Erythropoietin protects sensory axons against paclitaxel-induced distal degeneration

Paclitaxel causes a sensory polyneuropathy with characteristic features of distal axonal degeneration. Although the exact mechanisms underlying distal axonal degeneration are unknown, paclitaxel-induced axonal degeneration has been shown to be associated with an increase in detyrosinated tubulin. Here we show that recombinant human erythropoietin prevents axonal degeneration in sensory neurons in vitro and this effect is associated with downregulation of detyrosinated tubulin. Furthermore, in an animal model of paclitaxel-induced distal sensory polyneuropathy, recombinant human erythropoietin protects against distal axonal degeneration. These findings suggest that recombinant human erythropoietin may be useful as a therapy to prevent paclitaxel-induced sensory polyneuropathy in patients undergoing chemotherapy.     

薄束轴索变性小鼠的轴索变性和Ubiquitin的相互关系

目的 探索ＧＡＤ小鼠中枢神经系统的轴索变性和Ｕｂｉｑｕｔｉｎ的相互关系。方法 用免疫组织化学染色方法。结果 在ＧＡＤ小鼠中枢神经系统的轴索变性部位,出现了多数Ｕｂｉｑｕｉｔｉｎ阳性的点状构造物。这种ＤＳ从９周龄开始,首先在构成薄束路和脊髓小脑后路的上行纤维的远端区域－薄束核区和小脑白质出现,逐渐按照延髓,颈髓,胸髓,腰髓的顺序,向细胞体方向逆行性地进展。１８周龄时波及到锥体路,３２周龄时进一步波及     

轴突变性在帕金森病发病中的作用

帕金森病(PD)是常见的中枢神经系统变性疾病,目前认为PD的主要病理变化是黑质多巴(dopamine,DA)能神经元的凋亡,因此研究重点集中在DA能神经元凋亡机制昨治疗方面,而轴突变性被认为是神经元死亡的佯随产物,长期未受到重视.     

Axonal degeneration distal to the site of accumulation of vesicular profiles in the myelinated fiber axon in experimental isoniazid neuropathy

Summary Morphometric sequential studies of pathologic changes were carried out on myelinated fibers in the lumbar ventral root of Sprague-Dawley rats administered with isoniazid, 1,500 mg/kg body weight, in a single dose. Accumulation of axoplasmic organelles with secondary paranodal retraction of myelin sheath occurred in the middle part of the ventral root as early as day 2 after the administration. On day 3, axonal degeneration started to occur, distal to the middle part, where the accumulation of axoplasmic organelles is prominent. Such accumulation with the possible blockade of the fast axoplasmic transport in the proximal axon may be directly responsible for the distal axonal degeneration. Alternatively such accumulation may be secondary to the distal axonal degeneration. The morphological sequential findings described clearly reflects the pathological events in isoniazid neuropathy.Supported in part by grants nos. 83-16 and 84-06 from the National Center of Nervous, Mental and Muscular Disorders (NCNMMD) of the Ministry of Health and Welfare, Japan     

Peripheral nerve lesion in spongy degeneration of the central nervous system

Summary This report describes a peripheral nerve lesion found in a case of spongy degeneration of the central nervous system. The lesion consisted of abnormal cellular infiltrates in the peri- and endoneurium, axonal changes, and demyelination. Possible relation of the lesion to that of the central nervous system is discussed.Supported by grant NB-02255 from the National Institutes of Health, United States Public Health Service.     

P2-peptide induced experimental allergic neuritis: a model to study axonal degeneration

Summary In experimental allergic neuritis (EAN) severity of clincal disease and pathology correlate with the dose of antigen (Hahn et al., Lab Invest 59:115–125, 1988). To avoid axonal membrane contamination of the antigen, EAN was induced with a synthetic peptide, corresponding to residues 53–78 of bovine P₂ myelin protein. Severity of EAN correlated with the dose of peptide in the inoculate. The relationship between demyelination, inflammation and axonal degeneration was studied. Low doses resulted in pure demyelination. Axonal degeneration occurred only with high doses of inflammation. The role of macrophages in producing axonal damage is discussed.Supported by a grant of the Muscular Dystrophy Association of Canada and the Medical Research Council of Canada     

Degenerative axonal swellings in the trigeminal ganglia of cattle

We examined the acidophilic oval structures which were frequently encountered in the trigeminal ganglia of cattle that clinically showed trigeminal disturbance. Histopathologically, these structures were composed of numerous fine granules and were generally located near the neuronal cell bodies. They were demonstrated in silver preparations and, using neuron-specific enolase, tau and ubiquitin antibodies. Electron microscopy revealed an accumulation of large membranous vesicles thought to be derived from the smooth endoplasmic reticulum of axons, a few degenerative mitochondria and non-membrane-bound osmiophilic debris. Such pathological alterations were consistent with degenerative axonal changes or enlargements, although the pathogenesis was not clear. It should be emphasized that such axonal degeneration is frequently observed as a nonspecific reaction in the trigeminal ganglia in various diseases that cause trigeminal failure in cattle. Received: 4 December 1995 / Revised: 16 January 1996 / Revised, accepted: 22 April 1996     

Toxic axonal degeneration occurs independent of neurofilament accumulation

Alteration of neurofilament (NF) proteins is considered a critical component and a causative factor for a number of neuropathologies, especially certain neurotoxicities. Correlative observations have supported this hypothesis; the current study tests this relationship by exposure of neurotoxicants to crayfish, a species lacking NFs. Morphological and immunological tests verified the absence of NFs in crayfish peripheral nerve axons. Tail injections of acrylamide (ACR), 2,5-hexanedione (2,5-HD), or 3,4-dimethyl-2,5-HD (3,4-DMHD) produced ataxia and paralysis. Morphological expression of axonal degeneration in a spatial and temporal pattern of progression comparable to mammalian species possessing NFs was observed. With gamma-diketones, time to onset was slower than observed in mammals but relative potency between neurotoxic analogues was maintained. Non-neurotoxic analogues failed to produce any functional signs of neurotoxicity. These data are consistent with the conclusion that NF accumulations are not cause-effect related to axonal degeneration in these models of neurotoxicity and raise questions as to the relationship between accumulation of NF proteins and axonal degeneration in other neuropathological conditions. Copyright © 1994 Wiley-Liss, Inc.     

帕金森小鼠多巴胺能神经元轴突变性研究

目的建立1-甲基-4-苯基-1,2,3,6-四氢吡啶(MPTP)诱导的大龄(32～36 w)小鼠帕金森病慢性模型,探讨其多巴胺能神经元轴突变性在帕金森病发病机制中的作用。方法应用免疫组织化学染色、Fluoro-Jade C染色等方法,观察MPTP诱导的小鼠黑质多巴胺能神经元轴突变性与胞体凋亡的时效性关系。结果慢性MPTP腹腔注射大龄小鼠可诱导产生典型且稳定的帕金森病症状,并可引起黑质-纹状体多巴胺能神经元的凋亡与轴突变性,但轴突变性在发生时间上早于细胞凋亡。结论轴突变性在帕金森病发病机制中起着十分重要的作用,帕金森病可能与神经元-轴突-神经胶质细胞网络损伤密切相关。     

Developmental defects and neuromuscular alterations due to mitofusin 2 gene (MFN2) silencing in zebrafish: a new model for Charcot-Marie-Tooth type 2A neuropathy

The development of new animal models is a crucial step in determining the pathological mechanism underlying neurodegenerative diseases and is essential for the development of effective therapies. We have investigated the zebrafish (Danio rerio) as a new model to study CMT2A, a peripheral neuropathy characterized by the selective loss of motor neurons, caused by mutations of mitofusin 2 gene. Using a knock-down approach, we provide evidence that during embryonic development, mitofusin 2 loss of function is responsible of several morphological defects and motility impairment. Immunohistochemical investigations, revealing the presence of severe alterations in both motor neurons and muscles fibres, indicated the central role played by MFN2 in axonal and neuromuscular development. Finally, we demonstrated the ability of human MFN2 to balance the downregulation of endogenous mfn2 in zebrafish, further supporting the conserved function of the MFN2 gene. These results highlight the essential role of mitofusin 2 in the motor axon development and demonstrate the potential of zebrafish as a suitable and complementary platform for dissecting pathogenetic mechanisms of MFN2 mutations in vivo.     

Motor unit remodelling in multifocal motor neuropathy: The importance of axonal loss

Objective

To estimate the degree of axonal loss in patients diagnosed with multifocal motor neuropathy (MMN) using a novel assessment of motor unit numbers and size.

Microangiopathy of endoneurial vessels in hypoxemic chronic obstructive pulmonary disease (COPD)

Summary A peripheral neuropathy has been reported in patients with chronic respiratory insufficiency due to chronic obstructive pulmonary disease (COPD). It is mainly characterized by axonal degeneration, secondary demyelination and abnormal endoneurial vessels. The pathogenesis of these lesions remains obscure. To investigate whether relationships exist between neuritic and vascular lesions, a qualitative and quantitative ultrastructural study was performed on nerve biopsies in 13 patients with chronic respiratory insufficiency due to COPD, and in 9 normal controls without pulmonary lesions. A computer-assisted multiple regression analysis taking into account clinical, electrophysiological, biological and morphometric parameters was performed. Statistically significant differences in the endoneurial structure of microvessels were: (1) thickening of the basement membrane; (2) narrowing of the lumen; (3) mural pericytic debris deposits, occurring in the COPD group. In the latter, hypercapnia correlated positively with nerve fibers lesions (P=0.03) and endothelial area (P=0.03). No correlations were found between age and other parameters. These findings highlight the fact that the microangiopathy in peripheral nerves in patients with COPD may be diffuse and essentially due to hypoxia and reduction in blood flow, as in diabetic neuropathy.     

Electrophysiological evidence for axonal degeneration of locus coeruleus neurons following long-term forced running stress

Using electrophysiological methods, a change in the density of axon terminals of locus coeruleus (LC) neurons in the cerebral cortex of rats following long-term forced running stress was examined. The stressed animals were classified into two groups based on spontaneous running activity (SRA) measured for 2 weeks after the stress treatment: 1) animals showing early restoration of SRA (poststress active rat) and 2) animals showing little or no SRA (poststress inactive rat). To quantify the density of LC axon terminals in the cerebral cortex, the percentage of LC neurons antidromically activated by cortical stimulation (projection index, P-index) was assessed. The P-indices for the cortex decreased in the poststress inactive rats. Since the threshold currents for antidromic activation were not altered by the stress treatment, the observed change was considered to reflect a change of the density of LC axon terminals rather than physiological consequences. Therefore, when animals receive a prolonged, severe stress, LC neurons in a certain group of the animals may cause axonal retraction or degeneration in the cerebral cortex.     

Inducible nitric oxide synthase (iNOS) in immune-mediated demyelination and Wallerian degeneration of the rat peripheral nervous system

The inducible isoform of nitric oxide synthase (iNOS), produces nitric oxide (NO) from l-arginine in response to inflammatory stimuli. NO sub-serves different functions from cytotoxicity to neuroprotection and triggers either necrosis or apoptosis. This study shows by Northern blot analysis that during experimental allergic neuritis (EAN), at the beginning of clinical signs, there is a transient extensive iNOS mRNA induction in nerve roots, in which morphology is mainly characterized by severe demyelination, but not in sciatic nerve, where scattered axonal degeneration is evident. Immunocytochemistry performed on teased nerve fibers and ultrastructural analysis showed that iNOS was localized in both inflammatory and Schwann cells, and the study of cell membrane permeability detected with fluorescent dyes showed a diffuse necrotic phenotype in the whole peripheral nervous system (PNS). With EAN clinical progression toward spontaneous recovery, endoneurial iNOS was rapidly down-regulated and in nerve roots almost all cells shifted their membrane permeability to an apoptotic phenotype, while necrosis persisted in sciatic nerve, until complete clinical recovery, when both root and nerve returned to normal. During wallerian degeneration following sciatic nerve transection, iNOS was undetectable in PNS, while endoneurial cell membrane had a diffuse necrotic phenotype. These data support the hypothesis that, during cell-mediated demyelination, iNOS may influence Schwann cell-axon relationship causing axonal damage and regulating endoneurial cell life and death.     

Effects of eribulin,vincristine, paclitaxel and ixabepilone on fast axonal transport and kinesin-1 driven microtubule gliding: Implications for chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious, painful and dose-limiting side effect of cancer drugs that target microtubules. The mechanisms underlying the neuronal damage are unknown, but may include disruption of fast axonal transport, an essential microtubule-based process that moves cellular components over long distances between neuronal cell bodies and nerve terminals. This idea is supported by the “dying back” pattern of degeneration observed in CIPN, and by the selective vulnerability of sensory neurons bearing the longest axonal projections. In this study, we test the hypothesis that microtubule-targeting drugs disrupt fast axonal transport using vesicle motility assays in isolated squid axoplasm and a cell-free microtubule gliding assay with defined components. We compare four clinically-used drugs, eribulin, vincristine, paclitaxel and ixabepilone. Of these, eribulin is associated with a relatively low incidence of severe neuropathy, while vincristine has a relatively high incidence. In vesicle motility assays, we found that all four drugs inhibited anterograde (conventional kinesin-dependent) fast axonal transport, with the potency being vincristine = ixabepilone > paclitaxel = eribulin. Interestingly, eribulin and paclitaxel did not inhibit retrograde (cytoplasmic dynein-dependent) fast axonal transport, in contrast to vincristine and ixabepilone. Similarly, vincristine and ixabepilone both exerted significant inhibitory effects in an in vitro microtubule gliding assay consisting of recombinant kinesin (kinesin-1) and microtubules composed of purified bovine brain tubulin, whereas paclitaxel and eribulin had negligible effects. Our results suggest that (i) inhibition of microtubule-based fast axonal transport may be a significant contributor to neurotoxicity induced by microtubule-targeting drugs, and (ii) that individual microtubule-targeting drugs affect fast axonal transport through different mechanisms.     

Mild traumatic brain injury to the infant mouse causes robust white matter axonal degeneration which precedes apoptotic death of cortical and thalamic neurons

The immature brain in the first several years of childhood is very vulnerable to trauma. Traumatic brain injury (TBI) during this critical period often leads to neuropathological and cognitive impairment. Previous experimental studies in rodent models of infant TBI were mostly concentrated on neuronal degeneration, while axonal injury and its relationship to cell death have attracted much less attention. To address this, we developed a closed controlled head injury model in infant (P7) mice and characterized the temporospatial pattern of axonal degeneration and neuronal cell death in the brain following mild injury. Using amyloid precursor protein (APP) as marker of axonal injury we found that mild head trauma causes robust axonal degeneration in the cingulum/external capsule as early as 30 min post-impact. These levels of axonal injury persisted throughout a 24 h period, but significantly declined by 48 h. During the first 24 h injured axons underwent significant and rapid pathomorphological changes. Initial small axonal swellings evolved into larger spheroids and club-like swellings indicating the early disconnection of axons. Ultrastructural analysis revealed compaction of organelles, axolemmal and cytoskeletal defects. Axonal degeneration was followed by profound apoptotic cell death in the posterior cingulate and retrosplenial cortex and anterior thalamus which peaked between 16 and 24 h post-injury. At early stages post-injury no evidence of excitotoxic neuronal death at the impact site was found. At 48 h apoptotic cell death was reduced and paralleled with the reduction in the number of APP-labeled axonal profiles. Our data suggest that early degenerative response to injury in axons of the cingulum and external capsule may cause disconnection between cortical and thalamic neurons, and lead to their delayed apoptotic death.     

Axonal degeneration promotes abnormal accumulation of amyloid β-protein in ascending gracile tract of gracile axonal dystrophy (GAD) mouse

The GAD mouse is a spontaneous neurological mutant with axonal dystrophy in the gracile tract of the medulla oblongata and spinal cord. The immunoreactivity of amyloid precursor protein (APP-IR) and amyloid β-protein (AβP-IR) was examined in the gracile tract and the dorsal root ganglia of normal and GAD mice. The mice were studied at 4, 9, 18, and 32 weeks of age. These periods correspond clinically to the initial, progressive, critical, and terminal stages of the disease, respectively. The APR-IR in both axons and glial cells was already accentuated to a higher level as early as 4 weeks of age in the gracile nucleus of GAD mouse. Similarly there was increase in APR-IR of GAD mouse in the dorsal root ganglia. Almost all of the primary neurons in the dorsal root ganglia at the lumbar cord level of GAD mouse revealed stronger APP-IR than those of normal mouse throughout all stages. The cells showing immunoreactivity for amyloid β-protein became positive in axons and glial cells in the gracile nucleus by approximately the 9th week, and followed by an increase of AβP-IR in order of the cervical, thoracic and lumbar spinal cords. These results suggest that the initial feature in GAD mouse is an accumulation of amyloid precursor protein induced by axonal dystrophy which then leads to a deposition of amyloid β-protein within the cytoplasm of both axons and glial cells in the gracile tract.     

GFAP expression of human Schwann cells in tissue culture

We have studied the expression of the intermediate filament (IF) proteins, vimentin and glial fibrillary acidic protein (GFAP), in cultured human Schwann cells (SC) from patients with different neuropathies and normal control cases. SC cultures from sural nerve biopsies of 8 subjects with axonal neuropathies, 8 with demyelinating neuropathies and 3 normal controls were included in this study and processed with double immunofluorescence technique, using anti-vimentin and anti-GFAP antibodies, during the 2nd, 4th and 6th week of culture. Five cultures incubated with anti-GFAP antibodies were also processed for immunoelectron microscopy. Specificity tests of the used antibodies were performed. We have found that: (1) cultured human SC constantly express vimentin; (2) SC from normal controls are GFAP-negative in the first period of culture; (3) SC from pathologic nerves can contain GFAP-immunoreactive IF and the percentage of GFAP-positive SC is higher in axonal than in demyelinating neuropathies; (4) during the permanence in culture human SC from both normal and pathologic cases acquire the ability to synthesize GFAP. The obtained data suggest that the removal from axonal contact and the resulting loss of myelinating function induce a cytoskeletal cellular response in human SC characterized by the cytoplasmic accumulation of GFAP-immunoreactive IF.     

Neurotoxicity of halogenated phenylacetylureas is linked to abnormal onset of rapid axonal transport

A structure-activity study was performed to investigate the mechanism of neurotoxicity induced in rats by treatment with p-bromophenylacetylurea (BPAU). Phenylacetylurea and 7 derivatives were tested for their ability to induce hindlimb weakness after twice weekly administration in doses of 200 mg/kg, up to a cumulative maximum of 2000 mg/kg. In this test, BPAU and its chloro- analog were about equipotent, but none of the other analogs displayed any evidence of neurotoxicity. Since BPAU toxicity was believed to involve abnormalities in rapid axonal transport, selected analogs were examined in a transport experiment. None of the compounds led to alterations in the maximal rate of rapid anterograde transport, as measured after intraspinal injections of [35S]methionine in rats treated with 400 mg/kg of toxicant, 7 days earlier. However, both BPAU and its chloro- analog caused marked shortening of the delay between isotope injection and transport onset, an effect not seen with either of the two non-neurotoxic analogs tested. It is hypothesized that the accelerated transport onset is a key step in development of the neuropathy, possibly causing organelle abnormalities that interfere with turnaround and recirculation of transported particles.     

The utility of the Total Neuropathy Score as an instrument to assess neuropathy severity in chronic kidney disease: A validation study

Objective

To demonstrate construct validity of the Total Neuropathy Score (TNS) in assessing peripheral neuropathy in subjects with chronic kidney disease (CKD).