Proteomic analysis of hippocampal proteins in acrylamide-exposed Wistar rats

Parental exposure to acrylamide disrupts sphingolipid metabolism and impairs transgenerational neurodevelopment in zebrafish (Danio rerio) offspring

Acrylamide exposure has become an emerging environmental and food safety issue, and its toxicity poses a potential threat to public health worldwide. However, limited studies have paid attention to the detrimental effects of parental exposure to acrylamide on the neurodevelopment in zebrafish offspring. In this study, the embryos were life-cycle exposed to acrylamide (0.125 and 0.25 mM) for 180 days. Subsequently, these zebrafish (F0) were allowed to mate, and their offspring (F1) were collected to culture in clean water from embryos to adults. We employed developmental and morphological observations, behavioral profiles, metabolomics analyses, and transcriptional level examinations to investigate the transgenerational neurotoxicity with parental exposure to acrylamide. Our results showed that parental exposure to acrylamide harms the birth, development, and behavior characterization of the F1 zebrafish larvae, including poor egg quality, increased mortality rates, abnormal heart rates, slowed swimming activity, and heightened anxiety behavior, and continuously disturbs mental health in F1 adult zebrafish. The transcriptional analysis showed that parental chronic exposure to acrylamide deteriorates the neurodevelopment in F1 larvae. In addition, metabolomics analyses revealed that sphingolipid metabolism disruption may be associated with the observed abnormal development and behavioral response in unexposed F1 offspring. Overall, the present study provides pioneer evidence that acrylamide induces transgenerational neurotoxicity via targeting and disrupting sphingolipid metabolism, which reveals intergenerational transmission of acrylamide exposure and unravels its spatiotemporal toxicological effect on neurodevelopment.

The role of microRNAs in acrylamide toxicity

The chemical compound known as Acrylamide (AA) is employed in different industries worldwide and is also found in thermal-processed food. AA has been acting as a reproductive toxicant, carcinogen, and neurotoxic in various animals, which may promote several toxic impacts in animal and human species. Up to now, various studies have focused on the harmful mechanisms and intervention actions of AA. However, the underlying mechanisms that AA and its toxic effects can exert have remained uncertain. MicroRNAs (miRNAs) are a class of short, non-coding RNAs that are able to act as epigenetic regulators. These molecules can regulate a wide range of cellular and molecular processes. In this regard, it has been shown that different chemical agents can dysregulate miRNAs. To determine the possible AA targets along with mechanisms of its toxicity, it is helpful to study the alteration in the profiles of miRNA regulation following AA intake. The current research aimed to evaluate the miRNAs' mediatory roles upon the AA's toxic potentials. This review study discussed the AA, which is made within the food matrix, the way it is consumed, and the potential impacts of AA on miRNAs and its association with different cancer types and degenerative diseases. The findings of this review paper indicated that AA might be capable of altering miRNA signatures in different tissues and exerting its carcinogen effects.

Molecular determinants of acrylamide neurotoxicity through covalent docking

Acrylamide (ACR) is formed during food processing by Maillard reaction between sugars and proteins at high temperatures. It is also used in many industries, from water waste treatment to manufacture of paper, fabrics, dyes and cosmetics. Unfortunately, cumulative exposure to acrylamide, either from diet or at the workplace, may result in neurotoxicity. Such adverse effects arise from covalent adducts formed between acrylamide and cysteine residues of several neuronal proteins via a Michael addition reaction. The molecular determinants of acrylamide reactivity and its impact on protein function are not completely understood. Here we have compiled a list of acrylamide protein targets reported so far in the literature in connection with neurotoxicity and performed a systematic covalent docking study. Our results indicate that acrylamide binding to cysteine is favored in the presence of nearby positively charged amino acids, such as lysines and arginines. For proteins with more than one reactive Cys, docking scores were able to discriminate between the primary ACR modification site and secondary sites modified only at high ACR concentrations. Therefore, docking scores emerge as a potential filter to predict Cys reactivity against acrylamide. Inspection of the ACR-protein complex structures provides insights into the putative functional consequences of ACR modification, especially for non-enzyme proteins. Based on our study, covalent docking is a promising computational tool to predict other potential protein targets mediating acrylamide neurotoxicity.

In Vitro Exposure to Glucose Alters the Expression of Phosphorylated Proteins in Platelets

Diabetes mellitus (DM) is a pro-thrombotic state that can potentially cause serious cardiovascular complications. Platelet hyperactivation plays an important role in these pathological processes, however there is little or no information on the effect of hyperglycemia on platelet proteins. The aim of this study was to identify the molecular targets associated with platelet reactivity under hyperglycemia. Towards this goal, we examined the effects of the exposure of platelets to 1 and 2 h glucose (300 mg/dL) and control (vehicle and osmolality control using mannitol) on platelet proteins (n = 4 samples per group) using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) combined with MALDI-TOF/TOF tandem mass spectrometry. Two-hour exposure to glucose significantly up-regulated the expression of ATP synthase subunit beta, filamin-A, and L-lactate dehydrogenase A chain in platelets. Pro-Q Diamond staining confirmed the effect of 2 h glucose on vinculin, heat shock protein HSP 90-alpha, filamin-A, and fructose-bisphosphate aldolase A (platelet phosphorylated proteins). The identified proteins are involved in various cellular processes and functions and possibly in platelet reactivity under hyperglycemic conditions.

Paternal acrylamide exposure induces transgenerational effects on sperm parameters and learning capability in mice

Acrylamide (AA) has been shown to have neurological and reproductive toxicities, but little is known about transgenerational effects of AA. In this study, male C57BL/6 mice were exposed to AA (0.01, 1, 10 μg/mL) and its metabolite glycidamide (GA, 10 μg/mL) in drinking water, which were then mated with unexposed female mice to produce F1 and F2 generations. We found that both AA and GA at high concentrations decreased sperm motility in F0 mice and increased sperm malformation rates in mice from all the three generations. In addition, AA and GA increased sperm reactive oxygen species as well as decreased serum testosterone levels, and increased the escape latency time in exposed mice and their offspring. We further found that AA-induced mRNA expression changes in the hippocampus of F0 mice persist to the F2 generation. In the sperm of F0 mice, AA induced significant DNA methylation changes in genes involved in neural and reproduction; the mRNA expression levels of Dnmt3b, a DNA methyltransferase, were dramatically decreased in the testes of F0 and F1 mice. In conclusion, our study indicates that paternal AA exposure leads to DNA methylation-mediated transgenerational adverse effects on sperm parameters and leaning capability in mice.

Comprehensive analysis of metabolic changes in rats exposed to acrylamide

Acrylamide (ACR) is a widely used environmentally hazardous compound that is known to be neurotoxic, genotoxic, carcinogenic, and reproductive toxicity. It is widely present in soil, water, agents used in chemical industries, and food. It can be distributed to all organs and tissues, and can cause damage to various human systems and those of other animals. Previous metabolomics studies have mainly focused on metabolites in serum and urine, but have lacked comprehensive analysis of major organs and tissues. In the current study, a gas chromatography-massspectrometry method was used to investigate mechanisms underlying organ toxicity, in an effort to identify potentially sensitive biomarkers in the main target tissues of rats after ACR exposure. Male Sprague-Dawley rats were assigned to two groups; a control group and a group treated with 20 mg kg^-1 ACR intragastrically for 6 weeks. Metabolite changes in the two groups were statistically analyzed. The respective numbers of altered metabolites in the hippocampus, cortex, kidney, serum, heart, liver, and kidney fat were 21, 21, 17, 5, 15, 14, and 6. There were 14 metabolic pathways related to amino acid, fatty acid, purine, and energy metabolism, revealing that the toxic mechanism of ACR may involve oxidative stress, inflammation, and amino acid metabolism and energy disorders.

Acrylamide modulates the mouse epididymal proteome to drive alterations in the sperm small non-coding RNA profile and dysregulate embryo development

Paternal exposure to environmental stressors elicits distinct changes to the sperm sncRNA profile, modifications that have significant post-fertilization consequences. Despite this knowledge, there remains limited mechanistic understanding of how paternal exposures modify the sperm sncRNA landscape. Here, we report the acute sensitivity of the sperm sncRNA profile to the reproductive toxicant acrylamide. Furthermore, we trace the differential accumulation of acrylamide-responsive sncRNAs to coincide with sperm transit of the proximal (caput) segment of the epididymis, wherein acrylamide exposure alters the abundance of several transcription factors implicated in the expression of acrylamide-sensitive sncRNAs. We also identify extracellular vesicles secreted from the caput epithelium in relaying altered sncRNA profiles to maturing spermatozoa and dysregulated gene expression during early embryonic development following fertilization by acrylamide-exposed spermatozoa. These data provide mechanistic links to account for how environmental insults can alter the sperm epigenome and compromise the transcriptomic profile of early embryos.

Zinc-containing Mohs' paste affects blood flow and angiogenesis suppression

PURPOSE

Mohs' paste, which is composed of zinc chloride and zinc oxide starch, is used for hemostasis of superficial malignancy in the clinical setting. We investigated the concentration of intramuscular zinc in mice after Mohs' paste application and evaluated its relationship with angiogenesis from the perspective of blood flow levels within 24 h.

METHODS

Male C57BL/6JJmsSlc mice were administered single dose of Mohs' paste at 25%, 50%, and 75% after unilateral hind limb surgery, and glycerin, a viscosity modifier, was administered to the control group (0%). Hind limb blood flow levels were measured with a laser Doppler perfusion imaging system (n = 6). The amounts of intramuscular zinc and vascular endothelial growth factor-A (VEGF-A) expression were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and western blotting, respectively (n = 5 or 3).

RESULTS

Blood flow levels were significantly decreased in the 50% group after 8 h, and significantly decreased in the 25% and 50% groups after 24 h. Intramuscular zinc was significantly increased in the 50% and 75% groups after 8 h. Western blotting showed that VEGF-A levels were significantly increased in the 25% and 50% groups after 8 h. Based on analytical experiments and biological investigation, we predicated the pharmacological effect of Mohs' paste and found over 50% of it is critical in the blood flow and angiogenesis suppression after more than 8 h of its application.

CONCLUSIONS

The results suggest that the mechanism of blood flow suppression is independent of VEGF-A levels and might suppress future angiogenesis. Our findings support that of previous studies, in which Mohs' paste was expected to induce hemostasis and suppress angiogenesis. It is an excellent ointment that facilitates hemostasis by suppressing blood flow regardless of angiogenesis, and may be apt for situations where hemostasis is required in the clinical setting.

Proteomic Dissection of the Impact of Environmental Exposures on Mouse Seminal Vesicle Function

Seminal vesicles are an integral part of the male reproductive accessory gland system. They produce a complex array of secretions containing bioactive constituents that support gamete function and promote reproductive success, with emerging evidence suggesting these secretions are influenced by our environment. Despite their significance, the biology of seminal vesicles remains poorly defined. Here, we complete the first proteomic assessment of mouse seminal vesicles and assess the impact of the reproductive toxicant acrylamide. Mice were administered acrylamide (25 mg/kg bw/day) or control daily for five consecutive days prior to collecting seminal vesicle tissue. A total of 5013 proteins were identified in the seminal vesicle proteome with bioinformatic analyses identifying cell proliferation, protein synthesis, cellular death, and survival pathways as prominent biological processes. Secreted proteins were among the most abundant, and several proteins are linked with seminal vesicle phenotypes. Analysis of the effect of acrylamide on the seminal vesicle proteome revealed 311 differentially regulated (FC ± 1.5, p ≤ 0.05, 205 up-regulated, 106 downregulated) proteins, orthogonally validated via immunoblotting and immunohistochemistry. Pathways that initiate protein synthesis to promote cellular survival were prominent among the dysregulated pathways, and rapamycin-insensitive companion of mTOR (RICTOR, p = 6.69E-07) was a top-ranked upstream driver. Oxidative stress was implicated as contributing to protein changes, with acrylamide causing an increase in 8-OHdG in seminal vesicle epithelial cells (fivefold increase, p = 0.016) and the surrounding smooth muscle layer (twofold increase, p = 0.043). Additionally, acrylamide treatment caused a reduction in seminal vesicle secretion weight (36% reduction, p = 0.009) and total protein content (25% reduction, p = 0.017). Together these findings support the interpretation that toxicant exposure influences male accessory gland physiology and highlights the need to consider the response of all male reproductive tract tissues when interpreting the impact of environmental stressors on male reproductive function.

Genetic ablation of Nrf2 exacerbates neurotoxic effects of acrylamide in mice

Acrylamide (ACR), a recognized neurotoxicant in humans and experimental animals, is widely used in industry and in food generated through Maillard reaction. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of the cellular defense system and activates antioxidants and cytoprotective genes. The exact roles of Nrf2 in environmental electrophile-induced neurotoxicity is poorly understood. The aim of this study was to determine the roles of Nrf2 in ACR-induced neurotoxicity including degeneration of monoaminergic axons and sensorimotor dysfunction. Male 10-week-old C57BL/6JJcl Nrf2-knockout mice and wild type (WT) counterparts were each divided into four groups of 12 and provided with drinking water containing acrylamide at 0, 67, 110 or 200 ppm for four weeks. The effects of acrylamide were examined by landing foot spread test, immunohistochemistry for noradrenaline (NA) and serotonin (5-HT)-containing axons and Iba1-positive microglia in the prefrontal cortex as well as quantitative real-time polymerase chain reaction (qRT-PCR) on antioxidant, proinflammatory and anti-inflammatory genes in the prefrontal cortex. Relative to the wild type, exposure of Nrf2-knockout mice to acrylamide increased hindlimb splay length, microglial area and process length as well as decreasing the density of NA and 5-HT-immunoreactive axons to a greater extent. Moreover, deletion of Nrf2 gene suppressed acrylamide-induced mRNA upregulation of Nrf2-antioxidants, NAD(P): quinone oxidoreductase 1 (NQO1), superoxide dismutase-1 (SOD-1) and heme oxygenase-1 (HO-1) as well as anti-inflammatory markers such as, arginase-1 (Arg1), found in the inflammatory zone-1 (Fizz1), chitinase-like 3 (Chi3l3), interleukin-4 receptor alpha (IL-4Rα), cluster of differentiation  206 (CD206) and transforming growth factor beta-1 (TGFβ1) while enhancing acrylamide-induced upregulation of pro-inflammatory cytokines, interleukin-1 beta (IL-1β), tumor necrosis-alpha (TNF-α) and inducible nitric oxide synthase (iNOS) in the prefrontal cortex. The results demonstrate susceptibility of mice lacking the Nrf2 gene to acrylamide-induced neurotoxicity and neuroinflammation with the activation of microglia. Moreover, the results suggest the role of Nrf2 not only in induction of antioxidant gene expression, but also in suppression of proinflammatory cytokine gene expression.

Acrylamide inhibits autophagy, induces apoptosis and alters cellular metabolic profiles

Acrylamide (ACR) is generated during thermal processing of carbohydrate-rich foods at high temperature and can directly enter the body through ingestion, inhalation and skin contact. The toxicity of ACR has been widely studied. The main results of these studies show that exposure to ACR can cause neurotoxicity in both animals and humans, and show reproductive toxicity and carcinogenicity in rodent animal models. However, the mechanism of toxicity of ACR has not been studied by metabolomics approaches, and the effect of ACR on autophagy remains unknown. Here, U₂OS cell were treated with ACR 6 and 24 h and collected for further study. We have demonstrated that ACR inhibited autophagic flux, and increased ROS content. Accumulation of ROS resulted in increase of apoptosis rates and secretion of inflammatory factors. In addition, significant differences in metabolic profiles were observed between ACR treated and control cells according to multiple analysis models. A total of 73 key differential metabolites were identified. They were involved in multiple metabolic pathways. Among them, exposure to ACR caused glycolysis/gluconeogenesis attenuation by decreasing levels of glycolytic intermediates, reduced the rate of the TCA cycle, while elevating levels of several amino acid metabolites and lipid metabolites. In summary, our study provides useful evidence of cytotoxicity caused by ACR via metabolomics and multiple bioanalytic methods.

Proteomic analysis of liver proteins of mice exposed to 1,2-dichloropropane

1,2-Dichloropropane (1,2-DCP) is recognized as the causative agent for cholangiocarcinoma among offset color proof-printing workers in Japan. The aim of the present study was to characterize the molecular mechanisms of 1,2-DCP-induced hepatotoxic effects by proteomic analysis. We analyzed quantitatively the differential expression of proteins in the mouse liver and investigated the role of P450 in mediating the effects of 1,2-DCP. Male C57BL/6JJcl mice were exposed to 0, 50, 250, or 1250 ppm 1,2-DCP and treated with either 1-aminobenzotriazole (1-ABT), a nonselective P450 inhibitor, or saline, for 8 h/day for 4 weeks. Two-dimensional difference in gel electrophoresis (2D-DIGE) combined with matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF/MS) was used to detect and identify proteins affected by the treatment. PANTHER overrepresentation test on the identified proteins was conducted. 2D-DIGE detected 61 spots with significantly different intensity between 0 and 250 ppm 1,2-DCP groups. Among them, 25 spots were identified by MALDI-TOF/TOF/MS. Linear regression analysis showed significant trend with 1,2-DCP level in 17 proteins in mice co-treated with 1-ABT. 1-ABT mitigated the differential expression of these proteins. The gene ontology enrichment analysis showed overrepresentation of proteins functionally related to nickel cation binding, carboxylic ester hydrolase activity, and catalytic activity. The results demonstrated that exposure to 1,2-DCP altered the expression of proteins related with catalytic and carboxylic ester hydrolase activities, and that such effect was mediated by P450 enzymatic activity.