SOCS-1 rescues IL-1β-mediated suppression of epithelial sodium channel in mouse lung epithelial cells via ASK-1

// Lakshmi Galam 1 , Ramani Soundararajan 1 , Mason Breitzig 1 , Ashna Rajan 1 , Rajashekar Reddy Yeruva 1 , Alexander Czachor 1 , Francine Harris 1 , Richard F Lockey 1 , Narasaiah Kolliputi 1 1 Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA Correspondence to: Narasaiah Kolliputi, email: nkollipu@health.usf.edu Keywords: SOCS-1, edema, lung injury, inflammation, ASK-1 Received: March 01, 2016 Accepted: March 16, 2016 Published: April 1, 2016 ABSTRACT Background: Acute lung injury (ALI) is characterized by alveolar damage, increased levels of pro-inflammatory cytokines and impaired alveolar fluid clearance. Recently, we showed that the deletion of Apoptosis signal-regulating kinase 1 (ASK1) protects against hyperoxia-induced acute lung injury (HALI) by suppressing IL-1β and TNF-α. Previously, our data revealed that the suppressor of cytokine signaling-1 (SOCS-1) overexpression restores alveolar fluid clearance in HALI by inhibiting ASK-1 and suppressing IL-1β levels. Furthermore, IL-1β is known to inhibit the expression of epithelial sodium channel α-subunit (ENaC) via a p38 MAPK signaling pathway. Objective: To determine whether SOCS-1 overexpression in MLE-12 cells would protect against IL-1β-mediated depletion of αENaC by suppressing ASK-1 expression. Methods: We co-transfected MLE-12 cells with SOCS-1 overexpressing plasmid with or without IL-1β in the presence or absence of sodium channel inhibitor, amiloride. We measured potential difference, transepithelial current, resistance, and sodium uptake levels across MLE-12 cells. We studied the effect of ASK-1 depletion, as well as ASK-1 and SOCS-1 overexpression on αENaC expression. Results: SOCS-1 overexpression sufficiently restored transepithelial current and resistance in MLE-12 cells treated with either IL-1β or amiloride. The αENaC mRNA levels and sodium transport were increased in SOCS-1 overexpressing MLE-12 cells exposed to IL-1β. Depletion of ASK-1 in MLE-12 cells increased αENaC mRNA levels. Interestingly, SOCS-1 overexpression restored αENaC expression in MLE-12 cells in the presence of ASK-1 overexpression. Conclusion: Collectively, these findings suggest that SOCS-1 may exert its protective effect by rescuing αENaC expression via suppression of ASK-1.