Targeting T2 inflammation-evoked mechanical endotypes of ASM shortening in asthma

PROJECT SUMMARY:
Asthma is characterized by chronic inflammation and bronchial obstruction due to human airway smooth
muscle (HASM) shortening. However, the underlying basis for an enhanced shortening or the hyper-contractile
state of HASM in asthma is not known. Further, our incomplete understanding of type 2 (T2) inflammation-
regulated excitation-contraction (E-C) coupling in HASM shortening has hindered the development of new
HASM bronchodilators with a novel mechanism of action for over 60 years. This application seeks to gain a
foundational knowledge on the mechanical endotypes of HASM shortening in asthma (inflammation-dependent
and -independent) and identify improved bronchodilators that are less susceptible to tolerance and less
affected by immune inflammatory responses in asthma, focusing on previously unrecognized mechanisms
evoked by bitter taste receptors (TAS2Rs) expressed on HASM. Our preliminary data, in pre-clinical models,
support a premise that the immunologic and/or pathogenic mechanisms associated with a sustained
mechanical reinforcement of HASM shortening, and the loss of β2-adrenoceptor (β2AR)-mediated
bronchodilation, involve a transcriptional repressor function of the polycomb group (PcG) protein EZH2
(enhancer of zeste homolog 2). Further, our preliminary studies find a mechanistic role for microRNA-214
(miR-214) in TAS2R-evoked translational inhibition of EZH2. Based on these results, we hypothesize that
TAS2Rs on HASM inhibit T2 cytokine-regulated E-C coupling in HASM shortening and the physiological loss of
β2AR function in EZH2- and miR-214-dependent manners. Our goals are, first, to characterize T2- and non-T2-
mediated molecular kinetics and mechanics of E-C coupling in HASM shortening and, second, determine miR-
epigenetic nexus (i.e., non-genetic mechanisms) by which TAS2R activation promotes the functional efficacy of
β2ARs and inhibits the mechanical endotypes of HASM shortening in asthma. Toward this end, we will
leverage our unique technological innovations of single-molecule and single-cell micromechanical methods
and integrative genetics and genomics approaches in clinically relevant human precision cut lung slices
(hPCLS) and primary HASM cells derived from donor lungs of patients with and without severe asthma. When
successful, the knowledge gained from these experimental and computational studies will: 1) shed new light on
inflammation-dependent and -independent regulation of E-C coupling in HASM shortening; 2) uncover
previously unidentified TAS2R paradigms to mitigate the physiological loss of β2AR function; and 3) establish
new druggable targets and agents to treat β2-agonist-insenstivity in a large cohort of patients with difficult-to-
control and severe asthma. This line of research is underappreciated in asthma and represents a clear shift in
the asthma treatment paradigm.

Grant Number: 5R01HL164404-04
NIH Institute/Center: NIH
Principal Investigator: Steven An