Interferences of an environmental pollutant with estrogen-like action in the male reproductive system of the terrestrial vertebrate Podarcis sicula

Raman Microspectroscopy evidence of microplastics in human semen

The presence of microplastics (MPs) in human fluids and organs is a great concern, since, as highlighted by recent studies on animal models, they could cause alterations of several physiological functions, including reproduction. In this study, semen samples collected from men living in a polluted area of the Campania Region (Southern Italy), were analyzed to assess the presence of MPs. N. 16 pigmented microplastic fragments (ranging from 2 to 6 μm in size) with spheric or irregular shapes were found in six out of ten samples. All the detected MPs were characterized in terms of morphology (size, colour, and shape) and chemical composition by Raman Microspectroscopy. Chemical composition showed the presence of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), polyvinylchloride (PVC), polycarbonate (PC), polyoxymethylene (POM) and acrylic, suggesting ingestion and/or inhalation as a route of exposure to environmental MPs. In this work, we propose for the first time a mechanism by which MPs pass into the semen most likely through the epididymis and seminal vesicles, which are the most susceptible to inflammation.

The Italian Wall Lizard Podarcis siculus as a Biological Model for Research in Male Reproductive Toxicology

Spermatogenesis is a genetically driven differentiation process that occurs in the testis and leads to the formation of spermatozoa. This process is extensively studied in several experimental models, particularly in vertebrates that share the morphological structure and functionality of the mammalian testis. Although reptiles are not generally considered biological models, the lizard Podarcis siculus has represented a suitable organism for the study of spermatogenesis over the years. In this lizard, the process of spermatogenesis is regulated by the interaction between systemic factors such as gonadotropins and local factors, i.e., molecules produced by the somatic and germinal cells of the testis. Many exogenous substances are able to alter the production of these regulative factors, thus altering the course of spermatogenesis, and P. siculus has proven to be an excellent model for studying the effects of various endogenous or exogenous substances on mechanisms underlying spermatogenesis. This review summarizes the available data on the effects of different substances on the control of spermatogenesis, highlighting the induced morphological and molecular alterations. Overall, the data show that sex hormone levels as well as the final stages of spermatogenesis are most affected by an imbalance of endogenous compounds or contamination by environmental pollutants. This is helpful for the male individual, since the damage, not affecting the spermatogonial stem cells, can be considered transient and not irreversible.

Roles of Estrogens in the Healthy and Diseased Oviparous Vertebrate Liver

The liver is a vital organ that sustains multiple functions beneficial for the whole organism. It is sexually dimorphic, presenting sex-biased gene expression with implications for the phenotypic differences between males and females. Estrogens are involved in this sex dimorphism and their actions in the liver of several reptiles, fishes, amphibians, and birds are discussed. The liver participates in reproduction by producing vitellogenins (yolk proteins) and eggshell proteins under the control of estrogens that act via two types of receptors active either mainly in the cell nucleus (ESR) or the cell membrane (GPER1). Estrogens also control hepatic lipid and lipoprotein metabolisms, with a triglyceride carrier role for VLDL from the liver to the ovaries during oogenesis. Moreover, the activation of the vitellogenin genes is used as a robust biomarker for exposure to xenoestrogens. In the context of liver diseases, high plasma estrogen levels are observed in fatty liver hemorrhagic syndrome (FLHS) in chicken implicating estrogens in the disease progression. Fishes are also used to investigate liver diseases, including models generated by mutation and transgenesis. In conclusion, studies on the roles of estrogens in the non-mammalian oviparous vertebrate liver have contributed enormously to unveil hormone-dependent physiological and physiopathological processes.

Alkyphenol Exposure Alters Steroidogenesis in Male Lizard Podarcis siculus

BACKGROUND

Nonylphenol (NP) and Octylphenol (OP) are persistent and non-biodegradable environmental contaminants classified as endocrine disruptor chemicals (EDCs). These compounds are widely used in several industrial applications and present estrogen-like properties, which have extensively been studied in aquatic organisms. The present study aimed to verify the interference of these compounds alone, and in mixture, on the reproductive cycle of the male terrestrial vertebrate Podarcis siculus, focusing mainly on the steroidogenesis process.

METHODS

Male lizards have been treated with different injections of both NP and OP alone and in mixture, and evaluation has been carried out using a histological approach.

RESULTS

Results obtained showed that both substances are able to alter both testis histology and localization of key steroidogenic enzymes, such as 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β- hydroxysteroid dehydrogenase (17β-HSD) and P450 aromatase. Moreover, OP exerts a preponderant effect, and the P450 aromatase represents the major target of both chemicals.

CONCLUSIONS

In conclusion, NP and OP inhibit steroidogenesis, which in turn may reduce the reproductive capacity of the specimens.

Spermatogenesis and regulatory factors in the wall lizard Podarcis sicula

Spermatogenesis is an extraordinarily complex process, regulated by several factors, which leads to the differentiation of spermatogonia into spermatozoa. Among vertebrates, several reports have been focused on the lizard Podarcis sicula, a seasonal breeder and a good model for the study of reproductive processes. The goal of this review is to resume all the available data about systemic and above all local control factors involved in the control of P. sicula testicular activity. During the seasonal reproductive cycle, the variation of the expression levels of these factors determines significant variations that induce the activation or blocking of spermatogenesis. The data supplied in this review, in addition to analyze the current literature regarding the main actors of Podarcis sicula spermatogenesis, will hopefully provide a basic model that can be used for further studies on the intratesticular interaction between molecular factors that control spermatogenesis.

Role of estrogen receptors, P450 aromatase, PCNA and p53 in high-fat-induced impairment of spermatogenesis in rats

Obesity and overweight are frequently associated with male subfertility. To address new findings on the players involved in the obesity-induced impairment of spermatogenesis, we used a high-fat diet-induced overweight-rat model. Following four weeks of high-fat diet, the organization of seminiferous epithelium was affected, and tubules lumen showed immature/degenerated cells, typical signs of hormonal imbalance and testicular damage. Real-time PCR analysis allowed us to detect increased levels of ERα and decreased levels of aromatase CYP19 transcripts in testis, suggesting an increase in circulating estrogens derived from the accumulating adipose tissue rather than the induction of testicular estrogen synthesis. Moreover, in situ hybridization analysis showed an increased susceptibility towards estrogens in testis from high-fat fed rats, being ERs expressed not only in spermatogonia, as in control testis, but also in spermatids. Western blot and immunohistochemical analyses revealed an increase in the amount of p53 and PCNA, together with a change in their immunodetection, being the proteins localised on germ cells at different stages of maturation. Differences in p53 and PCNA expression may give evidence and be part of a cellular response to stress conditions and damage caused by the excessive intake of saturated fatty acids.

Reactive oxygen species and glutathione antioxidants in the testis of the soil biosentinel Podarcis sicula (Rafinesque 1810)

Important toxicological achievements have been made during the last decades using reptiles. We focus our investigation on gonadal reproductive health of the soil biosentinel Podarcis sicula which is very sensitive to endocrine-disrupting chemicals. The aim of this study is to quantitatively detect, by sensitive microassays, reactive oxygen species and the glutathione antioxidants in the testis and investigate if they are differentially expressed before and after remediation of a site of the "Land of Fires" (Campania, Italy) subject to illicit dumping of unknown material. The oxidative stress level was evaluated by electron spin resonance spectroscopy applying a spin-trapping procedure able to detect products of lipid peroxidation, DNA damage and repair by relative mobility shift, and poly(ADP-ribose) polymerase enzymatic activity, respectively, the expression of glutathione peroxidase 4 transcript by real-time quantitative PCR analysis, the antioxidant glutathione S-transferase, a well-assessed pollution index, by enzymatic assay and the total soluble antioxidant capacity. Experimental evidences from the different techniques qualitatively agree, thus confirming the robustness of the combined experimental approach. Collected data, compared to those from a reference unpolluted site constitute evidence that the reproductive health of this lizard is impacted by pollution exposure. Remediation caused significant reduction of reactive oxygen species and downregulation of glutathione peroxidase 4 mRNAs in correspondence of reduced levels of glutathione S-transferase, increase of antioxidant capacity, and repair of DNA integrity. Taken together, our results indicate directions to define new screening approaches in remediation assessment.

Metallothionein expression and synthesis in the testis of the lizard Podarcis sicula under natural conditions and following estrogenic exposure

Metallothionein (MT) is the main protein involved in the homeostasis of metallic micronutrients and in cellular defence against heavy metals and reactive oxygen species. Found in almost all vertebrate tissues, MT presence and localization in the testis has been controversial. In the present study, by using in situ hybridization and immunohistochemical analysis we assessed the localization of both MT transcript and protein in Podarcis sicula testes during two different phases of the reproductive cycle: the autumnal resumption and the springearly summer mating period. In addition, with the same methodological approach, we verified the effect of estradiol-1711and nonylphenol, a potent xenoestrogen, on MT expression and synthesis. These results, the first collected in a non-mammalian oviparous vertebrate, demonstrated that the expression profile of MT mRNA and protein changes during the reproductive cycle. In the fall resumption, MT transcripts are absent in spermatogonia and present in all the other cells of tubules, including spermatozoa; vice versa, the MT protein is evident only in spermatozoa and somatic cells. In the mating period, both MT transcripts and proteins are present in spermatogonia, spermatocytes and spermatids, whereas in the spermatozoa only the proteins are detected, thus suggesting that the MTs translated in the earlier germinal stages are stored up to spermatozoa. Results also demonstrated that in lizard testis the expression of MT gene undergoes a cell-specific regulation after estrogenic exposure; the possible role and the mechanism by which this regulation occurs have been discussed.

Neuroendocrine disruption of organizational and activational hormone programming in poikilothermic vertebrates

In vertebrates, sexual differentiation of the reproductive system and brain is tightly orchestrated by organizational and activational effects of endogenous hormones. In mammals and birds, the organizational period is typified by a surge of sex hormones during differentiation of specific neural circuits; whereas activational effects are dependent upon later increases in these same hormones at sexual maturation. Depending on the reproductive organ or brain region, initial programming events may be modulated by androgens or require conversion of androgens to estrogens. The prevailing notion based upon findings in mammalian models is that male brain is sculpted to undergo masculinization and defeminization. In absence of these responses, the female brain develops. While timing of organizational and activational events vary across taxa, there are shared features. Further, exposure of different animal models to environmental chemicals such as xenoestrogens such as bisphenol A-BPA and ethinylestradiol-EE2, gestagens, and thyroid hormone disruptors, broadly classified as neuroendocrine disrupting chemicals (NED), during these critical periods may result in similar alterations in brain structure, function, and consequently, behaviors. Organizational effects of neuroendocrine systems in mammals and birds appear to be permanent, whereas teleost fish neuroendocrine systems exhibit plasticity. While there are fewer NED studies in amphibians and reptiles, data suggest that NED disrupt normal organizational-activational effects of endogenous hormones, although it remains to be determined if these disturbances are reversible. The aim of this review is to examine how various environmental chemicals may interrupt normal organizational and activational events in poikilothermic vertebrates. By altering such processes, these chemicals may affect reproductive health of an animal and result in compromised populations and ecosystem-level effects.

Exploring the Role of Estrogens in Lizard Spermatogenesis through the Study of Clomiphene and FSH Effects

Spermatogenesis is a fascinating biological process aiming to generate haploid spermatozoa from diploid spermatogonia through a specific hormonal network between gonadotropins and steroids. Increasing evidence suggests that the primary female sex hormone estrogen plays an active role in this process. This research points out on the role of estrogen during lizard spermatogenesis by using three experimental approaches: (1) exposure to an analogue of nonsteroidal estrogen as Clomiphene citrate that acts both as estrogen agonist and antagonist; (2) exposure to the gonadotropin FSH; and (3) exposures to FSH followed by Clomiphene. Histological and immunohistochemical results demonstrate that in the lizard Podarcis sicula during the mating period, Clomiphene as well as FSH determines the breakdown of spermatogenesis and the epididymal regression, presumably through estrogens input as indirectly demonstrated by the appearance of ERα and vitellogenin in the liver. The ability of Clomiphene to restore the gonadal natural condition after FSH treatment is also demonstrated. Finally, data indicate that lizard testis and epididymis control their morphophysiology regulating the intracellular presence of ERα.

4-Nonylphenol induces autophagy and attenuates mTOR-p70S6K/4EBP1 signaling by modulating AMPK activation in Sertoli cells

The estrogenic chemical 4-nonylphenol (NP) is known to impair testicular devolopment and spermatogenesis in rodents. The objective of this study was to explore the effects of NP on autophagy induction and AMPK-mTOR signaling pathway in Sertoli cells (SCs), which are the "nursemaid cells" for meiosis of spermatocytes. In this study we exposed 7-week-old male rats to NP by intra-peritoneal injection at 0, 20, 50 or 100mg/kg body weight/2days for 20 consecutive days. Our results showed that exposure to NP dose-dependently induces the formation of autophagosomes in SCs, increases the expression of Beclin-1, the conversion of LC3-I to LC3-II and the mRNA expression of Atg3, Atg5, Atg7 and Atg12 in testis, and these effects are concomitant with the activation of AMPK, and the suppression of TSC2-mTOR-p70S6K/4EBP1 signaling cascade in testis. Furthermore, 10μM Compound C or AMPKα1 siRNA pre-treatment effectively attenuated autophagy and reversed AMPK-mTOR-p70S6K/4EBP1 signaling in NP-treated SCs. Co-treatment with 1mM AICAR remarkably strengthened NP-induced autophagy and mTOR inhibition in SCs. Together, these data suggest that NP stimulates Sertoli cell autophagy and inhibits mTOR-p70S6K/4EBP1 activity through AMPK activation, which is the potential mechanism responsible for the regulation of testis function and differentiation following NP exposure.

Evaluation of estrogenic activity in the Pearl River by using effect-directed analysis

This study investigated estrogenic activity of water, sediment, and fish bile of the Pearl River in southern China by effect-directed analysis based on in vitro yeast screen assay and chemical analysis. Results showed higher estradiol equivalents (EEQ) for surface water in dry season than in wet season. Simple risk assessment suggested that high estrogenic risk would be expected in Shima River and Danshui River receiving discharge of effluents from cities in the region. Fractionation and effect-directed analysis showed that estrogenic activity mainly occurred in relatively polar fractions of surface water. Seven target estrogenic compounds (bisphenol A, 4-nonylphenol, 4-tert-octylphenol, 17α-ethynyl estradiol, estrone, diethylstilbestrol, and 17β-estradiol) only accounted for part of the measured estrogenic activity, with the rest contributions from other potential estrogenic chemicals such as phenols. Findings from this study suggest that fish in the river could be affected by those estrogenic chemicals. Proper measures should be taken to reduce the estrogenic activity in wastewaters before they are discharged into the riverine system in order to protect aquatic organisms.

Ectopic synthesis of vitellogenin in testis and epididymis of estrogen-treated lizard Podarcis sicula

In oviparous vertebrates, vitellogenin (VTG) is the major yolk precursor synthesized in the liver of sexually mature females during the reproductive period. In males, the VTG gene is silent, but it may be activated by estradiol-17β (E2) or estrogen-like substances. Until now, extra-hepatic expression and synthesis of VTG after estrogen exposure has been reported only for aquatic vertebrates. This study demonstrates the ability of testis and epididymis of the terrestrial oviparous lacertid Podarcis sicula to synthesize VTG following E2 exposure. The results of in situ hybridization and immunohistochemistry analysis show the presence of both VTG mRNA and protein in these districts besides the known induction in the liver. The possible contemporaneous uptake of the E2-induced hepatic VTG by means of the specific vitellogenin receptor has been also evaluated. Finally, histological analysis shows that the E2-treatment during the mating season impairs spermatogenesis.

Nonylphenol Toxicity Evaluation and Discovery of Biomarkers in Rat Urine by a Metabolomics Strategy through HPLC-QTOF-MS

Nonylphenol (NP) was quantified using liquid chromatography tandem mass spectrometry (LC-MS/MS) in the urine and plasma of rats treated with 0, 50, and 250 mg/kg/day of NP for four consecutive days. A urinary metabolomic strategy was originally implemented by high performance liquid chromatography time of flight mass spectrometry (HPLC-QTOF-MS) to explore the toxicological effects of NP and determine the overall alterations in the metabolite profiles so as to find potential biomarkers. It is essential to point out that from the observation, the metabolic data were clearly clustered and separated for the three groups. To further identify differentiated metabolites, multivariate analysis, including principal component analysis (PCA), orthogonal partial least-squares discriminant analysis (OPLS-DA), high-resolution MS/MS analysis, as well as searches of Metlin and Massbank databases, were conducted on a series of metabolites between the control and dose groups. Finally, five metabolites, including glycine, glycerophosphocholine, 5-hydroxytryptamine, malonaldehyde (showing an upward trend), and tryptophan (showing a downward trend), were identified as the potential urinary biomarkers of NP-induced toxicity. In order to validate the reliability of these potential biomarkers, an independent validation was performed by using the multiple reaction monitoring (MRM)-based targeted approach. The oxidative stress reflected by urinary 8-oxo-deoxyguanosine (8-oxodG) levels was elevated in individuals highly exposed to NP, supporting the hypothesis that mitochondrial dysfunction was a result of xenoestrogen accumulation. This study reveals a promising approach to find biomarkers to assist researchers in monitoring NP.

Estrogenic contamination by manure fertilizer in organic farming: a case study with the lizard Podarcis sicula

In the last years, worldwide organic farming has grown exponentially; as a consequence, the use of animal manure as a soil fertility source has become the principal agricultural choice. However, the use of manure as fertilizer can increase the amount of steroid hormone metabolites in the soil. In southern Italy, lacertidae lizards are the most abundant vertebrate group in agroecosystems and have been identified as potential model species for ecotoxicological studies. The aim of this study was to understand if the manure applied in organic farming has estrogen-like effects in the lizard Podarcis sicula. Adult male lizards were captured in two organic agricultural fields (manure-treated sites) and in an uncultivated field (control site). Lizards from the two organic farms displayed hepatic biosynthetic alterations typical of an estrogenic contamination; hepatocytes contained both vitellogenin and estrogen receptor alpha transcripts and proteins, detected by in situ hybridization and immunocytochemistry. The same cells did not show cadmium, lead and metallothionein accumulation, indicative of the lack of inorganic contamination. These findings suggest that exogenous estrogens, arising from the use of manure, could affect the welfare of wild animals and animal breeding, leading to bioaccumulation of estrogens in food chain, with possible risk for human consumers. For this reason, organic farming should implement the use of sustainable practices such as crop rotation to preserve the soil biological activity, rather than organic manure as fertilizer.