Our goal is to understand the genetic and environmental basis of racial/ethnic differences in asthma and drug response. Results from this proposal will inform public health policy and clinical practice and aid in the understanding of the asthma racial paradox, which may lead to more targeted therapies.
Asthma is the most common chronic disease among children. Asthma prevalence, mortality, and drug response vary by race/ethnicity and genetic ancestry. In the U.S., asthma prevalence is highest among Puerto Ricans (36.5%), intermediate among African Americans (13.0%) and whites (12.1%), and lowest in Mexicans (7.5%). These disparities extend to asthma mortality, which is four-fold higher in Puerto Ricans and African Americans compared to Mexican Americans. Albuterol is the most commonly prescribed asthma medication in the world and is the mainstay of acute asthma management. Among low income and minority populations in the U.S., albuterol is often the only medication used regardless of asthma severity. Poor drug response contributes to racial/ethnic disparities in asthma morbidity and mortality. Disturbingly, Americans with the highest asthma prevalence and death rate also have the lowest drug response. Chronic albuterol use can decrease acute airway smooth muscle response to albuterol and increase airway inflammation through beta-agonist signaling in the airway epithelium, suggesting that chronic albuterol use may alter acute response through genomic and epigenomic modification of airway cells. Furthermore, acute bronchodilator drug response (BDR) to albuterol is a complex phenotype with an estimated heritability of 28.5%, indicating genetic factors contribute to BDR variability. Genome-wide and whole genome association analyses have revealed population-specific common and rare variants in non-coding regions of the genome associated with the extremes of BDR. The roles of genomic regulatory regions and population-specific variants in BDR have yet to be fully investigated. To this end, we have created an investigative system involving airway-specific cell types, patient-derived cells, and detailed clinical data to generate an encyclopedia of genes, regulatory regions, and pathways involved in BDR to albuterol. We will integrate RNA-seq, ChIP-seq, ATAC-seq, and whole genome sequencing data with detailed clinical data to identify trans-ethnic and population-specific variants contributing to differential expression and chromatin structure patterns in response to albuterol exposure. Furthermore, we will functionally characterize the regulatory regions that underlie acute and chronic albuterol BDR in multi-ethnic children with asthma using CRISPR-Cas9 activation/inhibition assays. These analyses will allow us to determine on a genomic scale the functional consequences of acute and chronic albuterol treatment on airway cells, and provide insight into potential targetable genes, regulatory elements, and pathways for improved asthma therapies in at-risk populations.