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Alexander SN, Reed OA, Burton MD. Spinal cord microglia drive sex differences in ethanol-mediated PGE2-induced allodynia. Brain Behav Immun 2024:S0889-1591(24)00549-X. [PMID: 39147173 DOI: 10.1016/j.bbi.2024.08.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 08/09/2024] [Accepted: 08/11/2024] [Indexed: 08/17/2024] Open
Abstract
The mechanisms of how long-term alcohol use can lead to persistent pain pathology are unclear. Understanding how earlier events of short-term alcohol use can lower the threshold of non-painful stimuli, described as allodynia could prove prudent to understand important initiating mechanisms. Previously, we observed that short-term low-dose alcohol intake induced female-specific allodynia and increased microglial activation in the spinal cord dorsal horn. Other literature describes how chronic ethanol exposure activates Toll-like receptor 4 (TLR4) to initiate inflammatory responses. TLR4 is expressed on many cell types, and we aimed to investigate whether TLR4 on microglia is sufficient to potentiate allodynia during a short-term/low-dose alcohol paradigm. Our study used a novel genetic model where TLR4 expression is removed from the entire body by introducing a floxed transcriptional blocker (TLR4-null background (TLR4LoxTB)), then restricted to microglia by breeding TLR4LoxTB animals with Cx3CR1:CreERT2 animals. As previously reported, after 14 days of ethanol administration alone, we observed no increased pain behavior. However, we observed significant priming effects 3 h post intraplantar injection of a subthreshold dose of prostaglandin E2 (PGE2) in wild-type and microglia-TLR4 restricted female mice. We also observed a significant female-specific shift to pro-inflammatory phenotype and morphological changes in microglia of the lumbar dorsal horn. Investigations in pain priming-associated neuronal subtypes showed an increase of c-Fos and FosB activity in PKCγ interneurons in the dorsal horn of female mice directly corresponding to increased microglial activity. This study uncovers cell- and female-specific roles of TLR4 in sexual dimorphisms in pain induction among non-pathological drinkers.
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Affiliation(s)
- Shevon N Alexander
- Neuroimmunology and Behavior Lab (NIB), Department of Neuroscience, School of Behavioral and Brain Science, Center for Advanced Pain Studies (CAPS), University of Texas at Dallas, Richardson, TX, USA
| | - Olivia A Reed
- Neuroimmunology and Behavior Lab (NIB), Department of Neuroscience, School of Behavioral and Brain Science, Center for Advanced Pain Studies (CAPS), University of Texas at Dallas, Richardson, TX, USA
| | - Michael D Burton
- Neuroimmunology and Behavior Lab (NIB), Department of Neuroscience, School of Behavioral and Brain Science, Center for Advanced Pain Studies (CAPS), University of Texas at Dallas, Richardson, TX, USA.
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Bertagna NB, Wilson L, Bailey CK, Cruz FC, Albrechet-Souza L, Wills TA. Long-lasting mechanical hypersensitivity and CRF receptor type-1 neuron activation in the BNST following adolescent ethanol exposure. ALCOHOL, CLINICAL & EXPERIMENTAL RESEARCH 2024; 48:48-57. [PMID: 38206283 PMCID: PMC10784637 DOI: 10.1111/acer.15228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 10/26/2023] [Accepted: 11/08/2023] [Indexed: 01/12/2024]
Abstract
BACKGROUND Adolescent alcohol use can produce long-lasting alterations in brain function, potentially leading to adverse health outcomes in adulthood. Emerging evidence suggests that chronic alcohol use can increase pain sensitivity or exacerbate existing pain conditions, but the potential neural mechanisms underlying these effects require further investigation. Here, we evaluate the impact of chronic ethanol vapor on mechanical sensitivity over the course of acute and protracted withdrawal in adolescent and adult male and female mice, and its potential association with alterations in corticotropin-releasing factor (CRF) signaling within the bed nucleus of the stria terminalis (BNST). METHODS Adolescent and adult male and female mice underwent intermittent ethanol vapor exposure on 4 days/week for 2 weeks. Mechanical thresholds were evaluated 5 h and 7, 14, 21, and 28 d after cessation of ethanol exposure using the von Frey test. For mice with a history of adolescent ethanol exposure, brains were collected for in situ RNAscope processing after the final test. Messenger RNA expression of c-Fos, Crfr1, and Crf in the BNST subregions was examined. RESULTS Exposure to intermittent ethanol vapor induced persistent mechanical hypersensitivity during withdrawal in both adolescent and adult mice. Notably, the effect was more transient in mice exposed to ethanol during adulthood, resolving by day 28 after ethanol exposure. Furthermore, both male and female mice with a history of adolescent ethanol exposure exhibited increased activation of CRF receptor type 1 (CRFR1) neurons within the dorsolateral BNST. CONCLUSIONS Our results support the conclusion that intermittent ethanol exposure can induce mechanical hypersensitivity, potentially through the activation of BNST CRFR1 neurons. These findings provide a basis for future studies aimed at evaluating specific subpopulations of BNST neurons and their contribution to pain in individuals with a history of alcohol use.
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Affiliation(s)
- Natalia B. Bertagna
- Department of Cell Biology & Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
- Department of Pharmacology, Federal University of São Paulo, São Paulo, SP, Brazil
| | - Lisa Wilson
- Department of Cell Biology & Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
- Alcohol & Drug Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
| | - Connor K. Bailey
- Department of Cell Biology & Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
| | - Fabio C. Cruz
- Department of Pharmacology, Federal University of São Paulo, São Paulo, SP, Brazil
| | - Lucas Albrechet-Souza
- Department of Cell Biology & Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
- Alcohol & Drug Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
| | - Tiffany A. Wills
- Department of Cell Biology & Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
- Alcohol & Drug Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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