Proliferation Inhibition, DNA Damage, and Cell-Cycle Arrest of Human Astrocytoma Cells after Acrylamide Exposure

Acrylamide in food: Occurrence, metabolism, molecular toxicity mechanism and detoxification by phytochemicals

Acrylamide (ACR) is a common pollutant formed during food thermal processing such as frying, baking and roasting. ACR and its metabolites can cause various negative effects on organisms. To date, there have been some reviews summarizing the formation, absorption, detection and prevention of ACR, but there is no systematic summary on the mechanism of ACR-induced toxicity. In the past five years, the molecular mechanism for ACR-induced toxicity has been further explored and the detoxification of ACR by phytochemicals has been partly achieved. This review summarizes the ACR level in foods and its metabolic pathways, as well as highlights the mechanisms underlying ACR-induced toxicity and ACR detoxification by phytochemicals. It appears that oxidative stress, inflammation, apoptosis, autophagy, biochemical metabolism and gut microbiota disturbance are involved in various ACR-induced toxicities. In addition, the effects and possible action mechanisms of phytochemicals, including polyphenols, quinones, alkaloids, terpenoids, as well as vitamins and their analogs on ACR-induced toxicities are also discussed. This review provides potential therapeutic targets and strategies for addressing various ACR-induced toxicities in the future.

Acrylamide, acrylic acid, or 2-acrylamido-2-methyl-1-propanesulfonic acid induced cytotoxic in Photobacterium phosphoreum, PC12, and SK-N-SH cells

In enhancing oil recovery, more and more new water-soluble polymers are developed to replace the high toxicity and low stability acrylamide (ACR) monomer. The common replacement monomer is acrylic acid (AA) and 2-acrylamido-2-methylamido-2-methyl-1-propanesulfonic acid (AMPS), which are considered safe and efficient. In this study, AA, ACR and AMPS caused remarkable cytotoxicity in Photobacterium phosphoreum, the rat pheochromocytoma cells (PC12) and the Human neuroblastoma cells (SK-N-SH). ACR is much more lethal than AA and AMPS in PC12 and SK-N-SH cells, meanwhile, the toxicity of AA and AMPS decreases with the decrease of acid. Furthermore, similar to ACR, AA, and AMPS can induce severe DNA double-strand breakage in PC12 and SK-N-SH cells. Both AA and ACR can cause cell cycle arrest in the G0/G1 phase in PC12 and SK-N-SH cells. In addition, like ACR, AA, and AMPS can generate reactive oxygen species (ROS) accumulation, mitochondrial dysfunction and mitochondrial-dependent apoptosis in both PC12 and SK-N-SH cells. The acute toxicity of AA and AMPS is lower than ACR, however, the decline in acute toxicity in monomers does not mean toxic-free. We should focus on the toxicity of AA and ACR and reduce occupational contact to protect employee occupational health.

Exposure to acrylamide induces zygotic genome activation defects of mouse embryos

Acrylamide (ACR) is an important chemical raw material for wastewater treatment, paper industry and textile industry, which is widely exposed from occupational, environmental and dietary situation. ACR has neurotoxicity, genotoxicity, potential carcinogenicity and reproductive toxicity. Recent study indicates that ACR affected oocyte maturation quality. In the present study, we reported the effects of ACR exposure on zygotic genome activation (ZGA) in embryos and its related mechanism. Our results showed that ACR treatment caused 2-cell arrest in mouse embryos, indicating the failure of ZGA, which was confirmed by decreased global transcription levels and aberrant expression of ZGA-related and maternal factors. We found that histone modifications such as H3K9me3, H3K27me3 and H3K27ac levels were altered, and this might be due to the occurrence of DNA damage, showing with positive γ-H2A.X signal. Moreover, mitochondrial dysfunction and high levels of ROS were detected in ACR treated embryos, indicating that ACR induced oxidative stress, and this might further cause abnormal distribution of endoplasmic reticulum, Golgi apparatus and lysosomes. In conclusion, our results indicated that ACR exposure disrupted ZGA by inducing mitochondria-based oxidative stress, which further caused DNA damage, aberrant histone modifications and organelles in mouse embryos.

ROS production in response to high-power microwave pulses induces p53 activation and DNA damage in brain cells: Radiosensitivity and biological dosimetry evaluation

Background: Pulsed high-power microwave (HPM) has many applications and is constantly being researched to expand its uses in the future. As the number of applications grows, the biological effects and safety level of pulsed HPM become a serious issue, requiring further research. Objective: The brain is regarded as the most vulnerable organ to radiation, raising concerns about determining an acceptable level of exposure. The effect of nanosecond pulses and the mechanisms underlying HPM on the brain has not been studied. For the first time, we observed the effect of pulsed 3.5 GHz HPM on brain normal astrocytes and cancer U87 MG cells, as well as the likely mechanisms involved. Methods: To generate 3.5 GHz HPM, an axial virtual cathode oscillator was constructed on pulsed power generator "Chundoong". The cells were directly exposed to HPM (10, 25, 40, and 60) pulses (1 mJ/pulse), with each pulse delivered after 1 min of charging time to evaluate the dose dependent effects. Results: A strong electric field (∼23 kV/cm) of HPM irradiation primarily causes the production of reactive oxygen species (ROS), altering cell viability, mitochondrial activity, and cell death rates in U87 and astrocytes at certain dosages. The ROS generation in response to HPM exposure was primarily responsible for DNA damage and p53 activation. The hazardous dosage of 60 pulses is acknowledged as having damaging effects on brain normal cells. Interestingly, the particular 25 pulses exhibited therapeutic effects on U87 cells via p53, Bax, and Caspase-3 activation. Conclusion: HPM pulses induced apoptosis-related events such as ROS burst and increased oxidative DNA damage at higher dosages in normal cells and specific 25 pulses in cancer U87. These findings are useful to understand the physiological mechanisms driving HPM-induced cell death, as well as the safety threshold range for HPM exposure on normal cells and therapeutic effects on cancer U87. As HPM technology advances, we believe this study is timely and will benefit humanity and future research.

Acrylamide-Derived Ionome, Metabolic, and Cell Cycle Alterations Are Alleviated by Ascorbic Acid in the Fission Yeast

Acrylamide (AA), is a chemical with multiple industrial applications, however, it can be found in foods that are rich in carbohydrates. Due to its genotoxic and cytotoxic effects, AA has been classified as a potential carcinogen. With the use of spectrophotometry, ICP-OES, fluorescence spectroscopy, and microscopy cell growth, metabolic activity, apoptosis, ROS production, MDA formation, CAT and SOD activity, ionome balance, and chromosome segregation were determined in Schizosaccharomyces pombe. AA caused growth and metabolic activity retardation, enhanced ROS and MDA production, and modulated antioxidant enzyme activity. This led to damage to the cell homeostasis due to ionome balance disruption. Moreover, AA-induced oxidative stress caused alterations in the cell cycle regulation resulting in chromosome segregation errors, as 4.07% of cells displayed sister chromatid non-disjunction during mitosis. Ascorbic acid (AsA, Vitamin C), a strong natural antioxidant, was used to alleviate the negative impact of AA. Cell pre-treatment with AsA significantly improved AA impaired growth, and antioxidant capacity, and supported ionome balance maintenance mainly due to the promotion of calcium uptake. Chromosome missegregation was reduced to 1.79% (44% improvement) by AsA pre-incubation. Results of our multiapproach analyses suggest that AA-induced oxidative stress is the major cause of alteration to cell homeostasis and cell cycle regulation.

MiR-205-5p promotes lung cancer progression and is valuable for the diagnosis of lung cancer

BACKGROUND

MicroRNAs (miRNAs) function as potential diagnostic biomarkers in various cancers. This study aimed to evaluate the roles of miR-205-5p in lung cancer progression and diagnosis.

MATERIALS AND METHODS

MiR-205-5p was detected by quantitative real-time PCR. The effect of miR-205-5p on cell proliferation and metastasis was estimated by MTT and flow cytometry. The expression of TP53INP1 and related genes was analyzed by immunoblotting. The diagnostic value of miR-205-5p was analyzed using receiver operating characteristic (ROC) curve analysis, sensitivity, and specificity.

RESULTS

The miR-205-5p was increased in lung cancer tissues. MiR-205-5p mimics were promoted but its inhibitor suppressed cell proliferation and metastasis compared with control treatment in vitro and in vivo. By regulating the 3' untranslated region, miR-205-5p could negatively regulate TP53INP1 expression, which further inhibited the expression of RB1 and P21, but increased that of cyclinD1. Moreover, the serum miR-205-5p levels of patients with lung cancer were significantly higher than those of normal controls, and they were correlated with patients' gender, drinking status, and clinical stage. The area under the ROC curve of serum miR-205-5p in the diagnosis of non-small-cell lung cancer was 0.8250, respectively. The finding supported its possession of high diagnostic efficiency for lung cancer.

CONCLUSIONS

MiR-205-5p promoted lung cancer cell proliferation and metastasis by negatively regulating the novel target TP53INP1, which further affected the expression of P21, RB1, and cyclin D1. Serum miR-205-5p is a novel and valuable biomarker for lung cancer diagnosis.

Multi-omics based strategy for toxicity analysis of acrylamide in Saccharomyces cerevisiae model

Although the toxicity of acrylamide (ACR) has been extensively investigated in different experimental models, its perturbations to multiple nodes of the cellular signaling network have not been systematically associated. In this study, changes at different omics layers in ACR exposed Saccharomyces cerevisiae cells were monitored using a multi-omics strategy. The results of the analysis highlighted the impairment of oxidative-reductive balance, energy metabolism, lipid metabolism, nucleotide metabolism, and ribosome function in yeast cells. Response to acute ACR damage, glutathione synthesis was upregulated, the process of protein degradation was accelerated, and the autophagy flux was initiated. Meanwhile, yeast upregulates gene expression levels of enzymes in carbohydrate metabolism and speeds up the oxidation process of fatty acids to compensate for energy depletion. Importantly, the multi-omics strategy captures features that have rarely been addressed in previous studies on the toxicology of ACR, including blocked de novo nucleotide synthesis, decreased levels of metabolic enzyme cofactors thiamine and D-biotin, increased intracellular concentrations of neurotoxic N-methyl d-aspartic acid and l-glutamic acid, and release of death mediators ceramide. The ACR perturbation network constructed in this work and the discovery of new damage features provide a theoretical basis for subsequent point-to-point toxicological studies.

Acrylamide induces intrinsic apoptosis and inhibits protective autophagy via the ROS mediated mitochondrial dysfunction pathway in U87-MG cells

Acrylamide (ACR) is a potential neurotoxin commonly found in the environment, as well as in food repeatedly exposed heat processing, but the mechanism underpinning ACR-induced neurotoxicity remains unclear. This study investigated the potential association and underlying signal transduction of oxidative stress, apoptosis, and autophagy associated with ACR-triggered neurotoxicity. Therefore, U87-MG cells were treated with varying ACR concentrations, while the cell activity reduction depended on the specific dosage and time parameters. Biochemical analyses showed that ACR significantly increased the reactive oxygen species (ROS), malondialdehyde (MDA), and Ca²⁺ levels while decreasing the glutathione (GSH) levels and mitochondrial membrane potential (ΔΨm), finally leading to a higher cell apoptotic rate. Moreover, ACR induced U87-MG cell apoptosis and autophagy via ROS-triggered expression in the mitochondrial apoptosis pathway, NF-κB activation, and autophagosome accumulation. In addition, the autophagosome accumulation induced by ACR could probably be ascribed to blocked autophagic flux, inhibiting the autophagosomes from combining with lysosomes, while the inhibition of autophagy caused by ACR further promoted the initiation of apoptosis. In conclusion, the results indicated that the apoptotic and autophagic pathways responded to ACR-induced neurotoxicity. However, inhibited protective autophagy further promoted apoptotic progression. New insights may be derived from these cellular responses that can help develop diverse pathway strategies for assessing the risk posed by ACR.HIGHLIGHTSACR induced mitochondrial- and caspase-dependent apoptosis in U87-MG cells.ACR regulated the autophagic markers and blocked autophagic flux in U87-MG cells.ACR inhibited protective autophagy and promoted apoptotic initiation in U87-MG cells.

MiR-193b-5p protects BRL-3A cells from acrylamide-induced cell cycle arrest by targeting FoxO3

Acrylamide (AA), an important by-product of the Maillard reaction, has been reported to be genotoxic and carcinogenic. The present study employed miRNAs to investigate the toxic mechanism of AA and their role against AA toxicity. Deep sequencing of small RNA libraries was performed and miR-193b-5p was applied for further study. AA significantly reduced the level of miR-193b-5p and its ectopic expression promoted cell cycle G1/S transition and cell proliferation by upregulating the cyclin-dependent kinase regulator Cyclin D1 and downregulating the cyclin-dependent kinase inhibitor p21, while miR-193b-5p inhibitor led to the opposite results. Dual luciferase assay demonstrated miR-193b-5p regulated the expression of FoxO3 by directly targeting the FoxO3 3'-untranslated region (3'-UTR). Knockdown of FoxO3 induced cell cycle G1/S transition and cell proliferation, which was suppressed by the inhibition of miR-193b-5p but promoted by miR-193b-5p mimics. MiR-193b-5p inhibitor strengthened the effect of FoxO3, contrary to the effect of miR-193b-5p mimics. In conclusion, miR-193b-5p acted as a regulator of cell cycle G1/S transition and cell proliferation by targeting FoxO3 to mediate the expression of p21 and Cyclin D1.

The Coffee-Acrylamide Apparent Paradox: An Example of Why the Health Impact of a Specific Compound in a Complex Mixture Should Not Be Evaluated in Isolation

The health implications of acrylamide in food are a matter of concern based on toxicological studies in rodents, which showed that doses of acrylamide more than 100 times higher than those estimated to result from dietary exposure in humans are carcinogenic; however, the cancer types reported in rodents are species-specific, and whether these results can be extrapolated to humans is still in question. In fact, human epidemiological studies revealed a general lack of association between dietary acrylamide exposure and the incidence of different cancer types. Even occupational exposure to acrylamide, resulting in acrylamide exposure nearly 10 times higher than dietary exposure, did not increase tumor occurrence. Furthermore, the consumption of coffee, which is a main contributor of dietary acrylamide exposure, actually decreases the overall incidence of cancer in humans and afford global health benefits, increasing both lifespan and healthspan on ageing. This paradox clearly illustrates the risk of evaluating an individual molecule independently of its complete food matrix, which may have other components that completely override the effects of the considered molecule.

Secretogranin III upregulation is involved in parkinsonian toxin-mediated astroglia activation

Environmental neurotoxins such as paraquat (PQ), manganese, and 1-1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are associated with a higher risk of Parkinson's disease (PD). These parkinsonian toxins exert certain common toxicological effects on astroglia; however, their role in the regulatory functions of astroglial secretory proteins remains unclear. In a previous study, we observed that secretogranin II (SCG2) and secretogranin III (SCG3), which are important components of the regulated secretory pathway, were elevated in PQ-activated U118 astroglia. In the current study, we used the parkinsonian toxins dopamine (DA), active metabolite of MPTP (MPP⁺), MnCl₂, and lipopolysaccharide (LPS) as inducers, and studied the potential regulation of SCG2 and SCG3. Our results showed that all the parkinsonian toxins except LPS affected astroglial viability but did not cause apoptosis. Exposure to DA, MPP⁺, and MnCl₂ upregulated glial fibrillary acidic protein (GFAP), a marker for astrocyte activation, and stimulated the levels of several astrocytic-derived factors. Further, DA, MPP⁺, and MnCl₂ exposure impeded astroglial cell cycle progression. Moreover, the expression of SCG3 was elevated, while its exosecretion was inhibited in astroglia activated by parkinsonian toxins. The level of SCG2 remained unchanged. In combination with our previous findings, the results of this study indicate that SCG3 may act as a cofactor in astrocyte activation stimulated by various toxins, and the regulation of SCG3 could be involved in the toxicological mechanism by which parkinsonian toxins affect astroglia.

Acrylamide exposure represses neuronal differentiation, induces cell apoptosis and promotes tau hyperphosphorylation in hESC-derived 3D cerebral organoids

Acrylamide (ACR) is a common food contaminant with neurotoxic effects that are formed in the Maillard browning reaction during the heat processing of food. Importantly, pregnant women are also exposed to ACR in food during pregnancy and thus, the fetus is likely affected. However, the mechanisms of ACR-caused neurotoxicity on human brain development are still unclear. Many recent studies employed cerebral organoids based on human embryonic stem cells (hESC) for investigating human neurodevelopmental disorders and toxicity. Here, we generated hESC-derived cerebral organoids to evaluate the neurodevelopmental toxicity of ACR. The results indicated that exposure to ACR significantly altered the transcriptional profile, increased nuclear factor erythroid 2-related factor 2 (NRF2)-mediated gene expression, induced cell apoptosis, repressed neuronal differentiation, and promoted tau hyperphosphorylation in cerebral organoids, which may contribute to ACR-induced neurodevelopmental toxicity. These results indicate that the risk of transplacental exposure of the fetus to ACR should be evaluated and pregnant mothers should limit their exposure to ACR.

Exposure to acrylamide inhibits uterine decidualization via suppression of cyclin D3/p21 and apoptosis in mice

Acrylamide (ACR), a neurotoxicity and carcinogenic chemical, has attracted considerable attention since it is present at high concentrations in thermally cooked carbohydrate-rich foods. ACR exposure significantly increased rate of fetal resorption, and decreased fetal body weights in mice. However, no detailed information is available about the effect of ACR on uterine decidualization, which is a vital process in the establishment of successful pregnancy. Thus, our aim of this study was to explore the effect and mechanism of ACR on uterine decidualization in vivo during mice pregnancy. Mice were gavaged with 0, 10, and 50 mg ACR /kg/day from gestational days (GD) 1 until GD 8, whereas pseudopregnant mice from pseudopregnant day (PPD) 4 until PPD 8. Results indicated ACR treatment dramatically reduced numbers of implanted embryos, and decreased the weights of implantation site and oil-induced uterus. Nevertheless, no significant difference was observed in the weights of no oil-induced uterus between control and ACR-treated group. Furthermore, ACR significantly reduced numbers of polyploidy and PCNA-positive decidual cells and expression of cyclin D3 and p21 proteins, and induced apoptosis of decidua, as presented by up-regulation of Bax and cleaved-caspase-3, and decreased Bcl-2 protein during normal pregnant and pseudopregnant process. In summary, ACR exposure significantly inhibited uterine endometrial decidualization via the apoptosis and suppression of cyclin D3/p21 in mice.

Gestational exposure to acrylamide inhibits mouse placental development in vivo

Acrylamide, a carcinogen and neurotoxic substance, recently has been discovered in various heat-treated carbohydrate-rich foods. The aim of this study was to investigate the effects of acrylamide exposure on placental development. Pregnant mice received acrylamide by gavage at dosages of 0, 10, and 50 mg/kg/day from gestational days (GD) 3 until GD 8 or GD 13. The results showed that acrylamide feeding significantly decreased the numbers of viable embryos and increased the numbers of resorbed embryos on GD 13. Acrylamide exposure reduced the absolute and relative weight of placentas and embryos, and inhibited the development of ectoplacental cone (EPC) and placenta, as shown by the atrophy of EPC and reduced placental area. Acrylamide markedly reduced the numbers of labyrinth vessels. Expression levels of most placental key genes such as Esx1, Hand1, and Hand2 mRNA dramatically decreased in acrylamide-treated placentas. Furthermore, acrylamide treatment inhibited proliferation and induced apoptosis of placentas, as shown by decreased Ki67-positive cells and Bcl-2 protein, and increased the expression of Bax, cleaved-caspase-3, and cleaved-caspase-8 proteins. In conclusion, our results indicated that gestational exposure to acrylamide inhibits placental development through dysregulation of placental key gene expression and labyrinth vessels, suppression of proliferation, and apoptosis induction in mice.

Acrylamide-derived cytotoxic, anti-proliferative, and apoptotic effects on A549 cells

BACKGROUND

Acrylamide is a very common compound even reaching up to our daily foods. It has been studied in a wealth of cell lines on which it proved to have various toxic effects. Among these cell lines, human lung adenocarcinoma cell line (A549) is one of that on which acrylamide's toxicity has not been studied well yet.

AIM

We intended to determine the half maximal inhibitory concentration (IC₅₀) dose of acrylamide and to investigate its cytotoxic, anti-proliferative and apoptotic effects on A549 cells.

METHODS

We determined the IC₅₀ dose by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Then, the mode of cell death was evaluated by flow cytometry using Annexin-V fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining. Next, we performed transmission electron microscopy (TEM) and confocal microscopy analyses for morphological alterations and apoptotic indices.

RESULTS

According to the MTT assay results, A549 cell viability decreases proportionally with increasing acrylamide concentrations and IC₅₀ for A549 was 4.6 mM for 24 h. Annexin-V FITC/PI assay results indicated that acrylamide induces apoptosis in 64% of the A549 cells. TEM and confocal microscopy analyses showed nuclear condensations, fragmentations, cytoskeleton laceration, and membrane blebbing, which are morphological characteristics of apoptosis.

CONCLUSION

Our research suggests that acrylamide causes cytotoxic, anti-proliferative, and apoptotic effects on A549 cells at 4.6 mM IC₅₀ dose in 24 h.

Role of tRNA selenocysteine 1 associated protein 1 in the proliferation and apoptosis of cardiomyocyte‑like H9c2 cells

Transfer RNA selenocysteine 1 associated protein 1 (Trnau1ap) serves an essential role in the synthesis of selenoproteins, which have critical functions in numerous biological processes. Selenium deficiency results in a variety of diseases, including cardiac disease. However, the mechanisms underlying myocardial injury induced by selenium deficiency remain unclear. The present study examined the effects of Trnau1ap under‑ and overexpression in cardiomyocyte‑like H9c2 cells, by transfection with small interfering RNA and an overexpression plasmid, respectively. Expression levels of glutathione peroxidase, thioredoxin reductase and selenoprotein K were decreased in Trnau1ap‑underexpressing cells, and increased in Trnau1ap‑overexpressing cells. Using MTT, proliferating cell nuclear antigen, annexin V and caspase‑3 activity assays, it was demonstrated that reducing Trnau1ap expression levels inhibited the proliferation of H9c2 cells and induced apoptosis. Conversely, increasing Trnau1ap expression levels promoted cell growth. Western blot analysis revealed that the phosphoinositide 3‑kinase/protein kinase B signaling pathway was activated in Trnau1ap‑underexpressing cells. Furthermore, the apoptotic pathway was activated in these cells, evidenced by relatively greater expression levels of B‑cell lymphoma (Bcl‑2)‑associated X protein and reduced expression levels of Bcl‑2. Taken together, these findings suggest that Trnau1ap serves a key role in the proliferation and apoptosis of H9c2 cells. The present study provides insight into the underlying mechanisms of myocardial injury induced by selenium deficiency.

Fluctuations in glucose levels induce glial toxicity with glutamatergic, oxidative and inflammatory implications

Astrocytes are dynamic cells that maintain brain homeostasis by regulating neurotransmitter systems, antioxidant defenses, inflammatory responses and energy metabolism. Astroglial cells are also primarily responsible for the uptake and metabolism of glucose in the brain. Diabetes mellitus (DM) is a pathological condition characterized by hyperglycemia and is associated with several changes in the central nervous system (CNS), including alterations in glial function. Classically, excessive glucose concentrations are used to induce experimental models of astrocyte dysfunction; however, hypoglycemic episodes may also cause several brain injuries. The main focus of the present study was to evaluate how fluctuations in glucose levels induce cytotoxicity. The culture medium of astroglial cells was replaced twice as follows: (1) from 6mM (control) to 12mM (high glucose), and (2) from 12mM to 0mM (glucose deprivation). Cell viability, mitochondrial function, oxidative/nitrosative stress, glutamate metabolism, inflammatory responses, nuclear factor κB (NFκB) transcriptional activity and p38 mitogen-activated protein kinase (p38 MAPK) levels were assessed. Our in vitro experimental model showed that up and down fluctuations in glucose levels decreased cell proliferation, induced mitochondrial dysfunction, increased oxidative/nitrosative stress with consequent cellular biomolecular damage, impaired glutamate metabolism and increased pro-inflammatory cytokine release. Additionally, activation of the NFκB and p38 signaling pathways were putative mechanisms of the effects of glucose fluctuations on astroglial cells. In summary, for the first time, we show that changes in glucose concentrations, from high-glucose levels to glucose deprivation, exacerbate glial injury.

TSPO PIGA Ligands Promote Neurosteroidogenesis and Human Astrocyte Well-Being

The steroidogenic 18 kDa translocator protein (TSPO) is an emerging, attractive therapeutic tool for several pathological conditions of the nervous system. Here, 13 high affinity TSPO ligands belonging to our previously described N,N-dialkyl-2-phenylindol-3-ylglyoxylamide (PIGA) class were evaluated for their potential ability to affect the cellular Oxidative Metabolism Activity/Proliferation index, which is used as a measure of astrocyte well-being. The most active PIGA ligands were also assessed for steroidogenic activity in terms of pregnenolone production, and the values were related to the metabolic index in rat and human models. The results showed a positive correlation between the increase in the Oxidative Metabolism Activity/Proliferation index and the pharmacologically induced stimulation of steroidogenesis. The specific involvement of steroid molecules in mediating the metabolic effects of the PIGA ligands was demonstrated using aminoglutethimide, a specific inhibitor of the first step of steroid biosynthesis. The most promising steroidogenic PIGA ligands were the 2-naphthyl derivatives that showed a long residence time to the target, in agreement with our previous data. In conclusion, TSPO ligand-induced neurosteroidogenesis was involved in astrocyte well-being.

Transcriptomics analysis and hormonal changes of male and female neonatal rats treated chronically with a low dose of acrylamide in their drinking water

Acrylamide is known to produce follicular cell tumors of the thyroid in rats. RccHan Wistar rats were exposed in utero to a carcinogenic dose of acrylamide (3 mg/Kg bw/day) from gestation day 6 to delivery and then through their drinking water to postnatal day 35. In order to identify potential mechanisms of carcinogenesis in the thyroid glands, we used a transcriptomics approach. Thyroid glands were collected from male pups at 10 PM and female pups at 10 AM or 10 PM in order to establish whether active exposure to acrylamide influenced gene expression patterns or pathways that could be related to carcinogenesis. While all animals exposed to acrylamide showed changes in expected target pathways related to carcinogenesis such as DNA repair, DNA replication, chromosome segregation, among others; animals that were sacrificed while actively drinking acrylamide-laced water during their active period at night showed increased changes in pathways related to oxidative stress, detoxification pathways, metabolism, and activation of checkpoint pathways, among others. In addition, thyroid hormones, triiodothyronine (T3) and thyroxine (T4), were increased in acrylamide-treated rats sampled at night, but not in quiescent animals when compared to controls. The data clearly indicate that time of day for sample collection is critical to identifying molecular pathways that are altered by the exposures. These results suggest that carcinogenesis in the thyroids of acrylamide treated rats may ensue from several different mechanisms such as hormonal changes and oxidative stress and not only from direct genotoxicity, as has been assumed to date.

Melatonin Attenuates Oxidative Damage Induced by Acrylamide In Vitro and In Vivo

Acrylamide (ACR) has been classified as a neurotoxic agent in animals and humans. Melatonin (MT) has been shown to be potentially effective in preventing oxidative stress related neurodegenerative disorders. In this study, whether MT exerted a protective effect against ACR-induced oxidative damage was investigated. Results in cells showed that reactive oxygen species (ROS) and malondialdehyde (MDA) significantly increased after ACR treatment for 24 h. MT preconditioning or cotreatment with ACR reduced ROS and MDA products, whereas the inhibitory effect of MT on oxidant generation was attenuated by blocking the MT receptor. Increased DNA fragmentation caused by ACR was significantly decreased by MT coadministration. In vivo, rats at 40 mg/kg/day ACR by gavage for 12 days showed weight loss and gait abnormality, Purkinje cell nuclear condensation, and DNA damage in rat cerebellum. MT (i.p) cotreatment with ACR not only recovered weight and gait of rats, but also decreased nuclear condensation and DNA damage in rat cerebellum. Using MDA generation, glutathione (GSH) level, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities in rat cerebellum as indicators, MT alleviated ACR-induced lipid peroxidation and depressed antioxidant capacity. Our results suggest that MT effectively prevents oxidative damage induced by ACR.

Inhibition of Neurosphere Formation in Neural Stem/Progenitor Cells by Acrylamide

Previous studies showed that transplantation of cultured neural stem/progenitor cells (NSPCs) could improve functional recovery for various neurological diseases. This study aims to develop a stem cell-based model for predictive toxicology of development in the neurological system after acrylamide exposure. Treatment of mouse (KT98/F1B-GFP) and human (U-1240 MG/F1B-GFP) NSPCs with 0.5 mM acrylamide resulted in the inhibition of neurosphere formation (definition of self-renewal ability in NSPCs), but not inhibition of cell proliferation. Apoptosis and differentiation of KT98 (a precursor of KT98/F1B-GFP) and KT98/F1B-GFP are not observed in acrylamide-treated neurospheres. Analysis of secondary neurosphere formation and differentiation of neurons and glia illustrated that acrylamide-treated KT98 and KT98/F1B-GFP neurospheres retain the NSPC properties, such as self-renewal and differentiation capacity. Correlation of acrylamide-inhibited neurosphere formation with cell-cell adhesion was observed in mouse NSPCs by live cell image analysis and the presence of acrylamide. Protein expression levels of cell adhesion molecules [neural cell adhesion molecule (NCAM) and N-cadherin] and extracellular signal-regulated kinases (ERK) in acrylamide-treated KT98/F1B-GFP and U-1240 MG/F1B-GFP neurospheres demonstrated that NCAM decreased and phospho-ERK (pERK) increased, whereas expression of N-cadherin remained unchanged. Analysis of AKT (protein kinase B, PKB)/β-catenin pathway showed decrease in phospho-AKT (p-AKT) and cyclin D1 expression in acrylamide-treated neurospheres of KT98/F1B-GFP. Furthermore, PD98059, an ERK phosphorylation inhibitor, attenuated acrylamide-induced ERK phosphorylation, indicating that pERK contributed to the cell proliferation, but not in neurosphere formation in mouse NSPCs. Coimmunoprecipitation results of KT98/F1B-GFP cell lysates showed that the complex of NCAM and fibroblast growth factor receptor 1 (FGFR1) is present in the neurosphere, and the amount of this complex decreases after acrylamide treatment. Our results reveal that acrylamide inhibits neurosphere formation through the disruption of the neurosphere architecture in NSPCs. The downregulation of cell-cell adhesion resulted from decreasing the levels of NCAM as well as the formation of NCAM/ FGFR complex.

Cytotoxic effects of acrylamide in nerve growth factor or fibroblast growth factor 1-induced neurite outgrowth in PC12 cells

Acrylamide is a neurological and reproductive toxicant in humans and laboratory animals; however, the neuron developmental toxicity of acrylamide remains unclear. The aims of this study are to investigate the cytotoxicity and neurite outgrowth inhibition of acrylamide in nerve growth factor (NGF)- or fibroblast growth factor 1 (FGF1)-mediated neural development of PC12 cells. MTS assay showed that acrylamide treatment suppresses NGF- or FGF1-induced PC12 cell proliferation in a time- and dose-dependent manner. Quantification of neurite outgrowth demonstrated that 0.5 mM acrylamide treatment resulted in significant decrease in differentiation of NGF- or FGF1-stimulated PC12 cells. This decrease is accompanied with the reduced expression of growth-associated protein-43, a neuronal marker. Moreover, relative levels of pERK, pAKT, pSTAT3 and pCREB were increased within 5-10 min when PC12 cells were treated with NGF or FGF1. Acrylamide (0.5 mM) decreases the NGF-induced activation of AKT-CREB but not ERK-STAT3 within 20 min. Similarly, acrylamide (0.5 mM) decreases the FGF1-induced activation of AKT-CREB within 20 min. In contrast to the NGF treatment, the ERK-STAT3 activation that was induced by FGF1 was slightly reduced by 0.5 mM acrylamide. We further showed that PI3K inhibitor (LY294002), but not MEK inhibitor (U0126), could synergize with acrylamide (0.5 mM) to reduce the cell viability and neurite outgrowth in NGF- or FGF1-stimulated PC12 cells. Moreover, acrylamide (0.5 mM) increased reactive oxygen species (ROS) activities in NGF- or FGF1-stimulated PC12 cells. This increase was reversed by Trolox (an ROS scavenging agent) co-treatment. Together, our findings reveal that NGF- or FGF1-stimulation of the neuronal differentiation of PC12 cells is attenuated by acrylamide through the inhibition of PI3K-AKT-CREB signaling, along with the production of ROS.