Acrylamide induces NLRP3 inflammasome activation via oxidative stress- and endoplasmic reticulum stress-mediated MAPK pathway in HepG2 cells

Effects of dietary acrylamide on kidney and liver health: Molecular mechanisms and pharmacological implications

Acrylamide (AA) has raised concerns throughout the world in recent years because of its potential negative effects on human health. Numerous researches on humans and animals have connected a high dietary exposure to AA to a possible risk of cancer. Additionally, higher consumption of acrylamide has also been associated with dysfunctioning of various organ systems from nervous system to the reproductive system. Acrylamide is primarily metabolised into the glycidamide inside the body which gets accumulated in different tissues including kidney and liver, and chronic exposure to this can lead to the nephrotoxicity and hepatotoxicity through different molecular mechanisms. This review summarizes the various sources, formation and metabolism of the dietary acrylamide along with the different molecular mechanisms such as oxidative stress, inflammation, DNA damage, autophagy, mitochondrial dysfunction and morphological changes in nephron and hepatocytes through which acrylamide exerts its deleterious effect on kidney and liver causing nephrotoxicity and hepatotoxicity. This review summarizes various animal and cellular studies that demonstrate AA-induced nephrotoxicity and hepatotoxicity. Lastly, the article emphasizes on underlying protective molecular mechanisms of various pharmacological interventions against acrylamide induced hepatotoxicity and nephrotoxicity.

Heat stress enhances the expression of METTL3 to mediate N6-methyladenosine modification of SOS2 and NLRP3 inflammasome activation in boar Sertoli cells

Heat stress negatively affects pig production by disrupting the immune homeostasis of Sertoli cells (SCs), which compromises sperm quality, culminating in male infertility. Herein, we aimed to study the mechanism by which the NLRP3 inflammasome is activated by heat stress through N6-methyladenosine (m6A) modification regulation in SCs. Initially, it was found that heat stress (44°C, 30 min) markedly activated ERK1/2 signaling, which subsequently promoted NLRP3 inflammasome activation and inflammatory cytokine release from SCs. Then, using an m6A dot-blot assay, m6A sequencing, and methylated RNA immunoprecipitation, we found that heat stress augmented the level of m6A modification in SCs, and METTL3 augmented the m6A modification of mRNA encoding SOS Ras/Rho guanine nucleotide exchange factor 2 (SOS2), a key activator of the ERK pathway. Furthermore, YTHDF1 recognized and bound to the m6A-modified SOS2 mRNA to enhance its translation efficiency, ultimately triggering ERK1/2 signaling activation. In vivo experiments demonstrated that heat stress-induced decline in semen quality in mice was associated with elevated levels of m6A modifications in the testis and NLRP3 inflammasome activation. However, the damage caused by heat stress could be attenuated by intraperitoneal injection of S-Adenosylhomocysteine (SAH), a specific methyltransferase inhibitor. Our results emphasize the critical roles of m6A in regulating NLRP3 inflammasome activation under heat stress, identifying a novel therapeutic avenue to address heat stress.

Acrylamide Intake and Metabolic Syndrome Risk: The Tehran Lipid and Glucose Study

This cohort study aimed to determine the relationship between acrylamide intake and the risk of metabolic syndrome (MetS) and its risk factors in Tehranian adults. A total of 1762 men and 2786 women, respectively, with a mean ± SD age of 38.6 ± 14.3 and 35.9 ± 11.8 years and body mass index of 25.8 ± 4.31 were evaluated in this secondary analysis of the Tehran Lipid and Glucose Study. Dietary data were collected using a standard food frequency questionnaire. Total acrylamide intake was computed using the amount of acrylamide measured in 30 food items. MetS was defined according to the Iranian-modified National Cholesterol Education Program. Multivariable Cox proportional hazard regression models were used to estimate the incidence of MetS and its risk factors associated with acrylamide intake, considering confounding factors (e.g., age, sex, physical activity, body mass index, smoking). During the average follow-up of 6.23 ± 2.58 years, 1279 (28% of total) subjects had MetS incidence. The incidence of MetS was not associated with quartiles of acrylamide intake. After adjusting for confounding factors, participants in the fourth quartile of acrylamide intake had 15% and 21% higher risk of high triglyceride and high waist circumference, respectively. Moreover, acrylamide intake was positively related to high blood pressure incidence (Hazard ratio [Confidence interval] Q1-Q4: 1, 1.0 [0.92-1.08], 1.10 [1.02-1.19], 1.16 [1.07-1.26], p trend = 0.003). Based on findings, no apparent association was observed between acrylamide intake and MetS incidence. Long-term intake of acrylamide is associated with an increased risk of hypertriglyceridemia, high blood pressure, and abdominal obesity.

Thiol-Based Redox Molecules: Potential Antidotes for Acrylamide Toxicity

Acrylamide (ACR) is a low-molecular weight, non-aromatic reagent, widely used in industry, such as in the manufacture of paper, textiles, plastics, cosmetics, and dyes. ACR is formed during the cooking of starchy food and its toxicity results mainly by conferring oxidative stress by elevating reactive oxygen species (ROS). To identify potential antidotes for ACR toxicity, we evaluated the efficacy of several thiol-based molecules known for ROS-scavenging, disulfide-reducing properties, and inhibition of oxidative stress-induced activation of the mitogen-activated protein kinases (MAPKs): the extracellular-signal-regulated-kinases (ERK1/2), p38-mitogen-activated-protein-kinases (p38MAPK), and c-Jun-N-terminal-kinases (JNKs). We established a reproducible assay testing N-acetylcysteine (NAC), AD4/NACA, and the N-and C-blocked tri- and tetra-thioredoxin-mimetic (TXM) peptides, in PC12 cells. Our results demonstrate that these compounds exhibited high efficacy in suppressing ACR-induced MAPK activation, either prior to or subsequent to ACR exposure. The inhibition by single cysteine (Cys) residue, NAC and AD4/NACA (NAC-amide), 2 Cys peptides TXM-CB30, AcDCys-Gly-DCysNH2, TXM-CB20, AcCys-Gly-CysNH2, SuperDopa (SD, Ac-CysL-Levodopa-CysNH2, TXM-CB13, AcCys-Met-Lys-CysNH2, and a 3-Cys peptide, TXM-CB16, AcCys-γGlu-Cys-CysNH2 was dose-dependent and potency displayed a direct correlation with the number of Cys residues. Cellular proteolysis of SD, which consists of levodopa flanked by two Cys, may suppress the manifestation of Parkinson's disease (PD)-like symptoms mediated by chronic ACR exposure not only through lowering oxidative stress but also by replenishing cellular levels of dopamine. Overall, these results could advance the clinical application of TXM peptides as potential treatments for acute and/or chronic exposure to ACR and show promise as antidotes for preventing ACR-triggered PD-like neurotoxic symptoms.

Environmental toxicants and nephrotoxicity: Implications on mechanisms and therapeutic strategies

Kidneys are one of the most important organs in the human body. In addition to filtering 200 liters of fluid every 24 hours, the kidney also regulates acid-base balance, maintains electrolyte balance, and removes waste and toxicants from the body. Nephrotoxicity is the term used to describe the deterioration of kidney function caused by the harmful effects of medications and various types of environmental toxicants. Exposure to environmental toxicants is an inevitable side effect in the world's increasing industrialization and even more prevalent in underdeveloped nations. Growing data over the past few years has illuminated the probable connection between environmental toxicants and nephrotoxicity. Phthalates, microplastics, acrylamide and bisphenol A are environmental toxicants of particular concern, which are known to have nephrotoxic effects. Such toxicants may accumulate in the kidneys of humans after being consumed, inhaled, or come into contact with the skin. They can enter cells through endocytosis and accumulate in the cytoplasm. Small-sized nephrotoxicants can cause a variety of ailments including inflammation with increased production of pro-inflammatory cytokines, oxidative stress, mitochondrial dysfunction, autophagy, and apoptosis. This study uncovers the potential for new insights concerning the relationship between various environmental toxicants and kidney health. The objectives of this review is to establish information gaps, assess and identify the toxicity mechanisms of different nephrotoxicants, identify innovative pharmacological therapies that demonstrate promising therapeutic benefits/ relevance, and discuss the predictions for the future based on the analysis of the literature.

Differential susceptibility of BRL cells with/without insulin resistance and the role of endoplasmic reticulum stress signaling pathway in response to acrylamide-exposure toxicity effects in vitro

Acrylamide (ACR) is an endogenous food contaminant, high levels of ACR have been detected in a large number of foods, causing widespread concern. Since different organism states respond differently to the toxic effects of pollutants, this study establishes an insulin-resistant BRL cell model to explore the differential susceptibility of BRL cells with/without insulin resistance in response to acrylamide-exposure (0.0002, 0.02, or 1 mM) toxicity effects and its mechanism. The results showed that ACR exposure decreased glucose uptake and increased intracellular lipid levels by promoting the expression of fatty acid synthesis, transport, and gluconeogenesis genes and inhibiting the expression of fatty acid metabolism genes, thereby further exacerbating disorders of gluconeogenesis and lipid metabolism in insulin-resistant BRL cells. Simultaneously, its exposure also exacerbated BRL cells with/without insulin-resistant damage. Meanwhile, insulin resistance significantly raised susceptibility to BRL cell response to ACR-induced toxicity. Furthermore, ACR exposure further activated the endoplasmic reticulum stress (ERS) signaling pathway (promoting phosphorylation of PERK, eIF-2α, and IRE-1α) and the apoptosis signaling pathway (activating Caspase-3 and increasing the Bax/Bcl-2 ratio) in BRL cells with insulin-resistant, which were also attenuated after ROS scavenging or ERS signaling pathway blockade. Overall results suggested that ACR evokes a severer toxicity effect on BRL cells with insulin resistance through the overactivation of the ERS signaling pathway.

Effects of a single phosphate-enriched test meal on inflammasome activity and postprandial inflammatory markers in healthy subjects

PURPOSE

The consumption of highly processed food is often associated with a high intake of inorganic phosphate. Hyperphosphatemia is accompanied by an inflammatory status in patients with chronic kidney disease. However, the immune response to high phosphorus intake in healthy individuals is largely unknown. Therefore, the aim of the present study was to evaluate the effect of a single phosphate-enriched meal on inflammasome activity and plasma levels of inflammatory markers.

METHODS

The analysis included 28 participants who received a single dose of either 700 mg phosphorus or a placebo with a test meal. At baseline, 4 and 8 h post-meal, plasma interleukin (IL)-6, IL-1β, IL-10, c-reactive protein (CRP), soluble IL-6 receptor (sIL-6R) and glycoprotein 130 (sgp130) levels were determined. At baseline and 4 h post-meal, peripheral blood mononuclear cells were isolated to assess inflammasome activity. Subsequently, the effect of phosphate with or without glucose on IL-6 and IL-1β gene expression and secretion in U937 monocytes was examined.

RESULTS

While both groups showed a marked postprandial increase in IL-6 plasma levels, neither plasma levels of IL-6, IL-1β, CRP, IL-10, sIL-6R, and sgp130 nor inflammasome activity were affected by phosphate compared to placebo. In U937 cells, there was also no effect of phosphate on IL-6 expression, but the addition of glucose increased it. Phosphate, however, reduced the IL-1β secretion of these cells.

CONCLUSION

Postprandial inflammatory markers were not affected by dietary phosphate. However, IL-6 plasma levels were markedly increased post-meal, which appears to be a metabolic rather than a pro-inflammatory phenomenon.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, NCT03771924, date of registration: 11th December 2018, retrospectively registered.

Asiaticoside Attenuates Blood-Spinal Cord Barrier Disruption by Inhibiting Endoplasmic Reticulum Stress in Pericytes After Spinal Cord Injury

The blood-spinal cord barrier (BSCB) plays a vital role in the recovery of spinal cord function after spinal cord injury (SCI). Pericytes, pluripotent members of the neurovascular unit (NVU), receive signals from neighboring cells and are critical for maintaining CNS function. Therapeutic targets for the BSCB include endothelial cells (ECs) and glial cells, but few drugs target pericytes. This study was designed to explore whether asiaticoside has a positively effect on pericytes and the integrity of the BSCB. In this study, we found that asiaticoside could inhibit the loss of junction proteins just 1 day after SCI in vivo, but our in vitro study showed no significant differences in the expression of endothelial junction proteins between the control and asiaticoside treatment groups. We also found that asiaticoside could inhibit endoplasmic reticulum (ER) stress and pericyte apoptosis, which might be associated with the inhibition of junction protein reduction in ECs. Thus, we investigated the interactions between pericytes and ECs. Our results showed that asiaticoside could decrease the release of matrix metalloproteinase (MMP)-9 in pericytes and therefore upregulate the expression of junction proteins in ECs. Furthermore, the protective effect of asiaticoside on pericytes is related to the inhibition of ER stress via the MAPK signaling pathway. Taken together, our results demonstrate that asiaticoside treatment inhibits BSCB disruption and enhances functional recovery after SCI.

Silicon dioxide-induced endoplasmic reticulum stress of alveolar macrophages and its role on the formation of silicosis fibrosis: a review article

Silicosis is a chronic lung inflammatory disease induced by long-term inhalation of high concentrations of silicon dioxide (SiO2), characterized by pulmonary fibrosis. Inhalation of silica invades alveolar macrophages (AMs) and changes the micro-environment of the cell, resulting in abnormal morphology and dysfunction of the endoplasmic reticulum (ER). Once beyond the range of cell regulation, the endoplasmic reticulum stress (ERS) will occur, which will lead to cell damage, necrosis, and apoptosis, eventually causing silicosis fibrosis through various mechanisms. This is a complex and delicate process accompanied by various macrophage-derived cytokines. Unfortunately, the details have not been systematically summarized yet. In this review, we systematically introduce the basic two processes: the process of inducing ERS by inhaling SiO2 and the process of inducing pulmonary fibrosis by ERS. Moreover, the underlying mechanism of the above two sequential events is also be discussed. We conclude that the ERS of alveolar macrophages caused by silica dust are involved deeply in the pathogenesis of silicosis. Therefore, changing the states of SiO2-induced ERS of macrophage may be an attractive therapeutic target for silicosis fibrosis.

Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

Environmental pollution is changing with economic development. Most environmental pollutants are characterized by stable chemical properties, strong migration, potential toxicity, and multiple exposure routes. Harmful substances are discharged excessively, and large quantities of unknown new compounds are emerging, being transmitted and amplifying in the food chain. The increasingly severe problems of environmental pollution have forced people to re-examine the relationship between environmental pollution and health. Pyroptosis and activation of the NLRP3 inflammasome are critical in maintaining the immune balance and regulating the inflammatory process. Numerous diseases caused by environmental pollutants are closely related to NLRP3 inflammasome activation and pyroptosis. We intend to systematically explain the steps and important events that are common in life but easily overlooked by which environmental pollutants activate the NLRP3 inflammasome and pyroptosis pathways. This comprehensive review also discusses the interaction network between environmental pollutants, the NLRP3 inflammasome, pyroptosis, and diseases. Thus, research progress on the impact of decreasing oxidative stress levels to inhibit the NLRP3 inflammasome and pyroptosis, thereby repairing homeostasis and reshaping health, is systematically examined. This review aims to deepen the understanding of the impact of environmental pollutants on life and health and provide a theoretical basis and potential programs for the development of corresponding treatment strategies.

Acrylamide induces the activation of BV2 microglial cells through TLR2/4-mediated LRRK2-NFATc2 signaling cascade

Acrylamide (ACR), a potential neurotoxin, is generated from the Maillard reaction between reducing sugars and free amino acids during food processing. Our work focuses on clarifying the role of the leucine-rich repeat kinase 2 (LRRK2) and nuclear factor of activated T cells, cytoplasmic 2 (NFATc2) in the polarization of BV2 cells to the M1 proinflammatory type induced by ACR. Specifically, ACR promoted the phosphorylation of LRRK2 and NFATc2 in BV2 microglia. Furthermore, selectively phosphorylated LRRK2 by ACR induced nuclear translocation of NFATc2 to trigger a neuroinflammatory cascade. Knock-down of LRRK2 by silencing significantly diminished ACR-induced microglial neurotoxic effect with the decline of IL-1β, IL-6, and iNOS levels and the decrease of NFATc2 expression in BV2 cells. After pretreated with Toll-Like Receptor 2 (TLR2) and TLR4 inhibitors separately, both the activation of LRRK2 and the release of pro-inflammatory factors were inhibited in BV2 cells. Gallic acid (GA) is ubiquitous in most parts of the medicinal plant. GA alleviated the increased CD11b expression, IL-6 and iNOS levels induced by ACR in BV2 microglia. In conclusion, this study shows that ACR leads to the cascade activation of LRRK2-NFATc2 mediated by TLR2 and TLR4 to induce microglial toxicity.

NLRP3 Inflammasome: A key contributor to the inflammation formation

Inflammation is an important part of the development of various organ diseases. The inflammasome, as an innate immune receptor, plays an important role in the formation of inflammation. Among various inflammasomes, the NLRP3 inflammasome is the most well studied. The NLRP3 inflammasome is composed of skeletal protein NLRP3, apoptosis-associated speck-like protein (ASC) and pro-caspase-1. There are three types of activation pathways: (1) "classical" activation pathway; (2) "non-canonical" activation pathway; (3) "alternative" activation pathway. The activation of NLRP3 inflammasome is involved in many inflammatory diseases. A variety of factors (such as genetic factors, environmental factors, chemical factors, viral infection, etc.) have been proved to activate NLRP3 inflammasome and promote the inflammatory response of the lung, heart, liver, kidney and other organs in the body. Especially, the mechanism of NLRP3 inflammation and its related molecules in its associated diseases remains not to be summarized, namely they may promote or delay inflammatory diseases in different cells and tissues. This article reviews the structure and function of the NLRP3 inflammasome and its role in various inflammations, including inflammations caused by chemically toxic substances.

Protective effect of Aronia melanocarpa juice against acrylamide-induced cellular toxicity

Acrylamide (AA) a widely used industrial chemical is also formed during food processing by the Maillard reaction, which makes its exposure to humans almost unavoidable. In this study, we used Schizosaccharomyces pombe as a model organism to investigate AA toxicity (10 or 20 mM concentration) in eukaryotes. In S. pombe, AA delays cell growth causes oxidative stress by enhancement of ROS production and triggers excitement of the antioxidant defence system resulting in the division arrest. Aronia fruit contains a variety of health-promoting substances with considerable antioxidant potential. Therefore, Aronia juice supplementation was tested to evaluate its protective effect against AA-derived perturbations of the organism. Cell treatment with several Aronia juice concentrations ranging from 0 to 2% revealed the best protective effect of 1 or 2% Aronia juice solutions. Both chosen Aronia juice concentrations alleviated AA toxicity through the improvement of the antioxidant cell capacity and metabolic activity by their strong ROS scavenging property. Efficiency of Aronia juice cell protection is dose dependent as the 2% solution led to significantly higher cellular defence compared with 1%. Due to the high similarity of biological processes of S. pombe with higher eukaryotes, the protective effect of Aronia juice against AA toxicity might also apply to higher organisms.

Carvacrol prevents acrylamide-induced oxidative and inflammatory liver damage and dysfunction in rats

Background: Acrylamide causes hepatotoxicity with the effect of oxidative stress and inflammatory processes. Carvacrol is a monoterpenic phenol with antioxidant and anti-inflammatory properties. Aims: To determine the effects of carvacrol on oxidative liver injury induced by acrylamide administration in rats. Methods: Rats were divided into three groups of six animals each: healthy group acrylamide group (ACR), and acrylamide + carvacrol group (TACR). First, carvacrol (50 mg/kg) was administered intraperitoneally to the CACR group. One hour later, acrylamide (20 mg/kg) was given orally to the ACR and CACR groups. This procedure was performed for 30 days, after which the animals were sacrificed. The malondialdehyde (MDA) and total glutathione (tGSH) levels, total oxidant (TOS) and total antioxidant status (TAS), tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), and nuclear factor kappa b (NF-κB) were measured in the excised liver tissues. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were determined in blood serum samples. Liver tissues were also examined histopathologically. Results: In the ACR group, malondialdehyde, TOS, ALT, AST levels, and NF-κB, IL-1β, and TNF-α levels were found to be high, and tGSH and total antioxidant status levels were low. In addition, diffuse degenerative changes and necrosis in hepatocytes, and moderate inflammation in the portal region were detected in the liver tissues of the ACR group. While carvacrol prevented the biochemical changes induced by acrylamide, it also alleviated the damage in the histological structure. Conclusion: Carvacrol may be used for liver damage caused by acrylamide.

Acrylamide induces ferroptosis in HSC-T6 cells by causing antioxidant imbalance of the XCT-GSH-GPX4 signaling and mitochondrial dysfunction

Acrylamide (AA) is a heat-induced food contaminant, mainly metabolized by the liver. Increasing evidences have proved that ferroptosis is linked to the pathogenesis of liver disease. In the current study, the underlying mechanism of AA-induced rat hepatic stellate (HSC-T6) cells ferroptosis was investigated by detecting changes in iron levels, expressions of ferroptosis-related proteins and indicators of mitochondrial dysfunction. The results showed that AA treatment led to iron levels increased and expressions of long-chain acyl-CoA synthase 4 (ACSL4), cyclooxygenase 2 (COX2) and ferritin heavy chain 1 (FTH1) proteins in HSC-T6 cells were all altered. Treatment with the ferroptosis inhibitor ferrostatin-1 (Fer-1) markedly reversed the impact of AA, suggesting that AA induced ferroptosis in HSC-T6 cells. Mechanistically, AA induced the onset of ferroptosis by affecting XCT-GSH-GPX4 antioxidant signaling. Moreover, AA created a peroxidative environment for ferroptosis by inducing oxidative stress in HSC-T6 cells through mitochondrial dysfunction, as evidenced by increased mitochondrial ROS (mtROS) release, mitochondrial membrane potential (MMP) depolarization, and decreased mitochondrial ATP. Our results indicated that AA resulted in mitochondrial dysfunction and ferroptosis, and dysregulation of XCT-GSH-GPX4 antioxidant signaling was a key factor in AA-induced ferroptosis.

Catechins protect against acrylamide- and glycidamide-induced cellular toxicity via rescuing cellular apoptosis and DNA damage

Acrylamide (AA) occurs in both various environmental and dietary sources and has raised widespread concern as a probable carcinogen. Glycidamide (GA) is the main genotoxic metabolite through P450 2E1 (CYP2E1). In the present study, we investigate the protective effect of (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin (EC) against AA- and GA-induced hepatotoxicity in HepG2 cells. The results demonstrated that EC and EGCG inhibited AA- and GA-induced cytotoxicity and mitochondria-mediated cellular apoptosis. Moreover, exposure to AA (100 μg/mL) and GA (50 μg/mL) caused cell cycle arrest and DNA damage, while EC and EGCG ranging from 12.5 to 50 μg/mL rescued cell cycle arrest and inhibited DNA damage. Furthermore, EC and EGCG down-regulated pro-apoptotic protein Bax and Caspase 3 after 24 h treatment in HepG2 cells exposed to AA (100 μg/mL) or GA (50 μg/mL). Also, the intervention with EC or EGCG up-regulated DNA repair related protein PARP and down-regulated expression of cleaved-PARP. Besides, EC exerted better protective effect than EGCG against AA- and GA-induced cytotoxicity in HepG2 cells. Altogether, EC and EGCG were effective in protecting AA- and GA-induced hepatotoxicity via rescuing cellular apoptosis and DNA damage, as well as promoting cell cycle progression in HepG2 cells.

Stimulating the expression of sphingosine kinase 1 (SphK1) is beneficial to reduce acrylamide-induced nerve cell damage

Sphingosine kinase 1 (SphK1) is an important signaling molecule for cell proliferation and survival. However, the role of SphK1 in acrylamide (ACR)-induced nerve injury remains unclear. The purpose of this study was to investigate the role and potential mechanism of SphK1 in ACR-induced nerve injury. Liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS) and reverse transcription-quantitative PCR (RT-qPCR) were used to detect sphingosine 1-phosphate (S1P) content in serum and SphK1 content in whole blood from an occupational work group exposed to ACR compared to a non-exposed group. For in vitro experiments, SphK1 in human SH-SY5Y neuroblastoma cells was activated using SphK1-specific activator phorbol 12-myristate 13-acetate (PMA). Our research also utilized cell viability assays, flow cytometry, western blots, RT-qPCR and related protein detection to assess activity of the mitogen activated protein kinase (MAPK) signaling pathway. The results of the population study showed that the contents of SphK1 and S1P in the ACR-exposed occupational contact group were lower than in the non-exposed group. The results of in vitro experiments showed that expression of SphK1 decreased with the increase in ACR concentration. Activating SphK1 improved the survival rate of SH-SY5Y cells and decreased the apoptosis rate. Activating SphK1 in SH-SY5Y cells also regulated MAPK signaling, including enhancing the phosphorylation of extracellular signal-regulated protein kinases (ERK) and inhibiting the phosphorylation of c-Jun N-terminal kinase (JNK) and p38. These results suggest that activating SphK1 can protect against nerve cell damage caused by ACR.

The toxicity of cooking oil fumes on human bronchial epithelial cells through ROS-mediated MAPK, NF-κB signaling pathways and NLRP3 inflammasome

Cooking oil fumes (COFs) are the main pollutants in kitchen and indoor air, which threaten human health. Exposure to COFs may lead to respiratory diseases and impair pulmonary function. To investigate the toxicity of COFs on human bronchial epithelial cells (Beas-2B) and explore the underlying mechanisms, MTT assay was conducted to detect the viability of Beas-2B. Intracellular reactive oxygen species (ROS) levels and nitric oxide (NO) levels were determined with DCFH-DA assay and DAF-FM assay. The expression of genes involved in inflammation were measured with quantitative real-time PCR (qRT-PCR). The phosphorylation and the expression of proteins related to Mitogen-activated protein kinase (MAPK), NF-κB signaling pathways were measured with western blot. Our results revealed that COFs decreased cell viability, increased the ROS levels and NO levels and induced apoptosis in Beas-2B cells. The results of qRT-PCR and western blot showed that the expression of NLRP3, p65, iNOS, IL-1β, and the factors related to oxidative stress and inflammation increased, NF-κB signaling pathway and MAPK signaling pathway were activated. This study provided some useful information to evaluate the toxicity of COFs and revealed the possible mechanism for the damage on respiratory system induced by COFs.

Acrylamide Neurotoxicity as a Possible Factor Responsible for Inflammation in the Cholinergic Nervous System

Acrylamide (ACR) is a chemical compound that exhibits neurotoxic and genotoxic effects. It causes neurological symptoms such as tremors, general weakness, numbness, tingling in the limbs or ataxia. Numerous scientific studies show the effect of ACR on nerve endings and its close connection with the cholinergic system. The cholinergic system is part of the autonomic nervous system that regulates higher cortical functions related to memory, learning, concentration and attention. Within the cholinergic system, there are cholinergic neurons, anatomical cholinergic structures, the neurotransmitter acetylcholine (ACh) and cholinergic receptors. Some scientific reports suggest a negative effect of ACR on the cholinergic system and inflammatory reactions within the body. The aim of the study was to review the current state of knowledge on the influence of acrylamide on the cholinergic system and to evaluate its possible effect on inflammatory processes. The cholinergic anti-inflammatory pathway (CAP) is a neuroimmunomodulatory pathway that is located in the blood and mucous membranes. The role of CAP is to stop the inflammatory response in the appropriate moment. It prevents the synthesis and the release of pro-inflammatory cytokines and ultimately regulates the local and systemic immune response. The cellular molecular mechanism for inhibiting cytokine synthesis is attributed to acetylcholine (ACh), the major vagal neurotransmitter, and the α7 nicotinic receptor (α7nAChR) subunit is a key receptor for the cholinergic anti-inflammatory pathway. The combination of ACh with α7nAChR results in inhibition of the synthesis and release of pro-inflammatory cytokines. The blood AChE is able to terminate the stimulation of the cholinergic anti-inflammatory pathway due to splitting ACh. Accordingly, cytokine production is essential for pathogen protection and tissue repair, but over-release of cytokines can lead to systemic inflammation, organ failure, and death. Inflammatory responses are precisely regulated to effectively protect against harmful stimuli. The central nervous system dynamically interacts with the immune system, modulating inflammation through the humoral and nervous pathways. The stress-induced rise in acetylcholine (ACh) level acts to ease the inflammatory response and restore homeostasis. This signaling process ends when ACh is hydrolyzed by acetylcholinesterase (AChE). There are many scientific reports indicating the harmful effects of ACR on AChE. Most of them indicate that ACR reduces the concentration and activity of AChE. Due to the neurotoxic effect of acrylamide, which is related to the disturbance of the secretion of neurotransmitters, and its influence on the disturbance of acetylcholinesterase activity, it can be concluded that it disturbs the normal inflammatory response.

The Effect of α-Tocopherol on the Reduction of Inflammatory Processes and the Negative Effect of Acrylamide

Our research aimed to show acrylamide's influence on inflammatory processes, the oxidative stress it causes in the cholinergic system, and the possibility of reducing inflammation via supplementation with α-tocopherol. For this purpose, an in ovo model was used where the embryos were exposed to acrylamide, α-tocopherol and a cocktail of these substances. After 48 h of exposure, we collected brain samples and performed biochemical assays to examine the effect of the chosen substances on oxidative stress (malondialdehyde-MDA and reduced glutathione-GSH) and acetylcholinesterase activity (AChE). The results showed that acrylamide decreased AChE activity in the examined brain samples by about 25% in comparison to the control group, and this effect was decreased by administering α-tocopherol. The concentration of malondialdehyde significantly increased in the group given acrylamide, while, in the group with α-tocopherol, the observed concentration was lower in comparison to the control group. Moreover, a decrease in glutathione concentration was observed after the administration of acrylamide; however, the protective effect of α-tocopherol was only slightly visible in this case. In conclusion, α-tocopherol minimizes the harmful effects of acrylamide on AchE, and it can minimize the concentration of MDA.

Modulatory Properties of Food and Nutraceutical Components Targeting NLRP3 Inflammasome Activation

Inflammasomes are key intracellular multimeric proteins able to initiate the cellular inflammatory signaling pathway. NLRP3 inflammasome represents one of the main protein complexes involved in the development of inflammatory events, and its activity has been largely demonstrated to be connected with inflammatory or autoinflammatory disorders, including diabetes, gouty arthritis, liver fibrosis, Alzheimer’s disease, respiratory syndromes, atherosclerosis, and cancer initiation. In recent years, it has been demonstrated how dietary intake and nutritional status represent important environmental elements that can modulate metabolic inflammation, since food matrices are an important source of several bioactive compounds. In this review, an updated status of knowledge regarding food bioactive compounds as NLRP3 inflammasome modulators is discussed. Several chemical classes, namely polyphenols, organosulfurs, terpenes, fatty acids, proteins, amino acids, saponins, sterols, polysaccharides, carotenoids, vitamins, and probiotics, have been shown to possess NLRP3 inflammasome-modulating activity through in vitro and in vivo assays, mainly demonstrating an anti-NLRP3 inflammasome activity. Plant foods are particularly rich in important bioactive compounds, each of them can have different effects on the pathway of inflammatory response, confirming the importance of the nutritional pattern (food model) as a whole rather than any single nutrient or functional compound.

Short-term exposure to acrylamide exacerbated metabolic disorders and increased metabolic toxicity susceptibility on adult male mice with diabetes

Diabetes mellitus is a common endocrine metabolic disorder, and previous studies have shown that diabetics are more sensitive to the toxic environmental contaminants. Acrylamide (ACR) is both an industrially multipurpose compound and a common endogenous food contaminant to which people are frequently exposed and at high risk. However, the toxicity of ACR on diabetes hasn't attracted much attention. In this study, both healthy mice and diabetic mice received ACR administration orally to investigate the ACR-induced metabolic toxicity, mechanism and susceptibility to ACR toxicity in adult diabetic male mice. The results showed that ACR significantly increased FBG level and decreased bodyweight, serum lipid and liver lipid biomarkers (TC, TG, LDL-C, HDL-C) levels as well as expression of lipid and glucose metabolism-related genes in diabetic mice, indicating that ACR can exacerbate metabolic disorders of glucose and lipid in diabetic male mice. Moreover, ACR exposure significantly increased levels of MDA and COX-2), decreased GSH level and antioxidant enzyme activity (SOD, GSH-PX and CAT) by downregulating expression of Nrf2 and Keap1 in diabetic mice. Factorial analysis showed ACR had a more significant disturbance in diabetic mice compared with healthy mice. Our results indicated that ACR exposure can cause oxidative stress and inflammatory damage, which can exacerbate abnormal glucose and lipid metabolism. This work helps to elucidate the effects and underlying mechanisms of ACR-induced metabolic toxicity in adults with diabetes.

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.

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.

Elaidic acid induced NLRP3 inflammasome activation via ERS-MAPK signaling pathways in Kupffer cells

Trans fatty acids (TFA) in food can cause liver inflammation. Activation of NOD-like receptor protein-3 (NLRP3) inflammasome is a key factor in the regulation of inflammation. Accumulating evidence suggests that ERS-induced NLRP3 inflammasome activation underlies the pathological basis of various inflammatory diseases, but the precise mechanism has not been fully elucidated. Therefore, this paper focused on TFA, represented by elaidic acid (EA), to investigate the mechanism of liver inflammation. Levels of mRNA and protein were detected by RT-qPCR and Western blotting, the release of proinflammatory cytokines was measured by ELISA, and intracellular Ca²⁺ levels were determined by flow cytometer using Fluo 4-AM fluorescent probes. Our research indicated that EA induced the endoplasmic reticulum stress (ERS) response in Kupffer cells (KCs), accompanied by the activation of the mitogen-activated protein kinase (MAPK) signaling pathway, which resulted in NLRP3 inflammasome formation, and eventually increased the release of inflammatory factors. NLRP3 inflammasome activation was inhibited when KCs were pretreated with ERS inhibitors (4-PBA) and MAPK selective inhibitors. Furthermore, when ERS was blocked, the MAPK pathway was inhibited.

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.

Allicin alleviated acrylamide-induced NLRP3 inflammasome activation via oxidative stress and endoplasmic reticulum stress in Kupffer cells and SD rats liver

Acrylamide (AA) in heat-processed food leads to widespread concerns due to its hepatotoxicity. Allicin, a plant-derived antioxidant, possesses a significant protective effect on AA-induced hepatotoxicity, but the mechanism is still unclear. Herein, we investigated the mechanism in Kupffer cells and SD rats liver. Molecular docking, molecular dynamics simulation and LigPlus software speculated that allicin inhibited the activity of CYP2E1 expression by binding to its amino acid residues Phe116, Phe207, Leu210, Phe298, Ala299, Thr303, Val364 and Phe478 through hydrophobic interactions. Allicin decreased the reactive oxygen species (ROS) release and CYP2E1 protein expression and then alleviated the appearance of OS. Meanwhile, allicin significantly reduced ERS characteristic proteins GRP78, CHOP and UPR branch IRE1α pathway key proteins p-IRE, p-ASK, TRAF2 and XBP-1s expression. Simultaneously, allicin ameliorated OS and ERS activation, which inhibited the activation of the MAPK and NF-κB pathways, and down-regulated JNK, ERK, p38, p65 and IκBα phosphorylation. Allicin pre-treatment inhibited AA-induced inflammation as evidenced by reducing NLRP3 inflammasome activation, decreasing Cleaved-Caspase-1 expression as well as IL-1β, IL-18, IL-6 and TNF-α secretion. Taken together, our data provide new insights into possible signaling pathways involved in allicin attenuating AA-induced hepatotoxicity in vivo and in vitro.