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Hydrogen peroxide generation by polymorphonuclear leukocytes exposed to peritoneal dialysis effluent
I Daniels1, K S Bhatia, C J Porter
1Medical Research Centre, City Hospital, Nottingham, United Kingdom.
Abstract:
In the presence of peritoneal dialysis effluent (PDE), human polymorphonuclear leukocytes (PMN) showed reduced production of hydrogen peroxide and hypochlorous acid (H2O2 and HOCl, respectively) when at rest and when stimulated with both soluble (formylmethionyl-leucyl-phenylalanine and phorbol myristate acetate) and particulate (Staphylococcus epidermidis) agonists. This effect occurred in a concentration-dependent manner between 0 and 70%. (vol/vol) dialysis effluent. The inhibition of H2O2 and HOCl observed in resting, formy-methionylleucyphenyalanine-stimulated, and S. epidermidis-stimulated PMN was confined to a low-molecular-mass (< 10,000-Da) fraction of PDE, whereas the inhibition of the PMA response was equally dispersed throughout both low (< 10,000-Da)- and high-molecular-mass (> 10,000-Da) fractions. Human serum albumin, a major component of PDE, also inhibited H2O2 and HOCl production by PMN; however, results from cell-free systems suggested that human serum albumin was not wholly responsible for the inhibition of PMN function seen with PDE. The solute(s) responsible did not affect myloperoxidase but very rapidly scavenged H2O2 and HOCl. These data suggest that the factors capable of affecting H2O2 and HOCl production by PMN accumulate in uremia and are removed from the circulation into dialysis effluent.
Insights
Peritoneal dialysis effluent (PDE) reduces the infection-fighting capacity of human white blood cells (PMN) by inhibiting key molecules like hydrogen peroxide (H2O2) and hypochlorous acid (HOCl). These inhibitory factors accumulate in uremia and are removed during dialysis.
Area of Science:
- Nephrology
- Immunology
- Biochemistry
Background:
- Polymorphonuclear leukocytes (PMN) are crucial for innate immunity.
- Uremia, a condition associated with kidney failure, can impair immune function.
- Peritoneal dialysis (PD) is a common treatment for kidney failure.
Purpose of the Study:
- To investigate the effect of peritoneal dialysis effluent (PDE) on PMN function.
- To identify factors in PDE that inhibit PMN production of reactive oxygen species.
- To understand how uremia and dialysis influence PMN activity.
Main Methods:
- Incubation of human PMN with varying concentrations of PDE.
- Stimulation of PMN with soluble and particulate agonists.
- Measurement of hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) production.
- Fractionation of PDE to isolate inhibitory components.
- Cell-free assays to assess scavenger activity.
Main Results:
- PDE significantly reduced H2O2 and HOCl production by PMN in a concentration-dependent manner.
- Inhibitory activity was primarily associated with low-molecular-mass fractions of PDE.
- Human serum albumin showed some inhibitory effect, but was not solely responsible.
- The responsible solute(s) rapidly scavenged H2O2 and HOCl without affecting myeloperoxidase.
Conclusions:
- Factors that inhibit PMN oxidative burst accumulate in uremia.
- These inhibitory factors are removed from circulation into PDE during dialysis.
- PDE can impair the immune defense capacity of PMN, potentially increasing infection risk in dialysis patients.