Mechanisms of Nanoparticle Modulation of Allergic Lung Disease

Project Summary
Multi-walled carbon nanotubes (MWCNTs) are engineered nanoparticles with numerous
applications and they are commonly ‘functionalized’ by the addition of chemical groups (e.g.,
carboxyl or amine groups) to modify their unique physicochemical properties. Increasing
evidence in rodent models indicate that MWCNTs are an emerging risk for lung diseases. In
particular, MWCNTs exacerbate allergen-induced airway disease in rodents, suggesting a
potential hazard for humans with allergic asthma. The long-term pathology of asthma features
airway fibrosis and mucous cell metaplasia, defined herein as allergic airway disease. Importantly,
current asthma therapies treat inflammation and bronchospasm, but do not reduce allergic airway
disease. Therefore, elucidating the mechanism(s) through which nanoparticles exacerbate
allergic airway disease would fill critical knowledge and treatment gaps. We propose a mechanism
of nanoparticle exacerbation of chronic airway disease mediated by the adsorption of proteolytic
house dust mite (HDM) allergens to the surface of MWCNTs to form an ‘allergen corona’.
Allergens in the corona have increased proteolytic activity and activate the protease-activated
receptor-2 (PAR2) on lung macrophages. Triggering of PARs has been implicated in M2-like ‘pro-
fibrotic’ polarization of macrophages, a process that is regulated by STAT transcription factors.
Our preliminary data show that PAR2 deficiency in cells or mice increases STAT1 signaling but
decreases STAT3 signaling. Therefore, we hypothesize that MWCNTs exacerbate allergic airway
disease by enhancing the proteolytic activity of allergens to increase PAR2 activation in
macrophages leading to induction of STAT3 signaling and suppression of STAT1 signaling. In
Aim 1 we will characterize the allergen corona on MWCNTs exposed to HDM extract, determine
that functionalization alters corona formation, and show that corona allergens have enhanced
proteolytic activity. In Aim 2 we will determine whether MWCNTs with HDM allergen corona
activate PAR2 in macrophages in vitro to induce STAT3 signaling or suppress STAT1 signaling
to enhance pro-fibrotic cytokine expression. In Aim 3 we will determine whether MWCNTs with
HDM allergen corona exacerbate allergic airway disease in mice and whether this is dependent
on PAR2 induction of STAT3 activation or suppression of STAT1 activation. Completion of these
studies will define a novel mechanism and fundamental basis through which nanoparticles
exacerbate allergic airway disease. This work will have significant and broad implications for a
variety of engineered nanoparticles and their impact on human health.

Grant Number: 5R01ES032443-05
NIH Institute/Center: NIH
Principal Investigator: James Bonner