Previous 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 (45)Ca(2+) influx and cell viability. Moreover, we investigated the pesticide effects on oxidative stress parameters, (14)C-α-methyl-amino-isobutyric acid ((14)C-MeAIB) accumulation, as well as glutamate uptake, release and metabolism. Results showed that acute exposure to Roundup(®) (30min) increases (45)Ca(2+) influx by activating NMDA receptors and voltage-dependent Ca(2+) 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 (3)H-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 (3)H-glutamate uptake and metabolism, while induced (45)Ca(2+) uptake and (14)C-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.

The decline in glucose transport coincided with increased lactate dehydrogenase activity, suggesting an adaptative response in EtOH-exposed offspring hippocampus, using lactate as an alternative fuel. These events were associated with oxidative damage, as demonstrated by changes in the enzymatic antioxidant defense system and lipid peroxidation. Taken together, the results demonstrate that maternal exposure to EtOH during pregnancy and lactation impairs glutamatergic transmission, as well as inducing oxidative stress and energy deficit in immature rat hippocampus.

In this study, we used an experimental model of congenital hypothyroidism to show that deficient thyroid hormones (TH) disrupt different neurochemical, morphological and functional aspects in the cerebral cortex of 15-day-old offspring. Our results showing decreased glutamine synthetase (GS) activity and Ca overload in the cerebral cortex of hypothyroid pups suggest misregulated glutamate metabolism associated with developmentally induced TH deficiency. The C-MeAIB accumulation indicates upregulated System A activity and glutamine uptake by neurons. Energy metabolism in hypothyroid cortical slices was preserved, as demonstrated by unaltered glucose metabolism. We also found upregulated acetylcholinesterase activity, depleting acetylcholine from the synaptic cleft, pointing to disrupted cholinergic system. Increased reactive oxygen species (ROS) generation, lipid peroxidation, glutathione (GSH) depletion, which were associated with glutathione peroxidase, superoxide dismutase and gamma-glutamyltransferase downregulation suggest redox imbalance. Disrupted astrocyte cytoskeleton was evidenced by downregulated and hyperphosphorylated glial fibrillary acidic protein (GFAP). Morphological and structural characterization of the sensorimotor cerebral cortex (SCC) showed unaltered thickness of the SCC. However, decreased size of neurons on the layers II& III and IV in the right SCC and increased NeuN positive neurons in specific SCC layers, suggest that they are differently affected by the low TH levels during neurodevelopment. Hypothyroid pups presented increased number of foot-faults in the gridwalk test indicating affected motor functions. Taken together, our results show that congenital hypothyroidism disrupts glutamatergic and cholinergic neurotransmission, Ca equilibrium, redox balance, cytoskeleton integrity, morphological and functional aspects in the cerebral cortex of young rats.

In the present study we provide evidence that 3,3',5'-triiodothyronine (reverse T, rT) restores neurochemical parameters induced by congenital hypothyroidism in rat hippocampus. Congenital hypothyroidism was induced by adding 0.05% propylthiouracil in the drinking water from gestation day 8 and continually up to lactation day 15. In the in vivo rT exposure, hypothyroid 12-day old pups were daily injected with rT (50 ng/kg body weight) or saline until day 14. In the ex vivo rT treatment, hippocampal slices from 15-day-old hypothyroid pups were incubated for 30 min with or without rT (1 nM). We found that ex vivo and/or in vivo exposure to rT failed in restoring the decreased C-glutamate uptake; however, restored the phosphorylation of glial fibrillary acidic protein (GFAP),Ca influx, aspartate transaminase (AST), glutamine synthetase (GS) and gamma-glutamate transferase (GGT) activities, as well as glutathione (GSH) levels in hypothyroid hippocampus. In addition, rT improved C-2-deoxy-D-glucose uptake and lactate dehydrogenase (LDH) activity. Receptor agonists/antagonists (RGD peptide and AP-5), kinase inhibitors of p38MAPK, ERK1/2, CaMKII, PKA (SB239063, PD98059, KN93 and H89, respectively), L-type voltage-dependent calcium channel blocker (nifedipine) and intracellular calcium chelator (BAPTA-AM) were used to determine the mechanisms of the nongenomic rT action on GGT activity. Using molecular docking analysis, we found rT interaction with αvβ3 integrin receptors, nongenomically activating signaling pathways (PKA, CaMKII, p38MAPK) that restored GGT activity. We provide evidence that rT is an active TH metabolite and our results represent an important contribution to elucidate the nonclassical mechanism of action of this metabolite in hypothyroidism.

Our objective was to investigate whether the pulp and paper mill industry effluent could affect the testis and Sertoli cells in a fast exposure period. For this, the present study was carried out in immature rats at 10-day-old. Testis treated in vitro with 4% effluent for 1 h presented changes in energy metabolism in terms of a decrease in lactate content and glucose uptake. Elevation in GSH content, as an antioxidant defense mechanism, was also detected. Sertoli cells treated with 4% effluent for 1 hour showed alterations in the mitochondrial metabolism that favor the decoupling of oxidative phosphorylation and the generation of oxygen reactive species and also a time and concentration-dependent delay secretion of acidic vesicles. Our results showed that pollutants present in the pulp and paper mill effluents, in a short time of exposure, are capable of inducing alterations in important metabolic functions in the testis and in Sertoli cells that are crucial for the correct progression of spermatogenesis and fertility.

In order to maintain body fluid balance after dehydration, hypothalamic neurons of the paraventricular nucleus (PVN) are activated to promote secretion of vasopressin (AVP) and oxytocin (OXT) from the neurohypophysis, and to modulate the behavioural allostatic responses of thirst and salt appetite. Gonadotropin inducible transcription factor (GIOT1) is a Krüppel-type zinc finger protein induced by gonadotropins and oestradiol (E2). This transcription factor is expressed in the hypothalamus, specifically in the PVN where expression of Giot1 mRNA increases following hydromineral challenges such as water deprivation or salt loading, although its physiological role is not clear. We hypothesize that GIOT1 has a central role in the integrated homeostatic and allostatic responses to disturbances in hydromineral balance, especially in the presence of female gonadal hormones. Female rats with intact ovaries or ovariectomized rats were subjected to specific microinjection of a lentiviral vector mediating Giot1 knockdown in the PVN. Three weeks after injection, rats were subjected to 48 h water deprivation, and thereafter water and salt intake were evaluated. Giot1 knockdown in PVN reduced water and saline intake as well as AVP and OXT secretion. Furthermore, Giot1 knockdown had profound effects on gene expression in the PVN, reducing the abundance of transcripts encoded by the Avp, Oxt, Nr4a1 and Crh genes. In conclusion, the present study shows for the first time that GIOT1 in the PVN regulates both transcription and fluid intake, although any connection to ovarian hormones remains to be established.

No abstract

Giot1 is a kruppel-type zinc finger protein induced by gonadotropin in teca cells of the ovary and also identified in the central nervous system areas related with hydroeletrolitic and energy homeostasis. Osmotic challenges induce simultaneously an increase in the Giot1 and AVP mRNA expressions in the paraventricular nucleus (PVN) of the hypothalamus. Our hypothesis was that Giot1 had a central role on hydromineral and energy balance modulating the ingestive behavior. To confirm this hypothesis, female Sprague-Dawley(200g) rats were maintained on metabolic cages with free access to diet and fluids. Water was offered during 8 days followed by water and 0.3M NaCl solution during 12 days. After these 20 days, animals were randomly assigned into the Giot1 gene knockdown group and submitted to a bilateral microinjection of small hairpin RNA expressing lentiviral vector (shGiot1) into the PVN. shGFP lentivirus was used as control group (Scramble group). After recovery, we evaluated the ingestive behavior during 20 days. The estrous cycle was verified daily along the experiment. This study was conducted following the “Guide for the Care and Use of Laboratory Animals” (NIH Publication nº85-23, 1996). The software STATISTICA 7.0 was used for statistical analysis. The Giot1 knockdown promoted a decrease of salt preference compared with the scramble group (63.37% ± 1.61, n=6 vs. 68.79% ± 2.02, n= 6; p =0.04). On the other hand, the Giot1 knockdown group had a higher food intake compared with the scramble group (12.39g ± 0.22, n= 6 vs. 10.21g ± 0.22, n= 6; p <0.0001). However, the final body weight of shGiot1 group was not significantly different from scramble group (252g ± 2.01, n= 6 vs. 246.1g ± 2.27, n= 6; p= 0,06). There was no difference in the content of white retroperitoneal and brown interscapular adipose tissue between Giot1 knockdown and control groups. It is well known that PVN neurons have a participation modulating locomotor activity, so we can suggest that Giot1 has a direct or indirect effect on central control of locomotor activity too. These data confirmed that Giot1 in PVN modulates salt preference and food intake. However the mechanisms involved in this behaviour remains unclear. Financial Support: FAPESP and CNPq.