Conditional Overexpression of Receptors for Advanced Glycation End-Products in the Adult Murine Lung Causes Airspace Enlargement and Induces Inflammation

Abstract

Receptors for advanced glycation end-products (RAGE) are multiligand surface receptors detected abundantly in pulmonary tissue. Our previous work revealed increased RAGE expression in cells and lungs exposed to tobacco smoke and RAGE-mediated cytokine expression via proinflammatory mechanisms involving NF-κB. RAGE expression is elevated in various pathological states, including chronic obstructive pulmonary disease; however, precise contributions of RAGE to the progression of emphysema and pulmonary inflammation in the adult lung are unknown. In the current study, we generated a RAGE transgenic (RAGE TG) mouse and conditionally induced adult alveolar epithelium to overexpress RAGE. RAGE was induced after the period of alveologenesis, from weaning (20 d of age) until animals were killed at 50, 80, and 110 days (representing 30, 60, and 90 d of RAGE overexpression). Hematoxylin and eosin staining and mean chord length revealed incremental dilation of alveolar spaces as RAGE overexpression persisted. TUNEL staining and electron microscopy confirmed increased apoptosis and blebbing of alveolar epithelium in lungs from RAGE TG mice when compared with control mice. Immunohistochemistry for matrix metalloproteinase 9 revealed an overall increase in matrix metalloproteinase 9, which correlated with decreased elastin expression in RAGE TG mice. Furthermore, RAGE TG mice manifested significant inflammation measured by elevated bronchoalveolar lavage protein, leukocyte infiltration, and secreted cytokines. These data support the concept that innovative transgenic mice that overexpress RAGE may model pulmonary inflammation and alveolar destabilization independent of tobacco smoke and validate RAGE signaling as a target pathway in the prevention or attenuation of smoke-related inflammatory lung diseases.

High-mobility group box 1 promotes extracellular matrix synthesis and wound repair in human bronchial epithelial cells

“…A recent study also revealed that HMGB1 release by airway epithelial cells contributes to pathophysiologic hallmarks of allergic asthma via mechanisms that involve RAGEand TLR4-mediated signaling (68). In the context of COPD and tissue repair, a study by Stogsdil et al (64) reported that conditional overexpression of RAGE in adult murine alveolar epithelia resulted in altered matrix turnover. To our knowledge, our study and those by Pittet et al (49) are unique in demonstrating a role for RAGE in mediating HMGB1-induced intracellular signaling and wound healing in airway epithelial cells.…”

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

“…Isolated protein was precisely quantified with a BCA Protein Assay kit (Fisher Scientific), and exactly 20 g of total lung protein was used in blotting. Immunoblotting for RAGE protein using a mouse polyclonal antibody (#AF1179; RnDSystems, Pittsburg, PA) and qPCR for RAGE mRNA were completed as already outlined (39). Band densitometry was performed using Un-Scan-It software (Silk Scientific, Orem, UT) and digitized images of the resulting immunoblots.…”

Conditional pulmonary over-expression of Claudin 6 during embryogenesis delays lung morphogenesis

“…Such pathways include those associated with fibroblast growth factors (Fgfs), sonic hedgehog (Shh), bone morphogenetic protein 4 (Bmp4), vascular endothelial growth factors (Vegfs), thyroid transcription factor 1 (TTF-1), and Wnts (Burri, 1984;Cardoso, 2001;Copland and Post, 2004;deMello et al, 1997;Gluck, 1978;Stogsdill et al, 2012;Ten Have-Opbroek, 1991;Torday, 1992). When these or other important genetic pathways are defective or delayed, pulmonary hypoplasia or pulmonary agenesis may occur resulting in abnormally low or absent bronchopulmonary segments and terminal alveoli (Ballard, 1980;Stogsdill et al, 2013).…”