Acute exposure to perfluorononanoic acid in prepubertal mice: Effect on germ cell dynamics and an insight into the possible mechanisms of its inhibitory action on testicular functions

Perfluorononanoic Acid Induces Neurotoxicity via Synaptogenesis Signaling in Zebrafish

Perfluorononanoic acid (PFNA), commonly used as an alternative polyfluorinated compound (PFC) of perfluorooctanoic acid (PFOA), has been widely detected in the aquatic environment. Previous ecotoxicological and epidemiological results suggested that some neurobehavioral effects were associated with PFC exposure; however, the ecological impacts and underlying neurotoxicity mechanisms remain unclear, particularly in aquatic organisms during sensitive, early developmental stages. In this study, zebrafish embryos were exposed to environmentally relevant concentrations of PFNA for 120 h, and the neurological effects of PFNA were comprehensively assessed using transcriptional, biochemical, morphological, and behavioral assays. RNA sequencing and advanced bioinformatics analyses predicted and characterized the key biological processes and pathways affected by PFNA exposure, which included the synaptogenesis signaling pathway, neurotransmitter synapse, and CREB signaling in neurons. Neurotransmitter levels (acetylcholine, glutamate, 5-hydroxytryptamine, γ-aminobutyric acid, dopamine, and noradrenaline) were significantly decreased in zebrafish larvae, and the Tg(gad67:GFP) transgenic line revealed a decreased number of GABAergic neurons in PFNA-treated larvae. Moreover, the swimming distance, rotation frequency, and activity degree were also significantly affected by PFNA, linking molecular-level changes to behavioral consequences.

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.

Effect of Trigonella foenum-graecum L. seed extract on the reproductive system of male mice and possible mechanism of its action on spermatogenesis

Fenugreek seed exhibits antidiabetic, antineoplastic, hepatoprotective, antidepressant and immunomodulatory properties. Fenugreek also causes antifertility effects in rodents. However, the impact of fenugreek seed on male reproduction and the possible mode of its action are not properly evaluated. Herein, we examined the effect of aqueous seed extract of fenugreek (FSE) and the possible mechanism of its action on male reproductive health in mice. Parkes mice were orally administered FSE (600 mg/kg body weight/day) or distilled water for 28 and 56 days, respectively. Various sperm parameters, histopathology, serum testosterone level and fertility indices were assessed. Furthermore, steroidogenic enzymes activities, oxidative status and germ cell dynamics in the testis were evaluated. Toxicological endpoints were also assessed. Treatment with FSE caused degenerative changes in the testis histoarchitecture. The treatment also affected various sperm parameters and concentrations of sialic acid and fructose in the epididymis and seminal vesicle, respectively. Fenugreek treatment also had negative impact on oxidative status and germ cell dynamics in the testis; fertility indices were also affected in female mice impregnated by the extract-treated male mice, though libido of the treated male mice remained unaffected. Results show that treatment with FSE caused adverse effects on the male reproductive health and pregnancy outcome in Parkes mice.

Risk to human health related to the presence of perfluoroalkyl substances in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluoroalkyl substances (PFASs) in food. Based on several similar effects in animals, toxicokinetics and observed concentrations in human blood, the CONTAM Panel decided to perform the assessment for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS. These made up half of the lower bound (LB) exposure to those PFASs with available occurrence data, the remaining contribution being primarily from PFASs with short half-lives. Equal potencies were assumed for the four PFASs included in the assessment. The mean LB exposure in adolescents and adult age groups ranged from 3 to 22, the 95th percentile from 9 to 70 ng/kg body weight (bw) per week. Toddlers and 'other children' showed a twofold higher exposure. Upper bound exposure was 4- to 49-fold higher than LB levels, but the latter were considered more reliable. 'Fish meat', 'Fruit and fruit products' and 'Eggs and egg products' contributed most to the exposure. Based on available studies in animals and humans, effects on the immune system were considered the most critical for the risk assessment. From a human study, a lowest BMDL 10 of 17.5 ng/mL for the sum of the four PFASs in serum was identified for 1-year-old children. Using PBPK modelling, this serum level of 17.5 ng/mL in children was estimated to correspond to long-term maternal exposure of 0.63 ng/kg bw per day. Since accumulation over time is important, a tolerable weekly intake (TWI) of 4.4 ng/kg bw per week was established. This TWI also protects against other potential adverse effects observed in humans. Based on the estimated LB exposure, but also reported serum levels, the CONTAM Panel concluded that parts of the European population exceed this TWI, which is of concern.

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.