Nicotine and its metabolite cotinine target MD2 and inhibit TLR4 signaling

Hongyuan Li; Yinghua Peng; Cong Lin; Xiaozheng Zhang; Tianshu Zhang; Yibo Wang; Yuanpeng Li; Siru Wu; Hongshuang Wang; Mark R. Hutchinson; Linda R. Watkins; Xiaohui Wang

The Innovation (May 2021)

Nicotine and its metabolite cotinine target MD2 and inhibit TLR4 signaling

Hongyuan Li,
Yinghua Peng,
Cong Lin,
Xiaozheng Zhang,
Tianshu Zhang,
Yibo Wang,
Yuanpeng Li,
Siru Wu,
Hongshuang Wang,
Mark R. Hutchinson,
Linda R. Watkins,
Xiaohui Wang

Affiliations

Hongyuan Li: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Yinghua Peng: Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences, Jilin 130112, China
Cong Lin: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Xiaozheng Zhang: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Tianshu Zhang: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Yibo Wang: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Yuanpeng Li: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Siru Wu: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Hongshuang Wang: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China
Mark R. Hutchinson: Discipline of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia; ARC Centre of Excellence for Nanoscale Biophotonics, University of Adelaide, Adelaide, SA 5000, Australia
Linda R. Watkins: Department of Psychology and Neuroscience, and the Center for Neuroscience, University of Colorado at Boulder, Boulder, CO 80309, USA
Xiaohui Wang: Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Jilin 130022, China; Department of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, China; Corresponding author

Journal volume & issue: Vol. 2, no. 2
p. 100111

Abstract

Read online

Nicotine is the principal alkaloid of tobacco often manufactured into cigarettes and belongs to a highly addictive class of drugs. Nicotine attenuates the neuroinflammation induced by microglial activation. However, the molecular target(s) underlying anti-inflammatory action of nicotine has not been fully understood. Considering the psychoactive substances morphine, cocaine, and methamphetamine act as xenobiotic-associated molecular patterns and can be specifically sensed by the innate immune receptor Toll-like receptor 4 (TLR4), here we sought to delineate whether nicotine and/or its metabolite cotinine may be recognized by the innate immune system via myeloid differentiation protein 2 (MD2), an accessory protein of TLR4 that is responsible for ligand recognition. MD2-intrinsic fluorescence titrations, surface plasmon resonance, and competitive displacement binding assays with curcumin (MD2 probe) demonstrated that both nicotine and cotinine targeted the lipopolysaccharide (LPS; TLR4 agonist) binding pocket of MD2 with similar affinities. The cellular thermal shift assay indicated that nicotine binding increased, while cotinine binding decreased, MD2 stability. These biophysical binding results were further supported by in silico simulations. In keeping with targeting MD2, both nicotine and cotinine inhibited LPS-induced production of nitric oxide and tumor necrosis factor alpha (TNF-α) and blocked microglial activation. Neither a pan nicotinic acetylcholine receptor (nAChR) inhibitor nor RNAi for nAChRs abolished the suppressive effect of nicotine- and cotinine-induced neuroinflammation. These data indicate that TLR4 inhibition by nicotine and cotinine at the concentrations tested in BV-2 cells is independent of classic neuronal nAChRs and validate that MD2 is a direct target of nicotine and cotinine in the inhibition of innate immunity. Public summary: • Nicotine and cotinine bind to MD2 in microglia cell • Nicotine and cotinine inhibit the expression of pro-inflammatory factors • The activity of nicotine and cotinine in microglia is independent of nAChRs

Published in The Innovation

ISSN: 2666-6758 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Science: Science (General)
Website: https://www.cell.com/the-innovation

About the journal

Abstract

Keywords