Monocrotaline induces acutely cerebrovascular lesions, astrogliosis and neuronal degeneration associated with behavior changes in rats: A model of vascular damage in perspective.

Pyrrolizidine alkaloids (PAs) are secondary plant metabolites playing an important role as phytotoxins in the plant defense mechanisms and can be present as contaminant in the food of humans and animals. The PA monocrotaline (MCT), one of the major plant derived toxin that affect humans and animals, is present in a high concentration in Crotalaria spp. (Leguminosae) seeds and can induce toxicity after consumption, characterized mainly by hepatotoxicity and pneumotoxicity. However, the effects of the ingestion of MCT in the central nervous system (CNS) are still poorly elucidated. Here we investigated the effects of MCT oral acute administration on the behavior and CNS toxicity in rats. Male adult Wistar were treated with MCT (109 mg/Kg, oral gavage) and three days later the Elevated Pluz Maze test demonstrated that MCT induced an anxiolytic-like effect, without changes in novelty habituation and in operational and spatial memory profiles. Histopathology revealed that the brain of MCT-intoxicated animals presented hyperemic vascular structures in the hippocampus, parahippocampal cortex and neocortex, mild perivascular edema in the neocortex, hemorrhagic focal area in the brain stem, hemorrhage and edema in the thalamus. MCT also induced neurotoxicity in the cortex and hippocampus, as revealed by Fluoro Jade-B and Cresyl Violet staining, as well astrocyte reactivity, revealed by immunocytochemistry for glial fibrillary acidic protein. Additionally, it was demonstrated by RT-qPCR that MCT induced up-regulation on mRNA expression of neuroinflammatory mediator, especially IL1ß and CCL2 in the hippocampus and cortex, and down-regulation on mRNA expression of neurotrophins HGDF and BDNF in the cortex. Together, these results demonstrate that the ingestion of MCT induces cerebrovascular lesions and toxicity to neurons that are associated to astroglial cell response and neuroinflammation in the cortex and hippocampus of rats, highlighting CNS damages after acute intoxication, also putting in perspective it uses as a model for cerebrovascular damage.

Cortical Bilateral Adaptations in Rats Submitted to Focal Cerebral Ischemia: Emphasis on Glial Metabolism.

This study was performed to evaluate the bilateral effects of focal permanent ischemia (FPI) on glial metabolism in the cerebral cortex. Two and 9 days after FPI induction, we analyze [18F]FDG metabolism by micro-PET, astrocyte morphology and reactivity by immunohistochemistry, cytokines and trophic factors by ELISA, glutamate transporters by RT-PCR, monocarboxylate transporters (MCTs) by western blot, and substrate uptake and oxidation by ex vivo slices model. The FPI was induced surgically by thermocoagulation of the blood in the pial vessels of the motor and sensorimotor cortices in adult (90 days old) male Wistar rats. Neurochemical analyses were performed separately on both ipsilateral and contralateral cortical hemispheres. In both cortical hemispheres, we observed an increase in tumor necrosis factor alpha (TNF-α), interleukin-1ß (IL-1ß), and glutamate transporter 1 (GLT-1) mRNA levels; lactate oxidation; and glutamate uptake and a decrease in brain-derived neurotrophic factor (BDNF) after 2 days of FPI. Nine days after FPI, we observed an increase in TNF-α levels and a decrease in BDNF, GLT-1, and glutamate aspartate transporter (GLAST) mRNA levels in both hemispheres. Additionally, most of the unilateral alterations were found only in the ipsilateral hemisphere and persisted until 9 days post-FPI. They include diminished in vivo glucose uptake and GLAST expression, followed by increased glial fibrillary acidic protein (GFAP) gray values, astrocyte reactivity, and glutamate oxidation. Astrocytes presented signs of long-lasting reactivity, showing a radial morphology. In the intact hemisphere, there was a decrease in MCT2 levels, which did not persist. Our study shows the bilateralism of glial modifications following FPI, highlighting the role of energy metabolism adaptations on brain recovery post-ischemia.

Gestational and postnatal low protein diet alters insulin sensitivity in female rats.

Nutrition during pregnancy and lactation can program an offspring's metabolism with regard to glucose and lipid homeostasis. A suboptimal environment during fetal, neonatal and infant development is associated with impaired glucose tolerance, type 2 diabetes and insulin resistance in later adult life. However, studies on the effects of a low protein diet imposed from the beginning of gestation until adulthood are scarce. This study's objective was to investigate the effects of a low protein diet imposed from the gestational period until 4 months of age on the parameters of glucose tolerance and insulin responsiveness in Wistar rats. The rats were divided into a low protein diet group and a control group and received a diet with either 7% or 25% protein, respectively. After birth, the rats received the same diet as their mothers, until 4 months of age. In the low protein diet group it was observed that: (i) the hepatic glycogen concentration and hepatic glycogen synthesis from glycerol were significantly greater than in the control group; (ii) the disposal of 2-deoxyglucose in soleum skeletal muscle slices was 29.8% higher than in the control group; (iii) there was both a higher glucose tolerance in the glucose tolerance test; and (iv) a higher insulin responsiveness in than in the control group. The results suggest that the low protein diet animals show higher glucose tolerance and insulin responsiveness relative to normally nourished rats. These findings were supported by the higher hepatic glycogen synthesis and the higher disposal of 2-deoxyglucose in soleum skeletal muscle found in the low protein diet rats.

Effect of 2-deoxy-D-glucose on aminoacids metabolism in rats' cerebral cortex slices.

We studied the effect of different concentrations of 2-deoxy-D-glucose on the L-[U-14C]leucine, L-[1-14C]leucine and [1-14C]glycine metabolism in slices of cerebral cortex of 10-day-old rats. 2-deoxy-D-glucose since 0.5 mM concentration has inhibited significantly the protein synthesis from L-[U-14C]leucine and from [1-14C]glycine in relation to the medium containing only Krebs Ringer bicarbonate. Potassium 8.0 mM in incubation medium did not stimulate the protein synthesis compared to the medium containing 2.7 mM, and at 50 mM diminishes more than 2.5 times the protein synthesis compared to the other concentration. Only at the concentration of 5.0 mM, 2-deoxy-D-glucose inhibited the CO2 production and lipid synthesis from L-[U-14C] leucine. This compound did not inhibit either CO2 production, or lipid synthesis from [1-14C]glycine. Lactate at 10 mM and glucose 5.0 mM did not revert the inhibitory effect of 2-deoxy-D-glucose on the protein synthesis from L-[U-14C]leucine. 2-deoxy-D-glucose at 2.0 mM did not show any effect either on CO2 production, or on lipid synthesis from L-[U-14C]lactate 10 mM and glucose 5.0 mM.