Cotinine-induced convergence of the cholinergic and PI3 kinase-dependent anti-inflammatory pathways in innate immune cells

Abstract

Nicotine [(S)-3-(1-methyl-2-pyrrolidinyl)pyridine] is a major component of tobacco and a highly efficient acetylcholine receptor (nAChR) agonist that triggers the cholinergic anti-inflammatory pathway. We demonstrate that pre-treatment of monocytes with the stable nicotine catabolite, cotinine [(S)-1-methyl-5-(3-pyridinyl)-2-pyrrolidinone], dramatically alters the nature of the inflammatory response to Gram negative bacteria by abrogating the production of cytokines that are under the transcriptional control of the NF-kappaB system (TNF-alpha, IL-1beta, IL-6, IL-12/IL-23 p40) and shifting the response towards an IL-10-dominated anti-inflammatory profile. This anti-inflammatory phenomenon is initiated specifically by engagement of the monocytic alpha7 nAChR; and is PI3K/GSK-3beta-dependent; but NF-kappaB-independent. These mechanistic insights suggest an ability to exploit convergent, endogenous anti-inflammatory pathway(s) to either up-regulate or down-regulate the production of specific cytokine groups (pro- or anti-inflammatory cytokines) depending on the clinical necessity.

Cotinine Exposure Increases Fallopian Tube PROKR1 Expression via Nicotinic AChRα-7

“…Nicotine is known to signal through nicotinic acetylcholine receptors (nAChR) 18 with cotinine reported to signal through a specific member of this family, nAChR␣Ϫ7. 19 We demonstrate that human Fallopian tube epithelium and the OE-E6/E7 cell line express nAChR␣Ϫ7. We also establish that treatment of OE-E6/E7 cells with a specific and potent nAChR␣Ϫ7 antagonist (␣-bungarotoxin), before cotinine treatment, negates the increase in PROKR expression observed when cells are treated with cotinine alone.…”

“…The growth medium was then removed and cells washed once with PBS, after which serum-free DMEM/ F12 (maintenance medium) was added and the cells maintained overnight. The medium was then removed and cells were either pretreated with 2 g/ml ␣-bungarotoxin, a nAChR␣Ϫ7 antagonist (Biotium, Hayward CA, USA) in maintenance medium for 30 minutes 19 after which 400 ng/ml cotinine (Sigma-Aldrich, Dorset, UK) in maintenance medium was added or cells were treated with 400 ng/ml cotinine alone. In all cases cells were also treated with an equivalent amount of ethanol to control for the cotinine diluent.…”

“…17 Cotinine, the most abundant metabolite of nicotine, has been identified as a stable biomarker of smoke exposure and has been used in cell culture to mimic the affects of smoke exposure in vitro, reportedly signaling though the nicotinic acetylcholine receptor ␣-7 (nAChR␣Ϫ7). [17][18][19] Thus, to objectively address our hypothesis, we compared serum cotinine levels to PROKR expression in human Fallopian tube. We also examined the effects of cotinine on tubal PROKR expression in Fallopian tube in vitro and investigated whether this was mediated via nAChR␣Ϫ7.…”

Differential effects on T-cell function following exposure to serum from schizophrenia smokers

“…The presence of these factors, rather than components of cigarette smoke, could have affected the observed difference in proliferation even though nicotine and cotinine are known to trigger cholinergic anti-inflammatory pathways and proliferation in non-excitable cells through activation of the a7 subtype of the nAChR (a7nAChR). [35][36][37] One previous study showed decreased levels of a7nAChR mRNA in peripheral blood lymphocytes from schizophrenia patients and the authors ruled out the possibility that this resulted from nicotine consumption as there was no difference between HC smokers and non-smokers. 38 However, they did not investigate whether there was any effect of smoking on a7nAChR expression within the schizophrenia patient group, a possibility that should be considered in the light of the results of the present study.…”

Neutrophils alter epithelial response to Porphyromonas gingivalis in a gingival crevice model.

“…Histopathological studies and clinical assays have established that, although some periodontal pathogens can invade epithelial cells or cause low level bacteremia (Saito et al, 2009;Castillo et al, 2011), plaque bacteria are, essentially, confined within the gingival crevice where a high density of functional neutrophils are recruited and form a wall between the dental biofilm and the junctional epithelium Scott & Krauss, 2011). Despite this, most studies of Porphyromonas gingivalis-host interactions have included epithelial cells or leukocytes, but not both, our own work included (Sandros et al, 2000;Rehani et al, 2008;Bagaitkar et al, 2009). …”