Involvement of NRF2 in Perfluorooctanoic Acid-Induced Testicular Damage in Male Mice

Comparative steroidogenic effects of hexafluoropropylene oxide trimer acid (HFPO-TA) and perfluorooctanoic acid (PFOA): Regulation of histone modifications

As a widely used alternative to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been detected in the environment and humans; however, little is known regarding its male reproductive toxicity. To compare the effects of HFPO-TA on steroid hormone synthesis with PFOA, we exposed Leydig cells (MLTC-1) to non-lethal doses (0.1, 1, and 10 μM) of PFOA and HFPO-TA for 48 h. It was found that the levels of steroid hormones, 17α-hydroxyprogesterone (OHP), androstenedione (ASD), and testosterone (T) were significantly increased in 1 and 10 μM of PFOA and HFPO-TA groups, with greater elevation being observed in the HFPO-TA groups than in the PFOA groups at 10 μM. We further showed that the two rate-limiting steroidogenic genes (Star and Cyp11a1) were up-regulated, while Hsd3b, Cyp17a1, and Hsd17b were down-regulated or unchanged after PFOA/HFPO-TA exposure. Moreover, PFOA exposure significantly up-regulated histone H3K4me1/3 and H3K9me1, while down-regulated H3K4me2 and H3K9me2/3 levels. By contrast, H3K4me2/3 and H3K9me2/3 were enhanced, while H3K4me1 and H3K9me1 were repressed after HFPO-TA treatment. It was further confirmed that H3K4me1/3 were increased and H3K9me2 was decreased in Star and Cyp11a1 promoters by PFOA, while HFPO-TA increased H3K4me2/3 and decreased H3K9me1 in the two gene promoters. Therefore, we propose that low levels of PFOA/HFPO-TA enhance the expression of Star and Cyp11a1 by regulating H3K4 and H3K9 methylation, thus stimulating the production of steroid hormones in MLTC-1 cells. Collectively, HFPO-TA exhibits stronger effects on steroidogenesis compared to PFOA, which may be ascribed to the distinct regulation of histone modifications. These data suggest that HFPO-TA does not appear to be a safer alternative to PFOA on the aspect of male reproductive toxicity.

Rutin ameliorates perfluorooctanoic acid-induced testicular injury in mice by reducing oxidative stress and improving lipid metabolism

This study investigated the protective effect of rutin on reproductive and blood-testis barrier (BTB) damage induced by perfluorooctanoic acid (PFOA) exposure. In this study, male ICR mice were randomly divided into three groups, Ctrl group (ddH2O, 5 mL/kg), PFOA group (PFOA, 20 mg/kg/d, 5 mL/kg), PFOA + rutin group (PFOA, 20 mg/kg/d, 5 mL/kg; rutin, 20 mg/kg/d, 5 mL/kg). Mice were exposed to PFOA for 28 days by gavage once daily in the presence or absence of rutin. Histopathological observations demonstrated that rutin treatment during PFOA exposure can reduce structural damage to testis and epididymis such as atrophy of spermatogenic epithelium and stenosis of epididymal lumen, while increase in the number and layers of spermatogenic cells. Biochemical detection demonstrated that rutin can reduce 8-hydroxy-2'-desoxyguanosine (8-OHdG) concentration in the serum and testis tissues. Rutin can also ameliorate glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) content, and reduce malondialdehyde (MDA) and total cholesterol (TC) content in testis tissues. Biotin tracking immunofluorescence and transmission electron microscopy demonstrated that rutin can ameliorate BTB structural damage during PFOA exposure. Rutin ameliorated the stress expression of tight junction proteins occludin and claudin-11. In conclusion, our findings suggested that rutin has a degree of protection in reproductive and BTB damage, which could put forward a new perspective on the application of rutin to prevent reproductive damage.

Neurodegenerative Proteinopathies Induced by Environmental Pollutants: Heat Shock Proteins and Proteasome as Promising Therapeutic Tools

Environmental pollutants' (EPs) amount and diversity have increased in recent years due to anthropogenic activity. Several neurodegenerative diseases (NDs) are theorized to be related to EPs, as their incidence has increased in a similar way to human EPs exposure and they reproduce the main ND hallmarks. EPs induce several neurotoxic effects, including accumulation and gradual deposition of misfolded toxic proteins, producing neuronal malfunction and cell death. Cells possess different mechanisms to eliminate these toxic proteins, including heat shock proteins (HSPs) and the proteasome system. The accumulation and deleterious effects of toxic proteins are induced through HSPs and disruption of proteasome proteins' homeostatic function by exposure to EPs. A therapeutic approach has been proposed to reduce accumulation of toxic proteins through treatment with recombinant HSPs/proteasome or the use of compounds that increase their expression or activity. Our aim is to review the current literature on NDs related to EP exposure and their relationship with the disruption of the proteasome system and HSPs, as well as to discuss the toxic effects of dysfunction of HSPs and proteasome and the contradictory effects described in the literature. Lastly, we cover the therapeutic use of developed drugs and recombinant proteasome/HSPs to eliminate toxic proteins and prevent/treat EP-induced neurodegeneration.

Perfluorooctanoic acid induces cell death in TM3 cells via the ER stress-mitochondrial apoptosis pathway

Perfluorooctanoic acid (PFOA) is an environmentally ubiquitous synthetic chemical highly persistent in organisms. PFOA exposure is pernicious to reproductive health as indicated by reports of male infertility. However, the PFOA toxicity mechanism to Leydig cells remains poorly understood. Therefore, this study aimed to investigate the toxicological events occurring in TM3 Leydig cells treated with PFOA (250, 500, 750µM) for 24h. PFOA was shown to significantly decrease cell viability resulting from inhibition of proliferation and elevation of apoptotic ratio in a dose dependent manner. Upregulation of pro-apoptotic gene expressions such as Bax, Bad, and p53, was observed in combination with an increase in the apoptosis-related protein levels of Bax, cleaved caspase-3, cleaved caspase-8, and phosphorylated p53. Furthermore, exposure of PFOA lead to mitochondrial damage involving mitochondrial membrane permeabilization. A release of cytochrome c and collapse of the mitochondrial membrane potential (∆Ψm) were observed compared to the untreated control. Additionally, PFOA stimulated unfolded protein response (UPR) upregulating ER stress marker, Bip/GRP78, and upregulated protein levels of UPR signal molecules IRE1, p-JNK, p-ERK1/2, p-p53, CHOP, and ERO1. Overall, the present study elucidated the ER stress-mitochondrial apoptosis pathway-related molecular mechanisms involved in PFOA-induced cell death in TM3 Leydig cells.

Perfluorooctanoic acid induces tight junction injury of Sertoli cells by blocking autophagic flux

Perfluorooctanoic acid (PFOA), a man-made chemical widely used in consumers, could cause male reproductive toxicity by disrupting blood-testis barrier (BTB) integrity. Autophagy in Sertoli cells is essential for regulation of spermatogenesis and BTB. However, it remains a mystery that whether PFOA-induced BTB injury is associated with autophagy in Sertoli cells. In this study, we found that PFOA dose-dependently disrupted tight junction (TJ) function in Sertoli cells in vivo and in vitro. Furthermore, the results from transmission electron microscopy, Western blot and immunofluorescence analysis revealed that PFOA induced the accumulation of autophagosome in testicular Sertoli cells as well as TM4 cells. Further study confirmed that autophagosome accumulation resulted from the blockage of autophagic degradation because of disruption of autophagosome and lysosome fusion via downregulation of the expression of α-SNAP. In parallel, the overexpressed MMP9 was also observed in vivo and in vitro. Conversely, overexpression of α-SNAP inhibited the expression of MMP9 in TM4 cells. In conclusion, PFOA blocks autophagic flux through downregulating the expression levels of α-SNAP in Sertoli cells, and then induces the accumulation of MMP9 leading to disruption of TJ function. This finding will provide clues for effective prevention and treatment of PFOA-induced male reproductive toxicity.

Effects of perfluorooctanoic acid on endoplasmic reticulum stress and lipid metabolism-related genes in human pancreatic cells

Perfluorooctanoic acid (PFOA) is environmentally persistent and has been classified by The International Cancer Research Agency (IARC) as a possible human pancreatic carcinogen. In this study, the epigenetic alteration, the changes in the expression levels of endoplasmic reticulum stress-related and metabolism-related genes, as well as DNA methyltransferase expression were investigated using RT-PCR and ELISA assays. PFOA induced a significant increase in the methylation ratio (5-mC%), impacted DNA methylation maintenance gene expression and decreased lipid metabolism-related genes except for PPARγ (≥ 13-fold increase). While PFOA induced the expression of ATF4 (≥ 5.41-folds), CHOP (≥ 5.41-folds) genes, it inhibited the expression of ATF6 (≥ 67.2%), GRP78 (≥ 64.3%), Elf2α (≥ 95.8%), IRE1 (≥ 95.5%), and PERK (≥ 91.7%) genes. It is thought that epigenetic mechanisms together with disruption in the glucose-lipid metabolism and changes in endoplasmic reticulum stress-related genes may play a key role in PFOA-induced pancreatic toxicity.

Efficacy and mechanism of lipoic acid in the treatment of reproductive injury caused by perfluorooctanoic acid

Environmental pollutants, including perfluorooctanoic acid (PFOA), cause severe reproductive damage to humans and animals. Lipoic acid (LA) is a strong antioxidant that alleviates the oxidative damage caused by heavy metals, environmental toxicants, chemical poisons, etc. Therefore, the present study investigated the curative effect and mechanism of LA in treating spermatogenesis dysfunction caused by PFOA. A rat reproductive injury model was established by gavage of PFOA for consecutive 30 days and then rats were treated with different doses of LA for 42 days. The effects were assessed by ELISA, western blotting, H&E staining and immunofluorescence staining. The results demonstrated that LA had ameliorating effects on PFOA-induced reproductive injury in rats, it increased the sperm counts, and the levels of serum succinate dehydrogenase, lactate dehydrogenase, glutathione peroxidase and superoxide dismutase returned to normal levels following LA treatment. In addition, LA promoted the expression of estradiol, reduced the expression of serum sex hormones, such as follicle-stimulating hormone, androgen receptor (AR) and malondialdehyde in the testes, and restored the structure of seminiferous tubules. Its therapeutic mechanisms include regulating the testicular oxidative stress pathway and hypothalamic-pituitary-testis axis.

Toxic effects of per- and polyfluoroalkyl substances on sperm: Epidemiological and experimental evidence

As emerging organic contaminants, per- and polyfluoroalkyl substances (PFASs) have aroused worldwide concern due to their environmental persistence, ubiquitous presence, bioaccumulation, and potential toxicity. It has been demonstrated that PFASs can accumulate in human body and cause multiple adverse health outcomes. Notably, PFASs have been detected in the semen of human, posing a potential hazard to male fecundity. This article reviews the evidence about the toxic effects of exposure to PFASs on male reproduction, focusing on the sperm quality. Epidemiological studies showed that PFASs, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), were adversely associated with the semen parameters in humans, including sperm count, morphology and motility. Experimental results also confirmed that PFAS exposure led to testicular and epididymal damage, therefore impairing spermatogenesis and sperm quality. The mechanisms of reproductive toxicity of PFASs may be involved in blood-testosterone barrier destruction, testicular apoptosis, testosterone synthesis disorder, and membrane lipid composition alteration, oxidative stress and Ca²⁺ influx in sperm. In conclusion, this review highlighted the potential threat of exposure to PFASs to human spermatozoa.

Perfluorooctanoic acid exposure in vivo perturbs mitochondrial metabolic during oocyte maturation

Perfluorooctanoic acid (PFOA), a member of a group of polyfluorinated and perfluorinated alkyl substances (PFAS), is associated with adverse pregnancy outcomes in mammals. However, the effects of in vivo exposure to PFOA on the female reproductive system and the underlying mechanisms remain unclear. In our study, we constructed a mouse model to investigate whether low-dose PFOA (1 mg/kg/day) or high-dose PFOA (5 mg/kg/day) affect meiosis maturation of oocytes and the potential mechanisms that may be associated with oocyte maturation disorder. Our results indicate that low-dose and high-dose PFOA can lead to impaired oocyte maturation, which is manifested by decreased rate of embryonic foam rupture and first polar body extrusion. Moreover, PFOA exposure harmed the mitochondrial metabolic, resulting in low levels of ATP contents, high reactive oxygen species, aberrant mitochondrial membrane potential. In addition, the proportion of DNA damage marker γ-H2AX was also significantly increased in PFOA exposure oocytes. These changes lead to abnormal arrangements of the spindle and chromosomes during oocyte maturation. In conclusion, our results for the first time illustrated that exposure to PFOA in vivo in female mice impaired the meiosis maturation of oocytes, which provided a basis for studying the mechanism of PFOA reproductive toxicity in female mammals.

Reduced Birth Weight and Exposure to Per- and Polyfluoroalkyl Substances: A Review of Possible Underlying Mechanisms Using the AOP-HelpFinder

Prenatal exposure to per- and polyfluorinated substances (PFAS) may impair fetal growth. Our knowledge of the underlying mechanisms is incomplete. We used the Adverse Outcome Pathway (AOP)-helpFinder tool to search PubMed for studies published until March 2021 that examined PFAS exposure in relation to birth weight, oxidative stress, hormones/hormone receptors, or growth signaling pathways. Of these 1880 articles, 106 experimental studies remained after abstract screening. One clear finding is that PFAS are associated with oxidative stress in in vivo animal studies and in vitro studies. It appears that PFAS-induced reactive-oxygen species (ROS) generation triggers increased peroxisome proliferator-activated receptor (PPAR)γ expression and activation of growth signaling pathways, leading to hyperdifferentiation of pre-adipocytes. Fewer proliferating pre-adipocytes result in lower adipose tissue weight and in this way may reduce birth weight. PFAS may also impair fetal growth through endocrine effects. Estrogenic effects have been noted in in vivo and in vitro studies. Overall, data suggest thyroid-damaging effects of PFAS affecting thyroid hormones, thyroid hormone gene expression, and histology that are associated in animal studies with decreased body and organ weight. The effects of PFAS on the complex relationships between oxidative stress, endocrine system function, adipogenesis, and fetal growth should be further explored.

Fumonisin B1 promotes germ cells apoptosis associated with oxidative stress-related Nrf2 signaling in mice testes

Fumonisins (FBs) are widespread Fusarium toxins commonly found in corn. This study aimed to establish the mechanism of oxidative stress via the Nrf2 signaling pathway associated with FB₁-induced toxicity in mice testis. Male mice were fed with 5 mg/kg FB₁ diet for 21 or 42 days, the expression of inflammatory related genes, apoptosis related genes and Nrf2 pathway genes were detected by RT-qPCR, Western blot and immunohistochemical. Furthermore, Sertoli cell was treatment with FB₁. Cell viability was measured by CCK8 assay, ROS level and apoptosis related genes were detected by immunofluorescence staining. The results showed that FB₁ had toxic effects on testis, which could increase the ROS level of Sertoli cells, affect the Keap1-Nrf2 pathway related factors, destroy the oxidative balance of testis, lead to the occurrence of inflammation and the initiation of apoptosis, and finally destroy the testicular tissue structure and affect the formation of sperm.

Recent progress and challenges on the removal of per- and poly-fluoroalkyl substances (PFAS) from contaminated soil and water

Currently, due to an increase in urbanization and industrialization around the world, a large volume of per- and poly-fluoroalkyl substances (PFAS) containing materials such as aqueous film-forming foam (AFFF), protective coatings, landfill leachates, and wastewater are produced. Most of the polluted wastewaters are left untreated and discharged into the environment, which causes high environmental risks, a threat to human beings, and hampered socioeconomic growth. Developing sustainable alternatives for removing PFAS from contaminated soil and water has attracted more attention from policymakers and scientists worldwide under various conditions. This paper reviews the recent emerging technologies for the degradation or sorption of PFAS to treat contaminated soil and water. It highlights the mechanisms involved in removing these persistent contaminants at a molecular level. Recent advances in developing nanostructured and advanced reduction remediation materials, challenges, and perspectives in the future are also discussed. Among the variety of nanomaterials, modified nano-sized iron oxides are the best sorbents materials due to their specific surface area and photogenerated holes and appear extremely promising in the remediation of PFAS from contaminated soil and water.

Investigation of the effects of hesperidin administration on abamectin-induced testicular toxicity in rats through oxidative stress, endoplasmic reticulum stress, inflammation, apoptosis, autophagy, and JAK2/STAT3 pathways

In this study, the potential effects of hesperidin (HES) on chronic toxicity caused by abamectin (ABM) in the testicular tissue were investigated through oxidative stress, inflammation, endoplasmic reticulum stress (ERS), apoptosis, and autophagy pathways. Male Sprague Dawley rats were used in the study. Animals in the ABM group were orally administered 1 mg/kg ABM every other day for 28 days, while HES used against ABM was given at 100 or 200 mg/kg 30 min after ABM administration for 28 days. Markers of oxidative stress, inflammation, ERS, apoptosis, and autophagy in the testicular tissues removed after the animals are sacrificed were analyzed using biochemical, real-time polymerase chain reaction (RT-PCR), or western blot techniques. The results obtained showed that ABM caused oxidative stress, and triggered ERS, inflammation, apoptosis, and autophagy. On the other hand, HES showed antioxidant effect by increasing superoxide dismutase, catalase, glutathione peroxidase enzyme activities, and glutathione levels in testis tissue and attenuated lipid peroxidation. Accordingly, MAPK14 reduced the NF-κB, IL-1β, TNF-α, and IL-6 expression levels, presenting an anti-inflammatory effect. In addition, Bax protected against apoptosis and autophagy by reducing the caspase-3, beclin-1, LC3A, and LC3B expressions, and increasing Bcl-2 expression. It was observed that HES also interrupted the JAK2/STAT3 signaling pathway by suppressing IL-6 expression. Taken into consideration together, HES provided significant protection against the destruction caused by ABM in testicular tissue with antioxidant, anti-inflammatory, antiapoptotic, and anti-autophagic effects. Thus, it was revealed that HES has the potential to serve as an alternative treatment option in ABM toxicity.

Low-dose perfluorooctanoic acid stimulates steroid hormone synthesis in Leydig cells: Integrated proteomics and metabolomics evidence

Perfluorooctanoic acid (PFOA), one of the well-known perfluoroalkyl substances (PFASs), has been widespread in the environment and associated with male reproductive toxicity. However, the molecular mechanism involved in low-level PFOA-induced male endocrine disruption remains to be elucidated. In this study, we performed a combined proteomics and metabolomics analysis to investigate the proteomic and metabolic alterations in MLTC-1 Leydig cells responsive to low levels of PFOA exposure. The results showed that PFOA significantly regulated the expressions of 67 proteins and 17 metabolites, among which 18 proteins and 7 metabolites were specifically tied to lipid and fatty acid metabolism as well as testicular steroidogenesis. It is further suggested that low-dose PFOA stimulates steroid hormone synthesis by accelerating fatty acid metabolism and steroidogenic process, which is involved in the repression of p38 and cAMP-dependent ERK signaling pathway. The animal studies also revealed that environmentally relevant levels of PFOA increased serum steroid hormone levels accompanied by the activated cAMP and inhibited p38/ERK pathway in testis, which confirmed our in vitro findings. Overall, the present study will provide novel insights into the toxicological mechanisms of low-level PFOA-mediated steroidogenic disturbance, and may implicate the reproductive health risk of humans with environmental PFOA exposure.

Effects of perfluoroundecanoic acid on the function of Leydig cells in adult male rats

Perfluoroundecanoic acid (PFUnA), a perfluorinated compound, has environmental persistence, bioaccumulation, and potential toxicity. However, its effect on Leydig cell function remains unclear. Rats (age of 56 days) were gavaged with 0 (corn oil), 0.1, 0.5, 1, or 5 mg/kg/day PFUnA for 28 days. PFUnA significantly reduced serum testosterone levels as low as 0.5 mg/kg. PFUnA markedly decreased Leydig cell number as low as 0.1 mg/kg. PFUnA markedly reduced transcript levels of Star and Insl3 in the testes at 1 mg/kg after adjusting to Leydig cell number. It also reduced their protein levels. PFUnA significantly decreased the phosphorylation of AKT1 and mTOR as low as 0.1 mg/kg and the phosphorylation of ERK1/2 at 1 mg/kg and the phosphorylation of AKT1, AKT2, ERK1/2, and mTOR in Leydig cells at various concentrations (0.01-10 μM) after 24 h of in vitro treatment. In conclusion, PFUnA inhibits Leydig cell function possibly via AKT/ERK1/2/mTOR signaling pathways.

Investigation of the effects of berberine on bortezomib-induced sciatic nerve and spinal cord damage in rats through pathways involved in oxidative stress and neuro-inflammation

Bortezomib (BTZ), a proteasome inhibitor, causes dose-limiting peripheral neuropathy in humans. Berberine (BBR), which has various biological and pharmacological properties, is known to have neuroprotective properties. The possible protective effects of BBR on peripheral neuropathy caused by BTZ were investigated in this study. For this purpose, BTZ was intraperitoneally given to Sprague dawley rats on the 1 st, 3rd, 5th, and 7th days with a cumulative dose of 0.8 mg/kg. Moreover, animals were orally administered 50 or 100 mg/kg BBR daily from day 1 to day 10. As a result of the analyzes performed on the sciatic nerve and spinal cord, it was observed that MDA levels and NRF-2, HO-1, NQO1, GCLC and GCLM mRNA transcript levels increased due to oxidative stress caused by BTZ, and the levels of these markers decreased after BBR administration. Also, it was determined that SOD, CAT, GPx and GSH levels increased after BBR treatment. It was observed that BTZ caused inflammation by triggering NF-κB, TNF-α, IL-1β and IL-6 cytokines, on the other hand, with BBR treatment, these cytokines were suppressed and inflammation was alleviated. In addition, it was determined that the expressions of RAGE, STAT3, NLRP3 and TLR4, which have important roles in inflammation, increased with BTZ administration, but BBR suppressed the expressions of these genes. It was determined that the expressions of SIRT1, which plays an important role in neuropathic pain, and CREB-LI neurons, which has an active role in neurite outgrowth and survival, decreased with BTZ administration. It was observed that GFAP levels increased with BTZ administration and decreased with BBR administration. Given all the findings, it was concluded that BBR exhibits protective qualities in the sciatic nerve and spinal cord induced by BTZ.

Combined effects of mixed per- and polyfluoroalkyl substances on the Nrf2-ARE pathway in ARE reporter-HepG2 cells

Although the Nrf2-ARE pathway plays a critical role in cellular protection against toxicity and oxidative stress from environmental chemical stressors, the association between exposure to per- and polyfluoroalkyl substances (PFAS) mixtures and the changes of Nrf2-ARE pathway remains largely unexplored. This study evaluated the potential of PFAS to induce the Nrf2-ARE pathway as individual compounds and as binary, ternary, and multicomponent mixtures in the ARE reporter-HepG2 cells and compared the mixture toxicity data to the predictions by concentration addition (CA) model. The toxicological interactions between PFAS mixture components were also determined by the model deviation ratio (MDR) between the CA predicted and mixture toxicity values. The induction of the Nrf2-ARE pathway was quantified using the luciferase system, and the endpoint assessed was the concentration that induced an induction ratio (IR) of 1.5 (EC_IR1.5). The results showed that exposures to both individual and mixed PFAS induced the Nrf2-ARE pathway in ARE reporter-HepG2 cells. Based on the MDRs, the combinations with PFOS showed synergistic interactive effects, while the combinations with PFOA showed additive effects. These results indicate that the CA model underestimated the mixture toxicity of PFAS with PFOS co-exposures and may have health risk assessment implications.

The impact of perfluoroalkyl substances on pregnancy, birth outcomes and offspring development: A review of data from mouse models1

Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are persistent in the environment and bioaccumulate in wildlife and humans, potentially causing adverse health effects at all stages of life. Studies from human pregnancy have shown that exposure to these contaminants are associated with placental dysfunction and fetal growth restriction; however, studies in humans are confounded by genetic and environmental factors. Here, we synthesize the available results from mouse models of pregnancy to show the causal effects of prenatal exposure to PFOA and PFOS on placental and fetal development and on neurocognitive function and metabolic disorders in offspring. We also propose gaps in the present knowledge and provide suggestions for future research studies.

Evaluation of the acute toxicity and neurodevelopmental inhibition of perfluorohexanoic acid (PFHxA) in zebrafish embryos

Perfluorohexanoic acid (PFHxA), a widely used emerging alternative for 8-carbon PFAAs, has been detected at a high level in the water environment. While its toxicity and environmental health risk are still largely unknown in aquatic life. The present study aimed to evaluated the possible developmental neurotoxicity induced by PFHxA exposure (0, 0.48, 2.4, and 12 mg/L for 120 h) in the zebrafish embryo. Here, both developmental endpoints, neurotransmitters concentrations, locomotor behavior were analyzed. No significant effects on mortality, malformation rate, and growth delay were detected in the low dose treatment groups except for in the high dose group (12 mg/L). A significant increase in swimming speed were noted in the 0.48 mg/L group. Other changes including neurotransmitters concentrations and green fluorescent protein (GFP) expression in Tg (HuC-GFP) zebrafish larvae were significantly increased in 12 mg/L group. Beyond that, genes related to neurodevelopment were significantly decreased in larvae. Moreover, downregulations of protein expression levels of α1-tubulin, elavl3, and gap43 were identified. These results demonstrate that the PFAAs alternative PFHxA have no significant neurodevelopmental effects on zebrafish larvae under acute low-dose exposure, while, it is important to note that PFHxA perform inhibiting effects on neurotransmitter and central nervous system under a relatively high dose. This in vivo study could provide reliable toxicity information for risk assessments of PFHxA on aquatic ecosystems. CAPSULE: PFHxA have no significant neurodevelopmental effects on zebrafish larvae under acute low-dose exposure, while exposed with relatively high-dose, could induced the alternations of neurotransmitter concentrations as well as the genes involved in the early developmental stages of zebrafish, leading to the impairment of the nervous system in zebrafish larvae.

Potential of sperm small non-coding RNAs as biomarkers of testicular toxicity in a doxorubicin-induced mouse model

Testicular toxicity is a major concern in cancer chemotherapy and drug development as it can result in infertility; however, there are no effective biomarkers for this adverse effect. To identify new biomarkers, we investigated the expression of small non-coding RNAs (sncRNAs) in a mouse model of doxorubicin (DXR)-induced testicular toxicity. First, we performed small RNA-seq analysis of sperm from DXR-treated or control mice and observed differential expression of many genome-derived sequences. We then performed real-time RT-PCR validation of these sequences and discovered that sncRNA detected by one primers, dxRN_3, showed similar differential expression as that seen in the RNA-seq experiment. These findings suggest that the sncRNAs present in sperm have potential as clinically acceptable biomarkers for testicular toxicity.

•

Testicular toxicity is a major concern in cancer chemotherapy and drug development.

•

There is a lack of effective biomarkers to assess testicular toxicity.

•

Small RNA-seq analysis was performed on sperm from doxorubicin-treated mice.

•

Differential RNA expression analyses identified a small non-coding RNA.

•

Small non-coding RNAs in sperm may be useful biomarkers for testicular toxicity.

Evaluation of the individual and combined toxicity of perfluoroalkyl substances to human liver cells using biomarkers of oxidative stress

Although human exposure is to mixtures of per- and polyfluoroalkyl substances (PFAS), their combined effects and underlying mechanisms remain largely unknown. In this study, the combined effects of PFAS was investigated by treating human liver cells (HepG2) with various concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFDA), perfluorononanoic acid (PFNA), and perfluorohexanoic acid (PFHxS) individually or in binary combinations (PFOS + PFOA, PFOS + PFDA, PFOS + PFNA, PFOS + PFHxS, PFOA + PFDA, PFOA + PFNA, and PFOA + PFHxS) for 24 h using an orthogonal design. The individual and binary combination effects of PFAS on the cytotoxicity, intracellular reactive oxygen species (ROS) production, and glutathione (GSH) levels were determined by MTS assay, dichlorofluorescein diacetate assay, and GSH-Glo™ Glutathione assay, respectively. The results showed that exposure to PFOA, PFOS, PFDA, PFNA, and PFHxS individually and in binary combinations caused concentration-dependent cytotoxicity to HepG2 cells. Also, intracellular ROS production was not significantly induced in both the individual and co-treatment groups, indicating that ROS production may not be likely influencing the combined cytotoxicity of PFAS to HepG2 cells. However, the depletion of the intracellular glutathione levels was correlated with cytotoxicity. Moreover, the factorial analysis results showed no significant interactive effects between PFOS + PFOA, PFOS + PFDA, PFOS + PFNA, PFOS + PFHxS, PFOA + PFDA, PFOA + PFNA, and PFOA + PFHxS. Taken together, the results showed that both individual and combined PFAS could induce concentration-dependent cytotoxicity and depletion of GSH levels, but could not induce significant increases in ROS production at the concentration range tested. Overall, these results provided valuable toxicological data on the combined effects of mixed PFAS that may help to better assess their human health risk.

Male reproductive toxicity of perfluorooctanoate (PFOA): Rodent studies

Perfluorooctanoic acid (PFOA) is an artificial organic substance widely used for decades, which seriously threatens human health. This study aimed to identify human-relevant correlates between PFOA exposure and the male rodent reproductive system. We performed a systematic literature review of the relevant literature of PubMed, Cochrane Library databases, Web of Science and Embase from the establishment to April 2020. Studies included the effects of PFOA on the reproductive system of male rodents. The meta-analysis was performed on the basis of the following points: level of testosterone and estradiol in serum, development of reproductive organs, pathological changes of reproduction organs and parameters of semen. A series of 16 studies was enrolled in this study. The standard mean difference (SMD) for PFOA-related reproductive toxicity was summarised as -0.39 (95% confidence interval [CI]: 0.71, -0.07). The lower serum testosterone levels, decreased absolute testicular and epididymal weights, higher serum estradiol levels, elevated relative testicular and seminal vesicle weights and increased incidence of Leydig cell adenoma and percentage of abnormal sperm were observed in the exposed group compared with the control group. However, no statistical difference was found in the day of preputial separation of pups and percentage of motile sperm. In conclusion, PFOA exposure heightens the reproductive system damage in male rodents. However, many studies included in the review did not identify mechanisms by which PFOA induces changes to the male reproductive system, which is an area for additional study.

Assessing the human health risks of per- and polyfluoroalkyl substances: A need for greater focus on their interactions as mixtures

Humans are exposed to complex mixtures of per- and polyfluoroalkyl substances (PFAS). However, human health risk assessment of PFAS currently relies on animal toxicity data derived from individual substance exposure, which may not adequately predict the risk from combined exposure due to possible interactions that can influence the overall risk. Long-chain perfluoroalkyl acids (PFAAs), particularly perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are recognised as global emerging contaminants of concern due to their ubiquitous distribution in all environmental media, wildlife, and humans, persistency, bioaccumulative-, toxic-, and human health-risk potentials. This article reviews the current understanding of the human health risks associated with PFAS exposure focusing on more recent toxicological and epidemiological studies from 2010 to 2020. The existing information on PFAA mixtures was also reviewed in an attempt to highlight the need for greater focus on their potential interactions as mixtures within the class of these chemicals. A growing number of toxicological studies have indicated several adverse health outcomes of PFAA exposure, including developmental and reproductive toxicity, neurotoxicity, hepatotoxicity, genotoxicity, immunotoxicity, thyroid disruption, and carcinogenicity. Epidemiological findings further support some of these adverse human health outcomes. However, the mechanisms underlying these adverse effects are not well defined. A few in vitro studies focusing on PFAA mixtures revealed that these compounds may act additively or interact synergistically/antagonistically depending on the species, dose level, dose ratio, and mixture components. Hence, the combined effects or potential interactions of PFAS mixtures should be considered and integrated into toxicity assessment to obtain a realistic and more refined human health risk assessment.

Perfluoroalkyl Chemicals and Male Reproductive Health: Do PFOA and PFOS Increase Risk for Male Infertility?

Poly- and perfluoroalkyl substances (PFAS) are manmade synthetic chemicals which have been in existence for over 70 years. Though they are currently being phased out, their persistence in the environment is widespread. There is increasing evidence linking PFAS exposure to health effects, an issue of concern since PFAS such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) bioaccumulate in humans, with a half-life of years. Many epidemiological studies suggest that, worldwide, semen quality has decreased over the past several decades. One of the most worrying effects of PFOS and PFOA is their associations with lower testosterone levels, similar to clinical observations in infertile men. This review thus focuses on PFOS/PFOA-associated effects on male reproductive health. The sources of PFAS in drinking water are listed. The current epidemiological studies linking increased exposure to PFAS with lowered testosterone and semen quality, and evidence from rodent studies supporting their function as endocrine disruptors on the reproductive system, exhibiting non-monotonic dose responses, are noted. Finally, their mechanisms of action and possible toxic effects on the Leydig, Sertoli, and germ cells are discussed. Future research efforts must consider utilizing better human model systems for exposure, using more accurate PFAS exposure susceptibility windows, and improvements in statistical modeling of data to account for the endocrine disruptor properties of PFAS.

Investigating Molecular Mechanisms of Immunotoxicity and the Utility of ToxCast for Immunotoxicity Screening of Chemicals Added to Food

The development of high-throughput screening methodologies may decrease the need for laboratory animals for toxicity testing. Here, we investigate the potential of assessing immunotoxicity with high-throughput screening data from the U.S. Environmental Protection Agency ToxCast program. As case studies, we analyzed the most common chemicals added to food as well as per- and polyfluoroalkyl substances (PFAS) shown to migrate to food from packaging materials or processing equipment. The antioxidant preservative tert-butylhydroquinone (TBHQ) showed activity both in ToxCast assays and in classical immunological assays, suggesting that it may affect the immune response in people. From the PFAS group, we identified eight substances that can migrate from food contact materials and have ToxCast data. In epidemiological and toxicological studies, PFAS suppress the immune system and decrease the response to vaccination. However, most PFAS show weak or no activity in immune-related ToxCast assays. This lack of concordance between toxicological and high-throughput data for common PFAS indicates the current limitations of in vitro screening for analyzing immunotoxicity. High-throughput in vitro assays show promise for providing mechanistic data relevant for immune risk assessment. In contrast, the lack of immune-specific activity in the existing high-throughput assays cannot validate the safety of a chemical for the immune system.

Male reproductive toxicity involved in spermatogenesis induced by perfluorooctane sulfonate and perfluorooctanoic acid in Caenorhabditis elegans

As a persistent organic pollutant, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have gained increasing research attention over recent years because of their potential risk to humans and the environment. In this paper, we investigated the reproductive toxicity of these pollutants using a C. elegans model to evaluate spermatogenesis throughout the entire developmental cycle of him-5 mutant by exposing to 0.001, 0.01, and 0.1 mmol/L PFOS or PFOA for 48 h. Experimental results suggested that PFOS and PFOA exposure led to reductions in brood size, germ cell number, spermatid size, and motility, and increases in rate of malformation spermatids. Analysis of variance (ANOVA) showed that exposure to PFOS resulted in higher levels of damage than PFOA in germ cells only in 0.001 mmol/L exposure group. RT-qPCR was used to further investigate the expression of genes associated with different stages of spermatogenesis, such as mitosis and meiosis, fibrous body-membranous organelles (FB-MOs), and sperm activation. The expression levels of wee-1.3, spe-4, spe-6, and spe-17 genes were increased, while those of puf-8, spe-10, fer-1, swm-1, try-5, and spe-15 genes were decreased. Our results suggesting that PFOS or PFOA may cause spermatogenesis damage by disrupting the mitotic proliferation, meiotic entry, formation of the MOs, fusion of the MOs and plasma membrane (PM), and pseudopods. Loss-of-function studies using puf-8 and spe-10 mutants revealed spe-10 gene was specifically involved in PFOS- or PFOA-induced reproductive toxicity via regulating one or more critical palmitoylation events, while puf-8 gene was not direct target of PFOS and PFOA, and PFOS and PFOA may act on the upstream gene of puf-8, thus affecting reproductive ability. Taken together, these results demonstrate the potential adverse impact of PFOS and PFOA exposure on spermatogenesis and provide valuable data for PFC risk assessment. Grapical abstract.

Comparative toxicometabolomics of perfluorooctanoic acid (PFOA) and next-generation perfluoroalkyl substances

Owing to environmental health concerns, a number of per- and polyfluoroalkyl substances (PFAS) have been phased-out, and increasingly replaced by various chemical analogs. Most prominent among these replacements are numerous perfluoroether carboxylic acids (PFECA). Toxicity, and environmental health concerns associated with these next-generation PFAS, however, remains largely unstudied. The zebrafish embryo was employed, in the present study, as a toxicological model system to investigate toxicity of a representative sample of PFECA, alongside perfluorooctanoic acid (PFOA) as one of the most widely used, and best studied, of the "legacy" PFAS. In addition, high-resolution magic angle spin (HRMAS) NMR was utilized for metabolic profiling of intact zebrafish embryos in order to characterize metabolic pathways associated with toxicity of PFAS. Acute embryotoxicity (i.e., lethality), along with impaired development, and variable effects on locomotory behavior, were observed for all PFAS in the zebrafish model. Median lethal concentration (LC₅₀) was significantly correlated with alkyl chain-length, and toxic concentrations were quantitatively similar to those reported previously for PFAS. Metabolic profiling of zebrafish embryos exposed to selected PFAS, specifically including PFOA and two representative PFECA (i.e., GenX and PFO3TDA), enabled elaboration of an integrated model of the metabolic pathways associated with toxicity of these representative PFAS. Alterations of metabolic profiles suggested targeting of hepatocytes (i.e., hepatotoxicity), as well as apparent modulation of neural metabolites, and moreover, were consistent with a previously proposed role of mitochondrial disruption and peroxisome proliferator-activated receptor (PPAR) activation as reflected by dysfunctions of carbohydrate, lipid and amino acid metabolism, and consistent with a previously proposed contribution of PFAS to metabolic syndrome. Taken together, it was generally concluded that toxicity of PFECA is quantitatively and qualitatively similar to PFOA, and these analogs, likewise, represent potential concerns as environmental toxicants.

Perfluoroalkyl substances cause Leydig cell dysfunction as endocrine disruptors

Perfluoroalkyl substances (PFASs) are a group of man-made organic substances. Some of PFASs have been classified as persistent organic pollutants and endocrine disruptors. They might interfere with the male sex endocrine system, causing the abnormal development of the male reproductive tract and failure of pubertal onset and infertility. The present review discusses the development and function of two generations of Leydig cells in rodents and the effects of PFASs on Leydig cell development after their exposure in gestational and postnatal periods. We also discuss human epidemiological data for the effects of PFASs on male sex hormone levels. The structure-activity relationship of PFASs on Leydig cell steroidogenesis and enzyme activities are also discussed.

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.

Gestational Perfluorooctanoic Acid Exposure Inhibits Placental Development by Dysregulation of Labyrinth Vessels and uNK Cells and Apoptosis in Mice

Perfluorooctanoic acid (PFOA) is a widely used perfluorinated compound and known to cause developmental toxicity which includes the increase of resorbed embryo, decrease of fetal survival, and fetal growth retardation. Nevertheless, whether it is associated with alteration of placental development remains unknown. Pregnant mice were gavaged with 0, 2.5, 5, 10 mg PFOA /kg/day from pregnancy day (PD) 1 to PD 13. Results showed that PFOA exposure markedly decreased the placental weight and caused interstitial edema of placenta. Laminin staining indicated that blood sinusoids area was shrunken in placenta of PFOA-exposed mice. Furthermore, PFOA treatment significantly reduced numbers of uNK cells. Western blot analysis revealed that levels of Bax and cleaved-caspase 3 proteins were markedly up-regulated in PFOA-treated groups. In addition, TEM examination showed that PFOA treatment caused rupture of nuclear membrane and nuclear pyknosis and fragmentation. Thus, our results suggested that gestational PFOA exposure significantly inhibited development of early placenta through shrinkage of labyrinth vessels and downregulation of uNK cells and apoptosis induction, which may result in adverse gestational outcomes.

Profiles of Emerging and Legacy Per-/Polyfluoroalkyl Substances in Matched Serum and Semen Samples: New Implications for Human Semen Quality

BACKGROUND

Epidemiological evidence remains equivocal on the associations between environmentally relevant levels of per-/polyfluoroalkyl substances (PFASs) and human semen quality.

OBJECTIVES

We aimed to test whether the potential effects on semen quality could be better observed when seminal PFAS levels were used as an exposure marker compared with serum PFAS levels.

METHODS

Matched semen and serum samples from 664 adult men were collected from a cross-sectional population in China from 2015 to 2016. Multiple semen parameters were assessed, along with measurement of 16 target PFASs in semen and serum. Partitioning between semen and serum was evaluated by the ratio of matrix-specific PFAS concentrations. Regression model results were expressed as the difference in each semen parameter associated with the per unit increase in the ln-transformed PFAS level after adjusting for confounders.

RESULTS

Perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and emerging chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) were detected at their highest concentrations in both semen and serum, with median concentrations of 0.23, 0.10, and 0.06 ng/mL in semen, respectively, and a semen-to-serum ratio of 1.3:3.1. The between-matrix correlations of these PFAS concentrations were high (R=0.70-0.83). Seminal PFOA, PFOS, and 6:2 Cl-PFESA levels were significantly associated with a lower percentage of progressive sperm and higher percentage of DNA fragmentation (false discovery rate-adjusted p-values of<0.05). Associations between serum PFAS levels and semen parameters were generally statistically weaker, except for DNA stainability, which was more strongly associated with serum-based PFASs than with semen-based PFASs.

CONCLUSIONS

Our results suggest the potential for deleterious effects following exposure to 6:2 Cl-PFESA and other PFASs. Compared with serum PFAS levels, the much clearer association of seminal PFAS levels with semen parameters suggests its advantage in hazard assessment on semen quality, although the potential for confounding might be higher. Exposure measurements in target tissue may be critical in clarifying effects related to PFAS exposure. https://doi.org/10.1289/EHP4431.

The potential effect of methylseleninic acid (MSA) against γ-irradiation induced testicular damage in rats: Impact on JAK/STAT pathway

This study suggested that methylseleninic acid (MSA) could respond to the inflammatory signaling associated with ionizing radiation-induced testicular damage. Mature male rats were divided into four groups: negative control, whole body γ-irradiated (IRR) (5 Gy), MSA (0.5 mg/kg, daily for nine consecutive days), and MSA+ IRR groups. MSA increased serum testosterone level and testicular glutathione peroxidase (GPx) as well as decreased the percentage of sperm abnormalities. Radiation prompted inflammatory signaling in the testes through increasing phospho-janus kinase1 (p-JAK1), phospho-signal transducers and activators of transcription 3 (p-STAT3) protein expressions. This induced increment in the inflammatory markers including nuclear factor- kappa B (NF-κB) and interleukin-1beta (IL-1β) levels. Also, radiation induced elevation of nitric oxide (NO) and malondialdhyde (MDA) levels with consequent reduction in testicular reduced glutathione level (GSH) and superoxide dismutase (SOD) activity. MSA significantly counteracted the radiation effect on testicular nuclear factor erythroid-2-related factor-2 (Nrf2) and suppressor of cytokine signaling (Socs3) protein expressions. In summary, this investigation proposed that MSA preserved spermatogenesis through increasing testosterone levels and GPx activity. Additionally, it diminished testicular inflammation by increasing of Nrf2 and Socs3 levels leading to reducing of p-JAK1, p-STAT3 and NF-κB levels. Histopathological examination results of testicular tissues showed a coincidence with the biochemical analysis.

Aucubin, a natural iridoid glucoside, attenuates oxidative stress-induced testis injury by inhibiting JNK and CHOP activation via Nrf2 up-regulation

BACKGROUND

Eucommia ulmoides has been used for many years as a successful strategy to treat male infertility. Aucubin (AU) is the active ingredient extracted from Eucommia ulmoides. However, its protective action and exact mechanism on testicular injury is not yet known.

PURPOSE

Here, the protective effect and the mechanism of action of AU on testis damage under oxidative stress was investigated in vivo and in vitro.

METHODS

As regard the in vivo experiment, male mice were divided into five groups and testicular injury model was established by Triptolide (TP) (120 μg/kg) intraperitoneal injection for two weeks. Animals in the treatment group were pretreated with an intraperitoneal injection of AU at different doses (5, 10 and 20 mg/kg) for 1 h and subsequently treated with TP (120 μg/kg). At the end of the experimental period, the testis was collected for biochemical and histological examination. As regard the in vitro experiment, Sertoli cells (SCs) were used to investigate the protective effect and mechanism of action of AU against disruption of the blood-testis-barrier (BTB) and apoptosis induced by TP via apoptosis detection, western blot, immunofluorescence analysis, and siRNA transient transfection.

RESULTS

TP-treated animals showed testicular atrophy, BTB disruption, increased ROS levels and spermatogenic dysfunction. Pre-administration of AU resulted in a significant protection on keeping a normal testicular weight, sperm morphology, BTB integrity, and a normal level of oxidative stress markers and antioxidants. Furthermore, AU prevented apoptosis through an effective inhibition of PERK/CHOP and JNK dependent apoptosis pathway, as well as protected the integrity of BTB by up-regulating the expression of tight junction proteins (ZO-1, Occludin, Claudin-11) and gap junction protein (Cx43). The mechanistic study revealed that AU significantly triggered Nrf2 translocation, thus increasing nuclear Nrf2 accumulation and then induced antioxidant enzymes expression in the testis and SCs. Furthermore, Nrf2 silencing unsuccessfully reversed the increased CHOP and p-JNK expression induced by TP, abolishing the protective effect of AU.

CONCLUSION

These results indicate that AU might be considered as a potential protective agent against testicular injury.

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.

Prepubertal exposure to perfluorononanoic acid interferes with spermatogenesis and steroidogenesis in male mice

Perfluoroalkyl acids (PFAAs) are widely used in industrial and commercial products and possess endocrine disrupting properties. Perfluorononanoic acid (PFNA), one of PFAAs, has been mainly reported to produce testicular toxicity in adult animals. The objective of the present study was to examine the effect of acute exposure of PFNA to prepubertal male Parkes (P) mice on spermatogenesis and testicular steroidogenesis, and to study the possible mechanism(s) of its action. PFNA (2 and 5 mg/kg) was orally administered to male P mice for 14 days from postnatal day 25-38. Histologically, testis in PFNA-treated mice showed non-uniform diverse degenerative changes in the seminiferous tubules; both normal and affected tubules were seen in the same testicular sections. The treatment caused a reduction in intra-testicular and serum testosterone levels accompanied by a decrease in testicular expression of SF1, StAR, CYP11A1, and 3β- and17β-HSD. Further, the activity of antioxidant enzymes and expression of Nrf2 and HO-1 in the testis were markedly decreased, while the level of lipid peroxidation and expression of IKKβ, NF-κB and caspase-3 were significantly increased in testis of PFNA-treated mice. There was also a decrease in PCNA expression and in PCNA-index and an increase in TUNEL-positive germ cells in testes of PFNA-treated mice. In conclusion, the results suggest that PFNA exposure to prepubertal male mice altered antioxidant enzymes activity and Nrf2-HO-1 signaling, leading to oxidative stress and a decrease in testosterone biosynthesis in the testis; these changes, in turn, caused increased apoptosis and decreased proliferation of germ cells, thereby suppression of spermatogenesis.

Perfluorooctanoic acid disrupts gap junction intercellular communication and induces reactive oxygen species formation and apoptosis in mouse ovaries

Perfluorooctanoic acid (PFOA) is a member of the perfluoroalkyl acid family of compounds. Due to the presence of strong carbon-fluorine bonds, it is practically nonbiodegradable and highly persistent in the environment. PFOA has been detected in the follicular fluid of women, and positively associated with reduced fecundability and infertility. However, there are no reports concerning the experimental evaluation of PFOA on oocyte toxicity in mammals. The aim of the present study was to determine if PFOA is able to induce oxidative stress in fetal ovaries and cause apoptosis in oocytes in vitro. In addition, since inhibition of the gap junction intercellular communication (GJIC) by PFOA has been demonstrated in liver cells in vivo and in vitro, the effect of PFOA on the GJIC between the oocyte and its supportive cumulus cells was studied. Results show that PFOA induced oocyte apoptosis and necrosis in vitro (medium lethal concentration, LC₅₀ = 112.8 μM), as evaluated with Annexin-V-Alexa 508 in combination with BOBO-1 staining. Reactive oxygen species (ROS) levels, as assessed by DCFH-DA, increased significantly in fetal ovaries exposed to ¼ LC₅₀ (28.2 μM, a noncytotoxic and relevant occupational exposure concentration) and LC₅₀ PFOA ex vivo. This perfluorinated compound also caused the blockage of GJIC in cumulus cells-oocyte complexes (COCs) obtained from female mice exposed in vivo, as evaluated by calcein transfer from cumulus cells to the oocyte. The ability of PFOA of disrupting the GJIC in COCs, generating ROS in the fetal ovary and causing apoptosis and necrosis in mammal's oocytes, might account for the reported association between increasing maternal plasma concentrations of PFOA with reduced fertility in women.

Perfluorododecanoic acid exposure induced developmental neurotoxicity in zebrafish embryos

Perfluorododecanoic acid (PFDoA), an artificial perfluorochemical, has been widely distributed in different ambient media and has been reported to have the potential to cause developmental neurotoxicity. However, the specific mechanism is largely unknown. In the current study, zebrafish embryos were treated with 0, 0.24, 1.2, and 6 mg/L PFDoA for 120 h. Exposure to PFDoA causes serious decreases in hatching delay, body length, as well as decreased locomotor speed in zebrafish larvae. Additionally, the acetylcholine (ACh) content as well as acetylcholinesterase (AChE) activity were determined to be significantly downregulated in PFDoA treatment groups. The level of dopamine was upregulated significantly after treating with 1.2 and 6 mg/L of PFDoA. Gene expressions related to the nervous system development were also analyzed, with the exception of the gene mesencephalic astrocyte-derived neurotrophic factor (manf), which is upregulated in the 6 mg/L treatment group. All other genes were significantly downregulated in larvae in the PFDoA group in different degrees. In general, the results demonstrated that PFDoA exposure could result in the disruption of the cholinergic system, dopaminergic signaling, and the central nervous system.

Per- and polyfluoroalkyl substances impact human spermatogenesis in a stem-cell-derived model

Per- and polyfluoroalkyl substances (PFASs) represent a highly ubiquitous group of synthetic chemicals used in products ranging from water and oil repellents and lubricants to firefighting foam. These substances can enter and accumulate in multiple tissue matrices in up to 100% of people assessed. Though animal models strongly identify these compounds as male reproductive toxicants, with exposed rodents experiencing declines in sperm count, alterations in hormones, and DNA damage in spermatids, among other adverse outcomes, human studies report conflicting conclusions as to the reproductive toxicity of these chemicals. Using an innovative, human stem-cell-based model of spermatogenesis, we assessed the effects of the PFASs perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and a mixture of PFOS, PFOA, and PFNA for their impacts on human spermatogenesis in vitro under conditions relevant to the general and occupationally exposed populations. Here, we show that PFOS, PFOA, PFNA, and a mixture of PFOS, PFOA, and PFNA do not decrease in vitro germ cell viability, consistent with reports from human studies. These compounds do not affect mitochondrial membrane potential or increase reactive oxygen species generation, and they do not decrease cell viability of spermatogonia, primary spermatocytes, secondary spermatocytes, or spermatids in vitro under the conditions examined. However, exposure to PFOS, PFOA, and PFNA reduces expression of markers for spermatogonia and primary spermatocytes. While not having direct effects on germ cell viability, these effects suggest the potential for long-term impacts on male fertility through the exhaustion of the spermatogonial stem cell pool and abnormalities in primary spermatocytes.

ABBREVIATIONS

CDC: Centers for Disease Control; DMSO: dimethyl sulfoxide; GHR: growth hormone receptor; hESCs: human embryonic stem cells; PFASs: per- and polyfluoroalkyl substances; PFCs: perfluorinated compounds; PFNA: perfluorononanoic acid; PFOS: perfluorooctanesulfonic acid; PFOA: perfluorooctanoic acid; PLZF: promyelocytic leukemia zinc finger; ROS: reactive oxygen species; HILI: RNA-mediated gene silencing 2; SSC: spermatogonial stem cell.

Triptolide induces Sertoli cell apoptosis in mice via ROS/JNK-dependent activation of the mitochondrial pathway and inhibition of Nrf2-mediated antioxidant response

Triptolide (TP), an oxygenated diterpene, has a variety of beneficial pharmacodynamic activities but its clinical applications are restricted due to severe testicular injury. This study aimed to delineate the molecular mechanisms of TP-induced testicular injury in vitro and in vivo. TP (5-50000 nmol/L) dose-dependently decreased the viability of TM4 Sertoli cells with an IC₅₀ value of 669.5-269.45 nmol/L at 24 h. TP (125, 250, and 500 nmol/L) dose-dependently increased the accumulation of ROS, the phosphorylation of JNK, mitochondrial dysfunction and activation of the intrinsic apoptosis pathway in TM4 cells. These processes were attenuated by co-treatment with the antioxidant N-acetyl cysteine (NAC, 1 mmol/L). Furthermore, TP treatment inhibited the translocation of Nrf2 from cytoplasm into the nucleus as well as the expression of downstream genes NAD(P)H quinone oxidoreductase1 (NQO1), catalase (CAT) and hemeoxygenase 1 (HO-1), thus abrogating Nrf2-mediated defense mechanisms against oxidative stress. Moreover, siRNA knockdown of Nrf2 significantly potentiated TP-induced apoptosis of TM4 cells. The above results from in vitro experiments were further validated in male mice after oral administration of TP (30, 60, and 120 mg·kg^-1·d^-1, for 14 d), as evidenced by the detected indexes, including dose-dependently decreased SDH activity, increased MDA concentration, altered testicle histomorphology, elevated caspase-3 activation, apoptosis induction, increased phosphorylation of JNK, and decreased gene expression of NQO1, CAT and HO-1 as well as nuclear protein expression of Nrf2 in testicular tissue. Our results demonstrate that TP activates apoptosis of Sertoli cells and injury of the testis via the ROS/JNK-mediated mitochondrial-dependent apoptosis pathway and down-regulates Nrf2 activation.

Maternal exposure to perfluorooctanoic acid inhibits luteal function via oxidative stress and apoptosis in pregnant mice

Perfluorooctanoic acid (PFOA) is a synthetic perfluorinated compound, which has been reported to exert adverse effect on the pregnancy. However, whether it is associated with alteration of luteal function remains unknown. Mice were administered PFOA by gavage from gestational days (GD) 1-7 or 13. PFOA treatment did not significantly affect numbers of embryo implantation. Nevertheless, on GD 13, 10mg/kg PFOA treatment significantly increased numbers of resorbed embryo. Furthermore, PFOA exposure markedly reduced serum progesterone levels but did not affect estradiol levels. Treatment also showed concomitant decreases in transcript levels for key steroidogenic enzymes, and reduced numbers and sizes of corpora lutea. In addition, PFOA administration inhibited activities of superoxide dismutase and catalase, and increased generation of hydrogen peroxide and malondialdehyde, and down-regulated level of Bcl-2 and up-regulated p53 and BAX proteins. In conclusion, PFOA exposure significantly inhibits luteal function via oxidative stress and apoptosis in pregnant mice.

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.