Activation of transient receptor potential ankyrin-1 by wood smoke particulate material

honors thesisCollege of ScienceBiologyChristopher A. ReillyExposure to wood smoke particulate matter (WSPM) has been linked to exacerbation of pre-existing respiratory conditions such as asthma, development of chronic obstructive pulmonary disease (COPD), and premature deaths. While it is clear that WSPM exposure is hazardous to human health, the molecular and cellular mechanisms through which it causes these adverse respiratory effects are not well understood. Transient receptor potential ankyrin-1 (TRPA1) is a cation channel that is expressed in sensory neurons, small airway epithelial cells, smooth muscle cells, and fibroblasts. TRPA1 has been implicated as a mediator of toxicity for several combustion-derived particulate materials (cdPM), including diesel exhaust (DEP) and cigarette smoke (CS). The hypothesis of this project was that WSPM would selectively activate TRPA1 through direct binding to ligand binding sites, including sites of covalent binding by electrophiles, and/or mechanical contact, which would then initiate cellular processes that culminate in pulmonary inflammation, lung injury, and respiratory dysfunction. Pine and mesquite PM were generated in the laboratory. These PM activated TRPA1 in a manner similar to DEP and CS in all cell lines tested: TRPA1 over-expressing HEK-293, primary mouse trigeminal (TG) neurons, and human alveolar adenocarcinoma (A549) cells. TRPA1 activation by WSPM was attenuated by a TRPA1 antagonist, HC-030031, in both A459 cells and TG neurons. Differential activation of TRPA1, as a function of particle size, demonstrated that respirable PM≤2.5 μm were most potent. Additionally, several known chemical components of WSPM were TRPA1 agonists. Both WSPM and agathic acid activated TRPA1 primarily though the electrophile/oxidant sensing site, while 3,5-ditert-butylphenol activated TRPA1 through the menthol-binding site. This study establishes WSPM as a potent and selective activator of TRPA1 and outlines a specific biochemical mechanism for how WSPM and associated chemical components activate TRPA1. These results provide key insights into how one could potentially develop therapeutics to reduce WSPM toxicity in the respiratory tract