polyamines and polyamine synthesis enzymes is often associated with tumor growth, and urinary and plasma contents of polyamines and their metabolites have been investigated as diagnostic markers for cancers. Of these, diacetylated derivatives of spermidine and spermine are elevated in the urine of cancer patients and present potential markers for early detection. Enhanced catabolism of cellular polyamines by polyamine oxidases (PAO), spermine oxidase (SMO) or acetylpolyamine oxidase (AcPAO), increases cellular oxidative stress and generates hydrogen peroxide and a reactive toxic metabolite, acrolein, which covalently incorporates into lysine residues of cellular proteins. Levels of protein-conjuagated acrolein (PC-Acro) and polyamine oxidizing enzymes were increased in the locus of brain infarction and in plasma in a mouse model of stroke and also in the plasma of stroke patients. When the combined measurements of PC-Acro, interleukin 6 (IL-6), and C-reactive protein (CRP) were evaluated, even silent brain infarction (SBI) was detected with high sensitivity and specificity. Considering that there are no reliable biochemical markers for early stage of stroke, PC-Acro and PAOs present promising markers. Thus the polyamine metabolites in plasma or urine provide useful tools in early diagnosis of cancer and stroke.