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Mechanisms of polymorphonuclear leukocyte mediated peritoneal mesothelial cell injury
S P Andreoli1, C Mallett, K Williams
1Department of Pediatrics, Indiana University School of Medicine, Indianapolis.
Abstract:
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/mm3 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 51chromium 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 51chromium 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 51chromium release. PMN adhesion, ATP depletion and 51chromium 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.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Activated polymorphonuclear leukocytes (PMNs) significantly injure human peritoneal mesothelial cells, causing ATP depletion and chromium release. This PMN-mediated mesothelial cell injury was inhibited by an anti-CD18 antibody.
Area of Science:
- Immunology
- Cell Biology
- Peritoneal Mesothelial Cell Biology
Background:
- Human peritoneal mesothelial cells (HPMCs) are crucial for peritoneal function.
- Polymorphonuclear leukocytes (PMNs) are key immune cells involved in inflammation and tissue injury.
- Understanding HPMC susceptibility to PMN-mediated injury is vital for peritoneal health.
Purpose of the Study:
- To investigate the susceptibility of HPMCs to injury induced by activated PMNs.
- To quantify PMN adhesion and subsequent HPMC damage.
- To identify potential mechanisms and inhibitory factors involved in PMN-mediated HPMC injury.
Main Methods:
- Cultured HPMCs were exposed to activated PMNs (phorbol myristate acetate or FMLP/cytochalasin B) at varying concentrations and time points.
- PMN adhesion was quantified using radiolabeled PMNs.
- HPMC injury was assessed by measuring adenosine triphosphate (ATP) depletion and 51chromium release.
- The effect of an anti-CD18 monoclonal antibody on PMN adhesion and HPMC injury was evaluated.
Main Results:
- Activated PMNs exhibited significantly increased adhesion to HPMCs compared to resting PMNs (up to 92.5% vs. 27%).
- HPMCs showed significant injury, evidenced by ATP depletion and 51chromium release, starting at 3-4 hours of exposure to activated PMNs.
- Increasing concentrations of activated PMNs led to greater HPMC injury.
- An anti-CD18 monoclonal antibody significantly inhibited PMN adhesion and protected HPMCs from injury.
Conclusions:
- Activated PMNs are capable of causing significant injury to human peritoneal mesothelial cells.
- PMN adhesion, mediated by the CD11/CD18 complex, is a key factor in PMN-induced HPMC damage.
- Targeting the CD11/CD18 adhesion pathway may offer a protective strategy against PMN-mediated peritoneal injury.