Low dose perfluorooctanoate exposure promotes cell proliferation in a human non-tumor liver cell line

Associations between the concentrations of α-klotho and selected perfluoroalkyl substances in the presence of eGFR based kidney function and albuminuria: Data for US adults aged 40-79 years

Exposures to per- and polyfluoroalkyl substances (PFAS) cause oxidative stress, a risk factor for tissue damage leading to kidney and cardiovascular diseases. The antiaging protein klotho is known to act as an anti-oxidative agent, and how klotho homeostasis interacts with PFAS has not been reported. This study among 3981 US adults aged 40-79 years old evaluated relationships of internal PFAS contamination to α-klotho across stages of estimated glomerular filtration rate or eGFR-based kidney function and albuminuria defined as urinary albumin creatinine ratio of >30 mg/g creatinine. In the absence of albuminuria and when eGFR based kidney function was in stage GF-1 (eGFR ≥ 90 mL/min/1.73 m²), statistically significant inverse associations between α-klotho and PFNA (β = -0.04930, p < 0.01), PFDA (β = -0.03307, p = 0.02), and PFUnDA (β = -0.03451, p = 0.01), PFHxS (β = -0.03011, p = 0.04) and PFOS (β = -0.03126, p = 0.03) were noted. No associations between α-klotho and PFAS were observed when kidney function was in stages GF-2 (60 ≤ eGFR < 90 mL/min/1.73 m²) or GF-3A (45 ≤ eGFR < 60 mL/min/1.73 m²) in the presence or absence of albuminuria. Unexpectedly, however, in the absence of albuminuria, with kidney function in stage GF-3B/4 (15 ≤ eGFR < 45 mL/min/1.73 m²), associations were positive between α-klotho and PFOA (β = 0.20989, p < 0.01), PFNA (β = 0.18373, p < 0.1), PFDA (β = 0.20413, p < 0.01), PFUnDA (β = 0.17660, p < 0.01), and PFOS (β = 0.14267, p < 0.01). The inverse relationship of PFAS to the antioxidant protein α-klotho in those with healthy kidney function has not been previously reported and should be evaluated in other populations.

Human Evidence of Perfluorooctanoic Acid (PFOA) Exposure on Hepatic Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Perfluorooctanoic acid (PFOA) is widely used throughout different industries, including the food industry, because it is resistant to heat and prevents water or oil from easily permeating into or contaminating materials coated by PFOA. Although many studies have reported an association between PFOA exposure and the risk of developing hepatic diseases, it is still in debate because they have shown conflicting results. Therefore, this study conducted a systematic review and meta-analysis on the relationship between PFOA exposure and hepatic diseases.

METHODS

This study searched studies related to hepatic diseases due to PFOA exposure until 31 December 2021, using PubMed, EMBASE, and Web of Science. This study performed a systematic review and meta-analysis through research question development, literature screening, data extraction, and risk of bias evaluation. This study found 8280 studies after excluding duplicate literature and selected 5 studies in the final stage. Among them, two studies were included in the meta-analysis.

RESULTS

The results of the meta-analysis showed that the ALT of people exposed to PFOA was 117% higher than the ALT of those not exposed to PFOA, and it was significantly different (OR = 1.167; 95% CI, 1.086-1.254).

CONCLUSION

However, since the number of studies included in the analysis was not large enough to conclude that PFOA exposure was associated with the development of hepatic diseases, more observational studies are needed to confirm its long-term effects.

Perfluorooctanoic acid exposure increases both proliferation and apoptosis of human placental trophoblast cells mediated by ER stress-induced ROS or UPR pathways

Perfluorooctanoate acid (PFOA) is a highly persistent and widespread chemical in the environment. PFOA serum levels in pregnant women are positively associated with an increased risk of placenta-related disorders. However, the mechanism of PFOA cytotoxicity involved in placental cells and cellular responses such as ER stress remains poorly understood. In this study, we studied the cellular toxicity of PFOA with a focus on proliferation and apoptosis in a human placental trophoblast cell line. Cell viability, number, apoptosis, stress response, activation of the involved signaling pathways were assessed. Our results showed PFOA affected cell viability, proliferation and also resulted in apoptosis. Besides, both pro-proliferation and pro-apoptosis effects were attenuated by endoplasmic reticulum (ER) stress inhibitors. Further experiments demonstrated that two different signaling pathways were activated by PFOA-induced ER stress and involved in PFOA toxicity: the reactive oxygen species (ROS)-dependent ERK signaling triggered trophoblast proliferation, while the ATF4-dependent C/EBP homologous protein (CHOP) signaling was the trigger of apoptosis. We conclude that PFOA-induced ER stress is the trigger of proliferation and apoptosis of trophoblast via ROS or UPR signaling pathway, which leads to the altered balance critical to the normal development and function of the placenta.

Perfluorooctanoic acid promotes proliferation of the human granulosa cell line HGrC1 and alters expression of cell cycle genes and Hippo pathway effector YAP1

Perfluorooctanoic acid (PFOA) is a common environmental contaminant that belongs to a group of manmade fluorinated chemicals called per- and polyfluoroalkyl substances (PFAS). Due to the pervasive nature of PFOA, the environmental health risks of PFOA contamination and exposure on reproductive health have increasing concern. In the present study, we exposed HGrC1 cells, an immortalized human granulosa cell line, to environmentally relevant (1-10 μM) concentrations of PFOA. Results indicated that HGrC1 cells treated with PFOA had increased proliferation and migration relative to vehicle treated controls. No differences in cell apoptosis were observed with 1-10 μM PFOA. Gene expression analysis revealed increases in mRNA transcripts for cell cycle regulators CCND1, CCNA2, and CCNB1. Upregulation of YAP1 protein and downstream target CTGF protein was also observed, suggesting that the Hippo pathway is involved in the proliferation and migratory effects of PFOA on HGrC1 cells. Further, the YAP1 inhibitor Verteporfin prevented the stimulatory effects of PFOA on HGrC1 cells. Together, these findings support a role for the Hippo pathway effector YAP1 in response to PFOA exposure in human granulosa cells.

Release of soil colloids during flow interruption increases the pore-water PFAS concentration in saturated soil

Groundwater flow through aquifer soils or packed bed systems can fluctuate for various reasons, which could affect the concentration of natural colloids and per- and polyfluoroalkyl substances (PFAS) in the pore water. In such cases, PFAS concentration could either decrease due to matrix diffusion of PFAS or increase by the detachment of colloids carrying PFAS. Yet, the effect of flow fluctuation on PFAS transport or release in porous media has not been examined. To examine the relative importance of either process, we interrupted the flow during an injection of groundwater spiked with perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA), and bromide as conservative tracer through clay-rich soil, so that diffusive transport would be prominent during flow interruption. After flow interruption, the PFAS concentration did not decrease indicating an insignificant contribution of matrix diffusion. The concentration increased, potentially due to enhanced release of colloid-associated PFAS. Analysis of samples before and after flow interruption by particle size analysis and SEM confirmed an increase in soil colloid concentration after the flow interruption. XRD analysis of soil and the colloids proved that PFAS were associated with specific sites of the colloids. Due to a higher affinity of PFOA to soil colloids, the total PFOA concentration in the effluent samples increased more than PFBA after the flow interruption process. The results indicate that colloids may have a disproportionally higher role in the transport of PFAS in conditions that release colloids from porous media. Thus, fluctuations in groundwater flow can increase this colloid facilitated mobility of PFAS.

Non-targeted metabolomics of multiple human cells revealing differential toxic effects of perfluorooctanoic acid

Differences in toxic effects of contaminants among human cells are essential for evaluating their health risks to humans. In this study, non-targeted metabolomics of multiple human cell lines (A549 (lung), DLD-1 (intestine) and L-02 (liver) cells) was used to address the differential toxicity of perfluorooctanoic acid (PFOA). The number of differential metabolites (DMs) identified in the PFOA-treated A549 cells (67) was highest, followed by DLD-1 (12) and L-02 cells (10). The categorization of DMs was almost uniquely specific to each of cell lines. PFOA significantly promoted linoleic acid metabolism in L-02 cells whereas this metabolism was inhibited in the PFOA-treated A549 cells. The levels of interleukin (IL)-1β, IL-6, IL-8 and IL-13 were about 1.5 times higher in the PFOA-treated A549 and L-02 cells than in the controls. PFOA stimulated the biosynthesis of arginine and the metabolism of vitamin B6 in A549 cells. Arginine and vitamin B6 supplemented into cell culture effectively decreased the levels of IL-6 and IL-8. The inhibition of purine metabolism by PFOA resulted in the arrestation of DLD-1 cells at the G₀/G₁-phase. Our results suggest that the differential toxicity of PFOA related to exposure pathways could be elucidated by metabolic profiles specific to various human cells.

An acute exposure to perfluorooctanoic acid causes non-reversible plasma membrane injury in HeLa cells

Health and environmental risks regarding perfluorooctanoic acid, a well-known perfluorinated compound, are still a subject of great concern. Ubiquitous exposure and disparity of results make it difficult to determine the underlying mechanism of action, especially at the cellular level. This study proposes an experimental design to assess the reversibility of adverse effects after a one-time exposure to the compound, in comparison with other more conventional timings. Complementary endpoints including total protein content, neutral red uptake and MTT reduction tests along with division rates and microscopic observations were evaluated in HeLa cells. In addition, PFOA quantification inside the cells was performed. The cellular effects exerted after 24 h exposure to perfluorooctanoic acid are non-reversible after a 48 h recovery period. In addition, we describe for the first time the induction of plasma membrane blebbing and the activation of membrane repair mechanisms after recovery from non-cytotoxic treatments with the compound. This experimental design has provided relevant information regarding the toxicity of this perfluorinated compound, relating all the adverse effects detected to its interaction with the plasma membrane.

Application of the Key Characteristics of Carcinogens to Per and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) constitute a large class of environmentally persistent chemicals used in industrial and consumer products. Human exposure to PFAS is extensive, and PFAS contamination has been reported in drinking water and food supplies as well as in the serum of nearly all people. The most well-studied member of the PFAS class, perfluorooctanoic acid (PFOA), induces tumors in animal bioassays and has been associated with elevated risk of cancer in human populations. GenX, one of the PFOA replacement chemicals, induces tumors in animal bioassays as well. Using the Key Characteristics of Carcinogens framework for cancer hazard identification, we considered the existing epidemiological, toxicological and mechanistic data for 26 different PFAS. We found strong evidence that multiple PFAS induce oxidative stress, are immunosuppressive, and modulate receptor-mediated effects. We also found suggestive evidence indicating that some PFAS can induce epigenetic alterations and influence cell proliferation. Experimental data indicate that PFAS are not genotoxic and generally do not undergo metabolic activation. Data are currently insufficient to assess whether any PFAS promote chronic inflammation, cellular immortalization or alter DNA repair. While more research is needed to address data gaps, evidence exists that several PFAS exhibit one or more of the key characteristics of carcinogens.

PFOS, PFOA, estrogen homeostasis, and birth size in Chinese infants

Laboratory studies have suggested that perfluoroalkyl substances (PFASs) could affect fetal growth by disrupting estrogen homeostasis, but there are limited data for human. For this, 424 mother-infant pairs were selected from a cohort established in Hebei Province of North China in 2013. Two typical PFASs, perfluorooctyl sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and three typical estrogens, estrone (E₁), β-estradiol (E₂), and estriol (E₃), were measured in cord serum. After adjusted for important covariates, serum PFOS was positively related to E₁ and E₃, but negatively related to E₂. Serum PFOA was positively related to serum E₁ and negatively related to head circumference at birth. Serum E₂ was negatively related to head circumference, body weight, and body length at birth and serum E₃ was positively related to body weight. Serum E₃ mediated the relationship between serum PFOS and body weight. There were sex-specific differences for the associations between PFOS/PFOA and estrogens/birth size. These findings suggested that exposure to PFASs could affect estrogen homeostasis and fetal growth during pregnancy and that estrogens might mediate the association between exposure to PFASs and fetal growth.

Molecular Mechanisms of Perfluorooctanoate-Induced Hepatocyte Apoptosis in Mice Using Proteomic Techniques

The stability of perfluorooctanoate (PFOA) coupled with its wide use cause serious concerns regarding its potential risk to human health. The molecular mechanisms of PFOA-induced hepatotoxicity relevant to human health was investigated using both in vivo (mouse model) and in vitro (human hepatocyte cells, HL-7702) techniques. Both male and female Balb/c mice were administered PFOA at 0.05, 0.5, or 2.5 mg/kg-d for 28-d, with serum PFOA concentrations after exposure being found at environmentally relevant levels. Liver samples were examined for histology and proteomic change using iTRAQ and Western Blotting, showing dose-dependent hepatocyte apoptosis and peroxisome proliferation. At high doses, genotoxicity resulting from ROS hypergeneration was due to suppression of Complex I subunits in the electron transport chain and activation of PPARα in both genders. However, at 0.05 mg/kg-d, Complex I suppression occurred only in females, making them more sensitive to PFOA-induced apoptosis. In vitro assays using HL-7702 cells confirmed that apoptosis was also induced through a similar mechanism. The dose/gender-dependent toxicity mechanisms help to explain some epidemiological phenomena, i.e., liver cancer is not often associated with PFOA exposure in professional workers. Our results demonstrated that a proteomic approach is a robust tool to explore molecular mechanisms of toxic chemicals at environmentally relevant levels.

Cytotoxicity of novel fluorinated alternatives to long-chain perfluoroalkyl substances to human liver cell line and their binding capacity to human liver fatty acid binding protein

Although shorter chain homologues and other types of fluorinated chemicals are currently used as alternatives to long-chain perfluoroalkyl substances (PFASs), their safety information remains unclear and urgently needed. Here, the cytotoxicity of several fluorinated alternatives (i.e., 6:2 fluorotelomer carboxylic acid (6:2 FTCA), 6:2 fluorotelomer sulfonic acid (6:2 FTSA), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), and hexafluoropropylene oxide (HFPO) homologues) to human liver HL-7702 cell line were measured and compared with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Their binding mode and affinity to human liver fatty acid binding protein (hL-FABP) were also determined. Compared with PFOA and PFOS, 6:2 Cl-PFESA, HFPO trimer acid (HFPO-TA), HFPO tetramer acid (HFPO-TeA), and 6:2 FTSA showed greater toxic effects on cell viabilities. At low exposure doses, these alternatives induced cell proliferation with similar mechanism which was different from that of PFOA and PFOS. Furthermore, binding affinity to hL-FABP decreased in the order of 6:2 FTCA < 6:2 FTSA < HFPO dimer acid (HFPO-DA) < PFOA < PFOS/6:2 Cl-PFESA/HFPO-TA. Due to their distinctive structure, 6:2 Cl-PFESA and HFPO homologues were bound to the hL-FABP inner pocket with unique binding modes and higher binding energy compared with PFOA and PFOS. This research enhances our understanding of the toxicity of PFAS alternatives during usage and provides useful evidence for the development of new alternatives.

PAL-12, a new anti-aging hexa-peptoid, inhibits UVB-induced photoaging in human dermal fibroblasts and 3D reconstructed human full skin model, Keraskin-FT™

Peptoids are a class of peptidomimetics whose pharmacological activities are widely investigated owing to their remarkable biological stability. However, the utilities of peptoids as cosmetic functional ingredients have not been fully explored. Here, we investigated anti-aging effects of PAL-12, a new hexa-peptoid, on UVB-induced photoaging in human dermal fibroblasts (HDFs) and a 3D reconstituted human full skin model, Keraskin-FT™. PAL-12 suppressed matrix metalloproteinase-1 (MMP-1) expression induced by UVB irradiation along with the attenuation of MMP-1 secretion as determined by ELISA assay. Interestingly PAL-12 slightly enhanced the expression levels of collagen-1 and fibronectin-1 in HDFs or Keraskin-FT™. In addition, PAL-12 prevented the decrease of cell viability following UVB irradiation. However, PAL-12 failed to affect ROS generation, cell necrosis and apoptosis significantly. Instead, PAL-12 suppressed UVB-induced activation of epidermal growth factor receptors (EGFR), extracellular signal-regulated kinase (ERK) and c-Jun, which may resulted in the attenuation of AP-1-promoted MMP-1 expression. Collectively, these results suggest that PAL-12 might be a novel cosmetic ingredient effective against UVB-induced skin photoaging.