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)-beta1 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-beta1, 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 NH(2)-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-beta1, 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.