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Wong CE, Hu CY, Lee PH, Huang CC, Huang HW, Huang CY, Lo HT, Liu W, Lee JS. Sciatic nerve stimulation alleviates acute neuropathic pain via modulation of neuroinflammation and descending pain inhibition in a rodent model. J Neuroinflammation 2022; 19:153. [PMID: 35706025 DOI: 10.1186/s12974-022-02513-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 06/01/2022] [Indexed: 11/12/2022] Open
Abstract
Background Neuropathic pain (NP) is characterized by abnormal activation of pain conducting pathways and manifests as mechanical allodynia and thermal hypersensitivity. Peripheral nerve stimulation is used for treatment of medically refractory chronic NP and has been shown to reduce neuroinflammation. However, whether sciatic nerve stimulation (SNS) is of therapeutic benefit to NP remains unclear. Moreover, the optimal frequency for SNS is unknown. To address this research gap, we investigated the effect of SNS in an acute NP rodent model. Methods Rats with right L5 nerve root ligation (NRL) or Sham surgery were used. Ipsilateral SNS was performed at 2 Hz, 20 Hz, and 60 Hz frequencies. Behavioral tests were performed to assess pain and thermal hypersensitivity before and after NRL and SNS. Expression of inflammatory proteins in the L5 spinal cord and the immunohistochemical alterations of spinal cord astrocytes and microglia were examined on post-injury day 7 (PID7) following NRL and SNS. The involvement of the descending pain modulatory pathway was also investigated. Results Following NRL, the rats showed a decreased pain threshold and latency on the von Frey and Hargreaves tests. The immunofluorescence results indicated hyperactivation of superficial spinal cord dorsal horn (SCDH) neurons. Both 2-Hz and 20-Hz SNS alleviated pain behavior and hyperactivation of SCDH neurons. On PID7, NRL resulted in elevated expression of spinal cord inflammatory proteins including NF-κB, TNF-α, IL-1β, and IL-6, which was mitigated by 2-Hz and 20-Hz SNS. Furthermore, 2-Hz and 20-Hz SNS suppressed the activation of spinal cord astrocytes and microglia following NRL on PID7. Activity of the descending serotoninergic pain modulation pathway showed an increase early on PID1 following 2-Hz and 20-Hz SNS. Conclusions Our results support that both 2-Hz and 20-Hz SNS can alleviate NP behaviors and hyperactivation of pain conducting pathways. We showed that SNS regulates neuroinflammation and reduces inflammatory protein expression, astrocytic gliosis, and microglia activation. During the early post-injury period, SNS also facilitates the descending pain modulatory pathway. Taken together, these findings support the therapeutic potential of SNS for acute NP. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-022-02513-y.
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Nguyen H, Sahbaie P, Goba L, Sul J, Suzaki A, Clark JD, Huang TT. Exposure to Gulf War Illness-related agents leads to the development of chronic pain and fatigue. Life Sci 2021; 283:119867. [PMID: 34358550 DOI: 10.1016/j.lfs.2021.119867] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 07/13/2021] [Accepted: 07/23/2021] [Indexed: 11/25/2022]
Abstract
AIMS A substantial contingent of veterans from the first Gulf War continues to suffer from a number of Gulf War-related illnesses (GWI) affecting the neurological and musculoskeletal systems; the most common symptoms include chronic pain and fatigue. Although animal models have recapitulated several aspects of cognitive impairments in GWI, the pain and fatigue symptoms have not been well documented to allow examination of potential pathogenic mechanisms. MAIN METHODS We used a mouse model of GWI by exposing mice repeatedly to a combination of Gulf War chemicals (pyridostigmine bromide, permethrin, DEET, and chlorpyrifos) and mild immobilization stress, followed by investigating their pain susceptibilities and fatigue symptoms. To assess whether enhanced antioxidant capacity can counter the effects of GW agents, transgenic mice overexpressing extracellular superoxide dismutase (SOD3OE) were also examined. KEY FINDINGS The mouse model recapitulated several aspects of the human illness, including hyperalgesia, impaired descending inhibition of pain, and increased tonic pain. There is a close association between chronic pain and fatigue in GWI patients. Consistent with this observation, the mouse model showed a significant reduction in physical endurance on the treadmill. Examination of skeletal muscles suggested reduction in mitochondrial functions may have contributed to the fatigue symptoms. Furthermore, the negative impacts of GW agents in pain susceptibilities were largely diminished in SOD3OE mice, suggesting that increased oxidative stress was associated with the emergence of these Gulf War symptoms. SIGNIFICANCE the mouse model will be suitable for delineating specific defects in the pain pathways and mechanisms of fatigue in GWI.
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Affiliation(s)
- Huy Nguyen
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States of America; Palo Alto Veterans Institute for Research, VA Palo Alto Health Care System, United States of America; Geriatric Research, Education, and Clinical Center, VA Palo Alto Health Care System, United States of America
| | - Peyman Sahbaie
- Department of Anesthesiology, Stanford University School of Medicine, United States of America; Palo Alto Veterans Institute for Research, VA Palo Alto Health Care System, United States of America; Anesthesiology Service, VA Palo Alto Health Care System, United States of America
| | - Lihle Goba
- Geriatric Research, Education, and Clinical Center, VA Palo Alto Health Care System, United States of America
| | - Julian Sul
- Palo Alto Veterans Institute for Research, VA Palo Alto Health Care System, United States of America
| | - Aoi Suzaki
- Palo Alto Veterans Institute for Research, VA Palo Alto Health Care System, United States of America
| | - J David Clark
- Department of Anesthesiology, Stanford University School of Medicine, United States of America; Anesthesiology Service, VA Palo Alto Health Care System, United States of America
| | - Ting-Ting Huang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States of America; Geriatric Research, Education, and Clinical Center, VA Palo Alto Health Care System, United States of America.
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Bäumler M, Feller M, Krafft S, Schiffer M, Sommer J, Straube A, Weinges F, Ruscheweyh R. Learned control over spinal nociception: Transfer and stability of training success in a long-term study. Clin Neurophysiol 2017; 128:2462-2469. [PMID: 29096221 DOI: 10.1016/j.clinph.2017.09.109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 08/16/2017] [Accepted: 09/20/2017] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Healthy subjects can learn to use cognitive-emotional strategies to suppress their spinal nociception, quantified by the nociceptive flexor reflex (RIII reflex), when given visual RIII feedback. This likely reflects learned activation of descending pain inhibition. Here, we investigated if training success persists 4 and 8 months after the end of RIII feedback training, and if transfer (RIII suppression without feedback) is possible. METHODS 18 and 8 subjects who had successfully completed feedback training were investigated 4 and 8 months later. RESULTS At 4 months, RIII suppression during feedback and transfer was similar to that achieved at the final RIII feedback training session (to 50 ± 22%, 53 ± 21% and 52 ± 21% of baseline, all differences n.s.). At 8 months, RIII suppression was somewhat (not significantly) smaller in the feedback run (to 64 ± 17%) compared to the final training session (56 ± 19%). Feedback and transfer runs were similar (to 64 ± 17% vs. 68 ± 24%, n.s.). Concomitant reductions in pain intensity ratings were stable at 4 and 8 months. CONCLUSIONS RIII feedback training success was completely maintained after 4 months, and somewhat attenuated 8 months after training. Transfer was successful. SIGNIFICANCE These results are an important pre-requisite for application of RIII feedback training in the context of clinical pain.
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Affiliation(s)
- Maximilian Bäumler
- Department of Neurology, Ludwig-Maximilians-University Munich, Germany; Department of Anesthesiology, Ludwig-Maximilians-University Munich, Germany
| | - Moritz Feller
- Department of Neurology, Ludwig-Maximilians-University Munich, Germany
| | - Stefanie Krafft
- Department of Neurology, Ludwig-Maximilians-University Munich, Germany; Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University Munich, Germany; Research Training Group 2175, Ludwig-Maximilians-University Munich, Germany
| | | | - Jens Sommer
- Department of Psychiatry, University of Marburg, Germany
| | - Andreas Straube
- Department of Neurology, Ludwig-Maximilians-University Munich, Germany; Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University Munich, Germany; Research Training Group 2175, Ludwig-Maximilians-University Munich, Germany
| | | | - Ruth Ruscheweyh
- Department of Neurology, Ludwig-Maximilians-University Munich, Germany; Department of Neurology, University of Münster, Germany; Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University Munich, Germany; Research Training Group 2175, Ludwig-Maximilians-University Munich, Germany.
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Andreoli M, Marketkar T, Dimitrov E. Contribution of amygdala CRF neurons to chronic pain. Exp Neurol 2017; 298:1-12. [PMID: 28830762 DOI: 10.1016/j.expneurol.2017.08.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 08/03/2017] [Accepted: 08/18/2017] [Indexed: 12/30/2022]
Abstract
We investigated the role of amygdala corticotropin-releasing factor (CRF) neurons in the perturbations of descending pain inhibition caused by neuropathic pain. Forced swim increased the tail-flick response latency in uninjured mice, a phenomenon known as stress-induced analgesia (SIA) but did not change the tail-flick response latency in mice with neuropathic pain caused by sciatic nerve constriction. Neuropathic pain also increased the expression of CRF in the central amygdala (CeAmy) and ΔFosB in the dorsal horn of the spinal cord. Next, we injected the CeAmy of CRF-cre mice with cre activated AAV-DREADD (Designer Receptors Exclusively Activated by Designer Drugs) vectors. Activation of CRF neurons by DREADD/Gq did not affect the impaired SIA but inhibition of CRF neurons by DREADD/Gi restored SIA and decreased allodynia in mice with neuropathic pain. The possible downstream circuitry involved in the regulation of SIA was investigated by combined injections of retrograde cre-virus (CAV2-cre) into the locus ceruleus (LC) and cre activated AAV-diphtheria toxin (AAV-FLEX-DTX) virus into the CeAmy. The viral injections were followed by a sciatic nerve constriction ipsilateral or contralateral to the injections. Ablation of amygdala projections to the LC on the side of injury but not on the opposite side, completely restored SIA, decreased allodynia and decreased ΔFosB expression in the spinal cord in mice with neuropathic pain. The possible lateralization of SIA impairment to the side of injury was confirmed by an experiment in which unilateral inhibition of the LC decreased SIA even in uninjured mice. The current view in the field of pain research attributes the process of pain chronification to abnormal functioning of descending pain inhibition. Our results demonstrate that the continuous activity of CRF neurons brought about by persistent pain leads to impaired SIA, which is a symptom of dysregulation of descending pain inhibition. Therefore, an over-activation of amygdala CRF neurons is very likely an important contributing factor for pain chronification.
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Affiliation(s)
- Matthew Andreoli
- Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, Unites States.
| | - Tanvi Marketkar
- Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, Unites States.
| | - Eugene Dimitrov
- Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, Unites States.
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Karshikoff B, Jensen KB, Kosek E, Kalpouzos G, Soop A, Ingvar M, Olgart Höglund C, Lekander M, Axelsson J. Why sickness hurts: A central mechanism for pain induced by peripheral inflammation. Brain Behav Immun 2016; 57:38-46. [PMID: 27058164 DOI: 10.1016/j.bbi.2016.04.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 03/29/2016] [Accepted: 04/02/2016] [Indexed: 11/17/2022] Open
Abstract
Low-grade systemic inflammation has been implicated in chronic pain, as well as in comorbid diseases like depression and fatigue. We have previously shown that women's pain perception and regulation is more affected by systemic inflammation than that of men. Here we investigated the neural substrates underlying these effects using an fMRI paradigm previously employed in a clinical population. Fifty-one participants (29 women) were injected with 0.6ng/kg lipopolysaccharide (LPS) or saline to induce a peripheral inflammatory response. The subjects were then tested with a pressure pain fMRI paradigm designed to capture descending pain inhibitory activity 2h after injection, and blood was sampled for cytokine analysis. The subjects injected with LPS became more pain sensitive compared to the placebo group, and the heightened pain sensitivity was paralleled by decreased activity in the ventrolateral prefrontal cortex and the rostral anterior cingulate cortex (rACC) compared to placebo; areas involved in descending pain regulation. The LPS group also had higher activity in the anterior insular cortex, an area underpinning affective and interoceptive pain processing. Women displayed overall less pain-evoked rACC activity compared to men, which may have rendered women less resilient to immune provocation, possibly explaining sex differences in LPS-induced pain sensitivity. Our findings elucidate the pain-related brain circuits affected by experimental peripheral inflammation, strengthening the theoretical link between systemic inflammation and weakened pain regulation in chronic pain disorders. The results further suggest a possible mechanism underlying the female predominance in many chronic pain disorders.
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Affiliation(s)
- B Karshikoff
- Karolinska Pain Center, Behavioral Medicine Pain Treatment Service, Karolinska University Hospital, Solna, Sweden; Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - K B Jensen
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Osher Center for Integrative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - E Kosek
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Osher Center for Integrative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - G Kalpouzos
- Aging Research Center (ARC), Department of Neurobiology, Cares Sciences and Society, Karolinska Institutet and Stockholm University, Sweden
| | - A Soop
- Department of Anesthesiology and Intensive Care, Karolinska University Hospital Huddinge, Stockholm, Sweden; Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
| | - M Ingvar
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Osher Center for Integrative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - C Olgart Höglund
- Osher Center for Integrative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; Department of Medicine Solna and CMM, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden
| | - M Lekander
- Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Osher Center for Integrative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - J Axelsson
- Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Osher Center for Integrative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
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Parent AJ, Beaudet N, Daigle K, Sabbagh R, Sansoucy Y, Marchand S, Sarret P, Goffaux P. Relationship between blood- and cerebrospinal fluid-bound neurotransmitter concentrations and conditioned pain modulation in pain-free and chronic pain subjects. J Pain 2015; 16:436-44. [PMID: 25659204 DOI: 10.1016/j.jpain.2015.01.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 01/12/2015] [Accepted: 01/16/2015] [Indexed: 02/07/2023]
Abstract
UNLABELLED Descending pain inhibition is an endogenous pain control system thought to depend partially on the activation of bulbospinal monoaminergic pathways. Deficits in descending pain inhibition have been reported in numerous human chronic pain conditions, but there is currently no consensus regarding the neurochemical correlates responsible for this deficit. The aims of this study were to 1) assess the efficacy of descending pain inhibition in pain-free and chronic pain subjects, 2) screen for changes in centrally (ie, cerebrospinal fluid) and peripherally (ie, plasma) acting monoamine concentrations, and 3) explore the relationship between descending pain inhibition and monoamine neurotransmitter concentrations. Our results clearly show a deficit in pain inhibition, along with lower plasma norepinephrine and metanephrine concentrations in chronic pain subjects, compared to pain-free subjects. No differences were found in cerebrospinal fluid neurotransmitter concentrations. Finally, our results revealed a positive relationship between blood-bound norepinephrine and metanephrine concentrations and the efficacy of descending pain inhibition. Thus, basal monoamine levels in blood were related to descending pain inhibition. This finding supports the emerging idea that individual differences in descending pain inhibition may be linked to individual differences in peripheral processes, such as monoamines release in blood, which are possibly related to cardiovascular control. PERSPECTIVES This article presents psychophysical and neurochemical findings that indicate that the latent potential of descending pain inhibitory responses is associated with differential activity in peripheral processes governed by monoamine neurotransmitter release, bringing insights into the relationship between descending pain inhibition and cardiovascular control in humans.
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