Background: Leukocyte migration into the peritoneal cavity is a diagnostic feature of peritonitis in patients treated with peritoneal dialysis (PD). While neutrophil (PMN) influx is characteristic of the acute phase of peritoneal infection, significant mononuclear cell (MNC) infiltration, occurs throughout the whole period of infection. Recent data suggests that human peritoneal mesothelial cell (HPMC) adhesion molecule expression and the synthesis of chemotactic cytokines may be important in the process.
Methods: In the present study we have examined, the regulation and directed secretion of chemokines (IL-8, MCP-1 and RANTES) and the basolateral to apical migration of unstimulated leukocytes across mesothelial cell monolayers using an in vitro model where HPMC were grown on the porous membrane of tissue culture inserts. Separate experiments have defined the importance of chemokine synthesis and ICAM-1 expression in the transmigration process.
Results: Apical stimulation of HPMC with IL-1 beta or TNF alpha resulted in a time and dose dependent up-regulation of IL-8, MCP-1 and RANTES mRNA expression and synthesis. This secretion was predominately into the apical compartment (> 85%) with all chemokines. Apical pre-stimulation of HPMC resulted in a dose- and time-dependent migration of both PMN and MNC across HPMC. Neutrophil migration was significantly reduced in the presence of appropriate concentrations of polyclonal IL-8 antibody (IL-1 beta (100 pg/ml) 153 +/- 12 versus anti-IL-8 (100 ng/ml) 71 +/- 7 (X 10(3)) PMN, N = 6, P < 0.02) and in the presence of anti-ICAM-1 F(ab)'2 fragments or soluble ICAM-1. Constitutive and cytokine stimulated mononuclear cell migration was significantly reduced in the simultaneous presence of polyclonal MCP-1 or RANTES antibody.
Conclusions: These data demonstrate that HPMC synthesize IL-8, MCP-1 and RANTES in response to inflammatory cytokines. HPMC-derived C-x-C and C-C chemokines might contribute to the intra-peritoneal recruitment of leukocytes during peritoneal inflammation.