Mechanisms underlying the neurotoxicity induced by glyphosate-based herbicide in immature rat hippocampus: Involvement of glutamate excitotoxicity

AbstractPrevious studies demonstrate that glyphosate exposure is associated with oxidative damage and neurotoxicity. Therefore, the mechanism of glyphosate-induced neurotoxic effects needs to be determined. The aim of this study was to investigate whether Roundup® (a glyphosate-based herbicide) leads to neurotoxicity in hippocampus of immature rats following acute (30min) and chronic (pregnancy and lactation) pesticide exposure. Maternal exposure to pesticide was undertaken by treating dams orally with 1% Roundup® (0.38% glyphosate) during pregnancy and lactation (till 15-day-old). Hippocampal slices from 15 day old rats were acutely exposed to Roundup® (0.00005–0.1%) during 30min and experiments were carried out to determine whether glyphosate affects 45Ca2+ influx and cell viability. Moreover, we investigated the pesticide effects on oxidative stress parameters, 14C-α-methyl-amino-isobutyric acid (14C-MeAIB) accumulation, as well as glutamate uptake, release and metabolism. Results showed that acute exposure to Roundup® (30min) increases 45Ca2+ influx by activating NMDA receptors and voltage-dependent Ca2+ channels, leading to oxidative stress and neural cell death. The mechanisms underlying Roundup®-induced neurotoxicity also involve the activation of CaMKII and ERK. Moreover, acute exposure to Roundup® increased 3H-glutamate released into the synaptic cleft, decreased GSH content and increased the lipoperoxidation, characterizing excitotoxicity and oxidative damage. We also observed that both acute and chronic exposure to Roundup® decreased 3H-glutamate uptake and metabolism, while induced 45Ca2+ uptake and 14C-MeAIB accumulation in immature rat hippocampus. Taken together, these results demonstrated that Roundup® might lead to excessive extracellular glutamate levels and consequently to glutamate excitotoxicity and oxidative stress in rat hippocampus

Role of Prefrontal Cortex on Recognition Memory Deficits in Rats following 6-OHDA-Induced Locus Coeruleus Lesion

Degeneration of the locus coeruleus (LC), the main source of cerebral noradrenaline (NA), has been reported in diverse neurodegenerative diseases, including Parkinson’s diseases (PD). There is increasing evidence indicating the role of NA deficiency in the prefrontal cortex (PFC) and the development of early cognitive impairments in PD. Here, we evaluated whether a selective noradrenergic lesion of LC caused by 6-hydroxydopamine (6-OHDA) may induce memory deficits and neurochemical alterations in the PFC. Adult male Wistar rats received stereotaxic bilateral injections of 6-OHDA (5 μg/2 μl) into the LC, and two stainless-steel guide cannulas were implanted in the PFC. The SHAM group received just vehicle. To induce a selective noradrenergic lesion, animals received nomifensine (10 mg/kg), a dopamine transporter blocker, one hour before surgery. 6-OHDA-lesioned rats displayed impairments of the short- and long-term object recognition memory associated to reduced content of tyrosine hydroxylase in the LC. Neurochemical analysis revealed an altered mitochondrial membrane potential in LC. Regarding the PFC, an increased ROS production, cell membrane damage, and mitochondrial membrane potential disruption were observed. Remarkably, bilateral NA (1 μg/0.2 μl) infusion into the PFC restored the recognition memory deficits in LC-lesioned rats. These findings indicate that a selective noradrenergic LC lesion induced by 6-OHDA deregulates a noradrenergic network in the PFC, which could be involved in the early memory impairments observed in nondemented PD patients

Guanosine Prevents Spatial Memory Impairment and Hippocampal Damage Following Amyloid-β1–42 Administration in Mice

Alzheimer’s disease (AD) is a progressive neurodegenerative illness responsible for cognitive impairment and dementia. Accumulation of amyloid-beta (Aβ) peptides in neurons and synapses causes cell metabolism to unbalance, and the production of reactive oxygen species (ROS), leading to neuronal death and cognitive damage. Guanosine is an endogenous nucleoside recognized as a neuroprotective agent since it prevents glutamate-induced neurotoxicity by a mechanism not yet completely elucidated. In this study, we evaluated behavioral and biochemical effects in the hippocampus caused by the intracerebroventricular (i.c.v.) infusion of Aβ1–42 peptide (400 pmol/site) in mice, and the neuroprotective effect of guanosine (8 mg/kg, i.p.). An initial evaluation on the eighth day after Aβ1–42 infusion showed no changes in the tail suspension test, although ex vivo analyses in hippocampal slices showed increased ROS production. In the second protocol, on the tenth day following Aβ1–42 infusion, no effect was observed in the sucrose splash test, but a reduction in the recognition index in the object location test showed impaired spatial memory. Analysis of hippocampal slices showed no ROS production and mitochondrial membrane potential alteration, but a tendency to increase glutamate release and a significant lactate release, pointing to a metabolic alteration. Those effects were accompanied by decreased cell viability and increased membrane damage. Guanosine treatment prevented behavioral and biochemical alterations evoked by Aβ1–42, suggesting a potential role against behavioral and biochemical damage evoked by Aβ in the hippocampus

Q1VA, a Synthetic Chalcone, Induces Apoptosis and Decreases Invasion on Primary Culture of Human Glioblastoma

Glioblastoma (GBM) is the most commonly occurring type of primary tumor of the central nervous system (CNS) and is considered the worst type of glioma. Despite the current standard treatment for newly diagnosed GBM, which involves surgery followed by chemotherapy with temozolomide (TMZ) and radiation therapy, the average survival time for patients with GBM is only about 15 months. This is due to GBM’s tendency to recur, its high proliferative rates, its ability to evade apoptosis, and its ability to invade healthy tissue. Therefore, it is crucial to explore new treatment options for GBM. This study investigated the potential anticancer activities of a new series of synthetic chalcones, which are natural compounds found in the biosynthesis of flavonoids in plants. Primary cell culture of glioblastoma (GBM1) from surgical resection was used to evaluate the effects of synthetic chalcones on viability, cell death, reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), cell cycle, and invasion. One chalcone, Q1VA (at concentrations of 10, 50, and 100 μM for 24 h) induced cytotoxicity by increasing apoptosis levels and depolarizing the mitochondrial membrane, as evidenced by a TMRE assay. Further analysis using the molecular fluorescent probe H2DCFDA indicated that the increased levels of reactive oxygen species (ROS) might be linked to altered mitochondrial membrane potential and cell death. Furthermore, viable cells were observed to be delayed in the cell cycle, primarily in the M phase, and the invasion process was reduced. The findings of this study indicate that Q1VA is a potential adjuvant therapeutic agent for GBM due to its significant antitumor effects. If its safety and efficacy can be confirmed in animal models, Q1VA may be considered for clinical trials in humans. However, additional research is required to determine the optimal dosage, treatment schedule, and potential side effects of Q1VA