Elafin expression is regulated by CFTR-mutation and TGFβ₁ in human bronchial epithelial cells

Cystic Fibrosis (CF) lung disease is characterized by inflammation and progressive matrix remodeling. These processes are influenced by genetic modifiers such as Transforming Growth Factor β₁, (TGFβ₁₎ which is enhanced by an imbalance of proteases, e.g. neutrophile elastase (NE) and its inhibitor elafin. Elevated TGFβ₁ concentrations in sputum are linked to impaired lung function in people with CF (pwCF); and decreased elafin levels in sputum are associated with P. aeruginosa infection. The direct influence of CFTR-mutations and the impact of TGFβ₁ on the expression of elafin has not yet been examined. Therefore, we investigated (1) the direct impact of the CFTR-mutation itself on elafin expression, (2) the interaction of TGFβ₁ and CFTR-mutation on elafin expression, and (3) the effect of inhibiting TGFβ₁ on the expression of elafin in human bronchial epithelial cells (HBE).

(1) Gene expression of elafin was measured by qRT-PCR and ELISA in CFTR-diseased (delF508 homozygous; CF-DHBE) and wildtype HBE cells (NHBE). (2) CF-DHBE and NHBE were stimulated with TGFβ₁ or vehicle and finally (3) TGFβ₁ was inhibited by Pirfenidone/SB43. Gene expression of elafin and inflammatory mediators, as well as inhibitors of proteases were analyzed by qRT-PCR or immunoblot.

(1) mRNA and protein expression of elafin is significantly reduced in CFTR-mutated HBE when compared to NHBE cells. (2) Furthermore, the expression of elafin is inhibited by the genetic modifier TGFβ₁. (3) Inhibition of TGFβ₁ induced elafin expression in CF-DHBE cells and abrogated the CFTR- TGFβ₁ mediated inhibitory effect in HBE.

Our study shows that CFTR-mutation itself mediates effects on the homeostasis of proteases by reducing the expression of elafin. Furthermore, the exposure to high TGFβ₁ concentrations increases the CFTR-mutation mediated reduction of elafin expression. Restoring elafin levels and/or inhibiting TGFβ₁ might be possible therapeutic options to reduce pulmonary inflammation and remodelling in CF.