Global liver proteome analysis using iTRAQ labeling quantitative proteomic technology to reveal biomarkers in mice exposed to perfluorooctane sulfonate (PFOS)

Evaluation of fatty acids and carnitine as biomarkers of PFOS exposure in biota (fish and dolphin) from Galveston Bay and the northwestern Gulf of Mexico

Perfluorooctane sulfonate (PFOS) is a ubiquitous pollutant that elicits a wide range of toxic effects in exposed biota. Coastal zones in highly urbanized or industrial areas are particularly vulnerable to PFOS pollution. At present, information is lacking on biomarkers to assess PFOS effects on aquatic wildlife. This study investigated the efficacy of l-carnitine (or carnitine) and fatty acids as biomarkers of PFOS exposure in aquatic biota. The levels of PFOS, total and free carnitine, and 24 fatty acids (measured as fatty acid methyl esters or FAMEs) were measured in the liver, and muscle or blubber, of fish and dolphins sampled from Galveston Bay and the northern Gulf of Mexico (nGoM). Overall, bottlenose dolphins (Tursiops truncatus) had the highest hepatic PFOS levels. Galveston Bay fish, gafftopsail catfish (Bagre marinus), red drum (Sciaenops ocellatus), and spotted seatrout (Cynoscion nebulosus), had hepatic PFOS levels ∼8-13× higher than nGoM pelagic fish species, red snapper (Lutjanus campechanus) and yellowfin tuna (Thunnus albacares). The multivariate analysis of PFOS liver body-burdens and biomarkers found carnitine to be a more modal biomarker of PFOS exposure than FAMEs. Significant positive correlation of hepatic PFOS levels with total carnitine was evident for biota from Galveston Bay (fish only), and a significant correlation between PFOS and total and free carnitine was evident for biota from the nGoM (fish and dolphins). Given the essential role of carnitine in mediating fatty acid β-oxidation, our results suggest carnitine to be a likely candidate biomarker of environmental PFOS exposure and indicative of potential dyslipidemia effects.

PFOS-induced dyslipidemia and impaired cholinergic neurotransmission in developing zebrafish: Insight into its mechanisms

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant that has been widely detected in the environment and is known to accumulate in organisms, including humans. The study investigated dose-dependent mortality, hatching rates, malformations, lipid accumulation, lipid metabolism alterations, and impacts on cholinergic neurotransmission. Increasing PFOS concentration led to higher mortality, hindered hatching, and caused concentration-dependent malformations, indicating severe abnormalities in developing zebrafish. The results also demonstrated that PFOS exposure led to a significant increase in total lipids, triglycerides, total cholesterol, and LDL in a concentration-dependent manner, while HDL cholesterol levels were significantly decreased. Additionally, PFOS exposure led to a significant decrease in glucose levels. The study identified TGs, TCHO, and glucose as the most sensitive biomarkers in assessing lipid metabolism alterations. The study also revealed altered expression of genes involved in lipid metabolism, including upregulation of fasn, acaca, and hmgcr and downregulation of ldlr, pparα, and abca1, as well as decreased lipoprotein lipase (LPL) and increased fatty acid synthase (FAS) activity,suggesting an impact on fatty acid synthesis, cholesterol uptake, and lipid transport. Additionally, PFOS exposure led to impaired cholinergic neurotransmission, evidenced by a concentration-dependent inhibition of acetylcholinesterase activity, altered gene expressions related to neural development and function, and reduced Na+/K+-ATPase activity. STRING network analysis highlighted two distinct gene clusters related to lipid metabolism and cholinergic neurotransmission, with potential interactions through the pparα-creb1 pathway. Overall, this study provide important insights into the potential health risks associated with PFOS exposure, including dyslipidemia, cardiovascular disease, impaired glucose metabolism, and neurotoxicity. Further research is needed to fully elucidate the underlying mechanisms and potential long-term effects of PFOS exposure.

Bioaccumulation and metabolic impact of environmental PFAS residue on wild-caught urban wetland tiger snakes (Notechis scutatus)

PFAS contamination of urban waters is widespread but understanding the biological impact of its accumulation is limited to humans and common ecotoxicological model organisms. Here, we combine PFAS exposure and bioaccumulation patterns with whole organism responses and omics-based ecosurveillance methods to investigate the potential impacts of PFAS on a top predator of wetlands, the tiger snake (Notechis scutatus). Tiger snakes (18 male and 17 female) were collected from four wetlands with varying PFAS chemical profiles and concentrations in Perth, Western Australia. Tiger snake livers were tested for 28 known PFAS compounds, and Σ28PFAS in liver tissues ranged between 322 ± 193 μg/kg at the most contaminated site to 1.31 ± 0.86 μg/kg at the least contaminated site. The dominant PFAS compound detected in liver tissues was PFOS. Lower body condition was associated with higher liver PFAS, and male snakes showed signs of high bioaccumulation whereas females showed signs of maternal offloading. Biochemical profiles of snake muscle, fat (adipose tissue), and gonads were analysed using a combination of liquid chromatography triple quadrupole (QqQ) and quadrupole time-of-flight (QToF) mass spectrometry methodologies. Elevated PFAS was associated with enriched energy production and maintenance pathways in the muscle, and had weak associations with energy-related lipids in the fat tissue, and lipids associated with cellular genesis and spermatogenesis in the gonads. These findings demonstrate the bioavailability of urban wetland PFAS in higher-order reptilian predators and suggest a negative impact on snake health and metabolic processes. This research expands on omics-based ecosurveillance tools for informing mechanistic toxicology and contributes to our understanding of the impact of PFAS residue on wildlife health to improve risk management and regulation.

The role of perfluorooctane sulfonic acid (PFOS) exposure in inflammation of intestinal tissues and intestinal carcinogenesis

PFAS (per- and polyfluoroalkyl substances) are organofluorine substances that are used commercially in products like non-stick cookware, food packaging, personal care products, fire-fighting foam, etc. These chemicals have several different subtypes made of varying numbers of carbon and fluorine atoms. PFAS substances that have longer carbon chains, such as PFOS (perfluorooctane sulfonic acid), can potentially pose a significant public health risk due to their ability to bioaccumulate and persist for long periods of time in the body and the environment. The National Academies Report suggests there is some evidence of PFOS exposure and gastrointestinal (GI) inflammation contributing to ulcerative colitis. Inflammatory bowel diseases such as ulcerative colitis are precursors to colorectal cancer. However, evidence about the association between PFOS and colorectal cancer is limited and has shown contradictory findings. This review provides an overview of population and preclinical studies on PFOS exposure and GI inflammation, metabolism, immune responses, and carcinogenesis. It also highlights some mitigation approaches to reduce the harmful effects of PFOS on GI tract and discusses the dietary strategies, such as an increase in soluble fiber intake, to reduce PFOS-induced alterations in cellular lipid metabolism. More importantly, this review demonstrates the urgent need to better understand the relationship between PFOS and GI pathology and carcinogenesis, which will enable development of better approaches for interventions in populations exposed to high levels of PFAS, and in particular to PFOS.

Newborn metabolomic signatures of maternal per- and polyfluoroalkyl substance exposure and reduced length of gestation

Marginalized populations experience disproportionate rates of preterm birth and early term birth. Exposure to per- and polyfluoroalkyl substances (PFAS) has been reported to reduce length of gestation, but the underlying mechanisms are unknown. In the present study, we characterized the molecular signatures of prenatal PFAS exposure and gestational age at birth outcomes in the newborn dried blood spot metabolome among 267 African American dyads in Atlanta, Georgia between 2016 and 2020. Pregnant people with higher serum perfluorooctanoic acid and perfluorohexane sulfonic acid concentrations had increased odds of an early birth. After false discovery rate correction, the effect of prenatal PFAS exposure on reduced length of gestation was associated with 8 metabolomic pathways and 52 metabolites in newborn dried blood spots, which suggested perturbed tissue neogenesis, neuroendocrine function, and redox homeostasis. These mechanisms explain how prenatal PFAS exposure gives rise to the leading cause of infant death in the United States.

Integrative multi-omics reveals analogous developmental neurotoxicity mechanisms between perfluorobutanesulfonic acid and perfluorooctanesulfonic acid in zebrafish

The molecular mechanism of perfluorobutanesulfonic acid (PFBS), an alternative to legacy perfluorooctanesulfonic acid (PFOS), is not fully understood yet. Therefore, we conducted a developmental toxicity evaluation on zebrafish embryos exposed to PFBS and PFOS and assessed neurobehavioral changes at concentrations below each point of departure (POD) determined by embryonic mortality. Using transcriptomics, proteomics, and metabolomics, biomolecular perturbations in response to PFBS were profiled and then integrated for comparison with those for PFOS. Although PFBS (7525.47 μM POD) was approximately 700 times less toxic than PFOS (11.42 μM POD), altered neurobehavior patterns and affected kinds of endogenous neurochemicals were similar between PFBS and PFOS at the corresponding POD-based concentrations. Multi-omics analysis revealed that the PFBS neurotoxicity mechanism was associated with oxidative stress, lipid metabolism, and glycolysis/glucogenesis. The commonalities in developmental neurotoxicity-related mechanisms between PFBS and PFOS interconnected by knowledge-based integration of multi-omics included the calcium signaling pathway, lipid homeostasis, and primary bile acid biosynthesis. Despite being less toxic than PFOS, PFBS exhibited similar dysregulated molecular mechanisms, suggesting that chain length differences do not affect the intrinsic toxicity mechanism. Overall, carefully managing potential toxicity of PFBS can secure its status as an alternative to PFOS.

Plasma levels of per- and polyfluoroalkyl substances (PFAS) are associated with altered levels of proteins previously linked to inflammation, metabolism and cardiovascular disease

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) have been linked to immunotoxic and cardiometabolic effects in both experimental and epidemiological studies, but with conflicting results.

AIM

The aim of the present study was to investigate potential associations between plasma PFAS levels and plasma levels of preselected proteomic biomarkers previously linked to inflammation, metabolism and cardiovascular disease.

METHODS

Three PFAS (perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS)) were measured by non-targeted metabolomics and 249 proteomic biomarkers were measured by the proximity extension assay (PEA) in plasma from 2,342 individuals within the Epidemiology for Health (EpiHealth) study from Sweden (45-75 years old, 50.6 % men).

RESULTS

After adjustment for age and sex, 92% of the significant associations between PFOS concentrations and proteins were inverse (p < 0.0002, Bonferroni-adjusted). The results were not as clear for PFOA and PFHxS, but still with 80% and 64 % of the significant associations with proteins being inverse. After adjustment for age, sex, smoking, education, exercise habits and alcohol consumption, levels of epidermal growth factor receptor (EGFR), and paraoxonase type 3 (PON3) remained positively associated with all three PFAS, while resistin (RETN) and urokinase plasminogen activator surface receptor (uPAR) showed inverse associations with all three PFAS.

CONCLUSIONS

Our findings imply that PFAS exposure is cross-sectionally linked to altered levels of proteins previously linked to inflammation, metabolism and cardiovascular disease in middle-aged humans.

Toxicoproteomics of Mono(2-ethylhexyl) phthalate and Perfluorooctanesulfonic Acid in Models of Prostatic Diseases

Benign and malignant prostatic diseases are common, costly, and burdensome; moreover, they share fundamental underlying molecular processes. Several ubiquitous contaminants may perturb these processes, possibly via peroxisome proliferator-activated receptor (PPAR) signaling, but the role of environmental exposures─particularly mixtures─in prostatic diseases is undefined. In the present study, nontumorigenic prostate stromal cells and metastatic prostate epithelial cells were exposed to ubiquitous exogenous PPAR ligands under different dosing paradigms, including a mixture, and effects were assessed via mass spectrometry-based global proteomics. In prostate stromal cells, environmentally relevant levels of mono(2-ethylhexyl) phthalate (MEHP), alone and in combination with perfluorooctanesulfonic acid, led to significant changes in proteins involved in key processes underlying prostatic diseases: oxidative stress defense, proteostasis, damage-associated molecular pattern signaling, and innate immune response signaling. A follow-up experiment in metastatic prostate epithelial cells showed that the occupationally relevant levels of MEHP perturbed similar processes, including lipid, cholesterol, steroid, and alcohol metabolism; apoptosis and coagulation regulation; wound response; and aging. This work shows that environmental exposures may contribute to prostatic diseases by perturbing key processes of a proposed adverse outcome pathway, including lipid metabolism, oxidative stress, and inflammation. Future in vivo research will investigate the role of contaminants in prostatic diseases and in preventative agents.

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.

A review of omics-based PFAS exposure studies reveals common biochemical response pathways

Per and Polyfluoroalkyl Substances (PFAS) are a diverse group of man-made chemicals with a range of industrial applications and which are widespread in the environment. They are structurally diverse but comprise a common chemical feature of at least one (though usually more) perfluorocarbon moiety (-C_nF_2n-) attached to a functional group such as a carboxylic or sulphonic acid. The strength of the Carbon-Fluorine bond means the compounds do not break down easily and can thus bioaccumulate. PFAS are of high concern to regulators and the public due to their potential toxicity and high persistence. At high exposure levels, PFAS have been implicated in a range of harmful effects on human and environmental health, particularly problems in/with development, cholesterol and endocrine disruption, immune system function, and oncogenesis. However, most environmental toxicology studies use far higher levels of PFAS than are generally found in the environment. Additionally, since the type of exposure, the PFAS used, and the organisms tested all vary between studies, so do the results. Traditional ecotoxicology studies may thus not identify PFAS effects at environmentally relevant exposures. Here we conduct a review of omics-based PFAS exposure studies using laboratory ecotoxicological methodologies and environmentally relevant exposure levels and show that common biochemical response pathways are identified in multiple studies. A major pathway identified was the pentose phosphate shunt pathway. Such molecular markers of sublethal PFAS exposure will greatly benefit accurate and effective risk assessments to ensure that new PFAS regulations can consider the full effects of PFAS exposure on environmental and human health receptors.

Toward a Mechanistic Understanding of Poly- and Perfluoroalkylated Substances and Cancer

Simple Summary

Poly- and perfluoroalkylated substances (PFAS) are industrial chemicals found in many household products that persist in the environment. While several excellent review articles exist on the potential harmful effects of PFAS, there are few focused on cancer. This concise and streamlined mini-review focuses on summarizing molecular mechanisms related to the potential cancer-promoting properties of PFAS. This review organizes and interprets the vast primary PFAS cancer biology literature and provides a coherent, unified, and digestible model of the molecular mechanisms that potentially explains PFAS cancer promotion.

Abstract

Poly- and perfluoroalkylated substances (PFAS) are chemicals that persist and bioaccumulate in the environment and are found in nearly all human populations through several routes of exposure. Human occupational and community exposure to PFAS has been associated with several cancers, including cancers of the kidney, testis, prostate, and liver. While evidence suggests that PFAS are not directly mutagenic, many diverse mechanisms of carcinogenicity have been proposed. In this mini-review, we organize these mechanisms into three major proposed pathways of PFAS action—metabolism, endocrine disruption, and epigenetic perturbation—and discuss how these distinct but interdependent pathways may explain many of the proposed pro-carcinogenic effects of the PFAS class of environmental contaminants. Notably, each of the pathways is predicted to be highly sensitive to the dose and window of exposure which may, in part, explain the variable epidemiologic and experimental evidence linking PFAS and cancer. We highlight testicular and prostate cancer as models to validate this concept.

Sulfonamide functional head on short-chain perfluorinated substance drives developmental toxicity

Per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in environmental and biological samples and cause adverse health effects. Studies have predominately focused on long-chain PFAS, with far fewer addressing short-chain alternatives. This study leveraged embryonic zebrafish to investigate developmental toxicity of a short-chain series: perfluorobutane sulfonate (PFBS), perfluoropentanoic acid (PFPeA), perfluorobutane sulfonamide (FBSA), and 4:2 fluorotelomer sulfonic acid (4:2 FTS). Following static exposures at 8 h postfertilization (hpf) to each chemical (1-100 μM), morphological and behavioral endpoints were assessed at 24 and 120 hpf. Only FBSA induced abnormal morphology, while exposure to all chemicals caused aberrant larval behavior. RNA sequencing at 48 hpf following 47 μM exposures revealed only FBSA significantly disrupted normal gene expression. Measured tissue concentrations were FBSA > PFBS > 4:2 FTS > PFPeA. This study demonstrates functional head groups impact bioactivity and bioconcentration.

Per- and Polyfluoroalkyl Substance Exposure Combined with High-Fat Diet Supports Prostate Cancer Progression

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals utilized in various industrial settings and include products such as flame retardants, artificial film-forming foams, cosmetics, and non-stick cookware, among others. Epidemiological studies suggest a link between increased blood PFAS levels and prostate cancer incidence, but the mechanism through which PFAS impact cancer development is unclear. To investigate the link between PFAS and prostate cancer, we evaluated the impact of metabolic alterations resulting from a high-fat diet combined with PFAS exposure on prostate tumor progression. We evaluated in vivo prostate cancer xenograft models exposed to perfluorooctane sulfonate (PFOS), a type of PFAS compound, and different diets to study the effects of PFAS on prostate cancer progression and metabolic activity. Metabolomics and transcriptomics were used to understand the metabolic landscape shifts upon PFAS exposure. We evaluated metabolic changes in benign or tumor cells that lead to epigenomic reprogramming and altered signaling, which ultimately increase tumorigenic risk and tumor aggressiveness. Our studies are the first in the field to provide new and clinically relevant insights regarding novel metabolic and epigenetic states as well as to support the future development of effective preventative and therapeutic strategies for PFAS-induced prostate cancers. Our findings enhance understanding of how PFAS synergize with high-fat diets to contribute to prostate cancer development and establish an important basis to mitigate PFAS exposure.

Perfluorooctanesulfonic Acid and Perfluorohexanesulfonic Acid Alter the Blood Lipidome and the Hepatic Proteome in a Murine Model of Diet-Induced Obesity

Perfluoroalkyl substances (PFAS) represent a family of environmental toxicants that have infiltrated the living world. This study explores diet-PFAS interactions and the impact of perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic (PFHxS) on the hepatic proteome and blood lipidomic profiles. Male C57BL/6J mice were fed with either a low-fat diet (10.5% kcal from fat) or a high fat (58% kcal from fat) high carbohydrate (42 g/l) diet with or without PFOS or PFHxS in feed (0.0003% wt/wt) for 29 weeks. Lipidomic, proteomic, and gene expression profiles were determined to explore lipid outcomes and hepatic mechanistic pathways. With administration of a high-fat high-carbohydrate diet, PFOS and PFHxS increased hepatic expression of targets involved in lipid metabolism and oxidative stress. In the blood, PFOS and PFHxS altered serum phosphatidylcholines, phosphatidylethanolamines, plasmogens, sphingomyelins, and triglycerides. Furthermore, oxidized lipid species were enriched in the blood lipidome of PFOS and PFHxS treated mice. These data support the hypothesis that PFOS and PFHxS increase the risk of metabolic and inflammatory disease induced by diet, possibly by inducing dysregulated lipid metabolism and oxidative stress.

Multilayered glycoproteomic analysis reveals the hepatotoxic mechanism in perfluorooctane sulfonate (PFOS) exposure mice

Perfluorooctane sulfonate (PFOS) is one of the most widely used and distributed perfluorinated compounds proven to cause adverse health outcomes. Datasets of ecotoxico-genomics and proteomics have given greater insights for PFOS toxicological effect. However, the molecular mechanisms of hepatotoxicity of PFOS on post-translational modifications (PTMs) regulation, which is most relevant for regulating the activity of proteins, are not well elucidated. Protein glycosylation is one of the most ubiquitous PTMs associated with diverse cellular functions, which are critical towards the understanding of the multiple biological processes and toxic mechanisms exposed to PFOS. Here, we exploit the multilayered glycoproteomics to quantify the global protein expression levels, glycosylation sites, and glycoproteins in PFOS exposure and wild-type mouse livers. The identified 2439 proteins, 1292 glycosites, and 799 glycoproteins were displayed complex heterogeneity in PFOS exposure mouse livers. Quantification results reveal that 241 dysregulated proteins (fold change ≥ 2, p < 0.05) in PFOS exposure mouse livers were involved in the lipid and xenobiotic metabolism. While, 16 overexpressed glycoproteins were exclusively related to neutrophil degranulation, cellular responses to stress, protein processing in endoplasmic reticulum (ER). Moreover, the interactome and functional network analysis identified HP and HSP90AA1 as the potential glycoprotein biomarkers. These results provide unique insights into a deep understanding of the mechanisms of PFOS induced hepatotoxicity and liver disease. Our platform of multilayered glycoproteomics can be adapted to diverse ecotoxicological research.

Associations between apolipoprotein B and selected perfluoroalkyl substances among diabetics and nondiabetics

Previous population investigation of perfluoroalkyl substances (PFAS) features associations with lipids in a number of populations; these investigations have seldom included consideration of apolipoproteins. Apolipoprotein B (Apo B) fractions were considered in this descriptive analysis because they are essential to the assembly, transport, and cellular uptake of lipid classes associated with poorer health outcomes, and they are associated with incident and prevalent disease. Regression models stratified by diabetes and lipid lowering medication (LLM) status for data from National Health and Nutrition Examination Survey for 2007-2014 were fitted to interrogate associations between selected PFAS and Apo B for US adults aged ≥ 20 years. Adjusted concentrations of Apo B were positively associated with perfluorooctanoic acid (PFOA β = 0.03878, p < 0.01), perfluorooctane sulfonic acid (PFOS β = .02029, p = 0.02), and perfluorononanoic acid (PFNA β = .01968, p = .03) for nondiabetics who were not taking lipid lowering medications. These associations were not seen among diabetic participants, except for perfluorodecanoic acid (PFDA) in those taking LLMs (β = 0.03831, p = 0.02). We also note that LLMs have an inferred greater impact on Apo B in the diabetics compared to the nondiabetic populations. We have considered several sources of confounding and think the data are most consistent with a weak causal association that PFAS exposure increases Apo B. The rodent toxicology literature also contains evidence that PFAS disrupt fatty acid trafficking including Apo B, although how the specific findings may relate to circulating human Apo B concentrations is unclear. We therefore advocate for attempts to replicate the findings in other populations and to consider additional types of mechanistic studies.

Proteomics Unravels Emodin Causes Liver Oxidative Damage Elicited by Mitochondrial Dysfunction

Emodin is one of the main active compounds in many Chinese traditional herbs. Due to its potential toxic effect on the liver, the possible injury mechanism needs to be explored. In the present study, we investigated liver injury mechanisms of emodin on rats by the technology of proteomics. Firstly, 4530 proteins were identified from the liver of rats treated with emodin by label free proteomics. Inside, 892 differential proteins were selected, presenting a downward trend. Bioinformatics analysis showed that proteins interfered with by emodin were mainly involved in oxidation-reduction biological processes and mitochondrial metabolic pathways, such as mitochondrial fatty acid β-oxidation, citric acid cycle, and oxidative phosphorylation, which were further confirmed by western blot. The decrease in maximal respiration, ATP production, spare respiratory capacity, and coupling efficiency and increase in proton leakage were detected by seahorse XFe 24 analyzer, which confirmed the damage of mitochondrial function. The down-regulated expressions in antioxidant proteins were verified by western blot and a significant increase of ROS levels were detected in emodin group, which showed that emodin disrupted redox homeostasis in livers. Molecular docking revealed that the main targets of emodin might be acadvl and complex IV. Generally, emodin could induce oxidative stress in livers by directly targeting acadvl/complex IV and inhibiting fatty acid β-oxidation, citric acid cycle, and oxidative phosphorylation taken place in mitochondria.

Probing the hepatotoxicity mechanisms of novel chlorinated polyfluoroalkyl sulfonates to zebrafish larvae: Implication of structural specificity

Hepatotoxicity in zebrafish (Danio rerio) larvae elicited by legacy perfluorooctane sulfonate (PFOS) and its three novel chlorinated alternatives, including chlorinated polyfluorooctane sulfonate (Cl-PFOS) and chlorinated polyfluoroalkyl ether sulfonates (6:2 and 8:2 Cl-PFESA analogs), was evaluated in this study. Upon 7-day separate exposure to the four target compounds at 1 µmol/L, significant hepatic steatosis in exposed larvae was evidenced by pathological micro/macro vacuolation, which was presumably attributed to the excess accumulation of lipid, especially the overloaded triglyceride (TG) level. Disruption on gene transcription was subjected to a structure-dependent manner. In general, PFOS, Cl-PFOS and 6:2 Cl-PFESA of the identical carbon chain length (i.e. C8), despite with different substituents, displayed a similar activation mode and comparable disruptive potency on lipid metabolism responsive genes, which particularly promoted fatty acid synthesis (acetyl-CoA carboxylase, acacb) and β-oxidation (cytochrome P450 enzymes-1A, cyp1a; peroxisomal acyl-CoA oxidase 1, acox1; and acyl-CoA dehy-drogenase, acadm). However, 8:2 Cl-PFESA with a prolonged carbon chain length (i.e. C10), preferentially disturbed fatty acid exportation (apolipoprotein-B100, apob) and triggered a different modulation pattern on fatty acid β-oxidation against the other three compounds. Molecular docking analysis indicated that 8:2 Cl-PFESA exhibited considerably higher peroxisome proliferator-activated receptors (PPARs) antagonism than others, corresponding to its unique suppression effect on fatty acid β-oxidation responsive genes. To our knowledge, this is the first in vivo study reporting hepatotoxicity of Cl-PFOS and Cl-PFESAs to aquatic organisms. Although characterized with different toxic mode-of-action, these novel alternatives can elicit hepatic steatosis as strong as PFOS, stressing the biological risks in view of their global contamination.

PFOA and PFOS promote diabetic renal injury in vitro by impairing the metabolisms of amino acids and purines

BACKGROUND

Environmental pollutants, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are common surfactants in various consumer products. Epidemiological studies have demonstrated the association of diabetic kidney diseases with PFOA and PFOS. However, mechanisms of metabolic alterations involved are still unclear.

METHODS

Considering their involvement of glomerular hemodynamics, rat mesangial cells (MCs) are used as an in vitro model of diabetic kidney diseases for exposure to PFOS/PFOA under diabetic condition. Non-targeted metabolomics studies based on liquid chromatography-high resolution mass spectrometry were conducted to determine how PFOA/PFOS promoted fibrotic and proinflammatory responses in the MCs under diabetic condition.

RESULTS

Exposure of PFOA/PFOS (10 μM) increased oxidative stress and the levels of fibrotic and proinflammatory markers in MCs under diabetic condition. We demonstrated for the first time that PFOA and PFOS altered amino acid biosynthesis, citrate cycle, and purine metabolism in MCs under diabetic condition. Compared with diabetic condition, the exposure of PFOA and PFOS under diabetic condition more significantly altered the levels of 13 intracellular metabolites, including L-tyrosine, L-phenylalanine, L-arginine, L-tryptophan, AMP, ADP, UMP, inosine, and hypoxanthine, which have been reported to be related to kidney injury. In addition, PFOA/PFOS treatment significantly altered the expression levels of key enzymes involved in these metabolisms. Treatment with L-tyrosine, L-phenylalanine, L-arginine, and L-tryptophan reduced the levels of fibrotic and inflammatory markers induced by PFOA/PFOS.

CONCLUSION

Our results suggest that under diabetic condition, exposure of PFOA or PFOS aggravated diabetic kidney injury in vitro by impairing metabolisms of amino acids and purines to induce more fibrosis and inflammation in MCs.

In ovo exposure to triclosan alters the hepatic proteome in chicken embryos

The occurrence of triclosan (TCS) in the eggs of wild avian species is an emerging concern. We previously evaluated the effects of in ovo exposure to TCS on the liver transcriptome of chicken embryos and proposed adverse outcome pathways (AOPs). However, the key molecular events identified to be affected need to be verified at the protein level. Herein, we investigated the changes in the spectrum of hepatic proteins in TCS-treated chicken embryos by proteomic analysis to validate the key signaling pathways involved in the AOPs. We identified and quantified 894 unique proteins using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry. In the 0.1 (low dose), 1 (median dose), and 10 μg triclosan/g egg (high dose) groups, TCS caused significant changes in the levels of 195, 233, and 233 proteins in males and 237, 188, and 156 proteins in females, respectively (fold changes > 1.3 or < 0.7). TCS exposure modulated the expression of proteins, predominantly involved in signaling pathways of lipid and energy metabolism in both genders. Among the proteins associated with TCS metabolism in the liver, phase I (e.g., CYP2C23a) and phase II (e.g., UGT1A1) enzymes mediated by chicken xenobiotic receptor, were only induced in males. In consonance with the malondialdehyde levels, which were increased upon TCS exposure in females in a dose-dependent manner, a battery of antioxidant enzymes, notably SOD2, GST, GSTz1, and PRDX1, was decreased and SOD1 and GSTK1 were increased in the embryos. Taken together, this proteome analysis complements the transcriptome profiling reported in our previous study and authenticates the AOPs proposed for chicken embryos in ovo exposed to TCS.

Identification of proteins responding to pathogen-infection in the red alga Pyropia yezoensis using iTRAQ quantitative proteomics

BACKGROUND

Pyropia yezoensis is an important marine crop which, due to its high protein content, is widely used as a seafood in China. Unfortunately, red rot disease, caused by Pythium porphyrae, seriously damages P. yezoensis farms every year in China, Japan, and Korea. Proteomic methods are often used to study the interactions between hosts and pathogens. Therefore, an iTRAQ-based proteomic analysis was used to identify pathogen-responsive proteins following the artificial infection of P. yezoensis with P. porphyrae spores.

RESULTS

A total of 762 differentially expressed proteins were identified, of which 378 were up-regulated and 384 were down-regulated following infection. A large amount of these proteins were involved in disease stress, carbohydrate metabolism, cell signaling, chaperone activity, photosynthesis, and energy metabolism, as annotated in the KEGG database. Overall, the data showed that P. yezoensis resists infection by inhibiting photosynthesis, and energy and carbohydrate metabolism pathways, as supported by changes in the expression levels of related proteins. The expression data are available via ProteomeXchange with the identifier PXD009363.

CONCLUSIONS

The current data provide an overall summary of the red algae responses to pathogen infection. This study improves our understanding of infection resistance in P. yezoensis, and may help in increasing the breeding of P. porphyrae-infection tolerant macroalgae.

Subchronic Hepatotoxicity Effects of 6:2 Chlorinated Polyfluorinated Ether Sulfonate (6:2 Cl-PFESA), a Novel Perfluorooctanesulfonate (PFOS) Alternative, on Adult Male Mice

The compound 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), an alternative to perfluorooctanesulfonate (PFOS) in the metal-plating industry, has been widely detected in various environmental matrices. However, its hepatotoxicity has yet to be clarified. Here, male mice were exposed to 0.04, 0.2, or 1 mg/kg/day of 6:2 Cl-PFESA for 56 days. Results demonstrated that relative liver weight increased significantly in the 0.2 and 1 mg/kg/day 6:2 Cl-PFESA groups, whereas liver lipid accumulation increased in all 6:2 Cl-PFESA groups. Serum enzyme activities of alanine transaminase and alkaline phosphatase were increased. Serum triglycerides and low-density lipoprotein cholesterol both increased, whereas serum total cholesterol and high-density lipoprotein cholesterol decreased following 6:2 Cl-PFESA exposure. A total of 264 differentially expressed proteins (127 up-regulated and 137 down-regulated), mainly involved in lipid metabolism, xenobiotic metabolism, and ribosome biogenesis, were identified by quantitative proteomics. Bioinformatics analysis highlighted the de-regulation of PPAR and PXR, which may contribute to the hepatotoxicity of 6:2 Cl-PFESA. Additionally, 6:2 Cl-PFESA induced both cell apoptosis and proliferation in the mouse liver. Compared to the overt toxicity of PFOS, 6:2 Cl-PFESA exhibited more-serious hepatotoxicity. Thus, caution should be exercised in the application of 6:2 Cl-PFESA as a replacement alternative to PFOS in industrial areas.

Emodin induces liver injury by inhibiting the key enzymes of FADH/NADPH transport in rat liver

Emodin is a natural anthraquinone derivative that occurs in many Chinese medicinal herbs. It might induce liver damage, but the mechanism is not clear. In this research, seven groups of Sprague-Dawley (SD) rats with three doses of emodin were used. The liver injury was examined by analyzing biochemical indexes and histopathology. Altered proteins between the control group (CG) and the liver injury group were determined by proteomic technology. The results showed that emodin causes liver injury in a time- and dose-dependent manner. In the high-dosage 1-week group (HG1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was downregulated, and the activity of malate dehydrogenase (MDH) was inhibited by emodin. These might cause the inhibition of FADH or NADH/NADPH transport from the cytoplasm to mitochondria. The WB results showed that the inhibition of FADH/NADPH transport induced a high activity of caspase-9 and caspase-3, and the expressions of cytochrome c (Cyt C), caspase-9 and caspase-3 were high in HG1, which might lead to mitochondrial apoptosis pathway activation. In addition, whatever the HG1 or low-dose group (LG), the effects of emodin on mitochondria were observed. Overall, for the first time, we showed that emodin inhibited proton transport and induced the activation of the mitochondrial apoptosis pathway, which might be the reason for liver injury.

Effects of perfluorooctane sulfonate on genes controlling hepatic fatty acid metabolism in livers of chicken embryos

Per- and polyfluoroalkyl substances (PFAS) are synthetic surfactants with a wide variety of applications; however, due to their stability, they are particularly resistant to degradation and, as such, are classed as persistent organic pollutants. Perfluorooctane sulfonate (PFOS) is one such PFAS that is still detectable in a range of different environmental settings, despite its use now being regulated in numerous countries. Elevated levels of PFOS have been detected in various avian species, and the impact of this on avian health is of interest when determining acceptable levels of PFOS in the environment. Due to its similarities to naturally occurring fatty acids, PFOS has potential to disrupt a range of biological pathways, particularly those associated with lipid metabolism, and this has been shown in various species. In this study, we have investigated how in ovo exposure to environmentally relevant levels of PFOS affects expression of genes involved in lipid metabolism of developing chicken embryos. We have found a broad suppression of transcription of genes involved in fatty acid oxidation and PPAR-mediated transcription with more significant effects apparent at lower doses of PFOS. These results highlight the need for more research investigating the biological impacts of low levels of PFAS to properly inform environmental policy governing their regulation.

Integrative Proteomics-Metabolomics Strategy for Pathological Mechanism of Vascular Depression Mouse Model

Vascular depression (VD), a subtype of depression, is caused by vascular diseases or cerebrovascular risk factors. Recently, the proportion of VD patients has increased significantly, which severely affects their quality of life. However, the current pathogenesis of VD has not yet been fully understood, and the basic research is not adequate. In this study, on the basis of the combination of LC-MS-based proteomics and metabolomics, we aimed to establish a protein metabolism regulatory network in a murine VD model to elucidate a more comprehensive impact of VD on organisms. We detected 44 metabolites and 304 proteins with different levels in the hippocampus samples from VD mice using a combination of metabolomic and proteomics analyses with an isobaric tags for relative and absolute quantification (iTRAQ) method. We constructed a protein-to-metabolic regulatory network by correlating and integrating the differential metabolites and proteins using ingenuity pathway analysis. Then we quantitatively validated the levels of the bimolecules shown in the bioinformatics analysis using LC-MS/MS and Western blotting. Validation results suggested changes in the regulation of neuroplasticity, transport of neurotransmitters, neuronal cell proliferation and apoptosis, and disorders of amino acids, lipids and energy metabolism. These proteins and metabolites involved in these dis-regulated pathways will provide a more targeted and credible direction to study the mechanism of VD. Therefore, this paper presents an approach and strategy that was applied in integrative proteomics and metabolomics for research and screening potential targets and biomarkers of VD, which could be more precise and credible in a field lacking adequate basic research.

iTRAQ quantitative proteomic analysis reveals the pathways for methanation of propionate facilitated by magnetite

Methanation of propionate requires syntrophic interaction of propionate-oxidizing bacteria and hydrogenotrophic methanogens, which is referred to as interspecies electron transfer. The present study showed that 10 mg/L conductive magnetite enhanced the methane production rate from propionate by around 44% in batch experiments, and both direct interspecies electron transfer and interspecies H₂ transfer were thermodynamically feasible with the addition of magnetite. The methanation of propionate facilitated by magnetite was also demonstrated in a long-term operated continuous reactor. The methane production rate from acetate by the enriched mixed culture with magnetite was higher than that without magnetite, while similar methane production rates were found from H₂/CO₂ by the enriched mixed culture with and without magnetite. The ability to utilize molecular H₂ indicated interspecies H₂ transfer played a role in the enriched culture with magnetite, and propionate-oxidizing bacteria relating with interspecies H₂ transfer were also detected by metagenomic sequencing. Metagenomic sequencing analysis also showed that Thauera, possibly relating with direct interspecies electron transfer, were enriched with the addition of magnetite. iTRAQ quantitative proteomic analysis, which was used in mixed culture for the first time, showed that magnetite induced the changes of protein expression levels involved in various pathways during the methanation of propionate. The up-regulation of proteins involved in propionate metabolism were found, and they were mainly originated from propionate-oxidizing bacteria which were not reported to be capable of direct interspecies electron transfer until now. Cytochrome c oxidase was also revealed as the possible protein relating with direct interspecies electron transfer considering its up-regulation with the addition of magnetite and origination from Thauera. Most of the up-regulated proteins in methane metabolism were originated from Methanosaeta, while most of the enzymes with down-regulated proteins were originated from Methanosarcina. However, the up-regulated proteins relating with hydrogenotrophic methanogenesis were originated from neither Methanosaeta nor Methanosarcina, indicating they were not involved in direct interspecies electron transfer. The hydrogenotrophic methanogens, e.g. Methanospirillum, Methanosphaerula et al., might be involved in direct interspecies electron transfer. Overall, the present study showed that both direct interspecies electron transfer and interspecies H₂ transfer were present during methanation of propionate facilitated by magnetite.

Combined proteomic and metallomic analyses in Scrobicularia plana clams to assess environmental pollution of estuarine ecosystems

Estuaries are very important ecosystems with great ecological and economic value, but usually highly impacted by anthropogenic pressure. Thus, the assessment of pollution levels in these habitats is critical in order to evaluate their environmental quality. In this work, we combined complementary metallomic and proteomic approaches with the aim to monitor the effects of environmental pollution on Scrobicularia plana clams captured in three estuarine systems from the south coast of Portugal; Arade estuary, Ria Formosa and Guadiana estuary. Multi-elemental profiling of digestive glands was carried out to evaluate the differential pollution levels in the three study areas. Then, proteomic analysis by means of two-dimensional gel electrophoresis and mass spectrometry revealed twenty-one differential proteins, which could be associated with multiple toxicological mechanisms induced in environmentally stressed organisms. Accordingly, it could be concluded that the combination of different omic approaches presents a great potential in environmental research.

Oral perfluorooctane sulfonate (PFOS) lessens tumor development in the APCmin mouse model of spontaneous familial adenomatous polyposis

Background

Colorectal cancer is the second most common cause of cancer deaths for both men and women, and the third most common cause of cancer in the U.S. Toxicity of current chemotherapeutic agents for colorectal cancer, and emergence of drug resistance underscore the need to develop new, potentially less toxic alternatives. Our recent cross-sectional study in a large Appalachian population, showed a strong, inverse, dose–response association of serum perfluorooctane sulfonate (PFOS) levels to prevalent colorectal cancer, suggesting PFOS may have therapeutic potential in the prevention and/or treatment of colorectal cancer. In these preliminary studies using a mouse model of familial colorectal cancer, the APC^min mouse, and exposures comparable to those reported in human populations, we assess the efficacy of PFOS for reducing tumor burden, and evaluate potential dose–response effects.

Methods

At 5–6 weeks of age, APC^min mice were randomized to receive 0, 20, 250 mg PFOS/kg (females) or 0, 10, 50 and 200 mg PFOS/kg (males) via their drinking water. At 15 weeks of age, gastrointestinal tumors were counted and scored and blood PFOS levels measured.

Results

PFOS exposure was associated with a significant, dose–response reduction in total tumor number in both male and female mice. This inverse dose–response effect of PFOS exposure was particularly pronounced for larger tumors (r² for linear trend = 0.44 for males, p’s <0.001).

Conclusions

The current study in a mouse model of familial adenomatous polyposis offers the first experimental evidence that chronic exposure to PFOS in drinking water can reduce formation of gastrointestinal tumors, and that these reductions are both significant and dose-dependent. If confirmed in further studies, these promising findings could lead to new therapeutic strategies for familial colorectal cancer, and suggest that PFOS testing in both preventive and therapeutic models for human colorectal cancer is warranted.

Chronic perfluorooctane sulfonate (PFOS) exposure induces hepatic steatosis in zebrafish

Perfluorooctane sulfonate (PFOS), one persistent organic pollutant, has been widely detected in the environment, wildlife and human. Currently few studies have documented the effects of chronic PFOS exposure on lipid metabolism, especially in aquatic organisms. The underlying mechanisms of hepatotoxicity induced by chronic PFOS exposure are still largely unknown. The present study defined the effects of chronic exposure to low level of PFOS on lipid metabolism using zebrafish as a model system. Our findings revealed a severe hepatic steatosis in the liver of males treated with 0.5μM PFOS as evidenced by hepatosomatic index, histological assessment and liver lipid profiles. Quantitative PCR assay further indicated that PFOS significantly increase the transcriptional expression of nuclear receptors (nr1h3, rara, rxrgb, nr1l2) and the genes associated with fatty acid oxidation (acox1, acadm, cpt1a). In addition, chronic PFOS exposure significantly decreased liver ATP content and serum level of VLDL/LDL lipoprotein in males. Taken together, these findings suggest that chronic PFOS exposure induces hepatic steatosis in zebrafish via disturbing lipid biosynthesis, fatty acid β-oxidation and excretion of VLDL/LDL lipoprotein, and also demonstrate the validity of using zebrafish as an alternative model for PFOS chronic toxicity screening.

Changes in iTRAQ-Based Proteomic Profiling of the Cladoceran Daphnia magna Exposed to Microcystin-Producing and Microcystin-Free Microcystis aeruginosa

Global warming and increased nutrient fluxes cause cyanobacterial blooms in freshwater ecosystems. These phenomena have increased the concern for human health and ecosystem services. The mass occurrences of toxic cyanobacteria strongly affect freshwater zooplankton communities, especially the unselective filter feeder Daphnia. However, the molecular mechanisms of cyanobacterial toxicity remain poorly understood. This study is the first to combine the established body growth rate (BGR), which is an indicator of life-history fitness, with differential peptide labeling (iTRAQ)-based proteomics in Daphnia magna influenced by microcystin-producing (MP) and microcystin-free (MF) Microcystis aeruginosa. A significant decrease in BGR was detected when D. magna was exposed to MP or MF M. aeruginosa. Conducting iTRAQ proteomic analyses, we successfully identified and quantified 211 proteins with significant changes in expression. A cluster of orthologous groups revealed that M. aeruginosa-affected differential proteins were strongly associated with lipid, carbohydrate, amino acid, and energy metabolism. These parameters could potentially explain the reduced fitness based on the cost of the substance metabolism.

Protein profiles of cardiomyocyte differentiation in murine embryonic stem cells exposed to perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS) is a persistent organic contaminant that may affect diverse systems in animals and humans, including the cardiovascular system. However, little is known about the mechanism by which it affects the biological systems. Herein, we used embryonic stem cell test procedure as a tool to assess the developmental cardiotoxicity of PFOS. The differentially expressed proteins were identified by quantitative proteomics that combines the stable isotope labeling of amino acids with high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. Results of the embryonic stem cell test procedure suggested that PFOS was a weak embryotoxic chemical. Nevertheless, a few marker proteins related to cardiovascular development (Brachyury, GATA4, MEF2C, α-actinin) were significantly reduced by exposure to PFOS. In total, 176 differential proteins were identified by proteomics analysis, of which 67 were upregulated and 109 were downregulated. Gene ontology annotation classified these proteins into 13 groups by molecular functions, 12 groups by cellular locations and 10 groups by biological processes. Most proteins were mainly relevant to either catalytic activity (25.6%), nucleus localization (28.9%) or to cellular component organization (19.8%). Pathway analysis revealed that 32 signaling pathways were affected, particularly these involved in metabolism. Changes in five proteins, including L-threonine dehydrogenase, X-ray repair cross-complementing 5, superoxide dismutase 2, and DNA methyltransferase 3b and 3a were confirmed by Western blotting, suggesting the reliability of the technique. These results revealed potential new targets of PFOS on the developmental cardiovascular system.

Effects of Perfluorooctanoic Acid on Metabolic Profiles in Brain and Liver of Mouse Revealed by a High-throughput Targeted Metabolomics Approach

Perfluorooctanoic acid (PFOA), a perfluoroalkyl acid, can result in hepatotoxicity and neurobehavioral effects in animals. The metabolome, which serves as a connection among transcriptome, proteome and toxic effects, provides pathway-based insights into effects of PFOA. Since understanding of changes in the metabolic profile during hepatotoxicity and neurotoxicity were still incomplete, a high-throughput targeted metabolomics approach (278 metabolites) was used to investigate effects of exposure to PFOA for 28 d on brain and liver of male Balb/c mice. Results of multivariate statistical analysis indicated that PFOA caused alterations in metabolic pathways in exposed individuals. Pathway analysis suggested that PFOA affected metabolism of amino acids, lipids, carbohydrates and energetics. Ten and 18 metabolites were identified as potential unique biomarkers of exposure to PFOA in brain and liver, respectively. In brain, PFOA affected concentrations of neurotransmitters, including serotonin, dopamine, norepinephrine, and glutamate in brain, which provides novel insights into mechanisms of PFOA-induced neurobehavioral effects. In liver, profiles of lipids revealed involvement of β-oxidation and biosynthesis of saturated and unsaturated fatty acids in PFOA-induced hepatotoxicity, while alterations in metabolism of arachidonic acid suggesting potential of PFOA to cause inflammation response in liver. These results provide insight into the mechanism and biomarkers for PFOA-induced effects.

Prolonged exposure to low-dose microcystin induces nonalcoholic steatohepatitis in mice: a systems toxicology study

Microcystin-LR (MCLR), a cyanotoxin widely present in freshwater, has been shown to have potent acute hepatotoxicity. However, the chronic toxicity of low-dose MCLR remains confusing by traditional measurements of toxicity. This has impeded understanding of the chronic liver damage of low-dose MCLR and corresponding safety risks of the human exposure guideline value. Here, iTRAQ-based proteomics and NMR-based metabonomics were used to decipher the molecular toxicological signatures of low doses of MCLR in mice exposed to this agent for 90 days. Low levels of MCLR, even under the reported no observed adverse effect level, significantly altered hepatic protein expression, especially of proteins associated with lipid metabolism, transport, immune and proteolysis. Coherently, MCLR induced marked perturbations in lipid metabolites in both liver and serum. Integrated analysis of proteomic, metabolic, histological and cytokine profiles revealed that MCLR significantly inhibited fatty acid β-oxidation and hepatic lipoprotein secretion and promoted hepatic inflammation, resulting in nonalcoholic steatohepatitis disease (NASH). These findings for the first time provide compelling evidence that chronic exposure to low-level MCLR can induce NASH. These results also indicate that current guidelines for MCs in drinking water may be inadequate and associated with risks to human health.

Role of miR-155 in fluorooctane sulfonate-induced oxidative hepatic damage via the Nrf2-dependent pathway

Studies demonstrated that perfluorooctane sulfonate (PFOS) tends to accumulate in the liver and is capable to cause hepatomegaly. In the present study, we investigated the roles of miR-155 in PFOS-induced hepatotoxicity in SD rats and HepG2 cells. Male SD rats were orally administrated with PFOS at 1 or 10mg/kg/day for 28 days while HepG2 cells were treated with 0-50 μM of PFOS for 24h or 50 μM of PFOS for 1, 3, 6, 12 or 24h, respectively. We found that PFOS significantly increased the liver weight and serum alanine transaminase (ALT) and aspartate amino transferase (AST) levels in rats. Morphologically, PFOS caused actin filament remodeling and endothelial permeability changes in the liver. Moreover, PFOS triggered reactive oxygen species (ROS) generation and induced apoptosis in both in vivo and in vitro assays. Immunoblotting data showed that NF-E2-related factor-2 (Nrf2) expression and activation and its target genes were all suppressed by PFOS in the liver and HepG2 cells. However, PFOS significantly increased miR-155 expression. Further studies showed that pretreatment of HepG2 cells with catalase significantly decreased miR-155 expression and substantially increased Nrf2 expression and activation, resulting in reduction of PFOS-induced cytotoxicity and oxidative stress. Taken together, these results indicated that miR-155 plays an important role in the PFOS-induced hepatotoxicity by disrupting Nrf2/ARE signaling pathway.

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.

Prenatal and neonatal exposure to perfluorooctane sulfonic acid results in aberrant changes in miRNA expression profile and levels in developing rat livers

Perfluorooctane sulfonate (PFOS) is an animal carcinogen. However, the underlying mechanism in cancer initiation is still largely unknown. Recently identified microRNAs (miRNAs) may play an important role in toxicant exposure and in the process of toxicant-induced tumorigenesis. We used PFOS to investigate PFOS-induced changes in miRNA expression in developing rat liver and the potential mechanism of PFOS-induced toxic action. Dams received 3.2 mg/kg PFOS in their feed from gestational day 1 (GD1) to postnatal day 7 (PND 7). Pups then had free access to treated feed until PND 7. We isolated RNAs from liver tissues on PND 1 and 7 and analyzed the expression profiles of 387 known rat miRNAs using microarray technology. PFOS exposure induced significant changes in miRNA expression profiles. Forty-six miRNAs had significant expression alterations on PND 1, nine miRNAs on PND 7. Specifically, expression of four miRNAs was up-regulated on PND 7 but down-regulated on PND1 (p < 0.05). Many aberrantly expressed miRNAs were related to various cancers. We found oncogenic and tumor-suppressing miRNAs, which included miR-19b, miR-21*, miR-17-3p, miR-125a-3p, miR-16, miR-26a, miR-1, miR-200c, and miR-451. In addition, four miRNAs were simultaneous significantly expressed on both PND 1 and 7. Functional Annotation analysis of the predicted transcript targets revealed that PFOS exposure potentially alters pathways associated with different cancers (cancer, melanoma, pancreatic cancer, colorectal cancer, and glioma), biological processes which include positive regulation of apoptosis and cell proliferation. Results showed PFOS exposure altered the expression of a suite of miRNAs. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 712-723, 2015.

Possible role of serotonin and neuropeptide Y on the disruption of the reproductive axis activity by perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS) is an endocrine disruptor, whose exposure can induce several alterations on the reproductive axis activity in males during adulthood. This study was undertaken to evaluate the possible role of serotonin and neuropeptide Y (NPY) on the disruption of the hypothalamic-pituitary-testicular (HPT) axis induced by PFOS in adult male rats. For that, adult male rats were orally treated with 0.5; 1.0; 3.0 and 6.0mg of PFOS/kg/day for 28 days. After PFOS exposure, serotonin concentration increased in the anterior and mediobasal hypothalamus as well as in the median eminence. The metabolism of this amine (expressed as the ratio 5-hydroxyindolacetic acid (5-HIAA)/serotonin) was diminished except in the anterior hypothalamus, with the doses of 3.0 and 6.0mg/kg/day, being this dose 0.5mg/kg/day in the median eminence. In general terms, PFOS-treated rats presented a decrease of the hypothalamic concentration of the gonadotropin releasing hormone (GnRH) and NPY. A diminution of the serum levels of the luteinizing hormone (LH), testosterone and estradiol were also shown. These results suggest that both serotonin and NPY could be involved in the inhibition induced by PFOS on the reproductive axis activity in adult male rats.

Elucidating the molecular basis of adverse health effects from exposure to anthropogenic polyfluorinated compounds using toxicoproteomic approaches

Linear, short-chain polyfluorinated and perfluorinated alkyl compounds, often referred to as PFCs, have been in worldwide use as surfactants and polymer precursors for decades, and environmental dispersal of these highly persistent compounds represents a public health threat. Whereas ubiquitous low-level exposure to these compounds has been demonstrated in human populations from around the world, the exact mechanisms of toxicity and their toxic potency remain subject to investigation and scientific dispute. As with other environmental exposures, a major hurdle for gaining a better understanding of their human health impacts is the limited utility of cell culture and animal models serving as convenient, yet imperfect proxies to human physiology and disease. The present communication provides a brief overview of the current understanding of potential health effects of PFC exposure and examines how new toxicoproteomic methodologies can provide insight into the molecular mechanism of PFC exposure. Furthermore, we showcase an exemplary data set to illustrate how toxicoproteomic, population-wide studies might overcome limitations of animal models to more fully understand the metabolism and effects of PFCs and other environmental stressors where it matters most, in human populations experiencing real-world, chronic, low-level exposures.

Proteomic investigation of signatures for geniposide-induced hepatotoxicity

Evaluating the safety of traditional medicinal herbs and their major active constituents is critical for their widespread usage. Geniposide, a major active constituent with a defined structure from the traditional medicinal herb Gardenia jasminoides ELLIS fruit, exhibits remarkable anti-inflammatory, antiapoptotic, and antifibrotic properties and has been used in a variety of medical fields, mainly for the treatment of liver diseases. However, geniposide-induced hepatotoxicity and methods for the early detection of hepatotoxicity have yet to be reported. In this study, geniposide-induced hepatotoxicity was investigated. In addition, candidate biomarkers for the earlier detection of geniposide-induced hepatotoxicity were identified using a label-free quantitative proteomics approach on a geniposide overdose-induced liver injury in a rat model. Using an accurate intensity-based, absolute quantification (iBAQ)-based, one-step discovery and verification approach, a candidate biomarker panel was easily obtained from individual samples in response to different conditions. To determine the biomarkers' early detection abilities, five candidate biomarkers were selected and tested using enzyme-linked immunosorbent assays (ELISAs). Two biomarkers, glycine N-methyltransferase (GNMT) and glycogen phosphorylase (PYGL), were found to indicate hepatic injuries significantly earlier than the current gold standard liver biomarker. This study provides a first insight into geniposide-induced hepatotoxicity in a rat model and describes a method for the earlier detection of this hepatotoxicity, facilitating the efficient monitoring of drug-induced hepatotoxicity.

Integrated proteomic and miRNA transcriptional analysis reveals the hepatotoxicity mechanism of PFNA exposure in mice

Perfluoroalkyl chemicals (PFASs) are a class of highly stable man-made compounds, and their toxicological impacts are currently of worldwide concern. Administration of perfluorononanoic acid (PFNA), a perfluorocarboxylic acid (PFCA) with a nine carbon backbone, resulted in dose-dependent hepatomegaly in mice (0, 0.2, 1, and 5 mg/kg body weight, once a day for 14 days) and an increase in hepatic triglycerides (TG) and total cholesterol (TCHO) in the median dose group as well as serum transaminases in the high dose group. Using isobaric tags for relative and absolute quantitation (iTRAQ), we identified 108 (80 up-regulated, 28 down-regulated) and 342 hepatic proteins (179 up-regulated, 163 down-regulated) that exhibited statistically significant changes (at least a 1.2-fold alteration and P < 0.05) in the 1 and 5 mg/kg/d PFNA treatment groups, respectively. Sixty-six proteins (54 up-regulated, 12 down-regulated) significantly changed in both of the two treatment groups. Among these 54 up-regulated proteins, most were proteins related to the lipid metabolism process (31 proteins). The mRNA analysis results further suggested that PFNA exposure not only resulted in a fatty acid oxidation effect but also activated mouse liver genes involved in fatty acid and cholesterol synthesis. Additionally, three (2 down-regulated, 1 up-regulated) and 30 (14 down-regulated, 16 up-regulated) microRNAs (miRNAs) exhibited at least a 2-fold alteration (P < 0.05) in the 1 and 5 mg/kg/d PFNA treatment groups, respectively, Three miRNAs (up-regulated: miR-34a; down-regulated: miR-362-3p and miR-338-3p) significantly changed in both of the two treatment groups. The repression effect of miR-34a on fucosyltransferase 8 (Fut8) and lactate dehydrogenase (Ldha) was confirmed by luciferase activity assay and Western blot analysis. The results implied that PFNA exerted a hepatic effect, at least partially, by miRNAs mediated post-translational protein repression.

A cross-omics toxicological evaluation of drinking water treated with different processes

Cross-omics profiling and phenotypic analysis were conducted to comprehensively assess the toxicities of source of drinking water (SDW), effluent of conventional treatment (ECT) and effluent of advanced treatment (EAT) in a water treatment plant. SDW feeding increased body weight, and relative liver and kidney weights of mice. Hepatic histopathological damages and serum biochemical alterations were observed in the mice fed with SDW and ECT, but EAT feeding showed no obvious effects. Transcriptomic analysis demonstrated that exposure to water samples caused differential expression of hundreds of genes in livers. Cluster analysis of the differentially expressed genes which generated by both microarrays and digital gene expression showed similar grouping patterns. Proteomic and metabolomics analyses indicated that drinking SDW, ECT and EAT generated 59, 145 and 41 significantly altered proteins in livers and 8, 2 and 0 altered metabolites in serum, respectively. SDW was found to affect several metabolic pathways including metabolism of xenobiotics by cytochrome P450 and fatty acid metabolism. SDW and ECT might induce molecular toxicities to mice, but the advanced treatment process can reduce the potential health risk by effectively removing toxic chemicals in drinking water.

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

Perfluorooctane sulfonate (PFOS) is one of the most commonly used perfluorinated compounds, whose environmental exposure has been associated with a number of adverse health outcomes. However, the molecular mechanisms involved in PFOS toxicity are still not well elucidated. In the present study, we applied iTRAQ labeling quantitative proteomic technology to investigate the differential protein expression profiles of non-tumor human hepatic cells (L-02) exposed to PFOS. A total of 18 proteins were differentially expressed in a dose-dependent manner in PFOS-treated cells versus the control. Among these, 11 proteins were up-regulated and 7 were down-regulated. Gene ontology analysis indicated that PFOS would exert toxic effects on L-02 cells by affecting multiple biological processes, including protein biosynthesis and degradation, mRNA processing and splicing, transcription, signal transduction and transport. Furthermore, the proteomic results especially proposed that the inhibition of HNRNPC, HUWE1 and UBQLN1, as well as the induction of PAF1 is involved in the activation of the p53 and c-myc signaling pathways, which then trigger the apoptotic process in L-02 cells exposed to PFOS. Overall, these data will aid our understanding of the mechanisms responsible for PFOS-mediated hepatotoxicity, and develop useful biomarkers for monitoring and evaluating PFOS contamination in the environment.

Toxicogenomic responses of zebrafish embryos/larvae to tris(1,3-dichloro-2-propyl) phosphate (TDCPP) reveal possible molecular mechanisms of developmental toxicity

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is frequently present in indoor dust and can be detected in human milk. In order to evaluate the effects of TDCPP on vertebrate development, zebrafish embryos/larvae were used as an animal model to examine developmental phenotypes and explore possible mechanisms of toxicity by employing microarrays and iTRAQ labeling quantitative proteomics. The results demonstrated that treatment with TDCPP (3 μM) from 0.75 h postfertilization (hpf) inhibited cell rearrangement at 4 hpf, caused delay in epiboly at 5.7 and 8.5 hpf, and led to abnormal development (e.g., short tail, reduced body size) and lethality between 14 and 45 hpf, which might be related with altered expression of genes regulating embryogenesis. Furthermore, trunk curvature was observed as the main phenotype in 96 hpf zebrafish larvae exposed to 1 or 3 μM TDCPP, possibly by changing somite formation and expression of proteins related to fast muscle and cartilage development. Collectively, our results suggest that exposure to TDCPP causes developmental toxicity in vertebrates and warrant the need for studies to evaluate the potential health risks of TDCPP to developing human embryos/infants/children, due to its frequent presence in indoor dust and potential for human exposure.