Embryonic Overexpression of Receptors for Advanced Glycation End-Products by Alveolar Epithelium Induces an Imbalance between Proliferation and Apoptosis

Abstract

Receptors for advanced glycation end-products (RAGEs) are multiligand cell surface receptors highly expressed in the lung that contribute to alveolar epithelial cell differentiation during embryogenesis and the modulation of pulmonary inflammation during disease. When RAGEs are overexpressed throughout embryogenesis, severe lung hypoplasia ensues, culminating in perinatal lethality. However, the possible mechanisms that lead to the disappearance of pulmonary tissue remain unclear. A time course of lung organogenesis, commencing on Embryonic Day (E) 12.5, demonstrated that increased RAGE expression primarily alters lung morphogenesis beginning on E16.5. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) immunohistochemistry and immunoblotting for active caspase-3 confirmed a shift toward apoptosis in lungs from RAGE-overexpressing mice, compared with wild-type control mice. This observation supports previous work where electron microscopy identified the cellular blebbing of alveolar epithelium in embryonic RAGE-overexpressing mice. Assaying for NF-κB also revealed elevated nuclear translocation in lungs from transgenic mice compared with control mice. An RT-PCR assessment of genes regulated by NF-κB demonstrated the elevated expression of Fas ligand, suggesting increased activity of the Fas-mediated signal transduction pathway in which ligand-receptor interactions trigger cell death. These data provide evidence that the expression of RAGEs must be tightly regulated during homeostatic organogenesis. Further elucidations of the RAGE signaling potentially involved in cell-cycle abnormalities may provide insights into the progression of RAGE-mediated lung diseases.

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).…”

“…Hematoxylin and eosin (H&E) staining was performed to observe general lung morphology. To perform immunostaining for specific markers and immunoflorescence, slide samples were dehydrated, deparaffinized, processed with antigen retrieval by citrate buffer, and incubated with primary and secondary antisera that utilize HRP conjugation with Vectors Elite Kit (Vector Laboratories; Burlingame, CA) (Reynolds et al, 2003;Reynolds et al, 2011;Stogsdill et al, 2012). Antibodies that were used include: Anti-Cldn6 goat polyclonal antibody (C-20, 1:100; Santa Cruz Biotechnologies, Santa Cruz, CA), proliferating cell nuclear antigen (PCNA, SC-7907, 1:500; Santa Cruz Biotechnology), thyroid transcription factor 1 (TTF-1, WRAB-1231, 1:100; Seven Hills BioReagents, Cincinnati, OH), forkhead box A2 (FoxA2, WRAB-1200, 1:100; Seven Hills BioReagents), Clara cell secretory protein (CCSP, WRAB-3950, 1:100; Seven Hills BioReagents), and Surfactant Protein-C (SP-C, WRAB-76694, 1:100; Seven Hills BioReagents).…”

Critical role of RAGE in lung physiology and tumorigenesis: a potential target of therapeutic intervention?

“…Furthermore, the optimal regulation of RAGE expression is a prerequisite for normal lung development. Mice overexpressing RAGE during lung embryogenesis show altered respiratory epithelial cell differentiation, severe lung hypoplasia and exhibit 100% perinatal mortality rates [64]. These observations suggest that tight regulation of RAGE expression is a requirement for alveolar epithelial cell differentiation.…”

“…Normal ATI cell differentiation and phenotype [22,50,51] Normal: embryonic stages [50,51] Tumorigenesis: cancer cell regression to embryonic phenotypes [37,[52][53][54][55][56][57][58] Normal ATI cell adhesion, spreading and stability [22] Decreased adhesiveness, increased migration, enhanced invasiveness [15,22,37,59-61] Normal alveolar cell apoptosis Evasion of apoptosis [15,16,29,59, 60] Normal alveolar function -gas exchange [22,62] Malignant behavior [59,60,61,63] Normal lung architecture [22,64] Malignant tissue and tumor stroma reorganization and modification [15,16,29,59-61] Normal cell-to-cell and cell-to-matrix communication Disruption of normal communication -cell isolation and autonomy explain the difference in binding affinity between different ligands, since each one of them possesses its own specific electrostatic signal. Touré et al showed that neutrophils exhibit enhanced adhesiveness and decreased migration on AGE-modified collagen in comparison to non-modified collagen [68].…”

Ligands of RAGE-Proteins: Role in Intercellular Communication and Pathogenesis of Inflammation

“…Эктодомен RAGE состоит из трех молекул Ig с V-, C1-и C2-доменами, которые отвечают за взаимодействие со специфичными лигандами [4]. RAGE опосредует многие физиологические функции, такие как рост нейронов, выживание и регенерация, игра-ет важную роль в воспалительных реакциях, индуцируя продукцию провоспалительных цитокинов и хемокинов, способствует элиминации апоптотических клеток, явля-ется главным медиатором врожденного иммунного ответа [1,5]. RAGE может участвовать и в ряде патологических процессов, включая сахарный диабет, болезнь Альцгей-мера, системный амилоидоз и опухолевый рост [6].…”