The α7 nicotinic acetylcholine receptor positive allosteric modulator prevents lipopolysaccharide-induced allodynia, hyperalgesia and TNF-α in the hippocampus in mice.

Abstract

BACKGROUND:

Previous studies have shown that α7 nicotinic acetylcholine receptor (nAChR) has a critical role in the regulation of pain sensitivity and neuroinflammation. However, pharmacological effects of α7 nAChR activation in the hippocampus on neuroinflammatory mechanisms associated with allodynia and hyperalgesia remain unknown. We have determined the effects of 3a,4,5,9b-tetrahydro-4-(1-naphthalenyl)-3H-cyclopentan[c]quinoline-8-sulfonamide (TQS), an α7 nAChR positive allosteric modulator, on lipopolysaccharide (LPS)-induced allodynia and hyperalgesia in mice. We also evaluated the effects of TQS on immunoreactivity of microglial marker ionized-calcium binding adaptor molecule 1 (Iba-1), phospho-nuclear factor-κB (p-NF-κB p65), tumor necrosis factor-alpha (TNF-α), and norepinephrine (NE) level.

METHODS:

Mice were treated with (0.25, 1 or 4 mg/kg, ip) followed by LPS (1 mg/kg, ip) administration. Allodynia and hyperalgesia were determined using von Frey filaments and hot plate respectively. Immunoreactivity of Iba-1, p-NF-κB p65, and TNF-α, were measured in the hippocampus using immunofluorescence assay. Hippocampal NE level was evaluated using high performance liquid chromatography.

RESULTS:

LPS administration resulted in allodynia and hyperalgesia in mice after six h. Systemic administration of TQS prevented LPS-induced allodynia and hyperalgesia. TQS pretreatment significantly decreased the immunoreactivity of Iba-1, p-NF-κB, and TNF-α in CA1 and DG regions of the hippocampus. In addition, TQS reversed LPS-induced NE reduction in the hippocampus.

CONCLUSIONS:

Taken together, our results suggest that TQS prevented LPS-induced allodynia and hyperalgesia, upregulation of TNF-α expression and NE level reduction involving microglial α7 nAChR in part in the hippocampus. Therefore, these findings highlight the important effects of α7 nAChR allosteric modulator against symptoms of inflammatory pain.

• Authors: Muzaffar Abbas, Sami Alzarea, Roger L Papke, Shafiqur Rahman
• Journal: Pharmacological reports : PR (Pharmacol Rep) Vol. 71 Issue 6 Pg. 1168-1176 (Dec 2019) ISSN: 2299-5684 [Electronic] Switzerland
• PMID: 31655281 (Publication Type: Journal Article)
• Copyright: Copyright © 2019 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Chemical References

• 4-naphthalene-1-yl-3a,4,5,9b-tetrahydro-3-H-cyclopenta(c)quinoline-8-sulfonic acid amide
• Lipopolysaccharides
• NF-kappa B
• Naphthalenes
• Quinolines
• Sulfonamides
• Tumor Necrosis Factor-alpha
• alpha7 Nicotinic Acetylcholine Receptor

Topics

• Allosteric Regulation (drug effects)
• Animals
• Hippocampus (drug effects, metabolism)
• Hyperalgesia (metabolism)
• Inflammation (metabolism)
• Lipopolysaccharides (pharmacology)
• Male
• Mice
• Mice, Inbred C57BL
• Microglia (drug effects, metabolism)
• NF-kappa B (metabolism)
• Naphthalenes (pharmacology)
• Pain (metabolism)
• Quinolines (pharmacology)
• Sulfonamides (pharmacology)
• Tumor Necrosis Factor-alpha (metabolism)
• alpha7 Nicotinic Acetylcholine Receptor (metabolism)