Receptor for Advanced Glycation End-Products Signals through Ras during Tobacco Smoke–Induced Pulmonary Inflammation

Abstract

We previously demonstrated up-regulation of the receptor for advanced glycation end-products (RAGE) and its ligands by cigarette smoke extract (CSE) in rat R3/1 cells, a type I-like alveolar epithelial cell line. However, RAGE-mediated intracellular signaling pathways that lead to pulmonary inflammation remained unclear. Using ELISAs, we demonstrate that alveolar epithelial cell lines exposed to 25% CSE for 2 hours induce the activation of Ras, a small GTPase that functions as a molecular switch in the control of several intracellular signaling networks. Conversely, cells treated with siRNA for RAGE (siRAGE) resulted in decreased Ras activation. Furthermore, Ras was significantly diminished in lungs from RAGE null mice exposed to chronic tobacco smoke when compared with smoke-exposed wild-type mice. The use of a luciferase reporter containing NF-κB binding sites also demonstrated elevated NF-κB activation in R3/1 cells after CSE stimulation and decreased NF-κB activation in cells transfected with siRAGE before CSE exposure. ELISA revealed an increase in the secretion of IL-1β and CCL5 by R3/1 cells, two cytokines induced by NF-κB and associated with leukocyte chemotaxis. Furthermore, real-time RT-PCR and ELISAs revealed decreased cytokine secretion in RAGE null mouse lung exposed to tobacco smoke compared with lungs from smoke-exposed wild-type animals. These results support the conclusion that CSE-induced RAGE expression functions in pathways that involve Ras-mediated NF-κB activation and cytokine elaboration. This RAGE-Ras-NF-κB axis likely contributes to inflammation associated with several smoking-related inflammatory lung diseases.

Acute secondhand smoke-induced pulmonary inflammation is diminished in RAGE knockout mice

“…Ras is a molecular switch already implicated in smoke-induced lung inflammation mediated by RAGE (27). Lungs from SHSexposed wild-type mice presented significantly increased levels of active Ras compared with room air controls (Fig.…”

“…Of interest to the current investigation, RAGE expression is prominently detected in the alveolar compartments of smokers with COPD (48). Additionally, studies have revealed inflammatory abrogation after siRNA knockdown of RAGE in human lung cells (27) and impaired smoke-induced lung inflammation mediated by primary pulmonary macrophages isolated from RAGE knockout mice (32). Due to its importance in diverse inflammatory conditions, RAGE abrogation has been suggested as a possible therapeutic intervention for COPD (5).…”

RAGE signaling by alveolar macrophages influences tobacco smoke-induced inflammation

“…To obtain BALF, mice were sedated and then exsanguinated to ensure euthanasia as outlined previously (39). BALF was specifically harvested through the instillation and recovery of 7 1-ml boluses of PBS attached to a catheter for a total of 7 ml.…”

“…The receptor for advanced glycation endproducts (RAGE) is a member of the immunoglobin superfamily of cell surface receptors found in various cell types including smooth muscle cells, fibroblasts, macrophages, and epithelium (39). RAGE is most abundant in the lung (2) with sparse expression by alveolar type (AT) II cells and abundant expression on membranes of differentiated ATI cells (43).…”

Update on Head and Neck Cancer: Current Knowledge on Epidemiology, Risk Factors, Molecular Features and Novel Therapies

“…They induce DNA adducts, mainly 6-methyl-guanine, interfere with DNA replication and can damage proliferating cells, including those of the immune system compartment [15]. Smoke derivatives induce upregulation of antiapoptotic factors and activation of the transcription factor NF-κB, whose function is associated with autoimmune and neoplastic processes [16]. Moreover, tobacco smoke induces reactive oxygen species (ROS) which activate the expression of proinflammatory genes, such as interleukin-8 and TNFα and promote chronic inflammation [17].…”