Anti-GD1a antibody targeted disruption of the node of Ranvier in a mouse model of acute motor axonal neuropathy

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McGonigal, Rhona ; Willison, H.J.

University:University of Glasgow

Department:Institute of Neuroscience and Psychology

关键词: GD1a ganglioside, node of Ranvier, complement, calpain, acute motor axonal neuropathy;   

Others  :  http://theses.gla.ac.uk/1453/1/2009McGonigalPhD.pdf

来源: University of Glasgow

【 摘 要 】

Guillain-Barré syndrome (GBS) is a peripheral neuropathy characterised byacute flaccid paralysis. The axonal variant is associated with anti-GD1aganglioside antibody-dependent, complement-mediated injury to the peripheralaxon with conduction block. The blood-nerve barrier (BNB) relatively protectsaxons from factors in the extra-neural environment; however, it does not extendover the neuromuscular junction, leaving this terminal portion of the axonunprotected. It is here that susceptibility to antibody attack in a mouse model ofGBS has previously been demonstrated. It was the aim of this thesis todetermine to what extent more proximal portions of the distal axon are at riskfrom circulating antibody and what exogenous protection can be providedtherapeutically.GD1a is expressed at the nodes of Ranvier (NoR) of intramuscular axons.To investigate the injury caused by anti-GD1a antibodies in relation to BNBpermeability, anti-GD1a antibodies were applied to mice genetically engineeredboth to over-express GD1a and to express cyan fluorescent protein (CFP) in thecytoplasm of axons. Endogenous fluorescence allowed identification ofintramuscular nerve bundles and their terminal branches, which werecategorized depending on bundle size. Within these categories, IgG and the finalproduct of the complement pathway (membrane attack complex, MAC)deposition were quantified after an acute injury, alongside the deleteriouseffects on NoR protein’s. Nerve conduction studies were also performed tobetter elucidate the pathological pathway.IgG and MAC were localized in a gradient-dependent manner, withsignificantly more deposition at NoR as the bundles progressively branch to asingle terminating fibre. Furthermore, MAC deposition was associated with theloss or disruption to immunostaining for nodal protein’s including voltage gatedsodium channel and ankyrin G. This is indicative of targeted injury to this regionof the distal axon in an acute model. The loss of nodal protein staining isassociated with the activation of complement and the Ca2+-dependent proteasecalpain as determined by the protection of staining by the complement inhibitorEculizumab and the calpain inhibitor AK295. A similar disruption to nodal proteinstaining is also shown at the proximal NoR of the desheathed phrenic nerve.Extracellular nerve recordings demonstrate a detrimental effect onfunction as there is a decrease in the peak of the compound nerve actionpotential over time, which can be associated with Nav channel staining loss.This study is suggestive of a resilient proximal barrier that becomes morepermeable towards the nerve terminal. Therefore, it is not only the axon at theterminal that can be a target of injury, but also the distal axons at their nodesof Ranvier, resulting in disruption at this site. Prevention of staining loss byEculizumab and AK295 exemplify the route of injury and identify a potentialpoint of therapeutic intervention in human disease.