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), w e exposed cultured human peritoneal mesothelial cells to 1250, 2500, 3 750, and 5000 PMNs/mm(3) activated with 50 ng/ml phorbol myristate ace tate (PMA) or with 10(-7) FMLP/cytochalasin B for one to five hours. P MN 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 mesotheli al cell line, PMN adhesion was significantly (P < 0.001) increased whe n PMNs were activated; 64 +/- 1.0 to 92.5 +/- 7.0% of the activated PM Ns were adherent to mesothelial cells compared to 6 +/- 1.8 to 27 +/- 2.4% of resting PMNs. Mesothelial cells responded to PMN mediated inju ry with a fall in ATP levels and (51)chromium release that was signifi cant (P < 0.05) by three to four hours. At five hours, ATP levels were markedly depressed to 5 to 41% of control values. Increasing concentr ations of activated PMNs caused significantly (P < 0.05) greater mesot helial cell injury as determined by ATP depletion and (51)chromium rel ease. PMN adhesion, ATP depletion and (51)chromium release were signif icantly (P < 0.01) prevented by an anti-CD18 monoclonal antibody that inhibits the CD11/CD18 adhesion molecule complex on PMNs. Similar inju ry and protection from injury was demonstrated when mesothelial cells were exposed to PMNs activated with FMLP/cytochalasin B. Immunohistoch emical studies demonstrated that the cultured mesothelial cells expres s intracellular adhesion molecule 1 (ICAM-1) and FAB fragments of a mo noclonal anti-ICAM-1 antibody partially reduced adhesion of activated PMNs to mesothelial cells and slightly reduced mesothelial cell injury . Staphylococcus aureus, Staphylococcus epidermidis, alpha streptococc i, and Pseudomonas aeruginosa at concentrations of 10(3) to 10(5) bact eria/ml caused little to no ATP depletion or (51)chromium release. We conclude that activated PMNs adhere to human mesothelial cells and ind uce mesothelial cell injury; such injury can be partially reduced by b locking adhesion of activated PMNs to mesothelial cells.