Continuous ambulatory peritoneal dialysis is known to interfere with the normal inflammatory responses of macrophages in the peritoneal cavity. Commercial peritoneal dialysis solution (CDS) has been shown to inhibit tumor necrosis factor α (TNFα) release from LPS stimulated peritoneal macrophages. To further dissect the mechanism of this inhibition, we used human blood-derived macrophages or the murine macrophage cell line, P388D1, that were stimulated with LPS after pretreatment with CDS, and tested TNFα mRNA levels by Northern hybridization or reverse transcriptase polymerase chain reaction. Time course studies demonstrated that CDS lowered TNFα mRNA levels within 15 minutes of pretreatment of cells. In addition, the CDS inhibited DNA binding activity of NF-κB that is probably involved in regulation of LPS-mediated transcriptional activation of the TNFα gene. Inhibition was dependent on both the low pH and the lactate in the CDS, but was independent of the osmolarity or glucose concentration. The rate of catabolism of TNFα mRNA was not affected by CDS as demonstrated by actinomycin D chase experiments. Thus, impairment of LPS-stimulated macrophage function by CDS is associated with low TNFα mRNA which may be the result of the low activity of NF-κB. Since NF-κB is involved in transcription regulation of a large number of 'early activation' genes, CDS may interfere with the production of additional immunomodulatory proteins that are encoded by genes possessing NF-κB site(s) in their promoter region.
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