Proteomic analysis of perfluorooctane sulfonate-induced apoptosis in human hepatic cells using the iTRAQ technique

Perfluorooctane sulfonate (PFOS) enhanced polystyrene particles uptake by human colon adenocarcinoma Caco-2 cells

As microplastics and nanoplastics (MNPs) are widely distributed in the environment and can be transferred to human body through food chain, their potential impact on human health is of great concern. Perfluorooctane sulfonate (PFOS) is persistent, bioaccumulative and can be adsorbed by MNPs. However, there are few studies on the combined human health effects of MNPs with PFOS. In this study, the effects of polystyrene (PS) particles and PFOS on human colon adenocarcinoma cell Caco-2 were investigated in vitro to explore the combined toxicity from cellular level, and the toxic mechanism was further illustrated. Results showed that the presence of PFOS significantly increased the cell uptake of PS nanoparticles by >30 %, which is related to variations of the surface properties of PS particles, including the decrease of hydration kinetic diameter, the rise of surface potential and the adsorption of hydrophobic PFOS molecules. The toxic effect of PFOS was weakened in the presence of PS particles under low PFOS concentration (10 μg/mL), which is because the bioavailability of PFOS was reduced after adsorption. PS particles with small particle size (20 nm) showed higher cell uptake and ROS production, while PS particles with large particle size (1 μm) led to higher lipid oxidation degree and related membrane damage as well as mitochondrial stress. This study provides the first evaluation of combined toxicity of MNPs and PFOS on human intestinal cells, in order to support the risk assessment of combined pollution of MNPs and PFOS on human health.

Studying the Impact of Persistent Organic Pollutants Exposure on Human Health by Proteomic Analysis: A Systematic Review

Persistent organic pollutants (POPs) are organic chemical substances that are widely distributed in environments around the globe. POPs accumulate in living organisms and are found at high concentrations in the food chain. Humans are thus continuously exposed to these chemical substances, in which they exert hepatic, reproductive, developmental, behavioral, neurologic, endocrine, cardiovascular, and immunologic adverse health effects. However, considerable information is unknown regarding the mechanism by which POPs exert their adverse effects in humans, as well as the molecular and cellular responses involved. Data are notably lacking concerning the consequences of acute and chronic POP exposure on changes in gene expression, protein profile, and metabolic pathways. We conducted a systematic review to provide a synthesis of knowledge of POPs arising from proteomics-based research. The data source used for this review was PubMed. This study was carried out following the PRISMA guidelines. Of the 742 items originally identified, 89 were considered in the review. This review presents a comprehensive overview of the most recent research and available solutions to explore proteomics datasets to identify new features relevant to human health. Future perspectives in proteomics studies are discussed.

Adverse Effects of Perfluorooctane Sulfonate on the Liver and Relevant Mechanisms

Perfluorooctane sulfonate (PFOS) is a persistent, widely present organic pollutant. PFOS can enter the human body through drinking water, ingestion of food, contact with utensils containing PFOS, and occupational exposure to PFOS, and can have adverse effects on human health. Increasing research shows that the liver is the major target of PFOS, and that PFOS can damage liver tissue and disrupt its function; however, the exact mechanisms remain unclear. In this study, we reviewed the adverse effects of PFOS on liver tissue and cells, as well as on liver function, to provide a reference for subsequent studies related to the toxicity of PFOS and liver injury caused by PFOS.

Chemoproteomic Approach toward Probing the Interactomes of Perfluoroalkyl Substances

Poly- and perfluoroalkyl substances (PFASs) are widely used in industrial products and consumer goods. Due to their extremely recalcitrant nature and potential bioaccumulation and toxicity, exposure to PFASs may result in adverse health outcomes in humans and wildlife. In this study, we developed a chemoproteomic strategy, based on the use of isotope-coded desthiobiotin-perfluorooctanephosphonic acid (PFOPA) probe and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis, to profile PFAS-binding proteins. Targeted proteins were labeled with the desthiobiotin-PFOPA probe, digested with trypsin, and the ensuing desthiobiotin-conjugated peptides were enriched with streptavidin beads for LC-MS/MS analysis. We were able to identify 469 putative PFOPA-binding proteins. By conducting competitive binding experiments using low (10 μM) and high (100 μM) concentrations of stable isotope-labeled PFOPA probes, we further identified 128 nonredundant peptides derived from 75 unique proteins that exhibit selective binding toward PFOPA. Additionally, we demonstrated that one of these proteins, fatty acid-binding protein 5 (FABP5), could interact directly with PFASs, including perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), and perfluorobutanesulfonic acid (PFBS). Furthermore, desthiobiotin-labeled lysine residues are located close to the fatty acid-binding pocket of FABP5, and the binding affinity varies with the structures of PFASs. Taken together, we developed a novel chemoproteomic method for interrogating the PFAS-interacting proteome. The identification of these proteins sets the stage for understanding the mechanisms through which exposure to PFASs confers adverse human health effects.

ROS-Triggered Autophagy Is Involved in PFOS-Induced Apoptosis of Human Embryo Liver L-02 Cells

The liver is the primary target organ for perfluorooctane sulphonate (PFOS), a recently discovered persistent organic pollutant. However, the mechanisms mediating hepatotoxicity remain unclear. Herein, we explored the relationship between reactive oxygen species (ROS) and autophagy and apoptosis induced by PFOS in L-02 cells, which are incubated with different concentrations of PFOS (0, 50, 100, 150, 200, or 250 μmol/L) for 24 or 48 hrs at 37°C. The results indicated that PFOS exposure decreased cell activities, enhanced ROS levels in a concentration-dependent manner, decreased mitochondrial membrane potential (MMP), and induced autophagy and apoptosis. Compared with the control, 200 μmol/L PFOS increased ROS levels; enhanced the expression of Bax, cleaved-caspase-3, and LC3-II; induced autophagy; decreased MMP; and lowered Bcl-2, p62, and Bcl-2/Bax ratio. The antioxidant N-acetyl cysteine (NAC) protected MMP against PFOS-induced changes and diminished apoptosis and autophagy. Compared with 200 μmol/L PFOS treatment, NAC pretreatment reversed the increase in ROS, Bax, and cleaved-caspase-3 protein caused by PFOS, lowered the apoptosis rate increased by PFOS, and increased the levels of MMP and Bcl-2/Bax ratio decreased by PFOS. The autophagy inhibitor 3-methyladenine and chloroquine decreased apoptosis and cleaved-caspase-3 protein level and increased the Bcl-2/Bax ratio. In summary, our results suggest that ROS-triggered autophagy is involved in PFOS-induced apoptosis in L-02 cells.

Chrysophanol exhibits inhibitory activities against colorectal cancer by targeting decorin

Colorectal cancer (CRC) is a common human malignancy that accounts for 600,000 deaths annually worldwide. Chrysophanol, a naturally occurring anthraquinone compound, exhibits anti-neoplastic effects in various cancer cells. The aim of this study was to explore the biological effects of chrysophanol on CRC cells, and determine the underlying mechanism. Chrysophanol inhibited proliferation of and promoted apoptosis in CRC cells by activating the intrinsic mitochondrial apoptotic pathway. In addition, chrysophanol also suppressed tumor growth in vivo and increased the percentage of apoptotic cells in tumor xenografts, without general toxicity. Proteomic iTRAQ analysis revealed decorin (DCN) as the major target of chrysophanol. DCN was upregulated in the tumor tissues following chrysophanol treatment, and ectopic DCN expression markedly augmented the pro-apoptotic effects of chrysophanol in CRC cells. In contrast, DCN knockdown significantly abrogated chrysophanol-induced apoptosis in CRC cells. Taken together, chrysophanol exerts anti-neoplastic effects in vitro and in vivo in CRC cells by modulating DCN, there by highlighting its therapeutic potential in CRC.

Identification of profilin 1 as the primary target for the anti-cancer activities of Furowanin A in colorectal cancer

BACKGROUND

Furowanin A (Fur A) is a flavonoid compound isolated from medicinal plant Millettia pachycarpa Benth. This study aims to explore the effect of Fur A on Colorectal cancer (CRC) and its molecular mechanisms.

METHODS

Cell proliferative capacity of CRC cells was assessed by CCK-8 assay. Cell apoptosis and cell cycle distribution were detected by flow cytometry. Cell migration and invasion were detected by wound healing and Transwell assay, respectively. EMT markers, apoptosis and profilin 1(Pfn1) expression were detected by immunohistochemistry (IHC). The protein expression levels were examined by western blotting. i-TRAQ analyses were conducted to identify the differentially expressed genes in CRC cells. CRC xenograft model was also used to validate the in vivo anti-cancer activity of Fur A.

RESULTS

Fur A exhibited anti-prolifertive, blocked cell cycle progression and promoted apoptotic cell death in CRC cells. Fur A suppressed the migration, invasion and epithelial-to-mesenchymal transition (EMT) in vitro, and tumor growth and pulmonary metastasis in vivo, without causing obvious toxicity. iTRAQ analysis identified Pfn1 as a gene up-regulated by Fur A. In xenograft tumor tissue, the expression of Pfn1 was also elevated by Fur A treatment. In clinical CRC samples, high expression of Pfn1 was correlated with lower stage and longer survival. Knockdown of Pfn1 significantly dampened the pro-apoptotic and anti-metastatic activities of Fur A in CRC cells. Ectopic Pfn1 expression augmented the anti-neoplastic activities of Fur A.

CONCLUSION

Fur A exhibited anti-cancer activities in vitro and in vivo in CRC by up-regulating Pfn1.

Assessing the human health risks of perfluorooctane sulfonate by in vivo and in vitro studies

The wide use of perfluorooctane sulfonate (PFOS) has led to increasing concern about its human health risks over the past decade. In vivo and in vitro studies are important and effective means to ascertain the toxic effects of PFOS on humans and its toxic mechanisms. This article systematically reviews the human health risks of PFOS based on the currently known facts found by in vivo and in vitro studies from 2008 to 2018. Exposure to PFOS has caused hepatotoxicity, neurotoxicity, reproductive toxicity, immunotoxicity, thyroid disruption, cardiovascular toxicity, pulmonary toxicity, and renal toxicity in laboratory animals and many in vitro human systems. These results and related epidemiological studies confirmed the human health risks of PFOS, especially for exposure via food and drinking water. Oxidative stress and physiological process disruption based on fatty acid similarity were widely studied mechanisms of PFOS toxicity. Future research for assessing the human health risks of PFOS is recommended in the chronic toxicity and molecular mechanisms, the application of various omics, and the integration of toxicological and epidemiological data.

Soyasapogenol B exhibits anti-growth and anti-metastatic activities in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common type of human malignancies of the urological system. Soyasapogenol B (Soy B), an ingredient of soybean, has been found to exert anti-proliferative activities in vitro in human breast cancer cells. Our current study aimed to evaluate the effectiveness of Soy B against ccRCC. The effect of Soy B on cell viability was assessed by Cell Counting Kit-8 (CCK-8) assay. The effect of Soy B on cell proliferation was determined by colony formation assay. Apoptotic percentage was determined by flow cytometry following annexin V-FITC/propidium iodide (PI) double staining. JC-1 staining was performed to examine the change in mitochondrial membrane potential. Western blotting was used to determine the level of relevant proteins. Isobaric tags for relative and absolute quantification (iTRAQ) was then performed to identify the potential targets of Soy B. Quantitative real-time PCR (qRT-PCR) was performed to determine the mRNA level of sphingosine kinase 1 (SphK1). The SphK1 expression in ccRCC tissue from patients was examined by immunohistochemistry (IHC) assay. To validate the role of SphK1 involved in the pro-apoptotic activities of Soy B, overexpressed SphK1 vectors and shRNA targeting of SphK1 were utilized to transfected ccRCC cells. Moreover, a ccRCC xenograft murine model was used to analyze the therapeutic efficacy of Soy B in vivo. Soy B incubation led to a decrease in the number of viable cells in ccRCC cell lines and primary ccRCC cells. Soy B also suppressed the proliferation of two model ccRCC cell lines. Soy B promoted apoptotic cell death in a caspase-dependent manner. Moreover, our results showed that both extrinsic and intrinsic apoptotic signaling pathways were involved in Soy B-induced apoptosis. ITRAQ analysis identified SphK1 as most profoundly altered after the treatment of Soy B in ACHN cells. The mediatory role of SphK1 was validated when the pro-apoptotic activity of Soy B was significantly blocked by SphK1 overexpression, while SphK1 knockdown sensitized the ccRCC cells to Soy B. Moreover, in vivo studies also showed that Soy B could exhibit anti-cancer activities against ccRCC. Soy B triggers apoptotic cell death in vitro and in vivo in ccRCC by down-regulating SphK1. Our results highlight the possibility of using Soy B as a chemotherapeutic agent in the prevention and treatment of ccRCC.

Transcriptome sequencing reveals prenatal PFOS exposure on liver disorders

Perfluorooctane sulfonate (PFOS), a hepatic toxicant and a potential hepatocarcinogen, is commonly used in industrial products. The widespread contamination of PFOS in human maternal and cord blood has raised concerns about its potential risks to the fetus. It is believed that adverse environmental exposure during the critical period of embryo development can have long-lasting consequences in later life. In this report, we used transcriptome sequencing, followed by bioinformatics analysis, to elucidate the potential hepatotoxic and hepatocarcinogenic effects of prenatal PFOS exposure in the fetus. Our results demonstrated that prenatal PFOS exposure could activate the synthesis and metabolism of fatty acids and lipids, leading to liver damage and interference with liver development in the fetus. In addition, a number of cancer-promoting signaling pathways, including Wnt/β-catenin, Rac, and TGF-β, were found to be activated in the fetal liver. More importantly, hepatic transaminase activity, including aspartate aminotransferase and alanine transaminase activity, was induced in the liver of mice offspring after prenatal PFOS exposure. For the first time, our results demonstrate that the hepatotoxic effects of prenatal exposure to PFOS may predispose to a long-term liver disorder in the offspring.

The expression of several reproductive hormone receptors can be modified by perfluorooctane sulfonate (PFOS) in adult male rats

This study was undertaken to evaluate the possible role of several reproductive hormone receptors on the disruption of the hypothalamic-pituitary-testis (HPT) axis activity induced by perfluorooctane sulfonate (PFOS). The studied receptors are the gonadotropin-releasing hormone receptor (GnRHr), luteinizing hormone receptor (LHr), follicle-stimulating hormone receptor (FSHr), and the androgen receptor (Ar). Adult male rats were orally treated with 1.0; 3.0 and 6.0 mg of PFOS kg(-1) d(-1) for 28 days. In general terms, PFOS can modify the relative gene and protein expressions of these receptors in several tissues of the reproductive axis. At the testicular level, apart from the expected inhibition of both gene and protein expressions of FSHr and Ar, PFOS also stimulates the GnRHr protein and the LHr gene expression. The receptors of the main hormones involved in the HPT axis may have an important role in the disruption exerted by PFOS on this axis.

Proteomic analysis of cell proliferation in a human hepatic cell line (HL-7702) induced by perfluorooctane sulfonate using iTRAQ

Perfluorooctane sulfonate (PFOS) is a commonly used and widely distributed perfluorinated compound proven to cause adverse health outcomes. However, how PFOS affects liver cell proliferation is not well understood. In this experiment, we exposed a human liver cell line (HL-7702) to 50 μM PFOS for 48 h and 96 h. We identified 52 differentially expressed proteins using a quantitative proteomic approach. Among them, 27 were associated with cell proliferation, including hepatoma-derived growth factor (Hdgf) and proliferation biomarkers Mk167 (Ki67) and Top2α. Results from MTT, cell counting, and cell cycle analysis showed low-dose PFOS (<200 μM) stimulated HL-7702 cell viability at 48 h and 96 h, reduced the G0/G1 percentage, and increased the S+G2/M percentage. Moreover, levels of Cyclin D1, Cyclin E2, Cyclin A2, Cyclin B1 and their partner Cdks were elevated, and the expression of regulating proteins like c-Myc, p53, p21 waf/cip1 and Myt1, as well as the phosphorylation levels of p-Wee1(S642), p-Chk1(S345) and p-Chk2(T68), were disturbed. We hypothesized that low-dose PFOS stimulated HL-7702 proliferation by driving cells into G1 through elevating cyclins/cdks expression, and by promoting cell cycle progression through altering other regulating proteins. This research will shed light on the mechanisms behind PFOS-mediated human hepatotoxicity.

Reduction of progesterone, estradiol and hCG secretion by perfluorooctane sulfonate via induction of apoptosis in human placental syncytiotrophoblasts

INTRODUCTION

Perfluorooctane sulfonate (PFOS) is widely used as surfactants, lubricants, adhesives, fire retardants and propellants. Animal experiments have shown that PFOS can potentially influence reproductive function. The objective of the present study was to investigate the effects of PFOS on the endocrine function of human placental syncytiotrophoblasts.

METHODS

Primary human placental cytotrophoblasts were isolated from term placenta. After syncytialization, the levels of aromatase and apoptosis-related proteins including caspase3, Bcl-2 and Bax were examined after treatment with PFOS from 0.0001 μM to 1 μM or PFOS (0.1 μM) in the presence and absence of apoptosis inhibitor Z-VAD-FMK (30 μM) for 24 h.

RESULTS

PFOS suppressed aromatase level and the secretion of estradiol, hCG and progesterone in a concentration-dependent manner from 0.0001 μM to 1 μM with a significant inhibition at 0.001 μM and above in human placental syncytiotrophoblasts. Furthermore PFOS reduced cell viability and induced apoptosis in human placental syncytiotrophoblasts as revealed by increases of pro-apoptosis proteins such as Bax and cleaved-caspase3, and decreases of pro-caspase3 and anti-apoptosis protein Bcl-2. The apoptosis induced by PFOS was further illustrated by increased DNA fragmentation and nuclear condensation. Blocking apoptosis with pan-caspase inhibitor Z-VAD-FMK, the impairment of placental endocrine function by PFOS was restored.

DISCUSSION

These results indicate that PFOS may disrupt the secretion of hCG, progesterone and estradiol by human placental syncytiotrophoblasts via induction of apoptosis.