Effects of in vitro exposure to natural levels of zearalenone and its derivatives on chromatin structure stability in equine spermatozoa

Equine Mycotoxins

The main mycotoxins involved in adverse equine health issues are aflatoxins, fumonisins, trichothecenes, and probably ergovaline (fescue grass endophyte toxicosis). Most exposures are through contaminated grains and grain byproducts, although grasses and hays can contain mycotoxins. Clinical signs are often nonspecific and include feed refusal, colic, diarrhea, and liver damage but can be dramatic with neurologic signs associated with equine leukoencephalomalacia and tremorgens. Specific antidotes for mycotoxicosis are rare, and treatment involves stopping the use of contaminated feed, switching to a "clean" feed source, and providing supportive care.

Reproductive Performance of Mares Fed Dietary Zearalenone

It is known that zearalenone (ZON) interacts directly with estrogen receptors, and its in vivo effects on reproduction have been well-documented in several species. In contrast, reports of ZON's impact on horse reproduction are conflicting and inconclusive, some studies confounded by the presence of mycotoxins such as deoxynivalenol in the feed. This study assesses the effect of chronic consumption of zearalenone on reproduction in cycling mares fed >95% pure ZON (0, 2, or 8 mg/da; n = 7 mares/treatment) for three estrous cycles, followed by artificial insemination, through 16 days of pregnancy. Animals were on ZON treatment for between 70 and 121 days (average 84) depending on individual cycle patterns. ZON-induced changes in serum concentration of estradiol (E₂) and progesterone (P₄), and total estrogenicity were measured using RIAs and the E-screen assay, respectively. Effects on reproductive physiology and pregnancy were monitored by ultrasound and clinical parameters. No significant changes were found in reproductive hormone levels of E₂, or P₄ for mares on ZON treatments compared to controls, although there was a significant (P < 0.01) increase in P₄ levels across Cycle number in High ZON (8 mg/da) treated mares. There was also an increasing trend in the interovulatory interval in the High ZON treatment group. The overall estrogenicity was similar across treatments and over time, not differing from controls or between ZON treatment groups. Adverse uterine and ovarian effects were also not observed, but pregnancy rates were mixed with only 4 of 7 mares on Low ZON becoming pregnant, and only 3 maintaining pregnancy and fetal heartbeat by Day 30, compared to 5 of 6 control mares and all 7 mares on High ZON. Because reproductive efficiency and hormone concentrations are highly variable across individuals, this study did not demonstrate that ZON at 2 or 8 mg/da was detrimental to mares' reproduction. Yet, inferring that ZON treatments were completely without effect is also not appropriate, as the absence of measurable significant differences could be attributed to the limited sample size. Most importantly, there were no extreme signs of toxicology, in contrast to previous reports when ZON was fed at these "doses."

Modified Fusarium Mycotoxins in Cereals and Their Products-Metabolism, Occurrence, and Toxicity: An Updated Review

Mycotoxins are secondary fungal metabolites, toxic to humans, animals and plants. Under the influence of various factors, mycotoxins may undergo modifications of their chemical structure. One of the methods of mycotoxin modification is a transformation occurring in plant cells or under the influence of fungal enzymes. This paper reviews the current knowledge on the natural occurrence of the most important trichothecenes and zearalenone in cereals/cereal products, their metabolism, and the potential toxicity of the metabolites. Only very limited data are available for the majority of the identified mycotoxins. Most studies concern biologically modified trichothecenes, mainly deoxynivalenol-3-glucoside, which is less toxic than its parent compound (deoxynivalenol). It is resistant to the digestion processes within the gastrointestinal tract and is not absorbed by the intestinal epithelium; however, it may be hydrolysed to free deoxynivalenol or deepoxy-deoxynivalenol by the intestinal microflora. Only one zearalenone derivative, zearalenone-14-glucoside, has been extensively studied. It appears to be more reactive than deoxynivalenol-3-glucoside. It may be readily hydrolysed to free zearalenone, and the carbonyl group in its molecule may be easily reduced to α/β-zearalenol and/or other unspecified metabolites. Other derivatives of deoxynivalenol and zearalenone are poorly characterised. Moreover, other derivatives such as glycosides of T-2 and HT-2 toxins have only recently been investigated; thus, the data related to their toxicological profile and occurrence are sporadic. The topics described in this study are crucial to ensure food and feed safety, which will be assisted by the provision of widespread access to such studies and obtained results.

Measurement of urinary concentrations of the mycotoxins zearalenone and sterigmatocystin as biomarkers of exposure in mares

Mycotoxins may affect animal health, including reproduction. Little is known about the clinical relevance of exposure of horses to contaminated feed. This study aimed at (i) monitoring the levels of the mycotoxins zearalenone (ZEN), with its metabolites α- and β-zearalenol (α- and β-ZOL), and sterigmatocystin (STC) in urine samples from thoroughbred mares in Japan and (ii) relating these findings to the potential effects on reproductive efficacy of breeding mares. Sixty-three urine samples of breeding mares from 59 breeding farms were used. Urine samples and reproductive records were collected from each mare when it was presented to the stallion station. Urinary concentrations of ZEN, α- and β-ZOL, and STC were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). ZEN, α- and β-ZOL were measurable in the urine of all examined mares, indicating the prevalence of ZEN in equine feeds. In seven of the 63 samples, STC was also detected at levels ranging from 1.3 to 18.0 pg/mg creatinine. No significant correlation between the concentrations of mycotoxins and pregnancy status was observed. In conclusion, measurement of mycotoxins in urine samples is a useful non-invasive method for monitoring the systemic exposure of mares to multiple mycotoxins.

Implication of the estrogen receptors GPER, ESR1, ESR2 in post-testicular maturations of equine spermatozoa

Estrogen receptors ESR1, ESR2 and GPER are present on mature ejaculated horse spermatozoa, suggesting these cells as putative targets for estrogens. Indeed, spermatozoa are exposed to high level of estrogens during the transit in the male and female genital tracts but their roles are not investigated. So, we evaluated in vitro the role of 17β-estradiol during post-testicular maturations: regulation of motility, capacitation and acrosome reaction. Moreover according to the pseudo-seasonal breeder status of the stallion, we analyzed the putative seasonal variations in the presence of ESRs in spermatozoa. We showed that ESRs are more present on stallion sperm during the breeding season. We showed that capacitation and acrosome reaction are independent of estradiol action in horse. Estradiol can weakly modulate the motility and this effect is strictly associated with GPER and not with ESR1 and ESR2. The subcellular localization of GPER in the neck on stallion sperm is coherent with this effect. It seems that estrogens are not major regulators of sperm maturations associated to mare genital tract, so they could act during the epididymal maturations.

The non-genomic effects of endocrine-disrupting chemicals on mammalian sperm

Exposure to toxicants present in the environment, especially the so-called endocrine-disrupting chemicals (EDCs), has been associated with decreased sperm quality and increased anomalies in male reproductive organs over the past decades. Both human and animal populations are continuously exposed to ubiquitous synthetic and natural-occurring EDCs through diet, dermal contact and/or inhalation, therefore potentially compromising male reproductive health. Although the effects of EDC are likely induced via multiple genomic-based pathways, their non-genomic effects may also be relevant. Furthermore, spermatozoa are transcriptionally inactive cells that can come in direct contact with EDCs in reproductive fluids and secretions and are therefore a good model to address non-genomic effects. This review thus focuses on the non-genomic effects of several important EDCs relevant to mammalian exposure. Notably, EDCs were found to interfere with pre-existing pathways inducing a panoply of deleterious effects to sperm function that included altered intracellular Ca2+oscillations, induction of oxidative stress, mitochondrial dysfunction, increased DNA damage and decreased sperm motility and viability, among others, potentially jeopardizing male fertility. Although many studies have used non-environmentally relevant concentrations of only one compound for mechanistic studies, it is important to remember that mammals are not exposed to one, but rather to a multitude of environmental EDCs, and synergistic effects may occur. Furthermore, some effects have been detected with single compounds at environmentally relevant concentrations.

Effects of Panax ginseng, zearalenol, and estradiol on sperm function

BACKGROUND

Estrogen signaling pathways are modulated by exogenous factors. Panax ginseng exerts multiple activities in biological systems and is classified as an adaptogen. Zearalenol is a potent mycoestrogen that may be present in herbs and crops arising from contamination or endophytic association. The goal of this study was to investigate the impact of P. ginseng, zearalenol and estradiol in tests on spermatozoal function.

METHODS

The affinity of these compounds for estrogen receptor (ER)-alpha and beta (ERα and ERβ)-was assessed in receptor binding assays. Functional tests on boar spermatozoa motility, movement and kinematic parameters were conducted using a computer-assisted sperm analyzer. Tests for capacitation, acrosome reaction (AR), and chromatin decondensation in spermatozoa were performed using microscopic analysis.

RESULTS

Zearalenol-but not estradiol (E2)- or ginseng-treated spermatozoa-decreased the percentage of overall, progressive, and rapid motile cells. Zearalenol also decreased spontaneous AR and increased chromatin decondensation. Ginseng decreased chromatin decondensation in response to calcium ionophore and decreased AR in response to progesterone (P4) and ionophore.

CONCLUSION

Zearalenol has adverse effects on sperm motility and function by targeting multiple signaling cascades, including P4, E2, and calcium pathways. Ginseng protects against chromatin damage and thus may be beneficial to reproductive fitness.

Applications of flow cytometry to toxicological mycotoxin effects in cultured mammalian cells: a review

This review gives an overview of flow cytometry applications to toxicological studies of several physiological target sites of mycotoxins on different mammalian cell lines. Mycotoxins are secondary metabolites of fungi that may be present in food, feed, air and water. The increasing presence of mycotoxins in crops, their wide distribution in the food chain, and their potential for toxicity demonstrate the need for further knowledge. Flow cytometry has become a valuable tool in mycotoxin studies in recent years for the rapid analysis of single cells in a mixture. In toxicology, the power of these methods lies in the possibility of determining a wide range of cell parameters, providing valuable information to elucidate cell growth and viability, metabolic activity, mitochondrial membrane potential and membrane integrity mechanisms. There are studies using flow cytometry technique on Alternaria, Aspergillus, Fusarium and Penicillium mycotoxins including information about cell type, assay conditions and functional parameters. Most of the studies collected in the literature are on deoxynivalenol and zearalenone mycotoxins. Cell cycle analysis and apoptosis are the processes more widely investigated.

The levels of zearalenone and its metabolites in plasma, urine and faeces of horses fed with naturally, Fusarium toxin-contaminated oats

Concentration profile of zearalenone (ZON) and its metabolites in plasma, urine and faeces samples of horses fed with Fusarium toxin-contaminated oats is described. In plasma, β-zearalenol (β-ZOL) was detected at high levels on day 10 of the study (3.21-6.24 μg/l). β-Zearalenol and α-zearalenol were the major metabolites in urine. Zearalenone, α-ZOL and β-ZOL were predominantly found in faeces. Zearalanone could also be detected in urine (1.34-5.79 μg/l) and faeces (1 μg/kg). The degree of glucuronidation was established in all sample types, approximately 100% in urine and plasma. Low per cent of glucuronidation (4-15%) was found in faeces samples. The results indicate the main conversion of ZON into β-ZOL in horse. This finding could explain why horse is not susceptible to ZON in comparison with swine which produce α-ZOL as a predominant metabolite.

Dose-response effects of estrogenic mycotoxins (zearalenone, alpha- and beta-zearalenol) on motility, hyperactivation and the acrosome reaction of stallion sperm

BACKGROUND

The aim of this study was to investigate the in vitro effects of the Fusarium fungus-derived mycotoxin, zearalenone and its derivatives alpha-zearalenol and beta-zearalenol on motility parameters and the acrosome reaction of stallion sperm. Since the toxic effects of zearalenone and its derivatives are thought to result from their structural similarity to 17beta-estradiol, 17beta-estradiol was used as a positive control for 'estrogen-like' effects.

METHODS

Stallion spermatozoa were exposed in vitro to zearalenone, alpha-zearalenol, beta-zearalenol or 17beta-estradiol at concentrations ranging from 1 pM - 0.1 mM. After 2 hours exposure, motility parameters were evaluated by computer-assisted analysis, and acrosome integrity was examined by flow cytometry after staining with fluoroscein-conjugated peanut agglutinin.

RESULTS

Mycotoxins affected sperm parameters only at the highest concentration tested (0.1 mM) after 2 hours exposure. In this respect, all of the compounds reduced the average path velocity, but only alpha-zearalenol reduced percentages of motile and progressively motile sperm. Induction of motility patterns consistent with hyperactivation was stimulated according to the following rank of potency: alpha-zearalenol > 17beta-estradiol > zearalenone = beta-zearalenol. The hyperactivity-associated changes observed included reductions in straight-line velocity and linearity of movement, and an increase in the amplitude of lateral head displacement, while curvilinear velocity was unchanged. In addition, whereas alpha- and beta- zearalenol increased the percentages of live acrosome-reacted sperm, zearalenone and 17beta-estradiol had no apparent effect on acrosome status. In short, alpha-zearalenol inhibited normal sperm motility, but stimulated hyperactive motility in the remaining motile cells and simultaneously induced the acrosome reaction. Beta-zearalenol induced the acrosome reaction without altering motility. Conversely, zearalenone and 17beta-estradiol did not induce the acrosome reaction but induced hyperactive motility albeit to a different extent.

CONCLUSIONS

Apparently, the mycotoxin zearalenone has 17beta-estradiol-like estrogenic activity that enables it to induce hyperactivated motility of equine sperm cells, whereas the zearalenol derivatives induce premature completion of the acrosome reaction and thereby adversely affect stallion sperm physiology. The alpha form of zearalenol still possessed the estrogenic ability to induce hyperactivated motility, whereas its beta stereo-isomere had lost this property.

In vitro and in vivo induction of chromosome aberrations by alpha- and beta-zearalenols: comparison with zearalenone

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin produced by Fusarium fungi. It contaminates different components of the food chain and can cause serious economic and public health problems. The major metabolites of ZEN in various animal species are alpha- and beta-zearalenol (α-, β-ZOL). Some in vivo studies have shown that these two metabolites are as toxic as the mother molecule (ZEN), but other investigations have demonstrated that α- and β-ZOL are less toxic than ZEN. Thus, the aim of the present study was to evaluate cytotoxicity and genotoxicity of α- and β-ZOL in vivo, in mouse bone-marrow cells and in vitro, in cultured HeLa cells, and to compare it with ZEN. ZEN showed the same cytotoxicity as α-ZOL and both are more cytotoxic than β-ZOL. Genotoxicity of ZEN and its derivatives was assessed by the chromosome aberration assay. Our results show that ZEN as well as α- and β-ZOL increased the percentage of chromosome aberrations in mouse bone-marrow cells and in HeLa cells. In the two systems, ZEN and α-ZOL exhibited the same range of genotoxicity and both were more genotoxic than β-ZOL. Furthermore, our results show that either ZEN or its two metabolites inhibited cell viability in a dose-dependent manner. We conclude that biotransformation of ZEN may be considered as only a partial detoxification pathway since the resulting metabolites remain relatively toxic.