title: Molecular basis and functional significance of Angiotensin II-induced increase in Discoidin Domain Receptor 2 gene expression in cardiac fibroblasts.
abstract: Delineation of mechanisms underlying the regulation of fibrosis-related genes in the heart is an important clinical goal as cardiac fibrosis is a major cause of myocardial dysfunction. This study probed the regulation of Discoidin Domain Receptor 2 (DDR2) gene expression and the regulatory links between Angiotensin II, DDR2 and collagen in Angiotensin II-stimulated cardiac fibroblasts. Real-time PCR and western blot analyses showed that Angiotensin II enhances DDR2 mRNA and protein expression in rat cardiac fibroblasts via NADPH oxidase-dependent reactive oxygen species induction. NF-κB activation, demonstrated by gel shift assay, abolition of DDR2 expression upon NF-κB inhibition, and luciferase and chromatin immunoprecipitation assays confirmed transcriptional control of DDR2 by NF-κB in Angiotensin II-treated cells. Inhibitors of Phospholipase C and Protein kinase C prevented Angiotensin II-dependent p38 MAPK phosphorylation that in turn blocked NF-κB activation. Angiotensin II also enhanced collagen gene expression. Importantly, the stimulatory effects of Angiotensin II on DDR2 and collagen were inter-dependent as siRNA-mediated silencing of one abolished the other. Angiotensin II promoted ERK1/2 phosphorylation whose inhibition attenuated Angiotensin II-stimulation of collagen but not DDR2. Furthermore, DDR2 knockdown prevented Angiotensin II-induced ERK1/2 phosphorylation, indicating that DDR2-dependent ERK1/2 activation enhances collagen expression in cells exposed to Angiotensin II. DDR2 knockdown was also associated with compromised wound healing response to Angiotensin II. To conclude, Angiotensin II promotes NF-κB activation that up-regulates DDR2 transcription. A reciprocal regulatory relationship between DDR2 and collagen, involving cross-talk between the GPCR and RTK pathways, is central to Angiotensin II-induced increase in collagen expression in cardiac fibroblasts.
authors.affiliation: Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695011, Kerala, India.
authors.forename: Mereena
authors.initials: M
authors.lastname: George
authors.affiliation: Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695011, Kerala, India.
authors.forename: Anupama
authors.initials: A
authors.lastname: Vijayakumar
authors.affiliation: Neuro Stem Cell Biology, Neurobiology Division, Rajiv Gandhi Center for Biotechnology, Trivandrum, 695014, Kerala, India.
authors.forename: Sivadasan Bindu
authors.initials: SB
authors.lastname: Dhanesh
authors.affiliation: Neuro Stem Cell Biology, Neurobiology Division, Rajiv Gandhi Center for Biotechnology, Trivandrum, 695014, Kerala, India.
authors.forename: Jackson
authors.initials: J
authors.lastname: James
authors.affiliation: Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695011, Kerala, India. Electronic address: shivak@sctimst.ac.in.
authors.forename: K
authors.initials: K
authors.lastname: Shivakumar
mesh_terms: D000804:Angiotensin II / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D024042:Collagen Type I / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000070818:Discoidin Domain Receptors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D011975:Receptors, Mitogen / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D011975:Receptors, Mitogen; D000804:Angiotensin II; D019255:NADPH Oxidases; D000070818:Discoidin Domain Receptors; D020794:Receptor Protein-Tyrosine Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases
keywords: Angiotensin II; Cardiac fibroblasts; Collagen type I; Discoidin domain receptor 2; NF-κB; p38 MAPK