Receptor for Advanced Glycation End-Products Regulates Lung Fluid Balance via Protein Kinase C–gp91^phox Signaling to Epithelial Sodium Channels

Abstract

The receptor for advanced glycation end-products (RAGE), a multiligand member of the Ig family, may play a crucial role in the regulation of lung fluid balance. We quantified soluble RAGE (sRAGE), a decoy isoform, and advanced glycation end-products (AGEs) from the bronchoalveolar lavage fluid of smokers and nonsmokers, and tested the hypothesis that AGEs regulate lung fluid balance through protein kinase C (PKC)-gp91 phox signaling to the epithelial sodium channel (ENaC). Human bronchoalveolar lavage samples from smokers showed increased AGEs (9.02 6 3.03 mg versus 2.48 6 0.53 mg), lower sRAGE (1,205 6 292 pg/ml versus 1,910 6 263 pg/ml), and lower volume(s) of epithelial lining fluid (97 6 14 ml versus 133 6 17 ml). sRAGE levels did not predict ELF volumes in nonsmokers; however, in smokers, higher volumes of ELF were predicted with higher levels of sRAGE. Single-channel patch clamp analysis of rat alveolar epithelial type 1 cells showed that AGEs increased ENaC activity measured as the product of the number of channels (N) and the open probability (Po) (NPo) from 0.19 6 0.08 to 0.83 6 0.22 (P = 0.017) and the subsequent addition of 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine-N-oxyl decreased ENaC NPo to 0.15 6 0.07 (P = 0.01). In type 2 cells, human AGEs increased ENaC NPo from 0.12 6 0.05 to 0.53 6 0.16 (P = 0.025) and the addition of 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine-N-oxyl decreased ENaC NPo to 0.10 6 0.03 (P = 0.013). Using molecular and biochemical techniques, we observed that inhibition of RAGE and PKC activity attenuated AGE-induced activation of ENaC. AGEs induced phosphorylation of p47 phox and increased gp91 phox -dependent reactive oxygen species production, a response that was abrogated with RAGE or PKC inhibition. Finally, tracheal instillation of AGEs promoted clearance of lung fluid, whereas concomitant inhibition of RAGE, PKC, and gp91 phox abrogated the response.Keywords: acute respiratory distress syndrome; chronic obstructive pulmonary disease; pulmonary edema; alveolar microenvironment; lung injury Clinical RelevanceReceptor for advanced glycation end-products (RAGE) plays a critical role in regulating inflammation in the lung and may be a therapeutic target in the treatment of acute and chronic lung diseases. Herein we describe the signal transduction pathway through which RAGE regulates the epithelial sodium channel.

Redox Signaling and Advanced Glycation Endproducts (AGEs) in Diet-Related Diseases

“…These data support the role that NADPH oxidases and mitochondria play in the intracellular production of ROS mediated by AGEs [23,24,26,72,95,96]. Moreover, when cells were pretreated with anti-RAGE or soluble (sRAGE), the expression of NOX-1, NOX-2, and NOX-4 was inhibited and hence, ROS production [23,24,26,97], thus confirming the role of the AGE-RAGE axis in ROS generation by NADPH oxidases.…”

Inhibition of the Receptor for Advanced Glycation End-Products in Acute Respiratory Distress Syndrome: A Randomised Laboratory Trial in Piglets

“…Our current findings also provide further insights into mechanisms by which manipulating the RAGE pathway might counteract ARDS by AFC restoration and lung expression of lung epithelial channels α1-Na,K-ATPase, AQP-5 and, to a lesser extent, α1-ENaC. RAGE activation has been reported to stimulate ENaC activity and lung fluid clearance in uninjured mice via advanced glycation end-products [44].…”

Soluble Receptor for Advanced Glycation End-Products Predicts Impaired Alveolar Fluid Clearance in Acute Respiratory Distress Syndrome

“…Although RAGE has the striking capacity to induce cellular attachment and spreading (35,36) and to enhance the adherence of epithelial cells to the collagen coated surfaces (37), the role of RAGE in the alveolar epithelial cell proliferation/differentiation and the regulation of the expression or function of epithelial membrane channels (e.g., Na + -K + -ATPase, sodium channels, aquaporins) remains underinvestigated (38). More importantly, whether the modulation of RAGE axis could lead to enhanced AFC has not been explored to date.…”