Heterogeneous responses of dorsal root ganglion neurons in neuropathies induced by peripheral nerve trauma and the antiretroviral drug stavudine

© 2014 The Authors. European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation - EFIC®. Funding sources E.K.B. was funded by a BBSRC PhD studentship. A.N., A.S.C.R. and T.P. were funded by a Wellcome Trust Strategic Award (London Pain Consortium; ref. 083259). A.S.C.R. and W.H. were funded by the Innovative Medicines Initiative Joint Undertaking (Europain; grant agreement no. 115007). We thank Pfizer for providing stavudine. Conflicts of interest None declared. Funded by BBSRC PhD studentship Wellcome Trust Strategic Award. Grant Number: 083259 Innovative Medicines Initiative Joint Undertaking. Grant Number: 115007Peer reviewedPublisher PD

Temporal expression of neurochemical markers in primary sensory neurones in traumatic and non-traumatic models of neuropathic pain

Introduction: Expression of neurochemical markers in dorsal root ganglion (DRG) has been shown to underlie nerve injury induced neuropathic pain and are usually examined once post injury in rodent models. Here I hypothesize that neurochemical markers are expressed differentially at various time points post nerve injury and that expression of these markers differ between traumatic and non-traumatic models of neuropathic pain, thus reflecting variations in pathophysiology. In two different rat models of neuropathic pain, namely, the tibial nerve transection (TNT) and the d4T (HIV antiretroviral drug) associated toxic neuropathy; immunohistochemical labelling was used to determine the expression of various neurochemical markers across time. Double labelling with peripherin or NF-200 (labels small and large neurons respectively) and a cell size analysis were conducted to validate cellular phenotype. Pain behaviour was measured in vivo using mechanical and thermal hypersensitivity assays. To confirm tibial nerve distribution in the DRGs, Fluorogold retrograde labelling was performed. I also explored the effect of the omega-3 polyunsaturated fatty acid dicosahexonoic acid (DHA) on TNT associated mechanical hypersensitivity and inflammation, as previous studies have shown DHA to be both anti-inflammatory and neuroprotective in animal models of spinal cord injury and stroke, and therefore could be relevant in peripheral nerve injury. Results: [Table of results appears here. To view, please open pdf attachment] From day 7, TNT rats developed mechanical hypersensitivity (↓62% from baseline at peak, day 28). Rats injected with d4T exhibited bilateral hind paw mechanical hypersensitivity (↓~47% from baseline at peak, day 22), but failed to exhibit any neurochemical changes in the DRG such as that observed in TNT injury. Seven days following Fluorogold injection into the tibial nerve of naive rats, labelling was identified in the L4 (38.5%) and L5 (27.5%) DRGs. Since DHA did not alter TNT induced mechanical hypersensitivity, key neurochemical markers were not evaluated. Investigations examined the potential of DHA to modulate the DRG macrophage response, and revealed no differences compared to saline controls at day 28 post TNT injury. Conclusion: The results of the study demonstrate completely different expression patterns of neurochemical markers following TNT injury and treatment with d4T, and highlight the mechanistic difference between nerve trauma and antiretroviral associated neuropathic pain

Myocardial ischemia reperfusion injury and cardioprotection in the presence of sensory neuropathy: therapeutic options

During the last decades, mortality of acute myocardial infarction has been dramatically improved, however, the incidence of post-infarction heart failure is still increasing. Cardioprotection by ischemic conditioning have been discovered more than 3 decades ago, however, its clinical translation is still an unmet need, mainly due to the disrupted cardioprotective signalling pathways in the presence of different cardiovascular risk factors and comorbidities and their medications. Sensory neuropathy is one of the comorbidities that has been shown to interfere with cardioprotection. In the present review we summarize the diverse aetiology of sensory neuropathies and the mechanisms by which neuropathies may interfere with ischemic heart disease and cardioprotective signalling. Moreover, we suggest future therapeutic options targeting ischemic heart and sensory neuropathy simultaneously

Monocyte / Macrophage Activation and Traffic Mediates HIV and SIV – Associated Peripheral Neuropathy

Thesis advisor: Tricia H. BurdoHuman immunodeficiency virus-associated peripheral neuropathy (HIVPN) continues to be a prevalent comorbidity of HIV infection, despite virologic control due to effective antiretroviral therapy (ART). Symptoms include bilateral tingling, numbness, and pain in distal extremities. Severity of symptoms is associated with a loss of intraepidermal nerve fiber density (IENFD) in the feet. Damage to the dorsal root ganglia (DRG) has also been observed in postmortem tissue analysis from patients with HIV-PN. Treatment options are limited due to a lack of understanding of the disease pathogenesis. Chronic monocyte activation and accumulation of macrophages in peripheral nervous system (PNS) tissues has been reported but few studies have directly demonstrated the role of monocyte/macrophage activation and traffic in the pathogenesis of HIV-PN. The central hypothesis of this thesis is that monocyte activation and traffic mediates PNS neuronal damage. We addressed this hypothesis in several ways. In chapter 2, we describe pathology seen in a rapid disease progression animal model of HIV-PN. We found that an early loss of IENFD preceded a loss of small diameter DRG neurons. In chapter 3, we associated DRG pathology with an accumulation of inflammatory macrophages surrounding DRG neurons. Increased monocyte traffic to the DRG was associated with severity of DRG pathology and with a loss of IENFD. In chapter 4, we directly tested the impact of monocyte traffic on DRG pathology by blocking leukocyte traffic with an anti-VLA-4 antibody, natalizumab. Blocking cell traffic reduced accumulation of macrophages in the DRG and improved pathology. Next we treated animals with methylglyoxal-bisguanylhydrazone (MGBG) to specifically target myeloid cells and reduce their activation. MGBG treatment improved DRG pathology and reduced accumulation of macrophages in tissues. Having demonstrated the role of monocyte traffic and activation, we aimed to identify signaling proteins and inflammatory proteins associated with PNS pathology. We found elevated monocyte chemoattractants in DRG tissue and elevated markers of monocyte activation in plasma that were associated with a loss of IENFD. Together, these studies demonstrate that systemic monocyte activation, macrophage accumulation in DRG tissue, and monocyte traffic plays a major role in SIV-PN pathogenesis. These studies provide novel insight into immune mechanisms that impact neuronal loss during SIV infection. Thus, modulating macrophage activation and reducing monocyte traffic may have therapeutic benefits to patients suffering from or at risk of developing HIV-PN.Thesis (PhD) — Boston College, 2016.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Biology

The test-retest reliability of the lower extremity functional scale in HIV-related distal sensory peripheral neuropathy

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the Degree of Master of Science (Physiotherapy). Johannesburg, 2018.Background: The Human Immunodeficiency Virus (HIV) and the Acquired Immune Deficiency Syndrome (AIDS) have posed a serious disease burden on society. The side effects issuing from the anti`-retroviral drugs (ARVs) include Distal Sensory Peripheral Neuropathy (DSPN), a common neurological complication. The Lower Extremity Functional Scale (LLFS) is a reliable and valid tool that has been used for measuring the lower limb functional capacity of patients presenting with DSPN in countries other than Botswana. As such, it is necessary to test its test-retest reliability in Botswana. Aim: The aim of this study was to determine the test-retest reliability of the Lower Extremity Functional Scale (LEFS) among HIV-related DSPN patients in Botswana. Methodology: This study involved a test-retest reliability study based on a time interval of seven to 10 days. A total of 320 HIV patients from six hospitals in Gaborone, Botswana, were screened for DSPN according to the relevant inclusion and exclusion criteria .The percentage of the total patients who were diagnosed with DSPN was 26.3% (84). The lower extremity functional scale LEFS questionnaire was administered twice with a seven to 10-day period interval and the results of the assessment were recorded and analysed. Measurements of central tendencies were used to summarize the demographic data and the clinical information for the lower extremity functional scale information obtained. Because the data sets were categorical, Spearman’s correlation analysis was conducted to determine the efficacy of the test-retest reliability. Furthermore, the Intraclass correlation (ICC) was used for measuring the internal consistency of the LEFS questionnaire. Demographic data such as age, gender, education and marital status, and clinical information pertaining to the participants were used to describe them. Results: A total of 84 HIV patients from six hospitals who were on anti-retroviral therapy (ART) and presenting with DSPN participated in the study. The test-retest reliability was found to range from rs=0.74-0.99, ICC = 0.96. SEM=4.88 Conclusion: The study results showed strong test-retest reliability and good internal consistency. Hence, the LEFS questionnaire can be considered reliable as a standard from which to monitor lower limb functionality in HIV-related Distal Sensory Peripheral Neuropathy among patients in Botswana.LG201

Axonal excitability in disorders of the peripheral and central nervous system

Peripheral axonal excitability techniques have given pathophysiological insights into many peripheral nerve disorders, with clinical application still in its infancy. Small excitability changes are usually seen compared to controls, raising questions of sensitivity. The remote effects of central lesions on peripheral excitability are not well defined. The purpose of this thesis was to correlate the changes of excitability in peripheral neuropathic disorders with their clinical signs and nerve conduction findings, and to examine for changes in peripheral nerves in a predominantly central nervous disease model. Three peripheral disorders were studied in this way for the first time. To look for a central effect on peripheral nerves, multiple sclerosis (MS) was studied, and compared with other lesional central nervous disorders. Ischaemic depolarisation was suggested in end-stage liver disease and this was not reversible one year after liver transplantation. Similar findings were noted in HIV-positive subjects but only in nucleoside drug-related neuropathy, distinguishing it from distal sensory polyneuropathy. In mitochondrial disease, motor studies showed no changes at rest or with experimental ischaemia. Sensitivity and subset comparisons indicate that in liver disease, some excitability changes correlated with peripheral clinical signs but not standard nerve conduction abnormalities. The reverse was true in mitochondrial disease. Roughly 20-25% of patients with end-stage liver neuropathy and nucleoside neuropathy were identified to fall outside control 95% confidence interval limits. Upregulated slow K+ channels seen in peripheral motor axons of MS are possibly a response to enhanced persistent inward currents (PICs) at the motoneuron following suprasegmental input interruption. In contrast, peripheral sensory studies show increased fast K+ conductance through altered gating kinetics, possibly because of humoral factors acting locally to loosen the paranodal seal

Desarrollo de modelos in vitro de dolor y su aplicación al cribado de alto rendimiento

A pesar de que el dolor neuropático es una patología con una gran prevalencia y altamente incapacitante, continúa siendo una necesidad terapéutica no cubierta debido a la escasa eficacia de los fármacos empleados para su tratamiento. Para buscar fármacos para el dolor neuropático con nuevos mecanismos de acción, en la presente tesis doctoral se desarrolló y caracterizó un modelo de cribado de alto rendimiento basado en una línea celular inmortalizada de origen neuronal; este modelo resulta adecuado para buscar moléculas que contrarresten tanto la hiperexcitabilidad de las neuronas sensoriales primarias como la neurodegeneración que producen algunos tratamientos antitumorales y antirretrovirales

A clinical investigation of chronic pain in subjects with HIV-associated sensory neuropathy

HIV-associated sensory neuropathy (HIV-SN) is a debilitating complication of HIV infection and its treatment. However, no commercially available pharmacotherapy has demonstrated consistent efficacy at clinical trial. This study aims to identify strategies to improve clinical trial design in HIV-SN by deeply phenotyping a cohort of people living with HIV, and through a meta-analysis of the placebo response in HIV-SN trials. 148 subjects were recruited, including 81 with HIV-SN. Age was the only independent predictor of neuropathy in this cohort. The prevalence of multiple chronic pain diagnoses was high, especially in those with HIV-SN (82.5% versus 61.2%, p=0.0008). This indicates that careful characterisation of painful conditions at trial entry is required to identify efficacy of the intervention with respect to HIV-SN-related symptoms specifically. Subjects showed heterogeneity of symptoms and signs, determined by symptom-based questionnaires and quantitative sensory testing, and could be allocated to distinct ‘sensory profiles’. Those with HIV-SN displayed predominantly ‘mechanical hyperalgesia’ (43.2%) and ‘sensory loss’ (30.3%) profiles. Similar profiling at clinical trial enrolment could allow for the identification of differential responses to therapy at a sub-group level. A preliminary healthy volunteer study allowed for assessment of reliability and measurement error in conditioned pain modulation (CPM). There was no difference in CPM response between those with and without neuropathy, but the response was heterogeneous. CPM may not yet be robust enough to recommend as a profiling measure in trials of HIV-SN. Corneal confocal microscopy and a point-of-care nerve conduction device were assessed for their effectiveness as tools for screening and monitoring HIV-SN. Both were shown to be useful and have the potential to increase the certainty of a diagnosis of neuropathic pain at trial enrolment. A 2012 meta-analysis identified a greater placebo response in trials of HIV-SN compared to other neuropathic pain conditions. Repeat meta-analysis identified no difference in placebo response between HIV-SN and a comparable sensory neuropathy, diabetic polyneuropathy.Open Acces

Pathogenesis of Encephalitis

Many infectious agents, such as viruses, bacteria, and parasites, can cause inflammation of the central nervous system (CNS). Encephalitis is an inflammation of the brain parenchyma, which may result in a more advanced and serious disease meningoencephalitis. To establish accurate diagnosis and develop effective vaccines and drugs to overcome this disease, it is important to understand and elucidate the mechanism of its pathogenesis. This book, which is divided into four sections, provides comprehensive commentaries on encephalitis. The first section (6 chapters) covers diagnosis and clinical symptoms of encephalitis with some neurological disorders. The second section (5 chapters) reviews some virus infections with the outlines of inflammatory and chemokine responses. The third section (7 chapters) deals with the non-viral causative agents of encephalitis. The last section (4 chapters) discusses the experimental model of encephalitis. The different chapters of this book provide valuable and important information not only to the researchers, but also to the physician and health care workers