TGF-Beta Downregulation of Distinct Chloride Channels in Cystic Fibrosis-Affected Epithelia

Abstract

RationaleThe cystic fibrosis transmembrane conductance regulator (CFTR) and Calcium-activated Chloride Conductance (CaCC) each play critical roles in maintaining normal hydration of epithelial surfaces including the airways and colon. TGF-beta is a genetic modifier of cystic fibrosis (CF), but how it influences the CF phenotype is not understood.ObjectivesWe tested the hypothesis that TGF-beta potently downregulates chloride-channel function and expression in two CF-affected epithelia (T84 colonocytes and primary human airway epithelia) compared with proteins known to be regulated by TGF-beta.Measurements and Main ResultsTGF-beta reduced CaCC and CFTR-dependent chloride currents in both epithelia accompanied by reduced levels of TMEM16A and CFTR protein and transcripts. TGF-beta treatment disrupted normal regulation of airway-surface liquid volume in polarized primary human airway epithelia, and reversed F508del CFTR correction produced by VX-809. TGF-beta effects on the expression and activity of TMEM16A, wtCFTR and corrected F508del CFTR were seen at 10-fold lower concentrations relative to TGF-beta effects on e-cadherin (epithelial marker) and vimentin (mesenchymal marker) expression. TGF-beta downregulation of TMEM16A and CFTR expression were partially reversed by Smad3 and p38 MAPK inhibition, respectively.ConclusionsTGF-beta is sufficient to downregulate two critical chloride transporters in two CF-affected tissues that precedes expression changes of two distinct TGF-beta regulated proteins. Our results provide a plausible mechanism for CF-disease modification by TGF-beta through effects on CaCC.

A novel regulatory role for tissue transglutaminase in epithelial-mesenchymal transition in cystic fibrosis

“…Working via interaction with its receptors, TGFβ1 is one of the key growth factors involved in fibrosis, including CF, with increased levels reported in CF lungs [11]. In addition to its pro-inflammatory properties TGFβ1 has been shown recently to inhibit the biosynthesis of CFTR and also prevent the bio-functional rescue of CFTR [29]. Importantly over-expression of TGFβ1 in the CF lung has been associated with a more severe CF phenotype and TGFβ1 is reported to be increased in the plasma of children with CF [30].…”

Platelet-Derived Growth Factor and Transforming Growth Factor β1 Regulate ARDS-Associated Lung Fibrosis Through Distinct Signaling Pathways

“…Moreover, TGF-β receptor signaling can be conducted through SMAD-independent pathway, e.g. p38 MAPK [29][30][31][32][33][34][35][36][37][38][39][40][41].…”

Airway Surface Dehydration by Transforming Growth Factor β (TGF-β) in Cystic Fibrosis Is Due to Decreased Function of a Voltage-dependent Potassium Channel and Can Be Rescued by the Drug Pirfenidone

“…Furthermore, increased TGF-␤1 was found in conditioned media of CF cells (14). TGF-␤1 also impairs therapeutic rescue of CFTR in cystic fibrosis airway epithelial (CFBE) cells (15,16).…”