Acrylamide tissue distribution and genotoxic effects in a common viral infection in mice

Dietary Exposure to Acrylamide Has Negative Effects on the Gastrointestinal Tract: A Review

Changing eating habits and an increase in consumption of thermally processed products have increased the risk of the harmful impact of chemical substances in food on consumer health. A 2002 report by the Swedish National Food Administration and scientists at Stockholm University on the formation of acrylamide in food products during frying, baking and grilling contributed to an increase in scientific interest in the subject. Acrylamide is a product of Maillard's reaction, which is a non-enzymatic chemical reaction between reducing sugars and amino acids that takes place during thermal processing. The research conducted over the past 20 years has shown that consumption of acrylamide-containing products leads to disorders in human and animal organisms. The gastrointestinal tract is a complex regulatory system that determines the transport, grinding, and mixing of food, secretion of digestive juices, blood flow, growth and differentiation of tissues, and their protection. As the main route of acrylamide absorption from food, it is directly exposed to the harmful effects of acrylamide and its metabolite-glycidamide. Despite numerous studies on the effect of acrylamide on the digestive tract, no comprehensive analysis of the impact of this compound on the morphology, innervation, and secretory functions of the digestive system has been made so far. Acrylamide present in food products modifies the intestine morphology and the activity of intestinal enzymes, disrupts enteric nervous system function, affects the gut microbiome, and increases apoptosis, leading to gastrointestinal tract dysfunction. It has also been demonstrated that it interacts with other substances in food in the intestines, which increases its toxicity. This paper summarises the current knowledge of the impact of acrylamide on the gastrointestinal tract, including the enteric nervous system, and refers to strategies aimed at reducing its toxic effect.

Flavonoids mitigation of typical food thermal processing contaminants: Potential mechanisms and analytical strategies

Due to unique chemical structure, flavonoids are secondary metabolites with numerous biological activities. Thermal processing of food usually produces some chemical contaminants, which cause an adverse effect on food quality and nutrition. Therefore, it is vital to reduce these contaminants in food processing. In this study, current researches around the inhibitory effect of flavonoids on acrylamide, furans, α-dicarbonyl compounds and heterocyclic amines (HAs) were summarized. It has been shown that flavonoids inhibited the formation of these contaminants to varying degrees in chemical or food models. The mechanism was mainly associated with natural chemical structure and partly with antioxidant activity of flavonoids. Additionally, methods and tools of analyzing interactions between flavonoids and contaminants were discussed. In summary, this review demonstrated potential mechanisms and analytical strategies of flavonoids in food thermal processing, providing new insight of flavonoids applying on the food engineering.

Mitochondrial dysfunction promotes the necroptosis of Purkinje cells in the cerebellum of acrylamide-exposed rats

Acrylamide (ACR) is a common neurotoxicant that can induce central-peripheral neuropathy in human beings. ACR from occupational setting and foods poses a potential threat to people's health. Purkinje cells are the only efferent source of cerebellum, and their output is responsible for coordinating motor activity. Recent studies have reported that Purkinje cell injury is one of the earliest neurotoxicity at any dose rate of ACR. However, the mechanism underlying ACR-mediated damage to Purkinje cells remains unclear. This research aimed to investigate whether necroptosis is involved in ACR-induced Purkinje cell death and its regulatory mechanism. In this study, rats were treated with ACR (40 mg/kg/every other day) for 6 weeks to establish an animal model of ACR neuropathy. Furthermore, an intervention experiment was achieved by rapamycin (RAPA), which is commonly used to activate mitophagy and maintain mitochondrial homeostasis. The results demonstrated ACR exposure caused necroptosis of Purkinje cells, mitochondrial dysfunction, and inflammatory response. By contrast, RAPA alleviated mitochondrial dysfunction and inhibited activation of necroptosis signaling pathway following ACR. In conclusion, our findings suggest that mitochondrial dysfunction and activation of necroptotic signaling are associated with the loss of Purkinje cells in ACR poisoning, which can be a potential therapeutic target for ACR neurotoxicity.

Analysis of silymarin-modulating effects against acrylamide-induced cerebellar damage in male rats: Biochemical and pathological markers

BACKGROUND

Acrylamide (ACR) is a well-proven neurotoxin and potential food carcinogen in humans and rodent models. Silymarin (SIL) is a flavonoid mixture isolated from seeds, leaves, and fruits of Silymarin marianum (milk thistle) that possesses a free-radical scavenging effect.

OBJECTIVE

In this work, the primary focus was to investigate the efficacy of SIL to mitigate ACR-induced subacute neurotoxic effects and oxidative changes in rat cerebellum.

METHODS

Adult male rats were treated intraperitoneally with ACR (50 mg/kg) with or without SIL (160 mg/kg). The neuropathology and biochemical parameters viz. lipid peroxidation (measured as levels of malondialdehyde or MDA), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), serotonin (5-hydroxytryptamine; 5-HT), dopamine (DA), and cathepsin D (CTSD) in the cerebellum have been evaluated.

RESULTS

The data showed that ACR induced redox disruptions as measured by increased MDA levels and inhibition of CAT, SOD, and GPx antioxidant enzyme activities. Besides, cerebellar monoamine neurotransmitters, 5-HT and DA, were depleted in ACR-treated rats. Furthermore, ACR administration caused a significant elevation of CTSD activity, indicating that ACR could trigger apoptosis or apoptosis-like death. At the tissue level, cerebellar cortex sections from ACR-treated animals were characterized by severe neuronal damage. The administration of SIL to ACR-treated rats remarkably alleviated all the aforementioned ACR-induced effects.

CONCLUSION

SIL has a potent therapeutic effect against ACR-induced cerebellar neurotoxicity in experimental rats via the attenuation of oxidative/antioxidative responses and the inhibition of CTSD-activity.

Exposure to acrylamide induces skeletal developmental toxicity in zebrafish and rat embryos

Acrylamide is a well-known carcinogen and neurotoxic substance that has been discovered in frying or baking carbohydrate-rich foods and is widely found in soils and groundwater. The purpose of this study was to investigate the adverse effects of exposure to acrylamide on skeletal development. After treatment with acrylamide in zebrafish embryos, the survival and hatching rates decreased, and the body length shortened, with cartilage malformation and a decrease in skeletal area. Exposure to acrylamide in maternal rats during the lactation period disturbed bone mineral density, serum levels of parathyroid hormone, and the expression of skeletal development-related genes in neonates. Exposure to acrylamide in pregnant rats during the pregnancy period decreased the trabecular density and inhibited cartilage formation by delaying the differentiation of osteoblasts and promoting the maturation of osteoclasts in rat embryos. Furthermore, acrylamide intervention downregulated the expression of chondrocyte and osteoblast differentiation-related genes (sox9a, bmp2, col2a1, and runx2), and upregulated the expression of osteoclast marker genes (rankl and mcsf) in zebrafish and rat embryos at different gestational stages. Our results indicated that exposure to acrylamide dysregulated signature gene and protein expression profiles of skeletal development by suppressing the differentiation and maturation of osteoblasts and cartilage matrix and promoting the formation of osteoclasts, and ultimately induced skeletal abnormality in morphology, which brings increasing attention to the intergenerational toxicity of acrylamide via mother-to-child transmission.

The adverse effects of acrylamide exposure on the early development of marine medaka (Oryzias melastigma) and its mechanisms

Acrylamide (AA) can have deleterious effects on freshwater fish. However, its adverse effects on euryhaline fish are still unknown. In this study, embryos of Oryzias melastigma were exposed to different concentrations of AA to investigate its effect on early developmental disorders. After 21 days of exposure, AA significantly inhibited the hatching rate and delayed the hatching time of embryos, and led to developmental delay, teratogenesis, and locomotion impairments in larvae. RNA-sequencing data of larvae indicated that AA upregulated the expression of hemoglobin and myoglobin involved in oxygen transport and angiopoietin 1, integrin, and matrix metallopeptidases related to angiogenesis and downregulated the expression of early growth response genes and synaptotagmin-2 related to neural plasticity and neurotransmitter release. Overall, our study showed that AA caused deleterious effects on the early development of euryhaline fish through hypoxic stress and neurotoxicity, providing a scientific basis for the environmental risk assessment of marine AA.

Histopathological, cytotoxicological, and genotoxic effects of the semi-synthetic compound dillapiole n-butyl ether in Balb/C mice

Dillapiole n-butyl ether is a substance derived from dillapiole, which exhibits potential insecticidal effects on Aedes aegypti, the principal vector of the Dengue fever, Zika, and Chikungunya viruses, as well as Aedes albopictus, a vector of Dengue fever. As these mosquitoes are resistant to synthetic insecticides, dillapiole n-butyl ether may represent a valuable, plant-based alternative for their control. Dillapiole n-butyl ether has insecticidal and genotoxic effects on A. aegypti and A. albopictus, as shown by the reduction in clutch size and egg viability, and increased mortality rates, as well as a high frequency of micronuclei and chromosomal aberrations. However, the potential cytotoxic and genotoxic effects of this substance in mammals are still unknown. In Balb/C mice, structural changes were detected in hepatic, renal, and cardiac tissues, which were directly proportional to the concentration of the dose applied, in both genders. The induction of genotoxic, mutagenic, and cytotoxic effects was also observed at the highest concentrations (150 and 328 mg/kg). Further research will be necessary to better characterize the potential genotoxicity of this substance at lower concentrations, for the evaluation of the potential health risks related to its presence in environmental features, such as drinking water.

Role of microglial activation and neuroinflammation in neurotoxicity of acrylamide in vivo and in vitro

Acrylamide, a soft electrophile, is widely used in the industry and laboratories, and also contaminates certain foods. Neurotoxicity and neurodegenerative effects of acrylamide have been reported in humans and experimental animals, although the underlying mechanism remains obscure. Activation of microglia and neuroinflammation has been demonstrated in various neurodegenerative diseases as well as other pathologies of the brain. The present study aimed to investigate the role of microglial activation and neuroinflammation in acrylamide neurotoxicity. Male 10-week-old Wistar rats were exposed to acrylamide by gavage at 0, 0.2, 2, or 20 mg/kg BW, once per day for 5 weeks. The results showed that 5-week exposure to acrylamide induced inflammatory responses in the cerebral cortex, evident by upregulated mRNA and protein expression of pro-inflammatory cytokines IL-1β, IL-6, and IL-18. Acrylamide also induced activation of microglia, indicated by increased expression of microglial markers, CD11b and CD40, and increased CD11b/c-positive microglial area and microglial process length. In vitro studies using BV-2 microglial cells confirmed microglial inflammatory response, as evident by time- (0-36 h; 50 μM) and dose- (0-500 μM; 24 h) dependent increase in mRNA expression of IL-1β and IL-18, as well as the inflammatory marker iNOS. Furthermore, acrylamide-induced upregulation of pro-inflammatory cytokines was mediated through the NLRP3 inflammasome pathway, as evident by increased expression of NLRP3, caspase 1, and ASC in the rat cerebral cortex, and by the inhibitory effects of NLRP3 inflammasome inhibitor on the acrylamide-induced upregulation of NLRP3, caspase 1, IL-1β, and IL-18 in BV-2 microglia.

Lack of adverse health effects following 30-weeks of dietary exposure to acrylamide at low doses in male F344 rats

Understanding the health hazards following exposure to food-borne acrylamide, especially at low levels typified by human diets, is an ongoing food safety issue. We recently published results from a study that aimed to understand the effects of acrylamide short-term exposure at doses known to cause tumors in rodents, demonstrating that a number of key toxicological end points were altered by acrylamide exposure. Additionally, we reported that at much lower doses for 30 weeks of exposure, dietary acrylamide was 'not a complete carcinogen' to the colon in an organ-specific rodent carcinogenesis study but acted as a co-carcinogen along with azoxymethane (AOM, a colon-specific carcinogen). Here, we present toxicological data from a sub-set of this long-term exposure study from animals that received saline (instead of AOM). Briefly, male F344 rats were randomized to receive acrylamide at 0.5, 1.0 and 2.0 mg/kg diet (∼0.02, 0.04, and 0.09 mg/kg BW/day, respectively) or no acrylamide (control), for 30 weeks; all rats were then euthanized and their tissues harvested and processed for toxicological evaluation. We report that at the doses tested, acrylamide did not cause any changes in general well-being, body weight or food intake. Similarly, acrylamide did not cause any biologically relevant change in parameters associated with immunophenotyping, serum biochemistry or hematology. Histopathology assessment of tissues showed no changes except in the testis, where non-specific mild lesions were observed in all the groups, inclusive of the controls. No neuropathological effects of acrylamide were observed in the brain and nerve tissues. Together, these results suggest that acrylamide administered to rats through the diet at low doses for 30 weeks did not cause any toxicologically relevant changes. Given that the doses of acrylamide in the current study are low and are comparable to human dietary exposure, this null-effect study provides data that contribute to the body of scientific evidence relevant to understanding the health effects of acrylamide.

The flame-retardant BDE-99 dose-dependently affects viral replication in CVB3-infected mice

The flame retardant component 2,2',4,4',5-penta-BDE (BDE-99) is found in the environment and in human tissues and fluids. In mice the common human coxsackievirus B3 (CVB3) infection has been shown to change the tissue distribution of BDE-99. We now investigate how CVB3 infection in mice affects liver uptake of (14)C at two doses of radiolabelled BDE-99, and whether increased tissue levels are related to changed virus replication and gene expression of the proinflammatory chemokine monocyte chemoattractant protein-1 (MCP-1). Mice were infected on day 0, orally treated either with 200μg or 20mg (14)C-BDE-99/kgbw on day 1, and euthanised on day 3. Serum and liver levels of (14)C-BDE-99, as well as virus levels and gene expressions of MCP-1 in the liver, were measured. In non-infected mice, there was a dose-dependent uptake of BDE-99 in both liver and serum, and in infected animals the liver BDE-99 levels was further increased. When comparing infected mice exposed to the two BDE-99 doses, the higher BDE dose resulted in increased virus amounts in the liver, and decreased infection-induced expression of MCP-1. Consequently, a high enough dose/tissue concentration of BDE-99 may result in a disturbed mobilisation of immune cells into infected tissues that could explain higher virus titres and a possibly altered clinical course of the disease. Moreover, the fact that CVB3 infection increased the BDE-99 levels in liver but not in serum may impair the risk assessment of polybrominated diphenyl ethers (PBDEs) in subclinical and clinically infected individuals, as serum levels is the common marker of exposure.

Interactions among infections, nutrients and xenobiotics

During recent years there have been several incidents in which symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Furthermore, outbreaks of infections in food-producing animals have attracted major attention regarding the safety of consumers, e.g., Bovine Spongiform Encephalitis (BSE) and influenza in chicken. As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and associated complications. Moreover, during ongoing infection, xenobiotic uptake and distribution are often changed resulting in increased toxic insult to the host. The interactions among infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology as well as in food-borne diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects among microorganisms, nutrients, and xenobiotics will have to be considered. Otherwise, such effects may gradually change the disease panorama in society.

Common viral infection affects pentabrominated diphenyl ether (PBDE) distribution and metabolic and hormonal activities in mice

A murine model infection with the human coxsackievirus B3 (CB3) has been shown to change uptake and tissue distribution of several environmental pollutants, in some cases followed by an aggravated disease. In this study, the model was tested for polybrominated diphenyl ethers (PBDEs), which we know are absorbed from the gastro-intestinal tract and further distributed throughout the body. On day 0, female Balb/c mice were infected with CB3; on day 1 of the infection, they were dosed orally with approximately 200 microg/kgbody weight (bw) (ca. 0.52 microCi) of 14C-labelled 2,2',4,4',5-pentabromodiphenyl ether (14C-BDE-99); and on day 3 of the infection, they were sacrificed for studies of 14C-BDE-99 distribution. In comparison with control values, 14C-BDE-99 concentrations were altered in the liver (186%, p < 0.05), lungs (47%, p < 0.05) and pancreas (51%, p < 0.05), but no change was seen in the blood, brain, heart, spleen, thymus or kidneys. Moreover, on day 3, plasma thyroxine (T4) levels (33%, p < 0.001), as well as ethoxyresorufin-O-dealkylase (EROD) (17%, p < 0.001) and pentoxyresorufin O-dealkylase (PROD) (31%, p < 0.001) activities were much lower in infected compared to non-infected control mice. It is suggested that the change in tissue distribution of 14C-BDE-99 as a result of the infection may be caused by an infection-induced specific change in the hepatic enzyme activities affecting this PBDE congener. The mechanism for virally induced T4 changes remains, however, unclear. The presented infection-induced alteration in distribution, which is different from other environmental pollutants (e.g., dioxin, acrylamide and cadmium), may have consequences for PBDEs toxicity, especially in relation to microsomal enzyme and thyroid hormone activities.