Expression of multidrug resistance (MDR) features by acute myeloid leukemia (AML) cells predicts a poor response to many treatments. The MDR phenotype often correlates with expression of ...P-glycoprotein (Pgp), and Pgp antagonists such as cyclosporine (CSA) have been used as chemosensitizing agents in AML. Gemtuzumab ozogamicin, an immunoconjugate of an anti-CD33 antibody linked to calicheamicin, is effective monotherapy for CD33+ relapsed AML. However, the contribution of Pgp to gemtuzumab ozogamicin resistance is poorly defined. In this study, blast cell samples from relapsed AML patients eligible for gemtuzumab ozogamicin clinical trials were assayed for Pgp surface expression and Pgp function using a dye efflux assay. In most cases, surface expression of Pgp correlated with Pgp function, as indicated by elevated dye efflux that was inhibited by CSA. Among samples from patients who either failed to clear marrow blasts or failed to achieve remission, 72% or 52%, respectively, exhibited CSA-sensitive dye efflux compared with 29% (P = .003) or 24% (P < .001) among samples from responders. In vitro gemtuzumab ozogamicin–induced apoptosis was also evaluated using an annexin V–based assay. Low levels of drug-induced apoptosis were associated with CSA-sensitive dye efflux, whereas higher levels correlated strongly with achievement of remission and marrow blast clearance. In vitro drug-induced apoptosis could be increased by CSA in 14 (29%) of 49 samples exhibiting low apoptosis in the absence of CSA. Together, these findings indicate that Pgp plays a role in clinical resistance to gemtuzumab ozogamicin and suggest that treatment trials combining gemtuzumab ozogamicin with MDR reversal agents are warranted.
This study investigated the clinical characteristics and somatosensory profiles of patients suffering from leprosy in Mumbai, India. A cross-sectional deep profiling study was conducted in 86 ...patients with leprosy (with and without pain) using an extensive battery of phenotyping measures including structured clinical examination, psychological state (General Health Questionnaire GHQ-12), and a quality-of-life condition-specific instrument (Brief Pain Inventory-short form). Quantitative sensory testing was performed according to the protocol of the German Research Network on Neuropathic Pain (DFNS) to assess the somatosensory profiles in the ulnar nerve innervation territory of all participants (dorsum of the hand). Reference data from 50 healthy Indian subjects were within the range of published DFNS values. Somatosensory profiles in leprosy patients with clinically or electroneurographically diagnosed neuropathy (with and without pain) revealed a profile of sensory loss to thermal and tactile stimuli combined with preservation of vibration and deep pressure detection. Sensory gain phenomena were not generally observed in patients with leprosy. In the group of subclinical neuropathy, a high degree of impaired thermal sensation was found, which could be clinically deployed to enhance identification of leprosy neuropathy at an early stage. Quantitative sensory testing can effectively document leprosy-associated neuropathy but does not distinguish between patients with or without pain. Patients with leprosy and neuropathic pain reported a poor quality of life and less psychological well-being compared with the pain-free patients with leprosy neuropathy.
Glial cell line-derived neurotrophic factor (GDNF) has potent trophic effects on adult sensory neurons after nerve injury and is one of a family of proteins that includes neurturin, persephin, and ...artemin. Sensitivity to these factors is conferred by a receptor complex consisting of a ligand binding domain (GFRalpha1-GFRalpha4) and a signal transducing domain RET. We have investigated the normal expression of GDNF family receptor components within sensory neurons and the response to nerve injury. In normal rats, RET and GFRalpha1 were expressed in a subpopulation of both small- and large-diameter afferents projecting through the sciatic nerve 60 and 40% of FluoroGold (FG)-labeled cells, respectively. GFRalpha2 and GFRalpha3 were both expressed principally within small-diameter DRG cells (30 and 40% of FG-labeled cells, respectively). Two weeks after sciatic axotomy, the expression of GFRalpha2 was markedly reduced (to 12% of sciatic afferents). In contrast, the proportion of sciatic afferents that expressed GFRalpha1 increased (to 66% of sciatic afferents) so that virtually all large-diameter afferents expressed this receptor component, and the expression of GFRalpha3 also increased (to 66% of sciatic afferents) so that almost all of the small-diameter afferents expressed this receptor component after axotomy. There was little change in RET expression. The changes in the proportions of DRG cells expressing different receptor components were mirrored by alterations in the total RNA levels within the DRG. The changes in GFRalpha1 and GFRalpha2 expression after axotomy could be largely reversed by treatment with GDNF.
Neurotrophic factors have an established developmental role in regulating the survival and specification of sensory neurons. However, these factors continue to exert an important influence on sensory ...neurons throughout the postnatal period and into adult life. In adulthood, approximately one-half of nociceptors are dependent on nerve growth factor (NGF) for trophic support, whereas the other half are sensitive to glial cell line-derived neurotrophic factor (GDNF). It is now known that many chronic pain states are maintained by widespread changes in the anatomy, neurochemistry, and function of the sensory nervous system both at the level of the primary sensory neuron and the dorsal horn of the spinal cord. Trophic factors appear to orchestrate many of these dynamic changes. This review highlights some of the key roles played by these molecules and in particular the role of NGF in the peripheral sensitization of nociceptors and brain-derived neurotrophic factor (BDNF) as a central pain modulator.
The acronym CANOMAD encompasses chronic ataxic neuropathy combined with ophthalmoplegia, M protein, cold agglutinins, and anti‐disialosyl antibodies.Herein we describe 2 patients presenting with ...progressive ataxic neuropathy who only developed ophthalmoplegia after a significant delay post‐presentation, which in 1 case had features indicative of brainstem dysfunction. Both patients were found to have an IgM paraprotein and anti‐disialosyl antibodies. They responded to treatment with intravenous immunoglobulin, thus illustrating the importance of diagnosing this condition. Muscle Nerve, 2011
Abstract
The aims of our study were to use whole genome sequencing in a cross-sectional cohort of patients to identify new variants in genes implicated in neuropathic pain, to determine the ...prevalence of known pathogenic variants and to understand the relationship between pathogenic variants and clinical presentation. Patients with extreme neuropathic pain phenotypes (both sensory loss and gain) were recruited from secondary care clinics in the UK and underwent whole genome sequencing as part of the National Institute for Health and Care Research Bioresource Rare Diseases project. A multidisciplinary team assessed the pathogenicity of rare variants in genes previously known to cause neuropathic pain disorders and exploratory analysis of research candidate genes was completed. Association testing for genes carrying rare variants was completed using the gene-wise approach of the combined burden and variance-component test SKAT-O. Patch clamp analysis was performed on transfected HEK293T cells for research candidate variants of genes encoding ion channels. The results include the following: (i) Medically actionable variants were found in 12% of study participants (205 recruited), including known pathogenic variants: SCN9A(ENST00000409672.1): c.2544T>C, p.Ile848Thr that causes inherited erythromelalgia, and SPTLC1(ENST00000262554.2):c.340T>G, p.Cys133Tr variant that causes hereditary sensory neuropathy type-1. (ii) Clinically relevant variants were most common in voltage-gated sodium channels (Nav). (iii) SCN9A(ENST00000409672.1):c.554G>A, pArg185His variant was more common in non-freezing cold injury participants than controls and causes a gain of function of NaV1.7 after cooling (the environmental trigger for non-freezing cold injury). (iv) Rare variant association testing showed a significant difference in distribution for genes NGF, KIF1A, SCN8A, TRPM8, KIF1A, TRPA1 and the regulatory regions of genes SCN11A, FLVCR1, KIF1A and SCN9A between European participants with neuropathic pain and controls. (v) The TRPA1(ENST00000262209.4):c.515C>T, p.Ala172Val variant identified in participants with episodic somatic pain disorder demonstrated gain-of-channel function to agonist stimulation. Whole genome sequencing identified clinically relevant variants in over 10% of participants with extreme neuropathic pain phenotypes. The majority of these variants were found in ion channels. Combining genetic analysis with functional validation can lead to a better understanding as to how rare variants in ion channels lead to sensory neuron hyper-excitability, and how cold, as an environmental trigger, interacts with the gain-of-function NaV1.7 p.Arg185His variant. Our findings highlight the role of ion channel variants in the pathogenesis of extreme neuropathic pain disorders, likely mediated through changes in sensory neuron excitability and interaction with environmental triggers.
Themistocleous et al. report that whole genome sequencing revealed clinically relevant variants in 12% of participants with extreme neuropathic pain disorders. The majority of variants were in ion channels, including new phenotype associations (SCN9A p.Arg185His and non-freezing cold injury) and novel gain-of-function variants (TRPA1 p.Ala172Val and episodic pain).
Graphical Abstract
Graphical abstract
Chronic pain represents a major health burden; this maladaptive pain state occurs as a consequence of hypersensitivity within the peripheral and central components of the somatosensory system. High ...throughput technologies (genomics, transciptomics, lipidomics, and proteomics) are now being applied to tissue derived from pain patients as well as experimental pain models to discover novel pain mediators. The use of clustering, meta‐analysis and other techniques can help refine potential candidates. Of particular importance are systems biology methods, such as co‐expression network generating algorithms, which infer potential associations/interactions between molecules and build networks based on these interactions. Protein–protein interaction networks allow the lists of potential targets generated by these different platforms to be analyzed in their biological context. Outputs from these different methods must also be related to the clinical pain phenotype. The improved and standardized phenotyping of pain symptoms and sensory signs enables much better subject stratification. Our hope is that, in the future, the use of computational approaches to integrate datasets including sensory phenotype as well as the outputs of high throughput technologies will help define novel pain mediators and provide insights into the pathogenesis of chronic pain. WIREs Syst Biol Med 2013, 5:11–35. doi: 10.1002/wsbm.1192
This article is categorized under:
Physiology > Mammalian Physiology in Health and Disease
Biological Mechanisms > Regulatory Biology
Laboratory Methods and Technologies > RNA Methods
Several lines of evidence suggest that neurotrophin administration may be of some therapeutic benefit in the treatment of peripheral neuropathy. However, a third of sensory neurons do not express ...receptors for the neurotrophins. These neurons are of small diameter and can be identified by the binding of the lectin IB4 and the expression of the enzyme thiamine monophosphatase (TMP). Here we show that these neurons express the receptor components for glial-derived neurotrophic factor (GDNF) signaling (RET, GFRalpha-1, and GFRalpha-2). In lumbar dorsal root ganglia, virtually all IB4-labeled cells express RET mRNA, and the majority of these cells (79%) also express GFRalpha-1, GFRalpha-2, or GFRalpha-1 plus GFRalpha-2. GDNF, but not nerve growth factor (NGF), can prevent several axotomy-induced changes in these neurons, including the downregulation of IB4 binding, TMP activity, and somatostatin expression. GDNF also prevents the slowing of conduction velocity that normally occurs after axotomy in a population of small diameter DRG cells and the A-fiber sprouting into lamina II of the dorsal horn. GDNF therefore may be useful in the treatment of peripheral neuropathies and may protect peripheral neurons that are refractory to neurotrophin treatment.
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