Multiple growth factors modulate mRNA expression of angiotensin II type-2 receptor in R3T3 cells
Ichiki, T.; Kambayashi, Y.; Inagami, T.
Circulation Research 77(6): 1070-1076
1995
ISSN/ISBN: 0009-7330 PMID: 7586218 Document Number: 447749
Previous studies showed that angiotensin II type-2 receptor (AT-2) sites were increased when R3T3 cells were growth arrested and decreased when they were stimulated with fibroblast growth factor or serum. We examined the effects of several other growth factors on the expression of AT-2 mRNA to clarify the relation between the AT-2 receptor and growth factors. R3T3 cells were cultured in the medium containing 10% FCS until they were confluent, and then serum was removed. AT-2 mRNA was increased after serum was depleted, and the expression level reached a plateau after 2 days of serum depletion. The presence of serum (10%), fibroblast growth factor (10 ng/mL), or lysophosphatidic acid (1 mu-mol/L) reduced the AT-2 mRNA expression. Phorbol ester (1 to 100 nmol/L) also suppressed the AT-2 mRNA expression in a dose-dependent manner. Interleukin-1-beta (1 ng/mL) enhanced the AT-2 mRNA expression 1.6-fold and the AT-2 receptor number 1.4-fold. Insulin (100 nmol/L) enhanced AT-2 mRNA expression 1.4-fold and the AT-2 receptor number 1.6-fold. These results suggest that AT-2 mRNA expression is modulated by multiple growth factors in both positive and negative directions. The presence of potential cis DNA elements that respond to interleukin-1-beta (CCAAT enhancer binding protein site), insulin (insulin response sequence of phospho(enol)pyruvate carboxykinase gene), and phorbol ester (AP-1 site) in the promoter region of the mouse AT-2 gene suggests that the effects of these growth factors and phorbol ester may be mediated via these cis DNA elements.