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Intra-peritoneal free elastase in CAPD peritonitis
K L Donovan1, S Pacholok, J L Humes
1Institute of Nephrology, Royal Infirmary, Cardiff, Wales, United Kingdom.
Abstract:
Neutrophil (PMN) recruitment into the peritoneum during acute bacterial peritonitis is an important part of the host defense barrier in CAPD patients. However, the subsequent phagocytosis of bacteria may also lead to PMN degranulation and the release of lysosomal enzymes. We determined the concentration of neutrophil elastase, both in complex with its natural inhibitor alpha 1Pi (E alpha 1Pi), and in uncomplexed, free form, in infected and normal CAPD peritoneal fluid by ELISA. In addition elastase activity was estimated in a casein degradation assay. Infected fluid contained a median (range) of 1.4 nM (0 to 9.2) free elastase by ELISA and 1.2 nM (0 to 11.9) activity. There were strong correlations between the peritoneal leukocyte count and both immunoreactive elastase and activity (r = 0.816, P < 0.001, 0.687, P < 0.01, respectively). In contrast, normal fluid contained 0.0 nM (0 to 0.32) immunoreactive elastase (P < 0.01) and 0.0 nM (0 to 0.6) elastase activity (P < 0.001). E alpha 1Pi complexes were raised significantly during peritonitis at 6.2 nM (0 to 34.3) and were barely detectable in normal fluid 0.0 nM (0 to 0.17; P < 0.005). The study shows that small but significant quantities of uninhibited elastase can be detected in the peritoneal fluid of CAPD patients with acute bacterial peritonitis. This observation may have important implications for the pathogenesis of peritoneal membrane damage and the phlogistic response to infection.
Insights
Infections in continuous ambulatory peritoneal dialysis (CAPD) patients release neutrophil elastase into peritoneal fluid. This enzyme, even in its free form, may contribute to peritoneal membrane damage and inflammation during bacterial peritonitis.
Area of Science:
- Nephrology
- Immunology
- Biochemistry
Background:
- Neutrophil (PMN) recruitment is crucial for host defense in CAPD patients with bacterial peritonitis.
- PMN degranulation during bacterial phagocytosis releases lysosomal enzymes like neutrophil elastase.
- The role of free neutrophil elastase in CAPD peritonitis pathogenesis requires further investigation.
Purpose of the Study:
- To quantify free and complexed neutrophil elastase in infected and normal CAPD peritoneal fluid.
- To assess elastase activity in CAPD peritoneal fluid.
- To correlate elastase levels with leukocyte counts and peritonitis.
Main Methods:
- Enzyme-linked immunosorbent assay (ELISA) to measure neutrophil elastase complexed with alpha 1Pi (E alpha 1Pi) and free elastase.
- Casein degradation assay to estimate elastase activity.
- Comparison of levels in infected vs. normal CAPD peritoneal fluid.
Main Results:
- Infected CAPD fluid showed significantly higher levels of free elastase (median 1.4 nM) and elastase activity (median 1.2 nM) compared to normal fluid (0.0 nM).
- Elevated E alpha 1Pi complexes (median 6.2 nM) were observed in infected fluid.
- Strong correlations were found between peritoneal leukocyte count and both immunoreactive elastase and activity.
Conclusions:
- Significant quantities of uninhibited neutrophil elastase are present in the peritoneal fluid of CAPD patients with acute bacterial peritonitis.
- The presence of free elastase may play a role in peritoneal membrane damage and inflammatory responses.
- These findings highlight potential therapeutic targets for managing peritonitis in CAPD patients.