Faculty Collaboration Database

Effects of cytokine treatment on angiotensin II type 1A receptor transcription and splicing in rat cardiac fibroblasts. Am J Physiol Heart Circ Physiol 2005 Sep;289(3):H1176-83

Date

05/10/2005

Pubmed ID

15879490

DOI

10.1152/ajpheart.00088.2005

Scopus ID

2-s2.0-23944509715 (requires institutional sign-in at Scopus site)   24 Citations

Abstract

Angiotensin II (ANG II) plays important roles in cardiac extracellular matrix remodeling via its type 1A (AT(1A)) receptor. The cytokines tumor necrosis factor-alpha and interleukin-1beta (IL-1beta) were shown previously to upregulate AT(1A) receptor mRNA and protein, thereby increasing the profibrotic response to ANG II in cardiac fibroblasts. The present experiments implicate increased nuclear factor-kappaB (NF-kappaB)-dependent transcription and also, to a lesser extent, altered mRNA splicing in the mechanism of receptor upregulation. Cytokine stimulation was found to increase AT(1A) heterogeneous nuclear RNA levels, which strongly suggests that mRNA upregulation occurs transcriptionally. The transcription factor NF-kappaB was previously deemed necessary for cytokine-induced AT(1A) receptor mRNA upregulation. Computer analysis of upstream DNA sequences revealed putative NF-kappaB elements at -365 and -2540 bp. Both isolated elements were shown to bind NF-kappaB (using gel-shift assays) and to transactivate a minimal promoter (using reporter assays), although the element at -365 bp appeared stronger. Three splice variants of AT(1A) receptor mRNA that have different 5' untranslated regions were detected in rat tissues, namely, exons 1-2-3 (predominant), 1-2-3+6, and 1-3. Cytokine treatment of fibroblasts upregulated all splice variants, but exon 1-3 increased more than the others. This differential upregulation, albeit of modest magnitude, was statistically significant with IL-1beta treatment. Exon 2 contains an inhibitory minicistron and a predicted inhibitory hairpin structure. Luciferase reporter assays indicated that each splice variant translates at a different efficiency, with exon 1-2-3+6 (both minicistron and hairpin) < exon 1-2-3 (minicistron only) < exon 1-3 (neither minicistron or hairpin). These results provide evidence that cytokines increase AT(1) protein levels by altering both transcription and splicing.

Author List

Cowling RT, Zhang X, Reese VC, Iwata M, Gurantz D, Dillmann WH, Greenberg BH

Author

Vanessa Mcfadden MD Associate Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Fibroblasts
Gene Expression Regulation
Interleukin-1
Myocardium
NF-kappa B
RNA Splicing
RNA, Messenger
Rats
Receptor, Angiotensin, Type 1
Transcription Initiation Site
Transcription, Genetic
Tumor Necrosis Factor-alpha
Up-Regulation