Protective effects of the dipeptidyl peptidase IV inhibitor sitagliptin in the blood-retinal barrier in a type 2 diabetes animal model.

AIM: The aim of this study was to evaluate the efficacy of sitagliptin, a dipeptidyl peptidase IV inhibitor (DPP-IV), in preventing the deleterious effects of diabetes on the blood-retinal barrier in male Zucker Diabetic Fatty (ZDF) rats. METHODS: ZDF rats at 20 weeks of age were treated with sitagliptin (10 mg/kg/day) during 6 weeks. The effect of the drug on glycaemia was assessed by evaluating glycated haemoglobin (HbA1c). The content and/or distribution of tight junction (TJ) proteins occludin and claudin-5, as well as nitrotyrosine residues, interleukin (IL)-1ß, BAX and Bcl-2 was evaluated in the retinas by western blotting and/or immunohistochemistry. Retinal cell apoptosis was assessed by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay. The number of CD34+ cells present in peripheral circulation was assessed by flow cytometry, and endothelial progenitor cells (EPC) adhesion ability to the retinal vessels was evaluated by immunohistochemistry. RESULTS: Sitagliptin improved glycaemic control as reflected by a significant decrease in HbA1c levels by about 1.2%. Treatment with sitagliptin prevented the changes in the endothelial subcellular distribution of the TJ proteins induced by diabetes. Sitagliptin also decreased the nitrosative stress, the inflammatory state and cell death by apoptosis in diabetic retinas. Diabetic animals presented decreased levels of CD34+ cells in the peripheral circulation and decreased adhesion ability of EPC to the retinal vessels. Sitagliptin allowed a recovery of the number of CD34+ cells present in the bloodstream to levels similar to their number in controls and increased the adhesion ability of EPC to the retinal vessels. CONCLUSIONS: Sitagliptin prevented nitrosative stress, inflammation and apoptosis in retinal cells and exerted beneficial effects on the blood-retinal barrier integrity in ZDF rat retinas.

Methamphetamine induces alterations on hippocampal NMDA and AMPA receptor subunit levels and impairs spatial working memory.

Methamphetamine (METH) is a powerful psychostimulant that increases glutamate (Glu) levels in the mammalian brain and it is currently known that hippocampi are particularly susceptible to METH. Moreover, it is well established that the overactivation of N-methyl-d-aspartate (NMDA) and AMPA ionotropic Glu receptors causes excitotoxicity. In the present study, we investigated the effect of acute (30 mg/kg) versus escalating dose (ED) administration of METH on NMDA receptor 1, NMDA receptor 2 and glutamate receptor 2 (GluR2) subunit expression in the hippocampus and on memory. Adult Sprague-Dawley rats were injected s.c. during six consecutive days with saline (control and acute groups) or with a growing dose of METH (10, 15, 15, 20, 20, 25 mg/kg/day; ED group). On the 7th day, both METH groups were injected with a 'bolus' of 30 mg/kg METH whereas controls received saline. Western blot analysis showed an increase of GluR2 and NR2A expression levels and no alterations on NR1 subunit in the acute group. On the other hand, in the ED group, GluR2 and NR2A expression levels were unaltered and there was a decrease on NR1 levels. Moreover, we did not observe neurodegeneration with both administration paradigms, as assessed by Fluoro-Jade C staining, but we did observe a strong astrogliosis in the acute administration group by using both immunohistochemistry and Western blot analysis. The impact of METH on working memory was evaluated using the Y maze test and revealed significant mnemonic deficit in the rats acutely treated with the drug. Overall, our results suggest a protection mechanism under conditions of METH administration by decreasing permeability and/or functionality of NMDA and AMPA receptors, which has implications on memory. So, the participation of the glutamatergic system should be considered as an important pharmacological target to design new strategies to prevent or diminish the harmful effect of drug consumption.

Monoamine oxidase activity in blood platelets of migraine patients.

Biochemical changes in platelets of migraine patients during the attacks have been reported before, however there are some conflicting results. In an attempt to define the biochemical lesion in the platelets, we have carried out a survey of platelets monoamine oxidase in migraine patients with and without aura. Platelet MAO activity in platelets from migraine patients was significantly reduced when compared with normal platelets.

Influence of hydrogen peroxide bleaching gels on color, opacity, and fluorescence of composite resins.

The aim of the present study was to evaluate the effect of 20% and 35% hydrogen peroxide bleaching gels on the color, opacity, and fluorescence of composite resins. Seven composite resin brands were tested and 30 specimens, 3-mm in diameter and 2-mm thick, of each material were fabricated, for a total of 210 specimens. The specimens of each tested material were divided into three subgroups (n=10) according to the bleaching therapy tested: 20% hydrogen peroxide gel, 35% hydroxide peroxide gel, and the control group. The baseline color, opacity, and fluorescence were assessed by spectrophotometry. Four 30-minute bleaching gel applications, two hours in total, were performed. The control group did not receive bleaching treatment and was stored in deionized water. Final assessments were performed, and data were analyzed by two-way analysis of variance and Tukey tests (p<0.05). Color changes were significant for different tested bleaching therapies (p<0.0001), with the greatest color change observed for 35% hydrogen peroxide gel. No difference in opacity was detected for all analyzed parameters. Fluorescence changes were influenced by composite resin brand (p<0.0001) and bleaching therapy (p=0.0016) used. No significant differences in fluorescence between different bleaching gel concentrations were detected by Tukey test. The greatest fluorescence alteration was detected on the brand Z350. It was concluded that 35% hydrogen peroxide bleaching gel generated the greatest color change among all evaluated materials. No statistical opacity changes were detected for all tested variables, and significant fluorescence changes were dependent on the material and bleaching therapy, regardless of the gel concentration.

Causality assessment of adverse drug reactions: comparison of the results obtained from published decisional algorithms and from the evaluations of an expert panel, according to different levels of imputability.

OBJECTIVES: To evaluate agreement between causality assessments of reported adverse drug reactions (ADRs) obtained from decisional algorithms, with those obtained from an expert panel using the WHO global introspection method (GI), according to different levels of imputability and to evaluate the influence of confounding variables. METHOD: Two hundred reports were included in this study. An independent researcher used decisional algorithms, while an expert panel assessed the same ADR reports using the GI, both aimed at evaluating causality. Reports were divided according to the presence, absence or lack of information on confounding variables. RESULTS: The rates of concordance between assessments made using the algorithms and GI according to levels of imputability were: 45% for 'certain', 61% for 'probable', 46% for 'possible' and 17% for drug unrelated terms. When confounding variables were taken into account, the rates of concordance for the 'absence of information', 'lack of information' and 'presence of confounding variables' in the 'certain' group were 49, 69 and 7%, respectively. The corresponding values for the 'probable' group were 80, 68 and 24% and 30, 51 and 51%, respectively for the 'possible' group. CONCLUSION: Full agreement with global introspection was not found for any level of causality assessment. Confounding variables were found to be associated with low levels of agreement between decision algorithms and the GI method compromising the algorithms' sensitivity and specificity.

Synaptosomal GABA release as influenced by valerian root extract--involvement of the GABA carrier.

The effect of an aqueous extract obtained from the roots of Valeriana officinalis was investigated on the uptake and release of GABA in synaptosomes isolated from rat brain cortex. Aqueous extract of valerian inhibited the uptake and stimulated the release of [3H]GABA, either in the absence or in the presence of K+ depolarization. The release was Na(+)-dependent and independent of the presence of Ca2+ in the external medium. It is concluded that valerian extract releases [3H]GABA by reversal of the GABA carrier, which is Na(+)-dependent and Ca(2+)-independent. This increase in [3H]GABA release appears to be independent from Na(+)-K(+)-ATPase activity and the membrane potential.

In vitro study on the interaction of Valeriana officinalis L. extracts and their amino acids on GABAA receptor in rat brain.

This work studied in vitro the interaction of aqueous and hydroalcoholic extracts of Valeriana officinalis L. and compounds that are present in the extracts (amino acids and valerenic acid) with the GABAA (gamma-aminobutyric acid) receptor, using the [3H] muscimol binding technique to crude synaptic membranes from rat brain cortices. Both extracts displaced [3H]muscimol bound and this effect is probably due only to their amino acid content, specially GABA. This fact explains the in vitro effect of valerian extracts on GABAA receptor but not their sedative effect.

Acute changes in dopamine release and turnover in rat caudate nucleus following a single dose of methamphetamine.

Acute changes in dopamine (DA) turnover were studied in the caudate nucleus (CN) of adult male rats between 0-24 h after a single injection of Methamphetamine (20 mg/kg, ip). A single dose of METH-induced an increase in DA turnover [(DOPAC + HVA)/DA] concomitant with an acute DA release followed by transient DA and DOPAC depletion in the rat CN.