Ether-A -go-go 1 (Eag1) Potassium Channel Expression in Dopaminergic Neurons of Basal Ganglia is Modulated by 6-Hydroxydopamine Lesion

The ether A go-go (Eag) gene encodes the voltage-gated potassium (K+) ion channel Kv10.1, whose function still remains unknown. As dopamine may directly affect K+ channels, we evaluated whether a nigrostriatal dopaminergic lesion induced by the neurotoxin 6-hydroxydopamine (6-OHDA) would alter Eag1-K+ channel expression in the rat basal ganglia and related brain regions. Male Wistar rats received a microinjection of either saline or 6-OHDA (unilaterally) into the medial forebrain bundle. The extent of the dopaminergic lesion induced by 6-OHDA was evaluated by apomorphine-induced rotational behavior and by tyrosine hydroxylase (TH) immunoreactivity. The 6-OHDA microinjection caused a partial or complete lesion of dopaminergic cells, as well as a reduction of Eag1+ cells in a manner proportional to the extent of the lesion. In addition, we observed a decrease in TH immunoreactivity in the ipsilateral striatum. In conclusion, the expression of the Eag1-K+-channel throughout the nigrostriatal pathway in the rat brain, its co-localization with dopaminergic cells and its reduction mirroring the extent of the lesion highlight a physiological circuitry where the functional role of this channel can be investigated. The Eag1-K+ channel expression in dopaminergic cells suggests that these channels are part of the diversified group of ion channels that generate and maintain the electrophysiological activity pattern of dopaminergic midbrain neurons.

Role of transient receptor potential vanilloid 4 in rat joint inflammation

Objective To determine whether activation of transient receptor potential vanilloid 4 (TRPV-4) induces inflammation in the rat temporomandibular joint (TMJ), and to assess the effects of TRPV-4 agonists and proinflammatory mediators, such as a protease-activated receptor 2 (PAR-2) agonist, on TRPV-4 responses. Methods Four hours after intraarticular injection of carrageenan into the rat joints, expression of TRPV-4 and PAR-2 in trigeminal ganglion (TG) neurons and in the TMJs were evaluated by real-time reverse transcriptionpolymerase chain reaction and immunofluorescence, followed by confocal microscopy. The functionality of TRPV-4 and its sensitization by a PAR-2activating peptide (PAR-2AP) were analyzed by measuring the intracellular Ca2+ concentration in TMJ fibroblast-like synovial cells or TG neurons. Plasma extravasation, myeloperoxidase activity, and the head-withdrawal threshold (index of mechanical allodynia) were evaluated after intraarticular injection of selective TRPV-4 agonists, either injected alone or coinjected with PAR-2AP. Results In the rat TMJs, TRPV-4 and PAR-2 expression levels were up-regulated after the induction of inflammation. Two TRPV-4 agonists specifically activated calcium influx in TMJ fibroblast-like synovial cells or TG neurons. In vivo, the agonists triggered dose-dependent increases in plasma extravasation, myeloperoxidase activity, and mechanical allodynia. In synovial cells or TG neurons, pretreatment with PAR-2AP potentiated a TRPV-4 agonistinduced increase in [Ca2+]i. In addition, TRPV-4 agonistinduced inflammation was potentiated by PAR-2AP in vivo. Conclusion In this rat model, TRPV-4 is expressed and functional in TG neurons and synovial cells, and activation of TRPV-4 in vivo causes inflammation in the TMJ. Proinflammatory mediators, such as PAR-2 agonists, sensitize the activity of TRPV-4. These results identify TRPV-4 as an important signal of inflammation in the joint.

Morphological Alterations in Newly Born Dentate Gyrus Granule Cells That Emerge after Status Epilepticus Contribute to Make Them Less Excitable

Computer simulations of external current stimulations of dentate gyrus granule cells of rats with Status Epilepticus induced by pilocarpine and control rats were used to evaluate whether morphological differences alone between these cells have an impact on their electrophysiological behavior. The cell models were constructed using morphological information from tridimensional reconstructions with Neurolucida software. To evaluate the effect of morphology differences alone, ion channel conductances, densities and distributions over the dendritic trees of dentate gyrus granule cells were the same for all models. External simulated currents were injected in randomly chosen dendrites belonging to one of three different areas of dentate gyrus granule cell molecular layer: inner molecular layer, medial molecular layer and outer molecular layer. Somatic membrane potentials were recorded to determine firing frequencies and inter-spike intervals. The results show that morphologically altered granule cells from pilocarpine-induced epileptic rats are less excitable than control cells, especially when they are stimulated in the inner molecular layer, which is the target area for mossy fibers that sprout after pilocarpine-induced cell degeneration. This suggests that morphological alterations may act as a protective mechanism to allow dentate gyrus granule cells to cope with the increase of stimulation caused by mossy fiber sprouting.

Crotamine Pharmacology Revisited: Novel Insights Based on the Inhibition of K-V Channels

Crotamine, a 5-kDa peptide, possesses a unique biological versatility. Not only has its cell-penetrating activity become of clinical interest but, moreover, its potential selective antitumor activity is of great pharmacological importance. In the past, several studies have attempted to elucidate the exact molecular target responsible for the crotamine-induced skeletal muscle spasm. The aim of this study was to investigate whether crotamine affects voltage-gated potassium (K-V) channels in an effort to explain its in vivo effects. Crotamine was studied on ion channel function using the two-electrode voltage clamp technique on 16 cloned ion channels (12 K-V channels and 4 Na-V channels), expressed in Xenopus laevis oocytes. Crotamine selectively inhibits K-V 1.1, K-V 1.2, and K-V 1.3 channels with an IC50 of similar to 300 nM, and the key amino acids responsible for this molecular interaction are suggested. Our results demonstrate for the first time that the symptoms, which are observed in the typical crotamine syndrome, may result from the inhibition of K-V channels. The ability of crotamine to inhibit the potassium current through K-V channels unravels it as the first snake peptide with the unique multifunctionality of cell-penetrating and antitumoral activity combined with K-V channel-inhibiting properties. This new property of crotamine might explain some experimental observations and opens new perspectives on pharmacological uses.

Signal transduction in Plasmodium-Red Blood Cells interactions and in cytoadherence

Malaria is responsible for more than 1.5 million deaths each year, especially among children (Snow et al. 2005). Despite of the severity of malaria situation and great effort to the development of new drug targets (Yuan et al. 2011) there is still a relative low investment toward antimalarial drugs. Briefly there are targets classes of antimalarial drugs currently being tested including: kinases, proteases, ion channel of GPCR, nuclear receptor, among others (Gamo et al. 2010). Here we review malaria signal transduction pathways in Red Blood Cells (RBC) as well as infected RBCs and endothelial cells interactions, namely cytoadherence. The last process is thought to play an important role in the pathogenesis of severe malaria. The molecules displayed on the surface of both infected erythrocytes (IE) and vascular endothelial cells (EC) exert themselves as important mediators in cytoadherence, in that they not only induce structural and metabolic changes on both sides, but also trigger multiple signal transduction processes, leading to alteration of gene expression, with the balance between positive and negative regulation determining endothelial pathology during a malaria infection.

NIR luminescent Er3+/Yb3+ co-doped SiO2-ZrO2 nanostructured planar and channel waveguides: Optical and structural properties

Optical and structural properties of planar and channel waveguides based on sol gel Er3+ and Yb3+ co-doped SiO2-ZrO2 are reported. Microstructured channels with high homogeneous surface profile were written onto the surface of multilayered densified films deposited on SiO2/Si substrates by a femtosecond laser etching technique. The densification of the planar waveguides was evaluated from changes in the refractive index and thickness, with full densification being achieved at 900 degrees C after annealing from 23 up to 500 min, depending on the ZrO2 content Crystal nucleation and growth took place together with densification, thereby producing transparent glass ceramic planar waveguides containing rare earth-doped ZrO2 nanocrystals dispersed in a silica-based glassy host Low roughness and crack-free surface as well as high confinement coefficient were achieved for all the compositions. Enhanced NIR luminescence of the Er3+ ions was observed for the Yb3+- codoped planar waveguides, denoting an efficient energy transfer from the Yb3+ to the Er3+ ion. (C) 2012 Elsevier B.V. All rights reserved.