PhD student, The Hebrew University of Jerusalem
The gradual decline in fertility of human and farm animals over the past few decades coincides with the intensive industrial and agricultural development. It involves releasing of synthetic chemicals into the environment. Many of these chemicals have been defined as environmental Endocrine Disrupting Chemicals (EDCs), man-made compounds that interfere with endocrine signaling pathways and they disrupt the normal function of the endocrine system. In particular, EDCs have deleterious effects on the thyroid gland and the reproductive and immune systems. However, the mechanism by which EDCs acts is not clear enough and seems to involve various pathways. My research project focus on Atrazine (ATZ), one of the most extensively used herbicides, which is ubiquitous environmental contaminant, detected in ground and surface water. Several studies have suggested that ATZ acts as an endocrine disruptor and can alter the reproductive function in different species such as amphibians and rats, even in low exposure doses. My study aims to examine whether pre-fertilization exposure of bovine sperm to ATZ and its major metabolite, diaminochlorotriazine (DACT), adversely affect gametes competence to undergo fertilization and successful embryonic development. A part of my findings was publicated in the journal Reproductive Toxicology. According to this findings, it seems that sperm at advanced stages of spermatogenesis i.e., through its passage and storage in the epididymis compartment and the ejaculate, are sensitive to environmental toxins, such as herbicides. The findings explore the harmful effect of ATZ, in particular at low, ecologically relevant doses and after short time of exposure, on sperm viability, acrosome integrity and mitochondrial function. These were associated with reduced fertilization competence and blastocyst formation (early stage of embryonic development). Importantly, the findings explore the risk associated with exposure to ecologically relevant ATZ doses that might take a part in reducing male fertility. I believe that the findings of the current research will bring new insights to the mechanisms by which ATZ and its metabolite disrupt the reproductive system. Such understanding is highly important to define the potential risk of environmental ATZ and to develop new strategies to ensure both public and farm animal health.
Abstract: The effect of low levels of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on in vitro oocyte maturation, in vitro capacitation of sperm, or in vitro fertilization of bovine oocytes and on the quality of blastocyst formation was studied. Bovine oocytes collected from abattoir ovaries were matured, fertilized, and developed to the blastocyst stage in vitro. Embryos that reached a morula or blastocyst stage were stained with Hoechst 33258 stain to determine the number of blastomeres per embryo. Three bulls whose fertilization rates were proven consistent among straws were used for this study. Atrazine was tested at concentrations of 0.01, 0.1, 1, and 10 microM in either the maturation medium, sperm capacitation medium, or the fertilization medium. Because atrazine was dissolved in ethanol, an ethanol control was used to determine any possible effects of ethanol on the in vitro process. The addition of atrazine to both the maturation and fertilization media did not result in any significant difference in fertilization rates between the controls and the treatments. In the capacitation medium, a significant difference between the controls and the atrazine levels of 0.1, 1, and 10 microM was noted for one bull. Atrazine did not affect the number of blastomeres per embryo. There was not a significant difference (p>0.05) in the number of blastomeres per embryo between the controls and the different levels of atrazine in each medium. This study indicates that low levels of atrazine do not have an effect on in vitro fertilization rates or the number of blastomeres per embryo produced in vitro.
Pub.: 07 May '02, Pinned: 13 Aug '17
Abstract: The recent decline in sperm concentration observed in men has developed over a short period of time, suggesting that it could be the result of environmental factors. The present study has evaluated the effects of insecticides Malathion and Diazinon, and herbicides Atrazine and Fenoxaprop-Ethyl on porcine sperm viability and motility patterns in vitro using the eosin-nigrosin staining and a computer-assisted semen analyzer (CASA), respectively. Malathion and Fenoxaprop-Ethyl exerted more deleterious effects than Diazinon and Atrazine. Progressive sperm motility was strongly affected whereas the effect on sperm viability was less pronounced. This suggests that a reduction of sperm motility is not necessarily the result of sperm death. Since sperm motility is dependent on energy metabolism the mechanism of action of these pesticides might be mediated at the level of the mitochondrion, producing a delay in motility and eventual cell death.
Pub.: 23 May '06, Pinned: 13 Aug '17
Abstract: Atrazine is a widely used triazine herbicide. Although controversy still exists, a number of recent studies have described its adverse effects on various animals including humans. Of particular interest is its effects on reproductive capacity. In this study, we investigated the mechanisms underlying the adverse effects of atrazine, with a focus on its effects on sperm. Here we show evidence that mitochondrial F(1)F(0)-ATP synthase is a molecular target of atrazine. A series of experiments with sperm and isolated mitochondria suggest that atrazine inhibits mitochondrial function through F(1)F(0)-ATP synthase. Moreover, affinity purification using atrazine as a ligand demonstrates that F(1)F(0)-ATP synthase is a major atrazine-binding protein in cells. The inhibitory activity against mitochondria and F(1)F(0)-ATP synthase is not limited to atrazine but is likely to be applicable to other triazine-based compounds. Thus, our findings may have wide relevance to pharmacology and toxicology.
Pub.: 07 Dec '07, Pinned: 13 Aug '17
Abstract: Atrazine is a herbicide of the chloro-s-triazine family. It inhibits photosynthesis in plants and is an endocrine disruptor, but its effects on human health are controversial. Fenoxaprop-ethyl, an aryloxy phenoxyalkanoic acid herbicide, inhibits the biosynthesis of fatty acids and provokes depolarization of membranes. The aim of this study is to evaluate the in vitro effects of both herbicides on capacitation, spontaneous acrosome reaction (SAR) and progesterone-induced acrosome reaction (PIAR) in boar sperm. Sperm capacitation is done in TALP-HEPES media for 4 hours. Capacitation and SAR are evaluated immediately; PIAR, 30 minutes later. LC50 for fenoxaprop-ethyl is 60 micromolar [corrected] and 40 micromolar [corrected] for atrazine. Fenoxaprop-ethyl induces capacitation at 60 micromolar [corrected] and SAR at all concentrations, also increases significantly PIAR. Atrazine decreased capacitation whereas increase significantly SAR and PIAR at all concentrations. It seems that fenoxaprop-ethyl and atrazine accelerate the capacitation and the acrosomal reaction, possibly via plasma membrane destabilization.
Pub.: 02 Jun '09, Pinned: 13 Aug '17
Abstract: To study the effects of atrazine on reproductive functions and testicular and epididymal antioxidant defense, rats were exposed to 0, 120, or 200 mg/kg body weight atrazine orally for 7 and 16 days. Animals exposed to the high-dose atrazine had their body weights, feed intake, and reproductive organs weights significantly reduced, whereas testicular weights remain unaffected independent of the dose used. In comparison to control, glutathione (GSH) and glutathione-S-transferase (GST) activities were elevated in the high-dose group, whereas the activity of superoxide dismutase (SOD), catalase (CAT); ascorbate (AA), and malondialdehyde (MDA) levels and hydrogen peroxide production were unchanged in the testis during the 7-day-exposure protocol. When atrazine treatment was increased to 16 days, GSH levels remained unchanged, but lipid peroxidation levels were significantly increased in both the testes and epididymides. This corresponded to the significant diminution in the activities of GST and SOD. CAT activities were unaffected in the testes and then dropped in the epididymides. Gamma-glutamyl transferase (gamma-GT) activities increased during both studies, whereas AA levels remained unaffected (p < 0.05). Atrazine exposure has a dose-dependent adverse effect on the testicular and epididymal sperm numbers, motility, viability, morphology, and daily sperm production. Although the testes of the atrazine-treated animals appear normal, few tubules had mild degeneration with the presence of defoliated cells. Likewise, no perceptible morphological changes were observed in the epididymis. The results suggest that atrazine impairs reproductive function and elicits a depletion of the antioxidant defense system in the testis and epididymis, indicating the induction of oxidative stress.
Pub.: 13 Aug '09, Pinned: 13 Aug '17
Abstract: Atrazine (ATZ), one of the most extensively used herbicides, is considered a ubiquitous environmental contaminant. ATZ is a known endocrine disruptor, and deleterious effects on reproductive function have been shown, even at low, ecologically relevant doses (0.1-3μg/L). Once it enters the body, ATZ is metabolized to various metabolites, which are further detected in the urine, serum and tissues. In mammals, the major ATZ metabolite is diaminochlorotriazine (DACT). The current study focuses on direct effects of low doses of ATZ and DACT on bovine sperm isolated from ejaculates or epididymis compartments (head, body and tail). Sperm were incubated under capacitation conditions with or without 0.1-10μM ATZ or 1-100μM DACT. The integrity and functionality of sperm membranes (plasma, acrosomal and mitochondrial) were examined simultaneously by fluorescence staining at 0, 2 and 4h of incubation. Acrosome reaction (AR) was induced by Ca(++) ionophore, after capacitation. The findings indicated that both ATZ and DACT adversely affect sperm, expressed by damaged sperm membranes. ATZ had a prominent effect on epididymal-tail sperm, expressed as disruption of all examined membranes, mostly at low (0.1 or 1μM) concentrations; pseudo-AR and that induced by Ca(++) ionophore were both affected by exposure to 0.1μM ATZ (P<0.05 and P<0.00004, respectively). A similar pattern was documented for sperm isolated from ejaculates (P<0.002 and P<0.001, respectively). ΔYm was affected by ATZ in sperm isolated from the epididymis tail (1μM, P<0.0009), but not in that isolated from ejaculates. DACT reduced sperm viability at all examined concentrations and in all fractions. DACT at 1μM impaired ΔΨm in sperm isolated from the epididymis tail and ejaculate (P<0.005). DACT at 100μM did not induce pseudo-AR in sperm isolated from the ejaculate, but did in sperm isolated from the epididymis tail (P<0.05). Induction of AR by Ca(++) ionophore was impaired in sperm isolated from ejaculate and exposed to 10 or 100μM DACT (P<0.05) and in sperm isolated from the epididymis tail and exposed to 1, 10 or 100μM DACT (P<0.0004). These findings reveal the harmful effect of exposure to ATZ and DACT, mainly at low ecologically relevant doses, on sperm viability, AR and mitochondrial function. We conclude that sperm at advanced stages of spermatogenesis, through its passage and storage in the epididymis compartments as well as in the ejaculate, is sensitive to herbicide. The results suggest that ATZ- or DACT-induced disruptions of sperm membranes might impair sperm fertilization competence.
Pub.: 12 Nov '16, Pinned: 13 Aug '17
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