Biology subjects

Levine, J. D.

Publications and source records attributed to Levine, J. D..

6 recordsLinked to original sources

bioRxiv2023

The Primary Cilium and its Hedgehog Signaling in Nociceptors Contribute to Inflammatory and Neuropathic Pain

The primary cilium, a 1-3 m long hair-like structure protruding from the surface of almost all cells in the vertebrate body, is critical for neuronal development and also functions in the adult. As the migratory neural crest settles into dorsal root ganglia (DRG) sensory neurons elaborate a single primary cilium at their soma that is maintained into adult stages. While it is not known if primary cilia are expressed in nociceptors, or their potential function in the mature DRG neuron, recent studies have shown a role for Hedgehog, whose signaling demonstrates a dependence on primary cilia, in nociceptor sensitization. Here we report the expression of primary cilia in rat and mouse nociceptors, where they modulate mechanical nociceptive threshold, and contribute to inflammatory and neuropathic pain. When siRNA targeting Ift88, a primary cilium-specific intra-flagellar transport (IFT) protein required for ciliary integrity, was administered by intrathecal injection, in the rat, it resulted in loss of Ift88 mRNA in DRG, and primary cilia in neuronal cell bodies, which was associated with an increase in mechanical nociceptive threshold, and abrogation of hyperalgesia induced by the pronociceptive inflammatory mediator, prostaglandin E2, and painful peripheral neuropathy induced by a neurotoxic chemotherapy drug, paclitaxel. To provide further support for the role of the primary cilium in nociceptor function we also administered siRNA for another IFT protein, Ift52. Ift52 siRNA results in loss of Ift52 in DRG and abrogates paclitaxel-induced painful peripheral neuropathy. Attenuation of Hedgehog-induced hyperalgesia by Ift88 knockdown supports a role for the primary cilium in the hyperalgesia induced by Hedgehog, and attenuation of paclitaxel chemotherapy-induced neuropathy (CIPN) by cyclopamine, which attenuates Hedgehog signaling, suggests a role of Hedgehog in CIPN. Our findings support a role of nociceptor primary cilia in the control of mechanical nociceptive threshold and in inflammatory and neuropathic pain, the latter, at least in part, Hedgehog dependent.

neuroscience↗

bioRxiv2023

Sensitization of Human and Rat Nociceptors by Low Dose Morphine is TLR4-dependent

While opioids remain amongst the most effective treatments for moderate-to-severe pain, their substantial side effect profile remains a major limitation to broader clinical use. One such side effect is opioid-induced hyperalgesia (OIH), which includes a transition from opioid-induced analgesia to pain enhancement. Evidence in rodents supports the suggestion that OIH may be produced by the action of opioids at Toll-like Receptor 4 (TLR4) either on immune cells that, in turn, produce pronociceptive mediators to act on nociceptors, or by a direct action at nociceptor TLR4. And, sub-analgesic doses of several opioids have been shown to induce hyperalgesia in rodents by their action as TLR4 agonists. In the present in vitro patch-clamp electrophysiology experiments, we demonstrate that low dose morphine directly sensitizes human as well as rodent dorsal root ganglion (DRG) neurons, an effect of this opioid analgesic that is antagonized by LPS-RS Ultrapure, a selective TLR4 antagonist. We found that morphine (100 nM) reduced rheobase in human (by 36%) and rat (by 26%) putative C-type nociceptors, an effect of morphine that was markedly attenuated by preincubation with LPS-RS Ultrapure. Our findings support the suggestion that in humans, as well as in rodents, OIH is mediated by the direct action of opioids at TLR4 on nociceptors.

neuroscience↗

bioRxiv2023

Isolectin B4 (IB4)-conjugated streptavidin for the selective knockdown of proteins in IB4-positive (+) nociceptors

In vivo analysis of protein function in nociceptor subpopulations using antisense oligonucleotides and short interfering RNAs is limited by their non-selective cellular uptake. To address the need for selective transfection methods, we covalently linked isolectin B4 (IB4) to streptavidin and analyzed whether it could be used to study protein function in IB4(+)-nociceptors. Rats treated intrathecally with IB4-conjugated streptavidin complexed with biotinylated antisense oligonucleotides for protein kinase C epsilon (PKC{varepsilon}) mRNA were found to have: a) less PKC{varepsilon} in dorsal root ganglia (DRG), b) reduced PKC{varepsilon} expression in IB4(+) but not IB4(-) DRG neurons, and c) fewer transcripts of the PKC{varepsilon} gene in the DRG. This knockdown in PKC{varepsilon} expression in IB4(+) DRG neurons is sufficient to reverse hyperalgesic priming, a rodent model of chronic pain that is dependent on PKC{varepsilon} in IB4(+)-nociceptors. These results establish that IB4-streptavidin can be used to study protein function in a defined subpopulation of nociceptive C-fiber afferents.

neuroscience↗

bioRxiv2023

A novel small molecule PKC epsilon inhibitor reduces hyperalgesia induced by paclitaxel or opioid withdrawal

Aggressive marketing and increased prescribing of opioids for treating pain have fueled a prominent increase in opioid use disorder. This acute public health problem has led to calls for the development of non-opioid alternatives to treat chronic pain. The enzyme protein kinase C epsilon (PKC{varepsilon}) plays an important role in nociceptor sensitization, in inflammatory and neuropathic pain. Here we investigated the effects of a novel small molecule that inhibits PKC{varepsilon} in a rodent model of chemotherapy-induced neuropathic pain produced by administration of the cancer chemotherapy, paclitaxel. Because transition of opioid-dependent individuals to a non-opioid pain medication can increase pain due to opioid withdrawal, we also investigated if the PKC{varepsilon} inhibitor alters features of opioid withdrawal and opioid self-administration. This novel PKC{varepsilon} inhibitor attenuated paclitaxel-induced hyperalgesia, reversed hyperalgesia produced by opioid withdrawal, and reduced somatic signs of opioid withdrawal. This PKC{varepsilon} inhibitor did not modify opioid self-administration, nor produce self-administration. These findings suggest that PKC{varepsilon} inhibition is an effective, non-addictive strategy to treat chemotherapy-induced neuropathic pain with the added benefit of limiting hyperalgesia due to opioid withdrawal, which could facilitate switching treatment of chronic pain, in opioid-dependent individuals.

neuroscience↗

bioRxiv2019

The Evolution of Social Organization: Climate Influences Variation in Drosophilid Social Networks

Cultural norms, collective decisions, reproductive behaviour, and pathogen transmission all emerge from interaction patterns within animal social groups. These patterns of interaction support group-level phenomena that can influence an individuals fitness. The aim of this study is to understand the evolution of social organization in Drosophila. Using a comparative ecological, phylogenetic and behavioural approach, we studied the different properties of social interaction networks (SINs) formed by 20 drosophilids and the different ways these species interact. We investigate whether animal network structures arise from common ancestry, a response to the species past ecological environment, other social behaviours, or a combination of these factors. We demonstrate that differences in past climate predicted the species current SIN properties. The drosophilid phylogeny offered no value to predicting species differences in SINs through phylogenetic signal tests. This suggests group-level social behaviours in drosophilid species are shaped by divergent climates. However, we find that the distance at which flies interact correlated with the drosophilid phylogeny, indicating that behavioural elements that comprise SINs have remained largely unchanged in their recent evolutionary history. We find a significant correlation of leg length to social distance, outlining the interdependence of anatomy and complex social structures. Although SINs display a complex evolutionary relationship across drosophilids, this study provides evidence of selective pressures acting on social behaviour in Drosophila. We speculate that conserved molecular mechanisms may be shared across drosophilids deep in their evolutionary history, similar to other pervasive mechanisms, like biological clocks.

evolutionary biology↗

bioRxiv2018

Swedish Nerve Growth Factor Mutation (NGFR100W) Defines a Role for TrkA and p75NTR in Nociception

Nerve growth factor (NGF) exerts multiple functions on target neurons throughout development. The recent discovery of a point mutation leading to a change from arginine to tryptophan at residue 100 in the mature NGF{beta} sequence (NGFR100W) in patients with hereditary sensory and autonomic neuropathy, type V (HSAN V), made it possible to distinguish the signaling mechanisms that lead to two functionally different outcomes of NGF: trophic versus nociceptive. We performed extensive biochemical, cellular and live imaging experiments to examine the binding and signaling properties of NGFR100W. Our results show that, similar to the wildtype NGF (wtNGF), the naturally occurring NGFR100W mutant was capable of binding to and activating the TrkA receptor and its downstream signaling pathways to support neuronal survival and differentiation. However, NGFR100W failed to bind and stimulate the 75kD neurotrophic factor receptor (p75NTR)-mediated signaling cascades (i.e. the RhoA-Cofilin pathway). Intraplantar injection of NGFR100W into adult rats induced neither TrkA-mediated thermal nor mechanical acute hyperalgesia, but retained the ability to induce chronic hyperalgesia based on agonism for TrkA signaling. Taken together, our studies provide evidence that NGFR100W retains trophic support capability through TrkA and one aspect of its nociceptive signaling, but fails to engage p75NTR signaling pathways. Our findings suggest that wtNGF acts through TrkA to regulate the delayed priming of nociceptive responses. The integration of both TrkA and p75NTR signaling thus appears to regulate neuroplastic effects of NGF in peripheral nociception.\n\nSignificance StatementIn the present study, we characterized the naturally occurring NGFR100W mutant that is associated with hereditary sensory and autonomic neuropathy, type V. We have demonstrated for the first time that NGFR100W retains trophic support capability through TrkA but fails to engage p75NTR signaling pathways. Furthermore, following Intraplantar injection into adult rats, NGFR100W induced neither thermal nor mechanical acute hyperalgesia, but retained the ability to induce chronic hyperalgesia. We have also provided evidence that the integration of both TrkA-and p75NTR-mediated signaling thus appears to regulate neuroplastic effects of NGF in peripheral nociception. Our study with NGFR100W suggests that it is possible to uncouple trophic effect from nociceptive function, both induced by wildtype NGF.\n\nAbbreviations

neuroscience↗