Low dose carbendazim disrupts mouse spermatogenesis might Be through estrogen receptor related histone and DNA methylation

Variation of sperm quality and circular RNA content in men exposed to environmental contamination with heavy metals in 'Land of Fires', Italy

STUDY QUESTION

Can illegal discharge of toxic waste into the environment induce a new condition of morpho-epigenetic pathozoospermia in normozoospermic young men?

SUMMARY ANSWER

Toxic environmental contaminants promote the onset of a new pathozoospermic condition in young normozoospermic men, consisting of morpho-functional defects and a sperm increase of low-quality circular RNA (circRNA) cargo, tightly linked to contaminant bioaccumulation in seminal plasma.

WHAT IS KNOWN ALREADY

Epidemiological findings have reported several reproductive anomalies depending on exposure to contaminants discharged into the environment, such as germ cell apoptosis, steroidogenesis defects, oxidative stress induction, blood-testis barrier dysfunctions, and poor sperm quality onset. In this scenario, a vast geographical area located in Campania, Italy, called the 'Land of Fires', has been associated with an excessive illegal discharge of toxic waste into the environment, negatively impacting human health, including male reproductive functions.

STUDY DESIGN, SIZE, DURATION

Semen samples were obtained from healthy normozoospermic men divided into two experimental groups, consisting of men living in the 'Land of Fires' (LF; n = 80) or not (CTRL; n = 80), with age ranging from 25 to 40 years. The study was carried out following World Health Organization guidelines.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Quality parameters of semen from CTRL- and LF-normozoospermic men were evaluated by computer-assisted semen analysis; high-quality spermatozoa from CTRL and LF groups (n = 80 for each experimental group) were obtained using a 80-40% discontinuous centrifugation gradient. Seminal plasma was collected following centrifugation and used for the dosage of chemical elements, dioxins and steroid hormones by liquid chromatography with tandem mass spectrometry. Sperm morpho-functional investigations (cellular morphology, acrosome maturation, IZUMO1 fertility marker analysis, plasma membrane lipid state, oxidative stress) were assessed on the purified high-quality spermatozoa fraction by immunochemistry/immunofluorescence and western blot analyses. Sperm circRNA cargo was evaluated by quantitative RT-PCR, and the physical interaction among circRNAs and fused in sarcoma (FUS) protein was detected using an RNA-binding protein immunoprecipitation assay. Protein immunoprecipitation experiments were carried out to demonstrate FUS/p-300 protein interaction in sperm cells. Lastly, in vitro lead (Pb) treatment of high-quality spermatozoa collected from normozoospermic controls was used to investigate a correlation between Pb accumulation and onset of the morpho-epigenetic pathozoospermic phenotype.

MAIN RESULTS AND THE ROLE OF CHANCE

Several morphological defects were identified in LF-spermatozoa, including: a significant increase (P < 0.05 versus CTRL) in the percentage of spermatozoa characterized by structural defects in sperm head and tail; and a high percentage (P < 0.01) of peanut agglutinin and IZUMO1 null signal cells. In agreement with these data, abnormal steroid hormone levels in LF seminal plasma suggest a premature acrosome reaction onset in LF-spermatozoa. The abnormal immunofluorescence signals of plasma membrane cholesterol complexes/lipid rafts organization (Filipin III and Flotillin-1) and of oxidative stress markers [3-nitrotyrosine and 3-nitrotyrosine and 4-hydroxy-2-nonenal] observed in LF-spermatozoa and associated with a sperm motility reduction (P < 0.01), demonstrated an affected membrane fluidity, potentially impacting sperm motility. Bioaccumulation of heavy metals and dioxins occurring in LF seminal plasma and a direct correlation between Pb and deregulated circRNAs related to high- and low-sperm quality was also revealed. In molecular terms, we demonstrated that Pb bioaccumulation promoted FUS hyperacetylation via physical interaction with p-300 and, in turn, its shuttling from sperm head to tail, significantly enhancing (P < 0.01 versus CTRL) the endogenous backsplicing of sperm low-quality circRNAs in LF-spermatozoa.

LIMITATIONS, REASONS FOR CAUTION

Participants were interviewed to better understand their area of origin, their eating habits as well as their lifestyles, however any information incorrectly communicated or voluntarily omitted that could potentially compromise experimental group determination cannot be excluded. A possible association between seminal Pb content and other heavy metals in modulating sperm quality should be explored further. Future investigations will be performed in order to identify potential synergistic or anti-synergistic effects of heavy metals on male reproduction.

WIDER IMPLICATIONS OF THE FINDINGS

Our study provides new findings regarding the effects of environmental contaminants on male reproduction, highlighting how a sperm phenotype classified as normozoospermic may potentially not match with a healthy morpho-functional and epigenetic one. Overall, our results improve the knowledge to allow a proper assessment of sperm quality through circRNAs as biomarkers to select spermatozoa with high morpho-epigenetic quality to use for ART.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by 'Convenzione Azienda Sanitaria Locale (ASL) Caserta, Regione Campania' (ASL CE Prot. N. 1217885/DIR. GE). The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Fabrication of a reusable electrochemical platform based on acid-responsive host-guest interaction with β- cyclodextrin

A reusable electrochemical glassy carbon electrode (GCE) platform based on the acid-responsive host-guest interaction between β-cyclodextrin (β-CD) and benzimidazole (BM) derivatives was developed. The β-CD can specifically recognize the BM derivative through the acid -responsive host-guest interaction. The electrode was first modified by eletrografting to immobilize a diamine linker (Boc-EDA), resulting in GCEBoc-EDA in which one amine was used for covalent immobilization to the electrode and another Boc protected amine was used to solid-phase synthesis on following step-by-step modifications on the electrode. After deprotection of the Boc group on the GCEBoc-EDA, carbonyldiimidazole (CDI)-activated β-CD was coupled with -NH2 on the electrode to result in GCEβ-CD. Due to the nonspecific interaction, we further improved the GCEβ-CD electrode by introducing immobilized poly(ethylene glycol) methyl ether (PEG-Me) to result in GCEβ-CD/PEG-Me, along with optimized procedures. CV, DPV, and EIS methods were applied for recording the electrochemistry signals. We utilized GCEβ-CD/PEG-Me to investigate the host-guest interaction and found the electrochemical signal exhibited dynamic behavior. The GCEβ-CD/PEG-Me was able to regenerate the β-CD surface more than 20 times after HCl acidic washes. We further investigated the interaction of carbendazim (CBZ), a commonly used fungicide in the agriculture and food industry, and observed a positive electrochemical response. The sensor design has potential applications in ensuring food safety.

Carbendazim exposure inhibits mouse oocytes meiotic maturation in vitro by destroying spindle assembly

Successful fertilization and early embryonic development heavily depend on the quality of the oocytes. Carbendazim (CBZ), a broad-spectrum fungicide, is widely available in the environment and has adverse effects on organisms. The present study focused on exploring the potential reproductive toxicity of CBZ exposure by investigating its effects on the maturation of mouse oocytes. The results demonstrated that although no disruptions were observed in the G2/M stage transition for meiosis resumption, CBZ did hinder the polar body extrusion (PBE) occurring during oocyte maturation. Cell cycle distribution analysis revealed that CBZ exposure interfered with the meiotic process, causing oocytes to be arrested at the metaphase I (MI) stage. The subsequent investigation highlighted that CBZ exposure impeded the spindle assembly and chromosomal alignment, which was linked to a decline in the level of p-MAPK. Additionally, CBZ exposure adversely affected the kinetochore-microtubule (K-MT) attachment, leading to the persistent activation of the spindle-assembly checkpoint (SAC). The study further noticed a substantial rise in the acetylation of α-tubulin and a reduction in spindle microtubule stability in CBZ-treated oocytes. In addition, the distribution pattern of estrogen receptor alpha (ERα) was altered in oocytes treated with CBZ, with abnormal aggregation on the spindles. CBZ exposure also resulted in altered histone modifications. A notable finding from this research was that the meiotic maturation of some oocytes remained unaffected even after CBZ treatment. However, during the ensuing metaphase II (MII) stage, these oocytes displayed anomalies in their spindle morphology and chromosome arrangement and diminished ability to bind to the sperm. The observations made in this study underscore the potential for CBZ to disrupt the meiotic maturation of oocytes, leading to a decline in the overall quality of oocytes.

Novel Aspects of cAMP-Response Element Modulator (CREM) Role in Spermatogenesis and Male Fertility

Spermatogenesis is a very complex process with an intricate transcriptional regulation. The transition from the diploid to the haploid state requires the involvement of specialized genes in meiosis, among other specific functions for the formation of the spermatozoon. The transcription factor cAMP-response element modulator (CREM) is a key modulator that triggers the differentiation of the germ cell into the spermatozoon through the modification of gene expression. CREM has multiple repressor and activator isoforms whose expression is tissue-cell-type specific and tightly regulated by various factors at the transcriptional, post-transcriptional and post-translational level. The activator isoform CREMτ controls the expression of several relevant genes in post-meiotic stages of spermatogenesis. In addition, exposure to xenobiotics negatively affects CREMτ expression, which is linked to male infertility. On the other hand, antioxidants could have a positive effect on CREMτ expression and improve sperm parameters in idiopathically infertile men. Therefore, CREM expression could be used as a biomarker to detect and even counteract male infertility. This review examines the importance of CREM as a transcription factor for sperm production and its relevance in male fertility, infertility and the response to environmental xenobiotics that may affect CREMτ expression and the downstream regulation that alters male fertility. Also, some health disorders in which CREM expression is altered are discussed.

Acute exposure to organophosphorus pesticide metabolites compromises buffalo sperm function and impairs fertility

Agrichemicals such as organophosphorus pesticides' metabolites (OPPMs) are more hazardous and pervasive than their parent pesticides. Parental germline exposure to such xenobiotics leads to an elevated susceptibility towards reproductive failures e.g. sub- or in-fertility. This study sought to examine the effects of low-dose, acute OPPM exposure on mammalian sperm function using buffalo as the model organism. The buffalo spermatozoa were briefly (2 h) exposed to metabolites of the three most prevalent organophosphorus pesticides (OPPs) viz. Omethoate (from Dimethoate), paraoxon-methyl (from methyl/ethyl parathion) and 3, 5, 6-trichloro-2-pyridinol (from chlorpyrifos). Exposure to OPPMs resulted in compromised structural and functional integrity (dose-dependent) of the buffalo spermatozoa typified by elevated membrane damage, increased lipid peroxidation, precocious capacitation and tyrosine phosphorylation, perturbed mitochondrial activity and function and (P < 0.05). This led to a decline in the in vitro fertilizing ability (P < 0.01) of the exposed spermatozoa, as indicated by reduced cleavage and blastocyst formation rates. Preliminary data indicate that acute exposure to OPPMs, akin to their parent pesticides, induces biomolecular and physiological changes in spermatozoa that compromise their health and function ultimately affecting their fertility. This is the first study demonstrating the in vitro spermatotoxic effects of multiple OPPMs on male gamete functional integrity.

Low Dose of Carbendazim and Tebuconazole: Accumulation in Tissues and Effects on Hepatic Oxidative Stress in Mice

As two commonly used fungicides, carbendazim and tebuconazole are widely found in the environment and in foods. Studies have reported that these fungicides can induce hepatic oxidative stress and other health risks. Nevertheless, the influences of exposure to carbendazim and tebuconazole at their acceptable daily intake (ADI) doses on hepatic oxidative stress, and the residual distributions in mice remain unclear. To fill these gaps, ICR (CD-1) mice were exposed to carbendazim and tebuconazole at their ADI doses by oral administration for 4 weeks in this study. The results showed that tebuconazole accumulated primarily in the epididymal fat of mice (16.84 μg/kg), whereas no significant residues of carbendazim in the tissues were observed. In addition, exposure to ADI doses of tebuconazole significantly reduced liver coefficients and induced hepatic oxidative stress in mice, including elevating the levels of glutathione and malonaldehyde. However, no significant impacts were observed on the hepatic redox homeostasis in mice after exposure to carbendazim at its ADI dose. The results could be helpful for understanding the exposure risks of carbendazim and tebuconazole in terms of low doses and long term.

Untargeted Metabolomics Reveals Lipid Impairment in the Liver of Adult Zebrafish (Danio rerio) Exposed to Carbendazim

Carbendazim is a systemic fungicide used in several countries, particularly in Brazil. However, studies suggest that it is related to the promotion of tumors, endocrine disruption, and toxicity to organisms, among other effects. As a result, carbendazim is not allowed in the United States, Australia, and some European Union countries. Therefore, further studies are necessary to evaluate its effects, and zebrafish is a model routinely used to provide relevant information regarding the acute and long-term effects of xenobiotics. In this way, zebrafish water tank samples (water samples from aquari containing zebrafish) and liver samples from animals exposed to carbendazim at a concentration of 120 μg/L were analyzed by liquid chromatography coupled to high-resolution mass spectrometry, followed by multivariate and univariate statistical analyses, using the metabolomics approach. Our results suggest impairment of lipid metabolism with a consequent increase in intrahepatic lipids and endocrine disruption. Furthermore, the results suggest two endogenous metabolites as potential biomarkers to determine carbendazim exposure. Finally, the present study showed that it is possible to use zebrafish water tank samples to assess the dysregulation of endogenous metabolites to understand biological effects. Environ Toxicol Chem 2023;42:437-448. © 2022 SETAC.

Urinary concentrations of fungicide carbendazim's metabolite and associations with oxidative stress biomarkers in young children

Carbendazim (CBDZ) is the most widely used fungicide in China. It is ubiquitous in environment and can induce oxidative stress in mammals, while data on occurrence of its metabolite in human urine are scarce, and the relationship between CBDZ and oxidative stress biomarkers (OSBs) in young children has not been examined. The aim of this study was to measure the concentrations of methyl 5-hydroxy-2-benzimidazolecarbamate (5-HBC, the main metabolite of CBDZ in urine) in 390 urine samples collected from 130 healthy young (< 6.6 years old) children from Shenzhen and Wuhan, in south and central China, respectively, and to evaluate the associations of 5-HBC with three selected OSBs (4-HNEMA, 8-OHG, and 8-OHdG, for lipid, RNA, and DNA, respectively). 5-HBC was found in 99.2% of the urine samples at concentrations ranging from below the method detection limit (< 0.005 ng/mL) to 10.9 ng/mL (median: 0.11 ng/mL). Moderate inter-day reproducibility was found for specific gravity-adjusted 5-HBC concentrations (intraclass correlation coefficient: 0.50). The urinary 5-HBC concentrations were significantly and positively associated with 4-HNEMA (p < 0.01). An interquartile range increase in urinary 5-HBC concentrations was associated with a 42.1% increase in 4-HNEMA, which implied that CBDZ exposure might be associated with lipid peroxidation in young children without occupational exposure. As far as we know, this pilot study is the first to report urinary 5-HBC and its associations with OSBs in children.

Assessment of Xenoestrogens in Jordanian Water System: Activity and Identification

Sex hormone disruptors (xenoestrogens) are a global concern due to their potential toxicity. However, to date, there has been no study to investigate the presence of xenoestrogen pollutants in the Jordanian water system. Samples in triplicates were collected from six locations in Jordan, including dams, surface water, tap or faucet water, and filtered water (drinking water-local company). Xenoestrogens were then extracted and evaluated with a yeast estrogen screen utilizing Saccharomyces cerevisiae. Later, possible pollutants were mined using ultrahigh-performance liquid chromatography (UPLC) coupled with a Bruker impact II Q-TOF-MS. Possible hits were identified using MetaboScape software (4000 compounds), which includes pesticide, pharmaceutical pollutant, veterinary drug, and toxic compound databases and a special library of 75 possible xenoestrogens. The presence of xenoestrogens in vegetable samples collected from two different locations was also investigated. The total estrogen equivalents according to the YES system were 2.9 ± 1.2, 9.5 ± 5, 2.5 ± 1.5, 1.4 ± 0.9 ng/L for King Talal Dam, As-Samra Wastewater Treatment Plant, King Abdullah Canal, and tap water, respectively. In Almujeb Dam and drinking water, the estrogenic activity was below the detection limit. Numbers of identified xenoestrogens were: As-Samra Wastewater Treatment Plant 27 pollutants, King Talal Dam 20 pollutants, Almujeb Dam 10 pollutants, King Abdullah Canal 16 pollutants, Irbid tap water 32 pollutants, Amman tap water 30 pollutants, drinking water 3 pollutants, and vegetables 7 pollutants. However, a large number of compounds remained unknown. Xenoestrogen pollutants were detected in all tested samples, but the total estrogenic capacities were within the acceptable range. The major source of xenoestrogen pollutants was agricultural resources. Risk evaluations for low xenoestrogen activity should be taken into account, and thorough pesticide monitoring systems and regular inspections should also be established.

Evolutionary Implications of Environmental Toxicant Exposure

Homo sapiens have been exposed to various toxins and harmful compounds that change according to various phases of human evolution. Population genetics studies showed that such exposures lead to adaptive genetic changes; while observing present exposures to different toxicants, the first molecular mechanism that confers plasticity is epigenetic remodeling and, in particular, DNA methylation variation, a molecular mechanism proposed for medium-term adaptation. A large amount of scientific literature from clinical and medical studies revealed the high impact of such exposure on human biology; thus, in this review, we examine and infer the impact that different environmental toxicants may have in shaping human evolution. We first describe how environmental toxicants shape natural human variation in terms of genetic and epigenetic diversity, and then we describe how DNA methylation may influence mutation rate and, thus, genetic variability. We describe the impact of these substances on biological fitness in terms of reproduction and survival, and in conclusion, we focus on their effect on brain evolution and physiology.

Carbendazim toxicity in different cell lines and mammalian tissues

The extensive production and use of harmful pesticides in agriculture to improve crop yield has raised concerns about their potential threat to living components of the environment. Pesticides cause serious environmental and health problems both to humans and animals. Carbendazim (CBZ) is a broad spectrum fungicide that is used to control or effectively kill pathogenic microorganisms. CBZ is a significant contaminant found in food, soil and water. It exerts immediate and delayed harmful effects on humans, invertebrates, aquatic animals and soil microbes when used extensively and repeatedly. CBZ is a teratogenic, mutagenic and aneugenic agent that imparts its toxicity by enhancing generation of reactive oxygen species generation. It elevates the oxidation of thiols, proteins and lipids and decreases the activities of antioxidant enzymes. CBZ is cytotoxic causing hematological abnormalities, mitotic spindle deformity, inhibits mitosis and alters cell cycle events which lead to apoptosis. CBZ is known to cause endocrine-disruption, embryo toxicity, infertility, hepatic dysfunction and has been reported to be one of the leading causes of neurodegenerative disorders. CBZ is dangerous to human health, the most common side effects upon chronic exposure are thyroid gland dysfunction and oxidative hepato-nephrotoxicity. In mammals, CBZ has been shown to disrupt the antioxidant defense system. In this review, CBZ-induced toxicity in different cells, tissues and organisms, under in vitro and in vivo conditions, has been systematically discussed.

Carbamate Pesticides: Shedding Light on Their Impact on the Male Reproductive System

Carbamates are widely used and known around the world as pesticides in spite of also having medical applications. This class of chemicals is classified as acetylcholinesterase inhibitors, blocking acetylcholine hydrolyzation in a reversible manner. Their lack of species selectivity and their reported high toxicity can induce, upon exposure, adverse outcomes in male fertility that may lead to infertility. In addition, they are also considered endocrine-disrupting chemicals and can interfere with the hypothalamic–pituitary–testicular axis, essential for the normal function of the male reproductive system, thus being able to provoke male reproductive dysfunctions. Although the molecular mechanisms are not fully understood, various signaling pathways, such as those mediated by acetylcholine or kisspeptin, are affected by exposure to carbamates, thus compromising steroidogenesis and spermatogenesis. Over the last decades, several studies, both in vitro and in vivo, have reported a myriad of negative effects of carbamates on the male reproductive system. In this review, an up-to-date overview of the impact of carbamates on the male reproductive system is discussed, with an emphasis on the role of these compounds on acetylcholine regulation and the male endocrine system.

Endocrine disrupting effects induced by levonorgestrel linked to altered DNA methylation in rare minnow (Gobiocypris rarus)

Progestins are worldwide environmental contaminants, however, their ecotoxicological risks and underlying molecular mechanisms of effects are not fully understood. In this study, newly hatched rare minnow (Gobiocypris rarus) larvae were exposed to environmentally realistic concentrations (1 and 10 ng/L) of levonorgestrel (LNG) for 6 months. The sex ratios were not affected by LNG at both concentrations, but the growth was significantly inhibited at 10 ng/L while promoted at 1 ng/L. Histological analysis revealed impaired gonadal development. Plasma concentrations of estradiol in females and testosterone in both sexes were significantly induced after exposure to 1 ng/L LNG; plasma concentrations of 11-ketotestosterone were markedly increased in females exposed to 10 ng/L LNG and in males exposed to both concentrations of LNG. The transcription of cyp19a1a was significantly up-regulated in ovaries exposed to LNG at both concentrations, while cyp17a1 was down-regulated in testes exposed to 10 ng/L LNG. The global DNA methylation level was significantly decreased in testes exposed to 10 ng/L LNG, which might be associated with inhibited spermatogenesis. Gender-specific changes in CpG methylation patterns were induced by LNG in the 5' flanking region of cyp19a1a, with hypomethylation in ovaries but hypermethylation in testes, which was linked to the regulation of cyp19a1a transcription. The results suggest that LNG could induce endocrine disrupting effects in fish at environmentally realistic concentrations, which may be linked to altered DNA methylation. This study indicates potentially high ecological risk of LNG to fish populations, and warrants researches on regulatory mechanisms of epigenetic modifications in progestin-induced effects.

Ameliorative effect of betulinic acid against zearalenone exposure triggers testicular dysfunction and oxidative stress in mice via p38/ERK MAPK inhibition and Nrf2-mediated antioxidant defense activation

Zearalenone (ZEA) is a nonsteroidal estrogenic mycotoxin, which mainly contaminates grains and has estrogen-like effects on the reproductive system. Betulinic acid (BA), a natural lupane-type pentacyclic triterpene, has anti-oxidative and anti-inflammatory properties. This study aimed to investigate whether BA alleviates ZEA-induced testicular damage and explore the possible mechanism. Here, BA ameliorated testicular damage by mitigating the disordered arrangement of seminiferous tubules, the exfoliation of lumen cells, and the increase of cell apoptosis caused by ZEA. Meanwhile, BA alleviated ZEA-triggered testicular damage by restoring hormone levels and sperm motility, and reconstructing the blood-testis-barrier. Moreover, BA alleviated ZEA-exposed testicular oxidative stress by activating Nrf2 pathway. Furthermore, BA moderated ZEA-evoked testicular inflammation by inhibiting p38/ERK MAPK pathway. Overall, our results revealed that BA has a therapeutic protective effect on ZEA-induced testicular injury and oxidative stress via p38/ERK MAPK inhibition and Nrf2-mediated antioxidant defense activation, which provides a viable alternative to alleviate ZEA-induced male reproductive toxicology.

Dietary folic acid supplementation improves semen quality and spermatogenesis through altering autophagy and histone methylation in the testis of aged broiler breeder roosters

The aging phenomenon often exerts a significant reduction in the reproduction performance of aged animals. The objective of this project was to investigate the effects of dietary Folic acid (FA) supplementation on the reproductive performance of aged broiler breeder roosters. A total of 16 aged ROSS 308 broiler breeder roosters (50-week-old) were randomly divided into two groups. The treatments were basal diet (CON), a basal diet supplemented with 10 mg/kg Folic acid (FAS) for four weeks. At the end of the experiment, semen quality, histopathological studies, serum concentrations of testosterone and relative mRNA and protein expressions of testes were evaluated. The results showed that dietary FA supplementation dramatically improved semen quality of aged roosters, manifested by increasing semen volume, sperm concentration, sperm motility, and sperm membrane functional integrity. Furthermore, seminiferous tubule epithelial height (SEH) and testis scores were increased by dietary supplementation with FA. Dietary FA also remarkably augmented the transcription level of spermatogenesis-related gene (CREM, PCK2, DDX4, and GDNF). No significant differences were observed in serum concentrations of testosterone between FAS and CON groups. We noted significant upregulation Beclin-1 and ATG5 protein expressions, and the ratio of LC3-Ⅱ/Ⅰ, as well as significant downregulation of p-mTOR protein expressions in testicular tissue of aged roosters with FA supplementation. In addition, dietary FA supplementation significantly increased the protein expression of H3K9me2 and reduced the protein expression of H3K27me2. In summary, dietary FA supplementation improved the testicular autophagy through the mTOR-signaling pathway, and altered histone methylation in the testis. Dietary supplementation with FA can ameliorate semen quality and spermatogenesis of aged roosters.

Pesticides and Male Fertility: A Dangerous Crosstalk

In recent decades, an increasing incidence of male infertility has been reported. Interestingly, and considering that pesticides have been used for a long time, the high incidence of this pathological state is concomitant with the increasing use of these chemicals, suggesting they are contributors for the development of human infertility. Data from literature highlight the ability of certain pesticides and/or their metabolites to persist in the environment for long periods of time, as well as to bioaccumulate in the food chain, thus contributing for their chronic exposure. Furthermore, pesticides can act as endocrine disrupting chemicals (EDCs), interfering with the normal function of natural hormones (which are responsible for the regulation of the reproductive system), or even as obesogens, promoting obesity and associated comorbidities, like infertility. Several in vitro and in vivo studies have focused on the effects and possible mechanisms of action of these pesticides on the male reproductive system that cause sundry negative effects, even though through diverse mechanisms, but all may lead to infertility. In this review, we present an up-to-date overview and discussion of the effects, and the metabolic and molecular features of pesticides on somatic cells and germinal tissues that affect germ cell differentiation.

L-carnitine extenuates endocrine disruption, inflammatory burst and oxidative stress in carbendazim-challenged male rats via upregulation of testicular StAR and FABP9, and downregulation of P38-MAPK pathways

We have addressed in the current study the potential of L-carnitine (LC) to extenuate the reproductive toxic insults of carbendazim (CBZ) in male rats, and the molecular mechanisms whereby carnitine would modify the spermatogenic and steroidogenic derangements invoked by the endocrine disruptor. Herein, animals received daily doses of carbendazim (100 mg/kg) by gavage for 8 weeks. Another CBZ-challenged group was co-supplemented with LC (500 mg/kg, IP) twice weekly for 8 weeks. Sperm quantity and quality (morphology, motility and viability), serum testosterone and gonadotropins, and thyroid hormone levels were assessed. Serum tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and interleukin-10 (IL-10) concentrations were determined by ELISA. Oxidant/antioxidant status in rat testis was investigated via measuring testicular contents of malondialdehyde (MDA) and reduced glutathione (GSH), as well as the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Immunohistochemical localizations of the junctional protein; occludin, and inflammatory markers; inducible nitric oxide synthase (iNOS) and nuclear factor kappa beta (NF-κB) were further analyzed. A host of transduction genes that regulate spermatogenic and steroidogenic pathways, and their encoded proteins namely, Steroidogenic Acute Regulatory Protein (StAR), Fatty acid binding protein 9 (FABP9) and P38-mitogen activated protein kinase (P38-MAPK) were assessed by real time quantitative (RT-qPCR) and Western blot. LC improved rat spermiogram, testicular histological alterations and endocrine perturbances, and modulated genes' expressions and their respective proteins. In conclusion, LC effects appear to reside for the most part on its endocrine-preserving, anti-oxidant and anti-inflammatory properties through a myriad of interlaced signal transductions that ultimately recapitulated its beneficial effects on spermatogenesis and steroidogenesis.

Environmental pollutants exposure and male reproductive toxicity: The role of epigenetic modifications

Male fertility rates have shown a progressive decrease in recent decades. There is a growing concern about the male reproductive dysfunction caused by environmental pollutants exposure, however the underlying molecular mechanisms are still not well understood. Epigenetic modifications play a key role in the biological responses to external stressors. Therefore, this review discusses the roles of epigenetic modifications in male reproductive toxicity induced by environmental pollutants, with a particular emphasis on DNA methylation, histone modifications and miRNAs. The available literature proposed that environmental pollutants can directly or cause oxidative stress and DNA damage to induce a variety of epigenetic changes, which lead to gene dysregulation, mitochondrial dysfunction and consequent male reproductive toxicity. However, future studies focusing on more kinds of epigenetic modifications and their crosstalk as well as epidemiological data are still required to fill in the current research gaps. In addition, the intrinsic links between pollutants-mediated epigenetic regulations and male reproduction-related physiological responses deserve to be further explored.

Reproductive toxicity in male juvenile rats: Antagonistic effects between isolated agrochemicals and in binary or ternary combinations

The management of agrochemicals in Brazilian agriculture impacts global environmental sustainability and food security, since this country is one of the major agro-food exporters in the world. Acephate, carbendazim, and dithiocarbamates (DTCs) such as mancozeb, are among the most detected agrochemicals in Brazilian agro-food products, occurring in combination in several crops, especially in fruit cultures. The present study evaluated the impact of the exposure to isolated agrochemicals and all the combined possible mixtures (binary and ternary forms) on the reproductive parameters of male juvenile rats, known to be a vulnerable biological system and developmental window. Data were analyzed using Generalized Linear Models (GzLM), considering each agrochemical as an independent factor. The study revealed higher reproductive toxicity exerted by isolated agrochemicals when compared to the combined treatments, which exhibited mostly an antagonistic effect. Results suggest endocrine disruptive effects of each one separately on the weight of reproductive organs and testicular histomorphometry, besides changes in testicular SOD activity. The full factorial experimental design employed here allowed us to conclude that it is not possible to scale-up the effects of the isolated treatments to the mixtures, showing how difficult it is to know beforehand the response and cross-talk among the multiple physiological mechanisms disturbed by complex mixtures. Considering that food products are shared on a global scale and that some of these three agrochemicals have already been prohibited in EU countries, the consumption of some Brazilian products puts global human health at risk, that of children.

Neonicotinoids, fipronil, chlorpyrifos, carbendazim, chlorotriazines, chlorophenoxy herbicides, bentazon, and selected pesticide transformation products in surface water and drinking water from northern Vietnam

Studies on the occurrence of emerging pesticides in surface and drinking water in Vietnam are limited. In this study, lake water (n = 7), river water (n = 1), tap water (n = 46), and bottled water (n = 3) collected from Hanoi and other four provinces in northern Vietnam were analyzed for selected pesticides (including insecticides such as neonicotinoids, fipronil, and chlorpyrifos; fungicide carbendazim; herbicides such as atrazine, terbuthylazine, simazine, 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, and bentazon) and some of their degradates by liquid chromatography-tandem mass spectrometry. Carbendazim (median: 86.7 ng/L) and triazines (49.3 ng/L) were the major pesticides found in lake water samples, followed by neonicotinoids and their degradation products (15.1 ng/L), chlorpyrifos and its degradate (13.4 ng/L), fipronil and its degradates (3.76 ng/L), chlorophenoxy acid herbicides (2.10 ng/L), and bentazon (0.62 ng/L). Triazines (164 ng/L) were the major pesticides in river water. Higher concentrations (median: 39.3 ng/L; range: 1.20-127) of selected pesticides were found in tap water from Hanoi than those from four other provinces studied (5.49 ng/L; 4.73-66.8 ng/L). Bottled water samples collected from Hanoi contained lower concentrations of pesticide residues (median: 3.54 ng/L, range: 2.18-8.09) than those of tap water samples. The calculated risks from pesticide exposure through ingestion of tap water by the general populations were low. However, fipronil concentrations in lake water exceeded the benchmark value recommended for freshwater in the United States or the Netherlands. Degradation of acetamiprid into desmethyl-acetamiprid was found in lake water.

Association between low-to-moderate fluoride exposure and bone mineral density in Chinese adults: Non-negligible role of RUNX2 promoter methylation

Bone mineral density (BMD) changes were reported to be associated with excessive fluoride exposure and abnormal expression of RUNX2. However, whether the alteration of methylation status, a most commonly used marker for the alteration of gene expression in epidemiological investigation, of RUNX2 is associated with low-to-moderate fluoride exposure and BMD changes has not been reported. Our study aims to explore the role of RUNX2 promoter methylation in BMD changes induced by low-to-moderate fluoride exposure. A total of 1124 adults (413 men and 711 women) were recruited from Kaifeng City in 2017. We measured BMD using ultrasound bone densitometer. Concentrations of urinary fluoride (UF) were measured using ion-selective electrode, and the participants were grouped into control group (CG) and excessive fluoride group (EFG) according to the concentration of UF. We extracted DNA from fasting peripheral blood samples and then detected the promoter methylation levels of RUNX2 using quantitative methylation-specific PCR. Relationships between UF concentration, RUNX2 promoter methylation and BMD changes were analyzed using generalized linear model and logistic regression. Results showed in EFG (UF concentration > 1.6 mg/L), BMD was negatively correlated with UF concentration (β: -0.14; 95%CI: -0.26, -0.01) and RUNX2 promoter methylation (β: -0.13; 95%CI: -0.22, -0.03) in women. The methylation rate of RUNX2 promoter increased by 2.16% for each 1 mg/L increment in UF concentration of women in EFG (95%CI: 0.37, 3.96). No any significant associations between UF concentration, RUNX2 promoter methylation, and BMD were observed in the individuals in CG. Mediation analysis showed that RUNX2 promoter methylation mediated 18.2% (95% CI: 4.2%, 53.2%) of the association between UF concentration and BMD of women in EFG. In conclusion, excessive fluoride exposure (>1.6 mg/L) is associated with changes of BMD in women, and this association is mediated by RUNX2 promoter methylation.

Sub-chronic carbendazim exposure induces hepatic glycolipid metabolism disorder accompanied by gut microbiota dysbiosis in adult zebrafish (Daino rerio)

Carbendazim (CBZ) as a broad spectrum fungicide is widely used in the whole world to contorl plant diseases. With the application of CBZ in the agriculture, it has been detected in vegetables and fruits. Nowadays, it even has been detected in the watercourse and indoor dust. However, the toxic effects of CBZ on aquatic organisms have received limited attention. In this study, male adult zebrafish were exposed at 0, 30 and 100 μg/L CBZ for 21 days to assess its effects on hepatic glycolipid metabolism. After exposure, the body weight and length decreased, but the condition factor increased significantly. Some hepatic biochemical parameters including the levels of glucose, pyruvate, low density lipoprotein (LDL) and triglyceride (TG) decreased significantly in the liver of zebrafish after exposure with CBZ. Two transaminases alanine transaminase (ALT) and aspartate transaminase (AST) also increased significantly, indicating that subchronic CBZ exposure influenced the liver function. Moreover, the relative mRNA levels of some key genes related to the glycolysis and lipid metabolism in the liver also changed significantly. Furthermore, the transcriptome analysis showed that the carbon metabolism, lipid metabolism and detoxification metabolism were also affected in the liver of CBZ exposed zebrafish. Interestingly, we also found the amounts of the Firmicutes, Bacteroidetes, Actinobacteria, α-Proteobacteria, γ-Proteobacteria and Verrucomicrobia at phylum level significantly decreased in the gut. Sequencing V3-V4 region of 16S rRNA also demonstrated gut microbiota composition changed significantly according to weighted UniFrac distance analysis. Consequently, subchronic CBZ exposure induced hepatic metabolic disorder accompanied by gut microbiota dysbiosis in adult male zebrafish.

Dietary alpha-lipoic acid supplementation improves spermatogenesis and semen quality via antioxidant and anti-apoptotic effects in aged breeder roosters

The purpose of the present study was to investigate the effects of dietary alpha-lipoic acid (ALA) supplementation on the reproductive performance of aged breeder roosters. Sixteen 50-wk-old ROSS 308 breeder roosters were randomly allocated to two groups: roosters received a basal diet (CON), or a basal diet supplemented with 300 mg/kg of ALA (ALA). The results indicated that dietary ALA supplementation significantly increased sperm concentration, motility, viability, and membrane functional integrity. ALA also dramatically increased seminiferous tubule epithelial height (SEH) and testis scores. The ALA group had a higher serum concentration of testosterone than the CON group. ALA supplementation remarkably increased total antioxidant capacity (T-AOC), the enzyme activities of glutathione peroxidase (GPx), and catalase (CAT) in the testes; following a decrease in malondialdehyde (MDA) levels. In addition, we noted significant upregulation of Nrf2 mRNA and protein expression of and mRNA expression of its Downstream Genes (GPx1, NQO1, and GCLC), as well as significant downregulation of Keap1 mRNA expression in testicular tissue of aged roosters with ALA supplementation. The protein expression of Caspase 3 was downregulated and the protein expression of proliferating cell nuclear antigen (PCNA) was upregulated by ALA supplementation. The mRNA expression of spermatogenesis-related genes (ER1, AKT1, and Cav1) were markedly augmented in the ALA group compared with the CON group. In conclusion, dietary ALA supplementation enhanced the testicular antioxidant capacity through the Nrf2-signaling pathway, exerted anti-apoptotic effects, and improved the reproductive performance of aged roosters.

Environmental Impact on Male (In)Fertility via Epigenetic Route

In the last 40 years, male reproductive health-which is very sensitive to both environmental exposure and metabolic status-has deteriorated and the poor sperm quality observed has been suggested to affect offspring development and its health in adult life. In this scenario, evidence now suggests that epigenetics shapes endocrine functions, linking genetics and environment. During fertilization, spermatozoa share with the oocyte their epigenome, along with their haploid genome, in order to orchestrate embryo development. The epigenetic signature of spermatozoa is the result of a dynamic modulation of the epigenetic marks occurring, firstly, in the testis-during germ cell progression-then, along the epididymis, where spermatozoa still receive molecules, conveyed by epididymosomes. Paternal lifestyle, including nutrition and exposure to hazardous substances, alters the phenotype of the next generations, through the remodeling of a sperm epigenetic blueprint that dynamically reacts to a wide range of environmental and lifestyle stressors. With that in mind, this review will summarize and discuss insights into germline epigenetic plasticity caused by environmental stimuli and diet and how spermatozoa may be carriers of induced epimutations across generations through a mechanism known as paternal transgenerational epigenetic inheritance.

Environmentally relevant exposures of male mice to carbendazim and thiram cause persistent genotoxicity in male mice

Carbendazim and thiram are fungicides used in combination to prevent mold destruction of crops. Studies have demonstrated genotoxicity by these agents, but have not used concentrations below their water solubility limits in drinking water to test for persistence of genotoxicity due to chronic exposure. Ten 8-week old male Swiss-Webster mice were exposed to tap water, or nominal concentrations of 20 μM carbendazim, 20 μM thiram or 20 μM of both fungicides for 90 days (total of 40 mice). Five mice from tap water controls, carbendazim, thiram and combination-treated groups (20 mice total) had genotoxicity detected by comet assay of lymphocytes at the termination of the exposure period. The other 20 mice (4 treatment groups) were all switched to tap water and allowed a 45-day recovery period to check for persistence of DNA damage. The damage was compared with commercial control cells exposed to increasingly harsh treatment by etopside. Comet assay (mean % tail DNA + SE) of control mice (9.8 + 0.9) was similar to commercial control (CC0) cells (8.5 + 0.9). Carbendazim, thiram or the combination treatment caused similar mean % tail DNA with 33.0 + 2.9, 30.1 + 3.3 and 29.1 + 1.8, respectively, comparable with commercial cells slightly damaged by etopside (CC1 with 31.4 + 2.9) with no statistical change in water or food intake, body weight or liver or kidney weights. The key result was that a 45-day recovery period had no observable difference in the DNA damage as assessed by DNA % in comet tail with tap water controls and CCO control cells at 7.0 + 0.7 and 9.7 + 1.2 versus 27.5 + 1.9, 29.3 + 2.2 and 32.0 + 1.8, respectively, for carbendazim, thiram and combination treatments. It is of concern that the use of these agents in developing countries with little training or regulation results in water pollution that may cause significant persistent DNA damage in animal or human populations that may not be subject to repair.

A novel and sensitive ratiometric fluorescence assay for carbendazim based on N-doped carbon quantum dots and gold nanocluster nanohybrid

A novel fluorescence "turn on" ratiometric fluorescent sensor was employed to determine carbendazim. The sensing process was achieved through the strong fluorescence resonance energy transfer (FRET) between nitrogen doped carbon quantum dots (N-CQDs) and gold nanocluster (AuNCs). The photoluminescence intensity of N-CQDs can be deactivated by AuNCs through FRET effect and recovered by the addition of carbendazim. The ratiometric detection of carbendazim is achieved by recording the photoluminescence and second-order Rayleigh scattering (SRS) signal of N-CQDs/AuNCs system. With the introduction of carbendazim to the sensing platform resulted in the photoluminescence and SRS signal of N-CQDS/AuNCs enhancing. UV-vis absorption, Zeta potential and fluorescence lifetime analyses indicate that the fluorescence turn on process can be attributed to the aggregation of AuNCs breaks the FRET process and increases SRS intensity. N-CQDs/AuNCs probe present a good sensitivity and selectivity for carbendazim detection, with two linear response ranges (1-100 μM, 150-1000 μM), low detection limit of 0.83 μM and 37.25 μM. Furthermore, real sample analyses indicate that the as-presented sensor has potentials in carbendazim determination in real sample analyses.

Mechanisms of action of agrochemicals acting as endocrine disrupting chemicals

Agrochemicals represent a significant class of endocrine disrupting chemicals that humans and animals around the world are exposed to constantly. Agrochemicals can act as endocrine disrupting chemicals through a variety of mechanisms. Recent studies have shown that several mechanisms of action involve the ability of agrochemicals to mimic the interaction of endogenous hormones with nuclear receptors such as estrogen receptors, androgen receptors, peroxisome proliferator activated receptors, the aryl hydrocarbon receptor, and thyroid hormone receptors. Further, studies indicate that agrochemicals can exert toxicity through non-nuclear receptor-mediated mechanisms of action. Such non-genomic mechanisms of action include interference with peptide, steroid, or amino acid hormone response, synthesis and degradation as well as epigenetic changes (DNA methylation and histone modifications). This review summarizes the major mechanisms of action by which agrochemicals target the endocrine system.

Low doses of carbendazim and chlorothalonil synergized to impair mouse spermatogenesis through epigenetic pathways

Pesticides have been extensively produced and used to help the agricultural production which leads to the contamination of the environment, soil, groundwater sources, and even foodstuffs. Fungicides carbendazim (CBZ) and chlorothalonil (Chl) are widely applied in agriculture and other aspects. CBZ or Chl have been reported to disrupt spermatogenesis and decrease semen quality. However, it is not understood the effects of pubertal exposure to low doses of CBZ and Chl together, and the underlying mechanisms. Therefore, the aim of current investigation was to explore the negative impacts of pubertal exposure to low doses of CBZ and Chl together on spermatogenesis and the role of epigenetic modifications in the process. We demonstrated that CBZ and Chl together synergize to decrease sperm motility in vitro (CBZ 1.0 + Chl 0.1, CBZ 10.0 + CHl 1.0, CBZ 100.0 + Chl 10 μM in incubation medium for 24 h) and sperm concentration and motility in vivo with ICR mice (CBZ 0.1 + Chl 0.1, CBZ 1.0 + CHl 1.0, CBZ 10.0 + Chl 10 mg/kg body weight; oral gavage for five weeks). CBZ + Chl significantly increase reactive oxygen species (ROS) and apoptosis by the increase in the protein level of caspase 8 in vitro. Moreover, CBZ + Chl synergized to disrupt mouse spermatogenesis with the disturbance in sperm production proteins and sperm proteins (VASA, A-Myb, STK31, AR, Acrosin). CBZ + Chl synergized to decrease the protein level of estrogen receptor alpha and the protein level of DNA methylation marker 5 mC in Leydig cells, and to increase the protein levels of histone methylation marker H3K9 and the methylation enzyme G9a in germ cells. Therefore, greater attention should be paid to the use of CBZ and Chl as pesticides to minimise their adverse impacts on spermatogenesis.