Angiotensin II-mediated activation of fibrotic pathways through ERK1/2 in rat peritoneal mesothelial cells

Abstract

Introduction: Peritoneal fibrosis is a common complication of peritoneal dialysis (PD) although the pathway involved is unclear. Of this article, angiotensin II (Ang II)-mediated upregulation of mitogen-activated protein kinase (MAPK) pathway as well as their downstream profibrotic genes including transforming growth factor (TGF)-β1 and fibronectin (FN) was investigated. Methods: Rat peritoneal mesothelial cells (RPMCs) were obtained by enzymatic digestion from the colic omentum. After incubated with Ang II, real-time PCR, ELISA, and Western blot analysis were used to determine RPMCs cellular and secretory (supernatants) levels of TGF-β1, FN, tissue inhibitor of metalloproteinase-1 (TIMP-1), and plasminogen activator inhibitor-1 (PAI-1) as well as the phosphorylation of extracellular signal-regulated kinase (ERK1/2), p38 MAPK, and stress-activated protein kinase/c-Jun NH₂-terminal kinase (JNK). We also determined the downstream pathways using the specific inhibitors including PD98059 (ERK1/2), SB230580 (p38 MAPK), SP600125 (JNK), and losartan [Ang II type-1 (AT1] receptor blocker). Results: Ang II increased mRNA and protein levels of TGF-β1, FN, TIMP-1, and PAI-1 in a time- and dose-dependent manner in RPMCs. Ang II induced a 1.5–2-fold increase in both mRNA and protein levels of the above molecules at 10 nmol/L. Ang II also upregulated the phosphorylation of ERK1/2 and p38 but not of JNK. Finally, inhibition of either AT1 or ERK1/2 was able to suppress Ang II-induced expression of FN. Conclusion: In cultured RPMCs, Ang II upregulated profibrotic signaling pathways through AT1-mediated ERK1/2 phosphorylation.

Keywords:

• angiotensin II
• mesothelial cell
• peritoneal fibrosis
• TGF-β1
• fibronectin
• MAPK

Acknowledgment

The authors wish to thank Wu Kaiyin, He Cijiang, and Yang Jiajin for their suggestions to the study. This work was supported by grants from the Leading Academic Discipline Project of Shanghai Health Bureau (05III 001 and 2003ZD002) and Shanghai Leading Academic Discipline Project (T0201). Xie Jingyuan is supported by the ISN COMGAN Fellowship.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.