MECHANISMS OF POLYMORPHONUCLEAR LEUKOCYTE-MEDIATED PERITONEAL MESOTHELIAL CELL INJURY

To determine the susceptibility of human peritoneal mesothelial cells to injury mediated by activated polymorphonuclear leukocytes (PMNs), we exposed cultured human peritoneal mesothelial cells to 1250, 2500, 3750, and 5000 PMNs/mm(3) activated with 50 ng/ml phorbol myristate acetate (PMA) or with 10(-7) FMLP/cytochalasin B for one to five hours. PMN adhesion to mesothelial cells was determined with radiolabeled PMNs. Mesothelial cell injury was determined in five different cell lines by measuring ATP depletion and (51)chromium release. In each mesothelial cell line, PMN adhesion was significantly (P < 0.001) increased when PMNs were activated; 64 +/- 1.0 to 92.5 +/- 7.0% of the activated PMNs were adherent to mesothelial cells compared to 6 +/- 1.8 to 27 +/- 2.4% of resting PMNs. Mesothelial cells responded to PMN mediated injury with a fall in ATP levels and (51)chromium release that was significant (P < 0.05) by three to four hours. At five hours, ATP levels were markedly depressed to 5 to 41% of control values. Increasing concentrations of activated PMNs caused significantly (P < 0.05) greater mesothelial cell injury as determined by ATP depletion and (51)chromium release. PMN adhesion, ATP depletion and (51)chromium release were significantly (P < 0.01) prevented by an anti-CD18 monoclonal antibody that inhibits the CD11/CD18 adhesion molecule complex on PMNs. Similar injury and protection from injury was demonstrated when mesothelial cells were exposed to PMNs activated with FMLP/cytochalasin B. Immunohistochemical studies demonstrated that the cultured mesothelial cells express intracellular adhesion molecule 1 (ICAM-1) and FAB fragments of a monoclonal anti-ICAM-1 antibody partially reduced adhesion of activated PMNs to mesothelial cells and slightly reduced mesothelial cell injury. Staphylococcus aureus, Staphylococcus epidermidis, alpha streptococci, and Pseudomonas aeruginosa at concentrations of 10(3) to 10(5) bacteria/ml caused little to no ATP depletion or (51)chromium release. We conclude that activated PMNs adhere to human mesothelial cells and induce mesothelial cell injury; such injury can be partially reduced by blocking adhesion of activated PMNs to mesothelial cells.