Phytoestrogen α-zearalanol ameliorates memory impairment and neuronal DNA oxidation in ovariectomized mice

Zearalenone alters the excitability of rat neuronal networks after acute in vitro exposure

Zearalenone (ZEA) is a mycotoxin produced by Fusarium species, detectable in various cereals and processed food products worldwide. ZEA displays a significant estrogenic activity, thus its main health risk is the interference with sexual maturation and reproduction processes. However, in addition to being key hormonal regulators of reproductive function, estrogenic compounds have a widespread role in brain, as neurotrophic and neuroprotective factors, and they may influence the activity of several brain areas not directly linked to reproduction, as well. Therefore, in the present study, acute effects of ZEA were studied on certain neuronal functions in rats. Experiments were performed on rat brain slices or live rats. Slices were incubated in ZEA-containing (10-100 μM) solution for 30 min. Electrically evoked and spontaneous field potentials were studied in the neocortex and in the hippocampus. At higher concentrations, ZEA incubation of the slices altered excitability and the pattern of epileptiform activity in neocortex and inhibited the development of LTP in hippocampus. For the verification of these in vitro results, in vivo electrophysiological and immunohistochemical investigations were also performed. ZEA was administered systemically (5 mg/kg, i.p.) to male rats and somatosensory evoked potentials and neuronal activation studied by c-fos expression were analyzed. No neuronal activation could be demonstrated in the hippocampus within 2 h of the injection. In the somatosensory cortex, ZEA did not change in vivo evoked potential parameters, but the activation of a small neuronal population could be demonstrated with the c-fos technique in this brain area. This result could be associated with the ZEA-induced alteration of epileptiform activity observed in vitro. Altogether, the toxin altered the excitability and plasticity of neuronal networks after direct treatment in slices, but the effects were less prominent on the given brain areas after systemic treatment in vivo. A probable explanation for the partial lack of in vivo effects may be that after a single injection, ZEA did not cross the blood-brain barrier at sufficient rate to allow the build-up of comparable concentrations in the investigated brain areas. However, in case of compromised blood-brain barrier functions or long-term repeated exposure, alterations in cortical and hippocampal functions cannot be ruled out.

Preadministration of high-dose alpha-tocopherol improved memory impairment and mitochondrial dysfunction induced by proteasome inhibition in rat hippocampus

Objective: The ubiquitin-proteasome system plays a key role in memory consolidation. Proteasome inhibition and free radical-induced neural damage were implicated in neurodegenerative states. In this study, it was tested whether alpha-tocopherol (αT) in low and high doses could improve the long-term memory impairment induced by proteasome inhibition and protects against hippocampal oxidative stress. Methods: Alpha-tocopherol (αT) (60, 200 mg/kg, i.p. for 5 days) was administered to rats with memory deficit and hippocampal oxidative stress induced by bilateral intra-hippocampal injection of lactacystin (32 ng/μl) and mitochondrial evaluations were performed for improvement assessments. Results: The results showed that lactacystin significantly reduced the passive avoidance memory performance and increased the level of malondialdehyde (MDA), reactive oxygen species (ROS) and diminished the mitochondrial membrane potential (MMP) in the rat hippocampus. Furthermore, Intraperitoneal administration of αT significantly increased the passive avoidance memory, glutathione content and reduced ROS, MDA levels and impaired MMP. Conclusions: The results suggested that αT has neuroprotective effects against lactacystin-induced oxidative stress and memory impairment via the enhancement of hippocampal antioxidant capacity and concomitant mitochondrial sustainability. This finding shows a way to prevent and also to treat neurodegenerative diseases associated with mitochondrial impairment.

Sexual hormones regulate the redox status and mitochondrial function in the brain. Pathological implications

Compared to other organs, the brain is especially exposed to oxidative stress. In general, brains from young females tend to present lower oxidative damage in comparison to their male counterparts. This has been attributed to higher antioxidant defenses and a better mitochondrial function in females, which has been linked to neuroprotection in this group. However, these differences usually disappear with aging, and the incidence of brain pathologies increases in aged females. Sexual hormones, which suffer a decrease with normal aging, have been proposed as the key factors involved in these gender differences. Here, we provide an overview of redox status and mitochondrial function regulation by sexual hormones and their influence in normal brain aging. Furthermore, we discuss how sexual hormones, as well as phytoestrogens, may play an important role in the development and progression of several brain pathologies, including neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, stroke or brain cancer.

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Sex hormones are reduced with aging, especially in females, affecting redox balance.

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Normal aging is associated to a worse redox homeostasis in the brain.

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Young females show better mitochondrial function and higher antioxidant defenses.

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Development of brain pathologies is influenced by sex hormones and phytoestrogens.

ERK activation by zeranol has neuroprotective effect in cerebral ischemia reperfusion

AIMS

Incidence of stroke increases in postmenopausal women with dangerous consequences. In this study we used zeranol to protect ovariectomized (OVX) rats against cerebral I/R damage and our target is to identify the mechanism of its protection, in addition to investigating whether this mechanism inhibits inflammation (by preventing glial cell activation) and apoptosis.

MAIN METHODS

First 18 ovariectomized rats were allocated into 3 groups: I/R group, zeranol+ I/R group and U0126, MEK1/2 inhibitor + zeranol+ I/R group. After 24 h reperfusion, protein expression of total extracellular signal-regulated protein kinase (t-ERK1/2), phosphorylated extracellular signal-regulated protein kinase (p-ERK1/2), Bcl-2, and Bax were quantified. Second 36 female rats were allocated into 3 groups: sham group, I/R group (after ovariectomy by 7 weeks, rats exposed to cerebral I/R) and zeranol group (after ovariectomy by 2 weeks, rats received zeranol for 5 weeks). After 24 h of reperfusion, the following parameters were measured; total nitrate/nitrite, interleukin-10, myeloperoxidase, caspase-3, and finally immunohistochemistry analysis of glial fibrillary acidic protein, cyclooxygenase-2 in cortex and hippocampus (CA1) regions were performed.

KEY FINDINGS

U-0126 administration reversed the neuroprotective effect induced by zeranol through decreasing ratio of p-ERK1/2:ERK1/2 and Bcl-2/Bax in brain tissue. Activation of ERK signaling pathway by zeranol caused reduction in brain apoptosis and inflammation.

SIGNIFICANCE

Zeranol showed protective effect in OVX rats that were exposed to cerebral I/R by activation of ERK signaling pathway which was blocked by U0126. This protective effect in turns led to decrease inflammation and apoptosis.

The protective effect of zeranol in cerebral ischemia reperfusion via p-CREB overexpression

AIMS

Cerebral ischemia reperfusion (I/R) is a neurovascular disease leading to cerebral damage. It was found that postmenopausal women are liable to more dangerous effects than men at same age in stroke. The objective of this study is to investigate the neuroprotective effect of zeranol against cerebral ischemia reperfusion in ovariectomized rats.

MAIN METHODS

36 female wistar rats divided in to 3 groups: sham group, I/R group (where I/R was induced 7 weeks after ovariectomy), zeranol group (0.5 mg/kg every 3 days for 5 weeks before I/R). Cerebral ischemia reperfusion (I/R) was performed by bilateral common carotid artery occlusion then de-ligated to restore blood flow. After 24 h of reperfusion, rats performed cylinder test to evaluate behavioral dysfunction followed by decapitation. Brain tissues were collected for biochemical measures such as oxidative stress marker malondialdehyde, antioxidant markers reduced glutathione, inflammatory markers (interleukin-1 beta, tumor necrosis factor alpha, and inducible nitric oxide synthase), matrix metalloproteinase-9, adenosine triphosphate, brain derived neurotrophic factor, glucose transporter-3, phosphorylated c-AMP response element binding protein and finally nissl staining for histopathological examination.

KEY FINDINGS

The zeranol administered group showed a reversal of neuronal damage caused by ischemia evidenced by the decrease in MDA, IL-1β, TNF-α, and MMP-9 levels, increase GSH, and ATP levels, decrease expression of iNOS in both regions cortex and hippocampus, increase protein level of p-CREB, GLUT-3 and BDNF, increase number of intact neuron cells in both regions and attenuated histological changes in both cortex and hippocampus regions.

SIGNIFICANCE

Zeranol has neuroprotective potential against cerebral ischemia reperfusion in ovariectomized rats.

Comparative Analysis of Zearalenone Effects on Thyroid Receptor Alpha (TRα) and Beta (TRβ) Expression in Rat Primary Cerebellar Cell Cultures

Thyroid receptors play an important role in postnatal brain development. Zearalenone (ZEN), a major mycotoxin of Fusarium fungi, is well known to cause serious health problems in animals and humans through various mechanisms, including the physiological pathways of thyroid hormone (TH). In the present study, we aimed to investigate the expression of thyroid receptors α (TRα) and β (TRβ) in primary cerebellar neurons in the presence or absence of glia and following ZEN treatment, using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. Primary cerebellar granule cells were treated with low doses of ZEN (0.1 nM) in combination with physiologically relevant concentrations of l-thyroxine (T4), 3,3′,5-triiodo-l-thyronine (T3) and 17β-estradiol (E2). Expression levels of TRα and TRβ at mRNA and protein levels were slightly modified by ZEN administered alone; however, along with thyroid and steroid hormones, modelling the physiological conditions, expression levels of TRs varied highly depending on the given treatment. Gene expression levels were also highly modulated by the presence or absence of glial cells, with mostly contrasting effects. Our results demonstrate divergent transcriptional and translational mechanisms involved in the expression of TRs implied by ZEN and hormonal milieu, as well as culturing conditions.

Preventive effect of Coriandrum sativum on neuronal damages in pentylentetrazole-induced seizure in rats

OBJECTIVE

Coriandrum sativum (C. sativum) as a medicinal plant has been pointed to have analgesic, hypnotic and anti-oxidant effects. In the current study, a possible preventive effect of the hydro-alcoholic extract of the plant on neuronal damages was examined in pentylenetetrazole (PTZ) rat model of seizure.

MATERIALS AND METHODS

Forty male rats were divided into five main groups and treated by (1) saline, (2) PTZ: 100 mg/kg PTZ (i.p) and (3-5) 50, 100 and 200 mg/kg of hydro-alcoholic extract of C. sativum during seven consecutive days before PTZ injection. After electrocorticography (ECoG), the brains were removed to use for histological examination.

RESULTS

All doses of the extract reduced duration, frequency and amplitude of the burst discharges while prolonged the latency of the seizure attacks (p<0.05, p<0.01, and p<0.001). Administration of all 3 doses of the extract significantly prevented from production of dark neurons (p<0.01, and p<0.001) and apoptotic cells (p<0.05, p<0.01, and p<0.001) in different areas of the hippocampus compared to PTZ group.

CONCLUSION

The results of this study allow us to conclude that C. sativum, because of its antioxidant properties, prevents from neuronal damages in PTZ rat model of seizure.

Zearalenone as an endocrine disruptor in humans

Zearalenone (ZEA), a fungal mycotoxin, is present in a wide range of human foods. Many animal studies have found ZEA to possess a disruptive effect on the hormonal balance, mainly due to its similarity to naturally-occurring estrogens. With increasing consciousness of the adverse effects of endocrine disruptors on human health, it is becoming more important to monitor ZEA concentrations in food and identify its potential effects on human health. Based on a review of recent studies on animal models and molecular pathways in which ZEA is reported to have an influence on humans, we postulate that ZEA might act as an endocrine disruptor in humans in a similar way to animals. Moreover, its endocrine-disrupting effect might be also a causative factor in carcinogenesis. This review article summarizes the latest knowledge about the influence of ZEA on the human hormonal balance.

Protective effects of beta glucan in brain tissues of post-menopausal rats: a histochemical and ultra-structural study

Decline of estrogen during menopause has been associated with numerous significant changes that have been linked to many pathophysiological complications. In addition, ovarian hormone deficiency increases the production of reactive oxygen radicals which could result in oxidative stress and cell damage. While estrogen therapy is often considered to overcome the behavioral and physiological shortcomings, antioxidants are gaining popularity for their beneficial property. For this purpose, in the present study, utilizing the antioxidant properties of beta glucan has been examined in treatment of menopause induced oxidative stress in cerebral neurons. Four groups of female Wistar rats were used: control, ovariectomy, ovariectomy + estrogen treated and ovariectomy + beta glucan treated. We observed a significant increase in neural degeneration in ovariectomized rats as compared to controls. Moreover, increased oxidative stress in the brains of the ovariectomized rats has been detected by performing immunohistochemical analysis. A large number of immuno-positive cerebral neurons have been observed in ovariectomy group rat brains. Interestingly, providing beta glucan treatment to ovariectomized rats reduced the number of degenerated neurons. Our study is the first to examine light and electron microscopic examination and immunohistochemical and stereological analysis of estrogen depletion in rats and to test protective role of beta glucan in the experimental study.