A selective cyclooxygenase‐2 inhibitor decreases transforming growth factor‐β1 synthesis and matrix production in human peritoneal mesothelial cells
Authors: Liu Hong , Peng Youming , Liu Fuyou , Li Jun , Chen Xing , Liu Yinghong , Zhang Hao 
Published: November 2006

High glucose concentration, which provides the chief driving force in peritoneal dialysis, has been considered to be an important initial factor that contributes to peritoneal thickening and fibrosis. Human peritoneal mesothelial cells (HPMCs) and the expansion of extracellular matrix (ECM) play important roles in the pathological process of peritoneal fibrosis. Peritoneal matrix accumulation is a characteristic of peritoneal fibrosis (PF). Continuous ambulatory peritoneal dialysis (CAPD) patients with upregulation of transforming growth factor‐β1 (TGF‐β1) in their drained effluent show an increased risk of PF. Inhibition of TGF‐β1 expression in human peritoneal mesothelial cells (HPMCs) may provide a potential treatment for PF. sc58236, a highly selective cyclooxygenase‐2 (COX‐2) inhibitor, reduces proteinuria and mRNA expression of TGF‐β1 and collagen III and IV in the remnant kidney, but their effects on ECM turnover in HPMCs are unknown. The aims of this study were to investigate the effects of sc58236 on TGF‐β1 expression and matrix production in HPMCs. HPMCs were cultured from human omentum by an enzyme digestion method. To examine the effect of sc58236 on TGF‐β1 and ECM secretion, HPMC were incubated in medium F12 with high concentration of d‐glucose (4.25%) in the presence and absence of 20 μM sc58236. The mRNA expression of COX‐2, TGF‐β1 and collagen I (Col I) were determined by semi‐quantification reverse transcription PCR (RT—PCR). Prostaglandin E2 (PGE2) concentration in the culture medium was measured by enzyme‐linked immunosorbent assay (ELISA). The protein of TGF‐β1 was determined by ELISA and the activity of TGF‐β1 present in the conditioned media was measured using the mink lung epithelial cell (MLEC) growth inhibition assay. Proteins of COX‐2 and Col were determined by Western blot. The results showed that primary cultures of HPMCs do express the mRNA for COX‐2 and stimulation of these cells with 4.25% d‐glucose induced a marked increase in COX‐2 mRNA expression and protein. PGE2 expression was obviously up‐regulated with stimulation by 4.25% d‐glucose. Addition of 20 μM sc58236 significantly inhibited PGE2 release into the culture medium. mRNA expression and bioactive and total protein of TGF‐β1 and Col I were significantly increased in HPMCs stimulated with 4.25% d‐glucose compared to the control group with F12 media, which was reversed in the presence of sc58236 (20 μM). An obvious decrease in TGF‐β1 mRNA expression and bioactive and total protein were found in sc58236 treated groups compared to the group stimulated with 4.25% d‐glucose. Exposure of HPMCs to sc58236 reduced Col I secretion. Sc58236 reduces the expression of TGF‐β1 in HPMCs stimulated by 4.25% d‐glucose and reduces ECM production through PGE2 production. These studies suggest that sc58236, a highly selective cyclooxygenase‐2 (COX‐2) inhibitor, may have a specific role in ameliorating the course of progressive peritoneal fibrosis under long‐term peritoneal dialysis states.