Influence of the dopaminergic system, CREB, and transcription factor-B on cocaine neurotoxicity

Cocaine is a widely used drug and its abuse is associated with physical, psychiatric and social problems. Abnormalities in newborns have been demonstrated to be due to the toxic effects of cocaine during fetal development. The mechanism by which cocaine causes neurological damage is complex and involves interactions of the drug with several neurotransmitter systems, such as the increase of extracellular levels of dopamine and free radicals, and modulation of transcription factors. The aim of this review was to evaluate the importance of the dopaminergic system and the participation of inflammatory signaling in cocaine neurotoxicity. Our study showed that cocaine activates the transcription factors NF-κB and CREB, which regulate genes involved in cellular death. GBR 12909 (an inhibitor of dopamine reuptake), lidocaine (a local anesthetic), and dopamine did not activate NF-κB in the same way as cocaine. However, the attenuation of NF-κB activity after the pretreatment of the cells with SCH 23390, a D1 receptor antagonist, suggests that the activation of NF-κB by cocaine is, at least partially, due to activation of D1 receptors. NF-κB seems to have a protective role in these cells because its inhibition increased cellular death caused by cocaine. The increase in BDNF (brain-derived neurotrophic factor) mRNA can also be related to the protective role of both CREB and NF-κB transcription factors. An understanding of the mechanisms by which cocaine induces cell death in the brain will contribute to the development of new therapies for drug abusers, which can help to slow down the progress of degenerative processes.

Effect of activation of canonical Wnt signaling by the Wnt-3a protein on the susceptibility of PC12 cells to oxidative and apoptotic insults

Wnt proteins are involved in tissue development and their signaling pathways play an important role during embryogenesis. Wnt signaling can promote cell survival, which is beneficial for neurons, but could also lead to tumor development in different tissues. The present study investigated the effects of a Wnt protein on the susceptibility of a neural tumor cell line (PC12 cells) to the cytotoxic compounds ferrous sulfate (10 mM), staurosporine (100 and 500 nM), 3-nitropropionic acid (5 mM), and amyloid β-peptide (Aβ25-35; 50 µM). Cells (1 x 10(6) cells/mL) were treated with the Wnt-3a recombinant peptide (200 ng/mL) for 24 h before exposure to toxic insults. The Wnt-3a protein partially protected PC12 cells, with a 6-15 percent increase in cell viability in the presence of toxic agents, similar to the effect measured using the MTT and lactate dehydrogenase cell viability assays. The Wnt-3a protein increased protein expression of β-catenin by 52 percent compared to control. These findings suggest that Wnt signaling can protect neural cells against apoptosis induced by toxic agents, which are relevant to the pathogenesis of Alzheimer’s and Huntington’s diseases.

Stress-induced neuroinflammation: mechanisms and new pharmacological targets

Stress is triggered by numerous unexpected environmental, social or pathological stimuli occurring during the life of animals, including humans, which determine changes in all of their systems. Although acute stress is essential for survival, chronic, long-lasting stress can be detrimental. In this review, we present data supporting the hypothesis that stress-related events are characterized by modifications of oxidative/nitrosative pathways in the brain in response to the activation of inflammatory mediators. Recent findings indicate a key role for nitric oxide (NO) and an excess of pro-oxidants in various brain areas as responsible for both neuronal functional impairment and structural damage. Similarly, cyclooxygenase-2 (COX-2), another known source of oxidants, may account for stress-induced brain damage. Interestingly, some of the COX-2-derived mediators, such as the prostaglandin 15d-PGJ2 and its peroxisome proliferator-activated nuclear receptor PPARγ, are activated in the brain in response to stress, constituting a possible endogenous anti-inflammatory mechanism of defense against excessive inflammation. The stress-induced activation of both biochemical pathways depends on the activation of the N-methyl-D-aspartate (NMDA) glutamate receptor and on the activation of the transcription factor nuclear factor kappa B (NFκB). In the case of inducible NO synthase (iNOS), release of the cytokine TNF-α also accounts for its expression. Different pharmacological strategies directed towards different sites in iNOS or COX-2 pathways have been shown to be neuroprotective in stress-induced brain damage: NMDA receptor blockers, inhibitors of TNF-α activation and release, inhibitors of NFκB, specific inhibitors of iNOS and COX-2 activities and PPARγ agonists. This article reviews recent contributions to this area addressing possible new pharmacological targets for the treatment of stress-induced neuropsychiatric disorders.

Therapeutic carbamazepine (CBZ) and valproic acid (VPA) monitoring in children using saliva as a biologic fluid / Monitoramento terapêutico de carbamazepina e ácido valproico em saliva de crianças

OBJECTIVE: The aim of the study was to analyze retrospectively carbamazepine (CBZ) and valproic acid (VPA) salivary data collected from epileptic children during a 3-year period. METHODS: Saliva samples stimulated by citric acid were assayed by FPIA method. One hundred and three patients (aged 1-14 years) were in CBZ or VPA monotherapy or in CBZ-VPA combined therapy. RESULTS: VPA salivary levels were linearly related with daily dose, but a non-linear relationship was found for CBZ, in patients under monotherapy. VPA did not alter saliva CBZ concentration. Conversely, CBZ reduced VPA salivary levels. Non-responsive children displayed higher VPA concentrations. CBZ levels in uncontrolled patients showed non-significant difference in relation with controlled subjects even though their daily doses were higher. CONCLUSION: Citric acid stimulated saliva is reliable enough to perform therapeutic drug monitoring. Saliva drug levels in non-responsive patients would be explained according to the generalized efflux transporter overexpression hypothesis.

OBJETIVO: O objetivo deste estudo foi avaliar retrospectivamente por 3 anos a partir de dados salivares, as terapias com carbamacepina (CBZ) e ácido valproico (VPA) em pacientes pediátricos. MÉTODOS: Foram avaliadas amostras de saliva estimuladas com ácido cítrico por método FPIA em 103 pacientes (idades 1-14 anos) em monoterapia com CBZ ou VPA ou terapia combinada CBZ-VPA. RESULTADOS: Níveis salivares de VPA se relacionaram linearmente com a dose diária, e a relação não linear foi encontrada em pacientes com CBZ. VPA não alterou as concentrações salivares de CBZ, porém a CBZ reduziu os níveis salivares de VPA em pacientes com terapia combinada. Pacientes refratários apresentaram altas concentrações de VPA. Os níveis de CBZ em pacientes não controlados não apresentaram diferenças significativas em relação aos pacientes controlados quando as doses diárias foram mais elevadas. CONCLUSÃO: Saliva estimulada com ácido cítrico é adequada para o monitoramento terapêutico. Níveis da droga na saliva em pacientes que não responderam ao tratamento pode ser explicado pelo transporte de efluxo generalizado.

Neutrophil function and metabolism in individuals with diabetes mellitus

Neutrophils act as first-line-of-defense cells and the reduction of their functional activity contributes to the high susceptibilityto and severity of infections in diabetes mellitus. Clinical investigations in diabetic patients and experimental studies in diabetic rats and mice clearly demonstrated consistent defects of neutrophil chemotactic, phagocytic and microbicidal activities. Other alterations that have been reported to occur during inflammation in diabetes mellitus include: decreased microvascular responses to inflammatory mediators such as histamine and bradykinin, reduced protein leakage and edema formation, reduced mast cell degranulation, impairment of neutrophil adhesionto the endothelium and migration to the site of inflammation, production of reactive oxygen species and reduced release of cytokines and prostaglandin by neutrophils, increased leukocyte apoptosis, and reduction in lymph node retention capacity. Since neutrophil function requires energy, metabolic changes (i.e., glycolytic and glutaminolytic pathways) may be involved in the reduction of neutrophil function observed in diabetic states. Metabolic routes by which hyperglycemia is linked to neutrophil dysfunction include the advanced protein glycosylation reaction, the polyol pathway, oxygen-free radical formation, the nitric oxide-cyclic guanosine-3'-5'monophosphate pathway, and the glycolytic and glutaminolytic pathways. Lowering of blood glucose levels by insulin treatment of diabetic patients or experimental animals has been reported to have significant correlation with improvement of neutrophil functional activity. Therefore, changes might be primarily linked to a continuing insulin deficiency or to secondary hyperglycemia occurring in the diabetic individual. Accordingly, effective control with insulin treatment is likely to be relevant during infection in diabetic patients.

Expression of inducible nitric oxide synthase is increased in patients with heart failure due to ischemic disease

The objective of the present study was to determine the relationship between nitric oxide synthases (NOS) and heart failure in cardiac tissue from patients with and without cardiac decompensation. Right atrial tissue was excised from patients with coronary artery disease (CAD) and left ventricular ejection fraction (LVEF) <35 percent (N = 10), and from patients with CAD and LVEF >60 percent (N = 10) during cardiac surgery. NOS activity was measured by the conversion of L-[H ]-arginine to L-[H ]-citrulline. Gene expression was quantified by the competitive reverse transcription-polymerase chain reaction. Both endothelial NOS (eNOS) activity and expression were significantly reduced in failing hearts compared to non-failing hearts: 0.36 ± 0.18 vs 1.51 ± 0.31 pmol mg-1 min-1 (P < 0.0001) and 0.37 ± 0.08 vs 0.78 ± 0.09 relative cDNA absorbance at 320 nm (P < 0.0001), respectively. In contrast, inducible NOS (iNOS) activity and expression were significantly higher in failing hearts than in non-failing hearts: 4.00 ± 0.90 vs 1.54 ± 0.65 pmol mg-1 min-1 (P < 0.0001) and 2.19 ± 0.27 vs 1.43 ± 0.13 cDNA absorbance at 320 nm (P < 0.0001), respectively. We conclude that heart failure down-regulates both eNOS activity and expression in cardiac tissue from patients with LVEF <35 percent. In contrast, iNOS activity and expression are increased in failing hearts and may represent an alternative mechanism for nitric oxide production in heart failure due to ischemic disease.

Circadian time-dependent effects of fencamfamine on inhibition of dopamine uptake and release in rat striatal slices

Fencamfamine (FCF) is a central stimulant that facilitates central dopaminergic transmission through inhibition of dopamine uptake and enhanced release of the transmitter. We evaluated the changes in the inhibition of uptake and the release of striatal [3H]-dopamine at 9:00 and 21:00 h, times corresponding to maximal and minimal behavioral responses to FCF, respectively. Adult male Wistar rats (200-250 g) maintained on a 12-h light/12-h dark cycle (lights on at 7:00 h) were used. In the behavioral experiments the rats (N = 8 for each group) received FCF (3.5 mg/kg, ip) or saline at 9:00 or 21:00 h. Fifteen minutes after treatment the duration of activity (sniffing, rearing and locomotion) was recorded for 120 min. The basal motor activity was higher (28.6 + 4.2 vs 8.4 + 3.5 s) after saline administration at 21:00 h than at 9:00 h. FCF at a sigle dose significantly enhanced the basal motor activity (38.3 + 4.5 vs 8.4 + 3.5 s) and increased the duration of exploratory activity (38.3 + 4.5 vs 32.1 + 4.6 s) during the light, but not the dark phase. Two other groups of rats (N = 6 for each group) were decapitated at 9:00 and 21:00 h and striata were dissected for dopamine uptake and release assays. The inhibition of uptake and release of [3H]-dopamine were higher at 9:00 than at 21:00 h, suggesting that uptake inhibition and the release properties of FCF undergo daily variation. These data suggest that the circadian time-dependent effects of FCF might be related to a higher susceptibility of dopamine presynaptic terminals to the action of FCF during the light phase which corresponds to the rats' resting period.

Hyperprolactinemia induced by long-term domperidone treatment does not alter the sensitivity of strial dopamine receptors

We investigated the effect of hyperprolactinemia by long-term domperidone treatment (10.0 mg/kg, single daily dose, ip) on striatal dopamine (DA) receptor sensitivity in male Wistar rats weighing 250-300 g(N=8). Domperidone treatment for days continued to produce an increased in serum concentration of prolactin (PRL) form 17.3 ñ 2.2 to 33.1 ñ 7.3 and from 16.8 ñ 2.3 to 21.9 ñ 2.1, 2 and 72 h after domperidone withdrawal, respectively. Hyperprolactinemia induced by long-term domperidone treatment did not change binding sites (B max) and dissociation constant (Kd) of [3***H]-spiroperidol binding when compared to controls. These results show that byperprolactinemia induced by long-term domperidone treatment does not effect the sensitivity of striatal DA receptors presumably because the effect of neuroleptic drugs is due to their interaction with the receptors and not to the concomitant hyperprolactinemia

Striatal dopamine receptor supersensitivity afte long-term haloperiodol treatment of hypophysectomized rats

Dopamine (DA) receptor sensitivity was studied after long-term treatment with haloperidol (0.5 ad 3.0 mg/Kg, ip, single daily dose) or saline in hypophysectomized and infact rats. Haloperidol treatment for seven days produced a 25 to 125% increase in [3H]-spiroperidol binding to strial DA receptors in a dose-dependent fashion. The increase in binding sits (Bmax) was ximilar in both hypophysectomized and intact rats when compared to controls. The present results show that haloperidol treatment

On the mechanism which mediates the effects of long-term administration of fencamfamine in rats

This study analyzes the changes in the sensitivity of striatal dopaminergic (DA) receptors to apomorphine following withdrawal from long-term treatment with fencamfamine (10 mg/kg, for 40 days). Fencamfamine treatment decreased (34.8 + or - 3.2 vs 25.8 + or - 2.8,P<0.05) the stereotyped behavior induced by apomorfhine (2.0 mg/kg, sc), but potentiated the effect of apomorphine (0.02 mg/kg, sc) in reducing the striatal levels of homovanillic acid (HVA) (0.41 + or - 0.02 micron g/g vs 0.31 + or - 0.03 microng/g, P<0.01) and dihydroxyphenylacetic acid (DOPAC) (0.45 + or - 0.04 microng/g vs 0.34 + or - 0.03 microng/g, P<0.01). These results suggest that changes in pre- or postsynaptic DA receptors may underlie the tolerance and sensitization to the effects of fencamfamine