2,4,6-Trinitrotoluene Induces Apoptosis via ROS-Regulated Mitochondrial Dysfunction and Endoplasmic Reticulum Stress in HepG2 and Hep3B Cells

2,4,6-trinitrotoluene causes mitochondrial toxicity in Caenorhabditis elegans by affecting electron transport

As a typical energetic compound widely used in military activities, 2,4,6-trinitrotoluene (TNT) has attracted great attention in recent years due to its heavy pollution and wide distribution in and around the training facilities, firing ranges, and demolition sites. However, the subcellular targets and the underlying toxic mechanism of TNT remain largely unknown. In this study, we explored the toxic effects of TNT biological reduction on the mitochondrial function and homeostasis in Caenorhabditis elegans (C. elegans). With short-term exposure of L4 larvae, 10-1000 ng/mL TNT reduced mitochondrial membrane potential and adenosine triphosphate (ATP) content, which was associated with decreased expression of specific mitochondrial complex involving gas-1 and mev-1 genes. Using fluorescence-labeled transgenic nematodes, we found that fluorescence expression of sod-3 (muls84) and gst-4 (dvls19) was increased, suggesting that TNT disrupted the mitochondrial antioxidant defense system. Furthermore, 10 ng/mL TNT exposure increased the expression of the autophagy-related gene pink-1 and activated mitochondrial unfolded protein response (mt UPR), which was indicated by the increased expression of mitochondrial stress activated transcription factor atfs-1, ubiquitin-like protein ubl-5, and homeobox protein dve-1. Our findings demonstrated that TNT biological reduction caused mitochondrial dysfunction and the development of mt UPR protective stress responses, and provided a basis for determining the potential risks of energetic compounds to living organisms.

Metabolic activation of 2,4,6-trinitrotoluene; a case for ROS-induced cell damage

The explosive compound 2,4,6-trinitrotoluene (TNT) is well known as a major component of munitions. In addition to its potential carcinogenicity and mutagenicity in humans, recent reports have highlighted TNT toxicities in diverse organisms due to its occurrence in the environment. These toxic effects have been linked to the intracellular metabolism of TNT, which is generally characterised by redox cycling and the generation of noxious reactive molecules. The reactive intermediates formed, such as nitroso and hydroxylamine compounds, also interact with oxygen molecules and cellular components to cause macromolecular damage and oxidative stress. The current review aims to highlight the crucial role of TNT metabolism in mediating TNT toxicity, via increased generation of reactive oxygen species. Cellular proliferation of reactive species results in depletion of cellular antioxidant enzymes, DNA and protein adduct formation, and oxidative stress. While TNT toxicity is well known, its ability to induce oxidative stress, resulting from its reductive activation, suggests that some of its toxic effects may be caused by its reactive metabolites. Hence, further research on TNT metabolism is imperative to elucidate TNT-induced toxicities.

Association between the prevalence rates of circadian syndrome and testosterone deficiency in US males: data from NHANES (2011-2016)

Objective

The objective of this study is to explore the association between the prevalence rates of circadian syndrome (CircS) and testosterone deficiency (TD).

Materials and methods

Cross-sectional analysis was conducted on the basis of the National Health and Nutrition Examination Survey 2011-2016. The target population was males aged ≥20 years old. A total of three multivariable logistic regression models were built to elucidate the association between the prevalence rates of CircS and TD. Interactive and stratified analyses were employed to explore whether some variables can modify the above association. Sensitivity analyses were also conducted to verify the stability of the results with extreme values removed.

Results

A total of 3,436 eligible participants were involved. Multivariable logistic regression in the fully adjusted model suggested the CircS group had a significantly higher prevalence rate of TD compared with the non-CircS group (OR = 2.284, 95%CI 1.569 to 3.323). No significant correlation between the number of CircS components and TD was observed in any of the three models. The interactive and stratified analyses showed the association was more obvious in the population with moderate or vigorous activities. The results were robust after extreme data were excluded.

Conclusion

There is a positive association between the prevalence rates of CircS and TD in US men. The association becomes more obvious owing to moderate or vigorous activities.

Selenocystine induces oxidative-mediated DNA damage via impairing homologous recombination repair of DNA double-strand breaks in human hepatoma cells

Selenocystine (SeC) has been identified as a novel compound with broad-spectrum anticancer activity. However, the effects of SeC on modifying DNA repair mechanism were less addressed. In this study, we demonstrated that SeC selectively induced cytotoxicity and genotoxicity against HepG2 hepatoma cell line. Comet assay revealed SeC-induced DNA damage in HepG2 cells, particularly in the form of DNA double strand breaks (DSBs), corroborated by the increase expression of the DSB marker, gamma-H2AX. We further demonstrated that SeC suppressed DNA homologous recombination repair, exacerbating DNA damage accumulation. Such effects on DNA damage and cell viability inhibition were alleviated by antioxidants, glutathione and Trolox, suggesting the involvement of reactive oxygen species (ROS). High levels of intracellular and mitochondrial ROS were detected in SeC-treated HepG2. In addition, SeC impaired the expression of antioxidant enzymes (superoxidase mutases and catalase), prompting the imbalance between antioxidant protection and excessive ROS formation and eliciting DSBs and cellular death. Decreased procaspase-3, 7, and 9 and Bcl-2 proteins and an increased Bax/Bcl-2 ratio, were observed after SeC treatment, but could be reversed by Torlox, confirming the action of SeC on ROS-induced apoptosis. In vivo, the xenograft tumor model of HepG2 cells validated the inhibition of SeC on tumor growth, and the induction of DSBs and apoptosis. In summary, SeC has the capability to induce ROS-dependent DNA damage and impeded DBS repair in HepG2 cells. Thus, SeC holds great promise as a therapeutic or adjuvant agent targeting DNA repair for cancer treatment.

Transgenerational reproductive toxicity of 2,4,6-trinitrotoluene (TNT) and its metabolite 4-ADNT in Caenorhabditis elegans

2,4,6-trinitrotoluene (TNT) as an energetic compound widely used in military applications has aroused great concerns in recent years due to its large-scale contamination in soil and water; however, its toxicity is still largely unknown. In this study, we investigated the reproductive toxicity and the transgenerational effects of TNT on Caenorhabditis elegans (C. elegans). Our data showed that exposure to TNT at concentrations ranging from 10 to 100 ng/mL resulted in decreasing the lifespan, brood size, number of oocytes and eggs in uterus, while increasing the number of germ cell apoptosis in C. elegans. The apoptotic effects of TNT were blocked in mutants of cep-1 (w40), egl-1 (n487), and hus-1 (op241), indicating conserved genotoxic response genes was involved in mediating TNT-induced germ cell apoptosis. Parental exposure to TNT significantly increased the germ cell apoptosis from P0 to F2 generation, but the toxicity faded away in F3 and F4 generations. Furthermore, TNT was rapidly metabolized in P0, and the accumulation of 4-aminodinitrotoluene (4-ADNT), the main metabolite of TNT in C. elegans, showed a significant decrease from P0 to F1 and a slow decrease in the subsequent generations. Our results demonstrated that ingested TNT can cause severe transgenerational reproductive toxicity and be rapidly converted to 4-ADNT in the nematodes. These data provided basis for future studies on the effects of energetic compounds across generations.

Induction of carbonyl reductase 1 (CR1) gene expression in Daphnia magna by TNT, but not its key metabolites 2-ADNT and 4-ADNT

2,4,6-trinitrotoluene (TNT) is a known source of reactive oxygen species (ROS), which cause oxidative stress in aquatic ecosystems. Carbonyl reductases (CRs) are one of several possible defense mechanisms induced against ROS products, especially those that result in the 'so-called' carbonyl stress. Daphnia magna, a freshwater organism living in stagnant freshwater bodies, expresses four copies of the CR gene (Dma_CR1, Dma_CR2, Dma_CR3 and Dma_CR4). In this study, induction of all four copies of Dma_CR by 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT), was investigated. Reverse transcription polymerase chain reaction (RT-PCR) analysis of treated daphnids revealed up-regulation of Dma_CR1 alone in response to TNT, but not 2-ADNT and 4-ADNT (which are key metabolites of TNT). This concentration- and time-dependent up-regulation in mRNA-expression was observed both in the presence and absence of light, in the same magnitude. Moreover, significant change in mRNA-expression could be observed 8 h after treatment with TNT. In the presence of TNT, the antioxidant N-acetylcysteine (NAc) could not reverse TNT-induced up-regulation of Dma_CR1 mRNA-expression. On the other hand, withdrawal of TNT from the culture medium caused a significant reduction in the TNT-induced mRNA-expression of Dma_CR1 within 24 h. These findings highlight the potential of Dma_CR1 as a biomarker for biomonitoring of TNT levels in freshwater bodies.

Obesity Promotes Experimental Colitis by Increasing Oxidative Stress and Mitochondrial Dysfunction in the Colon

Although obesity is associated with inflammatory bowel disease (IBD), the underlying molecular mechanism still remains unclear. In this study, we evaluated the effects of high-fat diet (HFD)-induced obesity on the development of experimental colitis in mice. The C57BL/6 mice were fed with a HFD for 12 weeks to develop obesity. The concentrations of free fatty acids (FFA), triglycerides, and cholesterol in plasma were significantly increased in HFD-fed mice compared to low-fat diet (LFD)-fed mice. We found that HFD-induced obesity could exacerbate 2,4,6-trinitro-benzene-sulfonic acid (TNBS)-induced experimental colitis in mice resembling Crohn's disease (CD). HFD-fed mice showed shorter colon length, higher clinical scores and histological scores, more production of mucosal tumor necrosis factor-α (TNF-α), and greater destruction of colonic epithelial barrier than LFD-fed mice after TNBS induction. HFD feeding also promoted reactive oxygen species (ROS) production in colonic epithelial cells, thus activating the pro-apoptotic pathway to damage colonic epithelial barrier induced by TNBS. After HCT116 cells were treated with palmitate acid (PA) and/or TNF-α for 24 h, the combination of PA and TNF-α increased ROS production, promoted mitochondrial dysfunction, and activated the pro-apoptotic pathway, but these effects were markedly attenuated by a ROS inhibitor. Taken together, these observations suggest that HFD-induced obesity promotes experimental colitis by increasing oxidative stress and mitochondrial dysfunction, which triggers the activation of pro-apoptotic pathway in the colon.

Screening for Combination Cancer Therapies With Dynamic Fuzzy Modeling and Multi-Objective Optimization

Combination therapies proved to be a valuable strategy in the fight against cancer, thanks to their increased efficacy in inducing tumor cell death and in reducing tumor growth, metastatic potential, and the risk of developing drug resistance. The identification of effective combinations of drug targets generally relies on costly and time consuming processes based on in vitro experiments. Here, we present a novel computational approach that, by integrating dynamic fuzzy modeling with multi-objective optimization, allows to efficiently identify novel combination cancer therapies, with a relevant saving in working time and costs. We tested this approach on a model of oncogenic K-ras cancer cells characterized by a marked Warburg effect. The computational approach was validated by its capability in finding out therapies already known in the literature for this type of cancer cell. More importantly, our results show that this method can suggest potential therapies consisting in a small number of molecular targets. In the model of oncogenic K-ras cancer cells, for instance, we identified combination of up to three targets, which affect different cellular pathways that are crucial for cancer proliferation and survival.

Psoralen induces liver injuries through endoplasmic reticulum stress signaling in female mice

Psoralen is the main coumarin component of Fructus psoraleae. Previously, we have found that psoralen induced hepatocytes apoptosis via PERK and ATF6 related ER stress pathways in vitro. In this study, we investigated the toxicity and ER stress induced by psoralen in female C57 mice. Mice were fed with 80 mg/kg of psoralen intra-gastrically for either 3, 7, or 21 days. Liver and kidney were weighed and their coefficients were calculated. The serum was isolated to examine the biochemical parameters including alanine aminotransferase (ALT) activity, aspartate aminotransferase (AST) activity, alkaline phosphatase (ALP) activity, blood urea nitrogen (BUN), total bile acid (TBA), total bilirubin (TBIL), and creatinine (CRE). The transcription and expression of ER stress-related markers were determined by Wes-automated Protein Simple system, Western blot and RT-PCR. Psoralen administration for 3 days significantly increased liver coefficients but decreased kidney coefficients of mice. Histopathological examination showed minimal inflammatory cell foci and vacuolar degeneration in the liver. Besides, serum levels of ALT, TBA, BUN, and CRE were markedly altered by psoralen. Moreover, psoralen significantly increased expression and transcription levels of ER stress related markers, including Grp78, PERK, eIF2α, ATF4, IRE1α, ATF6, and XBP1. These results illustrated that psoralen induced liver injuries through ER stress signaling in female mice.

Synergy Effects of Metformin and Berberine on Glyoxal-induced Carbonyl Stress in Isolated Rat Liver Mitochondria

Objective:

Carbonyl stress, resulting from toxic effects of alpha-dicarbonyls such as glyoxal (GO), plays an important role in mitochondrial dysfunction and subsequent development of diabetic complications. This study evaluated the ability of metformin (MET), berberine (BBR), and their combination to prevent GO-induced carbonyl stress in isolated rat liver mitochondria.

Methods:

Mitochondria (0.5 mg protein/mL) were isolated from the Wistar rat liver and incubated with various concentrations of GO (1, 2.5, 5, 7.5, and 10 mM) for 30 minutes and IC50 for GO was calculated. The suspensions of mitochondria were incubated with various concentrations of MET (2.5, 5, 10, and 20 mM) or BBR (2.5, 5, 10, and 20 μM) for 30 min and then GO in a dose of IC50 at 37 ºC for 30 min. Mitochondrial complex II activity, mitochondrial membrane potential (MMP), MDA level, reactive oxygen species (ROS) formation, reduced glutathione (GSH) content, and protein carbonylation were assessed. The combination index and isobologram of MET and BBR on GO toxicity were calculated.

Results:

IC50 of GO was assigned approximately 3 mM. GO disrupted the electron transfer chain and significantly increased mitochondrial ROS formation, protein carbonylation, and MDA level. GO decreased mitochondrial viability, MMP, and GSH content. Pre-treatment with MET and BBR could potentially reverse GO-induced deleterious effects in a concentration-dependent manner. Results of the drug combination indicated that CI for Fa 0.5 (Effect 50 %) was 0.83.

Conclusion:

These results suggest that BBR in combination with MET has a moderate synergistic effect on GO-induced carbonyl stress in isolated rat liver mitochondria.

The explosive trinitrotoluene (TNT) induces gene expression of carbonyl reductase in the blue mussel (Mytilus spp.): a new promising biomarker for sea dumped war relicts?

Millions of tons of all kind of munitions, including mines, bombs and torpedoes have been dumped after World War II in the marine environment and do now pose a new threat to the seas worldwide. Beside the acute risk of unwanted detonation, there is a chronic risk of contamination, because the metal vessels corrode and the toxic and carcinogenic explosives (trinitrotoluene (TNT) and metabolites) leak into the environment. While the mechanism of toxicity and carcinogenicity of TNT and its derivatives occurs through its capability of inducing oxidative stress in the target biota, we had the idea if TNT can induce the gene expression of carbonyl reductase in blue mussels. Carbonyl reductases are members of the short-chain dehydrogenase/reductase (SDR) superfamily. They metabolize xenobiotics bearing carbonyl functions, but also endogenous signal molecules such as steroid hormones, prostaglandins, biogenic amines, as well as sugar and lipid peroxidation derived reactive carbonyls, the latter providing a defence mechanism against oxidative stress and reactive oxygen species (ROS). Here, we identified and cloned the gene coding for carbonyl reductase from the blue mussel Mytilus spp. by a bioinformatics approach. In both laboratory and field studies, we could show that TNT induces a strong and concentration-dependent induction of gene expression of carbonyl reductase in the blue mussel. Carbonyl reductase may thus serve as a biomarker for TNT exposure on a molecular level which is useful to detect TNT contaminations in the environment and to perform a risk assessment both for the ecosphere and the human seafood consumer.

Sensitivity of allyl isothiocyanate to induce apoptosis via ER stress and the mitochondrial pathway upon ROS production in colorectal adenocarcinoma cells

Allyl isothiocyanate (AITC), a bioactive phytochemical compound that is a constituent of dietary cruciferous vegetables, possesses promising chemopreventive and anticancer effects. However, reports of AITC exerting antitumor effects on apoptosis induction of colorectal cancer (CRC) cells in vitro are not well elucidated. The present study focused on the functional mechanism of the endoplasmic reticulum (ER) stress-based apoptotic machinery induced by AITC in human colorectal cancer HT-29 cells. Our results indicated that AITC decreased cell growth and number, reduced viability, and facilitated morphological changes of apoptotic cell death. DNA analysis by flow cytometry showed G2/M phase arrest, and alterations in the modulated protein levels caused by AITC were detected via western blot analysis. AITC also triggered vital intrinsic apoptotic factors (caspase-9/caspase-3 activity), disrupted mitochondrial membrane potential, and stimulated mitochondrial-related apoptotic molecules (e.g., cytochrome c, apoptotic protease activating factor 1, apoptosis-inducing factor, and endonuclease G). Additionally, AITC prompted induced cytosolic Ca²⁺ release and Ca²⁺-dependent ER stress-related signals, such as calpain 1, activating transcription factor 6α, glucose-regulated proteins 78 and 94, growth arrest- and DNA damage-inducible protein 153 (GADD153), and caspase-4. The level of reactive oxygen species (ROS) production was found to induce the hallmark of ER stress GADD153, proapoptotic marker caspase-3, and calpain activity after AITC treatment. Our findings showed for the first time that AITC induced G2/M phase arrest and apoptotic death via ROS-based ER stress and the intrinsic pathway (mitochondrial-dependent) in HT-29 cells. Overall, AITC may exert an epigenetic effect and is a potential bioactive compound for CRC treatment.

Scoulerine promotes cell viability reduction and apoptosis by activating ROS-dependent endoplasmic reticulum stress in colorectal cancer cells

Scoulerine, an isoquinoline alkaloid isolated from Corydalis plants, has been reported to possess potent anti-proliferative and pro-apoptotic function in cancer cells. However, the effects and underlying mechanisms of scoulerine on colorectal cancer (CRC) progression remain elusive. CCK-8 and LDH assays were used to evaluate cell viability. Apoptosis was assessed by flow cytometry analysis, caspase-3/7 activity assay, and Western blot analysis of Bax, Bcl-2 and cytochrome c (Cyt C) expression. Oxidative stress level was examined by measuring reactive oxygen species (ROS) and glutathione (GSH) contents and superoxide dismutase (SOD) activity. Endoplasmic reticulum (ER) stress activation was detected by Western blot analysis of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) expression. Results showed that scoulerine dose-dependently suppressed CRC cell viability. Scoulerine induced apoptosis and increased caspase-3/7 activity in CRC cells. Bax and cytosolic Cyt C expression was enhanced while Bcl-2 and mitochondrial Cyt C expression was reduced in scoulerine-treated CRC cells. Additionally, scoulerine induced oxidative damage in CRC cells by increasing ROS generation and reducing GSH content and SOD activity. Scoulerine activated ER stress, as evidenced by the increased GRP78 and CHOP expression in CRC cells. Interestingly, blocking ROS production by ROS scavenger N-acetyl-cysteine (NAC) attenuated scoulerine-induced ER stress. Inhibition of ER stress by 4-phenyl butyric acid (4-PBA) abolished scoulerine-induced ROS generation in CRC cells. Blockage of ROS and ER stress attenuated scoulerine-induced cell viability reduction and apoptosis in CRC cells. In conclusion, scoulerine promoted cell viability reduction and apoptosis by activating ROS-dependent ER stress in CRC cells.

Retrochalcone Echinatin Triggers Apoptosis of Esophageal Squamous Cell Carcinoma via ROS- and ER Stress-Mediated Signaling Pathways

Esophageal squamous cell carcinoma (ESCC) is a poor prognostic cancer with a low five-year survival rate. Echinatin (Ech) is a retrochalone from licorice. It has been used as a herbal medicine due to its anti-inflammatory and anti-oxidative effects. However, its anticancer activity or underlying mechanism has not been elucidated yet. Thus, the objective of this study was to investigate the anti-tumor activity of Ech on ESCC by inducing ROS and ER stress dependent apoptosis. Ech inhibited ESCC cell growth in anchorage-dependent and independent analysis. Treatment with Ech induced G2/M phase of cell cycle and apoptosis of ESCC cells. It also regulated their related protein markers including p21, p27, cyclin B1, and cdc2. Ech also led to phosphorylation of JNK and p38. Regarding ROS and ER stress formation associated with apoptosis, we found that Ech increased ROS production, whereas its increase was diminished by NAC treatment. In addition, ER stress proteins were induced by treatment with Ech. Moreover, Ech enhanced MMP dysfunction and caspases activity. Furthermore, it regulated related biomarkers. Taken together, our results suggest that Ech can induce apoptosis in human ESCC cells via ROS/ER stress generation and p38 MAPK/JNK activation.

Toxicity of diuron in HepG2 cells and zebrafish embryos

Diuron is an herbicide, which is used to control a wide variety of annual and perennial broadleaf, grassy weeds, and mosses. However, the toxicity of diuron in HepG2 cells and zebrafish embryos was unclear. In this study, HpeG2 cells and zebrafish embryos were exposed to different concentrations of diuron for 24 h and 48 h, respectively. Results reveal the diuron caused cytotoxicity and the generation of reactive oxygen species (ROS) in the treated HepG2 cells. The effects of diuron on the expression of catalase and superoxide dismutase (SOD1 and SOD2), an antioxidant enzyme, were investigated. Results showed that only SOD1 was significantly induced after treated diuron 48 h, but the expression of catalase and SOD2 was unaffected. Additionally, the cytotoxicity of diuron was not attenuated in cells pretreated with of N-acetyl-cysteine (NAC), a well-known antioxidant, indicating that oxidative stress could not contribute to cellular death in the treated HepG2 cells. In zebrafish embryos, results from proteomic analysis show that 332 differentially upregulated proteins and 199 down-regulated proteins were detected in the treated embryos (P < 0.05). In addition to the up-regulated antioxidant proteins (prdx3, cat, prdx4, txnrd1, prdx1, sod1, prdx2, and sod2), some decreased proteins were related to cytoskeleton formation, tight junction, and gap junction, which could be related to the malformation of the treated zebrafish embryos. In summary, diuron caused cytotoxicity in HepG2 cells, and the mechanisms of toxicity in zebrafish were addressed using the proteomic analysis.

Crosstalk of oxidative damage, apoptosis, and autophagy under endoplasmic reticulum (ER) stress involved in thifluzamide-induced liver damage in zebrafish (Danio rerio)

Although the hepatotoxicity of thifluzamide in zebrafish has been characterized, its toxic mechanisms have not been fully explored. The present study demonstrated that thifluzamide damaged the zebrafish liver and endoplasmic reticulum (ER). In addition, thifluzamide significantly changed the expression of genes encoding antioxidant proteins and increased the malondialdehyde (MDA) content, leading to oxidative damage in zebrafish liver. Additionally, the autophagic ultrastructure was observed by transmission electron microscopy (TEM), and LC3-I/LC3-II conversion was obviously upregulated under western blotting (WB) measurements, verifying that autophagy was induced by thifluzamide. Moreover, the activities of Caspase-3 and Caspase-9 were obviously decreased, indicating that apoptosis was inhibited in adult zebrafish exposed to a higher concentration of thifluzamide. In summary, oxidative damage and autophagy but not apoptosis under ER injury might lead to the hepatotoxicity of thifluzamide in zebrafish. Our findings provide a new mechanistic insight into the toxicity of thifluzamide in zebrafish.

Induction of Human-Lung-Cancer-A549-Cell Apoptosis by 4-Hydroperoxy-2-decenoic Acid Ethyl Ester through Intracellular ROS Accumulation and the Induction of Proapoptotic CHOP Expression

Royal jelly, a natural product secreted by honeybees, contains several fatty acids, such as 10-hydroxy-2-decenoic acid (DE), and shows anti- and pro-apoptotic properties. 4-Hydroperoxy-2-decenoic acid ethyl ester (HPO-DAEE), a DE derivative, exhibits potent antioxidative activity; however, it currently remains unclear whether HPO-DAEE induces cancer-cell death. In the present study, treatment with HPO-DAEE induced human-lung-cancer-A549-cell death (52.7 ± 10.2%) that was accompanied by DNA fragmentation. Moreover, the accumulation of intracellular reactive oxygen species (ROS, 2.38 ± 0.1-fold) and the induction of proapoptotic CCAAT-enhancer-binding-protein-homologous-protein (CHOP) expression (18.4 ± 4.0-fold) were observed in HPO-DAEE-treated cells. HPO-DAEE-elicited CHOP expression and cell death were markedly suppressed by pretreatment with N-acetylcysteine (NAC), an antioxidant, by 2.40 ± 1.57-fold and 5.7 ± 1.6%, respectively. Pretreatment with 4-phenylbutyric acid (PBA), an inhibitor of endoplasmic reticulum stress, also suppressed A549-cell death (38.4 ± 1.1%). Furthermore, we demonstrated the involvement of extracellular-signal-regulated protein kinase (ERK) and p38-related signaling in HPO-DAEE-elicited cell-death events. Overall, we concluded that HPO-DAEE induces A549-cell apoptosis through the ROS-ERK-p38 pathway and, at least in part, the CHOP pathway.

Hypermethylation of endoplasmic reticulum disulfide oxidase 1α leads to trophoblast cell apoptosis through endoplasmic reticulum stress in preeclampsia

Abnormal trophoblast cell apoptosis is implicated in the pathogenesis of pregnancy-related disorders including preeclampsia (PE), and endoplasmic reticulum (ER) stress has been considered as a novel pathway in the regulation of cell apoptosis. In this study, we observed that both apoptosis and ER stress are triggered in trophoblast cells under hypoxia as well as in the placenta of PE rats. Quantitative polymerase chain reaction and Western blot analysis showed that the expression of endoplasmic reticulum disulfide oxidase 1α (ERO1α) is suppressed in trophoblast cells under hypoxia due to the hypermethylation of the ERO1α promoter region, and the inhibition of ERO1α expression plays an important role in ER stress and trophoblast cell apoptosis. Furthermore, we found that DNA methyltransferase 1 (DNMT1) is a key methyltransferase for DNA methylation in the regulation of ERO1α expression, and the binding level of DNMT1 to the ERO1α promoter is markedly elevated under hypoxia although DNMT1 expression is inhibited by hypoxia, suggesting that the binding level of DNMT1 to the ERO1α promoter region rather than the DNMT1 expression level contributes to the hypermethylation of ERO1α. Taken together, these results demonstrate that the hypermethylation of ERO1α mediated by increased binding of DNMT1 to the ERO1α promoter leads to trophoblast cell apoptosis through ER stress in the placenta of PE rats, which shed insight into the etiology of PE and might present a validated therapeutic target for the treatment of PE.

Differentially expressed genes of HepG2 cells treated with gecko polypeptide mixture

Gecko (Gekko japonicus) extracts have been used in traditional Chinese medicine for many years. It has been proven that the gecko polypeptide mixture (GPM) extracted from gecko can inhibit the growth of multiple types of tumor cells. In order to investigate the possible anti-tumor molecular mechanisms of GPM, we used RNA-seq technology to identify the differentially expressed genes (DEGs) of human hepatocellular carcinoma (HCC) HepG2 cells treated with or without GPM. MTT assay was used to detect the viability of HepG2 cells. DAPI fluorescence staining was performed to observe morphological changes in the nuclei of HepG2 cells. Western blot analysis was applied to observe the expressions of apoptosis-related and endoplasmic reticulum stress (ERS)-related proteins in HepG2 cells. Flow cytometry assay was performed to detect the apoptosis and reactive oxygen species (ROS) in HepG2 cells. Our results showed that GPM inhibited HepG2 cells proliferation and induced the apoptosis of HepG2 cells. RNA-seq analysis suggested that the ER-nucleus signaling pathway involved in the anti-cancer molecular mechanism of GPM. Therefore, GPM may induce apoptosis in HepG2 cells via the ERs pathway.

The integrated analysis of transcriptome and proteome for exploring the biodegradation mechanism of 2, 4, 6-trinitrotoluene by Citrobacter sp

Citrobacter sp. has been shown to degrade 2,4,6-trinitrotoluene (TNT). However, the mechanism of its TNT biodegradation is poorly understood. An integrated proteome and transcriptome analysis was performed for investigating the differential genes and differential proteins in bacterial growth at the onset of experiments and after 12 h treatment with TNT. With the RNA sequencing, we found a total of 3792 transcripts and 569 differentially expressed genes (≥2 fold, P < 0.05) by. Genes for amino acid transport, cellular metabolism and stress-shock proteins were up-regulated, while carbohydrate transport and metabolism were down-regulated. A total of 42 protein spots (≥1.5 fold, P < 0.05) showed differential expression on two-dimensional gel electrophoresis and these proteins were identified by mass spectrometry. The most prominent proteins up-regulated were involved in energy production and conversion, amino acid transport and metabolism, posttranslational modification, protein turnover and chaperones. Proteins involved in carbohydrate transport and metabolism were down-regulated. Most notably, we observed that nemA encoding N-ethylmaleimide reductase was the most up-regulated gene involved in TNT degradation, and further proved that it can transform TNT to 4-amino-2,6-dinitrotoluene (4-ADNT) and 2-amino-4,6-dinitrotoluene (2-ADNT). This study highlights the molecular mechanisms of Citrobacter sp. for TNT removal.

Connexin32 plays a crucial role in ROS-mediated endoplasmic reticulum stress apoptosis signaling pathway in ischemia reperfusion-induced acute kidney injury

BACKGROUND

Ischemia-reperfusion (I/R)-induced acute kidney injury (AKI) not only prolongs the length of hospital stay, but also seriously affects the patient's survival rate. Although our previous investigation has verified that reactive oxygen species (ROS) transferred through gap junction composed of connexin32 (Cx32) contributed to AKI, its underlying mechanisms were not fully understood and viable preventive or therapeutic regimens were still lacking. Among various mechanisms involved in organs I/R-induced injuries, endoplasmic reticulum stress (ERS)-related apoptosis is currently considered to be an important participant. Thus, in present study, we focused on the underlying mechanisms of I/R-induced AKI, and postulated that Cx32 mediated ROS/ERS/apoptosis signal pathway activation played an important part in I/R-induced AKI.

METHODS

We established renal I/R models with Cx32+/+ and Cx32-/- mice, which underwent double kidneys clamping and recanalization. ROS scavenger (N-acetylcysteine, NAC) and ERS inhibitors (4-phenyl butyric acid, 4-PBA, and tauroursodeoxycholic acid, TUDCA) were used to decrease the content of ROS and attenuate ERS activation, respectively.

RESULTS

Renal damage was progressively exacerbated in a time-dependent manner at the reperfusion stage, that was consistent with the alternation of ERS activation, including glucose regulated protein 78 (BiP/GRP78), X box-binding protein1, and C/EBP homologous protein expression. TUDCA or 4-PBA application attenuated I/R-induced ERS activation and protected against renal tubular epithelial cells apoptosis and renal damage. Cx32 deficiency decreased ROS generation and distribution between the neighboring cells, which attenuated I/R-induced ERS activation, and improved cell apoptosis and renal damage.

CONCLUSION

Cx32 mediated ROS/ERS/apoptosis signal pathway activation played an important part in I/R-induced AKI. Cx32 deficiency, ROS elimination, and ERS inhibition all could protect against I/R-induced AKI.

Chemical hypoxia-induced integrated stress response activation in oligodendrocytes is mediated by the transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2)

The extent of remyelination in multiple sclerosis lesions is often incomplete. Injury to oligodendrocyte progenitor cells can be a contributing factor for such incomplete remyelination. The precise mechanisms underlying insufficient repair remain to be defined, but oxidative stress appears to be involved. Here, we used immortalized oligodendrocyte cell lines as model systems to investigate a causal relation of oxidative stress and endoplasmic reticulum stress signaling cascades. OLN93 and OliNeu cells were subjected to chemical hypoxia by blocking the respiratory chain at various levels. Mitochondrial membrane potential and oxidative stress levels were quantified by flow cytometry. Endoplasmic reticulum stress was monitored by the expression induction of activating transcription factor 3 and 4 (Atf3, Atf4), DNA damage-inducible transcript 3 protein (Ddit3), and glucose-regulated protein 94. Lentiviral silencing of nuclear factor (erythroid-derived 2)-like 2 or kelch-like ECH-associated protein 1 was applied to study the relevance of NRF2 for endoplasmic reticulum stress responses. We demonstrate that inhibition of the respiratory chain induces oxidative stress in cultured oligodendrocytes which is paralleled by the expression induction of distinct mediators of the endoplasmic reticulum stress response, namely Atf3, Atf4, and Ddit3. Atf3 and Ddit3 expression induction is potentiated in kelch-like ECH-associated protein 1-deficient cells and absent in cells lacking the oxidative stress-related transcription factor NRF2. This study provides strong evidence that oxidative stress in oligodendrocytes activates endoplasmic reticulum stress response in a NRF2-dependent manner and, in consequence, might regulate oligodendrocyte degeneration in multiple sclerosis and other neurological disorders.