The nonopioid cholinergic agonist GTS-21 mitigates morphine-induced aggravation of burn injury pain together with inhibition of spinal microglia activation in young rats

Yang Ren; Yinhui Zhou; Zerong You; Hao Deng; William R Kem; Jianren Mao; Wei Zhang; J A Jeevendra Martyn

doi:10.1016/j.bja.2022.07.055

The nonopioid cholinergic agonist GTS-21 mitigates morphine-induced aggravation of burn injury pain together with inhibition of spinal microglia activation in young rats

Br J Anaesth. 2022 Dec;129(6):959-969. doi: 10.1016/j.bja.2022.07.055. Epub 2022 Oct 13.

Authors

Yang Ren¹, Yinhui Zhou², Zerong You³, Hao Deng⁴, William R Kem⁵, Jianren Mao³, Wei Zhang⁶, J A Jeevendra Martyn⁷

Affiliations

¹ Department of Anaesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Shriners Hospital for Children - Boston, Boston, MA, USA; Harvard Medical School, Boston, MA, USA; Department of Anaesthesiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China. Electronic address: jmartyn@mgh.harvard.edu.
² Department of Anaesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Shriners Hospital for Children - Boston, Boston, MA, USA; Harvard Medical School, Boston, MA, USA; Department of Anaesthesiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
³ Department of Anaesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
⁴ Department of Anaesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA; Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
⁵ Department of Pharmacology, University of Florida, Gainesville, FL USA.
⁶ Department of Anaesthesiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
⁷ Department of Anaesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Shriners Hospital for Children - Boston, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.

PMID: 36243579
DOI: 10.1016/j.bja.2022.07.055

Abstract

Background: Repetitive opioid use does not always alleviate basal pain, procedural pain, or both after burn injury. Mitigation of burn injury-site pain can be achieved by GTS-21 stimulation of α7-acetylcholine nicotinic receptors (α7AChRs) and reduced microglia activation in rat. We tested the hypothesis that morphine exaggerates burn injury-site pain and GTS-21 alleviates both morphine-induced aggravated burn injury pain and microglia activation.

Methods: Young rats with dorsal paw burn injury or sham-burn received intraperitoneal saline, morphine, GTS-21, or a combination twice daily for 14 days. Ipsilateral plantar pain thresholds were tested every other day before morning drugs from days 0-20. Spinal microglia activation, evidenced as pain-transducer (tumour necrosis factor-α [TNF-α], interleukin [IL]-6, IL-1β, nuclear factor kappa B [NF-κB], Toll-like receptor 4 [TLR4]) expression, was examined using immunohistochemistry and immunoblot. In cultured microglia, morphine-induced cytokine expression was measured (quantitative polymerase chain reaction/enzyme-linked immunosorbent assay [qPCR/ELISA]).

Results: Morphine aggravated allodynia at day 5 in sham-burn (P=0.039, n=8-11) but significantly aggravated burn injury site allodynia by day 3 (P=0.010, n=8-11). Microgliosis paralleled nociceptive behaviour changes where burn injury with morphine had highest microgliosis compared with burn injury, morphine alone, or controls (number of cells per field [SD]: 33.8 [2.4], 18.0 [4.1], 8.2 [1.9], and 4.8 [2.0], respectively; P<0.001, n=4-5]. GTS-21 reversed the morphine-induced pain component in sham-burn and burn injury rats together with reduced microgliosis and spinal pain-transducer expression (TNF-α, IL-6, IL-1β, NF-κB, and TLR4). Morphine-exposed microglial cells showed increased cytokine expression, which was mitigated by GTS-21.

Conclusions: Morphine or burn injury alone increases pain together with microgliosis and pain-transducer expression. Morphine administration augments burn injury-site nociception sooner and aggravated spinal microgliosis and inflammatory pain-transducer expression. GTS-21 has the potential to treat morphine-induced pain in burn injury.

Keywords: allodynia; antinociception; burn; hyperalgesia; microglia; morphine; neuroinflammation; opioids.

MeSH terms

Animals
Burns* / complications
Burns* / drug therapy
Cholinergic Agonists / metabolism
Hyperalgesia / chemically induced
Microglia / metabolism
Morphine*
NF-kappa B / metabolism
NF-kappa B / therapeutic use
Pain / drug therapy
Rats
Rats, Sprague-Dawley
Spinal Cord / metabolism
Toll-Like Receptor 4 / metabolism
Toll-Like Receptor 4 / therapeutic use
Tumor Necrosis Factor-alpha
alpha7 Nicotinic Acetylcholine Receptor / metabolism
alpha7 Nicotinic Acetylcholine Receptor / therapeutic use

Substances

3-(2,4-dimethoxybenzylidene)anabaseine
alpha7 Nicotinic Acetylcholine Receptor
Cholinergic Agonists
Morphine
NF-kappa B
Toll-Like Receptor 4
Tumor Necrosis Factor-alpha