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Organophosphorus Pesticides Stimulate Macrophages to Release Factors That Modulate M2 Muscarinic Receptors
Author(s) -
Proskocil Becky,
Lein Pamela,
Jacoby David,
Fryer Allison
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1003.3
Subject(s) - muscarinic acetylcholine receptor , diazinon , chemistry , paraoxon , muscarinic antagonist , pharmacology , methidathion , endocrinology , receptor , medicine , acetylcholinesterase , biology , chlorpyrifos , biochemistry , pesticide , agronomy , enzyme
BACKGROUND The organophosphorus pesticides (OP) parathion, chlorpyrifos, and diazinon are widely used agricultural pesticides. We found that OPs cause airway hyperreactivity via dysfunction of autoinhibitory M2 muscarinic receptor expressed by parasympathetic nerves in the airways of guinea pigs. OP‐induced airway hyperreactivity occurs at concentrations below currently recommended exposure limits. OP‐induced effects are prevented by depleting alveolar macrophages or blocking tumor necrosis factor α (TNFα). OBJECTIVE To determine if OPs and/or their oxon metabolites directly stimulate human macrophages to increase the expression of cytokines and growth factors known to modulate M2 receptors. Since OPs interact with nicotinic and muscarinic receptors, which are expressed on macrophages, and since OPs are a potent acetylcholinesterase (AChE) inhibitor, we also evaluated whether OP stimulation of macrophages is mediated by AChE inhibition and/or modulation of nicotinic or muscarinic receptor activity. METHODS THP1 cells, a human monocyte cell line differentiated into macrophages, were treated with 1–100 μM parathion, chlorpyrifos, or diazinon or 1 nM – 100 μM paraoxon, chlorpyrifos oxon, or diazoxon for 24 hr. Some THP1 cells were pretreated with 100 μM mecamylamine (nicotinic antagonist) or 100 μM atropine (muscarinic antagonist) 1 hr prior to addition of the OPs. Other cells were treated with 100 μM eserine (AChE inhibitor). Cells were harvested for RT‐PCR and supernatants were collected for ELISA. RESULTS Parathion, chlorpyrifos, and diazinon increased mRNA expression of TNFα, IL‐1β, platelet derived growth factor (PDGF), and transforming growth factor β (TGFβ) in a concentration‐dependent manner. TNFα protein was significantly increased at 100 μM, however IL‐1β and PDGF proteins were not increased and fibroblast growth factor (FGF) and TGFβ proteins were undetectable. No oxon metabolite increased mRNA or protein levels of these factors. Inhibiting nicotinic or muscarinic receptors did not prevent OP‐induced increase in IL‐1β, TNFα, PDGF, and TGFβ mRNA or secreted TNFα protein. Blocking AChE with eserine did not increase cytokine or growth factor expression. CONCLUSIONS Parent OP compounds, but not their metabolites, stimulate macrophages to express cytokines and growth factors that have previously been shown to modulate parasympathetic M2 muscarinic receptor function. Macrophage stimulation occurs via a non‐muscarinic, non‐nicotinic pathway and independent of AChE inhibition. Characterizing this pathway is important for determining biological effects of OPs and treatment following OP exposure. Support or Funding Information This work was supported by NIH grants ES017592, ES014521, ES014601, HL124165, HL113023, and AR061567.