Improved Working Memory but No Effect on Striatal Vesicular Monoamine Transporter Type 2 after Omega-3 Polyunsaturated Fatty Acid Supplementation

Studies in rodents indicate that diets deficient in omega-3 polyunsaturated fatty acids (n–3 PUFA) lower dopamine neurotransmission as measured by striatal vesicular monoamine transporter type 2 (VMAT2) density and amphetamine-induced dopamine release. This suggests that dietary supplementation with fish oil might increase VMAT2 availability, enhance dopamine storage and release, and improve dopamine-dependent cognitive functions such as working memory. To investigate this mechanism in humans, positron emission tomography (PET) was used to measure VMAT2 availability pre- and post-supplementation of n–3 PUFA in healthy individuals. Healthy young adult subjects were scanned with PET using [¹¹C]-(+)-α-dihydrotetrabenzine (DTBZ) before and after six months of n–3 PUFA supplementation (Lovaza, 2 g/day containing docosahexaenonic acid, DHA 750 mg/d and eicosapentaenoic acid, EPA 930 mg/d). In addition, subjects underwent a working memory task (n-back) and red blood cell membrane (RBC) fatty acid composition analysis pre- and post-supplementation. RBC analysis showed a significant increase in both DHA and EPA post-supplementation. In contrast, no significant change in [¹¹C]DTBZ binding potential (BP_ND) in striatum and its subdivisions were observed after supplementation with n–3 PUFA. No correlation was evident between n–3 PUFA induced change in RBC DHA or EPA levels and change in [¹¹C]DTBZ BP_ND in striatal subdivisions. However, pre-supplementation RBC DHA levels was predictive of baseline performance (i.e., adjusted hit rate, AHR on 3-back) on the n-back task (y = 0.19+0.07, r² = 0.55, p = 0.009). In addition, subjects AHR performance improved on 3-back post-supplementation (pre 0.65±0.27, post 0.80±0.15, p = 0.04). The correlation between n-back performance, and DHA levels are consistent with reports in which higher DHA levels is related to improved cognitive performance. However, the lack of change in [¹¹C]DBTZ BP_ND indicates that striatal VMAT2 regulation is not the mechanism of action by which n–3 PUFA improves cognitive performance.     

Acute Effects of Typical and Atypical Antipsychotic Drugs on the Release of Dopamine from Prefrontal Cortex, Nucleus Accumbens, and Striatum of the Rat: An In Vivo Microdialysis Study

In vivo microdialysis has been used to study the acute effects of antipsychotic drugs on the extracellular level of dopamine from the nucleus accumbens, striatum, and prefrontal cortex of the rat. (-)-Sulpiride (20, 50, and 100 mg/kg i.v.) and haloperidol (0.1 and 0.5 mg/kg i.v.) enhanced the outflow of dopamine in the striatum and nucleus accumbens. In the medial prefrontal cortex, (-)-sulpiride at all doses tested did not significantly affect the extracellular level of dopamine. The effect of haloperidol was also attenuated in the medial prefrontal cortex; 0.1 mg/kg did not increase the outflow of dopamine and the effect of 0.5 mg/kg haloperidol was of shorter duration in the prefrontal cortex than that observed in striatum and nucleus accumbens. The atypical antipsychotic drug clozapine (5 and 10 mg/kg) increased the extracellular concentration of dopamine in all three regions. In contrast to the effects of sulpiride and haloperidol, that of clozapine in the medial prefrontal cortex was profound. These data suggest that different classes of antipsychotic drugs may have distinct effects on the release of dopamine from the nigrostriatal, mesolimbic, and mesocortical terminals.     

Excitatory Amino Acid Receptors in the Ventral Tegmental Area Regulate Dopamine Release in the Ventral Striatum

Abstract: The role of excitatory amino acid (EAA) receptors located in the ventral tegmental area (VTA) in tonic and phasic regulation of dopamine release in the ventral striatum was investigated. Microdialysis in conscious rats was used to assess dopamine release primarily from the nucleus accumbens shell region of the ventral striatum while applying EAA antagonists or agonists to the VTA. Infusion of the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (25 and 100 µ M ) into the VTA did not affect dopamine release in the ventral striatum. In contrast, intra-VTA infusion of the NMDA receptor antagonist 2-amino-5-phosphopentanoic acid (100 and 500 µ M ) dose-dependently decreased the striatal release of dopamine. Intra-VTA application of the ionotropic EAA receptor agonists NMDA and AMPA dose-dependently (10 and 100 µ M ) increased dopamine efflux in the ventral striatum. However, infusion of 50 or 500 µ M trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD), a metabotropic EAA receptor agonist, did not significantly affect these levels. These data suggest that NMDA receptors in the VTA exert a tonic excitatory influence on dopamine release in the ventral striatum. Furthermore, dopamine neurotransmission in this region may be enhanced by activation of NMDA and AMPA receptors, but not ACPD-sensitive metabotropic receptors, located in the VTA. These data further suggest that EAA regulation of dopamine release primarily occurs in the VTA as opposed to presynaptically at the terminal level.     

Biocompatible scaffolds based on collagen and oxidized dextran for endothelial cell survival and function in tissue engineering

Angiogenesis is a vital step in tissue regeneration. Hence, the current study aimed to prepare oxidized dextran (Odex)/collagen (Col)-hydrogels with laminin (LMN), as an angiogenic extracellular matrix (ECM) component, for promoting human umbilical vein endothelial cell (HUVEC) proliferation and function. Odex/Col scaffolds were constructed at various concentrations and temperatures. Using oscillatory rheometry, scanning electron microscopy (SEM), and cell viability testing, the scaffolds were characterized, and then HUVEC proliferation and function was compared with or without LMN. The gelation time could be modified by altering the Odex/Col mass ratio as well as the temperature. SEM showed that Odex/Col hydrogels had a more regular three-dimensional (3D) porous structure than the Col hydrogels. Moreover, HUVECs grew faster in the Col scaffold (12 mg/mL), whereas the Odex (30 mg/mL)/Col (6 mg/mL) scaffold exhibited the lowest apoptosis index. Furthermore, the expression level of vascular endothelial growth factor (VEGF) mRNA in the group without LMN was higher than that with LMN, and the Odex (30 mg/mL)/Col (6 mg/mL) scaffold without LMN had the highest VEGF protein secretion, allowing the cells to survive and function effectively. Odex/Col scaffolds, with or without LMN, are proposed as a tissue engineering construct to improve HUVEC survival and function for angiogenesis.     

Enhancement of nitrogen release properties of urea–kaolinite fertilizer with chitosan binder

The use of controlled release fertilizer (CRF) has become a new trend to minimize environmental pollution. In this study, urea–kaolinite containing 20 wt% urea after one hour dry grinding was mixed with different concentrations of chitosan as a binder to prepare nitrogen-based CRF. Fourier transform infrared spectroscopy confirmed the hydrogen bonding between urea and kaolinite. Covalent interaction between urea–kaolinite and chitosan make the granules stronger. The nitrogen release was measured in 5 days interval using a diacetylmonoxime calorimetric method at a wavelength of 527 nm. The results illustrated that by increasing the chitosan concentration from 3 to 7.5%, nitrogen release decreased from 41.23 to 25.25% after one day and from 77.31 to 59.27% after 30 days incubation in water. Compressive stress at break tests confirmed that granules with chitosan 6% had the highest resistance and were chosen for ammonia volatilization tests. Ammonia volatilization was carried out using the forced-draft technique for a period of 10 weeks. The results showed that the total amount of ammonia loss for conventional urea fertilizer and urea–kaolinite–chitosan granules was 68.63 and 56.75%, respectively. This controlled release product could be applied in agricultural crop production purpose due to its controlled solubility in the soil, high nutrient use efficiency and potential economic benefits.     

Beta-arrestin and Mdm2 mediate IGF-1 receptor-stimulated ERK activation and cell cycle progression

Beta-arrestin1, which regulates many aspects of seven transmembrane receptor (7TMR) biology, has also been shown to serve as an adaptor, which brings Mdm2, an E3 ubiquitin ligase to the insulin-like growth factor-1 receptor (IGF-1R), leading to its proteasome-dependent destruction. Here we demonstrate that IGF-1R stimulation also leads to ubiquitination of beta-arrestin1, which regulates vesicular trafficking and activation of ERK1/2. This beta-arrestin1-dependent ERK activity can occur even when the classical tyrosine kinase signaling is impaired. siRNA-mediated suppression of beta-arrestin1 in human melanoma cells ablates IGF-1-stimulated ERK and prolongs the G1 phase of the cell cycle. These data suggest that beta-arrestin-dependent ERK signaling by the IGF-1R regulates cell cycle progression and may thus be an important regulator of the growth of normal and malignant cells.     

Preparation of superparamagnetic iron oxide/doxorubicin loaded chitosan nanoparticles as a promising glioblastoma theranostic tool

Theranostic nanoparticles (NPs) are promising for opening new windows toward personalized disease management. Using a single particle capable of both diagnosis and drug delivery, is the major benefit of such particles. In the present study, chitosan NPs were used as a dual action carrier for doxorubicin (DOX; chemotherapeutic agent) and superparamagnetic iron oxide nanoparticles (SPIONs; imaging agent). SPIONs and DOX were loaded at different concentrations within poly-l -arginine-chitosan-triphosphate matrix (ACSD) using the ionic gelation method. NPs’ size were in the range of 184.33 ± 4.4 nm. Drug release analysis of DOX loaded NPs (NP-DOX) showed burst release at pH 5.5 (as in tumor environment) and slow release at pH 7.4 (physiological condition), demonstrating pH-sensitive drug release profile. NP-DOX internalization was confirmed by flowcytometry and fluorescent microscopy. Uptake process results were corroborated by accumulation of drug in the intracellular space. Iron content was evaluated by inductively coupled plasma and prussian blue staining. In vitro magnetic resonance imaging (MRI) showed a decline in T ₂ relaxation times by increasing iron concentration. MRI analysis also confirmed uptake of NPs at the optimum concentration in C6 glioma cells. In conclusion, ACSD NPs could be utilized as a promising theranostic formulation for both diagnosis and treatment of glioblastoma.     

Control of proteolysis by norepinephrine and insulin in brown adipocytes: role of ATP,phosphatidylinositol 3-kinase,and p70 S6K

The objective of this study was to evaluate some of the mechanisms by which norepinephrine (NE) and insulin may influence protein degradation in mouse brown adipocytes differentiated in cultures. The effects of NE and insulin, alone or in combination, on three factors known to influence proteolysis (maintenance of cell ATP and 1-phosphatidylinositol 3-kinase (PI 3-kinase) and p70 ribosomal S6-kinase (p70 S6K) activities) were examined. It was proposed that NE affects proteolysis indirectly by decreasing cell ATP from activation of uncoupling protein-1 (UCP1)-dependent mitochondrial respiration. This was tested by comparing the effects of NE and fatty acids (which directly activate UCP1) on proteolysis in brown adipocytes, as well as in pre-adipocytes and 3T3-L1 adipocytes, which do not express UCP1. An inhibitory effect of insulin on proteolysis is observed in both pre-adipocytes and differentiated cells, whereas NE and exogenously added fatty acids inhibit proteolysis only in brown adipocytes. There is a linear relationship between reductions in cell ATP and proteolysis in response to increasing concentrations of NE or fatty acids. PI 3-kinase activity is required for proteolysis, because two selective inhibitors (wortmannin and LY294002) reduce proteolysis in both pre-adipocytes and differentiated cells. This effect is not additive to that of NE, which suggests they affect the same proteolytic pathway. In contrast to NE, insulin increases PI 3-kinase activity and phosphorylation of p70 S6K. Rapamycin, which prevented insulin-dependent increase in phosphorylation of p70 S6K, increases proteolysis in brown adipocytes and antagonizes the inhibitory effect of insulin on proteolysis, but not the inhibitory effect of NE. Thus, insulin inhibits proteolysis via rapamycin-sensitive activation of p70 S6K, whereas the effect of NE appears largely to be a function of decreasing cell ATP content.