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Do cytokine-inducing substances penetrate through dialysis membranes and stimulate monocytes?
Abstract:
Does a relatively low concentration of endotoxin in dialysate, seen in our clinical dialysis, enhance cytokine production of monocytes across high-flux membranes? Several investigators using extremely high concentrations of endotoxin in dialysate maintain that it does. In vitro experiments in this study were conducted to clarify this. Peripheral blood monocytes were isolated from healthy volunteers and incubated for 20 hours. The incubation medium was made of back-filtrates obtained either from Pseudomonas-contaminated water with endotoxin concentration of 621 pg/ml or water with 10 ng/ml or 1 microgram/ml of lipopolysaccharide (LPS), by passing it through a high-flux membrane dialyzer. Endotoxin free water and addition of LPS (0.01 to 10 ng/ml) were used as a negative and positive control. Interleukin-1 beta (IL-1 beta), IL-6 and tumor necrosis factor alpha (TNF alpha) were measured. Back-filtrate from Pseudomonas-contaminated water did not enhance cytokine production, while 50 pg/ml of endotoxin in culture medium induced a significant cytokine production. Back-filtrate of 1 microgram/ml of endotoxin solution marginally increased IL-6 production, but not the other two cytokines. However, none of the cytokines was induced by the back-filtrate of 10 ng/ml of endotoxin. Monocytes isolated from blood following three hour extracorporeal recirculation did not alter the production of cytokines. These results cannot confirm the transfer of cytokine inducing substances across the membrane at a relatively low endotoxin concentration in dialysate. Further study should be made as to the minimal requirement of dialysate purification for preventing monocyte stimulation.
Insights
This study found that low endotoxin concentrations in dialysis fluid do not significantly enhance monocyte cytokine production across high-flux membranes. Further research is needed on dialysate purification to prevent monocyte stimulation.
Area of Science:
- Nephrology
- Immunology
- Biomedical Engineering
Background:
- Dialysis fluid endotoxin levels are a concern for patient immune response.
- Previous studies suggested high endotoxin concentrations stimulate cytokine production.
- The effect of lower, clinically relevant endotoxin levels remains unclear.
Purpose of the Study:
- To investigate if low endotoxin concentrations in dialysis fluid enhance monocyte cytokine production across high-flux membranes.
- To determine the threshold of endotoxin concentration required for monocyte stimulation during hemodialysis.
- To assess the impact of endotoxin transfer through high-flux dialyzers on immune cells.
Main Methods:
- In vitro incubation of human monocytes with dialysate back-filtrates containing varying endotoxin concentrations (LPS).
- Use of high-flux membrane dialyzers to simulate clinical hemodialysis conditions.
- Measurement of key cytokines: Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), and Tumor Necrosis Factor alpha (TNF-α).
- Comparison with endotoxin-free water and varying concentrations of LPS as controls.
Main Results:
- Dialysate back-filtrates with low endotoxin concentrations (621 pg/ml or 10 ng/ml LPS) did not enhance cytokine production.
- A concentration of 50 pg/ml endotoxin in culture medium significantly induced cytokine production.
- High endotoxin concentration (1 µg/ml) marginally increased IL-6 but not IL-1β or TNF-α.
- Monocyte cytokine production was not altered after extracorporeal recirculation.
Conclusions:
- Low endotoxin concentrations in dialysis fluid do not appear to stimulate monocyte cytokine production across high-flux membranes.
- The study suggests that current clinical dialysis endotoxin levels may not pose a significant risk for immune cell activation via this route.
- Further investigation into the minimal dialysate purification requirements is recommended to prevent monocyte stimulation.