MiR-155-5p Elevated by Ochratoxin A Induces Intestinal Fibrosis and Epithelial-to-Mesenchymal Transition through TGF-ß Regulated Signaling Pathway In Vitro and In Vivo.

Ochratoxin A (OTA) is a mycotoxin that induces fibrosis and epithelial-to-mesenchymal transitions (EMT) in kidneys and livers. It enters our bodies through food consumption, where it is absorbed in the intestines. However, the impact of OTA on the intestines is yet to be studied. MicroRNA (miRNAs) are small non-coding single-stranded RNAs that block the transcription of specific mRNAs and are, therefore, involved in many biochemical processes. Our findings indicate that OTA can induce EMT and intestinal fibrosis both in vivo and in vitro. This study examines the impact of OTA on intestinal toxicity and the role of miRNAs in this process. Following OTA treatment, miR-155-5p was the most elevated miRNA by next-generation sequencing. Our research showed that OTA increased miR-155-5p levels through transforming growth factor ß (TGF-ß), leading to the development of intestinal fibrosis and EMT. Additionally, the study identified that the modulation of TGF-ß and miR-155-5p by OTA is linked to the inhibition of CCAAT/enhancer-binding protein ß (C/EBPß) and Smad2/3 accumulation in the progression of intestinal fibrosis.

Perfluorooctanoic acid (PFOA) and hexafluoropropylene oxide-dimer acid (GenX): Hepatic stress and bile acid metabolism with different pathways.

Per- and polyfluoroalkyl substances (PFASs) and perfluoroalkyl ether carboxylic acids (PFECAs) are organic chemicals that are widely used in the manufacture of a wide range of human-made products. Many monitoring findings revealed the presence of PFASs and PFECAs in numerous environmental sources, including water, soil, and air, which drew more attention to both chemicals. Because of their unknown toxicity, the discovery of PFASs and PFECAs in a variety of environmental sources was viewed as a cause for concern. In the present study, male mice were given orally one of the typical PFASs, perfluorooctanoic acid (PFOA), and one of the representative PFECAs, hexafluoropropylene oxide-dimer acid (HFPO-DA). The liver index showing hepatomegaly rose significantly after 90 d of exposure to PFOA and HFPO-DA, respectively. While sharing similar suppressor genes, both chemicals demonstrated unique hepatotoxic mechanisms. In different ways, these two substances altered the expression of hepatic stress-sensing genes as well as the regulation of nuclear receptors. Not only are bile acid metabolism-related genes in the liver altered, but cholesterol metabolism-related genes as well. These results indicate that PFOA and HFPO-DA both cause hepatotoxicity and bile acid metabolism impairment with distinct mechanisms.

Ochratoxin A induces endoplasmic reticulum stress and fibrosis in the kidney via the HIF-1α/miR-155-5p link.

Ochratoxin A (OTA) is a ubiquitous fungal toxin found in agricultural products and foods that is toxic to both humans and animals. OTA mainly affects kidney, but the mechanisms underlying OTA-induced nephrotoxicity remain not fully understood. MicroRNA (miRNA) is involved in key cellular processes. The toxic mechanism and regulatory effects of miRNAs on OTA toxicity in kidney, and particularly the role of HIFα-1/miR-155-5p on OTA-caused ER stress and fibrosis, were investigated in this study. OTA induced hypoxia-like conditions such as ER stress and fibrosis in HK-2 cells and renal tissues via modulating HIF-1α, which was followed by regulation of ER stress-related proteins (GRP78 and ATF-4), as well as fibrosis-related markers (fibronectin, α-SMA, and E-cadherin). Notably, a total of 62 miRNAs showed significant differential expression in kidney of OTA-treated mice. Under OTA exposure, HIF-1α enhanced miR-155-5p expression, causing ER stress and fibrosis in HK-2 cells. HIF-1α knockdown decreased OTA-induced miR-155-5p expression as well as ER stress and fibrotic responses, whereas miR-155-5p overexpression restored this. Our data suggest that OTA enhances ER stress and fibrosis in the kidney through upregulating the HIF-1α/miR-155-5p link.

Combined effects of cadmium and ochratoxin A on intestinal barrier dysfunction in human Caco-2 cells and pig small intestinal epithelial cells.

Hazardous chemicals are commonly found in cereals and cereal-based products. However, most studies focus on the individual effects of these mycotoxins or metals, rather than their combined toxicity. The main objective of this study was to evaluate the combined effects of cadmium (Cd) and ochratoxin A (OTA) on intestinal barrier integrity using Caco-2 cells and pig small intestinal epithelial (PSI) cells as models of intestinal epithelial cells and to measure alterations in cell survival and barrier integrity. The combined effects on cell viability were assessed in terms of a combination of index values. These findings showed that co-exposure to Cd + OTA had synergistic effects on Caco-2 and PSI cells at 25%, 50%, and 75% inhibitory concentrations (IC25, IC50, and IC75, respectively) against cell viability. Individual Cd and OTA treatments had no effect, but combined Cd + OTA exposure resulted in synergistic down-regulation of paracellular apical junction complex proteins, such as claudin-1, occludin, and E-cadherin. The current findings indicate that the combined effects of OTA + Cd may have consequences at the gut level, which should not be underestimated when considering their risk to human health.

Ochratoxin a induces hepatic fibrosis through TGF-ß receptor I/Smad2/3 signaling pathway.

Ochratoxin A (OTA) is a mycotoxin generated by Penicillium and Aspergillus species. It is often found in cereals. We hypothesized that OTA exposure induces epithelial-mesenchymal transition (EMT), leading to liver fibrosis. In this research, we explored whether the TGF-ß receptor I (TGF-ß RI)/Smad2/3 signaling pathway is related to EMT-induced hepatic fibrosis. In vitro and in vivo experiments, mRNA and protein expression of liver fibrosis-related markers such as fibronectin, α-smooth muscle actin (α-SMA) and E-cadherin were assessed. The levels of alkaline phosphatase, alanine transaminase, aspartate aminotransferase, and total bilirubin, which are used to assess damage, increased. We also confirmed the increase in mRNA and protein expression of TGF-ß RI, Smad2, and Smad3. The expression of liver fibrosis-related markers was decreased by siRNA-mediated silencing of Smad2/3, as well as TGF-RI suppression. Liver cells exposed to OTA showed enhanced TGF-ß RI expression on the cell membrane. These results demonstrated that OTA induces hepatic fibrosis through TGF-ß RI and Smad2/3 pathways in vitro and in vivo.

Methylglyoxal-Derived Advanced Glycation End Products (AGE4) Promote Cell Proliferation and Survival in Renal Cell Carcinoma Cells through the RAGE/Akt/ERK Signaling Pathways.

Advanced glycation end products (AGEs) are the products formed through a non-enzymatic reaction of reducing sugars with proteins or lipids. There is a potential for toxicity in the case of AGEs produced through glycation with dicarbonyl compounds including methylglyoxal, glyoxal, and 3-deoxyglucosone. The AGEs bind the receptor for advanced glycation end products (RAGE) and stimulate the mitogen-activated protein (MAP) kinase signaling pathway that can increase the production of matrix metalloproteinases (MMPs). In addition, AGE-induced protein kinase B (Akt) signaling can promote cancer cell proliferation and contribute to many diseases such as kidney cancer. In light of the lack of extensive study of the relationship between methylglyoxal-induced AGEs (AGE4) and renal cancer, we studied the proliferous and anti-apoptotic effects of AGE4 on renal cell carcinoma (RCC) in this study. AGE4 treatment was involved in the proliferation and migration of RCC cells in vitro by upregulating proliferating cell nuclear antigen (PCNA) and MMPs while suppressing apoptotic markers such as Bax and caspase 3. Moreover, Akt and extracellular-signal-regulated kinase (ERK) were phosphorylated in RCC cells with AGE4 treatment. As a result, this study demonstrated that AGE4-RAGE axis can promote the growth ability of RCC by inducing PCNA, MMPs, and inhibiting apoptosis in RCC via the Akt and ERK signaling pathways.

Hexafluoropropylene oxide dimer acid (GenX) exposure induces apoptosis in HepG2 cells.

Hexafluoropropylene oxide dimer acid, also known as GenX, is a poly- and perfluoroalkyl substance (PFAS). PFASs are nonvolatile synthetic substances that can be readily disseminated into the environment during processing and use, making them easy to implement in the soil, drinking water, and air. Compared to other PFASs, GenX has a comparatively short carbon chain length and is expected to have a lower tendency to accumulate in humans; therefore, GenX has recently been used as a substitute to other PFASs. However, the mechanisms underlying GenX action and intoxication in humans remains unclear. In this study, the apoptotic capacity of GenX in human liver cells was investigated. When representative human-derived liver cells (HepG2 cells) were treated with GenX for 12 h, cell viability was reduced, and apoptosis was greatly increased. In addition, GenX increased the generation of intracellular reactive oxygen species (ROS), indicating the induction of oxidative stress in a dose-dependent manner. GenX treatment increased the expression of major apoptosis-related genes relative to the untreated control group. This research indicates that GenX causes apoptosis through ROS mediation in HepG2 cells, which may expand our knowledge of the molecular and toxicological mechanisms of GenX.

Transcriptome Analysis Reveals the AhR, Smad2/3, and HIF-1α Pathways as the Mechanism of Ochratoxin A Toxicity in Kidney Cells.

Ochratoxin A (OTA) is a mycotoxin occurring in foods consumed by humans. Recently, there has been growing global concern regarding OTA toxicity. The main target organ of OTA is the kidney, but the mechanism underlying renal toxicity is not well known. In this study, human-derived proximal tubular epithelial cells, HK-2 cells, were used for RNA-sequencing (RNA-seq) and transcriptome analysis. In total, 3193 differentially expressed genes were identified upon treatment with 200 nM OTA in HK-2 cells; of these, 2224 were upregulated and 969 were downregulated. Transcriptome analysis revealed that OTA significantly affects hypoxia, epithelial-mesenchymal transition (EMT), apoptosis, and xenobiotic metabolism pathways in kidney cells. Quantitative real-time PCR analysis showed gene expression patterns similar to RNA-seq analysis. Expression of EMT markers (E-cadherin and fibronectin), apoptosis markers (caspase-3 and Bax), and kidney injury molecule-1 (KIM-1) was suppressed by inhibiting AhR expression using siRNA, and the related transcription factors, Smad2/3, and HIF-1α were downregulated. Smad2/3 suppression with siRNA could inhibit fibronetcin, caspase-3, Bax, and KIM-1 expression. Fibronetcin, caspase-3, Bax, and KIM-1 expression could be increased with HIF-1α suppression with siRNA. Taken together, these findings suggest that OTA-mediated kidney toxicity via the AhR-Smad2/3-HIF-1α signaling pathways leads to induction of EMT, apoptosis, and kidney injury.

Synergistic Interaction of Ochratoxin A and Acrylamide Toxins in Human Kidney and Liver Cells.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium, and it is found in many foods. Acrylamide (AA) can be produced in foods treated at high temperatures. In this study, we investigated the combined toxicity of OTA and AA against human renal and hepatic cells in vitro. The concentration at which the synergistic effect of OTA and AA occurs was determined using the combination index obtained from the cell viability results for OTA and AA individually or in combination. The synergistic toxicity of both substances was evaluated by cell viability and the production of reactive oxygen species. In addition, apoptosis-related markers were significantly upregulated by OTA and AA individually or in combination. To determine the combined toxic effects of OTA and AA on the cells, the levels of enzymes involved in the phase I reaction and apoptosis-related markers were determined using quantitative (q)PCR and Western blot. The expression levels of CYP enzymes CYP1A1 and CYP1A2 involved in the phase I reaction significantly increased when the cells were treated with OTA and AA in combination. The expression of apoptosis-related markers, Bcl2-associated X protein (Bax) and caspase 3, also increased when the cells were treated with OTA and AA in combination. Therefore, the synergistic toxicity of OTA and AA suggests that such effects may contribute to nephrotoxicity and hepatotoxicity.

Ochratoxin A induces epithelial-to-mesenchymal transition and renal fibrosis through TGF-ß/Smad2/3 and Wnt1/ß-catenin signaling pathways in vitro and in vivo.

Ochratoxin A (OTA) is a toxin produced by fungi such as Aspergillus spp. and Penicillium spp. The key target organ of OTA toxicity is the kidney, and it is known that epithelial-to-mesenchymal transition (EMT) leading to fibrosis is enhanced after long-term exposure of the kidney to OTA. However, the mechanisms responsible for this onset are not precisely known. Therefore, the purpose of this study was to investigate the mechanism of OTA-induced EMT and fibrosis in human proximal tubule HK-2 cells and mouse kidneys. Cells were treated for 48 h with various concentrations of OTA (50, 100, and 200 nM) and mice underwent oral administration of various doses of OTA (200 and 1000 µg/kg body weight) for 12 weeks. Blood urea nitrogen and creatinine levels were increased in the serum of OTA-treated mice, and fibrosis was observed in kidney tissues. Furthermore, alpha-smooth muscle actin (α-SMA) and fibronectin levels were increased, and E-cadherin level was decreased by OTA in both HK-2 cells and kidney tissues. In addition, the expression levels of TGF-ß, smad2/3, and ß-catenin were increased after OTA treatment. α-SMA, E-cadherin, and fibronectin were shown to be regulated by the activation of transcription factors, smad2/3 and ß-catenin. These results demonstrated that OTA induces EMT and renal fibrosis through Smad2/3 and ß-catenin signaling pathways in vitro and in vivo.

Two-Photon Probe for TNF-α. Assessment of the Transmembrane TNF-α Level in Human Colon Tissue by Two-Photon Microscopy.

We developed Pyr1-infliximab: a two-photon probe for TNF-α. Pyr1-infliximab showed absorption maxima at 280 and 438 nm and an emission maximum at 610 nm in an aqueous buffer and effective two-photon action cross-section values of (520-2830) × 10-50 cm4s/photon in RAW 264.7 cells. After this probe was labeled, it was possible to detect Pyr1-infliximab-transmembrane TNF-α complexes in a live cell and to determine the relative proportion of these complexes in human colon tissues. This proportion among healthy, possibly inflamed, and inflamed tissues of patients with ulcerative colitis was found to be 1.0/4.5/10. This probe may find useful applications for selective detection of transmembrane TNF-α in a live cell or tissue, for quantification of inflammation in human colon tissue or of antidrug antibodies in patients who stop responding to anti-TNF therapy, and for monitoring of the response to this therapy.

Inhibitory Effect of Chebulic Acid on Alveolar Epithelial to Mesenchymal Transition in Response to Urban Particulate Matter Using Co-treatment and Post-treatment Exposure.

Urban particulate matter (UPM) is atmospheric particulate samples obtained from industrialized urban areas. It is known that pulmonary fibrosis can result directly or indirectly from particulate matter. In this study, the protective effect of chebulic acid (CA) against UPM-induced epithelial-mesenchymal transition (EMT) in the pulmonary alveolar epithelial (PAE) cells were investigated. Our findings revealed that PAE cells were changed from the epithelial phenotype to mesenchymal one after exposure to UPM. Furthermore, co-treatment and post-treatment of CA inhibited EMT progression. Especially the key epithelial marker, E-cadherin, was down-regulated by UPM and recovered by CA. Also, gelatin zymogram showed that the activity of matrix metalloproteinase (MMP)-2 and MMP-9 was decreased by co-treatment and post-treatment of CA. Further investigation revealed that CA attenuated UPM-stimulated PAE cells invasion ability. These data showed that UPM promoted PAE cells invasion, reactive oxygen species-mediated extracellular matrix degradation and CA reduced the potential health risks associated with UPM.

Ochratoxin A-Induced Hepatotoxicity through Phase I and Phase II Reactions Regulated by AhR in Liver Cells.

Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of the genera Aspergillus and Penicillium. OTA exists in a variety of foods, including rice, oats, and coffee and is hepatotoxic, with a similar mode of action as aflatoxin B1. The precise mechanism of cytotoxicity is not yet known, but oxidative damage is suspected to contribute to its cytotoxic effects. In this study, human hepatocyte HepG2 cells were treated with various concentrations of OTA (5-500 nM) for 48 h. OTA triggered oxidative stress as demonstrated by glutathione depletion and increased reactive oxygen species, malondialdehyde level, and nitric oxide production. Apoptosis was observed with 500 nM OTA treatment. OTA increased both the mRNA and protein expression of phase I and II enzymes. The same results were observed in an in vivo study using ICR mice. Furthermore, the relationship between phase I and II enzymes was demonstrated by the knockdown of the aryl hydrocarbon receptor (AhR) and NF-E2-related factor 2 (Nrf2) with siRNA. Taken together, our results show that OTA induces oxidative stress through the phase I reaction regulated by AhR and induces apoptosis, and that the phase II reaction is activated by Nrf2 in the presence of oxidative stress.

ERK/Nrf2 pathway activation by caffeic acid in HepG2 cells alleviates its hepatocellular damage caused by t-butylhydroperoxide-induced oxidative stress.

BACKGROUND: Several studies have found that caffeic acid (CA), a well-known phytochemical, displays important antioxidant and anti-cancer activities. However, no evidence exists on the protective effect and its mechanisms that CA treatment alone has against oxidative stress induced by tert-butyl hydroperoxide (t-BHP) in HepG2 cells. METHODS: Hepatoprotective activities such as cell viability, mRNA expression, and report gene assay were measured using HepG2 cell. Three types of genes and proteins related with detoxification in liver were used for measuring the hepatoprotective effects. Statistical analysis was performed using one-way ANOVA test and differences among groups were evaluated by Tukey's studentized range tests. RESULTS: The present study indicate that treatment with CA up-regulates heme oxygenase-1 (HO-1) and glutamate-cysteine ligase (GCL) mRNA and protein expressions in a CA-dose-dependent manner. In addition, translocation of nuclear factor-E2 p45-related factor (Nrf2) from the cytoplasm to the nucleus and phosphorylation of extracellular signal-regulated kinase, ERK and c-Jun N-terminal kinase, JNK which have been shown to be involved in mitogen-activated protein kinases, MAPKs are significantly enhanced by CA treatment. Furthermore, in cell nuclei, CA enhances the 5'-flanking regulatory region of human antioxidant response element (ARE) and activates the ARE binding site. CONCLUSION: Therefore, CA proved to be a stimulant of the expression of detoxification enzymes such as HO-1, GCLC, and GCLM through the ERK/Nrf2 pathway, and it may be an effective chemoprotective agent for protecting liver damage against oxidative damage.

Protective effects of chebulic acid from Terminalia chebula Retz. against t-BHP-induced oxidative stress by modulations of Nrf2 and its related enzymes in HepG2 cells.

Although chebulic acid isolated from Terminalia chebular has diverse biological effects, its effects on the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and the expression of downstream genes have not been elucidated. The purpose of this research is to investigate the hepatoprotective mechanism of chebulic acid against oxidative stress produced by tert-butyl hydroperoxide (t-BHP) in liver cells. The treatment with chebulic acid attenuated cell death in t-BHP-induced HepG2 liver cells and increased intracellular glutathione content, upregulated the activity of heme oxygenase-1, and also increased the translocation of Nrf2 into the nucleus and Nrf2 target gene expression in a dose-dependent manner. The exposure of chebulic acid activated the phosphorylation of mitogen-activated protein kinases. The overall result is that chebulic acid has cytoprotective effect on t-BHP-induced hepatotoxicity in HepG2 cells through Nrf2-mediated antioxidant enzymes.

Renal toxicity through AhR, PXR, and Nrf2 signaling pathway activation of ochratoxin A-induced oxidative stress in kidney cells.

Because ochratoxin A (OTA) is widely found in foods, people are susceptible to OTA exposure. The mechanism leading to renal toxicity induced by OTA remains unclear. The aim of this study was to investigate OTA-induced toxicity in human proximal tubule HK-2 cells. OTA decreased cell viability, and the expression of kidney injury molecule-1 (KIM-1), a kidney damage marker, was increased when HK-2 cells were exposed to OTA. Additionally, OTA treatment of cells increased intracellular reactive oxygen species and malondialdehyde and decreased glutathione levels. OTA-treated cells induced the aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) genes followed by induction of the cytochrome P450 1A1 (CYP1A1), CYP1A2, and CYP3A4 genes representing phase I enzyme. The mRNA expression of phase II enzymes such as heme oxygenase-1, nicotinamide adenine dinucleotide phosphate-quinone oxidoreductase 1, and glutamate cysteine ligase catalytic subunit were upregulated by activation of NF-E2-related factor 2 (Nrf2) translocation by treatment with OTA. The response of OTA-orally administered mice also showed marked increases in these enzymes as well as KIM-1. These results indicate that OTA induces phase I and II enzymes through the AhR, PXR, and Nrf2 signaling pathways in HK-2 cells, which may lead to modulation of proximal tubule injury.

Anti-inflammatory effect of glucose-lysine Maillard reaction products on intestinal inflammation model in vivo.

Inflammatory bowel diseases (IBDs) are chronic disorders that are characterized by intestinal epithelial inflammation and injury. Currently, the most employed therapies are antibiotics and anti-inflammatory drugs; however, the side effects limit long-term effectiveness. We evaluated the impact of glucose-lysine Maillard reaction products (Glc-Lys MRPs) on colitis, induced in rats by an administration of 5% dextran sulfate sodium (DSS) in drinking water. Glc-Lys MRPs ameliorate DSS-induced colitis, as determined by a decrease in disease index activity, colon weight/length ratio, nitric oxide levels in serum, recovery of body weight loss, colon length and serum lysozyme levels. Furthermore, Glc-Lys MRPs increase the glutathione content and the activity of glutathione peroxidase, superoxide dismutase and catalase, and inhibit lipid peroxidation and myeloperoxidase activity in colon tissues. In particular, Glc-Lys MRPs suppress the mRNA level of the inflammatory cytokines and nuclear factor-κB in colon tissues. This study suggests the potential of Glc-Lys MRPs in preventing or treating IBDs.

Improved physicochemical properties and hepatic protection of Maillard reaction products derived from fish protein hydrolysates and ribose.

High amounts of waste products generated from fish-processing need to be disposed of despite their potential nutritional value. A variety of methods, such as enzymatic hydrolysis, have been developed for these byproducts. In the current study, we investigated the physicochemical, biological and antioxidative properties of fish protein hydrolysates (FPH) conjugated with ribose through the Maillard reaction. These glycated conjugates of FPH (GFPH) had more viscous rheological properties than FPH and exhibited higher heat, emulsification and foaming stability. They also protected liver HepG2 cells against t-BHP-induced oxidative stress with enhanced glutathione synthesis in vitro. Furthermore, it was shown that GFPH induced upregulation of phase II enzyme expression, such as that of HO-1 and γ-GCL, via nuclear translocation of Nrf2 and phosphorylation of ERK. Taken together, these results demonstrate the potential of GFPH for use as a functional food ingredient with improved rheological and antioxidative properties.

Protective Effects of Maillard Reaction Products of Whey Protein Concentrate against Oxidative Stress through an Nrf2-Dependent Pathway in HepG2 Cells.

Whey protein concentrate (WPC), which contains α-lactalbumin and ß-lactoglobulin, is utilized widely in the food industry. The Maillard reaction is a complex reaction that produces Maillard reaction products (MRPs), which are associated with the formation of antioxidant compounds. In this study, the hepatoprotection activity of MRPs of WPC against oxidative stress through the nuclear factor-E2-related factor 2 (Nrf2)-dependent antioxidant pathway in HepG2 cells was examined. Glucose-whey protein concentrate conjugate (Glc-WPC) was obtained from Maillard reaction between WPC and glucose. The fluorescence intensity of Glc-WPC increased after 7 d compared to native WPC, and resulted in loss of 48% of the free amino groups of WPC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of Glc-WPC showed the presence of a high-molecular-weight portion. Treatment of HepG2 cells with Glc-WPC increased cell viability in the presence of oxidative stress, inhibited the generation of intracellular reactive oxygen species by tert-butyl hydroperoxide (t-BHP), and increased the glutathione level. Nrf2 translocation and Nrf2, reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H)-quinone oxidoreductase 1 (NOQ1), heme oxygenase-1 (HO-1), glutamate-L-cysteine ligase (GCL)M and GCLC mRNA levels were increased by Glc-WPC. Also, Glc-WPC increased the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK). The results of this study demonstrate that Glc-WPC activates the Nrf2-dependent pathway through the phosphorylation of ERK1/2 and JNK in HepG2 cells, and induces production of antioxidant enzymes and phase II enzymes.

Chebulic acid prevents hepatic fibrosis induced by advanced glycation end-products in LX-2 cell by modulating Nrf2 translocation via ERK pathway.

Advanced glycation end-products (AGEs) are formed during normal aging, and at an accelerated rate in metabolic syndrome patients. Nonalcoholic steatohepatitis (NASH) can be caused by the AGEs in plasma, while glyceraldehyde-derived AGEs (glycer-AGEs) are significantly higher in the serum of NASH patients. In this study, we investigated the molecular mechanisms of chebulic acid, isolated from Terminalia chebula Retz., in the inhibition of glycer-AGEs induced production of reactive oxygen species (ROS) and collagen accumulation using the LX-2 cell line. Chebulic acid significantly inhibited the induction of ROS and accumulation of collagen proteins by glycer-AGEs. ERK phosphorylation and total nuclear factor E2-related factor 2 (Nrf2) protein expression were induced by chebulic acid in a dose-dependent manner. Chebulic acid was also found to induce translocation of Nrf2 into the nucleus, which was attenuated by inhibition of ERK phosphorylation through treatment with PD98059. Following translocation of Nrf2, chebulic acid induced the protein expressions of catalytic subunit of γ-glutamylcysteine synthetase and glutathione synthesis. Collagen accumulation was also significantly reduced by chebulic acid treatment. The observed effects of chebulic acid were all inhibited by PD98059 treatment. Taken together, these results suggest that chebulic acid prevents the glycer-AGEs-induced ROS formation of LX-2 cells and collagen accumulation by ERK-phosphorylation-mediated Nrf2 nuclear translocation, which causes upregulation of antioxidant protein production.