Endogenous retroelement expression in modeled airway epithelial repair.

Cystic fibrosis (CF) is an autosomal recessive genetic disorder characterized by impairment of the CF transmembrane conductance regulator (CFTR) via gene mutation. CFTR is expressed at the cellular membrane of epithelial cells and functions as an anion pump which maintains water and salt ion homeostasis. In pulmonary airways of CF patients, pathogens such as P. aeruginosa and subsequent uncontrolled inflammation damage the human airway epithelial cells (HAECs) and can be life-threatening. We previously identified that inhibiting endogenous retroelement (ERE) reverse transcriptase can hamper the inflammatory response to bacterial flagella in THP-1 cells. Here, we investigate how ERE expression is sensitive to HAEC repair and toll-like receptor 5 (TLR5) activation, a primary mechanism by which inflammation impacts disease outcome. Our results demonstrate that several human endogenous retroviruses (HERVs) and long interspersed nuclear elements (LINEs) fluctuate throughout the various stages of repair and that TLR5 activation further influences ERE expression. By considering the impact of the most common CF mutation F508del/F508del on ERE expression in unwounded HAECs, we also found that two specific EREs, L1FLnI_2p23.1c and HERVH_10p12.33, were downregulated in CF-derived HAECs. Collectively, we show that ERE expression in HAECs is sensitive to certain modalities reflective of CF pathogenesis, and specific EREs may be indicative of CF disease state and pathogenesis.