Inhibition of Mitochondrial Respiratory Chain in the Brain of Adult Rats After Acute and Chronic Administration of Methylphenidate

Methylphenidate (MPH) is frequently prescribed for the treatment of attention deficit/hyperactivity disorder. It was previously demonstrated that MPH altered brain metabolic activity. Most cell energy is obtained through oxidative phosphorylation, in the mitochondrial respiratory chain. However, there are still few studies about MPH effects on the brain of adult rats. Thus, in the present study we evaluated the effect of acute or chronic administration of MPH on the activities of mitochondrial respiratory chain complexes I–IV in the brain of adult rats. For acute administration, a single injection of MPH was given to 60-day-old rats. For chronic administration, MPH injections were given to 60-day-old rats once daily for 28 days. Our results showed that complexes I, II, III and IV were inhibited after acute or chronic MPH administration in the hippocampus, prefrontal cortex, striatum and cerebral cortex. On the other hand, cerebellum was not affected.     

Effect of Acute and Chronic Administration of Methylphenidate on Mitochondrial Respiratory Chain in the Brain of Young Rats

Methylphenidate is commonly used for the treatment of attention deficit/hyperactivity disorder. There are still few works regarding the effects of methylphenidate on brain energy metabolism. Thus, in the present study we evaluated the effect of chronic administration of methylphenidate on the activities of mitochondrial respiratory chain complexes I and III in the brain of young rats. The effect of acute administration of methylphenidate on mitochondrial respiratory chain complexes I, II, III and IV in the brain of young rats was also investigated. For acute administration, a single injection of methylphenidate was given to rats on postnatal day 25. For chronic administration, methylphenidate injections were given starting at postnatal day 25 once daily for 28 days. Our results showed that complexes I and III were not affected by chronic administration of methylphenidate. Moreover, the acute administration of methylphenidate decreased complex I activity in cerebellum and prefrontal cortex, whereas complexes II, III and IV were not altered.     

Maternal Hypermethioninemia Affects Neurons Number,Neurotrophins Levels,Energy Metabolism,and Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>-ATPase Expression/Content in Brain of Rat Offspring

In the current study, we verified the effects of maternal hypermethioninemia on the number of neurons, apoptosis, nerve growth factor, and brain-derived neurotrophic factor levels, energy metabolism parameters (succinate dehydrogenase, complex II, and cytochrome c oxidase), expression and immunocontent of Na⁺,K⁺-ATPase, edema formation, inflammatory markers (tumor necrosis factor-alpha and interleukin-6), and mitochondrial hydrogen peroxide levels in the encephalon from the offspring. Pregnant Wistar rats were divided into two groups: the first one received saline (control) and the second group received 2.68 μmol methionine/g body weight by subcutaneous injections twice a day during gestation (approximately 21 days). After parturition, pups were killed at the 21st day of life for removal of encephalon. Neuronal staining (anti-NeuN) revealed a reduction in number of neurons, which was associated to decreased nerve growth factor and brain-derived neurotrophic factor levels. Maternal hypermethioninemia also reduced succinate dehydrogenase and complex II activities and increased expression and immunocontent of Na⁺,K⁺-ATPase alpha subunits. These results indicate that maternal hypermethioninemia may be a predisposing factor for damage to the brain during the intrauterine life.     

Molecular Mechanisms Underlying the Anti-depressant Effects of Resveratrol: a Review

Major depression is a public health problem, affecting 121 million people worldwide. Patients suffering from depression present high rates of morbidity, causing profound economic and social impacts. Furthermore, patients with depression present cognitive impairments, which could influence on treatment adherence and long-term outcomes. The pathophysiology of major depression is not completely understood yet but involves reduced levels of monoamine neurotransmitters, bioenergetics, and redox disturbances, as well as inflammation and neuronal loss. Treatment with anti-depressants provides a complete remission of symptoms in approximately 50% of patients with major depression. However, these drugs may cause side effects, as sedation and weight gain. In this context, there is increasing interest in studies focusing on the anti-depressant effects of natural compounds found in the diet. Resveratrol is a polyphenolic phytoalexin (3,4′,5-trihydroxystilbene; C₁₄H₁₂O₃; MW 228.247 g/mol) and has been found in peanuts, berries, grapes, and wine and induces anti-oxidant, anti-inflammatory, and anti-apoptotic effects in several mammalian cell types. Resveratrol also elicits anti-depressant effects, as observed in experimental models using animals. Therefore, resveratrol may be viewed as a potential anti-depressant agent, as well as may serve as a model of molecule to be modified aiming to ameliorate depressive symptoms in humans. In the present review, we describe and discuss the anti-depressant effects of resveratrol focusing on the mechanism of action of this phytoalexin in different experimental models.     

Primate cathelicidin orthologues display different structures and membrane interactions

The human cathelicidin LL-37 displays both direct antibacterial activities and the capacity to modulate host-cell activities. These depend on structural characteristics that are subject to positive selection for variation, as observed in a previous analysis of the CAMP gene (encoding LL-37) in primates. The altered balance between cationic and anionic residues in different primate orthologues affects intramolecular salt-bridging and influences the stability of the helical conformation and tendency to aggregate in solution of the peptide. In the present study, we have analysed the effects of these structural variations on membrane interactions for human LL-37, rhesus RL-37 and orang-utan LL-37, using several complementary biophysical and biochemical methods. CD and ATR (attenuated total reflection)-FTIR (Fourier-transform IR) spectroscopy on model membranes indicate that RL-37, which is monomeric and unstructured in bulk solution [F-form (free form)], and human LL-37, which is partly structured and probably aggregated [A-form (aggregated form)], bind biological membranes in different manners. RL-37 may insert more deeply into the lipid bilayer than LL-37, which remains aggregated. AFM (atomic force microscopy) performed on the same supported bilayer as used for ATR-FTIR measurements suggests a carpet-like mode of permeabilization for RL37 and formation of more defined worm-holes for LL-37. Comparison of data from the biological activity on bacterial cells with permeabilization of model membranes indicates that the structure/aggregation state also affects the trajectory of the peptides from bulk solution through the outer cell-wall layers to the membrane. The results of the present study suggest that F-form cathelicidin orthologues may have evolved to have primarily a direct antimicrobial defensive capacity, whereas the A-forms have somewhat sacrificed this to gain host-cell modulating functions.     

Evaluation of citrate synthase activity in brain of rats submitted to an animal model of mania induced by ouabain

Bipolar disorder (BD) is a psychiatric disorder characterized by alternating episodes of mania and depression. The intracerebroventricular (i.c.v) administration of ouabain (a Na⁺/K⁺-ATPase inhibitor) in rats has been used as an animal model of mania, because present face, construct and predictive validities. Several studies strongly suggest that mitochondrial dysfunction play a central role in the pathophysiology of BD. Citrate synthase (CS) is an enzyme localized in the mitochondrial matrix and represents one of the most important steps of Krebs cycle. The aim of this study was to investigate CS activity in brain of rats after the administration of ouabain. Adult male Wistar rats received a single i.c.v. administration of ouabain (10^?2 and 10^?3 M) or vehicle (control group). Locomotor activity was measured using the open field task. CS activity was measured in the brain of rats immediately (1 h) and 7 days after ouabain administration. Our results showed that spontaneous locomotion was increased 1 h after ouabain administration, and that the hyperlocomotion persists 7 days after the administration. Moreover, CS activity was inhibited immediately after the administration of ouabain in the prefrontal cortex at the doses of 10^?3 and 10^?2 M. This inhibition remains by 7 days after the administration of ouabain. On the other hand, it was not observed any difference in CS activity in the hippocampus and striatum. Considering that inhibition of CS activity may reflect a mitochondrial dysfunction, it is tempting to speculate that the reduction of brain energy metabolism might be related to the pathophysiology of BD.     

Effect of Acute and Chronic Administration of l-Tyrosine on Nerve Growth Factor Levels in Rat Brain

Most inborn errors of tyrosine catabolism produce hypertyrosinemia. Neurological manifestations are variable and some patients are developmentally normal, while others show different degrees of developmental retardation. Considering that current data do not eliminate the possibility that elevated levels of tyrosine and/or its derivatives may have noxious effects on central nervous system development in some patients, the present study evaluated nerve growth factor (NGF) levels in hippocampus, striatum and posterior cortex of young rats. In our acute protocol, Wistar rats (10 and 30 days old) were killed 1 h after a single intraperitoneal administration of l-tyrosine (500 mg/kg) or saline. Chronic administration consisted of l-tyrosine (500 mg/kg) or saline injections 12 h apart for 24 days in Wistar rats (7 days old); the rats were killed 12 h after the last injection. NGF levels were then evaluated. Our findings showed that acute administration of l-tyrosine decreased NGF levels in striatum of 10-day-old rats. In the 30-day-old rats, NGF levels were decreased in hippocampus and posterior cortex. On the other hand, chronic administration of l-tyrosine increased NGF levels in posterior cortex. Decreased NGF may impair growth, differentiation, survival and maintenance of neurons.     

Central Nervous System Involvement in the Animal Model of Myodystrophy

Congenital muscular dystrophies present mutated gene in the LARGE mice model and it is characterized by an abnormal glycosylation of α-dystroglycan (α-DG), strongly implicated as having a causative role in the development of central nervous system abnormalities such as cognitive impairment seen in patients. However, the pathophysiology of the brain involvement remains unclear. Therefore, the objective of this study is to evaluate the oxidative damage and energetic metabolism in the brain tissue as well as cognitive involvement in the LARGE^(myd) mice model of muscular dystrophy. With this aim, we used adult homozygous, heterozygous, and wild-type mice that were divided into two groups: behavior and biochemical analyses. In summary, it was observed that homozygous mice presented impairment to the habituation and avoidance memory tasks; low levels of brain-derived neurotrophic factor (BDNF) in the prefrontal cortex, hippocampus, cortex and cerebellum; increased lipid peroxidation in the prefrontal cortex, hippocampus, striatum, and cerebellum; an increase of protein peroxidation in the prefrontal cortex, hippocampus, striatum, cerebellum, and cortex; a decrease of complex I activity in the prefrontal cortex and cerebellum; a decrease of complex II activity in the prefrontal cortex and cerebellum; a decrease of complex IV activity in the prefrontal cortex and cerebellum; an increase in the cortex; and an increase of creatine kinase activity in the striatum and cerebellum. This study shows the first evidence that abnormal glycosylation of α-DG may be affecting BDNF levels, oxidative particles, and energetic metabolism thus contributing to the memory storage and restoring process.     

Inhibition of mitochondrial respiratory chain in the brain of rats after hepatic failure induced by acetaminophen

To explore the effect of LYRM1 over-expression on basal and insulin-stimulated glucose uptake in rat skeletal muscle cells, and to understand the underlying mechanisms, Rat myoblasts (L6) transfected with either an empty expression vector (pcDNA3.1Myc/His B) or a LYRM1 expression vector were differentiated into myotubes. Glucose uptake was determined by measuring 2-deoxy-D-[(3)H] glucose uptake into L6 myotubes. Western blotting was performed to assess the translocation of insulin-sensitive glucose transporter 4 (GLUT4). It was also used to measure the phosphorylation and total protein contents of insulin-signaling proteins, such as the insulin receptor (IR), insulin receptor substrate (IRS)-1, phosphatidylinositol-3-kinase (PI3K) p85, Akt, ERK1/2, P38, and JNK. LYRM1 over-expression in L6 myotubes reduced insulin-stimulated glucose uptake and impaired insulin-stimulated GLUT4 translocation. It also diminished insulin-stimulated tyrosine phosphorylation of IRS-1, PI3K (p85), and serine phosphorylation of Akt without affecting the phosphorylation of IR, ERK1/2, P38, and JNK. LYRM1 regulates the function of IRS-1, PI3K, and Akt, and decreases GLUT4 translocation and glucose uptake in response to insulin. These observations highlight the potential role of LYRM1 in glucose homeostasis and possibly in the pathophysiology of type 2 diabetes related to obesity.