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Hale C, Moulton JK, Otis Y, Ganter G. ARMADILLO REGULATES NOCICEPTIVE SENSITIVITY IN THE ABSENCE OF INJURY. Mol Pain 2022; 18:17448069221111155. [PMID: 35712882 PMCID: PMC9500252 DOI: 10.1177/17448069221111155] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Abnormal pain has recently been estimated to affect ∼50 million adults each year within the United States. With many treatment options for abnormal pain, such as opioid analgesics, carrying numerous deleterious side effects, research into safer and more effective treatment options is crucial. To help elucidate the mechanisms controlling nociceptive sensitivity, the Drosophila melanogaster larval nociception model has been used to characterize well-conserved pathways through the use of genetic modification and/or injury to alter the sensitivity of experimental animals. Mammalian models have provided evidence of β-catenin signaling involvement in neuropathic pain development. By capitalizing on the conserved nature of β-catenin functions in the fruit fly, here we describe a role for Armadillo, the fly homolog to mammalian β-catenin, in regulating baseline sensitivity in the primary nociceptor of the fly, in the absence of injury, using under- and over-expression of Armadillo in a cell-specific manner. Underexpression of Armadillo resulted in hyposensitivity, while overexpression of wild-type Armadillo or expression of a degradation-resistant Armadillo resulted in hypersensitivity. Neither underexpression nor overexpression of Armadillo resulted in observed dendritic morphological changes that could contribute to behavioral phenotypes observed. These results showed that focused manipulation of Armadillo expression within the nociceptors is sufficient to modulate baseline response in the nociceptors to a noxious stimulus and that these changes are not shown to be associated with a morphogenetic effect.
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Affiliation(s)
- Christine Hale
- Graduate School of Biomedical Science and Engineering6251University of Maine System
| | | | - Yvonne Otis
- School of Biological Sciences172741University of New England College of Arts and Sciences
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McParland A, Moulton J, Brann C, Hale C, Otis Y, Ganter G. The brinker repressor system regulates injury-induced nociceptive sensitization in Drosophila melanogaster. Mol Pain 2021; 17:17448069211037401. [PMID: 34399634 PMCID: PMC8375337 DOI: 10.1177/17448069211037401] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Chronic pain is a debilitating condition affecting millions of people worldwide, and an improved understanding of the pathophysiology of chronic pain is urgently needed. Nociceptors are the sensory neurons that alert the nervous system to potentially harmful stimuli such as mechanical pressure or noxious thermal temperature. When an injury occurs, the nociceptive threshold for pain is reduced and an increased pain signal is produced. This process is called nociceptive sensitization. This sensitization normally subsides after the injury is healed. However, dysregulation can occur which results in sensitization that persists after the injury has healed. This process is thought to perpetuate chronic pain. The Hedgehog (Hh) signaling pathway has been previously implicated in nociceptive sensitization in response to injury in Drosophila melanogaster. Downstream of Hh signaling, the Bone Morphogenetic Protein (BMP) pathway has also been shown to be necessary for this process. Here, we describe a role for nuclear components of BMP’s signaling pathway in the formation of injury-induced nociceptive sensitization. Brinker (Brk), and Schnurri (Shn) were suppressed in nociceptors using an RNA-interference (RNAi) “knockdown” approach. Knockdown of Brk resulted in hypersensitivity in the absence of injury, indicating that it normally acts to suppress nociceptive sensitivity. Animals in which transcriptional activator Shn was knocked down in nociceptors failed to develop normal allodynia after ultraviolet irradiation injury, indicating that Shn normally acts to promote hypersensitivity after injury. These results indicate that Brk-related transcription regulators play a crucial role in the formation of nociceptive sensitization and may therefore represent valuable new targets for pain-relieving medications.
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Affiliation(s)
- Aidan McParland
- College of Arts and Sciences, University of New England, Biddeford, ME, USA.,University of British Columbia, Vancouver, British Columbia, Canada
| | - Julie Moulton
- College of Arts and Sciences, University of New England, Biddeford, ME, USA
| | - Courtney Brann
- College of Arts and Sciences, University of New England, Biddeford, ME, USA.,College of Osteopathic Medicine, University of New England, Biddeford, ME, USA
| | - Christine Hale
- College of Arts and Sciences, University of New England, Biddeford, ME, USA.,Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Yvonne Otis
- College of Arts and Sciences, University of New England, Biddeford, ME, USA
| | - Geoffrey Ganter
- College of Arts and Sciences, University of New England, Biddeford, ME, USA.,Center for Excellence in the Neurosciences, University of New England, Biddeford, ME, USA
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