Nerve Excitability Assessment in Chemotherapy-induced Neurotoxicity

Chemotherapy-induced neurotoxicity is a serious consequence of cancer treatment, which occurs with some of the most commonly used chemotherapies^1,2. Chemotherapy-induced peripheral neuropathy produces symptoms of numbness and paraesthesia in the limbs and may progress to difficulties with fine motor skills and walking, leading to functional impairment. In addition to producing troubling symptoms, chemotherapy-induced neuropathy may limit treatment success leading to dose reduction or early cessation of treatment. Neuropathic symptoms may persist long-term, leaving permanent nerve damage in patients with an otherwise good prognosis³. As chemotherapy is utilised more often as a preventative measure, and survival rates increase, the importance of long-lasting and significant neurotoxicity will increase.There are no established neuroprotective or treatment options and a lack of sensitive assessment methods. Appropriate assessment of neurotoxicity will be critical as a prognostic factor and as suitable endpoints for future trials of neuroprotective agents. Current methods to assess the severity of chemotherapy-induced neuropathy utilise clinician-based grading scales which have been demonstrated to lack sensitivity to change and inter-observer objectivity⁴. Conventional nerve conduction studies provide information about compound action potential amplitude and conduction velocity, which are relatively non-specific measures and do not provide insight into ion channel function or resting membrane potential. Accordingly, prior studies have demonstrated that conventional nerve conduction studies are not sensitive to early change in chemotherapy-induced neurotoxicity^4-6. In comparison, nerve excitability studies utilize threshold tracking techniques which have been developed to enable assessment of ion channels, pumps and exchangers in vivo in large myelinated human axons^7-9.Nerve excitability techniques have been established as a tool to examine the development and severity of chemotherapy-induced neurotoxicity^10-13. Comprising a number of excitability parameters, nerve excitability studies can be used to assess acute neurotoxicity arising immediately following infusion and the development of chronic, cumulative neurotoxicity. Nerve excitability techniques are feasible in the clinical setting, with each test requiring only 5 -10 minutes to complete. Nerve excitability equipment is readily commercially available, and a portable system has been devised so that patients can be tested in situ in the infusion centre setting. In addition, these techniques can be adapted for use in multiple chemotherapies.In patients treated with the chemotherapy oxaliplatin, primarily utilised for colorectal cancer, nerve excitability techniques provide a method to identify patients at-risk for neurotoxicity prior to the onset of chronic neuropathy. Nerve excitability studies have revealed the development of an acute Na⁺ channelopathy in motor and sensory axons^10-13. Importantly, patients who demonstrated changes in excitability in early treatment were subsequently more likely to develop moderate to severe neurotoxicity¹¹. However, across treatment, striking longitudinal changes were identified only in sensory axons which were able to predict clinical neurological outcome in 80% of patients¹⁰. These changes demonstrated a different pattern to those seen acutely following oxaliplatin infusion, and most likely reflect the development of significant axonal damage and membrane potential change in sensory nerves which develops longitudinally during oxaliplatin treatment¹⁰. Significant abnormalities developed during early treatment, prior to any reduction in conventional measures of nerve function, suggesting that excitability parameters may provide a sensitive biomarker.     

A Case Of Severe Neuropat Hy Associated With Hypertriglyceridemia

ObjectiveTo describe a case of severe neuropathy associated with hypertriglyceridemia.MethodsWe describe the clinical and laboratory findings of the study patient and review the relevant literature.ResultsA 45-year-old woman presented to the emergency department with recurrent abdominal pain and severe peripheral neuropathy. Her laboratory data revealed elevated lipase and a very high triglyceride concentration (> 10 000 mg/dL), consistent with a diagnosis of recurrent hypertriglyceridemia-induced pancreatitis. Workup for peripheral neuropathy showed normal concentrations of thyrotropin, fasting blood glucose, vitamin B₁₂, and creatinine, as well as a normal hemoglobin A_1c level, serum protein electrophoresis, and urine protein electrophoresis. Rapid plasma reagin antibodies, antinuclear antibodies, and lyme antibodies were not detected. In the absence of other identifiable causes, hypertriglyceridemia was deemed the likely etiology of severe neuropathy in this patient.ConclusionsPeripheral nerve conduction abnormalities can be identified in patients with mild hypertriglyceridemia in the absence of symptoms. Early recognition and aggressive management of hypertriglyceridemia may prevent the complications of severe peripheral neuropathy.(Endocr Pract. 2008;14:1020-1022)     

Inhibition of transient receptor potential melastatin 7 (TRPM7) protects against Schwann cell trans-dedifferentiation and proliferation during Wallerian degeneration

ABSTRACT

Irreversible peripheral neurodegenerative diseases such as diabetic peripheral neuropathy are becoming increasingly common due to rising rates of diabetes mellitus; however, no effective therapeutic treatments have been developed. One of main causes of irreversible peripheral neurodegenerative diseases is dysfunction in Schwann cells, which are neuroglia unique to the peripheral nervous system (PNS). Because homeostasis of calcium (Ca²⁺) and magnesium (Mg²⁺) is essential for Schwann cell dynamics, the regulation of these cations is important for controlling peripheral nerve degeneration and regeneration. Transient receptor potential melastatin 7 (TRPM7) is a non-selective ion (Ca²⁺ and Mg²⁺) channel that is expressed in Schwann cells. In the present study, we demonstrated in an ex vivo culture system that inhibition of TRPM7 during peripheral nerve degeneration (Wallerian degeneration) suppressed dedifferentiable or degenerative features (trans-dedifferentiation and proliferation) and conserved a differentiable feature of Schwann cells. Our results indicate that TRPM7 could be very useful as a molecular target for irreversible peripheral neurodegenerative diseases, facilitating discovery of new therapeutic methods for improving human health.     

Antibodies to L-periaxin in sera of patients with peripheral neuropathy produce experimental sensory nerve conduction deficits

L-Periaxin is a PDZ-domain protein localized to the plasma membrane of myelinating Schwann cells and plays a key role in the stabilization of mature myelin in peripheral nerves. Mutations in L-periaxin have recently been described in some patients with demyelinating peripheral neuropathy, suggesting that disruption of L-periaxin function may result in nerve injury. In this study, we report the presence of autoantibodies to L-periaxin in sera from two of 12 patients with diabetes mellitus (type 2)-associated neuropathy and three of 17 patients with IgG monoclonal gammopathy of undetermined significance (MGUS) neuropathy, an autoimmune peripheral nerve disorder. By comparison, anti-L-periaxin antibodies were not present in sera from nine patients with IgM MGUS neuropathy or in sera from 10 healthy control subjects. The effect of anti-L-periaxin serum antibody on peripheral nerve function was tested in vivo by intraneural injection. Sera containing anti-L-periaxin antibody, but not sera from age-matched control subjects, injected into the endoneurium of rat sciatic nerve significantly (p < 0.005, n = 3) attenuated sensory-evoked compound muscle action potential (CMAP) amplitudes in the absence of temporal dispersion. In contrast, motor-evoked CMAP amplitudes and latencies were not affected by intraneural injection of sera containing anti-L-periaxin antibody. Light and electron microscopy of anti-L-periaxin serum-injected nerves showed morphologic evidence of demyelination and axon enlargement. Depleting sera of anti-L-periaxin antibodies neutralized the serum-mediated effects on nerve function and nerve morphology. Together, these data support anti-L-periaxin antibody as the pathologic agent in these serum samples. We suggest that anti-L-periaxin antibodies, when present in sera of patients with IgG MGUS- or diabetes-associated peripheral neuropathy, may elicit sensory nerve conduction deficits.     

Hyperglycemia induces abnormal gene expression in hematopoietic stem cells and their progeny in diabetic neuropathy

Diabetic peripheral neuropathy is a major chronic diabetic complication. We have previously shown that in type 1 diabetic streptozotocin-treated mice, insulin- and TNF-α co-expressing bone marrow-derived cells (BMDCs) induced by hyperglycemia travel to nerve tissues where they fuse with nerve cells, causing premature apoptosis and nerve dysfunction. Here we show that similar BMDCs also occur in type 2 diabetic high-fat diet (HFD) mice. Furthermore, we found that hyperglycemia induces the co-expression of insulin and TNF-α in c-kit⁺Sca-1⁺lineage⁻ (KSL) progenitor cells, which maintain the same expression pattern in the progeny, which in turn participates in the fusion with neurons when transferred to normoglycemic animals.     

Sildenafil Ameliorates Long Term Peripheral Neuropathy in Type II Diabetic Mice

Diabetic peripheral neuropathy is a common complication of long-standing diabetes mellitus. To mimic clinical trials in which patients with diabetes enrolled have advanced peripheral neuropathy, we investigated the effect of sildenafil, a specific inhibitor of phosphodiesterase type 5 enzyme, on long term peripheral neuropathy in middle aged male mice with type II diabetes. Treatment of diabetic mice (BKS.Cg-m+/+Lepr^db/J, db/db) at age 36 weeks with sildenafil significantly increased functional blood vessels and regional blood flow in the sciatic nerve, concurrently with augmentation of intra-epidermal nerve fiber density in the skin and myelinated axons in the sciatic nerve. Functional analysis showed that the sildenafil treatment considerably improved motor and sensory conduction velocities in the sciatic nerve and peripheral thermal stimulus sensitivity compared with the saline treatment. In vitro studies showed that mouse dermal endothelial cells (MDE) cultured under high glucose levels exhibited significant down regulation of angiopoietin 1 (Ang1) expression and reduction of capillary-like tube formation, which were completely reversed by sildenafil. In addition, incubation of dorsal root ganglia (DRG) neurons with conditioned medium harvested from MDE under high glucose levels suppressed neurite outgrowth, where as conditional medium harvested from MDE treated with sildenafil under high glucose levels did not inhibit neurite outgrowth of DRG neurons. Moreover, blockage of the Ang1 receptor, Tie2, with a neutralized antibody against Tie2 abolished the beneficial effect of sildenafil on tube formation and neurite outgrowth. Collectively, our data indicate that sildenafil has a therapeutic effect on long term peripheral neuropathy of middle aged diabetic mice and that improvement of neurovascular dysfunction by sildenafil likely contributes to the amelioration of nerve function. The Ang1/Tie2 signaling pathway may play an important role in these restorative processes.     

Overexpression of mutant HSP27 causes axonal neuropathy in mice

Background

Mutations in heat shock 27 kDa protein 1 (HSP27 or HSPB1) cause distal hereditary motor neuropathy (dHMN) or Charcot-Marie-Tooth disease type 2 F (CMT2F) according to unknown factors. Mutant HSP27 proteins affect axonal transport by reducing acetylated tubulin.

Results

We generated a transgenic mouse model overexpressing HSP27-S135F mutant protein driven by Cytomegalovirus (CMV) immediate early promoter. The mouse phenotype was similar to dHMN patients in that they exhibit motor neuropathy. To determine the phenotypic aberration of transgenic mice, behavior test, magnetic resonance imaging (MRI), electrophysiological study, and pathology were performed. Rotarod test showed that founder mice exhibited lowered motor performance. MRI also revealed marked fatty infiltration in the anterior and posterior compartments at calf level. Electrophysiologically, compound muscle action potential (CMAP) but not motor nerve conduction velocity (MNCV) was reduced in the transgenic mice. Toluidine staining with semi-thin section of sciatic nerve showed the ratio of large myelinated axon fiber was reduced, which might cause reduced locomotion in the transgenic mice. Electron microscopy also revealed abundant aberrant myelination. Immunohistochemically, neuronal dysfunctions included elevated level of phosphorylated neurofilament and reduced level of acetylated tubulin in the sural nerve of transgenic mice. There was no additional phenotype besides motor neuronal defects.

Conclusions

Overexpression of HSP27-S135F protein causes peripheral neuropathy. The mouse model can be applied to future development of therapeutic strategies for dHMN or CMT2F.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0154-y) contains supplementary material, which is available to authorized users.     

Insulin-Induced Hypoglycemic Peripheral Motor Neuropathy in Spontaneously Diabetic WBN/Kob Rats

Intensive insulin therapy can lead to hypoglycemia, with patients sometimes developing hypoglycemic neuropathy. Spontaneously diabetic Wistar Bonn Kobori (WBN/Kob) rats develop diabetic peripheral motor neuropathy characterized by segmental demyelination and axonal degeneration. We examined the short-term effects of hypoglycemia on neuropathic changes in these rats. Spontaneous diabetic WBN/Kob rats received insulin implants for 40 d and were divided into 3 groups based on blood glucose levels: group N, normoglycemic to slightly hyperglycemic (150 to 250 mg/dL); group H, hypoglycemic to slightly hyperglycemic (50 to 200 mg/dL); and group D, nontreated spontaneously diabetic (350 to 420 mg/dL). Conduction velocity was measured in sciatic–tibial motor nerves; these nerves also underwent qualitative and quantitative histomorphologic analysis. Conduction velocity was not significantly different in N, D, and H groups. Morphologic analysis of the sciatic nerves of H rats showed severe changes, including axonal degeneration, myelin distention, and endoneurial fibrosis, that tended to occur in large, myelinated fibers. N and D rats showed relatively mild changes. The degree and distribution of degenerated nerve fibers in H rats were significantly higher than in N and D rats. These results suggest that hypoglycemia of less than 50 mg/dL induced severe peripheral neuropathy. Hypoglycemic lesions differed from the hyperglycemic lesions in diabetic WBN/Kob rats. This rat strain is an appropriate model for investigating the hypoglycemic peripheral neuropathy that can be associated with a diabetic condition.Peripheral neuropathy is a leading complication of diabetes mellitus. Although its exact pathogenesis is not fully understood, chronic hyperglycemia and resultant microenvironmental changes in peripheral nerve tissue contribute to the development of neuropathy.⁵ Therefore, intensive insulin therapy is needed to prevent such complications in patients with type 1 diabetes. However, intensive insulin therapy can lead to hypoglycemia, with patients sometimes developing hypoglycemic peripheral neuropathy.⁸Although experimental hypoglycemic peripheral neuropathy has been studied by using animal models of type 1 diabetes, few studies have included morphologic analyses.^4,7,14,15 These studies showed that hypoglycemia causes axonopathy involving both degenerative and regenerative events. However, hyperglycemic peripheral neuropathy characterized by axonal atrophy has also been induced in diabetic animal models, such that the hyperglycemic changes in these models were similar to hypoglycemic changes. Diabetic WBN/Kob rats spontaneously develop diabetic peripheral motor neuropathy characterized by segmental demyelination and secondary axonal degeneration.^12,13,19 Morphologic changes in diabetic peripheral motor neuropathy are characterized by various degenerative and regenerative changes in myelin sheath, demyelination, and a shift toward axons of smaller diameter. Therefore, WBN/Kob rats may be useful for distinguishing hyperglycemic from hypoglycemic changes. In addition, the threshold of hypoglycemia that induces the morphologic and clinical changes characteristic of peripheral neuropathy in diabetic animals remains unclear.¹⁴ In the present study, we investigated the effects of short-term hypoglycemia on peripheral neuropathic changes in diabetic WBN/Kob rats.     

Diabetes and the peripheral nerve

Diabetes-induced damage to peripheral nerve culminates in development of peripheral diabetic neuropathy (PDN), one of the most devastating complications of diabetes mellitus and a leading cause of foot amputation. The pathogenesis of PDN occurs as a consequence of complex interactions among multiple hyperglycemia-initiated mechanisms, impaired insulin signaling, inflammation, hypertension, and disturbances of fatty acid and lipid metabolism. This review describes experimental new findings in animal and cell culture models as well as clinical data suggesting the importance of 1) previously established hyperglycemia-initiated mechanisms such as increased aldose reductase activity, non-enzymatic glycation/glycooxidation, activation of protein kinase C, 2) oxidative–nitrosative stress and poly(ADP-ribose) polymerase activation; 3) mitogen-activated protein kinase and cyclooxygenase-2 activation, impaired Ca⁺⁺ homeostasis and signaling, and several other mechanisms, in PDN.     

Protein kinase associated with peripheral nerve myelin. 1. Phosphorylation of endogenous myelin proteins and exogenous substrates

When highly purified myelin from rat sciatic nerve was incubated with [γ-³²P]ATP, protein components of the membrane were phosphorylated indicating the presence of both the substrate (receptor protein) and an endogenous kinase in the membrane. Polyacrylamide gel electrophoresis of the phosphorylated membrane proteins followed by scintillation counting of gel slices and autoradiography showed that the polypeptides of molecular weights 28000, 23000 and 19000 were phosphorylated, and ³²P from [γ-³²P]ATP having been incorporated into serine residues of the substrate proteins. Phosphorylation of purified myelin was Mg²⁺-dependent, was optimal at pH 6.5 and was not stimulated by adenosine 3′,5′-monophosphate. We found that proteins other than those in myelin, such as phosvitin, casein, protamine and histones, can also act as a substrate for the membrane associated kinase. Muscle protein kinase inhibitor had no effect on the endogenous phosphorylation of myelin proteins or on the phosphorylation of phosvitin by peripheral nerve myelin protein kinase. However, the phosphorylation of histone by peripheral nerve myelin protein kinase was inhibited by the protein kinase inhibitor. After washing the membrane with 150 mM KCl the protein kinase that utilizes histone as substrate was found in the supernatant. In contrast, the endogenous phosphorylation of membrane proteins or the phosphorylation of phosvitin by the membrane associated kinase was not affected by washing.From these findings we conclude that at least two protein kinase systems exist in purified peripheral nerve myelin. One system is not inhibited by muscle kinase inhibitor, is tightly bound to the membrane and utilizes as its receptor proteins either exogenous phosvitin or endogenous membrane proteins. The second system is inhibited by muscle kinase inhibitor, is removable from the membrane and utilizes histones as its receptor proteins.     

Curcumin treatment abrogates endoplasmic reticulum retention and aggregation-induced apoptosis associated with neuropathy-causing myelin protein zero-truncating mutants

Mutations in MPZ, the gene encoding myelin protein zero (MPZ), the major protein constituent of peripheral myelin, can cause the adult-onset, inherited neuropathy Charcot-Marie-Tooth disease, as well as the more severe, childhood-onset Dejerine-Sottas neuropathy and congenital hypomyelinating neuropathy. Most MPZ-truncating mutations associated with severe forms of peripheral neuropathy result in premature termination codons within the terminal or penultimate exons that are not subject to nonsense-mediated decay and are stably translated into mutant proteins with potential dominant-negative activity. However, some truncating mutations at the 3' end of MPZ escape the nonsense-mediated decay pathway and cause a mild peripheral neuropathy phenotype. We examined the functional properties of MPZ-truncating proteins that escaped nonsense-mediated decay, and we found that frameshift mutations associated with severe disease cause an intracellular accumulation of mutant proteins, primarily within the endoplasmic reticulum (ER), which induces apoptosis. Curcumin, a chemical compound derived from the curry spice tumeric, releases the ER-retained MPZ mutants into the cytoplasm accompanied by a lower number of apoptotic cells. Our findings suggest that curcumin treatment is sufficient to relieve the toxic effect of mutant aggregation-induced apoptosis and may potentially have a therapeutic role in treating selected forms of inherited peripheral neuropathies.     

Photobiomodulation induces antinociception,recovers structural aspects and regulates mitochondrial homeostasis in peripheral nerve of diabetic mice

Diabetic peripheral neuropathy (DPN) is a nervous disorder caused by diabetes mellitus, affecting about 50% of patients in clinical medicine. Chronic pain is one of the major and most unpleasant symptoms developed by those patients, and conventional available treatments for the neuropathy, including the associated pain, are still unsatisfactory and benefit only a small number of patients. Photobiomodulation (PBM) has been gaining clinical acceptance once it is able to promote early nerve regeneration resulting in significant improvement in peripheral nerves disabilities. In this work, the effects of PBM (660 nm, 30 mW, 1.6 J/cm², 0.28 cm², 15 s in a continuous frequency) on treating DPN‐induced pain and nerve damage were evaluated in an experimental model of diabetic‐neuropathy induced by streptozotocin in mice. PBM‐induced antinociception in neuropathic‐pain mice was dependent on central opioids release. After 21 consecutive applications, PBM increased nerve growth factor levels and induced structural recovery increasing mitochondrial content and regulating Parkin in the sciatic nerve of DPN‐mice. Taking together, these data provide new insights into the mechanisms involved in the effects of PBM‐therapy emphasizing its therapeutic potential in the treatment of DPN.      

Hyperglycemia triggers abnormal signaling and proliferative responses in Schwann cells

Peripheral neuropathy is a serious diabetic complication. Delayed nerve regeneration in diabetic animal models suggests abnormalities in proliferation/differentiation of Schwann cells (SC). We recently reported that endothelins (ETs) regulate proliferation and phenotype in primary and immortalized SC (iSC). We now investigated changes in the effects of ETs on SC proliferation and signaling in nerve segments from streptozotocin-induced diabetic rats and in iSC exposed to high glucose. Cultured explants from diabetic rats displayed a delay in the time-course of [³H]-thymidine incorporation as well as enhanced sensitivity to endothelin-1 (ET-1) or insulin. iSC cultured in high (25 mM) glucose-containing media also exhibited higher [³H]-thymidine incorporation, along with an enhanced activation of p38 mitogen-activated protein kinase and phospholipase C in response to ET-1 or platelet-derived growth factor as compared to controls (5.5 mM glucose). These studies support an extra-vascular role of ETs in peripheral nerves and SC. The increased sensitivity to ET-1 in nerves and iSC exposed to high glucose may contribute to abnormal SC proliferation characterizing diabetic neuropathy.     

Subcellular Localization of Sulfated Glucuronic Acid-Containing Glycolipids Reacting with Anti-Myelin-Associated Glycoprotein Antibody

Peripheral nerve glycolipids, with which anti-myelin-associated glycoprotein (MAG) antibodies from patients with demyelinating neuropathy and plasma cell dyscrasia cross-react, proved to be novel glycosphingolipids containing a sulfated glucuronyl residue. Consequently, there has been much interest in the immunological role that these sulfated glucuronyl-glycosphingolipids (SGGLs) may play in the pathogenesis of this disorder. For the determination of the distribution of these glycolipids in various nervous tissues and, thereby, the elucidation of their pathogenicity, a quantitative immunostaining-TLC method for their detection has been devised. Using this method, we demonstrated that these glycolipids were distributed in greatly different amounts in the peripheral nerves from human, bovine, chicken, rat, and rabbit. Subcellular localization studies of bovine peripheral nerve also demonstrated that they were enriched in the axolemma-enriched fraction and present in glial-related membranes in lower concentrations. In addition, these glycolipids were present in bovine dura mater and transformed rat Schwann cells. These biochemical results suggest that not only myelin but also axons could be involved as targets of the anti-MAG antibody in macroglobulinemia neuropathy, and it may also be necessary to examine anti-SGGL activity in patients with axonal neuropathy associated with plasma cell dyscrasia.     

The therapeutic potential of gene transfer for the treatment of peripheral neuropathies

Peripheral neuropathy is a common medical problem with numerous aetiologies. Unfortunately, for the majority of cases there is no available medical solution for the underlying cause, and the only option is to try to treat the resulting symptoms. Treatment options exist when neuropathy results in positive symptoms such as pain, but there is a significant lack of treatments for negative symptoms such as numbness and weakness. Systemic application of growth factor peptides has shown promise in protecting nerves from neuropathic insults in preclinical animal studies, but translation into human trials has been problematic and disappointing. Significant advancements have been made in the past few years in utilising gene therapy approaches to treat peripheral neuropathy by expressing neuroprotective gene products either systemically or in specific nervous tissues. For example, plasmids expressing vascular endothelial growth factor injected into muscle, or herpes-simplex-virus-based vectors expressing neurotrophin gene products delivered to dorsal root ganglion neurons, have been used to protect peripheral nerve function in animal models of diabetes-associated peripheral neuropathy. Many published studies support the feasibility of this approach, although several questions still need to be addressed as gene therapy to treat peripheral neuropathy moves out of the laboratory and into the clinic.     

The Role of Oxidative Stress in Nervous System Aging

While oxidative stress is implicated in aging, the impact of oxidative stress on aging in the peripheral nervous system is not well understood. To determine a potential mechanism for age-related deficits in the peripheral nervous system, we examined both functional and morphological changes and utilized microarray technology to compare normal aging in wild-type mice to effects in copper/zinc superoxide dismutase-deficient (Sod1^−/−) mice, a mouse model of increased oxidative stress. Sod1^−/− mice exhibit a peripheral neuropathy phenotype with normal sensory nerve function and deficits in motor nerve function. Our data indicate that a decrease in the synthesis of cholesterol, which is vital to myelin formation, correlates with the structural deficits in axons, myelin, and the cell body of motor neurons in the Sod1^+/+ mice at 30 months and the Sod1^−/− mice at 20 months compared with mice at 2 months. Collectively, we have demonstrated that the functional and morphological changes within the peripheral nervous system in our model of increased oxidative stress are manifested earlier and resemble the deficits observed during normal aging.     

A Novel Missense Mutation in ADAMTS10 in Norwegian Elkhound Primary Glaucoma

Primary glaucoma is one of the most common causes of irreversible blindness both in humans and in dogs. Glaucoma is an optic neuropathy affecting the retinal ganglion cells and optic nerve, and elevated intraocular pressure is commonly associated with the disease. Glaucoma is broadly classified into primary open angle (POAG), primary closed angle (PCAG) and primary congenital glaucoma (PCG). Human glaucomas are genetically heterogeneous and multiple loci have been identified. Glaucoma affects several dog breeds but only three loci and one gene have been implicated so far. We have investigated the genetics of primary glaucoma in the Norwegian Elkhound (NE). We established a small pedigree around the affected NEs collected from Finland, US and UK and performed a genome-wide association study with 9 cases and 8 controls to map the glaucoma gene to 750 kb region on canine chromosome 20 (p_raw = 4.93×10⁻⁶, p_genome = 0.025). The associated region contains a previously identified glaucoma gene, ADAMTS10, which was subjected to mutation screening in the coding regions. A fully segregating missense mutation (p.A387T) in exon 9 was found in 14 cases and 572 unaffected NEs (p_Fisher = 3.5×10⁻²⁷) with a high carrier frequency (25.3%). The mutation interrupts a highly conserved residue in the metalloprotease domain of ADAMTS10, likely affecting its functional capacity. Our study identifies the genetic cause of primary glaucoma in NEs and enables the development of a genetic test for breeding purposes. This study establishes also a new spontaneous canine model for glaucoma research to study the ADAMTS10 biology in optical neuropathy.     

Defects in the Blood-Nerve Barrier in Mice with Leprosy Neuropathy

PERIPHERAL nerve damage is the most common and the most serious complication in patients with leprosy¹. The pathogenesis of leprosy neuropathy has not been studied systematically because of the impossibility of taking serial biopsies from proximal and distal parts of infected nerves in a series of patients, so that investigations have to be confined to chance biopsies from patients with early forms of the disease, limb amputation or post-mortem material.