Angiotensin II up-regulates osteopontin mRNA expression of RAW264.7 macrophages via p38MAPK signaling

Objective To investigate the changes of osteopontin (OPN) mRNA expression induced by angiotensin Ⅱ (Ang Ⅱ ) in RAW264. 7 macrophages, and to determine the role of p38 mitogen-activated protein kinase(p38MAPK) signaling in up-regulation of OPN mRNA expression. Methods RT-PCR was used for examining the OPN mRNA expression, and the phosphorylation of p38MAPK and activating transcription factor2 (ATF2) was detected by Western blot. Results (1) Ang Ⅱ (1 μmol/L) enhanced the expression of OPN mRNA in RAW264. 7 macrophages with time-dependent, including 0. 9 fold, 2. 3 folds and 2. 4 folds up-regulatoin at 6, 12, 24 h, respectively ( all P 0. 01 ) , whereas there was no significant change in negative control at 0 h and 24 h, suggesting that the mRNA expression of OPN is inducible. (2) Following excitation by Ang Ⅱ in vitro, there was substantial up-regulation of OPN mRNA expression in RAW264. 7 macrophages with dose-dependent; with a dose of 1 μmol/L incubated for 12 h, Ang Ⅱ increased the OPN mRNA expression by 2. 6 folds (P 0. 01). (3) Pre-treatment with SB202190 (5 μmol/L) for 30 min in RAW264. 7 macrophages before Ang Ⅱ (1 μmol/L) used, the expression of OPN mRNA was inhibited by 61.7% (P 0. 01) ; but no marked inhibition had happened at the time of treatment with both SB202190 (5 μmol/L) and Ang Ⅱ (1 μmol/L) added at the same time and with SB202190(5 μmoI/L) for 120 min after AngⅡ (1 μmol/L) used. (4) Pre-treatment with SB202190( 1,5, 10 μmol/L) for 30min in RAW264. 7 macrophages before AngⅡ (1 μmol/L) used, the expression of OPN mRNA was decreased by 43. 4% , 63. 0% 及 65. 5% , respectively ( all P 0. 01 ) . ( 5 ) There was a maximal expression of p38MAPK phosphorylation at 15 - 30 min induced by Ang Ⅱ ( 1 μmol/L) in RAW264. 7 macrophages, and the maximal expression of phosphorylated ATF2 was at 30 - 45 min. (6) Pre-treatment with SB202190 (1,5 μmol/L) for 30 min in RAW264.7 macrophages before Ang Ⅱ (1 μmol/L) used, the expression of p38MAPK phosphorylation was inhibited markedly with dose-dependent, and the phosphorylation of p38MAPK was decreased by 61. 7% (P 0. 01) after the SB202190 (5 μmol/L) was used. Conclusion Angiotensin Ⅱ may up-regulate osteopontin mRNA expression of RAW264. 7 macrophages via p38MAPK signaling.