gq1b-ganglioside and Disease-Models--Animal

Topics: Animals; Autoantibodies; Autoimmunity; Biomarkers; Disease Models, Animal; Epitopes; Gangliosides; Humans; Immunoglobulin G; Immunoglobulins, Intravenous; Miller Fisher Syndrome; Myelin Sheath; Neuromuscular Junction; Neurons, Afferent; Ophthalmoplegia; Plasmapheresis

Brain-derived neurotrophic factor (BDNF) plays crucial roles in memory impairments including Alzheimer's disease (AD). Previous studies have reported that tetrasialoganglioside GQ1b is involved in long-term potentiation and cognitive functions as well as BDNF expression. However, in vitro and in vivo functions of GQ1b against AD has not investigated yet. Consequently, treatment of oligomeric Aβ followed by GQ1b significantly restores Aβ

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Brain-Derived Neurotrophic Factor; Cells, Cultured; Cognitive Dysfunction; Disease Models, Animal; Gangliosides; Hippocampus; Mice, Transgenic; Neurons; Rats; tau Proteins; Up-Regulation

The neuromuscular junction is a tripartite synapse composed of the presynaptic nerve terminal, the muscle and perisynaptic Schwann cells. Its functionality is essential for the execution of body movements and is compromised in a number of disorders, including Miller Fisher syndrome, a variant of Guillain-Barré syndrome: this autoimmune peripheral neuropathy is triggered by autoantibodies specific for the polysialogangliosides GQ1b and GT1a present in motor axon terminals, including those innervating ocular muscles, and in sensory neurons. Their binding to the presynaptic membrane activates the complement cascade, leading to a nerve degeneration that resembles that caused by some animal presynaptic neurotoxins. Here we have studied the intra- and inter-cellular signaling triggered by the binding and complement activation of a mouse monoclonal anti-GQ1b/GT1a antibody to primary cultures of spinal cord motor neurons and cerebellar granular neurons. We found that a membrane attack complex is rapidly assembled following antibody binding, leading to calcium accumulation, which affects mitochondrial functionality. Consequently, using fluorescent probes specific for mitochondrial hydrogen peroxide, we found that this reactive oxygen species is rapidly produced by mitochondria of damaged neurons, and that it triggers the activation of the MAP kinase pathway in Schwann cells. These results throw light on the molecular and cellular pathogenesis of Miller Fisher syndrome, and may well be relevant to other pathologies of the motor axon terminals, including some subtypes of the Guillain Barré syndrome.

Topics: Animals; Cells, Cultured; Cerebellum; Coculture Techniques; Disease Models, Animal; Evoked Potentials; Gangliosides; Hydrogen Peroxide; Immunoglobulin G; Male; Mice; Miller Fisher Syndrome; Mitochondria; Neuromuscular Junction; Neurons; Presynaptic Terminals; Schwann Cells; Signal Transduction; Vesicular Acetylcholine Transport Proteins

The ganglioside GQ1b facilitates the influx of Ca2+ in brain synaptosomes and enhances ATP-induced long-term potentiation in hippocampal slices. Anti-GQ1b antibody impairs the function of peripheral neurons, for example, it had pathogenic effects on presynaptic neuronal membranes and perisynaptic Schwann cells in a mouse model of Guillain-Barré syndrome. The present study demonstrated in vivo that the level of endogenous GQ1b was relevant to neural function in the brain, in that it increased following seizures in amygdaloid kindling mice. GQ1b is subject to epileptogenic regulation and may play a role in the development of epilepsy.

Topics: Amygdala; Animals; Disease Models, Animal; Epilepsy; Gangliosides; Growth Cones; Hippocampus; Kindling, Neurologic; Lipid Metabolism; Male; Mice; Mice, Inbred C57BL; Nerve Fibers, Myelinated; Neuronal Plasticity; Neurons; Up-Regulation

Anti-GQ1b ganglioside antibodies are the serological hallmark of the Miller Fisher syndrome (MFS) variant of the paralytic neuropathy, Guillain-Barré syndrome, and are believed to be the principal pathogenic mediators of the disease. In support of this, we previously showed in an in vitro mouse model of MFS that anti-GQ1b antibodies were able to bind and disrupt presynaptic motor nerve terminals at the neuromuscular junction (NMJ) as one of their target sites, thereby causing muscle paralysis. This injury only occurred through activation of complement, culminating in the formation and deposition of membrane attack complex (MAC, C5b-9) in nerve membranes. Since this step is crucial to the neuropathic process and an important convergence point for antibody and complement mediated membrane injury in general, it forms an attractive pharmacotherapeutic target. Here, we assessed the efficacy of the humanized monoclonal antibody eculizumab, which blocks the formation of human C5a and C5b-9, in preventing the immune-mediated motor neuropathy exemplified in this model. Eculizumab completely prevented electrophysiological and structural lesions at anti-GQ1b antibody pre-incubated NMJs in vitro when using normal human serum (NHS) as a complement source. In a novel in vivo mouse model of MFS generated through intraperitoneal injection of anti-GQ1b antibody and NHS, mice developed respiratory paralysis due to transmission block at diaphragm NMJs, resulting from anti-GQ1b antibody binding and complement activation. Intravenous injection of eculizumab effectively prevented respiratory paralysis and associated functional and morphological hallmarks of terminal motor neuropathy. We show that eculizumab protects against complement-mediated damage in murine MFS, providing the rationale for undertaking clinical trials in this disease and other antibody-mediated neuropathies in which complement activation is believed to be involved.

Topics: Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Complement Activation; Disease Models, Animal; Drug Evaluation, Preclinical; Gangliosides; Male; Mice; Mice, Inbred BALB C; Miller Fisher Syndrome; Muscle Contraction; Nervous System Autoimmune Disease, Experimental; Neuromuscular Junction; Respiratory Paralysis; Synapses; Tissue Culture Techniques

Anti-GQ1b antibodies are present in the Miller Fisher syndrome (MFS), a monophasic neuropathy characterized by ataxia, areflexia, ophthalmoplegia, and sometimes cranial muscle weakness. We have previously shown, at the mouse neuromuscular junction (NMJ) ex vivo, that anti-GQ1b antibodies, through complement classic pathway activation, block synaptic transmission in a way that resembles the effect of the pore-forming alpha-latrotoxin (alphaLTx). In order to clarify the mechanism of these alphaLTx-like effects, including possible involvement of the alternative and mannose-binding protein complement pathways, we studied the effects of concanavalin A (ConA), a lectin known to block the action of alphaLTx, immunoglobulins, and early complement components. With electrophysiological, immunohistological, and bioassay experiments, we showed that the alphaLTx-like effects of anti-GQ1b antibody and complement were inhibited by pre- and coincubation with ConA. However, ConA was not able to inhibit evolution of alphaLTx-like effects when coincubated upon addition of complement at NMJs that had already bound anti-GQ1b antibody. Our data suggest that the mannose-binding protein pathway is not involved in the alphaLTx-like effect and that the inhibiting effect of ConA principally arises through interference with presynaptic binding of anti-GQ1b antibody. In control experiments, ConA prevented the neuroexocytotic effects of alphaLTx, indicating that alphaLTx receptors were inhibited under these conditions. We conclude that, although the physiological effects at the NMJ of anti-GQ1b antibody and alphaLTx are very similar, the activity of anti-GQ1b antibody is not mediated through activation of alphaLTx receptors, but rather is caused by direct presynaptic membrane damage through classic complement pathway activation.

Topics: Animals; Autoantibodies; Binding Sites; Binding, Competitive; Complement System Proteins; Concanavalin A; Disease Models, Animal; Gangliosides; Male; Mice; Miller Fisher Syndrome; Neuromuscular Junction; Protein Binding; Receptors, Peptide; Spider Venoms; Synaptic Membranes; Synaptic Transmission

Miller-Fisher syndrome is an autoimmune neuropathy characterized by ataxia, areflexia and ophthalmoplegia, and in the majority of cases the presence of high titres of anti-GQ1b ganglioside antibodies. In an ex vivo model, human and mouse anti-GQ1b antibodies have been shown previously to induce a complement-dependent alpha-latrotoxin-like effect on the murine motor endplate, i.e. they bring about massive quantal release of acetylcholine and eventually block neuromuscular transmission. Using immunofluorescence microscopy with image analysis, we show here that the late stages of this electrophysiological effect temporally coincide with the loss of heavy neurofilament (200 kDa) and type III beta-tubulin immunostaining and structural breakdown of the nerve terminal, as demonstrated by electron microscopy. Ultrastructurally, axon terminals were disorganized, depleted of vesicles, and subdivided by the infiltrating processes of capping Schwann cells. These findings provide clear pathological evidence to support a role for anti-ganglioside antibodies in mediating nerve terminal injury and further advance the view that this site may be of importance as a target in some human neuropathies.

Topics: Alkaline Phosphatase; Animals; Autoantibodies; Complement Activation; Disease Models, Animal; Gangliosides; Image Processing, Computer-Assisted; In Vitro Techniques; Male; Mice; Microscopy, Electron; Microscopy, Fluorescence; Miller Fisher Syndrome; Motor Neurons; Neurofilament Proteins; Neuromuscular Junction; Phosphorylation; Schwann Cells; Synaptic Transmission; Tubulin