We have demonstrated that in a guinea pig model, organophosphorus pesticides (OPs) cause airway hyperreactivity that is dose-related and associated with the functional loss of autoinhibitory muscarinic M2 receptors that normally limit acetylcholine release from parasympathetic nerves that innervate airway smooth muscle. We recently reported that sensitization to antigen alters the mechanisms underlying OP-induced airway hyperreactivity to involve IL-5-dependent mechanisms in the sensitized but not the non-sensitized guinea pig. How OPs cause neuronal M2 dysfunction in the non-sensitized animal is not known but our preliminary data indicate that this effect is not mediated by cholinesterase inhibition or direct antagonistic interactions with neuronal M2 receptors. Rather, OPs appear to influence neuronal M2 receptor function indirectly via effects on macrophages since depletion of macrophages using liposome-encapsulated clodronate protects against OP-induced airway hyperreactivity. It is our hypothesis that OPs activate macrophages to upregulate expression and release of inflammatory cytokines previously shown to cause M2 receptor dysfunction in various models of airway hyperreactivity. We propose four Aims to test this hypothesis.
In Aim 1, we will use in vivo physiological measurements to confirm that macrophages mediate airway hyperreactivity caused by OPs and determine whether their role changes over time, as has been observed for eosinophils in ozone-induced airway hyperreactivity.
Aim 2 will utilize macrophages isolated from bronchoalveolar lavage collected from OP-treated versus untreated guinea pigs guinea pigs to examine the effect of OPs on macrophage expression and release of inflammatory cytokines implicated in airway hyperreactivity.
In Aim 3, we will use primary nerve cell cultures to determine whether OP- induced macrophage mediators interact with nerves directly to alter M2 receptor expression or function or the structural plasticity of nerves.
Aim 4 will confirm the in vivo physiological relevance of OP-induced macrophage mediators identified in aims 2 and 3. Mechanistic studies are critical to developing preventive and therapeutic approaches for OP-induced airway hyperreactivity, which are likely to differ between sensitized (allergic) and non-sensitized individuals, and for determining the risks to human health posed by OP exposures. The public health implications of these studies are significant in light of the increasing prevalence of asthma, the wide spread exposure of humans and especially children to OPs and the credible threat of terrorist use of OP pesticides and nerve agents.

Public Health Relevance

Recent epidemiological studies suggest a link between exposure to organophosphorus pesticides (OPs) and asthma. Our previous work confirms this link by demonstrating that OPs cause airway hyperreactivity, a major symptom of asthma, in a guinea pig model. The goal of this project is to elucidate the mechanism(s) by which OPs cause airway hyperreactivity, which will be critical to developing effective preventive and therapeutic approaches to OP-induced airway hyperreactivity. Given the documented widespread exposure to OPs not only in the U.S. but worldwide, and the credible threat of terrorist use of OPs, the proposed work is of significant public health relevance.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES017592-03
Application #
8272650
Study Section
Special Emphasis Panel (ZRG1-CVRS-J (04))
Program Officer
Nadadur, Srikanth
Project Start
2010-07-07
Project End
2015-04-30
Budget Start
2012-05-01
Budget End
2013-04-30
Support Year
3
Fiscal Year
2012
Total Cost
$342,943
Indirect Cost
$60,050
Name
University of California Davis
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
047120084
City
Davis
State
CA
Country
United States
Zip Code
95618
Scott, Gregory D; Blum, Emily D; Fryer, Allison D et al. (2014) Tissue optical clearing, three-dimensional imaging, and computer morphometry in whole mouse lungs and human airways. Am J Respir Cell Mol Biol 51:43-55
Rynko, Abby E; Fryer, Allison D; Jacoby, David B (2014) Interleukin-1? mediates virus-induced m2 muscarinic receptor dysfunction and airway hyperreactivity. Am J Respir Cell Mol Biol 51:494-501
Proskocil, Becky J; Bruun, Donald A; Jacoby, David B et al. (2013) Macrophage TNF-ýý mediates parathion-induced airway hyperreactivity in guinea pigs. Am J Physiol Lung Cell Mol Physiol 304:L519-29
Grodzki, Ana Cristina G; Giulivi, Cecilia; Lein, Pamela J (2013) Oxygen tension modulates differentiation and primary macrophage functions in the human monocytic THP-1 cell line. PLoS One 8:e54926
Buels, K S; Jacoby, D B; Fryer, A D (2012) Non-bronchodilating mechanisms of tiotropium prevent airway hyperreactivity in a guinea-pig model of allergic asthma. Br J Pharmacol 165:1501-14
Verhein, Kirsten C; Hazari, Mehdi S; Moulton, Bart C et al. (2011) Three days after a single exposure to ozone, the mechanism of airway hyperreactivity is dependent on substance P and nerve growth factor. Am J Physiol Lung Cell Mol Physiol 300:L176-84
Moulton, Bart C; Fryer, Allison D (2011) Muscarinic receptor antagonists, from folklore to pharmacology; finding drugs that actually work in asthma and COPD. Br J Pharmacol 163:44-52