Figure 7. Proposed model for IL‐13 action on ENaC‐dependent Na⁺ absorption .

The stimulation with DBA (dexamethasone, butyrate and aldosterone) leads to the up‐regulation of β‐ and γ‐ENaC subunit as well as SGK1 expression. On the one hand this is achieved via activation of the p38 MAPK and on the other hand by transactivation of target genes via activated mineralocorticoid receptor (MR) and glucocorticoid receptor (GR). IL‐13 binds to the IL‐13Rα1/IL‐4Rα type‐I receptor leading to the activation of JAK1/2. Subsequently, STAT6 is phosphorylated and this in turn leads to the inhibition of the DBA‐stimulated activation of p38 MAPK. These signalling events promote the decrease in DBA‐stimulated ENaC activity due to reduction of β‐ and γ‐ENaC and/or SGK1 expression. Technical terms used in this figure are also listed in the abbreviations.