Specific ion channels contribute to key elements of pathology during secondary degeneration following neurotrauma

Background: Following partial injury to the central nervous system, cells beyond the initial injury site undergo secondary degeneration, exacerbating loss of neurons, compact myelin and function. Changes in Ca 2+ flux are associated with metabolic and structural changes, but it is not yet clear how flux through specific ion channels contributes to the various pathologies. Here, partial optic nerve transection in adult female rats was used to model secondary degeneration. Treatment with combinations of three ion channel inhibitors was used as a tool to investigate which elements of oxidative and structural damage related to long term functional outcomes. The inhibitors employed were the voltage gated Ca 2+ channel inhibitor Lomerizine (Lom), the Ca 2+ permeable AMPA receptor inhibitor YM872 and the P2X 7 receptor inhibitor oxATP. Results: Following partial optic nerve transection, hyper-phosphorylation of Tau and acetylated tubulin immunoreactivity were increased, and Nogo-A immunoreactivity was decreased, indicating that axonal changes occurred acutely. All combinations of ion channel inhibitors reduced hyper-phosphorylation of Tau and increased Nogo-A immunoreactivity at day 3 after injury. However, only Lom/oxATP or all three inhibitors in combination significantly reduced acetylated tubulin immunoreactivity. Most combinations of ion channel inhibitors were effective in restoring the lengths of the paranode and the paranodal gap, indicative of the length of the node of Ranvier, following injury. However, only all three inhibitors in combination restored to normal Ankyrin G length at the node of Ranvier. Similarly, HNE immunoreactivity and loss of oligodendrocyte precursor cells were only limited by treatment with all three ion channel inhibitors in combination. Conclusions: Data indicate that inhibiting any of a range of ion channels preserves certain elements of axon and node structure and limits some oxidative damage following injury, whereas ionic flux through all three channels must be inhibited to prevent lipid peroxidation and preserve Ankyrin G distribution and OPCs

Three Ca2+ channel inhibitors in combination limit chronic secondary degeneration following neurotrauma

Following neurotrauma, cells beyond the initial trauma site undergo secondary degeneration, with excess Ca 2+ a likely trigger for loss of neurons, compact myelin and function. Treatment using inhibitors of specific Ca 2+ channels has shown promise in preclinical studies, but clinical trials have been disappointing and combinatorial approaches are needed. We assessed efficacy of multiple combinations of three Ca 2+ channel inhibitors at reducing secondary degeneration following partial optic nerve transection in rat. We used lomerizine to inhibit voltage gated Ca 2+ channels; oxidised adenosine-triphosphate (oxATP) to inhibit purinergic P2X 7 receptors and/or 2-[7-(1H-imidazol-1-yl)-6-nitro-2,3-dioxo-1,2,3,4- tetrahydro quinoxalin-1-yl]acetic acid (INQ) to inhibit Ca 2+ permeable a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Only the three Ca 2+ channel inhibitors delivered in combination significantly preserved visual function, as assessed using the optokinetic nystagmus visual reflex, at 3 months after injury. Preservation of retinal ganglion cells was partial and is unlikely to have accounted for differential effects on function. A range of the Ca 2+ channel inhibitor combinations prevented swelling of optic nerve vulnerable to secondary degeneration. Each of the treatments involving lomerizine significantly increased the proportion of axons with normal compact myelin. Nevertheless, limiting decompaction of myelin was not sufficient for preservation of function in our model. Multiple combinations of Ca 2+ channel inhibitors reduced formation of atypical node/paranode complexes; outcomes were not associated with preservation of visual function. However, prevention of lengthening of the paranodal gap that was only achieved by treatment with the three Ca 2+ channel inhibitors in combination was an important additional effect that likely contributed to the associated preservation of the optokinetic reflex using this combinatorial treatment strategy

Ubiquitous Web Application Development - A Framework for Understanding

E-commerce and m-commerce have dramatically boosted the demand for services which enable ubiquitous access. Ubiquity with its anytime/anywhere/anymedia nature requiring contextaware computing and personalisation calls for new engineering techniques supporting these kind of services. In this paper, we propose the notion of customisation as the uniform mechanism to provide the necessary flexibility with respect to both contextaware computing and personalisation. Customisation is realised in terms of a reflective architecture consisting of context, profile and customisation rule management

Myelin internode length following partial ON transection.

<p>Representative images of a single slice from the z stacks show ventral axons of control animals (A) and at 3 months following injury (B) anterogradely traced with CTB (green); paranodes are immunohistochemically labelled with Caspr and nodes with Nav1.6. C: The length of myelin internodes (indicated by <) under 110 µm were measured between paranodes (Caspr+ structures, red, confirmed by the presence of Nav1.6+ sodium channels, blue, at the node, indicated by brackets) and the data range, 25% and 75% percentile, median and mean (indicated by *) were displayed in the box plot. D: Mean number of internodes visible per FOV ± S.E (*p<0.05). Scale bar: 20 µm.</p

Proliferation of oligodendroglia subpopulations following partial ON transection.

<p>Oligodendroglia and other olig2+ glia were identified with antibodies to NG2 (A), olig2 (B) and Ki67 (C), or with CC1 (E), olig2 (F) and Ki67 (G). D: Cells indicated are Ki67+/NG2+/olig2+ (>) and Ki67−/NG2+/olig2+ (>>). H: Cells indicated are Ki67+/CC1+/olig2+ (>) and Ki67−/CC1+/olig2+ (>>). Proliferating Ki67+/IBA1+ cells (I, indicated by >) and to a lesser extent Ki67+/GFAP+ cells (J) were observed after injury; representative examples at 3 days shown. K–P: Quantification of the mean density ± S.E of oligodendroglia and other olig2+ glia populations following partial transection. Densities of Ki67– cells are represented by black bars while densities of Ki67+ cells are represented by red bars and differences from control indicated by Δ(p≤0.05). Overall differences in total density (combined Ki67+ and Ki67– values) compared to control are indicated by *(p≤0.05). Q: Summary graph of Ki67+ mean densities of all oligodendroglia and other olig2+ glia subpopulations. Scale bar A–H: 20 µm, I–J: 10 µm.</p

Oligodendroglia subpopulations of varying maturity in adult control ON.

<p>A: Schematic diagram illustrates changes in the expression of NG2 and CC1 markers, and olig2 transcription factor across oligodendroglia subpopulations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065710#pone.0065710-Nishiyama1" target="_blank">[24]</a>. Oligodendroglia and olig2+ glia were identified with combinations of antibodies to NG2 (B, D) and olig2 (C, D), or CC1 (E, G) and olig2 (F, G). D: Cells indicated are NG2+/olig2– (>), NG2+/olig2+ (>>) or NG2−/olig2+ (>l). G: Cells indicated are CC1+/olig2– (>) or CC1+/olig2+ (>>). H: Desmin+ cells (>) were not NG2+ (>>). Olig2 staining colocalises with Hoechst nuclear stain (I) and Nkx2.2+ nuclei (J). K: MBP+ myelin surrounds CC1+ oligodendrocyte somata. L: GFAP immunoreactivity surrounds some olig2+ nuclei (example >) but does not colocalise with CC1 (>>). M: Quantification of immunopositive oligodendroglia in control ON was expressed as the mean density of cells per mm² ± S.E. Scale bars: B–G: 20 µm, H–L: 10 µm.</p