MCP-1 levels are elevated in peritonitis fluid from CAPD patients due to secretion by peritoneal macrophages.

The migration of leukocytes, including polymorphonuclear neutrophils and monocytes, into the peritoneal cavity is a key event of intraperitoneal inflammation. We investigated the levels of two members of the chemokine family, interleukin 8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), in the dialysate effluent of 18 continuous ambulatory peritoneal dialysis (CAPD) patients with peritonitis and compared them with chemokine levels in noninfected CAPD effluent. Being a major source of inflammatory cytokines, we also isolated peritoneal macrophages from peritonitis effluent to determine the mRNA expression directly after isolation. The mean (SEM) concentrations of IL-8 and MCP-1 were significantly higher in the effluent of peritonitis patients than in noninfected effluents MCP-1: 22.5 +/- (6.27) versus 0.37 +/- (0.1) ng/mL and IL-8: 2.39 +/- (1.15) versus 0.04 +/- (0.01) ng/mL. Northern blot analysis of isolated effluent macrophages revealed strong signals for MCP-1 and IL-8. Our findings showed that CAPD effluent from patients with peritonitis contains markedly elevated MCP-1 and IL-8 levels, suggesting that these chemokines participate in leukocyte recruitment during CAPD peritonitis. Isolation of mRNA of peritonitis-derived peritoneal macrophages revealed strong signals for MCP-1 and IL-8, suggesting that macrophages are a major source of these inflammatory mediators.