James Wymer

Voltage-gated sodium channel expression in rat and human epidermal keratinocytes: evidence for a role in pain.

Abstract Keratinocytes are implicated in sensory transduction and can influence nociception, but whether these contribute to chronic pain is not known. In neurons, voltage‐gated sodium channels (Nav) are involved in neuropathic pain and are activated by depolarization. Since keratinocytes can also show changes in membrane potential, we used RT‐PCR, in situ hybridization, and immunohistochemistry to investigate the expression of sodium channels in these cells. Nav1.1, Nav1.6, and Nav1.8 were localized within keratinocytes in rat epidermis. In addition, sodium channels contribute to the release of ATP from rat keratinocytes in response to increased [K+]o, implicating sodium channels in keratinocyte ligand release and nociception. To examine whether keratinocytes may contribute to human pain states, we analyzed sodium channel expression in human skin biopsies from subjects with complex regional pain syndrome Type 1 (CRPS) and post‐herpetic neuralgia (PHN) using immunohistochemistry. Control skin exhibited immunolabeling for Nav1.5, Nav1.6 and Nav1.7. In contrast, painful skin from CRPS and PHN subjects displayed Nav1.1, Nav1.2, and Nav1.8 immunolabeling, in addition to substantially increased signal for Nav1.5, Nav1.6, Nav1.7. These observations lead us to propose that pathological increases in keratinocyte sodium channel expression may contribute to pain by increasing epidermal ATP release, resulting in excessive activation of P2X receptors on primary sensory axons. Consistent with this hypothesis, animal models of neuropathic pain exhibit increases in subcutaneous ATP release and activity of primary sensory neurons, and peripheral administration of P2X antagonists has been shown to reduce neuropathic pain in humans.

Randomized, controlled trial of dextromethorphan/quinidine for pseudobulbar affect in multiple sclerosis†

To evaluate the efficacy and safety of DM/Q (capsules containing dextromethorphan [DM] and quinidine [Q]) compared with placebo, taken twice daily, for the treatment of pseudobulbar affect over a 12‐week period in multiple sclerosis patients.

Keratinocyte expression of calcitonin gene-related peptide β: implications for neuropathic and inflammatory pain mechanisms.

Summary In a variety of chronic pain conditions, calcitonin gene‐related peptide (CGRP) is expressed at high levels in the skin, blood, and cerebrospinal fluid. Our results reveal that much of the increase may be due to the CGRPβ isoform made by epidermal keratinocytes, which express high levels of CGRP immunoreactivity in a variety of human and animal chronic pain conditions. ABSTRACT Calcitonin gene‐related peptide (CGRP) is a vasodilatory peptide that has been detected at high levels in the skin, blood, and cerebrospinal fluid (CSF) under a variety of inflammatory and chronic pain conditions, presumably derived from peptidergic C and Aδ innervation. Herein, CGRP immunolabeling (IL) was detected in epidermal keratinocytes at levels that were especially high and widespread in the skin of humans from locations afflicted with postherpetic neuralgia (PHN) and complex region pain syndrome type 1 (CRPS), of monkeys infected with simian immunodeficiency virus, and of rats subjected to L5/L6 spinal nerve ligation, sciatic nerve chronic constriction, and subcutaneous injection of complete Freund’s adjuvant. Increased CGRP‐IL was also detected in epidermal keratinocytes of transgenic mice with keratin‐14 promoter driven overexpression of noggin, an antagonist to BMP‐4 signaling. Transcriptome microarray, quantitative Polymerase Chain Reaction (qPCR), and Western blot analyses using laser‐captured mouse epidermis from transgenics, monolayer cultures of human and mouse keratinocytes, and multilayer human keratinocyte organotypic cultures, revealed that keratinocytes express predominantly the beta isoform of CGRP. Cutaneous peptidergic innervation has been shown to express predominantly the alpha isoform of CGRP. Keratinocytes also express the cognate CGRP receptor components, Calcitonin receptor‐like receptor (CRLR), Receptor activity‐modifying protein 1 (RAMP1), CGRP‐receptor component protein (RCP) consistent with known observations that CGRP promotes several functional changes in keratinocytes, including proliferation and cytokine production. Our results indicate that keratinocyte‐derived CGRPβ may modulate epidermal homeostasis through autocrine/paracrine signaling and may contribute to chronic pain under pathological conditions.

Excessive Peptidergic Sensory Innervation of Cutaneous Arteriole–Venule Shunts (AVS) in the Palmar Glabrous Skin of Fibromyalgia Patients: Implications for Widespread Deep Tissue Pain and Fatigue

OBJECTIVE To determine if peripheral neuropathology exists among the innervation of cutaneous arterioles and arteriole-venule shunts (AVS) in fibromyalgia (FM) patients. SETTING Cutaneous arterioles and AVS receive a convergence of vasoconstrictive sympathetic innervation, and vasodilatory small-fiber sensory innervation. Given our previous findings of peripheral pathologies in chronic pain conditions, we hypothesized that this vascular location may be a potential site of pathology and/or serotonergic and norepinephrine reuptake inhibitors (SNRI) drug action. SUBJECTS Twenty-four female FM patients and nine female healthy control subjects were enrolled for study, with 14 additional female control subjects included from previous studies. AVS were identified in hypothenar skin biopsies from 18/24 FM patient and 14/23 control subjects. METHODS Multimolecular immunocytochemistry to assess different types of cutaneous innervation in 3 mm skin biopsies from glabrous hypothenar and trapezius regions. RESULTS AVS had significantly increased innervation among FM patients. The excessive innervation consisted of a greater proportion of vasodilatory sensory fibers, compared with vasoconstrictive sympathetic fibers. In contrast, sensory and sympathetic innervation to arterioles remained normal. Importantly, the sensory fibers express α2C receptors, indicating that the sympathetic innervation exerts an inhibitory modulation of sensory activity. CONCLUSIONS The excessive sensory innervation to the glabrous skin AVS is a likely source of severe pain and tenderness in the hands of FM patients. Importantly, glabrous AVS regulate blood flow to the skin in humans for thermoregulation and to other tissues such as skeletal muscle during periods of increased metabolic demand. Therefore, blood flow dysregulation as a result of excessive innervation to AVS would likely contribute to the widespread deep pain and fatigue of FM. SNRI compounds may provide partial therapeutic benefit by enhancing the impact of sympathetically mediated inhibitory modulation of the excess sensory innervation.

Absence of pain with hyperhidrosis: A new syndrome where vascular afferents may mediate cutaneous sensation

ABSTRACT Congenital absence of pain perception is a rare phenotype. Here we report two unrelated adult individuals who have a previously unreported neuropathy consisting of congenital absence of pain with hyperhidrosis (CAPH). Both subjects had normal intelligence and productive lives despite failure to experience pain due to broken bones, severe cold or burns. Functional assessments revealed that both are generally hypesthetic with thresholds greater than two standard deviations above normal for a several of modalities in addition to noxious stimuli. Sweating was 3 to 8‐fold greater than normal. Sural nerve biopsy showed that all types of myelinated and unmyelinated fibers were severely reduced. Extensive multi‐antibody immunofluorescence analyses were conducted on several skin biopsies from the hands and back of one CAPH subject and two normal subjects. The CAPH subject had all normal types of immunochemically and morphologically distinct sensory and autonomic innervation to the vasculature and sweat glands, including a previously unknown cholinergic arterial innervation. Virtually all other types of normal cutaneous C, Aδ and Aβ‐fiber endings were absent. This subject had no mutations in the genes SCN9A, SCN10A, SCN11A, NGFB, TRKA, NRTN and GFRA2. Our findings suggest three hypotheses: (1) that development or maintenance of sensory innervation to cutaneous vasculature and sweat glands may be under separate genetic control from that of all other cutaneous sensory innervation, (2) the latter innervation is preferentially vulnerable to some environmental factor, and (3) vascular and sweat gland afferents may contribute to conscious cutaneous perception.

Double-blind, placebo-controlled study of HGF gene therapy in diabetic neuropathy.

To evaluate the safety and efficacy of a plasmid (VM202) containing two human hepatocyte growth factor isoforms given by intramuscular injections in patients with painful diabetic neuropathy.

Sodium channel Nav1.7 in vascular myocytes, endothelium, and innervating axons in human skin

BackgroundThe skin is a morphologically complex organ that serves multiple complementary functions, including an important role in thermoregulation, which is mediated by a rich vasculature that is innervated by sympathetic and sensory endings. Two autosomal dominant disorders characterized by episodes of severe pain, inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD) have been directly linked to mutations that enhance the function of sodium channel Nav1.7. Pain attacks are accompanied by reddening of the skin in both disorders. Nav1.7 is known to be expressed at relatively high levels within both dorsal root ganglion (DRG) and sympathetic ganglion neurons, and mutations that enhance the activity of Nav1.7 have been shown to have profound effects on the excitability of both cell-types, suggesting that dysfunction of sympathetic and/or sensory fibers, which release vasoactive peptides at skin vasculature, may contribute to skin reddening in IEM and PEPD.ResultsIn the present study, we demonstrate that smooth muscle cells of cutaneous arterioles and arteriole-venule shunts (AVS) in the skin express sodium channel Nav1.7. Moreover, Nav1.7 is expressed by endothelial cells lining the arterioles and AVS and by sensory and sympathetic fibers innervating these vascular elements.ConclusionsThese observations suggest that the activity of mutant Nav1.7 channels in smooth muscle cells of skin vasculature and innervating sensory and sympathetic fibers contribute to the skin reddening and/or pain in IEM and PEPD.

Defining SOD1 ALS natural history to guide therapeutic clinical trial design

Importance Understanding the natural history of familial amyotrophic lateral sclerosis (ALS) caused by SOD1 mutations (ALSSOD1) will provide key information for optimising clinical trials in this patient population. Objective To establish an updated natural history of ALSSOD1. Design, setting and participants Retrospective cohort study from 15 medical centres in North America evaluated records from 175 patients with ALS with genetically confirmed SOD1 mutations, cared for after the year 2000. Main outcomes and measures Age of onset, survival, ALS Functional Rating Scale (ALS-FRS) scores and respiratory function were analysed. Patients with the A4V (Ala-Val) SOD1 mutation (SOD1A4V), the largest mutation population in North America with an aggressive disease progression, were distinguished from other SOD1 mutation patients (SOD1non-A4V) for analysis. Results Mean age of disease onset was 49.7±12.3 years (mean±SD) for all SOD1 patients, with no statistical significance between SOD1A4V and SOD1non-A4V (p=0.72, Kruskal-Wallis). Total SOD1 patient median survival was 2.7 years. Mean disease duration for all SOD1 was 4.6±6.0 and 1.4±0.7 years for SOD1A4V. SOD1A4V survival probability (median survival 1.2 years) was significantly decreased compared with SOD1non-A4V (median survival 6.8 years; p<0.0001, log-rank). A statistically significant increase in ALS-FRS decline in SOD1A4V compared with SOD1non-A4V participants (p=0.02) was observed, as well as a statistically significant increase in ALS-forced vital capacity decline in SOD1A4V compared with SOD1non-A4V (p=0.02). Conclusions and relevance SOD1A4V is an aggressive, but relatively homogeneous form of ALS. These SOD1-specific ALS natural history data will be important for the design and implementation of clinical trials in the ALSSOD1 patient population.

The evaluation of bulbar dysfunction in amyotrophic lateral sclerosis: survey of clinical practice patterns in the United States

Abstract Objective: Speech and swallowing impairments are highly prevalent in individuals with amyotrophic lateral sclerosis (ALS) and contribute to reduced quality of life, malnutrition, aspiration, pneumonia and death. Established practice parameters for bulbar dysfunction in ALS do not currently exist. The aim of this study was to identify current practice patterns for the evaluation of speech and swallowing function within participating Northeast ALS clinics in the United States. Methods and results: A 15-item survey was emailed to all registered NEALS centres. Thirty-eight sites completed the survey. The majority (92%) offered Speech-Language Pathology, augmentative and alternative communication (71%), and dietician (92%) health care services. The ALS Functional Rating Scale-Revised and body weight represented the only parameters routinely collected in greater then 90% of responding sites. Referral for modified barium swallow study was routinely utilised in only 27% of sites and the use of percutaneous gastrostomy tubes in ALS patient care was found to vary considerably. Conclusions: This survey reveals significant variability and inconsistency in the management of bulbar dysfunction in ALS across NEALS sites. We conclude that a great need exists for the development of bulbar practice guidelines in ALS clinical care to accurately detect and monitor bulbar dysfunction.

Increasing Evidence for an Association Between Amyotrophic Lateral Sclerosis and Psychiatric Disorders

As our knowledge of amyotrophic lateral sclerosis (ALS) increases, the salient question has become: Is ALS a single disease or a group of diseases with a final common pathway? Traditionally, ALS has been defined as a rapidly progressive neurodegenerative disorder that affects the large motor neurons of the brain and spinal cord. It presents with an upper or lower motor neuron pattern of weakness but progresses to include all motor neurons (upper and lower, bulbar, cervical, thoracic, and lumbar). Cognition was thought to be affected in only a small subset of patients with ALS. The primary causation theory was that ALS was the result of a single common exposure or genetic mutation, and the primary pathologic finding was simple motor neuron degeneration. Recent studies on the genetics of ALS have changed this view. At present, cases of ALS are considered familial or sporadic. Only 10% of cases carry a mutation, most commonly a C9orf72 expansion or a superoxide dismutase 1 (SOD1) mutation. Despite the 2 classifications of sporadic and familial ALS and the multiple types of onset, it was thought that patients with ALS were a homogeneous group, given the stereotypical, invariable, and unrelentingclinicalpresentation.WiththeidentificationoftheC9orf72 mutation and the characterization of the phenotypes within ALS kindred, ithasbecomeclearthatpatientswiththeC9orf72expansion can present with a motor neuron pattern of weakness, frontotemporal dementia, or a combination of the 2 phenotypes within the same kindred.1-3 Cognitive and psychiatric changes, excluding depression and anxiety often found in those with terminal illnesses, are now recognized as part of ALS. A recent survey of patients with ALS found that 68% had cognitive or behavioral changes.4 In addition, a population-based study identified increased schizophrenia and suicidal behaviors in the relatives of patients with ALS with and without the C9orf72 expansion.5 Whether these cognitive and behavioral changes of C9orf72associated ALS reflect varied presentations of ALS due to a shared polygenic risk with relatives with schizophrenia or to differing penetranceorpleiotropyinALSkindredsisunknown.Cangenetic heterogeneity with additional unidentified genes be involved in the presentation? Overall, there is a limited understanding of the genetics and association between these manifestations. In this issue of JAMA Neurology, O’Brien et al6 present a casecontrol family aggregation study of genetic pleiotropy within ALS kindreds. Some of the authors had previously studied a large cohort of patients with ALS for schizophrenia and psychotic illness and found overlap associated with the C9orf72 variant and in kindreds who did not carry the expansion.5 The current study used a cohort of 127 patients with ALS who were distinct from those in the first study.6 Ageand sex-matched controls were randomly derived from the records of the patient’s primary physician or from a geographically close physician’s records. Patients and controls were interviewed and asked about first-degree and seconddegreerelativeswithschizophrenia,bipolardisorder,autism,suicide, obsessive-compulsive disorder, addiction, and alcoholism using definitions from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. They collected survey data on 2116 relatives of patients with ALS and 2139 relatives of control participants. Confirming results of the previous study, they identified a relative risk of 3.4 (P = .02) for developing schizophrenia or other psychotic disorders in relatives of patients with ALS compared with controls. There was also an association between ALS and the development of autism (relative risk, 10.1; P = .03), alcoholism (relative risk, 1.48; P = .045), and obsessivecompulsive disorder (relative risk, 5.6; P = .02). Clustering of psychiatric disease with 3 or more affected family members was higherintheALSkindredsthanthecontrolkindreds.TheC9orf72 mutation did not fully explain these findings, as only 17% of the 29 kindreds with 3 or more affected relatives had the expansion; 81% did not have the expansion. Is there a link between ALS and these particular psychiatric disorders? At first glance, they appear to be very different diseases. Amyotrophic lateral sclerosis is a progressive neurodegenerative disorder and the others are chronic psychiatric disorders without evidence of neurodegeneration. Within these psychiatric diseases, there are important demographic and symptom differences. Schizophrenia typically presents in early adulthood, between the ages of 15 and 25 years; however, autism presents in the first few years of life. In contrast, symptoms of ALS appear muchlater inlife,withdiagnosistypicallymadebetweentheages of 55 and 75 years. Environmental factors have been linked with all these diseases, but the list of potential exposures for each disease is different. In ALS, smoking, toxins, heavy metals, athleticism, chronic traumatic encephalopathy, military service, electromagnetic fields, and pesticides have all been identified as possible associated exposures. However, the only consistently identified risk factors are male sex and older age. Smoking has been confirmed in several studies and is likely a factor, but not all studies have confirmed it.7 In schizophrenia and autism, the focus has been quite different. Studies have been directed toward neurodevelopmental exposures, examining the in utero and postnatal periods for toxin exposure, nutritional deprivation, and exposure to trauma. Additional research on schizophrenia has focused on migration patterns, drug abuse, and social disparities.8 Although studies have Related article Opinion