title: Loss of phosphatase and tensin homolog (PTEN) induces leptin-mediated leptin gene expression: feed-forward loop operating in the lung.
abstract: Elevated levels of systemic and pulmonary leptin are associated with diseases related to lung injury and lung cancer. However, the role of leptin in lung biology and pathology, including the mechanism of leptin gene expression in the pathogenesis of lung diseases, including lung cancer, remains elusive. Here, using conditional deletion of tumor suppressor gene Pten in the lung epithelium in vivo in transgenic mice and human PTEN-null lung epithelial cells, we identify the leptin-driven feed-forward signaling loop in the lung epithelial cells. Leptin-mediated leptin/leptin-receptor gene expression likely amplifies leptin signaling that may contribute to the pathogenesis and severity of lung diseases, resulting in poor clinical outcomes. Loss of Pten in the lung epithelial cells in vivo activated adipokine signaling and induced leptin synthesis as ascertained by genome-wide mRNA profiling and pathway analysis. Leptin gene transcription was mediated by binding of transcription factors NRF-1 and CCAAT/enhancer-binding protein δ (C/EBP) to the proximal promoter regions and STAT3 to the distal promoter regions as revealed by leptin promoter-mutation, chromatin immunoprecipitation, and gain- and loss-of-function studies in lung epithelial cells. Leptin treatment induced expression of the leptin/leptin receptor in the lung epithelial cells via activation of MEK/ERK, PI3K/AKT/mammalian target of rapamycin (mTOR), and JAK2/STAT3 signaling pathways. Expression of constitutively active MEK-1, AKT, and STAT3 proteins increased expression, and treatment with MEK, PI3K, AKT, and mTOR inhibitors decreased LEP expression, indicating that leptin via MAPK/ERK1/2, PI3K/AKT/mTOR, and JAK2/STAT3 pathways, in turn, further induces its own gene expression. Thus, targeted inhibition of the leptin-mediated feed-forward loop provides a novel rationale for pharmacotherapy of disease associated with lung injury and remodeling, including lung cancer.
authors: From the Department of Pathology and Cell Biology, Morsani College of Medicine.
authors: Ravi Ramesh
authors: RR
authors: Pathak
authors: Aditya
authors: A
authors: Grover
authors: Prerna
authors: P
authors: Malaney
authors: Waise
authors: W
authors: Quarni
authors: Ashish
authors: A
authors: Pandit
authors: Diane
authors: D
authors: Allen-Gipson
authors: Vrushank
authors: V
authors: Davé
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D020738:Leptin / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D051265:NF-E2-Related Factor 1 / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D051059:PTEN Phosphohydrolase / Q000235:genetics* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D054411:Receptors, Leptin / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D020738:Leptin; D051265:NF-E2-Related Factor 1; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; D051743:CCAAT-Enhancer-Binding Protein-delta; D019869:Phosphatidylinositol 3-Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D051059:PTEN Phosphohydrolase
keywords: Adipokines; Electric Cell Substrate Impedance Sensing; Gene Regulation; Inflammation; Lung; Molecular Cell Biology
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