Downmodulation of peroxiredoxin-3 expression by angiotensin II in cardiac fibroblasts through phosphorylation of FOXO3a by Akt

Paul J. Lijnen, Yvette Piccart, Tamara Coenen, Tri Maharani, Nuruda Finahari, Jos F. van Pelt, John S. Prihadi

Abstract
The aim of this study was to determine whether angiotensin II (ANG II) affects the protein and mRNA expression of the mitochondrial antioxidant peroxiredoxin-3 (Prx-3) in cardiac fibroblasts through inducing the phosphorylation of the proteins Akt and FOXO3a. Cardiac fibroblasts from normal male adult rats were cultured to confluency and incubated in serum-free Dulbecco’s modified Eagle’s medium for 24 h. The cells were then preincubated with(out) the tested inhibitors for 30 min to 1 h and further incubated with(out) ANG II (1 µmol/l) for 24 h. ANG II decreased (p<0.01) the mRNA and protein expression of Prx-3 by 36.9±3.0% and 29.7±2.7% (n=4), respectively. The likely mechanism through which ANG II produces the effect of reducing Prx-3 expression is by reducing the extent of binding of Foxo3a to the Prx-3 promoter. In control fibroblasts inhibition of FOXO3a transcription with small-interfering RNA (siRNA) led to a reduction in Prx-3 gene expression. Our data also shown that when Akt is phosphorylated by ANG II, P-Akt is translocated from the cytoplasm to the nucleus, subsequently nuclear phosphorylation of FOXO3a by P-Akt leads to relocalization of FOXO3a from the nucleus to the cytosol, resulting in a decrease its transcriptional activity, and consequently in Prx-3 expression.

Key words: Akt; Angiotensin II; Cardiac fibroblasts; FOXO3a; Peroxiredoxin-3